Head injury assessment of non-lethal projectile impacts: A combined experimental/computational method.

PubMed

Sahoo, Debasis; Robbe, Cyril; Deck, Caroline; Meyer, Frank; Papy, Alexandre; Willinger, Remy

2016-11-01

The main objective of this study is to develop a methodology to assess this risk based on experimental tests versus numerical predictive head injury simulations. A total of 16 non-lethal projectiles (NLP) impacts were conducted with rigid force plate at three different ranges of impact velocity (120, 72 and 55m/s) and the force/deformation-time data were used for the validation of finite element (FE) NLP. A good accordance between experimental and simulation data were obtained during validation of FE NLP with high correlation value (>0.98) and peak force discrepancy of less than 3%. A state-of-the art finite element head model with enhanced brain and skull material laws and specific head injury criteria was used for numerical computation of NLP impacts. Frontal and lateral FE NLP impacts to the head model at different velocities were performed under LS-DYNA. It is the very first time that the lethality of NLP is assessed by axonal strain computation to predict diffuse axonal injury (DAI) in NLP impacts to head. In case of temporo-parietal impact the min-max risk of DAI is 0-86%. With a velocity above 99.2m/s there is greater than 50% risk of DAI for temporo-parietal impacts. All the medium- and high-velocity impacts are susceptible to skull fracture, with a percentage risk higher than 90%. This study provides tool for a realistic injury (DAI and skull fracture) assessment during NLP impacts to the human head. Copyright © 2016 Elsevier Ltd. All rights reserved.

Practical and adequate approach to modeling light propagation in an adult head with low-scattering regions by use of diffusion theory.

PubMed

Koyama, Tatsuya; Iwasaki, Atsushi; Ogoshi, Yosuke; Okada, Eiji

2005-04-10

A practical and adequate approach to modeling light propagation in an adult head with a low-scattering cerebrospinal fluid (CSF) region by use of diffusion theory was investigated. The diffusion approximation does not hold in a nonscattering or low-scattering regions. The hybrid radiosity-diffusion method was adopted to model the light propagation in the head with a nonscattering region. In the hybrid method the geometry of the nonscattering region is acquired as a priori information. In reality, low-level scattering occurs in the CSF region and may reduce the error caused by the diffusion approximation. The partial optical path length and the spatial sensitivity profile calculated by the finite-element method agree well with those calculated by the Monte Carlo method in the case in which the transport scattering coefficient of the CSF layer is greater than 0.3 mm(-1). Because it is feasible to assume that the transport scattering coefficient of a CSF layer is 0.3 mm(-1), it is practical to adopt diffusion theory to the modeling of light propagation in an adult head as an alternative to the hybrid method.

Practical and adequate approach to modeling light propagation in an adult head with low-scattering regions by use of diffusion theory

NASA Astrophysics Data System (ADS)

Koyama, Tatsuya; Iwasaki, Atsushi; Ogoshi, Yosuke; Okada, Eiji

2005-04-01

A practical and adequate approach to modeling light propagation in an adult head with a low-scattering cerebrospinal fluid (CSF) region by use of diffusion theory was investigated. The diffusion approximation does not hold in a nonscattering or low-scattering regions. The hybrid radiosity-diffusion method was adopted to model the light propagation in the head with a nonscattering region. In the hybrid method the geometry of the nonscattering region is acquired as a priori information. In reality, low-level scattering occurs in the CSF region and may reduce the error caused by the diffusion approximation. The partial optical path length and the spatial sensitivity profile calculated by the finite-element method agree well with those calculated by the Monte Carlo method in the case in which the transport scattering coefficient of the CSF layer is greater than 0.3 mm^-1. Because it is feasible to assume that the transport scattering coefficient of a CSF layer is 0.3 mm^-1, it is practical to adopt diffusion theory to the modeling of light propagation in an adult head as an alternative to the hybrid method.

Simplified realistic human head model for simulating Tumor Treating Fields (TTFields).

PubMed

Wenger, Cornelia; Bomzon, Ze'ev; Salvador, Ricardo; Basser, Peter J; Miranda, Pedro C

2016-08-01

Tumor Treating Fields (TTFields) are alternating electric fields in the intermediate frequency range (100-300 kHz) of low-intensity (1-3 V/cm). TTFields are an anti-mitotic treatment against solid tumors, which are approved for Glioblastoma Multiforme (GBM) patients. These electric fields are induced non-invasively by transducer arrays placed directly on the patient's scalp. Cell culture experiments showed that treatment efficacy is dependent on the induced field intensity. In clinical practice, a software called NovoTalTM uses head measurements to estimate the optimal array placement to maximize the electric field delivery to the tumor. Computational studies predict an increase in the tumor's electric field strength when adapting transducer arrays to its location. Ideally, a personalized head model could be created for each patient, to calculate the electric field distribution for the specific situation. Thus, the optimal transducer layout could be inferred from field calculation rather than distance measurements. Nonetheless, creating realistic head models of patients is time-consuming and often needs user interaction, because automated image segmentation is prone to failure. This study presents a first approach to creating simplified head models consisting of convex hulls of the tissue layers. The model is able to account for anisotropic conductivity in the cortical tissues by using a tensor representation estimated from Diffusion Tensor Imaging. The induced electric field distribution is compared in the simplified and realistic head models. The average field intensities in the brain and tumor are generally slightly higher in the realistic head model, with a maximal ratio of 114% for a simplified model with reasonable layer thicknesses. Thus, the present pipeline is a fast and efficient means towards personalized head models with less complexity involved in characterizing tissue interfaces, while enabling accurate predictions of electric field distribution.

Water Flow Performance of a Superscale Model of the Fastrac Liquid Oxygen Pump

NASA Technical Reports Server (NTRS)

Skelley, Stephen; Zoladz, Thomas

1999-01-01

As part of the National Aeronautics and Space Administration's ongoing effort to lower the cost of access to space, the Marshall Space Flight Center has developed a rocket engine with 60,000 pounds of thrust for use on the Reusable Launch Vehicle technology demonstrator slated for launch in 2000. This gas generator cycle engine, known as the Fastrac engine, uses liquid oxygen and RP-1 for propellants and includes single stage liquid oxygen and RP-1 pumps and a single stage supersonic turbine on a common shaft. The turbopump design effort included the first use and application of new suction capability prediction codes and three-dimensional blade generation codes in an attempt to reduce the turbomachinery design and certification costs typically associated with rocket engine development. To verify the pump's predicted cavitation performance, a water flow test of a superscale model of the Fastrac liquid oxygen pump was conducted to experimentally evaluate the liquid oxygen pump's performance at and around the design point. The water flow test article replicated the flow path of the Fastrac liquid oxygen pump in a 1.582x scale model, including scaled seal clearances for correct leakage flow at a model operating speed of 5000 revolutions per minute. Flow entered the 3-blade axial-flow inducer, transitioned to a shrouded, 6-blade radial impeller, and discharged into a vaneless radial diffuser and collection volute. The test article included approximately 50 total and static pressure measurement locations as well as flush-mounted, high frequency pressure transducers for complete mapping of the pressure environment. The primary objectives of the water flow test were to measure the steady-state and dynamic pressure environment of the liquid oxygen pump versus flow coefficient, suction specific speed, and back face leakage flow rate. Results showed excellent correlation between the predicted and experimentally measured pump head rise at low suction specific speeds. Likewise, only small circumferential variations in steady-state impeller exit and radial diffuser pressure distributions were observed from 80% to 120% of the design flow coefficient, matching the computational predictions and confirming that the integrated design approach has minimized any exit volute-induced distortions. The test article exhibited suction performance trends typically observed in inducer designs with virtually constant head rise with decreasing inlet pressure until complete pump head breakdown. Unfortunately, the net positive suction head at 3% head fall-off occurred far below that predicted at all tested flow coefficients, resulting in a negative net positive suction head margin at the design point in water. Additional testing to map the unsteady pressure environment was conducted and interesting rotating phenomena at the inducer inlet were observed. These rotating phenomena's cell numbers, direction, and speed were correlated with pump operating parameters. The impact of the unsteady phenomena and their corresponding energy losses on the unexpectedly poor pump performance is also discussed.

Non-Gaussian analysis of diffusion weighted imaging in head and neck at 3T: a pilot study in patients with nasopharyngeal carcinoma.

PubMed

Yuan, Jing; Yeung, David Ka Wai; Mok, Greta S P; Bhatia, Kunwar S; Wang, Yi-Xiang J; Ahuja, Anil T; King, Ann D

2014-01-01

To technically investigate the non-Gaussian diffusion of head and neck diffusion weighted imaging (DWI) at 3 Tesla and compare advanced non-Gaussian diffusion models, including diffusion kurtosis imaging (DKI), stretched-exponential model (SEM), intravoxel incoherent motion (IVIM) and statistical model in the patients with nasopharyngeal carcinoma (NPC). After ethics approval was granted, 16 patients with NPC were examined using DWI performed at 3T employing an extended b-value range from 0 to 1500 s/mm(2). DWI signals were fitted to the mono-exponential and non-Gaussian diffusion models on primary tumor, metastatic node, spinal cord and muscle. Non-Gaussian parameter maps were generated and compared to apparent diffusion coefficient (ADC) maps in NPC. Diffusion in NPC exhibited non-Gaussian behavior at the extended b-value range. Non-Gaussian models achieved significantly better fitting of DWI signal than the mono-exponential model. Non-Gaussian diffusion coefficients were substantially different from mono-exponential ADC both in magnitude and histogram distribution. Non-Gaussian diffusivity in head and neck tissues and NPC lesions could be assessed by using non-Gaussian diffusion models. Non-Gaussian DWI analysis may reveal additional tissue properties beyond ADC and holds potentials to be used as a complementary tool for NPC characterization.

Non-Gaussian Analysis of Diffusion Weighted Imaging in Head and Neck at 3T: A Pilot Study in Patients with Nasopharyngeal Carcinoma

PubMed Central

Yuan, Jing; Yeung, David Ka Wai; Mok, Greta S. P.; Bhatia, Kunwar S.; Wang, Yi-Xiang J.; Ahuja, Anil T.; King, Ann D.

2014-01-01

Purpose To technically investigate the non-Gaussian diffusion of head and neck diffusion weighted imaging (DWI) at 3 Tesla and compare advanced non-Gaussian diffusion models, including diffusion kurtosis imaging (DKI), stretched-exponential model (SEM), intravoxel incoherent motion (IVIM) and statistical model in the patients with nasopharyngeal carcinoma (NPC). Materials and Methods After ethics approval was granted, 16 patients with NPC were examined using DWI performed at 3T employing an extended b-value range from 0 to 1500 s/mm2. DWI signals were fitted to the mono-exponential and non-Gaussian diffusion models on primary tumor, metastatic node, spinal cord and muscle. Non-Gaussian parameter maps were generated and compared to apparent diffusion coefficient (ADC) maps in NPC. Results Diffusion in NPC exhibited non-Gaussian behavior at the extended b-value range. Non-Gaussian models achieved significantly better fitting of DWI signal than the mono-exponential model. Non-Gaussian diffusion coefficients were substantially different from mono-exponential ADC both in magnitude and histogram distribution. Conclusion Non-Gaussian diffusivity in head and neck tissues and NPC lesions could be assessed by using non-Gaussian diffusion models. Non-Gaussian DWI analysis may reveal additional tissue properties beyond ADC and holds potentials to be used as a complementary tool for NPC characterization. PMID:24466318

Noncontact diffuse optical assessment of blood flow changes in head and neck free tissue transfer flaps (Conference Presentation)

NASA Astrophysics Data System (ADS)

Huang, Chong; Radabaugh, Jeffrey P.; Aouad, Rony K.; Lin, Yu; Gal, Thomas J.; Patel, Amit B.; Valentino, Joseph; Shang, Yu; Yu, Guoqiang

2016-02-01

Head and neck cancer accounts for 3 to 5% of all cancers in the United States. Primary or salvage surgeries are extensive and often lead to major head and neck defects that require complex reconstructions with local, regional, or free tissue transfer flaps. Knowledge of tissue blood flow (BF) changes after free tissue transfer may enable surgeons to predict the failure of flap thrombosis at an early stage. This study used our recently developed noncontact diffuse correlation spectroscopy to monitor dynamic BF changes in free flaps without getting in contact with the targeted tissue. Eight free flaps were elevated in patients with head and neck cancer; one of the flaps failed. Multiple BF measurements probing the transferred tissue were performed during and post the surgical operation. Postoperative BF values were normalized to the intraoperative baselines (assigning '1') for the calculation of relative BF change (rBF). The rBF changes over the seven successful flaps were 1.89 +/- 0.15, 2.26 +/- 0.13, and 2.43 +/- 0.13 (mean +/- standard error) respectively on postoperative days 2, 4, and 7. These postoperative values were significantly higher than the intraoperative baseline values (p < 0.001), indicating a gradual recovery of flap vascularity after the tissue transfer. By contrast, rBF changes observed from the unsuccessful flap were 1.14 and 1.34 respectively on postoperative days 2 and 4, indicating a less flow recovery. Measurement of BF recovery after flap anastomosis holds the potential to act early to salvage ischemic flaps.

Treatment outcomes of temporal bone osteoradionecrosis.

PubMed

Kammeijer, Quinten; van Spronsen, Erik; Mirck, Piet G B; Dreschler, Wouter A

2015-04-01

To investigate the clinical relevance of the classification systems used for temporal bone osteoradionecrosis (ORN) and to define a treatment protocol for temporal bone ORN. Retrospective case series. Amsterdam, department of otorhinolaryngology and head and neck surgery. Classification of temporal bone ORN was performed through use of clinical data and radiologic imaging. Outcomes of conservative and surgical treatment were investigated and compared for different grades of ORN. Of the 49 ears included in this study, 35 were primarily treated conservatively. At start of conservative treatment, 23 were classified as a localized and 8 as a diffuse form of ORN; 4 could not be classified. There was a significant difference in clinical outcome between the localized and diffuse forms of ORN (χ(2) = 5.862, P = .015), and mastoid air cell destruction on preoperative computed tomography scan was found to be a significant predictor for a negative outcome of conservative treatment (χ(2) = 4.34, P = .037). Fourteen ears with diffuse ORN were primarily treated surgically, and 11 were secondarily treated surgically following a period of conservative treatment. Twenty-two patients were treated with subtotal petrosectomy, of which 20 were cured. Three patients were treated with canal wall down mastoidectomy, and 2 had recurrence of disease. Ramsden's classification system is clinically relevant in predicting conservative treatment outcomes. Mastoid air cell destruction on computed tomography differentiates between the localized and diffuse forms of ORN. Given our results and experience with treating temporal bone ORN, we propose a treatment protocol. © American Academy of Otolaryngology—Head and Neck Surgery Foundation 2015.

Multi-Scale Computational Models for Electrical Brain Stimulation

PubMed Central

Seo, Hyeon; Jun, Sung C.

2017-01-01

Electrical brain stimulation (EBS) is an appealing method to treat neurological disorders. To achieve optimal stimulation effects and a better understanding of the underlying brain mechanisms, neuroscientists have proposed computational modeling studies for a decade. Recently, multi-scale models that combine a volume conductor head model and multi-compartmental models of cortical neurons have been developed to predict stimulation effects on the macroscopic and microscopic levels more precisely. As the need for better computational models continues to increase, we overview here recent multi-scale modeling studies; we focused on approaches that coupled a simplified or high-resolution volume conductor head model and multi-compartmental models of cortical neurons, and constructed realistic fiber models using diffusion tensor imaging (DTI). Further implications for achieving better precision in estimating cellular responses are discussed. PMID:29123476

Intravoxel Incoherent Motion MR Imaging in the Head and Neck: Correlation with Dynamic Contrast-Enhanced MR Imaging and Diffusion-Weighted Imaging.

PubMed

Xu, Xiao Quan; Choi, Young Jun; Sung, Yu Sub; Yoon, Ra Gyoung; Jang, Seung Won; Park, Ji Eun; Heo, Young Jin; Baek, Jung Hwan; Lee, Jeong Hyun

2016-01-01

To investigate the correlation between perfusion- and diffusion-related parameters from intravoxel incoherent motion (IVIM) and those from dynamic contrast-enhanced MR imaging (DCE-MRI) and diffusion-weighted imaging in tumors and normal muscles of the head and neck. We retrospectively enrolled 20 consecutive patients with head and neck tumors with MR imaging performed using a 3T MR scanner. Tissue diffusivity (D), pseudo-diffusion coefficient (D(*)), and perfusion fraction (f) were derived from bi-exponential fitting of IVIM data obtained with 14 different b-values in three orthogonal directions. We investigated the correlation between D, f, and D(*) and model-free parameters from the DCE-MRI (wash-in, Tmax, Emax, initial AUC60, whole AUC) and the apparent diffusion coefficient (ADC) value in the tumor and normal masseter muscle using a whole volume-of-interest approach. Pearson's correlation test was used for statistical analysis. No correlation was found between f or D(*) and any of the parameters from the DCE-MRI in all patients or in patients with squamous cell carcinoma (p > 0.05). The ADC was significantly correlated with D values in the tumors (p < 0.001, r = 0.980) and muscles (p = 0.013, r = 0.542), despite its significantly higher value than D. The difference between ADC and D showed significant correlation with f values in the tumors (p = 0.017, r = 0.528) and muscles (p = 0.003, r = 0.630), but no correlation with D(*) (p > 0.05, respectively). Intravoxel incoherent motion shows no significant correlation with model-free perfusion parameters derived from the DCE-MRI but is feasible for the analysis of diffusivity in both tumors and normal muscles of the head and neck.

Parsing the roles of neck-linker docking and tethered head diffusion in the stepping dynamics of kinesin.

PubMed

Zhang, Zhechun; Goldtzvik, Yonathan; Thirumalai, D

2017-11-14

Kinesin walks processively on microtubules (MTs) in an asymmetric hand-over-hand manner consuming one ATP molecule per 16-nm step. The individual contributions due to docking of the approximately 13-residue neck linker to the leading head (deemed to be the power stroke) and diffusion of the trailing head (TH) that contributes in propelling the motor by 16 nm have not been quantified. We use molecular simulations by creating a coarse-grained model of the MT-kinesin complex, which reproduces the measured stall force as well as the force required to dislodge the motor head from the MT, to show that nearly three-quarters of the step occurs by bidirectional stochastic motion of the TH. However, docking of the neck linker to the leading head constrains the extent of diffusion and minimizes the probability that kinesin takes side steps, implying that both the events are necessary in the motility of kinesin and for the maintenance of processivity. Surprisingly, we find that during a single step, the TH stochastically hops multiple times between the geometrically accessible neighboring sites on the MT before forming a stable interaction with the target binding site with correct orientation between the motor head and the [Formula: see text] tubulin dimer.

Analysis of head impact exposure and brain microstructure response in a season-long application of a jugular vein compression collar: a prospective, neuroimaging investigation in American football

PubMed Central

Myer, Gregory D; Yuan, Weihong; Barber Foss, Kim D; Thomas, Staci; Smith, David; Leach, James; Kiefer, Adam W; Dicesare, Chris; Adams, Janet; Gubanich, Paul J; Kitchen, Katie; Schneider, Daniel K; Braswell, Daniel; Krueger, Darcy; Altaye, Mekibib

2016-01-01

Background Historical approaches to protect the brain from outside the skull (eg, helmets and mouthpieces) have been ineffective in reducing internal injury to the brain that arises from energy absorption during sports-related collisions. We aimed to evaluate the effects of a neck collar, which applies gentle bilateral jugular vein compression, resulting in cerebral venous engorgement to reduce head impact energy absorption during collision. Specifically, we investigated the effect of collar wearing during head impact exposure on brain microstructure integrity following a competitive high school American football season. Methods A prospective longitudinal controlled trial was employed to evaluate the effects of collar wearing (n=32) relative to controls (CTRL; n=30) during one competitive football season (age: 17.04±0.67 years). Impact exposure was collected using helmet sensors and white matter (WM) integrity was quantified based on diffusion tensor imaging (DTI) serving as the primary outcome. Results With similar overall g-forces and total head impact exposure experienced in the two study groups during the season (p>0.05), significant preseason to postseason changes in mean diffusivity, axial diffusivity and radial diffusivity in the WM integrity were noted in the CTRL group (corrected p<0.05) but not in the collar group (p>0.05). The CTRL group demonstrated significantly larger preseason to postseason DTI change in multiple WM regions compared with the collar group (corrected p<0.05). Discussion Reduced WM diffusivity alteration was noted in participants wearing a neck collar after a season of competitive football. Collar wearing may have provided a protective effect against brain microstructural changes after repetitive head impacts. Trial registration number NCT02696200. PMID:27307271

Electrostatically Biased Binding of Kinesin to Microtubules

PubMed Central

Zheng, Wenjun; Alonso, Maria; Huber, Gary; Dlugosz, Maciej; McCammon, J. Andrew; Cross, Robert A.

2011-01-01

The minimum motor domain of kinesin-1 is a single head. Recent evidence suggests that such minimal motor domains generate force by a biased binding mechanism, in which they preferentially select binding sites on the microtubule that lie ahead in the progress direction of the motor. A specific molecular mechanism for biased binding has, however, so far been lacking. Here we use atomistic Brownian dynamics simulations combined with experimental mutagenesis to show that incoming kinesin heads undergo electrostatically guided diffusion-to-capture by microtubules, and that this produces directionally biased binding. Kinesin-1 heads are initially rotated by the electrostatic field so that their tubulin-binding sites face inwards, and then steered towards a plus-endwards binding site. In tethered kinesin dimers, this bias is amplified. A 3-residue sequence (RAK) in kinesin helix alpha-6 is predicted to be important for electrostatic guidance. Real-world mutagenesis of this sequence powerfully influences kinesin-driven microtubule sliding, with one mutant producing a 5-fold acceleration over wild type. We conclude that electrostatic interactions play an important role in the kinesin stepping mechanism, by biasing the diffusional association of kinesin with microtubules. PMID:22140358

Two cases of traumatic head injury mimicking acute encephalopathy with biphasic seizures and late reduced diffusion.

PubMed

Nishiyama, Masahiro; Fujita, Kyoko; Maruyama, Azusa; Nagase, Hiroaki

2014-11-01

Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) presents a distinct clinical course of biphasic seizures and impaired consciousness. These symptoms are followed by reduced diffusion in the subcortical white matter on magnetic resonance imaging that is typically observed between 3 and 9 days after illness onset. Here, we report two cases of traumatic head injury with clinical and radiological features similar to those for AESD. The similarities between our cases and AESD may be useful in understanding the pathogenesis of AESD. Copyright © 2013 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

Comments on the Diffusive Behavior of Two Upwind Schemes

NASA Technical Reports Server (NTRS)

Wood, William A.; Kleb, William L.

1998-01-01

The diffusive characteristics of two upwind schemes, multi-dimensional fluctuation splitting and locally one-dimensional finite volume, are compared for scalar advection-diffusion problems. Algorithms for the two schemes are developed for node-based data representation on median-dual meshes associated with unstructured triangulations in two spatial dimensions. Four model equations are considered: linear advection, non-linear advection, diffusion, and advection-diffusion. Modular coding is employed to isolate the effects of the two approaches for upwind flux evaluation, allowing for head-to-head accuracy and efficiency comparisons. Both the stability of compressive limiters and the amount of artificial diffusion generated by the schemes is found to be grid-orientation dependent, with the fluctuation splitting scheme producing less artificial diffusion than the finite volume scheme. Convergence rates are compared for the combined advection-diffusion problem, with a speedup of 2.5 seen for fluctuation splitting versus finite volume when solved on the same mesh. However, accurate solutions to problems with small diffusion coefficients can be achieved on coarser meshes using fluctuation splitting rather than finite volume, so that when comparing convergence rates to reach a given accuracy, fluctuation splitting shows a speedup of 29 over finite volume.

Diffusion Characteristics of Upwind Schemes on Unstructured Triangulations

NASA Technical Reports Server (NTRS)

Wood, William A.; Kleb, William L.

1998-01-01

The diffusive characteristics of two upwind schemes, multi-dimensional fluctuation splitting and dimensionally-split finite volume, are compared for scalar advection-diffusion problems. Algorithms for the two schemes are developed for node-based data representation on median-dual meshes associated with unstructured triangulations in two spatial dimensions. Four model equations are considered: linear advection, non-linear advection, diffusion, and advection-diffusion. Modular coding is employed to isolate the effects of the two approaches for upwind flux evaluation, allowing for head-to-head accuracy and efficiency comparisons. Both the stability of compressive limiters and the amount of artificial diffusion generated by the schemes is found to be grid-orientation dependent, with the fluctuation splitting scheme producing less artificial diffusion than the dimensionally-split finite volume scheme. Convergence rates are compared for the combined advection-diffusion problem, with a speedup of 2-3 seen for fluctuation splitting versus finite volume when solved on the same mesh. However, accurate solutions to problems with small diffusion coefficients can be achieved on coarser meshes using fluctuation splitting rather than finite volume, so that when comparing convergence rates to reach a given accuracy, fluctuation splitting shows a 20-25 speedup over finite volume.

Noncontact diffuse optical assessment of blood flow changes in head and neck free tissue transfer flaps

NASA Astrophysics Data System (ADS)

Huang, Chong; Radabaugh, Jeffrey P.; Aouad, Rony K.; Lin, Yu; Gal, Thomas J.; Patel, Amit B.; Valentino, Joseph; Shang, Yu; Yu, Guoqiang

2015-07-01

Knowledge of tissue blood flow (BF) changes after free tissue transfer may enable surgeons to predict the failure of flap thrombosis at an early stage. This study used our recently developed noncontact diffuse correlation spectroscopy to monitor dynamic BF changes in free flaps without getting in contact with the targeted tissue. Eight free flaps were elevated in patients with head and neck cancer; one of the flaps failed. Multiple BF measurements probing the transferred tissue were performed during and post the surgical operation. Postoperative BF values were normalized to the intraoperative baselines (assigning "1") for the calculation of relative BF change (rBF). The rBF changes over the seven successful flaps were 1.89±0.15, 2.26±0.13, and 2.43±0.13 (mean±standard error), respectively, on postoperative days 2, 4, and 7. These postoperative values were significantly higher than the intraoperative baseline values (p<0.001), indicating a gradual recovery of flap vascularity after the tissue transfer. By contrast, rBF changes observed from the unsuccessful flaps were 1.14 and 1.34, respectively, on postoperative days 2 and 4, indicating less flow recovery. Measurement of BF recovery after flap anastomosis holds the potential to act early to salvage ischemic flaps.

Cerebral blood flow during paroxysmal EEG activation induced by sleep in patients with complex partial seizures

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

Gozukirmizi, E.; Meyer, J.S.; Okabe, T.

1982-01-01

Cerebral blood flow (CBF) measurements were combined with sleep polysomnography in nine patients with complex partial seizures. Two methods were used: the 133Xe method for measuring regional (rCBF) and the stable xenon CT method for local (LCBF). Compared to nonepileptic subjects, who show diffuse CBF decreases during stages I-II, non-REM sleep onset, patients with complex partial seizures show statistically significant increases in CBF which are maximal in regions where the EEG focus is localized and are predominantly seen in one temporal region but are also propagated to other cerebral areas. Both CBF methods gave comparable results, but greater statistical significancemore » was achieved by stable xenon CT methodology. CBF increases are more diffuse than predicted by EEG paroxysmal activity recorded from scalp electrodes. An advantage of the 133Xe inhalation method was achievement of reliable data despite movement of the head. This was attributed to the use of a helmet which maintained the probes approximated to the scalp. Disadvantages were poor resolution (7 cm3) and two-dimensional information. The advantage of stable xenon CT method is excellent resolution (80 mm3) in three dimensions, but a disadvantage is that movement of the head in patients with seizure disorders may limit satisfactory measurements.« less

Noncontact diffuse optical assessment of blood flow changes in head and neck free tissue transfer flaps

PubMed Central

Huang, Chong; Radabaugh, Jeffrey P.; Aouad, Rony K.; Lin, Yu; Gal, Thomas J.; Patel, Amit B.; Valentino, Joseph; Shang, Yu; Yu, Guoqiang

2015-01-01

Abstract. Knowledge of tissue blood flow (BF) changes after free tissue transfer may enable surgeons to predict the failure of flap thrombosis at an early stage. This study used our recently developed noncontact diffuse correlation spectroscopy to monitor dynamic BF changes in free flaps without getting in contact with the targeted tissue. Eight free flaps were elevated in patients with head and neck cancer; one of the flaps failed. Multiple BF measurements probing the transferred tissue were performed during and post the surgical operation. Postoperative BF values were normalized to the intraoperative baselines (assigning “1”) for the calculation of relative BF change (rBF). The rBF changes over the seven successful flaps were 1.89±0.15, 2.26±0.13, and 2.43±0.13 (mean±standard error), respectively, on postoperative days 2, 4, and 7. These postoperative values were significantly higher than the intraoperative baseline values (p<0.001), indicating a gradual recovery of flap vascularity after the tissue transfer. By contrast, rBF changes observed from the unsuccessful flaps were 1.14 and 1.34, respectively, on postoperative days 2 and 4, indicating less flow recovery. Measurement of BF recovery after flap anastomosis holds the potential to act early to salvage ischemic flaps. PMID:26187444

Stochastic Spectral Analysis for Characterizing Hydraulic Diffusivity in an Alluvial Fan Aquifer with River Stimulus

NASA Astrophysics Data System (ADS)

Wang, Y. L.; Zha, Y.; Yeh, T. C. J.; Wen, J. C.

2015-12-01

Estimation of subsurface hydraulic diffusivity was carried out to understand the characteristics of Zhuoshui River alluvial fan, Taiwan. The fan, an important agricultural and industrial region with high water demand, is located at middle Taiwan with an area of 1800 km2. The prior geo-investigations suggest that the main recharge region of the fan is at an apex along the river. The distribution of soil hydraulic diffusivity was estimated by fusing naturally recurring stimulus provided by river and groundwater head. Specifically, the variance and power spectrum provided by temporal and spatial change of groundwater head in response to river stage variations are analyzed to estimate hydraulic diffusivity distribution. It is found that the hydraulic diffusivity of the fan is at the range from 0.08 to 16 m2/s. The average hydraulic diffusivity at the apex, middle, and tail of the fan along the river is about 0.4, 0.6, and 1.0 m2/s, respectively.

Peripapillary choroidal thickness in healthy controls and patients with focal, diffuse, and sclerotic glaucomatous optic disc damage.

PubMed

Roberts, Kenneth F; Artes, Paul H; O'Leary, Neil; Reis, Alexandre S C; Sharpe, Glen P; Hutchison, Donna M; Chauhan, Balwantray C; Nicolela, Marcelo T

2012-08-01

To examine peripapillary choroidal thickness in healthy controls and in patients with glaucoma who have focal, diffuse, and sclerotic optic disc damage. Healthy controls (n=92) and patients with glaucoma who have focal (n=34), diffuse (n=35), and sclerotic (n=34) optic disc damage were imaged with spectral-domain optical coherence tomography (12° circular scan protocol centered on optic nerve head). Peripapillary choroidal thickness was measured as the distance between the automatically segmented retinal pigment epithelium/Bruch's membrane and the manually outlined interface between the posterior choroid and the anterior border of the sclera in eyes in which the anterior scleral border was visible over more than 85% of the scan circumference. The anterior scleral border was visible in 76 controls (83%) and 89 patients (86%). Peripapillary choroidal thickness in healthy controls decreased linearly with age (-11 μm/decade; P.001; r2=0.16), with a predicted value of 137 μm at age 70 years (95% prediction interval, 62-212 μm). While this value was similar in patients with focal and diffuse optic disc damage (126 and 130 μm, respectively; P=.22 compared with controls), it was approximately 30% lower in patients with sclerotic optic disc damage (96 μm; P.001 compared with controls). The peripapillary choroid of patients with glaucoma who have sclerotic optic disc damage was approximately 25% to 30% thinner compared with that in patients with focal and diffuse optic disc damage and with that in healthy controls. The role of the choroid in the pathophysiology of sclerotic glaucomatous optic disc damage needs further investigation.

Analysis of head impact exposure and brain microstructure response in a season-long application of a jugular vein compression collar: a prospective, neuroimaging investigation in American football.

PubMed

Myer, Gregory D; Yuan, Weihong; Barber Foss, Kim D; Thomas, Staci; Smith, David; Leach, James; Kiefer, Adam W; Dicesare, Chris; Adams, Janet; Gubanich, Paul J; Kitchen, Katie; Schneider, Daniel K; Braswell, Daniel; Krueger, Darcy; Altaye, Mekibib

2016-10-01

Historical approaches to protect the brain from outside the skull (eg, helmets and mouthpieces) have been ineffective in reducing internal injury to the brain that arises from energy absorption during sports-related collisions. We aimed to evaluate the effects of a neck collar, which applies gentle bilateral jugular vein compression, resulting in cerebral venous engorgement to reduce head impact energy absorption during collision. Specifically, we investigated the effect of collar wearing during head impact exposure on brain microstructure integrity following a competitive high school American football season. A prospective longitudinal controlled trial was employed to evaluate the effects of collar wearing (n=32) relative to controls (CTRL; n=30) during one competitive football season (age: 17.04±0.67 years). Impact exposure was collected using helmet sensors and white matter (WM) integrity was quantified based on diffusion tensor imaging (DTI) serving as the primary outcome. With similar overall g-forces and total head impact exposure experienced in the two study groups during the season (p>0.05), significant preseason to postseason changes in mean diffusivity, axial diffusivity and radial diffusivity in the WM integrity were noted in the CTRL group (corrected p<0.05) but not in the collar group (p>0.05). The CTRL group demonstrated significantly larger preseason to postseason DTI change in multiple WM regions compared with the collar group (corrected p<0.05). Reduced WM diffusivity alteration was noted in participants wearing a neck collar after a season of competitive football. Collar wearing may have provided a protective effect against brain microstructural changes after repetitive head impacts. NCT02696200. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Corpus callosum vasculature predicts white matter microstructure abnormalities following pediatric mild traumatic brain injury.

PubMed

Wendel, Kara M; Lee, Jeong Bin; Affeldt, Bethann; Hamer, Mary; Harahap-Carrillo, Indira S; Pardo, Andrea C; Obenaus, Andre

2018-05-09

Emerging data suggest that pediatric traumatic brain injury (TBI) is associated with impaired developmental plasticity and poorer neuropsychological outcomes than adults with similar head injuries. Unlike adult mild TBI (mTBI), the effects of mTBI on white matter (WM) microstructure and vascular supply are not well-understood in the pediatric population. The cerebral vasculature plays an important role providing necessary nutrients and removing waste. To address this critical element, we examined the microstructure of the corpus callosum (CC) following pediatric mTBI using diffusion tensor imaging (DTI), and investigated myelin, oligodendrocytes, and vasculature of WM with immunohistochemistry. We hypothesized that pediatric mTBI leads to abnormal WM microstructure and impacts the vasculature within the CC, and that these alterations to WM vasculature contribute to the long-term altered microstructure. We induced a closed head injury mTBI at postnatal day 14, then at 4, 14, and 60 days post injury (DPI) mice were sacrificed for analysis. We observed persistent changes in apparent diffusion coefficient (ADC) within the ipsilateral CC following mTBI, indicating microstructural changes, but surprisingly changes in myelin and oligodendrocyte densities were minimal. However, vasculature features of the ipsilateral CC such as vessel density, length, and number of junctions were persistently altered following mTBI. Correlative analysis showed a strong inverse relationship between ADC and vessel density at 60 DPI, suggesting increased vessel density following mTBI may restrict WM diffusion characteristics. Our findings suggest that WM vasculature contributes to the long-term microstructural changes within the ipsilateral CC following mTBI.

Estimation of body density based on hydrostatic weighing without head submersion in young Japanese adults.

PubMed

Demura, S; Sato, S; Kitabayashi, T

2006-06-01

This study examined a method of predicting body density based on hydrostatic weighing without head submersion (HWwithoutHS). Donnelly and Sintek (1984) developed a method to predict body density based on hydrostatic weight without head submersion. This method predicts the difference (D) between HWwithoutHS and hydrostatic weight with head submersion (HWwithHS) from anthropometric variables (head length and head width), and then calculates body density using D as a correction factor. We developed several prediction equations to estimate D based on head anthropometry and differences between the sexes, and compared their prediction accuracy with Donnelly and Sintek's equation. Thirty-two males and 32 females aged 17-26 years participated in the study. Multiple linear regression analysis was performed to obtain the prediction equations, and the systematic errors of their predictions were assessed by Bland-Altman plots. The best prediction equations obtained were: Males: D(g) = -164.12X1 - 125.81X2 - 111.03X3 + 100.66X4 + 6488.63, where X1 = head length (cm), X2 = head circumference (cm), X3 = head breadth (cm), X4 = head thickness (cm) (R = 0.858, R2 = 0.737, adjusted R2 = 0.687, standard error of the estimate = 224.1); Females: D(g) = -156.03X1 - 14.03X2 - 38.45X3 - 8.87X4 + 7852.45, where X1 = head circumference (cm), X2 = body mass (g), X3 = head length (cm), X4 = height (cm) (R = 0.913, R2 = 0.833, adjusted R2 = 0.808, standard error of the estimate = 137.7). The effective predictors in these prediction equations differed from those of Donnelly and Sintek's equation, and head circumference and head length were included in both equations. The prediction accuracy was improved by statistically selecting effective predictors. Since we did not assess cross-validity, the equations cannot be used to generalize to other populations, and further investigation is required.

Corseting: a new technique for the management of diffuse venous malformations in the head and neck region.

PubMed

Nair, S C; Chawla, J P; Shroff, S S; Kumar, B; Shah, A

2018-05-19

A new surgical technique of intra-tumoural ligation for the treatment of low-flow vascular malformations in the head and neck region is proposed. Ninety patients with diffuse low-flow vascular malformations diagnosed clinically and/or radiologically were treated surgically with the corset suturing technique. All patient records and clinical photographs were reviewed retrospectively. Significant clinical results were obtained: a reduction of the turnout tumour mass and a return of the regional facial outline was evident within 4 weeks after surgery. Recurrence of the lesion (seen in 10 patients) and transient facial nerve palsy (seen in seven patients) were the main complications. All incisions were placed within the junction lines of cosmetic subunits and skin tension lines of the head and neck. The advantages of this technique over the widely used and popular Popescu technique are discussed. Also, the indications, disadvantages, operative technique, and complications are described. In conclusion, corset suturing was found to be a simple, aesthetic, and cost-effective method of treating diffuse low-flow vascular malformations of the head and neck. Copyright © 2018 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Longitudinal diffusion MRI for treatment response assessment: Preliminary experience using an MRI-guided tri-cobalt 60 radiotherapy system.

PubMed

Yang, Yingli; Cao, Minsong; Sheng, Ke; Gao, Yu; Chen, Allen; Kamrava, Mitch; Lee, Percy; Agazaryan, Nzhde; Lamb, James; Thomas, David; Low, Daniel; Hu, Peng

2016-03-01

To demonstrate the preliminary feasibility of a longitudinal diffusion magnetic resonance imaging (MRI) strategy for assessing patient response to radiotherapy at 0.35 T using an MRI-guided radiotherapy system (ViewRay). Six patients (three head and neck cancer, three sarcoma) who underwent fractionated radiotherapy were enrolled in this study. A 2D multislice spin echo single-shot echo planar imaging diffusion pulse sequence was implemented on the ViewRay system and tested in phantom studies. The same pulse sequence was used to acquire longitudinal diffusion data (every 2-5 fractions) on the six patients throughout the entire course of radiotherapy. The reproducibility of the apparent diffusion coefficient (ADC) measurements was assessed using reference regions and the temporal variations of the tumor ADC values were evaluated. In diffusion phantom studies, the ADC values measured on the ViewRay system matched well with reference ADC values with <5% error for a range of ground truth diffusion coefficients of 0.4-1.1 × 10(-3) mm(2)/s. The remote reference regions (i.e., brainstem in head and neck patients) had consistent ADC values throughout the therapy for all three head and neck patients, indicating acceptable reproducibility of the diffusion imaging sequence. The tumor ADC values changed throughout therapy, with the change differing between patients, ranging from a 40% drop in ADC within the first week of therapy to gradually increasing throughout therapy. For larger tumors, intratumoral heterogeneity was observed. For one sarcoma patient, postradiotherapy biopsy showed less than 10% necrosis score, which correlated with the observed 40% decrease in ADC from the fifth fraction to the eighth treatment fraction. This pilot study demonstrated that longitudinal diffusion MRI is feasible using the 0.35 T ViewRay MRI. Larger patient cohort studies are warranted to correlate the longitudinal diffusion measurements to patient outcomes. Such an approach may enable response-guided adaptive radiotherapy.

Changes in multimodality functional imaging parameters early during chemoradiation predict treatment response in patients with locally advanced head and neck cancer.

PubMed

Wong, Kee H; Panek, Rafal; Dunlop, Alex; Mcquaid, Dualta; Riddell, Angela; Welsh, Liam C; Murray, Iain; Koh, Dow-Mu; Leach, Martin O; Bhide, Shreerang A; Nutting, Christopher M; Oyen, Wim J; Harrington, Kevin J; Newbold, Kate L

2018-05-01

To assess the optimal timing and predictive value of early intra-treatment changes in multimodality functional and molecular imaging (FMI) parameters as biomarkers for clinical remission in patients receiving chemoradiation for head and neck squamous cell carcinoma (HNSCC). Thirty-five patients with stage III-IVb (AJCC 7th edition) HNSCC prospectively underwent 18 F-FDG-PET/CT, and diffusion-weighted (DW), dynamic contrast-enhanced (DCE) and susceptibility-weighted MRI at baseline, week 1 and week 2 of chemoradiation. Patients with evidence of persistent or recurrent disease during follow-up were classed as non-responders. Changes in FMI parameters at week 1 and week 2 were compared between responders and non-responders with the Mann-Whitney U test. The significance threshold was set at a p value of <0.05. There were 27 responders and 8 non-responders. Responders showed a greater reduction in PET-derived tumor total lesion glycolysis (TLG 40% ; p = 0.007) and maximum standardized uptake value (SUV max ; p = 0.034) after week 1 than non-responders but these differences were absent by week 2. In contrast, it was not until week 2 that MRI-derived parameters were able to discriminate between the two groups: larger fractional increases in primary tumor apparent diffusion coefficient (ADC; p < 0.001), volume transfer constant (K trans ; p = 0.012) and interstitial space volume fraction (V e ; p = 0.047) were observed in responders versus non-responders. ADC was the most powerful predictor (∆ >17%, AUC 0.937). Early intra-treatment changes in FDG-PET, DW and DCE MRI-derived parameters are predictive of ultimate response to chemoradiation in HNSCC. However, the optimal timing for assessment with FDG-PET parameters (week 1) differed from MRI parameters (week 2). This highlighted the importance of scanning time points for the design of FMI risk-stratified interventional studies.

Parallel Solver for Diffuse Optical Tomography on Realistic Head Models With Scattering and Clear Regions.

PubMed

Placati, Silvio; Guermandi, Marco; Samore, Andrea; Scarselli, Eleonora Franchi; Guerrieri, Roberto

2016-09-01

Diffuse optical tomography is an imaging technique, based on evaluation of how light propagates within the human head to obtain the functional information about the brain. Precision in reconstructing such an optical properties map is highly affected by the accuracy of the light propagation model implemented, which needs to take into account the presence of clear and scattering tissues. We present a numerical solver based on the radiosity-diffusion model, integrating the anatomical information provided by a structural MRI. The solver is designed to run on parallel heterogeneous platforms based on multiple GPUs and CPUs. We demonstrate how the solver provides a 7 times speed-up over an isotropic-scattered parallel Monte Carlo engine based on a radiative transport equation for a domain composed of 2 million voxels, along with a significant improvement in accuracy. The speed-up greatly increases for larger domains, allowing us to compute the light distribution of a full human head ( ≈ 3 million voxels) in 116 s for the platform used.

Brain injury tolerance limit based on computation of axonal strain.

PubMed

Sahoo, Debasis; Deck, Caroline; Willinger, Rémy

2016-07-01

Traumatic brain injury (TBI) is the leading cause of death and permanent impairment over the last decades. In both the severe and mild TBIs, diffuse axonal injury (DAI) is the most common pathology and leads to axonal degeneration. Computation of axonal strain by using finite element head model in numerical simulation can enlighten the DAI mechanism and help to establish advanced head injury criteria. The main objective of this study is to develop a brain injury criterion based on computation of axonal strain. To achieve the objective a state-of-the-art finite element head model with enhanced brain and skull material laws, was used for numerical computation of real world head trauma. The implementation of new medical imaging data such as, fractional anisotropy and axonal fiber orientation from Diffusion Tensor Imaging (DTI) of 12 healthy patients into the finite element brain model was performed to improve the brain constitutive material law with more efficient heterogeneous anisotropic visco hyper-elastic material law. The brain behavior has been validated in terms of brain deformation against Hardy et al. (2001), Hardy et al. (2007), and in terms of brain pressure against Nahum et al. (1977) and Trosseille et al. (1992) experiments. Verification of model stability has been conducted as well. Further, 109 well-documented TBI cases were simulated and axonal strain computed to derive brain injury tolerance curve. Based on an in-depth statistical analysis of different intra-cerebral parameters (brain axonal strain rate, axonal strain, first principal strain, Von Mises strain, first principal stress, Von Mises stress, CSDM (0.10), CSDM (0.15) and CSDM (0.25)), it was shown that axonal strain was the most appropriate candidate parameter to predict DAI. The proposed brain injury tolerance limit for a 50% risk of DAI has been established at 14.65% of axonal strain. This study provides a key step for a realistic novel injury metric for DAI. Copyright © 2016 Elsevier Ltd. All rights reserved.

Co-Expression of Bmi-1 and Podoplanin Predicts Overall Survival in Patients With Squamous Cell Carcinoma of the Head and Neck Treated With Radio(chemo)therapy

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

Vormittag, Laurenz; Thurnher, Dietmar; Geleff, Silvana

2009-03-01

Purpose: This study was conducted to determine the expression of Bmi-1 and podoplanin in healthy oral mucosa and in untreated tumor tissues samples of patients with squamous cell carcinomas of the head and neck. All patients were treated by primary radio(chemo)therapy. Methods and Materials: The expression of Bmi-1 and podoplanin was immunohistochemically evaluated in 12 normal oral mucosa and 63 tumor specimens and correlated with patients' clinical data. Results: In healthy mucosa expression of Bmi-1 and podoplanin was restricted to the basal cell layer. Expression of both proteins was found in 79% and 86% of our tumor samples, respectively. Inmore » 17 and 8 samples, Bmi-1 and podoplanin were co-expressed at the invasive border or diffuse in the bulk of the tumor, respectively. Univariate analysis showed that the co-expression of Bmi-1 and podoplanin correlated to decreased overall survival (p = 0.044). Moreover, multivariate testing identified high expression of podoplanin (p = 0.044), co-expression of Bmi-1 and podoplanin (p = 0.007) and lack of response to therapy (p < 0.0001) as predictors of shortened overall survival in patients treated with primary radio(chemo)therapy. Conclusions: Bmi-1 and podoplanin are expressed at the invasive front of squamous cell carcinomas of the head and neck. Co-expression of Bmi-1 and podoplanin predicts significantly overall survival of patients treated with primary radio(chemo)therapy.« less

Robust estimation of cerebral hemodynamics in neonates using multilayered diffusion model for normal and oblique incidences

NASA Astrophysics Data System (ADS)

Steinberg, Idan; Harbater, Osnat; Gannot, Israel

2014-07-01

The diffusion approximation is useful for many optical diagnostics modalities, such as near-infrared spectroscopy. However, the simple normal incidence, semi-infinite layer model may prove lacking in estimation of deep-tissue optical properties such as required for monitoring cerebral hemodynamics, especially in neonates. To answer this need, we present an analytical multilayered, oblique incidence diffusion model. Initially, the model equations are derived in vector-matrix form to facilitate fast and simple computation. Then, the spatiotemporal reflectance predicted by the model for a complex neonate head is compared with time-resolved Monte Carlo (TRMC) simulations under a wide range of physiologically feasible parameters. The high accuracy of the multilayer model is demonstrated in that the deviation from TRMC simulations is only a few percent even under the toughest conditions. We then turn to solve the inverse problem and estimate the oxygen saturation of deep brain tissues based on the temporal and spatial behaviors of the reflectance. Results indicate that temporal features of the reflectance are more sensitive to deep-layer optical parameters. The accuracy of estimation is shown to be more accurate and robust than the commonly used single-layer diffusion model. Finally, the limitations of such approaches are discussed thoroughly.

Effect of diffuser vane shape on the performance of a centrifugal compressor stage

NASA Astrophysics Data System (ADS)

Reddy, T. Ch Siva; Ramana Murty, G. V.; Prasad, M. V. S. S. S. M.

2014-04-01

The present paper reports the results of experimental investigations on the effect of diffuser vane shape on the performance of a centrifugal compressor stage. These studies were conducted on the chosen stage having a backward curved impeller of 500 mm tip diameter and 24.5 mm width and its design flow coefficient is ϕd=0.0535. Three different low solidity diffuser vane shapes namely uncambered aerofoil, constant thickness flat plate and circular arc cambered constant thickness plate were chosen as the variants for diffuser vane shape and all the three shapes have the same thickness to chord ratio (t/c=0.1). Flow coefficient, polytropic efficiency, total head coefficient, power coefficient and static pressure recovery coefficient were chosen as the parameters for evaluating the effect of diffuser vane shape on the stage performance. The results show that there is reasonable improvement in stage efficiency and total head coefficient with the use of the chosen diffuser vane shapes as compared to conventional vaneless diffuser. It is also noticed that the aero foil shaped LSD has shown better performance when compared to flat plate and circular arc profiles. The aerofoil vane shape of the diffuser blade is seen to be tolerant over a considerable range of incidence.

Short-term and long-term outcome of athletic closed head injuries.

PubMed

Webbe, Frank M; Barth, Jeffrey T

2003-07-01

The continued development of the sport environment as a laboratory for clinical investigation of mild head injury has greatly advanced the use of neuropsychological assessment in evaluating brain-injured athletes, and tracking their symptoms and recovery in an objective manner. The use of neurocognitive baseline measures has become critical in determining whether a brain-injured athlete has recovered function sufficiently to return to play. The rapid growth of computerized and web-based neurocognitive assessment measures provides an efficient, valid technology to put such testing within the reach of most institutions and organizations that field sport teams. Moreover, the knowledge of the recovery curve following mild head injury in the sport environment can be generalized to the management of MTBI in general clinical environments where baseline measures are unlikely. What we know today is that sideline assessments of severity are not predictive of which athletes will show the most typical 5- to 10-day recovery period and which will report persistent PCS complaints and exhibit impaired neurocognitive performance for an extended time. The research on mechanisms of brain injury in MTBI suggests that unpredictable, diffuse white-matter damage may control much of the variability in functional impairments and recovery duration.

The applicability of a computer model for predicting head injury incurred during actual motor vehicle collisions.

PubMed

Moran, Stephan G; Key, Jason S; McGwin, Gerald; Keeley, Jason W; Davidson, James S; Rue, Loring W

2004-07-01

Head injury is a significant cause of both morbidity and mortality. Motor vehicle collisions (MVCs) are the most common source of head injury in the United States. No studies have conclusively determined the applicability of computer models for accurate prediction of head injuries sustained in actual MVCs. This study sought to determine the applicability of such models for predicting head injuries sustained by MVC occupants. The Crash Injury Research and Engineering Network (CIREN) database was queried for restrained drivers who sustained a head injury. These collisions were modeled using occupant dynamic modeling (MADYMO) software, and head injury scores were generated. The computer-generated head injury scores then were evaluated with respect to the actual head injuries sustained by the occupants to determine the applicability of MADYMO computer modeling for predicting head injury. Five occupants meeting the selection criteria for the study were selected from the CIREN database. The head injury scores generated by MADYMO were lower than expected given the actual injuries sustained. In only one case did the computer analysis predict a head injury of a severity similar to that actually sustained by the occupant. Although computer modeling accurately simulates experimental crash tests, it may not be applicable for predicting head injury in actual MVCs. Many complicating factors surrounding actual MVCs make accurate computer modeling difficult. Future modeling efforts should consider variables such as age of the occupant and should account for a wider variety of crash scenarios.

Diffusion-Weighted Magnetic Resonance Imaging Early After Chemoradiotherapy to Monitor Treatment Response in Head-and-Neck Squamous Cell Carcinoma

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

Vandecaveye, Vincent, E-mail: Vincent.Vandecaveye@uzleuven.be; Dirix, Piet; De Keyzer, Frederik

2012-03-01

Purpose: To evaluate diffusion-weighted imaging (DWI) for assessment of treatment response in head and neck squamous cell carcinoma (HNSCC) three weeks after the end of chemoradiotherapy (CRT). Methods and Materials: Twenty-nine patients with HNSCC underwent magnetic resonance imaging (MRI) prior to and 3 weeks after CRT, including T{sub 2}-weighted and pre- and postcontrast T{sub 1}-weighted sequences and an echo-planar DWI sequence with six b values (0 to 1,000 s/mm{sup 2}), from which the apparent diffusion coefficient (ADC) was calculated. ADC changes 3 weeks posttreatment compared to baseline ( Increment ADC) between responding and nonresponding primary lesions and adenopathies were correlatedmore » with 2 years locoregional control and compared with a Mann-Whitney test. In a blinded manner, the Increment ADC was compared to conventional MRI 3 weeks post-CRT and the routinely implemented CT, on average 3 months post-CRT, which used size-related and morphological criteria. Positive and negative predictive values (PPV and NPV, respectively) were compared between the Increment ADC and anatomical imaging. Results: The Increment ADC of lesions with later tumor recurrence was significantly lower than lesions with complete remission for both primary lesions (-2.3% {+-} 0.3% vs. 80% {+-} 41%; p < 0.0001) and adenopathies (19.9% {+-} 32% vs. 63% {+-} 36%; p = 0.003). The Increment ADC showed a PPV of 89% and an NPV of 100% for primary lesions and a PPV of 70% and an NPV of 96% for adenopathies per neck side. DWI improved PPV and NPV compared to anatomical imaging. Conclusion: DWI with the Increment ADC 3 weeks after concluding CRT for HNSCC allows for early assessment of treatment response.« less

Near-infrared diffuse optical monitoring of cerebral blood flow and oxygenation for the prediction of vasovagal syncope

NASA Astrophysics Data System (ADS)

Cheng, Ran; Shang, Yu; Wang, Siqi; Evans, Joyce M.; Rayapati, Abner; Randall, David C.; Yu, Guoqiang

2014-01-01

Significant drops in arterial blood pressure and cerebral hemodynamics have been previously observed during vasovagal syncope (VVS). Continuous and simultaneous monitoring of these physiological variables during VVS is rare, but critical for determining which variable is the most sensitive parameter to predict VVS. The present study used a novel custom-designed diffuse correlation spectroscopy flow-oximeter and a finger plethysmograph to simultaneously monitor relative changes of cerebral blood flow (rCBF), cerebral oxygenation (i.e., oxygenated/deoxygenated/total hemoglobin concentration: r[HbO2]/r[Hb]/rTHC), and mean arterial pressure (rMAP) during 70 deg head-up tilt (HUT) in 14 healthy adults. Six subjects developed presyncope during HUT. Two-stage physiological responses during HUT were observed in the presyncopal group: slow and small changes in measured variables (i.e., Stage I), followed by rapid and dramatic decreases in rMAP, rCBF, r[HbO2], and rTHC (i.e., Stage II). Compared to other physiological variables, rCBF reached its breakpoint between the two stages earliest and had the largest decrease (76±8%) during presyncope. Our results suggest that rCBF has the best sensitivity for the assessment of VVS. Most importantly, a threshold of ˜50% rCBF decline completely separated the subjects from those without presyncope, suggesting its potential for predicting VVS.

Diffuse axonal injury by assault.

PubMed

Imajo, T; Challener, R C; Roessmann, U

1987-09-01

A case of diffuse axonal injury (DAI) by assault is reported. The majority of DAI cases documented have been due to traffic accidents and some due to falls from height. DAI is caused by angular or rotational acceleration of the victim's head. The condition is common and is the second most important head injury after subdural hematoma with regard to death. Its clinical picture is characterized by immediate and prolonged coma or demented state. Because of the subtle nature of histological changes in DAI, awareness and intentional search for the lesion is essential. The triad of DAI is as follows: focal lesions (hemorrhages and/or lacerations) in the corpus callosum and brain stem, and microscopic demonstration of axonal damage--retraction balls. The concept of DAI will elucidate and enhance the understanding of many head trauma cases.

Bayesian estimation of optical properties of the human head via 3D structural MRI

NASA Astrophysics Data System (ADS)

Barnett, Alexander H.; Culver, Joseph P.; Sorensen, A. Gregory; Dale, Anders M.; Boas, David A.

2003-10-01

Knowledge of the baseline optical properties of the tissues of the human head is essential for absolute cerebral oximetry, and for quantitative studies of brain activation. In this work we numerically model the utility of signals from a small 6-optode time-resolved diffuse optical tomographic apparatus for inferring baseline scattering and absorption coefficients of the scalp, skull and brain, when complete geometric information is available from magnetic resonance imaging (MRI). We use an optical model where MRI-segmented tissues are assumed homogeneous. We introduce a noise model capturing both photon shot noise and forward model numerical accuracy, and use Bayesian inference to predict errorbars and correlations on the measurments. We also sample from the full posterior distribution using Markov chain Monte Carlo. We conclude that ~ 106 detected photons are sufficient to measure the brain"s scattering and absorption to a few percent. We present preliminary results using a fast multi-layer slab model, comparing the case when layer thicknesses are known versus unknown.

Cranial Ultrasound Lesions in the NICU Predict Cerebral Palsy at Age 2 Years in Children Born at Extremely Low Gestational Age

PubMed Central

Kuban, Karl C. K.; Allred, Elizabeth N.; O’Shea, T. Michael; Paneth, Nigel; Pagano, Marcello; Dammann, Olaf; Leviton, Alan; Du Plessis, Adré; Westra, Sjirk J.; Miller, Cindy R.; Bassan, Haim; Krishnamoorthy, Kalpathy; Junewick, Joseph; Olomu, Nicholas; Romano, Elaine; Seibert, Joanna; Engelke, Steve; Karna, Padmani; Batton, Daniel; O’Connor, Sunila E.; Keller, Cecelia E.

2009-01-01

Our prospective cohort study of extremely low gestational age newborns evaluated the association of neonatal head ultrasound abnormalities with cerebral palsy at age 2 years. Cranial ultrasounds in 1053 infants were read with respect to intraventricular hemorrhage, ventriculomegaly, and echolucency, by multiple sonologists. Standardized neurological examinations classified cerebral palsy, and functional impairment was assessed. Forty-four percent with ventriculomegaly and 52% with echolucency developed cerebral palsy. Compared with no ultrasound abnormalities, children with echolucency were 24 times more likely to have quadriparesis and 29 times more likely to have hemiparesis. Children with ventriculomegaly were 17 times more likely to have quadriparesis or hemiparesis. Forty-three percent of children with cerebral palsy had normal head ultrasound. Focal white matter damage (echolucency) and diffuse damage (late ventriculomegaly) are associated with a high probability of cerebral palsy, especially quadriparesis. Nearly half the cerebral palsy identified at 2 years is not preceded by a neonatal brain ultrasound abnormality. PMID:19168819

Bottom head to shell junction assembly for a boiling water nuclear reactor

DOEpatents

Fife, Alex Blair; Ballas, Gary J.

1998-01-01

A bottom head to shell junction assembly which, in one embodiment, includes an annular forging having an integrally formed pump deck and shroud support is described. In the one embodiment, the annular forging also includes a top, cylindrical shaped end configured to be welded to one end of the pressure vessel cylindrical shell and a bottom, conical shaped end configured to be welded to the disk shaped bottom head. Reactor internal pump nozzles also are integrally formed in the annular forging. The nozzles do not include any internal or external projections. Stubs are formed in each nozzle opening to facilitate welding a pump housing to the forging. Also, an upper portion of each nozzle opening is configured to receive a portion of a diffuser coupled to a pump shaft which extends through the nozzle opening. Diffuser openings are formed in the integral pump deck to provide additional support for the pump impellers. The diffuser opening is sized so that a pump impeller can extend at least partially therethrough. The pump impeller is connected to the pump shaft which extends through the nozzle opening.

Bottom head to shell junction assembly for a boiling water nuclear reactor

DOEpatents

Fife, A.B.; Ballas, G.J.

1998-02-24

A bottom head to shell junction assembly which, in one embodiment, includes an annular forging having an integrally formed pump deck and shroud support is described. In the one embodiment, the annular forging also includes a top, cylindrical shaped end configured to be welded to one end of the pressure vessel cylindrical shell and a bottom, conical shaped end configured to be welded to the disk shaped bottom head. Reactor internal pump nozzles also are integrally formed in the annular forging. The nozzles do not include any internal or external projections. Stubs are formed in each nozzle opening to facilitate welding a pump housing to the forging. Also, an upper portion of each nozzle opening is configured to receive a portion of a diffuser coupled to a pump shaft which extends through the nozzle opening. Diffuser openings are formed in the integral pump deck to provide additional support for the pump impellers. The diffuser opening is sized so that a pump impeller can extend at least partially therethrough. The pump impeller is connected to the pump shaft which extends through the nozzle opening. 5 figs.

Three Year RSA Evaluation of Vitamin E Diffused Highly Cross-linked Polyethylene Liners and Cup Stability.

PubMed

Sillesen, Nanna H; Greene, Meridith E; Nebergall, Audrey K; Nielsen, Poul T; Laursen, Mogens B; Troelsen, Anders; Malchau, Henrik

2015-07-01

Vitamin E diffusion into highly cross-linked polyethylene (E-XLPE) is a method for enhancing oxidative stability of acetabular liners. The purpose of this study was to evaluate in vivo penetration of E-XLPE using radiostereometric analysis (RSA). Eighty-four hips were recruited into a prospective 10-year RSA. This is the first evaluation of the multicenter cohort after 3-years. All patients received E-XLPE liners (E1, Biomet) and porous-titanium coated cups (Regenerex, Biomet). There was no difference (P=0.450) in median femoral head penetration into the E-XLPE liners at 3-years comparing cobalt-chrome heads (-0.028mm; inter-quartile range (IQR) - 0.065 to 0.047) with ceramic heads (-0.043mm, IQR - 0.143to0.042). The 3-year follow-up indicates minimal E-XLPE liner penetration regardless of head material and minimal early cup movement. Copyright © 2015 Elsevier Inc. All rights reserved.

Water Flow Performance of a Superscale Model of the Fastrac Liquid Oxygen Pump

NASA Technical Reports Server (NTRS)

Skelley, Stephen; Zoladz, Thomas

2001-01-01

As part of the National Aeronautics and Space Administration's ongoing effort to lower the cost of access to space, the Marshall Space Flight Center has developed a rocket engine with 60,000 pounds of thrust for use on the Reusable Launch Vehicle technology demonstrator slated for launch in 2000. This gas generator cycle engine, known as the Fastrac engine, uses liquid oxygen and RP-1 for propellants and includes single stage liquid oxygen and RP-1 pumps and a single stage supersonic turbine on a common shaft. The turbopump design effort included the first use and application of new suction capability prediction codes and three-dimensional blade generation codes in an attempt to reduce the turbomachinery design and certification costs typically associated with rocket engine development. To verify the pump's predicted cavitation performance, a water flow test of a superscale model of the Fastrac liquid oxygen pump was conducted to experimentally evaluate the liquid oxygen pump's performance at and around the design point. The water flow test article replicated the flow path of the Fastrac liquid oxygen pump in a 1.582x scale model, including scaled seal clearances for correct leakage flow at a model operating speed of 5000 revolutions per minute. Flow entered the 3-blade axial-flow inducer, transitioned to a shrouded, 6- blade radial impeller, and discharged into a vaneless radial diffuser and collection volute. The test article included approximately 50 total and static pressure measurement locations as well as flush-mounted, high frequency pressure transducers for complete mapping of the pressure environment. The primary objectives of the water flow test were to measure the steady-state and dynamic pressure environment of the liquid oxygen pump versus flow coefficient, suction specific speed, and back face leakage flow rate. Initial results showed acceptable correlation between the predicted and experimentally measured pump head rise at low suction specific speeds. Likewise, only small circumferential variations in steady-state were observed from 80% to 120% of the design flow coefficient, matching the computational predictions and confirming that the integrated design approach has minimized any exit volute-induced distortions. The test article exhibited suction performance trends typically observed in inducer designs with virtually constant head rise with decreasing inlet pressure until complete pump head breakdown. Unfortunately, the net positive suction head at 3% head fall-off occurred far below that predicted at all tested flow coefficients, resulting in a negative net positive suction head margin at the design point in water. Additional testing to map the unsteady pressure environment was conducted and cavitation-induced flow disturbances at the inducer inlet were observed. Two distinct disturbances were identified, one rotating and one stationary relative to the fixed frame of reference, while the transition from one regime to the next produced significant effects on the steady state pump performance. The impact of the unsteady phenomena and the corresponding energy losses on the unexpectedly poor pump performance is also discussed.

Combining the Finite Element Method with Structural Connectome-based Analysis for Modeling Neurotrauma: Connectome Neurotrauma Mechanics

PubMed Central

Kraft, Reuben H.; Mckee, Phillip Justin; Dagro, Amy M.; Grafton, Scott T.

2012-01-01

This article presents the integration of brain injury biomechanics and graph theoretical analysis of neuronal connections, or connectomics, to form a neurocomputational model that captures spatiotemporal characteristics of trauma. We relate localized mechanical brain damage predicted from biofidelic finite element simulations of the human head subjected to impact with degradation in the structural connectome for a single individual. The finite element model incorporates various length scales into the full head simulations by including anisotropic constitutive laws informed by diffusion tensor imaging. Coupling between the finite element analysis and network-based tools is established through experimentally-based cellular injury thresholds for white matter regions. Once edges are degraded, graph theoretical measures are computed on the “damaged” network. For a frontal impact, the simulations predict that the temporal and occipital regions undergo the most axonal strain and strain rate at short times (less than 24 hrs), which leads to cellular death initiation, which results in damage that shows dependence on angle of impact and underlying microstructure of brain tissue. The monotonic cellular death relationships predict a spatiotemporal change of structural damage. Interestingly, at 96 hrs post-impact, computations predict no network nodes were completely disconnected from the network, despite significant damage to network edges. At early times () network measures of global and local efficiency were degraded little; however, as time increased to 96 hrs the network properties were significantly reduced. In the future, this computational framework could help inform functional networks from physics-based structural brain biomechanics to obtain not only a biomechanics-based understanding of injury, but also neurophysiological insight. PMID:22915997

Orbital Transfer Vehicle Engine Technology High Velocity Ratio Diffusing Crossover

NASA Technical Reports Server (NTRS)

Lariviere, Brian W.

1992-01-01

High speed, high efficiency head rise multistage pumps require continuous passage diffusing crossovers to effectively convey the pumped fluid from the exit of one impeller to the inlet of the next impeller. On Rocketdyne's Orbital Transfer Vehicle (OTV), the MK49-F, a three stage high pressure liquid hydrogen turbopump, utilizes a 6.23 velocity ratio diffusing crossover. This velocity ratio approaches the diffusion limits for stable and efficient flow over the operating conditions required by the OTV system. The design of the high velocity ratio diffusing crossover was based on advanced analytical techniques anchored by previous tests of stationary two-dimensional diffusers with steady flow. To secure the design and the analytical techniques, tests were required with the unsteady whirling characteristics produced by an impeller. A tester was designed and fabricated using a 2.85 times scale model of the MK49-F turbopumps first stage, including the inducer, impeller, and the diffusing crossover. Water and air tests were completed to evaluate the large scale turbulence, non-uniform velocity, and non-steady velocity on the pump and crossover head and efficiency. Suction performance tests from 80 percent to 124 percent of design flow were completed in water to assess these pump characteristics. Pump and diffuser performance from the water and air tests were compared with the actual MK49-F test data in liquid hydrogen.

Apparent Diffusion Coefficient Histograms of Human Papillomavirus-Positive and Human Papillomavirus-Negative Head and Neck Squamous Cell Carcinoma: Assessment of Tumor Heterogeneity and Comparison with Histopathology.

PubMed

de Perrot, T; Lenoir, V; Domingo Ayllón, M; Dulguerov, N; Pusztaszeri, M; Becker, M

2017-11-01

Head and neck squamous cell carcinoma associated with human papillomavirus infection represents a distinct tumor entity. We hypothesized that diffusion phenotypes based on the histogram analysis of ADC values reflect distinct degrees of tumor heterogeneity in human papillomavirus-positive and human papillomavirus-negative head and neck squamous cell carcinomas. One hundred five consecutive patients (mean age, 64 years; range, 45-87 years) with primary oropharyngeal ( n = 52) and oral cavity ( n = 53) head and neck squamous cell carcinoma underwent MR imaging with anatomic and diffusion-weighted sequences ( b = 0, b = 1000 s/mm 2 , monoexponential ADC calculation). The collected tumor voxels from the contoured ROIs provided histograms from which position, dispersion, and form parameters were computed. Histogram data were correlated with histopathology, p16-immunohistochemistry, and polymerase chain reaction for human papillomavirus DNA. There were 21 human papillomavirus-positive and 84 human papillomavirus-negative head and neck squamous cell carcinomas. At histopathology, human papillomavirus-positive cancers were more often nonkeratinizing (13/21, 62%) than human papillomavirus-negative cancers (19/84, 23%; P = .001), and their mitotic index was higher (71% versus 49%; P = .005). ROI-based mean and median ADCs were significantly lower in human papillomavirus-positive (1014 ± 178 × 10 -6 mm 2 /s and 970 ± 187 × 10 -6 mm 2 /s, respectively) than in human papillomavirus-negative tumors (1184 ± 168 × 10 -6 mm 2 /s and 1161 ± 175 × 10 -6 mm 2 /s, respectively; P < .001), whereas excess kurtosis and skewness were significantly higher in human papillomavirus-positive (1.934 ± 1.386 and 0.923 ± 0.510, respectively) than in human papillomavirus-negative tumors (0.643 ± 0.982 and 0.399 ± 0.516, respectively; P < .001). Human papillomavirus-negative head and neck squamous cell carcinoma had symmetric normally distributed ADC histograms, which corresponded histologically to heterogeneous tumors with variable cellularity, high stromal component, keratin pearls, and necrosis. Human papillomavirus-positive head and neck squamous cell carcinomas had leptokurtic skewed right histograms, which corresponded to homogeneous tumors with back-to-back densely packed cells, scant stromal component, and scattered comedonecrosis. Diffusion phenotypes of human papillomavirus-positive and human papillomavirus-negative head and neck squamous cell carcinomas show significant differences, which reflect their distinct degree of tumor heterogeneity. © 2017 by American Journal of Neuroradiology.

Introducing anisotropic Minkowski functionals and quantitative anisotropy measures for local structure analysis in biomedical imaging

NASA Astrophysics Data System (ADS)

Wismüller, Axel; De, Titas; Lochmüller, Eva; Eckstein, Felix; Nagarajan, Mahesh B.

2013-03-01

The ability of Minkowski Functionals to characterize local structure in different biological tissue types has been demonstrated in a variety of medical image processing tasks. We introduce anisotropic Minkowski Functionals (AMFs) as a novel variant that captures the inherent anisotropy of the underlying gray-level structures. To quantify the anisotropy characterized by our approach, we further introduce a method to compute a quantitative measure motivated by a technique utilized in MR diffusion tensor imaging, namely fractional anisotropy. We showcase the applicability of our method in the research context of characterizing the local structure properties of trabecular bone micro-architecture in the proximal femur as visualized on multi-detector CT. To this end, AMFs were computed locally for each pixel of ROIs extracted from the head, neck and trochanter regions. Fractional anisotropy was then used to quantify the local anisotropy of the trabecular structures found in these ROIs and to compare its distribution in different anatomical regions. Our results suggest a significantly greater concentration of anisotropic trabecular structures in the head and neck regions when compared to the trochanter region (p < 10-4). We also evaluated the ability of such AMFs to predict bone strength in the femoral head of proximal femur specimens obtained from 50 donors. Our results suggest that such AMFs, when used in conjunction with multi-regression models, can outperform more conventional features such as BMD in predicting failure load. We conclude that such anisotropic Minkowski Functionals can capture valuable information regarding directional attributes of local structure, which may be useful in a wide scope of biomedical imaging applications.

Introducing Anisotropic Minkowski Functionals and Quantitative Anisotropy Measures for Local Structure Analysis in Biomedical Imaging

PubMed Central

Wismüller, Axel; De, Titas; Lochmüller, Eva; Eckstein, Felix; Nagarajan, Mahesh B.

2017-01-01

The ability of Minkowski Functionals to characterize local structure in different biological tissue types has been demonstrated in a variety of medical image processing tasks. We introduce anisotropic Minkowski Functionals (AMFs) as a novel variant that captures the inherent anisotropy of the underlying gray-level structures. To quantify the anisotropy characterized by our approach, we further introduce a method to compute a quantitative measure motivated by a technique utilized in MR diffusion tensor imaging, namely fractional anisotropy. We showcase the applicability of our method in the research context of characterizing the local structure properties of trabecular bone micro-architecture in the proximal femur as visualized on multi-detector CT. To this end, AMFs were computed locally for each pixel of ROIs extracted from the head, neck and trochanter regions. Fractional anisotropy was then used to quantify the local anisotropy of the trabecular structures found in these ROIs and to compare its distribution in different anatomical regions. Our results suggest a significantly greater concentration of anisotropic trabecular structures in the head and neck regions when compared to the trochanter region (p < 10−4). We also evaluated the ability of such AMFs to predict bone strength in the femoral head of proximal femur specimens obtained from 50 donors. Our results suggest that such AMFs, when used in conjunction with multi-regression models, can outperform more conventional features such as BMD in predicting failure load. We conclude that such anisotropic Minkowski Functionals can capture valuable information regarding directional attributes of local structure, which may be useful in a wide scope of biomedical imaging applications. PMID:29170580

Modelling and validation of diffuse reflectance of the adult human head for fNIRS: scalp sub-layers definition

NASA Astrophysics Data System (ADS)

Herrera-Vega, Javier; Montero-Hernández, Samuel; Tachtsidis, Ilias; Treviño-Palacios, Carlos G.; Orihuela-Espina, Felipe

2017-11-01

Accurate estimation of brain haemodynamics parameters such as cerebral blood flow and volume as well as oxygen consumption i.e. metabolic rate of oxygen, with funcional near infrared spectroscopy (fNIRS) requires precise characterization of light propagation through head tissues. An anatomically realistic forward model of the human adult head with unprecedented detailed specification of the 5 scalp sublayers to account for blood irrigation in the connective tissue layer is introduced. The full model consists of 9 layers, accounts for optical properties ranging from 750nm to 950nm and has a voxel size of 0.5mm. The whole model is validated comparing the predicted remitted spectra, using Monte Carlo simulations of radiation propagation with 108 photons, against continuous wave (CW) broadband fNIRS experimental data. As the true oxy- and deoxy-hemoglobin concentrations during acquisition are unknown, a genetic algorithm searched for the vector of parameters that generates a modelled spectrum that optimally fits the experimental spectrum. Differences between experimental and model predicted spectra was quantified using the Root mean square error (RMSE). RMSE was 0.071 +/- 0.004, 0.108 +/- 0.018 and 0.235+/-0.015 at 1, 2 and 3cm interoptode distance respectively. The parameter vector of absolute concentrations of haemoglobin species in scalp and cortex retrieved with the genetic algorithm was within histologically plausible ranges. The new model capability to estimate the contribution of the scalp blood flow shall permit incorporating this information to the regularization of the inverse problem for a cleaner reconstruction of brain hemodynamics.

Electrochemical measurement of lateral diffusion coefficients of ubiquinones and plastoquinones of various isoprenoid chain lengths incorporated in model bilayers.

PubMed Central

Marchal, D; Boireau, W; Laval, J M; Moiroux, J; Bourdillon, C

1998-01-01

The long-range diffusion coefficients of isoprenoid quinones in a model of lipid bilayer were determined by a method avoiding fluorescent probe labeling of the molecules. The quinone electron carriers were incorporated in supported dimyristoylphosphatidylcholine layers at physiological molar fractions (<3 mol%). The elaborate bilayer template contained a built-in gold electrode at which the redox molecules solubilized in the bilayer were reduced or oxidized. The lateral diffusion coefficient of a natural quinone like UQ10 or PQ9 was 2.0 +/- 0.4 x 10(-8) cm2 s(-1) at 30 degrees C, two to three times smaller than the diffusion coefficient of a lipid analog in the same artificial bilayer. The lateral mobilities of the oxidized or reduced forms could be determined separately and were found to be identical in the 4-13 pH range. For a series of isoprenoid quinones, UQ2 or PQ2 to UQ10, the diffusion coefficient exhibited a marked dependence on the length of the isoprenoid chain. The data fit very well the quantitative behavior predicted by a continuum fluid model in which the isoprenoid chains are taken as rigid particles moving in the less viscous part of the bilayer and rubbing against the more viscous layers of lipid heads. The present study supports the concept of a homogeneous pool of quinone located in the less viscous region of the bilayer. PMID:9545054

Predicting spread of invasive exotic plants into de-watered reservoirs following dam removal on the Elwha River, Olympic National Park, Washington

USGS Publications Warehouse

Woodward, Andrea; Torgersen, Christian E.; Chenoweth, Joshua; Beirne, Katherine; Acker, Steve

2011-01-01

The National Park Service is planning to start the restoration of the Elwha River ecosystem in Olympic National Park by removing two high head dams beginning in 2011. The potential for dispersal of exotic plants into dewatered reservoirs following dam removal, which would inhibit restoration of native vegetation, is of great concern. We focused on predicting long-distance dispersal of invasive exotic plants rather than diffusive spread because local sources of invasive species have been surveyed. We included the long-distance dispersal vectors: wind, water, birds, beavers, ungulates, and users of roads and trails. Using information about the current distribution of invasive species from two surveys, various geographic information system techniques and models, and statistical methods, we identified high-priority areas for Park staff to treat prior to dam removal, and areas of the dewatered reservoirs at risk after dam removal.

Effective scattering coefficient of the cerebral spinal fluid in adult head models for diffuse optical imaging

NASA Astrophysics Data System (ADS)

Custo, Anna; Wells, William M., III; Barnett, Alex H.; Hillman, Elizabeth M. C.; Boas, David A.

2006-07-01

An efficient computation of the time-dependent forward solution for photon transport in a head model is a key capability for performing accurate inversion for functional diffuse optical imaging of the brain. The diffusion approximation to photon transport is much faster to simulate than the physically correct radiative transport equation (RTE); however, it is commonly assumed that scattering lengths must be much smaller than all system dimensions and all absorption lengths for the approximation to be accurate. Neither of these conditions is satisfied in the cerebrospinal fluid (CSF). Since line-of-sight distances in the CSF are small, of the order of a few millimeters, we explore the idea that the CSF scattering coefficient may be modeled by any value from zero up to the order of the typical inverse line-of-sight distance, or approximately 0.3 mm-1, without significantly altering the calculated detector signals or the partial path lengths relevant for functional measurements. We demonstrate this in detail by using a Monte Carlo simulation of the RTE in a three-dimensional head model based on clinical magnetic resonance imaging data, with realistic optode geometries. Our findings lead us to expect that the diffusion approximation will be valid even in the presence of the CSF, with consequences for faster solution of the inverse problem.

Types of traumatic brain injury and regional cerebral blood flow assessed by 99mTc-HMPAO SPECT.

PubMed

Yamakami, I; Yamaura, A; Isobe, K

1993-01-01

To investigate the relationship between focal and diffuse traumatic brain injury (TBI) and regional cerebral blood flow (rCBF), rCBF changes in the first 24 hours post-trauma were studied in 12 severe head trauma patients using single photon emission computed tomography (SPECT) with 99mtechnetium-hexamethyl propyleneamine oxime. Patients were classified as focal or diffuse TBI based on x-ray computed tomographic (X-CT) findings and neurological signs. In six patients with focal damage, SPECT demonstrated 1) perfusion defect (focal severe ischemia) in the brain region larger than the brain contusion by X-CT, 2) hypoperfusion (focal CBF reduction) in the brain region without abnormality by X-CT, and 3) localized hyperperfusion (focal CBF increase) in the surgically decompressed brain after decompressive craniectomy. Focal damage may be associated with a heterogeneous CBF change by causing various focal CBF derangements. In six patients with diffuse damage, SPECT revealed hypoperfusion in only one patient. Diffuse damage may be associated with a homogeneous CBF change by rarely causing focal CBF derangements. The type of TBI, focal or diffuse, determines the type of CBF change, heterogeneous or homogeneous, in the acute severe head trauma patient.

Interactions of diffuse and focused allogenic recharge in an eogenetic karst aquifer (Florida, USA)

NASA Astrophysics Data System (ADS)

Langston, Abigail L.; Screaton, Elizabeth J.; Martin, Jonathan B.; Bailly-Comte, Vincent

2012-06-01

The karstic upper Floridan aquifer in north-central Florida (USA) is recharged by both diffuse and allogenic recharge. To understand how recharged water moves within the aquifer, water levels and specific conductivities were monitored and slug tests were conducted in wells installed in the aquifer surrounding the Santa Fe River Sink and Rise. Results indicate that diffuse recharge does not mix rapidly within the aquifer but instead flows horizontally. Stratification may be aided by the high matrix porosity of the eogenetic karst aquifer. Purging wells for sample collection perturbed conductivity for several days, reflecting mixing of the stratified water and rendering collection of representative samples difficult. Interpretive numerical simulations suggest that diffuse recharge impacts the intrusion of allogenic water from the conduit by increasing hydraulic head in the surrounding aquifer and thereby reducing influx to the aquifer from the conduit. In turn, the increase of head within the conduits affects flow paths of diffuse recharge by moving newly recharged water vertically as the water table rises and falls. This movement may result in a broad vertical zone of dissolution at the water table above the conduit system, with thinner and more focused water-table dissolution at greater distance from the conduit.

The Role of Diffusion-Weighted Magnetic Resonance Imaging in the Differentiation of Head and Neck Masses.

PubMed

Kanmaz, Lutfi; Karavas, Erdal

2018-05-29

The purpose of this study was to evaluate the value of diffusion-weighted MRI (DW-MRI) in differentiating benign and malignant head and neck masses by comparing their apparent diffusion coefficient (ADC) values. The study included 32 patients with a neck mass >1 cm in diameter who were examined with echo planar DW-MRI. Two different diffusion gradients (b values of b = 0 and b = 1000 s/mm²) were applied. DWI and ADC maps of 32 neck masses in 32 patients were obtained. Mean ADC values of benign and malignant neck lesions were measured and compared statistically. A total of 15 (46.9%) malignant masses and 17 (53.1%) benign masses were determined. Of all the neck masses, the ADC value of cystic masses was the highest and that of lymphomas was the lowest. The mean ADC values of benign and malignant neck masses were 1.57 × 10 -3 mm²/s and 0.90 × 10 -3 mm²/s, respectively. The difference between mean ADC values of benign and malignant neck masses was significant ( p < 0.01). Diffusion-weighted MRI with ADC measurements can be useful in the differential diagnosis of neck masses.

Traumatic Brain Injury as a Cause of Behavior Disorders.

ERIC Educational Resources Information Center

Nordlund, Marcia R.

There is increasing evidence that many children and adolescents who display behavior disorders have sustained a traumatic brain injury. Traumatic brain injury can take the following forms: closed head trauma in which the brain usually suffers diffuse damage; open head injury which usually results in specific focal damage; or internal trauma (e.g.,…

A new model for diffuse brain injury by rotational acceleration: I model, gross appearance, and astrocytosis.

PubMed

Gutierrez, E; Huang, Y; Haglid, K; Bao, F; Hansson, H A; Hamberger, A; Viano, D

2001-03-01

Rapid head rotation is a major cause of brain damage in automobile crashes and falls. This report details a new model for rotational acceleration about the center of mass of the rabbit head. This allows the study of brain injury without translational acceleration of the head. Impact from a pneumatic cylinder was transferred to the skull surface to cause a half-sine peak acceleration of 2.1 x 10(5) rad/s2 and 0.96-ms pulse duration. Extensive subarachnoid hemorrhages and small focal bleedings were observed in the brain tissue. A pronounced reactive astrogliosis was found 8-14 days after trauma, both as networks around the focal hemorrhages and more diffusely in several brain regions. Astrocytosis was prominent in the gray matter of the cerebral cortex, layers II-V, and in the granule cell layer and around the axons of the pyramidal neurons in the hippocampus. The nuclei of cranial nerves, such as the hypoglossal and facial nerves, also showed intense astrocytosis. The new model allows study of brain injuries from head rotation in the absence of translational influences.

Parental determinants of offspring head circumference using a sample of patients attending a government hospital in Lagos, Nigeria.

PubMed

Taiwo, I A; Adeleye, A

2013-01-01

Head circumference at birth is an important neonatal parameter in view of its association with perinatal and postnatal morbidity and mortality. It is an indicator of brain volume and a tool for assessing the development of the central nervous system. Being a complex hereditary trait, predicting baby's head circumference from parental anthropometrics could complement the already existing ultrasonographic method of prediction. To identify the parental anthropometric determinants of baby's head circumference in Lagos, Nigeria, using a sample of patients attending a government hospital. Parental anthropometric parameters were obtained from 250 couples. The baby's head circumference was measured immediately after birth. The data were subjected to multivariate analysis. The parental variables that were most predictive of babies' head circumference were mid-parental weight, maternal height, maternal weight gain during pregnancy and maternal age. Assessment of these parental attributes can complement ultrasonographic data in predicting baby's head circumference for better perinatal outcome.

Direct comparison of the impact of head tracking, reverberation, and individualized head-related transfer functions on the spatial perception of a virtual speech source

NASA Technical Reports Server (NTRS)

Begault, D. R.; Wenzel, E. M.; Anderson, M. R.

2001-01-01

A study of sound localization performance was conducted using headphone-delivered virtual speech stimuli, rendered via HRTF-based acoustic auralization software and hardware, and blocked-meatus HRTF measurements. The independent variables were chosen to evaluate commonly held assumptions in the literature regarding improved localization: inclusion of head tracking, individualized HRTFs, and early and diffuse reflections. Significant effects were found for azimuth and elevation error, reversal rates, and externalization.

Prediction and validation of diffusion coefficients in a model drug delivery system using microsecond atomistic molecular dynamics simulation and vapour sorption analysis.

PubMed

Forrey, Christopher; Saylor, David M; Silverstein, Joshua S; Douglas, Jack F; Davis, Eric M; Elabd, Yossef A

2014-10-14

Diffusion of small to medium sized molecules in polymeric medical device materials underlies a broad range of public health concerns related to unintended leaching from or uptake into implantable medical devices. However, obtaining accurate diffusion coefficients for such systems at physiological temperature represents a formidable challenge, both experimentally and computationally. While molecular dynamics simulation has been used to accurately predict the diffusion coefficients, D, of a handful of gases in various polymers, this success has not been extended to molecules larger than gases, e.g., condensable vapours, liquids, and drugs. We present atomistic molecular dynamics simulation predictions of diffusion in a model drug eluting system that represent a dramatic improvement in accuracy compared to previous simulation predictions for comparable systems. We find that, for simulations of insufficient duration, sub-diffusive dynamics can lead to dramatic over-prediction of D. We present useful metrics for monitoring the extent of sub-diffusive dynamics and explore how these metrics correlate to error in D. We also identify a relationship between diffusion and fast dynamics in our system, which may serve as a means to more rapidly predict diffusion in slowly diffusing systems. Our work provides important precedent and essential insights for utilizing atomistic molecular dynamics simulations to predict diffusion coefficients of small to medium sized molecules in condensed soft matter systems.

Diffusion coefficients in organic-water solutions and comparison with Stokes-Einstein predictions

NASA Astrophysics Data System (ADS)

Evoy, E.; Kamal, S.; Bertram, A. K.

2017-12-01

Diffusion coefficients of organic species in particles containing secondary organic material (SOM) are necessary for predicting the growth and reactivity of these particles in the atmosphere. Previously, the Stokes-Einstein equation combined with viscosity measurements have been used to predict these diffusion coefficients. However, the accuracy of the Stokes-Einstein equation for predicting diffusion coefficients in SOM-water particles has not been quantified. To test the Stokes-Einstein equation, diffusion coefficients of fluorescent organic probe molecules were measured in citric acid-water and sorbitol-water solutions. These solutions were used as proxies for SOM-water particles found in the atmosphere. Measurements were performed as a function of water activity, ranging from 0.26-0.86, and as a function of viscosity ranging from 10-3 to 103 Pa s. Diffusion coefficients were measured using fluorescence recovery after photobleaching. The measured diffusion coefficients were compared with predictions made using the Stokes-Einstein equation combined with literature viscosity data. Within the uncertainties of the measurements, the measured diffusion coefficients agreed with the predicted diffusion coefficients, in all cases.

Mathematical models for optimization of the centrifugal stage of a refrigerating compressor

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

Nuzhdin, A.S.

1987-09-01

The authors describe a general approach to the creating of mathematical models of energy and head losses in the flow part of the centrifugal compressor. The mathematical model of the pressure head and efficiency of a two-section stage proposed in this paper is meant for determining its characteristics for the assigned geometric dimensions and for optimizing by variance calculations. Characteristic points on the plot of velocity distribution over the margin of the vanes of the impeller and the diffuser of the centrifugal stage with a combined diffuser are presented. To assess the reliability of the mathematical model the authors comparedmore » some calculated data with the experimental ones.« less

The puzzle of high heads beneath the West Cumbrian coast, UK: a possible solution

NASA Astrophysics Data System (ADS)

Black, John H.; Barker, John A.

2016-03-01

A region of high heads within the Borrowdale Volcanic Group (BVG; a fractured crystalline rock) beneath the coastal plain of West Cumbria, England (UK), is identified as a possible relic left over by the Late Devensian ice sheet. It was found during investigations in the 1990s. Contemporary modelling work failed to produce a satisfactory explanation of the high heads compatible with the `cold recharge' isotopic signature of the groundwater. This study has reassessed the original hydraulic testing results. By plotting density-adjusted heads versus their depth below the water table in the immediate vicinity of the borehole in which they were measured, a depth profile resembling a `wave' was revealed with a peak value located at 1,100 m depth. The possibility that this wave represents relic heads from the last major ice sheet has been assessed using one-dimensional mathematical analysis based on a poroelastic approach. It is found that a wet-based ice sheet above the West Cumbrian coast was probably thick enough and sufficiently long-lasting to leave such relic heads providing that the hydraulic diffusivity of the BVG is in the order of 10-6 m s-1. Initial assessment 20 years ago of the long-interval slug tests suggested that such low values are not likely. More recent interpretation argues for such low values of hydraulic diffusivity. It is concluded that ice sheet recharge is the most likely cause of the raised heads, that the BVG contains significant patches of very low conductivity rock, and that long-interval single-hole tests should be avoided in fractured crystalline rock.

Effect of bulk modulus on deformation of the brain under rotational accelerations

NASA Astrophysics Data System (ADS)

Ganpule, S.; Daphalapurkar, N. P.; Cetingul, M. P.; Ramesh, K. T.

2018-01-01

Traumatic brain injury such as that developed as a consequence of blast is a complex injury with a broad range of symptoms and disabilities. Computational models of brain biomechanics hold promise for illuminating the mechanics of traumatic brain injury and for developing preventive devices. However, reliable material parameters are needed for models to be predictive. Unfortunately, the properties of human brain tissue are difficult to measure, and the bulk modulus of brain tissue in particular is not well characterized. Thus, a wide range of bulk modulus values are used in computational models of brain biomechanics, spanning up to three orders of magnitude in the differences between values. However, the sensitivity of these variations on computational predictions is not known. In this work, we study the sensitivity of a 3D computational human head model to various bulk modulus values. A subject-specific human head model was constructed from T1-weighted MRI images at 2-mm3 voxel resolution. Diffusion tensor imaging provided data on spatial distribution and orientation of axonal fiber bundles for modeling white matter anisotropy. Non-injurious, full-field brain deformations in a human volunteer were used to assess the simulated predictions. The comparison suggests that a bulk modulus value on the order of GPa gives the best agreement with experimentally measured in vivo deformations in the human brain. Further, simulations of injurious loading suggest that bulk modulus values on the order of GPa provide the closest match with the clinical findings in terms of predicated injured regions and extent of injury.

Facial exposure to ultraviolet radiation: Predicted sun protection effectiveness of various hat styles.

PubMed

Backes, C; Religi, A; Moccozet, L; Vuilleumier, L; Vernez, D; Bulliard, J-L

2018-04-23

Solar ultraviolet radiation (UVR) doses received by individuals are highly influenced by behavioural and environmental factors. This study aimed at quantifying hats' sun protection effectiveness in various exposure conditions, by predicting UVR exposure doses and their anatomical distributions. A well-defined three-dimensional head morphology and four hat styles (a cap, a helmet, a middle- and a wide-brimmed hat) were added to a previously published model. Midday (12:00-14:00) and daily (08:00 - 17:00) seasonal UVR doses were estimated at various facial skin zones, with and without hat-wear, accounting for each UVR component. Protection effectiveness was calculated by the relative reduction of predicted UVR dose, expressed as a predictive protection factor (PPF). The unprotected entire face received 2.5 times higher UVR doses during a summer midday compared to a winter midday (3.3 vs. 1.3 SED) with highest doses received at the nose (6.1 SED). During a cloudless summer day, the lowest mean UVR dose is received by the entire face protected by a wide-brimmed hat (1.7 SED). No hat reached 100% protection at any facial skin zone (PPF max : 76%). Hats' sun protection effectiveness varied highly with environmental conditions and were mainly limited by the high contribution of diffuse UVR, irrespective of hat style. Larger brim sizes afforded greater facial protection than smaller brim sizes except around midday when the sun position is high. Consideration of diffuse and reflected UVR in sun educational messages could improve sun protection effectiveness. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Transcranial magnetic stimulation over the cerebellum delays predictive head movements in the coordination of gaze.

PubMed

Zangemeister, W H; Nagel, M

2001-01-01

We investigated coordinated saccadic eye and head movements following predictive horizontal visual targets at +/- 30 degrees by applying transcranial magnetic stimulation (TMS) over the cerebellum before the start of the gaze movement in 10 young subjects. We found three effects of TMS on eye-head movements: 1. Saccadic latency effect. When stimulation took place shortly before movements commenced (75-25 ms before), significantly shorter latencies were found between predictive target presentation and initiation of saccades. Eye latencies were significantly decreased by 45 ms on average, but head latencies were not. 2. Gaze amplitude effect. Without TMS, for the 60 degrees target amplitudes, head movements usually preceded eye movements, as expected (predictive gaze type 3). With TMS 5-75 ms before the gaze movement, the number of eye movements preceding head movements by 20-50 ms was significantly increased (p < 0.001) and the delay between eye and head movements was reversed (p < 0.001), i.e. we found eye-predictive gaze type 1. 3. Saccadic peak velocity effect. For TMS 5-25 s before the start of head movement, mean peak velocity of synkinetic eye saccades increased by 20-30% up to 600 degrees/s, compared to 350-400 degrees/s without TMS. We conclude that transient functional cerebellar deficits exerted by means of TMS can change the central synkinesis of eye-head coordination, including the preprogramming of the saccadic pulse and step of a coordinated gaze movement.

A 4-channel 3 Tesla phased array receive coil for awake rhesus monkey fMRI and diffusion MRI experiments.

PubMed

Khachaturian, Mark Haig

2010-01-01

Awake monkey fMRI and diffusion MRI combined with conventional neuroscience techniques has the potential to study the structural and functional neural network. The majority of monkey fMRI and diffusion MRI experiments are performed with single coils which suffer from severe EPI distortions which limit resolution. By constructing phased array coils for monkey MRI studies, gains in SNR and anatomical accuracy (i.e., reduction of EPI distortions) can be achieved using parallel imaging. The major challenges associated with constructing phased array coils for monkeys are the variation in head size and space constraints. Here, we apply phased array technology to a 4-channel phased array coil capable of improving the resolution and image quality of full brain awake monkey fMRI and diffusion MRI experiments. The phased array coil is that can adapt to different rhesus monkey head sizes (ages 4-8) and fits in the limited space provided by monkey stereotactic equipment and provides SNR gains in primary visual cortex and anatomical accuracy in conjunction with parallel imaging and improves resolution in fMRI experiments by a factor of 2 (1.25 mm to 1.0 mm isotropic) and diffusion MRI experiments by a factor of 4 (1.5 mm to 0.9 mm isotropic).

A 4-channel 3 Tesla phased array receive coil for awake rhesus monkey fMRI and diffusion MRI experiments

PubMed Central

Khachaturian, Mark Haig

2010-01-01

Awake monkey fMRI and diffusion MRI combined with conventional neuroscience techniques has the potential to study the structural and functional neural network. The majority of monkey fMRI and diffusion MRI experiments are performed with single coils which suffer from severe EPI distortions which limit resolution. By constructing phased array coils for monkey MRI studies, gains in SNR and anatomical accuracy (i.e., reduction of EPI distortions) can be achieved using parallel imaging. The major challenges associated with constructing phased array coils for monkeys are the variation in head size and space constraints. Here, we apply phased array technology to a 4-channel phased array coil capable of improving the resolution and image quality of full brain awake monkey fMRI and diffusion MRI experiments. The phased array coil is that can adapt to different rhesus monkey head sizes (ages 4–8) and fits in the limited space provided by monkey stereotactic equipment and provides SNR gains in primary visual cortex and anatomical accuracy in conjunction with parallel imaging and improves resolution in fMRI experiments by a factor of 2 (1.25 mm to 1.0 mm isotropic) and diffusion MRI experiments by a factor of 4 (1.5 mm to 0.9 mm isotropic). PMID:21243106

Communication: Stiff and soft nano-environments and the "Octopus Effect" are the crux of ionic liquid structural and dynamical heterogeneity

NASA Astrophysics Data System (ADS)

Daly, Ryan P.; Araque, Juan C.; Margulis, Claudio J.

2017-08-01

In a recent set of articles [J. C. Araque et al., J. Phys. Chem. B 119(23), 7015-7029 (2015) and J. C. Araque et al., J. Chem. Phys. 144, 204504 (2016)], we proposed the idea that for small neutral and charged solutes dissolved in ionic liquids, deviation from simple hydrodynamic predictions in translational and rotational dynamics can be explained in terms of diffusion through nano-environments that are stiff (high electrostriction, charge density, and number density) and others that are soft (charge depleted). The current article takes a purely solvent-centric approach in trying to provide molecular detail and intuitive visual understanding of time-dependent local mobility focusing on the most common case of an ionic liquid with well defined polar and apolar nano-domains. We find that at intermediate time scales, apolar regions are fluid, whereas the charge network is much less mobile. Because apolar domains and cationic heads must diffuse as single species, at long time the difference in mobility also necessarily dissipates.

Artificial neural networks: Predicting head CT findings in elderly patients presenting with minor head injury after a fall.

PubMed

Dusenberry, Michael W; Brown, Charles K; Brewer, Kori L

2017-02-01

To construct an artificial neural network (ANN) model that can predict the presence of acute CT findings with both high sensitivity and high specificity when applied to the population of patients≥age 65years who have incurred minor head injury after a fall. An ANN was created in the Python programming language using a population of 514 patients ≥ age 65 years presenting to the ED with minor head injury after a fall. The patient dataset was divided into three parts: 60% for "training", 20% for "cross validation", and 20% for "testing". Sensitivity, specificity, positive and negative predictive values, and accuracy were determined by comparing the model's predictions to the actual correct answers for each patient. On the "cross validation" data, the model attained a sensitivity ("recall") of 100.00%, specificity of 78.95%, PPV ("precision") of 78.95%, NPV of 100.00%, and accuracy of 88.24% in detecting the presence of positive head CTs. On the "test" data, the model attained a sensitivity of 97.78%, specificity of 89.47%, PPV of 88.00%, NPV of 98.08%, and accuracy of 93.14% in detecting the presence of positive head CTs. ANNs show great potential for predicting CT findings in the population of patients ≥ 65 years of age presenting with minor head injury after a fall. As a good first step, the ANN showed comparable sensitivity, predictive values, and accuracy, with a much higher specificity than the existing decision rules in clinical usage for predicting head CTs with acute intracranial findings. Copyright © 2016 Elsevier Inc. All rights reserved.

Linear ground-water flow, flood-wave response program for programmable calculators

USGS Publications Warehouse

Kernodle, John Michael

1978-01-01

Two programs are documented which solve a discretized analytical equation derived to determine head changes at a point in a one-dimensional ground-water flow system. The programs, written for programmable calculators, are in widely divergent but commonly encountered languages and serve to illustrate the adaptability of the linear model to use in situations where access to true computers is not possible or economical. The analytical method assumes a semi-infinite aquifer which is uniform in thickness and hydrologic characteristics, bounded on one side by an impermeable barrier and on the other parallel side by a fully penetrating stream in complete hydraulic connection with the aquifer. Ground-water heads may be calculated for points along a line which is perpendicular to the impermeable barrie and the fully penetrating stream. Head changes at the observation point are dependent on (1) the distance between that point and the impermeable barrier, (2) the distance between the line of stress (the stream) and the impermeable barrier, (3) aquifer diffusivity, (4) time, and (5) head changes along the line of stress. The primary application of the programs is to determine aquifer diffusivity by the flood-wave response technique. (Woodard-USGS)

Chemistry-driven structural alterations in short-term retrieved ceramic-on-metal hip implants: Evidence for in vivo incompatibility between ceramic and metal counterparts.

PubMed

Zhu, Wenliang; Pezzotti, Giuseppe; Boffelli, Marco; Chotanaphuti, Thanainit; Khuangsirikul, Saradej; Sugano, Nobuhiko

2017-08-01

Ceramic-on-metal (CoM) hip implants were reported to experience lower wear rates in vitro as compared to metal-on-metal (MoM) bearings, thus hinting metal-ion release at lower levels in vivo. In this article, we show a spectroscopic study of two short-term retrieval cases of zirconia-toughened alumina (ZTA) femoral heads belonging to CoM hip prostheses, which instead showed poor wear performances in vivo. Metal contamination and abnormally high fractions of tetragonal-to-monoclinic (t→m) polymorphic transformation of the zirconia phase could be found on both ZTA heads, which contrasted with the optimistic predictions of in vitro experiments. At the molecular scale, incorporation of metal ions into the ceramic lattices could be recognized as due to frictionally assisted phenomena occurring at the ceramic surface. Driven by abnormal friction, diffusion of metal ions induced lattice shrinkage in the zirconia phases, while residual stress fields became stored at the surface of the femoral head. Diffusional alterations destabilized the chemistry of the ceramic surface and resulted in an abnormal increase in t→m phase transformation in vivo. Frictionally driven metal transfer to the ceramic lattice thus hinders the in vivo performance of CoM prostheses. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1469-1480, 2017. © 2016 Wiley Periodicals, Inc.

Advantages and limitations of multiple-trait genomic prediction for Fusarium head blight severity in hybrid wheat (Triticum aestivum L.).

PubMed

Schulthess, Albert W; Zhao, Yusheng; Longin, C Friedrich H; Reif, Jochen C

2018-03-01

Predictabilities for wheat hybrids less related to the estimation set were improved by shifting from single- to multiple-trait genomic prediction of Fusarium head blight severity. Breeding for improved Fusarium head blight resistance (FHBr) of wheat is a very laborious and expensive task. FHBr complexity is mainly due to its highly polygenic nature and because FHB severity (FHBs) is greatly influenced by the environment. Associated traits plant height and heading date may provide additional information related to FHBr, but this is ignored in single-trait genomic prediction (STGP). The aim of our study was to explore the benefits in predictabilities of multiple-trait genomic prediction (MTGP) over STGP of target trait FHBs in a population of 1604 wheat hybrids using information on 17,372 single nucleotide polymorphism markers along with indicator traits plant height and heading date. The additive inheritance of FHBs allowed accurate hybrid performance predictions using information on general combining abilities or average performance of both parents without the need of markers. Information on molecular markers and indicator trait(s) improved FHBs predictabilities for hybrids less related to the estimation set. Indicator traits must be observed on the predicted individuals to benefit from MTGP. Magnitudes of genetic and phenotypic correlations along with improvements in predictabilities made plant height a better indicator trait for FHBs than heading date. Thus, MTGP having only plant height as indicator trait already maximized FHBs predictabilities. Provided a good indicator trait was available, MTGP could reduce the impacts of genotype environment [Formula: see text] interaction on STGP for hybrids less related to the estimation set.

Toward real-time diffuse optical tomography: accelerating light propagation modeling employing parallel computing on GPU and CPU

NASA Astrophysics Data System (ADS)

Doulgerakis, Matthaios; Eggebrecht, Adam; Wojtkiewicz, Stanislaw; Culver, Joseph; Dehghani, Hamid

2017-12-01

Parameter recovery in diffuse optical tomography is a computationally expensive algorithm, especially when used for large and complex volumes, as in the case of human brain functional imaging. The modeling of light propagation, also known as the forward problem, is the computational bottleneck of the recovery algorithm, whereby the lack of a real-time solution is impeding practical and clinical applications. The objective of this work is the acceleration of the forward model, within a diffusion approximation-based finite-element modeling framework, employing parallelization to expedite the calculation of light propagation in realistic adult head models. The proposed methodology is applicable for modeling both continuous wave and frequency-domain systems with the results demonstrating a 10-fold speed increase when GPU architectures are available, while maintaining high accuracy. It is shown that, for a very high-resolution finite-element model of the adult human head with ˜600,000 nodes, consisting of heterogeneous layers, light propagation can be calculated at ˜0.25 s/excitation source.

Centrifugal and Axial Pump Design and Off-Design Performance Prediction

NASA Technical Reports Server (NTRS)

Veres, Joseph P.

1995-01-01

A meanline pump-flow modeling method has been developed to provide a fast capability for modeling pumps of cryogenic rocket engines. Based on this method, a meanline pump-flow code PUMPA was written that can predict the performance of pumps at off-design operating conditions, given the loss of the diffusion system at the design point. The design-point rotor efficiency and slip factors are obtained from empirical correlations to rotor-specific speed and geometry. The pump code can model axial, inducer, mixed-flow, and centrifugal pumps and can model multistage pumps in series. The rapid input setup and computer run time for this meanline pump flow code make it an effective analysis and conceptual design tool. The map-generation capabilities of the code provide the information needed for interfacing with a rocket engine system modeling code. The off-design and multistage modeling capabilities of PUMPA permit the user to do parametric design space exploration of candidate pump configurations and to provide head-flow maps for engine system evaluation.

Fluorescence Diffusion in the Presence of Optically Clear Tissues in a Mouse Head Model.

PubMed

Ancora, Daniele; Zacharopoulos, Athanasios; Ripoll, Jorge; Zacharakis, Giannis

2017-05-01

Diffuse Optical Tomography commonly neglects or assumes as insignificant the presence of optically clear regions in biological tissues, estimating their contribution as a small perturbation to light transport. The inaccuracy introduced by this practice is examined in detail in the context of a complete, based on realistic geometry, virtual fluorescence Diffuse Optical Tomography experiment where a mouse head is imaged in the presence of cerebral spinal fluid. Despite the small thickness of such layer, we point out that an error is introduced when neglecting it from the model with possibly reduction in the accuracy of the reconstruction and localization of the fluorescence distribution within the brain. The results obtained in the extensive study presented here suggest that fluorescence diffuse neuroimaging studies can be improved in terms of quantitative and qualitative reconstruction by accurately taking into account optically transparent regions especially in the cases where the reconstruction is aided by the prior knowledge of the structural geometry of the specimen. Thus, this has only recently become an affordable choice, thanks to novel computation paradigms that allow to run Monte Carlo photon propagation on a simple graphic card, hence speeding up the process a thousand folds compared to CPU-based solutions.

The structural basis of moderate disability after traumatic brain damage

PubMed Central

Adams, J; Graham, D; Jennett, B

2001-01-01

The objective was to discover the nature of brain damage in survivors of head injury who are left with moderate disability. Macroscopic and microscopic examination was carried out on the brains of 20 persons who had died long after a head injury that had been treated in a neurosurgical unit. All had become independent but had various disabilities (moderate disability on the Glasgow outcome scale) Most deaths had been sudden, which had led to their referral from forensic pathologists. Post-traumatic epilepsy was a feature in 75%. An intracranial haematoma had been evacuated in 75%, and in 11 of the 15 with epilepsy. Diffuse axonal injury was found in six patients, five of the mildest type (grade 1) and one of grade 2. No patient had diffuse thalamic damage but one had a small focal ischaemic lesion in the thalamus. No patient had severe ischaemic brain damage, but three had moderate lesions which were bilateral in only one. No patient had severe cortical contusions. In conclusion, the dominant lesion was focal damage from an evacuated intracranial haematoma. Severe diffuse damage was not found, with diffuse axonal injury only mild and thalamic damage in only one patient.

 PMID:11561038

A Unified Approach to Diffusion Direction Sensitive Slice Registration and 3-D DTI Reconstruction From Moving Fetal Brain Anatomy

PubMed Central

Fogtmann, Mads; Seshamani, Sharmishtaa; Kroenke, Christopher; Cheng, Xi; Chapman, Teresa; Wilm, Jakob; Rousseau, François

2014-01-01

This paper presents an approach to 3-D diffusion tensor image (DTI) reconstruction from multi-slice diffusion weighted (DW) magnetic resonance imaging acquisitions of the moving fetal brain. Motion scatters the slice measurements in the spatial and spherical diffusion domain with respect to the underlying anatomy. Previous image registration techniques have been described to estimate the between slice fetal head motion, allowing the reconstruction of 3-D a diffusion estimate on a regular grid using interpolation. We propose Approach to Unified Diffusion Sensitive Slice Alignment and Reconstruction (AUDiSSAR) that explicitly formulates a process for diffusion direction sensitive DW-slice-to-DTI-volume alignment. This also incorporates image resolution modeling to iteratively deconvolve the effects of the imaging point spread function using the multiple views provided by thick slices acquired in different anatomical planes. The algorithm is implemented using a multi-resolution iterative scheme and multiple real and synthetic data are used to evaluate the performance of the technique. An accuracy experiment using synthetically created motion data of an adult head and a experiment using synthetic motion added to sedated fetal monkey dataset show a significant improvement in motion-trajectory estimation compared to a state-of-the-art approaches. The performance of the method is then evaluated on challenging but clinically typical in utero fetal scans of four different human cases, showing improved rendition of cortical anatomy and extraction of white matter tracts. While the experimental work focuses on DTI reconstruction (second-order tensor model), the proposed reconstruction framework can employ any 5-D diffusion volume model that can be represented by the spatial parameterizations of an orientation distribution function. PMID:24108711

Temperature Dependence of Nonelectrolyte Permeation across Red Cell Membranes

PubMed Central

Galey, W. R.; Owen, J. D.; Solomon, A. K.

1973-01-01

The temperature dependence of permeation across human red cell membranes has been determined for a series of hydrophilic and lipophilic solutes, including urea and two methyl substituted derivatives, all the straight-chain amides from formamide through valeramide and the two isomers, isobutyramide and isovaleramide. The temperature coefficient for permeation by all the hydrophilic solutes is 12 kcal mol-1 or less, whereas that for all the lipophilic solutes is 19 kcal mol-1 or greater. This difference is consonant with the view that hydrophilic molecules cross the membrane by a path different from that taken by the lipophilic ones. The thermodynamic parameters associated with lipophile permeation have been studied in detail. ΔG is negative for adsorption of lipophilic amides onto an oil-water interface, whereas it is positive for transfer of the polar head from the aqueous medium to bulk lipid solvent. Application of absolute reaction rate theory makes it possible to make a clear distinction between diffusion across the water-red cell membrane interface and diffusion within the membrane. Diffusion coefficients and apparent activation enthalpies and entropies have been computed for each process. Transfer of the polar head from the solvent into the interface is characterized by ΔG ‡ = 0 kcal mol-1 and ΔS ‡ negative, whereas both of these parameters have large positive values for diffusion within the membrane. Diffusion within the membrane is similar to what is expected for diffusion through a highly associated viscous fluid. PMID:4708405

Standardization of Sonographic Lung-to-Head Ratio Measurements in Isolated Congenital Diaphragmatic Hernia: Impact on the Reproducibility and Efficacy to Predict Outcomes.

PubMed

Britto, Ingrid Schwach Werneck; Sananes, Nicolas; Olutoye, Oluyinka O; Cass, Darrell L; Sangi-Haghpeykar, Haleh; Lee, Timothy C; Cassady, Christopher I; Mehollin-Ray, Amy; Welty, Stephen; Fernandes, Caraciolo; Belfort, Michael A; Lee, Wesley; Ruano, Rodrigo

2015-10-01

The purpose of this study was to evaluate the impact of standardization of the lung-to-head ratio measurements in isolated congenital diaphragmatic hernia on prediction of neonatal outcomes and reproducibility. We conducted a retrospective cohort study of 77 cases of isolated congenital diaphragmatic hernia managed in a single center between 2004 and 2012. We compared lung-to-head ratio measurements that were performed prospectively in our institution without standardization to standardized measurements performed according to a defined protocol. The standardized lung-to-head ratio measurements were statistically more accurate than the nonstandardized measurements for predicting neonatal mortality (area under the receiver operating characteristic curve, 0.85 versus 0.732; P = .003). After standardization, there were no statistical differences in accuracy between measurements regardless of whether we considered observed-to-expected values (P > .05). Standardization of the lung-to-head ratio did not improve prediction of the need for extracorporeal membrane oxygenation (P> .05). Both intraoperator and interoperator reproducibility were good for the standardized lung-to-head ratio (intraclass correlation coefficient, 0.98 [95% confidence interval, 0.97-0.99]; bias, 0.02 [limits of agreement, -0.11 to +0.15], respectively). Standardization of lung-to-head ratio measurements improves prediction of neonatal outcomes. Further studies are needed to confirm these results and to assess the utility of standardization of other prognostic parameters.

TADPOLE GALAXIES IN THE HUBBLE ULTRA DEEP FIELD

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

Elmegreen, Bruce G.; Elmegreen, Debra Meloy, E-mail: bge@watson.ibm.co, E-mail: elmegreen@vassar.ed

2010-10-20

Tadpole galaxies have a head-tail shape with a large clump of star formation at the head and a diffuse tail or streak of stars off to one side. We measured the head and tail masses, ages, surface brightnesses, and sizes for 66 tadpoles in the Hubble Ultra Deep Field (UDF) and looked at the distribution of neighbor densities and tadpole orientations with respect to neighbors. The heads have masses of 10{sup 7}-10{sup 8} M{sub sun} and photometric ages of {approx}0.1 Gyr for z {approx} 2. The tails have slightly larger masses than the heads and comparable or slightly older ages.more » The most obvious interpretation of tadpoles as young merger remnants is difficult to verify. They have no enhanced proximity to other resolved galaxies as a class, and the heads, typically <0.2 kpc in diameter, usually have no obvious double-core structure. Another possibility is ram pressure interaction between a gas-rich galaxy and a diffuse cosmological flow. Ram pressure can trigger star formation on one side of a galaxy disk, giving the tadpole shape when viewed edge-on. Ram pressure can also strip away gas from a galaxy and put it into a tail, which then forms new stars and gravitationally drags along old stars with it. Such an effect might have already been observed in the Virgo Cluster. Another possibility is that tadpoles are edge-on disks with large, off-center clumps. Analogous lop-sided star formation in UDF clump clusters is shown.« less

Structure-based molecular simulations reveal the enhancement of biased Brownian motions in single-headed kinesin.

PubMed

Kanada, Ryo; Kuwata, Takeshi; Kenzaki, Hiroo; Takada, Shoji

2013-01-01

Kinesin is a family of molecular motors that move unidirectionally along microtubules (MT) using ATP hydrolysis free energy. In the family, the conventional two-headed kinesin was experimentally characterized to move unidirectionally through "walking" in a hand-over-hand fashion by coordinated motions of the two heads. Interestingly a single-headed kinesin, a truncated KIF1A, still can generate a biased Brownian movement along MT, as observed by in vitro single molecule experiments. Thus, KIF1A must use a different mechanism from the conventional kinesin to achieve the unidirectional motions. Based on the energy landscape view of proteins, for the first time, we conducted a set of molecular simulations of the truncated KIF1A movements over an ATP hydrolysis cycle and found a mechanism exhibiting and enhancing stochastic forward-biased movements in a similar way to those in experiments. First, simulating stand-alone KIF1A, we did not find any biased movements, while we found that KIF1A with a large friction cargo-analog attached to the C-terminus can generate clearly biased Brownian movements upon an ATP hydrolysis cycle. The linked cargo-analog enhanced the detachment of the KIF1A from MT. Once detached, diffusion of the KIF1A head was restricted around the large cargo which was located in front of the head at the time of detachment, thus generating a forward bias of the diffusion. The cargo plays the role of a diffusional anchor, or cane, in KIF1A "walking."

[Correlations of 18F-Fluorodeoxyglucose Positron Emission Tomography/Magnetic Resonance Imaging Parameters with the Pathological Differentiation of Head and Neck Squamous Cell Carcinoma and Their Diagnostic Efficiencies].

PubMed

Dang, Hao Dan; Chen, Yu; Shi, Xiao Hua; Hou, Bo; Xing, Hai Qun; Zhang, Tao; Chen, Xing Ming; Zhang, Zhu Hua; Xue, Hua Dan; Jin, Zheng Yu

2018-04-28

Objective To evaluate the correlation of the positron emission tomography/magnetic resonance imaging (PET/MR) parameters with the pathological differentiation of head and neck squamous cell carcinoma(HNSCC) and the diagnostic efficiencies of PET/MR parameters. Methods Patients with clinical suspicion of HNSCC were included and underwent PET/MR scan. HNSCC was pathologically confirmed in all these patients. The PET/MR examination included PET and MR sequences of diffusion-weighted imaging (DWI) and T2-and T1-weighted imaging. The multiple parameters of PET/MR included the mean values of apparent diffusion coefficient(ADC mean ) and the maximum and mean values of standardized uptake value (SUV max and SUV mean ) were measured and estimated. The correlations of all the parameters and distribution between the different tumor differentiation groups were analyzed. Logistic regression was utilized to build the model as the PET/MR combined parameter for predicting the differentiation by multiple parameters of PET/MR. The receiver operating characteristic curve was calculated for each parameter and the combination. Results Totally 23 patients were included in this study:9 patients (9 males and 0 female) had well-differentiated tumor,with an average age of (61.0±6.8)years;14 cases had moderately-differentiated (n=10) or poorly-differentiated tumors (n=4),with an average age of (62.0±9.1) years. All the patients were males. There was statistical correlation between SUV mean and SUV max (P<0.001);however,ADC mean showed no statistical correlation with SUV max and with SUV mean (P=0.42,P=0.13). ADC mean and SUV mean showed significant difference between well-differentiated group and moderately-poorly-differentiated group (P=0.005,P=0.007). Compared with the individual parameters,the combination of PET/MR parameters with SUV mean and ADC mean had higher efficacy in predicting tumor differentiation,with an area under curve of 0.84. Conclusions The distributions of ADC mean ,SUV max and SUV mean differ among HNSCC with different pathological differentiation. Compared with the individual parameters,the combination of the PET/MR parameters has higher efficiency in predicting tumor differentiation.

Predicting diffusion paths and interface motion in gamma/gamma + beta, Ni-Cr-Al diffusion couples

NASA Technical Reports Server (NTRS)

Nesbitt, J. A.; Heckel, R. W.

1987-01-01

A simplified model has been developed to predict Beta recession and diffusion paths in ternary gamma/gamma + beta diffusion couples (gamma:fcc, beta: NiAl structure). The model was tested by predicting beta recession and diffusion paths for four gamma/gamma + beta, Ni-Cr-Al couples annealed for 100 hours at 1200 C. The model predicted beta recession within 20 percent of that measured for each of the couples. The model also predicted shifts in the concentration of the gamma phase at the gamma/gamma + beta interface within 2 at. pct Al and 6 at. pct Cr of that measured in each of the couples. A qualitative explanation based on simple kinetic and mass balance arguments has been given which demonstrates the necessity for diffusion in the two-phase region of certain gamma/gamma + beta, Ni-Cr-Al couples.

Predictive Compensator Optimization for Head Tracking Lag in Virtual Environments

NASA Technical Reports Server (NTRS)

Adelstein, Barnard D.; Jung, Jae Y.; Ellis, Stephen R.

2001-01-01

We examined the perceptual impact of plant noise parameterization for Kalman Filter predictive compensation of time delays intrinsic to head tracked virtual environments (VEs). Subjects were tested in their ability to discriminate between the VE system's minimum latency and conditions in which artificially added latency was then predictively compensated back to the system minimum. Two head tracking predictors were parameterized off-line according to cost functions that minimized prediction errors in (1) rotation, and (2) rotation projected into translational displacement with emphasis on higher frequency human operator noise. These predictors were compared with a parameterization obtained from the VE literature for cost function (1). Results from 12 subjects showed that both parameterization type and amount of compensated latency affected discrimination. Analysis of the head motion used in the parameterizations and the subsequent discriminability results suggest that higher frequency predictor artifacts are contributory cues for discriminating the presence of predictive compensation.

Diffusion-weighted-preparation (D-prep) MRI as a future extension of SPECT/CT based surgical planning for sentinel node procedures in the head and neck area?

PubMed

Buckle, Tessa; KleinJan, Gijs H; Engelen, Thijs; van den Berg, Nynke S; DeRuiter, Marco C; van der Heide, Uulke; Valdes Olmos, Renato A; Webb, Andrew; van Buchem, Mark A; Balm, Alfons J; van Leeuwen, Fijs W B

2016-09-01

Even when guided by SPECT/CT planning of nodal resection in the head-and-neck area is challenging due to the many critical anatomical structures present within the surgical field. In this study the potential of a (SPECT/)MRI-based surgical planning method was explored. Hereby MRI increases the identification of SNs within clustered lymph nodes (LNs) and vital structures located adjacent to the SN (such as cranial nerve branches). SPECT/CT and pathology reports from 100 head-and-neck melanoma and 40 oral cavity cancer patients were retrospectively assessed for SN locations in levels I-V and degree of nodal clustering. A diffusion-weighted-preparation magnetic resonance neurography (MRN) sequence was used in eight healthy volunteers to detect LNs and peripheral nerves. In 15% of patients clustered nodes were retrospectively shown to be present at the location where the SN was identified on SPECT/CT (level IIA: 37.2%, level IIB: 21.6% and level III: 15.5%). With MRN, improved LN delineation enabled discrimination of individual LNs within a cluster. Uniquely, this MRI technology also provided insight in LN distribution (23.2±4 LNs per subject) and size (range 21-372mm(3)), and enabled non-invasive assessment of anatomical variances in the location of the LNs and facial nerves. Diffusion-weighted-preparation MRN enabled improved delineation of LNs and their surrounding delicate anatomical structures in the areas that most often harbor SNs in the head-and-neck. Based on our findings a combined SPECT/MRI approach is envisioned for future surgical planning of complex SN resections in this region. Copyright © 2016 Elsevier Ltd. All rights reserved.

Migration of the guinea pig sperm membrane protein PH-20 from one localized surface domain to another does not occur by a simple diffusion-trapping mechanism.

PubMed

Cowan, A E; Myles, D G; Koppel, D E

1991-03-01

The redistribution of membrane proteins on the surface of cells is a prevalent feature of differentiation in a variety of cells. In most cases the mechanism responsible for such redistribution is poorly understood. Two potential mechanisms for the redistribution of surface proteins are: (1) passive diffusion coupled with trapping, and (2) active translocation. We have studied the process of membrane protein redistribution for the PH-20 protein of guinea pig sperm, a surface protein required for sperm binding to the egg zona pellucida (P. Primakoff, H. Hyatt, and D. G. Myles (1985). J. Cell Biol. 101, 2239-2244). PH-20 protein is localized to the posterior head plasma menbrane of the mature sperm cell. Following the exocytotic acrosome reaction, PH-20 protein moves into the newly incorporated inner acrosomal membrane (IAM), placing it in a position favorable for a role in binding sperm to the egg zona pellucida (D. G. Myles, and P. Primakoff (1984), J. Cell Biol. 99, 1634-1641). To analyze the mechanistic basis for this protein migration, we have used fluorescence microscopy and digital image processing to characterize PH-20 protein migration in individual cells. PH-20 protein was observed to move against a concentration gradient in the posterior head plasma membrane. This result argues strongly against a model of passive diffusion followed by trapping in the IAM, and instead suggests that an active process serves to concentrate PH-20 protein toward the boundary separating the posterior head and IAM regions. A transient gradient of PH-20 concentration observed in the IAM suggests that once PH-20 protein reaches the IAM, it is freely diffusing. Additionally, we observed that migration of PH-20 protein was calcium dependent.

Accessing the dynamics of end-grafted flexible polymer chains by atomic force-electrochemical microscopy. Theoretical modeling of the approach curves by the elastic bounded diffusion model and Monte Carlo simulations. Evidence for compression-induced lateral chain escape.

PubMed

Abbou, Jeremy; Anne, Agnès; Demaille, Christophe

2006-11-16

The dynamics of a molecular layer of linear poly(ethylene glycol) (PEG) chains of molecular weight 3400, bearing at one end a ferrocene (Fc) label and thiol end-grafted at a low surface coverage onto a gold substrate, is probed using combined atomic force-electrochemical microscopy (AFM-SECM), at the scale of approximately 100 molecules. Force and current approach curves are simultaneously recorded as a force-sensing microelectrode (tip) is inserted within the approximately 10 nm thick, redox labeled, PEG chain layer. Whereas the force approach curve gives access to the structure of the compressed PEG layer, the tip-current, resulting from tip-to-substrate redox cycling of the Fc head of the chain, is controlled by chain dynamics. The elastic bounded diffusion model, which considers the motion of the Fc head as diffusion in a conformational field, complemented by Monte Carlo (MC) simulations, from which the chain conformation can be derived for any degree of confinement, allows the theoretical tip-current approach curve to be calculated. The experimental current approach curve can then be very satisfyingly reproduced by theory, down to a tip-substrate separation of approximately 2 nm, using only one adjustable parameter characterizing the chain dynamics: the effective diffusion coefficient of the chain head. At closer tip-substrate separations, an unpredicted peak is observed in the experimental current approach curve, which is shown to find its origin in a compression-induced escape of the chain from within the narrowing tip-substrate gap. MC simulations provide quantitative support for lateral chain elongation as the escape mechanism.

LOFAR discovery of an ultra-steep radio halo and giant head-tail radio galaxy in Abell 1132

NASA Astrophysics Data System (ADS)

Wilber, A.; Brüggen, M.; Bonafede, A.; Savini, F.; Shimwell, T.; van Weeren, R. J.; Rafferty, D.; Mechev, A. P.; Intema, H.; Andrade-Santos, F.; Clarke, A. O.; Mahony, E. K.; Morganti, R.; Prandoni, I.; Brunetti, G.; Röttgering, H.; Mandal, S.; de Gasperin, F.; Hoeft, M.

2018-01-01

Low-Frequency Array (LOFAR) observations at 144 MHz have revealed large-scale radio sources in the unrelaxed galaxy cluster Abell 1132. The cluster hosts diffuse radio emission on scales of ∼650 kpc near the cluster centre and a head-tail (HT) radio galaxy, extending up to 1 Mpc, south of the cluster centre. The central diffuse radio emission is not seen in NRAO VLA FIRST Survey, Westerbork Northern Sky Survey, nor in C & D array VLA observations at 1.4 GHz, but is detected in our follow-up Giant Meterwave Radio Telescope (GMRT) observations at 325 MHz. Using LOFAR and GMRT data, we determine the spectral index of the central diffuse emission to be α = -1.75 ± 0.19 (S ∝ να). We classify this emission as an ultra-steep spectrum radio halo and discuss the possible implications for the physical origin of radio haloes. The HT radio galaxy shows narrow, collimated emission extending up to 1 Mpc and another 300 kpc of more diffuse, disturbed emission, giving a full projected linear size of 1.3 Mpc - classifying it as a giant radio galaxy (GRG) and making it the longest HT found to date. The head of the GRG coincides with an elliptical galaxy (SDSS J105851.01+564308.5) belonging to Abell 1132. In our LOFAR image, there appears to be a connection between the radio halo and the GRG. The turbulence that may have produced the halo may have also affected the tail of the GRG. In turn, the GRG may have provided seed electrons for the radio halo.

Nanoscopic dynamics in hybrid hydroxyapatite-CTAB composite

NASA Astrophysics Data System (ADS)

Dubey, P. S.; Sharma, V. K.; Mitra, S.; Verma, G.; Hassan, P. A.; Dutta, B.; Johnson, M.; Mukhopadhyay, R.

2017-06-01

Synthetic hydroxyapatite (HAp) is an important material in biomedical engineering due to its excellent biocompatibility and bioactivity. HAp nanoparticles were synthesized by the co-precipitation method using cetyltrimethylammonium bromide (CTAB) micelles as a template and are characterized using x-ray diffraction, electron microscopy, and thermal gravimetric measurements. Transmission electron microscope (TEM) demonstrates the formation of rod-shaped HAp. Dynamics of CTAB in HAp-CTAB composite as studied by using quasielastic neutron scattering (QENS) technique is reported here. HAp-CTAB composite provides an ideal system for studying the dynamics of CTAB micelles without any aqueous media. QENS data indicate that the observed dynamics are reminiscent of localized motions in ionic micellar systems, consisting of segmental and fast torsional motions. Segmental dynamics has been described with a model, in which hydrogen atoms in the alkyl chain undergoes localized translation diffusion and the CH3 unit associated with the head group undergo 3-fold jump rotation. Within this model, the hydrogen atoms in the alkyl chain undergo diffusion within spherical domains having different radii and diffusivities. A simple linear distribution of the radius and diffusivity has been assumed, in which the CH2 unit nearest to the head group has the least value and the ones furthest from the head group, that is, at the end of the alkyl chain has the largest value. The fast torsional motion is described by a 2-fold jump rotation model. Quantitative estimate of the different parameters characterizing various dynamical motions active within the time scale of the instrument is also presented. We have provided a detailed description of the observed dynamical features in hybrid HAp-CTAB composite, a potential candidate for biomedical applications.

The Influence of Preferential Flow on Pressure Propagation and Landslide Triggering of the Rocca Pitigliana Landslide

NASA Astrophysics Data System (ADS)

Shao, W.; Bogaard, T.; Bakker, M.; Berti, M.; Savenije, H. H. G.

2016-12-01

The fast pore water pressure response to rain events is an important triggering factor for slope instability. The fast pressure response may be caused by preferential flow that bypasses the soil matrix. Currently, most of the hydro-mechanical models simulate pore water pressure using a single-permeability model, which cannot quantify the effects of preferential flow on pressure propagation and landslide triggering. Previous studies showed that a model based on the linear-diffusion equation can simulate the fast pressure propagation in near-saturated landslides such as the Rocca Pitigliana landslide. In such a model, the diffusion coefficient depends on the degree of saturation, which makes it difficult to use the model for predictions. In this study, the influence of preferential flow on pressure propagation and slope stability is investigated with a 1D dual-permeability model coupled with an infinite-slope stability approach. The dual-permeability model uses two modified Darcy-Richards equations to simultaneously simulate the matrix flow and preferential flow in hillslopes. The simulated pressure head is used in an infinite-slope stability analysis to identify the influence of preferential flow on the fast pressure response and landslide triggering. The dual-permeability model simulates the height and arrival of the pressure peak reasonably well. Performance of the dual-permeability model is as good as or better than the linear-diffusion model even though the dual-permeability model is calibrated for two single pulse rain events only, while the linear-diffusion model is calibrated for each rain event separately.

Brain-water diffusion coefficients reflect the severity of inherited prion disease

PubMed Central

Hyare, H.; Wroe, S.; Siddique, D.; Webb, T.; Fox, N. C.; Stevens, J.; Collinge, J.; Yousry, T.; Thornton, J. S.

2010-01-01

Objective: Inherited prion diseases are progressive neurodegenerative conditions, characterized by cerebral spongiosis, gliosis, and neuronal loss, caused by mutations within the prion protein (PRNP) gene. We wished to assess the potential of diffusion-weighted MRI as a biomarker of disease severity in inherited prion diseases. Methods: Twenty-five subjects (mean age 45.2 years) with a known PRNP mutation including 19 symptomatic patients, 6 gene-positive asymptomatic subjects, and 7 controls (mean age 54.1 years) underwent conventional and diffusion-weighted MRI. An index of normalized brain volume (NBV) and region of interest (ROI) mean apparent diffusion coefficient (ADC) for the head of caudate, putamen, and pulvinar nuclei were recorded. ADC histograms were computed for whole brain (WB) and gray matter (GM) tissue fractions. Clinical assessment utilized standardized clinical scores. Mann-Whitney U test and regression analyses were performed. Results: Symptomatic patients exhibited an increased WB mean ADC (p = 0.006) and GM mean ADC (p = 0.024) compared to controls. Decreased NBV and increased mean ADC measures significantly correlated with clinical measures of disease severity. Using a stepwise multivariate regression procedure, GM mean ADC was an independent predictor of Clinician's Dementia Rating score (p = 0.001), Barthel Index of activities of daily living (p = 0.001), and Rankin disability score (p = 0.019). Conclusions: Brain volume loss in inherited prion diseases is accompanied by increased cerebral apparent diffusion coefficient (ADC), correlating with increased disease severity. The association between gray matter ADC and clinical neurologic status suggests this measure may prove a useful biomarker of disease activity in inherited prion diseases. GLOSSARY ADAS-Cog = Alzheimer's Disease Assessment Scale–Cognitive subscale; ADC = apparent diffusion coefficient; ADL = Barthel Activities of Daily Living scale; BET = brain extraction tool; BPRS = Brief Psychiatric Rating Scale; BSE = bovine spongiform encephalopathy; CDR = Clinician's Dementia Rating Scale; CGIS = Clinician's Global Impression of Disease; CI = confidence interval; DWI = diffusion-weighted imaging; FLAIR = fluid-attenuated inversion recovery; FOV = field of view; GM = gray matter; LC = left head of caudate; LP = left putamen; LPu = left pulvinar; MMSE = Mini-Mental State Examination; NBV = normalized brain volume; PH = peak height; PL = peak location; RC = right head of caudate; RP = right putamen; RPu = right pulvinar; ROI = region of interest; sCJD = sporadic Creutzfeldt-Jakob disease; TE = echo time; TI = inversion time; TR = repetition time; vCJD = variant Creutzfeldt-Jakob disease; WB = whole brain; WM = white matter. PMID:20177119

Catastrophic head injuries in high school and college football players.

PubMed

Boden, Barry P; Tacchetti, Robin L; Cantu, Robert C; Knowles, Sarah B; Mueller, Frederick O

2007-07-01

Catastrophic head injuries in football are rare but tragic events. To update the profile of catastrophic head injuries in high school and college football players and to describe relevant risk factors. Case series; Level of evidence, 4. We reviewed 94 incidents of severe football head injuries reported to the National Center for Catastrophic Sports Injury Research during 13 academic years (September 1989 through June 2002). In the study period there were an average of 7.23 (standard deviation = 2.05) direct high school and college catastrophic head injuries in scholastic football participants per year. There were 0.67 injuries per 100 000 (95% confidence interval: 0.54, 0.81 per 100 000) high school and 0.21 injuries per 100 000 (95% confidence interval: 0.0, 0.49 per 100 000) college participants for a risk ratio of 3.28 (95% confidence interval: 0.81, 13.3). The injuries resulted in subdural hematoma in 75 athletes, subdural hematoma with diffuse brain edema in 10 athletes, diffuse brain edema in 5 athletes, and arteriovenous malformation or aneurysm in 4 athletes. Fifty-nine percent of the contacts reported that the athlete had a history of a previous head injury, of which 71% occurred within the same season as the catastrophic event. Thirty-nine percent of the athletes (21 of 54) were playing with residual neurologic symptoms from the prior head injury. There were 8 (9%) deaths as a result of the injury, 46 (51%) permanent neurologic injuries, and 36 (40%) serious injuries with full recovery. Most players sustained a major impact to the head either from tackling or being tackled. The incidence of catastrophic head injuries in football has remained low since the advent of the modern day football helmet in the early 1970s. The incidence of catastrophic head injuries in football is dramatically higher at the high school level than at the college level. Although the reason for this discrepancy is unclear, an unacceptably high percentage of high school players were playing with residual symptoms from a prior head injury. Coaches, athletes, athletic trainers, and medical personnel need to adhere to the guideline that an athlete with any neurologic symptoms from a head injury should be strongly discouraged from returning to play.

Focal traumatic brain stem injury is a rare type of head injury resulting from assault: a forensic neuropathological study.

PubMed

Al-Sarraj, Safa; Fegan-Earl, Ashley; Ugbade, Antonia; Bodi, Istvan; Chapman, Rob; Poole, Simon; Swift, Ben; Jerreat, Peter; Cary, Nat

2012-04-01

Brainstem haemorrhage is common in cases of head injury when it is associated with space-occupying lesion and increases in the intracranial pressure (duret haemorrhage), in cases of diffuse axonal injury (in dorso-lateral quadrant) and diffuses vascular injury (in the periventricular tissue). However focal traumatic brainstem injury is rare. We identified 12 cases of focal traumatic brainstem injury from review of 319 case of head injury. The head trauma had been caused by different mechanisms of complex fall from height and assault. 10/12 are associated with skull fracture, 11/12 with contre coup contusions in the frontal and temporal lobes, 5/12 direct contusions to cerebellum, 5/12 haemorrhage in corpus callosum and 2/11 have gliding contusions. None of the cases had pathological evidence of increase in the intracranial pressure. The bleeding in the pons was at the edge in 2/12 and cross the section in 10/12. The majority of patients were unconscious immediately after the incident (10/12) and 9/12 died within one day. Focal traumatic brainstem injury occurs most likely due to direct impact at the back of the head or stretching forces affecting the brainstem in cases of complex fall from height and after assault, particularly those associated with kicks. It is a serious and commonly fatal brain damage, which needed to be differentiated from other causes of brainstem haemorrhages. Copyright © 2012 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.

Correlating steric hydration forces with water dynamics through surface force and diffusion NMR measurements in a lipid–DMSO–H2O system

PubMed Central

Schrader, Alex M.; Donaldson, Stephen H.; Song, Jinsuk; Cheng, Chi-Yuan; Lee, Dong Woog; Han, Songi; Israelachvili, Jacob N.

2015-01-01

Dimethyl sulfoxide (DMSO) is a common solvent and biological additive possessing well-known utility in cellular cryoprotection and lipid membrane permeabilization, but the governing mechanisms at membrane interfaces remain poorly understood. Many studies have focused on DMSO–lipid interactions and the subsequent effects on membrane-phase behavior, but explanations often rely on qualitative notions of DMSO-induced dehydration of lipid head groups. In this work, surface forces measurements between gel-phase dipalmitoylphosphatidylcholine membranes in DMSO–water mixtures quantify the hydration- and solvation-length scales with angstrom resolution as a function of DMSO concentration from 0 mol% to 20 mol%. DMSO causes a drastic decrease in the range of the steric hydration repulsion, leading to an increase in adhesion at a much-reduced intermembrane distance. Pulsed field gradient NMR of the phosphatidylcholine (PC) head group analogs, dimethyl phosphate and tetramethylammonium ions, shows that the ion hydrodynamic radius decreases with increasing DMSO concentration up to 10 mol% DMSO. The complementary measurements indicate that, at concentrations below 10 mol%, the primary effect of DMSO is to decrease the solvated volume of the PC head group and that, from 10 mol% to 20 mol%, DMSO acts to gradually collapse head groups down onto the surface and suppress their thermal motion. This work shows a connection between surface forces, head group conformation and dynamics, and surface water diffusion, with important implications for soft matter and colloidal systems. PMID:26261313

Integrating Models of Diffusion and Behavior to Predict Innovation Adoption, Maintenance, and Social Diffusion.

PubMed

Smith, Rachel A; Kim, Youllee; Zhu, Xun; Doudou, Dimi Théodore; Sternberg, Eleanore D; Thomas, Matthew B

2018-01-01

This study documents an investigation into the adoption and diffusion of eave tubes, a novel mosquito vector control, during a large-scale scientific field trial in West Africa. The diffusion of innovations (DOI) and the integrated model of behavior (IMB) were integrated (i.e., innovation attributes with attitudes and social pressures with norms) to predict participants' (N = 329) diffusion intentions. The findings showed that positive attitudes about the innovation's attributes were a consistent positive predictor of diffusion intentions: adopting it, maintaining it, and talking with others about it. As expected by the DOI and the IMB, the social pressure created by a descriptive norm positively predicted intentions to adopt and maintain the innovation. Drawing upon sharing research, we argued that the descriptive norm may dampen future talk about the innovation, because it may no longer be seen as a novel, useful topic to discuss. As predicted, the results showed that as the descriptive norm increased, the intention to talk about the innovation decreased. These results provide broad support for integrating the DOI and the IMB to predict diffusion and for efforts to draw on other research to understand motivations for social diffusion.

Design of a frequency domain instrument for simultaneous optical tomography and magnetic resonance imaging of small animals

NASA Astrophysics Data System (ADS)

Masciotti, James M.; Rahim, Shaheed; Grover, Jarrett; Hielscher, Andreas H.

2007-02-01

We present a design for frequency domain instrument that allows for simultaneous gathering of magnetic resonance and diffuse optical tomographic imaging data. This small animal imaging system combines the high anatomical resolution of magnetic resonance imaging (MRI) with the high temporal resolution and physiological information provided by diffuse optical tomography (DOT). The DOT hardware comprises laser diodes and an intensified CCD camera, which are modulated up to 1 GHz by radio frequency (RF) signal generators. An optical imaging head is designed to fit inside the 4 cm inner diameter of a 9.4 T MRI system. Graded index fibers are used to transfer light between the optical hardware and the imaging head within the RF coil. Fiducial markers are integrated into the imaging head to allow the determination of the positions of the source and detector fibers on the MR images and to permit co-registration of MR and optical tomographic images. Detector fibers are arranged compactly and focused through a camera lens onto the photocathode of the intensified CCD camera.

A morphological study of diffuse axonal injury in a rat model by lateral head rotation trauma.

PubMed

Xiaoshengi, He; Guitao, Yang; Xiang, Zhang; Zhou, Fei

2010-03-01

Morphology in diffuse axonal injury (DAI) by lateral head rotation was investigated. SD rats were divided into injury (n=9) and sham (n=3) groups. A device was used to produce lateral rotational acceleration of the rats' heads. At different survival times three rats were killed for light and electron microscopic examination of the brain tissue. Sagittal sections were made from medulla oblongata and immunolabelled for NF68. At post-traumatic 30 min, NF68 immunolabelling showed a small number ofswollen and irregular axons. Ultrastructurally slightly-separated myelin lamellae and disorderly arranged neurofilaments occurred. At 2 and 24 h axonal damage became more severe. Increases in immunolabelled axonal swellings, disconnected axons and axonal retraction bulbs appeared. EM provided evidence of myelin separation, peri-axonal spaces, blank areas in axoplasm, loss of microtubules, peripheral accumulation of mitochondria and clumped neurofilaments for DAI. A tendency was noted for greater labelling with NF68 as axonal damage increased. The disorderly arrangement of NFs occurred at early stage of post-traumatic axonal changes.

Deep intracerebral (basal ganglia) haematomas in fatal non-missile head injury in man.

PubMed Central

Adams, J H; Doyle, D; Graham, D I; Lawrence, A E; McLellan, D R

1986-01-01

Deep intracerebral (basal ganglia) haematomas were found post mortem in 63 of 635 fatal non-missile head injuries. In patients with a basal ganglia haematoma, contusions were more severe, there was a reduced incidence of a lucid interval, and there was an increased incidence of road traffic accidents, gliding contusions and diffuse axonal injury than in patients without this type of haematoma. Intracranial haematoma is usually thought to be a secondary event, that is a complication of the original injury, but these results suggest that a deep intracerebral haematoma is a primary event. If a deep intracerebral haematoma is identified on an early CT scan it is likely that the patient has sustained severe diffuse brain damage at the time of injury. In the majority of head injuries damage to blood vessels or axons predominates. In patients with a traumatic deep intracerebral haematoma, it would appear that the deceleration/acceleration forces are such that both axons and blood vessels within the brain are damaged at the time of injury. Images PMID:3760892

Using the abbreviated injury severity and Glasgow Coma Scale scores to predict 2-week mortality after traumatic brain injury.

PubMed

Timmons, Shelly D; Bee, Tiffany; Webb, Sharon; Diaz-Arrastia, Ramon R; Hesdorffer, Dale

2011-11-01

Prediction of outcome after traumatic brain injury (TBI) remains elusive. We tested the use of a single hospital Glasgow Coma Scale (GCS) Score, GCS Motor Score, and the Head component of the Abbreviated Injury Scale (AIS) Score to predict 2-week cumulative mortality in a large cohort of TBI patients admitted to the eight U.S. Level I trauma centers in the TBI Clinical Trials Network. Data on 2,808 TBI patients were entered into a centralized database. These TBI patients were categorized as severe (GCS score, 3-8), moderate (9-12), or complicated mild (13-15 with positive computed tomography findings). Intubation and chemical paralysis were recorded. The cumulative incidence of mortality in the first 2 weeks after head injury was calculated using Kaplan-Meier survival analysis. Cox proportional hazards regression was used to estimate the magnitude of the risk for 2-week mortality. Two-week cumulative mortality was independently predicted by GCS, GCS Motor Score, and Head AIS. GCS Severity Category and GCS Motor Score were stronger predictors of 2-week mortality than Head AIS. There was also an independent effect of age (<60 vs. ≥60) on mortality after controlling for both GCS and Head AIS Scores. Anatomic and physiologic scales are useful in the prediction of mortality after TBI. We did not demonstrate any added benefit to combining the total GCS or GCS Motor Scores with the Head AIS Score in the short-term prediction of death after TBI.

Sports-related Head Injury

MedlinePlus

... The force of a professional boxer's fist is equivalent to being hit with a 13-pound bowling ... concussions frequently affect athletes in both contact and non-contact sports. Cerebral concussions are considered diffuse brain ...

Prediction of skull fracture risk for children 0-9 months old through validated parametric finite element model and cadaver test reconstruction.

PubMed

Li, Zhigang; Liu, Weiguo; Zhang, Jinhuan; Hu, Jingwen

2015-09-01

Skull fracture is one of the most common pediatric traumas. However, injury assessment tools for predicting pediatric skull fracture risk is not well established mainly due to the lack of cadaver tests. Weber conducted 50 pediatric cadaver drop tests for forensic research on child abuse in the mid-1980s (Experimental studies of skull fractures in infants, Z Rechtsmed. 92: 87-94, 1984; Biomechanical fragility of the infant skull, Z Rechtsmed. 94: 93-101, 1985). To our knowledge, these studies contained the largest sample size among pediatric cadaver tests in the literature. However, the lack of injury measurements limited their direct application in investigating pediatric skull fracture risks. In this study, 50 pediatric cadaver tests from Weber's studies were reconstructed using a parametric pediatric head finite element (FE) model which were morphed into subjects with ages, head sizes/shapes, and skull thickness values that reported in the tests. The skull fracture risk curves for infants from 0 to 9 months old were developed based on the model-predicted head injury measures through logistic regression analysis. It was found that the model-predicted stress responses in the skull (maximal von Mises stress, maximal shear stress, and maximal first principal stress) were better predictors than global kinematic-based injury measures (peak head acceleration and head injury criterion (HIC)) in predicting pediatric skull fracture. This study demonstrated the feasibility of using age- and size/shape-appropriate head FE models to predict pediatric head injuries. Such models can account for the morphological variations among the subjects, which cannot be considered by a single FE human model.

Updated numerical model with uncertainty assessment of 1950-56 drought conditions on brackish-water movement within the Edwards aquifer, San Antonio, Texas

USGS Publications Warehouse

Brakefield, Linzy K.; White, Jeremy T.; Houston, Natalie A.; Thomas, Jonathan V.

2015-01-01

Predictive results of total spring discharge during the 7-year period, as well as head predictions at Bexar County index well J-17, were much different than the dissolved-solids concentration change results at the production wells. These upper bounds are an order of magnitude larger than the actual prediction which implies that (1) the predictions of total spring discharge at Comal and San Marcos Springs and head at Bexar County index well J-17 made with this model are not reliable, and (2) parameters that control these predictions are not informed well by the observation dataset during historymatching, even though the history-matching process yielded parameters to reproduce spring discharges and heads at these locations during the history-matching period. Furthermore, because spring discharges at these two springs and heads at Bexar County index well J-17 represent more of a cumulative effect of upstream conditions over a larger distance (and longer time), many more parameters (with their own uncertainties) are potentially controlling these predictions than the prediction of dissolved-solids concentration change at the prediction wells, and therefore contributing to a large posterior uncertainty.

Analysis of bending wave transmission using beam tracing with advanced statistical energy analysis for periodic box-like structures affected by spatial filtering

NASA Astrophysics Data System (ADS)

Wilson, D.; Hopkins, C.

2015-04-01

For bending wave transmission across periodic box-like arrangements of plates, the effects of spatial filtering can be significant and this needs to be considered in the choice of prediction model. This paper investigates the errors that can occur with Statistical Energy Analysis (SEA) and the potential of using Advanced SEA (ASEA) to improve predictions. The focus is on the low- and mid-frequency range where plates only support local modes with low mode counts and the in situ modal overlap is relatively high. To increase the computational efficiency when using ASEA on large systems, a beam tracing method is introduced which groups together all rays with the same heading into a single beam. Based on a diffuse field on the source plate, numerical experiments are used to determine the angular distribution of incident power on receiver plate edges on linear and cuboid box-like structures. These show that on receiver plates which do not share a boundary with the source plate, the angular distribution on the receiver plate boundaries differs significantly from a diffuse field. SEA and ASEA predictions are assessed through comparison with finite element models. With rain-on-the-roof excitation on the source plate, the results show that compared to SEA, ASEA provides significantly better estimates of the receiver plate energy, but only where there are at least one or two bending modes in each one-third octave band. Whilst ASEA provides better accuracy than SEA, discrepancies still exist which become more apparent when the direct propagation path crosses more than three nominally identical structural junctions.

Six Degree-of-Freedom Measurements of Human Mild Traumatic Brain Injury.

PubMed

Hernandez, Fidel; Wu, Lyndia C; Yip, Michael C; Laksari, Kaveh; Hoffman, Andrew R; Lopez, Jaime R; Grant, Gerald A; Kleiven, Svein; Camarillo, David B

2015-08-01

This preliminary study investigated whether direct measurement of head rotation improves prediction of mild traumatic brain injury (mTBI). Although many studies have implicated rotation as a primary cause of mTBI, regulatory safety standards use 3 degree-of-freedom (3DOF) translation-only kinematic criteria to predict injury. Direct 6DOF measurements of human head rotation (3DOF) and translation (3DOF) have not been previously available to examine whether additional DOFs improve injury prediction. We measured head impacts in American football, boxing, and mixed martial arts using 6DOF instrumented mouthguards, and predicted clinician-diagnosed injury using 12 existing kinematic criteria and 6 existing brain finite element (FE) criteria. Among 513 measured impacts were the first two 6DOF measurements of clinically diagnosed mTBI. For this dataset, 6DOF criteria were the most predictive of injury, more than 3DOF translation-only and 3DOF rotation-only criteria. Peak principal strain in the corpus callosum, a 6DOF FE criteria, was the strongest predictor, followed by two criteria that included rotation measurements, peak rotational acceleration magnitude and Head Impact Power (HIP). These results suggest head rotation measurements may improve injury prediction. However, more 6DOF data is needed to confirm this evaluation of existing injury criteria, and to develop new criteria that considers directional sensitivity to injury.

Diffusion weighted imaging: a comprehensive evaluation of a fast spin echo DWI sequence with BLADE (PROPELLER) k-space sampling at 3 T, using a 32-channel head coil in acute brain ischemia.

PubMed

Attenberger, Ulrike I; Runge, Val M; Stemmer, Alto; Williams, Kenneth D; Naul, L Gill; Michaely, Henrik J; Schoenberg, Stefan O; Reiser, Maximilian F; Wintersperger, Bernd J

2009-10-01

To evaluate the signal-to-noise ratio (SNR) and diagnostic quality of diffusion weighted imaging (DWI) using a fast spin echo (FSE) sequence with BLADE k-space trajectory at 3 T in combination with a 32-channel head coil. The scan was compared with a standard spin echo (SE) echo-planar imaging (EPI) DWI and a high resolution SE EPI DWI sequence. Fourteen patients with acute brain ischemia were included in this Institutional Review Board approved study. All patients were evaluated with 3 different image sequences, using a 3 T scanner and a 32-channel head coil: (a) a standard SE EPI DWI (matrix size 192 x 192), (b) a high resolution SE EPI DWI (matrix size of 256 x 256) and (c) a FSE DWI BLADE (matrix size 192 x 192). The SNR of the 3 scans was compared in 10 healthy volunteers by a paired student t test. Image quality was evaluated with 4 dedicated questions in a blinded read: (1) The scans were ranked in terms of bulk susceptibility artifact. (2) The scan preference for diagnosis of any diffusion abnormality that might occur and (3) the preference for visualization of the diffusion abnormality actually present was determined. (4) The influence of bulk susceptibility on image evaluation for the diffusion abnormality present was assessed. For visualization of the diffusion abnormality present, BLADE DWI was the scan sequence preferred most by both readers (reader 1: 41.7%, reader 2: 35.7%). For visualization of any diffusion abnormality present, BLADE DWI was the preferred scan in 13 of 14 cases for reader 1 (93%) and in 11 of 14 cases for reader 2 (78.6%). No high resolution SE EPI DWI scan was rated best by reader 1. Reader 2 rated the high resolution SE EPI DWI scan superior in only 1 of 56 judgments. The standard EPI DWI sequence (21.8 +/- 5.3) had in comparison to the high resolution EPI DWI (11.9 +/- 2.6) and the BLADE DWI scans (11.3 +/- 3.8) significantly higher SNR mean values. Our preliminary data demonstrates the feasibility of a FSE EPI DWI scan with radial-like k-space sampling, using a 32-channel coil at 3 T in acute brain ischemia. The BLADE DWI was the preferred scan for the detection of acute diffusion abnormalities because of the lack of bulk susceptibility artifacts.

Modeling of Diffuse-Diffuse Photon Coupling via a Nonscattering Region: a Comparative Study

NASA Astrophysics Data System (ADS)

Lee, Jae Hoon; Kim, Seunghwan; Kim, Youn Tae

2004-06-01

It is well established that diffusion approximation is valid for light propagation in highly scattering media, but it breaks down in nonscattering regions. The previous methods that manipulate nonscattering regions are essentially boundary-to-boundary coupling (BBC) methods through a nonscattering void region based on the radiosity theory. We present a boundary-to-interior coupling (BIC) method. BIC is based on the fact that the collimated pencil beam incident on the medium can be replaced by an isotropic point source positioned at one reduced scattering length inside the medium from an illuminated point. A similar replacement is possible for the nondiffuse lights that enter the diffuse medium through the void, and it is formulated as the BIC method. We implemented both coupling methods using the finite element method (FEM) and tested for the circle with a void gap and for a four-layer adult head model. For mean time of flight, the BIC shows better agreement with Monte Carlo (MC) simulation results than BBC. For intensity, BIC shows a comparable match with MC data compared with that of BBC. The effect of absorption of the clear layer in the adult head model was investigated. Both mean time and intensity decrease as absorption of the clear layer increases.

Modeling of diffuse-diffuse photon coupling via a nonscattering region: a comparative study.

PubMed

Lee, Jae Hoon; Kim, Seunghwan; Kim, Youn Tae

2004-06-20

It is well established that diffusion approximation is valid for light propagation in highly scattering media, but it breaks down in nonscattering regions. The previous methods that manipulate nonscattering regions are essentially boundary-to-boundary coupling (BBC) methods through a nonscattering void region based on the radiosity theory. We present a boundary-to-interior coupling (BIC) method. BIC is based on the fact that the collimated pencil beam incident on the medium can be replaced by an isotropic point source positioned at one reduced scattering length inside the medium from an illuminated point. A similar replacement is possible for the nondiffuse lights that enter the diffuse medium through the void, and it is formulated as the BIC method. We implemented both coupling methods using the finite element method (FEM) and tested for the circle with a void gap and for a four-layer adult head model. For mean time of flight, the BIC shows better agreement with Monte Carlo (MC) simulation results than BBC. For intensity, BIC shows a comparable match with MC data compared with that of BBC. The effect of absorption of the clear layer in the adult head model was investigated. Both mean time and intensity decrease as absorption of the clear layer increases.

Fréchet derivative with respect to the shape of a strongly convex nonscattering region in optical tomography

NASA Astrophysics Data System (ADS)

Hyvönen, Nuutti

2007-10-01

The aim of optical tomography is to reconstruct the optical properties inside a physical body, e.g. a neonatal head, by illuminating it with near-infrared light and measuring the outward flux of photons on the object boundary. Because a brain consists of strongly scattering tissue with imbedded cavities filled by weakly scattering cerebrospinal fluid, propagation of near-infrared photons in the human head can be treated by combining the diffusion approximation of the radiative transfer equation with geometrical optics to obtain the radiosity-diffusion forward model of optical tomography. At the moment, a disadvantage with the radiosity-diffusion model is that the locations of the transparent cavities must be known in advance in order to be able to reconstruct the physiologically interesting quantities, i.e., the absorption and the scatter in the strongly scattering brain tissue. In this work we show that the boundary measurement map of optical tomography is Fréchet differentiable with respect to the shape of a strongly convex nonscattering region. Using this result, we introduce a numerical algorithm for approximating an unknown nonscattering cavity by a ball if the background diffuse optical properties of the object are known. The functionality of the method is demonstrated through two-dimensional numerical experiments.

Toward real-time diffuse optical tomography: accelerating light propagation modeling employing parallel computing on GPU and CPU.

PubMed

Doulgerakis, Matthaios; Eggebrecht, Adam; Wojtkiewicz, Stanislaw; Culver, Joseph; Dehghani, Hamid

2017-12-01

Parameter recovery in diffuse optical tomography is a computationally expensive algorithm, especially when used for large and complex volumes, as in the case of human brain functional imaging. The modeling of light propagation, also known as the forward problem, is the computational bottleneck of the recovery algorithm, whereby the lack of a real-time solution is impeding practical and clinical applications. The objective of this work is the acceleration of the forward model, within a diffusion approximation-based finite-element modeling framework, employing parallelization to expedite the calculation of light propagation in realistic adult head models. The proposed methodology is applicable for modeling both continuous wave and frequency-domain systems with the results demonstrating a 10-fold speed increase when GPU architectures are available, while maintaining high accuracy. It is shown that, for a very high-resolution finite-element model of the adult human head with ∼600,000 nodes, consisting of heterogeneous layers, light propagation can be calculated at ∼0.25  s/excitation source. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Comparison of diffusion-weighted MRI acquisition techniques for normal pancreas at 3.0 Tesla.

PubMed

Yao, Xiu-Zhong; Kuang, Tiantao; Wu, Li; Feng, Hao; Liu, Hao; Cheng, Wei-Zhong; Rao, Sheng-Xiang; Wang, He; Zeng, Meng-Su

2014-01-01

We aimed to optimize diffusion-weighted imaging (DWI) acquisitions for normal pancreas at 3.0 Tesla. Thirty healthy volunteers were examined using four DWI acquisition techniques with b values of 0 and 600 s/mm2 at 3.0 Tesla, including breath-hold DWI, respiratory-triggered DWI, respiratory-triggered DWI with inversion recovery (IR), and free-breathing DWI with IR. Artifacts, signal-to-noise ratio (SNR) and apparent diffusion coefficient (ADC) of normal pancreas were statistically evaluated among different DWI acquisitions. Statistical differences were noticed in artifacts, SNR, and ADC values of normal pancreas among different DWI acquisitions by ANOVA (P <0.001). Normal pancreas imaging had the lowest artifact in respiratory-triggered DWI with IR, the highest SNR in respiratory-triggered DWI, and the highest ADC value in free-breathing DWI with IR. The head, body, and tail of normal pancreas had statistically different ADC values on each DWI acquisition by ANOVA (P < 0.05). The highest image quality for normal pancreas was obtained using respiratory-triggered DWI with IR. Normal pancreas displayed inhomogeneous ADC values along the head, body, and tail structures.

Safety Study of SEA-CD40 in Cancer Patients

ClinicalTrials.gov

2018-06-21

Cancer; Carcinoma; Carcinoma, Non-Small-Cell Lung; Carcinoma, Squamous Cell; Hematologic Malignancies; Hodgkin Disease; Lymphoma; Lymphoma, B-Cell; Lymphoma, Follicular; Lymphoma, Large B-Cell, Diffuse; Melanoma; Neoplasms; Neoplasm Metastasis; Neoplasms, Head and Neck; Neoplasms, Squamous Cell; Non-Small Cell Lung Cancer; Non-Small Cell Lung Cancer Metastatic; Non-small Cell Carcinoma; Squamous Cell Cancer; Squamous Cell Carcinoma; Squamous Cell Carcinoma of the Head and Neck; Squamous Cell Neoplasm; Lymphoma, Non-Hodgkin

Evaluation of the extent and distribution of diffuse axonal injury from real world motor vehicle crashes - biomed 2013.

PubMed

Lillie, Elizabeth M; Urban, Jillian E; Lynch, Sarah K; Whitlow, Christopher T; Stitzel, Joel D

2013-01-01

Diffuse axonal injury (DAI) is a common traumatic brain injury (TBI) often seen as a result of motor vehicle crashes (MVC). Twelve (12) cases of DAI were selected from the Crash Injury Research and Engineering Network (CIREN) to determine the extent and distribution of injury with respect to the head contact location. Head computed tomography (CT) scans were collected for each subject and segmented using semi-automated methods to establish the volumes of DAI. The impacted area on the subject's head was approximated from evidence of a soft tissue scalp contusion on the CT scan. This was used in conjunction with subject images and identified internal vehicle contact locations to ascertain a label map of the contact location. A point cloud was developed from the contact location label map and the centroid of the point cloud was calculated as the subject's head impact location. The injury and contact location were evaluated in spherical coordinates and grouped into 0.2 by 0.2 radial increments of azimuth and elevation. The radial increments containing DAI were projected onto a meshed sphere to evaluate the radial distance from the impact location to primary location of DAI and approximate anatomical location. Of the 170 injuries observed, 123 were identified in the frontal lobe and 36 in the parietal lobe. The distribution of the DAI in relation to the change in azimuth from the contact loca y correlated with contact to the head superficial to this lobe. Results from this study provide further insight into the biomechanics of traumatic brain injury and can be used in future work as an aid to validate finite element models of the head.

Extranodal involvement of diffuse large B-cell lymphoma in the head and neck: An indicator of good prognosis.

PubMed

Lee, Doh Young; Kang, Karam; Jung, Hwaejoon; Park, Young Min; Cho, Jae-Gu; Baek, Seung-Kuk; Kwon, Soon-Young; Jung, Kwang-Yoon; Woo, Jeong-Soo

2018-05-31

In this study, we analyzed clinicopathological characteristics and survival outcomes according to extranodal involvement of diffuse large B-cell lymphoma (DLBCL) in the head and neck. A retrospective analysis was conducted on 110 patients from 2004 to 2014 with CD20-positive DLBCL involving the head and neck area. Patients were categorized into two groups, extranodal and nodal, according to involvement of extranodal sites in the head and neck. Outcome measurements for the groups included clinical response to treatment and recurrence rates. Palatine tonsils were the most frequently involved extranodal site in the head and neck (29.1%). Among clinicopathological parameters, proportion of patients with lactate dehydrogenase over 350 IU/L (p=0.033), cell of origin (p<0.001), and treatment outcomes (p=0.007) were significantly different between the two groups. Among cell origin markers CD10, Bcl6, and MUM1, MUM1 was significantly correlated with extranodal involvement (p=0.029). Recurrence rates were similar between groups, while disease-specific survival was significantly higher in the extranodal group (p=0.011). Disease-specific survival of the extranodal group was also higher than the nodal group with extranodal involvement of other body sites (p=0.010). Among patients with negative expression of CD10 (p=0.015), Bcl6 (p=0.018), and MUM1 (p=0.005), survival was longer in the extranodal than the nodal group. DLBCL patients with extranodal involvement of the head and neck may have longer survival outcomes than patients with solely nodal involvement. Increased survival may be more prominent in patients with negative expression of CD10, Bcl6, and MUM1. Copyright © 2018 Elsevier B.V. All rights reserved.

Monte Carlo simulation of near-infrared light propagation in realistic adult head models with hair follicles

NASA Astrophysics Data System (ADS)

Pan, Boan; Fang, Xiang; Liu, Weichao; Li, Nanxi; Zhao, Ke; Li, Ting

2018-02-01

Near infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS) has been used to measure brain activation, which are clinically important. Monte Carlo simulation has been applied to the near infrared light propagation model in biological tissue, and has the function of predicting diffusion and brain activation. However, previous studies have rarely considered hair and hair follicles as a contributing factor. Here, we attempt to use MCVM (Monte Carlo simulation based on 3D voxelized media) to examine light transmission, absorption, fluence, spatial sensitivity distribution (SSD) and brain activation judgement in the presence or absence of the hair follicles. The data in this study is a series of high-resolution cryosectional color photograph of a standing Chinse male adult. We found that the number of photons transmitted under the scalp decreases dramatically and the photons exported to detector is also decreasing, as the density of hair follicles increases. If there is no hair follicle, the above data increase and has the maximum value. Meanwhile, the light distribution and brain activation have a stable change along with the change of hair follicles density. The findings indicated hair follicles make influence of NIRS in light distribution and brain activation judgement.

Effects of radial diffuser hydraulic design on a double-suction centrifugal pump

NASA Astrophysics Data System (ADS)

Hou, H. C.; Zhang, Y. X.; Xu, C.; Zhang, J. Y.; Li, Z. L.

2016-05-01

In order to study effects of radial diffuser on hydraulic performance of crude oil pump, the steady CFD numerical method is applied and one large double-suction oil pump running in long-distance pipeline is considered. The research focuses on analysing the influence of its diffuser vane profile on hydraulic performance of oil pump. The four different types of cylindrical vane have been designed by in-house codes mainly including double arcs (DA), triple arcs (TA), equiangular spiral line (ES) and linear variable angle spiral line (LVS). During design process diffuser vane angles at inlet and outlet are tentatively given within a certain range and then the wrapping angle of the four types of diffuser vanes can be calculated automatically. Under the given inlet and outlet angles, the linear variable angle spiral line profile has the biggest wrapping angle and profile length which is good to delay channel diffusion but bring more friction hydraulic loss. Finally the vane camber line is thickened at the certain uniform thickness distribution and the 3D diffuser models are generated. The whole flow passage of oil pump with different types of diffusers under various flow rate conditions are numerically simulated based on RNG k-ɛ turbulent model and SIMPLEC algorithm. The numerical results show that different types of diffusers can bring about great difference on the hydraulic performance of oil pump, of which the ES profile diffuser with its proper setting angle shows the best hydraulic performance and its inner flow field is improved obviously. Compared with the head data from model sample, all designed diffusers can make a certain improvement on head characteristic. At the large flow rate conditions the hydraulic efficiency increases obviously and the best efficiency point shift to the large flow rate range. The ES profile diffuser embodies the better advantages on pump performance which can be explained theoretically that the diffuser actually acts as a diffusion device and is good to transform the dynamic energy to pressure energy. Then through the hydraulic loss analysis of each pump component for all diffusers, it shows that the impeller takes up the biggest part of the whole loss about 8.19% averagely, the radial diffuser about 3.70% and the volute about 1.65%. The hydraulic loss of impeller is dominant at the large flow rate while the radial diffuser is at the small flow rate. Among all diffusers, the ES profile diffuser generates the least loss and combined to the distribution of velocity vector and turbulent kinetic energy for two kinds of diffusers it also shows that ES profile is fit to apply in radial diffuser. This research can offer a significant reference for the radial diffuser hydraulic design of such centrifugal pumps.

Elemental Water Impact Test: Phase 3 Plunge Depth of a 36-Inch Aluminum Tank Head

NASA Technical Reports Server (NTRS)

Vassilakos, Gregory J.

2014-01-01

Spacecraft are being designed based on LS-DYNA water landing simulations. The Elemental Water Impact Test (EWIT) series was undertaken to assess the accuracy of LS-DYNA water impact simulations. Phase 3 featured a composite tank head that was tested at a range of heights to verify the ability to predict structural failure of composites. To support planning for Phase 3, a test series was conducted with an aluminum tank head dropped from heights of 2, 6, 10, and 12 feet to verify that the test article would not impact the bottom of the test pool. This report focuses on the comparisons of the measured plunge depths to LS-DYNA predictions. The results for the tank head model demonstrated the following. 1. LS-DYNA provides accurate predictions for peak accelerations. 2. LS-DYNA consistently under-predicts plunge depth. An allowance of at least 20% should be added to the LS-DYNA predictions. 3. The LS-DYNA predictions for plunge depth are relatively insensitive to the fluid-structure coupling stiffness.

Prediction of postnatal outcomes in fetuses with isolated congenital diaphragmatic hernias using different lung-to-head ratio measurements.

PubMed

Kehl, Sven; Siemer, Jörn; Brunnemer, Suna; Weiss, Christel; Eckert, Sven; Schaible, Thomas; Sütterlin, Marc

2014-05-01

The purpose of this study was to compare different methods for measuring the fetal lung area-to-head circumference ratio and to investigate their prediction of postpartum survival and the need for neonatal extracorporeal membrane oxygenation (ECMO) therapy in fetuses with isolated congenital diaphragmatic hernias. This prospective study included 118 fetuses of at least 20 weeks' gestation with isolated left-sided congenital diaphragmatic hernias. The lung-to-head ratio was measured with 3 different methods (longest diameter, anteroposterior diameter, and tracing). To eliminate the influence of gestational age, the observed-to-expected lung-to-head ratio was calculated. Receiver operating characteristic (ROC) curves were calculated for the statistical prediction of survival and need for ECMO therapy by the observed-to-expected lung-to-head ratio measured with the different methods. For survival and ECMO necessity 118 and 102 cases (16 neonates were not eligible for ECMO) were assessed, respectively. For prediction of postpartum survival and ECMO necessity, the areas under the ROC curves and 95% confidence intervals showed very similar results for the 3 methods for prediction of survival (tracing, 0.8445 [0.7553-0.9336]; longest diameter, 0.8248 [0.7360-0.9136]; and anteroposterior diameter, 0.8002 [0.7075-0.8928]) and for ECMO necessity (tracing, 0.7344 [0.6297-0.8391]; longest diameter, 0.7128 [0.6027-0.8228]; and anteroposterior diameter, 0.7212 [0.6142-0.8281]). Comparisons between the areas under the ROC curves showed that the tracing method was superior to the anteroposterior diameter method in predicting postpartum survival (P = .0300). Lung-to-head ratio and observed-to-expected lung-to-head ratio measurements were shown to accurately predict postnatal survival and the need for ECMO therapy in fetuses with left-sided congenital diaphragmatic hernias. Tracing the limits of the lungs seems to be the favorable method for calculating the fetal lung area.

Noggin4 is a long-range inhibitor of Wnt8 signalling that regulates head development in Xenopus laevis.

PubMed

Eroshkin, Fedor M; Nesterenko, Alexey M; Borodulin, Alexander V; Martynova, Natalia Yu; Ermakova, Galina V; Gyoeva, Fatima K; Orlov, Eugeny E; Belogurov, Alexey A; Lukyanov, Konstantin A; Bayramov, Andrey V; Zaraisky, Andrey G

2016-03-14

Noggin4 is a Noggin family secreted protein whose molecular and physiological functions remain unknown. In this study, we demonstrate that in contrast to other Noggins, Xenopus laevis Noggin4 cannot antagonise BMP signalling; instead, it specifically binds to Wnt8 and inhibits the Wnt/β -catenin pathway. Live imaging demonstrated that Noggin4 diffusivity in embryonic tissues significantly exceeded that of other Noggins. Using the Fluorescence Recovery After Photobleaching (FRAP) assay and mathematical modelling, we directly estimated the affinity of Noggin4 for Wnt8 in living embryos and determined that Noggin4 fine-tune the Wnt8 posterior-to-anterior gradient. Our results suggest a role for Noggin4 as a unique, freely diffusing, long-range inhibitor of canonical Wnt signalling, thus explaining its ability to promote head development.

Study of water diffusion on single-supported bilayer lipid membranes by quasielastic neutron scattering

NASA Astrophysics Data System (ADS)

Bai, M.; Miskowiec, A.; Hansen, F. Y.; Taub, H.; Jenkins, T.; Tyagi, M.; Diallo, S. O.; Mamontov, E.; Herwig, K. W.; Wang, S.-K.

2012-05-01

High-energy-resolution quasielastic neutron scattering has been used to elucidate the diffusion of water molecules in proximity to single bilayer lipid membranes supported on a silicon substrate. By varying sample temperature, level of hydration, and deuteration, we identify three different types of diffusive water motion: bulk-like, confined, and bound. The motion of bulk-like and confined water molecules is fast compared to those bound to the lipid head groups (7-10 H2O molecules per lipid), which move on the same nanosecond time scale as H atoms within the lipid molecules.

Photon migration through fetal head in utero using continuous wave, near infrared spectroscopy: development and evaluation of experimental and numerical models

NASA Astrophysics Data System (ADS)

Vishnoi, Gargi; Hielscher, Andreas H.; Ramanujam, Nirmala; Chance, Britton

2000-04-01

In this work experimental tissue phantoms and numerical models were developed to estimate photon migration through the fetal head in utero. The tissue phantoms incorporate a fetal head within an amniotic fluid sac surrounded by a maternal tissue layer. A continuous wave, dual-wavelength ((lambda) equals 760 and 850 nm) spectrometer was employed to make near-infrared measurements on the tissue phantoms for various source-detector separations, fetal-head positions, and fetal-head optical properties. In addition, numerical simulations of photon propagation were performed with finite-difference algorithms that provide solutions to the equation of radiative transfer as well as the diffusion equation. The simulations were compared with measurements on tissue phantoms to determine the best numerical model to describe photon migration through the fetal head in utero. Evaluation of the results indicates that tissue phantoms in which the contact between fetal head and uterine wall is uniform best simulates the fetal head in utero for near-term pregnancies. Furthermore, we found that maximum sensitivity to the head can be achieved if the source of the probe is positioned directly above the fetal head. By optimizing the source-detector separation, this signal originating from photons that have traveled through the fetal head can drastically be increased.

Can Predictive Modeling Identify Head and Neck Oncology Patients at Risk for Readmission?

PubMed

Manning, Amy M; Casper, Keith A; Peter, Kay St; Wilson, Keith M; Mark, Jonathan R; Collar, Ryan M

2018-05-01

Objective Unplanned readmission within 30 days is a contributor to health care costs in the United States. The use of predictive modeling during hospitalization to identify patients at risk for readmission offers a novel approach to quality improvement and cost reduction. Study Design Two-phase study including retrospective analysis of prospectively collected data followed by prospective longitudinal study. Setting Tertiary academic medical center. Subjects and Methods Prospectively collected data for patients undergoing surgical treatment for head and neck cancer from January 2013 to January 2015 were used to build predictive models for readmission within 30 days of discharge using logistic regression, classification and regression tree (CART) analysis, and random forests. One model (logistic regression) was then placed prospectively into the discharge workflow from March 2016 to May 2016 to determine the model's ability to predict which patients would be readmitted within 30 days. Results In total, 174 admissions had descriptive data. Thirty-two were excluded due to incomplete data. Logistic regression, CART, and random forest predictive models were constructed using the remaining 142 admissions. When applied to 106 consecutive prospective head and neck oncology patients at the time of discharge, the logistic regression model predicted readmissions with a specificity of 94%, a sensitivity of 47%, a negative predictive value of 90%, and a positive predictive value of 62% (odds ratio, 14.9; 95% confidence interval, 4.02-55.45). Conclusion Prospectively collected head and neck cancer databases can be used to develop predictive models that can accurately predict which patients will be readmitted. This offers valuable support for quality improvement initiatives and readmission-related cost reduction in head and neck cancer care.

Utility of MRI with morphologic and diffusion weighted imaging in the detection of post-treatment nodal disease in head and neck squamous cell carcinoma.

PubMed

Mundada, Pravin; Varoquaux, Arthur Damien; Lenoir, Vincent; de Vito, Claudio; Dulguerov, Nicolas; Ailianou, Angeliki; Caparrotti, Francesca; Becker, Minerva

2018-04-01

To determine the diagnostic performance of morphologic MRI with diffusion weighted imaging (DWIMRI) for the detection of post-treatment lymph node (LN) recurrence of head and neck squamous cell carcinoma (HNSCC). This retrospective study is based on 33 HNSCC patients who underwent DWIMRI with apparent diffusion coefficient (ADC) measurements for suspected post-treatment loco-regional failure. Two radiologists, blinded to clinical/histopathological data, analyzed MR images according to established morphologic criteria and measured ADC values by drawing regions of interest on each normal/abnormal looking lymph node (LN). Histopathological findings in 40 neck dissections, 133 LN-levels and 755 LNs served as gold standard. Malignant LNs had lower ADCmean values than benign LNs (1.15 ± 0.35 × 10 -3  mm 2 /s versus 1.28 ± 0.28 × 10 -3  mm 2 /s, p = .028). The optimal ADCmean threshold to differentiate malignant from benign LNs was 1.1695 × 10 -3  mm 2 /s. Sensitivity, specificity, positive (PPV) and negative (NPV) predictive values (95%CI in parentheses) of DWIMRI with morphologic criteria and ADCmean <1.1695 × 10 -3  mm 2 /s were: (a) 100%(86.2;100), 44.4%(15.3;77.3), 86.1%(69.7;94.7), and 100%(39.5;100) per neck dissection; (b) 83.6%(69.7;92.2), 91.6%(83.0;96.2), 85.4%(71.6;93.4), and 90.5%(81.7;95.5) per LN-level; (c) 53.1%(43.5;62.4), 95.5%(93.5;96.9), 67.4%(56.6;76.7), and 92.0%(89.6;93.9) per LN, respectively. The high NPV of DWIMRI irrespective of analysis type (per neck dissection/per neck level/per lymph node) make it a useful follow-up tool after treatment. Copyright © 2018 Elsevier B.V. All rights reserved.

Diffusion Barriers to Increase the Oxidative Life of Overlay Coatings

NASA Technical Reports Server (NTRS)

Nesbitt, James A.; Lei, Jih-Fen

1999-01-01

Currently, most blades and vanes in the hottest section of aero gas turbine engines require some type of coating for oxidation protection. Newly developed single crystal superalloys have the mechanical potential to operate at increasingly higher component temperatures. However, at these elevated temperatures, coating/substrate interdiffusion can shorten the protective life of the coating. Diffusion barriers between overlay coatings and substrates are being examined to extend the protective life of the coating. A previously- developed finite-difference diffusion model has been modified to predict the oxidative life enhancement due to use of a diffusion barrier. The original diffusion model, designated COSIM, simulates Al diffusion in the coating to the growing oxide scale as well as Al diffusion into the substrate. The COSIM model incorporates an oxide growth and spalling model to provide the rate of Al consumption during cyclic oxidation. Coating failure is predicted when the Al concentration at the coating surface drops to a defined critical level. The modified COSIM model predicts the oxidative life of an overlay coating when a diffusion barrier is present eliminating diffusion of Al from the coating into the substrate. Both the original and the modified diffusion models have been used to predict the effectiveness of a diffusion barrier in extending the protective life of a NiCrAl overlay coating undergoing cyclic oxidation at 1100 C.

Prediction value of the Canadian CT head rule and the New Orleans criteria for positive head CT scan and acute neurosurgical procedures in minor head trauma: a multicenter external validation study.

PubMed

Bouida, Wahid; Marghli, Soudani; Souissi, Sami; Ksibi, Hichem; Methammem, Mehdi; Haguiga, Habib; Khedher, Sonia; Boubaker, Hamdi; Beltaief, Kaouthar; Grissa, Mohamed Habib; Trimech, Mohamed Naceur; Kerkeni, Wiem; Chebili, Nawfel; Halila, Imen; Rejeb, Imen; Boukef, Riadh; Rekik, Noureddine; Bouhaja, Bechir; Letaief, Mondher; Nouira, Semir

2013-05-01

The New Orleans Criteria and the Canadian CT Head Rule have been developed to decrease the number of normal computed tomography (CT) results in mild head injury. We compare the performance of both decision rules for identifying patients with intracranial traumatic lesions and those who require an urgent neurosurgical intervention after mild head injury. This was an observational cohort study performed between 2008 and 2011 on patients with mild head injury who were aged 10 years or older. We collected prospectively clinical head CT scan findings and outcome. Primary outcome was need for neurosurgical intervention, defined as either death or craniotomy, or the need of intubation within 15 days of the traumatic event. Secondary outcome was the presence of traumatic lesions on head CT scan. New Orleans Criteria and Canadian CT Head Rule decision rules were compared by using sensitivity specifications and positive and negative predictive value. We enrolled 1,582 patients. Neurosurgical intervention was performed in 34 patients (2.1%) and positive CT findings were demonstrated in 218 patients (13.8%). Sensitivity and specificity for need for neurosurgical intervention were 100% (95% confidence interval [CI] 90% to 100%) and 60% (95% CI 44% to 76%) for the Canadian CT Head Rule and 82% (95% CI 69% to 95%) and 26% (95% CI 24% to 28%) for the New Orleans Criteria. Negative predictive values for the above-mentioned clinical decision rules were 100% and 99% and positive values were 5% and 2%, respectively, for the Canadian CT Head Rule and New Orleans Criteria. Sensitivity and specificity for clinical significant head CT findings were 95% (95% CI 92% to 98%) and 65% (95% CI 62% to 68%) for the Canadian CT Head Rule and 86% (95% CI 81% to 91%) and 28% (95% CI 26% to 30%) for the New Orleans Criteria. A similar trend of results was found in the subgroup of patients with a Glasgow Coma Scale score of 15. For patients with mild head injury, the Canadian CT Head Rule had higher sensitivity than the New Orleans Criteria, with higher negative predictive value. The question of whether the use of the Canadian CT Head Rule would have a greater influence on head CT scan reduction requires confirmation in real clinical practice. Copyright © 2012 American College of Emergency Physicians. Published by Mosby, Inc. All rights reserved.

Evaluation and statistical inference for human connectomes.

PubMed

Pestilli, Franco; Yeatman, Jason D; Rokem, Ariel; Kay, Kendrick N; Wandell, Brian A

2014-10-01

Diffusion-weighted imaging coupled with tractography is currently the only method for in vivo mapping of human white-matter fascicles. Tractography takes diffusion measurements as input and produces the connectome, a large collection of white-matter fascicles, as output. We introduce a method to evaluate the evidence supporting connectomes. Linear fascicle evaluation (LiFE) takes any connectome as input and predicts diffusion measurements as output, using the difference between the measured and predicted diffusion signals to quantify the prediction error. We use the prediction error to evaluate the evidence that supports the properties of the connectome, to compare tractography algorithms and to test hypotheses about tracts and connections.

Molecular surface area based predictive models for the adsorption and diffusion of disperse dyes in polylactic acid matrix.

PubMed

Xu, Suxin; Chen, Jiangang; Wang, Bijia; Yang, Yiqi

2015-11-15

Two predictive models were presented for the adsorption affinities and diffusion coefficients of disperse dyes in polylactic acid matrix. Quantitative structure-sorption behavior relationship would not only provide insights into sorption process, but also enable rational engineering for desired properties. The thermodynamic and kinetic parameters for three disperse dyes were measured. The predictive model for adsorption affinity was based on two linear relationships derived by interpreting the experimental measurements with molecular structural parameters and compensation effect: ΔH° vs. dye size and ΔS° vs. ΔH°. Similarly, the predictive model for diffusion coefficient was based on two derived linear relationships: activation energy of diffusion vs. dye size and logarithm of pre-exponential factor vs. activation energy of diffusion. The only required parameters for both models are temperature and solvent accessible surface area of the dye molecule. These two predictive models were validated by testing the adsorption and diffusion properties of new disperse dyes. The models offer fairly good predictive ability. The linkage between structural parameter of disperse dyes and sorption behaviors might be generalized and extended to other similar polymer-penetrant systems. Copyright © 2015 Elsevier Inc. All rights reserved.

Progesterone receptors identified in vascular malformations of the head and neck.

PubMed

Duyka, Landon J; Fan, Chun Y; Coviello-Malle, Jean M; Buckmiller, Lisa; Suen, James Y

2009-10-01

To identify hormone receptors within vascular malformations (arteriovenous malformations [AVMs], venous malformations [VMs], and lymphatic malformations [LMs]) of the head and neck. Immunohistochemical staining for estrogen receptor (ER) and progesterone receptor (PR) was performed on archival vascular malformation tissue collected from both pediatric and adult patients. Tertiary referral center from 2006 to 2008. Twelve AVM, 10 VM, and eight LM specimens were stained for both ER and PR. Ten breast carcinoma specimens were used as controls, with the carcinoma cells serving as positive controls, and the endothelium and smooth muscle cells of the blood vessels serving as negative controls. Five normal supraglottic mucosal samples served as head and neck controls. The Fisher exact test was used for statistical analysis. Ten of the 12 (83%) AVM specimens stained diffusely positive for PR within the nuclei of the endothelium and smooth muscle of the malformed vessels (P < 0.0001). Five of the 10 (50%) VM specimens stained positive for PR (2 [20%] focal, 3 [30%] diffuse) within the nuclei of the endothelium and smooth muscle of the malformed vessels (P = 0.0325). Four of the eight (50%) LM specimens stained focally positive for PR within the nuclei of the endothelium of the malformed vessels (P = 0.0229). None of the vascular malformation specimens stained positive for ER. Our data suggest that PR, but not ER, is expressed in AVMs, VMs, and LMs of the head and neck.

Characterization of single-file diffusion in one-dimensional dusty plasma

NASA Astrophysics Data System (ADS)

Theisen, W. L.; Sheridan, T. E.

2010-11-01

Single-file diffusion occurs in one-dimensional systems when particles cannot pass each other and the mean-squared displacement (msd) of these particles increases with time t. Diffusive processes that follow Ficks law predict that the msd increases as t, however, single-file diffusion is sub-Fickean meaning that the msd is predicted to increase as t^1/2. One-dimensional dusty plasma rings have been created under strongly coupled, over-damped conditions. Particle position data from these rings will be analyzed to determine the scaling of the msd with time. Results will be compared with predictions of single-file diffusion theory.

Wavelet analysis of head acceleration response under dirac excitation for early oedema detection.

PubMed

Kostopoulos, V; Loutas, T H; Derdas, C; Douzinas, E

2008-04-01

The present work deals with the application of an innovative in-house developed wavelet-based methodology for the analysis of the acceleration responses of a human head complex model as a simulated diffused oedema progresses. The human head complex has been modeled as a structure consisting of three confocal prolate spheroids, whereas the three defined regions by the system of spheroids, from the outside to the inside, represent the scull, the region of cerebrospinal fluid, and the brain tissue. A Dirac-like pulse has been used to excite the human head complex model and the acceleration response of the system has been calculated and analyzed via the wavelet-based methodology. For the purpose of the present analysis, a wave propagation commercial finite element code, LS-DYNA 3D, has been used. The progressive diffused oedema was modeled via consecutive increases in brain volume accompanied by a decrease in brain density. It was shown that even a small increase in brain volume (at the level of 0.5%) can be identified by the effect it has on the vibration characteristics of the human head complex. More precisely, it was found that for some of the wavelet decomposition levels, the energy content changes monotonically as the brain volume increases, thus providing a useful index of monitoring an oncoming brain oedema before any brain damage appears due to uncontrolled intracranial hypertension. For the purpose of the present work and for the levels of brain volume increase considered in the present analysis, no pressure increase was assumed into the cranial vault and, associatively, no brain compliance variation.

Microstructure analysis and wear behavior of titanium cermet femoral head with hard TiC layer.

PubMed

Luo, Yong; Ge, Shirong; Liu, Hongtao; Jin, Zhongmin

2009-12-11

Titanium cermet was successfully synthesized and formed a thin gradient titanium carbide coating on the surface of Ti6Al4V alloy by using a novel sequential carburization under high temperature, while the titanium cermet femoral head was produced. The titanium cermet phase and surface topography were characterized with X-ray diffraction (XRD) and backscattered electron imaging (BSE). And then the wear behavior of titanium cermet femoral head was investigated by using CUMT II artificial joint hip simulator. The surface characterization indicates that carbon effectively diffused into the titanium alloys and formed a hard TiC layer on the Ti6Al4V alloys surface with a micro-porous structure. The artificial hip joint experimental results show that titanium cermet femoral head could not only improve the wear resistance of artificial femoral head, but also decrease the wear of UHMWPE joint cup. In addition, the carburized titanium alloy femoral head could effectively control the UHMWPE debris distribution, and increase the size of UHMWPE debris. All of the results suggest that titanium cermet is a prospective femoral head material in artificial joint.

Diffuse Staining for Activated NOTCH1 Correlates With NOTCH1 Mutation Status and Is Associated With Worse Outcome in Adenoid Cystic Carcinoma.

PubMed

Sajed, Dipti P; Faquin, William C; Carey, Chris; Severson, Eric A; H Afrogheh, Amir; A Johnson, Carl; Blacklow, Stephen C; Chau, Nicole G; Lin, Derrick T; Krane, Jeffrey F; Jo, Vickie Y; Garcia, Joaquín J; Sholl, Lynette M; Aster, Jon C

2017-11-01

NOTCH1 is frequently mutated in adenoid cystic carcinoma (ACC). To test the idea that immunohistochemical (IHC) staining can identify ACCs with NOTCH1 mutations, we performed IHC for activated NOTCH1 (NICD1) in 197 cases diagnosed as ACC from 173 patients. NICD1 staining was positive in 194 cases (98%) in 2 major patterns: subset positivity, which correlated with tubular/cribriform histology; and diffuse positivity, which correlated with a solid histology. To determine the relationship between NICD1 staining and NOTCH1 mutational status, targeted exome sequencing data were obtained on 14 diffusely NICD1-positive ACC specimens from 11 patients and 15 subset NICD1-positive ACC specimens from 15 patients. This revealed NOTCH1 gain-of-function mutations in 11 of 14 diffusely NICD1-positive ACC specimens, whereas all subset-positive tumors had wild-type NOTCH1 alleles. Notably, tumors with diffuse NICD1 positivity were associated with significantly worse outcomes (P=0.003). To determine whether NOTCH1 activation is unique among tumors included in the differential diagnosis with ACC, we performed NICD1 IHC on a cohort of diverse salivary gland and head and neck tumors. High fractions of each of these tumor types were positive for NICD1 in a subset of cells, particularly in basaloid squamous cell carcinomas; however, sequencing of basaloid squamous cell carcinomas failed to identify NOTCH1 mutations. These findings indicate that diffuse NICD1 positivity in ACC correlates with solid growth pattern, the presence of NOTCH1 gain-of-function mutations, and unfavorable outcome, and suggest that staining for NICD1 can be helpful in distinguishing ACC with solid growth patterns from other salivary gland and head and neck tumors.

Head losses prediction and analysis in a bulb turbine draft tube under different operating conditions using unsteady simulations

NASA Astrophysics Data System (ADS)

Wilhelm, S.; Balarac, G.; Métais, O.; Ségoufin, C.

2016-11-01

Flow prediction in a bulb turbine draft tube is conducted for two operating points using Unsteady RANS (URANS) simulations and Large Eddy Simulations (LES). The inlet boundary condition of the draft tube calculation is a rotating two dimensional velocity profile exported from a RANS guide vane- runner calculation. Numerical results are compared with experimental data in order to validate the flow field and head losses prediction. Velocity profiles prediction is improved with LES in the center of the draft tube compared to URANS results. Moreover, more complex flow structures are obtained with LES. A local analysis of the predicted flow field using the energy balance in the draft tube is then introduced in order to detect the hydrodynamic instabilities responsible for head losses in the draft tube. In particular, the production of turbulent kinetic energy next to the draft tube wall and in the central vortex structure is found to be responsible for a large part of the mean kinetic energy dissipation in the draft tube and thus for head losses. This analysis is used in order to understand the differences in head losses for different operating points. The numerical methodology could then be improved thanks to an in-depth understanding of the local flow topology.

The influence of preferential flow on pressure propagation and landslide triggering of the Rocca Pitigliana landslide

NASA Astrophysics Data System (ADS)

Shao, Wei; Bogaard, Thom; Bakker, Mark; Berti, Matteo

2016-12-01

The fast pore water pressure response to rain events is an important triggering factor for slope instability. The fast pressure response may be caused by preferential flow that bypasses the soil matrix. Currently, most of the hydro-mechanical models simulate pore water pressure using a single-permeability model, which cannot quantify the effects of preferential flow on pressure propagation and landslide triggering. Previous studies showed that a model based on the linear-diffusion equation can simulate the fast pressure propagation in near-saturated landslides such as the Rocca Pitigliana landslide. In such a model, the diffusion coefficient depends on the degree of saturation, which makes it difficult to use the model for predictions. In this study, the influence of preferential flow on pressure propagation and slope stability is investigated with a 1D dual-permeability model coupled with an infinite-slope stability approach. The dual-permeability model uses two modified Darcy-Richards equations to simultaneously simulate the matrix flow and preferential flow in hillslopes. The simulated pressure head is used in an infinite-slope stability analysis to identify the influence of preferential flow on the fast pressure response and landslide triggering. The dual-permeability model simulates the height and arrival of the pressure peak reasonably well. Performance of the dual-permeability model is as good as or better than the linear-diffusion model even though the dual-permeability model is calibrated for two single pulse rain events only, while the linear-diffusion model is calibrated for each rain event separately. In conclusion, the 1D dual-permeability model is a promising tool for landslides under similar conditions.

Diffusion-Weighted Imaging of Traumatic Optic Neuropathy: Diagnosis and Predicting the Prognosis

DTIC Science & Technology

2014-01-01

AFRL-SA-WP-SR-2014-0004 Diffusion-Weighted Imaging of Traumatic Optic Neuropathy : Diagnosis and Predicting the Prognosis...Diffusion-Weighted Imaging of Traumatic Optic Neuropathy : Diagnosis and Predicting the Prognosis 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c...Skills Institute C-STARS Baltimore 2510 Fifth St. Wright-Patterson AFB, OH 45433-7913 8 . PERFORMING ORGANIZATION REPORT NUMBER AFRL-SA

MRI with DWI for the Detection of Posttreatment Head and Neck Squamous Cell Carcinoma: Why Morphologic MRI Criteria Matter.

PubMed

Ailianou, A; Mundada, P; De Perrot, T; Pusztaszieri, M; Poletti, P-A; Becker, M

2018-04-01

Although diffusion-weighted imaging combined with morphologic MRI (DWIMRI) is used to detect posttreatment recurrent and second primary head and neck squamous cell carcinoma, the diagnostic criteria used so far have not been clarified. We hypothesized that precise MRI criteria based on signal intensity patterns on T2 and contrast-enhanced T1 complement DWI and therefore improve the diagnostic performance of DWIMRI. We analyzed 1.5T MRI examinations of 100 consecutive patients treated with radiation therapy with or without additional surgery for head and neck squamous cell carcinoma. MRI examinations included morphologic sequences and DWI ( b =0 and b =1000 s/mm 2 ). Histology and follow-up served as the standard of reference. Two experienced readers, blinded to clinical/histologic/follow-up data, evaluated images according to clearly defined criteria for the diagnosis of recurrent head and neck squamous cell carcinoma/second primary head and neck squamous cell carcinoma occurring after treatment, post-radiation therapy inflammatory edema, and late fibrosis. DWI analysis included qualitative (visual) and quantitative evaluation with an ADC threshold. Recurrent head and neck squamous cell carcinoma/second primary head and neck squamous cell carcinoma occurring after treatment was present in 36 patients, whereas 64 patients had post-radiation therapy lesions only. The Cohen κ for differentiating tumor from post-radiation therapy lesions with MRI and qualitative DWIMRI was 0.822 and 0.881, respectively. Mean ADCmean in recurrent head and neck squamous cell carcinoma/second primary head and neck squamous cell carcinoma occurring after treatment (1.097 ± 0.295 × 10 -3 mm 2 /s) was significantly lower ( P < .05) than in post-radiation therapy inflammatory edema (1.754 ± 0.343 × 10 -3 mm 2 /s); however, it was similar to that in late fibrosis (0.987 ± 0.264 × 10 -3 mm 2 /s, P > .05). Although ADCs were similar in tumors and late fibrosis, morphologic MRI criteria facilitated distinction between the 2 conditions. The sensitivity, specificity, positive and negative predictive values, and positive and negative likelihood ratios (95% CI) of DWIMRI with ADCmean < 1.22 × 10 -3 mm 2 /s and precise MRI criteria were 92.1% (83.5-100.0), 95.4% (90.3-100.0), 92.1% (83.5-100.0), 95.4% (90.2-100.0), 19.9 (6.58-60.5), and 0.08 (0.03-0.24), respectively, indicating a good diagnostic performance to rule in and rule out disease. Adding precise morphologic MRI criteria to quantitative DWI enables reproducible and accurate detection of recurrent head and neck squamous cell carcinoma/second primary head and neck squamous cell carcinoma occurring after treatment. © 2018 by American Journal of Neuroradiology.

Characterization of a clay-rich rock through development and installation of specific hydrogeological and diffusion test equipment in deep boreholes

NASA Astrophysics Data System (ADS)

Delay, Jacques; Distinguin, Marc; Dewonck, Sarah

Andra (Agence Nationale pour la Gestion des Déchets Radioactifs - National Radioactive Waste Management Agency) has developed specific tools and methodologies to evaluate and understand the main transport mechanisms of solute species in an argillaceous rock in the framework of the scientific program of the Meuse/Haute-Marne Underground Research Laboratory. This paper focuses on three specific equipments already installed in boreholes for the determination of convection and diffusion parameters in a very low permeability environment. The first one is a specific borehole completion for head and permeability measurements with an integrated wireless telemetry device. In 1995, Andra devised a probe equipped with a pressure sensor to monitor the long-term evolution of electro-magnetically transmitted pore pressures. The data gathered by this first device, and a second one installed in 2001, have shown the occurrence of overpressures in very low permeability formations. The second device is derived from the multipacker system used for monitoring the drainage of the Oxfordian limestone due to the sinking of the shaft above the Callovo-Oxfordian. It is used for obtaining from a single borehole, a pressure profile of the argillaceous formation and its encasing units. To date, the major information obtained with these two borehole equipments is the existence of a 25-35 m anomalous excess hydraulic head in the 130 m thick Callovo-Oxfordian argillaceous formation. Head values in the argillaceous rock exceed those in the overlying Oxfordian limestone by 25-35 m, and those in the underlying Dogger by over 45 m. The third equipment described in the paper, is derived from the experiment carried out at the Mont Terri rock laboratory since 1996 for the characterization of diffusion and retention processes. The system is adapted for a borehole drilled from the surface. The objectives of this experiment are as follows: Verification of the predominant role played by molecular diffusion compared with convection; Acquisition of data required to extrapolate and /or interpolate chemical retention and diffusion parameters. The diffusion test performed from the borehole makes it possible to test in situ a small number of tracers (HTO, 36Cl, 134Cs) at a scale of 10 cm for the non sorbing tracers.

Predicting the weathering of fuel and oil spills: A diffusion-limited evaporation model.

PubMed

Kotzakoulakis, Konstantinos; George, Simon C

2018-01-01

The majority of the evaporation models currently available in the literature for the prediction of oil spill weathering do not take into account diffusion-limited mass transport and the formation of a concentration gradient in the oil phase. The altered surface concentration of the spill caused by diffusion-limited transport leads to a slower evaporation rate compared to the predictions of diffusion-agnostic evaporation models. The model presented in this study incorporates a diffusive layer in the oil phase and predicts the diffusion-limited evaporation rate. The information required is the composition of the fluid from gas chromatography or alternatively the distillation data. If the density or a single viscosity measurement is available the accuracy of the predictions is higher. Environmental conditions such as water temperature, air pressure and wind velocity are taken into account. The model was tested with synthetic mixtures, petroleum fuels and crude oils with initial viscosities ranging from 2 to 13,000 cSt. The tested temperatures varied from 0 °C to 23.4 °C and wind velocities from 0.3 to 3.8 m/s. The average absolute deviation (AAD) of the diffusion-limited model ranged between 1.62% and 24.87%. In comparison, the AAD of a diffusion-agnostic model ranged between 2.34% and 136.62% against the same tested fluids. Copyright © 2017 Elsevier Ltd. All rights reserved.

Worst case prediction of additives migration from polystyrene for food safety purposes: a model update.

PubMed

Martínez-López, Brais; Gontard, Nathalie; Peyron, Stéphane

2018-03-01

A reliable prediction of migration levels of plastic additives into food requires a robust estimation of diffusivity. Predictive modelling of diffusivity as recommended by the EU commission is carried out using a semi-empirical equation that relies on two polymer-dependent parameters. These parameters were determined for the polymers most used by packaging industry (LLDPE, HDPE, PP, PET, PS, HIPS) from the diffusivity data available at that time. In the specific case of general purpose polystyrene, the diffusivity data published since then shows that the use of the equation with the original parameters results in systematic underestimation of diffusivity. The goal of this study was therefore, to propose an update of the aforementioned parameters for PS on the basis of up to date diffusivity data, so the equation can be used for a reasoned overestimation of diffusivity.

Exploiting Information Diffusion Feature for Link Prediction in Sina Weibo

NASA Astrophysics Data System (ADS)

Li, Dong; Zhang, Yongchao; Xu, Zhiming; Chu, Dianhui; Li, Sheng

2016-01-01

The rapid development of online social networks (e.g., Twitter and Facebook) has promoted research related to social networks in which link prediction is a key problem. Although numerous attempts have been made for link prediction based on network structure, node attribute and so on, few of the current studies have considered the impact of information diffusion on link creation and prediction. This paper mainly addresses Sina Weibo, which is the largest microblog platform with Chinese characteristics, and proposes the hypothesis that information diffusion influences link creation and verifies the hypothesis based on real data analysis. We also detect an important feature from the information diffusion process, which is used to promote link prediction performance. Finally, the experimental results on Sina Weibo dataset have demonstrated the effectiveness of our methods.

Exploiting Information Diffusion Feature for Link Prediction in Sina Weibo.

PubMed

Li, Dong; Zhang, Yongchao; Xu, Zhiming; Chu, Dianhui; Li, Sheng

2016-01-28

The rapid development of online social networks (e.g., Twitter and Facebook) has promoted research related to social networks in which link prediction is a key problem. Although numerous attempts have been made for link prediction based on network structure, node attribute and so on, few of the current studies have considered the impact of information diffusion on link creation and prediction. This paper mainly addresses Sina Weibo, which is the largest microblog platform with Chinese characteristics, and proposes the hypothesis that information diffusion influences link creation and verifies the hypothesis based on real data analysis. We also detect an important feature from the information diffusion process, which is used to promote link prediction performance. Finally, the experimental results on Sina Weibo dataset have demonstrated the effectiveness of our methods.

The angular distribution of diffusely backscattered light

NASA Astrophysics Data System (ADS)

Vera, M. U.; Durian, D. J.

1997-03-01

The diffusion approximation predicts the angular distribution of light diffusely transmitted through an opaque slab to depend only on boundary reflectivity, independent of scattering anisotropy, and this has been verified by experiment(M.U. Vera and D.J. Durian, Phys. Rev. E 53) 3215 (1996). Here, by contrast, we demonstrate that the angular distribution of diffusely backscattered light depends on scattering anisotropy as well as boundary reflectivity. To model this observation scattering anisotropy is added to the diffusion approximation by a discontinuity in the photon concentration at the source point that is proportional to the average cosine of the scattering angle. We compare the resulting predictions with random walk simulations and with measurements of diffusely backscattered intensity versus angle for glass frits and aqueous suspensions of polystyrene spheres held in air or immersed in a water bath. Increasing anisotropy and boundary reflectivity each tend to flatten the predicted distributions, and for different combinations of anisotropy and reflectivity the agreement between data and predictions ranges from qualitatively to quantitatively good.

A Chimeric Kinesin-1 Head/Kinesin-5 Tail Motor Switches between Diffusive and Processive Motility

PubMed Central

Thiede, Christina; Lakämper, Stefan; Wessel, Alok D.; Kramer, Stefanie; Schmidt, Christoph F.

2013-01-01

Homotetrameric kinesin-5 motors are essential for chromosome separation and assembly of the mitotic spindle. These kinesins bind between two microtubules (MTs) and slide them apart, toward the spindle poles. This process must be tightly regulated in mitosis. In in vitro assays, Eg5 moves diffusively on single MTs and switches to a directed mode between MTs. How allosteric communication between opposing motor domains works remains unclear, but kinesin-5 tail domains may be involved. Here we present a single-molecule fluorescence study of a tetrameric kinesin-1 head/kinesin-5 tail chimera, DK4mer. This motor exhibited fast processive motility on single MTs interrupted by pauses. Like Eg5, DK4mer diffused along MTs with ADP, and slid antiparallel MTs apart with ATP. In contrast to Eg5, diffusive and processive periods were clearly distinguishable. This allowed us to measure transition rates among states and for unbinding as a function of buffer ionic strength. These data, together with results from controls using tail-less dimers, indicate that there are two modes of interaction with MTs, separated by an energy barrier. This result suggests a scheme of motor regulation that involves switching between two bound states, possibly allosterically controlled by the opposing tetramer end. Such a scheme is likely to be relevant for the regulation of native kinesin-5 motors. PMID:23442865

Simulation of radiation driven fission gas diffusion in UO 2, ThO 2 and PuO 2

DOE PAGES

Cooper, Michael William D.; Stanek, Christopher Richard; Turnbull, James Anthony; ...

2016-12-01

Below 1000 K it is thought that fission gas diffusion in nuclear fuel during irradiation occurs through atomic mixing due to radiation damage. Here we present a molecular dynamics (MD) study of Xe, Kr, Th, U, Pu and O diffusion due to irradiation. It is concluded that the ballistic phase does not sufficiently account for the experimentally observed diffusion. Thermal spike simulations are used to confirm that electronic stopping remedies the discrepancy with experiment and the predicted diffusivities lie within the scatter of the experimental data. Here, our results predict that the diffusion coefficients are ordered such that D* 0more » > D* Kr > D* Xe > D* U. For all species >98.5% of diffusivity is accounted for by electronic stopping. Fission gas diffusivity was not predicted to vary significantly between ThO 2, UO 2 and PuO 2, indicating that this process would not change greatly for mixed oxide fuels.« less

Diffusion Coefficients from Molecular Dynamics Simulations in Binary and Ternary Mixtures

NASA Astrophysics Data System (ADS)

Liu, Xin; Schnell, Sondre K.; Simon, Jean-Marc; Krüger, Peter; Bedeaux, Dick; Kjelstrup, Signe; Bardow, André; Vlugt, Thijs J. H.

2013-07-01

Multicomponent diffusion in liquids is ubiquitous in (bio)chemical processes. It has gained considerable and increasing interest as it is often the rate limiting step in a process. In this paper, we review methods for calculating diffusion coefficients from molecular simulation and predictive engineering models. The main achievements of our research during the past years can be summarized as follows: (1) we introduced a consistent method for computing Fick diffusion coefficients using equilibrium molecular dynamics simulations; (2) we developed a multicomponent Darken equation for the description of the concentration dependence of Maxwell-Stefan diffusivities. In the case of infinite dilution, the multicomponent Darken equation provides an expression for [InlineEquation not available: see fulltext.] which can be used to parametrize the generalized Vignes equation; and (3) a predictive model for self-diffusivities was proposed for the parametrization of the multicomponent Darken equation. This equation accurately describes the concentration dependence of self-diffusivities in weakly associating systems. With these methods, a sound framework for the prediction of mutual diffusion in liquids is achieved.

Prediction of stream volatilization coefficients

USGS Publications Warehouse

Rathbun, Ronald E.

1990-01-01

Equations are developed for predicting the liquid-film and gas-film reference-substance parameters for quantifying volatilization of organic solutes from streams. Molecular weight and molecular-diffusion coefficients of the solute are used as correlating parameters. Equations for predicting molecular-diffusion coefficients of organic solutes in water and air are developed, with molecular weight and molal volume as parameters. Mean absolute errors of prediction for diffusion coefficients in water are 9.97% for the molecular-weight equation, 6.45% for the molal-volume equation. The mean absolute error for the diffusion coefficient in air is 5.79% for the molal-volume equation. Molecular weight is not a satisfactory correlating parameter for diffusion in air because two equations are necessary to describe the values in the data set. The best predictive equation for the liquid-film reference-substance parameter has a mean absolute error of 5.74%, with molal volume as the correlating parameter. The best equation for the gas-film parameter has a mean absolute error of 7.80%, with molecular weight as the correlating parameter.

Atlas-based head modeling and spatial normalization for high-density diffuse optical tomography: in vivo validation against fMRI.

PubMed

Ferradal, Silvina L; Eggebrecht, Adam T; Hassanpour, Mahlega; Snyder, Abraham Z; Culver, Joseph P

2014-01-15

Diffuse optical imaging (DOI) is increasingly becoming a valuable neuroimaging tool when fMRI is precluded. Recent developments in high-density diffuse optical tomography (HD-DOT) overcome previous limitations of sparse DOI systems, providing improved image quality and brain specificity. These improvements in instrumentation prompt the need for advancements in both i) realistic forward light modeling for accurate HD-DOT image reconstruction, and ii) spatial normalization for voxel-wise comparisons across subjects. Individualized forward light models derived from subject-specific anatomical images provide the optimal inverse solutions, but such modeling may not be feasible in all situations. In the absence of subject-specific anatomical images, atlas-based head models registered to the subject's head using cranial fiducials provide an alternative solution. In addition, a standard atlas is attractive because it defines a common coordinate space in which to compare results across subjects. The question therefore arises as to whether atlas-based forward light modeling ensures adequate HD-DOT image quality at the individual and group level. Herein, we demonstrate the feasibility of using atlas-based forward light modeling and spatial normalization methods. Both techniques are validated using subject-matched HD-DOT and fMRI data sets for visual evoked responses measured in five healthy adult subjects. HD-DOT reconstructions obtained with the registered atlas anatomy (i.e. atlas DOT) had an average localization error of 2.7mm relative to reconstructions obtained with the subject-specific anatomical images (i.e. subject-MRI DOT), and 6.6mm relative to fMRI data. At the group level, the localization error of atlas DOT reconstruction was 4.2mm relative to subject-MRI DOT reconstruction, and 6.1mm relative to fMRI. These results show that atlas-based image reconstruction provides a viable approach to individual head modeling for HD-DOT when anatomical imaging is not available. Copyright © 2013. Published by Elsevier Inc.

Predictions of heading date in bread wheat (Triticum aestivum L.) using QTL-based parameters of an ecophysiological model

PubMed Central

Bogard, Matthieu; Ravel, Catherine; Paux, Etienne; Bordes, Jacques; Balfourier, François; Chapman, Scott C.; Le Gouis, Jacques; Allard, Vincent

2014-01-01

Prediction of wheat phenology facilitates the selection of cultivars with specific adaptations to a particular environment. However, while QTL analysis for heading date can identify major genes controlling phenology, the results are limited to the environments and genotypes tested. Moreover, while ecophysiological models allow accurate predictions in new environments, they may require substantial phenotypic data to parameterize each genotype. Also, the model parameters are rarely related to all underlying genes, and all the possible allelic combinations that could be obtained by breeding cannot be tested with models. In this study, a QTL-based model is proposed to predict heading date in bread wheat (Triticum aestivum L.). Two parameters of an ecophysiological model (V sat and P base, representing genotype vernalization requirements and photoperiod sensitivity, respectively) were optimized for 210 genotypes grown in 10 contrasting location × sowing date combinations. Multiple linear regression models predicting V sat and P base with 11 and 12 associated genetic markers accounted for 71 and 68% of the variance of these parameters, respectively. QTL-based V sat and P base estimates were able to predict heading date of an independent validation data set (88 genotypes in six location × sowing date combinations) with a root mean square error of prediction of 5 to 8.6 days, explaining 48 to 63% of the variation for heading date. The QTL-based model proposed in this study may be used for agronomic purposes and to assist breeders in suggesting locally adapted ideotypes for wheat phenology. PMID:25148833

The predictive value of single-photon emission computed tomography/computed tomography for sentinel lymph node localization in head and neck cutaneous malignancy.

PubMed

Remenschneider, Aaron K; Dilger, Amanda E; Wang, Yingbing; Palmer, Edwin L; Scott, James A; Emerick, Kevin S

2015-04-01

Preoperative localization of sentinel lymph nodes in head and neck cutaneous malignancies can be aided by single-photon emission computed tomography/computed tomography (SPECT/CT); however, its true predictive value for identifying lymph nodes intraoperatively remains unquantified. This study aims to understand the sensitivity, specificity, and positive and negative predictive values of SPECT/CT in sentinel lymph node biopsy for cutaneous malignancies of the head and neck. Blinded retrospective imaging review with comparison to intraoperative gamma probe confirmed sentinel lymph nodes. A consecutive series of patients with a head and neck cutaneous malignancy underwent preoperative SPECT/CT followed by sentinel lymph node biopsy with a gamma probe. Two nuclear medicine physicians, blinded to clinical data, independently reviewed each SPECT/CT. Activity within radiographically defined nodal basins was recorded and compared to intraoperative gamma probe findings. Sensitivity, specificity, and negative and positive predictive values were calculated with subgroup stratification by primary tumor site. Ninety-two imaging reads were performed on 47 patients with cutaneous malignancy who underwent SPECT/CT followed by sentinel lymph node biopsy. Overall sensitivity was 73%, specificity 92%, positive predictive value 54%, and negative predictive value 96%. The predictive ability of SPECT/CT to identify the basin or an adjacent basin containing the single hottest node was 92%. SPECT/CT overestimated uptake by an average of one nodal basin. In the head and neck, SPECT/CT has higher reliability for primary lesions of the eyelid, scalp, and cheek. SPECT/CT has high sensitivity, specificity, and negative predictive value, but may overestimate relevant nodal basins in sentinel lymph node biopsy. © 2014 The American Laryngological, Rhinological and Otological Society, Inc.

The importance of structural anisotropy in computational models of traumatic brain injury.

PubMed

Carlsen, Rika W; Daphalapurkar, Nitin P

2015-01-01

Understanding the mechanisms of injury might prove useful in assisting the development of methods for the management and mitigation of traumatic brain injury (TBI). Computational head models can provide valuable insight into the multi-length-scale complexity associated with the primary nature of diffuse axonal injury. It involves understanding how the trauma to the head (at the centimeter length scale) translates to the white-matter tissue (at the millimeter length scale), and even further down to the axonal-length scale, where physical injury to axons (e.g., axon separation) may occur. However, to accurately represent the development of TBI, the biofidelity of these computational models is of utmost importance. There has been a focused effort to improve the biofidelity of computational models by including more sophisticated material definitions and implementing physiologically relevant measures of injury. This paper summarizes recent computational studies that have incorporated structural anisotropy in both the material definition of the white matter and the injury criterion as a means to improve the predictive capabilities of computational models for TBI. We discuss the role of structural anisotropy on both the mechanical response of the brain tissue and on the development of injury. We also outline future directions in the computational modeling of TBI.

Establishment of a Physical Model for Solute Diffusion in Hydrogel: Understanding the Diffusion of Proteins in Poly(sulfobetaine methacrylate) Hydrogel.

PubMed

Zhou, Yuhang; Li, Junjie; Zhang, Ying; Dong, Dianyu; Zhang, Ershuai; Ji, Feng; Qin, Zhihui; Yang, Jun; Yao, Fanglian

2017-02-02

Prediction of the diffusion coefficient of solute, especially bioactive molecules, in hydrogel is significant in the biomedical field. Considering the randomness of solute movement in a hydrogel network, a physical diffusion RMP-1 model based on obstruction theory was established in this study. The physical properties of the solute and the polymer chain and their interactions were introduced into this model. Furthermore, models RMP-2 and RMP-3 were established to understand and predict the diffusion behaviors of proteins in hydrogel. In addition, zwitterionic poly(sulfobetaine methacrylate) (PSBMA) hydrogels with wide range and fine adjustable mesh sizes were prepared and used as efficient experimental platforms for model validation. The Flory characteristic ratios, Flory-Huggins parameter, mesh size, and polymer chain radii of PSBMA hydrogels were determined. The diffusion coefficients of the proteins (bovine serum albumin, immunoglobulin G, and lysozyme) in PSBMA hydrogels were studied by the fluorescence recovery after photobleaching technique. The measured diffusion coefficients were compared with the predictions of obstruction models, and it was found that our model presented an excellent predictive ability. Furthermore, the assessment of our model revealed that protein diffusion in PSBMA hydrogel would be affected by the physical properties of the protein and the PSBMA network. It was also confirmed that the diffusion behaviors of protein in zwitterionic hydrogels can be adjusted by changing the cross-linking density of the hydrogel and the ionic strength of the swelling medium. Our model is expected to possess accurate predictive ability for the diffusion coefficient of solute in hydrogel, which will be widely used in the biomedical field.

Impact of creatine kinase correction on the predictive value of S-100B after mild traumatic brain injury.

PubMed

Bazarian, Jeffrey J; Beck, Christopher; Blyth, Brian; von Ahsen, Nicolas; Hasselblatt, Martin

2006-01-01

To validate a correction factor for the extracranial release of the astroglial protein, S-100B, based on concomitant creatine kinase (CK) levels. The CK- S-100B relationship in non-head injured marathon runners was used to derive a correction factor for the extracranial release of S-100B. This factor was then applied to a separate cohort of 96 mild traumatic brain injury (TBI) patients in whom both CK and S-100B levels were measured. Corrected S-100B was compared to uncorrected S-100B for the prediction of initial head CT, three-month headache and three-month post concussive syndrome (PCS). Corrected S-100B resulted in a statistically significant improvement in the prediction of 3-month headache (area under curve [AUC] 0.46 vs 0.52, p=0.02), but not PCS or initial head CT. Using a cutoff that maximizes sensitivity (> or = 90%), corrected S-100B improved the prediction of initial head CT scan (negative predictive value from 75% [95% CI, 2.6%, 67.0%] to 96% [95% CI: 83.5%, 99.8%]). Although S-100B is overall poorly predictive of outcome, a correction factor using CK is a valid means of accounting for extracranial release. By increasing the proportion of mild TBI patients correctly categorized as low risk for abnormal head CT, CK-corrected S100-B can further reduce the number of unnecessary brain CT scans performed after this injury.

Noninvasive assessment of hemodynamic and brain metabolism parameters following closed head injury in a mouse model by comparative diffuse optical reflectance approaches.

PubMed

Abookasis, David; Volkov, Boris; Shochat, Ariel; Kofman, Itamar

2016-04-01

Optical techniques have gained substantial interest over the past four decades for biomedical imaging due to their unique advantages, which may suggest their use as alternatives to conventional methodologies. Several optical techniques have been successfully adapted to clinical practice and biomedical research to monitor tissue structure and function in both humans and animal models. This paper reviews the analysis of the optical properties of brain tissue in the wavelength range between 500 and 1000 nm by three different diffuse optical reflectance methods: spatially modulated illumination, orthogonal diffuse light spectroscopy, and dual-wavelength laser speckle imaging, to monitor changes in brain tissue morphology, chromophore content, and metabolism following head injury. After induction of closed head injury upon anesthetized mice by weight-drop method, significant changes in hemoglobin oxygen saturation, blood flow, and metabolism were readily detectible by all three optical setups, up to 1 h post-trauma. Furthermore, the experimental results clearly demonstrate the feasibility and reliability of the three methodologies, and the differences between the system performances and capabilities are also discussed. The long-term goal of this line of study is to combine these optical systems to study brain pathophysiology in high spatiotemporal resolution using additional models of brain trauma. Such combined use of complementary algorithms should fill the gaps in each system's capabilities, toward the development of a noninvasive, quantitative tool to expand our knowledge of the principles underlying brain function following trauma, and to monitor the efficacy of therapeutic interventions in the clinic.

Noninvasive assessment of hemodynamic and brain metabolism parameters following closed head injury in a mouse model by comparative diffuse optical reflectance approaches

PubMed Central

Abookasis, David; Volkov, Boris; Shochat, Ariel; Kofman, Itamar

2016-01-01

Abstract. Optical techniques have gained substantial interest over the past four decades for biomedical imaging due to their unique advantages, which may suggest their use as alternatives to conventional methodologies. Several optical techniques have been successfully adapted to clinical practice and biomedical research to monitor tissue structure and function in both humans and animal models. This paper reviews the analysis of the optical properties of brain tissue in the wavelength range between 500 and 1000 nm by three different diffuse optical reflectance methods: spatially modulated illumination, orthogonal diffuse light spectroscopy, and dual-wavelength laser speckle imaging, to monitor changes in brain tissue morphology, chromophore content, and metabolism following head injury. After induction of closed head injury upon anesthetized mice by weight-drop method, significant changes in hemoglobin oxygen saturation, blood flow, and metabolism were readily detectible by all three optical setups, up to 1 h post-trauma. Furthermore, the experimental results clearly demonstrate the feasibility and reliability of the three methodologies, and the differences between the system performances and capabilities are also discussed. The long-term goal of this line of study is to combine these optical systems to study brain pathophysiology in high spatiotemporal resolution using additional models of brain trauma. Such combined use of complementary algorithms should fill the gaps in each system’s capabilities, toward the development of a noninvasive, quantitative tool to expand our knowledge of the principles underlying brain function following trauma, and to monitor the efficacy of therapeutic interventions in the clinic. PMID:27175372

Femoral head epiphysis growth and development among Chinese children aged 0-5 years.

PubMed

Luo, Jiayou; Tang, Jin; Zhou, Libo; Zeng, Rong; Mou, Jinsong; Zhang, Lingli

2009-05-01

The aim of this study was to examine the pattern of femoral head epiphysis growth and development among Chinese children. Between January and December, 2007, we randomly sampled 1,450 healthy Chinese children (0-5 years old) from Hunan Provincial Children's Hospital in Changsha, Hunan, China. The diameter of femoral head epiphysis was measured by pelvic X-ray photography and processed by medical image processing software. The growth of femoral head epiphysis in girls was 2-3 months earlier than that in boys. The diameter of femoral head epiphysis increased with advancing age in both girls and boys, but the diameter of femoral head epiphysis in 2, 3, 4, 6, and 10-month-old girls was significantly larger than that in boys. Cubic regression equations between the diameter of femoral head epiphysis and age were created for boys and girls that could be used to predict the diameter of femoral head epiphysis. In conclusion, there was gender difference in femoral head epiphysis growth and development among Chinese children, and our prediction models will provide the guidance for early diagnosis of diseases related to the growth and development of the femoral head epiphysis.

Turbulent flow near the wall of a conical diffuser

NASA Astrophysics Data System (ADS)

Satyaprakash, B. R.; Azad, R. S.; Nagabushana, K. A.; Kassab, S. Z.

The turbulent flow in a conical diffuser is predicted adapting the boundary layer calculation method of Bradshaw, Ferris and Atwell. The predicted mean velocity and shear stress profiles, using the experimental data as initial input, agree well with the measured profiles. The universal low of the wall present at the inlet vahishes in the initial region and reappears later, but the width of validity is diminished considerably. The effect of divergence is present in the initial region of the diffuser only. This technique fails to predict beyond one half the total length of the diffuser.

Testing the accuracy of correlations for multicomponent mass transport of adsorbed gases in metal-organic frameworks: diffusion of H2/CH4 mixtures in CuBTC.

PubMed

Keskin, Seda; Liu, Jinchen; Johnson, J Karl; Sholl, David S

2008-08-05

Mass transport of chemical mixtures in nanoporous materials is important in applications such as membrane separations, but measuring diffusion of mixtures experimentally is challenging. Methods that can predict multicomponent diffusion coefficients from single-component data can be extremely useful if these methods are known to be accurate. We present the first test of a method of this kind for molecules adsorbed in a metal-organic framework (MOF). Specifically, we examine the method proposed by Skoulidas, Sholl, and Krishna (SSK) ( Langmuir, 2003, 19, 7977) by comparing predictions made with this method to molecular simulations of mixture transport of H 2/CH 4 mixtures in CuBTC. These calculations provide the first direct information on mixture transport of any species in a MOF. The predictions of the SSK approach are in good agreement with our direct simulations of binary diffusion, suggesting that this approach may be a powerful one for examining multicomponent diffusion in MOFs. We also use our molecular simulation data to test the ideal adsorbed solution theory method for predicting binary adsorption isotherms and a method for predicting mixture self-diffusion coefficients.

Development of the scanning system to detect the concentration of oxy- and deoxy-hemoglobin by tracking the head

NASA Astrophysics Data System (ADS)

Ko, Woo Seok; Darwish, Naser; Gratton, Enrico; Kim, Soo Hyun

2005-04-01

We measure the concentration of oxy-, deoxy- and total hemoglobin by using the frequency-domain, near-infrared spectroscopy(NIRS) scanner. It is a non-invasive instrument that can provide real-time measurements of the changes in concentration. It can provide a diagnostic tool for the study of the brain in infants and children. However, it is difficult to apply it to the baby's head because of the contact of the probe on the soft baby's head. Therefore, we suggest the NIRS scanning system that can track the baby' head movement and detect NIRS parameters on the same position of the head. This system has three key components. The vision system performs the pattern matching for tracking the head by using the normalized cross correlation method with the target as a cross-line on the head during the diagnostic experiment. We can use the change of the position of the baby's head to re-target the light by the scanning system that uses four laser sources, a wavelength selector, and an x-y scanner. The detector system analyzes the resulting signal from the head using the diffusion model. Therefore, NIRS scanning system can provide a diagnostic tool to measure the changes of the NIRS parameters for the study of the baby's brain.

FDA Benchmark Medical Device Flow Models for CFD Validation.

PubMed

Malinauskas, Richard A; Hariharan, Prasanna; Day, Steven W; Herbertson, Luke H; Buesen, Martin; Steinseifer, Ulrich; Aycock, Kenneth I; Good, Bryan C; Deutsch, Steven; Manning, Keefe B; Craven, Brent A

Computational fluid dynamics (CFD) is increasingly being used to develop blood-contacting medical devices. However, the lack of standardized methods for validating CFD simulations and blood damage predictions limits its use in the safety evaluation of devices. Through a U.S. Food and Drug Administration (FDA) initiative, two benchmark models of typical device flow geometries (nozzle and centrifugal blood pump) were tested in multiple laboratories to provide experimental velocities, pressures, and hemolysis data to support CFD validation. In addition, computational simulations were performed by more than 20 independent groups to assess current CFD techniques. The primary goal of this article is to summarize the FDA initiative and to report recent findings from the benchmark blood pump model study. Discrepancies between CFD predicted velocities and those measured using particle image velocimetry most often occurred in regions of flow separation (e.g., downstream of the nozzle throat, and in the pump exit diffuser). For the six pump test conditions, 57% of the CFD predictions of pressure head were within one standard deviation of the mean measured values. Notably, only 37% of all CFD submissions contained hemolysis predictions. This project aided in the development of an FDA Guidance Document on factors to consider when reporting computational studies in medical device regulatory submissions. There is an accompanying podcast available for this article. Please visit the journal's Web site (www.asaiojournal.com) to listen.

Putting atomic diffusion theory of magnetic ApBp stars to the test: evaluation of the predictions of time-dependent diffusion models

NASA Astrophysics Data System (ADS)

Kochukhov, O.; Ryabchikova, T. A.

2018-02-01

A series of recent theoretical atomic diffusion studies has address the challenging problem of predicting inhomogeneous vertical and horizontal chemical element distributions in the atmospheres of magnetic ApBp stars. Here we critically assess the most sophisticated of such diffusion models - based on a time-dependent treatment of the atomic diffusion in a magnetized stellar atmosphere - by direct comparison with observations as well by testing the widely used surface mapping tools with the spectral line profiles predicted by this theory. We show that the mean abundances of Fe and Cr are grossly underestimated by the time-dependent theoretical diffusion model, with discrepancies reaching a factor of 1000 for Cr. We also demonstrate that Doppler imaging inversion codes, based either on modelling of individual metal lines or line-averaged profiles simulated according to theoretical three-dimensional abundance distribution, are able to reconstruct correct horizontal chemical spot maps despite ignoring the vertical abundance variation. These numerical experiments justify a direct comparison of the empirical two-dimensional Doppler maps with theoretical diffusion calculations. This comparison is generally unfavourable for the current diffusion theory, as very few chemical elements are observed to form overabundance rings in the horizontal field regions as predicted by the theory and there are numerous examples of element accumulations in the vicinity of radial field zones, which cannot be explained by diffusion calculations.

Field theory and diffusion creep predictions in polycrystalline aggregates

NASA Astrophysics Data System (ADS)

Villani, A.; Busso, E. P.; Forest, S.

2015-07-01

In polycrystals, stress-driven vacancy diffusion at high homologous temperatures leads to inelastic deformation. In this work, a novel continuum mechanics framework is proposed to describe the strain fields resulting from such a diffusion-driven process in a polycrystalline aggregate where grains and grain boundaries are explicitly considered. The choice of an anisotropic eigenstrain in the grain boundary region provides the driving force for the diffusive creep processes. The corresponding inelastic strain rate is shown to be related to the gradient of the vacancy flux. Dislocation driven deformation is then introduced as an additional mechanism, through standard crystal plasticity constitutive equations. The fully coupled diffusion-mechanical model is implemented into the finite element method and then used to describe the biaxial creep behaviour of FCC polycrystalline aggregates. The corresponding results revealed for the first time that such a coupled diffusion-stress approach, involving the gradient of the vacancy flux, can accurately predict the well-known macroscopic strain rate dependency on stress and grain size in the diffusion creep regime. They also predict strongly heterogeneous viscoplastic strain fields, especially close to grain boundaries triple junctions. Finally, a smooth transition from Herring and Coble to dislocation creep behaviour is predicted and compared to experimental results for copper.

Underbody Blast Models of TBI Caused by Hyper-Acceleration and Secondary Head Impact

DTIC Science & Technology

2015-02-01

or behavioral indices of brain injury . 2.0 Technical Requirements: 2 Fig. 1. Diffusion tensor imaging of water diffusion in the internal capsule...demonstrates relative differences between blast (left) and sham (right) and also the similarities between the two animals in each group. vWF Bcl - 2 Fo ld...C ha ng e -8 -6 -4 - 2 0 2 4 6 8 10 12 ** ** Figure 6. Quantitative real-time polymerase chain reaction (qPCR) validation of vWF and Bcl - 2

Effects of spin transition on diffusion of Fe2+ in ferropericlase in Earth's lower mantle

NASA Astrophysics Data System (ADS)

Saha, Saumitra; Bengtson, Amelia; Crispin, Katherine L.; van Orman, James A.; Morgan, Dane

2011-11-01

Knowledge of Fe composition in lower-mantle minerals (primarily perovskite and ferropericlase) is essential to a complete understanding of the Earth's interior. Fe cation diffusion potentially controls many aspects of the distribution of Fe in the Earth's lower mantle, including mixing of chemical heterogeneities, element partitioning, and the extent of core-mantle communications. Fe in ferropericlase has been shown to undergo a spin transition starting at about 40 GPa and exists in a mixture of high-spin and low-spin states over a wide range of pressures. Present experimental data on Fe transport in ferropericlase is limited to pressures below 35 GPa and provides little information on the pressure dependence of the activation volume and none on the impact of the spin transition on diffusion. Therefore, known experimental data on Fe diffusion cannot be reliably extrapolated to predict diffusion throughout the lower mantle. Here, first-principles and statistical modeling are combined to predict diffusion of Fe in ferropericlase over the entire lower mantle, including the effects of the Fe spin transition. A thorough statistical thermodynamic treatment is given to fully incorporate the coexistence of high- and low-spin Fe in the model of overall Fe diffusion in the lower mantle. Pure low-spin Fe diffuses approximately 104 times slower than high-spin Fe in ferropericlase but Fe diffusion of the mixed-spin state is only about 10 times slower than that of high-spin Fe. The predicted Fe diffusivities demonstrate that ferropericlase is unlikely to be rate limiting in transporting Fe in deep earth since much slower Fe diffusion in perovskite is predicted.

Predicted percentage dissatisfied with ankle draft.

PubMed

Liu, S; Schiavon, S; Kabanshi, A; Nazaroff, W W

2017-07-01

Draft is unwanted local convective cooling. The draft risk model of Fanger et al. (Energy and Buildings 12, 21-39, 1988) estimates the percentage of people dissatisfied with air movement due to overcooling at the neck. There is no model for predicting draft at ankles, which is more relevant to stratified air distribution systems such as underfloor air distribution (UFAD) and displacement ventilation (DV). We developed a model for predicted percentage dissatisfied with ankle draft (PPD AD ) based on laboratory experiments with 110 college students. We assessed the effect on ankle draft of various combinations of air speed (nominal range: 0.1-0.6 m/s), temperature (nominal range: 16.5-22.5°C), turbulence intensity (at ankles), sex, and clothing insulation (<0.7 clo; lower legs uncovered and covered). The results show that whole-body thermal sensation and air speed at ankles are the dominant parameters affecting draft. The seated subjects accepted a vertical temperature difference of up to 8°C between ankles (0.1 m) and head (1.1 m) at neutral whole-body thermal sensation, 5°C more than the maximum difference recommended in existing standards. The developed ankle draft model can be implemented in thermal comfort and air diffuser testing standards. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Reactivity of young chars via energetic distribution measurements

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

Calo, J.M.; Lilly, W.D.

1991-01-01

The current project is directed at developing related techniques for the characterization and prediction/correlation of the reactivity of young'' chars to steam and oxygen. Of particular interest is mapping of the reactivity behavior of the resultant chars, as revealed by the energetic heterogeneity of the complexes with char preparation conditions; i.e., heating rate and ultimate temperature. In this first quarterly technical progress report we present the background of the project and the research program for the proposed investigations. The following work was accomplished on the experimental apparatus: a new set of electronics for the UTi quadrupole mass spectrometer head wasmore » purchased and delivered. The Temperature Programmed Desorption (TPD) System was moved to another laboratory and interfaced with the mass spectrometer system. A Polycold{trademark} freon refrigeration system was repaired and interfaced with the vacuum system for the TPD apparatus. It will be used to cool the diffusion pump trap. 60 refs.« less

Mutual diffusion of binary liquid mixtures containing methanol, ethanol, acetone, benzene, cyclohexane, toluene, and carbon tetrachloride

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

Guevara-Carrion, Gabriela; Janzen, Tatjana; Muñoz-Muñoz, Y. Mauricio

Mutual diffusion coefficients of all 20 binary liquid mixtures that can be formed out of methanol, ethanol, acetone, benzene, cyclohexane, toluene, and carbon tetrachloride without a miscibility gap are studied at ambient conditions of temperature and pressure in the entire composition range. The considered mixtures show a varying mixing behavior from almost ideal to strongly non-ideal. Predictive molecular dynamics simulations employing the Green-Kubo formalism are carried out. Radial distribution functions are analyzed to gain an understanding of the liquid structure influencing the diffusion processes. It is shown that cluster formation in mixtures containing one alcoholic component has a significant impactmore » on the diffusion process. The estimation of the thermodynamic factor from experimental vapor-liquid equilibrium data is investigated, considering three excess Gibbs energy models, i.e., Wilson, NRTL, and UNIQUAC. It is found that the Wilson model yields the thermodynamic factor that best suits the simulation results for the prediction of the Fick diffusion coefficient. Four semi-empirical methods for the prediction of the self-diffusion coefficients and nine predictive equations for the Fick diffusion coefficient are assessed and it is found that methods based on local composition models are more reliable. Finally, the shear viscosity and thermal conductivity are predicted and in most cases favorably compared with experimental literature values.« less

A theoretical study of fluid forces on a centrifugal impeller rotating and whirling in a vaned diffuser

NASA Technical Reports Server (NTRS)

Tsujimoto, Yoshinobu; Acosta, Allan J.; Yoshida, Yoshiki

1989-01-01

The fluid forces on a centrifugal impeller rotating and whirling in a vaned diffuser are analyzed on the assumption that the number of impeller and diffuser vanes is so large that the flows are perfectly guided by the vanes. The flow is taken to be two dimensional, inviscid, and incompressible, but the effects of impeller and diffuser losses are taken into account. It is shown that the interaction with the vaned diffuser may cause destabilizing fluid forces. From these discussions, it is found that the whirling forces are closely related to the steady head-capacity characteristics of the impeller. This physical understanding of the whirling forces can be applied also to the cases with volute casings. At partial capacities, it is shown that the impeller forces change greatly when the flow rate and whirl velocity are near to the impeller or vaned diffuser attributed rotating stall onset capacity, and the stall propagation velocity, respectively. In such cases the impeller forces may become destabilizing for impeller whirl.

Development of a child head analytical dynamic model considering cranial nonuniform thickness and curvature - Applying to children aged 0-1 years old.

PubMed

Li, Zhigang; Ji, Cheng; Wang, Lishu

2018-07-01

Although analytical models have been used to quickly predict head response under impact condition, the existing models generally took the head as regular shell with uniform thickness which cannot account for the actual head geometry with varied cranial thickness and curvature at different locations. The objective of this study is to develop and validate an analytical model incorporating actual cranial thickness and curvature for child aged 0-1YO and investigate their effects on child head dynamic responses at different head locations. To develop the new analytical model, the child head was simplified into an irregular fluid-filled shell with non-uniform thickness and the cranial thickness and curvature at different locations were automatically obtained from CT scans using a procedure developed in this study. The implicit equation of maximum impact force was derived as a function of elastic modulus, thickness and radius of curvature of cranium. The proposed analytical model are compared with cadaver test data of children aged 0-1 years old and it is shown to be accurate in predicting head injury metrics. According to this model, obvious difference in injury metrics were observed among subjects with the same age, but different cranial thickness and curvature; and the injury metrics at forehead location are significant higher than those at other locations due to large thickness it owns. The proposed model shows good biofidelity and can be used in quickly predicting the dynamics response at any location of head for child younger than 1 YO. Copyright © 2018 Elsevier B.V. All rights reserved.

Predicting complex traits using a diffusion kernel on genetic markers with an application to dairy cattle and wheat data

PubMed Central

2013-01-01

Background Arguably, genotypes and phenotypes may be linked in functional forms that are not well addressed by the linear additive models that are standard in quantitative genetics. Therefore, developing statistical learning models for predicting phenotypic values from all available molecular information that are capable of capturing complex genetic network architectures is of great importance. Bayesian kernel ridge regression is a non-parametric prediction model proposed for this purpose. Its essence is to create a spatial distance-based relationship matrix called a kernel. Although the set of all single nucleotide polymorphism genotype configurations on which a model is built is finite, past research has mainly used a Gaussian kernel. Results We sought to investigate the performance of a diffusion kernel, which was specifically developed to model discrete marker inputs, using Holstein cattle and wheat data. This kernel can be viewed as a discretization of the Gaussian kernel. The predictive ability of the diffusion kernel was similar to that of non-spatial distance-based additive genomic relationship kernels in the Holstein data, but outperformed the latter in the wheat data. However, the difference in performance between the diffusion and Gaussian kernels was negligible. Conclusions It is concluded that the ability of a diffusion kernel to capture the total genetic variance is not better than that of a Gaussian kernel, at least for these data. Although the diffusion kernel as a choice of basis function may have potential for use in whole-genome prediction, our results imply that embedding genetic markers into a non-Euclidean metric space has very small impact on prediction. Our results suggest that use of the black box Gaussian kernel is justified, given its connection to the diffusion kernel and its similar predictive performance. PMID:23763755

Measurement and Modeling of the Optical Scattering Properties of Crop Canopies

NASA Technical Reports Server (NTRS)

Vanderbilt, V. C. (Principal Investigator)

1985-01-01

The specular reflection process is shown to be a key aspect of radiation transfer by plant canopies. Polarization measurements are demonstrated as the tool for determining the specular and diffuse portions of the canopy radiance. The magnitude of the specular fraction of the reflectance is significant compared to the magnitude of the diffuse fraction. Therefore, it is necessary to consider specularly reflected light in developing and evaluating light-canopy interaction models for wheat canopies. Models which assume leaves are diffuse reflectors correctly predict only the diffuse fraction of the canopy reflectance factor. The specular reflectance model, when coupled with a diffuse leaf model, would predict both the specular and diffuse portions of the reflectance factor. The specular model predicts and the data analysis confirms that the single variable, angle of incidence of specularly reflected sunlight on the leaf, explains much of variation in the polarization data as a function of view-illumination directions.

Diffusion coefficients of organic molecules in sucrose-water solutions and comparison with Stokes-Einstein predictions

NASA Astrophysics Data System (ADS)

Chenyakin, Yuri; Ullmann, Dagny A.; Evoy, Erin; Renbaum-Wolff, Lindsay; Kamal, Saeid; Bertram, Allan K.

2017-02-01

The diffusion coefficients of organic species in secondary organic aerosol (SOA) particles are needed to predict the growth and reactivity of these particles in the atmosphere. Previously, viscosity measurements, along with the Stokes-Einstein relation, have been used to estimate the diffusion rates of organics within SOA particles or proxies of SOA particles. To test the Stokes-Einstein relation, we have measured the diffusion coefficients of three fluorescent organic dyes (fluorescein, rhodamine 6G and calcein) within sucrose-water solutions with varying water activity. Sucrose-water solutions were used as a proxy for SOA material found in the atmosphere. Diffusion coefficients were measured using fluorescence recovery after photobleaching. For the three dyes studied, the diffusion coefficients vary by 4-5 orders of magnitude as the water activity varied from 0.38 to 0.80, illustrating the sensitivity of the diffusion coefficients to the water content in the matrix. At the lowest water activity studied (0.38), the average diffusion coefficients were 1.9 × 10-13, 1.5 × 10-14 and 7.7 × 10-14 cm2 s-1 for fluorescein, rhodamine 6G and calcein, respectively. The measured diffusion coefficients were compared with predictions made using literature viscosities and the Stokes-Einstein relation. We found that at water activity ≥ 0.6 (which corresponds to a viscosity of ≤ 360 Pa s and Tg/T ≤ 0.81), predicted diffusion rates agreed with measured diffusion rates within the experimental uncertainty (Tg represents the glass transition temperature and T is the temperature of the measurements). When the water activity was 0.38 (which corresponds to a viscosity of 3.3 × 106 Pa s and a Tg/T of 0.94), the Stokes-Einstein relation underpredicted the diffusion coefficients of fluorescein, rhodamine 6G and calcein by a factor of 118 (minimum of 10 and maximum of 977), a factor of 17 (minimum of 3 and maximum of 104) and a factor of 70 (minimum of 8 and maximum of 494), respectively. This disagreement is significantly smaller than the disagreement observed when comparing measured and predicted diffusion coefficients of water in sucrose-water mixtures.

Multi-sector thermo-physiological head simulator for headgear research

NASA Astrophysics Data System (ADS)

Martinez, Natividad; Psikuta, Agnes; Corberán, José Miguel; Rossi, René M.; Annaheim, Simon

2017-02-01

A novel thermo-physiological human head simulator for headgear testing was developed by coupling a thermal head manikin with a thermo-physiological model. As the heat flux at head-site is directly measured by the head manikin, this method provides a realistic quantification of the heat transfer phenomena occurring in the headgear, such as moisture absorption-desorption cycles, condensation, or moisture migration across clothing layers. Before coupling, the opportunities of the head manikin for representing the human physiology were evaluated separately. The evaluation revealed reduced precision in forehead and face temperature predictions under extreme heterogeneous temperature distributions and no initial limitation for simulating temperature changes observed in the human physiology. The thermo-physiological model predicted higher sweat rates when applied for coupled than for pure virtual simulations. After coupling, the thermo-physiological human head simulator was validated using eight human experiments. It precisely predicted core, mean skin, and forehead temperatures with average rmsd values within the average experimental standard deviation (rmsd of 0.20 ± 0.15, 0.83 ± 0.34, and 1.04 ± 0.54 °C, respectively). However, in case of forehead, precision was lower for the exposures including activity than for the sedentary exposures. The representation of the human sweat evaporation could be affected by a reduced evaporation efficiency and the manikin sweat dynamics. The industry will benefit from this thermo-physiological human head simulator leading to the development of helmet designs with enhanced thermal comfort and, therefore, with higher acceptance by users.

Non-parametric representation and prediction of single- and multi-shell diffusion-weighted MRI data using Gaussian processes

PubMed Central

Andersson, Jesper L.R.; Sotiropoulos, Stamatios N.

2015-01-01

Diffusion MRI offers great potential in studying the human brain microstructure and connectivity. However, diffusion images are marred by technical problems, such as image distortions and spurious signal loss. Correcting for these problems is non-trivial and relies on having a mechanism that predicts what to expect. In this paper we describe a novel way to represent and make predictions about diffusion MRI data. It is based on a Gaussian process on one or several spheres similar to the Geostatistical method of “Kriging”. We present a choice of covariance function that allows us to accurately predict the signal even from voxels with complex fibre patterns. For multi-shell data (multiple non-zero b-values) the covariance function extends across the shells which means that data from one shell is used when making predictions for another shell. PMID:26236030

Finite Difference Formulation for Prediction of Water Pollution

NASA Astrophysics Data System (ADS)

Johari, Hanani; Rusli, Nursalasawati; Yahya, Zainab

2018-03-01

Water is an important component of the earth. Human being and living organisms are demand for the quality of water. Human activity is one of the causes of the water pollution. The pollution happened give bad effect to the physical and characteristic of water contents. It is not practical to monitor all aspects of water flow and transport distribution. So, in order to help people to access to the polluted area, a prediction of water pollution concentration must be modelled. This study proposed a one-dimensional advection diffusion equation for predicting the water pollution concentration transport. The numerical modelling will be produced in order to predict the transportation of water pollution concentration. In order to approximate the advection diffusion equation, the implicit Crank Nicolson is used. For the purpose of the simulation, the boundary condition and initial condition, the spatial steps and time steps as well as the approximations of the advection diffusion equation have been encoded. The results of one dimensional advection diffusion equation have successfully been used to predict the transportation of water pollution concentration by manipulating the velocity and diffusion parameters.

Diffusion Rates of Organic Molecules in Secondary Organic Aerosol Particle

NASA Astrophysics Data System (ADS)

Bertram, A. K.; Chenyakin, Y.; Song, M.; Grayson, J. W.; Ullmann, D.; Evoy, E.; Renbaum-Wolff, L.; Liu, P.; Zhang, Y.; Kamal, S.; Martin, S. T.

2016-12-01

Information on the diffusion rates of organic molecules in secondary organic aerosol (SOA) particles are needed when predicting their size distribution, growth rates, photochemistry and heterogeneous chemistry. We have used two approaches to determine diffusion rates of organic molecules in SOA particles and proxies of SOA. In the first approach, we measured viscosities and then predicted diffusion rates using the Stokes-Einstein relation. In the second approach, we measured diffusion rates directly using a technique referred to as fluorescence recovery after photobleaching. Results from these measurements, including diffusion coefficients as a function of water activity, will be presented and the implications discussed.

Sub-Fickean Diffusion in a One-Dimensional Plasma Ring

NASA Astrophysics Data System (ADS)

Theisen, W. L.

2013-12-01

A one-dimensional dusty plasma ring is formed in a strongly-coupled complex plasma. The dust particles in the ring can be characterized as a one-dimensional system where the particles cannot pass each other. The particles perform random walks due to thermal motions. This single-file self diffusion is characterized by the mean-squared displacement (msd) of the individual particles which increases with time t. Diffusive processes that follow Ficks law predict that the msd increases as t, however, single-file diffusion is sub-Fickean meaning that the msd is predicted to increase as t^(1/2). Particle position data from the dusty plasma ring is analyzed to determine the scaling of the msd with time. Results are compared with predictions of single-file diffusion theory.

Predictive classification of pediatric bipolar disorder using atlas-based diffusion weighted imaging and support vector machines.

PubMed

Mwangi, Benson; Wu, Mon-Ju; Bauer, Isabelle E; Modi, Haina; Zeni, Cristian P; Zunta-Soares, Giovana B; Hasan, Khader M; Soares, Jair C

2015-11-30

Previous studies have reported abnormalities of white-matter diffusivity in pediatric bipolar disorder. However, it has not been established whether these abnormalities are able to distinguish individual subjects with pediatric bipolar disorder from healthy controls with a high specificity and sensitivity. Diffusion-weighted imaging scans were acquired from 16 youths diagnosed with DSM-IV bipolar disorder and 16 demographically matched healthy controls. Regional white matter tissue microstructural measurements such as fractional anisotropy, axial diffusivity and radial diffusivity were computed using an atlas-based approach. These measurements were used to 'train' a support vector machine (SVM) algorithm to predict new or 'unseen' subjects' diagnostic labels. The SVM algorithm predicted individual subjects with specificity=87.5%, sensitivity=68.75%, accuracy=78.12%, positive predictive value=84.62%, negative predictive value=73.68%, area under receiver operating characteristic curve (AUROC)=0.7812 and chi-square p-value=0.0012. A pattern of reduced regional white matter fractional anisotropy was observed in pediatric bipolar disorder patients. These results suggest that atlas-based diffusion weighted imaging measurements can distinguish individual pediatric bipolar disorder patients from healthy controls. Notably, from a clinical perspective these findings will contribute to the pathophysiological understanding of pediatric bipolar disorder. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Glasgow Coma Scale score, mortality, and functional outcome in head-injured patients.

PubMed

Udekwu, Pascal; Kromhout-Schiro, Sharon; Vaslef, Steven; Baker, Christopher; Oller, Dale

2004-05-01

Preresuscitation Glasgow Coma Scale (P-GCS) score is frequently obtained in injured patients and incorporated into mortality prediction. Data on functional outcome in head injury is sparse. A large group of patients with head injuries was analyzed to assess relationships between P-GCS score, mortality, and functional outcome as measured by the Functional Independence Measure (FIM). Records for patients with International Classification of Diseases, Ninth Revision diagnosis codes indicating head injury in a statewide trauma registry between 1994 and 2002 were selected. P-GCS score, mortality, and FIM score at hospital discharge were integrated and analyzed. Of 138,750 patients, 22,924 patients were used for the mortality study and 7,150 patients for the FIM study. A good correlation exists between P-GCS score and FIM, as determined by rank correlation coefficients, whereas mortality falls steeply between a P-GCS score of 3 and a P-GCS score of 7 followed by a shallow fall. Although P-GCS score is related to mortality in head-injured patients, its relationship is nonlinear, which casts doubt on its use as a continuous measure or an equivalent set of categorical measures incorporated into outcome prediction models. The average FIM scores indicate substantial likelihood of good outcomes in survivors with low P-GCS scores, further complicating the use of the P-GCS score in the prediction of poor outcome at the time of initial patient evaluation. Although the P-GCS score is related to functional outcome as measured by the FIM score and mortality in head injury, current mortality prediction models may need to be modified to account for the nonlinear relationship between P-GCS score and mortality. The P-GCS score is not a good clinical tool for outcome prediction in individual head-injured patients, given the variability in mortality rates and functional outcomes at all scores.

Head Start Program Quality: Examination of Classroom Quality and Parent Involvement in Predicting Children's Vocabulary, Literacy, and Mathematics Achievement Trajectories

ERIC Educational Resources Information Center

Wen, Xiaoli; Bulotsky-Shearer, Rebecca J.; Hahs-Vaughn, Debbie L.; Korfmacher, Jon

2012-01-01

Guided by a developmental-ecological framework and Head Start's two-generational approach, this study examined two dimensions of Head Start program quality, classroom quality and parent involvement and their unique and interactive contribution to children's vocabulary, literacy, and mathematics skills growth from the beginning of Head Start…

Use of a Machine-learning Method for Predicting Highly Cited Articles Within General Radiology Journals.

PubMed

Rosenkrantz, Andrew B; Doshi, Ankur M; Ginocchio, Luke A; Aphinyanaphongs, Yindalon

2016-12-01

This study aimed to assess the performance of a text classification machine-learning model in predicting highly cited articles within the recent radiological literature and to identify the model's most influential article features. We downloaded from PubMed the title, abstract, and medical subject heading terms for 10,065 articles published in 25 general radiology journals in 2012 and 2013. Three machine-learning models were applied to predict the top 10% of included articles in terms of the number of citations to the article in 2014 (reflecting the 2-year time window in conventional impact factor calculations). The model having the highest area under the curve was selected to derive a list of article features (words) predicting high citation volume, which was iteratively reduced to identify the smallest possible core feature list maintaining predictive power. Overall themes were qualitatively assigned to the core features. The regularized logistic regression (Bayesian binary regression) model had highest performance, achieving an area under the curve of 0.814 in predicting articles in the top 10% of citation volume. We reduced the initial 14,083 features to 210 features that maintain predictivity. These features corresponded with topics relating to various imaging techniques (eg, diffusion-weighted magnetic resonance imaging, hyperpolarized magnetic resonance imaging, dual-energy computed tomography, computed tomography reconstruction algorithms, tomosynthesis, elastography, and computer-aided diagnosis), particular pathologies (prostate cancer; thyroid nodules; hepatic adenoma, hepatocellular carcinoma, non-alcoholic fatty liver disease), and other topics (radiation dose, electroporation, education, general oncology, gadolinium, statistics). Machine learning can be successfully applied to create specific feature-based models for predicting articles likely to achieve high influence within the radiological literature. Copyright © 2016 The Association of University Radiologists. Published by Elsevier Inc. All rights reserved.

Mortality prediction of head Abbreviated Injury Score and Glasgow Coma Scale: analysis of 7,764 head injuries.

PubMed

Demetriades, Demetrios; Kuncir, Eric; Murray, James; Velmahos, George C; Rhee, Peter; Chan, Linda

2004-08-01

We assessed the prognostic value and limitations of Glasgow Coma Scale (GCS) and head Abbreviated Injury Score (AIS) and correlated head AIS with GCS. We studied 7,764 patients with head injuries. Bivariate analysis was performed to examine the relationship of GCS, head AIS, age, gender, and mechanism of injury with mortality. Stepwise logistic regression analysis was used to identify the independent risk factors associated with mortality. The overall mortality in the group of head injury patients with no other major extracranial injuries and no hypotension on admission was 9.3%. Logistic regression analysis identified head AIS, GCS, age, and mechanism of injury as significant independent risk factors of death. The prognostic value of GCS and head AIS was significantly affected by the mechanism of injury and the age of the patient. Patients with similar GCS or head AIS but different mechanisms of injury or ages had significantly different outcomes. The adjusted odds ratio of death in penetrating trauma was 5.2 (3.9, 7.0), p < 0.0001, and in the age group > or = 55 years the adjusted odds ratio was 3.4 (2.6, 4.6), p < 0.0001. There was no correlation between head AIS and GCS (correlation coefficient -0.31). Mechanism of injury and age have a major effect in the predictive value of GCS and head AIS. There is no good correlation between GCS and head AIS.

Fall Risk Assessment Predicts Fall-Related Injury, Hip Fracture, and Head Injury in Older Adults.

PubMed

Nilsson, Martin; Eriksson, Joel; Larsson, Berit; Odén, Anders; Johansson, Helena; Lorentzon, Mattias

2016-11-01

To investigate the role of a fall risk assessment, using the Downton Fall Risk Index (DFRI), in predicting fall-related injury, fall-related head injury and hip fracture, and death, in a large cohort of older women and men residing in Sweden. Cross sectional observational study. Sweden. Older adults (mean age 82.4 ± 7.8) who had a fall risk assessment using the DFRI at baseline (N = 128,596). Information on all fall-related injuries, all fall-related head injuries and hip fractures, and all-cause mortality was collected from the Swedish Patient Register and Cause of Death Register. The predictive role of DFRI was calculated using Poisson regression models with age, sex, height, weight, and comorbidities as covariates, taking time to outcome or end of study into account. During a median follow-up of 253 days (interquartile range 90-402 days) (>80,000 patient-years), 15,299 participants had a fall-related injury, 2,864 a head injury, and 2,557 a hip fracture, and 23,307 died. High fall risk (DFRI ≥3) independently predicted fall-related injury (hazard ratio (HR) = 1.43, 95% confidence interval (CI) = 1.39-1.49), hip fracture (HR = 1.51, 95% CI =1.38-1.66), head injury (HR = 1.12, 95% CI = 1.03-1.22), and all-cause mortality (HR = 1.39, 95% CI = 1.35-1.43). DFRI more strongly predicted head injury (HR = 1.29, 95% CI = 1.21-1.36 vs HR = 1.08, 95% CI = 1.04-1.11) and hip fracture (HR = 1.41, 95% CI = 1.30-1.53 vs HR = 1.08, 95% CI = 1.05-1.11) in 70-year old men than in 90-year old women (P < .001). Fall risk assessment using DFRI independently predicts fall-related injury, fall-related head injury and hip fracture, and all-cause mortality in older men and women, indicating its clinical usefulness to identify individuals who would benefit from interventions. © 2016 The Authors. The Journal of the American Geriatrics Society published by Wiley Periodicals, Inc. on behalf of The American Geriatrics Society.

[Evaluation of diffuse cerebral atrophy in patients with a history of traumatic brain injury and its relation to cognitive deterioration].

PubMed

Narberhaus, A; Segarra-Castells, M D; Verger-Maestre, K; Serra-Grabulosa, J M; Salgado-Pineda, P; Bartomeus-Jené, F; Mercader-Sobrequés, J M

Diffuse damage secondary to traumatic brain injury (TBI) can be studied through volumetric analysis of several structures that are sensible to this kind of injury, such as corpus callosum, ventricular system, hippocampus, basal ganglia and the volume of cerebrospinal fluid spaces. Our aim is to describe how closed head injury (CHI) occurred in early years produce diffuse damage, and how this damage affects general cognitive functioning at long term. Initially the group of subjects was composed of 27 head injured children and adolescents following paediatric moderate to severe TBI. From this initial group we selected 15 patients without focal lesion, or in case of having suffered focal lesion, this was smaller than 2,600 mm3. These subjects were assessed by means of volumetric analysis of cerebrospinal fluid spaces, corpus callosum, hippocampus and caudate nucleus, comparing the results with a matched control group. We calculated the degree of general cognitive ability of these subjects through tests of intellectual, memory, frontal lobe and motor speed functioning. This study demonstrates that early CHI produce a volume decrease in all measured structures. Corpus callosum atrophy is the factor that better explains general cognitive impairment. Diffuse damage secondary to moderate to severe peadiatric TBI has long term effects on several cerebral structures and on cognitive performance. Corpus callosum atrophy is the best predictor for general cognitive impairment, compared with other affected structures.

Role of susceptibility-weighted imaging in demonstration of cerebral fat embolism

PubMed Central

Yeap, Pheyming; Kanodia, Avinash Kumar; Main, Gavin; Yong, Aiwain

2015-01-01

Cerebral fat embolism (CFE) is a rare but potentially lethal complication of long bone fractures. Many cases of CFE occur as subclinical events and remain undiagnosed. We report a case of a 22-year-old man, with multiple long bone fractures from a road traffic accident, who subsequently developed hypoxia, neurological abnormality and petechial rash. CT of the head was normal. MRI of the head confirmed the diagnosis with lesions markedly conspicuous and most widespread on susceptibility-weighted imaging as compared to all other sequences including diffusion-weighted imaging. PMID:25572601

Experimental high-velocity missile head injury.

PubMed

Allen, I V; Scott, R; Tanner, J A

1982-09-01

A standardized experimental high-velocity penetrating head-injury model has been produced in which pathological lesions were observed, not only in the wound track but at sites more remote from the track in the hypothalamus, brain stem and cerebellum. Diffuse subarachnoid haemorrhage was common and intraventricular haemorrhage was a constant feature. Other constant histological abnormalities were:L 1. Perivascular "ring' haemorrhages. 2. Perivascular haemorrhage with a surrounding zone of decreased staining intensity. 3. Perivascular increased staining intensity. 4. Areas of decreased staining intensity apparently dissociated from areas of haemorrhage. The pathogenesis of the perivascular lesions is discussed and preliminary studies suggest that these may be the site of early oedema. The implications of this experiment for military surgery and for ballistic protection of the head are discussed.

Single-lipid tracking on nanoscale membrane buds: The effects of curvature on lipid diffusion and sorting.

PubMed

Woodward, Xinxin; Stimpson, Eric E; Kelly, Christopher V

2018-05-29

Nanoscale membrane curvature in cells is critical for endocytosis/exocytosis and membrane trafficking. However, the biophysical ramifications of nanoscale membrane curvature on the behavior of lipids remain poorly understood. Here, we created an experimental model system of membrane curvature at a physiologically-relevant scale and obtained nanoscopic information on single-lipid distributions and dynamics. Supported lipid bilayers were created over 50 and 70 nm radius nanoparticles to create membrane buds. Single-molecule localization microscopy was performed with diverse mixtures of fluorescent and non-fluorescent lipids. Variations in lipid acyl tales length, saturation, head-group, and fluorescent labeling strategy were tested while maintaining a single fluid lipid phase throughout the membrane. Monte Carlo simulations were used to fit our experimental results and quantify the effects of curvature on the lipid diffusion and sorting. Whereas varying the composition of the non-fluorescent lipids yielded minimal changes to the curvature effects, the labeling strategy of the fluorescent lipids yielded highly varying effects of curvature. Most conditions yield single-population Brownian diffusion throughout the membrane; however, curvature-induced lipid sorting, slowing, and aggregation were observed in some conditions. Head-group labeled lipids such as DPPE-Texas Red and POPE-Rhodamine diffused >2.4× slower on the curved vs. the planar membranes; tail-labeled lipids such as NBD-PPC, TopFluor-PPC, TopFluor-PIP2, DiIC 12 , and DiIC 18 displayed no significant changes in diffusion due to the membrane curvature. This article is part of a Special Issue entitled: Emergence of Complex Behavior in Biomembranes edited by Marjorie Longo. Copyright © 2018. Published by Elsevier B.V.

Sex differences in white matter alterations following repetitive subconcussive head impacts in collegiate ice hockey players.

PubMed

Sollmann, Nico; Echlin, Paul S; Schultz, Vivian; Viher, Petra V; Lyall, Amanda E; Tripodis, Yorghos; Kaufmann, David; Hartl, Elisabeth; Kinzel, Philipp; Forwell, Lorie A; Johnson, Andrew M; Skopelja, Elaine N; Lepage, Christian; Bouix, Sylvain; Pasternak, Ofer; Lin, Alexander P; Shenton, Martha E; Koerte, Inga K

2018-01-01

Repetitive subconcussive head impacts (RSHI) may lead to structural, functional, and metabolic alterations of the brain. While differences between males and females have already been suggested following a concussion, whether there are sex differences following exposure to RSHI remains unknown. The aim of this study was to identify and to characterize sex differences following exposure to RSHI. Twenty-five collegiate ice hockey players (14 males and 11 females, 20.6 ± 2.0 years), all part of the Hockey Concussion Education Project (HCEP), underwent diffusion-weighted magnetic resonance imaging (dMRI) before and after the Canadian Interuniversity Sports (CIS) ice hockey season 2011-2012 and did not experience a concussion during the season. Whole-brain tract-based spatial statistics (TBSS) were used to compare pre- and postseason imaging in both sexes for fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD). Pre- and postseason neurocognitive performance were assessed by the Immediate Post-Concussion Assessment and Cognitive Test (ImPACT). Significant differences between the sexes were primarily located within the superior longitudinal fasciculus (SLF), the internal capsule (IC), and the corona radiata (CR) of the right hemisphere (RH). In significant voxel clusters (p < 0.05), decreases in FA (absolute difference pre- vs. postseason: 0.0268) and increases in MD (0.0002), AD (0.00008), and RD (0.00005) were observed in females whereas males showed no significant changes. There was no significant correlation between the change in diffusion scalar measures over the course of the season and neurocognitive performance as evidenced from postseason ImPACT scores. The results of this study suggest sex differences in structural alterations following exposure to RSHI. Future studies need to investigate further the underlying mechanisms and association with exposure and clinical outcomes.

Homogenization Theory for the Prediction of Obstructed Solute Diffusivity in Macromolecular Solutions.

PubMed

Donovan, Preston; Chehreghanianzabi, Yasaman; Rathinam, Muruhan; Zustiak, Silviya Petrova

2016-01-01

The study of diffusion in macromolecular solutions is important in many biomedical applications such as separations, drug delivery, and cell encapsulation, and key for many biological processes such as protein assembly and interstitial transport. Not surprisingly, multiple models for the a-priori prediction of diffusion in macromolecular environments have been proposed. However, most models include parameters that are not readily measurable, are specific to the polymer-solute-solvent system, or are fitted and do not have a physical meaning. Here, for the first time, we develop a homogenization theory framework for the prediction of effective solute diffusivity in macromolecular environments based on physical parameters that are easily measurable and not specific to the macromolecule-solute-solvent system. Homogenization theory is useful for situations where knowledge of fine-scale parameters is used to predict bulk system behavior. As a first approximation, we focus on a model where the solute is subjected to obstructed diffusion via stationary spherical obstacles. We find that the homogenization theory results agree well with computationally more expensive Monte Carlo simulations. Moreover, the homogenization theory agrees with effective diffusivities of a solute in dilute and semi-dilute polymer solutions measured using fluorescence correlation spectroscopy. Lastly, we provide a mathematical formula for the effective diffusivity in terms of a non-dimensional and easily measurable geometric system parameter.

Emulation of recharge and evapotranspiration processes in shallow groundwater systems

NASA Astrophysics Data System (ADS)

Doble, Rebecca C.; Pickett, Trevor; Crosbie, Russell S.; Morgan, Leanne K.; Turnadge, Chris; Davies, Phil J.

2017-12-01

In shallow groundwater systems, recharge and evapotranspiration are highly sensitive to changes in the depth to water table. To effectively model these fluxes, complex functions that include soil and vegetation properties are often required. Model emulation (surrogate modelling or meta-modelling) can provide a means of incorporating detailed conceptualisation of recharge and evapotranspiration processes, while maintaining the numerical tractability and computational performance required for regional scale groundwater models and uncertainty analysis. A method for emulating recharge and evapotranspiration processes in groundwater flow models was developed, and applied to the South East region of South Australia and western Victoria, which is characterised by shallow groundwater, wetlands and coastal lakes. The soil-vegetation-atmosphere transfer (SVAT) model WAVES was used to generate relationships between net recharge (diffuse recharge minus evapotranspiration from groundwater) and depth to water table for different combinations of climate, soil and land cover types. These relationships, which mimicked previously described soil, vegetation and groundwater behaviour, were combined into a net recharge lookup table. The segmented evapotranspiration package in MODFLOW was adapted to select values of net recharge from the lookup table depending on groundwater depth, and the climate, soil and land use characteristics of each cell. The model was found to be numerically robust in steady state testing, had no major increase in run time, and would be more efficient than tightly-coupled modelling approaches. It made reasonable predictions of net recharge and groundwater head compared with remotely sensed estimates of net recharge and a standard MODFLOW comparison model. In particular, the method was better able to predict net recharge and groundwater head in areas with steep hydraulic gradients.

Monitoring longitudinal changes in irradiated head and neck cancer xenografts using diffuse reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Vishwanath, Karthik; Jiang, Shudong; Gunn, Jason R.; Marra, Kayla; Andreozzi, Jacqueline M.; Pogue, Brian W.

2016-02-01

Radiation therapy is often used as the preferred clinical treatment for control of localized head and neck cancer. However, during the course of treatment (6-8 weeks), feedback about functional and/or physiological changes within impacted tissue are not obtained, given the onerous financial and/or logistical burdens of scheduling MRI, PET or CT scans. Diffuse optical sensing is well suited to address this problem since the instrumentation can be made low-cost and portable while still being able to non-invasively provide information about vascular oxygenation in vivo. Here we report results from studies that employed an optical fiber-based portable diffuse reflectance spectroscopy (DRS) system to longitudinally monitor changes in tumor vasculature within two head and neck cancer cell lines (SCC-15 and FaDu) xenografted in the flanks of nude mice, in two separate experiments. Once the tumor volumes were 100mm3, 67% of animals received localized (electron beam) radiation therapy in five fractions (8Gy/day, for 5 days) while 33% of the animals served as controls. DRS measurements were obtained from each animal on each day of treatment and then for two weeks post-treatment. Reflectance spectra were parametrized to extract total hemoglobin concentration and blood oxygen-saturation and the resulting time-trends of optical parameters appear to be dissimilar for the two cell-lines. These findings are also compared to previous animal experiments (using the FaDu line) that were irradiated using a photon beam radiotherapy protocol. These results and implications for the use of fiber-based DRS measurements made at local (irradiated) tumor site as a basis for identifying early radiotherapy-response are presented and discussed.

Application of Cardiac Gating to Improve the Reproducibility of Intravoxel Incoherent Motion Measurements in the Head and Neck.

PubMed

Kang, Koung Mi; Choi, Seung Hong; Kim, Dong Eun; Yun, Tae Jin; Kim, Ji-Hoon; Sohn, Chul-Ho; Park, Sun-Won

2017-07-10

To prospectively evaluate whether cardiac gating can improve the reproducibility of intravoxel incoherent motion (IVIM) parameters in the head and neck, we performed IVIM diffusion-weighted imaging (DWI) using 4 b values (4b), 4 b values with cardiac gating (4b gating) and 17 b values (17b). We performed IVIM DWI twice per person on nine healthy volunteers using 4b, 4b gating and 17b and five patients with head and neck masses using 4b gating and 17b. The ADC, perfusion fraction (f), diffusion coefficient (D) and perfusion-related diffusion coefficient (D*) were calculated in the brain, masticator muscle, parotid gland, submandibular gland, tonsil and masses. Intraclass coefficient (ICC), Bland-Altman analysis (BAA) and coefficient of variation (CV) were used to assess short-term test-retest reproducibility. Kruskal-Wallis test and Mann-Whitney test were used to investigate whether 4b, 4b gating or 17b had significant influences on the parameters. For normal tissues and masses, ICC was excellent for all maps except the D* map. All parameters showed the lowest CV in the 4b gating. BAA also revealed the narrowest 95% limits of agreement using 4b gating for all parameters. In the subgroup analysis, almost all parameters in brain, muscle, parotid gland and submandibular gland showed the best reproducibility using 4b gating. In the muscle, parotid gland and submandibular gland, the values of ADC, f and D were not significantly different between among the three methods. 4b gating was more reproducible with respect to measurements of IVIM parameters in comparison with 4b or 17b.

Patch Based Synthesis of Whole Head MR Images: Application to EPI Distortion Correction.

PubMed

Roy, Snehashis; Chou, Yi-Yu; Jog, Amod; Butman, John A; Pham, Dzung L

2016-10-01

Different magnetic resonance imaging pulse sequences are used to generate image contrasts based on physical properties of tissues, which provide different and often complementary information about them. Therefore multiple image contrasts are useful for multimodal analysis of medical images. Often, medical image processing algorithms are optimized for particular image contrasts. If a desirable contrast is unavailable, contrast synthesis (or modality synthesis) methods try to "synthesize" the unavailable constrasts from the available ones. Most of the recent image synthesis methods generate synthetic brain images, while whole head magnetic resonance (MR) images can also be useful for many applications. We propose an atlas based patch matching algorithm to synthesize T 2 -w whole head (including brain, skull, eyes etc) images from T 1 -w images for the purpose of distortion correction of diffusion weighted MR images. The geometric distortion in diffusion MR images due to in-homogeneous B 0 magnetic field are often corrected by non-linearly registering the corresponding b = 0 image with zero diffusion gradient to an undistorted T 2 -w image. We show that our synthetic T 2 -w images can be used as a template in absence of a real T 2 -w image. Our patch based method requires multiple atlases with T 1 and T 2 to be registeLowRes to a given target T 1 . Then for every patch on the target, multiple similar looking matching patches are found on the atlas T 1 images and corresponding patches on the atlas T 2 images are combined to generate a synthetic T 2 of the target. We experimented on image data obtained from 44 patients with traumatic brain injury (TBI), and showed that our synthesized T 2 images produce more accurate distortion correction than a state-of-the-art registration based image synthesis method.

Asymmetries and three-dimensional features of vestibular cross-coupled stimuli illuminated through modeling

PubMed Central

Holly, Jan E.; Masood, M. Arjumand; Bhandari, Chiran S.

2017-01-01

Head movements during sustained rotation can cause angular cross-coupling which leads to tumbling illusions. Even though angular vectors predict equal magnitude illusions for head movements in opposite directions, the magnitudes of the illusions are often surprisingly asymmetric, such as during leftward versus rightward yaw while horizontal in a centrifuge. This paper presents a comprehensive investigation of the angular-linear stimulus combinations from eight different published papers in which asymmetries were found. Interactions between all angular and linear vectors, including gravity, are taken into account to model the three-dimensional consequences of the stimuli. Three main results followed. First, for every pair of head yaw movements, an asymmetry was found in the stimulus itself when considered in a fully three-dimensional manner, and the direction of the asymmetry matched the subjectively reported magnitude asymmetry. Second, for pitch and roll head movements for which motion sickness was measured, the stimulus was found symmetric in every case except one, and motion sickness generally aligned with other factors such as the existence of a head rest. Third, three-dimensional modeling predicted subjective inconsistency in the direction of perceived rotation when linear and angular components were oppositely-directed, and predicted surplus illusory rotation in the direction of head movement. PMID:27814310

Numerical study of centrifugal compressor stage vaneless diffusers

NASA Astrophysics Data System (ADS)

Galerkin, Y.; Soldatova, K.; Solovieva, O.

2015-08-01

The authors analyzed CFD calculations of flow in vaneless diffusers with relative width in range from 0.014 to 0.100 at inlet flow angles in range from 100 to 450 with different inlet velocity coefficients, Reynolds numbers and surface roughness. The aim is to simulate calculated performances by simple algebraic equations. The friction coefficient that represents head losses as friction losses is proposed for simulation. The friction coefficient and loss coefficient are directly connected by simple equation. The advantage is that friction coefficient changes comparatively little in range of studied parameters. Simple equations for this coefficient are proposed by the authors. The simulation accuracy is sufficient for practical calculations. To create the complete algebraic model of the vaneless diffuser the authors plan to widen this method of modeling to diffusers with different relative length and for wider range of Reynolds numbers.

A Diffusive-Particle Theory of Free Recall

PubMed Central

Fumarola, Francesco

2017-01-01

Diffusive models of free recall have been recently introduced in the memory literature, but their potential remains largely unexplored. In this paper, a diffusive model of short-term verbal memory is considered, in which the psychological state of the subject is encoded as the instantaneous position of a particle diffusing over a semantic graph. The model is particularly suitable for studying the dependence of free-recall observables on the semantic properties of the words to be recalled. Besides predicting some well-known experimental features (forward asymmetry, semantic clustering, word-length effect), a novel prediction is obtained on the relationship between the contiguity effect and the syllabic length of words; shorter words, by way of their wider semantic range, are predicted to be characterized by stronger forward contiguity. A fresh analysis of archival free-recall data allows to confirm this prediction. PMID:29085521

Local recurrence of squamous cell carcinoma of the head and neck after radio(chemo)therapy: Diagnostic performance of FDG-PET/MRI with diffusion-weighted sequences.

PubMed

Becker, Minerva; Varoquaux, Arthur D; Combescure, Christophe; Rager, Olivier; Pusztaszeri, Marc; Burkhardt, Karim; Delattre, Bénédicte M A; Dulguerov, Pavel; Dulguerov, Nicolas; Katirtzidou, Eirini; Caparrotti, Francesca; Ratib, Osman; Zaidi, Habib; Becker, Christoph D

2018-02-01

To determine the diagnostic performance of FDG-PET/MRI with diffusion-weighted imaging (FDG-PET/DWIMRI) for detection and local staging of head and neck squamous cell carcinoma (HNSCC) after radio(chemo)therapy. This was a prospective study that included 74 consecutive patients with previous radio(chemo)therapy for HNSCC and in whom tumour recurrence or radiation-induced complications were suspected clinically. The patients underwent hybrid PET/MRI examinations with morphological MRI, DWI and FDG-PET. Experienced readers blinded to clinical/histopathological data evaluated images according to established diagnostic criteria taking into account the complementarity of multiparametric information. The standard of reference was histopathology with whole-organ sections and follow-up ≥24 months. Statistical analysis considered data clustering. The proof of diagnosis was histology in 46/74 (62.2%) patients and follow-up (mean ± SD = 34 ± 8 months) in 28/74 (37.8%). Thirty-eight patients had 43 HNSCCs and 46 patients (10 with and 36 without tumours) had 62 benign lesions/complications. Sensitivity, specificity, and positive and negative predictive value of PET/DWIMRI were 97.4%, 91.7%, 92.5% and 97.1% per patient, and 93.0%, 93.5%, 90.9%, and 95.1% per lesion, respectively. Agreement between imaging-based and pathological T-stage was excellent (kappa = 0.84, p < 0.001). FDG-PET/DWIMRI yields excellent results for detection and T-classification of HNSCC after radio(chemo)therapy. • FDG-PET/DWIMRI yields excellent results for the detection of post-radio(chemo)therapy HNSCC recurrence. • Prospective one-centre study showed excellent agreement between imaging-based and pathological T-stage. • 97.5% of positive concordant MRI, DWI and FDG-PET results correspond to recurrence. • 87% of discordant MRI, DWI and FDG-PET results correspond to benign lesions. • Multiparametric FDG-PET/DWIMRI facilitates planning of salvage surgery in the irradiated neck.

Using variable importance measures to identify a small set of single nucleotide polymorphisms capable of predicting heading date in perennial ryegrass

USDA-ARS?s Scientific Manuscript database

Prior knowledge on heading date enables the selection of parents for synthetic cultivars that are well-matched with respect to heading date, which is necessary to ensure plants put together will successfully cross with each other. Heading date of individual plants can be determined directly, which h...

A Statistical Skull Geometry Model for Children 0-3 Years Old

PubMed Central

Li, Zhigang; Park, Byoung-Keon; Liu, Weiguo; Zhang, Jinhuan; Reed, Matthew P.; Rupp, Jonathan D.; Hoff, Carrie N.; Hu, Jingwen

2015-01-01

Head injury is the leading cause of fatality and long-term disability for children. Pediatric heads change rapidly in both size and shape during growth, especially for children under 3 years old (YO). To accurately assess the head injury risks for children, it is necessary to understand the geometry of the pediatric head and how morphologic features influence injury causation within the 0–3 YO population. In this study, head CT scans from fifty-six 0–3 YO children were used to develop a statistical model of pediatric skull geometry. Geometric features important for injury prediction, including skull size and shape, skull thickness and suture width, along with their variations among the sample population, were quantified through a series of image and statistical analyses. The size and shape of the pediatric skull change significantly with age and head circumference. The skull thickness and suture width vary with age, head circumference and location, which will have important effects on skull stiffness and injury prediction. The statistical geometry model developed in this study can provide a geometrical basis for future development of child anthropomorphic test devices and pediatric head finite element models. PMID:25992998

A statistical skull geometry model for children 0-3 years old.

PubMed

Li, Zhigang; Park, Byoung-Keon; Liu, Weiguo; Zhang, Jinhuan; Reed, Matthew P; Rupp, Jonathan D; Hoff, Carrie N; Hu, Jingwen

2015-01-01

Head injury is the leading cause of fatality and long-term disability for children. Pediatric heads change rapidly in both size and shape during growth, especially for children under 3 years old (YO). To accurately assess the head injury risks for children, it is necessary to understand the geometry of the pediatric head and how morphologic features influence injury causation within the 0-3 YO population. In this study, head CT scans from fifty-six 0-3 YO children were used to develop a statistical model of pediatric skull geometry. Geometric features important for injury prediction, including skull size and shape, skull thickness and suture width, along with their variations among the sample population, were quantified through a series of image and statistical analyses. The size and shape of the pediatric skull change significantly with age and head circumference. The skull thickness and suture width vary with age, head circumference and location, which will have important effects on skull stiffness and injury prediction. The statistical geometry model developed in this study can provide a geometrical basis for future development of child anthropomorphic test devices and pediatric head finite element models.

Multi-sector thermo-physiological head simulator for headgear research.

PubMed

Martinez, Natividad; Psikuta, Agnes; Corberán, José Miguel; Rossi, René M; Annaheim, Simon

2017-02-01

A novel thermo-physiological human head simulator for headgear testing was developed by coupling a thermal head manikin with a thermo-physiological model. As the heat flux at head-site is directly measured by the head manikin, this method provides a realistic quantification of the heat transfer phenomena occurring in the headgear, such as moisture absorption-desorption cycles, condensation, or moisture migration across clothing layers. Before coupling, the opportunities of the head manikin for representing the human physiology were evaluated separately. The evaluation revealed reduced precision in forehead and face temperature predictions under extreme heterogeneous temperature distributions and no initial limitation for simulating temperature changes observed in the human physiology. The thermo-physiological model predicted higher sweat rates when applied for coupled than for pure virtual simulations. After coupling, the thermo-physiological human head simulator was validated using eight human experiments. It precisely predicted core, mean skin, and forehead temperatures with average rmsd values within the average experimental standard deviation (rmsd of 0.20 ± 0.15, 0.83 ± 0.34, and 1.04 ± 0.54 °C, respectively). However, in case of forehead, precision was lower for the exposures including activity than for the sedentary exposures. The representation of the human sweat evaporation could be affected by a reduced evaporation efficiency and the manikin sweat dynamics. The industry will benefit from this thermo-physiological human head simulator leading to the development of helmet designs with enhanced thermal comfort and, therefore, with higher acceptance by users.

Prevalence and impact of diffuse axonal injury in patients with moderate and severe head injury: a cohort study of early magnetic resonance imaging findings and 1-year outcome.

PubMed

Skandsen, Toril; Kvistad, Kjell Arne; Solheim, Ole; Strand, Ingrid Haavde; Folvik, Mari; Vik, Anne

2010-09-01

In this prospective cohort study the authors examined patients with moderate to severe head injuries using MR imaging in the early phase. The objective was to explore the occurrence of diffuse axonal injury (DAI) and determine whether DAI was related to level of consciousness and patient outcome. One hundred and fifty-nine patients (age range 5-65 years) with traumatic brain injury, who survived the acute phase, and who had a Glasgow Coma Scale (GCS) score of 3-13 were admitted between October 2004 and August 2008. Of these 159 patients, 106 were examined using MR imaging within 4 weeks postinjury. Patients were classified into 1 of 3 stages of DAI: Stage 1, in which lesions were confined to the lobar white matter; Stage 2, in which there were callosal lesions; and Stage 3, in which lesions occurred in the dorsolateral brainstem. The outcome measure used 12 months postinjury was the Glasgow Outcome Scale-Extended (GOSE). Diffuse axonal injury was detected in 72% of the patients and a combination of DAI and contusions or hematomas was found in 50%. The GCS score was significantly lower in patients with "pure DAI" (median GCS Score 9) than in patients without DAI (median GCS Score 12; p < 0.001). The GCS score was related to outcome only in those patients with DAI (r = 0.47; p = 0.001). Patients with DAI had a median GOSE score of 7, and patients without DAI had a median GOSE score of 8 (p = 0.10). Outcome was better in patients with DAI Stage 1 (median GOSE Score 8) and DAI Stage 2 (median GOSE Score 7.5) than in patients with DAI Stage 3 (median GOSE Score 4; p < 0.001). Thus, in patients without any brainstem injury, there was no difference in good recovery between patients with DAI (67%) and patients without DAI (66%). Diffuse axonal injury was found in almost three-quarters of the patients with moderate and severe head injury who survived the acute phase. Diffuse axonal injury influenced the level of consciousness, and only in patients with DAI was GCS score related to outcome. Finally, DAI was a negative prognostic sign only when located in the brainstem.

Artificial gravity: head movements during short-radius centrifugation

NASA Technical Reports Server (NTRS)

Young, L. R.; Hecht, H.; Lyne, L. E.; Sienko, K. H.; Cheung, C. C.; Kavelaars, J.

2001-01-01

Short-radius centrifugation is a potential countermeasure to long-term weightlessness. Unfortunately, head movements in a rotating environment induce serious discomfort, non-compensatory vestibulo-ocular reflexes, and subjective illusions of body tilt. In two experiments we investigated the effects of pitch and yaw head movements in participants placed supine on a rotating bed with their head at the center of rotation, feet at the rim. The vast majority of participants experienced motion sickness, inappropriate vertical nystagmus and illusory tilt and roll as predicted by a semicircular canal model. However, a small but significant number of the 28 participants experienced tilt in the predicted plane but in the opposite direction. Heart rate was elevated following one-second duration head turns. Significant adaptation occurred following a series of head turns in the light. Vertical nystagmus, motion sickness and illusory tilt all decreased with adaptation. Consequences for artificial gravity produced by short-radius centrifuges as a countermeasure are discussed. Grant numbers: NCC 9-58. c 2001. Elsevier Science Ltd. All rights reserved.

Diffusion-Weighted Magnetic Resonance Imaging of Cholesteatoma Using PROPELLER at 1.5T: A Single-Centre Retrospective Study.

PubMed

Clarke, Sharon E; Mistry, Dipan; AlThubaiti, Talal; Khan, M Naeem; Morris, David; Bance, Manohar

2017-05-01

The purpose of this study was to evaluate the sensitivity, specificity, and positive and negative predictive values of the diffusion-weighted periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) technique in the detection of cholesteatoma at our institution with surgical confirmation in all cases. A retrospective review of 21 consecutive patients who underwent diffusion-weighted PROPELLER magnetic resonance imaging (MRI) on a 1.5T MRI scanner prior to primary or revision/second-look surgery for suspected cholesteatoma from 2009-2012 was performed. Diffusion-weighted PROPELLER had a sensitivity of 75%, specificity of 60%, positive predictive value of 86%, and negative predictive value of 43%. In the 15 patients for whom the presence or absence of cholesteatoma was correctly predicted, there were 2 cases where the reported locations of diffusion restriction did not correspond to the location of the cholesteatoma observed at surgery. On the basis of our retrospective study, we conclude that diffusion-weighted PROPELLER MRI is not sufficiently accurate to replace second look surgery at our institution. Copyright © 2016 Canadian Association of Radiologists. Published by Elsevier Inc. All rights reserved.

Cerebral fat embolism and the "starfield" pattern: a case report.

PubMed

Aravapalli, Amit; Fox, James; Lazaridis, Christos

2009-11-19

Nearly all long-bone fractures are accompanied by some form of fat embolism. The rare complication of clinically significant fat embolism syndrome, however, occurs in only 0.9-2.2% of cases. The clinical triad of fat embolism syndrome consists of respiratory distress, altered mental status, and petechial rash. Cerebral fat embolism causes the neurologic involvement seen in fat embolism syndrome. A 19-year-old African-American male was admitted with gunshot wounds to his right hand and right knee. He had diffuse hyperactive deep tendon reflexes, bilateral ankle clonus and decerebrate posturing with a Glasgow Coma Scale (GCS) score of 4T. Subsequent MRI of the brain showed innumerable punctate areas of restricted diffusion consistent with "starfield" pattern. On a 10-week follow up he has a normal neurological examination and he is discharged home. Despite the severity of the neurologic insult upon initial presentation, the majority of case reports on cerebral fat embolism illustrate that cerebral dysfunction associated with cerebral fat embolism is reversible. When neurologic deterioration occurs in the non-head trauma patient, then a systemic cause such as fat emboli should be considered. We describe a patient with non-head trauma who demonstrated the classic "starfield" pattern on diffusion-weighted MRI imaging.

Temporal changes of diffusion patterns in mild traumatic brain injury via group-based semi-blind source separation.

PubMed

Jing, Min; McGinnity, T Martin; Coleman, Sonya; Fuchs, Armin; Kelso, J A Scott

2015-07-01

Despite the emerging applications of diffusion tensor imaging (DTI) to mild traumatic brain injury (mTBI), very few investigations have been reported related to temporal changes in quantitative diffusion patterns, which may help to assess recovery from head injury and the long term impact associated with cognitive and behavioral impairments caused by mTBI. Most existing methods are focused on detection of mTBI affected regions rather than quantification of temporal changes following head injury. Furthermore, most methods rely on large data samples as required for statistical analysis and, thus, are less suitable for individual case studies. In this paper, we introduce an approach based on spatial group independent component analysis (GICA), in which the diffusion scalar maps from an individual mTBI subject and the average of a group of controls are arranged according to their data collection time points. In addition, we propose a constrained GICA (CGICA) model by introducing the prior information into the GICA decomposition process, thus taking available knowledge of mTBI into account. The proposed method is evaluated based on DTI data collected from American football players including eight controls and three mTBI subjects (at three time points post injury). The results show that common spatial patterns within the diffusion maps were extracted as spatially independent components (ICs) by GICA. The temporal change of diffusion patterns during recovery is revealed by the time course of the selected IC. The results also demonstrate that the temporal change can be further influenced by incorporating the prior knowledge of mTBI (if available) based on the proposed CGICA model. Although a small sample of mTBI subjects is studied, as a proof of concept, the preliminary results provide promising insight for applications of DTI to study recovery from mTBI and may have potential for individual case studies in practice.

NIR time domain diffuse optical tomography experiments on human forearm

NASA Astrophysics Data System (ADS)

Zhao, Huijuan; Gao, Feng; Tanikawa, Yukari; Homma, Kazuhiro; Yamada, Yukio

2003-07-01

To date, the applications of near infrared (NIR) diffusion optical tomography (DOT) are mostly focused on the potential of imaging woman breast, human head hemodynamics and neonatal head. For the neonates, who are suffered from ischaemia or hemorrhages in brain, bedside monitoring of the cerebral perfusion situation, e.g., the blood oxygen saturation and blood volume, is necessary for avoiding permanent injure. NIR DOT is on the promising tools because it is noninvasive, smaller in size, and moveable. Prior to achieving the ultimate goal of imaging infant brain and woman breast using DOT, in this paper, the developed methodologies are justified by imaging in vivo human forearms. The absolute absorption- and scattering-coefficient images revealed the inner structure of the forearm and the bones were clearly distinguished from the muscle. The differential images showed the changes in oxy-hemoglobin, deoxy-hemoglobin and blood volume during the hand-gripping exercises, which are consistent with the physiological process reported on literatures.

Acromegaly resolution after traumatic brain injury: a case report.

PubMed

Cob, Alejandro

2014-09-02

Anterior hypopituitarism is a common complication of head trauma, with a prevalence of 30% to 70% among long-term survivors. This is a much higher frequency than previously thought and suggests that most cases of post-traumatic hypopituitarism remain undiagnosed and untreated. Symptoms of hypopituitarism are very unspecific and very similar to those in traumatic brain injury patients in general, which makes hypopituitarism difficult to diagnose. The factors that predict the likelihood of developing hypopituitarism following traumatic brain injury remain poorly understood. The incidence of a specific hormone deficiency is variable, with growth hormone deficiency reported in 18% to 23% of cases. A 23-year-old Hispanic man with a 2-year history of hypertension and diabetes presented with severe closed-head trauma producing diffuse axonal injury, subarachnoid hemorrhage and a brain concussion. A computed tomography scan showed a pituitary macroadenoma. The patient has clinical features of acromegaly and gigantism without other pituitary hyperfunctional manifestations or mass effect syndrome. A short-term post-traumatic laboratory test showed high levels of insulin like growth factor 1 and growth hormone, which are compatible with a growth hormone-producing pituitary tumor. At the third month post-trauma, the patient's levels of insulin like growth factor 1 had decreased to low normal levels, with basal low levels of growth hormone. A glucose tolerance test completely suppressed the growth hormone, which confirmed resolution of acromegaly. An insulin tolerance test showed lack of stimulation of growth hormone and cortisol, demonstrating hypopituitarism of both axes. Even though hypopituitarism is a frequent complication of traumatic brain injury, there are no reports in the literature, to the best of my knowledge, of patients with hyperfunctional pituitary adenomas, such as growth hormone-producing adenoma, that resolved after head trauma. A clear protocol has not yet been established to identify which patients should be screened for hypopituitarism. Predictive factors that might determine the likelihood of developing post-traumatic hypopituitarism have not been clearly established, but there is no evidence of the presence of pituitary adenomas as a risk factor in otherwise healthy patients.

Computational Fluid Dynamics (CFD) Analysis for the Reduction of Impeller Discharge Flow Distortion

NASA Technical Reports Server (NTRS)

Garcia, R.; McConnaughey, P. K.; Eastland, A.

1993-01-01

The use of Computational Fluid Dynamics (CFD) in the design and analysis of high performance rocket engine pumps has increased in recent years. This increase has been aided by the activities of the Marshall Space Flight Center (MSFC) Pump Stage Technology Team (PSTT). The team's goals include assessing the accuracy and efficiency of several methodologies and then applying the appropriate methodology(s) to understand and improve the flow inside a pump. The PSTT's objectives, team membership, and past activities are discussed in Garcia1 and Garcia2. The PSTT is one of three teams that form the NASA/MSFC CFD Consortium for Applications in Propulsion Technology (McConnaughey3). The PSTT first applied CFD in the design of the baseline consortium impeller. This impeller was designed for the Space Transportation Main Engine's (STME) fuel turbopump. The STME fuel pump was designed with three impeller stages because a two-stage design was deemed to pose a high developmental risk. The PSTT used CFD to design an impeller whose performance allowed for a two-stage STME fuel pump design. The availability of this design would have lead to a reduction in parts, weight, and cost had the STME reached production. One sample of the baseline consortium impeller was manufactured and tested in a water rig. The test data showed that the impeller performance was as predicted and that a two-stage design for the STME fuel pump was possible with minimal risk. The test data also verified another CFD predicted characteristic of the design that was not desirable. The classical 'jet-wake' pattern at the impeller discharge was strengthened by two aspects of the design: by the high head coefficient necessary for the required pressure rise and by the relatively few impeller exit blades, 12, necessary to reduce manufacturing cost. This 'jet-wake pattern produces an unsteady loading on the diffuser vanes and has, in past rocket engine programs, lead to diffuser structural failure. In industrial applications, this problem is typically avoided by increasing the space between the impeller and the diffuser to allow the dissipation of this pattern and, hence, the reduction of diffuser vane unsteady loading. This approach leads to small performance losses and, more importantly in rocket engine applications, to significant increases in the pump's size and weight. This latter consideration typically makes this approach unacceptable in high performance rocket engines.

[Spanish versions of the Simplified Motor Score and the Glasgow Coma Scale in out-of-hospital treatment of head injury in adults: a preliminary study of each scale's ability to predict adverse events].

PubMed

Roca, Guillem; Mayol, Sergi; García, Esteban; Casajuana, Edgar; Quintana, Salvador

2015-06-01

To determine the ability of the modified (Spanish) version of the Simplified Motor Score (mSMS) to predict adverse events during hospitalization and to compare its predictive ability to that of the Glasgow Coma Scale (GCS) in adults with head injuries treated outside the hospital. Observational study of retrospective cohorts including all patients over the age of 14 years attended for head injuries occurring within 24 hours of treatment by an advanced life-support unit staffed by nurses between May 1, 2013, and May 1, 2014. The mSMS was a translation of the English original, created through a process of discussions of direct and back translations to arrive at consensus. Out-of-hospital patient records were searched to find GCS and mSMS scores. To predict the ability of each scale to predict brain injuries, neurosurgery, intubation, and/or inhospital death, we calculated the area under the receiving operator characteristic curves (AUCs). Of the total of 115 head-injury patients attended, 64 met the inclusion criteria. The mean (SD) age was 47 (24) years. Twelve (18.8%) patients developed some form of adverse event during hospitalization; 91.6% had brain damage, 58.3% required intubation, 8.3% required surgery, and 41.6% died. The AUC for the GCS was 0.907 (95% CI, 0.81-1.00; P<.001); the AUC for the mSMS was 0.796 (95% CI, 0.64-0.95; P=.001). Although the ability of the mSMS to predict in-hospital adverse outcomes is good, it is inferior to the GCS in adults with head injuries attended outside the hospital.

Do behavioural self-blame and stigma predict positive health changes in survivors of lung or head and neck cancers?

PubMed

Lebel, Sophie; Feldstain, Andrea; McCallum, Megan; Beattie, Sara; Irish, Jonathan; Bezjak, Andrea; Devins, Gerald M

2013-01-01

Survivors of lung or head and neck cancers often change tobacco and alcohol consumption after diagnosis, but few studies have examined other positive health changes (PHCs) or their determinants in these groups. The present study aims to: (a) document PHCs in survivors of lung (n = 107) or head and neck cancers (n = 99) and (b) examine behavioural self-blame and stigma as determinants of PHCs. We hypothesised that: (a) survivors would make a variety of PHCs; (b) behavioural self-blame for the disease would positively predict making PHCs; and (c) stigma would negatively predict making PHCs. Respondents self-administered measures of PHC, behavioural self-blame, and stigma. Hierarchical multiple regression analysis tested the hypotheses. More than 65% of respondents reported making PHCs, the most common being changes in diet (25%), exercise (23%) and tobacco consumption (16.5%). Behavioural self-blame significantly predicted PHCs but stigma did not. However, both behavioural self-blame and stigma significantly predicted changes in tobacco consumption. Many survivors of lung or head and neck cancers engage in PHCs, but those who do not attribute the disease to their behaviour are less likely to do so. Attention to this problem and additional counselling may help people to adopt PHCs.

Novel Model of Frontal Impact Closed Head Injury in the Rat

PubMed Central

Kilbourne, Michael; Kuehn, Reed; Tosun, Cigdem; Caridi, John; Keledjian, Kaspar; Bochicchio, Grant; Scalea, Thomas; Gerzanich, Volodymyr

2009-01-01

Abstract Frontal impact, closed head trauma is a frequent cause of traumatic brain injury (TBI) in motor vehicle and sports accidents. Diffuse axonal injury (DAI) is common in humans and experimental animals, and results from shearing forces that develop within the anisotropic brain. Because the specific anisotropic properties of the brain are axis-dependent, the anatomical site where force is applied as well as the resultant acceleration, be it linear, rotational, or some combination, are important determinants of the resulting pattern of brain injury. Available rodent models of closed head injury do not reproduce the frontal impact commonly encountered in humans. Here we describe a new rat model of closed head injury that is a modification of the impact-acceleration model of Marmarou. In our model (the Maryland model), the impact force is applied to the anterior part of the cranium and produces TBI by causing anterior-posterior plus sagittal rotational acceleration of the brain inside the intact cranium. Skull fractures, prolonged apnea, and mortality were absent. The animals exhibited petechial hemorrhages, DAI marked by a bead-like pattern of β-amyloid precursor protein (β-APP) in damaged axons, and widespread upregulation of β-APP in neurons, with regions affected including the orbitofrontal cortex (coup), corpus callosum, caudate, putamen, thalamus, cerebellum, and brainstem. Activated caspase-3 was prominent in hippocampal neurons and Purkinje cells at the grey-white matter junction of the cerebellum. Neurobehavioral dysfunction, manifesting as reduced spontaneous exploration, lasted more than 1 week. We conclude that the Maryland model produces diffuse injuries that may be relevant to human brain injury. PMID:19929375

Whole-head functional brain imaging of neonates at cot-side using time-resolved diffuse optical tomography

NASA Astrophysics Data System (ADS)

Dempsey, Laura A.; Cooper, Robert J.; Powell, Samuel; Edwards, Andrea; Lee, Chuen-Wai; Brigadoi, Sabrina; Everdell, Nick; Arridge, Simon; Gibson, Adam P.; Austin, Topun; Hebden, Jeremy C.

2015-07-01

We present a method for acquiring whole-head images of changes in blood volume and oxygenation from the infant brain at cot-side using time-resolved diffuse optical tomography (TR-DOT). At UCL, we have built a portable TR-DOT device, known as MONSTIR II, which is capable of obtaining a whole-head (1024 channels) image sequence in 75 seconds. Datatypes extracted from the temporal point spread functions acquired by the system allow us to determine changes in absorption and reduced scattering coefficients within the interrogated tissue. This information can then be used to define clinically relevant measures, such as oxygen saturation, as well as to reconstruct images of relative changes in tissue chromophore concentration, notably those of oxy- and deoxyhaemoglobin. Additionally, the effective temporal resolution of our system is improved with spatio-temporal regularisation implemented through a Kalman filtering approach, allowing us to image transient haemodynamic changes. By using this filtering technique with intensity and mean time-of-flight datatypes, we have reconstructed images of changes in absorption and reduced scattering coefficients in a dynamic 2D phantom. These results demonstrate that MONSTIR II is capable of resolving slow changes in tissue optical properties within volumes that are comparable to the preterm head. Following this verification study, we are progressing to imaging a 3D dynamic phantom as well as the neonatal brain at cot-side. Our current study involves scanning healthy babies to demonstrate the quality of recordings we are able to achieve in this challenging patient population, with the eventual goal of imaging functional activation and seizures.

Diagnostic and Prognostic Capability of Newer Magnetic Resonance Imaging Brain Sequences in Diffuse Axonal Injury Patient.

PubMed

Bansal, Mayank; Sinha, Virendra Deo; Bansal, Juhi

2018-01-01

Diffuse axonal injury is one of the major causes of unconsciousness, profound neurologic deficits and persistent vegetative state after head trauma. In recent years, MR imaging has been gaining popularity as an adjunctive imaging method in patients with DAI. Our study aims to assess the relative diagnostic and prognostic capability of various MRI sequences. Retrospective observational study done in 1 year duration on 30 DAI patients. Clinical assessment done with GCS at admission and GOS at 6 month. MRI Brain FLAIR, DWI, T2*GRE AND SWI sequences taken. DAI grade were evaluated for different MRI sequences. Prognosis was correlated to total number of lesion/locations and DAI grade of patients. Statistical analysis was done using SPSS Statistical software (ver.20.0.0) and XL-Stat and ANOVA one way test, post hoc test (Turkey test) and Chi square test. We studied 30 male patients, mean age 32.57±8.72 ranges. The commonest mode of injury is RTA-80%, fall-16% followed by assault-3.33%. Out of 30 patients, 17 patients (56.67%) had GCS <=8, 13 patients (43.33%) had GCS between 9 and 12 and no patient had a GCS score between 13 and 15. The mean GCS score was 8.47±1.50. At a 6 month follow up, out of a total of 30 patients, 2 patients (6.66%) expired (GOS-1), 3 patients (10%) remained in persistent vegetative state (GOS-2), 11 patients (36.67%) and 10 patients (33.33%) were found to be severely (GOS-3) and moderately (GOS-4) disabled respectively and 4 patients (13.33%) showed good recovery (GOS-5). Mean GOS is 3.37+/-1.06. Newer imaging -SWI able to detects lesion better (diagnosis of DAI) as compared to other older sequences like FLAIR,DWI,T2*GRE. But no statistically significant found between total number of lesion/locations to the outcome and also newer imaging do not change the grade of DAI patients. Although advanced imaging in head injury, SWI helps in diagnosing the diffuse axonal injury more efficiently than other imaging sequences, but it is the grade of patients at admission that predicts the outcome best.

The association between surgical complications and the POSSUM score in head and neck reconstruction: a retrospective single-center study.

PubMed

Makino, Yohjiroh; Ishida, Katsuhiro; Kishi, Keita; Kodama, Hiroki; Miyawaki, Takeshi

2018-06-01

The Physiological and Operative Severity Score for the Enumeration of Mortality and Morbidity (POSSUM) is widely used to predict surgical complications affecting various organs. However, there are few reports about objective evaluation methods for head and neck surgery. In this study, we retrospectively examined the association between POSSUM score and actual surgical complications of head and neck reconstruction surgery. In total, 711 patients who underwent head and neck reconstruction after cancer extirpation between January 2007 and January 2015 were studied. The predicted risk of complications was calculated using the POSSUM score and compared with the actual rate of perioperative complications. Perioperative complications occurred in 178 (25%) patients, comprising systemic complications in 52 (7%) patients, surgical site infection of the head and neck area in 78 (11%) patients and failure of the free flap in 55 (8.8%) patients. When patients were divided into a perioperative complication group and a no-complication group, a significant difference between the two groups was observed in the predicted postoperative rate calculated from the POSSUM score (p < .0001, odds ratio 1.03, 95% confidence interval = 1.02-1.04). Furthermore, the cutoff value of the POSSUM score calculated from the receiver operating characteristic curve using Youden's index was 43.0%. POSSUM is a useful risk indicator for head and neck reconstruction surgery. It is possible to objectively calculate the prediction level using a standard assessment method without adding burden to any medical facility. Therefore, patients may be considered at high risk for perioperative complications when the POSSUM score is 43.0% or higher.

Self-diagnosis of active head lice infestation by individuals from an impoverished community: high sensitivity and specificity.

PubMed

Pilger, Daniel; Khakban, Adak; Heukelbach, Jorg; Feldmeier, Hermann

2008-01-01

To compare sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of self-diagnosis for head lice infestation with visual inspection, we conducted a study in an urban slum in Brazil. Individuals were asked about active head lice infestation (self-diagnosis); we performed visual inspection and thereafter wet combing (gold standard). Of the 175 individuals included, 77 (44%) had an active head lice infestation. For self-diagnosis, sensitivity (80.5%), specificity (91.8%), PPV (88.6%) and NPV (85.7%) were high. Sensitivity of visual inspection was 35.1%. Public health professionals can use self-diagnosis as a diagnostic tool, to estimate accurately prevalence of pediculosis in a community, and to monitor ongoing intervention strategies.

Parent Involvement in Head Start and Children's Development: Indirect Effects Through Parenting.

PubMed

Ansari, Arya; Gershoff, Elizabeth

2016-04-01

The authors examined the extent to which parent involvement in Head Start programs predicted changes in both parent and child outcomes over time, using a nationally representative sample of 1,020 three-year-old children over 3 waves of the Family and Child Experiences Survey. Center policies that promote involvement predicted greater parent involvement, and parents who were more involved in Head Start centers demonstrated increased cognitive stimulation and decreased spanking and controlling behaviors. In turn, these changes in parenting behaviors were associated with gains in children's academic and behavioral skills. These findings suggest that Head Start programs should do even more to facilitate parent involvement because it can serve as an important means for promoting both parent and child outcomes.

Risk factors for work-related stress and health in head teachers.

PubMed

Phillips, Samantha J; Sen, Dil; McNamee, Roseanne

2008-12-01

Work-related stress (WRS) is known to cause ill-health and decreased productivity. Work in the education sector is thought to be particularly stressful. Few studies have considered risk factors for WRS and health in head teachers. To investigate health in head teachers in West Sussex. To determine personal risk factors most likely to predict cases of WRS and of poor health in head teachers. A cross-sectional study, in a population of 290 head teachers and principals of colleges of further education, using a validated questionnaire, 'a short stress evaluation tool' (ASSET) and additional questions derived from earlier studies. Results were compared with the ASSET database 'norm' groups: a general population of workers (GPN) group and a group of managers and professionals (MPN). 'Caseness' was defined as respondents who felt work was 'very or extremely stressful'. Head teachers had poor physical and mental health compared to the GPN group. Psychological well-being, particularly of females and primary head teachers was worse than a comparative group of managers and professionals. Teaching<5 h/week was a significant predictor of caseness and being female was the main risk factor for poor psychological well-being. Prevalence of self-reported stress in head teachers in West Sussex is high. Female head teachers had worse health outcomes. Our study identified possible personal risk factors predicting WRS and/or poor health in head teachers.

Pretreatment Prediction of Brain Tumors' Response to Radiation Therapy Using High b-Value Diffusion-Weighted MRI1

PubMed Central

Mardor, Yael; Roth, Yiftach; Ocherashvilli, Aharon; Spiegelmann, Roberto; Tichler, Thomas; Daniels, Dianne; Maier, Stephan E; Nissim, Ouzi; Ram, Zvi; Baram, Jacob; Orenstein, Arie; Pfeffer, Raphael

2004-01-01

Abstract Diffusion-weighted magnetic resonance imaging (DWMRI) is sensitive to tissues' biophysical characteristics, including apparent diffusion coefficients (ADCs) and volume fractions of water in different populations. In this work, we evaluate the clinical efficacy of DWMRI and high diffusion-weighted magnetic resonance imaging (HDWMRI), acquired up to b = 4000 sec/mm2 to amplify sensitivity to water diffusion properties, in pretreatment prediction of brain tumors' response to radiotherapy. Twelve patients with 20 brain lesions were studied. Six ring-enhancing lesions were excluded due to their distinct diffusion characteristics. Conventional and DWMRI were acquired on a 0.5-T MRI. Response to therapy was determined from relative changes in tumor volumes calculated from contrast-enhanced T1-weighted MRI, acquired before and a mean of 46 days after beginning therapy. ADCs and a diffusion index, RD, reflecting tissue viability based on water diffusion were calculated from DWMRIs. Pretreatment values of ADC and RD were found to correlate significantly with later tumor response/nonresponse (r = 0.76, P < .002 and r = 0.77, P < .001). This correlation implies that tumors with low pretreatment diffusion values, indicating high viability, will respond better to radiotherapy than tumors with high diffusion values, indicating necrosis. These results demonstrate the feasibility of using DWMRI for pretreatment prediction of response to therapy in patients with brain tumors undergoing radiotherapy. PMID:15140402

Pretreatment prediction of brain tumors' response to radiation therapy using high b-value diffusion-weighted MRI.

PubMed

Mardor, Yael; Roth, Yiftach; Ochershvilli, Aharon; Spiegelmann, Roberto; Tichler, Thomas; Daniels, Dianne; Maier, Stephan E; Nissim, Ouzi; Ram, Zvi; Baram, Jacob; Orenstein, Arie; Pfeffer, Raphael

2004-01-01

Diffusion-weighted magnetic resonance imaging (DWMRI) is sensitive to tissues' biophysical characteristics, including apparent diffusion coefficients (ADCs) and volume fractions of water in different populations. In this work, we evaluate the clinical efficacy of DWMRI and high diffusion-weighted magnetic resonance imaging (HDWMRI), acquired up to b = 4000 sec/mm(2) to amplify sensitivity to water diffusion properties, in pretreatment prediction of brain tumors' response to radiotherapy. Twelve patients with 20 brain lesions were studied. Six ring-enhancing lesions were excluded due to their distinct diffusion characteristics. Conventional and DWMRI were acquired on a 0.5-T MRI. Response to therapy was determined from relative changes in tumor volumes calculated from contrast-enhanced T1-weighted MRI, acquired before and a mean of 46 days after beginning therapy. ADCs and a diffusion index, R(D), reflecting tissue viability based on water diffusion were calculated from DWMRIs. Pretreatment values of ADC and R(D) were found to correlate significantly with later tumor response/nonresponse (r = 0.76, P <.002 and r = 0.77, P <.001). This correlation implies that tumors with low pretreatment diffusion values, indicating high viability, will respond better to radiotherapy than tumors with high diffusion values, indicating necrosis. These results demonstrate the feasibility of using DWMRI for pretreatment prediction of response to therapy in patients with brain tumors undergoing radiotherapy.

Thermogravimetric analysis for rapid assessment of moisture diffusivity in polydisperse powder and thin film matrices.

PubMed

Thirunathan, Praveena; Arnz, Patrik; Husny, Joeska; Gianfrancesco, Alessandro; Perdana, Jimmy

2018-03-01

Accurate description of moisture diffusivity is key to precisely understand and predict moisture transfer behaviour in a matrix. Unfortunately, measuring moisture diffusivity is not trivial, especially at low moisture values and/or elevated temperatures. This paper presents a novel experimental procedure to accurately measure moisture diffusivity based on thermogravimetric approach. The procedure is capable to measure diffusivity even at elevated temperatures (>70°C) and low moisture values (>1%). Diffusivity was extracted from experimental data based on "regular regime approach". The approach was tailored to determine diffusivity from thin film and from poly-dispersed powdered samples. Subsequently, measured diffusivity was validated by comparing to available literature data, showing good agreement. Ability of this approach to accurately measure diffusivity at a wider range of temperatures provides better insight on temperature dependency of diffusivity. Thus, this approach can be crucial to ensure good accuracy of moisture transfer description/prediction especially when involving elevated temperatures. Copyright © 2017 Elsevier Ltd. All rights reserved.

Diffusion-weighted magnetic resonance imaging of femoral head osteonecrosis in two groups of patients: Legg-Perthes-Calve and Avascular necrosis.

PubMed

Ozel, Betul Duran; Ozel, Deniz; Ozkan, Fuat; Halefoglu, Ahmet M

2016-03-01

The aim of this prospective study was to evaluate the value of diffusion-weighted magnetic resonance imaging (DW-MRI) in patients with osteonecrosis. Patients were divided into two subgroups as avascular necrosis (AVN) of femoral head for adult group and Legg-Calvé-Perthes (LCP) patients for children. Seventeen patients with femoral head AVN (mean age 42.3 years) and 17 patients with LCP (mean age 8.2 years) were included in this study. Diagnosis confirmed with clinical and other imaging procedures among the patients complaining hip pain. DW images were obtained using the single-shot echo planar sequence and had b values of 0, 500, 1000 s/mm(2). The apparent diffusion coefficient (ADC) values were measured from ADC maps in epiphysis of patients with AVN, both from metaphysis and epiphysis in patients with LCP, respectively. Mann-Whitney U test was used to compare ADC values. The mean ADC value of femoral heads (1.285 ± 0.204 × 10(-3) mm(2)/s) was increased in patients with AVN when compared to normal bone tissue (0.209 ± 0.214 × 10(-3) mm(2)/s) (p < 0.01). The mean ADC values (×10(-3) mm(2)/s) of both metaphysis (0.852 ± 0.293) and epiphysis (0.843 ± 0.332) were also increased in patients with LCP and differences were statistically significant (p < 0.01). As a result, osteonecrosis shows increased ADC values. But it is a controversial concept that DWI offers a valuable data to conventional MRI or not. However, as there are report states, there is a correlation between the stage of the disease with ADC values in the LCP disease. DWI is a fast, without-contrast administration technique and provides quantitative values additional to conventional MR techniques; we believe DWI may play an additional assistance to the diagnosis and treatment for LCP patients. Multicentric larger group studies may provide additional data to this issue.

Effects of low-level sarin and cyclosarin exposure on white matter integrity in Gulf War Veterans.

PubMed

Chao, Linda L; Zhang, Yu; Buckley, Shannon

2015-05-01

We previously found evidence of reduced gray and white matter volume in Gulf War (GW) veterans with predicted low-level exposure to sarin (GB) and cyclosarin (GF). Because loss of white matter tissue integrity has been linked to both gray and white matter atrophy, the current study sought to test the hypothesis that GW veterans with predicted GB/GF exposure have evidence of disrupted white matter microstructural integrity. Measures of fractional anisotropy and directional (i.e., axial and radial) diffusivity were assessed from the 4T diffusion tensor images (DTI) of 59 GW veterans with predicted GB/GF exposure and 59 "matched" unexposed GW veterans (mean age: 48 ± 7 years). The DTI data were analyzed using regions of interest (ROI) analyses that accounted for age, sex, total brain gray and white matter volume, trauma exposure, posttraumatic stress disorder, current major depression, and chronic multisymptom illness status. There were no significant group differences in fractional anisotropy or radial diffusivity. However, there was increased axial diffusivity in GW veterans with predicted GB/GF exposure compared to matched, unexposed veterans throughout the brain, including the temporal stem, corona radiata, superior and inferior (hippocampal) cingulum, inferior and superior fronto-occipital fasciculus, internal and external capsule, and superficial cortical white matter blades. Post hoc analysis revealed significant correlations between higher fractional anisotropy and lower radial diffusivity with better neurobehavioral performance in unexposed GW veterans. In contrast, only increased axial diffusivity in posterior limb of the internal capsule was associated with better psychomotor function in GW veterans with predicted GB/GF exposure. The finding that increased axial diffusivity in a region of the brain that contains descending corticospinal fibers was associated with better psychomotor function and the lack of significant neurobehavioral deficits in veterans with predicted GB/GF exposure hint at the possibility that the widespread increases in axial diffusivity that we observed in GW veterans with predicted GB/GF exposure relative to unexposed controls may reflect white matter reorganization after brain injury (i.e., exposure to GB/GF). Published by Elsevier B.V.

Relating Neuronal to Behavioral Performance: Variability of Optomotor Responses in the Blowfly

PubMed Central

Rosner, Ronny; Warzecha, Anne-Kathrin

2011-01-01

Behavioral responses of an animal vary even when they are elicited by the same stimulus. This variability is due to stochastic processes within the nervous system and to the changing internal states of the animal. To what extent does the variability of neuronal responses account for the overall variability at the behavioral level? To address this question we evaluate the neuronal variability at the output stage of the blowfly's (Calliphora vicina) visual system by recording from motion-sensitive interneurons mediating head optomotor responses. By means of a simple modelling approach representing the sensory-motor transformation, we predict head movements on the basis of the recorded responses of motion-sensitive neurons and compare the variability of the predicted head movements with that of the observed ones. Large gain changes of optomotor head movements have previously been shown to go along with changes in the animals' activity state. Our modelling approach substantiates that these gain changes are imposed downstream of the motion-sensitive neurons of the visual system. Moreover, since predicted head movements are clearly more reliable than those actually observed, we conclude that substantial variability is introduced downstream of the visual system. PMID:22066014

Interaction of Neuritic Plaques and Education Predicts Dementia

PubMed Central

Roe, Catherine M.; Xiong, Chengjie; Miller, J. Phillip; Cairns, Nigel J.; Morris, John C.

2009-01-01

In exploring the cognitive reserve hypothesis in persons with substantial Alzheimer disease neuropathology, we aimed to determine the extent to which educational attainment and densities of diffuse plaques, neuritic plaques, and neurofibrillary tangles predict dementia. Participants were 1563 individuals aged 65 years or above who were assessed for dementia within 1 year of death. Generalized linear mixed models were used to examine whether education and density ratings of diffuse plaques and neuritic plaques, and neurofibrillary tangle stage were associated with a dementia diagnosis. Education interacted with densities of neuritic plaques to predict dementia. Tangle density independently predicted dementia, but did not interact with education. Diffuse plaque density was unrelated to dementia when adjusted for densities of neuritic plaques and tangles. Among individuals with Alzheimer disease neuropathology, educational attainment, as a surrogate of cognitive reserve, modifies the influence of neuritic, but not diffuse, plaque neuropathology on the expression of dementia. PMID:18525294

Combination of acoustical radiosity and the image source method.

PubMed

Koutsouris, Georgios I; Brunskog, Jonas; Jeong, Cheol-Ho; Jacobsen, Finn

2013-06-01

A combined model for room acoustic predictions is developed, aiming to treat both diffuse and specular reflections in a unified way. Two established methods are incorporated: acoustical radiosity, accounting for the diffuse part, and the image source method, accounting for the specular part. The model is based on conservation of acoustical energy. Losses are taken into account by the energy absorption coefficient, and the diffuse reflections are controlled via the scattering coefficient, which defines the portion of energy that has been diffusely reflected. The way the model is formulated allows for a dynamic control of the image source production, so that no fixed maximum reflection order is required. The model is optimized for energy impulse response predictions in arbitrary polyhedral rooms. The predictions are validated by comparison with published measured data for a real music studio hall. The proposed model turns out to be promising for acoustic predictions providing a high level of detail and accuracy.

Advances in modeling sorption and diffusion of moisture in porous reactive materials.

PubMed

Harley, Stephen J; Glascoe, Elizabeth A; Lewicki, James P; Maxwell, Robert S

2014-06-23

Water-vapor-uptake experiments were performed on a silica-filled poly(dimethylsiloxane) (PDMS) network and modeled by using two different approaches. The data was modeled by using established methods and the model parameters were used to predict moisture uptake in a sample. The predictions are reasonably good, but not outstanding; many of the shortcomings of the modeling are discussed. A high-fidelity modeling approach is derived and used to improve the modeling of moisture uptake and diffusion. Our modeling approach captures the physics and kinetics of diffusion and adsorption/desorption, simultaneously. It predicts uptake better than the established method; more importantly, it is also able to predict outgassing. The material used for these studies is a filled-PDMS network; physical interpretations concerning the sorption and diffusion of moisture in this network are discussed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Plasma processes in inert gas thrusters

NASA Technical Reports Server (NTRS)

Kaufman, H. R.; Robinson, R. S.

1979-01-01

Inert gas thrusters, particularly with large diameters, have continued to be of interest for space propulsion applications. Two plasma processes are treated in this study: electron diffusion across magnetic fields and double ion production in inert-gas thrusters. A model is developed to describe electron diffusion across a magnetic field that is driven by both density and potential gradients, with Bohm diffusion used to predict the diffusion rate. This model has applications to conduction across magnetic fields inside a discharge chamber, as well as through a magnetic baffle region used to isolate a hollow cathode from the main chamber. A theory for double ion production is presented, which is not as complete as the electron diffusion theory described, but it should be a useful tool for predicting double ion sputter erosion. Correlations are developed that may be used, without experimental data, to predict double ion densities for the design of new and especially larger ion thrusters.

Measurement and modeling of diffusion time dependence of apparent diffusion coefficient and fractional anisotropy in prostate tissue ex vivo.

PubMed

Bourne, Roger; Liang, Sisi; Panagiotaki, Eleftheria; Bongers, Andre; Sved, Paul; Watson, Geoffrey

2017-10-01

The purpose of this study was to measure and model the diffusion time dependence of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) derived from conventional prostate diffusion-weighted imaging methods as used in recommended multiparametric MRI protocols. Diffusion tensor imaging (DTI) was performed at 9.4 T with three radical prostatectomy specimens, with diffusion times in the range 10-120 ms and b-values 0-3000 s/mm 2 . ADC and FA were calculated from DTI measurements at b-values of 800 and 1600 s/mm 2 . Independently, a two-component model (restricted isotropic plus Gaussian anisotropic) was used to synthesize DTI data, from which ADC and FA were predicted and compared with the measured values. Measured ADC and FA exhibited a diffusion time dependence, which was closely predicted by the two-component model. ADC decreased by about 0.10-0.15 μm 2 /ms as diffusion time increased from 10 to 120 ms. FA increased with diffusion time at b-values of 800 and 1600 s/mm 2 but was predicted to be independent of diffusion time at b = 3000 s/mm 2 . Both ADC and FA exhibited diffusion time dependence that could be modeled as two unmixed water pools - one having isotropic restricted dynamics, and the other unrestricted anisotropic dynamics. These results highlight the importance of considering and reporting diffusion times in conventional ADC and FA calculations and protocol recommendations, and inform the development of improved diffusion methods for prostate cancer imaging. Copyright © 2017 John Wiley & Sons, Ltd.

Homogenization Theory for the Prediction of Obstructed Solute Diffusivity in Macromolecular Solutions

PubMed Central

Donovan, Preston; Chehreghanianzabi, Yasaman; Rathinam, Muruhan; Zustiak, Silviya Petrova

2016-01-01

The study of diffusion in macromolecular solutions is important in many biomedical applications such as separations, drug delivery, and cell encapsulation, and key for many biological processes such as protein assembly and interstitial transport. Not surprisingly, multiple models for the a-priori prediction of diffusion in macromolecular environments have been proposed. However, most models include parameters that are not readily measurable, are specific to the polymer-solute-solvent system, or are fitted and do not have a physical meaning. Here, for the first time, we develop a homogenization theory framework for the prediction of effective solute diffusivity in macromolecular environments based on physical parameters that are easily measurable and not specific to the macromolecule-solute-solvent system. Homogenization theory is useful for situations where knowledge of fine-scale parameters is used to predict bulk system behavior. As a first approximation, we focus on a model where the solute is subjected to obstructed diffusion via stationary spherical obstacles. We find that the homogenization theory results agree well with computationally more expensive Monte Carlo simulations. Moreover, the homogenization theory agrees with effective diffusivities of a solute in dilute and semi-dilute polymer solutions measured using fluorescence correlation spectroscopy. Lastly, we provide a mathematical formula for the effective diffusivity in terms of a non-dimensional and easily measurable geometric system parameter. PMID:26731550

Stability of Gradient Field Corrections for Quantitative Diffusion MRI.

PubMed

Rogers, Baxter P; Blaber, Justin; Welch, E Brian; Ding, Zhaohua; Anderson, Adam W; Landman, Bennett A

2017-02-11

In magnetic resonance diffusion imaging, gradient nonlinearity causes significant bias in the estimation of quantitative diffusion parameters such as diffusivity, anisotropy, and diffusion direction in areas away from the magnet isocenter. This bias can be substantially reduced if the scanner- and coil-specific gradient field nonlinearities are known. Using a set of field map calibration scans on a large (29 cm diameter) phantom combined with a solid harmonic approximation of the gradient fields, we predicted the obtained b-values and applied gradient directions throughout a typical field of view for brain imaging for a typical 32-direction diffusion imaging sequence. We measured the stability of these predictions over time. At 80 mm from scanner isocenter, predicted b-value was 1-6% different than intended due to gradient nonlinearity, and predicted gradient directions were in error by up to 1 degree. Over the course of one month the change in these quantities due to calibration-related factors such as scanner drift and variation in phantom placement was <0.5% for b-values, and <0.5 degrees for angular deviation. The proposed calibration procedure allows the estimation of gradient nonlinearity to correct b-values and gradient directions ahead of advanced diffusion image processing for high angular resolution data, and requires only a five-minute phantom scan that can be included in a weekly or monthly quality assurance protocol.

A model describing diffusion in prostate cancer.

PubMed

Gilani, Nima; Malcolm, Paul; Johnson, Glyn

2017-07-01

Quantitative diffusion MRI has frequently been studied as a means of grading prostate cancer. Interpretation of results is complicated by the nature of prostate tissue, which consists of four distinct compartments: vascular, ductal lumen, epithelium, and stroma. Current diffusion measurements are an ill-defined weighted average of these compartments. In this study, prostate diffusion is analyzed in terms of a model that takes explicit account of tissue compartmentalization, exchange effects, and the non-Gaussian behavior of tissue diffusion. The model assumes that exchange between the cellular (ie, stromal plus epithelial) and the vascular and ductal compartments is slow. Ductal and cellular diffusion characteristics are estimated by Monte Carlo simulation and a two-compartment exchange model, respectively. Vascular pseudodiffusion is represented by an additional signal at b = 0. Most model parameters are obtained either from published data or by comparing model predictions with the published results from 41 studies. Model prediction error is estimated using 10-fold cross-validation. Agreement between model predictions and published results is good. The model satisfactorily explains the variability of ADC estimates found in the literature. A reliable model that predicts the diffusion behavior of benign and cancerous prostate tissue of different Gleason scores has been developed. Magn Reson Med 78:316-326, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Modeling Sediment Detention Ponds Using Reactor Theory and Advection-Diffusion Concepts

NASA Astrophysics Data System (ADS)

Wilson, Bruce N.; Barfield, Billy J.

1985-04-01

An algorithm is presented to model the sedimentation process in detention ponds. This algorithm is based on a mass balance for an infinitesimal layer that couples reactor theory concepts with advection-diffusion processes. Reactor theory concepts are used to (1) determine residence time of sediment particles and to (2) mix influent sediment with previously stored flow. Advection-diffusion processes are used to model the (1) settling characteristics of sediment and the (2) vertical diffusion of sediment due to turbulence. Predicted results of the model are compared to those observed on two pilot scale ponds for a total of 12 runs. The average percent error between predicted and observed trap efficiency was 5.2%. Overall, the observed sedimentology values were predicted with reasonable accuracy.

Portable vapor diffusion coefficient meter

DOEpatents

Ho, Clifford K [Albuquerque, NM

2007-06-12

An apparatus for measuring the effective vapor diffusion coefficient of a test vapor diffusing through a sample of porous media contained within a test chamber. A chemical sensor measures the time-varying concentration of vapor that has diffused a known distance through the porous media. A data processor contained within the apparatus compares the measured sensor data with analytical predictions of the response curve based on the transient diffusion equation using Fick's Law, iterating on the choice of an effective vapor diffusion coefficient until the difference between the predicted and measured curves is minimized. Optionally, a purge fluid can forced through the porous media, permitting the apparatus to also measure a gas-phase permeability. The apparatus can be made lightweight, self-powered, and portable for use in the field.

Preliminary investigation of single-file diffusion in complex plasma rings

NASA Astrophysics Data System (ADS)

Theisen, W. L.; Sheridan, T. E.

2010-04-01

Particles in one-dimensional (1D) systems cannot pass each other. However, it is still possible to define a diffusion process where the mean-squared displacement (msd) of an ensemble of particles in a 1D chain increases with time t. This process is called single-file diffusion. In contrast to diffusive processes that follow Fick's law, msdt, single-file diffusion is sub-Fickean and the msd is predicted to increase as t^1/2. We have recently created 1D dusty (complex) plasma rings in the DONUT (Dusty ONU experimenT) apparatus. Particle position data from these rings will be analyzed to determine the scaling of the msd with time and results will be compared with predictions of single-file diffusion theory.

Understanding Coupling of Global and Diffuse Solar Radiation with Climatic Variability

NASA Astrophysics Data System (ADS)

Hamdan, Lubna

Global solar radiation data is very important for wide variety of applications and scientific studies. However, this data is not readily available because of the cost of measuring equipment and the tedious maintenance and calibration requirements. Wide variety of models have been introduced by researchers to estimate and/or predict the global solar radiations and its components (direct and diffuse radiation) using other readily obtainable atmospheric parameters. The goal of this research is to understand the coupling of global and diffuse solar radiation with climatic variability, by investigating the relationships between these radiations and atmospheric parameters. For this purpose, we applied multilinear regression analysis on the data of National Solar Radiation Database 1991--2010 Update. The analysis showed that the main atmospheric parameters that affect the amount of global radiation received on earth's surface are cloud cover and relative humidity. Global radiation correlates negatively with both variables. Linear models are excellent approximations for the relationship between atmospheric parameters and global radiation. A linear model with the predictors total cloud cover, relative humidity, and extraterrestrial radiation is able to explain around 98% of the variability in global radiation. For diffuse radiation, the analysis showed that the main atmospheric parameters that affect the amount received on earth's surface are cloud cover and aerosol optical depth. Diffuse radiation correlates positively with both variables. Linear models are very good approximations for the relationship between atmospheric parameters and diffuse radiation. A linear model with the predictors total cloud cover, aerosol optical depth, and extraterrestrial radiation is able to explain around 91% of the variability in diffuse radiation. Prediction analysis showed that the linear models we fitted were able to predict diffuse radiation with efficiency of test adjusted R2 values equal to 0.93, using the data of total cloud cover, aerosol optical depth, relative humidity and extraterrestrial radiation. However, for prediction purposes, using nonlinear terms or nonlinear models might enhance the prediction of diffuse radiation.

Predicting Ga and Cu Profiles in Co-Evaporated Cu(In,Ga)Se 2 Using Modified Diffusion Equations and a Spreadsheet

DOE PAGES

Repins, Ingrid L.; Harvey, Steve; Bowers, Karen; ...

2017-05-15

Cu(In,Ga)Se 2(CIGS) photovoltaic absorbers frequently develop Ga gradients during growth. These gradients vary as a function of growth recipe, and are important to device performance. Prediction of Ga profiles using classic diffusion equations is not possible because In and Ga atoms occupy the same lattice sites and thus diffuse interdependently, and there is not yet a detailed experimental knowledge of the chemical potential as a function of composition that describes this interaction. Here, we show how diffusion equations can be modified to account for site sharing between In and Ga atoms. The analysis has been implemented in an Excel spreadsheet,more » and outputs predicted Cu, In, and Ga profiles for entered deposition recipes. A single set of diffusion coefficients and activation energies are chosen, such that simulated elemental profiles track with published data and those from this study. Extent and limits of agreement between elemental profiles predicted from the growth recipes and the spreadsheet tool are demonstrated.« less

Predicting Ga and Cu Profiles in Co-Evaporated Cu(In,Ga)Se 2 Using Modified Diffusion Equations and a Spreadsheet

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

Repins, Ingrid L.; Harvey, Steve; Bowers, Karen

Cu(In,Ga)Se 2(CIGS) photovoltaic absorbers frequently develop Ga gradients during growth. These gradients vary as a function of growth recipe, and are important to device performance. Prediction of Ga profiles using classic diffusion equations is not possible because In and Ga atoms occupy the same lattice sites and thus diffuse interdependently, and there is not yet a detailed experimental knowledge of the chemical potential as a function of composition that describes this interaction. Here, we show how diffusion equations can be modified to account for site sharing between In and Ga atoms. The analysis has been implemented in an Excel spreadsheet,more » and outputs predicted Cu, In, and Ga profiles for entered deposition recipes. A single set of diffusion coefficients and activation energies are chosen, such that simulated elemental profiles track with published data and those from this study. Extent and limits of agreement between elemental profiles predicted from the growth recipes and the spreadsheet tool are demonstrated.« less

Realistic numerical modelling of human head tissue exposure to electromagnetic waves from cellular phones

NASA Astrophysics Data System (ADS)

Scarella, Gilles; Clatz, Olivier; Lanteri, Stéphane; Beaume, Grégory; Oudot, Steve; Pons, Jean-Philippe; Piperno, Sergo; Joly, Patrick; Wiart, Joe

2006-06-01

The ever-rising diffusion of cellular phones has brought about an increased concern for the possible consequences of electromagnetic radiation on human health. Possible thermal effects have been investigated, via experimentation or simulation, by several research projects in the last decade. Concerning numerical modeling, the power absorption in a user's head is generally computed using discretized models built from clinical MRI data. The vast majority of such numerical studies have been conducted using Finite Differences Time Domain methods, although strong limitations of their accuracy are due to heterogeneity, poor definition of the detailed structures of head tissues (staircasing effects), etc. In order to propose numerical modeling using Finite Element or Discontinuous Galerkin Time Domain methods, reliable automated tools for the unstructured discretization of human heads are also needed. Results presented in this article aim at filling the gap between human head MRI images and the accurate numerical modeling of wave propagation in biological tissues and its thermal effects. To cite this article: G. Scarella et al., C. R. Physique 7 (2006).

Experimental and predicted cavitation performance of an 80.6 deg helical inducer in high temperature water

NASA Technical Reports Server (NTRS)

Kovich, G.

1972-01-01

The cavitating performance of a stainless steel 80.6 degree flat-plate helical inducer was investigated in water over a range of liquid temperatures and flow coefficients. A semi-empirical prediction method was used to compare predicted values of required net positive suction head in water with experimental values obtained in water. Good agreement was obtained between predicted and experimental data in water. The required net positive suction head in water decreased with increasing temperature and increased with flow coefficient, similar to that observed for a like inducer in liquid hydrogen.

Traumatic head injury mimicking acute encephalopathy with biphasic seizures and late reduced diffusion.

PubMed

Inoue, Hirofumi; Hasegawa, Shunji; Kajimoto, Madoka; Matsushige, Takeshi; Ichiyama, Takashi

2014-10-01

Many studies have reported acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) associated with viral infection at onset, but few studies have reported AESD without infection. We report the case of a 9-month-old boy who had a clinical course mimicking AESD after a traffic accident. The traffic accident caused a mild subdural hematoma without neurological abnormalities on admission. The boy became unconscious on the second day, and he was diagnosed with non-convulsive status epilepticus on the third day. Diffusion-weighted imaging showed reduced water diffusion in the subcortical white matter. On laboratory analysis interleukin (IL)-6 was elevated in the cerebrospinal fluid (CSF), but not in the serum. He had severe neurological sequelae with mental retardation, spastic tetraplegia, and epilepsy. We suggest that brain damage mimicking AESD was caused by the traffic accident and the prolonged seizure during infancy. © 2014 Japan Pediatric Society.

Changing head model extent affects finite element predictions of transcranial direct current stimulation distributions

NASA Astrophysics Data System (ADS)

Indahlastari, Aprinda; Chauhan, Munish; Schwartz, Benjamin; Sadleir, Rosalind J.

2016-12-01

Objective. In this study, we determined efficient head model sizes relative to predicted current densities in transcranial direct current stimulation (tDCS). Approach. Efficiency measures were defined based on a finite element (FE) simulations performed using nine human head models derived from a single MRI data set, having extents varying from 60%-100% of the original axial range. Eleven tissue types, including anisotropic white matter, and three electrode montages (T7-T8, F3-right supraorbital, Cz-Oz) were used in the models. Main results. Reducing head volume extent from 100% to 60%, that is, varying the model’s axial range from between the apex and C3 vertebra to one encompassing only apex to the superior cerebellum, was found to decrease the total modeling time by up to half. Differences between current density predictions in each model were quantified by using a relative difference measure (RDM). Our simulation results showed that {RDM} was the least affected (a maximum of 10% error) for head volumes modeled from the apex to the base of the skull (60%-75% volume). Significance. This finding suggested that the bone could act as a bioelectricity boundary and thus performing FE simulations of tDCS on the human head with models extending beyond the inferior skull may not be necessary in most cases to obtain reasonable precision in current density results.

The Head Tracks and Gaze Predicts: How the World’s Best Batters Hit a Ball

PubMed Central

Mann, David L.; Spratford, Wayne; Abernethy, Bruce

2013-01-01

Hitters in fast ball-sports do not align their gaze with the ball throughout ball-flight; rather, they use predictive eye movement strategies that contribute towards their level of interceptive skill. Existing studies claim that (i) baseball and cricket batters cannot track the ball because it moves too quickly to be tracked by the eyes, and that consequently (ii) batters do not – and possibly cannot – watch the ball at the moment they hit it. However, to date no studies have examined the gaze of truly elite batters. We examined the eye and head movements of two of the world’s best cricket batters and found both claims do not apply to these batters. Remarkably, the batters coupled the rotation of their head to the movement of the ball, ensuring the ball remained in a consistent direction relative to their head. To this end, the ball could be followed if the batters simply moved their head and kept their eyes still. Instead of doing so, we show the elite batters used distinctive eye movement strategies, usually relying on two predictive saccades to anticipate (i) the location of ball-bounce, and (ii) the location of bat-ball contact, ensuring they could direct their gaze towards the ball as they hit it. These specific head and eye movement strategies play important functional roles in contributing towards interceptive expertise. PMID:23516460

Interstitial diffusion in lithium-ion battery electrodes and structural phase transitions in crystalline solids from first principles

NASA Astrophysics Data System (ADS)

Bhattacharya, Jishnu

We perform first-principles investigations of thermally activated phase transitions and diffusion in solids. The atomic scale energy landscapes are evaluated with first-principles total energy calculations for different structural and configurational microstates. Effective Hamiltonians constructed from the total energies are subjected to Monte Carlo simulations to study thermodynamic and kinetic properties of the solids at finite temperatures. Cubic to tetragonal martensitic phase transitions are investigated beyond the harmonic approximation. As an example, stoichiometric TiH2 is studied where a cubic phase becomes stable at high temperature while ab-initio energy calculations predict the cubic phase to be mechanically unstable with respect to tetragonal distortions at zero Kelvin. An anharmonic Hamiltonian is used to explain the stability of the cubic phase at higher temperature. The importance of anharmonic terms is emphasized and the true nature of the high temperature phase is elucidated beyond the traditional Landau-like explanation. In Li-ion battery electrodes, phase transitions due to atomic redistribution with changes in Li concentration occur with insertion (removal) of Li-ions during discharge (charge). A comprehensive study of the thermodynamics and the non-dilute Li-diffusion mechanisms in spinel-Li1+xTi2 O4 is performed. Two distinct phases are predicted at different lithium compositions. The predicted voltage curve qualitatively matches with experimental observation. The predicted fast diffusion arises from crystallographic features unique to the spinel crystal structure elucidating the crucial role of crystal structure on Li diffusion in intercalation compounds. Effects of anion and guest species on diffusion are elucidated with Li- and Cu-diffusion in spinel-LixTiS2. We predict strong composition dependence of the diffusion coefficients. A unique feature about spinel-LixTiS2 is that the intermediate site of a Li-hop is coordinated by four Li-sites. This results in di- and triple-vacancy mechanisms at non-dilute concentrations with very different migration barriers. The strong dependence of hop mechanisms on local Li-arrangement is at the origin of large concentration dependence of the diffusion coefficients. This contrasts with spinel-Li xTiO2 where the transition states are coordinated only by the end states of the hop, thereby restricting hops to a single vacancy mechanism. Cu ions are predicted to have much slower diffusion rate in TiS 2 host compared to Li ions.

Validation of concussion risk curves for collegiate football players derived from HITS data.

PubMed

Funk, James R; Rowson, Steven; Daniel, Ray W; Duma, Stefan M

2012-01-01

For several years, Virginia Tech and other schools have measured the frequency and severity of head impacts sustained by collegiate American football players in real time using the Head Impact Telemetry (HIT) System of helmet-mounted accelerometers. In this study, data from 37,128 head impacts collected at Virginia Tech during games from 2006 to 2010 were analyzed. Peak head acceleration exceeded 100 g in 516 impacts, and the Head Injury Criterion (HIC) exceeded 200 in 468 impacts. Four instrumented players in the dataset sustained a concussion. These data were used to develop risk curves for concussion as a function of peak head acceleration and HIC. The validity of this biomechanical approach was assessed using epidemiological data on concussion incidence from other sources. Two specific aspects of concussion incidence were addressed: the variation by player position, and the frequency of repeat concussions. The HIT System data indicated that linemen sustained the highest overall number of head impacts, while skill positions sustained a higher number of more severe head impacts (peak acceleration > 100 g or HIC > 200). When weighted using injury risk curves, the HIT System data predicted a higher incidence of concussion in skill positions compared to linemen at rates that were in strong agreement with the epidemiological literature (Pearson's r = 0.72-0.87). The predicted rates of repeat concussions (21-39% over one season and 33-50% over five seasons) were somewhat higher than the ranges reported in the epidemiological literature. These analyses demonstrate that simple biomechanical parameters that can be measured by the HIT System possess a high level of power for predicting concussion.

An Analytical Calculation of Frictional and Bending Moments at the Head-Neck Interface of Hip Joint Implants during Different Physiological Activities.

PubMed

Farhoudi, Hamidreza; Oskouei, Reza H; Pasha Zanoosi, Ali A; Jones, Claire F; Taylor, Mark

2016-12-05

This study predicts the frictional moments at the head-cup interface and frictional torques and bending moments acting on the head-neck interface of a modular total hip replacement across a range of activities of daily living. The predicted moment and torque profiles are based on the kinematics of four patients and the implant characteristics of a metal-on-metal implant. Depending on the body weight and type of activity, the moments and torques had significant variations in both magnitude and direction over the activity cycles. For the nine investigated activities, the maximum magnitude of the frictional moment ranged from 2.6 to 7.1 Nm. The maximum magnitude of the torque acting on the head-neck interface ranged from 2.3 to 5.7 Nm. The bending moment acting on the head-neck interface varied from 7 to 21.6 Nm. One-leg-standing had the widest range of frictional torque on the head-neck interface (11 Nm) while normal walking had the smallest range (6.1 Nm). The widest range, together with the maximum magnitude of torque, bending moment, and frictional moment, occurred during one-leg-standing of the lightest patient. Most of the simulated activities resulted in frictional torques that were near the previously reported oxide layer depassivation threshold torque. The predicted bending moments were also found at a level believed to contribute to the oxide layer depassivation. The calculated magnitudes and directions of the moments, applied directly to the head-neck taper junction, provide realistic mechanical loading data for in vitro and computational studies on the mechanical behaviour and multi-axial fretting at the head-neck interface.

An Analytical Calculation of Frictional and Bending Moments at the Head-Neck Interface of Hip Joint Implants during Different Physiological Activities

PubMed Central

Farhoudi, Hamidreza; Oskouei, Reza H.; Pasha Zanoosi, Ali A.; Jones, Claire F.; Taylor, Mark

2016-01-01

This study predicts the frictional moments at the head-cup interface and frictional torques and bending moments acting on the head-neck interface of a modular total hip replacement across a range of activities of daily living. The predicted moment and torque profiles are based on the kinematics of four patients and the implant characteristics of a metal-on-metal implant. Depending on the body weight and type of activity, the moments and torques had significant variations in both magnitude and direction over the activity cycles. For the nine investigated activities, the maximum magnitude of the frictional moment ranged from 2.6 to 7.1 Nm. The maximum magnitude of the torque acting on the head-neck interface ranged from 2.3 to 5.7 Nm. The bending moment acting on the head-neck interface varied from 7 to 21.6 Nm. One-leg-standing had the widest range of frictional torque on the head-neck interface (11 Nm) while normal walking had the smallest range (6.1 Nm). The widest range, together with the maximum magnitude of torque, bending moment, and frictional moment, occurred during one-leg-standing of the lightest patient. Most of the simulated activities resulted in frictional torques that were near the previously reported oxide layer depassivation threshold torque. The predicted bending moments were also found at a level believed to contribute to the oxide layer depassivation. The calculated magnitudes and directions of the moments, applied directly to the head-neck taper junction, provide realistic mechanical loading data for in vitro and computational studies on the mechanical behaviour and multi-axial fretting at the head-neck interface. PMID:28774104

Can Functional Movement Assessment Predict Football Head Impact Biomechanics?

PubMed

Ford, Julia M; Campbell, Kody R; Ford, Cassie B; Boyd, Kenneth E; Padua, Darin A; Mihalik, Jason P

2018-06-01

The purposes of this study was to determine functional movement assessments' ability to predict head impact biomechanics in college football players and to determine whether head impact biomechanics could explain preseason to postseason changes in functional movement performance. Participants (N = 44; mass, 109.0 ± 20.8 kg; age, 20.0 ± 1.3 yr) underwent two preseason and postseason functional movement assessment screenings: 1) Fusionetics Movement Efficiency Test and 2) Landing Error Scoring System (LESS). Fusionetics is scored 0 to 100, and participants were categorized into the following movement quality groups as previously published: good (≥75), moderate (50-75), and poor (<50). The LESS is scored 0 to 17, and participants were categorized into the following previously published movement quality groups: good (≤5 errors), moderate (6-7 errors), and poor (>7 errors). The Head Impact Telemetry (HIT) System measured head impact frequency and magnitude (linear acceleration and rotational acceleration). An encoder with six single-axis accelerometers was inserted between the padding of a commercially available Riddell football helmet. We used random intercepts general linear-mixed models to analyze our data. There were no effects of preseason movement assessment group on the two Head Impact Telemetry System impact outcomes: linear acceleration and rotational acceleration. Head impact frequency did not significantly predict preseason to postseason score changes obtained from the Fusionetics (F1,36 = 0.22, P = 0.643, R = 0.006) or the LESS (F1,36 < 0.01, P = 0.988, R < 0.001) assessments. Previous research has demonstrated an association between concussion and musculoskeletal injury, as well as functional movement assessment performance and musculoskeletal injury. The functional movement assessments chosen may not be sensitive enough to detect neurological and neuromuscular differences within the sample and subtle changes after sustaining head impacts.

Alternative metrics for real-ear-to-coupler difference average values in children.

PubMed

Blumsack, Judith T; Clark-Lewis, Sandra; Watts, Kelli M; Wilson, Martha W; Ross, Margaret E; Soles, Lindsey; Ennis, Cydney

2014-10-01

Ideally, individual real-ear-to-coupler difference (RECD) measurements are obtained for pediatric hearing instrument-fitting purposes. When RECD measurements cannot be obtained, age-related average RECDs based on typically developing North American children are used. Evidence suggests that these values may not be appropriate for populations of children with retarded growth patterns. The purpose of this study was to determine if another metric, such as head circumference, height, or weight, can be used for prediction of RECDs in children. Design was a correlational study. For all participants, RECD values in both ears, head circumference, height, and weight were measured. The sample consisted of 68 North American children (ages 3-11 yr). Height, weight, head circumference, and RECDs were measured and were analyzed for both ears at 500, 750, 1000, 1500, 2000, 3000, 4000, and 6000 Hz. A backward elimination multiple-regression analysis was used to determine if age, height, weight, and/or head circumference are significant predictors of RECDs. For the left ear, head circumference was retained as the only statistically significant variable in the final model. For the right ear, head circumference was retained as the only statistically significant independent variable at all frequencies except at 2000 and 4000 Hz. At these latter frequencies, weight was retained as the only statistically significant independent variable after all other variables were eliminated. Head circumference can be considered as a metric for RECD prediction in children when individual measurements cannot be obtained. In developing countries where equipment is often unavailable and stunted growth can reduce the value of using age as a metric, head circumference can be considered as an alternative metric in the prediction of RECDs. American Academy of Audiology.

[Trichological examinations in women suffering from diabetes mellitus].

PubMed

Brzezińska-Wcisło, L; Bogdanowski, T; Koślacz, E; Hawrot, A

2000-01-01

The lack of data on the process of alopecia in women suffering from diabetes mellitus made us undertake research in this area. The aim of this paper was the assessment of the state of head hair in trichological and clinical examinations, and on the basis of questionnaire. 50 women (age 44-82 years) were included in the study. Alopecia in women with diabetes mellitus is diffuse, located on the apex of the head and basic hair loss lies in telogenic pathomechanism. The highest percentage of telogenic hair is found in women treated with biguanides, and the lowest one in female patients taking insulin.

Role of susceptibility-weighted imaging in demonstration of cerebral fat embolism.

PubMed

Yeap, Pheyming; Kanodia, Avinash Kumar; Main, Gavin; Yong, Aiwain

2015-01-08

Cerebral fat embolism (CFE) is a rare but potentially lethal complication of long bone fractures. Many cases of CFE occur as subclinical events and remain undiagnosed. We report a case of a 22-year-old man, with multiple long bone fractures from a road traffic accident, who subsequently developed hypoxia, neurological abnormality and petechial rash. CT of the head was normal. MRI of the head confirmed the diagnosis with lesions markedly conspicuous and most widespread on susceptibility-weighted imaging as compared to all other sequences including diffusion-weighted imaging. 2015 BMJ Publishing Group Ltd.

A variational image-based approach to the correction of susceptibility artifacts in the alignment of diffusion weighted and structural MRI.

PubMed

Tao, Ran; Fletcher, P Thomas; Gerber, Samuel; Whitaker, Ross T

2009-01-01

This paper presents a method for correcting the geometric and greyscale distortions in diffusion-weighted MRI that result from inhomogeneities in the static magnetic field. These inhomogeneities may due to imperfections in the magnet or to spatial variations in the magnetic susceptibility of the object being imaged--so called susceptibility artifacts. Echo-planar imaging (EPI), used in virtually all diffusion weighted acquisition protocols, assumes a homogeneous static field, which generally does not hold for head MRI. The resulting distortions are significant, sometimes more than ten millimeters. These artifacts impede accurate alignment of diffusion images with structural MRI, and are generally considered an obstacle to the joint analysis of connectivity and structure in head MRI. In principle, susceptibility artifacts can be corrected by acquiring (and applying) a field map. However, as shown in the literature and demonstrated in this paper, field map corrections of susceptibility artifacts are not entirely accurate and reliable, and thus field maps do not produce reliable alignment of EPIs with corresponding structural images. This paper presents a new, image-based method for correcting susceptibility artifacts. The method relies on a variational formulation of the match between an EPI baseline image and a corresponding T2-weighted structural image but also specifically accounts for the physics of susceptibility artifacts. We derive a set of partial differential equations associated with the optimization, describe the numerical methods for solving these equations, and present results that demonstrate the effectiveness of the proposed method compared with field-map correction.

Comparison of the Canadian CT head rule and the New Orleans criteria in patients with minor head injury in a Spanish hospital.

PubMed

Valle Alonso, Joaquín; Fonseca Del Pozo, Francisco Javier; Vaquero Álvarez, Manuel; Lopera Lopera, Elisa; Garcia Segura, Marisol; García Arévalo, Ricardo

2016-12-16

To compare two scales for assessment of patients with mild head injury. The Canadian CT Head Rule (CCHR) and New Orleans Criteria (NOC) according to their diagnostic accuracy in patients attending an emergency department, and to determine the most important predictive values. Cross-sectional study in a first-level Hospital in the period of January 2011 to January 2013. Patients with mild head injury criteria were included. All the patients underwent a computed tomography (CT) of the head as part of internal protocol and the CCHR and NOC criteria were recorded for each patient. We consider the main variable the presence of traumatic lesions on CT and, as secondary variables, neurosurgical intervention and post-concussion syndrome. Sensitivity, specificity, predictive values and validity index (VI) of the CCHR and the NO criteria in the subgroup of patients with a Glasgow Coma Scale (GCS) score of 15 points were compared. A total of 217 patients, of whom 197 had a GCS score of 15 points were evaluated. Both rules showed 100% sensitivity when a significant injury was presented in the CT, the CCHR 100% (95% CI: 97.4%-100%) and the NO criteria 100% (95% CI: 97.4%-100%); but the CCHR achieved higher values of specificity 25.3% (95% CI: 18.6%-32%), positive predictive value (PPV) and VI. The two rules showed a 100% sensitivity regarding neurosurgical intervention; however the CCHR with high-risk criteria showed better specificity, PPV and VI 55.2 (95% CI: 8.3%-62.2%) compared to the NO criteria 7.6 (95% CI: 3.8%-11.5%). With regard to post-concussion syndrome criteria NO criteria showed better sensitivity 100% (95% CI: 96.2%-100%) and predictive values, but lower specificity and VI compared with the CCHR 76.9% (95% CI: 50.2%-100%). Our study demonstrates the high sensitivity of the CCHR and the NO criteria in patients with mild head injury, both to detect a significant clinical lesion on CT or the need for neurosurgical intervention and better specificity of CCHR compared with NO criteria. The adoption of clinical prediction rules, especially the CCHR, to request a CT scan in patients with mild head injury should be recommended in the emergency department. Copyright © 2016 Elsevier España, S.L.U. All rights reserved.

Predicting pain relief: Use of pre-surgical trigeminal nerve diffusion metrics in trigeminal neuralgia.

PubMed

Hung, Peter S-P; Chen, David Q; Davis, Karen D; Zhong, Jidan; Hodaie, Mojgan

2017-01-01

Trigeminal neuralgia (TN) is a chronic neuropathic facial pain disorder that commonly responds to surgery. A proportion of patients, however, do not benefit and suffer ongoing pain. There are currently no imaging tools that permit the prediction of treatment response. To address this paucity, we used diffusion tensor imaging (DTI) to determine whether pre-surgical trigeminal nerve microstructural diffusivities can prognosticate response to TN treatment. In 31 TN patients and 16 healthy controls, multi-tensor tractography was used to extract DTI-derived metrics-axial (AD), radial (RD), mean diffusivity (MD), and fractional anisotropy (FA)-from the cisternal segment, root entry zone and pontine segment of trigeminal nerves for false discovery rate-corrected Student's t -tests. Ipsilateral diffusivities were bootstrap resampled to visualize group-level diffusivity thresholds of long-term response. To obtain an individual-level statistical classifier of surgical response, we conducted discriminant function analysis (DFA) with the type of surgery chosen alongside ipsilateral measurements and ipsilateral/contralateral ratios of AD and RD from all regions of interest as prediction variables. Abnormal diffusivity in the trigeminal pontine fibers, demonstrated by increased AD, highlighted non-responders (n = 14) compared to controls. Bootstrap resampling revealed three ipsilateral diffusivity thresholds of response-pontine AD, MD, cisternal FA-separating 85% of non-responders from responders. DFA produced an 83.9% (71.0% using leave-one-out-cross-validation) accurate prognosticator of response that successfully identified 12/14 non-responders. Our study demonstrates that pre-surgical DTI metrics can serve as a highly predictive, individualized tool to prognosticate surgical response. We further highlight abnormal pontine segment diffusivities as key features of treatment non-response and confirm the axiom that central pain does not commonly benefit from peripheral treatments.

Effect of annealing on structural changes and oxygen diffusion in amorphous HfO2 using classical molecular dynamics

NASA Astrophysics Data System (ADS)

Shen, Wenqing; Kumari, Niru; Gibson, Gary; Jeon, Yoocharn; Henze, Dick; Silverthorn, Sarah; Bash, Cullen; Kumar, Satish

2018-02-01

Non-volatile memory is a promising alternative to present memory technologies. Oxygen vacancy diffusion has been widely accepted as one of the reasons for the resistive switching mechanism of transition-metal-oxide based resistive random access memory. In this study, molecular dynamics simulation is applied to investigate the diffusion coefficient and activation energy of oxygen in amorphous hafnia. Two sets of empirical potential, Charge-Optimized Many-Body (COMB) and Morse-BKS (MBKS), were considered to investigate the structural and diffusion properties at different temperatures. COMB predicts the activation energy of 0.53 eV for the temperature range of 1000-2000 K, while MBKS predicts 2.2 eV at high temperature (1600-2000 K) and 0.36 eV at low temperature (1000-1600 K). Structural changes and appearance of nano-crystalline phases with increasing temperature might affect the activation energy of oxygen diffusion predicted by MBKS, which is evident from the change in coordination number distribution and radial distribution function. None of the potentials make predictions that are fully consistent with density functional theory simulations of both the structure and diffusion properties of HfO2. This suggests the necessity of developing a better multi-body potential that considers charge exchange.

Preference bias of head orientation in choosing between two non-durables.

PubMed

Funaya, Hiroyuki; Shibata, Tomohiro

2015-01-01

The goal of this study is to investigate how customers' gaze, head and body orientations reflect their choices. Although the relationship between human choice and gaze behavior has been well-studied, other behaviors such as head and body are unknown. We conducted a two-alternatives-forced-choice task to examine (1) whether preference bias, i.e., a positional bias in gaze, head and body toward the item that was later chosen, exists in choice, (2) when preference bias is observed and when prediction of the resulting choice becomes possible (3) whether human choice is affected when the body orientations are manipulated. We used real non-durable products (cheap snacks and clothing) on a shopping shelf. The results showed that there was a significant preference bias in head orientation at the beginning 1 s when the subjects stood straight toward the shelf, and that the head orientation was more biased toward the selected item than the gaze and the center of pressure at the ending 1 s. Manipulating body orientation did not affect the result of choice. The preference bias detected by observing the head orientation would be useful in marketing science for predicting customers' choice.

Parent Involvement in Head Start and Children’s Development: Indirect Effects Through Parenting

PubMed Central

Ansari, Arya; Gershoff, Elizabeth

2015-01-01

The authors examined the extent to which parent involvement in Head Start programs predicted changes in both parent and child outcomes over time, using a nationally representative sample of 1,020 three-year-old children over 3 waves of the Family and Child Experiences Survey. Center policies that promote involvement predicted greater parent involvement, and parents who were more involved in Head Start centers demonstrated increased cognitive stimulation and decreased spanking and controlling behaviors. In turn, these changes in parenting behaviors were associated with gains in children’s academic and behavioral skills. These findings suggest that Head Start programs should do even more to facilitate parent involvement because it can serve as an important means for promoting both parent and child outcomes. PMID:27022200

Ion diffusion may introduce spurious current sources in current-source density (CSD) analysis.

PubMed

Halnes, Geir; Mäki-Marttunen, Tuomo; Pettersen, Klas H; Andreassen, Ole A; Einevoll, Gaute T

2017-07-01

Current-source density (CSD) analysis is a well-established method for analyzing recorded local field potentials (LFPs), that is, the low-frequency part of extracellular potentials. Standard CSD theory is based on the assumption that all extracellular currents are purely ohmic, and thus neglects the possible impact from ionic diffusion on recorded potentials. However, it has previously been shown that in physiological conditions with large ion-concentration gradients, diffusive currents can evoke slow shifts in extracellular potentials. Using computer simulations, we here show that diffusion-evoked potential shifts can introduce errors in standard CSD analysis, and can lead to prediction of spurious current sources. Further, we here show that the diffusion-evoked prediction errors can be removed by using an improved CSD estimator which accounts for concentration-dependent effects. NEW & NOTEWORTHY Standard CSD analysis does not account for ionic diffusion. Using biophysically realistic computer simulations, we show that unaccounted-for diffusive currents can lead to the prediction of spurious current sources. This finding may be of strong interest for in vivo electrophysiologists doing extracellular recordings in general, and CSD analysis in particular. Copyright © 2017 the American Physiological Society.

Structure of myosin filaments from relaxed Lethocerus flight muscle by cryo-EM at 6 Å resolution

PubMed Central

Hu, Zhongjun; Taylor, Dianne W.; Reedy, Michael K.; Edwards, Robert J.; Taylor, Kenneth A.

2016-01-01

We describe a cryo–electron microscopy three-dimensional image reconstruction of relaxed myosin II–containing thick filaments from the flight muscle of the giant water bug Lethocerus indicus. The relaxed thick filament structure is a key element of muscle physiology because it facilitates the reextension process following contraction. Conversely, the myosin heads must disrupt their relaxed arrangement to drive contraction. Previous models predicted that Lethocerus myosin was unique in having an intermolecular head-head interaction, as opposed to the intramolecular head-head interaction observed in all other species. In contrast to the predicted model, we find an intramolecular head-head interaction, which is similar to that of other thick filaments but oriented in a distinctly different way. The arrangement of myosin’s long α-helical coiled-coil rod domain has been hypothesized as either curved layers or helical subfilaments. Our reconstruction is the first report having sufficient resolution to track the rod α helices in their native environment at resolutions ~5.5 Å, and it shows that the layer arrangement is correct for Lethocerus. Threading separate paths through the forest of myosin coiled coils are four nonmyosin peptides. We suggest that the unusual position of the heads and the rod arrangement separated by nonmyosin peptides are adaptations for mechanical signal transduction whereby applied tension disrupts the myosin heads as a component of stretch activation. PMID:27704041

Utilizing multiple scale models to improve predictions of extra-axial hemorrhage in the immature piglet.

PubMed

Scott, Gregory G; Margulies, Susan S; Coats, Brittany

2016-10-01

Traumatic brain injury (TBI) is a leading cause of death and disability in the USA. To help understand and better predict TBI, researchers have developed complex finite element (FE) models of the head which incorporate many biological structures such as scalp, skull, meninges, brain (with gray/white matter differentiation), and vasculature. However, most models drastically simplify the membranes and substructures between the pia and arachnoid membranes. We hypothesize that substructures in the pia-arachnoid complex (PAC) contribute substantially to brain deformation following head rotation, and that when included in FE models accuracy of extra-axial hemorrhage prediction improves. To test these hypotheses, microscale FE models of the PAC were developed to span the variability of PAC substructure anatomy and regional density. The constitutive response of these models were then integrated into an existing macroscale FE model of the immature piglet brain to identify changes in cortical stress distribution and predictions of extra-axial hemorrhage (EAH). Incorporating regional variability of PAC substructures substantially altered the distribution of principal stress on the cortical surface of the brain compared to a uniform representation of the PAC. Simulations of 24 non-impact rapid head rotations in an immature piglet animal model resulted in improved accuracy of EAH prediction (to 94 % sensitivity, 100 % specificity), as well as a high accuracy in regional hemorrhage prediction (to 82-100 % sensitivity, 100 % specificity). We conclude that including a biofidelic PAC substructure variability in FE models of the head is essential for improved predictions of hemorrhage at the brain/skull interface.

A new model integrating short- and long-term aging of copper added to soils

PubMed Central

Zeng, Saiqi; Li, Jumei; Wei, Dongpu

2017-01-01

Aging refers to the processes by which the bioavailability/toxicity, isotopic exchangeability, and extractability of metals added to soils decline overtime. We studied the characteristics of the aging process in copper (Cu) added to soils and the factors that affect this process. Then we developed a semi-mechanistic model to predict the lability of Cu during the aging process with descriptions of the diffusion process using complementary error function. In the previous studies, two semi-mechanistic models to separately predict short-term and long-term aging of Cu added to soils were developed with individual descriptions of the diffusion process. In the short-term model, the diffusion process was linearly related to the square root of incubation time (t1/2), and in the long-term model, the diffusion process was linearly related to the natural logarithm of incubation time (lnt). Both models could predict short-term or long-term aging processes separately, but could not predict the short- and long-term aging processes by one model. By analyzing and combining the two models, we found that the short- and long-term behaviors of the diffusion process could be described adequately using the complementary error function. The effect of temperature on the diffusion process was obtained in this model as well. The model can predict the aging process continuously based on four factors—soil pH, incubation time, soil organic matter content and temperature. PMID:28820888

Predicting Salt Permeability Coefficients in Highly Swollen, Highly Charged Ion Exchange Membranes.

PubMed

Kamcev, Jovan; Paul, Donald R; Manning, Gerald S; Freeman, Benny D

2017-02-01

This study presents a framework for predicting salt permeability coefficients in ion exchange membranes in contact with an aqueous salt solution. The model, based on the solution-diffusion mechanism, was tested using experimental salt permeability data for a series of commercial ion exchange membranes. Equilibrium salt partition coefficients were calculated using a thermodynamic framework (i.e., Donnan theory), incorporating Manning's counterion condensation theory to calculate ion activity coefficients in the membrane phase and the Pitzer model to calculate ion activity coefficients in the solution phase. The model predicted NaCl partition coefficients in a cation exchange membrane and two anion exchange membranes, as well as MgCl 2 partition coefficients in a cation exchange membrane, remarkably well at higher external salt concentrations (>0.1 M) and reasonably well at lower external salt concentrations (<0.1 M) with no adjustable parameters. Membrane ion diffusion coefficients were calculated using a combination of the Mackie and Meares model, which assumes ion diffusion in water-swollen polymers is affected by a tortuosity factor, and a model developed by Manning to account for electrostatic effects. Agreement between experimental and predicted salt diffusion coefficients was good with no adjustable parameters. Calculated salt partition and diffusion coefficients were combined within the framework of the solution-diffusion model to predict salt permeability coefficients. Agreement between model and experimental data was remarkably good. Additionally, a simplified version of the model was used to elucidate connections between membrane structure (e.g., fixed charge group concentration) and salt transport properties.

Test of the diffusing-diffusivity mechanism using near-wall colloidal dynamics

NASA Astrophysics Data System (ADS)

Matse, Mpumelelo; Chubynsky, Mykyta V.; Bechhoefer, John

2017-10-01

The mechanism of diffusing diffusivity predicts that, in environments where the diffusivity changes gradually, the displacement distribution becomes non-Gaussian, even though the mean-square displacement grows linearly with time. Here, we report single-particle tracking measurements of the diffusion of colloidal spheres near a planar substrate. Because the local effective diffusivity is known, we have been able to carry out a direct test of this mechanism for diffusion in inhomogeneous media.

Persistent, Long-term Cerebral White Matter Changes after Sports-Related Repetitive Head Impacts

PubMed Central

Bazarian, Jeffrey J.; Zhu, Tong; Zhong, Jianhui; Janigro, Damir; Rozen, Eric; Roberts, Andrew; Javien, Hannah; Merchant-Borna, Kian; Abar, Beau; Blackman, Eric G.

2014-01-01

Introduction Repetitive head impacts (RHI) sustained in contact sports are thought to be necessary for the long-term development of chronic traumatic encephalopathy (CTE). Our objectives were to: 1) characterize the magnitude and persistence of RHI-induced white matter (WM) changes; 2) determine their relationship to kinematic measures of RHI; and 3) explore their clinical relevance. Methods Prospective, observational study of 10 Division III college football players and 5 non-athlete controls during the 2011-12 season. All subjects underwent diffusion tensor imaging (DTI), physiologic, cognitive, and balance testing at pre-season (Time 1), post-season (Time 2), and after 6-months of no-contact rest (Time 3). Head impact measures were recorded using helmet-mounted accelerometers. The percentage of whole-brain WM voxels with significant changes in fractional anisotropy (FA) and mean diffusivity (MD) from Time 1 to 2, and Time 1 to 3 was determined for each subject and correlated to head impacts and clinical measures. Results Total head impacts for the season ranged from 431–1,850. No athlete suffered a clinically evident concussion. Compared to controls, athletes experienced greater changes in FA and MD from Time 1 to 2 as well as Time 1 to 3; most differences at Time 2 persisted to Time 3. Among athletes, the percentage of voxels with decreased FA from Time 1 to 2 was positively correlated with several helmet impact measures. The persistence of WM changes from Time 1 to 3 was also associated with changes in serum ApoA1 and S100B autoantibodies. WM changes were not consistently associated with cognition or balance. Conclusions A single football season of RHIs without clinically-evident concussion resulted in WM changes that correlated with multiple helmet impact measures and persisted following 6 months of no-contact rest. This lack of WM recovery could potentially contribute to cumulative WM changes with subsequent RHI exposures. PMID:24740265

Cybersickness Onset With Reflexive Head Movements During Land and Shipboard Head-Mounted Display Flight Simulation

DTIC Science & Technology

2010-09-09

provoked a predictable OKCR coronal head tilt (p < 0.001) whenever aircraft angle of bank (AOB) increased (Fig. 2). With 90º of simulated AOB, land... head pitch were –3.3 ± 3.8 to 6.8 ± 5.9 on land, and –4.0º ± 5.6 to 7.6º ± 9.7 at sea (Fig. 3). 7 Combined Coronal OKCR ( Head Tilt ) Data for...Land OKCR Figure 2: Coronal OKCR ( head tilt ) vs. angle of bank, during both land based and shipboard HMD/VR flight simulation. Combined

Fiber-based hybrid probe for non-invasive cerebral monitoring in neonatology

NASA Astrophysics Data System (ADS)

Rehberger, Matthias; Giovannella, Martina; Pagliazzi, Marco; Weigel, Udo; Durduran, Turgut; Contini, Davide; Spinelli, Lorenzo; Pifferi, Antonio; Torricelli, Alessandro; Schmitt, Robert

2015-07-01

Improved cerebral monitoring systems are needed to prevent preterm infants from long-term cognitive and motor restrictions. Combining advanced near-infrared diffuse spectroscopy measurement technologies, time-resolved spectroscopy (TRS) and diffuse correlation spectroscopy (DCS) will introduce novel indicators of cerebral oxygen metabolism and blood flow for neonatology. For non-invasive sensing a fiber-optical probe is used to send and receive light from the infant head. In this study we introduce a new fiber-based hybrid probe that is designed for volume production. The probe supports TRS and DCS measurements in a cross geometry, thus both technologies gain information on the same region inside the tissue. The probe is highly miniaturized to perform cerebral measurements on heads of extreme preterm infants down to head diameters of 6cm. Considerations concerning probe production focus on a reproducible accuracy in shape and precise optical alignment. In this way deviations in measurement data within a series of probes should be minimized. In addition to that, requirements for clinical use like robustness and hygiene are considered. An additional soft-touching sleeve made of FDA compatible silicone allows for a flexible attachment with respect to the individual anatomy of each patient. We present the technical concept of the hybrid probe and corresponding manufacturing methods. A prototype of the probe is shown and tested on tissue phantoms as well as in vivo to verify its operational reliability.

Soccer Heading Is Associated with White Matter Microstructural and Cognitive Abnormalities

PubMed Central

Kim, Namhee; Zimmerman, Molly E.; Kim, Mimi; Stewart, Walter F.; Branch, Craig A.

2013-01-01

Purpose: To investigate the association of soccer heading with subclinical evidence of traumatic brain injury. Materials and Methods: With institutional review board approval and compliance with HIPAA guidelines, 37 amateur soccer players (mean age, 30.9 years; 78% [29] men, 22% [eight] women) gave written informed consent and completed a questionnaire to quantify heading in the prior 12 months and lifetime concussions. Diffusion-tensor magnetic resonance (MR) imaging at 3.0 T was performed (32 directions; b value, 800 sec/mm2; 2 × 2 × 2-mm voxels). Cognitive function was measured by using a computerized battery of tests. Voxelwise linear regression (heading vs fractional anisotropy [FA]) was applied to identify significant regional associations. FA at each location and cognition were tested for a nonlinear relationship to heading by using an inverse logit model that incorporated demographic covariates and history of concussion. Results: Participants had headed 32–5400 times (median, 432 times) over the previous year. Heading was associated with lower FA at three locations in temporo-occipital white matter with a threshold that varied according to location (885–1550 headings per year) (P < .00001). Lower levels of FA were also associated with poorer memory scores (P < .00001), with a threshold of 1800 headings per year. Lifetime concussion history and demographic features were not significantly associated with either FA or cognitive performance. Conclusion: Heading is associated with abnormal white matter microstructure and with poorer neurocognitive performance. This relationship is not explained by a history of concussion. © RSNA, 2013 PMID:23757503

Optimal estimation of spatially variable recharge and transmissivity fields under steady-state groundwater flow. Part 2. Case study

NASA Astrophysics Data System (ADS)

Graham, Wendy D.; Neff, Christina R.

1994-05-01

The first-order analytical solution of the inverse problem for estimating spatially variable recharge and transmissivity under steady-state groundwater flow, developed in Part 1 is applied to the Upper Floridan Aquifer in NE Florida. Parameters characterizing the statistical structure of the log-transmissivity and head fields are estimated from 152 measurements of transmissivity and 146 measurements of hydraulic head available in the study region. Optimal estimates of the recharge, transmissivity and head fields are produced throughout the study region by conditioning on the nearest 10 available transmissivity measurements and the nearest 10 available head measurements. Head observations are shown to provide valuable information for estimating both the transmissivity and the recharge fields. Accurate numerical groundwater model predictions of the aquifer flow system are obtained using the optimal transmissivity and recharge fields as input parameters, and the optimal head field to define boundary conditions. For this case study, both the transmissivity field and the uncertainty of the transmissivity field prediction are poorly estimated, when the effects of random recharge are neglected.

Differentiation of benign and malignant lesions of the tongue by using diffusion-weighted MRI at 3.0 T.

PubMed

Li, S; Cheng, J; Zhang, Y; Zhang, Z

2015-01-01

Diffusion-weighted MRI (DWI) has been introduced in head and neck lesions and adds important information to the findings obtained through conventional MRI. The purpose of this study was to assess the role of DWI in differentiating benign and malignant lesions of the tongue at 3.0-T field strength imaging. 78 patients with 78 lingual lesions underwent conventional MRI and DWI with b-values of 0 and 1000 s mm(-2) before therapy. The apparent diffusion coefficient (ADC) maps were reconstructed, and the ADC values of the lingual lesions were calculated and compared between benign and malignant lesions of the tongue. The mean ADC values of the malignant tumours, benign solid lesions and cystic lesions were (1.08±0.16)×10(-3), (1.68±0.33)×10(-3) and (2.21±0.35)×10(-3) mm2 s(-1), respectively. The mean ADC values of malignant tumours were significantly lower (p<0.001) than those of benign solid lesions, and the mean ADC values of benign solid lesions were significantly lower (p<0.001) than those of cystic lesions. Receiver operating characteristic analysis showed that when an ADC value<.31×10(-3) mm2 s(-1) was used for predicting malignancy, the highest accuracy of 95.3%, sensitivity of 92.6% and specificity of 97.3% were obtained. ADC values of benign and malignant lesions are significantly different at 3.0-T imaging. DWI can be applied as a complementary tool in the differentiation of benign and malignant lesions of the tongue.

Association of contact loading in diffuse axonal injuries from motor vehicle crashes.

PubMed

Yoganandan, Narayan; Gennarelli, Thomas A; Zhang, Jiangyue; Pintar, Frank A; Takhounts, Erik; Ridella, Stephen A

2009-02-01

Although studies have been conducted to analyze brain injuries from motor vehicle crashes, the association of head contact has not been fully established. This study examined the association in occupants sustaining diffuse axonal injuries (DAIs). The 1997 to 2006 motor vehicle Crash Injury Research Engineering Network database was used. All crash modes and all changes in velocity were included; ejections and rollovers were excluded; injuries to front and rear seat occupants with and without restraint use were considered. DAI were coded in the database using Abbreviated Injury Scale 1990. Loss of consciousness was included and head contact was based on medical- and crash-related data. Sixty-seven occupants with varying ages were coded with DAI. Forty-one adult occupants (mean, 33 years of age, 171-cm tall, 71-kg weight; 30 drivers, 11 passengers) were analyzed. Mean change in velocity was 41.2 km/h and Glasgow Coma Scale score was 4. There were 33 lateral, 6 frontal, and 2 rear crashes with 32 survivors and 9 were fatalities. Two occupants in the same crash did not sustain DAI. Although skull fractures and scalp injuries occurred in some impacts, head contact was identified in all frontal, rear, and far side, and all but one nearside crashes. Using a large sample size of occupants sustaining DAI in 1991 to 2006 model year vehicles, DAI occurred more frequently in side than frontal crashes, is most commonly associated with impact load transfer, and is not always accompanied by skull fractures. The association of head contact in >95% of cases underscores the importance of evaluating crash-related variables and medical information for trauma analysis. It would be prudent to include contact loading in addition to angular kinematics in the analysis and characterization of DAI.

Quantifying the association between white matter integrity changes and subconcussive head impact exposure from a single season of youth and high school football using 3D convolutional neural networks

NASA Astrophysics Data System (ADS)

Saghafi, Behrouz; Murugesan, Gowtham; Davenport, Elizabeth; Wagner, Ben; Urban, Jillian; Kelley, Mireille; Jones, Derek; Powers, Alexander; Whitlow, Christopher; Stitzel, Joel; Maldjian, Joseph; Montillo, Albert

2018-02-01

The effect of subconcussive head impact exposure during contact sports, including American football, on brain health is poorly understood particularly in young and adolescent players, who may be more vulnerable to brain injury during periods of rapid brain maturation. This study aims to quantify the association between cumulative effects of head impact exposure from a single season of football on white matter (WM) integrity as measured with diffusion MRI. The study targets football players aged 9-18 years old. All players were imaged pre- and post-season with structural MRI and diffusion tensor MRI (DTI). Fractional Anisotropy (FA) maps, shown to be closely correlated with WM integrity, were computed for each subject, co-registered and subtracted to compute the change in FA per subject. Biomechanical metrics were collected at every practice and game using helmet mounted accelerometers. Each head impact was converted into a risk of concussion, and the risk of concussion-weighted cumulative exposure (RWE) was computed for each player for the season. Athletes with high and low RWE were selected for a two-category classification task. This task was addressed by developing a 3D Convolutional Neural Network (CNN) to automatically classify players into high and low impact exposure groups from the change in FA maps. Using the proposed model, high classification performance, including ROC Area Under Curve score of 85.71% and F1 score of 83.33% was achieved. This work adds to the growing body of evidence for the presence of detectable neuroimaging brain changes in white matter integrity from a single season of contact sports play, even in the absence of a clinically diagnosed concussion.

Player and Game Characteristics and Head Impacts in Female Youth Ice Hockey Players.

PubMed

Reed, Nick; Taha, Tim; Greenwald, Richard; Keightley, Michelle

2017-08-01

  Despite the growing popularity of ice hockey among female youth and interest in the biomechanics of head impacts in sport, the head impacts sustained by this population have yet to be characterized.   To describe the number of, biomechanical characteristics of, and exposure to head impacts of female youth ice hockey players during competition and to investigate the influences of player and game characteristics on head impacts.   Cohort study.   Twenty-seven female youth ice hockey players (mean age = 12.5 ± 0.52 years) wore instrumented ice hockey helmets during 66 ice hockey games over a 3-year period. Data specific to player, game, and biomechanical head impact characteristics were recorded. A multiple regression analysis identified factors most associated with head impacts of greater frequency and severity.   A total of 436 total head impacts were sustained during 6924 minutes of active ice hockey participation (0.9 ± 0.6 impacts per player per game; range, 0-2.1). A higher body mass index (BMI) significantly predicted a higher number of head impacts sustained per game (P = .008). Linear acceleration of head impacts was greater in older players and those who played the forward position, had a greater BMI, and spent more time on the ice (P = .008), whereas greater rotational acceleration was present in older players who had a greater BMI and played the forward position (P = .008). During tournament games, increased ice time predicted increased severity of head impacts (P = .03).   This study reveals for the first time that head impacts are occurring in female youth ice hockey players, albeit at a lower rate and severity than in male youth ice hockey players, despite the lack of intentional body checking.

Prediction of an Apparent Flame Length in a Co-Axial Jet Diffusion Flame Combustor.

DTIC Science & Technology

1983-04-01

This report is comprised of two parts. In Part I a predictive model for an apparent flame length in a co-axial jet diffusion flame combustor is...Overall mass transfer coefficient, evaluated from an empirically developed correlation, is employed to predict total flame length . Comparison of the...experimental and predicted data on total flame length shows a reasonable agreement within sixteen percent over the investigated air and fuel flow rate

Brain damage in fatal non-missile head injury without high intracranial pressure.

PubMed Central

Graham, D I; Lawrence, A E; Adams, J H; Doyle, D; McLellan, D R

1988-01-01

As part of a comprehensive study of brain damage in 635 fatal non-missile head injuries, the type and prevalence of brain damage occurring in the absence of high intracranial pressure were analysed. Of 71 such cases, 53 sustained their injury as a result of a road traffic accident; only 25 experienced a lucid interval. Thirty eight had a fractured skull, a mean total contusion index of 12.9 and diffuse axonal injury in 29: severe to moderate ischaemic damage was present in the cerebral cortex in 25, brain swelling in 13, and acute bacterial meningitis in nine. The prevalence and range of brain damage that may occur in the absence of high intracranial pressure are important to forensic pathologists in the medicolegal interpretation of cases of fatal head injury. PMID:3343378

The Prediction of Nozzle Performance and Heat Transfer in Hydrogen/Oxygen Rocket Engines with Transpiration Cooling, Film Cooling, and High Area Ratios

NASA Technical Reports Server (NTRS)

Kacynski, Kenneth J.; Hoffman, Joe D.

1994-01-01

An advanced engineering computational model has been developed to aid in the analysis of chemical rocket engines. The complete multispecies, chemically reacting and diffusing Navier-Stokes equations are modelled, including the Soret thermal diffusion and Dufour energy transfer terms. Demonstration cases are presented for a 1030:1 area ratio nozzle, a 25 lbf film-cooled nozzle, and a transpiration-cooled plug-and-spool rocket engine. The results indicate that the thrust coefficient predictions of the 1030:1 nozzle and the film-cooled nozzle are within 0.2 to 0.5 percent, respectively, of experimental measurements. Further, the model's predictions agree very well with the heat transfer measurements made in all of the nozzle test cases. It is demonstrated that thermal diffusion has a significant effect on the predicted mass fraction of hydrogen along the wall of the nozzle and was shown to represent a significant fraction of the diffusion fluxes occurring in the transpiration-cooled rocket engine.

Physical re-examination of parameters on a molecular collisions-based diffusion model for diffusivity prediction in polymers.

PubMed

Ohashi, Hidenori; Tamaki, Takanori; Yamaguchi, Takeo

2011-12-29

Molecular collisions, which are the microscopic origin of molecular diffusive motion, are affected by both the molecular surface area and the distance between molecules. Their product can be regarded as the free space around a penetrant molecule defined as the "shell-like free volume" and can be taken as a characteristic of molecular collisions. On the basis of this notion, a new diffusion theory has been developed. The model can predict molecular diffusivity in polymeric systems using only well-defined single-component parameters of molecular volume, molecular surface area, free volume, and pre-exponential factors. By consideration of the physical description of the model, the actual body moved and which neighbor molecules are collided with are the volume and the surface area of the penetrant molecular core. In the present study, a semiempirical quantum chemical calculation was used to calculate both of these parameters. The model and the newly developed parameters offer fairly good predictive ability. © 2011 American Chemical Society

Sucrose diffusion in aqueous solution

PubMed Central

Murray, Benjamin J.

2016-01-01

The diffusion of sugar in aqueous solution is important both in nature and in technological applications, yet measurements of diffusion coefficients at low water content are scarce. We report directly measured sucrose diffusion coefficients in aqueous solution. Our technique utilises a Raman isotope tracer method to monitor the diffusion of non-deuterated and deuterated sucrose across a boundary between the two aqueous solutions. At a water activity of 0.4 (equivalent to 90 wt% sucrose) at room temperature, the diffusion coefficient of sucrose was determined to be approximately four orders of magnitude smaller than that of water in the same material. Using literature viscosity data, we show that, although inappropriate for the prediction of water diffusion, the Stokes–Einstein equation works well for predicting sucrose diffusion under the conditions studied. As well as providing information of importance to the fundamental understanding of diffusion in binary solutions, these data have technological, pharmaceutical and medical implications, for example in cryopreservation. Moreover, in the atmosphere, slow organic diffusion may have important implications for aerosol growth, chemistry and evaporation, where processes may be limited by the inability of a molecule to diffuse between the bulk and the surface of a particle. PMID:27364512

Study of the benzocaine transfer from aqueous solution to the interior of a biological membrane.

PubMed

Porasso, Rodolfo D; Bennett, W F Drew; Oliveira-Costa, S D; López Cascales, J J

2009-07-23

The precise molecular mechanism of general anesthetics remains unknown. It is therefore important to understand where molecules with anesthetic properties localize within biological membranes. We have determined the free energy profile of a benzocaine molecule (BZC) across a biological membrane using molecular dynamics simulation. We use an asymmetric phospholipid bilayer with DPPS in one leaflet of a DPPC bilayer (Lopez Cascales et al. J. Phys. Chem. B 2006, 110, 2358-2363) to model a biological bilayer. From the free energy profile, we predict the zone of actuation of a benzocaine is located in the hydrocarbon region or at the end of the lipid head, depending of the presence of charged lipids (DPPS) in the leaflet. We observe a moderate increase in the disorder of the membrane and in particular an increase in the disorder of DPPS. Static and dynamic physicochemical properties of the benzocaine, such as its dipole orientation, translational diffusion coefficient, and rotational relaxation time were measured.

Robust cubature Kalman filter for GNSS/INS with missing observations and colored measurement noise.

PubMed

Cui, Bingbo; Chen, Xiyuan; Tang, Xihua; Huang, Haoqian; Liu, Xiao

2018-01-01

In order to improve the accuracy of GNSS/INS working in GNSS-denied environment, a robust cubature Kalman filter (RCKF) is developed by considering colored measurement noise and missing observations. First, an improved cubature Kalman filter (CKF) is derived by considering colored measurement noise, where the time-differencing approach is applied to yield new observations. Then, after analyzing the disadvantages of existing methods, the measurement augment in processing colored noise is translated into processing the uncertainties of CKF, and new sigma point update framework is utilized to account for the bounded model uncertainties. By reusing the diffused sigma points and approximation residual in the prediction stage of CKF, the RCKF is developed and its error performance is analyzed theoretically. Results of numerical experiment and field test reveal that RCKF is more robust than CKF and extended Kalman filter (EKF), and compared with EKF, the heading error of land vehicle is reduced by about 72.4%. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Severe Pediatric Head Injury During the Iraq and Afghanistan Conflicts.

PubMed

Klimo, Paul; Ragel, Brian T; Jones, G Morgan; McCafferty, Randall

2015-07-01

Much has been written about injuries sustained by US and coalition soldiers during the Global War on Terrorism campaigns. However, injuries to civilians, including children, have been less well documented. To describe the epidemiologic features and outcomes associated with isolated severe head injury in children during Operations Enduring Freedom and Iraqi Freedom (OEF and OIF). A retrospective review of children (<18 years old) in the Joint Theater Trauma Registry with isolated head injury (defined as an Abbreviated Injury Score Severity Code >3) and treated at a US combat support hospital in Iraq or Afghanistan (2004-2012). The primary outcome was in-hospital mortality. We identified 647 children with severe isolated head injuries: 337 from OEF, 268 from OIF, and 42 nontheater specific. Most were boys (76%; median age = 8 years). Penetrating injuries were most common (60.6%). Overall, 330 (51%) children underwent a craniotomy/craniectomy; 156 (24.1%) succumbed to their injuries. Admission Glasgow Coma Score was predictive of survival among the entire cohort and each of the individual conflicts. Male sex also significantly increased the odds of survival for the entire group and OEF, but not for OIF. Closed-head injury improved the predictive ability of our model but did not reach statistical significance as an independent factor. This is the largest study of combat-related isolated head injuries in children. Admission Glasgow Coma Score and male sex were found to be predictive of survival. Assets to comprehensively care for the pediatric patient should be established early in future conflicts.

Who Drops out of Early Head Start Home Visiting Programs?

ERIC Educational Resources Information Center

Roggman, Lori A.; Cook, Gina A.; Peterson, Carla A.; Raikes, Helen H.

2008-01-01

Research Findings: Early Head Start home-based programs provide services through weekly home visits to families with children up to age 3, but families vary in how long they remain enrolled. In this study of 564 families in home-based Early Head Start programs, "dropping out" was predicted by specific variations in home visits and certain family…

The Prediction of Elementary School Failure Among High Risk Children.

ERIC Educational Resources Information Center

Goodstein, H. A.; And Others

This report briefly summarizes the educational progress of a sample of children who took part in one of the earliest Head Start programs (1966). The report addresses the following questions: (1) Was participation in Head Start a factor in preventing retention in grade and/or special class placement? (2) Were there differences between Head Start…

Effects of body position on the carbon monoxide diffusing capacity in patients with chronic heart failure: relation to hemodynamic changes.

PubMed

Faggiano, P; D'Aloia, A; Simoni, P; Gualeni, A; Foglio, K; Ambrosino, N; Giordano, A

1998-01-01

Pulmonary diffusion has been found to be reduced in patients with congestive heart failure. The effects of postural changes on the diffusing capacity had been evaluated in healthy subjects, but not in patients with heart failure. The aim of this study was to evaluate the posture-induced changes in diffusing capacity in patients with chronic heart failure and their relation to the hemodynamic profile. The pulmonary carbon monoxide diffusing capacity (DLCO) was measured in the supine position, with 20 degrees passive head elevation, and in the sitting position, both postures maintained for 10 min, in a group of 32 male patients with mild to moderate chronic heart failure due to left ventricular systolic dysfunction (ejection fraction <35%). On a separate day, in the absence of any changes in clinical status and therapy, the hemodynamic parameters were measured by right-heart catheterization. The sequence of postures was assigned randomly. The mean values of DLCO were slightly reduced and did not differ in the two positions (20.3 +/- 5.7 vs. 19.4 +/- 5.6 ml/min/mm Hg, 77 +/- 23 vs. 75 +/- 20% of predicted, respectively). The patients were then subdivided according to changes in DLCO from the supine to the sitting position: DLCO increased (+23%) in 9 patients (28%, group 1), decreased (-17.5%) in 17 patients (53%, group 2), and remained within the coefficient of reproducibility ( +/- 5 %) in 6 patients (group 3). As compared with group 2, group 1 patients showed a significant increase in mean pulmonary artery pressure (+7 vs. -15%, p < 0.01) and pulmonary capillary wedge pressure (+8 vs. -22%, p < 0.005) from the supine to the sitting position, while the cardiac index showed a smaller - but not significant - decrease in group 1 (-5 vs. -12%). The percent changes in DLCO significantly correlated with changes in pulmonary capillary wedge (r = 0.54, p < 0.0005) and mean pulmonary artery (r = 0.47, p < 0.005) pressures. In chronic heart failure postural changes may induce different responses in diffusing capacity. To a greater extent than in healthy subjects, the most common response is a decrease in DLCO in the sitting as compared with the supine position. The DLCO changes correlate with variations in pulmonary circulation pressure, probably due to changes in pulmonary vascular recruitment and pulmonary capillary blood volume.

Ultrasonographic fetal head position to predict mode of delivery: a systematic review and bivariate meta-analysis.

PubMed

Verhoeven, C J M; Rückert, M E P F; Opmeer, B C; Pajkrt, E; Mol, B W J

2012-07-01

We performed a systematic review to determine whether sonographic assessment of occipital position of the fetal head can contribute to the prediction of the mode of delivery. We performed a systematic literature search of electronic databases from inception to May 2011. Two reviewers independently extracted data from the included studies. We used a bivariate model to estimate point estimates for sensitivity and specificity curves for the outcome Cesarean delivery. Eligible studies were cohort studies or cross-sectional studies that reported on both the position of the fetal head, as assessed by ultrasound, before or at the beginning of active labor as well as the outcome of labor in women at term. We included 11 primary articles reporting on 5053 women, of whom 898 had a Cesarean section. All studies indicated disappointing values for sensitivity and specificity in the prediction of Cesarean section. Summary point estimates of sensitivity and specificity were 0.39 (95% CI, 0.32-0.48) and 0.71 (95% CI, 0.67-0.74), respectively. Sonographic assessment of occipital position of the fetal head before delivery should not be used in the prediction of mode of delivery. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.

Review and developments of dissemination models for airborne carbon fibers

NASA Technical Reports Server (NTRS)

Elber, W.

1980-01-01

Dissemination prediction models were reviewed to determine their applicability to a risk assessment for airborne carbon fibers. The review showed that the Gaussian prediction models using partial reflection at the ground agreed very closely with a more elaborate diffusion analysis developed for the study. For distances beyond 10,000 m the Gaussian models predicted a slower fall-off in exposure levels than the diffusion models. This resulting level of conservatism was preferred for the carbon fiber risk assessment. The results also showed that the perfect vertical-mixing models developed herein agreed very closely with the diffusion analysis for all except the most stable atmospheric conditions.

Correlation and prediction of gaseous diffusion coefficients.

NASA Technical Reports Server (NTRS)

Marrero, T. R.; Mason, E. A.

1973-01-01

A new correlation method for binary gaseous diffusion coefficients from very low temperatures to 10,000 K is proposed based on an extended principle of corresponding states, and having greater range and accuracy than previous correlations. There are two correlation parameters that are related to other physical quantities and that are predictable in the absence of diffusion measurements. Quantum effects and composition dependence are included, but high-pressure effects are not. The results are directly applicable to multicomponent mixtures.

A quantitative property-property relationship for the internal diffusion coefficients of organic compounds in solid materials.

PubMed

Huang, L; Fantke, P; Ernstoff, A; Jolliet, O

2017-11-01

Indoor releases of organic chemicals encapsulated in solid materials are major contributors to human exposures and are directly related to the internal diffusion coefficient in solid materials. Existing correlations to estimate the diffusion coefficient are only valid for a limited number of chemical-material combinations. This paper develops and evaluates a quantitative property-property relationship (QPPR) to predict diffusion coefficients for a wide range of organic chemicals and materials. We first compiled a training dataset of 1103 measured diffusion coefficients for 158 chemicals in 32 consolidated material types. Following a detailed analysis of the temperature influence, we developed a multiple linear regression model to predict diffusion coefficients as a function of chemical molecular weight (MW), temperature, and material type (adjusted R 2 of .93). The internal validations showed the model to be robust, stable and not a result of chance correlation. The external validation against two separate prediction datasets demonstrated the model has good predicting ability within its applicability domain (Rext2>.8), namely MW between 30 and 1178 g/mol and temperature between 4 and 180°C. By covering a much wider range of organic chemicals and materials, this QPPR facilitates high-throughput estimates of human exposures for chemicals encapsulated in solid materials. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Role of muscle pulleys in producing eye position-dependence in the angular vestibuloocular reflex: a model-based study

NASA Technical Reports Server (NTRS)

Thurtell, M. J.; Kunin, M.; Raphan, T.; Wall, C. C. (Principal Investigator)

2000-01-01

It is well established that the head and eye velocity axes do not always align during compensatory vestibular slow phases. It has been shown that the eye velocity axis systematically tilts away from the head velocity axis in a manner that is dependent on eye-in-head position. The mechanisms responsible for producing these axis tilts are unclear. In this model-based study, we aimed to determine whether muscle pulleys could be involved in bringing about these phenomena. The model presented incorporates semicircular canals, central vestibular pathways, and an ocular motor plant with pulleys. The pulleys were modeled so that they brought about a rotation of the torque axes of the extraocular muscles that was a fraction of the angle of eye deviation from primary position. The degree to which the pulleys rotated the torque axes was altered by means of a pulley coefficient. Model input was head velocity and initial eye position data from passive and active yaw head impulses with fixation at 0 degrees, 20 degrees up and 20 degrees down, obtained from a previous experiment. The optimal pulley coefficient required to fit the data was determined by calculating the mean square error between data and model predictions of torsional eye velocity. For active head impulses, the optimal pulley coefficient varied considerably between subjects. The median optimal pulley coefficient was found to be 0.5, the pulley coefficient required for producing saccades that perfectly obey Listing's law when using a two-dimensional saccadic pulse signal. The model predicted the direction of the axis tilts observed in response to passive head impulses from 50 ms after onset. During passive head impulses, the median optimal pulley coefficient was found to be 0.21, when roll gain was fixed at 0.7. The model did not accurately predict the alignment of the eye and head velocity axes that was observed early in the response to passive head impulses. We found that this alignment could be well predicted if the roll gain of the angular vestibuloocular reflex was modified during the initial period of the response, while pulley coefficient was maintained at 0.5. Hence a roll gain modification allows stabilization of the retinal image without requiring a change in the pulley effect. Our results therefore indicate that the eye position-dependent velocity axis tilts could arise due to the effects of the pulleys and that a roll gain modification in the central vestibular structures may be responsible for countering the pulley effect.

Generation of Accurate Lateral Boundary Conditions for a Surface-Water Groundwater Interaction Model

NASA Astrophysics Data System (ADS)

Khambhammettu, P.; Tsou, M.; Panday, S. M.; Kool, J.; Wei, X.

2010-12-01

The 106 mile long Peace River in Florida flows south from Lakeland to Charlotte Harbor and has a drainage basin of approximately 2,350 square miles. A long-term decline in stream flows and groundwater potentiometric levels has been observed in the region. Long-term trends in rainfall, along with effects of land use changes on runoff, surface-water storage, recharge and evapotranspiration patterns, and increased groundwater and surface-water withdrawals have contributed to this decline. The South West Florida Water Management District (SWFWMD) has funded the development of the Peace River Integrated Model (PRIM) to assess the effects of land use, water use, and climatic changes on stream flows and to evaluate the effectiveness of various management alternatives for restoring stream flows. The PRIM was developed using MODHMS, a fully integrated surface-water groundwater flow and transport simulator developed by HydroGeoLogic, Inc. The development of the lateral boundary conditions (groundwater inflow and outflow) for the PRIM in both historical and predictive contexts is discussed in this presentation. Monthly-varying specified heads were used to define the lateral boundary conditions for the PRIM. These head values were derived from the coarser Southern District Groundwater Model (SDM). However, there were discrepancies between the simulated SDM heads and measured heads: the likely causes being spatial (use of a coarser grid) and temporal (monthly average pumping rates and recharge rates) approximations in the regional SDM. Finer re-calibration of the SDM was not feasible, therefore, an innovative approach was adopted to remove the discrepancies. In this approach, point discrepancies/residuals between the observed and simulated heads were kriged with an appropriate variogram to generate a residual surface. This surface was then added to the simulated head surface of the SDM to generate a corrected head surface. This approach preserves the trends associated with groundwater pumping / recharge in the SDM and adds the kriged residual surface as variations back to the trend. The variations could be from the scale effects of grid resolution and from the temporal averaging of stresses (pumping, recharge, etc.,). The validity of the approach is demonstrated by visual and statistical comparison of the observed and simulated heads before and after correction. For predictive simulations, an Artificial Neural Network was trained to predict heads at monitoring wells based on precipitation and pumping. These predicted head values could then be used as surrogate observations for correcting the results of the regional SDM. In summary, an appropriate approach to link a regional groundwater model to a detailed surface-water groundwater interaction model is demonstrated with an example.

Neuropsychological impairment as a consequence of football (soccer) play and football heading: preliminary analyses and report on university footballers.

PubMed

Rutherford, A; Stephens, R; Potter, D; Fernie, G

2005-04-01

Previous research has claimed neuropsychological impairment occurs as a result of professional and amateur football play, and, specifically, football heading. However, much of this research exhibits substantial methodological problems. By investigating less committed amateur level footballers, the current study sought to gain some insight into the developmental history of any neuropsychological consequences of football play. University football, rugby and noncontact sports players were compared on a range of biographical and neuropsychological test variables. While playing their chosen sports, rugby players sustained many more head injuries than footballers and noncontact sportsmen, but footballers did not sustain significantly more head injuries than noncontact sportsmen. The number of head injuries sustained predicted Trails B and TAP Divided Attention latencies in a positive fashion. After controlling for the number of head injuries sustained, sport group effects were detected with TAP Divided Attention accuracy scores, with footballers exhibiting poorest performance. After controlling for the number of head injuries sustained, the total amount of heading done by footballers predicted the number of Wisconsin Card Sorting category shifts in a negative fashion. Nevertheless, over interpretation of all of these results should be resisted because of the exploratory nature of the analyses and the possibility that the sport groups may differ in ways other than just the nature of their sports activities.

Factors Influencing Helmet Use, Head Injury, and Hospitalization Among Children Involved in Skateboarding and Snowboarding Accidents.

PubMed

Sadeghian, Homa; Nguyen, Brian; Huynh, Nhan; Rouch, Joshua; Lee, Steven L; Bazargan-Hejazi, Shahrzad

2017-01-01

Up to 75% of skateboarders and snowboarders admitted to the hospital sustain head injuries. It is unclear why not all children and teenagers wear helmets while snowboarding and skateboarding given the protection they afford. To report on the prevalence of, and factors associated with, skateboarding and snowboarding in injured children and to explore factors that influence helmet use, head injury, and hospitalization in this sample. A cross-sectional study of skateboard- and snowboard-associated injuries from 2003 to 2012 among individuals younger than age 18 years using National Electronic Injury Surveillance System (NEISS) data from approximately 100 hospitals. Helmet use, head injury, and hospitalization. Of 1742 patients in the study, 852 (48.9%) and 890 (51.1%) were skateboarders and snowboarders, respectively. Overall, 907 (52.1%) did not use helmets, and 704 (40.4%) sustained head injuries. Multiple logistic regression analysis showed that age, race/ethnicity, location of boarding, and engaging in skateboarding influenced helmet use. Sex, race/ethnicity, helmet use, and skateboarding predicted head injury. Age, sex, skateboarding, and head injury predicted hospital admission. Statistically significant differences exist in helmet use, head injury, and hospitalization rates between skateboarders and snowboarders. Our findings suggest that injury prevention and outreach programs are needed to increase helmet use and reduce the risk of head injury and hospitalization in skateboarders and other at-risk groups. Further studies are needed to clarify the association between race/ethnicity and helmet use among skateboarders and snowboarders.

Noninvasive cerebral hemoglobin oxygenation quantification of fetal sheep under hypoxic stress in utero using frequency-domain diffuse optical two-layer model

NASA Astrophysics Data System (ADS)

Choe, Regine; Durduran, Turgut; Yu, Guoqiang; Nijland, Mark J. M.; Nathanielsz, Peter W.; Chance, Britton; Yodh, Arjun G.; Ramanujam, Nirmala

2003-07-01

A study using pregnant sheep was designed to simulate fetal hypoxia in order to investigate the ability of near-infrared spectroscopy (NIRS) to detect and quantify fetal hypoxia in utero. The near-infrared spectroscopic probe consisted of two detectors and six source positions. It was placed on the maternal ewe abdomen above the fetal head. The light sources were modulated at 70 MHz and frequency-encoded so that simultaneous measurements at 675, 786, 830 nm for each source position were possible. After the baseline measurements, fetal hypoxia was induced by blocking the aorta of pregnant ewe and thus compromising the blood supply to the uterus. Blood gas samples were concurrently drawn from the fetal brachial artery and jugular veins. Analysis of the diffuse optical data used a two-layer model to separate the maternal layer from the fetal head. The analysis also employed a priori spectral information about tissue chromophores. This approach provided good quantification of blood oxygenation changes, which correlated well with the blood gas analyses. By contrast the homogeneous model underestimated oxygenation changes during hypoxia.

Unusual presentation of a metastatic uveal melanoma in a cat.

PubMed

Planellas, Marta; Pastor, Josep; Torres, Ma Dolores; Peña, Teresa; Leiva, Marta

2010-11-01

A 10 year-old, spayed female Domestic Short-Haired (DSH) cat was diagnosed with a large primary uveal melanoma and exenteration was recommended. Thoracic radiographs, abdominal ultrasonography, and complete blood count and serum biochemistry panel did not reveal any abnormality compatible with metastatic disease and surgery was performed. Histopathologic study of the eye confirmed a diffuse iris melanoma. Five months later, the cat presented with a lameness of the right anterior extremity. On physical exam the right elbow was swollen and painful. Radiographs showed a severe osteolysis of the radial head and proximal diaphysis. Fine needle aspiration of the radius head identified a round cell neoplasm with scattered cells containing intracytoplasmatic pigmented granules, compatible with metastatic melanoma. The owners decided not to treat the patient with chemotherapy and declined a biopsy. Two months later, the cat died and necropsy was performed confirming bone metastasis of the uveal melanoma. A diagnosis of generalized metastasis from primary diffuse iris melanoma was made. This report describes, for the first time, long bone metastasis from an uveal melanoma in a cat. © 2010 American College of Veterinary Ophthalmologists.

A diffusivity model for predicting VOC diffusion in porous building materials based on fractal theory.

PubMed

Liu, Yanfeng; Zhou, Xiaojun; Wang, Dengjia; Song, Cong; Liu, Jiaping

2015-12-15

Most building materials are porous media, and the internal diffusion coefficients of such materials have an important influences on the emission characteristics of volatile organic compounds (VOCs). The pore structure of porous building materials has a significant impact on the diffusion coefficient. However, the complex structural characteristics bring great difficulties to the model development. The existing prediction models of the diffusion coefficient are flawed and need to be improved. Using scanning electron microscope (SEM) observations and mercury intrusion porosimetry (MIP) tests of typical porous building materials, this study developed a new diffusivity model: the multistage series-connection fractal capillary-bundle (MSFC) model. The model considers the variable-diameter capillaries formed by macropores connected in series as the main mass transfer paths, and the diameter distribution of the capillary bundles obeys a fractal power law in the cross section. In addition, the tortuosity of the macrocapillary segments with different diameters is obtained by the fractal theory. Mesopores serve as the connections between the macrocapillary segments rather than as the main mass transfer paths. The theoretical results obtained using the MSFC model yielded a highly accurate prediction of the diffusion coefficients and were in a good agreement with the VOC concentration measurements in the environmental test chamber. Copyright © 2015 Elsevier B.V. All rights reserved.

Artificial neural network approach to predict surgical site infection after free-flap reconstruction in patients receiving surgery for head and neck cancer.

PubMed

Kuo, Pao-Jen; Wu, Shao-Chun; Chien, Peng-Chen; Chang, Shu-Shya; Rau, Cheng-Shyuan; Tai, Hsueh-Ling; Peng, Shu-Hui; Lin, Yi-Chun; Chen, Yi-Chun; Hsieh, Hsiao-Yun; Hsieh, Ching-Hua

2018-03-02

The aim of this study was to develop an effective surgical site infection (SSI) prediction model in patients receiving free-flap reconstruction after surgery for head and neck cancer using artificial neural network (ANN), and to compare its predictive power with that of conventional logistic regression (LR). There were 1,836 patients with 1,854 free-flap reconstructions and 438 postoperative SSIs in the dataset for analysis. They were randomly assigned tin ratio of 7:3 into a training set and a test set. Based on comprehensive characteristics of patients and diseases in the absence or presence of operative data, prediction of SSI was performed at two time points (pre-operatively and post-operatively) with a feed-forward ANN and the LR models. In addition to the calculated accuracy, sensitivity, and specificity, the predictive performance of ANN and LR were assessed based on area under the curve (AUC) measures of receiver operator characteristic curves and Brier score. ANN had a significantly higher AUC (0.892) of post-operative prediction and AUC (0.808) of pre-operative prediction than LR (both P <0.0001). In addition, there was significant higher AUC of post-operative prediction than pre-operative prediction by ANN (p<0.0001). With the highest AUC and the lowest Brier score (0.090), the post-operative prediction by ANN had the highest overall predictive performance. The post-operative prediction by ANN had the highest overall performance in predicting SSI after free-flap reconstruction in patients receiving surgery for head and neck cancer.

Biased Brownian motion mechanism for processivity and directionality of single-headed myosin-VI.

PubMed

Iwaki, Mitsuhiro; Iwane, Atsuko Hikikoshi; Ikebe, Mitsuo; Yanagida, Toshio

2008-01-01

Conventional form to function as a vesicle transporter is not a 'single molecule' but a coordinated 'two molecules'. The coordinated two molecules make it complicated to reveal its mechanism. To overcome the difficulty, we adopted a single-headed myosin-VI as a model protein. Myosin-VI is an intracellular vesicle and organelle transporter that moves along actin filaments in a direction opposite to most other known myosin classes. The myosin-VI was expected to form a dimer to move processively along actin filaments with a hand-over-hand mechanism like other myosin organelle transporters. However, wild-type myosin-VI was demonstrated to be monomer and single-headed, casting doubt on its processivity. Using single molecule techniques, we show that green fluorescent protein (GFP)-fused single-headed myosin-VI does not move processively. However, when coupled to a 200 nm polystyrene bead (comparable to an intracellular vesicle in size) at a ratio of one head per bead, single-headed myosin-VI moves processively with large (40 nm) steps. Furthermore, we found that a single-headed myosin-VI-bead complex moved more processively in a high-viscous solution (40-fold higher than water) similar to cellular environment. Because diffusion of the bead is 60-fold slower than myosin-VI heads alone in water, we propose a model in which the bead acts as a diffusional anchor for the myosin-VI, enhancing the head's rebinding following detachment and supporting processive movement of the bead-monomer complex. This investigation will help us understand how molecular motors utilize Brownian motion in cells.

Long Term Survivorship of a Severely Notched Femoral Stem after Replacing the Fractured Ceramic head with a Cobalt-Chromium Head

PubMed Central

Panagopoulos, Andreas; Tatani, Irini; Megas, Panagiotis

2016-01-01

Background: Although ceramic head fracture occurs infrequently today, in the event of a fracture, the resulting revision surgery can prove very challenging, since the ceramic particles lodge into the surrounding soft tissue and can cause rapid implant failure Case Presentation: A case of long term survivorship of a severed notched femoral stem after replacing the fractured femoral head with a cobalt-chromium one is reported in a 40-year old woman with hip dysplasia who underwent an uncomplicated total hip arthroplasty. The incident of ceramic femoral head fracture occurred 14 months postoperatively without reporting any significant trauma. Intraoperative findings at revision were a multifragmented femoral head and a damaged polyethylene insert along with diffuse metallosis and excessive wear of the cone of the stem. Both the stem and the acetabular component were stable. After removal of ceramic fragments, metallotic tissue excision and careful lavage of the joint, the inlay was replaced by a similar one and a cobalt-chromium femoral head was placed to the existing notched taper of the firmly incorporated stem. At the 13th year follow up examination, the patient had no pain, used no walking aids, and had normal activity with no signs of wearing or loosening in the plain x-rays. Conclusion: Despite current recommendations of using ceramic femoral heads in cases of fracture or to revise the severely damaged stems we were able to provide a long term survivorship up to 13 years postoperatively of a cobalt-chromium femoral head applied to a severe damaged stem. PMID:28217203

Long Term Survivorship of a Severely Notched Femoral Stem after Replacing the Fractured Ceramic head with a Cobalt-Chromium Head.

PubMed

Panagopoulos, Andreas; Tatani, Irini; Megas, Panagiotis

2016-01-01

Although ceramic head fracture occurs infrequently today, in the event of a fracture, the resulting revision surgery can prove very challenging, since the ceramic particles lodge into the surrounding soft tissue and can cause rapid implant failure. A case of long term survivorship of a severed notched femoral stem after replacing the fractured femoral head with a cobalt-chromium one is reported in a 40-year old woman with hip dysplasia who underwent an uncomplicated total hip arthroplasty. The incident of ceramic femoral head fracture occurred 14 months postoperatively without reporting any significant trauma. Intraoperative findings at revision were a multifragmented femoral head and a damaged polyethylene insert along with diffuse metallosis and excessive wear of the cone of the stem. Both the stem and the acetabular component were stable. After removal of ceramic fragments, metallotic tissue excision and careful lavage of the joint, the inlay was replaced by a similar one and a cobalt-chromium femoral head was placed to the existing notched taper of the firmly incorporated stem. At the 13 th year follow up examination, the patient had no pain, used no walking aids, and had normal activity with no signs of wearing or loosening in the plain x-rays. Despite current recommendations of using ceramic femoral heads in cases of fracture or to revise the severely damaged stems we were able to provide a long term survivorship up to 13 years postoperatively of a cobalt-chromium femoral head applied to a severe damaged stem.

Reliability-Based Life Assessment of Stirling Convertor Heater Head

NASA Technical Reports Server (NTRS)

Shah, Ashwin R.; Halford, Gary R.; Korovaichuk, Igor

2004-01-01

Onboard radioisotope power systems being developed and planned for NASA's deep-space missions require reliable design lifetimes of up to 14 yr. The structurally critical heater head of the high-efficiency Stirling power convertor has undergone extensive computational analysis of operating temperatures, stresses, and creep resistance of the thin-walled Inconel 718 bill of material. A preliminary assessment of the effect of uncertainties in the material behavior was also performed. Creep failure resistance of the thin-walled heater head could show variation due to small deviations in the manufactured thickness and in uncertainties in operating temperature and pressure. Durability prediction and reliability of the heater head are affected by these deviations from nominal design conditions. Therefore, it is important to include the effects of these uncertainties in predicting the probability of survival of the heater head under mission loads. Furthermore, it may be possible for the heater head to experience rare incidences of small temperature excursions of short duration. These rare incidences would affect the creep strain rate and, therefore, the life. This paper addresses the effects of such rare incidences on the reliability. In addition, the sensitivities of variables affecting the reliability are quantified, and guidelines developed to improve the reliability are outlined. Heater head reliability is being quantified with data from NASA Glenn Research Center's accelerated benchmark testing program.

Electrical stimulation of rhesus monkey nucleus reticularis gigantocellularis. II. Effects on metrics and kinematics of ongoing gaze shifts to visual targets.

PubMed

Freedman, Edward G; Quessy, Stephan

2004-06-01

Saccade kinematics are altered by ongoing head movements. The hypothesis that a head movement command signal, proportional to head velocity, transiently reduces the gain of the saccadic burst generator (Freedman 2001, Biol Cybern 84:453-462) can account for this observation. Using electrical stimulation of the rhesus monkey nucleus reticularis gigantocellularis (NRG) to alter the head contribution to ongoing gaze shifts, two critical predictions of this gaze control hypothesis were tested. First, this hypothesis predicts that activation of the head command pathway will cause a transient reduction in the gain of the saccadic burst generator. This should alter saccade kinematics by initially reducing velocity without altering saccade amplitude. Second, because this hypothesis does not assume that gaze amplitude is controlled via feedback, the added head contribution (produced by NRG stimulation on the side ipsilateral to the direction of an ongoing gaze shift) should lead to hypermetric gaze shifts. At every stimulation site tested, saccade kinematics were systematically altered in a way that was consistent with transient reduction of the gain of the saccadic burst generator. In addition, gaze shifts produced during NRG stimulation were hypermetric compared with control movements. For example, when targets were briefly flashed 30 degrees from an initial fixation location, gaze shifts during NRG stimulation were on average 140% larger than control movements. These data are consistent with the predictions of the tested hypothesis, and may be problematic for gaze control models that rely on feedback control of gaze amplitude, as well as for models that do not posit an interaction between head commands and the saccade burst generator.

Material Science Experiments on Mir

NASA Technical Reports Server (NTRS)

Kroes, Roger L.

1999-01-01

This paper describes the microgravity materials experiments carried out on the Shuttle/Mir program. There were six experiments, all of which investigated some aspect of diffusivity in liquid melts. The Liquid Metal Diffusion (LMD) experiment investigated the diffusivity of molten Indium samples at 185 C using a radioactive tracer, In-114m. By monitoring two different gamma ray energies (190 keV and 24 keV) emitted by the samples it was possible to measure independently the diffusion rates in the bulk and at the surface of the samples. The Queens University Experiment in Liquid Diffusion (QUELD) was the furnace facility used to process 213 samples for the five other experiments. These experiments investigated the diffusion, ripening, crystal growth, and glass formation in metal, semiconductor, and glass samples. This facility had the capability to process samples in an isothermal or gradient configuration for varying periods of time at temperatures up to 900 C. Both the LMD and the QUELD furnaces were mounted on the Microgravity Isolation Mount (MIM) which provided isolation from g-jitter. All the microgravity experiments were supported by the Space Acceleration Measurement System (SAMS); a three head three axes acceleration monitoring system which measured and recorded the acceleration environment.

Fatal pediatric head injuries: a 20-year review of cases through the Auckland coroner's office.

PubMed

John, Simon Mathew; Jones, Peter; Kelly, Patrick; Vincent, Andrea

2013-09-01

Inflicted pediatric head injury is a significant issue in New Zealand, fatal cases receiving extensive media attention. The primary aims of this article were to analyze injury patterns and reported mechanisms against both age and cause (accidental or inflicted). The secondary aims were to quantify these deaths and identify trends over time. We retrospectively reviewed pediatric deaths due to head injury in children younger than 15 years referred to the Coronial Service of Auckland, New Zealand, from January 1, 1991, to December 31, 2010. One hundred sixty-seven cases were identified. Overall incidence was stable over time; however, the rate of inflicted head injury increased significantly (from 0.1 to 0.4/100,000 per year). Evidence of impact was seen in 90% of cases. In children younger than 2 years, in the absence of motor vehicle or pedestrian trauma, subdural hemorrhage and diffuse axonal injury were both highly suggestive of inflicted injury. The absence of a history of trauma or a history of a fall less than 1 m was also highly suggestive of inflicted injury. Retinal hemorrhages in these fatal head injuries were severe in 77% of cases and moderate in the remainder.

Defining an Analytic Framework to Evaluate Quantitative MRI Markers of Traumatic Axonal Injury: Preliminary Results in a Mouse Closed Head Injury Model

PubMed Central

Sadeghi, N.; Namjoshi, D.; Irfanoglu, M. O.; Wellington, C.; Diaz-Arrastia, R.

2017-01-01

Diffuse axonal injury (DAI) is a hallmark of traumatic brain injury (TBI) pathology. Recently, the Closed Head Injury Model of Engineered Rotational Acceleration (CHIMERA) was developed to generate an experimental model of DAI in a mouse. The characterization of DAI using diffusion tensor magnetic resonance imaging (MRI; diffusion tensor imaging, DTI) may provide a useful set of outcome measures for preclinical and clinical studies. The objective of this study was to identify the complex neurobiological underpinnings of DTI features following DAI using a comprehensive and quantitative evaluation of DTI and histopathology in the CHIMERA mouse model. A consistent neuroanatomical pattern of pathology in specific white matter tracts was identified across ex vivo DTI maps and photomicrographs of histology. These observations were confirmed by voxelwise and regional analysis of DTI maps, demonstrating reduced fractional anisotropy (FA) in distinct regions such as the optic tract. Similar regions were identified by quantitative histology and exhibited axonal damage as well as robust gliosis. Additional analysis using a machine-learning algorithm was performed to identify regions and metrics important for injury classification in a manner free from potential user bias. This analysis found that diffusion metrics were able to identify injured brains almost with the same degree of accuracy as the histology metrics. Good agreement between regions detected as abnormal by histology and MRI was also found. The findings of this work elucidate the complexity of cellular changes that give rise to imaging abnormalities and provide a comprehensive and quantitative evaluation of the relative importance of DTI and histological measures to detect brain injury. PMID:28966972

Predicting the need for CT imaging in children with minor head injury using an ensemble of Naive Bayes classifiers.

PubMed

Klement, William; Wilk, Szymon; Michalowski, Wojtek; Farion, Ken J; Osmond, Martin H; Verter, Vedat

2012-03-01

Using an automatic data-driven approach, this paper develops a prediction model that achieves more balanced performance (in terms of sensitivity and specificity) than the Canadian Assessment of Tomography for Childhood Head Injury (CATCH) rule, when predicting the need for computed tomography (CT) imaging of children after a minor head injury. CT is widely considered an effective tool for evaluating patients with minor head trauma who have potentially suffered serious intracranial injury. However, its use poses possible harmful effects, particularly for children, due to exposure to radiation. Safety concerns, along with issues of cost and practice variability, have led to calls for the development of effective methods to decide when CT imaging is needed. Clinical decision rules represent such methods and are normally derived from the analysis of large prospectively collected patient data sets. The CATCH rule was created by a group of Canadian pediatric emergency physicians to support the decision of referring children with minor head injury to CT imaging. The goal of the CATCH rule was to maximize the sensitivity of predictions of potential intracranial lesion while keeping specificity at a reasonable level. After extensive analysis of the CATCH data set, characterized by severe class imbalance, and after a thorough evaluation of several data mining methods, we derived an ensemble of multiple Naive Bayes classifiers as the prediction model for CT imaging decisions. In the first phase of the experiment we compared the proposed ensemble model to other ensemble models employing rule-, tree- and instance-based member classifiers. Our prediction model demonstrated the best performance in terms of AUC, G-mean and sensitivity measures. In the second phase, using a bootstrapping experiment similar to that reported by the CATCH investigators, we showed that the proposed ensemble model achieved a more balanced predictive performance than the CATCH rule with an average sensitivity of 82.8% and an average specificity of 74.4% (vs. 98.1% and 50.0% for the CATCH rule respectively). Automatically derived prediction models cannot replace a physician's acumen. However, they help establish reference performance indicators for the purpose of developing clinical decision rules so the trade-off between prediction sensitivity and specificity is better understood. Copyright © 2011 Elsevier B.V. All rights reserved.

Wanted: Scalable Tracers for Diffusion Measurements

PubMed Central

2015-01-01

Scalable tracers are potentially a useful tool to examine diffusion mechanisms and to predict diffusion coefficients, particularly for hindered diffusion in complex, heterogeneous, or crowded systems. Scalable tracers are defined as a series of tracers varying in size but with the same shape, structure, surface chemistry, deformability, and diffusion mechanism. Both chemical homology and constant dynamics are required. In particular, branching must not vary with size, and there must be no transition between ordinary diffusion and reptation. Measurements using scalable tracers yield the mean diffusion coefficient as a function of size alone; measurements using nonscalable tracers yield the variation due to differences in the other properties. Candidate scalable tracers are discussed for two-dimensional (2D) diffusion in membranes and three-dimensional diffusion in aqueous solutions. Correlations to predict the mean diffusion coefficient of globular biomolecules from molecular mass are reviewed briefly. Specific suggestions for the 3D case include the use of synthetic dendrimers or random hyperbranched polymers instead of dextran and the use of core–shell quantum dots. Another useful tool would be a series of scalable tracers varying in deformability alone, prepared by varying the density of crosslinking in a polymer to make say “reinforced Ficoll” or “reinforced hyperbranched polyglycerol.” PMID:25319586

Migration and head penetration of Vitamin-E diffused cemented polyethylene cup compared to standard cemented cup in total hip arthroplasty: study protocol for a randomised, double-blind, controlled trial (E1 HIP).

PubMed

Sköldenberg, Olof; Rysinska, Agata; Chammout, Ghazi; Salemyr, Mats; Muren, Olle; Bodén, Henrik; Eisler, Thomas

2016-07-07

In vitro, Vitamin-E-diffused, highly cross-linked polyethylene (PE) has been shown to have superior wear resistance and improved mechanical properties when compared to those of standard highly cross-linked PE liners used in total hip arthroplasty (THA). The aim of the study is to evaluate the safety of a new cemented acetabular cup with Vitamin-E-doped PE regarding migration, head penetration and clinical results. In this single-centre, double-blinded, randomised controlled trial, we will include 50 patients with primary hip osteoarthritis scheduled for THA and randomise them in a 1:1 ratio to a cemented cup with either argon gas-sterilised PE (control group) or Vitamin-E-diffused PE (vitamin-e group). All patients and the assessor of the primary outcome will be blinded and the same uncemented stem will be used for all participants. The primary end point will be proximal migration of the cup at 2 years after surgery measured with radiostereometry. Secondary end points include proximal migration at other follow-ups, total migration, femoral head penetration, clinical outcome scores and hip-related complications. Patients will be followed up at 3 months and at 1, 2, 5 and 10 years postoperatively. Results will be analysed using 95% CIs for the effect size. A regression model will also be used to adjust for stratification factors. The ethical committee at Karolinska Institutet has approved the study. The first results from the study will be disseminated to the medical community via presentations and publications in relevant medical journals when the last patient included has been followed up for 2 years. NCT02254980. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Histogram analysis of apparent diffusion coefficient maps for the differentiation between lymphoma and metastatic lymph nodes of squamous cell carcinoma in head and neck region.

PubMed

Wang, Yan-Jun; Xu, Xiao-Quan; Hu, Hao; Su, Guo-Yi; Shen, Jie; Shi, Hai-Bin; Wu, Fei-Yun

2018-06-01

Background To clarify the nature of cervical malignant lymphadenopathy is highly important for the diagnosis and differential diagnosis of head and neck tumors. Purpose To investigate the role of first-order apparent diffusion coefficient (ADC) histogram analysis for differentiating lymphoma from metastatic lymph nodes of squamous cell carcinoma (SCC) in the head and neck region. Material and Methods Diffusion-weighted imaging (DWI) data of 67 patients (lymphoma, n = 20; SCC, n = 47) with malignant lymphadenopathy were retrospectively analyzed. The SCC group was divided into nasopharyngeal SCC and non-nasopharyngeal SCC groups. The ADC histogram features (ADC 10 , ADC 25 , ADC mean , ADC median , ADC 75 , ADC 90 , skewness, and kurtosis) were derived and then compared by independent-samples t-test and one-way analysis of variance test, respectively. Receiver operating characteristic curve analyses were employed to investigate diagnostic performance of the significant parameters. Results Lymphoma showed significantly lower ADC mean , ADC median , ADC 75 , and ADC 90 than SCC (all P < 0.05). Setting ADC 90  = 0.719 × 10 -3  mm 2 /s as the threshold value, optimal diagnostic performance was achieved (area under the curve [AUC] = 0.719, sensitivity = 95.7%, specificity = 50.0%). Subgroup analyses showed no significant difference between lymphoma and NPC (all P > 0.05). Lymphoma showed significantly lower ADC 25 , ADC mean , ADC median , ADC 75 , and ADC 90 than non-nasopharyngeal SCC (all P < 0.05). Optimal diagnostic performance (AUC = 0.847, sensitivity = 86.7%, specificity = 80.0%) could be achieved when setting ADC 90  = 0.943 × 10 -3  mm 2 /s as the threshold value. Conclusion Given its limitations, our study has shown that first-order ADC histogram analysis is capable of differentiating lymphoma from metastatic lymph nodes of SCC, especially those of non-nasopharyngeal SCC.

Migration and head penetration of Vitamin-E diffused cemented polyethylene cup compared to standard cemented cup in total hip arthroplasty: study protocol for a randomised, double-blind, controlled trial (E1 HIP)

PubMed Central

Sköldenberg, Olof; Rysinska, Agata; Chammout, Ghazi; Salemyr, Mats; Muren, Olle; Bodén, Henrik; Eisler, Thomas

2016-01-01

Introduction In vitro, Vitamin-E-diffused, highly cross-linked polyethylene (PE) has been shown to have superior wear resistance and improved mechanical properties when compared to those of standard highly cross-linked PE liners used in total hip arthroplasty (THA). The aim of the study is to evaluate the safety of a new cemented acetabular cup with Vitamin-E-doped PE regarding migration, head penetration and clinical results. Methods and analysis In this single-centre, double-blinded, randomised controlled trial, we will include 50 patients with primary hip osteoarthritis scheduled for THA and randomise them in a 1:1 ratio to a cemented cup with either argon gas-sterilised PE (control group) or Vitamin-E-diffused PE (vitamin-e group). All patients and the assessor of the primary outcome will be blinded and the same uncemented stem will be used for all participants. The primary end point will be proximal migration of the cup at 2 years after surgery measured with radiostereometry. Secondary end points include proximal migration at other follow-ups, total migration, femoral head penetration, clinical outcome scores and hip-related complications. Patients will be followed up at 3 months and at 1, 2, 5 and 10 years postoperatively. Results Results will be analysed using 95% CIs for the effect size. A regression model will also be used to adjust for stratification factors. Ethics and dissemination The ethical committee at Karolinska Institutet has approved the study. The first results from the study will be disseminated to the medical community via presentations and publications in relevant medical journals when the last patient included has been followed up for 2 years. Trial registration number NCT02254980. PMID:27388352

Study on compensation algorithm of head skew in hard disk drives

NASA Astrophysics Data System (ADS)

Xiao, Yong; Ge, Xiaoyu; Sun, Jingna; Wang, Xiaoyan

2011-10-01

In hard disk drives (HDDs), head skew among multiple heads is pre-calibrated during manufacturing process. In real applications with high capacity of storage, the head stack may be tilted due to environmental change, resulting in additional head skew errors from outer diameter (OD) to inner diameter (ID). In case these errors are below the preset threshold for power on recalibration, the current strategy may not be aware, and drive performance under severe environment will be degraded. In this paper, in-the-field compensation of small DC head skew variation across stroke is proposed, where a zone table has been equipped. Test results demonstrating its effectiveness to reduce observer error and to enhance drive performance via accurate prediction of DC head skew are provided.

Prediction of competitive diffusion on complex networks

NASA Astrophysics Data System (ADS)

Zhao, Jiuhua; Liu, Qipeng; Wang, Lin; Wang, Xiaofan

2018-10-01

In this paper, we study the prediction problem of diffusion process on complex networks in competitive circumstances. With this problem solved, the competitors could timely intervene the diffusion process if needed such that an expected outcome might be obtained. We consider a model with two groups of competitors spreading opposite opinions on a network. A prediction method based on the mutual influences among the agents is proposed, called Influence Matrix (IM for short), and simulations on real-world networks show that the proposed IM method has quite high accuracy on predicting both the preference of any normal agent and the final competition result. For comparison purpose, classic centrality measures are also used to predict the competition result. It is shown that PageRank, Degree, Katz Centrality, and the IM method are suitable for predicting the competition result. More precisely, in undirected networks, the IM method performs better than these centrality measures when the competing group contains more than one agent; in directed networks, the IM method performs only second to PageRank.

Carrying capacity in a heterogeneous environment with habitat connectivity.

PubMed

Zhang, Bo; Kula, Alex; Mack, Keenan M L; Zhai, Lu; Ryce, Arrix L; Ni, Wei-Ming; DeAngelis, Donald L; Van Dyken, J David

2017-09-01

A large body of theory predicts that populations diffusing in heterogeneous environments reach higher total size than if non-diffusing, and, paradoxically, higher size than in a corresponding homogeneous environment. However, this theory and its assumptions have not been rigorously tested. Here, we extended previous theory to include exploitable resources, proving qualitatively novel results, which we tested experimentally using spatially diffusing laboratory populations of yeast. Consistent with previous theory, we predicted and experimentally observed that spatial diffusion increased total equilibrium population abundance in heterogeneous environments, with the effect size depending on the relationship between r and K. Refuting previous theory, however, we discovered that homogeneously distributed resources support higher total carrying capacity than heterogeneously distributed resources, even with species diffusion. Our results provide rigorous experimental tests of new and old theory, demonstrating how the traditional notion of carrying capacity is ambiguous for populations diffusing in spatially heterogeneous environments. © 2017 John Wiley & Sons Ltd/CNRS.

A consistent transported PDF model for treating differential molecular diffusion

NASA Astrophysics Data System (ADS)

Wang, Haifeng; Zhang, Pei

2016-11-01

Differential molecular diffusion is a fundamentally significant phenomenon in all multi-component turbulent reacting or non-reacting flows caused by the different rates of molecular diffusion of energy and species concentrations. In the transported probability density function (PDF) method, the differential molecular diffusion can be treated by using a mean drift model developed by McDermott and Pope. This model correctly accounts for the differential molecular diffusion in the scalar mean transport and yields a correct DNS limit of the scalar variance production. The model, however, misses the molecular diffusion term in the scalar variance transport equation, which yields an inconsistent prediction of the scalar variance in the transported PDF method. In this work, a new model is introduced to remedy this problem that can yield a consistent scalar variance prediction. The model formulation along with its numerical implementation is discussed, and the model validation is conducted in a turbulent mixing layer problem.

First-principles-based kinetic Monte Carlo studies of diffusion of hydrogen in Ni–Al and Ni–Fe binary alloys

DOE PAGES

Tafen, De Nyago

2015-02-14

The diffusion of dilute hydrogen in fcc Ni–Al and Ni–Fe binary alloys was examined using kinetic Monte Carlo method with input kinetic parameters obtained from first-principles density functional theory. The simulation involves the implementation of computationally efficient energy barrier model that describes the configuration dependence of the hydrogen hopping. The predicted hydrogen diffusion coefficients in Ni and Ni 89.4Fe 10.6 are compared well with the available experimental data. In Ni–Al, the model predicts lower hydrogen diffusivity compared to that in Ni. Overall, diffusion prefactors and the effective activation energies of H in Ni–Fe and Ni–Al are concentration dependent of themore » alloying element. Furthermore, the changes in their values are the results of the short-range order (nearest-neighbor) effect on the interstitial diffusion of hydrogen in fcc Ni-based alloys.« less

Diffusion kinetics of the glucose/glucose oxidase system in swift heavy ion track-based biosensors

NASA Astrophysics Data System (ADS)

Fink, Dietmar; Vacik, Jiri; Hnatowicz, V.; Muñoz Hernandez, G.; Garcia Arrelano, H.; Alfonta, Lital; Kiv, Arik

2017-05-01

For understanding of the diffusion kinetics and their optimization in swift heavy ion track-based biosensors, recently a diffusion simulation was performed. This simulation aimed at yielding the degree of enrichment of the enzymatic reaction products in the highly confined space of the etched ion tracks. A bunch of curves was obtained for the description of such sensors that depend only on the ratio of the diffusion coefficient of the products to that of the analyte within the tracks. As hitherto none of these two diffusion coefficients is accurately known, the present work was undertaken. The results of this paper allow one to quantify the previous simulation and hence yield realistic predictions of glucose-based biosensors. At this occasion, also the influence of the etched track radius on the diffusion coefficients was measured and compared with earlier prediction.

Carrying capacity in a heterogeneous environment with habitat connectivity

USGS Publications Warehouse

Zhang, Bo; Kula, Alex; Mack, Keenan M.L.; Zhai, Lu; Ryce, Arrix L.; Ni, Wei-Ming; DeAngelis, Donald L.; Van Dyken, J. David

2017-01-01

A large body of theory predicts that populations diffusing in heterogeneous environments reach higher total size than if non-diffusing, and, paradoxically, higher size than in a corresponding homogeneous environment. However, this theory and its assumptions have not been rigorously tested. Here, we extended previous theory to include exploitable resources, proving qualitatively novel results, which we tested experimentally using spatially diffusing laboratory populations of yeast. Consistent with previous theory, we predicted and experimentally observed that spatial diffusion increased total equilibrium population abundance in heterogeneous environments, with the effect size depending on the relationship between r and K. Refuting previous theory, however, we discovered that homogeneously distributed resources support higher total carrying capacity than heterogeneously distributed resources, even with species diffusion. Our results provide rigorous experimental tests of new and old theory, demonstrating how the traditional notion of carrying capacity is ambiguous for populations diffusing in spatially heterogeneous environments.

The Steady-State Transport of Oxygen through Hemoglobin Solutions

PubMed Central

Keller, K. H.; Friedlander, S. K.

1966-01-01

The steady-state transport of oxygen through hemoglobin solutions was studied to identify the mechanism of the diffusion augmentation observed at low oxygen tensions. A novel technique employing a platinum-silver oxygen electrode was developed to measure the effective diffusion coefficient of oxygen in steady-state transport. The measurements were made over a wider range of hemoglobin and oxygen concentrations than previously reported. Values of the Brownian motion diffusion coefficient of oxygen in hemoglobin solution were obtained as well as measurements of facilitated transport at low oxygen tensions. Transport rates up to ten times greater than ordinary diffusion rates were found. Predictions of oxygen flux were made assuming that the oxyhemoglobin transport coefficient was equal to the Brownian motion diffusivity which was measured in a separate set of experiments. The close correlation between prediction and experiment indicates that the diffusion of oxyhemoglobin is the mechanism by which steady-state oxygen transport is facilitated. PMID:5943608

Biomarkers of head and neck cancer, tools or a gordian knot?

PubMed

Lampri, Evangeli S; Chondrogiannis, Georgios; Ioachim, Elli; Varouktsi, Anna; Mitselou, Antigoni; Galani, Aggeliki; Briassoulis, Evangelos; Kanavaros, Panagiotis; Galani, Vasiliki

2015-01-01

Head and neck tumors comprise a wide spectrum of heterogeneous neoplasms for which biomarkers are needed to aid in earlier diagnosis, risk assessment and therapy response. Personalized medicine based on predictive markers linked to drug response, it is hoped, will lead to improvements in outcomes and avoidance of unnecessary treatment in carcinoma of the head and neck. Because of the heterogeneity of head and neck tumors, the integration of multiple selected markers in association with the histopathologic features is advocated for risk assessment. Validation of each biomarker in the context of clinical trials will be required before a specific marker can be incorporated into daily practice. Furthermore, we will give evidence that some proteins implicated in cell-cell interaction, such as CD44 may be involved in the multiple mechanism of the development and progression of laryngeal lesions and may help to predict the risk of transformation of the benign or precancerous lesions to cancer.

Anomalous diffusion and scaling in coupled stochastic processes

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

Bel, Golan; Nemenman, Ilya

2009-01-01

Inspired by problems in biochemical kinetics, we study statistical properties of an overdamped Langevin processes with the friction coefficient depending on the state of a similar, unobserved, process. Integrating out the latter, we derive the Pocker-Planck the friction coefficient of the first depends on the state of the second. Integrating out the latter, we derive the Focker-Planck equation for the probability distribution of the former. This has the fonn of diffusion equation with time-dependent diffusion coefficient, resulting in an anomalous diffusion. The diffusion exponent can not be predicted using a simple scaling argument, and anomalous scaling appears as well. Themore » diffusion exponent of the Weiss-Havlin comb model is derived as a special case, and the same exponent holds even for weakly coupled processes. We compare our theoretical predictions with numerical simulations and find an excellent agreement. The findings caution against treating biochemical systems with unobserved dynamical degrees of freedom by means of standandard, diffusive Langevin descritpion.« less

Monte Carlo simulations of particle acceleration at oblique shocks: Including cross-field diffusion

NASA Technical Reports Server (NTRS)

Baring, M. G.; Ellison, D. C.; Jones, F. C.

1995-01-01

The Monte Carlo technique of simulating diffusive particle acceleration at shocks has made spectral predictions that compare extremely well with particle distributions observed at the quasi-parallel region of the earth's bow shock. The current extension of this work to compare simulation predictions with particle spectra at oblique interplanetary shocks has required the inclusion of significant cross-field diffusion (strong scattering) in the simulation technique, since oblique shocks are intrinsically inefficient in the limit of weak scattering. In this paper, we present results from the method we have developed for the inclusion of cross-field diffusion in our simulations, namely model predictions of particle spectra downstream of oblique subluminal shocks. While the high-energy spectral index is independent of the shock obliquity and the strength of the scattering, the latter is observed to profoundly influence the efficiency of injection of cosmic rays into the acceleration process.

Perceptual thresholds for non-ideal diffuse field reverberation.

PubMed

Romblom, David; Guastavino, Catherine; Depalle, Philippe

2016-11-01

The objective of this study is to understand listeners' sensitivity to directional variations in non-ideal diffuse field reverberation. An ABX discrimination test was conducted using a semi-spherical 28-loudspeaker array; perceptual thresholds were estimated by systematically varying the level of a segment of loudspeakers for lateral, height, and frontal conditions. The overall energy was held constant using a gain compensation scheme. When compared to an ideal diffuse field, the perceptual threshold for detection is -2.5 dB for the lateral condition, -6.8 dB for the height condition, and -3.2 dB for the frontal condition. Measurements of the experimental stimuli were analyzed using a Head and Torso Simulator as well as with opposing cardioid microphones aligned on the three Cartesian axes. Additionally, opposing cardioid measurements made in an acoustic space demonstrate that level differences corresponding to the perceptual thresholds can be found in practice. These results suggest that non-ideal diffuse field reverberation may be a previously unrecognized component of spatial impression.

Application of a groundwater flow model for real-time well field management - lessons learned

NASA Astrophysics Data System (ADS)

Marti, B.; Kaiser, H.-P.; Kuhlmann, U.; Hendricks Franssen, H.-J.; Kinzelbach, W.

2012-04-01

The Hardhof well field, which lies in the city of Zurich, Switzerland, provides roughly 15 % of the towns drinking water demand from the Limmat valley aquifer. Groundwater and river filtrate are withdrawn in four large horizontal wells, each with a capacity of up to 48'000 m3 per day. The well field is threatened by potential pollution from leachate of a nearby land fill, possible accidents on the adjacent rail and road lines, and by diffuse pollution from former industrial sites and sewers located upstream of the well field. A line of recharge wells and basins forms a hydraulic barrier against the potentially contaminated water and increases the capacity of the well field. Currently, a genetic algorithm coupled to a 3-dimensional groundwater flow model is applied at the well field to determine optimal infiltration rates on a daily basis. This real-time control is based on particle backtracking in a quasi-stationary flow field. It estimates the origin of the water in the four horizontal wells and calculates the amount of potentially contaminated water in each well. Running the model iteratively and refining the parameters of the genetic algorithm at the end of each step yields the recommended daily infiltration rates. The current model accurately predicts the change of piezometric head due to changes in the river stage. However, during periods of large abstraction rates, the model underestimates the piezometric heads in the Hardhof area. In addition, the infiltration rates suggested by the control do not always agree with the experience of the Zurich water works (e.g. during periods with large abstraction rates) and hence the actually applied infiltration rates are sometimes chosen differently from the calculated ones. This work analyzes the performance of the model and the control during the year 2011. The computed heads of the on-line model are compared to the measured piezometric heads in over 80 measurement locations in the model area. Furthermore, differences between the computed management decisions and the actual management decisions are analyzed and suggestions for an improved management are made.

Serial MR diffusion to predict treatment response in high-grade pediatric brain tumors: a comparison of regional and voxel-based diffusion change metrics

PubMed Central

Rodriguez Gutierrez, Daniel; Manita, Muftah; Jaspan, Tim; Dineen, Robert A.; Grundy, Richard G.; Auer, Dorothee P.

2013-01-01

Background Assessment of treatment response by measuring tumor size is known to be a late and potentially confounded response index. Serial diffusion MRI has shown potential for allowing earlier and possibly more reliable response assessment in adult patients, with limited experience in clinical settings and in pediatric brain cancer. We present a retrospective study of clinical MRI data in children with high-grade brain tumors to assess and compare the values of several diffusion change metrics to predict treatment response. Methods Eighteen patients (age range, 1.9–20.6 years) with high-grade brain tumors and serial diffusion MRI (pre- and posttreatment interval range, 1–16 weeks posttreatment) were identified after obtaining parental consent. The following diffusion change metrics were compared with the clinical response status assessed at 6 months: (1) regional change in absolute and normalized apparent diffusivity coefficient (ADC), (2) voxel-based fractional volume of increased (fiADC) and decreased ADC (fdADC), and (3) a new metric based on the slope of the first principal component of functional diffusion maps (fDM). Results Responders (n = 12) differed significantly from nonresponders (n = 6) in all 3 diffusional change metrics demonstrating higher regional ADC increase, larger fiADC, and steeper slopes (P < .05). The slope method allowed the best response prediction (P < .01, η2 = 0.78) with a classification accuracy of 83% for a slope of 58° using receiver operating characteristic (ROC) analysis. Conclusions We demonstrate that diffusion change metrics are suitable response predictors for high-grade pediatric tumors, even in the presence of variable clinical diffusion imaging protocols. PMID:23585630

The investigation of soot and temperature distributions in a visualized direct injection diesel engine using laser diagnostics

NASA Astrophysics Data System (ADS)

Han, Yong-taek; Kim, Ki-bum; Lee, Ki-hyung

2008-11-01

Based upon the method of temperature calibration using the diffusion flame, the temperature and soot concentrations of the turbulent flame in a visualized diesel engine were qualitatively measured. Two different cylinder heads were used to investigate the effect of swirl ratio within the combustion chamber. From this experiment, we find that the highest flame temperature of the non-swirl head engine is approximately 2400 K and that of the swirl head engine is 2100 K. In addition, as the pressure of fuel injection increases, the in-cylinder temperature increases due to the improved combustion of a diesel engine. This experiment represented the soot quantity in the KL factor and revealed that the KL factor was high when the fuel collided with the cylinder wall. Moreover, the KL factor was also high in the area of the chamber where the temperature dropped rapidly.

The Role of Predictability in Saccadic Eye Responses in the Suppression Head Impulse Test of Horizontal Semicircular Canal Function.

PubMed

Rey-Martinez, Jorge; Yanes, Joaquin; Esteban, Jonathan; Sanz, Ricardo; Martin-Sanz, Eduardo

2017-01-01

In the suppression head impulse paradigm (SHIMP) vHIT protocol, the participant is instructed to follow with his gaze a mobile target generated by a laser placed on the participant's head. Recent studies have reported that the refixation saccade latencies are in relation with the time evolution of the vestibular dysfunction in both (standard and SHIMP) procedures. We hypothesized that some central mechanisms like head impulse prediction could be one of the causes for the differences in the saccadic eye responses. A prospective cohort non-randomized study was designed. For the SHIMP protocol, recorded with the ICS Impulse ver. 4.0 ® (Otometrics A/S, Taastrup, Denmark) vHIT device, three different algorithms were performed: "predictable," "less predictable," and "unpredictable" depending on the target's predictability. A mathematical method was developed to analyze the SHIMP responses. The method was implemented as an additional tool to the MATLAB open source script for the extended analysis of the vHIT responses named HITCal. In cohort 1, 52 participants were included in "predictable" SHIMP protocol. In cohort 2, 60 patients were included for the "less predictable" and 35 patients for the "unpredictable" SHIMP protocol. The participants made more early saccades when instructed to perform the "predictable" paradigm compared with the "less predictable" paradigm ( p  < 0.001). The less predictable protocol did not reveal any significant difference when compared with the unpredictable protocol ( p  = 0.189). For the latency of the first saccade, there was statistical difference between the "unpredictable" and "predictable" protocols ( p  < 0.001) and between the "less predictable" and "predictable" protocols ( p  < 0.001). Finally, we did not find any relationship between the horizontal vestibulo-ocular reflex (hVOR) gain and the latency of the saccades. We developed a specific method to analyze and detect early SHIMP saccades. Our findings offer evidence regarding the influence of predictability on the latency of the SHIMP saccadic responses, suggesting that early saccades are probably caused by a conditioned response of the participant. The lack of relationship between the hVOR gain and the latency of the saccades suggests that the predictive behavior that caused the early eye saccades are independent of the vestibular function.

The role of cerebral spinal fluid in light propagation through the mouse head: improving fluorescence tomography with Monte Carlo modeling

NASA Astrophysics Data System (ADS)

Ancora, Daniele; Zacharopoulos, Athanasios; Ripoll, Jorge; Zacharakis, Giannis

2016-03-01

Optical Neuroimaging is a highly dynamical field of research owing to the combination of many advanced imaging techniques and computational tools that uncovered unexplored paths through the functioning of the brain. Light propagation modelling through such complicated structures has always played a crucial role as the basis for a high resolution and quantitative imaging where even the slightest improvement could lead to significant results. Fluorescence Diffuse Optical Tomography (fDOT), a widely used technique for three dimensional imaging of small animals and tissues, has been proved to be inaccurate for neuroimaging the mouse head without the knowledge of a-priori anatomical information of the subject. Commonly a normalized Born approximation model is used in fDOT reconstruction based on forward photon propagation using Diffusive Equation (DE) which has strong limitations in the optically clear regime. The presence of the Cerebral Spinal Fluid (CSF) instead, a thin optically clear layer surrounding the brain, can be more accurately taken into account using Monte Carlo approaches which nowadays is becoming more usable thanks to parallelized GPU algorithms. In this work we discuss the results of a synthetic experimental comparison, resulting to the increase of the accuracy for the Born approximation by introducing the CSF layer in a realistic mouse head structure with respect to the current model. We point out the importance of such clear layer for complex geometrical models, while for simple slab phantoms neglecting it does not introduce a significant error.

Solute diffusion in liquid metals

NASA Technical Reports Server (NTRS)

Bhat, B. N.

1973-01-01

A gas model of diffusion in liquid metals is presented. In this model, ions of liquid metals are assumed to behave like the molecules in a dense gas. Diffusion coefficient of solute is discussed with reference to its mass, ionic size, and pair potential. The model is applied to the case of solute diffusion in liquid silver. An attempt was made to predict diffusion coefficients of solutes with reasonable accuracy.

Mortality and Epidemiology in 256 Cases of Pediatric Traumatic Brain Injury: Korean Neuro-Trauma Data Bank System (KNTDBS) 2010-2014.

PubMed

Jeong, Hee-Won; Choi, Seung-Won; Youm, Jin-Young; Lim, Jeong-Wook; Kwon, Hyon-Jo; Song, Shi-Hun

2017-11-01

Among pediatric injury, brain injury is a leading cause of death and disability. To improve outcomes, many developed countries built neurotrauma databank (NTDB) system but there was not established nationwide coverage NTDB until 2009 and there have been few studies on pediatric traumatic head injury (THI) patients in Korea. Therefore, we analyzed epidemiology and outcome from the big data of pediatric THI. We collected data on pediatric patients from 23 university hospitals including 9 regional trauma centers from 2010 to 2014 and analyzed their clinical factors (sex, age, initial Glasgow coma scale, cause and mechanism of head injury, presence of surgery). Among all the 2617 THI patients, total number of pediatric patients was 256. The average age of the subjects was 9.07 (standard deviation±6.3) years old. The male-to female ratio was 1.87 to 1 and male dominance increases with age. The most common cause for trauma were falls and traffic accidents. Age ( p =0.007), surgery ( p <0.001), mechanism of trauma ( p =0.016), subdural hemorrhage (SDH) ( p <0.001), diffuse axonal injury (DAI) ( p <0.001) were statistically significant associated with severe brain injury. Falls were the most common cause of trauma, and age, surgery, mechanism of trauma, SDH, DAI increased with injury severity. There is a critical need for effective fall and traffic accidents prevention strategies for children, and we should give attention to these predicting factors for more effective care.

Simultaneous PET/MRI in assessing the response to chemo/radiotherapy in head and neck carcinoma: initial experience.

PubMed

Romeo, Valeria; Iorio, Brigida; Mesolella, Massimo; Ugga, Lorenzo; Verde, Francesco; Nicolai, Emanuele; Covello, Mario

2018-06-19

The purpose of the study was to assess by simultaneous positron emission tomography/magnetic resonance imaging (PET/MRI) the response to chemotherapy (CHT) and/or radiotherapy (RT) in patients with head and neck squamous cell carcinoma (HNSCC). Five patients with HNSCC underwent simultaneous PET/MRI examination before and after CHT and/or RT. Standard uptake volume (SUV), apparent diffusion coefficient (ADC), Ktrans, Kep, Ve, and iAUC pre- and post-treatment values were extracted and compared. The response to treatment was assessed according to RECIST criteria and classified as complete response (CR), partial response (PR), stable disease (SD), and progression disease (PD). In patient 1, PR was observed with increased ADC, Ktrans, and Ve values and reduction of SUV, iAUC, and Kep values; during clinical and instrumental follow-up, the patient experienced disease progression. Patient 2, classified as PR, showed increased ADC values and reduction of SUV and all perfusion parameters; follow-up demonstrated disease stability. Patient 3, considered as SD, showed increase of ADC and all perfusion values with a mild decrease of SUV; PD was observed during clinical and instrumental follow-up. Patients 4 and 5 showed a CR with no detectable tumor lesions at post-treatment PET/MRI examination, confirmed by 1-year follow-up. Multiparametric evaluation with simultaneous PET/MRI could be a useful tool to assess and predict the response to CHT and/or RT in patients with HNSCC.

Bridging the gap between marker-assisted and genomic selection of heading time and plant height in hybrid wheat.

PubMed

Zhao, Y; Mette, M F; Gowda, M; Longin, C F H; Reif, J C

2014-06-01

Based on data from field trials with a large collection of 135 elite winter wheat inbred lines and 1604 F1 hybrids derived from them, we compared the accuracy of prediction of marker-assisted selection and current genomic selection approaches for the model traits heading time and plant height in a cross-validation approach. For heading time, the high accuracy seen with marker-assisted selection severely dropped with genomic selection approaches RR-BLUP (ridge regression best linear unbiased prediction) and BayesCπ, whereas for plant height, accuracy was low with marker-assisted selection as well as RR-BLUP and BayesCπ. Differences in the linkage disequilibrium structure of the functional and single-nucleotide polymorphism markers relevant for the two traits were identified in a simulation study as a likely explanation for the different trends in accuracies of prediction. A new genomic selection approach, weighted best linear unbiased prediction (W-BLUP), designed to treat the effects of known functional markers more appropriately, proved to increase the accuracy of prediction for both traits and thus closes the gap between marker-assisted and genomic selection.

Bridging the gap between marker-assisted and genomic selection of heading time and plant height in hybrid wheat

PubMed Central

Zhao, Y; Mette, M F; Gowda, M; Longin, C F H; Reif, J C

2014-01-01

Based on data from field trials with a large collection of 135 elite winter wheat inbred lines and 1604 F1 hybrids derived from them, we compared the accuracy of prediction of marker-assisted selection and current genomic selection approaches for the model traits heading time and plant height in a cross-validation approach. For heading time, the high accuracy seen with marker-assisted selection severely dropped with genomic selection approaches RR-BLUP (ridge regression best linear unbiased prediction) and BayesCπ, whereas for plant height, accuracy was low with marker-assisted selection as well as RR-BLUP and BayesCπ. Differences in the linkage disequilibrium structure of the functional and single-nucleotide polymorphism markers relevant for the two traits were identified in a simulation study as a likely explanation for the different trends in accuracies of prediction. A new genomic selection approach, weighted best linear unbiased prediction (W-BLUP), designed to treat the effects of known functional markers more appropriately, proved to increase the accuracy of prediction for both traits and thus closes the gap between marker-assisted and genomic selection. PMID:24518889

Modeling gravity-dependent plasticity of the angular vestibuloocular reflex with a physiologically based neural network.

PubMed

Xiang, Yongqing; Yakushin, Sergei B; Cohen, Bernard; Raphan, Theodore

2006-12-01

A neural network model was developed to explain the gravity-dependent properties of gain adaptation of the angular vestibuloocular reflex (aVOR). Gain changes are maximal at the head orientation where the gain is adapted and decrease as the head is tilted away from that position and can be described by the sum of gravity-independent and gravity-dependent components. The adaptation process was modeled by modifying the weights and bias values of a three-dimensional physiologically based neural network of canal-otolith-convergent neurons that drive the aVOR. Model parameters were trained using experimental vertical aVOR gain values. The learning rule aimed to reduce the error between eye velocities obtained from experimental gain values and model output in the position of adaptation. Although the model was trained only at specific head positions, the model predicted the experimental data at all head positions in three dimensions. Altering the relative learning rates of the weights and bias improved the model-data fits. Model predictions in three dimensions compared favorably with those of a double-sinusoid function, which is a fit that minimized the mean square error at every head position and served as the standard by which we compared the model predictions. The model supports the hypothesis that gravity-dependent adaptation of the aVOR is realized in three dimensions by a direct otolith input to canal-otolith neurons, whose canal sensitivities are adapted by the visual-vestibular mismatch. The adaptation is tuned by how the weights from otolith input to the canal-otolith-convergent neurons are adapted for a given head orientation.

Predicting the Kinetics of Ice Recrystallization in Aqueous Sugar Solutions

PubMed Central

2018-01-01

The quality of stored frozen products such as foods and biomaterials generally degrades in time due to the growth of large ice crystals by recrystallization. While there is ample experimental evidence that recrystallization within such products (or model systems thereof) is often dominated by diffusion-limited Ostwald ripening, the application of Ostwald-ripening theories to predict measured recrystallization rates has only met with limited success. For a model system of polycrystalline ice within an aqueous solution of sugars, we here show recrystallization rates can be predicted on the basis of Ostwald ripening theory, provided (1) the theory accounts for the fact the solution can be nonideal, nondilute and of different density than the crystals, (2) the effect of ice-phase volume fraction on the diffusional flux of water between crystals is accurately described, and (3) all relevant material properties (involving binary Fick diffusion coefficients, the thermodynamic factor of the solution, and the surface energy of ice) are carefully estimated. To enable calculation of material properties, we derive an alternative formulation of Ostwald ripening in terms of the Maxwell–Stefan instead of the Fick approach to diffusion. First, this leads to a cancellation of the thermodynamic factor (a measure for the nonideality of a solution), which is a notoriously difficult property to obtain. Second, we show that Maxwell–Stefan diffusion coefficients can to a reasonable approximation be related to self-diffusion coefficients, which are relatively easy to measure or predict in comparison to Fick diffusion coefficients. Our approach is validated for a binary system of water and sucrose, for which we show predicted recrystallization rates of ice compare well to experimental results, with relative deviations of at most a factor of 2. PMID:29651228

Predicting the Kinetics of Ice Recrystallization in Aqueous Sugar Solutions.

PubMed

van Westen, Thijs; Groot, Robert D

2018-04-04

The quality of stored frozen products such as foods and biomaterials generally degrades in time due to the growth of large ice crystals by recrystallization. While there is ample experimental evidence that recrystallization within such products (or model systems thereof) is often dominated by diffusion-limited Ostwald ripening, the application of Ostwald-ripening theories to predict measured recrystallization rates has only met with limited success. For a model system of polycrystalline ice within an aqueous solution of sugars, we here show recrystallization rates can be predicted on the basis of Ostwald ripening theory, provided (1) the theory accounts for the fact the solution can be nonideal, nondilute and of different density than the crystals, (2) the effect of ice-phase volume fraction on the diffusional flux of water between crystals is accurately described, and (3) all relevant material properties (involving binary Fick diffusion coefficients, the thermodynamic factor of the solution, and the surface energy of ice) are carefully estimated. To enable calculation of material properties, we derive an alternative formulation of Ostwald ripening in terms of the Maxwell-Stefan instead of the Fick approach to diffusion. First, this leads to a cancellation of the thermodynamic factor (a measure for the nonideality of a solution), which is a notoriously difficult property to obtain. Second, we show that Maxwell-Stefan diffusion coefficients can to a reasonable approximation be related to self-diffusion coefficients, which are relatively easy to measure or predict in comparison to Fick diffusion coefficients. Our approach is validated for a binary system of water and sucrose, for which we show predicted recrystallization rates of ice compare well to experimental results, with relative deviations of at most a factor of 2.

Predicting dermal penetration for ToxCast chemicals using in silico estimates for diffusion in combination with physiologically based pharmacokinetic (PBPK) modeling.

EPA Science Inventory

Predicting dermal penetration for ToxCast chemicals using in silico estimates for diffusion in combination with physiologically based pharmacokinetic (PBPK) modeling.Evans, M.V., Sawyer, M.E., Isaacs, K.K, and Wambaugh, J.With the development of efficient high-throughput (HT) in ...

A QSPR model for prediction of diffusion coefficient of non-electrolyte organic compounds in air at ambient condition.

PubMed

Mirkhani, Seyyed Alireza; Gharagheizi, Farhad; Sattari, Mehdi

2012-03-01

Evaluation of diffusion coefficients of pure compounds in air is of great interest for many diverse industrial and air quality control applications. In this communication, a QSPR method is applied to predict the molecular diffusivity of chemical compounds in air at 298.15K and atmospheric pressure. Four thousand five hundred and seventy nine organic compounds from broad spectrum of chemical families have been investigated to propose a comprehensive and predictive model. The final model is derived by Genetic Function Approximation (GFA) and contains five descriptors. Using this dedicated model, we obtain satisfactory results quantified by the following statistical results: Squared Correlation Coefficient=0.9723, Standard Deviation Error=0.003 and Average Absolute Relative Deviation=0.3% for the predicted properties from existing experimental values. Copyright © 2011 Elsevier Ltd. All rights reserved.

Factors Influencing Helmet Use, Head Injury, and Hospitalization Among Children Involved in Skateboarding and Snowboarding Accidents

PubMed Central

Sadeghian, Homa; Nguyen, Brian; Huynh, Nhan; Rouch, Joshua; Lee, Steven L; Bazargan-Hejazi, Shahrzad

2017-01-01

Context Up to 75% of skateboarders and snowboarders admitted to the hospital sustain head injuries. It is unclear why not all children and teenagers wear helmets while snowboarding and skateboarding given the protection they afford. Objectives To report on the prevalence of, and factors associated with, skateboarding and snowboarding in injured children and to explore factors that influence helmet use, head injury, and hospitalization in this sample. Design A cross-sectional study of skateboard- and snowboard-associated injuries from 2003 to 2012 among individuals younger than age 18 years using National Electronic Injury Surveillance System (NEISS) data from approximately 100 hospitals. Main Outcome Measures: Helmet use, head injury, and hospitalization. Results Of 1742 patients in the study, 852 (48.9%) and 890 (51.1%) were skateboarders and snowboarders, respectively. Overall, 907 (52.1%) did not use helmets, and 704 (40.4%) sustained head injuries. Multiple logistic regression analysis showed that age, race/ethnicity, location of boarding, and engaging in skateboarding influenced helmet use. Sex, race/ethnicity, helmet use, and skateboarding predicted head injury. Age, sex, skateboarding, and head injury predicted hospital admission. Conclusion Statistically significant differences exist in helmet use, head injury, and hospitalization rates between skateboarders and snowboarders. Our findings suggest that injury prevention and outreach programs are needed to increase helmet use and reduce the risk of head injury and hospitalization in skateboarders and other at-risk groups. Further studies are needed to clarify the association between race/ethnicity and helmet use among skateboarders and snowboarders. PMID:28406787

The value of non-echo planar HASTE diffusion-weighted MR imaging in the detection, localisation and prediction of extent of postoperative cholesteatoma.

PubMed

Khemani, S; Lingam, R K; Kalan, A; Singh, A

2011-08-01

To evaluate the diagnostic performance of half-Fourier-acquisition single-shot turbo-spin-echo (HASTE) diffusion-weighted magnetic resonance imaging in the detection, localisation and prediction of extent of cholesteatoma following canal wall up mastoid surgery. Prospective blinded observational study. University affiliated teaching hospital. Forty-eight patients undergoing second-look surgery after previous canal wall up mastoid surgery for primary acquired cholesteatoma. All patients underwent non-echo planar HASTE diffusion-weighted imaging prior to being offered 'second-look' surgery. Radiological findings were correlated with second-look intra-operative findings in 38 cases with regard to presence, location and maximum dimensions of cholesteatoma. Half-Fourier-acquisition single-shot turbo-spin-echo diffusion-weighted imaging accurately predicted the presence of cholesteatoma in 23 of 28 cases, and it correctly excluded in nine of 10 cases. Five false negatives were caused by keratin pearls of <2 mm and in one case 5 mm. Overall sensitivity and specificity for detection of cholesteatoma were 82% (95% confidence interval [CI] 62-94%) and 90% (CI 55-100%), respectively. Positive predictive value and negative predictive value were 96% (CI 79-100%) and 64% (CI 35-87%), respectively. Overall accuracy for detection of cholesteatoma was 84% (CI 69-94%). Half-Fourier-acquisition single-shot turbo-spin-echo diffusion-weighted imaging has good performance in localising cholesteatoma to a number of anatomical sub-sites within the middle ear and mastoid (sensitivity ranging from 75% to 88% and specificity ranging from 94% to 100%). There was no statistically significant difference in the size of cholesteatoma detected radiologically and that found during surgery (paired t-test, P = 0.16). However, analysis of size agreement suggests possible radiological underestimation of size when using HASTE diffusion-weighted imaging (mean difference -0.6 mm, CI -5.3 to 4.6 mm). Half-Fourier-acquisition single-shot turbo-spin-echo diffusion-weighted imaging performs reasonably well in predicting the presence and location of postoperative cholesteatoma but may miss small foci of disease and may underestimate the true size of cholesteatoma. © 2011 Blackwell Publishing Ltd.

Artificial neural network approach to predict surgical site infection after free-flap reconstruction in patients receiving surgery for head and neck cancer

PubMed Central

Kuo, Pao-Jen; Wu, Shao-Chun; Chien, Peng-Chen; Chang, Shu-Shya; Rau, Cheng-Shyuan; Tai, Hsueh-Ling; Peng, Shu-Hui; Lin, Yi-Chun; Chen, Yi-Chun; Hsieh, Hsiao-Yun; Hsieh, Ching-Hua

2018-01-01

Background The aim of this study was to develop an effective surgical site infection (SSI) prediction model in patients receiving free-flap reconstruction after surgery for head and neck cancer using artificial neural network (ANN), and to compare its predictive power with that of conventional logistic regression (LR). Materials and methods There were 1,836 patients with 1,854 free-flap reconstructions and 438 postoperative SSIs in the dataset for analysis. They were randomly assigned tin ratio of 7:3 into a training set and a test set. Based on comprehensive characteristics of patients and diseases in the absence or presence of operative data, prediction of SSI was performed at two time points (pre-operatively and post-operatively) with a feed-forward ANN and the LR models. In addition to the calculated accuracy, sensitivity, and specificity, the predictive performance of ANN and LR were assessed based on area under the curve (AUC) measures of receiver operator characteristic curves and Brier score. Results ANN had a significantly higher AUC (0.892) of post-operative prediction and AUC (0.808) of pre-operative prediction than LR (both P<0.0001). In addition, there was significant higher AUC of post-operative prediction than pre-operative prediction by ANN (p<0.0001). With the highest AUC and the lowest Brier score (0.090), the post-operative prediction by ANN had the highest overall predictive performance. Conclusion The post-operative prediction by ANN had the highest overall performance in predicting SSI after free-flap reconstruction in patients receiving surgery for head and neck cancer. PMID:29568393

Experimental Test of Spatial Updating Models for Monkey Eye-Head Gaze Shifts

PubMed Central

Van Grootel, Tom J.; Van der Willigen, Robert F.; Van Opstal, A. John

2012-01-01

How the brain maintains an accurate and stable representation of visual target locations despite the occurrence of saccadic gaze shifts is a classical problem in oculomotor research. Here we test and dissociate the predictions of different conceptual models for head-unrestrained gaze-localization behavior of macaque monkeys. We adopted the double-step paradigm with rapid eye-head gaze shifts to measure localization accuracy in response to flashed visual stimuli in darkness. We presented the second target flash either before (static), or during (dynamic) the first gaze displacement. In the dynamic case the brief visual flash induced a small retinal streak of up to about 20 deg at an unpredictable moment and retinal location during the eye-head gaze shift, which provides serious challenges for the gaze-control system. However, for both stimulus conditions, monkeys localized the flashed targets with accurate gaze shifts, which rules out several models of visuomotor control. First, these findings exclude the possibility that gaze-shift programming relies on retinal inputs only. Instead, they support the notion that accurate eye-head motor feedback updates the gaze-saccade coordinates. Second, in dynamic trials the visuomotor system cannot rely on the coordinates of the planned first eye-head saccade either, which rules out remapping on the basis of a predictive corollary gaze-displacement signal. Finally, because gaze-related head movements were also goal-directed, requiring continuous access to eye-in-head position, we propose that our results best support a dynamic feedback scheme for spatial updating in which visuomotor control incorporates accurate signals about instantaneous eye- and head positions rather than relative eye- and head displacements. PMID:23118883

Shoulder instability in the setting of bipolar (glenoid and humeral head) bone loss: the glenoid track concept.

PubMed

Trivedi, Suraj; Pomerantz, Michael L; Gross, Daniel; Golijanan, Petar; Provencher, Matthew T

2014-08-01

An assortment of variables has been used in predicting anterior shoulder instability resulting from pathologic engagement of Hill-Sachs lesions on the glenoid. The glenoid track is a unique biomechanical model that relates both Hill-Sachs and bony Bankart lesions to predict shoulder engagement. We examined the glenoid track concept to determine if it provides a model that unifies glenoid rim and humeral head bone loss in predicting engagement. In this review we addressed two questions: (1) How are humeral head and glenoid rim bony defects and their interactions quantified? (2) Why is the concept of the glenoid track important? We performed a systematic review of the literature using PubMed (MEDLINE) and OVID for biomechanical studies and peer-reviewed articles published until March 2013. Twenty-four studies fit the inclusion criteria. These were subdivided into four anatomic studies, four studies quantifying glenohumeral bone loss, nine studies biomechanically defining shoulder engagement, six studies analyzing current treatment models, and one clinical study to be included in the final review. Data demonstrate pathologic engagement is dependent on the medial margin of the Hill-Sachs lesion traveling outside the glenoid track. The width of the glenoid track decreases accordingly if there is a glenoid defect, making engagement more likely. Most treatment models focus on widening the glenoid track before addressing Hill-Sachs lesions. The glenoid track uses both glenoid and humeral head bone loss to predict subsequent risk of humeral head engagement and possible dislocation. The glenoid track shows us that restoring the track to its natural width should be among the surgeon's first priority in restoring shoulder stability. Humeral head lesions, also known as Hill-Sachs lesions, are surgically addressed when they cause clinical symptoms. Symptoms arise when the medial margin of the defect engages the glenoid track.

Neuroimaging Cerebrovascular Function and Diffuse Axonal Injury after Traumatic Brain Injury and Response to Sildenafil Treatment

DTIC Science & Technology

2016-04-05

pathoanatomic classification of TBI focusing on two mechanisms, and demonstrates assessment of mechanism-specific therapy . Our results suggest that sildenafil... therapies . x TABLE OF CONTENTS LIST OF TABLES...mechanism-specific targeted therapies (28; 61; 106). At the time of the primary injury, rapid acceleration-decceleration of the head causes

Anisotropic hydrogen diffusion in α-Zr and Zircaloy predicted by accelerated kinetic Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Zhang, Yongfeng; Jiang, Chao; Bai, Xianming

2017-01-01

This report presents an accelerated kinetic Monte Carlo (KMC) method to compute the diffusivity of hydrogen in hcp metals and alloys, considering both thermally activated hopping and quantum tunneling. The acceleration is achieved by replacing regular KMC jumps in trapping energy basins formed by neighboring tetrahedral interstitial sites, with analytical solutions for basin exiting time and probability. Parameterized by density functional theory (DFT) calculations, the accelerated KMC method is shown to be capable of efficiently calculating hydrogen diffusivity in α-Zr and Zircaloy, without altering the kinetics of long-range diffusion. Above room temperature, hydrogen diffusion in α-Zr and Zircaloy is dominated by thermal hopping, with negligible contribution from quantum tunneling. The diffusivity predicted by this DFT + KMC approach agrees well with that from previous independent experiments and theories, without using any data fitting. The diffusivity along is found to be slightly higher than that along , with the anisotropy saturated at about 1.20 at high temperatures, resolving contradictory results in previous experiments. Demonstrated using hydrogen diffusion in α-Zr, the same method can be extended for on-lattice diffusion in hcp metals, or systems with similar trapping basins.

Anisotropic hydrogen diffusion in α-Zr and Zircaloy predicted by accelerated kinetic Monte Carlo simulations

PubMed Central

Zhang, Yongfeng; Jiang, Chao; Bai, Xianming

2017-01-01

This report presents an accelerated kinetic Monte Carlo (KMC) method to compute the diffusivity of hydrogen in hcp metals and alloys, considering both thermally activated hopping and quantum tunneling. The acceleration is achieved by replacing regular KMC jumps in trapping energy basins formed by neighboring tetrahedral interstitial sites, with analytical solutions for basin exiting time and probability. Parameterized by density functional theory (DFT) calculations, the accelerated KMC method is shown to be capable of efficiently calculating hydrogen diffusivity in α-Zr and Zircaloy, without altering the kinetics of long-range diffusion. Above room temperature, hydrogen diffusion in α-Zr and Zircaloy is dominated by thermal hopping, with negligible contribution from quantum tunneling. The diffusivity predicted by this DFT + KMC approach agrees well with that from previous independent experiments and theories, without using any data fitting. The diffusivity along is found to be slightly higher than that along , with the anisotropy saturated at about 1.20 at high temperatures, resolving contradictory results in previous experiments. Demonstrated using hydrogen diffusion in α-Zr, the same method can be extended for on-lattice diffusion in hcp metals, or systems with similar trapping basins. PMID:28106154

Anisotropic hydrogen diffusion in α-Zr and Zircaloy predicted by accelerated kinetic Monte Carlo simulations

DOE PAGES

Zhang, Yongfeng; Jiang, Chao; Bai, Xianming

2017-01-20

Here, this report presents an accelerated kinetic Monte Carlo (KMC) method to compute the diffusivity of hydrogen in hcp metals and alloys, considering both thermally activated hopping and quantum tunneling. The acceleration is achieved by replacing regular KMC jumps in trapping energy basins formed by neighboring tetrahedral interstitial sites, with analytical solutions for basin exiting time and probability. Parameterized by density functional theory (DFT) calculations, the accelerated KMC method is shown to be capable of efficiently calculating hydrogen diffusivity in α-Zr and Zircaloy, without altering the kinetics of long-range diffusion. Above room temperature, hydrogen diffusion in α-Zr and Zircaloy ismore » dominated by thermal hopping, with negligible contribution from quantum tunneling. The diffusivity predicted by this DFT + KMC approach agrees well with that from previous independent experiments and theories, without using any data fitting. The diffusivity along < c > is found to be slightly higher than that along < a >, with the anisotropy saturated at about 1.20 at high temperatures, resolving contradictory results in previous experiments. Demonstrated using hydrogen diffusion in α-Zr, the same method can be extended for on-lattice diffusion in hcp metals, or systems with similar trapping basins.« less

Improved Fiber-Optic-Coupled Pressure And Vibration Sensors

NASA Technical Reports Server (NTRS)

Zuckerwar, Allan J.; Cuomo, Frank W.

1994-01-01

Improved fiber-optic coupler enables use of single optical fiber to carry light to and from sensor head. Eliminates problem of alignment of multiple fibers in sensor head and simplifies calibration by making performance both more predictable and more stable. Sensitivities increased, sizes reduced. Provides increased margin for design of compact sensor heads not required to contain amplifier circuits and withstand high operating temperatures.

Autonomous Motion Planning Using a Predictive Temporal Method

DTIC Science & Technology

2009-01-01

interception test. ......150 5-20 Target and solution path heading angles for target interception test. ..............................151 10 LIST...environment as a series of distances and angles . Regardless of the technique, this knowledge of the surrounding area is crucial for the issue of...to, the rather simplistic vector driver algorithms which compute the angle between the current vehicle heading and the heading to the goal and

Performance of Subsurface Tube Drainage System in Saline Soils: A Case Study

NASA Astrophysics Data System (ADS)

Pali, A. K.

2015-06-01

In order to improve the saline and water logged soils caused due to groundwater table rise, installation of subsurface drainage system is considered as one of the best remedies. However, the design of the drainage system has to be accurate so that the field performance results conform to the designed results. In this investigation, the field performance of subsurface tube drainage system installed at the study area was evaluated. The performance was evaluated on the basis of comparison of the designed value of water table drop as 30 cm after 2 days of drainage and predicted and field measured hydraulic heads for a consecutive drainage period of 14 days. The investigation revealed that the actual drop of water table after 2 days of drainage was 25 cm, about 17 % less than the designed value of 30 cm after 2 days of drainage. The comparison of hydraulic heads predicted by Van Schilfgaarde equation of unsteady drainage with the field-measured hydraulic heads showed that the deviation of predicted hydraulic heads varied within a range of ±8 % indicating high acceptability of Van Schlifgaarde equation for designing subsurface drainage system in saline and water logged soils resembling to that of the study area.

Application of Molecular Dynamics Simulations in Molecular Property Prediction II: Diffusion Coefficient

PubMed Central

Wang, Junmei; Hou, Tingjun

2011-01-01

In this work, we have evaluated how well the General AMBER force field (GAFF) performs in studying the dynamic properties of liquids. Diffusion coefficients (D) have been predicted for 17 solvents, 5 organic compounds in aqueous solutions, 4 proteins in aqueous solutions, and 9 organic compounds in non-aqueous solutions. An efficient sampling strategy has been proposed and tested in the calculation of the diffusion coefficients of solutes in solutions. There are two major findings of this study. First of all, the diffusion coefficients of organic solutes in aqueous solution can be well predicted: the average unsigned error (AUE) and the root-mean-square error (RMSE) are 0.137 and 0.171 ×10−5 cm−2s−1, respectively. Second, although the absolute values of D cannot be predicted, good correlations have been achieved for 8 organic solvents with experimental data (R2 = 0.784), 4 proteins in aqueous solutions (R2 = 0.996) and 9 organic compounds in non-aqueous solutions (R2 = 0.834). The temperature dependent behaviors of three solvents, namely, TIP3P water, dimethyl sulfoxide (DMSO) and cyclohexane have been studied. The major MD settings, such as the sizes of simulation boxes and with/without wrapping the coordinates of MD snapshots into the primary simulation boxes have been explored. We have concluded that our sampling strategy that averaging the mean square displacement (MSD) collected in multiple short-MD simulations is efficient in predicting diffusion coefficients of solutes at infinite dilution. PMID:21953689

Density functional calculation of activation energies for lattice and grain boundary diffusion in alumina

NASA Astrophysics Data System (ADS)

Lei, Yinkai; Gong, Yu; Duan, Zhiyao; Wang, Guofeng

2013-06-01

To acquire knowledge on the lattice and grain boundary diffusion processes in alumina, we have determined the activation energies of elementary O and Al diffusive jumps in the bulk crystal, Σ3(0001) grain boundaries, and Σ3(101¯0) grain boundaries of α-Al2O3 using the first-principles density functional theory method. Specifically, we calculated the activation energies for four elementary jumps of both O and Al lattice diffusion in alumina. It was predicted that the activation energy of O lattice diffusion varied from 3.58 to 5.03 eV, while the activation energy of Al lattice diffusion ranged from 1.80 to 3.17 eV. As compared with experimental measurements, the theoretical predictions of the activation energy for lattice diffusion were lower and thus implied that there might be other high-energy diffusive jumps in the experimental alumina samples. Moreover, our results suggested that the Al lattice diffusion was faster than the O lattice diffusion in alumina, in agreement with experiment observations. Furthermore, it was found from our calculations for α-Al2O3 that the activation energies of O and Al grain boundary diffusion in the high-energy Σ3(0001) grain boundaries were significantly lower than those of the lattice diffusion. In contrast, the activation energies of O and Al grain boundary diffusion in the low-energy Σ3(101¯0) grain boundaries could be even higher than those of the lattice diffusion.

Solute redistribution in dendritic solidification with diffusion in the solid

NASA Technical Reports Server (NTRS)

Ganesan, S.; Poirier, D. R.

1989-01-01

An investigation of solute redistribution during dendritic solidification with diffusion in the solid has been performed using numerical techniques. The extent of diffusion is characterized by the instantaneous and average diffusion parameters. These parameters are functions of the diffusion Fourier number, the partition ratio and the fraction solid. Numerical results are presented as an approximate model, which is used to predict the average diffusion parameter and calculate the composition of the interdendritic liquid during solidification.

Diffusion in thorium carbide: A first-principles study

NASA Astrophysics Data System (ADS)

Pérez Daroca, D.; Llois, A. M.; Mosca, H. O.

2015-12-01

The prediction of the behavior of Th compounds under irradiation is an important issue for the upcoming Generation-IV nuclear reactors. The study of self-diffusion and hetero-diffusion is a central key to fulfill this goal. As a first approach, we obtained, by means of first-principles methods, migration and activation energies of Th and C atoms self-diffusion and diffusion of He atoms in ThC. We also calculate diffusion coefficients as a function of temperature.

Multiple regression analysis of anthropometric measurements influencing the cephalic index of male Japanese university students.

PubMed

Hossain, Md Golam; Saw, Aik; Alam, Rashidul; Ohtsuki, Fumio; Kamarul, Tunku

2013-09-01

Cephalic index (CI), the ratio of head breadth to head length, is widely used to categorise human populations. The aim of this study was to access the impact of anthropometric measurements on the CI of male Japanese university students. This study included 1,215 male university students from Tokyo and Kyoto, selected using convenient sampling. Multiple regression analysis was used to determine the effect of anthropometric measurements on CI. The variance inflation factor (VIF) showed no evidence of a multicollinearity problem among independent variables. The coefficients of the regression line demonstrated a significant positive relationship between CI and minimum frontal breadth (p < 0.01), bizygomatic breadth (p < 0.01) and head height (p < 0.05), and a negative relationship between CI and morphological facial height (p < 0.01) and head circumference (p < 0.01). Moreover, the coefficient and odds ratio of logistic regression analysis showed a greater likelihood for minimum frontal breadth (p < 0.01) and bizygomatic breadth (p < 0.01) to predict round-headedness, and morphological facial height (p < 0.05) and head circumference (p < 0.01) to predict long-headedness. Stepwise regression analysis revealed bizygomatic breadth, head circumference, minimum frontal breadth, head height and morphological facial height to be the best predictor craniofacial measurements with respect to CI. The results suggest that most of the variables considered in this study appear to influence the CI of adult male Japanese students.

Laser inscription of pseudorandom structures for microphotonic diffuser applications.

PubMed

Alqurashi, Tawfiq; Alhosani, Abdulla; Dauleh, Mahmoud; Yetisen, Ali K; Butt, Haider

2018-04-19

Optical diffusers provide a solution for a variety of applications requiring a Gaussian intensity distribution including imaging systems, biomedical optics, and aerospace. Advances in laser ablation processes have allowed the rapid production of efficient optical diffusers. Here, we demonstrate a novel technique to fabricate high-quality glass optical diffusers with cost-efficiency using a continuous CO2 laser. Surface relief pseudorandom microstructures were patterned on both sides of the glass substrates. A numerical simulation of the temperature distribution showed that the CO2 laser drills a 137 μm hole in the glass for every 2 ms of processing time. FFT simulation was utilized to design predictable optical diffusers. The pseudorandom microstructures were characterized by optical microscopy, Raman spectroscopy, and angle-resolved spectroscopy to assess their chemical properties, optical scattering, transmittance, and polarization response. Increasing laser exposure and the number of diffusing surfaces enhanced the diffusion and homogenized the incident light. The recorded speckle pattern showed high contrast with sharp bright spot free diffusion in the far field view range (250 mm). A model of glass surface peeling was also developed to prevent its occurrence during the fabrication process. The demonstrated method provides an economical approach in fabricating optical glass diffusers in a controlled and predictable manner. The produced optical diffusers have application in fibre optics, LED systems, and spotlights.

Modeling diffusion in foamed polymer nanocomposites.

PubMed

Ippalapalli, Sandeep; Ranaprathapan, A Dileep; Singh, Sachchida N; Harikrishnan, G

2013-04-15

Two-way multicomponent diffusion processes in polymeric nanocomposite foams, where the condensed phase is nanoscopically reinforced with impermeable fillers, are investigated. The diffusion process involves simultaneous outward permeation of the components of the dispersed gas phase and inward diffusion of atmospheric air. The transient variation in thermal conductivity of foam is used as the macroscopic property to track the compositional variations of the dispersed gases due to the diffusion process. In the continuum approach adopted, the unsteady-state diffusion process is combined with tortuosity theory. The simulations conducted at ambient temperature reveal distinct regimes of diffusion processes in the nanocomposite foams owing to the reduction in the gas-transport rate induced by nanofillers. Simulations at a higher temperature are also conducted and the predictions are compared with experimentally determined thermal conductivities under accelerated diffusion conditions for polyurethane foams reinforced with clay nanoplatelets of varying individual lamellar dimensions. Intermittent measurements of foam thermal conductivity are performed while the accelerated diffusion proceeded. The predictions under accelerated diffusion conditions show good agreement with experimentally measured thermal conductivities for nanocomposite foams reinforced with low and medium aspect-ratios fillers. The model shows higher deviations for foams with fillers that have a high aspect ratio. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermodynamic evaluation of mass diffusion in ionic mixtures

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

Kagan, Grigory; Tang, Xian-Zhu

2014-02-15

The thermodynamic technique of Landau and Lifshitz originally developed for inter-species diffusion in a binary neutral gas mixture is extended to a quasi-neutral plasma with two ion species. It is shown that, while baro- and electro-diffusion coefficients depend on the choice of the thermodynamic system, prediction for the total diffusive mass flux is invariant.

Nonlinear-regression flow model of the Gulf Coast aquifer systems in the south-central United States

USGS Publications Warehouse

Kuiper, L.K.

1994-01-01

A multiple-regression methodology was used to help answer questions concerning model reliability, and to calibrate a time-dependent variable-density ground-water flow model of the gulf coast aquifer systems in the south-central United States. More than 40 regression models with 2 to 31 regressions parameters are used and detailed results are presented for 12 of the models. More than 3,000 values for grid-element volume-averaged head and hydraulic conductivity are used for the regression model observations. Calculated prediction interval half widths, though perhaps inaccurate due to a lack of normality of the residuals, are the smallest for models with only four regression parameters. In addition, the root-mean weighted residual decreases very little with an increase in the number of regression parameters. The various models showed considerable overlap between the prediction inter- vals for shallow head and hydraulic conductivity. Approximate 95-percent prediction interval half widths for volume-averaged freshwater head exceed 108 feet; for volume-averaged base 10 logarithm hydraulic conductivity, they exceed 0.89. All of the models are unreliable for the prediction of head and ground-water flow in the deeper parts of the aquifer systems, including the amount of flow coming from the underlying geopressured zone. Truncating the domain of solution of one model to exclude that part of the system having a ground-water density greater than 1.005 grams per cubic centimeter or to exclude that part of the systems below a depth of 3,000 feet, and setting the density to that of freshwater does not appreciably change the results for head and ground-water flow, except for locations close to the truncation surface.

Flow interaction in the combustor-diffusor system of industrial gas turbines

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

Agrawal, A.K.; Kapat, J.S.; Yang, T.

1996-05-01

This paper presents an experimental/computational study of cold flow in the combustor-diffuser system of industrial gas turbines to address issues relating to flow interactions and pressure losses in the pre- and dump diffusers. The present configuration with can annular combustors differs substantially from the aircraft engines which typically use a 360 degree annular combustor. Experiments were conducted in a one-third scale, annular 360-degree model using several can combustors equispaced around the turbine axis. A 3-D computational fluid dynamics analysis employing the multidomain procedure was performed to supplement the flow measurements. The measured data correlated well with the computations. The airflowmore » in the dump diffuser adversely affected the prediffuser flow by causing it to accelerate in the outer region at the prediffuser exit. This phenomenon referred to as the sink-effect also caused a large fraction of the flow to bypass much of the dump diffuser and go directly from the prediffuser exit to the bypass air holes on the combustor casing, thereby, rendering the dump diffuser ineffective in diffusing the flow. The dump diffuser was occupied by a large recirculation region which dissipated the flow kinetic energy. Approximately 1.2 dynamic head at the prediffuser inlet was lost in the combustor-diffuser system; much of it in the dump diffuser where the fluid passed through the narrow gaps and pathways. Strong flow interactions in the combustor-diffuser system indicate the need for design modifications which could not be addressed by empirical correlations based on simple flow configurations.« less

Activation volume for phosphorus diffusion in silicon and Si0.93Ge0.07

NASA Astrophysics Data System (ADS)

Zhao, Yuechao; Aziz, Michael J.; Zangenberg, Nikolaj R.; Larsen, Arne Nylandsted

2005-04-01

The hydrostatic pressure dependence of the diffusivity of P in compressively strained Si0.93Ge0.07 and unalloyed Si has been measured. In both cases the diffusivity is almost independent of pressure, characterized by an activation volume V* of (+0.09±0.11) times the atomic volume Ω for the unalloyed Si, and (+0.01±0.06) Ω for Si0.93Ge0.07. The results are used in conjunction with the reported effect of biaxial strain on diffusion normal to the surface to test the prediction for an interstitialcy-based mechanism of Aziz's phenomenological thermodynamic treatment of diffusion under uniform nonhydrostatic stress states. The prediction agrees well with measured behavior, lending additional credence to the interstitial-based mechanism and supporting the nonhydrostatic thermodynamic treatment.

Reference values for pulmonary diffusing capacity for adult native Finns.

PubMed

Kainu, Annette; Toikka, Jyri; Vanninen, Esko; Timonen, Kirsi L

2017-04-01

Measurement standards for pulmonary diffusing capacity were updated in 2005 by the ATS/ERS Task Force. However, in Finland reference values published in 1982 by Viljanen et al. have been used to date. The main aim of this study was to produce updated reference models for single-breath diffusing capacity for carbon monoxide for Finnish adults. Single-breath diffusing capacity for carbon monoxide was measured in 631 healthy non-smoking volunteers (41.5% male). Reference values for diffusing capacity (DLCO), alveolar volume (VA), diffusing capacity per unit of lung volume (DLCO/VA), and lung volumes were calculated using a linear regression model. Previously used Finnish reference values were found to produce too low predicted values, with mean predicted DLCO 111.0 and 104.4%, and DLCO/VA of 103.5 and 102.7% in males and females, respectively. With the European Coalition for Steel and Coal (ECSC) reference values there was a significant sex difference in DLCO/VA with mean predicted 105.4% in males and 92.8% in females (p < .001). New reference values for DLCO, DLCO/VA, VA, vital capacity (VC), inspiratory vital capacity (IVC), and inspiratory capacity (IC) are suggested for clinical use to replace technically outdated reference values for clinical applications.

Numerical simulation of flow in a high head Francis turbine with prediction of efficiency, rotor stator interaction and vortex structures in the draft tube

NASA Astrophysics Data System (ADS)

Jošt, D.; Škerlavaj, A.; Morgut, M.; Mežnar, P.; Nobile, E.

2015-01-01

The paper presents numerical simulations of flow in a model of a high head Francis turbine and comparison of results to the measurements. Numerical simulations were done by two CFD (Computational Fluid Dynamics) codes, Ansys CFX and OpenFOAM. Steady-state simulations were performed by k-epsilon and SST model, while for transient simulations the SAS SST ZLES model was used. With proper grid refinement in distributor and runner and with taking into account losses in labyrinth seals very accurate prediction of torque on the shaft, head and efficiency was obtained. Calculated axial and circumferential velocity components on two planes in the draft tube matched well with experimental results.

Child Care Enrollment Decisions Among Dual Language Learner Families: The Role of Spanish Language Instruction in the Child Care Setting

PubMed Central

Miller, Elizabeth B.

2016-01-01

Data from the Head Start Impact Study (N = 1,141) and the Head Start Family and Child Experiences Survey, 2009 Cohort (N = 825) were used to describe child care enrollment decisions among Spanish-speaking Dual Language Learner (DLL) families. In particular, logistic regression models tested which child, family, and institutional characteristics predicted enrollment in early care and education (ECE) settings that used Spanish for instruction versus enrollment in settings that did not use Spanish. Results showed that whether the child’s first language was exclusively Spanish and whether other DLL families previously attended the ECE arrangement strongly predicted whether that child enrolled. Policy implications for Head Start-eligible Spanish-speaking DLLs are discussed. PMID:26900255

Analysis of the moisture diffusion transfer through fibrous porous membrane used for waterproof breathable fabrics

NASA Astrophysics Data System (ADS)

Zhu, Fanglong; Zhou, Yu; Liu, Suyan

2013-10-01

In this paper, we propose a new fractal model to determine the moisture effective diffusivity of porous membrane such as expanded polytetrafluorethylene membrane, by taking account of both parallel and perpendicular channels to diffusion flow direction. With the consideration of both the Knudsen and bulk diffusion effect, a relationship between micro-structural parameters and effective moisture diffusivity is deduced. The effective moisture diffusivities predicted by the present fractal model are compared with moisture diffusion experiment data and calculated values obtained from other theoretical models.

The diffusion of ions in unconsolidated sediments

USGS Publications Warehouse

Manheim, F.T.

1970-01-01

Diffusion in unconsolidated sediments generally proceeds at rates ranging from half to one twentieth of those applying to diffusion of ions and molecules in free solution. Diffusion rates are predictable with respect to porosity and path tortuosity in host sediments, and can be conveniently measured by determinations of electrical resistivity on bulk sediment samples. Net ion flux is further influenced by reactions of diffusing species with enclosing sediments, but such influences should not be confused with or lumped with diffusion processes. ?? 1970.

Turbulent flow separation in three-dimensional asymmetric diffusers

NASA Astrophysics Data System (ADS)

Jeyapaul, Elbert

2011-12-01

Turbulent three-dimensional flow separation is more complicated than 2-D. The physics of the flow is not well understood. Turbulent flow separation is nearly independent of the Reynolds number, and separation in 3-D occurs at singular points and along convergence lines emanating from these points. Most of the engineering turbulence research is driven by the need to gain knowledge of the flow field that can be used to improve modeling predictions. This work is motivated by the need for a detailed study of 3-D separation in asymmetric diffusers, to understand the separation phenomena using eddy-resolving simulation methods, assess the predictability of existing RANS turbulence models and propose modeling improvements. The Cherry diffuser has been used as a benchmark. All existing linear eddy-viscosity RANS models k--o SST,k--epsilon and v2- f fail in predicting such flows, predicting separation on the wrong side. The geometry has a doubly-sloped wall, with the other two walls orthogonal to each other and aligned with the diffuser inlet giving the diffuser an asymmetry. The top and side flare angles are different and this gives rise to different pressure gradient in each transverse direction. Eddyresolving simulations using the Scale adaptive simulation (SAS) and Large Eddy Simulation (LES) method have been used to predict separation in benchmark diffuser and validated. A series of diffusers with the same configuration have been generated, each having the same streamwise pressure gradient and parametrized only by the inlet aspect ratio. The RANS models were put to test and the flow physics explored using SAS-generated flow field. The RANS model indicate a transition in separation surface from top sloped wall to the side sloped wall at an inlet aspect ratio much lower than observed in LES results. This over-sensitivity of RANS models to transverse pressure gradients is due to lack of anisotropy in the linear Reynolds stress formulation. The complexity of the flow separation is due to effects of lateral straining, streamline curvature, secondary flow of second kind, transverse pressure gradient on turbulence. Resolving these effects is possible with anisotropy turbulence models as the Explicit Algebraic Reynolds stress model (EARSM). This model has provided accurate prediction of streamwise and transverse velocity, however the wall pressure is under predicted. An improved EARSM model is developed by correcting the coefficients, which predicts a more accurate wall pressure. There exists scope for improvement of this model, by including convective effects and dynamics of velocity gradient invariants.

Prediction of the diffuse-field transmission loss of interior natural-ventilation openings and silencers.

PubMed

Bibby, Chris; Hodgson, Murray

2017-01-01

The work reported here, part of a study on the performance and optimal design of interior natural-ventilation openings and silencers ("ventilators"), discusses the prediction of the acoustical performance of such ventilators, and the factors that affect it. A wave-based numerical approach-the finite-element method (FEM)-is applied. The development of a FEM technique for the prediction of ventilator diffuse-field transmission loss is presented. Model convergence is studied with respect to mesh, frequency-sampling and diffuse-field convergence. The modeling technique is validated by way of predictions and the comparison of them to analytical and experimental results. The transmission-loss performance of crosstalk silencers of four shapes, and the factors that affect it, are predicted and discussed. Performance increases with flow-path length for all silencer types. Adding elbows significantly increases high-frequency transmission loss, but does not increase overall silencer performance which is controlled by low-to-mid-frequency transmission loss.

Effects of Barometric Fluctuations on Well Water-Level Measurements and Aquifer Test Data

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

Spane, Frank A.

1999-12-16

This report examines the effects of barometric fluctuations on well water-level measurements and evaluates adjustment and removal methods for determining areal aquifer head conditions and aquifer test analysis. Two examples of Hanford Site unconfined aquifer tests are examined that demonstrate baro-metric response analysis and illustrate the predictive/removal capabilities of various methods for well water-level and aquifer total head values. Good predictive/removal characteristics were demonstrated with best corrective results provided by multiple-regression deconvolution methods.

Changes of normal appearing optic nerve head on diffusion-weighted imaging in patients with diabetic retinopathy.

PubMed

Yılmaz, Sevda; Yumusak, Erhan; Burulday, Veysel

To investigate whether there is any change by measuring ADC values particularly of the optic nerve head (ONH) in patients with diabetic retinopathy (DR). ADC values at the ONHs was measured in 56 patients and 68 controls. ADC values of ONHs were significantly higher in patients with DR compared to controls (p=0.011). ADC values in patients with macular edema were higher than those without macular edema (p=0.017). DWI of ONHs can be useful in cases where it is difficult to assess macular edema during fundus examination, especially in diabetic patients with cataract. Copyright © 2016 Elsevier Inc. All rights reserved.

Modeling diffusion and reaction in soils: 9. The Buckingham-Burdine-Campbell equation for gas diffusivity in undisturbed soil

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

Moldrup, P.; Olesen, T.; Yamaguchi, T.

1999-08-01

Accurate description of gas diffusivity (ratio of gas diffusion coefficients in soil and free air, D{sub s}/D{sub 0}) in undisturbed soils is a prerequisite for predicting in situ transport and fate of volatile organic chemicals and greenhouse gases. Reference point gas diffusivities (R{sub p}) in completely dry soil were estimated for 20 undisturbed soils by assuming a power function relation between gas diffusivity and air-filled porosity ({epsilon}). Among the classical gas diffusivity models, the Buckingham (1904) expression, equal to the soil total porosity squared, best described R{sub p}. Inasmuch, as their previous works implied a soil-type dependency of D{sub s}/D{submore » 0}({epsilon}) in undisturbed soils, the Buckingham R{sub p} expression was inserted in two soil-type-dependent D{sub s}/D{sub 0}({epsilon}) models. One D{sub s}/D{sub 0}({epsilon}) model is a function of pore-size distribution (the Campbell water retention parameter used in a modified Burdine capillary tube model), and the other is a calibrated, empirical function of soil texture (silt + sand fraction). Both the Buckingham-Burdine-Campbell (BBC) and the Buckingham/soil texture-based D{sub s}/D{sub 0}({epsilon}) models described well the observed soil type effects on gas diffusivity and gave improved predictions compared with soil type independent models when tested against an independent data set for six undisturbed surface soils. This study emphasizes that simple but soil-type-dependent power function D{sub s}/D{sub 0}({epsilon}) models can adequately describe and predict gas diffusivity in undisturbed soil. The authors recommend the new BBC model as basis for modeling gas transport and reactions in undisturbed soil systems.« less

Extensional rheology of active suspensions

NASA Astrophysics Data System (ADS)

Saintillan, David

2010-05-01

A simple model is presented for the effective extensional rheology of a dilute suspension of active particles, such as self-propelled microswimmers, extending previous classical studies on suspensions of passive rodlike particles. Neglecting particle-particle hydrodynamic interactions, we characterize the configuration of the suspension by an orientation distribution, which satisfies a Fokker-Planck equation including the effects of an external flow field and of rotary diffusion. Knowledge of this orientation distribution then allows the determination of the particle extra stress as a configurational average of the force dipoles exerted by the particles on the fluid, which involve contributions from the imposed flow, rotary diffusion, and the permanent dipoles resulting from activity. Analytical expressions are obtained for the stress tensor in uniaxial extensional and compressional flows, as well as in planar extensional flow. In all types of flows, the effective viscosity is found to increase as a result of activity in suspensions of head-actuated swimmers (pullers) and to decrease in suspensions of tail-actuated swimmers (pushers). In the latter case, a negative particle viscosity is found to occur in weak flows. In planar extensional flow, we also characterize normal stresses, which are enhanced by activity in suspensions of pullers but reduced in suspensions of pushers. Finally, an energetic interpretation of the seemingly unphysical decrease in viscosity predicted in suspensions of pushers is proposed, where the decrease is explained as a consequence of the active power input generated by the swimming particles and is shown not to be directly related to viscous dissipative processes.

Free testosterone levels in umbilical-cord blood predict infant head circumference in females.

PubMed

Whitehouse, Andrew J O; Maybery, Murray T; Hart, Roger; Sloboda, Deborah M; Stanley, Fiona J; Newnham, John P; Hickey, Martha

2010-03-01

Fetal androgens influence fetal growth as well as postnatal neurocognitive ability. However, to our knowledge, no published study has prospectively examined the impact of early-life androgens on infant brain growth. We report the association between circulating fetal androgen levels, measured from umbilical-cord blood at birth, and a proxy measure of brain growth: head circumference. Participants were 82 unselected female infants from a large representative birth cohort (mean gestational age 39.4 wks, SD 1.7). Umbilical-cord blood was obtained at birth and analysed for androgen concentrations (total testosterone, androstenedione, dehyrdroepiandrosterone, and its sulphated metabolite). Head circumference and two other measures of growth - weight (mean 3311.4 g, SD 461.3) and length - were measured within 3 days of birth and again at approximately 1 year of age (mean age 13.1 mo, SD 1.1). Multivariate linear regressions found an inverse association between levels of free testosterone and growth in head circumference (correlation=-.24), even when adjusting for sociodemographic/obstetric covariates and head size at birth. Growth in weight and length could not be predicted by free testosterone concentration. This is the first report of an association between prenatal androgen levels and postnatal growth in head circumference. These findings suggest that early-life androgens may impact brain development during infancy.

Diffuse-flow conceptualization and simulation of the Edwards aquifer, San Antonio region, Texas

USGS Publications Warehouse

Lindgren, R.J.

2006-01-01

A numerical ground-water-flow model (hereinafter, the conduit-flow Edwards aquifer model) of the karstic Edwards aquifer in south-central Texas was developed for a previous study on the basis of a conceptualization emphasizing conduit development and conduit flow, and included simulating conduits as one-cell-wide, continuously connected features. Uncertainties regarding the degree to which conduits pervade the Edwards aquifer and influence ground-water flow, as well as other uncertainties inherent in simulating conduits, raised the question of whether a model based on the conduit-flow conceptualization was the optimum model for the Edwards aquifer. Accordingly, a model with an alternative hydraulic conductivity distribution without conduits was developed in a study conducted during 2004-05 by the U.S. Geological Survey, in cooperation with the San Antonio Water System. The hydraulic conductivity distribution for the modified Edwards aquifer model (hereinafter, the diffuse-flow Edwards aquifer model), based primarily on a conceptualization in which flow in the aquifer predominantly is through a network of numerous small fractures and openings, includes 38 zones, with hydraulic conductivities ranging from 3 to 50,000 feet per day. Revision of model input data for the diffuse-flow Edwards aquifer model was limited to changes in the simulated hydraulic conductivity distribution. The root-mean-square error for 144 target wells for the calibrated steady-state simulation for the diffuse-flow Edwards aquifer model is 20.9 feet. This error represents about 3 percent of the total head difference across the model area. The simulated springflows for Comal and San Marcos Springs for the calibrated steady-state simulation were within 2.4 and 15 percent of the median springflows for the two springs, respectively. The transient calibration period for the diffuse-flow Edwards aquifer model was 1947-2000, with 648 monthly stress periods, the same as for the conduit-flow Edwards aquifer model. The root-mean-square error for a period of drought (May-November 1956) for the calibrated transient simulation for 171 target wells is 33.4 feet, which represents about 5 percent of the total head difference across the model area. The root-mean-square error for a period of above-normal rainfall (November 1974-July 1975) for the calibrated transient simulation for 169 target wells is 25.8 feet, which represents about 4 percent of the total head difference across the model area. The root-mean-square error ranged from 6.3 to 30.4 feet in 12 target wells with long-term water-level measurements for varying periods during 1947-2000 for the calibrated transient simulation for the diffuse-flow Edwards aquifer model, and these errors represent 5.0 to 31.3 percent of the range in water-level fluctuations of each of those wells. The root-mean-square errors for the five major springs in the San Antonio segment of the aquifer for the calibrated transient simulation, as a percentage of the range of discharge fluctuations measured at the springs, varied from 7.2 percent for San Marcos Springs and 8.1 percent for Comal Springs to 28.8 percent for Leona Springs. The root-mean-square errors for hydraulic heads for the conduit-flow Edwards aquifer model are 27, 76, and 30 percent greater than those for the diffuse-flow Edwards aquifer model for the steady-state, drought, and above-normal rainfall synoptic time periods, respectively. The goodness-of-fit between measured and simulated springflows is similar for Comal, San Marcos, and Leona Springs for the diffuse-flow Edwards aquifer model and the conduit-flow Edwards aquifer model. The root-mean-square errors for Comal and Leona Springs were 15.6 and 21.3 percent less, respectively, whereas the root-mean-square error for San Marcos Springs was 3.3 percent greater for the diffuse-flow Edwards aquifer model compared to the conduit-flow Edwards aquifer model. The root-mean-square errors for San Antonio and San Pedro Springs were appreciably greater, 80.2 and 51.0 percent, respectively, for the diffuse-flow Edwards aquifer model. The simulated water budgets for the diffuse-flow Edwards aquifer model are similar to those for the conduit-flow Edwards aquifer model. Differences in percentage of total sources or discharges for a budget component are 2.0 percent or less for all budget components for the steady-state and transient simulations. The largest difference in terms of the magnitude of water budget components for the transient simulation for 1956 was a decrease of about 10,730 acre-feet per year (about 2 per-cent) in springflow for the diffuse-flow Edwards aquifer model compared to the conduit-flow Edwards aquifer model. This decrease in springflow (a water budget discharge) was largely offset by the decreased net loss of water from storage (a water budget source) of about 10,500 acre-feet per year.

Molecular dynamics simulation of real-fluid mutual diffusion coefficients with the Lennard-Jones potential model

NASA Astrophysics Data System (ADS)

Stoker, J. M.; Rowley, R. L.

1989-09-01

Mutual diffusion coefficients for selected alkanes in carbon tetrachloride were calculated using molecular dynamics and Lennard-Jones (LJ) potentials. Use of effective spherical LJ parameters is desirable when possible for two reasons: (i) computer time is saved due to the simplicity of the model and (ii) the number of parameters in the model is kept to a minimum. Results of this study indicate that mutual diffusivity is particularly sensitive to the molecular size cross parameter, σ12, and that the commonly used Lorentz-Berthelot rules are inadequate for mixtures in which the component structures differ significantly. Good agreement between simulated and experimental mutual diffusivities is obtained with a combining rule for σ12 which better represents these asymmetric mixtures using pure component LJ parameters obtained from self-diffusion coefficient data. The effect of alkane chain length on the mutual diffusion coefficient is correctly predicted. While the effects of alkane branching upon the diffusion coefficient are comparable in size to the uncertainty of these calculations, the qualitative trend due to branching is also correctly predicted by the MD results.

The Green's functions for peridynamic non-local diffusion.

PubMed

Wang, L J; Xu, J F; Wang, J X

2016-09-01

In this work, we develop the Green's function method for the solution of the peridynamic non-local diffusion model in which the spatial gradient of the generalized potential in the classical theory is replaced by an integral of a generalized response function in a horizon. We first show that the general solutions of the peridynamic non-local diffusion model can be expressed as functionals of the corresponding Green's functions for point sources, along with volume constraints for non-local diffusion. Then, we obtain the Green's functions by the Fourier transform method for unsteady and steady diffusions in infinite domains. We also demonstrate that the peridynamic non-local solutions converge to the classical differential solutions when the non-local length approaches zero. Finally, the peridynamic analytical solutions are applied to an infinite plate heated by a Gauss source, and the predicted variations of temperature are compared with the classical local solutions. The peridynamic non-local diffusion model predicts a lower rate of variation of the field quantities than that of the classical theory, which is consistent with experimental observations. The developed method is applicable to general diffusion-type problems.

Flame Shapes of Luminous NonBuoyant Laminar Coflowing Jet Diffusion Flames

NASA Technical Reports Server (NTRS)

Lin, K.-C.; Faeth, G. M.

1999-01-01

Laminar diffusion flames are of interest as model flame systems that are more tractable for analysis and experiments than practical turbulent diffusion flames. Certainly understanding laminar flames must precede understanding more complex turbulent flames while man'y laminar diffusion flame properties are directly relevant to turbulent diffusion flames using laminar flamelet concepts. Laminar diffusion flame shapes have been of interest since the classical study of Burke and Schumann because they involve a simple nonintrusive measurement that is convenient for evaluating flame structure predictions. Motivated by these observations, the shapes of laminar flames were considered during the present investigation. The present study was limited to nonbuoyant flames because most practical flames are not buoyant. Effects of buoyancy were minimized by observing flames having large flow velocities at small pressures. Present methods were based on the study of the shapes of nonbu,3yant round laminar jet diffusion flames of Lin et al. where it was found that a simple analysis due to Spalding yielded good predictions of the flame shapes reported by Urban et al. and Sunderland et al.

Experimental evaluation of radiosity for room sound-field prediction.

PubMed

Hodgson, Murray; Nosal, Eva-Marie

2006-08-01

An acoustical radiosity model was evaluated for how it performs in predicting real room sound fields. This was done by comparing radiosity predictions with experimental results for three existing rooms--a squash court, a classroom, and an office. Radiosity predictions were also compared with those by ray tracing--a "reference" prediction model--for both specular and diffuse surface reflection. Comparisons were made for detailed and discretized echograms, sound-decay curves, sound-propagation curves, and the variations with frequency of four room-acoustical parameters--EDT, RT, D50, and C80. In general, radiosity and diffuse ray tracing gave very similar predictions. Predictions by specular ray tracing were often very different. Radiosity agreed well with experiment in some cases, less well in others. Definitive conclusions regarding the accuracy with which the rooms were modeled, or the accuracy of the radiosity approach, were difficult to draw. The results suggest that radiosity predicts room sound fields with some accuracy, at least as well as diffuse ray tracing and, in general, better than specular ray tracing. The predictions of detailed echograms are less accurate, those of derived room-acoustical parameters more accurate. The results underline the need to develop experimental methods for accurately characterizing the absorptive and reflective characteristics of room surfaces, possible including phase.

Apatite U-Pb thermochronolgy applied to complex geological settings - insights from geo/thermochronology and geochemistry

NASA Astrophysics Data System (ADS)

Paul, Andre; Spikings, Richard; Ulyanov, Alexey; Chew, David

2016-04-01

Application of high temperature (>350oC) thermochronology is limited to the U-Pb system of accessory minerals, such as apatite, under the assumption that radiogenic lead is lost to thermally activated volume diffusion into an infinite reservoir. Cochrane et al. (2015) have demonstrated a working example from the northern Andes of South America. Predictions from volume diffusion theory were compared with measured single grain U-Pb date correlated to shortest diffusion radius and in-situ profiles measured by LA-ICP-MS. Results from both techniques were found to be in agreement with predictions from thermally activated, volume diffusion. However, outliers from the ID-TIMS data suggested some complexity, as grains were found to be too young relative to their diffusion radius. Interaction of multiple processes can be responsible for the alteration of apatite U-Pb dates such as: (1) metamorphic (over)growth, (2) fluid aided alteration/recrystallization and (3) metamictization and fracturing of the grain. Further, predictions from volume diffusion rely on the input parameters: (a) diffusivity, (b) activation energy and (c) shortest diffusion radius. Diffusivity and activation energy are potentially influenced by the chemical composition and subsequent changes in crystal structure. Currently there is one value for diffusion parameter and activation energy established for (Durango) apatite (Cherniak et al., 1991). Correlation between diffusivity/activation energy and composition has not been established. We investigate if correlations exist between diffusivity/activation energy and composition by obtaining single grain apatite U-Pb date and chemical compostion and correlating these to their diffusion radius. We test the consistency of apatite closure temperature, by comparing the apatite U-Pb dates with lower temperature thermochronometers such as white mica and K-feldspar Ar/Ar and by petrographic observations. We test if chemical information can be a proxy to identify metamorphic (over)growth and fluid aided alteration/recrystallization. We seek to evaluate if apatite U-Pb thermochronology can be applied to a broad range of rock types and geological environments or if limitations must be drawn.

Optical tomography in the presence of void regions

PubMed

Dehghani; Arridge; Schweiger; Delpy

2000-09-01

There is a growing interest in the use of near-infrared spectroscopy for the noninvasive determination of the oxygenation level within biological tissue. Stemming from this application, there has been further research in the use of this technique for obtaining tomographic images of the neonatal head, with the view of determining the levels of oxygenated and deoxygenated blood within the brain. Owing to computational complexity, methods used for numerical modeling of photon transfer within tissue have usually been limited to the diffusion approximation of the Boltzmann transport equation. The diffusion approximation, however, is not valid in regions of low scatter, such as the cerebrospinal fluid. Methods have been proposed for dealing with nonscattering regions within diffusing materials through the use of a radiosity-diffusion model. Currently, this new model assumes prior knowledge of the void region location; therefore it is instructive to examine the errors introduced in applying a simple diffusion-based reconstruction scheme in cases in which there exists a nonscattering region. We present reconstructed images of objects that contain a nonscattering region within a diffusive material. Here the forward data is calculated with the radiosity-diffusion model, and the inverse problem is solved with either the radiosity-diffusion model or the diffusion-only model. The reconstructed images show that even in the presence of only a thin nonscattering layer, a diffusion-only reconstruction will fail. When a radiosity-diffusion model is used for image reconstruction, together with a priori information about the position of the nonscattering region, the quality of the reconstructed image is considerably improved. The accuracy of the reconstructed images depends largely on the position of the anomaly with respect to the nonscattering region as well as the thickness of the nonscattering region.

Diffusion of Small Sticky Nanoparticles in a Polymer Melt: A Dynamic Light Scattering Study

NASA Astrophysics Data System (ADS)

Carroll, Bobby; Bocharova, Vera; Cheng, Shiwang; Yamamoto, Umi; Kisliuk, Alex; Schweizer, Ken; Sokolov, Alexei

The study of dynamics in complex fluids such as polymers has gained a broad interest in advanced materials and biomedical applications. Of particular interest is the motion of nanoparticles in these systems, which influences the mechanical and structural properties of composite materials, properties of colloidal systems, and biochemical processes in biological systems. Theoretical work predicts a violation of Stokes-Einstein (SE) relationship for diffusion of small nanoparticles in strongly-entangled polymer melt systems, with diffusion of nanoparticles much faster than expected DSE. It is attributed to differences between local and macroscopic viscosity. In this study, the diffusion of nanoparticles in polymer melts below and above entanglement molecular weight is measured using dynamic light scattering. The measured results are compared with simulations that provide quantitative predictions for SE violations. Our results are two-fold: (1) diffusion at lower molecular weights is slower than expected DSE due to chain absorption; and (2) diffusion becomes much (20 times) faster than DSE, at higher entanglements due to a reduced local viscosity.

The faint galaxy contribution to the diffuse extragalactic background light

NASA Technical Reports Server (NTRS)

Cole, Shaun; Treyer, Marie-Agnes; Silk, Joseph

1992-01-01

Models of the faint galaxy contribution to the diffuse extragalactic background light are presented, which are consistent with current data on faint galaxy number counts and redshifts. The autocorrelation function of surface brightness fluctuations in the extragalactic diffuse light is predicted, and the way in which these predictions depend on the cosmological model and assumptions of biasing is determined. It is confirmed that the recent deep infrared number counts are most compatible with a high density universe (Omega-0 is approximately equal to 1) and that the steep blue counts then require an extra population of rapidly evolving blue galaxies. The faintest presently detectable galaxies produce an interesting contribution to the extragalactic diffuse light, and still fainter galaxies may also produce a significant contribution. These faint galaxies still only produce a small fraction of the total optical diffuse background light, but on scales of a few arcminutes to a few degrees, they produce a substantial fraction of the fluctuations in the diffuse light.

Cohort change and the diffusion of environmental concern: A cross-national analysis

PubMed Central

Nawrotzki, Raphael J.; Pampel, Fred C.

2013-01-01

This study explores value change across cohorts for a multinational population sample. Employing a diffusion-of-innovations approach, we combine competing theories predicting the relationship between socio-economic status (SES) and environmentalism: post-materialism and affluence theories, and global environmentalism theory. The diffusion argument suggests that high-SES groups first adopt pro-environmental views, but as time passes by, environmentalism diffuses to lower-SES groups. We test the diffusion argument using a sample of 18 countries for two waves (years 1993 and 2000) from the International Social Survey Project (ISSP). Cross-classified multilevel modeling allows us to identify a non-linear interaction between cohort and education, our core measure of SES, in predicting environmental concern, while controlling for age and period. We find support for the diffusion argument and demonstrate that the positive effect of education on environmental concern first increases among older cohorts, then starts to level off until a bend-point is reached for individuals born around 1940 and becomes progressively weaker for younger cohorts. PMID:24179313

Cohort change and the diffusion of environmental concern: A cross-national analysis.

PubMed

Nawrotzki, Raphael J; Pampel, Fred C

2013-09-01

This study explores value change across cohorts for a multinational population sample. Employing a diffusion-of-innovations approach, we combine competing theories predicting the relationship between socio-economic status (SES) and environmentalism: post-materialism and affluence theories, and global environmentalism theory. The diffusion argument suggests that high-SES groups first adopt pro-environmental views, but as time passes by, environmentalism diffuses to lower-SES groups. We test the diffusion argument using a sample of 18 countries for two waves (years 1993 and 2000) from the International Social Survey Project (ISSP). Cross-classified multilevel modeling allows us to identify a non-linear interaction between cohort and education, our core measure of SES, in predicting environmental concern, while controlling for age and period. We find support for the diffusion argument and demonstrate that the positive effect of education on environmental concern first increases among older cohorts, then starts to level off until a bend-point is reached for individuals born around 1940 and becomes progressively weaker for younger cohorts.

Pretherapeutic Functional Imaging Allows Prediction of Head Tremor Arrest After Thalamotomy for Essential Tremor: The Role of Altered Interconnectivity Between Thalamolimbic and Supplementary Motor Circuits.

PubMed

Tuleasca, Constantin; Régis, Jean; Najdenovska, Elena; Witjas, Tatiana; Girard, Nadine; Champoudry, Jérôme; Faouzi, Mohamed; Thiran, Jean-Philippe; Cuadra, Meritxell Bach; Levivier, Marc; Van De Ville, Dimitri

2018-04-01

To correlate pretherapeutic resting-state functional magnetic resonance imaging (rs-fMRI) measures with pretherapeutic head tremor presence and/or further improvement 1 year after stereotactic radiosurgical thalamotomy (SRS-T) for essential tremor (ET). We prospectively collected head tremor scores (range, 0-3) and rs-fMRI data for a cohort of 17 consecutive ET patients in pretherapeutic and 1 year after SRS-T states. We additionally acquired rs-fMRI data for a healthy control (HC) group (n = 12). Group-level independent component analysis (n = 17 for pretherapeutic rs-fMRI) was applied to decompose neuroimaging data into 20 large-scale brain networks using a standard approach. Through spatial regression, we projected 1 year after SRS-T and HC rs-fMRI time points, on the same 20 brain networks. Pretherapeutic interconnectivity (IC) strength between the network including bilateral thalamus and limbic system with left supplementary motor area predicted head tremor improvement at 1 year after SRS-T (family-wise corrected P < 0.001, cluster size K c  = 146). For the statistically significant cluster, IC strength was strongest in HCs (mean, 4.6; median, 3.8) compared with pre- (mean, 0.1; median, 0.2) or posttherapeutic (mean, -0.2; median, 0.09) states. Baseline measures of IC between bilateral thalamus and limbic system with left supplementary motor area may predict head tremor arrest after thalamotomy. However, procedures such as SRS-T, for this particular clinical feature, do not align patients to HCs in terms of functional brain connectivity. We postulate that supplementary motor area is modulating head tremor appearance, by abnormal connectivity with the thalamolimbic system. Copyright © 2018 Elsevier Inc. All rights reserved.

Understanding uncertainties in modeling the galactic diffuse gamma-ray emission

NASA Astrophysics Data System (ADS)

Storm, Emma; Calore, Francesca; Weniger, Christoph

2017-01-01

The nature of the Galactic diffuse gamma-ray emission as measured by the Fermi Gamma-ray Space Telescope has remained an active area of research for the last several years. A standard technique to disentangle the origins of the diffuse emission is the template fitting approach, where predictions for various diffuse components, such as emission from cosmic rays derived from Galprop or Dragon, are compared to the data. However, this method always results in an overall bad fit to the data, with strong residuals that are difficult to interpret. Additionally, there are instrinsic uncertainties in the predicted templates that are not accounted for naturally with this method. We therefore introduce a new template fitting approach to study the various components of the Galactic diffuse gamma-ray emission, and their correlations and uncertainties. We call this approach Sky Factorization with Adaptive Constrained Templates (SkyFACT). Rather than using fixed predictions from cosmic-ray propagation codes and examining the residuals to evaluate the quality of fits and the presence of excesses, we introduce additional fine-grained variations in the templates that account for uncertainties in the predictions, such as uncertainties in the gas tracers and from small scale variations in the density of cosmic rays. We show that fits to the gamma-ray diffuse emission can be dramatically improved by including an appropriate level of uncertainty in the initial spatial templates from cosmic-ray propagation codes. We further show that we can recover the morphology of the Fermi Bubbles from its spectrum alone with SkyFACT.

DTI and VBM reveal white matter changes without associated gray matter changes in patients with idiopathic restless legs syndrome

PubMed Central

Belke, Marcus; Heverhagen, Johannes T; Keil, Boris; Rosenow, Felix; Oertel, Wolfgang H; Stiasny-Kolster, Karin; Knake, Susanne; Menzler, Katja

2015-01-01

Background and Purpose We evaluated cerebral white and gray matter changes in patients with iRLS in order to shed light on the pathophysiology of this disease. Methods Twelve patients with iRLS were compared to 12 age- and sex-matched controls using whole-head diffusion tensor imaging (DTI) and voxel-based morphometry (VBM) techniques. Evaluation of the DTI scans included the voxelwise analysis of the fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (AD). Results Diffusion tensor imaging revealed areas of altered FA in subcortical white matter bilaterally, mainly in temporal regions as well as in the right internal capsule, the pons, and the right cerebellum. These changes overlapped with changes in RD. Voxel-based morphometry did not reveal any gray matter alterations. Conclusions We showed altered diffusion properties in several white matter regions in patients with iRLS. White matter changes could mainly be attributed to changes in RD, a parameter thought to reflect altered myelination. Areas with altered white matter microstructure included areas in the internal capsule which include the corticospinal tract to the lower limbs, thereby supporting studies that suggest changes in sensorimotor pathways associated with RLS. PMID:26442748

A comparative study on the effect of Curcumin and Chlorin-p6 on the diffusion of two organic cations across a negatively charged lipid bilayer probed by second harmonic spectroscopy

NASA Astrophysics Data System (ADS)

Saini, R. K.; Varshney, G. K.; Dube, A.; Gupta, P. K.; Das, K.

2014-09-01

The influence of Curcumin and Chlorin-p6 (Cp6) on the real time diffusion kinetics of two organic cations, LDS (LDS-698) and Malachite Green (MG) across a negatively charged phospholipid bilayer is investigated by Second Harmonic (SH) spectroscopy. The diffusion time constant of LDS at neutral pH in liposomes containing either Curcumin or Cp6 is significantly reduced, the effect being more pronounced with Curcumin. At acidic pH, the quantum of reduction in the diffusion time constant of MG by both the drugs was observed to be similar. The relative changes in the average diffusion time constants of the cations with increasing drug concentration at pH 5.0 and 7.4 shows a substantial pH effect for Curcumin induced membrane permeability, while a modest pH effect was observed for Cp6 induced membrane permeability. Based on available evidence this can be attributed to the increased interaction between the drug and the polar head groups of the lipid at pH 7.4 where the drug resides closer to the lipid-water interface.

Prediction of the blowout of jet diffusion flames in a coflowing stream of air

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

Karbasi, M.; Wierzba, I.

1995-12-31

The blowout limits of a lifted diffusion flame in a coflowing stream of air are estimated using a simple model for extinction, for a range of fuels, jet diameters and co-flowing stream velocities. The proposed model uses a parameter which relates to the ratio of a time associated with the mixing processes in a turbulent jet to a characteristic chemical time. The Kolmogorov microscale of time is used as time scale in this model. It is shown that turbulent diffusion flames are quenched by excessive turbulence for a critical value of this parameter. The predicted blowout velocity of diffusion flamesmore » obtained using this model is in good agreement with the available experimental data.« less

Diffuse Mesangial Sclerosis in a Child With Dyskeratosis Congenita Leading to End-stage Renal Disease.

PubMed

Kamel, Abidi; Sayari, Taha; Jellouli, Manel; Hammi, Yousra; Louzir, Rim Ghoucha; Gargah, Tahar

2016-11-01

Dyskeratosis congenita (DC) is a very rare inherited disorder. It is caused by dysfunction of telomere maintenance. It involves RNA telomerase components relevant to various mutations leading to a classic triad of physical findings consisting of nail dystrophy of the hands and feet, mucosal leukoplakia, and reticular pigmentation of the skin, most commonly on the head, neck, and trunk. Bone marrow failure along with pulmonary complications and malignancies are all common causes of premature death in patients with DC as well as other abnormalities. We report a new case of DC with impure nephrotic syndrome relevant to histopathologic signs of a diffuse mesangial sclerosis, leading to an early end-stage renal disease. Challenges remain to understand the diverse spectrum of DC especially in children. To the best of our knowledge this is the first case of DC associated to diffuse mesangial sclerosis.

Advances in magnetic resonance neuroimaging techniques in the evaluation of neonatal encephalopathy.

PubMed

Panigrahy, Ashok; Blüml, Stefan

2007-02-01

Magnetic resonance (MR) imaging has become an essential tool in the evaluation of neonatal encephalopathy. Magnetic resonance-compatible neonatal incubators allow sick neonates to be transported to the MR scanner, and neonatal head coils can improve signal-to-noise ratio, critical for advanced MR imaging techniques. Refinement of conventional imaging techniques include the use of PROPELLER techniques for motion correction. Magnetic resonance spectroscopic imaging and diffusion tensor imaging provide quantitative assessment of both brain development and brain injury in the newborn with respect to metabolite abnormalities and hypoxic-ischemic injury. Knowledge of normal developmental changes in MR spectroscopy metabolite concentration and diffusion tensor metrics is essential to interpret pathological cases. Perfusion MR and functional MR can provide additional physiological information. Both MR spectroscopy and diffusion tensor imaging can provide additional information in the differential of neonatal encephalopathy, including perinatal white matter injury, hypoxic-ischemic brain injury, metabolic disease, infection, and birth injury.

Geometrically complex 3D-printed phantoms for diffuse optical imaging.

PubMed

Dempsey, Laura A; Persad, Melissa; Powell, Samuel; Chitnis, Danial; Hebden, Jeremy C

2017-03-01

Tissue-equivalent phantoms that mimic the optical properties of human and animal tissues are commonly used in diffuse optical imaging research to characterize instrumentation or evaluate an image reconstruction method. Although many recipes have been produced for generating solid phantoms with specified absorption and transport scattering coefficients at visible and near-infrared wavelengths, the construction methods are generally time-consuming and are unable to create complex geometries. We present a method of generating phantoms using a standard 3D printer. A simple recipe was devised which enables printed phantoms to be produced with precisely known optical properties. To illustrate the capability of the method, we describe the creation of an anatomically accurate, tissue-equivalent premature infant head optical phantom with a hollow brain space based on MRI atlas data. A diffuse optical image of the phantom is acquired when a high contrast target is inserted into the hollow space filled with an aqueous scattering solution.

Effect of Non-laminar Regime on the Efficiency of a Thermal Diffusion Column. Report No. 26; INFLUENCIA DEL REGIMEN NO LAMINAR SOBRE LA EFICIENCIA DE UNA COLUMNA DE DIFUSION TERMICA. Informe No. 26

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

Espanol, C.E.

1960-01-01

The effect of the appearance of localized perturbations on the separation factor and operation time of a thermal diffusion column is studied. The separation factor of a column was obtained experimentally and the enrichment was recorded continuously as a function of time by measurement of the thermal conductivity of the gaseous mixture at the foot and head of the column. A mixture of Ar and CO/sub 2/ was used as it behaves as an isotopic mixture. The results showed the linear decrease of the separation factor with the number of stages and the operation time practically does not vary. Themore » introduction of localized turbulences in a thermal diffusion column reduces the column yield. (J.S.R.)« less

Importance of hydrophobic traps for proton diffusion in lyotropic liquid crystals

DOE PAGES

McDaniel, Jesse G.; Yethiraj, Arun

2016-03-04

The diffusion of protons in self-assembled systems is potentially important for the design of efficient proton exchange membranes. In this work, we study proton dynamics in a low-water content, lamellar phase of an sodium-carboxylate gemini surfactant/water system using computer simulations. The hopping of protons via the Grotthuss mechanism is explicity allowed through the multi-state empirical valence bond (MS-EVB) method. We find that the hydronium ion is trapped on the hydrophobic side of the surfactant-water interface, and proton diffusion then proceeds by hopping between surface sites. The importance of hydrophobic traps is surprising, because one would expect the hydronium ions tomore » be trapped at the charged head-groups. Finally, the physics illustrated in this system should be relevant to the proton dynamics in other amphiphilic membrane systems, whenever there exists exposed hydrophobic surface regions.« less

Hg diffusion in books of XVIII and XIX centuries by synchrotron microprobe

NASA Astrophysics Data System (ADS)

Pessanha, S.; Carvalho, M. L.; Manso, M.; Guilherme, A.; Marques, A. F.; Perez, C. A.

2009-08-01

The pigment vermilion (HgS) was used to color the fore edge, tail and head of books. Dissemination and quantification of Hg present in the ink used to color books from XVIII and XIX centuries are reported. Mercury is a very toxic element for the human body, therefore it is extremely important to know whether Hg tends to disseminate throughout the paper or stays confined to the borders of the books with less danger for readers. Synchrotron X-ray microprobe was used to evaluate Hg dissemination from the border to the centre of the paper sheet. The diffusion pattern of Hg was compared with the results obtained by a portable X-ray fluorescence spectrometer and mean quantitative calculations were obtained by a stationary X-ray fluorescence system with triaxial geometry. The results showed high concentrations of Hg in the external regions, but no diffusion was observed for the inner parts of the paper.

Geometrically complex 3D-printed phantoms for diffuse optical imaging

PubMed Central

Dempsey, Laura A.; Persad, Melissa; Powell, Samuel; Chitnis, Danial; Hebden, Jeremy C.

2017-01-01

Tissue-equivalent phantoms that mimic the optical properties of human and animal tissues are commonly used in diffuse optical imaging research to characterize instrumentation or evaluate an image reconstruction method. Although many recipes have been produced for generating solid phantoms with specified absorption and transport scattering coefficients at visible and near-infrared wavelengths, the construction methods are generally time-consuming and are unable to create complex geometries. We present a method of generating phantoms using a standard 3D printer. A simple recipe was devised which enables printed phantoms to be produced with precisely known optical properties. To illustrate the capability of the method, we describe the creation of an anatomically accurate, tissue-equivalent premature infant head optical phantom with a hollow brain space based on MRI atlas data. A diffuse optical image of the phantom is acquired when a high contrast target is inserted into the hollow space filled with an aqueous scattering solution. PMID:28663863

Modern Display Technologies for Airborne Applications.

DTIC Science & Technology

1983-04-01

the case of LED head-down direct view displays, this requires that special attention be paid to the optical filtering , the electrical drive/address...effectively attenuates the LED specular reflectance component, the colour and neutral density filtering attentuate the diffuse component and the... filter techniques are planned for use with video, multi- colour and advanced versions of numeric, alphanumeric and graphic displays; this technique

Passive Rocket Diffuser Testing: Reacting Flow Performance of Four Second-Throat Geometries

NASA Technical Reports Server (NTRS)

Jones, Daniel R.; Allgood, Daniel C.; Saunders, Grady P.

2016-01-01

Second-throat diffusers serve to isolate rocket engines from the effects of ambient back pressure. As one of the nation's largest rocket testing facilities, the performance and design limitations of diffusers are of great interest to NASA's Stennis Space Center. This paper describes a series of tests conducted on four diffuser configurations to better understand the effects of inlet geometry and throat area on starting behavior and boundary layer separation. The diffusers were tested for a duration of five seconds with a 1455-pound thrust, LO2/GH2 thruster to ensure they each reached aerodynamic steady state. The effects of a water spray ring at the diffuser exits and a water-cooled deflector plate were also evaluated. Static pressure and temperature measurements were taken at multiple axial locations along the diffusers, and Computational Fluid Dynamics (CFD) simulations were used as a tool to aid in the interpretation of data. The hot combustion products were confirmed to enable the diffuser start condition with tighter second throats than predicted by historical cold-flow data or the theoretical normal shock method. Both aerodynamic performance and heat transfer were found to increase with smaller diffuser throats. Spray ring and deflector cooling water had negligible impacts on diffuser boundary layer separation. CFD was found to accurately capture diffuser shock structures and full-flowing diffuser wall pressures, and the qualitative behavior of heat transfer. However, the ability to predict boundary layer separated flows was not consistent.

Modeling evaporation from spent nuclear fuel storage pools: A diffusion approach

NASA Astrophysics Data System (ADS)

Hugo, Bruce Robert

Accurate prediction of evaporative losses from light water reactor nuclear power plant (NPP) spent fuel storage pools (SFPs) is important for activities ranging from sizing of water makeup systems during NPP design to predicting the time available to supply emergency makeup water following severe accidents. Existing correlations for predicting evaporation from water surfaces are only optimized for conditions typical of swimming pools. This new approach modeling evaporation as a diffusion process has yielded an evaporation rate model that provided a better fit of published high temperature evaporation data and measurements from two SFPs than other published evaporation correlations. Insights from treating evaporation as a diffusion process include correcting for the effects of air flow and solutes on evaporation rate. An accurate modeling of the effects of air flow on evaporation rate is required to explain the observed temperature data from the Fukushima Daiichi Unit 4 SFP during the 2011 loss of cooling event; the diffusion model of evaporation provides a significantly better fit to this data than existing evaporation models.

Anatomical and Functional Images of in vitro and in vivo Tissues by NIR Time-domain Diffuse Optical Tomography

NASA Astrophysics Data System (ADS)

Zhao, Huijuan; Gao, Feng; Tanikawa, Yukari; Homma, Kazuhiro; Onodera, Yoichi; Yamada, Yukio

Near infra-red (NIR) diffuse optical tomography (DOT) has gained much attention and it will be clinically applied to imaging breast, neonatal head, and the hemodynamics of the brain because of its noninvasiveness and deep penetration in biological tissue. Prior to achieving the imaging of infant brain using DOT, the developed methodologies need to be experimentally justified by imaging some real organs with simpler structures. Here we report our results of an in vitro chicken leg and an in vivo exercising human forearm from the data measured by a multi-channel time-resolved NIR system. Tomographic images were reconstructed by a two-dimensional image reconstruction algorithm based on a modified generalized pulse spectrum technique for simultaneous reconstruction of the µa and µs´. The absolute µa- and µs´-images revealed the inner structures of the chicken leg and the forearm, where the bones were clearly distinguished from the muscle. The Δµa-images showed the blood volume changes during the forearm exercise, proving that the system and the image reconstruction algorithm could potentially be used for imaging not only the anatomic structure but also the hemodynamics in neonatal heads.

Molecular motor traffic: From biological nanomachines to macroscopic transport

NASA Astrophysics Data System (ADS)

Lipowsky, Reinhard; Chai, Yan; Klumpp, Stefan; Liepelt, Steffen; Müller, Melanie J. I.

2006-12-01

All cells of animals and plants contain complex transport systems based on molecular motors which walk along cytoskeletal filaments. These motors are rather small and have a size of 20-100 nm but are able to pull vesicles, organelles and other types of cargo over large distances, from micrometers up to meters. There are several families of motors: kinesins, dyneins, and myosins. Most of these motors have two heads which are used as legs and perform discrete steps along the filaments. Several aspects of the motor behavior will be discussed: motor cycles of two-headed motors; walks of single motors or cargo particles which consist of directed movements interrupted by random, diffusive motion; cargo transport through tube-like compartments; active diffusion of cargo particles in slab-like compartments; cooperative transport of cargo by several motors which may be uni- or bi-directional; and systems with many interacting motors that exhibit traffic jams, self-organized density and flux patterns, and traffic phase transitions far from equilibrium. It is necessary to understand these traffic phenomena in a quantitative manner in order to construct and optimize biomimetic transport systems based on motors and filaments with many possible applications in bioengineering, pharmacology, and medicine.

Salivary duct carcinoma with rhabdoid features: Report of 2 cases with immunohistochemical and ultrastructural analyses

PubMed Central

Kusafuka, Kimihide; Onitsuka, Tetsuro; Muramatsu, Koji; Miki, Tomoko; Murai, Chika; Suda, Toshihito; Fuke, Tomohito; Kamijo, Tomoyuki; Iida, Yoshiyuki; Nakajima, Takashi

2014-01-01

Background Salivary duct carcinoma with rhabdoid features is extremely rare. Methods We report 2 cases of salivary duct carcinoma with rhabdoid features treated at our institution. Results Case 1 was a 44-year-old Japanese man who had swelling in the left parotid region. This tumor consisted of residual pleomorphic adenoma and widely invasive carcinoma, which showed a diffuse growth pattern by atypical rhabdoid cells. Case 2 was a 66-year-old Japanese man who had swelling of the right cervical region. This submandibular tumor was also composed of both residual pleomorphic adenoma region and invasive adenocarcinoma components, whereas some metastatic lesions were purely composed of rhabdoid cells. Such cells were strongly and diffusely positive for cytokeratins (CKs), gross cystic disease fluid protein-15 (GCDFP), and androgen receptor (AR). Case 1 was also positive for Her-2 and p53. Conclusion Both patients were diagnosed with carcinoma ex pleomorphic adenoma and their carcinomatous components were composed of salivary duct carcinoma with rhabdoid features, which is a highly aggressive tumor, similar to salivary duct carcinoma. © 2013 The Authors. Head & Neck published by Wiley Periodicals, Inc. Head Neck 36: E28–E35, 2014 PMID:24038506

Injuries among powered two-wheeler users in eight European countries: a descriptive analysis of hospital discharge data.

PubMed

Forman, Jason L; Lopez-Valdes, Francisco J; Pollack, Keshia; Heredero-Ordoyo, Rafael; Molinero, Aquilino; Mansilla, Alberto; Fildes, Brian; Segui-Gomez, Maria

2012-11-01

Powered two-wheelers (PTWs--mopeds, motorcycles, and scooters) remain the most dangerous form of travel on today's roads. This study used hospital discharge data from eight European countries to examine the frequencies and patterns of injury among PTW users (age≥14 years), the predicted incidence of the loss of functional ability, and the mechanisms of the head injuries observed (all in light of increased helmet use). Of 977,557 injured patients discharged in 2004, 12,994 were identified as having been injured in PTW collisions. Lower extremity injuries accounted for 26% (25.6-26.7, 95% C.I.) of the total injuries, followed by upper extremity injuries (20.7%: 20.3-21.2), traumatic brain injuries (TBI) (18.5%: 18-19), and thoracic injuries (8.2%: 7.8-8.5). Approximately 80% of the lower extremity injury cases were expected to exhibit some functional disability one year following discharge (predicted Functional Capacity Index, pFCI-AIS98<100), compared to 47% of the upper extremity injury cases and 24% of the TBI cases. Although it occurred less frequently, patients that were expected to experience some functional limitation from TBI were predicted to fair worse on average (lose more functional ability) than patients expected to have functional limitations from extremity injuries. Cerebral concussion was the most common head injury observed (occurring in 56% of head injury cases), with most concussion cases (78%) exhibiting no other head injury. Among the AIS3+ head injuries that could be mapped to an injury mechanism, 48% of these were associated with a translational-impact mechanism, and 37% were associated with a rotational mechanism. The observation of high rates of expected long-term disability suggests that future efforts aim to mitigate lower and upper extremity injuries among PTW users. Likewise, the high rates of concussion and head injuries associated with a rotational mechanism provide goals for the next phase of PTW user head protection. Copyright © 2011 Elsevier Ltd. All rights reserved.

Prioritization of candidate disease genes by topological similarity between disease and protein diffusion profiles.

PubMed

Zhu, Jie; Qin, Yufang; Liu, Taigang; Wang, Jun; Zheng, Xiaoqi

2013-01-01

Identification of gene-phenotype relationships is a fundamental challenge in human health clinic. Based on the observation that genes causing the same or similar phenotypes tend to correlate with each other in the protein-protein interaction network, a lot of network-based approaches were proposed based on different underlying models. A recent comparative study showed that diffusion-based methods achieve the state-of-the-art predictive performance. In this paper, a new diffusion-based method was proposed to prioritize candidate disease genes. Diffusion profile of a disease was defined as the stationary distribution of candidate genes given a random walk with restart where similarities between phenotypes are incorporated. Then, candidate disease genes are prioritized by comparing their diffusion profiles with that of the disease. Finally, the effectiveness of our method was demonstrated through the leave-one-out cross-validation against control genes from artificial linkage intervals and randomly chosen genes. Comparative study showed that our method achieves improved performance compared to some classical diffusion-based methods. To further illustrate our method, we used our algorithm to predict new causing genes of 16 multifactorial diseases including Prostate cancer and Alzheimer's disease, and the top predictions were in good consistent with literature reports. Our study indicates that integration of multiple information sources, especially the phenotype similarity profile data, and introduction of global similarity measure between disease and gene diffusion profiles are helpful for prioritizing candidate disease genes. Programs and data are available upon request.

Model coupling intraparticle diffusion/sorption, nonlinear sorption, and biodegradation processes

USGS Publications Warehouse

Karapanagioti, Hrissi K.; Gossard, Chris M.; Strevett, Keith A.; Kolar, Randall L.; Sabatini, David A.

2001-01-01

Diffusion, sorption and biodegradation are key processes impacting the efficiency of natural attenuation. While each process has been studied individually, limited information exists on the kinetic coupling of these processes. In this paper, a model is presented that couples nonlinear and nonequilibrium sorption (intraparticle diffusion) with biodegradation kinetics. Initially, these processes are studied independently (i.e., intraparticle diffusion, nonlinear sorption and biodegradation), with appropriate parameters determined from these independent studies. Then, the coupled processes are studied, with an initial data set used to determine biodegradation constants that were subsequently used to successfully predict the behavior of a second data set. The validated model is then used to conduct a sensitivity analysis, which reveals conditions where biodegradation becomes desorption rate-limited. If the chemical is not pre-equilibrated with the soil prior to the onset of biodegradation, then fast sorption will reduce aqueous concentrations and thus biodegradation rates. Another sensitivity analysis demonstrates the importance of including nonlinear sorption in a coupled diffusion/sorption and biodegradation model. While predictions based on linear sorption isotherms agree well with solution concentrations, for the conditions evaluated this approach overestimates the percentage of contaminant biodegraded by as much as 50%. This research demonstrates that nonlinear sorption should be coupled with diffusion/sorption and biodegradation models in order to accurately predict bioremediation and natural attenuation processes. To our knowledge this study is unique in studying nonlinear sorption coupled with intraparticle diffusion and biodegradation kinetics with natural media.

Utility of Clinical Parameters and Multiparametric MRI as Predictive Factors for Differentiating Uterine Sarcoma From Atypical Leiomyoma.

PubMed

Bi, Qiu; Xiao, Zhibo; Lv, Fajin; Liu, Yao; Zou, Chunxia; Shen, Yiqing

2018-02-05

The objective of this study was to find clinical parameters and qualitative and quantitative magnetic resonance imaging (MRI) features for differentiating uterine sarcoma from atypical leiomyoma (ALM) preoperatively and to calculate predictive values for uterine sarcoma. Data from 60 patients with uterine sarcoma and 88 patients with ALM confirmed by surgery and pathology were collected. Clinical parameters, qualitative MRI features, diffusion-weighted imaging with apparent diffusion coefficient values, and quantitative parameters of dynamic contrast-enhanced MRI of these two tumor types were compared. Predictive values for uterine sarcoma were calculated using multivariable logistic regression. Patient clinical manifestations, tumor locations, margins, T2-weighted imaging signals, mean apparent diffusion coefficient values, minimum apparent diffusion coefficient values, and time-signal intensity curves of solid tumor components were obvious significant parameters for distinguishing between uterine sarcoma and ALM (all P <.001). Abnormal vaginal bleeding, tumors located mainly in the uterine cavity, ill-defined tumor margins, and mean apparent diffusion coefficient values of <1.272 × 10 -3  mm 2 /s were significant preoperative predictors of uterine sarcoma. When the overall scores of these four predictors were greater than or equal to 7 points, the sensitivity, the specificity, the accuracy, and the positive and negative predictive values were 88.9%, 99.9%, 95.7%, 97.0%, and 95.1%, respectively. The use of clinical parameters and multiparametric MRI as predictive factors was beneficial for diagnosing uterine sarcoma preoperatively. These findings could be helpful for guiding treatment decisions. Copyright © 2018 The Association of University Radiologists. Published by Elsevier Inc. All rights reserved.

Application of molecular dynamics simulations in molecular property prediction II: diffusion coefficient.

PubMed

Wang, Junmei; Hou, Tingjun

2011-12-01

In this work, we have evaluated how well the general assisted model building with energy refinement (AMBER) force field performs in studying the dynamic properties of liquids. Diffusion coefficients (D) have been predicted for 17 solvents, five organic compounds in aqueous solutions, four proteins in aqueous solutions, and nine organic compounds in nonaqueous solutions. An efficient sampling strategy has been proposed and tested in the calculation of the diffusion coefficients of solutes in solutions. There are two major findings of this study. First of all, the diffusion coefficients of organic solutes in aqueous solution can be well predicted: the average unsigned errors and the root mean square errors are 0.137 and 0.171 × 10(-5) cm(-2) s(-1), respectively. Second, although the absolute values of D cannot be predicted, good correlations have been achieved for eight organic solvents with experimental data (R(2) = 0.784), four proteins in aqueous solutions (R(2) = 0.996), and nine organic compounds in nonaqueous solutions (R(2) = 0.834). The temperature dependent behaviors of three solvents, namely, TIP3P water, dimethyl sulfoxide, and cyclohexane have been studied. The major molecular dynamics (MD) settings, such as the sizes of simulation boxes and with/without wrapping the coordinates of MD snapshots into the primary simulation boxes have been explored. We have concluded that our sampling strategy that averaging the mean square displacement collected in multiple short-MD simulations is efficient in predicting diffusion coefficients of solutes at infinite dilution. Copyright © 2011 Wiley Periodicals, Inc.

Conformational dynamics of a crystalline protein from microsecond-scale molecular dynamics simulations and diffuse X-ray scattering.

PubMed

Wall, Michael E; Van Benschoten, Andrew H; Sauter, Nicholas K; Adams, Paul D; Fraser, James S; Terwilliger, Thomas C

2014-12-16

X-ray diffraction from protein crystals includes both sharply peaked Bragg reflections and diffuse intensity between the peaks. The information in Bragg scattering is limited to what is available in the mean electron density. The diffuse scattering arises from correlations in the electron density variations and therefore contains information about collective motions in proteins. Previous studies using molecular-dynamics (MD) simulations to model diffuse scattering have been hindered by insufficient sampling of the conformational ensemble. To overcome this issue, we have performed a 1.1-μs MD simulation of crystalline staphylococcal nuclease, providing 100-fold more sampling than previous studies. This simulation enables reproducible calculations of the diffuse intensity and predicts functionally important motions, including transitions among at least eight metastable states with different active-site geometries. The total diffuse intensity calculated using the MD model is highly correlated with the experimental data. In particular, there is excellent agreement for the isotropic component of the diffuse intensity, and substantial but weaker agreement for the anisotropic component. Decomposition of the MD model into protein and solvent components indicates that protein-solvent interactions contribute substantially to the overall diffuse intensity. We conclude that diffuse scattering can be used to validate predictions from MD simulations and can provide information to improve MD models of protein motions.

The multiple roles of small-angle tilt grain boundaries in annihilating radiation damage in SiC

DOE PAGES

Jiang, Hao; Wang, Xing; Szlufarska, Izabela

2017-02-09

Lattice defects generated by radiation damage can diffuse to grain boundaries (GBs) and be annihilated at GBs. However, the precise role of GBs in annihilating the segregated defects remains unclear. Here, we employed multi-scale models to determine how interstitials are annihilated at small-angle tilt GBs (STGBs) in SiC. First of all, we found the pipe diffusion of interstitials in STGBs is slower than bulk diffusion. This is because the increased interatomic distance at dislocation cores raises the migration barrier of interstitial dumbbells. Furthermore, we found both the annihilation of interstitials at jogs and jog nucleation from clusters are diffusion-controlled andmore » can occur under off-stoichiometric interstitial fluxes. Finally, a dislocation line model is developed to predict the role of STGBs in annihilating radiation damage. This model includes defect flux to GBs, pipe diffusion in STGBs, and the interaction of defects with jogs. The model predicts the role of STGBs in annihilating defects depends on the rate of defects segregation to and diffusion along STGBs. STGBs mainly serve as diffusion channel for defects to reach other sinks when defect diffusivity is high at boundaries. As a result, when defect diffusivity is low, most of the defects segregated to STGBs are annihilated by dislocation climb.« less

The multiple roles of small-angle tilt grain boundaries in annihilating radiation damage in SiC

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

Jiang, Hao; Wang, Xing; Szlufarska, Izabela

Lattice defects generated by radiation damage can diffuse to grain boundaries (GBs) and be annihilated at GBs. However, the precise role of GBs in annihilating the segregated defects remains unclear. Here, we employed multi-scale models to determine how interstitials are annihilated at small-angle tilt GBs (STGBs) in SiC. First of all, we found the pipe diffusion of interstitials in STGBs is slower than bulk diffusion. This is because the increased interatomic distance at dislocation cores raises the migration barrier of interstitial dumbbells. Furthermore, we found both the annihilation of interstitials at jogs and jog nucleation from clusters are diffusion-controlled andmore » can occur under off-stoichiometric interstitial fluxes. Finally, a dislocation line model is developed to predict the role of STGBs in annihilating radiation damage. This model includes defect flux to GBs, pipe diffusion in STGBs, and the interaction of defects with jogs. The model predicts the role of STGBs in annihilating defects depends on the rate of defects segregation to and diffusion along STGBs. STGBs mainly serve as diffusion channel for defects to reach other sinks when defect diffusivity is high at boundaries. As a result, when defect diffusivity is low, most of the defects segregated to STGBs are annihilated by dislocation climb.« less

Atomistic modeling of water diffusion in hydrolytic biomaterials.

PubMed

Gautieri, Alfonso; Mezzanzanica, Andrea; Motta, Alberto; Redealli, Alberto; Vesentini, Simone

2012-04-01

One of the most promising applications of hydrolytically degrading biomaterials is their use as drug release carriers. These uses, however, require that the degradation and diffusion of drug are reliably predicted, which is complex to achieve through present experimental methods. Atomistic modeling can help in the knowledge-based design of degrading biomaterials with tuned drug delivery properties, giving insights on the small molecules diffusivity at intermediate states of the degradation process. We present here an atomistic-based approach to investigate the diffusion of water (through which hydrolytic degradation occurs) in degrading bulk models of poly(lactic acid) or PLA. We determine the water diffusion coefficient for different swelling states of the polymeric matrix (from almost dry to pure water) and for different degrees of degradation. We show that water diffusivity is highly influenced by the swelling degree, while little or not influenced by the degradation state. This approach, giving water diffusivity for different states of the matrix, can be combined with diffusion-reaction analytical methods in order to predict the degradation path on longer time scales. Furthermore, atomistic approach can be used to investigate diffusion of other relevant small molecules, eventually leading to the a priori knowledge of degradable biomaterials transport properties, helping the design of the drug delivery systems.

[CT scans in children with head/brain injury: five years after the revision of the guideline on "mild traumatic head/brain injury"].

PubMed

Hageman, G Gerard

2015-01-01

In 2010 the guideline on mild traumatic head/ brain injury for both adults and children was revised under the supervision of the Dutch Neurology Society. The revised guideline endorsed rules for decisions on whether to carry out diagnostic imaging investigations (brain CT scanning) and formulates indications for admission. Unfortunately, 5 years after its introduction, it is clear that the guideline rules result in excessive brain CT scanning, in which no more serious head injury is diagnosed. Brain injury may be present in (small) children even if symptoms are absent at first presentation. Also, clinical signs do not predict intracranial complications. This was nicely demonstrated in a study by Tilma, Bekhof and Brand of 410 children with mTBI: no clinical symptom or sign reliably predicted the risk of intracranial bleeding. They advise hospitalisation for observation instead of brain CT scanning. It may be necessary to review part of the Dutch guideline on mTBI.

Biomarkers of head and neck cancer, tools or a gordian knot?

PubMed Central

Lampri, Evangeli S; Chondrogiannis, Georgios; Ioachim, Elli; Varouktsi, Anna; Mitselou, Antigoni; Galani, Aggeliki; Briassoulis, Evangelos; Kanavaros, Panagiotis; Galani, Vasiliki

2015-01-01

Head and neck tumors comprise a wide spectrum of heterogeneous neoplasms for which biomarkers are needed to aid in earlier diagnosis, risk assessment and therapy response. Personalized medicine based on predictive markers linked to drug response, it is hoped, will lead to improvements in outcomes and avoidance of unnecessary treatment in carcinoma of the head and neck. Because of the heterogeneity of head and neck tumors, the integration of multiple selected markers in association with the histopathologic features is advocated for risk assessment. Validation of each biomarker in the context of clinical trials will be required before a specific marker can be incorporated into daily practice. Furthermore, we will give evidence that some proteins implicated in cell-cell interaction, such as CD44 may be involved in the multiple mechanism of the development and progression of laryngeal lesions and may help to predict the risk of transformation of the benign or precancerous lesions to cancer. PMID:26379825

Microfluidic diffusion diluter: bulging of PDMS microchannels under pressure-driven flow

NASA Astrophysics Data System (ADS)

Holden, Matthew A.; Kumar, Saurabh; Beskok, Ali; Cremer, Paul S.

2003-05-01

The bulging of microfluidic systems during pressure-driven flow is potentially a major consideration for polydimethylsiloxane (PDMS)-based devices. Microchannel cross-sectional areas can change drastically as a function of flow rate and downstream microchannel position. Such geometrical flexibility leads to difficulties in predicting convective/diffusive transport for these systems. We have previously introduced a non-dimensional parameter, kappa, for characterizing convection and diffusion behavior for pressure-driven flow in rigid all-glass systems. This paper describes a modification of that concept for application to non-rigid systems, which is accomplished by incorporating an experimental step to account for the bulging in PDMS/glass microsystems. Specifically, an experimental measurement of channel height by fluorescence microscopy is combined with the aforementioned theory to characterize convective/diffusive behavior at a single location in the device. This allowed the parameter kappa to be determined at that point and applied to predict fluid flow in the subsequent portion of the PDMS microsystem. This procedure was applied to a PDMS/glass microfluidic diffusion dilution (muDD) device designed for generating concentration gradients. Theoretically predicted and experimentally measured distributions of concentrations within the microsystem matched well.

3-D residual eddy current field characterisation: applied to diffusion weighted magnetic resonance imaging.

PubMed

O'Brien, Kieran; Daducci, Alessandro; Kickler, Nils; Lazeyras, Francois; Gruetter, Rolf; Feiweier, Thorsten; Krueger, Gunnar

2013-08-01

Clinical use of the Stejskal-Tanner diffusion weighted images is hampered by the geometric distortions that result from the large residual 3-D eddy current field induced. In this work, we aimed to predict, using linear response theory, the residual 3-D eddy current field required for geometric distortion correction based on phantom eddy current field measurements. The predicted 3-D eddy current field induced by the diffusion-weighting gradients was able to reduce the root mean square error of the residual eddy current field to ~1 Hz. The model's performance was tested on diffusion weighted images of four normal volunteers, following distortion correction, the quality of the Stejskal-Tanner diffusion-weighted images was found to have comparable quality to image registration based corrections (FSL) at low b-values. Unlike registration techniques the correction was not hindered by low SNR at high b-values, and results in improved image quality relative to FSL. Characterization of the 3-D eddy current field with linear response theory enables the prediction of the 3-D eddy current field required to correct eddy current induced geometric distortions for a wide range of clinical and high b-value protocols.

Traumatic midline subarachnoid hemorrhage on initial computed tomography as a marker of severe diffuse axonal injury.

PubMed

Mata-Mbemba, Daddy; Mugikura, Shunji; Nakagawa, Atsuhiro; Murata, Takaki; Ishii, Kiyoshi; Kushimoto, Shigeki; Tominaga, Teiji; Takahashi, Shoki; Takase, Kei

2018-01-05

OBJECTIVE The objective of this study was to test the hypothesis that midline (interhemispheric or perimesencephalic) traumatic subarachnoid hemorrhage (tSAH) on initial CT may implicate the same shearing mechanism that underlies severe diffuse axonal injury (DAI). METHODS The authors enrolled 270 consecutive patients (mean age [± SD] 43 ± 23.3 years) with a history of head trauma who had undergone initial CT within 24 hours and brain MRI within 30 days. Six initial CT findings, including intraventricular hemorrhage (IVH) and tSAH, were used as candidate predictors of DAI. The presence of tSAH was determined at the cerebral convexities, sylvian fissures, sylvian vallecula, cerebellar folia, interhemispheric fissure, and perimesencephalic cisterns. Following MRI, patients were divided into negative and positive DAI groups, and were assigned to a DAI stage: 1) stage 0, negative DAI; 2) stage 1, DAI in lobar white matter or cerebellum; 3) stage 2, DAI involving the corpus callosum; and 4) stage 3, DAI involving the brainstem. Glasgow Outcome Scale-Extended (GOSE) scores were obtained in 232 patients. RESULTS Of 270 patients, 77 (28.5%) had DAI; tSAH and IVH were independently associated with DAI (p < 0.05). Of tSAH locations, midline tSAH was independently associated with both overall DAI and DAI stage 2 or 3 (severe DAI; p < 0.05). The midline tSAH on initial CT had sensitivity of 60.8%, specificity of 81.7%, and positive and negative predictive values of 43.7% and 89.9%, respectively, for severe DAI. When adjusted for admission Glasgow Coma Score, the midline tSAH independently predicted poor GOSE score at both hospital discharge and after 6 months. CONCLUSIONS Midline tSAH could implicate the same shearing mechanism that underlies severe DAI, for which midline tSAH on initial CT is a probable surrogate.

Cerebral vasoreactivity in response to a head-of-bed position change is altered in patients with moderate and severe obstructive sleep apnea.

PubMed

Gregori-Pla, Clara; Cotta, Gianluca; Blanco, Igor; Zirak, Peyman; Giovannella, Martina; Mola, Anna; Fortuna, Ana; Durduran, Turgut; Mayos, Mercedes

2018-01-01

Obstructive sleep apnea (OSA) can impair cerebral vasoreactivity and is associated with an increased risk of cerebrovascular disease. Unfortunately, an easy-to-use, non-invasive, portable monitor of cerebral vasoreactivity does not exist. Therefore, we have evaluated the use of near-infrared diffuse correlation spectroscopy to measure the microvascular cerebral blood flow (CBF) response to a mild head-of-bed position change as a biomarker for the evaluation of cerebral vasoreactivity alteration due to chronic OSA. Furthermore, we have monitored the effect of two years of continuous positive airway pressure (CPAP) treatment on the cerebral vasoreactivity. CBF was measured at different head-of-bed position changes (supine to 30° to supine) in sixty-eight patients with OSA grouped according to severity (forty moderate to severe, twenty-eight mild) and in fourteen control subjects without OSA. A subgroup (n = 13) with severe OSA was measured again after two years of CPAP treatment. All patients and controls showed a similar CBF response after changing position from supine to 30° (p = 0.819), with a median (confidence interval) change of -17.5 (-10.3, -22.9)%. However, when being tilted back to the supine position, while the control group (p = 0.091) and the mild patients with OSA (p = 0.227) recovered to the initial baseline, patients with moderate and severe OSA did not recover to the baseline (9.8 (0.8, 12.9)%, p < 0.001) suggesting altered cerebral vasoreactivity. This alteration was correlated with OSA severity defined by the apnea-hypopnea index, and with mean nocturnal arterial oxygen saturation. The CBF response was normalized after two years of CPAP treatment upon follow-up measurements. In conclusion, microvascular CBF response to a head-of-bed challenge measured by diffuse correlation spectroscopy suggests that moderate and severe patients with OSA have altered cerebral vasoreactivity related to OSA severity. This may normalize after two years of CPAP treatment.

Simple and Reliable Determination of Intravoxel Incoherent Motion Parameters for the Differential Diagnosis of Head and Neck Tumors

PubMed Central

Sasaki, Miho; Sumi, Misa; Eida, Sato; Katayama, Ikuo; Hotokezaka, Yuka; Nakamura, Takashi

2014-01-01

Intravoxel incoherent motion (IVIM) imaging can characterize diffusion and perfusion of normal and diseased tissues, and IVIM parameters are authentically determined by using cumbersome least-squares method. We evaluated a simple technique for the determination of IVIM parameters using geometric analysis of the multiexponential signal decay curve as an alternative to the least-squares method for the diagnosis of head and neck tumors. Pure diffusion coefficients (D), microvascular volume fraction (f), perfusion-related incoherent microcirculation (D*), and perfusion parameter that is heavily weighted towards extravascular space (P) were determined geometrically (Geo D, Geo f, and Geo P) or by least-squares method (Fit D, Fit f, and Fit D*) in normal structures and 105 head and neck tumors. The IVIM parameters were compared for their levels and diagnostic abilities between the 2 techniques. The IVIM parameters were not able to determine in 14 tumors with the least-squares method alone and in 4 tumors with the geometric and least-squares methods. The geometric IVIM values were significantly different (p<0.001) from Fit values (+2±4% and −7±24% for D and f values, respectively). Geo D and Fit D differentiated between lymphomas and SCCs with similar efficacy (78% and 80% accuracy, respectively). Stepwise approaches using combinations of Geo D and Geo P, Geo D and Geo f, or Fit D and Fit D* differentiated between pleomorphic adenomas, Warthin tumors, and malignant salivary gland tumors with the same efficacy (91% accuracy = 21/23). However, a stepwise differentiation using Fit D and Fit f was less effective (83% accuracy = 19/23). Considering cumbersome procedures with the least squares method compared with the geometric method, we concluded that the geometric determination of IVIM parameters can be an alternative to least-squares method in the diagnosis of head and neck tumors. PMID:25402436

Prediction of the body rotation-induced torques on the arm during reaching movements: evidence from a proprioceptively deafferented subject.

PubMed

Guillaud, Etienne; Simoneau, Martin; Blouin, Jean

2011-06-01

Reaching for a target while rotating the trunk generates substantial Coriolis and centrifugal torques that push the arm in the opposite direction of the rotations. These torques rarely perturb movement accuracy, suggesting that they are compensated for during the movement. Here we tested whether signals generated during body motion (e.g., vestibular) can be used to predict the torques induced by the body rotation and to modify the motor commands accordingly. We asked a deafferented subject to reach for a memorized visual target in darkness. At the onset of the reaching, the patient was rotated 25° or 40° in the clockwise or the counterclockwise directions. During the rotation, the patient's head remained either fixed in space (Head-Fixed condition) or fixed on the trunk (Head Rotation condition). At the rotation onset, the deafferented patient's hand largely deviated from the mid-sagittal plane in both conditions. The hand deviations were compensated for in the Head Rotation condition only. These results highlight the computational faculty of the brain and show that body rotation-related information can be processed for predicting the consequence of the rotation dynamics on the reaching arm movements. Copyright © 2011 Elsevier Ltd. All rights reserved.

Evaluating observations in the context of predictions for the death valley regional groundwater system

USGS Publications Warehouse

Ely, D.M.; Hill, M.C.; Tiedeman, C.R.; O'Brien, G. M.

2004-01-01

When a model is calibrated by nonlinear regression, calculated diagnostic and inferential statistics provide a wealth of information about many aspects of the system. This work uses linear inferential statistics that are measures of prediction uncertainty to investigate the likely importance of continued monitoring of hydraulic head to the accuracy of model predictions. The measurements evaluated are hydraulic heads; the predictions of interest are subsurface transport from 15 locations. The advective component of transport is considered because it is the component most affected by the system dynamics represented by the regional-scale model being used. The problem is addressed using the capabilities of the U.S. Geological Survey computer program MODFLOW-2000, with its Advective Travel Observation (ADV) Package. Copyright ASCE 2004.

Detecting chaos, determining the dimensions of tori and predicting slow diffusion in Fermi-Pasta-Ulam lattices by the Generalized Alignment Index method

NASA Astrophysics Data System (ADS)

Skokos, C.; Bountis, T.; Antonopoulos, C.

2008-12-01

The recently introduced GALI method is used for rapidly detecting chaos, determining the dimensionality of regular motion and predicting slow diffusion in multi-dimensional Hamiltonian systems. We propose an efficient computation of the GALIk indices, which represent volume elements of k randomly chosen deviation vectors from a given orbit, based on the Singular Value Decomposition (SVD) algorithm. We obtain theoretically and verify numerically asymptotic estimates of GALIs long-time behavior in the case of regular orbits lying on low-dimensional tori. The GALIk indices are applied to rapidly detect chaotic oscillations, identify low-dimensional tori of Fermi-Pasta-Ulam (FPU) lattices at low energies and predict weak diffusion away from quasiperiodic motion, long before it is actually observed in the oscillations.

Development of a short length combustor for a supersonic cruise turbofan engine using a 90 deg sector of a full annulus

NASA Technical Reports Server (NTRS)

Clements, T. R.

1972-01-01

A performance development program has been conducted on a short length, double-annular, ram-induction combustor. The combustor was designed for a large augmented turbofan engine capable of sustained flight speeds up to Mach 3.0. Performance tests were conducted at an inlet temperature and Mach number simulating engine sea level takeoff conditions. At the design temperature rise of 1600 F, combustion efficiency was 100%, pattern factor was 0.20, and combined diffuser-combustor pressure loss was 4.4% or 1.12 times the diffuser inlet velocity head. A temperature rise in excess of 2400 F with a combustion efficiency of 94% was demonstrated.

Sea water in coastal aquifers

USGS Publications Warehouse

Cooper, Hilton Hammond

1964-01-01

Investigations in the coastal part of the Biscayne aquifer, a highly productive aquifer of limestone and sand in the Miami area, Florida, show that the salt-water front is dynamically stable as much as 8 miles seaward of the position computed according to the Ghyben-Herzberg principle. This discrepancy results, at least in part, from the fact that the salt water in the Biscayne aquifer is not static, as explanations of the dynamic balance commonly assume. Cross sections showing lines of equal fresh-water potential indicate that during periods of heavy recharge, the fresh-water head is high enough to cause the fresh water, the salt water, and the zone of diffusion between them to move seaward. When the fresh-water head is low, salt water in the lower part of the aquifer intrudes inland, but some of the diluted sea water in the zone of diffusion continues to flow seaward. Thus, salt water circulates inland from the floor of the sea through the lower part of the aquifer becoming progressively diluted with fresh water to a line along which there is no horizontal component of flow, after which it moves upward and returns to the sea. This cyclic flow is demonstrated by a flow net which is constructed by the use of horizontal gradients determined from the low-head equipotential diagram. The flow net shows that about seven-eights of the total discharge at the shoreline originates as fresh water in inland parts of the aquifer. The remaining one-eighth represents a return of sea water entering the aquifer through the floor of the sea.

AptRank: an adaptive PageRank model for protein function prediction on   bi-relational graphs.

PubMed

Jiang, Biaobin; Kloster, Kyle; Gleich, David F; Gribskov, Michael

2017-06-15

Diffusion-based network models are widely used for protein function prediction using protein network data and have been shown to outperform neighborhood-based and module-based methods. Recent studies have shown that integrating the hierarchical structure of the Gene Ontology (GO) data dramatically improves prediction accuracy. However, previous methods usually either used the GO hierarchy to refine the prediction results of multiple classifiers, or flattened the hierarchy into a function-function similarity kernel. No study has taken the GO hierarchy into account together with the protein network as a two-layer network model. We first construct a Bi-relational graph (Birg) model comprised of both protein-protein association and function-function hierarchical networks. We then propose two diffusion-based methods, BirgRank and AptRank, both of which use PageRank to diffuse information on this two-layer graph model. BirgRank is a direct application of traditional PageRank with fixed decay parameters. In contrast, AptRank utilizes an adaptive diffusion mechanism to improve the performance of BirgRank. We evaluate the ability of both methods to predict protein function on yeast, fly and human protein datasets, and compare with four previous methods: GeneMANIA, TMC, ProteinRank and clusDCA. We design four different validation strategies: missing function prediction, de novo function prediction, guided function prediction and newly discovered function prediction to comprehensively evaluate predictability of all six methods. We find that both BirgRank and AptRank outperform the previous methods, especially in missing function prediction when using only 10% of the data for training. The MATLAB code is available at https://github.rcac.purdue.edu/mgribsko/aptrank . gribskov@purdue.edu. Supplementary data are available at Bioinformatics online. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com

Can 3'-Deoxy-3'-((18)F) Fluorothymidine Out Perform 2-Deoxy-2-((18)F) Fluoro-D-Glucose Positron Emission Tomography/Computed Tomography in the Diagnosis of Cervical Lymphadenopathy in Patients With Oral/Head and Neck Cancer?

PubMed

Schaefferkoetter, Joshua D; Carlson, Eric R; Heidel, Robert E

2015-07-01

The present study investigated the performance of cellular metabolism imaging with 2-deoxy-2-((18)F) fluoro-D-glucose (FDG) versus cellular proliferation imaging with 3'-deoxy-3'-((18)F) fluorothymidine (FLT) in the detection of cervical lymph node metastases in oral/head and neck cancer. We conducted a prospective cohort study to assess a head-to-head performance of FLT imaging and clinical FDG imaging for characterizing cervical lymph node metastases in patients with squamous cell carcinoma (SCC) of the oral/head and neck region. The primary predictor variable of the study was the presence of FDG or FLT avidity within the cervical lymph nodes. The primary outcome variable was the histologic presence of metastatic SCC in the cervical lymph nodes. The performance was reported in terms of the sensitivity, specificity, accuracy, and positive and negative predictive values. The overall accuracy for discriminating positive from negative lymph nodes was evaluated as a function of the positron emission tomography (PET) standardized uptake value (SUV). Receiver operating characteristic (ROC) analyses were performed for both tracers. Eleven patients undergoing surgical resection of SCC of the oral/head and neck region underwent preoperative FDG and FLT PET-computed tomography (CT) scans on separate days. The interpretation of the FDG PET-CT imaging resulted in sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of 43.2, 99.5, 94.4, 88.9, and 94.7%, respectively. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value for FLT PET-CT imaging was 75.7, 99.2, 97.1, 90.3, and 97.7%, respectively. The areas under the curve for the ROC curves were 0.9 and 0.84 for FDG and FLT, respectively. Poor correlation was observed between the SUV for FDG and FLT within the lymph nodes and tumors. FLT showed better overall performance for detecting lymphadenopathy on qualitative assessment within the total nodal population. This notwithstanding, FDG SUV performed better for pathologic discrimination within the visible lymph nodes. Copyright © 2015 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.

Out-of-Position Rear Impact Tissue-Level Investigation Using Detailed Finite Element Neck Model.

PubMed

Shateri, Hamed; Cronin, Duane S

2015-01-01

Whiplash injuries can occur in automotive crashes and may cause long-term health issues such as neck pain, headache, and visual and auditory disturbance. Evidence suggests that nonneutral head posture can significantly increase the potential for injury in a given impact scenario, but epidemiological and experimental data are limited and do not provide a quantitative assessment of the increased potential for injury. Although there have been some attempts to evaluate this important issue using finite element models, none to date have successfully addressed this complex problem. An existing detailed finite element neck model was evaluated in nonneutral positions and limitations were identified, including musculature implementation and attachment, upper cervical spine kinematics in axial rotation, prediction of ligament failure, and the need for repositioning the model while incorporating initial tissue strains. The model was enhanced to address these issues and an iterative procedure was used to determine the upper cervical spine ligament laxities. The neck model was revalidated using neutral position impacts and compared to an out-of-position cadaver experiment in the literature. The effects of nonneutral position (axial head rotation) coupled with muscle activation were studied at varying impact levels. The laxities for the ligaments of the upper cervical spine were determined using 4 load cases and resulted in improved response and predicted failure loads relative to experimental data. The predicted head response from the model was similar to an experimental head-turned bench-top rear impact experiment. The parametric study identified specific ligaments with increased distractions due to an initial head-turned posture and the effect of active musculature leading to reduced ligament distractions. The incorporation of ligament laxity in the upper cervical spine was essential to predict range of motion and traumatic response, particularly for repositioning of the neck model prior to impact. The results of this study identify a higher potential for injury in out-of-position rear collisions and identified at-risk locations based on ligament distractions. The model predicted higher potential for injury by as much as 50% based on ligament distraction for the out-of-position posture and reduced potential for injury with muscle activation. Importantly, this study demonstrated that the location of injury or pain depends on the initial occupant posture, so that both the location of injury and kinematic threshold may vary when considering common head positions while driving.

Prediction of pulmonary hypertension in idiopathic pulmonary fibrosis☆

PubMed Central

Zisman, David A.; Ross, David J.; Belperio, John A.; Saggar, Rajan; Lynch, Joseph P.; Ardehali, Abbas; Karlamangla, Arun S.

2007-01-01

Summary Background Reliable, noninvasive approaches to the diagnosis of pulmonary hypertension in idiopathic pulmonary fibrosis are needed. We tested the hypothesis that the forced vital capacity to diffusing capacity ratio and room air resting pulse oximetry may be combined to predict mean pulmonary artery pressure (MPAP) in idiopathic pulmonary fibrosis. Methods Sixty-one idiopathic pulmonary fibrosis patients with available right-heart catheterization were studied. We regressed measured MPAP as a continuous variable on pulse oximetry (SpO2) and percent predicted forced vital capacity (FVC) to percent-predicted diffusing capacity ratio (% FVC/% DLco) in a multivariable linear regression model. Results Linear regression generated the following equation: MPAP = −11.9+0.272 × SpO2+0.0659 × (100−SpO2)2+3.06 × (% FVC/% DLco); adjusted R2 = 0.55, p<0.0001. The sensitivity, specificity, positive predictive and negative predictive value of model-predicted pulmonary hypertension were 71% (95% confidence interval (CI): 50–89%), 81% (95% CI: 68–92%), 71% (95% CI: 51–87%) and 81% (95% CI: 68–94%). Conclusions A pulmonary hypertension predictor based on room air resting pulse oximetry and FVC to diffusing capacity ratio has a relatively high negative predictive value. However, this model will require external validation before it can be used in clinical practice. PMID:17604151

The role of tissue microstructure and water exchange in biophysical modelling of diffusion in white matter.

PubMed

Nilsson, Markus; van Westen, Danielle; Ståhlberg, Freddy; Sundgren, Pia C; Lätt, Jimmy

2013-08-01

Biophysical models that describe the outcome of white matter diffusion MRI experiments have various degrees of complexity. While the simplest models assume equal-sized and parallel axons, more elaborate ones may include distributions of axon diameters and axonal orientation dispersions. These microstructural features can be inferred from diffusion-weighted signal attenuation curves by solving an inverse problem, validated in several Monte Carlo simulation studies. Model development has been paralleled by microscopy studies of the microstructure of excised and fixed nerves, confirming that axon diameter estimates from diffusion measurements agree with those from microscopy. However, results obtained in vivo are less conclusive. For example, the amount of slowly diffusing water is lower than expected, and the diffusion-encoded signal is apparently insensitive to diffusion time variations, contrary to what may be expected. Recent understandings of the resolution limit in diffusion MRI, the rate of water exchange, and the presence of microscopic axonal undulation and axonal orientation dispersions may, however, explain such apparent contradictions. Knowledge of the effects of biophysical mechanisms on water diffusion in tissue can be used to predict the outcome of diffusion tensor imaging (DTI) and of diffusion kurtosis imaging (DKI) studies. Alterations of DTI or DKI parameters found in studies of pathologies such as ischemic stroke can thus be compared with those predicted by modelling. Observations in agreement with the predictions strengthen the credibility of biophysical models; those in disagreement could provide clues of how to improve them. DKI is particularly suited for this purpose; it is performed using higher b-values than DTI, and thus carries more information about the tissue microstructure. The purpose of this review is to provide an update on the current understanding of how various properties of the tissue microstructure and the rate of water exchange between microenvironments are reflected in diffusion MRI measurements. We focus on the use of biophysical models for extracting tissue-specific parameters from data obtained with single PGSE sequences on clinical MRI scanners, but results obtained with animal MRI scanners are also considered. While modelling of white matter is the central theme, experiments on model systems that highlight important aspects of the biophysical models are also reviewed.

[Clinicopathologic features of primary mucosal CD30-positive T-cell lymphoproliferative disorders in head and neck region].

PubMed

Liu, F; Li, M; Zhang, L Y; Guo, L; Hu, W W; Rao, H L

2018-06-08

Objective: To study clinicopathologic features, prognosis and differential diagnoses of primary mucosal CD30-positive T-cell lymphoproliferative disorders of the head and neck(mCD30(+) TLPD-head and neck). Methods: Three cases of mCD30(+) TLPD-head and neck were collected from January 2014 to April 2017 at Sun Yat-Sen University Foshan Hospital. A literature review of mCD30(+) TLPD of head and neck was provided. Results: All three cases presented with either bulging/exophytic nodule or mucosal ulcer/erosion. Morphologically, the tumor consisted of diffuse proliferation of uniform, large atypical mononuclear lymphoid cells that showed irregular or polymorphic nuclei with small nucleoli, and abundant pale or amphophilic cytoplasm. Hallmark cells with eccentric, horseshoe, kidney-like, or doughnut-shaped nuclei were present. While mitotic figures were present, no tumor necrosis was found. Eosinophilc infiltration was obvious in the background. The atypical large lymphoid cells had a immunophenotype of CD30(+) /CD3(+) /CD4(+) /CD56(-) along with positive cytotoxic molecule. While being negative for EBER/ALK/CD20/CD8, TCR rearrangement was found in 2 out of 3 cases. Three patients were cured after excision without relapse and metastasis.The two patients with TCR rearrangement didn't show aggressive clinical course. Conclusions: mCD30(+) TLPD-head and neck is a rare benign lymphoproliferative disorder with spontaneous regression. It should be differentiated from cutaneous CD30(+) anaplstic large cell lymphoma, lymphomatoid papulosis, and EBV-related mucocutaneous ulcer. Correct recognition of mCD30(+) TLPD of head and neck is important to avoid overtreatment.

40 CFR 227.29 - Initial mixing.

Code of Federal Regulations, 2012 CFR

2012-07-01

...) Initial mixing is defined to be that dispersion or diffusion of liquid, suspended particulate, and solid... adequate to predict initial dispersion and diffusion of the waste, these shall be used, if necessary, in.... (2) When field data on the dispersion and diffusion of a waste of characteristics similar to that...

40 CFR 227.29 - Initial mixing.

Code of Federal Regulations, 2011 CFR

2011-07-01

...) Initial mixing is defined to be that dispersion or diffusion of liquid, suspended particulate, and solid... adequate to predict initial dispersion and diffusion of the waste, these shall be used, if necessary, in.... (2) When field data on the dispersion and diffusion of a waste of characteristics similar to that...

40 CFR 227.29 - Initial mixing.

Code of Federal Regulations, 2014 CFR

2014-07-01

...) Initial mixing is defined to be that dispersion or diffusion of liquid, suspended particulate, and solid... adequate to predict initial dispersion and diffusion of the waste, these shall be used, if necessary, in.... (2) When field data on the dispersion and diffusion of a waste of characteristics similar to that...

40 CFR 227.29 - Initial mixing.

Code of Federal Regulations, 2013 CFR

2013-07-01

...) Initial mixing is defined to be that dispersion or diffusion of liquid, suspended particulate, and solid... adequate to predict initial dispersion and diffusion of the waste, these shall be used, if necessary, in.... (2) When field data on the dispersion and diffusion of a waste of characteristics similar to that...

Prediction and interpretation of infrared intensities of polymethylene chain molecules

NASA Astrophysics Data System (ADS)

Jona, P.; Gussoni, M.; Zerbi, G.

1986-03-01

We have calculated the IR intensities of some polymethylene chain molecules containing conformational defects or polar heads. Calculations provide spectroscopic markers of end-TG, GTG', GTG, GG and GGTGG defects. Further, a spectroscopical study of interactions between polar heads and alkyl chain is allowed.

Vascular anomalies of the head and neck.

PubMed

Donald, P J

2001-02-01

Vascular abnormalities of the head and neck are relatively uncommon lesions. An understanding of these anomalies based on their pathogenesis and natural history clearly divides them into hemangiomas and vascular malformations. Treatment strategies that are reasonable and predictable can then be devised based on the aforementioned factors.

Clinical assessment scoring system for tracheostomy (CASST) criterion: Objective criteria to predict pre-operatively the need for a tracheostomy in head and neck malignancies.

PubMed

Gupta, Karan; Mandlik, Dushyant; Patel, Daxesh; Patel, Purvi; Shah, Bankim; Vijay, Devanhalli G; Kothari, Jagdish M; Toprani, Rajendra B; Patel, Kaustubh D

2016-09-01

Tracheostomy is a mainstay modality for airway management for patients with head-neck cancer undergoing surgery. This study aims to define factors predicting need of tracheostomy and define an effective objective criterion to predict tracheostomy need. 486 patients undergoing composite resections were studied. Factors analyzed were age, previous surgery, extent of surgery, trismus, extent of mandibular resection and reconstruction etc. Factors were divided into major and minor, using the clinical assessment scoring system for tracheostomy (CASST) criterion. Sixty seven (13.7%) patients required tracheostomy for their peri-operative management. Elective tracheostomies were done in 53 cases during surgery and post-operatively in 14 patients. All patients in whom tracheostomies were anticipated had a score of seven or more. A decision on whether or not an elective tracheotomy in head and neck surgery is necessary and can be facilitated using CASST criterion, which has a sensitivity of 95.5% and a negative predictive value (NPV) of 99.3%. It may reduce post-operative complications and contribute to safer treatment. Copyright © 2016 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Head Pose Estimation Using Multilinear Subspace Analysis for Robot Human Awareness

NASA Technical Reports Server (NTRS)

Ivanov, Tonislav; Matthies, Larry; Vasilescu, M. Alex O.

2009-01-01

Mobile robots, operating in unconstrained indoor and outdoor environments, would benefit in many ways from perception of the human awareness around them. Knowledge of people's head pose and gaze directions would enable the robot to deduce which people are aware of the its presence, and to predict future motions of the people for better path planning. To make such inferences, requires estimating head pose on facial images that are combination of multiple varying factors, such as identity, appearance, head pose, and illumination. By applying multilinear algebra, the algebra of higher-order tensors, we can separate these factors and estimate head pose regardless of subject's identity or image conditions. Furthermore, we can automatically handle uncertainty in the size of the face and its location. We demonstrate a pipeline of on-the-move detection of pedestrians with a robot stereo vision system, segmentation of the head, and head pose estimation in cluttered urban street scenes.

Image quality stability of whole-body diffusion weighted imaging.

PubMed

Chen, Yun-bin; Hu, Chun-miao; Zhong, Jing; Sun, Fei

2009-06-01

To assess the reproducibility of whole-body diffusion weighted imaging (WB-DWI) technique in healthy volunteers under normal breathing with background body signal suppression. WB-DWI was performed on 32 healthy volunteers twice within two-week period using short TI inversion-recovery diffusion-weighted echo-planar imaging sequence and built-in body coil. The volunteers were scanned across six stations continuously covering the entire body from the head to the feet under normal breathing. The bone apparent diffusion coefficient (ADC) and exponential ADC (eADC) of regions of interest (ROIs) were measured. We analyzed correlation of the results using paired-t-test to assess the reproducibility of the WB-DWI technique. We were successful in collecting and analyzing data of 64 WB-DWI images. There was no significant difference in bone ADC and eADC of 824 ROIs between the paired observers and paired scans (P>0.05). Most of the images from all stations were of diagnostic quality. The measurements of bone ADC and eADC have good reproducibility. WB-DWI technique under normal breathing with background body signal suppression is adequate.

Nanoscale modeling for ultrathin liquid films: Spreading and coupled layering

NASA Astrophysics Data System (ADS)

Phillips, David Michael

The hard disk drive (HDD) industry is currently experiencing a compound annual growth rate of 100% for the areal density. Current production drives have an areal density of 80 Gbit in-2, and drives with an areal density of 100 Gbit in-2 have been recently demonstrated. While much of this growth has been fueled by the development of new read/write heads, some of this gain was achieved by reducing the spacing between the heads and the magnetic media. This in turn reduces the spacing at the head-disk interface (HDI). The HDI in a HDD system consists of a slider, which contains the read/write heads, flying over the disk surface on an air bearing. The current designed separation distance, or fly height, is less than 10 nm. This spacing is expected to reduce to a mere 5 nm within the next few years. With the reduced fly height, intermittent contacts at the HDI become more probable. Only a thin lubricant film of perfluoropolyether (PFPE) and a sputtered carbon overcoat on the disk surface protect the slider and the stored data from mechanical and thermal damage. The PFPE film is quite thin, with a thickness of less than 2 nm or about a monolayer of molecules. During an HDI contact, the PFPE film is considered sacrificial and is often depleted in the contact area. In order to maintain adequate protection for the disk surface, PFPE molecules from the surrounding film must replenish the depleted area. This replenishment ability directly opposes the requirement that the PFPE film must not spin-off of the disk surface due to the disk rotation rate, which is as high as 10,000 RPM in current drives. To balance the PFPE films to sufficiently meet both requirements, HDD manufacturers functionalized the endgroups of the PFPE molecules to allow some portion of the lubricant film to reversibly bond with the disk overcoat. The result is a lubricant film that has a slower replenishment but does not spin-off. The work presented here focuses on the replenishment ability of thin films of liquid PFPE. The experimental analogue of replenishment is the one-dimensional spreading analysis. PFPEs with functional endgroups demonstrated coupled molecular layering and dewetting phenomena during the spreading analysis, while PFPEs with nonfunctional endgroups did not. All of the PFPE thin films spread via a diffusive process and had diffusion coefficients that depended on the local film thickness. A theoretical analysis is presented here for both the governing equation and the disjoining pressure driving force for the PFPE thin film spreading. For PFPEs with non-functional endgroups, a reasonable analysis is performed on the diffusion coefficient for two classes of film: submonolayer and multilayer. The diffusion coefficient of PFPEs with functional endgroups are qualitatively linked to the gradient of the film disjoining pressure. To augment this theory, both lattice-based and off-lattice Monte Carlo simulations are conducted for PFPE film models. The lattice-based model shows the existence of a critical functional endgroup interaction strength. It is also used to study the break-up of molecular layers for a spreading film via a fractal analysis. The off-lattice model is used to calculate the anisotropic pressure tensor for the model PFPE thin film and subsequently the film disjoining pressure. The model also qualitatively analyzes of the self diffusion in the film.

Modeling the reversible, diffusive sink effect in response to transient contaminant sources.

PubMed

Zhao, D; Little, J C; Hodgson, A T

2002-09-01

A physically based diffusion model is used to evaluate the sink effect of diffusion-controlled indoor materials and to predict the transient contaminant concentration in indoor air in response to several time-varying contaminant sources. For simplicity, it is assumed the predominant indoor material is a homogeneous slab, initially free of contaminant, and the air within the room is well mixed. The model enables transient volatile organic compound (VOC) concentrations to be predicted based on the material/air partition coefficient (K) and the material-phase diffusion coefficient (D) of the sink. Model predictions are made for three scenarios, each mimicking a realistic situation in a building. Styrene, phenol, and naphthalene are used as representative VOCs. A styrene butadiene rubber (SBR) backed carpet, vinyl flooring (VF), and a polyurethane foam (PUF) carpet cushion are considered as typical indoor sinks. In scenarios involving a sinusoidal VOC input and a double exponential decaying input, the model predicts the sink has a modest impact for SBR/styrene, but the effect increases for VF/phenol and PUF/naphthalene. In contrast, for an episodic chemical spill, SBR is predicted to reduce the peak styrene concentration considerably. A parametric study reveals for systems involving a large equilibrium constant (K), the kinetic constant (D) will govern the shape of the resulting gasphase concentration profile. On the other hand, for systems with a relaxed mass transfer resistance, K will dominate the profile.

Prediction of erodibility in Oxisols using iron oxides, soil color and diffuse reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Arantes Camargo, Livia; Marques, José, Jr.

2015-04-01

The prediction of erodibility using indirect methods such as diffuse reflectance spectroscopy could facilitate the characterization of the spatial variability in large areas and optimize implementation of conservation practices. The aim of this study was to evaluate the prediction of interrill erodibility (Ki) and rill erodibility (Kr) by means of iron oxides content and soil color using multiple linear regression and diffuse reflectance spectroscopy (DRS) using regression analysis by least squares partial (PLSR). The soils were collected from three geomorphic surfaces and analyzed for chemical, physical and mineralogical properties, plus scanned in the spectral range from the visible and infrared. Maps of spatial distribution of Ki and Kr were built with the values calculated by the calibrated models that obtained the best accuracy using geostatistics. Interrill-rill erodibility presented negative correlation with iron extracted by dithionite-citrate-bicarbonate, hematite, and chroma, confirming the influence of iron oxides in soil structural stability. Hematite and hue were the attributes that most contributed in calibration models by multiple linear regression for the prediction of Ki (R2 = 0.55) and Kr (R2 = 0.53). The diffuse reflectance spectroscopy via PLSR allowed to predict Interrill-rill erodibility with high accuracy (R2adj = 0.76, 0.81 respectively and RPD> 2.0) in the range of the visible spectrum (380-800 nm) and the characterization of the spatial variability of these attributes by geostatistics.

A critical examination of the validity of simplified models for radiant heat transfer analysis.

NASA Technical Reports Server (NTRS)

Toor, J. S.; Viskanta, R.

1972-01-01

Examination of the directional effects of the simplified models by comparing the experimental data with the predictions based on simple and more detailed models for the radiation characteristics of surfaces. Analytical results indicate that the constant property diffuse and specular models do not yield the upper and lower bounds on local radiant heat flux. In general, the constant property specular analysis yields higher values of irradiation than the constant property diffuse analysis. A diffuse surface in the enclosure appears to destroy the effect of specularity of the other surfaces. Semigray and gray analyses predict the irradiation reasonably well provided that the directional properties and the specularity of the surfaces are taken into account. The uniform and nonuniform radiosity diffuse models are in satisfactory agreement with each other.

Less head motion during MRI under task than resting-state conditions.

PubMed

Huijbers, Willem; Van Dijk, Koene R A; Boenniger, Meta M; Stirnberg, Rüdiger; Breteler, Monique M B

2017-02-15

Head motion reduces data quality of neuroimaging data. In three functional magnetic resonance imaging (MRI) experiments we demonstrate that people make less head movements under task than resting-state conditions. In Experiment 1, we observed less head motion during a memory encoding task than during the resting-state condition. In Experiment 2, using publicly shared data from the UCLA Consortium for Neuropsychiatric Phenomics LA5c Study, we again found less head motion during several active task conditions than during a resting-state condition, although some task conditions also showed comparable motion. In the healthy controls, we found more head motion in men than in women and more motion with increasing age. When comparing clinical groups, we found that patients with a clinical diagnosis of bipolar disorder, or schizophrenia, move more compared to healthy controls or patients with ADHD. Both these experiments had a fixed acquisition order across participants, and we could not rule out that a first or last scan during a session might be particularly prone to more head motion. Therefore, we conducted Experiment 3, in which we collected several task and resting-state fMRI runs with an acquisition order counter-balanced. The results of Experiment 3 show again less head motion during several task conditions than during rest. Together these experiments demonstrate that small head motions occur during MRI even with careful instruction to remain still and fixation with foam pillows, but that head motion is lower when participants are engaged in a cognitive task. These finding may inform the choice of functional runs when studying difficult-to-scan populations, such as children or certain patient populations. Our findings also indicate that differences in head motion complicate direct comparisons of measures of functional neuronal networks between task and resting-state fMRI because of potential differences in data quality. In practice, a task to reduce head motion might be especially useful when acquiring structural MRI data such as T1/T2-weighted and diffusion MRI in research and clinical settings. Copyright © 2016 Elsevier Inc. All rights reserved.

Reliability and relative weighting of visual and nonvisual information for perceiving direction of self-motion during walking

PubMed Central

Saunders, Jeffrey A.

2014-01-01

Direction of self-motion during walking is indicated by multiple cues, including optic flow, nonvisual sensory cues, and motor prediction. I measured the reliability of perceived heading from visual and nonvisual cues during walking, and whether cues are weighted in an optimal manner. I used a heading alignment task to measure perceived heading during walking. Observers walked toward a target in a virtual environment with and without global optic flow. The target was simulated to be infinitely far away, so that it did not provide direct feedback about direction of self-motion. Variability in heading direction was low even without optic flow, with average RMS error of 2.4°. Global optic flow reduced variability to 1.9°–2.1°, depending on the structure of the environment. The small amount of variance reduction was consistent with optimal use of visual information. The relative contribution of visual and nonvisual information was also measured using cue conflict conditions. Optic flow specified a conflicting heading direction (±5°), and bias in walking direction was used to infer relative weighting. Visual feedback influenced heading direction by 16%–34% depending on scene structure, with more effect with dense motion parallax. The weighting of visual feedback was close to the predictions of an optimal integration model given the observed variability measures. PMID:24648194

Prenatal and Neonatal Brain Structure and White Matter Maturation in Children at High Risk for Schizophrenia

PubMed Central

Gilmore, John H.; Kang, Chaeryon; Evans, Dianne D.; Wolfe, Honor M.; Smith, J. Keith; Lieberman, Jeffrey A.; Lin, Weili; Hamer, Robert M.; Styner, Martin; Gerig, Guido

2011-01-01

Objective Schizophrenia is a neurodevelopmental disorder associated with abnormalities of brain structure and white matter, although little is known about when these abnormalities arise. This study was conducted to identify structural brain abnormalities in the prenatal and neonatal periods associated with genetic risk for schizophrenia. Method Prenatal ultrasound scans and neonatal structural magnetic resonance imaging (MRI) and diffusion tensor imaging were prospectively obtained in the offspring of mothers with schizophrenia or schizoaffective disorder (N=26) and matched comparison mothers without psychiatric illness (N=26). Comparisons were made for prenatal lateral ventricle width and head circumference, for neonatal intracranial, CSF, gray matter, white matter, and lateral ventricle volumes, and for neonatal diffusion properties of the genu and splenium of the corpus callosum and corticospinal tracts. Results Relative to the matched comparison subjects, the offspring of mothers with schizophrenia did not differ in prenatal lateral ventricle width or head circumference. Overall, the high-risk neonates had nonsignificantly larger intracranial, CSF, and lateral ventricle volumes. Subgroup analysis revealed that male high-risk infants had significantly larger intracranial, CSF, total gray matter, and lateral ventricle volumes; the female high-risk neonates were similar to the female comparison subjects. There were no group differences in white matter diffusion tensor properties. Conclusions Male neonates at genetic risk for schizophrenia had several larger than normal brain volumes, while females did not. To the authors' knowledge, this study provides the first evidence, in the context of its limitations, that early neonatal brain development may be abnormal in males at genetic risk for schizophrenia. PMID:20516153

The Superior Frontal Transsulcal Approach to the Anterior Ventricular System: Exploring the Sulcal and Subcortical Anatomy Using Anatomic Dissections and Diffusion Tensor Imaging Tractography.

PubMed

Koutsarnakis, Christos; Liakos, Faidon; Kalyvas, Aristotelis V; Skandalakis, Georgios P; Komaitis, Spyros; Christidi, Fotini; Karavasilis, Efstratios; Liouta, Evangelia; Stranjalis, George

2017-10-01

To explore the superior frontal sulcus (SFS) morphology, trajectory of the applied surgical corridor, and white matter bundles that are traversed during the superior frontal transsulcal transventricular approach. Twenty normal, adult, formalin-fixed cerebral hemispheres and 2 cadaveric heads were included in the study. The topography, morphology, and dimensions of the SFS were recorded in all specimens. Fourteen hemispheres were investigated through the fiber dissection technique whereas the remaining 6 were explored using coronal cuts. The cadaveric heads were used to perform the superior frontal transsulcal transventricular approach. In addition, 2 healthy volunteers underwent diffusion tensor imaging and tractography reconstruction studies. The SFS was interrupted in 40% of the specimens studied and was always parallel to the interhemispheric fissure. The proximal 5 cm of the SFS (starting from the SFS precentral sulcus meeting point) were found to overlie the anterior ventricular system in all hemispheres. Five discrete white matter layers were identified en route to the anterior ventricular system (i.e., the arcuate fibers, the frontal aslant tract, the external capsule, internal capsule, and the callosal radiations). Diffusion tensor imaging studies confirmed the fiber tract architecture. When feasible, the superior frontal transsulcal transventricular approach offers a safe and effective corridor to the anterior part of the lateral ventricle because it minimizes brain retraction and transgression and offers a wide and straightforward working corridor. Meticulous preoperative planning coupled with a sound microneurosurgical technique are prerequisites to perform the approach successfully. Copyright © 2017 Elsevier Inc. All rights reserved.

White-headed woodpecker nesting ecology after wildfire

Treesearch

Catherine S. Wightman; Victoria A. Saab; Chris Forristal; Kim Mellen-Mclean; Amy Markus

2010-01-01

Within forests susceptible to wildfire and insect infestations, land managers need to balance dead tree removal and habitat requirements for wildlife species associated with snags. We used Mahalanobis distance methods to develop predictive models of white-headed woodpecker (Picoides albolarvatus) nesting habitat in postfire ponderosa pine (Pinus ponderosa)-dominated...

Assessing Mastery Motivation in a Head Start Sample.

ERIC Educational Resources Information Center

MacPhee, David; Fritz, Janet J.; Miller-Heyl, Jan; Hite, Judy

Although mastery motivation appears to predict school success, individual assessment of mastery motivation is too time consuming and limits the application of this research. This study examined the psychometric properties of the Dimensions of Mastery Questionnaire (DMQ). The study focused on the validity of the measure for Head Start parents,…

The Relationship of Family Variables to Head Start Children's Preacademic Competence.

ERIC Educational Resources Information Center

Mantzicopoulos, Panayota Y.

1997-01-01

Examined contribution of family variables such as parenting and literacy activities to the pre-academic competence of 93 Head Start children. Found that maternal educational expectations, home literacy variables, and maternal school involvement were predictive of children's competence even after accounting for the effects of maternal education,…

Atomistic Modeling of Cation Diffusion in Transition Metal Perovskites La1-xSrxMnO3+/-δfor Solid Oxide Fuel Cell Cathodes Applications

NASA Astrophysics Data System (ADS)

Lee, Yueh-Lin; Duan, Yuhua; Morgan, Dane; Sorescu, Dan; Abernathy, Harry

Cation diffusion in La1-xSrxMnO3+/-δ (LSM) and in related perovskite materials play an important role in controlling long term performance and stability of solid oxide fuel cell (SOFCs) cathodes. Due to sluggish rates of cation diffusion and complex coupling between defect chemistry and cation diffusion pathways, currently there is still lack of quantitative theoretical model predictions on cation diffusivity vs. T and P(O2) to describe experimental cation tracer diffusivities. In this work, based on ab initio modeling of LSM defect chemistry and migration barriers of the possible cation diffusion pathways, we assess the rates of A-site and B-site cation diffusion in a wide range of T and P(O2) at x =0.0 and 0.2 for SOFC applications. We demonstrate the active cation diffusion pathways in LSM involve cation defect clusters as cation transport carriers, where reduction in the cation migration barriers, which are governed by the steric effect associated with the metal-oxygen cage in the perovskite lattice, is much greater than the penalty of repulsive interaction in the A-site and B-site cation vacancy clusters, leading to higher cation diffusion rates as compared to those of single cation vacancy hopping mechanisms. The predicted Mn and La/Sr cation self-diffusion coefficients of LSM at at x =0.0 and 0.2 along with their 1/T and P(O2) dependences, are in good agreement with the experimental tracer diffusion coefficients.

Role of MRI in osteosarcoma for evaluation and prediction of chemotherapy response: correlation with histological necrosis.

PubMed

Bajpai, Jyoti; Gamnagatti, Shivanand; Kumar, Rakesh; Sreenivas, Vishnubhatla; Sharma, Mehar Chand; Khan, Shah Alam; Rastogi, Shishir; Malhotra, Arun; Safaya, Rajni; Bakhshi, Sameer

2011-04-01

Histological necrosis, the current standard for response evaluation in osteosarcoma, is attainable after neoadjuvant chemotherapy. To establish the role of surrogate markers of response prediction and evaluation using MRI in the early phases of the disease. Thirty-one treatment-naïve osteosarcoma patients received three cycles of neoadjuvant chemotherapy followed by surgery during 2006-2008. All patients underwent baseline and post-chemotherapy conventional, diffusion-weighted and dynamic contrast-enhanced MRI. Taking histological response (good response ≥90% necrosis) as the reference standard, various parameters of MRI were compared to it. A tumor was considered ellipsoidal; volume, average tumor plane and its relative value (average tumor plane relative/body surface area) was calculated using the standard formula for ellipse. Receiver operating characteristic curves were generated to assess best threshold and predictability. After deriving thresholds for each parameter in univariable analysis, multivariable analysis was carried out. Both pre-and post-chemotherapy absolute and relative-size parameters correlated well with necrosis. Apparent diffusion coefficient did not correlate with necrosis; however, on adjusting for volume, significant correlation was found. Thus, we could derive a new parameter: diffusion per unit volume. In osteosarcoma, chemotherapy response can be predicted and evaluated by conventional and diffusion-weighted MRI early in the disease course and it correlates well with necrosis. Further, newly derived parameter diffusion per unit volume appears to be a sensitive substitute for response evaluation in osteosarcoma.

Prediction of future subsurface temperatures in Korea

NASA Astrophysics Data System (ADS)

Lee, Y.; Kim, S. K.; Jeong, J.; SHIN, E.

2017-12-01

The importance of climate change has been increasingly recognized because it has had the huge amount of impact on social, economic, and environmental aspect. For the reason, paleoclimate change has been studied intensively using different geological tools including borehole temperatures and future surface air temperatures (SATs) have been predicted for the local areas and the globe. Future subsurface temperatures can have also enormous impact on various areas and be predicted by an analytical method or a numerical simulation using measured and predicted SATs, and thermal diffusivity data of rocks. SATs have been measured at 73 meteorological observatories since 1907 in Korea and predicted at same locations up to the year of 2100. Measured SATs at the Seoul meteorological observatory increased by about 3.0 K from the year of 1907 to the present. Predicted SATs have 4 different scenarios depending on mainly CO2 concentration and national action plan on climate change in the future. The hottest scenario shows that SATs in Korea will increase by about 5.0 K from the present to the year of 2100. In addition, thermal diffusivity values have been measured on 2,903 rock samples collected from entire Korea. Data pretreatment based on autocorrelation analysis was conducted to control high frequency noise in thermal diffusivity data. Finally, future subsurface temperatures in Korea were predicted up to the year of 2100 by a FEM simulation code (COMSOL Multiphysics) using measured and predicted SATs, and thermal diffusivity data in Korea. At Seoul, the results of predictions show that subsurface temperatures will increase by about 5.4 K, 3.0 K, 1.5 K, and 0.2 K from the present to 2050 and then by about 7.9 K, 4.8 K, 2.5 K, and 0.5 K to 2100 at the depths of 10 m, 50 m, 100 m, and 200 m, respectively. We are now proceeding numerical simulations for subsurface temperature predictions for 73 locations in Korea.

Theoretical and experimental study on near infrared time-resolved optical diffuse tomography

NASA Astrophysics Data System (ADS)

Zhao, Huijuan; Gao, Feng; Tanikawa, Yukari; Yamada, Yukio

2006-08-01

Parts of the works of our group in the past five years on near infrared time-resolved (TR) optical tomography are summarized in this paper. The image reconstruction algorithm is based on Newton Raphson scheme with a datatype R generated from modified Generalized Pulse Spectrum Technique. Firstly, the algorithm is evaluated with simulated data from a 2-D model and the datatype R is compared with other popularly used datatypes. In this second part of the paper, the in vitro and in vivo NIR DOT imaging on a chicken leg and a human forearm, respectively are presented for evaluating both the image reconstruction algorithm and the TR measurement system. The third part of this paper is about the differential pathlength factor of human head while monitoring head activity with NIRS and applying the modified Lambert-Beer law. Benefiting from the TR system, the measured DPF maps of the three import areas of human head are presented in this paper.

Predicting drug-target interactions by dual-network integrated logistic matrix factorization

NASA Astrophysics Data System (ADS)

Hao, Ming; Bryant, Stephen H.; Wang, Yanli

2017-01-01

In this work, we propose a dual-network integrated logistic matrix factorization (DNILMF) algorithm to predict potential drug-target interactions (DTI). The prediction procedure consists of four steps: (1) inferring new drug/target profiles and constructing profile kernel matrix; (2) diffusing drug profile kernel matrix with drug structure kernel matrix; (3) diffusing target profile kernel matrix with target sequence kernel matrix; and (4) building DNILMF model and smoothing new drug/target predictions based on their neighbors. We compare our algorithm with the state-of-the-art method based on the benchmark dataset. Results indicate that the DNILMF algorithm outperforms the previously reported approaches in terms of AUPR (area under precision-recall curve) and AUC (area under curve of receiver operating characteristic) based on the 5 trials of 10-fold cross-validation. We conclude that the performance improvement depends on not only the proposed objective function, but also the used nonlinear diffusion technique which is important but under studied in the DTI prediction field. In addition, we also compile a new DTI dataset for increasing the diversity of currently available benchmark datasets. The top prediction results for the new dataset are confirmed by experimental studies or supported by other computational research.

Fabrication of All-SiC Fiber-Optic Pressure Sensors for High-Temperature Applications

PubMed Central

Jiang, Yonggang; Li, Jian; Zhou, Zhiwen; Jiang, Xinggang; Zhang, Deyuan

2016-01-01

Single-crystal silicon carbide (SiC)-based pressure sensors can be used in harsh environments, as they exhibit stable mechanical and electrical properties at elevated temperatures. A fiber-optic pressure sensor with an all-SiC sensor head was fabricated and is herein proposed. SiC sensor diaphragms were fabricated via an ultrasonic vibration mill-grinding (UVMG) method, which resulted in a small grinding force and low surface roughness. The sensor head was formed by hermetically bonding two layers of SiC using a nickel diffusion bonding method. The pressure sensor illustrated a good linearity in the range of 0.1–0.9 MPa, with a resolution of 0.27% F.S. (full scale) at room temperature. PMID:27763494

Fabrication of All-SiC Fiber-Optic Pressure Sensors for High-Temperature Applications.

PubMed

Jiang, Yonggang; Li, Jian; Zhou, Zhiwen; Jiang, Xinggang; Zhang, Deyuan

2016-10-17

Single-crystal silicon carbide (SiC)-based pressure sensors can be used in harsh environments, as they exhibit stable mechanical and electrical properties at elevated temperatures. A fiber-optic pressure sensor with an all-SiC sensor head was fabricated and is herein proposed. SiC sensor diaphragms were fabricated via an ultrasonic vibration mill-grinding (UVMG) method, which resulted in a small grinding force and low surface roughness. The sensor head was formed by hermetically bonding two layers of SiC using a nickel diffusion bonding method. The pressure sensor illustrated a good linearity in the range of 0.1-0.9 MPa, with a resolution of 0.27% F.S. (full scale) at room temperature.

Conventional vs. reduced field of view diffusion weighted imaging of the prostate: Comparison of image quality, correlation with histology, and inter-reader agreement.

PubMed

Warndahl, Brent A; Borisch, Eric A; Kawashima, Akira; Riederer, Stephen J; Froemming, Adam T

2018-04-01

To evaluate if Field of view Optimized and Constrained Undistorted Single shot (FOCUS) (GE Healthcare, Waukesha, WI) diffusion weighted images (DWI) provide more reliable imaging than conventional DWI, with non-inferior quantitative apparent diffusion coefficient (ADC) results. IRB approval was obtained for this study of 43 patients (44 exams, one patient with two visits) that underwent multiparametric prostate MRI with two DWI sequences and subsequent radical prostatectomy with histology as the gold standard. Randomized DWI sequence images were graded independently by two blinded experienced prostate MRI radiologists with a period of memory extinction between the two separate reading sessions. Blinded images were also reviewed head to head in a later session for direct comparison. Multiple parameters were measured from a region of interest in a dominant lesion as well as two control areas. Patient characteristics were collected by chart review. There was good correlation between the mean ADC value for lesions obtained by conventional and FOCUS DWI (ρ=0.85), with no trend toward any systematic difference, and equivalent correlation between ADC measurements and Gleason score. Agreement between the two readers was significantly higher for lesion ROI analysis with the FOCUS DWI derived ADC values (CCC 0.839) compared with the conventional ADC values (CCC 0.618; difference 0.221, 95% CI 0.01-0.46). FOCUS showed significantly better image quality scores (separate review: mean 2.17±0.6, p<0.001) compared to the conventional sequence (mean 2.65±0.6, p<0.001). In 13 cases the image quality was improved from grade of 3+ with conventional DWI to <3 with FOCUS DWI, a clinically meaningful improvement. Head-to-head blinded review found 61 ratings showed strong to slight preference for FOCUS, 13 no preference, and 14 slight preference for the conventional sequence. There was also a strong and equivalent correlation between both sequences and PIRADS version 2 grading (ρ=-0.56 and -0.58 for FOCUS and conventional, respectively, p<0.001 for both). FOCUS DWI of the prostate shows significant improvement in inter-reader agreement and image quality. As opposed to previous conflicting smaller studies, we found equivalent ADC metrics compared with the conventional DWI sequence, and preserved correlation with Gleason score. In 52% of patients the improved image quality with FOCUS had the potential to salvage exams with otherwise limited to non-diagnostic DWI. Copyright © 2017 Elsevier Inc. All rights reserved.

SEAWAT Version 4: A Computer Program for Simulation of Multi-Species Solute and Heat Transport

USGS Publications Warehouse

Langevin, Christian D.; Thorne, Daniel T.; Dausman, Alyssa M.; Sukop, Michael C.; Guo, Weixing

2008-01-01

The SEAWAT program is a coupled version of MODFLOW and MT3DMS designed to simulate three-dimensional, variable-density, saturated ground-water flow. Flexible equations were added to the program to allow fluid density to be calculated as a function of one or more MT3DMS species. Fluid density may also be calculated as a function of fluid pressure. The effect of fluid viscosity variations on ground-water flow was included as an option. Fluid viscosity can be calculated as a function of one or more MT3DMS species, and the program includes additional functions for representing the dependence on temperature. Although MT3DMS and SEAWAT are not explicitly designed to simulate heat transport, temperature can be simulated as one of the species by entering appropriate transport coefficients. For example, the process of heat conduction is mathematically analogous to Fickian diffusion. Heat conduction can be represented in SEAWAT by assigning a thermal diffusivity for the temperature species (instead of a molecular diffusion coefficient for a solute species). Heat exchange with the solid matrix can be treated in a similar manner by using the mathematically equivalent process of solute sorption. By combining flexible equations for fluid density and viscosity with multi-species transport, SEAWAT Version 4 represents variable-density ground-water flow coupled with multi-species solute and heat transport. SEAWAT Version 4 is based on MODFLOW-2000 and MT3DMS and retains all of the functionality of SEAWAT-2000. SEAWAT Version 4 also supports new simulation options for coupling flow and transport, and for representing constant-head boundaries. In previous versions of SEAWAT, the flow equation was solved for every transport timestep, regardless of whether or not there was a large change in fluid density. A new option was implemented in SEAWAT Version 4 that allows users to control how often the flow field is updated. New options were also implemented for representing constant-head boundaries with the Time-Variant Constant-Head (CHD) Package. These options allow for increased flexibility when using CHD flow boundaries with the zero-dispersive flux solute boundaries implemented by MT3DMS at constant-head cells. This report contains revised input instructions for the MT3DMS Dispersion (DSP) Package, Variable-Density Flow (VDF) Package, Viscosity (VSC) Package, and CHD Package. The report concludes with seven cases of an example problem designed to highlight many of the new features.

Hemodynamic and morphologic responses in mouse brain during acute head injury imaged by multispectral structured illumination

NASA Astrophysics Data System (ADS)

Volkov, Boris; Mathews, Marlon S.; Abookasis, David

2015-03-01

Multispectral imaging has received significant attention over the last decade as it integrates spectroscopy, imaging, tomography analysis concurrently to acquire both spatial and spectral information from biological tissue. In the present study, a multispectral setup based on projection of structured illumination at several near-infrared wavelengths and at different spatial frequencies is applied to quantitatively assess brain function before, during, and after the onset of traumatic brain injury in an intact mouse brain (n=5). For the production of head injury, we used the weight drop method where weight of a cylindrical metallic rod falling along a metal tube strikes the mouse's head. Structured light was projected onto the scalp surface and diffuse reflected light was recorded by a CCD camera positioned perpendicular to the mouse head. Following data analysis, we were able to concurrently show a series of hemodynamic and morphologic changes over time including higher deoxyhemoglobin, reduction in oxygen saturation, cell swelling, etc., in comparison with baseline measurements. Overall, results demonstrates the capability of multispectral imaging based structured illumination to detect and map of brain tissue optical and physiological properties following brain injury in a simple noninvasive and noncontact manner.

Modeling the mechanics of axonal fiber tracts using the embedded finite element method.

PubMed

Garimella, Harsha T; Kraft, Reuben H

2017-05-01

A subject-specific human head finite element model with embedded axonal fiber tractography obtained from diffusion tensor imaging was developed. The axonal fiber tractography finite element model was coupled with the volumetric elements in the head model using the embedded element method. This technique enables the calculation of axonal strains and real-time tracking of the mechanical response of the axonal fiber tracts. The coupled model was then verified using pressure and relative displacement-based (between skull and brain) experimental studies and was employed to analyze a head impact, demonstrating the applicability of this method in studying axonal injury. Following this, a comparison study of different injury criteria was performed. This model was used to determine the influence of impact direction on the extent of the axonal injury. The results suggested that the lateral impact loading is more dangerous compared to loading in the sagittal plane, a finding in agreement with previous studies. Through this analysis, we demonstrated the viability of the embedded element method as an alternative numerical approach for studying axonal injury in patient-specific human head models. Copyright © 2016 John Wiley & Sons, Ltd.

Chronic Traumatic Encephalopathy: A Potential Late Effect of Sport-Related Concussive and Subconcussive Head Trauma1

PubMed Central

Gavett, Brandon E.; Stern, Robert A.; McKee, Ann C.

2010-01-01

Synopsis Chronic traumatic encephalopathy (CTE) is a form of neurodegeneration that is believed to result from repeated head injuries. Originally termed dementia pugilistica due to its association with boxing, the neuropathology of CTE was first described by Corsellis in 1973 in a case series of 15 retired boxers. CTE has recently been found to occur following other causes of repeated head trauma, suggesting that any repeated blows to the head, such as those that occur due to American football, hockey, soccer, professional wrestling, and physical abuse, can also lead to neurodegenerative changes. These changes often include cerebral atrophy, cavum septum pellucidum with fenestrations, shrinkage of the mammillary bodies, dense tau immunoreactive inclusions (neurofibrillary tangles, glial tangles, and neuropil neurites), diffuse axonal injury, and, in some cases, a TDP-43 proteinopathy. In association with these pathological changes, affected individuals often exhibit disordered memory and executive functioning, behavioral and personality disturbances (e.g., apathy, depression, irritability, impulsiveness, suicidality), parkinsonism, and, occasionally, motor neuron disease. At the present time, there are no formal clinical or pathological diagnostic criteria for CTE, but the distinctive neuropathological profile of the disorder lends promise for future research into its prevention, diagnosis, and treatment. PMID:21074091

The Green’s functions for peridynamic non-local diffusion

PubMed Central

Wang, L. J.; Xu, J. F.

2016-01-01

In this work, we develop the Green’s function method for the solution of the peridynamic non-local diffusion model in which the spatial gradient of the generalized potential in the classical theory is replaced by an integral of a generalized response function in a horizon. We first show that the general solutions of the peridynamic non-local diffusion model can be expressed as functionals of the corresponding Green’s functions for point sources, along with volume constraints for non-local diffusion. Then, we obtain the Green’s functions by the Fourier transform method for unsteady and steady diffusions in infinite domains. We also demonstrate that the peridynamic non-local solutions converge to the classical differential solutions when the non-local length approaches zero. Finally, the peridynamic analytical solutions are applied to an infinite plate heated by a Gauss source, and the predicted variations of temperature are compared with the classical local solutions. The peridynamic non-local diffusion model predicts a lower rate of variation of the field quantities than that of the classical theory, which is consistent with experimental observations. The developed method is applicable to general diffusion-type problems. PMID:27713658

Release brochure for Amethyst Germplasm Hoary Tansyaster (Machaeranthera canescens)

Treesearch

Derek Tilley

2014-01-01

Hoary tansyaster is a short-lived perennial forb with pale to dark purple flowers. Plants are 6 to 30 inches tall with diffuse branching. Leaves are about 2 inches long and oblong or lance shaped with entire to sharply toothed margin. The flower heads have many subtending bracts that reflex away from the flower at the tip. These bracts are white and membranous at the...

Plant Guide: Hoary tansyaster (Machaeranthera canescens)

Treesearch

Derek Tilley; Dan Ogle; Loren St. John

2014-01-01

Sunflower family (Asteraceae). Hoary tansyaster is a short-lived perennial forb with pale to dark purple flowers. Plants are 15 to 75 cm (6 to 30 in) tall with diffuse branching. Leaves are about 5 cm (2 in) long and 6 mm (0.25 in) wide, oblong or lance shaped with entire to sharply toothed margin. Flower heads have many subtending bracts that reflex away from the...

The effect of solute concentration on hindered gradient diffusion in polymeric gels

NASA Astrophysics Data System (ADS)

Buck, Kristan K. S.; Dungan, Stephanie R.; Phillips, Ronald J.

1999-10-01

The effect of solute concentration on hindered diffusion of sphere-like colloidal solutes in stiff polymer hydrogels is examined theoretically and experimentally. In the theoretical development, it is shown that the presence of the gel fibres enhances the effect of concentration on the thermodynamic driving force for gradient diffusion, while simultaneously reducing the effect of concentration on the hydrodynamic drag. The result is that gradient diffusion depends more strongly on solute concentration in gels than it does in pure solution, by an amount that depends on the partition coefficient and hydraulic permeability of the gel solute system. Quantitative calculations are made to determine the concentration-dependent diffusivity correct to first order in solute concentration. In order to compare the theoretical predictions with experimental data, rates of diffusion have been measured for nonionic micelles and globular proteins in solution and agarose hydrogels at two gel concentrations. The measurements were performed by using holographic interferometry, through which one monitors changes in refractive index as gradient diffusion takes place within a transparent gel. If the solutes are modelled as spheres with short-range repulsive interactions, then the experimentally measured concentration dependence of the diffusivities of both the protein and micelles is in good agreement with the theoretical predictions.

Diffusion and convection in collagen gels: implications for transport in the tumor interstitium.

PubMed Central

Ramanujan, Saroja; Pluen, Alain; McKee, Trevor D; Brown, Edward B; Boucher, Yves; Jain, Rakesh K

2002-01-01

Diffusion coefficients of tracer molecules in collagen type I gels prepared from 0-4.5% w/v solutions were measured by fluorescence recovery after photobleaching. When adjusted to account for in vivo tortuosity, diffusion coefficients in gels matched previous measurements in four human tumor xenografts with equivalent collagen concentrations. In contrast, hyaluronan solutions hindered diffusion to a lesser extent when prepared at concentrations equivalent to those reported in these tumors. Collagen permeability, determined from flow through gels under hydrostatic pressure, was compared with predictions obtained from application of the Brinkman effective medium model to diffusion data. Permeability predictions matched experimental results at low concentrations, but underestimated measured values at high concentrations. Permeability measurements in gels did not match previous measurements in tumors. Visualization of gels by transmission electron microscopy and light microscopy revealed networks of long collagen fibers at lower concentrations along with shorter fibers at high concentrations. Negligible assembly was detected in collagen solutions pregelation. However, diffusion was similarly hindered in pre and postgelation samples. Comparison of diffusion and convection data in these gels and tumors suggests that collagen may obstruct diffusion more than convection in tumors. These findings have significant implications for drug delivery in tumors and for tissue engineering applications. PMID:12202388

High-b-value diffusion-weighted MR imaging for pretreatment prediction and early monitoring of tumor response to therapy in mice.

PubMed

Roth, Yiftach; Tichler, Thomas; Kostenich, Genady; Ruiz-Cabello, Jesus; Maier, Stephan E; Cohen, Jack S; Orenstein, Arie; Mardor, Yael

2004-09-01

To evaluate the use of diffusion-weighted magnetic resonance (MR) imaging with standard and high b values for pretreatment prediction and early detection of tumor response to various antineoplastic therapies in an animal model. Mice bearing C26 colon carcinoma tumors were treated with doxorubicin (n = 25) and with aminolevulinic acid-based photodynamic therapy (n = 23). Fourteen mice served as controls. Conventional T2-weighted fast spin-echo and diffusion-weighted MR images were acquired once before therapy and at 6, 24, and 48 hours after treatment. Pretreatment and early (1-2 days) posttreatment water diffusion parameters were calculated and compared with later changes in tumor volumes measured on conventional MR images by using the Pearson correlation test. In chemotherapy-treated tumors, a significant correlation (P <.002, r = 0.6) was observed between diffusion parameters that reflected tumor viability, measured prior to treatment, and changes in tumor volumes after therapy. This correlation implies that tumors with high pretreatment viability will respond better to chemotherapy than more necrotic tumors. In tumors treated with photodynamic therapy, no such correlation was found. Changes observed in water diffusion 1-2 days after treatment significantly correlated with later tumor growth rate for both therapies (P <.002, r = 0.54 for photodynamic therapy; P <.0003, r = 0.61 for chemotherapy). High-b-value diffusion-weighted MR imaging has potential use for the early detection of response to therapy and for predicting treatment outcome prior to initiation of chemotherapy. Copyright RSNA, 2004

Micro-scale pollution mechanism of dust diffusion in a blasting driving face based on CFD-DEM coupled model.

PubMed

Yu, Haiming; Cheng, Weimin; Xie, Yao; Peng, Huitian

2018-05-23

In order to investigate the diffuse pollution mechanisms of high-concentration dusts in the blasting driving face, the airflow-dust coupled model was constructed based on CFD-DEM coupled model; the diffusion rules of the dusts with different diameters at microscopic scale were analyzed in combination with the field measured results. The simulation results demonstrate that single-exhaust ventilation exhibited more favorable dust suppression performance than single-forced ventilation. Under single-exhaust ventilation condition, the motion trajectories of the dusts with the diameter smaller than 20 μm were close to the airflow streamline and these dusts were mainly distributed near the footway walls; by contrast, under single-forced ventilation condition, the motion trajectories of the dust particles with a diameter range of 20~40 μm were close to the airflow streamlines, and a large number of dusts with the diameter smaller than 20 μm accumulated in the regions 5 m and 17~25 m away from the head-on section. Moreover, under the single-exhaust ventilation, the relationship between dust diameter D and negative-pressured-induced dust emission ratio P can be expressed as P = - 25.03ln(D) + 110.39, and the dust emission ratio was up to 74.36% for 7-μm dusts, and the path-dependent settling behaviors of the dusts mainly occurred around the head-on section; under single-forced ventilation condition, the z value of the dusts with the diameter over 20 μm decreased and the dusts with a diameter smaller than 7 μm are particularly harmful to human health, but their settling ratios were below 22.36%. Graphical abstract The airflow-dust CFD-DEM coupling model was established. The numerical simulation results were verified. The migration laws of airflow field were obtained in a blasting driving face. The diffusion laws of dusts were obtained after blasting.

TU-F-CAMPUS-I-01: Head and Neck Squamous Cell Carcinoma: Short-Term Repeatability of Apparent Diffusion Coefficient and Intravoxel Incoherent Motion Parameters at 3.0T

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

Ding, Y; Fuller, C; Mohamed, A

2015-06-15

Purpose: Many published studies have recently demonstrated the potential value of intravoxel incoherent motion (IVIM) analysis for disease evaluation. However, few have questioned its measurement repeatability/reproducibility when applied. The purpose of this study was to determine the short-term measurement repeatability of apparent diffusion coefficient ADC, true diffusion coefficient D, pseudodiffusion coefficient D* and perfusion fraction f, in head and neck squamous cell carcinoma (HNSCC) primary tumors and metastatic nodes. Methods: Ten patients with known HNSCC were examined twice using echo-planar DW-MRI with 12 b values (0 to 800 s/mm2) 1hour to 24 hours apart before radiation treatment. All patients weremore » scanned with the customized radiation treatment immobilization devices to reduce motion artifacts and to improve image registration in repeat scans. Regions of interests were drawn in primary tumor and metastases node in each patient (Fig. 1). ADC and IVIM parameters D, D* and f were calculated by least squares data fitting. Short-term test–retest repeatability of ADC and IVIM parameters were assessed by measuring Bland–Altman limits of agreements (BA-LA). Results: Sixteen HNSCC lesions were assessed in 10 patients. Repeatability of perfusion-sensitive parameters, D* and f, in HNSCC lesions was poor (BA-LA: -144% to 88% and −57% to 96% for D* and f, respectively); a lesser extent was observed for the diffusion-sensitive parameters of ADC and D (BA-LA: −34% to 39% and −37% to 40%, for ADC and D, respectively) (Fig. 2). Conclusion: Poor repeatability of D*/f and good repeatability for ADC/D were observed in HNSCC primary tumors and metastatic nodes. Efforts should be made to improve the measurement repeatability of perfusion-sensitive IVIM parameters.« less

Conformational dynamics of a crystalline protein from microsecond-scale molecular dynamics simulations and diffuse X-ray scattering

DOE PAGES

Wall, Michael E.; Van Benschoten, Andrew H.; Sauter, Nicholas K.; ...

2014-12-01

X-ray diffraction from protein crystals includes both sharply peaked Bragg reflections and diffuse intensity between the peaks. The information in Bragg scattering is limited to what is available in the mean electron density. The diffuse scattering arises from correlations in the electron density variations and therefore contains information about collective motions in proteins. Previous studies using molecular-dynamics (MD) simulations to model diffuse scattering have been hindered by insufficient sampling of the conformational ensemble. To overcome this issue, we have performed a 1.1-μs MD simulation of crystalline staphylococcal nuclease, providing 100-fold more sampling than previous studies. This simulation enables reproducible calculationsmore » of the diffuse intensity and predicts functionally important motions, including transitions among at least eight metastable states with different active-site geometries. The total diffuse intensity calculated using the MD model is highly correlated with the experimental data. In particular, there is excellent agreement for the isotropic component of the diffuse intensity, and substantial but weaker agreement for the anisotropic component. The decomposition of the MD model into protein and solvent components indicates that protein–solvent interactions contribute substantially to the overall diffuse intensity. In conclusion, diffuse scattering can be used to validate predictions from MD simulations and can provide information to improve MD models of protein motions.« less

Conformational dynamics of a crystalline protein from microsecond-scale molecular dynamics simulations and diffuse X-ray scattering

PubMed Central

Wall, Michael E.; Van Benschoten, Andrew H.; Sauter, Nicholas K.; Adams, Paul D.; Fraser, James S.; Terwilliger, Thomas C.

2014-01-01

X-ray diffraction from protein crystals includes both sharply peaked Bragg reflections and diffuse intensity between the peaks. The information in Bragg scattering is limited to what is available in the mean electron density. The diffuse scattering arises from correlations in the electron density variations and therefore contains information about collective motions in proteins. Previous studies using molecular-dynamics (MD) simulations to model diffuse scattering have been hindered by insufficient sampling of the conformational ensemble. To overcome this issue, we have performed a 1.1-μs MD simulation of crystalline staphylococcal nuclease, providing 100-fold more sampling than previous studies. This simulation enables reproducible calculations of the diffuse intensity and predicts functionally important motions, including transitions among at least eight metastable states with different active-site geometries. The total diffuse intensity calculated using the MD model is highly correlated with the experimental data. In particular, there is excellent agreement for the isotropic component of the diffuse intensity, and substantial but weaker agreement for the anisotropic component. Decomposition of the MD model into protein and solvent components indicates that protein–solvent interactions contribute substantially to the overall diffuse intensity. We conclude that diffuse scattering can be used to validate predictions from MD simulations and can provide information to improve MD models of protein motions. PMID:25453071

Measurement of effective air diffusion coefficients for trichloroethene in undisturbed soil cores.

PubMed

Bartelt-Hunt, Shannon L; Smith, James A

2002-06-01

In this study, we measure effective diffusion coefficients for trichloroethene in undisturbed soil samples taken from Picatinny Arsenal, New Jersey. The measured effective diffusion coefficients ranged from 0.0053 to 0.0609 cm2/s over a range of air-filled porosity of 0.23-0.49. The experimental data were compared to several previously published relations that predict diffusion coefficients as a function of air-filled porosity and porosity. A multiple linear regression analysis was developed to determine if a modification of the exponents in Millington's [Science 130 (1959) 100] relation would better fit the experimental data. The literature relations appeared to generally underpredict the effective diffusion coefficient for the soil cores studied in this work. Inclusion of a particle-size distribution parameter, d10, did not significantly improve the fit of the linear regression equation. The effective diffusion coefficient and porosity data were used to recalculate estimates of diffusive flux through the subsurface made in a previous study performed at the field site. It was determined that the method of calculation used in the previous study resulted in an underprediction of diffusive flux from the subsurface. We conclude that although Millington's [Science 130 (1959) 100] relation works well to predict effective diffusion coefficients in homogeneous soils with relatively uniform particle-size distributions, it may be inaccurate for many natural soils with heterogeneous structure and/or non-uniform particle-size distributions.

Cu-Zn binary phase diagram and diffusion couples

NASA Technical Reports Server (NTRS)

Mccoy, Robert A.

1992-01-01

The objectives of this paper are to learn: (1) what information a binary phase diagram can yield; (2) how to construct and heat treat a simple diffusion couple; (3) how to prepare a metallographic sample; (4) how to operate a metallograph; (5) how to correlate phases found in the diffusion couple with phases predicted by the phase diagram; (6) how diffusion couples held at various temperatures could be used to construct a phase diagram; (7) the relation between the thickness of an intermetallic phase layer and the diffusion time; and (8) the effect of one species of atoms diffusing faster than another species in a diffusion couple.

Transverse Diffusivity of Cerebral Parenchyma Predicts Visual Tracking Performance in Relapsing-Remitting Multiple Sclerosis

ERIC Educational Resources Information Center

Warlop, Nele P.; Achten, Eric; Fieremans, Els; Debruyne, Jan; Vingerhoets, Guy

2009-01-01

This study investigated the relation between cerebral damage related to multiple sclerosis (MS) and cognitive decline as determined by two classical mental tracking tests. Cerebral damage in 15 relapsing-remitting MS patients was measured by diffusion tensor imaging (DTI). Fractional anisotropy, longitudinal and transverse diffusivity were defined…

Experimental and computational data from a small rocket exhaust diffuser

NASA Astrophysics Data System (ADS)

Stephens, Samuel E.

1993-06-01

The Diagnostics Testbed Facility (DTF) at the NASA Stennis Space Center in Mississippi is a versatile facility that is used primarily to aid in the development of nonintrusive diagnostics for liquid rocket engine testing. The DTF consists of a fixed, 1200 lbf thrust, pressure fed, liquid oxygen/gaseous hydrogen rocket engine, and associated support systems. An exhaust diffuser has been fabricated and installed to provide subatmospheric pressures at the exit of the engine. The diffuser aerodynamic design was calculated prior to fabrication using the PARC Navier-Stokes computational fluid dynamics code. The diffuser was then fabricated and tested at the DTF. Experimental data from these tests were acquired to determine the operational characteristics of the system and to correlate the actual and predicted flow fields. The results show that a good engineering approximation of overall diffuser performance can be made using the PARC Navier-Stokes code and a simplified geometry. Correlations between actual and predicted cell pressure and initial plume expansion in the diffuser are good; however, the wall pressure profiles do not correlate as well with the experimental data.

Sorption and modeling of mass transfer of toxic chemical vapors in activated-carbon fiber-cloth adsorbers

USGS Publications Warehouse

Lordgooei, M.; Sagen, J.; Rood, M.J.; Rostam-Abadi, M.

1998-01-01

A new activated-carbon fiber-cloth (ACFC) adsorber coupled with an electrothermal regenerator and a cryogenic condenser was designed and developed to efficiently capture and recover toxic chemical vapors (TCVs) from simulated industrial gas streams. The system was characterized for adsorption by ACFC, electrothermal desorption, and cryogenic condensation to separate acetone and methyl ethyl ketone from gas streams. Adsorption dynamics are numerically modeled to predict system characteristics during scale-up and optimization of the process in the future. The model requires diffusivities of TCVs into an activated-carbon fiber (ACF) as an input. Effective diffusivities of TCVs into ACFs were modeled as a function of temperature, concentration, and pore size distribution. Effective diffusivities for acetone at 65 ??C and 30-60 ppmv were measured using a chromatography method. The energy factor for surface diffusion was determined from comparison between the experimental and modeled effective diffusivities. The modeled effective diffusivities were used in a dispersive computational model to predict mass transfer zones of TCVs in fixed beds of ACFC under realistic conditions for industrial applications.

Experimental measurement of coil-rod-coil block copolymer tracer diffusion through entangled coil homopolymers

PubMed Central

Wang, Muzhou; Timachova, Ksenia; Olsen, Bradley D.

2014-01-01

The diffusion of coil-rod-coil triblock copolymers in entangled coil homopolymers is experimentally measured and demonstrated to be significantly slower than rod or coil homopolymers of the same molecular weight. A model coil-rod-coil triblock was prepared by expressing rodlike alanine-rich α-helical polypeptides in E. coli and conjugating coillike poly(ethylene oxide) (PEO) to both ends to form coil-rod-coil triblock copolymers. Tracer diffusion through entangled PEO homopolymer melts was measured using forced Rayleigh scattering at various rod lengths, coil molecular weights, and coil homopolymer concentrations. For rod lengths, L, that are close to the entanglementh length, a, the ratio between triblock diffusivity and coil homopolymer diffusivity decreases monotonically and is only a function of L/a, in quantitative agreement with previous simulation results. For large rod lengths, diffusion follows an arm retraction scaling, which is also consistent with previous theoretical predictions. These experimental results support the key predictions of theory and simulation, suggesting that the mismatch in curvature between rod and coil entanglement tubes leads to the observed diffusional slowing. PMID:25484454

Motion Artifact Reduction in Pediatric Diffusion Tensor Imaging Using Fast Prospective Correction

PubMed Central

Alhamud, A.; Taylor, Paul A.; Laughton, Barbara; van der Kouwe, André J.W.; Meintjes, Ernesta M.

2014-01-01

Purpose To evaluate the patterns of head motion in scans of young children and to examine the influence of corrective techniques, both qualitatively and quantitatively. We investigate changes that both retrospective (with and without diffusion table reorientation) and prospective (implemented with a short navigator sequence) motion correction induce in the resulting diffusion tensor measures. Materials and Methods Eighteen pediatric subjects (aged 5–6 years) were scanned using 1) a twice-refocused, 2D diffusion pulse sequence, 2) a prospectively motion-corrected, navigated diffusion sequence with reacquisition of a maximum of five corrupted diffusion volumes, and 3) a T1-weighted structural image. Mean fractional anisotropy (FA) values in white and gray matter regions, as well as tractography in the brainstem and projection fibers, were evaluated to assess differences arising from retrospective (via FLIRT in FSL) and prospective motion correction. In addition to human scans, a stationary phantom was also used for further evaluation. Results In several white and gray matter regions retrospective correction led to significantly (P < 0.05) reduced FA means and altered distributions compared to the navigated sequence. Spurious tractographic changes in the retrospectively corrected data were also observed in subject data, as well as in phantom and simulated data. Conclusion Due to the heterogeneity of brain structures and the comparatively low resolution (~2 mm) of diffusion data using 2D single shot sequencing, retrospective motion correction is susceptible to distortion from partial voluming. These changes often negatively bias diffusion tensor imaging parameters. Prospective motion correction was shown to produce smaller changes. PMID:24935904

Motion artifact reduction in pediatric diffusion tensor imaging using fast prospective correction.

PubMed

Alhamud, A; Taylor, Paul A; Laughton, Barbara; van der Kouwe, André J W; Meintjes, Ernesta M

2015-05-01

To evaluate the patterns of head motion in scans of young children and to examine the influence of corrective techniques, both qualitatively and quantitatively. We investigate changes that both retrospective (with and without diffusion table reorientation) and prospective (implemented with a short navigator sequence) motion correction induce in the resulting diffusion tensor measures. Eighteen pediatric subjects (aged 5-6 years) were scanned using 1) a twice-refocused, 2D diffusion pulse sequence, 2) a prospectively motion-corrected, navigated diffusion sequence with reacquisition of a maximum of five corrupted diffusion volumes, and 3) a T1 -weighted structural image. Mean fractional anisotropy (FA) values in white and gray matter regions, as well as tractography in the brainstem and projection fibers, were evaluated to assess differences arising from retrospective (via FLIRT in FSL) and prospective motion correction. In addition to human scans, a stationary phantom was also used for further evaluation. In several white and gray matter regions retrospective correction led to significantly (P < 0.05) reduced FA means and altered distributions compared to the navigated sequence. Spurious tractographic changes in the retrospectively corrected data were also observed in subject data, as well as in phantom and simulated data. Due to the heterogeneity of brain structures and the comparatively low resolution (∼2 mm) of diffusion data using 2D single shot sequencing, retrospective motion correction is susceptible to distortion from partial voluming. These changes often negatively bias diffusion tensor imaging parameters. Prospective motion correction was shown to produce smaller changes. © 2014 Wiley Periodicals, Inc.

Predictors of early growth in academic achievement: the head-toes-knees-shoulders task

PubMed Central

McClelland, Megan M.; Cameron, Claire E.; Duncan, Robert; Bowles, Ryan P.; Acock, Alan C.; Miao, Alicia; Pratt, Megan E.

2014-01-01

Children's behavioral self-regulation and executive function (EF; including attentional or cognitive flexibility, working memory, and inhibitory control) are strong predictors of academic achievement. The present study examined the psychometric properties of a measure of behavioral self-regulation called the Head-Toes-Knees-Shoulders (HTKS) by assessing construct validity, including relations to EF measures, and predictive validity to academic achievement growth between prekindergarten and kindergarten. In the fall and spring of prekindergarten and kindergarten, 208 children (51% enrolled in Head Start) were assessed on the HTKS, measures of cognitive flexibility, working memory (WM), and inhibitory control, and measures of emergent literacy, mathematics, and vocabulary. For construct validity, the HTKS was significantly related to cognitive flexibility, working memory, and inhibitory control in prekindergarten and kindergarten. For predictive validity in prekindergarten, a random effects model indicated that the HTKS significantly predicted growth in mathematics, whereas a cognitive flexibility task significantly predicted growth in mathematics and vocabulary. In kindergarten, the HTKS was the only measure to significantly predict growth in all academic outcomes. An alternative conservative analytical approach, a fixed effects analysis (FEA) model, also indicated that growth in both the HTKS and measures of EF significantly predicted growth in mathematics over four time points between prekindergarten and kindergarten. Results demonstrate that the HTKS involves cognitive flexibility, working memory, and inhibitory control, and is substantively implicated in early achievement, with the strongest relations found for growth in achievement during kindergarten and associations with emergent mathematics. PMID:25071619

On the Nature of the Variability Power Decay towards Soft Spectral States in X-Ray Binaries. Case Study in Cyg X-1

NASA Technical Reports Server (NTRS)

Titarchuk, Lev; Shaposhinikov, Nikolai

2007-01-01

A characteristic feature of the Fourier Power Density Spectrum (PDS) observed from black hole X-ray binaries in low/hard and intermediate spectral states is a broad band-limited noise, characterized by a constant below some frequency (a "break" frequency) and a power law above this frequency. It has been shown that the variability of this type can be produced by the inward diffusion of the local driving perturbations in a bounded configuration (accretion disk or corona). In the framework of this model, the perturbation diffusion time to is related to the phenomenological break frequency, while the PDS power-law slope above the "break" is determined by the viscosity distribution over the configuration. The perturbation diffusion scenario explains the decay of the power of X-ray variability observed in a number of compact sources (containing black hole and neutron star) during an evolution of theses sources from low/hard to high/soft states. We compare the model predictions with the subset of data from Cyg X-1 collected by the Rossi X-ray Time Explorer (RXTE). Our extensive analysis of the Cyg X-1 PDSs demonstrates that the observed integrated power P(sub x), decreases approximately as a square root of the characteristic frequency of the driving oscillations v(sub dr). The RXTE observations of Cyg X-1 allow us to infer P(sub dr), and t(sub o) as a function of v(sub dr). We also apply the basic parameters of observed PDSs, power-law index and low frequency quasiperiodic oscillations. to infer Reynolds (Re) number from the observations using the method developed in our previous paper. Our analysis shows that Re-number increases from values about 10 in low/hard state to that about 70 during the high/soft state. Subject headings: accretion, accretion disks-black hole physics-stars:individual (Cyg X-1) :radiation mechanisms: nonthermal-physical data and processes

Interferometric measurements of a dendritic growth front solutal diffusion layer

NASA Technical Reports Server (NTRS)

Hopkins, John A.; Mccay, T. D.; Mccay, Mary H.

1991-01-01

An experimental study was undertaken to measure solutal distributions in the diffusion layer produced during the vertical directional solidification (VDS) of an ammonium chloride - water (NH4Cl-H2O) solution. Interferometry was used to obtain concentration measurements in the 1-2 millimeter region defining the diffusion layer. These measurements were fitted to an exponential form to extract the characteristic diffusion parameter for various times after the start of solidification. The diffusion parameters are within the limits predicted by steady state theory and suggest that the effective solutal diffusivity is increasing as solidification progresses.

Sensitivity study on durability variables of marine concrete structures

NASA Astrophysics Data System (ADS)

Zhou, Xin'gang; Li, Kefei

2013-06-01

In order to study the influence of parameters on durability of marine concrete structures, the parameter's sensitivity analysis was studied in this paper. With the Fick's 2nd law of diffusion and the deterministic sensitivity analysis method (DSA), the sensitivity factors of apparent surface chloride content, apparent chloride diffusion coefficient and its time dependent attenuation factor were analyzed. The results of the analysis show that the impact of design variables on concrete durability was different. The values of sensitivity factor of chloride diffusion coefficient and its time dependent attenuation factor were higher than others. Relative less error in chloride diffusion coefficient and its time dependent attenuation coefficient induces a bigger error in concrete durability design and life prediction. According to probability sensitivity analysis (PSA), the influence of mean value and variance of concrete durability design variables on the durability failure probability was studied. The results of the study provide quantitative measures of the importance of concrete durability design and life prediction variables. It was concluded that the chloride diffusion coefficient and its time dependent attenuation factor have more influence on the reliability of marine concrete structural durability. In durability design and life prediction of marine concrete structures, it was very important to reduce the measure and statistic error of durability design variables.