Visual and semiochemical disruption of host finding in the southern pine beetle

Treesearch

B.L. Strom; L.M. Roton; R.A. Goyer; J.R. Meeker

1999-01-01

The importance of visual silhouettes for host finding by the southern pine beetle (SPB), Dendroctonus frontalis (Coleoptera: Scolytidae), and the potential for disruption of this process using visual deterrents were evaluated with multiple-funnel traps, painted white or black, and with clear, white or black Plexiglas sticky panel.The results show that both SPB and T....

Geoacoustic inversion with two source-receiver arrays in shallow water.

PubMed

Sukhovich, Alexey; Roux, Philippe; Wathelet, Marc

2010-08-01

A geoacoustic inversion scheme based on a double beamforming algorithm in shallow water is proposed and tested. Double beamforming allows identification of multi-reverberated eigenrays propagating between two vertical transducer arrays according to their emission and reception angles and arrival times. Analysis of eigenray intensities yields the bottom reflection coefficient as a function of angle of incidence. By fitting the experimental reflection coefficient with a theoretical prediction, values of the acoustic parameters of the waveguide bottom can be extracted. The procedure was initially tested in a small-scale tank experiment for a waveguide with a Plexiglas bottom. Inversion results for the speed of shear waves in Plexiglas are in good agreement with the table values. A similar analysis was applied to data collected during an at-sea experiment in shallow coastal waters of the Mediterranean. Bottom reflection coefficient was fitted with the theory in which bottom sediments are modeled as a multi-layered system. Retrieved bottom parameters are in quantitative agreement with those determined from a prior inversion scheme performed in the same area. The present study confirms the interest in processing source-receiver array data through the double beamforming algorithm, and indicates the potential for application of eigenray intensity analysis to geoacoustic inversion problems.

Modeling of the Non-Auditory Response to Blast Overpressure. Calculation of the Internal Mechanical Response of Sheep to Blast Loading

DTIC Science & Technology

1990-01-01

through the esophagus into the left lung lobe and fially to the left rib surface. Spinal Process of Sixth Vertebra Seventh Vertebra Scapula Esophagus...for the calculations are as follows: 2.54 cm 12.7 cm 2.64 cm ’ J End Plate + Transducer Plexiglas (hard) or_ Closed-Cell Neoprene (soft) Figure 4

The effect of substrate properties, size, position, sheltering and shading on dew: An experimental approach in the Negev Desert

NASA Astrophysics Data System (ADS)

Kidron, Giora J.

2010-11-01

Affected by the interrelationships between the air mass and the substrate properties, dew measurements entail numerous difficulties. Inattentiveness to the complexities involved may result in inconsistent and consequently unreliable data and thus in misleading conclusions. This is especially important in dew deserts such as the Negev where dew may be regarded as an important water source. In an attempt to highlight some of the factors that may affect dew condensation, an experimental approach was adapted during which dew condensation at different surfaces (smooth and ragged Plexiglas, bright limestone and dark flint cobbles), at various size substrata with identical axes (of 2.5, 5, 10, 20, 30 and 40 cm) or different size axes (of 10 × 20, 10 × 30 and 10 × 40 cm), and substrata at different heights and settings was measured. Some of the settings explored were also sheltered by a shrub, a cave, an 80-cm-tall cliff and neighboring cobbles. No significant differences were found in the dew amounts condensing on the limestone and the flint cobbles. Smooth Plexiglas surfaces yielded significantly higher amounts than a ragged Plexiglas surface. As for the substratum height and size, the dew amounts increased with height (from 0.7 to 10.0 cm) and size (from 2.5 × 2.5 cm to 40 × 40 cm). However, an increase in the long axis (a-axis) to 20, 30 and 40 cm while leaving the b-axis constant (at 10 cm) resulted in only a slight increase in the dew amounts in comparison to a 10 × 10 cm substratum. While confined to non-sheltered habitats, dew at partially sheltered habitats (such as the margin of a shrub or a cave, the vicinity of a cliff and on 7-cm-high cobble surrounded by 15-cm-high cobbles) was significantly lower than at the exposed habitats. The differences in dew amounts coincided with minute differences in the surface temperatures, explained as resulting from differences in the outgoing nocturnal longwave radiational cooling. The findings may shed light on the dew regime of lithobionts at different microhabitats and upon inconsistent values reported in the literature.

Controls on mid-ocean ridge segmentation and transform fault formation from laboratory experiments using fluids of complex rheology.

NASA Astrophysics Data System (ADS)

Sibrant, A.; Mittelstaedt, E. L.; Davaille, A.

2017-12-01

Mid-ocean ridges are tectonically segmented at scales of 10s to 100s of kilometers by several types of offsets including transform faults (TF), overlapping spreading centers (OSC), and slow-spreading non-transform offsets (NTO). Differences in segmentation along axis have been attributed to changes in numerous processes including magma supply from the upwelling mantle, viscous flow in the asthenosphere, ridge migration, and plate spreading direction. The wide variety of proposed mechanisms demonstrate that the origin of tectonic offsets and their relationship to segment-scale magmatic processes remain actively debated; each of the above processes, however, invoke combinations of tectonic and magmatic processes to explain changes in segmentation. To address the role of tectonic deformation and magmatic accretion on the development of ridge offsets, we present a series of analogue experiments using colloidal silica dispersions as an Earth analogue. Saline water solutions placed in contact with these fluids, cause formation of a skin through salt diffusion, whose rheology evolves from purely viscous to elastic and brittle with increasing salinity. Experiments are performed in a Plexiglas tank with two Plexiglas plates suspended above the base of the tank. The tank is filled with the colloidal fluid to just above the suspended plates, a thin layer of saline water is spread across the surface, and spreading initiated by moving the suspended Plexiglas plates apart at a fixed rate. Results show formation of OSCs, NTOs, and TFs. For parameters corresponding to the Earth, TF offsets are < 5 mm and form at all spreading velocities, corresponding to transform offsets of < 100 km on Earth. Measured TF offset size and ridge segment lengths exhibit a Poisson-type distribution with no apparent dependence on spreading rate. Observations of TF offset size on Earth show a similar distribution for TFs <100 km long and supports the hypothesis that TFform spontaneously through a mechanical instability of the axis. Here, we present an analysis of the magmatic and tectonic controls on axis instability leading to the formation of TFs, OSCs, and NTOs, and their implications for the evolution of mid-ocean ridges.

Environmentally Acceptable Medium Caliber Ammunition Percussion Primers

DTIC Science & Technology

2007-10-31

tetrazol-5-amino)-s-tetrazine or Bis-aminotetrazolyl-tetrazine CAD Cartridge Actuated Device CFR Code of Federal Regulations cm Centimeter cm3...approximately 120mg each, were placed on the Plexiglas slab . The piles were separated by a potassium chloride window estimated to transmit at least...for cartridge actuated device/propellant actuated device ( CAD /PAD) application. The NSWC-IH was working with the SDSMT and IMP in developing unique

COMBINED EXPOSURE TO PYRIDOSTIGMINE BROMIDE (PB), DEET, AND PERMETHRIN WITH STRESS INCREASE BLOOD-BRAIN BARRIER (BBB) PERMEABILITY AND INHIBITS BRAIN ACETYLCHOLINESTERASE IN RATS.

EPA Science Inventory

Two groups of 15 male Sprague-Dawley rats weighing 225-250 g, were administered PB (1.3mg/kg/d, oral), DEET (40mg/kg/d, dermal), and permethrin (0.13mg/kg/d, dermal) for 28 days. Animals in one group were stressed by placing them in a Plexiglas restraint tube for 5 mins. eac...

Comparison of the lateral retention forces on sessile and pendant water drops on a solid surface

NASA Astrophysics Data System (ADS)

de la Madrid, Rafael; Whitehead, Taylor; Irwin, George M.

2015-06-01

We present a simple experiment that demonstrates how a water drop hanging from a Plexiglas surface (pendant drop) experiences a lateral retention force that is comparable to, and in some cases larger than, the lateral retention force on a drop resting on top of the surface (sessile drop). The experiment also affords a simple demonstration of the Coriolis effect in two dimensions.

Ocean Engineering Studies Compiled 1991. Volume 6. Acrylic Windows - Typical Applications in Pressure Housings

DTIC Science & Technology

1991-01-01

either the metallic or plastic composite pressure envelope. The ASME Boiler and Pressure Vessel Code Section 8 provides such design criteria, and the...fabricated of metallic or piastic composite materials. To preclude potential catastrophic failures of windows designed on the basis of inadequate data, in...pressure-resistant acrylic windows (reference 12). Acrylic windows are usually machined from Plexiglas G plate, which is limited in thickness to 4 inches

Air ion exposure system for plants

NASA Technical Reports Server (NTRS)

Morrow, R. C.; Tibbitts, T. W.

1987-01-01

A system was developed for subjecting plants to elevated air ion levels. This system consisted of a rectangular Plexiglas chamber lined with a Faraday cage. Air ions were generated by corona discharge from frayed stainless steel fibers placed at one end of the chamber. This source was capable of producing varying levels of either positive or negative air ions. During plant exposures, environmental conditions were controlled by operating the unit in a growth chamber.

Air ion exposure system for plants.

PubMed

Morrow, R C; Tibbitts, T W

1987-02-01

A system was developed for subjecting plants to elevated air ion levels. This system consisted of a rectangular Plexiglas chamber lined with a Faraday cage. Air ions were generated by corona discharge from frayed stainless steel fibers placed at one end of the chamber. This source was capable of producing varying levels of either positive or negative air ions. During plant exposures, environmental conditions were controlled by operating the unit in a growth chamber.

An Experimental Study of the Dynamics of an Unsteady Turbulent Boundary Layer.

DTIC Science & Technology

1982-12-01

honeycomb combination into the screen box. The screen box is made of plexiglas, and the screens are made of stainless steel wire (24 gauge, 70% porosity...port plug was modified to accommodate at its cen- ter a stainless steel stem with a disk on the end toward the inside of the tunnel. The stem is spring...necessay and Identify by block nomber) * turbulent boundary layers fluid dynamics free stream velocity A B r R CT si royy.rs ebb it ,imseesa nd ideiiit

Toxic Hazard to the Rabbit from Direct and Vapor Contact with HD-Contaminated Plexiglas, Concrete, or XM40 Nylon Carrier Material

DTIC Science & Technology

1986-07-01

for vapor transfer. A toxicological test was c’isigned to evaluate the above models. Animals were exposed to agant vapor and to direct contact with...surfaces contaminated with HD. If the toxicological response is the same from direct contact as from vapor, then only vapor transfer is significant...study were chosen to deter- mine whether partitioning is applicable to nonpermeable materials such as the polymethyl methacrylate ( PMMA ) sheeting or to

Mesopause Winds and OH Intensities at Mid-Latitudes-Fabry-Perot Interferometer Observations of the OH Emission at 8430 A from Bear Lake Observatory

DTIC Science & Technology

1993-01-01

73 1 5.1 The Fabry-Perot Interferometer ............................................................ 73 5.1.1. The Scanning Mirror System...instrument to view the sky aided by a mirror system, and a Plexiglas dome cover protects the instrument and electronics from the elements. I Because the...sections describe the individual components of the instrument at Bear Lake and refer to Figure 19. I 5.1.1. The Scanning Mirror System The scanning

In Vitro Partial-Body Dose Assessment Using a Radiation Responsive Protein Biomarker

DTIC Science & Technology

2005-01-01

would design and evaluate the dosimetry of the murine in vivo partial-body irradiation set-up. Thermo-luminescent dosimeter (TLD) chips or Optically...Stimulated Luminescent ( OSL ) should be placed near the mice in the plexiglass tubes in order to measure the dose profile to the mice. GAFCHROMIC...TLDs) chips or ( OSLs ) will be placed near the mice in the Plexiglas tubes in order to measure the dose to the mice. TLDs or OSLs will be placed

Free-surface phenomena under low- and zero-gravity conditions

NASA Technical Reports Server (NTRS)

Coles, D.

1985-01-01

An apparatus to measure contact angle was constructed to exploit the proposed internal-corner criterion. If 2 alfa is the internal angle between two intersecting vertical planes and gamma is the contact angle, a meniscus at the corner rises to a finite height if alfa + gamma pi/2 and to an infinite height if alfa + gamma pi/2. The apparatus operates by decreasing the angle alfa from pi/2 until the meniscus height changes abruptly. A number of liquids are tested on glass and plexiglas.

A new device to test cutting efficiency of mechanical endodontic instruments.

PubMed

Giansiracusa Rubini, Alessio; Plotino, Gianluca; Al-Sudani, Dina; Grande, Nicola M; Sonnino, Gianpaolo; Putorti, Ermanno; Cotti, Elisabetta; Testarelli, Luca; Gambarini, Gianluca

2014-03-06

The purpose of the present study was to introduce a new device specifically designed to evaluate the cutting efficiency of mechanically driven endodontic instruments. Twenty new Reciproc R25 (VDW, Munich, Germany) files were used to be investigated in the new device developed to test the cutting ability of endodontic instruments. The device consists of a main frame to which a mobile plastic support for the hand-piece is connected and a stainless-steel block containing a Plexiglas block against which the cutting efficiency of the instruments was tested. The length of the block cut in 1 minute was measured in a computerized program with a precision of 0.1mm. The instruments were activated by using a torque-controlled motor (Silver Reciproc; VDW, Munich, Germany) in a reciprocating movement by the "Reciproc ALL" program (Group 1) and in counter-clockwise rotation at 300 rpm (Group 2). Mean and standard deviations of each group were calculated and data were statistically analyzed with a one-way ANOVA test (P<0.05). Reciproc in reciprocation (Group 1) mean cut in the Plexiglas block was 8.6 mm (SD=0.6 mm), while Reciproc in rotation mean cut was 8.9 mm (SD=0.7 mm). There was no statistically significant difference between the 2 groups investigated (P>0.05). The cutting testing device evaluated in the present study was reliable and easy to use and may be effectively used to test cutting efficiency of both rotary and reciprocating mechanical endodontic instruments.

Impact of the vaginal applicator and dummy pellets on the dosimetry parameters of Cs-137 brachytherapy source.

PubMed

Sina, Sedigheh; Faghihi, Reza; Meigooni, Ali S; Mehdizadeh, Simin; Mosleh Shirazi, M Amin; Zehtabian, Mehdi

2011-05-19

In this study, dose rate distribution around a spherical 137Cs pellet source, from a low-dose-rate (LDR) Selectron remote afterloading system used in gynecological brachytherapy, has been determined using experimental and Monte Carlo simulation techniques. Monte Carlo simulations were performed using MCNP4C code, for a single pellet source in water medium and Plexiglas, and measurements were performed in Plexiglas phantom material using LiF TLD chips. Absolute dose rate distribution and the dosimetric parameters, such as dose rate constant, radial dose functions, and anisotropy functions, were obtained for a single pellet source. In order to investigate the effect of the applicator and surrounding pellets on dosimetric parameters of the source, the simulations were repeated for six different arrangements with a single active source and five non-active pellets inside central metallic tubing of a vaginal cylindrical applicator. In commercial treatment planning systems (TPS), the attenuation effects of the applicator and inactive spacers on total dose are neglected. The results indicate that this effect could lead to overestimation of the calculated F(r,θ), by up to 7% along the longitudinal axis of the applicator, especially beyond the applicator tip. According to the results obtained in this study, in a real situation in treatment of patients using cylindrical vaginal applicator and using several active pellets, there will be a large discrepancy between the result of superposition and Monte Carlo simulations.

Catchment science on a shoestring -- Luddites, labor, and a little high-tech

NASA Astrophysics Data System (ADS)

Shanley, J. B.; Denner, J. C.; Clark, S. F.; Chalmers, A.; Smith, T. E.; Sebestyen, S. D.; McGlynn, B.; Hjerdt, K. N.; McDonnell, J. J.

2004-05-01

At Sleepers River Research Watershed in northeastern Vermont, the USGS has operated a long-term global change hydrology site with a limited equipment budget for more than 12 years. Most of the research takes place at a remote 41-ha catchment without A/C power, 15-minutes walk from the nearest road. The overall approach of the project is the combined use of hydrologic, chemical, and isotopic measurements to understand hydrologic flow paths and biogeochemical evolution of waters. Measurements and water samples are taken at various nodes in the system. Some of our cost-effective ways to conduct these measurements include: (1) a horse to pull a drill rig for installing wells in the catchment; (2) small stream V-notch weirs fashioned from plywood and plexiglas (12 years and going strong); (3) a knocking pole penetrometer to determine soil depths and infer soil properties; (4) solar panels to charge batteries; (5) frost depth measurements using methylene blue solution in flexible tubing suspended within PVC housing (6) two versions of snowmelt lysimeters constructed of PVC pipe and plexiglas (both silicone caulk and duct tape were used on the latter); (7) arrays of washing machine peepers, which are small inexpensive on/off float sensors mounted at land surface to determine surface saturation (recorded with a datalogger). These creative low-cost solutions to "getting the job done" have helped to keep this long-term site operating during budget shortfalls.

A new device to test cutting efficiency of mechanical endodontic instruments

PubMed Central

Rubini, Alessio Giansiracusa; Plotino, Gianluca; Al-Sudani, Dina; Grande, Nicola M.; Putorti, Ermanno; Sonnino, GianPaolo; Cotti, Elisabetta; Testarelli, Luca; Gambarini, Gianluca

2014-01-01

Background The purpose of the present study was to introduce a new device specifically designed to evaluate the cutting efficiency of mechanically driven endodontic instruments. Material/Methods Twenty new Reciproc R25 (VDW, Munich, Germany) files were used to be investigated in the new device developed to test the cutting ability of endodontic instruments. The device consists of a main frame to which a mobile plastic support for the hand-piece is connected and a stainless-steel block containing a Plexiglas block against which the cutting efficiency of the instruments was tested. The length of the block cut in 1 minute was measured in a computerized program with a precision of 0.1mm. The instruments were activated by using a torque-controlled motor (Silver Reciproc; VDW, Munich, Germany) in a reciprocating movement by the “Reciproc ALL” program (Group 1) and in counter-clockwise rotation at 300 rpm (Group 2). Mean and standard deviations of each group were calculated and data were statistically analyzed with a one-way ANOVA test (P<0.05). Results Reciproc in reciprocation (Group 1) mean cut in the Plexiglas block was 8.6 mm (SD=0.6 mm), while Reciproc in rotation mean cut was 8.9 mm (SD=0.7 mm). There was no statistically significant difference between the 2 groups investigated (P>0.05). Conclusions The cutting testing device evaluated in the present study was reliable and easy to use and may be effectively used to test cutting efficiency of both rotary and reciprocating mechanical endodontic instruments. PMID:24603777

A Characterization of the Radiation from a Rod-Pinch Diode

NASA Astrophysics Data System (ADS)

Swanekamp, Stephen B.; Allen, Raymond J.; Hinshelwood, David D.; Mosher, David; Schumer, Joseph W.

2002-12-01

Coupled PIC-Monte-Carlo simulations of the electron-flow and radiation production in a rod-pinch diode show that multiple scatterings in the rod produce incident electron energies that ranging from zero to slightly higher than the applied voltage. It is speculated that those electrons that gain energy do so by remaining in phase with a rapidly varying electric field near the tip of the rod. The simulations also show that multiple passes in the rod produce a wide spread in incident electron angles. For diode voltages of V=2 MV, the angular distribution of electrons incident on the rod is broad and peaked near 90° to the axis of the rod with a larger fraction of electrons striking the rod at angles less than 90°. The electron angular distribution for V=4 MV is narrower and peaked at 105° with a larger fraction of electrons incident on the rod with angles greater than 90°. The photon distributions are peaked along the direction of the high-energy electrons. For V=2 MV the dose filtered through 21/4-cm thick Plexiglas is peaked at 90° and is 1.8 times higher than the forward-directed [0°] dose. For V=4 MV the dose filtered through 21/4-cm thick Plexiglas is peaked at 120° and is 2.3 times higher than the forward-directed dose. Similar angular variation of the dose has been observed on the 4-MV Asterix accelerator [2] and on 1-2 MV accelerators at the Atomic Weapons Establishment [8].

Experimental study of the penetrating of plates by projectile at low initial speeds

NASA Astrophysics Data System (ADS)

Orlov, M. Yu; Orlova, Yu N.; Smakotin, Ig L.; Glazyrin, V. P.; Orlov, Yu N.

2017-11-01

The research of the penetration process of lightweight plates by a projectile in the range of initial velocities up to 325 m/s was attempted. The projectile was a shell bullet and the barriers were of ice, MDF-panels and plexiglas barriers. The response of barriers to impact loading is studied. High-speed shooting of each experiment is obtained, including photos of the front and rear sides of the barriers. An attempt was made to reproduce the scenario of the destruction of barriers. The results of experiments can be interpreted only as qualitative tests. Projectile was not destroyed.

The effect of thermal neutron field slagging caused by cylindrical BF3 counters in diffusion media

NASA Technical Reports Server (NTRS)

Gorshkov, G. V.; Tsvetkov, O. S.; Yakovlev, R. M.

1975-01-01

Computations are carried out in transport approximation (first collision method) for the attenuation of the field of thermal neutrons formed in counters of the CHM-8 and CHMO-5 type. The deflection of the thermal neutron field is also obtained near the counters and in the air (shade effect) and in various decelerating media (water, paraffin, plexiglas) for which the calculations are carried out on the basis of diffusion theory. To verify the calculations, the distribution of the density of the thermal neutrons at various distances from the counter in the water is measured.

Polishing compound for plastic surfaces

DOEpatents

Stowell, Michael S.

1995-01-01

A polishing compound for plastic surfaces. The compound contains by weight approximately 4 to 17 parts at least one petroleum distillate lubricant, 1 to 6 parts mineral spirits, 2.5 to 15 parts abrasive particles, and 2.5 to 10 parts water. The abrasive is tripoli or a similar material that contains fine particles silica. Preferably, most of the abrasive particles are less than approximately 10 microns, more preferably less than approximately 5 microns in size. The compound is used on PLEXIGLAS.TM., LEXAN.TM., LUCITE.TM., polyvinyl chloride (PVC) and similar plastic materials whenever a smooth, clear polished surface is desired.

Polishing compound for plastic surfaces

DOEpatents

Stowell, M.S.

1993-01-01

A polishing compound for plastic surfaces is disclosed. The compound contains by weight approximately 4 to 17 parts at least one petroleum distillate lubricant, 1 to 6 parts mineral spirits, 2.5 to 15 parts abrasive particles, and 2.5 to 10 parts water. The abrasive is tripoli or a similar material that contains colloidal silica. Preferably, most of the abrasive particles are less than approximately 10 microns, more preferably less than approximately 5 microns in size. The compound is used on PLEXIGLAS{sup TM}, LEXAN{sup TM}, LUCITE{sup TM}, polyvinyl chloride (PVC) and similar plastic materials whenever a smooth, clear polished surface is desired.

Polishing compound for plastic surfaces

DOEpatents

Stowell, M.S.

1995-08-22

A polishing compound for plastic surfaces is disclosed. The compound contains by weight approximately 4 to 17 parts at least one petroleum distillate lubricant, 1 to 6 parts mineral spirits, 2.5 to 15 parts abrasive particles, and 2.5 to 10 parts water. The abrasive is tripoli or a similar material that contains fine particles silica. Preferably, most of the abrasive particles are less than approximately 10 microns, more preferably less than approximately 5 microns in size. The compound is used on PLEXIGLAS{trademark}, LEXAN{trademark}, LUCITE{trademark}, polyvinyl chloride (PVC) and similar plastic materials whenever a smooth, clear polished surface is desired. 5 figs.

Observational learning without a model is influenced by the observer's possibility to act: evidence from the Simon task.

PubMed

Iani, Cristina; Rubichi, Sandro; Ferraro, Luca; Nicoletti, Roberto; Gallese, Vittorio

2013-07-01

We assessed whether observational learning in perceptual-motor tasks is affected by the visibility of an action producing perceived environmental effects and by the observer's possibility to act during observation. To this end, we conducted three experiments in which participants were required to observe a spatial compatibility task in which only the effects of computer-generated responses were visible before executing a Simon task. In Experiment 1, we compared the effects of a passively observed practice with either a spatially compatible or incompatible stimulus-response (S-R) association. In Experiment 2, during the observed spatially incompatible practice participants were prevented from potentially acting, either because a plexiglas barrier separated the participant from the response device rendering it out of reach; or because the participant's hands were tied; or the device affording a response was absent. In Experiment 3, the plexiglas presented an opening that could allow the participant to potentially reach and interact with it. As when the practice is physically performed, we found an elimination of the Simon effect following a spatially incompatible observed practice, suggesting that participants learned an incompatible S-R association by observing and transferred this knowledge to the subsequent Simon task. No evidence of transfer of learning was found when, during passive observation, the participant's hands were tied, or a barrier prevented him/her from potentially interacting with the device, or no response device was present. Differently, a transfer-of-learning effect was observed when the barrier presented an opening. These results suggest that learning can derive from the mere observation of action effects, even when an action is not visible, as long as the observer has the potential to act. Copyright © 2013 Elsevier B.V. All rights reserved.

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

Yarotski, Dmitry Anatolievitch

On Thursday November 19, 2015, LANL postdoc received an eye injury from a reflected, nonvisible laser beam (Class 4, pulsed, wavelength 800 nanometer). The setup is configured to split the laser output into two work areas in which qualified operators conduct research experiments. During this incident, the laser output beam was being projected to both experimental work areas, although only one experimental area was actively being used. The second laser beam directed to the second work area was blocked by an inappropriate device (Plexiglas, reflective, non-normal incidence) that reflected substantial portion of the beam toward the first setup. In preparationmore » for the measurements, worker stepped on the stepstool and decided to remove the laser goggles to better see the micrometer readings which were difficult to see due to insufficient lighting. Immediately, he noticed a flash of light in his eye. The operator quickly replaced the laser eye-wear and then, using an infrared viewer, located a stray laser beam being reflected from the plexiglas beam block. The operator did not think he had sustained any injury and continued working. Later that day, however, he noticed a blurry spot in the vision of his left eye. He notified his supervisor on Friday morning, November 20, 2015, and was taken by CINT management to Sandia National Laboratories (SNL) medical facility for evaluation. SNL Medical did not find any abnormalities, but referred the operator to a local ophthalmologist for further evaluation. Further evaluations by the ophthalmologist on November 21 and November 23 identified a small spot of inflammation near the fovea on the retina in his left eye. The ophthalmologist stated that this spot would most likely heal on its own and that the blurry spot on the operator's vision would go away. A follow-up visit was scheduled. The employee was released back to work without restrictions.« less

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

Wilczek, Krzysztof; Petelenz, Barbara; Strzala, Alicja

Purpose. Biological effects of intravascular brachytherapy are very sensitive to discrepancies between the prescription and the applied dose. If brachytherapy is aimed at in-stent restenosis, shielding and shadowing effects of metallic stents may change the dose distribution relative to that produced by the bare source. The development of new generations of stents inspired us to a new experimental study in this field. The effect was studied for 14 stents which we have recently encountered in clinical practice. Methods. The model source was a continuous 20-mm column of {sup 90}Sr/{sup 90}Y solution sealed in a 1-mm-I.D. Plexiglas capillary. The dose distributionmore » in the Plexiglas phantom was mapped using GafChromic MD-55-2 film. The stent masses varied from 2.5 to 25 mg; the strut thicknesses, from 0.075 to 0.15 mm; and the atomic numbers of stent materials, from 24 (Cr) to 79 (Au). Results. Dose perturbations depend on a variety of stent features. Local reduction of the mean dose rates near the reference distance (r{sub 0} = 2 mm) varied from 11% to 47%. No simple correlation was found between these data and stent characteristics, but it seems that the atomic number of the stent material is less important than the strut thickness and mesh density. Conclusion. The results provide a warning that clinical indications for in-stent radiation therapy must always be confronted with another aspect of the patient's history: the kind of implanted stent. Intravascular brachytherapy using pure beta sources may be recommended only for patients 'wearing' light, thin-strut stents. The presence of thick-strut stents is a contraindication for this modality, due to excessive dose perturbation.« less

BRIEF COMMUNICATIONS: Experimental study of the energy balance in the interaction of a pulsed CO2 laser with metal and insulating targets in air

NASA Astrophysics Data System (ADS)

Babaeva, N. A.; Vas'kovskiĭ, Yu M.; Rovinskiĭ, R. E.; Ryabinkina, V. A.

1991-09-01

Measurements were made of components of the energy balance in the interaction of pulsed CO2 laser radiation with Dural, glass, quartz, ebonite, and Plexiglas in air at atmospheric pressure. At laser energy densities between 1 and 20 J/cm2 and in the spectral range 0.2-7 μm, the re-emission of radiation by the laser plasma was found to be less than 1 %. At energy densities exceeding 10 J/cm2, up to 90% of the laser energy failed to reach the irradiated surface.

Can eccentric arterial plaques alone cause flow stagnation points and favour thrombus incorporation?

PubMed Central

Beneli, Cristina T; Barbosa, Priscila F; Floriano, Elaine M; Abreu, Mônica A; Ramalho, Fernando S; Júnior, Jorge Elias; Rossi, Marcos A; Ramos, Simone G

2009-01-01

We have used an experimental model of aorta stenosis, with a Plexiglas plug, simulating a stable atheromatous plaque that promotes local turbulence and thrombosis. With animal survival of more than 24 h, we followed the partial fibrinolysis of the thrombus as well as its posterior organization and incorporation to the arterial wall as a neointima for up to 30 days. The mushroom plug form permitted the development of recirculation and stasis areas around it, favouring this evolution. Despite noted limitations, this study demonstrates that thrombus incorporation can contribute to plaque extension, as it can promote recirculation and stasis areas. PMID:19563612

Turbulent slurry flow measurement using ultrasonic Doppler method in rectangular pipe

NASA Astrophysics Data System (ADS)

Bareš, V.; Krupička, J.; Picek, T.; Brabec, J.; Matoušek, V.

2014-03-01

Distribution of velocity and Reynolds stress was measured using ultrasonic velocimetry in flows of water and Newtonian water-ballotini slurries in a pressurized Plexiglas pipe. Profiles of the measured parameters were sensed in the vertical plane at the centreline of a rectangular cross section of the pipe. Reference measurements in clear water produced expected symmetrical velocity profiles the shape of which was affected by secondary currents developed in the rectangular pipe. Slurry-flow experiments provided information on an effect of the concentration of solid grains on the internal structure of the flow. Strong attenuation of velocity fluctuations caused by a presence of grains was identified. The attenuation increased with the increasing local concentration of the grains.

Fabrication of resonant patterns using thermal nano-imprint lithography for thin-film photovoltaic applications.

PubMed

Khaleque, Tanzina; Svavarsson, Halldor Gudfinnur; Magnusson, Robert

2013-07-01

A single-step, low-cost fabrication method to generate resonant nano-grating patterns on poly-methyl-methacrylate (PMMA; plexiglas) substrates using thermal nano-imprint lithography is reported. A guided-mode resonant structure is obtained by subsequent deposition of thin films of transparent conductive oxide and amorphous silicon on the imprinted area. Referenced to equivalent planar structures, around 25% and 45% integrated optical absorbance enhancement is observed over the 450-nm to 900-nm wavelength range in one- and two-dimensional patterned samples, respectively. The fabricated elements provided have 300-nm periods. Thermally imprinted thermoplastic substrates hold potential for low-cost fabrication of nano-patterned thin-film solar cells for efficient light management.

Modification of os calcis bone mineral profiles during bedrest

NASA Technical Reports Server (NTRS)

Vogel, J. M.

1977-01-01

The mineral content of the left central os calcis was determined using the photon absorptiometric technique modified for the space missions to permit area scanning, and was compared with total body calcium balance changes. The instrument consists of a rectilinear scanner that is programmed by a specially designed control module to move a low energy X-ray emitting radionuclide placed in opposition to a detector to scan the foot which is places between them. The foot is placed in a plexiglas box filled with water to provide tissue equivalence and to compensate for irregularities in thickness of tissue cover that surrounds the bone. The mineral content is obtained from basic attenuation equation.

Polishing compound for plastic surfaces

DOEpatents

Stowell, M.S.

1991-01-01

This invention is comprised of a polishing compound for plastic materials. The compound includes approximately by approximately by weight 25 to 80 parts at least one petroleum distillate lubricant, 1 to 12 parts mineral spirits, 50 to 155 parts abrasive paste, and 15 to 60 parts water. Preferably, the compound includes approximately 37 to 42 parts at least one petroleum distillate lubricant, up to 8 parts mineral spirits, 95 to 110 parts abrasive paste, and 50 to 55 parts water. The proportions of the ingredients are varied in accordance with the particular application. The compound is used on PLEXIGLAS{trademark}, LEXAN{trademark}, LUCITE{trademark}, polyvinyl chloride (PVC), and similar plastic materials whenever a smooth, clear polished surface is desired.

Acute and transient activation of pituitary-thyroid axis during unforced restriction in rats: component of nonshivering thermogenesis in conscious animals?

PubMed

Langer, P; Földes, O; Macho, L; Kvetnanský, R

1983-01-01

Groups of 6-8 male Wistar Olac SPF rats weighing about 300 g were subjected to unforced restriction (UR) in small cages with a metallic bottom and a Plexiglas cover for various intervals from 2 min to 72 h. An acute activation of the pituitary-thyroid axis was found which was manifested by an increase of thyrotropin (TSH) and thyroxine (T4) levels at 2-5 min of UR. This was presumably due to the emotional effect of a rapid transfer and to the placing of the animals into restriction cages. Later, between 3 and 6 h of UR, another, and more pronounced period of activation of the pituitary-thyroid axis and of the peripheral thyroid hormone metabolism was repeatedly observed which lasted until about 36-48 h and was manifested by a highly significant increase of TSH, T4, 3,5,3'-triiodothyronine (T3) and 3,3',5'-triiodothyronine (rT3) levels. It was concluded that this phenomenon presumably may be a component of nonshivering thermogenesis resulting from a decreased muscular activity and resembling the conditions occurring under cold stress. Such a view was supported by findings of highly increased nonesterified fatty acid levels in plasma in restricted animals, by unchanged levels of TSH and thyroid hormones found in unrestricted animals kept individually in regular group cages and, finally, by a preventive effect of ambient temperature of 32 degrees C on the pituitary-thyroid activation at 6 h of UR. In some experiments, no substantial differences in hormone levels were found between the animals kept in Plexiglas or stainless wire-mesh restriction cages. Finally, a multifold increase of prolactin level in plasma was found as early as 2 min of UR, the peak being observed between 5 and 20 min and a decrease to about the initial level at about 360 min.

Pyroclast acceleration and energy partitioning in fake explosive eruptions

NASA Astrophysics Data System (ADS)

Gaudin, Damien; Taddeucci, Jacopo; Scheu, Bettina; Valentine, Greg; Capponi, Antonio; Kueppers, Ulrich; Graettiger, Allison; Sonder, Ingo

2014-05-01

Explosive eruptions are characterized by the fast release of energy, with gas expansion playing a lead role. An excess of pressure may be generated either by the exsolution and accumulation of volatiles (e.g., vulcanian and strombolian explosions) or by in situ vaporization of water (e.g., phreato-magmatic explosions). The release of pressurized gas ejects magma and country rock pyroclasts at velocities that can reach several hundred of meters per second. The amount and velocity of pyroclasts is determined not only by the total released energy, but also by the system-specific dynamics of the energy transfer from gas to pyroclasts. In this context, analogue experiments are crucial, since the amount of available energy is determined. Here, we analyze three different experiments, designed to reproduce different aspects of explosive volcanism, focusing on the acceleration phase of the pyroclasts, in order to compare how the potential energy is transferred to the pyroclasts in different systems. In the first, shock-tube-type experiment, salt crystals resting in a pressurized Plexiglas cylinder are accelerated when a diaphragm set is suddenly opened, releasing the gas. In the second experiment, a pressurized air bubble is released in a water-filled Plexiglas pipe; diaphragm opening causes sudden expansion and bursting of the bubble and ejection of water droplets. In the last experiment, specifically focusing on phreatomagmatic eruptions, buried explosive charges accelerate the overlying loose material. All experiments were monitored by multiple high speed cameras and a variety of sensors. Despite the largely differing settings and processes, particle ejection velocity above the vent from the three experiments share a non-linear decay over time. Fitting this decay allows to estimate a characteristic depth that is related to the specific acceleration processes. Given that the initial available energy is experimentally controlled a priori, the information on the acceleration processes (and related kinetic energy) can be used to brings new constraints on the energy partition and general pyroclasts ejection mechanisms during eruptions.

ARRAYS OF BOTTLES OF PLUTONIUM NITRATE SOLUTION

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

Margaret A. Marshall

2012-09-01

In October and November of 1981 thirteen approaches-to-critical were performed on a remote split table machine (RSTM) in the Critical Mass Laboratory of Pacific Northwest Laboratory (PNL) in Richland, Washington using planar arrays of polyethylene bottles filled with plutonium (Pu) nitrate solution. Arrays of up to sixteen bottles were used to measure the critical number of bottles and critical array spacing with a tight fitting Plexiglas® reflector on all sides of the arrays except the top. Some experiments used Plexiglas shells fitted around each bottles to determine the effect of moderation on criticality. Each bottle contained approximately 2.4 L ofmore » Pu(NO3)4 solution with a Pu content of 105 g Pu/L and a free acid molarity H+ of 5.1. The plutonium was of low 240Pu (2.9 wt.%) content. These experiments were sponsored by Rockwell Hanford Operations because of the lack of experimental data on the criticality of arrays of bottles of Pu solution such as might be found in storage and handling at the Purex Facility at Hanford. The results of these experiments were used “to provide benchmark data to validate calculational codes used in criticality safety assessments of [the] plant configurations” (Ref. 1). Data for this evaluation were collected from the published report (Ref. 1), the approach to critical logbook, the experimenter’s logbook, and communication with the primary experimenter, B. Michael Durst. Of the 13 experiments preformed 10 were evaluated. One of the experiments was not evaluated because it had been thrown out by the experimenter, one was not evaluated because it was a repeat of another experiment and the third was not evaluated because it reported the critical number of bottles as being greater than 25. Seven of the thirteen evaluated experiments were determined to be acceptable benchmark experiments. A similar experiment using uranyl nitrate was benchmarked as U233-SOL-THERM-014.« less

Planform structure of turbulent Rayleigh-Benard convection

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

Theerthan, S.A.; Arakeri, J.H.

The planform structure of turbulent Rayleigh-Benard convection is obtained from visualizing a liquid crystal sheet stuck to the bottom hot surface. The bottom plate of the convection cell is Plexiglas and the top plate is glass. Water is the test liquid and the Rayleigh number is 4 [times] 10[sup 7]. The planform pattern reveals randomly moving hot streaks surrounded by cold regions suggesting that turbulent Rayleigh-Benard convection is dominated by quasi-two-dimensional randomly moving plumes. Simultaneous temperature traces from two vertically separated thermocouples indicate that these plumes may be inclined forward in the direction of horizontal motion. The periodic eruption ofmore » thermals observed by Sparrow et al and which forms the basis of Howard's model is not observed.« less

Compendium of Shock Wave Data. Volume 3. Section C. Organic Compounds Excluding Hydrocarbons. Section D. Mixtures. Section E. Mixtures and Solutions Without Chemical Characterization. Compendium Index

DTIC Science & Technology

1977-06-01

THAN THE ABOVE. 23-2-1(5-8-2) --- I2 AND 15 LESS COMPRESSIBLE THAN THE ABOVY FITS 23-2-1(5-9-2)---9 QUITE SOFT COMPARED TO THE AMERICAN PRODUCTS •3o8... PRODUCTS REMA I NDER TO - 17-36 DEe. C CO 0.93 KIQSEC VO a 0.356- 0.348 CC/O "IN THE TABLE, TEMPERATURE (T) IS OIVEN IN DEGREES CENTirRA1. DE14NSITY IN G...34 I " U IS THE BULLET VELOCITY. NO WAVE ATTENUATION HAS OBSERVED, UNLIKE IN PLEXIGLAS 4) THIS POLYMER IS A CONDENSATION PRODUCT OF GISPHENOL-A AND

Noise reduction characteristics of general aviation type dual-pane windows

NASA Technical Reports Server (NTRS)

Grosveld, F.; Navaneethan, R.; Roskam, J.

1980-01-01

The noise reduction characteristics of general-aviation-type, dual-pane windows in various configurations have been experimentally investigated. The effects of inner and outer pane thickness, spacing between the panes, edge conditions, inclination of the inner pane and depressurization of the air in between the panes are presented. The space in between the two window panes is sealed airtight in all cases. Results show that increasing the mass of a 'floating' window pane does not increase the noise reduction below the fundamental resonance frequency. It is concluded that the concept of depressurization of the air between thin (1/8 in) Plexiglas panes and application of multiple-freedom edge conditions for the inner pane are promising to reduce noise levels in general aviation airplanes.

Variability of Deuterium Fractionation Associated With Soil Uptake of Atmospheric Molecular Hydrogen

NASA Astrophysics Data System (ADS)

Rahn, T.; Randerson, J. T.; Eiler, J.

2005-12-01

Molecular hydrogen (H2) is the second most abundant reduced gas in the atmosphere (after methane) with a globally averaged mixing ratio of ~530 nmol/mol. Its largest sources are photochemical oxidation of methane and non-methane hydrocarbons with other recognized sources that include biomass burning, fossil fuel burning, nitrogen fixation, and ocean degassing. These sources are balanced by reaction of H2 with hydroxyl radicals (~25%) in the atmosphere and by deposition at the terrestrial soil surface (~75%). As with other atmospheric trace gases, the stable isotopic content of H2 has the potential to help quantify the various aspects of its production and destruction. The average deuterium content of H2 is dDH2 = ~130 ‰ relative to Standard Mean Ocean Water. While recent studies have begun to elucidate the deuterium content of the individual sources of H2 and the fractionation associated with hydroxyl oxidation has been well established in the laboratory, there are still few data documenting the fractionation associated with soil uptake. We measured the fractionation associated with soil uptake in May, June and August of 2002 in three upland ecosystems that were part of an Alaskan fire chronosequence. Fire occurred at these sites in 1999, 1987, and ~1920. Grasses and herbaceous vegetation establish initially after fire and are gradually replaced by deciduous trees and finally by evergreen trees and moss. All three sites were in interior Alaska near the town of Delta Junction (63° 54'N, 145° 40'W). Fluxes were measured with a Plexiglas flux chamber (8 liter volume) with a manifold of four ~400 ml double-valved glass flasks in parallel and a diaphragm pump for circulation (5 SLPM). Flasks were continuously flushed by the circulating system and isolated sequentially; they were then returned to the laboratory at Caltech for subsequent analysis. In the field, the chamber was seated on Plexiglas collars that were installed prior to initiating the study and left in place for the duration of the study. Permanent collars insured that placement of the chamber/collar system did not cause any localized disturbance and unintentionally perturb the H2 flux and that sampling locations could be reoccupied to investigate seasonal differences. Prior to field deployment the entire system was tested on a plain sheet of Plexiglas to ensure that no H2 was produced or consumed by the diaphragm pump or any of the system parts. While earlier studies have measured HD/HH deposition velocities with a ratio of ~0.96, results of our Alaskan study show deposition velocity ratios of 0.89 ± 0.03 (n=17). Furthermore, sorting of data by season reveals no significant variability in this ratio but sorting by location over all seasons reveals the greatest fractionation at the most recent burn, 0.87 ± 0.02 (n=8) and the least fractionation at the mature spruce forest, 0.93 ± 0.01 (n=3) with fractionation at the intermediate burn site being 0.90 ± 0.02 (n=6). While not statistically conclusive, our results suggest that soil/ecosystem variability may affect fractionation associated with soil uptake of H2, adding further complication to modeling efforts that until now have assumed this parameter to be a constant value.

Vibro-acoustic model of an active aircraft cabin window

NASA Astrophysics Data System (ADS)

Aloufi, Badr; Behdinan, Kamran; Zu, Jean

2017-06-01

This paper presents modeling and design of an active structural acoustic control (ASAC) system for controlling the low frequency sound field transmitted through an aircraft cabin window. The system uses stacked piezoelectric elements arranged in a manner to generate out-of-plane actuation point forces acting on the window panel boundaries. A theoretical vibro-acoustic model for an active quadruple-panel system is developed to characterize the dynamic behavior of the system and achieve a good understanding of the active control performance and the physical phenomena of the sound transmission loss (STL) characteristics. The quadruple-panel system represents the passenger window design used in some classes of modern aircraft with an exterior double pane of Plexiglas, an interior dust cover pane and a glazed dimmable pane, all separated by thin air cavities. The STL characteristics of identical pane window configurations with different piezoelectric actuator sets are analyzed. A parametric study describes the influence of important active parameters, such as the input voltage, number and location of the actuator elements, on the STL is investigated. In addition, a mathematical model for obtaining the optimal input voltage is developed to improve the acoustic attenuation capability of the control system. In general, the achieved results indicate that the proposed ASAC design offers a considerable improvement in the passive sound loss performance of cabin window design without significant effects, such as weight increase, on the original design. Also, the results show that the acoustic control of the active model with piezoelectric actuators bonded to the dust cover pane generates high structural vibrations in the radiating panel (dust cover) and an increase in sound power radiation. High active acoustic attenuation can be achieved by designing the ASAC system to apply active control forces on the inner Plexiglas panel or dimmable panel by installing the actuators on the boundaries of one of the two panels. In some cases, increasing the actuator numbers in the structure advances the active control performance by controlling more structural modes; however, this decreases the STL of the passive control system because of the increase in structure-borne sound transmission paths of the stiffer piezoelectric actuators.

Pulsed electromagnetic acceleration

NASA Technical Reports Server (NTRS)

Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.

1973-01-01

Direct measurements of the power deposited in the anode of a multimegawatt MPD accelerator using thermocouples attached to a thin shell anode reveal a dramatic decrease in the fractional anode power from 50% at 200 KW input power to less than 10% at 20 MW power. The corresponding local power flux peak at a value of 10,000 W/sq cm at the lip of the anode exhaust orifice, a distribution traced to a corresponding peak in the local current density at the anode. A comparison of voltage-current characteristics and spectral photographs of the MPD discharge using quartz, boron nitride and plexiglas insulators with various mass injection configurations led to the identification of different voltage modes and regions of ablation free operation. The technique of piezoelectric impact pressure measurement in the MPD exhaust flow was refined to account for the effects due to probe yaw angle.

Systematic model researches on the stability limits of the DVL series of float designs

NASA Technical Reports Server (NTRS)

Sottorf, W.

1949-01-01

To determine the trim range in which a seaplane can take off without porpoising, stability tests were made of a Plexiglas model, composed of float, wing, and tailplane, which corresponded to a full-size research airplane. The model and full-size stability limits are in good agreement. After all structural parts pertaining to the air frame were removed gradually, the aerodynamic forces replaced by weight forces, and the moment of inertia and position of the center of gravity changed, no marked change of limits of the stable zone was noticeable. The latter, therefore, is for practical purposes affected only by hydrodynamic phenomena. The stability limits of the DVL family of floats were determined by a systematic investigation independent of any particular sea-plane design, thus a seaplane may be designed to give a run free from porpoising.

Pulsed electromagnetic gas acceleration

NASA Technical Reports Server (NTRS)

Jahn, R. G.; Vonjaskowsky, W. F.; Clark, K. E.

1971-01-01

Experimental data were combined with one-dimensional conservation relations to yield information on the energy deposition ratio in a parallel-plate accelerator, where the downstream flow was confined to a constant area channel. Approximately 70% of the total input power was detected in the exhaust flow, of which only about 20% appeared as directed kinetic energy, thus implying that a downstream expansion to convert chamber enthalpy into kinetic energy must be an important aspect of conventional high power MPD arcs. Spectroscopic experiments on a quasi-steady MPD argon accelerator verified the presence of A(III) and the absence of A(I), and indicated an azimuthal structure in the jet related to the mass injection locations. Measurements of pressure in the arc chamber and impact pressure in the exhaust jet using a piezocrystal backed by a Plexiglas rod were in good agreement with the electromagnetic thrust model.

How Patients and Nurses Experience an Open Versus an Enclosed Nursing Station on an Inpatient Psychiatric Unit.

PubMed

Shattell, Mona; Bartlett, Robin; Beres, Kyle; Southard, Kelly; Bell, Claire; Judge, Christine A; Duke, Patricia

2015-01-01

The inpatient environment is a critical space for nurses and patients in psychiatric settings. In this article, we describe nurses' and patients' perceptions of the inpatient environment both before the removal of a Plexiglas enclosure around a nurses' station and after its removal. Nurses had mixed feelings about the enclosure, reporting that it provided for confidentiality and a concentrated work space but also acknowledged the challenge of the barrier for communication with their patients. Patients unanimously preferred the nurses' station without the barrier, reporting increased feelings of freedom, safety, and connection with the nurses after its removal. It is important to consider the implications of environmental decisions in inpatient settings in order to promote a healthy workplace and healing environment for all community members. © The Author(s) 2015.

Effects of volute geometry and impeller orbit on the hydraulic performance of a centrifugal pump

NASA Technical Reports Server (NTRS)

Flack, R. D.; Lanes, R. F.

1983-01-01

Overall performance data was taken for a Plexiglas water pump with a logarithmic spiral volute and rectangular cross sectioned flow channels. Parametric studies were made in which the center of the impeller was offset from the design center of the volute. The rig was also designed such that the impeller was allowed to synchronously orbit by a fixed amount about any center. The studies indicate that decreasing the tongue clearance decreases the head at low flowrates and increases the head at high flowrates. Also, decreasing the volute area in the first half of the volute and holding the tongue clearance the same, resulted in a decreased head for low flowrates but performance at high flowrates was not affected. Finally, the overall hydraulic performance was not affected by the impeller orbitting about the volute center.

An investigation of the cratering-induced motions occurring during the formation of bowl-shaped craters. [using high explosive charges as the cratering source

NASA Technical Reports Server (NTRS)

Piekutowski, A. J.

1980-01-01

The effects of the dynamic processes which occur during crater formation were examined using small hemispherical high-explosive charges detonated in a tank which had one wall constructed of a thick piece of clear plexiglas. Crater formation and the motions of numerous tracer particles installed in the cratering medium at the medium-wall interface were viewed through the wall of this quarter-space tank and recorded with high-speed cameras. Subsequent study and analysis of particle motions and events recorded on the film provide data needed to develop a time-sequence description of the formation of a bowl-shaped crater. Tables show the dimensions of craters produced in a quarter-space tank compared with dimensions of craters produced in normal half-space tanks. Crater growth rate summaries are also tabulated.

Flight response ofHeliothis subflexa (Gn.) females (Lepidoptera: Noctuidae) to an attractant from groundcherry,Physalis angulata L.

PubMed

Tingle, F C; Heath, R R; Mitchell, E R

1989-01-01

Mated femaleHeliothis subflexa (Gn.) (HS) moths 1-7 days old responded positively in a Plexiglas flight tunnel to an attractant extracted with methanol from fresh whole-leaf washes of groundcherry,Physalis angulata L. Response to the groundcherry extract, as indicated by plume-tracking (i.e., upwind flight toward the odor source) and contact with the chemical dispenser did not change significantly during the first 5 hr of scotophase. Overall, ca. 50% of the responding moths also landed on the chemical dispenser; ca. 50% of the moths that landed also deposited eggs. There were no significant differences in the behavioral responses of females mating only once and those that had mated two or more times. Virgin females and male moths were significantly less responsive to the groundcherry attractant than mated females. The flight tunnel bioassay described provides an excellent system for evaluating plant allelochemics associated with host-plant selection.

Spectroscopic studies of the exhaust plume of a quasi-steady MPD accelerator. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Bruckner, A. P.

1972-01-01

Spectroscopic and photographic investigations are reported that reveal a complex azimuthal species structure in the exhaust plume of a quasi-steady argon MPD accelerator. Over a wide range of operating conditions the injected argon remains collimated in discrete jets which are azimuthally in line with the six propellant injector orifices. The regions between these argon jets, including the central core of the exhaust flow, are occupied by impurities such as carbon, hydrogen and oxygen ablated from the Plexiglas back plate of the arc chamber. The features of this plume structure are found to be dependent on the arc current and mass flow rate. It is found that nearly half the observed velocity is attained in an acceleration region well downstream of the region of significant electromagnetic interaction. Recombination calculations show that the ionization energy is essentially frozen.

Pulsed electromagnetic gas accelleration. [incorporation of hollow cathode in plasma discharge and suitability determination of MPD discharge as plasmadynamic laser source

NASA Technical Reports Server (NTRS)

Jahn, R. G.

1973-01-01

Direct measurement with thermocouples of the power deposited in the anode of a multi-megawatt magnetoplasmadynamic discharge has shown the fractional anode power to decrease from 50% at 200 kW to 10% at 20 MW. Using local measurements of current density, electric potential, and electron temperature, the traditional model for heat conduction to the anode is found to be inadequate. Other experiments in which the voltage-current characteristics and exhaust velocities of MPD arcs using Plexiglas and boron nitride chamber insulators and various mass injection configurations show that ablation can affect nominal accelerator operation in several distinct ways. The incorporation of a hollow cathode in a 7 kA plasma discharge has shown that a stable current attachment can be realized in the cavity without the aid of cathode heaters, keeper electrodes, or emissive coatings.

Visualization studies of turbulent transition flows in a porous medium

NASA Technical Reports Server (NTRS)

Bilardo, V. J.

1983-01-01

Results are reported for flow-visualization studies of the flow regimes of water passing through a porous medium consisting of cylindrical glass and plexiglas rods arranged in a complex and fixed three-dimensional geometry. The Reynolds number (Re) varied from 50 to 700; the flow was visualized by injecting a 5% potassium permanganate dye solution into the pores and photographing the resulting dye streaklines with both a still camera and a movie camera. The results indicate that four distinct flow regimes exist in the porous medium: (1) Darcy or creeping flow up to Re = 3; (2) steady inertia-dominated laminar flow for Re = 3-150; (3) unsteady transitional laminar flow for Re = 150-250; and (4) fully turbulent flow for Re greater than 250. It is concluded that a laminar wake instability mechanism typical of the external flow about bluff bodies may be responsible for the overall transition from laminar to turbulent flow in porous media.

Design and development of Shuttle Get-Away-Special experiment G-0074. [off-load capability for a full-tank propellant acquisition system

NASA Technical Reports Server (NTRS)

Orton, G. F.

1984-01-01

An experiment to investigate more versatile, lower cost surface tension propellant acquisition approaches for future satellite and spacecraft propellant tanks is designed to demonstrate a propellant off-load capability for a full-tank gallery surface tension device, such as that employed in the shuttle reaction control subsystem, and demonstrate a low-cost refillable trap concept that could be used in future orbit maneuver propulsion systems for multiple engine restarts. A Plexiglas test tank, movie camera and lights, auxiliary liquid accumulator, control electronics, battery pack, and associated valving and plumbing are used. The test liquid is Freon 113, dyed blue for color movie coverage. The fully loaded experiments weighs 106 pounds and is to be installed in a NASA five-cubic-foot flight canister. Vibration tests, acoustic tests, and high and low temperature tests were performed to quality the experiment for flight.

Novel On-wafer Radiation Pattern Measurement Technique for MEMS Actuator Based Reconfigurable Patch Antennas

NASA Technical Reports Server (NTRS)

Simons, Rainee N.

2002-01-01

The paper presents a novel on-wafer, antenna far field pattern measurement technique for microelectromechanical systems (MEMS) based reconfigurable patch antennas. The measurement technique significantly reduces the time and the cost associated with the characterization of printed antennas, fabricated on a semiconductor wafer or dielectric substrate. To measure the radiation patterns, the RF probe station is modified to accommodate an open-ended rectangular waveguide as the rotating linearly polarized sampling antenna. The open-ended waveguide is attached through a coaxial rotary joint to a Plexiglas(Trademark) arm and is driven along an arc by a stepper motor. Thus, the spinning open-ended waveguide can sample the relative field intensity of the patch as a function of the angle from bore sight. The experimental results include the measured linearly polarized and circularly polarized radiation patterns for MEMS-based frequency reconfigurable rectangular and polarization reconfigurable nearly square patch antennas, respectively.

Experimental investigation of leaky lamb modes by an optically induced grating.

PubMed

Van de Rostyne, Kris; Glorieux, Christ; Gao, Weimin; Lauriks, Walter; Thoen, Jan

2002-09-01

By removing the symmetry of a free plate configuration, fluid loading significantly modifies the nature of acoustic waves travelling along a plate, and it even gives existence to new acoustic modes. We present theoretical predictions for the existence, dispersive behavior, and spatial distribution of leaky Lamb waves in a fluid-loaded film. Although Lamb modes are often investigated by studying the radiated fluid waves resulting from their leakage, here their properties are assessed by detecting the wave displacements directly using laser beam deflection. By using crossed laser beam excitation, the detection and analysis of the different modes is done at a fixed wavelength, allowing one to verify the existence, the velocity, and the damping of each predicted mode in a simple and unambiguous way. Our theoretical predictions for the nature of the modes in a water-loaded Plexiglas film, including parts of looping modes, are experimentally confirmed.

Analogue modeling for science outreach: glacier flows at Antarctic National Museum, Italy

NASA Astrophysics Data System (ADS)

Zeoli, A.; Corti, G.; Folco, L.; Ossola, C.

2012-12-01

Comprehension of internal deformation and of ice flow in the Antarctic ice sheet in relation with the bedrock topography and with the thickness variation induced by climatic variations represent an important target for the scientific community. Analogue modelling technique aims to analyze geological or geomorphological processes through physical models built at a reduced geometrical scale in laboratory and deformed at reasonable scale of times. Corti et al. (2003 and 2008) have shown that this technique could also be used successfully for ice flow dynamic. Moreover, this technique gives a three-dimensional view of the processes. The models, that obviously simplify the geometry and rheology of natural processes, represent a geometrically, cinematically, dynamically and rheologically scaled analogue of the natural glacial environment. Following a procedure described in previous papers, proper materials have been selected to simulate the rheological behaviour of ice. In particular, during the experiments a Polydimethilsyloxane (PDMS) has been used to simulate glacial flow. PDMS is a transparent Newtonian silicone with a viscosity of 1.4 104 Pa s and a density of 965 kg m-3 (see material properties in Weijermars, 1986). The scaling of the model to natural conditions let to obtain reliable results for a correct comparison with the glacial processes under investigation. Models have been built with a with a geometrical scaling ratio of ~1.5 10-5, such that 1 cm in the model represents ~700 m in nature. The physical models have been deformed in terrestrial gravity field by allowing the PDMS to flow inside a Plexiglas box. In particular, the silicone has been poured inside the Plexiglas box and allowed to settle in order to obtain a flat free surface; the box has been then inclined of some degrees in order to allow the silicone to flow. Several boxes illustrating different glacial processes have been realized; each of them could be easily performed in short time and in standard laboratories. One of the main aims of the Antarctic National Museum in Siena (Italy) is to establish a strategy to deliver results to a broader scientific community. Time and spatial small scale of the experiments lead the analogue modeling technique easy to be shown to non-technical audiences through direct participation during Museum visits. All these experiments engage both teachers and students from primary and secondary schools and the general public.

Accuracy of real time radiography burning rate measurement

NASA Astrophysics Data System (ADS)

Olaniyi, Bisola

The design of a solid propellant rocket motor requires the determination of a propellant's burning-rate and its dependency upon environmental parameters. The requirement that the burning-rate be physically measured, establishes the need for methods and equipment to obtain such data. A literature review reveals that no measurement has provided the desired burning rate accuracy. In the current study, flash x-ray modeling and digitized film-density data were employed to predict motor-port area to length ratio. The pre-fired port-areas and base burning rate were within 2.5% and 1.2% of their known values, respectively. To verify the accuracy of the method, a continuous x-ray and a solid propellant rocket motor model (Plexiglas cylinder) were used. The solid propellant motor model was translated laterally through a real-time radiography system at different speeds simulating different burning rates. X-ray images were captured and the burning-rate was then determined. The measured burning rate was within 1.65% of the known values.

PIV measurements of the single-mode Richtmyer-Meshkov instability.

NASA Astrophysics Data System (ADS)

Aure, Roger; Jacobs, Jeff

2006-11-01

Experiments will be presented where a system of two gases of different densities (A = 0.66) is impulsively accelerated to produce Richtmeyer-Meshkov (RM) instability. An interface is created by filling the driven section of a 9.8 meter long vertical shock tube with opposing gas flows of air and Sulfur Hexafluoride (SF6). The interface forms in the top of the Plexiglas test section where the two gasses meet and exit through two slots. The gases are seeded with 0.3 μm polystyrene Latex spheres. An initial 2-D perturbation in the form of a standing wave of sinusoidal shape is created by oscillating the driven section in the horizontal direction. The interface between the gases is impulsively accelerated by an M=1.2 shockwave. One image per experiment is captured with a cooled CCD camera. The image is doubly exposed by a double-pulsed ND-YAG laser and is analyzed using autocorrelation PIV techniques. Results will be presented showing velocity and vorticity distribution in the RM flow.

Water and the conservation movement

USGS Publications Warehouse

Leopold, Luna Bergere

1958-01-01

Every age has its unique touchstone, its hallmark. The Nineties were thought gay. The Twenties had jazz and John Held, Jr. The Thirties had breadlines, dust bowls, the forgotten man. And each recent period has been studded with so many flashy gems, both paste and genuine, that no hallmark would alone be enough to label it.Of the present age, one of the nameplates will carry the word "Conservation." The first time a museum visitor walks by that label he will probably stop, push back the plexiglas globe of his space helmet and say to himself, "I never thought that conservation was a keynote of the Fifties." But I imagine he might agree as the pathetic truth of that label dawned on his tired body, accustomed to canned entertainment, synthetic flavors, and fighting the afternoon traffic of the jet lanes. I can imagine him musing: "Conservation, the hallmark of the Fifties. Somebody about that time said about something or other, 'too little and too late.'"

A Cool Sport Full of Physics

NASA Astrophysics Data System (ADS)

Haché, Alain

2008-10-01

Of all sports, ice hockey is possibly the one with the widest array of physics elements in it. The game provides many examples that can bring physics to life in the classroom. Ice hockey (or just "hockey" as many Canadians would say) sees athletes sliding on ice at high speeds and in various ways, shooting and slapping pucks, and colliding against each other. The interaction between the skate blade and the ice is a problem of great physical complexity. The question "Why is ice so slippery?" has puzzled generations of scientists and, surprisingly, clear answers have come relatively recently. There is even some optics involved in hockey: how many sports are watched behind tempered glass (or Plexiglas) windows? The optical and mechanical properties of these materials are worth a physics classroom discussion. In this paper, I will review a few topics discussed at length in my book The Physics of Hockey.1,2 Interested readers may also find additional articles on our website.3

Effects of insulator ablation on the operation of a quasi-steady MPD arc

NASA Technical Reports Server (NTRS)

Boyle, M. J.; Jahn, R. G.

1973-01-01

Multimegawatt operation of quasi-steady MPD arcjets can involve serious ablation of the insulator surfaces within the arc discharge chamber. Various degrees of insulator ablation manifest themselves by significantly perturbing the voltage-current characteristics and the exhaust velocity profiles. Voltage-current characteristics for two different insulator materials, Plexiglas and boron nitride, are interpreted in terms of an empirical Ohm's law. Use of the refractory insulator material eliminates the ablation-dominated nature of the terminal voltage, but the exhaust stream is still disturbed by insulator material. An Alfven critical velocity model can be applied to this influence of insulator ablation on exhaust velocity. Appropriate changes in the propellant injection geometry eliminate this influence and result in arcjet operation which is independent of insulator material. A particular combination of propellant injection geometries reduces the terminal voltage for a given current and mass flow while maintaining insulator-independent operation, thus implying an improvement in the overall efficiency of the device.

Moon orientation in adult and young sandhoppers under artificial light.

PubMed

Ugolini, Alberto; Boddi, Vieri; Mercatelli, Luca; Castellini, Carlo

2005-10-22

Our experiments, carried out at night and during the day on adults and laboratory-born young of the sandhopper Talitrus saltator, deal with the identification and use of the moon as an orientating factor. Sandhoppers were released in an apparatus (a Plexiglas dome) that produced a scenario similar to the natural one (with artificial sky, moon or sun illuminated at different intensities). When tested at night, the adult and young sandhoppers used the artificial moon like the natural one, independently of the intensity of illumination of the artificial sky and moon. In other words, sandhoppers tested at night always identified the artificial moon as the moon and never as the sun. In daytime releases, the seaward orientation failed at low intensities of artificial sky and sun illumination (3.07 and 1.55 microW cm2, respectively), whereas the sun compass was used effectively at higher levels of artificial sun and sky illumination. The innate ability of moon compass orientation in inexpert young sandhoppers was demonstrated even under artificial light.

A laboratory investigation of mixing dynamics between biofuels and surface waters

NASA Astrophysics Data System (ADS)

Wang, Xiaoxiang; Cotel, Aline

2017-11-01

Recently, production and usage of ethanol-blend fuels or biofuels have increased dramatically along with increasing risk of spilling into surface waters. Lack of understanding of the environmental impacts and absence of standard clean-up procedures make it crucial to study the mixing behavior between biofuels and water. Biofuels are represented by a solution of ethanol and glycol. A Plexiglas tank in conjunction with a wave generator is used to simulate the mixing of surface waters and biofuels under different natural conditions. In our previous experiments, two distinct mixing regimes were observed. One regime was driven by turbulence and the other by interfacial instabilities. However, under more realistic situations, without wind driven waves, only the first mixing regime was found. After one minute of rapid turbulent mixing, biofuels and water were fully mixed and no interface was formed. During the mixing process, chemical reactions happened simultaneously and influenced mixing dynamics. Current experiments are investigating the effect of waves on the mixing dynamics. Support from NSF CBET 1335878.

Adjustable long duration high-intensity point light source

NASA Astrophysics Data System (ADS)

Krehl, P.; Hagelweide, J. B.

1981-06-01

A new long duration high-intensity point light source with adjustable light duration and a small light spot locally stable in time has been developed. The principle involved is a stationary high-temperature plasma flow inside a partly constrained capillary of a coaxial spark gap which is viewed end on through a terminating Plexiglas window. The point light spark gap is operated via a resistor by an artificial transmission line. Using two exchangeable inductance sets in the line, two ranges of photoduration 10-130 μs and 100-600 μs can be covered. For a light spot size of 1.5 mm diameter the corresponding peak light output amounts to 5×106 and 1.6×106 candelas, respectively. Within these ranges the duration is controlled by an ignitron crowbar to extinguish the plasma. The adjustable photoduration is very useful for the application of continuous writing rotating mirror cameras, thus preventing multiple exposures. The essentially uniform exposure within the visible spectral range makes the new light source suitable for color cinematography.

Experimental Comparison of two Active Vibration Control Approaches: Velocity Feedback and Negative Capacitance Shunt Damping

NASA Technical Reports Server (NTRS)

Beck, Benjamin; Schiller, Noah

2013-01-01

This paper outlines a direct, experimental comparison between two established active vibration control techniques. Active vibration control methods, many of which rely upon piezoelectric patches as actuators and/or sensors, have been widely studied, showing many advantages over passive techniques. However, few direct comparisons between different active vibration control methods have been made to determine the performance benefit of one method over another. For the comparison here, the first control method, velocity feedback, is implemented using four accelerometers that act as sensors along with an analog control circuit which drives a piezoelectric actuator. The second method, negative capacitance shunt damping, consists of a basic analog circuit which utilizes a single piezoelectric patch as both a sensor and actuator. Both of these control methods are implemented individually using the same piezoelectric actuator attached to a clamped Plexiglas window. To assess the performance of each control method, the spatially averaged velocity of the window is compared to an uncontrolled response.

Pore water pressure variations in Subpermafrost groundwater : Numerical modeling compared with experimental modeling

NASA Astrophysics Data System (ADS)

Rivière, Agnès.; Goncalves, Julio; Jost, Anne; Font, Marianne

2010-05-01

Development and degradation of permafrost directly affect numerous hydrogeological processes such as thermal regime, exchange between river and groundwater, groundwater flows patterns and groundwater recharge (Michel, 1994). Groundwater in permafrost area is subdivided into two zones: suprapermafrost and subpermafrost which are separated by permafrost. As a result of the volumetric expansion of water upon freezing and assuming ice lenses and frost heave do not form freezing in a saturated aquifer, the progressive formation of permafrost leads to the pressurization of the subpermafrost groundwater (Wang, 2006). Therefore disappearance or aggradation of permafrost modifies the confined or unconfined state of subpermafrost groundwater. Our study focuses on modifications of pore water pressure of subpermafrost groundwater which could appear during thawing and freezing of soil. Numerical simulation allows elucidation of some of these processes. Our numerical model accounts for phase changes for coupled heat transport and variably saturated flow involving cycles of freezing and thawing. The flow model is a combination of a one-dimensional channel flow model which uses Manning-Strickler equation and a two-dimensional vertically groundwater flow model using Richards equation. Numerical simulation of heat transport consisted in a two dimensional model accounting for the effects of latent heat of phase change of water associated with melting/freezing cycles which incorporated the advection-diffusion equation describing heat-transfer in porous media. The change of hydraulic conductivity and thermal conductivity are considered by our numerical model. The model was evaluated by comparing predictions with data from laboratory freezing experiments. Experimental design was undertaken at the Laboratory M2C (Univesité de Caen-Basse Normandie, CNRS, France). The device consisted of a Plexiglas box insulated on all sides except on the top. Precipitation and ambient temperature are imposed. The Plexiglas box is filled with glass beads of which hydraulics and thermal parameters are known. All parameters required for our numerical model are controlled and continuous monitoring of soil temperatures and pore water pressure are reported. Our results of experimental model allow us to test the relevance of processes described by our numerical simulation and to quantify the impact of permafrost on pore water pressure of subpermafrost groundwater during a cycle of freezing and thawing. Michel, Frederick A. and Van Everdingen, Robert O. 1994. Changes in hydrogeologic regimes in permafrost regions due to climatic change. Permafrost and Periglacial Processes, 5: 191-195. Wang, Chi-yuen and Manga, Michael and Hanna, Jeffrey C. 2006. Can freezing cause floods on Mars? Geophysical Research Letters, 33

Airbreathing Laser Propulsion Experiments with 1 {mu}m Terawatt Pharos IIILaser: Part 2

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

Myrabo, L. N.; Lyons, P. W.; Jones, R. A.

This basic research study examines the physics of airbreathing laser propulsion at the extreme flux range of 1-2x10{sup 11} W/cm{sup 2}--within the air breakdown threshold for l {mu}m radiation--using the terawatt Pharos III neodymium-glass pulsed laser. Six different experimental setups were employed using a 34 mm line focus with 66 {mu}m focal waist, positioned near the flat impulse surface. The 2nd Campaign investigated impulse generation with the laser beam focused at grazing incidence across near horizontal target surfaces, with pulse energies ranging from 55 to 186 J, and pulse-widths of 2 to 30 ns FWHM. Laser generated impulse was measuredmore » with a horizontal Plexiglas registered ballistic pendulum equipped with either a steel target insert or 0.5 Tesla permanent magnet (NEIT-40), to quantify changes in the momentum coupling coefficient (C{sub M}). Part 2 of this 2-part paper covers Campaign no. 2 results including C{sub M} performance data, and long exposure color photos of LP plasma phenomena.« less

Basic determinants of epicardial transudation.

PubMed

Stewart, R H; Rohn, D A; Allen, S J; Laine, G A

1997-09-01

Myocardial edema formation, which has been shown to compromise cardiac function, and increased epicardial transudation (pericardial effusion) have been shown to occur after elevation of myocardial venous and lymphatic outflow pressures. The purposes of this study were to estimate the hydraulic conductance and osmotic reflection coefficient for the epicardium and to determine the effect of coronary sinus hypertension and cardiac lymphatic obstruction on epicardial fluid flux (JV,e/Ae). A Plexiglas hemispheric capsule was attached to the left ventricular epicardial surface of anesthetized dogs. JV,e/Ae was determined over 30-min periods for three intracapsular pressures (-5, -15, and -25 mmHg) and two intracapsular solutions exerting colloid osmotic pressures of 7.0 and 2.0 mmHg. Hydraulic conductance was estimated to be 3.7 +/- 0.5 microliters.h-1.cm-2.mmHg-1. An osmotic reflection coefficient of 0.9 was calculated from the difference in JV,e/Ae of 16.5 +/- 8.4 microliters.h-1.cm-2 between the two solutions. Graded coronary sinus hypertension induced a linear increase in JV,e/Ae, which was significantly greater in dogs without cardiac lymphatic occlusion than in those with occlusion.

Using a Replica of Leeuwenhoek's Microscope to Teach the History of Science and to Motivate Students to Discover the Vision and the Contributions of the First Microscopists

PubMed Central

Loreto, Elgion L.S.; Rocha, João B.T.

2009-01-01

The history of science should be incorporated into science teaching as a means of improving learning and also to increase the students' understanding about the nature of science. In biology education, the history of microscopy deserves a special place. The discovery of this instrument not only opened a new and fantastic microworld but also led to the development of one unifying principle of biological sciences (i.e., cell theory). The microscopes of Leeuwenhoek and Hooke opened windows into the microworld of living organisms. In the present work, the knowledge of these themes was analyzed in a group of students beginning an undergraduate biology course. Our data suggest that the history of microscopy is poorly treated at the secondary school level. We propose a didactic activity using a replica of Leeuwenhoek's microscope made with Plexiglas and a lens obtained from a key chain laser pointer or from a broken CD drive. The proposed activity motivated students to learn about microscopy and helped them to appreciate scientific knowledge from a historical perspective. PMID:19952102

Using a replica of Leeuwenhoek's microscope to teach the history of science and to motivate students to discover the vision and the contributions of the first microscopists.

PubMed

Sepel, Lenira M N; Loreto, Elgion L S; Rocha, João B T

2009-01-01

The history of science should be incorporated into science teaching as a means of improving learning and also to increase the students' understanding about the nature of science. In biology education, the history of microscopy deserves a special place. The discovery of this instrument not only opened a new and fantastic microworld but also led to the development of one unifying principle of biological sciences (i.e., cell theory). The microscopes of Leeuwenhoek and Hooke opened windows into the microworld of living organisms. In the present work, the knowledge of these themes was analyzed in a group of students beginning an undergraduate biology course. Our data suggest that the history of microscopy is poorly treated at the secondary school level. We propose a didactic activity using a replica of Leeuwenhoek's microscope made with Plexiglas and a lens obtained from a key chain laser pointer or from a broken CD drive. The proposed activity motivated students to learn about microscopy and helped them to appreciate scientific knowledge from a historical perspective.

Evaluation of noise in the neonatal intensive care unit.

PubMed

Benini, F; Magnavita, V; Lago, P; Arslan, E; Pisan, P

1996-01-01

This study evaluated the noise level inside the incubators in a neonatal intensive care unit and identified its sources in order to attempt to reduce it. Although noise is not a proven risk factor as far as the sensory integrity of newborns is concerned, it is certainly an important cause of stress to them and a source of serious and dangerous changes in their behavioral and physiologic states. Noise recorded inside the incubators had two components. The first was background noise from the incubator motors, which varied from 74.2 to 79.9 dB, and was similar to environmental noise. The second source was impulsive events beyond 80 dB. These events were the result of voluntary and involuntary contact with the incubators' Plexiglas surface or to the abrupt opening and closing of their access ports. Considering its decibel levels and frequency, this latter component is undoubtedly an important source of stress to newborns. Moreover, these data reveal the need to train health care personnel on how to reduce such noise by taking more care in the handling of infants.

Theoretical vibro-acoustic modeling of acoustic noise transmission through aircraft windows

NASA Astrophysics Data System (ADS)

Aloufi, Badr; Behdinan, Kamran; Zu, Jean

2016-06-01

In this paper, a fully vibro-acoustic model for sound transmission across a multi-pane aircraft window is developed. The proposed model is efficiently applied for a set of window models to perform extensive theoretical parametric studies. The studied window configurations generally simulate the passenger window designs of modern aircraft classes which have an exterior multi-Plexiglas pane, an interior single acrylic glass pane and a dimmable glass ("smart" glass), all separated by thin air cavities. The sound transmission loss (STL) characteristics of three different models, triple-, quadruple- and quintuple-paned windows identical in size and surface density, are analyzed for improving the acoustic insulation performances. Typical results describing the influence of several system parameters, such as the thicknesses, number and spacing of the window panes, on the transmission loss are then investigated. In addition, a comparison study is carried out to evaluate the acoustic reduction capability of each window model. The STL results show that the higher frequencies sound transmission loss performance can be improved by increasing the number of window panels, however, the low frequency performance is decreased, particularly at the mass-spring resonances.

Plantar soft tissue thickness during ground contact in walking

NASA Technical Reports Server (NTRS)

Cavanagh, P. R.

1999-01-01

A technique is introduced for the measurement of plantar soft tissue thickness during barefoot walking. Subjects stepped into an adjustable Plexiglas frame which ensured that the required bony landmarks were appropriately positioned relative to a linear ultrasound probe connected to a conventional 7.5 MHz ultrasound scanner. Clear images of the metatarsal condyles or other foot bones were obtained throughout ground contact. Subsequent analysis of the video taped images using a motion analysis system allowed the tissue displacement to be calculated as a function of time. The tissue underneath the second metatarsal head was shown to undergo an average maximum compression of 45.7% during the late stages of ground contact during first step gait in a group of five normal subjects with a mean unloaded tissue thickness of 15.2 mm. The technique has a number of applications, including use in the validation of deformation predicted by finite element models of the soft tissue of the foot, and the study of alterations in the cushioning properties of the heel by devices which constrain the displacement of the heel pad.

A sampler for capturing larval and juvenile Atlantic menhaden

USGS Publications Warehouse

Hedrick, J.D.; Hedrick, L.R.; Margraf, F.J.

2005-01-01

Interest in capturing larval and juvenile Atlantic menhaden Brevoortia tyrannus for use in laboratory studies required the design and construction of a sampling device that would allow us to make collections of live fish from open-water areas. Our device for capturing 1-2.5-in larval-juvenile fish was constructed of a stainless steel frame that supported a 9.84-ft-long (3-m-long)5 cone plankton net with a 3.28-ft-diameter (1-m-diameter) opening and a 0.04-in (1-mm) mesh size. Although the plankton net was similar to that used during typical larval fish collections, the cod end was constructed of Plexiglas and was nearly watertight; this prevented impingement and injury to larval fish and provided a calm-water environment. The cod end was designed for quick release from the plankton net, and the entire cod end could be submerged into a 75-gal onboard holding tank. This design and technique obviated the netting or emerging of fish from the water until they were returned to the laboratory. ?? Copyright by the American Fisheries Society 2005.

A simple and cost-effective method, as an appropriate alternative for visible spectrophotometry: development of a dopamine biosensor.

PubMed

Abbaspour, Abdolkarim; Khajehzadeh, Abdolreza; Ghaffarinejad, Ali

2009-08-01

In this study, a new, simple, fast and inexpensive method as an alternative to visible spectrophotometry is developed. In this method the cells containing the sample solution were scanned with a scanner, then the color of each cell was analyzed with software written in visual basic (VB 6) media to red, green and blue values. The cells were built by creating holes in the Plexiglas sheet. The dimensions of identical cells were examined by Cr (III) solution with known concentrations. The validity of this new method was studied by determination of dopamine (DA) without using any other reagent. The parameters which affect the system were optimized. The comparison between the current and traditional UV-Vis spectrophotometry methods was studied and the results revealed similar trends in both methods. The developed method was successfully applied to the determination of dopamine in serum and urine without using any pretreatment. Finally comparing the results obtained in the developed method showed that microwave irradiation of the solution can decrease the experimental time, increase sensitivity and improve the limit of detection.

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

Abraham, W.M.; Kim, C.S.; King, M.M.

The airway effects of a 4-hr exposure (via a Plexiglas hood) to 1.6 ppm nitric acid vapor were evaluated in seven normal and seven allergic sheep, i.e., animals that have a history of reacting with bronchospasm to inhalation challenge with Ascaris suum antigen. The nitric acid vapor was generated by ultrasonic nebulization of a 2% nitric acid solution. Airway effects were assessed by measuring the change in specific pulmonary flow resistance before and after a standard inhalation challenge with 2.5% carbachol aerosol. Nitric acid exposure did not produce bronchoconstriction in either group. Pre-exposure increases in specific pulmonary flow resistance aftermore » carbachol inhalation were 68% (SD+/- 13%) and 82% (SD+/- 35%) for the normal and allergic sheep, respectively. Within 24 hr, the largest post-exposure increases in specific pulmonary flow resistance for the normal and allergic sheep were 108% (SD+/- 51%(P<.06)) and 175% (SD+/- 87% (p<.02)), respectively. We conclude that a short-term exposure to nitric acid vapor at levels below the industrial threshold limit (2 ppm), produces airway hyperreactivity to aerosolized carbachol in allergic sheep.« less

Neutron detection of the Triga Mark III reactor, using nuclear track methodology

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

Espinosa, G., E-mail: espinosa@fisica.unam.mx; Golzarri, J. I.; Raya-Arredondo, R.

Nuclear Track Methodology (NTM), based on the neutron-proton interaction is one often employed alternative for neutron detection. In this paper we apply NTM to determine the Triga Mark III reactor operating power and neutron flux. The facility nuclear core, loaded with 85 Highly Enriched Uranium as fuel with control rods in a demineralized water pool, provide a neutron flux around 2 × 10{sup 12} n cm{sup −2} s{sup −1}, at the irradiation channel TO-2. The neutron field is measured at this channel, using Landauer{sup ®} PADC as neutron detection material, covered by 3 mm Plexiglas{sup ®} as converter. After exposure, plasticmore » detectors were chemically etched to make observable the formed latent tracks induced by proton recoils. The track density was determined by a custom made Digital Image Analysis System. The resulting average nuclear track density shows a direct proportionality response for reactor power in the range 0.1-7 kW. We indicate several advantages of the technique including the possibility to calibrate the neutron flux density measured at low reactor power.« less

Development of a Practical Broadband Active Vibration Control System

NASA Technical Reports Server (NTRS)

Schiller, Noah H.; Perey, Daniel F.; Cabell, Randolph H.

2011-01-01

The goal of this work is to develop robust, lightweight, and low-power control units that can be used to suppress structural vibration in flexible aerospace structures. In particular, this paper focuses on active damping, which is implemented using compact decentralized control units distributed over the structure. Each control unit consists of a diamond-shaped piezoelectric patch actuator, three miniature accelerometers, and analog electronics. The responses from the accelerometers are added together and then integrated to give a signal proportional to velocity. The signal is then inverted, amplified, and applied to the actuator, which generates a control force that is out of phase with the measured velocity. This paper describes the development of the control system, including a detailed description of the control and power electronics. The paper also presents experimental results acquired on a Plexiglas window blank. Five identical control units installed around the perimeter of the window achieved 10 dB peak reductions and a 2.4 dB integrated reduction of the spatially averaged velocity of the window between 500 and 3000 Hz.

Probing young drinking water biofilms with hard and soft particles.

PubMed

Paris, Tony; Skali-Lami, Salaheddine; Block, Jean-Claude

2009-01-01

The aim of our study was to investigate, through the use of soft (Escherichia coli) and hard (polystyrene microspheres) particles, the distribution and persistence of allochthonous particles inoculated in drinking water flow chambers. Biofilms were allowed to grow for 7-10 months in tap water from Nancy's drinking water network and were composed of bacterial aggregates and filamentous fungi. Both model particles adhered almost exclusively on the biofilms (i.e. on the bacterial aggregates and on the filamentous structures) and not directly on the uncolonized walls (glass or Plexiglas). Biofilm age (i.e. bacterial density and biofilm properties) and convective-diffusion were found to govern particle accumulation: older biofilms and higher wall shear rates both increased the velocity and the amount of particle deposition on the biofilm. Persistence of the polystyrene particles was measured over a two-month period after inoculation. Accumulation amounts were found to be very different between hard and soft particles as only 0.03 per thousand of the soft particles inoculated accumulated in the biofilm against 0.3-0.8% for hard particles.

Multi-fuel combustor for gas turbine engines: Phase 1, Final report

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

Melconian, J.O.; Marden, W.W., III

An innovative can combustor configuration has been developed for gas turbine engines which has the potential of burning fuels ranging from gasoline to coal/water slurries at high efficiencies. The design is based on a Variable Residence Time (VRT) concept which allows large and agglomerated fuel particles adequate time to completely burn. High durability of the combustor is achieved by dual function use of the incoming air. For applications which require the burning of coal/water slurries, the design has the capability of removing the ash particles directly from the primary zone of the combustor. It is anticipated that because of themore » small size requirement of this combustor design, existing gas turbine engines could be retrofitted within the confines of the current engine envelope. In Phase 1, the feasibility of the concept was successfully demonstrated by three-dimensional mathematical modeling and water analogue tests. The Plexiglas model used in the water analogue tests was designed to fit the current production engine of a major manufacturer. 19 figs., 2 tabs.« less

An evaluation of lake trout reproductive habitat on Clay Banks Reef, northwestern Lake Michigan

USGS Publications Warehouse

Edsall, Thomas A.; Holey, Mark E.; Manny, Bruce A.; Kennedy, Gregory W.

1995-01-01

The extinction of the native populations of lake trout (Salvelinus namaycush) in Lake Michigan in about 1956 has been followed by a decades-long attempt to reestablish self-sustaining populations of this valuable species in habitats it formerly occupied throughout the lake. One of the most recent management strategies designed to facilitate recovery was to make a primary management objective the establishment of sanctuaries where stocked lake trout could be protected and self-sustaining populations reestablished. In the present study we employed habitat survey and mapping techniques, field and laboratory bioassays, egg traps, sediment traps, and gill nets to examine the potential for successful natural reproduction by stocked lake trout on Clay Banks Reef in the Door-Kewaunee sanctuary in Wisconsin waters of Lake Michigan. Our study revealed (1) there was suitable habitat on the reef to support the production of viable fry, (2) spawner abundance on the reef was the highest recorded in the great lakes, and (3) eggs taken from spawners on the reef and held on the reef in plexiglas incubators hatched and produced fry that survived through swim-up. We conclude that Clay Banks Reef has the potential to support successful natural reproduction by stocked lake trout.

Evaluation of avoidance behavior of tadpole madtoms (Noturus gyrinus) as a surrogate for the endangered northern madtom (Noturus stigmosus) in response to granular Bayluscide®

USGS Publications Warehouse

Boogaard, Michael A.; Erickson, Richard A.; Hubert, Terrance D.

2016-09-02

The vertical avoidance behavior of the tadpole madtom (Noturus gyrinus) exposed to environmentally relevant concentrations of the granular formulation of the lampricide Bayluscide® was evaluated. The lampricide formulation (3.2 percent active ingredient coated on a sand granule) is used to control larval sea lamprey populations in the Great Lakes. The tadpole madtom was chosen as a surrogate to the federally endangered northern madtom (Noturus stigmosus) based on similar life history characteristics and habitat requirements. Vertical avoidance of tadpole madtoms in response to the granular formulation was documented in clear Plexiglas columns (107 centimeters in height, 30.5 centimeters in diameter) for 1 hour after chemical application. Each avoidance trial produced data consisting of the number of tadpole madtoms avoiding the chemical at a given time. Based on the overall data, tadpole madtoms in treated columns were 11.7 times more likely to display avoidance compared to those in untreated controls. Results indicate that it is likely that northern madtoms will be able to detect and avoid Bayluscide® from granular applications if their response is similar to that of the tadpole madtom.

Evaluation of Eight Methods for Aligning Orientation of Two Coordinate Systems.

PubMed

Mecheri, Hakim; Robert-Lachaine, Xavier; Larue, Christian; Plamondon, André

2016-08-01

The aim of this study was to evaluate eight methods for aligning the orientation of two different local coordinate systems. Alignment is very important when combining two different systems of motion analysis. Two of the methods were developed specifically for biomechanical studies, and because there have been at least three decades of algorithm development in robotics, it was decided to include six methods from this field. To compare these methods, an Xsens sensor and two Optotrak clusters were attached to a Plexiglas plate. The first optical marker cluster was fixed on the sensor and 20 trials were recorded. The error of alignment was calculated for each trial, and the mean, the standard deviation, and the maximum values of this error over all trials were reported. One-way repeated measures analysis of variance revealed that the alignment error differed significantly across the eight methods. Post-hoc tests showed that the alignment error from the methods based on angular velocities was significantly lower than for the other methods. The method using angular velocities performed the best, with an average error of 0.17 ± 0.08 deg. We therefore recommend this method, which is easy to perform and provides accurate alignment.

Confined Impinging Jets in Porous Media

NASA Astrophysics Data System (ADS)

Buonomo, B.; Cirillo, L.; Manca, O.; Mansi, N.; Nardini, S.

2016-09-01

Impinging jets are adopted in drying of textiles, paper, cooling of gas turbine components, freezing of tissue in cryosurgery and manufacturing, electronic cooling. In this paper an experimental investigation is carried out on impinging jets in porous media with the wall heated from below with a uniform heat flux. The fluid is air. The experimental apparatus is made up of a fun systems, a test section, a tube, to reduce the section in a circular section. The tube is long 1.0 m and diameter of 0.012 m. The test section has a diameter of 0.10 m and it has the thickness of 10, 20 and 40 mm. In the test section the lower plate is in aluminum and is heated by an electrical resistance whereas the upper plate is in Plexiglas. The experiments are carried out employing a aluminum foam 40 PPI at three thickness as the test section. Results are obtained in a Reynolds number range from 5100 to 15300 and wall heat flux range from 510 W/m2 to 1400 W/m2. Results are given in terms of wall temperature profiles, local and average Nusselt numbers, pressure drops, friction factor and Richardson number.

[Study of the electrical properties of retinal horizontal cell syncytia by the technic of uniform polarization].

PubMed

Shura-Bura, T M; Trifonov, Iu A

1980-01-01

For uniform polarization of syncytial or cable structures at a large area with current passed via extracellular electrodes the extracellular longitudinal gradient of potential must be proportional to distance from the edge of preparation. In this paper the profile of conducting plate was found analytically which allows to obtain such a distribution of potentials. The profile is formed by hyperbola and its orthogonal asymptotes. Two polarizing electrodes are applied to places where the hyperbola is near to asymptotes. On the surfaces formed by asymptotes the gradient of potential is proportional to distance from intersection of these surfaces. Such a conducting plate was made as cavity in plexiglas filled by Ringer solution in agar. The plate was used for obtaining the voltage-current curves of horizontal cell membrane in gold fish retina. The area of uniform polarization was 4-5 mm long. Measurements inside this area allowed to determine the space constant of horizontal cell layer. The space constant measured in bright light (when resistance of subsynaptic membrane is high) depends on the membrane potential, being high (approximately 1,5 mm) during depolarization and low (0,2-0,4 mm) during hyperpolarization.

Efficacy of oxfendazole and fenbendazole against tortoise (Testudo hermanni) oxyurids.

PubMed

Giannetto, S; Brianti, E; Poglayen, G; Sorgi, C; Capelli, G; Pennisi, M G; Coci, G

2007-04-01

Thirty-six tortoises (Testudo hermanni) with naturally acquired oxyurids infections were used to assess the anthelmintic efficacy of oxfendazole (Dolthene; Merial) and fenbendazole (Panacur; Hoechst Roussel Vet). Animals were randomly assigned to three groups (A, B, and C) based on sex and weight. Animals in group A (seven males and six females) were orally treated with oxfendazole at dose rate of 66 mg/kg, group B animals (nine males and eight females) were orally treated with fenbendazole at dose rate of 100 mg/kg, and group C animals (three males and three females) were not treated and served as controls. All animals were individually stabled in plexiglas boxes under controlled conditions of temperature, humidity, and light beginning 7 days pretreatment and continuing for the duration of the trial. Individual tortoises feces were examined daily by the McMaster technique and drugs efficacy was assessed by the fecal eggs count reduction (FECR) test. Both drugs showed 100% of FECR. However, oxfendazole reached this level 12 days after treatment, whereas 31 days after treatment were necessary to obtain the same stable result with fenbendazole. The two drugs were well tolerated by all the animals and no adverse reactions were observed after treatment.

Developmental testing resulting in a simplified liquid oxygen check valve for the Space Shuttle Main Propulsion System

NASA Technical Reports Server (NTRS)

Aber, Gregory S.; Barrett, Michael J.; Reith, Timothy W.

1993-01-01

The coil spring in a Space Shuttle liquid oxygen check valve failed due to cyclic fatigue in September, 1991. The dual-flapper, swing check valve is used to prevent reverse flow to the Space Shuttle Main Engines. Upon inspection of the failed component, the spring tangs were found to be missing and heavy wear was observed on the inner diameter of the spring coils. The fracture surfaces revealed that the metal had been steadily worn away until a simple overload caused the final fracture. A series of flow tests using water and a water/gas mixture was conducted to identify the flow phenomenon which produced the cyclic wear. A Plexiglas outlet housing was utilized to view the flapper behavior under different flow conditions and to aid in high speed photography. The tests revealed that flow instabilities induced two oscillatory flapper responses: a rocking mode and a chattering mode. Initially, attempts were made to reduce the spring-flapper oscillations. However, the final solution to the problem was a springless configuration which satisfied the valve's design requirements and eliminated the oscillations. The springless design relied on the inherent ability of the reverse flow momentum to close the flappers.

Aperture excited dielectric antennas

NASA Technical Reports Server (NTRS)

Crosswell, W. F.; Chatterjee, J. S.; Mason, V. B.; Tai, C. T.

1974-01-01

The results of a comprehensive experimental and theoretical study of the effect of placing dielectric objects over the aperture of waveguide antennas are presented. Experimental measurements of the radiation patterns, gain, impedance, near-field amplitude, and pattern and impedance coupling between pairs of antennas are given for various Plexiglas shapes, including the sphere and the cube, excited by rectangular, circular, and square waveguide feed apertures. The waveguide excitation of a dielectric sphere is modeled using the Huygens' source, and expressions for the resulting electric fields, directivity, and efficiency are derived. Calculations using this model show good overall agreement with experimental patterns and directivity measurements. The waveguide under an infinite dielectric slab is used as an impedance model. Calculations using this model agree qualitatively with the measured impedance data. It is concluded that dielectric loaded antennas such as the waveguide excited sphere, cube, or sphere-cylinder can produce directivities in excess of that obtained by a uniformly illuminated aperture of the same cross section, particularly for dielectric objects with dimensions of 2 wavelengths or less. It is also shown that for certain configurations coupling between two antennas of this type is less than that for the same antennas without dielectric loading.

Avoidance behavior of juvenile lake sturgeon (Acipenser fulvescens) exposed to Bayluscide 3.2% Granular Sea Lamprey Larvicide

USGS Publications Warehouse

Boogaard, Michael A; Rivera, Jane E; Gaikowski, Mark P

2008-01-01

Avoidance of juvenile lake sturgeons < 100 mm in length in response to application of the Bayluscide 3.2% Granular Sea Lamprey Larvicide was assessed. Clear plexiglas columns (107 cm in height, 30.5 cm in diameter) to evaluate the potential for the normally bottom-dwelling fishes to move vertically in the water column to avoid niclosamide dissolving from the Bayluscide granules. Vertical migration of lake sturgeons to > 15 cm off the bottom of the column was considered avoidance. Lake sturgeons began displaying avoidance behaviors within 4 to 8 min after the granules were applied and continued for up to 60 min. After 60 min, most or all of the sturgeons were near the surface in the treated columns. In contrast, little movement above the 15-cm mark was observed at any time in any of the control columns. The results of this study are similar to a previous study where juvenile lake sturgeons > 100 mm in length showed the ability to avoid granular Bayluscide. Taken together, we conclude that juvenile lake sturgeons of any size range can detect and avoid granular Bayluscide applications.

Design and analysis of tactile optical sensor for endovascular surgery

NASA Astrophysics Data System (ADS)

Qasaimeh, M. A.; Dargahi, J.; Kahrizi, M.; Packirisamy, M.

2007-06-01

In this paper, design and Finite Element analysis of a new tactile optical sensor for the measurement of contact-pressure and tissue compliance in endovascular surgeries are presented. Using Micro-Electro-Mechanical-Systems (MEMS) technology, this sensor can be fabricated and integrated with the medical tools for endovascular surgeries such as Catheter tool. The designed sensor is capable of detecting the magnitude of the applied forces, the pressure distribution on contact objects, and also estimating the compliance of the contact tissue. The designed sensor is made of three layers, the upper layer is fabricated from monocrystalline silicon to form silicon membranes, the middle layer which is the supporting element is fabricated from both silicon and silicone rubber as a soft material and the lower layer is a supporting Plexiglas substrate to connect the designed sensor to the optical fibers. Simulation results show that for the given contact forces, the magnitude and the distribution of contacting tissues pressure along with tissue compliance can be determined. This sensor as proposed is a good candidate for batch micromachining, which is yet another commercial advantage for this design. Because of its less expensive cost, the surgeon can use it as a disposal part of the endovascular tools, requiring no re-sterilization and reducing the cost of surgery.

Experimental Observations of Multiscale Dynamics of Viscous Fluid Behavior: Implications in Volcanic Systems

NASA Astrophysics Data System (ADS)

Arciniega-Ceballos, A.; Spina, L.; Scheu, B.; Dingwell, D. B.

2015-12-01

We have investigated the dynamics of Newtonian fluids with viscosities (10-1000 Pa s; corresponding to mafic to intermediate silicate melts) during slow decompression, in a Plexiglas shock tube. As an analogue fluid we used silicon oil saturated with Argon gas for 72 hours. Slow decompression, dropping from 10 MPa to ambient pressure, acts as the excitation mechanism, initiating several processes with their own distinct timescales. The evolution of this multi-timescale phenomenon generates complex non-stationary microseismic signals, which have been recorded with 7 high-dynamic piezoelectric sensors located along the conduit. Correlation analysis of these time series with the associated high-speed imaging enables characterization of distinct phases of the dynamics of these viscous fluids and the extraction of the time and the frequency characteristics of the individual processes. We have identified fluid-solid elastic interaction, degassing, fluid mass expansion and flow, bubble nucleation, growth, coalescence and collapse, foam building and vertical wagging. All these processes (in fine and coarse scales) are sequentially coupled in time, occur within specific pressure intervals, and exhibit a localized distribution in space. Their coexistence and interactions constitute the stress field and driving forces that determine the dynamics of the system. Our observations point to the great potential of this experimental approach in the understanding of volcanic processes and volcanic seismicity.

Physical modeling of the influence of bedrock topography and ablation on ice flow and meteorite concentration in Antarctica

NASA Astrophysics Data System (ADS)

Corti, Giacomo; Zeoli, Antonio; Belmaggio, Pietro; Folco, Luigi

2008-03-01

Three-dimensional laboratory physical experiments have been used to investigate the influence of bedrock topography and ablation on ice flow. Different models were tested in a Plexiglas box, where a transparent silicone simulating ice in nature was allowed to flow. Experimental results show how the flow field (in terms of both flow lines and velocity) and variations in the topography of the free surface and internal layers of the ice are strongly influenced by the presence and height of bedrock obstacles. In particular, the buttressing effect forces the ice to slow down, rise up, and avoid the obstacle; the higher the bedrock barrier, the more pronounced the process. Only limited uplift of internal layers is observed in these experiments. In order to exhume deep material embedded in the ice, ablation (simulated by physically removing portions of silicone from the model surface to maintain a constant topographic depression) must be included in the physical models. In this case, the analogue ice replenishes the area of material removal, thereby allowing deep layers to move vertically to the surface and severely altering the local ice flow pattern. This process is analogous to the ice flow model proposed in the literature for the origin of meteorite concentrations in blue ice areas of the Antarctic plateau.

Magnetically Actuated Propellant Orientation Experiment, Controlling Fluid Motion With Magnetic Fields in a Low-Gravity Environment

NASA Technical Reports Server (NTRS)

Martin, J. J.; Holt, J. B.

2000-01-01

This report details the results of a series of fluid motion experiments to investigate the use of magnets to orient fluids in a low-gravity environment. The fluid of interest for this project was liquid oxygen (LO2) since it exhibits a paramagnetic behavior (is attracted to magnetic fields). However, due to safety and handling concerns, a water-based ferromagnetic mixture (produced by Ferrofluidics Corporation) was selected to simplify procedures. Three ferromagnetic fluid mixture strengths and a nonmagnetic water baseline were tested using three different initial fluid positions with respect to the magnet. Experiment accelerometer data were used with a modified computational fluid dynamics code termed CFX-4 (by AEA Technologies) to predict fluid motion. These predictions compared favorably with experiment video data, verifying the code's ability to predict fluid motion with and without magnetic influences. Additional predictions were generated for LO2 with the same test conditions and geometries used in the testing. Test hardware consisted of a cylindrical Plexiglas tank (6-in. bore with 10-in. length), a 6,000-G rare Earth magnet (10-in. ring), three-axis accelerometer package, and a video recorder system. All tests were conducted aboard the NASA Reduced-Gravity Workshop, a KC-135A aircraft.

Highly efficient TiO2-based microreactor for photocatalytic applications.

PubMed

Krivec, Matic; Žagar, Kristina; Suhadolnik, Luka; Čeh, Miran; Dražić, Goran

2013-09-25

A photocatalytic, TiO2-based microreactor is designed and fabricated on a metal-titanium foil. The microchannel is mechanically engraved in the substrate foil, and a double-layered TiO2 anatase film is immobilized on its inner walls with a two-step synthesis, which included anodization and a hydrothermal treatment. X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirm the presence of an approximately 10-μm-thick layer of titania nanotubes and anatase nanoparticles. The SEM and transmission electron microscopy (TEM) of the cross sections show a dense interface between the titanium substrate and the TiO2 nanotubes. An additional layer of TiO2-anatase nanoparticles on the top of the film provides a large, photocatalytic surface area. The metal-titanium substrate with a functionalized serpentine channel is sealed with UV-transparent Plexiglas, and four 0.8-mW UV LEDs combined with a power controller on a small printed-circuit board are fixed over the substrate. The photocatalytic activity and the kinetic properties for the degradation of caffeine are provided, and the longer-term stability of the TiO2 film is evaluated. The results show that after 6 months of use and 3600 working cycles the microreactor still exhibits 60% of its initial efficiency.

Scaling law governing the roughness of the swash edge line

NASA Astrophysics Data System (ADS)

Bormashenko, E.; Musin, A.; Grynyov, R.

2014-09-01

The paper is devoted to the analysis of the shape of the swash edge line. Formation of the swash boundary is treated as an interfacial phenomenon. The simplest quantitative characteristic of the roughness of interface is its width w, defined as the root-mean-square fluctuation around the average position. For rough interfaces, the scaling with size of the system L is observed in the form w(L)~Lζ. The concept of scaling supplies a simple framework for classifying interfaces. It is suggested that the fine structure of the swash boundary results from the combined action of the pinning force applied by random defects of the beach and elasticity of distorted swash boundary. The roughness of the swash front was studied at the Mediterranean Sea coast for uprush and backwash flows. Value of exponent ζ for receding swash front line was 0.64 +/- 0.02, when in the case of advancing swash the value 0.73 +/- 0.03 was calculated. The scaling exponent established for the receding phase of the swash is very close to the values of the exponent established for the roughness of the triple line for water droplets deposited on rough surfaces, crack propagation front in Plexiglas, and for the motion of a magnetic domain walls.

Structural-change localization and monitoring through a perturbation-based inverse problem.

PubMed

Roux, Philippe; Guéguen, Philippe; Baillet, Laurent; Hamze, Alaa

2014-11-01

Structural-change detection and characterization, or structural-health monitoring, is generally based on modal analysis, for detection, localization, and quantification of changes in structure. Classical methods combine both variations in frequencies and mode shapes, which require accurate and spatially distributed measurements. In this study, the detection and localization of a local perturbation are assessed by analysis of frequency changes (in the fundamental mode and overtones) that are combined with a perturbation-based linear inverse method and a deconvolution process. This perturbation method is applied first to a bending beam with the change considered as a local perturbation of the Young's modulus, using a one-dimensional finite-element model for modal analysis. Localization is successful, even for extended and multiple changes. In a second step, the method is numerically tested under ambient-noise vibration from the beam support with local changes that are shifted step by step along the beam. The frequency values are revealed using the random decrement technique that is applied to the time-evolving vibrations recorded by one sensor at the free extremity of the beam. Finally, the inversion method is experimentally demonstrated at the laboratory scale with data recorded at the free end of a Plexiglas beam attached to a metallic support.

A new method for ultrasound detection of interfacial position in gas-liquid two-phase flow.

PubMed

Coutinho, Fábio Rizental; Ofuchi, César Yutaka; de Arruda, Lúcia Valéria Ramos; Neves, Flávio; Morales, Rigoberto E M

2014-05-22

Ultrasonic measurement techniques for velocity estimation are currently widely used in fluid flow studies and applications. An accurate determination of interfacial position in gas-liquid two-phase flows is still an open problem. The quality of this information directly reflects on the accuracy of void fraction measurement, and it provides a means of discriminating velocity information of both phases. The algorithm known as Velocity Matched Spectrum (VM Spectrum) is a velocity estimator that stands out from other methods by returning a spectrum of velocities for each interrogated volume sample. Interface detection of free-rising bubbles in quiescent liquid presents some difficulties for interface detection due to abrupt changes in interface inclination. In this work a method based on velocity spectrum curve shape is used to generate a spatial-temporal mapping, which, after spatial filtering, yields an accurate contour of the air-water interface. It is shown that the proposed technique yields a RMS error between 1.71 and 3.39 and a probability of detection failure and false detection between 0.89% and 11.9% in determining the spatial-temporal gas-liquid interface position in the flow of free rising bubbles in stagnant liquid. This result is valid for both free path and with transducer emitting through a metallic plate or a Plexiglas pipe.

A New Method for Ultrasound Detection of Interfacial Position in Gas-Liquid Two-Phase Flow

PubMed Central

Coutinho, Fábio Rizental; Ofuchi, César Yutaka; de Arruda, Lúcia Valéria Ramos; Jr., Flávio Neves; Morales, Rigoberto E. M.

2014-01-01

Ultrasonic measurement techniques for velocity estimation are currently widely used in fluid flow studies and applications. An accurate determination of interfacial position in gas-liquid two-phase flows is still an open problem. The quality of this information directly reflects on the accuracy of void fraction measurement, and it provides a means of discriminating velocity information of both phases. The algorithm known as Velocity Matched Spectrum (VM Spectrum) is a velocity estimator that stands out from other methods by returning a spectrum of velocities for each interrogated volume sample. Interface detection of free-rising bubbles in quiescent liquid presents some difficulties for interface detection due to abrupt changes in interface inclination. In this work a method based on velocity spectrum curve shape is used to generate a spatial-temporal mapping, which, after spatial filtering, yields an accurate contour of the air-water interface. It is shown that the proposed technique yields a RMS error between 1.71 and 3.39 and a probability of detection failure and false detection between 0.89% and 11.9% in determining the spatial-temporal gas-liquid interface position in the flow of free rising bubbles in stagnant liquid. This result is valid for both free path and with transducer emitting through a metallic plate or a Plexiglas pipe. PMID:24858961

Simulation Study on Jet Formability and Damage Characteristics of a Low-Density Material Liner

PubMed Central

Tang, Wenhui; Ran, Xianwen

2018-01-01

The shaped charge tandem warhead is an effective weapon against the ERA (explosive reactive armor). Whether the pre-warhead can reliably initiate the ERA directly determines the entire performance of the tandem warhead. The existing shaped charge pre-warhead mostly adopts a metal shaped jet, which effectively initiates the ERA, but interferes the main shaped jet. This article, on the other hand, explores the possibility of producing a pre-warhead using a low-density material as the liner. The nonlinear dynamic analysis software Autodyn-2D is used to simulate and compare three kinds of low-density shaped jets, including floatglass, Lucite, and Plexiglas, to the copper shaped jet in the effectiveness of impacting ERA. Based on the integrative criteria (including u-d initiation criterion, explosive reactive degree, explosive pressure, and particle velocity of the panels), it can be determined whether the low-density shaped jet can reliably initiate the sandwich charge. The results show that the three kinds of low-density shaped jets can not only initiate the reaction armor, but are also superior to the existing copper shaped jet in ductility, jet tip velocity, jet tip diameter, and the mass; namely, it is feasible to use the low-density material shaped jet to destroy the ERA. PMID:29300351

Microchip Module for Blood Sample Preparation and Nucleic Acid Amplification Reactions

PubMed Central

Yuen, Po Ki; Kricka, Larry J.; Fortina, Paolo; Panaro, Nicholas J.; Sakazume, Taku; Wilding, Peter

2001-01-01

A computer numerical control-machined plexiglas-based microchip module was designed and constructed for the integration of blood sample preparation and nucleic acid amplification reactions. The microchip module is comprised of a custom-made heater-cooler for thermal cycling, a series of 254 μm × 254 μm microchannels for transporting human whole blood and reagents in and out of an 8–9 μL dual-purpose (cell isolation and PCR) glass-silicon microchip. White blood cells were first isolated from a small volume of human whole blood (<3 μL) in an integrated cell isolation–PCR microchip containing a series of 3.5-μm feature-sized “weir-type” filters, formed by an etched silicon dam spanning the flow chamber. A genomic target, a region in the human coagulation Factor V gene (226-bp), was subsequently directly amplified by microchip-based PCR on DNA released from white blood cells isolated on the filter section of the microchip mounted onto the microchip module. The microchip module provides a convenient means to simplify nucleic acid analyses by integrating two key steps in genetic testing procedures, cell isolation and PCR and promises to be adaptable for additional types of integrated assays. PMID:11230164

COMPARISON STUDY OF VARIOUS PLASTICS AS THE WALL MATERIAL OF THGEM-BASED MICRODOSEMETERS FOR FAST NEUTRON MEASUREMENTS.

PubMed

Moslehi, A; Raisali, G; Lamehi, M

2017-04-15

To find appropriate substitutions for the expensive plastics of A-150 and rexolite used in the construction of thick gas electron multiplier (THGEM)-based tissue-equivalent proportional counters, in the present work, the responses of a THGEM-based microdosimetric detector made of A-150 and rexolite and three others composed of plexiglas (PMMA), polyethylene and polystyrene plastics as the wall materials have been compared. Lineal energy distribution, frequency-averaged lineal energy, dose-averaged lineal energy, mean quality factor and dose-equivalent for 0.1, 1 and 10 MeV neutrons and also for 241Am-Be neutrons are calculated using Geant4 simulation toolkit. Frequency-averaged lineal energy, dose-averaged lineal energy, mean quality factor and dose-equivalent values for all plastics are found similar. In addition, the response of an indigenously constructed microdosemeter with PMMA walls is also measured for 241Am-Be neutrons. The experimental results are in good agreement with the simulation predictions. Conclusively, it was found that the three considered plastics can be used as good candidates instead of A-150 and rexolite plastics in fast neutron microdosimetry. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

The electromagnetic radiation from simple sources in the presence of a homogeneous dielectric sphere

NASA Technical Reports Server (NTRS)

Mason, V. B.

1973-01-01

In this research, the effect of a homogeneous dielectric sphere on the electromagnetic radiation from simple sources is treated as a boundary value problem, and the solution is obtained by the technique of dyadic Green's functions. Exact representations of the electric fields in the various regions due to a source located inside, outside, or on the surface of a dielectric sphere are formulated. Particular attention is given to the effect of sphere size, source location, dielectric constant, and dielectric loss on the radiation patterns and directivity of small spheres (less than 5 wavelengths in diameter) using the Huygens' source excitation. The computed results are found to closely agree with those measured for waveguide-excited plexiglas spheres. Radiation patterns for an extended Huygens' source and for curved electric dipoles located on the sphere's surface are also presented. The resonance phenomenon associated with the dielectric sphere is studied in terms of the modal representation of the radiated fields. It is found that when the sphere is excited at certain frequencies, much of the energy is radiated into the sidelobes. The addition of a moderate amount of dielectric loss, however, quickly attenuates this resonance effect. A computer program which may be used to calculate the directivity and radiation pattern of a Huygens' source located inside or on the surface of a lossy dielectric sphere is listed.

Multiscale Behavior of Viscous Fluids Dynamics: Experimental Observations

NASA Astrophysics Data System (ADS)

Arciniega-Ceballos, Alejandra; Spina, Laura; Scheu, Bettina; Dingwell, Donald B.

2016-04-01

The dynamics of Newtonian fluids with viscosities of mafic to intermediate silicate melts (10-1000 Pa s) during slow decompression present multi-time scale processes. To observe these processes we have performed several experiments on silicon oil saturated with Argon gas for 72 hours, in a Plexiglas autoclave. The slow decompression, dropping from 10 MPa to ambient pressure, acting as the excitation mechanism, triggered several processes with their own distinct timescales. These processes generate complex non-stationary microseismic signals, which have been recorded with 7 high-dynamic piezoelectric sensors located along the conduit flanked by high-speed video recordings. The analysis in time and frequency of these time series and their correlation with the associated high-speed imaging enables the characterization of distinct phases and the extraction of the individual processes during the evolution of decompression of these viscous fluids. We have observed fluid-solid elastic interaction, degassing, fluid mass expansion and flow, bubble nucleation, growth, coalescence and collapse, foam building and vertical wagging. All these processes (in fine and coarse scales) are sequentially coupled in time, occur within specific pressure intervals, and exhibit a localized distribution along the conduit. Their coexistence and interactions constitute the stress field and driving forces that determine the dynamics of the conduit system. Our observations point to the great potential of this experimental approach in the understanding of volcanic conduit dynamics and volcanic seismicity.

Richtmyer-Meshkov instability experiments of miscible and immiscible incompressible fluids

NASA Astrophysics Data System (ADS)

Krivets, Vitaliy; Holt, Brason; Mokler, Matthew; Jacobs, Jeffrey

2017-11-01

Experiments were conducted in a 3 m tall vertical drop tower setup. A flat interface separating two liquids of differing density is formed in the Plexiglas tank with the heavier fluid in the bottom and the lighter one on top. Two liquids pairs were utilized, one - miscible (isopropyl alcohol and a calcium nitrate water mixture) and the other immiscible (silicone oil with the same heavy liquid), both with Atwood near 0.2. The tank is mounted on a rail mounted sled at 2 m initial height where an initial perturbation is generated using vertical periodic motion with 10 Hz frequency and 1 mm displacement, thus producing 3D interfacial waves. An impulsive acceleration, with approximately 100g magnitude, is imparted to the sled by a rail mounted weight released and allowed to fall, impacting the sled from above. Both weight and sled then travel freely down the rails where they are smoothly decelerated at the bottom of drop tower by magnetic brakes. PLIF is used to visualize mixing process by seeding fluorescein in the bottom fluid and illuminating using laser diode from above forming thin vertical sheet. The resulting fluorescent image sequences are captured using a digital camera mounted to the sled operating at a 100 Hz framing rate. Comparisons of the measured growth of the mixing zone for both immiscible and miscible liquid combinations with theoretical models are presented.

Preparing cytotoxic agents in an isolator.

PubMed

Favier, M; Hansel, S; Bressolle, F

1993-11-01

The design of an isolator and its use by an oncology satellite pharmacy for preparing cytotoxic drugs are described. The isolator (Iso Concept, Boulogne, France) is a totally enclosed ventilated biological-safety cabinet of class III polyvinyl chloride (PVC) with positive air pressure, a half-suit with a rotating seal, and attached neoprene gloves. There are three work-stations, one for the half-suit and two along one side of the isolator. The ventilation and air filtration system consists of one entry pipe with a full ventilation-filtration box fitted with one prefilter, one blower, one ball valve, one high-efficiency particulate air (HEPA) filter, one airtight nipple connected to an automatic sterilizer, alarms, and one exhaust pipe protected by a HEPA filter. The air lock consists of a rigid, transparent Plexiglas pass-through. The chamber is sterilized with heated compressed air mixed with 3.5% peracetic acid. Maintenance includes regular changing of gloves and HEPA filters; checking of the integrity of the PVC, half-suit, and gloves; and washing and decontamination procedures. Preparation of cytotoxics is planned in advance with prescription data and manufacturing sheets. In the half-suit, a pharmacy technician reads the label, supervises preparation of the sterile admixture, and writes a label. The operators on the side of the unit read the manufacturing sheet and prepare the dose identified by the label.(ABSTRACT TRUNCATED AT 250 WORDS)

Primate Drum Kit: A System for Studying Acoustic Pattern Production by Non-Human Primates Using Acceleration and Strain Sensors

PubMed Central

Ravignani, Andrea; Olivera, Vicente Matellán; Gingras, Bruno; Hofer, Riccardo; Hernández, Carlos Rodríguez; Sonnweber, Ruth-Sophie; Fitch, W. Tecumseh

2013-01-01

The possibility of achieving experimentally controlled, non-vocal acoustic production in non-human primates is a key step to enable the testing of a number of hypotheses on primate behavior and cognition. However, no device or solution is currently available, with the use of sensors in non-human animals being almost exclusively devoted to applications in food industry and animal surveillance. Specifically, no device exists which simultaneously allows: (i) spontaneous production of sound or music by non-human animals via object manipulation, (ii) systematical recording of data sensed from these movements, (iii) the possibility to alter the acoustic feedback properties of the object using remote control. We present two prototypes we developed for application with chimpanzees (Pan troglodytes) which, while fulfilling the aforementioned requirements, allow to arbitrarily associate sounds to physical object movements. The prototypes differ in sensing technology, costs, intended use and construction requirements. One prototype uses four piezoelectric elements embedded between layers of Plexiglas and foam. Strain data is sent to a computer running Python through an Arduino board. A second prototype consists in a modified Wii Remote contained in a gum toy. Acceleration data is sent via Bluetooth to a computer running Max/MSP. We successfully pilot tested the first device with a group of chimpanzees. We foresee using these devices for a range of cognitive experiments. PMID:23912427

Anaerobic digestibility of beef hooves with swine manure or slaughterhouse sludge.

PubMed

Xia, Yun; Wang, Ding-Kang; Kong, Yunhong; Ungerfeld, Emilio M; Seviour, Robert; Massé, Daniel I

2015-04-01

Anaerobic digestion is an effective method for treating animal by-products, generating at the same time green energy as methane (CH4). However, the methods and mechanisms involved in anaerobic digestion of α-keratin wastes like hair, nails, horns and hooves are still not clear. In this study we investigated the feasibility of anaerobically co-digesting ground beef hooves in the presence of swine manure or slaughterhouse sludge at 25 °C using eight 42-L Plexiglas lab-scale digesters. Our results showed addition of beef hooves statistically significantly increased the rate of CH4 production with swine manure, but only increased it slightly with slaughterhouse sludge. After 90-day digestion, 73% of beef hoof material added to the swine manure-inoculated digesters had been converted into CH4, which was significantly higher than the 45% level achieved in the slaughterhouse sludge inoculated digesters. BODIPY-Fluorescent casein staining detected proteolytic bacteria in all digesters with and without added beef hooves, and their relative abundances corresponded to the rate of methanogenesis of the digesters with the different inocula. Fluorescence in situ hybridization in combination with BODIPY-Fluorescent casein staining identified most proteolytic bacteria as members of genus Alkaliphilus in the subfamily Clostridiaceae 2 of family Clostridiaceae. They thus appear to be the bacteria mainly responsible for digestion of beef hooves. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

Comparative assessment of chlorine, heat, ozone, and UV light for killing Legionella pneumophila within a model plumbing system.

PubMed Central

Muraca, P; Stout, J E; Yu, V L

1987-01-01

Nosocomial Legionnaires disease can be acquired by exposure to the organism from the hospital water distribution system. As a result, many hospitals have instituted eradication procedures, including hypercholorination and thermal eradication. We compared the efficacy of ozonation, UV light, hyperchlorination, and heat eradication using a model plumbing system constructed of copper piping, brass spigots, Plexiglas reservoir, electric hot water tank, and a pump. Legionella pneumophila was added to the system at 10(7) CFU/ml. Each method was tested under three conditions; (i) nonturbid water at 25 degrees C, (ii) turbid water at 25 degrees C, and (iii) nonturbid water at 43 degrees C. UV light and heat killed L. pneumophila most rapidly and required minimal maintenance. Both UV light and heat (60 degrees C) produced a 5 log kill in less than 1 h. In contrast, both chlorine and ozone required 5 h of exposure to produce a 5 log decrease. Neither turbidity nor the higher temperature of 43 degrees C impaired the efficacy of any of the disinfectant methods. Surprisingly, higher temperature enhanced the disinfecting efficacy of chlorine. However, higher temperature accelerated the decomposition of the chlorine residual such that an additional 120% volume of chlorine was required. All four methods proved efficacious in eradicating L. pneumophila from a model plumbing system. Images PMID:3566272

Primate drum kit: a system for studying acoustic pattern production by non-human primates using acceleration and strain sensors.

PubMed

Ravignani, Andrea; Matellán Olivera, Vicente; Gingras, Bruno; Hofer, Riccardo; Rodríguez Hernández, Carlos; Sonnweber, Ruth-Sophie; Fitch, W Tecumseh

2013-07-31

The possibility of achieving experimentally controlled, non-vocal acoustic production in non-human primates is a key step to enable the testing of a number of hypotheses on primate behavior and cognition. However, no device or solution is currently available, with the use of sensors in non-human animals being almost exclusively devoted to applications in food industry and animal surveillance. Specifically, no device exists which simultaneously allows: (i) spontaneous production of sound or music by non-human animals via object manipulation, (ii) systematical recording of data sensed from these movements, (iii) the possibility to alter the acoustic feedback properties of the object using remote control. We present two prototypes we developed for application with chimpanzees (Pan troglodytes) which, while fulfilling the aforementioned requirements, allow to arbitrarily associate sounds to physical object movements. The prototypes differ in sensing technology, costs, intended use and construction requirements. One prototype uses four piezoelectric elements embedded between layers of Plexiglas and foam. Strain data is sent to a computer running Python through an Arduino board. A second prototype consists in a modified Wii Remote contained in a gum toy. Acceleration data is sent via Bluetooth to a computer running Max/MSP. We successfully pilot tested the first device with a group of chimpanzees. We foresee using these devices for a range of cognitive experiments.

Optimizing total reflection X-ray fluorescence for direct trace element quantification in proteins I: Influence of sample homogeneity and reflector type

NASA Astrophysics Data System (ADS)

Wellenreuther, G.; Fittschen, U. E. A.; Achard, M. E. S.; Faust, A.; Kreplin, X.; Meyer-Klaucke, W.

2008-12-01

Total reflection X-ray fluorescence (TXRF) is a very promising method for the direct, quick and reliable multi-elemental quantification of trace elements in protein samples. With the introduction of an internal standard consisting of two reference elements, scandium and gallium, a wide range of proteins can be analyzed, regardless of their salt content, buffer composition, additives and amino acid composition. This strategy also enables quantification of matrix effects. Two potential issues associated with drying have been considered in this study: (1) Formation of heterogeneous residues of varying thickness and/or density; and (2) separation of the internal standard and protein during drying (which has to be prevented to allow accurate quantification). These issues were investigated by microbeam X-ray fluorescence (μXRF) with special emphasis on (I) the influence of sample support and (II) the protein / buffer system used. In the first part, a model protein was studied on well established sample supports used in TXRF, PIXE and XRF (Mylar, siliconized quartz, Plexiglas and silicon). In the second part we imaged proteins of different molecular weight, oligomerization state, bound metals and solubility. A partial separation of protein and internal standard was only observed with untreated silicon, suggesting it may not be an adequate support material. Siliconized quartz proved to be the least prone to heterogeneous drying of the sample and yielded the most reliable results.

Field test of a bioassay procedure for assessing habitat quality on fish spawning grounds

USGS Publications Warehouse

Manny, Bruce A.; Jude, David J.; Eshenroder, Randy L.

1989-01-01

A bioassay procedure to assess habitat quality was tested on Port Austin reef in southern Lake Huron, a spawning area of lake trout Salvelinus namaycush. In 1986, Plexiglas incubators filled with fertilized lake trout eggs were buried by scuba divers in rock rubble at two sites. The incubators then were attached to chains between large trap-net anchors on the bottom and left over winter. At one site, egg hatch rate was significantly higher in incubators that remained buried in substrate (24%) than in incubators that were dislodged out onto the substrate (13%). At the other, more exposed site, no significant difference was found in percent hatch between eggs that incubated in (10%) and on (8%) the substrate. Percent hatch at both sites was significantly lower than that (40%) of eggs from the same source that were incubated in controlled laboratory conditions. In autumn, concentrations of dissolved ammonia, hydrogen sulfide, and nitrate near bottom and in the substrate posed no threat to lake trout embryos and were not correlated with hatch rate; concentrations differed significantly between the two sites. During winter, 15 cm of sediment settled from the water onto the reef but did not accumulate or smother the eggs. The bioassay procedure is easy to implement, is recommended for use in the Great Lakes, and could be adapted easily for use elsewhere.

Simplified two-dimensional microwave imaging scheme using metamaterial-loaded Vivaldi antenna

NASA Astrophysics Data System (ADS)

Johari, Esha; Akhter, Zubair; Bhaskar, Manoj; Akhtar, M. Jaleel

2017-03-01

In this paper, a highly efficient, low-cost scheme for two-dimensional microwave imaging is proposed. To this end, the AZIM (anisotropic zero index metamaterial) cell-loaded Vivaldi antenna is designed and tested as effective electromagnetic radiation beam source required in the microwave imaging scheme. The designed antenna is first individually tested in the anechoic chamber, and its directivity along with the radiation pattern is obtained. The measurement setup for the imaging here involves a vector network analyzer, the AZIM cell-loaded ultra-wideband Vivaldi antenna, and other associated microwave components. The potential of the designed antenna for the microwave imaging is tested by first obtaining the two-dimensional reflectivity images of metallic samples of different shapes placed in front of the antenna, using the proposed scheme. In the next step, these sets of samples are hidden behind wooden blocks of different thicknesses and the reflectivity image of the test media is reconstructed by using the proposed scheme. Finally, the reflectivity images of various dielectric samples (Teflon, Plexiglas, permanent magnet moving coil) along with the copper sheet placed on a piece of cardboard are reconstructed by using the proposed setup. The images obtained for each case are plotted and compared with the actual objects, and a close match is observed which shows the applicability of the proposed scheme for through-wall imaging and the detection of concealed objects.

Phantom experiments to improve parathyroid lesion detection

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

Nichols, Kenneth J.; Tronco, Gene G.; Tomas, Maria B.

2007-12-15

This investigation tested the hypothesis that visual analysis of iteratively reconstructed tomograms by ordered subset expectation maximization (OSEM) provides the highest accuracy for localizing parathyroid lesions using {sup 99m}Tc-sestamibi SPECT data. From an Institutional Review Board approved retrospective review of 531 patients evaluated for parathyroid localization, image characteristics were determined for 85 {sup 99m}Tc-sestamibi SPECT studies originally read as equivocal (EQ). Seventy-two plexiglas phantoms using cylindrical simulated lesions were acquired for a clinically realistic range of counts (mean simulated lesion counts of 75{+-}50 counts/pixel) and target-to-background (T:B) ratios (range=2.0 to 8.0) to determine an optimal filter for OSEM. Two experiencedmore » nuclear physicians graded simulated lesions, blinded to whether chambers contained radioactivity or plain water, and two observers used the same scale to read all phantom and clinical SPECT studies, blinded to pathology findings and clinical information. For phantom data and all clinical data, T:B analyses were not statistically different for OSEM versus FB, but visual readings were significantly more accurate than T:B (88{+-}6% versus 68{+-}6%, p=0.001) for OSEM processing, and OSEM was significantly more accurate than FB for visual readings (88{+-}6% versus 58{+-}6%, p<0.0001). These data suggest that visual analysis of iteratively reconstructed MIBI tomograms should be incorporated into imaging protocols performed to localize parathyroid lesions.« less

Bubble video experiments in the marine waters off Panarea Island (Italy): real-world data for modelling CO2 bubble dissolution and evolution

NASA Astrophysics Data System (ADS)

Beaubien, Stan; De Vittor, Cinzia; McGinnis, Dan; Bigi, Sabina; Comici, Cinzia; Ingrosso, Gianmarco; Lombardi, Salvatore; Ruggiero, Livio

2014-05-01

Carbon capture and storage is expected to provide an important, short-term contribution to mitigate global climate change due to anthropogenic emissions of CO2. Offshore reservoirs are particularly favourable, however concerns exist regarding the potential for CO2 leakage into the water column (with possible ecosystem impacts) and the atmosphere. Although laboratory experiments and modelling can examine these issues, the study of natural systems can provide a more complete and realistic understanding. For this reason the natural CO2 emission site off the coast of Panarea Island (Italy) was chosen for study within the EC-funded ECO2 project. The present paper discusses the results of field experiments conducted at this site to better understand the fate of CO2 gas bubbles as they rise through the water column, and to use this real-world data as input to test the predictive capabilities of a bubble model. Experiments were conducted using a 1m wide x 1m deep x 3m tall, hollow-tube structure equipped with a vertical guide on the front face and a dark, graduated cloth for contrast and depth reference on the back. A Plexiglas box was filled with the naturally emitted gas and fixed on the seafloor inside the structure. Tubes exit the top of the box to make bubbles of different diameters, while valves on each tube control bubble release rate. Bubble rise velocity was measured by tracking each bubble with a HD video camera mounted in the guide and calculating values over 20 cm intervals. Bubble diameter was measured by filming the bubbles as they collide with a graduated Plexiglas sheet deployed horizontally at the measurement height. Bubble gas was collected at different heights using a funnel and analysed in the laboratory for CO2, O2+Ar, N2, and CH4. Water parameters were measured by performing a CTD cast beside the structure and collecting water samples at four depths using a Niskin bottle; samples were analysed in the laboratory for all carbonate system species, DO, and dissolved gases. An in-house developed GasPro sensor was also mounted on the structure to monitor pCO2 over the entire 2.5 hour duration of the experiment. The obtained data were used as input into the Discrete Bubble Model (DBM) (e.g., McGinnis et al., 2011, doi:10.1029/2010JC006557). The DBM uses mass balance to predict the gas flux across the bubble surface, whereby gas flux direction depends on internal bubble gas concentration and ambient concentration, and considering the Henry's coefficient and partial pressure of the gas. The model uses bubble-size dependent relationships for the mass transfer rate and the bubble rise velocity. Important model input parameters include: bubble size; depth; ambient dissolved gas concentrations, temperature and salinity; and initial bubble gas concentrations. Measured and modelled results are compared, showing good general agreement. Based on the concentrations measured at the lowest level, the modelled and measured bubble concentrations match very closely. Bubble size values do not match as well if this initial concentration is used, however they improve as a value closer to 100% CO2 is applied. This preliminary study has shown promising results and highlight areas where experimental design and data quality should be improved in the next phase of the study.

Infant multiple breath washout using a new commercially available device: Ready to replace the previous setup?

PubMed

Kentgens, Anne-Christianne; Guidi, Marisa; Korten, Insa; Kohler, Lena; Binggeli, Severin; Singer, Florian; Latzin, Philipp; Anagnostopoulou, Pinelopi

2018-05-01

Multiple breath washout (MBW) is a sensitive test to measure lung volumes and ventilation inhomogeneity from infancy on. The commonly used setup for infant MBW, based on ultrasonic flowmeter, requires extensive signal processing, which may reduce robustness. A new setup may overcome some previous limitations but formal validation is lacking. We assessed the feasibility of infant MBW testing with the new setup and compared functional residual capacity (FRC) values of the old and the new setup in vivo and in vitro. We performed MBW in four healthy infants and four infants with cystic fibrosis, as well as in a Plexiglas lung simulator using realistic lung volumes and breathing patterns, with the new (Exhalyzer D, Spiroware 3.2.0, Ecomedics) and the old setup (Exhalyzer D, WBreath 3.18.0, ndd) in random sequence. The technical feasibility of MBW with the new device-setup was 100%. Intra-subject variability in FRC was low in both setups, but differences in FRC between the setups were considerable (mean relative difference 39.7%, range 18.9; 65.7, P = 0.008). Corrections of software settings decreased FRC differences (14.0%, -6.4; 42.3, P = 0.08). Results were confirmed in vitro. MBW measurements with the new setup were feasible in infants. However, despite attempts to correct software settings, outcomes between setups were not interchangeable. Further work is needed before widespread application of the new setup can be recommended. © 2018 Wiley Periodicals, Inc.

Modifying cochlear implant design: advantages of placing a return electrode in the modiolus.

PubMed

Ho, Steven Y; Wiet, Richard J; Richter, Claus-Peter

2004-07-01

A modiolar return electrode significantly increases the current flow across spiral ganglion cells into the modiolus, and may decrease the cochlear implant's power requirements. Ideal cochlear implants should maximize current flow into the modiolus to stimulate auditory neurons. Previous efforts to facilitate current flow through the modiolus included the fabrication and use of precurved electrodes designed to "hug" the modiolus and silastic positioners designed to place the electrodes closer to the modiolus. In contrast to earlier efforts, this study explores the effects of return electrode placement on current distributions in the modiolus. The effects of return electrode positioning on current flow in the modiolus were studied in a Plexiglas model of the cochlea. Results of model measurements were confirmed by measurements in the modiolus of human temporal bones. The return electrode was placed either within the modiolus, or remotely, outside the temporal bone, simulating contemporary cochlear implant configurations using monopolar stimulation. Cochlear model results clearly show that modiolar current amplitudes can be influenced significantly by the location of the return electrode, being larger when placed into the modiolus. Temporal bone data show similar findings. Voltages recorded in the modiolus are, on average, 2.8 times higher with the return electrode in the modiolus compared with return electrode locations outside the temporal bone. Placing a cochlear implant's return electrode in the modiolus should significantly reduce its power consumption. Reducing power requirements should lead to improved efficiency, safer long-term use, and longer device life.

Tensile Bond Strength of So-called Universal Primers and Universal Multimode Adhesives to Zirconia and Lithium Disilicate Ceramics.

PubMed

Elsayed, Adham; Younes, Feras; Lehmann, Frank; Kern, Matthias

2017-01-01

To test the bond strength and durability after artificial aging of so-called universal primers and universal multimode adhesives to lithium disilicate or zirconia ceramics. A total of 240 ceramic plates, divided into two groups, were produced and conditioned: 120 acid-etched lithium disilicate plates (IPS e.max CAD) and 120 air-abraded zirconia plates (Zenostar T). Each group was divided into five subgroups (n = 24), and a universal restorative primer or multimode universal adhesive was used for each subgroup to bond plexiglas tubes filled with a composite resin to the ceramic plate. The specimens were stored in water at 37°C for 3 days without thermal cycling, or for 30 or 150 days with 7500 or 37,500 thermal cycles between 5°C and 55°C, respectively. All specimens then underwent tensile bond strength testing. Initially, all bonding systems exhibited high TBS, but some showed a significant reduction after 30 and 150 days of storage. After 3, 30, and 150 days, Monobond Plus, which contains silane and phosphate monomer, showed significantly higher bond strengths than the other universal primer and adhesive systems. The bond strength to lithium disilicate and zirconia ceramic is significantly affected by the bonding system used. Using a separate primer containg silane and phosphate monomer provides more durable bonding than do silanes incorporated in universal multimode adhesives. Only one of five so-called universal primers and adhesives provided durable bonding to lithium disilicate and zirconia ceramic.

Preliminary evaluation of an aqueous wax emulsion for controlled-release coating.

PubMed

Walia, P S; Stout, P J; Turton, R

1998-02-01

The purpose of this work was to evaluate the use of an aqueous carnauba wax emulsion (Primafresh HS, Johnson Wax) in a spray-coating process. This involved assessing the effectiveness of the wax in sustaining the release of the drug, theophylline. Second, the process by which the drug was released from the wax-coated pellets was modeled. Finally, a method to determine the optimum blend of pellets with different wax thicknesses, in order to yield a zero-order release profile of the drug, was addressed. Nonpareil pellets were loaded with theophylline using a novel powder coating technique. These drug-loaded pellets were then coated with different levels of carnauba wax in a 6-in. diameter Plexiglas fluid bed with a 3.5-in. diameter Wurster partition. Drug release was measured using a spin-filter dissolution device. The study resulted in continuous carnauba wax coatings which showed sustained drug release profile characteristics typical of a barrier-type, diffusion-controlled system. The effect of varying wax thickness on the release profiles was investigated. It was observed that very high wax loadings would be required to achieve long sustained-release times. The diffusion model, developed to predict the release of the drug, showed good agreement with the experimental data. However, the data exhibited an initial lag-time for drug release which could not be predicted a priori based on the wax coating thickness. A method of mixing pellets with different wax thicknesses was proposed as a way to approximate zero-order release.

Dynamics of liquid slug using particle image velocimetry technique

NASA Astrophysics Data System (ADS)

Siddiqui, M. I.; Aziz, A. Rashid A.; Heikal, M. R.

2016-11-01

Two phase liquid-gas slug flow is a source of vibration and fatigue on pipe walls and downstream equipment. This paper examines the effect of inlet conditions on the stream-wise velocity profiles and on the shear stresses induced by the liquid phase on the pipe wall during the slug flow. Instantaneous velocity vector fields of the liquid-gas (water-air) slug flow regime were obtained using particle image velocimetry (PIV) technique at various inlet conditions. A 6-m long Plexiglas pipe having an internal diameter 74-mm with a slight inclination of about 1.16° was considered for the visualization of the flow pattern. Test section was employed at a point 3.5m from the inlet, mounted with optical correction box filled with water to minimize the curvature effect of pipe on the PIV snapshots. Stream-wise velocity profiles are obtained at the wake of the liquid slug and the effect of inlet conditions were analyzed. A direct relationship was observed in between superficial gas velocity and the liquid stream-wise velocity at wake section of the slug flow. Further, the lower wall shear stresses were obtained using PIV velocity profiles at liquid film and the slug wake sections in a unit slug. The wall shear stress remained higher in the liquid slugy body as compared to the liquid film. Moreover, an increase in the wall shear stress was observed by increasing the gas superficial velocities.

Pollen mitosis and pollen tube growth inhibition by SO/sub 2/ in cultured pollen tubes of Tradescantia

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

Ma, T.H.; Khan, S.H.

Mature pollen of Tradescantia paludosa Anders, Sax clone-3 was collected from greenhouse grown plants and desiccated in the dark for 4--5 hours. The pollen was sown on microslides coated with lactose agar medium (supplemented with 0.02 percent colchicine). Five minutes after sowing, pollen cultures were treated with various concentrations (0.075--2000 ppM) of SO/sub 2/ obtained from the chemical reaction between K/sub 2/S/sub 2/O/sub 5/ and HCl. Treatments were carried out in an airtight Plexiglas chamber throughout the full incubation period of 19 hours. Treated and control pollen cultures were fixed and stained in aceto-carmine or Feulgen reaction to determine themore » tube lengths and mitotic indices. Results of repeated experiments indicated that the values of mitotic indices dropped from the normal 38.7 percent in the control to the range of 24.3--3.8 percent when treated with 0.075--50.00 ppM of SO/sub 2/. Pollen tube growth was inhibited from the normal length of 1.5 mm in the control to the range of 800--100 ..mu..m when treated with 10--2000 ppM of SO/sub 2/. The inhibitory effect of SO/sub 2/ presumably resulted from physiological disturbance of the cell and severe damage to chromosomes of both generative and tube nuclei of the pollen tubes.« less

Optimization and experimental validation of stiff porous phononic plates for widest complete bandgap of mixed fundamental guided wave modes

NASA Astrophysics Data System (ADS)

Hedayatrasa, Saeid; Kersemans, Mathias; Abhary, Kazem; Uddin, Mohammad; Van Paepegem, Wim

2018-01-01

Phononic crystal plates (PhPs) have promising application in manipulation of guided waves for design of low-loss acoustic devices and built-in acoustic metamaterial lenses in plate structures. The prominent feature of phononic crystals is the existence of frequency bandgaps over which the waves are stopped, or are resonated and guided within appropriate defects. Therefore, maximized bandgaps of PhPs are desirable to enhance their phononic controllability. Porous PhPs produced through perforation of a uniform background plate, in which the porous interfaces act as strong reflectors of wave energy, are relatively easy to produce. However, the research in optimization of porous PhPs and experimental validation of achieved topologies has been very limited and particularly focused on bandgaps of flexural (asymmetric) wave modes. In this paper, porous PhPs are optimized through an efficient multiobjective genetic algorithm for widest complete bandgap of mixed fundamental guided wave modes (symmetric and asymmetric) and maximized stiffness. The Pareto front of optimization is analyzed and variation of bandgap efficiency with respect to stiffness is presented for various optimized topologies. Selected optimized topologies from the stiff and compliant regimes of Pareto front are manufactured by water-jetting an aluminum plate and their promising bandgap efficiency is experimentally observed. An optimized Pareto topology is also chosen and manufactured by laser cutting a Plexiglas (PMMA) plate, and its performance in self-collimation and focusing of guided waves is verified as compared to calculated dispersion properties.

A new model of diffuse brain injury in rats. Part I: Pathophysiology and biomechanics.

PubMed

Marmarou, A; Foda, M A; van den Brink, W; Campbell, J; Kita, H; Demetriadou, K

1994-02-01

This report describes the development of an experimental head injury model capable of producing diffuse brain injury in the rodent. A total of 161 anesthetized adult rats were injured utilizing a simple weight-drop device consisting of a segmented brass weight free-falling through a Plexiglas guide tube. Skull fracture was prevented by cementing a small stainless-steel disc on the calvaria. Two groups of rats were tested: Group 1, consisting of 54 rats, to establish fracture threshold; and Group 2, consisting of 107 animals, to determine the primary cause of death at severe injury levels. Data from Group 1 animals showed that a 450-gm weight falling from a 2-m height (0.9 kg-m) resulted in a mortality rate of 44% with a low incidence (12.5%) of skull fracture. Impact was followed by apnea, convulsions, and moderate hypertension. The surviving rats developed decortication flexion deformity of the forelimbs, with behavioral depression and loss of muscle tone. Data from Group 2 animals suggested that the cause of death was due to central respiratory depression; the mortality rate decreased markedly in animals mechanically ventilated during the impact. Analysis of mathematical models showed that this mass-height combination resulted in a brain acceleration of 900 G and a brain compression gradient of 0.28 mm. It is concluded that this simple model is capable of producing a graded brain injury in the rodent without a massive hypertensive surge or excessive brain-stem damage.

Active Damping Using Distributed Anisotropic Actuators

NASA Technical Reports Server (NTRS)

Schiller, Noah H.; Cabell, Randolph H.; Quinones, Juan D.; Wier, Nathan C.

2010-01-01

A helicopter structure experiences substantial high-frequency mechanical excitation from powertrain components such as gearboxes and drive shafts. The resulting structure-borne vibration excites the windows which then radiate sound into the passenger cabin. In many cases the radiated sound power can be reduced by adding damping. This can be accomplished using passive or active approaches. Passive treatments such as constrained layer damping tend to reduce window transparency. Therefore this paper focuses on an active approach utilizing compact decentralized control units distributed around the perimeter of the window. Each control unit consists of a triangularly shaped piezoelectric actuator, a miniature accelerometer, and analog electronics. Earlier work has shown that this type of system can increase damping up to approximately 1 kHz. However at higher frequencies the mismatch between the distributed actuator and the point sensor caused control spillover. This paper describes new anisotropic actuators that can be used to improve the bandwidth of the control system. The anisotropic actuators are composed of piezoelectric material sandwiched between interdigitated electrodes, which enables the application of the electric field in a preferred in-plane direction. When shaped correctly the anisotropic actuators outperform traditional isotropic actuators by reducing the mismatch between the distributed actuator and point sensor at high frequencies. Testing performed on a Plexiglas panel, representative of a helicopter window, shows that the control units can increase damping at low frequencies. However high frequency performance was still limited due to the flexible boundary conditions present on the test structure.

Evaluation of dose delivery accuracy of gamma knife using MRI polymer gel dosimeter in an inhomogeneous phantom

NASA Astrophysics Data System (ADS)

Pourfallah T, A.; Alam N, Riahi; M, Allahverdi; M, Ay; M, Zahmatkesh

2009-05-01

Polymer gel dosimetry is still the only dosimetry method for directly measuring three-dimensional dose distributions. MRI Polymer gel dosimeters are tissue equivalent and can act as a phantom material. Because of high dose response sensitivity, the MRI was chosen as readout device. In this study dose profiles calculated with treatment-planning software (LGP) and measurements with the MR polymer gel dosimeter for single-shot irradiations were compared. A custom-built 16 cm diameter spherical plexiglas head phantom was used in this study. Inside the phantom, there is a cubic cutout for insertion of gel phantoms and another cutout for inserting the inhomogeneities. The phantoms were scanned with a 1.5T MRI (Siemens syngo MR 2004A 4VA25A) scanner. The multiple spin-echo sequence with 32 echoes was used for the MRI scans. Calibration relations between the spin-spin relaxation rate and the absorbed dose were obtained by using small cylindrical vials, which were filled with the PAGAT polymer gel from the same batch as for the spherical phantom. 1D and 2D data obtained using gel dosimeter for homogeneous and inhomogeneous phantoms were compared with dose obtained using LGP calculation. The distance between relative isodose curves obtained for homogeneous phantom and heterogeneous phantoms exceed the accepted total positioning error (>±2mm). The findings of this study indicate that dose measurement using PAGAT gel dosimeter can be used for verifying dose delivering accuracy in GK unit in presence of inhomogeneities.

Revisiting the horizontal redistribution of water in soils: Experiments and numerical modeling.

PubMed

Zhuang, L; Hassanizadeh, S M; Kleingeld, P J; van Genuchten, M Th

2017-09-01

A series of experiments and related numerical simulations were carried out to study one-dimensional water redistribution processes in an unsaturated soil. A long horizontal Plexiglas box was packed as homogenously as possible with sand. The sandbox was divided into two sections using a very thin metal plate, with one section initially fully saturated and the other section only partially saturated. Initial saturation in the dry section was set to 0.2, 0.4, or 0.6 in three different experiments. Redistribution between the wet and dry sections started as soon as the metal plate was removed. Changes in water saturation at various locations along the sandbox were measured as a function of time using a dual-energy gamma system. Also, air and water pressures were measured using two different kinds of tensiometers at various locations as a function of time. The saturation discontinuity was found to persist during the entire experiments, while observed water pressures were found to become continuous immediately after the experiments started. Two models, the standard Richards equation and an interfacial area model, were used to simulate the experiments. Both models showed some deviations between the simulated water pressures and the measured data at early times during redistribution. The standard model could only simulate the observed saturation distributions reasonably well for the experiment with the lowest initial water saturation in the dry section. The interfacial area model could reproduce observed saturation distributions of all three experiments, albeit by fitting one of the parameters in the surface area production term.

Novel sonar signal processing tool using Shannon entropy

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

Quazi, A.H.

1996-06-01

Traditionally, conventional signal processing extracts information from sonar signals using amplitude, signal energy or frequency domain quantities obtained using spectral analysis techniques. The object is to investigate an alternate approach which is entirely different than that of traditional signal processing. This alternate approach is to utilize the Shannon entropy as a tool for the processing of sonar signals with emphasis on detection, classification, and localization leading to superior sonar system performance. Traditionally, sonar signals are processed coherently, semi-coherently, and incoherently, depending upon the a priori knowledge of the signals and noise. Here, the detection, classification, and localization technique will bemore » based on the concept of the entropy of the random process. Under a constant energy constraint, the entropy of a received process bearing finite number of sample points is maximum when hypothesis H{sub 0} (that the received process consists of noise alone) is true and decreases when correlated signal is present (H{sub 1}). Therefore, the strategy used for detection is: (I) Calculate the entropy of the received data; then, (II) compare the entropy with the maximum value; and, finally, (III) make decision: H{sub 1} is assumed if the difference is large compared to pre-assigned threshold and H{sub 0} is otherwise assumed. The test statistics will be different between entropies under H{sub 0} and H{sub 1}. Here, we shall show the simulated results for detecting stationary and non-stationary signals in noise, and results on detection of defects in a Plexiglas bar using an ultrasonic experiment conducted by Hughes. {copyright} {ital 1996 American Institute of Physics.}« less

A dual RF resonator system for high-field functional magnetic resonance imaging of small animals.

PubMed

Ludwig, R; Bodgdanov, G; King, J; Allard, A; Ferris, C F

2004-01-30

A new apparatus has been developed that integrates an animal restrainer arrangement for small animals with an actively tunable/detunable dual radio-frequency (RF) coil system for in vivo anatomical and functional magnetic resonance imaging of small animals at 4.7 T. The radio-frequency coil features an eight-element microstrip line configuration that, in conjunction with a segmented outer copper shield, forms a transversal electromagnetic (TEM) resonator structure. Matching and active tuning/detuning is achieved through fixed/variable capacitors and a PIN diode for each resonator element. These components along with radio-frequency chokes (RFCs) and blocking capacitors are placed on two printed circuit boards (PCBs) whose copper coated ground planes form the front and back of the volume coil and are therefore an integral part of the resonator structure. The magnetic resonance signal response is received with a dome-shaped single-loop surface coil that can be height-adjustable with respect to the animal's head. The conscious animal is immobilized through a mechanical arrangement that consists of a Plexiglas body tube and a head restrainer. This restrainer has a cylindrical holder with a mouthpiece and position screws to receive and restrain the head of the animal. The apparatus is intended to perform anatomical and functional magnetic resonance imaging in conscious animals such as mice, rats, hamsters, and marmosets. Cranial images acquired from fully conscious rats in a 4.7 T Bruker 40 cm bore animal scanner underscore the feasibility of this approach and bode well to extend this system to the imaging of other animals.

AN EXPERIMENTAL STUDY OF SHOCK WAVES RESULTING FROM THE IMPACT OF HIGH VELOCITY MISSILES ON ANIMAL TISSUES

PubMed Central

Harvey, E. Newton; McMillen, J. Howard

1947-01-01

The spark shadowgram method of studying shock waves is described. It has been used to investigate the properties of such waves produced by the impact of a high velocity missile on the surface of water. The method can be adapted for study of behavior of shock waves in tissue by placing the tissue on a water surface or immersing it in water. Spark shadowgrams then reveal waves passing from tissue to water or reflected from tissue surfaces. Reflection and transmission of shock waves from muscle, liver, stomach, and intestinal wall are compared with reflection from non-living surfaces such as gelatin gel, steel, plexiglas, cork, and air. Because of its heterogeneous structure, waves transmitted by tissue are dispersed and appear as a series of wavelets. When the accoustical impedance (density x wave velocity) of a medium is less than that in which the wave is moving, reflection will occur with inversion of the wave; i.e., a high pressure wave will become a low pressure wave. This inversion occurs at an air surface and is illustrated by shadowgrams of reflection from stomach wall, from a segment of colon filled with gas, and from air-filled rubber balloons. Bone (human skull and beef ribs) shows good reflection and some transmission of shock waves. When steel is directly hit by a missile, clearly visible elastic waves pass from metal to water, but a similar direct hit on bone does not result in elastic waves strong enough to be detected by a spark shadowgram. PMID:19871617

The effect of storage conditions, contamination modes and cleaning procedures on the resin bond strength to lithium disilicate ceramic.

PubMed

Klosa, Karsten; Wolfart, Stefan; Lehmann, Frank; Wenz, Hans-Jürgen; Kern, Matthias

2009-04-01

The purpose of this in-vitro study was to evaluate the resin bond strength to pre-etched lithium disilicate ceramic using different cleaning methods after two contamination modes (saliva or saliva and silicone). Plexiglas tubes filled with composite resin (MultiCore Flow) were bonded to etched and silanized ceramic disks made of lithium disilicate ceramic (IPS e.max Press) using a luting resin (Multilink Automix). Either etched or unetched ceramic surfaces were contaminated with saliva or with saliva followed by a disclosing silicone. Groups of 16 specimens each were bonded after pretreatment using 4 surface cleaning agents (37% phosphoric acid, 5% hydrofluoric acid, 96% isopropanol, air polishing device with sodium bicarbonate) in different combinations. Before measuring tensile bond strength, specimens were stored for 3 or 150 days with thermocycling. After 150 days of storage, etching of saliva-contaminated surfaces with 5% hydrofluoric acid and/or 37% phosphoric acid provided statistically significantly higher bond strengths (37.9 to 49.5 MPa) than the other cleaning methods (1.7 to 15.5 MPa). After saliva and silicone contamination, etching with 5% hydrofluoric acid provided statistically significantly higher bond strengths (44.5 to 50.3 MPa) than all other cleaning methods (0.3 to 13.5 MPa). Ceramic cleaning methods after try-in procedures have a significant influence on the resin bond strength and are dependent on the type of contamination. Re-etching lithium disilicate ceramic with 5% hydrofluoric acid is most effective in removing contamination with saliva and/or a silicone disclosing medium.

Within arm's reach: Measuring forearm length to assess growth patterns in captive bonobos and chimpanzees.

PubMed

Behringer, Verena; Stevens, Jeroen M G; Kivell, Tracy L; Neufuss, Johanna; Boesch, Christophe; Hohmann, Gottfried

2016-09-01

Bonobos and chimpanzees are known to differ in various morphological traits, a dichotomy that is sometimes used as an analogy for evolutionary splits during human evolution. The aim of our study was to measure the forearm length of immature and adult bonobos and adult chimpanzees to assess the extent of age-related changes of forearm length in bonobos and sex-dimorphism in bonobos and chimpanzees. As a proxy of somatic growth we measured forearm length of captive bonobos and chimpanzees ranging in age from 1 to 55 years. Measures were taken from subjects inserting their arms into a transparent Plexiglas® tube, a novel technique facilitating repeated measures of nonanesthetized apes in captivity. Measures from adult females (>12 years) showed that bonobos exceed chimpanzees in terms of forearm length and that sexual dimorphism in forearm length is pronounced in chimpanzees, but not in bonobos. Forearm length increased significantly with chronological age in bonobos. Validation tests revealed that the device generates useful data on morphometric dimensions. In most primates, sexual dimorphism in body size is male-biased and the differences in forearm length in chimpanzees follow this trend. Given that males of the two species did not differ in forearm length, the absence/presence of sexual dimorphism of this trait must be due to differences in somatic growth in females. Our novel method offers an alternative to obtain morphometric measures and facilitates longitudinal studies on somatic growth. Am J Phys Anthropol 161:37-43, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Cutting efficiency of Reciproc and waveOne reciprocating instruments.

PubMed

Plotino, Gianluca; Giansiracusa Rubini, Alessio; Grande, Nicola M; Testarelli, Luca; Gambarini, Gianluca

2014-08-01

The aim of the present study was to evaluate the cutting efficiency of 2 new reciprocating instruments, Reciproc and WaveOne. Twenty-four new Reciproc R25 and 24 new WaveOne Primary files were activated by using a torque-controlled motor (Silver Reciproc) and divided into 4 groups (n = 12): group 1, Reciproc activated by Reciproc ALL program; group 2, Reciproc activated by WaveOne ALL program; group 3, WaveOne activated by Reciproc ALL program; and group 4, WaveOne activated by WaveOne ALL program. The device used for the cutting test consisted of a main frame to which a mobile plastic support for the handpiece is connected and a stainless steel block containing a Plexiglas block (inPlexiglass, Rome, Italy) against which the cutting efficiency of the instruments was tested. The length of the block cut in 1 minute was measured in a computerized program with a precision of 0.1 mm. Means and standard deviations of each group were calculated, and data were statistically analyzed with 1-way analysis of variance and Bonferroni test (P < .05). Reciproc R25 displayed greater cutting efficiency than WaveOne Primary for both the movements used (P < .05); in particular, Reciproc instruments used with their proper reciprocating motion presented a statistically significant higher cutting efficiency than WaveOne instruments used with their proper reciprocating motion (P < .05). There was no statistically significant difference between the 2 movements for both instruments (P > .05). Reciproc instruments demonstrated statistically higher cutting efficiency than WaveOne instruments. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Influence of contamination on bonding to zirconia ceramic.

PubMed

Yang, Bin; Scharnberg, Michael; Wolfart, Stefan; Quaas, Anne C; Ludwig, Klaus; Adelung, Rainer; Kern, Matthias

2007-05-01

The purpose of this study was to investigate the influences of contaminations and cleaning methods on bonding to dental zirconia ceramic. After saliva immersion and using silicone disclosing agent, airborne-particle abraded ceramic specimens were cleaned with isopropanol (AL), acetone (AC), 37% phosphoric acid (PA), additional airborne-particle abrasion (AA), or only with water rinsing (SS). Airborne-particle abraded specimens without contaminations (CL) were used as control group. For chemical analysis specimens of all groups were examined with X-ray photoelectron spectroscopy (XPS). Plexiglas tubes filled with composite resin were bonded to ceramic specimens using a phosphate-monomer containing composite luting resin. After 3-day water storage, tensile bond strengths (TBS) were tested. XPS analysis of group SS showed the presence of saliva and silicone (Si) contamination on the surface. The ratios of carbon/zirconium and oxygen/zirconium for groups PA and AA were comparable to those ratios obtained for group CL, indicating the removal of the organic saliva contamination. Airborne-particle abrasion and acetone completely removed Si contamination from ceramic surfaces. Isopropanol had little cleaning effect on the two contaminants. TBS (median +/- standard deviation) in MPa of the groups SS (11.6 +/- 3.1), AL (10.0 +/- 2.9), and AC (13.0 +/- 2.8) were statistically lower than those of groups PA (33.6 +/- 5.5), AA (40.1 +/- 3.6), and CL (47.0 +/- 8.1) (p < 0.001), while no differences were found in TBS between groups AA and CL (p > 0.5). Contamination significantly reduced bond strengths to zirconia ceramic. Airborne-particle abrasion was the most effective cleaning method.

Prenatal exposure to restraint or predator stresses attenuates field excitatory postsynaptic potentials in infant rats.

PubMed

Saboory, Ehsan; Ahmadzadeh, Ramin; Roshan-Milani, Shiva

2011-12-01

Exposure to stress is known to change synaptic plasticity and results in long-term depression; further, this stress precipitates seizures. In the study described here, the prenatal restraint and predator stress models were used to test the hypothesis that indirect prenatal stresses influence hippocampal synaptic potentiation and may affect seizures susceptibility in infant rats. Pregnant female Wistar rats were divided into 3 groups: control, restraint-stressed, and predator-stressed groups. Both stressed groups were exposed to the stressor on gestation days 15, 16, and 17. The restraint stress involved 1-h sessions twice daily in a Plexiglas tube and the predator stress involved 2-h sessions once daily in a cage placed within the visual range of a caged cat. Blood corticosterone (COS) levels were measured in different time points. Hippocampal slices were prepared and field excitatory postsynaptic potentials (fEPSP) were studied on postnatal day 15. Pilocarpine was administered on postnatal day 25 and mortality rates were measured after 2 and 24h. Restraint and predator stresses resulted in significantly elevated COS blood levels in dams and pups. Both the amplitude and slope of fEPSP in the CA1 area decreased significantly in the stressed groups as compared to the control. Prenatal restraint and predator stresses significantly increased the fatal effect of pilocarpine at 24h after injection. Exposure to prenatal stresses and COS blood levels elevation reduce hippocampal synaptic potentiation and increase mortality rate of seizure in infant rats and may affect on later seizure susceptibility and prognosis. Copyright © 2011 ISDN. Published by Elsevier Ltd. All rights reserved.

Inhalation of Nebulized Perfluorochemical Enhances Recombinant Adenovirus and Adeno-Associated Virus-Mediated Gene Expression in Lung Epithelium

PubMed Central

Beckett, Travis; Bonneau, Laura; Howard, Alan; Blanchard, James; Borda, Juan; Weiner, Daniel J.; Wang, Lili; Gao, Guang Ping; Kolls, Jay K.; Bohm, Rudolf; Liggitt, Denny

2012-01-01

Abstract Use of perfluorochemical liquids during intratracheal vector administration enhances recombinant adenovirus and adeno-associated virus (AAV)-mediated lung epithelial gene expression. We hypothesized that inhalation of nebulized perfluorochemical vapor would also enhance epithelial gene expression after subsequent intratracheal vector administration. Freely breathing adult C57BL/6 mice were exposed for selected times to nebulized perflubron or sterile saline in a sealed Plexiglas chamber. Recombinant adenoviral vector was administered by transtracheal puncture at selected times afterward and mice were killed 3 days after vector administration to assess transgene expression. Mice tolerated the nebulized perflubron without obvious ill effects. Vector administration 6 hr after nebulized perflubron exposure resulted in an average 540% increase in gene expression in airway and alveolar epithelium, compared with that with vector alone or saline plus vector control (p<0.05). However, vector administration 1 hr, 1 day, or 3 days after perflubron exposure was not different from either nebulized saline with vector or vector alone and a 60-min exposure to nebulized perflubron is required. In parallel pilot studies in macaques, inhalation of nebulized perflubron enhanced recombinant AAV2/5 vector expression throughout the lung. Serial chest radiographs, bronchoalveolar lavages, and results of complete blood counts and serum biochemistries demonstrated no obvious adverse effects of nebulized perflubron. Further, one macaque receiving nebulized perflubron only was monitored for 1 year with no obvious adverse effects of exposure. These results demonstrate that inhalation of nebulized perflubron, a simple, clinically more feasible technique than intratracheal administration of liquid perflubron, safely enhances lung gene expression. PMID:22568624

A wind tunnel for measuring selenium volatilization under field-like conditions

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

Dungan, R.S.; Stork, A.; Frankenberger, W.T. Jr.

2000-04-01

A wind tunnel was developed to measure the loss of volatile selenium (Se) from soil under field-like conditions. The wind tunnel consisted of a volatilization chamber made of Plexiglas (2.4 m long x 0.8 m wide x 1.2 m high), which was set above a stainless steel lysimeter (0.5 m{sup 2} surface area x 0.8 m deep). High air exchange rates (avg. 700 air changes h{sup {minus}1}) were used to simulate field-like environmental conditions inside the wind tunnel. To monitor the fate and transport of the Se, radiolabeled {sup 75}Se as sodium selenite (Na{sub 2}{sup 75}SeO{sub 3}) was incorporated intomore » the top 5 cm of soil. Volatile Se was trapped on activated carbon filters and measured directly using gamma counting. A 135-d bare-soil experiment was carried out, during which 2.7% of the Se was released through volatilization without added C. The average flux rate of gaseous Se was 17 mg m{sup {minus}2} h{sup {minus}1}, with a high of 72 mg m{sup {minus}2} h{sup {minus}1} occurring on Day 6. After 135 d, 59 and 43% of the {sup 75}Se was located in the 0 to 5 and 5 to 10 cm soil layers, respectively. A total of 84.5% of all applied {sup 75}Se was recovered. The purpose of this study was to improve estimates on Se volatilization from seleniferous soils and help close the gap between previous laboratory and field experiments.« less

The Use of Barker Coded Signal on the Measurement of Wave Velocity of Rock

NASA Astrophysics Data System (ADS)

Zhu, W.; Wu, H.

2016-12-01

The wave velocity of the rock is important petro physics parameters; it can be used to calculate the elastic parameters, monitor the variations in the stress suffered by rock; and the velocity anisotropy reflects the rock anisotropy. Furthermore, since the coda wave is more sensitive to the change in rock properties, its velocity variation has been applied to monitor the variations in rock structures caused by varying temperature, stress, water saturation and other factors. However, the measurements of velocities heavily depend on signal-to-noise ratio (SNR) of the signals, because low signal-to-noise ratio would result in the difficulty in the identification of information. Fortunately coded excitation technique, widely used in radar, and medical system, just can solve the problem above. Although this technique can effectively improve the SNR and resolution of received signal, there exits very high sidelobes after traditional matched filter. So a pseudo inverse filter was successfully applied to suppress the side lobes. After comparing different coded signals, Barker coded signal are selected to measure the velocity of P wave of Plexiglas, sandstone, granite, marble with automatic measurement method, which are compared with the measurement results of single pulse; the results showed that the measurement of coded signals is more closely to the manual measurement. Moreover, coda wave measurement of loading granite was also made with Barker coded signal, the results of which also showed that the detection result of coded signals is better than that of the single pulse. In conclusion, the experiments verify the effectiveness and reliability of coded signals used on the measurement of wave velocity of rock.

A spot check for assessing static orientation consistency of inertial and magnetic sensing units.

PubMed

Picerno, Pietro; Cereatti, Andrea; Cappozzo, Aurelio

2011-03-01

Despite the widespread use of Magnetic and Inertial Measurement Units (MIMUs) for movement reconstruction, only a few studies have tackled issues related to their accuracy. It has been proved that their performance decreases over a period of use since calibration parameters become no longer effective. Good practice rules recommend to assess, prior to any experimental session, the instrumental errors associated to the relevant measures. Aim of this study was to provide a practical and reproducible spot check for assessing the performance of MIMUs in terms of consistency in determining their orientation with respect to a common (inter-MIMUs consistency, IC) and invariant (self-MIMU consistency, SC) global frame. IC was assessed by verifying the hypothesis that the orientation of 9 MIMUs aligned to each other on a rigid Plexiglas plank coincided at any orientation of the plank. SC was assessed separately by verifying differences between measured and imposed known rotations imparted to each MIMU. The orientation of MIMUs relative to the global frame was expressed in terms of quaternion. IC test showed that MIMUs defined their orientation differently. This difference was not constant but varied according to the plank's orientation. The least consistent MIMU showed discrepancy up to 5.7°. SC test confirmed the same MIMU as that affected by the highest inaccuracy (8.4°), whereas it revealed errors within limits (1°) in correspondence to other MIMUs. A tool has been proposed that allows the users to be aware of the errors that may be expected when using MIMUs for the estimate of absolute and relative segments kinematics. Copyright © 2010 Elsevier B.V. All rights reserved.

Differential effects of sertraline in a predator exposure animal model of post-traumatic stress disorder.

PubMed

Wilson, C Brad; McLaughlin, Leslie D; Ebenezer, Philip J; Nair, Anand R; Dange, Rahul; Harre, Joseph G; Shaak, Thomas L; Diamond, David M; Francis, Joseph

2014-01-01

Serotonin (5-HT), norepinephrine (NE), and other neurotransmitters are modulated in post-traumatic stress disorder (PTSD). In addition, pro-inflammatory cytokines (PIC) are elevated during the progression of the disorder. Currently, the only approved pharmacologic treatments for PTSD are the selective-serotonin reuptake inhibitors (SSRI) sertraline and paroxetine, but their efficacy in treating PTSD is marginal at best. In combat-related PTSD, SSRIs are of limited effectiveness. Thus, this study sought to analyze the effects of the SSRI sertraline on inflammation and neurotransmitter modulation via a predator exposure/psychosocial stress animal model of PTSD. We hypothesized that sertraline would diminish inflammatory components and increase 5-HT but might also affect levels of other neurotransmitters, particularly NE. PTSD-like effects were induced in male Sprague-Dawley rats (n = 6/group × 4 groups). The rats were secured in Plexiglas cylinders and placed in a cage with a cat for 1 h on days 1 and 11 of a 31-day stress regimen. PTSD rats were also subjected to psychosocial stress via daily cage cohort changes. At the conclusion of the stress regimen, treatment group animals were injected intraperitoneally (i.p.) with sertraline HCl at 10 mg/kg for 7 consecutive days, while controls received i.p. vehicle. The animals were subsequently sacrificed on day 8. Sertraline attenuated inflammatory markers and normalized 5-HT levels in the central nervous system (CNS). In contrast, sertraline produced elevations in NE in the CNS and systemic circulation of SSRI treated PTSD and control groups. This increase in NE suggests SSRIs produce a heightened noradrenergic response, which might elevate anxiety in a clinical setting.

Adult vitamin D deficiency exacerbates impairments caused by social stress in BALB/c and C57BL/6 mice.

PubMed

Groves, Natalie J; Zhou, Mei; Jhaveri, Dhanisha J; McGrath, John J; Burne, Thomas H J

2017-12-01

Vitamin D deficiency is prevalent in adults throughout the world. Epidemiological studies have shown significant associations between vitamin D deficiency and an increased risk of various neuropsychiatric and neurodegenerative disorders, such as schizophrenia, depression, Alzheimer's disease and cognitive impairment. However, studies based on observational epidemiology cannot address questions of causality; they cannot determine if vitamin D deficiency is a causal factor leading to the adverse health outcome. The main aim of this study was to determine if AVD deficiency would exacerbate the effects of a secondary exposure, in this case social stress, in BALB/c mice and in the more resilient C57BL/6 mice. Ten-week old male BALB/c and C57BL/6 mice were fed a control or vitamin D deficient diet for 10 weeks, and the mice were further separated into one of two groups for social treatment, either Separated (SEP) or Social Defeat (DEF). SEP mice were placed two per cage with a perforated Plexiglas divider, whereas the DEF mice underwent 10days of social defeat prior to behavioural testing. We found that AVD-deficient mice were more vulnerable to the effects of social stress using a social avoidance test, and this was dependent on strain. These results support the hypothesis that vitamin D deficiency may exacerbate behavioural outcomes in mice vulnerable to stress, a finding that can help guide future studies. Importantly, these discoveries support the epidemiological link between vitamin D deficiency and neuropsychiatric and neurodegenerative disorders; and has provided clues that can guide future studies related to unravelling the mechanisms of action linking adult vitamin D deficiency and adverse brain related outcomes. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

The improvement of adhesive properties of PEEK through different pre-treatments

NASA Astrophysics Data System (ADS)

Hallmann, Lubica; Mehl, Albert; Sereno, Nuno; Hämmerle, Christoph H. F.

2012-07-01

The purpose of this in vitro study was the evaluation of the bond strength of the adhesives/composite resin to Poly Ether Ether Ketone (PEEK) based dental polymer after using different surface conditioning methods. PEEK blanks were cut into discs. All disc specimens were polished with 800 grit SiC paper and divided into 6 main groups. Main groups were divided into 2 subgroups. The main groups of 32 specimens each were treated as follow: (1) control specimens (no treatment), (2) piranha solution etching, (3) abraded with 50 μm alumina particles and chemical etching, (4) abraded with 110 μm alumina particles and chemical etching, (5) abraded with 30 μm silica-coated alumina particles and chemical etching, (6) abraded with 110 μm silica-coated alumina particles and chemical etching. Plexiglas tubes filled with a composite resin (RelyX Unicem) were bonded to the specimens. The adhesives used were Heliobond and Clearfil Ceramic Primer. Each specimen was stored in distilled water (37 °C) for 3 days. Tensile bond strength was measured in a universal testing machine and failure methods were evaluated. Abraded surface with 50 μm alumina particles followed by etching with piranha solution lead to the highest bond strength of 21.4 MPa when Heliobond like adhesive was used. Tribochemical silica coated/etched PEEK surfaces did not have an effect on the bond strength. Non-treated PEEK surface was not able to establish a bond with composite resin. The proper choice of adhesive/composite resin system leads to a strong bond. ConclusionAirborne particle abrasion in combination with piranha solution etching improves the adhesive properties of PEEK.

Non-ferromagnetic retinal tacks are a tolerable risk in magnetic resonance imaging.

PubMed

Kuethe, D O; Small, K W; Blinder, R A

1991-01-01

Should patients with cobalt alloy (ASTM F563) retinal tacks (Grieshaber cat. #611.95) in their eyes be subjected to the magnetic fields used in magnetic resonance imaging? Although the tacks are not ferromagnetic, they will experience a retarding torque when they are moved at the high angular velocities of human eye motion. Because retinal tacks are small (2.85 mm x 0.9 mm), the torque is difficult to measure. Rather, we measured the torque on a model 25.4 times larger and used a scaling law derived from Maxwell's equations to calculate the force on the tack. The scaling law states that the torque varies with the cube of the object's length. To mimic the motion, models of retinal tacks were attached to Plexiglas rods and the assemblies were swung as pendulums. The pendulums were oriented in the magnetic field of a 1.5 T imager to experience the greatest retardation. Retarding torques were estimated from the rate of decrease of the pendulum amplitude, both inside and outside the magnet. Even if the retinal tacks were as conductive as 6061T6 aluminum alloy (25 MS/m) and the velocity of the surface of the eye were 24 cm/s (angular vel. of 1130 deg/s), the retarding torque would be only 1.6 times the weight of the tack acting with a lever arm as long as the distance from its tip to its center of gravity. The maximum retarding torque on an implanted retinal tack in a 1.5 T magnet is similar to the torque produced by gravity alone acting on the tack and is a tolerable risk.(ABSTRACT TRUNCATED AT 250 WORDS)

Spectral variation of high power microwave pulse propagating in a self-generated plasma

NASA Technical Reports Server (NTRS)

Ren, A.; Kuo, S. P.; Kossey, Paul

1995-01-01

A systematic study to understand the spectral variation of a high power microwave pulse propagating in a self-generated plasma is carried out. It includes the theoretical formulation, experimental demonstration, and computer simulations and computer experiments. The experiment of pulse propagation is conducted in a vacuum chamber filled with dry air (approximately 0.2 torr); the chamber is made of a 2 ft. cube of Plexiglas. A rectangular microwave pulse (1 microsec pulse width and 3.27 GHz carrier frequency) is fed into the cube through an S band microwave horn placed at one side of the chamber. A second S-band horn placed at the opposite side of the chamber is used to receive the transmitted pulse. The spectra of the incident pulse and transmitted pulse are then compared. As the power of the incident pulse is only slightly (less than 15%) above the breakdown threshold power of the background air, the peak of the spectrum of the transmitted pulse is upshifted from the carrier frequency 3.27 GHz of the incident pulse. However, as the power of the incident pulse exceeds the breakdown threshold power of the background air by 30%, a different phenomenon appears. The spectrum of the transmitted pulse begins to have two peaks. One is upshifted and the other one downshifted from the single peak location of the incident pulse. The amount of frequency downshift is comparable to that of the upshifted frequency. A theoretical model describing the experiment of pulse propagation in a self-generated plasma is developed. There are excellent agreements between the experimental results and computer simulations based on this theoretical model, which is also used to further carry out computer experiments identifying the role of plasma introduced wave loss on the result of frequency downshift phenomenon.

Interactive effects of prenatal exposure to restraint stress and alcohol on pentylenetetrazol-induced seizure behaviors in rat offspring.

PubMed

Hashemi, Paria; Roshan-Milani, Shiva; Saboory, Ehsan; Ebrahimi, Loghman; Soltanineghad, Maryam

2016-11-01

Prenatal exposure to stress or alcohol increases vulnerability of brain regions involved in neurobehavioral development and programs susceptibility to seizure. To examine how prenatal alcohol interferes with stress-sensitive seizures, corticosterone (COS) blood levels and pentylenetetrazol (PTZ)-induced seizure behaviors were investigated in rat pups, prenatally exposed to stress, alcohol, or both. Pregnant rats were exposed to stress and saline/alcohol on 17, 18, and 19 days of pregnancy and divided into four groups of control-saline (CS), control-alcohol (CA), restraint stress-saline (RS), and restraint stress-alcohol (RA). In CS/CA groups, rats received saline/alcohol (20%, 2 g/kg, intraperitoneally [i.p.]). In RS/RA groups, rats were exposed to restraint stress by being held immobile in a Plexiglas ® tube (twice/day, 1 h/session), and received saline/alcohol, simultaneously. After parturition, on postnatal days 6 and 15 (P6 & P15), blood samples were collected from the pups to determine COS level. On P15 and P25, PTZ (45 mg/kg) was injected into the rest of the pups and seizure behaviors were then recorded. COS levels increased in pups of the RS group but not in pups of the RA group. Both focal and tonic-clonic seizures were prevalent and severe in pups of the RS group, whereas only focal seizures were prominent in pups of the CA group. However, pups prenatally exposed to co-administration of alcohol and stress, unexpectedly, did not show additive epileptic effects. The failure of pups prenatally exposed to alcohol to show progressive or facilitatory epileptic responses to stressors, indicates decreased plasticity and adaptability, which may negatively affect HPA-axis performance or hippocampal structure/function. Copyright © 2016 Elsevier Inc. All rights reserved.

Hyperosmolality in the plasma modulates behavioral thermoregulation in mice: the quantitative and multilateral assessment using a new experimental system.

PubMed

Lin, Cheng-Hsien; Tokizawa, Ken; Nakamura, Mayumi; Uchida, Yuki; Mori, Hisae; Nagashima, Kei

2012-01-18

We evaluated the effect of plasma hyperosmolality on behavioral thermoregulation in mice, using a new experimental system. The system consisted of Plexiglas box (dimensions: 50×12×19 cm) with five computer-controlled Peltier boards (dimensions: 10×10 cm) at the bottom. Experiments were conducted in two different settings of the system. An operant behavior setting: each board was first set to 39°C, and the right-end board was changed to 20°C for 1 min when a mouse moved to a specific position. A temperature mosaic setting: each board was randomly set to 15°C, 22°C, 28°C, 35°C, or 39°C with a 6-min interval, but each board temperature was different from the others at a given time point. Mice were injected subcutaneous (s.c.) isotonic or hypertonic saline (154 mM (IS group) or 2,500 mM (HS group), 10 ml/kg body wt), and exposed to either setting for 90 min. In the operant setting, the HS group showed fewer operant behavior counts than the IS group (11±5 and 25±4 counts, respectively; P<0.05) with greater increase in body temperature (1.6±0.4°C vs. 0.0±0.2°C, respectively; P<0.05). In the mosaic setting, the HS group selected the board temperature of 35°C more frequently than the other temperatures (P<0.05) with the same increase in body temperature. These results may suggest that plasma hyperosmolality modulates behavioral thermoregulatory response to heat and induce regulated hyperthermia. Copyright © 2011 Elsevier Inc. All rights reserved.

Settling-driven gravitational instabilities associated with volcanic clouds: new insights from experimental investigations

NASA Astrophysics Data System (ADS)

Scollo, Simona; Bonadonna, Costanza; Manzella, Irene

2017-06-01

Downward propagating instabilities are often observed at the bottom of volcanic plumes and clouds. These instabilities generate fingers that enhance the sedimentation of fine ash. Despite their potential influence on tephra dispersal and deposition, their dynamics is not entirely understood, undermining the accuracy of volcanic ash transport and dispersal models. Here, we present new laboratory experiments that investigate the effects of particle size, composition and concentration on finger generation and dynamics. The experimental set-up consists of a Plexiglas tank equipped with a removable plastic sheet that separates two different layers. The lower layer is a solution of water and sugar, initially denser than the upper layer, which consists of water and particles. Particles in the experiments include glass beads as well as andesitic, rhyolitic and basaltic volcanic ash. During the experiments, we removed the horizontal plastic sheet separating the two fluids. Particles were illuminated with a laser and filmed with a HD camera; particle image velocimetry (PIV) is used to analyse finger dynamics. Results show that both the number and the downward advance speed of fingers increase with particle concentration in the upper layer, while finger speed increases with particle size but is independent of particle composition. An increase in particle concentration and turbulence is estimated to take place inside the fingers, which could promote aggregation in subaerial fallout events. Finally, finger number, finger speed and particle concentration were observed to decrease with time after the formation of fingers. A similar pattern could occur in volcanic clouds when the mass supply from the eruptive vent is reduced. Observed evolution of the experiments through time also indicates that there must be a threshold of fine ash concentration and mass eruption rate below which fingers do not form; this is also confirmed by field observations.

Tributyltin affects shoaling and anxiety behavior in female rare minnow (Gobiocypris rarus).

PubMed

Zhang, Jiliang; Zhang, Chunnuan; Sun, Ping; Shao, Xian

2016-09-01

Effects of tributyltin (TBT) on reproduction are well established in many fish species. However, few studies report the effects of TBT on non-reproductive behaviors, which is a novel aspect of endocrine disruption in fish. Thus, the present study used rare minnow (Gobiocypris rarus) to investigate the effects of TBT, at environmental concentrations of 1, 10 and 100ng/L, on shoaling and anxiety behaviors. The results showed that fish exposed to TBT had less group cohesion during the course of the 10-min observation period as compared with the control fish. Further, TBT altered the shoaling in the Novel tank test, where shoaling is determined as the tendency to leave a shoal of littermates trapped behind a Plexiglas barrier at one end of the test tank. Fish exposed to TBT had shorter latency before leaving shoal mates and spent more time away from shoal than control fish. In addition, we also used Novel tanks to study the anxiety behavior as the tendency to stay at the bottom when introduced into an unfamiliar environment. The fish exposed to TBT showed increased anxiety, manifested as increased latency to enter the upper half and decreased time in upper half when compared with the control fish. TBT exposure increased the levels of dopamine and its metabolite 3,4-dihydroxyphenylacetic acid, and decreased the levels of 5-hydroxytryptamine and its metabolite 5-hydroxy indole acetic acid in the brain. Thus, the hypofunction of the dopaminergic system or of the serotoninergic system or the combination of the two may underlie the observed behavioral change, which might affect the fitness of fish in their natural environment. Copyright © 2016 Elsevier B.V. All rights reserved.

Laboratory analog and numerical study of groundwater flow and solute transport in a karst aquifer with conduit and matrix domains.

PubMed

Faulkner, Jonathan; Hu, Bill X; Kish, Stephen; Hua, Fei

2009-11-03

New mathematical and laboratory methods have been developed for simulating groundwater flow and solute transport in karst aquifers having conduits imbedded in a porous medium, such as limestone. The Stokes equations are used to model the flow in the conduits and the Darcy equation is used for the flow in the matrix. The Beavers-Joseph interface boundary conditions are adopted to describe the flow exchange at the interface boundary between the two domains. A laboratory analog is used to simulate the conduit and matrix domains of a karst aquifer. The conduit domain is located at the bottom of the transparent plexiglas laboratory analog and glass beads occupy the remaining space to represent the matrix domain. Water flows into and out of the two domains separately and each has its own supply and outflow reservoirs. Water and solute are exchanged through an interface between the two domains. Pressure transducers located within the matrix and conduit domains of the analog provide data that is processed and stored in digital format. Dye tracing experiments are recorded using time-lapse imaging. The data and images produced are analyzed by a spatial analysis program. The experiments provide not only hydraulic head distribution but also capture solute front images and mass exchange measurements between the conduit and matrix domains. In the experiment, we measure and record pressures, and quantify flow rates and solute transport. The results present a plausible argument that laboratory analogs can characterize groundwater water flow, solute transport, and mass exchange between the conduit and matrix domains in a karst aquifer. The analog validates the predictions of a numerical model and demonstrates the need of laboratory analogs to provide verification of proposed theories and the calibration of mathematical models.

Reduction of hydraulic conductivity in column simulations of unconsolidated sediments by growth of in situ microflora

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

Bertetti, F.P.; Birnbaum, S.J.

1992-01-01

Laboratory experiments were employed to determine the effects of microbial growth upon the hydraulic conductivity (K) of unconsolidated sediments at Kelly Air Force Base, Texas. Indigenous microflora were isolated from sediment samples collected at sites contaminated with toxic organic compounds (e.g. dichlorobenzene) by plating on concentrated and dilute media. Plexiglas columns were packed with silica beads or Kelly AFB sediment and used to simulate ground water flow conditions. Grain sizes were selected to yield realistic K values (2.0 [times] 10[sup [minus]1] to 8.0 [times] 10[sup [minus]3] cm/sec) defined by field data from the contaminated sites. Both individual and mixed microbialmore » colonies, selected based on morphological characteristics individual and mixed microbial colonies, selected based on morphological characteristics deemed favorable for porosity obstruction, were injected into sterile, saturated columns. Growth was stimulated by adding sterile liquid nutrient media. Media flow rates were based upon field derived hydraulic conductivity values and water table gradients. Flow rates were controlled using a peristaltic pump. Growth of the microorganisms produced biomass which reduced the column hydraulic conductivity by up to 90% in 11 days. Reduction in K was accomplished via clogging of pore throats by cell attachment and accumulation on bead surfaces, and extracellular biofilm development. Sediment packed columns showed reduction in K values similar to that of bead packed columns of equivalent grain size. Porosity obstruction and corresponding reduction in K persisted in the columns even when subjected to hydraulic gradients significantly exceeding gradients measured in the field thereby demonstrating the robust nature of biological barrier to flow.« less

Heat dissipation in controlled environment enclosures through the application of water screens

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

Warrington, I.J.; Halligan, E.A.; Ruby, L.C.

1994-12-31

The use of plate glass-water thermal barriers in controlled environment facilities effectively reduces the thermal load within the plant growth chamber. This allows high PPFs to be provided for plant growth and development studies, adequate simulation of daily light integrals, and simulation of peak PPFs. Further, substantial amounts of incandescent lamp supplementation can be used to achieve simulation of daylight R:FR ratios which are needed to ensure adequate stem development in some species. While the focus in this paper has been on the use of entire thermal barriers which separate the lighting enclosure from the plant growth chamber, the samemore » principles apply to the use of water jackets for cooling individual lamps (such as can occur with xenon-arc lamps). In this instance, the barrier separating the lamps from the plant chamber can be much simpler (e.g., plexiglas) as the main function of the barrier is to separate the air ventilation of the lamp enclosure from the air system within the plant growth chamber. The main advantage of water as a thermal barrier is the negligible absorption of radiation in the photosynthetically-active and near infra-red wavebands. Consequently, plate glass-water barriers typically allow transmission of approximately 90% of radiation in these regions. While ventilated double and triple glazing systems appear to be attractive alternative to water barriers from an operating standpoint, their significant absorption in the biologically-important wavebands (7 - 12 %) with each glass layer and longer-wave cut-offs (typically 2500 - 4000 nm) makes them a much less attractive alternative. The data presented demonstrate clearly that measurement of PPF alone is not an adequate representation of the radiation environment being used in a controlled environment study.« less

Grain orientation effects on dynamic strength of FCC multicrystals at low shock pressures: a hydrodynamic instability study

DOE PAGES

Peralta, P.; Loomis, E.; Chen, Y.; ...

2015-04-09

Variability in local dynamic plasticity due to material anisotropy in polycrystalline metals is likely to be important on damage nucleation and growth at low pressures. Hydrodynamic instabilities could be used to study these plasticity effects by correlating measured changes in perturbation amplitudes at free surfaces to local plastic behaviour and grain orientation, but amplitude changes are typically too small to be measured reliably at low pressures using conventional diagnostics. Correlations between strength at low shock pressures and grain orientation were studied in copper (grain size ≈ 800 μm) using the Richtmyer–Meshkov instability with a square-wave surface perturbation (wavelength = 150 μm, amplitude = 5 μm), shocked at 2.7 GPa using symmetric plate impacts. A Plexiglas window was pressed against the peaks of the perturbation, keeping valleys as free surfaces. This produced perturbation amplitude changes much larger than those predicted without the window. Amplitude reductions from 64 to 88% were measured in recovered samples and grains oriented close tomore » $$\\langle$$0 0 1$$\\rangle$$ parallel to the shock had the largest final amplitude, whereas grains with shocks directions close to $$\\langle$$1 0 1$$\\rangle$$ had the lowest. Finite element simulations were performed with elastic-perfectly plastic models to estimate yield strengths leading lead to those final amplitudes. Anisotropic elasticity and these yield strengths were used to calculate the resolved shear stresses at yielding for the two orientations. In conclusion, results are compared with reports on orientation dependence of dynamic yielding in Cu single crystals and the higher values obtained suggest that strength estimations via hydrodynamic instabilities are sensitive to strain hardening and strain rate effects.« less

Characterization of real objects by an active electrolocation sensor

NASA Astrophysics Data System (ADS)

Metzen, Michael G.; Al Ghouz, Imène; Krueger, Sandra; Bousack, Herbert; von der Emde, Gerhard

2012-04-01

Weakly electric fish use a process called 'active electrolocation' to orientate in their environment and to localize objects based on their electrical properties. To do so, the fish discharge an electric organ which emits brief electrical current pulses (electric organ discharge, EOD) and in return sense the generated electric field which builds up surrounding the animal. Caused by the electrical properties of nearby objects, fish measure characteristic signal modulations with an array of electroreceptors in their skin. The fish are able to gain important information about the geometrical properties of an object as well as its complex impedance and its distance. Thus, active electrolocation is an interesting feature to be used in biomimetic approaches. We used this sensory principle to identify different insertions in the walls of Plexiglas tubes. The insertions tested were composed of aluminum, brass and graphite in sizes between 3 and 20 mm. A carrier signal was emitted and perceived with the poles of a commercial catheter for medical diagnostics. Measurements were performed with the poles separated by 6.3 to 55.3 mm. Depending on the length of the insertion in relation to the sender-receiver distance, we observed up to three peaks in the measured electric images. The first peak was affected by the material of the insertion, while the distance between the second and third peak strongly correlated with the length of the insertion. In a second experiment we tested whether various materials could be detected by using signals of different frequency compositions. Based on their electric images we were able to discriminate between objects having different resistive properties, but not between objects of complex impedances.

Transformation of fault slip modes in laboratory experiments

NASA Astrophysics Data System (ADS)

Martynov, Vasilii; Alexey, Ostapchuk; Markov, Vadim

2017-04-01

Slip mode of crust fault can vary because of many reasons. It's well known that fault structure, material of fault gouge, pore fluid et al. in many ways determines slip modes from creep and slow slip events to mega-earthquakes [1-3]. Therefore, the possibility of fault slip transformation due to external action is urgent question. There is popular and developing approach of fluid injection into central part of fault. The phenomenon of earthquakes induced due to pumping of water was investigated on small and large scales [4, 5]. In this work the laboratory experiments were conducted to study the evolution of the experimental fault slip when changing the properties of the interstitial fluid. The scheme of experiments is the classical slider-model set-up, in which the block under the shear force slips along the interface. In our experiments the plexiglas block 8x8x3 cm3 in size was put on the plexiglas base. The contact of the blocks was filled with a thin layer (about 3 mm thick) of a granular material. The normal load varied from 31 to 156 kPa. The shear load was applied through a spring with stiffness 60 kN/m, and the rate of spring deformation was 20 or 5 mcm/s. Two parameters were recorded during experiments: the shear force acting on the upper block (with an accuracy of 1 N) and its displacement relatively the base (with an accuracy of 0.1 μm). The gouge was composed of quartz sand (97.5%) and clay (2.5%). As a moisturizer were used different fluids with viscosity varying from 1 to 103 mPa x s. Different slip modes were simulated during slider-experiments. In our experiments slip mode is the act of instability manifested in an increase of slip velocity and a drop of shear stress acting on a movable block. The amplitude of a shear stress drop and the peak velocity of the upper block were chosen as the characteristics of the slip mode. In the laboratory experiments, slip events of one type can be achieved either as regularly recurring (regular mode) or as random stochastic (irregular mode). To investigate regularities of transformation and get statistically correct results we simulated only regular mode. During the experiments, after the establishment of a regular mode, we injected fluid into central part of interblock contact. Varying injecting fluid we were able both to decrease and increase amplitude of events. For example, after injection of 1 mPa x s fluid (water) in gouge, moisturized with 100 mPa x s fluid (ethylene glycol), peak velocity rose by almost an order. But after injection of an aqueous solution of starch (big viscosity and dilatant rheology) amplitude decreased 1.5 times and then slip almost completely stabilized. It's probably connected with the viscosity of solution, which increases with quick shift. Time of injection also has the significant impact on the possibility of transformation and its efficiency. Thus, it is well known that if the time of injection is in the vicinity of loss of strength moment, any external influence only initiates slip events. Preliminary results of our laboratory experiments show that the fluid injection can both reduce the part of deformation energy going seismic wave radiation, and to increase it. The most effective action observed in experinemts with injection of dilatant fluid. Findings demonstrate the prospectivity of further research in this direction. The work was supported by the Russian Science Foundation (Grant No. 16-17-00095) [1] Fagereng A., Sibson R.H. 2010. Melange rheology and seismic style. Geology. Vol.38, p.751-754. [2] Kocharyan G.G., et al. 2017. A study of different fault slip modes governed by the gouge material composition in laboratory experiments. Geophys. J. Int. Vol.208, p. 521-528. [3] Yamashita T. 2013. Generation of slow slip coupled with tremor due to fluid flow along a fault. Geophys. J. Int. Vol.193, p.375-393. [4] Guglielmi Y., et. al. 2015. Seismicity triggered by fluid injection-induced aseismic slip. Science. Vol.348, p.1224-1226. [5] Wei S., et al. 2015. The 2012 Brawley swarm triggered by injection-induced aseismic slip. EPSL. Vol. 422, p.115-122.

Percent recovery of low influent concentrations of microorganism surrogates in small sand columns

NASA Astrophysics Data System (ADS)

Stevenson, M. E.; Blaschke, A. P.

2012-04-01

In order to develop a dependable method to calculate the setback distance of a drinking water well from a potential point of microbiological contamination, surrogates are used to perform field tests to avoid using pathogenic micro-organisms. One such surrogate used to model the potential travel time of microbial contamination is synthetic microspheres. The goal of this study is to examine the effect of differing influent colloid concentrations on the percent recovery of microbial surrogates after passing through a soil column. Similar studies have been done to investigate blocking of ideal attachment sites using concentrations between 106 and 1010 particles ml-1. These high concentrations were necessary due to the detection limit of the measuring technique used; however, our measuring technique allows us to test input concentrations ranging from 101 to 106 particles ml-1. These low concentrations are more similar to the concentrations of pathogenic microorganisms present in nature. We have tested the enumeration of 0.5 μm microspheres using a solid-phase cytometer and evaluated their transport in small sand columns. Fluorescent microspheres were purchased for this study with carboxylated surfaces. The soil columns consist of Plexiglas tubes, 30 cm long and 7 cm in diameter, both filled with the same coarse sand. Bromide was used as a conservative tracer, to estimate pore-water velocity and dispersivity, and bromide concentrations were analysed using ion chromatography and bromide probes. Numerical modelling was done using CXTFIT and HYDRUS-1D software programs. The 0.5 μm beads were enumerated in different environmental waters using solid-phase cytometry and compared to counts in sterile water in order to confirm the accuracy of the method. The solid-phase cytometer was able to differentiate the 0.5 μm beads from naturally present autofluorescent particles and bacteria, and therefore, is an appropriate method to enumerate this surrogate.

Experimental field study of problem-solving using tools in free-ranging capuchins (Sapajus nigritus, formerly Cebus nigritus).

PubMed

Garber, P A; Gomes, D F; Bicca-Marques, J C

2012-04-01

Some populations of capuchins are reported to use tools to solve foraging problems in the wild. In most cases, this involves the act of pounding and digging. The use of probing tools by wild capuchins is considerably less common. Here we report on the results of an experimental field study conducted in southern Brazil designed to examine the ability of wild black-horned capuchins (Sapajus nigritus) to use a wooden dowel as a lever or a probe to obtain an embedded food reward. A group of eight capuchins was presented with two experimental platforms, each housing a clear Plexiglas box containing two bananas on a shelf and four inserted dowels. Depending on the conditions of the experiment, the capuchins were required either to pull (Condition I) or push (Conditions II and III) the dowels, in order to dislodge the food reward from the shelf so that it could be manually retrieved. In Condition I, four individuals spontaneously solved the foraging problem by pulling the dowels in 25% (72/291) of visits. In Conditions II and III, however, no capuchin successfully pushed the dowels forward to obtain the food reward. During these latter two experimental conditions, the capuchins continued to pull the dowels (41/151 or 27% of visits), even though this behavior did not result in foraging success. The results of these field experiments are consistent with an identical study conducted on wild Cebus capucinus in Costa Rica, and suggest that when using an external object as a probe to solve a foraging problem, individual capuchins were able to rapidly learn an association between the tool and the food reward, but failed to understand exactly how the tool functioned in accomplishing the task. The results also suggest that once a capuchin learned to solve this tool-mediated foraging problem, the individual persisted in using the same solution even in the face of repeated failure (slow rate of learning extinction). © 2011 Wiley Periodicals, Inc.

A Monte Carlo approach applied to ultrasonic non-destructive testing

NASA Astrophysics Data System (ADS)

Mosca, I.; Bilgili, F.; Meier, T. M.; Sigloch, K.

2011-12-01

Non-destructive testing based on ultrasound allows us to detect, characterize and size discrete flaws in geotechnical and engineering structures and materials. This information is needed to determine whether such flaws can be tolerated in future service. In typical ultrasonic experiments, only the first-arriving P-wave is interpreted, and the remainder of the recorded waveform is neglected. Our work aims at understanding surface waves, which are strong signals in the later wave train, with the ultimate goal of full waveform tomography. At present, even the structural estimation of layered media is still challenging because material properties of the samples can vary widely, and good initial models for inversion do not often exist. The aim of the present study is to analyze ultrasonic waveforms measured at the surface of Plexiglas and rock samples, and to define the behaviour of surface waves in structures of increasing complexity. The tremendous potential of ultrasonic surface waves becomes an advantage only if numerical forward modelling tools are available to describe the waveforms accurately. We compute synthetic full seismograms as well as group and phase velocities for the data. We invert them for the elastic properties of the sample via a global search of the parameter space, using the Neighbourhood Algorithm. Such a Monte Carlo approach allows us to perform a complete uncertainty and resolution analysis, but the computational cost is high and increases quickly with the number of model parameters. Therefore it is practical only for defining the seismic properties of media with a limited number of degrees of freedom, such as layered structures. We have applied this approach to both synthetic layered structures and real samples. The former contributed to benchmark the propagation of ultrasonic surface waves in typical materials tested with a non-destructive technique (e.g., marble, unweathered and weathered concrete and natural stone).

  Ultrasonic monitoring of fish thawing process optimal time of thawing and effect of freezing/thawing.

PubMed

El Kadi, Youssef Ait; Moudden, Ali; Faiz, Bouazza; Maze, Gerard; Decultot, Dominique

2013-01-01

Fish quality is traditionally controlled by chemical and microbiological analysis. The non-destructive control presents an enormous professional interest thanks to the technical contribution and precision of the analysis to which it leads. This paper presents the results obtained from a characterisation of fish thaw-ing process by the ultrasonic technique, with monitoring thermal processing from frozen to defrosted states. The study was carried out on fish type red drum and salmon cut into fillets of 15 mm thickness. After being frozen at -20°C, the sample is enclosed in a plexiglas vessel with parallel walls at the ambient temperature 30°C and excited in perpendicular incidence at 0.5 MHz by an ultrasonic pulser-receiver Sofranel 5052PR. the technique of measurement consists to study the signals reflected by fish during its thawing, the specific techniques of signal processing are implemented to deduce informations characterizing the state of fish and its thawing process by examining the evolution of the position echoes reflected by the sample and the viscoelastic parameters of fish during its thawing. The obtained results show a relationship between the thermal state of fish and its acoustic properties, which allowed to deduce the optimal time of the first thawing in order to restrict the growth of microbial flora. For salmon, the results show a decrease of 36% of the time of the second thawing and an increase of 10.88% of the phase velocity, with a decrease of 65.5% of the peak-to-peak voltage of the signal reflected, thus a decrease of the acoustic impedance. This study shows an optimal time and an evolution rate of thawing specific to each type offish and a correlation between the acoustic behavior of fish and its thermal state which approves that this technique of ultrasonic monitoring can substitute the control using the destructive chemical analysis in order to monitor the thawing process and to know whether a fish has suffered an accidental thawing.

A new anthropometric phantom for calibrating in vivo measurements of stable lead in the human leg using X-ray fluorescence

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

Spitz, H.; Jenkins, M.; Lodwick, J.

2000-02-01

A new anthropometric phantom has been developed for calibrating in vivo measurements of stable lead deposited in bone using x-ray fluorescence. The phantom reproduces the shape of the mid shaft of the adult human leg and is fabricated using polyurethanes and calcium carbonate to produce materials that exhibit the same density, energy transmission, and calcium content as cortical bone, bone marrow, and muscle. The phantom includes a removable tibia fabricated using simulants for cortical bone and bone marrow to which a precise amount of stable lead has been added to cortical bone. The formulations used in fabricating the new anthropometricmore » phantom are much more uniform in density and composition than the conventional phantom made from Plexiglas cylinders filled with plaster-of-Paris. The energy spectrum from an x-ray fluorescence measurement of the phantom using a {sup 109}Cd source is indistinguishable from an in vivo x-ray fluorescence measurement of the human leg, demonstrating that the materials used in the phantom exhibit the same radiological properties as human tissue. Likewise, results from x-ray fluorescence measurements of the phantom exhibit the same positional dependency as the human leg and vary by approximately 36% when, for example, the phantom containing 54 ppm of stable lead in the tibia was rotated by only 15 degrees. The detection limit for a 30 min {sup 109}Cd K shell x-ray fluorescence in vivo measurement is approximately 20 ppm determined from a background measurement using the new phantom containing no added lead in the muscle, bone, or bone marrow. The new anthropometric phantom significantly improves in vivo x-ray fluorescence calibration measurements by (1) faithfully reproducing the anatomy of the human leg, (2) having components that exhibit radiological properties similar to that of human tissue, and (3) providing a realistic calibration standard that can be used for in vivo x-ray fluorescence intercomparison measurements.« less

Obduction: Why, how and where. Clues from analog models

NASA Astrophysics Data System (ADS)

Agard, P.; Zuo, X.; Funiciello, F.; Bellahsen, N.; Faccenna, C.; Savva, D.

2014-05-01

Obduction is an odd geodynamic process characterized by the emplacement of dense oceanic “ophiolites” atop light continental plates in convergent settings. We herein present analog models specifically designed to explore the conditions (i.e., sharp increase of plate velocities - herein coined as ‘acceleration’, slab interaction with the 660 km discontinuity, ridge subduction) under which obduction may develop as a result of subduction initiation. The experimental setup comprises an upper mantle modeled as a low-viscosity transparent Newtonian glucose syrup filling a rigid Plexiglas tank and high-viscosity silicone plates. Convergence is simulated by pushing a piston with plate tectonics like velocities (1-10 cm/yr) onto a model comprising a continental margin, a weakness zone with variable resistance and dip (W), an oceanic plate (with or without a spreading ridge), a preexisting subduction zone (S) dipping away from the piston and an upper active continental margin, below which the oceanic plate is being subducted at the start of the model (as for the Neotethyan natural example). Several configurations were tested over thirty-five parametric models, with special emphasis on comparing different types of weakness zone and the degree of mechanical coupling across them. Measurements of displacements and internal deformation allow for a precise and reproducible tracking of deformation. Models consistently demonstrate that once conditions to initiate subduction are reached, obduction may develop further depending on the effective strength of W. Results (1) constrain the range of physical conditions required for obduction to develop/nucleate and (2) underline the key role of such perturbations for triggering obduction, particularly plate ‘acceleration’. They provide an explanation to the short-lived Peri-Arabic obduction, which took place along thousands of km almost synchronously (within ∼50-10 Myr), from Turkey to Oman, while the subduction zone beneath Eurasia became temporarily jammed. They also demonstrate that the emplacement of dense, oceanic material on continental lithosphere is not a mysterious process requiring extraordinary boundary conditions but results from large-scale, normal (oceanic then continental) subduction processes.

Novel single-cell mega-size chambers for electrochemical etching of panorama position-sensitive polycarbonate ion image detectors

NASA Astrophysics Data System (ADS)

Sohrabi, Mehdi

2017-11-01

A novel development is made here by inventing panorama single-cell mega-size electrochemical etching (MS-ECE) chamber systems for processing panorama position-sensitive mega-size polycarbonate ion image detectors (MS-PCIDs) of potential for many neutron and ion detection applications in particular hydrogen ions or proton tracks and images detected for the first time in polycarbonates in this study. The MS-PCID is simply a large polycarbonate sheet of a desired size. The single-cell MS-ECE invented consists of two large equally sized transparent Plexiglas sheets as chamber walls holding a MS-PCID and the ECE chamber components tightly together. One wall has a large flat stainless steel electrode (dry cell) attached to it which is directly in contact with the MS-PCID and the other wall has a rod electrode with two holes to facilitate feeding and draining out the etching solution from the wet cell. A silicon rubber washer plays the role of the wet cell to hold the etchant and the electrical insulator to isolate the dry cell from the wet cell. A simple 50 Hz-HV home-made generator provides an adequate field strength through the two electrodes across the MS-ECE chamber. Two panorama single-cell MS-ECE chamber systems (circular and rectangular shapes) constructed were efficiently applied to processing the MS-PCIDs for 4π ion emission image detection of different gases in particular hydrogen ions or protons in a 3.5 kJ plasma focus device (PFD as uniquely observed by the unaided eyes). The panorama MS-PCID/MS-ECE image detection systems invented are novel with high potential for many applications in particular as applied to 4π panorama ion emission angular distribution image detection studies in PFD space, some results of which are presented and discussed.

On the importance of continental lithospheric roots in plume-continent interaction: implication for India motions over the last 130 Ma

NASA Astrophysics Data System (ADS)

Sibrant, A.; Davaille, A.

2015-12-01

Over the last 130 Ma, the India plate migration varied in velocity and direction. The oceanic magnetic anomalies indicates that the India-Asia convergence rate increase at ~ 90 Ma and at ~ 67 Ma. These episodes of acceleration correspond to the emplacement of Morondava and Deccan large igneous provinces, respectively. They therefore may be generated by the arrival of a mantle plume in the vicinity of India. We carried out laboratory experiments to examine and quantify the possible links between plume head impact and the acceleration of a continental plate. The latter is modelled by a buoyant raft, floating on the surface of a plexiglas tank containing Sugar Syrup, a temperature-dependent viscosity fluid. Plumes are generated by heating from below. The initial distance between the plume impact and the raft, as well as the raft size and density were systematically varied. The latter allows to evaluate the influence of a cratonic keel on the plate migration. Experimental results suggest that: (1) a continent can migrate under the influence of a plume head only if the thickness ratio between the keel and the plume head impact is greater than a critical value; (2) the maximum velocity achieved by the raft depends on the distance between the raft and the plume centre and (3) the direction taken by the raft is directly related to the position of the plume impact compared to the keel's. Given the Deccan Traps plume characteristics, the scaling laws derived from the experiments suggest that India could migrate after the plume impact with a velocity ranging between 61 and 125 mm/yr. This estimated range is fully coherent with the India plate velocity calculated from the oceanic magnetic anomalies, but it put strong constraints on the existence and position of cratonic keels under India. Moreover, India migration during the last 130 Ma can be quantitavely related to the successive impacts of three mantle plumes.

Automatic analysis of altered gait in arylsulphatase A-deficient mice in the open field.

PubMed

Leroy, Toon; Stroobants, Stijn; Aerts, Jean-Marie; D'Hooge, Rudi; Berckmans, Daniel

2009-08-01

In current research with laboratory animals, observing their dynamic behavior or locomotion is a labor-intensive task. Automatic continuous monitoring can provide quantitative data on each animal's condition and coordination ability. The objective of the present work is to develop an automated mouse observation system integrated with a conventional open-field test for motor function evaluation. Data were acquired from 86 mice having a targeted disruption of the arylsulphatase A (ASA) gene and having lowered coordinated locomotion abilities as a symptom. The mice used were 36 heterozygotes (12 females) and 50 knockout mice (30 females) at the age of 6 months. The mice were placed one at a time into the test setup, which consisted of a Plexiglas cage (53x34.5x26 cm) and two fluorescent bulbs for proper illumination. The transparent cage allowed images to be captured from underneath the cage, so image information could be obtained about the dynamic variation of the positions of the limbs of the mice for gait reconstruction. Every mouse was recorded for 10 min. Background subtraction and color filtering were used to measure and calculate image features, which are variables that contain crucial information, such as the mouse's position, orientation, body outline, and possible locations for the mouse's paws. A set of heuristic rules was used to prune implausible paw features and label the remaining ones as front/hind and left/right. After we had pruned the implausible paw features, the paw features that were consistent over subsequent images were matched to footprints. Finally, from the measured footprint sequence, eight parameters were calculated in order to quantify the gait of the mouse. This automatic observation technique can be integrated with a regular open-field test, where the trajectory and motor function of a free-moving mouse are measured simultaneously.

Effect of Gold Nanoparticles on Prostate Dose Distribution under Ir-192 Internal and 18 MV External Radiotherapy Procedures Using Gel Dosimetry and Monte Carlo Method.

PubMed

Khosravi, H; Hashemi, B; Mahdavi, S R; Hejazi, P

2015-03-01

Gel polymers are considered as new dosimeters for determining radiotherapy dose distribution in three dimensions. The ability of a new formulation of MAGIC-f polymer gel was assessed by experimental measurement and Monte Carlo (MC) method for studying the effect of gold nanoparticles (GNPs) in prostate dose distributions under the internal Ir-192 and external 18MV radiotherapy practices. A Plexiglas phantom was made representing human pelvis. The GNP shaving 15 nm in diameter and 0.1 mM concentration were synthesized using chemical reduction method. Then, a new formulation of MAGIC-f gel was synthesized. The fabricated gel was poured in the tubes located at the prostate (with and without the GNPs) and bladder locations of the phantom. The phantom was irradiated to an Ir-192 source and 18 MV beam of a Varian linac separately based on common radiotherapy procedures used for prostate cancer. After 24 hours, the irradiated gels were read using a Siemens 1.5 Tesla MRI scanner. The absolute doses at the reference points and isodose curves resulted from the experimental measurement of the gels and MC simulations following the internal and external radiotherapy practices were compared. The mean absorbed doses measured with the gel in the presence of the GNPs in prostate were 15% and 8 % higher than the corresponding values without the GNPs under the internal and external radiation therapies, respectively. MC simulations also indicated a dose increase of 14 % and 7 % due to presence of the GNPs, for the same experimental internal and external radiotherapy practices, respectively. There was a good agreement between the dose enhancement factors (DEFs) estimated with MC simulations and experiment gel measurements due to the GNPs. The results indicated that the polymer gel dosimetry method as developed and used in this study, can be recommended as a reliable method for investigating the DEF of GNPs in internal and external radiotherapy practices.

Characterization of granular collapse onto hard substrates by acoustic emissions

NASA Astrophysics Data System (ADS)

Farin, Maxime; Mangeney, Anne; Toussaint, Renaud; De Rosny, Julien

2013-04-01

Brittle deformation in granular porous media can generate gravitational instabilities such as debris flows and rock avalanches. These phenomena constitute a major natural hazard for the population in mountainous, volcanic and coastal areas but their direct observation on the field is very dangerous. Recent studies showed that gravitational instabilities can be detected and characterized (volume, duration,...) thanks to the seismic signal they generate. In an avalanche, individual block bouncing and rolling on the ground are expected to generated signals of higher frequencies than the main flow spreading. The identification of the time/frequency signature of individual blocks in the recorded signal remains however difficult. Laboratory experiments were conducted to investigate the acoustic signature of diverse simple sources corresponding to grains falling over thin plates of plexiglas and rock blocks. The elastic energy emitted by a single bouncing steel bead into the support was first quantitatively estimated and compared to the potential energy of fall and to the potential energy change during the shock. Next, we consider the collapse of granular columns made of steel spherical beads onto hard substrates. Initially, these columns were held by a magnetic field allowing to suppress suddenly the cohesion between the beads, and thus to minimize friction effects that would arise from side walls. We varied systematically the column volume, the column aspect ratio (height over length) and the grain size. This is shown to affect the signal envelope and frequency content. In the experiments, two types of acoustic sensors were used to record the signals in a wide frequency range: accelerometers (1 Hz to 56 kHz) and piezoelectric sensors (100 kHz to 1 MHz). The experiments were also monitored optically using fast cameras. We developed a technique to use quantitatively both types of sensors to evaluate the elastic energy emitted by the sources. Eventually, we looked at what types of features in the signal are affected by individual shocks or by the large scale geometry of the avalanche.

Characterization of blocks impacts from acoustic emissions: insights from laboratory experiments

NASA Astrophysics Data System (ADS)

Farin, Maxime; Mangeney, Anne; de Rosny, Julien; Toussaint, Renaud; Shapiro, Nikolaï

2014-05-01

Rockfalls, debris flows and rock avalanches represent a major natural hazard for the population in mountainous, volcanic and coastal areas but their direct observation on the field is very dangerous. Recent studies showed that gravitational instabilities can be detected and characterized (volume, duration,...) thanks to the seismic signal they generate. In an avalanche, individual block bouncing and rolling on the ground are expected to generated signals of higher frequencies than the main flow spreading. The identification of the time/frequency signature of individual blocks in the recorded signal remains however difficult. Laboratory experiments were conducted to investigate the acoustic signature of diverse simple sources corresponding to grains falling over thin plates of plexiglas and glass and over rock blocks. The elastic energy emitted by a single bouncing bead into the support was first quantitatively estimated and compared to the potential energy of fall and to the potential energy change during the shock. We obtained simple scaling laws relating the impactor characteristics (size, height of fall, material,...) to the elastic energy and spectral content. Next, we consider the collapse of granular columns made of steel spherical beads onto hard substrates. Initially, these columns were held by a magnetic field allowing to suppress suddenly the cohesion between the beads, and thus to minimize friction effects that would arise from side walls. We varied systematically the column volume, the column aspect ratio (height over length) and the grain size. This is shown to affect the signal envelope and frequency content. In the experiments, accelerometers (1 Hz to 56 kHz) were used to record the signals in a wide frequency range. The experiments were also monitored optically using fast cameras. Eventually, we looked at what types of features in the signal are affected by individual impacts, rolling of beads or by the large scale geometry of the avalanche.

Characterization of blocks impacts from elastic waves: insights from laboratory experiments

NASA Astrophysics Data System (ADS)

Farin, M.; Mangeney, A.; Toussaint, R.; De Rosny, J.; Shapiro, N.

2013-12-01

Rockfalls, debris flows and rock avalanches constitute a major natural hazard for the population in mountainous, volcanic and coastal areas but their direct observation on the field is very dangerous. Recent studies showed that gravitational instabilities can be detected and characterized (volume, duration,...) thanks to the seismic signal they generate. In an avalanche, individual block bouncing and rolling on the ground are expected to generated signals of higher frequencies than the main flow spreading. The identification of the time/frequency signature of individual blocks in the recorded signal remains however difficult. Laboratory experiments were conducted to investigate the acoustic signature of diverse simple sources corresponding to grains falling over thin plates of plexiglas and rock blocks. The elastic energy emitted by a single bouncing steel bead into the support was first quantitatively estimated and compared to the potential energy of fall and to the potential energy change during the shock. Next, we consider the collapse of granular columns made of steel spherical beads onto hard substrates. Initially, these columns were held by a magnetic field allowing to suppress suddenly the cohesion between the beads, and thus to minimize friction effects that would arise from side walls. We varied systematically the column volume, the column aspect ratio (height over length) and the grain size. This is shown to affect the signal envelope and frequency content. In the experiments, two types of acoustic sensors were used to record the signals in a wide frequency range: accelerometers (1 Hz to 56 kHz) and piezoelectric sensors (100 kHz to 1 MHz). The experiments were also monitored optically using fast cameras. We developed a technique to use quantitatively both types of sensors to evaluate the elastic energy emitted by the sources. Eventually, we looked at what types of features in the signal are affected by individual shocks or by the large scale geometry of the avalanche.

Effects of Intra- and Interpatch Host Density on Egg Parasitism by Three Species of Trichogramma

PubMed Central

Grieshop, Matthew J.; Flinn, Paul W.; Nechols, James R.

2010-01-01

Host-foraging responses to different intra- and interpatch densities were used to assess three Trichogramma spp. (Hymenoptera: Trichogrammatidae) Trichogramma deion Pinto and Oatman, T. ostriniae Pang and Chen, and T. pretiosum Riley — as potential biological control agents for the Indian meal moth, Plodia interpunctella Hübner (Lepidoptera: Pyralidae). Single naïve females were allowed 6 h to forage in Plexiglas arenas with four different spatial arrangements of host eggs, nine single-egg patches), nine four-egg patches, 36 single-egg patches, and 36 four-egg patches. No significant differences were found among species in the number of patches parasitized. As expected, all three species parasitized the most eggs in the 36 four-egg patch treatment and the least in the nine single-egg patch treatment. T. deion parasitized significantly more eggs than T. pretiosum on the nine four-egg patches. T. ostriniae parasitized significantly more patches when intrapatch density was greater, regardless of interpatch density. In contrast, T. deion only parasitized more patches at the greater intrapatch density when the interpatch density was low. Patch density had no effect on T. pretiosum. The spatial pattern of parasitism was more aggregated for T. deion and T. ostriniae in the 36 four-egg patches treatment compared to the 36 single-egg patches treatment. Therefore, intrapatch density was more important than interpatch density for T. ostriniae, and potentially for T. deion, but not for T. pretiosum. T. deion may be the best candidate for augmentative biological control because it parasitized either slightly or significantly more eggs than the other two species in all four treatments. Furthermore, the pattern of parasitism by T. deion in the 36 four-egg patches treatment was the most aggregated among the three species, suggesting a more thorough searching pattern. In contrast, T. pretiosum had the least aggregated pattern of parasitism and therefore may have used a more random foraging pattern. PMID:20673123

Effects of intra- and interpatch host density on egg parasitism by three species of Trichogramma.

PubMed

Grieshop, Matthew J; Flinn, Paul W; Nechols, James R

2010-01-01

Host-foraging responses to different intra- and interpatch densities were used to assess three Trichogramma spp. (Hymenoptera: Trichogrammatidae) Trichogramma deion Pinto and Oatman, T. ostriniae Pang and Chen, and T. pretiosum Riley - as potential biological control agents for the Indian meal moth, Plodia interpunctella Hübner (Lepidoptera: Pyralidae). Single naïve females were allowed 6 h to forage in Plexiglas arenas with four different spatial arrangements of host eggs, nine single-egg patches), nine four-egg patches, 36 single-egg patches, and 36 four-egg patches. No significant differences were found among species in the number of patches parasitized. As expected, all three species parasitized the most eggs in the 36 four-egg patch treatment and the least in the nine single-egg patch treatment. T. deion parasitized significantly more eggs than T. pretiosum on the nine four-egg patches. T. ostriniae parasitized significantly more patches when intrapatch density was greater, regardless of interpatch density. In contrast, T. deion only parasitized more patches at the greater intrapatch density when the interpatch density was low. Patch density had no effect on T. pretiosum. The spatial pattern of parasitism was more aggregated for T. deion and T. ostriniae in the 36 four-egg patches treatment compared to the 36 single-egg patches treatment. Therefore, intrapatch density was more important than interpatch density for T. ostriniae, and potentially for T. deion, but not for T. pretiosum. T. deion may be the best candidate for augmentative biological control because it parasitized either slightly or significantly more eggs than the other two species in all four treatments. Furthermore, the pattern of parasitism by T. deion in the 36 four-egg patches treatment was the most aggregated among the three species, suggesting a more thorough searching pattern. In contrast, T. pretiosum had the least aggregated pattern of parasitism and therefore may have used a more random foraging pattern.

Study on the reduction of atmospheric mercury emissions from mine waste enriched soils through native grass cover in the Mt. Amiata region of Italy.

PubMed

Fantozzi, L; Ferrara, R; Dini, F; Tamburello, L; Pirrone, N; Sprovieri, F

2013-08-01

Atmospheric mercury emissions from mine-waste enriched soils were measured in order to compare the mercury fluxes of bare soils with those from other soils covered by native grasses. Our research was conducted near Mt. Amiata in central Italy, an area that was one of the largest and most productive mining centers in Europe up into the 1980s. To determine in situ mercury emissions, we used a Plexiglas flux chamber connected to a portable mercury analyzer (Lumex RA-915+). This allowed us to detect, in real time, the mercury vapor in the air, and to correlate this with the meteorological parameters that we examined (solar radiation, soil temperature, and humidity). The highest mercury flux values (8000ngm(-2)h(-1)) were observed on bare soils during the hours of maximum insulation, while lower values (250ngm(-2)h(-1)) were observed on soils covered by native grasses. Our results indicate that two main environmental variables affect mercury emission: solar radiation intensity and soil temperature. The presence of native vegetation, which can shield soil surfaces from incident light, reduced mercury emissions, a result that we attribute to a drop in the efficiency of mercury photoreduction processes rather than to decreases in soil temperature. This finding is consistent with decreases in mercury flux values down to 3500ngm(-2)h(-1), which occurred under cloudy conditions despite high soil temperatures. Moreover, when the soil temperature was 28°C and the vegetation was removed from the experimental site, mercury emissions increased almost four-fold. This increase occurred almost immediately after the grasses were cut, and was approximately eight-fold after 20h. Thus, this study demonstrates that enhancing wild vegetation cover could be an inexpensive and effective approach in fostering a natural, self-renewing reduction of mercury emissions from mercury-contaminated soils. Copyright © 2013 Elsevier Inc. All rights reserved.

Transpressive systems - 4D analogue modelling with X-ray computed tomography

NASA Astrophysics Data System (ADS)

Klinkmueller, M.; Schreurs, G.

2009-04-01

A series of 4D transpressional analogue models was analyzed with X-ray computed tomography (CT). A new modular sandbox with two base-plates was used to simulate strike-slip transpressional deformation and oblique basin inversion. The model itself is constructed on top of an assemblage made up of plexiglas- and foam-bars that enable strain distribution. Models consisted of a basal polydimethylsiloxane (PDMS) layer overlain by a quartz sand pack (Schreurs 1994; Schreurs & Colletta, 1998). The PDMS layer distributes the strike-slip shear component of deformation evenly over the entire model. The initial length of the model was 80 cm. The initial width of the model was 25 cm and was extended to maximal 27 cm to form graben structures. During extension a syn-sedimentary sequence of granular materials was added before transpression was started. Different ratios of shear strain rate and shortening strain rate were applied to investigate the influence on fault generation in both set-ups. To avoid side effects, our fault analysis focused on the central part of the model with a safety distance to the strike-slip orthogonal sidewalls of 20 cm. At low-angle transpression, strike-slip faults form predominantly during initial stages of deformation. They merge in part with pre-existing graben structures and form an anastomosing major fault zone that strikes subparallel to the long dimension of the model. At high-angle transpression, thrusts striking parallel to the long dimension of the model dominate. Thrust localisation is strongly controlled by the position of the pre-existing graben. REFERENCES Schreurs, G. (1994). Experiments on strike-slip faulting and block rotation. Geology, 22, 567-570. Schreurs, G. & Colletta, B. (1998). Analogue modelling of faulting in zones of continental transpression and transtension. In: Holdsworth, R.E., Strachan, R.A. & Dewey, J.F. (eds.). Continental Transpressional and Transtensional Tectonics. Geological Society, London, Special Publications, 135, 59-79.

Changes in soil solution Zn and pH and uptake of Zn by arbuscular mycorrhizal red clover in Zn-contaminated soil.

PubMed

Li, X; Christie, P

2001-01-01

Red clover plants inoculated with Glomus mosseae were grown in a sterile pasture soil containing 50 mg Zn kg(-1) in 'Plexiglas' (acrylic) containers with nylon net partitions (30 microm mesh) designed to separate the soil into a central root zone and two outer zones for hyphal growth with no root penetration. Two porous plastic soil moisture samplers were installed in each pot, one in the root compartment and the other in one of the hyphal compartments. The soil in the outer compartments was amended with one of the four application rates of Zn (as ZnSO4) ranging from 0 to 1000 mg kg(-1). Non-mycorrhizal controls were included, and there were five replicates of each treatment in a randomised block in a glasshouse. Uninoculated plants received supplementary P to avoid yield limitation due to low soil P status. Plants grew in the central compartment for nine weeks. Soil moisture samples were collected 4, 24 and 62 days after sowing to monitor changes in the Zn concentration and pH of the soil solution. At harvest, the mean mycorrhizal infection rate of inoculated plants ranged from 29% to 34% of total root length and was little affected by Zn application. Root and shoot yields were not affected by mycorrhizal infection. Plant Zn concentration and uptake were lower in mycorrhizal plants than non-mycorrhizal controls, and this effect was more pronounced with increasing Zn application rate to the soil. Soil solution Zn concentrations were lower and pH values were higher in mycorrhizal treatments than non-mycorrhizal controls and the mycorrhiza effect was more pronounced at higher Zn application rates. The protective effect of mycorrhiza against plant Zn uptake may have been associated with changes in Zn solubility mediated by changes in the soil solution pH, or by immobilisation of Zn in the extraradical mycelium.

Novel single-cell mega-size chambers for electrochemical etching of panorama position-sensitive polycarbonate ion image detectors.

PubMed

Sohrabi, Mehdi

2017-11-01

A novel development is made here by inventing panorama single-cell mega-size electrochemical etching (MS-ECE) chamber systems for processing panorama position-sensitive mega-size polycarbonate ion image detectors (MS-PCIDs) of potential for many neutron and ion detection applications in particular hydrogen ions or proton tracks and images detected for the first time in polycarbonates in this study. The MS-PCID is simply a large polycarbonate sheet of a desired size. The single-cell MS-ECE invented consists of two large equally sized transparent Plexiglas sheets as chamber walls holding a MS-PCID and the ECE chamber components tightly together. One wall has a large flat stainless steel electrode (dry cell) attached to it which is directly in contact with the MS-PCID and the other wall has a rod electrode with two holes to facilitate feeding and draining out the etching solution from the wet cell. A silicon rubber washer plays the role of the wet cell to hold the etchant and the electrical insulator to isolate the dry cell from the wet cell. A simple 50 Hz-HV home-made generator provides an adequate field strength through the two electrodes across the MS-ECE chamber. Two panorama single-cell MS-ECE chamber systems (circular and rectangular shapes) constructed were efficiently applied to processing the MS-PCIDs for 4π ion emission image detection of different gases in particular hydrogen ions or protons in a 3.5 kJ plasma focus device (PFD as uniquely observed by the unaided eyes). The panorama MS-PCID/MS-ECE image detection systems invented are novel with high potential for many applications in particular as applied to 4π panorama ion emission angular distribution image detection studies in PFD space, some results of which are presented and discussed.

Cooling profile following prosthetic preparation of 1-piece dental implants.

PubMed

Cohen, Omer; Gabay, Eran; Machtei, Eli E

2010-01-01

The aim of this study was to evaluate the effect of water irrigation on heat dissipation kinetics following abutment preparation of 1-piece dental implants. UNO 1-piece dental implants were mounted on Plexiglas apparatus clamping the implant at the collar. T-type thermocouple was attached to the first thread of the implant and recorded thermal changes at 100 millisecond intervals. Implants were prepared using highspeed dental turbine at 400,000 RPM with a coarse diamond bur. Once temperature reached 47 degrees C, abutment preparation was discontinued. Thirty implants were divided into 2 groups. Group A: Passive cooling without water irrigation. Group B: Cooling with turbine's water spray adjacent to the implant (30 mL/min). The following parameters were measured: T47 (time from peak temperature to 47 degrees C), T50%, T75% (time until the temperature amplitude decayed by 50% and 75%, respectively), dTemp50%/dt decay, and dTemp75%/dt decay (cooling rate measured at 50% and 75% of amplitude decay, respectively). Water spray irrigation significantly reduced T47 (1.37+/-0.29 seconds vs 19.97+/-3.06 seconds, P<0.0001), T50% (3.04+/-0.34 seconds vs 27.37+/-2.56 seconds, P<0.0001), and T75% (5.71+/-0.57 seconds vs 57.61+/-5.47 seconds, P<0.0001). Water spray irrigation also increased cooling capacity ninefold: dTemp50%/dt decay (4.14+/-0.61 degrees C/s vs 0.48+/-0.06 degrees C/s, P<0.0001), and dTemp50%/dt decay (1.70+/-0.29 degrees C/s vs 0.19+/-0.03 degrees C/s, P<0.0001). The continuous use of water spray adjacent to the abutment following the cessation of implant preparation might prove beneficial for rapid cooling of the implant.

Test equipment data package for the KC-135 fiber pulling apparatus

NASA Technical Reports Server (NTRS)

Kosten, Sue; Smith, Guy A.; Workman, Gary; Tucker, Dennis

1991-01-01

The Fiber Pulling Apparatus (FPA) is a device designed to produce continuous glass fibers from simulated lunar soil, and to determine the effects of reduced gravity, specifically 1/6 g on fiber formation and resultant properties. Briefly, pre-melt simulated lunar soil will be placed in a pint crucible and heated to 1200 C or higher, up to a maximum temperature of 1400 C. At a given temperature, a quartz fiber will be immersed into the melt and then pulled through a chill block and wound onto a cylindrical bobbin using a servo motor control. A high resolution video camera will record the fiber as it is being pulled. This assembly wil be enclosed in Plexiglas. Before fiber pulling commences, the apparatus will be backfilled with dry nitrogen. A separate data acquisition system will support this apparatus. This system will contain a personal computer, video recorder, and monitor. Temperature, acceleration, winding speed, and video images will be controlled and recorded using the data acquisition system. Thus, the FPA will consist of two hardware packages, the fiber production assembly and the data acquisition rack. The primary objective of this test is to determine the effects of 1/6 g on the formation of continuous glass fiber made from simulated lunar soil. Baseline studies using the FPA on the ground will provide a reference for the 1/6 g studies. Of particular interest will be the effect of 1/6 g on the free fluid zone where the fiber exits the crucible. In the fiber spinning parlance this zone is known as the upper jet region, where the boundary slope is greater than one tenth. The properties of the resulting glass fiber will depend on the jet shape as well as distributions of velocity, temperature and tension within the jet. It is unknown at this time how 1/6 g will effect these parameters.

An investigation of the microstructure and mechanical properties of electrochemically coated Ag(4)Sn dental alloy particles condensed in vitro

NASA Astrophysics Data System (ADS)

Marquez, Jose Antonio

As part of the ongoing scientific effort to develop a new amalgam-like material without mercury, a team of metallurgists and electrochemists at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland, announced in 1993 the development of a new Ag-Sn dental alloy system without mercury that sought to replace conventional dental amalgams. They used spherical Ag3Sn and Ag4Sn intermetallic dental alloy particles, commonly used in conventional dental alloys, and coated them with electrodeposited silver with newly-developed electrolytic and immersion techniques. The particles had relatively pure silver coatings that were closely adherent to the intermetalfic cores. These silver-coated particles, due to silver's plasticity at room temperature, were condensed into PlexiglasRTM molds with the aid of an acidic surface activating solution (HBF4) and a mechanical condensing device, producing a metal-matrix composite with Ag3,4Sn filler particles surrounded by a cold-welded silver matrix. Since silver strain hardens rather easily, the layers had to be condensed in less than 0.5 mm increments to obtain a dense structure. Mechanical testing at NIST produced compressive strength values equal to or greater than those of conventional dental amalgams. Because of its potential for eliminating mercury as a constituent in dental amalgam, this material created a stir in dental circles when first developed and conceivably could prove to be a major breakthrough in the field of dental restoratives. To date, the chief impediments to its approval for human clinical applications by the Food and Drug Administration are the potentially-toxic surface activating solution used for oxide reduction, and the high condensation pressures needed for cold welding because of the tendency for silver to strain harden. In this related study, the author, who has practiced general dentistry for 25 years, evaluates some of the mechanical and microstructural properties of these electrochemically coated particles when they are amalgamated with mercury. Because of patent restrictions for the coated particles that protect the cold-welding work being done at NIST, these particles necessarily had to include mercury as a constituent for this investigation. (Abstract shortened by UMI.)

A comparison of total inward leakage measured using sodium chloride (NaCl) and corn oil aerosol methods for air-purifying respirators.

PubMed

Rengasamy, Samy; Zhuang, Ziqing; Niezgoda, George; Walbert, Gary; Lawrence, Robert; Boutin, Brenda; Hudnall, Judith; Monaghan, William P; Bergman, Michael; Miller, Colleen; Harris, James; Coffey, Christopher

2018-05-21

The International Organization for Standardization (ISO) standard 16900-1:2014 specifies the use of sodium chloride (NaCl) and corn oil aerosols, and sulfur hexafluoride gas for measuring total inward leakage (TIL). However, a comparison of TIL between different agents is lacking. The objective of this study was to measure and compare TIL for respirators using corn oil and NaCl aerosols. TIL was measured with 10 subjects donning two models of filtering facepiece respirators (FFRs) including FFP1, N95, P100, and elastomeric half-mask respirators (ERs) in NaCl and corn oil aerosol test chambers, using continuous sampling methods. After fit testing with a PortaCount (TSI, St. Paul, MN) using the Occupational Safety and Health Administration (OSHA) protocol, five subjects were tested in the NaCl chamber first and then in the corn oil chamber, while other subjects tested in the reverse order. TIL was measured as a ratio of mass-based aerosol concentrations in-mask to the test chamber, while the subjects performed ISO 16900-1-defined exercises. The concentration of NaCl aerosol was measured using two flame photometers, and corn oil aerosol was measured with one light scattering photometer. The same instruments were used to measure filter penetration in both chambers using a Plexiglas® setup. The size distribution of aerosols was determined using a scanning mobility particle sizer and charge was measured with an electrometer. Filter efficiency was measured using an 8130 Automated Filter Tester (TSI). Results showed the geometric mean TIL for corn oil aerosol for one model each of all respirator categories, except P100, were significantly (p<0.05) greater than for NaCl aerosol. Filter penetration in the two test chambers showed a trend similar to TIL. The count median diameter was ∼82 nm for NaCl and ∼200 nm for corn oil aerosols. The net positive charge for NaCl aerosol was relatively larger. Both fit factor and filter efficiency influence TIL measurement. Overall, TIL determination with aerosols of different size distributions and charges using different methodologies may produce dissimilar results.

Tomato Infection by Whitefly-Transmitted Circulative and Non-Circulative Viruses Induce Contrasting Changes in Plant Volatiles and Vector Behaviour

PubMed Central

Fereres, Alberto; Peñaflor, Maria Fernanda G. V.; Favaro, Carla F.; Azevedo, Kamila E. X.; Landi, Carolina H.; Maluta, Nathalie K. P.; Bento, José Mauricio S.; Lopes, Joao R.S.

2016-01-01

Virus infection frequently modifies plant phenotypes, leading to changes in behaviour and performance of their insect vectors in a way that transmission is enhanced, although this may not always be the case. Here, we investigated Bemisia tabaci response to tomato plants infected by Tomato chlorosis virus (ToCV), a non-circulative-transmitted crinivirus, and Tomato severe rugose virus (ToSRV), a circulative-transmitted begomovirus. Moreover, we examined the role of visual and olfactory cues in host plant selection by both viruliferous and non-viruliferous B. tabaci. Visual cues alone were assessed as targets for whitefly landing by placing leaves underneath a Plexiglas plate. A dual-choice arena was used to assess whitefly response to virus-infected and mock-inoculated tomato leaves under light and dark conditions. Thereafter, we tested the whitefly response to volatiles using an active air-flow Y-tube olfactometer, and chemically characterized the blends using gas chromatography coupled to mass spectrometry. Visual stimuli tests showed that whiteflies, irrespective of their infectious status, always preferred to land on virus-infected rather than on mock-inoculated leaves. Furthermore, whiteflies had no preference for either virus-infected or mock-inoculated leaves under dark conditions, but preferred virus-infected leaves in the presence of light. ToSRV-infection promoted a sharp decline in the concentration of some tomato volatiles, while an increase in the emission of some terpenes after ToCV infection was found. ToSRV-viruliferous whiteflies preferred volatiles emitted from mock-inoculated plants, a conducive behaviour to enhance virus spread, while volatiles from ToCV-infected plants were avoided by non-viruliferous whiteflies, a behaviour that is likely detrimental to the secondary spread of the virus. In conclusion, the circulative persistent begomovirus, ToSRV, seems to have evolved together with its vector B. tabaci to optimise its own spread. However, this type of virus-induced manipulation of vector behaviour was not observed for the semi persistent crinivirus, ToCV, which is not specifically transmitted by B. tabaci and has a much less intimate virus-vector relationship. PMID:27529271

Replicating the Conditions on Mars: the Possibility of Sustaining Life

NASA Astrophysics Data System (ADS)

Abdul-Masih, Michael; Guinan, E. F.

2013-01-01

We describe a laboratory experiment that replicates environmental conditions on Mars’s surface to determine the viability of Earth-based life under conditions on Mars. Of all the organisms currently known, the ones that are best suited for the harsh environments found throughout our solar system are the extremophiles found on Earth that tolerate extreme environmental conditions. The environmental conditions on Mars are the least extreme of all the planets in our solar system excluding Earth. The average temperature near the equator varies from +10 C to -20 C and the surface pressure is P ~ 0.01 Atm. The thin atmosphere means that the UV radiation from the Sun is relatively unshielded. Carbon Dioxide (CO2) makes up approximately 95% of Mars’ atmosphere and the soil is composed primarily of iron oxides. This being said, water can exist in liquid form under the surface and because of this, so can life. To test this, we constructed an air-tight chamber out of Plexiglas that replicates the environmental conditions on Mars. As a first step, two different organisms were tested for survival: E-coli, which was the control, and Hypsibius (Tardigrades), a member of the Tardigradas phylum. We hypothesized that the E-coli would perish while the more hardy Tardigrades would survive. The trials were two days each and the chosen temperature was ~4°C. Many trials were conducted. After the first compilation of the results, the hypothesis did not hold. The E-coli surprisingly survived while the Tardigrades did not survive. The E-coli did not grow while in the chamber, but after being removed they grew showing that they were still viable and that the conditions were not harsh enough to kill them. After these initial results, the experiment was altered slightly to ensure that the Tardigrades were able to successfully enter their hibernation like state that allows them to survive extreme conditions. These experiments are continuing and we will discuss the results under controlled differing environmental conditions. This research is supported by a grant from Villanova University Center for Undergraduate Research and Fellowships & also supported by NSF/RUI Grant AST-1009903.

Positively reinforcing effects of the neurokinin substance P in the basal forebrain: mediation by its C-terminal sequence.

PubMed

Hasenöhrl, R U; Gerhardt, P; Huston, J P

1992-02-01

The conditioned corral preference paradigm was used to assess reinforcing effects of substance P (SP) and its N- and C-terminal fragments injected unilaterally into the region of the nucleus basalis magnocellularis (NBM) in rats. Behavioral testing was carried out in a circular open field, consisting of 4 quadrants equally preferred by the animals prior to conditioning. A single conditioning trial was performed. Rats received one microinjection (0.5 microliter) of SP (0.74 pmol), of the N-terminal fragment SP (1-7) and the C-terminal fragment analog DiMe-C7 (each at doses of 0.074, 0.74, and 74 pmol), or vehicle (phosphate-buffered saline; PBS). After injection the rats were placed into the open field with the four quadrants being separated by Plexiglas barriers (closed corral). During the test for conditioned corral preference, when provided a choice between the four quadrants, only those rats injected with SP and the equimolar dose of DiMe-C7 (0.74 pmol) spent more time in the treatment corral, indicative of a positively reinforcing action. None of the other doses of DiMe-C7 and of SP(1-7) influenced the preference behavior. For rats injected with 0.74 pmol SP, SP (1-7), and DiMe-C7, a behavioral analysis was performed for the 15 min conditioning trial. SP and DiMe-C7 reduced rearing and grooming behavior, whereas DiMe-C7 and SP(1-7) increased locomotor activity. However, the acute behavioral effects of SP and its fragments were not correlated with the subsequent place preference behavior during the test trial. The results are discussed in the framework of a structure/activity relationship for the positively reinforcing properties of SP in the region of the NBM. Furthermore, neuropathological implications of the present data are considered, since the homologous nucleus basalis of Meynert in man is known to degenerate in Alzheimer's disease, which is characterized behaviorally by a progressive deterioration in associative functioning.

The Origin of Chondrites: Metal-Silicate Separation Experiments Under Microgravity Conditions, Experiment 2

NASA Technical Reports Server (NTRS)

Moore, S. R.; Franzen, M.; Benoit, P. H.; Sears, D. W. G.; Holley, A.; Myers, M.; Godsey, R.; Czlapinski, J.

2003-01-01

Chondrites are categorized into different groups by several properties, including the metal-to-silicate ratio. Various processes have been suggested to produce distinct metal/silicate ratios, some based on sorting in the early solar nebular and others occurring after accretion on the parent body. Huang et al. suggested that a weak gravitational field accompanied by degassing, could result in metal/silicate separation on parent bodies. We suggest that asteroids were volatile-rich, at least early in their histories. Spectroscopic evidence from asteroid surfaces indicates that one-third of all asteroids maybe rich in clays and hydrated minerals, similar to carbonaceous chondrites. Internal and/or external heating could have caused volatiles to evaporate and pass through a surface dust layer. Spacecraft images of asteroids show they have a thick regoliths. Housen, and Asphaug and Nolan proposed that even a 10 km diameter asteroid could potentially have a significant regolith. Grain size and grain density sorting could occur in the unconsolidated layer by the process known as fluidization. This process occurs when an upward stream of gas is passed through a bed of particles which are lifted against a gravitational force. Fluidization is commonly used commercially to sort particulates. This type of behavior is based upon the bed, as a whole, and differs from aerodynamic sorting. Two sets of reduced gravity experiments were conducted during parabolic flights aboard NASA's KC-135 aircraft. The first experiment employed 310 tubes of 2.5 cm diameter, containing mixtures of sand and metal grains. A gas source was used to fluidize the mixture at reduced gravity conditions and mixtures were analyzed after the flight. However, this experiment did not allow a description of the fluidization as a function of gravity. A second experiment was conducted on the KC-135 aircraft in the summer of 2001, consisting of two Plexiglas cylinders containing a metal/silicate mixture, and video cameras to record the experiment on tape. Here we summarize this experiment and discusses the implications for metalsilicate separation on asteroid bodies.

Rhizoslides: paper-based growth system for non-destructive, high throughput phenotyping of root development by means of image analysis.

PubMed

Le Marié, Chantal; Kirchgessner, Norbert; Marschall, Daniela; Walter, Achim; Hund, Andreas

2014-01-01

A quantitative characterization of root system architecture is currently being attempted for various reasons. Non-destructive, rapid analyses of root system architecture are difficult to perform due to the hidden nature of the root. Hence, improved methods to measure root architecture are necessary to support knowledge-based plant breeding and to analyse root growth responses to environmental changes. Here, we report on the development of a novel method to reveal growth and architecture of maize root systems. The method is based on the cultivation of different root types within several layers of two-dimensional, large (50 × 60 cm) plates (rhizoslides). A central plexiglass screen stabilizes the system and is covered on both sides with germination paper providing water and nutrients for the developing root, followed by a transparent cover foil to prevent the roots from falling dry and to stabilize the system. The embryonic roots grow hidden between a Plexiglas surface and paper, whereas crown roots grow visible between paper and the transparent cover. Long cultivation with good image quality up to 20 days (four fully developed leaves) was enhanced by suppressing fungi with a fungicide. Based on hyperspectral microscopy imaging, the quality of different germination papers was tested and three provided sufficient contrast to distinguish between roots and background (segmentation). Illumination, image acquisition and segmentation were optimised to facilitate efficient root image analysis. Several software packages were evaluated with regard to their precision and the time investment needed to measure root system architecture. The software 'Smart Root' allowed precise evaluation of root development but needed substantial user interference. 'GiaRoots' provided the best segmentation method for batch processing in combination with a good analysis of global root characteristics but overestimated root length due to thinning artefacts. 'WhinRhizo' offered the most rapid and precise evaluation of root lengths in diameter classes, but had weaknesses with respect to image segmentation and analysis of root system architecture. A new technique has been established for non-destructive root growth studies and quantification of architectural traits beyond seedlings stages. However, automation of the scanning process and appropriate software remains the bottleneck for high throughput analysis.

Apparent Brecciation Gradient, Mount Desert Island, Maine

NASA Astrophysics Data System (ADS)

Hawkins, A. T.; Johnson, S. E.

2004-05-01

Mount Desert Island, Maine, comprises a shallow level, Siluro-Devonian igneous complex surrounded by a distinctive breccia zone ("shatter zone" of Gilman and Chapman, 1988). The zone is very well exposed on the southern and eastern shores of the island and provides a unique opportunity to examine subvolcanic processes. The breccia of the Shatter Zone shows wide variation in percent matrix and clast, and may represent a spatial and temporal gradient in breccia formation due to a single eruptive or other catastrophic volcanic event. The shatter zone was divided into five developmental stages based on the extent of brecciation: Bar Harbor Formation, Sols Cliffs breccia, Seeley Road breccia, Dubois breccia, and Great Head breccia. A digital camera was employed to capture scale images of representative outcrops using a 0.5 m square Plexiglas frame. Individual images were joined in Adobe Photoshop to create a composite image of each outcrop. The composite photo was then exported to Adobe Illustrator, which was used to outline the clasts and produce a digital map of the outcrop for analysis. The fractal dimension (Fd) of each clast was calculated using NIH Image and a Euclidean distance mapping method described by Bérubé and Jébrak (1999) to quantify the morphology of the fragments, or the complexity of the outline. The more complex the fragment outline, the higher the fractal dimension, indicating that the fragment is less "mature" or has had less exposure to erosional processes, such as the injection of an igneous matrix. Sols Cliffs breccia has an average Fd of 1.125, whereas Great Head breccia has an average Fd of 1.040, with the stages between having intermediate values. The more complex clasts of the Sols Cliffs breccia with a small amount (26.38%) of matrix material suggests that it is the first stage in a sequence of brecciation ending at the more mature, matrix-supported (71.37%) breccia of Great Head. The results of this study will be used to guide isotopic and geochemical analysis of the matrix igneous material in the attempt to better understand the dynamic processes that occur in subvolcanic environments and the mechanisms involved in breccia formation.

Tomato Infection by Whitefly-Transmitted Circulative and Non-Circulative Viruses Induce Contrasting Changes in Plant Volatiles and Vector Behaviour.

PubMed

Fereres, Alberto; Peñaflor, Maria Fernanda G V; Favaro, Carla F; Azevedo, Kamila E X; Landi, Carolina H; Maluta, Nathalie K P; Bento, José Mauricio S; Lopes, Joao R S

2016-08-11

Virus infection frequently modifies plant phenotypes, leading to changes in behaviour and performance of their insect vectors in a way that transmission is enhanced, although this may not always be the case. Here, we investigated Bemisia tabaci response to tomato plants infected by Tomato chlorosis virus (ToCV), a non-circulative-transmitted crinivirus, and Tomato severe rugose virus (ToSRV), a circulative-transmitted begomovirus. Moreover, we examined the role of visual and olfactory cues in host plant selection by both viruliferous and non-viruliferous B. tabaci. Visual cues alone were assessed as targets for whitefly landing by placing leaves underneath a Plexiglas plate. A dual-choice arena was used to assess whitefly response to virus-infected and mock-inoculated tomato leaves under light and dark conditions. Thereafter, we tested the whitefly response to volatiles using an active air-flow Y-tube olfactometer, and chemically characterized the blends using gas chromatography coupled to mass spectrometry. Visual stimuli tests showed that whiteflies, irrespective of their infectious status, always preferred to land on virus-infected rather than on mock-inoculated leaves. Furthermore, whiteflies had no preference for either virus-infected or mock-inoculated leaves under dark conditions, but preferred virus-infected leaves in the presence of light. ToSRV-infection promoted a sharp decline in the concentration of some tomato volatiles, while an increase in the emission of some terpenes after ToCV infection was found. ToSRV-viruliferous whiteflies preferred volatiles emitted from mock-inoculated plants, a conducive behaviour to enhance virus spread, while volatiles from ToCV-infected plants were avoided by non-viruliferous whiteflies, a behaviour that is likely detrimental to the secondary spread of the virus. In conclusion, the circulative persistent begomovirus, ToSRV, seems to have evolved together with its vector B. tabaci to optimise its own spread. However, this type of virus-induced manipulation of vector behaviour was not observed for the semi persistent crinivirus, ToCV, which is not specifically transmitted by B. tabaci and has a much less intimate virus-vector relationship.

Effect of cleaning methods after reduced-pressure air abrasion on bonding to zirconia ceramic.

PubMed

Attia, Ahmed; Kern, Matthias

2011-12-01

To evaluate in vitro the influence of different cleaning methods after low-pressure air abrasion on the bond strength of a phosphate monomer-containing luting resin to zirconia ceramic. A total of 112 zirconia ceramic disks were divided into 7 groups (n = 16). In the test groups, disks were air abraded at low pressure (L) 0.05 MPa using 50-μm alumina particles. Prior to bonding, the disks were ultrasonically (U) cleaned either in isopropanol alcohol (AC), hydrofluoric acid (HF), demineralized water (DW), or tap water (TW), or they were used without ultrasonic cleaning. Disks air abraded at a high (H) pressure of 0.25 MPa and cleaned ultrasonically in isopropanol served as positive control; original (O) milled disks used without air abrasion served as the negative control group. Plexiglas tubes filled with composite resin were bonded with the adhesive luting resin Panavia 21 to the ceramic disks. Prior to testing tensile bond strength (TBS), each main group was further subdivided into 2 subgroups (n=8) which were stored in distilled water either at 37°C for 3 days or for 30 days with 7500 thermal cycles. Statistical analyses were conducted with two- and one-way analyses of variance (ANOVA) and Tukey's HSD test. Initial tensile bond strength (TBS) ranged from 32.6 to 42.8 MPa. After 30 days storage in water with thermocycling, TBS ranged from 21.9 to 36.3 MPa. Storage in water and thermocycling significantly decreased the TBS of test groups which were not air abraded (p = 0.05) or which were air abraded but cleaned in tap water (p = 0.002), but not the TBS of the other groups (p > 0.05). Also, the TBS of air-abraded groups were significantly higher than the TBS of the original milled (p < 0.01). Cleaning procedures did not significantly affect TBS either after 3 days or 30 days storage in water and thermocycling (p > 0.05). Air abrasion at 0.05 MPa and ultrasonic cleaning are important factors for improving bonding to zirconia ceramic.

Technical Note: Construction of heterogeneous head phantom for quality control in stereotactic radiosurgery.

PubMed

Najafi, Mohsen; Teimouri, Javad; Shirazi, Alireza; Geraily, Ghazale; Esfahani, Mahbod; Shafaei, Mostafa

2017-10-01

Stereotactic radiosurgery is a high precision modality for conformally delivering high doses of radiation to the brain lesion with a large dose volume. Several studies for the quality control of this technique were performed to measure the dose delivered to the target with a homogenous head phantom and some dosimeters. Some studies were also performed with one or two instances of heterogeneity in the head phantom to measure the dose delivered to the target. But these studies assumed the head as a sphere and simple shape heterogeneity. The construction of an adult human head phantom with the same size, shape, and real inhomogeneity as an adult human head is needed. Only then is measuring the accurate dose delivered to the area of interest and comparison with the calculated dose possible. According to the ICRU Report 44, polytetrafluoroethylene (PTFE) and methyl methacrylate were selected as a bone and soft tissue, respectively. A set of computed tomography (CT) scans from a standard human head were taken, and simplification of the CT images was used to design the layers of the phantom. The parts of each slice were cut and attached together. Tests of density and CT number were done to compare the material of the phantom with tissues of the head. The dose delivered to the target was measured with an EBT3 film. The density of the PTFE and Plexiglas that were inserted in the phantom are in good agreement with bone and soft tissue. Also, the CT numbers of these materials have a low difference. The dose distribution from the EBT3 film and the treatment planning system is similar. The constructed phantom with a size and inhomogeneity like an adult human head is suitable to measure the dose delivered to the area of interest. It also helps make an accurate comparison with the calculated dose by the treatment planning system. By using this phantom, the actual dose delivered to the target was obtained. This anthropomorphic head phantom can be used in other modalities of radiosurgery as well. © 2017 American Association of Physicists in Medicine.

Combustion of LOX with H2(sub g) under subcritical, critical, and supercritical conditions and experimental observation of dense spray and mixing of impinging jets

NASA Technical Reports Server (NTRS)

Kuo, Kenneth K.; Hsieh, W. H.; Yang, A. S.; Brown, J. J.; Cheung, F. B.; Woodward, R. D.; Kline, M. C.

1992-01-01

Progress made during the period of February 1 to October 15, 1992 is reported. The overall objective of Task 1 of the investigation is to achieve a better understanding of the combustion processes of liquid oxygen and gaseous hydrogen under subcritical, critical, and supercritical conditions. Specific objectives of the research program are: (1) to determine the evaporation- and burning-rate characteristics of LOX in hydrogen/helium environments under broad ranges of operating conditions; (2) to measure species concentration profile and surface temperature of LOX employing the gas chromatography and fine-wire thermocouples under non-reacting flow situations; (3) to perform a fugacity-based multicomponent thermodynamic phase equilibrium analysis for examining the high-pressure vapor-liquid equilibrium behavior at the liquid surface of LOX; (4) to formulate and solve a theoretical model for simulating the evaporation and combustion processes in a LOX/H2/He system; and (5) to validate the theoretical model with the measured experimental data. Task 2 of the investigation is described. Observation of a like-on-like injector element in the near-injector region performed in the previous phase of this project has identified the existence of a high Reynolds number regime in which the pre-impingement jets are fully turbulent and undergoing surface breakup. The new spray regime, which has not been observed by previous investigators, is characterized by the presence of many fine droplets and the disappearance of the well-defined liquid breakup wave pattern in the post-impingement region. It is speculated that a cavitating region may be present within the orifice so that it could induce strong turbulence, leading to an onset of atomization of the jets prior to impingement. To further investigate the dense spray behavior of the impinging jets in the high Reynolds number region, experiments were conducted using Plexiglas injector components for direct internal flow observation. The main objective is to determine under what conditions a cavitating region would form and whether or not the cavitation is reponsible for the development of the high Reynolds number spray regime. The procedure and major findings of the injector cavitation study are described.

Study on the reduction of atmospheric mercury emissions from mine waste enriched soils through native grass cover in the Mt. Amiata region of Italy

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

Fantozzi, L., E-mail: l.fantozzi@iia.cnr.it; Ferrara, R., E-mail: romano.ferrara@pi.ibf.cnr.it; Dini, F., E-mail: fdiniprotisti@gmail.com

2013-08-15

Atmospheric mercury emissions from mine-waste enriched soils were measured in order to compare the mercury fluxes of bare soils with those from other soils covered by native grasses. Our research was conducted near Mt. Amiata in central Italy, an area that was one of the largest and most productive mining centers in Europe up into the 1980s. To determine in situ mercury emissions, we used a Plexiglas flux chamber connected to a portable mercury analyzer (Lumex RA-915+). This allowed us to detect, in real time, the mercury vapor in the air, and to correlate this with the meteorological parameters thatmore » we examined (solar radiation, soil temperature, and humidity). The highest mercury flux values (8000 ng m{sup −2} h{sup −1}) were observed on bare soils during the hours of maximum insulation, while lower values (250 ng m{sup −2} h{sup −1}) were observed on soils covered by native grasses. Our results indicate that two main environmental variables affect mercury emission: solar radiation intensity and soil temperature. The presence of native vegetation, which can shield soil surfaces from incident light, reduced mercury emissions, a result that we attribute to a drop in the efficiency of mercury photoreduction processes rather than to decreases in soil temperature. This finding is consistent with decreases in mercury flux values down to 3500 ng m{sup −2} h{sup −1}, which occurred under cloudy conditions despite high soil temperatures. Moreover, when the soil temperature was 28 °C and the vegetation was removed from the experimental site, mercury emissions increased almost four-fold. This increase occurred almost immediately after the grasses were cut, and was approximately eight-fold after 20 h. Thus, this study demonstrates that enhancing wild vegetation cover could be an inexpensive and effective approach in fostering a natural, self-renewing reduction of mercury emissions from mercury-contaminated soils. -- Highlights: ► Mercury air/surface exchange from grass covered soil is different from bare soil. ► Light enhances mercury emissions and is the main parameter driving the process. ► The presence of wild vegetation covering the soil reduces mercury emission. ► Vegetative covers could be a solution to reduce atmospheric mercury pollution.« less

A novel simulation model for minimally invasive spine surgery.

PubMed

Walker, James B; Perkins, Eddie; Harkey, H Louis

2009-12-01

Minimally invasive spine surgery (MISS) is among the fastest growing technologies in general neurosurgical practice. In addition, great demand exists to teach these skills to neurosurgery residents. With newly enforced work hour restrictions, opportunities to acquire these skills are limited, necessitating development of alternative strategies of education. We describe a novel simulation model for MISS supplemented by resident self-assessment analysis and evaluation. The simulator was constructed using a nontransparent Plexiglas frame supplemented with a modified halo frame on which to affix spine specimens. Interchangeable copper tubing was affixed to a 360-degree pivot system to replicate a working portal. Deer skulls and spines were then collected and prepared accordingly. Laboratory exercises were based on the resident's level of training with emphasis on proper drilling techniques. Eight neurosurgery residents were asked to complete the exercises and complete a self-assessment survey regarding their competence level on a scale of 0 to 5, both before and after completing the skill sets. Additionally, they were asked to complete an exit survey that was used to assess the simulation exercises. All exercises were completed successfully with the exception of placing 2 separate pedicle screws through the same portal, which posed difficulty on some specimens because of the of lack of lordosis of the specimens, leading to unfavorable trajectories using a free-hand technique. With regard to the resident self-assessment analysis, the mean confidence rating for performing an MISS laminectomy improved by a difference of 1.25 points (n = 8; 95% confidence interval, 0.66-1.84; P = 0.0015), from 2.50 to 3.75 before and after simulation exercises, respectively, and reached statistical significance. For the senior-level residents, the mean confidence rating for performing MISS placement of pedicle screws using a free-hand technique improved by a difference of 1.00 (n = 3; 95% confidence interval, -1.48-3.48; P = 0.225), from 3.33 to 4.33 before and after simulation exercises, respectively. Results of the exit survey were encouraging. The MISS simulator is a feasible, inexpensive, and reproducible adjunct to neurosurgery resident training and provides a new teaching method for spine surgery. Further investigation of this technology is warranted, although multicenter, randomized, controlled trials assessing its validity may not be practical because of ethical constraints with regard to patient safety.

Trace element distribution in the water and sediments of certain storage lakes from the Jijia catchment, (Romania)

NASA Astrophysics Data System (ADS)

Dughila, A.; Iancu, O. G.; Romanescu, G. T.

2012-04-01

The present study aims at investigating the concentrations and distribution levels of a series of trace elements in water and sediment samples collected from six storage lakes located in the Jijia catchment - NE of Romania. The lakes are multi-purpose water reservoirs, three of them being mainly used as a source of municipal drinking water, or for fishing, irrigation for the farms in the area, protection against floods and the regulation of river flows. By contrast, agricultural wastes, fertilizers, raw sewage effluents and road runoff constitute the predominant anthropogenic sources, which supply the lakes in question with Cd, Cu, Pb and Zn. The present study was conducted on a series of 63 sediment samples and 18 water samples, collected from the same locations, in order to establish the distribution levels of certain trace elements from the water through sediments. Sediment cores were collected from two sections across each lake by means of a motor boat, using a system that consists of a graduated sampling tube (0.9 m in length and 72.5 mm in diameter) made of Plexiglas (Eijkelkamp sample tube guide). Prior to the analyses, the samples were air-dried, ground and homogenized using an agate mortar, oven-dried at 50 °C for 6 days and then sieved through 63 µm sieves. The sediment and water samples were subjected to a digestion technique with concentrated nitric acid using a microwave oven (Berghof type), and analyzed for the following elements: Pb, Zn, Cu, Cd, Cr and Ni. The total concentration of the elements was measured through atomic absorption spectrometry (AAS) with an RSD of < 10 % from solutions. The vertical distribution of most elements in the cores examined could be characterized as relatively uniform, with higher concentrations for those collected from the lakes which are more influenced by anthropogenic factors, compared to those situated in forested areas. The lake-water quality characteristics were below the recommended drinking water standards imposed by the current legislation (MMGA Ord. No. 161/16.02.2006 - Normative regarding the classification of surface waters in order to establish the ecological status of water bodies, which combines European and Romanian provisions), with the exception of copper (with very high concentrations in all the water samples), lead and cadmium. Keywords: AAS, Jijia catchment (Romania), lake water, sediment core, trace elements

Gravitational Instabilities associated with volcanic clouds: new insights from experimental investigations

NASA Astrophysics Data System (ADS)

Scollo, Simona; Bonadonna, Costanza; Manzella, Irene

2016-04-01

Gravitational instabilities are often observed at the bottom of volcanic plumes and clouds generating fingers that propagate downward enhancing sedimentation of fine ash. Regardless of their potential influence on tephra dispersal and deposition, their dynamics is not completely understood, undermining the accuracy of volcanic ash transport and dispersal models. Here we present new laboratory experiments that investigate the effects of particle size, composition and concentration on finger dynamics and generation. The experimental set-up consists of a Plexiglas tank of 50 x 30.3 x 7.5 cm equipped with a removable banner for the partition of two separate layers. The lower partition is a solution of water and sugar and is therefore characterized by a higher density than the upper partition which is filled with water and particles. The upper layer is quiescent (unmixed experiments), or continually mixed using a rotary stirrer (mixed experiments). After removing the horizontal barrier that separates the two fluids, particles are illuminated with a 2W Nd-YAG laser named RayPower 2000 and filmed with a HD camera (1920x1080 pixels). Images are analysed by the Dynamic Studio Software (DANTEC) that is a tool for the acquisition and analysis of velocity and related properties of particles inside the fluids. Each particle that follows the flow and scatters light captured by the camera is analysed based on velocity vectors. Experiments are carried out in order to evaluate the main features of fingers (number, width and speed) as a function of particle type, size and initial concentration. Particles include Glass Beads (GB) with diameter < 32 μm, 45-63 μm, and 63-90 μm and Andesitic, Rhyolitic, and Basaltic Volcanic Ash with diameter < 32 μm, 45-63 μm, 63-90 μm, 90-125 μm, 125-180 μm and > 180 μm. Three initial particle concentrations in the upper layer were employed: 3 g/l, 4 g/l and 5 g/l. Results show that the number and the speed of fingers increases with particle concentration and the speed increases with particles size while it is independent on particle types. Finally, experiments point out that development of instability leads to particle aggregation inside the fingers.

[Influence of human mesenchymal stem cells on hyperoxia-exposed newborn rats by RAGE-NF-κB signaling in lung].

PubMed

Tian, Zhao-fang; Ji, Ping; Li, Yu-hong; Zhao, Sai; Wang, Xiang

2012-05-01

To investigate the influence of high oxygen exposure on signaling pathway of the receptor for advanced glycation end products (RAGE)-NF-κB of lung in newborn rats and the mechanisms of protecting lung injury for human mesenchymal stem cells (hMSC). Twenty-four newborn Sprague-Dawley rats from three litters were randomly divided into three groups, as hyperoxia exposed + hMSC group (group A), hyperoxia exposed group (group B), and air-exposed group (group C). The rats from the group A and B were placed in a sealed Plexiglas chamber with a minimal in-and outflow, providing six to seven exchanges per hour of the chamber volume and maintaining O(2) levels above 95%, while rats in the group C only exposed to air simultaneously. Seven days later, rats in the group A were injected intravenously with hMSC (5×10(4)) after hyperoxia exposure, but rats in group B and C received subcutaneous injection with PBS alone at the same time point. Then all the rats were exposed to air, and were sacrificed three days later. Immunohistochemistry was used to evaluate the expression of RAGE in lung tissue. The levels of TNF-α and sRAGE in bronchoalveolar lavage fluid (BALF) and in serum were detected by ELASA, RAGE mRNA and NF-κB mRNA in tissue homogenates were detected by RT-PCR, RAGE and NF-κB by Western blotting; also the value of lung damage score were calculated with histology under light microscope. There were significant differences among three groups in the fields of lung damage score (F = 51.59, P = 0.000), mRNA and protein of RAGE (F = 37.21, P = 0.000; F = 15.88, P = 0.000) and NF-κB (F = 5.695, P = 0.011; F = 4.223, P = 0.0288) in lung tissue homogenates, and the level of TNF-α (F = 38.29, P = 0.000) in BALF, all these parameters in group A and group B were higher than that in group C. While sRAGE in BALF in group A and group B were less than that in group C (F = 4.804, P = 0.0191). There were also significant differences between group A and group B in these parameters (P < 0.05). There were also no significant differences neither in TNF-α nor in sRAGE in serum among three groups. hMSC protects hyperoxia-induced lung injury via downregulating the signaling pathway of RAGE-NF-κB.

Improving mating performance of mass-reared sterile Mediterranean fruit flies (Diptera: Tephritidae) through changes in adult holding conditions: demography and mating competitiveness

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

Liedo, P.; Salgado, S.; Oropeza, A.

Mass rearing conditions affect the mating behavior of Mediterranean fruit flies (medflies) Ceratitis capitata (Wiedemann). We evaluated the effect of slight changes in the adult holding conditions of adult flies maintained for egg production on their mating performance. Colonization was initiated from wild flies collected as larvae from infested coffee berries (Coffea arabica L.). When pupae were close to adult emergence, they were randomly divided into 3 groups and the emerging adults were reared under the following conditions: (1) Metapa System (MS, control), consisting of 70 x 45 x 15 cm aluminum frame, mesh covered cages, with a density ofmore » 2,200 flies per cage and a 1:1 initial sex ratio; (2) Insert System (IS), with the same type of cage, and the same fly density and sex ratio as in the MS treatment, but containing twelve Plexiglas pieces (23 x 8.5 cm) to provide additional horizontal surface areas inside the cage; and (3) Sex-ratio System (SS), same as IS, but in this case the initial male: female ratio was 4:1. Three d later, newly emerged females were introduced, so the ratio became 3:1 and on the 6th d another group of newly emerged females was added to provide a 2:1 final sex ratio, at which the final density reached 1,675 flies per cage. The eggs collected from each of the 3 treatments were reared independently following standard procedures and the adults were held under the same experimental conditions. This process was repeated for over 10 to 13 generations (1 year). The experiment was repeated 3 times in 3 consecutive years, starting each replicate with a new collection of wild flies. Life tables were constructed for each treatment at the parental, 3rd, 6th, and 9th generations. Standard quality control parameters (pupation at 24 h, pupal weight, adult emergence, and flight ability), were estimated for each treatment every third generation in the third year. For the last generation each year, mating competitiveness was evaluated in field cage tests with wild flies. As colonization progressed, life expectancy and fecundity rates increased in the 3 rearing systems. There was no significant difference in standard quality control parameters among the 3 rearing systems. Wild males always achieved more matings than any of the mass reared males. Mating competitiveness of males from the IS, although surprisingly not from the SS, was significantly greater than that of males from the MS. Our results indicate that these slight changes in the adult holding conditions can significantly reduce the harmful effects of mass rearing on the mating performance of sterile flies. (author) [Spanish] Se ha demostrado que las condiciones de cria masiva afectan el comportamiento de apareamiento de la mosca del Mediterraneo Ceratitis capitata (Wiedemann). Nosotros evaluamos el efecto de ligeros cambios en las condiciones en las que los adultos son mantenidos para la produccion de huevos, en el desempeno de apareamiento de las moscas esteriles. La colonizacion se inicio con moscas silvestres colectadas como larvas en cerezas de cafe (Coffea arabica L.) infestadas. Cuando las pupas estuvieron cerca de la emergencia de los adultos, se dividieron en tres grupos al azar y los adultos recien emergidos fueron criados en las siguientes condiciones: (1) Sistema Metapa (MS, testigo), consistente en jaulas con marco de aluminio de 70 x 45 x 15 cm, cubiertas con malla, con una densidad de 2,200 moscas por jaula y una relacion de sexos inicial de 1:1; (2); Sistema Insertos (IS), con el mismo tipo de jaula, densidad de moscas, y relacion de sexos que en el MS, pero conteniendo 12 piezas de plexiglas (23 x 8.5 cm) para proporcionar superficie horizontal al interior de la jaula; y (3) Sistema de Relacion de Sexos (SS), igual que el IS, pero en este caso la relacion inicial macho: hembra fue de 4:1, tres dias despues se introdujeron hembras recien emergidas para tener una relacion de 3:1 y en el 6 dia se anadio otro grupo de hembras para tener una relacion final de sexos de 2:1, que equivale a una densidad final de 1,675 moscas por jaula. Los huevos colectados de cada tratamiento fueron criados independientemente siguiendo los procedimientos estandares y los adultos fueron mantenidos en las mismas condiciones experimentales. Esto se repitio por 10 a 13 generaciones (un ano). El experimento se repitio en tres ocasiones en anos consecutivos, iniciando cada repeticion con una nueva colecta de moscas silvestres. Se construyeron tablas de vida de cada tratamiento en las generaciones parental, 3 a, 6 a y 9 a . Se estimaron los parametros estandares de calidad (pupacion a las 24 h, peso de pupa, emergencia de adultos y habilidad de vuelo) para cada tratamiento, cada tercera generacion en el tercer ano. En la ultima generacion de cada ano, se evaluo la competitividad sexual en pruebas en jaulas de campo con moscas silvestres. Conforme avanzo la colonizacion, se encontro que la esperanza de vida y las tasas de fecundidad se incrementaron en los tres sistemas de cria. No hubo diferencia significativa en los parametros estandar de control de calidad entre los tres sistemas. Los machos silvestres siempre lograron mas apareamientos que los machos procedentes de cada sistema de cria masiva. La competitividad de los machos del sistema IS fue significativamente mayor que la de los machos del sistema MS. Nuestros resultados indican que estas ligeras modificaciones en las condiciones de la colonia de adultos reducen los efectos adversos de la cria masiva sobre el desempeno de apareamiento de los machos esteriles. (author)« less

Nimodipine prevents memory impairment caused by nitroglycerin-induced hypotension in adult mice.

PubMed

Bekker, Alex; Haile, Michael; Li, Yong-Sheng; Galoyan, Samuel; Garcia, Edwardo; Quartermain, David; Kamer, Angela; Blanck, Thomas

2009-12-01

Hypotension and a resultant decrease in cerebral blood flow have been implicated in the development of cognitive dysfunction. We tested the hypothesis that nimodipine (NIMO) administered at the onset of nitroglycerin (NTG)-induced hypotension would preserve long-term associative memory. The passive avoidance (PA) paradigm was used to assess memory retention. For PA training, latencies (seconds) were recorded for entry from a suspended platform into a Plexiglas tube where a shock was automatically delivered. Latencies were recorded 48 h later for a testing trial. Ninety-six Swiss-Webster mice (30-35 g, 6-8 wk), were randomized into 6 groups 1) saline (control), 2) NTG immediately after learning, 3) NTG 3 h after learning, 4) NTG and NIMO, 5) vehicle, and 6) NIMO alone. The extent of hypotension and changes in brain tissue oxygenation (PbtO(2)) and in cerebral blood flow were studied in a separate group of animals. All groups exhibited similar training latencies (17.0 +/- 4.6 s). Mice subjected to hypotensive episodes showed a significant decrease in latency time (178 +/- 156 s) compared with those injected with saline, NTG + NIMO, or delayed NTG (580 +/- 81 s, 557 +/- 67 s, and 493 +/- 146 s, respectively). A Kruskal-Wallis 1-way analysis of variance indicated a significant difference among the 4 treatment groups (H = 15.34; P < 0.001). In a separate group of mice not subjected to behavioral studies, the same dose of NTG (n = 3) and NTG + NIMO (n = 3) caused mean arterial blood pressure to decrease from 85.9 +/- 3.8 mm Hg sem to 31.6 +/- 0.8 mm Hg sem and from 86.2 +/- 3.7 mm Hg sem to 32.6 +/- 0.2 mm Hg sem, respectively. Mean arterial blood pressure in mice treated with NIMO alone decreased from 88.1 +/- 3.8 mm Hg to 80.0 +/- 2.9 mm Hg. The intergroup difference was statistically significant (P < 0.05). PbtO(2) decreased from 51.7 +/- 4.5 mm Hg sem to 33.8 +/- 5.2 mm Hg sem in the NTG group and from 38.6 +/- 6.1 mm Hg sem to 25.4 +/- 2.0 mm Hg sem in the NTG + NIMO groups, respectively. There were no significant differences among groups. In a PA retention paradigm, the injection of NTG immediately after learning produced a significant impairment of long-term associative memory in mice, whereas delayed induced hypotension had no effect. NIMO attenuated the disruption in consolidation of long-term memory caused by NTG but did not improve latency in the absence of hypotension. The observed effect of NIMO may have been attributable to the preservation of calcium homeostasis during hypotension, because there were no differences in the PbtO(2) indices among groups.

Tabletop Tectonics: Diverse Mountain Ranges Using Flour and Graphite

NASA Astrophysics Data System (ADS)

Davis, D. M.

2006-12-01

It has been recognized for some time that the frontal deformation zones where plates converge (foreland fold- and-thrust belts on continents and accretionary wedges at subduction zones) involve shortening over a decoupling layer, or decollement. A simple but successful way of explaining many aspects of their behavior is called the critical Coulomb wedge model, which regards these contractional wedges as analogous to the wedge-shaped mass of soil accreted in front of a bulldozer, or the wedge of snow that piles up in front of a snow plow. The shape and deformation history of the accreted wedge of soil or snow will depend upon the frictional strength of the material being plowed up and the surface over which it is being plowed. The same is true of `bulldozer' wedges consisting of many km thick piles of sediment at convergent plate margins. Using flour (or powdered milk), sandpaper, graphite, transparency sheets, and athletic field marker chalk, manipulated with sieves, brushes, pastry bags and blocks and sheets of wood, it is possible to demonstrate a wide variety of processes and tectonic styles observed at convergent plate boundaries. Model fold-and-thrust belts that behave like natural examples with a decollement that is strong (e.g., in rock without high pore fluid pressure) or weak (e.g., in a salt horizon or with elevated pore fluid pressure) can be generated simply by placing wither sandpaper or graphite beneath the flour that is pushed across the tabletop using a block of wood (the strong basement and hiterland rocks behind the fold-thrust belt). Depending upon the strength of the decollement, the cross-sectional taper of the deforming wedge will be thin or broad, the internal deformation mild or intense, and the structures either close to symmetric or strongly forward-vergent, just as at the analogous natural fold-thrust belts. Including a horizontal sheet of wood or Plexiglas in front of the pushing block allows generation of an accretionary wedge, outer-are high, and forearc basin, just as over a subduction zone. Any dark material emplaced (a pastry bag works well) atop the experiment before deformation in the form of football-field `hash marks' every 10 cm allows for easy calculation of strain distribution at any time during or after the experiment. Finally, the entire orogen can be excavated using a plastic photocopier transparency sheet. If the original set-up included occasional thin layers of red and blue field marker chalk within sedimentary column (the rest of which consists of white flour or powdered milk), excavation reveals (quite colorfully) many internal details of the fold-thrust belts that have been generated.

Calcium Carbonate Crystal Growth in Porous Media, in the presence of Water Miscible and Non-Miscible Organic Fluids

NASA Astrophysics Data System (ADS)

Jaho, Sofia; Sygouni, Varvara; Paraskeva, Christakis A.

2015-04-01

The deposition of sparingly soluble salts (scaling) within porous media is a major problem encountered in many industrial and environmental applications. In the oil industry scaling causes severe operational malfunctions and, therefore, increasing the total operating and maintenance cost [1]. The most common types of sparingly soluble salts located in oil fields include carbonate and sulfate salts of calcium, strondium and barium[1,2]. Multiple phase flow and tubing surface properties are some of the factors affecting scale formation [3]. The main purpose of the present work was the investigation of the precipitation mechanisms of calcium carbonate (CaCO3) through in situ mixing of two soluble salt solutions in a flow granular medium, in the presence of water miscible organic fluid (ethylene glycol) or non-miscible organic fluid (n-dodecane). All series of experiments were carried out in a two dimensional porous medium made of Plexiglas. For all solutions used in the experiments, the contact angles with the surface of the porous medium and the interfacial tensions were measured. During the experiments, the calcium carbonate crystal growth was continuously monitored and recorded through an optical microscope equipped with a digital programmed video camera. The snap-shots were taken within specific time intervals and their detailed procession gave information concerning the crystal growth rate and kinetics. The pH of the effluent was measured and fluids samples were collected for calcium analysis using Atomic Absorption Spectroscopy (AAS). In all experiments effluent calcium concentration decreased as a function of time, suggesting that CaCO3 precipitation took place inside the porous medium. Crystals of the precipitated salt were identified using Infrared Spectroscopy (IR) and the morphology of the crystals was examined using Scanning Electron Microscopy (SEM). The induction time for precipitation of CaCO3 crystals in the presence of n-dodecane was significantly reduced compared to the induction time where no oil phase was present. The interface of n-dodecane and supersaturated solutions seems to be very active and favored the formation of the CaCO3 crystalline enhancing the heterogeneous nucleation which generally demands a decreased energy barrier. Acknowledgments This research was partially funded by the European Union (European Social Fund-ESF) and Greek National Funds through the Operational Program "Education and Lifelong Learning" under the action Aristeia II (Code No4420). References 1. Merdhah A. B. and Yassin A. A., Scale formation in oil reservoir during water injection at high-salinity formation water, Journal of Applied Sciences, 7, 3198-3207 (2007). 2. Moghadasi J., Muller-Steinhagen H., Jamialahmadi M. and Sharif A., Model study on the kinetics of oil field formation damage due to salt precipitation from injection, Journal of Petroleum Science and Engineering, 43, 201-217 (2004). 3. Nancollas G. H. and Reddy M. M., The crystallization of calcium carbonate II. Calcite growth mechanism, Journal of Colloid and Interface Science, 37, 824-830 (1971).

Experimental study on the effects of fixed boundaries in channelized free surface dry granular flows

NASA Astrophysics Data System (ADS)

Sarno, Luca; Carleo, Luigi; Nicolina Papa, Maria

2017-04-01

The dynamics of granular mixtures, involved in geophysical flows like avalanches and debris flows, is far from being completely understood. Several features of their motion, such as rheological stratification, non-local and boundary effects, still represent open problems. Experimental investigations at laboratory scale are an important tool that can provide insights about the dynamics of gravity driven granular flows. The measuring techniques should be non-invasive in order to measure undisturbed flows. In this work we present an experimental campaign devoted to the measurement of the velocity profiles of free surface steady granular flows in an open channel. To achieve this goal the flows were recorded by two cameras and velocity profiles were obtained by image analysis. The employed granular medium consists of acetal-polymeric beads with a mean diameter of 3mm and an estimated internal friction angle of 27°. All the experiments have been performed in a 2m-long plexiglas flume with a rectangular cross-section and a slope angle of 30°. The upper part of the channel was used as a reservoir where the material was loaded before each run and then let flow down through an adjustable gate. Several mass flow rates were investigated. Three different basal surfaces were employed so as to observe slip and non-slip boundary conditions: a smooth Bakelite surface, a roughened surface, obtained by gluing a layer of grains on the bed surface and a sandpaper surface with characteristic length of the roughness equal to 425 µm. The flume is equipped with two high-speed cameras, one placed aside the channel and the other one perpendicular to the channel bed, as to get both side-wall and free surface velocity profiles. The particle image velocimetry open-source code, PIVlab, is employed for estimating the flow velocities. All the free surface velocity profiles show an approximately parabolic shape with a maximum at the cross-section midpoint and a minimum at the side-walls, due to the wall friction. Different kinds of side-wall velocity profiles are observed. As regards the smooth basal surface, a slip velocity at the bed is observed. The profiles are Bagnold-type near the free surface and become linear as the depth increases. On the glued-grain basal surface the flow velocity at the bed is null and all the velocity profiles show a rheological stratification with a lower exponential tail and an upper linear profile. Grain rolling is observed at the sandpaper bed, instead. With the increase of flow depths, the velocity profiles gradually shift from the ones observed on the smooth bed to the ones observed on the glued-grain bed. In order to further understand the constitutive behaviour of granular mixtures, it is useful to perform simultaneous measurements of flow velocity and volume fraction. In this perspective, a new series of experiments is actually undergoing for the measurement of the volume fraction.

Analog modelling of obduction processes

NASA Astrophysics Data System (ADS)

Agard, P.; Zuo, X.; Funiciello, F.; Bellahsen, N.; Faccenna, C.; Savva, D.

2012-04-01

Obduction corresponds to one of plate tectonics oddities, whereby dense, oceanic rocks (ophiolites) are presumably 'thrust' on top of light, continental ones, as for the short-lived, almost synchronous Peri-Arabic obduction (which took place along thousands of km from Turkey to Oman in c. 5-10 Ma). Analog modelling experiments were performed to study the mechanisms of obduction initiation and test various triggering hypotheses (i.e., plate acceleration, slab hitting the 660 km discontinuity, ridge subduction; Agard et al., 2007). The experimental setup comprises (1) an upper mantle, modelled as a low-viscosity transparent Newtonian glucose syrup filling a rigid Plexiglas tank and (2) high-viscosity silicone plates (Rhodrosil Gomme with PDMS iron fillers to reproduce densities of continental or oceanic plates), located at the centre of the tank above the syrup to simulate the subducting and the overriding plates - and avoid friction on the sides of the tank. Convergence is simulated by pushing on a piston at one end of the model with velocities comparable to those of plate tectonics (i.e., in the range 1-10 cm/yr). The reference set-up includes, from one end to the other (~60 cm): (i) the piston, (ii) a continental margin containing a transition zone to the adjacent oceanic plate, (iii) a weakness zone with variable resistance and dip (W), (iv) an oceanic plate - with or without a spreading ridge, (v) a subduction zone (S) dipping away from the piston and (vi) an upper, active continental margin, below which the oceanic plate is being subducted at the start of the experiment (as is known to have been the case in Oman). Several configurations were tested and over thirty different parametric tests were performed. Special emphasis was placed on comparing different types of weakness zone (W) and the extent of mechanical coupling across them, particularly when plates were accelerated. Displacements, together with along-strike and across-strike internal deformation in all plates were systematically measured, allowing for a very precise and reproducible tracking of deformation. Experiments demonstrate that obduction chiefly depends on how the overall shortening (or convergence) is partitionned between the weakness zone (W) and the preexisting subduction zone (S). Conditions favorable to obduction are shown to correspond to a specific range of coupling across (S) and resistance across (W). Our results thereby (1) constrain the range of physical conditions required for obduction to develop/nucleate and (2) underline the key role of acceleration for triggering obduction (rather than ridge subduction or slab resistance to penetration at the 660 km discontinuity). They also demonstrate that the emplacement of dense, oceanic material on continental lithosphere is not a mysterious process but results from some large scale, normal subduction process that do not require exotic boundary conditions. Agard P., Jolivet L., Vrielynck B., Burov E. & Monié P., 2007. Plate acceleration : the obduction trigger? Earth and Planetary Science Letters, 258, 428-441.

Subduction initiation and Obduction: insights from analog models

NASA Astrophysics Data System (ADS)

Agard, P.; Zuo, X.; Funiciello, F.; Bellahsen, N.; Faccenna, C.; Savva, D.

2013-12-01

Subduction initiation and obduction are two poorly constrained geodynamic processes which are interrelated in a number of natural settings. Subduction initiation can be viewed as the result of a regional-scale change in plate convergence partitioning between the set of existing subduction (and collision or obduction) zones worldwide. Intraoceanic subduction initiation may also ultimately lead to obduction of dense oceanic "ophiolites" atop light continental plates. A classic example is the short-lived Peri-Arabic obduction, which took place along thousands of km almost synchronously (within ~5-10 myr), from Turkey to Oman, while the subduction zone beneath Eurasia became temporarily jammed. We herein present analog models designed to study both processes and more specifically (1) subduction initiation through the partitioning of deformation between two convergent zones (a preexisting and a potential one) and, as a consequence, (2) the possible development of obduction, which has so far never been modeled. These models explore the mechanisms of subduction initiation and obduction and test various triggering hypotheses (i.e., plate acceleration, slab crossing the 660 km discontinuity, ridge subduction; Agard et al., 2007). The experimental setup comprises an upper mantle modelled as a low-viscosity transparent Newtonian glucose syrup filling a rigid Plexiglas tank and high-viscosity silicone plates. Convergence is simulated by pushing on a piston at one end of the model with plate tectonics like velocities (1-10 cm/yr) onto (i) a continental margin, (ii) a weakness zone with variable resistance and dip (W), (iii) an oceanic plate - with or without a spreading ridge, (iv) a subduction zone (S) dipping away from the piston and (v) an upper active continental margin, below which the oceanic plate is being subducted at the start of the experiment (as for the Oman case). Several configurations were tested over thirty-five parametric experiments. Special emphasis was placed on comparing different types of weakness zone (W) and the extent of mechanical coupling across them, particularly when plates were accelerated. Measurements of displacements and internal deformation allow for a very precise and reproducible tracking of deformation. Experiments consistently demonstrate that subduction initiation chiefly depends on how the overall shortening (or convergence) is partitionned between the weakness zone (W) and the preexisting subduction zone (S). Part of the deformation is transfered to W as soon as the increased coupling across S results in 5-10% of the convergence being transfered to the upper plate. Whether obduction develops further depends on the effective strength of W. Results (1) constrain the range of physical conditions required for subduction initiation and obduction to develop/nucleate and (2) underline the key role of acceleration for triggering obduction, rather than ridge subduction or slab resistance to penetration at the 660 km discontinuity. [Agard P., Jolivet L., Vrielynck B., Burov E. & Monié P., 2007. Plate acceleration : the obduction trigger? Earth and Planetary Science Letters, 258, 428-441.

Computational Modeling of Magnetically Actuated Propellant Orientation

NASA Technical Reports Server (NTRS)

Hochstein, John I.

1996-01-01

Unlike terrestrial applications where gravity positions liquid at the "bottom" of the tank, the location of liquid propellant in spacecraft tanks is uncertain unless specific actions are taken or special features are built into the tank. Some mission events require knowledge of liquid position prior to a particular action: liquid must be positioned over the tank outlet prior to starting the main engines and must be moved away from the tank vent before vapor can be released overboard to reduce pressure. It may also be desirable to positively position liquid to improve propulsion system performance: moving liquid away from the tank walls will dramatically decrease the rate of heat transfer to the propellant, suppressing the boil-off rate, thereby reducing overall mission propellant requirements. The process of moving propellant to a desired position is referred to as propellant orientation or reorientation. Propulsive reorientation relies on small auxiliary thrusters to accelerate the tank. The inertia of the liquid causes it to collect in the aft-end of the tank if the acceleration is forward. Liquid Acquisition Devices (LAD's) rely on surface tension to hold the liquid within special geometries, (i.e. vanes, wire-mesh channels, start-baskets), to positively position propellants. Both of these technologies add significant weight and complexity to the spacecraft and can be limiting systems for long duration missions. The subject of the present research is an alternate technique for positively positioning liquid within spacecraft propellant tanks: magnetic fields. LOX is paramagnetic (attracted toward a magnet) and LH2 is diamagnetic (repelled from a magnet). Order-of-magnitude analyses, performed in the 1960's to determine required magnet size, concluded that the magnets would be prohibitively massive and this option has remained dormant during the intervening years. Recent advances in high-temperature superconducting materials hold the promise of electromagnets with sufficient performance to support cryogenic propellant management tasks. In late 1992, NASA MSFC began a new investigation in this technology commencing with the design of the Magnetically-Actuated Propellant Orientation (MAPO) experiment. A mixture of ferrofluid and water is used to simulate the paramagnetic properties of LOX and the experiment is being flown on the KC-135 aircraft to provide a reduced gravity environment. The influence of a 0.4 Tesla ring magnet on flow into and out of a subscale Plexiglas tank is being recorded on video tape. The most efficient approach to evaluating the feasibility of MAPO is to compliment the experimental program with development of a computational tool to model the process of interest. The goal of the present research is to develop such a tool. Once confidence in its fidelity is established by comparison to data from the MAPO experiment, it can be used to assist in the design of future experiments and to study the parameter space of the process. Ultimately, it is hoped that the computational model can serve as a design tool for full-scale spacecraft applications.

Experiments on the Richtmyer-Meshkov Instability of Incompressible Fluids

NASA Technical Reports Server (NTRS)

Jacobs, J.; Niederhaus, C.

2000-01-01

Richtmyer-Meshkov (R-M) instability occurs when two different density fluids are impulsively accelerated in the direction normal to their nearly planar interface. The instability causes small perturbations on the interface to grow and possibly become turbulent given the proper initial conditions. R-M instability is similar to the Rayleigh-Taylor (R-T) instability, which is generated when the two fluids undergo a constant acceleration. R-M instability is a fundamental fluid instability that is important to fields ranging from astrophysics to high-speed combustion. For example, R-M instability is currently the limiting factor in achieving a net positive yield with inertial confinement fusion. The experiments described here utilize a novel technique that circumvents many of the experimental difficulties previously limiting the study of the R-M instability. A Plexiglas tank contains two unequal density liquids and is gently oscillated horizontally to produce a controlled initial fluid interface shape. The tank is mounted to a sled on a high speed, low friction linear rail system, constraining the main motion to the vertical direction. The sled is released from an initial height and falls vertically until it bounces off of a movable spring, imparting an impulsive acceleration in the upward direction. As the sled travels up and down the rails, the spring retracts out of the way, allowing the instability to evolve in free-fall until impacting a shock absorber at the end of the rails. The impulsive acceleration provided to the system is measured by a piezoelectric accelerometer mounted on the tank, and a capacitive accelerometer measures the low-level drag of the bearings. Planar Laser-Induced Fluorescence is used for flow visualization, which uses an Argon ion laser to illuminate the flow and a CCD camera, mounted to the sled, to capture images of the interface. This experimental study investigates the instability of an interface between incompressible, miscible liquids with an initial sinusoidal perturbation. The amplitude of the disturbance during the experiment is measured and compared to theory. The results show good agreement (within 10%) with linear stability theory up to nondimensional amplitude ka = 0.7 (wavenumber x amplitude). These results hold true for an initial ka (before acceleration) of -0.7 less than ka less than -0.06, while the linear theory was developed for absolute value of ka much less than 1. In addition, a third order weakly nonlinear perturbation theory is shown to be accurate for amplitudes as large as ka = 1.3, even though the interface becomes double-valued at ka = 1.1. As time progresses, the vorticity on the interface concentrates, and the interface spirals around the alternating sign vortex centers to form a mushroom pattern. At higher Reynolds Number (based on circulation), an instability of the vortex cores has been observed. While time limitations of the apparatus prevent determination of a critical Reynolds Number, the lowest Reynolds Number this vortex instability has been observed at is 5000.

Agricultural pathogen decontamination technology-reducing the threat of infectious agent spread.

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

Betty, Rita G.; Bieker, Jill Marie; Tucker, Mark David

Outbreaks of infectious agricultural diseases, whether natural occurring or introduced intentionally, could have catastrophic impacts on the U.S. economy. Examples of such agricultural pathogens include foot and mouth disease (FMD), avian influenza (AI), citrus canker, wheat and soy rust, etc. Current approaches to mitigate the spread of agricultural pathogens include quarantine, development of vaccines for animal diseases, and development of pathogen resistant crop strains in the case of plant diseases. None of these approaches is rapid, and none address the potential persistence of the pathogen in the environment, which could lead to further spread of the agent and damage aftermore » quarantine is lifted. Pathogen spread in agricultural environments commonly occurs via transfer on agricultural equipment (transportation trailers, tractors, trucks, combines, etc.), having components made from a broad range of materials (galvanized and painted steel, rubber tires, glass and Plexiglas shields, etc), and under conditions of heavy organic load (mud, soil, feces, litter, etc). A key element of stemming the spread of an outbreak is to ensure complete inactivation of the pathogens in the agricultural environment and on the equipment used in those environments. Through the combination of enhanced agricultural pathogen decontamination chemistry and a validated inactivation verification methodology, important technologies for incorporation as components of a robust response capability will be enabled. Because of the potentially devastating economic impact that could result from the spread of infectious agricultural diseases, the proposed capability components will promote critical infrastructure protection and greater border and food supply security. We investigated and developed agricultural pathogen decontamination technologies to reduce the threat of infectious-agent spread, and thus enhance agricultural biosecurity. Specifically, enhanced detergency versions of the patented Sandia decontamination chemistry were developed and tested against a few surrogate pathogens under conditions of relatively heavy organic load. Tests were conducted on surfaces commonly found in agricultural environments. Wide spectrum decontamination efficacy, low corrosivity, and biodegradability issues were addressed in developing an enhanced detergency formulation. A method for rapid assessment of loss of pathogenic activity (inactivation) was also assessed. This enhanced technology will enable rapid assessment of contamination following an intentional event, and will also be extremely useful in routine assessment of agricultural environments. The primary effort during the second year was progress towards a demonstration of both decontamination and viral inactivation technologies of Foot and Mouth virus (FMDv) using the modified SNL chemistry developed through this project. Lab studies using a surrogate virus (bovine enterovirus) were conducted using DF200, modified DF200 chemistry, and decontaminants currently recommended for use in heavily loaded organic, agricultural environments (VirkonS, 10% bleach, sodium hydroxide and citric acid). Tests using actual FMD virus will be performed at the Department of Homeland Security's Plum Island facilities in the fall of 2005. Success and the insight gained from this project will lead to enhanced response capability, which will benefit agencies such as USDA, DHS, DOD, and the agricultural industry.« less

Development of Integrated and Flexible Ultrasonic Transducers for Aerospace Applications

NASA Astrophysics Data System (ADS)

Wu, Kuo-Ting

2011-12-01

High temperature (HT) integrated (IUTs) and flexible ultrasonic transducers (FUTs) for potential aerospace applications in the area of nondestructive testing (NDT) and structural health monitoring (SHM) are developed. The main merits are that IUTs can be fabricated on-site and FUTs are feasible and attractive for on-site installation. The piezoelectric composite films of these HT ultrasonic transducers (HTUTs) are made by sol-gel spray fabrication. Lead-zirconate titanate composite (PZT-c), bismuth titanate composite (BIT-c), or lithium niobate composite (LiNbO3-c) films were coated onto metallic substrates with planar and curved surfaces and investigated as IUTs. Their maximum operating temperatures were demonstrated at up to 150°C, 400°C, and 800°C, respectively. PZT-c or BIT-c films were coated onto 75 mum or 38 mum thick metallic membranes and were investigated as FUTs. They can be bonded onto flat or curved surfaces for NDT and SHM. An FUT made of BIT-c film coated onto a stainless steel membrane glued onto a steel plate was performed at up to 300°C. Besides being coated onto metallic materials, sol-gel sprayed composite films were also coated onto graphite/epoxy (Gr/Ep) plates as IUTs and 50 mum thick polyimide films as FUTs for the thickness and delamination evaluation. Using acoustic mode conversion techniques, HTUTs for shear (S) wave, surface acoustic wave (SAW), and plate acoustic wave (PAW), have been developed. HT ultrasonic probes simultaneously producing one longitudinal (L) and two orthogonally polarized S waves were demonstrated in metallic and Plexiglas probes. The potential applications of these probes were discussed. Also applying mode conversion approaches, HT symmetrical, anti-symmetrical, and shear horizontal (SH) PAWs UTs for NDT and SHM were developed. The results showed that the SH PAWs may be the best candidate for NDT and SHM purposes for plate structures. Generation and detection of guided acoustic waves for NDT were demonstrated by using IUTs or FUTs with metallic wedges, mechanical gratings or interdigital transducers as well. The experiments with these three approaches were performed at up to 300°C. Furthermore, two non-contact ultrasonic measurement techniques by sol-gel sprayed composite films were presented in this thesis. One is using lasers to generate ultrasound and IUTs as receivers, and the other is using induction-based non-contact ultrasonic measurement technique with IUTs. NDT of bonded composite patches on aluminum plates was performed using laser generated ultrasound and IUT receivers. The induction-based ultrasonic measurement of a Gr/Ep composite plate rotated at 1000 rpm was demonstrated. The IUTs and FUTs developed in this thesis are able to provide signals with good signal-to-noise ratios at elevated temperature on structures and parts having a curved surface. They are light weight and miniature in size. They may be used for real-time, in situ, nondestructive local and global (large area) damage detection and assessment in aerospace NDT and SHM applications.

Thermal instabilities in a soft and complex lithosphere: laboratory experiments and numerical simulations

NASA Astrophysics Data System (ADS)

Massmeyer, A.; Davaille, A. B.; Rolf, T.; Tackley, P. J.; Di Giuseppe, E.

2012-12-01

The upwelling of hot material in the lithosphere remains far from understood. This is due to the complexity of the mechanical behaviour of lithospheric material, which presents solid as well as viscous properties. Mushroom-shaped less viscous plumes or more viscous finger-shaped diapirs, depending on the viscosity ratio between the rising and the matrix materials, are known to migrate through ductile, quasi-newtonian lithosphere; while dikes fracture and propagate through a solid matrix. But what happens in between these two end-members? To answer this question, we perform a combined study of laboratory experiments and numerical simulations on the development of thermal plumes in aqueous solutions of Carbopol, a polymer gel suspension forming a continous network of micrometric sponges. This fluid is shear thinning and presents a yield-stress, whereby flow occurs only if the local stress exceeds a critical value. Below this value, the fluid acts as an elastic solid. Our experimental setup consists of a localized heat-source, placed in the center of a squared plexiglas tank. At t=0, a constant thermal power is applied locally to the fluid. For the numerical simulations, we replace the rigid plastic regions by an extremely viscous fluid, and therefore neglect the elastic contribution to the local stress. We systematically studied the influence of the rheological parameters, as well as the supplied heat. Depending on the Yield number Y0, which compares the thermally-induced stress to the yield stress, three different regims are observed. For low Y0, no convection develops; while for intermediate values, a small-scale convection cell appears and remains confined around the heater. For high Y0, thermal instabilities rise through the tank. Their morphology differs from the mushroom-shape typically encountered in newtonian fluids. Combined temperature and velocity field measurements show that a plug flow develops within the plume thermal anomaly, therefore producing a rising finger-shape with strong shear zones confined along its edges. The characteristics of the instability, as well as the existence of unyielded regions and the development of a damaged zone ahead of the plume as it rises, depend on Y0 but also on the other rheological parameters. The numerical simulations recover well the features observed in the laboratory experiments. This allows us to extend the parameter range of study. Our experimental finger-shaped diapirs present strong similarities with an off-axis diapir in Oman emplaced in a ridge context. This geological object, several kilometers in diameter presents in particular strong shear localization along its edges. Within our fluid mechanics framework, the existence of such an instability in the lithosphere places strong constraints on its parameter range. It suggests that this diapir was emplaced in a partially molten lithosphere. Therefore Herschel-Bulkley fluids like Carbopol might be good candidates to get new insights into the behavior of "soft" geological systems like mid-ocean ridge systems.

The Potential of Bee-Generated Carbon Dioxide for Control of Varroa Mite (Mesostigmata: Varroidae) in Indoor Overwintering Honey bee (Hymenoptera: Apidae) Colonies.

PubMed

Bahreini, Rassol; Currie, Robert W

2015-10-01

The objective of this study was to manipulate ventilation rate to characterize interactions between stocks of honey bees (Apis mellifera L.) and ventilation setting on varroa mite (Varroa destructor Anderson and Trueman) mortality in honey bee colonies kept indoors over winter. The first experiment used colonies established from stock selected locally for wintering performance under exposure to varroa (n = 6) and unselected bees (n = 6) to assess mite and bee mortality and levels of carbon dioxide (CO2) and oxygen (O2) in the bee cluster when kept under a simulated winter condition at 5°C. The second experiment, used colonies from selected bees (n = 10) and unselected bees (n = 12) that were exposed to either standard ventilation (14.4 liter/min per hive) or restricted ventilation (0.24 liter/min per hive, in a Plexiglas ventilation chamber) during a 16-d treatment period to assess the influence of restricted air flow on winter mortality rates of varroa mites and honey bees. Experiment 2 was repeated in early, mid-, and late winter. The first experiment showed that under unrestricted ventilation with CO2 concentrations averaging <2% there was no correlation between CO2 and varroa mite mortality when colonies were placed under low temperature. CO2 was negatively correlated with O2 in the bee cluster in both experiments. When ventilation was restricted, mean CO2 level (3.82 ± 0.31%, range 0.43-8.44%) increased by 200% relative to standard ventilation (1.29 ± 0.31%; range 0.09-5.26%) within the 16-d treatment period. The overall mite mortality rates and the reduction in mean abundance of varroa mite over time was greater under restricted ventilation (37 ± 4.2%) than under standard ventilation (23 ± 4.2%) but not affected by stock of bees during the treatment period. Selected bees showed overall greater mite mortality relative to unselected bees in both experiments. Restricting ventilation increased mite mortality, but did not affect worker bee mortality relative to that for colonies under standard ventilation. Restricted ventilation did not affect the overall level of Nosema compared with the control. However, there was an interaction between stock, season, and time of the trial. Unselected stock showed an increase in Nosema over time in the late winter trial that did not occur in the selected stock. In conclusion, these findings suggested that restricted ventilation has potential to suppress varroa mite in overwintering honey bee colonies via a low-cost and environmentally friendly measure. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

The costal landslide from analogue experiments: perspectives and limitation

NASA Astrophysics Data System (ADS)

Del Ventisette, C.; Nolesini, T.; Moretti, S.; Fanti, R.

2010-12-01

Understanding the triggering mechanism of coastal landslides (triggered and/or developed at air-water interface) and their evolution is fundamental to evaluate their hazard and, predicting the energy, the associated tsunami risk. The aim of this work is to verify the suitability of analogue modelling to understand the triggering mechanism and the evolution of landslide along the costal line. As a starting case study the Sciara del Fuoco (SdF), northwest flank of the volcanic island of Stromboli (Italy), was chosen. The analogue modelling technique has been proven to represent an useful tool to understand many geological processes, as it allows studying the progressive deformation, providing also useful indications about the role of distinct factors controlling the final deformation pattern. The models simulated at a first approximation the geological geometries observed at Stromboli, a composite volcano forming the northernmost island of the Aeolian Archipelago (Tyrrhenian Sea). The activity of Stromboli volcano is characterized by a persistent mild explosive activity at the summit craters sporadically interrupted by episodes of lava effusion and violent paroxysmal explosions as in 2002-2003 and in 2007. During the 2002 effusion a large landslide occurred on the SdF. The landslide caused a tsunami, which produced severe damages along the island shores. A series of analogue models was performed to investigate the influence of two different types of triggering mechanism and the behaviour of landslides both in air and air-water interface: 1) surface bulging due to the intrusion of a dike; 2) accumulation of material due to an uppermost landslide or due to opening of a new vent. The models, constructed in a Plexiglas tank, were scaled to the natural prototype following the geometrical, rheological, kinematical and dynamical similarities (e.g. Hubbert, 1937; Ramberg, 1981). The modelling material (Fontainbleau sand and rice) was sieved on a slope, inclination of which varing between 35° and 25°, depending on whether the simulated environment is subaerial or submarine, according to the inclination Average Sciara del Fuoco (Boldini et al. 2005; Chiocci et al., 2008). During models construction several difficulties came out as the difficulties to chose the suitable material for analogue models in the presence of water. Indeed the presence of water causes in the analogue materials a very fast capillary rising. In this work we propose some technical devices to minimize this limitations, such as impermeable barriers. References Boldini D., Wang F. W., Sassa K., Tommasi P., 2005. Mechanism of landslide causing the December 2002 tsunami at Stromboli volcano. Landslide: Risk Analysis and Sustainable Disaster Management, 173-180, Springer, New York. Chiocci F. L., Romagnoli C., Tommasi P., Bosman A., 2008. The Stromboli tsunamigenic submarine slide: Characteristic and possible failure mechanism. Journal of Geophysical research vol. 113, B 10102. Hubbert M.K., 1937. Theory of scale models as applied to the study of geologic structures. Geol. Soc. Am. Bull. 48, 1459-1520. Ramberg H., 1981. Gravity, deformation and the Earth’s crust in theory, experiments and geologic application, 2nd Edition. Academic, London, pp 1-452.

Physical Hydraulic Model of Side-Channel Spillway of Lambuk DAM, Bali

NASA Astrophysics Data System (ADS)

Harifa, A. C.; Sholichin, M.; Othman, F. B.

2013-12-01

The spillway is among the most important structures of a dam project. A spillway is designed to prevent overtopping of a dam at a place that is not designed for overtopping. Side-channel spillways are commonly used to release water flow from a reservoir in places where the sides are steep and have a considerable height above the dam. Experimental results were collected with a hydraulic model of the side-channel spillway for releasing the peak overflow of Lambuk Dam. This dam is, located on the Lambuk River, which is a tributary of the Yeh Hoo River ~ 34.6 km north of Denpasar on the island of Bali. The bituminous geomembrane faced dam is 24 m in height, with a 35-m wide spillway. The length of the side channel is 35 m long, with 58 m of transition channel, 67.37 m of chuteway channel and 22.71 m of stilling basin. The capacity of the spillway is 231.91 m3/s and the outlet works capacity is 165.28 m3/s. The reservoir is designed for irrigation and water supply. The purpose of this study was to optimize the designed of the structure and to ensure its safe operation. In hydraulic model may help the decision-makers to visualize the flow field before selecting a ';suitable' design. The hydraulic model study was performed to ensure passage of the maximum discharge at maximum reservoir capacity; to study the spillway approach conditions, water surface profiles, and flow patterns in the chuteway; and to reveal potential demerits of the proposed hydraulic design of various structures and explore solutions. The model was constructed at 1 : 40 scale, Reservoir topography was modeled using concrete, the river bed using sand and some gravel, the river berm using concrete, and the spillway and channel using Plexiglas. Water was measured using Rectangular contracted weir. Design floods (with return period in year) were Q2 = 111.40 m3/s, Q5 = 136.84 m3/s, Q10 = 159.32 m3/s, Q25 = 174.61 m3/s, Q50 = 185.13 m3/s, Q100 = 198.08 m3/s, Q200 = 210.55 m3/s, Q1000 = 231.91 m3/s and the probable maximum flood was 476.88 m3/s. Hydraulic analysis of spillway used USBR method for spillway, Hind's equation for the side channel, energy equation with standard step method for the transition and chuteway channel. Local scouring depth was calculated using the Schotlisch and Veronise equation. Total head on crest spillway for Q2 = 0.92 m, Q1000 = 1.68 m and for QPMF = 1.92 m. The highest measurement error is 3.16% according to the total head on crest spillway. Cavitation was observed in chuteway. Flow is subcritical (Froude < 1) in the side channel and supercritical in the transition channel. The final design for the spillway and chuteway were safe from impact of cavitation, pulsating flow, and local scouring.

Comparison of the incipient lesion enamel fluoride uptake from various prescription and OTC fluoride toothpastes and gels.

PubMed

Schemehorn, B R; DiMarino, J C; Movahed, N

2014-01-01

The objective of this in vitro study was to compare the fluoride uptake into incipient enamel lesions of a novel 970 ppm F- ion SnF2 over-the-counter (OTC) gel (Enamelon Preventive Treatment Gel) and a novel 1150 ppm F- ion OTC toothpaste (Enamelon), each delivering amorphous calcium phosphate (ACP), to the uptake from two different prescription strength, 5000 ppm F- ion dentifrices containing tri-calcium phosphate (TCP) and a prescription 900 ppm F- ion paste containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP). The test procedure followed method #40 in the US-FDA Anticaries Drug Products for OTC Human Use, Final Monograph testing procedures. Eight sets of twelve incisor enamel cores were mounted in Plexiglas rods and the exposed surfaces were polished. The indigenous fluoride levels of each specimen were determined prior to treatment. The treatments were performed using slurries of a negative control (water) and the following products applied to a set of sound enamel cores: 5000 ppm F- ion, sodium fluoride (NaF) prescription (Rx) dentifrice "A" containing TCP; 5000 ppm F- ion, NaF Rx dentifrice "B" containing TCP; 900 ppm F- ion, NaF Rx paste with CPP-ACP; 1150 ppm F- ion, NaF OTC toothpaste; 1150 ppm F- ion, stannous fluoride (SnF2) OTC toothpaste delivering ACP (Enamelon); 1100 ppm F- ion, SnF2 OTC toothpaste; and 970 ppm F- ion, SnF2 OTC gel delivering ACP (Enamelon Preventive Treatment Gel). The twelve specimens of each group were immersed into 25 ml of their assigned slurry with constant stirring (350 rpm) for 30 minutes. Following treatment, one layer of enamel was removed from each specimen and analyzed for fluoride and calcium. The pre-treatment fluoride (indigenous) level of each specimen was subtracted from the post-treatment value to determine the change in enamel fluoride due to the test treatment. The increase in the average fluoride uptake for treated enamel cores was: 10,263 ± 295 ppm for the 970 ppm F- ion, Enamelon Preventive Treatment Gel; 7,016 ± 353 ppm for the 1150 ppm F- ion Enamelon Toothpaste; 4,138 ± 120 ppm for the 5000 ppm F- ion, NaF prescription dentifrice "A" with TCP; 3801 ± 121 ppm for the 5000 ppm F- ion, NaF prescription dentifrice "B" with TCP; 2,647 ± 57 ppm for the 1100 ppm F- ion, SnF2 OTC toothpaste; 1470 ± 40 ppm for the 1150 ppm F- ion, NaF OTC toothpaste; and 316 ± 9 ppm for the 900 ppm F- ion, NaF paste with CPP-ACP. The differences among all the products tested were statistically significant (p < 0.05), except for the two 5000 ppm F- ion products with TCP that were not statistically different from one another, and the 900 ppm F ion, NaF paste with CPP-ACP that was not statistically different from the negative water control. The Enamelon products (970 ppm and 150 ppm F ion, SnF2OTC dentifrices) delivering ACP provide statistically significantly more fluoride to incipient enamel lesions than two prescription strength 5000 ppm F- ion toothpastes containing TCP, the 900 ppm F- ion prescription paste containing CPP-ACP, and the other OTC toothpastes compared in this study.

Experimental analysis of the levees safety based on geophysical monitoring

NASA Astrophysics Data System (ADS)

Rizzo, Enzo; Valeria, Giampaolo; Mario, Votta; Lapenna, Vincenzo; Moramarco, Tommaso; Aricò, Costanza; Camici, S.; Morbidelli, Renato; Sinagra, M.; Tucciarelli, T.

2010-05-01

Several flood events brought river levees into the focus of attention for some disasters due to their collapse. This phenomena is quite complex to investigate, because of different factors that can affect the stability of levees, among them the non uniformity of material properties, which influencing the permeability of the embankment, might induce high percolation velocity of flux thus triggering the unstability. Thus, to apply a fast and integrate investigation methods with a non-destructive characteristics should have a large interest, if they are able to furnish ready and usable information necessary to hydrogeological models. In order to achieve this goal, the University of Perugia (Department of Civil and Environmental Engineering) and the National Research Council (IRPI and IMAA research institutes) developed a collaborating project on the study of the internal structure of the river embankment by carrying out experiments in laboratory. The purpose of this study is to show the preliminary results of the experimental investigation. The laboratory embankment was built using material coming from a real levee and gathered inside a 1.5m x 1.2m plexiglas box. The box has two compartments: a water reservoir at one hand where a constant water head was reached after some time and a soil simulating the presence of levee. We perform a geoelectrical multichannel acquisition system with three parallel profiles characterized by 16 mini-electrodes connected to georesistivimeter Syscal Pro. An automatic acquisition protocol has been performed to obtain time slice electrical tomographies during the experiments. The geophysical results show the effect of the water table inside the embankment during the wetting and emptying. In order to assess the capability of the geophysical monitoring for addressing the soil parameters estimate, the resistivity results are investigated by using two analytical and one hydraulic numerical models. The analytical models represent a linear solution of Laplace's equation where Dupuit hypothesis holds (the vertical gradients of the flow velocity in the medium are neglected). In particular, the Marchi and Supino solutions are investigated here by assuming the upstream water level variations in the river negligible with respect to the ones inside the groundwater under the steady state condition. Two different seepage fronts are calculated and compared with the ones inferred from the resistivity maps. The experimental data have been also compared with the results computed by a numerical code. The governing equation for the unsaturated-saturated medium is the continuity equation written in terms of the piezometric head unknown while the Brooks-Corey law relates the water content and the relative hydraulic conductivity to the piezometric head. The numerical model is a time splitting technique and the solution is obtained by solving consecutively a convective and a diffusive component. The medium has been discretized in space using a generally unstructured triangular mesh. The governing equations are discretized using the edge centred mixed hybrid finite element scheme. The computational domain is schematized as 1D network of cells located at the middle point of each edge and linked by fictitious channels and the storage capacity is concentrated in the cells. A linear variation of unknown is assumed inside each triangle. The positive outcomes of hydraulic model application have certainly had benefit from the information coming from the geophysical monitoring. Based on these preliminary results it was noticeable as the geophysical monitoring can be conveniently adopted for addressing the levee safety control and to provide information on soil parameters.

Soil Greenhouse Gas Fluxes in a Pacific Northwest Douglas-Fir Forest: Results from a Soil Fertilization and Biochar Addition Experiment

NASA Astrophysics Data System (ADS)

Hawthorne, I.; Johnson, M. S.; Jassal, R. S.; Black, T. A.

2013-12-01

Rising atmospheric concentrations of greenhouse gases (GHGs), carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), linked to current climate change has stimulated a scientific response to provide robust accounting of sources and sinks of these gases. There is an urgent need to increase awareness of land management impacts on GHG flux dynamics to facilitate the development of management strategies that minimize GHG emissions. Biochar (pyrolyzed organic matter) has been identified as a strategy to reduce net GHG fluxes from soils. This is due to its potential to sequester large amounts of carbon for significant time periods, as well as its modification of biotic and abiotic soil conditions, which in turn can alter the GHG balance. This study describes the effect of biochar and urea-N application on soil surface CO2, CH4 and N2O fluxes in a Pacific Northwest Douglas-fir forest on Vancouver Island, BC, Canada (49o 52' N, 125o 20' W). We used a randomized complete-block design with four replicates of the following treatments: i) control, ii) 5 Mg ha-1 biochar surface application, iii) 200 kg N ha-1 urea pellets surface application, and iv) 5 Mg ha-1 biochar plus 200 kg N ha-1 urea. Soil GHG flux measurements were made biweekly for two years beginning in September 2011 using a non-steady-state non-flow through chamber technique. Biochar was added in February 2012, with urea applied in March 2013. A collar made from 21-cm diameter x 11-cm long PVC piping was installed in each of the 16 plots between two large trees on the forest floor, penetrating the organic layer to the mineral soil at the 5-8 cm depth. A clear Plexiglas lid, equipped with a 10-cm long vent tube and 9-V fan, was placed on each collar when making measurements, with 20-mL samples of chamber headspace air collected at 0, 3, 6, 9 and 12 min using a medical syringe with 21-gauge needle inserted through a rubber septum in the chamber lid. Samples were injected into and transported in previously evacuated 12-mL vials and analyzed by gas chromatography. Chamber headspace GHG mixing ratios vs. time data were fit to linear and exponential models in R (Version 2.14.0) and fluxes were calculated. Results showed high variability in GHG fluxes over time in all treatments. Higher CO2 emissions were observed during early summer (119 μg CO2 m-2 s-1 in the control plots), decreasing with drought (19 μg CO2 m-2 s-1 in the control plots). CH4 uptake by soil increased during summer months from -0.004 μg CH4 m-2 s-1 to -0.089 μg CH4 m-2 s-1 in the control plots, in response to drying conditions in the upper soil profile. N2O was both consumed and emitted in all treatments, with fluxes ranging from -0.0009 to 0.0019 μg N2O m-2 s-1 in the control plots. Analysis of variance indicated that there were significant differences in GHG fluxes between treatments over time. We also investigated the potential effects of large volume headspace removal, and H2O vapour saturation leading to a dilution effect by using a closed-path infra-red gas analyzer with an inline humidity sensor.

A New Method for Determining Hamaker Constants of Solids Based on the Dynamic Approach Behavior of an Atomic Force Microscope

NASA Astrophysics Data System (ADS)

Fronczak, Sean G.

The Hamaker constant, A, is a quantitative measure of the fundamental attractive van der Waals (vdW) interaction for microscale and nanoscale materials. This parameter captures each material's compositional effects on the vdW force, which is often needed as input for predicting the vdW interactions between particles and surfaces. Experimental attempts to determine A using an atomic force microscope (AFM) are typically hindered by issues inherent to the cantilever-tip-surface contact regime, such as surface roughness and deformation, and contact separation distance. Thus, we developed a new method for estimating Hamaker constants from the non-contact approach regime of an AFM experiment (Fronczak et al., 2017, Langmuir 33, 714-725). This method invokes a quasi-dynamic description of the cantilever tip's approach to contact, in which the inertial effects of the tip motion are accounted for when analyzing the trajectory of the tip's approach towards the substrate. The method was tested experimentally using silica, alumina and polystyrene substrates, and was demonstrated to yield estimates of A for these materials that were in very good agreement with previously published Lifshitz calculations. As with various other approaches to determining A, our new method relies heavily on the accuracy of the geometric model used to predict the interaction between the AFM tip and the substrate. For the initial validation experiments of our new method, we therefore focused on describing the shape of the cantilever tip as closely as possible, utilizing a complex model of a truncated pyramid with a spherical cap. Although this pyramidal geometry can be confirmed and the dimensions estimated via scanning electron microscopy (SEM), even high-resolution SEM images of the tip cannot provide sufficient detail to allow precise enough determination of the tip's geometric parameters. Consequently, we also propose an adaptation of the method, in which these difficult to quantify geometric effects are still fully captured via the convenient description of the tip as an 'effective' perfect sphere. Hence, the geometric complexity of the cantilever tip is no longer explicitly required for the determination of A. First, a tip is 'calibrated', whereby the deflection at first contact between the cantilever tip and a smooth surface of known vdW properties is determined and an effective radius, Reff, of the tip is calculated. The tip's approach to contact toward other similarly smooth surfaces can then be well-described by using only this single geometric parameter. We demonstrate the practicality and accuracy of this updated method by comparing the results with both the original pyramid model and Lifshitz approximations (when available) for flat substrates composed of silica, polystyrene, highly ordered pyrolytic graphite (HOPG), sapphire (alpha-Al3O2), Plexiglas (PMMA), and acrylonitrile butadiene styrene (ABS). Then, the modified quasi-dynamic model was employed to study the strength of the adhesive interaction between TNT and several swab materials which are used as explosive detection devices at security checkpoints. This information is crucial for the development and improvement of next-generation swab detection protocols to further advance this field. Finally, we also include the effects of thermal noise into our quasi-dynamic description of the cantilever motion to better understand how such noise might influence the accuracy of our method. We likewise determine, for the first time, the effects of instrument noise on the accuracy of other approach-to-contact methodologies for determining A.

Determination of strength behaviour of slope supported by vegetated crib walls using centrifuge model testing

NASA Astrophysics Data System (ADS)

Sudan Acharya, Madhu

2010-05-01

The crib retaining structures made of wooden/bamboo logs with live plants inside are called vegetative crib walls which are now becoming popular due to their advantages over conventional civil engineering walls. Conventionally, wooden crib walls were dimensioned based on past experiences. At present, there are several guidelines and design standards for machine finished wooden crib walls, but only few guidelines for the design and construction of vegetative log crib walls are available which are generally not sufficient for an economic engineering design of such walls. Analytical methods are generally used to determine the strength of vegetated crib retaining walls. The crib construction is analysed statically by satisfying the condition of static equilibrium with acceptable level of safety. The crib wall system is checked for internal and external stability using conventional monolithic and silo theories. Due to limitations of available theories, the exact calculation of the strength of vegetated wooden/bamboo crib wall cannot be made in static calculation. Therefore, experimental measurements are generally done to verify the static analysis. In this work, a model crib construction (1:20) made of bamboo elements is tested in the centrifuge machine to determine the strength behaviour of the slope supported by vegetated crib retaining wall. A geotechnical centrifuge is used to conduct model tests to study geotechnical problems such as the strength, stiffness and bearing capacity of different structures, settlement of embankments, stability of slopes, earth retaining structures etc. Centrifuge model testing is particularly well suited to modelling geotechnical events because the increase in gravitational force creates stresses in the model that are equivalent to the much larger prototype and hence ensures that the mechanisms of ground movements observed in the tests are realistic. Centrifuge model testing provides data to improve our understanding of basic mechanisms of deformation and failure and provides benchmarks useful for verification of numerical models. In this case this test is mainly carried out to verify the stability analysis and deformation characteristics of a bamboo crib wall. Models of crib wall of dimensions 37x13x10 cm and 37x13x14cm were placed inside a Plexiglas box of internal dimensions of 42.5x42.5x30 cm and slope was formed leaving a space about 10 cm in the front. The model crib wall tests were all performed at 40-70 times earth's gravity. This means that the 5 mm diameters bamboo rods in model used represents a prototype diameter of 20-35 cm. The horizontal and vertical displacements were measured with the help of three displacements sensor fixed horizontally and one sensor fixed vertically at the top of the model crib wall. All together nine tests were carried out with varying model parameters. Standard medium sand and coarse sand were used as fill material in the testing. Two wall heights variations and three slopes variations were used in the testing. The test model was constructed either compacted or uncompacted. The compaction in the model was carried out by hand to about 90% of the Proctor density. Three slopes inclinations were used. For flat slope the slope angle was less than 25° , and for steep slope it was 25° -35° and for extremely steep slope it was > 35° . The test results and conclusions are presented in this paper.

Nimodipine-induced hypotension but not nitroglycerin-induced hypotension preserves long- and short-term memory in adult mice.

PubMed

Haile, Michael; Galoyan, Samuel; Li, Yong-Sheng; Cohen, Barry H; Quartermain, David; Blanck, Thomas; Bekker, Alex

2012-05-01

Acute hypotension may be implicated in cognitive dysfunction. L-type calcium channel blockers in the setting of hypoxia are protective of learning and memory. We tested the hypothesis that hypotension induced by nimodipine (NIMO) and nicardipine (NICA) would be protective of long- and short-term memory compared to hypotension induced by nitroglycerin (NTG). Forty Swiss-Webster mice (30 to 35 g, 6 to 8 weeks) were randomized into 4 groups for i.p. injection immediately after passive avoidance (PA) learning on day 0: (1) NTG (30 mg/kg); (2) NICA (40 mg/kg); (3) NIMO (40 mg/kg); and (4) saline. PA training latencies (seconds) were recorded for entry from a suspended platform into a Plexiglas tube where a shock (0.3 mA; 2-second duration) was automatically delivered. On day 2 latencies were recorded during a testing trial during which no shock was delivered. Latencies >900 seconds were assigned this value. Lower testing latency is indicative of an impairment of long-term associative memory. Forty-nine additional mice were randomized into similar groups for object recognition testing (ORT) and given i.p. injections on day 0. ORT measures short-term memory by exploiting the tendency of mice to prefer novel objects where a familiar object is present. On day 5 during training, 2 identical objects were placed in a circular arena and mice explored both for 15 minutes. A testing trial was conducted 1 hour later for 3 minutes after a novel object replaced a familiar one. Mice with intact memory spend about 65% of the time exploring the novel object. Mice with impaired memory devote equal time to each object. Recognition index (RI) is defined as the ratio of time spent exploring the novel object to time spent exploring both objects was the measure of memory. Mean arterial blood pressure (MAP), cerebral bloodflow, and body and brain oxygenation (PO(2)) studies were done in separate groups of mice to determine the dosages for matched degrees of hypotension and the physiological profile of each treatment. The median PA latencies for the different conditions were as follows: NTG (219.5 ± 93.5 second semi-interquartile range [SIQR]), NICA (372.5 ± 75.5 second SIQR), NIMO (540 ± 200 second SIQR) and saline (804 ± 257.5 second SIQR). Rank methods were used to analyze the PA latencies for significant differences. NTG latency was significantly shorter than NIMO latency (P = 0.012) and saline latency (P = 0.006), but not NICA latency (P = 0.126). ORT RI values showed a similar pattern. We found that NTG RI (47.2 ± 5.9% SEM) was different from NIMO RI (60.2 ± 4.6% SEM, P = 0.031) and different from saline RI (66.9 + 3.7% SEM, P = 0.006). Physiological experiments showed that MAP decreased to 45 to 50 mm Hg in all animals who became minimally responsive to external stimuli within 10 to 15 minutes of injection. Intergroup differences for MAP, body and brain oxygenation, and cerebral bloodflow were not statistically significant. Acute hypotension induced by NIMO was protective of 2 categories of memory formation relevant to the clinical posttreatment period. Both immediate long-term associative memory consolidation as measured by the PA learning paradigm and delayed short-term working memory function as measured by the ORT paradigm were significantly improved compared to matched levels of hypotension induced by NTG. These results indicate the utility of further investigation of l-type calcium channel blockers as a potential means of preserving cognition in the setting of hypotensive and low flow states.

Our solution for fusion of simultaneusly acquired whole body scintigrams and optical images, as usesful tool in clinical practice in patients with differentiated thyroid carcinomas after radioiodine therapy. A useful tool in clinical practice.

PubMed

Matovic, Milovan; Jankovic, Milica; Barjaktarovic, Marko; Jeremic, Marija

2017-01-01

After radioiodine therapy of differentiated thyroid cancer (DTC) patients, whole body scintigraphy (WBS) is standard procedure before releasing the patient from the hospital. A common problem is the precise localization of regions where the iod-avide tissue is located. Sometimes is practically impossible to perform precise topographic localization of such regions. In order to face this problem, we have developed a low-cost Vision-Fusion system for web-camera image acquisition simultaneously with routine scintigraphic whole body acquisition including the algorithm for fusion of images given from both cameras. For image acquisition in the gamma part of the spectra we used e.cam dual head gamma camera (Siemens, Erlangen, Germany) in WBS modality, with matrix size of 256×1024 pixels and bed speed of 6cm/min, equipped with high energy collimator. For optical image acquisition in visible part of spectra we have used web-camera model C905 (Logitech, USA) with Carl Zeiss® optics, native resolution 1600×1200 pixels, 34 o field of view, 30g weight, with autofocus option turned "off" and auto white balance turned "on". Web camera is connected to upper head of gamma camera (GC) by a holder of lightweight aluminum rod and a plexiglas adapter. Our own Vision-Fusion software for image acquisition and coregistration was developed using NI LabVIEW programming environment 2015 (National Instruments, Texas, USA) and two additional LabVIEW modules: NI Vision Acquisition Software (VAS) and NI Vision Development Module (VDM). Vision acquisition software enables communication and control between laptop computer and web-camera. Vision development module is image processing library used for image preprocessing and fusion. Software starts the web-camera image acquisition before starting image acquisition on GC and stops it when GC completes the acquisition. Web-camera is in continuous acquisition mode with frame rate f depending on speed of patient bed movement v (f=v/∆ cm , where ∆ cm is a displacement step that can be changed in Settings option of Vision-Fusion software; by default, ∆ cm is set to 1cm corresponding to ∆ p =15 pixels). All images captured while patient's bed is moving are processed. Movement of patient's bed is checked using cross-correlation of two successive images. After each image capturing, algorithm extracts the central region of interest (ROI) of the image, with the same width as captured image (1600 pixels) and the height that is equal to the ∆ p displacement in pixels. All extracted central ROI are placed next to each other in the overall whole-body image. Stacking of narrow central ROI introduces negligible distortion in the overall whole-body image. The first step for fusion of the scintigram and the optical image was determination of spatial transformation between them. We have made an experiment with two markers (point radioactivity sources of 99m Tc pertechnetate 1MBq) visible in both images (WBS and optical) to find transformation of coordinates between images. The distance between point markers is used for spatial coregistration of the gamma and optical images. At the end of coregistration process, gamma image is rescaled in spatial domain and added to the optical image (green or red channel, amplification changeable from user interface). We tested our system for 10 patients with DTC who received radioiodine therapy (8 women and two men, with average age of 50.10±12.26 years). Five patients received 5.55Gbq, three 3.70GBq and two 1.85GBq. Whole-body scintigraphy and optical image acquisition were performed 72 hours after application of radioiodine therapy. Based on our first results during clinical testing of our system, we can conclude that our system can improve diagnostic possibility of whole body scintigraphy to detect thyroid remnant tissue in patients with DTC after radioiodine therapy.

[Influence of human bone marrow-derived mesenchymal stem cells on the lung of newborn rats damaged by hyperoxia].

PubMed

Tian, Zhao-fang; Du, Jiang; Fu, Xue-mei; Wang, Bin; Hong, Xiao-yang; Feng, Zhi-chun

2008-01-01

To evaluate whether human mesenchymal stem cells (hMSCs) administration alter the clinical course of hyperoxia-induced lung injury. hMSCs were obtained from bone marrow aspirates from healthy donors after informed consent was signed, hMSCs were separated, cultured, amplified, identified and labeled with BrdU. For BrdU labeling, a sterile stock solution was added to the culture medium 48 h before the end of culture, at a final concentration of 10 micromol/L. Thirty-two 3-day old SD rats from four litters were randomly divided into four groups, as hyperoxia exposed + hMSC group (A), air-exposed + hMSC group (B), hyperoxia exposed group (C), and air-exposed group (D). The rats from the group A and the group C were placed in a sealed Plexiglas chamber with a minimal in- and outflow, providing six to seven exchanges per hour of the chamber volume and maintaining O2 levels above 95%, while the rats in the group B and the group D were only exposed to room air. Seven days later, all of them were taken out of the chamber, rats in the group A and B were injected intraperitoneally with hMSCs (1 x 10(5) in 50 microl of PBS) immediately, while the rats in the group C and D were only treated with 50 microl of PBS 3 days later. All the animals were sacrificed by an injection of sodium pentobarbital (120 mg/kg), perfused with cold 0.9% NaCl, and the left lungs were removed, the upper lobes of which were ground as tissue homogenates and used for ELISA, while the inferior lobes were stored at -70 degrees C until use for RT-PCR. The right lungs were fixed in situ for 2 h by the intratracheal instillation with 10% neutral formalin and then postfixed for 24 h. Sagittal sections (4-microm) of paraffin-embedded middle lobe and upper lobe of the right lung were used for immunohistochemistry and histology, respectively. (1) There was a significant difference in the value of RAC (raditive alveoli coant) among the 4 groups (11.145 +/- 1.331, 13.941 +/- 0.985, 9.595 +/- 0.672, 14.819 +/- 1.080, F = 43.234, P = 0.000). RAC in group A and C were significantly reduced compared with subjects in group D (P < 0.05, P < 0.05); and there was also a significant difference between group A and group C (P < 0.05), but not between group B and D subjects (P > 0.05). (2) There were significant differences in the levels of both TNFalpha and TGFbeta(1) in the homogenate of lungs among the 4 groups (142.933 +/- 24.017, 79.033 +/- 11.573, 224.088 +/- 41.915, 76.500 +/- 10.373, F = 59.970, P = 0.000; 1726.484 +/- 91.086, 1530.359 +/- 173.441, 2047.717 +/- 152.057, 1515.777 +/- 131.049, F = 24.977, P = 0.000). The levels of TNFalpha and TGFbeta1 were significantly elevated in both group A and group C when compared with subjects in group D (P < 0.05 for both). Concentrations of TNFalpha and TGFbeta1 were both significantly decreased in group A versus group C (P < 0.05 for both). There was no significant difference between group B and D subjects in the fields of TNFalpha and TGFbeta(1) (P > 0.05 for both). (3) BrdU-labelled cells were observed at alveolar wall and bronchioles in both group A and group B, and there was a significant difference in BrdU-labeled cells between two groups (0.230 +/- 0.026, 0.190 +/- 0.015; t = 3.769, P = 0.002), but none was found in group C and group D. Electrophoresis of the PCR products showed a 224 bp band, specific for Alu mRNA, in 7 of 8 rats of group A and 5 of 8 rats of group B, respectively, but no such band was found in group C and group D. hMSCs administered by intraperitoneal injection could be implanted in the lungs of newborn rats, and they could effectively protect the rats against damage to the lungs caused by hyperoxia.

Developpement d'un systeme pour la mesure du taux de vide dans un ecoulement diphasique par une methode utilisant des micro-ondes

NASA Astrophysics Data System (ADS)

Pochet, Steven

The measurement of the void fraction is an important parameter in many industrial fields. Whether it is to prevent the phenomenon of critical heat flux in heat tube of thermal power plants, the explosion of gas pockets in oil rigs’ pipes or to detect bubbles in medical catheters, the knowledge of the void fraction can be a key parameter in many diverse applications. Several invasive and non-invasive measurements techniques have been developed these last decades and are based on the difference between the physical properties of liquid and gas. Some of these techniques are not always possible to implement due to restrictions in the geometry of tubes or regulatory standards limiting their use. Throughout this work we propose a new non-invasive void fraction measurement technique based on the reflection of electromagnetic waves on the water-air interface of the mixture. The reflection of electromagnetic wave is induced by a change in the impedance of the propagation medium. The impedance is function of the dielectric properties of the medium. The characteristics of air and water being distinct, it is possible to calculate the complex reflection coefficient at the interface of a double phase mixture. To this end, mathematical modeling of the response of an electromagnetic wave in a tube containing a two phase mixture was made using the model of transmission lines, applicable to microwave frequencies we use. The effects of the amount of air in water and the position of the bubbles in the section of the tube were simulated. It was shown that the phase of the reflected wave was sensitive to the position of bubbles in the tube’s section and that the magnitude of the reflection coefficient varied with the mixture’s void fraction. Subsequently, we designed and built a six-ports reflectometer operating at 2.45 GHz. This system allows the processing and calculation of the reflected wave from the incident wave. A six-ports network, a patch antenna, a wave generator and an amplifier were simulated using HFSS and ADS software. They were then built using the technology of micro-strips on dielectric laminates and the entire system was then calibrated at 6 different frequencies near 2.45 GHz. To this end, we used 4 and 5 loads calibration algorithms that gave us calibrated results with less than 2 % errors. Afterwards, the system was implemented: the antenna was placed tangent to the wall of a vertical tube and connected to the six-ports which was connected to a computer recording and displaying the results in real time. A valve positioned under the tube allows air into the tube and to vary the flow rate. The results showed that the system was sensitive to changes in void fraction from 1% and followed the predictions of the simulated model to a void fraction of about 10%. Possibly du to a change in the structure of the flow for a void fraction of 10%, the signal no longer varies monotonically with respect to the increasing void fraction possibly because of a change in the flow’s configuration. It was shown that the Rayleigh scattering phenomena of air bubbles was involved in the reflection coefficient response. Pictures of the stream at various void fraction state were taken and confirmed a change in the flow’s configuration. By placing a Plexiglas rod to simulate a flow geometry located in the section of the tube, it was noted that the change in phase of the reflected wave was the same as the model when the rod was placed in an empty tube (very few attenuation loss environment). Hence, it is possible to determine the distance of an object in a section of tube from the measurement of the reflected wave’s phase. When the rod is in a very absorbent medium such as water, it is possible to detect a moving rod when it is sufficiently close to the antenna (less than two wavelengths) thanks again to the phase variation. However, detection is still much more difficult due to the absorption of water and can not function effectively for tubes with high diameters compared with the electromagnetic wavelength used.

Comparative analysis of charged particle-induced autosomal mutations in murine cells and tissues

NASA Astrophysics Data System (ADS)

Kronenberg, Amy; Gauny, Stacey; Turker, Mitchell; Dan, Cristian; Kwoh, Ely

Carcinogenesis requires the accumulation of mutations and most of these mutations of occur on autosomes. This study seeks to determine the effect of the tissue microenvironment on the frequency and types of autosomal mutations in epithelial cells exposed to the types of charged particles in space radiation environments. Epithelial cells are the principal cells at risk for the development of solid cancers in humans. Aprt heterozygous mice from a cross between C57BL/6 and DBA/2 mice (B6D2F1) are used for these studies. The tissue of interest here is the kidney. We evaluated the effects of Fe ion on cytotoxicity, mutant frequency, and mutant spectra in kidney epithelium exposed in vivo. In vitro studies use primary kidney clones from B6D2F1 mice. Animals or cells were exposed to graded doses (0-2 Gy) of 1 GeV/amu Fe ions at the NASA Space Radiation Laboratories at Brookhaven National Laboratory. Animals were given whole body exposure in plexiglas holders. Cells were irradiated in T-75 flasks as monolayers. Cytotoxicity for cells exposed as monolayers were performed immediately post-irradiation. In vitro mutation assays were performed after a 5-6 day expression period post-irradiation, at which time cells were seeded in standard medium supplemented with 2,6 diaminopurine to screen for Aprt mutants. Colony formation was assessed in parallel in standard medium. In contrast, mice were euthanized after 2-4 months post-irradiation (early) or 8-10 months post-irradiation (late) to determine the cytotoxic and mutagenic response to Fe ion irradiation. Once the kidneys were digested, the cytotoxicity and mutation assays were performed using the same methodology employed for cells in vitro. Individual Apr t mutant colonies were collected from separate flasks exposed in vitro to 2 Gy of Fe ions. A similar group of Aprt mutants were collected from separate, un-irradiated flasks Aprt mutant colonies were also collected from individual kidneys for un-irradiated mice and for mice exposed to 2 Gy of Fe ions. Mutant spectra were analyzed via PCR using a series of heterozygous markers along mouse chromosome 8. Cytotoxicity assays were performed immediately after Fe ion exposure of cells from two primary clones. Cells irradiated in vitro demonstrated a dose-dependent decrement in cloning efficiency with no evidence of a shoulder. The results demonstrate the two clones behave similarly (unpaired t-test, p>0.3) with a D0 of 84.3 cGy for the combined data set. Mutation data were obtained using cells from one of the primary clones. In three experiments, we observed a linear dose-response for Aprt mutation with an induced mutant frzction of 1.06 x 10-3 /Gy. Kidney epithelial cells irradiated in vivo and incubated for 2-4 months in situ prior to harvest also showed an exponential reduction of cloning efficiency. Cells harvested 8-10 months postirradiation showed evidence of recovery for doses up to 1.5 Gy, but there was no improvement in cloning efficiency for kidney cells exposed to 2 Gy Fe ions in vivo evaluated at the late time point. Results for Aprt mutation induction in vivo indicated considerable inter-animal variation within each dose group (0, 1.0, 1.5 and 2 Gy). Fe ion exposures were mutagenic to the kidney, even at the lowest dose (p<0.01). A comparison of the mutant frequency results at the two harvest times indicates that the dose response did not vary with incubation time in vivo. Analysis of the pooled data from the 2-4 months harvests and the 8-10 month harvests indicated an increase in mutant frequency of 1.49 fold per Gy (p=0.01, CI 1.11-2.01). Molecular analysis of Aprtdeficient cells collected after a 2 Gy exposure to Fe ions in vitro showed an increased proportion of mutants arising via interstitial deletion or mitotic recombination, with an indication of an increase in chromosome loss. Similar results have been obtained for Aprt mutants isolated from mice exposed to 2 Gy of Fe ions, as compared with mutants collected from sham-irradiated mice. Taken together, the results to date demonstrate that Fe ions are mutagenic to mouse kidney epithelium exposed in vitro assayed at short times post-irradiation and they are also mutagenic to kidney epithelium exposed in vivo. While cytotoxicity is somewhat ameliorated in vivo, toxicity was evident at the highest dose up to 8-10 months post-exposure. A comparison of the Aprt mutant frequency analyses (in vitro vs. in vivo) and mutation spectra analyses (in vitro vs. in vivo) reflect similar trends. Supported by NASA grant T-403X to A. Kronenberg.

Motion of Drops on Surfaces with Wettability Gradients

NASA Technical Reports Server (NTRS)

Subramanian, R. Shankar; McLaughlin, John B.; Moumen, Nadjoua; Qian, Dongying

2002-01-01

A liquid drop present on a solid surface can move because of a gradient in wettability along the surface, as manifested by a gradient in the contact angle. The contact angle at a given point on the contact line between a solid and a liquid in a gaseous medium is the angle between the tangent planes to the liquid and the solid surfaces at that point and is measured within the liquid side, by convention. The motion of the drop occurs in the direction of increasing wettability. The cause of the motion is the net force exerted on the drop by the solid surface because of the variation of the contact angle around the periphery. This force causes acceleration of an initially stationary drop, and leads to its motion in the direction of decreasing contact angle. The nature of the motion is determined by the balance between the motivating force and the resisting hydrodynamic force from the solid surface and the surrounding gaseous medium. A wettability gradient can be chemically induced as shown by Chaudhury and Whitesides who provided unambiguous experimental evidence that drops can move in such gradients. The phenomenon can be important in heat transfer applications in low gravity, such as when condensation occurs on a surface. Daniel et al have demonstrated that the velocity of a drop on a surface due to a wettability gradient in the presence of condensation can be more than two orders of magnitude larger than that observed in the absence of condensation. In the present research program, we have begun to study the motion of a drop in a wettability gradient systematically using a model system. Our initial efforts will be restricted to a system in which no condensation occurs. The experiments are performed as follows. First, a rectangular strip of approximate dimensions 10 x 20 mm is cut out of a silicon wafer. The strip is cleaned thoroughly and its surface is exposed to the vapor from an alkylchlorosilane for a period lasting between one and two minutes inside a desiccator. This is done using an approximate line source of the vapor in the form of a string soaked in the alkylchlorosilane. Ordinarily, many fluids, including water, wet the surface of silicon quite well. This means that the contact angle is small. But the silanized surface resists wetting, with contact angles that are as large as 100 degs. Therefore, a gradient of wettability is formed on the silicon surface. The region near the string is highly hydrophobic, and the contact angle decreases gradually toward a small value at the hydrophilic end away from this region. The change in wettability occurs over a distance of several mm. The strip is placed on a platform within a Plexiglas cell. Drops of a suitable liquid are introduced on top of the strip near the hydrophobic end. An optical system attached to a video camera is trained on the drop so that images of the moving drop can be captured on videotape for subsequent analysis. We have performed preliminary experiments with water as well as ethylene glycol drops. Results from these experiments will be presented in the poster. Future plans include the refinement of the experimental system so as to permit images to be recorded from the side as well as the top, and the conduct of a systematic study in which the drop size is varied over a good range. Experiments will be conducted with different fluids so as to obtain the largest possible range of suitably defined Reynolds and Capillary numbers. Also, an effort will be initiated on theoretical modeling of this motion. The challenges in the development of the theoretical description lie in the proper analysis of the region in the vicinity of the contact line, as well as in the free boundary nature of the problem. It is known that continuum models assuming the no slip condition all the way to the contact line fail by predicting that the stress on the solid surface becomes singular as the contact line is approached. One approach for dealing with this issue has been to relax the no-slip boundary condition using the Navier model. Molecular dynamics simulations of the contact line region show that for a non-polar liquid on a solid surface, the no-slip boundary condition is in fact incorrect near the contact line. Furthermore, the same simulations also show that the usual relationship between stress and the rate of deformation breaks down in the vicinity of the contact line. In developing continuum theoretical models of the system, we shall accommodate this knowledge to the extent possible.