Laser induced damage thresholds and laser safety levels. Do the units of measurement matter?

NASA Astrophysics Data System (ADS)

Wood, R. M.

1998-04-01

The commonly used units of measurement for laser induced damage are those of peak energy or power density. However, the laser induced damage thresholds, LIDT, of all materials are well known to be absorption, wavelength, spot size and pulse length dependent. As workers using these values become divorced from the theory it becomes increasingly important to use the correct units and to understand the correct scaling factors. This paper summarizes the theory and highlights the danger of using the wrong LIDT units in the context of potentially hazardous materials, laser safety eyewear and laser safety screens.

Research on laser-induced damage resistance of fused silica optics by the fluid jet polishing method.

PubMed

Lv, Liang; Ma, Ping; Huang, Jinyong; He, Xiang; Cai, Chao; Zhu, Heng

2016-03-20

Laser-induced damage threshold (LIDT) is one important evaluation index for optical glasses applied in large laser instruments which are exposed to high light irradiation flux. As a new kind of precise polishing technology, fluid jet polishing (FJP) has been widely used in generating planar, spherical, and aspherical optics with high-accuracy surfaces. Laser damage resistances of fused silica optics by the FJP process are studied in this paper. Fused silica samples with various FJP parameters are prepared, and laser damage experiments are performed with 351 nm wavelength and a 5.5 ns pulse width laser. Experimental results demonstrate that the LIDT of the samples treated with FJP processes did not increase, compared to their original state. The surface quality of the samples is one factor for the decrease of LIDT. For ceria solution polished samples, the cerium element remaining is another factor of the lower LIDT.

Multiple pulse nanosecond laser induced damage threshold on hybrid mirrors

NASA Astrophysics Data System (ADS)

Vanda, Jan; Muresan, Mihai-George; Bilek, Vojtech; Sebek, Matej; Hanus, Martin; Lucianetti, Antonio; Rostohar, Danijela; Mocek, Tomas; Škoda, Václav

2017-11-01

So-called hybrid mirrors, consisting of broadband metallic surface coated with dielectric reflector designed for specific wavelength, becoming more important with progressing development of broadband mid-IR sources realized using parametric down conversion system. Multiple pulse nanosecond laser induced damage on such mirrors was tested by method s-on-1, where s stands for various numbers of pulses. We show difference in damage threshold between common protected silver mirrors and hybrid silver mirrors prepared by PVD technique and their variants prepared by IAD. Keywords: LIDT,

Assessing the impact of atomic oxygen in the damage threshold and stress of Hafnia films grown by ion beam sputter deposition

NASA Astrophysics Data System (ADS)

Patel, D.; Wang, Y.; Larotonda, M.; Lovewell, J.; Jensen, J.; Hsiao, K. J.; Krous, E.; Rocca, J. J.; Menoni, C. S.; Tomasel, F.; Kholi, S.; McCurdy, P.

2007-01-01

Hafnium oxide (HfO II) is undoubtedly one of the most desirable high-index optical coatings for high power laser applications. One of the key goals in the fabrication of oxide films with high Laser Induced Damage Threshold (LIDT) is to minimize the number of film imperfections, in particular stoichiometric defects. For HfO II films deposited by ion beam (reactive) sputtering (IBS) of a hafnium metal target, stoichiometry is controlled by the injection of molecular oxygen, either close to the substrate or mixed with the sputtering gas or some other combination. Good stoichiometry is important to reduce the density of unoxidized particles buried in the coatings, which affect the LIDT. This work evaluates the potential advantages of using pre-activation of oxygen in the IBS of HfO II, with special emphasis on its impact on LIDT and film stress. For the experiments, oxygen was activated by an independent plasma source and then introduced into a commercial IBS chamber. The optical properties of the films were characterized using spectrophotometry and ellipsometry. Their structural quality and composition were determined from x-ray diffraction and x-ray photoelectron emission spectroscopy. The stress was determined from interferometer measurements. For optimized conditions, 2.5 J/cm2 LIDT was measured on HfO II films at λ=800 nm with 1 ps and 25 mJ pulses from a chirped amplification Ti:Sapphire laser. In the range of oxygen variations under consideration the effects on LIDT are shown to be minimal.

Laser damage properties of TiO{sub 2}/Al{sub 2}O{sub 3} thin films grown by atomic layer deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wei Yaowei; Liu Hao; Sheng Ouyang

2011-08-20

Research on thin film deposited by atomic layer deposition (ALD) for laser damage resistance is rare. In this paper, it has been used to deposit TiO{sub 2}/Al{sub 2}O{sub 3} films at 110 deg. C and 280 deg. C on fused silica and BK7 substrates. Microstructure of the thin films was investigated by x-ray diffraction. The laser-induced damage threshold (LIDT) of samples was measured by a damage test system. Damage morphology was studied under a Nomarski differential interference contrast microscope and further checked under an atomic force microscope. Multilayers deposited at different temperatures were compared. The results show that the filmsmore » deposited by ALD had better uniformity and transmission; in this paper, the uniformity is better than 99% over 100 mm {Phi} samples, and the transmission is more than 99.8% at 1064 nm. Deposition temperature affects the deposition rate and the thin film microstructure and further influences the LIDT of the thin films. As to the TiO{sub 2}/Al{sub 2}O{sub 3} films, the LIDTs were 6.73{+-}0.47 J/cm{sup 2} and 6.5{+-}0.46 J/cm{sup 2} at 110 deg. C on fused silica and BK7 substrates, respectively. The LIDTs at 110 deg. C are notably better than 280 deg. C.« less

Nanosecond laser-induced damage at different initial temperatures of Ta{sub 2}O{sub 5} films prepared by dual ion beam sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Cheng, E-mail: xucheng@cumt.edu.cn; Jia, Jiaojiao; Fan, Heliang

2014-08-07

Ta{sub 2}O{sub 5} films were deposited by dual ion beam sputtering method. The nanosecond laser-induced damage threshold (LIDT) at different initial temperatures and time of the films was investigated by an in situ high temperature laser-induced damage testing platform. It was shown that, when the initial temperature increased from 298 K to 383 K, the LIDT at 1064 nm and 12 ns significantly decreased by nearly 14%. Then the LIDT at 1064 nm and 12 ns decreased slower with the same temperature increment. Different damage morphologies were found at different initial temperatures. At low initial temperatures, it was the defects-isolated damage while at high initial temperaturesmore » it was the defects-combined damage. The theoretical calculations based on the defect-induced damage model revealed that both the significant increase of the highest temperature and the duration contributed to the different damage morphologies. With the initial temperature being increased, the thermal-stress coupling damage mechanism transformed gradually to the thermal dominant damage mechanism.« less

Laser pulse transmission and damage threshold of silica fibers with antireflective coatings

NASA Astrophysics Data System (ADS)

Meister, Stefan; Wosniok, Alexander; Riesbeck, Thomas; Scharfenorth, Chris; Eichler, Hans J.

2005-03-01

Standard 200 μm multimode fibers with Ta2O5/SiO2 antireflective coatings reach a transmission of more than 99.5% below the threshold of stimulated Brillouin scattering. The laser-induced damage threshold measured at 1064 nm and 24 ns pulse duration was about half than the LIDT of uncoated fibers.

Low Group Delay Dispersion Optical Coating for Broad Bandwidth High Reflection at 45° Incidence, P Polarization of Femtosecond Pulses with 900 nm Center Wavelength

DOE PAGES

Bellum, John C.; Field, Ella S.; Winstone, Trevor B.; ...

2016-03-01

We describe an optical coating design suitable for broad bandwidth high reflection (BBHR) at 45° angle of incidence (AOI), P polarization (Ppol) of femtosecond (fs) laser pulses whose wavelengths range from 800 to 1000 nm. The design process is guided by quarter-wave HR coating properties. Our design must afford low group delay dispersion (GDD) for reflected light over the broad, 200 nm bandwidth in order to minimize temporal broadening of the fs pulses due to dispersive alteration of relative phases between their frequency components. The design should also be favorable to high laser-induced damage threshold (LIDT). We base the coatingmore » on TiO 2/SiO 2 layer pairs produced by means of e-beam evaporation with ion-assisted deposition, and use OptiLayer Thin Film Software to explore designs starting with TiO 2/SiO 2 layers having thicknesses in a reverse chirped arrangement. This approach led to a design with R > 99% from 800 to 1000 nm and GDD < 20 fs 2 from 843 to 949 nm (45° AOI, Ppol). The design’s GDD behaves in a smooth way, suitable for GDD compensation techniques, and its electric field intensities show promise for high LIDTs. Reflectivity and GDD measurements for the initial test coating indicate good performance of the BBHR design. Subsequent coating runs with improved process calibration produced two coatings whose HR bands satisfactorily meet the design goals. Lastly, for the sake of completeness, we summarize our previously reported transmission spectra and LIDT test results with 800 ps, 8 ps and 675 fs pulses for these two coatings, and present a table of the LIDT results we have for all of our TiO 2/SiO 2 BBHR coatings, showing the trends with test laser pulse duration from the ns to sub-ps regimes.« less

Characterization of LaF 3 coatings prepared at different temperatures and rates

NASA Astrophysics Data System (ADS)

Yu, Hua; Shen, Yanming; Cui, Yun; Qi, Hongji; Shao, JianDa; Fan, ZhengXiu

2008-01-01

LaF 3 thin films were prepared by thermal boat evaporation at different substrate temperatures and various deposition rates. X-ray diffraction (XRD), Lambda 900 spectrophotometer and X-ray photoelectron spectroscopy (XPS) were employed to study crystal structure, transmittance and chemical composition of the coatings, respectively. Laser-induce damage threshold (LIDT) was determined by a tripled Nd:YAG laser system with a pulse width of 8 ns. It is found that the crystal structure became more perfect and the refractive index increased gradually with the temperature rising. The LIDT was comparatively high at high temperature. In the other hand, the crystallization status also became better and the refractive index increased when the deposition rate enhanced at a low level. If the rate was super rapid, the crystallization worsened instead and the refractive index would lessen greatly. On the whole, the LIDT decreased with increasing rate.

Laser Induced Damage of Potassium Dihydrogen Phosphate (KDP) Optical Crystal Machined by Water Dissolution Ultra-Precision Polishing Method

PubMed Central

Gao, Hang; Wang, Xu; Guo, Dongming; Liu, Ziyuan

2018-01-01

Laser induced damage threshold (LIDT) is an important optical indicator for nonlinear Potassium Dihydrogen Phosphate (KDP) crystal used in high power laser systems. In this study, KDP optical crystals are initially machined with single point diamond turning (SPDT), followed by water dissolution ultra-precision polishing (WDUP) and then tested with 355 nm nanosecond pulsed-lasers. Power spectral density (PSD) analysis shows that WDUP process eliminates the laser-detrimental spatial frequencies band of micro-waviness on SPDT machined surface and consequently decreases its modulation effect on the laser beams. The laser test results show that LIDT of WDUP machined crystal improves and its stability has a significant increase by 72.1% compared with that of SPDT. Moreover, a subsequent ultrasonic assisted solvent cleaning process is suggested to have a positive effect on the laser performance of machined KDP crystal. Damage crater investigation indicates that the damage morphologies exhibit highly thermal explosion features of melted cores and brittle fractures of periphery material, which can be described with the classic thermal explosion model. The comparison result demonstrates that damage mechanisms for SPDT and WDUP machined crystal are the same and WDUP process reveals the real bulk laser resistance of KDP optical crystal by removing the micro-waviness and subsurface damage on SPDT machined surface. This improvement of WDUP method makes the LIDT more accurate and will be beneficial to the laser performance of KDP crystal. PMID:29534032

Influence of Deposition Temperature on Optical and Laser-Induced Damage Properties of LaTiO3 Films

NASA Astrophysics Data System (ADS)

Su, Junhong; Xu, Junqi; Yang, Chen; Cheng, Yaojin

2015-08-01

LaTiO3 films were prepared at room temperature, 60, 140 and 220°C using a thermal vapor deposition technique with an electronic beam gun to investigate the relationship between deposition temperatures and the optical properties of the samples. In the ellipsometric analysis, the corresponding refractive indexes were 1.8993, 1.9123, 1.9197 and 1.9283 at a wavelength of 1064 nm. At the same time, extremely low absorption characteristics of all the samples presented in the visible and IR regions. With the same high-energy testing laser of 200 mJ (about 40 J/cm2) at a wavelength of 1064 nm and a pulse width of 10 ns, the laser-induced damage threshold (LIDT) of the LaTiO3 samples prepared at different temperatures were 15.5, 16.7, 18.5 and 18.2 J/cm2, respectively. This shows that a higher LIDT may be obtained at higher deposition temperatures.

Selected technologies for integration of the ALADIN transmitreceive optics (TRO)

NASA Astrophysics Data System (ADS)

Bittner, Hermann; Mosebach, Herbert; Sang, Bernhard; Erhard, Markus; Hilbrand, Bernhard; Mazuray, Laurent; Thibault, Dominique

2017-11-01

Selected technologies for the integration of the TRANSMIT/RECEIVE OPTICS (TRO) are presented. One of the challenging characteristics of the TRO is its stringent requirement on opto-mechanical stability. The stability performance of the TRO must be ensured for the relevant interface environments (thermal, structural) over the 3 years mission lifetime. Comprehensive analyses have been conducted, which have confirmed the need for the development of special integration technologies. Also, dedicated test equipment has been developed to precisely verify the TRO's optomechanical stability. Another important feature of the TRO is its exposure to the high power laser beam of the ADALIN instrument. The corresponding optical elements and their mounts must survive exposure to light intensities up to the required laser-induced damage thresholds (LIDT). Two types of adhesives for gluing of the TRO optics have been selected. Their qualification w.r.t. outgassing was necessary since LIDT's of optical surfaces are significantly reduced when organic outgassing products are deposited there.

Silicon Dioxide Planarization: Impacts on Optical Coatings for High Energy Laser

NASA Astrophysics Data System (ADS)

Day, Travis E.

The work of this thesis is devoted to examining the impact of silicon dioxide (silica or SiO2) planarization on the optical properties and laser damage resistance of thin-film coatings. SiO2 planarization is a process to smooth out fluence limiting nodular defects within multilayer coatings for high-energy laser applications. Mitigating these defects will improve the power handling abilities and improve the lifetime of laser coatings. Presented here is a combination of work with the aim of evaluating the optical and laser damage properties of SiO2 planarization within single layers, bilayers, and multilayers. As compared to control (non-planarized) samples, a 2-3x increase in the thin-film absorption, which decreases with post-process annealing, was discovered for SiO2 planarized samples. This suggests that planarization creates oxygen-related defects which can be annealed out and little impurity implantation. Investigations of laser damage resistance were carried out at lambda = 1030nm and pulse durations of tau = 220ps and 9ps. The laser damage of single and bilayer coatings is known to be dependent on the substrate-coating interface and this is further evidenced within this thesis. This is because the effects of planarization are masked by the extrinsic laser damage processes within the single and bilayers. Slight change (< 15%) in the laser induced damage threshold (LIDT) at 220ps and 9ps was observed for planarized single and bilayers. Depending on coating design, post-process annealing was shown to increase the LIDT by 10% to 75% at 220ps and 10% to 45% at 9ps. Although the fused silica substrate surface LIDT was shown to follow the √tau pulse scaling law for pulses above 10ps, the single and bilayer coatings do not follow this pulse scaling. The divergence from the √tau pulse scaling on the coatings suggests a variation in the laser damage initiation mechanisms between 220ps and 9ps. Multilayer high-reflecting (HR) mirrors with varying planarization design were also damage tested. A 6-7 J/cm2 LIDT, with 220ps, was observed for HR coatings with SiO2 planarization layers within high electric-field areas within the coating. However, SiO2 planarization at the substrate-coating interface, where the electric-field is minimal, and control (non-planarized) was shown to have a LIDT of 63 +/- 1.2 J/cm 2 and 21.5 +/- 0.5 J/cm2 for 220ps, respectively. At 9ps, the LIDT varied less than 90% difference between the various planarization designs. The substrate-coating planarization multilayer and control coating had an equal LIDT of 9.6 +/- .3 J/cm2 at 9ps.

Influence of substrate temperature on properties of MgF 2 coatings

NASA Astrophysics Data System (ADS)

Yu, Hua; Qi, Hongji; Cui, Yun; Shen, Yanming; Shao, JianDa; Fan, ZhengXiu

2007-05-01

Thermal boat evaporation was employed to prepare MgF 2 single-layer coatings upon both JGS1 and UBK7 substrates at different substrate temperatures. Microstructure, transmittance and residual stress of these coatings were measured by X-ray diffraction, spectrophotometer, and optical interferometer, respectively. Measurement of laser induced damage threshold (LIDT) of the samples was performed at 355 nm, 8 ns pulses. The results showed that high substrate temperature was beneficial to crystallization of the film. Above 244 °C, the refractive index increased gradually with the substrate temperature rising. Whereas, it was exceptional at 210 °C that the refractive index was higher than those deposited at 244 and 277 °C. The tensile residual stresses were exhibited in all MgF 2 films, but not well correlated with the substrate temperature. In addition, the stresses were comparatively smaller upon JGS1 substrates. A tendency could be seen that the LIDTs reached the highest values at about 244 °C, and the films upon JGS1 had higher LIDTs than those upon UBK7 substrates at the same temperature. Meanwhile, the damage morphologies showed that the laser damage of the coating resulted from an absorbing center at the film-substrate interface. The features of the damages were displayed by an absorbing center dominated model. Furthermore, the reason of the difference in LIDT values was discussed in detail.

Laser-induced bulk damage of silica glass at 355nm and 266nm

NASA Astrophysics Data System (ADS)

Kashiwagi, R.; Aramomi, S.

2016-12-01

Laser processing machines using Nd:YAG 3rd harmonic wave (355 nm) and 4th harmonic wave (266 nm) have been developed and put into practical use lately. Due to this, optical elements with high laser durability to 355 nm and 266 nm are required. Silica glass is the optical element which has high UV transmission and high laser durability. Laser-induced surface damage of the silica glass has been studied in detail, but we hardly have the significant knowledge of laserinduced bulk damage. This knowledge is required in order to evaluate the silica glass itself. That is because cracks and scratches on the surface give rise to a higher possibility of damage. Therefore, we studied the laser durability of a variety of the silica glass samples by 1-on-1 and S-on-1 laser-induced bulk damage threshold (LIDT) at 355 nm and 266 nm. In this study, we gained knowledge in three areas about bulk damage to the silica glass. First, the LIDT became lower as shot counts increased. Second, the LIDT decreased as the hydroxyl content in the silica glass increased. Last, the LIDT became higher as the hydrogen concentration in the silica glass increased. Under the UV irradiation, impurities are generated and the silica glass absorbs more light. Therefore, the LIDT decreased as shot counts increased. Also, the hydroxyl in particular generates more impurities, so damage easily occurs. On the other hand, the hydrogen reacts with impurities and absorption is suppressed. Based on these results, we can improve laser durability at 355 nm and 266 nm by reducing the hydroxyl content and increasing the hydrogen concentration in the silica glass.

CW laser damage testing of RAR nano-textured fused silica and YAG

NASA Astrophysics Data System (ADS)

MacLeod, Bruce D.; Hobbs, Douglas S.; Manni, Anthony D.; Sabatino, Ernest; Bernot, David M.; DeFrances, Sage; Randi, Joseph A.; Thomas, Jeffrey

2017-11-01

A study of the continuous wave (CW) laser induced damage threshold (LiDT) of fused silica and yttrium aluminum garnet (YAG) optics was conducted to further illustrate the enhanced survivability within high power laser systems of an anti-reflection (AR) treatment consisting of randomly distributed surface relief nanostructures (RAR). A series of three CW LiDT tests using the 1070nm wavelength, 16 KW fiber laser test bed at Penn State Electro-Optic Center (PSEOC) were designed and completed, with improvements in the testing protocol, areal coverage, and maximum exposure intensities implemented between test cycles. Initial results for accumulated power, stationary site exposures of RAR nano-textured optics showed no damage and low surface temperatures similar to the control optics with no AR treatment. In contrast, optics with thin-film AR coatings showed high surface temperatures consistent with absorption by the film layers. Surface discriminating absorption measurements made using the Photothermal Common-path Interferometry (PCI) method, showed zero added surface absorption for the RAR nanotextured optics, and absorption levels in the 2-5 part per million range for thin-film AR coated optics. In addition, the surface absorption of thin-film AR coatings was also found to have localized absorption spikes that are likely pre-cursors for damage. Subsequent CW LiDT testing protocol included raster scanning an increased intensity focused beam over the test optic surface where it was found that thin-film AR coated optics damaged at intensities in the 2 to 5 MW/cm2 range with surface temperatures over 250C during the long-duration exposures. Significantly, none of the 10 RAR nano-textured fused silica optics tested could be damaged up to the maximum system intensity of 15.5 MW/cm2, and surface temperatures remained low. YAG optics tested during the final cycle exhibited a similar result with RAR nano-textured surfaces surviving intensities over 3 times higher than thin-film AR coated surfaces. This result was correlated with PCI measurements that also show zero-added surface absorption for the RAR nano-textured YAG optics.

ALD anti-reflection coatings at 1ω, 2ω, 3ω, and 4ω for high-power ns-laser application

NASA Astrophysics Data System (ADS)

Liu, Hao; Jensen, Lars; Ma, Ping; Ristau, Detlev

2018-04-01

Atomic layer deposition (ALD) facilitates the deposition of coatings with precise thickness, high surface conformity, structural uniformity, and nodular-free structure, which are properties desired in high-power laser coatings. ALD was studied to produce uniform and stable Al2O3 and HfO2 single layers and was employed to produce anti-reflection coatings for the harmonics (1ω, 2ω, 3ω, and 4ω) of the Nd:YAG laser. In order to qualify the ALD films for high-power laser applications, the band gap energy, absorption, and element content of single layers were characterized. The damage tests of anti-reflection coatings were carried out with a laser system operated at 1ω, 2ω, 3ω, and 4ω, respectively. The damage mechanism was discussed by analyzing the damage morphology and electric field intensity difference. ALD coatings exhibit stable growth rates, low absorption, and rather high laser-induced damage threshold (LIDT). The LIDT is limited by HfO2 as the employed high-index material. These properties indicate the high versatility of ALD films for applications in high-power coatings.

Investigation of optical fibers for high-repetition-rate, ultraviolet planar laser-induced fluorescence of OH.

PubMed

Hsu, Paul S; Kulatilaka, Waruna D; Roy, Sukesh; Gord, James R

2013-05-01

We investigate the fundamental transmission characteristics of nanosecond-duration, 10 kHz repetition rate, ultraviolet (UV) laser pulses through state-of-the-art, UV-grade fused-silica fibers being used for hydroxyl radical (OH) planar laser-induced fluorescence (PLIF) imaging. Studied in particular are laser-induced damage thresholds (LIDTs), nonlinear absorption, and optical transmission stability during long-term UV irradiation. Solarization (photodegradation) effects are significantly enhanced when the fiber is exposed to high-repetition-rate, 283 nm UV irradiation. For 10 kHz laser pulses, two-photon absorption is strong and LIDTs are low, as compared to those of laser pulses propagating at 10 Hz. The fiber characterization results are utilized to perform single-laser-shot, OH-PLIF imaging in pulsating turbulent flames with a laser that operates at 10 kHz. The nearly spatially uniform output beam that exits a long multimode fiber becomes ideal for PLIF measurements. The proof-of-concept measurements show significant promise for extending the application of a fiber-coupled, high-speed OH-PLIF system to harsh environments such as combustor test beds, and potential system improvements are suggested.

Mechanism for atmosphere dependence of laser damage morphology in HfO2/SiO2 high reflective films

NASA Astrophysics Data System (ADS)

Pu, Yunti; Ma, Ping; Chen, Songlin; Zhu, Jiliang; Wang, Gang; Pan, Feng; Sun, Ping; Zhu, Xiaohong; Zhu, Jianguo; Xiao, Dingquan

2012-07-01

We show in this paper single-shot and multi-shot laser-induced damage thresholds (LIDTs) of HfO2/SiO2 high reflective films (the reflectance = 99.9%) are affected by the presence of a water layer absorbed on the surface of the porous films. When the water layer was removed with the process of pumping, the single-shot LIDT measured in vacuum dropped to ˜48% of that measured in air, while the multi-shot LIDT in vacuum dropped to ˜47% of its atmospheric value for the high reflective films. Typical damage micrographs of the films in air and in vacuum were obtained, showing distinct damage morphologies. Such atmosphere dependence of the laser damage morphology was found to originate from that formation of a water layer on the surface of porous films could cause an increase of horizontal thermal conductivity and a reduction of vertical thermal conductivity. Moreover, laser-induced periodic ripple damages in air were found in the SiO2 layer from the micrographs. A model of deformation kinematics was used to illustrate the occurrence of the periodic ripple damage, showing that it could be attributed to a contraction of the HfO2 layer under irradiation by the 5-ns laser pulses in air.

Reduction of the 355-nm laser-induced damage initiators by removing the subsurface cracks in fused silica

NASA Astrophysics Data System (ADS)

Yang, Minghong; Qi, Hongji; Zhao, Yuanan; Yi, Kui

2012-01-01

The 355 nm laser-induced damage thresholds (LIDTs) of polished fused silica with and without the residual subsurface cracks were explored. HF based wet etching and magnetorheological finishing was used to remove the subsurface cracks. To isolate the effect of subsurface cracks, chemical leaching was used to eliminate the photoactive impurities in the polishing layer. Results show that the crack number density decreased from~103 to <1cm-2, and the LIDT was improved as high as 2.8-fold with both the subsurface cracks and the polishing layer being removed. Subsurface cracks play a significant role in laser damage at fluencies between 15~31 J/cm2 (355nm, 8ns). HF Etching of the cracks was shown to increase the damage performance as nearly high as that of the samples in which subsurface cracks are well controlled.

Improved LIDT values for dielectric dispersive compensating mirrors applying ternary composites

NASA Astrophysics Data System (ADS)

Willemsen, T.; Schlichting, S.; Gyamfi, M.; Jupé, M.; Ehlers, H.; Morgner, U.; Ristau, D.

2016-12-01

The present contribution is addressed to an improved method to fabricate dielectric dispersive compensating mirrors (CMs) with an increased laser induced damage threshold (LIDT) by the use of ternary composite layers. Taking advantage of a novel in-situ phase monitor system, it is possible to control the sensitive deposition process more precisely. The study is initiated by a design synthesis, to achieve optimum reflection and GDD values for a conventional high low stack (HL)n. Afterwards the field intensity is analyzed, and layers affected by highest electric field intensities are exchanged by ternary composites of TaxSiyOz. Both designs have similar target specifications whereby one design is using ternary composites and the other one is distinguished by a (HL)n. The first layers of the stack are switched applying in-situ optical broad band monitoring in conjunction with a forward re-optimization algorithm, which also manipulates the layers remaining for deposition at each switching event. To accomplish the demanded GDD-spectra, the last layers are controlled by a novel in-situ white light interferometer operating in the infrared spectral range. Finally the CMs are measured in a 10.000 on 1 procedure according to ISO 21254 applying pulses with a duration of 130 fs at a central wavelength of 775 nm to determine the laser induced damage threshold.

Summary Report: NMSBA CY 2016 - AEgis Technologies Group Inc. #12458.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bellum, John Curtis; Field, Ella Suzanne

2016-12-01

AEgis requires large area partial mirror optics consisting of partially reflecting optical coatings on large dimension substrates for high energy laser (HEL) applications. The partial mirrors should transmit nearly the same small fraction of HEL radiation incident from a wide range of angles of incidence (AOIs), and the laser-induced damage threshold (LIDT) of the coatings should be high enough for them to be able to withstand direct exposure to near infrared CW HEL radiation at multi-kilowatt/cm2 power levels. The transmitted fraction of incident HEL radiation should reach an array of detectors at power levels high enough for reliable detection butmore » low enough to not damage the detectors. The reflected fraction of incident HEL radiation should scatter into a divergent pattern so as to be eye safe at a distance of ~ 200 m from the mirror in the case of 100 kilowatt incident laser power. The detector array together with the partial mirror optic and possible additional optics that provide divergent scattering of reflected HEL radiation constitute what AEgis refers to as a target board. The target board use environment may vary from benign, indoor laboratory conditions to harsh, outdoor conditions in tests on the ground as well as in air. Under this NMSBA project, Sandia agreed to apply its extensive expertise and capability in the design and production of high LIDT coatings on large dimension optics for high power pulsed laser radiation to advise and assist AEgis in the design and development of high LIDT coatings for the partial mirror optic. Sandia and AEgis met several times to discuss the partial mirror and target board requirements, and Sandia was guided in its work by these discussions as well as by the partial mirror and target board requirement summaries of Tables 1 and 2, respectively, that were provided by AEgis.« less

The performance studies of DKDP crystals grown by a rapid horizontal growth method

NASA Astrophysics Data System (ADS)

Xie, Xiaoyi; Qi, Hongji; Wang, Bin; Wang, Hu; Chen, Duanyang; Shao, Jianda

2018-04-01

A deuterated potassium dihydrogen phosphate (DKDP) crystal with about 70% deuterium level was grown by a rapid horizontal growth method with independent design equipment, which includes a continuous filtration system. The cooling program during crystal growth was designed according to a self-developed software to catch the size of growing crystal in real time. The crystal structure, optical performance and laser induced damage threshold (LIDT) of this DKDP crystal were investigated in this paper. The deuterium concentration of the crystal was confirmed by the neutron diffraction technique, which was effective and available in determining a complete range of deuteration level. The dielectric property was measured to evaluate the perfection of the lattice. The transmittance and LIDT were carried out further to evaluate the optical and functional properties of this DKDP crystal grown in the rapid horizontal growth technique. All of the detailed characterization for DKDP figured out that the 70% deuterated KDP crystal grown in this way had relatively good qualities.

Microstructure-related properties at 193 nm of MgF2 and GdF3 films deposited by a resistive-heating boat.

PubMed

Liu, Ming-Chung; Lee, Cheng-Chung; Kaneko, Masaaki; Nakahira, Kazuhide; Takano, Yuuichi

2006-03-01

MgF2 and GdF3 materials, used for a single-layer coating at 193 nm, are deposited by a resistive-heating boat at specific substrate temperatures. Optical characteristics (transmittance, refractive index, extinction coefficient, and optical loss) and microstructures (morphology and crystalline structure) are investigated and discussed. Furthermore, MgF2 is used as a low-index material, and GdF3 is used as a high-index material for multilayer coatings. Reflectance, stress, and the laser-induced damage threshold (LIDT) are studied. It is shown that MgF2 and GdF3 thin films, deposited on the substrate at a temperature of 300 degrees C, obtain good quality thin films with high transmittance and little optical loss at 193 nm. For multilayer coatings, the stress mainly comes from MgF2, and the absorption comes from GdF3. Among those coatings, the sixteen-layer design, sub/(1.4L 0.6H)8/air, shows the largest LIDT.

Repair of a Mirror Coating on a Large Optic for High Laser Damage Applications using Ion Milling and Over-Coating Methods.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Field, Ella Suzanne; Bellum, John Curtis; Kletecka, Damon E.

When an optical coating is damaged, deposited incorrectly, or is otherwise unsuitable, the conventional method to restore the optic often entails repolishing the optic surface, which can incur a large cost and long lead time. We propose three alternative options to repolishing, including (i) burying the unsuitable coating under another optical coating, (ii) using ion milling to etch the unsuitable coating completely from the optic surface, and then recoating the optic, and (iii) using ion milling to etch through a number of unsuitable layers, leaving the rest of the coating intact, and then recoating the layers that were etched. Repairsmore » were made on test optics with dielectric mirror coatings according to the above three options. The mirror coatings to be repaired were quarter wave stacks of HfO 2 and SiO 2 layers for high reflection at 1054 nm at 45° incidence in P-polarization. One of the coating layers was purposely deposited incorrectly as Hf metal instead of HfO 2 to evaluate the ability of each repair method to restore the coating’s high laser-induced damage threshold (LIDT) of 64.0 J/cm 2. Finally, the repaired coating with the highest resistance to laser-induced damage was achieved using repair method (ii) with an LIDT of 49.0 – 61.0 J/cm 2.« less

Repair of a mirror coating on a large optic for high laser damage applications using ion milling and over-coating methods

NASA Astrophysics Data System (ADS)

Field, Ella S.; Bellum, John C.; Kletecka, Damon E.

2017-01-01

When an optical coating is damaged, deposited incorrectly, or is otherwise unsuitable, the conventional method to restore the optic often entails repolishing the optic surface, which can incur a large cost and long lead time. We propose three alternative options to repolishing, including (i) burying the unsuitable coating under another optical coating, (ii) using ion milling to etch the unsuitable coating completely from the optic surface and then recoating the optic, and (iii) using ion milling to etch through a number of unsuitable layers, leaving the rest of the coating intact, and then recoating the layers that were etched. Repairs were made on test optics with dielectric mirror coatings according to the above three options. The mirror coatings to be repaired were quarter wave stacks of HfO2 and SiO2 layers for high reflection at 1054 nm at 45 deg incidence in P-polarization. One of the coating layers was purposely deposited incorrectly as Hf metal instead of HfO2 to evaluate the ability of each repair method to restore the coating's high laser-induced damage threshold (LIDT) of 64.0 J/cm2. The repaired coating with the highest resistance to laser-induced damage was achieved using repair method (ii) with an LIDT of 49.0 to 61.0 J/cm2.

Repair of a mirror coating on a large optic for high laser damage applications using ion milling and over-coating methods

DOE PAGES

Field, Ella S.; Bellum, John C.; Kletecka, Damon E.

2016-07-08

Here, when an optical coating is damaged, deposited incorrectly, or is otherwise unsuitable, the conventional method to restore the optic often entails repolishing the optic surface, which can incur a large cost and long lead time. We propose three alternative options to repolishing, including (i) burying the unsuitable coating under another optical coating, (ii) using ion milling to etch the unsuitable coating completely from the optic surface and then recoating the optic, and (iii) using ion milling to etch through a number of unsuitable layers, leaving the rest of the coating intact, and then recoating the layers that were etched.more » Repairs were made on test optics with dielectric mirror coatings according to the above three options. The mirror coatings to be repaired were quarter wave stacks of HfO 2 and SiO 2 layers for high reflection at 1054 nm at 45 deg incidence in P-polarization. One of the coating layers was purposely deposited incorrectly as Hf metal instead of HfO2 to evaluate the ability of each repair method to restore the coating’s high laser-induced damage threshold (LIDT) of 64.0 J/cm 2. The repaired coating with the highest resistance to laser-induced damage was achieved using repair method (ii) with an LIDT of 49.0 to 61.0 J/cm 2.« less

Repair of a Mirror Coating on a Large Optic for High Laser Damage Applications using Ion Milling and Over-Coating Methods.

DOE PAGES

Field, Ella Suzanne; Bellum, John Curtis; Kletecka, Damon E.

2016-06-01

When an optical coating is damaged, deposited incorrectly, or is otherwise unsuitable, the conventional method to restore the optic often entails repolishing the optic surface, which can incur a large cost and long lead time. We propose three alternative options to repolishing, including (i) burying the unsuitable coating under another optical coating, (ii) using ion milling to etch the unsuitable coating completely from the optic surface, and then recoating the optic, and (iii) using ion milling to etch through a number of unsuitable layers, leaving the rest of the coating intact, and then recoating the layers that were etched. Repairsmore » were made on test optics with dielectric mirror coatings according to the above three options. The mirror coatings to be repaired were quarter wave stacks of HfO 2 and SiO 2 layers for high reflection at 1054 nm at 45° incidence in P-polarization. One of the coating layers was purposely deposited incorrectly as Hf metal instead of HfO 2 to evaluate the ability of each repair method to restore the coating’s high laser-induced damage threshold (LIDT) of 64.0 J/cm 2. Finally, the repaired coating with the highest resistance to laser-induced damage was achieved using repair method (ii) with an LIDT of 49.0 – 61.0 J/cm 2.« less

Repair of a mirror coating on a large optic for high laser damage applications using ion milling and over-coating methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Field, Ella S.; Bellum, John C.; Kletecka, Damon E.

Here, when an optical coating is damaged, deposited incorrectly, or is otherwise unsuitable, the conventional method to restore the optic often entails repolishing the optic surface, which can incur a large cost and long lead time. We propose three alternative options to repolishing, including (i) burying the unsuitable coating under another optical coating, (ii) using ion milling to etch the unsuitable coating completely from the optic surface and then recoating the optic, and (iii) using ion milling to etch through a number of unsuitable layers, leaving the rest of the coating intact, and then recoating the layers that were etched.more » Repairs were made on test optics with dielectric mirror coatings according to the above three options. The mirror coatings to be repaired were quarter wave stacks of HfO 2 and SiO 2 layers for high reflection at 1054 nm at 45 deg incidence in P-polarization. One of the coating layers was purposely deposited incorrectly as Hf metal instead of HfO2 to evaluate the ability of each repair method to restore the coating’s high laser-induced damage threshold (LIDT) of 64.0 J/cm 2. The repaired coating with the highest resistance to laser-induced damage was achieved using repair method (ii) with an LIDT of 49.0 to 61.0 J/cm 2.« less

The improvement of laser induced damage resistance of optical workpiece surface by hydrodynamic effect polishing

NASA Astrophysics Data System (ADS)

Peng, Wenqiang; Guan, Chaoliang; Li, Shengyi; Wang, Zhuo

2016-10-01

Surface and subsurface damage in optical element will greatly decrease the laser induced damage threshold (LIDT) in the intense laser optical system. Processing damage on the workpiece surface can be inevitably caused when the material is removed in brittle or plastic mode. As a non-contact polishing technology, hydrodynamic effect polishing (HEP) shows very good performance on generating an ultra-smooth surface without damage. The material is removed by chemisorption between nanoparticle and workpiece surface in the elastic mode in HEP. The subsurface damage and surface scratches can be effectively removed after the polishing process. Meanwhile ultra-smooth surface with atomic level surface roughness can be achieved. To investigate the improvement of LIDT of optical workpiece, polishing experiment was conducted on a magnetorheological finishing (MRF) silica glass sample. AFM measurement results show that all the MRF directional plastic marks have been removed clearly and the root-mean-square (rms) surface roughness has decreased from 0.673nm to 0.177nm after HEP process. Laser induced damage experiment was conducted with laser pulse of 1064nm wavelength and 10ns time width. Compared with the original state, the LEDT of the silica glass sample polished by HEP has increased from 29.78J/cm2 to 45.47J/cm2. It demonstrates that LIDT of optical element treated by HEP can be greatly improved for ultra low surface roughness and nearly defect-free surface/subsurface.

Laser-driven formation of a high-pressure phase in amorphous silica.

PubMed

Salleo, Alberto; Taylor, Seth T; Martin, Michael C; Panero, Wendy R; Jeanloz, Raymond; Sands, Timothy; Génin, François Y

2003-12-01

Because of its simple composition, vast availability in pure form and ease of processing, vitreous silica is often used as a model to study the physics of amorphous solids. Research in amorphous silica is also motivated by its ubiquity in modern technology, a prominent example being as bulk material in transmissive and diffractive optics for high-power laser applications such as inertial confinement fusion (ICF). In these applications, stability under high-fluence laser irradiation is a key requirement, with optical breakdown occurring when the fluence of the beam is higher than the laser-induced damage threshold (LIDT) of the material. The optical strength of polished fused silica transmissive optics is limited by their surface LIDT. Surface optical breakdown is accompanied by densification, formation of point defects, cratering, material ejection, melting and cracking. Through a combination of electron diffraction and infrared reflectance measurements we show here that synthetic vitreous silica transforms partially into a defective form of the high-pressure stishovite phase under high-intensity (GW cm(-2)) laser irradiation. This phase transformation offers one suitable mechanism by which laser-induced damage grows catastrophically once initiated, thereby dramatically shortening the service lifetime of optics used for high-power photonics.

Study of diamond film growth and properties

NASA Technical Reports Server (NTRS)

Albin, Sacharial

1990-01-01

The objective was to study diamond film growth and its properties in order to enhance the laser damage threshold of substrate materials. Calculations were performed to evaluate laser induced thermal stress parameter, R(sub T) of diamond. It is found that diamond has several orders of magnitude higher in value for R(sub T) compared to other materials. Thus, the laser induced damage threshold (LIDT) of diamond is much higher. Diamond films were grown using a microwave plasma enhanced chemical vapor deposition (MPECVD) system at various conditions of gas composition, pressure, temperature, and substrate materials. A 0.5 percent CH4 in H2 at 20 torr were ideal conditions for growing of high quality diamond films on substrates maintained at 900 C. The diamond films were polycrystalline which were characterized by scanning electron microscopy (SEM) and Raman scattering spectroscopy. The top surface of the growing film is always rough due to the facets of polycrystalline film while the back surface of the film replicates the substrate surface. An analytical model based on two dimensional periodic heat flow was developed to calculate the effective in-plane (face parallel) diffusivity of a two layer system. The effective diffusivity of diamond/silicon samples was measured using a laser pulse technique. The thermal conductivity of the films was measured to be 13.5 W/cm K, which is better than that of a type Ia natural diamond. Laser induced damage experiments were performed on bare Si substrates, diamond film coated Si, and diamond film windows. Significant improvements in the LIDT were obtained for diamond film coated Si compared to the bare Si.

Research on growth and defects of 5 in. YCOB single crystal

NASA Astrophysics Data System (ADS)

Tu, Xiaoniu; Wang, Sheng; Xiong, Kainan; Zheng, Yanqing; Shi, Erwei

2018-04-01

YCa4O(BO3)3 (YCOB) is an important nonlinear optical crystal, which is a key optical element in the SHG and OPCPA process to obtain high repetition rate, multi-petawatt laser pulse. In this work, we have grown 5 in. YCOB crystals by Czochralski method and investigated phase separation, defects, as well as their formation mechanism. Laser induced damage threshold (LiDT), rocking curve and transmission spectrum is characterized using the sample without defects. It is believed that, based on this work, large-sized YCOB crystal without defects will be obtained in the near future.

Nano-indentation and laser-induced damage testing in optical multilayer-dielectric gratings [Nanomechanics and laser-induced damage in optical multilayer dielectric gratings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mehrotra, K.; Corning Research & Development Corp., Coming, NY; Taylor, B. N.

Here, we demonstrate how a nanomechanical test can be used to generate metrics to complement laser-induced–damage testing (LIDT) measurements and show that differences in optical performance of the gratings (arising from changes in cleaning process and/or fabrication methods) can be related to their mechanical reliability. Data are presented on LIDT measurements in diffractive gratings of silica deposited on optical multilayers. The nano-indentation response of the diffraction gratings is measured in a new mode that allows for the extraction of a measurable metric characterizing the brittleness of the gratings, as well as their ductility. We show that lower LIDT’s are positivelymore » correlated with an increased grating brittleness, and therefore identify a nanomechanical approach to describe LIDT’s. We present extensive numerical simulations of nano-indentation tests and identify different deformation modes including stretching, shear concentration, and bending as precursors to mechanical failure in the nano-indentation test. The effects of geometrical inhomogeneities on enhanced stress generation in these gratings are specifically examined and addressed.« less

Nano-indentation and laser-induced damage testing in optical multilayer-dielectric gratings [Nanomechanics and laser-induced damage in optical multilayer dielectric gratings

DOE PAGES

Mehrotra, K.; Corning Research & Development Corp., Coming, NY; Taylor, B. N.; ...

2017-03-16

Here, we demonstrate how a nanomechanical test can be used to generate metrics to complement laser-induced–damage testing (LIDT) measurements and show that differences in optical performance of the gratings (arising from changes in cleaning process and/or fabrication methods) can be related to their mechanical reliability. Data are presented on LIDT measurements in diffractive gratings of silica deposited on optical multilayers. The nano-indentation response of the diffraction gratings is measured in a new mode that allows for the extraction of a measurable metric characterizing the brittleness of the gratings, as well as their ductility. We show that lower LIDT’s are positivelymore » correlated with an increased grating brittleness, and therefore identify a nanomechanical approach to describe LIDT’s. We present extensive numerical simulations of nano-indentation tests and identify different deformation modes including stretching, shear concentration, and bending as precursors to mechanical failure in the nano-indentation test. The effects of geometrical inhomogeneities on enhanced stress generation in these gratings are specifically examined and addressed.« less

Link between mechanical strength and laser damage threshold for antireflective coating made by sol-gel

NASA Astrophysics Data System (ADS)

Avice, J.; Piombini, H.; Boscher, C.; Belleville, P.; Vaudel, G.; Brotons, G.; Ruello, P.; Gusev, V.

2017-11-01

The MegaJoule Laser (LMJ) for inertial confinement fusion experiments is currently in operation at CEA-CESTA in France. All the lenses are coated by an antireflective (AR) layer to optimize the light power transmission. This AR layer is manufactured by sol-gel process, a soft chemical process, associated with a liquid phase coating technique to realize thin film of metal oxide. These optical components are hardened into ammoniac vapors in order to mechanically reinforce the AR coating and to make them more handling. This hardening induces a thickness reduction of the layer so an increase of the stiffness and sometimes a crazing of the layer. As these optical components undergo a high-power laser beam, so, it is important to verify if the AR properties (optical and mechanical) influence the value of the threshold laser damage. A series of coated samples have been manufactured having variable elastic moduli to discuss this point. In that purpose, a homemade Laser Induced Damage Threshold (LIDT) setup has been developed to test the layers under laser flux. We describe the used methods and different results are given. Preliminary results obtained on several coated samples with variable elastic moduli are presented. We show that whatever are the elastic stiffness of the AR coating, an overall decrease of the threshold appears with no noticeable effect of the mechanical properties of the AR coatings. Some possible explanations are given.

Sodern development of a high LIDT laser beam expander for ATLID

NASA Astrophysics Data System (ADS)

Battarel, Denis C.; Barnasson, Elodie

2017-11-01

Sodern has been contracted for the development of the laser beam expander used on the lidar of the ATLID instrument developed by Airbus Defence & Space France and Germany (Formerly ASTRIUM) embarked on the EathCARE satellite, element of the ESA (European Space Agency) Living Planet Programme. The ATLID emission beam expander (E-BEX) has two functions: one is to reduce the divergence of the laser in order to achieve a high spatial resolution and the other is to enlarge the laser beam to reduce the power density and thus reduce Laser Induced Contamination (LIC) and Laser Induced Damage Threshold (LIDT) effects on the outer surface exposed to vacuum. This paper exposes the design drivers of the beam expander which are: having optical components withstanding very high laser fluence at a wavelength of 355nm and exhibiting a very low depolarization ratio., hermetically sealing the cavity with metallic gaskets in order to keep the pressure constant so that beam collimation is not affected, choosing housing material compatible with both hermiticity requirements and thermal control. To obtain a high spatial resolution on Earth, ATLID requires a means for controlling beam collimation. This is ensured by an active thermal control on the beam expander in order to change its Wavefront Error (WFE) by a few tens of nanometers.

Magnetorheological elastic super-smooth finishing for high-efficiency manufacturing of ultraviolet laser resistant optics

NASA Astrophysics Data System (ADS)

Shi, Feng; Shu, Yong; Dai, Yifan; Peng, Xiaoqiang; Li, Shengyi

2013-07-01

Based on the elastic-plastic deformation theory, status between abrasives and workpiece in magnetorheological finishing (MRF) process and the feasibility of elastic polishing are analyzed. The relationship among material removal mechanism and particle force, removal efficiency, and surface topography are revealed through a set of experiments. The chemical dominant elastic super-smooth polishing can be fulfilled by changing the components of magnetorheological (MR) fluid and optimizing polishing parameters. The MR elastic super-smooth finishing technology can be applied in polishing high-power laser-irradiated components with high efficiency, high accuracy, low damage, and high laser-induced damage threshold (LIDT). A 430×430×10 mm fused silica (FS) optic window is polished and surface error is improved from 538.241 nm [peak to valley (PV)], 96.376 nm (rms) to 76.372 nm (PV), 8.295 nm (rms) after 51.6 h rough polishing, 42.6 h fine polishing, and 54.6 h super-smooth polishing. A 50×50×10 mm sample is polished with exactly the same parameters. The roughness is improved from 1.793 nm [roughness average (Ra)] to 0.167 nm (Ra) and LIDT is improved from 9.77 to 19.2 J/cm2 after MRF elastic polishing.

Characterization of laser induced damage of HR coatings with picosecond pulses

NASA Astrophysics Data System (ADS)

Li, Cheng; Zhao, Yuan'an; Cui, Yun; Wang, Yueliang; Peng, Xiaocong; Shan, Chong; Zhu, Meiping; Wang, Jianguo; Shao, Jianda

2017-11-01

The effect of protective layer on the picosecond laser-induced damage behaviors of HfO2/SiO2 high-reflective (HR) coatings are explored. Two kinds of 1064nm HR coatings with and without protective layer are deposited by electron beam evaporation. Laser-induced damage tests are conducted with 1064nm, 30ps S-polarized and P-polarized pulses with different angle of incidence (AOI) to make the electric fields intensity in the HR coatings discrepantly. Damage morphology and cross section of damage sites were characterized by scanning electron microscope (SEM) and focused ion beam (FIB), respectively. It is found that SiO2 protective layer have a certain degree of improvement on laser induced damage threshold (LIDT) for every AOIs. The onset damage initiated very near to the Max peak of e-field, after which forms ripple-like pits. The damage morphology presents as layer delamination at high fluence. The Laser damage resistance is correspond with the maximum E-intensity in the coating stacks.

Post-processing of fused silica and its effects on damage resistance to nanosecond pulsed UV lasers.

PubMed

Ye, Hui; Li, Yaguo; Zhang, Qinghua; Wang, Wei; Yuan, Zhigang; Wang, Jian; Xu, Qiao

2016-04-10

HF-based (hydrofluoric acid) chemical etching has been a widely accepted technique to improve the laser damage performance of fused silica optics and ensure high-power UV laser systems at designed fluence. Etching processes such as acid concentration, composition, material removal amount, and etching state (etching with additional acoustic power or not) may have a great impact on the laser-induced damage threshold (LIDT) of treated sample surfaces. In order to find out the effects of these factors, we utilized the Taguchi method to determine the etching conditions that are helpful in raising the LIDT. Our results show that the most influential factors are concentration of etchants and the material etched away from the viewpoint of damage performance of fused silica optics. In addition, the additional acoustic power (∼0.6  W·cm^-2) may not benefit the etching rate and damage performance of fused silica. Moreover, the post-cleaning procedure of etched samples is also important in damage performances of fused silica optics. Different post-cleaning procedures were, thus, experiments on samples treated under the same etching conditions. It is found that the "spraying + rinsing + spraying" cleaning process is favorable to the removal of etching-induced deposits. Residuals on the etched surface are harmful to surface roughness and optical transmission as well as laser damage performance.

LIDT-DD: A New Self-Consistent Debris Disc Model Including Radiation Pressure and Coupling Dynamical and Collisional Evolution

NASA Astrophysics Data System (ADS)

Kral, Q.; Thebault, P.; Charnoz, S.

2014-01-01

The first attempt at developing a fully self-consistent code coupling dynamics and collisions to study debris discs (Kral et al. 2013) is presented. So far, these two crucial mechanisms were studied separately, with N-body and statistical collisional codes respectively, because of stringent computational constraints. We present a new model named LIDT-DD which is able to follow over long timescales the coupled evolution of dynamics (including radiation forces) and collisions in a self-consistent way.

Optical characterisation of hydroxide catalysed bonds applied to phosphate glass

NASA Astrophysics Data System (ADS)

Lacaille, Grégoire; Mangano, Valentina; van Veggel, Anna-Maria A.; Killow, Christian J.; MacKay, Peter E.; Rowan, Sheila; Hough, James

2017-10-01

We apply the Hydroxide Catalysis Bonding (HCB) technique to phosphate glass and measure the reflectivity and Light Induced Damage Threshold (LITD) of the newly formed interface. HCB is a room temperature, high performing process which was designed for astronomical research glass assemblies and played a key role in the detection of gravitational waves, a breakthrough in contemporary science. The bonds have numerous assets including mechanical strength, stability, no outgassing and resistance to contamination which are of high interest in the precision optics industry. However only little research has been done on their optical properties and mostly on silica based materials. In this paper, we use HCB to bond phosphate glass at room temperature with the goal of designing composite components for solid state laser gain media. We change the solution parameters to identify how they influence the final properties of the bonds: the LIDT at 1535 nm in long pulse regime and the reflectivity at 532 nm are investigated. The measurement of the incidence dependent reflectance allows estimating the thickness and refractive index of the bond in a non destructive process. The best performing set of parameters yields a LIDT of 1.6 GW/cm2 (16 J/cm2) and a reflectivity below 0.03 % which makes it suitable for use in high power lasers. The bond thickness is derived both from Scanning Electron Microscopy and the reflectivity measurements and is in the range of 50-150 nm depending on the parameters. Finally, the bonds survive cutting and polishing which is promising for manufacturing purpose.

Femtosecond optical parametric amplification in BBO and KTA driven by a Ti:sapphire laser for LIDT testing and diagnostic development

NASA Astrophysics Data System (ADS)

Meadows, Alexander R.; Cupal, Josef; Hříbek, Petr; Durák, Michal; Kramer, Daniel; Rus, Bedřich

2017-05-01

We present the design of a collinear femtosecond optical parametric amplification (OPA) system producing a tunable output at wavelengths between 1030 nm and 1080 nm from a Ti:Sapphire pump laser at a wavelength of 795 nm. Generation of a supercontinuum seed pulse is followed by one stage of amplification in Beta Barium Borate (BBO) and two stages of amplification in Potassium Titanyle Arsenate (KTA), resulting in a 225 μJ output pulse with a duration of 90 fs. The output of the system has been measured by self-referenced spectral interferometry to yield the complete spectrum and spectral phase of the pulse. When compared to KTP, the greater transparency of KTA in the spectral range from 3 - 4 μm allows for reduced idler absorption and enhanced gain from the OPA process when it is pumped by the fundamental frequency of a Ti:sapphire laser. In turn, the use of the Ti:sapphire fundamental at 795 nm as a pump improves the efficiency with which light can be converted to wavelengths between 1030 nm and 1080 nm and subsequently used to test components for Nd-based laser systems. This OPA system is operated at 1 kHz for diagnostic development and laser-induced damage threshold testing of optical components for the ELI-Beamlines project.

LIDT-DD: A new self-consistent debris disc model that includes radiation pressure and couples dynamical and collisional evolution

NASA Astrophysics Data System (ADS)

Kral, Q.; Thébault, P.; Charnoz, S.

2013-10-01

Context. In most current debris disc models, the dynamical and the collisional evolutions are studied separately with N-body and statistical codes, respectively, because of stringent computational constraints. In particular, incorporating collisional effects (especially destructive collisions) into an N-body scheme has proven a very arduous task because of the exponential increase of particles it would imply. Aims: We present here LIDT-DD, the first code able to mix both approaches in a fully self-consistent way. Our aim is for it to be generic enough to be applied to any astrophysical case where we expect dynamics and collisions to be deeply interlocked with one another: planets in discs, violent massive breakups, destabilized planetesimal belts, bright exozodiacal discs, etc. Methods: The code takes its basic architecture from the LIDT3D algorithm for protoplanetary discs, but has been strongly modified and updated to handle the very constraining specificities of debris disc physics: high-velocity fragmenting collisions, radiation-pressure affected orbits, absence of gas that never relaxes initial conditions, etc. It has a 3D Lagrangian-Eulerian structure, where grains of a given size at a given location in a disc are grouped into super-particles or tracers whose orbits are evolved with an N-body code and whose mutual collisions are individually tracked and treated using a particle-in-a-box prescription designed to handle fragmenting impacts. To cope with the wide range of possible dynamics for same-sized particles at any given location in the disc, and in order not to lose important dynamical information, tracers are sorted and regrouped into dynamical families depending on their orbits. A complex reassignment routine that searches for redundant tracers in each family and reassignes them where they are needed, prevents the number of tracers from diverging. Results: The LIDT-DD code has been successfully tested on simplified cases for which robust results have been obtained in past studies: we retrieve the classical features of particle size distributions in unperturbed discs and the outer radial density profiles in ~r-1.5 outside narrow collisionally active rings as well as the depletion of small grains in dynamically cold discs. The potential of the new code is illustrated with the test case of the violent breakup of a massive planetesimal within a debris disc. Preliminary results show that we are able for the first time to quantify the timescale over which the signature of such massive break-ups can be detected. In addition to studying such violent transient events, the main potential future applications of the code are planet and disc interactions, and more generally, any configurations where dynamics and collisions are expected to be intricately connected.

Prize of the best thesis 2015: Study of debris discs through state-of-the-art numerical modelling

NASA Astrophysics Data System (ADS)

Kral, Q.; Thébault, P.

2015-12-01

This proceeding summarises the thesis entitled ``Study of debris discs with a new generation numerical model'' by Quentin Kral, for which he obtained the prize of the best thesis in 2015. The thesis brought major contributions to the field of debris disc modelling. The main achievement is to have created, almost ex-nihilo, the first truly self-consistent numerical model able to simultaneously follow the coupled collisional and dynamical evolutions of debris discs. Such a code has been thought as being the ``Holy Grail'' of disc modellers for the past decade, and while several codes with partial dynamics/collisions coupling have been presented, the code developed in this thesis, called ``LIDT-DD'' is the first to achieve a full coupling. The LIDT-DD model, which is the first of a new-generation of fully self-consistent debris disc models is able to handle both planetesimals and dust and create new fragments after each collision. The main idea of LIDT-DD development was to merge into one code two approaches that were so far used separately in disc modelling, that is, an N-body algorithm to investigate the dynamics, and a statistical scheme to explore the collisional evolution. This complex scheme is not straightforward to develop as there are major difficulties to overcome: 1) collisions in debris discs are highly destructive and produce clouds of small fragments after each single impact, 2) the smallest (and most numerous) of these fragments have a strongly size-dependent dynamics because of the radiation pressure, and 3) the dust usually observed in discs is precisely these smallest grains. These extreme constraints had so far prevented all previous attempts at developing self-consistent disc models to succeed. The thesis contains many examples of the use of LIDT-DD that are not yet published but the case of the collision between two asteroid-like bodies is studied in detail. In particular, LIDT-DD is able to predict the different stages that should be observed after such massive collisions that happen mainly in the latest stages of planetary formation. Some giant impact signatures and observability predictions for VLT/SPHERE and JWST/MIRI are given. JWST should be able to detect many of such impacts and would enable to see on-going planetary formation in dozens of planetary systems.

Enhanced thermomechanical stability on laser-induced damage by functionally graded layers in quasi-rugate filters

NASA Astrophysics Data System (ADS)

Pu, Yunti; Ma, Ping; Lv, Liang; Zhang, Mingxiao; Lu, Zhongwen; Qiao, Zhao; Qiu, Fuming

2018-05-01

Ta2O5-SiO2 quasi-rugate filters with a reasonable optimization of rugate notch filter design were prepared by ion-beam sputtering. The optical properties and laser-induced damage threshold are studied. Compared with the spectrum of HL-stacks, the spectrum of quasi-rugate filters have weaker second harmonic peaks and narrower stopbands. According to the effect of functionally graded layers (FGLs), 1-on-1 and S-on-1 Laser induced damage threshold (LIDT) of quasi-rugate filters are about 22% and 50% higher than those of HL stacks, respectively. Through the analysis of the damage morphologies, laser-induced damage of films under nanosecond multi-pulse are dominated by a combination of thermal shock stress and thermomechanical instability due to nodules. Compared with catastrophic damages, the damage sits of quasi-rugate filters are developed in a moderate way. The damage growth behavior of defect-induced damage sites have been effectively restrained by the structure of FGLs. Generally, FGLs are used to reduce thermal stress by the similar thermal-expansion coefficients of neighboring layers and solve the problems such as instability and cracking raised by the interface discontinuity of nodular boundaries, respectively.

Effects of pulse durations and environments on femtosecond laser ablation of stainless steel

NASA Astrophysics Data System (ADS)

Xu, Shizhen; Ding, Renjie; Yao, Caizhen; Liu, Hao; Wan, Yi; Wang, Jingxuan; Ye, Yayun; Yuan, Xiaodong

2018-04-01

The influence of pulse durations (35fs and 260 fs) and environments (air and vacuum) on the laser-induced damage thresholds (LIDTs) and ablation rates of 304 stainless steel were studied. Two distinct ablation regimes were obtained from the ablation rate curves. At low fluence regime, the ablation rates were similar in spite of the differences of pulse durations and experiment environments. At high fluence regime, the ablation rates of 35 fs pulse duration in vacuum were obviously higher than others. The ablation craters showed smooth edges, moth-eye such as structures, and laser-induced periodic surface structures (LIPSSs). At a fixed fluence, the periods of LIPSSs decreased monotonously in their mean spatial period between 700 nm (5 pulses) and 540 nm (200 pulses) with the increase of pulse numbers in air with 35 fs pulse duration. The formation mechanisms of moth-eye like structures and LIPSSs were also discussed.

Finite element analysis and clinical complications in mandibular implant-overdentures opposing maxillary dentures.

PubMed

Khuder, Tameem; Yunus, Norsiah; Sulaiman, Eshamsul; Dabbagh, Ali

2017-11-01

Denture fracture is a common clinical complication caused by improper material selection, design, or fabrication technique. This study aimed to investigate the effect of two attachment systems on fracture risk of the implant-overdentures (IOD) via finite element analysis (FEA), using the force distributions obtained from patients' occlusal analyses and to compare the obtained results with the clinical complications associated with these attachments. A three-dimensional jaw model comprised of the edentulous bones was constructed. Three types of mandibular prostheses including complete denture (CD) (model LCD), IOD with Locator attachment (model LID-L), and IOD with telescopic attachment (model LID-T), as well as a maxillary CD (model UCD) were assembled. The vertical occlusal forces at anterior and posterior quadrants were obtained from the patients wearing mandibular CDs or IODs. The FEA results were further compared with the mechanical failures of different prostheses observed at patient recalls. In overall, the fracture risk of mandibular prostheses was lower than the maxillary compartments. The UCD opposing LCD underwent higher strains than that opposing LID-L and LID-T, which was mostly concentrated at the anterior mid-palatal polished surface. On the other hand, LID-L showed the lowest strain, followed by LID-T, and LCD. The obtained results were consistent with the clinical complications observed in the patient recalls. Copyright © 2017 Elsevier Ltd. All rights reserved.

LIDT-DD: A new hybrid model to understand debris discs observations - The case of massive collisions.

NASA Astrophysics Data System (ADS)

Kral, Q.; Thébault, P.; Augereau, J.-C.; Boccaletti, A.; Charnoz, S.

2014-12-01

LIDT-DD is a new hybrid model coupling the collisional and dynamical evolution in debris discs in a self-consistent way. It has been developed in a way that allows to treat a large number of different astrophysical cases where collisions and dynamics have an important role. This interplay was often totally neglected in previous studies whereas, even for the simplest configurations, the real physics of debris discs imposes strong constraints and interactions between dynamics and collisions. After presenting the LIDT-DD model, we will describe the evolution of violent stochastic collisional events with this model. These massive impacts have been invoked as a possible explanation for some debris discs displaying pronounced azimuthal asymmetries or having a luminosity excess exceeding that expected for systems at collisional steady-state. So far, no thorough modelling of the consequences of such stochastic events has been carried out, mainly because of the extreme numerical challenge of coupling the dynamical and collisional evolution of the released dust. We follow the collisional and dynamical evolution of dust released after the breakup of a Ceres-sized body at 6 AU from its central star. We investigate the duration, magnitude and spatial structure of the signature left by such a violent event, as well as its observational detectability. We use the GRaTer package to estimate the system's luminosity at different wavelengths and derive synthetic images for the SPHERE/VLT and MIRI/JWST instruments.

Massive collisions in debris disks: possible application to the beta Pic disc

NASA Astrophysics Data System (ADS)

Kral, Q.; Thébault, P.; Augereau, J.-C.; Boccaletti, A.; Charnoz, S.

2014-09-01

The new LIDT-DD code has been used to study massive collisions in debris discs. This new hybrid model is a fully self-consistent code coupling dynamics and collisions to study debris discs (Kral et al. 2013). It models the full complexity of debris discs' physics such as high velocity collisions, radiation-pressure affected orbits, wide range of grains' dynamical behaviour, etc. LIDT-DD can be used on many possible applications. Our first test case concerns the violent breakup of a massive planetesimal such as the ones happening during the late stages of planetary formation or with the biggest bodies in debris belts. We investigate the duration, magnitude and spatial structure of the signature left by such a violent event, as well as its observational detectability. We find that the breakup of a Ceres-sized body creates an asymmetric dust disc that is homogenized, by the coupled action of collisions and dynamics. The luminosity excess in the breakup's aftermath should be detectable by mid-IR photometry, from a 30 pc distance. As for the asymmetric structures, we derive synthetic images for the SPHERE/VLT and MIRI/JWST instruments, showing that they should be clearly visible and resolved from a 10 pc distance. We explain the observational signature of such impacts and give scaling laws to extrapolate our results to different configurations. These first results confirm that our code can be used to study the massive collision scenario to explain some asymmetries in the Beta-Pic disc.

DOE Office of Scientific and Technical Information (OSTI.GOV)

McNally, J.J.

The effects on the properties of Ta/sub 2/O/sub 5/, Al/sub 2/O/sub 3/, SiO/sub 2/ and HfO/sub 2/ single- and multi-layer optical coatings deposited using ion-assisted deposition (IAD) were investigated. IAD is a novel deposition technique which utilizes a separate ion source to direct a beam of ions at the growing film. A Kaufman ion source was used to provide a monoenergetic, neutralized beam of oxygen ions independent of the material evaporation process. The optical and physical properties, as well as laser induced damage threshold (LIDT) values, were studied for coatings bombarded with 200, 300, 500 and 1000 eV oxygen ionsmore » at values of current density from 0 to 200 microAmp/sq cm. IAD was successfully applied to deposit coatings at low temperature on heavy metal fluoride (HMF) glass substrates. The coatings deposited using IAD were hard and dense. The IAD coatings improved the durability and abrasion resistance of the HMF glass substrates. The results of this investigation show that IAD can be used to improve the optical and physical properties of optical coatings.« less

Laser-induced damage threshold of camera sensors and micro-opto-electro-mechanical systems

NASA Astrophysics Data System (ADS)

Schwarz, Bastian; Ritt, Gunnar; Körber, Michael; Eberle, Bernd

2016-10-01

The continuous development of laser systems towards more compact and efficient devices constitutes an increasing threat to electro-optical imaging sensors such as complementary metal-oxide-semiconductors (CMOS) and charge-coupled devices (CCD). These types of electronic sensors are used in day-to-day life but also in military or civil security applications. In camera systems dedicated to specific tasks, also micro-opto-electro-mechanical systems (MOEMS) like a digital micromirror device (DMD) are part of the optical setup. In such systems, the DMD can be located at an intermediate focal plane of the optics and it is also susceptible to laser damage. The goal of our work is to enhance the knowledge of damaging effects on such devices exposed to laser light. The experimental setup for the investigation of laser-induced damage is described in detail. As laser sources both pulsed lasers and continuous-wave (CW) lasers are used. The laser-induced damage threshold (LIDT) is determined by the single-shot method by increasing the pulse energy from pulse to pulse or in the case of CW-lasers, by increasing the laser power. Furthermore, we investigate the morphology of laser-induced damage patterns and the dependence of the number of destructed device elements on the laser pulse energy or laser power. In addition to the destruction of single pixels, we observe aftereffects like persisting dead columns or rows of pixels in the sensor image.

The improvement of surface roughness for OAP aluminum mirrors: from terahertz to ultraviolet

NASA Astrophysics Data System (ADS)

Peng, Jilong; Yu, Qian; Shao, Yajun; Wang, Dong; Yi, Zhong; Wang, Shanshan

2018-01-01

Aluminum reflector, especially OAP (Off-Axis Parabolic) reflector, has been widely used in terahertz and infrared systems for its low cost, lightweight, good machinability, small size, simple structure, and having the same thermal expansion and contraction with the system structure which makes it have a wide temperature adaptability. Thorlabs, Daheng and other large optical components companies even have Aluminum OAP sold on shelf. Most of the precision Aluminum OAP is fabricated by SPDT (single point diamond turing). Affected by intermittent shock, the roughness of aluminum OAP mirrors through conventional single-point diamond lathes is around 7 nm which limits the scope of application for aluminum mirrors, like in the high power density terahertz/infrared systems and visible/UV optical systems. In this paper, a continuous process frock is proposed, which effectively reduces the influence of turning impact on the mirror roughness. Using this process, an off-axis parabolic aluminum reflector with an effective diameter of 50 mm, off-axis angle of 90 degree is fabricated, and the performances are validated. Measurement by VEECO NT1100 optical profiler with 20× objects, the surface roughness achieves 2.3 nm, and the surface figure error is within λ/7 RMS (λ= 632.8 nm) tested by FISB Aμ Phase laser interferometer with the help of a standard flat mirror. All these technical specifications are close to the traditional glass-based reflectors, and make it possible for using Aluminum reflectors in the higher LIDT (laser induced damage threshold) systems and even for the micro sensor of ionospheric for vacuum ultraviolet micro nano satellites.

Properties of AlF3 and LaF3 films at 193nm

NASA Astrophysics Data System (ADS)

Xue, Chunrong; Shao, Jianda

2010-10-01

In order to develop low loss, high-performance 193nm Fluoride HR mirrors and anti-reflection coatings, LaF3 and AlF3 materials, used for a single-layer coating, were deposited by a molybdenum boat evaporation process. Various microstructures that formed under different substrate temperatures and with deposition rates were investigated. The relation between these microstructures (including cross section morphology, surface roughness and crystalline structure), the optical properties (including refractive index and optical loss) and mechanical properties (stress) were investigated. Furthermore, AlF3 used as a low-index material and LaF3 used as a high-index material were designed and deposited for multilayer coatings. Transmittance, reflectance, stress, and the laser-induced damage threshold (LIDT) were studied. It is shown that AlF3 and LaF3 thin films, deposited on the substrate at a temperature of 300 °C, obtained good quality thin films with high transmittance and little optical loss at 193 nm. For multilayer coatings, the absorption mainly comes from LaF3. Based on these studies, The thickness of 193nm films was controled by a 1/3 baffle with pre-coating technology. the LaF3/AlF3 AR coantings and HR mirrors at 193nm were designed and deposited. Under the present experimental conditions, the reflectance of LaF3/AlF3 HR mirror is up to 96%, and its transmittance is 1.5%. the LaF3/AlF3 AR coanting's residual reflectance is less than 0.14%, and single-sided transmittance is 93.85%. To get a high-performance 193nm AR coating, super-polished substrate is the best choice.

A Pilot Study of the Snap & Sniff Threshold Test.

PubMed

Jiang, Rong-San; Liang, Kai-Li

2018-05-01

The Snap & Sniff ® Threshold Test (S&S) has been recently developed to determine the olfactory threshold. The aim of this study was to further evaluate the validity and test-retest reliability of the S&S. The olfactory thresholds of 120 participants were determined using both the Smell Threshold Test (STT) and the S&S. The participants included 30 normosmic volunteers and 90 patients (60 hyposmic, 30 anosmic). The normosmic participants were retested using the STT and S&S at an intertest interval of at least 1 day. The mean olfactory threshold determined with the S&S was -6.76 for the normosmic participants, -3.79 for the hyposmic patients, and -2 for the anosmic patients. The olfactory thresholds were significantly different across the 3 groups ( P < .001). Snap & Sniff-based and STT-based olfactory thresholds were correlated weakly in the normosmic group (correlation coefficient = 0.162, P = .391) but more strongly correlated in the patient groups (hyposmic: correlation coefficient = 0.376, P = .003; anosmic: correlation coefficient = 1.0). The test-retest correlation for the S&S-based olfactory thresholds was 0.384 ( P = .036). Based on validity and test-retest reliability, we concluded that the S&S is a proper test for olfactory thresholds.

Threshold Assessment of Gear Diagnostic Tools on Flight and Test Rig Data

NASA Technical Reports Server (NTRS)

Dempsey, Paula J.; Mosher, Marianne; Huff, Edward M.

2003-01-01

A method for defining thresholds for vibration-based algorithms that provides the minimum number of false alarms while maintaining sensitivity to gear damage was developed. This analysis focused on two vibration based gear damage detection algorithms, FM4 and MSA. This method was developed using vibration data collected during surface fatigue tests performed in a spur gearbox rig. The thresholds were defined based on damage progression during tests with damage. The thresholds false alarm rates were then evaluated on spur gear tests without damage. Next, the same thresholds were applied to flight data from an OH-58 helicopter transmission. Results showed that thresholds defined in test rigs can be used to define thresholds in flight to correctly classify the transmission operation as normal.

Network meta-analysis of diagnostic test accuracy studies identifies and ranks the optimal diagnostic tests and thresholds for health care policy and decision-making.

PubMed

Owen, Rhiannon K; Cooper, Nicola J; Quinn, Terence J; Lees, Rosalind; Sutton, Alex J

2018-07-01

Network meta-analyses (NMA) have extensively been used to compare the effectiveness of multiple interventions for health care policy and decision-making. However, methods for evaluating the performance of multiple diagnostic tests are less established. In a decision-making context, we are often interested in comparing and ranking the performance of multiple diagnostic tests, at varying levels of test thresholds, in one simultaneous analysis. Motivated by an example of cognitive impairment diagnosis following stroke, we synthesized data from 13 studies assessing the efficiency of two diagnostic tests: Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA), at two test thresholds: MMSE <25/30 and <27/30, and MoCA <22/30 and <26/30. Using Markov chain Monte Carlo (MCMC) methods, we fitted a bivariate network meta-analysis model incorporating constraints on increasing test threshold, and accounting for the correlations between multiple test accuracy measures from the same study. We developed and successfully fitted a model comparing multiple tests/threshold combinations while imposing threshold constraints. Using this model, we found that MoCA at threshold <26/30 appeared to have the best true positive rate, whereas MMSE at threshold <25/30 appeared to have the best true negative rate. The combined analysis of multiple tests at multiple thresholds allowed for more rigorous comparisons between competing diagnostics tests for decision making. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Rational use of Xpert testing in patients with presumptive TB: clinicians should be encouraged to use the test-treat threshold.

PubMed

Decroo, Tom; Henríquez-Trujillo, Aquiles R; De Weggheleire, Anja; Lynen, Lutgarde

2017-10-11

A recently published Ugandan study on tuberculosis (TB) diagnosis in HIV-positive patients with presumptive smear-negative TB, which showed that out of 90 patients who started TB treatment, 20% (18/90) had a positive Xpert MTB/RIF (Xpert) test, 24% (22/90) had a negative Xpert test, and 56% (50/90) were started without Xpert testing. Although Xpert testing was available, clinicians did not use it systematically. Here we aim to show more objectively the process of clinical decision-making. First, we estimated that pre-test probability of TB, or the prevalence of TB in smear-negative HIV infected patients with signs of presumptive TB in Uganda, was 17%. Second, we argue that the treatment threshold, the probability of disease at which the utility of treating and not treating is the same, and above which treatment should be started, should be determined. In Uganda, the treatment threshold was not yet formally established. In Rwanda, the calculated treatment threshold was 12%. Hence, one could argue that the threshold was reached without even considering additional tests. Still, Xpert testing can be useful when the probability of disease is above the treatment threshold, but only when a negative Xpert result can lower the probability of disease enough to cross the treatment threshold. This occurs when the pre-test probability is lower than the test-treat threshold, the probability of disease at which the utility of testing and the utility of treating without testing is the same. We estimated that the test-treatment threshold was 28%. Finally, to show the effect of the presence or absence of arguments on the probability of TB, we use confirming and excluding power, and a log10 odds scale to combine arguments. If the pre-test probability is above the test-treat threshold, empirical treatment is justified, because even a negative Xpert will not lower the post-test probability below the treatment threshold. However, Xpert testing for the diagnosis of TB should be performed in patients for whom the probability of TB was lower than the test-treat threshold. Especially in resource constrained settings clinicians should be encouraged to take clinical decisions and use scarce resources rationally.

Properties of perimetric threshold estimates from Full Threshold, SITA Standard, and SITA Fast strategies.

PubMed

Artes, Paul H; Iwase, Aiko; Ohno, Yuko; Kitazawa, Yoshiaki; Chauhan, Balwantray C

2002-08-01

To investigate the distributions of threshold estimates with the Swedish Interactive Threshold Algorithms (SITA) Standard, SITA Fast, and the Full Threshold algorithm (Humphrey Field Analyzer; Zeiss-Humphrey Instruments, Dublin, CA) and to compare the pointwise test-retest variability of these strategies. One eye of 49 patients (mean age, 61.6 years; range, 22-81) with glaucoma (Mean Deviation mean, -7.13 dB; range, +1.8 to -23.9 dB) was examined four times with each of the three strategies. The mean and median SITA Standard and SITA Fast threshold estimates were compared with a "best available" estimate of sensitivity (mean results of three Full Threshold tests). Pointwise 90% retest limits (5th and 95th percentiles of retest thresholds) were derived to assess the reproducibility of individual threshold estimates. The differences between the threshold estimates of the SITA and Full Threshold strategies were largest ( approximately 3 dB) for midrange sensitivities ( approximately 15 dB). The threshold distributions of SITA were considerably different from those of the Full Threshold strategy. The differences remained of similar magnitude when the analysis was repeated on a subset of 20 locations that are examined early during the course of a Full Threshold examination. With sensitivities above 25 dB, both SITA strategies exhibited lower test-retest variability than the Full Threshold strategy. Below 25 dB, the retest intervals of SITA Standard were slightly smaller than those of the Full Threshold strategy, whereas those of SITA Fast were larger. SITA Standard may be superior to the Full Threshold strategy for monitoring patients with visual field loss. The greater test-retest variability of SITA Fast in areas of low sensitivity is likely to offset the benefit of even shorter test durations with this strategy. The sensitivity differences between the SITA and Full Threshold strategies may relate to factors other than reduced fatigue. They are, however, small in comparison to the test-retest variability.

New developments in supra-threshold perimetry.

PubMed

Henson, David B; Artes, Paul H

2002-09-01

To describe a series of recent enhancements to supra-threshold perimetry. Computer simulations were used to develop an improved algorithm (HEART) for the setting of the supra-threshold test intensity at the beginning of a field test, and to evaluate the relationship between various pass/fail criteria and the test's performance (sensitivity and specificity) and how they compare with modern threshold perimetry. Data were collected in optometric practices to evaluate HEART and to assess how the patient's response times can be analysed to detect false positive response errors in visual field test results. The HEART algorithm shows improved performance (reduced between-eye differences) over current algorithms. A pass/fail criterion of '3 stimuli seen of 3-5 presentations' at each test location reduces test/retest variability and combines high sensitivity and specificity. A large percentage of false positive responses can be detected by comparing their latencies to the average response time of a patient. Optimised supra-threshold visual field tests can perform as well as modern threshold techniques. Such tests may be easier to perform for novice patients, compared with the more demanding threshold tests.

Automated Smartphone Threshold Audiometry: Validity and Time Efficiency.

PubMed

van Tonder, Jessica; Swanepoel, De Wet; Mahomed-Asmail, Faheema; Myburgh, Hermanus; Eikelboom, Robert H

2017-03-01

Smartphone-based threshold audiometry with automated testing has the potential to provide affordable access to audiometry in underserved contexts. To validate the threshold version (hearTest) of the validated hearScreen™ smartphone-based application using inexpensive smartphones (Android operating system) and calibrated supra-aural headphones. A repeated measures within-participant study design was employed to compare air-conduction thresholds (0.5-8 kHz) obtained through automated smartphone audiometry to thresholds obtained through conventional audiometry. A total of 95 participants were included in the study. Of these, 30 were adults, who had known bilateral hearing losses of varying degrees (mean age = 59 yr, standard deviation [SD] = 21.8; 56.7% female), and 65 were adolescents (mean age = 16.5 yr, SD = 1.2; 70.8% female), of which 61 had normal hearing and the remaining 4 had mild hearing losses. Threshold comparisons were made between the two test procedures. The Wilcoxon signed-ranked test was used for comparison of threshold correspondence between manual and smartphone thresholds and the paired samples t test was used to compare test time. Within the adult sample, 94.4% of thresholds obtained through smartphone and conventional audiometry corresponded within 10 dB or less. There was no significant difference between smartphone (6.75-min average, SD = 1.5) and conventional audiometry test duration (6.65-min average, SD = 2.5). Within the adolescent sample, 84.7% of thresholds obtained at 0.5, 2, and 4 kHz with hearTest and conventional audiometry corresponded within ≤5 dB. At 1 kHz, 79.3% of the thresholds differed by ≤10 dB. There was a significant difference (p < 0.01) between smartphone (7.09 min, SD = 1.2) and conventional audiometry test duration (3.23 min, SD = 0.6). The hearTest application with calibrated supra-aural headphones provides a cost-effective option to determine valid air-conduction hearing thresholds. American Academy of Audiology

Influence of aging on thermal and vibratory thresholds of quantitative sensory testing.

PubMed

Lin, Yea-Huey; Hsieh, Song-Chou; Chao, Chi-Chao; Chang, Yang-Chyuan; Hsieh, Sung-Tsang

2005-09-01

Quantitative sensory testing has become a common approach to evaluate thermal and vibratory thresholds in various types of neuropathies. To understand the effect of aging on sensory perception, we measured warm, cold, and vibratory thresholds by performing quantitative sensory testing on a population of 484 normal subjects (175 males and 309 females), aged 48.61 +/- 14.10 (range 20-86) years. Sensory thresholds of the hand and foot were measured with two algorithms: the method of limits (Limits) and the method of level (Level). Thresholds measured by Limits are reaction-time-dependent, while those measured by Level are independent of reaction time. In addition, we explored (1) the correlations of thresholds between these two algorithms, (2) the effect of age on differences in thresholds between algorithms, and (3) differences in sensory thresholds between the two test sites. Age was consistently and significantly correlated with sensory thresholds of all tested modalities measured by both algorithms on multivariate regression analysis compared with other factors, including gender, body height, body weight, and body mass index. When thresholds were plotted against age, slopes differed between sensory thresholds of the hand and those of the foot: for the foot, slopes were steeper compared with those for the hand for each sensory modality. Sensory thresholds of both test sites measured by Level were highly correlated with those measured by Limits, and thresholds measured by Limits were higher than those measured by Level. Differences in sensory thresholds between the two algorithms were also correlated with age: thresholds of the foot were higher than those of the hand for each sensory modality. This difference in thresholds (measured with both Level and Limits) between the hand and foot was also correlated with age. These findings suggest that age is the most significant factor in determining sensory thresholds compared with the other factors of gender and anthropometric parameters, and this provides a foundation for investigating the neurobiologic significance of aging on the processing of sensory stimuli.

The Development of the Text Reception Threshold Test: A Visual Analogue of the Speech Reception Threshold Test

ERIC Educational Resources Information Center

Zekveld, Adriana A.; George, Erwin L. J.; Kramer, Sophia E.; Goverts, S. Theo; Houtgast, Tammo

2007-01-01

Purpose: In this study, the authors aimed to develop a visual analogue of the widely used Speech Reception Threshold (SRT; R. Plomp & A. M. Mimpen, 1979b) test. The Text Reception Threshold (TRT) test, in which visually presented sentences are masked by a bar pattern, enables the quantification of modality-aspecific variance in speech-in-noise…

Should Malaria Treatment Be Guided by a Point of Care Rapid Test? A Threshold Approach to Malaria Management in Rural Burkina Faso

PubMed Central

Bisoffi, Zeno; Tinto, Halidou; Sirima, Bienvenu Sodiomon; Gobbi, Federico; Angheben, Andrea; Buonfrate, Dora; Van den Ende, Jef

2013-01-01

Background In Burkina Faso, rapid diagnostic tests for malaria have been made recently available. Previously, malaria was managed clinically. This study aims at assessing which is the best management option of a febrile patient in a hyperendemic setting. Three alternatives are: treating presumptively, testing, or refraining from both test and treatment. The test threshold is the tradeoff between refraining and testing, the test-treatment threshold is the tradeoff between testing and treating. Only if the disease probability lies between the two should the test be used. Methods and Findings Data for this analysis was obtained from previous studies on malaria rapid tests, involving 5220 patients. The thresholds were calculated, based on disease risk, treatment risk and cost, test accuracy and cost. The thresholds were then matched against the disease probability. For a febrile child under 5 in the dry season, the pre-test probability of clinical malaria (3.2%), was just above the test/treatment threshold. In the rainy season, that probability was 63%, largely above the test/treatment threshold. For febrile children >5 years and adults in the dry season, the probability was 1.7%, below the test threshold, while in the rainy season it was higher (25.1%), and situated between the two thresholds (3% and 60.9%), only if costs were not considered. If they were, neither testing nor treating with artemisinin combination treatments (ACT) would be recommended. Conclusions A febrile child under 5 should be treated presumptively. In the dry season, the probability of clinical malaria in adults is so low, that neither testing nor treating with any regimen should be recommended. In the rainy season, if costs are considered, a febrile adult should not be tested, nor treated with ACT, but a possible alternative would be a presumptive treatment with amodiaquine plus sulfadoxine-pyrimethamine. If costs were not considered, testing would be recommended. PMID:23472129

High-frequency (8 to 16 kHz) reference thresholds and intrasubject threshold variability relative to ototoxicity criteria using a Sennheiser HDA 200 earphone.

PubMed

Frank, T

2001-04-01

The first purpose of this study was to determine high-frequency (8 to 16 kHz) thresholds for standardizing reference equivalent threshold sound pressure levels (RETSPLs) for a Sennheiser HDA 200 earphone. The second and perhaps more important purpose of this study was to determine whether repeated high-frequency thresholds using a Sennheiser HDA 200 earphone had a lower intrasubject threshold variability than the ASHA 1994 significant threshold shift criteria for ototoxicity. High-frequency thresholds (8 to 16 kHz) were obtained for 100 (50 male, 50 female) normally hearing (0.25 to 8 kHz) young adults (mean age of 21.2 yr) in four separate test sessions using a Sennheiser HDA 200 earphone. The mean and median high-frequency thresholds were similar for each test session and increased as frequency increased. At each frequency, the high-frequency thresholds were not significantly (p > 0.05) different for gender, test ear, or test session. The median thresholds at each frequency were similar to the 1998 interim ISO RETSPLs; however, large standard deviations and wide threshold distributions indicated very high intersubject threshold variability, especially at 14 and 16 kHz. Threshold repeatability was determined by finding the threshold differences between each possible test session comparison (N = 6). About 98% of all of the threshold differences were within a clinically acceptable range of +/-10 dB from 8 to 14 kHz. The threshold differences between each subject's second, third, and fourth minus their first test session were also found to determine whether intrasubject threshold variability was less than the ASHA 1994 criteria for determining a significant threshold shift due to ototoxicity. The results indicated a false-positive rate of 0% for a threshold shift > or = 20 dB at any frequency and a false-positive rate of 2% for a threshold shift >10 dB at two consecutive frequencies. This study verified that the output of high-frequency audiometers at 0 dB HL using Sennheiser HDA 200 earphones should equal the 1998 interim ISO RETSPLs from 8 to 16 kHz. Further, because the differences between repeated thresholds were well within +/-10 dB and had an extremely low false-positive rate in reference to the ASHA 1994 criteria for a significant threshold shift due to ototoxicity, a Sennheiser HDA 200 earphone can be used for serial monitoring to determine whether significant high-frequency threshold shifts have occurred for patients receiving potentially ototoxic drug therapy.

Going wireless and booth-less for hearing testing in industry.

PubMed

Meinke, Deanna K; Norris, Jesse A; Flynn, Brendan P; Clavier, Odile H

2017-01-01

To assess the test-retest variability of hearing thresholds obtained with an innovative, mobile wireless automated hearing-test system (WAHTS) with enhanced sound attenuation to test industrial workers at a worksite as compared to standardised automated hearing thresholds obtained in a mobile trailer sound booth. A within-subject repeated-measures design was used to compare air-conducted threshold tests (500-8000 Hz) measured with the WAHTS in six workplace locations, and a third test using computer-controlled audiometry obtained in a mobile trailer sound booth. Ambient noise levels were measured in all test environments. Twenty workers served as listeners and 20 workers served as operators. On average, the WAHTS resulted in equivalent thresholds as the mobile trailer audiometry at 1000, 2000, 3000 and 8000 Hz and thresholds were within ±5 dB at 500, 4000 and 6000 Hz. Comparable performance may be obtained with the WAHTS in occupational audiometry and valid thresholds may be obtained in diverse test locations without the use of sound-attenuating enclosures.

The stability of color discrimination threshold determined using pseudoisochromatic test plates

NASA Astrophysics Data System (ADS)

Zutere, B.; Jurasevska Luse, K.; Livzane, A.

2014-09-01

Congenital red-green color vision deficiency is one of the most common genetic disorders. A previously printed set of pseudoisochromatic plates (KAMS test, 2012) was created for individual discrimination threshold determination in case of mild congenital red-green color vision deficiency using neutral colors (colors confused with gray). The diagnostics of color blind subjects was performed with Richmond HRR (4th edition, 2002) test, Oculus HMC anomaloscope, and further the examination was made using the KAMS test. 4 male subjects aged 20 to 24 years old participated in the study: all of them were diagnosed with deuteranomalia. Due to the design of the plates, the threshold of every subject in each trial was defined as the plate total color difference value ΔE at which the stimulus was detected 75% of the time, so the just-noticeable difference (jnd) was calculated in CIE LAB DeltaE (ΔE) units. Authors performed repeated discrimination threshold measurements (5 times) for all four subjects under controlled illumination conditions. Psychophysical data were taken by sampling an observer's performance on a psychophysical task at a number of different stimulus saturation levels. Results show that a total color difference value ΔE threshold exists for each individual tested with the KAMS pseudoisochromatic plates, this threshold value does not change significantly in multiple measurements. Deuteranomal threshold values aquired using greenish plates of KAMS test are significantly higher than thresholds acquired using reddish plates. A strong positive correlation (R=0.94) exists between anomaloscope matching range (MR) and deuteranomal thresholds aquired by the KAMS test and (R=0.81) between error score in the Richmond HRR test and thresholds aquired by the KAMS test.

Hydroxyisohexyl 3-cyclohexene carboxaldehyde allergy: relationship between patch test and repeated open application test thresholds.

PubMed

Fischer, L A; Menné, T; Avnstorp, C; Kasting, G B; Johansen, J D

2009-09-01

Hydroxyisohexyl 3-cyclohexene carboxaldehyde (HICC) is a synthetic fragrance ingredient. Case reports of allergy to HICC appeared in the 1980s, and HICC has recently been included in the European baseline series. Human elicitation dose-response studies performed with different allergens have shown a significant relationship between the patch-test threshold and the repeated open application test (ROAT) threshold, which mimics some real-life exposure situations. Fragrance ingredients are special as significant amounts of allergen may evaporate from the skin. The study aimed to investigate the relationship between elicitation threshold doses at the patch test and the ROAT, using HICC as the allergen. The expected evaporation rate was calculated. Seventeen HICC-allergic persons were tested with a dilution series of HICC in a patch test and a ROAT (duration up to 21 days). Seventeen persons with no HICC allergy were included as control group for the ROAT. Results The response frequency to the ROAT (in microg HICC cm(-2) per application) was significantly higher than the response frequency to the patch test at one of the tested doses. Furthermore the response rate to the accumulated ROAT dose was significantly lower at half of the doses compared with the patch test. The evaporation rate of HICC was calculated to be 72% over a 24-h period. The ROAT threshold in dose per area per application is lower than the patch test threshold; furthermore the accumulated ROAT threshold is higher than the patch test threshold, which can probably be explained by the evaporation of HICC from the skin in the open test.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maienschein, J.L.; Garcia, F.; Garza, R.G.

Tritium-handling apparatus has been decontaminated as part of the downsizing of the LLNL Tritium Facility. Two stainless-steel glove boxes that had been used to process lithium deuteride-tritide (LiDT) slat were decontaminated using the Portable Cleanup System so that they could be flushed with room air through the facility ventilation system. In this paper the details on the decontamination operation are provided. A series of metal (palladium and vanadium) hydride storage beds have been drained of tritium and flushed with deuterium, in order to remove as much tritium as possible. The bed draining and flushing procedure is described, and a calculationalmore » method is presented which allows estimation of the tritium remaining in a bed after it has been drained and flushed. Data on specific bed draining and flushing are given.« less

CHANGES IN THE ANAEROBIC THRESHOLD IN AN ANNUAL CYCLE OF SPORT TRAINING OF YOUNG SOCCER PLAYERS

PubMed Central

Andrzejewski, M.; Wieczorek, A.; Barinow-Wojewódzki, A.; Jadczak, Ł.; Adrian, S.; Pietrzak, M.; Wieczorek, S.

2013-01-01

The aim of the study was to assess changes in the anaerobic threshold of young soccer players in an annual training cycle. A group of highly trained 15-18 year old players of KKS Lech Poznań were tested. The tests included an annual training macrocycle, and its individual stages resulted from the time structure of the sports training. In order to assess the level of exercise capacities of the players, a field exercise test of increasing intensity was carried out on a soccer pitch. The test made it possible to determine the 4 millimolar lactate threshold (T LA 4 mmol · l-1) on the basis of the lactate concentration in blood [LA], to establish the threshold running speed and the threshold heart rate [HR]. The threshold running speed at the level of the 4 millimolar lactate threshold was established using the two-point form of the equation of a straight line. The obtained indicators of the threshold running speed allowed for precise establishment of effort intensity used in individual training in developing aerobic endurance. In order to test the significance of differences in mean values between four dates of tests, a non-parametric Friedman ANOVA test was used. The significance of differences between consecutive dates of tests was determined using a post-hoc Friedman ANOVA test. The tests showed significant differences in values of selected indicators determined at the anaerobic threshold in various stages of an annual training cycle of young soccer players. The most beneficial changes in terms of the threshold running speed were noted on the fourth date of tests, when the participants had the highest values of 4.01 m · s-1 for older juniors, and 3.80 m · s-1 for younger juniors. This may be indicative of effective application of an individualized programme of training loads and of good preparation of teams for competition in terms of players’ aerobic endurance. PMID:24744480

Changes in the anaerobic threshold in an annual cycle of sport training of young soccer players.

PubMed

Sliwowski, R; Andrzejewski, M; Wieczorek, A; Barinow-Wojewódzki, A; Jadczak, L; Adrian, S; Pietrzak, M; Wieczorek, S

2013-06-01

The aim of the study was to assess changes in the anaerobic threshold of young soccer players in an annual training cycle. A group of highly trained 15-18 year old players of KKS Lech Poznań were tested. The tests included an annual training macrocycle, and its individual stages resulted from the time structure of the sports training. In order to assess the level of exercise capacities of the players, a field exercise test of increasing intensity was carried out on a soccer pitch. The test made it possible to determine the 4 millimolar lactate threshold (T LA 4 mmol · l(-1)) on the basis of the lactate concentration in blood [LA], to establish the threshold running speed and the threshold heart rate [HR]. The threshold running speed at the level of the 4 millimolar lactate threshold was established using the two-point form of the equation of a straight line. The obtained indicators of the threshold running speed allowed for precise establishment of effort intensity used in individual training in developing aerobic endurance. In order to test the significance of differences in mean values between four dates of tests, a non-parametric Friedman ANOVA test was used. The significance of differences between consecutive dates of tests was determined using a post-hoc Friedman ANOVA test. The tests showed significant differences in values of selected indicators determined at the anaerobic threshold in various stages of an annual training cycle of young soccer players. The most beneficial changes in terms of the threshold running speed were noted on the fourth date of tests, when the participants had the highest values of 4.01 m · s(-1) for older juniors, and 3.80 m · s(-1) for younger juniors. This may be indicative of effective application of an individualized programme of training loads and of good preparation of teams for competition in terms of players' aerobic endurance.

Study of blur discrimination for 3D stereo viewing

NASA Astrophysics Data System (ADS)

Subedar, Mahesh; Karam, Lina J.

2014-03-01

Blur is an important attribute in the study and modeling of the human visual system. Blur discrimination was studied extensively using 2D test patterns. In this study, we present the details of subjective tests performed to measure blur discrimination thresholds using stereoscopic 3D test patterns. Specifically, the effect of disparity on the blur discrimination thresholds is studied on a passive stereoscopic 3D display. The blur discrimination thresholds are measured using stereoscopic 3D test patterns with positive, negative and zero disparity values, at multiple reference blur levels. A disparity value of zero represents the 2D viewing case where both the eyes will observe the same image. The subjective test results indicate that the blur discrimination thresholds remain constant as we vary the disparity value. This further indicates that binocular disparity does not affect blur discrimination thresholds and the models developed for 2D blur discrimination thresholds can be extended to stereoscopic 3D blur discrimination thresholds. We have presented fitting of the Weber model to the 3D blur discrimination thresholds measured from the subjective experiments.

A ruggedness evaluation of procedures for damage threshold testing optical materials

NASA Technical Reports Server (NTRS)

Hooker, Matthew W.; Thomas, Milfred E.; Wise, Stephanie A.; Tappan, Nina D.

1995-01-01

A ruggedness evaluation of approaches to damage threshold testing was performed to determine the influence of three procedural variables on damage threshold data. The differences between the number of test sites evaluated at an applied fluence level (1 site versus 10 sites), the number of laser pulses at each test site (1 pulse versus 200 pulses), and the beam diameter (0.35 mm versus 0.70 mm) were all found to significantly influence the damage threshold data over a 99-percent confidence interval.

Determination of a Testing Threshold for Lumbar Puncture in the Diagnosis of Subarachnoid Hemorrhage after a Negative Head Computed Tomography: A Decision Analysis.

PubMed

Taylor, Richard Andrew; Singh Gill, Harman; Marcolini, Evie G; Meyers, H Pendell; Faust, Jeremy Samuel; Newman, David H

2016-10-01

The objective was to determine the testing threshold for lumbar puncture (LP) in the evaluation of aneurysmal subarachnoid hemorrhage (SAH) after a negative head computed tomography (CT). As a secondary aim we sought to identify clinical variables that have the greatest impact on this threshold. A decision analytic model was developed to estimate the testing threshold for patients with normal neurologic findings, being evaluated for SAH, after a negative CT of the head. The testing threshold was calculated as the pretest probability of disease where the two strategies (LP or no LP) are balanced in terms of quality-adjusted life-years. Two-way and probabilistic sensitivity analyses (PSAs) were performed. For the base-case scenario the testing threshold for performing an LP after negative head CT was 4.3%. Results for the two-way sensitivity analyses demonstrated that the test threshold ranged from 1.9% to 15.6%, dominated by the uncertainty in the probability of death from initial missed SAH. In the PSA the mean testing threshold was 4.3% (95% confidence interval = 1.4% to 9.3%). Other significant variables in the model included probability of aneurysmal versus nonaneurysmal SAH after negative head CT, probability of long-term morbidity from initial missed SAH, and probability of renal failure from contrast-induced nephropathy. Our decision analysis results suggest a testing threshold for LP after negative CT to be approximately 4.3%, with a range of 1.4% to 9.3% on robust PSA. In light of these data, and considering the low probability of aneurysmal SAH after a negative CT, classical teaching and current guidelines addressing testing for SAH should be revisited. © 2016 by the Society for Academic Emergency Medicine.

The Purpose of Generating Fatigue Crack Growth Threshold Data

NASA Technical Reports Server (NTRS)

Forth, Scott

2006-01-01

Test data shows that different width and thickness C(T), M(T) and ESE(T) specimens generate different thresholds Structures designed for "infinite life" are being re-evaluated: a) Threshold changes from 6 to 3 ksi in(sup 1/2); b) Computational life changes from infinite to 4 missions. Multi-million dollar test programs required to substantiate operation. Using ASTM E647 as standard guidance to generate threshold data is not practical. A threshold test approach needs to be standardized that will provide positive margin for high cycle fatigue applications.

Comparison of algorithms of testing for use in automated evaluation of sensation.

PubMed

Dyck, P J; Karnes, J L; Gillen, D A; O'Brien, P C; Zimmerman, I R; Johnson, D M

1990-10-01

Estimates of vibratory detection threshold may be used to detect, characterize, and follow the course of sensory abnormality in neurologic disease. The approach is especially useful in epidemiologic and controlled clinical trials. We studied which algorithm of testing and finding threshold should be used in automatic systems by comparing among algorithms and stimulus conditions for the index finger of healthy subjects and for the great toe of patients with mild neuropathy. Appearance thresholds obtained by linear ramps increasing at a rate less than 4.15 microns/sec provided accurate and repeatable thresholds compared with thresholds obtained by forced-choice testing. These rates would be acceptable if only sensitive sites were studied, but they were too slow for use in automatic testing of insensitive parts. Appearance thresholds obtained by fast linear rates (4.15 or 16.6 microns/sec) overestimated threshold, especially for sensitive parts. Use of the mean of appearance and disappearance thresholds, with the stimulus increasing exponentially at rates of 0.5 or 1.0 just noticeable difference (JND) units per second, and interspersion of null stimuli, Békésy with null stimuli, provided accurate, repeatable, and fast estimates of threshold for sensitive parts. Despite the good performance of Békésy testing, we prefer forced choice for evaluation of the sensation of patients with neuropathy.

The self-perception of dyspnoea threshold during the 6-min walk test: a good alternative to estimate the ventilatory threshold in chronic obstructive pulmonary disease.

PubMed

Couillard, Annabelle; Tremey, Emilie; Prefaut, Christian; Varray, Alain; Heraud, Nelly

2016-12-01

To determine and/or adjust exercise training intensity for patients when the cardiopulmonary exercise test is not accessible, the determination of dyspnoea threshold (defined as the onset of self-perceived breathing discomfort) during the 6-min walk test (6MWT) could be a good alternative. The aim of this study was to evaluate the feasibility and reproducibility of self-perceived dyspnoea threshold and to determine whether a useful equation to estimate ventilatory threshold from self-perceived dyspnoea threshold could be derived. A total of 82 patients were included and performed two 6MWTs, during which they raised a hand to signal self-perceived dyspnoea threshold. The reproducibility in terms of heart rate (HR) was analysed. On a subsample of patients (n=27), a stepwise regression analysis was carried out to obtain a predictive equation of HR at ventilatory threshold measured during a cardiopulmonary exercise test estimated from HR at self-perceived dyspnoea threshold, age and forced expiratory volume in 1 s. Overall, 80% of patients could identify self-perceived dyspnoea threshold during the 6MWT. Self-perceived dyspnoea threshold was reproducibly expressed in HR (coefficient of variation=2.8%). A stepwise regression analysis enabled estimation of HR at ventilatory threshold from HR at self-perceived dyspnoea threshold, age and forced expiratory volume in 1 s (adjusted r=0.79, r=0.63, and relative standard deviation=9.8 bpm). This study shows that a majority of patients with chronic obstructive pulmonary disease can identify a self-perceived dyspnoea threshold during the 6MWT. This HR at the dyspnoea threshold is highly reproducible and enable estimation of the HR at the ventilatory threshold.

Demand for Colonoscopy in Colorectal Cancer Screening Using a Quantitative Fecal Immunochemical Test and Age/Sex-Specific Thresholds for Test Positivity.

PubMed

Chen, Sam Li-Sheng; Hsu, Chen-Yang; Yen, Amy Ming-Fang; Young, Graeme P; Chiu, Sherry Yueh-Hsia; Fann, Jean Ching-Yuan; Lee, Yi-Chia; Chiu, Han-Mo; Chiou, Shu-Ti; Chen, Hsiu-Hsi

2018-06-01

Background: Despite age and sex differences in fecal hemoglobin (f-Hb) concentrations, most fecal immunochemical test (FIT) screening programs use population-average cut-points for test positivity. The impact of age/sex-specific threshold on FIT accuracy and colonoscopy demand for colorectal cancer screening are unknown. Methods: Using data from 723,113 participants enrolled in a Taiwanese population-based colorectal cancer screening with single FIT between 2004 and 2009, sensitivity and specificity were estimated for various f-Hb thresholds for test positivity. This included estimates based on a "universal" threshold, receiver-operating-characteristic curve-derived threshold, targeted sensitivity, targeted false-positive rate, and a colonoscopy-capacity-adjusted method integrating colonoscopy workload with and without age/sex adjustments. Results: Optimal age/sex-specific thresholds were found to be equal to or lower than the universal 20 μg Hb/g threshold. For older males, a higher threshold (24 μg Hb/g) was identified using a 5% false-positive rate. Importantly, a nonlinear relationship was observed between sensitivity and colonoscopy workload with workload rising disproportionately to sensitivity at 16 μg Hb/g. At this "colonoscopy-capacity-adjusted" threshold, the test positivity (colonoscopy workload) was 4.67% and sensitivity was 79.5%, compared with a lower 4.0% workload and a lower 78.7% sensitivity using 20 μg Hb/g. When constrained on capacity, age/sex-adjusted estimates were generally lower. However, optimizing age/-sex-adjusted thresholds increased colonoscopy demand across models by 17% or greater compared with a universal threshold. Conclusions: Age/sex-specific thresholds improve FIT accuracy with modest increases in colonoscopy demand. Impact: Colonoscopy-capacity-adjusted and age/sex-specific f-Hb thresholds may be useful in optimizing individual screening programs based on detection accuracy, population characteristics, and clinical capacity. Cancer Epidemiol Biomarkers Prev; 27(6); 704-9. ©2018 AACR . ©2018 American Association for Cancer Research.

A study of the high-frequency hearing thresholds of dentistry professionals

PubMed Central

Lopes, Andréa Cintra; de Melo, Ana Dolores Passarelli; Santos, Cibele Carmelo

2012-01-01

Summary Introduction: In the dentistry practice, dentists are exposed to harmful effects caused by several factors, such as the noise produced by their work instruments. In 1959, the American Dental Association recommended periodical hearing assessments and the use of ear protectors. Aquiring more information regarding dentists', dental nurses', and prosthodontists' hearing abilities is necessary to propose prevention measures and early treatment strategies. Objective: To investigate the auditory thresholds of dentists, dental nurses, and prosthodontists. Method: In this clinical and experimental study, 44 dentists (Group I; GI), 36 dental nurses (Group II; GII), and 28 prosthodontists (Group III; GIII) were included, , with a total of 108 professionals. The procedures that were performed included a specific interview, ear canal inspection, conventional and high-frequency threshold audiometry, a speech reception threshold test, and an acoustic impedance test. Results: In the 3 groups that were tested, the comparison between the mean hearing thresholds provided evidence of worsened hearing ability relative to the increase in frequency. For the tritonal mean at 500 to 2,000 Hz and 3,000 to 6,000 Hz, GIII presented the worst thresholds. For the mean of the high frequencies (9,000 and 16,000 Hz), GII presented the worst thresholds. Conclusion: The conventional hearing threshold evaluation did not demonstrate alterations in the 3 groups that were tested; however, the complementary tests such as high-frequency audiometry provided greater efficacy in the early detection of hearing problems, since this population's hearing loss impaired hearing ability at frequencies that are not tested by the conventional tests. Therefore, we emphasize the need of utilizing high-frequency threshold audiometry in the hearing assessment routine in combination with other audiological tests. PMID:25991940

Speech-in-Noise Tests and Supra-threshold Auditory Evoked Potentials as Metrics for Noise Damage and Clinical Trial Outcome Measures.

PubMed

Le Prell, Colleen G; Brungart, Douglas S

2016-09-01

In humans, the accepted clinical standards for detecting hearing loss are the behavioral audiogram, based on the absolute detection threshold of pure-tones, and the threshold auditory brainstem response (ABR). The audiogram and the threshold ABR are reliable and sensitive measures of hearing thresholds in human listeners. However, recent results from noise-exposed animals demonstrate that noise exposure can cause substantial neurodegeneration in the peripheral auditory system without degrading pure-tone audiometric thresholds. It has been suggested that clinical measures of auditory performance conducted with stimuli presented above the detection threshold may be more sensitive than the behavioral audiogram in detecting early-stage noise-induced hearing loss in listeners with audiometric thresholds within normal limits. Supra-threshold speech-in-noise testing and supra-threshold ABR responses are reviewed here, given that they may be useful supplements to the behavioral audiogram for assessment of possible neurodegeneration in noise-exposed listeners. Supra-threshold tests may be useful for assessing the effects of noise on the human inner ear, and the effectiveness of interventions designed to prevent noise trauma. The current state of the science does not necessarily allow us to define a single set of best practice protocols. Nonetheless, we encourage investigators to incorporate these metrics into test batteries when feasible, with an effort to standardize procedures to the greatest extent possible as new reports emerge.

Normal Threshold Size of Stimuli in Children Using a Game-Based Visual Field Test.

PubMed

Wang, Yanfang; Ali, Zaria; Subramani, Siddharth; Biswas, Susmito; Fenerty, Cecilia; Henson, David B; Aslam, Tariq

2017-06-01

The aim of this study was to demonstrate and explore the ability of novel game-based perimetry to establish normal visual field thresholds in children. One hundred and eighteen children (aged 8.0 ± 2.8 years old) with no history of visual field loss or significant medical history were recruited. Each child had one eye tested using a game-based visual field test 'Caspar's Castle' at four retinal locations 12.7° (N = 118) from fixation. Thresholds were established repeatedly using up/down staircase algorithms with stimuli of varying diameter (luminance 20 cd/m 2 , duration 200 ms, background luminance 10 cd/m 2 ). Relationships between threshold and age were determined along with measures of intra- and intersubject variability. The Game-based visual field test was able to establish threshold estimates in the full range of children tested. Threshold size reduced with increasing age in children. Intrasubject variability and intersubject variability were inversely related to age in children. Normal visual field thresholds were established for specific locations in children using a novel game-based visual field test. These could be used as a foundation for developing a game-based perimetry screening test for children.

A brief peripheral motion contrast threshold test predicts older drivers' hazardous behaviors in simulated driving.

PubMed

Henderson, Steven; Woods-Fry, Heather; Collin, Charles A; Gagnon, Sylvain; Voloaca, Misha; Grant, John; Rosenthal, Ted; Allen, Wade

2015-05-01

Our research group has previously demonstrated that the peripheral motion contrast threshold (PMCT) test predicts older drivers' self-report accident risk, as well as simulated driving performance. However, the PMCT is too lengthy to be a part of a battery of tests to assess fitness to drive. Therefore, we have developed a new version of this test, which takes under two minutes to administer. We assessed the motion contrast thresholds of 24 younger drivers (19-32) and 25 older drivers (65-83) with both the PMCT-10min and the PMCT-2min test and investigated if thresholds were associated with measures of simulated driving performance. Younger participants had significantly lower motion contrast thresholds than older participants and there were no significant correlations between younger participants' thresholds and any measures of driving performance. The PMCT-10min and the PMCT-2min thresholds of older drivers' predicted simulated crash risk, as well as the minimum distance of approach to all hazards. This suggests that our tests of motion processing can help predict the risk of collision or near collision in older drivers. Thresholds were also correlated with the total lane deviation time, suggesting a deficiency in processing of peripheral flow and delayed detection of adjacent cars. The PMCT-2min is an improved version of a previously validated test, and it has the potential to help assess older drivers' fitness to drive. Copyright © 2015 Elsevier Ltd. All rights reserved.

Corona-vacuum failure mechanism test facilities

NASA Technical Reports Server (NTRS)

Lalli, V. R.; Mueller, L. A.; Koutnik, E. A.

1975-01-01

A nondestructive corona-vacuum test facility for testing high-voltage power system components has been developed using commercially available hardware. The facility simulates operating temperature and vacuum while monitoring coronal discharges with residual gases. Corona threshold voltages obtained from statorette tests with various gas-solid dielectric systems and comparison with calculated data support the following conclusions: (1) air gives the highest corona threshold voltage and helium the lowest, with argon and helium-xenon mixtures intermediate; (2) corona threshold voltage increases with gas pressure; (3) corona threshold voltage for an armature winding can be accurately calculated by using Paschen curves for a uniform field; and (4) Paschen curves for argon can be used to calculate the corona threshold voltage in He-Xe mixtures, for which Paschen curves are unavailable.-

How Well Do Engineering Students Retain Core Mathematical Knowledge after a Series of High Threshold Online Mathematics Tests?

ERIC Educational Resources Information Center

Carr, Michael; Prendergast, Mark; Breen, Cormac; Faulkner, Fiona

2017-01-01

In the Dublin Institute of Technology, high threshold core skills assessments are run in mathematics for third-year engineering students. Such tests require students to reach a threshold of 90% on a multiple choice test based on a randomized question bank. The material covered by the test consists of the more important aspects of undergraduate…

Extended high-frequency thresholds in college students: effects of music player use and other recreational noise.

PubMed

Le Prell, Colleen G; Spankovich, Christopher; Lobariñas, Edward; Griffiths, Scott K

2013-09-01

Human hearing is sensitive to sounds from as low as 20 Hz to as high as 20,000 Hz in normal ears. However, clinical tests of human hearing rarely include extended high-frequency (EHF) threshold assessments, at frequencies extending beyond 8000 Hz. EHF thresholds have been suggested for use monitoring the earliest effects of noise on the inner ear, although the clinical usefulness of EHF threshold testing is not well established for this purpose. The primary objective of this study was to determine if EHF thresholds in healthy, young adult college students vary as a function of recreational noise exposure. A retrospective analysis of a laboratory database was conducted; all participants with both EHF threshold testing and noise history data were included. The potential for "preclinical" EHF deficits was assessed based on the measured thresholds, with the noise surveys used to estimate recreational noise exposure. EHF thresholds measured during participation in other ongoing studies were available from 87 participants (34 male and 53 female); all participants had hearing within normal clinical limits (≤25 HL) at conventional frequencies (0.25-8 kHz). EHF thresholds closely matched standard reference thresholds [ANSI S3.6 (1996) Annex C]. There were statistically reliable threshold differences in participants who used music players, with 3-6 dB worse thresholds at the highest test frequencies (10-16 kHz) in participants who reported long-term use of music player devices (>5 yr), or higher listening levels during music player use. It should be possible to detect small changes in high-frequency hearing for patients or participants who undergo repeated testing at periodic intervals. However, the increased population-level variability in thresholds at the highest frequencies will make it difficult to identify the presence of small but potentially important deficits in otherwise normal-hearing individuals who do not have previously established baseline data. American Academy of Audiology.

A longitudinal study on the ammonia threshold in junior cyclists

PubMed Central

Yuan, Y; Chan, K

2004-01-01

Objectives: To identify the effect of a one year non-specific training programme on the ammonia threshold of a group of junior cyclists and to correlate ammonia threshold with other common physiological variables. Methods: The cyclists performed tests at three time points (T1, T2, T3) during the year. Follow up tests were conducted every six months after the original test. Ammonia threshold was obtained from a graded exercise with four minute steps. Results: The relatively non-specific one year training programme was effective in inducing an increase in peak VO2 (60.6 (5.9), 65.9 (7.4), and 64.6 (6.5) ml/min/kg at T1, T2, and T3 respectively) and endurance time (18.3 (4.5), 20.1 (5.2), and 27.0 (6.1) minutes at T1, T2, and T3 respectively), but was not effective for the sprint related variables. Ammonia threshold, together with lactate threshold and ventilatory threshold, was not significantly different at the three test times. Only endurance time correlated significantly with ammonia threshold (r  =  0.915, p  =  0.001). Conclusions: The findings suggest that a relatively non-specific one year training programme does not modify the ammonia threshold of junior cyclists. The significant correlation between ammonia threshold and endurance time further confirms that ammonia threshold is a measure of the ability to sustain exercise at submaximal intensities. PMID:15039242

A principled approach to setting optimal diagnostic thresholds: where ROC and indifference curves meet.

PubMed

Irwin, R John; Irwin, Timothy C

2011-06-01

Making clinical decisions on the basis of diagnostic tests is an essential feature of medical practice and the choice of the decision threshold is therefore crucial. A test's optimal diagnostic threshold is the threshold that maximizes expected utility. It is given by the product of the prior odds of a disease and a measure of the importance of the diagnostic test's sensitivity relative to its specificity. Choosing this threshold is the same as choosing the point on the Receiver Operating Characteristic (ROC) curve whose slope equals this product. We contend that a test's likelihood ratio is the canonical decision variable and contrast diagnostic thresholds based on likelihood ratio with two popular rules of thumb for choosing a threshold. The two rules are appealing because they have clear graphical interpretations, but they yield optimal thresholds only in special cases. The optimal rule can be given similar appeal by presenting indifference curves, each of which shows a set of equally good combinations of sensitivity and specificity. The indifference curve is tangent to the ROC curve at the optimal threshold. Whereas ROC curves show what is feasible, indifference curves show what is desirable. Together they show what should be chosen. Copyright © 2010 European Federation of Internal Medicine. Published by Elsevier B.V. All rights reserved.

Meta‐analysis of test accuracy studies using imputation for partial reporting of multiple thresholds

PubMed Central

Deeks, J.J.; Martin, E.C.; Riley, R.D.

2017-01-01

Introduction For tests reporting continuous results, primary studies usually provide test performance at multiple but often different thresholds. This creates missing data when performing a meta‐analysis at each threshold. A standard meta‐analysis (no imputation [NI]) ignores such missing data. A single imputation (SI) approach was recently proposed to recover missing threshold results. Here, we propose a new method that performs multiple imputation of the missing threshold results using discrete combinations (MIDC). Methods The new MIDC method imputes missing threshold results by randomly selecting from the set of all possible discrete combinations which lie between the results for 2 known bounding thresholds. Imputed and observed results are then synthesised at each threshold. This is repeated multiple times, and the multiple pooled results at each threshold are combined using Rubin's rules to give final estimates. We compared the NI, SI, and MIDC approaches via simulation. Results Both imputation methods outperform the NI method in simulations. There was generally little difference in the SI and MIDC methods, but the latter was noticeably better in terms of estimating the between‐study variances and generally gave better coverage, due to slightly larger standard errors of pooled estimates. Given selective reporting of thresholds, the imputation methods also reduced bias in the summary receiver operating characteristic curve. Simulations demonstrate the imputation methods rely on an equal threshold spacing assumption. A real example is presented. Conclusions The SI and, in particular, MIDC methods can be used to examine the impact of missing threshold results in meta‐analysis of test accuracy studies. PMID:29052347

Cool, warm, and heat-pain detection thresholds: testing methods and inferences about anatomic distribution of receptors.

PubMed

Dyck, P J; Zimmerman, I; Gillen, D A; Johnson, D; Karnes, J L; O'Brien, P C

1993-08-01

We recently found that vibratory detection threshold is greatly influenced by the algorithm of testing. Here, we study the influence of stimulus characteristics and algorithm of testing and estimating threshold on cool (CDT), warm (WDT), and heat-pain (HPDT) detection thresholds. We show that continuously decreasing (for CDT) or increasing (for WDT) thermode temperature to the point at which cooling or warming is perceived and signaled by depressing a response key ("appearance" threshold) overestimates threshold with rapid rates of thermal change. The mean of the appearance and disappearance thresholds also does not perform well for insensitive sites and patients. Pyramidal (or flat-topped pyramidal) stimuli ranging in magnitude, in 25 steps, from near skin temperature to 9 degrees C for 10 seconds (for CDT), from near skin temperature to 45 degrees C for 10 seconds (for WDT), and from near skin temperature to 49 degrees C for 10 seconds (for HPDT) provide ideal stimuli for use in several algorithms of testing and estimating threshold. Near threshold, only the initial direction of thermal change from skin temperature is perceived, and not its return to baseline. Use of steps of stimulus intensity allows the subject or patient to take the needed time to decide whether the stimulus was felt or not (in 4, 2, and 1 stepping algorithms), or whether it occurred in stimulus interval 1 or 2 (in two-alternative forced-choice testing). Thermal thresholds were generally significantly lower with a large (10 cm2) than with a small (2.7 cm2) thermode.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of extrinsic noise in the sensitivity of the rod pathway: rapid dark adaptation of nocturnal vision in humans.

PubMed

Reeves, Adam; Grayhem, Rebecca

2016-03-01

Rod-mediated 500 nm test spots were flashed in Maxwellian view at 5 deg eccentricity, both on steady 10.4 deg fields of intensities (I) from 0.00001 to 1.0 scotopic troland (sc td) and from 0.2 s to 1 s after extinguishing the field. On dim fields, thresholds of tiny (5') tests were proportional to √I (Rose-DeVries law), while thresholds after extinction fell within 0.6 s to the fully dark-adapted absolute threshold. Thresholds of large (1.3 deg) tests were proportional to I (Weber law) and extinction thresholds, to √I. rod thresholds are elevated by photon-driven noise from dim fields that disappears at field extinction; large spot thresholds are additionally elevated by neural light adaptation proportional to √I. At night, recovery from dimly lit fields is fast, not slow.

Assessment of the Anticonvulsant Potency of Ursolic Acid in Seizure Threshold Tests in Mice.

PubMed

Nieoczym, Dorota; Socała, Katarzyna; Wlaź, Piotr

2018-05-01

Ursolic acid (UA) is a plant derived compound which is also a component of the standard human diet. It possesses a wide range of pharmacological properties, i.e., antioxidant, anti-inflammatory, antimicrobial and antitumor, which have been used in folk medicine for centuries. Moreover, influence of UA on central nervous system-related processes, i.e., pain, anxiety and depression, was proved in experimental studies. UA also revealed anticonvulsant properties in animal models of epilepsy and seizures. The aim of the present study was to investigate the influence of UA on seizure thresholds in three acute seizure models in mice, i.e., the 6 Hz-induced psychomotor seizure threshold test, the maximal electroshock threshold (MEST) test and the timed intravenous pentylenetetrazole (iv PTZ) infusion test. We also examined its effect on the muscular strength (assessed in the grip strength test) and motor coordination (estimated in the chimney test) in mice. UA at doses of 50 and 100 mg/kg significantly increased the seizure thresholds in the 6 Hz and MEST tests. The studied compound did not influence the seizure thresholds in the iv PTZ test. Moreover, UA did not affect the motor coordination and muscular strength in mice. UA displays only a weak anticonvulsant potential which is dependent on the used seizure model.

Do Optimal Prognostic Thresholds in Continuous Physiological Variables Really Exist? Analysis of Origin of Apparent Thresholds, with Systematic Review for Peak Oxygen Consumption, Ejection Fraction and BNP

PubMed Central

Leong, Tora; Rehman, Michaela B.; Pastormerlo, Luigi Emilio; Harrell, Frank E.; Coats, Andrew J. S.; Francis, Darrel P.

2014-01-01

Background Clinicians are sometimes advised to make decisions using thresholds in measured variables, derived from prognostic studies. Objectives We studied why there are conflicting apparently-optimal prognostic thresholds, for example in exercise peak oxygen uptake (pVO2), ejection fraction (EF), and Brain Natriuretic Peptide (BNP) in heart failure (HF). Data Sources and Eligibility Criteria Studies testing pVO2, EF or BNP prognostic thresholds in heart failure, published between 1990 and 2010, listed on Pubmed. Methods First, we examined studies testing pVO2, EF or BNP prognostic thresholds. Second, we created repeated simulations of 1500 patients to identify whether an apparently-optimal prognostic threshold indicates step change in risk. Results 33 studies (8946 patients) tested a pVO2 threshold. 18 found it prognostically significant: the actual reported threshold ranged widely (10–18 ml/kg/min) but was overwhelmingly controlled by the individual study population's mean pVO2 (r = 0.86, p<0.00001). In contrast, the 15 negative publications were testing thresholds 199% further from their means (p = 0.0001). Likewise, of 35 EF studies (10220 patients), the thresholds in the 22 positive reports were strongly determined by study means (r = 0.90, p<0.0001). Similarly, in the 19 positives of 20 BNP studies (9725 patients): r = 0.86 (p<0.0001). Second, survival simulations always discovered a “most significant” threshold, even when there was definitely no step change in mortality. With linear increase in risk, the apparently-optimal threshold was always near the sample mean (r = 0.99, p<0.001). Limitations This study cannot report the best threshold for any of these variables; instead it explains how common clinical research procedures routinely produce false thresholds. Key Findings First, shifting (and/or disappearance) of an apparently-optimal prognostic threshold is strongly determined by studies' average pVO2, EF or BNP. Second, apparently-optimal thresholds always appear, even with no step in prognosis. Conclusions Emphatic therapeutic guidance based on thresholds from observational studies may be ill-founded. We should not assume that optimal thresholds, or any thresholds, exist. PMID:24475020

A randomized trial of the effect of automated ventricular capture on device longevity and threshold measurement in pacemaker patients.

PubMed

Koplan, Bruce A; Gilligan, David M; Nguyen, Luc S; Lau, Theodore K; Thackeray, Lisa M; Berg, Kellie Chase

2008-11-01

An automatic capture (AC) algorithm adjusts ventricular pacing output to capture the ventricle while optimizing output to 0.5 V above threshold. AC maintains this output and confirms capture on a beat-to-beat basis in bipolar and unipolar pacing and sensing. To assess the AC algorithm and its impact on device longevity. Patients implanted with a pacemaker were randomized 1:1 to have the AC feature on or off for 12 months. Two threshold tests were conducted at each visit- automatic threshold and manual threshold. Average ventricular voltage output and projected device longevity were compared between AC on and off using nonparametric tests. Nine hundred ten patients were enrolled and underwent device implantation. Average ventricular voltage output was 1.6 V for the AC on arm (n = 444) and 3.1 V for the AC off arm (n = 446) (P < 0.001). Projected device longevity was 10.3 years for AC on and 8.9 years for AC off (P < 0.0001), or a 16% increase in longevity for AC on. The proportion of patients in whom there was a difference between automatic threshold and manual threshold of

Equivalence and test-retest reproducibility of conventional and extended-high-frequency audiometric thresholds obtained using pure-tone and narrow-band-noise stimuli.

PubMed

John, Andrew B; Kreisman, Brian M

2017-09-01

Extended high-frequency (EHF) audiometry is useful for evaluating ototoxic exposures and may relate to speech recognition, localisation and hearing aid benefit. There is a need to determine whether common clinical practice for EHF audiometry using tone and noise stimuli is reliable. We evaluated equivalence and compared test-retest (TRT) reproducibility for audiometric thresholds obtained using pure tones and narrowband noise (NBN) from 0.25 to 16 kHz. Thresholds and test-retest reproducibility for stimuli in the conventional (0.25-6 kHz) and EHF (8-16 kHz) frequency ranges were compared in a repeated-measures design. A total of 70 ears of adults with normal hearing. Thresholds obtained using NBN were significantly lower than thresholds obtained using pure tones from 0.5 to 16 kHz, but not 0.25 kHz. Good TRT reproducibility (within 2 dB) was observed for both stimuli at all frequencies. Responses at the lower limit of the presentation range for NBN centred at 14 and 16 kHz suggest unreliability for NBN as a threshold stimulus at these frequencies. Thresholds in the conventional and EHF ranges showed good test-retest reproducibility, but differed between stimulus types. Care should be taken when comparing pure-tone thresholds with NBN thresholds especially at these frequencies.

R-on-1 automatic mapping: A new tool for laser damage testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hue, J.; Garrec, P.; Dijon, J.

1996-12-31

Laser damage threshold measurement is statistical in nature. For a commercial qualification or for a user, the threshold determined by the weakest point is a satisfactory characterization. When a new coating is designed, threshold mapping is very useful. It enables the technology to be improved and followed more accurately. Different statistical parameters such as the minimum, maximum, average, and standard deviation of the damage threshold as well as spatial parameters such as the threshold uniformity of the coating can be determined. Therefore, in order to achieve a mapping, all the tested sites should give data. This is the major interestmore » of the R-on-1 test in spite of the fact that the laser damage threshold obtained by this method may be different from the 1-on-1 test (smaller or greater). Moreover, on the damage laser test facility, the beam size is smaller (diameters of a few hundred micrometers) than the characteristic sizes of the components in use (diameters of several centimeters up to one meter). Hence, a laser damage threshold mapping appears very interesting, especially for applications linked to large optical components like the Megajoule project or the National Ignition Facility (N.I.F). On the test bench used, damage detection with a Nomarski microscope and scattered light measurement are almost equivalent. Therefore, it becomes possible to automatically detect on line the first defects induced by YAG irradiation. Scattered light mappings and laser damage threshold mappings can therefore be achieved using a X-Y automatic stage (where the test sample is located). The major difficulties due to the automatic capabilities are shown. These characterizations are illustrated at 355 nm. The numerous experiments performed show different kinds of scattering curves, which are discussed in relation with the damage mechanisms.« less

Influence of intrinsic noise generated by a thermotesting device on thermal sensory detection and thermal pain detection thresholds.

PubMed

Pavlaković, G; Züchner, K; Zapf, A; Bachmann, C G; Graf, B M; Crozier, T A; Pavlaković, H

2009-08-01

Various factors can influence thermal perception threshold measurements and contribute significantly to unwanted variability of the tests. To minimize this variability, testing should be performed under strictly controlled conditions. Identifying the factors that increase the variability and eliminating their influence should increase reliability and reproducibility. Currently available thermotesting devices use a water-cooling system that generates a continuous noise of approximately 60 dB. In order to analyze whether this noise could influence the thermal threshold measurements we compared the thresholds obtained with a silent thermotesting device to those obtained with a commercially available device. The subjects were tested with one randomly chosen device on 1 day and with the other device 7 days later. At each session, heat, heat pain, cold, and cold pain thresholds were determined with three measurements. Bland-Altman analysis was used to assess agreement in measurements obtained with different devices and it was shown that the intersubject variability of the thresholds obtained with the two devices was comparable for all four thresholds tested. In contrast, the intrasubject variability of the thresholds for heat, heat pain, and cold pain detection was significantly lower with the silent device. Our results show that thermal sensory thresholds measured with the two devices are comparable. However, our data suggest that, for studies with repeated measurements on the same subjects, a silent thermotesting device may allow detection of smaller differences in the treatment effects and/or may permit the use of a smaller number of tested subjects. Muscle Nerve 40: 257-263, 2009.

Sensitivity and specificity of auditory steady‐state response testing

PubMed Central

Rabelo, Camila Maia; Schochat, Eliane

2011-01-01

INTRODUCTION: The ASSR test is an electrophysiological test that evaluates, among other aspects, neural synchrony, based on the frequency or amplitude modulation of tones. OBJECTIVE: The aim of this study was to determine the sensitivity and specificity of auditory steady‐state response testing in detecting lesions and dysfunctions of the central auditory nervous system. METHODS: Seventy volunteers were divided into three groups: those with normal hearing; those with mesial temporal sclerosis; and those with central auditory processing disorder. All subjects underwent auditory steady‐state response testing of both ears at 500 Hz and 2000 Hz (frequency modulation, 46 Hz). The difference between auditory steady‐state response‐estimated thresholds and behavioral thresholds (audiometric evaluation) was calculated. RESULTS: Estimated thresholds were significantly higher in the mesial temporal sclerosis group than in the normal and central auditory processing disorder groups. In addition, the difference between auditory steady‐state response‐estimated and behavioral thresholds was greatest in the mesial temporal sclerosis group when compared to the normal group than in the central auditory processing disorder group compared to the normal group. DISCUSSION: Research focusing on central auditory nervous system (CANS) lesions has shown that individuals with CANS lesions present a greater difference between ASSR‐estimated thresholds and actual behavioral thresholds; ASSR‐estimated thresholds being significantly worse than behavioral thresholds in subjects with CANS insults. This is most likely because the disorder prevents the transmission of the sound stimulus from being in phase with the received stimulus, resulting in asynchronous transmitter release. Another possible cause of the greater difference between the ASSR‐estimated thresholds and the behavioral thresholds is impaired temporal resolution. CONCLUSIONS: The overall sensitivity of auditory steady‐state response testing was lower than its overall specificity. Although the overall specificity was high, it was lower in the central auditory processing disorder group than in the mesial temporal sclerosis group. Overall sensitivity was also lower in the central auditory processing disorder group than in the mesial temporal sclerosis group. PMID:21437442

An investigation of mechanical nociceptive thresholds in dogs with hind limb joint pain compared to healthy control dogs.

PubMed

Harris, L K; Whay, H R; Murrell, J C

2018-04-01

This study investigated the effects of osteoarthritis (OA) on somatosensory processing in dogs using mechanical threshold testing. A pressure algometer was used to measure mechanical thresholds in 27 dogs with presumed hind limb osteoarthritis and 28 healthy dogs. Mechanical thresholds were measured at the stifles, radii and sternum, and were correlated with scores from an owner questionnaire and a clinical checklist, a scoring system that quantified clinical signs of osteoarthritis. The effects of age and bodyweight on mechanical thresholds were also investigated. Multiple regression models indicated that, when bodyweight was taken into account, dogs with presumed osteoarthritis had lower mechanical thresholds at the stifles than control dogs, but not at other sites. Non-parametric correlations showed that clinical checklist scores and questionnaire scores were negatively correlated with mechanical thresholds at the stifles. The results suggest that mechanical threshold testing using a pressure algometer can detect primary, and possibly secondary, hyperalgesia in dogs with presumed osteoarthritis. This suggests that the mechanical threshold testing protocol used in this study might facilitate assessment of somatosensory changes associated with disease progression or response to treatment. Copyright © 2017. Published by Elsevier Ltd.

Total protein of whole saliva as a biomarker of anaerobic threshold.

PubMed

Bortolini, Miguel Junior Sordi; De Agostini, Guilherme Gularte; Reis, Ismair Teodoro; Lamounier, Romeu Paulo Martins Silva; Blumberg, Jeffrey B; Espindola, Foued Salmen

2009-09-01

Saliva provides a convenient and noninvasive matrix for assessing specific physiological parameters, including some biomarkers of exercise. We investigated whether the total protein concentration of whole saliva (TPWS) would reflect the anaerobic threshold during an incremental exercise test. After a warm-up period, 13 nonsmoking men performed a maximum incremental exercise on a cycle ergometer. Blood and stimulated saliva were collected during the test. The TPWS anaerobic threshold (PAT) was determined using the Dmax method. The PAT was correlated with the blood lactate anaerobic threshold (AT; r = .93, p < .05). No significant difference (p = .16) was observed between PAT and AT. Thus, TPWS provides a convenient and noninvasive matrix for determining the anaerobic threshold during incremental exercise tests.

AN EVALUATION OF HEURISTICS FOR THRESHOLD-FUNCTION TEST-SYNTHESIS,

DTIC Science & Technology

Linear programming offers the most attractive procedure for testing and obtaining optimal threshold gate realizations for functions generated in...The design of the experiments may be of general interest to students of automatic problem solving; the results should be of interest in threshold logic and linear programming. (Author)

A Continuous Threshold Expectile Model.

PubMed

Zhang, Feipeng; Li, Qunhua

2017-12-01

Expectile regression is a useful tool for exploring the relation between the response and the explanatory variables beyond the conditional mean. A continuous threshold expectile regression is developed for modeling data in which the effect of a covariate on the response variable is linear but varies below and above an unknown threshold in a continuous way. The estimators for the threshold and the regression coefficients are obtained using a grid search approach. The asymptotic properties for all the estimators are derived, and the estimator for the threshold is shown to achieve root-n consistency. A weighted CUSUM type test statistic is proposed for the existence of a threshold at a given expectile, and its asymptotic properties are derived under both the null and the local alternative models. This test only requires fitting the model under the null hypothesis in the absence of a threshold, thus it is computationally more efficient than the likelihood-ratio type tests. Simulation studies show that the proposed estimators and test have desirable finite sample performance in both homoscedastic and heteroscedastic cases. The application of the proposed method on a Dutch growth data and a baseball pitcher salary data reveals interesting insights. The proposed method is implemented in the R package cthreshER .

Ultrafast Passive Shields for Laser and Ballistic Protection

DTIC Science & Technology

1991-07-15

chemically polymerized P(DPA)) as a binder, and these were tested for ablation (i.e. laser damage threshold ) limits. Table IV below summarizes these results...50, 100, 250 and 500 AJ/pulse o 1.G, 2.5, 5.0 mJ/pulse. The following energies were used for the preliminary laser damage threshold tests: o 2.5, 5.0...these were tested for ablation (i.e. laser damage threshold ) limits. Table VI summarizes these results which are all for tests in the absence of an iris

Anaerobic Threshold and Salivary α-amylase during Incremental Exercise.

PubMed

Akizuki, Kazunori; Yazaki, Syouichirou; Echizenya, Yuki; Ohashi, Yukari

2014-07-01

[Purpose] The purpose of this study was to clarify the validity of salivary α-amylase as a method of quickly estimating anaerobic threshold and to establish the relationship between salivary α-amylase and double-product breakpoint in order to create a way to adjust exercise intensity to a safe and effective range. [Subjects and Methods] Eleven healthy young adults performed an incremental exercise test using a cycle ergometer. During the incremental exercise test, oxygen consumption, carbon dioxide production, and ventilatory equivalent were measured using a breath-by-breath gas analyzer. Systolic blood pressure and heart rate were measured to calculate the double product, from which double-product breakpoint was determined. Salivary α-amylase was measured to calculate the salivary threshold. [Results] One-way ANOVA revealed no significant differences among workloads at the anaerobic threshold, double-product breakpoint, and salivary threshold. Significant correlations were found between anaerobic threshold and salivary threshold and between anaerobic threshold and double-product breakpoint. [Conclusion] As a method for estimating anaerobic threshold, salivary threshold was as good as or better than determination of double-product breakpoint because the correlation between anaerobic threshold and salivary threshold was higher than the correlation between anaerobic threshold and double-product breakpoint. Therefore, salivary threshold is a useful index of anaerobic threshold during an incremental workload.

Effect of Age and Severity of Facial Palsy on Taste Thresholds in Bell's Palsy Patients

PubMed Central

Park, Jung Min; Kim, Myung Gu; Jung, Junyang; Kim, Sung Su; Jung, A Ra; Kim, Sang Hoon

2017-01-01

Background and Objectives To investigate whether taste thresholds, as determined by electrogustometry (EGM) and chemical taste tests, differ by age and the severity of facial palsy in patients with Bell's palsy. Subjects and Methods This study included 29 patients diagnosed with Bell's palsy between January 2014 and May 2015 in our hospital. Patients were assorted into age groups and by severity of facial palsy, as determined by House-Brackmann Scale, and their taste thresholds were assessed by EGM and chemical taste tests. Results EGM showed that taste thresholds at four locations on the tongue and one location on the central soft palate, 1 cm from the palatine uvula, were significantly higher in Bell's palsy patients than in controls (p<0.05). In contrast, chemical taste tests showed no significant differences in taste thresholds between the two groups (p>0.05). The severity of facial palsy did not affect taste thresholds, as determined by both EGM and chemical taste tests (p>0.05). The overall mean electrical taste thresholds on EGM were higher in younger Bell's palsy patients than in healthy subjects, with the difference at the back-right area of the tongue differing significantly (p<0.05). In older individuals, however, no significant differences in taste thresholds were observed between Bell's palsy patients and healthy subjects (p>0.05). Conclusions Electrical taste thresholds were higher in Bell's palsy patients than in controls. These differences were observed in younger, but not in older, individuals. PMID:28417103

Evaluation of three different histamine concentrations in intradermal testing of normal cats and attempted determination of 'irritant' threshold concentrations for 48 allergens.

PubMed

Austel, Michaela; Hensel, Patrick; Jackson, Dawn; Vidyashankar, Anand; Zhao, Ying; Medleau, Linda

2006-06-01

The purpose of this study was to determine the optimal histamine concentration and 'irritant' allergen threshold concentrations in intradermal testing (IDT) in normal cats. Thirty healthy cats were tested with three different histamine concentrations and four different concentrations of each allergen. The optimal histamine concentration was determined to be 1: 50,000 w/v (0.05 mg mL(-1)). Using this histamine concentration, the 'irritant' threshold concentration for most allergens was above the highest concentrations tested (4,000 PNU mL(-1) for 41 allergens and 700 PNU mL(-1) for human dander). The 'irritant' threshold concentration for flea antigen was determined to be 1:750 w/v. More than 10% of the tested cats showed positive reactions to Dermatophagoides farinae, Dermatophagoides pteronyssinus, housefly, mosquito and moth at every allergen concentration, which suggests that the 'irritant' threshold concentration for these allergens is below 1,000 PNU mL(-1), the lowest allergen concentration tested. Our results confirm previous studies in indicating that allergen and histamine concentrations used in feline IDT may need to be revised.

Crack Growth Behavior in the Threshold Region for High Cycle Fatigue Loading

NASA Technical Reports Server (NTRS)

Forman, R. G.; Zanganeh, M.

2014-01-01

This paper describes the results of a research program conducted to improve the understanding of fatigue crack growth rate behavior in the threshold growth rate region and to answer a question on the validity of threshold region test data. The validity question relates to the view held by some experimentalists that using the ASTM load shedding test method does not produce valid threshold test results and material properties. The question involves the fanning behavior observed in threshold region of da/dN plots for some materials in which the low R-ratio data fans out from the high R-ratio data. This fanning behavior or elevation of threshold values in the low R-ratio tests is generally assumed to be caused by an increase in crack closure in the low R-ratio tests. Also, the increase in crack closure is assumed by some experimentalists to result from using the ASTM load shedding test procedure. The belief is that this procedure induces load history effects which cause remote closure from plasticity and/or roughness changes in the surface morphology. However, experimental studies performed by the authors have shown that the increase in crack closure is a result of extensive crack tip bifurcations that can occur in some materials, particularly in aluminum alloys, when the crack tip cyclic yield zone size becomes less than the grain size of the alloy. This behavior is related to the high stacking fault energy (SFE) property of aluminum alloys which results in easier slip characteristics. Therefore, the fanning behavior which occurs in aluminum alloys is a function of intrinsic dislocation property of the alloy, and therefore, the fanned data does represent the true threshold properties of the material. However, for the corrosion sensitive steel alloys tested in laboratory air, the occurrence of fanning results from fretting corrosion at the crack tips, and these results should not be considered to be representative of valid threshold properties because the fanning is eliminated when testing is performed in dry air.

NASA GRC and MSFC Space-Plasma Arc Testing Procedures

NASA Technical Reports Server (NTRS)

Ferguson, Dale C.; Vayner, Boris V.; Galofaro, Joel T,; Hillard, G. Barry; Vaughn, Jason; Schneider, Todd

2005-01-01

Tests of arcing and current collection in simulated space plasma conditions have been performed at the NASA Glenn Research Center (GRC) in Cleveland, Ohio, for over 30 years and at the Marshall Space Flight Center (MSFC) in Huntsville, Alabama, for almost as long. During this period, proper test conditions for accurate and meaningful space simulation have been worked out, comparisons with actual space performance in spaceflight tests and with real operational satellites have been made, and NASA has achieved our own internal standards for test protocols. It is the purpose of this paper to communicate the test conditions, test procedures, and types of analysis used at NASA GRC and MSFC to the space environmental testing community at large, to help with international space-plasma arcing-testing standardization. To be discussed are: 1.Neutral pressures, neutral gases, and vacuum chamber sizes. 2. Electron and ion densities, plasma uniformity, sample sizes, and Debuy lengths. 3. Biasing samples versus self-generated voltages. Floating samples versus grounded. 4. Power supplies and current limits. Isolation of samples from power supplies during arcs. 5. Arc circuits. Capacitance during biased arc-threshold tests. Capacitance during sustained arcing and damage tests. Arc detection. Prevention sustained discharges during testing. 6. Real array or structure samples versus idealized samples. 7. Validity of LEO tests for GEO samples. 8. Extracting arc threshold information from arc rate versus voltage tests. 9. Snapover and current collection at positive sample bias. Glows at positive bias. Kapon (R) pyrolisis. 10. Trigger arc thresholds. Sustained arc thresholds. Paschen discharge during sustained arcing. 11. Testing for Paschen discharge threshold. Testing for dielectric breakdown thresholds. Testing for tether arcing. 12. Testing in very dense plasmas (ie thruster plumes). 13. Arc mitigation strategies. Charging mitigation strategies. Models. 14. Analysis of test results. Finally, the necessity of testing will be emphasized, not to the exclusion of modeling, but as part of a complete strategy for determining when and if arcs will occur, and preventing them from occurring in space.

NASA GRC and MSFC Space-Plasma Arc Testing Procedures

NASA Technical Reports Server (NTRS)

Ferguson, Dale C.a; Vayner, Boris V.; Galofaro, Joel T.; Hillard, G. Barry; Vaughn, Jason; Schneider, Todd

2005-01-01

Tests of arcing and current collection in simulated space plasma conditions have been performed at the NASA Glenn Research Center (GRC) in Cleveland, Ohio, for over 30 years and at the Marshall Space flight Center (MSFC) for almost as long. During this period, proper test conditions for accurate and meaningful space simulation have been worked out, comparisons with actual space performance in spaceflight tests and with real operational satellites have been made, and NASA has achieved our own internal standards for test protocols. It is the purpose of this paper to communicate the test conditions, test procedures, and types of analysis used at NASA GRC and MSFC to the space environmental testing community at large, to help with international space-plasma arcing testing standardization. To be discussed are: 1. Neutral pressures, neutral gases, and vacuum chamber sizes. 2. Electron and ion densities, plasma uniformity, sample sizes, and Debye lengths. 3. Biasing samples versus self-generated voltages. Floating samples versus grounded. 4. Power supplies and current limits. Isolation of samples from power supplies during arcs. Arc circuits. Capacitance during biased arc-threshold tests. Capacitance during sustained arcing and damage tests. Arc detection. Preventing sustained discharges during testing. 5. Real array or structure samples versus idealized samples. 6. Validity of LEO tests for GEO samples. 7. Extracting arc threshold information from arc rate versus voltage tests. 8 . Snapover and current collection at positive sample bias. Glows at positive bias. Kapton pyrolization. 9. Trigger arc thresholds. Sustained arc thresholds. Paschen discharge during sustained arcing. 10. Testing for Paschen discharge thresholds. Testing for dielectric breakdown thresholds. Testing for tether arcing. 11. Testing in very dense plasmas (ie thruster plumes). 12. Arc mitigation strategies. Charging mitigation strategies. Models. 13. Analysis of test results. Finally, the necessity of testing will be emphasized, not to the exclusion of modeling, but as part of a complete strategy for determining when and if arcs will occur, and preventing them from occurring in space.

Intelligence and Creativity: Over the Threshold Together?

ERIC Educational Resources Information Center

Welter, Marisete Maria; Jaarsveld, Saskia; van Leeuwen, Cees; Lachmann, Thomas

2016-01-01

Threshold theory predicts a positive correlation between IQ and creativity scores up to an IQ level of 120 and no correlation above this threshold. Primary school children were tested at beginning (N = 98) and ending (N = 70) of the school year. Participants performed the standard progressive matrices (SPM) and the Test of Creative…

Oxygen Concentration Flammability Threshold Tests for the Constellation Program

NASA Technical Reports Server (NTRS)

Williams, James H.

2007-01-01

CEV atmosphere will likely change because craft will be used as LEO spacecraft, lunar spacecraft, orbital spacecraft. Possible O2 % increase and overall pressure decrease pressure vessel certs on spacecraft. Want 34% minimum threshold. Higher, better when atmosphere changes. WSTF suggests testing all materials/components to find flammability threshold, pressure and atmosphere.

Comparison of the anticonvulsant potency of various diuretic drugs in the maximal electroshock-induced seizure threshold test in mice.

PubMed

Załuska, Katarzyna; Kondrat-Wróbel, Maria W; Łuszczki, Jarogniew J

2018-05-01

The coexistence of seizures and arterial hypertension requires an adequate and efficacious treatment involving both protection from seizures and reduction of high arterial blood pressure. Accumulating evidence indicates that some diuretic drugs (with a well-established position in the treatment of arterial hypertension) also possess anticonvulsant properties in various experimental models of epilepsy. The aim of this study was to assess the anticonvulsant potency of 6 commonly used diuretic drugs (i.e., amiloride, ethacrynic acid, furosemide, hydrochlorothiazide, indapamide, and spironolactone) in the maximal electroshock-induced seizure threshold (MEST) test in mice. Doses of the studied diuretics and their corresponding threshold increases were linearly related, allowing for the determination of doses which increase the threshold for electroconvulsions in drug-treated animals by 20% (TID20 values) over the threshold in control animals. Amiloride, hydrochlorothiazide and indapamide administered systemically (intraperitoneally - i.p.) increased the threshold for maximal electroconvulsions in mice, and the experimentally-derived TID20 values in the maximal electroshock seizure threshold test were 30.2 mg/kg for amiloride, 68.2 mg/kg for hydrochlorothiazide and 3.9 mg/kg for indapamide. In contrast, ethacrynic acid (up to 100 mg/kg), furosemide (up to 100 mg/kg) and spironolactone (up to 50 mg/kg) administered i.p. had no significant impact on the threshold for electroconvulsions in mice. The studied diuretics can be arranged with respect to their anticonvulsant potency in the MEST test as follows: indapamide > amiloride > hydrochlorothiazide. No anticonvulsant effects were observed for ethacrynic acid, furosemide or spironolactone in the MEST test in mice.

A critique of the use of indicator-species scores for identifying thresholds in species responses

USGS Publications Warehouse

Cuffney, Thomas F.; Qian, Song S.

2013-01-01

Identification of ecological thresholds is important both for theoretical and applied ecology. Recently, Baker and King (2010, King and Baker 2010) proposed a method, threshold indicator analysis (TITAN), to calculate species and community thresholds based on indicator species scores adapted from Dufrêne and Legendre (1997). We tested the ability of TITAN to detect thresholds using models with (broken-stick, disjointed broken-stick, dose-response, step-function, Gaussian) and without (linear) definitive thresholds. TITAN accurately and consistently detected thresholds in step-function models, but not in models characterized by abrupt changes in response slopes or response direction. Threshold detection in TITAN was very sensitive to the distribution of 0 values, which caused TITAN to identify thresholds associated with relatively small differences in the distribution of 0 values while ignoring thresholds associated with large changes in abundance. Threshold identification and tests of statistical significance were based on the same data permutations resulting in inflated estimates of statistical significance. Application of bootstrapping to the split-point problem that underlies TITAN led to underestimates of the confidence intervals of thresholds. Bias in the derivation of the z-scores used to identify TITAN thresholds and skewedness in the distribution of data along the gradient produced TITAN thresholds that were much more similar than the actual thresholds. This tendency may account for the synchronicity of thresholds reported in TITAN analyses. The thresholds identified by TITAN represented disparate characteristics of species responses that, when coupled with the inability of TITAN to identify thresholds accurately and consistently, does not support the aggregation of individual species thresholds into a community threshold.

Rod-cone interaction in light adaptation

PubMed Central

Latch, M.; Lennie, P.

1977-01-01

1. The increment-threshold for a small test spot in the peripheral visual field was measured against backgrounds that were red or blue. 2. When the background was a large uniform field, threshold over most of the scotopic range depended exactly upon the background's effect upon rods. This confirms Flamant & Stiles (1948). But when the background was small, threshold was elevated more by a long wave-length than a short wave-length background equated for its effect on rods. 3. The influence of cones was explored in a further experiment. The scotopic increment-threshold was established for a short wave-length test spot on a large, short wave-length background. Then a steady red circular patch, conspicuous to cones, but below the increment-threshold for rod vision, was added to the background. When it was small, but not when it was large, this patch substantially raised the threshold for the test. 4. When a similar experiment was made using, instead of a red patch, a short wave-length one that was conspicuous in rod vision, threshold varied similarly with patch size. These results support the notion that the influence of small backgrounds arises in some size-selective mechanism that is indifferent to the receptor system in which visual signals originate. Two corollaries of this hypothesis were tested in further experiments. 5. A small patch was chosen so as to lift scotopic threshold substantially above its level on a uniform field. This threshold elevation persisted for minutes after extinction of the patch, but only when the patch was small. A large patch made bright enough to elevate threshold by as much as the small one gave rise to no corresponding after-effect. 6. Increment-thresholds for a small red test spot, detected through cones, followed the same course whether a large uniform background was long- or short wave-length. When the background was small, threshold upon the short wave-length one began to rise for much lower levels of background illumination, suggesting the influence of rods. This was confirmed by repeating the experiment after a strong bleach when the cones, but not rods, had fully recovered their sensitivity. Increment-thresholds upon small backgrounds of long or short wave-lengths then followed the same course. PMID:894602

Reliability of the method of levels for determining cutaneous temperature sensitivity

NASA Astrophysics Data System (ADS)

Jakovljević, Miroljub; Mekjavić, Igor B.

2012-09-01

Determination of the thermal thresholds is used clinically for evaluation of peripheral nervous system function. The aim of this study was to evaluate reliability of the method of levels performed with a new, low cost device for determining cutaneous temperature sensitivity. Nineteen male subjects were included in the study. Thermal thresholds were tested on the right side at the volar surface of mid-forearm, lateral surface of mid-upper arm and front area of mid-thigh. Thermal testing was carried out by the method of levels with an initial temperature step of 2°C. Variability of thermal thresholds was expressed by means of the ratio between the second and the first testing, coefficient of variation (CV), coefficient of repeatability (CR), intraclass correlation coefficient (ICC), mean difference between sessions (S1-S2diff), standard error of measurement (SEM) and minimally detectable change (MDC). There were no statistically significant changes between sessions for warm or cold thresholds, or between warm and cold thresholds. Within-subject CVs were acceptable. The CR estimates for warm thresholds ranged from 0.74°C to 1.06°C and from 0.67°C to 1.07°C for cold thresholds. The ICC values for intra-rater reliability ranged from 0.41 to 0.72 for warm thresholds and from 0.67 to 0.84 for cold thresholds. S1-S2diff ranged from -0.15°C to 0.07°C for warm thresholds, and from -0.08°C to 0.07°C for cold thresholds. SEM ranged from 0.26°C to 0.38°C for warm thresholds, and from 0.23°C to 0.38°C for cold thresholds. Estimated MDC values were between 0.60°C and 0.88°C for warm thresholds, and 0.53°C and 0.88°C for cold thresholds. The method of levels for determining cutaneous temperature sensitivity has acceptable reliability.

Quantitative Sensory Testing and Current Perception Threshold Testing in Patients With Chronic Pain Following Lower Extremity Fracture.

PubMed

Griffioen, Mari A; Greenspan, Joel D; Johantgen, Meg; Von Rueden, Kathryn; O'Toole, Robert V; Dorsey, Susan G; Renn, Cynthia L

2018-01-01

Chronic pain is a significant problem for patients with lower extremity injuries. While pain hypersensitivity has been identified in many chronic pain conditions, it is not known whether patients with chronic pain following lower extremity fracture report pain hypersensitivity in the injured leg. To quantify and compare peripheral somatosensory function and sensory nerve activation thresholds in persons with chronic pain following lower extremity fractures with a cohort of persons with no history of lower extremity fractures. This was a cross-sectional study where quantitative sensory testing and current perception threshold testing were conducted on the injured and noninjured legs of cases and both legs of controls. A total of 14 cases and 28 controls participated in the study. Mean time since injury at the time of testing for cases was 22.3 (standard deviation = 12.1) months. The warmth detection threshold ( p = .024) and nerve activation thresholds at 2,000 Hz ( p < .001) and 250 Hz ( p = .002), respectively, were significantly higher in cases compared to controls. This study suggests that patients with chronic pain following lower extremity fractures may experience hypoesthesia in the injured leg, which contrasts with the finding of hyperesthesia previously observed in other chronic pain conditions but is in accord with patients with nerve injuries and surgeries. This is the first study to examine peripheral sensory nerve function at the site of injury in patients with chronic pain following lower extremity fractures using quantitative sensory testing and current perception threshold testing.

Determination of threshold and maximum operating electric stresses for selected high voltage insulations. Task 2: Investigation of oil-filled paper insulated cables

NASA Astrophysics Data System (ADS)

Sosnowski, M.; Eager, G. S., Jr.

1983-06-01

Threshold voltage of oil-impregnated paper insulated cables are investigaed. Experimental work was done on model cables specially manufactured for this project. The cables were impregnated with mineral and with synthetic oils. Standard impulse breakdown voltage tests and impulse voltage breakdown tests with dc prestressing were performed at room temperature and at 1000C. The most important result is the finding of very high level of threshold voltage stress for oil-impregnated paper insulated cables. This threshold voltage is approximately 1.5 times higher than the threshold voltage or crosslinked polyethylene insulated cables.

Hypoxia, color vision deficiencies, and blood oxygen saturation.

PubMed

Hovis, Jeffery K; Milburn, Nelda J; Nesthus, Thomas E

2012-02-01

Chromatic thresholds were measured using the Cambridge Colour Test (CCT), the Colour Assessment and Diagnosis (CAD) test, and the Cone Specific Contrast Test (CSCT) at ground and 3780 m (12,400 ft) for subjects with normal color vision and red-green color vision defects. The CAD revealed a small (~10%) increase in the red-green thresholds for the trichromatic subjects and a similar increase in the blue-yellow thresholds for the dichromats. The other two color vision tests did not reveal any significant change in chromatic thresholds. The CAD results for the trichromats were consistent with a rotation of the discrimination ellipse counterclockwise with little change in the elliptical area. This alteration in the color discrimination ellipse can occur when retinal illumination is lowered. © 2012 Optical Society of America

Correlation of gas exchange threshold and first muscle oxyhemoglobin inflection point with time-to-exhaustion during heavy-intensity exercise.

PubMed

Coquart, Jérémy B; Mucci, Patrick; L'hermette, Maxime; Chamari, Karim; Tourny, Claire; Garcin, Murielle

2017-03-01

The twofold aim of the study was to: 1) compare the gas exchange threshold (GET), the first oxyhemoglobin inflection point ([O2Hb]-T), and perceptual threshold as determined during an incremental exercise test, and 2) investigate the link between each threshold and time-to-exhaustion during heavy intensity exercise. Fourteen competitive cyclists performed an incremental exercise test to exhaustion on a cycloergometer to determine the different thresholds and peak workload (Wpeak). The participants then performed a sub-maximal constant workload test (90% Wpeak) to exhaustion to determine time-to-exhaustion. The thresholds were identified from: 1) the first breakpoint in the oxygen uptake vs. carbon dioxide output curve (GET), 2) the [O2Hb]-T, and 3) a rating of 13 in perceived exertion (perceptual threshold: RPE13-T). Oxygen uptake at the different thresholds was not significantly different (P>0.05). Moreover, GET and [O2Hb]-T were significantly correlated: 1) to each other (r≥0.79; P≤0.001), and 2) to time-to-exhaustion (r=0.81 and r=0.72, respectively; P<0.01). RPE13-T, however, was not significantly correlated with the time-to-exhaustion (P=0.148). The anaerobic threshold as identified from GET was concomitant to [O2Hb]-T. Both thresholds were correlated to time-to-exhaustion, and could therefore be used as a performance index in middle-duration events.

Retesting The Validity Of A Specific Field Test For Judo Training

PubMed Central

Santos, Luis; González, Vicente; Iscar, Marta; Brime, Juan I.; Fernández-Río, Javier; Rodríguez, Blanca; Montoliu, Mª Ángeles

2011-01-01

The main goal of this research project was to retest the validity of a specifically designed judo field test (Santos Test) in a different group of judokas. Eight (n=8) national-level male judokas underwent laboratory and field testing. The mean data (mean +/− SD) obtained in the laboratory tests was: HRmax: 200 ± 4.0 beats × min−1, VO2 max: 52.8 ± 7.9 ± ml × kg−1 × min−1, lactate max: 12 ± 2.5 mmol × l−1, HR at the anaerobic threshold: 174.2 ± 9.4 beats × min−1, percentage of maximum heart rate at which the anaerobic threshold appears: 87 ± 3.6 %, lactate threshold: 4.0 ± 0.2 mmol × l−1, and RPE: 17.2 ± 1.0. The mean data obtained in the field test (Santos) was: HRmax: 201.3 ± 4.1 beats × min−1, VO2 max: 55.6 ± 5.8 ml × kg−1 × min−1, lactate max: 15.6 ± 2.8 mmol × l−1, HR at the anaerobic threshold: 173.2 ± 4.3 beats × min−1, percentage of maximum heart rate at which the anaerobic threshold appears: 86 ± 2.5 %, lactate threshold: 4.0 ± 0.2 mmol × l−1, and RPE: 16.7 ± 1.0. There were no significant differences between the data obtained on both tests in any of the parameters, except for maximum lactate concentration. Therefore, the Santos test can be considered a valid tool specific for judo training. PMID:23486994

Overcoming the effects of false positives and threshold bias in graph theoretical analyses of neuroimaging data.

PubMed

Drakesmith, M; Caeyenberghs, K; Dutt, A; Lewis, G; David, A S; Jones, D K

2015-09-01

Graph theory (GT) is a powerful framework for quantifying topological features of neuroimaging-derived functional and structural networks. However, false positive (FP) connections arise frequently and influence the inferred topology of networks. Thresholding is often used to overcome this problem, but an appropriate threshold often relies on a priori assumptions, which will alter inferred network topologies. Four common network metrics (global efficiency, mean clustering coefficient, mean betweenness and smallworldness) were tested using a model tractography dataset. It was found that all four network metrics were significantly affected even by just one FP. Results also show that thresholding effectively dampens the impact of FPs, but at the expense of adding significant bias to network metrics. In a larger number (n=248) of tractography datasets, statistics were computed across random group permutations for a range of thresholds, revealing that statistics for network metrics varied significantly more than for non-network metrics (i.e., number of streamlines and number of edges). Varying degrees of network atrophy were introduced artificially to half the datasets, to test sensitivity to genuine group differences. For some network metrics, this atrophy was detected as significant (p<0.05, determined using permutation testing) only across a limited range of thresholds. We propose a multi-threshold permutation correction (MTPC) method, based on the cluster-enhanced permutation correction approach, to identify sustained significant effects across clusters of thresholds. This approach minimises requirements to determine a single threshold a priori. We demonstrate improved sensitivity of MTPC-corrected metrics to genuine group effects compared to an existing approach and demonstrate the use of MTPC on a previously published network analysis of tractography data derived from a clinical population. In conclusion, we show that there are large biases and instability induced by thresholding, making statistical comparisons of network metrics difficult. However, by testing for effects across multiple thresholds using MTPC, true group differences can be robustly identified. Copyright © 2015. Published by Elsevier Inc.

A Size Effect on the Fatigue Crack Growth Rate Threshold of Alloy 718

NASA Technical Reports Server (NTRS)

Garr, K. R.; Hresko, G. C., III

1998-01-01

Fatigue crack growth rate (FCGR) tests were conducted on Alloy 718 in the solution annealed and aged condition at room temperature. In each test, the FCGR threshold was measured using the decreasing (Delta)K method. Initial testing was at two facilities, one of which used C(T) specimens with W = 127 mm. Previous data at the other facility had been obtained with specimens with W = 50.8 mm. A comparison of test results at R = 0.1 showed that the threshold for the 127 mm specimen was considerably higher than that of the 50.8 mm specimen. A check showed that this difference was not due to a heat-to-heat or lab-to-lab variation. Additional tests were conducted on specimens with W = 25.4 mm and at other R values. Data for the various specimens is presented along with parameters usually used to describe threshold behavior.

Experimental Psychological Stress on Quantitative Sensory Testing Response in Patients with Temporomandibular Disorders.

PubMed

Araújo Oliveira Ferreira, Dyna Mara; Costa, Yuri Martins; de Quevedo, Henrique Müller; Bonjardim, Leonardo Rigoldi; Rodrigues Conti, Paulo César

2018-05-15

To assess the modulatory effects of experimental psychological stress on the somatosensory evaluation of myofascial temporomandibular disorder (TMD) patients. A total of 20 women with myofascial TMD and 20 age-matched healthy women were assessed by means of a standardized battery of quantitative sensory testing. Cold detection threshold (CDT), warm detection threshold (WDT), cold pain threshold (CPT), heat pain threshold (HPT), mechanical pain threshold (MPT), wind-up ratio (WUR), and pressure pain threshold (PPT) were performed on the facial skin overlying the masseter muscle. The variables were measured in three sessions: before (baseline) and immediately after the Paced Auditory Serial Addition Task (PASAT) (stress) and then after a washout period of 20 to 30 minutes (poststress). Mixed analysis of variance (ANOVA) was applied to the data, and the significance level was set at P = .050. A significant main effect of the experimental session on all thermal tests was found (ANOVA: F > 4.10, P < .017), where detection tests presented an increase in thresholds in the poststress session compared to baseline (CDT, P = .012; WDT, P = .040) and pain thresholds were reduced in the stress (CPT, P < .001; HPT, P = .001) and poststress sessions (CPT, P = .005; HPT, P = .006) compared to baseline. In addition, a significant main effect of the study group on all mechanical tests (MPT, WUR, and PPT) was found (ANOVA: F > 4.65, P < .037), where TMD patients were more sensitive than healthy volunteers. Acute mental stress conditioning can modulate thermal sensitivity of the skin overlying the masseter in myofascial TMD patients and healthy volunteers. Therefore, psychological stress should be considered in order to perform an unbiased somatosensory assessment of TMD patients.

Effects of reference analgesics and psychoactive drugs on the noxious heat threshold of mice measured by an increasing-temperature water bath.

PubMed

Boros, Melinda; Benkó, Rita; Bölcskei, Kata; Szolcsányi, János; Barthó, Loránd; Pethő, Gábor

2013-12-01

The study aimed at validating an increasing-temperature water bath suitable for determining the noxious heat threshold for use in mice. The noxious heat threshold was determined by immersing the tail of the gently held awake mouse into a water container whose temperature was near-linearly increased at a rate of 24°C/min. until the animal withdrew its tail, that is, heating attained the noxious threshold. The effects of standard analgesic, neuroleptic and anxiolytic drugs were investigated in a parallel way on both the noxious heat threshold and the psychomotor activity assessed by the open field test. Morphine, diclofenac and metamizol (dipyrone) elevated the heat threshold of mice with minimum effective doses of 6, 30 and 1000 mg/kg i.p., respectively. These doses of morphine and diclofenac failed to induce any remarkable effect on psychomotor activity in the open field test while that of metamizol exerted a profound inhibition. The anxiolytic diazepam and the neuroleptic droperidol at doses evoking a mild and moderate, respectively, psychomotor inhibition failed to alter the heat threshold. Combination of a subliminal dose of morphine (regarding both antinociceptive and psychomotor inhibitory action) with diclofenac, metamizol, diazepam or droperidol at doses also subliminal regarding the thermal antinociceptive effect elevated the noxious heat threshold without major additional effects in the open field test. It is concluded that the increasing-temperature water bath is suitable for studying the thermal antinociceptive effects of morphine and diclofenac as well as the morphine-sparing action of diclofenac, metamizol, droperidol and diazepam. Behavioural testing is recommended when testing analgesics. © 2013 Nordic Pharmacological Society. Published by John Wiley & Sons Ltd.

The effect of cockpit noise on the temporary threshold shift of Cessna 172SP flight instructors

NASA Astrophysics Data System (ADS)

Bellini, Andrew Robert

The purpose of this thesis was to study the temporary threshold shift of general aviation flight instructors resulting from their working environment. Exposure to noise before a temporary threshold shift completely recovers can cause a permanent threshold shift with no possibility of recovery, resulting in permanent hearing loss. A result showing minimal to no temporary threshold shift would indicate that hearing personal protective equipment is working properly. This study used sound-level measurements, and audiometric testing, together with survey data to determine whether or not flight instructors were at risk for potential hearing impairment due to temporary threshold shift. Independent t-tests and descriptive statistics were used in analyzing the data. It was determined that there was a difference in temporary threshold shift based on the number of hours a flight instructor flies in a Cessna 172SP for only one frequency - 2000Hz in the left ear. All other frequencies tested in both ears showed no difference. Because there was a very low mean temporary threshold shift at 2000Hz in the left ear and no differences shown for all other frequencies in both ears, it was concluded that there was no need to improve or require additional hearing personal protective equipment, or to require decreased exposure times to aircraft noise.

Role of ocular VEMP test in assessing the occurrence of vertigo in otosclerosis patients.

PubMed

Lin, Kuei-You; Young, Yi-Ho

2015-01-01

This study adopted an inner ear test battery comprising audiometry, caloric test, ocular vestibular-evoked myogenic potential (oVEMP) test and cervical VEMP (cVEMP) test to find the factors related to the occurrence of vertigo in patients with otosclerosis. Fifty otosclerosis patients comprising 27 patients with vertigo (Group A) and 23 patients without vertigo/dizziness (Group B) were enrolled. Each patient underwent otoscopy, image study, audiometry, caloric test, and oVEMP and cVEMP tests via bone vibration stimuli. The sequence of inner ear deficits in Group A was in the order from oVEMP test (84%), cVEMP test (51%), caloric test (38%) and mean bone-conducted (BC) hearing threshold (14%), exhibiting a significantly declining trend (p<0.001). The rate of inner ear dysfunction in Group B also declined significantly but in a different order - cVEMP test (55%), oVEMP test (52%), mean BC hearing threshold (33%), and caloric test (18%). Comparison between the two groups revealed a significant difference in the oVEMP test results (p<0.01), but not in the results of the BC hearing threshold, caloric test or cVEMP test (p>0.05). Further, no significant differences existed between the BC hearing threshold and vestibular function test results. Otosclerosis patients with vertigo have more frequent abnormalities of oVEMPs to impulsive stimulation than do those without, consistent with more frequent abnormalities of the utricle. Abnormalities of oVEMPs and cVEMPs are more frequent than for caloric testing and BC hearing thresholds. The relative frequency of abnormalities may reflect the degree of pathological involvement of the utricle, saccule, semicircular canals and cochlea in otosclerosis patients with vertigo. Copyright © 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Effects of programming threshold and maplaw settings on acoustic thresholds and speech discrimination with the MED-EL COMBI 40+ cochlear implant.

PubMed

Boyd, Paul J

2006-12-01

The principal task in the programming of a cochlear implant (CI) speech processor is the setting of the electrical dynamic range (output) for each electrode, to ensure that a comfortable loudness percept is obtained for a range of input levels. This typically involves separate psychophysical measurement of electrical threshold ([theta] e) and upper tolerance levels using short current bursts generated by the fitting software. Anecdotal clinical experience and some experimental studies suggest that the measurement of [theta]e is relatively unimportant and that the setting of upper tolerance limits is more critical for processor programming. The present study aims to test this hypothesis and examines in detail how acoustic thresholds and speech recognition are affected by setting of the lower limit of the output ("Programming threshold" or "PT") to understand better the influence of this parameter and how it interacts with certain other programming parameters. Test programs (maps) were generated with PT set to artificially high and low values and tested on users of the MED-EL COMBI 40+ CI system. Acoustic thresholds and speech recognition scores (sentence tests) were measured for each of the test maps. Acoustic thresholds were also measured using maps with a range of output compression functions ("maplaws"). In addition, subjective reports were recorded regarding the presence of "background threshold stimulation" which is occasionally reported by CI users if PT is set to relatively high values when using the CIS strategy. Manipulation of PT was found to have very little effect. Setting PT to minimum produced a mean 5 dB (S.D. = 6.25) increase in acoustic thresholds, relative to thresholds with PT set normally, and had no statistically significant effect on speech recognition scores on a sentence test. On the other hand, maplaw setting was found to have a significant effect on acoustic thresholds (raised as maplaw is made more linear), which provides some theoretical explanation as to why PT has little effect when using the default maplaw of c = 500. Subjective reports of background threshold stimulation showed that most users could perceive a relatively loud auditory percept, in the absence of microphone input, when PT was set to double the behaviorally measured electrical thresholds ([theta]e), but that this produced little intrusion when microphone input was present. The results of these investigations have direct clinical relevance, showing that setting of PT is indeed relatively unimportant in terms of speech discrimination, but that it is worth ensuring that PT is not set excessively high, as this can produce distracting background stimulation. Indeed, it may even be set to minimum values without deleterious effect.

Are pain location and physical examinations useful in locating a tear site of the rotator cuff?

PubMed

Itoi, Eiji; Minagawa, Hiroshi; Yamamoto, Nobuyuki; Seki, Nobutoshi; Abe, Hidekazu

2006-02-01

Pain is the most common symptom of patients with rotator cuff tendinopathy, but little is known about the relationship between the site of pain and the site of cuff pathologic lesions. Also, accuracies of physical examinations used to locate a tear by assessing the muscle strength seem to be affected by the threshold for muscle weakness, but no studies have been reported regarding the efficacies of physical examinations in reference to their threshold. Pain location is useful in locating a tear site. Efficacies of physical examinations to evaluate the function of the cuff muscles depend on the threshold for muscle weakness. Case series; Level of evidence, 4. The authors retrospectively reviewed the clinical charts of 160 shoulders of 149 patients (mean age, 53 years) with either rotator cuff tears (140 shoulders) or cuff tendinitis (20 shoulders). The location of pain was recorded on a standardized form with 6 different areas. The diagnostic accuracies of the following tests were assessed with various thresholds for muscle weakness: supraspinatus test, the external rotation strength test, and the lift-off test. Lateral and anterior portions of the shoulder were the most common sites of pain regardless of existence of tear or tear location. The supraspinatus test was most accurate when it was assessed to have positive results with the muscle strength less than manual muscle testing grade 5, whereas the lift-off test was most accurate with a threshold less than grade 3. The external rotation strength test was most accurate with a threshold of less than grade 4+. The authors conclude that pain location is not useful in locating the site of a tear, whereas the physical examinations aiming to locate the tear site are clinically useful when assessed to have positive results with appropriate threshold for muscle weakness.

Evaluation of Anticonvulsant, Antidepressant-, and Anxiolytic-like Effects of an Aqueous Extract from Cultured Mycelia of the Lingzhi or Reishi Medicinal Mushroom Ganoderma lucidum (Higher Basidiomycetes) in Mice.

PubMed

Socala, Katarzyna; Nieoczym, Dorota; Grzywnowicz, Krzysztof; Stefaniuk, Dawid; Wlaz, Piotr

2015-01-01

Ganoderma lucidum is a well-known medicinal mushroom with a long history of use. This study was designed to assess the anticonvulsant potential of an aqueous extract from cultured G. lucidum mycelium in 3 acute seizure models: timed intravenous pentylenetetrazole infusion, maximal electroshock seizure threshold, and 6-Hz-induced psychomotor seizure tests in mice. Moreover, antidepressant-like and anxiolytic-like effects of G. lucidum were evaluated using the forced swim test and the elevated plus maze test in mice, respectively. No changes in seizure thresholds in the intravenous pentylenetetrazole and maximal electroshock seizure threshold tests after acute treatment with G. lucidum extract (200-600 mg/kg) was observed. However, the studied extract (100-400 mg/kg) significantly increased the threshold for psychomotor seizures in the 6-Hz seizure test. In the forced swim test, G. lucidum (100-400 mg/kg) significantly reduced the duration of immobility. No anxiolytic-like or sedative effects were reported in mice pretreated with the extract (400-600 mg/kg). G. lucidum extract (50-2400 mg/kg) did not produce toxic effects in the chimney test (motor coordination) or grip-strength test (neuromuscular strength). Further studies are required to explain the neuropharmacological effects of G. lucidum and to identify its active ingredients that may affect seizure threshold, mood, or anxiety.

Salicylate-induced changes in auditory thresholds of adolescent and adult rats.

PubMed

Brennan, J F; Brown, C A; Jastreboff, P J

1996-01-01

Shifts in auditory intensity thresholds after salicylate administration were examined in postweanling and adult pigmented rats at frequencies ranging from 1 to 35 kHz. A total of 132 subjects from both age levels were tested under two-way active avoidance or one-way active avoidance paradigms. Estimated thresholds were inferred from behavioral responses to presentations of descending and ascending series of intensities for each test frequency value. Reliable threshold estimates were found under both avoidance conditioning methods, and compared to controls, subjects at both age levels showed threshold shifts at selective higher frequency values after salicylate injection, and the extent of shifts was related to salicylate dose level.

Comparisons between detection threshold and loudness perception for individual cochlear implant channels

PubMed Central

Bierer, Julie Arenberg; Nye, Amberly D

2014-01-01

Objective The objective of the present study, performed in cochlear implant listeners, was to examine how the level of current required to detect single-channel electrical pulse trains relates to loudness perception on the same channel. The working hypothesis was that channels with relatively high thresholds, when measured with a focused current pattern, interface poorly to the auditory nerve. For such channels a smaller dynamic range between perceptual threshold and the most comfortable loudness would result, in part, from a greater sensitivity to changes in electrical field spread compared to low-threshold channels. The narrower range of comfortable listening levels may have important implications for speech perception. Design Data were collected from eight, adult cochlear implant listeners implanted with the HiRes90k cochlear implant (Advanced Bionics Corp.). The partial tripolar (pTP) electrode configuration, consisting of one intracochlear active electrode, two flanking electrodes carrying a fraction (σ) of the return current, and an extracochlear ground, was used for stimulation. Single-channel detection thresholds and most comfortable listening levels were acquired using the most focused pTP configuration possible (σ ≥ 0.8) to identify three channels for further testing – those with the highest, median, and lowest thresholds – for each subject. Threshold, equal-loudness contours (at 50% of the monopolar dynamic range), and loudness growth functions were measured for each of these three test channels using various partial tripolar fractions. Results For all test channels, thresholds increased as the electrode configuration became more focused. The rate of increase with the focusing parameter σ was greatest for the high-threshold channel compared to the median- and low-threshold channels. The 50% equal-loudness contours exhibited similar rates of increase in level across test channels and subjects. Additionally, test channels with the highest thresholds had the narrowest dynamic ranges (for σ ≥ 0.5) and steepest growth of loudness functions for all electrode configurations. Conclusions Together with previous studies using focused stimulation, the results suggest that auditory responses to electrical stimuli at both threshold and suprathreshold current levels are not uniform across the electrode array of individual cochlear implant listeners. Specifically, the steeper growth of loudness and thus smaller dynamic ranges observed for high-threshold channels are consistent with a degraded electrode-neuron interface, which could stem from lower numbers of functioning auditory neurons or a relatively large distance between the neurons and electrodes. These findings may have potential implications for how stimulation levels are set during the clinical mapping procedure, particularly for speech-processing strategies that use focused electrical fields. PMID:25036146

A Specimen Size Effect on the Fatigue Crack Growth Rate Threshold of IN 718

NASA Technical Reports Server (NTRS)

Garr, K. R.; Hresko, G. C., III

1998-01-01

Fatigue crack growth rate (FCGR) tests were conducted on IN 718 in the solution annealed and aged condition at room temperature in accordance with E647-87. As part of each test, the FCGR threshold was measured using the decreasing Delta K method. A new heat of material was being tested and some of this material was sent to a different laboratory which wanted to use a specimen with a 127 mm width. Threshold data previously had been established on specimens with a width of 50.8 mm. As a check of the laboratory, tests were conducted at room temperature and R equal to 0.1 for comparison with the earlier data. The results were a threshold significantly higher than previously observed. Interchanging of specimen sizes and laboratories showed that the results were not due to a heat-to-heat or lab-to-lab variation. The results to be presented here are those obtained at the original laboratory. Growth rates were measured using the electric potential drop technique at R values of 0.1, 0.7, and 0.9. Compact tension specimen sizes with planer dimensions of 25.4 mm, 50.8 mm, and 127 mm were used. Crack growth rates at threshold were generally below 2.5 X 10(exp -8) mm / cycle. Closure measurements were made on some of the specimens by a manual procedure using a clip gage. When the crack growth rate data for the specimens tested at R equal to 0.1 were plotted as a function of applied Delta K, the thresholds varied with specimen width. The larger the width, the higher the threshold. The thresholds varied from 6.5 MPa-m(exp 1/2) for the 25.4 mm specimen to 15.4 MPa-m(exp 1/2) for the 127 mm specimen. At R equal to 0.7, the 25.4 mm and 50.8 mm specimens had essentially the same threshold, about 2.9 MPa-m(exp 1/2)while the 127 mm specimen had a threshold of 4.5 MPa-m(exp 1/2). When plotted as a function of effective Delta K, the R equal to 0.1 data are essentially normalized. Various aspects of the test procedure will be discussed as well as the results of analysis of the data using some different closure models.

A window on perception: Response times of odontocete cetaceans in audiometric tests

NASA Astrophysics Data System (ADS)

Blackwood, Diane J.; Ridgway, Sam H.; Evans, William E.

2002-05-01

A standard psychometric measurement is response time, the interval elapsing between a stimulus and a response. While studies of response time have been published for humans and other terrestrial mammals, this study marks the first report of response times for odontocete cetaceans at threshold in an audiometric task. Two white whales (Delphinapterus leucas) and four Atlantic bottlenose dolphins (Tursiops truncatus) were given audiometric tests to determine masked hearing thresholds. Animals were tested at 26 frequencies over a range from 200 Hz to 100 kHz using pure tones. The test tone amplitudes covered a range of 20 dB re 1 microPascal including the hearing threshold of the animal at that frequency. Hearing thresholds varied from 87.5 dB to 125.5 dB depending on frequency, masking noise intensity and individual animal. Data was analyzed to determine characteristic relationships between response time and amplitude of test tone for each frequency and animal. The two whales responded significantly slower (640 ms, 0.001) than the four dolphins (430 ms). As in terrestrial animals, reaction time became shorter as stimulus strength increased. At threshold, median response time across frequencies within each animal varied about 150 ms.

Testing for a Debt-Threshold Effect on Output Growth.

PubMed

Lee, Sokbae; Park, Hyunmin; Seo, Myung Hwan; Shin, Youngki

2017-12-01

Using the Reinhart-Rogoff dataset, we find a debt threshold not around 90 per cent but around 30 per cent, above which the median real gross domestic product (GDP) growth falls abruptly. Our work is the first to formally test for threshold effects in the relationship between public debt and median real GDP growth. The null hypothesis of no threshold effect is rejected at the 5 per cent significance level for most cases. While we find no evidence of a threshold around 90 per cent, our findings from the post-war sample suggest that the debt threshold for economic growth may exist around a relatively small debt-to-GDP ratio of 30 per cent. Furthermore, countries with debt-to-GDP ratios above 30 per cent have GDP growth that is 1 percentage point lower at the median.

Testing for a Debt‐Threshold Effect on Output Growth†

PubMed Central

Lee, Sokbae; Park, Hyunmin; Seo, Myung Hwan; Shin, Youngki

2017-01-01

Abstract Using the Reinhart–Rogoff dataset, we find a debt threshold not around 90 per cent but around 30 per cent, above which the median real gross domestic product (GDP) growth falls abruptly. Our work is the first to formally test for threshold effects in the relationship between public debt and median real GDP growth. The null hypothesis of no threshold effect is rejected at the 5 per cent significance level for most cases. While we find no evidence of a threshold around 90 per cent, our findings from the post‐war sample suggest that the debt threshold for economic growth may exist around a relatively small debt‐to‐GDP ratio of 30 per cent. Furthermore, countries with debt‐to‐GDP ratios above 30 per cent have GDP growth that is 1 percentage point lower at the median. PMID:29263562

MISR Level 2 Aerosol and Land Versioning

Atmospheric Science Data Center

2017-10-11

... surfaces was changed: instead of using a surface contrast threshold, a new test is used which is based on a weighted mean equivalent reflectance threshold. A regional angular correlation screening test was added to aerosol ...

Effect of Heavy Consumption of Alcoholic Beverages on the Perception of Sweet and Salty Taste.

PubMed

Silva, Camile S; Dias, Vaneria R; Almeida, Juliane A Regis; Brazil, Jamile M; Santos, Ramon A; Milagres, Maria P

2016-05-01

To determine the threshold index of sweet and salty tastes in alcoholics undergoing treatment. Taste threshold was assessed using type 3-Alternative Forced Choice in a control group (92 non-alcoholic volunteers) and a test group (92 alcoholics in therapy). The test group completed a structured questionnaire on lifestyle and habits. Significant difference were found between the threshold rates found in the test (3.78) and control groups (1.39). In the salty stimulus, no significant difference was noted in the threshold detection between the control (0.17) and test groups (0.30). A significant correlation was observed between the index Pearson's threshold to sweet taste in the test group and their reported alcohol consumption. The test group reported characteristics such as loss of appetite (93%), weight loss during consumption (62%) and weight gain after quitting drinking (72%). That the alcoholic group reported less sensitivity to sweet taste suggests that drinking habits may influence choice of foods, with a greater preference for foods with higher sucrose concentration. This contribute to poor health, because excess consumption of sugar raises risk for several diseases. No conclusive results were found for the salty stimulus. © The Author 2015. Medical Council on Alcohol and Oxford University Press. All rights reserved.

The effect of acclimatization and ambient temperature on heat withdrawal threshold in rats.

PubMed

Vítková, J; Loučka, M; Boček, J; Vaculín, S

2015-01-01

Nociception in rats is frequently measured in terms of latency of withdrawal reaction to radiant heat (thermal nociceptive threshold). The aim of this study was to determine how much housing acclimatization and ambient temperature affect the results of thermal pain threshold testing. All experiments used adult male Wistar rats. Thermal pain thresholds were tested using the radiant heat withdrawal reaction at three different body sites: forepaws, hind paws and tail. Skin temperature was measured using an Infrared thermometer and ambient temperature was set at 18, 20, 24 or 26 °C. The results demonstrate that (1) thermal pain threshold was inversely related to both ambient and skin temperature; (2) housing acclimatization and repeated testing had no effect on nociceptive thresholds at any of the three body sites; (3) a resting, cranio-caudal distribution, of nociceptive sensitivity was observed; (4) hind paws and tail were more sensitive to changes of skin and ambient temperature than forepaws. These findings show the importance of recording laboratory conditions in experiments and their influence on results. © 2014 European Pain Federation - EFIC®

Threshold and variability properties of matrix frequency-doubling technology and standard automated perimetry in glaucoma.

PubMed

Artes, Paul H; Hutchison, Donna M; Nicolela, Marcelo T; LeBlanc, Raymond P; Chauhan, Balwantray C

2005-07-01

To compare test results from second-generation Frequency-Doubling Technology perimetry (FDT2, Humphrey Matrix; Carl-Zeiss Meditec, Dublin, CA) and standard automated perimetry (SAP) in patients with glaucoma. Specifically, to examine the relationship between visual field sensitivity and test-retest variability and to compare total and pattern deviation probability maps between both techniques. Fifteen patients with glaucoma who had early to moderately advanced visual field loss with SAP (mean MD, -4.0 dB; range, +0.2 to -16.1) were enrolled in the study. Patients attended three sessions. During each session, one eye was examined twice with FDT2 (24-2 threshold test) and twice with SAP (Swedish Interactive Threshold Algorithm [SITA] Standard 24-2 test), in random order. We compared threshold values between FDT2 and SAP at test locations with similar visual field coordinates. Test-retest variability, established in terms of test-retest intervals and standard deviations (SDs), was investigated as a function of visual field sensitivity (estimated by baseline threshold and mean threshold, respectively). The magnitude of visual field defects apparent in total and pattern deviation probability maps were compared between both techniques by ordinal scoring. The global visual field indices mean deviation (MD) and pattern standard deviation (PSD) of FDT2 and SAP correlated highly (r > 0.8; P < 0.001). At test locations with high sensitivity (>25 dB with SAP), threshold estimates from FDT2 and SAP exhibited a close, linear relationship, with a slope of approximately 2.0. However, at test locations with lower sensitivity, the relationship was much weaker and ceased to be linear. In comparison with FDT2, SAP showed a slightly larger proportion of test locations with absolute defects (3.0% vs. 2.2% with SAP and FDT2, respectively, P < 0.001). Whereas SAP showed a significant increase in test-retest variability at test locations with lower sensitivity (P < 0.001), there was no relationship between variability and sensitivity with FDT2 (P = 0.46). In comparison with SAP, FDT2 exhibited narrower test-retest intervals at test locations with lower sensitivity (SAP thresholds <25 dB). A comparison of the total and pattern deviation maps between both techniques showed that the total deviation analyses of FDT2 may slightly underestimate the visual field loss apparent with SAP. However, the pattern-deviation maps of both instruments agreed well with each other. The test-retest variability of FDT2 is uniform over the measurement range of the instrument. These properties may provide advantages for the monitoring of patients with glaucoma that should be investigated in longitudinal studies.

A de-noising method using the improved wavelet threshold function based on noise variance estimation

NASA Astrophysics Data System (ADS)

Liu, Hui; Wang, Weida; Xiang, Changle; Han, Lijin; Nie, Haizhao

2018-01-01

The precise and efficient noise variance estimation is very important for the processing of all kinds of signals while using the wavelet transform to analyze signals and extract signal features. In view of the problem that the accuracy of traditional noise variance estimation is greatly affected by the fluctuation of noise values, this study puts forward the strategy of using the two-state Gaussian mixture model to classify the high-frequency wavelet coefficients in the minimum scale, which takes both the efficiency and accuracy into account. According to the noise variance estimation, a novel improved wavelet threshold function is proposed by combining the advantages of hard and soft threshold functions, and on the basis of the noise variance estimation algorithm and the improved wavelet threshold function, the research puts forth a novel wavelet threshold de-noising method. The method is tested and validated using random signals and bench test data of an electro-mechanical transmission system. The test results indicate that the wavelet threshold de-noising method based on the noise variance estimation shows preferable performance in processing the testing signals of the electro-mechanical transmission system: it can effectively eliminate the interference of transient signals including voltage, current, and oil pressure and maintain the dynamic characteristics of the signals favorably.

Peaks Over Threshold (POT): A methodology for automatic threshold estimation using goodness of fit p-value

NASA Astrophysics Data System (ADS)

Solari, Sebastián.; Egüen, Marta; Polo, María. José; Losada, Miguel A.

2017-04-01

Threshold estimation in the Peaks Over Threshold (POT) method and the impact of the estimation method on the calculation of high return period quantiles and their uncertainty (or confidence intervals) are issues that are still unresolved. In the past, methods based on goodness of fit tests and EDF-statistics have yielded satisfactory results, but their use has not yet been systematized. This paper proposes a methodology for automatic threshold estimation, based on the Anderson-Darling EDF-statistic and goodness of fit test. When combined with bootstrapping techniques, this methodology can be used to quantify both the uncertainty of threshold estimation and its impact on the uncertainty of high return period quantiles. This methodology was applied to several simulated series and to four precipitation/river flow data series. The results obtained confirmed its robustness. For the measured series, the estimated thresholds corresponded to those obtained by nonautomatic methods. Moreover, even though the uncertainty of the threshold estimation was high, this did not have a significant effect on the width of the confidence intervals of high return period quantiles.

Coherent motion threshold measurements for M-cell deficit differ for above- and below-average readers.

PubMed

Solan, Harold A; Hansen, Peter C; Shelley-Tremblay, John; Ficarra, Anthony

2003-11-01

Research during the past 20 years has influenced the management of diagnosis and treatment of children identified as having learning-related vision problems. The intent of this study is to determine whether coherent motion threshold testing can distinguish better-than-average non-disabled (ND) readers from those who are moderately reading disabled (RD) among sixth-grade students. A sample of 23 better-than-average non-disabled readers (> or = 80th percentile) and 27 moderately disabled readers (< or = 32nd percentile) were identified using a standardized reading comprehension test. Each participant was tested for coherent motion threshold. Previous psychophysical and fMRI research with adults suggests that coherent motion threshold is a valid measure of magnocellular (M-cell) integrity. The average of two coherent motion threshold trials was significantly greater for moderately reading disabled subjects than for above-average readers (p < 0.01). The mean threshold percentage of dots required to observe lateral motion was 9.2% for moderately reading disabled readers and 4.6% for superior readers (p = 0.001). The outcome of this preliminary study provides an efficient procedure to identify sixth-grade students whose reading disability may be associated with an M-cell deficit. Our previous investigations involving visual processing, visual attention, and oculomotor therapy have resulted in significant improvements in reading comprehension, visual attention, and eye movements. It remains to be demonstrated whether vision therapy has an impact on the M-cell deficit, as measured with coherent motion threshold testing for moderately disabled readers.

Effect of Tadalafil on Seizure Threshold and Activity of Antiepileptic Drugs in Three Acute Seizure Tests in Mice.

PubMed

Socała, Katarzyna; Nieoczym, Dorota; Pieróg, Mateusz; Wyska, Elżbieta; Szafarz, Małgorzata; Doboszewska, Urszula; Wlaź, Piotr

2018-02-09

Tadalafil, a selective phosphodiesterase type 5 inhibitor, is a long-acting oral agent for the treatment of erectile dysfunction of multiple etiologies. Although generalized tonic-clonic seizures were reported in a healthy man after taking tadalafil, the influence of tadalafil on seizure susceptibility has not been studied so far. Therefore, the aim of the present study was to investigate the effect of tadalafil on seizure threshold as well as on the activity of some first- and second-generation antiepileptic drugs in three acute seizure tests in mice. The obtained results showed that tadalafil, at the highest dose tested (20 mg/kg), significantly decreased the threshold for the first myoclonic twitch in the intravenous pentylenetetrazole (i.v. PTZ) seizure test. It did not affect the threshold for generalized clonic seizure and forelimb tonus in the i.v. PTZ, for tonic hindlimb extension in the maximal electroshock seizure threshold test, and for psychomotor seizure in the 6-Hz-induced seizure threshold test. Tadalafil did not alter the anticonvulsant activity of any of the studied antiepileptic drugs in electrically induced seizure tests. Interestingly, tadalafil potentiated the anticonvulsant activity of clonazepam and decreased the anticonvulsant activity of oxcarbazepine in the i.v. PTZ test. These interactions were pharmacodynamic in nature, as tadalafil did not alter clonazepam and oxcarbazepine concentrations both in serum and brain tissue. Furthermore, neither tadalafil alone nor its combinations with the studied antiepileptic drugs produced any significant impairment of motor coordination (assessed in the chimney test), muscular strength (investigated in the grip-strength test), and long-term memory (assessed in the passive avoidance task). In conclusion, tadalafil may increase the risk of myoclonic seizure and decrease the anticonvulsant efficacy of oxcarbazepine. Further studies are warranted to evaluate the safety of tadalafil usage in patients with epilepsy.

A computer-controlled color vision test for children based on the Cambridge Colour Test.

PubMed

Goulart, Paulo R K; Bandeira, Marcio L; Tsubota, Daniela; Oiwa, Nestor N; Costa, Marcelo F; Ventura, Dora F

2008-01-01

The present study aimed at providing conditions for the assessment of color discrimination in children using a modified version of the Cambridge Colour Test (CCT, Cambridge Research Systems Ltd., Rochester, UK). Since the task of indicating the gap of the Landolt C used in that test proved counterintuitive and/or difficult for young children to understand, we changed the target stimulus to a patch of color approximately the size of the Landolt C gap (about 7 degrees of visual angle at 50 cm from the monitor). The modifications were performed for the CCT Trivector test which measures color discrimination for the protan, deutan and tritan confusion lines. Experiment 1 sought to evaluate the correspondence between the CCT and the child-friendly adaptation with adult subjects (n = 29) with normal color vision. Results showed good agreement between the two test versions. Experiment 2 tested the child-friendly software with children 2 to 7 years old (n = 25) using operant training techniques for establishing and maintaining the subjects' performance. Color discrimination thresholds were progressively lower as age increased within the age range tested (2 to 30 years old), and the data--including those obtained for children--fell within the range of thresholds previously obtained for adults with the CCT. The protan and deutan thresholds were consistently lower than tritan thresholds, a pattern repeatedly observed in adults tested with the CCT. The results demonstrate that the test is fit for assessment of color discrimination in young children and may be a useful tool for the establishment of color vision thresholds during development.

Barn owls have ageless ears.

PubMed

Krumm, Bianca; Klump, Georg; Köppl, Christine; Langemann, Ulrike

2017-09-27

We measured the auditory sensitivity of the barn owl ( Tyto alba ), using a behavioural Go/NoGo paradigm in two different age groups, one younger than 2 years ( n = 4) and another more than 13 years of age ( n = 3). In addition, we obtained thresholds from one individual aged 23 years, three times during its lifetime. For computing audiograms, we presented test frequencies of between 0.5 and 12 kHz, covering the hearing range of the barn owl. Average thresholds in quiet were below 0 dB sound pressure level (SPL) for frequencies between 1 and 10 kHz. The lowest mean threshold was -12.6 dB SPL at 8 kHz. Thresholds were the highest at 12 kHz, with a mean of 31.7 dB SPL. Test frequency had a significant effect on auditory threshold but age group had no significant effect. There was no significant interaction between age group and test frequency. Repeated threshold estimates over 21 years from a single individual showed only a slight increase in thresholds. We discuss the auditory sensitivity of barn owls with respect to other species and suggest that birds, which generally show a remarkable capacity for regeneration of hair cells in the basilar papilla, are naturally protected from presbycusis. © 2017 The Author(s).

Tests of English Language as Significant Thresholds for College-Bound Chinese and the Washback of Test-Preparation

ERIC Educational Resources Information Center

Matoush, Marylou M.; Fu, Danling

2012-01-01

Tests of English language mark significantly high thresholds for all college-bound students in the People's Republic of China. Many Chinese students hope to seek their fortunes at universities in the United States, or other English speaking countries. These students spend long hours, year after year, in test-preparation centres in order to develop…

Refinement of a thermal threshold probe to prevent burns.

PubMed

Dixon, M J; Taylor, P M; Slingsby, L C; Murrell, J C

2016-02-01

Thermal threshold testing is commonly used for pain research. The stimulus may cause burning and merits prevention. Thermal probe modifications hypothesized to reduce burning were evaluated for practicality and effect. Studies were conducted on two humans and eight cats. Unmodified probe 0 was tested on two humans and promising modifications were also evaluated on cats. Probe 1 incorporated rapid cooling after threshold was reached: probe 1a used a Peltier system and probe 1b used water cooling. Probe 2 released skin contact immediately after threshold. Probe 3 (developed in the light of evidence of 'hot spots' in probe 0) incorporated reduced thermal mass and even heating across the skin contact area. Human skin was heated to 48℃ (6℃ above threshold) and the resulting burn was evaluated using area of injury and a simple descriptive scale (SDS). Probe 1a cooled the skin but required further heat dissipation, excessive power, was not 'fail-safe' and was inappropriate for animal mounting. Probe 1b caused less damage than no cooling (27 ± 13 and 38 ± 11 mm(2) respectively, P = 0.0266; median SDS 1.5 and 4 respectively, P = 0.0317) but was cumbersome. Probe 2 was unwieldy and was not evaluated further. Probe 3 produced even heating without blistering in humans. With probe 3 in cats, after opioid treatment, thermal threshold reached cut-out (55℃) on 24 occasions, exceeded 50℃ in a further 32 tests and exceeded 48℃ in the remainder. No skin damage was evident immediately after testing and mild hyperaemia in three cats at 2-3 days resolved rapidly. Probe 3 appeared to be suitable for thermal threshold testing. © The Author(s) 2015.

Motor unit behaviour and contractile changes during fatigue in the human first dorsal interosseus

PubMed Central

Carpentier, Alain; Duchateau, Jacques; Hainaut, Karl

2001-01-01

In 67 single motor units, the mechanical properties, the recruitment and derecruitment thresholds, and the discharge rates were recorded concurrently in the first dorsal interosseus (FDI) of human subjects during intermittent fatiguing contractions. The task consisted of isometric ramp-and-hold contractions performed at 50% of the maximal voluntary contraction (MVC). The purpose of this study was to examine the influence of fatigue on the behaviour of motor units with a wide range of activation thresholds. For low-threshold (< 25% MVC) motor units, the mean twitch force increased with fatigue and the recruitment threshold either did not change or increased. In contrast, the twitch force and the activation threshold decreased for the high-threshold (> 25% MVC) units. The observation that in low-threshold motor units a quick stretch of the muscle at the end of the test reset the unit force and recruitment threshold to the prefatigue value suggests a significant role for fatigue-related changes in muscle stiffness but not twitch potentiation or motor unit synchronization. Although the central drive intensified during the fatigue test, as indicated by an increase in surface electromyogram (EMG), the discharge rate of the motor units during the hold phase of each contraction decreased progressively over the course of the task for motor units that were recruited at the beginning of the test, especially the low-threshold units. In contrast, the discharge rates of newly activated units first increased and then decreased. Such divergent behaviour of low- and high-threshold motor units could not be individually controlled by the central drive to the motoneurone pool. Rather, the different behaviours must be the consequence of variable contributions from motoneurone adaptation and afferent feedback from the muscle during the fatiguing contraction. PMID:11483719

Aided and Unaided Speech Perception by Older Hearing Impaired Listeners

PubMed Central

Woods, David L.; Arbogast, Tanya; Doss, Zoe; Younus, Masood; Herron, Timothy J.; Yund, E. William

2015-01-01

The most common complaint of older hearing impaired (OHI) listeners is difficulty understanding speech in the presence of noise. However, tests of consonant-identification and sentence reception threshold (SeRT) provide different perspectives on the magnitude of impairment. Here we quantified speech perception difficulties in 24 OHI listeners in unaided and aided conditions by analyzing (1) consonant-identification thresholds and consonant confusions for 20 onset and 20 coda consonants in consonant-vowel-consonant (CVC) syllables presented at consonant-specific signal-to-noise (SNR) levels, and (2) SeRTs obtained with the Quick Speech in Noise Test (QSIN) and the Hearing in Noise Test (HINT). Compared to older normal hearing (ONH) listeners, nearly all unaided OHI listeners showed abnormal consonant-identification thresholds, abnormal consonant confusions, and reduced psychometric function slopes. Average elevations in consonant-identification thresholds exceeded 35 dB, correlated strongly with impairments in mid-frequency hearing, and were greater for hard-to-identify consonants. Advanced digital hearing aids (HAs) improved average consonant-identification thresholds by more than 17 dB, with significant HA benefit seen in 83% of OHI listeners. HAs partially normalized consonant-identification thresholds, reduced abnormal consonant confusions, and increased the slope of psychometric functions. Unaided OHI listeners showed much smaller elevations in SeRTs (mean 6.9 dB) than in consonant-identification thresholds and SeRTs in unaided listening conditions correlated strongly (r = 0.91) with identification thresholds of easily identified consonants. HAs produced minimal SeRT benefit (2.0 dB), with only 38% of OHI listeners showing significant improvement. HA benefit on SeRTs was accurately predicted (r = 0.86) by HA benefit on easily identified consonants. Consonant-identification tests can accurately predict sentence processing deficits and HA benefit in OHI listeners. PMID:25730423

A comparison of the ability of a 4:1 ketogenic diet and a 6.3:1 ketogenic diet to elevate seizure thresholds in adult and young rats.

PubMed

Nylen, Kirk; Likhodii, Sergei; Abdelmalik, Peter A; Clarke, Jasper; Burnham, W McIntyre

2005-08-01

The pentylenetetrazol (PTZ) infusion test was used to compare seizure thresholds in adult and young rats fed either a 4:1 ketogenic diet (KD) or a 6.3:1 KD. We hypothesized that both KDs would significantly elevate seizure thresholds and that the 4:1 KD would serve as a better model of the KD used clinically. Ninety adult rats and 75 young rats were placed on one of five experimental diets: (a) a 4:1 KD, (b) a control diet balanced to the 4:1 KD, (c) a 6.3:1 KD, (d) a standard control diet, or (e) an ad libitum standard control diet. All subjects were seizure tested by using the PTZ infusion test. Blood glucose and beta-hydroxybutyrate (beta-OHB) levels were measured. Neither KD elevated absolute "latencies to seizure" in young or adult rats. Similarly, neither KD elevated "threshold doses" in adult rats. In young rats, the 6.3:1 KD, but not the 4:1 KD, significantly elevated threshold doses. The 6.3:1 KD group showed poorer weight gain than the 4:1 KD group when compared with respective controls. The most dramatic discrepancies were seen in young rats. "Threshold doses" and "latency to seizure" data provided conflicting measures of seizure threshold. This was likely due to the inflation of threshold doses calculated by using the much smaller body weights found in the 6.3:1 KD group. Ultimately, the PTZ infusion test in rats may not be a good preparation to model the anticonvulsant effects of the KD seen clinically, especially when dietary treatments lead to significantly mismatched body weights between the groups.

Cervical and Ocular VEMP Testing in Diagnosing Superior Semicircular Canal Dehiscence.

PubMed

Hunter, Jacob B; Patel, Neil S; O'Connell, Brendan P; Carlson, Matthew L; Shepard, Neil T; McCaslin, Devin L; Wanna, George B

2017-05-01

Objective To determine the sensitivity and specificity of ocular and cervical vestibular evoked myogenic potentials (VEMPs) in the diagnosis of superior semicircular canal dehiscence (SCD) and to describe the VEMP response characteristics that are most sensitive to SCD and compare the findings to previous reports. Study Design Case series with chart review. Setting Two tertiary neurotologic referral centers. Subjects and Methods Cervical and ocular VEMP peak-to-peak amplitudes and thresholds from 39 adult patients older than 18 years with surgically confirmed SCD were compared with 84 age-matched controls. Results Using receiver operating characteristic (ROC) curves, cervical VEMP (cVEMP) amplitudes, cVEMP thresholds, and ocular VEMP (oVEMP) amplitudes had areas under the curve of 0.731, 0.912, and 0.856, respectively, all of which were statistically significant ( P < .0001). For cVEMP thresholds, at the clinical equivalent ≤85-dB normalized hearing level (nHL) threshold, the sensitivity and specificity were 97.3% and 31.3%, respectively. At the ≤70-dB nHL threshold, the sensitivity and specificity were 73.0% and 94.0%, respectively. For oVEMP amplitudes >12.0 µV, the sensitivity and specificity were 78.6% and 81.7%, respectively. Conclusion Data from this multicenter study suggest that both cVEMP thresholds and oVEMP amplitudes remain good diagnostic tests for identifying SCD, with each test dependent on a number of factors. The sensitivity and specificity of these individual tests may vary slightly between centers depending on testing parameters used.

Multisampling suprathreshold perimetry: a comparison with conventional suprathreshold and full-threshold strategies by computer simulation.

PubMed

Artes, Paul H; Henson, David B; Harper, Robert; McLeod, David

2003-06-01

To compare a multisampling suprathreshold strategy with conventional suprathreshold and full-threshold strategies in detecting localized visual field defects and in quantifying the area of loss. Probability theory was applied to examine various suprathreshold pass criteria (i.e., the number of stimuli that have to be seen for a test location to be classified as normal). A suprathreshold strategy that requires three seen or three missed stimuli per test location (multisampling suprathreshold) was selected for further investigation. Simulation was used to determine how the multisampling suprathreshold, conventional suprathreshold, and full-threshold strategies detect localized field loss. To determine the systematic error and variability in estimates of loss area, artificial fields were generated with clustered defects (0-25 field locations with 8- and 16-dB loss) and, for each condition, the number of test locations classified as defective (suprathreshold strategies) and with pattern deviation probability less than 5% (full-threshold strategy), was derived from 1000 simulated test results. The full-threshold and multisampling suprathreshold strategies had similar sensitivity to field loss. Both detected defects earlier than the conventional suprathreshold strategy. The pattern deviation probability analyses of full-threshold results underestimated the area of field loss. The conventional suprathreshold perimetry also underestimated the defect area. With multisampling suprathreshold perimetry, the estimates of defect area were less variable and exhibited lower systematic error. Multisampling suprathreshold paradigms may be a powerful alternative to other strategies of visual field testing. Clinical trials are needed to verify these findings.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitchell K Meyer

Blister–threshold testing of fuel plates is a standard method through which the safety margin for operation of plate-type in research and test reactors is assessed. The blister-threshold temperature is indicative of the ability of fuel to operate at high temperatures for short periods of time (transient conditions) without failure. This method of testing was applied to the newly developed U-Mo monolithic fuel system. Blister annealing studies on the U-Mo monolithic fuel plates began in 2007, with the Reduced Enrichment for Research and Test Reactors (RERTR)-6 experiment, and they have continued as the U-Mo fuel system has evolved through the researchmore » and development process. Blister anneal threshold temperatures from early irradiation experiments (RERTR-6 through RERTR-10) ranged from 400 to 500°C. These temperatures were projected to be acceptable for NRC-licensed research reactors and the high-power Advanced Test Reactor (ATR) and the High Flux Isotope Reactor (HFIR) based on current safety-analysis reports (SARs). Initial blister testing results from the RERTR-12 experiment capsules X1 and X2 showed a decrease in the blister-threshold temperatures. Blister threshold temperatures from this experiment ranged from 300 to 400°C. Selected plates from the AFIP-4 experiment, which was fabricated using a process similar to that used to fabricate the RERTR-12 experiment, also underwent blister testing to determine whether results would be similar. The measured blister-threshold temperatures from the AFIP-4 plates fell within the same blister-threshold temperature range measured in the RERTR-12 plates. Investigation of the cause of this decrease in bister threshold temperature is being conducted under the guidance of Idaho National Laboratory PLN-4155, “Analysis of Low Blister Threshold Temperatures in the RERTR-12 and AFIP-4 Experiments,” and is driven by hypotheses. The main focus of the investigation is in the following areas: 1. Fabrication variables 2. Pre-irradiation characterization 3. Irradiation conditions 4. Post-irradiation examination 5. Additional blister testing 6. Mechanical modeling This report documents the preliminary results of this investigation. Several hypotheses can be dismissed as a result of this investigation. Two primary categories of causes remain. The most prominent theory, supported by the data, is that low blister-threshold temperature is the result of mechanical energy imparted on the samples during the fabrication process (hot and cold rolling) without adequate post processing (annealing). The mechanisms are not clearly understood and require further investigation, but can be divided into two categories: • Residual Stress • Undesirable interaction boundary and/or U-Mo microstructure change A secondary theory that cannot be dismissed with the information that is currently available is that a change in the test conditions has resulted in a statistically significant downward shift of measured blister temperature. This report outlines the results of the forensic investigations conducted to date. The data and conclusions presented in this report are preliminary. Definitive cause and effect relationships will be established by future experimental programs.« less

Learning and extinction of conditioned hearing sensation change in the beluga whale (Delphinapterus leucas).

PubMed

Nachtigall, Paul E; Supin, Alexander Ya; Estaban, Jose-Antonio; Pacini, Aude F

2016-02-01

Ice-dwelling beluga whales are increasingly being exposed to anthropogenic loud sounds. Beluga's hearing sensitivity measured during a warning sound just preceding a loud sound was tested using pip-train stimuli and auditory evoked potential recording. When the test/warning stimulus with a frequency of 32 or 45 kHz preceded the loud sound with a frequency of 32 kHz and a sound pressure level of 153 dB re 1 μPa, 2 s, hearing thresholds before the loud sound increased relative to the baseline. The threshold increased up to 15 dB for the test frequency of 45 kHz and up to 13 dB for the test frequency of 32 kHz. These threshold increases were observed during two sessions of 36 trials each. Extinction tests revealed no change during three experimental sessions followed by a jump-like return to baseline thresholds. The low exposure level producing the hearing-dampening effect (156 dB re 1 µPa(2)s in each trial), and the manner of extinction, may be considered as evidence that the observed hearing threshold increases were a demonstration of conditioned dampening of hearing when the whale anticipated the quick appearance of a loud sound in the same way demonstrated in the false killer whale and bottlenose dolphin.

An enhancement of ROC curves made them clinically relevant for diagnostic-test comparison and optimal-threshold determination.

PubMed

Subtil, Fabien; Rabilloud, Muriel

2015-07-01

The receiver operating characteristic curves (ROC curves) are often used to compare continuous diagnostic tests or determine the optimal threshold of a test; however, they do not consider the costs of misclassifications or the disease prevalence. The ROC graph was extended to allow for these aspects. Two new lines are added to the ROC graph: a sensitivity line and a specificity line. Their slopes depend on the disease prevalence and on the ratio of the net benefit of treating a diseased subject to the net cost of treating a nondiseased one. First, these lines help researchers determine the range of specificities within which test comparisons of partial areas under the curves is clinically relevant. Second, the ROC curve point the farthest from the specificity line is shown to be the optimal threshold in terms of expected utility. This method was applied: (1) to determine the optimal threshold of ratio specific immunoglobulin G (IgG)/total IgG for the diagnosis of congenital toxoplasmosis and (2) to select, among two markers, the most accurate for the diagnosis of left ventricular hypertrophy in hypertensive subjects. The two additional lines transform the statistically valid ROC graph into a clinically relevant tool for test selection and threshold determination. Copyright © 2015 Elsevier Inc. All rights reserved.

The Evaluation of Olfactory Function in Patients With Schizophrenia.

PubMed

Robabeh, Soleimani; Mohammad, Jalali Mir; Reza, Ahmadi; Mahan, Badri

2015-04-23

The aim of this study was to compare olfactory threshold, smell identification, intensity and pleasantness ratings between patients with schizophrenia and healthy controls, and (2) to evaluate correlations between ratings of olfactory probes and illness characteristics. Thirty one patients with schizophrenia and 31 control subjects were assessed with the olfactory n-butanol threshold test, the Iran smell identification test (Ir-SIT), and the suprathreshold amyl acetate odor intensity and odor pleasantness rating test. All olfactory tasks were performed unirhinally. Patients with schizophrenia showed disrupted olfaction in all four measures. Longer duration of schizophrenia was associated with a larger impairment of olfactory threshold or microsmic range on the Ir-SIT (P=0.04, P=0.05, respectively). In patients with schizophrenia, female subjects' ratings of pleasantness followed the same trend as control subjects, whereas male patients' ratings showed an opposite trend. Patients exhibiting high positive score on the positive and negative syndrome scale (PANSS) performed better on the olfactory threshold test (r=0.37, P=0.04). The higher odor pleasantness ratings of patients were associated with presence of positive symptoms. The results suggest that both male and female patients with schizophrenia had difficulties on the olfactory threshold and smell identification tests, but appraisal of odor pleasantness was more disrupted in male patients.

A field test for determining the speed obtained through anaerobic glycolysis in runners.

PubMed

Borsetto, C; Ballarin, E; Casoni, I; Cellini, M; Vitiello, P; Conconi, F

1989-10-01

A field test for the evaluation of the speed generated by the anaerobic lactacid mechanism has been developed in runners. The test consists of 1200 m of continuous running: in the first 1000 m the speed corresponding to the anaerobic threshold is progressively reached; in the last 200 m an all-out sprint is performed. The speed at the anaerobic threshold is subtracted from the speed reached in the final 200-m all-out sprint. In 39 runners examined (marathon runners, n = 13; 5000-10000-m runners, n = 10; 400-800-m runners, n = 7; sprinters, n = 9), the additional speed generated above the anaerobic threshold was correlated with the venous blood lactate concentration reached 5 min after the all-out effort (r = 0.93). The anaerobic speeds measured by the test were in keeping with the characteristics of the runners under study, i.e., anaerobic speeds were highest for the sprinters, intermediate for the middle-distance runners, and lowest for the marathon runners. Since the speed generated above the anaerobic threshold by the aerobic fuel breakdown can be subtracted, the contribution of creatine phosphate is minimal, and the speed exceeding the anaerobic threshold is highly correlated with lactate accumulation, the present test should measure the speed generated by anaerobic glycolysis.

Underwater hearing in the loggerhead turtle (Caretta caretta): a comparison of behavioral and auditory evoked potential audiograms.

PubMed

Martin, Kelly J; Alessi, Sarah C; Gaspard, Joseph C; Tucker, Anton D; Bauer, Gordon B; Mann, David A

2012-09-01

The purpose of this study was to compare underwater behavioral and auditory evoked potential (AEP) audiograms in a single captive adult loggerhead sea turtle (Caretta caretta). The behavioral audiogram was collected using a go/no-go response procedure and a modified staircase method of threshold determination. AEP thresholds were measured using subdermal electrodes placed beneath the frontoparietal scale, dorsal to the midbrain. Both methods showed the loggerhead sea turtle to have low frequency hearing with best sensitivity between 100 and 400 Hz. AEP testing yielded thresholds from 100 to 1131 Hz with best sensitivity at 200 and 400 Hz (110 dB re. 1 μPa). Behavioral testing using 2 s tonal stimuli yielded underwater thresholds from 50 to 800 Hz with best sensitivity at 100 Hz (98 dB re. 1 μPa). Behavioral thresholds averaged 8 dB lower than AEP thresholds from 100 to 400 Hz and 5 dB higher at 800 Hz. The results suggest that AEP testing can be a good alternative to measuring a behavioral audiogram with wild or untrained marine turtles and when time is a crucial factor.

Perfect Detection of Spikes in the Linear Sub-threshold Dynamics of Point Neurons

PubMed Central

Krishnan, Jeyashree; Porta Mana, PierGianLuca; Helias, Moritz; Diesmann, Markus; Di Napoli, Edoardo

2018-01-01

Spiking neuronal networks are usually simulated with one of three main schemes: the classical time-driven and event-driven schemes, and the more recent hybrid scheme. All three schemes evolve the state of a neuron through a series of checkpoints: equally spaced in the first scheme and determined neuron-wise by spike events in the latter two. The time-driven and the hybrid scheme determine whether the membrane potential of a neuron crosses a threshold at the end of the time interval between consecutive checkpoints. Threshold crossing can, however, occur within the interval even if this test is negative. Spikes can therefore be missed. The present work offers an alternative geometric point of view on neuronal dynamics, and derives, implements, and benchmarks a method for perfect retrospective spike detection. This method can be applied to neuron models with affine or linear subthreshold dynamics. The idea behind the method is to propagate the threshold with a time-inverted dynamics, testing whether the threshold crosses the neuron state to be evolved, rather than vice versa. Algebraically this translates into a set of inequalities necessary and sufficient for threshold crossing. This test is slower than the imperfect one, but can be optimized in several ways. Comparison confirms earlier results that the imperfect tests rarely miss spikes (less than a fraction 1/108 of missed spikes) in biologically relevant settings. PMID:29379430

CHOW PARAMETERS IN THRESHOLD LOGIC,

DTIC Science & Technology

respect to threshold functions, they provide the optimal test-synthesis method for completely specified 7-argument (or less) functions, reflect the...signs and relative magnitudes of realizing weights and threshold , and can be used themselves as approximating weights. Results are reproved in a

Rationality, practice variation and person‐centred health policy: a threshold hypothesis

PubMed Central

Hamm, Robert M.; Mayrhofer, Thomas; Hozo, Iztok; Van den Ende, Jef

2015-01-01

Abstract Variation in practice of medicine is one of the major health policy issues of today. Ultimately, it is related to physicians' decision making. Similar patients with similar likelihood of having disease are often managed by different doctors differently: some doctors may elect to observe the patient, others decide to act based on diagnostic testing and yet others may elect to treat without testing. We explain these differences in practice by differences in disease probability thresholds at which physicians decide to act: contextual social and clinical factors and emotions such as regret affect the threshold by influencing the way doctors integrate objective data related to treatment and testing. However, depending on a theoretical construct each of the physician's behaviour can be considered rational. In fact, we showed that the current regulatory policies lead to predictably low thresholds for most decisions in contemporary practice. As a result, we may expect continuing motivation for overuse of treatment and diagnostic tests. We argue that rationality should take into account both formal principles of rationality and human intuitions about good decisions along the lines of Rawls' ‘reflective equilibrium/considered judgment’. In turn, this can help define a threshold model that is empirically testable. PMID:26639018

Testing of selected metallic reinforcing bars for extending the service life of concrete bridges : testing in solutions.

DOT National Transportation Integrated Search

2003-01-01

Stainless steel-clad rebar provides an opportunity to significantly increase the Cl- threshold concentration associated with active corrosion initiation compared to plain carbon steel. However, threshold Cl- concentrations for 316L stainless steel-cl...

A comparison of five serological tests for bovine brucellosis.

PubMed Central

Dohoo, I R; Wright, P F; Ruckerbauer, G M; Samagh, B S; Robertson, F J; Forbes, L B

1986-01-01

Five serological assays: the buffered plate antigen test, the standard tube agglutination test, the complement fixation test, the hemolysis-in-gel test and the indirect enzyme immunoassay were diagnostically evaluated. Test data consisted of results from 1208 cattle in brucellosis-free herds, 1578 cattle in reactor herds of unknown infection status and 174 cattle from which Brucella abortus had been cultured. The complement fixation test had the highest specificity in both nonvaccinated and vaccinated cattle. The indirect enzyme immunoassay, if interpreted at a high threshold, also exhibited a high specificity in both groups of cattle. The hemolysis-in-gel test had a very high specificity when used in nonvaccinated cattle but quite a low specificity among vaccinates. With the exception of the complement fixation test, all tests had high sensitivities if interpreted at the minimum threshold. However, the sensitivities of the standard tube agglutination test and indirect enzyme immunoassay, when interpreted at high thresholds were comparable to that of the complement fixation test. A kappa statistic was used to measure the agreement between the various tests. In general the kappa statistics were quite low, suggesting that the various tests may detect different antibody isotypes. There was however, good agreement between the buffered plate antigen test and standard tube agglutination test (the two agglutination tests evaluated) and between the complement fixation test and the indirect enzyme immunoassay when interpreted at a high threshold. With the exception of the buffered plate antigen test, all tests were evaluated as confirmatory tests by estimating their specificity and sensitivity on screening-test positive samples.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3539295

Multivariate Analyses of Balance Test Performance, Vestibular Thresholds, and Age

PubMed Central

Karmali, Faisal; Bermúdez Rey, María Carolina; Clark, Torin K.; Wang, Wei; Merfeld, Daniel M.

2017-01-01

We previously published vestibular perceptual thresholds and performance in the Modified Romberg Test of Standing Balance in 105 healthy humans ranging from ages 18 to 80 (1). Self-motion thresholds in the dark included roll tilt about an earth-horizontal axis at 0.2 and 1 Hz, yaw rotation about an earth-vertical axis at 1 Hz, y-translation (interaural/lateral) at 1 Hz, and z-translation (vertical) at 1 Hz. In this study, we focus on multiple variable analyses not reported in the earlier study. Specifically, we investigate correlations (1) among the five thresholds measured and (2) between thresholds, age, and the chance of failing condition 4 of the balance test, which increases vestibular reliance by having subjects stand on foam with eyes closed. We found moderate correlations (0.30–0.51) between vestibular thresholds for different motions, both before and after using our published aging regression to remove age effects. We found that lower or higher thresholds across all threshold measures are an individual trait that account for about 60% of the variation in the population. This can be further distributed into two components with about 20% of the variation explained by aging and 40% of variation explained by a single principal component that includes similar contributions from all threshold measures. When only roll tilt 0.2 Hz thresholds and age were analyzed together, we found that the chance of failing condition 4 depends significantly on both (p = 0.006 and p = 0.013, respectively). An analysis incorporating more variables found that the chance of failing condition 4 depended significantly only on roll tilt 0.2 Hz thresholds (p = 0.046) and not age (p = 0.10), sex nor any of the other four threshold measures, suggesting that some of the age effect might be captured by the fact that vestibular thresholds increase with age. For example, at 60 years of age, the chance of failing is roughly 5% for the lowest roll tilt thresholds in our population, but this increases to 80% for the highest roll tilt thresholds. These findings demonstrate the importance of roll tilt vestibular cues for balance, even in individuals reporting no vestibular symptoms and with no evidence of vestibular dysfunction. PMID:29167656

Detecting fatigue thresholds from electromyographic signals: A systematic review on approaches and methodologies.

PubMed

Ertl, Peter; Kruse, Annika; Tilp, Markus

2016-10-01

The aim of the current paper was to systematically review the relevant existing electromyographic threshold concepts within the literature. The electronic databases MEDLINE and SCOPUS were screened for papers published between January 1980 and April 2015 including the keywords: neuromuscular fatigue threshold, anaerobic threshold, electromyographic threshold, muscular fatigue, aerobic-anaerobictransition, ventilatory threshold, exercise testing, and cycle-ergometer. 32 articles were assessed with regard to their electromyographic methodologies, description of results, statistical analysis and test protocols. Only one article was of very good quality. 21 were of good quality and two articles were of very low quality. The review process revealed that: (i) there is consistent evidence of one or two non-linear increases of EMG that might reflect the additional recruitment of motor units (MU) or different fiber types during fatiguing cycle ergometer exercise, (ii) most studies reported no statistically significant difference between electromyographic and metabolic thresholds, (iii) one minute protocols with increments between 10 and 25W appear most appropriate to detect muscular threshold, (iv) threshold detection from the vastus medialis, vastus lateralis, and rectus femoris is recommended, and (v) there is a great variety in study protocols, measurement techniques, and data processing. Therefore, we recommend further research and standardization in the detection of EMGTs. Copyright © 2016 Elsevier Ltd. All rights reserved.

A high-throughput method to measure NaCl and acid taste thresholds in mice.

PubMed

Ishiwatari, Yutaka; Bachmanov, Alexander A

2009-05-01

To develop a technique suitable for measuring NaCl taste thresholds in genetic studies, we conducted a series of experiments with outbred CD-1 mice using conditioned taste aversion (CTA) and two-bottle preference tests. In Experiment 1, we compared conditioning procedures involving either oral self-administration of LiCl or pairing NaCl intake with LiCl injections and found that thresholds were the lowest after LiCl self-administration. In Experiment 2, we compared different procedures (30-min and 48-h tests) for testing conditioned mice and found that the 48-h test is more sensitive. In Experiment 3, we examined the effects of varying strength of conditioned (NaCl or LiCl taste intensity) and unconditioned (LiCl toxicity) stimuli and concluded that 75-150 mM LiCl or its mixtures with NaCl are the optimal stimuli for conditioning by oral self-administration. In Experiment 4, we examined whether this technique is applicable for measuring taste thresholds for other taste stimuli. Results of these experiments show that conditioning by oral self-administration of LiCl solutions or its mixtures with other taste stimuli followed by 48-h two-bottle tests of concentration series of a conditioned stimulus is an efficient and sensitive method to measure taste thresholds. Thresholds measured with this technique were 2 mM for NaCl and 1 mM for citric acid. This approach is suitable for simultaneous testing of large numbers of animals, which is required for genetic studies. These data demonstrate that mice, like several other species, generalize CTA from LiCl to NaCl, suggesting that they perceive taste of NaCl and LiCl as qualitatively similar, and they also can generalize CTA of a binary mixture of taste stimuli to mixture components.

Smartphone threshold audiometry in underserved primary health-care contexts.

PubMed

Sandström, Josefin; Swanepoel, De Wet; Carel Myburgh, Hermanus; Laurent, Claude

2016-01-01

To validate a calibrated smartphone-based hearing test in a sound booth environment and in primary health-care clinics. A repeated-measure within-subject study design was employed whereby air-conduction hearing thresholds determined by smartphone-based audiometry was compared to conventional audiometry in a sound booth and a primary health-care clinic environment. A total of 94 subjects (mean age 41 years ± 17.6 SD and range 18-88; 64% female) were assessed of whom 64 were tested in the sound booth and 30 within primary health-care clinics without a booth. In the sound booth 63.4% of conventional and smartphone thresholds indicated normal hearing (≤15 dBHL). Conventional thresholds exceeding 15 dB HL corresponded to smartphone thresholds within ≤10 dB in 80.6% of cases with an average threshold difference of -1.6 dB ± 9.9 SD. In primary health-care clinics 13.7% of conventional and smartphone thresholds indicated normal hearing (≤15 dBHL). Conventional thresholds exceeding 15 dBHL corresponded to smartphone thresholds within ≤10 dB in 92.9% of cases with an average threshold difference of -1.0 dB ± 7.1 SD. Accurate air-conduction audiometry can be conducted in a sound booth and without a sound booth in an underserved community health-care clinic using a smartphone.

Assessment of central auditory processing in a group of workers exposed to solvents.

PubMed

Fuente, Adrian; McPherson, Bradley; Muñoz, Verónica; Pablo Espina, Juan

2006-12-01

Despite having normal hearing thresholds and speech recognition thresholds, results for central auditory tests were abnormal in a group of workers exposed to solvents. Workers exposed to solvents may have difficulties in everyday listening situations that are not related to a decrement in hearing thresholds. A central auditory processing disorder may underlie these difficulties. To study central auditory processing abilities in a group of workers occupationally exposed to a mix of organic solvents. Ten workers exposed to a mix of organic solvents and 10 matched non-exposed workers were studied. The test battery comprised pure-tone audiometry, tympanometry, acoustic reflex measurement, acoustic reflex decay, dichotic digit, pitch pattern sequence, masking level difference, filtered speech, random gap detection and hearing-in-noise tests. All the workers presented normal hearing thresholds and no signs of middle ear abnormalities. Workers exposed to solvents had lower results in comparison with the control group and previously reported normative data, in the majority of the tests.

A comparison of the antinociceptive effects of xylazine, detomidine and romifidine on experimental pain in horses.

PubMed

Moens, Yves; Lanz, Francisca; Doherr, Marcus G; Schatzmann, Urs

2003-07-01

To study the analgesic potency of the alpha2-agonist romifidine in the horse using both an electrical current and a mechanical pressure model for nociceptive threshold testing. In addition, a comparison was made with doses of detomidine and xylazine that produce equivalent degrees of sedation. Randomized, placebo-controlled, blinded cross-over study. Six adult Swiss warmblood horses, one mare and five geldings, weighing from 530 to 650 kg and aged 6-15 years. Nociceptive thresholds were measured using an electrical stimulus applied to the coronary band and using a pneumatically operated pin pressing on the cannon bone. Measurements were made immediately before and every 15 minutes for 2 hours after IV injection of the test substances. Lifting of the foot indicated the test end point. The three alpha2-agonists caused a temporary increase in nociceptive thresholds with a maximal effect within 15 minutes and a return to baseline levels within 1 hour. Using electrical current testing nociceptive thresholds were significantly different from placebo (mean +/- SD) for detomidine at 15 minutes (from control 5.8 +/- 0.9 to 23.3 +/- 3.9 mA, p = 0.0066) and 30 minutes (from control 6.6 +/- 1.1 to 18.8 +/- 3.3 mA, p = 0.0091). The difference was significant for romifidine at 15 minutes only (from control 5.8 +/- 0.9 to 18.7 +/- 3.8 mA, p = 0.0066). With mechanical pressure testing nociceptive thresholds were significantly different from control for detomidine at 15 minutes (from 3.2 +/- 0.2 to 6.2 +/- 0.5 N, p = 0.00076) and 30 minutes (from 3.2 +/- 0.7 to 5.7 +/- 0.8 N, p = 0.0167). The difference was significant for xylazine at 15 minutes (from control 3.2 +/- 0.2 to 5.6 +/- 0.7 N, p = 0.0079). At 15 minutes the order of magnitude of the measured antinociceptive effect was significantly different between the two pain tests for both romifidine and detomidine, but not for xylazine. For romifidine, the increase of mean thresholds compared to placebo was 4.0 +/- 1.3 times placebo levels with the electrical current test compared to 1.3 +/- 0.3 times for the mechanical pressure test (p = 0.037). For detomidine, the increase of mean thresholds compared to placebo was 5.4 +/- 1.7 times control levels with the electrical current test compared to 2.0 +/- 0.2 times for the mechanical pressure test (p = 0.040). This represents a 2.7 (romifidine) and 3.4 times (detomidine) greater increase in thresholds using electrical current testing compared to the use of mechanical pressure testing. This study demonstrates the analgesic potential of alpha2-agonists in the horse for somatic pain and that they can have quantitatively different antinociceptive effects according to the antinociceptive test used.

Computer simulation of fibrillation threshold measurements and electrophysiologic testing procedures

NASA Technical Reports Server (NTRS)

Grumbach, M. P.; Saxberg, B. E.; Cohen, R. J.

1987-01-01

A finite element model of cardiac conduction was used to simulate two experimental protocols: 1) fibrillation threshold measurements and 2) clinical electrophysiologic (EP) testing procedures. The model consisted of a cylindrical lattice whose properties were determined by four parameters: element length, conduction velocity, mean refractory period, and standard deviation of refractory periods. Different stimulation patterns were applied to the lattice under a given set of lattice parameter values and the response of the model was observed through a simulated electrocardiogram. The studies confirm that the model can account for observations made in experimental fibrillation threshold measurements and in clinical EP testing protocols.

Test-retest reliability of neurophysiological tests of hand-arm vibration syndrome in vibration exposed workers and unexposed referents.

PubMed

Gerhardsson, Lars; Gillström, Lennart; Hagberg, Mats

2014-01-01

Exposure to hand-held vibrating tools may cause the hand-arm vibration syndrome (HAVS). The aim was to study the test-retest reliability of hand and muscle strength tests, and tests for the determination of thermal and vibration perception thresholds, which are used when investigating signs of neuropathy in vibration exposed workers. In this study, 47 vibration exposed workers who had been investigated at the department of Occupational and Environmental Medicine in Gothenburg were compared with a randomized sample of 18 unexposed subjects from the general population of the city of Gothenburg. All participants passed a structured interview, answered several questionnaires and had a physical examination including hand and finger muscle strength tests, determination of vibrotactile (VPT) and thermal perception thresholds (TPT). Two weeks later, 23 workers and referents, selected in a randomized manner, were called back for the same test-procedures for the evaluation of test-retest reliability. The test-retest reliability after a two week interval expressed as limits of agreement (LOA; Bland-Altman), intra-class correlation coefficients (ICC) and Pearson correlation coefficients was excellent for tests with the Baseline hand grip, Pinch-grip and 3-Chuck grip among the exposed workers and referents (N = 23: percentage of differences within LOA 91 - 100%; ICC-values ≥0.93; Pearson r ≥0.93). The test-retest reliability was also excellent (percentage of differences within LOA 96-100 %) for the determination of vibration perception thresholds in digits 2 and 5 bilaterally as well as for temperature perception thresholds in digits 2 and 5, bilaterally (percentage of differences within LOA 91 - 96%). For ICC and Pearson r the results for vibration perception thresholds were good for digit 2, left hand and for digit 5, bilaterally (ICC ≥ 0.84; r ≥0.85), and lower (ICC = 0.59; r = 0.59) for digit 2, right hand. For the latter two indices the test-retest reliability for the determination of temperature thresholds was lower and showed more varying results. The strong test-retest reliability for hand and muscle strength tests as well as for the determination of VPTs makes these procedures useful for diagnostic purposes and follow-up studies in vibration exposed workers.

Performance, usability and comparison of two versions of a new macular vision test: the handheld Radial Shape Discrimination test

PubMed Central

Ku, Jae Y.; Milling, Ashli F.; Pitrelli Vazquez, Noelia

2016-01-01

Background Central vision, critical for everyday tasks such as reading and driving, is impacted by age-related changes in the eye and by diseases such as age-related macular degeneration. The detection of changes in macular function is therefore important. The Radial Shape Discrimination (RSD) test measures the threshold at which distortions in a radial frequency pattern can be detected and there is evidence that it is more sensitive to macular pathology than visual acuity (VA). It also provides a more quantitative measure of macular function than the commonly available Amsler grid. Recently, handheld versions of the test (hRSD) in which stimuli are presented on mobile devices (e.g., Apple iPod Touch, iPhone) have been developed. We investigated the characteristics of the hRSD test in healthy participants. Methods Data were collected using both three-alternative forced choice (3AFC) and 4AFC versions of the hRSD test, presented on an Apple iPod Touch. For the 3AFC version, data from a single test session were available for 186 (72 male; mean ± SD age 42 ± 17y; range 16–90y) healthy participants. Test-retest data were available for subgroups of participants (intra-session: N = 74; tests approximately 2 months apart: N = 30; tests 39 months apart: N = 15). The 3AFC and 4AFC versions were directly compared in 106 participants who also completed a usability questionnaire. Distance and near VA and Pelli Robson Contrast Sensitivity (CS) data were collected and undilated fundoscopy performed on the majority of participants. Results Mean (±SD) 3AFC hRSD threshold was −0.77 ± 0.14 logMAR, and was statistically significantly correlated with age (Pearson r = 0.35; p < 0.001). The linear regression of hRSD threshold on age had a slope of +0.0026 compared to +0.0051 for near VA (which also correlated with age: r = 0.51; p < 0.001). There were no statistically significant differences in hRSD thresholds for any of the test-retest subgroups. We also observed no statistically significant difference between 3AFC (−0.82 ± 0.11 logMAR) and 4AFC (−0.80 ± 0.12 logMAR) hRSD thresholds (t = 1.85, p = 0.067) and participants reported excellent test usability with no strong preference expressed between the 3AFC and 4AFC versions of the test. Discussion The 3AFC hRSD thresholds we report are consistent with a number of previous studies, as is its greater stability in ageing compared to VA. We have also shown that in the absence of pathology, thresholds are stable over short and long timescales. The 4AFC thresholds we have reported provide a baseline for future investigations, and we have confirmed that 3AFC and 4AFC thresholds are similar, providing a basis of comparisons between studies using the different versions. As the hRSD test is easy to use and relatively inexpensive, clinical studies are now required to establish its ability to detect and monitor macular pathologies. PMID:27833815

[The analysis of threshold effect using Empower Stats software].

PubMed

Lin, Lin; Chen, Chang-zhong; Yu, Xiao-dan

2013-11-01

In many studies about biomedical research factors influence on the outcome variable, it has no influence or has a positive effect within a certain range. Exceeding a certain threshold value, the size of the effect and/or orientation will change, which called threshold effect. Whether there are threshold effects in the analysis of factors (x) on the outcome variable (y), it can be observed through a smooth curve fitting to see whether there is a piecewise linear relationship. And then using segmented regression model, LRT test and Bootstrap resampling method to analyze the threshold effect. Empower Stats software developed by American X & Y Solutions Inc has a threshold effect analysis module. You can input the threshold value at a given threshold segmentation simulated data. You may not input the threshold, but determined the optimal threshold analog data by the software automatically, and calculated the threshold confidence intervals.

Thermal perception thresholds among workers in a cold climate.

PubMed

Burström, Lage; Björ, Bodil; Nilsson, Tohr; Pettersson, Hans; Rödin, Ingemar; Wahlström, Jens

2017-10-01

To investigate whether exposure to cold could influence the thermal perception thresholds in a working population. This cross-sectional study was comprised of 251 males and females and was carried out at two mines in the northern part of Norway and Sweden. The testing included a baseline questionnaire, a clinical examination and measurements of thermal perception thresholds, on both hands, the index (Digit 2) and little (Digit 5) fingers, for heat and cold. The thermal perception thresholds were affected by age, gender and test site. The thresholds were impaired by experiences of frostbite in the fingers and the use of medication that potentially could affect neurosensory functions. No differences were found between the calculated normative values for these workers and those in other comparative investigations conducted in warmer climates. The study provided no support for the hypothesis that living and working in cold climate will lead to impaired thermal perception thresholds. Exposure to cold that had caused localized damage in the form of frostbite was shown to lead to impaired thermal perception.

Development of color vision discrimination during childhood: differences between Blue-Yellow, Red-Green, and achromatic thresholds.

PubMed

Ling, Barbara Y; Dain, Stephen J

2018-04-01

Nonvisual demands of tests affect vision test results in children. 150 children (79 females and 71 males, 5.3-12.7 years of age) were examined. Isoluminant Blue, Yellow, Red, Green, and Black and White thresholds were established with a four-alternative forced-choice and pseudo-10-bit system with adaptive staircase and gaming elements. Where Threshold=b 0 +b 1 *age -1 , b 1 for RG=6.26±1.90 (95% confidence limits), Achr=3.96±1.07 and BY=12.48±2.76 were significantly different. The noncolor demands of the test are the same for RG, BY, and Achr, so the later development of BY discrimination is not an artifact of the test.

High-resolution audiometry: an automated method for hearing threshold acquisition with quality control.

PubMed

Bian, Lin

2012-01-01

In clinical practice, hearing thresholds are measured at only five to six frequencies at octave intervals. Thus, the audiometric configuration cannot closely reflect the actual status of the auditory structures. In addition, differential diagnosis requires quantitative comparison of behavioral thresholds with physiological measures, such as otoacoustic emissions (OAEs) that are usually measured in higher resolution. The purpose of this research was to develop a method to improve the frequency resolution of the audiogram. A repeated-measure design was used in the study to evaluate the reliability of the threshold measurements. A total of 16 participants with clinically normal hearing and mild hearing loss were recruited from a population of university students. No intervention was involved in the study. Custom developed system and software were used for threshold acquisition with quality control (QC). With real-ear calibration and monitoring of test signals, the system provided accurate and individualized measure of hearing thresholds that were determined by an analysis based on signal detection theory (SDT). The reliability of the threshold measure was assessed by correlation and differences between the repeated measures. The audiometric configurations were diverse and unique to each individual ear. The accuracy, within-subject reliability, and between-test repeatability are relatively high. With QC, the high-resolution audiograms can be reliably and accurately measured. Hearing thresholds measured as ear canal sound pressures with higher frequency resolution can provide more customized hearing-aid fitting. The test system may be integrated with other physiological measures, such as OAEs, into a comprehensive evaluative tool. American Academy of Audiology.

Estimation of the geochemical threshold and its statistical significance

USGS Publications Warehouse

Miesch, A.T.

1981-01-01

A statistic is proposed for estimating the geochemical threshold and its statistical significance, or it may be used to identify a group of extreme values that can be tested for significance by other means. The statistic is the maximum gap between adjacent values in an ordered array after each gap has been adjusted for the expected frequency. The values in the ordered array are geochemical values transformed by either ln(?? - ??) or ln(?? - ??) and then standardized so that the mean is zero and the variance is unity. The expected frequency is taken from a fitted normal curve with unit area. The midpoint of an adjusted gap that exceeds the corresponding critical value may be taken as an estimate of the geochemical threshold, and the associated probability indicates the likelihood that the threshold separates two geochemical populations. The adjusted gap test may fail to identify threshold values if the variation tends to be continuous from background values to the higher values that reflect mineralized ground. However, the test will serve to identify other anomalies that may be too subtle to have been noted by other means. ?? 1981.

Discrimination thresholds of normal and anomalous trichromats: Model of senescent changes in ocular media density on the Cambridge Colour Test

PubMed Central

Shinomori, Keizo; Panorgias, Athanasios; Werner, John S.

2017-01-01

Age-related changes in chromatic discrimination along dichromatic confusion lines were measured with the Cambridge Colour Test (CCT). One hundred and sixty-two individuals (16 to 88 years old) with normal Rayleigh matches were the major focus of this paper. An additional 32 anomalous trichromats classified by their Rayleigh matches were also tested. All subjects were screened to rule out abnormalities of the anterior and posterior segments. Thresholds on all three chromatic vectors measured with the CCT showed age-related increases. Protan and deutan vector thresholds increased linearly with age while the tritan vector threshold was described with a bilinear model. Analysis and modeling demonstrated that the nominal vectors of the CCT are shifted by senescent changes in ocular media density, and a method for correcting the CCT vectors is demonstrated. A correction for these shifts indicates that classification among individuals of different ages is unaffected. New vector thresholds for elderly observers and for all age groups are suggested based on calculated tolerance limits. PMID:26974943

Auditory threshold shifts after glycerol administration to patients with suspected Menière's disease: a retrospective analysis.

PubMed

Basel, Türker; Lütkenhöner, Bernd

2013-01-01

Nearly half a century ago, administration of glycerol was shown to temporarily improve the threshold of hearing in patients with suspected Menière's disease (glycerol test). Although a positive test result provides strong evidence of Menière's disease, the test has not gained widespread acceptance. A probable reason is that there is no consensus as to the definition of positive. Moreover, a negative test result is of little diagnostic value because Menière's disease cannot be excluded. By reanalyzing archived data, the authors sought to understand the test in light of signal detection theory. Moreover, they explored the possibility of estimating the probability of a positive test result from the pretest audiogram. The study is based on audiograms from 347 patients (356 ears) who underwent a glycerol test to corroborate a suspected diagnosis of Menière's disease. Subsequent to an initial pure-tone audiogram, glycerol (1.2 mL/kg body weight) was orally administered; follow-up audiograms were obtained after 1, 2, 3, and 4 hr. Transcription of the audiograms into a computer-readable form made them available for automated reanalysis. Averaged difference audiograms provided detailed insight into the frequency dependence and the temporal dynamics of the glycerol-induced threshold reduction. The strongest threshold reduction was observed 4 hr after glycerol intake, although nearly the same effect was already found after 3 hr. Strong overall threshold reductions were associated with a pronounced maximum at approximately 1000 Hz; weaker effects were associated with a plateau between 125 and 1000 Hz and a rapid decrease toward higher frequencies. To date, criteria suggested for a positive test result vastly differ in both sensitivity (with regard to the detection of a threshold reduction) and specificity (1 minus false-positive rate). Here, a criterion based on the aggregate threshold reduction in adjacent audiometric frequencies is suggested. This approach does not only seem to be more robust but also permits to freely adjust the false-positive rate. A positive test result is particularly likely when the mean low-frequency hearing loss is approximately 60 dB and the mean high-frequency hearing loss does not exceed 50 dB. If the pretest audiogram does not render a positive test result unlikely, a state-of-the-art implementation of the glycerol test is a competitive method for corroborating a suspected diagnosis of Menière's disease.

Impairment of retinal increment thresholds in Huntington's disease.

PubMed

Paulus, W; Schwarz, G; Werner, A; Lange, H; Bayer, A; Hofschuster, M; Müller, N; Zrenner, E

1993-10-01

We have investigated detection thresholds for a foveal blue test light using a Maxwellian view system in 61 normal subjects, 19 patients with Huntington's chorea, 14 patients with Tourette's syndrome, and 20 patients with schizophrenia. Ten measurements were made: The blue test light (1 degree diameter, 500 msec duration) was presented either superimposed on a yellow adaptation field (5 degree diameter) or 500 msec after switching off this field (transient tritanopia effect). In both cases five different background intensities were presented. The only abnormality found was in patients with Huntington's chorea. During adaptation these patients' thresholds are significantly higher than normal (p < 0.005). No change was found in the transient tritanopia effect. Huntington's disease causes degeneration of several different transmitter systems in the brain. Increment threshold testing allows for noninvasive investigation of patients and confirms the involvement of the retina in the degenerative process in Huntington's chorea.

Safety and clinical performance of acoustic reflex tests.

PubMed

Hunter, L L; Ries, D T; Schlauch, R S; Levine, S C; Ward, W D

1999-12-01

Safety and effectiveness of acoustic reflex tests are important issues because these tests are widely applied to screen for retrocochlear pathology. Previous studies have reported moderately high sensitivity and specificity for detection of acoustic neuroma. However, there have been reports of possible iatrogenic hearing loss resulting from acoustic reflex threshold (ART) and decay (ARD) tests. This study assessed safety and clinical performance of ART tests for detection of acoustic neuroma. We report a case in which ARD testing resulted in a significant bilateral permanent threshold shift. This case was the impetus for us to investigate the clinical utility of ART and ARD tests. We analyzed sensitivity and specificity of ART, as well as asymmetry in pure-tone thresholds (PTT) for detection of acoustic neuroma in 56 tumor and 108 non-tumor ears. Sensitivity and specificity were higher for PTT asymmetry than for ART. Ipsilateral ART at 1000 Hz had poor sensitivity and specificity for detection of acoustic neuroma, and involves some potential risk to residual hearing for presentation levels higher than 115 dB SPL. Approximately half of the acoustic neuroma group had ipsilateral ARTs that would require administration of ARD tests at levels exceeding 115 dB SPL. Therefore, we conclude that PTT asymmetry is a more effective test for detection of acoustic neuroma, and involves no risk to residual hearing. Future studies of contralateral reflex threshold and ARD in combination with PTT asymmetry are recommended.

Two-flash thresholds as a function of comparison stimulus duration.

DOT National Transportation Integrated Search

1970-09-01

The proposal that two-flash thresholds may be used as direct measures of the critical duration (tc) of Bloch's law was tested. Two-flash threshold was found to be an increasing function of comparison stimulus duration for durations of 3 to 22 msec. i...

When is rational to order a diagnostic test, or prescribe treatment: the threshold model as an explanation of practice variation.

PubMed

Djulbegovic, Benjamin; van den Ende, Jef; Hamm, Robert M; Mayrhofer, Thomas; Hozo, Iztok; Pauker, Stephen G

2015-05-01

The threshold model represents an important advance in the field of medical decision-making. It is a linchpin between evidence (which exists on the continuum of credibility) and decision-making (which is a categorical exercise - we decide to act or not act). The threshold concept is closely related to the question of rational decision-making. When should the physician act, that is order a diagnostic test, or prescribe treatment? The threshold model embodies the decision theoretic rationality that says the most rational decision is to prescribe treatment when the expected treatment benefit outweighs its expected harms. However, the well-documented large variation in the way physicians order diagnostic tests or decide to administer treatments is consistent with a notion that physicians' individual action thresholds vary. We present a narrative review summarizing the existing literature on physicians' use of a threshold strategy for decision-making. We found that the observed variation in decision action thresholds is partially due to the way people integrate benefits and harms. That is, explanation of variation in clinical practice can be reduced to a consideration of thresholds. Limited evidence suggests that non-expected utility threshold (non-EUT) models, such as regret-based and dual-processing models, may explain current medical practice better. However, inclusion of costs and recognition of risk attitudes towards uncertain treatment effects and comorbidities may improve the explanatory and predictive value of the EUT-based threshold models. The decision when to act is closely related to the question of rational choice. We conclude that the medical community has not yet fully defined criteria for rational clinical decision-making. The traditional notion of rationality rooted in EUT may need to be supplemented by reflective rationality, which strives to integrate all aspects of medical practice - medical, humanistic and socio-economic - within a coherent reasoning system. © 2015 Stichting European Society for Clinical Investigation Journal Foundation.

Yields of Soviet underground nuclear explosions from seismic surface waves: Compliance with the Threshold Test Ban Treaty

PubMed Central

Sykes, Lynn R.; Cifuentes, Inés L.

1984-01-01

Magnitudes of the larger Soviet underground nuclear weapons tests from the start of the Threshold Test Ban Treaty in 1976 through 1982 are determined for short- and long-period seismic waves. Yields are calculated from the surface wave magnitude for those explosions at the eastern Kazakh test site that triggered a small-to-negligible component of tectonic stress and are used to calibrate body wave magnitude-yield relationship that can be used to determine the sizes of other explosions at that test site. The results confirm that a large bias, related to differential attenuation of P waves, exists between Nevada and Central Asia. The yields of the seven largest Soviet explosions are nearly identical and are close to 150 kilotons, the limit set by the Threshold Treaty. PMID:16593440

Rationality, practice variation and person-centred health policy: a threshold hypothesis.

PubMed

Djulbegovic, Benjamin; Hamm, Robert M; Mayrhofer, Thomas; Hozo, Iztok; Van den Ende, Jef

2015-12-01

Variation in practice of medicine is one of the major health policy issues of today. Ultimately, it is related to physicians' decision making. Similar patients with similar likelihood of having disease are often managed by different doctors differently: some doctors may elect to observe the patient, others decide to act based on diagnostic testing and yet others may elect to treat without testing. We explain these differences in practice by differences in disease probability thresholds at which physicians decide to act: contextual social and clinical factors and emotions such as regret affect the threshold by influencing the way doctors integrate objective data related to treatment and testing. However, depending on a theoretical construct each of the physician's behaviour can be considered rational. In fact, we showed that the current regulatory policies lead to predictably low thresholds for most decisions in contemporary practice. As a result, we may expect continuing motivation for overuse of treatment and diagnostic tests. We argue that rationality should take into account both formal principles of rationality and human intuitions about good decisions along the lines of Rawls' 'reflective equilibrium/considered judgment'. In turn, this can help define a threshold model that is empirically testable. © 2015 The Authors. Journal of Evaluation in Clinical Practice published by John Wiley & Sons, Ltd.

Development of an anaerobic threshold (HRLT, HRVT) estimation equation using the heart rate threshold (HRT) during the treadmill incremental exercise test

PubMed Central

Ham, Joo-ho; Park, Hun-Young; Kim, Youn-ho; Bae, Sang-kon; Ko, Byung-hoon

2017-01-01

[Purpose] The purpose of this study was to develop a regression model to estimate the heart rate at the lactate threshold (HRLT) and the heart rate at the ventilatory threshold (HRVT) using the heart rate threshold (HRT), and to test the validity of the regression model. [Methods] We performed a graded exercise test with a treadmill in 220 normal individuals (men: 112, women: 108) aged 20–59 years. HRT, HRLT, and HRVT were measured in all subjects. A regression model was developed to estimate HRLT and HRVT using HRT with 70% of the data (men: 79, women: 76) through randomization (7:3), with the Bernoulli trial. The validity of the regression model developed with the remaining 30% of the data (men: 33, women: 32) was also examined. [Results] Based on the regression coefficient, we found that the independent variable HRT was a significant variable in all regression models. The adjusted R2 of the developed regression models averaged about 70%, and the standard error of estimation of the validity test results was 11 bpm, which is similar to that of the developed model. [Conclusion] These results suggest that HRT is a useful parameter for predicting HRLT and HRVT. PMID:29036765

Development of an anaerobic threshold (HRLT, HRVT) estimation equation using the heart rate threshold (HRT) during the treadmill incremental exercise test.

PubMed

Ham, Joo-Ho; Park, Hun-Young; Kim, Youn-Ho; Bae, Sang-Kon; Ko, Byung-Hoon; Nam, Sang-Seok

2017-09-30

The purpose of this study was to develop a regression model to estimate the heart rate at the lactate threshold (HRLT) and the heart rate at the ventilatory threshold (HRVT) using the heart rate threshold (HRT), and to test the validity of the regression model. We performed a graded exercise test with a treadmill in 220 normal individuals (men: 112, women: 108) aged 20-59 years. HRT, HRLT, and HRVT were measured in all subjects. A regression model was developed to estimate HRLT and HRVT using HRT with 70% of the data (men: 79, women: 76) through randomization (7:3), with the Bernoulli trial. The validity of the regression model developed with the remaining 30% of the data (men: 33, women: 32) was also examined. Based on the regression coefficient, we found that the independent variable HRT was a significant variable in all regression models. The adjusted R2 of the developed regression models averaged about 70%, and the standard error of estimation of the validity test results was 11 bpm, which is similar to that of the developed model. These results suggest that HRT is a useful parameter for predicting HRLT and HRVT. ©2017 The Korean Society for Exercise Nutrition

Are there any differences between different testing sites? A cross-sectional study of a Norwegian low-threshold HIV testing service for men who have sex with men.

PubMed

Moseng, Bera Ulstein; Bjørnshagen, Vegar

2017-10-06

To describe a Norwegian low-threshold HIV testing service targeting men who have sex with men (MSM). After the HIV testing consultation, all users of the HIV testing service were invited to answer the study questionnaire. The study setting included the sites where testing was performed, that is, the testing service's office in Oslo, cruising areas, bars/clubs and in hotels in other Norwegian cities. MSM users of the testing service. Data were collected on demographics, HIV testing and sexual behaviour as well as the participant's motivations for choosing to take an HIV test at this low-threshold HIV testing service. The data are stratified by testing site. 1577 HIV testing consultations were performed, the study sample consisted of 732 MSM users. 11 tested positive for HIV. 21.7% had a non-western background, 27.1% reported having a non-gay sexual orientation. 21.9% had 10 or more male sexual partners during the last year, 27.9% reported also having had a female sexual partner. 56.4% reported having practised unprotected anal intercourse during the last 6 months. 20.1% had never tested for HIV before. Most of these user characteristics varied by testing sites. The Norwegian low-threshold testing service recruits target groups that are otherwise hard to reach with HIV testing. This may indicate that the testing service contributes to increase HIV testing rates among MSM in Norway. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Quantitative sensory studies in complex regional pain syndrome type 1/RSD.

PubMed

Tahmoush, A J; Schwartzman, R J; Hopp, J L; Grothusen, J R

2000-12-01

Patients with complex regional pain syndrome type I (CRPSD1) may have thermal allodynia after application of a non-noxious thermal stimulus to the affected limb. We measured the warm, cold, heat-evoked pain threshold and the cold-evoked pain threshold in the affected area of 16 control patients and patients with complex regional pain syndrome type 1/RSD to test the hypothesis that allodynia results from an abnormality in sensory physiology. A contact thermode was used to apply a constant 1 degrees C/second increasing (warm and heat-evoked pain) or decreasing (cold and cold-evoked pain) thermal stimulus until the patient pressed the response button to show that a temperature change was felt by the patient. Student t test was used to compare thresholds in patients and control patients. The cold-evoked pain threshold in patients with CRPSD1/RSD (p <0.001) was significantly decreased when compared with the thresholds in control patients (i.e., a smaller decrease in temperature was necessary to elicit cold-pain in patients with CRPSD1/RSD than in control patients). The heat-evoked pain threshold in patients with CRPS1/RSD was (p <0.05) decreased significantly when compared with thresholds in control patients. The warm- and cold-detection thresholds in patients with CRPS1/RSD were similar to the thresholds in control patients. This study suggests that thermal allodynia in patients with CRPS1/RSD results from decreased cold-evoked and heat-evoked pain thresholds. The thermal pain thresholds are reset (decreased) so that non-noxious thermal stimuli are perceived to be pain (allodynia).

Functional sensibility of the hand in leprosy patients.

PubMed

van Brakel, W H; Kets, C M; van Leerdam, M E; Khawas, I B; Gurung, K S

1997-03-01

The aims of this cross-sectional comparative study was to compare the results of Semmes-Weinstein monofilament testing (SWM) and moving 2-point discrimination (M2PD) with four tests of functional sensibility: recognition of objects, discrimination of size and texture and detection of dots. Ninety-eight leprosy in- and outpatients at Green Pastures Hospital in Pokhara, Nepal were tested with each of the above tests and the results were compared to see how well they agreed. Using the tests of functional sensibility as reference points, we examined the validity of the SWM and M2PD as predictors of functional sensibility. There was definite, but only moderate correlation between thresholds of monofilaments and M2PD and functional sensibility of the hand. A normal result with the SWM and/or M2PD had a good predictive value for normal functional sensibility. Sensitivity was reasonable against recognition of objects and discrimination of textures as reference tests (80-90% and 88-93%), but poor against discrimination of size and detection of dots (50-75% and 43-65%). Specificity was high for most combinations of SWM or M2PD with any of the tests of functional sensibility (85-99%). Above a monofilament threshold of 2 g, the predictive value of an abnormal test was 100% for dot detection and 83-92% for textural discrimination. This indicates that impairment of touch sensibility at this level correlates well with loss of dot detection and textural discrimination in patients with leprous neuropathy. For M2PD the pattern was very similar. Above a threshold of 5 mm, 95-100% of affected hands had loss of dot detection and 73-80% had loss of textural discrimination. Monofilament testing and M2PD did not seem suitable as proxy measures of functional sensibility of the hand in leprosy patients. However, a normal threshold with monofilaments and/or M2PD had a good predictive value for normal functional sensibility. Above a monofilament threshold of 2 g and/or a M2PD threshold of 5 mm, textural discrimination was abnormal in most hands.

In-air hearing of a diving duck: A comparison of psychoacoustic and auditory brainstem response thresholds

USGS Publications Warehouse

Crowell, Sara E.; Wells-Berlin, Alicia M.; Therrien, Ronald E.; Yannuzzi, Sally E.; Carr, Catherine E.

2016-01-01

Auditory sensitivity was measured in a species of diving duck that is not often kept in captivity, the lesser scaup. Behavioral (psychoacoustics) and electrophysiological [the auditory brainstem response (ABR)] methods were used to measure in-air auditory sensitivity, and the resulting audiograms were compared. Both approaches yielded audiograms with similar U-shapes and regions of greatest sensitivity (2000−3000 Hz). However, ABR thresholds were higher than psychoacoustic thresholds at all frequencies. This difference was least at the highest frequency tested using both methods (5700 Hz) and greatest at 1000 Hz, where the ABR threshold was 26.8 dB higher than the behavioral measure of threshold. This difference is commonly reported in studies involving many different species. These results highlight the usefulness of each method, depending on the testing conditions and availability of the animals.

In-air hearing of a diving duck: A comparison of psychoacoustic and auditory brainstem response thresholds.

PubMed

Crowell, Sara E; Wells-Berlin, Alicia M; Therrien, Ronald E; Yannuzzi, Sally E; Carr, Catherine E

2016-05-01

Auditory sensitivity was measured in a species of diving duck that is not often kept in captivity, the lesser scaup. Behavioral (psychoacoustics) and electrophysiological [the auditory brainstem response (ABR)] methods were used to measure in-air auditory sensitivity, and the resulting audiograms were compared. Both approaches yielded audiograms with similar U-shapes and regions of greatest sensitivity (2000-3000 Hz). However, ABR thresholds were higher than psychoacoustic thresholds at all frequencies. This difference was least at the highest frequency tested using both methods (5700 Hz) and greatest at 1000 Hz, where the ABR threshold was 26.8 dB higher than the behavioral measure of threshold. This difference is commonly reported in studies involving many different species. These results highlight the usefulness of each method, depending on the testing conditions and availability of the animals.

Auditory steady state response in sound field.

PubMed

Hernández-Pérez, H; Torres-Fortuny, A

2013-02-01

Physiological and behavioral responses were compared in normal-hearing subjects via analyses of the auditory steady-state response (ASSR) and conventional audiometry under sound field conditions. The auditory stimuli, presented through a loudspeaker, consisted of four carrier tones (500, 1000, 2000, and 4000 Hz), presented singly for behavioral testing but combined (multiple frequency technique), to estimate thresholds using the ASSR. Twenty normal-hearing adults were examined. The average differences between the physiological and behavioral thresholds were between 17 and 22 dB HL. The Spearman rank correlation between ASSR and behavioral thresholds was significant for all frequencies (p < 0.05). Significant differences were found in the ASSR amplitude among frequencies, and strong correlations between the ASSR amplitude and the stimulus level (p < 0.05). The ASSR in sound field testing was found to yield hearing threshold estimates deemed to be reasonably well correlated with behaviorally assessed thresholds.

A comparison of underwater hearing sensitivity in bottlenose dolphins (Tursiops truncatus) determined by electrophysiological and behavioral methods.

PubMed

Houser, Dorian S; Finneran, James J

2006-09-01

Variable stimulus presentation methods are used in auditory evoked potential (AEP) estimates of cetacean hearing sensitivity, each of which might affect stimulus reception and hearing threshold estimates. This study quantifies differences in underwater hearing thresholds obtained by AEP and behavioral means. For AEP estimates, a transducer embedded in a suction cup (jawphone) was coupled to the dolphin's lower jaw for stimulus presentation. Underwater AEP thresholds were obtained for three dolphins in San Diego Bay and for one dolphin in a quiet pool. Thresholds were estimated from the envelope following response at carrier frequencies ranging from 10 to 150 kHz. One animal, with an atypical audiogram, demonstrated significantly greater hearing loss in the right ear than in the left. Across test conditions, the range and average difference between AEP and behavioral threshold estimates were consistent with published comparisons between underwater behavioral and in-air AEP thresholds. AEP thresholds for one animal obtained in-air and in a quiet pool demonstrated a range of differences of -10 to 9 dB (mean = 3 dB). Results suggest that for the frequencies tested, the presentation of sound stimuli through a jawphone, underwater and in-air, results in acceptable differences to AEP threshold estimates.

Effects of acute hypoxia on the determination of anaerobic threshold using the heart rate-work rate relationships during incremental exercise tests.

PubMed

Ozcelik, O; Kelestimur, H

2004-01-01

Anaerobic threshold which describes the onset of systematic increase in blood lactate concentration is a widely used concept in clinical and sports medicine. A deflection point between heart rate-work rate has been introduced to determine the anaerobic threshold non-invasively. However, some researchers have consistently reported a heart rate deflection at higher work rates, while others have not. The present study was designed to investigate whether the heart rate deflection point accurately predicts the anaerobic threshold under the condition of acute hypoxia. Eight untrained males performed two incremental exercise tests using an electromagnetically braked cycle ergometer: one breathing room air and one breathing 12 % O2. The anaerobic threshold was estimated using the V-slope method and determined from the increase in blood lactate and the decrease in standard bicarbonate concentration. This threshold was also estimated by in the heart rate-work rate relationship. Not all subjects exhibited a heart rate deflection. Only two subjects in the control and four subjects in the hypoxia groups showed a heart rate deflection. Additionally, the heart rate deflection point overestimated the anaerobic threshold. In conclusion, the heart rate deflection point was not an accurate predictor of anaerobic threshold and acute hypoxia did not systematically affect the heart rate-work rate relationships.

Comparison of two insulin assays for first-phase insulin release in type 1 diabetes prediction and prevention studies

PubMed Central

Mahon, Jeffrey L.; Beam, Craig A.; Marcovina, Santica M.; Boulware, David C.; Palmer, Jerry P.; Winter, William E.; Skyler, Jay S.; Krischer, Jeffrey P.

2018-01-01

Background Detection of below-threshold first-phase insulin release or FPIR (1 + 3 minute insulin concentrations during an intravenous glucose tolerance test [IVGTT]) is important in type 1 diabetes prediction and prevention studies including the TrialNet Oral Insulin Prevention Trial. We assessed whether an insulin immunoenzymometric assay (IEMA) could replace the less practical but current standard of a radioimmunoassay (RIA) for FPIR. Methods One hundred thirty-three islet autoantibody positive relatives of persons with type 1 diabetes underwent 161 IVGTTs. Insulin concentrations were measured by both assays in 1056 paired samples. A rule classifying FPIR (below-threshold, above-threshold, uncertain) by the IEMA was derived and validated against FPIR by the RIA. Results The insulin IEMA-based rule accurately classified below- and above-threshold FPIRs by the RIA in 110/161 (68%) IVGTTs, but was uncertain in 51/161 (32%) tests for which FPIR by RIA is needed. An uncertain FPIR by the IEMA was more likely among below-threshold vs above-threshold FPIRs by the RIA (64% [30/47] vs. 18% [21/114], respectively; p < 0.05). Conclusions An insulin IEMA for FPIR in subjects at risk for type 1 diabetes accurately determined below- and above-threshold FPIRs in 2/3 of tests relative to the current standard of the insulin RIA, but could not reliably classify the remaining FPIRs. TrialNet is limiting the insulin RIA for FPIR to the latter given the practical advantages of the more specific IEMA. PMID:21843518

Evaluation of Mandarin Chinese Speech Recognition in Adults with Cochlear Implants Using the Spectral Ripple Discrimination Test

PubMed Central

Dai, Chuanfu; Zhao, Zeqi; Zhang, Duo; Lei, Guanxiong

2018-01-01

Background The aim of this study was to explore the value of the spectral ripple discrimination test in speech recognition evaluation among a deaf (post-lingual) Mandarin-speaking population in China following cochlear implantation. Material/Methods The study included 23 Mandarin-speaking adult subjects with normal hearing (normal-hearing group) and 17 deaf adults who were former Mandarin-speakers, with cochlear implants (cochlear implantation group). The normal-hearing subjects were divided into men (n=10) and women (n=13). The spectral ripple discrimination thresholds between the groups were compared. The correlation between spectral ripple discrimination thresholds and Mandarin speech recognition rates in the cochlear implantation group were studied. Results Spectral ripple discrimination thresholds did not correlate with age (r=−0.19; p=0.22), and there was no significant difference in spectral ripple discrimination thresholds between the male and female groups (p=0.654). Spectral ripple discrimination thresholds of deaf adults with cochlear implants were significantly correlated with monosyllabic recognition rates (r=0.84; p=0.000). Conclusions In a Mandarin Chinese speaking population, spectral ripple discrimination thresholds of normal-hearing individuals were unaffected by both gender and age. Spectral ripple discrimination thresholds were correlated with Mandarin monosyllabic recognition rates of Mandarin-speaking in post-lingual deaf adults with cochlear implants. The spectral ripple discrimination test is a promising method for speech recognition evaluation in adults following cochlear implantation in China. PMID:29806954

Evaluation of Mandarin Chinese Speech Recognition in Adults with Cochlear Implants Using the Spectral Ripple Discrimination Test.

PubMed

Dai, Chuanfu; Zhao, Zeqi; Shen, Weidong; Zhang, Duo; Lei, Guanxiong; Qiao, Yuehua; Yang, Shiming

2018-05-28

BACKGROUND The aim of this study was to explore the value of the spectral ripple discrimination test in speech recognition evaluation among a deaf (post-lingual) Mandarin-speaking population in China following cochlear implantation. MATERIAL AND METHODS The study included 23 Mandarin-speaking adult subjects with normal hearing (normal-hearing group) and 17 deaf adults who were former Mandarin-speakers, with cochlear implants (cochlear implantation group). The normal-hearing subjects were divided into men (n=10) and women (n=13). The spectral ripple discrimination thresholds between the groups were compared. The correlation between spectral ripple discrimination thresholds and Mandarin speech recognition rates in the cochlear implantation group were studied. RESULTS Spectral ripple discrimination thresholds did not correlate with age (r=-0.19; p=0.22), and there was no significant difference in spectral ripple discrimination thresholds between the male and female groups (p=0.654). Spectral ripple discrimination thresholds of deaf adults with cochlear implants were significantly correlated with monosyllabic recognition rates (r=0.84; p=0.000). CONCLUSIONS In a Mandarin Chinese speaking population, spectral ripple discrimination thresholds of normal-hearing individuals were unaffected by both gender and age. Spectral ripple discrimination thresholds were correlated with Mandarin monosyllabic recognition rates of Mandarin-speaking in post-lingual deaf adults with cochlear implants. The spectral ripple discrimination test is a promising method for speech recognition evaluation in adults following cochlear implantation in China.

Determining lower threshold concentrations for synergistic effects.

PubMed

Bjergager, Maj-Britt Andersen; Dalhoff, Kristoffer; Kretschmann, Andreas; Nørgaard, Katrine Banke; Mayer, Philipp; Cedergreen, Nina

2017-01-01

Though only occurring rarely, synergistic interactions between chemicals in mixtures have long been a point of focus. Most studies analyzing synergistic interactions used unrealistically high chemical concentrations. The aim of the present study is to determine the threshold concentration below which proven synergists cease to act as synergists towards the aquatic crustacean Daphnia magna. To do this, we compared several approaches and test-setups to evaluate which approach gives the most conservative estimate for the lower threshold for synergy for three known azole synergists. We focus on synergistic interactions between the pyrethroid insecticide, alpha-cypermethrin, and one of the three azole fungicides prochloraz, propiconazole or epoxiconazole measured on Daphnia magna immobilization. Three different experimental setups were applied: A standard 48h acute toxicity test, an adapted 48h test using passive dosing for constant chemical exposure concentrations, and a 14-day test. Synergy was defined as occuring in mixtures where either EC 50 values decreased more than two-fold below what was predicted by concentration addition (horizontal assessment) or as mixtures where the fraction of immobile organisms increased more than two-fold above what was predicted by independent action (vertical assessment). All three tests confirmed the hypothesis of the existence of a lower azole threshold concentration below which no synergistic interaction was observed. The lower threshold concentration, however, decreased with increasing test duration from 0.026±0.013μM (9.794±4.897μgL -1 ), 0.425±0.089μM (145.435±30.46μgL -1 ) and 0.757±0.253μM (249.659±83.44μgL -1 ) for prochloraz, propiconazole and epoxiconazole in standard 48h toxicity tests to 0.015±0.004μM (5.651±1.507μgL -1 ), 0.145±0.025μM (49.619±8.555μgL -1 ) and 0.122±0.0417μM (40.236±13.75μgL -1 ), respectively, in the 14-days tests. Testing synergy in relation to concentration addition provided the most conservative values. The threshold values for the vertical assessments in tests where the two could be compared were in general 1.2 to 4.7 fold higher than the horizontal assessments. Using passive dosing rather than dilution series or spiking did not lower the threshold significantly. Below the threshold for synergy, slight antagony could often be observed. This is most likely due to induction of enzymes active in metabolization of alpha-cypermethrin. The results emphasize the importance of test duration when assessing synergy, but also show that azole concentrations within the typically monitored range of up to 0.5μgL -1 are not likely to cause severe synergy concerning Daphnia magna immobilization. Copyright © 2016 Elsevier B.V. All rights reserved.

Changes of pressure and humidity affect olfactory function.

PubMed

Kuehn, Michael; Welsch, Heiko; Zahnert, Thomas; Hummel, Thomas

2008-03-01

The present study aimed at investigating the question whether olfactory function changes in relation to barometric pressure and humidity. Using climate chambers, odor threshold and discrimination for butanol were tested in 75 healthy volunteers under hypobaric and hyperbaric, and different humidity conditions. Among other effects, olfactory sensitivity at threshold level, but not suprathreshold odor discrimination, was impaired in a hypobaric compared to a hyperbaric milieu, and thresholds were lower in humid, compared to relatively dry conditions. In conclusion, environmental conditions modulate the sense of smell, and may, consecutively, influence results from olfactory tests.

Controversies in the physiological basis of the 'anaerobic threshold' and their implications for clinical cardiopulmonary exercise testing.

PubMed

Hopker, J G; Jobson, S A; Pandit, J J

2011-02-01

This article reviews the notion of the 'anaerobic threshold' in the context of cardiopulmonary exercise testing. Primarily, this is a review of the proposed mechanisms underlying the ventilatory and lactate response to incremental exercise, which is important to the clinical interpretation of an exercise test. Since such tests are often conducted for risk stratification before major surgery, a failure to locate or justify the existence of an anaerobic threshold will have some implications for clinical practice. We also consider alternative endpoints within the exercise response that might be better used to indicate a patient's capacity to cope with the metabolic demands encountered both during and following major surgery. © 2011 The Authors. Anaesthesia © 2011 The Association of Anaesthetists of Great Britain and Ireland.

Effect of mental stress on cold pain in chronic tension-type headache sufferers.

PubMed

Cathcart, Stuart; Winefield, Anthony H; Lushington, Kurt; Rolan, Paul

2009-10-01

Mental stress is a noted contributing factor in chronic tension-type headache (CTH), however the mechanisms underlying this are not clearly understood. One proposition is that stress aggravates already increased pain sensitivity in CTH sufferers. This hypothesis could be partially tested by examining effects of mental stress on threshold and supra-threshold experimental pain processing in CTH sufferers. Such studies have not been reported to date. The present study measured pain detection and tolerance thresholds and ratings of supra-threshold pain stimulation from cold pressor test in CTH sufferers (CTH-S) and healthy Control (CNT) subjects exposed to a 60-min stressful mental task, and in CTH sufferers exposed to a 60-min neutral condition (CTH-N). Headache sufferers had lower pain tolerance thresholds and increased pain intensity ratings compared to controls. Pain detection and tolerance thresholds decreased and pain intensity ratings increased during the stress task, with a greater reduction in pain detection threshold and increase in pain intensity ratings in the CTH-S compared to CNT group. The results support the hypothesis that mental stress contributes to CTH through aggravating already increased pain sensitivity in CTH sufferers.

Result on speech perception after conversion from Spectra® to Freedom®.

PubMed

Magalhães, Ana Tereza de Matos; Goffi-Gomez, Maria Valéria Schmidt; Hoshino, Ana Cristina; Tsuji, Robinson Koji; Bento, Ricardo Ferreira; Brito, Rubens

2012-04-01

New technology in the Freedom® speech processor for cochlear implants was developed to improve how incoming acoustic sound is processed; this applies not only for new users, but also for previous generations of cochlear implants. To identify the contribution of this technology-- the Nucleus 22®--on speech perception tests in silence and in noise, and on audiometric thresholds. A cross-sectional cohort study was undertaken. Seventeen patients were selected. The last map based on the Spectra® was revised and optimized before starting the tests. Troubleshooting was used to identify malfunction. To identify the contribution of the Freedom® technology for the Nucleus22®, auditory thresholds and speech perception tests were performed in free field in sound-proof booths. Recorded monosyllables and sentences in silence and in noise (SNR = 0dB) were presented at 60 dBSPL. The nonparametric Wilcoxon test for paired data was used to compare groups. Freedom® applied for the Nucleus22® showed a statistically significant difference in all speech perception tests and audiometric thresholds. The Freedom® technology improved the performance of speech perception and audiometric thresholds of patients with Nucleus 22®.

Uncertainty Estimates of Psychoacoustic Thresholds Obtained from Group Tests

NASA Technical Reports Server (NTRS)

Rathsam, Jonathan; Christian, Andrew

2016-01-01

Adaptive psychoacoustic test methods, in which the next signal level depends on the response to the previous signal, are the most efficient for determining psychoacoustic thresholds of individual subjects. In many tests conducted in the NASA psychoacoustic labs, the goal is to determine thresholds representative of the general population. To do this economically, non-adaptive testing methods are used in which three or four subjects are tested at the same time with predetermined signal levels. This approach requires us to identify techniques for assessing the uncertainty in resulting group-average psychoacoustic thresholds. In this presentation we examine the Delta Method of frequentist statistics, the Generalized Linear Model (GLM), the Nonparametric Bootstrap, a frequentist method, and Markov Chain Monte Carlo Posterior Estimation and a Bayesian approach. Each technique is exercised on a manufactured, theoretical dataset and then on datasets from two psychoacoustics facilities at NASA. The Delta Method is the simplest to implement and accurate for the cases studied. The GLM is found to be the least robust, and the Bootstrap takes the longest to calculate. The Bayesian Posterior Estimate is the most versatile technique examined because it allows the inclusion of prior information.

Laser-Induced Damage Threshold and Certification Procedures for Optical Materials

NASA Technical Reports Server (NTRS)

1997-01-01

This document provides instructions for performing laser-induced-damage-threshold tests and pass-fail certification tests on optical materials used in pulsed-laser systems. The optical materials to which these procedures apply include coated and uncoated optical substrates, laser crystals, Q-switches, polarizers, and other optical components employed in pulsed-laser systems.

Thermal Threshold Testing for Evaluation of Analgesics in New Zealand White Rabbits

PubMed Central

Barter, Linda S; Kwiatkowski, Anna

2013-01-01

We adapted a thermal analgesiometric device developed for cats for use in unrestrained rabbits. A probe composed of an electrical element and temperature sensor was held against shaved skin by using an elasticized band placed circumferentially around the thorax. An inflated bladder located between the probe and elastic maintained constant contact between probe and skin. The probe was heated until the rabbit displayed a behavioral reaction or the safety cutoff of 55 °C was reached. Threshold temperatures in unmedicated rabbits were stable over a 5-h period provided that tests were 15 min or more apart. Careful acclimation and testing resulted in no false-negative responses, and sham testing did not produce false-positive results. When compared with baseline values, thermal thresholds were significantly increased from 30 to 240 min, but not 300 min, after the administration of morphine at 3 mg/kg. Administration of equivalent volumes of saline via the same route had no effect on thermal threshold. This device may be suitable for investigating analgesic pharmacology in rabbits. PMID:23562032

THRESHOLD STUDIES ON TNT, COMPOSITION B, C-4, AND ANFO EXPLOSIVES USING THE STEVEN IMPACT TEST

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vandersall, K S; Switzer, L L; Garcia, F

2006-06-20

Steven Impact Tests were performed at low velocity on the explosives TNT (trinitrotolulene), Composition B (63% RDX, 36% TNT, and 1% wax by weight), C-4 (91% RDX, 5.3% Di (2-ethylhexyl) sebacate, 2.1% Polyisobutylene, and 1.6% motor oil by weight) and ANFO (94% ammonium Nitrate with 6% Fuel Oil) in attempts to obtain a threshold for reaction. A 76 mm helium driven gas gun was used to accelerate the Steven Test projectiles up to approximately 200 m/s in attempts to react (ignite) the explosive samples. Blast overpressure gauges, acoustic microphones, standard video and high-speed photography were used to characterize the levelmore » of any high explosive reaction violence. No bulk reactions were observed in the TNT, Composition B, C-4 or ANFO explosive samples impacted up to velocities in the range of 190-200 m/s. This work will outline the experimental details and discuss the lack of reaction when compared to the reaction thresholds of other common explosives. These results will also be compared to that of the Susan Test and reaction thresholds observed in the common small-scale safety tests such as the drop hammer and friction tests in hopes of drawing a correlation.« less

Higher certainty of the laser-induced damage threshold test with a redistributing data treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jensen, Lars; Mrohs, Marius; Gyamfi, Mark

2015-10-15

As a consequence of its statistical nature, the measurement of the laser-induced damage threshold holds always risks to over- or underestimate the real threshold value. As one of the established measurement procedures, the results of S-on-1 (and 1-on-1) tests outlined in the corresponding ISO standard 21 254 depend on the amount of data points and their distribution over the fluence scale. With the limited space on a test sample as well as the requirements on test site separation and beam sizes, the amount of data from one test is restricted. This paper reports on a way to treat damage testmore » data in order to reduce the statistical error and therefore measurement uncertainty. Three simple assumptions allow for the assignment of one data point to multiple data bins and therefore virtually increase the available data base.« less

Near-threshold fatigue behavior of copper alloys in air and aqueous environments: A high cyclic frequency study

NASA Astrophysics Data System (ADS)

Ahmed, Tawfik M.

The near-threshold fatigue crack propagation behavior of alpha-phase copper alloys in desiccated air and several aqueous environments has been investigated. Three commercial alloys of nominal composition Cu-30Ni (Cu-Ni), Cu-30Zn (Cu-Zn) and 90Cu-7Al-3Fe (Cu-Al) were tested. Fatigue tests were conducted using standard prefatigued single edged notched (SEN) specimens loaded in tension at a high frequency of ˜100 Hz. Different R-ratios were employed, mostly at R-ratios of 0.5. Low loading levels were used that corresponded to the threshold and near-threshold regions where Delta Kth ≤ DeltaK ≤ 11 MPa√m. Fatigue tests in the aqueous solutions showed that the effect of different corrosive environments during high frequency testing (˜100 Hz) was not as pronounced as was expected when compared relative to air. Further testing revealed that environmental effects were present and fatigue crack growth rates were influenced by the fluid-induced closure effects which are generally reported in the fatigue literature to be operative only in viscous liquids, not in aqueous solutions. It was concluded that high frequency testing in aqueous environments consistently decreased crack growth rates in a manner similar to crack retardation effects in viscous fluids. Several theoretical models reported in the literature have underestimated, if not failed, to adequately predict the fluid induced closure in aqueous solutions. Results from the desiccated air tests confirmed that, under closure-free conditions (high R-ratios), both threshold values and fatigue crack growth rate of stage II can be related to Young's modulus, in agreement with results from the literature. The role of different mechanical and environmental variables on fatigue behavior becomes most visible in the low R -ratio regime, and contribute to various closure processes.

Quantitative somatosensory testing of the penis: optimizing the clinical neurological examination.

PubMed

Bleustein, Clifford B; Eckholdt, Haftan; Arezzo, Joseph C; Melman, Arnold

2003-06-01

Quantitative somatosensory testing, including vibration, pressure, spatial perception and thermal thresholds of the penis, has demonstrated neuropathy in patients with a history of erectile dysfunction of all etiologies. We evaluated which measurement of neurological function of the penis was best at predicting erectile dysfunction and examined the impact of location on the penis for quantitative somatosensory testing measurements. A total of 107 patients were evaluated. All patients were required to complete the erectile function domain of the International Index of Erectile Function (IIEF) questionnaire, of whom 24 had no complaints of erectile dysfunction and scored within the "normal" range on the IIEF. Patients were subsequently tested on ventral middle penile shaft, proximal dorsal midline penile shaft and glans penis (with foreskin retracted) for vibration, pressure, spatial perception, and warm and cold thermal thresholds. Mixed models repeated measures analysis of variance controlling for age, diabetes and hypertension revealed that method of measurement (quantitative somatosensory testing) was predictive of IIEF score (F = 209, df = 4,1315, p <0.001), while site of measurement on the penis was not. To determine the best method of measurement, we used hierarchical regression, which revealed that warm temperature was the best predictor of erectile dysfunction with pseudo R(2) = 0.19, p <0.0007. There was no significant improvement in predicting erectile dysfunction when another test was added. Using 37C and greater as the warm thermal threshold yielded a sensitivity of 88.5%, specificity 70.0% and positive predictive value 85.5%. Quantitative somatosensory testing using warm thermal threshold measurements taken at the glans penis can be used alone to assess the neurological status of the penis. Warm thermal thresholds alone offer a quick, noninvasive accurate method of evaluating penile neuropathy in an office setting.

Neurosensory findings among electricians with self-reported remaining symptoms after an electrical injury: A case series.

PubMed

Rådman, Lisa; Gunnarsson, Lars-Gunnar; Nilsagård, Ylva; Nilsson, Tohr

2016-12-01

Symptoms described in previous studies indicate that electrical injury can cause longstanding injuries to the neurosensory nerves. The aim of the present case series was to objectively assess the profile of neurosensory dysfunction in electricians in relation to high voltage or low voltage electrical injury and the "no-let-go phenomenon". Twenty-three Swedish male electricians exposed to electrical injury were studied by using a battery of clinical instruments, including quantitative sensory testing (QST). The clinical test followed a predetermined order of assessments: thermal perceptions thresholds, vibration perception thresholds, tactile gnosis (the Shape and Texture Identification test), manual dexterity (Purdue Pegboard Test), and grip strength. In addition, pain was studied by means of a questionnaire, and a colour chart was used for estimation of white fingers. The main findings in the present case series were reduced thermal perceptions thresholds, where half of the group showed abnormal values for warm thermal perception and/or cold thermal perception. Also, the tactile gnosis and manual dexterity were reduced. High voltage injury was associated with more reduced sensibility compared to those with low voltage. Neurosensory injury can be objectively assessed after an electrical injury by using QST with thermal perception thresholds. The findings are consistent with injuries to small nerve fibres. In the clinical setting thermal perception threshold is therefore recommended, in addition to tests of tactile gnosis and manual dexterity (Purdue Pegboard). Copyright © 2016 Elsevier Ltd and ISBI. All rights reserved.

Psychophysical assessment of low visual function in patients with retinal degenerative diseases (RDDs) with the Diagnosys full-field stimulus threshold (D-FST).

PubMed

Klein, M; Birch, D G

2009-12-01

To determine whether the Diagnosys full-field stimulus threshold (D-FST) is a valid, sensitive and repeatable psychophysical method of measuring and following visual function in low-vision subjects. Fifty-three affected eyes of 42 subjects with severe retinal degenerative diseases (RDDs) were tested with achromatic stimuli on the D-FST. Included were subjects who were either unable to perform a static perimetric field or had non-detectable or sub-microvolt electroretinograms (ERGs). A subset of 21 eyes of 17 subjects was tested on both the D-FST and the FST2, a previous established full-field threshold test. Seven eyes of 7 normal control subjects were tested on both the D-FST and the FST2. Results for the two methods were compared with the Bland-Altman test. On the D-FST, a threshold could successfully be determined for 13 of 14 eyes with light perception (LP) only (median 0.9 +/- 1.4 log cd/m2), and all eyes determined to be counting fingers (CF; median 0.3 +/- 1.8 log cd/m2). The median full-field threshold for the normal controls was -4.3 +/- 0.6 log cd/m2 on the D-FST and -4.8 +/- 0.9 log cd/m2 on the FST2. The D-FST offers a commercially available method with a robust psychophysical algorithm and is a useful tool for following visual function in low vision subjects.

Thermoreception and nociception of the skin: a classic paper of Bessou and Perl and analyses of thermal sensitivity during a student laboratory exercise.

PubMed

Kuhtz-Buschbeck, Johann P; Andresen, Wiebke; Göbel, Stephan; Gilster, René; Stick, Carsten

2010-06-01

About four decades ago, Perl and collaborators were the first ones who unambiguously identified specifically nociceptive neurons in the periphery. In their classic work, they recorded action potentials from single C-fibers of a cutaneous nerve in cats while applying carefully graded stimuli to the skin (Bessou P, Perl ER. Response of cutaneous sensory units with unmyelinated fibers to noxious stimuli. J Neurophysiol 32: 1025-1043, 1969). They discovered polymodal nociceptors, which responded to mechanical, thermal, and chemical stimuli in the noxious range, and differentiated them from low-threshold thermoreceptors. Their classic findings form the basis of the present method that undergraduate medical students experience during laboratory exercises of sensory physiology, namely, quantitative testing of the thermal detection and pain thresholds. This diagnostic method examines the function of thin afferent nerve fibers. We collected data from nearly 300 students that showed that 1) women are more sensitive to thermal detection and thermal pain at the thenar than men, 2) habituation shifts thermal pain thresholds during repetititve testing, 3) the cold pain threshold is rather variable and lower when tested after heat pain than in the reverse case (order effect), and 4) ratings of pain intensity on a visual analog scale are correlated with the threshold temperature for heat pain but not for cold pain. Median group results could be reproduced in a retest. Quantitative sensory testing of thermal thresholds is feasible and instructive in the setting of a laboratory exercise and is appreciated by the students as a relevant and interesting technique.

The effect of prolonged standing on touch sensitivity threshold of the foot: a pilot study.

PubMed

Wiggermann, Neal E; Werner, Robert A; Keyserling, W Monroe

2012-02-01

To determine the effect of prolonged standing on touch sensitivity of the foot. An observational study with replications. University laboratory. Ten healthy college students (5 men and 5 women), with a mean ± SD age of 23.5 ± 4.1 years and body mass of 67.4 ± 12.6 kg. Semmes-Weinstein monofilament tests were administered to 12 locations on the dorsal and plantar surfaces of the foot before and after 4 hours of standing. These locations were formed into several groupings (toes, metatarsal heads, midfoot, heel, all plantar sites, all dorsal sites), and paired t-tests were used to test for significant changes in sensitivity threshold after standing. The difference between sensitivity thresholds measured before and after standing for different locations on the foot. The average of all sensitivity thresholds on the plantar surface of the foot decreased (indicating increased sensitivity) from 0.56 to 0.36 g (P < .01) after 4 hours of prolonged standing. This change in threshold equated to a difference of 1 Semmes-Weinstein monofilament level. Changes in the sensitivity threshold of the dorsal aspect of the foot were not significant. Analysis of the results suggests that the plantar foot has greater sensitivity to touch after prolonged standing. These findings may be useful for identifying potential unintended bias in clinical touch sensitivity testing. Future research is necessary to understand the underlying mechanisms for this sensitivity change and to determine the onset and recovery times for sensitivity changes. Copyright © 2012 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.

Step length and individual anaerobic threshold assessment in swimming.

PubMed

Fernandes, R J; Sousa, M; Machado, L; Vilas-Boas, J P

2011-12-01

Anaerobic threshold is widely used for diagnosis of swimming aerobic endurance but the precise incremental protocols step duration for its assessment is controversial. A physiological and biomechanical comparison between intermittent incremental protocols with different step lengths and a maximal lactate steady state (MLSS) test was conducted. 17 swimmers performed 7×200, 300 and 400 m (30 s and 24 h rest between steps and protocols) in front crawl until exhaustion and an MLSS test. The blood lactate concentration values ([La-]) at individual anaerobic threshold were 2.1±0.1, 2.2±0.2 and 1.8±0.1 mmol.l - 1 in the 200, 300 and 400 m protocols (with significant differences between 300 and 400 m tests), and 2.9±1.2 mmol.l - 1 at MLSS (higher than the incremental protocols); all these values are much lower than the traditional 4 mmol.l - 1 value. The velocities at individual anaerobic threshold obtained in incremental protocols were similar (and highly related) to the MLSS, being considerably lower than the velocity at 4 mmol.l - 1. Stroke rate increased and stroke length decreased throughout the different incremental protocols. It was concluded that it is valid to use intermittent incremental protocols of 200 and 300 m lengths to assess the swimming velocity corresponding to individual anaerobic threshold, the progressive protocols tend to underestimate the [La-] at anaerobic threshold assessed by the MLSS test, and swimmers increase velocity through stroke rate increases. © Georg Thieme Verlag KG Stuttgart · New York.

Exploration of the psychophysics of a motion displacement hyperacuity stimulus.

PubMed

Verdon-Roe, Gay Mary; Westcott, Mark C; Viswanathan, Ananth C; Fitzke, Frederick W; Garway-Heath, David F

2006-11-01

To explore the summation properties of a motion-displacement hyperacuity stimulus with respect to stimulus area and luminance, with the goal of applying the results to the development of a motion-displacement test (MDT) for the detection of early glaucoma. A computer-generated line stimulus was presented with displacements randomized between 0 and 40 minutes of arc (min arc). Displacement thresholds (50% seen) were compared for stimuli of equal area but different edge length (orthogonal to the direction of motion) at four retinal locations. Also, MDT thresholds were recorded at five values of Michelson contrast (25%-84%) for each of five line lengths (11-128 min arc) at a single nasal location (-27,3). Frequency-of-seeing (FOS) curves were generated and displacement thresholds and interquartile ranges (IQR, 25%-75% seen) determined by probit analysis. Equivalent displacement thresholds were found for stimuli of equal area but half the edge length. Elevations of thresholds and IQR were demonstrated as line length and contrast were reduced. Equivalent displacement thresholds were also found for stimuli of equivalent energy (stimulus area x [stimulus luminance - background luminance]), in accordance with Ricco's law. There was a linear relationship (slope -0.5) between log MDT threshold and log stimulus energy. Stimulus area, rather than edge length, determined displacement thresholds within the experimental conditions tested. MDT thresholds are linearly related to the square root of the total energy of the stimulus. A new law, the threshold energy-displacement (TED) law, is proposed to apply to MDT summation properties, giving the relationship T = K logE where, T is the MDT threshold, Kis the constant, and E is the stimulus energy.

A study of life prediction differences for a nickel-base Alloy 690 using a threshold and a non-threshold model

NASA Astrophysics Data System (ADS)

Young, B. A.; Gao, Xiaosheng; Srivatsan, T. S.

2009-10-01

In this paper we compare and contrast the crack growth rate of a nickel-base superalloy (Alloy 690) in the Pressurized Water Reactor (PWR) environment. Over the last few years, a preponderance of test data has been gathered on both Alloy 690 thick plate and Alloy 690 tubing. The original model, essentially based on a small data set for thick plate, compensated for temperature, load ratio and stress-intensity range but did not compensate for the fatigue threshold of the material. As additional test data on both plate and tube product became available the model was gradually revised to account for threshold properties. Both the original and revised models generated acceptable results for data that were above 1 × 10 -11 m/s. However, the test data at the lower growth rates were over-predicted by the non-threshold model. Since the original model did not take the fatigue threshold into account, this model predicted no operating stress below which the material would effectively undergo fatigue crack growth. Because of an over-prediction of the growth rate below 1 × 10 -11 m/s, due to a combination of low stress, small crack size and long rise-time, the model in general leads to an under-prediction of the total available life of the components.

Why do adults with dyslexia have poor global motion sensitivity?

PubMed

Conlon, Elizabeth G; Lilleskaret, Gry; Wright, Craig M; Stuksrud, Anne

2013-01-01

Two experiments aimed to determine why adults with dyslexia have higher global motion thresholds than typically reading controls. In Experiment 1, the dot density and number of animation frames presented in the dot stimulus were manipulated because of findings that use of a high dot density can normalize coherence thresholds in individuals with dyslexia. Dot densities were 14.15 and 3.54 dots/deg(2). These were presented for five (84 ms) or eight (134 ms) frames. The dyslexia group had higher coherence thresholds in all conditions than controls. However, in the high dot density, long duration condition, both reader groups had the lowest thresholds indicating normal temporal recruitment. These results indicated that the dyslexia group could sample the additional signals dots over space and then integrate these with the same efficiency as controls. In Experiment 2, we determined whether briefly presenting a fully coherent prime moving in either the same or opposite direction of motion to a partially coherent test stimulus would systematically increase and decrease global motion thresholds in the reader groups. When the direction of motion in the prime and test was the same, global motion thresholds increased for both reader groups. The increase in coherence thresholds was significantly greater for the dyslexia group. When the motion of the prime and test were presented in opposite directions, coherence thresholds were reduced in both groups. No group threshold differences were found. We concluded that the global motion processing deficit found in adults with dyslexia can be explained by undersampling of the target motion signals. This might occur because of difficulties directing attention to the relevant motion signals in the random dot pattern, and not a specific difficulty integrating global motion signals. These effects are most likely to occur in the group with dyslexia when more complex computational processes are required to process global motion.

Why do adults with dyslexia have poor global motion sensitivity?

PubMed Central

Conlon, Elizabeth G.; Lilleskaret, Gry; Wright, Craig M.; Stuksrud, Anne

2013-01-01

Two experiments aimed to determine why adults with dyslexia have higher global motion thresholds than typically reading controls. In Experiment 1, the dot density and number of animation frames presented in the dot stimulus were manipulated because of findings that use of a high dot density can normalize coherence thresholds in individuals with dyslexia. Dot densities were 14.15 and 3.54 dots/deg2. These were presented for five (84 ms) or eight (134 ms) frames. The dyslexia group had higher coherence thresholds in all conditions than controls. However, in the high dot density, long duration condition, both reader groups had the lowest thresholds indicating normal temporal recruitment. These results indicated that the dyslexia group could sample the additional signals dots over space and then integrate these with the same efficiency as controls. In Experiment 2, we determined whether briefly presenting a fully coherent prime moving in either the same or opposite direction of motion to a partially coherent test stimulus would systematically increase and decrease global motion thresholds in the reader groups. When the direction of motion in the prime and test was the same, global motion thresholds increased for both reader groups. The increase in coherence thresholds was significantly greater for the dyslexia group. When the motion of the prime and test were presented in opposite directions, coherence thresholds were reduced in both groups. No group threshold differences were found. We concluded that the global motion processing deficit found in adults with dyslexia can be explained by undersampling of the target motion signals. This might occur because of difficulties directing attention to the relevant motion signals in the random dot pattern, and not a specific difficulty integrating global motion signals. These effects are most likely to occur in the group with dyslexia when more complex computational processes are required to process global motion. PMID:24376414

Comparison of two insulin assays for first-phase insulin release in type 1 diabetes prediction and prevention studies.

PubMed

Mahon, Jeffrey L; Beam, Craig A; Marcovina, Santica M; Boulware, David C; Palmer, Jerry P; Winter, William E; Skyler, Jay S; Krischer, Jeffrey P

2011-11-20

Detection of below-threshold first-phase insulin release or FPIR (1+3 minute insulin concentrations during an intravenous glucose tolerance test [IVGTT]) is important in type 1 diabetes prediction and prevention studies including the TrialNet Oral Insulin Prevention Trial. We assessed whether an insulin immunoenzymometric assay (IEMA) could replace the less practical but current standard of a radioimmunoassay (RIA) for FPIR. One hundred thirty-three islet autoantibody positive relatives of persons with type 1 diabetes underwent 161 IVGTTs. Insulin concentrations were measured by both assays in 1056 paired samples. A rule classifying FPIR (below-threshold, above-threshold, uncertain) by the IEMA was derived and validated against FPIR by the RIA. The insulin IEMA-based rule accurately classified below- and above-threshold FPIRs by the RIA in 110/161 (68%) IVGTTs, but was uncertain in 51/161 (32%) tests for which FPIR by RIA is needed. An uncertain FPIR by the IEMA was more likely among below-threshold vs above-threshold FPIRs by the RIA (64% [30/47] vs. 18% [21/114], respectively; p<0.05). An insulin IEMA for FPIR in subjects at risk for type 1 diabetes accurately determined below- and above-threshold FPIRs in 2/3 of tests relative to the current standard of the insulin RIA, but could not reliably classify the remaining FPIRs. TrialNet is limiting the insulin RIA for FPIR to the latter given the practical advantages of the more specific IEMA. Copyright © 2011 Elsevier B.V. All rights reserved.

Determination of Anaerobic Threshold by Heart Rate or Heart Rate Variability using Discontinuous Cycle Ergometry.

PubMed

Park, Sung Wook; Brenneman, Michael; Cooke, William H; Cordova, Alberto; Fogt, Donovan

The purpose was to determine if heart rate (HR) and heart rate variability (HRV) responses would reflect anaerobic threshold (AT) using a discontinuous, incremental, cycle test. AT was determined by ventilatory threshold (VT). Cyclists (30.6±5.9y; 7 males, 8 females) completed a discontinuous cycle test consisting of 7 stages (6 min each with 3 min of rest between). Three stages were performed at power outputs (W) below those corresponding to a previously established AT, one at W corresponding to AT, and 3 at W above those corresponding to AT. The W at the intersection of the trend lines was considered each metric's "threshold". The averaged stage data for Ve, HR, and time- and frequency-domain HRV metrics were plotted versus W. The W at the "threshold" for the metrics of interest were compared using correlation analysis and paired-sample t -test. In all, several heart rate-related parameters accurately reflected AT with significant correlations (p≤0.05) were observed between AT W and HR, mean RR interval (MRR), low and high frequency spectral energy (LF and HR, respectively), high frequency peak (fHF), and HFxfHF metrics' threshold W (i.e., MRRTW, etc.). Differences in HR or HRV metric threshold W and AT for all subjects were less than 14 W. The steady state data from discontinuous protocols may allow for a true indication of steady-state physiologic stress responses and corresponding W at AT, compared to continuous protocols using 1-2 min exercise stages.

Validity of the Talk Test for exercise prescription after myocardial revascularization.

PubMed

Zanettini, Renzo; Centeleghe, Paola; Franzelli, Cristina; Mori, Ileana; Benna, Stefania; Penati, Chiara; Sorlini, Nadia

2013-04-01

For exercise prescription, rating of perceived exertion is the subjective tool most frequently used in addition to methods based on percentage of peak exercise variables. The aim of this study was the validation of a subjective method widely called the Talk Test (TT) for optimization of training intensity in patients with recent myocardial revascularization. Fifty patients with recent myocardial revascularization (17 by coronary artery bypass grafting and 33 by percutaneous coronary intervention) were enrolled in a cardiac rehabilitation programme. Each patient underwent three repetitions of the TT during three different exercise sessions to evaluate the within-patient and between-operators reliability in assessing the workload (WL) at TT thresholds. These parameters were then compared with the data of a final cardiopulmonary exercise testing, and the WL range between the individual aerobic threshold (AeT) and anaerobic threshold (AnT) was considered as the optimal training zone. The within-patient and between-operators reliability in assessing TT thresholds were satisfactory. No significant differences were found between patients' and physiotherapists' evaluations of WL at different TT thresholds. WL at Last TT+ was between AeT and AnT in 88% of patients and slightly

Olfactory Threshold of Chlorine in Oxygen.

DTIC Science & Technology

1977-09-01

The odor threshold of chlorine in oxygen was determined. Measurements were conducted in an altitude chamber, which provided an odor-free and noise...free background. Human male volunteers, with no previous olfactory acuity testing experience, served as panelists. Threshold values were affected by...time intervals between trials and by age differences. The mean threshold value for 11 subjects was 0.08 ppm obtained by positive responses to the lowest detectable level of chlorine in oxygen, 50% of the time. (Author)

A threshold method for immunological correlates of protection

PubMed Central

2013-01-01

Background Immunological correlates of protection are biological markers such as disease-specific antibodies which correlate with protection against disease and which are measurable with immunological assays. It is common in vaccine research and in setting immunization policy to rely on threshold values for the correlate where the accepted threshold differentiates between individuals who are considered to be protected against disease and those who are susceptible. Examples where thresholds are used include development of a new generation 13-valent pneumococcal conjugate vaccine which was required in clinical trials to meet accepted thresholds for the older 7-valent vaccine, and public health decision making on vaccination policy based on long-term maintenance of protective thresholds for Hepatitis A, rubella, measles, Japanese encephalitis and others. Despite widespread use of such thresholds in vaccine policy and research, few statistical approaches have been formally developed which specifically incorporate a threshold parameter in order to estimate the value of the protective threshold from data. Methods We propose a 3-parameter statistical model called the a:b model which incorporates parameters for a threshold and constant but different infection probabilities below and above the threshold estimated using profile likelihood or least squares methods. Evaluation of the estimated threshold can be performed by a significance test for the existence of a threshold using a modified likelihood ratio test which follows a chi-squared distribution with 3 degrees of freedom, and confidence intervals for the threshold can be obtained by bootstrapping. The model also permits assessment of relative risk of infection in patients achieving the threshold or not. Goodness-of-fit of the a:b model may be assessed using the Hosmer-Lemeshow approach. The model is applied to 15 datasets from published clinical trials on pertussis, respiratory syncytial virus and varicella. Results Highly significant thresholds with p-values less than 0.01 were found for 13 of the 15 datasets. Considerable variability was seen in the widths of confidence intervals. Relative risks indicated around 70% or better protection in 11 datasets and relevance of the estimated threshold to imply strong protection. Goodness-of-fit was generally acceptable. Conclusions The a:b model offers a formal statistical method of estimation of thresholds differentiating susceptible from protected individuals which has previously depended on putative statements based on visual inspection of data. PMID:23448322

Analyses of Fatigue Crack Growth and Closure Near Threshold Conditions for Large-Crack Behavior

NASA Technical Reports Server (NTRS)

Newman, J. C., Jr.

1999-01-01

A plasticity-induced crack-closure model was used to study fatigue crack growth and closure in thin 2024-T3 aluminum alloy under constant-R and constant-K(sub max) threshold testing procedures. Two methods of calculating crack-opening stresses were compared. One method was based on a contact-K analyses and the other on crack-opening-displacement (COD) analyses. These methods gave nearly identical results under constant-amplitude loading, but under threshold simulations the contact-K analyses gave lower opening stresses than the contact COD method. Crack-growth predictions tend to support the use of contact-K analyses. Crack-growth simulations showed that remote closure can cause a rapid rise in opening stresses in the near threshold regime for low-constraint and high applied stress levels. Under low applied stress levels and high constraint, a rise in opening stresses was not observed near threshold conditions. But crack-tip-opening displacement (CTOD) were of the order of measured oxide thicknesses in the 2024 alloy under constant-R simulations. In contrast, under constant-K(sub max) testing the CTOD near threshold conditions were an order-of-magnitude larger than measured oxide thicknesses. Residual-plastic deformations under both constant-R and constant-K(sub max) threshold simulations were several times larger than the expected oxide thicknesses. Thus, residual-plastic deformations, in addition to oxide and roughness, play an integral part in threshold development.

High-Pressure Oxygen Test Evaluations

NASA Technical Reports Server (NTRS)

Schwinghamer, R. J.; Key, C. F.

1974-01-01

The relevance of impact sensitivity testing to the development of the space shuttle main engine is discussed in the light of the special requirements for the engine. The background and history of the evolution of liquid and gaseous oxygen testing techniques and philosophy is discussed also. The parameters critical to reliable testing are treated in considerable detail, and test apparatus and procedures are described and discussed. Materials threshold sensitivity determination procedures are considered and a decision logic diagram for sensitivity threshold determination was plotted. Finally, high-pressure materials sensitivity test data are given for selected metallic and nonmetallic materials.

Optimization of a matched-filter receiver for frequency hopping code acquisition in jamming

NASA Astrophysics Data System (ADS)

Pawlowski, P. R.; Polydoros, A.

A matched-filter receiver for frequency hopping (FH) code acquisition is optimized when either partial-band tone jamming or partial-band Gaussian noise jamming is present. The receiver is matched to a segment of the FH code sequence, sums hard per-channel decisions to form a test, and uses multiple tests to verify acquisition. The length of the matched filter and the number of verification tests are fixed. Optimization is then choosing thresholds to maximize performance based upon the receiver's degree of knowledge about the jammer ('side-information'). Four levels of side-information are considered, ranging from none to complete. The latter level results in a constant-false-alarm-rate (CFAR) design. At each level, performance sensitivity to threshold choice is analyzed. Robust thresholds are chosen to maximize performance as the jammer varies its power distribution, resulting in simple design rules which aid threshold selection. Performance results, which show that optimum distributions for the jammer power over the total FH bandwidth exist, are presented.

Determination of the anaerobic threshold in the pre-operative assessment clinic: inter-observer measurement error.

PubMed

Sinclair, R C F; Danjoux, G R; Goodridge, V; Batterham, A M

2009-11-01

The variability between observers in the interpretation of cardiopulmonary exercise tests may impact upon clinical decision making and affect the risk stratification and peri-operative management of a patient. The purpose of this study was to quantify the inter-reader variability in the determination of the anaerobic threshold (V-slope method). A series of 21 cardiopulmonary exercise tests from patients attending a surgical pre-operative assessment clinic were read independently by nine experienced clinicians regularly involved in clinical decision making. The grand mean for the anaerobic threshold was 10.5 ml O(2).kg body mass(-1).min(-1). The technical error of measurement was 8.1% (circa 0.9 ml.kg(-1).min(-1); 90% confidence interval, 7.4-8.9%). The mean absolute difference between readers was 4.5% with a typical random error of 6.5% (6.0-7.2%). We conclude that the inter-observer variability for experienced clinicians determining the anaerobic threshold from cardiopulmonary exercise tests is acceptable.

Automated Vision Test Development and Validation

DTIC Science & Technology

2016-11-01

Deputy Chief, Aerosp Med Consultation Div Chair, Aerospace Medicine Department This report is published in the interest of...produce software for desktop displays; and to evaluate features such as user interfaces, threshold algorithms, validity of results, and screening...cost of performing full threshold testing on over 30% of normal subjects, which is quite time consuming. This effort was accomplished using desktop

Identifying failure in a tree network of a parallel computer

DOEpatents

Archer, Charles J.; Pinnow, Kurt W.; Wallenfelt, Brian P.

2010-08-24

Methods, parallel computers, and products are provided for identifying failure in a tree network of a parallel computer. The parallel computer includes one or more processing sets including an I/O node and a plurality of compute nodes. For each processing set embodiments include selecting a set of test compute nodes, the test compute nodes being a subset of the compute nodes of the processing set; measuring the performance of the I/O node of the processing set; measuring the performance of the selected set of test compute nodes; calculating a current test value in dependence upon the measured performance of the I/O node of the processing set, the measured performance of the set of test compute nodes, and a predetermined value for I/O node performance; and comparing the current test value with a predetermined tree performance threshold. If the current test value is below the predetermined tree performance threshold, embodiments include selecting another set of test compute nodes. If the current test value is not below the predetermined tree performance threshold, embodiments include selecting from the test compute nodes one or more potential problem nodes and testing individually potential problem nodes and links to potential problem nodes.

The Random-Threshold Generalized Unfolding Model and Its Application of Computerized Adaptive Testing

ERIC Educational Resources Information Center

Wang, Wen-Chung; Liu, Chen-Wei; Wu, Shiu-Lien

2013-01-01

The random-threshold generalized unfolding model (RTGUM) was developed by treating the thresholds in the generalized unfolding model as random effects rather than fixed effects to account for the subjective nature of the selection of categories in Likert items. The parameters of the new model can be estimated with the JAGS (Just Another Gibbs…

Automated audiometry using apple iOS-based application technology.

PubMed

Foulad, Allen; Bui, Peggy; Djalilian, Hamid

2013-11-01

The aim of this study is to determine the feasibility of an Apple iOS-based automated hearing testing application and to compare its accuracy with conventional audiometry. Prospective diagnostic study. Setting Academic medical center. An iOS-based software application was developed to perform automated pure-tone hearing testing on the iPhone, iPod touch, and iPad. To assess for device variations and compatibility, preliminary work was performed to compare the standardized sound output (dB) of various Apple device and headset combinations. Forty-two subjects underwent automated iOS-based hearing testing in a sound booth, automated iOS-based hearing testing in a quiet room, and conventional manual audiometry. The maximum difference in sound intensity between various Apple device and headset combinations was 4 dB. On average, 96% (95% confidence interval [CI], 91%-100%) of the threshold values obtained using the automated test in a sound booth were within 10 dB of the corresponding threshold values obtained using conventional audiometry. When the automated test was performed in a quiet room, 94% (95% CI, 87%-100%) of the threshold values were within 10 dB of the threshold values obtained using conventional audiometry. Under standardized testing conditions, 90% of the subjects preferred iOS-based audiometry as opposed to conventional audiometry. Apple iOS-based devices provide a platform for automated air conduction audiometry without requiring extra equipment and yield hearing test results that approach those of conventional audiometry.

Vestibular evoked myogenic potential (VEMP) testing: normative threshold response curves and effects of age.

PubMed

Janky, Kristen L; Shepard, Neil

2009-09-01

Vestibular evoked myogenic potential (VEMP) testing has gained increased interest in the diagnosis of a variety of vestibular etiologies. P13/N23 latency, amplitude and threshold response curves have been used to compare pathologic groups to normal controls. Appropriate characterization of these etiologies requires normative data across the frequency spectrum and age range. The objective of the current study was to test the hypothesis that significant changes in VEMP responses occur as a function of increased age across all test stimuli as well as characterize the VEMP threshold response curve across age. This project incorporated a prospective study design using a sample of convenience. Openly recruited subjects were assigned to groups according to age. Forty-six normal controls ranging between 20 and 76 years of age participated in the study. Participants were separated by decade into five age categories from 20 to 60 plus years. Normal participants were characterized by having normal hearing sensitivity, no history of neurologic or balance/dizziness involvement, and negative results on a direct office vestibular examination. VEMP responses were measured at threshold to click and 250, 500, 750, and 1000 Hz tone burst stimuli and at a suprathreshold level to 500 Hz toneburst stimuli at123 dB SPL. A mixed group factorial ANOVA (analysis of variance) and linear regression were performed to examine the effects of VEMP characteristics on age. There were no significant differences between ears for any of the test parameters. There were no significant differences between age groups for n23 latency or amplitude in response to any of the stimuli. Significant mean differences did exist between age groups for p13 latency (250, 750, and 1000 Hz) and threshold (500 and 750 Hz). Age was significantly correlated with VEMP parameters. VEMP threshold was positively correlated (250, 500, 750, 1000 Hz); and amplitude was negatively correlated (500 Hz maximum). The threshold response curves revealed best frequency tuning at 500 Hz with the highest thresholds in response to click stimuli. However, this best frequency tuning dissipated with increased age. VEMP response rates also decreased with increased age. We have demonstrated that minor differences in VEMP responses occur with age. Given the reduced response rates and flattened frequency tuning curve for individuals over the age of 60, frequency tuning curves may not be a good diagnostic indicator for this age group.

Feature-based attention potentiates recovery of fine direction discrimination in cortically blind patients.

PubMed

Cavanaugh, Matthew R; Barbot, Antoine; Carrasco, Marisa; Huxlin, Krystel R

2017-12-10

Training chronic, cortically-blind (CB) patients on a coarse [left-right] direction discrimination and integration (CDDI) task recovers performance on this task at trained, blind field locations. However, fine direction difference (FDD) thresholds remain elevated at these locations, limiting the usefulness of recovered vision in daily life. Here, we asked if this FDD impairment can be overcome by training CB subjects with endogenous, feature-based attention (FBA) cues. Ten CB subjects were recruited and trained on CDDI and FDD with an FBA cue or FDD with a neutral cue. After completion of each training protocol, FDD thresholds were re-measured with both neutral and FBA cues at trained, blind-field locations and at corresponding, intact-field locations. In intact portions of the visual field, FDD thresholds were lower when tested with FBA than neutral cues. Training subjects in the blind field on the CDDI task improved FDD performance to the point that a threshold could be measured, but these locations remained impaired relative to the intact field. FDD training with neutral cues resulted in better blind field FDD thresholds than CDDI training, but thresholds remained impaired relative to intact field levels, regardless of testing cue condition. Importantly, training FDD in the blind field with FBA lowered FDD thresholds relative to CDDI training, and allowed the blind field to reach thresholds similar to the intact field, even when FBA trained subjects were tested with a neutral rather than FBA cue. Finally, FDD training appeared to also recover normal integration thresholds at trained, blind-field locations, providing an interesting double dissociation with respect to CDDI training. In summary, mechanisms governing FBA appear to function normally in both intact and impaired regions of the visual field following V1 damage. Our results mark the first time that FDD thresholds in CB fields have been seen to reach intact field levels of performance. Moreover, FBA can be leveraged during visual training to recover normal, fine direction discrimination and integration performance at trained, blind-field locations, potentiating visual recovery of more complex and precise aspects of motion perception in cortically-blinded fields. Copyright © 2017 Elsevier Ltd. All rights reserved.

Use of the FDA nozzle model to illustrate validation techniques in computational fluid dynamics (CFD) simulations

PubMed Central

Hariharan, Prasanna; D’Souza, Gavin A.; Horner, Marc; Morrison, Tina M.; Malinauskas, Richard A.; Myers, Matthew R.

2017-01-01

A “credible” computational fluid dynamics (CFD) model has the potential to provide a meaningful evaluation of safety in medical devices. One major challenge in establishing “model credibility” is to determine the required degree of similarity between the model and experimental results for the model to be considered sufficiently validated. This study proposes a “threshold-based” validation approach that provides a well-defined acceptance criteria, which is a function of how close the simulation and experimental results are to the safety threshold, for establishing the model validity. The validation criteria developed following the threshold approach is not only a function of Comparison Error, E (which is the difference between experiments and simulations) but also takes in to account the risk to patient safety because of E. The method is applicable for scenarios in which a safety threshold can be clearly defined (e.g., the viscous shear-stress threshold for hemolysis in blood contacting devices). The applicability of the new validation approach was tested on the FDA nozzle geometry. The context of use (COU) was to evaluate if the instantaneous viscous shear stress in the nozzle geometry at Reynolds numbers (Re) of 3500 and 6500 was below the commonly accepted threshold for hemolysis. The CFD results (“S”) of velocity and viscous shear stress were compared with inter-laboratory experimental measurements (“D”). The uncertainties in the CFD and experimental results due to input parameter uncertainties were quantified following the ASME V&V 20 standard. The CFD models for both Re = 3500 and 6500 could not be sufficiently validated by performing a direct comparison between CFD and experimental results using the Student’s t-test. However, following the threshold-based approach, a Student’s t-test comparing |S-D| and |Threshold-S| showed that relative to the threshold, the CFD and experimental datasets for Re = 3500 were statistically similar and the model could be considered sufficiently validated for the COU. However, for Re = 6500, at certain locations where the shear stress is close the hemolysis threshold, the CFD model could not be considered sufficiently validated for the COU. Our analysis showed that the model could be sufficiently validated either by reducing the uncertainties in experiments, simulations, and the threshold or by increasing the sample size for the experiments and simulations. The threshold approach can be applied to all types of computational models and provides an objective way of determining model credibility and for evaluating medical devices. PMID:28594889

Use of the FDA nozzle model to illustrate validation techniques in computational fluid dynamics (CFD) simulations.

PubMed

Hariharan, Prasanna; D'Souza, Gavin A; Horner, Marc; Morrison, Tina M; Malinauskas, Richard A; Myers, Matthew R

2017-01-01

A "credible" computational fluid dynamics (CFD) model has the potential to provide a meaningful evaluation of safety in medical devices. One major challenge in establishing "model credibility" is to determine the required degree of similarity between the model and experimental results for the model to be considered sufficiently validated. This study proposes a "threshold-based" validation approach that provides a well-defined acceptance criteria, which is a function of how close the simulation and experimental results are to the safety threshold, for establishing the model validity. The validation criteria developed following the threshold approach is not only a function of Comparison Error, E (which is the difference between experiments and simulations) but also takes in to account the risk to patient safety because of E. The method is applicable for scenarios in which a safety threshold can be clearly defined (e.g., the viscous shear-stress threshold for hemolysis in blood contacting devices). The applicability of the new validation approach was tested on the FDA nozzle geometry. The context of use (COU) was to evaluate if the instantaneous viscous shear stress in the nozzle geometry at Reynolds numbers (Re) of 3500 and 6500 was below the commonly accepted threshold for hemolysis. The CFD results ("S") of velocity and viscous shear stress were compared with inter-laboratory experimental measurements ("D"). The uncertainties in the CFD and experimental results due to input parameter uncertainties were quantified following the ASME V&V 20 standard. The CFD models for both Re = 3500 and 6500 could not be sufficiently validated by performing a direct comparison between CFD and experimental results using the Student's t-test. However, following the threshold-based approach, a Student's t-test comparing |S-D| and |Threshold-S| showed that relative to the threshold, the CFD and experimental datasets for Re = 3500 were statistically similar and the model could be considered sufficiently validated for the COU. However, for Re = 6500, at certain locations where the shear stress is close the hemolysis threshold, the CFD model could not be considered sufficiently validated for the COU. Our analysis showed that the model could be sufficiently validated either by reducing the uncertainties in experiments, simulations, and the threshold or by increasing the sample size for the experiments and simulations. The threshold approach can be applied to all types of computational models and provides an objective way of determining model credibility and for evaluating medical devices.

Quantitative sensory testing and pain tolerance in patients with mild to moderate Alzheimer disease compared to healthy control subjects.

PubMed

Jensen-Dahm, Christina; Werner, Mads U; Dahl, Jørgen B; Jensen, Troels Staehelin; Ballegaard, Martin; Hejl, Anne-Mette; Waldemar, Gunhild

2014-08-01

Patients with Alzheimer disease (AD) report pain less frequently than their cognitively intact peers. It has been hypothesized that pain processing is altered in AD. The aim of this study was to investigate agreement and reliability of 3 pain sensitivity tests and to examine pain threshold and tolerance in patients with AD. We examined 29 patients with mild to moderate AD and 29 age- and gender-matched healthy control subjects with quantitative sensory testing, ie, assessments of detection threshold (warmth detection threshold [WDT]) and pain threshold (heat pain threshold [HPT], pressure algometry, cold pressor test), and assessments of tolerance (pressure algometry, cold pressor test). All procedures were done twice on day 1, 1 hour apart, and repeated on day 2. We found no difference between groups for WDT (patient vs control subjects: mean [95% confidence interval]: 35.5°C [33.4°C to 37.6°C] vs 35.4°C [34.3°C to 36.5°C], P=.8) or HPT (41.2°C [40.0°C to 42.4°C] vs 42.3°C [41.1°C to 43.5°C], P=.24). We observed comparable thresholds for pressure algometry (median [25% to 75% interquartile range]: 120 kPa [100 to 142 kPa] vs 131 kPa [113 to 192 kPa], P=.10), but significantly lower tolerance in AD patients (213 kPa [188 to 306 kPa] vs 289 kPa [262 to 360 kPa], P=.008). No differences were found for the cold pressor test. The study demonstrated good replicability of the sensory testing data with comparable data variability, for both groups, which supports the use of these methods in studies of patients with mild to moderate AD. Contrary to previous studies, we observed a reduced pain tolerance in patients with mild to moderate AD, which suggests that the reduced report of pain cannot be explained by reduced processing of painful stimuli. Copyright © 2014 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Impact of beta-blockers on cardiopulmonary exercise testing in patients with advanced liver disease.

PubMed

Wallen, M P; Hall, A; Dias, K A; Ramos, J S; Keating, S E; Woodward, A J; Skinner, T L; Macdonald, G A; Arena, R; Coombes, J S

2017-10-01

Patients with advanced liver disease may develop portal hypertension that can result in variceal haemorrhage. Beta-blockers reduce portal pressure and minimise haemorrhage risk. These medications may attenuate measures of cardiopulmonary performance, such as the ventilatory threshold and peak oxygen uptake measured via cardiopulmonary exercise testing. To determine the effect of beta-blockers on cardiopulmonary exercise testing variables in patients with advanced liver disease. This was a cross-sectional analysis of 72 participants who completed a cardiopulmonary exercise test before liver transplantation. All participants remained on their usual beta-blocker dose and timing prior to the test. Variables measured during cardiopulmonary exercise testing included the ventilatory threshold, peak oxygen uptake, heart rate, oxygen pulse, the oxygen uptake efficiency slope and the ventilatory equivalents for carbon dioxide slope. Participants taking beta-blockers (n = 28) had a lower ventilatory threshold (P <.01) and peak oxygen uptake (P = .02), compared to participants not taking beta-blockers. After adjusting for age, the model of end-stage liver-disease score, liver-disease aetiology, presence of refractory ascites and ventilatory threshold remained significantly lower in the beta-blocker group (P = .04). The oxygen uptake efficiency slope was not impacted by beta-blocker use. Ventilatory threshold is reduced in patients with advanced liver disease taking beta-blockers compared to those not taking the medication. This may incorrectly risk stratify patients on beta-blockers and has implications for patient management before and after liver transplantation. The oxygen uptake efficiency slope was not influenced by beta-blockers and may therefore be a better measure of cardiopulmonary performance in this patient population. © 2017 John Wiley & Sons Ltd.

Speech Perception in Older Hearing Impaired Listeners: Benefits of Perceptual Training

PubMed Central

Woods, David L.; Doss, Zoe; Herron, Timothy J.; Arbogast, Tanya; Younus, Masood; Ettlinger, Marc; Yund, E. William

2015-01-01

Hearing aids (HAs) only partially restore the ability of older hearing impaired (OHI) listeners to understand speech in noise, due in large part to persistent deficits in consonant identification. Here, we investigated whether adaptive perceptual training would improve consonant-identification in noise in sixteen aided OHI listeners who underwent 40 hours of computer-based training in their homes. Listeners identified 20 onset and 20 coda consonants in 9,600 consonant-vowel-consonant (CVC) syllables containing different vowels (/ɑ/, /i/, or /u/) and spoken by four different talkers. Consonants were presented at three consonant-specific signal-to-noise ratios (SNRs) spanning a 12 dB range. Noise levels were adjusted over training sessions based on d’ measures. Listeners were tested before and after training to measure (1) changes in consonant-identification thresholds using syllables spoken by familiar and unfamiliar talkers, and (2) sentence reception thresholds (SeRTs) using two different sentence tests. Consonant-identification thresholds improved gradually during training. Laboratory tests of d’ thresholds showed an average improvement of 9.1 dB, with 94% of listeners showing statistically significant training benefit. Training normalized consonant confusions and improved the thresholds of some consonants into the normal range. Benefits were equivalent for onset and coda consonants, syllables containing different vowels, and syllables presented at different SNRs. Greater training benefits were found for hard-to-identify consonants and for consonants spoken by familiar than unfamiliar talkers. SeRTs, tested with simple sentences, showed less elevation than consonant-identification thresholds prior to training and failed to show significant training benefit, although SeRT improvements did correlate with improvements in consonant thresholds. We argue that the lack of SeRT improvement reflects the dominant role of top-down semantic processing in processing simple sentences and that greater transfer of benefit would be evident in the comprehension of more unpredictable speech material. PMID:25730330

A test for measuring gustatory function.

PubMed

Smutzer, Gregory; Lam, Si; Hastings, Lloyd; Desai, Hetvi; Abarintos, Ray A; Sobel, Marc; Sayed, Nabil

2008-08-01

The purpose of this study was to determine the usefulness of edible taste strips for measuring human gustatory function. The physical properties of edible taste strips were examined to determine their potential for delivering threshold and suprathreshold amounts of taste stimuli to the oral cavity. Taste strips were then assayed by fluorescence to analyze the uniformity and distribution of bitter tastant in the strips. Finally, taste recognition thresholds for sweet taste were examined to determine whether or not taste strips could detect recognition thresholds that were equal to or better than those obtained from aqueous tests. Edible strips were prepared from pullulan-hydroxypropyl methylcellulose solutions that were dried to a thin film. The maximal amount of a tastant that could be incorporated in a 2.54 cm2 taste strip was identified by including representative taste stimuli for each class of tastant (sweet, sour, salty, bitter, and umami) during strip formation. Distribution of the bitter tastant quinine hydrochloride in taste strips was assayed by fluorescence emission spectroscopy. The efficacy of taste strips for evaluating human gustatory function was examined by using a single series ascending method of limits protocol. Sucrose taste recognition threshold data from edible strips was then compared with results that were obtained from a standard "sip and spit" recognition threshold test. Edible films that formed from a pullulan-hydroxypropyl methylcellulose polymer mixture can be used to prepare clear, thin strips that have essentially no background taste and leave no physical presence after release of tastant. Edible taste strips could uniformly incorporate up to 5% of their composition as tastant. Taste recognition thresholds for sweet taste were over one order of magnitude lower with edible taste strips when compared with an aqueous taste test. Edible taste strips are a highly sensitive method for examining taste recognition thresholds in humans. This new means of presenting taste stimuli should have widespread applications for examining human taste function in the laboratory, in the clinic, or at remote locations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maienschein, J.L.; Garcia, F.; Garza, R.G.

Tritium-handling apparatus has been decontaminated as part of the shutdown of the LLNL Tritium Facility. Two stainless-steel gloveboxes that had been used to process lithium deuteride-tritide (LiDT) salt were decontaminated using the Portable Cleanup System so that they could be flushed with room air through the facility ventilation system. Further surface decontamination was performed by scrubbing the interior with paper towels and ethyl alcohol or Swish{trademark}. The surface contamination, as shown by swipe surveys, was reduced from 4{times}10{sup 4}--10{sup 6} disintegrations per minute (dpm)/cm{sup 2} to 2{times}10{sup 2}--4{times}10{sup 4} dpm/cm{sup 2}. Details on the decontamination operation are provided. A seriesmore » of metal (palladium and vanadium) hydride storage beds have been drained of tritium and flushed with deuterium in order to remove as much tritium as possible. The bed draining and flushing procedure is described, and a calculational method is presented which allows estimation of the tritium remaining in a bed after it has been drained and flushed. Data on specific bed draining and flushing are given.« less

"Now I see it, now I don't": Determining Threshold Levels of Facial Emotion Recognition for Use in Patient Populations.

PubMed

Chiu, Isabelle; Gfrörer, Regina I; Piguet, Olivier; Berres, Manfred; Monsch, Andreas U; Sollberger, Marc

2015-08-01

The importance of including measures of emotion processing, such as tests of facial emotion recognition (FER), as part of a comprehensive neuropsychological assessment is being increasingly recognized. In clinical settings, FER tests need to be sensitive, short, and easy to administer, given the limited time available and patient limitations. Current tests, however, commonly use stimuli that either display prototypical emotions, bearing the risk of ceiling effects and unequal task difficulty, or are cognitively too demanding and time-consuming. To overcome these limitations in FER testing in patient populations, we aimed to define FER threshold levels for the six basic emotions in healthy individuals. Forty-nine healthy individuals between 52 and 79 years of age were asked to identify the six basic emotions at different intensity levels (25%, 50%, 75%, 100%, and 125% of the prototypical emotion). Analyses uncovered differing threshold levels across emotions and sex of facial stimuli, ranging from 50% up to 100% intensities. Using these findings as "healthy population benchmarks", we propose to apply these threshold levels to clinical populations either as facial emotion recognition or intensity rating tasks. As part of any comprehensive social cognition test battery, this approach should allow for a rapid and sensitive assessment of potential FER deficits.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chace, D.A.; Roberts, R.M.; Palmer, J.B.

WIPP Salado Hydrology Program Data Report {number_sign}3 presents hydrologic data collected during permeability testing, coupled permeability and hydrofracture testing, and gas-threshold-pressure testing of the Salado Formation performed from November 1991 through October 1995. Fluid-pressure monitoring data representing August 1989 through May 1995 are also included. The report presents data from the drilling and testing of three boreholes associated with the permeability testing program, nine boreholes associated with the coupled permeability and hydrofracture testing program, and three boreholes associated with the gas-threshold-pressure testing program. The purpose of the permeability testing program was to provide data with which to interpret the disturbedmore » and undisturbed permeability and pore pressure characteristics of the different Salado Formation lithologies. The purpose of the coupled permeability and hydrofracture testing program was to provide data with which to characterize the occurrence, propagation, and direction of pressure induced fractures in the Salado Formation lithologies, especially MB139. The purpose of the gas-threshold-pressure testing program was to provide data with which to characterize the conditions under which pressurized gas displaces fluid in the brine-saturated Salado Formation lithologies. All of the holes were drilled from the WIPP underground facility 655 m below ground surface in the Salado Formation.« less

The influence of weight loss on anaerobic threshold in obese women.

PubMed

Zak-Golab, Agnieszka; Zahorska-Markiewicz, Barbara; Langfort, Józef; Kocelak, Piotr; Holecki, Michal; Mizia-Stec, Katarzyna; Olszanecka-Glinianowicz, Magdalena; Chudek, Jerzy

2010-01-01

Obesity is associated with decreased physical activity. The aim of the study was to assess the anaerobic threshold in obese and normal weight women and to analyse the effect of weight-reduction therapy on the determined thresholds. 42 obese women without concomitant disease (age 30.5 ± 6.9y; BMI 33.6 ± 3.7 kg·m(-2)) and 19 healthy normal weight women (age 27.6 ± 7.0y; BMI 21.2 ± 1.9 kg·m(-2)) performed cycle ergometer incremental ramp exercise test up to exhaustion. The test was repeated in 19 obese women after 12.3 ± 4.2% weight loss. The lactate threshold (LT) and the ventilatory threshold (VT) were determined. Obese women had higher lactate (expressed as oxygen consumption) and ventilator threshold than normal weight women. The lactate threshold was higher than ventilatory one both in obese and normal weight women (1.11 ± 0.21 vs 0.88 ± 0.18 L·min(-1), p < 0.001; 0.94 ± 0.15 vs 0.79 ± 0.23 L·min(- 1), p < 0.01, respectively). After weight reduction therapy neither the lactate nor the ventilatory threshold changed significantly. The results concluded that; 1. The higher lactate threshold noted in obese women may be related to the increased fat acid usage in metabolism. 2. Both in obese and normal weight women lactate threshold appears at higher oxygen consumption than ventilatory threshold. 3. The obtained weight reduction, without weight normalisation was insufficient to cause significant changes of lactate and ventilatory thresholds in obese women. Key pointsResults showed that adolescent young female gymnasts have an altered serum inflammatory markers and endothelial activation, compared to their less physically active peers.Physical activities improved immune system.Differences in these biochemical data kept significant after adjustment for body weight and height.

An innovative iterative thresholding algorithm for tumour segmentation and volumetric quantification on SPECT images: Monte Carlo-based methodology and validation.

PubMed

Pacilio, M; Basile, C; Shcherbinin, S; Caselli, F; Ventroni, G; Aragno, D; Mango, L; Santini, E

2011-06-01

Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) imaging play an important role in the segmentation of functioning parts of organs or tumours, but an accurate and reproducible delineation is still a challenging task. In this work, an innovative iterative thresholding method for tumour segmentation has been proposed and implemented for a SPECT system. This method, which is based on experimental threshold-volume calibrations, implements also the recovery coefficients (RC) of the imaging system, so it has been called recovering iterative thresholding method (RIThM). The possibility to employ Monte Carlo (MC) simulations for system calibration was also investigated. The RIThM is an iterative algorithm coded using MATLAB: after an initial rough estimate of the volume of interest, the following calculations are repeated: (i) the corresponding source-to-background ratio (SBR) is measured and corrected by means of the RC curve; (ii) the threshold corresponding to the amended SBR value and the volume estimate is then found using threshold-volume data; (iii) new volume estimate is obtained by image thresholding. The process goes on until convergence. The RIThM was implemented for an Infinia Hawkeye 4 (GE Healthcare) SPECT/CT system, using a Jaszczak phantom and several test objects. Two MC codes were tested to simulate the calibration images: SIMIND and SimSet. For validation, test images consisting of hot spheres and some anatomical structures of the Zubal head phantom were simulated with SIMIND code. Additional test objects (flasks and vials) were also imaged experimentally. Finally, the RIThM was applied to evaluate three cases of brain metastases and two cases of high grade gliomas. Comparing experimental thresholds and those obtained by MC simulations, a maximum difference of about 4% was found, within the errors (+/- 2% and +/- 5%, for volumes > or = 5 ml or < 5 ml, respectively). Also for the RC data, the comparison showed differences (up to 8%) within the assigned error (+/- 6%). ANOVA test demonstrated that the calibration results (in terms of thresholds or RCs at various volumes) obtained by MC simulations were indistinguishable from those obtained experimentally. The accuracy in volume determination for the simulated hot spheres was between -9% and 15% in the range 4-270 ml, whereas for volumes less than 4 ml (in the range 1-3 ml) the difference increased abruptly reaching values greater than 100%. For the Zubal head phantom, errors ranged between 9% and 18%. For the experimental test images, the accuracy level was within +/- 10%, for volumes in the range 20-110 ml. The preliminary test of application on patients evidenced the suitability of the method in a clinical setting. The MC-guided delineation of tumor volume may reduce the acquisition time required for the experimental calibration. Analysis of images of several simulated and experimental test objects, Zubal head phantom and clinical cases demonstrated the robustness, suitability, accuracy, and speed of the proposed method. Nevertheless, studies concerning tumors of irregular shape and/or nonuniform distribution of the background activity are still in progress.

Cadmium (Tank) Electroplating Alternative

DTIC Science & Technology

2011-08-01

ASTM F519 HE: 75% NFS 200 hrs HRE : 45% NFS 150 hrs Threshold limit greater than /equal to LHE Cd (AMS 2417G) ASETS Defense Focused Workshop (2011...Test Specimens  Reporting Sustained/Threshold load (%NFS), Time to failure. HRE Testing Cd Zn-Ni IVD Al LHE Cd Re-Embrittlement Test Fluids:  DI...Hydrogen Embrittlement/ HRE ASTM F519 A5, Type 1.a.1 Brush Plating ASETS Defense Focused Workshop (2011) Luzmarie G. Santiago Materials Engineer Naval Air

Contrast gain control in first- and second-order motion perception.

PubMed

Lu, Z L; Sperling, G

1996-12-01

A novel pedestal-plus-test paradigm is used to determine the nonlinear gain-control properties of the first-order (luminance) and the second-order (texture-contrast) motion systems, that is, how these systems' responses to motion stimuli are reduced by pedestals and other masking stimuli. Motion-direction thresholds were measured for test stimuli consisting of drifting luminance and texture-contrast-modulation stimuli superimposed on pedestals of various amplitudes. (A pedestal is a static sine-wave grating of the same type and same spatial frequency as the moving test grating.) It was found that first-order motion-direction thresholds are unaffected by small pedestals, but at pedestal contrasts above 1-2% (5-10 x pedestal threshold), motion thresholds increase proportionally to pedestal amplitude (a Weber law). For first-order stimuli, pedestal masking is specific to the spatial frequency of the test. On the other hand, motion-direction thresholds for texture-contrast stimuli are independent of pedestal amplitude (no gain control whatever) throughout the accessible pedestal amplitude range (from 0 to 40%). However, when baseline carrier contrast increases (with constant pedestal modulation amplitude), motion thresholds increase, showing that gain control in second-order motion is determined not by the modulator (as in first-order motion) but by the carrier. Note that baseline contrast of the carrier is inherently independent of spatial frequency of the modulator. The drastically different gain-control properties of the two motion systems and prior observations of motion masking and motion saturation are all encompassed in a functional theory. The stimulus inputs to both first- and second-order motion process are normalized by feedforward, shunting gain control. The different properties arise because the modulator is used to control the first-order gain and the carrier is used to control the second-order gain.

Development and Validation of a Portable Hearing Self-Testing System Based on a Notebook Personal Computer.

PubMed

Liu, Yan; Yang, Dong; Xiong, Fen; Yu, Lan; Ji, Fei; Wang, Qiu-Ju

2015-09-01

Hearing loss affects more than 27 million people in mainland China. It would be helpful to develop a portable and self-testing audiometer for the timely detection of hearing loss so that the optimal clinical therapeutic schedule can be determined. The objective of this study was to develop a software-based hearing self-testing system. The software-based self-testing system consisted of a notebook computer, an external sound card, and a pair of 10-Ω insert earphones. The system could be used to test the hearing thresholds by individuals themselves in an interactive manner using software. The reliability and validity of the system at octave frequencies of 0.25 Hz to 8.0 kHz were analyzed in three series of experiments. Thirty-seven normal-hearing particpants (74 ears) were enrolled in experiment 1. Forty individuals (80 ears) with sensorineural hearing loss (SNHL) participated in experiment 2. Thirteen normal-hearing participants (26 ears) and 37 participants (74 ears) with SNHL were enrolled in experiment 3. Each participant was enrolled in only one of the three experiments. In all experiments, pure-tone audiometry in a sound insulation room (standard test) was regarded as the gold standard. SPSS for Windows, version 17.0, was used for statistical analysis. The paired t-test was used to compare the hearing thresholds between the standard test and software-based self-testing (self-test) in experiments 1 and 2. In experiment 3 (main study), one-way analysis of variance and post hoc comparisons were used to compare the hearing thresholds among the standard test and two rounds of the self-test. Linear correlation analysis was carried out for the self-tests performed twice. The concordance was analyzed between the standard test and the self-test using the kappa method. p < 0.05 was considered statistically significant. Experiments 1 and 2: The hearing thresholds determined by the two methods were not significantly different at frequencies of 250, 500, or 8000 Hz (p > 0.05) but were significantly different at frequencies of 1000, 2000, and 4000 Hz (p < 0.05), except for 1000 Hz in the right ear in experiment 2. Experiment 3: The hearing thresholds determined by the standard test and self-tests repeated twice were not significantly different at any frequency (p > 0.05). The overall sensitivity of the self-test method was 97.6%, and the specificity was 98.3%. The sensitivity was 97.6% and the specificity was 97% for the patients with SNHL. The self-test had significant concordance with the standard test (kappa value = 0.848, p < 0.001). This portable hearing self-testing system based on a notebook personal computer is a reliable and sensitive method for hearing threshold assessment and monitoring. American Academy of Audiology.

Reading behind the Lines: The Factors Affecting the Text Reception Threshold in Hearing Aid Users

ERIC Educational Resources Information Center

Zekveld, Adriana A.; Pronk, Marieke; Danielsson, Henrik; Rönnberg, Jerker

2018-01-01

Purpose: The visual Text Reception Threshold (TRT) test (Zekveld et al., 2007) has been designed to assess modality-general factors relevant for speech perception in noise. In the last decade, the test has been adopted in audiology labs worldwide. The 1st aim of this study was to examine which factors best predict interindividual differences in…

Optimizing the rapid measurement of detection thresholds in infants

PubMed Central

Jones, Pete R.; Kalwarowsky, Sarah; Braddick, Oliver J.; Atkinson, Janette; Nardini, Marko

2015-01-01

Accurate measures of perceptual threshold are difficult to obtain in infants. In a clinical context, the challenges are particularly acute because the methods must yield meaningful results quickly and within a single individual. The present work considers how best to maximize speed, accuracy, and reliability when testing infants behaviorally and suggests some simple principles for improving test efficiency. Monte Carlo simulations, together with empirical (visual acuity) data from 65 infants, are used to demonstrate how psychophysical methods developed with adults can produce misleading results when applied to infants. The statistical properties of an effective clinical infant test are characterized, and based on these, it is shown that (a) a reduced (false-positive) guessing rate can greatly increase test efficiency, (b) the ideal threshold to target is often below 50% correct, and (c) simply taking the max correct response can often provide the best measure of an infant's perceptual sensitivity. PMID:26237298

Evaluation of olfaction and taste function in type 2 diabetic patients with and without peripheral neuropathy.

PubMed

Yazla, Semih; Özmen, Süay; Kıyıcı, Sinem; Yıldız, Demet; Haksever, Mehmet; Gencay, Sündüz

2018-03-01

Olfaction and gustation in patients with diabetes mellitus have great significance on quality of life, and their impairment may result in possible hazards. A limited number of studies have been performed to determine the alteration of both gustatory and olfactory function in type 2 diabetic patients with diabetic peripheral neuropathy (DPN). The aim of this study was to determine whether type 2 diabetic patients, with and without DPN, exhibit major olfactory and gustatory dysfunction using validated and dependable techniques. An observational-analytical case-control study was conducted. Sixty patients with type 2 diabetes mellitus (T2DM) and 30 healthy control subjects with a mean age of 57.1 ± 8.4 were included in the study. Patients with T2DM were recruited from the endocrinology outpatient clinic. After clinical evaluation and electromyography examination, patients with T2DM were divided into the 2 groups, with and without DPN. After a 10-hour fasting period, blood samples were taken for the measurement of serum creatinine, lipids, and HbA1c. For the quantitative assessment of olfactory function, all participants underwent butanol threshold test and odour identification test. Gustatory function was tested administering a whole-mouth above-threshold test using sucrose solutions. The control subjects showed significantly higher Sniffin' sticks and butanol threshold scores than the diabetic patients without DPN (P = .001 and P = .009). No significant difference was found in the gustatory function test between these 2 groups (P = .116). Diabetic patients with DPN had lower Sniffin' sticks scores, butanol threshold scores, and higher sucrose thresholds compared to the controls (P < .001, P < .001, and P = .002). There were no significant differences between diabetic patients with or without DPN regarding Sniffin' sticks scores, butanol threshold, and sucrose thresholds (P = .302, P = .181, and P = .118). In conclusion, this study demonstrates that T2DM is associated with olfactory and gustatory dysfunction. The fact that there was no difference between the diabetic patients with and without DPN elicits the idea of central neuropathy. This novel finding might facilitate the addition of olfactory and gustatory tests to the methodological spectrum of afferent pathway investigations. Copyright © 2017 John Wiley & Sons, Ltd.

Absolute auditory threshold: testing the absolute.

PubMed

Heil, Peter; Matysiak, Artur

2017-11-02

The mechanisms underlying the detection of sounds in quiet, one of the simplest tasks for auditory systems, are debated. Several models proposed to explain the threshold for sounds in quiet and its dependence on sound parameters include a minimum sound intensity ('hard threshold'), below which sound has no effect on the ear. Also, many models are based on the assumption that threshold is mediated by integration of a neural response proportional to sound intensity. Here, we test these ideas. Using an adaptive forced choice procedure, we obtained thresholds of 95 normal-hearing human ears for 18 tones (3.125 kHz carrier) in quiet, each with a different temporal amplitude envelope. Grand-mean thresholds and standard deviations were well described by a probabilistic model according to which sensory events are generated by a Poisson point process with a low rate in the absence, and higher, time-varying rates in the presence, of stimulation. The subject actively evaluates the process and bases the decision on the number of events observed. The sound-driven rate of events is proportional to the temporal amplitude envelope of the bandpass-filtered sound raised to an exponent. We find no evidence for a hard threshold: When the model is extended to include such a threshold, the fit does not improve. Furthermore, we find an exponent of 3, consistent with our previous studies and further challenging models that are based on the assumption of the integration of a neural response that, at threshold sound levels, is directly proportional to sound amplitude or intensity. © 2017 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Southeast PAVE PAWS Radar System. Environmental Assessment.

DTIC Science & Technology

1983-03-01

reported, including fatigue, irritability, sleepiness, partial loss of memory, lower heart- beat rates, hypertension, hypotension, cardiac pain, and...Because such audiograms do not test hearing above 8 klz, binaural hearing thresholds were also determined for seven of the subjects for frequencies...perception and hearing ability above 8 kl:z as determined from the binaural thresholds. The average threshold pulse power density for 15-microsecond

Frequency Discrimination Deficits in People with Specific Language Impairment: Reliability, Validity, and Linguistic Correlates

ERIC Educational Resources Information Center

McArthur, G. M.; Bishop, D. V. M.

2004-01-01

The reliability and validity of a frequency discrimination (FD) task were tested in 16 people with specific language impairment (SLI) and 16 people with normal spoken language (controls). The FD thresholds of the 2 groups indicated that FD thresholds for 25-ms and 250-ms tones were remarkably stable across 18 months. The FD thresholds were lower…

Effective Identification of Functional Hearing Loss Using Behavioral Threshold Measures

ERIC Educational Resources Information Center

Schlauch, Robert S.; Koerner, Tess K.; Marshall, Lynne

2015-01-01

Purpose: Four functional hearing loss protocols were evaluated. Method: For each protocol, 30 participants feigned a hearing loss first on an audiogram and then for a screening test that began a threshold search from extreme levels (-10 or 90 dB HL). Two-tone and 3-tone protocols compared thresholds for ascending and descending tones for 2 (0.5…

A novel automated instrument designed to determine photosensitivity thresholds (Conference Presentation)

NASA Astrophysics Data System (ADS)

Aguilar, Mariela C.; Gonzalez, Alex; Rowaan, Cornelis; De Freitas, Carolina; Rosa, Potyra R.; Alawa, Karam; Lam, Byron L.; Parel, Jean-Marie A.

2016-03-01

As there is no clinically available instrument to systematically and reliably determine the photosensitivity thresholds of patients with dry eyes, blepharospasms, migraines, traumatic brain injuries, and genetic disorders such as Achromatopsia, retinitis pigmentosa and other retinal dysfunctions, a computer-controlled optoelectronics system was designed. The BPEI Photosensitivity System provides a light stimuli emitted from a bi-cupola concave, 210 white LED array with varying intensity ranging from 1 to 32,000 lux. The system can either utilize a normal or an enhanced testing mode for subjects with low light tolerance. The automated instrument adjusts the intensity of each light stimulus. The subject is instructed to indicate discomfort by pressing a hand-held button. Reliability of the responses is tracked during the test. The photosensitivity threshold is then calculated after 10 response reversals. In a preliminary study, we demonstrated that subjects suffering from Achromatopsia experienced lower photosensitivity thresholds than normal subjects. Hence, the system can safely and reliably determine the photosensitivity thresholds of healthy and light sensitive subjects by detecting and quantifying the individual differences. Future studies will be performed with this system to determine the photosensitivity threshold differences between normal subjects and subjects suffering from other conditions that affect light sensitivity.

Experimental and Finite Element Modeling of Near-Threshold Fatigue Crack Growth for the K-Decreasing Test Method

NASA Technical Reports Server (NTRS)

Smith, Stephen W.; Seshadri, Banavara R.; Newman, John A.

2015-01-01

The experimental methods to determine near-threshold fatigue crack growth rate data are prescribed in ASTM standard E647. To produce near-threshold data at a constant stress ratio (R), the applied stress-intensity factor (K) is decreased as the crack grows based on a specified K-gradient. Consequently, as the fatigue crack growth rate threshold is approached and the crack tip opening displacement decreases, remote crack wake contact may occur due to the plastically deformed crack wake surfaces and shield the growing crack tip resulting in a reduced crack tip driving force and non-representative crack growth rate data. If such data are used to life a component, the evaluation could yield highly non-conservative predictions. Although this anomalous behavior has been shown to be affected by K-gradient, starting K level, residual stresses, environmental assisted cracking, specimen geometry, and material type, the specifications within the standard to avoid this effect are limited to a maximum fatigue crack growth rate and a suggestion for the K-gradient value. This paper provides parallel experimental and computational simulations for the K-decreasing method for two materials (an aluminum alloy, AA 2024-T3 and a titanium alloy, Ti 6-2-2-2-2) to aid in establishing clear understanding of appropriate testing requirements. These simulations investigate the effect of K-gradient, the maximum value of stress-intensity factor applied, and material type. A material independent term is developed to guide in the selection of appropriate test conditions for most engineering alloys. With the use of such a term, near-threshold fatigue crack growth rate tests can be performed at accelerated rates, near-threshold data can be acquired in days instead of weeks without having to establish testing criteria through trial and error, and these data can be acquired for most engineering materials, even those that are produced in relatively small product forms.

Improvement in taste sensitivity following pulmonary rehabilitation in patients with chronic obstructive pulmonary disease.

PubMed

Ito, Kumiko; Kohzuki, Masahiro; Takahashi, Tamao; Ebihara, Satoru

2014-10-01

Weight loss is common in patients with chronic obstructive pulmonary disease (COPD). Anorexia, postulated to be associated with alteration in taste sensitivity, may contribute to weight loss in these patients. Pulmonary rehabilitation is known to lead to improved exercise performance in patients with COPD. However, the relationship between pulmonary rehabilitation and taste sensitivity has not been evaluated. The objective of this study was to compare taste sensitivity before and after pulmonary rehabilitation in patients with COPD. Single-group intervention trial. Twenty-two patients with COPD. The six-min walk distance (6MWD), COPD assessment test, body mass index, fat mass index, fat-free mass index and taste test were conducted before and after 4-week pulmonary rehabilitation. Taste sensitivity was evaluated using the filter-paper disc method for 4 taste stimuli. Taste stimuli were salty, sweet, sour, and bitter tastes. Taste sensitivity was evaluated before and after pulmonary rehabilitation using the taste recognition threshold. Following pulmonary rehabilitation, the 6MWD, COPD assessment test, salty recognition threshold, sweet recognition threshold and bitter recognition threshold improved significantly, whereas there were no significant improvements in body mass index, fat mass index, fat-free mass index or sour recognition threshold. Pulmonary rehabilitation may improve taste sensitivity in patients with COPD.

Running economy and body composition between competitive and recreational level distance runners.

PubMed

Mooses, Martin; Jürimäe, J; Mäestu, J; Mooses, K; Purge, P; Jürimäe, T

2013-09-01

The aim of the present study was to compare running economy between competitive and recreational level athletes at their individual ventilatory thresholds on track and to compare body composition parameters that are related to the individual running economy measured on track. We performed a cross-sectional analysis of a total 45 male runners classified as competitive runners (CR; n = 28) and recreational runners (RR; n = 17). All runners performed an incremental test on treadmill until voluntary exhaustion and at least 48 h later a 2 × 2000 m test at indoor track with intensities according to ventilatory threshold 1, ventilator threshold 2. During the running tests, athletes wore portable oxygen analyzer. Body composition was measured with Dual energy X-ray absorptiometry (DXA) method. Running economy at the first ventilatory threshold was not significantly related to any of the measured body composition values or leg mass ratios either in the competitive or in the recreational runners group. This study showed that there was no difference in the running economy between distance runners with different performance level when running on track, while there was a difference in the second ventilatory threshold speed in different groups of distance runners. Differences in running economy between competitive and recreational athletes cannot be explained by body composition and/or different leg mass ratios.

Breast Cancer Risk Prediction and Mammography Biopsy Decisions

PubMed Central

Armstrong, Katrina; Handorf, Elizabeth A.; Chen, Jinbo; Demeter, Mirar N. Bristol

2012-01-01

Background Controversy continues about screening mammography, in part because of the risk of false-negative and false-positive mammograms. Pre-test breast cancer risk factors may improve the positive and negative predictive value of screening. Purpose To create a model that estimates the potential impact of pre-test risk prediction using clinical and genomic information on the reclassification of women with abnormal mammograms (BI-RADS3 and BI-RADS4 [Breast Imaging-Reporting and Data System]) above and below the threshold for breast biopsy. Methods The current study modeled 1-year breast cancer risk in women with abnormal screening mammograms using existing data on breast cancer risk factors, 12 validated breast cancer single nucleotide polymorphisms (SNPs), and probability of cancer given the BI-RADS category. Examination was made of reclassification of women above and below biopsy thresholds of 1%, 2%, and 3% risk. The Breast Cancer Surveillance Consortium data were collected from 1996 to 2002. Data analysis was conducted in 2010 and 2011. Results Using a biopsy risk threshold of 2% and the standard risk factor model, 5% of women with a BI-RADS3 mammogram had a risk above the threshold, and 3% of women with BIRADS4A mammograms had a risk below the threshold. The addition of 12 SNPs in the model resulted in 8% of women with a BI-RADS3 mammogram above the threshold for biopsy and 7% of women with BI-RADS4A mammograms below the threshold. Conclusions The incorporation of pre-test breast cancer risk factors could change biopsy decisions for a small proportion of women with abnormal mammograms. The greatest impact comes from standard breast cancer risk factors. PMID:23253645

Repeated-Sprint Sequences During Female Soccer Matches Using Fixed and Individual Speed Thresholds.

PubMed

Nakamura, Fábio Y; Pereira, Lucas A; Loturco, Irineu; Rosseti, Marcelo; Moura, Felipe A; Bradley, Paul S

2017-07-01

Nakamura, FY, Pereira, LA, Loturco, I, Rosseti, M, Moura, FA, and Bradley, PS. Repeated-sprint sequences during female soccer matches using fixed and individual speed thresholds. J Strength Cond Res 31(7): 1802-1810, 2017-The main objective of this study was to characterize the occurrence of single sprint and repeated-sprint sequences (RSS) during elite female soccer matches, using fixed (20 km·h) and individually based speed thresholds (>90% of the mean speed from a 20-m sprint test). Eleven elite female soccer players from the same team participated in the study. All players performed a 20-m linear sprint test, and were assessed in up to 10 official matches using Global Positioning System technology. Magnitude-based inferences were used to test for meaningful differences. Results revealed that irrespective of adopting fixed or individual speed thresholds, female players produced only a few RSS during matches (2.3 ± 2.4 sequences using the fixed threshold and 3.3 ± 3.0 sequences using the individually based threshold), with most sequences composing of just 2 sprints. Additionally, central defenders performed fewer sprints (10.2 ± 4.1) than other positions (fullbacks: 28.1 ± 5.5; midfielders: 21.9 ± 10.5; forwards: 31.9 ± 11.1; with the differences being likely to almost certainly associated with effect sizes ranging from 1.65 to 2.72), and sprinting ability declined in the second half. The data do not support the notion that RSS occurs frequently during soccer matches in female players, irrespective of using fixed or individual speed thresholds to define sprint occurrence. However, repeated-sprint ability development cannot be ruled out from soccer training programs because of its association with match-related performance.

Antinociception induced by epidural motor cortex stimulation in naive conscious rats is mediated by the opioid system.

PubMed

Fonoff, Erich Talamoni; Dale, Camila Squarzoni; Pagano, Rosana Lima; Paccola, Carina Cicconi; Ballester, Gerson; Teixeira, Manoel Jacobsen; Giorgi, Renata

2009-01-03

Epidural motor cortex stimulation (MCS) has been used for treating patients with neuropathic pain resistant to other therapeutic approaches. Experimental evidence suggests that the motor cortex is also involved in the modulation of normal nociceptive response, but the underlying mechanisms of pain control have not been clarified yet. The aim of this study was to investigate the effects of epidural electrical MCS on the nociceptive threshold of naive rats. Electrodes were placed on epidural motor cortex, over the hind paw area, according to the functional mapping accomplished in this study. Nociceptive threshold and general activity were evaluated under 15-min electrical stimulating sessions. When rats were evaluated by the paw pressure test, MCS induced selective antinociception in the paw contralateral to the stimulated cortex, but no changes were noticed in the ipsilateral paw. When the nociceptive test was repeated 15 min after cessation of electrical stimulation, the nociceptive threshold returned to basal levels. On the other hand, no changes in the nociceptive threshold were observed in rats evaluated by the tail-flick test. Additionally, no behavioral or motor impairment were noticed in the course of stimulation session at the open-field test. Stimulation of posterior parietal or somatosensory cortices did not elicit any changes in the general activity or nociceptive response. Opioid receptors blockade by naloxone abolished the increase in nociceptive threshold induced by MCS. Data shown herein demonstrate that epidural electrical MCS elicits a substantial and selective antinociceptive effect, which is mediated by opioids.

Effect of intrathecal baclofen on evoked pain perception: an evoked potentials and quantitative thermal testing study.

PubMed

Kumru, H; Kofler, M; Flores, M C; Portell, E; Robles, V; Leon, N; Vidal, J

2013-08-01

Somatic antinociceptive effects of baclofen have been demonstrated in animal models. We hypothesized that if enhanced thermal or pain sensitivity is produced by loss of gamma-aminobutyric acid (GABA)-ergic tone in the central nervous system, spinal administration of GABA agonists might be predicted to be effective in thermal and/or pain perception changes and pain-related evoked potentials in candidates for intrathecal baclofen (ITB) treatment. Eleven patients with severe spinal cord injury (SCI) who suffered from severe spasticity were evaluated during a 50-μg ITB bolus test. Warm and heat pain thresholds, evoked heat pain perception, and contact heat-evoked potentials (CHEPs) were determined above SCI level from the right and left sides. Nine age- and gender-matched healthy volunteers undergoing repeat testing without any placebo injection served as control group. In patients, heat pain perception threshold increased, and evoked pain perception and amplitude of CHEPs decreased significantly after ITB bolus application in comparison with baseline (p < 0.005), with no change in warm perception threshold. In controls, no significant changes were observed in repeat testing over time. Our findings indicate that ITB modulates heat pain perception threshold, evoked heat pain perception and heat pain-related evoked potentials without inducing warm perception threshold changes in SCI patients. This phenomenon should be taken into account in the clinical evaluation and management of pain in patients receiving baclofen. © 2012 European Federation of International Association for the Study of Pain Chapters.

Molecular Signaling Network Motifs Provide a Mechanistic Basis for Cellular Threshold Responses

PubMed Central

Bhattacharya, Sudin; Conolly, Rory B.; Clewell, Harvey J.; Kaminski, Norbert E.; Andersen, Melvin E.

2014-01-01

Background: Increasingly, there is a move toward using in vitro toxicity testing to assess human health risk due to chemical exposure. As with in vivo toxicity testing, an important question for in vitro results is whether there are thresholds for adverse cellular responses. Empirical evaluations may show consistency with thresholds, but the main evidence has to come from mechanistic considerations. Objectives: Cellular response behaviors depend on the molecular pathway and circuitry in the cell and the manner in which chemicals perturb these circuits. Understanding circuit structures that are inherently capable of resisting small perturbations and producing threshold responses is an important step towards mechanistically interpreting in vitro testing data. Methods: Here we have examined dose–response characteristics for several biochemical network motifs. These network motifs are basic building blocks of molecular circuits underpinning a variety of cellular functions, including adaptation, homeostasis, proliferation, differentiation, and apoptosis. For each motif, we present biological examples and models to illustrate how thresholds arise from specific network structures. Discussion and Conclusion: Integral feedback, feedforward, and transcritical bifurcation motifs can generate thresholds. Other motifs (e.g., proportional feedback and ultrasensitivity)produce responses where the slope in the low-dose region is small and stays close to the baseline. Feedforward control may lead to nonmonotonic or hormetic responses. We conclude that network motifs provide a basis for understanding thresholds for cellular responses. Computational pathway modeling of these motifs and their combinations occurring in molecular signaling networks will be a key element in new risk assessment approaches based on in vitro cellular assays. Citation: Zhang Q, Bhattacharya S, Conolly RB, Clewell HJ III, Kaminski NE, Andersen ME. 2014. Molecular signaling network motifs provide a mechanistic basis for cellular threshold responses. Environ Health Perspect 122:1261–1270; http://dx.doi.org/10.1289/ehp.1408244 PMID:25117432

Reverse lactate threshold: a novel single-session approach to reliable high-resolution estimation of the anaerobic threshold.

PubMed

Dotan, Raffy

2012-06-01

The multisession maximal lactate steady-state (MLSS) test is the gold standard for anaerobic threshold (AnT) estimation. However, it is highly impractical, requires high fitness level, and suffers additional shortcomings. Existing single-session AnT-estimating tests are of compromised validity, reliability, and resolution. The presented reverse lactate threshold test (RLT) is a single-session, AnT-estimating test, aimed at avoiding the pitfalls of existing tests. It is based on the novel concept of identifying blood lactate's maximal appearance-disappearance equilibrium by approaching the AnT from higher, rather than from lower exercise intensities. Rowing, cycling, and running case data (4 recreational and competitive athletes, male and female, aged 17-39 y) are presented. Subjects performed the RLT test and, on a separate session, a single 30-min MLSS-type verification test at the RLT-determined intensity. The RLT and its MLSS verification exhibited exceptional agreement at 0.5% discrepancy or better. The RLT's training sensitivity was demonstrated by a case of 2.5-mo training regimen following which the RLT's 15-W improvement was fully MLSS-verified. The RLT's test-retest reliability was examined in 10 trained and untrained subjects. Test 2 differed from test 1 by only 0.3% with an intraclass correlation of 0.997. The data suggest RLT to accurately and reliably estimate AnT (as represented by MLSS verification) with high resolution and in distinctly different sports and to be sensitive to training adaptations. Compared with MLSS, the single-session RLT is highly practical and its lower fitness requirements make it applicable to athletes and untrained individuals alike. Further research is needed to establish RLT's validity and accuracy in larger samples.

Sensory function assessment. A pilot comparison study of touch pressure threshold with texture and tactile discrimination.

PubMed

King, P M

1997-01-01

The purpose of this study was to determine if a correlation exists between touch-pressure threshold testing and sensory discrimination function, specifically tactile gnosis for texture and object recognition. Twenty-nine patients diagnosed with carpal tunnel syndrome (CTS), as confirmed by electromyography or nerve conduction velocity tests, were administered three sensibility tests: the Semmes-Weinstein monofilament test, a texture discrimination test, and an object identification test. Norms were established for texture and object recognition tests using 100 subjects (50 females and 50 males) with normal touch-pressure thresholds as assessed by the Semmes-Weinstein monofilament test. The CTS patients were grouped into three categories of sensibility as determined by their performance on the Semmes-Weinstein monofilament test: normal, diminished light touch, and diminished protective sensation. Through an independent t test statistical procedure, each of the three categories mean response times for identification of textures of objects were compared with the normed response times. Accurate responses were given for identification of all textures and objects. No significant difference (p < .05) was noted in mean response times of the CTS patients with normal touch-pressure thresholds. A significant difference (p < .05) in response times by those CTS patients with diminished light touch was detected in identification in four out of six objects. Subjects with diminished protective sensation had significantly longer response times (p < .05) for identification of the textures of cork, coarse and fine sandpaper, and rubber. Significantly longer response times were recorded by the same subjects for identification of such objects as a screw and a button, and for the shapes of a square, triangle, and oval.

The effect of pre-test carbohydrate ingestion on the anaerobic threshold, as determined by the lactate-minimum test.

PubMed

Rotstein, Arie; Dotan, Raffy; Zigel, Levana; Greenberg, Tally; Benyamini, Yael; Falk, Bareket

2007-12-01

The purpose of this study was to investigate the effect of pre-test carbohydrate (CHO) ingestion on anaerobic-threshold assessment using the lactate-minimum test (LMT). Fifteen competitive male distance runners capable of running 10 km in 33.5-43 min were used as subjects. LMT was performed following CHO (2x300 mL, 7% solution) or comparable placebo (Pl) ingestion, in a double-blind, randomized order. The LMT consisted of two high-intensity 1 min treadmill runs (17-21 km.h(-1)), followed by an 8 min recovery period. Subsequently, subjects performed 5 min running stages, incremented by 0.6 km.h(-1) and separated by 1 min blood-sampling intervals. Tests were terminated after 3 consecutive increases in blood-lactate concentration ([La]) had been observed. Finger-tip capillary blood was sampled for [La] and blood-glucose determination 30 min before the test's onset, during the recovery phase following the 2 high-intensity runs, and following each of the subsequent 5 min stages. Heart rate (HR) and rating of perceived exertion (RPE) were recorded after each stage. The lactate-minimum speed (LMS) was determined from the individual [La]-velocity plots and was considered reflective of the anaerobic threshold. Pre-test CHO ingestion had no effect on LMS (13.19+/-1.12 km.h(-1) vs. 13.17+/-1.08 km.h(-1) in CHO and Pl, respectively), nor on [La] and glucose concentration at that speed, or on HR and RPE responses. Pre-test CHO ingestion therefore does not affect LMS or the LMT-estimated anaerobic threshold.

An Evaluation of Performance Thresholds in Nursing Home Pay-for-Performance.

PubMed

Werner, Rachel M; Skira, Meghan; Konetzka, R Tamara

2016-12-01

Performance thresholds are commonly used in pay-for-performance (P4P) incentives, where providers receive a bonus payment for achieving a prespecified target threshold but may produce discontinuous incentives, with providers just below the threshold having the strongest incentive to improve and providers either far below or above the threshold having little incentive. We investigate the effect of performance thresholds on provider response in the setting of nursing home P4P. The Minimum Data Set (MDS) and Online Survey, Certification, and Reporting (OSCAR) datasets. Difference-in-differences design to test for changes in nursing home performance in three states that implemented threshold-based P4P (Colorado, Georgia, and Oklahoma) versus three comparator states (Arizona, Tennessee, and Arkansas) between 2006 and 2009. We find that those farthest below the threshold (i.e., the worst-performing nursing homes) had the largest improvements under threshold-based P4P while those farthest above the threshold worsened. This effect did not vary with the percentage of Medicaid residents in a nursing home. Threshold-based P4P may provide perverse incentives for nursing homes above the performance threshold, but we do not find evidence to support concerns about the effects of performance thresholds on low-performing nursing homes. © Health Research and Educational Trust.

A Study on the Relationship between English Vocabulary Threshold and Word Guessing Strategy for Pre-University Chinese Students in Malaysia

ERIC Educational Resources Information Center

Juan, Wu Xiao; Abidin, Mohamad Jafre Zainol; Eng, Lin Siew

2013-01-01

This survey aims at studying the relationship between English vocabulary threshold and word guessing strategy that is used in reading comprehension learning among 80 pre-university Chinese students in Malaysia. T-test is the main statistical test for this research, and the collected data is analysed using SPSS. From the standard deviation test…

Effects of simulated lightning on composite and metallic joints

NASA Technical Reports Server (NTRS)

Howell, W. E.; Plumer, J. A.

1982-01-01

The effects of simulated lightning strikes and currents on aircraft bonded joints and access/inspection panels were investigated. Both metallic and composite specimens were tested. Tests on metal fuel feed through elbows in graphite/epoxy structures were evaluated. Sparking threshold and residual strength of single lap bonded joints and sparking threshold of access/inspection panels and metal fuel feed through elbows are reported.

Comparing the ISO-recommended and the cumulative data-reduction algorithms in S-on-1 laser damage test by a reverse approach method

NASA Astrophysics Data System (ADS)

Zorila, Alexandru; Stratan, Aurel; Nemes, George

2018-01-01

We compare the ISO-recommended (the standard) data-reduction algorithm used to determine the surface laser-induced damage threshold of optical materials by the S-on-1 test with two newly suggested algorithms, both named "cumulative" algorithms/methods, a regular one and a limit-case one, intended to perform in some respects better than the standard one. To avoid additional errors due to real experiments, a simulated test is performed, named the reverse approach. This approach simulates the real damage experiments, by generating artificial test-data of damaged and non-damaged sites, based on an assumed, known damage threshold fluence of the target and on a given probability distribution function to induce the damage. In this work, a database of 12 sets of test-data containing both damaged and non-damaged sites was generated by using four different reverse techniques and by assuming three specific damage probability distribution functions. The same value for the threshold fluence was assumed, and a Gaussian fluence distribution on each irradiated site was considered, as usual for the S-on-1 test. Each of the test-data was independently processed by the standard and by the two cumulative data-reduction algorithms, the resulting fitted probability distributions were compared with the initially assumed probability distribution functions, and the quantities used to compare these algorithms were determined. These quantities characterize the accuracy and the precision in determining the damage threshold and the goodness of fit of the damage probability curves. The results indicate that the accuracy in determining the absolute damage threshold is best for the ISO-recommended method, the precision is best for the limit-case of the cumulative method, and the goodness of fit estimator (adjusted R-squared) is almost the same for all three algorithms.

Diurnal Variation of Sweet Taste Recognition Thresholds Is Absent in Overweight and Obese Humans

PubMed Central

Sanematsu, Keisuke; Nakamura, Yuki; Nomura, Masatoshi; Shigemura, Noriatsu; Ninomiya, Yuzo

2018-01-01

Sweet taste thresholds are positively related to plasma leptin levels in normal weight humans: both show parallel diurnal variations and associations with postprandial glucose and insulin rises. Here, we tested whether this relationship also exists in overweight and obese (OW/Ob) individuals with hyperleptinemia. We tested 36 Japanese OW/Ob subjects (body mass index (BMI) > 25 kg/m2) for recognition thresholds for various taste stimuli at seven different time points from 8:00 a.m. to 10:00 p.m. using the staircase methodology, and measured plasma leptin, insulin, and blood glucose levels before each taste threshold measurement. We also used the homeostatic model assessment of insulin resistance (HOMA-IR) to evaluate insulin resistance. The results demonstrated that, unlike normal weight subjects, OW/Ob subjects showed no significant diurnal variations in the recognition thresholds for sweet stimuli but exhibited negative associations between the diurnal variations of both leptin and sweet recognition thresholds and the HOMA-IR scores. These findings suggest that in OW/Ob subjects, the basal leptin levels (~20 ng/mL) may already exceed leptin’s effective concentration for the modulation of sweet sensitivity and that this leptin resistance-based attenuation of the diurnal variations of the sweet taste recognition thresholds may also be indirectly linked to insulin resistance in OW/Ob subjects. PMID:29498693

The threshold signal:noise ratio in the perception of fragmented figures.

PubMed

Merkul'ev, A V; Pronin, S V; Semenov, L A; Foreman, N; Chikhman, V N; Shelepin, Yu E

2006-01-01

Perception thresholds were measured for fragmented outline figures (the Gollin test). A new approach to the question of the perception of incomplete images was developed. In this approach, figure fragmentation consisted of masking with multiplicative texture-like noise--this interference was termed "invisible" masking. The first series of studies established that the "similarity" between the amplitude-frequency spectra of test figures and "invisible" masks, expressed as a linear correlation coefficient, had significant effects on the recognition thresholds of these figures. The second series of experiments showed that progressing formation of the figures was accompanied by increases in the correlation between their spatial-frequency characteristics and the corresponding characteristics of the incomplete figure, while the correlation with the "invisible" mask decreased. It is suggested that the ratio of the correlation coefficients, characterizing the "similarity" of the fragmented figure with the intact figure and the "invisible" mask, corresponds to the signal:noise ratio. The psychophysical recognition threshold for figures for naive subjects not familiar with the test image alphabet was reached after the particular level of fragmentation at which this ratio was unity.

Gravitropic responses of the Avena coleoptile in space and on clinostats. I. Gravitropic response thresholds

NASA Technical Reports Server (NTRS)

Brown, A. H.; Chapman, D. K.; Johnsson, A.; Heathcote, D.

1995-01-01

We conducted a series of gravitropic experiments on Avena coleoptiles in the weightlessness environment of Spacelab. The purpose was to test the threshold stimulus, reciprocity rule and autotropic reactions to a range of g-force stimulations of different intensities and durations The tests avoided the potentially complicating effects of earth's gravity and the interference from clinostat ambiguities. Using slow-speed centrifuges, coleoptiles received transversal accelerations in the hypogravity range between 0.l and 1.0 g over periods that ranged from 2 to 130 min. All responses that occurred in weightlessness were compared to clinostat experiments on earth using the same apparatus. Characteristic gravitropistic response patterns of Atuena were not substantially different from those observed in ground-based experiments. Gravitropic presentation times were extrapolated. The threshold at 1.0 g was less than 1 min (shortest stimulation time 2 min), in agreement with values obtained on the ground. The least stimulus tested, 0.1 g for 130 min, produced a significant response. Therefore the absolute threshold for a gravitropic response is less than 0.1 g.

The Topo-trigger: a new concept of stereo trigger system for imaging atmospheric Cherenkov telescopes

NASA Astrophysics Data System (ADS)

López-Coto, R.; Mazin, D.; Paoletti, R.; Blanch Bigas, O.; Cortina, J.

2016-04-01

Imaging atmospheric Cherenkov telescopes (IACTs) such as the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes endeavor to reach the lowest possible energy threshold. In doing so the trigger system is a key element. Reducing the trigger threshold is hampered by the rapid increase of accidental triggers generated by ambient light (the so-called Night Sky Background NSB). In this paper we present a topological trigger, dubbed Topo-trigger, which rejects events on the basis of their relative orientation in the telescope cameras. We have simulated and tested the trigger selection algorithm in the MAGIC telescopes. The algorithm was tested using MonteCarlo simulations and shows a rejection of 85% of the accidental stereo triggers while preserving 99% of the gamma rays. A full implementation of this trigger system would achieve an increase in collection area between 10 and 20% at the energy threshold. The analysis energy threshold of the instrument is expected to decrease by ~ 8%. The selection algorithm was tested on real MAGIC data taken with the current trigger configuration and no γ-like events were found to be lost.

[Loss of capture by myocardial ischemia: A case report].

PubMed

Sonou, A; Adjagba, P M; Hounkponou, M; Codjo, L; Houéhanou-Sonou, C; Assani, S; Yessoufou, T; Sacca, J; Houénassi, M

2017-02-01

We report the case of a patient with pacemaker who presented chest pain during exercise followed by fainting. He has a history of arterial hypertension and diabetes. The initial examination was normal; the ventricular stimulation threshold was 1.125 volts (V) and cardiac enzymes were normal. Stress test has reproduced chest pain followed by loss of pacemaker capture and asystole. Coronary angiography showed a tight stenosis of the proximal anterior interventricular artery dilated by a drug-eluting stent. The control of stress test was normal. A stent thrombosis eight days later led to an acute coronary syndrome with recurrent syncope due to the loss of ventricular capture. The ventricular pacing threshold was then 2.25V. After revascularization and stabilization of the patient's clinical status, this threshold returned to 1.125V. This clinic case has confirmed that coronary artery disease could increase pacing threshold. It also highlights the usefulness of automatic capture algorithms in coronary patients. The stress test cannot only help to detect coronary artery disease but also allows the optimization of programming the pacemaker. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Pressure Effects on Oxygen Concentration Flammability Thresholds of Materials for Aerospace Applications

NASA Technical Reports Server (NTRS)

Hirsch, David; Williams, Jim; Beeson, Harold

2006-01-01

Spacecraft materials selection is based on an upward flammability test conducted in a quiescent environment in the highest-expected oxygen-concentration environment. However, NASA s advanced space exploration program is anticipating using various habitable environments. Because limited data is available to support current program requirements, a different test logic is suggested to address these expanded atmospheric environments through the determination of materials self-extinguishment limits. This paper provides additional pressure effects data on oxygen concentration and partial pressure self-extinguishment limits under quiescent conditions. For the range of total pressures tested, the oxygen concentration and oxygen partial pressure flammability thresholds show a near linear function of total pressure. The oxygen concentration/oxygen partial pressure flammability thresholds depend on the total pressure and appear to increase with increasing oxygen concentration (and oxygen partial pressure). For the Constellation Program, the flammability threshold information will allow NASA to identify materials with increased flammability risk because of oxygen concentration and total pressure changes, minimize potential impacts, and allow for development of sound requirements for new spacecraft and extraterrestrial landers and habitats.

Forecasting the probability of future groundwater levels declining below specified low thresholds in the conterminous U.S.

USGS Publications Warehouse

Dudley, Robert W.; Hodgkins, Glenn A.; Dickinson, Jesse

2017-01-01

We present a logistic regression approach for forecasting the probability of future groundwater levels declining or maintaining below specific groundwater-level thresholds. We tested our approach on 102 groundwater wells in different climatic regions and aquifers of the United States that are part of the U.S. Geological Survey Groundwater Climate Response Network. We evaluated the importance of current groundwater levels, precipitation, streamflow, seasonal variability, Palmer Drought Severity Index, and atmosphere/ocean indices for developing the logistic regression equations. Several diagnostics of model fit were used to evaluate the regression equations, including testing of autocorrelation of residuals, goodness-of-fit metrics, and bootstrap validation testing. The probabilistic predictions were most successful at wells with high persistence (low month-to-month variability) in their groundwater records and at wells where the groundwater level remained below the defined low threshold for sustained periods (generally three months or longer). The model fit was weakest at wells with strong seasonal variability in levels and with shorter duration low-threshold events. We identified challenges in deriving probabilistic-forecasting models and possible approaches for addressing those challenges.

TTCs for oral exposure: Identification of outliers in Cramer class I, II and III using the combined database of RepDose (FhG), Toxbase (TNO), Munro and ToxRefDB (USEPA)

EPA Science Inventory

The Thresholds of Toxicological Concern (TTC) are generic human exposure threshold for structural groups of chemicals below which no risk to human health is assumed and therefore no further testing is needed. Different thresholds have been developed for oral exposure e.g. for gen...

Test-retest agreement and reliability of quantitative sensory testing 1 year after breast cancer surgery.

PubMed

Andersen, Kenneth Geving; Kehlet, Henrik; Aasvang, Eske Kvanner

2015-05-01

Quantitative sensory testing (QST) is used to assess sensory dysfunction and nerve damage by examining psychophysical responses to controlled, graded stimuli such as mechanical and thermal detection and pain thresholds. In the breast cancer population, 4 studies have used QST to examine persistent pain after breast cancer treatment, suggesting neuropathic pain being a prominent pain mechanism. However, the agreement and reliability of QST has not been described in the postsurgical breast cancer population, hindering exact interpretation of QST studies in this population. The aim of the present study was to assess test-retest properties of QST after breast cancer surgery. A total of 32 patients recruited from a larger ongoing prospective trial were examined with QST 12 months after breast cancer surgery and reexamined a week later. A standardized QST protocol was used, including sensory mapping for mechanical, warmth and cold areas of sensory dysfunction, mechanical thresholds using monofilaments and pin-prick, thermal thresholds including warmth and cold detection thresholds and heat pain threshold, with bilateral examination. Agreement and reliability were assessed by Bland-Altman plots, descriptive statistics, coefficients of variance, and intraclass correlation. Bland-Altman plots showed high variation on the surgical side. Intraclass coefficients ranged from 0.356 to 0.847 (moderate to substantial reliability). Between-patient variation was generally higher (0.9 to 14.5 SD) than within-patient variation (0.23 to 3.55 SD). There were no significant differences between pain and pain-free patients. The individual test-retest variability was higher on the operated side compared with the nonoperated side. The QST protocol reliability allows for group-to-group comparison of sensory function, but less so for individual follow-up after breast cancer surgery.

Application of Executable Architectures in Early Concept Evaluation

DTIC Science & Technology

2015-12-01

xi List of Tables Page Table 1: Confusion Matrix Format (with example threshold values) ............................... 37 Table 2: Confusion... Matrix Logic Example ...................................................................... 37 Table 3: Test Case Matrix ...43 Table 4: Sensor Low Target Detection Threshold Confusion Matrix

Characterizing Decision-Analysis Performances of Risk Prediction Models Using ADAPT Curves.

PubMed

Lee, Wen-Chung; Wu, Yun-Chun

2016-01-01

The area under the receiver operating characteristic curve is a widely used index to characterize the performance of diagnostic tests and prediction models. However, the index does not explicitly acknowledge the utilities of risk predictions. Moreover, for most clinical settings, what counts is whether a prediction model can guide therapeutic decisions in a way that improves patient outcomes, rather than to simply update probabilities.Based on decision theory, the authors propose an alternative index, the "average deviation about the probability threshold" (ADAPT).An ADAPT curve (a plot of ADAPT value against the probability threshold) neatly characterizes the decision-analysis performances of a risk prediction model.Several prediction models can be compared for their ADAPT values at a chosen probability threshold, for a range of plausible threshold values, or for the whole ADAPT curves. This should greatly facilitate the selection of diagnostic tests and prediction models.

The effect of guessing on the speech reception thresholds of children.

PubMed

Moodley, A

1990-01-01

Speech audiometry is an essential part of the assessment of hearing impaired children and it is now widely used throughout the United Kingdom. Although instructions are universally agreed upon as an important aspect in the administration of any form of audiometric testing, there has been little, if any, research towards evaluating the influence which instructions that are given to a listener have on the Speech Reception Threshold obtained. This study attempts to evaluate what effect guessing has on the Speech Reception Threshold of children. A sample of 30 secondary school pupils between 16 and 18 years of age with normal hearing was used in the study. It is argued that the type of instruction normally used for Speech Reception Threshold in audiometric testing may not provide a sufficient amount of control for guessing and the implications of this, using data obtained in the study, are examined.

A low-ignition energy, SCB, thermite igniter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bickes, R.W. Jr.; Grubelich, M.C.; Wackerbarth, D.E.

1996-06-01

The authors describe threshold ignition studies for semiconductor bridge, SCB, ignition of aluminum/copper oxide (Al/CuO) thermite as a function of the capacitor discharge unit (CDU) firing set discharge capacitance, the charge holder material and the morphology of the CuO. All of the tests were carried out with the devices cooled to 0 F ({minus}18 C). They compared ignition thresholds using a brass charge holder and a G10 charge holder; G10 is a non-conducting, fiber-glass-epoxy composite material. They determined that at 50 V on the discharge capacitor, the thresholds were 30.1 {micro}F and 2.0 {micro}F respectively. The tests revealed that differentmore » CuO morphologies affected the function time (interval between start of the firing set current and the output of the thermite device) but did not significantly affect the threshold sensitivity.« less

Equivalent threshold sound pressure levels (ETSPL) for Sennheiser HDA 280 supra-aural audiometric earphones in the frequency range 125 Hz to 8000 Hz.

PubMed

Poulsen, Torben; Oakley, Sebastian

2009-05-01

Hearing threshold sound pressure levels were measured for the Sennheiser HDA 280 audiometric earphone. Hearing thresholds were measured for 25 normal-hearing test subjects at the 11 audiometric test frequencies from 125 Hz to 8000 Hz. Sennheiser HDA 280 is a supra-aural earphone that may be seen as a substitute for the classical Telephonics TDH 39. The results are given as the equivalent threshold sound pressure level (ETSPL) measured in an acoustic coupler specified in IEC 60318-3. The results are in good agreement with an independent investigation from PTB, Braunschweig, Germany. From acoustic laboratory measurements ETSPL values are calculated for the ear simulator specified in IEC 60318-1. Fitting of earphone and coupler is discussed. The data may be used for a future update of the RETSPL standard for supra-aural audiometric earphones, ISO 389-1.

High mobility high efficiency organic films based on pure organic materials

DOEpatents

Salzman, Rhonda F [Ann Arbor, MI; Forrest, Stephen R [Ann Arbor, MI

2009-01-27

A method of purifying small molecule organic material, performed as a series of operations beginning with a first sample of the organic small molecule material. The first step is to purify the organic small molecule material by thermal gradient sublimation. The second step is to test the purity of at least one sample from the purified organic small molecule material by spectroscopy. The third step is to repeat the first through third steps on the purified small molecule material if the spectroscopic testing reveals any peaks exceeding a threshold percentage of a magnitude of a characteristic peak of a target organic small molecule. The steps are performed at least twice. The threshold percentage is at most 10%. Preferably the threshold percentage is 5% and more preferably 2%. The threshold percentage may be selected based on the spectra of past samples that achieved target performance characteristics in finished devices.

Threshold dose for discrimination of nicotine via cigarette smoking.

PubMed

Perkins, Kenneth A; Kunkle, Nicole; Karelitz, Joshua L; Michael, Valerie C; Donny, Eric C

2016-06-01

The lowest nicotine threshold "dose" in cigarettes discriminated from a cigarette containing virtually no nicotine may help inform the minimum dose maintaining dependence. Spectrum research cigarettes (from NIDA) differing in nicotine content were used to evaluate a procedure to determine discrimination thresholds. Dependent smokers (n = 18; 13 M, 5 F) were tested on ability to discriminate cigarettes with nicotine contents of 11, 5, 2.4, and 1.3 mg/g, one per session, from the "ultralow" cigarette with 0.4 mg/g, after having discriminated 16 mg/g from 0.4 mg/g (all had 9-10 mg "tar"). Exposure to each was limited to 4 puffs/trial. All subjects were abstinent from smoking overnight prior to each session, and the number of sessions was determined by the participant's success in discrimination behavior on >80 % of trials. Subjective perceptions and behavioral choice between cigarettes were also assessed and related to discrimination behavior. The median threshold was 11 mg/g, but the range was 2.4 to 16 mg/g, suggesting wide variability in discrimination threshold. Compared to the ultralow, puff choice was greater for the subject's threshold dose but only marginal for the subthreshold (next lowest nicotine) cigarette. Threshold and subthreshold also differed on subjective perceptions but not withdrawal relief. Under these testing conditions, threshold content for discriminating nicotine via cigarettes may be 11 mg/g or greater for most smokers, but some can discriminate nicotine contents one-half or one-quarter this amount. Further study with other procedures and cigarette exposure amounts may identify systematic differences in nicotine discrimination thresholds.

Hydrodynamic sensory threshold in harbour seals (Phoca vitulina) for artificial flatfish breathing currents.

PubMed

Niesterok, Benedikt; Dehnhardt, Guido; Hanke, Wolf

2017-07-01

Harbour seals have the ability to detect benthic fish such as flatfish using the water currents these fish emit through their gills (breathing currents). We investigated the sensory threshold in harbour seals for this specific hydrodynamic stimulus under conditions which are realistic for seals hunting in the wild. We used an experimental platform where an artificial breathing current was emitted through one of eight different nozzles. Two seals were trained to search for the active nozzle. Each experimental session consisted of eight test trials of a particular stimulus intensity and 16 supra-threshold trials of high stimulus intensity. Test trials were conducted with the animals blindfolded. To determine the threshold, a series of breathing currents differing in intensity was used. For each intensity, three sessions were run. The threshold in terms of maximum water velocity within the breathing current was 4.2 cm s -1 for one seal and 3.7 cm s -1 for the other. We measured background flow velocities from 1.8 to 3.4 cm s -1 Typical swimming speeds for both animals were around 0.5 m s -1 Swimming speed differed between successful and unsuccessful trials. It appears that swimming speed is restricted for the successful detection of a breathing current close to the threshold. Our study is the first to assess a sensory threshold of the vibrissal system for a moving harbour seal under near-natural conditions. Furthermore, this threshold was defined for a natural type of stimulus differing from classical dipole stimuli which have been widely used in threshold determination so far. © 2017. Published by The Company of Biologists Ltd.

Minimum Performance on Clinical Tests of Physical Function to Predict Walking 6,000 Steps/Day in Knee Osteoarthritis: An Observational Study.

PubMed

Master, Hiral; Thoma, Louise M; Christiansen, Meredith B; Polakowski, Emily; Schmitt, Laura A; White, Daniel K

2018-07-01

Evidence of physical function difficulties, such as difficulty rising from a chair, may limit daily walking for people with knee osteoarthritis (OA). The purpose of this study was to identify minimum performance thresholds on clinical tests of physical function predictive to walking ≥6,000 steps/day. This benchmark is known to discriminate people with knee OA who develop functional limitation over time from those who do not. Using data from the Osteoarthritis Initiative, we quantified daily walking as average steps/day from an accelerometer (Actigraph GT1M) worn for ≥10 hours/day over 1 week. Physical function was quantified using 3 performance-based clinical tests: 5 times sit-to-stand test, walking speed (tested over 20 meters), and 400-meter walk test. To identify minimum performance thresholds for daily walking, we calculated physical function values corresponding to high specificity (80-95%) to predict walking ≥6,000 steps/day. Among 1,925 participants (mean ± SD age 65.1 ± 9.1 years, mean ± SD body mass index 28.4 ± 4.8 kg/m 2 , and 55% female) with valid accelerometer data, 54.9% walked ≥6,000 steps/day. High specificity thresholds of physical function for walking ≥6,000 steps/day ranged 11.4-14.0 seconds on the 5 times sit-to-stand test, 1.13-1.26 meters/second for walking speed, or 315-349 seconds on the 400-meter walk test. Not meeting these minimum performance thresholds on clinical tests of physical function may indicate inadequate physical ability to walk ≥6,000 steps/day for people with knee OA. Rehabilitation may be indicated to address underlying impairments limiting physical function. © 2017, American College of Rheumatology.

Pure-tone audiometry outside a sound booth using earphone attentuation, integrated noise monitoring, and automation.

PubMed

Swanepoel, De Wet; Matthysen, Cornelia; Eikelboom, Robert H; Clark, Jackie L; Hall, James W

2015-01-01

Accessibility of audiometry is hindered by the cost of sound booths and shortage of hearing health personnel. This study investigated the validity of an automated mobile diagnostic audiometer with increased attenuation and real-time noise monitoring for clinical testing outside a sound booth. Attenuation characteristics and reference ambient noise levels for the computer-based audiometer (KUDUwave) was evaluated alongside the validity of environmental noise monitoring. Clinical validity was determined by comparing air- and bone-conduction thresholds obtained inside and outside the sound booth (23 subjects). Twenty-three normal-hearing subjects (age range, 20-75 years; average age 35.5) and a sub group of 11 subjects to establish test-retest reliability. Improved passive attenuation and valid environmental noise monitoring was demonstrated. Clinically, air-conduction thresholds inside and outside the sound booth, corresponded within 5 dB or less > 90% of instances (mean absolute difference 3.3 ± 3.2 SD). Bone conduction thresholds corresponded within 5 dB or less in 80% of comparisons between test environments, with a mean absolute difference of 4.6 dB (3.7 SD). Threshold differences were not statistically significant. Mean absolute test-retest differences outside the sound booth was similar to those in the booth. Diagnostic pure-tone audiometry outside a sound booth, using automated testing, improved passive attenuation, and real-time environmental noise monitoring demonstrated reliable hearing assessments.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elhadj, Selim; Yoo, Jae-hyuck; Negres, Raluca A.

The optical damage performance of electrically conductive gallium nitride (GaN) and indium tin oxide (ITO) films is addressed using large area, high power laser beam exposures at 1064 nm sub-bandgap wavelength. Analysis of the laser damage process assumes that onset of damage (threshold) is determined by the absorption and heating of a nanoscale region of a characteristic size reaching a critical temperature. We use this model to rationalize semi-quantitatively the pulse width scaling of the damage threshold from picosecond to nanosecond timescales, along with the pulse width dependence of the damage threshold probability derived by fitting large beam damage densitymore » data. Multi-shot exposures were used to address lifetime performance degradation described by an empirical expression based on the single exposure damage model. A damage threshold degradation of at least 50% was observed for both materials. Overall, the GaN films tested had 5-10 × higher optical damage thresholds than the ITO films tested for comparable transmission and electrical conductivity. This route to optically robust, large aperture transparent electrodes and power optoelectronics may thus involve use of next generation widegap semiconductors such as GaN.« less

From innervation density to tactile acuity: 1. Spatial representation.

PubMed

Brown, Paul B; Koerber, H Richard; Millecchia, Ronald

2004-06-11

We tested the hypothesis that the population receptive field representation (a superposition of the excitatory receptive field areas of cells responding to a tactile stimulus) provides spatial information sufficient to mediate one measure of static tactile acuity. In psychophysical tests, two-point discrimination thresholds on the hindlimbs of adult cats varied as a function of stimulus location and orientation, as they do in humans. A statistical model of the excitatory low threshold mechanoreceptive fields of spinocervical, postsynaptic dorsal column and spinothalamic tract neurons was used to simulate the population receptive field representations in this neural population of the one- and two-point stimuli used in the psychophysical experiments. The simulated and observed thresholds were highly correlated. Simulated and observed thresholds' relations to physiological and anatomical variables such as stimulus location and orientation, receptive field size and shape, map scale, and innervation density were strikingly similar. Simulated and observed threshold variations with receptive field size and map scale obeyed simple relationships predicted by the signal detection model, and were statistically indistinguishable from each other. The population receptive field representation therefore contains information sufficient for this discrimination.

Salicylate-Induced Hearing Loss and Gap Detection Deficits in Rats

PubMed Central

Radziwon, Kelly E.; Stolzberg, Daniel J.; Urban, Maxwell E.; Bowler, Rachael A.; Salvi, Richard J.

2015-01-01

To test the “tinnitus gap-filling” hypothesis in an animal psychoacoustic paradigm, rats were tested using a go/no-go operant gap detection task in which silent intervals of various durations were embedded within a continuous noise. Gap detection thresholds were measured before and after treatment with a dose of sodium salicylate (200 mg/kg) that reliably induces tinnitus in rats. Noise-burst detection thresholds were also measured to document the amount of hearing loss and aid in interpreting the gap detection results. As in the previous human psychophysical experiments, salicylate had little or no effect on gap thresholds measured in broadband noise presented at high-stimulus levels (30–60 dB SPL); gap detection thresholds were always 10 ms or less. Salicylate also did not affect gap thresholds presented in narrowband noise at 60 dB SPL. Therefore, rats treated with a dose of salicylate that reliably induces tinnitus have no difficulty detecting silent gaps as long as the noise in which they are embedded is clearly audible. PMID:25750635

Observed physical processes in mechanical tests of PBX9501 and recomendations for experiments to explore a possible plasticity/damage threshold

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buechler, Miles A.

2012-05-02

This memo discusses observations that have been made in regards to a series of monotonic and cyclic uniaxial experiments performed on PBX9501 by Darla Thompson under Enhanced Surveilance Campaign support. These observations discussed in Section Cyclic compression observations strongly suggest the presence of viscoelastic, plastic, and damage phenomena in the mechanical response of the material. In Secton Uniaxial data analysis and observations methods are discussed for separating out the viscoelastic effects. A crude application of those methods suggests the possibility of a critical stress below which plasticity and damage may be negligible. The threshold should be explored because if itmore » exists it will be an important feature of any constitutive model. Additionally, if the threshold exists then modifications of experimental methods may be feasible which could potentially simplify future experiments or provide higher quality data from those experiments. A set of experiments to explore the threshold stress are proposed in Section Exploratory tests program for identifying threshold stress.« less

Vestibular Evoked Myogenic Potential (VEMP) Testing: Normative Threshold Response Curves and Effects of Age

PubMed Central

Janky, Kristen L.; Shepard, Neil

2009-01-01

Background Vestibular Evoked Myogenic Potential (VEMP) testing has gained increased interest in the diagnosis of a variety of vestibular etiologies. Comparisons of P13 / N23 latency, amplitude and threshold response curves have been used to compare pathologic groups to normal controls. Appropriate characterization of these etiologies requires normative data across the frequency spectrum and age range. Purpose The objective of the current study was to test the hypothesis that significant changes in VEMP responses occur as a function of increased age across all test stimuli as well as characterize the VEMP threshold response curve across age. Research Design This project incorporated a prospective study design using a sample of convenience. Openly recruited subjects were assigned to groups according to age. Study Sample Forty-six normal controls ranging between 20 and 76 years of age participated in the study. Participants were separated by decade into 5 age categories from 20 to 60 plus years. Normal participants were characterized by having normal hearing sensitivity, no history of neurologic or balance/dizziness involvement and negative results on a direct office vestibular examination. Intervention VEMP responses were measured at threshold to click and 250, 500, 750, and 1000 Hz tone burst stimuli and at a suprathreshold level to 500 Hz toneburst stimuli at123 dBSPL. Data Collection and Analysis A mixed group factorial ANOVA and linear regression were performed to examine the effects of VEMP characteristics upon age. Results There were no significant differences between ears for any of the test parameters. There were no significant differences between age groups for n23 latency or amplitude in response to any of the stimuli. Significant mean differences did exist between age groups for p13 latency (250, 750, and 1000 Hz) and threshold (500 and 750 Hz). Age was significantly correlated with VEMP parameters. VEMP threshold was positively correlated (250, 500, 750, 1000 Hz); and amplitude was negatively correlated (500 Hz Maximum). The threshold response curves revealed best frequency tuning at 500 Hz with the highest thresholds in response to click stimuli. However, this best frequency tuning dissipated with increased age. VEMP response rates also decreased with increased age. Conclusion We have demonstrated that minor differences in VEMP responses occur with age. Given the reduced response rates and flattened frequency tuning curve for individuals over the age of 60, frequency tuning curves may not be a good diagnostic indicator for this age group. PMID:19764171

Seasonal variations in body composition, maximal oxygen uptake, and gas exchange threshold in cross-country skiers.

PubMed

Polat, Metin; Korkmaz Eryılmaz, Selcen; Aydoğan, Sami

2018-01-01

In order to ensure that athletes achieve their highest performance levels during competitive seasons, monitoring their long-term performance data is crucial for understanding the impact of ongoing training programs and evaluating training strategies. The present study was thus designed to investigate the variations in body composition, maximal oxygen uptake (VO 2max ), and gas exchange threshold values of cross-country skiers across training phases throughout a season. In total, 15 athletes who participate in international cross-country ski competitions voluntarily took part in this study. The athletes underwent incremental treadmill running tests at 3 different time points over a period of 1 year. The first measurements were obtained in July, during the first preparation period; the second measurements were obtained in October, during the second preparation period; and the third measurements were obtained in February, during the competition period. Body weight, body mass index (BMI), body fat (%), as well as VO 2max values and gas exchange threshold, measured using V-slope method during the incremental running tests, were assessed at all 3 time points. The collected data were analyzed using SPSS 20 package software. Significant differences between the measurements were assessed using Friedman's twoway variance analysis with a post hoc option. The athletes' body weights and BMI measurements at the third point were significantly lower compared with the results of the second measurement ( p <0.001). Moreover, the incremental running test time was significantly higher at the third measurement, compared with both the first ( p <0.05) and the second ( p <0.01) measurements. Similarly, the running speed during the test was significantly higher at the third measurement time point compared with the first measurement time point ( p <0.05). Body fat (%), time to reach the gas exchange threshold, running speed at the gas exchange threshold, VO 2max , amount of oxygen consumed at gas exchange threshold level (VO 2GET ), maximal heart rate (HR max ), and heart rate at gas exchange threshold level (HR GET ) values did not significantly differ between the measurement time points ( p >0.05). VO 2max and gas exchange threshold values recorded during the third measurements, the timing of which coincided with the competitive season of the cross-country skiers, did not significantly change, but their incremental running test time and running speed significantly increased while their body weight and BMI significantly decreased. These results indicate that the cross-country skiers developed a tolerance for high-intensity exercise and reached their highest level of athletic performance during the competitive season.

Meta-analysis of diagnostic accuracy studies in mental health

PubMed Central

Takwoingi, Yemisi; Riley, Richard D; Deeks, Jonathan J

2015-01-01

Objectives To explain methods for data synthesis of evidence from diagnostic test accuracy (DTA) studies, and to illustrate different types of analyses that may be performed in a DTA systematic review. Methods We described properties of meta-analytic methods for quantitative synthesis of evidence. We used a DTA review comparing the accuracy of three screening questionnaires for bipolar disorder to illustrate application of the methods for each type of analysis. Results The discriminatory ability of a test is commonly expressed in terms of sensitivity (proportion of those with the condition who test positive) and specificity (proportion of those without the condition who test negative). There is a trade-off between sensitivity and specificity, as an increasing threshold for defining test positivity will decrease sensitivity and increase specificity. Methods recommended for meta-analysis of DTA studies --such as the bivariate or hierarchical summary receiver operating characteristic (HSROC) model --jointly summarise sensitivity and specificity while taking into account this threshold effect, as well as allowing for between study differences in test performance beyond what would be expected by chance. The bivariate model focuses on estimation of a summary sensitivity and specificity at a common threshold while the HSROC model focuses on the estimation of a summary curve from studies that have used different thresholds. Conclusions Meta-analyses of diagnostic accuracy studies can provide answers to important clinical questions. We hope this article will provide clinicians with sufficient understanding of the terminology and methods to aid interpretation of systematic reviews and facilitate better patient care. PMID:26446042

Threshold Studies on TNT, Composition B, and C-4 Explosives Using the Steven Impact Test

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vandersall, K S; Switzer, L L; Garcia, F

2005-09-26

Steven Impact Tests were performed at low velocity on the explosives TNT, Comp B, and C-4 in attempts to obtain a threshold for reaction. A 76 mm helium driven gas gun was used to accelerate the Steven Test projectiles up to approximately 200 m/s in attempts to react (ignite) the explosive samples. Blast overpressure gauges, acoustic microphones, standard video and high-speed photography were used to characterize the level of any high explosive reaction violence. No bulk reactions were observed in the TNT, Composition B, or C-4 explosive samples impacted up to velocities in the range of 190-200 m/s. This workmore » will outline the experimental details and discuss the lack of reaction when compared to the reaction thresholds of other common explosives.« less

Thresholds of Toxicological Concern - Setting a threshold for testing below which there is little concern.

PubMed

Hartung, Thomas

2017-01-01

Low dose, low risk; very low dose, no real risk. Setting a pragmatic threshold below which concerns become negligible is the purpose of thresholds of toxicological concern (TTC). The idea is that such threshold values do not need to be established for each and every chemical based on experimental data, but that by analyzing the distribution of lowest or no-effect doses of many chemicals, a TTC can be defined - typically using the 5th percentile of this distribution and lowering it by an uncertainty factor of, e.g., 100. In doing so, TTC aims to compare exposure information (dose) with a threshold below which any hazard manifestation is very unlikely to occur. The history and current developments of this concept are reviewed and the application of TTC for different regulated products and their hazards is discussed. TTC lends itself as a pragmatic filter to deprioritize testing needs whenever real-life exposures are much lower than levels where hazard manifestation would be expected, a situation that is called "negligible exposure" in the REACH legislation, though the TTC concept has not been fully incorporated in its implementation (yet). Other areas and regulations - especially in the food sector and for pharmaceutical impurities - are more proactive. Large, curated databases on toxic effects of chemicals provide us with the opportunity to set TTC for many hazards and substance classes and thus offer a precautionary second tier for risk assessments if hazard cannot be excluded. This allows focusing testing efforts better on relevant exposures to chemicals.

Effect of Mild Cognitive Impairment and Alzheimer Disease on Auditory Steady-State Responses

PubMed Central

Shahmiri, Elaheh; Jafari, Zahra; Noroozian, Maryam; Zendehbad, Azadeh; Haddadzadeh Niri, Hassan; Yoonessi, Ali

2017-01-01

Introduction: Mild Cognitive Impairment (MCI), a disorder of the elderly people, is difficult to diagnose and often progresses to Alzheimer Disease (AD). Temporal region is one of the initial areas, which gets impaired in the early stage of AD. Therefore, auditory cortical evoked potential could be a valuable neuromarker for detecting MCI and AD. Methods: In this study, the thresholds of Auditory Steady-State Response (ASSR) to 40 Hz and 80 Hz were compared between Alzheimer Disease (AD), MCI, and control groups. A total of 42 patients (12 with AD, 15 with MCI, and 15 elderly normal controls) were tested for ASSR. Hearing thresholds at 500, 1000, and 2000 Hz in both ears with modulation rates of 40 and 80 Hz were obtained. Results: Significant differences in normal subjects were observed in estimated ASSR thresholds with 2 modulation rates in 3 frequencies in both ears. However, the difference was significant only in 500 Hz in the MCI group, and no significant differences were observed in the AD group. In addition, significant differences were observed between the normal subjects and AD patients with regard to the estimated ASSR thresholds with 2 modulation rates and 3 frequencies in both ears. A significant difference was observed between the normal and MCI groups at 2000 Hz, too. An increase in estimated 40 Hz ASSR thresholds in patients with AD and MCI suggests neural changes in auditory cortex compared to that in normal ageing. Conclusion: Auditory threshold estimation with low and high modulation rates by ASSR test could be a potentially helpful test for detecting cognitive impairment. PMID:29158880

Thematic mapper protoflight model preshipment review data package. Volume 4: Appendix. Part A: Multiplexer data book 2

NASA Technical Reports Server (NTRS)

1982-01-01

Final performance test data for the thematic mapper flight model multiplexer are presented in tables. Aspects covered include A/D thresholds for bands 5, 6, and 7; cross talk; the thermistor; bilevel commands signal parameters; A/D threshold ambient, voltage margin low bus; serial data and bit clock parameters; and the wire check. Tests were conducted at ambient temperature.

Threshold Theory Tested in an Organizational Setting: The Relation between Perceived Innovativeness and Intelligence in a Large Sample of Leaders

ERIC Educational Resources Information Center

Christensen, Bo T.; Hartmann, Peter V. W.; Rasmussen, Thomas Hedegaard

2017-01-01

A large sample of leaders (N = 4257) was used to test the link between leader innovativeness and intelligence. The threshold theory of the link between creativity and intelligence assumes that below a certain IQ level (approximately IQ 120), there is some correlation between IQ and creative potential, but above this cutoff point, there is no…

Olfactory Impairment in Chronic Rhinosinusitis Using Threshold, Discrimination, and Identification Scores

PubMed Central

Kohli, Preeti; Storck, Kristina A.; Schlosser, Rodney J.

2016-01-01

Differences in testing modalities and cut-points used to define olfactory dysfunction contribute to the wide variability in estimating the prevalence of olfactory dysfunction in chronic rhinosinusitis (CRS). The aim of this study is to report the prevalence of olfactory impairment using each component of the Sniffin’ Sticks test (threshold, discrimination, identification, and total score) with age-adjusted and ideal cut-points from normative populations. Patients meeting diagnostic criteria for CRS were enrolled from rhinology clinics at a tertiary academic center. Olfaction was assessed using the Sniffin’ Sticks test. The study population consisted of 110 patients. The prevalence of normosmia, hyposmia, and anosmia using total Sniffin’ Sticks score was 41.8%, 20.0%, and 38.2% using age-appropriate cut-points and 20.9%, 40.9%, and 38.2% using ideal cut-points. Olfactory impairment estimates for each dimension mirrored these findings, with threshold yielding the highest values. Threshold, discrimination, and identification were also found to be significantly correlated to each other (P < 0.001). In addition, computed tomography scores, asthma, allergy, and diabetes were found to be associated with olfactory dysfunction. In conclusion, the prevalence of olfactory dysfunction is dependent upon olfactory dimension and if age-adjusted cut-points are used. The method of olfactory testing should be chosen based upon specific clinical and research goals. PMID:27469973

The borderline range of toxicological methods: Quantification and implications for evaluating precision.

PubMed

Leontaridou, Maria; Urbisch, Daniel; Kolle, Susanne N; Ott, Katharina; Mulliner, Denis S; Gabbert, Silke; Landsiedel, Robert

2017-01-01

Test methods to assess the skin sensitization potential of a substance usually use threshold criteria to dichotomize continuous experimental read-outs into yes/no conclusions. The threshold criteria are prescribed in the respective OECD test guidelines and the conclusion is used for regulatory hazard assessment, i.e., classification and labelling of the substance. We can identify a borderline range (BR) around the classification threshold within which test results are inconclusive due to a test method's biological and technical variability. We quantified BRs in the prediction models of the non-animal test methods DPRA, LuSens and h-CLAT, and of the animal test LLNA, respectively. Depending on the size of the BR, we found that between 6% and 28% of the substances in the sets tested with these methods were considered borderline. When the results of individual non-animal test methods were combined into integrated testing strategies (ITS), borderline test results of individual tests also affected the overall assessment of the skin sensitization potential of the testing strategy. This was analyzed for the 2-out-of-3 ITS: Four out of 40 substances (10%) were considered borderline. Based on our findings we propose expanding the standard binary classification of substances into "positive"/"negative" or "hazardous"/"non-hazardous" by adding a "borderline" or "inconclusive" alert for cases where test results fall within the borderline range.

Comparison of software and human observers in reading images of the CDMAM test object to assess digital mammography systems

NASA Astrophysics Data System (ADS)

Young, Kenneth C.; Cook, James J. H.; Oduko, Jennifer M.; Bosmans, Hilde

2006-03-01

European Guidelines for quality control in digital mammography specify minimum and achievable standards of image quality in terms of threshold contrast, based on readings of images of the CDMAM test object by human observers. However this is time-consuming and has large inter-observer error. To overcome these problems a software program (CDCOM) is available to automatically read CDMAM images, but the optimal method of interpreting the output is not defined. This study evaluates methods of determining threshold contrast from the program, and compares these to human readings for a variety of mammography systems. The methods considered are (A) simple thresholding (B) psychometric curve fitting (C) smoothing and interpolation and (D) smoothing and psychometric curve fitting. Each method leads to similar threshold contrasts but with different reproducibility. Method (A) had relatively poor reproducibility with a standard error in threshold contrast of 18.1 +/- 0.7%. This was reduced to 8.4% by using a contrast-detail curve fitting procedure. Method (D) had the best reproducibility with an error of 6.7%, reducing to 5.1% with curve fitting. A panel of 3 human observers had an error of 4.4% reduced to 2.9 % by curve fitting. All automatic methods led to threshold contrasts that were lower than for humans. The ratio of human to program threshold contrasts varied with detail diameter and was 1.50 +/- .04 (sem) at 0.1mm and 1.82 +/- .06 at 0.25mm for method (D). There were good correlations between the threshold contrast determined by humans and the automated methods.

Accurate motor mapping in awake common marmosets using micro-electrocorticographical stimulation and stochastic threshold estimation

NASA Astrophysics Data System (ADS)

Kosugi, Akito; Takemi, Mitsuaki; Tia, Banty; Castagnola, Elisa; Ansaldo, Alberto; Sato, Kenta; Awiszus, Friedemann; Seki, Kazuhiko; Ricci, Davide; Fadiga, Luciano; Iriki, Atsushi; Ushiba, Junichi

2018-06-01

Objective. Motor map has been widely used as an indicator of motor skills and learning, cortical injury, plasticity, and functional recovery. Cortical stimulation mapping using epidural electrodes is recently adopted for animal studies. However, several technical limitations still remain. Test-retest reliability of epidural cortical stimulation (ECS) mapping has not been examined in detail. Many previous studies defined evoked movements and motor thresholds by visual inspection, and thus, lacked quantitative measurements. A reliable and quantitative motor map is important to elucidate the mechanisms of motor cortical reorganization. The objective of the current study was to perform reliable ECS mapping of motor representations based on the motor thresholds, which were stochastically estimated by motor evoked potentials and chronically implanted micro-electrocorticographical (µECoG) electrode arrays, in common marmosets. Approach. ECS was applied using the implanted µECoG electrode arrays in three adult common marmosets under awake conditions. Motor evoked potentials were recorded through electromyographical electrodes implanted in upper limb muscles. The motor threshold was calculated through a modified maximum likelihood threshold-hunting algorithm fitted with the recorded data from marmosets. Further, a computer simulation confirmed reliability of the algorithm. Main results. Computer simulation suggested that the modified maximum likelihood threshold-hunting algorithm enabled to estimate motor threshold with acceptable precision. In vivo ECS mapping showed high test-retest reliability with respect to the excitability and location of the cortical forelimb motor representations. Significance. Using implanted µECoG electrode arrays and a modified motor threshold-hunting algorithm, we were able to achieve reliable motor mapping in common marmosets with the ECS system.

Accurate motor mapping in awake common marmosets using micro-electrocorticographical stimulation and stochastic threshold estimation.

PubMed

Kosugi, Akito; Takemi, Mitsuaki; Tia, Banty; Castagnola, Elisa; Ansaldo, Alberto; Sato, Kenta; Awiszus, Friedemann; Seki, Kazuhiko; Ricci, Davide; Fadiga, Luciano; Iriki, Atsushi; Ushiba, Junichi

2018-06-01

Motor map has been widely used as an indicator of motor skills and learning, cortical injury, plasticity, and functional recovery. Cortical stimulation mapping using epidural electrodes is recently adopted for animal studies. However, several technical limitations still remain. Test-retest reliability of epidural cortical stimulation (ECS) mapping has not been examined in detail. Many previous studies defined evoked movements and motor thresholds by visual inspection, and thus, lacked quantitative measurements. A reliable and quantitative motor map is important to elucidate the mechanisms of motor cortical reorganization. The objective of the current study was to perform reliable ECS mapping of motor representations based on the motor thresholds, which were stochastically estimated by motor evoked potentials and chronically implanted micro-electrocorticographical (µECoG) electrode arrays, in common marmosets. ECS was applied using the implanted µECoG electrode arrays in three adult common marmosets under awake conditions. Motor evoked potentials were recorded through electromyographical electrodes implanted in upper limb muscles. The motor threshold was calculated through a modified maximum likelihood threshold-hunting algorithm fitted with the recorded data from marmosets. Further, a computer simulation confirmed reliability of the algorithm. Computer simulation suggested that the modified maximum likelihood threshold-hunting algorithm enabled to estimate motor threshold with acceptable precision. In vivo ECS mapping showed high test-retest reliability with respect to the excitability and location of the cortical forelimb motor representations. Using implanted µECoG electrode arrays and a modified motor threshold-hunting algorithm, we were able to achieve reliable motor mapping in common marmosets with the ECS system.

Perspective: Uses and misuses of thresholds in diagnostic decision making.

PubMed

Warner, Jeremy L; Najarian, Robert M; Tierney, Lawrence M

2010-03-01

The concept of thresholds plays a vital role in decisions involving the initiation, continuation, and completion of diagnostic testing. Much research has focused on the development of explicit thresholds, in the form of practice guidelines and decision analyses. However, these tools are used infrequently; most medical decisions are made at the bedside, using implicit thresholds. Study of these thresholds can lead to a deeper understanding of clinical decision making. The authors examine some factors constituting individual clinicians' implicit thresholds. They propose a model for static thresholds using the concept of situational gravity to explain why some thresholds are high, and some low. Next, they consider the hypothetical effects of incorrect placement of thresholds (miscalibration) and changes to thresholds during diagnosis (manipulation). They demonstrate these concepts using common clinical scenarios. Through analysis of miscalibration of thresholds, the authors demonstrate some common maladaptive clinical behaviors, which are nevertheless internally consistent. They then explain how manipulation of thresholds gives rise to common cognitive heuristics including premature closure and anchoring. They also discuss the case where no threshold has been exceeded despite exhaustive collection of data, which commonly leads to application of the availability or representativeness heuristics. Awareness of implicit thresholds allows for a more effective understanding of the processes of medical decision making and, possibly, to the avoidance of detrimental heuristics and their associated medical errors. Research toward accurately defining these thresholds for individual physicians and toward determining their dynamic properties during the diagnostic process may yield valuable insights.

The Montreal Cognitive Assessment and the mini-mental state examination as screening instruments for cognitive impairment: item analyses and threshold scores.

PubMed

Damian, Anne M; Jacobson, Sandra A; Hentz, Joseph G; Belden, Christine M; Shill, Holly A; Sabbagh, Marwan N; Caviness, John N; Adler, Charles H

2011-01-01

To perform an item analysis of the Montreal Cognitive Assessment (MoCA) versus the Mini-Mental State Examination (MMSE) in the prediction of cognitive impairment, and to examine the characteristics of different MoCA threshold scores. 135 subjects enrolled in a longitudinal clinicopathologic study were administered the MoCA by a single physician and the MMSE by a trained research assistant. Subjects were classified as cognitively impaired or cognitively normal based on independent neuropsychological testing. 89 subjects were found to be cognitively normal, and 46 cognitively impaired (20 with dementia, 26 with mild cognitive impairment). The MoCA was superior in both sensitivity and specificity to the MMSE, although not all MoCA tasks were of equal predictive value. A MoCA threshold score of 26 had a sensitivity of 98% and a specificity of 52% in this population. In a population with a 20% prevalence of cognitive impairment, a threshold of 24 was optimal (negative predictive value 96%, positive predictive value 47%). This analysis suggests the potential for creating an abbreviated MoCA. For screening in primary care, the MoCA threshold of 26 appears optimal. For testing in a memory disorders clinic, a lower threshold has better predictive value. Copyright © 2011 S. Karger AG, Basel.

Auditory enhancement of visual perception at threshold depends on visual abilities.

PubMed

Caclin, Anne; Bouchet, Patrick; Djoulah, Farida; Pirat, Elodie; Pernier, Jacques; Giard, Marie-Hélène

2011-06-17

Whether or not multisensory interactions can improve detection thresholds, and thus widen the range of perceptible events is a long-standing debate. Here we revisit this question, by testing the influence of auditory stimuli on visual detection threshold, in subjects exhibiting a wide range of visual-only performance. Above the perceptual threshold, crossmodal interactions have indeed been reported to depend on the subject's performance when the modalities are presented in isolation. We thus tested normal-seeing subjects and short-sighted subjects wearing their usual glasses. We used a paradigm limiting potential shortcomings of previous studies: we chose a criterion-free threshold measurement procedure and precluded exogenous cueing effects by systematically presenting a visual cue whenever a visual target (a faint Gabor patch) might occur. Using this carefully controlled procedure, we found that concurrent sounds only improved visual detection thresholds in the sub-group of subjects exhibiting the poorest performance in the visual-only conditions. In these subjects, for oblique orientations of the visual stimuli (but not for vertical or horizontal targets), the auditory improvement was still present when visual detection was already helped with flanking visual stimuli generating a collinear facilitation effect. These findings highlight that crossmodal interactions are most efficient to improve perceptual performance when an isolated modality is deficient. Copyright © 2011 Elsevier B.V. All rights reserved.

Facial arthralgia and myalgia: can they be differentiated by trigeminal sensory assessment?

PubMed

Eliav, Eli; Teich, Sorin; Nitzan, Dorit; El Raziq, Daood Abid; Nahlieli, Oded; Tal, Michael; Gracely, Richard H; Benoliel, Rafael

2003-08-01

Heat and electrical detection thresholds were assessed in 72 patients suffering from painful temporomandibular disorder. Employing widely accepted criteria, 44 patients were classified as suffering from temporomandibular joint (TMJ) arthralgia (i.e. pain originating from the TMJ) and 28 from myalgia (i.e. pain originating from the muscles of mastication). Electrical stimulation was employed to assess thresholds in large myelinated nerve fibers (Abeta) and heat application to assess thresholds in unmyelinated nerve fibers (C). The sensory tests were performed bilaterally in three trigeminal nerve sites: the auriculotemporal nerve territory (AUT), buccal nerve territory (BUC) and the mental nerve territory (MNT). In addition, 22 healthy asymptomatic controls were examined. A subset of ten arthralgia patients underwent arthrocentesis and electrical detection thresholds were additionally assessed following the procedure. Electrical detection threshold ratios were calculated by dividing the affected side by the control side, thus reduced ratios indicate hypersensitivity of the affected side. In control patients, ratios obtained at all sites did not vary significantly from the expected value of 'one' (mean with 95% confidence intervals; AUT, 1:0.95-1.06; BUC, 1.01:0.93-1.11; MNT, 0.97:0.88-1.05, all areas one sample analysis P>0.05). In arthralgia patients mean ratios (+/-SEM) obtained for the AUT territory (0.63+/-0.03) were significantly lower compared to ratios for the MNT (1.02+/-0.03) and BUC (0.96+/-0.04) territories (repeated measures analysis of variance (RANOVA), P<0.0001) and compared to the AUT ratios in myalgia (1.27+/-0.09) and control subjects (1+/-0.06, ANOVA, P<0.0001). In the myalgia group the electrical detection threshold ratios in the AUT territory were significantly elevated compared to the AUT ratios in control subjects (Dunnett test, P<0.05), but only approached statistical significance compared to the MNT (1.07+/-0.04) and BUC (1.11+/-0.06) territories (RANOVA, F(2,27)=3.12, P=0.052). There were no significant differences between and within the groups for electrical detection threshold ratios in the BUC and MNT nerve territories, and for the heat detection thresholds in all tested sites. Following arthrocentesis, mean electrical detection threshold ratios in the AUT territory were significantly elevated from 0.64+/-0.06 to 0.99+/-0.04 indicating resolution of the hypersensitivity (paired t-test, P=0.001). In conclusion, large myelinated fiber hypersensitivity is found in the skin overlying TMJs with clinical pain and pathology but is not found in controls. In patients with muscle-related facial pain there was significant elevation of the electrical detection threshold in the AUT region.

Comparison between implant-supported prostheses and teeth regarding passive threshold level.

PubMed

Jacobs, R; van Steenberghe, D

1993-01-01

A passive threshold determination was carried out on 31 patients subdivided into four test groups according to different prosthesis types supported by osseointegrated implants. They were compared to a control group of 10 patients with nonrestored natural test teeth. Forces were generated by a solenoid-driven stimulating device, which was placed in contact with the implant or tooth prior to the actual force rise to avoid impact forces. The findings indicate that the threshold level of implants is 50 times higher than that of natural teeth when tapping is avoided, which might otherwise trigger distant receptors. Bone deformation triggering the periosteal mechanoreceptors is the most logical explanation for the sensation reported.

Injury tolerance and moment response of the knee joint to combined valgus bending and shear loading.

PubMed

Bose, Dipan; Bhalla, Kavi S; Untaroiu, Costin D; Ivarsson, B Johan; Crandall, Jeff R; Hurwitz, Shepard

2008-06-01

Valgus bending and shearing of the knee have been identified as primary mechanisms of injuries in a lateral loading environment applicable to pedestrian-car collisions. Previous studies have reported on the structural response of the knee joint to pure valgus bending and lateral shearing, as well as the estimated injury thresholds for the knee bending angle and shear displacement based on experimental tests. However, epidemiological studies indicate that most knee injuries are due to the combined effects of bending and shear loading. Therefore, characterization of knee stiffness for combined loading and the associated injury tolerances is necessary for developing vehicle countermeasures to mitigate pedestrian injuries. Isolated knee joint specimens (n=40) from postmortem human subjects were tested in valgus bending at a loading rate representative of a pedestrian-car impact. The effect of lateral shear force combined with the bending moment on the stiffness response and the injury tolerances of the knee was concurrently evaluated. In addition to the knee moment-angle response, the bending angle and shear displacement corresponding to the first instance of primary ligament failure were determined in each test. The failure displacements were subsequently used to estimate an injury threshold function based on a simplified analytical model of the knee. The validity of the determined injury threshold function was subsequently verified using a finite element model. Post-test necropsy of the knees indicated medial collateral ligament injury consistent with the clinical injuries observed in pedestrian victims. The moment-angle response in valgus bending was determined at quasistatic and dynamic loading rates and compared to previously published test data. The peak bending moment values scaled to an average adult male showed no significant change with variation in the superimposed shear load. An injury threshold function for the knee in terms of bending angle and shear displacement was determined by performing regression analysis on the experimental data. The threshold values of the bending angle (16.2 deg) and shear displacement (25.2 mm) estimated from the injury threshold function were in agreement with previously published knee injury threshold data. The continuous knee injury function expressed in terms of bending angle and shear displacement enabled injury prediction for combined loading conditions such as those observed in pedestrian-car collisions.

Amyloid and tau signatures of brain metabolic decline in preclinical Alzheimer's disease.

PubMed

Pascoal, Tharick A; Mathotaarachchi, Sulantha; Shin, Monica; Park, Ah Yeon; Mohades, Sara; Benedet, Andrea L; Kang, Min Su; Massarweh, Gassan; Soucy, Jean-Paul; Gauthier, Serge; Rosa-Neto, Pedro

2018-06-01

We aimed to determine the amyloid (Aβ) and tau biomarker levels associated with imminent Alzheimer's disease (AD) - related metabolic decline in cognitively normal individuals. A threshold analysis was performed in 120 cognitively normal elderly individuals by modelling 2-year declines in brain glucose metabolism measured with [ 18 F]fluorodeoxyglucose ([ 18 F]FDG) as a function of [ 18 F]florbetapir Aβ positron emission tomography (PET) and cerebrospinal fluid phosphorylated tau biomarker thresholds. Additionally, using a novel voxel-wise analytical framework, we determined the sample sizes needed to test an estimated 25% drugeffect with 80% of power on changes in FDG uptake over 2 years at every brain voxel. The combination of [ 18 F]florbetapir standardized uptake value ratios and phosphorylated-tau levels more than one standard deviation higher than their respective thresholds for biomarker abnormality was the best predictor of metabolic decline in individuals with preclinical AD. We also found that a clinical trial using these thresholds would require as few as 100 individuals to test a 25% drug effect on AD-related metabolic decline over 2 years. These results highlight the new concept that combined Aβ and tau thresholds can predict imminent neurodegeneration as an alternative framework with a high statistical power for testing the effect of disease-modifying therapies on [ 18 F]FDG uptake decline over a typical 2-year clinical trial period in individuals with preclinical AD.

Lubiprostone does not Influence Visceral Pain Thresholds in Patients with Irritable Bowel Syndrome

PubMed Central

Whitehead, William E.; Palsson, Olafur S.; Gangarosa, Lisa; Turner, Marsha; Tucker, Jane

2011-01-01

Background In clinical trials, lubiprostone reduced the severity of abdominal pain. Aims The primary aim was to determine whether lubiprostone raises the threshold for abdominal pain induced by intraluminal balloon distention. A secondary aim was to determine whether changes in pain sensitivity influence clinical pain independently of changes in transit time. Methods Sixty-two patients with irritable bowel syndrome with constipation (IBS-C) participated in an 8-week crossover study. All subjects completed a 14-day baseline ending with a barostat test of pain and urge sensory thresholds. Half, randomly selected, then received 48 ug/day of lubiprostone for 14 days ending with a pain sensitivity test and a Sitzmark test of transit time. This was followed by a 14-day washout and then a crossover to 14 days of placebo with tests of pain sensitivity and transit time. The other half of the subjects received placebo before lubiprostone. All kept symptom diaries. Results Stools were significantly softer when taking lubiprostone compared to placebo (Bristol Stool scores 4.20 vs. 3.44, p<0.001). However, thresholds for pain (17.36 vs. 17.83 mmHg, lubiprostone vs. placebo) and urgency to defecate (14.14 vs. 14.53 mmHg) were not affected by lubiprostone. Transit time was not significantly different between lubiprostone and placebo (51.27 vs. 51.81 hours), and neither pain sensitivity nor transit time was a significant predictor of clinical pain. Conclusions Lubiprostone has no effect on visceral sensory thresholds. The reductions in clinical pain that occur while taking lubiprostone appear to be secondary to changes in stool consistency. PMID:21914041

The effect of the impactor diameter and temperature on low velocity impact behavior of CFRP laminates

NASA Astrophysics Data System (ADS)

Evci, C.; Uyandıran, I.

2017-02-01

Impact damage is one of the major concerns that should be taken into account with the new aircraft and spacecraft structures which employ ever-growing use of composite materials. Considering the thermal loads encountered at different altitudes, both low and high temperatures can affect the properties and impact behavior of composite materials. This study aims to investigate the effect of temperature and impactor diameter on the impact behavior and damage development in balanced and symmetrical CFRP laminates which were manufactured by employing vacuum bagging process with autoclave cure. Instrumented drop-weight impact testing system is used to perform the low velocity impact tests in a range of temperatures ranged from 60 down to -50 °C. Impact tests for each temperature level were conducted using three different hemispherical impactor diameters varying from 10 to 20 mm. Energy profile method is employed to determine the impact threshold energies for damage evolution. The level of impact damage is determined from the dent depth on the impacted face and delamination damage detected using ultrasonic C-Scan technique. Test results reveal that the threshold of penetration energy, main failure force and delamination area increase with impactor diameter at all temperature levels. No clear influence of temperature on the critical force thresholds could be derived. However, penetration threshold energy decreased as the temperature was lowered. Drop in the penetration threshold was more obvious with quite low temperatures. Delamination damage area increased while the temperature decreased from +60 °C to -50 °C.

Exercise may cause myocardial ischemia at the anaerobic threshold in cardiac rehabilitation programs.

PubMed

Fuchs, A R C N; Meneghelo, R S; Stefanini, E; De Paola, A V; Smanio, P E P; Mastrocolla, L E; Ferraz, A S; Buglia, S; Piegas, L S; Carvalho, A A C

2009-03-01

Myocardial ischemia may occur during an exercise session in cardiac rehabilitation programs. However, it has not been established whether it is elicited when exercise prescription is based on heart rate corresponding to the anaerobic threshold as measured by cardiopulmonary exercise testing. Our objective was to determine the incidence of myocardial ischemia in cardiac rehabilitation programs according to myocardial perfusion SPECT in exercise programs based on the anaerobic threshold. Thirty-nine patients (35 men and 4 women) diagnosed with coronary artery disease by coronary angiography and stress technetium-99m-sestamibi gated SPECT associated with a baseline cardiopulmonary exercise test were assessed. Ages ranged from 45 to 75 years. A second cardiopulmonary exercise test determined training intensity at the anaerobic threshold. Repeat gated-SPECT was obtained after a third cardiopulmonary exercise test at the prescribed workload and heart rate. Myocardial perfusion images were analyzed using a score system of 6.4 at rest, 13.9 at peak stress, and 10.7 during the prescribed exercise (P < 0.05). The presence of myocardial ischemia during exercise was defined as a difference > or = 2 between the summed stress score and summed rest score. Accordingly, 25 (64%) patients were classified as ischemic and 14 (36%) as nonischemic. MIBI-SPECT showed myocardial ischemia during exercise within the anaerobic threshold. The 64% prevalence of ischemia observed in the study should not be looked on as representative of the whole population of patients undergoing exercise programs. Changes in patient care and exercise programs were implemented as a result of our finding of ischemia during the prescribed exercise.

Evaluation of the pentylenetetrazole seizure threshold test in epileptic mice as surrogate model for drug testing against pharmacoresistant seizures.

PubMed

Töllner, Kathrin; Twele, Friederike; Löscher, Wolfgang

2016-04-01

Resistance to antiepileptic drugs (AEDs) is a major problem in epilepsy therapy, so that development of more effective AEDs is an unmet clinical need. Several rat and mouse models of epilepsy with spontaneous difficult-to-treat seizures exist, but because testing of antiseizure drug efficacy is extremely laborious in such models, they are only rarely used in the development of novel AEDs. Recently, the use of acute seizure tests in epileptic rats or mice has been proposed as a novel strategy for evaluating novel AEDs for increased antiseizure efficacy. In the present study, we compared the effects of five AEDs (valproate, phenobarbital, diazepam, lamotrigine, levetiracetam) on the pentylenetetrazole (PTZ) seizure threshold in mice that were made epileptic by pilocarpine. Experiments were started 6 weeks after a pilocarpine-induced status epilepticus. At this time, control seizure threshold was significantly lower in epileptic than in nonepileptic animals. Unexpectedly, only one AED (valproate) was less effective to increase seizure threshold in epileptic vs. nonepileptic mice, and this difference was restricted to doses of 200 and 300 mg/kg, whereas the difference disappeared at 400mg/kg. All other AEDs exerted similar seizure threshold increases in epileptic and nonepileptic mice. Thus, induction of acute seizures with PTZ in mice pretreated with pilocarpine does not provide an effective and valuable surrogate method to screen drugs for antiseizure efficacy in a model of difficult-to-treat chronic epilepsy as previously suggested from experiments with this approach in rats. Copyright © 2016 Elsevier Inc. All rights reserved.

Thermal and mechanical quantitative sensory testing in Chinese patients with burning mouth syndrome--a probable neuropathic pain condition?

PubMed

Mo, Xueyin; Zhang, Jinglu; Fan, Yuan; Svensson, Peter; Wang, Kelun

2015-01-01

To explore the hypothesis that burning mouth syndrome (BMS) probably is a neuropathic pain condition, thermal and mechanical sensory and pain thresholds were tested and compared with age- and gender-matched control participants using a standardized battery of psychophysical techniques. Twenty-five BMS patients (men: 8, women: 17, age: 49.5 ± 11.4 years) and 19 age- and gender-matched healthy control participants were included. The cold detection threshold (CDT), warm detection threshold (WDT), cold pain threshold (CPT), heat pain threshold (HPT), mechanical detection threshold (MDT) and mechanical pain threshold (MPT), in accordance with the German Network of Neuropathic Pain guidelines, were measured at the following four sites: the dorsum of the left hand (hand), the skin at the mental foramen (chin), on the tip of the tongue (tongue), and the mucosa of the lower lip (lip). Statistical analysis was performed using ANOVA with repeated measures to compare the means within and between groups. Furthermore, Z-score profiles were generated, and exploratory correlation analyses between QST and clinical variables were performed. Two-tailed tests with a significance level of 5 % were used throughout. CDTs (P < 0.02) were significantly lower (less sensitivity) and HPTs (P < 0.001) were significantly higher (less sensitivity) at the tongue and lip in BMS patients compared to control participants. WDT (P = 0.007) was also significantly higher at the tongue in BMS patients compared to control subjects . There were no significant differences in MDT and MPT between the BMS patients and healthy subjects at any of the four test sites. Z-scores showed that significant loss of function can be identified for CDT (Z-scores = -0.9±1.1) and HPT (Z-scores = 1.5±0.4). There were no significant correlations between QST and clinical variables (pain intensity, duration, depressions scores). BMS patients had a significant loss of thermal function but not mechanical function, supporting the hypothesis that BMS may be a probable neuropathic pain condition. Further studies including e.g. electrophysiological or imaging techniques are needed to clarify the underlying mechanisms of BMS.

Cost-effectiveness of the faecal immunochemical test at a range of positivity thresholds compared with the guaiac faecal occult blood test in the NHS Bowel Cancer Screening Programme in England

PubMed Central

Halloran, Stephen

2017-01-01

Objectives Through the National Health Service (NHS) Bowel Cancer Screening Programme (BCSP), men and women in England aged between 60 and 74 years are invited for colorectal cancer (CRC) screening every 2 years using the guaiac faecal occult blood test (gFOBT). The aim of this analysis was to estimate the cost–utility of the faecal immunochemical test for haemoglobin (FIT) compared with gFOBT for a cohort beginning screening aged 60 years at a range of FIT positivity thresholds. Design We constructed a cohort-based Markov state transition model of CRC disease progression and screening. Screening uptake, detection, adverse event, mortality and cost data were taken from BCSP data and national sources, including a recent large pilot study of FIT screening in the BCSP. Results Our results suggest that FIT is cost-effective compared with gFOBT at all thresholds, resulting in cost savings and quality-adjusted life years (QALYs) gained over a lifetime time horizon. FIT was cost-saving (p<0.001) and resulted in QALY gains of 0.014 (95% CI 0.012 to 0.017) at the base case threshold of 180 µg Hb/g faeces. Greater health gains and cost savings were achieved as the FIT threshold was decreased due to savings in cancer management costs. However, at lower thresholds, FIT was also associated with more colonoscopies (increasing from 32 additional colonoscopies per 1000 people invited for screening for FIT 180 µg Hb/g faeces to 421 additional colonoscopies per 1000 people invited for screening for FIT 20 µg Hb/g faeces over a 40-year time horizon). Parameter uncertainty had limited impact on the conclusions. Conclusions This is the first published economic analysis of FIT screening in England using data directly comparing FIT with gFOBT in the NHS BSCP. These results for a cohort starting screening aged 60 years suggest that FIT is highly cost-effective at all thresholds considered. Further modelling is needed to estimate economic outcomes for screening across all age cohorts simultaneously. PMID:29079605

Computerized Color Vision Test Based Upon Postreceptoral Channel Sensitivities

PubMed Central

E, Miyahara; J, Pokorny; VC, Smith; E, Szewczyk; J, McCartin; K, Caldwell; A, Klerer

2006-01-01

An automated, computerized color vision test was designed to diagnose congenital red-green color vision defects. The observer viewed a yellow appearing CRT screen. The principle was to measure increment thresholds for three different chromaticities, the background yellow, a red, and a green chromaticity. Spatial and temporal parameters were chosen to favor parvocellular pathway mediation of thresholds. Thresholds for the three test stimuli were estimated by 4AFC, randomly interleaved staircases. Four 1.5°, 4.2 cd/m2 square pedestals were arranged as a 2 x 2 matrix around the center of the display with 15’ separations. A trial incremented all four squares by 1.0 cd/m2 for 133 msec. One randomly chosen square included an extra increment of a test chromaticity. The observer identified the different appearing square using the cursor. Administration time was ~5 minutes. Normal trichromats showed clear Sloan notch as defined by log (ΔY/ΔR), whereas red-green color defectives generally showed little or no Sloan notch, indicating that their thresholds were mediated by their luminance system, not by the chromatic system. Data from 107 normal trichromats showed a mean Sloan notch of 0.654 (SD = 0.123). Among 16 color vision defectives tested (2 protanopes, 1 protanomal, 6 deuteranopes, 7 deuteranomals), the Sloan notch was between −0.062 and 0.353 for deutans and was < −0.10 for protans. A sufficient number of color defective observers have not yet been tested to determine whether the test can reliably discriminate between protans and deutans. Nevertheless, the current data show that the test can work as a quick diagnostic procedure (functional trichromatism or dichromatism) of red-green color vision defect. PMID:15518231

Viscoplastic Model Development to Account for Strength Differential: Application to Aged Inconel 718 at Elevated Temperature. Degree awarded by Pennsylvania State Univ., 2000

NASA Technical Reports Server (NTRS)

Iyer, Saiganesh; Lerch, Brad (Technical Monitor)

2001-01-01

The magnitude of yield and flow stresses in aged Inconel 718 are observed to be different in tension and compression. This phenomenon, called the Strength differential (SD), contradicts the metal plasticity axiom that the second deviatoric stress invariant alone is sufficient for representing yield and flow. Apparently, at least one of the other two stress invariants is also significant. A unified viscoplastic model was developed that is able to account for the SD effect in aged Inconel 718. Building this model involved both theory and experiments. First, a general threshold function was proposed that depends on all three stress invariants and then the flow and evolution laws were developed using a potential-based thermodynamic framework. Judiciously chosen shear and axial tests were conducted to characterize the material. Shear tests involved monotonic loading, relaxation, and creep tests with different loading rates and load levels. The axial tests were tension and compression tests that resulted in sufficiently large inelastic strains. All tests were performed at 650 C. The viscoplastic material parameters were determined by optimizing the fit to the shear tests, during which the first and the third stress invariants remained zero. The threshold surface parameters were then fit to the tension and compression test data. An experimental procedure was established to quantify the effect of each stress invariant on inelastic deformation. This requires conducting tests with nonproportional three-dimensional load paths. Validation of the model was done using biaxial tests on tubular specimens of aged Inconel 718 using proportional and nonproportional axial-torsion loading. These biaxial tests also helped to determine the most appropriate form of the threshold function; that is, how to combine the stress invariants. Of the set of trial threshold functions, the ones that incorporated the third stress invariant give the best predictions. However, inclusion of the first stress invariant does not significantly improve the model predictions. The model shows excellent predictive capability for nonproportional load paths. Additionally, it reduces to the well-known models of Mises Drucker and Drucker-Prager. The requisite experiments involve reasonably simple load paths in the axial-shear stress plane and hence can be performed on a variety of different materials: be they metallic, geological. polymeric, ceramic or granular. The general form of the threshold function allows representation of inelastic deformation in a range of materials.

AutoNR: an automated system that measures ECAP thresholds with the Nucleus Freedom cochlear implant via machine intelligence.

PubMed

Botros, Andrew; van Dijk, Bas; Killian, Matthijs

2007-05-01

AutoNRT is an automated system that measures electrically evoked compound action potential (ECAP) thresholds from the auditory nerve with the Nucleus Freedom cochlear implant. ECAP thresholds along the electrode array are useful in objectively fitting cochlear implant systems for individual use. This paper provides the first detailed description of the AutoNRT algorithm and its expert systems, and reports the clinical success of AutoNRT to date. AutoNRT determines thresholds by visual detection, using two decision tree expert systems that automatically recognise ECAPs. The expert systems are guided by a dataset of 5393 neural response measurements. The algorithm approaches threshold from lower stimulus levels, ensuring recipient safety during postoperative measurements. Intraoperative measurements use the same algorithm but proceed faster by beginning at stimulus levels much closer to threshold. When searching for ECAPs, AutoNRT uses a highly specific expert system (specificity of 99% during training, 96% during testing; sensitivity of 91% during training, 89% during testing). Once ECAPs are established, AutoNRT uses an unbiased expert system to determine an accurate threshold. Throughout the execution of the algorithm, recording parameters (such as implant amplifier gain) are automatically optimised when needed. In a study that included 29 intraoperative and 29 postoperative subjects (a total of 418 electrodes), AutoNRT determined a threshold in 93% of cases where a human expert also determined a threshold. When compared to the median threshold of multiple human observers on 77 randomly selected electrodes, AutoNRT performed as accurately as the 'average' clinician. AutoNRT has demonstrated a high success rate and a level of performance that is comparable with human experts. It has been used in many clinics worldwide throughout the clinical trial and commercial launch of Nucleus Custom Sound Suite, significantly streamlining the clinical procedures associated with cochlear implant use.

Color vision testing with a computer graphics system: preliminary results.

PubMed

Arden, G; Gündüz, K; Perry, S

1988-06-01

We report a method for computer enhancement of color vision tests. In our graphics system 256 colors are selected from a much larger range and displayed on a screen divided into 768 x 288 pixels. Eight-bit digital-to-analogue converters drive a high quality monitor with separate inputs to the red, green, and blue amplifiers and calibrated gun chromaticities. The graphics are controlled by a PASCAL program written for a personal computer, which calculates the values of the red, green, and blue signals and specifies them in Commité Internationale d'Eclairage X, Y, and Z fundamentals, so changes in chrominance occur without changes in luminance. The system for measuring color contrast thresholds with gratings is more than adequate in normal observers. In patients with mild retinal damage in whom other tests of visual function are normal, this method of testing color vision shows specific increases in contrast thresholds along tritan color-confusion lines. By the time the Hardy-Rand-Rittler and Farnsworth-Munsell 100-hue tests disclose abnormalities, gross defects in color contrast threshold can be seen with our system.

Infrasonic and low-frequency insert earphone hearing threshold.

PubMed

Kuehler, Robert; Fedtke, Thomas; Hensel, Johannes

2015-04-01

Low-frequency and infrasonic pure-tone monaural hearing threshold data down to 2.5 Hz are presented. These measurements were made by means of a newly developed insert-earphone source. The source is able to generate pure-tone sound pressure levels up to 130 dB between 2 and 250 Hz with very low harmonic distortions. Behavioral hearing thresholds were determined in the frequency range from 2.5 to 125 Hz for 18 otologically normal test persons. The median hearing thresholds are comparable to values given in the literature. They are intended for stimulus calibration in subsequent brain imaging investigations.

A fuzzy optimal threshold technique for medical images

NASA Astrophysics Data System (ADS)

Thirupathi Kannan, Balaji; Krishnasamy, Krishnaveni; Pradeep Kumar Kenny, S.

2012-01-01

A new fuzzy based thresholding method for medical images especially cervical cytology images having blob and mosaic structures is proposed in this paper. Many existing thresholding algorithms may segment either blob or mosaic images but there aren't any single algorithm that can do both. In this paper, an input cervical cytology image is binarized, preprocessed and the pixel value with minimum Fuzzy Gaussian Index is identified as an optimal threshold value and used for segmentation. The proposed technique is tested on various cervical cytology images having blob or mosaic structures, compared with various existing algorithms and proved better than the existing algorithms.

Harm is all you need? Best interests and disputes about parental decision-making

PubMed Central

Birchley, Giles

2016-01-01

A growing number of bioethics papers endorse the harm threshold when judging whether to override parental decisions. Among other claims, these papers argue that the harm threshold is easily understood by lay and professional audiences and correctly conforms to societal expectations of parents in regard to their children. English law contains a harm threshold which mediates the use of the best interests test in cases where a child may be removed from her parents. Using Diekema's seminal paper as an example, this paper explores the proposed workings of the harm threshold. I use examples from the practical use of the harm threshold in English law to argue that the harm threshold is an inadequate answer to the indeterminacy of the best interests test. I detail two criticisms: First, the harm standard has evaluative overtones and judges are loath to employ it where parental behaviour is misguided but they wish to treat parents sympathetically. Thus, by focusing only on ‘substandard’ parenting, harm is problematic where the parental attempts to benefit their child are misguided or wrong, such as in disputes about withdrawal of medical treatment. Second, when harm is used in genuine dilemmas, court judgments offer different answers to similar cases. This level of indeterminacy suggests that, in practice, the operation of the harm threshold would be indistinguishable from best interests. Since indeterminacy appears to be the greatest problem in elucidating what is best, bioethicists should concentrate on discovering the values that inform best interests. PMID:26401048

Psychophysical Measurement of Rod and Cone Thresholds in Stargardt Disease with Full-Field Stimuli

PubMed Central

Collison, Frederick T.; Fishman, Gerald A.; McAnany, J. Jason; Zernant, Jana; Allikmets, Rando

2014-01-01

Purpose To investigate psychophysical thresholds in Stargardt disease with the full-field stimulus test (FST). Methods Visual acuity (VA), spectral-domain optical coherence tomography (SD-OCT), full-field electroretinogram (ERG), and FST measurements were made in one eye of 24 patients with Stargardt disease. Dark-adapted rod FST thresholds were measured with short-wavelength stimuli, and cone FST thresholds were obtained from the cone plateau phase of dark adaptation using long-wavelength stimuli. Correlation coefficients were calculated for FST thresholds versus macular thickness, VA and ERG amplitudes. Results Stargardt patient FST cone thresholds correlated significantly with VA, macular thickness, and ERG cone-response amplitudes (all P<0.01). The patients’ FST rod thresholds correlated with ERG rod-response amplitudes (P<0.01), but not macular thickness (P=0.05). All Stargardt disease patients with flecks confined to the macula and most of the patients with flecks extending outside of the macula had normal FST thresholds. All patients with extramacular atrophic changes had elevated FST cone thresholds and most had elevated FST rod thresholds. Conclusion FST rod and cone threshold elevation in Stargardt disease patients correlated well with measures of structure and function, as well as ophthalmoscopic retinal appearance. FST appears to be a useful tool for assessing rod and cone function in Stargardt disease. PMID:24695063

Acoustic Reflex Testing in Neonatal Hearing Screening and Subsequent Audiological Evaluation.

PubMed

Jacob-Corteletti, Lilian Cássia Bórnia; Araújo, Eliene Silva; Duarte, Josilene Luciene; Zucki, Fernanda; Alvarenga, Kátia de Freitas

2018-06-18

The aims of the study were to examine the acoustic reflex screening and threshold in healthy neonates and those at risk of hearing loss and to determine the effect of birth weight and gestational age on acoustic stapedial reflex (ASR). We assessed 18 healthy neonates (Group I) and 16 with at least 1 risk factor for hearing loss (Group II); all of them passed the transient evoked otoacoustic emission test that assessed neonatal hearing. The test battery included an acoustic reflex screening with activators of 0.5, 1, 2, and 4 kHz and broadband noise and an acoustic reflex threshold test with all of them, except for the broadband noise activator. In the evaluated neonates, the main risk factors were the gestational age at birth and a low birth weight; hence, these were further analyzed. The lower the gestational age at birth and birth weight, the less likely that an acoustic reflex would be elicited by pure-tone activators. This effect was significant at the frequencies of 0.5, 1, and 2 kHz for gestational age at birth and at the frequencies of 1 and 2 kHz for birth weight. When the broadband noise stimulus was used, a response was elicited in all neonates in both groups. When the pure-tone stimulus was used, the Group II showed the highest acoustic reflex thresholds and the highest percentage of cases with an absent ASR. The ASR threshold varied from 50 to 100 dB HL in both groups. Group II presented higher mean ASR thresholds than Group I, this difference being significant at frequencies of 1, 2, and 4 kHz. Birth weight and gestational age at birth were related to the elicitation of the acoustic reflex. Neonates with these risk factors for hearing impairment were less likely to exhibit the acoustic reflex and had higher thresholds.

Three Dimensional Constraint Effects on the Estimated (Delta)CTOD during the Numerical Simulation of Different Fatigue Threshold Testing Techniques

NASA Technical Reports Server (NTRS)

Seshadri, Banavara R.; Smith, Stephen W.

2007-01-01

Variation in constraint through the thickness of a specimen effects the cyclic crack-tip-opening displacement (DELTA CTOD). DELTA CTOD is a valuable measure of crack growth behavior, indicating closure development, constraint variations and load history effects. Fatigue loading with a continual load reduction was used to simulate the load history associated with fatigue crack growth threshold measurements. The constraint effect on the estimated DELTA CTOD is studied by carrying out three-dimensional elastic-plastic finite element simulations. The analysis involves numerical simulation of different standard fatigue threshold test schemes to determine how each test scheme affects DELTA CTOD. The American Society for Testing and Materials (ASTM) prescribes standard load reduction procedures for threshold testing using either the constant stress ratio (R) or constant maximum stress intensity (K(sub max)) methods. Different specimen types defined in the standard, namely the compact tension, C(T), and middle cracked tension, M(T), specimens were used in this simulation. The threshold simulations were conducted with different initial K(sub max) values to study its effect on estimated DELTA CTOD. During each simulation, the DELTA CTOD was estimated at every load increment during the load reduction procedure. Previous numerical simulation results indicate that the constant R load reduction method generates a plastic wake resulting in remote crack closure during unloading. Upon reloading, this remote contact location was observed to remain in contact well after the crack tip was fully open. The final region to open is located at the point at which the load reduction was initiated and at the free surface of the specimen. However, simulations carried out using the constant Kmax load reduction procedure did not indicate remote crack closure. Previous analysis results using various starting K(sub max) values and different load reduction rates have indicated DELTA CTOD is independent of specimen size. A study of the effect of specimen thickness and geometry on the measured DELTA CTOD for various load reduction procedures and its implication in the estimation of fatigue crack growth threshold values is discussed.

Frequency-tuning characteristics of cervical and ocular vestibular evoked myogenic potentials induced by air-conducted tone bursts.

PubMed

Park, Hong Ju; Lee, In-Sik; Shin, Jung Eun; Lee, Yeo Jin; Park, Mun Su

2010-01-01

To better characterize both ocular and cervical vestibular evoked myogenic potentials (VEMP) responses at different frequencies of sound in 20 normal subjects. Cervical and ocular VEMPs were recorded. The intensities of sound stimulation decreased from the maximal intensity, until no responses were evoked. Thresholds, amplitudes, latencies and interaural amplitude difference ratio (IADR) at the maximal stimulation were calculated. Both tests showed the similar frequency tuning, with the lowest threshold and highest amplitude for 500-Hz tone-burst stimuli. Sound stimulation at 500Hz showed the response rates of 100% in both tests. Cervical VEMPs showed higher incidence than ocular VEMPs. Ocular VEMP thresholds were significantly higher than those of cervical VEMP. Cervical VEMP amplitudes were significantly higher than ocular VEMP amplitudes. IADRs of ocular and cervical VEMPs did not differ significantly. Ocular VEMP showed the similar frequency tuning to cervical VEMP. Cervical VEMP responses showed higher incidence, lower thresholds and larger amplitudes than ocular VEMP. Cervical VEMP is a more reliable measure than ocular VEMP, though the results of both tests will be complementary. Five hundred Hertz is the optimal frequency to use. Copyright 2009 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Effects of spectral smearing on performance of the spectral ripple and spectro-temporal ripple tests.

PubMed

Narne, Vijaya Kumar; Sharma, Mridula; Van Dun, Bram; Bansal, Shalini; Prabhu, Latika; Moore, Brian C J

2016-12-01

The main aim of this study was to use spectral smearing to evaluate the efficacy of a spectral ripple test (SRt) using stationary sounds and a recent variant with gliding ripples called the spectro-temporal ripple test (STRt) in measuring reduced spectral resolution. In experiment 1 the highest detectable ripple density was measured using four amounts of spectral smearing (unsmeared, mild, moderate, and severe). The thresholds worsened with increasing smearing and were similar for the SRt and the STRt across the three conditions with smearing. For unsmeared stimuli, thresholds were significantly higher (better) for the STRt than for the SRt. An amplitude fluctuation at the outputs of simulated (gammatone) auditory filters centered above 6400 Hz was identified as providing a potential detection cue for the STRt stimuli. Experiment 2 used notched noise with energy below and above the passband of the SRt and STRt stimuli to reduce confounding cues in the STRt. Thresholds were almost identical for the STRt and SRt for both unsmeared and smeared stimuli, indicating that the confounding cue for the STRt was eliminated by the notched noise. Thresholds obtained with notched noise present could be predicted reasonably accurately using an excitation-pattern model.

Inquiring Ears Want to Know: A Fact Sheet about Your Hearing Test

MedlinePlus

... track changes in hearing over time • Your hearing threshold levels (the quietest sounds you can hear) are ... Do I have normal hearing? Compare your hearing threshold levels to this scale: -10 – 25 dB 26 – ...

Impact of early developmental fluoride exposure on the peripheral pain sensitivity in mice.

PubMed

Ma, Jing; Liu, Fei; Liu, Peng; Dong, Ying-Ying; Chu, Zheng; Hou, Tie-Zhou; Dang, Yong-Hui

2015-12-01

Consumption of high concentration of fluoride in the drinking water would cause the fluorosis and chronic pain. Similar pain syndrome appeared in the patients in fluoride therapy of osteoporotic. The aim of the current study was to examine whether exposing immature mice to fluoride would modify the peripheral pain sensitivity or even cause a pain syndrome. We gave developmental fluoride exposure to mice in different concentration (0mg/L, 50mg/L and 100mg/L) and evaluated their basal pain threshold. Von Frey hair test, hot plate test and formalin test were conducted to examine the mechanical, thermal nociceptive threshold and inflammatory pain, respectively. In addition, the expression of hippocampal brain-derived neurotrophic factor (BDNF) was also evaluated by Western blotting. Hyperalgesia in fluoride exposure mice was exhibited in the Von Frey hair test, hot plate test and formalin test. Meanwhile, the expression of BDNF was significantly higher than that of control group. The results suggest that early developmental fluoride exposure may lower the basal pain threshold and be associated with the increasing of BDNF expression in hippocampus. Copyright © 2015 Elsevier Ltd. All rights reserved.

[Characteristics, advantages, and limits of matrix tests].

PubMed

Brand, T; Wagener, K C

2017-03-01

Deterioration of communication abilities due to hearing problems is particularly relevant in listening situations with noise. Therefore, speech intelligibility tests in noise are required for audiological diagnostics and evaluation of hearing rehabilitation. This study analyzed the characteristics of matrix tests assessing the 50 % speech recognition threshold in noise. What are their advantages and limitations? Matrix tests are based on a matrix of 50 words (10 five-word sentences with same grammatical structure). In the standard setting, 20 sentences are presented using an adaptive procedure estimating the individual 50 % speech recognition threshold in noise. At present, matrix tests in 17 different languages are available. A high international comparability of matrix tests exists. The German language matrix test (OLSA, male speaker) has a reference 50 % speech recognition threshold of -7.1 (± 1.1) dB SNR. Before using a matrix test for the first time, the test person has to become familiar with the basic speech material using two training lists. Hereafter, matrix tests produce constant results even if repeated many times. Matrix tests are suitable for users of hearing aids and cochlear implants, particularly for assessment of benefit during the fitting process. Matrix tests can be performed in closed form and consequently with non-native listeners, even if the experimenter does not speak the test person's native language. Short versions of matrix tests are available for listeners with a shorter memory span, e.g., children.

Sugar Detection Threshold After Laparoscopic Sleeve Gastrectomy in Adolescents.

PubMed

Abdeen, Ghalia N; Miras, Alexander D; Alqhatani, Aayed R; le Roux, Carel W

2018-05-01

Obesity in young people is one of the most serious public health problems worldwide. Moreover, the mechanisms preventing obese adolescents from losing and maintaining weight loss have been elusive. Laparoscopic sleeve gastrectomy (LSG) is successful at achieving long-term weight loss in patients across all age groups, including children and adolescents. Anecdotal clinical observation as well as evidence in rodents suggests that LSG induces a shift in preference of sugary foods. However, it is not known whether this shift is due to a change in the threshold for gustatory detection of sucrose, or whether LSG induces behavioral change without affecting the gustatory threshold for sugar. The objective of this study was to determine whether adolescents who undergo LSG experience a change in their threshold for detecting sweet taste. We studied the sucrose detection threshold of 14 obese adolescents (age 15.3 ± 0.5 years, range 12-18) who underwent LSG 2 weeks before surgery and at 12 and 52 weeks after surgery. Matched non-surgical subjects were tested on two occasions 12 weeks apart to control for potential learning of the test that may have confounded the results. Seven sucrose concentrations were used and were tested in eight blocks with each block consisting of a random seven sucrose and seven water stimuli. The subjects were asked to report whether the sample contained water or not after they tasted 15 ml of the fluid for 10 s. The bodyweight of the LSG group decreased from 136.7 ± 5.4 to 109.6 ± 5.1 and 86.5 ± 4.0 kg after 12 and 52 weeks, respectively (p < 0.001). There was no significant difference after surgery in taste detection threshold of patients after LSG (p = 0.60), and no difference was observed comparing the taste detection threshold of the LSG group with the non-surgical controls (p = 0.38). LSG did not affect the taste detection threshold for sucrose, suggesting that the shift in preference for sugary foods may be due to factors other than fundamental changes in taste sensitivity.

Chronic Widespread Back Pain is Distinct From Chronic Local Back Pain: Evidence From Quantitative Sensory Testing, Pain Drawings, and Psychometrics.

PubMed

Gerhardt, Andreas; Eich, Wolfgang; Janke, Susanne; Leisner, Sabine; Treede, Rolf-Detlef; Tesarz, Jonas

2016-07-01

Whether chronic localized pain (CLP) and chronic widespread pain (CWP) have different mechanisms or to what extent they overlap in their pathophysiology is controversial. The study compared quantitative sensory testing profiles of nonspecific chronic back pain patients with CLP (n=48) and CWP (n=29) with and fibromyalgia syndrome (FMS) patients (n=90) and pain-free controls (n = 40). The quantitative sensory testing protocol of the "German-Research-Network-on-Neuropathic-Pain" was used to measure evoked pain on the painful area in the lower back and the pain-free hand (thermal and mechanical detection and pain thresholds, vibration threshold, pain sensitivity to sharp and blunt mechanical stimuli). Ongoing pain and psychometrics were captured with pain drawings and questionnaires. CLP patients did not differ from pain-free controls, except for lower pressure pain threshold (PPT) on the back. CWP and FMS patients showed lower heat pain threshold and higher wind-up ratio on the back and lower heat pain threshold and cold pain threshold on the hand. FMS showed lower PPT on back and hand, and higher comorbidity of anxiety and depression and more functional impairment than all other groups. Even after long duration CLP presents with a local hypersensitivity for PPT, suggesting a somatotopically specific sensitization of nociceptive processing. However, CWP patients show widespread ongoing pain and hyperalgesia for different stimuli that is generalized in space, suggesting the involvement of descending control systems, as also suggested for FMS patients. Because mechanisms in nonspecific chronic back pain with CLP and CWP differ, these patients should be distinguished in future research and allocated to different treatments.

Threshold dose for behavioral discrimination of cigarette nicotine content in menthol vs. non-menthol smokers.

PubMed

Perkins, Kenneth A; Kunkle, Nicole; Karelitz, Joshua L

2017-04-01

The lowest threshold content (or "dose") of nicotine discriminated in cigarettes may differ due to menthol preference. Menthol and non-menthol Spectrum research cigarettes differing in nicotine content were used to determine discrimination thresholds. Dependent smokers preferring menthol (n = 40) or non-menthol (n = 21) brands were tested on ability to discriminate cigarettes (matched for their menthol preference) with nicotine contents of 16-17, 11-12, 5, 2, and 1 mg/g, one per session, from an "ultra-low" cigarette with 0.4 mg/g. Controlled exposure to each cigarette was four puffs/trial, and the number of sessions was determined by the lowest nicotine content they could discriminate on >80% of trials (i.e., ≥5 of 6). We also assessed subjective perceptions and behavioral choice between cigarettes to relate them to discrimination responses. Controlling for Fagerstrom Test of Nicotine Dependence score, discrimination thresholds were more likely to be at higher nicotine content cigarettes for menthol vs. non-menthol smokers (p < .005), with medians of 16 vs. 11 mg/g, respectively. Compared to the ultra-low, threshold and subthreshold (next lowest) cigarettes differed on most perceptions and puff choice, but menthol preference did not alter these associations. Notably, threshold cigarettes did, but subthreshold did not, increase choice over the ultra-low. Threshold for discriminating nicotine via smoking may be generally higher for menthol vs. non-menthol smokers. More research is needed to identify why menthol smoking is related to higher nicotine thresholds and to verify that cigarettes unable to be discriminated do not support reinforcement.

Influence of fatiguing noise on auditory evoked responses to stimuli of various levels in a beluga whale, Delphinapterus leucas.

PubMed

Popov, Vladimir V; Sysueva, Evgeniya V; Nechaev, Dmitry I; Rozhnov, Viatcheslav V; Supin, Alexander Ya

2017-03-15

The negative impact of man-made noise on the hearing of odontocetes has attracted considerable recent attention. In the majority of studies, permanent or temporary reductions in sensitivity, known as permanent or temporary threshold shift (PTS or TTS, respectively), have been investigated. In the present study, the effects of a fatiguing sound on the hearing of a beluga whale, Delphinapterus leucas , within a wide range of levels of test signals was investigated. The fatiguing noise was half-octave band-limited noise centered at 32 kHz. Post-exposure effects of this noise on the evoked responses to test stimuli (rhythmic pip trains with a 45-kHz center frequency) at various levels (from threshold to 60 dB above threshold) were measured. For baseline (pre-exposure) responses, the magnitude-versus-level function featured a segment of steep magnitude dependence on level (up to 30 dB above threshold) that was followed by a plateau segment that featured little dependence on level (30 to 55 dB above threshold). Post-exposure, the function shifted upward along the level scale. The shift was 23 dB at the threshold and up to 33 dB at the supra-threshold level. Owing to the plateau in the magnitude-versus-level function, post-exposure suppression of responses depended on the stimulus level such that higher levels corresponded to less suppression. The experimental data may be modeled based on the compressive non-linearity of the cochlea. According to the model, post-exposure responses of the cochlea to high-level stimuli are minimally suppressed compared with the pre-exposure responses, despite a substantially increased threshold. © 2017. Published by The Company of Biologists Ltd.

Global Motion Perception in 2-Year-Old Children: A Method for Psychophysical Assessment and Relationships With Clinical Measures of Visual Function

PubMed Central

Yu, Tzu-Ying; Jacobs, Robert J.; Anstice, Nicola S.; Paudel, Nabin; Harding, Jane E.; Thompson, Benjamin

2013-01-01

Purpose. We developed and validated a technique for measuring global motion perception in 2-year-old children, and assessed the relationship between global motion perception and other measures of visual function. Methods. Random dot kinematogram (RDK) stimuli were used to measure motion coherence thresholds in 366 children at risk of neurodevelopmental problems at 24 ± 1 months of age. RDKs of variable coherence were presented and eye movements were analyzed offline to grade the direction of the optokinetic reflex (OKR) for each trial. Motion coherence thresholds were calculated by fitting psychometric functions to the resulting datasets. Test–retest reliability was assessed in 15 children, and motion coherence thresholds were measured in a group of 10 adults using OKR and behavioral responses. Standard age-appropriate optometric tests also were performed. Results. Motion coherence thresholds were measured successfully in 336 (91.8%) children using the OKR technique, but only 31 (8.5%) using behavioral responses. The mean threshold was 41.7 ± 13.5% for 2-year-old children and 3.3 ± 1.2% for adults. Within-assessor reliability and test–retest reliability were high in children. Children's motion coherence thresholds were significantly correlated with stereoacuity (LANG I & II test, ρ = 0.29, P < 0.001; Frisby, ρ = 0.17, P = 0.022), but not with binocular visual acuity (ρ = 0.11, P = 0.07). In adults OKR and behavioral motion coherence thresholds were highly correlated (intraclass correlation = 0.81, P = 0.001). Conclusions. Global motion perception can be measured in 2-year-old children using the OKR. This technique is reliable and data from adults suggest that motion coherence thresholds based on the OKR are related to motion perception. Global motion perception was related to stereoacuity in children. PMID:24282224

Perspectives on the Pure-Tone Audiogram.

PubMed

Musiek, Frank E; Shinn, Jennifer; Chermak, Gail D; Bamiou, Doris-Eva

The pure-tone audiogram, though fundamental to audiology, presents limitations, especially in the case of central auditory involvement. Advances in auditory neuroscience underscore the considerably larger role of the central auditory nervous system (CANS) in hearing and related disorders. Given the availability of behavioral audiological tests and electrophysiological procedures that can provide better insights as to the function of the various components of the auditory system, this perspective piece reviews the limitations of the pure-tone audiogram and notes some of the advantages of other tests and procedures used in tandem with the pure-tone threshold measurement. To review and synthesize the literature regarding the utility and limitations of the pure-tone audiogram in determining dysfunction of peripheral sensory and neural systems, as well as the CANS, and to identify other tests and procedures that can supplement pure-tone thresholds and provide enhanced diagnostic insight, especially regarding problems of the central auditory system. A systematic review and synthesis of the literature. The authors independently searched and reviewed literature (journal articles, book chapters) pertaining to the limitations of the pure-tone audiogram. The pure-tone audiogram provides information as to hearing sensitivity across a selected frequency range. Normal or near-normal pure-tone thresholds sometimes are observed despite cochlear damage. There are a surprising number of patients with acoustic neuromas who have essentially normal pure-tone thresholds. In cases of central deafness, depressed pure-tone thresholds may not accurately reflect the status of the peripheral auditory system. Listening difficulties are seen in the presence of normal pure-tone thresholds. Suprathreshold procedures and a variety of other tests can provide information regarding other and often more central functions of the auditory system. The audiogram is a primary tool for determining type, degree, and configuration of hearing loss; however, it provides the clinician with information regarding only hearing sensitivity, and no information about central auditory processing or the auditory processing of real-world signals (i.e., speech, music). The pure-tone audiogram offers limited insight into functional hearing and should be viewed only as a test of hearing sensitivity. Given the limitations of the pure-tone audiogram, a brief overview is provided of available behavioral tests and electrophysiological procedures that are sensitive to the function and integrity of the central auditory system, which provide better diagnostic and rehabilitative information to the clinician and patient. American Academy of Audiology

Neohesperidin dihydrochalcone is not a taste enhancer in aqueous sucrose solutions.

PubMed

Kroeze, J H

2000-10-01

Neohesperidin dihydrochalcone (NHDC) is an intensive sweetener, obtained by alkaline hydrogenation of neohesperidin. In this investigation a supposed taste enhancing effect of this substance was tested. A three-step procedure was used. In the first experiment, using a pool of 31 subjects, NHDC and sucrose detection thresholds were measured. In the second experiment, psychophysical functions for both tastants were determined. Then, 15 participants closest to the group threshold who, in addition, had produced monotonic psychophysical taste functions were selected to participate in the next two experiments. In the third experiment, taste enhancement was tested. Three psychophysical sucrose functions were constructed, one with a near-threshold amount of NHDC added to each of seven sucrose concentrations, one with a near-threshold amount of sucrose added (control 1) and one without any addition (control 2). No difference was found between the NHDC-enriched sucrose function and the sucrose-enriched sucrose function. Finally, in experiment 4, differential threshold functions were constructed with either NHDC or sucrose added. Neither the overall shape of the functions nor a comparison of the points of subjective equality showed enhancement. It was concluded that weak NHDC does not enhance the taste of aqueous sucrose solutions.

Underwater temporary threshold shift induced by octave-band noise in three species of pinniped.

PubMed

Kastak, D; Schusterman, R J; Southall, B L; Reichmuth, C J

1999-08-01

Pure-tone sound detection thresholds were obtained in water for one harbor seal (Phoca vitulina), two California sea lions (Zalophus californianus), and one northern elephant seal (Mirounga angustirostris) before and immediately following exposure to octave-band noise. Additional thresholds were obtained following a 24-h recovery period. Test frequencies ranged from 100 Hz to 2000 Hz and octave-band exposure levels were approximately 60-75 dB SL (sensation level at center frequency). Each subject was trained to dive into a noise field and remain stationed underwater during a noise-exposure period that lasted a total of 20-22 min. Following exposure, three of the subjects showed threshold shifts averaging 4.8 dB (Phoca), 4.9 dB (Zalophus), and 4.6 dB (Mirounga). Recovery to baseline threshold levels was observed in test sessions conducted within 24 h of noise exposure. Control sessions in which the subjects completed a simulated noise exposure produced shifts that were significantly smaller than those observed following noise exposure. These results indicate that noise of moderate intensity and duration is sufficient to induce TTS under water in these pinniped species.

Effect of gap detection threshold on consistency of speech in children with speech sound disorder.

PubMed

Sayyahi, Fateme; Soleymani, Zahra; Akbari, Mohammad; Bijankhan, Mahmood; Dolatshahi, Behrooz

2017-02-01

The present study examined the relationship between gap detection threshold and speech error consistency in children with speech sound disorder. The participants were children five to six years of age who were categorized into three groups of typical speech, consistent speech disorder (CSD) and inconsistent speech disorder (ISD).The phonetic gap detection threshold test was used for this study, which is a valid test comprised six syllables with inter-stimulus intervals between 20-300ms. The participants were asked to listen to the recorded stimuli three times and indicate whether they heard one or two sounds. There was no significant difference between the typical and CSD groups (p=0.55), but there were significant differences in performance between the ISD and CSD groups and the ISD and typical groups (p=0.00). The ISD group discriminated between speech sounds at a higher threshold. Children with inconsistent speech errors could not distinguish speech sounds during time-limited phonetic discrimination. It is suggested that inconsistency in speech is a representation of inconsistency in auditory perception, which causes by high gap detection threshold. Copyright © 2016 Elsevier Ltd. All rights reserved.

Optical damage performance of conductive widegap semiconductors: spatial, temporal, and lifetime modeling

DOE PAGES

Elhadj, Selim; Yoo, Jae-hyuck; Negres, Raluca A.; ...

2016-12-19

The optical damage performance of electrically conductive gallium nitride (GaN) and indium tin oxide (ITO) films is addressed using large area, high power laser beam exposures at 1064 nm sub-bandgap wavelength. Analysis of the laser damage process assumes that onset of damage (threshold) is determined by the absorption and heating of a nanoscale region of a characteristic size reaching a critical temperature. We use this model to rationalize semi-quantitatively the pulse width scaling of the damage threshold from picosecond to nanosecond timescales, along with the pulse width dependence of the damage threshold probability derived by fitting large beam damage densitymore » data. Multi-shot exposures were used to address lifetime performance degradation described by an empirical expression based on the single exposure damage model. A damage threshold degradation of at least 50% was observed for both materials. Overall, the GaN films tested had 5-10 × higher optical damage thresholds than the ITO films tested for comparable transmission and electrical conductivity. This route to optically robust, large aperture transparent electrodes and power optoelectronics may thus involve use of next generation widegap semiconductors such as GaN.« less

Validity and reliability of in-situ air conduction thresholds measured through hearing aids coupled to closed and open instant-fit tips.

PubMed

O'Brien, Anna; Keidser, Gitte; Yeend, Ingrid; Hartley, Lisa; Dillon, Harvey

2010-12-01

Audiometric measurements through a hearing aid ('in-situ') may facilitate provision of hearing services where these are limited. This study investigated the validity and reliability of in-situ air conduction hearing thresholds measured with closed and open domes relative to thresholds measured with insert earphones, and explored sources of variability in the measures. Twenty-four adults with sensorineural hearing impairment attended two sessions in which thresholds and real-ear-to-dial-difference (REDD) values were measured. Without correction, significantly higher low-frequency thresholds in dB HL were measured in-situ than with insert earphones. Differences were due predominantly to differences in ear canal SPL, as measured with the REDD, which were attributed to leaking low-frequency energy. Test-retest data yielded higher variability with the closed dome coupling due to inconsistent seals achieved with this tip. For all three conditions, inter-participant variability in the REDD values was greater than intra-participant variability. Overall, in-situ audiometry is as valid and reliable as conventional audiometry provided appropriate REDD corrections are made and ambient sound in the test environment is controlled.

The (in)famous GWAS P-value threshold revisited and updated for low-frequency variants.

PubMed

Fadista, João; Manning, Alisa K; Florez, Jose C; Groop, Leif

2016-08-01

Genome-wide association studies (GWAS) have long relied on proposed statistical significance thresholds to be able to differentiate true positives from false positives. Although the genome-wide significance P-value threshold of 5 × 10(-8) has become a standard for common-variant GWAS, it has not been updated to cope with the lower allele frequency spectrum used in many recent array-based GWAS studies and sequencing studies. Using a whole-genome- and -exome-sequencing data set of 2875 individuals of European ancestry from the Genetics of Type 2 Diabetes (GoT2D) project and a whole-exome-sequencing data set of 13 000 individuals from five ancestries from the GoT2D and T2D-GENES (Type 2 Diabetes Genetic Exploration by Next-generation sequencing in multi-Ethnic Samples) projects, we describe guidelines for genome- and exome-wide association P-value thresholds needed to correct for multiple testing, explaining the impact of linkage disequilibrium thresholds for distinguishing independent variants, minor allele frequency and ancestry characteristics. We emphasize the advantage of studying recent genetic isolate populations when performing rare and low-frequency genetic association analyses, as the multiple testing burden is diminished due to higher genetic homogeneity.

Deriving freshwater safety thresholds for hexabromocyclododecane and comparison of toxicity of brominated flame retardants.

PubMed

Dong, Liang; Zheng, Lei; Yang, Suwen; Yan, Zhenguang; Jin, Weidong; Yan, Yuhong

2017-05-01

Hexabromocyclododecane (HBCD) is a brominated flame retardant used throughout the world. It has been detected in various environmental media and has been shown toxic to aquatic life. The toxic effects of HBCD to aquatic organisms in Chinese freshwater ecosystems are discussed here. Experiments were conducted with nine types of acute toxicity testing and three types of chronic toxicity testing. After comparing a range of species sensitivity distribution models, the optimal model of Bull III was used to derive the safety thresholds for HBCD. The acute safety threshold and the chronic safety threshold of HBCD for Chinese freshwater organisms were found to be 2.32mg/L and 0.128mg/L, respectively. Both values were verified by the methods of the Netherlands and the United States. HBCD was found to be less toxic compared to other widely used brominated flame retardants. The present results provide valuable information for revision of the water quality standard of HBCD in China. Copyright © 2017 Elsevier Inc. All rights reserved.

What Temperature of Coffee Exceeds the Pain Threshold? Pilot Study of a Sensory Analysis Method as Basis for Cancer Risk Assessment.

PubMed

Dirler, Julia; Winkler, Gertrud; Lachenmeier, Dirk W

2018-06-01

The International Agency for Research on Cancer (IARC) evaluates "very hot (>65 °C) beverages" as probably carcinogenic to humans. However, there is a lack of research regarding what temperatures consumers actually perceive as "very hot" or as "too hot". A method for sensory analysis of such threshold temperatures was developed. The participants were asked to mix a very hot coffee step by step into a cooler coffee. Because of that, the coffee to be tasted was incrementally increased in temperature during the test. The participants took a sip at every addition, until they perceive the beverage as too hot for consumption. The protocol was evaluated in the form of a pilot study using 87 participants. Interestingly, the average pain threshold of the test group (67 °C) and the preferred drinking temperature (63 °C) iterated around the IARC threshold for carcinogenicity. The developed methodology was found as fit for the purpose and may be applied in larger studies.

Lactate Accumulation for Runners and Non-Runners during Various Exercise Tests,

DTIC Science & Technology

1980-08-21

individual reaches a point at which lactate begins to increase exponentially in the blood. Anaerobic threshold (AT) and lactate turning point (LTP) are terms...Workloads were assigned based upon a previous assessment of the subject’s anaerobic threshold , however, there was no indication of the individual’s...Vodak, 3.H. Wilmore, J. Vodak and P Kurtz. Anaerobic threshold and maximal aerobic power for three modes of exercise. J. Appl. Physiol. 41(4):544-550

Weight bearing of the limb as a confounding factor in assessment of mechanical allodynia in the rat.

PubMed

Kauppila, T; Kontinen, V K; Pertovaara, A

1998-01-01

Effect of weight bearing of the hindlimbs on the assessment of mechanically-induced hindlimb withdrawal threshold was determined in intact rats and in rats with various pathophysiological conditions causing allodynia or hyperalgesia. Hindlimb withdrawal was elicited by applying a series of calibrated monofilaments to the plantar or the dorsal surface of the paw. During testing the rat was either in a restraint tube with hindlimbs hanging semi-extended without weight bearing or it was standing on a metal grid (bearing its own weight). In intact rats, the withdrawal thresholds were significantly lower when the stimulus site was the dorsal hairy skin rather than the plantar glabrous skin. Also, thresholds were significantly lower when the hindlimbs were not bearing weight. Following carrageenan-induced unilateral inflammation of the plantar paw or a tibial nerve cut there was a marked threshold decrease to test stimuli applied to plantar or dorsal paw, respectively, ipsilateral to the pathological condition in standing rats. However, when the hindlimbs were not weight bearing the unilateral threshold decrease was markedly attenuated (carrageenan-treated rats) or completely abolished (tibial cut). In contrast, in rats with a unilateral spinal nerve ligation the threshold decrease ipsilateral to the nerve lesion was highly significant independent of the weight bearing of the hindlimbs. The results indicate that weight bearing of hindlimbs is an important confounding factor in the assessment of tactile allodynia in rats.

Acoustic reflex on newborns: the influence of the 226 and 1,000 Hz probes.

PubMed

Jacob-Corteletti, Lilian Cássia Bórnia; Duarte, Josilene Luciene; Zucki, Fernanda; Mariotto, Luciane Domingues Figueiredo; Lauris, José Roberto Pereira; Alvarenga, Kátia de Freitas

2015-01-01

To analyze the occurrence of acoustic reflex and its threshold on newborns using the 226 and 1,000 Hz probes. Thirty-six newborns with "PASS" results in newborn hearing screening and tympanogram with one or two peaks for both probe tones were included. Group I comprised 20 full-term newborns without risk indicator for hearing loss, and Group II comprised 16 newborns with at least one risk indicator. The study about ipsilateral acoustic reflex thresholds was conducted in 500, 1,000, 2,000, and 4,000 Hz. The groups presented the acoustic reflex thresholds between 50 and 100 dB for both probe tones. In the comparison between the probes, there were differences in all frequencies evaluated in Group I, with the lowest threshold mean for the 1,000 Hz probe. In Group II, differences were detected at 2,000 Hz. The mean acoustic reflex thresholds were similar in both groups for the 226 Hz probe. There was a difference for the 1,000 Hz probe in all tested frequencies. The percentage of response was higher in both groups for the 1,000 Hz probe. The kappa test showed extremely poor agreement in the comparison of results between both probes. The occurrence of acoustic reflex was higher in newborns and its thresholds were lower with the 1,000 Hz probe both for healthy newborns and for newborns at risk.

Characteristics of grouping colors for figure segregation on a multicolored background.

PubMed

Nagai, Takehiro; Uchikawa, Keiji

2008-11-01

A figure is segregated from its background when the colored elements belonging to the figure are grouped together. We investigated the range of color distribution conditions in which a figure could be segregated from its background using the color distribution differences. The stimulus was a multicolored texture composed of randomly shaped pieces. It was divided into two regions: a test region and a background region. The pieces in these two regions had different color distributions in the OSA Uniform Color Space. In our experiments, the subject segregated the figure of the test region using two different procedures. Since the Euclidean distance in the OSA Uniform Color Space corresponds to perceived color difference, if segregation thresholds are determined by only color difference, the thresholds should be independent of position and direction in the color space. In the results, however, the thresholds did depend on position and direction in the OSA Uniform Color Space. This suggests that color difference is not the only factor in figure segregation by color. Moreover, the threshold dependence on position and direction is influenced by the distances in the cone-opponent space whose axes are normalized by discrimination thresholds, suggesting that figure segregation threshold is determined by similar factors in the cone-opponent space for color discrimination. The analysis of the results by categorical color naming suggests that categorical color perception may affect figure segregation only slightly.

Threshold magnitudes for a multichannel correlation detector in background seismicity

DOE PAGES

Carmichael, Joshua D.; Hartse, Hans

2016-04-01

Colocated explosive sources often produce correlated seismic waveforms. Multichannel correlation detectors identify these signals by scanning template waveforms recorded from known reference events against "target" data to find similar waveforms. This screening problem is challenged at thresholds required to monitor smaller explosions, often because non-target signals falsely trigger such detectors. Therefore, it is generally unclear what thresholds will reliably identify a target explosion while screening non-target background seismicity. Here, we estimate threshold magnitudes for hypothetical explosions located at the North Korean nuclear test site over six months of 2010, by processing International Monitoring System (IMS) array data with a multichannelmore » waveform correlation detector. Our method (1) accounts for low amplitude background seismicity that falsely triggers correlation detectors but is unidentifiable with conventional power beams, (2) adapts to diurnally variable noise levels and (3) uses source-receiver reciprocity concepts to estimate thresholds for explosions spatially separated from the template source. Furthermore, we find that underground explosions with body wave magnitudes m b = 1.66 are detectable at the IMS array USRK with probability 0.99, when using template waveforms consisting only of P -waves, without false alarms. We conservatively find that these thresholds also increase by up to a magnitude unit for sources located 4 km or more from the Feb.12, 2013 announced nuclear test.« less

Lubiprostone does not influence visceral pain thresholds in patients with irritable bowel syndrome.

PubMed

Whitehead, W E; Palsson, O S; Gangarosa, L; Turner, M; Tucker, J

2011-10-01

In clinical trials, lubiprostone reduced the severity of abdominal pain. The primary aim was to determine whether lubiprostone raises the threshold for abdominal pain induced by intraluminal balloon distention. A secondary aim was to determine whether changes in pain sensitivity influence clinical pain independently of changes in transit time. Sixty-two patients with irritable bowel syndrome with constipation (IBS-C) participated in an 8-week cross-over study. All subjects completed a 14-day baseline ending with a barostat test of pain and urge sensory thresholds. Half, randomly selected, then received 48 μg day(-1) of lubiprostone for 14 days ending with a pain sensitivity test and a Sitzmark test of transit time. This was followed by a 14-day washout and then a crossover to 14 days of placebo with tests of pain sensitivity and transit time. The other half of the subjects received placebo before lubiprostone. All kept symptom diaries. Stools were significantly softer when taking lubiprostone compared to placebo (Bristol Stool scores 4.20 vs 3.44, P < 0.001). However, thresholds for pain (17.36 vs 17.83 mmHg, lubiprostone vs placebo) and urgency to defecate (14.14 vs 14.53 mmHg) were not affected by lubiprostone. Transit time was not significantly different between lubiprostone and placebo (51.27 vs 51.81 h), and neither pain sensitivity nor transit time was a significant predictor of clinical pain. Lubiprostone has no effect on visceral sensory thresholds. The reductions in clinical pain that occur while taking lubiprostone appear to be secondary to changes in stool consistency. © 2011 Blackwell Publishing Ltd.

In vivo measurements of maximal occlusal force and minimal pressure threshold on overdentures supported by implants or natural roots: a comparative study, Part 1.

PubMed

Mericske-Stern, R; Hofmann, J; Wedig, A; Geering, A H

1993-01-01

Numerous investigations give evidence of improvement of masticatory performance when edentulous patients have had implants placed. A comparative study was carried out to investigate the oral function and tactile sensibility of patients restored with implant-supported overdentures. Twenty-six patients with ITI implants and 18 patients with natural-tooth roots were selected. The minimal pressure threshold perceived in vertical and horizontal directions was registered with dynamometers. Maximal occlusal force was recorded with a miniature bite recorder placed between each pair of antagonistic teeth on both jaw sides separately. All measurements were repeated three times and the average was calculated. The records of minimal perceived pressure revealed a significantly higher threshold (factor 100) for the implant group. In both test groups, values registered in the vertical direction were slightly increased. A tendency for test subjects with implants to reach higher maximal occlusal force was observed, but not at a statistically significant level. In both test groups, the average maximum was found on the second premolar. The minimal pressure threshold seems to depend on the presence of receptors in the periodontal ligament. The records of maximal occlusal force, which were similar in both test groups, lead to the assumption that the limitation in maximal occlusal capacity of overdenture wearers is multifactorial and does not depend on the presence of a periodontal ligament.

Telephone screening tests for functionally impaired hearing: current use in seven countries and development of a US version.

PubMed

Watson, Charles S; Kidd, Gary R; Miller, James D; Smits, Cas; Humes, Larry E

2012-01-01

An estimated 36 million US citizens have impaired hearing, but nearly half of them have never had a hearing test. As noted by a recent National Institutes of Health/National Institute on Deafness and Other Communication Disorders (NIH/NIDCD) Working Group, "In the United States (in contrast to many other nations) there are no readily accessible low cost hearing screening programs…" (Donahue et al, 2010, p. 2). Since 2004, telephone administered screening tests utilizing three-digit sequences presented in noise have been developed, validated, and implemented in seven countries. Each of these tests has been based on a test protocol conceived by Smits and colleagues in The Netherlands. Investigators from Communication Disorders Technology, Inc., Indiana University, and VU University Medical Center of Amsterdam agreed to collaborate in the development and validation of a screening test for hearing impairment suitable for delivery over the telephone, for use in the United States. This test, utilizing spoken three-digit sequences (triplets), was to be based on the design of Smits and his colleagues. A version of the digits-in-noise test was developed utilizing digit triplets spoken in Middle American dialect. The stimuli were individually adjusted to speech-to-noise ratio (SNR) values yielding 50% correct identification, on the basis of data collected from a group of 10 young adult listeners with normal hearing. A final set of 64 homogeneous stimuli were selected from an original 160 recorded triplets. Each test consisted of a series of 40 triplets drawn at random, presented in a noise background. The SNR threshold for 50% correct identification of the triplets was determined by a one-down, one-up adaptive procedure. The test was implemented by telephone, and administered to listeners with varying levels of hearing impairment. The listeners were then evaluated with pure-tone tests and other audiometric measures as clinically appropriate. Ninety participants included 72 who were volunteers from the regular client population at the Indiana University Hearing Clinic, and 18 who were recruited with a newspaper ad offering a free hearing test. Of the 90 participants, 49 were later determined to have mean pure-tone thresholds greater than 20 dB hearing level (HL). The primary data analyses were correlations between telephone test thresholds and other measures, including pure-tone thresholds and speech recognition tests, collected for the same participants. The correlation between the telephone test and pure-tone thresholds (r = 0.74) was within the range of correlations observed with successful telephone screening tests in use in other countries. Thresholds based on the average of only 21 trials (trials five through 25 of the 40-trial tracking history) yielded sensitivity and specificity values of 0.80 and 0.83, respectively, using pure-tone average((0.5, 1.0, 2.0 kHz)) >20 dB HL as the criterion measure. This US version of the digits-in-noise telephone screening test is sufficiently valid to be implemented for use by the general public. Its properties are quite similar to those telephone screening tests currently in use in most European countries. Telephone tests provide efficient, easy to use, and valid screening for functional hearing impairment. The results of this test are a reasonable basis for advising those who fail to seek a comprehensive hearing evaluation by an audiologist. American Academy of Audiology.

Differences in taste detection thresholds between normal-weight and obese young adults.

PubMed

Park, Dong Choon; Yeo, Joon Hyung; Ryu, In Yong; Kim, Sang Hoon; Jung, Junyang; Yeo, Seung Geun

2015-05-01

Compared with normal-weight individuals, obese young adults exhibited a significantly higher taste threshold for salty taste. Smoking also affected taste functions in this population. The aim of this study was to investigate the differences in taste detection thresholds between normal-weight and obese young adults. Taste threshold was measured using electrogustometry (EGM) and chemically with sucrose, NaCl, citric acid, and quinine hydrochloride in 41 volunteers in their twenties, 23 with body mass index (BMI) <23 kg/m(2) (normal-weight group) and 18 with BMI >25 kg/m(2) (obese group). BMI was significantly higher in the obese than in the normal-weight group (p < 0.05). The obese group exhibited significantly higher EGM thresholds than the normal-weight group on the right (p < 0.05) and left (p < 0.05) posterior tongue. In chemical taste tests, the obese group had higher thresholds for sweet, salty, sour, and bitter tastes than the normal-weight group, although the difference in threshold was significant only for salty taste (p < 0.05). Smoking had an impact on taste threshold, with smokers having higher thresholds than non-smokers, with significantly higher EGM thresholds on the right anterior and posterior and the left anterior tongue (p < 0.05 each).

Twelve automated thresholding methods for segmentation of PET images: a phantom study.

PubMed

Prieto, Elena; Lecumberri, Pablo; Pagola, Miguel; Gómez, Marisol; Bilbao, Izaskun; Ecay, Margarita; Peñuelas, Iván; Martí-Climent, Josep M

2012-06-21

Tumor volume delineation over positron emission tomography (PET) images is of great interest for proper diagnosis and therapy planning. However, standard segmentation techniques (manual or semi-automated) are operator dependent and time consuming while fully automated procedures are cumbersome or require complex mathematical development. The aim of this study was to segment PET images in a fully automated way by implementing a set of 12 automated thresholding algorithms, classical in the fields of optical character recognition, tissue engineering or non-destructive testing images in high-tech structures. Automated thresholding algorithms select a specific threshold for each image without any a priori spatial information of the segmented object or any special calibration of the tomograph, as opposed to usual thresholding methods for PET. Spherical (18)F-filled objects of different volumes were acquired on clinical PET/CT and on a small animal PET scanner, with three different signal-to-background ratios. Images were segmented with 12 automatic thresholding algorithms and results were compared with the standard segmentation reference, a threshold at 42% of the maximum uptake. Ridler and Ramesh thresholding algorithms based on clustering and histogram-shape information, respectively, provided better results that the classical 42%-based threshold (p < 0.05). We have herein demonstrated that fully automated thresholding algorithms can provide better results than classical PET segmentation tools.

Twelve automated thresholding methods for segmentation of PET images: a phantom study

NASA Astrophysics Data System (ADS)

Prieto, Elena; Lecumberri, Pablo; Pagola, Miguel; Gómez, Marisol; Bilbao, Izaskun; Ecay, Margarita; Peñuelas, Iván; Martí-Climent, Josep M.

2012-06-01

Tumor volume delineation over positron emission tomography (PET) images is of great interest for proper diagnosis and therapy planning. However, standard segmentation techniques (manual or semi-automated) are operator dependent and time consuming while fully automated procedures are cumbersome or require complex mathematical development. The aim of this study was to segment PET images in a fully automated way by implementing a set of 12 automated thresholding algorithms, classical in the fields of optical character recognition, tissue engineering or non-destructive testing images in high-tech structures. Automated thresholding algorithms select a specific threshold for each image without any a priori spatial information of the segmented object or any special calibration of the tomograph, as opposed to usual thresholding methods for PET. Spherical 18F-filled objects of different volumes were acquired on clinical PET/CT and on a small animal PET scanner, with three different signal-to-background ratios. Images were segmented with 12 automatic thresholding algorithms and results were compared with the standard segmentation reference, a threshold at 42% of the maximum uptake. Ridler and Ramesh thresholding algorithms based on clustering and histogram-shape information, respectively, provided better results that the classical 42%-based threshold (p < 0.05). We have herein demonstrated that fully automated thresholding algorithms can provide better results than classical PET segmentation tools.

Electromyographic and neuromuscular fatigue thresholds as concepts of fatigue.

PubMed

Mäestu, Jarek; Cicchella, Antonio; Purge, Priit; Ruosi, Sergio; Jürimäe, Jaak; Jürimäe, Toivo

2006-11-01

The aim of this study was to investigate the concepts of electromyographic (EMG) threshold (EMGT) by integrated EMG (iEMG) signals and neuromuscular fatigue threshold (NMFT) concepts in trained male athletes. Nine competitive national-level male rowers (21.8 +/- 4.4 years; 186.2 +/- 4.6 cm; 79.6 +/- 8.4 kg) took part in this investigation. Subjects were asked to participate in the graded exercise test to volitional exhaustion and 500-, 1,000-, and 2,000-m all-out rowing ergometer tests on a rowing ergometer. During all tests, oxygen consumption parameters, average power, and iEMG of the musculus vastus lateralis were recorded. The second ventilatory threshold (248.9 +/- 26.67 W) and EMGT (258.89 +/- 27.13 W) were not significantly different but were significantly lower than the NMFT (302.25 +/- 45.10 W). During 1,000- and 2,000-m all-out distances, VO(2) increased during the first minute and then leveled on a plateau with a slight decrease at the end of the exercise. Vastus lateralis activity showed a slight increase during all distances that was accompanied by a remarkable increase towards the end of the distance. All measured threshold values were significantly correlated (r > 0.70; p < 0.05) to the rowing ergometer performance characteristics. It was concluded that EMGT is closely related to the aerobic-anaerobic transition phase, because NMFT represents the local fatigue accumulation in the muscle. NMFT indicates the performance capacity of the muscles; therefore, it helps coaches to better predict top athletes' performance.

A New Protocol to Evaluate the Effect of Topical Anesthesia

PubMed Central

List, Thomas; Mojir, Katerina; Svensson, Peter; Pigg, Maria

2014-01-01

This double-blind, placebo-controlled, randomized cross-over clinical experimental study tested the reliability, validity, and sensitivity to change of punctuate pain thresholds and self-reported pain on needle penetration. Female subjects without orofacial pain were tested in 2 sessions at 1- to 2-week intervals. The test site was the mucobuccal fold adjacent to the first upper right premolar. Active lidocaine hydrochloride 2% (Dynexan) or placebo gel was applied for 5 minutes, and sensory testing was performed before and after application. The standardized quantitative sensory test protocol included mechanical pain threshold (MPT), pressure pain threshold (PPT), mechanical pain sensitivity (MPS), and needle penetration sensitivity (NPS) assessments. Twenty-nine subjects, mean (SD) age 29.0 (10.2) years, completed the study. Test-retest reliability intraclass correlation coefficient at 10-minute intervals between examinations was MPT 0.69, PPT 0.79, MPS 0.72, and NPS 0.86. A high correlation was found between NPS and MPS (r = 0.84; P < .001), whereas NPS and PPT were not significantly correlated. The study found good to excellent test-retest reliability for all measures. None of the sensory measures detected changes in sensitivity following lidocaine 2% or placebo gel. Electronic von Frey assessments of MPT/MPS on oral mucosa have good validity. PMID:25517548

A new characterization of three-dimensional conductivity backbone above and below the percolation threshold

NASA Astrophysics Data System (ADS)

Skal, Asya S.

1996-08-01

A new definition of three-dimensional conductivity backbone, obtained from a distribution function of Joule heat and the Hall coefficient is introduced. The fractal dimension d fB = d - ( {g}/{v}) = 2.25 of conductivity backbone for both sides of the threshold is obtained from a critical exponent of the Hall coefficient g = 0.6. This allows one to construct, below the threshold, a new order parameter of metal-conductor transition—the two-component infinite conductivity back-bone and tested scaling relation, proposed by Alexander and Orbach [ J. Phys. Rev. Lett.43, 1982, L625] for both sides of a threshold.

Thresher: an improved algorithm for peak height thresholding of microbial community profiles.

PubMed

Starke, Verena; Steele, Andrew

2014-11-15

This article presents Thresher, an improved technique for finding peak height thresholds for automated rRNA intergenic spacer analysis (ARISA) profiles. We argue that thresholds must be sample dependent, taking community richness into account. In most previous fragment analyses, a common threshold is applied to all samples simultaneously, ignoring richness variations among samples and thereby compromising cross-sample comparison. Our technique solves this problem, and at the same time provides a robust method for outlier rejection, selecting for removal any replicate pairs that are not valid replicates. Thresholds are calculated individually for each replicate in a pair, and separately for each sample. The thresholds are selected to be the ones that minimize the dissimilarity between the replicates after thresholding. If a choice of threshold results in the two replicates in a pair failing a quantitative test of similarity, either that threshold or that sample must be rejected. We compare thresholded ARISA results with sequencing results, and demonstrate that the Thresher algorithm outperforms conventional thresholding techniques. The software is implemented in R, and the code is available at http://verenastarke.wordpress.com or by contacting the author. vstarke@ciw.edu or http://verenastarke.wordpress.com Supplementary data are available at Bioinformatics online. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Definition of temperature thresholds: the example of the French heat wave warning system.

PubMed

Pascal, Mathilde; Wagner, Vérène; Le Tertre, Alain; Laaidi, Karine; Honoré, Cyrille; Bénichou, Françoise; Beaudeau, Pascal

2013-01-01

Heat-related deaths should be somewhat preventable. In France, some prevention measures are activated when minimum and maximum temperatures averaged over three days reach city-specific thresholds. The current thresholds were computed based on a descriptive analysis of past heat waves and on local expert judgement. We tested whether a different method would confirm these thresholds. The study was set in the six cities of Paris, Lyon, Marseille, Nantes, Strasbourg and Limoges between 1973 and 2003. For each city, we estimated the excess in mortality associated with different temperature thresholds, using a generalised additive model, controlling for long-time trends, seasons and days of the week. These models were used to compute the mortality predicted by different percentiles of temperatures. The thresholds were chosen as the percentiles associated with a significant excess mortality. In all cities, there was a good correlation between current thresholds and the thresholds derived from the models, with 0°C to 3°C differences for averaged maximum temperatures. Both set of thresholds were able to anticipate the main periods of excess mortality during the summers of 1973 to 2003. A simple method relying on descriptive analysis and expert judgement is sufficient to define protective temperature thresholds and to prevent heat wave mortality. As temperatures are increasing along with the climate change and adaptation is ongoing, more research is required to understand if and when thresholds should be modified.

Effects of Ultrasound Frequency and Tissue Stiffness on the Histotripsy Intrinsic Threshold for Cavitation

PubMed Central

Vlaisavljevich, Eli; Lin, Kuang-Wei; Maxwell, Adam; Warnez, Matthew; Mancia, Lauren; Singh, Rahul; Putnam, Andrew J.; Fowlkes, Brian; Johnsen, Eric; Cain, Charles; Xu, Zhen

2015-01-01

Histotripsy is an ultrasound ablation method that depends on the initiation of a cavitation bubble cloud to fractionate soft tissue. Previous work has demonstrated a cavitation cloud can be formed by a single pulse with one high amplitude negative cycle, when the negative pressure amplitude directly exceeds a pressure threshold intrinsic to the medium. We hypothesize that the intrinsic threshold in water-based tissues is determined by the properties of the water inside the tissue and changes in tissue stiffness or ultrasound frequency will have a minimal impact on the histotripsy intrinsic threshold. To test this hypothesis, the histotripsy intrinsic threshold was investigated both experimentally and theoretically. The probability of cavitation was measured by subjecting tissue phantoms with adjustable mechanical properties and ex vivo tissues to a histotripsy pulse of 1–2 cycles produced by 345 kHz, 500 kHz, 1.5 MHz, and 3 MHz histotripsy transducers. Cavitation was detected and characterized by passive cavitation detection and high-speed photography, from which the probability of cavitation was measured vs. pressure amplitude. The results demonstrated that the intrinsic threshold (the negative pressure at which probability=0.5) is independent of stiffness for Young’s moduli (E) < 1 MPa with only a small increase (~2–3 MPa) in the intrinsic threshold for tendon (E=380 MPa). Additionally, results for all samples showed only a small increase of ~2–3 MPa when the frequency was increased from 345 kHz to 3 MHz. The intrinsic threshold was measured to be between 24.7–30.6 MPa for all samples and frequencies tested in this study. Overall, the results of this study indicate that the intrinsic threshold to initiate a histotripsy bubble cloud is not significantly impacted by tissue stiffness or ultrasound frequency in hundreds of kHz to MHz range. PMID:25766571

Effects of ultrasound frequency and tissue stiffness on the histotripsy intrinsic threshold for cavitation.

PubMed

Vlaisavljevich, Eli; Lin, Kuang-Wei; Maxwell, Adam; Warnez, Matthew T; Mancia, Lauren; Singh, Rahul; Putnam, Andrew J; Fowlkes, Brian; Johnsen, Eric; Cain, Charles; Xu, Zhen

2015-06-01

Histotripsy is an ultrasound ablation method that depends on the initiation of a cavitation bubble cloud to fractionate soft tissue. Previous work has indicated that a cavitation cloud can be formed by a single pulse with one high-amplitude negative cycle, when the negative pressure amplitude directly exceeds a pressure threshold intrinsic to the medium. We hypothesize that the intrinsic threshold in water-based tissues is determined by the properties of the water inside the tissue, and changes in tissue stiffness or ultrasound frequency will have a minimal impact on the histotripsy intrinsic threshold. To test this hypothesis, the histotripsy intrinsic threshold was investigated both experimentally and theoretically. The probability of cavitation was measured by subjecting tissue phantoms with adjustable mechanical properties and ex vivo tissues to a histotripsy pulse of 1-2 cycles produced by 345-kHz, 500-kHz, 1.5-MHz and 3-MHz histotripsy transducers. Cavitation was detected and characterized by passive cavitation detection and high-speed photography, from which the probability of cavitation was measured versus pressure amplitude. The results revealed that the intrinsic threshold (the negative pressure at which probability = 0.5) is independent of stiffness for Young's moduli (E) <1 MPa, with only a small increase (∼2-3 MPa) in the intrinsic threshold for tendon (E = 380 MPa). Additionally, results for all samples revealed only a small increase of ∼2-3 MPa when the frequency was increased from 345 kHz to 3 MHz. The intrinsic threshold was measured to be between 24.7 and 30.6 MPa for all samples and frequencies tested in this study. Overall, the results of this study indicate that the intrinsic threshold to initiate a histotripsy bubble cloud is not significantly affected by tissue stiffness or ultrasound frequency in the hundreds of kilohertz to megahertz range. Copyright © 2015 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Crack Growth Behavior in the Threshold Region for High Cycle Fatigue Loading

NASA Technical Reports Server (NTRS)

Forman, Royce G.; Figert, J.; Beek, J.; Ventura, J.; Martinez, J.; Samonski, F.

2011-01-01

This presentation describes results obtained from a research project conducted at the NASA Johnson Space Center (JSC) that was jointly supported by the FAA Technical Center and JSC. The JSC effort was part of a multi-task FAA program involving several U.S. laboratories and initiated for the purpose of developing enhanced analysis tools to assess damage tolerance of rotorcraft and aircraft propeller systems. The research results to be covered in this presentation include a new understanding of the behavior of fatigue crack growth in the threshold region. This behavior is important for structural life analysis of aircraft propeller systems and certain rotorcraft structural components (e.g., the mast). These components are often designed to not allow fatigue crack propagation to exceed an experimentally determined fatigue crack growth threshold value. During the FAA review meetings for the program, disagreements occurred between the researchers regarding the observed fanning (spread between the da/dN curves of constant R) in the threshold region at low stress ratios, R. Some participants believed that the fanning was a result of the ASTM load shedding test method for threshold testing, and thus did not represent the true characteristics of the material. If the fanning portion of the threshold value is deleted or not included in a life analysis, a significant penalty in the calculated life and design of the component would occur. The crack growth threshold behavior was previously studied and reported by several research investigators in the time period: 1970-1980. Those investigators used electron microscopes to view the crack morphology of the fatigue fracture surfaces. Their results showed that just before reaching threshold, the crack morphology often changed from a striated to a faceted or cleavage-like morphology. This change was reported to have been caused by particular dislocation properties of the material. Based on the results of these early investigations, a program was initiated at JSC to repeat these examinations on a number of aircraft structural alloys that were currently being tested for obtaining fatigue crack growth properties. These new scanning electron microscope (SEM) examinations of the fatigue fracture faces confirmed the change in crack morphology in the threshold crack tip region. In addition, SEM examinations were further performed in the threshold crack-tip region before breaking the specimens open (not done in the earlier published studies). In these examinations, extensive crack forking and even 90-degree crack bifurcations were found to have occurred in the final threshold crack-tip region. The forking and bifurcations caused numerous closure points to occur that prevented full crack closure in the threshold region, and thus were the cause of the fanning at low-R values. Therefore, we have shown that the fanning behavior was caused by intrinsic dislocation properties of the different alloy materials and were not the result of a plastic wake that remains from the load-shedding test phase. Also, to accommodate the use of da/dN data which includes fanning at low R-values, an updated fanning factor term has been developed and will be implemented into the NASGRO fatigue crack growth software. The term can be set to zero if it is desired that the fanning behavior is not be modeled for particular cases, such as when fanning is not a result of the intrinsic properties of a material.

Using machine learning to examine medication adherence thresholds and risk of hospitalization.

PubMed

Lo-Ciganic, Wei-Hsuan; Donohue, Julie M; Thorpe, Joshua M; Perera, Subashan; Thorpe, Carolyn T; Marcum, Zachary A; Gellad, Walid F

2015-08-01

Quality improvement efforts are frequently tied to patients achieving ≥80% medication adherence. However, there is little empirical evidence that this threshold optimally predicts important health outcomes. To apply machine learning to examine how adherence to oral hypoglycemic medications is associated with avoidance of hospitalizations, and to identify adherence thresholds for optimal discrimination of hospitalization risk. A retrospective cohort study of 33,130 non-dual-eligible Medicaid enrollees with type 2 diabetes. We randomly selected 90% of the cohort (training sample) to develop the prediction algorithm and used the remaining (testing sample) for validation. We applied random survival forests to identify predictors for hospitalization and fit survival trees to empirically derive adherence thresholds that best discriminate hospitalization risk, using the proportion of days covered (PDC). Time to first all-cause and diabetes-related hospitalization. The training and testing samples had similar characteristics (mean age, 48 y; 67% female; mean PDC=0.65). We identified 8 important predictors of all-cause hospitalizations (rank in order): prior hospitalizations/emergency department visit, number of prescriptions, diabetes complications, insulin use, PDC, number of prescribers, Elixhauser index, and eligibility category. The adherence thresholds most discriminating for risk of all-cause hospitalization varied from 46% to 94% according to patient health and medication complexity. PDC was not predictive of hospitalizations in the healthiest or most complex patient subgroups. Adherence thresholds most discriminating of hospitalization risk were not uniformly 80%. Machine-learning approaches may be valuable to identify appropriate patient-specific adherence thresholds for measuring quality of care and targeting nonadherent patients for intervention.

Preliminary test of cigarette nicotine discrimination threshold in non-dependent versus dependent smokers.

PubMed

Perkins, Kenneth A; Kunkle, Nicole; Karelitz, Joshua L; Perkins, K A; Kunkle, N; Karelitz, J L

2017-06-01

Despite its potential for understanding tobacco dependence, behavioral discrimination of nicotine via smoking has not been formally examined as a function of nicotine dependence level. Spectrum research cigarettes were used to compare non-dependent with dependent smokers on the lowest content of nicotine they could discriminate (i.e., "threshold"). Dependent (n=21; 16M, 5F) or non-dependent (n=7; 4M, 3F) smokers were tested on ability to discriminate between cigarettes with nicotine contents of 17, 11, 5, 2, and 1mg/g, one per session, from an "ultra-low" cigarette with 0.4mg/g (all had 9-10mg "tar"). All abstained from smoking overnight prior to sessions, and number of sessions was determined by the lowest nicotine content they could reliably discriminate from the ultra-low on >80% of trials (i.e., ≥5 of 6). Subjective perceptions and cigarette choice behavior were also assessed and related to discrimination behavior. Discrimination thresholds (and most perceptions) did not differ between dependent and non-dependent smokers, with median thresholds of 11mg/g for both subgroups. Yet, "liking" and puff choice for threshold cigarettes were greater in dependent but not non-dependent smokers, while cigarettes with nicotine contents below threshold did not support "liking" or choice in both groups. In sum, this preliminary study suggests threshold for discriminating nicotine via smoking may not vary by dependence level, and further study is needed to confirm that cigarettes unable to be discriminated are also not reinforcing. Copyright © 2017 Elsevier B.V. All rights reserved.

Reliability and validity of a brief method to assess nociceptive flexion reflex (NFR) threshold.

PubMed

Rhudy, Jamie L; France, Christopher R

2011-07-01

The nociceptive flexion reflex (NFR) is a physiological tool to study spinal nociception. However, NFR assessment can take several minutes and expose participants to repeated suprathreshold stimulations. The 4 studies reported here assessed the reliability and validity of a brief method to assess NFR threshold that uses a single ascending series of stimulations (Peak 1 NFR), by comparing it to a well-validated method that uses 3 ascending/descending staircases of stimulations (Staircase NFR). Correlations between the NFR definitions were high, were on par with test-retest correlations of Staircase NFR, and were not affected by participant sex or chronic pain status. Results also indicated the test-retest reliabilities for the 2 definitions were similar. Using larger stimulus increments (4 mAs) to assess Peak 1 NFR tended to result in higher NFR threshold estimates than using the Staircase NFR definition, whereas smaller stimulus increments (2 mAs) tended to result in lower NFR threshold estimates than the Staircase NFR definition. Neither NFR definition was correlated with anxiety, pain catastrophizing, or anxiety sensitivity. In sum, a single ascending series of electrical stimulations results in a reliable and valid estimate of NFR threshold. However, caution may be warranted when comparing NFR thresholds across studies that differ in the ascending stimulus increments. This brief method to assess NFR threshold is reliable and valid; therefore, it should be useful to clinical pain researchers interested in quickly assessing inter- and intra-individual differences in spinal nociceptive processes. Copyright © 2011 American Pain Society. Published by Elsevier Inc. All rights reserved.

Effect of strong fragrance on olfactory detection threshold.

PubMed

Fasunla, Ayotunde James; Douglas, David Dayo; Adeosun, Aderemi Adeleke; Steinbach, Silke; Nwaorgu, Onyekwere George Benjamin

2014-09-01

To assess the olfactory threshold of healthy volunteers at the University College Hospital, Ibadan and to investigate the effect of perfume on their olfactory detection thresholds. A quasi-experimental study on olfactory detection thresholds of healthy volunteers from September 2013 to November 2013. Tertiary health institution. A structured questionniare was administered to the participants in order to obtain information on sociodemographics, occupation, ability to perceive smell, use of perfume, effects of perfume on appetite and self-confidence, history of allergy, and previous nasal surgery. Participants subjectively rated their olfactory performance. Subsequently, they had olfactory detection threshold testing done at baseline and after exposure to perfume with varied concentrations of n-butanol in a forced triple response and staircase fashion. Healthy volunteers, 37 males and 63 females, were evaluated. Their ages ranged from 19 to 59 years with a mean of 31 years ± 8. Subjectively, 94% of the participants had excellent olfactory function. In the pre-exposure forced triple response, 88% were able to detect the odor at ≤.25 mmol/l concentration while in the post-exposure forced triple response, only 66% were able to detect the odor at ≤.25 mmol/l concentration. There is also a statistical significant difference in the olfactory detection threshold score between the pre-exposure and post-exposure period in the participants (P < .05). Use of strong fragrances affects the olfactory detection threshold. Therefore patients and clinicians should be aware of this and its effects on the outcome of test of olfaction. © American Academy of Otolaryngology—Head and Neck Surgery Foundation 2014.

The effect of olfactory training on the odor threshold in patients with traumatic anosmia.

PubMed

Jiang, Rong-San; Twu, Chih-Wen; Liang, Kai-Li

2017-09-01

Olfactory training is a novel intervention that has been used to treat olfactory dysfunction. This study attempted to investigate the effect of olfactory training in patients with traumatic anosmia. Patients with a clear history of anosmia after experiencing a head injury and whose phenyl ethyl alcohol (PEA) odor detection thresholds were -1 after steroid and zinc treatment were included. The patients were randomly divided into two groups, with patients in one group given a bottle of PEA and those in another group given a bottle of mineral oil for 3-month olfactory training. All the patients were followed up with a PEA threshold test and the traditional Chinese version of the University of Pennsylvania Smell Identification Test (UPSIT-TC). Magnetic resonance imaging was performed to measure the volume of the olfactory bulbs. Any patient whose PEA threshold result was below -1.01 or whose UPSIT-TC score increased four or more points was considered to have shown improvement in their olfactory function. Forty-two patients received PEA olfactory training, whereas 39 received olfactory training with mineral oil. The improvement of PEA thresholds function was observed in 10 patients within the PEA group and in 2 patients in the mineral oil group. The frequency of improvement of threshold within the PEA group was significantly higher than that of the mineral oil group. Neither olfactory bulb volume nor UPSIT-TC score was significantly different between the two groups. Our results showed that olfactory training with PEA can improve PEA odor threshold levels in patients with traumatic anosmia.

Tactile Acuity Charts: A Reliable Measure of Spatial Acuity

PubMed Central

Bruns, Patrick; Camargo, Carlos J.; Campanella, Humberto; Esteve, Jaume; Dinse, Hubert R.; Röder, Brigitte

2014-01-01

For assessing tactile spatial resolution it has recently been recommended to use tactile acuity charts which follow the design principles of the Snellen letter charts for visual acuity and involve active touch. However, it is currently unknown whether acuity thresholds obtained with this newly developed psychophysical procedure are in accordance with established measures of tactile acuity that involve passive contact with fixed duration and control of contact force. Here we directly compared tactile acuity thresholds obtained with the acuity charts to traditional two-point and grating orientation thresholds in a group of young healthy adults. For this purpose, two types of charts, using either Braille-like dot patterns or embossed Landolt rings with different orientations, were adapted from previous studies. Measurements with the two types of charts were equivalent, but generally more reliable with the dot pattern chart. A comparison with the two-point and grating orientation task data showed that the test-retest reliability of the acuity chart measurements after one week was superior to that of the passive methods. Individual thresholds obtained with the acuity charts agreed reasonably with the grating orientation threshold, but less so with the two-point threshold that yielded relatively distinct acuity estimates compared to the other methods. This potentially considerable amount of mismatch between different measures of tactile acuity suggests that tactile spatial resolution is a complex entity that should ideally be measured with different methods in parallel. The simple test procedure and high reliability of the acuity charts makes them a promising complement and alternative to the traditional two-point and grating orientation thresholds. PMID:24504346

Serum ferritin thresholds for the diagnosis of iron deficiency in pregnancy: a systematic review.

PubMed

Daru, J; Allotey, J; Peña-Rosas, J P; Khan, K S

2017-06-01

The aim of this review was to understand the landscape of serum ferritin in diagnosing iron deficiency in the aetiology of anaemia in pregnancy. Iron deficiency in pregnancy is a major public health problem leading to the development of anaemia. Reducing the global prevalence of anaemia in women of reproductive age is a 2025 global nutrition target. Bone marrow aspiration is the gold standard test for iron deficiency but requires an invasive procedure; therefore, serum ferritin is the most clinically useful test. We undertook a systematic search of electronic databases and trial registers from inception to January 2016. Studies of iron or micronutrient supplementation in pregnancy with pre-defined serum ferritin thresholds were included. Two independent reviewers selected studies, extracted data and assessed quality. There were 76 relevant studies mainly of observational study design (57%). The most commonly used thresholds of serum ferritin for the diagnosis of iron deficiency were <12 and <15 ng mL -1 (68%). Most primary studies provided no justification for the choice of serum ferritin threshold used, but 25 studies (33%) used thresholds defined by expert consensus in a guideline development process. There were five studies (7%) using a serum ferritin threshold defining iron deficiency derived from primary studies of bone marrow aspiration. Unified international thresholds of iron deficiency for women throughout pregnancy are required for accurate assessments of the global disease burden and for evaluating effectiveness of interventions addressing this problem. © 2017 World Health Organization licensed by Transfusion Medicine published by John Wiley & Sons Ltd on behalf of British Blood Transfusion Society.

Exhibition of Stochastic Resonance in Vestibular Perception

NASA Technical Reports Server (NTRS)

Galvan-Garza, R. C.; Clark, T. K.; Merfeld, D. M.; Bloomberg, J. J.; Oman, C. M.; Mulavara, A. P.

2016-01-01

Astronauts experience sensorimotor changes during spaceflight, particularly during G-transitions. Post flight sensorimotor changes include spatial disorientation, along with postural and gait instability that may degrade operational capabilities of the astronauts and endanger the crew. A sensorimotor countermeasure that mitigates these effects would improve crewmember safety and decrease risk. The goal of this research is to investigate the potential use of stochastic vestibular stimulation (SVS) as a technology to improve sensorimotor function. We hypothesize that low levels of SVS will improve sensorimotor perception through the phenomenon of stochastic resonance (SR), when the response of a nonlinear system to a weak input signal is enhanced by the application of a particular nonzero level of noise. This study aims to advance the development of SVS as a potential countermeasure by 1) demonstrating the exhibition of stochastic resonance in vestibular perception, a vital component of sensorimotor function, 2) investigating the repeatability of SR exhibition, and 3) determining the relative contribution of the semicircular canals (SCC) and otolith (OTO) organs to vestibular perceptual SR. A constant current stimulator was used to deliver bilateral bipolar SVS via electrodes placed on each of the mastoid processes, as previously done. Vestibular perceptual motion recognition thresholds were measured using a 6-degree of freedom MOOG platform and a 150 trial 3-down/1-up staircase procedure. In the first test session, we measured vestibular perceptual thresholds in upright roll-tilt at 0.2 Hz (SCC+OTO) with SVS ranging from 0-700 µA. In a second test session a week later, we re-measured roll-tilt thresholds with 0, optimal (from test session 1), and 1500 µA SVS levels. A subset of these subjects, plus naive subjects, participated in two additional test sessions in which we measured thresholds in supine roll-rotation at 0.2 Hz (SCC) and upright y-translation at 1 Hz (OTO) with SVS up to 700 µA. A sinusoidal galvanic vestibular stimulation (GVS) perceptual threshold was also measured on each test day and used to normalize the SVS levels across subjects. In roll-tilt thresholds with SVS, the characteristic SR curve was qualitatively exhibited in 10 of 12 subjects, and the improvement in motion threshold was significant in 6 subjects, indicating that optimal SVS improved passive body motion perception in a way that is consistent with classical SR theory. A probabilistic comparison to numeric simulations further validated these experimental results. On the second test session, 4 out of the 10 SR exhibitors showed repeated improvement with SVS compared to the no SVS condition. Data collection is ongoing for the last two test sessions in which SCC and OTO only perceptual motion recognition thresholds are being measured with SVS. The final results of these test sessions will give insight into whether vestibular perceptual SR can occur when only one type of vestibular sensor is sensing motion or if it is more evident when sensory integration between the SCC and OTO is occurring during the motion. The overall purpose of this research is to further quantify the effects of SVS on various sensorimotor tasks and to gain a more fundamental understanding of how SVS causes SR in the vestibular system. In the context of human space flight, results from this research will help in understanding how SVS may be practically implemented in the future as a component of a comprehensive countermeasure plan for G-transition adaptation.

UV fatigue investigations with non-destructive tools in silica

NASA Astrophysics Data System (ADS)

Natoli, Jean-Yves; Beaudier, Alexandre; Wagner, Frank R.

2017-08-01

A fatigue effect is often observed under multiple laser irradiations, overall in UV. This decrease of LIDT, is a critical parameter for laser sources with high repetition rates and with a need of long-term life, as in spatial applications at 355nm. A challenge is also to replace excimer lasers by solid laser sources, this challenge requires to improve drastically the lifetime of optical materials at 266nm. Main applications of these sources are devoted to material surface nanostructuration, spectroscopy and medical surgeries. In this work we focus on the understanding of the laser matter interaction at 266nm in silica in order to predict the lifetime of components and study parameters links to these lifetimes to give keys of improvement for material suppliers. In order to study the mechanism involved in the case of multiple irradiations, an interesting approach is to involve the evolution of fluorescence, in order to observe the first stages of material changes just before breakdown. We will show that it is sometime possible to estimate the lifetime of component only with the fluorescence measurement, saving time and materials. Moreover, the data from the diagnostics give relevant informations to highlight "defects" induced by multiple laser irradiations.

Brief communication: Using averaged soil moisture estimates to improve the performances of a regional-scale landslide early warning system

NASA Astrophysics Data System (ADS)

Segoni, Samuele; Rosi, Ascanio; Lagomarsino, Daniela; Fanti, Riccardo; Casagli, Nicola

2018-03-01

We communicate the results of a preliminary investigation aimed at improving a state-of-the-art RSLEWS (regional-scale landslide early warning system) based on rainfall thresholds by integrating mean soil moisture values averaged over the territorial units of the system. We tested two approaches. The simplest can be easily applied to improve other RSLEWS: it is based on a soil moisture threshold value under which rainfall thresholds are not used because landslides are not expected to occur. Another approach deeply modifies the original RSLEWS: thresholds based on antecedent rainfall accumulated over long periods are substituted with soil moisture thresholds. A back analysis demonstrated that both approaches consistently reduced false alarms, while the second approach reduced missed alarms as well.

Assessment of ventilatory thresholds during graded and maximal exercise test using time varying analysis of respiratory sinus arrhythmia.

PubMed

Blain, G; Meste, O; Bouchard, T; Bermon, S

2005-07-01

To test whether ventilatory thresholds, measured during an exercise test, could be assessed using time varying analysis of respiratory sinus arrhythmia frequency (f(RSA)). Fourteen sedentary subjects and 12 endurance athletes performed a graded and maximal exercise test on a cycle ergometer: initial load 75 W (sedentary subjects) and 150 W (athletes), increments 37.5 W/2 min. f(RSA) was extracted from heart period series using an evolutive model. First (T(V1)) and second (T(V2)) ventilatory thresholds were determined from the time course curves of ventilation and ventilatory equivalents for O(2) and CO(2). f(RSA) was accurately extracted from all recordings and positively correlated to respiratory frequency (r = 0.96 (0.03), p<0.01). In 21 of the 26 subjects, two successive non-linear increases were determined in f(RSA), defining the first (T(RSA1)) and second (T(RSA2)) f(RSA) thresholds. When expressed as a function of power, T(RSA1) and T(RSA2) were not significantly different from and closely linked to T(V1) (r = 0.99, p<0.001) and T(V2) (r = 0.99, p<0.001), respectively. In the five remaining subjects, only one non-linear increase was observed close to T(V2). Significant differences (p<0.04) were found between athlete and sedentary groups when T(RSA1) and T(RSA2) were expressed in terms of absolute and relative power and percentage of maximal aerobic power. In the sedentary group, T(RSA1) and T(RSA2) were 150.3 (18.7) W and 198.3 (28.8) W, respectively, whereas in the athlete group T(RSA1) and T(RSA2) were 247.3 (32.8) W and 316.0 (28.8) W, respectively. Dynamic analysis of f(RSA) provides a useful tool for identifying ventilatory thresholds during graded and maximal exercise test in sedentary subjects and athletes.

Assessment of ventilatory thresholds during graded and maximal exercise test using time varying analysis of respiratory sinus arrhythmia

PubMed Central

Blain, G; Meste, O; Bouchard, T; Bermon, S; Segura, R.

2005-01-01

Objective: To test whether ventilatory thresholds, measured during an exercise test, could be assessed using time varying analysis of respiratory sinus arrhythmia frequency (fRSA). Methods: Fourteen sedentary subjects and 12 endurance athletes performed a graded and maximal exercise test on a cycle ergometer: initial load 75 W (sedentary subjects) and 150 W (athletes), increments 37.5 W/2 min. fRSA was extracted from heart period series using an evolutive model. First (TV1) and second (TV2) ventilatory thresholds were determined from the time course curves of ventilation and ventilatory equivalents for O2 and CO2. Results: fRSA was accurately extracted from all recordings and positively correlated to respiratory frequency (r = 0.96 (0.03), p<0.01). In 21 of the 26 subjects, two successive non-linear increases were determined in fRSA, defining the first (TRSA1) and second (TRSA2) fRSA thresholds. When expressed as a function of power, TRSA1 and TRSA2 were not significantly different from and closely linked to TV1 (r = 0.99, p<0.001) and TV2 (r = 0.99, p<0.001), respectively. In the five remaining subjects, only one non-linear increase was observed close to TV2. Significant differences (p<0.04) were found between athlete and sedentary groups when TRSA1 and TRSA2 were expressed in terms of absolute and relative power and percentage of maximal aerobic power. In the sedentary group, TRSA1 and TRSA2 were 150.3 (18.7) W and 198.3 (28.8) W, respectively, whereas in the athlete group TRSA1 and TRSA2 were 247.3 (32.8) W and 316.0 (28.8) W, respectively. Conclusions: Dynamic analysis of fRSA provides a useful tool for identifying ventilatory thresholds during graded and maximal exercise test in sedentary subjects and athletes. PMID:15976169

Impact of endoscopic sinus surgery on olfaction and use of alternative components in odor threshold measurement.

PubMed

Gupta, Divya; Gulati, Achal; Singh, Ishwar; Tekur, Uma

2015-01-01

One of the major causes of olfactory disturbances is chronic rhinosinusitis (CRS), and the main surgical modality to treat CRS is functional endoscopic sinus surgery (FESS). It, therefore, is essential to assess the effect of this surgery on olfaction. Also, it is necessary to find new ways of measuring olfaction so as to reduce dependability on standard tests available. To study the prevalence of olfactory impairment in patients with CRS and to evaluate the impact of FESS on olfaction. The study also aims at investigating the use of other odorants in place of butanol-1 in the Connecticut Chemosensory Clinical Research Center test. Forty patients of CRS without nasal polyposis were included in the study to analyze the prevalence of olfactory dysfunction and examine the influence of FESS at 1 and 3 months after surgery. Computed tomography scores (Lund Mackay scores) were calculated preoperatively, whereas other tests, viz., visual analog scale scoring, nasal endoscopy (Lund Kennedy scoring), and composite olfactory testing with odor thresholds of butanol-1, peppermint, lemon, clove, and ethyl acetate were carried out before surgery and after surgery at 1 and 3 months. Of 40 patients, 70% had symptoms of hyposmia or of anosmia before surgery, which dropped to 22.5% at 1 month after surgery and to 10% at 3 months after surgery. Nasal endoscopy and visual analog scale scores improved significantly. Odor threshold and odor identification scores also improved compared with the preoperative levels. A significant positive correlation was found between the threshold scores of butanol-1 and other odorants, both before and after surgery. Significant improvement was observed in olfaction after FESS, both in patient responses and in objective testing. The olfactory results with peppermint, lemon, clove, and ethyl acetate were close to those with butanol-1, and, hence, these other odorants can be used in place of butanol-1 in measuring the odor threshold.

A multi-SNP association test for complex diseases incorporating an optimal P-value threshold algorithm in nuclear families.

PubMed

Wang, Yi-Ting; Sung, Pei-Yuan; Lin, Peng-Lin; Yu, Ya-Wen; Chung, Ren-Hua

2015-05-15

Genome-wide association studies (GWAS) have become a common approach to identifying single nucleotide polymorphisms (SNPs) associated with complex diseases. As complex diseases are caused by the joint effects of multiple genes, while the effect of individual gene or SNP is modest, a method considering the joint effects of multiple SNPs can be more powerful than testing individual SNPs. The multi-SNP analysis aims to test association based on a SNP set, usually defined based on biological knowledge such as gene or pathway, which may contain only a portion of SNPs with effects on the disease. Therefore, a challenge for the multi-SNP analysis is how to effectively select a subset of SNPs with promising association signals from the SNP set. We developed the Optimal P-value Threshold Pedigree Disequilibrium Test (OPTPDT). The OPTPDT uses general nuclear families. A variable p-value threshold algorithm is used to determine an optimal p-value threshold for selecting a subset of SNPs. A permutation procedure is used to assess the significance of the test. We used simulations to verify that the OPTPDT has correct type I error rates. Our power studies showed that the OPTPDT can be more powerful than the set-based test in PLINK, the multi-SNP FBAT test, and the p-value based test GATES. We applied the OPTPDT to a family-based autism GWAS dataset for gene-based association analysis and identified MACROD2-AS1 with genome-wide significance (p-value=2.5×10(-6)). Our simulation results suggested that the OPTPDT is a valid and powerful test. The OPTPDT will be helpful for gene-based or pathway association analysis. The method is ideal for the secondary analysis of existing GWAS datasets, which may identify a set of SNPs with joint effects on the disease.

Interpreting results of cluster surveys in emergency settings: is the LQAS test the best option?

PubMed

Bilukha, Oleg O; Blanton, Curtis

2008-12-09

Cluster surveys are commonly used in humanitarian emergencies to measure health and nutrition indicators. Deitchler et al. have proposed to use Lot Quality Assurance Sampling (LQAS) hypothesis testing in cluster surveys to classify the prevalence of global acute malnutrition as exceeding or not exceeding the pre-established thresholds. Field practitioners and decision-makers must clearly understand the meaning and implications of using this test in interpreting survey results to make programmatic decisions. We demonstrate that the LQAS test--as proposed by Deitchler et al.--is prone to producing false-positive results and thus is likely to suggest interventions in situations where interventions may not be needed. As an alternative, to provide more useful information for decision-making, we suggest reporting the probability of an indicator's exceeding the threshold as a direct measure of "risk". Such probability can be easily determined in field settings by using a simple spreadsheet calculator. The "risk" of exceeding the threshold can then be considered in the context of other aggravating and protective factors to make informed programmatic decisions.

Should sensory function after median nerve injury and repair be quantified using two-point discrimination as the critical measure?

PubMed

Jerosch-Herold, C

2000-12-01

Two-point discrimination (2PD) is widely used for evaluating outcome from peripheral nerve injury and repair. It is the only quantifiable measure used in the British Medical Research Council (MRC) classification that was developed by Highet in 1954. This paper reports the results of a study of 41 patients with complete median nerve lacerations to the wrist or forearm. Two-point discrimination thresholds were assessed together with locognosia (locognosia is the ability to localise a sensory stimulus on the body's surface), tactile gnosis, and touch threshold. Using the MRC classification 29 (71%) patients had a result of S2 or below, 11 (27%) were S3, and only one scored S3+. Patients scored much better on the other tests and showed progressive recovery. It remains too difficult for patients to obtain a measurable threshold value on 2PD and the test therefore lacks responsiveness. The rating of outcome from peripheral nerve repair should not be based solely on 2PD testing and must include other tests of tactile sensibility.

Comments on Jeong-Won Lee and Diane Lemonnier Schallert's "The Relative Contribution of L2 Language Proficiency and L1 Reading Ability to L2 Reading Performance: A Test of the Threshold Hypothesis in an EFL Context."

ERIC Educational Resources Information Center

Bamford, Julian; Day, Richard R.; Schallert, Diane Lemonnier; Lee, Jeong-Won

1998-01-01

Provides reactions to an article, "The Relative Contribution of L2 Language Proficiency and L1 Reading Ability to L2 Reading Performance: A Test of the Threshold Hypothesis in an EFL Context" published in an earlier issue of this journal (v31 n4). The authors of the article respond to these reactions. (Author/VWL)

Near-Threshold Fatigue Crack Growth Behavior of Fine-Grain Nickel-Based Alloys

NASA Technical Reports Server (NTRS)

Newman, John A.; Piascik, Robert S.

2003-01-01

Constant-Kmax fatigue crack growth tests were performed on two finegrain nickel-base alloys Inconel 718 (DA) and Ren 95 to determine if these alloys exhibit near-threshold time-dependent crack growth behavior observed for fine-grain aluminum alloys in room-temperature laboratory air. Test results showed that increases in K(sub max) values resulted in increased crack growth rates, but no evidence of time-dependent crack growth was observed for either nickel-base alloy at room temperature.

Outlier removal, sum scores, and the inflation of the Type I error rate in independent samples t tests: the power of alternatives and recommendations.

PubMed

Bakker, Marjan; Wicherts, Jelte M

2014-09-01

In psychology, outliers are often excluded before running an independent samples t test, and data are often nonnormal because of the use of sum scores based on tests and questionnaires. This article concerns the handling of outliers in the context of independent samples t tests applied to nonnormal sum scores. After reviewing common practice, we present results of simulations of artificial and actual psychological data, which show that the removal of outliers based on commonly used Z value thresholds severely increases the Type I error rate. We found Type I error rates of above 20% after removing outliers with a threshold value of Z = 2 in a short and difficult test. Inflations of Type I error rates are particularly severe when researchers are given the freedom to alter threshold values of Z after having seen the effects thereof on outcomes. We recommend the use of nonparametric Mann-Whitney-Wilcoxon tests or robust Yuen-Welch tests without removing outliers. These alternatives to independent samples t tests are found to have nominal Type I error rates with a minimal loss of power when no outliers are present in the data and to have nominal Type I error rates and good power when outliers are present. PsycINFO Database Record (c) 2014 APA, all rights reserved.

Ambient noise levels in industrial audiometric test rooms.

PubMed

Frank, T; Williams, D L

1994-05-01

In 1983 the Occupational Safety and Health Administration (OSHA) specified maximum permissible ambient noise levels (MPANLs) that would allow valid hearing threshold measurements in an audiometric test room. However, ambient noise sound pressure levels (SPLs) in rooms used for industrial hearing tests are unknown. The present study reports octave band (125 to 8000 Hz) ambient noise SPLs measured in 490 single-walled prefabricated audiometric test rooms located in industrial settings that were obtained from eight sources. The ambient noise SPLs were highest in the lower frequencies and decreased as frequency increased. All 490 rooms met the OSHA MPANLs. Fortunately, the ambient noise SPLs were considerably lower than the OSHA MPANLs, since previous research has demonstrated that hearing thresholds cannot be obtained down to 0-dB HL in a test room having ambient noise levels equal to the OSHA MPANLs. In fact, 33%, or 162 of the 490 test rooms, met the more stringent MPANLs recently specified by the American National Standards Institute (ANSI) for industrial hearing testing. Given that the OSHA MPANLs are too high and that the test room ambient noise SPLs were considerably less than the OSHA MPANLs, that authors recommend that the OSHA MPANLs be revised to the more stringent ANSI 1991 MPANLs so that hearing thresholds for baseline and annual audiograms can be measured down to 0-dB HL.

Simulated Critical Differences for Speech Reception Thresholds

ERIC Educational Resources Information Center

Pedersen, Ellen Raben; Juhl, Peter Møller

2017-01-01

Purpose: Critical differences state by how much 2 test results have to differ in order to be significantly different. Critical differences for discrimination scores have been available for several decades, but they do not exist for speech reception thresholds (SRTs). This study presents and discusses how critical differences for SRTs can be…

Total Protein of Whole Saliva as a Biomarker of Anaerobic Threshold

ERIC Educational Resources Information Center

Bortolini, Miguel Junior Sordi; De Agostini, Guilherme Gularte; Reis, Ismair Teodoro; Lamounier, Romeu Paulo Martins Silva; Blumberg, Jeffrey B.; Espindola, Foued Salmen

2009-01-01

Saliva provides a convenient and noninvasive matrix for assessing specific physiological parameters, including some biomarkers of exercise. We investigated whether the total protein concentration of whole saliva (TPWS) would reflect the anaerobic threshold during an incremental exercise test. After a warm-up period, 13 nonsmoking men performed a…

Normative data for the "Sniffin' Sticks" including tests of odor identification, odor discrimination, and olfactory thresholds: an upgrade based on a group of more than 3,000 subjects.

PubMed

Hummel, T; Kobal, G; Gudziol, H; Mackay-Sim, A

2007-03-01

"Sniffin' Sticks" is a test of nasal chemosensory function that is based on pen-like odor dispensing devices, introduced some 10 years ago by Kobal and co-workers. It consists of tests for odor threshold, discrimination, and identification. Previous work established its test-retest reliability and validity. Results of the test are presented as "TDI score", the sum of results obtained for threshold, discrimination, and identification measures. While normative data have been established they are based on a relatively small number of subjects, especially with regard to subjects older than 55 years where data from only 30 healthy subjects have been used. The present study aimed to remedy this situation. Now data are available from 3,282 subjects as compared to data from 738 subjects published previously. Disregarding sex-related differences, the TDI score at the tenth percentile was 24.9 in subjects younger than 15 years, 30.3 for ages from 16 to 35 years, 27.3 for ages from 36 to 55 years, and 19.6 for subjects older than 55 years. Because the tenth percentile has been defined to separate hyposmia from normosmia, these data can be used as a guide to estimate individual olfactory ability in relation to subject's age. Absolute hyposmia was defined as the tenth percentile score of 16-35 year old subjects. Other than previous reports the present norms are also sex-differentiated with women outperforming men in the three olfactory tests. Further, the present data suggest specific changes of individual olfactory functions in relation to age, with odor thresholds declining most dramatically compared to odor discrimination and odor identification.

A low dose of three local anesthetic solutions for interscalene blockade tested by thermal quantitative sensory testing: a randomized controlled trial.

PubMed

Sermeus, Luc A; Schepens, Tom; Hans, Guy H; Morrison, Stuart G; Wouters, Kristien; Breebaart, Margaretha B; Smitz, Carine J; Vercauteren, Marcel P

2018-05-03

This randomized double-blind controlled trial compared the block characteristics of three low-dose local anesthetics at different roots in an ultrasound-guided interscalene block, using thermal quantitative sensory testing for assessing the functioning of cutaneous small nerve fibres. A total of 37 adults scheduled to undergo shoulder arthroscopy were randomized to receive 5 mL of either 0.5% levobupivacaine with and without epinephrine 1/200,000 or 0.75% ropivacaine in a single-shot interscalene block. Thermal quantitative sensory testing was performed in the C4, C5, C6 and C7 dermatomes. Detection thresholds for cold/warm sensation and cold/heat pain were measured before and at 30 min, 6, 10 and 24 h after infiltration around C5. The need for rescue medication was recorded. No significant differences between groups were found for any sensation (lowest P = 0.28). At 6 h, the largest differences in sensory thresholds were observed for the C5 dermatome. The increase in thresholds were less in C4 and C6 and minimal in C7 for all sensations. The analgesic effect lasted the longest in C5 (time × location mixed model P < 0.001 for all sensory tests). The time to rescue analgesia was significantly shorter with 0.75% ropivacaine (P = 0.02). The quantitative sensory findings showed no difference in intensity between the local anesthetics tested. A decrease in block intensity, with minimal changes in pain detection thresholds, was observed in the roots adjacent to C5, with the lowest block intensity in C7. A clinically relevant shorter duration was found with 0.75% ropivacaine compared to the other groups. Trial registration NCT 02691442.

SERIAL PERCENT-FREE PSA IN COMBINATION WITH PSA FOR POPULATION-BASED EARLY DETECTION OF PROSTATE CANCER

PubMed Central

Ankerst, Donna Pauler; Gelfond, Jonathan; Goros, Martin; Herrera, Jesus; Strobl, Andreas; Thompson, Ian M.; Hernandez, Javier; Leach, Robin J.

2016-01-01

PURPOSE To characterize the diagnostic properties of serial percent-free prostate-specific antigen (PSA) in relation to PSA in a multi-ethnic, multi-racial cohort of healthy men. MATERIALS AND METHODS 6,982 percent-free PSA and PSA measures were obtained from participants in a 12 year+ Texas screening study comprising 1625 men who never underwent biopsy, 497 who underwent one or more biopsies negative for prostate cancer, and 61 diagnosed with prostate cancer. Area underneath the receiver-operating-characteristic-curve (AUC) for percent-free PSA, and the proportion of patients with fluctuating values across multiple visits were determined according to two thresholds (under 15% versus 25%) were evaluated. The proportion of cancer cases where percent-free PSA indicated a positive test before PSA > 4 ng/mL did and the number of negative biopsies that would have been spared by percent-free PSA testing negative were computed. RESULTS Percent-free PSA fluctuated around its threshold of < 25% (< 15%) in 38.3% (78.1%), 42.2% (20.9%), and 11.4% (25.7%) of patients never biopsied, with negative and positive biopsies, respectively. At the same thresholds, percent-free PSA tested positive earlier than PSA in 71.4% (34.2%) of cancer cases, and among men with multiple negative biopsies and a PSA > 4 ng/mL, percent-free PSA would have tested negative in 31.6% (65.8%) instances. CONCLUSIONS Percent-free PSA should accompany PSA testing in order to potentially spare unnecessary biopsies or detect cancer earlier. When near the threshold, both tests should be repeated due to commonly observed fluctuation. PMID:26979652

Sensitivity and Specificity of Swedish Interactive Threshold Algorithm and Standard Full Threshold Perimetry in Primary Open-angle Glaucoma.

PubMed

Bamdad, Shahram; Beigi, Vahid; Sedaghat, Mohammad Reza

2017-01-01

Perimetry is one of the mainstays in glaucoma diagnosis and treatment. Various strategies offer different accuracies in glaucoma testing. Our aim was to determine and compare the diagnostic sensitivity and specificity of Swedish Interactive Threshold Algorithm (SITA) Fast and Standard Full Threshold (SFT) strategies of the Humphrey Field Analyzer (HFA) in identifying patients with visual field defect in glaucoma disease. This prospective observational case series study was conducted in a university-based eye hospital. A total of 37 eyes of 20 patients with glaucoma were evaluated using the central 30-2 program and both the SITA Fast and SFT strategies. Both strategies were performed for each strategy in each session and for four times in a 2-week period. Data were analyzed using the Student's t-test, analysis of variance, and chi-square test. The SITA Fast and SFT strategies had similar sensitivity of 93.3%. The specificity of SITA Fast and SFT strategies was 57.4% and 71.4% respectively. The mean duration of SFT tests was 14.6 minutes, and that of SITA Fast tests was 5.45 minutes (a statistically significant 62.5% reduction). In gray scale plots, visual field defect was less deep in SITA Fast than in SFT; however, more points had significant defect (p < 0.5% and p < 1%) in pattern deviation plots in SITA Fast than in SFT; these differences were not clinically significant. In conclusion, the SITA Fast strategy showed higher sensitivity for detection of glaucoma compared to the SFT strategy, yet with reduced specificity; however, the shorter test duration makes it a more acceptable choice in many clinical situations, especially for children, elderly, and those with musculoskeletal diseases.

Self-test web-based pure-tone audiometry: validity evaluation and measurement error analysis.

PubMed

Masalski, Marcin; Kręcicki, Tomasz

2013-04-12

Potential methods of application of self-administered Web-based pure-tone audiometry conducted at home on a PC with a sound card and ordinary headphones depend on the value of measurement error in such tests. The aim of this research was to determine the measurement error of the hearing threshold determined in the way described above and to identify and analyze factors influencing its value. The evaluation of the hearing threshold was made in three series: (1) tests on a clinical audiometer, (2) self-tests done on a specially calibrated computer under the supervision of an audiologist, and (3) self-tests conducted at home. The research was carried out on the group of 51 participants selected from patients of an audiology outpatient clinic. From the group of 51 patients examined in the first two series, the third series was self-administered at home by 37 subjects (73%). The average difference between the value of the hearing threshold determined in series 1 and in series 2 was -1.54dB with standard deviation of 7.88dB and a Pearson correlation coefficient of .90. Between the first and third series, these values were -1.35dB±10.66dB and .84, respectively. In series 3, the standard deviation was most influenced by the error connected with the procedure of hearing threshold identification (6.64dB), calibration error (6.19dB), and additionally at the frequency of 250Hz by frequency nonlinearity error (7.28dB). The obtained results confirm the possibility of applying Web-based pure-tone audiometry in screening tests. In the future, modifications of the method leading to the decrease in measurement error can broaden the scope of Web-based pure-tone audiometry application.

Contralateral Occlusion Test: The effect of external ear canal occlusion on hearing thresholds.

PubMed

Reis, Luis Roque; Fernandes, Paulo; Escada, Pedro

Bedside testing with tuning forks may decrease turnaround time and improve decision making for a quick qualitative assessment of hearing loss. The purpose of this study was to quantify the effects of ear canal occlusion on hearing, in order to decide which tuning fork frequency is more appropriate to use for quantifying hearing loss with the Contralateral Occlusion Test. Twenty normal-hearing adults (forty ears) underwent sound field pure tone audiometry with and without ear canal occlusion. Each ear was tested with the standard frequencies. The contralateral ear was suppressed with by masking. Ear occlusion was performed by two examiners. Participants aged between 21 and 30 years (25.6±3.03 years) showed an increase in hearing thresholds with increasing frequencies from 19.94dB (250Hz) to 39.25dB (2000Hz). The threshold difference between occluded and unoccluded conditions was statistically significant and increased from 10.69dB (250Hz) to 32.12dB (2000Hz). There were no statistically significant differences according to gender or between the examiners. The occlusion effect increased the hearing thresholds and became more evident with higher frequencies. The occlusion method as performed demonstrated reproducibility. In the Contralateral Occlusion Test, 256Hz or 512Hz tuning forks should be used for diagnosis of mild hearing loss, and a 2048Hz tuning fork should be used for moderate hearing loss. Copyright © 2017 Elsevier España, S.L.U. and Sociedad Española de Otorrinolaringología y Cirugía de Cabeza y Cuello. All rights reserved.

Predictive validities of several clinical color vision tests for aviation signal light gun performance.

DOT National Transportation Integrated Search

1975-01-01

Scores on the American Optical Company (AOC) test (1965 edition), Dvorine test, Farnsworth Lantern test, Color Threshold Tester, Farnsworth-Munsell 100-Hue test, Farnsworth Panel D-15 test, and Schmidt-Haensch Anomaloscope were obtained from 137 men ...

Immuno-Oncology Biomarkers for Gastric and Gastroesophageal Junction Adenocarcinoma: Why PD-L1 Testing May Not Be Enough.

PubMed

Weinberg, Benjamin A; Xiu, Joanne; Hwang, Jimmy J; Shields, Anthony F; Salem, Mohamed E; Marshall, John L

2018-04-27

The treatment of patients with advanced gastric and gastroesophageal junction (G/GEJ) adenocarcinomas has been transformed by the U.S. Food and Drug Administration approval of pembrolizumab. Tumor and adjacent tissue must stain positively for the programmed cell death ligand 1 (PD-L1) protein by companion diagnostic testing. However, some patients with PD-L1-negative tumors also benefit from pembrolizumab. High microsatellite instability (MSI) and tumor mutational load (TML) are positive predictive biomarkers for immune checkpoint inhibition (ICI) in other tumors. We sought to identify more patients who could benefit from ICI using alternative PD-L1 thresholds, MSI, and TML. Tumor specimens underwent next-generation sequencing (NGS) and PD-L1 testing using immunohistochemistry. NGS was used to determine TML and MSI. We profiled 581 G/GEJ adenocarcinoma specimens. PD-L1 staining was scored for intensity (0, none; 1+, weak; 2+, moderate; 3+, strong). Using 2+ staining at a 5% threshold, 9.3% of tumors were PD-L1 positive, and using 1+ staining at 1%, 16.2% were PD-L1 positive. 6.9% of tumors had high MSI. High TML (≥17 mutations per megabase) was seen in 6.9%, and medium TML (≥7) was seen in 56.5% of tumors. Thirty (5.2%) PD-L1-negative tumors at the 1+, 1% threshold had high TML or high MSI. Primary tumors had higher rates of high TML (8.8% vs. 3.9%; p  = .0377) and high MSI (8.5% vs. 3.9%; p  = .0471) than metastases. PD-L1 testing alone fails to detect patients who may benefit from ICI. Lower PD-L1 thresholds and TML testing should be considered in future clinical trials. Pembrolizumab is approved by the U.S. Food and Drug Administration for patients with refractory gastric and gastroesophageal cancers if the tumor and adjacent tissue stain positively for the programmed cell death ligand 1 (PD-L1) protein by companion diagnostic testing. Tumor mutational load, microsatellite instability (MSI), and alternative PD-L1 testing thresholds may serve as predictive biomarkers for response to immune checkpoint inhibition, and standard PD-L1 testing will not identify all patients who may benefit from this therapy. © AlphaMed Press 2018.

Laser-induced damage threshold tests of ultrafast multilayer dielectric coatings in various environmental conditions relevant for operation of ELI beamlines laser systems

NASA Astrophysics Data System (ADS)

Ďurák, Michal; Velpula, Praveen Kumar; Kramer, Daniel; Cupal, Josef; Medřík, Tomáš; Hřebíček, Jan; Golasowski, Jiří; Peceli, Davorin; Kozlová, Michaela; Rus, Bedřich

2017-01-01

Increasing the laser-induced damage resistance of optical components is one of the major challenges in the development of Peta-watt (PW) class laser systems. The extreme light infrastructure (ELI) beamlines project will provide ultrafast laser systems with peak powers up to 10 PW available every minute and PW class beams at 10 Hz complemented by a 5-TW, 1-kHz beamline. Sustainable performance of PW class laser systems relies on the durability of the employed optical components. As part of an effort to evaluate the damage resistance of components utilized in ELI beamlines systems, damage thresholds of several optical multilayer dielectric coatings were measured with different laser parameters and in different environments. Three coatings were tested with 10 Hz and 1 kHz pulse repetition rates, and the effect of a cleaning treatment on their damage resistance was examined. To explore the damage threshold behavior at different vacuum levels, one coating was subject to tests at various residual gas pressures. No change of damage threshold in a high vacuum with respect to ambient pressure was recorded. The effect of the cleaning treatment was found to be inconsistent, suggesting that development of the optimal cleaning treatment for a given coating requires consideration of its specific properties.

A comparison of auditory brainstem responses across diving bird species

USGS Publications Warehouse

Crowell, Sara E.; Berlin, Alicia; Carr, Catherine E.; Olsen, Glenn H.; Therrien, Ronald E.; Yannuzzi, Sally E.; Ketten, Darlene R.

2015-01-01

There is little biological data available for diving birds because many live in hard-to-study, remote habitats. Only one species of diving bird, the black-footed penguin (Spheniscus demersus), has been studied in respect to auditory capabilities (Wever et al., Proc Natl Acad Sci USA 63:676–680, 1969). We, therefore, measured in-air auditory threshold in ten species of diving birds, using the auditory brainstem response (ABR). The average audiogram obtained for each species followed the U-shape typical of birds and many other animals. All species tested shared a common region of the greatest sensitivity, from 1000 to 3000 Hz, although audiograms differed significantly across species. Thresholds of all duck species tested were more similar to each other than to the two non-duck species tested. The red-throated loon (Gavia stellata) and northern gannet (Morus bassanus) exhibited the highest thresholds while the lowest thresholds belonged to the duck species, specifically the lesser scaup (Aythya affinis) and ruddy duck (Oxyura jamaicensis). Vocalization parameters were also measured for each species, and showed that with the exception of the common eider (Somateria mollisima), the peak frequency, i.e., frequency at the greatest intensity, of all species' vocalizations measured here fell between 1000 and 3000 Hz, matching the bandwidth of the most sensitive hearing range.

A comparison of auditory brainstem responses across diving bird species

PubMed Central

Crowell, Sara E.; Wells-Berlin, Alicia M.; Carr, Catherine E.; Olsen, Glenn H.; Therrien, Ronald E.; Yannuzzi, Sally E.; Ketten, Darlene R.

2015-01-01

There is little biological data available for diving birds because many live in hard-to-study, remote habitats. Only one species of diving bird, the black-footed penguin (Spheniscus demersus), has been studied in respect to auditory capabilities (Wever et al. 1969). We therefore measured in-air auditory threshold in ten species of diving birds, using the auditory brainstem response (ABR). The average audiogram obtained for each species followed the U-shape typical of birds and many other animals. All species tested shared a common region of greatest sensitivity, from 1000 to 3000 Hz, although audiograms differed significantly across species. Thresholds of all duck species tested were more similar to each other than to the two non-duck species tested. The red-throated loon (Gavia stellata) and northern gannet (Morus bassanus) exhibited the highest thresholds while the lowest thresholds belonged to the duck species, specifically the lesser scaup (Aythya affinis) and ruddy duck (Oxyura jamaicensis). Vocalization parameters were also measured for each species, and showed that with the exception of the common eider (Somateria mollisima), the peak frequency, i.e. frequency at the greatest intensity, of all species’ vocalizations measured here fell between 1000 and 3000 Hz, matching the bandwidth of the most sensitive hearing range. PMID:26156644

No effects of hydrocortisone and dexamethasone on pain sensitivity in healthy individuals.

PubMed

Wingenfeld, K; Wolf, S; Kunz, M; Krieg, J-C; Lautenbacher, S

2015-07-01

There is some evidence that stress-induced cortisol increase leads to a decrease in pain, while lowering cortisol levels enhances pain sensitivity, but no study has yet investigated both pharmacological enhancement and reduction of cortisol levels in the same individuals. Firstly, we tested in 16 healthy individuals whether the treatment with hydrocortisone and dexamethasone, respectively, results in altered pain thresholds. Secondly, we aimed to test whether hormone effects are different across the pain range by using ratings for pain stimuli with varying intensity; and thirdly, we tested whether cortisol levels influence the discrimination ability for painful stimuli. Despite substantial effects of dexamethasone and hydrocortisone administration on cortisol levels, no effect of these drugs was seen in terms of pain sensitivity (pain threshold, pain rating, pain discrimination ability), although comprehensively examined. However, in the placebo condition, a significant negative correlation between cortisol and pain thresholds was seen. Similarly, there were also strong negative associations between cortisol levels in the placebo condition and pain thresholds after drug treatment (especially after hydrocortisone). These findings suggest that short-term variations of cortisol do not influence pain sensitivity whereas, in general, high levels of cortisol are associated with increased pain sensitivity, at least for weak to moderate stimuli. © 2014 European Pain Federation - EFIC®

Association between the electromyographic fatigue threshold and ventilatory threshold.

PubMed

Camata, T V; Lacerda, T R; Altimari, L R; Bortolloti, H; Fontes, E B; Dantas, J L; Nakamura, F Y; Abrão, T; Chacon-Mikahil, M P T; Moraes, A C

2009-01-01

The objective of this study is to verify the coincidence between the occurrence of the electromyographic fatigue threshold (EMGth) and the ventilatory threshold (Vth) in an incremental test in the cyclosimulator, as well as to compare the calculation of the RMS from the EMG signal using different time windows. Thirteen male cyclists (73.7 +/- 12.4 kg and 174.3 +/- 6.2 cm) performed a ramp incremental test (TI) in a cyclosimulator until voluntary exhaustion. Before the start of each TI subjects had the active bipolar electrodes placed over the superficial muscles of the quadriceps femoris (QF) of the right leg: rectus femoris (RF), vastus medialis (VM) and vastus lateralis (VL). The paired student's t test, pearson's correlation coefficient and the analysis method described by Bland and Altman for the determination of the concordance level were used for statistical analysis. The significance level adopted was P < 0.05. Although no significant differences were found between Vth and the EMGth calculated from windows of 2, 5, 10, 30 and 60 seconds in the studied muscles, it is suggested that the EMGth values determined from the calculation of the RMS curve with windows of 5 and 10 seconds seem to be more appropriate for the calculation of the RMS curve and determination of EMGth from visual inspection.

Non-invasive indices for the estimation of the anaerobic threshold of oarsmen.

PubMed

Erdogan, A; Cetin, C; Karatosun, H; Baydar, M L

2010-01-01

This study compared four common non-invasive indices with an invasive index for determining the anaerobic threshold (AT) in 22 adult male rowers using a Concept2 rowing ergometer. A criterion-standard progressive incremental test (invasive method) measured blood lactate concentrations to determine the 4 mmol/l threshold (La4-AT) and Dmax AT (Dm-AT). This was compared with three indices obtained by analysis of respiratory gases and one that was based on the heart rate (HR) deflection point (HRDP) all of which used the Conconi test (non-invasive methods). In the Conconi test, the HRDP was determined whilst continuously increasing the power output (PO) by 25 W/min and measuring respiratory gases and HR. The La4-AT and Dm-AT values differed slightly with respect to oxygen uptake, PO and HR however, AT values significantly correlated with each other and with the four non-invasive methods. In conclusion, the non-invasive indices were comparable with the invasive index and could, therefore, be used in the assessment of AT during rowing ergometer use. In this population of elite rowers, Conconi threshold (Con-AT), based on the measurement of HRDP tended to be the most adequate way of estimating AT for training regulation purposes.

The Harvard Beat Assessment Test (H-BAT): a battery for assessing beat perception and production and their dissociation.

PubMed

Fujii, Shinya; Schlaug, Gottfried

2013-01-01

Humans have the abilities to perceive, produce, and synchronize with a musical beat, yet there are widespread individual differences. To investigate these abilities and to determine if a dissociation between beat perception and production exists, we developed the Harvard Beat Assessment Test (H-BAT), a new battery that assesses beat perception and production abilities. H-BAT consists of four subtests: (1) music tapping test (MTT), (2) beat saliency test (BST), (3) beat interval test (BIT), and (4) beat finding and interval test (BFIT). MTT measures the degree of tapping synchronization with the beat of music, whereas BST, BIT, and BFIT measure perception and production thresholds via psychophysical adaptive stair-case methods. We administered the H-BAT on thirty individuals and investigated the performance distribution across these individuals in each subtest. There was a wide distribution in individual abilities to tap in synchrony with the beat of music during the MTT. The degree of synchronization consistency was negatively correlated with thresholds in the BST, BIT, and BFIT: a lower degree of synchronization was associated with higher perception and production thresholds. H-BAT can be a useful tool in determining an individual's ability to perceive and produce a beat within a single session.

The Harvard Beat Assessment Test (H-BAT): a battery for assessing beat perception and production and their dissociation

PubMed Central

Fujii, Shinya; Schlaug, Gottfried

2013-01-01

Humans have the abilities to perceive, produce, and synchronize with a musical beat, yet there are widespread individual differences. To investigate these abilities and to determine if a dissociation between beat perception and production exists, we developed the Harvard Beat Assessment Test (H-BAT), a new battery that assesses beat perception and production abilities. H-BAT consists of four subtests: (1) music tapping test (MTT), (2) beat saliency test (BST), (3) beat interval test (BIT), and (4) beat finding and interval test (BFIT). MTT measures the degree of tapping synchronization with the beat of music, whereas BST, BIT, and BFIT measure perception and production thresholds via psychophysical adaptive stair-case methods. We administered the H-BAT on thirty individuals and investigated the performance distribution across these individuals in each subtest. There was a wide distribution in individual abilities to tap in synchrony with the beat of music during the MTT. The degree of synchronization consistency was negatively correlated with thresholds in the BST, BIT, and BFIT: a lower degree of synchronization was associated with higher perception and production thresholds. H-BAT can be a useful tool in determining an individual's ability to perceive and produce a beat within a single session. PMID:24324421

STIMULUS AND TRANSDUCER EFFECTS ON THRESHOLD

PubMed Central

Flamme, Gregory A.; Geda, Kyle; McGregor, Kara; Wyllys, Krista; Deiters, Kristy K.; Murphy, William J.; Stephenson, Mark R.

2015-01-01

Objective This study examined differences in thresholds obtained under Sennheiser HDA200 circumaural earphones using pure tone, equivalent rectangular noise bands, and 1/3 octave noise bands relative to thresholds obtained using Telephonics TDH-39P supra-aural earphones. Design Thresholds were obtained via each transducer and stimulus condition six times within a 10-day period. Study Sample Forty-nine adults were selected from a prior study to represent low, moderate, and high threshold reliability. Results The results suggested that (1) only small adjustments were needed to reach equivalent TDH-39P thresholds, (2) pure-tone thresholds obtained with HDA200 circumaural earphones had reliability equal to or better than those obtained using TDH-39P earphones, (3) the reliability of noise-band thresholds improved with broader stimulus bandwidth and was either equal to or better than pure-tone thresholds, and (4) frequency-specificity declined with stimulus bandwidths greater than one Equivalent Rectangular Band, which could complicate early detection of hearing changes that occur within a narrow frequency range. Conclusions These data suggest that circumaural earphones such as the HDA200 headphones provide better reliability for audiometric testing as compared to the TDH-39P earphones. These data support the use of noise bands, preferably ERB noises, as stimuli for audiometric monitoring. PMID:25549164

Patterns of threshold evolution in polyphenic insects under different developmental models.

PubMed

Tomkins, Joseph L; Moczek, Armin P

2009-02-01

Two hypotheses address the evolution of polyphenic traits in insects. Under the developmental reprogramming model, individuals exceeding a threshold follow a different developmental pathway from individuals below the threshold. This decoupling is thought to free selection to independently hone alternative morphologies, increasing phenotypic plasticity and morphological diversity. Under the alternative model, extreme positive allometry explains the existence of alternative phenotypes and divergent phenotypes are developmentally coupled by a continuous reaction norm, such that selection on either morph acts on both. We test the hypothesis that continuous reaction norm polyphenisms, evolve through changes in the allometric parameters of even the smallest males with minimal trait expression, whereas threshold polyphenisms evolve independent of the allometric parameters of individuals below the threshold. We compare two polyphenic species; the dung beetle Onthophagus taurus, whose allometry has been modeled both as a threshold polyphenism and a continuous reaction norm and the earwig Forficula auricularia, whose allometry is best modeled with a discontinuous threshold. We find that across populations of both species, variation in forceps or horn allometry in minor males are correlated to the population's threshold. These findings suggest that regardless of developmental mode, alternative morphs do not evolve independently of one another.

A factorization approach to next-to-leading-power threshold logarithms

NASA Astrophysics Data System (ADS)

Bonocore, D.; Laenen, E.; Magnea, L.; Melville, S.; Vernazza, L.; White, C. D.

2015-06-01

Threshold logarithms become dominant in partonic cross sections when the selected final state forces gluon radiation to be soft or collinear. Such radiation factorizes at the level of scattering amplitudes, and this leads to the resummation of threshold logarithms which appear at leading power in the threshold variable. In this paper, we consider the extension of this factorization to include effects suppressed by a single power of the threshold variable. Building upon the Low-Burnett-Kroll-Del Duca (LBKD) theorem, we propose a decomposition of radiative amplitudes into universal building blocks, which contain all effects ultimately responsible for next-to-leading-power (NLP) threshold logarithms in hadronic cross sections for electroweak annihilation processes. In particular, we provide a NLO evaluation of the radiative jet function, responsible for the interference of next-to-soft and collinear effects in these cross sections. As a test, using our expression for the amplitude, we reproduce all abelian-like NLP threshold logarithms in the NNLO Drell-Yan cross section, including the interplay of real and virtual emissions. Our results are a significant step towards developing a generally applicable resummation formalism for NLP threshold effects, and illustrate the breakdown of next-to-soft theorems for gauge theory amplitudes at loop level.

Kv1 channels control spike threshold dynamics and spike timing in cortical pyramidal neurones

PubMed Central

Higgs, Matthew H; Spain, William J

2011-01-01

Abstract Previous studies showed that cortical pyramidal neurones (PNs) have a dynamic spike threshold that functions as a high-pass filter, enhancing spike timing in response to high-frequency input. While it is commonly assumed that Na+ channel inactivation is the primary mechanism of threshold accommodation, the possible role of K+ channel activation in fast threshold changes has not been well characterized. The present study tested the hypothesis that low-voltage activated Kv1 channels affect threshold dynamics in layer 2–3 PNs, using α-dendrotoxin (DTX) or 4-aminopyridine (4-AP) to block these conductances. We found that Kv1 blockade reduced the dynamic changes of spike threshold in response to a variety of stimuli, including stimulus-evoked synaptic input, current steps and ramps of varied duration, and noise. Analysis of the responses to noise showed that Kv1 channels increased the coherence of spike output with high-frequency components of the stimulus. A simple model demonstrates that a dynamic spike threshold can account for this effect. Our results show that the Kv1 conductance is a major mechanism that contributes to the dynamic spike threshold and precise spike timing of cortical PNs. PMID:21911608

Active damping of the e-p instability at the Los Alamos Proton Storage Ring

NASA Astrophysics Data System (ADS)

Macek, R. J.; Assadi, S.; Byrd, J. M.; Deibele, C. E.; Henderson, S. D.; Lee, S. Y.; McCrady, R. C.; Pivi, M. F. T.; Plum, M. A.; Walbridge, S. B.; Zaugg, T. J.

2007-12-01

A prototype of an analog, transverse (vertical) feedback system for active damping of the two-stream (e-p) instability has been developed and successfully tested at the Los Alamos Proton Storage Ring (PSR). This system was able to improve the instability threshold by approximately 30% (as measured by the change in RF buncher voltage at instability threshold). The feedback system configuration, setup procedures, and optimization of performance are described. Results of several experimental tests of system performance are presented including observations of instability threshold improvement and grow-damp experiments, which yield estimates of instability growth and damping rates. A major effort was undertaken to identify and study several factors limiting system performance. Evidence obtained from these tests suggests that performance of the prototype was limited by higher instability growth rates arising from beam leakage into the gap at lower RF buncher voltage and the onset of instability in the horizontal plane, which had no feedback.

Detection of impact damage on thermal protection systems using thin-film piezoelectric sensors for integrated structural health monitoring

NASA Astrophysics Data System (ADS)

Na, Jeong K.; Kuhr, Samuel J.; Jata, Kumar V.

2008-03-01

Thermal Protection Systems (TPS) can be subjected to impact damage during flight and/or during ground maintenance and/or repair. AFRL/RXLP is developing a reliable and robust on-board sensing/monitoring capability for next generation thermal protection systems to detect and assess impact damage. This study was focused on two classes of metallic thermal protection tiles to determine threshold for impact damage and develop sensing capability of the impacts. Sensors made of PVDF piezoelectric film were employed and tested to evaluate the detectability of impact signals and assess the onset or threshold of impact damage. Testing was performed over a range of impact energy levels, where the sensors were adhered to the back of the specimens. The PVDF signal levels were analyzed and compared to assess damage, where digital microscopy, visual inspection, and white light interferometry were used for damage verification. Based on the impact test results, an assessment of the impact damage thresholds for each type of metallic TPS system was made.

Eagle-eyed visual acuity: an experimental investigation of enhanced perception in autism.

PubMed

Ashwin, Emma; Ashwin, Chris; Rhydderch, Danielle; Howells, Jessica; Baron-Cohen, Simon

2009-01-01

Anecdotal accounts of sensory hypersensitivity in individuals with autism spectrum conditions (ASC) have been noted since the first reports of the condition. Over time, empirical evidence has supported the notion that those with ASC have superior visual abilities compared with control subjects. However, it remains unclear whether these abilities are specifically the result of differences in sensory thresholds (low-level processing), rather than higher-level cognitive processes. This study investigates visual threshold in n = 15 individuals with ASC and n = 15 individuals without ASC, using a standardized optometric test, the Freiburg Visual Acuity and Contrast Test, to investigate basic low-level visual acuity. Individuals with ASC have significantly better visual acuity (20:7) compared with control subjects (20:13)-acuity so superior that it lies in the region reported for birds of prey. The results of this study suggest that inclusion of sensory hypersensitivity in the diagnostic criteria for ASC may be warranted and that basic standardized tests of sensory thresholds may inform causal theories of ASC.

Threshold and channel interaction in cochlear implant users: evaluation of the tripolar electrode configuration.

PubMed

Bierer, Julie Arenberg

2007-03-01

The efficacy of cochlear implants is limited by spatial and temporal interactions among channels. This study explores the spatially restricted tripolar electrode configuration and compares it to bipolar and monopolar stimulation. Measures of threshold and channel interaction were obtained from nine subjects implanted with the Clarion HiFocus-I electrode array. Stimuli were biphasic pulses delivered at 1020 pulses/s. Threshold increased from monopolar to bipolar to tripolar stimulation and was most variable across channels with the tripolar configuration. Channel interaction, quantified by the shift in threshold between single- and two-channel stimulation, occurred for all three configurations but was largest for the monopolar and simultaneous conditions. The threshold shifts with simultaneous tripolar stimulation were slightly smaller than with bipolar and were not as strongly affected by the timing of the two channel stimulation as was monopolar. The subjects' performances on clinical speech tests were correlated with channel-to-channel variability in tripolar threshold, such that greater variability was related to poorer performance. The data suggest that tripolar channels with high thresholds may reveal cochlear regions of low neuron survival or poor electrode placement.

Field hearing measurements of the Atlantic sharpnose shark Rhizoprionodon terraenovae.

PubMed

Casper, B M; Mann, D A

2009-12-01

Field measurements of hearing thresholds were obtained from the Atlantic sharpnose shark Rhizoprionodon terraenovae using the auditory evoked potential method (AEP). The fish had most sensitive hearing at 20 Hz, the lowest frequency tested, with decreasing sensitivity at higher frequencies. Hearing thresholds were lower than AEP thresholds previously measured for the nurse shark Ginglymostoma cirratum and yellow stingray Urobatis jamaicensis at frequencies <200 Hz, and similar at 200 Hz and above. Rhizoprionodon terraenovae represents the closest comparison in terms of pelagic lifestyle to the sharks which have been observed in acoustic field attraction experiments. The sound pressure levels that would be equivalent to the particle acceleration thresholds of R. terraenovae were much higher than the sound levels which attracted closely related sharks suggesting a discrepancy between the hearing threshold experiments and the field attraction experiments.

Detecting wood surface defects with fusion algorithm of visual saliency and local threshold segmentation

NASA Astrophysics Data System (ADS)

Wang, Xuejuan; Wu, Shuhang; Liu, Yunpeng

2018-04-01

This paper presents a new method for wood defect detection. It can solve the over-segmentation problem existing in local threshold segmentation methods. This method effectively takes advantages of visual saliency and local threshold segmentation. Firstly, defect areas are coarsely located by using spectral residual method to calculate global visual saliency of them. Then, the threshold segmentation of maximum inter-class variance method is adopted for positioning and segmenting the wood surface defects precisely around the coarse located areas. Lastly, we use mathematical morphology to process the binary images after segmentation, which reduces the noise and small false objects. Experiments on test images of insect hole, dead knot and sound knot show that the method we proposed obtains ideal segmentation results and is superior to the existing segmentation methods based on edge detection, OSTU and threshold segmentation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carmichael, Joshua D.; Hartse, Hans

Colocated explosive sources often produce correlated seismic waveforms. Multichannel correlation detectors identify these signals by scanning template waveforms recorded from known reference events against "target" data to find similar waveforms. This screening problem is challenged at thresholds required to monitor smaller explosions, often because non-target signals falsely trigger such detectors. Therefore, it is generally unclear what thresholds will reliably identify a target explosion while screening non-target background seismicity. Here, we estimate threshold magnitudes for hypothetical explosions located at the North Korean nuclear test site over six months of 2010, by processing International Monitoring System (IMS) array data with a multichannelmore » waveform correlation detector. Our method (1) accounts for low amplitude background seismicity that falsely triggers correlation detectors but is unidentifiable with conventional power beams, (2) adapts to diurnally variable noise levels and (3) uses source-receiver reciprocity concepts to estimate thresholds for explosions spatially separated from the template source. Furthermore, we find that underground explosions with body wave magnitudes m b = 1.66 are detectable at the IMS array USRK with probability 0.99, when using template waveforms consisting only of P -waves, without false alarms. We conservatively find that these thresholds also increase by up to a magnitude unit for sources located 4 km or more from the Feb.12, 2013 announced nuclear test.« less

Measures for assessing architectural speech security (privacy) of closed offices and meeting rooms.

PubMed

Gover, Bradford N; Bradley, John S

2004-12-01

Objective measures were investigated as predictors of the speech security of closed offices and rooms. A new signal-to-noise type measure is shown to be a superior indicator for security than existing measures such as the Articulation Index, the Speech Intelligibility Index, the ratio of the loudness of speech to that of noise, and the A-weighted level difference of speech and noise. This new measure is a weighted sum of clipped one-third-octave-band signal-to-noise ratios; various weightings and clipping levels are explored. Listening tests had 19 subjects rate the audibility and intelligibility of 500 English sentences, filtered to simulate transmission through various wall constructions, and presented along with background noise. The results of the tests indicate that the new measure is highly correlated with sentence intelligibility scores and also with three security thresholds: the threshold of intelligibility (below which speech is unintelligible), the threshold of cadence (below which the cadence of speech is inaudible), and the threshold of audibility (below which speech is inaudible). The ratio of the loudness of speech to that of noise, and simple A-weighted level differences are both shown to be well correlated with these latter two thresholds (cadence and audibility), but not well correlated with intelligibility.

Modulation by alpha-difluoromethyl-ornithine and aminoguanidine of pain threshold, morphine analgesia and tolerance.

PubMed

Lu, Gang; Su, Rui-Bin; Li, Jin; Qin, Bo-Yi

2003-10-08

The effects of alpha-difluoromethyl-ornithine (DFMO) and aminoguanidine, which might influence the metabolism of endogenous agmatine, on pain threshold, morphine analgesia and tolerance were investigated in mice. In the mouse acetic acid writhing test, intracerebroventricular (i.c.v.) injection of DFMO or aminoguanidine significantly elevated the pain threshold as indicated by a decrease in the number of writhings. DFMO or aminoguanidine obviously increased the analgesic effect of morphine in the mouse acetic acid writhing test and the mouse heat radiation tail-flick assay. These effects of DFMO and aminoguanidine were antagonized by idazoxan (3 mg/kg, i.p.), which is a selective antagonist of the imidazoline receptor. In the mouse heat radiation tail-flick assay, aminoguanidine significantly prolonged the tail-flick latency of animals, suggesting that the pain threshold was elevated. Furthermore, both DFMO and aminoguanidine enhanced morphine analgesia and inhibited acute morphine tolerance in the mouse heat radiation tail-flick assay. Neither DFMO nor aminoguanidine inhibited the activity of nitric oxide synthase in different brain areas in mice in vivo. These results indicate that the substances involved in the metabolism of endogenous agmatine could modulate the pain threshold, morphine analgesia and tolerance, indicating the possible role of endogenous agmatine in the pharmacological effects of morphine.

Normal Perceptual Sensitivity Arising From Weakly Reflective Cone Photoreceptors

PubMed Central

Bruce, Kady S.; Harmening, Wolf M.; Langston, Bradley R.; Tuten, William S.; Roorda, Austin; Sincich, Lawrence C.

2015-01-01

Purpose To determine the light sensitivity of poorly reflective cones observed in retinas of normal subjects, and to establish a relationship between cone reflectivity and perceptual threshold. Methods Five subjects (four male, one female) with normal vision were imaged longitudinally (7–26 imaging sessions, representing 82–896 days) using adaptive optics scanning laser ophthalmoscopy (AOSLO) to monitor cone reflectance. Ten cones with unusually low reflectivity, as well as 10 normally reflective cones serving as controls, were targeted for perceptual testing. Cone-sized stimuli were delivered to the targeted cones and luminance increment thresholds were quantified. Thresholds were measured three to five times per session for each cone in the 10 pairs, all located 2.2 to 3.3° from the center of gaze. Results Compared with other cones in the same retinal area, three of 10 monitored dark cones were persistently poorly reflective, while seven occasionally manifested normal reflectance. Tested psychophysically, all 10 dark cones had thresholds comparable with those from normally reflecting cones measured concurrently (P = 0.49). The variation observed in dark cone thresholds also matched the wide variation seen in a large population (n = 56 cone pairs, six subjects) of normal cones; in the latter, no correlation was found between cone reflectivity and threshold (P = 0.0502). Conclusions Low cone reflectance cannot be used as a reliable indicator of cone sensitivity to light in normal retinas. To improve assessment of early retinal pathology, other diagnostic criteria should be employed along with imaging and cone-based microperimetry. PMID:26193919

An adaptive design for updating the threshold value of a continuous biomarker

PubMed Central

Spencer, Amy V.; Harbron, Chris; Mander, Adrian; Wason, James; Peers, Ian

2017-01-01

Potential predictive biomarkers are often measured on a continuous scale, but in practice, a threshold value to divide the patient population into biomarker ‘positive’ and ‘negative’ is desirable. Early phase clinical trials are increasingly using biomarkers for patient selection, but at this stage, it is likely that little will be known about the relationship between the biomarker and the treatment outcome. We describe a single-arm trial design with adaptive enrichment, which can increase power to demonstrate efficacy within a patient subpopulation, the parameters of which are also estimated. Our design enables us to learn about the biomarker and optimally adjust the threshold during the study, using a combination of generalised linear modelling and Bayesian prediction. At the final analysis, a binomial exact test is carried out, allowing the hypothesis that ‘no population subset exists in which the novel treatment has a desirable response rate’ to be tested. Through extensive simulations, we are able to show increased power over fixed threshold methods in many situations without increasing the type-I error rate. We also show that estimates of the threshold, which defines the population subset, are unbiased and often more precise than those from fixed threshold studies. We provide an example of the method applied (retrospectively) to publically available data from a study of the use of tamoxifen after mastectomy by the German Breast Study Group, where progesterone receptor is the biomarker of interest. PMID:27417407

Measurement and interpretation of threshold stress intensity factors for steels in high-pressure hydrogen gas.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dadfarnia, Mohsen; Nibur, Kevin A.; San Marchi, Christopher W.

2010-07-01

Threshold stress intensity factors were measured in high-pressure hydrogen gas for a variety of low alloy ferritic steels using both constant crack opening displacement and rising crack opening displacement procedures. The sustained load cracking procedures are generally consistent with those in ASME Article KD-10 of Section VIII Division 3 of the Boiler and Pressure Vessel Code, which was recently published to guide design of high-pressure hydrogen vessels. Three definitions of threshold were established for the two test methods: K{sub THi}* is the maximum applied stress intensity factor for which no crack extension was observed under constant displacement; K{sub THa} ismore » the stress intensity factor at the arrest position for a crack that extended under constant displacement; and K{sub JH} is the stress intensity factor at the onset of crack extension under rising displacement. The apparent crack initiation threshold under constant displacement, K{sub THi}*, and the crack arrest threshold, K{sub THa}, were both found to be non-conservative due to the hydrogen exposure and crack-tip deformation histories associated with typical procedures for sustained-load cracking tests under constant displacement. In contrast, K{sub JH}, which is measured under concurrent rising displacement and hydrogen gas exposure, provides a more conservative hydrogen-assisted fracture threshold that is relevant to structural components in which sub-critical crack extension is driven by internal hydrogen gas pressure.« less

Measurement and interpretation of threshold stress intensity factors for steels in high-pressure hydrogen gas.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nibur, Kevin A.

2010-11-01

Threshold stress intensity factors were measured in high-pressure hydrogen gas for a variety of low alloy ferritic steels using both constant crack opening displacement and rising crack opening displacement procedures. The sustained load cracking procedures are generally consistent with those in ASME Article KD-10 of Section VIII Division 3 of the Boiler and Pressure Vessel Code, which was recently published to guide design of high-pressure hydrogen vessels. Three definitions of threshold were established for the two test methods: K{sub THi}* is the maximum applied stress intensity factor for which no crack extension was observed under constant displacement; K{sub THa} ismore » the stress intensity factor at the arrest position for a crack that extended under constant displacement; and K{sub JH} is the stress intensity factor at the onset of crack extension under rising displacement. The apparent crack initiation threshold under constant displacement, K{sub THi}*, and the crack arrest threshold, K{sub THa}, were both found to be non-conservative due to the hydrogen exposure and crack-tip deformation histories associated with typical procedures for sustained-load cracking tests under constant displacement. In contrast, K{sub JH}, which is measured under concurrent rising displacement and hydrogen gas exposure, provides a more conservative hydrogen-assisted fracture threshold that is relevant to structural components in which sub-critical crack extension is driven by internal hydrogen gas pressure.« less

A bottom-up approach in estimating the measurement uncertainty and other important considerations for quantitative analyses in drug testing for horses.

PubMed

Leung, Gary N W; Ho, Emmie N M; Kwok, W Him; Leung, David K K; Tang, Francis P W; Wan, Terence S M; Wong, April S Y; Wong, Colton H F; Wong, Jenny K Y; Yu, Nola H

2007-09-07

Quantitative determination, particularly for threshold substances in biological samples, is much more demanding than qualitative identification. A proper assessment of any quantitative determination is the measurement uncertainty (MU) associated with the determined value. The International Standard ISO/IEC 17025, "General requirements for the competence of testing and calibration laboratories", has more prescriptive requirements on the MU than its superseded document, ISO/IEC Guide 25. Under the 2005 or 1999 versions of the new standard, an estimation of the MU is mandatory for all quantitative determinations. To comply with the new requirement, a protocol was established in the authors' laboratory in 2001. The protocol has since evolved based on our practical experience, and a refined version was adopted in 2004. This paper describes our approach in establishing the MU, as well as some other important considerations, for the quantification of threshold substances in biological samples as applied in the area of doping control for horses. The testing of threshold substances can be viewed as a compliance test (or testing to a specified limit). As such, it should only be necessary to establish the MU at the threshold level. The steps in a "Bottom-Up" approach adopted by us are similar to those described in the EURACHEM/CITAC guide, "Quantifying Uncertainty in Analytical Measurement". They involve first specifying the measurand, including the relationship between the measurand and the input quantities upon which it depends. This is followed by identifying all applicable uncertainty contributions using a "cause and effect" diagram. The magnitude of each uncertainty component is then calculated and converted to a standard uncertainty. A recovery study is also conducted to determine if the method bias is significant and whether a recovery (or correction) factor needs to be applied. All standard uncertainties with values greater than 30% of the largest one are then used to derive the combined standard uncertainty. Finally, an expanded uncertainty is calculated at 99% one-tailed confidence level by multiplying the standard uncertainty with an appropriate coverage factor (k). A sample is considered positive if the determined concentration of the threshold substance exceeds its threshold by the expanded uncertainty. In addition, other important considerations, which can have a significant impact on quantitative analyses, will be presented.

Bayesian estimation of sensitivity and specificity of a milk pregnancy-associated glycoprotein-based ELISA and of transrectal ultrasonographic exam for diagnosis of pregnancy at 28-45 days following breeding in dairy cows.

PubMed

Dufour, Simon; Durocher, Jean; Dubuc, Jocelyn; Dendukuri, Nandini; Hassan, Shereen; Buczinski, Sébastien

2017-05-01

Using a milk sample for pregnancy diagnosis in dairy cattle is extremely convenient due to the low technical inputs required for collection of biological materials. Determining accuracy of a novel pregnancy diagnostic test that relies on a milk sample is, however, difficult since no gold standard test is available for comparison. The objective of the current study was to estimate diagnostic accuracy of the milk PAG-based ELISA and of transrectal ultrasonographic (TUS) exam for determining pregnancy status of individual dairy cows using a methodology suited for test validation in the absence of gold standard. Secondary objectives were to evaluate whether test accuracy varies with cow's characteristics and to identify the optimal ELISA optical density threshold for PAG test interpretation. Cows (n=519) from 18 commercial dairies tested with both TUS and PAG between 28 and 45days following breeding were included in the study. Other covariates (number of days since breeding, parity, and daily milk production) hypothesized to affect TUS or PAG test accuracy were measured. A Bayesian hierarchical latent class model (LCM) methodology assuming conditional independence between tests was used to obtain estimates of tests' sensitivities (Se) and specificities (Sp), to evaluate impact of covariates on these, and to compute misclassification costs across a range of ELISA thresholds. Very little disagreement was observed between tests with only 23 cows yielding discordant results. Using the LCM model with non-informative priors for tests accuracy parameters, median (95% credibility intervals [CI]) TUS Se and Sp estimates of 0.96 (0.91, 1.00) and 0.99 (0.97, 1.0) were obtained. For the PAG test, median (95% CI) Se of 0.99 (0.98, 1.00) and Sp of 0.95 (0.89, 1.0) were observed. The impact of adjusting for conditional dependence between tests was negligible. Test accuracy of the PAG test varied slightly by parity number. When assuming false negative to false positive costs ratio≥3:1, the optimal ELISA optical density threshold allowing minimization of misclassification costs was 0.25. In conclusion, both TUS and PAG showed excellent accuracy for pregnancy diagnosis in dairy cows. When using the PAG test, a threshold of 0.25 could be used for test interpretation. Copyright © 2017 Elsevier B.V. All rights reserved.

Digital music exposure reliably induces temporary threshold shift in normal-hearing human subjects.

PubMed

Le Prell, Colleen G; Dell, Shawna; Hensley, Brittany; Hall, James W; Campbell, Kathleen C M; Antonelli, Patrick J; Green, Glenn E; Miller, James M; Guire, Kenneth

2012-01-01

One of the challenges for evaluating new otoprotective agents for potential benefit in human populations is the availability of an established clinical paradigm with real-world relevance. These studies were explicitly designed to develop a real-world digital music exposure that reliably induces temporary threshold shift (TTS) in normal-hearing human subjects. Thirty-three subjects participated in studies that measured effects of digital music player use on hearing. Subjects selected either rock or pop music, which was then presented at 93 to 95 (n = 10), 98 to 100 (n = 11), or 100 to 102 (n = 12) dBA in-ear exposure level for a period of 4 hr. Audiograms and distortion product otoacoustic emissions (DPOAEs) were measured before and after music exposure. Postmusic tests were initiated 15 min, 1 hr 15 min, 2 hr 15 min, and 3 hr 15 min after the exposure ended. Additional tests were conducted the following day and 1 week later. Changes in thresholds after the lowest-level exposure were difficult to distinguish from test-retest variability; however, TTS was reliably detected after higher levels of sound exposure. Changes in audiometric thresholds had a "notch" configuration, with the largest changes observed at 4 kHz (mean = 6.3 ± 3.9 dB; range = 0-14 dB). Recovery was largely complete within the first 4 hr postexposure, and all subjects showed complete recovery of both thresholds and DPOAE measures when tested 1 week postexposure. These data provide insight into the variability of TTS induced by music-player use in a healthy, normal-hearing, young adult population, with music playlist, level, and duration carefully controlled. These data confirm the likelihood of temporary changes in auditory function after digital music-player use. Such data are essential for the development of a human clinical trial protocol that provides a highly powered design for evaluating novel therapeutics in human clinical trials. Care must be taken to fully inform potential subjects in future TTS studies, including protective agent evaluations, that some noise exposures have resulted in neural degeneration in animal models, even when both audiometric thresholds and DPOAE levels returned to pre-exposure values.

Comparison of field olfactometers in a controlled chamber using hydrogen sulfide as the test odorant.

PubMed

McGinley, M A; McGinley, C M

2004-01-01

A standard method for measuring and quantifying odour in the ambient air utilizes a portable odour detecting and measuring device known as a field olfactometer (US Public Health Service Project Grant A-58-541). The field olfactometer dynamically dilutes the ambient air with carbon-filtered air in distinct ratios known as "Dilutions-to-Threshold" dilution factors (D/Ts), i.e. 2, 4, 7, 15, etc. Thirteen US states and several cities in North America currently utilize field olfactometry as a key component of determining compliance to odour regulations and ordinances. A controlled environmental chamber was utilized, with hydrogen sulfide as the known test odorant. A hydrogen sulfide environment was created in this controlled chamber using an Advanced Calibration Designs, Inc. Cal2000 Hydrogen Sulfide Generator. The hydrogen sulfide concentration inside the chamber was monitored using an Arizona Instruments, Inc. Jerome Model 631 H2S Analyzer. When the environmental chamber reached a desired test concentration, test operators entered the chamber. The dilution-to-threshold odour concentration was measured using a Nasal Ranger Field Olfactometer (St Croix Sensory, Inc.) and a Barnebey Sutcliffe Corp. Scentometer. The actual hydrogen sulfide concentration was also measured at the location in the room where the operators were standing while using the two types of field olfactometers. This paper presents a correlation between dilution-to-threshold values (D/T) and hydrogen sulfide ambient concentration. For example, a D/T of 7 corresponds to ambient H2S concentrations of 5.7-15.6 microg/m3 (4-11 ppbv). During this study, no significant difference was found between results obtained using the Scentometer or the Nasal Ranger (r = 0.82). Also, no significant difference was found between results of multiple Nasal Ranger users (p = 0.309). The field olfactometers yielded hydrogen sulfide thresholds of 0.7-3.0 microg/m3 (0.5-2.0 ppbv). Laboratory olfactometry yielded comparable thresholds of 0.64-1.3 microg/m3 (0.45-0.9 ppbv). These thresholds are consistent with published values.

[Determination of the anaerobic threshold by the rate of ventilation and cardio interval variability].

PubMed

Seluianov, V N; Kalinin, E M; Pak, G D; Maevskaia, V I; Konrad, A H

2011-01-01

The aim of this work is to develop methods for determining the anaerobic threshold according to the rate of ventilation and cardio interval variability during the test with stepwise increases load on the cycle ergometer and treadmill. In the first phase developed the method for determining the anaerobic threshold for lung ventilation. 49 highly skilled skiers took part in the experiment. They performed a treadmill ski-walking test with sticks with gradually increasing slope from 0 to 25 degrees, the slope increased by one degree every minute. In the second phase we developed a method for determining the anaerobic threshold according dynamics ofcardio interval variability during the test. The study included 86 athletes of different sports specialties who performed pedaling on the cycle ergometer "Monarch" in advance. Initial output was 25 W, power increased by 25 W every 2 min. The pace was steady--75 rev/min. Measurement of pulmonary ventilation and oxygen and carbon dioxide content was performed using gas analyzer COSMED K4. Sampling of arterial blood was carried from the ear lobe or finger, blood lactate concentration was determined using an "Akusport" instrument. RR-intervals registration was performed using heart rate monitor Polar s810i. As a result, it was shown that the graphical method for determining the onset of anaerobic threshold ventilation (VAnP) coincides with the accumulation of blood lactate 3.8 +/- 0.1 mmol/l when testing on a treadmill and 4.1 +/- 0.6 mmol/1 on the cycle ergometer. The connection between the measure of oxygen consumption at VAnP and the dispersion of cardio intervals (SD1), derived regression equation: VO2AnT = 0.35 + 0.01SD1W + 0.0016SD1HR + + 0.106SD1(ms), l/min; (R = 0.98, error evaluation function 0.26 L/min, p < 0.001), where W (W)--Power, HR--heart rate (beats/min), SD1--cardio intervals dispersion (ms) at the moment of registration of cardio interval threshold.

Childhood Otitis Media: A Cohort Study With 30-Year Follow-Up of Hearing (The HUNT Study).

PubMed

Aarhus, Lisa; Tambs, Kristian; Kvestad, Ellen; Engdahl, Bo

2015-01-01

To study the extent to which otitis media (OM) in childhood is associated with adult hearing thresholds. Furthermore, to study whether the effects of OM on adult hearing thresholds are moderated by age or noise exposure. Population-based cohort study of 32,786 participants who had their hearing tested by pure-tone audiometry in primary school and again at ages ranging from 20 to 56 years. Three thousand sixty-six children were diagnosed with hearing loss; the remaining sample had normal childhood hearing. Compared with participants with normal childhood hearing, those diagnosed with childhood hearing loss caused by otitis media with effusion (n = 1255), chronic suppurative otitis media (CSOM; n = 108), or hearing loss after recurrent acute otitis media (rAOM; n = 613) had significantly increased adult hearing thresholds in the whole frequency range (2 dB/17-20 dB/7-10 dB, respectively). The effects were adjusted for age, sex, and noise exposure. Children diagnosed with hearing loss after rAOM had somewhat improved hearing thresholds as adults. The effects of CSOM and hearing loss after rAOM on adult hearing thresholds were larger in participants tested in middle adulthood (ages 40 to 56 years) than in those tested in young adulthood (ages 20 to 40 years). Eardrum pathology added a marginally increased risk of adult hearing loss (1-3 dB) in children with otitis media with effusion or hearing loss after rAOM. The study could not reveal significant differences in the effect of self-reported noise exposure on adult hearing thresholds between the groups with OM and the group with normal childhood hearing. This cohort study indicates that CSOM and rAOM in childhood are associated with adult hearing loss, underlining the importance of optimal treatment in these conditions. It appears that ears with a subsequent hearing loss after OM in childhood age at a faster rate than those without; however this should be confirmed by studies with several follow-up tests through adulthood.

Amplification of transcutaneous and percutaneous bone-conduction devices with a test-band in an induced model of conductive hearing loss.

PubMed

Park, Marn Joon; Lee, Jae Ryung; Yang, Chan Joo; Yoo, Myung Hoon; Jin, In Suk; Choi, Chi Ho; Park, Hong Ju

2016-11-01

Transcutaneous devices have a disadvantage, the dampening effect by soft tissue between the bone and devices. We investigated hearing outcomes with percutaneous and transcutaneous devices using test-bands in an induced unilateral conductive hearing loss. Comparison of hearing outcomes of two devices in the same individuals. The right ear was plugged in 30 subjects and a test-band with devices (Cochlear™ Baha® BP110 Power and Sophono® Alpha-2 MPO™) was applied on the right mastoid tip with the left ear masked. Sound-field thresholds, speech recognition thresholds (SRTs), and word recognition scores (WRSs) were compared. Aided thresholds of Sophono were significantly better than those of Baha at most frequencies. Sophono WRSs (86 ± 12%) at 40 dB SPL and SRTs (14 ± 5 dB HL) were significantly better than those (73 ± 24% and 23 ± 8 dB HL) of Baha. However, Sophono WRSs (98 ± 3%) at 60 dB SPL did not differ from Baha WRSs (95 ± 12%). Amplifications of the current transcutaneous device were not inferior to those of percutaneous devices with a test-band in subjects with normal bone-conduction thresholds. Since the percutaneous devices can increase the gain when fixed to the skull by eliminating the dampening effect, both devices are expected to provide sufficient hearing amplification.

Feasibility and repeatability of cold and mechanical quantitative sensory testing in normal dogs

PubMed Central

Briley, Jessica D.; Williams, Morika D.; Freire, Mila; Griffith, Emily H.; Lascelles, B. Duncan X.

2015-01-01

Feasibility and inter-session repeatability of cold and mechanical quantitative sensory testing (QST) were assessed in 24 normal dogs. Cold thermal latencies were evaluated using a thermal probe (0 °C) applied to three pelvic limb sites. Mechanical thresholds were measured using an electronic von Frey anesthesiometer (EVF) and a blunt-probed pressure algometer (PA) applied to the dorsal aspect of the metatarsus. All QST trials were performed with dogs in lateral recumbency. Collection of cold QST data was easy (feasible) in 19/24 (79%) dogs. However, only 18.4%, 18.9% and 13.2% of cold QST trials elicited a response at the medial tibia, third digital pad and plantar metatarsal regions, respectively. Collection of mechanical QST data was easy (feasible) in 20/24 (83%) dogs for both EVF and PA. At consecutive sampling times, approximately 2 weeks apart, the average EVF sensory thresholds were 414 ± 186 g and 379 ± 166 g, respectively, and the average PA sensory thresholds were 1089 ± 414 g and 1028 ± 331 g, respectively. There was no significant difference in inter-session or inter-limb threshold values for either mechanical QST device. The cold QST protocol in this study was achievable, but did not provide consistently quantifiable results. Both mechanical QST devices tested provided repeatable, reliable sensory threshold measurements in normal, client-owned dogs. These findings contribute to the validation of the EVF and PA as tools to obtain repeated QST data over time in dogs to assess somatosensory processing changes. PMID:24268475

Classification of HCV and HIV-1 Sequences with the Branching Index

PubMed Central

Hraber, Peter; Kuiken, Carla; Waugh, Mark; Geer, Shaun; Bruno, William J.; Leitner, Thomas

2009-01-01

SUMMARY Classification of viral sequences should be fast, objective, accurate, and reproducible. Most methods that classify sequences use either pairwise distances or phylogenetic relations, but cannot discern when a sequence is unclassifiable. The branching index (BI) combines distance and phylogeny methods to compute a ratio that quantifies how closely a query sequence clusters with a subtype clade. In the hypothesis-testing framework of statistical inference, the BI is compared with a threshold to test whether sufficient evidence exists for the query sequence to be classified among known sequences. If above the threshold, the null hypothesis of no support for the subtype relation is rejected and the sequence is taken as belonging to the subtype clade with which it clusters on the tree. This study evaluates statistical properties of the branching index for subtype classification in HCV and HIV-1. Pairs of BI values with known positive and negative test results were computed from 10,000 random fragments of reference alignments. Sampled fragments were of sufficient length to contain phylogenetic signal that groups reference sequences together properly into subtype clades. For HCV, a threshold BI of 0.71 yields 95.1% agreement with reference subtypes, with equal false positive and false negative rates. For HIV-1, a threshold of 0.66 yields 93.5% agreement. Higher thresholds can be used where lower false positive rates are required. In synthetic recombinants, regions without breakpoints are recognized accurately; regions with breakpoints do not uniquely represent any known subtype. Web-based services for viral subtype classification with the branching index are available online. PMID:18753218

Algorithm for improving psychophysical threshold estimates by detecting sustained inattention in experiments using PEST.

PubMed

Rinderknecht, Mike D; Ranzani, Raffaele; Popp, Werner L; Lambercy, Olivier; Gassert, Roger

2018-05-10

Psychophysical procedures are applied in various fields to assess sensory thresholds. During experiments, sampled psychometric functions are usually assumed to be stationary. However, perception can be altered, for example by loss of attention to the presentation of stimuli, leading to biased data, which results in poor threshold estimates. The few existing approaches attempting to identify non-stationarities either detect only whether there was a change in perception, or are not suitable for experiments with a relatively small number of trials (e.g., [Formula: see text] 300). We present a method to detect inattention periods on a trial-by-trial basis with the aim of improving threshold estimates in psychophysical experiments using the adaptive sampling procedure Parameter Estimation by Sequential Testing (PEST). The performance of the algorithm was evaluated in computer simulations modeling inattention, and tested in a behavioral experiment on proprioceptive difference threshold assessment in 20 stroke patients, a population where attention deficits are likely to be present. Simulations showed that estimation errors could be reduced by up to 77% for inattentive subjects, even in sequences with less than 100 trials. In the behavioral data, inattention was detected in 14% of assessments, and applying the proposed algorithm resulted in reduced test-retest variability in 73% of these corrected assessments pairs. The novel algorithm complements existing approaches and, besides being applicable post hoc, could also be used online to prevent collection of biased data. This could have important implications in assessment practice by shortening experiments and improving estimates, especially for clinical settings.

Crack Growth Behavior in the Threshold Region for High Cycle Fatigue Loading

NASA Technical Reports Server (NTRS)

Forman, Royce G.; Zanganehgheshlaghi, Mohannad

2014-01-01

The research results described in this paper presents a new understanding of the behavior of fatigue crack growth in the threshold region. It is believed by some crack growth experts that the ASTM load shedding test method does not produce true or valid threshold properties. The concern involves the observed fanning of threshold region da/dN data plots for some materials in which the low R-ratio data fans out or away from the high R-ratio data. This data fanning or elevation of threshold values is obviously caused by an increase in crack closure in the low R-ratio tested specimens. This increase in crack closure is assumed by some investigators to be caused by a plastic wake on the crack surfaces that was created during the load shedding test phase. This study shows that the increase in crack closure is the result of an extensive occurrence of crack bifurcation behavior in some materials, particularly in aluminum alloys, when the crack tip cyclic yield zone size becomes less than the grain size of the alloy. This behavior is related to the high stacking fault energy (SFE) property of aluminum alloys which results in easier slip characteristics. Therefore, the particular fanning behavior in aluminum alloys is a function of intrinsic dislocation property of the materials and that the fanned data represents valid material properties. However, for corrosion sensitive steel alloys used in this study the fanning was caused by a build-up of iron oxide at the crack tip from fretting corrosion.

Beam test results of the BTeV silicon pixel detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gabriele Chiodini et al.

2000-09-28

The authors have described the results of the BTeV silicon pixel detector beam test. The pixel detectors under test used samples of the first two generations of Fermilab pixel readout chips, FPIX0 and FPIX1, (indium bump-bonded to ATLAS sensor prototypes). The spatial resolution achieved using analog charge information is excellent for a large range of track inclination. The resolution is still very good using only 2-bit charge information. A relatively small dependence of the resolution on bias voltage is observed. The resolution is observed to depend dramatically on the discriminator threshold, and it deteriorates rapidly for threshold above 4000e{sup {minus}}.

Sporadic adult onset primary torsion dystonia is a genetic disorder by the temporal discrimination test.

PubMed

Kimmich, Okka; Bradley, David; Whelan, Robert; Mulrooney, Nicola; Reilly, Richard B; Hutchinson, Siobhan; O'Riordan, Sean; Hutchinson, Michael

2011-09-01

Adult-onset primary torsion dystonia is an autosomal dominant disorder with markedly reduced penetrance; patients with sporadic adult-onset primary torsion dystonia are much more prevalent than familial. The temporal discrimination threshold is the shortest time interval at which two stimuli are detected to be asynchronous and has been shown to be abnormal in adult-onset primary torsion dystonia. The aim was to determine the frequency of abnormal temporal discrimination thresholds in patients with sporadic adult-onset primary torsion dystonia and their first-degree relatives. We hypothesized that abnormal temporal discrimination thresholds in first relatives would be compatible with an autosomal dominant endophenotype. Temporal discrimination thresholds were examined in 61 control subjects (39 subjects <50 years of age; 22 subjects >50 years of age), 32 patients with sporadic adult-onset primary torsion dystonia (cervical dystonia n = 30, spasmodic dysphonia n = 1 and Meige's syndrome n = 1) and 73 unaffected first-degree relatives (36 siblings, 36 offspring and one parent) using visual and tactile stimuli. Z-scores were calculated for all subjects; a Z > 2.5 was considered abnormal. Abnormal temporal discrimination thresholds were found in 1/61 (2%) control subjects, 27/32 (84%) patients with adult-onset primary torsion dystonia and 32/73 (44%) unaffected relatives [siblings (20/36; 56%), offspring (11/36; 31%) and one parent]. When two or more relatives were tested in any one family, 22 of 24 families had at least one first-degree relative with an abnormal temporal discrimination threshold. The frequency of abnormal temporal discrimination thresholds in first-degree relatives of patients with sporadic adult-onset primary torsion dystonia is compatible with an autosomal dominant disorder and supports the hypothesis that apparently sporadic adult-onset primary torsion dystonia is genetic in origin.

Dental ceramics: a CIEDE2000 acceptability thresholds for lightness, chroma and hue differences.

PubMed

Perez, María Del Mar; Ghinea, Razvan; Herrera, Luis Javier; Ionescu, Ana Maria; Pomares, Héctor; Pulgar, Rosa; Paravina, Rade D

2011-12-01

To determine the visual 50:50% acceptability thresholds for lightness, chroma and hue for dental ceramics using CIEDE2000(K(L):K(C):K(H)) formula, and to evaluate the formula performance using different parametric factors. A 30-observer panel evaluated three subsets of ceramic samples: lightness subset (|ΔL'/ΔE(00)| ≥ 0.9), chroma subset (|ΔC'/ΔE(00)| ≥ 0.9) and hue subset (|ΔH'/ΔE(00)| ≥ 0.9). A Takagi-Sugeno-Kang Fuzzy Approximation was used as fitting procedure, and the 50:50% acceptability thresholds were calculated. A t-test was used in statistical analysis of the thresholds values. The performance of the CIEDE2000(1:1:1) and CIEDE2000(2:1:1) colour difference formulas against visual results was tested using PF/3 performance factor. The 50:50% CIEDE2000 acceptability thresholds were ΔL' = 2.92 (95% CI 1.22-4.96; r(2) = 0.76), ΔC' = 2.52 (95% CI 1.31-4.19; r(2) = 0.71) and ΔH' = 1.90 (95% CI 1.63-2.15; r(2) = 0.88). The 50:50% acceptability threshold for colour difference (ΔE') for CIEDE2000(1:1:1) was 1.87, whilst corresponding value for CIEDE2000(2:1:1) was 1.78. The PF/3 values were 139.86 for CIEDE2000(1:1:1), and 132.31 for CIEDE2000(2:1:1). There was a statistically significant difference amongst CIEDE2000 50:50% acceptability thresholds for lightness, chroma and hue differences for dental ceramics. The CIEDE2000(2:1:1) formula performed better than CIEDE2000(1:1:1). Copyright © 2011 Elsevier Ltd. All rights reserved.

Assessment of Maximum Aerobic Capacity and Anaerobic Threshold of Elite Ballet Dancers.

PubMed

Wyon, Matthew A; Allen, Nick; Cloak, Ross; Beck, Sarah; Davies, Paul; Clarke, Frances

2016-09-01

An athlete's cardiorespiratory profile, maximal aerobic capacity, and anaerobic threshold is affected by training regimen and competition demands. The present study aimed to ascertain whether there are company rank differences in maximal aerobic capacity and anaerobic threshold in elite classical ballet dancers. Seventy-four volunteers (M 34, F 40) were recruited from two full-time professional classical ballet companies. All participants completed a continuous incremental treadmill protocol with a 1-km/hr speed increase at the end of each 1-min stage until termination criteria had been achieved (e.g., voluntary cessation, respiratory exchange ratio <1.15, HR ±5 bpm of estimated HRmax). Peak VO2 (5-breathe smooth) was recorded and anaerobic threshold calculated using ventilatory curve and ventilatory equivalents methods. Statistical analysis reported between-subject effects for gender (F1,67=35.18, p<0.001) and rank (F1,67=8.67, p<0.001); post hoc tests reported soloists (39.5±5.15 mL/kg/min) as having significantly lower VO2 peak than artists (45.9±5.75 mL/kg/min, p<0.001) and principal dancers (48.07±3.24 mL/kg/min, p<0.001). Significant differences in anaerobic threshold were reported for age (F1,67=7.68, p=0.008) and rank (F1,67=3.56, p=0.034); post hoc tests reported artists (75.8±5.45%) having significantly lower anaerobic threshold than soloists (80.9±5.71, p<0.01) and principals (84.1±4.84%, p<0.001). The observed differences in VO2 peak and anaerobic threshold between the ranks in ballet companies are probably due to the different rehearsal and performance demands.

Pleasure and pain: the effect of (almost) having an orgasm on genital and nongenital sensitivity.

PubMed

Paterson, Laurel Q P; Amsel, Rhonda; Binik, Yitzchak M

2013-06-01

The effect of sexual arousal and orgasm on genital sensitivity has received little research attention, and no study has assessed sensation pleasurableness as well as painfulness. To clarify the relationship between sexual arousal, orgasm, and sensitivity in a healthy female sample. Twenty-six women privately masturbated to orgasm and almost to orgasm at two separate sessions, during which standardized pressure stimulation was applied to the glans clitoris, vulvar vestibule, and volar forearm at three testing times: (i) baseline; (ii) immediately following masturbation; and (iii) following a subsequent 15-minute rest period. Touch thresholds (tactile detection sensitivity), sensation pleasurableness ratings (pleasurable sensitivity), and pain thresholds (pain sensitivity). Pleasurableness ratings were higher on the glans clitoris than the vulvar vestibule, and at most testing times on the vulvar vestibule than the volar forearm; and at baseline and immediately after masturbation than 15 minutes later, mainly on the genital locations only. Pain thresholds were lower on the genital locations than the volar forearm, and immediately and 15 minutes after masturbation than at baseline. After orgasm, genital pleasurableness ratings and vulvar vestibular pain thresholds were lower than after masturbation almost to orgasm. Post-masturbation pleasurableness ratings were positively correlated with pain thresholds but only on the glans clitoris. Hormonal contraception users had lower pleasurableness ratings and pain thresholds on all locations than nonusers. There were no significant effects for touch thresholds. Masturbation appears to maintain pleasurable genital sensitivity but increase pain sensitivity, with lower genital pleasurable sensitivity and higher vulvar vestibular pain sensitivity when orgasm occurs. Findings suggest that enhancing stimulation pleasurableness, psychological sexual arousal and lubrication mitigate normative increases in pain sensitivity during sexual activity, and underscore the importance of measuring both pleasure and pain in sensation research. © 2013 International Society for Sexual Medicine.

Harm is all you need? Best interests and disputes about parental decision-making.

PubMed

Birchley, Giles

2016-02-01

A growing number of bioethics papers endorse the harm threshold when judging whether to override parental decisions. Among other claims, these papers argue that the harm threshold is easily understood by lay and professional audiences and correctly conforms to societal expectations of parents in regard to their children. English law contains a harm threshold which mediates the use of the best interests test in cases where a child may be removed from her parents. Using Diekema's seminal paper as an example, this paper explores the proposed workings of the harm threshold. I use examples from the practical use of the harm threshold in English law to argue that the harm threshold is an inadequate answer to the indeterminacy of the best interests test. I detail two criticisms: First, the harm standard has evaluative overtones and judges are loath to employ it where parental behaviour is misguided but they wish to treat parents sympathetically. Thus, by focusing only on 'substandard' parenting, harm is problematic where the parental attempts to benefit their child are misguided or wrong, such as in disputes about withdrawal of medical treatment. Second, when harm is used in genuine dilemmas, court judgments offer different answers to similar cases. This level of indeterminacy suggests that, in practice, the operation of the harm threshold would be indistinguishable from best interests. Since indeterminacy appears to be the greatest problem in elucidating what is best, bioethicists should concentrate on discovering the values that inform best interests. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Pain threshold, tolerance and intensity in adolescents born very preterm or with low birth weight.

PubMed

van Ganzewinkel, Christ-Jan J L M; Been, Jasper V; Verbeek, Inge; van der Loo, Tera Boelen; van der Pal, Sylvia M; Kramer, Boris W; Andriessen, Peter

2017-07-01

Data on long-term consequences of neonatal pain is limited. To assess whether perinatal factors, later pain experience and pain coping strategies are associated with altered pain threshold, pain tolerance and pain intensity in adolescents born preterm. Observational, longitudinal study (Project on Preterm and SGA-infants, POPS-19). We analyzed data of 412 adolescents at the age of 19years, who were born at a gestational age<32weeks or with a birth weight<1500g. Participants performed a standardized cold pressor test to assess pain threshold, tolerance and intensity. Furthermore, they completed a pain coping questionnaire (PCQ). In univariate analysis, female gender and necrotizing enterocolitis (NEC) were associated with lower pain tolerance, indicated by reaching the ceiling time of 180s in ice water (females 19% vs males 29%, NEC 7% vs no NEC 25%). Female gender was associated with higher pain intensity (mean difference 0.58; 95%CI 0.21; 0.95) and lower pain threshold (log rank test p 0.007). In a multivariate Cox regression analyses, emotion focused avoidance pain coping style was significantly associated with lower pain threshold (hazard ratio HR 1.38; 95%CI 1.02; 1.87) and pain tolerance (HR 1.72; 95%CI 1.21; 2.42). NEC was significantly associated with lower pain threshold (HR 1.47; 95%CI 1.01; 2.14) and pain tolerance (HR 1.63; 95%CI 1.09; 2.41). In adolescence, maladaptive pain coping strategy was associated with lower pain threshold, pain tolerance and higher pain intensity. NEC was associated with altered pain response in adolescents born preterm. Copyright © 2017 Elsevier B.V. All rights reserved.

Automatic threshold optimization in nonlinear energy operator based spike detection.

PubMed

Malik, Muhammad H; Saeed, Maryam; Kamboh, Awais M

2016-08-01

In neural spike sorting systems, the performance of the spike detector has to be maximized because it affects the performance of all subsequent blocks. Non-linear energy operator (NEO), is a popular spike detector due to its detection accuracy and its hardware friendly architecture. However, it involves a thresholding stage, whose value is usually approximated and is thus not optimal. This approximation deteriorates the performance in real-time systems where signal to noise ratio (SNR) estimation is a challenge, especially at lower SNRs. In this paper, we propose an automatic and robust threshold calculation method using an empirical gradient technique. The method is tested on two different datasets. The results show that our optimized threshold improves the detection accuracy in both high SNR and low SNR signals. Boxplots are presented that provide a statistical analysis of improvements in accuracy, for instance, the 75th percentile was at 98.7% and 93.5% for the optimized NEO threshold and traditional NEO threshold, respectively.

Disruption in the relationship between blood pressure and salty taste thresholds among overweight and obese children

PubMed Central

Bobowski, Nuala K.

2015-01-01

Background Prevalence of high blood pressure (BP) among American children has increased over the past two decades, due in part to increasing rates of obesity and excessive dietary salt intake. Objective We tested the hypotheses that the relationships among BP, salty taste sensitivity, and salt intake differ between normal-weight and overweight/obese children. Design In an observational study, sodium chloride (NaCl) and monosodium glutamate (MSG) taste detection thresholds were measured using the Monell two-alternative, forced-choice, paired-comparison tracking method. Weight and BP were measured, and salt intake was determined by 24-hour dietary recall. Participants/Setting Eight- to 14-year-olds (N=97; 52% overweight or obese) from the Philadelphia area completed anthropometrics and BP measurements; 97% completed one or both thresholds. Seventy-six percent provided valid dietary recall data. Testing was completed between December 2011 and August 2012. Main outcome measures NaCl and MSG detection thresholds, BP, and dietary salt intake. Statistical analyses Outcome measures were compared between normal-weight and overweight/obese children with t-tests. Relationships among outcome measures within groups were examined with Pearson correlations, and multiple regression analysis was used to examine the relationship between BP and thresholds, controlling for age, BMI-Z score, and dietary salt intake. Results Salt and MSG thresholds were positively correlated (r(71)=0.30, p=0.01) and did not differ between body-weight groups (p>0.20). Controlling for age, BMI-Z score, and salt intake, systolic BP was associated with NaCl thresholds among normal-weight children (p=0.01), but not among overweight/obese children. All children consumed excess salt (>8 g/day). Grain and meat products were the primary source of dietary sodium. Conclusions The apparent disruption in the relationship between salty taste response and BP among overweight/obese children suggests the relationship may be influenced by body weight. Further research is warranted to explore this relationship as a potential measure to prevent development of hypertension. PMID:25843808

Towards a unifying basis of auditory thresholds: binaural summation.

PubMed

Heil, Peter

2014-04-01

Absolute auditory threshold decreases with increasing sound duration, a phenomenon explainable by the assumptions that the sound evokes neural events whose probabilities of occurrence are proportional to the sound's amplitude raised to an exponent of about 3 and that a constant number of events are required for threshold (Heil and Neubauer, Proc Natl Acad Sci USA 100:6151-6156, 2003). Based on this probabilistic model and on the assumption of perfect binaural summation, an equation is derived here that provides an explicit expression of the binaural threshold as a function of the two monaural thresholds, irrespective of whether they are equal or unequal, and of the exponent in the model. For exponents >0, the predicted binaural advantage is largest when the two monaural thresholds are equal and decreases towards zero as the monaural threshold difference increases. This equation is tested and the exponent derived by comparing binaural thresholds with those predicted on the basis of the two monaural thresholds for different values of the exponent. The thresholds, measured in a large sample of human subjects with equal and unequal monaural thresholds and for stimuli with different temporal envelopes, are compatible only with an exponent close to 3. An exponent of 3 predicts a binaural advantage of 2 dB when the two ears are equally sensitive. Thus, listening with two (equally sensitive) ears rather than one has the same effect on absolute threshold as doubling duration. The data suggest that perfect binaural summation occurs at threshold and that peripheral neural signals are governed by an exponent close to 3. They might also shed new light on mechanisms underlying binaural summation of loudness.

Statistical Criteria for Setting Thresholds in Medical School Admissions

ERIC Educational Resources Information Center

Albanese, Mark A.; Farrell, Philip; Dottl, Susan

2005-01-01

In 2001, Dr. Jordan Cohen, President of the AAMC, called for medical schools to consider using an Medical College Admission Test (MCAT) threshold to eliminate high-risk applicants from consideration and then to use non-academic qualifications for further consideration. This approach would seem to be consistent with the recent Supreme Court ruling…

Ototraumatic Effects of Hard Rock Music

PubMed Central

Reddell, Rayford C.; Lebo, Charles P.

1972-01-01

Temporary and permanent shifts in auditory thresholds were found in 43 hard rock musicians and temporary shifts were also observed in some listeners. The threshold shifts involved all of the conventional puretone test frequencies. Custom-fitted polyvinyl chloride ear protectors were found to be effective in prevention of these noise-induced hearing losses. PMID:5008499

A test of critical thresholds and their indicators in a desertification-prone ecosystem: more resilience than we thought

USDA-ARS?s Scientific Manuscript database

Theoretical models predict that dryland ecosystems can cross critical thresholds after which vegetation loss is independent of initial drivers, but experimental data are nonexistent. We used a long-term (13 year) pulse-perturbation experiment featuring heavy grazing and shrub removal to determine i...

Neurosensory effects of chronic exposure to arsenic via drinking water in Inner Mongolia: II. Vibrotactile and visual function.

PubMed

Otto, David; He, Linlin; Xia, Yanhong; Li, Yajuan; Wu, Kegong; Ning, Zhixiong; Zhao, Baixiao; Hudnell, H Kenneth; Kwok, Richard; Mumford, Judy; Geller, Andrew; Wade, Timothy

2006-03-01

This study was designed to assess the effects of exposure to arsenic in drinking water on visual and vibrotactile function in residents of the Bamen region of Inner Mongolia, China. Arsenic was measured by hydride generation atomic fluorescence. 321 participants were divided into three exposure groups- low (non-detectable-20), medium (100-300) and high (400-700 microg/l) arsenic in drinking water (AsW). Three visual tests were administered: acuity, contrast sensitivity and color discrimination (Lanthony's Desaturated 15 Hue Test). Vibration thresholds were measured with a vibrothesiometer. Vibration thresholds were significantly elevated in the high exposure group compared to other groups. Further analysis using a spline regression model suggested that the threshold for vibratory effects is between 150-170 microg/l AsW. These findings provide the first evidence that chronic exposure to arsenic in drinking water impairs vibrotactile thresholds. The results also indicate that arsenic affects neurological function well below the 1000 microg/I concentration reported by NRC (1999). No evidence of arsenic-related effects on visual function was found.

Interlaminar shear fracture toughness and fatigue thresholds for composite materials

NASA Technical Reports Server (NTRS)

Obrien, T. Kevin; Murri, Gretchen B.; Salpekar, Satish A.

1987-01-01

Static and cyclic end notched flexure tests were conducted on a graphite epoxy, a glass epoxy, and graphite thermoplastic to determine their interlaminar shear fracture toughness and fatigue thresholds for delamination in terms of limiting values of the mode II strain energy release rate, G-II, for delamination growth. The influence of precracking and data reduction schemes are discussed. Finite element analysis indicated that the beam theory calculation for G-II with the transverse shear contribution included was reasonably accurate over the entire range of crack lengths. Cyclic loading significantly reduced the critical G-II for delamination. A threshold value of the maximum cyclic G-II below which no delamination occurred after one million cycles was identified for each material. Also, residual static toughness tests were conducted on glass epoxy specimens that had undergone one million cycles without delamination. A linear mixed-mode delamination criteria was used to characterize the static toughness of several composite materials; however, a total G threshold criterion appears to characterize the fatigue delamination durability of composite materials with a wide range of static toughness.

A flexible cure rate model with dependent censoring and a known cure threshold.

PubMed

Bernhardt, Paul W

2016-11-10

We propose a flexible cure rate model that accommodates different censoring distributions for the cured and uncured groups and also allows for some individuals to be observed as cured when their survival time exceeds a known threshold. We model the survival times for the uncured group using an accelerated failure time model with errors distributed according to the seminonparametric distribution, potentially truncated at a known threshold. We suggest a straightforward extension of the usual expectation-maximization algorithm approach for obtaining estimates in cure rate models to accommodate the cure threshold and dependent censoring. We additionally suggest a likelihood ratio test for testing for the presence of dependent censoring in the proposed cure rate model. We show through numerical studies that our model has desirable properties and leads to approximately unbiased parameter estimates in a variety of scenarios. To demonstrate how our method performs in practice, we analyze data from a bone marrow transplantation study and a liver transplant study. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Estimation of Crack Initiation and Propagation Thresholds of Confined Brittle Coal Specimens Based on Energy Dissipation Theory

NASA Astrophysics Data System (ADS)

Ning, Jianguo; Wang, Jun; Jiang, Jinquan; Hu, Shanchao; Jiang, Lishuai; Liu, Xuesheng

2018-01-01

A new energy-dissipation method to identify crack initiation and propagation thresholds is introduced. Conventional and cyclic loading-unloading triaxial compression tests and acoustic emission experiments were performed for coal specimens from a 980-m deep mine with different confining pressures of 10, 15, 20, 25, 30, and 35 MPa. Stress-strain relations, acoustic emission patterns, and energy evolution characteristics obtained during the triaxial compression tests were analyzed. The majority of the input energy stored in the coal specimens took the form of elastic strain energy. After the elastic-deformation stage, part of the input energy was consumed by stable crack propagation. However, with an increase in stress levels, unstable crack propagation commenced, and the energy dissipation and coal damage were accelerated. The variation in the pre-peak energy-dissipation ratio was consistent with the coal damage. This new method demonstrates that the crack initiation threshold was proportional to the peak stress ( σ p) for ratios that ranged from 0.4351 to 0.4753 σ p, and the crack damage threshold ranged from 0.8087 to 0.8677 σ p.

Laser damage of HR, AR-coatings, monolayers and bare surfaces at 1064 nm

NASA Technical Reports Server (NTRS)

Garnov, S. V.; Klimentov, S. M.; Said, A. A.; Soileau, M. J.

1993-01-01

Laser induced damage thresholds and morphologies were investigated in a variety of uncoated and coated surfaces, including monolayers and multi-layers of different chemical compositions. Both antireflective (AR) and highly reflective (HR) were tested. Testing was done at 1064 nm with 25 picosecond and 8 nanosecond YAG/Nd laser single pulses. Spot diameter in the experiments varied from 0.09 to 0.22 mm. The laser damage measurement procedure consisted of 1-on-1 (single laser pulse in the selected site) and N-on-1 experiments including repeated irradiation by pulses of the same fluence and subsequently raised from pulse to pulse fluence until damage occurred. The highest picosecond damage thresholds of commercially available coatings averaged 12 - 14 J/sq cm, 50 percent less than thresholds obtained in bare fused silica. Some coatings and bare surfaces revealed a palpable preconditioning effect (an increase in threshold of 1.2 to 1.8 times). Picosecond and nanosecond data were compared to draw conclusions about pulse width dependence. An attempt was made to classify damage morphologies according to the type of coating, class of irradiating, and damage level.

[A cloud detection algorithm for MODIS images combining Kmeans clustering and multi-spectral threshold method].

PubMed

Wang, Wei; Song, Wei-Guo; Liu, Shi-Xing; Zhang, Yong-Ming; Zheng, Hong-Yang; Tian, Wei

2011-04-01

An improved method for detecting cloud combining Kmeans clustering and the multi-spectral threshold approach is described. On the basis of landmark spectrum analysis, MODIS data is categorized into two major types initially by Kmeans method. The first class includes clouds, smoke and snow, and the second class includes vegetation, water and land. Then a multi-spectral threshold detection is applied to eliminate interference such as smoke and snow for the first class. The method is tested with MODIS data at different time under different underlying surface conditions. By visual method to test the performance of the algorithm, it was found that the algorithm can effectively detect smaller area of cloud pixels and exclude the interference of underlying surface, which provides a good foundation for the next fire detection approach.

Have the temperature time series a structural change after 1998?

NASA Astrophysics Data System (ADS)

Werner, Rolf; Valev, Dimitare; Danov, Dimitar

2012-07-01

The global and hemisphere temperature GISS and Hadcrut3 time series were analysed for structural changes. We postulate the continuity of the preceding temperature function depending from the time. The slopes are calculated for a sequence of segments limited by time thresholds. We used a standard method, the restricted linear regression with dummy variables. We performed the calculations and tests for different number of thresholds. The thresholds are searched continuously in determined time intervals. The F-statistic is used to obtain the time points of the structural changes.

Effects of threshold on single-target detection by using modified amplitude-modulated joint transform correlator

NASA Astrophysics Data System (ADS)

Kaewkasi, Pitchaya; Widjaja, Joewono; Uozumi, Jun

2007-03-01

Effects of threshold value on detection performance of the modified amplitude-modulated joint transform correlator are quantitatively studied using computer simulation. Fingerprint and human face images are used as test scenes in the presence of noise and a contrast difference. Simulation results demonstrate that this correlator improves detection performance for both types of image used, but moreso for human face images. Optimal detection of low-contrast human face images obscured by strong noise can be obtained by selecting an appropriate threshold value.

Prioritizing CD4 Count Monitoring in Response to ART in Resource-Constrained Settings: A Retrospective Application of Prediction-Based Classification

PubMed Central

Liu, Yan; Li, Xiaohong; Johnson, Margaret; Smith, Collette; Kamarulzaman, Adeeba bte; Montaner, Julio; Mounzer, Karam; Saag, Michael; Cahn, Pedro; Cesar, Carina; Krolewiecki, Alejandro; Sanne, Ian; Montaner, Luis J.

2012-01-01

Background Global programs of anti-HIV treatment depend on sustained laboratory capacity to assess treatment initiation thresholds and treatment response over time. Currently, there is no valid alternative to CD4 count testing for monitoring immunologic responses to treatment, but laboratory cost and capacity limit access to CD4 testing in resource-constrained settings. Thus, methods to prioritize patients for CD4 count testing could improve treatment monitoring by optimizing resource allocation. Methods and Findings Using a prospective cohort of HIV-infected patients (n = 1,956) monitored upon antiretroviral therapy initiation in seven clinical sites with distinct geographical and socio-economic settings, we retrospectively apply a novel prediction-based classification (PBC) modeling method. The model uses repeatedly measured biomarkers (white blood cell count and lymphocyte percent) to predict CD4+ T cell outcome through first-stage modeling and subsequent classification based on clinically relevant thresholds (CD4+ T cell count of 200 or 350 cells/µl). The algorithm correctly classified 90% (cross-validation estimate = 91.5%, standard deviation [SD] = 4.5%) of CD4 count measurements <200 cells/µl in the first year of follow-up; if laboratory testing is applied only to patients predicted to be below the 200-cells/µl threshold, we estimate a potential savings of 54.3% (SD = 4.2%) in CD4 testing capacity. A capacity savings of 34% (SD = 3.9%) is predicted using a CD4 threshold of 350 cells/µl. Similar results were obtained over the 3 y of follow-up available (n = 619). Limitations include a need for future economic healthcare outcome analysis, a need for assessment of extensibility beyond the 3-y observation time, and the need to assign a false positive threshold. Conclusions Our results support the use of PBC modeling as a triage point at the laboratory, lessening the need for laboratory-based CD4+ T cell count testing; implementation of this tool could help optimize the use of laboratory resources, directing CD4 testing towards higher-risk patients. However, further prospective studies and economic analyses are needed to demonstrate that the PBC model can be effectively applied in clinical settings. Please see later in the article for the Editors' Summary PMID:22529752

Rainfall thresholds for the triggering of landslides in Slovenia

NASA Astrophysics Data System (ADS)

Peternel, Tina; Jemec Auflič, Mateja; Rosi, Ascanio; Segoni, Samuele; Komac, Marko; Casagli, Nicola

2017-04-01

Both at the worldwide level and in Slovenia, precipitation and related phenomena represent one of the most important triggering factors for the occurrence of slope mass movements. In the past decade, extreme rainfall events with a very high amount of precipitation occurs in a relatively short rainfall period have become increasingly important and more frequent, that causing numerous undesirable consequences. Intense rainstorms cause flash floods and mostly trigger shallow landslides and soil slips. On the other hand, the damage of long lasting rainstorms depends on the region's adaptation and its capacity to store or infiltrate excessive water from the rain. The amount and, consequently, the intensity of daily precipitation that can cause floods in the eastern part of Slovenia is a rather common event for the north-western part of the country. Likewise, the effect of rainfall is very dependent on the prior soil moisture, periods of full soil saturation and the creation of drifts in groundwater levels due to the slow melting of snow, growing period, etc. Landslides could be identified and to some extent also prevent with better knowledge of the relation between landslides and rainfall. In this paper the definition of rainfall thresholds for rainfall-induced landslides in Slovenia is presented. The thresholds have been calculated by collecting approximately 900 landslide data and the relative rainfall amounts, which have been collected from 41 rain gauges all over the country. The thresholds have been defined by the (1) use of an existing procedure, characterized by a high degree of objectiveness and (2) software that was developed for a test site with very different geological and climatic characteristics (Tuscany, central Italy). Firstly, a single national threshold has been defined, later the country was divided into four zones, on the basis of major the river basins and a single threshold has been calculated for each of them. Validation of the calculated thresholds has been verified by the use of several statistical parameters. Equations of thresholds of each specific zone are quite different mainly due to different climate regime and the density of the rain gauge network. In general, all thresholds have good capacity of avoiding false alarms, but at the same time, some missed alarm can be expected from local threshold, while the national threshold will lead to less missed alarm. Beside the setting of a threshold system, directly usable for civil protection purposes at national scale, an additional outcome of this work is possibility of applying methodology to another region, therefore testing its degree of exportability in different geological and climatological settings.

Osmophobia and olfactory functions in patients with migraine.

PubMed

Kayabaşoglu, Gürkan; Altundag, Aytug; Kotan, Dilcan; Dizdar, Denizhan; Kaymaz, Recep

2017-02-01

Olfactory dysfunction and migraine has been associated for a long time. In this study, we planned to compare olfactory functions in patients with migraine and osmophobia with patients having migraine but no osmophobia, in addition with a normal control group using "Sniffin' Sticks" test. The main distinction of this study is that all qualitative and quantitative properties of olfactory functions; threshold, discrimination and identification, are evaluated separately and jointly. Thirty healthy person aged between 16 and 56 (18 women, 12 men) and 60 migraine patients aged between 15 and 54 (39 women, 21 man) were included in the study. All patients have been inquired about osmophobia and have been assessed with Hedonic tone assessment. Osmophobia has been tested for perfume, cigarette smoke, leather, stale food, soy sauce, fish, spices and coffee smells. Olfactory functions has been assessed with "Sniffin' Sticks" smell test. Thresholds, discrimination and identification have been determined for each patient. In migraine patients with osmophobia, threshold was 7.75 ± 2.3, in migraine patients without osmophobia threshold was 8.25 ± 1.5 and threshold was 10.75 ± 1.3 for the control group. Discrimination score was 6 ± 1.2 in migraine patients with osmophobia, 9 ± 0.8 in patients without osmophobia and was 12 ± 1.4 in the control group. In migraine patient with or without osmophobia Threshold/Discrimination/Identification (TDI) scores were lower than the control group. The most important parameter in our study is that discrimination scores were especially lower in patients with osmophobia. We believe that this decrease in discrimination in migraine patients with osmophobia; who claim that they smell everything and they are sensitive to all smells, is significant. Further studies about smell discrimination will help better understand some conditions; especially anosmia and hyposmia after upper respiratory tract infections and parosmia.

The development of rating of perceived exertion-based tests of physical working capacity.

PubMed

Mielke, Michelle; Housh, Terry J; Malek, Moh H; Beck, Travis W; Schmidt, Richard J; Johnson, Glen O

2008-01-01

The purpose of the present study was to use ratings of perceived exertion (RPE) from the Borg (6-20) and OMNI-Leg (0-10) scales to determine the Physical Working Capacity at the Borg and OMNI thresholds (PWC(BORG) and PWC(OMNI)). PWC(BORG) and PWC(OMNI) were compared with other fatigue thresholds determined from the measurement of heart rate (the Physical Working Capacity at the Heart Rate Threshold: PWC(HRT)), and oxygen consumption (the Physical Working Capacity at the Oxygen Consumption Threshold, PWC(VO2)), as well as the ventilatory threshold (VT). Fifteen men and women volunteers (mean age +/- SD = 22 +/- 1 years) performed an incremental test to exhaustion on an electronically braked ergometer for the determination of VO2 peak and VT. The subjects also performed 4 randomly ordered workbouts to exhaustion at different power outputs (ranging from 60 to 206W) for the determination of PWC(BORG), PWC(OMNI), PWC(HRT), and PWC(VO2). The results indicated that there were no significant mean differences among the fatigue thresholds: PWC(BORG) (mean +/- SD = 133 +/- 37W; 67 +/- 8% of VO2 peak), PWC(OMNI) (137 +/- 44W; 68 +/- 9% of VO2 peak), PWC(HRT) (135 +/- 36W; 68 +/- 8% of VO2 peak), PWC(VO2) (145 +/- 41W; 72 +/- 7% of VO2 peak) and VT (131 +/- 45W; 66 +/- 8% of VO2 peak). The results of this study indicated that the mathematical model used to estimate PWC(HRT) and PWC(VO2) can be applied to ratings of perceived exertion to determine PWC(BORG) and PWC(OMNI) during cycle ergometry. Salient features of the PWC(BORG) and PWC(OMNI) tests are that they are simple to administer and require the use of only an RPE scale, a stopwatch, and a cycle ergometer. Furthermore, the power outputs at the PWC(BORG) and PWC(OMNI) may be useful to estimate the VT noninvasively and without the need for expired gas analysis.

Predicting reactivity threshold in children with anaphylaxis to peanut.

PubMed

Reier-Nilsen, T; Michelsen, M M; Lødrup Carlsen, K C; Carlsen, K-H; Mowinckel, P; Nygaard, U C; Namork, E; Borres, M P; Håland, G

2018-04-01

Peanut allergy necessitates dietary restrictions, preferably individualized by determining reactivity threshold through an oral food challenge (OFC). However, risk of systemic reactions often precludes OFC in children with severe peanut allergy. We aimed to determine whether clinical and/or immunological characteristics were associated with reactivity threshold in children with anaphylaxis to peanut and secondarily, to investigate whether these characteristics were associated with severity of the allergic reaction during OFC. A double-blinded placebo-controlled food challenge (DBPCFC) with peanut was performed in 96 5- to 15-year-old children with a history of severe allergic reactions to peanut and/or sensitization to peanut (skin prick test [SPT] ≥3 mm or specific immunoglobulin E [s-IgE] ≥0.35 kUA/L). Investigations preceding the DBPCFC included a structured interview, SPT, lung function measurements, serological immunology assessment (IgE, IgG and IgG 4 ), basophil activation test (BAT) and conjunctival allergen provocation test (CAPT). International standards were used to define anaphylaxis and grade the allergic reaction during OFC. During DBPCFC, all 96 children (median age 9.3, range 5.1-15.2) reacted with anaphylaxis (moderate objective symptoms from at least two organ systems). Basophil activation (CD63 + basophils ≥15%), peanut SPT and the ratio of peanut s-IgE/total IgE were significantly associated with reactivity threshold and lowest observed adverse events level (LOAEL) (all P < .04). Basophil activation best predicted very low threshold level (<3 mg of peanut protein), with an optimal cut-off of 75.8% giving a 93.5% negative predictive value. None of the characteristics were significantly associated with the severity of allergic reaction. In children with anaphylaxis to peanut, basophil activation, peanut SPT and the ratio of peanut s-IgE/total IgE were associated with reactivity threshold and LOAEL, but not with allergy reaction severity. © 2017 John Wiley & Sons Ltd.

Revised standards for statistical evidence.

PubMed

Johnson, Valen E

2013-11-26

Recent advances in Bayesian hypothesis testing have led to the development of uniformly most powerful Bayesian tests, which represent an objective, default class of Bayesian hypothesis tests that have the same rejection regions as classical significance tests. Based on the correspondence between these two classes of tests, it is possible to equate the size of classical hypothesis tests with evidence thresholds in Bayesian tests, and to equate P values with Bayes factors. An examination of these connections suggest that recent concerns over the lack of reproducibility of scientific studies can be attributed largely to the conduct of significance tests at unjustifiably high levels of significance. To correct this problem, evidence thresholds required for the declaration of a significant finding should be increased to 25-50:1, and to 100-200:1 for the declaration of a highly significant finding. In terms of classical hypothesis tests, these evidence standards mandate the conduct of tests at the 0.005 or 0.001 level of significance.

Cytology versus HPV testing for cervical cancer screening in the general population.

PubMed

Koliopoulos, George; Nyaga, Victoria N; Santesso, Nancy; Bryant, Andrew; Martin-Hirsch, Pierre Pl; Mustafa, Reem A; Schünemann, Holger; Paraskevaidis, Evangelos; Arbyn, Marc

2017-08-10

Cervical cancer screening has traditionally been based on cervical cytology. Given the aetiological relationship between human papillomavirus (HPV) infection and cervical carcinogenesis, HPV testing has been proposed as an alternative screening test. To determine the diagnostic accuracy of HPV testing for detecting histologically confirmed cervical intraepithelial neoplasias (CIN) of grade 2 or worse (CIN 2+), including adenocarcinoma in situ, in women participating in primary cervical cancer screening; and how it compares to the accuracy of cytological testing (liquid-based and conventional) at various thresholds. We performed a systematic literature search of articles in MEDLINE and Embase (1992 to November 2015) containing quantitative data and handsearched the reference lists of retrieved articles. We included comparative test accuracy studies if all women received both HPV testing and cervical cytology followed by verification of the disease status with the reference standard, if positive for at least one screening test. The studies had to include women participating in a cervical cancer screening programme who were not being followed up for previous cytological abnormalities. We completed a 2 x 2 table with the number of true positives (TP), false positives (FP), true negatives (TN), and false negatives for each screening test (HPV test and cytology) used in each study. We calculated the absolute and relative sensitivities and the specificities of the tests for the detection of CIN 2+ and CIN 3+ at various thresholds and computed sensitivity (TP/(TP + TN) and specificity (TN/ (TN + FP) for each test separately. Relative sensitivity and specificity of one test compared to another test were defined as sensitivity of test-1 over sensitivity of test-2 and specificity of test-1 over specificity of test-2, respectively. To assess bias in the studies, we used the Quality Assessment of Diagnostic test Accuracy Studies (QUADAS) tool. We used a bivariate random-effects model for computing pooled accuracy estimates. This model takes into account the within- and between-study variability and the intrinsic correlation between sensitivity and specificity. We included a total of 40 studies in the review, with more than 140,000 women aged between 20 and 70 years old. Many studies were at low risk of bias. There were a sufficient number of included studies with adequate methodology to perform the following test comparisons: hybrid capture 2 (HC2) (1 pg/mL threshold) versus conventional cytology (CC) (atypical squamous cells of undetermined significance (ASCUS)+ and low-grade squamous intraepithelial lesions (LSIL)+ thresholds) or liquid-based cytology (LBC) (ASCUS+ and LSIL+ thresholds), other high-risk HPV tests versus conventional cytology (ASCUS+ and LSIL+ thresholds) or LBC (ASCUS+ and LSIL+ thresholds). For CIN 2+, pooled sensitivity estimates for HC2, CC and LBC (ASCUS+) were 89.9%, 62.5% and 72.9%, respectively, and pooled specificity estimates were 89.9%, 96.6%, and 90.3%, respectively. The results did not differ by age of women (less than or greater than 30 years old), or in studies with verification bias. Accuracy of HC2 was, however, greater in European countries compared to other countries. The results for the sensitivity of the tests were heterogeneous ranging from 52% to 94% for LBC, and 61% to 100% for HC2. Overall, the quality of the evidence for the sensitivity of the tests was moderate, and high for the specificity.The relative sensitivity of HC2 versus CC for CIN 2+ was 1.52 (95% CI: 1.24 to 1.86) and the relative specificity 0.94 (95% CI: 0.92 to 0.96), and versus LBC for CIN 2+ was 1.18 (95% CI: 1.10 to 1.26) and the relative specificity 0.96 (95% CI: 0.95 to 0.97). The relative sensitivity of HC2 versus CC for CIN 3+ was 1.46 (95% CI: 1.12 to 1.91) and the relative specificity 0.95 (95% CI: 0.93 to 0.97). The relative sensitivity of HC2 versus LBC for CIN 3+ was 1.17 (95% CI: 1.07 to 1.28) and the relative specificity 0.96 (95% CI: 0.95 to 0.97). Whilst HPV tests are less likely to miss cases of CIN 2+ and CIN 3+, these tests do lead to more unnecessary referrals. However, a negative HPV test is more reassuring than a negative cytological test, as the cytological test has a greater chance of being falsely negative, which could lead to delays in receiving the appropriate treatment. Evidence from prospective longitudinal studies is needed to establish the relative clinical implications of these tests.

Marginally perceptible outcome feedback, motor learning and implicit processes.

PubMed

Masters, Rich S W; Maxwell, Jon P; Eves, Frank F

2009-09-01

Participants struck 500 golf balls to a concealed target. Outcome feedback was presented at the subjective or objective threshold of awareness of each participant or at a supraliminal threshold. Participants who received fully perceptible (supraliminal) feedback learned to strike the ball onto the target, as did participants who received feedback that was only marginally perceptible (subjective threshold). Participants who received feedback that was not perceptible (objective threshold) showed no learning. Upon transfer to a condition in which the target was unconcealed, performance increased in both the subjective and the objective threshold condition, but decreased in the supraliminal condition. In all three conditions, participants reported minimal declarative knowledge of their movements, suggesting that deliberate hypothesis testing about how best to move in order to perform the motor task successfully was disrupted by the impoverished disposition of the visual outcome feedback. It was concluded that sub-optimally perceptible visual feedback evokes implicit processes.

Robust Adaptive Thresholder For Document Scanning Applications

NASA Astrophysics Data System (ADS)

Hsing, To R.

1982-12-01

In document scanning applications, thresholding is used to obtain binary data from a scanner. However, due to: (1) a wide range of different color backgrounds; (2) density variations of printed text information; and (3) the shading effect caused by the optical systems, the use of adaptive thresholding to enhance the useful information is highly desired. This paper describes a new robust adaptive thresholder for obtaining valid binary images. It is basically a memory type algorithm which can dynamically update the black and white reference level to optimize a local adaptive threshold function. The results of high image quality from different types of simulate test patterns can be obtained by this algorithm. The software algorithm is described and experiment results are present to describe the procedures. Results also show that the techniques described here can be used for real-time signal processing in the varied applications.

Dual Processing Model for Medical Decision-Making: An Extension to Diagnostic Testing

PubMed Central

Tsalatsanis, Athanasios; Hozo, Iztok; Kumar, Ambuj; Djulbegovic, Benjamin

2015-01-01

Dual Processing Theories (DPT) assume that human cognition is governed by two distinct types of processes typically referred to as type 1 (intuitive) and type 2 (deliberative). Based on DPT we have derived a Dual Processing Model (DPM) to describe and explain therapeutic medical decision-making. The DPM model indicates that doctors decide to treat when treatment benefits outweigh its harms, which occurs when the probability of the disease is greater than the so called “threshold probability” at which treatment benefits are equal to treatment harms. Here we extend our work to include a wider class of decision problems that involve diagnostic testing. We illustrate applicability of the proposed model in a typical clinical scenario considering the management of a patient with prostate cancer. To that end, we calculate and compare two types of decision-thresholds: one that adheres to expected utility theory (EUT) and the second according to DPM. Our results showed that the decisions to administer a diagnostic test could be better explained using the DPM threshold. This is because such decisions depend on objective evidence of test/treatment benefits and harms as well as type 1 cognition of benefits and harms, which are not considered under EUT. Given that type 1 processes are unique to each decision-maker, this means that the DPM threshold will vary among different individuals. We also showed that when type 1 processes exclusively dominate decisions, ordering a diagnostic test does not affect a decision; the decision is based on the assessment of benefits and harms of treatment. These findings could explain variations in the treatment and diagnostic patterns documented in today’s clinical practice. PMID:26244571

Dual Processing Model for Medical Decision-Making: An Extension to Diagnostic Testing.

PubMed

Tsalatsanis, Athanasios; Hozo, Iztok; Kumar, Ambuj; Djulbegovic, Benjamin

2015-01-01

Dual Processing Theories (DPT) assume that human cognition is governed by two distinct types of processes typically referred to as type 1 (intuitive) and type 2 (deliberative). Based on DPT we have derived a Dual Processing Model (DPM) to describe and explain therapeutic medical decision-making. The DPM model indicates that doctors decide to treat when treatment benefits outweigh its harms, which occurs when the probability of the disease is greater than the so called "threshold probability" at which treatment benefits are equal to treatment harms. Here we extend our work to include a wider class of decision problems that involve diagnostic testing. We illustrate applicability of the proposed model in a typical clinical scenario considering the management of a patient with prostate cancer. To that end, we calculate and compare two types of decision-thresholds: one that adheres to expected utility theory (EUT) and the second according to DPM. Our results showed that the decisions to administer a diagnostic test could be better explained using the DPM threshold. This is because such decisions depend on objective evidence of test/treatment benefits and harms as well as type 1 cognition of benefits and harms, which are not considered under EUT. Given that type 1 processes are unique to each decision-maker, this means that the DPM threshold will vary among different individuals. We also showed that when type 1 processes exclusively dominate decisions, ordering a diagnostic test does not affect a decision; the decision is based on the assessment of benefits and harms of treatment. These findings could explain variations in the treatment and diagnostic patterns documented in today's clinical practice.

Cardiovascular testing in Fabry disease: exercise capacity reduction, chronotropic incompetence and improved anaerobic threshold after enzyme replacement.

PubMed

Lobo, T; Morgan, J; Bjorksten, A; Nicholls, K; Grigg, L; Centra, E; Becker, G

2008-06-01

The aim of this study was to document exercise capacity and serial electrocardiogram and echocardiograph findings in a cohort of Australian patients with Fabry disease, in relation to their history of enzyme replacement therapy (ERT). Fabry disease has multifactorial effects on the cardiovascular system. Most previous studies have focused on electrocardiographic and echocardiographic parameters. Exercise capacity can be used as an integrated measure of cardiovascular function and allows the effects of treatment to be monitored. A total of 38 patients (30 men and 8 women) with Fabry disease were monitored by 12-lead electrocardiograms every 6-12 months, and by annual standardized-protocol echocardiograms. Bicycle stress tests with VO(2) max measurement and once-only 6 minutes' walk tests were also carried out in subsets of patients whose general health status allowed testing. Seventy per cent of patients met electrocardiogram criteria for left ventricular hypertrophy. Left ventricular hypertrophy on echocardiograph was present in 64% of patients (80% of men). Exercise capacity was reduced in patients with Fabry disease compared with that predicted from normative population data. Mild improvement in anaerobic threshold was seen in the first year of ERT (14.1 +/- 3.0 to 15.8 +/- 3.0, P = 0.02), but no consistent further increase was seen beyond the first year. Most patients had resting bradycardia, with impaired ability to increase heart rate during exercise. Serial testing on ERT showed an improvement in anaerobic threshold but no significant change in VO(2) max. Male patients with Fabry disease were unable to attain predicted maximal heart rate on exercise or to achieve normal exercise levels. ERT was associated with a small improvement in anaerobic threshold over the first year.

Lexical-Access Ability and Cognitive Predictors of Speech Recognition in Noise in Adult Cochlear Implant Users

PubMed Central

Smits, Cas; Merkus, Paul; Festen, Joost M.; Goverts, S. Theo

2017-01-01

Not all of the variance in speech-recognition performance of cochlear implant (CI) users can be explained by biographic and auditory factors. In normal-hearing listeners, linguistic and cognitive factors determine most of speech-in-noise performance. The current study explored specifically the influence of visually measured lexical-access ability compared with other cognitive factors on speech recognition of 24 postlingually deafened CI users. Speech-recognition performance was measured with monosyllables in quiet (consonant-vowel-consonant [CVC]), sentences-in-noise (SIN), and digit-triplets in noise (DIN). In addition to a composite variable of lexical-access ability (LA), measured with a lexical-decision test (LDT) and word-naming task, vocabulary size, working-memory capacity (Reading Span test [RSpan]), and a visual analogue of the SIN test (text reception threshold test) were measured. The DIN test was used to correct for auditory factors in SIN thresholds by taking the difference between SIN and DIN: SRTdiff. Correlation analyses revealed that duration of hearing loss (dHL) was related to SIN thresholds. Better working-memory capacity was related to SIN and SRTdiff scores. LDT reaction time was positively correlated with SRTdiff scores. No significant relationships were found for CVC or DIN scores with the predictor variables. Regression analyses showed that together with dHL, RSpan explained 55% of the variance in SIN thresholds. When controlling for auditory performance, LA, LDT, and RSpan separately explained, together with dHL, respectively 37%, 36%, and 46% of the variance in SRTdiff outcome. The results suggest that poor verbal working-memory capacity and to a lesser extent poor lexical-access ability limit speech-recognition ability in listeners with a CI. PMID:29205095

Accuracy of a Laryngopharyngeal Endoscopic Esthesiometer (LPEER) for Evaluating Laryngopharyngeal Mechanosensitivity: A Validation Study in a Prospectively Recruited Cohort of Patients.

PubMed

Giraldo-Cadavid, Luis F; Burguete, Javier; Rueda, Felipe; Galvis, Ana M; Castaneda, Natalia; Arbulu, Mario; Balaguera, Jorge I; Paez, Nelson; Fernandez, Secundino

2018-02-01

Recent studies have shown an association between alterations in laryngopharyngeal mechanosensitivity (LPMS) and dysphagia, obstructive sleep apnea, and chronic cough hypersensitivity syndrome. A previous reliability study of a new laryngopharyngeal endoscopic esthesiometer and rangefinder (LPEER) showed high intra- and inter-rater reliability; however, its accuracy has not been tested. We performed an accuracy study of the LPEER in a prospectively and consecutively recruited cohort of 118 patients at two tertiary care university hospitals. Most of the patients were suffering from dysphagia, and all of them underwent a standard clinical evaluation and fiberoptic endoscopic evaluation of swallowing with sensory testing (FEESST) using a new sensory testing protocol. The sensory test included determinations of the laryngeal adductor reflex threshold (LART), the cough reflex threshold (CRT) and the gag reflex threshold (GRT). Abnormalities on these reflex thresholds were evaluated for associations with major alterations in swallowing safety (pharyngeal residues, penetration, and aspiration). We evaluated the discriminative capacity of the LPMS test using ROC curves and the area under the curve (AUC-ROC) and its relationship with the eight-point penetration-aspiration scale (PAS) using the Spearman's ρ correlation coefficient (SCC). We found a positive correlation between the PAS and LART (SCC 0.47; P < 0.001), CRT (SCC 0.46; P < 0.001) and GRT (SCC 0.34; P = 0.002). The AUC-ROC values for detecting a PAS ≥7 were as follows: LART, 0.83 (P < 0.0001); CRT, 0.79 (P < 0.0001); GRT, 0.72 (P < 0.0001). In this study, the LPEER showed good accuracy for evaluating LPMS. These results justify further validation studies in independent populations.

Evaluation of anaerobic threshold in non-pregnant and pregnant rats.

PubMed

Netto, Aline Oliveira; Macedo, Nathália C D; Gallego, Franciane Q; Sinzato, Yuri K; Volpato, Gustavo T; Damasceno, Débora C

2017-01-01

Several studies present different methodologies and results about intensity exercise, and many of them are performed in male rats. However, the impact of different type, intensity, frequency and duration of exercise on female rats needs more investigation. From the analysis of blood lactate concentration during lactate minimum test (LacMin) in the swimming exercise, the anaerobic threshold (AT) was identified, which parameter is defined as the transition point between aerobic and anaerobic metabolism. LacMin test is considered a good indicator of aerobic conditioning and has been used in prescription of training in different exercise modalities. However, there is no evidence of LacMin test in female rats. The objective was to determine AT in non-pregnant and pregnant Wistar rats. The LacMin test was performed and AT defined for mild exercise intensity was from a load equivalent to 1% of body weight (bw), moderate exercise as carrying 4% bw and severe intensity as carrying 7% bw. In pregnant rats, the AT was reached at a lower loading from 5.0% to 5.5% bw, while in non-pregnant the load was from 5.5% to 6.0% bw. Thus, this study was effective to identify exercise intensities in pregnant and non-pregnant rats using anaerobic threshold by LacMin test.

Experimental elicitation with hydroxyisohexyl-3-cyclohexene carboxaldehyde-containing deodorants.

PubMed

Jørgensen, Pia Haslund; Jensen, Charlotte Devantier; Rastogi, Suresh; Andersen, Klaus Ejner; Johansen, Jeanne Duus

2007-03-01

Hydroxyisohexyl-3-cyclohexene carboxaldehyde (HICC) known as Lyral is a frequent allergen. It is used in more than 50% of marketed deodorants. The aim of the present study was to determine elicitation thresholds for HICC under simulated conditions of deodorant use. 15 patients with previously diagnosed contact allergy to HICC were patch tested with 5 solutions of HICC-scented and HICC-unscented deodorants. Patients and 10 healthy controls performed a use test in the axillae using deodorants scented with HICC in increasing concentrations and unscented deodorants as control. The concentration of HICC was increased every second week (200, 600, and 1800 p.p.m.) until either a reaction developed or for 6 weeks. 14 patients completed the study, and all developed unilateral eczema from the HICC-containing deodorant, while controls were all negative (P= 0.004). In 9/14 patients, a positive use test developed during the first 2 weeks to the deodorant containing 200 p.p.m. HICC. Positive correlations were found between the day of positive use and patch test threshold concentration of the HICC solutions (r= 0.71, P= 0.01) as well as the patch test thresholds of the HICC-scented deodorants (r= 0.74, P= 0.007). In conclusion, HICC elicits allergic contact dermatitis in a high proportion of sensitized individuals at common usage concentrations in deodorants.

Reliability of TMS phosphene threshold estimation: Toward a standardized protocol.

PubMed

Mazzi, Chiara; Savazzi, Silvia; Abrahamyan, Arman; Ruzzoli, Manuela

Phosphenes induced by transcranial magnetic stimulation (TMS) are a subjectively described visual phenomenon employed in basic and clinical research as index of the excitability of retinotopically organized areas in the brain. Phosphene threshold estimation is a preliminary step in many TMS experiments in visual cognition for setting the appropriate level of TMS doses; however, the lack of a direct comparison of the available methods for phosphene threshold estimation leaves unsolved the reliability of those methods in setting TMS doses. The present work aims at fulfilling this gap. We compared the most common methods for phosphene threshold calculation, namely the Method of Constant Stimuli (MOCS), the Modified Binary Search (MOBS) and the Rapid Estimation of Phosphene Threshold (REPT). In two experiments we tested the reliability of PT estimation under each of the three methods, considering the day of administration, participants' expertise in phosphene perception and the sensitivity of each method to the initial values used for the threshold calculation. We found that MOCS and REPT have comparable reliability when estimating phosphene thresholds, while MOBS estimations appear less stable. Based on our results, researchers and clinicians can estimate phosphene threshold according to MOCS or REPT equally reliably, depending on their specific investigation goals. We suggest several important factors for consideration when calculating phosphene thresholds and describe strategies to adopt in experimental procedures. Copyright © 2017 Elsevier Inc. All rights reserved.

Photoacoustic signals denoising of the glucose aqueous solutions using an improved wavelet threshold method

NASA Astrophysics Data System (ADS)

Ren, Zhong; Liu, Guodong; Xiong, Zhihua

2016-10-01

The photoacoustic signals denoising of glucose is one of most important steps in the quality identification of the fruit because the real-time photoacoustic singals of glucose are easily interfered by all kinds of noises. To remove the noises and some useless information, an improved wavelet threshld function were proposed. Compared with the traditional wavelet hard and soft threshold functions, the improved wavelet threshold function can overcome the pseudo-oscillation effect of the denoised photoacoustic signals due to the continuity of the improved wavelet threshold function, and the error between the denoised signals and the original signals can be decreased. To validate the feasibility of the improved wavelet threshold function denoising, the denoising simulation experiments based on MATLAB programmimg were performed. In the simulation experiments, the standard test signal was used, and three different denoising methods were used and compared with the improved wavelet threshold function. The signal-to-noise ratio (SNR) and the root-mean-square error (RMSE) values were used to evaluate the performance of the improved wavelet threshold function denoising. The experimental results demonstrate that the SNR value of the improved wavelet threshold function is largest and the RMSE value is lest, which fully verifies that the improved wavelet threshold function denoising is feasible. Finally, the improved wavelet threshold function denoising was used to remove the noises of the photoacoustic signals of the glucose solutions. The denoising effect is also very good. Therefore, the improved wavelet threshold function denoising proposed by this paper, has a potential value in the field of denoising for the photoacoustic singals.

Is the diagnostic threshold for bulimia nervosa clinically meaningful?

PubMed

Chapa, Danielle A N; Bohrer, Brittany K; Forbush, Kelsie T

2018-01-01

The DSM-5 differentiates full- and sub-threshold bulimia nervosa (BN) according to average weekly frequencies of binge eating and inappropriate compensatory behaviors. This study was the first to evaluate the modified frequency criterion for BN published in the DSM-5. The purpose of this study was to test whether community-recruited adults (N=125; 83.2% women) with current full-threshold (n=77) or sub-threshold BN (n=48) differed in comorbid psychopathology and eating disorder (ED) illness duration, symptom severity, and clinical impairment. Participants completed the Clinical Impairment Assessment and participated in semi-structured clinical interviews of ED- and non-ED psychopathology. Differences between the sub- and full-threshold BN groups were assessed using MANOVA and Chi-square analyses. ED illness duration, age-of-onset, body mass index (BMI), alcohol and drug misuse, and the presence of current and lifetime mood or anxiety disorders did not differ between participants with sub- and full-threshold BN. Participants with full-threshold BN had higher levels of clinical impairment and weight concern than those with sub-threshold BN. However, minimal clinically important difference analyses suggested that statistically significant differences between participants with sub- and full-threshold BN on clinical impairment and weight concern were not clinically significant. In conclusion, sub-threshold BN did not differ from full-threshold BN in clinically meaningful ways. Future studies are needed to identify an improved frequency criterion for BN that better distinguishes individuals in ways that will more validly inform prognosis and effective treatment planning for BN. Copyright © 2017 Elsevier Ltd. All rights reserved.

[Is olfactory function impaired in moderate height?].

PubMed

Kühn, M; Welsch, H; Zahnert, T; Hummel, Thomas

2009-09-01

The human sense of smell seems to be influenced by the surrounding barometric pressure. These factors appear to be especially important during flights, for example, in order to recognize the smell of fire etc. Thus, questions are whether pilots or passengers exhibit an impaired smell sensitivity when tested at moderate heights, or, whether changes in humidity would affect the sense of smell. Using climate chambers, odor discrimination and butanol odor thresholds were tested in 77 healthy normosmic volunteers (5 female, 72 male; aged 25+/-8 years from 18 up to 53 years) under hypobaric (2 700+/-20 m, 20 degrees C+/-1 K, rh=50+/-5%) and hyperbaric, (10+/-0.5 m (2 bar)) and different humidity conditions (30 vs. 80%, 20 degrees C+/-1 K, normobaric). During all conditions cognitive performance was tested. Among other effects, olfactory sensitivity was impaired at threshold, but not suprathreshold level, in a hypobaric compared to a hyperbaric milieu, and thresholds were lower in humid, compared to relatively dry conditions. In conclusion, environmental conditions modulate the sense of smell, and may, consecutively, influence results from olfactory tests. During flight hypobaric conditions, mild hypoxia and dry air may cause impaired sensitivity of smell. Georg Thieme Verlag KG Stuttgart * New York.

Orion MPCV Touchdown Detection Threshold Development and Testing

NASA Technical Reports Server (NTRS)

Daum, Jared; Gay, Robert

2013-01-01

A robust method of detecting Orion Multi-Purpose Crew Vehicle (MPCV) splashdown is necessary to ensure crew and hardware safety during descent and after touchdown. The proposed method uses a triple redundant system to inhibit Reaction Control System (RCS) thruster firings, detach parachute risers from the vehicle, and transition to the post-landing segment of the Flight Software (FSW). An in-depth trade study was completed to determine optimal characteristics of the touchdown detection method resulting in an algorithm monitoring filtered, lever-arm corrected, 200 Hz Inertial Measurement Unit (IMU) vehicle acceleration magnitude data against a tunable threshold using persistence counter logic. Following the design of the algorithm, high fidelity environment and vehicle simulations, coupled with the actual vehicle FSW, were used to tune the acceleration threshold and persistence counter value to result in adequate performance in detecting touchdown and sufficient safety margin against early detection while descending under parachutes. An analytical approach including Kriging and adaptive sampling allowed for a sufficient number of finite element analysis (FEA) impact simulations to be completed using minimal computation time. The combination of a persistence counter of 10 and an acceleration threshold of approximately 57.3 ft/s2 resulted in an impact performance factor of safety (FOS) of 1.0 and a safety FOS of approximately 2.6 for touchdown declaration. An RCS termination acceleration threshold of approximately 53.1 ft/s(exp)2 with a persistence counter of 10 resulted in an increased impact performance FOS of 1.2 at the expense of a lowered under-parachutes safety factor of 2.2. The resulting tuned algorithm was then tested on data from eight Capsule Parachute Assembly System (CPAS) flight tests, showing an experimental minimum safety FOS of 6.1. The formulated touchdown detection algorithm will be flown on the Orion MPCV FSW during the Exploration Flight Test 1 (EFT-1) mission in the second half of 2014.

The influence of ambient temperature on power at anaerobic threshold determined based on blood lactate concentration and myoelectric signals.

PubMed

Tyka, Aleksander; Pałka, Tomasz; Tyka, Anna; Cisoń, Tomasz; Szyguła, Zbigniew

2009-01-01

To compare the mechanical power and physiological parameters in males at the lactate (LAAT) and integrated electromyographic (IEMGAT) anaerobic thresholds during exercise testing at 23 degrees C, 31 degrees C and 37 degrees C. Fifteen men aged 21.9+/-1.80 years performed an incremental exercise test on a cycle ergometer at pedal frequency of 60 rpm. The test began at the power output of 120 W which was increased by 30 W every 3 min. Heart rate, oxygen uptake, carbon dioxide in expired air and minute ventilation were monitored. Venous blood samples were collected at 30 s before termination of each 3-min stage of test to determine the lactate anaerobic threshold. IEMGAT for vastus lateralis (VL) and rectus femoris (RF) muscles were regarded as the inflection point at which a non-linear increase in IEMGAT occurred. IEMGAT for VL and RF were similar for all the three temperatures. IEMGAT (VL and RF) correlated closely with LAAT at ambient temperatures of 23 degrees C (r = 0.91), 31 degrees C (r = 0.96) and 37 degrees C (r = 0.97). Repeated measures analysis of variance (ANOVA) revealed that the mechanical power at LAAT and IEMGAT was higher at 23 degrees C (202+/-26.5 W vs. 205+/-22.9 W) than at 31 degrees C (186+/-20.2 W vs. 186.2+/-20.2 W) and 37 degrees C (175.5+/-25.2 W vs. 175.3+/-20.0 W) for LAAT and IEMGAT respectively (p < 0.01). Higher ambient temperature induced a decrease in the mechanical power at which the anaerobic threshold occurred. The high correlation between LAAT and IEMGAT (r = 0.91-0.97) indicated that IEMGAT can be used as a practical and reliable, non-invasive method for assessment of the anaerobic threshold.

Effects of cochlear-implant pulse rate and inter-channel timing on channel interactions and thresholds

NASA Astrophysics Data System (ADS)

Middlebrooks, John C.

2004-07-01

Interactions among the multiple channels of a cochlear prosthesis limit the number of channels of information that can be transmitted to the brain. This study explored the influence on channel interactions of electrical pulse rates and temporal offsets between channels. Anesthetized guinea pigs were implanted with 2-channel scala-tympani electrode arrays, and spike activity was recorded from the auditory cortex. Channel interactions were quantified as the reduction of the threshold for pulse-train stimulation of the apical channel by sub-threshold stimulation of the basal channel. Pulse rates were 254 or 4069 pulses per second (pps) per channel. Maximum threshold reductions averaged 9.6 dB when channels were stimulated simultaneously. Among nonsimultaneous conditions, threshold reductions at the 254-pps rate were entirely eliminated by a 1966-μs inter-channel offset. When offsets were only 41 to 123 μs, however, maximum threshold shifts averaged 3.1 dB, which was comparable to the dynamic ranges of cortical neurons in this experimental preparation. Threshold reductions at 4069 pps averaged up to 1.3 dB greater than at 254 pps, which raises some concern in regard to high-pulse-rate speech processors. Thresholds for various paired-pulse stimuli, pulse rates, and pulse-train durations were measured to test possible mechanisms of temporal integration.

Fatigue threshold studies in Fe, Fe-Si, and HSLA steel: Part II. thermally activated behavior of the effective stress intensity at threshold

NASA Astrophysics Data System (ADS)

Yu, W.; Esaklul, K.; Gerberich, W. W.

1984-05-01

It is shown that closure mechanisms alone cannot fully explain increasing fatigue thresholds with decreasing test temperature for a sequence of Fe-Si binary alloys and an HSLA steel. Implications are that fatigue crack propagation near threshold is a thermally activated process. The effective threshold stress intensity, which was obtained by subtracting the closure portion from the fatigue threshold, was examined. This effective stress intensity was found to correlate very well to the thermal component of the flow stress. A detailed fractographic study of the fatigue surface was performed. Water vapor in the room air was found to promote the formation of oxide and intergranular crack growth. At lower temperature, a brittle-type cyclic cleavage fatigue surface was observed but the ductile process persisted even at 123 K. Arrest marks were found on all three modes of fatigue crack growth. The regular spacings between these lines and dislocation modeling suggested that fatigue crack growth was controlled by the subcell structure near threshold. A model based on the slip-off of dislocations was examined. From this, it is shown that the effective fatigue threshold may be related to the square root of (one plus the strain rate sensitivity).

A systematic review and meta-analysis of the diagnostic accuracy of point-of-care tests for the detection of hyperketonemia in dairy cows.

PubMed

Tatone, Elise H; Gordon, Jessica L; Hubbs, Jessie; LeBlanc, Stephen J; DeVries, Trevor J; Duffield, Todd F

2016-08-01

Several rapid tests for use on farm have been validated for the detection of hyperketonemia (HK) in dairy cattle, however the reported sensitivity and specificity of each method varies and no single study has compared them all. Meta-analysis of diagnostic test accuracy is becoming more common in human medical literature but there are few veterinary examples. The objective of this work was to perform a systematic review and meta-analysis to determine the point-of-care testing method with the highest combined sensitivity and specificity, the optimal threshold for each method, and to identify gaps in the literature. A comprehensive literature search resulted in 5196 references. After removing duplicates and performing relevance screening, 23 studies were included for the qualitative synthesis and 18 for the meta-analysis. The three index tests evaluated in the meta-analysis were: the Precision Xtra(®) handheld device measuring beta-hydroxybutyrate (BHB) concentration in whole blood, and Ketostix(®) and KetoTest(®) semi-quantitative strips measuring the concentration of acetoacetate in urine and BHB in milk, respectively. The diagnostic accuracy of the 3 index tests relative to the reference standard measurement of BHB in serum or whole blood between 1.0-1.4mmol/L was compared using the hierarchical summary receiver operator characteristic (HSROC) method. Subgroup analysis was conducted for each index test to examine the accuracy at different thresholds. The impact of the reference standard threshold, the reference standard method, the prevalence of HK in the population, the primary study source and risk of bias of the primary study was explored using meta-regression. The Precision Xtra(®) device had the highest summary sensitivity in whole blood BHB at 1.2mmol/L, 94.8% (CI95%: 92.6-97.0), and specificity, 97.5% (CI95%: 96.9-98.1). The threshold employed (1.2-1.4mmol/L) did not impact the diagnostic accuracy of the test. The Ketostix(®) and KetoTest(®) strips had the highest summary sensitivity and specificity when the trace and weak positive thresholds were used, respectively. Controlling for the source of publication, HK prevalence and reference standard employed did not impact the estimated sensitivity and specificity of the tests. Including only peer-reviewed studies reduced the number of primary studies evaluating the Precision Xtra(®) by 43% and Ketostix(®) by 33%. Diagnosing HK with blood, urine or milk are valid options, however, the diagnostic inaccuracy of urine and milk should be considered when making economic and treatment decisions. Copyright © 2016 Elsevier B.V. All rights reserved.

Barostat testing of rectal sensation and compliance in humans: comparison of results across two centres and overall reproducibility.

PubMed

Cremonini, F; Houghton, L A; Camilleri, M; Ferber, I; Fell, C; Cox, V; Castillo, E J; Alpers, D H; Dewit, O E; Gray, E; Lea, R; Zinsmeister, A R; Whorwell, P J

2005-12-01

We assessed reproducibility of measurements of rectal compliance and sensation in health in studies conducted at two centres. We estimated samples size necessary to show clinically meaningful changes in future studies. We performed rectal barostat tests three times (day 1, day 1 after 4 h and 14-17 days later) in 34 healthy participants. We measured compliance and pressure thresholds for first sensation, urgency, discomfort and pain using ascending method of limits and symptom ratings for gas, urgency, discomfort and pain during four phasic distensions (12, 24, 36 and 48 mmHg) in random order. Results obtained at the two centres differed minimally. Reproducibility of sensory end points varies with type of sensation, pressure level and method of distension. Pressure threshold for pain and sensory ratings for non-painful sensations at 36 and 48 mmHg distension were most reproducible in the two centres. Sample size calculations suggested that crossover design is preferable in therapeutic trials: for each dose of medication tested, a sample of 21 should be sufficient to demonstrate 30% changes in all sensory thresholds and almost all sensory ratings. We conclude that reproducibility varies with sensation type, pressure level and distension method, but in a two-centre study, differences in observed results of sensation are minimal and pressure threshold for pain and sensory ratings at 36-48 mmHg of distension are reproducible.