Desquamative interstitial pneumonia associated with chrysotile asbestos fibres.

PubMed Central

Freed, J A; Miller, A; Gordon, R E; Fischbein, A; Kleinerman, J; Langer, A M

1991-01-01

The drywall construction trade has in the past been associated with exposure to airborne asbestos fibres. This paper reports a drywall construction worker with 32 years of dust exposure who developed dyspnoea and diminished diffusing capacity, and showed diffuse irregular opacities on chest radiography. He did not respond to treatment with corticosteroids. Open lung biopsy examination showed desquamative interstitial pneumonia. Only a single ferruginous body was seen on frozen section, but tissue examination by electron microscopy showed an extraordinary pulmonary burden of mineral dust with especially high concentrations of chrysotile asbestos fibres. This report emphasises the need to consider asbestos fibre as an agent in the aetiology of desquamative interstitial pneumonia. The coexistent slight interstitial fibrosis present in this case is also considered to have resulted from exposure to mineral dust, particularly ultramicroscopic asbestos fibres. Images PMID:1645584

Partitioning and diffusion of PBDEs through an HDPE geomembrane.

PubMed

Rowe, R Kerry; Saheli, Pooneh T; Rutter, Allison

2016-09-01

Polybrominated diphenyl ether (PBDE) has been measured in MSW landfill leachate and its migration through a modern landfill liner has not been investigated previously. To assure environmental protection, it is important to evaluate the efficacy of landfill liners for controlling the release of PBDE to the environment to a negligible level. The partitioning and diffusion of a commercial mixture of PBDEs (DE-71: predominantly containing six congeners) with respect to a high-density polyethylene (HDPE) geomembrane is examined. The results show that the partitioning coefficients of the six congeners in this mixture range from 700,000 to 7,500,000 and the diffusion coefficients range from 1.3 to 6.0×10(-15)m(2)/s depending on the congener. This combination of very high partitioning coefficients and very low diffusion coefficients suggest that a well constructed HDPE geomembrane liner will be an extremely effective barrier for PBDEs with respect to diffusion from a municipal solid waste landfill, as illustrated by an example. The results for pure diffusion scenario showed that the congeners investigated meet the guidelines by at least a factor of three for an effective geomembrane liner where diffusion is the controlling transport mechanism. Copyright © 2016 Elsevier Ltd. All rights reserved.

Modeling gas displacement kinetics in coal with Maxwell-Stefan diffusion theory

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

Wei, X.R.; Wang, G.X.; Massarotto, P.

2007-12-15

The kinetics of binary gas counter-diffusion and Darcy flow in a large coal sample were modeled, and the results compared with data from experimental laboratory investigations. The study aimed for a better understanding of the CO{sub 2}-sequestration enhanced coalbed methane (ECBM) recovery process. The transport model used was based on the bidisperse diffusion mechanism and Maxwell-Stefan (MS) diffusion theory. This provides an alternative approach to simulate multicomponent gas diffusion and flow in bulk coals. A series of high-stress core flush tests were performed on a large coal sample sourced from a Bowen Basin coal mine in Queensland, Australia to investigatemore » the kinetics of one gas displacing another. These experimental results were used to derive gas diffusivities, and to examine the predictive capability of the diffusion model. The simulations show good agreements with the displacement experiments revealing that MS diffusion theory is superior for describing diffusion of mixed gases in coals compared with the constant Fick diffusivity model. The optimized effective micropore and macropore diffusivities are comparable with experimental measurements achieved by other researchers.« less

Basal cell carcinoma: CD56 and cytokeratin 5/6 staining patterns in the differential diagnosis with Merkel cell carcinoma.

PubMed

Panse, Gauri; McNiff, Jennifer M; Ko, Christine J

2017-06-01

Basal cell carcinoma (BCC) can resemble Merkel cell carcinoma (MCC) on histopathological examination and while CK20 is a useful marker in this differential, it is occasionally negative in MCC. CD56, a sensitive marker of neuroendocrine differentiation, is sometimes used to identify MCC, but has been reportedly variably positive in BCC as well. In contrast, CK5/6 consistently labels BCC but is not expressed in neuroendocrine tumors. We evaluated 20 cases of BCC for the pattern of CD56 and cytokeratin 5/6 (CK5/6) staining, hypothesizing that these 2 stains could differentiate BCC from MCC in difficult cases. Seventeen cases of MCC previously stained with CD56 were also examined. All BCCs showed patchy expression of CD56 except for 2 cases, which showed staining of greater than 70% of tumor. CK5/6 was diffusely positive in all cases of BCC. Fifteen of 17 MCCs were diffusely positive for CD56. The difference in the pattern of CD56 expression between MCC and BCC (diffuse vs patchy, respectively) was statistically significant (P < .05). BCC typically shows patchy CD56 expression and diffuse CK5/6 positivity. These 2 markers can be used to distinguish between BCC and MCC in challenging cases. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

An MRI study of white matter tract integrity in regular cannabis users: effects of cannabis use and age.

PubMed

Jakabek, David; Yücel, Murat; Lorenzetti, Valentina; Solowij, Nadia

2016-10-01

Conflicting evidence exists on the effects of cannabis use on brain white matter integrity. The extant literature has exclusively focused on younger cannabis users, with no studies sampling older cannabis users. We recruited a sample with a broad age range to examine the integrity of major white matter tracts in association with cannabis use parameters and neurodevelopmental stage. Regular cannabis users (n = 56) and non-users (n = 20) with a mean age of 32 (range 18-55 years) underwent structural and diffusion MRI scans. White matter was examined using voxel-based statistics and via probabilistic tract reconstruction. The integrity of tracts was assessed using average fractional anisotropy, axial diffusivity and radial diffusivity. Diffusion measures were compared between users and non-users and as group-by-age interactions. Correlations between diffusion measures and age of onset, duration, frequency and dose of current cannabis use were examined. Cannabis users overall had lower fractional anisotropy than healthy non-users in the forceps minor tract only (p = .015, partial eta = 0.07), with no voxel-wise differences observed. Younger users showed predominantly reduced axial diffusivity, whereas older users had higher radial diffusivity in widespread tracts. Higher axial diffusivity was associated with duration of cannabis use in the cingulum angular bundle (beta = 5.00 × 10(-5), p = .003). Isolated higher AD in older cannabis users was also observed. The findings suggest that exogenous cannabinoids alter normal brain maturation, with differing effects at various neurodevelopmental stages of life. These age-related differences are posited to account for the disparate results described in the literature.

Genetic relatedness of axial and radial diffusivity indices of cerebral white matter microstructure in late middle age.

PubMed

Hatton, Sean N; Panizzon, Matthew S; Vuoksimaa, Eero; Hagler, Donald J; Fennema-Notestine, Christine; Rinker, Daniel; Eyler, Lisa T; Franz, Carol E; Lyons, Michael J; Neale, Michael C; Tsuang, Ming T; Dale, Anders M; Kremen, William S

2018-05-01

Two basic neuroimaging-based characterizations of white matter tracts are the magnitude of water diffusion along the principal tract orientation (axial diffusivity, AD) and water diffusion perpendicular to the principal orientation (radial diffusivity, RD). It is generally accepted that decreases in AD reflect disorganization, damage, or loss of axons, whereas increases in RD are indicative of disruptions to the myelin sheath. Previous reports have detailed the heritability of individual AD and RD measures, but have not examined the extent to which the same or different genetic or environmental factors influence these two phenotypes (except for corpus callosum). We implemented bivariate twin analyses to examine the shared and independent genetic influences on AD and RD. In the Vietnam Era Twin Study of Aging, 393 men (mean age = 61.8 years, SD = 2.6) underwent diffusion-weighted magnetic resonance imaging. We derived fractional anisotropy (FA), mean diffusivity (MD), AD, and RD estimates for 11 major bilateral white matter tracts and the mid-hemispheric corpus callosum, forceps major, and forceps minor. Separately, AD and RD were each highly heritable. In about three-quarters of the tracts, genetic correlations between AD and RD were >.50 (median = .67) and showed both unique and common variance. Genetic variance of FA and MD were predominately explained by RD over AD. These findings are important for informing genetic association studies of axonal coherence/damage and myelination/demyelination. Thus, genetic studies would benefit from examining the shared and unique contributions of AD and RD. © 2018 Wiley Periodicals, Inc.

Clinical, pathological, and neuroimaging analyses of two cases of Leigh syndrome in a Chinese family.

PubMed

Jin, Taoran; Shen, Hongrui; Zhao, Zhe; Hu, Jing

2014-11-01

In this study, the authors examined the clinical manifestations, skeletal muscle pathological characteristics, and neuroimaging results of 2 cases of Leigh syndrome in a Chinese family. The 2 patients presented with general weakness, and 1 of them presented with an impairment of vision. Skeletal muscle biopsies showed a deficiency in cytochrome c oxidase levels. Brain magnetic resonance imaging showed increased T1 and T2 signal intensities in the centrum ovale and dentate nucleus. Diffusion-weighted imaging showed a high-intensity signal. Magnetic resonance spectroscopy showed elevated levels of lactic acid in lesions. The examination of 1 patient at disease onset and during disease remission showed that the lesions detected by magnetic resonance imaging and diffusion-weighted imaging, and the peak for lactic acid detected by magnetic resonance spectroscopy, decreased during remission. These data suggest that changes in the imaging results of patients with Leigh syndrome correlate with disease course and pathogenetic condition. © The Author(s) 2014.

A Combination of Ex vivo Diffusion MRI and Multiphoton to Study Microglia/Monocytes Alterations after Spinal Cord Injury

PubMed Central

Noristani, Harun N.; Boukhaddaoui, Hassan; Saint-Martin, Guillaume; Auzer, Pauline; Sidiboulenouar, Rahima; Lonjon, Nicolas; Alibert, Eric; Tricaud, Nicolas; Goze-Bac, Christophe; Coillot, Christophe; Perrin, Florence E.

2017-01-01

Central nervous system (CNS) injury has been observed to lead to microglia activation and monocytes infiltration at the lesion site. Ex vivo diffusion magnetic resonance imaging (diffusion MRI or DWI) allows detailed examination of CNS tissues, and recent advances in clearing procedures allow detailed imaging of fluorescent-labeled cells at high resolution. No study has yet combined ex vivo diffusion MRI and clearing procedures to establish a possible link between microglia/monocytes response and diffusion coefficient in the context of spinal cord injury (SCI). We carried out ex vivo MRI of the spinal cord at different time-points after spinal cord transection followed by tetrahydrofuran based clearing and examined the density and morphology of microglia/monocytes using two-photon microscopy. Quantitative analysis revealed an early marked increase in microglial/monocytes density that is associated with an increase in the extension of the lesion measured using diffusion MRI. Morphological examination of microglia/monocytes somata at the lesion site revealed a significant increase in their surface area and volume as early as 72 hours post-injury. Time-course analysis showed differential microglial/monocytes response rostral and caudal to the lesion site. Microglia/monocytes showed a decrease in reactivity over time caudal to the lesion site, but an increase was observed rostrally. Direct comparison of microglia/monocytes morphology, obtained through multiphoton, and the longitudinal apparent diffusion coefficient (ADC), measured with diffusion MRI, highlighted that axonal integrity does not correlate with the density of microglia/monocytes or their somata morphology. We emphasize that differential microglial/monocytes reactivity rostral and caudal to the lesion site may thus coincide, at least partially, with reported temporal differences in debris clearance. Our study demonstrates that the combination of ex vivo diffusion MRI and two-photon microscopy may be used to follow structural tissue alteration. Lesion extension coincides with microglia/monocytes density; however, a direct relationship between ADC and microglia/monocytes density and morphology was not observed. We highlighted a differential rostro-caudal microglia/monocytes reactivity that may correspond to a temporal difference in debris clearance and axonal integrity. Thus, potential therapeutic strategies targeting microglia/monocytes after SCI may need to be adjusted not only with the time after injury but also relative to the location to the lesion site. PMID:28769787

Quantifying white matter tract diffusion parameters in the presence of increased extra-fiber cellularity and vasogenic edema

PubMed Central

Chiang, Chia-Wen; Wang, Yong; Sun, Peng; Lin, Tsen-Hsuan; Trinkaus, Kathryn; Cross, Anne H.; Song, Sheng-Kwei

2014-01-01

The effect of extra-fiber structural and pathological components confounding diffusion tensor imaging (DTI) computation was quantitatively investigated using data generated by both Monte-Carlo simulations and tissue phantoms. Increased extent of vasogenic edema, by addition of various amount of gel to fixed normal mouse trigeminal nerves or by increasing non-restricted isotropic diffusion tensor components in Monte-Carlo simulations, significantly decreased fractional anisotropy (FA), increased radial diffusivity, while less significantly increased axial diffusivity derived by DTI. Increased cellularity, mimicked by graded increase of the restricted isotropic diffusion tensor component in Monte-Carlo simulations, significantly decreased FA and axial diffusivity with limited impact on radial diffusivity derived by DTI. The MC simulation and tissue phantom data were also analyzed by the recently developed diffusion basis spectrum imaging (DBSI) to simultaneously distinguish and quantify the axon/myelin integrity and extra-fiber diffusion components. Results showed that increased cellularity or vasogenic edema did not affect the DBSI-derived fiber FA, axial or radial diffusivity. Importantly, the extent of extra-fiber cellularity and edema estimated by DBSI correlated with experimentally added gel and Monte-Carlo simulations. We also examined the feasibility of applying 25-direction diffusion encoding scheme for DBSI analysis on coherent white matter tracts. Results from both phantom experiments and simulations suggested that the 25-direction diffusion scheme provided comparable DBSI estimation of both fiber diffusion parameters and extra-fiber cellularity/edema extent as those by 99-direction scheme. An in vivo 25-direction DBSI analysis was performed on experimental autoimmune encephalomyelitis (EAE, an animal model of human multiple sclerosis) optic nerve as an example to examine the validity of derived DBSI parameters with post-imaging immunohistochemistry verification. Results support that in vivo DBSI using 25-direction diffusion scheme correctly reflect the underlying axonal injury, demyelination, and inflammation of optic nerves in EAE mice. PMID:25017446

Many-body Effects in a Laterally Inhomogeneous Semiconductor Quantum Well

NASA Technical Reports Server (NTRS)

Ning, Cun-Zheng; Li, Jian-Zhong; Biegel, Bryan A. (Technical Monitor)

2002-01-01

Many body effects on conduction and diffusion of electrons and holes in a semiconductor quantum well are studied using a microscopic theory. The roles played by the screened Hartree-Fock (SHE) terms and the scattering terms are examined. It is found that the electron and hole conductivities depend only on the scattering terms, while the two-component electron-hole diffusion coefficients depend on both the SHE part and the scattering part. We show that, in the limit of the ambipolax diffusion approximation, however, the diffusion coefficients for carrier density and temperature are independent of electron-hole scattering. In particular, we found that the SHE terms lead to a reduction of density-diffusion coefficients and an increase in temperature-diffusion coefficients. Such a reduction or increase is explained in terms of a density-and temperature dependent energy landscape created by the bandgap renormalization.

First-principles study of transition-metal nitrides as diffusion barriers against Al

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

Mei, Zhi-Gang; Yacout, Abdellatif M.; Kim, Yeon Soo

2016-04-01

Using density-functional theory based first-principles calculations we provided a comparative study of the diffusion barrier properties of TiN, ZrN, and HfN against Al for U-Mo dispersion fuel applications. We firstly examined the thermodynamic stability of these transition-metal nitrides with Al. The calculated heats of reaction show that both TiN and ZrN are thermodynamically unstable diffusion barrier materials, which might be decomposed by Al at relatively high temperatures. As a comparison, HfN is a stable diffusion barrier material for Al. To evaluate the kinetic stability of these nitride systems against Al diffusion, we investigated the diffusion mechanisms of Al in TiN,more » ZrN and HfN using atomic scale simulations. The effect of non-stoichiometry on the defect formation and Al migration was systematically studied. (C) 2015 ELSEVIER B.V. All rights reserved« less

Effect of field-aligned-beam in parallel diffusion of energetic particles in the Earth's foreshock

NASA Astrophysics Data System (ADS)

Matsukiyo, S.; Nakanishi, K.; Otsuka, F.; Kis, A.; Lemperger, I.; Hada, T.

2016-12-01

Diffusive shock acceleration (DSA) is one of the plausible acceleration mechanisms of cosmic rays. In the standard DSA model the partial density of the accelerated particles, diffused into upstream, exponentially decreases as the distance to the shock increases. Kis et al. (GRL, 31, L20801, 2004) examined the density gradients of energetic ions upstream of the bow shock with high accuracy by using Cluster data. They estimated the diffusion coefficients of energetic ions for the event in February 18, 2003 and showed that the obtained diffusion coefficients are significantly smaller than those estimated in the past statistical study. This implies that particle acceleration at the bow shock can be more efficient than considered before. Here, we focus on the effect of the field-aligned-beam (FAB) which is often observed in the foreshock, and examine how the FAB affects the efficiency of diffusion of the energetic ions by performing test particle simulations. The upstream turbulence is given by the superposition of parallel Alfven waves with power-law energy spectrum with random phase approximation. In the spectrum we further add a peak corresponding to the waves resonantly generated by the FAB. The dependence of the diffusion coefficient on the presence of the FAB as well as total energy of the turbulence, power-law index of the turbulence, and intensity of FAB oriented waves are discussed.

Dynamics of a molecular glass former: Energy landscapes for diffusion in ortho-terphenyl

NASA Astrophysics Data System (ADS)

Niblett, S. P.; de Souza, V. K.; Stevenson, J. D.; Wales, D. J.

2016-07-01

Relaxation times and transport processes of many glass-forming supercooled liquids exhibit a super-Arrhenius temperature dependence. We examine this phenomenon by computer simulation of the Lewis-Wahnström model for ortho-terphenyl. We propose a microscopic definition for a single-molecule cage-breaking transition and show that, when correlation behaviour is taken into account, these rearrangements are sufficient to reproduce the correct translational diffusion constants over an intermediate temperature range in the supercooled regime. We show that super-Arrhenius behaviour can be attributed to increasing negative correlation in particle movement at lower temperatures and relate this to the cage-breaking description. Finally, we sample the potential energy landscape of the model and show that it displays hierarchical ordering. Substructures in the landscape, which may correspond to metabasins, have boundaries defined by cage-breaking transitions. The cage-breaking formulation provides a direct link between the potential energy landscape and macroscopic diffusion behaviour.

[Primary diffuse large B-cell lymphoma of the uterine cervix--a case report].

PubMed

Okudaira, Taeko; Nagasaki, Akitoshi; Miyagi, Takashi; Nakazato, Tetsuro; Taira, Naoya; Kudaka, Wataru; Maehama, Toshiyuki; Takasu, Nobuyuki

2008-08-01

Primary malignant lymphoma of the female genital tract is an extremely rare clinical entity. We report a case of primary non-Hodgkin lymphoma of the uterine cervix. A 68-year-old woman presented with abnormal genital bleeding in May 2002. A coloposcopic examination revealed a mass in the uterine cervix. Magnetic resonance imaging showed a bulky cervical tumor(7.5 x 8 cm)invading the right parametrium and adjacent levator ani muscle. Involvement of pelvic lymph nodes was also observed. The uterine lesion exhibited homogenous hypointensity on T1 weight image and isointense to hyperintense on T2-weight image. No other lesions were detected by the whole-body computed tomography, gallium scintigraphy, and bone marrow examination. Although cytology of the smear from the uterine cervix was nondiagnostic, the histologic examination of the punch biopsy material showed a diffuse proliferation of atypical lymphoid cells. Immunophenotypic studies revealed tumor cells were positive for CD19, CD20, CD30, and k-chain. A diagnosis of diffuse large B-cell lymphoma of the uterine cervix, clinical stage IIE was made. The patient was treated with 6 cycles of cyclophosphamide, doxorubicin, vincristine, and prednisone(CHOP)chemotherapy followed by the involved field irradiation. She remains alive and free of disease more than 5 years after the diagnosis.

Non-moving Hadamard matrix diffusers for speckle reduction in laser pico-projectors

NASA Astrophysics Data System (ADS)

Thomas, Weston; Middlebrook, Christopher

2014-12-01

Personal electronic devices such as cell phones and tablets continue to decrease in size while the number of features and add-ons keep increasing. One particular feature of great interest is an integrated projector system. Laser pico-projectors have been considered, but the technology has not been developed enough to warrant integration. With new advancements in diode technology and MEMS devices, laser-based projection is currently being advanced for pico-projectors. A primary problem encountered when using a pico-projector is coherent interference known as speckle. Laser speckle can lead to eye irritation and headaches after prolonged viewing. Diffractive optical elements known as diffusers have been examined as a means to lower speckle contrast. This paper presents a binary diffuser known as a Hadamard matrix diffuser. Using two static in-line Hadamard diffusers eliminates the need for rotation or vibration of the diffuser for temporal averaging. Two Hadamard diffusers were fabricated and contrast values measured showing good agreement with theory and simulated values.

METAL DIFFUSION IN SMOOTHED PARTICLE HYDRODYNAMICS SIMULATIONS OF DWARF GALAXIES

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

Williamson, David; Martel, Hugo; Kawata, Daisuke, E-mail: david-john.williamson.1@ulaval.ca

2016-05-10

We perform a series of smoothed particle hydrodynamics simulations of isolated dwarf galaxies to compare different metal mixing models. In particular, we examine the role of diffusion in the production of enriched outflows and in determining the metallicity distributions of gas and stars. We investigate different diffusion strengths by changing the pre-factor of the diffusion coefficient, by varying how the diffusion coefficient is calculated from the local velocity distribution, and by varying whether the speed of sound is included as a velocity term. Stronger diffusion produces a tighter [O/Fe]–[Fe/H] distribution in the gas and cuts off the gas metallicity distributionmore » function at lower metallicities. Diffusion suppresses the formation of low-metallicity stars, even with weak diffusion, and also strips metals from enriched outflows. This produces a remarkably tight correlation between “metal mass-loading” (mean metal outflow rate divided by mean metal production rate) and the strength of diffusion, even when the diffusion coefficient is calculated in different ways. The effectiveness of outflows at removing metals from dwarf galaxies and the metal distribution of the gas is thus dependent on the strength of diffusion. By contrast, we show that the metallicities of stars are not strongly dependent on the strength of diffusion, provided that some diffusion is present.« less

A Diffusion Approach to Study Leadership Reform

ERIC Educational Resources Information Center

Adams, Curt M.; Jean-Marie, Gaetane

2011-01-01

Purpose: This study aims to draw on elements of diffusion theory to understand leadership reform. Many diffusion studies examine the spread of an innovation across social units but the objective is to examine diffusion of a collective leadership model within school units. Specifically, the strength of reform diffusion is tested to account for…

Effects of Impeller-Diffuser Interaction on Centrifugal Compressor Performance

NASA Technical Reports Server (NTRS)

Tan, Choon S.

2003-01-01

This research program focuses on characterizing the effect of impeller-diffuser interactions in a centrifugal compressor stage on its performance using unsteady threedimensional Reynolds-averaged Navier-Stokes simulations. The computed results show that the interaction between the downstream diffuser pressure field and the impeller tip clearance flow can account for performance changes in the impeller. The magnitude of performance change due to this interaction was examined for an impeller with varying tip clearance followed by a vaned or vaneless diffuser. The impact of unsteady impeller-diffuser interaction, primarily through the impeller tip clearance flow, is reflected through a time-averaged change in impeller loss, blockage and slip. The results show that there exists a tip clearance where the beneficial effect of the impeller-diffuser interaction on the impeller performance is at a maximum. A flow feature that consists of tip flow back leakage was shown to occur at design speed for the centrifugal compressor stage. This flow phenomenon is described as tip flow that originates in one passage, flows downstream of the impeller trailing edge and then returns to upstream of the impeller trailing edge of a neighboring passage. Such a flow feature is a source of loss in the impeller. A hypothesis is put forth to show that changing the diffuser vane count and changing impeller-diffuser gap has an analogous effect on the impeller performance. The centrifugal compressor stage was analyzed using diffusers of different vane counts, producing an impeller performance trend similar to that when the impeller-diffuser gap was varied, thus supporting the hypothesis made. This has the implication that the effect impeller performance associated with changing the impeller-diffuser gap and changing diffuser vane count can be described by the non-dimensional ratio of impeller-diffuser gap to diffuser vane pitch. A procedure is proposed and developed for isolating impeller passage blockage change without the need to define the region of blockage generation (which may incur a certain degree of arbitrariness). This method has been assessed for its applicability and utility.

Complex mammary carcinoma with metastases to lymph nodes, subcutaneous tissue, and multiple joints in a dog.

PubMed

McCourt, Maggie R; Dieterly, Alexandra M; Mackey, Paige E; Lyon, Shane D; Rizzi, Theresa E; Ritchey, Jerry W

2018-05-07

An 8-year-old, intact female, mixed-breed dog presented to the Oklahoma State University Boren Veterinary Medical Teaching Hospital for evaluation of progressive lameness and joint effusion of multiple joints. Physical examination revealed joint effusion of the elbow, hock, and stifle joints bilaterally, enlarged left axillary and right popliteal lymph nodes, a subcutaneous mass over the left elbow, and a subcutaneous mass involving the left second and third mammary glands. Cytologic examination of the mammary mass, enlarged lymph nodes, and joint fluid from most affected joints revealed a monomorphic population of loosely cohesive neoplastic epithelial cells. The patient was humanely euthanized, and subsequent necropsy with histopathologic examination revealed a complex mammary carcinoma with metastases to enlarged lymph nodes, subcutaneous tissue over the left elbow, and the synovium of multiple joints. Immunohistochemical stains were performed and showed diffusely positive pan cytokeratin, CK8/18, and CK19 staining in the neoplastic luminal epithelial cells of the mammary carcinoma, synovium, and lymph nodes, and showed diffusely positive vimentin staining of the myoepithelial cells. Myoepithelial calponin positivity was diffuse in the mammary mass and lymph nodes but minimal in the synovium. Only the mammary mass showed p63 positivity. Metastatic mammary neoplasia is relatively common in dogs; however, metastasis to the synovium has only been reported once previously in the literature. This is the first case utilizing immunohistochemistry for confirmation and characterization of metastases. © 2018 American Society for Veterinary Clinical Pathology.

Reflectance spectroscopy for noninvasive evaluation of hair follicle stage

NASA Astrophysics Data System (ADS)

Liu, Caihua; Guan, Yue; Wang, Jianru; Zhong, Xiewei; Liu, Xiuli; Zhu, Dan

2015-05-01

Hair follicle offers an excellent model for systems biology and regenerative medicine. So far, the stages of hair follicle growth have been evaluated by histological examination. In this work, a noninvasive spectroscopy was proposed by measuring the diffuse reflectance of mouse skin and analyzing the melanin value. Results show that the skin diffuse reflectance was relatively high when hair follicles were at the telogen stage and at the beginning of the anagen stage, and decreased with the progression of the anagen stage. When the hair follicle entered into the catagen stage, the diffuse reflectance gradually increased. The changes in the melanin content of skin had contrary dynamics. Substages of the hair follicle cycle could be distinguished by comparing the changes in melanin value with the histological examination. This study provided a new method for noninvasive evaluation of the hair follicle stage, and should be valuable for basic and therapeutic investigations on hair regeneration.

Magnetic resonance imaging evidence for presymptomatic change in thalamus and caudate in familial Alzheimer's disease.

PubMed

Ryan, Natalie S; Keihaninejad, Shiva; Shakespeare, Timothy J; Lehmann, Manja; Crutch, Sebastian J; Malone, Ian B; Thornton, John S; Mancini, Laura; Hyare, Harpreet; Yousry, Tarek; Ridgway, Gerard R; Zhang, Hui; Modat, Marc; Alexander, Daniel C; Rossor, Martin N; Ourselin, Sebastien; Fox, Nick C

2013-05-01

Amyloid imaging studies of presymptomatic familial Alzheimer's disease have revealed the striatum and thalamus to be the earliest sites of amyloid deposition. This study aimed to investigate whether there are associated volume and diffusivity changes in these subcortical structures during the presymptomatic and symptomatic stages of familial Alzheimer's disease. As the thalamus and striatum are involved in neural networks subserving complex cognitive and behavioural functions, we also examined the diffusion characteristics in connecting white matter tracts. A cohort of 20 presenilin 1 mutation carriers underwent volumetric and diffusion tensor magnetic resonance imaging, neuropsychological and clinical assessments; 10 were symptomatic, 10 were presymptomatic and on average 5.6 years younger than their expected age at onset; 20 healthy control subjects were also studied. We conducted region of interest analyses of volume and diffusivity changes in the thalamus, caudate, putamen and hippocampus and examined diffusion behaviour in the white matter tracts of interest (fornix, cingulum and corpus callosum). Voxel-based morphometry and tract-based spatial statistics were also used to provide unbiased whole-brain analyses of group differences in volume and diffusion indices, respectively. We found that reduced volumes of the left thalamus and bilateral caudate were evident at a presymptomatic stage, together with increased fractional anisotropy of bilateral thalamus and left caudate. Although no significant hippocampal volume loss was evident presymptomatically, reduced mean diffusivity was observed in the right hippocampus and reduced mean and axial diffusivity in the right cingulum. In contrast, symptomatic mutation carriers showed increased mean, axial and in particular radial diffusivity, with reduced fractional anisotropy, in all of the white matter tracts of interest. The symptomatic group also showed atrophy and increased mean diffusivity in all of the subcortical grey matter regions of interest, with increased fractional anisotropy in bilateral putamen. We propose that axonal injury may be an early event in presymptomatic Alzheimer's disease, causing an initial fall in axial and mean diffusivity, which then increases with loss of axonal density. The selective degeneration of long-coursing white matter tracts, with relative preservation of short interneurons, may account for the increase in fractional anisotropy that is seen in the thalamus and caudate presymptomatically. It may be owing to their dense connectivity that imaging changes are seen first in the thalamus and striatum, which then progress to involve other regions in a vulnerable neuronal network.

Effect of the computational domain size and shape on the self-diffusion coefficient in a Lennard-Jones liquid.

PubMed

Kikugawa, Gota; Ando, Shotaro; Suzuki, Jo; Naruke, Yoichi; Nakano, Takeo; Ohara, Taku

2015-01-14

In the present study, molecular dynamics (MD) simulations on the monatomic Lennard-Jones liquid in a periodic boundary system were performed in order to elucidate the effect of the computational domain size and shape on the self-diffusion coefficient measured by the system. So far, the system size dependence in cubic computational domains has been intensively investigated and these studies showed that the diffusion coefficient depends linearly on the inverse of the system size, which is theoretically predicted based on the hydrodynamic interaction. We examined the system size effect not only in the cubic cell systems but also in rectangular cell systems which were created by changing one side length of the cubic cell with the system density kept constant. As a result, the diffusion coefficient in the direction perpendicular to the long side of the rectangular cell significantly increases more or less linearly with the side length. On the other hand, the diffusion coefficient in the direction along the long side is almost constant or slightly decreases. Consequently, anisotropy of the diffusion coefficient emerges in a rectangular cell with periodic boundary conditions even in a bulk liquid simulation. This unexpected result is of critical importance because rectangular fluid systems confined in nanospace, which are present in realistic nanoscale technologies, have been widely studied in recent MD simulations. In order to elucidate the underlying mechanism for this serious system shape effect on the diffusion property, the correlation structures of particle velocities were examined.

Kinetics of dodecanoic acid adsorption from caustic solution by activated carbon.

PubMed

Pendleton, Phillip; Wu, Sophie Hua

2003-10-15

This study examines the influences of adsorbent porosity and surface chemistry and of carbon dosage on dodecanoic acid adsorption kinetics from aqueous and 2 M NaOH solutions as batch adsorption processes. Both adsorbents are steam-activated carbons prepared from either coconut or coal precursors. Prior to use the adsorbents were washed in deionized water or 2 M NaOH. Mass transfer coefficients and effective overall diffusion coefficients indicate a minor contribution from adsorbent porosity. In contrast, high surface oxygen content impedes transport to and into the adsorbent structure. Carbon dosage shows a proportional increase in transport coefficients with increasing mass; these coefficients are constant when normalized per unit mass. Neither water nor NaOH treatment of the adsorbents has a significant influence on dodecanoic acid adsorption kinetics. Molecular and Knudsen diffusion coefficients are defined to demonstrate that the overall effective diffusion coefficient values and the diffusion process are controlled by surface diffusion.

Multiphoton microscopy guides neurotrophin modification with poly(ethylene glycol) to enhance interstitial diffusion

NASA Astrophysics Data System (ADS)

Stroh, Mark; Zipfel, Warren R.; Williams, Rebecca M.; Ma, Shu Chin; Webb, Watt W.; Saltzman, W. Mark

2004-07-01

Brain-derived neurotrophic factor (BDNF) is a promising therapeutic agent for the treatment of neurodegenerative diseases. However, the limited distribution of this molecule after administration into the brain tissue considerably hampers its efficacy. Here, we show how multiphoton microscopy of fluorescently tagged BDNF in brain-tissue slices provides a useful and rapid screening method for examining the diffusion of large molecules in tissues, and for studying the effects of chemical modifications-for example, conjugating with polyethylene glycol (PEG)-on the diffusion constant. This single variable, obtained by monitoring short-term diffusion in real time, can be effectively used for rational drug design. In this study on fluorescently tagged BDNF and BDNF-PEG, we identify slow diffusion as a major contributing factor to the limited penetration of BDNF, and demonstrate how chemical modification can be used to overcome this barrier.

Diffusion-weighted imaging in the evaluation of odontogenic cysts and tumours.

PubMed

Srinivasan, K; Seith Bhalla, A; Sharma, R; Kumar, A; Roychoudhury, A; Bhutia, O

2012-10-01

The differentiation between keratocystic odontogenic tumour (KCOT) and other cystic/predominantly cystic odontogenic tumours is difficult on conventional CT and MR sequences as there is overlap in the imaging characteristics of these lesions. The purpose of this study was to evaluate the role of diffusion-weighted imaging (DWI) and to assess the performance of apparent diffusion coefficients (ADCs) in the differential diagnosis of odontogenic cysts and tumours. 20 patients with odontogenic cysts and tumours of the maxillomandibular region were examined with DWI. Diffusion-weighted images were obtained with a single-shot echoplanar technique with b-values of 0, 500 and 1000 s mm(-2). An ADC map was obtained at each slice position. The cystic areas of ameloblastoma (n=10) showed free diffusion with a mean ADC value of 2.192±0.33×10(-3) mm(2) s(-1), whereas the solid areas showed restricted diffusion with a mean ADC value of 1.041±0.41×10(-3) mm(2) s(-1). KCOT (n=5) showed restricted diffusion with a mean ADC value of 1.019±0.07×10(-3) mm(2) s(-1). There was a significant difference between the ADC values of KCOT and cystic ameloblastoma (p<0.01, Mann-Whitney U-test). The cut-off with which KCOT and predominantly cystic ameloblastomas were optimally differentiated was 2.013×10(-3) mm(2) s(-1), which yielded 100% sensitivity and 100% specificity. DWI can be used to differentiate KCOT from cystic (or predominantly cystic) odontogenic tumours.

Radiation effects on interface reactions of U/Fe, U/(Fe+Cr), and U/(Fe+Cr+Ni)

DOE PAGES

Shao, Lin; Chen, Di; Wei, Chaochen; ...

2014-10-01

We study the effects of radiation damage on interdiffusion and intermetallic phase formation at the interfaces of U/Fe, U/(Fe + Cr), and U/(Fe + Cr + Ni) diffusion couples. Magnetron sputtering is used to deposit thin films of Fe, Fe + Cr, or Fe + Cr + Ni on U substrates to form the diffusion couples. One set of samples are thermally annealed under high vacuum at 450 C or 550 C for one hour. A second set of samples are annealed identically but with concurrent 3.5 MeV Fe++ ion irradiation. The Fe++ ion penetration depth is sufficient to reachmore » the original interfaces. Rutherford backscattering spectrometry analysis with high fidelity spectral simulations is used to obtain interdiffusion profiles, which are used to examine differences in U diffusion and intermetallic phase formation at the buried interfaces. For all three diffusion systems, Fe++ ion irradiations enhance U diffusion. Furthermore, the irradiations accelerate the formation of intermetallic phases. In U/Fe couples, for example, the unirradiated samples show typical interdiffusion governed by Fick’s laws, while the irradiated ones show step-like profiles influenced by Gibbs phase rules.« less

The role of grain boundaries in hydrogen diffusion in metals at 25 C

NASA Technical Reports Server (NTRS)

Danford, M. D.

1993-01-01

The effect of grain size on hydrogen diffusion at 25 C was examined for 4340 steel (body-centered cubic) and for Inconel 718 (face-centered cubic). It was found that the effect of grain size is important for body-centered cubic structures, but plays a much less important role in face centered cubic structures. Accurate measurements of hydrogen desorption coefficients during hydrogen desorption show that these are not greatly different for both types of structures.

Structure and dynamics of solvated polyethylenimine chains

NASA Astrophysics Data System (ADS)

Beu, Titus A.; Farcaş, Alexandra

2017-12-01

Polimeric gene-delivery carriers have attracted great interest in recent years, owing to their applicability in gene therapy. In particular, cationic polymers represent the most promising delivery vectors for nucleic acids into the cells. This study presents extensive atomistic molecular dynamics simulations of linear polyethylenimine chains. The simulations show that the variation of the chain size and protonation fraction causes a substantial change of the diffusion coefficient. Examination of the solvated chains suggests the possibility of controlling the polymer diffusion mobility in solution.

pH imaging reveals worsened tissue acidification in diffusion kurtosis lesion than the kurtosis/diffusion lesion mismatch in an animal model of acute stroke.

PubMed

Wang, Enfeng; Wu, Yin; Cheung, Jerry S; Zhou, Iris Yuwen; Igarashi, Takahiro; Zhang, XiaoAn; Sun, Phillip Zhe

2017-10-01

Diffusion weighted imaging (DWI) has been commonly used in acute stroke examination, yet a portion of DWI lesion may be salvageable. Recently, it has been shown that diffusion kurtosis imaging (DKI) defines the most severely damaged DWI lesion that does not renormalize following early reperfusion. We postulated that the diffusion and kurtosis lesion mismatch experience heterogeneous hemodynamic and/or metabolic injury. We investigated tissue perfusion, pH, diffusion, kurtosis and relaxation from regions of the contralateral normal area, diffusion lesion, kurtosis lesion and their mismatch in an animal model of acute stroke. Our study revealed significant kurtosis and diffusion lesion volume mismatch (19.7 ± 10.7%, P < 0.01). Although there was no significant difference in perfusion and diffusion between the kurtosis lesion and kurtosis/diffusion lesion mismatch, we showed lower pH in the kurtosis lesion (pH = 6.64 ± 0.12) from that of the kurtosis/diffusion lesion mismatch (6.84 ± 0.11, P < 0.05). Moreover, pH in the kurtosis lesion and kurtosis/diffusion mismatch agreed well with literature values for regions of ischemic core and penumbra, respectively. Our work documented initial evidence that DKI may reveal the heterogeneous metabolic derangement within the commonly used DWI lesion.

Evaluation of breast cancer using intravoxel incoherent motion (IVIM) histogram analysis: comparison with malignant status, histological subtype, and molecular prognostic factors.

PubMed

Cho, Gene Young; Moy, Linda; Kim, Sungheon G; Baete, Steven H; Moccaldi, Melanie; Babb, James S; Sodickson, Daniel K; Sigmund, Eric E

2016-08-01

To examine heterogeneous breast cancer through intravoxel incoherent motion (IVIM) histogram analysis. This HIPAA-compliant, IRB-approved retrospective study included 62 patients (age 48.44 ± 11.14 years, 50 malignant lesions and 12 benign) who underwent contrast-enhanced 3 T breast MRI and diffusion-weighted imaging. Apparent diffusion coefficient (ADC) and IVIM biomarkers of tissue diffusivity (Dt), perfusion fraction (fp), and pseudo-diffusivity (Dp) were calculated using voxel-based analysis for the whole lesion volume. Histogram analysis was performed to quantify tumour heterogeneity. Comparisons were made using Mann-Whitney tests between benign/malignant status, histological subtype, and molecular prognostic factor status while Spearman's rank correlation was used to characterize the association between imaging biomarkers and prognostic factor expression. The average values of the ADC and IVIM biomarkers, Dt and fp, showed significant differences between benign and malignant lesions. Additional significant differences were found in the histogram parameters among tumour subtypes and molecular prognostic factor status. IVIM histogram metrics, particularly fp and Dp, showed significant correlation with hormonal factor expression. Advanced diffusion imaging biomarkers show relationships with molecular prognostic factors and breast cancer malignancy. This analysis reveals novel diagnostic metrics that may explain some of the observed variability in treatment response among breast cancer patients. • Novel IVIM biomarkers characterize heterogeneous breast cancer. • Histogram analysis enables quantification of tumour heterogeneity. • IVIM biomarkers show relationships with breast cancer malignancy and molecular prognostic factors.

Effects of inlet flow field conditions on the performance of centrifugal compressor diffusers: Part 2 -- Straight-channel diffuser

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

Deniz, S.; Greitzer, E.M.; Cumpsty, N.A.

2000-01-01

This is Part 2 of an examination of the influence of inlet flow conditions on the performance and operating range of centrifugal compressor vaned diffusers. The paper describes tests of a straight-channel type diffuser, sometimes called a wedge-vane diffuser, and compares the results with those from the discrete-passage diffusers described in Part 1. Effects of diffuser inlet Mach number, flow angle, blockage, and axial flow nonuniformity on diffuser pressure recovery and operating range are addressed. The straight-channel diffuser investigated has 30 vanes and was designed for the same aerodynamic duty as the discrete-passage diffuser described in Part 1. The rangesmore » of the overall pressure recovery coefficients were 0.50--0.78 for the straight-channel diffuser and 0.50--0.70 for the discrete-passage diffuser, except when the diffuser was choked. In other words, the maximum pressure recovery of the straight-channel diffuser was found to be roughly 10% higher than that of the discrete-passage diffuser investigated. The two types of diffuser showed similar behavior regarding the dependence of pressure recovery on diffuser inlet flow angle and the insensitivity of the performance to inlet flow field axial distortion and Mach number. The operating range of the straight-channel diffuser, as for the discrete-passage diffusers, was limited by the onset of rotating stall at a fixed momentum-averaged flow angle into the diffuser, which was for the straight-channel diffuser, {alpha}{sub crit} = 70 {+-} 0.5 deg. The background, nomenclature, and description of the facility and method are all given in Part 1.« less

Diffusion pseudonormalization and clinical outcome in term neonates with hypoxic-ischemic encephalopathy.

PubMed

Hayakawa, Katsumi; Koshino, Sachiko; Tanda, Koichi; Nishimura, Akira; Sato, Osamu; Morishita, Hiroyuki; Ito, Takaaki

2018-06-01

Pseudonormalization of diffusion-weighted magnetic resonance imaging (MRI) can lead to underestimation of brain injury in newborns with hypoxic-ischemic encephalopathy (HIE), posing a significant problem. We have noticed that some neonates show pseudonormalization negativity on diffusion-weighted imaging. To compare pseudonormalization negativity with clinical outcomes. Seventeen term neonates with moderate or severe HIE underwent therapeutic hypothermia. They were examined by MRI twice at mean ages of 3 days and 10 days. We evaluated the presence of restricted diffusion, and also the presence or absence of pseudonormalization, by diffusion-weighted imaging at the time of the second MRI, and correlated the results with clinical outcome. DWI demonstrated no abnormality in seven neonates. Among the 10 neonates with abnormal diffusion-weighted imaging findings, 2 were positive for pseudonormalization and 8 were negative. Among neonates with normal diffusion-weighted imaging findings and with positivity for pseudonormalization, none had major disability. Among the eight neonates with pseudonormalization negativity, all but one, who was lost to follow-up, had major disability. Abnormal diffusion-weighted imaging with pseudonormalization negativity might be predictive of severe brain injury and major disability. The second-week MRI is important for the judgment of pseudonormalization.

Differentiation between phyllodes tumours and fibroadenomas using intravoxel incoherent motion magnetic resonance imaging: comparison with conventional diffusion-weighted imaging.

PubMed

Kawashima, Hiroko; Miyati, Tosiaki; Ohno, Naoki; Ohno, Masako; Inokuchi, Masafumi; Ikeda, Hiroko; Gabata, Toshifumi

2018-04-01

To investigate whether the parameters derived from intravoxel incoherent motion (IVIM) MRI could differentiate phyllodes tumours (PTs) from fibroadenomas (FAs) by comparing the apparent diffusion coefficient (ADC) values. This retrospective study included 7 FAs, 10 benign PTs (BPTs), 4 borderline PTs, and one malignant PT. Biexponential analyses of IVIM were performed using a 3 T MRI scanner. Quantitative IVIM parameters [pure diffusion coefficient (D), perfusion-related diffusion coefficient (D*), and fraction (f)] were calculated. The ADC was also calculated using monoexponential fitting. The D and ADC values showed an increasing tendency in the order of FA, BPT, and borderline or malignant PT (BMPT). No significant difference was found in the D value among the three groups. The ADC value of the BMPT group was significantly higher than that of the FA group (p = 0.048). The D* value showed an increasing tendency in the order of BMPT, BPT, and FA, and the D* value of the BMPT group was significantly lower than that of the FA group (p = 0.048). The D* derived from IVIM and the ADC were helpful for differentiating between FA and BMPT. Advances in knowledge: IVIM MRI examination showed that the perfusion-related diffusion coefficient is lower in borderline and malignant PTs than in FAs and the opposite is true for the ADC.

Diffusive behavior of a greedy traveling salesman.

PubMed

Lipowski, Adam; Lipowska, Dorota

2011-06-01

Using Monte Carlo simulations we examine the diffusive properties of the greedy algorithm in the d-dimensional traveling salesman problem. Our results show that for d=3 and 4 the average squared distance from the origin (r(2)) is proportional to the number of steps t. In the d=2 case such a scaling is modified with some logarithmic corrections, which might suggest that d=2 is the critical dimension of the problem. The distribution of lengths also shows marked differences between d=2 and d>2 versions. A simple strategy adopted by the salesman might resemble strategies chosen by some foraging and hunting animals, for which anomalous diffusive behavior has recently been reported and interpreted in terms of Lévy flights. Our results suggest that broad and Lévy-like distributions in such systems might appear due to dimension-dependent properties of a search space.

Examining Transformative Faculty Development Factors to Advance Technology Adoption and Diffusion at a Campus-Based Institution

ERIC Educational Resources Information Center

McKissic, Stephanie Camille

2012-01-01

The purpose of this mixed-method research, in the context of a case study was to examine faculty concerns with integrating technologies and the influences and motivations that lead to technology adoption and diffusion in the classroom. Specifically, the study examined the conceptual frameworks of Rogers' Innovation Diffusion Theory (IDT) and…

Multi-wavelength speckle reduction for laser pico-projectors using diffractive optics

NASA Astrophysics Data System (ADS)

Thomas, Weston H.

Personal electronic devices, such as cell phones and tablets, continue to decrease in size while the number of features and add-ons keep increasing. One particular feature of great interest is an integrated projector system. Laser pico-projectors have been considered, but the technology has not been developed enough to warrant integration. With new advancements in diode technology and MEMS devices, laser-based projection is currently being advanced for pico-projectors. A primary problem encountered when using a pico-projector is coherent interference known as speckle. Laser speckle can lead to eye irritation and headaches after prolonged viewing. Diffractive optical elements known as diffusers have been examined as a means to lower speckle contrast. Diffusers are often rotated to achieve temporal averaging of the spatial phase pattern provided by diffuser surface. While diffusers are unable to completely eliminate speckle, they can be utilized to decrease the resultant contrast to provide a more visually acceptable image. This dissertation measures the reduction in speckle contrast achievable through the use of diffractive diffusers. A theoretical Fourier optics model is used to provide the diffuser's stationary and in-motion performance in terms of the resultant contrast level. Contrast measurements of two diffractive diffusers are calculated theoretically and compared with experimental results. In addition, a novel binary diffuser design based on Hadamard matrices will be presented. Using two static in-line Hadamard diffusers eliminates the need for rotation or vibration of the diffuser for temporal averaging. Two Hadamard diffusers were fabricated and contrast values were subsequently measured, showing good agreement with theory and simulated values. Monochromatic speckle contrast values of 0.40 were achieved using the Hadamard diffusers. Finally, color laser projection devices require the use of red, green, and blue laser sources; therefore, using a monochromatic diffractive diffuser may not optimal for color speckle contrast reduction. A simulation of the Hadamard diffusers is conducted to determine the optimum spacing between the two diffusers for polychromatic speckle reduction. Experimental measured results are presented using the optimal spacing of Hadamard diffusers for RGB color speckle reduction, showing 60% reduction in contrast.

A cross-age study of student understanding of the concept of diffusion

NASA Astrophysics Data System (ADS)

Westbrook, Susan L.; Marek, Edmund A.

This study examined 7th-grade life science students, 10th-grade biology students, and college zoology students for understanding of the concept of diffusion. Responses from 100 students from each grade level were randomly selected for data analysis. Each student responded to a test packet consisting of a biographical questionnaire, two Piagetian-like developmental tasks, and a Concept Evaluation Statement (CES). The CESs were used to measure the students' understandings of the concept of diffusion. None of the 300 students across the three grade levels exhibited complete understanding of the diffusion concept. There was no appreciable difference among the grade levels in sound or partial understanding, misconceptions, or no understanding. An analysis of the misconceptions exhibited by the college sample showed that many of the misconceptions could be traced to a misapplication of scientific terminology.

Dynamics of the diffusive DM-DE interaction – Dynamical system approach

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

Haba, Zbigniew; Stachowski, Aleksander; Szydłowski, Marek, E-mail: zhab@ift.uni.wroc.pl, E-mail: aleksander.stachowski@uj.edu.pl, E-mail: marek.szydlowski@uj.edu.pl

We discuss dynamics of a model of an energy transfer between dark energy (DE) and dark matter (DM) . The energy transfer is determined by a non-conservation law resulting from a diffusion of dark matter in an environment of dark energy. The relativistic invariance defines the diffusion in a unique way. The system can contain baryonic matter and radiation which do not interact with the dark sector. We treat the Friedman equation and the conservation laws as a closed dynamical system. The dynamics of the model is examined using the dynamical systems methods for demonstration how solutions depend on initialmore » conditions. We also fit the model parameters using astronomical observation: SNIa, H ( z ), BAO and Alcock-Paczynski test. We show that the model with diffuse DM-DE is consistent with the data.« less

Converting Multi-Shell and Diffusion Spectrum Imaging to High Angular Resolution Diffusion Imaging

PubMed Central

Yeh, Fang-Cheng; Verstynen, Timothy D.

2016-01-01

Multi-shell and diffusion spectrum imaging (DSI) are becoming increasingly popular methods of acquiring diffusion MRI data in a research context. However, single-shell acquisitions, such as diffusion tensor imaging (DTI) and high angular resolution diffusion imaging (HARDI), still remain the most common acquisition schemes in practice. Here we tested whether multi-shell and DSI data have conversion flexibility to be interpolated into corresponding HARDI data. We acquired multi-shell and DSI data on both a phantom and in vivo human tissue and converted them to HARDI. The correlation and difference between their diffusion signals, anisotropy values, diffusivity measurements, fiber orientations, connectivity matrices, and network measures were examined. Our analysis result showed that the diffusion signals, anisotropy, diffusivity, and connectivity matrix of the HARDI converted from multi-shell and DSI were highly correlated with those of the HARDI acquired on the MR scanner, with correlation coefficients around 0.8~0.9. The average angular error between converted and original HARDI was 20.7° at voxels with signal-to-noise ratios greater than 5. The network topology measures had less than 2% difference, whereas the average nodal measures had a percentage difference around 4~7%. In general, multi-shell and DSI acquisitions can be converted to their corresponding single-shell HARDI with high fidelity. This supports multi-shell and DSI acquisitions over HARDI acquisition as the scheme of choice for diffusion acquisitions. PMID:27683539

Detection of Hepatic Fibrosis in Ex Vivo Liver Samples Using an Open-Photoacoustic-Cell Method: Feasibility Study

NASA Astrophysics Data System (ADS)

Stolik, S.; Fabila, D. A.; de la Rosa, J. M.; Escobedo, G.; Suárez-Álvarez, K.; Tomás, S. A.

2015-09-01

Design of non-invasive and accurate novel methods for liver fibrosis diagnosis has gained growing interest. Different stages of liver fibrosis were induced in Wistar rats by intraperitoneally administering different doses of carbon tetrachloride. The liver fibrosis degree was conventionally determined by means of histological examination. An open-photoacoustic-cell (OPC) technique for the assessment of liver fibrosis was developed and is reported here. The OPC technique is based on the fact that the thermal diffusivity can be accurately measured by photoacoustics taking into consideration the photoacoustic signal amplitude versus the modulation frequency. This technique measures directly the heat generated in a sample, due to non-radiative de-excitation processes, following the absorption of light. The thermal diffusivity was measured with a home-made open-photoacoustic-cell system that was specially designed to perform the measurement from ex vivo liver samples. The human liver tissue showed a significant increase in the thermal diffusivity depending on the fibrosis stage. Specifically, liver samples from rats exhibiting hepatic fibrosis showed a significantly higher value of the thermal diffusivity than for control animals.

Magnetic resonance imaging evidence for presymptomatic change in thalamus and caudate in familial Alzheimer’s disease

PubMed Central

Keihaninejad, Shiva; Shakespeare, Timothy J.; Lehmann, Manja; Crutch, Sebastian J.; Malone, Ian B.; Thornton, John S.; Mancini, Laura; Hyare, Harpreet; Yousry, Tarek; Ridgway, Gerard R.; Zhang, Hui; Modat, Marc; Alexander, Daniel C.; Rossor, Martin N.; Ourselin, Sebastien; Fox, Nick C.

2013-01-01

Amyloid imaging studies of presymptomatic familial Alzheimer’s disease have revealed the striatum and thalamus to be the earliest sites of amyloid deposition. This study aimed to investigate whether there are associated volume and diffusivity changes in these subcortical structures during the presymptomatic and symptomatic stages of familial Alzheimer’s disease. As the thalamus and striatum are involved in neural networks subserving complex cognitive and behavioural functions, we also examined the diffusion characteristics in connecting white matter tracts. A cohort of 20 presenilin 1 mutation carriers underwent volumetric and diffusion tensor magnetic resonance imaging, neuropsychological and clinical assessments; 10 were symptomatic, 10 were presymptomatic and on average 5.6 years younger than their expected age at onset; 20 healthy control subjects were also studied. We conducted region of interest analyses of volume and diffusivity changes in the thalamus, caudate, putamen and hippocampus and examined diffusion behaviour in the white matter tracts of interest (fornix, cingulum and corpus callosum). Voxel-based morphometry and tract-based spatial statistics were also used to provide unbiased whole-brain analyses of group differences in volume and diffusion indices, respectively. We found that reduced volumes of the left thalamus and bilateral caudate were evident at a presymptomatic stage, together with increased fractional anisotropy of bilateral thalamus and left caudate. Although no significant hippocampal volume loss was evident presymptomatically, reduced mean diffusivity was observed in the right hippocampus and reduced mean and axial diffusivity in the right cingulum. In contrast, symptomatic mutation carriers showed increased mean, axial and in particular radial diffusivity, with reduced fractional anisotropy, in all of the white matter tracts of interest. The symptomatic group also showed atrophy and increased mean diffusivity in all of the subcortical grey matter regions of interest, with increased fractional anisotropy in bilateral putamen. We propose that axonal injury may be an early event in presymptomatic Alzheimer’s disease, causing an initial fall in axial and mean diffusivity, which then increases with loss of axonal density. The selective degeneration of long-coursing white matter tracts, with relative preservation of short interneurons, may account for the increase in fractional anisotropy that is seen in the thalamus and caudate presymptomatically. It may be owing to their dense connectivity that imaging changes are seen first in the thalamus and striatum, which then progress to involve other regions in a vulnerable neuronal network. PMID:23539189

Diffusion tensor imaging in children with tuberous sclerosis complex: tract-based spatial statistics assessment of brain microstructural changes.

PubMed

Zikou, Anastasia K; Xydis, Vasileios G; Astrakas, Loukas G; Nakou, Iliada; Tzarouchi, Loukia C; Tzoufi, Meropi; Argyropoulou, Maria I

2016-07-01

There is evidence of microstructural changes in normal-appearing white matter of patients with tuberous sclerosis complex. To evaluate major white matter tracts in children with tuberous sclerosis complex using tract-based spatial statistics diffusion tensor imaging (DTI) analysis. Eight children (mean age ± standard deviation: 8.5 ± 5.5 years) with an established diagnosis of tuberous sclerosis complex and 8 age-matched controls were studied. The imaging protocol consisted of T1-weighted high-resolution 3-D spoiled gradient-echo sequence and a spin-echo, echo-planar diffusion-weighted sequence. Differences in the diffusion indices were evaluated using tract-based spatial statistics. Tract-based spatial statistics showed increased axial diffusivity in the children with tuberous sclerosis complex in the superior and anterior corona radiata, the superior longitudinal fascicle, the inferior fronto-occipital fascicle, the uncinate fascicle and the anterior thalamic radiation. No significant differences were observed in fractional anisotropy, mean diffusivity and radial diffusivity between patients and control subjects. No difference was found in the diffusion indices between the baseline and follow-up examination in the patient group. Patients with tuberous sclerosis complex have increased axial diffusivity in major white matter tracts, probably related to reduced axonal integrity.

Determination of the optical properties of semi-infinite turbid media from frequency-domain reflectance close to the source.

PubMed

Kienle, A; Patterson, M S

1997-09-01

We investigate theoretically the errors in determining the reduced scattering and absorption coefficients of semi-infinite turbid media from frequency-domain reflectance measurements made at small distances between the source and the detector(s). The errors are due to the uncertainties in the measurement of the phase, the modulation and the steady-state reflectance as well as to the diffusion approximation which is used as a theoretical model to describe light propagation in tissue. Configurations using one and two detectors are examined for the measurement of the phase and the modulation and for the measurement of the phase and the steady-state reflectance. Three solutions of the diffusion equation are investigated. We show that measurements of the phase and the steady-state reflectance at two different distances are best suited for the determination of the optical properties close to the source. For this arrangement the errors in the absorption coefficient due to typical uncertainties in the measurement are greater than those resulting from the application of the diffusion approximation at a modulation frequency of 200 MHz. A Monte Carlo approach is also examined; this avoids the errors due to the diffusion approximation.

Lateral eddy diffusivity estimates from simulated and observed drifter trajectories: a case study for the Agulhas Current system

NASA Astrophysics Data System (ADS)

Rühs, Siren; Zhurbas, Victor; Durgadoo, Jonathan V.; Biastoch, Arne

2017-04-01

The Lagrangian description of fluid motion by sets of individual particle trajectories is extensively used to characterize connectivity between distinct oceanic locations. One important factor influencing the connectivity is the average rate of particle dispersal, generally quantified as Lagrangian diffusivity. In addition to Lagrangian observing programs, Lagrangian analyses are performed by advecting particles with the simulated flow field of ocean general circulation models (OGCMs). However, depending on the spatio-temporal model resolution, not all scale-dependent processes are explicitly resolved in the simulated velocity fields. Consequently, the dispersal of advective Lagrangian trajectories has been assumed not to be sufficiently diffusive compared to observed particle spreading. In this study we present a detailed analysis of the spatially variable lateral eddy diffusivity characteristics of advective drifter trajectories simulated with realistically forced OGCMs and compare them with estimates based on observed drifter trajectories. The extended Agulhas Current system around South Africa, known for its intricate mesoscale dynamics, serves as a test case. We show that a state-of-the-art eddy-resolving OGCM indeed features theoretically derived dispersion characteristics for diffusive regimes and realistically represents Lagrangian eddy diffusivity characteristics obtained from observed surface drifter trajectories. The estimates for the maximum and asymptotic lateral single-particle eddy diffusivities obtained from the observed and simulated drifter trajectories show a good agreement in their spatial pattern and magnitude. We further assess the sensitivity of the simulated lateral eddy diffusivity estimates to the temporal and lateral OGCM output resolution and examine the impact of the different eddy diffusivity characteristics on the Lagrangian connectivity between the Indian Ocean and the South Atlantic.

Diffuse Scattering from Lead-Containing Ferroelectric Perovskite Oxides

DOE PAGES

Goossens, D. J.

2013-01-01

Ferroelectric materials rely on some type of non-centrosymmetric displacement correlations to give rise to a macroscopic polarisation. These displacements can show short-range order (SRO) that is reflective of the local chemistry, and so studying it reveals important information about how the structure gives rise to the technologically useful properties. A key means of exploring this SRO is diffuse scattering. Conventional structural studies use Bragg peak intensitiesto determine the average structure. In a single crystal diffuse scattering (SCDS) experiment, the coherent scattered intensity is measured at non-integer Miller indices, and can be used to examine the population of local configurations. Thismore » is because the diffuse scattering is sensitive to two-body averages, whereas the Bragg intensity gives single-body averages. This review outlines key results of SCDS studies on several materials and explores the similarities and differences in their diffuse scattering. Random strains are considered, as are models based on a phonon-like picture or a more local-chemistry oriented picture. Limitations of the technique are discussed.« less

Diffusion of biomass pyrolysis products in H-ZSM-5 by molecular dynamics simulations

DOE PAGES

Bu, Lintao; Nimlos, Mark R.; Robichaud, David J.; ...

2016-12-13

Diffusion of biomass pyrolysis vapors and their upgraded products is an essential catalytic property of zeolites during catalytic fast pyrolysis and likely plays a critical role in the selectivity of these catalysts. Characterizing the diffusivities of representative biofuel molecules is critical to understand shape selectivity and interpret product distribution. Yet, experimental measurements on the diffusivities of oxygenated biofuel molecules at pyrolysis temperatures are very limited in the literature. As an alternative approach, we conducted MD simulations to measure the diffusion coefficients of several selected molecules that are representative of biomass pyrolysis vapors, namely water, methanol, glycolaldehyde, and toluene in H-ZSM-5more » zeolite. The results show the diffusion coefficients calculated via MD simulations are consistent with available NMR measurements at room temperature. The effect of molecular weight and molecular critical diameter on the diffusivity among the chosen model compounds is also examined. Furthermore, we have characterized the diffusivities of representative biofuel molecules, namely xylene isomers, in H-ZSM-5. Our calculations determined that the ratio of the diffusion coefficients for xylene isomers is p-xylene: o-xylene: m-xylene ≈ 83:3:1 at 700 K. Furthermore, our results also demonstrate the different diffusivity between p-xylene and toluene is due to the molecular orientations when the molecules diffuse along the channels in H-ZSM-5 and provide deep insight into the effect of molecular orientation on its diffusivity.« less

Photoflash thermal diffusivity measurement of carbon nanotube-filled PVDF composite at low temperature

NASA Astrophysics Data System (ADS)

Moksin, M. M.; Haydari, M.; Husin, M. S.; Yahya, N.; Azmi, B. Z.

2013-09-01

The suitability of a simple photoflash technique was further examined in the measurement of thermal diffusivity of nanotube-filled polyvinylidene difluoride (PVDF) film composites at low temperature. The effect of temperature and carbon nanotube (CNT) composition in PVDF composite on its thermal diffusivity is presented as equivalent to the effect of changing thermal phonon mean free path. It is done by assuming no other thermal carrier effects other than from phonons detected during measurement by using photoflash technique. The results show that thermal diffusivity of CNT-filled PVDF film composites was found to have consistently increased with increasing the CNT concentration or decreasing temperature, as in the case of insulators with dominant phonon thermal carriers. At any particular temperature, a dramatic increase in thermal diffusivity was noticed at the beginning as the CNT concentration was systematically increased up to a 1% turning point, from which the thermal diffusivity increased further at a much smaller rate with the CNT addition up to 10%. The thermal diffusivity of the samples was in the range of about (10-35) × 10- 8 m2/s depending on the temperature and the CNT concentration of the composites.

Heat transfer in suspensions of rigid particles

NASA Astrophysics Data System (ADS)

Brandt, Luca; Niazi Ardekani, Mehdi; Abouali, Omid

2016-11-01

We study the heat transfer in laminar Couette flow of suspensions of rigid neutrally buoyant particles by means of numerical simulations. An Immersed Boundary Method is coupled with a VOF approach to simulate the heat transfer in the fluid and solid phase, enabling us to fully resolve the heat diffusion. First, we consider spherical particles and show that the proposed algorithm is able to reproduce the correlations between heat flux across the channel, the particle volume fraction and the heat diffusivity obtained in laboratory experiments and recently proposed in the literature, results valid in the limit of vanishing inertia. We then investigate the role of inertia on the heat transfer and show an increase of the suspension diffusivity at finite particle Reynolds numbers. Finally, we vary the relativity diffusivity of the fluid and solid phase and investigate its effect on the effective heat flux across the channel. The data are analyzed by considering the ensemble averaged energy equation and decomposing the heat flux in 4 different contributions, related to diffusion in the solid and fluid phase, and the correlations between wall-normal velocity and temperature fluctuations. Results for non-spherical particles will be examined before the meeting. Supported by the European Research Council Grant No. ERC-2013- CoG-616186, TRITOS. The authors acknowledge computer time provided by SNIC (Swedish National Infrastructure for Computing).

Medulloblastoma with Atypical Dynamic Imaging Changes: Case Report with Literature Review.

PubMed

Song, Shuang-Shuang; Wang, Jian-Hong; Fu, Wei-Wei; Li, Ying; Sui, Qing-Lan; Liu, Xue-Jun

2017-09-01

We analyzed a case of medulloblastoma with atypical dynamic imaging changes retrospectively to summarize the atypical magnetic resonance imaging (MRI) features of medulloblastoma by reviewing the literature. An atypical case of medulloblastoma in the cerebellar hemisphere confirmed by pathology was analyzed retrospectively, and the literature about it was reviewed. The radiologic findings of the patient were based on 3 examinations. The first examination showed that the cortex of the bilateral cerebellar hemisphere had diffuse nodular thickening, with a high signal on diffusion-weighted imaging and significant enhancement. Contrast enhancement MRI 1 year later showed the signal of cerebellar hemisphere returned to normal but revealed an enhanced nodule. A reexamination 6 months later showed an irregular mass with a high-density shadow in the cerebellar vermis on CT scan. The T2-weighted image revealed multiple degenerative cysts, and the mass had significant enhancement. The radiologic characteristics of atypical medulloblastomas vary in adults and children. Understanding the radiologic characteristics of medulloblastomas, such as MRI features, age of onset, and location of atypical medulloblastomas, can help improve the diagnosis of medulloblastomas. Copyright © 2017. Published by Elsevier Inc.

Interpreting the Weibull fitting parameters for diffusion-controlled release data

NASA Astrophysics Data System (ADS)

Ignacio, Maxime; Chubynsky, Mykyta V.; Slater, Gary W.

2017-11-01

We examine the diffusion-controlled release of molecules from passive delivery systems using both analytical solutions of the diffusion equation and numerically exact Lattice Monte Carlo data. For very short times, the release process follows a √{ t } power law, typical of diffusion processes, while the long-time asymptotic behavior is exponential. The crossover time between these two regimes is determined by the boundary conditions and initial loading of the system. We show that while the widely used Weibull function provides a reasonable fit (in terms of statistical error), it has two major drawbacks: (i) it does not capture the correct limits and (ii) there is no direct connection between the fitting parameters and the properties of the system. Using a physically motivated interpolating fitting function that correctly includes both time regimes, we are able to predict the values of the Weibull parameters which allows us to propose a physical interpretation.

White matter tractography using diffusion tensor deflection.

PubMed

Lazar, Mariana; Weinstein, David M; Tsuruda, Jay S; Hasan, Khader M; Arfanakis, Konstantinos; Meyerand, M Elizabeth; Badie, Benham; Rowley, Howard A; Haughton, Victor; Field, Aaron; Alexander, Andrew L

2003-04-01

Diffusion tensor MRI provides unique directional diffusion information that can be used to estimate the patterns of white matter connectivity in the human brain. In this study, the behavior of an algorithm for white matter tractography is examined. The algorithm, called TEND, uses the entire diffusion tensor to deflect the estimated fiber trajectory. Simulations and imaging experiments on in vivo human brains were performed to investigate the behavior of the tractography algorithm. The simulations show that the deflection term is less sensitive than the major eigenvector to image noise. In the human brain imaging experiments, estimated tracts were generated in corpus callosum, corticospinal tract, internal capsule, corona radiata, superior longitudinal fasciculus, inferior longitudinal fasciculus, fronto-occipital fasciculus, and uncinate fasciculus. This approach is promising for mapping the organizational patterns of white matter in the human brain as well as mapping the relationship between major fiber trajectories and the location and extent of brain lesions. Copyright 2003 Wiley-Liss, Inc.

Suppression of Lateral Diffusion and Surface Leakage Currents in nBn Photodetectors Using an Inverted Design

NASA Astrophysics Data System (ADS)

Du, X.; Savich, G. R.; Marozas, B. T.; Wicks, G. W.

2018-02-01

Surface leakage and lateral diffusion currents in InAs-based nBn photodetectors have been investigated. Devices fabricated using a shallow etch processing scheme that etches through the top contact and stops at the barrier exhibited large lateral diffusion current but undetectably low surface leakage. Such large lateral diffusion current significantly increased the dark current, especially in small devices, and causes pixel-to-pixel crosstalk in detector arrays. To eliminate the lateral diffusion current, two different approaches were examined. The conventional solution utilized a deep etch process, which etches through the top contact, barrier, and absorber. This deep etch processing scheme eliminated lateral diffusion, but introduced high surface current along the device mesa sidewalls, increasing the dark current. High device failure rate was also observed in deep-etched nBn structures. An alternative approach to limit lateral diffusion used an inverted nBn structure that has its absorber grown above the barrier. Like the shallow etch process on conventional nBn structures, the inverted nBn devices were fabricated with a processing scheme that only etches the top layer (the absorber, in this case) but avoids etching through the barrier. The results show that inverted nBn devices have the advantage of eliminating the lateral diffusion current without introducing elevated surface current.

Ultrasound findings of diffuse metastasis of gastric signet-ring-cell carcinoma to the thyroid gland.

PubMed

Morita, Koji; Sakamoto, Takahiko; Ota, Shuji; Masugi, Hideo; Chikuta, Ikumi; Mashimo, Yamato; Edo, Naoki; Tokairin, Takuo; Seki, Nobuhiko; Ishikawa, Toshio

2017-01-01

It has been shown that metastases to the thyroid from extrathyroidal malignancies occur as solitary or multiple nodules, or may involve the whole thyroid gland diffusely. However, diffuse metastasis of gastric cancer to the thyroid is extremely rare. Here, we report a case of a 74-year-old woman with diffuse infiltration of gastric adenocarcinoma (signet-ring-cell carcinoma/poorly differentiated adenocarcinoma) cells in the thyroid. The pathological diagnosis was made based on upper gastrointestinal endoscopy with biopsy and fine-needle aspiration cytology of the thyroid. An 18F-FDG PET/CT revealed multiple lesions with increased uptake, including the bilateral thyroid gland. On thyroid ultrasound examination, diffuse enlargement with internal heterogeneity and hypoechoic reticular lines was observed. On color Doppler imaging, a blood-flow signal was not detected in these hypoechoic lines. These findings were similar to those of diffuse metastases caused by other primary cancers, such as lung cancer, as reported earlier. Therefore, the presence of hypoechoic reticular lines without blood-flow signals is probably common to diffuse thyroid metastasis from any origin and an important diagnostic finding. This is the first report to show detailed ultrasound findings of diffuse gastric cancer metastasis to the thyroid gland using color Doppler.

Ras Diffusion Is Sensitive to Plasma Membrane Viscosity

PubMed Central

Goodwin, J. Shawn; Drake, Kimberly R.; Remmert, Catha L.; Kenworthy, Anne K.

2005-01-01

The cell surface contains a variety of barriers and obstacles that slow the lateral diffusion of glycosylphosphatidylinositol (GPI)-anchored and transmembrane proteins below the theoretical limit imposed by membrane viscosity. How the diffusion of proteins residing exclusively on the inner leaflet of the plasma membrane is regulated has been largely unexplored. We show here that the diffusion of the small GTPase Ras is sensitive to the viscosity of the plasma membrane. Using confocal fluorescence recovery after photobleaching, we examined the diffusion of green fluorescent protein (GFP)-tagged HRas, NRas, and KRas in COS-7 cells loaded with or depleted of cholesterol, a well-known modulator of membrane bilayer viscosity. In cells loaded with excess cholesterol, the diffusional mobilities of GFP-HRas, GFP-NRas, and GFP-KRas were significantly reduced, paralleling the behavior of the viscosity-sensitive lipid probes DiIC16 and DiIC18. However, the effects of cholesterol depletion on protein and lipid diffusion in cell membranes were highly dependent on the depletion method used. Cholesterol depletion with methyl-β-cyclodextrin slowed Ras diffusion by a viscosity-independent mechanism, whereas overnight cholesterol depletion slightly increased both protein and lipid diffusion. The ability of Ras to sense membrane viscosity may represent a general feature of proteins residing on the cytoplasmic face of the plasma membrane. PMID:15923235

Technique of diffusion weighted imaging and its application in stroke

NASA Astrophysics Data System (ADS)

Li, Enzhong; Tian, Jie; Han, Ying; Wang, Huifang; Li, Wu; He, Huiguang

2003-05-01

To study the application of diffusion weighted imaging and image post processing in the diagnosis of stroke, especially in acute stroke, 205 patients were examined by 1.5 T or 1.0 T MRI scanner and the images such as T1, T2 and diffusion weighted images were obtained. Image post processing was done with "3D Med System" developed by our lab to analyze data and acquire the apparent diffusion coefficient (ADC) map. In acute and subacute stage of stroke, the signal in cerebral infarction areas changed to hyperintensity in T2- and diffusion-weighted images, normal or hypointensity in T1-weighted images. In hyperacute stage, however, the signal was hyperintense just in the diffusion weighted imaes; others were normal. In the chronic stage, the signal in T1- and diffusion-weighted imaging showed hypointensity and hyperintensity in T2 weighted imaging. Because ADC declined obviously in acute and subacute stage of stroke, the lesion area was hypointensity in ADC map. With the development of the disease, ADC gradually recovered and then changed to hyperintensity in ADC map in chronic stage. Using diffusion weighted imaging and ADC mapping can make a diagnosis of stroke, especially in the hyperacute stage of stroke, and can differentiate acute and chronic stroke.

Evaluation of Proteins' Rotational Diffusion Coefficients from Simulations of Their Free Brownian Motion in Volume-Occupied Environments.

PubMed

Długosz, Maciej; Antosiewicz, Jan M

2014-01-14

We have investigated the rotational dynamics of hen egg white lysozyme in monodisperse aqueous solutions of concentrations up to 250 mg/mL, using a rigid-body Brownian dynamics method that accurately accounts for anisotropies of diffusing objects. We have examined the validity of the free diffusion concept in the analysis of computer simulations of volume-occupied molecular solutions. We have found that, when as the only intermolecular interaction, the excluded volume effect is considered, rotational diffusion of molecules adheres to the free diffusion model. Further, we present a method based on the exact (in the case of the free diffusion) analytic forms of autocorrelation functions of particular vectors rigidly attached to diffusing objects, which allows one to obtain from results of molecular simulations the three principal rotational diffusion coefficients characterizing rotational Brownian motion of an arbitrarily shaped rigid particle for an arbitrary concentration of crowders. We have applied this approach to trajectories resulting from Brownian dynamics simulations of hen egg white lysozyme solutions. We show that the apparent anisotropy of proteins' rotational motions increases with an increasing degree of crowding. Finally, we demonstrate that even if the hydrodynamic anisotropy of molecules is neglected and molecules are simulated using their average translational and rotational diffusion coefficients, excluded volume effects still lead to their anisotropic rotational dynamics.

Measuring the diffusion of linguistic change

PubMed Central

Nerbonne, John

2010-01-01

We examine situations in which linguistic changes have probably been propagated via normal contact as opposed to via conquest, recent settlement and large-scale migration. We proceed then from two simplifying assumptions: first, that all linguistic variation is the result of either diffusion or independent innovation, and, second, that we may operationalize social contact as geographical distance. It is clear that both of these assumptions are imperfect, but they allow us to examine diffusion via the distribution of linguistic variation as a function of geographical distance. Several studies in quantitative linguistics have examined this relation, starting with Séguy (Séguy 1971 Rev. Linguist. Romane 35, 335–357), and virtually all report a sublinear growth in aggregate linguistic variation as a function of geographical distance. The literature from dialectology and historical linguistics has mostly traced the diffusion of individual features, however, so that it is sensible to ask what sort of dynamic in the diffusion of individual features is compatible with Séguy's curve. We examine some simulations of diffusion in an effort to shed light on this question. PMID:21041207

Measuring the diffusion of linguistic change.

PubMed

Nerbonne, John

2010-12-12

We examine situations in which linguistic changes have probably been propagated via normal contact as opposed to via conquest, recent settlement and large-scale migration. We proceed then from two simplifying assumptions: first, that all linguistic variation is the result of either diffusion or independent innovation, and, second, that we may operationalize social contact as geographical distance. It is clear that both of these assumptions are imperfect, but they allow us to examine diffusion via the distribution of linguistic variation as a function of geographical distance. Several studies in quantitative linguistics have examined this relation, starting with Séguy (Séguy 1971 Rev. Linguist. Romane 35, 335-357), and virtually all report a sublinear growth in aggregate linguistic variation as a function of geographical distance. The literature from dialectology and historical linguistics has mostly traced the diffusion of individual features, however, so that it is sensible to ask what sort of dynamic in the diffusion of individual features is compatible with Séguy's curve. We examine some simulations of diffusion in an effort to shed light on this question.

Molecular version of the resistive pulse technique: counting ATP by a single ion channel

NASA Astrophysics Data System (ADS)

Rostovtseva, T. K.; Bezrukov, S. M.

1998-03-01

The ``molecular Coulter counter'' concept has been used to study transport of ATP molecules through the nanometer-scale aqueous pore of the voltage-dependent mitochondrial ion channel, VDAC. We examine the ATP-induced current fluctuations and the change in average current through a single fully open channel reconstituted into a planar lipid bilayer. At high salt concentration (1M NaCl), the addition of ATP reduces both solution specific conductivity and channel conductance, but the effect on the channel is several times stronger and shows saturation behavior at 50 mM ATP concentration. ATP addition also generates an excess noise in the ionic current through the channel. By relating the low-frequency spectral density of the noise to the equilibrium diffusion of ATP molecules in the aqueous pore, we calculate a diffusion coefficient D = (1.6-3.3)x10-11 m^2 /s. We show that the mesoscopic VDAC pore is a Coulter counter with the added features of attraction and diffusion.

Alpha-mannosidosis in goats caused by the swainsonine-containing plant Ipomoea verbascoidea

USDA-ARS?s Scientific Manuscript database

A disease of the nervous system is reported in goats in the semiarid region of northeastern Brazil. Histological examination showed diffuse vacuolation of neurons and epithelial cells of the pancreas, thyroid, renal tubules, and liver. The swainsonine-containing plant Ipomoea verbascoidea was found ...

Double perovskite cathodes for proton-conducting ceramic fuel cells: are they triple mixed ionic electronic conductors?

NASA Astrophysics Data System (ADS)

Téllez Lozano, Helena; Druce, John; Cooper, Samuel J.; Kilner, John A.

2017-12-01

18O and 2H diffusion has been investigated at a temperature of 300 °C in the double perovskite material PrBaCo2O5+δ (PBCO) in flowing air containing 200 mbar of 2H216O. Secondary ion mass spectrometry (SIMS) depth profiling of exchanged ceramics has shown PBCO still retains significant oxygen diffusivity ( 1.3 × 10-11 cm2s-1) at this temperature and that the presence of water (2H216O), gives rise to an enhancement of the surface exchange rate over that in pure oxygen by a factor of 3. The 2H distribution, as inferred from the 2H216O- SIMS signal, shows an apparent depth profile which could be interpreted as 2H diffusion. However, examination of the 3-D distribution of the signal shows it to be nonhomogeneous and probably related to the presence of hydrated layers in the interior walls of pores and is not due to proton diffusion. This suggests that PBCO acts mainly as an oxygen ion mixed conductor when used in PCFC devices, although the presence of a small amount of protonic conductivity cannot be discounted in these materials.

Particle transport through hydrogels is charge asymmetric.

PubMed

Zhang, Xiaolu; Hansing, Johann; Netz, Roland R; DeRouchey, Jason E

2015-02-03

Transport processes within biological polymer networks, including mucus and the extracellular matrix, play an important role in the human body, where they serve as a filter for the exchange of molecules and nanoparticles. Such polymer networks are complex and heterogeneous hydrogel environments that regulate diffusive processes through finely tuned particle-network interactions. In this work, we present experimental and theoretical studies to examine the role of electrostatics on the basic mechanisms governing the diffusion of charged probe molecules inside model polymer networks. Translational diffusion coefficients are determined by fluorescence correlation spectroscopy measurements for probe molecules in uncharged as well as cationic and anionic polymer solutions. We show that particle transport in the charged hydrogels is highly asymmetric, with diffusion slowed down much more by electrostatic attraction than by repulsion, and that the filtering capability of the gel is sensitive to the solution ionic strength. Brownian dynamics simulations of a simple model are used to examine key parameters, including interaction strength and interaction range within the model networks. Simulations, which are in quantitative agreement with our experiments, reveal the charge asymmetry to be due to the sticking of particles at the vertices of the oppositely charged polymer networks. Copyright © 2015 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Radiologic-Pathologic Analysis of Contrast-enhanced and Diffusion-weighted MR Imaging in Patients with HCC after TACE: Diagnostic Accuracy of 3D Quantitative Image Analysis

PubMed Central

Chapiro, Julius; Wood, Laura D.; Lin, MingDe; Duran, Rafael; Cornish, Toby; Lesage, David; Charu, Vivek; Schernthaner, Rüdiger; Wang, Zhijun; Tacher, Vania; Savic, Lynn Jeanette; Kamel, Ihab R.

2014-01-01

Purpose To evaluate the diagnostic performance of three-dimensional (3Dthree-dimensional) quantitative enhancement-based and diffusion-weighted volumetric magnetic resonance (MR) imaging assessment of hepatocellular carcinoma (HCChepatocellular carcinoma) lesions in determining the extent of pathologic tumor necrosis after transarterial chemoembolization (TACEtransarterial chemoembolization). Materials and Methods This institutional review board–approved retrospective study included 17 patients with HCChepatocellular carcinoma who underwent TACEtransarterial chemoembolization before surgery. Semiautomatic 3Dthree-dimensional volumetric segmentation of target lesions was performed at the last MR examination before orthotopic liver transplantation or surgical resection. The amount of necrotic tumor tissue on contrast material–enhanced arterial phase MR images and the amount of diffusion-restricted tumor tissue on apparent diffusion coefficient (ADCapparent diffusion coefficient) maps were expressed as a percentage of the total tumor volume. Visual assessment of the extent of tumor necrosis and tumor response according to European Association for the Study of the Liver (EASLEuropean Association for the Study of the Liver) criteria was performed. Pathologic tumor necrosis was quantified by using slide-by-slide segmentation. Correlation analysis was performed to evaluate the predictive values of the radiologic techniques. Results At histopathologic examination, the mean percentage of tumor necrosis was 70% (range, 10%–100%). Both 3Dthree-dimensional quantitative techniques demonstrated a strong correlation with tumor necrosis at pathologic examination (R2 = 0.9657 and R2 = 0.9662 for quantitative EASLEuropean Association for the Study of the Liver and quantitative ADCapparent diffusion coefficient, respectively) and a strong intermethod agreement (R2 = 0.9585). Both methods showed a significantly lower discrepancy with pathologically measured necrosis (residual standard error [RSEresidual standard error] = 6.38 and 6.33 for quantitative EASLEuropean Association for the Study of the Liver and quantitative ADCapparent diffusion coefficient, respectively), when compared with non-3Dthree-dimensional techniques (RSEresidual standard error = 12.18 for visual assessment). Conclusion This radiologic-pathologic correlation study demonstrates the diagnostic accuracy of 3Dthree-dimensional quantitative MR imaging techniques in identifying pathologically measured tumor necrosis in HCChepatocellular carcinoma lesions treated with TACEtransarterial chemoembolization. © RSNA, 2014 Online supplemental material is available for this article. PMID:25028783

Effects of inlet flow field conditions on the performance of centrifugal compressor diffusers: Part 1 -- Discrete-passage diffuser

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

Filipenco, V.G.; Deniz, S.; Johnston, J.M.

2000-01-01

This is Part 1 of a two-part paper considering the performance of radial diffusers for use in a high-performance centrifugal compressor. Part 1 reports on discrete-passage diffusers, while Part 2 describes a test of a straight-channel diffuser designed for equivalent duty. Two builds of discrete-passage diffuser were tested, with 30 and 38 separate passages. Both the 30 and 38 passage diffusers investigated showed comparable range of unstalled operation and similar level of overall diffuser pressure recovery. The paper concentrates on the influence of inlet flow conditions on the pressure recovery and operating range of radial diffusers for centrifugal compressor stages.more » The flow conditions examined include diffuser inlet Mach number, flow angle, blockage, and axial flow nonuniformity. The investigation was carried out in a specially built test facility, designed to provide a controlled inlet flow field to the test diffusers. The facility can provide a wide range of diffuser inlet velocity profile distortion and skew with Mach numbers up to unity and flow angles of 63 to 75 deg from the radical direction. The consequences of different averaging methods for the inlet total pressure distributions, which are needed in the definition of diffuser pressure recovery coefficient for nonuniform diffuser inlet conditions, were also assessed. The overall diffuser pressure recovery coefficient, based on suitably averaged inlet total pressure, was found to correlate well with the momentum-averaged flow angle into the diffuser. It is shown that the generally accepted sensitivity of diffuser pressure recovery performance to inlet flow distortion and boundary layer blockage can be largely attributed to inappropriate quantification of the average dynamic pressure at diffuser inlet. Use of an inlet dynamic pressure based on availability or mass-averaging in combination with definition of inlet flow angle based on mass average of the radial and tangential velocity at diffuser inlet removes this sensitivity.« less

Molecular dynamic simulation of dicationic ionic liquids: effects of anions and alkyl chain length on liquid structure and diffusion.

PubMed

Yeganegi, Saeid; Soltanabadi, Azim; Farmanzadeh, Davood

2012-09-20

Structures and dynamics of nine geminal dicationic ionic liquids (DILs) Cn(mim)2X2, where n = 3, 6, and 9 and X = PF6(-), BF4(-), and Br(-), were studied by molecular dynamic simulations (J. Phys. Chem.B2004, 108, 2038-2047). A force field with a minor modification for C3(mim)2 × 2 was adopted for the simulations. Densities, detailed microscopic structures, mean-square displacements (MSD), and self-diffusivities for various ion pairs from MD simulations have been presented. The calculated densities for C9(mim)2X2 (X = Br(-) and BF4(-)) agreed well with the experimental values. The calculated RDFs show that anions are well organized around the imidazolium rings. The calculated RDFs indicate that, unlike the mono cationic ILs, the anions and cations in DILs distribute homogeneously. Enthalpies of vaporization were calculated and correlated with the structural features of DILs. The local structure of C9(mim)2X2 (X = Br, PF6) was examined by the spatial distribution function (SDF). The calculated SDFs show that similar trends were found by other groups for mono cationic ionic liquids (ILs). The highest probability densities are located around the imidazolium ring hydrogens. The calculated diffusion coefficients show that the ion diffusivities are 1 order of magnitude smaller than that of the mono cationic ionic liquids. The effects of alkyl chain length and anion type on the diffusion coefficient were also studied. The dynamics of the imidazolium rings and the alkyl chain in different time scales have also discussed. The calculated transference numbers show that the anions have the major role in carrying the electric current in a DIL.

Multi-Component Diffusion with Application To Computational Aerothermodynamics

NASA Technical Reports Server (NTRS)

Sutton, Kenneth; Gnoffo, Peter A.

1998-01-01

The accuracy and complexity of solving multicomponent gaseous diffusion using the detailed multicomponent equations, the Stefan-Maxwell equations, and two commonly used approximate equations have been examined in a two part study. Part I examined the equations in a basic study with specified inputs in which the results are applicable for many applications. Part II addressed the application of the equations in the Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA) computational code for high-speed entries in Earth's atmosphere. The results showed that the presented iterative scheme for solving the Stefan-Maxwell equations is an accurate and effective method as compared with solutions of the detailed equations. In general, good accuracy with the approximate equations cannot be guaranteed for a species or all species in a multi-component mixture. 'Corrected' forms of the approximate equations that ensured the diffusion mass fluxes sum to zero, as required, were more accurate than the uncorrected forms. Good accuracy, as compared with the Stefan- Maxwell results, were obtained with the 'corrected' approximate equations in defining the heating rates for the three Earth entries considered in Part II.

Recovery of an injured fornix in a stroke patient.

PubMed

Yeo, Sang Seok; Jang, Sung Ho

2013-11-01

Knowledge about recovery of an injured fornix following brain injury is limited. We describe here a patient who showed recovery of an injured fornix following stroke. A 57-year-old female patient underwent coiling for a ruptured anterior communicating cerebral artery aneurysm, and conservative management for subarachnoid and intraventricular haemorrhage. The patient showed severe cognitive impairment 6 weeks after onset. However, her cognition showed continuous improvement with time; based on the Mini-Mental State Examination and the Memory Assessment Scale, her cognition was within the normal range 7 months after onset. Findings from diffusion tensor tractography at 6 weeks and 7 months showed discontinuations in both columns of the fornix. The proximal portion of both crus also showed discontinuation on diffusion tensor tractography at 6 weeks and 7 months; however, on 7-month diffusion tensor tractography, the end of the fornical body was shown to be connected to the splenium of the corpus callosum and then branched to the right medial temporal lobe and right thalamus. The unusual neural connection between the injured fornix and the thalamus appears to be a recovery phenomenon, which allows the injured fornix and the medial temporal lobe to obtain cholinergic innervation from cholinergic nuclei in the brainstem rather than from cholinergic nuclei in the basal forebrain.

4.7-T diffusion tensor imaging of acute traumatic peripheral nerve injury

PubMed Central

Boyer, Richard B.; Kelm, Nathaniel D.; Riley, D. Colton; Sexton, Kevin W.; Pollins, Alonda C.; Shack, R. Bruce; Dortch, Richard D.; Nanney, Lillian B.; Does, Mark D.; Thayer, Wesley P.

2015-01-01

Diagnosis and management of peripheral nerve injury is complicated by the inability to assess microstructural features of injured nerve fibers via clinical examination and electrophysiology. Diffusion tensor imaging (DTI) has been shown to accurately detect nerve injury and regeneration in crush models of peripheral nerve injury, but no prior studies have been conducted on nerve transection, a surgical emergency that can lead to permanent weakness or paralysis. Acute sciatic nerve injuries were performed microsurgically to produce multiple grades of nerve transection in rats that were harvested 1 hour after surgery. High-resolution diffusion tensor images from ex vivo sciatic nerves were obtained using diffusion-weighted spin-echo acquisitions at 4.7 T. Fractional anisotropy was significantly reduced at the injury sites of transected rats compared with sham rats. Additionally, minor eigenvalues and radial diffusivity were profoundly elevated at all injury sites and were negatively correlated to the degree of injury. Diffusion tensor tractography showed discontinuities at all injury sites and significantly reduced continuous tract counts. These findings demonstrate that high-resolution DTI is a promising tool for acute diagnosis and grading of traumatic peripheral nerve injuries. PMID:26323827

Diffuse sclerosing variant of thyroid carcinoma presenting as Hashimoto thyroiditis: a case report.

PubMed

Vukasović, Anamarija; Kuna, Sanja Kusacić; Ostović, Karmen Trutin; Prgomet, Drago; Banek, Tomislav

2012-11-01

The aim of report is to present a case of a rare diffuse sclerosing variant of a papillary thyroid carcinoma. A 15-year old girl referred for ultrasound examination because of painless thyroid swelling lasting 10 days before. An ultrasound of the neck showed diffusely changed thyroid parenchyma, without nodes, looking as lymphocytic thyroiditis Hashimoto at first, but with snow-storm appearance, predominantly in the right lobe. Positive thyroid peroxidase antibodies (TPO-AT) also suggested Hashimoto thyroiditis. Repeated US-FNAB (fine needle-aspiration biopsy) of the right lobe revealed diffuse sclerosing variant of papillary thyroid carcinoma and patient underwent total thyreoidectomy. Patohistologic finding confirmed diffuse sclerosing variant of a papillary thyroid carcinoma in the both thyroid lobes and several metastatic lymph nodes. Two months later patient recived radioablative therapy with 3700 MBq (100 mCi) of 1-131 followed by levothyroxine replacement. At the moment, patient is without evidence of local or distant metastases and next regular control is scheduled in 6 months. In conclusion, a diffuse sclerosing variant is rare form of papillary thyroid carcinoma that echographically looks similar to Hashimoto thyroiditis and sometimes could be easily overlooked.

Clinically granulomatous cheilitis with plasma cells

PubMed Central

Sarkar, Somenath; Ghosh, Sarmistha; Sengupta, Dipayan

2016-01-01

Plasma cell cheilitis, also known as plasma cell orificial mucositis is a benign inflammatory condition clinically characterized by erythematous plaque on lips that may be ulcerated. Histopathologically it is characterized by dense plasma cell infiltrates in a band-like pattern in dermis, which corresponds to Zoon's plasma cell balanitis. On the other hand, granulomatous cheilitis, as a part of orofacial granulomatosis, manifests as sudden diffuse or nodular swelling involving lip and cheek. Initial swelling is soft to firm, but with recurrent episodes swelling gradually become firm rubbery in consistency. We hereby report a case of cheilitis in a 52-year-old man with diffuse swelling involving lower lip, which clinically resembles granulomatous cheilitis, but histopathological examination showed diffuse infiltrate of plasma cells predominantly in upper and mid-dermis. PMID:27057489

The effect of personal characteristics on the relationship between diffusion and adoption of telecentre with value creation

NASA Astrophysics Data System (ADS)

Dahalin, Zulkhairi Md.

2016-08-01

This paper examines personal characteristics of respondents in the rural areas and the extent of its effect on the diffusion and adoption of the telecentre. Understanding the personal characteristics of the participants is needed in order to encourage better participation. A survey was conducted among participants of telecentres situated in rural areas in the northern states of Malaysia. Results showed that whilst family size had a significant effect on the relationships between diffusion and adoption with value creation, other personal characteristics were found not to affect the relationships. The results have important implications to sustainability of the telecentre, in which focus should be placed in small-sized families rather than based on background and other demographic profile of participants.

Beyond Economy: Impact of National Cultural Values on Nationwide Broadband Internet Diffusion

ERIC Educational Resources Information Center

Joo, Sung-Hee

2010-01-01

This study examines how the non-conventional factors of national cultural values and government involvement affect the diffusion of broadband Internet technologies in various nations around the world. An innovative element of the study was the examination of the influence patterns at different stages of diffusion, which was measured by the number…

Lithium ion solvation and diffusion in bulk organic electrolytes from first-principles and classical reactive molecular dynamics.

PubMed

Ong, Mitchell T; Verners, Osvalds; Draeger, Erik W; van Duin, Adri C T; Lordi, Vincenzo; Pask, John E

2015-01-29

Lithium-ion battery performance is strongly influenced by the ionic conductivity of the electrolyte, which depends on the speed at which Li ions migrate across the cell and relates to their solvation structure. The choice of solvent can greatly impact both the solvation and diffusivity of Li ions. In this work, we used first-principles molecular dynamics to examine the solvation and diffusion of Li ions in the bulk organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC), and a mixture of EC and EMC. We found that Li ions are solvated by either carbonyl or ether oxygen atoms of the solvents and sometimes by the PF6(-) anion. Li(+) prefers a tetrahedrally coordinated first solvation shell regardless of which species are involved, with the specific preferred solvation structure dependent on the organic solvent. In addition, we calculated Li diffusion coefficients in each electrolyte, finding slightly larger diffusivities in the linear carbonate EMC compared to the cyclic carbonate EC. The magnitude of the diffusion coefficient correlates with the strength of Li(+) solvation. Corresponding analysis for the PF6(-) anion shows greater diffusivity associated with a weakly bound, poorly defined first solvation shell. These results can be used to aid in the design of new electrolytes to improve Li-ion battery performance.

Flagella-Driven Flows Circumvent Diffusive Bottlenecks that Inhibit Metabolite Exchange

NASA Astrophysics Data System (ADS)

Short, Martin; Solari, Cristian; Ganguly, Sujoy; Kessler, John; Goldstein, Raymond; Powers, Thomas

2006-03-01

The evolution of single cells to large and multicellular organisms requires matching the organisms' needs to the rate of exchange of metabolites with the environment. This logistic problem can be a severe constraint on development. For organisms with a body plan that approximates a spherical shell, such as colonies of the volvocine green algae, the required current of metabolites grows quadratically with colony radius whereas the rate at which diffusion can exchange metabolites grows only linearly with radius. Hence, there is a bottleneck radius beyond which the diffusive current cannot keep up with metabolic demands. Using Volvox carteri as a model organism, we examine experimentally and theoretically the role that advection of fluid by surface-mounted flagella plays in enhancing nutrient uptake. We show that fluid flow driven by the coordinated beating of flagella produces a convective boundary layer in the concentration of a diffusing solute which in turn renders the metabolite exchange rate quadratic in the colony radius. This enhanced transport circumvents the diffusive bottleneck, allowing increase in size and thus evolutionary transitions to multicellularity in the Volvocales.

Dispersion-relation phase spectroscopy of neuron transport

NASA Astrophysics Data System (ADS)

Wang, Ru; Wang, Zhuo; Millet, Larry; Gillette, Martha; Leigh, Joseph Robert; Sobh, Nahil; Levine, Alex; Popescu, Gabreil

2012-02-01

Molecular motors move materials along prescribed biopolymer tracks. This sort of active transport is required to rapidly move products over large distances within the cell, where passive diffusion is too slow. We examine intracellular traffic patterns using a new application of spatial light interference microscopy (SLIM) and measure the dispersion relation, i.e. decay rate vs. spatial mode, associated with mass transport in live cells. This approach applies equally well to both discrete and continuous mass distributions without the need for particle tracking. From the quadratic experimental curve specific to diffusion, we extracted the diffusion coefficient as the only fitting parameter. The linear portion of the dispersion relation reveals the deterministic component of the intracellular transport. Our data show a universal behavior where the intracellular transport is diffusive at small scales and deterministic at large scales. We further applied this method to studying transport in neurons and are able to use SLIM to map the changes in index of refraction across the neuron and its extended processes. We found that in dendrites and axons, the transport is mostly active, i.e., diffusion is subdominant.

Gaussian fluctuation of the diffusion exponent of virus capsid in a living cell nucleus

NASA Astrophysics Data System (ADS)

Itto, Yuichi

2018-05-01

In their work [4], Bosse et al. experimentally showed that virus capsid exhibits not only normal diffusion but also anomalous diffusion in nucleus of a living cell. There, it was found that the distribution of fluctuations of the diffusion exponent characterizing them takes the Gaussian form, which is, quite remarkably, the same form for two different types of the virus. This suggests high robustness of such fluctuations. Here, the statistical property of local fluctuations of the diffusion exponent of the virus capsid in the nucleus is studied. A maximum-entropy-principle approach (originally proposed for a different virus in a different cell) is applied for obtaining the fluctuation distribution of the exponent. Largeness of the number of blocks identified with local areas of interchromatin corrals is also examined based on the experimental data. It is shown that the Gaussian distribution of the local fluctuations can be derived, in accordance with the above form. In addition, it is quantified how the fluctuation distribution on a long time scale is different from the Gaussian distribution.

Diffusion-weighted MR imaging of upper abdominal organs at different time points: Apparent diffusion coefficient normalization using a reference organ.

PubMed

Song, Ji Soo; Kwak, Hyo Sung; Byon, Jung Hee; Jin, Gong Yong

2017-05-01

To compare the apparent diffusion coefficient (ADC) of upper abdominal organs acquired at different time points, and to investigate the usefulness of normalization. We retrospectively evaluated 58 patients who underwent three rounds of magnetic resonance (MR) imaging including diffusion-weighted imaging of the upper abdomen. MR examinations were performed using three different 3.0 Tesla (T) and one 1.5T systems, with variable b value combinations and respiratory motion compensation techniques. The ADC values of the upper abdominal organs from three different time points were analyzed, using the ADC values of the paraspinal muscle (ADC psm ) and spleen (ADC spleen ) for normalization. Intraclass correlation coefficients (ICC) and comparison of dependent ICCs were used for statistical analysis. The ICCs of the original ADC and ADC psm showed fair to substantial agreement, while ADC spleen showed substantial to almost perfect agreement. The ICC of ADC spleen of all anatomical regions showed less variability compared with that of the original ADC (P < 0.005). Normalized ADC using the spleen as a reference organ significantly decreased variability in measurement of the upper abdominal organs in different MR systems at different time points and could be regarded as an imaging biomarker for future multicenter, longitudinal studies. 5 J. MAGN. RESON. IMAGING 2017;45:1494-1501. © 2016 International Society for Magnetic Resonance in Medicine.

Coupled diffusion processes and 2D affinities of adhesion molecules at synthetic membrane junctions

NASA Astrophysics Data System (ADS)

Peel, Christopher; Choudhuri, Kaushik; Schmid, Eva M.; Bakalar, Matthew H.; Ann, Hyoung Sook; Fletcher, Daniel A.; Journot, Celine; Turberfield, Andrew; Wallace, Mark; Dustin, Michael

A more complete understanding of the physically intrinsic mechanisms underlying protein mobility at cellular interfaces will provide additional insights into processes driving adhesion and organization in signalling junctions such as the immunological synapse. We observed diffusional slowing of structurally diverse binding proteins at synthetic interfaces formed by giant unilamellar vesicles (GUVs) on supported lipid bilayers (SLBs) that shows size dependence not accounted for by existing models. To model the effects of size and intermembrane spacing on interfacial reaction-diffusion processes, we describe a multistate diffusion model incorporating entropic effects of constrained binding. This can be merged with hydrodynamic theories of receptor-ligand diffusion and coupling to thermal membrane roughness. A novel synthetic membrane adhesion assay based on reversible and irreversible DNA-mediated interactions between GUVs and SLBs is used to precisely vary length, affinity, and flexibility, and also provides a platform to examine these effects on the dynamics of processes such as size-based segregation of binding and non-binding species.

In vivo burn diagnosis by camera-phone diffuse reflectance laser speckle detection.

PubMed

Ragol, S; Remer, I; Shoham, Y; Hazan, S; Willenz, U; Sinelnikov, I; Dronov, V; Rosenberg, L; Bilenca, A

2016-01-01

Burn diagnosis using laser speckle light typically employs widefield illumination of the burn region to produce two-dimensional speckle patterns from light backscattered from the entire irradiated tissue volume. Analysis of speckle contrast in these time-integrated patterns can then provide information on burn severity. Here, by contrast, we use point illumination to generate diffuse reflectance laser speckle patterns of the burn. By examining spatiotemporal fluctuations in these time-integrated patterns along the radial direction from the incident point beam, we show the ability to distinguish partial-thickness burns in a porcine model in vivo within the first 24 hours post-burn. Furthermore, our findings suggest that time-integrated diffuse reflectance laser speckle can be useful for monitoring burn healing over time post-burn. Unlike conventional diffuse reflectance laser speckle detection systems that utilize scientific or industrial-grade cameras, our system is designed with a camera-phone, demonstrating the potential for burn diagnosis with a simple imager.

In vivo burn diagnosis by camera-phone diffuse reflectance laser speckle detection

PubMed Central

Ragol, S.; Remer, I.; Shoham, Y.; Hazan, S.; Willenz, U.; Sinelnikov, I.; Dronov, V.; Rosenberg, L.; Bilenca, A.

2015-01-01

Burn diagnosis using laser speckle light typically employs widefield illumination of the burn region to produce two-dimensional speckle patterns from light backscattered from the entire irradiated tissue volume. Analysis of speckle contrast in these time-integrated patterns can then provide information on burn severity. Here, by contrast, we use point illumination to generate diffuse reflectance laser speckle patterns of the burn. By examining spatiotemporal fluctuations in these time-integrated patterns along the radial direction from the incident point beam, we show the ability to distinguish partial-thickness burns in a porcine model in vivo within the first 24 hours post-burn. Furthermore, our findings suggest that time-integrated diffuse reflectance laser speckle can be useful for monitoring burn healing over time post-burn. Unlike conventional diffuse reflectance laser speckle detection systems that utilize scientific or industrial-grade cameras, our system is designed with a camera-phone, demonstrating the potential for burn diagnosis with a simple imager. PMID:26819831

Coumafuryl (Fumarin) toxicity in chicks.

PubMed

Munger, L L; Su, J J; Barnes, H J

1993-01-01

Coumafuryl (Fumarin) toxicity was diagnosed in chickens less than 1 week of age. Mortality rate was 100%. Necropsy showed crops and gizzards to be full of feed. There was diffuse hemorrhage and unclotted blood in the abdomen and thorax. Histological examination showed congestion and hemorrhage. Chemical analysis of crop and gizzard contents contained approximately 340 ppm coumafuryl. The source of the coumafuryl was found to be the wood-straw mats in the chick boxes.

Arterial changes in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) in relation to pathogenesis of diffuse myelin loss of cerebral white matter: examination of cerebral medullary arteries by reconstruction of serial sections of an autopsy case.

PubMed

Okeda, Riki; Arima, Kunimasa; Kawai, Mitsuru

2002-11-01

There is little information regarding the pathogenesis underlying diffuse myelin loss in the cerebral white matter and sparing of the U fibers in cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), in which the medial smooth muscle cells of systemic arteries are characteristically involved. We sought to examine the precise extent and severity of changes in the cerebral arteries in an autopsy case of CADASIL in relation to pathogenesis of the diffuse myelin loss. We reconstructed 1000 serial sections of the frontal cerebral medullary arteries of an autopsy subject, which was the first identified Japanese case of CADASIL, as confirmed by the presence of ultrastructural deposits of granular osmiophilic material in the media of some visceral arteries and by genetic analysis. We reconstructed 11 medullary arteries of the frontal lobe showing diffuse myelin loss and atrophy of the white matter with sparing of the U fibers. All of these showed complete loss of medial smooth muscle cells over their entire length and severe adventitial fibrosis. Although intimal fibrosis or hyalinosis was present, luminal occlusion was scarce. These changes were also observed in the small and large arachnoidal arteries but were relatively mild in the latter and in the cortical and subcortical medullary arteries. These arterial changes resulted in transformation of the cerebral arteries, in particular almost all the medullary arteries, to a so-called earthen pipe state. This supports the reported findings of a reduction in vascular reactivity to fluctuations in CO2 levels and systemic blood pressure in CADASIL.

Pleural mesothelioma - case report.

PubMed

Klawiter, Anna; Damaszke, Tomasz

2010-10-01

Pleural mesothelioma is a very rare neoplasm; especially the local form. The diagnostics is difficult and the prognosis unfavourable. We presented a case of a man with dyspnoea and cough. His chest radiogram showed hydrothorax on the left side. Neither the examinations of the pleural liquid, nor the CT-guided fine needle biopsy established the diagnosis. CT showed features suggestive of pleural mesothelioma. The diagnosis was confirmed by thoracoscopy. Although no neoplastic cells were found in the thoracoscopic specimen from the supradiaphragmatic tumor, we assumed that to be a case of a diffuse, primarily local form of mesothelioma. Diagnostics of pleural mesothelioma is very difficult. CT and thoracoscopy seem to be very valuable diagnostic methods. It is worth remembering that pleural mesothelioma can have a local form which may transform into a diffuse one.

Statistical assessment of bi-exponential diffusion weighted imaging signal characteristics induced by intravoxel incoherent motion in malignant breast tumors

PubMed Central

Wong, Oi Lei; Lo, Gladys G.; Chan, Helen H. L.; Wong, Ting Ting; Cheung, Polly S. Y.

2016-01-01

Background The purpose of this study is to statistically assess whether bi-exponential intravoxel incoherent motion (IVIM) model better characterizes diffusion weighted imaging (DWI) signal of malignant breast tumor than mono-exponential Gaussian diffusion model. Methods 3 T DWI data of 29 malignant breast tumors were retrospectively included. Linear least-square mono-exponential fitting and segmented least-square bi-exponential fitting were used for apparent diffusion coefficient (ADC) and IVIM parameter quantification, respectively. F-test and Akaike Information Criterion (AIC) were used to statistically assess the preference of mono-exponential and bi-exponential model using region-of-interests (ROI)-averaged and voxel-wise analysis. Results For ROI-averaged analysis, 15 tumors were significantly better fitted by bi-exponential function and 14 tumors exhibited mono-exponential behavior. The calculated ADC, D (true diffusion coefficient) and f (pseudo-diffusion fraction) showed no significant differences between mono-exponential and bi-exponential preferable tumors. Voxel-wise analysis revealed that 27 tumors contained more voxels exhibiting mono-exponential DWI decay while only 2 tumors presented more bi-exponential decay voxels. ADC was consistently and significantly larger than D for both ROI-averaged and voxel-wise analysis. Conclusions Although the presence of IVIM effect in malignant breast tumors could be suggested, statistical assessment shows that bi-exponential fitting does not necessarily better represent the DWI signal decay in breast cancer under clinically typical acquisition protocol and signal-to-noise ratio (SNR). Our study indicates the importance to statistically examine the breast cancer DWI signal characteristics in practice. PMID:27709078

Diffusion tensor imaging of normal-appearing white matter in mild cognitive impairment and early Alzheimer disease: preliminary evidence of axonal degeneration in the temporal lobe.

PubMed

Huang, J; Friedland, R P; Auchus, A P

2007-01-01

Diffusion tensor imaging (DTI) is a sensitive technique for studying cerebral white matter. We used DTI to characterize microstructural white matter changes and their associations with cognitive dysfunction in Alzheimer disease (AD) and mild cognitive impairment (MCI). We studied elderly subjects with mild AD (n = 6), MCI (n = 11), or normal cognition (n = 8). A standardized clinical and neuropsychological evaluation was conducted on each subject. DTI images were acquired, and fractional anisotropy (FA), axial diffusivity (DA), and radial diffusivity (DR) of normal-appearing white matter (NAWM) in frontal, temporal, parietal, and occipital lobes were determined. These diffusion measurements were compared across the 3 groups, and significant differences were further examined for correlations with tests of cognitive function. Compared with normal controls, AD subjects demonstrated decreased FA and increased DR in the temporal, parietal, and frontal NAWM and decreased DA in temporal NAWM. MCI subjects also showed decreased FA and decreased DA in temporal NAWM, with decreased FA and increased DR in parietal NAWM. Diffusion measurements showed no differences in occipital NAWM. Across all subjects, temporal lobe FA and DR correlated with episodic memory, frontal FA and DR correlated with executive function, and parietal DR significantly correlated with visuospatial ability. We found evidence for functionally relevant microstructural changes in the NAWM of patients with AD and MCI. These changes were present in brain regions serving higher cortical functions, but not in regions serving primary functions, and are consistent with a hypothesized loss of axonal processes in the temporal lobe.

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.

Choice of data types in time resolved fluorescence enhanced diffuse optical tomography.

PubMed

Riley, Jason; Hassan, Moinuddin; Chernomordik, Victor; Gandjbakhche, Amir

2007-12-01

In this paper we examine possible data types for time resolved fluorescence enhanced diffuse optical tomography (FDOT). FDOT is a particular case of diffuse optical tomography, where our goal is to analyze fluorophores deeply embedded in a turbid medium. We focus on the relative robustness of the different sets of data types to noise. We use an analytical model to generate the expected temporal point spread function (TPSF) and generate the data types from this. Varying levels of noise are applied to the TPSF before generating the data types. We show that local data types are more robust to noise than global data types, and should provide enhanced information to the inverse problem. We go on to show that with a simple reconstruction algorithm, depth and lifetime (the parameters of interest) of the fluorophore are better reconstructed using the local data types. Further we show that the relationship between depth and lifetime is better preserved for the local data types, suggesting they are in some way not only more robust, but also self-regularizing. We conclude that while the local data types may be more expensive to generate in the general case, they do offer clear advantages over the standard global data types.

Diffusion Dominant Solute Transport Modelling in Fractured Media Under Deep Geological Environment - 12211

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

Kwong, S.; Jivkov, A.P.

2012-07-01

Deep geologic disposal of high activity and long-lived radioactive waste is gaining increasing support in many countries, where suitable low permeability geological formation in combination with engineered barriers are used to provide long term waste contaminant and minimise the impacts to the environment and risk to the biosphere. This modelling study examines the solute transport in fractured media under low flow velocities that are relevant to a deep geological environment. In particular, reactive solute transport through fractured media is studied using a 2-D model, that considers advection and diffusion, to explore the coupled effects of kinetic and equilibrium chemical processes.more » The effects of water velocity in the fracture, matrix porosity and diffusion on solute transport are investigated and discussed. Some illustrative modelled results are presented to demonstrate the use of the model to examine the effects of media degradation on solute transport, under the influences of hydrogeological (diffusion dominant) and microbially mediated chemical processes. The challenges facing the prediction of long term degradation such as cracks evolution, interaction and coalescence are highlighted. The potential of a novel microstructure informed modelling approach to account for these effects is discussed, particularly with respect to investigating multiple phenomena impact on material performance. The GRM code is used to examine the effects of media degradation for a geological waste disposal package, under the combined hydrogeological (diffusion dominant) and chemical effects in low groundwater flow conditions that are typical of deep geological disposal systems. An illustrative reactive transport modelling application demonstrates the use of the code to examine the interplay of kinetic controlled biogeochemical reactive processes with advective and diffusive transport, under the influence of media degradation. The initial model results are encouraging which show the disposal system to evolve in a physically realistic manner. In the example presented the reactive-transport coupling develops chemically reducing zones, which limit the transport of uranium. This illustrates the potential significance of media degradation and chemical effect on the transport of radionuclides which would need to be taken into account when examining the long-term behaviour and containment properties of the geological disposal system. Microstructure-informed modelling and its potential linkage with continuum flow modelling is a subject of ongoing studies. The approach of microstructure-informed modelling is discussed to provide insight and a mechanistic understanding of macroscopic parameters and their evolution. The proposed theoretical and methodological basis for microstructure-informed modelling of porous quasi-brittle media has the potential to develop into an explanatory and predictive tool for deriving mechanism-based, as opposed to phenomenological, evolution laws for macroscopic properties. These concepts in micro-scale modelling are likely to be applicable to the diffusion process, in addition to advective transport illustrated here for porous media. (authors)« less

Diffuse Thyroid Metastasis From Lung Cancer Mimicking Thyroiditis on 99mTc-Pertechnetate Scintigraphy.

PubMed

Gao, Rui; Gao, Shan; Feng, Jinteng; Wang, Yuanbo; Zhang, Guangjian

2017-09-01

Possible thyroiditis was suspected in a 56-year-old man who initially presented sore throat because laboratory examinations revealed decreased serum thyroid hormone and the Tc-pertechnetate scintigraphy showed no tracer uptake by the thyroid gland. However, subsequent examination demonstrated that the absence of pertechnetate activity in the thyroid was due to complete replacement of thyroid gland by the metastasis from lung adenocarcinoma, which was unknown at the initial presentation.

Whole Tumor Histogram-profiling of Diffusion-Weighted Magnetic Resonance Images Reflects Tumorbiological Features of Primary Central Nervous System Lymphoma.

PubMed

Schob, Stefan; Münch, Benno; Dieckow, Julia; Quäschling, Ulf; Hoffmann, Karl-Titus; Richter, Cindy; Garnov, Nikita; Frydrychowicz, Clara; Krause, Matthias; Meyer, Hans-Jonas; Surov, Alexey

2018-04-01

Diffusion weighted imaging (DWI) quantifies motion of hydrogen nuclei in biological tissues and hereby has been used to assess the underlying tissue microarchitecture. Histogram-profiling of DWI provides more detailed information on diffusion characteristics of a lesion than the standardly calculated values of the apparent diffusion coefficient (ADC)-minimum, mean and maximum. Hence, the aim of our study was to investigate, which parameters of histogram-profiling of DWI in primary central nervous system lymphoma can be used to specifically predict features like cellular density, chromatin content and proliferative activity. Pre-treatment ADC maps of 21 PCNSL patients (8 female, 13 male, 28-89 years) from a 1.5T system were used for Matlab-based histogram profiling. Results of histopathology (H&E staining) and immunohistochemistry (Ki-67 expression) were quantified. Correlations between histogram-profiling parameters and neuropathologic examination were calculated using SPSS 23.0. The lower percentiles (p10 and p25) showed significant correlations with structural parameters of the neuropathologic examination (cellular density, chromatin content). The highest percentile, p90, correlated significantly with Ki-67 expression, resembling proliferative activity. Kurtosis of the ADC histogram correlated significantly with cellular density. Histogram-profiling of DWI in PCNSL provides a comprehensible set of parameters, which reflect distinct tumor-architectural and tumor-biological features, and hence, are promising biomarkers for treatment response and prognosis. Copyright © 2018. Published by Elsevier Inc.

Significance of diffusion weighted imaging (DWI) as an improving factor in contrast enhanced magnetic resonance imaging (MRI) enterography in evaluation of patients with Crohn's disease.

PubMed

Imširović, Bilal; Zerem, Enver; Efendić, Alma; Mekić Abazović, Alma; Zerem, Omar; Djedović, Muhamed

2018-08-01

Aim To determine capabilities and potential of contrast enhanced magnetic resonance imaging (MRI) enterography in order to establish the diagnosis and to evaluate severity and activity of intestinal inflammation. Methods Fifty-five patients with suspicion for presence of Crohn's disease were evaluated. All patients underwent contrast enhanced MRI enterography and diffusion weighted imaging (DWI), and subsequently endoscopic examination or surgical treatment. Four parameters were analysed: thickening of the bowel wall, and presence of abscess, fistula and lymphadenopathy. Results Comparing results of DWI and contrast enhanced MRI enterography a significant difference between results given through diffusion and histopathological test was found, e.g. a significant difference between results obtained through diffusion and MRI enterography was found. MRI enterography sensitiveness for bowel wall thickening was 97.7% and specificity 70%, whilst DWI sensitivity for bowel wall thickening was 84% and specificity 100%. The diagnostics of abscess and fistula showed no significant difference between DWI and MRI, while in lymphadenopathy significant difference between contrast enhanced MRI enterography and DWI was found. Conclusion Contrast enhanced MRI enterography in combination with DWI allows for excellent evaluation of disease activity, but also problems or complications following it. The examination can be repeated, controlled, and it can contribute to monitoring of patients with this disease. Copyright© by the Medical Assotiation of Zenica-Doboj Canton.

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.

Double perovskite cathodes for proton-conducting ceramic fuel cells: are they triple mixed ionic electronic conductors?

PubMed Central

Téllez Lozano, Helena; Druce, John; Cooper, Samuel J.; Kilner, John A.

2017-01-01

Abstract 18O and 2H diffusion has been investigated at a temperature of 300 °C in the double perovskite material PrBaCo2O5+δ (PBCO) in flowing air containing 200 mbar of 2H2 16O. Secondary ion mass spectrometry (SIMS) depth profiling of exchanged ceramics has shown PBCO still retains significant oxygen diffusivity (~1.3 × 10−11 cm2s−1) at this temperature and that the presence of water (2H2 16O), gives rise to an enhancement of the surface exchange rate over that in pure oxygen by a factor of ~3. The 2H distribution, as inferred from the 2H2 16O− SIMS signal, shows an apparent depth profile which could be interpreted as 2H diffusion. However, examination of the 3-D distribution of the signal shows it to be nonhomogeneous and probably related to the presence of hydrated layers in the interior walls of pores and is not due to proton diffusion. This suggests that PBCO acts mainly as an oxygen ion mixed conductor when used in PCFC devices, although the presence of a small amount of protonic conductivity cannot be discounted in these materials. PMID:29383047

The influence of the diffusion of responsibility effect on outcome evaluations: electrophysiological evidence from an ERP study.

PubMed

Li, Peng; Jia, Shiwei; Feng, Tingyong; Liu, Qiang; Suo, Tao; Li, Hong

2010-10-01

Previous studies have revealed that personal responsibility has an influence on outcome evaluation, although the way this influence works is still unclear. This study imitated the phenomenon of responsibility diffusion in a laboratory to examine the influence of the effect of responsibility diffusion on the processing of outcome evaluation using the event-related potential (ERP) technique. Participants of the study were required to perform the gambling task individually in the high-responsibility condition and with others in the low-responsibility scenario. Self-rating results showed that the participants felt more responsible for monetary loss and believed that they had more contributions to the monetary gains in the high-responsibility condition than in the low-responsibility situation. Both the feedback-related negativity (FRN) and the P300 were sensitive to the responsibility level, as evidenced by the enhanced amplitudes in the high-responsibility condition for both components. Further correlation analysis showed a negative correlation between FRN amplitudes and subjective rating scores (i.e., the higher the responsibility level, the larger the FRN amplitude). The results probably indicate that the FRN and P300 reflect personal responsibility processing under the social context of diffusion of responsibility. Copyright 2010 Elsevier Inc. All rights reserved.

Modelling the effect of diffuse light on canopy photosynthesis in controlled environments

NASA Technical Reports Server (NTRS)

Cavazzoni, James; Volk, Tyler; Tubiello, Francesco; Monje, Oscar; Janes, H. W. (Principal Investigator)

2002-01-01

A layered canopy model was used to analyze the effects of diffuse light on canopy gross photosynthesis in controlled environment plant growth chambers, where, in contrast to the field, highly diffuse light can occur at high irradiance. The model suggests that high diffuse light fractions (approximately 0.7) and irradiance (1400 micromoles m-2 s-1) may enhance crop life-cycle canopy gross photosynthesis for hydroponic wheat by about 20% compared to direct light at the same irradiance. Our simulations suggest that high accuracy is not needed in specifying diffuse light fractions in chambers between approximately 0.7 and 1, because simulated photosynthesis for closed canopies plateau in this range. We also examined the effect of leaf angle distribution on canopy photosynthesis under growth chamber conditions, as these distributions determine canopy extinction coefficients for direct and diffuse light. We show that the spherical leaf angle distribution is not suitable for modeling photosynthesis of planophile canopies (e.g., soybean and peanut) in growth chambers. Also, the absorption of the light reflected from the surface below the canopy should generally be included in model simulations, as the corresponding albedo values in the photosynthetically active range may be quite high in growth chambers (e.g., approximately 0.5). In addition to the modeling implications, our results suggest that diffuse light conditions should be considered when drawing conclusions from experiments in controlled environments.

Lithium Ion Solvation and Diffusion in Bulk Organic Electrolytes from First-Principles and Classical Reactive Molecular Dynamics

DOE PAGES

Ong, Mitchell T.; Verners, Osvalds; Draeger, Erik W.; ...

2014-12-19

We report that lithium-ion battery performance is strongly influenced by the ionic conductivity of the electrolyte, which depends on the speed at which Li ions migrate across the cell and relates to their solvation structure. The choice of solvent can greatly impact both the solvation and diffusivity of Li ions. In this work, we used first-principles molecular dynamics to examine the solvation and diffusion of Li ions in the bulk organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC), and a mixture of EC and EMC. We found that Li ions are solvated by either carbonyl or ether oxygen atoms of the solvents and sometimes by the PF more » $$\\bar{6}$$ anion. Li + prefers a tetrahedrally coordinated first solvation shell regardless of which species are involved, with the specific preferred solvation structure dependent on the organic solvent. In addition, we calculated Li diffusion coefficients in each electrolyte, finding slightly larger diffusivities in the linear carbonate EMC compared to the cyclic carbonate EC. The magnitude of the diffusion coefficient correlates with the strength of Li + solvation. Corresponding analysis for the PF $$\\bar{6}$$ anion shows greater diffusivity associated with a weakly bound, poorly defined first solvation shell. In conclusion, these results can be used to aid in the design of new electrolytes to improve Li-ion battery performance.« less

Studies of the Terrestrial Molecular Oxygen and Carbon Cycles in Sand Dune Gases and in Biosphere 2.

NASA Astrophysics Data System (ADS)

Severinghaus, Jeffrey Peck

Molecular oxygen in the atmosphere is coupled tightly to the terrestrial carbon cycle by the processes of photosynthesis, respiration, and burning. This dissertation examines different aspects of this coupling in four chapters. Chapter 1 explores the feasibility of using air from sand dunes to reconstruct atmospheric O_2 composition centuries ago. Such a record would reveal changes in the mass of the terrestrial biosphere, after correction for known fossil fuel combustion, and constrain the fate of anthropogenic CO_2. Test drilling in sand dunes shows that sand dunes do contain old air, as shown by the concentrations of chlorofluorocarbons and ^{85}Kr. Diffusion is shown to dominate mixing rather than advection. However, biological respiration in dunes corrupts the signal, and isotopic analysis of O_2 and N _2 shows that fractionation of the gases precludes use of sand dunes as archives. Chapter 2 further explores this fractionation, revealing a previously unknown "water vapor flux fractionation" process. A flux of water vapor out of the moist dune into the dry desert air sweeps out the other gases, forcing them to diffuse back into the dune. The heavy isotopes of N_2 and O_2 diffuse more slowly, creating a steady state depletion of heavy isotopes in the dune interior. Molecular diffusion theory and a laboratory simulation of the effect agree well with the observations. Additional fractionation of the dune air occurs via thermal diffusion and gravitational settling, and it is predicted that soil gases in general will enjoy all three effects. Chapter 3 examines the cause of a mysterious drop in O _2 concentrations in the closed ecosystem of Biosphere 2, located near Tucson, Arizona. The organic -rich soil manufactured for the experiment is shown to be the culprit, with CO_2 produced by bacterial respiration of the organic matter reacting with the extensive concrete surfaces inside. Chapter 4 examines the O_2:C stoichiometry of terrestrial soil respiration and photosynthesis, in the context of using atmospheric O_2 measurements to constrain the size of the "missing sink" of CO_2. Direct measurements of soil respiration and biomatter elemental abundance suggest a value of 1.1 +/- 0.05 oxygen molecules per CO_2 molecule.

[A case of MM1+2 Creutzfeldt-Jakob disease with a longitudinal study of EEG and MRI].

PubMed

Katsube, Mizuho; Shiota, Yuri; Harada, Takayuki; Shibata, Hiroshi; Nagai, Atsushi

2013-11-01

We report a case of definite MM1 + 2 sporadic Creutzfeldt-Jakob disease (sCJD). A 66-year-old woman was admitted to our hospital with memory disturbance and disorientation for three months. On admission she presented a progressive cognitive insufficiency. Electroencephalography (EEG) revealed a frontal intermittent rhythmical delta activity (FIRDA) and the brain magnetic resonance imaging (MRI) showed high signal intensities in cerebral cortex on diffusion weighted images (DWI). After four months from the onset, she reached the akinetic mutism state followed by myoclonus. Follow up examination revealed that periodic synchronous discharge (PSD) was found in EEG, and DWI revealed enlargement of high signal intensity lesions in cerebral cortex. At seven months from the onset, PSD and high signal intensities of cortex became unclear with disappearance of myoclonus, and brain white matter lesions were evident on MRI. Serial studies of EEG and MRI revealed that PSD generalized from frontal lobe dominant pattern, while high signal intensity lesions of cortex diffusely increased on DWI. At ten months from the onset patient died. Pathological examination in brain showed moderate and diffuse neuronal cell loss and gliosis in cerebral cortex corresponding with DWI changes. The genotype at codon 129 of the prion protein (PrP) was homozygous methionine (MM) and the type of protease-resistant PrP (PrPres) was the mixed type of 1 and 2 in Western blot analysis. It has been rare to analyze the changes of EEG and MRI in the entire stage and to investigate pathological finding in the case of sCJD-MM1 + 2. A longitudinal examination of EEG and MRI is useful for early diagnosis of CJD. Also we could correlate these findings with clinical and histopathological phenotype.

Self-Diffusion of small Ag and Ni islands on Ag(111) and Ni(111) using the self-learning kinetic Monte Carlo method

NASA Astrophysics Data System (ADS)

Islamuddin Shah, Syed; Nandipati, Giridhar; Kara, Abdelkader; Rahman, Talat S.

2012-02-01

We have applied a modified Self-Learning Kinetic Monte Carlo (SLKMC) method [1] to examine the self-diffusion of small Ag and Ni islands, containing up to 10 atom, on the (111) surface of the respective metal. The pattern recognition scheme in this new SLKMC method allows occupancy of the fcc, hcp and top sites on the fcc(111) surface and employs them to identify the local neighborhood around a central atom. Molecular static calculations with semi empirical interatomic potential and reliable techniques for saddle point search revealed several new diffusion mechanisms that contribute to the diffusion of small islands. For comparison we have also evaluated the diffusion characteristics of Cu clusters on Cu(111) and compared results with previous findings [2]. Our results show a linear increase in effective energy barriers scaling almost as 0.043, 0.051 and 0.064 eV/atom for the Cu/Cu(111), Ag/Ag(111), and Ni/Ni(111) systems, respectively. For all three systems, diffusion of small islands proceeds mainly through concerted motion, although several multiple and single atom processes also contribute. [1] Oleg Trushin et al. Phys. Rev. B 72, 115401 (2005) [2] Altaf Karim et al. Phys. Rev. B 73, 165411 (2006)

Mechanisms Underlying the Confined Diffusion of Cholera Toxin B-Subunit in Intact Cell Membranes

PubMed Central

Day, Charles A.; Kenworthy, Anne K.

2012-01-01

Multivalent glycolipid binding toxins such as cholera toxin have the capacity to cluster glycolipids, a process thought to be important for their functional uptake into cells. In contrast to the highly dynamic properties of lipid probes and many lipid-anchored proteins, the B-subunit of cholera toxin (CTxB) diffuses extremely slowly when bound to its glycolipid receptor GM1 in the plasma membrane of living cells. In the current study, we used confocal FRAP to examine the origins of this slow diffusion of the CTxB/GM1 complex at the cell surface, relative to the behavior of a representative GPI-anchored protein, transmembrane protein, and fluorescent lipid analog. We show that the diffusion of CTxB is impeded by actin- and ATP-dependent processes, but is unaffected by caveolae. At physiological temperature, the diffusion of several cell surface markers is unchanged in the presence of CTxB, suggesting that binding of CTxB to membranes does not alter the organization of the plasma membrane in a way that influences the diffusion of other molecules. Furthermore, diffusion of the B-subunit of another glycolipid-binding toxin, Shiga toxin, is significantly faster than that of CTxB, indicating that the confined diffusion of CTxB is not a simple function of its ability to cluster glycolipids. By identifying underlying mechanisms that control CTxB dynamics at the cell surface, these findings help to delineate the fundamental properties of toxin-receptor complexes in intact cell membranes. PMID:22511973

Does transbilayer diffusion have a role in membrane transport of drugs?

PubMed Central

Balaz, Stefan

2012-01-01

The existing consensus on coexistence of transbilayer diffusion and carrier-mediated transport as two main mechanisms for drugs crossing biological membranes was recently challenged by a systems biology group. Their transporters-only hypothesis is examined in this article using published experimental evidence. The main focus is on the key claim of their hypothesis, stating that ‘the drug molecules cross pure phospholipid bilayers through transient pores that cannot form in the bilayers of cell membranes, and thus transbilayer drug transport does not exist in cells’. The analysis shows that the prior consensus remains a valid scientific view of the membrane transport of drugs. PMID:22705388

A rare case of mycetoma due to curvularia.

PubMed

Shinde, Rupali S; Hanumantha, Sreedevi; Mantur, Basappa G; Parande, Mahantesh V

2015-01-01

Mycetoma due to Curvularia is a rare clinical entity. Here, we report a case of 27-year-old female presented with multiple swellings and discharging wounds around left shoulder joint since 12 years. Local examination showed diffuse nodular swellings over left anterior chest wall, posterior chest wall, and axilla. Multiple nodules and discharging sinuses were seen. Fungal culture of the biopsy of the lesion revealed Curvularia species. Patient showed significant clinical improvement with itraconazole therapy.

Thermal transport at the nanoscale: A Fourier's law vs. phonon Boltzmann equation study

NASA Astrophysics Data System (ADS)

Kaiser, J.; Feng, T.; Maassen, J.; Wang, X.; Ruan, X.; Lundstrom, M.

2017-01-01

Steady-state thermal transport in nanostructures with dimensions comparable to the phonon mean-free-path is examined. Both the case of contacts at different temperatures with no internal heat generation and contacts at the same temperature with internal heat generation are considered. Fourier's law results are compared to finite volume method solutions of the phonon Boltzmann equation in the gray approximation. When the boundary conditions are properly specified, results obtained using Fourier's law without modifying the bulk thermal conductivity are in essentially exact quantitative agreement with the phonon Boltzmann equation in the ballistic and diffusive limits. The errors between these two limits are examined in this paper. For the four cases examined, the error in the apparent thermal conductivity as deduced from a correct application of Fourier's law is less than 6%. We also find that the Fourier's law results presented here are nearly identical to those obtained from a widely used ballistic-diffusive approach but analytically much simpler. Although limited to steady-state conditions with spatial variations in one dimension and to a gray model of phonon transport, the results show that Fourier's law can be used for linear transport from the diffusive to the ballistic limit. The results also contribute to an understanding of how heat transport at the nanoscale can be understood in terms of the conceptual framework that has been established for electron transport at the nanoscale.

Spin pumping and inverse spin Hall effects in heavy metal/antiferromagnet/Permalloy trilayers

NASA Astrophysics Data System (ADS)

Saglam, Hilal; Zhang, Wei; Jungfleisch, M. Benjamin; Jiang, Wanjun; Pearson, John E.; Hoffmann, Axel

Recent work shows efficient spin transfer via spin waves in insulating antiferromagnets (AFMs), suggesting that AFMs can play a more active role in the manipulation of ferromagnets. We use spin pumping and inverse spin Hall effect experiments on heavy metal (Pt and W)/AFMs/Py (Ni80Fe20) trilayer structures, to examine the possible spin transfer phenomenon in metallic AFMs, i . e . , FeMn and PdMn. Previous work has studied electronic effects of the spin transport in these materials, yielding short spin diffusion length on the order of 1 nm. However, the work did not examine whether besides diffusive spin transport by the conduction electrons, there are additional spin transport contributions from spin wave excitations. We clearly observe spin transport from the Py spin reservoir to the heavy metal layer through the sandwiched AFMs with thicknesses well above the previously measured spin diffusion lengths, indicating that spin transport by spin waves may lead to non-negligible contributions This work was supported by US DOE, OS, Materials Sciences and Engineering Division. Lithographic patterning was carried out at the CNM, which is supported by DOE, OS under Contract No. DE-AC02-06CH11357.

Gerstmann-Straeussler-Scheinker disease with P102L prion protein gene mutation presenting with rapidly progressive clinical course.

PubMed

Iwasaki, Yasushi; Mori, Keiko; Ito, Masumi; Nokura, Kazuya; Tatsumi, Shinsui; Mimuro, Maya; Kitamoto, Tetsuyuki; Yoshida, Mari

2014-01-01

We describe an autopsied case of a Japanese woman with Gerstmann-Straeussler-Scheinker disease (GSS) presenting with a rapidly progressive clinical course. Disease onset occurred at the age of 54 with dementia and gait disturbance. Her clinical course progressively deteriorated until she reached a bedridden state with myoclonus 9 months after onset. Two months later, she reached the akinetic mutism state. Nasal tube feeding was introduced at this point and continued for several years. Electroencephalograms showed diffuse slowing without periodic sharp-wave complexes. Diffusion-weighted magnetic resonance imaging (MRI) showed widespread cerebral cortical hyperintensity. Prion protein (PrP) gene analysis revealed a Pro to Leu point mutation at codon 102 with methionine homozygosity at codon 129. The patient died of respiratory failure after a total disease duration of 62 months. Neuropathologic examination revealed widespread spongiform change with numerous eosinophilic amyloid plaques (Kuru plaques) in the cerebral and cerebellar cortices by H & E staining. Diffuse myelin pallor with axon loss of the cerebral white matter, suggestive of panencephalopathic-type pathology was observed. Numerous PrP immunopositive plaques and diffuse synaptic-type PrP deposition were extensively observed, particularly in the cerebral and cerebellar cortices. Western blot analysis of proteinase Kresistant PrP showed a characteristic band pattern with a small molecular band of 6 kDa. The reason for the similarity in clinicopathologic findings between the present case and Creutzfeldt-Jakob disease is uncertain; however, the existence of an unknown disease-modifying factor is suspected.

Optimization and development of solar power system under diffused sunlight condition in rural areas with supercapacitor integration

NASA Astrophysics Data System (ADS)

Castelino, Roystan V.; Jana, Suman; Kumhar, Rajesh; Singh, Niraj K.

2018-04-01

The simulation and hardware based experiment in this presented paper shows a possibility of increasing the reliability of solar power under diffused condition by using super capacitor module. This experimental setup can be used in those areas where the sun light is intermittent and under the diffused radiation condition. Due to diffused radiation, solar PV cells operate very poorly, but by using this setup the power efficiency can be increased greatly. Sometimes dependent numerical models are used to measure the voltage and current response of the hardware setup in MATLAB Simulink based environment. To convert the scattered solar radiation to electricity using the conventional solar PV module, batteries have to be linked with the rapid charging or discharging device like super capacitor module. The conventional method consists of a charging circuit, which dumps the power if the voltage is below certain voltage level, but this circuit utilizes the entire power even if the voltage is low under diffused sun light conditions. There is no power dumped in this circuit. The efficiency and viability of this labscale experimental setup can be examined with further experiment and industrial model.

Functional localization of the human color center by decreased water displacement using diffusion-weighted fMRI.

PubMed

Williams, Rebecca J; Reutens, David C; Hocking, Julia

2015-11-01

Decreased water displacement following increased neural activity has been observed using diffusion-weighted functional MRI (DfMRI) at high b-values. The physiological mechanisms underlying the diffusion signal change may be unique from the standard blood oxygenation level-dependent (BOLD) contrast and closer to the source of neural activity. Whether DfMRI reflects neural activity more directly than BOLD outside the primary cerebral regions remains unclear. Colored and achromatic Mondrian visual stimuli were statistically contrasted to functionally localize the human color center Area V4 in neurologically intact adults. Spatial and temporal properties of DfMRI and BOLD activation were examined across regions of the visual cortex. At the individual level, DfMRI activation patterns showed greater spatial specificity to V4 than BOLD. The BOLD activation patterns were more prominent in the primary visual cortex than DfMRI, where activation was localized to the ventral temporal lobe. Temporally, the diffusion signal change in V4 and V1 both preceded the corresponding hemodynamic response, however the early diffusion signal change was more evident in V1. DfMRI may be of use in imaging applications implementing cognitive subtraction paradigms, and where highly precise individual functional localization is required.

Asymptomatic diffuse "encephalitic" cerebral toxoplasmosis in a woman with systemic lupus erythematosus.

PubMed

Murro, Diana; Novo, Jorge; Arvanitis, Leonidas

2016-07-01

Classic cerebral toxoplasmosis typically presents with neurologic symptoms such as seizures and mental status changes and histological examination shows focal lesions with necrosis. However, in the diffuse "encephalitic" form, patients are asymptomatic with diffuse, inflammatory, non-necrotic lesions. Asymptomatic diffuse "encephalitic" toxoplasmosis has been reported only in four acquired immunodeficiency syndrome patients and one human immunodeficiency virus (HIV) negative patient with chronic lymphocytic leukemia. We present a 36-year-old HIV-negative woman with systemic lupus erythematosus and lupus nephritis who was on immunosuppression for 9years after cadaveric renal transplant and died from pulmonary hemorrhage and cytomegalovirus pneumonia. Brain autopsy findings revealed multifocal microglial nodules containing Toxoplasma bradyzoites and associated astrogliosis. These nodules were prominent in the cerebellum, midbrain and medulla and also present in the cortex and thalamus. No coagulative necrosis, necrotizing abscesses, or other opportunistic infections were present. The patient had previously exhibited no neurologic symptoms and there was no clinical suspicion for toxoplasmosis. To the best of our knowledge, this is the first case of diffuse, non-necrotizing, "encephalitic" cerebral toxoplasmosis reported in a lupus patient and also the first reported female case. Copyright © 2016 Elsevier Ltd. All rights reserved.

Enzyme localization, crowding, and buffers collectively modulate diffusion-influenced signal transduction: Insights from continuum diffusion modeling

PubMed Central

Kekenes-Huskey, Peter M.; Eun, Changsun; McCammon, J. A.

2015-01-01

Biochemical reaction networks consisting of coupled enzymes connect substrate signaling events with biological function. Substrates involved in these reactions can be strongly influenced by diffusion “barriers” arising from impenetrable cellular structures and macromolecules, as well as interactions with biomolecules, especially within crowded environments. For diffusion-influenced reactions, the spatial organization of diffusion barriers arising from intracellular structures, non-specific crowders, and specific-binders (buffers) strongly controls the temporal and spatial reaction kinetics. In this study, we use two prototypical biochemical reactions, a Goodwin oscillator, and a reaction with a periodic source/sink term to examine how a diffusion barrier that partitions substrates controls reaction behavior. Namely, we examine how conditions representative of a densely packed cytosol, including reduced accessible volume fraction, non-specific interactions, and buffers, impede diffusion over nanometer length-scales. We find that diffusion barriers can modulate the frequencies and amplitudes of coupled diffusion-influenced reaction networks, as well as give rise to “compartments” of decoupled reactant populations. These effects appear to be intensified in the presence of buffers localized to the diffusion barrier. These findings have strong implications for the role of the cellular environment in tuning the dynamics of signaling pathways. PMID:26342355

Various Manifestations of Hyperthyroidism in an Ambulatory Clinic: Case Studies

PubMed Central

Tripp, Warren; Rao, Vijaya; Creary, Ludlow B.

1987-01-01

This study reviews five cases of women with hyperthyroidism, three black women and two Hispanic women. Initially, two patients presented with voice changes, weight loss, and increased appetite. Only two patients presented with classical symptoms of hyperthyroidism. Examination showed all patients had diffusely enlarged thyroids and exaggerated reflexes. Two patients showed Graves' opthalmopathy. These cases document the variety of presentations of hyperthyroidism. Hence, a high index of suspicion must exist for this disease, even in the absence of a number of the classical manifestations of hyperthyroidism. When patients present to primary care centers with a constellation of symptoms, an examination of the thyroid gland is essential. PMID:3694696

On the Ageing of High Energy Lithium-Ion Batteries—Comprehensive Electrochemical Diffusivity Studies of Harvested Nickel Manganese Cobalt Electrodes

PubMed Central

Jaguemont, Joris; Van Den Bossche, Peter; Omar, Noshin; Van Mierlo, Joeri

2018-01-01

This paper examines the impact of the characterisation technique considered for the determination of the Li+ solid state diffusion coefficient in uncycled as in cycled Nickel Manganese Cobalt oxide (NMC) electrodes. As major characterisation techniques, Cyclic Voltammetry (CV), Galvanostatic Intermittent Titration Technique (GITT) and Electrochemical Impedance Spectroscopy (EIS) were systematically investigated. Li+ diffusion coefficients during the lithiation process of the uncycled and cycled electrodes determined by CV at 3.71 V are shown to be equal to 3.48×10−10 cm2·s−1 and 1.56×10−10 cm2·s−1 , respectively. The dependency of the Li+ diffusion with the lithium content in the electrodes is further studied in this paper with GITT and EIS. Diffusion coefficients calculated by GITT and EIS characterisations are shown to be in the range between 1.76×10−15 cm2·s−1 and 4.06×10−12 cm2·s−1, while demonstrating the same decreasing trend with the lithiation process of the electrodes. For both electrode types, diffusion coefficients calculated by CV show greater values compared to those determined by GITT and EIS. With ageing, CV and EIS techniques lead to diffusion coefficients in the electrodes at 3.71 V that are decreasing, in contrast to GITT for which results indicate increasing diffusion coefficient. After long-term cycling, ratios of the diffusion coefficients determined by GITT compared to CV become more significant with an increase about 1 order of magnitude, while no significant variation is seen between the diffusion coefficients calculated from EIS in comparison to CV. PMID:29360787

Pulsed field gradient magic angle spinning NMR self-diffusion measurements in liquids

NASA Astrophysics Data System (ADS)

Viel, Stéphane; Ziarelli, Fabio; Pagès, Guilhem; Carrara, Caroline; Caldarelli, Stefano

2008-01-01

Several investigations have recently reported the combined use of pulsed field gradient (PFG) with magic angle spinning (MAS) for the analysis of molecular mobility in heterogeneous materials. In contrast, little attention has been devoted so far to delimiting the role of the extra force field induced by sample rotation on the significance and reliability of self-diffusivity measurements. The main purpose of this work is to examine this phenomenon by focusing on pure liquids for which its impact is expected to be largest. Specifically, we show that self-diffusion coefficients can be accurately determined by PFG MAS NMR diffusion measurements in liquids, provided that specific experimental conditions are met. First, the methodology to estimate the gradient uniformity and to properly calibrate its absolute strength is briefly reviewed and applied on a MAS probe equipped with a gradient coil aligned along the rotor spinning axis, the so-called 'magic angle gradient' coil. Second, the influence of MAS on the outcome of PFG MAS diffusion measurements in liquids is investigated for two distinct typical rotors of different active volumes, 12 and 50 μL. While the latter rotor led to totally unreliable results, especially for low viscosity compounds, the former allowed for the determination of accurate self-diffusion coefficients both for fast and slowly diffusing species. Potential implications of this work are the possibility to measure accurate self-diffusion coefficients of sample-limited mixtures or to avoid radiation damping interferences in NMR diffusion measurements. Overall, the outlined methodology should be of interest to anyone who strives to improve the reliability of MAS diffusion studies, both in homogeneous and heterogeneous media.

On the Ageing of High Energy Lithium-Ion Batteries-Comprehensive Electrochemical Diffusivity Studies of Harvested Nickel Manganese Cobalt Electrodes.

PubMed

Capron, Odile; Gopalakrishnan, Rahul; Jaguemont, Joris; Van Den Bossche, Peter; Omar, Noshin; Van Mierlo, Joeri

2018-01-23

This paper examines the impact of the characterisation technique considered for the determination of the L i + solid state diffusion coefficient in uncycled as in cycled Nickel Manganese Cobalt oxide (NMC) electrodes. As major characterisation techniques, Cyclic Voltammetry (CV), Galvanostatic Intermittent Titration Technique (GITT) and Electrochemical Impedance Spectroscopy (EIS) were systematically investigated. L i + diffusion coefficients during the lithiation process of the uncycled and cycled electrodes determined by CV at 3.71 V are shown to be equal to 3 . 48 × 10 - 10 cm 2 ·s - 1 and 1 . 56 × 10 - 10 cm 2 ·s - 1 , respectively. The dependency of the L i + diffusion with the lithium content in the electrodes is further studied in this paper with GITT and EIS. Diffusion coefficients calculated by GITT and EIS characterisations are shown to be in the range between 1 . 76 × 10 - 15 cm 2 ·s - 1 and 4 . 06 × 10 - 12 cm 2 ·s - 1 , while demonstrating the same decreasing trend with the lithiation process of the electrodes. For both electrode types, diffusion coefficients calculated by CV show greater values compared to those determined by GITT and EIS. With ageing, CV and EIS techniques lead to diffusion coefficients in the electrodes at 3.71 V that are decreasing, in contrast to GITT for which results indicate increasing diffusion coefficient. After long-term cycling, ratios of the diffusion coefficients determined by GITT compared to CV become more significant with an increase about 1 order of magnitude, while no significant variation is seen between the diffusion coefficients calculated from EIS in comparison to CV.

Multisite longitudinal reliability of tract-based spatial statistics in diffusion tensor imaging of healthy elderly subjects.

PubMed

Jovicich, Jorge; Marizzoni, Moira; Bosch, Beatriz; Bartrés-Faz, David; Arnold, Jennifer; Benninghoff, Jens; Wiltfang, Jens; Roccatagliata, Luca; Picco, Agnese; Nobili, Flavio; Blin, Oliver; Bombois, Stephanie; Lopes, Renaud; Bordet, Régis; Chanoine, Valérie; Ranjeva, Jean-Philippe; Didic, Mira; Gros-Dagnac, Hélène; Payoux, Pierre; Zoccatelli, Giada; Alessandrini, Franco; Beltramello, Alberto; Bargalló, Núria; Ferretti, Antonio; Caulo, Massimo; Aiello, Marco; Ragucci, Monica; Soricelli, Andrea; Salvadori, Nicola; Tarducci, Roberto; Floridi, Piero; Tsolaki, Magda; Constantinidis, Manos; Drevelegas, Antonios; Rossini, Paolo Maria; Marra, Camillo; Otto, Josephin; Reiss-Zimmermann, Martin; Hoffmann, Karl-Titus; Galluzzi, Samantha; Frisoni, Giovanni B

2014-11-01

Large-scale longitudinal neuroimaging studies with diffusion imaging techniques are necessary to test and validate models of white matter neurophysiological processes that change in time, both in healthy and diseased brains. The predictive power of such longitudinal models will always be limited by the reproducibility of repeated measures acquired during different sessions. At present, there is limited quantitative knowledge about the across-session reproducibility of standard diffusion metrics in 3T multi-centric studies on subjects in stable conditions, in particular when using tract based spatial statistics and with elderly people. In this study we implemented a multi-site brain diffusion protocol in 10 clinical 3T MRI sites distributed across 4 countries in Europe (Italy, Germany, France and Greece) using vendor provided sequences from Siemens (Allegra, Trio Tim, Verio, Skyra, Biograph mMR), Philips (Achieva) and GE (HDxt) scanners. We acquired DTI data (2 × 2 × 2 mm(3), b = 700 s/mm(2), 5 b0 and 30 diffusion weighted volumes) of a group of healthy stable elderly subjects (5 subjects per site) in two separate sessions at least a week apart. For each subject and session four scalar diffusion metrics were considered: fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD) and axial (AD) diffusivity. The diffusion metrics from multiple subjects and sessions at each site were aligned to their common white matter skeleton using tract-based spatial statistics. The reproducibility at each MRI site was examined by looking at group averages of absolute changes relative to the mean (%) on various parameters: i) reproducibility of the signal-to-noise ratio (SNR) of the b0 images in centrum semiovale, ii) full brain test-retest differences of the diffusion metric maps on the white matter skeleton, iii) reproducibility of the diffusion metrics on atlas-based white matter ROIs on the white matter skeleton. Despite the differences of MRI scanner configurations across sites (vendors, models, RF coils and acquisition sequences) we found good and consistent test-retest reproducibility. White matter b0 SNR reproducibility was on average 7 ± 1% with no significant MRI site effects. Whole brain analysis resulted in no significant test-retest differences at any of the sites with any of the DTI metrics. The atlas-based ROI analysis showed that the mean reproducibility errors largely remained in the 2-4% range for FA and AD and 2-6% for MD and RD, averaged across ROIs. Our results show reproducibility values comparable to those reported in studies using a smaller number of MRI scanners, slightly different DTI protocols and mostly younger populations. We therefore show that the acquisition and analysis protocols used are appropriate for multi-site experimental scenarios. Copyright © 2014 Elsevier Inc. All rights reserved.

NASA/DoD Aerospace Knowledge Diffusion Research Project, Paper Sixteen: Aerospace Knowledge Diffusion Research

DTIC Science & Technology

1991-01-01

Understanding how STI is commun- aerospace knowledge- efficient and effective transfer and cated in the process of technolgical diffusion of knowledge within...However, as important international levels, diffusion of knowledge in the aeros- as the transfer and utilisation of STI is to which will help to pace...diffused is neces- diffusion of knowledge . Phase 3 ex- formation specialist). Phase 2 examined sary to successfully manage technolog- plores the information

Investigation to develop a method to apply diffusion barrier to high strength fibers

NASA Technical Reports Server (NTRS)

Veltri, R. D.; Paradis, R. D.; Douglas, F. C.

1975-01-01

A radio frequency powered ion plating process was used to apply the diffusion barriers of aluminum oxide, yttrium oxide, hafnium oxide and titanium carbide to a substrate tungsten fiber. Each of the coatings was examined as to its effect on both room temperature strength and tensile strength of the base tungsten fiber. The coated fibers were then overcoated with a nickel alloy to become single cell diffusion couples. These diffusion couples were exposed to 1093 C for 24 hours, cycled between room temperature and 1093 C, and given a thermal anneal for 100 hours at 1200 C. Tensile testing and metallographic examinations determined that the hafnium oxide coating produced the best high temperature diffusion barrier for tungsten of the four coatings.

Pleural mesothelioma – case report

PubMed Central

Klawiter, Anna; Damaszke, Tomasz

2010-01-01

Summary Background: Pleural mesothelioma is a very rare neoplasm; especially the local form. The diagnostics is difficult and the prognosis unfavourable. Case Report: We presented a case of a man with dyspnoea and cough. His chest radiogram showed hydrothorax on the left side. Neither the examinations of the pleural liquid, nor the CT-guided fine needle biopsy established the diagnosis. CT showed features suggestive of pleural mesothelioma. The diagnosis was confirmed by thoracoscopy. Although no neoplastic cells were found in the thoracoscopic specimen from the supradiaphragmatic tumor, we assumed that to be a case of a diffuse, primarily local form of mesothelioma. Conclusions: Diagnostics of pleural mesothelioma is very difficult. CT and thoracoscopy seem to be very valuable diagnostic methods. It is worth remembering that pleural mesothelioma can have a local form which may transform into a diffuse one. PMID:22802809

Attentional Focus versus Diffuse Attention: Which is Better in Toddlers?

ERIC Educational Resources Information Center

Rivière, James; Cordonnier, Aurore; Fouasse, Christie

2017-01-01

How toddlers' attention is distributed in the visual field during a magic trick was examined using three expectation conditions. Results showed that 2.5-year-old children assigned to the condition with major task-relevant information (i.e., a verbal cue to attend to one of the visual targets) (i) outperformed those who were assigned to the…

Post-earthquake dilatancy recovery

NASA Technical Reports Server (NTRS)

Scholz, C. H.

1974-01-01

Geodetic measurements of the 1964 Niigata, Japan earthquake and of three other examples are briefly examined. They show exponentially decaying subsidence for a year after the quakes. The observations confirm the dilatancy-fluid diffusion model of earthquake precursors and clarify the extent and properties of the dilatant zone. An analysis using one-dimensional consolidation theory is included which agrees well with this interpretation.

Unique white matter microstructural patterns in ADHD presentations-a diffusion tensor imaging study.

PubMed

Svatkova, Alena; Nestrasil, Igor; Rudser, Kyle; Goldenring Fine, Jodene; Bledsoe, Jesse; Semrud-Clikeman, Margaret

2016-09-01

Attention-deficit/hyperactivity disorder predominantly inattentive (ADHD-PI) and combined (ADHD-C) presentations are likely distinct disorders that differ neuroanatomically, neurochemically, and neuropsychologically. However, to date, little is known about specific white matter (WM) regions differentiating ADHD presentations. This study examined differences in WM microstructure using diffusion tensor imaging (DTI) data from 20 ADHD-PI, 18 ADHD-C, and 27 typically developed children. Voxel-wise analysis of DTI measurements in major fiber bundles was carried out using tract-based spatial statistics (TBSS). Clusters showing diffusivity abnormalities were used as regions of interest for regression analysis between fractional anisotropy (FA) and neuropsychological outcomes. Compared to neurotypicals, ADHD-PI children showed higher FA in the anterior thalamic radiations (ATR), bilateral inferior longitudinal fasciculus (ILF), and in the left corticospinal tract (CST). In contrast, the ADHD-C group exhibited higher FA in the bilateral cingulum bundle (CB). In the ADHD-PI group, differences in FA in the left ILF and ATR were accompanied by axial diffusivity (AD) abnormalities. In addition, the ADHD-PI group exhibited atypical mean diffusivity in the forceps minor (FMi) and left ATR and AD differences in right CB compared to healthy subjects. Direct comparison between ADHD presentations demonstrated radial diffusivity differences in FMi. WM clusters with FA irregularities in ADHD were associated with neurobehavioral performance across groups. In conclusion, differences in WM microstructure in ADHD presentations strengthen the theory that ADHD-PI and ADHD-C are two distinct disorders. Regions with WM irregularity seen in both ADHD presentations might serve as predictors of executive and behavioral functioning across groups. Hum Brain Mapp 37:3323-3336, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Steady-state solutions of a diffusive energy-balance climate model and their stability

NASA Technical Reports Server (NTRS)

Ghil, M.

1975-01-01

A diffusive energy-balance climate model, governed by a nonlinear parabolic partial differential equation, was studied. Three positive steady-state solutions of this equation are found; they correspond to three possible climates of our planet: an interglacial (nearly identical to the present climate), a glacial, and a completely ice-covered earth. Models similar to the main one are considered, and the number of their steady states was determined. All the models have albedo continuously varying with latitude and temperature, and entirely diffusive horizontal heat transfer. The stability under small perturbations of the main model's climates was investigated. A stability criterion is derived, and its application shows that the present climate and the deep freeze are stable, whereas the model's glacial is unstable. The dependence was examined of the number of steady states and of their stability on the average solar radiation.

Fgf8 morphogen gradient forms by a source-sink mechanism with freely diffusing molecules.

PubMed

Yu, Shuizi Rachel; Burkhardt, Markus; Nowak, Matthias; Ries, Jonas; Petrásek, Zdenek; Scholpp, Steffen; Schwille, Petra; Brand, Michael

2009-09-24

It is widely accepted that tissue differentiation and morphogenesis in multicellular organisms are regulated by tightly controlled concentration gradients of morphogens. How exactly these gradients are formed, however, remains unclear. Here we show that Fgf8 morphogen gradients in living zebrafish embryos are established and maintained by two essential factors: fast, free diffusion of single molecules away from the source through extracellular space, and a sink function of the receiving cells, regulated by receptor-mediated endocytosis. Evidence is provided by directly examining single molecules of Fgf8 in living tissue by fluorescence correlation spectroscopy, quantifying their local mobility and concentration with high precision. By changing the degree of uptake of Fgf8 into its target cells, we are able to alter the shape of the Fgf8 gradient. Our results demonstrate that a freely diffusing morphogen can set up concentration gradients in a complex multicellular tissue by a simple source-sink mechanism.

Dispersive—diffusive transport of non-sorbed solute in multicomponent solutions

NASA Astrophysics Data System (ADS)

Hu, Qinhong; Brusseau, Mark L.

1995-10-01

The composition of fuels, mixed-solvent wastes and other contaminants that find their way into the subsurface are frequently chemically complex. The dispersion and diffusion characteristics of multicomponent solutions in soil have rarely been compared to equivalent single-solute systems. The purpose of this work was to examine the diffusive and dispersive transport of single- and multi-component solutions in homogeneous porous media. The miscible displacement technique was used to investigate the transport behavior of 14C-labelled 2,4-dichlorophenoxyacetic acid ( 2,4-D) in two materials for which sorption of 2,4-D was minimal. Comparison of breakthrough curves collected for 2,4-D in single- and multi-component solutions shows that there is little, if any, difference in transport behavior over a wide range of pore-water velocities (70, 7, 0.66 and 0.06 cm h -1). Thus, dispersivities measured with a non-sorbing single-solute solution should be applicable to multicomponent systems.

Electronic spectra of astrophysically interesting cations

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

Maier, John P., E-mail: j.p.maier@unibas.ch; Rice, Corey A., E-mail: j.p.maier@unibas.ch; Mazzotti, Fabio J., E-mail: j.p.maier@unibas.ch

2015-01-22

The electronic spectra of polyacetylene cations were recorded at 20K in the laboratory in an ion trap instrument. These can then be compared with diffuse interstellar band (DIB) absorptions. Examination of recently published data shows that the attribution of a weak DIB at ∼506.9 nm to diacetylene cation is not justified. Study of the higher excited electronic states of polyacetylene cations shows that their widths can still be sufficiently narrow for consideration as DIB carriers.

Atomisti modeling of the microstructure and transport properties of lead-free solder alloys

NASA Astrophysics Data System (ADS)

Sellers, Michael S.

Damage mechanics models of lead-free solder joints in nanoelectronics continue to improve, and in doing so begin to utilize quantitative values describing processes at the atomic level, governing phenomena like electromigration and thermomigration. In particular, knowledge of the transport properties of specific microstructures helps continuum level models fully describe these larger-scale damage phenomena via multi-scale analysis. For example, diffusivities for different types of grain boundaries (fast diffusion paths for solvent and solute atoms, and vacancies), and a description of the boundary structure as a function of temperature, are critical in modeling solder microstructure evolution and, consequently, joint behavior under extreme temperature and electric current. Moreover, for damage that develops at larger length scales, surface energies and diffusivities play important roles in characterizing void stability and morphology. Unfortunately, experiments that investigate these kind of damage phenomena in the atomistic realm are often inconsistent or unable to directly quantify important parameters. One case is the particular transport and structural properties of grain boundaries in Sn (the main component in lead-free solder alloys) and their behavior in the presence of Ag and Cu impurities. This information is crucial in determining accurate diffusivity values for the common SnAgCu (SAC) type solder. Although an average grain boundary diffusivity has been reported for polycrystalline Sn in several works, the value for grain boundary width is estimated and specific diffusivities for boundaries known to occur in Sn have not been reported, to say nothing of solute effects on Sn diffusivity and grain boundary structure. Similarly, transport properties of Sn surfaces remain relatively uninvestigated as well. These gaps and inconsistencies in atomistic data must be remedied for micro- and macro-scale modeling to improve. As a complement to experimental work and possessing the ability to fill in the gaps, molecular simulation serves to reinforce experimental predictions and provide insight into the atomistic processes that govern studied phenomena. In the present body of work, we employ molecular statics and dynamics simulations in the characterization and computation of betaSn surface energies and surface diffusivities, the determination of diffusivities and structural properties of specific betaSn grain boundaries, and the investigation of Cu and Ag solute effects on betaSn grain boundaries. In our study of betaSn surfaces, energies for low number Miller index surfaces are computed and the (100) plane is found to have the lowest un-relaxed energy. We then find that two simple hopping mechanisms dominate adatom diffusion transitions on this surface. For each, we determine hopping rates of the adatom and compute its tracer diffusivity. Our work on grain boundaries investigates the self-diffusion properties and structure of several betaSn symmetric tilt grain boundaries using molecular dynamics simulations. We find that larger diffusive widths are exhibited by higher excess potential energy grain boundaries. Diffusivities in the directions parallel to the interface plane are also computed and activation energies are found with the Arrhenius relation. These are shown to agree well with experimental data. Finally, we examine the effect that solute atoms of Ag and Cu have on the microstructure of betaSn. Excess energies of the (101) symmetric tilt betaSn grain boundary are computed as a function of solute concentration at the interface, and we show that Ag lowers the energy at a greater rate than Cu. We also quantify segregation enthalpies and critical solute concentrations (where the excess energy of the boundary is reduced to zero). The effect of solute type on shear stress is also examined, and we show that solute has a strong effect on the stabilization of higher energy grain boundaries under shear stress. We then look at the self-diffusivity of Sn in the (101) symmetric tilt betaSn grain boundary and show that adding both Ag or Cu decrease the grain boundary self-diffusivity of Sn as solute amount in the interface increases. Effects of larger concentrations of Cu in particular are also investigated.

Ex vivo rabbit cornea diffusion studies with a soluble insert of moxifloxacin.

PubMed

Sebastián-Morelló, María; Calatayud-Pascual, María Aracely; Rodilla, Vicent; Balaguer-Fernández, Cristina; López-Castellano, Alicia

2018-02-01

The objective of this research was to develop and evaluate an ocular insert for the controlled drug delivery of moxifloxacin which could perhaps be used in the treatment of corneal keratitis or even bacterial endophthalmitis. We have evaluated the ex vivo ocular diffusion of moxifloxacin through rabbit cornea, both fresh and preserved under different conditions. Histological studies were also carried out. Subsequently, drug matrix inserts were prepared using bioadhesive polymers. The inserts were evaluated for their physicochemical parameters. Ophthalmic ex vivo permeation of moxifloxacin was carried out with the most promising insert. The formulate insert was thin and provided higher ocular diffusion than commercial formulations. Ocular diffusion studies revealed significant differences between fresh and frozen corneas. Histological examinations also showed differences in the thickness of stroma between fresh and frozen corneas. The ophthalmic insert we have developed allows a larger quantity of moxifloxacin to permeate through the cornea than existing commercial formulations of the drug. Ocular delivery of moxifloxacin with this insert could be a new approach for the treatment of eye diseases.

Brain aging in humans, chimpanzees (Pan troglodytes), and rhesus macaques (Macaca mulatta): magnetic resonance imaging studies of macro- and microstructural changes

PubMed Central

Chen, Xu; Errangi, Bhargav; Li, Longchuan; Glasser, Matthew F.; Westlye, Lars T.; Fjell, Anders M.; Walhovd, Kristine B.; Hu, Xiaoping; Herndon, James G.; Preuss, Todd M.; Rilling, James K.

2013-01-01

Among primates, humans are uniquely vulnerable to many age-related neurodegenerative disorders. We used structural and diffusion magnetic resonance imaging (MRI) to examine the brains of chimpanzees and rhesus monkeys across each species' adult lifespan, and compared these results with published findings in humans. As in humans, gray matter volume decreased with age in chimpanzees and rhesus monkeys. Also like humans, chimpanzees showed a trend for decreased white matter volume with age, but this decrease occurred proportionally later in the chimpanzee lifespan than in humans. Diffusion MRI revealed widespread age-related decreases in fractional anisotropy and increases in radial diffusivity in chimpanzees and macaques. However, both the fractional anisotropy decline and the radial diffusivity increase started at a proportionally earlier age in humans than in chimpanzees. Thus, even though overall patterns of gray and white matter aging are similar in humans and chimpanzees, the longer lifespan of humans provides more time for white matter to deteriorate before death, with the result that some neurological effects of aging may be exacerbated in our species. PMID:23623601

Diffusion in confinement: kinetic simulations of self- and collective diffusion behavior of adsorbed gases

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

Abouelnasr, MKF; Smit, B

2012-01-01

The self- and collective-diffusion behaviors of adsorbed methane, helium, and isobutane in zeolite frameworks LTA, MFI, AFI, and SAS were examined at various concentrations using a range of molecular simulation techniques including Molecular Dynamics (MD), Monte Carlo (MC), Bennett-Chandler (BC), and kinetic Monte Carlo (kMC). This paper has three main results. (1) A novel model for the process of adsorbate movement between two large cages was created, allowing the formulation of a mixing rule for the re-crossing coefficient between two cages of unequal loading. The predictions from this mixing rule were found to agree quantitatively with explicit simulations. (2) Amore » new approach to the dynamically corrected Transition State Theory method to analytically calculate self-diffusion properties was developed, explicitly accounting for nanoscale fluctuations in concentration. This approach was demonstrated to quantitatively agree with previous methods, but is uniquely suited to be adapted to a kMC simulation that can simulate the collective-diffusion behavior. (3) While at low and moderate loadings the self- and collective-diffusion behaviors in LTA are observed to coincide, at higher concentrations they diverge. A change in the adsorbate packing scheme was shown to cause this divergence, a trait which is replicated in a kMC simulation that explicitly models this behavior. These phenomena were further investigated for isobutane in zeolite MFI, where MD results showed a separation in self- and collective-diffusion behavior that was reproduced with kMC simulations.« less

Diffusion in confinement: kinetic simulations of self- and collective diffusion behavior of adsorbed gases.

PubMed

Abouelnasr, Mahmoud K F; Smit, Berend

2012-09-07

The self- and collective-diffusion behaviors of adsorbed methane, helium, and isobutane in zeolite frameworks LTA, MFI, AFI, and SAS were examined at various concentrations using a range of molecular simulation techniques including Molecular Dynamics (MD), Monte Carlo (MC), Bennett-Chandler (BC), and kinetic Monte Carlo (kMC). This paper has three main results. (1) A novel model for the process of adsorbate movement between two large cages was created, allowing the formulation of a mixing rule for the re-crossing coefficient between two cages of unequal loading. The predictions from this mixing rule were found to agree quantitatively with explicit simulations. (2) A new approach to the dynamically corrected Transition State Theory method to analytically calculate self-diffusion properties was developed, explicitly accounting for nanoscale fluctuations in concentration. This approach was demonstrated to quantitatively agree with previous methods, but is uniquely suited to be adapted to a kMC simulation that can simulate the collective-diffusion behavior. (3) While at low and moderate loadings the self- and collective-diffusion behaviors in LTA are observed to coincide, at higher concentrations they diverge. A change in the adsorbate packing scheme was shown to cause this divergence, a trait which is replicated in a kMC simulation that explicitly models this behavior. These phenomena were further investigated for isobutane in zeolite MFI, where MD results showed a separation in self- and collective- diffusion behavior that was reproduced with kMC simulations.

Experimental and theoretical comparison of Sb, As, and P diffusion mechanisms and doping in CdTe

NASA Astrophysics Data System (ADS)

Colegrove, E.; Yang, J.-H.; Harvey, S. P.; Young, M. R.; Burst, J. M.; Duenow, J. N.; Albin, D. S.; Wei, S.-H.; Metzger, W. K.

2018-02-01

Fundamental material doping challenges have limited CdTe electro-optical applications. In this work, the As atomistic diffusion mechanisms in CdTe are examined by spatially resolving dopant incorporation in both single-crystalline and polycrystalline CdTe over a range of experimental conditions. Density-functional theory calculations predict experimental activation energies and indicate that As diffuses slowly through the Te sublattice and quickly along GBs similar to Sb. Because of its atomic size and associated defect chemistry, As does not have a fast interstitial diffusion component similar to P. Experiments to incorporate and activate P, As, and Sb in polycrystalline CdTe are conducted to examine if ex situ Group V doping can overcome historic polycrystalline doping limits. The distinct P, As, and Sb diffusion characteristics create different strategies for increasing hole density. Because fast interstitial diffusion is prominent for P, less aggressive diffusion conditions followed by Cd overpressure to relocate the Group V element to the Te lattice site is effective. For larger atoms, slower diffusion through the Te sublattice requires more aggressive diffusion, however further activation is not always necessary. Based on the new physical understanding, we have obtained greater than 1016 cm-3 hole density in polycrystalline CdTe films by As and P diffusion.

Experimental and theoretical comparison of Sb, As, and P diffusion mechanisms and doping in CdTe

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

Colegrove, E.; Yang, J-H; Harvey, S. P.

Fundamental material doping challenges have limited CdTe electro-optical applications. In this work, the As atomistic diffusion mechanisms in CdTe are examined by spatially resolving dopant incorporation in both single-crystalline and polycrystalline CdTe over a range of experimental conditions. Density-functional theory calculations predict experimental activation energies and indicate As diffuses slowly through the Te sublattice and quickly along GBs similar to Sb. Because of its atomic size and associated defect chemistry, As does not have a fast interstitial diffusion component similar to P. Experiments to incorporate and activate P, As, and Sb in polycrystalline CdTe are conducted to examine if ex-situmore » Group V doping can overcome historic polycrystalline doping limits. The distinct P, As, and Sb diffusion characteristics create different strategies for increasing hole density. Because fast interstitial diffusion is prominent for P, less aggressive diffusion conditions followed by Cd overpressure to relocate the Group V element to the Te lattice site is effective. For larger atoms, slower diffusion through the Te sublattice requires more aggressive diffusion, however further activation is not always necessary. Based on the new physical understanding, we have obtained greater than 10^16 cm^-3 hole density in polycrystalline CdTe films by As and P diffusion.« less

Experimental and theoretical comparison of Sb, As, and P diffusion mechanisms and doping in CdTe

DOE PAGES

Colegrove, E.; Yang, J-H; Harvey, S. P.; ...

2018-01-29

Fundamental material doping challenges have limited CdTe electro-optical applications. In this work, the As atomistic diffusion mechanisms in CdTe are examined by spatially resolving dopant incorporation in both single-crystalline and polycrystalline CdTe over a range of experimental conditions. Density-functional theory calculations predict experimental activation energies and indicate As diffuses slowly through the Te sublattice and quickly along GBs similar to Sb. Because of its atomic size and associated defect chemistry, As does not have a fast interstitial diffusion component similar to P. Experiments to incorporate and activate P, As, and Sb in polycrystalline CdTe are conducted to examine if ex-situmore » Group V doping can overcome historic polycrystalline doping limits. The distinct P, As, and Sb diffusion characteristics create different strategies for increasing hole density. Because fast interstitial diffusion is prominent for P, less aggressive diffusion conditions followed by Cd overpressure to relocate the Group V element to the Te lattice site is effective. For larger atoms, slower diffusion through the Te sublattice requires more aggressive diffusion, however further activation is not always necessary. Based on the new physical understanding, we have obtained greater than 10^16 cm^-3 hole density in polycrystalline CdTe films by As and P diffusion.« less

Hemoglobin encapsulation in vesicles retards NO and CO binding and O2 release when perfused through narrow gas-permeable tubes.

PubMed

Sakai, Hiromi; Okuda, Naoto; Sato, Atsushi; Yamaue, Tatsuya; Takeoka, Shinji; Tsuchida, Eishun

2010-03-01

Intravenous administration of cell-free Hb induces vasoconstriction and circulatory disorders, presumably because of the intrinsic affinities to endogenous nitric oxide (NO) and carbon monoxide (CO) as vasorelaxation factors and because of the facilitated O(2) release that might induce autoregulatory vasoconstriction. We examined these gas reactions when Hb-containing solutions of four kinds were perfused through artificial narrow tubes at a practical Hb concentration (10 g/dl). Purified Hb solution, polymerized bovine Hb (Poly(B)Hb), encapsulated Hb [Hb-vesicles (HbV), 279 nm], and red blood cells (RBCs) were perfused through a gas-permeable narrow tube (25 microm inner diameter) at 1 mm/s centerline velocity. The level of reactions was determined microscopically based on the visible-light absorption spectrum of Hb. When the tube was immersed in NO and CO atmospheres, both NO binding and CO binding of deoxygenated Hb (deoxy-Hb) and Poly(B)Hb in the tube was faster than those of HbV and RBCs, and HbV and RBCs showed almost identical binding rates. When the tube was immersed in a N(2) atmosphere, oxygenated Hb and Poly(B)Hb showed much faster O(2) release than did HbV and RBCs. Poly(B)Hb showed a faster reaction than Hb because of the lower O(2) affinity of Poly(B)Hb than Hb. The diffusion process of the particles was simulated using Navier-Stokes and Maxwell-Stefan equations. Results clarified that small Hb (6 nm) diffuses laterally and mixes rapidly. However, the large-dimension HbV shows no such rapid diffusion. The purely physicochemical differences in diffusivity of the particles and the resulting reactivity with gas molecules are one factor inducing biological vasoconstriction of Hb-based oxygen carriers.

Inferring Recent Demography from Isolation by Distance of Long Shared Sequence Blocks

PubMed Central

Ringbauer, Harald; Coop, Graham

2017-01-01

Recently it has become feasible to detect long blocks of nearly identical sequence shared between pairs of genomes. These identity-by-descent (IBD) blocks are direct traces of recent coalescence events and, as such, contain ample signal to infer recent demography. Here, we examine sharing of such blocks in two-dimensional populations with local migration. Using a diffusion approximation to trace genetic ancestry, we derive analytical formulas for patterns of isolation by distance of IBD blocks, which can also incorporate recent population density changes. We introduce an inference scheme that uses a composite-likelihood approach to fit these formulas. We then extensively evaluate our theory and inference method on a range of scenarios using simulated data. We first validate the diffusion approximation by showing that the theoretical results closely match the simulated block-sharing patterns. We then demonstrate that our inference scheme can accurately and robustly infer dispersal rate and effective density, as well as bounds on recent dynamics of population density. To demonstrate an application, we use our estimation scheme to explore the fit of a diffusion model to Eastern European samples in the Population Reference Sample data set. We show that ancestry diffusing with a rate of σ≈50−−100 km/gen during the last centuries, combined with accelerating population growth, can explain the observed exponential decay of block sharing with increasing pairwise sample distance. PMID:28108588

The Management of Refractory Dry Eye With Semi-Scleral Contact Lens.

PubMed

Yuksel, Erdem; Bilgihan, Kamil; Novruzlu, Şahin; Yuksel, Nilay; Koksal, Murat

2018-05-01

We presented a case of refractory dry eye management with semi-scleral contact lens. Dry eye was associated with facial nerve (cranial nerve VII) palsy as a result of cerebellopontine angle tumor surgery. She was treated with several topical treatments and punctal plug. Despite the treatments, her symptoms still persisted. Her ophthalmic examination revealed scleral exposure because of lagophthalmos, conjunctival hyperemia, corneal debris, scar, and diffuse punctate epitheliopathy on her right eye. Lissamine green staining showed diffuse conjunctival and corneal staining. Therapeutic semi-scleral lenses were fitted. The corneal findings were resolved and the quality of patient life was improved with the aid of semi-scleral lens after 3 months.

Diffuse large B-cell lymphoma presenting as a unilateral solitary round pulmonary hilar node infarction.

PubMed

Yonemori, Kan; Kusumoto, Masahiko; Matsuno, Yoshihiro; Tateishi, Ukihide; Watanabe, Shun-Ichi; Watanabe, Takashi; Moriyama, Noriyuki

2006-03-01

Unilateral solitary pulmonary hilar node adenopathy is a rare presentation of diffuse large B-cell lymphoma. In this report, the authors present a case with a solitary pulmonary hilar lymph node infarction caused by diffuse large B-cell lymphoma. Enhanced CT examinations revealed a well-defined round mass with homogenous low attenuation in the left pulmonary hilum. Both radiological imaging and pathological examination can provide useful information for the interpretation of abnormalities and may enable the diagnosis of rare aetiologies.

An extended source for CN jets in Comet P/Halley

NASA Technical Reports Server (NTRS)

Klavetter, James Jay; A'Hearn, Michael F.

1994-01-01

We examined radial intensity profiles of CN jets in comparison with the diffuse, isotropic component of the CN coma of Comet P/Halley. All images were bias-subtracted, flat-fielded, and continuum-subtracted. We calculated the diffuse profiles by finding the azimuthal mean of the coma least contaminated by jets yielding profiles similar to those of vectorial and Haser models of simple photodissociation. We found the jet profiles by calculating a mean around a Gaussian-fitted center in r-theta space. There is an unmistakable difference between the profiles of the CN jets and the profiles of the diffuse CN. Spatial derivatives of these profiles, corrected for geometrical expansion, show that the diffuse component is consistent with a simple photodissociation process, but the jet component is not. The peak production of the jet profile occurs 6000 km from the nucleus at a heliocentric distance of 1.4 AU. Modeling of both components of the coma indicate results that are consistent with the diffuse CN photochemically produced, but the CN jets need an additional extended source. We found that about one-half of the CN in the coma of Comet P/Halley originated from the jets, the rest from the diffuse component. These features, along with the width of the jet being approximately constant, are consistent with a CHON grain origin for the jets.

Diffusion of Web Supported Instruction in Higher Education--The Case of Tel-Aviv University

ERIC Educational Resources Information Center

Soffer, Tal; Nachmias, Rafi; Ram, Judith

2010-01-01

This paper describes a study that focused on long-term web-supported learning diffusion among lecturers at Tel Aviv University (TAU), from an organizational point of view. The theoretical models we used to examine this process are Rogers' model for "Diffusion of Innovation" (1995) and Bass's "Diffusion Model" (1969). The study…

The Diffusion of Institute Concepts Beyond the Participants of an NDEA Institute in Critical and Appreciative Reading.

ERIC Educational Resources Information Center

Edmonds, Bernyce Scott

This research examined the diffusion activities of 35 administrators, specialists, and classroom teachers in implementing NDEA Institute recommended concepts in their schools. Extensiveness of diffusion activities was measured by the number of concepts diffused and the number of concepts adopted by colleagues. The study was conducted in three…

Aging and Predicting Inferences: A Diffusion Model Analysis

ERIC Educational Resources Information Center

McKoon, Gail; Ratcliff, Roger

2013-01-01

In the domain of discourse processing, it has been claimed that older adults (60-0-year-olds) are less likely to encode and remember some kinds of information from texts than young adults. The experiment described here shows that they do make a particular kind of inference to the same extent that college-age adults do. The inferences examined were…

Analytical performance bounds for multi-tensor diffusion-MRI.

PubMed

Ahmed Sid, Farid; Abed-Meraim, Karim; Harba, Rachid; Oulebsir-Boumghar, Fatima

2017-02-01

To examine the effects of MR acquisition parameters on brain white matter fiber orientation estimation and parameter of clinical interest in crossing fiber areas based on the Multi-Tensor Model (MTM). We compute the Cramér-Rao Bound (CRB) for the MTM and the parameter of clinical interest such as the Fractional Anisotropy (FA) and the dominant fiber orientations, assuming that the diffusion MRI data are recorded by a multi-coil, multi-shell acquisition system. Considering the sum-of-squares method for the reconstructed magnitude image, we introduce an approximate closed-form formula for Fisher Information Matrix that has the simplicity and easy interpretation advantages. In addition, we propose to generalize the FA and the mean diffusivity to the multi-tensor model. We show the application of the CRB to reduce the scan time while preserving a good estimation precision. We provide results showing how the increase of the number of acquisition coils compensates the decrease of the number of diffusion gradient directions. We analyze the impact of the b-value and the Signal-to-Noise Ratio (SNR). The analysis shows that the estimation error variance decreases with a quadratic rate with the SNR, and that the optimum b-values are not unique but depend on the target parameter, the context, and eventually the target cost function. In this study we highlight the importance of choosing the appropriate acquisition parameters especially when dealing with crossing fiber areas. We also provide a methodology for the optimal tuning of these parameters using the CRB. Copyright © 2016 Elsevier Inc. All rights reserved.

Parameterization of large-scale turbulent diffusion in the presence of both well-mixed and weakly mixed patchy layers

NASA Astrophysics Data System (ADS)

Osman, M. K.; Hocking, W. K.; Tarasick, D. W.

2016-06-01

Vertical diffusion and mixing of tracers in the upper troposphere and lower stratosphere (UTLS) are not uniform, but primarily occur due to patches of turbulence that are intermittent in time and space. The effective diffusivity of regions of patchy turbulence is related to statistical parameters describing the morphology of turbulent events, such as lifetime, number, width, depth and local diffusivity (i.e., diffusivity within the turbulent patch) of the patches. While this has been recognized in the literature, the primary focus has been on well-mixed layers, with few exceptions. In such cases the local diffusivity is irrelevant, but this is not true for weakly and partially mixed layers. Here, we use both theory and numerical simulations to consider the impact of intermediate and weakly mixed layers, in addition to well-mixed layers. Previous approaches have considered only one dimension (vertical), and only a small number of layers (often one at each time step), and have examined mixing of constituents. We consider a two-dimensional case, with multiple layers (10 and more, up to hundreds and even thousands), having well-defined, non-infinite, lengths and depths. We then provide new formulas to describe cases involving well-mixed layers which supersede earlier expressions. In addition, we look in detail at layers that are not well mixed, and, as an interesting variation on previous models, our procedure is based on tracking the dispersion of individual particles, which is quite different to the earlier approaches which looked at mixing of constituents. We develop an expression which allows determination of the degree of mixing, and show that layers used in some previous models were in fact not well mixed and so produced erroneous results. We then develop a generalized model based on two dimensional random-walk theory employing Rayleigh distributions which allows us to develop a universal formula for diffusion rates for multiple two-dimensional layers with general degrees of mixing. We show that it is the largest, most vigorous and less common turbulent layers that make the major contribution to global diffusion. Finally, we make estimates of global-scale diffusion coefficients in the lower stratosphere and upper troposphere. For the lower stratosphere, κeff ≈ 2x10-2 m2 s-1, assuming no other processes contribute to large-scale diffusion.

Molecular dynamics and Monte Carlo simulations resolve apparent diffusion rate differences for proteins confined in nanochannels

DOE PAGES

Tringe, J. W.; Ileri, N.; Levie, H. W.; ...

2015-08-01

We use Molecular Dynamics and Monte Carlo simulations to examine molecular transport phenomena in nanochannels, explaining four orders of magnitude difference in wheat germ agglutinin (WGA) protein diffusion rates observed by fluorescence correlation spectroscopy (FCS) and by direct imaging of fluorescently-labeled proteins. We first use the ESPResSo Molecular Dynamics code to estimate the surface transport distance for neutral and charged proteins. We then employ a Monte Carlo model to calculate the paths of protein molecules on surfaces and in the bulk liquid transport medium. Our results show that the transport characteristics depend strongly on the degree of molecular surface coverage.more » Atomic force microscope characterization of surfaces exposed to WGA proteins for 1000 s show large protein aggregates consistent with the predicted coverage. These calculations and experiments provide useful insight into the details of molecular motion in confined geometries.« less

Collision of Lymphoepithelioma-like Carcinoma with Diffuse Large B-cell Lymphoma of the Stomach: A Case Report.

PubMed

Liu, Liyan; Zhao, Huishan; Sheng, Lin; Yang, Ping; Zhou, Huihui; Wang, Ruizheng

2017-08-01

Collision of Epstein-Barr virus (EBV)-associated lymphoepithelioma-like carcinoma (LELC) with non-Hodgkin's lymphoma of the stomach is extremely rare. Herein we report a case of LELC with primary diffuse large B-cell lymphoma (DLBCL) of the stomach in a 65-year-old patient. Gastric endoscopy showed a poorly differentiated adenocarcinoma of the stomach. The patient underwent radical gastrectomy, and histopathological examinations revealed the collision of LELC and DLBCL of the stomach. In situ hybridization showed that most carcinoma cells of LELC were positive for EBV-encoded small RNA (EBER) suggesting that the virus infection happened in the early stage of tumorigenesis, while DLBCL was negative. This is the first report of collision of EBV-associated LELC with primary DLBCL of the stomach. Copyright© 2017, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.

Microstructural abnormalities in white and gray matter in obese adolescents with and without type 2 diabetes.

PubMed

Nouwen, Arie; Chambers, Alison; Chechlacz, Magdalena; Higgs, Suzanne; Blissett, Jacqueline; Barrett, Timothy G; Allen, Harriet A

2017-01-01

In adults, type 2 diabetes and obesity have been associated with structural brain changes, even in the absence of dementia. Some evidence suggested similar changes in adolescents with type 2 diabetes but comparisons with a non-obese control group have been lacking. The aim of the current study was to examine differences in microstructure of gray and white matter between adolescents with type 2 diabetes, obese adolescents and healthy weight adolescents. Magnetic resonance imaging data were collected from 15 adolescents with type 2 diabetes, 21 obese adolescents and 22 healthy weight controls. Volumetric differences in the gray matter between the three groups were examined using voxel based morphology, while tract based spatial statistics was used to examine differences in the microstructure of the white matter. Adolescents with type 2 diabetes and obese adolescents had reduced gray matter volume in the right hippocampus, left putamen and caudate, bilateral amygdala and left thalamus compared to healthy weight controls. Type 2 diabetes was also associated with significant regional changes in fractional anisotropy within the corpus callosum, fornix, left inferior fronto-occipital fasciculus, left uncinate, left internal and external capsule. Fractional anisotropy reductions within these tracts were explained by increased radial diffusivity, which may suggest demyelination of white matter tracts. Mean diffusivity and axial diffusivity did not differ between the groups. Our data shows that adolescent obesity alone results in reduced gray matter volume and that adolescent type 2 diabetes is associated with both white and gray matter abnormalities.

Consume, Modify, Share (CMS): The Interplay between Individual Decisions and Structural Network Properties in the Diffusion of Information

PubMed Central

Koren, Hila; Kaminer, Ido

2016-01-01

Widely used information diffusion models such as Independent Cascade Model, Susceptible Infected Recovered (SIR) and others fail to acknowledge that information is constantly subject to modification. Some aspects of information diffusion are best explained by network structural characteristics while in some cases strong influence comes from individual decisions. We introduce reinvention, the ability to modify information, as an individual level decision that affects the diffusion process as a whole. Based on a combination of constructs from the Diffusion of Innovations and the Critical Mass Theories, the present study advances the CMS (consume, modify, share) model which accounts for the interplay between network structure and human behavior and interactions. The model's building blocks include processes leading up to and following the formation of a critical mass of information adopters and disseminators. We examine the formation of an inflection point, information reach, sustainability of the diffusion process and collective value creation. The CMS model is tested on two directed networks and one undirected network, assuming weak or strong ties and applying constant and relative modification schemes. While all three networks are designed for disseminating new knowledge they differ in structural properties. Our findings suggest that modification enhances the diffusion of information in networks that support undirected connections and carries the biggest effect when information is shared via weak ties. Rogers' diffusion model and traditional information contagion models are fine tuned. Our results show that modifications not only contribute to a sustainable diffusion process, but also aid information in reaching remote areas of the network. The results point to the importance of cultivating weak ties, allowing reciprocal interaction among nodes and supporting the modification of information in promoting diffusion processes. These results have theoretical and practical implications for designing networks aimed at accelerating the creation and diffusion of information. PMID:27798636

Consume, Modify, Share (CMS): The Interplay between Individual Decisions and Structural Network Properties in the Diffusion of Information.

PubMed

Koren, Hila; Kaminer, Ido; Raban, Daphne Ruth

2016-01-01

Widely used information diffusion models such as Independent Cascade Model, Susceptible Infected Recovered (SIR) and others fail to acknowledge that information is constantly subject to modification. Some aspects of information diffusion are best explained by network structural characteristics while in some cases strong influence comes from individual decisions. We introduce reinvention, the ability to modify information, as an individual level decision that affects the diffusion process as a whole. Based on a combination of constructs from the Diffusion of Innovations and the Critical Mass Theories, the present study advances the CMS (consume, modify, share) model which accounts for the interplay between network structure and human behavior and interactions. The model's building blocks include processes leading up to and following the formation of a critical mass of information adopters and disseminators. We examine the formation of an inflection point, information reach, sustainability of the diffusion process and collective value creation. The CMS model is tested on two directed networks and one undirected network, assuming weak or strong ties and applying constant and relative modification schemes. While all three networks are designed for disseminating new knowledge they differ in structural properties. Our findings suggest that modification enhances the diffusion of information in networks that support undirected connections and carries the biggest effect when information is shared via weak ties. Rogers' diffusion model and traditional information contagion models are fine tuned. Our results show that modifications not only contribute to a sustainable diffusion process, but also aid information in reaching remote areas of the network. The results point to the importance of cultivating weak ties, allowing reciprocal interaction among nodes and supporting the modification of information in promoting diffusion processes. These results have theoretical and practical implications for designing networks aimed at accelerating the creation and diffusion of information.

Equatorial ground ice on Mars: Steady-state stability

NASA Technical Reports Server (NTRS)

Mellon, Michael T.; Jakosky, Bruce M.; Postawko, Susan E.

1993-01-01

Current Martian equatorial surface temperatures are too warm for water ice to exist at the surface for any appreciable length of time before subliming into the atmosphere. Subsurface temperatures are generally warmer still and, despite the presence of a diffusive barrier of porous regolith material, it has been shown by Smoluchowski, Clifford and Hillel, and Fanale et al. that buried ground ice will also sublime and be lost to the atmosphere in a relatively short time. We investigate the behavior of this subliming subsurface ice and show that it is possible for ice to maintain at a steady-state depth, where sublimation and diffusive loss to the atmosphere is balanced by resupply from beneath by diffusion and recondensation of either a deeper buried ice deposits or ground water. We examine the behavior of equatorial ground ice with a numercial time-marching molecular diffusion model. In our model we allow for diffusion of water vapor through a porous regolith, variations in diffusivity and porosity with ice content, and recondensation of sublimed water vapor. A regolith containing considerable amounts of ice can still be very porous, allowing water vapor to diffuse up from deeper within the ice layer where temperatures are warmer due to the geothermal gradient. This vapor can then recondense nearer to the surface where ice had previously sublimed and been lost to the atmosphere. As a result we find that ice deposits migrate to find a steady-state depth, which represents a balance between diffusive loss to the atmosphere through the overlying porous regolith and diffusive resupply through a porous icy regolith below. This depth depends primarily on the long-term mean surface temperature and the nature of the geothermal gradient, and is independent of the ice-free porosity and the regolith diffusivity. Only the rate of loss of ground ice depends on diffusive properties.

System-size corrections for self-diffusion coefficients calculated from molecular dynamics simulations: The case of CO2, n-alkanes, and poly(ethylene glycol) dimethyl ethers

NASA Astrophysics Data System (ADS)

Moultos, Othonas A.; Zhang, Yong; Tsimpanogiannis, Ioannis N.; Economou, Ioannis G.; Maginn, Edward J.

2016-08-01

Molecular dynamics simulations were carried out to study the self-diffusion coefficients of CO2, methane, propane, n-hexane, n-hexadecane, and various poly(ethylene glycol) dimethyl ethers (glymes in short, CH3O-(CH2CH2O)n-CH3 with n = 1, 2, 3, and 4, labeled as G1, G2, G3, and G4, respectively) at different conditions. Various system sizes were examined. The widely used Yeh and Hummer [J. Phys. Chem. B 108, 15873 (2004)] correction for the prediction of diffusion coefficient at the thermodynamic limit was applied and shown to be accurate in all cases compared to extrapolated values at infinite system size. The magnitude of correction, in all cases examined, is significant, with the smallest systems examined giving for some cases a self-diffusion coefficient approximately 15% lower than the infinite system-size extrapolated value. The results suggest that finite size corrections to computed self-diffusivities must be used in order to obtain accurate results.

Demonstrating Diffusion: Why the Confusion?

ERIC Educational Resources Information Center

Panizzon, Debra Lee

1998-01-01

Examines the principles of diffusion and how it may be confused with convection. Suggests that educators may be misleading students and clouding their understanding of the process. Provides two contemporary examples to explain the process of diffusion and how it differs from convection. (Author/CCM)

Examination of factors dominating the sediment-water diffusion flux of DDT-related compounds measured by passive sampling in an urbanized estuarine bay.

PubMed

Feng, Yan; Wu, Chen-Chou; Bao, Lian-Jun; Shi, Lei; Song, Lin; Zeng, Eddy Y

2016-12-01

The fate of hydrophobic organic compounds in aquatic environment are largely determined by their exchange at sediment-water interface, which is highly dynamic and subject to rapidly evolving environmental conditions. In turn, environmental conditions may be governed by both physicochemical parameters and anthropogenic events. To examine the importance of various impact factors, passive sampling devices were deployed at the seafloor of Hailing Bay, an urbanized estuarine bay in Guangdong Province of South China to measure the sediment-water diffusion fluxes of several metabolites of dichlorodiphenyltrichloroethane (DDT), p,p'-DDE, p,p'-DDD and o,p'-DDD. The physicochemical properties of water (temperature, pH, salinity and dissolved oxygen) and surface sediment (sediment organic matter, physical composition, pH, water content, colony forming unit and catalase activity) were also measured. The results showed that the diffusion fluxes of o,p'-DDD, p,p'-DDD and p,p'-DDE at sites A1 and A2 near a fishing boat maintenance facility ranged from 0.42 to 4.73 ng m -2 d -1 (from sediment to overlying water), whereas those at offshore sites varied between -0.03 and -3.02 ng m -2 d -1 (from overlying water to sediment), implicating A1 and A2 as the sources of the target compounds. The distribution patterns of the diffusion fluxes of the target compounds were different from those of water and sediment parameters (water temperature, salinity, sediment texture, pH, colony forming unit and catalase activity) at six sampling sites. This finding suggested that none of these parameters were critical in dictating the sediment-water diffusion fluxes. Besides, decreases in the contents of kerogen and black carbon by 6.7% and 11% would enhance the diffusion fluxes of the target compounds by 11-14% and 12-23%, respectively, at site A1, indicating that kerogen and black carbon were the key factors in mediating the sediment-water diffusion fluxes of DDT-related compounds in field environments. Copyright © 2016 Elsevier Ltd. All rights reserved.

Voxelwise Correlational Analyses of White Matter Integrity in Multiple Cognitive Domains in Schizophrenia

PubMed Central

Lim, Kelvin O.; Ardekani, Babak A.; Nierenberg, Jay; Butler, Pamela D.; Javitt, Daniel C.; Hoptman, Matthew J.

2007-01-01

Patients with schizophrenia show deficits in several neurocognitive domains. However, the relationship between white matter integrity and performance in these domains is poorly understood. The authors conducted neurocognitive testing and diffusion tensor imaging in 25 patients with schizophrenia. Performance was examined for tests of verbal declarative memory, attention, and executive function. Relationships between fractional anisotropy and cognitive performance were examined by using voxelwise correlational analyses. In each case, better performance on these tasks was associated with higher levels of fractional anisotropy in task-relevant regions. PMID:17074956

[Cortico-suprarenal carcinoma].

PubMed

Alecu, L; Costan, I; Viţalariu, Adriana; Lungu, C; Obrocea, F; Gulinescu, L

2002-01-01

The authors show the case of a 69 years old male with a large corticosuprarenalian tumor that was detected on an random abdominal echographic examination. The patient was operated in the General Surgery Department. of Prof. Agrippa Ionescu Hospital, Bucharest. We performed ablation of the large left suprarenalian gland malign tumor with left nephrectomy, splenectomy and partial pancreatectomy. The hystopathological examination reveals a diffuse corticosuprenalian carcinoma. The case is interesting because of low incidence of this kind of malign tumor and also of the unusual tumor evolution in a long time up to its large size (12 cm in diameter).

Risk Assessment of Alzheimer's Disease using the Information Diffusion Model from Structural Magnetic Resonance Imaging.

PubMed

Beheshti, Iman; Olya, Hossain G T; Demirel, Hasan

2016-04-05

Recently, automatic risk assessment methods have been a target for the detection of Alzheimer's disease (AD) risk. This study aims to develop an automatic computer-aided AD diagnosis technique for risk assessment of AD using information diffusion theory. Information diffusion is a fuzzy mathematics logic of set-value that is used for risk assessment of natural phenomena, which attaches fuzziness (uncertainty) and incompleteness. Data were obtained from voxel-based morphometry analysis of structural magnetic resonance imaging. The information diffusion model results revealed that the risk of AD increases with a reduction of the normalized gray matter ratio (p > 0.5, normalized gray matter ratio <40%). The information diffusion model results were evaluated by calculation of the correlation of two traditional risk assessments of AD, the Mini-Mental State Examination and the Clinical Dementia Rating. The correlation results revealed that the information diffusion model findings were in line with Mini-Mental State Examination and Clinical Dementia Rating results. Application of information diffusion model contributes to the computerization of risk assessment of AD, which has a practical implication for the early detection of AD.

[Primary diffuse large B-cell lymphoma of the uterus complicated with hydronephrosis].

PubMed

Isosaka, Mai; Hayashi, Toshiaki; Mitsuhashi, Kei; Tanaka, Michihiro; Adachi, Takeya; Kondo, Yoshihiro; Suzuki, Takashi; Shinomura, Yasuhisa

2013-04-01

Malignant lymphoma sometimes originates from extranodal sites; however, the uterus has rarely been reported as the site of the primary lesion. We present a patient with malignant lymphoma of the uterus complicating bilateral hydronephrosis. A 67-year-old previously healthy woman was seen at a clinic because of massive genital bleeding. She was referred to our hospital for further examination of a uterine tumor. Computed tomography scans revealed a pelvic tumor invading to the retroperitoneal region, which caused bilateral obstruction of the ureters and hydronephrosis. No lymph node swelling was detected. Magnetic resonance imaging showed a bulky uterine tumor that was homogenously low on T1-weighted imaging and isointense on T2-weighted imaging, while the endometrium was intact. A pathological examination of the biopsy specimen from the uterine cervix revealed diffuse infiltration of CD20-positive atypical large lymphoid cells, which was compatible with diffuse large B-cell lymphoma (DLBCL). Since the tumor expanded from the uterus and no other abnormal lesion was observed in imaging studies including gallium scintigraphy, a diagnosis of DLBCL of the uterus, clinical stage IE was made. The patient received six cycles of rituximab plus CHOP chemotherapy followed by involved field irradiation. She achieved complete remission and has been alive for more than two years without relapse.

In vitro sensitivity of Hungarian Actinobaculum suis strains to selected antimicrobials.

PubMed

Biksi, I; Major, Andrea; Fodor, L; Szenci, O; Vetési, F

2003-01-01

In vitro antimicrobial sensitivity of 12 Hungarian isolates and the type strain ATCC 33144 of Actinobaculum suis to different antimicrobial compounds was determined both by the agar dilution and by the disc diffusion method. By agar dilution, MIC50 values in the range of 0.05-3.125 micrograms/ml were determined for penicillin, ampicillin, ceftiofur, doxycycline, tylosin, pleuromutilins, chloramphenicol, florfenicol, enrofloxacin and lincomycin. The MIC50 value of oxytetracycline and spectinomycin was 6.25 and 12.5 micrograms/ml, respectively. For ofloxacin, flumequine, neomycin, streptomycin, gentamicin, nalidixic acid, nitrofurantoin and sulphamethoxazole + trimethoprim MIC50 values were in the range of 25-100 micrograms/ml. With the disc diffusion method, all strains were sensitive to penicillin, cephalosporins examined, chloramphenicol and florfenicol, tetracyclines examined, pleuromutilins, lincomycin and tylosin. Variable sensitivity was observed for fluoroquinolones (flumequine, enrofloxacin, ofloxacin), most of the strains were susceptible to marbofloxacin. Almost all strains were resistant to aminoglycosides but most of them were sensitive to spectinomycin. A strong correlation was determined for disc diffusion and MIC results (Spearman's rho 0.789, p < 0001). MIC values of the type strain and MIC50 values of other tested strains did not differ significantly. Few strains showed a partially distinct resistance pattern for erythromycin, lincomycin and ampicillin in both methods.

Sex differences in adolescent white matter architecture.

PubMed

Bava, Sunita; Boucquey, Veronique; Goldenberg, Diane; Thayer, Rachel E; Ward, Megan; Jacobus, Joanna; Tapert, Susan F

2011-02-23

Sex-specific trajectories in white matter development during adolescence may help explain cognitive and behavioral divergences between males and females. Knowledge of sex differences in typically developing adolescents can provide a basis for interpreting sexual dimorphisms in abilities and actions. We examined 58 healthy adolescents (12-14years of age) with diffusion tensor imaging (DTI). Diffusion parameters fractional anisotropy (FA), and mean (MD), radial (RD), and axial diffusivities (AD) were subjected to whole-brain voxel-wise group comparisons using tract-based spatial statistics. Sex differences in white matter microstructure were examined in relation to pubertal development. Early adolescent females (n=29) evidenced higher FA in the right superior corona radiata, higher FA and AD in bilateral corticospinal tracts (≥164μl, p<.01), and lower MD in the right inferior longitudinal fasciculus (ILF) and left forceps major (≥164μl, p<.01) than age-matched males (n=29). Males did not show any areas of higher FA or lower MD than females, but had higher AD in the right superior longitudinal fasciculus, ILF, and forceps minor (≥ 164μl, p<.01). Pubertal stage did not account for sex disparities. In early adolescence, females' motor tracts may reflect widespread changes, while males may undergo relatively more microstructural change in projection and association fibers. Copyright © 2010 Elsevier B.V. All rights reserved.

An improved procedure for determining grain boundary diffusion coefficients from averaged concentration profiles

NASA Astrophysics Data System (ADS)

Gryaznov, D.; Fleig, J.; Maier, J.

2008-03-01

Whipple's solution of the problem of grain boundary diffusion and Le Claire's relation, which is often used to determine grain boundary diffusion coefficients, are examined for a broad range of ratios of grain boundary to bulk diffusivities Δ and diffusion times t. Different reasons leading to errors in determining the grain boundary diffusivity (DGB) when using Le Claire's relation are discussed. It is shown that nonlinearities of the diffusion profiles in lnCav-y6/5 plots and deviations from "Le Claire's constant" (-0.78) are the major error sources (Cav=averaged concentration, y =coordinate in diffusion direction). An improved relation (replacing Le Claire's constant) is suggested for analyzing diffusion profiles particularly suited for small diffusion lengths (short times) as often required in diffusion experiments on nanocrystalline materials.

Mass Transport of Macromolecules within an In Vitro Model of Supragingival Plaque

PubMed Central

Thurnheer, Thomas; Gmür, Rudolf; Shapiro, Stuart; Guggenheim, Bernhard

2003-01-01

The aim of this study was to examine the diffusion of macromolecules through an in vitro biofilm model of supragingival plaque. Polyspecies biofilms containing Actinomyces naeslundii, Fusobacterium nucleatum, Streptococcus oralis, Streptococcus sobrinus, Veillonella dispar, and Candida albicans were formed on sintered hydroxyapatite disks and then incubated at room temperature for defined periods with fluorescent markers with molecular weights ranging from 3,000 to 900,000. Subsequent examination by confocal laser scanning microscopy revealed that the mean square penetration depths for all tested macromolecules except immunoglobulin M increased linearly with time, diffusion coefficients being linearly proportional to the cube roots of the molecular weights of the probes (range, 10,000 to 240,000). Compared to diffusion in bulk water, diffusion in the biofilms was markedly slower. The rate of diffusion for each probe appeared to be constant and not a function of biofilm depth. Analysis of diffusion phenomena through the biofilms suggested tortuosity as the most probable explanation for retarded diffusion. Selective binding of probes to receptors present in the biofilms could not explain the observed extent of retardation of diffusion. These results are relevant to oral health, as selective attenuated diffusion of fermentable carbohydrates and acids produced within dental plaque is thought to be essential for the development of carious lesions. PMID:12620862

Altered white matter microstructure is associated with social cognition and psychotic symptoms in 22q11.2 microdeletion syndrome

PubMed Central

Jalbrzikowski, Maria; Villalon-Reina, Julio E.; Karlsgodt, Katherine H.; Senturk, Damla; Chow, Carolyn; Thompson, Paul M.; Bearden, Carrie E.

2014-01-01

22q11.2 Microdeletion Syndrome (22q11DS) is a highly penetrant genetic mutation associated with a significantly increased risk for psychosis. Aberrant neurodevelopment may lead to inappropriate neural circuit formation and cerebral dysconnectivity in 22q11DS, which may contribute to symptom development. Here we examined: (1) differences between 22q11DS participants and typically developing controls in diffusion tensor imaging (DTI) measures within white matter tracts; (2) whether there is an altered age-related trajectory of white matter pathways in 22q11DS; and (3) relationships between DTI measures, social cognition task performance, and positive symptoms of psychosis in 22q11DS and typically developing controls. Sixty-four direction diffusion weighted imaging data were acquired on 65 participants (36 22q11DS, 29 controls). We examined differences between 22q11DS vs. controls in measures of fractional anisotropy (FA), axial diffusivity (AD), and radial diffusivity (RD), using both a voxel-based and region of interest approach. Social cognition domains assessed were: Theory of Mind and emotion recognition. Positive symptoms were assessed using the Structured Interview for Prodromal Syndromes. Compared to typically developing controls, 22q11DS participants showed significantly lower AD and RD in multiple white matter tracts, with effects of greatest magnitude for AD in the superior longitudinal fasciculus. Additionally, 22q11DS participants failed to show typical age-associated changes in FA and RD in the left inferior longitudinal fasciculus. Higher AD in the left inferior fronto-occipital fasciculus (IFO) and left uncinate fasciculus was associated with better social cognition in 22q11DS and controls. In contrast, greater severity of positive symptoms was associated with lower AD in bilateral regions of the IFO in 22q11DS. White matter microstructure in tracts relevant to social cognition is disrupted in 22q11DS, and may contribute to psychosis risk. PMID:25426042

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

Wong, May Wai San; Ovchinnikov, Mikhail; Wang, Minghuai

Potential ways of parameterizing vertical turbulent fluxes of hydrometeors are examined using a high-resolution cloud-resolving model. The cloud-resolving model uses the Morrison microphysics scheme, which contains prognostic variables for rain, graupel, ice, and snow. A benchmark simulation with a horizontal grid spacing of 250 m of a deep convection case carried out to evaluate three different ways of parameterizing the turbulent vertical fluxes of hydrometeors: an eddy-diffusion approximation, a quadrant-based decomposition, and a scaling method that accounts for within-quadrant (subplume) correlations. Results show that the down-gradient nature of the eddy-diffusion approximation tends to transport mass away from concentrated regions, whereasmore » the benchmark simulation indicates that the vertical transport tends to transport mass from below the level of maximum to aloft. Unlike the eddy-diffusion approach, the quadri-modal decomposition is able to capture the signs of the flux gradient but underestimates the magnitudes. The scaling approach is shown to perform the best by accounting for within-quadrant correlations, and improves the results for all hydrometeors except for snow. A sensitivity study is performed to examine how vertical transport may affect the microphysics of the hydrometeors. The vertical transport of each hydrometeor type is artificially suppressed in each test. Results from the sensitivity tests show that cloud-droplet-related processes are most sensitive to suppressed rain or graupel transport. In particular, suppressing rain or graupel transport has a strong impact on the production of snow and ice aloft. Lastly, a viable subgrid-scale hydrometeor transport scheme in an assumed probability density function parameterization is discussed.« less

Differential susceptibility of white matter tracts to inflammatory mediators in schizophrenia: an integrated DTI study.

PubMed

Prasad, Konasale M; Upton, Catherine H; Nimgaonkar, Vishwajit L; Keshavan, Matcheri S

2015-01-01

The pathophysiological underpinnings of impaired anatomical and functional connectivity are not precisely known. Emerging data suggest that immune mediators may underlie such dysconnectivity. We examined anatomical brain connections using diffusion tensor imaging (DTI) data in relation to interleukin-6 (IL-6) and C-reactive protein (CRP) levels among early-course clinically stable schizophrenia subjects compared to healthy controls (HC). DTI data were acquired in 30 directions with 2 averages. Fractional anisotropy (FA) and radial diffusivity (RD) maps were separately processed using FSL4.1.9 and Tract-Based Spatial Statistics (TBSS). Threshold free cluster enhancements (TFCE) were examined employing familywise error (FWE) corrections for multiple testing within linear regression models including age, sex and socioeconomic status as covariates. IL-6 and CRP were assayed using highly sensitive and specific sandwich immunosorbent assays. The groups did not differ in age and sex as well as in the IL-6 and CRP levels. IL-6 levels were negatively correlated with the FA and positively correlated with RD among schizophrenia subjects but not HC. The voxel clusters that showed significant correlations were localized to the forceps major, the inferior longitudinal fasciculus and the inferior fronto-occipital fasciculus. CRP levels showed similar pattern except for lack of correlation with RD on any cluster that corresponded to the forceps major. Our results suggest that the IL-6 and CRP contribute to impaired anisotropy of water diffusion in selected pathways that have been previously associated with schizophrenia suggesting differential susceptibility of selected neural pathways to immune mediators. Copyright © 2014 Elsevier B.V. All rights reserved.

Applying social innovation theory to examine how community co-designed health services develop: using a case study approach and mixed methods.

PubMed

Farmer, Jane; Carlisle, Karen; Dickson-Swift, Virginia; Teasdale, Simon; Kenny, Amanda; Taylor, Judy; Croker, Felicity; Marini, Karen; Gussy, Mark

2018-01-31

Citizen participation in health service co-production is increasingly enacted. A reason for engaging community members is to co-design services that are locally-appropriate and harness local assets. To date, much literature examines processes of involving participants, with little consideration of innovative services are designed, how innovations emerge, develop and whether they sustain or diffuse. This paper addresses this gap by examining co-designed initiatives through the lens of social innovation - a conceptualisation more attuned to analysing grassroots innovation than common health services research approaches considering top-down, technical innovations. This paper considers whether social innovation is a useful frame for examining co-designed services. Eighty-eight volunteer community-based participants from six rural Australian communities were engaged using the same, tested co-design framework for a 12-month design and then 12-month implementation phase, in 24 workshops (2014-16). Mixed, qualitative data were collected and used to formulate five case studies of community co-designed innovations. A social innovation theory, derived from literature, was applied as an analytical frame to examine co-design cases at 3 stages: innovation growth, development and sustainability/diffusion. Social innovation theory was found relevant in examining and understanding what occurred at each stage of innovation development. Innovations themselves were all adaptations of existing ideas. They emerged due to local participants combining knowledge from local context, own experiences and exemplars. External facilitation brought resources together. The project provided a protective niche in which pilot innovations developed, but they needed support from managers and/or policymakers to be implemented; and to be compatible with existing health system practices. For innovations to move to sustainability/diffusion required political relationships. Challenging existing practice without these was problematical. Social innovation provides a useful lens to understand the grassroots innovation process implied in community participation in service co-design. It helps to show problems in co-design processes and highlights the need for strong partnerships and advocacy beyond the immediate community for new ideas to thrive. Regional commissioning organisations are intended to diffuse useful, co-designed service innovations. Efforts are required to develop an innovation system to realise the potential of community involvement in co-design.

Diffuse colonies of human skin fibroblasts in relation to cellular senescence and proliferation.

PubMed

Zorin, Vadim; Zorina, Alla; Smetanina, Nadezhda; Kopnin, Pavel; Ozerov, Ivan V; Leonov, Sergey; Isaev, Artur; Klokov, Dmitry; Osipov, Andreyan N

2017-05-16

Development of personalized skin treatment in medicine and skin care may benefit from simple and accurate evaluation of the fraction of senescent skin fibroblasts that lost their proliferative capacity. We examined whether enriched analysis of colonies formed by primary human skin fibroblasts, a simple and widely available cellular assay, could reveal correlations with the fraction of senescent cells in heterogenic cell population. We measured fractions of senescence associated β-galactosidase (SA-βgal) positive cells in either mass cultures or colonies of various morphological types (dense, mixed and diffuse) formed by skin fibroblasts from 10 human donors. Although the donors were chosen to be within the same age group (33-54 years), the colony forming efficiency of their fibroblasts (ECO-f) and the percentage of dense, mixed and diffuse colonies varied greatly among the donors. We showed, for the first time, that the SA-βgal positive fraction was the largest in diffuse colonies, confirming that they originated from cells with the least proliferative capacity. The percentage of diffuse colonies was also found to correlate with the SA-βgal positive cells in mass culture. Using Ki67 as a cell proliferation marker, we further demonstrated a strong inverse correlation (r=-0.85, p=0.02) between the percentage of diffuse colonies and the fraction of Ki67+ cells. Moreover, a significant inverse correlation (r=-0.94, p=0.0001) between the percentage of diffuse colonies and ECO-f was found. Our data indicate that quantification of a fraction of diffuse colonies may provide a simple and useful method to evaluate the extent of cellular senescence in human skin fibroblasts.

An Examination of the Acceptance, Adoption, and Diffusion of Smartphone Devices with Senior Citizens

ERIC Educational Resources Information Center

Reneau, James M.

2013-01-01

This research looked at the process of the diffusion of an innovation in the context of smartphones with American senior citizens. The subject of diffusion, or spread of a technology, is a rich and varied topic with more than 60 years of research. Much of this diffusion research does not go beyond the study of the original acceptance of a new…

In vivo assessment of liver fibrosis using diffuse reflectance and fluorescence spectroscopy: a proof of concept.

PubMed

Fabila, Diego; de la Rosa, José Manuel; Stolik, Suren; Moreno, Edgard; Suárez-Álvarez, Karina; López-Navarrete, Giuliana; Guzmán, Carolina; Aguirre-García, Jesús; Acevedo-García, Christian; Kershenobich, David; Escobedo, Galileo

2012-12-01

A novel application of diffuse reflectance and fluorescence spectroscopy in the assessment of liver fibrosis is here reported. To induce different stages of liver fibrosis, a sufficient number of male Wistar rats were differentially exposed to chronic administration with carbon tetrachloride. Then, diffuse reflectance and fluorescence spectra were in vivo measured from the liver surface of each animal by a minimal invasive laparoscopic procedure. The liver fibrosis degree was conventionally determined by means of histological examination using the Mason's Trichrome stain, accompanied by hepatic expression of α-sma, and evaluation of the ALT/AST serum levels. The liver from rats exhibiting higher grades of fibrosis showed a significant increase in diffuse reflectance and fluorescence intensity when compared with control animals. At 365 nm, the diffuse reflectance spectrum exhibited an increase of 4 and 3-fold in mild and advanced fibrotic rats, respectively, when compared to the control group. Similarly, the fluorescence emission at 493 nm was 2-fold higher in fibrotic animals than in controls. By using fluorescence intensity, discrimination algorithms indicated 73% sensitivity and 94% specificity for recognition of hepatic fibrosis, while for diffuse reflectance, these values increased up to 85% and 100%, respectively. Taking into consideration there is a special need for developing new diagnostic approaches focused on detecting different stages of liver fibrosis with minimal invasiveness, these results suggest that diffuse reflectance and fluorescence spectroscopy could be worthy of further exploration in patients with liver disease. Copyright © 2012 Elsevier B.V. All rights reserved.

Transport of Internetwork Magnetic Flux Elements in the Solar Photosphere

NASA Astrophysics Data System (ADS)

Agrawal, Piyush; Rast, Mark P.; Gošić, Milan; Bellot Rubio, Luis R.; Rempel, Matthias

2018-02-01

The motions of small-scale magnetic flux elements in the solar photosphere can provide some measure of the Lagrangian properties of the convective flow. Measurements of these motions have been critical in estimating the turbulent diffusion coefficient in flux-transport dynamo models and in determining the Alfvén wave excitation spectrum for coronal heating models. We examine the motions of internetwork flux elements in Hinode/Narrowband Filter Imager magnetograms and study the scaling of their mean squared displacement and the shape of their displacement probability distribution as a function of time. We find that the mean squared displacement scales super-diffusively with a slope of about 1.48. Super-diffusive scaling has been observed in other studies for temporal increments as small as 5 s, increments over which ballistic scaling would be expected. Using high-cadence MURaM simulations, we show that the observed super-diffusive scaling at short increments is a consequence of random changes in barycenter positions due to flux evolution. We also find that for long temporal increments, beyond granular lifetimes, the observed displacement distribution deviates from that expected for a diffusive process, evolving from Rayleigh to Gaussian. This change in distribution can be modeled analytically by accounting for supergranular advection along with granular motions. These results complicate the interpretation of magnetic element motions as strictly advective or diffusive on short and long timescales and suggest that measurements of magnetic element motions must be used with caution in turbulent diffusion or wave excitation models. We propose that passive tracer motions in measured photospheric flows may yield more robust transport statistics.

An Experimental and Computational Evaluation of the Importance of Molecular Diffusion in Gas Gravity Currents

NASA Astrophysics Data System (ADS)

Herman, Jeremy J.

The accidental release of hazardous, denser-than-air gases during their transport or manufacture is a vital area of study for process safety researchers. This project examines the importance of molecular diffusion on the developing concentration field of a gas gravity current released into a calm environment. Questions which arose from the unexpectedly severe explosion in 2005 at Buncefield, England were of particular interest. The accidental overfilling of a large tank with gasoline on a completely calm morning led to a massive open air explosion. Forensic evidence showed that at the time of ignition, a vapor cloud, most of which now appears to have been within the flammability limits, covered approximately 120,000 m2. Neither the severity of the explosion, nor the size of the vapor cloud would have been anticipated. Experiments were conducted in which carbon dioxide was released from a sunken source into a one meter wide channel devoid of any wind. These experiments were designed in such a way as to mitigate the formation of a raised head at the front of the gravity current which would have resulted in turbulent entrainment of air. This was done to create a flow in which molecular diffusion was the controlling form of mixing between the carbon dioxide and air. Concentration measurements were taken using flame ionization detection at varying depths and down channel locations. A model of the experiments was developed using COMSOL Multiphysics. The only form of mixing allowed between carbon dioxide and air in the model was molecular diffusion. In this manner the accuracy of the assertion that molecular diffusion was controlling in our experiments was checked and verified. Experimental measurements showed a large variation of gas concentration with depth of the gravity current at the very beginning of the channel where the gas emerged up from the sunken source and began flowing down channel. Due to this variation, molecular diffusion caused the vertical concentration profile to get more uniform as the gravity current flowed down the channel. A COMSOL model was developed which showed an overall increase in the depth of the flammable region of a cloud with increasing time, due to this effect.

Two-Oxide Disequilibrium: A New Geospeedometer Based on Diffusion in Ilmenite

NASA Astrophysics Data System (ADS)

Williams, K. B.; Krawczynski, M. J.; Van Orman, J. A.

2016-12-01

Diffusion-annealing experiments were conducted in a 0.5" piston cylinder apparatus to investigate diffusivity of Fe2+, Mg2+, and Mn2+ in ilmenite solid solutions between 800ºC and 1000ºC. Polycrystalline ilmenite (FeTiO3) was juxtaposed against either an oriented geikielite (MgTiO3) single crystal or polycrystalline Mn-bearing (5 mol% Mn) ilmenite, in a "diffusion-couple" geometry. Geikielite single crystals were synthesized at Los Alamos National Laboratory, cut into 1 mm edge-length cubes, and polished either perpendicular or parallel to the c-axis. Polycrystalline ilmenite starting materials were synthesized by mixing high purity reagent-grade oxides (FeO, MnO, and TiO2) and sintering in a piston cylinder apparatus, then cut into wafers and polished. Experimental run products were analyzed by electron microprobe at Washington University in St. Louis. Microprobe analyses were obtained perpendicularly across the diffusion interface for each experiment. Experimental diffusion profiles create smooth curves that, when fit with an error function, define Fe-Mg and Fe-Mn interdiffusion coefficients in ilmenite. The diffusion coefficients do not appear compositionally dependent, but do show significant anisotropy. Preliminary results suggest diffusion activation energies are lower in ilmenite than in titanomagnetite [1]. Ilmenite-titanomagnetite equilibria define pre-eruptive temperatures and oxygen fugacities. However, oxides often exist out of equilibrium [2]. We use the cation diffusion data for ilmenite and existing data on titanomagnetite to establish two-oxide disequilibrium as a geospeedometer. Our data constrain oxide-oxide re-equilibration timescales at Mt. Unzen to months, consistent with estimates from zoned, single crystals of magnetite [3,4]. Future experiments will examine the effect of oxygen fugacity on diffusivity in ilmenite solid solutions. References:[1] Van Orman & Crispin (2010) RiMG 72, 757-825.[2] Bacon & Hirschmann (1988) Am. Min. 73, 57-61.[3] Nakamura (1995) Geology 23, 807-810.[4] Venezky & Rutherford (1999) J. Volc. Geo. Res. 89, 213-230.

Prognostic impact of MYC protein expression in central nervous system diffuse large B-cell lymphoma: comparison with MYC rearrangement and MYC mRNA expression.

PubMed

Son, Seung-Myoung; Ha, Sang-Yun; Yoo, Hae-Yong; Oh, Dongryul; Kim, Seok-Jin; Kim, Won-Seog; Ko, Young-Hyeh

2017-01-01

The prognostic role of MYC has been well documented in non-central nervous system diffuse large B-cell lymphoma; however, it remains controversial in central nervous system diffuse large B-cell lymphoma. To investigate the prognostic value of MYC, we analyzed the MYC protein expression by immunohistochemistry, mRNA expression by RNA in situ hybridization, and gene status by fluorescence in situ hybridization in 74 cases of central nervous system diffuse large B-cell lymphoma. Moreover, we examined the correlation between MYC translocation, mRNA expression, and protein expression. The mean percentage of MYC immunopositive cells was 49%. Using a 44% cutoff value, 49 (66%) cases showed MYC protein overexpression. The result of mRNA in situ hybridization using the RNA scope technology was obtained using the H-scoring system; the median value was 34.2. Using the cutoff value of 63.5, 16 (22%) cases showed MYC mRNA overexpression. MYC gene rearrangement was detected in five out of 68 (7%) cases. MYC translocation showed no statistically significant correlation with mRNA expression; however, all MYC translocation-positive cases showed MYC protein overexpression, with a higher mean percentage of MYC protein expression than that of translocation-negative cases (78 vs 48%, P=0.001). The level of MYC mRNA expression was moderately correlated with the level of MYC protein expression (P<0.001). The mean percentage of MYC protein expression in the high MYC mRNA group was higher than that in the low MYC mRNA group (70 vs 47%, P<0.001). A univariate analysis showed that age over 60 years, Eastern Cooperative Oncology Group (ECOG) performance status ≥2 and MYC protein overexpression were significantly associated with an increased risk of death. MYC translocation and MYC mRNA expression had no prognostic significance. On multivariate analysis, MYC protein overexpression and ECOG score retained prognostic significance.

NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 59: Japanese Technological Innovation. Implications for Large Commercial Aircraft and Knowledge Diffusion

NASA Technical Reports Server (NTRS)

Pinelli, Thomas E.; Barclay, Rebecca O.; Kotler, Mindy L.

1997-01-01

This paper explores three factors-public policy, the Japanese (national) innovation system, and knowledge-that influence technological innovation in Japan. To establish a context for the paper, we examine Japanese culture and the U.S. and Japanese patent systems in the background section. A brief history of the Japanese aircraft industry as a source of knowledge and technology for other industries is presented. Japanese and U.S. alliances and linkages in three sectors-biotechnology, semiconductors, and large commercial aircraft (LCA)-and the importation, absorption, and diffusion of knowledge and technology are examined next. The paper closes with implications for diffusing knowledge and technology, U.S. public policy, and LCA.

Observation and interpretation of energy efficient, diffuse direct current glow discharge at atmospheric pressure

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

Tang, Jie, E-mail: tangjie1979@opt.ac.cn; Jiang, Weiman; Wang, Yishan

2015-08-24

A diffuse direct-current glow discharge was realized with low energy consumption and high energy utilization efficiency at atmospheric pressure. The formation of diffuse discharge was demonstrated by examining and comparing the electrical properties and optical emissions of plasmas. In combination with theoretical derivation and calculation, we draw guidelines that appearance of nitrogen ions at low electron density is crucial to enhance the ambipolar diffusion for the expansion of discharge channel and the increasing ambipolar diffusion near the cathode plays a key role in the onset of diffuse discharge. An individual-discharge-channel expansion model is proposed to explain the diffuse discharge formation.

Distribution of lead in the brain tissues from DNTC patients using synchrotron radiation microbeams

NASA Astrophysics Data System (ADS)

Ide-Ektessabi, Ari; Ota, Yukihide; Ishihara, Ryoko; Mizuno, Yutaka; Takeuchi, Tohru

2005-12-01

Diffuse neurofibrillary tangles with calcification (DNTC) is a form of dementia with certain characteristics. Its pathology is characterized by cerebrum atrophy, calcification on globus pallidus and dentate nucleus and diffuse neurofibrillary tangles without senile plaques. In the present study brain tissues were prepared from patients with patients DNTC, calcified and non-calcified Alzheimer's disease (AD) patients. The brain tissues were examined non-destructively by X-ray fluorescence (XRF) spectroscopy using synchrotron radiation (SR) microbeams for trace metallic elements Ca, Fe, Cu, Zn and Pb. The XRF analysis showed that there were Pb concentrations in the calcified areas in the brain tissues with both DNTC and AD but there was none in those with non-calcified AD.

Unilateral uveitis masquerade syndrome caused by diffuse large B-cell lymphoma diagnosed using multiparametric flow cytometry of the aqueous humor.

PubMed

Monsalvo, Silvia; Serrano, Cristina; Prieto, Elena; Fernández-Sanz, Guillermo; Puente, Maria-Camino; Rodriguez-Pinilla, Maria; Garcia Raso, Aranzazu; Llamas, Pilar; Cordoba, Raul

2017-07-01

The uveitis masquerade syndromes (UMS) are a group of ocular diseases that may mimic chronic intraocular inflammation. Many malignant entities such as non-Hodgkin's lymphomas may masquerade as uveitis. We report a case of an HIV-positive patient with masquerade syndrome presenting unilateral uveitis. 45-year-old Caucasian man with a diagnosis of diffuse large B-cell lymphoma (DLBCL). The patient was diagnosed by a biopsy of an abdominal mass which showed fragments of gastric mucosa with diffuse growth of neoplastic cells. At diagnosis, the patient suffered from unilateral blurring of vision and a sudden decrease of left-eye visual acuity. A slit-lamp examination of the left eye revealed a diagnosis of anterior uveitis. The patient exhibited no signs of posterior uveitis. An anterior-chamber paracentesis was performed and analyzed by multiparameter flow cytometry (MFC), showing cells CD45, CD19, CD20, CD22, and CD38 positives, and moderate expression of CD10 with kappa light chain restriction, showing a monoclonal B-cell population. The patient received CHOP-R with intrathecal methotrexate followed by consolidation high dose methotrexate obtaining a complete response which is ongoing. Differential diagnosis between chronic uveitis and ocular lymphoma may be challenging. We advocate anterior-chamber paracentesis in cases of refractory uveitis in patients with hematologic malignancies. © 2016 International Clinical Cytometry Society. © 2016 International Clinical Cytometry Society.

Geolinguistic Diffusion and the U.S.-Canada Border.

ERIC Educational Resources Information Center

Boberg, Charles

2000-01-01

Uses data from both sides of the U.S.-Canada border to test a model regarding the way language changes diffuse over space. Two cases are examined: the non-diffusion of phonetic features from Detroit to Windsor and the gradual infiltration into Canadian English of American foreign (a) pronunciations. (Author/VWL)

Undergraduate Laboratory Module on Skin Diffusion

ERIC Educational Resources Information Center

Norman, James J.; Andrews, Samantha N.; Prausnitz, Mark R.

2011-01-01

To introduce students to an application of chemical engineering directly related to human health, we developed an experiment for the unit operations laboratory at Georgia Tech examining diffusion across cadaver skin in the context of transdermal drug delivery. In this laboratory module, students prepare mouse skin samples, set up diffusion cells…

Developing chemotherapy for diffuse pontine intrinsic gliomas (DIPG).

PubMed

Gwak, Ho-Shin; Park, Hyeon Jin

2017-12-01

Prognosis of diffuse intrinsic pontine glioma (DIPG) is poor, with a median survival of 10 months after radiation. At present, chemotherapy has failed to show benefits over radiation. Advances in biotechnology have enabled the use of autopsy specimens for genomic analyses and molecular profiling of DIPG, which are quite different from those of supratentorial high grade glioma. Recently, combined treatments of cytotoxic agents with target inhibitors, based on biopsied tissue, are being examined in on-going trials. Spontaneous DIPG mice models have been recently developed that is useful for preclinical studies. Finally, the convection-enhanced delivery could be used to infuse drugs directly into the brainstem parenchyma, to which conventional systemic administration fails to achieve effective concentration. The WHO glioma classification defines a diffuse midline glioma with a H3-K27M-mutation, and we expect increase of tissue confirmation of DIPG, which will give us the biological information helping the development of a targeted therapy. Copyright © 2017 Elsevier B.V. All rights reserved.

Antibiotic resistance patterns and occurrence of mecA gene in Staphylococcus intermedius strains of canine origin.

PubMed

Kizerwetter-Swida, M; Chrobak, D; Rzewuska, M; Binek, M

2009-01-01

We have evaluated 102 Staphylococcus intermedius isolates of canine origin for susceptibility to antimicrobial primary agents, i.e. penicillin, amoxicillin, amoxicillin with clavulanic acid, cefuroxime, trimethoprim/sulfonamides, neomycin, streptomycin, gentamicin, norfloxacin, tetracycline, vancomycin, erythromycin and secondary agents, i.e., chloramphenicol, ciprofloxacin, lincomycin, teicoplanin, rifampicin, imipenem, mupirocin. Antimicrobial sensitivity was examined using the disk diffusion method and performed according to NCCLS quidelines. Methicillin resistance was detected using the disk diffusion method with oxacillin, and the occurrence of mecA gene was detected by PCR. Resistance to streptomycin, penicillin, amoxicillin, neomycin, followed by tetracycline was predominant. From 14 mecA-positive strains, 12 were multidrug-resitant, and the remaining two showed atypical susceptibility. One strain resistant to oxacillin in the disc diffusion method was mecA-negative, suggesting a different mechanism of resistance. Our results indicate that the emergence of S. intermedius resistance to methicillin may be underestimated. In case of clinical multidrug-resitant S. intermedius isolates, resistance to methicillin should be considered.

A prodrug approach to enhance azelaic acid percutaneous availability.

PubMed

Al-Marabeh, Sara; Khalil, Enam; Khanfar, Mohammad; Al-Bakri, Amal G; Alzweiri, Muhammed

2017-06-01

Azelaic acid is a dicarboxylic acid compound used in treatment of acne vulgaris. However, high concentration (ca 20%) is needed to guarantee the drug availability in the skin. The latter increases the incidence of side effects such as local irritation. The prodrug strategy to enhance azelaic acid diffusion through skin was not reported before. Thus, a lipophilic prodrug of azelaic acid (diethyl azelate [DEA]) was synthesized and investigated to improve percutaneous availability of azelaic acid, with a subsequent full physical, chemical, and biological characterization. Expectedly, DEA exhibited a significant increase in diffusion compared to azelaic acid through silicone membrane. In contrast, the diffusion results through human stratum corneum (SC) displayed weaker permeation for DEA with expected retention in the SC. Therefore, a desorption study of DEA from SC was conducted to examine the reservoir behavior in SC. Results showed an evidence of sustained release behavior of DEA from SC. Consequently, enhancement of keratolytic effect is expected due to azelaic acid produced from enzymatic conversion of DEA released from SC.

The mechanistic basis of internal conductance: a theoretical analysis of mesophyll cell photosynthesis and CO2 diffusion.

PubMed

Tholen, Danny; Zhu, Xin-Guang

2011-05-01

Photosynthesis is limited by the conductance of carbon dioxide (CO(2)) from intercellular spaces to the sites of carboxylation. Although the concept of internal conductance (g(i)) has been known for over 50 years, shortcomings in the theoretical description of this process may have resulted in a limited understanding of the underlying mechanisms. To tackle this issue, we developed a three-dimensional reaction-diffusion model of photosynthesis in a typical C(3) mesophyll cell that includes all major components of the CO(2) diffusion pathway and associated reactions. Using this novel systems model, we systematically and quantitatively examined the mechanisms underlying g(i). Our results identify the resistances of the cell wall and chloroplast envelope as the most significant limitations to photosynthesis. In addition, the concentration of carbonic anhydrase in the stroma may also be limiting for the photosynthetic rate. Our analysis demonstrated that higher levels of photorespiration increase the apparent resistance to CO(2) diffusion, an effect that has thus far been ignored when determining g(i). Finally, we show that outward bicarbonate leakage through the chloroplast envelope could contribute to the observed decrease in g(i) under elevated CO(2). Our analysis suggests that physiological and anatomical features associated with g(i) have been evolutionarily fine-tuned to benefit CO(2) diffusion and photosynthesis. The model presented here provides a novel theoretical framework to further analyze the mechanisms underlying diffusion processes in the mesophyll.

The Mechanistic Basis of Internal Conductance: A Theoretical Analysis of Mesophyll Cell Photosynthesis and CO2 Diffusion1[W][OA

PubMed Central

Tholen, Danny; Zhu, Xin-Guang

2011-01-01

Photosynthesis is limited by the conductance of carbon dioxide (CO2) from intercellular spaces to the sites of carboxylation. Although the concept of internal conductance (gi) has been known for over 50 years, shortcomings in the theoretical description of this process may have resulted in a limited understanding of the underlying mechanisms. To tackle this issue, we developed a three-dimensional reaction-diffusion model of photosynthesis in a typical C3 mesophyll cell that includes all major components of the CO2 diffusion pathway and associated reactions. Using this novel systems model, we systematically and quantitatively examined the mechanisms underlying gi. Our results identify the resistances of the cell wall and chloroplast envelope as the most significant limitations to photosynthesis. In addition, the concentration of carbonic anhydrase in the stroma may also be limiting for the photosynthetic rate. Our analysis demonstrated that higher levels of photorespiration increase the apparent resistance to CO2 diffusion, an effect that has thus far been ignored when determining gi. Finally, we show that outward bicarbonate leakage through the chloroplast envelope could contribute to the observed decrease in gi under elevated CO2. Our analysis suggests that physiological and anatomical features associated with gi have been evolutionarily fine-tuned to benefit CO2 diffusion and photosynthesis. The model presented here provides a novel theoretical framework to further analyze the mechanisms underlying diffusion processes in the mesophyll. PMID:21441385

Early Corneal Innervation and Trigeminal Alterations in Parkinson Disease: A Pilot Study.

PubMed

Arrigo, Alessandro; Rania, Laura; Calamuneri, Alessandro; Postorino, Elisa Imelde; Mormina, Enricomaria; Gaeta, Michele; Marino, Silvia; Di Lorenzo, Giuseppe; Quartarone, Angelo; Anastasi, Giuseppe; Puzzolo, Domenico; Aragona, Pasquale

2018-04-01

To describe corneal innervation and trigeminal alterations in drug-naive patients with Parkinson disease (PD). A case series study was conducted by recruiting 3 early drug-naive patients with PD, 2 men and 1 woman (age: 72, 68, and 66, respectively). Ophthalmologic assessment included Ocular Surface Disease Index questionnaire, visual acuity by the logarithm of the minimum angle of resolution score, pupillary light reflexes, extrinsic ocular movements, corneal sensitivity, and slit-lamp examination. Corneal innervation parameter changes were evaluated in vivo using the Confoscan 4 confocal microscope, and they were compared with a control data set. The Heidelberg Retina Tomograph 3 (HRT3) has been used to assess retinal alterations in our patients, if compared with normal range values provided by the HRT3. Moreover, 3T magnetic resonance imaging (MRI) analysis of water diffusion property changes of trigeminal nerves was performed. All data were analyzed and compared with 2 control data sets made by 14 age-matched controls. Patients with PD showed profound alterations of corneal innervation and of trigeminal diffusion MRI parameters, compared with controls. Strong differences (PD vs. controls) were found for deep nerve tortuosity (Kallinikos mean 19.94 vs. 2.13) and the number of beadings (mean 34.2 vs. 15.5). HRT3 retinal evaluation revealed less structural changes compared with the normal range. Diffusion MRI showed profound changes of white matter diffusion properties (PD vs. controls), with fractional anisotropy decrement (mean 0.3029 vs. 0.3329) and mean diffusivity increment (mean 0.00127 vs. 0.00106). Corneal innervation changes might occur earlier in patients with PD than in retinal ones. Confocal corneal innervation analysis might provide possible early biomarkers for a better PD evaluation and for its earlier diagnosis.

Spatio-temporal diffusion pattern and hotspot detection of dengue in Chachoengsao province, Thailand.

PubMed

Jeefoo, Phaisarn; Tripathi, Nitin Kumar; Souris, Marc

2011-01-01

In recent years, dengue has become a major international public health concern. In Thailand it is also an important concern as several dengue outbreaks were reported in last decade. This paper presents a GIS approach to analyze the spatial and temporal dynamics of dengue epidemics. The major objective of this study was to examine spatial diffusion patterns and hotspot identification for reported dengue cases. Geospatial diffusion pattern of the 2007 dengue outbreak was investigated. Map of daily cases was generated for the 153 days of the outbreak. Epidemiological data from Chachoengsao province, Thailand (reported dengue cases for the years 1999-2007) was used for this study. To analyze the dynamic space-time pattern of dengue outbreaks, all cases were positioned in space at a village level. After a general statistical analysis (by gender and age group), data was subsequently analyzed for temporal patterns and correlation with climatic data (especially rainfall), spatial patterns and cluster analysis, and spatio-temporal patterns of hotspots during epidemics. The results revealed spatial diffusion patterns during the years 1999-2007 representing spatially clustered patterns with significant differences by village. Villages on the urban fringe reported higher incidences. The space and time of the cases showed outbreak movement and spread patterns that could be related to entomologic and epidemiologic factors. The hotspots showed the spatial trend of dengue diffusion. This study presents useful information related to the dengue outbreak patterns in space and time and may help public health departments to plan strategies to control the spread of disease. The methodology is general for space-time analysis and can be applied for other infectious diseases as well.

The Diffusion of Information Technology in the Human Services: Implications for Social Work Education

ERIC Educational Resources Information Center

Fitch, Dale

2005-01-01

The spread and utilization of information technology in the human services is examined using innovation diffusion theory. This examination is contextualized within the values basis of social work. Literature from the human services, the business sector, and the social sciences regarding the role of information technology is used to promote a…

Brain aging in humans, chimpanzees (Pan troglodytes), and rhesus macaques (Macaca mulatta): magnetic resonance imaging studies of macro- and microstructural changes.

PubMed

Chen, Xu; Errangi, Bhargav; Li, Longchuan; Glasser, Matthew F; Westlye, Lars T; Fjell, Anders M; Walhovd, Kristine B; Hu, Xiaoping; Herndon, James G; Preuss, Todd M; Rilling, James K

2013-10-01

Among primates, humans are uniquely vulnerable to many age-related neurodegenerative disorders. We used structural and diffusion magnetic resonance imaging (MRI) to examine the brains of chimpanzees and rhesus monkeys across each species' adult lifespan, and compared these results with published findings in humans. As in humans, gray matter volume decreased with age in chimpanzees and rhesus monkeys. Also like humans, chimpanzees showed a trend for decreased white matter volume with age, but this decrease occurred proportionally later in the chimpanzee lifespan than in humans. Diffusion MRI revealed widespread age-related decreases in fractional anisotropy and increases in radial diffusivity in chimpanzees and macaques. However, both the fractional anisotropy decline and the radial diffusivity increase started at a proportionally earlier age in humans than in chimpanzees. Thus, even though overall patterns of gray and white matter aging are similar in humans and chimpanzees, the longer lifespan of humans provides more time for white matter to deteriorate before death, with the result that some neurological effects of aging may be exacerbated in our species. Copyright © 2013 Elsevier Inc. All rights reserved.

Identifying mechanisms for superdiffusive dynamics in cell trajectories

NASA Astrophysics Data System (ADS)

Passucci, Giuseppe; Brasch, Megan; Henderson, James; Manning, M. Lisa

Self-propelled particle (SPP) models have been used to explore features of active matter such as motility-induced phase separation, jamming, and flocking, and are often used to model biological cells. However, many cells exhibit super-diffusive trajectories, where displacements scale faster than t 1 / 2 in all directions, and these are not captured by traditional SPP models. We extract cell trajectories from image stacks of mouse fibroblast cells moving on 2D substrates and find super-diffusive mean-squared displacements in all directions across varying densities. Two SPP model modifications have been proposed to capture super-diffusive dynamics: Levy walks and heterogeneous motility parameters. In mouse fibroblast cells displacement probability distributions collapse when time is rescaled by a power greater than 1/2, which is consistent with Levy walks. We show that a simple SPP model with heterogeneous rotational noise can also generate a similar collapse. Furthermore, a close examination of statistics extracted directly from cell trajectories is consistent with a heterogeneous mobility SPP model and inconsistent with a Levy walk model. Our work demonstrates that a simple set of analyses can distinguish between mechanisms for anomalous diffusion in active matter.

Exit, cohesion, and consensus: social psychological moderators of consensus among adolescent peer groups

PubMed Central

Fisher, Jacob C.

2017-01-01

Virtually all social diffusion work relies on a common formal basis, which predicts that consensus will develop among a connected population as the result of diffusion. In spite of the popularity of social diffusion models that predict consensus, few empirical studies examine consensus, or a clustering of attitudes, directly. Those that do either focus on the coordinating role of strict hierarchies, or on the results of online experiments, and do not consider how consensus occurs among groups in situ. This study uses longitudinal data on adolescent social networks to show how meso-level social structures, such as informal peer groups, moderate the process of consensus formation. Using a novel method for controlling for selection into a group, I find that centralized peer groups, meaning groups with clear leaders, have very low levels of consensus, while cohesive peer groups, meaning groups where more ties hold the members of the group together, have very high levels of consensus. This finding is robust to two different measures of cohesion and consensus. This suggests that consensus occurs either through central leaders’ enforcement or through diffusion of attitudes, but that central leaders have limited ability to enforce when people can leave the group easily. PMID:29335675

Influence of cavitation bubble growth by rectified diffusion on cavitation-enhanced HIFU

NASA Astrophysics Data System (ADS)

Okita, Kohei; Sugiyama, Kazuyasu; Takagi, Shu; Matsumoto, Yoichiro

2017-11-01

Cavitation is becoming increasingly important in therapeutic ultrasound applications such as diagnostic, tumor ablation and lithotripsy. Mass transfer through gas-liquid interface due to rectified diffusion is important role in an initial stage of cavitation bubble growth. In the present study, influences of the rectified diffusion on cavitation-enhanced high-intensity focused ultrasound (HIFU) was investigated numerically. Firstly, the mass transfer rate of gas from the surrounding medium to the bubble was examined as function of the initial bubble radius and the driving pressure amplitude. As the result, the pressure required to bubble growth was decreases with increasing the initial bubble radius. Next, the cavitation-enhanced HIFU, which generates cavitation bubbles by high-intensity burst and induces the localized heating owing to cavitation bubble oscillation by low-intensity continuous waves, was reproduced by the present simulation. The heating region obtained by the simulation is agree to the treatment region of an in vitro experiment. Additionally, the simulation result shows that the localized heating is enhanced by the increase of the equilibrium bubble size due to the rectified diffusion. This work was supported by JSPS KAKENHI Grant Numbers JP26420125,JP17K06170.

Ab initio study of novel carbon nanofoam structure as an anode material for Li secondary battery

NASA Astrophysics Data System (ADS)

Park, Hanjin; Park, Sora; Kang, Seoung-Hun; Kwon, Young-Kyun

2014-03-01

Using ab inito density functional theory, we investigate the adsorption and diffusion properties of Li atoms on a new carbon nanostructure, which may be used as an anode of Li secondary battery. We focus on a special carbon nanofoam structure consisting of Schwarzite structures with negative Gaussian curvature as core parts, which are interconnected through (4,4) CNT segments. Considering the symmetry of the nanofoam structure, we find various Li adsorption sites exhibiting relatively large binding energies (>= 2 . 00 eV). Based on these adsorption sites, we identify several diffusion paths on the outside or inside surface of the nanofoam structure and examine the diffusion barriers along the paths. Our results show that Li atom can diffuse almost freely due to its low energy barriers on both outside and inside surfaces. Finally, we also evaluate the energy gain tendency and the volume expansion as well as the average binding energy while adding Li atoms to estimate the Li-capacity and recyclability of the system, which are important characterisitics for anode materials. We conclude that the carbon nanofoam structure would be better as an anode material than graphite in Li capacity and volume expansion.

Facial emotion recognition in patients with focal and diffuse axonal injury.

PubMed

Yassin, Walid; Callahan, Brandy L; Ubukata, Shiho; Sugihara, Genichi; Murai, Toshiya; Ueda, Keita

2017-01-01

Facial emotion recognition impairment has been well documented in patients with traumatic brain injury. Studies exploring the neural substrates involved in such deficits have implicated specific grey matter structures (e.g. orbitofrontal regions), as well as diffuse white matter damage. Our study aims to clarify whether different types of injuries (i.e. focal vs. diffuse) will lead to different types of impairments on facial emotion recognition tasks, as no study has directly compared these patients. The present study examined performance and response patterns on a facial emotion recognition task in 14 participants with diffuse axonal injury (DAI), 14 with focal injury (FI) and 22 healthy controls. We found that, overall, participants with FI and DAI performed more poorly than controls on the facial emotion recognition task. Further, we observed comparable emotion recognition performance in participants with FI and DAI, despite differences in the nature and distribution of their lesions. However, the rating response pattern between the patient groups was different. This is the first study to show that pure DAI, without gross focal lesions, can independently lead to facial emotion recognition deficits and that rating patterns differ depending on the type and location of trauma.

White matter microstructure and volitional motor activity in schizophrenia: A diffusion kurtosis imaging study.

PubMed

Docx, Lise; Emsell, Louise; Van Hecke, Wim; De Bondt, Timo; Parizel, Paul M; Sabbe, Bernard; Morrens, Manuel

2017-02-28

Avolition is a core feature of schizophrenia and may arise from altered brain connectivity. Here we used diffusion kurtosis imaging (DKI) to investigate the association between white matter (WM) microstructure and volitional motor activity. Multi-shell diffusion MRI and 24-h actigraphy data were obtained from 20 right-handed patients with schizophrenia and 16 right-handed age and gender matched healthy controls. We examined correlations between fractional anisotropy (FA), mean diffusivity (MD), mean kurtosis (MK), and motor activity level, as well as group differences in these measures. In the patient group, increasing motor activity level was positively correlated with MK in the inferior, medial and superior longitudinal fasciculus, the corpus callosum, the posterior fronto-occipital fasciculus and the posterior cingulum. This association was not found in control subjects or in DTI measures. These results show that a lack of volitional motor activity in schizophrenia is associated with potentially altered WM microstructure in posterior brain regions associated with cognitive function and motivation. This could reflect both illness related dysconnectivity which through altered cognition, manifests as reduced volitional motor activity, and/or the effects of reduced physical activity on brain WM. Copyright © 2016. Published by Elsevier B.V.

Effective temperatures and the breakdown of the Stokes-Einstein relation for particle suspensions.

PubMed

Mendoza, Carlos I; Santamaría-Holek, I; Pérez-Madrid, A

2015-09-14

The short- and long-time breakdown of the classical Stokes-Einstein relation for colloidal suspensions at arbitrary volume fractions is explained here by examining the role that confinement and attractive interactions play in the intra- and inter-cage dynamics executed by the colloidal particles. We show that the measured short-time diffusion coefficient is larger than the one predicted by the classical Stokes-Einstein relation due to a non-equilibrated energy transfer between kinetic and configuration degrees of freedom. This transfer can be incorporated in an effective kinetic temperature that is higher than the temperature of the heat bath. We propose a Generalized Stokes-Einstein relation (GSER) in which the effective temperature replaces the temperature of the heat bath. This relation then allows to obtain the diffusion coefficient once the viscosity and the effective temperature are known. On the other hand, the temporary cluster formation induced by confinement and attractive interactions of hydrodynamic nature makes the long-time diffusion coefficient to be smaller than the corresponding one obtained from the classical Stokes-Einstein relation. Then, the use of the GSER allows to obtain an effective temperature that is smaller than the temperature of the heat bath. Additionally, we provide a simple expression based on a differential effective medium theory that allows to calculate the diffusion coefficient at short and long times. Comparison of our results with experiments and simulations for suspensions of hard and porous spheres shows an excellent agreement in all cases.

Gold Nanoparticle Labels and Heterogeneous Immunoassays: The Case for the Inverted Substrate.

PubMed

Crawford, Alexis C; Young, Colin C; Porter, Marc D

2018-06-15

This paper examines how the difference in the spatial orientation of the capture substrate influences the analytical sensitivity and limits of detection for immunoassays that use gold nanoparticle labels (AuNPs) and rely on diffusion in quiet solution in the antigen capture and labeling steps. Ideally, the accumulation of both reactants should follow a dependence governed by the rate in which diffusion delivers reactants to the capture surface. In other words, the accumulation of reactants should increase with the square root of the incubation time, i.e., t1/2. The work herein shows, however, that this expectation is only obeyed when the capture substrate is oriented to direct the gravity-induced sedimentation of the AuNP labels away from the substrate. Using an assay for human IgG, the results show that circumventing the sedimentation of the gold nanoparticle labels by substrate inversion enables the dependence of the labeling step on diffusion, reduces nonspecific label adsorption, and improves the estimated detection limit by ~30×. High-density maps of the signal across the two types of substrates also demonstrate that inversion in the labeling step results in a more uniform distribution of AuNP labels across the surface, which translates to a greater measurement reproducibility. These results, which are supported by model simulations via the Mason-Weaver sedimentation-diffusion equation, and their potential implications when using other nanoparticle labels and related materials in diagnostic tests and other applications, are briefly discussed.

Combined diffusion-weighted, blood oxygen level-dependent, and dynamic contrast-enhanced MRI for characterization and differentiation of renal cell carcinoma.

PubMed

Notohamiprodjo, Mike; Staehler, Michael; Steiner, Nicole; Schwab, Felix; Sourbron, Steven P; Michaely, Henrik J; Helck, Andreas D; Reiser, Maximilian F; Nikolaou, Konstantin

2013-06-01

To investigate a multiparametric magnetic resonance imaging (MRI) approach comprising diffusion-weighted imaging (DWI), blood oxygen-dependent (BOLD), and dynamic contrast-enhanced (DCE) MRI for characterization and differentiation of primary renal cell carcinoma (RCC). Fourteen patients with clear-cell carcinoma and four patients with papillary RCC were examined with DWI, BOLD MRI, and DCE MRI at 1.5T. The apparent diffusion coefficient (ADC) was calculated with a monoexponential decay. The spin-dephasing rate R2* was derived from parametric R2* maps. DCE-MRI was analyzed using a two-compartment exchange model allowing separation of perfusion (plasma flow [FP] and plasma volume [VP]), permeability (permeability surface area product [PS]), and extravascular extracellular volume (VE). Statistical analysis was performed with Wilcoxon signed-rank test, Pearson's correlation coefficient, and receiver operating characteristic curve analysis. Clear-cell RCC showed higher ADC and lower R2* compared to papillary subtypes, but differences were not significant. FP of clear-cell subtypes was significantly higher than in papillary RCC. Perfusion parameters showed moderate but significant inverse correlation with R2*. VE showed moderate inverse correlation with ADC. Fp and Vp showed best sensitivity for histological differentiation. Multiparametric MRI comprising DWI, BOLD, and DCE MRI is feasible for assessment of primary RCC. BOLD moderately correlates to DCE MRI-derived perfusion. ADC shows moderate correlation to the extracellular volume, but does not correlate to tumor oxygenation or perfusion. In this preliminary study DCE-MRI appeared superior to BOLD and DWI for histological differentiation. Copyright © 2013 AUR. Published by Elsevier Inc. All rights reserved.

Diffusion models for innovation: s-curves, networks, power laws, catastrophes, and entropy.

PubMed

Jacobsen, Joseph J; Guastello, Stephen J

2011-04-01

This article considers models for the diffusion of innovation would be most relevant to the dynamics of early 21st century technologies. The article presents an overview of diffusion models and examines the adoption S-curve, network theories, difference models, influence models, geographical models, a cusp catastrophe model, and self-organizing dynamics that emanate from principles of network configuration and principles of heat diffusion. The diffusion dynamics that are relevant to information technologies and energy-efficient technologies are compared. Finally, principles of nonlinear dynamics for innovation diffusion that could be used to rehabilitate the global economic situation are discussed.

System-size corrections for self-diffusion coefficients calculated from molecular dynamics simulations: The case of CO{sub 2}, n-alkanes, and poly(ethylene glycol) dimethyl ethers

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

Moultos, Othonas A.; Economou, Ioannis G.; Zhang, Yong

Molecular dynamics simulations were carried out to study the self-diffusion coefficients of CO{sub 2}, methane, propane, n-hexane, n-hexadecane, and various poly(ethylene glycol) dimethyl ethers (glymes in short, CH{sub 3}O–(CH{sub 2}CH{sub 2}O){sub n}–CH{sub 3} with n = 1, 2, 3, and 4, labeled as G1, G2, G3, and G4, respectively) at different conditions. Various system sizes were examined. The widely used Yeh and Hummer [J. Phys. Chem. B 108, 15873 (2004)] correction for the prediction of diffusion coefficient at the thermodynamic limit was applied and shown to be accurate in all cases compared to extrapolated values at infinite system size. Themore » magnitude of correction, in all cases examined, is significant, with the smallest systems examined giving for some cases a self-diffusion coefficient approximately 15% lower than the infinite system-size extrapolated value. The results suggest that finite size corrections to computed self-diffusivities must be used in order to obtain accurate results.« less

Abnormal Injury Response in Spontaneous Mild Ventriculomegaly Wistar Rat Brains: A Pathological Correlation Study of Diffusion Tensor and Magnetization Transfer Imaging in Mild Traumatic Brain Injury.

PubMed

Tu, Tsang-Wei; Lescher, Jacob D; Williams, Rashida A; Jikaria, Neekita; Turtzo, L Christine; Frank, Joseph A

2017-01-01

Spontaneous mild ventriculomegaly (MVM) was previously reported in ∼43% of Wistar rats in association with vascular anomalies without phenotypic manifestation. This mild traumatic brain injury (TBI) weight drop model study investigates whether MVM rats (n = 15) have different injury responses that could inadvertently complicate the interpretation of imaging studies compared with normal rats (n = 15). Quantitative MRI, including diffusion tensor imaging (DTI) and magnetization transfer imaging (MTI), and immunohistochemistry (IHC) analysis were used to examine the injury pattern up to 8 days post-injury in MVM and normal rats. Prior to injury, the MVM brain showed significant higher mean diffusivity, axial diffusivity, and radial diffusivity, and lower fractional anisotropy (FA) and magnetization transfer ratio (MTR) in the corpus callosum than normal brain (p < 0.05). Following TBI, normal brains exhibited significant decreases of FA in the corpus callosum, whereas MVM brains demonstrated insignificant changes in FA, suggesting less axonal injury. At day 8 after mild TBI, MTR of the normal brains significantly decreased whereas the MTR of the MVM brains significantly increased. IHC staining substantiated the MRI findings, demonstrating limited axonal injury with significant increase of microgliosis and astrogliosis in MVM brain compared with normal animals. The radiological-pathological correlation data showed that both DTI and MTI were sensitive in detecting mild diffuse brain injury, although DTI metrics were more specific in correlating with histologically identified pathologies. Compared with the higher correlation levels reflecting axonal injury pathology in the normal rat mild TBI, the DTI and MTR metrics were more affected by the increased inflammation in the MVM rat mild TBI. Because MVM Wistar rats appear normal, there was a need to screen rats prior to TBI research to rule out the presence of ventriculomegaly, which may complicate the interpretation of imaging and IHC observations.

Abnormal Injury Response in Spontaneous Mild Ventriculomegaly Wistar Rat Brains: A Pathological Correlation Study of Diffusion Tensor and Magnetization Transfer Imaging in Mild Traumatic Brain Injury

PubMed Central

Lescher, Jacob D.; Williams, Rashida A.; Jikaria, Neekita; Turtzo, L. Christine; Frank, Joseph A.

2017-01-01

Abstract Spontaneous mild ventriculomegaly (MVM) was previously reported in ∼43% of Wistar rats in association with vascular anomalies without phenotypic manifestation. This mild traumatic brain injury (TBI) weight drop model study investigates whether MVM rats (n = 15) have different injury responses that could inadvertently complicate the interpretation of imaging studies compared with normal rats (n = 15). Quantitative MRI, including diffusion tensor imaging (DTI) and magnetization transfer imaging (MTI), and immunohistochemistry (IHC) analysis were used to examine the injury pattern up to 8 days post-injury in MVM and normal rats. Prior to injury, the MVM brain showed significant higher mean diffusivity, axial diffusivity, and radial diffusivity, and lower fractional anisotropy (FA) and magnetization transfer ratio (MTR) in the corpus callosum than normal brain (p < 0.05). Following TBI, normal brains exhibited significant decreases of FA in the corpus callosum, whereas MVM brains demonstrated insignificant changes in FA, suggesting less axonal injury. At day 8 after mild TBI, MTR of the normal brains significantly decreased whereas the MTR of the MVM brains significantly increased. IHC staining substantiated the MRI findings, demonstrating limited axonal injury with significant increase of microgliosis and astrogliosis in MVM brain compared with normal animals. The radiological-pathological correlation data showed that both DTI and MTI were sensitive in detecting mild diffuse brain injury, although DTI metrics were more specific in correlating with histologically identified pathologies. Compared with the higher correlation levels reflecting axonal injury pathology in the normal rat mild TBI, the DTI and MTR metrics were more affected by the increased inflammation in the MVM rat mild TBI. Because MVM Wistar rats appear normal, there was a need to screen rats prior to TBI research to rule out the presence of ventriculomegaly, which may complicate the interpretation of imaging and IHC observations. PMID:26905805

Evenly spaced Detrended Fluctuation Analysis: Selecting the number of points for the diffusion plot

NASA Astrophysics Data System (ADS)

Liddy, Joshua J.; Haddad, Jeffrey M.

2018-02-01

Detrended Fluctuation Analysis (DFA) has become a widely-used tool to examine the correlation structure of a time series and provided insights into neuromuscular health and disease states. As the popularity of utilizing DFA in the human behavioral sciences has grown, understanding its limitations and how to properly determine parameters is becoming increasingly important. DFA examines the correlation structure of variability in a time series by computing α, the slope of the log SD- log n diffusion plot. When using the traditional DFA algorithm, the timescales, n, are often selected as a set of integers between a minimum and maximum length based on the number of data points in the time series. This produces non-uniformly distributed values of n in logarithmic scale, which influences the estimation of α due to a disproportionate weighting of the long-timescale regions of the diffusion plot. Recently, the evenly spaced DFA and evenly spaced average DFA algorithms were introduced. Both algorithms compute α by selecting k points for the diffusion plot based on the minimum and maximum timescales of interest and improve the consistency of α estimates for simulated fractional Gaussian noise and fractional Brownian motion time series. Two issues that remain unaddressed are (1) how to select k and (2) whether the evenly-spaced DFA algorithms show similar benefits when assessing human behavioral data. We manipulated k and examined its effects on the accuracy, consistency, and confidence limits of α in simulated and experimental time series. We demonstrate that the accuracy and consistency of α are relatively unaffected by the selection of k. However, the confidence limits of α narrow as k increases, dramatically reducing measurement uncertainty for single trials. We provide guidelines for selecting k and discuss potential uses of the evenly spaced DFA algorithms when assessing human behavioral data.

Mutual influence of molecular diffusion in gas and surface phases

NASA Astrophysics Data System (ADS)

Hori, Takuma; Kamino, Takafumi; Yoshimoto, Yuta; Takagi, Shu; Kinefuchi, Ikuya

2018-01-01

We develop molecular transport simulation methods that simultaneously deal with gas- and surface-phase diffusions to determine the effect of surface diffusion on the overall diffusion coefficients. The phenomenon of surface diffusion is incorporated into the test particle method and the mean square displacement method, which are typically employed only for gas-phase transport. It is found that for a simple cylindrical pore, the diffusion coefficients in the presence of surface diffusion calculated by these two methods show good agreement. We also confirm that both methods reproduce the analytical solution. Then, the diffusion coefficients for ink-bottle-shaped pores are calculated using the developed method. Our results show that surface diffusion assists molecular transport in the gas phase. Moreover, the surface tortuosity factor, which is known to be uniquely determined by physical structure, is influenced by the presence of gas-phase diffusion. This mutual influence of gas-phase diffusion and surface diffusion indicates that their simultaneous calculation is necessary for an accurate evaluation of the diffusion coefficients.

Market Aspects of Diffusion: A Spatial Perspective on the Diffusion of Innovations in Thailand.

ERIC Educational Resources Information Center

Pontius, Steven K.

How market factors affected the diffusion of four agricultural inputs (fertilizer, herbicide, insecticide, and fungicide) among farmers on the Central Plain of Thailand is examined. Market factors investigated were the distribution policies of the propagators and the travel behavior of the potential adopters. Data were gathered through personal…

[Pathology of the nervous system in conscripts with drug abuse in past medical history: symptomatology, diagnostics methods].

PubMed

Litvintsev, B S; Odinak, M M; Kovalenko, A P; Efimtsev, A Iu; Tarumov, D A; Petrov, A D; Lisianskiĭ, D A

2014-08-01

Authors examined 60 female and male patients (average age 25.8±2.7 years) with confirmed diagnosis - drug abuse. Average duration of drug abuse was approximately 9±3.3 years. At the moment of examination patients had been fully in remission for 3 weeks. The following non-invasive procedures were undertaken: stimulation electroneuromyogrphy and brain MRI. Received results showed that drug abuse leads to diffuse lesion of the nervous system, which manifests itself as vegetative disorders, scattered neurological symptoms, polyneuropathy. Authors gave recommendations in the field of military examination with the aim of detection of nervous disorders caused by drug abuse.

Evidence and role of phlebitis and lipid infiltration in the onset and pathogenesis of Wooden Breast Disease in modern broiler chickens.

PubMed

Papah, Michael B; Brannick, Erin M; Schmidt, Carl J; Abasht, Behnam

2017-12-01

Wooden Breast Disease (WBD), a myopathy that frequently affects modern broiler chickens, is a disorder that has been associated with significant economic losses in the poultry industry. To examine tissue changes associated with the onset and early pathogenesis of this disorder, a time-series experiment was conducted using chickens from a high-breast-muscle-yield, purebred commercial broiler line. Birds were raised for up to seven weeks, with a subset of birds sampled weekly. Breast muscle tissues were extracted at necropsy and processed for analysis by light microscopy and transmission electron microscopy. Histologic presentation indicated localized phlebitis with lipogranulomas in Week 1, focal single-myofibril degeneration in Week 2 preceding an inflammatory response that started in Week 3. Lesions in Week 4 were characterized by multifocal to diffuse muscle fibre degeneration, necrosis, interstitial oedema accompanied by increased lipid and inflammatory cell infiltration. Lesions in Weeks 5-7 revealed diffuse muscle degeneration, necrosis, fibrosis and fatty infiltration with lipogranulomas. Ultrastructural examination showed myofibrillar splitting and degeneration, irregular, displaced and degenerated Z-lines, mitochondrial degeneration and interstitial fibrosis with dense regular collagen fibres. This study, therefore, demonstrates that WBD exhibits an earlier onset in modern broilers than when detectable by clinical examination. Further, this study shows that the disease assumes a progressive course with acute vasculitis, lipid deposition and myodegeneration occurring in the earlier stages, followed by a chronic fibrotic phase.

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.

Giant intramuscular lipoma of the tongue: a case report and literature review.

PubMed

Colella, Giuseppe; Biondi, Paolo; Caltabiano, Rosario; Vecchio, Giada Maria; Amico, Paolo; Magro, Gaetano

2009-06-22

We herein report a rare case of giant intramuscular lipoma of the tongue. A 75-year-old Italian male presented at our department with a large tumor at the tip of the tongue that had been present for over 30 years. Clinical examination revealed a yellowish lesion, measuring 10 cm in maximum diameter, protruding from lingual surface. Histological examination showed an unencapsulated lipomatous tumor composed of mature adipocytes, uniform in size and shape, diffusely infiltrating striated muscle fibers of the tongue. The patient is well with no local recurrence after a 15-month follow-up period.

Giant intramuscular lipoma of the tongue: a case report and literature review

PubMed Central

2009-01-01

We herein report a rare case of giant intramuscular lipoma of the tongue. A 75-year-old Italian male presented at our department with a large tumor at the tip of the tongue that had been present for over 30 years. Clinical examination revealed a yellowish lesion, measuring 10 cm in maximum diameter, protruding from lingual surface. Histological examination showed an unencapsulated lipomatous tumor composed of mature adipocytes, uniform in size and shape, diffusely infiltrating striated muscle fibers of the tongue. The patient is well with no local recurrence after a 15-month follow-up period. PMID:19830025

A two-dimensional microscale model of gas exchange during photosynthesis in maize (Zea mays L.) leaves.

PubMed

Retta, Moges; Ho, Quang Tri; Yin, Xinyou; Verboven, Pieter; Berghuijs, Herman N C; Struik, Paul C; Nicolaï, Bart M

2016-05-01

CO2 exchange in leaves of maize (Zea mays L.) was examined using a microscale model of combined gas diffusion and C4 photosynthesis kinetics at the leaf tissue level. Based on a generalized scheme of photosynthesis in NADP-malic enzyme type C4 plants, the model accounted for CO2 diffusion in a leaf tissue, CO2 hydration and assimilation in mesophyll cells, CO2 release from decarboxylation of C4 acids, CO2 fixation in bundle sheath cells and CO2 retro-diffusion from bundle sheath cells. The transport equations were solved over a realistic 2-D geometry of the Kranz anatomy obtained from light microscopy images. The predicted responses of photosynthesis rate to changes in ambient CO2 and irradiance compared well with those obtained from gas exchange measurements. A sensitivity analysis showed that the CO2 permeability of the mesophyll-bundle sheath and airspace-mesophyll interfaces strongly affected the rate of photosynthesis and bundle sheath conductance. Carbonic anhydrase influenced the rate of photosynthesis, especially at low intercellular CO2 levels. In addition, the suberin layer at the exposed surface of the bundle sheath cells was found beneficial in reducing the retro-diffusion. The model may serve as a tool to investigate CO2 diffusion further in relation to the Kranz anatomy in C4 plants. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Theory and simulation of ion conduction in the pentameric GLIC channel.

PubMed

Zhu, Fangqiang; Hummer, Gerhard

2012-10-09

GLIC is a bacterial member of the large family of pentameric ligand-gated ion channels. To study ion conduction through GLIC and other membrane channels, we combine the one-dimensional potential of mean force for ion passage with a Smoluchowski diffusion model, making it possible to calculate single-channel conductance in the regime of low ion concentrations from all-atom molecular dynamics (MD) simulations. We then perform MD simulations to examine sodium ion conduction through the GLIC transmembrane pore in two systems with different bulk ion concentrations. The ion potentials of mean force, calculated from umbrella sampling simulations with Hamiltonian replica exchange, reveal a major barrier at the hydrophobic constriction of the pore. The relevance of this barrier for ion transport is confirmed by a committor function that rises sharply in the barrier region. From the free evolution of Na(+) ions starting at the barrier top, we estimate the effective diffusion coefficient in the barrier region, and subsequently calculate the conductance of the pore. The resulting diffusivity compares well with the position-dependent ion diffusion coefficient obtained from restrained simulations. The ion conductance obtained from the diffusion model agrees with the value determined via a reactive-flux rate calculation. Our results show that the conformation in the GLIC crystal structure, with an estimated conductance of ~1 picosiemens at 140 mM ion concentration, is consistent with a physiologically open state of the channel.

Solute diffusion through fibrotic tissue formed around protective cage system for implantable devices.

PubMed

Prihandana, Gunawan Setia; Ito, Hikaru; Tanimura, Kohei; Yagi, Hiroshi; Hori, Yuki; Soykan, Orhan; Sudo, Ryo; Miki, Norihisa

2015-08-01

This article presents the concept of an implantable cage system that can house and protect implanted biomedical sensing and therapeutic devices in the body. Cylinder-shaped cages made of porous polyvinyl alcohol (PVA) sheets with an 80-µm pore size and/or stainless steel meshes with 0.54-mm openings were implanted subcutaneously in the dorsal region of rats for 5 weeks. Analysis of the explanted cages showed the formation of fibrosis tissue around the cages. PVA cages had fibrotic tissue growing mostly along the outer surface of cages, while stainless steel cages had fibrotic tissue growing into the inside surface of the cage structure, due to the larger porosity of the stainless steel meshes. As the detection of target molecules with short time lags for biosensors and mass transport with low diffusion resistance into and out of certain therapeutic devices are critical for the success of such devices, we examined whether the fibrous tissue formed around the cages were permeable to molecules of our interest. For that purpose, bath diffusion and microfluidic chamber diffusion experiments using solutions containing the target molecules were performed. Diffusion of sodium, potassium and urea through the fibrosis tissue was confirmed, thus suggesting the potential of these cylindrical cages surrounded by fibrosis tissue to successfully encase implantable sensors and therapeutic apparatus. © 2014 Wiley Periodicals, Inc.

Patchy reaction-diffusion and population abundance: the relative importance of habitat amount and arrangement

Treesearch

Curtis H. Flather; Michael Bevers

2002-01-01

A discrete reaction-diffusion model was used to estimate long-term equilibrium populations of a hypothetical species inhabiting patchy landscapes to examine the relative importance of habitat amount and arrangement in explaining population size. When examined over a broad range of habitat amounts and arrangements, population size was largely determined by a pure amount...

Diffuse charge dynamics in ionic thermoelectrochemical systems.

PubMed

Stout, Robert F; Khair, Aditya S

2017-08-01

Thermoelectrics are increasingly being studied as promising electrical generators in the ongoing search for alternative energy sources. In particular, recent experimental work has examined thermoelectric materials containing ionic charge carriers; however, the majority of mathematical modeling has been focused on their steady-state behavior. Here, we determine the time scales over which the diffuse charge dynamics in ionic thermoelectrochemical systems occur by analyzing the simplest model thermoelectric cell: a binary electrolyte between two parallel, blocking electrodes. We consider the application of a temperature gradient across the device while the electrodes remain electrically isolated from each other. This results in a net voltage, called the thermovoltage, via the Seebeck effect. At the same time, the Soret effect results in migration of the ions toward the cold electrode. The charge dynamics are described mathematically by the Poisson-Nernst-Planck equations for dilute solutions, in which the ion flux is driven by electromigration, Brownian diffusion, and thermal diffusion under a temperature gradient. The temperature evolves according to the heat equation. This nonlinear set of equations is linearized in the (experimentally relevant) limit of a "weak" temperature gradient. From this, we show that the time scale on which the thermovoltage develops is the Debye time, 1/Dκ^{2}, where D is the Brownian diffusion coefficient of both ion species, and κ^{-1} is the Debye length. However, the concentration gradient due to the Soret effect develops on the bulk diffusion time, L^{2}/D, where L is the distance between the electrodes. For thin diffuse layers, which is the condition under which most real devices operate, the Debye time is orders of magnitude less than the diffusion time. Therefore, rather surprisingly, the majority of ion motion occurs after the steady thermovoltage has developed. Moreover, the dynamics are independent of the thermal diffusion coefficients, which simply set the magnitude of the steady-state thermovoltage.

Diffuse charge dynamics in ionic thermoelectrochemical systems

NASA Astrophysics Data System (ADS)

Stout, Robert F.; Khair, Aditya S.

2017-08-01

Thermoelectrics are increasingly being studied as promising electrical generators in the ongoing search for alternative energy sources. In particular, recent experimental work has examined thermoelectric materials containing ionic charge carriers; however, the majority of mathematical modeling has been focused on their steady-state behavior. Here, we determine the time scales over which the diffuse charge dynamics in ionic thermoelectrochemical systems occur by analyzing the simplest model thermoelectric cell: a binary electrolyte between two parallel, blocking electrodes. We consider the application of a temperature gradient across the device while the electrodes remain electrically isolated from each other. This results in a net voltage, called the thermovoltage, via the Seebeck effect. At the same time, the Soret effect results in migration of the ions toward the cold electrode. The charge dynamics are described mathematically by the Poisson-Nernst-Planck equations for dilute solutions, in which the ion flux is driven by electromigration, Brownian diffusion, and thermal diffusion under a temperature gradient. The temperature evolves according to the heat equation. This nonlinear set of equations is linearized in the (experimentally relevant) limit of a "weak" temperature gradient. From this, we show that the time scale on which the thermovoltage develops is the Debye time, 1 /D κ2 , where D is the Brownian diffusion coefficient of both ion species, and κ-1 is the Debye length. However, the concentration gradient due to the Soret effect develops on the bulk diffusion time, L2/D , where L is the distance between the electrodes. For thin diffuse layers, which is the condition under which most real devices operate, the Debye time is orders of magnitude less than the diffusion time. Therefore, rather surprisingly, the majority of ion motion occurs after the steady thermovoltage has developed. Moreover, the dynamics are independent of the thermal diffusion coefficients, which simply set the magnitude of the steady-state thermovoltage.

The effect of pH, temperature and plaque thickness on the hydrolysis of monofluorophosphate in experimental dental plaque.

PubMed

Pearce, E I F; Dibdin, G H

2003-01-01

Monofluorophosphate (MFP), an anti-caries agent commonly used in toothpaste, is known to be degraded to fluoride and orthophosphate by bacterial phosphatases in dental plaque. We have examined the effect of pH, temperature, plaque thickness and some ions on this process. Both natural plaque and artificial microcosm plaque incubated with purified MFP at pH 4-10 showed an optimum pH of approximately 8 for hydrolysis. Diffusion and concomitant hydrolysis were examined in an apparatus in which artificial plaque was held between rigid membranes separating two chambers. When MFP diffused through a plaque of 0.51-mm thickness over 4 h it was almost completely hydrolysed at pH 8, but hydrolysis on diffusion decreased as the pH deviated from 8. MFP in toothpaste extract showed a similar pH susceptibility to hydrolysis, according to the inherent pH of the toothpaste. Hydrolysis of MFP in the toothpaste was reduced by no more than 10% when compared with a matched-pH control, suggesting that other toothpaste ingredients had no major influence on hydrolysis. Transport was slower and hydrolysis at pH 6 more complete the thicker the plaque, but hydrolysis was not significantly slower at 23 degrees C than at 37 degrees C. The addition of various potential activating or inhibiting ions at 0.1 and 1.0 mmol/l had small and non-significant effects on hydrolysis. The results suggest that MFP toothpaste should be formulated and used to maximise enzymic hydrolysis of this complex anion, and that plaque pH control is probably the most important factor. Copyright 2003 S. Karger AG, Basel

Shear heating and solid state diffusion: Constraints from clumped isotope thermometry in carbonate faults

NASA Astrophysics Data System (ADS)

Siman-Tov, S.; Affek, H. P.; Matthews, A.; Aharonov, E.; Reches, Z.

2015-12-01

Natural faults are expected to heat rapidly during seismic slip and to cool quite quickly after the event. Here we examine clumped isotope thermometry for its ability to identify short duration elevated temperature events along frictionally heated carbonate faults. This method is based on measured Δ47 values that indicate the relative atomic order of oxygen and carbon stable isotopes in the calcite lattice, which is affected by heat and thus can serve as a thermometer. We examine three types of calcite rock samples: (1) samples that were rapidly heated and then cooled in static laboratory experiments, simulating the temperature cycle experienced by fault rock during earthquake slip; (2) limestone samples that were experimentally sheared to simulate earthquake slip events; and (3) samples taken from principle slip zones of natural carbonate faults that likely experienced earthquake slip. Experimental results show that Δ47 values decrease rapidly (in the course of seconds) and systematically both with increasing temperature and shear velocity. On the other hand, carbonate shear zone from natural faults do not show such Δ47 reduction. We propose that the experimental Δ47 response is controlled by the presence of high-stressed nano-grains within the fault zone that can reduce the activation energy for diffusion by up to 60%, and thus lead to an increased rate of solid-state diffusion in the experiments. However, the lowering of activation energy is a double-edged sword in terms of clumped isotopes: In laboratory experiments, it allows for rapid disordering so that isotopic signal appears after very short heating, but in natural faults it also leads to relatively fast isotopic re-ordering after the cessation of frictional heating, thus erasing the high temperature signature in Δ47 values within relatively short geological times (<1 Ma).

Characteristics of Matrix Metals in Which Fast Diffusion of Foreign Metallic Elements Occurs

NASA Astrophysics Data System (ADS)

Mae, Yoshiharu

2018-04-01

A few foreign elements are known to diffuse faster than the self-diffusion of the matrix metal. However, the characteristics of the matrix metal, which contribute to such fast diffusion remain unknown. In this study, the diffusion coefficients of various elements were plotted on a TC-YM diagram. The matrix metals that show fast diffusion are located in the low thermal conductivity range of the TC-YM diagram, while diffuser elements that undergo fast diffusion are mainly gulf elements such as Fe, Ni, Co, Cr, and Cu. The gulf elements are those that show the largest combination of thermal conductivity and Young's modulus. The great difference in the electron mobility between the matrix metal and diffuser elements generates a repulsive force between them, and the repulsive force—acting between the soft and large atoms of the matrix metal and the hard and small atoms of the diffuser elements—deforms the atoms of the matrix metal to open passageways for fast diffusion of diffuser elements.

MRI assessment of the thigh musculature in dermatomyositis and healthy subjects using diffusion tensor imaging, intravoxel incoherent motion and dynamic DTI.

PubMed

Sigmund, E E; Baete, S H; Luo, T; Patel, K; Wang, D; Rossi, I; Duarte, A; Bruno, M; Mossa, D; Femia, A; Ramachandran, S; Stoffel, D; Babb, J S; Franks, A; Bencardino, J

2018-06-04

Dermatomyositis (DM) is an idiopathic inflammatory myopathy involving severe debilitation in need of diagnostics. We evaluated the proximal lower extremity musculature with diffusion tensor imaging (DTI), intravoxel incoherent motion (IVIM) and dynamic DTI in DM patients and controls and compared with standard clinical workup.  METHODS: In this IRB-approved, HIPAA-compliant study with written informed consent, anatomical, Dixon fat/water and diffusion imaging were collected in bilateral thigh MRI of 22 controls and 27 DM patients in a 3T scanner. Compartments were scored on T1/T2 scales. Single voxel dynamic DTI metrics in quadriceps before and after 3-min leg exercise were measured. Spearman rank correlation and mixed model analysis of variance/covariance (ANOVA/ANCOVA) were used to correlate with T1 and T2 scores and to compare patients with controls. DM patients showed significantly lower pseudo-diffusion and volume in quadriceps than controls. All subjects showed significant correlation between T1 score and signal-weighted fat fraction; tissue diffusion and pseudo-diffusion varied significantly with T1 and T2 score in patients. Radial and mean diffusion exercise response in patients was significantly higher than controls. Static and dynamic diffusion imaging metrics show correlation with conventional imaging scores, reveal spatial heterogeneity, and provide means to differentiate dermatomyositis patients from controls. • Diffusion imaging shows regional differences between thigh muscles of dermatomyositis patients and controls. • Signal-weighted fat fraction and diffusion metrics correlate with T1/T2 scores of disease severity. • Dermatomyositis patients show significantly higher radial diffusion exercise response than controls.

White matter tract abnormalities are associated with cognitive dysfunction in secondary progressive multiple sclerosis.

PubMed

Meijer, Kim A; Muhlert, Nils; Cercignani, Mara; Sethi, Varun; Ron, Maria A; Thompson, Alan J; Miller, David H; Chard, Declan; Geurts, Jeroen Jg; Ciccarelli, Olga

2016-10-01

While our knowledge of white matter (WM) pathology underlying cognitive impairment in relapsing remitting multiple sclerosis (MS) is increasing, equivalent understanding in those with secondary progressive (SP) MS lags behind. The aim of this study is to examine whether the extent and severity of WM tract damage differ between cognitively impaired (CI) and cognitively preserved (CP) secondary progressive multiple sclerosis (SPMS) patients. Conventional magnetic resonance imaging (MRI) and diffusion MRI were acquired from 30 SPMS patients and 32 healthy controls (HC). Cognitive domains commonly affected in MS patients were assessed. Linear regression was used to predict cognition. Diffusion measures were compared between groups using tract-based spatial statistics (TBSS). A total of 12 patients were classified as CI, and processing speed was the most commonly affected domain. The final regression model including demographic variables and radial diffusivity explained the greatest variance of cognitive performance (R 2  = 0.48, p = 0.002). SPMS patients showed widespread loss of WM integrity throughout the WM skeleton when compared with HC. When compared with CP patients, CI patients showed more extensive and severe damage of several WM tracts, including the fornix, superior longitudinal fasciculus and forceps major. Loss of WM integrity assessed using TBSS helps to explain cognitive decline in SPMS patients. © The Author(s), 2016.

Physicochemical code for quinary protein interactions in Escherichia coli

PubMed Central

Mu, Xin; Choi, Seongil; Lang, Lisa; Mowray, David; Danielsson, Jens; Oliveberg, Mikael

2017-01-01

How proteins sense and navigate the cellular interior to find their functional partners remains poorly understood. An intriguing aspect of this search is that it relies on diffusive encounters with the crowded cellular background, made up of protein surfaces that are largely nonconserved. The question is then if/how this protein search is amenable to selection and biological control. To shed light on this issue, we examined the motions of three evolutionary divergent proteins in the Escherichia coli cytoplasm by in-cell NMR. The results show that the diffusive in-cell motions, after all, follow simplistic physical−chemical rules: The proteins reveal a common dependence on (i) net charge density, (ii) surface hydrophobicity, and (iii) the electric dipole moment. The bacterial protein is here biased to move relatively freely in the bacterial interior, whereas the human counterparts more easily stick. Even so, the in-cell motions respond predictably to surface mutation, allowing us to tune and intermix the protein’s behavior at will. The findings show how evolution can swiftly optimize the diffuse background of protein encounter complexes by just single-point mutations, and provide a rational framework for adjusting the cytoplasmic motions of individual proteins, e.g., for rescuing poor in-cell NMR signals and for optimizing protein therapeutics. PMID:28536196

Stochastic simulation of reaction-diffusion systems: A fluctuating-hydrodynamics approach

NASA Astrophysics Data System (ADS)

Kim, Changho; Nonaka, Andy; Bell, John B.; Garcia, Alejandro L.; Donev, Aleksandar

2017-03-01

We develop numerical methods for stochastic reaction-diffusion systems based on approaches used for fluctuating hydrodynamics (FHD). For hydrodynamic systems, the FHD formulation is formally described by stochastic partial differential equations (SPDEs). In the reaction-diffusion systems we consider, our model becomes similar to the reaction-diffusion master equation (RDME) description when our SPDEs are spatially discretized and reactions are modeled as a source term having Poisson fluctuations. However, unlike the RDME, which becomes prohibitively expensive for an increasing number of molecules, our FHD-based description naturally extends from the regime where fluctuations are strong, i.e., each mesoscopic cell has few (reactive) molecules, to regimes with moderate or weak fluctuations, and ultimately to the deterministic limit. By treating diffusion implicitly, we avoid the severe restriction on time step size that limits all methods based on explicit treatments of diffusion and construct numerical methods that are more efficient than RDME methods, without compromising accuracy. Guided by an analysis of the accuracy of the distribution of steady-state fluctuations for the linearized reaction-diffusion model, we construct several two-stage (predictor-corrector) schemes, where diffusion is treated using a stochastic Crank-Nicolson method, and reactions are handled by the stochastic simulation algorithm of Gillespie or a weakly second-order tau leaping method. We find that an implicit midpoint tau leaping scheme attains second-order weak accuracy in the linearized setting and gives an accurate and stable structure factor for a time step size of an order of magnitude larger than the hopping time scale of diffusing molecules. We study the numerical accuracy of our methods for the Schlögl reaction-diffusion model both in and out of thermodynamic equilibrium. We demonstrate and quantify the importance of thermodynamic fluctuations to the formation of a two-dimensional Turing-like pattern and examine the effect of fluctuations on three-dimensional chemical front propagation. By comparing stochastic simulations to deterministic reaction-diffusion simulations, we show that fluctuations accelerate pattern formation in spatially homogeneous systems and lead to a qualitatively different disordered pattern behind a traveling wave.

Stochastic simulation of reaction-diffusion systems: A fluctuating-hydrodynamics approach

DOE PAGES

Kim, Changho; Nonaka, Andy; Bell, John B.; ...

2017-03-24

Here, we develop numerical methods for stochastic reaction-diffusion systems based on approaches used for fluctuating hydrodynamics (FHD). For hydrodynamic systems, the FHD formulation is formally described by stochastic partial differential equations (SPDEs). In the reaction-diffusion systems we consider, our model becomes similar to the reaction-diffusion master equation (RDME) description when our SPDEs are spatially discretized and reactions are modeled as a source term having Poisson fluctuations. However, unlike the RDME, which becomes prohibitively expensive for an increasing number of molecules, our FHD-based description naturally extends from the regime where fluctuations are strong, i.e., each mesoscopic cell has few (reactive) molecules,more » to regimes with moderate or weak fluctuations, and ultimately to the deterministic limit. By treating diffusion implicitly, we avoid the severe restriction on time step size that limits all methods based on explicit treatments of diffusion and construct numerical methods that are more efficient than RDME methods, without compromising accuracy. Guided by an analysis of the accuracy of the distribution of steady-state fluctuations for the linearized reaction-diffusion model, we construct several two-stage (predictor-corrector) schemes, where diffusion is treated using a stochastic Crank-Nicolson method, and reactions are handled by the stochastic simulation algorithm of Gillespie or a weakly second-order tau leaping method. We find that an implicit midpoint tau leaping scheme attains second-order weak accuracy in the linearized setting and gives an accurate and stable structure factor for a time step size of an order of magnitude larger than the hopping time scale of diffusing molecules. We study the numerical accuracy of our methods for the Schlögl reaction-diffusion model both in and out of thermodynamic equilibrium. We demonstrate and quantify the importance of thermodynamic fluctuations to the formation of a two-dimensional Turing-like pattern and examine the effect of fluctuations on three-dimensional chemical front propagation. Furthermore, by comparing stochastic simulations to deterministic reaction-diffusion simulations, we show that fluctuations accelerate pattern formation in spatially homogeneous systems and lead to a qualitatively different disordered pattern behind a traveling wave.« less

[Contribution of multimodal imaging in the various stages of Stargardt disease].

PubMed

El Matri, L; Falfoul, Y; Kortli, M; Hassairi, A; Charfi, H; Turki, A; Kort, F; Chebil, A

2017-10-01

To describe the contribution of multimodal imaging in the various stages of Stargardt disease (STGD). We retrospectively reviewed 46 eyes of 23 STGD patients with identified ABCA4 mutations. All patients underwent a complete ophthalmic examination, spectral-domain optical coherence tomography (SD-OCT), fundus autofluorescence (FAF), fluorescein angiography (FA) and Indocyanine green angiography (ICGA). The mean age of patients was 25.5 years (range 8-56). Fundus examination was normal in 2 patients (subclinical stage), where SD-OCT showed localized retrofoveolar retinal pigment epithelium (RPE) thickening. FAF was normal in 1 eye and showed mild heterogeneous hyper-FAF in 3 eyes. Twelve eyes had mild salt and pepper changes in the macula (early stage) with diffuse retinal atrophy on SD-OCT and mixed hyper and hypoautofluorescence on FAF. Nine patients showed central atrophy with white-yellow flecks distributed in the posterior pole and mid-periphery. This phenotype showed total foveal atrophy on SD-OCT and normal peripapillary area on FAF. Twelve eyes had a large demarcated area of RPE atrophy, pigment clumping and migration extending to the peripheral retina associated with peripapillary atrophy. These eyes showed diffuse retinochoroidal atrophy on OCT with diffuse alterations reaching the peripapillary area on FAF. On FA, it was difficult to analyze the choroidal silence sign in patients with advanced stages of the disease. A hyperfluorescent window defect pattern was also found in patients with white-yellow flecks and did not correspond exactly to them, or to the areas of peripheral autofluorescent lesions. ICGA showed hypocyanescent areas seen at intermediate and late phases with multiple cyanescent points adjacent to them. On ICGA, hypocyanescent areas were more extensive than lesions observed on FAF. Multimodal imaging is helpful for the diagnosis of early stages of STGD disease and to better understand its pathophysiology. FAF and mostly SD-OCT have supplanted FA in the early, especially subclinical, stages. Over all, ICGA shows more extensive damage, making this tool useful for better understanding STGD and suggesting possible direct damage to the choriocapillaris associated with RPE lesions. In advanced stages, only DNA testing can confirm the diagnosis of STGD. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Probing transcription factor diffusion dynamics in the living mammalian embryo with photoactivatable fluorescence correlation spectroscopy.

PubMed

Kaur, Gurpreet; Costa, Mauro W; Nefzger, Christian M; Silva, Juan; Fierro-González, Juan Carlos; Polo, Jose M; Bell, Toby D M; Plachta, Nicolas

2013-01-01

Transcription factors use diffusion to search the DNA, yet the mechanisms controlling transcription factor diffusion during mammalian development remain poorly understood. Here we combine photoactivation and fluorescence correlation spectroscopy to study transcription factor diffusion in developing mouse embryos. We show that the pluripotency-associated transcription factor Oct4 displays both fast and Brownian and slower subdiffusive behaviours that are controlled by DNA interactions. Following cell lineage specification, the slower DNA-interacting diffusion fraction distinguishes pluripotent from extraembryonic cell nuclei. Similar to Oct4, Sox2 shows slower diffusion in pluripotent cells while Cdx2 displays opposite dynamics, suggesting that slow diffusion may represent a general feature of transcription factors in lineages where they are essential. Slow Oct4 subdiffusive behaviours are conserved in embryonic stem cells and induced pluripotent stem cells (iPS cells), and lost during differentiation. We also show that Oct4 diffusion depends on its interaction with ERG-associated protein with SET domain. Photoactivation and fluorescence correlation spectroscopy provides a new intravital approach to study transcription factor diffusion in complex in vivo systems.

Theory of long-range diffusion of proteins on a spherical biological membrane: application to protein cluster formation and actin-comet tail growth.

PubMed

Amatore, Christian; Oleinick, Alexander I; Klymenko, Oleksiy V; Svir, Irina

2009-07-13

Breaking of symmetry is often required in biology in order to produce a specific function. In this work we address the problem of protein diffusion over a spherical vesicle surface towards one pole of the vesicle in order to produce ultimately an active protein cluster performing a specific biological function. Such a process is, for example, prerequisite for the assembling of proteins which then cooperatively catalyze the polymerization of actin monomers to sustain the growth of actin tails as occurs in natural vesicles such as those contained in Xenopus eggs. By this process such vesicles may propel themselves within the cell by the principle of action-reaction. In this work the physicochemical treatment of diffusion of large biomolecules within a cellular membrane is extended to encompass the case when proteins may be transiently poised by corral-like structures partitioning the membrane as has been recently documented in the literature. In such case the exchange of proteins between adjacent corrals occurs by energy-gated transitions instead of classical Brownian motion, yet the present analysis shows that long-range movements of the biomolecules may still be described by a classical diffusion law though the diffusion coefficient has then a different physical meaning. Such a model explains why otherwise classical diffusion of proteins may give rise to too small diffusion coefficients compared to predictions based on the protein dimension. This model is implemented to examine the rate of proteins clustering at one pole of a spherical vesicle and its outcome is discussed in relevance to the mechanism of actin comet tails growth.

Nitrogen diffusion in hafnia and the impact of nitridation on oxygen and hydrogen diffusion: A first-principles study

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

Sathiyanarayanan, Rajesh, E-mail: rajessat@in.ibm.com, E-mail: rajesh.sathiyanarayanan@gmail.com; Pandey, R. K.; Murali, K. V. R. M.

2015-01-21

Using first-principles simulations, we have computed incorporation energies and diffusion barriers of ammonia, the nitrogen molecule and atomic nitrogen in monoclinic hafnia (m-HfO{sub 2}). Our calculations show that ammonia is likely to dissociate into an NH{sub 2} molecular unit, whereas the nitrogen molecule remains as a molecule either in the interstitial space or at an oxygen lattice site. The lowest energy pathway for the diffusion of atomic nitrogen interstitials consists of the hopping of the nitrogen interstitial between neighboring three-coordinated lattice oxygen atoms that share a single Hf atom, and the barrier for such hops is determined by a switchingmore » mechanism. The substitutional nitrogen atom shows a preference for diffusion through the doubly positive oxygen vacancy-mediated mechanism. Furthermore, we have investigated the impact of nitrogen atoms on the diffusion barriers of oxygen and hydrogen interstitials in m-HfO{sub 2}. Our results show that nitrogen incorporation has a significant impact on the barriers for oxygen and hydrogen diffusion: nitrogen atoms attract oxygen and hydrogen interstitials diffusing in the vicinity, thereby slowing down (reducing) their diffusion (diffusion length)« less

Diagnostic performance of magnetic resonance imaging and 3D endoanal ultrasound in detection, staging and assessment post treatment, in anal cancer.

PubMed

Reginelli, Alfonso; Granata, Vincenza; Fusco, Roberta; Granata, Francesco; Rega, Daniela; Roberto, Luca; Pellino, Gianluca; Rotondo, Antonio; Selvaggi, Francesco; Izzo, Francesco; Petrillo, Antonella; Grassi, Roberto

2017-04-04

We compared Magnetic Resonance Imaging (MRI) and 3D Endoanal Ultrasound (EAUS) imaging performance to confirm anal carcinoma and to monitor treatment response.58 patients with anal cancer were retrospectively enrolled. All patients underwent clinical examination, anoscopic examination; EAUS and contrast-enhanced MRI study before and after treatment. Four radiologists evaluated the presence of lesions, using a 4-point confidence scale, features of the lesion and nodes on EAUS images, T1-weighted (T1-W), T2-weighted (T2-W) and diffusion-weighted images (DWI) signal intensity (SI), the apparent diffusion coefficient (ADC) map for nodes and lesion, as well as enhancement pattern during dynamic MRI were assessed.All lesions were detected by EAUS while MRI detected 93.1% of anal cancer. MRI showed a good correlation with EAUS, anoscopy and clinical examination. The residual tissue not showed significant difference in EAUS assessment and T2-W SI in pre and post treatment. We found significant difference in dynamic study, in SI of DWI, in ADC map and values among responder's patients in pre and post treatment. The neoplastic nodes were hypoecoic on EAUS, with hyperintense signal on T2-W sequences and hypointense signal on T1-W. The neoplastic nodes showed SI on DWI sequences and ADC value similar to anal cancer. We found significant difference in nodes status in pre and post therapy on DWI data.3D EAUS and MRI are accurate techniques in anal cancer staging, although EAUS is more accurate than MRI for T1 stage. MRI allows correct detection of neoplastic nodes and can properly stratify patients into responders or non responders.

The contribution of the diffuse light component to the topographic effect on remotely sensed data

NASA Technical Reports Server (NTRS)

Justice, C.; Holben, B.

1980-01-01

The topographic effect is measured by the difference between the global radiance from inclined surfaces as a function of their orientation relative to the sensor position and light source. The short wave radiant energy incident on a surface is composed of direct sunlight, scattered skylight, and light reflected from surrounding terrain. The latter two components are commonly known as the diffuse component. The contribution of the diffuse light component to the topographic effect was examined and the significance of this diffuse component with respect to two direct radiance models was assessed. Diffuse and global spectral radiances were measured for a series of slopes and aspects of a uniform and surface in the red and photographic infrared parts of the spectrum, using a nadir pointing two channel handheld radiometer. The diffuse light was found to produce a topographic effect which varied from the topographic effect for direct light. The topographic effect caused by diffuse light was found to increase slightly with solar elevation and wavelength for the channels examined. The correlations between data derived from two simple direct radiance simulation models and the field data were not significantly affected when the diffuse component was removed from the radiances. Radiances from a 60 percent reflective surface, assuming no atmospheric path radiance, the diffuse light topographic effect contributed a maximum range of 3 pixel values in simulated LANDSAT data from all aspects with slopes up to 30 degrees.

The Adoption and Diffusion of eLearning in UK Universities: A Comparative Case Study Using Giddens's Theory of Structuration

ERIC Educational Resources Information Center

Hardaker, Glenn; Singh, Gurmak

2011-01-01

Purpose: This exploratory study seeks to identify the factors that influence the adoption and diffusion of instructional technology at five prominent universities in the UK. The study aims to examine the organisational factors that enable and inhibit organisational adoption and diffusion of innovation. Design/methodology/approach: A qualitative…

Diffusion Tensor Imaging: Application to the Study of the Developing Brain

ERIC Educational Resources Information Center

Cascio, Carissa J.; Gerig, Guido; Piven, Joseph

2007-01-01

Objective: To provide an overview of diffusion tensor imaging (DTI) and its application to the study of white matter in the developing brain in both healthy and clinical samples. Method: The development of DTI and its application to brain imaging of white matter tracts is discussed. Forty-eight studies using DTI to examine diffusion properties of…

Red Onions, "Elodea," or Decalcified Chicken Eggs? Selecting & Sequencing Representations for Teaching Diffusion & Osmosis

ERIC Educational Resources Information Center

Lankford, Deanna; Friedrichsen, Patricia

2012-01-01

Diffusion and osmosis are important biological concepts that students often struggle to understand. These are important concepts because they are the basis for many complex biological processes, such as photosynthesis and cellular respiration. We examine a wide variety of representations used by experienced teachers to teach diffusion and osmosis.…

NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 10: The NASA/DOD Aerospace Knowledge Diffusion Research Project

NASA Technical Reports Server (NTRS)

Pinelli, Thomas E.; Kennedy, John M.; Barclay, Rebecca O.

1991-01-01

The role of the NASA/DOD Aerospace Knowledge DIffusion Research Project in helping to maintain U.S. competitiveness is addressed. The phases of the project are examined in terms of the focus, emphasis, subjects, methods, and desired outcomes. The importance of the project to aerospace R&D is emphasized.

Neurocognitive and neuroimaging correlates of pediatric traumatic brain injury: A diffusion tensor imaging (DTI) study

PubMed Central

Wozniak, Jeffrey R.; Krach, Linda; Ward, Erin; Mueller, Bryon A.; Muetzel, Ryan; Schnoebelen, Sarah; Kiragu, Andrew; Lim, Kelvin O.

2010-01-01

This study examined the sensitivity of diffusion tensor imaging (DTI) to microstructural white matter (WM) damage in mild and moderate pediatric traumatic brain injury (TBI). Fourteen children with TBI and 14 controls ages 10–18 had DTI scans and neurocognitive evaluations at 6–12 months post-injury. Groups did not differ in intelligence, but children with TBI showed slower processing speed, working memory and executive deficits, and greater behavioral dysregulation. The TBI group had lower fractional anisotropy (FA) in three WM regions: inferior frontal, superior frontal, and supracallosal. There were no group differences in corpus callosum. FA in the frontal and supracallosal regions was correlated with executive functioning. Supracallosal FA was also correlated with motor speed. Behavior ratings showed correlations with supracallosal FA. Parent-reported executive deficits were inversely correlated with FA. Results suggest that DTI measures are sensitive to long-term WM changes and associated with cognitive functioning following pediatric TBI. PMID:17446039

Rapid resolution of diffusion weighted MRI abnormality in a patient with a stuttering stroke

PubMed Central

Peters, Jurriaan M; MacLean, Ainsley V; Young, Geoffrey S

2010-01-01

We report the unusually rapid and spontaneous normalisation of low diffusivity that accompanied resolution of acute neurological deficits in a stroke patient who underwent two magnetic resonance imaging examinations within 24 h of symptom onset. Diffusion weighted imaging obtained within hours of onset of left sided weakness demonstrated a focal right capsular area of low diffusivity that resolved within 24 h, coinciding with resolution of the patient’s symptoms. PMID:22315635

Predicting Treatment Response of Colorectal Cancer Liver Metastases to Conventional Lipiodol-Based Transarterial Chemoembolization Using Diffusion-Weighted MR Imaging: Value of Pretreatment Apparent Diffusion Coefficients (ADC) and ADC Changes Under Therapy

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

Lahrsow, Maximilian, E-mail: mlahrsow@gmail.com; Albrecht, Moritz H.; Bickford, Matthew W.

PurposeTo use absolute pretreatment apparent diffusion coefficients (ADC) derived from diffusion-weighted MR imaging (DWI) to predict response to repetitive cTACE for unresectable liver metastases of colorectal carcinoma (CRLM) at 1 and 3 months after start of treatment.Materials and MethodsFifty-five metastases in 34 patients were examined with DWI prior to treatment and 1 month after initial cTACE. Treatment was performed in 4-week intervals. Response was evaluated at 1 and 3 months after start of therapy. Metastases showing a decrease of ≥30% in axial diameter were classified as responding lesions.ResultsOne month after initial cTACE, seven lesions showed early response. There was no significant differencemore » in absolute pretreatment ADC values between responding and non-responding lesions (p = 0.94). Three months after initial cTACE, 17 metastases showed response. There was a significant difference (p = 0.021) between absolute pretreatment ADC values of lesions showing response (median 1.08 × 10{sup −3} mm{sup 2}/s) and no response (median 1.30 × 10{sup −3} mm{sup 2}/s). Pretreatment ADC showed fair diagnostic value to predict response (AUC 0.7). Lesions showing response at 3 months also revealed a significant increase in ADC between measurements before treatment and at one month after initial cTACE (p < 0.001). Applying an increase in ADC of 12.17%, response at 3 months after initial cTACE could be predicted with a sensitivity and specificity of 77 and 74%, respectively (AUC 0.817). Furthermore, there was a strong and significant correlation (r = 0.651, p < 0.001) between percentage change in size after third cTACE and percentage change in ADC.ConclusionIn patients with CRLM, ADC measurements are potential biomarkers for assessing response to cTACE.« less

Diffusion of Innovation Theory and Xbox Live: Examining Minority Gamers' Responses and Rate of Adoption to Changes in Xbox Live

ERIC Educational Resources Information Center

Gray, Kishonna L.

2012-01-01

This article examines the response of minority gamers as they adopt new innovations in Xbox Live. Using diffusion of innovation theory, specific attention is given to gamers' rate of adoption of the new Xbox Live environment, which was a recent update to the Xbox Live interface. By employing virtual ethnography, observations, and interviews reveal…

Region of Interest Correction Factors Improve Reliability of Diffusion Imaging Measures Within and Across Scanners and Field Strengths

PubMed Central

Venkatraman, Vijay K; Gonzalez, Christopher E.; Landman, Bennett; Goh, Joshua; Reiter, David A.; An, Yang; Resnick, Susan M.

2017-01-01

Diffusion tensor imaging (DTI) measures are commonly used as imaging markers to investigate individual differences in relation to behavioral and health-related characteristics. However, the ability to detect reliable associations in cross-sectional or longitudinal studies is limited by the reliability of the diffusion measures. Several studies have examined reliability of diffusion measures within (i.e. intra-site) and across (i.e. inter-site) scanners with mixed results. Our study compares the test-retest reliability of diffusion measures within and across scanners and field strengths in cognitively normal older adults with a follow-up interval less than 2.25 years. Intra-class correlation (ICC) and coefficient of variation (CoV) of fractional anisotropy (FA) and mean diffusivity (MD) were evaluated in sixteen white matter and twenty-six gray matter bilateral regions. The ICC for intra-site reliability (0.32 to 0.96 for FA and 0.18 to 0.95 for MD in white matter regions; 0.27 to 0.89 for MD and 0.03 to 0.79 for FA in gray matter regions) and inter-site reliability (0.28 to 0.95 for FA in white matter regions, 0.02 to 0.86 for MD in gray matter regions) with longer follow-up intervals were similar to earlier studies using shorter follow-up intervals. The reliability of across field strengths comparisons was lower than intra- and inter-site reliability. Within and across scanner comparisons showed that diffusion measures were more stable in larger white matter regions (> 1500 mm3). For gray matter regions, the MD measure showed stability in specific regions and was not dependent on region size. Linear correction factor estimated from cross-sectional or longitudinal data improved the reliability across field strengths. Our findings indicate that investigations relating diffusion measures to external variables must consider variable reliability across the distinct regions of interest and that correction factors can be used to improve consistency of measurement across field strengths. An important result of this work is that inter-scanner and field strength effects can be partially mitigated with linear correction factors specific to regions of interest. These data-driven linear correction techniques can be applied in cross-sectional or longitudinal studies. PMID:26146196

Molecular dynamics simulations of lithium silicate/vanadium pentoxide interfacial lithium ion diffusion in thin film lithium ion-conducting devices

NASA Astrophysics Data System (ADS)

Li, Weiqun

The lithium ion diffusion behavior and mechanism in the glassy electrolyte and the electrolyte/cathode interface during the initial stage of lithium ion diffusing from electrolyte into cathode were investigated using Molecular Dynamics simulation technique. Lithium aluminosilicate glass electrolytes with different R (ratio of the concentration of Al to Li) were simulated. The structural features of the simulated glasses are analyzed using Radial Distribution Function (RDF) and Pair Distribution Function (PDF). The diffusion coefficient and activation energy of lithium ion diffusion in simulated lithium aluminosilicate glasses were calculated and the values are consistent with those in experimental glasses. The behavior of lithium ion diffusion from the glassy electrolyte into a polycrystalline layered intercalation cathode has been studied. The solid electrolyte was a model lithium silicate glass while the cathode was a nanocrystalline vanadia with amorphous V2O5 intergranular films (IGF) between the V2O5 crystals. Two different orientations between the V2O5 crystal planes are presented for lithium ion intercalation via the amorphous vanadia IGF. A series of polycrystalline vanadia cathodes with 1.3, 1.9, 2.9 and 4.4 nm thickness IGFs were simulated to examine the effects of the IGF thickness on lithium ion transport in the polycrystalline vanadia cathodes. The simulated results showed that the lithium ions diffused from the glassy electrolyte into the IGF of the polycrystalline vanadia cathode and then part of those lithium ions diffused into the crystalline V2O5 from the IGF. The simulated results also showed an ordering of the vanadium ion structure in the IGF near the IGF/V2 O5 interface. The ordering structure still existed with glass former silica additive in IGF. Additionally, 2.9 run is suggested to be the optimal thickness of the IGF, which is neither too thick to decrease the capacity of the cathode nor too thin to impede the transport of lithium from glassy electrolyte into the cathode. Parallel molecular dynamic simulation technique was also used for a larger electrolyte/cathode interface system, which include more atoms and more complicated microstructures. Simulation results from larger electrolyte/cathode interface system prove that there is no size effect on simulation of smaller electrolyte/cathode interface system from statistical point of view.

The Corneal Epithelial Barrier and Its Developmental Role in Isolating Corneal Epithelial and Conjunctival Cells From One Another

PubMed Central

Kubilus, James K.; Zapater i Morales, Carolina; Linsenmayer, Thomas F.

2017-01-01

Purpose During development, the corneal epithelium (CE) and the conjunctiva are derived from the surface ectoderm. Here we have examined how, during development, the cells of these two issues become isolated from each other. Methods Epithelia from the anterior eyes of chicken embryos were labeled with the fluorescent, lipophilic dye, 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate (DiI). DiI was placed on the epithelial surface of the developing anterior eye and its diffusion was monitored by fluorescence microscopy. Concomitant morphologic changes in the surface cells of these epithelial were examined by scanning electron microscopy. Immunofluorescence was used to analyze the expression of cytokeratin K3, ZO-1, N-cadherin and Connexin-43 and the function of gap junctions was analyzed using a cut-loading with the fluorescent dye rhodamine-dextran. Results Prior to embryonic day 8 (E8), DiI placed on the surface of the CE spreads throughout all the epithelial cells of the anterior eye. When older eyes were similarly labeled, dye diffusion was restricted to the CE. Similarly, diffusion of DiI placed on the conjunctival surface after E8 was restricted to the conjunctiva. Scanning electron microscopy showed that developmentally (1) physical separations progressively form between the cells of the CE and those of the conjunctiva, and (2) by E8 these separations form a ring that completely encompasses the cornea. The functional restriction of gap junctions between these tissues did not occur until E14. Conclusions During ocular development, a barrier to the diffusion of DiI forms between the contiguous CE and conjunctiva prior to the differential expression of gap junctions within these tissues. PMID:28319640

Longitudinal Processing Speed Impairments in Males with Autism and the Effects of White Matter Microstructure

PubMed Central

Travers, Brittany G.; Bigler, Erin D.; Tromp, Do P. M.; Adluru, Nagesh; Froehlich, Alyson L.; Ennis, Chad; Lange, Nicholas; Nielsen, Jared A.; Prigge, Molly B. D.; Alexander, Andrew L.; Lainhart, Janet E.

2014-01-01

The present study used an accelerated longitudinal design to examine group differences and age-related changes in processing speed in 81 individuals with Autism Spectrum Disorder (ASD) compared to 56 age-matched individuals with typical development (ages 6–39 years). Processing speed was assessed using the Wechsler Intelligence Scale for Children-3rd edition (WISC-III) and the Wechsler Adult Intelligence Scale-3rd edition (WAIS-III). Follow-up analyses examined processing speed subtest performance and relations between processing speed and white matter microstructure (as measured with diffusion tensor imaging [DTI] in a subset of these participants). After controlling for full scale IQ, the present results show that processing speed index standard scores were on average 12 points lower in the group with ASD compared to the group with typical development. There were, however, no significant group differences in standard score age-related changes within this age range. For subtest raw scores, the group with ASD demonstrated robustly slower processing speeds in the adult versions of the IQ test (i.e., WAIS-III) but not in the child versions (WISC-III), even though age-related changes were similar in both the ASD and typically developing groups. This pattern of results may reflect difficulties that become increasingly evident in ASD on more complex measures of processing speed. Finally, DTI measures of whole-brain white matter microstructure suggested that fractional anisotropy (but not mean diffusivity, radial diffusivity, or axial diffusivity) made significant but small-sized contributions to processing speed standard scores across our entire sample. Taken together, the present findings suggest that robust decreases in processing speed may be present in ASD, more pronounced in adulthood, and partially attributable to white matter microstructural integrity. PMID:24269298

Influence of dislocation strain fields on the diffusion of interstitial iron impurities in silicon

NASA Astrophysics Data System (ADS)

Ziebarth, Benedikt; Mrovec, Matous; Elsässer, Christian; Gumbsch, Peter

2015-09-01

The efficiency of silicon (Si)-based solar cells is strongly affected by crystal defects and impurities. Metallic impurities, in particular interstitial iron (Fe) atoms, cause large electric losses because they act as recombination centers for photogenerated charge carriers. Here, we present a systematic first-principles density functional theory (DFT) study focusing on the influence of hydrostatic, uniaxial, and shear strains on the thermodynamic stability and the diffusivity of Fe impurities in crystalline Si. Our calculations show that the formation energy of neutral Fe interstitials in tetrahedral interstitial sites is almost unaffected by uniform deformations of the Si crystal up to strains of 5%. In contrast, the migration barrier varies significantly with strain, especially for hydrostatic deformation. In order to determine effective diffusion coefficients for different strain states, a kinetic Monte Carlo (kMC) model was set up based on the activation energy barriers and frequency factors obtained from the DFT simulations. By using the strain dependence of the migration barrier, we examined the migration of Fe interstitials in the vicinity of perfect 1 /2 <110 > screw and 60∘ mixed dislocations, and 1 /6 <112 > 90∘ and 30∘ partial dislocations. While the strain field of the perfect screw dislocation always enhances the local Fe diffusion, the existence of tensile and compressive regions around the 60∘ mixed dislocation results in a strong anisotropic diffusion profile with significantly faster and slower diffusivities on its tensile and compressive sides. The influences of the partial dislocations are qualitatively similar to that of the 60∘ mixed dislocation.

Is 3-Tesla Gd-EOB-DTPA-Enhanced MRI with Diffusion-Weighted Imaging Superior to 64-Slice Contrast-Enhanced CT for the Diagnosis of Hepatocellular Carcinoma?

PubMed Central

Maiwald, Bettina; Lobsien, Donald; Kahn, Thomas; Stumpp, Patrick

2014-01-01

Objectives To compare 64-slice contrast-enhanced computed tomography (CT) with 3-Tesla magnetic resonance imaging (MRI) using Gd-EOB-DTPA for the diagnosis of hepatocellular carcinoma (HCC) and evaluate the utility of diffusion-weighted imaging (DWI) in this setting. Methods 3-phase-liver-CT was performed in fifty patients (42 male, 8 female) with suspected or proven HCC. The patients were subjected to a 3-Tesla-MRI-examination with Gd-EOB-DTPA and diffusion weighted imaging (DWI) at b-values of 0, 50 and 400 s/mm2. The apparent diffusion coefficient (ADC)-value was determined for each lesion detected in DWI. The histopathological report after resection or biopsy of a lesion served as the gold standard, and a surrogate of follow-up or complementary imaging techniques in combination with clinical and paraclinical parameters was used in unresected lesions. Diagnostic accuracy, sensitivity, specificity, and positive and negative predictive values were evaluated for each technique. Results MRI detected slightly more lesions that were considered suspicious for HCC per patient compared to CT (2.7 versus 2.3, respectively). ADC-measurements in HCC showed notably heterogeneous values with a median of 1.2±0.5×10−3 mm2/s (range from 0.07±0.1 to 3.0±0.1×10−3 mm2/s). MRI showed similar diagnostic accuracy, sensitivity, and positive and negative predictive values compared to CT (AUC 0.837, sensitivity 92%, PPV 80% and NPV 90% for MRI vs. AUC 0.798, sensitivity 85%, PPV 79% and NPV 82% for CT; not significant). Specificity was 75% for both techniques. Conclusions Our study did not show a statistically significant difference in detection in detection of HCC between MRI and CT. Gd-EOB-DTPA-enhanced MRI tended to detect more lesions per patient compared to contrast-enhanced CT; therefore, we would recommend this modality as the first-choice imaging method for the detection of HCC and therapeutic decisions. However, contrast-enhanced CT was not inferior in our study, so that it can be a useful image modality for follow-up examinations. PMID:25375778

Diffusion heterogeneity tensor MRI (?-Dti): mathematics and initial applications in spinal cord regeneration after trauma - biomed 2009.

PubMed

Ellington, Benjamin M; Schmit, Brian D; Gourab, Krishnaj; Sieber-Blum, Maya; Hu, Yao F; Schmainda, Kathleen M

2009-01-01

Diffusion weighted magnetic resonance imaging (DWI) is a powerful tool for evaluation of microstructural anomalies in numerous central nervous system pathologies. Diffusion tensor imaging (DTI) allows for the magnitude and direction of water self diffusion to be estimated by sampling the apparent diffusion coefficient (ADC) in various directions. Clinical DWI and DTI performed at a single level of diffusion weighting, however, does not allow for multiple diffusion compartments to be elicited. Furthermore, assumptions made regarding the precise number of diffusion compartments intrinsic to the tissue of interest have resulted in a lack of consensus between investigations. To overcome these challenges, a stretched-exponential model of diffusion was applied to examine the diffusion coefficient and "heterogeneity index" within highly compartmentalized brain tumors. The purpose of the current study is to expand on the stretched-exponential model of diffusion to include directionality of both diffusion heterogeneity and apparent diffusion coefficient. This study develops the mathematics of this new technique along with an initial application in quantifying spinal cord regeneration following acute injection of epidermal neural crest stem cell (EPI-NCSC) grafts.

Langevin equation with fluctuating diffusivity: A two-state model

NASA Astrophysics Data System (ADS)

Miyaguchi, Tomoshige; Akimoto, Takuma; Yamamoto, Eiji

2016-07-01

Recently, anomalous subdiffusion, aging, and scatter of the diffusion coefficient have been reported in many single-particle-tracking experiments, though the origins of these behaviors are still elusive. Here, as a model to describe such phenomena, we investigate a Langevin equation with diffusivity fluctuating between a fast and a slow state. Namely, the diffusivity follows a dichotomous stochastic process. We assume that the sojourn time distributions of these two states are given by power laws. It is shown that, for a nonequilibrium ensemble, the ensemble-averaged mean-square displacement (MSD) shows transient subdiffusion. In contrast, the time-averaged MSD shows normal diffusion, but an effective diffusion coefficient transiently shows aging behavior. The propagator is non-Gaussian for short time and converges to a Gaussian distribution in a long-time limit; this convergence to Gaussian is extremely slow for some parameter values. For equilibrium ensembles, both ensemble-averaged and time-averaged MSDs show only normal diffusion and thus we cannot detect any traces of the fluctuating diffusivity with these MSDs. Therefore, as an alternative approach to characterizing the fluctuating diffusivity, the relative standard deviation (RSD) of the time-averaged MSD is utilized and it is shown that the RSD exhibits slow relaxation as a signature of the long-time correlation in the fluctuating diffusivity. Furthermore, it is shown that the RSD is related to a non-Gaussian parameter of the propagator. To obtain these theoretical results, we develop a two-state renewal theory as an analytical tool.

De novo CD5-positive primary cardiac diffuse large B-cell lymphoma diagnosed by pleural fluid cytology.

PubMed

Cioc, Adina M; Jessurun, José; Vercellotti, Gregory M; Pambuccian, Stefan E

2014-03-01

Primary cardiac lymphomas are exceedingly rare. The presence and extent of the intracardiac mass is determined by echocardiography, computed tomography (CT), or magnetic resonance imaging (MRI); however, the diagnosis is established by endomyocardial biopsy or by pericardial or pleural effusion cytology. We describe the pleural effusion cytologic features of a primary cardiac lymphoma in a 55-year-old woman who presented with progressive shortness of breath, fatigue, mild dizziness, dull chest ache, and lower extremity edema. Transthoracic echocardiography, CT, and MRI showed a large mass centered in the right atrium and extending into the right ventricle, associated with pericardial effusion and bilateral pleural effusions. Cytologic examination of the pleural fluid showed very large pleomorphic malignant cell, some of which were binucleated and multinucleated and had anaplastic features. Flow cytometry showed a kappa monotypic population of large cells coexpressing CD5, CD19, and CD20; and immunoperoxidase stains performed on the cell block sections showed that the large neoplastic cells were positive for CD20, PAX5, CD5, and MUM1 and showed a very high proliferation rate (over 90%) by Ki67 staining. The cytologic, flow cytometry, and immunohistochemistry findings established the diagnosis of de novo CD5-positive primary cardiac diffuse large B-cell lymphoma (DLBCL), anaplastic variant, which was confirmed by the subsequent endomyocardial biopsy. This is, to the best of our knowledge, the first report of de novo CD5-positive primary cardiac diffuse large B-cell lymphoma, and the first report of the anaplastic variant of DLBCL diagnosed by effusion cytology. Copyright © 2012 Wiley Periodicals, Inc., a Wiley company.

Trinity Bay Study: Dye tracing experiments

NASA Technical Reports Server (NTRS)

Ward, G. H., Jr.

1972-01-01

An analysis of the heat balance and temperature distribution within Trinity Bay near Galveston, Texas is presented. The effects of tidal currents, wind driven circulations, and large volume inflows are examined. Emphasis is placed on the effects of turbulent diffusion and local shears in currents. The technique of dye tracing to determine the parameters characterizing dispersion is described. Aerial photographs and maps are provided to show the flow conditions existing at different times and seasons.

On the channel width-dependence of the thermal conductivity in ultra-narrow graphene nanoribbons

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

Karamitaheri, Hossein; Neophytou, Neophytos, E-mail: N.Neophytou@warwick.ac.uk

The thermal conductivity of low-dimensional materials and graphene nanoribbons, in particular, is limited by the strength of line-edge-roughness scattering. One way to characterize the roughness strength is the dependency of the thermal conductivity on the channel's width in the form W{sup β}. Although in the case of electronic transport, this dependency is very well studied, resulting in W{sup 6} for nanowires and quantum wells and W{sup 4} for nanoribbons, in the case of phonon transport it is not yet clear what this dependence is. In this work, using lattice dynamics and Non-Equilibrium Green's Function simulations, we examine the width dependencemore » of the thermal conductivity of ultra-narrow graphene nanoribbons under the influence of line edge-roughness. We show that the exponent β is in fact not a single well-defined number, but it is different for different parts of the phonon spectrum depending on whether phonon transport is ballistic, diffusive, or localized. The exponent β takes values β < 1 for semi-ballistic phonon transport, values β ≫ 1 for sub-diffusive or localized phonons, and β = 1 only in the case where the transport is diffusive. The overall W{sup β} dependence of the thermal conductivity is determined by the width-dependence of the dominant phonon modes (usually the acoustic ones). We show that due to the long phonon mean-free-paths, the width-dependence of thermal conductivity becomes a channel length dependent property, because the channel length determines whether transport is ballistic, diffusive, or localized.« less

Multimodal imaging of bilateral diffuse uveal melanocytic proliferation associated with an iris mass lesion.

PubMed

Naysan, Jonathan; Pang, Claudine E; Klein, Robert W; Freund, K Bailey

2016-01-01

Bilateral diffuse uveal melanocytic proliferation (BDUMP) is a rare, paraneoplastic syndrome characterized by bilateral painless visual loss and proliferation of choroidal melanocytes in association with an underlying systemic malignancy. We report a case of bilateral diffuse uveal melanocytic proliferation associated with an underlying gynecological malignancy that also features the infrequent finding of an iris mass lesion, using multimodal imaging including ultra-widefield imaging, spectral domain and swept-source optical coherence tomography. A 59-year-old white female with a prior history of gynecological malignancy in remission presented with progressive bilateral visual loss over several weeks. The patient was noted to have a focal iris mass lesion in her right eye. Ultra-widefield color fundus photography showed a characteristic bilateral 'giraffe pattern' of pigmentary changes extending into the periphery as well as multiple discrete deeply pigmented lesions. Ultra-widefield autofluorescence was useful for visualizing the full extent of involvement. Indocyanine green angiography helped to demarcate the discrete pigmented choroidal lesions. Swept-source OCT clearly delineated the alternating zones of retinal pigment epithelium (RPE) thickening and RPE loss, as well as the prominent choroidal infiltration and thickening. BDUMP is an important diagnosis to consider in the presence of multiple discrete melanocytic choroidal lesions, diffuse choroidal thickening, characteristic RPE changes, iris mass lesions and exudative retinal detachment. Ultra-widefield imaging may demonstrate more extensive lesions than that detected on clinical examination or standard field imaging. Imaging with SS-OCT shows choroidal and RPE characteristics that correlate well with known histopathology of this entity.

Clinical team functioning and IT innovation: a study of the diffusion of a point-of-care online evidence system.

PubMed

Gosling, A Sophie; Westbrook, Johanna I; Braithwaite, Jeffrey

2003-01-01

To investigate the association between clinical team functioning and diffusion (awareness, use, and impact) of a 24-hour online evidence retrieval system. To examine the relationships between clinical team characteristics and the adoption of the online evidence system. 18 clinical teams, consisting of 180 clinicians from three Australian hospitals, were identified and studied. Teams were categorized as small ( 15). Clinical team functioning was assessed using the Team Climate Inventory (TCI). Awareness, use, and impact of an online evidence retrieval system were measured using a self-administered questionnaire. The relationships between TCI scores and awareness, use, and impact were examined using t-tests and one-way ANOVAs. Chi square analyses were used to examine differences between small and large teams. RESULTS were interpreted within a diffusion of innovations framework. Clinical team functioning was not related to awareness or use of the online evidence retrieval system. However, clinical team functioning was significantly associated with the impact of online evidence in terms of reported experience of improved patient care following system use. Clinicians in small teams ( 15) teams. Team functioning had the greatest impact on the fourth stage of innovation diffusion, the effective use of online evidence for clinical care. This supports Rogers' diffusion of innovation theory, to the effect that different types of communication about an innovation are important at different stages in the diffusion process. Members of small teams were more aware of the system than members of large teams. Team functioning is amenable to improvement through interventions. The findings suggest that the role of team climate in the diffusion of information systems is a promising area for future research.

Principal component analysis for protein folding dynamics.

PubMed

Maisuradze, Gia G; Liwo, Adam; Scheraga, Harold A

2009-01-09

Protein folding is considered here by studying the dynamics of the folding of the triple beta-strand WW domain from the Formin-binding protein 28. Starting from the unfolded state and ending either in the native or nonnative conformational states, trajectories are generated with the coarse-grained united residue (UNRES) force field. The effectiveness of principal components analysis (PCA), an already established mathematical technique for finding global, correlated motions in atomic simulations of proteins, is evaluated here for coarse-grained trajectories. The problems related to PCA and their solutions are discussed. The folding and nonfolding of proteins are examined with free-energy landscapes. Detailed analyses of many folding and nonfolding trajectories at different temperatures show that PCA is very efficient for characterizing the general folding and nonfolding features of proteins. It is shown that the first principal component captures and describes in detail the dynamics of a system. Anomalous diffusion in the folding/nonfolding dynamics is examined by the mean-square displacement (MSD) and the fractional diffusion and fractional kinetic equations. The collisionless (or ballistic) behavior of a polypeptide undergoing Brownian motion along the first few principal components is accounted for.

Characteristics of Gaseous Diffusion Flames with High Temperature Combustion Air in Microgravity

NASA Technical Reports Server (NTRS)

Ghaderi, M.; Gupta, A. K.

2003-01-01

The characteristics of gaseous diffusion flames have been obtained using high temperature combustion air under microgravity conditions. The time resolved flame images under free fall microgravity conditions were obtained from the video images obtained. The tests results reported here were conducted using propane as the fuel and about 1000 C combustion air. The burner included a 0.686 mm diameter central fuel jet injected into the surrounding high temperature combustion air. The fuel jet exit Reynolds number was 63. Several measurements were taken at different air preheats and fuel jet exit Reynolds number. The resulting hybrid color flame was found to be blue at the base of the flame followed by a yellow color flame. The length and width of flame during the entire free fall conditions has been examined. Also the relative flame length and width for blue and yellow portion of the flame has been examined under microgravity conditions. The results show that the flame length decreases and width increases with high air preheats in microgravity condition. In microgravity conditions the flame length is larger with normal temperature combustion air than high temperature air.

Spatially inhomogeneous acceleration of electrons in solar flares

NASA Astrophysics Data System (ADS)

Stackhouse, Duncan J.; Kontar, Eduard P.

2018-04-01

The imaging spectroscopy capabilities of the Reuven Ramaty high energy solar spectroscopic imager (RHESSI) enable the examination of the accelerated electron distribution throughout a solar flare region. In particular, it has been revealed that the energisation of these particles takes place over a region of finite size, sometimes resolved by RHESSI observations. In this paper, we present, for the first time, a spatially distributed acceleration model and investigate the role of inhomogeneous acceleration on the observed X-ray emission properties. We have modelled transport explicitly examining scatter-free and diffusive transport within the acceleration region and compare with the analytic leaky-box solution. The results show the importance of including this spatial variation when modelling electron acceleration in solar flares. The presence of an inhomogeneous, extended acceleration region produces a spectral index that is, in most cases, different from the simple leaky-box prediction. In particular, it results in a generally softer spectral index than predicted by the leaky-box solution, for both scatter-free and diffusive transport, and thus should be taken into account when modelling stochastic acceleration in solar flares.

[Primary central nervous system lymphoma mimicking ventriculitis].

PubMed

Yamamoto, Shiro; Nagano, Seiji; Shibata, Sumiya; Kunieda, Takeharu; Imai, Yukihiro; Kohara, Nobuo

2013-01-01

A 66-year-old man presented with deteriorated bradykinesia, gait disturbance, disorientation, and urinary incontinence for three weeks. Magnetic resonance imaging (MRI) showed dilatation of the ventricles. Cerebrospinal fluid (CSF) examination demonstrated lymphocytic pleocytosis, elevation of protein levels, and decreased of glucose levels. A gadolinium-enhanced MRI revealed lesions in the ventricular wall and choroid plexus, mimicking ventriculitis. No evidence of bacterial, fungal, mycobacterial, or viral infections were observed in the CSF. Flow cytometry of CSF showed predominance of CD20+, λ+ cells. PCR examination of CSF revealed positive IgH gene rearrangement, suggesting B cell lymphoma. Endoscopic brain biopsy showed diffuse large B cell lymphoma. As the patient had no evidence of lymphoma in the other organs, we made a diagnosed of primary central nervous system lymphoma (PCNSL). A limited intraventricular spread of PCNSL is rare but important as one of differential diagnosis of ventriculitis.

Diffusion across the modified polyethylene separator GX in the heat-sterilizable AgO-Zn battery

NASA Technical Reports Server (NTRS)

Lutwack, R.

1973-01-01

Models of diffusion across an inert membrane have been studied using the computer program CINDA. The models were constructed to simulate various conditions obtained in the consideration of the diffusion of Ag (OH)2 ions in the AgO-Zn battery. The effects on concentrations across the membrane at the steady state and on the fluxout as a function of time were used to examine the consequences of stepwise reducing the number of sources of ions, of stepwise blocking the source and sink surfaces, of varying the magnitude of the diffusion coefficient for a uniform membrane, of varying the diffusion coefficient across the membrane, and of excluding volumes to diffusion.

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.

A global ocean climatological atlas of the Turner angle: implications for double-diffusion and water-mass structure

NASA Astrophysics Data System (ADS)

You, Yuzhu

2002-11-01

The 1994 Levitus climatological atlas is used to calculate the Turner angle (named after J. Stewart Turner) to examine which oceanic water masses are favorable for double-diffusion in the form of diffusive convection or salt-fingering and which are doubly stable. This atlas complements the Levitus climatology. It reveals the major double-diffusive signals associated with large-scale water-mass structure. In total, about 44% of the oceans display double-diffusion, of which 30% is salt-fingering and 14% is diffusive double-diffusion. Results show that various central and deep waters are favorable for salt-fingering. The former is due to positive evaporation minus precipitation, and the latter is due to thermohaline circulation, i.e. the southward spreading of relatively warm, salty North Atlantic Deep Water (NADW) overlying cold, fresh Antarctic Bottom Water. In the northern Indian Ocean and eastern North Atlantic, favorable conditions for salt-fingering are found throughout the water column. The Red Sea (including the Persian Gulf) and Mediterranean Sea are the sources of warm, salty water for the ocean. As consequence, temperature and salinity in these outflow regions both decrease from the sea surface to the bottom. On the other hand, ocean currents are in general sluggish in these regions. In the polar and subpolar regions of Arctic and Antarctic, Okhotsk Sea, Gulf of Alaska, the subpolar gyre of the North Pacific, the Labrador Sea, and the Norwegian Sea, the upper layer water is favorable for diffusive convection because of high latitude surface cooling and ice melting. Weak and shallow diffusive convection is also found throughout tropical regions and the Bay of Bengal. The former is due to excessive precipitation over evaporation and rain cooling, and the latter is due to both precipitation and river runoff. Diffusive convection in the ocean's interior is unique to the South Atlantic between Antarctic Intermediate Water and upper NADW (uNADW). It is the consequence of the intrusive equatorward flow of upper Circumpolar Deep Water, which carries with it the minimum temperature and very low salinity overlying warm, salty uNADW.

Modeling the diffusion of complex innovations as a process of opinion formation through social networks.

PubMed

Assenova, Valentina A

2018-01-01

Complex innovations- ideas, practices, and technologies that hold uncertain benefits for potential adopters-often vary in their ability to diffuse in different communities over time. To explain why, I develop a model of innovation adoption in which agents engage in naïve (DeGroot) learning about the value of an innovation within their social networks. Using simulations on Bernoulli random graphs, I examine how adoption varies with network properties and with the distribution of initial opinions and adoption thresholds. The results show that: (i) low-density and high-asymmetry networks produce polarization in influence to adopt an innovation over time, (ii) increasing network density and asymmetry promote adoption under a variety of opinion and threshold distributions, and (iii) the optimal levels of density and asymmetry in networks depend on the distribution of thresholds: networks with high density (>0.25) and high asymmetry (>0.50) are optimal for maximizing diffusion when adoption thresholds are right-skewed (i.e., barriers to adoption are low), but networks with low density (<0.01) and low asymmetry (<0.25) are optimal when thresholds are left-skewed. I draw on data from a diffusion field experiment to predict adoption over time and compare the results to observed outcomes.

Microstructure and mechanical properties of diffusion bonded W/steel joint using V/Ni composite interlayer

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

Liu, W.S.; Cai, Q.S., E-mail: cai2009pm@163.com; Ma, Y.Z.

2013-12-15

Diffusion bonding between W and steel using V/Ni composite interlayer was carried out in vacuum at 1050 °C and 10 MPa for 1 h. The microstructural examination and mechanical property evaluation of the joints show that the bonding of W to steel was successful. No intermetallic compound was observed at the steel/Ni and V/W interfaces for the joints bonded. The electron probe microanalysis and X-ray diffraction analysis revealed that Ni{sub 3}V, Ni{sub 2}V, Ni{sub 2}V{sub 3} and NiV{sub 3} were formed at the Ni/V interface. The tensile strength of about 362 MPa was obtained for as-bonded W/steel joint and themore » failure occurred at W near the V/W interface. The nano-indentation test across the joining interfaces demonstrated the effect of solid solution strengthening and intermetallic compound formation in the diffusion zone. - Highlights: • Diffusion bonding of W to steel was realized using V/Ni composite interlayer. • The interfacial microstructure of the joint was clarified. • Several V–Ni intermetallic compounds were formed in the interface region. • The application of V/Ni composite interlayer improved the joining quality.« less

Movement of Cations through Cuticles of Citrus aurantium and Acer saccharum1

PubMed Central

Tyree, Melvin T.; Tabor, Christopher A.; Wescott, Charles R.

1990-01-01

We examined some biophysical mechanisms of ion migration across leaf cuticles enzymatically isolated from Acer saccharum L. and Citrus aurantium L. leaves. Diffusion potential measurements were used to calculate the permeabilities of Cl-, Li+, Na+, and Cs+ ions all as a ratio with respect to the permeability of K+ in cuticles. In 2 millimolar ionic strength solutions the permeability sequence from high to low was K = Cs > Na > Li » Cl. When the outer and inner surfaces of cuticles were bathed in artificial precipitation and artificial apoplast, respectively, diffusion potentials ranging from −52 to −91 millivolts were measured (inside negative). The Goldman equation predicted that the measured potentials were enough to increase the driving force on the accumulation of heavy metals by a factor of 4 to 7. Other ions migrate with forces 3 to 10 times less than predicted by the Goldman equation for concentration differences alone. Our analysis showed that Ca2+, and perhaps Mg2+, might even be accumulated against concentration gradients under some circumstances. Their uptake was apparently driven by the diffusion potentials created by the outward migration of monovalent salts. We feel that future models predicting leaching of nutrients from trees during acid rain events must be modified to account for the probable influence of diffusion potentials on ion migration. PMID:16667677

Performance of gas diffusion layer from coconut waste for proton exchange membrane fuel cell

NASA Astrophysics Data System (ADS)

Widodo, H.; Destyorini, F.; Insiyanda, D. R.; Subhan, A.

2017-04-01

The performance of Gas Diffusion Layer (GDL) synthesized from coconut waste. Gas Diffusion Layer (GDL), produced from coconut waste, as a part of Proton Exchange Membrane Fuel Cell (PEMFC) component, has been characterized. In order to know the performance, the commercial products were used as the remaining parts of PEMFC. The proposed GDL possesses 69% porosity for diffusion of Hydrogen fuel and Oxygen, as well as for transporting electron. With the electrical conductivity of 500 mS.cm-1, it also has hydrophobic properties, which is important to avoid the reaction with water, with the contact angle of 139°. The 5 × 5 cm2 GDL paper was co-assembled with the catalyst, Nafion membrane, bipolar plate, current collector, end plate to obtain single Stack PEMFC. The performance was examined by flowing fuel and gas with the flow rate of 500 and 1000 ml.min-1, respectively, and analyse the I-V polarization curve. The measurements were carried out at 30, 35, and 40°C for 5 cycles to ensure the repeatability. The results shows that the current density and the maximum power density reaches 203 mA.cm-2 and 143 mW.cm-2, respectively, with a given voltage 0.6 V, at 40°C.

An assessment of optical and biogeochemical multi-decadal trends in the Sargasso Sea

NASA Astrophysics Data System (ADS)

Allen, J. G.; Siegel, D.; Nelson, N. B.

2016-02-01

Observations of optical and biogeochemical data, made as part of the Bermuda Bio-Optics Project (BBOP) at the Bermuda Atlantic Time-series Study (BATS) site in the Sargasso Sea, allow for the examination of temporal trends in vertical light attenuation and their potential controls. Trends in both the magnitude and spectral slope of the diffuse attenuation coefficient should reflect changes in chlorophyll and chromophoric dissolved organic matter (CDOM) concentrations in the Sargasso Sea. The length and methodological consistency of this time series provides an excellent opportunity to extend analyses of seasonal cycles of apparent optical properties to interannual and multi-year time scales. Here, we characterize changes in the size and shape of diffuse attenuation coefficient spectra and compare them to temperature, chlorophyll a concentration, and to discrete measurements of phytoplankton and CDOM absorption. The time series analyses reveal up to a 1.2% annual increase of the magnitude of the diffuse attenuation coefficient over the upper 70 m of the water column while showing no significant change in the spectral slope of diffuse attenuation over the course of the study. These observations indicate that increases in phytoplankton pigment concentration rather than changes in CDOM are the primary driver for the attenuation trends on multi-year timescales for this region.

Modification of the flow pass method as applied to problems of chemistry of planet atmospheres

NASA Technical Reports Server (NTRS)

Parshev, V. A.

1980-01-01

It was shown that the modified flow pass method possesses considerable effectiveness, both in the case when the coefficient of diffusion changes severely in the examined region and in the case when diffusion is the prevalent process, as compared with chemical reactions. The case when a regular pass proves inapplicable, or applicable in a limited interval of the decisive parameters, was examined.

Modeling and experiments for the time-dependent diffusion coefficient during methane desorption from coal

NASA Astrophysics Data System (ADS)

Cheng-Wu, Li; Hong-Lai, Xue; Cheng, Guan; Wen-biao, Liu

2018-04-01

Statistical analysis shows that in the coal matrix, the diffusion coefficient for methane is time-varying, and its integral satisfies the formula μt κ /(1 + β κ ). Therefore, a so-called dynamic diffusion coefficient model (DDC model) is developed. To verify the suitability and accuracy of the DDC model, a series of gas diffusion experiments were conducted using coal particles of different sizes. The results show that the experimental data can be accurately described by the DDC and bidisperse models, but the fit to the DDC model is slightly better. For all coal samples, as time increases, the effective diffusion coefficient first shows a sudden drop, followed by a gradual decrease before stabilizing at longer times. The effective diffusion coefficient has a negative relationship with the size of the coal particle. Finally, the relationship between the constants of the DDC model and the effective diffusion coefficient is discussed. The constant α (μ/R 2 ) denotes the effective coefficient at the initial time, and the constants κ and β control the attenuation characteristic of the effective diffusion coefficient.

Visual White Matter Integrity in Schizophrenia

PubMed Central

Butler, Pamela D.; Hoptman, Matthew J.; Nierenberg, Jay; Foxe, John J.; Javitt, Daniel C.; Lim, Kelvin O.

2007-01-01

Objective Patients with schizophrenia have visual-processing deficits. This study examines visual white matter integrity as a potential mechanism for these deficits. Method Diffusion tensor imaging was used to examine white matter integrity at four levels of the visual system in 17 patients with schizophrenia and 21 comparison subjects. The levels examined were the optic radiations, the striate cortex, the inferior parietal lobule, and the fusiform gyrus. Results Schizophrenia patients showed a significant decrease in fractional anisotropy in the optic radiations but not in any other region. Conclusions This finding indicates that white matter integrity is more impaired at initial input, rather than at higher levels of the visual system, and supports the hypothesis that visual-processing deficits occur at the early stages of processing. PMID:17074957

Estimation of Sorption Behavior of Europium(III) Using Biotite Flakes - 13272

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

Sasaki, Go; Niibori, Yuichi; Mimura, Hitoshi

2013-07-01

The interaction of biotite and Eu(III) (europium (III)) was examined by using secondary ion-microprobe mass spectrometer (SIMS), fluorescence emission spectrum and decay behavior of fluorescence emission spectrum in addition to the time-changes of Eu(III) and potassium ions concentrations in a solution, using the flake form samples. The results of SIMS showed that the intensity of Eu was gradually decreasing with depth, while the intensity of Eu in the case shaken for 30 days exceeded that in the case for 1 day. Furthermore, the spatial distribution of Eu(III) and potassium ions in the flake of biotite suggested that Eu ions diffusemore » mainly from the edges of biotite flake, while Eu ions can slightly diffuse through some small cracks existing on the flake surface far from the edges. Besides, the elution amount of potassium from the biotite flakes into a solution was proportional to the sorption amount of Eu(III). The changes nearly revealed ion exchange between these ions, while muscovite flake sample did not show such ion exchange reaction. In addition, from the time-change of Eu(III) concentration, an apparent diffusion coefficient was estimated to be 8.0x10{sup -12} m{sup 2}/s, by using two-dimensional diffusion model coupled with a film between the solid phase and the liquid phase. Furthermore, the fluorescent intensity decreased with the shaking (contacting) time. This means that Eu(III) gradually diffuses into the inside of biotite edges of the biotite flakes, after the sorption of Eu(III) in the edges. This tendency was observed also in the powder samples. The observed fluorescence decay (at 592 nm in wave length) showed almost similar curve in any samples, indicating a certain sorption form of Eu(III) onto the edges of the biotite flakes. These results mentioned above suggest that the diffusion processes through internal layer in biotite mainly control the sorption behavior of multivalent ions. Such diffusion processes affect the retardation-effects on fracture surfaces in the rock matrix, depending on the fluid flow velocity of groundwater. That is, a more reliable model considering the mass transfer in the internal layer of biotite may be required to estimate the sorption behavior of RNs with biotite which controls the whole sorption behavior of granite. (authors)« less

Collective diffusion and quantum chaos in holography

NASA Astrophysics Data System (ADS)

Wu, Shao-Feng; Wang, Bin; Ge, Xian-Hui; Tian, Yu

2018-05-01

We define a particular combination of charge and heat currents that is decoupled with the heat current. This "heat-decoupled" (HD) current can be transported by diffusion at long distances, when some thermoelectric conductivities and susceptibilities satisfy a simple condition. Using the diffusion condition together with the Kelvin formula, we show that the HD diffusivity can be same as the charge diffusivity and also the heat diffusivity. We illustrate that such mechanism is implemented in a strongly coupled field theory, which is dual to a Lifshitz gravity with the dynamical critical index z =2 . In particular, it is exhibited that both charge and heat diffusivities build the relationship to the quantum chaos. Moreover, we study the HD diffusivity without imposing the diffusion condition. In some homogeneous holographic lattices, it is found that the diffusivity/chaos relation holds independently of any parameters, including the strength of momentum relaxation, chemical potential, or temperature. We also show a counter example of the relation and discuss its limited universality.

Immunohistochemical assessment of NY-ESO-1 expression in esophageal adenocarcinoma resection specimens.

PubMed

Hayes, Stephen J; Hng, Keng Ngee; Clark, Peter; Thistlethwaite, Fiona; Hawkins, Robert E; Ang, Yeng

2014-04-14

To assess NY-ESO-1 expression in a cohort of esophageal adenocarcinomas. A retrospective search of our tissue archive for esophageal resection specimens containing esophageal adenocarcinoma was performed, for cases which had previously been reported for diagnostic purposes, using the systematised nomenclature of human and veterinary medicine coding system. Original haematoxylin and eosin stained sections were reviewed, using light microscopy, to confirm classification and tumour differentiation. A total of 27 adenocarcinoma resection specimens were then assessed using immunohistochemistry for NY-ESO-1 expression: 4 well differentiated, 14 moderately differentiated, 4 moderate-poorly differentiated, and 5 poorly differentiated. Four out of a total of 27 cases of esophageal adenocarcinoma examined (15%) displayed diffuse cytoplasmic and nuclear expression for NY-ESO-1. They displayed a heterogeneous and mosaic-type pattern of diffuse staining. Diffuse cytoplasmic staining was not identified in any of these structures: stroma, normal squamous epithelium, normal submucosal gland and duct, Barrett's esophagus (goblet cell), Barrett's esophagus (non-goblet cell) and high grade glandular dysplasia. All adenocarcinomas showed an unexpected dot-type pattern of staining at nuclear, paranuclear and cytoplasmic locations. Similar dot-type staining, with varying frequency and size of dots, was observed on examination of Barrett's metaplasia, esophageal submucosal gland acini and the large bowel negative control, predominantly at the crypt base. Furthermore, a prominent pattern of apical (luminal) cytoplasmic dot-type staining was observed in some cases of Barrett's metaplasia and also adenocarcinoma. A further morphological finding of interest was noted on examination of haematoxylin and eosin stained sections, as aggregates of lymphocytes were consistently noted to surround submucosal glands. We have demonstrated for the first time NY-ESO-1 expression by esophageal adenocarcinomas, Barrett's metaplasia and normal tissues other than germ cells.

Immunohistochemical assessment of NY-ESO-1 expression in esophageal adenocarcinoma resection specimens

PubMed Central

Hayes, Stephen J; Hng, Keng Ngee; Clark, Peter; Thistlethwaite, Fiona; Hawkins, Robert E; Ang, Yeng

2014-01-01

AIM: To assess NY-ESO-1 expression in a cohort of esophageal adenocarcinomas. METHODS: A retrospective search of our tissue archive for esophageal resection specimens containing esophageal adenocarcinoma was performed, for cases which had previously been reported for diagnostic purposes, using the systematised nomenclature of human and veterinary medicine coding system. Original haematoxylin and eosin stained sections were reviewed, using light microscopy, to confirm classification and tumour differentiation. A total of 27 adenocarcinoma resection specimens were then assessed using immunohistochemistry for NY-ESO-1 expression: 4 well differentiated, 14 moderately differentiated, 4 moderate-poorly differentiated, and 5 poorly differentiated. RESULTS: Four out of a total of 27 cases of esophageal adenocarcinoma examined (15%) displayed diffuse cytoplasmic and nuclear expression for NY-ESO-1. They displayed a heterogeneous and mosaic-type pattern of diffuse staining. Diffuse cytoplasmic staining was not identified in any of these structures: stroma, normal squamous epithelium, normal submucosal gland and duct, Barrett’s esophagus (goblet cell), Barrett’s esophagus (non-goblet cell) and high grade glandular dysplasia. All adenocarcinomas showed an unexpected dot-type pattern of staining at nuclear, paranuclear and cytoplasmic locations. Similar dot-type staining, with varying frequency and size of dots, was observed on examination of Barrett’s metaplasia, esophageal submucosal gland acini and the large bowel negative control, predominantly at the crypt base. Furthermore, a prominent pattern of apical (luminal) cytoplasmic dot-type staining was observed in some cases of Barrett’s metaplasia and also adenocarcinoma. A further morphological finding of interest was noted on examination of haematoxylin and eosin stained sections, as aggregates of lymphocytes were consistently noted to surround submucosal glands. CONCLUSION: We have demonstrated for the first time NY-ESO-1 expression by esophageal adenocarcinomas, Barrett’s metaplasia and normal tissues other than germ cells. PMID:24744590

In vivo tomographic imaging of lung colonization of tumour in mouse with simultaneous fluorescence and X-ray CT.

PubMed

Zhang, Bin; Gao, Fuping; Wang, Mengjiao; Cao, Xu; Liu, Fei; Wang, Xin; Luo, Jianwen; Wang, Guangzhi; Bai, Jing

2014-01-01

Non-invasive in vivo imaging of diffuse and wide-spread colonization within the lungs, rather than distinct solid primary tumors, is still a challenging work. In this work, a lung colonization mouse model bearing A549 human lung tumor was simultaneously scanned by a dual-modality fluorescence molecular tomography (FMT) and X-ray computed tomography (CT) system in vivo. A two steps method which incorporates CT structural information into the FMT reconstruction procedure is employed to provide concurrent anatomical and functional information. By using the target-specific fluorescence agent, the fluorescence tomographic results show elevated fluorescence intensity deep within the lungs which is colonized with diffuse and wide-spread tumors. The results were confirmed with ex vivo fluorescence reflectance imaging and histological examination of the lung tissues. With FMT reconstruction combined with the CT information, the dual-modality FMT/micro-CT system is expected to offer sensitive and noninvasive imaging of diffuse tumor colonization within the lungs in vivo. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stretched-to-compressed-exponential crossover observed in the electrical degradation kinetics of some spinel-metallic screen-printed structures

NASA Astrophysics Data System (ADS)

Balitska, V.; Shpotyuk, O.; Brunner, M.; Hadzaman, I.

2018-02-01

Thermally-induced (170 °C) degradation-relaxation kinetics is examined in screen-printed structures composed of spinel Cu0.1Ni0.1Co1.6Mn1.2O4 ceramics with conductive Ag or Ag-Pd layered electrodes. Structural inhomogeneities due to Ag and Ag-Pd diffusants in spinel phase environment play a decisive role in non-exponential kinetics of negative relative resistance drift. If Ag migration in spinel is inhibited by Pd addition due to Ag-Pd alloy, the kinetics attains stretched exponential behavior with ∼0.58 exponent, typical for one-stage diffusion in structurally-dispersive media. Under deep Ag penetration into spinel ceramics, as for thick films with Ag-layered electrodes, the degradation kinetics drastically changes, attaining features of two-step diffusing process governed by compressed-exponential dependence with power index of ∼1.68. Crossover from stretched- to compressed-exponential kinetics in spinel-metallic structures is mapped on free energy landscape of non-barrier multi-well system under strong perturbation from equilibrium, showing transition with a character downhill scenario resulting in faster than exponential decaying.

Active compound diffusivity of particle size reduced S. aromaticum and C. cassia fused starch edible films and the shelf life of mutton (Capra aegagrus hircus) meat.

PubMed

Chandra Mohan, C; Radha Krishnan, K; Babuskin, S; Sudharsan, K; Aafrin, Vajiha; Lalitha Priya, U; Mariyajenita, P; Harini, K; Madhushalini, D; Sukumar, M

2017-06-01

In the present study, mathematical models were used to examine the effect of active compound diffusion from edible film (supplemented with S. aromaticum and C. cassia) on the microbial, physical and chemical quality of mutton stored at 4 and 10°C. Cinnamaldehyde and eugenol release from edible film into liquid was found to be 80% and 75% of the equilibrium concentration. Active compound release into meat was 42-51% for cinnamaldehyde and 38-48% for eugenol, in storage temperatures of 4-15°C. Developed mathematical models showed the diffusivity of cinnamaldehyde (0.45×10 -15 ±0.04×10 -15 ) and eugenol (0.63×10 -10 ±0.01×10 -10 ) into meat, which was about 40% of that in liquid medium. On comparing physical, chemical and microbial results, shelf life of mutton meat was found to be increased by 1week at storage temperature of 10°C and 3weeks at storage temperature of 4°C. Copyright © 2017 Elsevier Ltd. All rights reserved.

Search for the source of an apparent interfacial resistance to mass transfer of CnEm surfactants to the water/oil interface.

PubMed

Huston, Kyle J; Kiemen, Ashley; Larson, Ronald G

2018-06-12

Experiments have shown that relaxation of oil/water interfacial tension by adsorption of alkyl ethoxylate surfactants from water onto an oil droplet is delayed relative to diffusion-controlled adsorption. We examine possible causes of this delay, and we show that several are implausible. We find that re-dissolution of the surfactant in the oil droplet cannot explain the apparent interfacial resistance at short times, because the interface will preferentially fill before any such re-dissolution occurs. We also perform umbrella sampling with molecular dynamics simulation and do not find any evidence of a free energy barrier or low-diffusivity zone near the interface. Nor do we find evidence from simulation that pre-micellar aggregation slows diffusion enough to cause the observed resistance to interfacial adsorption. We are therefore unable to pinpoint the cause of the resistance, but we suggest that "dead time" associated with the experimental method could be responsible - specifically a local depletion of surfactant by the ejected droplet when creating the fresh interface between the oil and water.

NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 5: Aerospace librarians and technical information specialists as information intermediaries: A report of phase 2 activities of the NASA/DOD Aerospace Knowledge Diffusion Research Project

NASA Technical Reports Server (NTRS)

Pinelli, Thomas E.; Kennedy, John M.

1990-01-01

The flow of U.S. government-funded and foreign scientific and technical information (STI) through libraries and related facilities to users in government and industry is examined, summarizing preliminary results of Phase 2 of the NASA/DOD Aerospace Knowledge Diffusion Research Project (NAKDRP). The design and objectives of NAKDRP are reviewed; the NAKDRP model of STI transfer among producers, STI intermediaries, surrogates (technical report repositories or clearinghouses), and users is explained and illustrated with diagrams; and particular attention is given to the organization and operation of aerospace libraries. In a survey of North American libraries it was found that 25-30 percent of libraries regularly receive technical reports from ESA and the UK; the corresponding figures for Germany and for France, Sweden, and Japan are 18 and 5 percent, respectively. Also included is a series of bar graphs showing the librarians' assessments of the quality and use of NASA Technical Reports.

Can phoretic particles swim in two dimensions?

NASA Astrophysics Data System (ADS)

Sondak, David; Hawley, Cory; Heng, Siyu; Vinsonhaler, Rebecca; Lauga, Eric; Thiffeault, Jean-Luc

2016-12-01

Artificial phoretic particles swim using self-generated gradients in chemical species (self-diffusiophoresis) or charges and currents (self-electrophoresis). These particles can be used to study the physics of collective motion in active matter and might have promising applications in bioengineering. In the case of self-diffusiophoresis, the classical physical model relies on a steady solution of the diffusion equation, from which chemical gradients, phoretic flows, and ultimately the swimming velocity may be derived. Motivated by disk-shaped particles in thin films and under confinement, we examine the extension to two dimensions. Because the two-dimensional diffusion equation lacks a steady state with the correct boundary conditions, Laplace transforms must be used to study the long-time behavior of the problem and determine the swimming velocity. For fixed chemical fluxes on the particle surface, we find that the swimming velocity ultimately always decays logarithmically in time. In the case of finite Péclet numbers, we solve the full advection-diffusion equation numerically and show that this decay can be avoided by the particle moving to regions of unconsumed reactant. Finite advection thus regularizes the two-dimensional phoretic problem.

Gauge calibration by diffusion

NASA Technical Reports Server (NTRS)

Brock, F. J.; Feakes, F. (Inventor)

1968-01-01

Vacuum gage calibration by diffusing a known quantity of gas through a heated barrier into a gauge is examined. The gas flow raises the pressure in the gauge to known level and is then compared with the gauge's pressure reading.

Ultra-Widefield Fluorescein Angiography in Intermediate Uveitis.

PubMed

Laovirojjanakul, Wipada; Acharya, Nisha; Gonzales, John A

2017-10-17

To examine associations between pattern of vascular leakage on ultrawide-field fluorescein angiography (UWFFA) and visual acuity, cystoid macular edema (CME), and inflammatory activity in intermediate uveitis. Single center cross-sectional, retrospective review of medical records, spectral domain optical coherence tomography (SD-OCT) and angiographic images of intermediate uveitis patients who underwent UWFFA over a 12-month period. Forty-one eyes from 24 patients were included. Twelve eyes (29%) exhibited peripheral leakage, 26 eyes (64%) had diffuse leakage and three eyes (7%) had no leakage. Diffuse leakage was associated with 0.2 logMAR worse visual acuity than peripheral leakage (p = 0.02). There was no statistically significant difference in the odds of having CME when diffuse leakage was compared to peripheral leakage. UWFFA identifies retinal vascular pathology in intermediate uveitis not present on clinical examination. Diffuse retinal vascular leakage was associated with worse visual acuity when compared to peripheral and no leakage patterns.

Is the kinetic equation for turbulent gas-particle flows ill posed?

PubMed

Reeks, M; Swailes, D C; Bragg, A D

2018-02-01

This paper is about the kinetic equation for gas-particle flows, in particular its well-posedness and realizability and its relationship to the generalized Langevin model (GLM) probability density function (PDF) equation. Previous analyses, e.g. [J.-P. Minier and C. Profeta, Phys. Rev. E 92, 053020 (2015)PLEEE81539-375510.1103/PhysRevE.92.053020], have concluded that this kinetic equation is ill posed, that in particular it has the properties of a backward heat equation, and as a consequence, its solution will in the course of time exhibit finite-time singularities. We show that this conclusion is fundamentally flawed because it ignores the coupling between the phase space variables in the kinetic equation and the time and particle inertia dependence of the phase space diffusion tensor. This contributes an extra positive diffusion that always outweighs the negative diffusion associated with the dispersion along one of the principal axes of the phase space diffusion tensor. This is confirmed by a numerical evaluation of analytic solutions of these positive and negative contributions to the particle diffusion coefficient along this principal axis. We also examine other erroneous claims and assumptions made in previous studies that demonstrate the apparent superiority of the GLM PDF approach over the kinetic approach. In so doing, we have drawn attention to the limitations of the GLM approach, which these studies have ignored or not properly considered, to give a more balanced appraisal of the benefits of both PDF approaches.

Persistent Microstructural Deficits of Internal Capsule in One-Year Abstinent Male Methamphetamine Users: a Longitudinal Diffusion Tensor Imaging Study.

PubMed

Zhuang, Wenxu; Tang, Yingying; Zhong, Na; Jiang, Haifeng; Du, Jiang; Wang, Jijun; Zhao, Min

2016-09-01

White matter (WM) alterations have been reported in methamphetamine (MA) users. However, knowledge about longitudinal changes in WM during abstinence from MA remains unknown. The present study aimed to examine how WM changes in long-term MA abstinent, in particular, whether the WM deficits would recover as the duration of abstinence extended. Twenty male MA dependent individuals and 19 healthy controls (HCs) were recruited and participated in both clinical assessments and diffusion tensor imaging (DTI) scans. The MA group underwent two DTI scans, a baseline scan with a duration of abstinence of 6.4 months and and a follow-up scan with a duration of abstinence of 13.0 months. Tract-Based Spatial Statistics was utilized to conduct baseline DTI analysis of MA group compared with HCs. The clusters with significant group differences of factional anisotropy (FA) were extracted as region of interests (ROIs). Mean values of DTI measurements (FA, mean diffusivity, axial diffusivity and radial diffusivity) were calculated within the ROIs in each subject's native space at baseline and follow-up. The MA group showed significant lower FA in the right internal capsule and superior corona radiate than HCs. The deficits did not recover when the duration of abstinence from MA reached 13 months. No significant correlations were found between FA and clinical measurements. Our results suggested persistent microstructure deficits of WM tracts surrounding the basal ganglia in MA dependent individuals.

[A novel compound heterozygous mutation in ABCA3 gene in a child with diffuse parenchymal lung disease].

PubMed

Bao, Y M; Liu, X L; Liu, X L; Chen, J H; Zheng, Y J

2017-11-02

Objective: To summarize the clinical characteristics of the diffuse parenchymal lung diseases in a child caused by a novel compound heterozygous ABCA3 mutation and explore the association between the phenotype and ABCA3 mutation. Method: The clinical material of a patient diagnosed with diffuse parenchymal lung disease with ABCA3 mutation in December 2016 in Shenzhen Children's Hospital was analyzed. The information about ABCA3 gene mutation updated before April, 2017 was searched and collected from the gene databases (including 1000Genomes, HGMD, EXAC) and the literatures (including Wanfang Chinese database and Pubmed). Result: The girl was one year and nine months old. She presented with chronic cough, tachypnea, cyanosis and failure to thrive since she was one year and three months old. Her condition gradually deteriorated after she was empirically treated. Physical examination showed malnutrition, tachypnea and clubbed-fingers. Her high resolution computed tomography (HRCT) revealed diffused ground-glass opacities, thickened interlobular septum, and multiple subpleural small air-filled lung cysts. The second generation sequencing study identified a novel compound heterozygous mutation (c.1755delC+c.2890G>A) in her ABCA3 gene, which derived respectively from her parents and has not been reported in the database and the literatures mentioned above. Conclusion: c.1755delC+c.2890G>A is a new kind of compound heterozygous mutation in ABCA3, which can cause children's diffuse parenchymal lung disease. Its phenotype is related to its genotype.

A Babcock-Leighton Solar Dynamo Model with Multi-cellular Meridional Circulation in Advection- and Diffusion-dominated Regimes

NASA Astrophysics Data System (ADS)

Belucz, Bernadett; Dikpati, Mausumi; Forgács-Dajka, Emese

2015-06-01

Babcock-Leighton type-solar dynamo models with single-celled meridional circulation are successful in reproducing many solar cycle features. Recent observations and theoretical models of meridional circulation do not indicate a single-celled flow pattern. We examine the role of complex multi-cellular circulation patterns in a Babcock-Leighton solar dynamo in advection- and diffusion-dominated regimes. We show from simulations that the presence of a weak, second, high-latitude reverse cell speeds up the cycle and slightly enhances the poleward branch in the butterfly diagram, whereas the presence of a second cell in depth reverses the tilt of the butterfly wing to an antisolar type. A butterfly diagram constructed from the middle of convection zone yields a solar-like pattern, but this may be difficult to realize in the Sun because of magnetic buoyancy effects. Each of the above cases behaves similarly in higher and lower magnetic diffusivity regimes. However, our dynamo with a meridional circulation containing four cells in latitude behaves distinctly differently in the two regimes, producing solar-like butterfly diagrams with fast cycles in the higher diffusivity regime, and complex branches in butterfly diagrams in the lower diffusivity regime. We also find that dynamo solutions for a four-celled pattern, two in radius and two in latitude, prefer to quickly relax to quadrupolar parity if the bottom flow speed is strong enough, of similar order of magnitude as the surface flow speed.

Reconstructing in-vivo reflectance spectrum of pigmented skin lesion by Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Wang, Shuang; He, Qingli; Zhao, Jianhua; Lui, Harvey; Zeng, Haishan

2012-03-01

In dermatology applications, diffuse reflectance spectroscopy has been extensively investigated as a promising tool for the noninvasive method to distinguish melanoma from benign pigmented skin lesion (nevus), which is concentrated with the skin chromophores like melanin and hemoglobin. We carried out a theoretical study to examine melanin distribution in human skin tissue and establish a practical optical model for further pigmented skin investigation. The theoretical simulation was using junctional nevus as an example. A multiple layer skin optical model was developed on established anatomy structures of skin, the published optical parameters of different skin layers, blood and melanin. Monte Carlo simulation was used to model the interaction between excitation light and skin tissue and rebuild the diffuse reflectance process from skin tissue. A testified methodology was adopted to determine melanin contents in human skin based on in vivo diffuse reflectance spectra. The rebuild diffuse reflectance spectra were investigated by adding melanin into different layers of the theoretical model. One of in vivo reflectance spectra from Junctional nevi and their surrounding normal skin was studied by compare the ratio between nevus and normal skin tissue in both the experimental and simulated diffuse reflectance spectra. The simulation result showed a good agreement with our clinical measurements, which indicated that our research method, including the spectral ratio method, skin optical model and modifying the melanin content in the model, could be applied in further theoretical simulation of pigmented skin lesions.

A BABCOCK–LEIGHTON SOLAR DYNAMO MODEL WITH MULTI-CELLULAR MERIDIONAL CIRCULATION IN ADVECTION- AND DIFFUSION-DOMINATED REGIMES

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

Belucz, Bernadett; Forgács-Dajka, Emese; Dikpati, Mausumi, E-mail: bbelucz@astro.elte.hu, E-mail: dikpati@ucar.edu

Babcock–Leighton type-solar dynamo models with single-celled meridional circulation are successful in reproducing many solar cycle features. Recent observations and theoretical models of meridional circulation do not indicate a single-celled flow pattern. We examine the role of complex multi-cellular circulation patterns in a Babcock–Leighton solar dynamo in advection- and diffusion-dominated regimes. We show from simulations that the presence of a weak, second, high-latitude reverse cell speeds up the cycle and slightly enhances the poleward branch in the butterfly diagram, whereas the presence of a second cell in depth reverses the tilt of the butterfly wing to an antisolar type. A butterflymore » diagram constructed from the middle of convection zone yields a solar-like pattern, but this may be difficult to realize in the Sun because of magnetic buoyancy effects. Each of the above cases behaves similarly in higher and lower magnetic diffusivity regimes. However, our dynamo with a meridional circulation containing four cells in latitude behaves distinctly differently in the two regimes, producing solar-like butterfly diagrams with fast cycles in the higher diffusivity regime, and complex branches in butterfly diagrams in the lower diffusivity regime. We also find that dynamo solutions for a four-celled pattern, two in radius and two in latitude, prefer to quickly relax to quadrupolar parity if the bottom flow speed is strong enough, of similar order of magnitude as the surface flow speed.« less

Quantum enhancement of momentum diffusion in the delta-kicked rotor.

PubMed

d'Arcy, M B; Godun, R M; Oberthaler, M K; Cassettari, D; Summy, G S

2001-08-13

We present detailed observations of the quantum delta-kicked rotor in the vicinity of a quantum resonance. Our experiment consists of an ensemble of cold cesium atoms subject to a pulsed off-resonant standing wave of light. We measure the mean energy and show clearly that at the quantum resonance it is a local maximum. We also examine the effect of noise on the system and find that the greatest sensitivity to this occurs at the resonances. This makes these regions ideal for examining quantum-classical correspondence. A picture based on diffraction is developed which allows the experiments to be readily understood.

A Study of Aerosol Direct Radiative Effect and Its Impacts on Global Terrestrial Ecosystem Cycles

NASA Astrophysics Data System (ADS)

Zhang, J.; Shao, S.; Zhou, L.

2017-12-01

Aerosols can absorb and scatter solar radiation, thus cause the total solar radiation reaching the surface to drop and the fraction of diffuse radiation to increase, which influence the surface radiation budget. The global surface radiation with and without consideration of aerosols are calculated by the Fu-Liou atmospheric radiative transfer model based on the MODIS aerosol products, CERES cloud products and other remote sensing data. The aerosol direct radiative effect is calculated based on the two scenarios of aerosols. Our calculation showed that in 2007, aerosols decreased the global total radiation by 9.16 W m-2 on average. Large decrease generally occurred in places with high AOD. As for the diffuse radiation, aerosol-induced changes were either positive or negative. Large increase generally occurred in places with high surface albedo, while large decrease generally occurred in places with high cloud fraction. The global aerosol-induced diffuse radiation change averaged 8.17 W m-2 in 2007. The aerosol direct radiative effect causes the photosynthetic active radiation to increase, and its influences on the global carbon cycle of terrestrial ecosystem are studied by using the Community Land Model (CLM). Calculations show that the aerosol direct radiative effects caused the global averages of terrestrial gross primary productivity (GPP), net primary productivity (NPP), heterotrophic respiration (RH), autotrophic respiration (RA), and net ecosystem productivity (Reco) to increase in 2007, with significant spatial variations however. The global average changes of GPP, NPP, NEP, RA, RH and Reco in 2007 were +6.47 gC m-2, +2.23 gC m-2, +0.34 gC m-2, +4.24 gC m-2, +1.89 gC m-2, +6.13 gC m-2, respectively. Examinations of the carbon fluxes show that the aerosol direct radiative effects influence the terrestrial ecosystem carbon cycles via the following two approaches: First, the diffuse fertilization effect, i.e. more diffuse radiation absorbed by vegetation shade leaves (photosynthetic active radiation, PAR) results in higher photosynthetic rates; Second, the radiation changes lead to changes in temperature and humidity, thereby changing the rates of the plant biophysical and chemical processes.

Anomalous fast diffusion in Cu-NiFe nanolaminates.

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

Jankowski, Alan F.

2017-09-01

For this work, the decomposition of the one-dimensional composition wave in Cu-NiFe nanolaminate structures is examined using x-ray diffraction to assess the kinetics of phase decomposition. The anomalously high diffusivity value found for long-term aging at room temperature is attributed to the inherent nanostructure that features paths for short-circuit diffusion in nanolaminates as attributed to interlayer grain boundaries.

Relationship between the anomalous diffusion and the fractal dimension of the environment

NASA Astrophysics Data System (ADS)

Zhokh, Alexey; Trypolskyi, Andrey; Strizhak, Peter

2018-03-01

In this letter, we provide an experimental study highlighting a relation between the anomalous diffusion and the fractal dimension of the environment using the methanol anomalous transport through the porous solid pellets with various pores geometries and different chemical compositions. The anomalous diffusion exponent was derived from the non-integer order of the time-fractional diffusion equation that describes the methanol anomalous transport through the solid media. The surface fractal dimension was estimated from the nitrogen adsorption isotherms using the Frenkel-Halsey-Hill method. Our study shows that decreasing the fractal dimension leads to increasing the anomalous diffusion exponent, whereas the anomalous diffusion constant is independent on the fractal dimension. We show that the obtained results are in a good agreement with the anomalous diffusion model on a fractal mesh.

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.

Malignant anterior uveal melanoma with diffuse metastasis in a dog.

PubMed

Minami, T; Patnaik, A K

1992-12-15

Enucleation was performed in 10-year-old sexually intact female mixed-breed German Shepherd Dog. Histologic examination revealed that the dog had an uveal amelanotic melanoma of the eye. The tumor consisted of anaplastic cells with a high mitotic index, indicating malignancy. On examination 3 months after enucleation, the dog had difficulty breathing and nasal discharge. Radiography revealed pulmonary metastasis. The dog was euthanatized. Necropsy revealed diffuse metastasis involving various organs.

Identification of prefrontal cortex (BA10) activation while performing Stroop test using diffuse optical tomography

NASA Astrophysics Data System (ADS)

Khadka, Sabin; Chityala, Srujan R.; Tian, Fenghua; Liu, Hanli

2011-03-01

Stroop test is commonly used as a behavior-testing tool for psychological examinations that are related to attention and cognitive control of the human brain. Studies have shown activations in Broadmann area 10 (BA10) of prefrontal cortex (PFC) during attention and cognitive process. The use of diffuse optical tomography (DOT) for human brain mapping is becoming more prevalent. In this study we expect to find neural correlates between the performed cognitive tasks and hemodynamic signals detected by a DOT system. Our initial observation showed activation of oxy-hemoglobin concentration in BA 10, which is consistent with some results seen by positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). Our study demonstrates the possibility of combining DOT with Stroop test to quantitatively investigate cognitive functions of the human brain at the prefrontal cortex.

Disentangling Random Motion and Flow in a Complex Medium

PubMed Central

Koslover, Elena F.; Chan, Caleb K.; Theriot, Julie A.

2016-01-01

We describe a technique for deconvolving the stochastic motion of particles from large-scale fluid flow in a dynamic environment such as that found in living cells. The method leverages the separation of timescales to subtract out the persistent component of motion from single-particle trajectories. The mean-squared displacement of the resulting trajectories is rescaled so as to enable robust extraction of the diffusion coefficient and subdiffusive scaling exponent of the stochastic motion. We demonstrate the applicability of the method for characterizing both diffusive and fractional Brownian motion overlaid by flow and analytically calculate the accuracy of the method in different parameter regimes. This technique is employed to analyze the motion of lysosomes in motile neutrophil-like cells, showing that the cytoplasm of these cells behaves as a viscous fluid at the timescales examined. PMID:26840734

m=1 diocotron mode damping in the Electron Diffusion Gauge (EDG) experiment

NASA Astrophysics Data System (ADS)

Paul, Stephen F.; Morrison, Kyle A.; Davidson, Ronald C.; Jenkins, Thomas G.

2002-01-01

The evolution of the amplitude of the m=1 diocotron mode is used to measure the background neutral pressure in the Electron Diffusion Gauge (EDG), a Malmberg-Penning trap. Below 5×10-8 Torr, the dependence on pressure scales as P1/4, and is sensitive to pressure changes as small as ΔP=5×10-11 Torr. Previous studies on the EDG showed that the diocotron mode is more strongly damped at higher neutral pressures. Both the diocotron mode damping rate and the plasma expansion rate depend similarly on experimental parameters, i.e., conditions which favor expansion also favor suppression of the diocotron mode. The sensitivity of the mode evolution is examined as a function of the resistive growth driving conditions, which are controlled by the amount of wall resistance connected to the trap.

Investigating axial diffusion in cylindrical pores using confocal single-particle fluorescence correlation spectroscopy.

PubMed

Chen, Fang; Neupane, Bhanu; Li, Peiyuan; Su, Wei; Wang, Gufeng

2016-08-01

We explored the feasibility of using confocal fluorescence correlation spectroscopy to study small nanoparticle diffusion in hundred-nanometer-sized cylindrical pores. By modeling single particle diffusion in tube-like confined three-dimensional space aligned parallel to the confocal optical axis, we showed that two diffusion dynamics can be observed in both original intensity traces and the autocorrelation functions (ACFs): the confined two-dimensional lateral diffusion and the unconfined one-dimensional (1D) axial diffusion. The separation of the axial and confined lateral diffusion dynamics provides an opportunity to study diffusions in different dimensions separately. We further experimentally studied 45 nm carboxylated polystyrene particles diffusing in 300 nm alumina pores. The experimental data showed consistency with the simulation. To extract the accurate axial diffusion coefficient, we found that a 1D diffusion model with a Lorentzian axial collection profile needs to be used to analyze the experimental ACFs. The diffusion of the 45 nm nanoparticles in polyethyleneglycol-passivated 300 nm pores slowed down by a factor of ∼2, which can be satisfactorily explained by hydrodynamic frictions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electron microscopy of antigen precipitates extracted from gel diffusion plates

PubMed Central

Watson, D. H.; Le Bouvier, G. L.; Tomlinson, J. A.; Walkey, D. G. A.

1966-01-01

A method is described whereby material from virus precipitin lines from agar gel diffusion plates may be examined in the electron microscope by a negative staining technique. ImagesFIGS. 1-2FIGS. 3-4 PMID:4286708

Computational and Experimental Study of the Structure of Diffusion Flames of Jet Fuel and Its Surrogates at Pressures up to 40 ATM

DTIC Science & Technology

2012-11-21

examination of some of the aromatics show that the model captures well benzene from toluene decomposition in BF, but underpredicts styrene and ethylbenzene ...critical toluene pyrolysis products and stable soot precursors were compared with computational models using two semi-detailed chemical mechanisms... ethylbenzene , which at least one of the mechanisms reproduces quite well. The largest measured species in the incipiently sooting flame is indene, whose

The hydrogen diffusion in liquid aluminum alloys from ab initio molecular dynamics

NASA Astrophysics Data System (ADS)

Jakse, N.; Pasturel, A.

2014-09-01

We study the hydrogen diffusion in liquid aluminum alloys through extensive ab initio molecular dynamics simulations. At the microscopic scale, we show that the hydrogen motion is characterized by a broad distribution of spatial jumps that does not correspond to a Brownian motion. To determine the self-diffusion coefficient of hydrogen in liquid aluminum alloys, we use a generalized continuous time random walk model recently developed to describe the hydrogen diffusion in pure aluminum. In particular, we show that the model successfully accounts the effects of alloying elements on the hydrogen diffusion in agreement with experimental features.

General solution for diffusion-controlled dissolution of spherical particles. 1. Theory.

PubMed

Wang, J; Flanagan, D R

1999-07-01

Three classical particle dissolution rate expressions are commonly used to interpret particle dissolution rate phenomena. Our analysis shows that an assumption used in the derivation of the traditional cube-root law may not be accurate under all conditions for diffusion-controlled particle dissolution. Mathematical analysis shows that the three classical particle dissolution rate expressions are approximate solutions to a general diffusion layer model. The cube-root law is most appropriate when particle size is much larger than the diffusion layer thickness, the two-thirds-root expression applies when the particle size is much smaller than the diffusion layer thickness. The square-root expression is intermediate between these two models. A general solution to the diffusion layer model for monodispersed spherical particles dissolution was derived for sink and nonsink conditions. Constant diffusion layer thickness was assumed in the derivation. Simulated dissolution data showed that the ratio between particle size and diffusion layer thickness (a0/h) is an important factor in controlling the shape of particle dissolution profiles. A new semiempirical general particle dissolution equation is also discussed which encompasses the three classical particle dissolution expressions. The success of the general equation in explaining limitations of traditional particle dissolution expressions demonstrates the usefulness of the general diffusion layer model.

Solution of the nonlinear Poisson-Boltzmann equation: Application to ionic diffusion in cementitious materials

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

Arnold, J.; Kosson, D.S., E-mail: david.s.kosson@vanderbilt.edu; Garrabrants, A.

2013-02-15

A robust numerical solution of the nonlinear Poisson-Boltzmann equation for asymmetric polyelectrolyte solutions in discrete pore geometries is presented. Comparisons to the linearized approximation of the Poisson-Boltzmann equation reveal that the assumptions leading to linearization may not be appropriate for the electrochemical regime in many cementitious materials. Implications of the electric double layer on both partitioning of species and on diffusive release are discussed. The influence of the electric double layer on anion diffusion relative to cation diffusion is examined.

On the Occurrence of Liquation During Linear Friction Welding of Ni-Based Superalloys

NASA Astrophysics Data System (ADS)

Masoumi, F.; Shahriari, D.; Jahazi, M.; Cormier, J.; Flipo, B. C. D.

2017-06-01

A combination of experimental and analytical methods was used to study the possible occurrence of liquation during LFW of the newly developed AD730TM Ni-based superalloy. LFWed joints were produced using a semi-industrial size facility and the interfaces of the joints as well as the ejected flash were examined using optical and Field Emission Gun Scanning Electron Microscopy (FEG-SEM). Physical simulation of the LFW thermal cycle, using thermomechanical simulator Gleeble™ 3800, showed that incipient melting started from 1473 K (1200 °C). The analytical model, calibrated by experiments, predicted that the highest temperature of the interface was about 1523 K (1250 °C). The constitutive equations based on lattice and pipe diffusion models were developed to quantify the self-diffusivity of the elements and control the extent of liquation by considering the effect of LFW process parameters. Analytical results show that the application of compressive stresses during LFW results in 25 times increase in the diffusion of Ni atoms at the weld interface. Therefore, no presence of re-solidified phases, i.e., occurrence of liquation, was observed in the microstructure of the weld zone or the flash in the present study. Based on the obtained results, a methodology was developed for designing the optimum pressure above which no liquation, and hence cracking, will be observable.

The presence of Epstein-Barr virus (EBV) in diffuse large B-cell lymphomas (DLBCLs) in Turkey: special emphasis on 'EBV-positive DLBCL of the elderly'.

PubMed

Uner, Aysegul; Akyurek, Nalan; Saglam, Arzu; Abdullazade, Samir; Uzum, Nuket; Onder, Sevgen; Barista, Ibrahim; Benekli, Mustafa

2011-04-01

Accumulated evidence has shown the importance of Epstein-Barr virus in the pathogenesis of various lymphomas. This study aimed to determine the prevalence of Epstein-Barr virus expression and its effect on survival amongst diffuse large B-cell lymphoma (DLBCL) cases from two large tertiary care centres in Turkey with a particular interest in identifying cases of 'Epstein-Barr virus-positive DLBCL of the elderly'. Diffuse large B-cell lymphoma cases diagnosed between 1999 and 2009 were retrieved and 340 cases were used to construct tissue microarrays. The presence of Epstein-Barr virus small ribonucleic acids was examined by in situ hybridization using Epstein-Barr virus (EBV)-encoded small RNA (EBER) oligonucleotides. A total of 18 cases (5.3%) showed Epstein-Barr virus expression. Twelve cases were classified as Epstein-Barr virus-positive DLBCL of the elderly. Epstein-Barr virus-positive DLBCL cases showed a significantly inferior overall survival as compared with Epstein-Barr virus-negative cases (p < 0.001). In our study group Epstein-Barr virus expression is not prevalent in DLBCLs. Epstein-Barr virus-positive DLBCL of the elderly is also rare in the Turkish population. The presence of Epstein-Barr virus, however, is associated with poor prognosis. © 2011 The Authors. APMIS © 2011 APMIS.

Characteristics of elderly patients with COPD and newly diagnosed lung cancer, and factors associated with treatment decision.

PubMed

Qin, Jianwen; Li, Guangsheng; Zhou, Jingmin

2016-01-01

To investigate the clinical features, diagnosis, and treatment status of elderly patients with chronic obstructive pulmonary disease (COPD) complicated with lung cancer. This was a retrospective study of 206 patients aged >60 years with COPD and newly diagnosed lung cancer at the Tianjin Chest Hospital Respiratory Centre between September 2008 and September 2013. Lung function, radiology, and clinical data were retrieved. Among all patients, 57% (117/206) were hospitalized due to acute COPD aggravation, 47% (96/206) had COPD grade III or IV, 95% (195/206), showed diffusion dysfunction in pulmonary function examination, 90% (185/206) had a history of smoking, and 26% (54/206) were treated with inhaled corticosteroids for COPD treatment. Ninety-eight patients suffered from squamous carcinoma, 73 from adenocarcinoma, and 35 from small-cell carcinoma. Clinical staging was I in 36 patients, II in 47 patients, III in 78 patients, and IV in 45 patients. Initial treatments were surgery in 59 patients, chemotherapy in 30 patients, and no treatment in 117 patients. Multivariate analysis showed that age (P<0.001), COPD grades (P=0.01), clinical staging (P<0.001), and pulmonary diffusion function (P=0.007) were independent factors associated with patients with COPD being given treatments for lung cancer. Younger patients with lower COPD grades, earlier lung cancer stage, and better pulmonary diffusion function are more likely to receive treatments.

Collective dissolution of microbubbles

NASA Astrophysics Data System (ADS)

Michelin, Sébastien; Guérin, Etienne; Lauga, Eric

2018-04-01

A microscopic bubble of soluble gas always dissolves in finite time in an undersaturated fluid. This diffusive process is driven by the difference between the gas concentration near the bubble, whose value is governed by the internal pressure through Henry's law, and the concentration in the far field. The presence of neighboring bubbles can significantly slow down this process by increasing the effective background concentration and reducing the diffusing flux of dissolved gas experienced by each bubble. We develop theoretical modeling of such diffusive shielding process in the case of small microbubbles whose internal pressure is dominated by Laplace pressure. We first use an exact semianalytical solution to capture the case of two bubbles and analyze in detail the shielding effect as a function of the distance between the bubbles and their size ratio. While we also solve exactly for the Stokes flow around the bubble, we show that hydrodynamic effects are mostly negligible except in the case of almost-touching bubbles. In order to tackle the case of multiple bubbles, we then derive and validate two analytical approximate yet generic frameworks, first using the method of reflections and then by proposing a self-consistent continuum description. Using both modeling frameworks, we examine the dissolution of regular one-, two-, and three-dimensional bubble lattices. Bubbles located at the edge of the lattices dissolve first, while innermost bubbles benefit from the diffusive shielding effect, leading to the inward propagation of a dissolution front within the lattice. We show that diffusive shielding leads to severalfold increases in the dissolution time, which grows logarithmically with the number of bubbles in one-dimensional lattices and algebraically in two and three dimensions, scaling respectively as its square root and 2 /3 power. We further illustrate the sensitivity of the dissolution patterns to initial fluctuations in bubble size or arrangement in the case of large and dense lattices, as well as nonintuitive oscillatory effects.

Effective gaseous diffusion coefficients of select ultra-fine, super-fine and medium grain nuclear graphite

DOE PAGES

Kane, Joshua J.; Matthews, Austin C.; Orme, Christopher J.; ...

2018-05-05

Understanding “Where?” and “How much?” oxidation has occurred in a nuclear graphite component is critical to predicting any deleterious effects to physical, mechanical, and thermal properties. A key factor in answering these questions is characterizing the effective mass transport rates of gas species in nuclear graphites. Effective gas diffusion coefficients were determined for twenty-six graphite specimens spanning six modern grades of nuclear graphite. A correlation was established for the majority of grades examined allowing a reasonable estimate of the effective diffusion coefficient to be determined purely from an estimate of total porosity. The importance of Knudsen diffusion to the measuredmore » diffusion coefficients is also shown for modern grades. Furthermore, Knudsen diffusion has not historically been considered to contribute to measured diffusion coefficients of nuclear graphite.« less

Effective gaseous diffusion coefficients of select ultra-fine, super-fine and medium grain nuclear graphite

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

Kane, Joshua J.; Matthews, Austin C.; Orme, Christopher J.

Understanding “Where?” and “How much?” oxidation has occurred in a nuclear graphite component is critical to predicting any deleterious effects to physical, mechanical, and thermal properties. A key factor in answering these questions is characterizing the effective mass transport rates of gas species in nuclear graphites. Effective gas diffusion coefficients were determined for twenty-six graphite specimens spanning six modern grades of nuclear graphite. A correlation was established for the majority of grades examined allowing a reasonable estimate of the effective diffusion coefficient to be determined purely from an estimate of total porosity. The importance of Knudsen diffusion to the measuredmore » diffusion coefficients is also shown for modern grades. Furthermore, Knudsen diffusion has not historically been considered to contribute to measured diffusion coefficients of nuclear graphite.« less

Facilitated Diffusion of Transcription Factor Proteins with Anomalous Bulk Diffusion.

PubMed

Liu, Lin; Cherstvy, Andrey G; Metzler, Ralf

2017-02-16

What are the physical laws of the diffusive search of proteins for their specific binding sites on DNA in the presence of the macromolecular crowding in cells? We performed extensive computer simulations to elucidate the protein target search on DNA. The novel feature is the viscoelastic non-Brownian protein bulk diffusion recently observed experimentally. We examine the influence of the protein-DNA binding affinity and the anomalous diffusion exponent on the target search time. In all cases an optimal search time is found. The relative contribution of intermittent three-dimensional bulk diffusion and one-dimensional sliding of proteins along the DNA is quantified. Our results are discussed in the light of recent single molecule tracking experiments, aiming at a better understanding of the influence of anomalous kinetics of proteins on the facilitated diffusion mechanism.

Temperature driven annealing of perforations in bicellar model membranes.

PubMed

Nieh, Mu-Ping; Raghunathan, V A; Pabst, Georg; Harroun, Thad; Nagashima, Kazuomi; Morales, Hannah; Katsaras, John; Macdonald, Peter

2011-04-19

Bicellar model membranes composed of 1,2-dimyristoylphosphatidylcholine (DMPC) and 1,2-dihexanoylphosphatidylcholine (DHPC), with a DMPC/DHPC molar ratio of 5, and doped with the negatively charged lipid 1,2-dimyristoylphosphatidylglycerol (DMPG), at DMPG/DMPC molar ratios of 0.02 or 0.1, were examined using small angle neutron scattering (SANS), (31)P NMR, and (1)H pulsed field gradient (PFG) diffusion NMR with the goal of understanding temperature effects on the DHPC-dependent perforations in these self-assembled membrane mimetics. Over the temperature range studied via SANS (300-330 K), these bicellar lipid mixtures exhibited a well-ordered lamellar phase. The interlamellar spacing d increased with increasing temperature, in direct contrast to the decrease in d observed upon increasing temperature with otherwise identical lipid mixtures lacking DHPC. (31)P NMR measurements on magnetically aligned bicellar mixtures of identical composition indicated a progressive migration of DHPC from regions of high curvature into planar regions with increasing temperature, and in accord with the "mixed bicelle model" (Triba, M. N.; Warschawski, D. E.; Devaux, P. E. Biophys. J.2005, 88, 1887-1901). Parallel PFG diffusion NMR measurements of transbilayer water diffusion, where the observed diffusion is dependent on the fractional surface area of lamellar perforations, showed that transbilayer water diffusion decreased with increasing temperature. A model is proposed consistent with the SANS, (31)P NMR, and PFG diffusion NMR data, wherein increasing temperature drives the progressive migration of DHPC out of high-curvature regions, consequently decreasing the fractional volume of lamellar perforations, so that water occupying these perforations redistributes into the interlamellar volume, thereby increasing the interlamellar spacing. © 2011 American Chemical Society

The Hall effect in star formation

NASA Astrophysics Data System (ADS)

Braiding, C. R.; Wardle, M.

2012-05-01

Magnetic fields play an important role in star formation by regulating the removal of angular momentum from collapsing molecular cloud cores. Hall diffusion is known to be important to the magnetic field behaviour at many of the intermediate densities and field strengths encountered during the gravitational collapse of molecular cloud cores into protostars, and yet its role in the star formation process is not well studied. We present a semianalytic self-similar model of the collapse of rotating isothermal molecular cloud cores with both Hall and ambipolar diffusion, and similarity solutions that demonstrate the profound influence of the Hall effect on the dynamics of collapse. The solutions show that the size and sign of the Hall parameter can change the size of the protostellar disc by up to an order of magnitude and the protostellar accretion rate by 50 per cent when the ratio of the Hall to ambipolar diffusivities is varied between -0.5 ≤ηH/ηA≤ 0.2. These changes depend upon the orientation of the magnetic field with respect to the axis of rotation and create a preferred handedness to the solutions that could be observed in protostellar cores using next-generation instruments such as ALMA. Hall diffusion also determines the strength and position of the shocks that bound the pseudo and rotationally supported discs, and can introduce subshocks that further slow accretion on to the protostar. In cores that are not initially rotating (not examined here), Hall diffusion can even induce rotation, which could give rise to disc formation and resolve the magnetic braking catastrophe. The Hall effect clearly influences the dynamics of gravitational collapse and its role in controlling the magnetic braking and radial diffusion of the field merits further exploration in numerical simulations of star formation.

Radial diffusion comparing a THEMIS statistical model with geosynchronous measurements as the outer boundary

NASA Astrophysics Data System (ADS)

Li, Z.; Hudson, M. K.; Chen, Y.

2013-12-01

The outer boundary energetic electron flux is used as a driver in radial diffusion calculations, and its precise determination is critical to the solution. A new model was proposed recently based on THEMIS measurements to express the boundary flux as three fit functions of solar wind parameters in a response window, that depend on energy and which solar parameter is used: speed, density, or both (Shin and Lee, 2013). The Dartmouth radial diffusion model has been run using LANL geosynchronous satellite measurements as the outer boundary for a one-month interval in July to August 2004 and the calculated phase space density (PSD) is compared with GPS measurements at the GPS orbit (L=4.16), at magnetic equatorial plane crossings, as a test of the model. We also used the outer boundary generated from the Shin and Lee model and examined this boundary condition by computing the error relative to the simulation using a LANL geosynchronous spacecraft data-driven outer boundary. The calculation shows that there is overestimation and underestimation at different times, however the new boundary condition can be used to drive the radial diffusion model generally, producing the phase space density increase and dropout during a storm with a relatively small error. Having this new method based on a solar wind parametrized data set, we can run the radial diffusion model for storms when particle measurements are not available at the outer boundary. We chose the Whole Heliosphere Interval (WHI) as an example and compared the result with MHD/test-particle simulations (Hudson et al., 2012), obtaining much better agreement with PSD based on GPS measurements at L=4.16 using the diffusion model, which incorporates atmospheric losses.

Extravascular transport of drugs in tumor tissue: effect of lipophilicity on diffusion of tirapazamine analogues in multicellular layer cultures.

PubMed

Pruijn, Frederik B; Sturman, Joanna R; Liyanage, H D Sarath; Hicks, Kevin O; Hay, Michael P; Wilson, William R

2005-02-24

The extravascular diffusion of antitumor agents is a key determinant of their therapeutic activity, but the relationships between physicochemical properties of drugs and their extravascular transport are poorly understood. It is well-known that drug lipophilicity plays an important role in transport across biological membranes, but the net effect of lipophilicity on transport through multiple layers of tumor cells is less clear. This study examines the influence of lipophilicity (measured as the octanol-water partition coefficient P) on the extravascular transport properties of the hypoxic cytotoxin tirapazamine (TPZ, 1) and a series of 13 neutral analogues, using multicellular layers (MCLs) of HT29 human colon carcinoma cells as an in vitro model for the extravascular compartment of tumors. Flux of drugs across MCLs was determined using diffusion chambers, with the concentration-time profile on both sides of the MCL measured by HPLC. Diffusion coefficients in the MCLs (D(MCL)) were inversely proportional to M(r)(0.5) (M(r), relative molecular weight), although this was a minor contributor to differences between compounds over the narrow M(r) range investigated. Differences in lipophilicity had a larger effect, with a sigmoidal dependence of D(MCL) on log P. Correcting for M(r) differences, lipophilic compounds (log P > 1.5) had ca. 15-fold higher D(MCL) than hydrophilic compounds (log P < -1). Using a pharmacokinetic/pharmacodynamic (PK/PD) model in which diffusion in the extravascular compartment of tumors is considered explicitly, we demonstrated that hypoxic cell kill is very sensitive to changes in extravascular diffusion coefficient of TPZ analogues within this range. This study shows that simple monosubstitution of TPZ can alter log P enough to markedly improve extravascular transport and activity against target cells, especially if rates of metabolic activation are also optimized.

Effects of electric field on micro-scale flame properties of biobutanol fuel

PubMed Central

Xu, Tao; Chen, Qinglin; Zhang, Bingjian; Lu, Shushen; Mo, Dongchuan; Zhang, Zhengguo; Gao, Xuenong

2016-01-01

With the increasing need of smaller power sources for satellites, energy systems and engine equipment, microcombustion pose a potential as alternative power source to conventional batteries. As the substitute fuel source for gasoline, biobutanol shows more promising characteristics than ethanol. In this study, the diffusion microflame of liquid biobutanol under electric field have been examined through in-lab experiment and numerical simulation. It is found that traditional gas jet diffusion flame theory shows significant inconsistency with the experimental results of micro scale flame in electric field. The results suggest that with the increase of electric field intensity, the quenching flow rate decrease first and increase after it reach its minimum, while the flame height and highest flame temperature increase first and drop after its peak value. In addition, it was also observed that the flame height and highest temperature for smaller tube can reach its maximum faster. Therefore, the interaction between microscale effect and electric field plays a significant role on understanding the microcombustion of liquid fuel. Therefore, FLUENT simulation was adopted to understand and measure the impacts of microflame characteristic parameters. The final numerical results are consistent with the experimental data and show a high reliability. PMID:27609428

Thermal resistance of pressed contacts of aluminum and niobium at liquid helium temperatures

DOE PAGES

Dhuley, R. C.; Geelhoed, M. I.; Thangaraj, J. C. T.

2018-06-15

Here, we examine the resistance to heat flow across contacts of mechanically pressed aluminum and niobium near liquid helium temperatures for designing a thermally conducting joint of aluminum and superconducting niobium. Measurements in the temperature range of 3.5 K to 5.5 K show the thermal contact resistance to grow as a near-cubic function of decreasing temperature, indicating phonons to be the primary heat carriers across the interface. In the 4 kN to 14 kN range of pressing force the contact resistance shows linear drop with the increasing force, in agreement with the model of micro-asperity plastic deformation at pressed contacts.more » Several thermal contact resistance models as well as the phonon diffuse mismatch model of interface thermal resistance are compared with the experimental data. The diffuse mismatch model shows closest agreement. The joints are further augmented with thin foil of indium, which lowers the joint resistance by an order of magnitude. The developed joint has nearly 1 K*cm2/W of thermal resistance at 4.2 K, is demountable, and free of the thermally resistive interfacial alloy layer that typically exists at welded, casted, or soldered joints of dissimilar metals.« less

Thermal resistance of pressed contacts of aluminum and niobium at liquid helium temperatures

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

Dhuley, R. C.; Geelhoed, M. I.; Thangaraj, J. C. T.

Here, we examine the resistance to heat flow across contacts of mechanically pressed aluminum and niobium near liquid helium temperatures for designing a thermally conducting joint of aluminum and superconducting niobium. Measurements in the temperature range of 3.5 K to 5.5 K show the thermal contact resistance to grow as a near-cubic function of decreasing temperature, indicating phonons to be the primary heat carriers across the interface. In the 4 kN to 14 kN range of pressing force the contact resistance shows linear drop with the increasing force, in agreement with the model of micro-asperity plastic deformation at pressed contacts.more » Several thermal contact resistance models as well as the phonon diffuse mismatch model of interface thermal resistance are compared with the experimental data. The diffuse mismatch model shows closest agreement. The joints are further augmented with thin foil of indium, which lowers the joint resistance by an order of magnitude. The developed joint has nearly 1 K*cm2/W of thermal resistance at 4.2 K, is demountable, and free of the thermally resistive interfacial alloy layer that typically exists at welded, casted, or soldered joints of dissimilar metals.« less

Intravoxel incoherent motion modeling in the kidneys: Comparison of mono-, bi-, and triexponential fit.

PubMed

van Baalen, Sophie; Leemans, Alexander; Dik, Pieter; Lilien, Marc R; Ten Haken, Bennie; Froeling, Martijn

2017-07-01

To evaluate if a three-component model correctly describes the diffusion signal in the kidney and whether it can provide complementary anatomical or physiological information about the underlying tissue. Ten healthy volunteers were examined at 3T, with T 2 -weighted imaging, diffusion tensor imaging (DTI), and intravoxel incoherent motion (IVIM). Diffusion tensor parameters (mean diffusivity [MD] and fractional anisotropy [FA]) were obtained by iterative weighted linear least squares fitting of the DTI data and mono-, bi-, and triexponential fit parameters (D 1 , D 2 , D 3 , f fast2 , f fast3 , and f interm ) using a nonlinear fit of the IVIM data. Average parameters were calculated for three regions of interest (ROIs) (cortex, medulla, and rest) and from fiber tractography. Goodness of fit was assessed with adjusted R 2 ( Radj2) and the Shapiro-Wilk test was used to test residuals for normality. Maps of diffusion parameters were also visually compared. Fitting the diffusion signal was feasible for all models. The three-component model was best able to describe fast signal decay at low b values (b < 50), which was most apparent in Radj2 of the ROI containing high diffusion signals (ROI rest ), which was 0.42 ± 0.14, 0.61 ± 0.11, 0.77 ± 0.09, and 0.81 ± 0.08 for DTI, one-, two-, and three-component models, respectively, and in visual comparison of the fitted and measured S 0 . None of the models showed significant differences (P > 0.05) between the diffusion constant of the medulla and cortex, whereas the f fast component of the two and three-component models were significantly different (P < 0.001). Triexponential fitting is feasible for the diffusion signal in the kidney, and provides additional information. 2 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:228-239. © 2016 The Authors Journal of Magnetic Resonance Imaging published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

Compositional Zoning in Kilauea Olivine: A Geochemical Tool for Investigating Magmatic Processes at Hawaiian Volcanoes

NASA Astrophysics Data System (ADS)

Lynn, Kendra J.

Olivine compositions and zoning patterns have been widely used to investigate the evolution of magmas from their source to the Earthfs surface. Modeling the formation of compositional zoning in olivine crystals has been used to retrieve timescales of magma residence, mixing, and transit. This dissertation is composed of three projects that apply diffusion chronometry principles to investigate how zoned olivine phenocrysts record magmatic processes at Hawaiian volcanoes. Olivine phenocrysts from K.lauea, the most active and thoroughly studied volcano in Hawaiei, are used to develop a better understanding of how Hawaiian olivine crystals record magmatic histories. This work begins by examining how crustal processes such as magma mixing and diffusive reequilibration can modify olivine compositions inherited from growth in parental magmas (Chapter 2). Diffusive re-equilibration of Fe-Mg, Mn, and Ni in olivine crystals overprints the chemical relationships inherited during growth, which strongly impacts interpretations about mantle processes and source components. These issues are further complicated by sectioning effects, where small (400 ƒEm along the c-axis) olivine crystals are more susceptible to overprinting compared to large (800 ƒEm) crystals. Olivine compositions and zoning patterns are then used to show that magmas during K.laueafs explosive Keanak.koei Tephra period (1500-1823 C.E.) were mixed and stored in crustal reservoirs for weeks to months prior to eruption (Chapter 3). Fe-Mg disequilibrium between olivine rims and their surrounding glasses show that a late-stage mixing event likely occurred hours to days prior to eruption, but the exact timescale is difficult to quantify using Fe-Mg and Ni diffusion. Lithium, a rapidly diffusing trace element in olivine, is modeled for the first time in a natural volcanic system to quantify this late-stage, short-duration mixing event (Chapter 4). Lithium zoning in olivine records both growth and diffusion processes that are affected by charge balancing requirements with growth zoning of P. Timescales from modeling diffuse Li zoning range from a few hours to three weeks, but most record short storage durations of four days or less. These timescales correspond to short storage periods after mixing. Thus, Li probably records the final perturbation of a magmatic system prior to eruption.

A rare type of Usher's syndrome.

PubMed

Antunica, Antonela Gverović; Kastelan, Snjezana; Bućan, Kajo; Ivanković, Mira; Radman, Maja; Karaman, Ksenija

2013-12-01

A case is presented of a very rare type of Usher's syndrome detected in a 30-year-old woman in her 28th week of pregnancy. She reported left eye visual impairment with a one-month history. She underwent standard ophthalmologic examination with additional procedures scheduled after childbirth, including fluorescein angiography, visual field (Goldman and Octopus) and electroretinography. Fundus examination revealed pallor of the optic disk, diffuse retinal blood vessel narrowing, no retinal pigmentation, left macular edema, vitreous liquefaction, and posterior vitreous detachment. Goldman perimetry showed narrowing of all isopters to 10 degrees, and Octopus perimetry showed peripheral decrease of retinal sensitivity. Electroretinography confirmed the diagnosis of retinitis pigmentosa sine pigmento. Upon collecting case history records, hearing disorders originating from childhood were discovered. To our knowledge, this type of retinitis in Usher's syndrome has been reported only once in the available literature.

Diffusion-weighted and T2-weighted MR imaging for colorectal liver metastases detection in a rat model at 7 T: a comparative study using histological examination as reference.

PubMed

Wagner, Mathilde; Maggiori, Léon; Ronot, Maxime; Paradis, Valérie; Vilgrain, Valérie; Panis, Yves; Van Beers, Bernard E

2013-08-01

To compare diffusion-weighted (DW) and T2-weighted MR imaging in detecting colorectal liver metastases in a rat model, using histological examination as a reference method. Eighteen rats had four liver injections of colon cancer cells. MR examinations at 7 T included FSE-T2-weighted imaging and SE-DW MR imaging (b = 0, 20 and 150 s/mm(2)) and were analysed by two independent readers. Histological examination was performed on 0.4-mm slices. McNemar's test was used to compare the sensitivities and the Wilcoxon matched pairs test to compare the average number of false-positives per rat. One hundred and sixty-six liver metastases were identified on histological examination. The sensitivity in detecting liver metastases was significantly higher on DW MR than on T2-weighted images (99/166 (60 %) (reader 1) and 92/166 (55 %) (reader 2) versus 77/166 (46 %), P ≤ 0.001), without an increase in false-positives per rat (P = 0.773/P = 0.850). After stratification according to metastasis diameter, DW MR imaging had a significantly higher sensitivity than T2-weighted imaging only for metastases with a diameter (0.6-1.2 mm) similar to that of the spatial resolution of MR imaging in the current study. This MR study with histological correlations shows the higher sensitivity of DW relative to T2-weighted imaging at 7 T for detecting liver metastases, especially small ones. • Diffusion weighted (DW) sequences are increasingly used in magnetic resonance imaging (MRI). • DW has higher sensitivity for liver metastases than T2-weighted imaging at 7 T. • This increase in sensitivity is especially marked for small liver metastasis detection. • This higher sensitivity is confirmed in an animal model with histological correlation. • DW imaging has the potential for earlier diagnosis of small liver metastases.

Structural and Mechanical Repair of Diffuse Damage in Cortical Bone in vivo

PubMed Central

Seref-Ferlengez, Zeynep; Basta-Pljakic, Jelena; Kennedy, Oran D.; Philemon, Claudy J.; Schaffler, Mitchell B.

2014-01-01

Physiological wear and tear causes bone microdamage at several hierarchical levels, and these have different biological consequences. Bone remodeling is widely held to be the mechanism by which bone microdamage is repaired. However, recent studies showed that unlike typical linear microcracks, small crack damage, the clusters of submicron-sized matrix cracks also known as diffuse damage (Dif.Dx), does not activate remodeling. Thus, the fate of diffuse damage in vivo is not known. To examine this, we induced selectively Dif.Dx in rat ulnae in vivo by using end-load ulnar bending creep model. Changes in damage content were assessed by histomorphometry and mechanical testing immediately after loading (i.e., acute loaded) or at 14 days after damage induction (i.e., survival ulnae). Dif.Dx area was markedly reduced over the 14-day survival period after loading (p<0.02). We did not observe any intracortical resorption and there was no increase in cortical bone area in survival ulnae. The reduction in whole bone stiffness in acute loaded ulnae was restored to baseline levels in survival ulnae (p>0.6). Microindentation studies showed that Dif.Dx caused a highly localized reduction in elastic modulus in diffuse damage regions of the ulnar cortex. Moduli in these previously damaged bone areas were restored to control values by 14 days after loading. Our current findings indicate that small crack damage in bone can be repaired without bone remodeling, and suggest that alternative repair mechanisms exist in bone to deal with submicron-sized matrix cracks. Those mechanisms are currently unknown and further investigations are needed to elucidate the mechanisms by which this direct repair occurs. PMID:25042459

Modeling chemical accumulation in sediment of small waterbodies accounting for sediment transport and water-sediment exchange processes over long periods.

PubMed

Patterson, David Albert; Strehmel, Alexander; Erzgräber, Beate; Hammel, Klaus

2017-12-01

In a recent scientific opinion of the European Food Safety Authority it is argued that the accumulation of plant protection products in sediments over long time periods may be an environmentally significant process. Therefore, the European Food Safety Authority proposed a calculation to account for plant protection product accumulation. This calculation, however, considers plant protection product degradation within sediment as the only dissipation route, and does not account for sediment dynamics or back-diffusion into the water column. The hydraulic model Hydrologic Engineering Center-River Analysis System (HEC-RAS; US Army Corps of Engineers) was parameterized to assess sediment transport and deposition dynamics within the FOrum for Co-ordination of pesticide fate models and their USe (FOCUS) scenarios in simulations spanning 20 yr. The results show that only 10 to 50% of incoming sediment would be deposited. The remaining portion of sediment particles is transported across the downstream boundary. For a generic plant protection product substance this resulted in deposition of only 20 to 50% of incoming plant protection product substance. In a separate analysis, the FOCUS TOXSWA model was utilized to examine the relative importance of degradation versus back-diffusion as loss processes from the sediment compartment for a diverse range of generic plant protection products. In simulations spanning 20 yr, it was shown that back-diffusion was generally the dominant dissipation process. The results of the present study show that sediment dynamics and back-diffusion should be considered when calculating long-term plant protection product accumulation in sediment. Neglecting these may lead to a systematic overestimation of accumulation. Environ Toxicol Chem 2017;36:3223-3231. © 2017 SETAC. © 2017 SETAC.

Exciton diffusion in disordered small molecules for organic photovoltaics: insights from first-principles simulations.

PubMed

Li, Z; Zhang, X; Lu, G

2014-05-07

Exciton diffusion in small molecules 3,6-bis(5-(benzofuran-2-yl)thiophen-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione [DPP(TBFu)2] is studied using first-principles simulations. We have examined dependence of exciton diffusion on structure disorder, temperature and exciton energy. We find that exciton diffusion length and diffusivity increase with structural order, temperature and the initial exciton energy. Compared to conjugated polymer poly(3-hexylthiophene) (P3HT), DPP(TBFu)2 small molecules exhibit a much higher exciton diffusivity, but a shorter lifetime. The exciton diffusion length in DPP(TBFu)2 is 50% longer than that in P3HT, yielding a higher exciton harvesting efficiency; the physical origin behind these differences is discussed. The time evolutions of exciton energy, electron-hole distance, and exciton localization are explored, and the widely speculated exciton diffusion mechanism is confirmed theoretically. The connection between exciton diffusion and carrier mobilities is also studied. Finally we point out the possibility to estimate exciton diffusivity by measuring carrier mobilities under AC electric fields.

Examination of a demyelinated fiber by action-potential-encoded second harmonic generation

NASA Astrophysics Data System (ADS)

Chen, Xin-guang; Luo, Zhi-hui; Yang, Hong-qin; Huang, Yi-mei; Xie, Shu-sen

2012-03-01

Axonal demyelination is a common phenomenon in the nervous system in human. Conventional measured approaches such as surface recording electrode and diffusion tensor imaging, are hard to fast and accurately determine the demyelinated status of a fiber. In this study, we first presented a mathematical model of nerve fiber demyelination, and it was combined with second harmonic generation(SHG) technique to study the characteristics of action-potential-encoded SHG and analyze the sensitivity of SHG signals responded to membrane potential. And then, we used this approach to fast examine the injured myelin sheaths resulted from demyelination. Each myelin sheath of a fiber was examined simultaneously by this approach. The results showed that fiber demyelination led to observable attenuation of action potential amplitude. The delay of action potential conduction would be markedly observed when the fiber demyelination was more than 80%. Furthermore, the normal and injured myelin sheaths of a myelinated fiber could be distinguished via the changes of SHG signals, which revealed the possibility of SHG technique in the examination of a demyelinated fiber. Our study shows that this approach may have potential application values in clinic.

Elevated left and reduced right orbitomedial prefrontal fractional anisotropy in adults with bipolar disorder revealed by tract-based spatial statistics.

PubMed

Versace, Amelia; Almeida, Jorge R C; Hassel, Stefanie; Walsh, Nicholas D; Novelli, Massimiliano; Klein, Crystal R; Kupfer, David J; Phillips, Mary L

2008-09-01

Diffusion tensor imaging (DTI) studies in adults with bipolar disorder (BD) indicate altered white matter (WM) in the orbitomedial prefrontal cortex (OMPFC), potentially underlying abnormal prefrontal corticolimbic connectivity and mood dysregulation in BD. To use tract-based spatial statistics (TBSS) to examine WM skeleton (ie, the most compact whole-brain WM) in subjects with BD vs healthy control subjects. Cross-sectional, case-control, whole-brain DTI using TBSS. University research institute. Fifty-six individuals, 31 having a DSM-IV diagnosis of BD type I (mean age, 35.9 years [age range, 24-52 years]) and 25 controls (mean age, 29.5 years [age range, 19-52 years]). Fractional anisotropy (FA) longitudinal and radial diffusivities in subjects with BD vs controls (covarying for age) and their relationships with clinical and demographic variables. Subjects with BD vs controls had significantly greater FA (t > 3.0, P 3.0, P

The NASA/DOD aerospace knowledge diffusion research project: A research agenda

NASA Technical Reports Server (NTRS)

Pinelli, Thomas E.; Kennedy, John M.

1990-01-01

The project has both immediate and long term purposes. In the first instance it provides a practical and pragmatic basis for understanding how the results of NASA/DoD research diffuse into the aerospace R and D process. Over the long term it provides an empirical basis for understanding the aerospace knowledge diffusion process itself, and its implications at the individual, organizational, national, and international levels. The project is studying the major barriers to effective knowledge diffusion. This project will provide descriptive and analytical data regarding the flow of scientific and technical information (STI). It will examine both channels used to communicate information and the social system of the aerospace knowledge diffusion process.

Kinetics of pack aluminization of nickel

NASA Technical Reports Server (NTRS)

Seigle, L. L.; Gupta, B. K.; Shankar, R.; Sarkhel, A. K.

1978-01-01

The kinetics of pack aluminization of unalloyed nickel in packs of varying aluminum activity with various halide activators were studied. Surface compositions of the coatings as functions of time, temperature, and pack composition were obtained in order to establish the boundary conditions for diffusion in the system. The structure of the packs was also examined in order to clarify the mechanism of aluminum transport. The results indicate that the kinetics of pack aluminization are controlled jointly by gas diffusion in the pack and solid diffusion in the coating. Levine and Caves' model for gas diffusion was combined with calculations of rates of diffusion in the solid to formulate a more complete theory for the kinetics of pack aluminization.

The Shannon entropy as a measure of diffusion in multidimensional dynamical systems

NASA Astrophysics Data System (ADS)

Giordano, C. M.; Cincotta, P. M.

2018-05-01

In the present work, we introduce two new estimators of chaotic diffusion based on the Shannon entropy. Using theoretical, heuristic and numerical arguments, we show that the entropy, S, provides a measure of the diffusion extent of a given small initial ensemble of orbits, while an indicator related with the time derivative of the entropy, S', estimates the diffusion rate. We show that in the limiting case of near ergodicity, after an appropriate normalization, S' coincides with the standard homogeneous diffusion coefficient. The very first application of this formulation to a 4D symplectic map and to the Arnold Hamiltonian reveals very successful and encouraging results.

On the role of adhesion in single-file dynamics

NASA Astrophysics Data System (ADS)

Fouad, Ahmed M.; Noel, John A.

2017-08-01

For a one-dimensional interacting system of Brownian particles with hard-core interactions (a single-file model), we study the effect of adhesion on both the collective diffusion (diffusion of the entire system with respect to its center of mass) and the tracer diffusion (diffusion of the individual tagged particles). For the case with no adhesion, all properties of these particle systems that are independent of particle labeling (symmetric in all particle coordinates and velocities) are identical to those of non-interacting particles (Lebowitz and Percus, 1967). We clarify this last fact twice. First, we derive our analytical predictions that show that the probability-density functions of single-file (ρsf) and ordinary (ρord) diffusion are identical, ρsf =ρord, predicting a nonanomalous (ordinary) behavior for the collective single-file diffusion, where the average second moment with respect to the center of mass, < x(t) 2 > , is calculated from ρ for both diffusion processes. Second, for single-file diffusion, we show, both analytically and through large-scale simulations, that < x(t) 2 > grows linearly with time, confirming the nonanomalous behavior. This nonanomalous collective behavior comes in contrast to the well-known anomalous sub-diffusion behavior of the individual tagged particles (Harris, 1965). We introduce adhesion to single-file dynamics as a second inter-particle interaction rule and, interestingly, we show that adding adhesion does reduce the magnitudes of both < x(t) 2 > and the mean square displacement per particle Δx2; but the diffusion behavior remains intact independent of adhesion in both cases. Moreover, we study the dependence of both the collective diffusion constant D and the tracer diffusion constant DT on the adhesion coefficient α.

Understanding molecular structure dependence of exciton diffusion in conjugated small molecules

NASA Astrophysics Data System (ADS)

Li, Zi; Zhang, Xu; Woellner, Cristiano F.; Lu, Gang

2014-04-01

First-principles simulations are carried out to understand molecular structure dependence of exciton diffusion in a series of small conjugated molecules arranged in a disordered, crystalline, and blend structure. Exciton diffusion length (LD), lifetime, and diffusivity in four diketopyrrolopyrrole derivatives are calculated and the results compare very well with experimental values. The correlation between exciton diffusion and molecular structure is examined in detail. In the disordered molecule structure, a longer backbone length leads to a shorter exciton lifetime and a higher exciton diffusivity, but it does not change LD substantially. Removal of the end alkyl chains or the extra branch on the side alkyl chains reduces LD. In the crystalline structure, exciton diffusion exhibits a strong anisotropy whose origin can be elucidated from the intermolecular transition density interaction point of view. In the blend structure, LD increases with the crystalline ratios, which are estimated and consistent with the experimental results.

Sodium Ion Diffusion in Nasicon (Na3Zr2Si2PO12) Solid Electrolytes: Effects of Excess Sodium.

PubMed

Park, Heetaek; Jung, Keeyoung; Nezafati, Marjan; Kim, Chang-Soo; Kang, Byoungwoo

2016-10-04

The Na superionic conductor (aka Nasicon, Na 1+x Zr 2 Si x P 3-x O 12 , where 0 ≤ x ≤ 3) is one of the promising solid electrolyte materials used in advanced molten Na-based secondary batteries that typically operate at high temperature (over ∼270 °C). Nasicon provides a 3D diffusion network allowing the transport of the active Na-ion species (i.e., ionic conductor) while blocking the conduction of electrons (i.e., electronic insulator) between the anode and cathode compartments of cells. In this work, the standard Nasicon (Na 3 Zr 2 Si 2 PO 12 , bare sample) and 10 at% Na-excess Nasicon (Na 3.3 Zr 2 Si 2 PO 12 , Na-excess sample) solid electrolytes were synthesized using a solid-state sintering technique to elucidate the Na diffusion mechanism (i.e., grain diffusion or grain boundary diffusion) and the impacts of adding excess Na at relatively low and high temperatures. The structural, thermal, and ionic transport characterizations were conducted using various experimental tools including X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). In addition, an ab initio atomistic modeling study was carried out to computationally examine the detailed microstructures of Nasicon materials, as well as to support the experimental observations. Through this combination work comprising experimental and computational investigations, we show that the predominant mechanisms of Na-ion transport in the Nasicon structure are the grain boundary and the grain diffusion at low and high temperatures, respectively. Also, it was found that adding 10 at% excess Na could give rise to a substantial increase in the total conductivity (e.g., ∼1.2 × 10 -1 S/cm at 300 °C) of Nasicon electrolytes resulting from the enlargement of the bottleneck areas in the Na diffusion channels of polycrystalline grains.

Participation and diffusion effects of a peer-intervention for HIV prevention among adults in rural Malawi.

PubMed

Crittenden, Kathleen S; Kaponda, Chrissie P N; Jere, Diana L; McCreary, Linda L; Norr, Kathleen F

2015-05-01

This paper examines whether a peer group intervention that reduced self-reported risky behaviors for rural adults in Malawi also had impacts on non-participants in the same communities. We randomly assigned two districts to the intervention and control conditions, and conducted surveys at baseline and 18 months post-intervention using unmatched independent random samples of intervention and control communities in 2003-2006. The six-session peer group intervention was offered to same-gender groups by trained volunteers. In this analysis, we divided the post-intervention sample into three exposure groups: 243 participants and 170 non-participants from the intervention district (total n = 415) and 413 control individuals. Controlling for demographics and participation, there were significant favorable diffusion effects on five partially overlapping behavioral outcomes: partner communication, ever used condoms, unprotected sex, recent HIV test, and a community HIV prevention index. Non-participants in the intervention district had more favorable outcomes on these behaviors than survey respondents in the control district. One behavioral outcome, community HIV prevention, showed both participation and diffusion effects. Participating in the intervention had a significant effect on six psychosocial outcomes: HIV knowledge (two measures), hope, condom attitudes, and self-efficacy for community HIV prevention and for safer sex; there were no diffusion effects. This pattern of results suggests that the behavioral changes promoted in the intervention spread to others in the same community, most likely through direct contact between participants and non-participants. These findings support the idea that diffusion of HIV-related behavior changes can occur for peer group interventions in communities, adding to the body of research supporting diffusion of innovations theory as a robust approach to accelerating change. If diffusion occurs, peer group intervention may be more cost-effective than previously realized. Wider implementation of peer group interventions can help meet the global goal of reducing new HIV infections. Copyright © 2015 Elsevier Ltd. All rights reserved.

Experimental and computational models of neurite extension at a choice point in response to controlled diffusive gradients

NASA Astrophysics Data System (ADS)

Catig, G. C.; Figueroa, S.; Moore, M. J.

2015-08-01

Ojective. Axons are guided toward desired targets through a series of choice points that they navigate by sensing cues in the cellular environment. A better understanding of how microenvironmental factors influence neurite growth during development can inform strategies to address nerve injury. Therefore, there is a need for biomimetic models to systematically investigate the influence of guidance cues at such choice points. Approach. We ran an adapted in silico biased turning axon growth model under the influence of nerve growth factor (NGF) and compared the results to corresponding in vitro experiments. We examined if growth simulations were predictive of neurite population behavior at a choice point. We used a biphasic micropatterned hydrogel system consisting of an outer cell restrictive mold that enclosed a bifurcated cell permissive region and placed a well near a bifurcating end to allow proteins to diffuse and form a gradient. Experimental diffusion profiles in these constructs were used to validate a diffusion computational model that utilized experimentally measured diffusion coefficients in hydrogels. The computational diffusion model was then used to establish defined soluble gradients within the permissive region of the hydrogels and maintain the profiles in physiological ranges for an extended period of time. Computational diffusion profiles informed the neurite growth model, which was compared with neurite growth experiments in the bifurcating hydrogel constructs. Main results. Results indicated that when applied to the constrained choice point geometry, the biased turning model predicted experimental behavior closely. Results for both simulated and in vitro neurite growth studies showed a significant chemoattractive response toward the bifurcated end containing an NGF gradient compared to the control, though some neurites were found in the end with no NGF gradient. Significance. The integrated model of neurite growth we describe will allow comparison of experimental studies against growth cone guidance computational models applied to axon pathfinding at choice points.

Participation and Diffusion Effects of a Peer-Intervention for HIV Prevention among Adults in Rural Malawi

PubMed Central

Crittenden, Kathleen S.; Kaponda, Chrissie P. N.; Jere, Diana L.; McCreary, Linda L.; Norr, Kathleen F.

2015-01-01

This paper examines whether a peer group intervention that reduced self-reported risky behaviors for rural adults in Malawi also had impacts on non-participants in the same communities. We randomly assigned two districts to the intervention and control conditions, and conducted surveys at baseline and 18 months post-intervention using unmatched independent random samples of intervention and control communities in 2003-2006. The six-session peer group intervention was offered to same-gender groups by trained volunteers. In this analysis, we divided the post-intervention sample into three exposure groups: 243 participants and 170 non-participants from the intervention district (total n=415) and 413 control individuals. Controlling for demographics and participation, there were significant favorable diffusion effects on five partially overlapping behavioral outcomes: partner communication, ever used condoms, unprotected sex, recent HIV test, and a community HIV prevention index. Non-participants in the intervention district had more favorable outcomes on these behaviors than survey respondents in the control district. One behavioral outcome, community HIV prevention, showed both participation and diffusion effects. Participating in the intervention had a significant effect on six psychosocial outcomes: HIV knowledge (two measures), hope, condom attitudes, and self-efficacy for community HIV prevention and for safer sex; there were no diffusion effects. This pattern of results suggests that the behavioral changes promoted in the intervention spread to others in the same community, most likely through direct contact between participants and non-participants. These findings support the idea that diffusion of HIV-related behavior changes can occur for peer group interventions in communities, adding to the body of research supporting diffusion of innovations theory as a robust approach to accelerating change. If diffusion occurs, peer group intervention may be more cost-effective than previously realized. Wider implementation of peer group interventions can help meet the global goal of reducing new HIV infections. PMID:25864150

Data mining of molecular dynamics data reveals Li diffusion characteristics in garnet Li7La3Zr2O12

PubMed Central

Chen, Chi; Lu, Ziheng; Ciucci, Francesco

2017-01-01

Understanding Li diffusion in solid conductors is essential for the next generation Li batteries. Here we show that density-based clustering of the trajectories computed using molecular dynamics simulations helps elucidate the Li diffusion mechanism within the Li7La3Zr2O12 (LLZO) crystal lattice. This unsupervised learning method recognizes lattice sites, is able to give the site type, and can identify Li hopping events. Results show that, while the cubic LLZO has a much higher hopping rate compared to its tetragonal counterpart, most of the Li hops in the cubic LLZO do not contribute to the diffusivity due to the dominance of back-and-forth type jumps. The hopping analysis and local Li configuration statistics give evidence that Li diffusivity in cubic LLZO is limited by the low vacancy concentration. The hopping statistics also shows uncorrelated Poisson-like diffusion for Li in the cubic LLZO, and correlated diffusion for Li in the tetragonal LLZO in the temporal scale. Further analysis of the spatio-temporal correlation using site-to-site mutual information confirms the weak site dependence of Li diffusion in the cubic LLZO as the origin for the uncorrelated diffusion. This work puts forward a perspective on combining machine learning and information theory to interpret results of molecular dynamics simulations. PMID:28094317

Data mining of molecular dynamics data reveals Li diffusion characteristics in garnet Li7La3Zr2O12

NASA Astrophysics Data System (ADS)

Chen, Chi; Lu, Ziheng; Ciucci, Francesco

2017-01-01

Understanding Li diffusion in solid conductors is essential for the next generation Li batteries. Here we show that density-based clustering of the trajectories computed using molecular dynamics simulations helps elucidate the Li diffusion mechanism within the Li7La3Zr2O12 (LLZO) crystal lattice. This unsupervised learning method recognizes lattice sites, is able to give the site type, and can identify Li hopping events. Results show that, while the cubic LLZO has a much higher hopping rate compared to its tetragonal counterpart, most of the Li hops in the cubic LLZO do not contribute to the diffusivity due to the dominance of back-and-forth type jumps. The hopping analysis and local Li configuration statistics give evidence that Li diffusivity in cubic LLZO is limited by the low vacancy concentration. The hopping statistics also shows uncorrelated Poisson-like diffusion for Li in the cubic LLZO, and correlated diffusion for Li in the tetragonal LLZO in the temporal scale. Further analysis of the spatio-temporal correlation using site-to-site mutual information confirms the weak site dependence of Li diffusion in the cubic LLZO as the origin for the uncorrelated diffusion. This work puts forward a perspective on combining machine learning and information theory to interpret results of molecular dynamics simulations.

Evaluation of glymphatic system activity with the diffusion MR technique: diffusion tensor image analysis along the perivascular space (DTI-ALPS) in Alzheimer's disease cases.

PubMed

Taoka, Toshiaki; Masutani, Yoshitaka; Kawai, Hisashi; Nakane, Toshiki; Matsuoka, Kiwamu; Yasuno, Fumihiko; Kishimoto, Toshifumi; Naganawa, Shinji

2017-04-01

The activity of the glymphatic system is impaired in animal models of Alzheimer's disease (AD). We evaluated the activity of the human glymphatic system in cases of AD with a diffusion-based technique called diffusion tensor image analysis along the perivascular space (DTI-ALPS). Diffusion tensor images were acquired to calculate diffusivities in the x, y, and z axes of the plane of the lateral ventricle body in 31 patients. We evaluated the diffusivity along the perivascular spaces as well as projection fibers and association fibers separately, to acquire an index for diffusivity along the perivascular space (ALPS-index) and correlated them with the mini mental state examinations (MMSE) score. We found a significant negative correlation between diffusivity along the projection fibers and association fibers. We also observed a significant positive correlation between diffusivity along perivascular spaces shown as ALPS-index and the MMSE score, indicating lower water diffusivity along the perivascular space in relation to AD severity. Activity of the glymphatic system may be evaluated with diffusion images. Lower diffusivity along the perivascular space on DTI-APLS seems to reflect impairment of the glymphatic system. This method may be useful for evaluating the activity of the glymphatic system.

Fluid Registration of Diffusion Tensor Images Using Information Theory

PubMed Central

Chiang, Ming-Chang; Leow, Alex D.; Klunder, Andrea D.; Dutton, Rebecca A.; Barysheva, Marina; Rose, Stephen E.; McMahon, Katie L.; de Zubicaray, Greig I.; Toga, Arthur W.; Thompson, Paul M.

2008-01-01

We apply an information-theoretic cost metric, the symmetrized Kullback-Leibler (sKL) divergence, or J-divergence, to fluid registration of diffusion tensor images. The difference between diffusion tensors is quantified based on the sKL-divergence of their associated probability density functions (PDFs). Three-dimensional DTI data from 34 subjects were fluidly registered to an optimized target image. To allow large image deformations but preserve image topology, we regularized the flow with a large-deformation diffeomorphic mapping based on the kinematics of a Navier-Stokes fluid. A driving force was developed to minimize the J-divergence between the deforming source and target diffusion functions, while reorienting the flowing tensors to preserve fiber topography. In initial experiments, we showed that the sKL-divergence based on full diffusion PDFs is adaptable to higher-order diffusion models, such as high angular resolution diffusion imaging (HARDI). The sKL-divergence was sensitive to subtle differences between two diffusivity profiles, showing promise for nonlinear registration applications and multisubject statistical analysis of HARDI data. PMID:18390342

Control of reaction-diffusion equations on time-evolving manifolds.

PubMed

Rossi, Francesco; Duteil, Nastassia Pouradier; Yakoby, Nir; Piccoli, Benedetto

2016-12-01

Among the main actors of organism development there are morphogens, which are signaling molecules diffusing in the developing organism and acting on cells to produce local responses. Growth is thus determined by the distribution of such signal. Meanwhile, the diffusion of the signal is itself affected by the changes in shape and size of the organism. In other words, there is a complete coupling between the diffusion of the signal and the change of the shapes. In this paper, we introduce a mathematical model to investigate such coupling. The shape is given by a manifold, that varies in time as the result of a deformation given by a transport equation. The signal is represented by a density, diffusing on the manifold via a diffusion equation. We show the non-commutativity of the transport and diffusion evolution by introducing a new concept of Lie bracket between the diffusion and the transport operator. We also provide numerical simulations showing this phenomenon.

Multicomponent diffusion in molten salt NaF-ZrF4: Dynamical correlations and Maxwell-Stefan diffusivities

NASA Astrophysics Data System (ADS)

Baig, Mohammad Saad; Chakraborty, Brahmananda; Ramaniah, Lavanya M.

2016-05-01

NaF-ZrF4 is used as a waste incinerator and as a coolant in Generation IV reactors.Structural and dynamical properties of molten NaF-ZrF4 system were studied along with Onsagercoefficients and Maxwell-Stefan (MS) Diffusivities applying Green-Kubo formalism and molecular dynamics (MD) simulations. The zirconium ions are found to be 8 fold coordinated with fluoride ions for all temperatures and concentrations. All the diffusive flux correlations show back-scattering. Even though the MS diffusivities are expected to depend very lightly on the composition because of decoupling of thermodynamic factor, the diffusivity ĐNa-F shows interesting behavior with the increase in concentration of ZrF4. This is because of network formation in NaF-ZrF4. Positive entropy constraints have been plotted to authenticate negative diffusivities observed.

Computational Analysis on Performance of Thermal Energy Storage (TES) Diffuser

NASA Astrophysics Data System (ADS)

Adib, M. A. H. M.; Adnan, F.; Ismail, A. R.; Kardigama, K.; Salaam, H. A.; Ahmad, Z.; Johari, N. H.; Anuar, Z.; Azmi, N. S. N.

2012-09-01

Application of thermal energy storage (TES) system reduces cost and energy consumption. The performance of the overall operation is affected by diffuser design. In this study, computational analysis is used to determine the thermocline thickness. Three dimensional simulations with different tank height-to-diameter ratio (HD), diffuser opening and the effect of difference number of diffuser holes are investigated. Medium HD tanks simulations with double ring octagonal diffuser show good thermocline behavior and clear distinction between warm and cold water. The result show, the best performance of thermocline thickness during 50% time charging occur in medium tank with height-to-diameter ratio of 4.0 and double ring octagonal diffuser with 48 holes (9mm opening ~ 60%) acceptable compared to diffuser with 6mm ~ 40% and 12mm ~ 80% opening. The conclusion is computational analysis method are very useful in the study on performance of thermal energy storage (TES).

Characterization of a Dynamic String Method for the Construction of Transition Pathways in Molecular Reactions

PubMed Central

Johnson, Margaret E.; Hummer, Gerhard

2012-01-01

We explore the theoretical foundation of different string methods used to find dominant reaction pathways in high-dimensional configuration spaces. Pathways are assessed by the amount of reactive flux they carry and by their orientation relative to the committor function. By examining the effects of transforming between different collective coordinates that span the same underlying space, we unmask artificial coordinate dependences in strings optimized to follow the free energy gradient. In contrast, strings optimized to follow the drift vector produce reaction pathways that are significantly less sensitive to reparameterizations of the collective coordinates. The differences in these paths arise because the drift vector depends on both the free energy gradient and the diffusion tensor of the coarse collective variables. Anisotropy and position dependence of diffusion tensors arise commonly in spaces of coarse variables, whose generally slow dynamics are obtained by nonlinear projections of the strongly coupled atomic motions. We show here that transition paths constructed to account for dynamics by following the drift vector will (to a close approximation) carry the maximum reactive flux both in systems with isotropic position dependent diffusion, and in systems with constant but anisotropic diffusion. We derive a simple method for calculating the committor function along paths that follow the reactive flux. Lastly, we provide guidance for the practical implementation of the dynamic string method. PMID:22616575

Age at First Exposure to Football Is Associated with Altered Corpus Callosum White Matter Microstructure in Former Professional Football Players

PubMed Central

Stamm, Julie M.; Koerte, Inga K.; Muehlmann, Marc; Pasternak, Ofer; Bourlas, Alexandra P.; Baugh, Christine M.; Giwerc, Michelle Y.; Zhu, Anni; Coleman, Michael J.; Bouix, Sylvain; Fritts, Nathan G.; Martin, Brett M.; Chaisson, Christine; McClean, Michael D.; Lin, Alexander P.; Cantu, Robert C.; Tripodis, Yorghos; Shenton, Martha E.

2015-01-01

Abstract Youth football players may incur hundreds of repetitive head impacts (RHI) in one season. Our recent research suggests that exposure to RHI during a critical neurodevelopmental period prior to age 12 may lead to greater later-life mood, behavioral, and cognitive impairments. Here, we examine the relationship between age of first exposure (AFE) to RHI through tackle football and later-life corpus callosum (CC) microstructure using magnetic resonance diffusion tensor imaging (DTI). Forty retired National Football League (NFL) players, ages 40–65, were matched by age and divided into two groups based on their AFE to tackle football: before age 12 or at age 12 or older. Participants underwent DTI on a 3 Tesla Siemens (TIM-Verio) magnet. The whole CC and five subregions were defined and seeded using deterministic tractography. Dependent measures were fractional anisotropy (FA), trace, axial diffusivity, and radial diffusivity. Results showed that former NFL players in the AFE <12 group had significantly lower FA in anterior three CC regions and higher radial diffusivity in the most anterior CC region than those in the AFE ≥12 group. This is the first study to find a relationship between AFE to RHI and later-life CC microstructure. These results suggest that incurring RHI during critical periods of CC development may disrupt neurodevelopmental processes, including myelination, resulting in altered CC microstructure. PMID:26200068

Age at First Exposure to Football Is Associated with Altered Corpus Callosum White Matter Microstructure in Former Professional Football Players.

PubMed

Stamm, Julie M; Koerte, Inga K; Muehlmann, Marc; Pasternak, Ofer; Bourlas, Alexandra P; Baugh, Christine M; Giwerc, Michelle Y; Zhu, Anni; Coleman, Michael J; Bouix, Sylvain; Fritts, Nathan G; Martin, Brett M; Chaisson, Christine; McClean, Michael D; Lin, Alexander P; Cantu, Robert C; Tripodis, Yorghos; Stern, Robert A; Shenton, Martha E

2015-11-15

Youth football players may incur hundreds of repetitive head impacts (RHI) in one season. Our recent research suggests that exposure to RHI during a critical neurodevelopmental period prior to age 12 may lead to greater later-life mood, behavioral, and cognitive impairments. Here, we examine the relationship between age of first exposure (AFE) to RHI through tackle football and later-life corpus callosum (CC) microstructure using magnetic resonance diffusion tensor imaging (DTI). Forty retired National Football League (NFL) players, ages 40-65, were matched by age and divided into two groups based on their AFE to tackle football: before age 12 or at age 12 or older. Participants underwent DTI on a 3 Tesla Siemens (TIM-Verio) magnet. The whole CC and five subregions were defined and seeded using deterministic tractography. Dependent measures were fractional anisotropy (FA), trace, axial diffusivity, and radial diffusivity. Results showed that former NFL players in the AFE <12 group had significantly lower FA in anterior three CC regions and higher radial diffusivity in the most anterior CC region than those in the AFE ≥12 group. This is the first study to find a relationship between AFE to RHI and later-life CC microstructure. These results suggest that incurring RHI during critical periods of CC development may disrupt neurodevelopmental processes, including myelination, resulting in altered CC microstructure.

IgV(H) and bcl6 somatic mutation analysis reveals the heterogeneity of cutaneous B-cell lymphoma, and indicates the presence of undisclosed local antigens.

PubMed

Franco, Renato; Camacho, Francisca I; Fernández-Vázquez, Amalia; Algara, Patrocinio; Rodríguez-Peralto, José L; De Rosa, Gaetano; Piris, Miguel A

2004-06-01

Our understanding of the ontology of B-cell lymphomas (BCL) has been improved by the study of mutational status of IgV(H) and bcl6 genes, but only a few cases of cutaneous BCL have been examined for this status. We analyzed IgV(H) and bcl6 somatic mutations in 10 cutaneous BCL, classified as follicular (three primary and one secondary), primary marginal zone (two cases), and diffuse large BCL (three primary and one secondary). We observed a lower rate (<2%) of IgV(H) mutation in all marginal zone lymphomas, and a preferential usage of V(H)2-70 (one primary follicular and two primary diffuse large BCL). Fewer than expected replacement mutations in framework regions (FR) were observed in three primary follicular lymphomas (FLs) and in all diffuse large BCL, indicating a negative antigen selection pressure. Ongoing mutations were observed in eight of 10 cases. Only two primary FLs and two diffuse large BCL showed bcl6 somatic mutation. These data support the heterogeneous nature of the different cutaneous BCL, and specifically the distinction between cutaneous follicular and marginal zone lymphomas. The biased usage of V(H)2-70, the low rate of replacement mutation in the FR, and the presence of ongoing mutation imply that local antigens could modulate the growth of primary cutaneous BCL.

Diffusion-weighted magnetic resonance imaging in the characterization of testicular germ cell neoplasms: Effect of ROI methods on apparent diffusion coefficient values and interobserver variability.

PubMed

Tsili, Athina C; Ntorkou, Alexandra; Astrakas, Loukas; Xydis, Vasilis; Tsampalas, Stavros; Sofikitis, Nikolaos; Argyropoulou, Maria I

2017-04-01

To evaluate the difference in apparent diffusion coefficient (ADC) measurements at diffusion-weighted (DW) magnetic resonance imaging of differently shaped regions-of-interest (ROIs) in testicular germ cell neoplasms (TGCNS), the diagnostic ability of differently shaped ROIs in differentiating seminomas from nonseminomatous germ cell neoplasms (NSGCNs) and the interobserver variability. Thirty-three TGCNs were retrospectively evaluated. Patients underwent MR examinations, including DWI on a 1.5-T MR system. Two observers measured mean tumor ADCs using four distinct ROI methods: round, square, freehand and multiple small, round ROIs. The interclass correlation coefficient was analyzed to assess interobserver variability. Statistical analysis was used to compare mean ADC measurements among observers, methods and histologic types. All ROI methods showed excellent interobserver agreement, with excellent correlation (P<0.001). Multiple, small ROIs provided the lower mean ADC in TGCNs. Seminomas had lower mean ADC compared to NSGCNs for each ROI method (P<0.001). Round ROI proved the most accurate method in characterizing TGCNS. Interobserver variability in ADC measurement is excellent, irrespective of the ROI shape. Multiple, small round ROIs and round ROI proved the more accurate methods for ADC measurement in the characterization of TGCNs and in the differentiation between seminomas and NSGCNs, respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

Preliminary analysis of the distribution of water in human hair by small-angle neutron scattering.

PubMed

Kamath, Yash; Murthy, N Sanjeeva; Ramaprasad, Ram

2014-01-01

Diffusion and distribution of water in hair can reveal the internal structure of hair that determines the penetration of various products used to treat hair. The distribution of water into different morphological components in unmodified hair, cuticle-free hair, and hair saturated with oil at various levels of humidity was examined using small-angle neutron scattering (SANS) by substituting water with deuterium oxide (D(2)O). Infrared spectroscopy was used to follow hydrogen-deuterium exchange. Water present in hair gives basically two types of responses in SANS: (i) interference patterns, and (ii) central diffuse scattering (CDS) around the beam stop. The amount of water in the matrix between the intermediate filaments that gives rise to interference patterns remained essentially constant over the 50-98% humidity range without swelling this region of the fiber extensively. This observation suggests that a significant fraction of water in the hair, which contributes to the CDS, is likely located in a different morphological region of hair that is more like pores in a fibrous structure, which leads to significant additional swelling of the fiber. Comparison of the scattering of hair treated with oil shows that soybean oil, which diffuses less into hair, allows more water into hair than coconut oil. These preliminary results illustrate the utility of SANS for evaluating and understanding the diffusion of deuterated liquids into different morphological structures in hair.

c-Ski overexpression promotes tumor growth and angiogenesis through inhibition of transforming growth factor-beta signaling in diffuse-type gastric carcinoma.

PubMed

Kiyono, Kunihiko; Suzuki, Hiroshi I; Morishita, Yasuyuki; Komuro, Akiyoshi; Iwata, Caname; Yashiro, Masakazu; Hirakawa, Kosei; Kano, Mitsunobu R; Miyazono, Kohei

2009-10-01

c-Ski, originally identified as a proto-oncogene product, is an important negative regulator of transforming growth factor (TGF)-beta family signaling through interaction with Smad2, Smad3, and Smad4. High expression of c-Ski has been found in some cancers, including gastric cancer. We previously showed that disruption of TGF-beta signaling by dominant-negative TGF-beta type II receptor in a diffuse-type gastric carcinoma model accelerated tumor growth through induction of tumor angiogenesis by decreased expression of the anti-angiogenic factor thrombospondin (TSP)-1. Here, we examined the function of c-Ski in human diffuse-type gastric carcinoma OCUM-2MLN cells. Overexpression of c-Ski inhibited TGF-beta signaling in OCUM-2MLN cells. Interestingly, c-Ski overexpression resulted in extensive acceleration of the growth of subcutaneous xenografts in BALB/c nu/nu female mice (6 weeks of age). Similar to tumors expressing dominant-negative TGF-beta type II receptor, histochemical studies revealed less fibrosis and increased angiogenesis in xenografted tumors expressing c-Ski compared to control tumors. Induction of TSP-1 mRNA by TGF-beta was attenuated by c-Ski in vitro, and expression of TSP-1 mRNA was decreased in tumors expressing c-Ski in vivo. These findings suggest that c-Ski overexpression promotes the growth of diffuse-type gastric carcinoma through induction of angiogenesis.

Can H2CCC be the Carrier of Broad Diffuse Bands?

NASA Astrophysics Data System (ADS)

Krełowski, J.; Galazutdinov, G.; Kołos, R.

2011-07-01

The recent assignment of two broad diffuse interstellar bands (DIBs) near 4882 and 5450 Å to the propadienylidene (l-C3H2) molecule is examined using a statistically meaningful sample of targets. Our spectra clearly show that the strength ratio of two broad DIBs is strongly variable, contrary to what should be observed if both features are due to l-C3H2, since the proposed transitions are lifetime broadened and start from the same level. Moreover, even in directions where the 4882 DIB and 5450 DIB are strong, the third expected l-C3H2 band, in the 5165-5185 Å region, is absent. Another puzzling characteristic of l-C3H2 as the proposed carrier of both broad diffuse bands is its column density of several 1014 cm-2, inferred from the equivalent width of the 5450 DIB. This value is one order of magnitude higher than N(CH) toward the same objects and two to three orders of magnitude higher than N(H2CCC), measured at radio frequencies in absorption, for comparable samples of the diffuse medium. We conclude that the proposed identification of broad DIBs is unjustified. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere, Chile; programs 073.C-0337(A) and 082.C-0566(A).

Edge-based nonlinear diffusion for finite element approximations of convection-diffusion equations and its relation to algebraic flux-correction schemes.

PubMed

Barrenechea, Gabriel R; Burman, Erik; Karakatsani, Fotini

2017-01-01

For the case of approximation of convection-diffusion equations using piecewise affine continuous finite elements a new edge-based nonlinear diffusion operator is proposed that makes the scheme satisfy a discrete maximum principle. The diffusion operator is shown to be Lipschitz continuous and linearity preserving. Using these properties we provide a full stability and error analysis, which, in the diffusion dominated regime, shows existence, uniqueness and optimal convergence. Then the algebraic flux correction method is recalled and we show that the present method can be interpreted as an algebraic flux correction method for a particular definition of the flux limiters. The performance of the method is illustrated on some numerical test cases in two space dimensions.

Grain boundary diffusion behaviors in hot-deformed Nd2Fe14B magnets by PrNd-Cu low eutectic alloys

NASA Astrophysics Data System (ADS)

Tang, Xu; Chen, Renjie; Li, Ming; Jin, Chaoxiang; Yin, Wenzong; Lee, Don; Yan, Aru

2018-01-01

High coercivity of hot-deformed Nd2Fe14B magnets was obtained by grain boundary diffusion. Comparable squareness and similar magnetic properties for samples diffusing from side and pole surfaces show little discrepancies if quantities of the infiltrated PrNd-Cu low eutectic alloys is enough to obtain sufficient diffusion. However, the microstructures and higher characteristic peak ratios show preferable orientation of grains near surfaces of the sample diffused from side surfaces than that from pole surfaces. Amorphous Nd-rich phases and crystal Fe-rich phases were both observed in the diffused magnets. The enhancement of coercivity is considered to be resulted from grain boundary optimization and magnetic isolation which is caused by the thickened nonmagnetic intergranular phases.

Advantages of diffuse light for horticultural production and perspectives for further research

PubMed Central

Li, Tao; Yang, Qichang

2015-01-01

Plants use diffuse light more efficiently than direct light, which is well established due to diffuse light penetrates deeper into the canopy and photosynthetic rate of a single leaf shows a non-linear response to the light flux density. Diffuse light also results in a more even horizontal and temporal light distribution in the canopy, which plays substantial role for crop photosynthesis enhancement as well as production improvement. Here we show some of the recent findings about the effect of diffuse light on light distribution over the canopy and its direct and indirect effects on crop photosynthesis and plant growth, and suggest some perspectives for further research which could strengthen the scientific understanding of diffuse light modulate plant processes and its application in horticultural production. PMID:26388890

Controllable uncertain opinion diffusion under confidence bound and unpredicted diffusion probability

NASA Astrophysics Data System (ADS)

Yan, Fuhan; Li, Zhaofeng; Jiang, Yichuan

2016-05-01

The issues of modeling and analyzing diffusion in social networks have been extensively studied in the last few decades. Recently, many studies focus on uncertain diffusion process. The uncertainty of diffusion process means that the diffusion probability is unpredicted because of some complex factors. For instance, the variety of individuals' opinions is an important factor that can cause uncertainty of diffusion probability. In detail, the difference between opinions can influence the diffusion probability, and then the evolution of opinions will cause the uncertainty of diffusion probability. It is known that controlling the diffusion process is important in the context of viral marketing and political propaganda. However, previous methods are hardly feasible to control the uncertain diffusion process of individual opinion. In this paper, we present suitable strategy to control this diffusion process based on the approximate estimation of the uncertain factors. We formulate a model in which the diffusion probability is influenced by the distance between opinions, and briefly discuss the properties of the diffusion model. Then, we present an optimization problem at the background of voting to show how to control this uncertain diffusion process. In detail, it is assumed that each individual can choose one of the two candidates or abstention based on his/her opinion. Then, we present strategy to set suitable initiators and their opinions so that the advantage of one candidate will be maximized at the end of diffusion. The results show that traditional influence maximization algorithms are not applicable to this problem, and our algorithm can achieve expected performance.

Diffusion of Technical Agricultural Information in Chile.

ERIC Educational Resources Information Center

Brown, Marion Ray

This study examined current thought concerning the role of mass communication in economic development in developing nations; analyzed existing efforts to diffuse agricultural technology in Chile; assessed the effectiveness of various approaches; and tested the effects (primarily on knowledge levels) of an experimental technical information service…

Identifying Role Diffusion in School Counseling

ERIC Educational Resources Information Center

Astramovich, Randall L.; Hoskins, Wendy J.; Gutierrez, Antonio P.; Bartlett, Kerry A.

2013-01-01

Role ambiguity in professional school counseling is an ongoing concern despite recent advances with comprehensive school counseling models. The study outlined in this article examined role diffusion as a possible factor contributing to ongoing role ambiguity in school counseling. Participants included 109 graduate students enrolled in a…

Spatial variability of the Arctic Ocean's double-diffusive staircase

NASA Astrophysics Data System (ADS)

Shibley, N. C.; Timmermans, M.-L.; Carpenter, J. R.; Toole, J. M.

2017-02-01

The Arctic Ocean thermohaline stratification frequently exhibits a staircase structure overlying the Atlantic Water Layer that can be attributed to the diffusive form of double-diffusive convection. The staircase consists of multiple layers of O(1) m in thickness separated by sharp interfaces, across which temperature and salinity change abruptly. Through a detailed analysis of Ice-Tethered Profiler measurements from 2004 to 2013, the double-diffusive staircase structure is characterized across the entire Arctic Ocean. We demonstrate how the large-scale Arctic Ocean circulation influences the small-scale staircase properties. These staircase properties (layer thicknesses and temperature and salinity jumps across interfaces) are examined in relation to a bulk vertical density ratio spanning the staircase stratification. We show that the Lomonosov Ridge serves as an approximate boundary between regions of low density ratio (approximately 3-4) on the Eurasian side and higher density ratio (approximately 6-7) on the Canadian side. We find that the Eurasian Basin staircase is characterized by fewer, thinner layers than that in the Canadian Basin, although the margins of all basins are characterized by relatively thin layers and the absence of a well-defined staircase. A double-diffusive 4/3 flux law parametrization is used to estimate vertical heat fluxes in the Canadian Basin to be O(0.1) W m-2. It is shown that the 4/3 flux law may not be an appropriate representation of heat fluxes through the Eurasian Basin staircase. Here molecular heat fluxes are estimated to be between O(0.01) and O(0.1) W m-2. However, many uncertainties remain about the exact nature of these fluxes.

Compartment models of the diffusion MR signal in brain white matter: a taxonomy and comparison.

PubMed

Panagiotaki, Eleftheria; Schneider, Torben; Siow, Bernard; Hall, Matt G; Lythgoe, Mark F; Alexander, Daniel C

2012-02-01

This paper aims to identify the minimum requirements for an accurate model of the diffusion MR signal in white matter of the brain. We construct a taxonomy of multi-compartment models of white matter from combinations of simple models for the intra- and the extra-axonal spaces. We devise a new diffusion MRI protocol that provides measurements with a wide range of imaging parameters for diffusion sensitization both parallel and perpendicular to white matter fibres. We use the protocol to acquire data from two fixed rat brains, which allows us to fit, study and compare the different models. The study examines a total of 47 analytic models, including several well-used models from the literature, which we place within the taxonomy. The results show that models that incorporate intra-axonal restriction, such as ball and stick or CHARMED, generally explain the data better than those that do not, such as the DT or the biexponential models. However, three-compartment models which account for restriction parallel to the axons and incorporate pore size explain the measurements most accurately. The best fit comes from combining a full diffusion tensor (DT) model of the extra-axonal space with a cylindrical intra-axonal component of single radius and a third spherical compartment of non-zero radius. We also measure the stability of the non-zero radius intra-axonal models and find that single radius intra-axonal models are more stable than gamma distributed radii models with similar fitting performance. Copyright © 2011 Elsevier Inc. All rights reserved.

Self-diffusion Coefficient and Structure of Binary n-Alkane Mixtures at the Liquid-Vapor Interfaces.

PubMed

Chilukoti, Hari Krishna; Kikugawa, Gota; Ohara, Taku

2015-10-15

The self-diffusion coefficient and molecular-scale structure of several binary n-alkane liquid mixtures in the liquid-vapor interface regions have been examined using molecular dynamics simulations. It was observed that in hexane-tetracosane mixture hexane molecules are accumulated in the liquid-vapor interface region and the accumulation intensity decreases with increase in a molar fraction of hexane in the examined range. Molecular alignment and configuration in the interface region of the liquid mixture change with a molar fraction of hexane. The self-diffusion coefficient in the direction parallel to the interface of both tetracosane and hexane in their binary mixture increases in the interface region. It was found that the self-diffusion coefficient of both tetracosane and hexane in their binary mixture is considerably higher in the vapor side of the interface region as the molar fraction of hexane goes lower, which is mostly due to the increase in local free volume caused by the local structure of the liquid in the interface region.

Diffusion tensor imaging demonstrates brainstem and cerebellar abnormalities in congenital central hypoventilation syndrome.

PubMed

Kumar, Rajesh; Macey, Paul M; Woo, Mary A; Alger, Jeffry R; Harper, Ronald M

2008-09-01

Congenital central hypoventilation syndrome (CCHS) patients show reduced breathing drive during sleep, decreased hypoxic and hypercapnic ventilatory responses, and autonomic and affective deficits, suggesting both brainstem and forebrain injuries. Forebrain damage was previously described in CCHS, but methodological limitations precluded detection of brainstem injury, a concern because genetic mutations in CCHS target brainstem autonomic nuclei. To assess brainstem and cerebellar areas, we used diffusion tensor imaging-based measures, namely axial diffusivity, reflecting water diffusion parallel to fibers, and sensitive to axonal injury, and radial diffusivity, measuring diffusion perpendicular to fibers, and indicative of myelin injury. Diffusion tensor imaging was performed in 12 CCHS and 26 controls, and axial and radial diffusivity maps were compared between groups using analysis of covariance (covariates; age and gender). Increased axial diffusivity in CCHS appeared within the lateral medulla and clusters with injury extended from the dorsal midbrain through the periaqueductal gray, raphé, and superior cerebellar decussation, ventrally to the basal-pons. Cerebellar cortex and deep nuclei, and the superior and inferior cerebellar peduncles showed increased radial diffusivity. Midbrain, pontine, and lateral medullary structures, and the cerebellum and its fiber systems are injured in CCHS, likely contributing to the characteristics found in the syndrome.

Interplay between translational diffusion and large-amplitude angular jumps of water molecules

NASA Astrophysics Data System (ADS)

Liu, Chao; Zhang, Yangyang; Zhang, Jian; Wang, Jun; Li, Wenfei; Wang, Wei

2018-05-01

Understanding the microscopic mechanism of water molecular translational diffusion is a challenging topic in both physics and chemistry. Here, we report an investigation on the interplay between the translational diffusion and the large-amplitude angular jumps of water molecules in bulk water using molecular dynamics simulations. We found that large-amplitude angular jumps are tightly coupled to the translational diffusions. Particularly, we revealed that concurrent rotational jumps of spatially neighboring water molecules induce inter-basin translational jumps, which contributes to the fast component of the water translational diffusion. Consequently, the translational diffusion shows positional heterogeneity; i.e., the neighbors of the water molecules with inter-basin translational jumps have larger probability to diffuse by inter-basin translational jumps. Our control simulations showed that a model water molecule with moderate hydrogen bond strength can diffuse much faster than a simple Lennard-Jones particle in bulk water due to the capability of disturbing the hydrogen bond network of the surrounding water molecules. Our results added to the understanding of the microscopic picture of the water translational diffusion and demonstrated the unique features of water diffusion arising from their hydrogen bond network structure compared with those of the simple liquids.

Relationship between tissue tension and thermal diffusion to peripheral tissue using an energy device.

PubMed

Kondo, Akihiro; Nishizawa, Yuji; Ito, Masaaki; Saito, Norio; Fujii, Satoshi; Akamoto, Shintaro; Fujiwara, Masao; Okano, Keiichi; Suzuki, Yasuyuki

2016-08-01

The aim of the study was to assess the relationship between tissue tension and thermal diffusion to peripheral tissues using an electric scalpel, ultrasonically activated device, or a bipolar sealing system. The mesentery of pigs was excised with each energy device (ED) at three tissue tensions (0, 300, 600 g). The excision time and thermal diffusion area were monitored with thermography, measured for each ED, and then histologically examined. Correlations between tissue tension and thermal diffusion area were examined. The excision time was inversely correlated with tissue tension for all ED (electric scalpel, r = 0.718; ultrasonically activated device, r = 0.949; bipolar sealing system, r = 0.843), and tissue tension was inversely correlated with the thermal diffusion area with the electric scalpel (r = 0.718) and bipolar sealing system (r = 0.869). Histopathologically, limited deep thermal denaturation occurred at a tension of 600 g with all ED. We conclude that thermal damage can be avoided with adequate tissue tension when any ED is used. © 2016 Japan Society for Endoscopic Surgery, Asia Endosurgery Task Force and John Wiley & Sons Australia, Ltd.

Chemical and Temperature Effects on Diffusion in a Model Polymer/Nanoparticle Composite

NASA Astrophysics Data System (ADS)

Janes, Dustin; Durning, Christopher

Polymers and inks used in medical devices may be strengthened with nanoparticle fillers, so an understanding of how they may affect the release of residuals and additives via diffusion will help modernize biocompatibility testing. Transport of small molecules in polymers with increasing volume fraction of impermeable nanoparticles is often poorly predicted by the simple Maxwell model for heterogeneous media. In this presentation we will examine two diffusant classes, only one of which possesses hydrogen bonding interactions with the nanoparticle surface. Since similar reductions in mutual diffusion coefficients were observed in both cases we attribute the enhancement of the ''blocking effect'' in nanocomposites to a reduction in polymer mobility in the interfacial volume near the nanoparticle. The temperature and penetrant concentration dependence of the diffusion coefficients were examined in the context of a Vrentas-Duda free volume model that includes a thermally activated prefactor. While data obtained for rubbery poly(methyl acrylate) clearly obeys the expected Arrhenius scaling with EA = 11 kJ/mol, results for films containing d = 14 nm spherical silica nanoparticles do not, providing more evidence that polymer free volume is perturbed in unexpected ways even for conceptually simple systems. National Science Foundation IGERT Program, Pall Corporation.

On the use of water phantom images to calibrate and correct eddy current induced artefacts in MR diffusion tensor imaging.

PubMed

Bastin, M E; Armitage, P A

2000-07-01

The accurate determination of absolute measures of diffusion anisotropy in vivo using single-shot, echo-planar imaging techniques requires the acquisition of a set of high signal-to-noise ratio, diffusion-weighted images that are free from eddy current induced image distortions. Such geometric distortions can be characterized and corrected in brain imaging data using magnification (M), translation (T), and shear (S) distortion parameters derived from separate water phantom calibration experiments. Here we examine the practicalities of using separate phantom calibration data to correct high b-value diffusion tensor imaging data by investigating the stability of these distortion parameters, and hence the eddy currents, with time. It is found that M, T, and S vary only slowly with time (i.e., on the order of weeks), so that calibration scans need not be performed after every patient examination. This not only minimises the scan time required to collect the calibration data, but also the computational time needed to characterize these eddy current induced distortions. Examples of how measurements of diffusion anisotropy are improved using this post-processing scheme are also presented.

Asbestos bodies and the diagnosis of asbestosis in chrysotile workers

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

Holden, J.; Churg, A.

1986-01-01

It has been suggested that because chrysotile asbestos forms asbestos bodies poorly, use of the traditional histologic requirements (diffuse interstitial fibrosis plus asbestos bodies) for the diagnosis of asbestosis, may lead to an underdiagnosis of this condition in workers exposed only to chrysotile. Lungs from 25 chrysotile miners with diffuse interstitial fibrosis were examined. Asbestos bodies were found easily in histologic section using hematoxylin and eosin stains in all cases. Mineralogic analysis of four cases showed that 46 of 72 (64%) bodies isolated and examined contained chrysotile cores, and 21 of 72 (29%) bodies contained cores of the amphiboles tremolitemore » and actinolite. By contrast, tremolite and actinolite constituted the majority of uncoated fibers in these cases. The mean length for bodies formed on chrysotile was 35 ..mu..m, and for bodies formed on tremolite or actinolite, 36 ..mu..m. The authors conclude that (1) the usual histologic criteria for the diagnosis of asbestos are applicable to chrysotile-exposed workers; (2) in workers with occupational chrysotile exposure, bodies form readily on this mineral; and (3) asbestos bodies in these lungs reflect the presence of long asbestos fibers.« less

The Relationship of Dynamical Heterogeneity to the Adam-Gibbs and Random First-Order Transition Theories of Glass Formation

NASA Astrophysics Data System (ADS)

Starr, Francis; Douglas, Jack; Sastry, Srikanth

2013-03-01

We examine measures of dynamical heterogeneity for a bead-spring polymer melt and test how these scales compare with the scales hypothesized by the Adam and Gibbs (AG) and random first-order transition (RFOT) theories. We show that the time scale of the high-mobility clusters and strings is associated with a diffusive time scale, while the low-mobility particles' time scale relates to a structural relaxation time. The difference of the characteristic times naturally explains the decoupling of diffusion and structural relaxation time scales. We examine the appropriateness of identifying the size scales of mobile particle clusters or strings with the size of cooperatively rearranging regions (CRR) in the AG and RFOT theories. We find that the string size appears to be the most consistent measure of CRR for both the AG and RFOT models. Identifying strings or clusters with the``mosaic'' length of the RFOT model relaxes the conventional assumption that the``entropic droplet'' are compact. We also confirm the validity of the entropy formulation of the AG theory, constraining the exponent values of the RFOT theory. This constraint, together with the analysis of size scales, enables us to estimate the characteristic exponents of RFOT.

The crack problem in bonded nonhomogeneous materials

NASA Technical Reports Server (NTRS)

Erdogan, Fazil; Kaya, A. C.; Joseph, P. F.

1988-01-01

The plane elasticity problem for two bonded half planes containing a crack perpendicular to the interface was considered. The effect of very steep variations in the material properties near the diffusion plane on the singular behavior of the stresses and stress intensity factors were studied. The two materials were thus, assumed to have the shear moduli mu(o) and mu(o) exp (Beta x), x=0 being the diffusion plane. Of particular interest was the examination of the nature of stress singularity near a crack tip terminating at the interface where the shear modulus has a discontinuous derivative. The results show that, unlike the crack problem in piecewise homogeneous materials for which the singularity is of the form r/alpha, 0 less than alpha less than 1, in this problem the stresses have a standard square-root singularity regardless of the location of the crack tip. The nonhomogeneity constant Beta has, however, considerable influence on the stress intensity factors.

The crack problem in bonded nonhomogeneous materials

NASA Technical Reports Server (NTRS)

Erdogan, F.; Joseph, P. F.; Kaya, A. C.

1991-01-01

The plane elasticity problem for two bonded half planes containing a crack perpendicular to the interface was considered. The effect of very steep variations in the material properties near the diffusion plane on the singular behavior of the stresses and stress intensity factors were studied. The two materials were thus, assumed to have the shear moduli mu(o) and mu(o) exp (Beta x), x=0 being the diffusion plane. Of particular interest was the examination of the nature of stress singularity near a crack tip termination at the interface where the shear modulus has a discontinuous derivative. The results show that, unlike the crack problem in piecewise homogeneous materials for which the singularity is of the form r/alpha, 0 less than alpha less than 1, in this problem the stresses have a standard square-root singularity regardless of the location of the crack tip. The nonhomogeneity constant Beta has, however, considerable influence on the stress intensity factors.

Pulmonary functions in patients with subclinical hypothyroidism.

PubMed

Cakmak, Gulfidan; Saler, Tayyibe; Saglam, Zuhal Aydan; Yenigun, Mustafa; Ataoglu, Esra; Demir, Tuncalp; Temiz, Levent Umit

2011-10-01

To determine whether alterations in pulmonary function takes place in subclinical hypothyroidism by examining the diffusion lung capacity and muscle strength of such patients. This is a descriptive study conducted in 2009 at Haseki Training and Research Hospital, Istanbul, Turkey. Hundred and twenty-six patients with subclinical hypothyroidism and 58 age and sex matched individuals were recruited. Simple spirometry tests were performed, and pulmonary diffusion capacity (DLco) and muscle strength were measured. ScH patients showed a significant reduciton of the following pulmonary function tests (% predicted value) as compared with control subjects: FVC, FEV1, FEV1%, FEF25-75, FEF25-75%, DLco, DLco/VA, Pimax, Pimax% and Pemax%. These data indicate that pulmonary functions are effected in subclinical hypothyrodism. Therefore patients with or who are at high risk of having subclinical hypothyroidism, should be subjected to evaluation of pulmonary functions with simple spirometry.

A diffusion modelling approach to understanding contextual cueing effects in children with ADHD

PubMed Central

Weigard, Alexander; Huang-Pollock, Cynthia

2014-01-01

Background Strong theoretical models suggest implicit learning deficits may exist among children with Attention Deficit Hyperactivity Disorder (ADHD). Method We examine implicit contextual cueing (CC) effects among children with ADHD (n=72) and non-ADHD Controls (n=36). Results Using Ratcliff’s drift diffusion model, we found that among Controls, the CC effect is due to improvements in attentional guidance and to reductions in response threshold. Children with ADHD did not show a CC effect; although they were able to use implicitly acquired information to deploy attentional focus, they had more difficulty adjusting their response thresholds. Conclusions Improvements in attentional guidance and reductions in response threshold together underlie the CC effect. Results are consistent with neurocognitive models of ADHD that posit sub-cortical dysfunction but intact spatial attention, and encourage the use of alternative data analytic methods when dealing with reaction time data. PMID:24798140

Meeting the challenge in performance management: the diffusion and implementation of the balanced scorecard in Chinese hospitals.

PubMed

Gao, Tian; Gurd, Bruce

2015-03-01

The bonus system used in Chinese hospitals has been criticized for eroding doctors' professional ethics and aggravating patient expense. This research article focuses on one system to improve hospital performance, the balanced scorecard (BSC). We use three data sources to examine the diffusion and implementation of the BSC in China: a questionnaire survey in Shandong Province, a print-media indicators and content analysis of the published BSC papers and semi-structured interviews with managers of Chinese hospitals that use the BSC. The research evidence shows that bonus systems are important, partially because of the poor pay of hospital professionals, and the BSC is perceived as providing a fair system to award such bonuses. This helps explain the relative endurance of the BSC in Chinese hospitals. Published by Oxford University Press in association with The London School of Hygiene and Tropical Medicine © The Author 2014; all rights reserved.

All-Particle Multiscale Computation of Hypersonic Rarefied Flow

NASA Astrophysics Data System (ADS)

Jun, E.; Burt, J. M.; Boyd, I. D.

2011-05-01

This study examines a new hybrid particle scheme used as an alternative means of multiscale flow simulation. The hybrid particle scheme employs the direct simulation Monte Carlo (DSMC) method in rarefied flow regions and the low diffusion (LD) particle method in continuum flow regions. The numerical procedures of the low diffusion particle method are implemented within an existing DSMC algorithm. The performance of the LD-DSMC approach is assessed by studying Mach 10 nitrogen flow over a sphere with a global Knudsen number of 0.002. The hybrid scheme results show good overall agreement with results from standard DSMC and CFD computation. Subcell procedures are utilized to improve computational efficiency and reduce sensitivity to DSMC cell size in the hybrid scheme. This makes it possible to perform the LD-DSMC simulation on a much coarser mesh that leads to a significant reduction in computation time.

THORON-SCOUT - first diffusion based active Radon and Thoron monitor

NASA Astrophysics Data System (ADS)

Wagner, W.; Streil, T.; Oeser, V.; Horak, G.; Duzynski, M.

2016-10-01

THORON-SCOUT is a stand-alone diffusion based active Radon and Thoron monitor for long term indoor measurements to evaluate the human health risk due to activity concentration in the breathing air. Alpha-particle spectroscopy of Po isotopes, being the progeny of the decay of the radioactive noble gas Radon, is applied to separately monitor activity contributions of 222Rn and 220Rn (Thoron) as well. In this work we show that the portion of Thoron (Tn) may locally be remarkable and even dominating and cannot be neglected as often has been assumed up to now. Along with tobacco consumption, Rn radioactivity turned out to be a dangerous cause of lung cancer, especially in older badly vented buildings situated in regions of radioactive geological formations. THORON-SCOUT allows a precise examination of the indoor atmosphere with respect to Rn and Inactivity concentration and, therefore, a realistic evaluation of corresponding health risk.

RANS modeling of scalar dispersion from localized sources within a simplified urban-area model

NASA Astrophysics Data System (ADS)

Rossi, Riccardo; Capra, Stefano; Iaccarino, Gianluca

2011-11-01

The dispersion of a passive scalar downstream a localized source within a simplified urban-like geometry is examined by means of RANS scalar flux models. The computations are conducted under conditions of neutral stability and for three different incoming wind directions (0°, 45°, 90°) at a roughness Reynolds number of Ret = 391. A Reynolds stress transport model is used to close the flow governing equations whereas both the standard eddy-diffusivity closure and algebraic flux models are employed to close the transport equation for the passive scalar. The comparison with a DNS database shows improved reliability from algebraic scalar flux models towards predicting both the mean concentration and the plume structure. Since algebraic flux models do not increase substantially the computational effort, the results indicate that the use of tensorial-diffusivity can be promising tool for dispersion simulations for the urban environment.

Emphysematous cystitis occurred in the case treated with steroid for autoimmune hepatitis.

PubMed

Yoshino, Tateki; Ohara, Shinya; Moriyama, Hiroyuki

2013-01-01

Emphysematous cystitis is a rare clinically entity, more commonly seen in diabetic, immunocompromised patients, which was characterized by air within the bladder wall and lumen. A 83-year-old woman was introduced to our department with fever elevation and abnormal findings of computed tomography (CT). She took orally prednisolone for autoimmune hepatitis. Pelvic CT revealed diffuse air throughout the bladder wall. Urinalysis showed combined hematuria and pyuria. Escherichia coli was detected in blood culture. Abnormal findings of complete blood count and laboratory examination included an elevated WBC count (12,200/μL), C-reactive protein (11.7 mg/dL), and creatinine (1.07 mg/dL). Cystoscopy confirmed diffuse submucosal emphysema throughout. On the basis of diagnosis with emphysematous cystitis, she was treated with antibiotics based on the results of blood culture and indwelling Foley catheter. After treatment, the improvement of inflammatory findings and submucosal emphysema on cystoscopy and CT were achieved.

Gas exchange across the air-sea interface

NASA Astrophysics Data System (ADS)

Hasse, L.; Liss, P. S.

1980-10-01

The physics of gas exchange at the air-sea interface are reviewed. In order to describe the transfer of gases in the liquid near the boundary, a molecular plus eddy diffusivity concept is used, which has been found useful for smooth flow over solid surfaces. From consideration of the boundary conditions, a similar dependence of eddy diffusivity on distance from the interface can be derived for the flow beneath a gas/liquid interface, at least in the absence of waves. The influence of waves is then discussed. It is evident from scale considerations that the effect of gravity waves is small. It is known from wind tunnel work that capillary waves enhance gas transfer considerably. The existing hypotheses are apparently not sufficient to explain the observations. Examination of field data is even more frustrating since the data do not show the expected increase of gas exchange with wind speed.

Development of a High-Performance Wind Turbine Equipped with a Brimmed Diffuser Shroud

NASA Astrophysics Data System (ADS)

Ohya, Yuji; Karasudani, Takashi; Sakurai, Akira; Inoue, Masahiro

We have developed a new wind turbine system that consists of a diffuser shroud with a broad-ring brim at the exit periphery and a wind turbine inside it. The brimmed-diffuser shroud plays the role of a device for collecting and accelerating the approaching wind. Emphasis is placed on positioning the brim at the exit of the diffuser shroud. Namely, the brim generates a very low-pressure region in the exit neighborhood of the diffuser by strong vortex formation and draws more mass flow to the wind turbine inside the diffuser shroud. To obtain a higher power output of the shrouded wind turbine, we have examined the optimal form for the brimmed diffuser, such as the diffuser open angle, brim height, hub ratio, centerbody length, inlet shroud shape and so on. As a result, a shrouded wind turbine equipped with a brimmed diffuser has been developed, and demonstrated power augmentation for a given turbine diameter and wind speed by a factor of about five compared to a standard (bare) wind turbine.

The influence of polarizability and charge transfer on specific ion effects in the dynamics of aqueous salt solutions

NASA Astrophysics Data System (ADS)

Nguyen, Mary; Rick, Steven W.

2018-06-01

The diffusion rates for water molecules in salt solutions depend on the identity of the ions, as well as their concentration. Among the alkali metal ions, cesium and potassium increase and sodium strongly decreases the diffusion constant of water. The origin of the difference can be understood by examining the simulation results using different potential models. In this work, aqueous solutions of salts are simulated with a variety of models. Commonly used non-polarizable models, which otherwise reproduce many experimental properties, do not capture the trend in the diffusion constant, while models which include polarization and/or charge transfer interactions do. For the non-polarizable models, the diffusion constant decreases too strongly with salt concentration. The changes in the water diffusion constant with increasing salt concentration match the diffusion constant of the ion. The ion diffusion constant is dependent on the residence time for water in the ion solvation shell. The non-polarizable models over-estimate the residence time, relative to the translational diffusion constant and so tend to under-estimate the ion and water diffusion constants.

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.

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

Bu, Lintao; Nimlos, Mark R.; Robichaud, David J.

Hierarchical mesoporous zeolites exhibit higher catalytic activities and longer lifetime compared to the traditional microporous zeolites due to improved diffusivity of substrate molecules and their enhanced access to the zeolite active sites. Understanding diffusion of biomass pyrolysis vapors and their upgraded products in such materials is fundamentally important during catalytic fast pyrolysis (CFP) of lignocellulosic biomass, since diffusion makes major contribution to determine shape selectivity and product distribution. However, diffusivities of biomass relevant species in hierarchical mesoporous zeolites are poorly characterized, primarily due to the limitations of the available experimental technology. In this work, molecular dynamics (MD) simulations are utilizedmore » to investigate the diffusivities of several selected coke precursor molecules, benzene, naphthalene, and anthracene, in hierarchical mesoporous H-ZSM-5 zeolite. The effects of temperature and size of mesopores on the diffusivity of the chosen model compounds are examined. The simulation results demonstrate that diffusion within the microspores as well as on the external surface of mesoporous H-ZSM-5 dominates only at low temperature. At pyrolysis relevant temperatures, mass transfer is essentially conducted via diffusion along the mesopores. Additionally, the results illustrate the heuristic diffusion model, such as the extensively used Knudsen diffusion, overestimates the diffusion of bulky molecules in the mesopores, thus making MD simulation a powerful and compulsory approach to explore diffusion in zeolites.« less

Development of lithium diffused radiation resistant solar cells, part 2

NASA Technical Reports Server (NTRS)

Payne, P. R.; Somberg, H.

1971-01-01

The work performed to investigate the effect of various process parameters on the performance of lithium doped P/N solar cells is described. Effort was concentrated in four main areas: (1) the starting material, (2) the boron diffusion, (3) the lithium diffusion, and (4) the contact system. Investigation of starting material primarily involved comparison of crucible grown silicon (high oxygen content) and Lopex silicon (low oxygen content). In addition, the effect of varying growing parameters of crucible grown silicon on lithium cell output was also examined. The objective of the boron diffusion studies was to obtain a diffusion process which produced high efficiency cells with minimal silicon stressing and could be scaled up to process 100 or more cells per diffusion. Contact studies included investigating sintering of the TiAg contacts and evaluation of the contact integrity.

Diffusion Weighted Image Denoising Using Overcomplete Local PCA

PubMed Central

Manjón, José V.; Coupé, Pierrick; Concha, Luis; Buades, Antonio; Collins, D. Louis; Robles, Montserrat

2013-01-01

Diffusion Weighted Images (DWI) normally shows a low Signal to Noise Ratio (SNR) due to the presence of noise from the measurement process that complicates and biases the estimation of quantitative diffusion parameters. In this paper, a new denoising methodology is proposed that takes into consideration the multicomponent nature of multi-directional DWI datasets such as those employed in diffusion imaging. This new filter reduces random noise in multicomponent DWI by locally shrinking less significant Principal Components using an overcomplete approach. The proposed method is compared with state-of-the-art methods using synthetic and real clinical MR images, showing improved performance in terms of denoising quality and estimation of diffusion parameters. PMID:24019889

Dynamic Distortion in a Short S-Shaped Subsonic Diffuser with Flow Separation. [Lewis 8 by 6 foot Supersonic Wind Tunnel

NASA Technical Reports Server (NTRS)

Stumpf, R.; Neumann, H. E.; Giamati, C. C.

1983-01-01

An experimental investigation of the time varying distortion at the diffuser exit of a subscale HiMAT forebody and inlet was conducted at Mach 0.9 in the Lewis 8 by 6 foot Supersonic Wind Tunnel. A transitory separation was detected within the subsonic diffuser. Vortex generators were installed to eliminate the flow separation. Results from a study of the instantaneous pressure variations at the diffuser exit are presented. The time unsteady total pressures at the diffuser exit are computer interpolated and presented in the form of a movie showing the transitory separation. Limited data showing the instantaneous distortion levels is also presented.

Prediction of the moments in advection-diffusion lattice Boltzmann method. II. Attenuation of the boundary layers via double-Λ bounce-back flux scheme.

PubMed

Ginzburg, Irina

2017-01-01

Impact of the unphysical tangential advective-diffusion constraint of the bounce-back (BB) reflection on the impermeable solid surface is examined for the first four moments of concentration. Despite the number of recent improvements for the Neumann condition in the lattice Boltzmann method-advection-diffusion equation, the BB rule remains the only known local mass-conserving no-flux condition suitable for staircase porous geometry. We examine the closure relation of the BB rule in straight channel and cylindrical capillary analytically, and show that it excites the Knudsen-type boundary layers in the nonequilibrium solution for full-weight equilibrium stencil. Although the d2Q5 and d3Q7 coordinate schemes are sufficient for the modeling of isotropic diffusion, the full-weight stencils are appealing for their advanced stability, isotropy, anisotropy and anti-numerical-diffusion ability. The boundary layers are not covered by the Chapman-Enskog expansion around the expected equilibrium, but they accommodate the Chapman-Enskog expansion in the bulk with the closure relation of the bounce-back rule. We show that the induced boundary layers introduce first-order errors in two primary transport properties, namely, mean velocity (first moment) and molecular diffusion coefficient (second moment). As a side effect, the Taylor-dispersion coefficient (second moment), skewness (third moment), and kurtosis (fourth moment) deviate from their physical values and predictions of the fourth-order Chapman-Enskog analysis, even though the kurtosis error in pure diffusion does not depend on grid resolution. In two- and three-dimensional grid-aligned channels and open-tubular conduits, the errors of velocity and diffusion are proportional to the diagonal weight values of the corresponding equilibrium terms. The d2Q5 and d3Q7 schemes do not suffer from this deficiency in grid-aligned geometries but they cannot avoid it if the boundaries are not parallel to the coordinate lines. In order to vanish or attenuate the disparity of the modeled transport coefficients with the equilibrium weights without any modification of the BB rule, we propose to use the two-relaxation-times collision operator with free-tunable product of two eigenfunctions Λ. Two different values Λ_{v} and Λ_{b} are assigned for bulk and boundary nodes, respectively. The rationale behind this is that Λ_{v} is adjustable for stability, accuracy, or other purposes, while the corresponding Λ_{b}(Λ_{v}) controls the primary accommodation effects. Two distinguished but similar functional relations Λ_{b}(Λ_{v}) are constructed analytically: they preserve advection velocity in parabolic profile, exactly in the two-dimensional channel and very accurately in a three-dimensional cylindrical capillary. For any velocity-weight stencil, the (local) double-Λ BB scheme produces quasi-identical solutions with the (nonlocal) specular-forward reflection for first four moments in a channel. In a capillary, this strategy allows for the accurate modeling of the Taylor-dispersion and non-Gaussian effects. As illustrative example, it is shown that in the flow around a circular obstacle, the double-Λ scheme may also vanish the dependency of mean velocity on the velocity weight; the required value for Λ_{b}(Λ_{v}) can be identified in a few bisection iterations in given geometry. A positive solution for Λ_{b}(Λ_{v}) may not exist in pure diffusion, but a sufficiently small value of Λ_{b} significantly reduces the disparity in diffusion coefficient with the mass weight in ducts and in the presence of rectangular obstacles. Although Λ_{b} also controls the effective position of straight or curved boundaries, the double-Λ scheme deals with the lower-order effects. Its idea and construction may help understanding and amelioration of the anomalous, zero- and first-order behavior of the macroscopic solution in the presence of the bulk and boundary or interface discontinuities, commonly found in multiphase flow and heterogeneous transport.

Prediction of the moments in advection-diffusion lattice Boltzmann method. II. Attenuation of the boundary layers via double-Λ bounce-back flux scheme

NASA Astrophysics Data System (ADS)

Ginzburg, Irina

2017-01-01

Impact of the unphysical tangential advective-diffusion constraint of the bounce-back (BB) reflection on the impermeable solid surface is examined for the first four moments of concentration. Despite the number of recent improvements for the Neumann condition in the lattice Boltzmann method-advection-diffusion equation, the BB rule remains the only known local mass-conserving no-flux condition suitable for staircase porous geometry. We examine the closure relation of the BB rule in straight channel and cylindrical capillary analytically, and show that it excites the Knudsen-type boundary layers in the nonequilibrium solution for full-weight equilibrium stencil. Although the d2Q5 and d3Q7 coordinate schemes are sufficient for the modeling of isotropic diffusion, the full-weight stencils are appealing for their advanced stability, isotropy, anisotropy and anti-numerical-diffusion ability. The boundary layers are not covered by the Chapman-Enskog expansion around the expected equilibrium, but they accommodate the Chapman-Enskog expansion in the bulk with the closure relation of the bounce-back rule. We show that the induced boundary layers introduce first-order errors in two primary transport properties, namely, mean velocity (first moment) and molecular diffusion coefficient (second moment). As a side effect, the Taylor-dispersion coefficient (second moment), skewness (third moment), and kurtosis (fourth moment) deviate from their physical values and predictions of the fourth-order Chapman-Enskog analysis, even though the kurtosis error in pure diffusion does not depend on grid resolution. In two- and three-dimensional grid-aligned channels and open-tubular conduits, the errors of velocity and diffusion are proportional to the diagonal weight values of the corresponding equilibrium terms. The d2Q5 and d3Q7 schemes do not suffer from this deficiency in grid-aligned geometries but they cannot avoid it if the boundaries are not parallel to the coordinate lines. In order to vanish or attenuate the disparity of the modeled transport coefficients with the equilibrium weights without any modification of the BB rule, we propose to use the two-relaxation-times collision operator with free-tunable product of two eigenfunctions Λ . Two different values Λv and Λb are assigned for bulk and boundary nodes, respectively. The rationale behind this is that Λv is adjustable for stability, accuracy, or other purposes, while the corresponding Λb(Λv) controls the primary accommodation effects. Two distinguished but similar functional relations Λb(Λv) are constructed analytically: they preserve advection velocity in parabolic profile, exactly in the two-dimensional channel and very accurately in a three-dimensional cylindrical capillary. For any velocity-weight stencil, the (local) double-Λ BB scheme produces quasi-identical solutions with the (nonlocal) specular-forward reflection for first four moments in a channel. In a capillary, this strategy allows for the accurate modeling of the Taylor-dispersion and non-Gaussian effects. As illustrative example, it is shown that in the flow around a circular obstacle, the double-Λ scheme may also vanish the dependency of mean velocity on the velocity weight; the required value for Λb(Λv) can be identified in a few bisection iterations in given geometry. A positive solution for Λb(Λv) may not exist in pure diffusion, but a sufficiently small value of Λb significantly reduces the disparity in diffusion coefficient with the mass weight in ducts and in the presence of rectangular obstacles. Although Λb also controls the effective position of straight or curved boundaries, the double-Λ scheme deals with the lower-order effects. Its idea and construction may help understanding and amelioration of the anomalous, zero- and first-order behavior of the macroscopic solution in the presence of the bulk and boundary or interface discontinuities, commonly found in multiphase flow and heterogeneous transport.

Iron Impregnated Activated Carbon as an Efficient Adsorbent for the Removal of Methylene Blue: Regeneration and Kinetics Studies

PubMed Central

Shah, Irfan; Adnan, Rohana; Wan Ngah, Wan Saime; Mohamed, Norita

2015-01-01

In this study, iron impregnated activated carbon (FeAC) was synthesized following an oxidation and iron impregnation of activated carbon (AC). Both the AC and FeAC were characterized by pHZPC and FTIR spectroscopy. The removal of Methylene Blue (MB) by AC and FeAC was examined under various experimental conditions. The FeAC showed up to 95% (higher than AC) MB removal in the pH range of 7–10. Although the reaction kinetics was pseudo–second order, the overall rate was controlled by a number of processes such as film diffusion, pore diffusion and intraparticle diffusion. The activation energy values for the MB uptake by AC and FeAC (21.79 and 14.82 kJ/mol, respectively) revealed a physisorption process. In the regeneration study, FeAC has shown consistently ≥ 90% MB removal even up to 10 repeated cycles. The reusable characteristic of the spent FeAC improved the practical use of activated carbon and can be a breakthrough for continuous flow system applications where it can work effectively without any significant reduction in its performance. PMID:25849291

Increased working memory related fMRI signal in children following Tick Borne Encephalitis.

PubMed

Henrik, Ullman; Åsa, Fowler; Ronny, Wickström

2016-01-01

Tick Borne Encephalitis (TBE) is a viral infection in the central nervous system endemic in Europe and Asia. While pediatric infection may carry a lower risk for serious neurological sequelae compared to adults, a large proportion of children experience long term cognitive problems, most markedly decreased working memory capacity. We explored whether task related functional magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) could reveal a biological correlate of status-post TBE in children. We examined 11 serologically verified pediatric TBE patients with central nervous system involvement with 55 healthy controls with working memory tests and MRI. The TBE patients showed a prominent deficit in working memory capacity and an increased task related functional MRI signal in working memory related cortical areas during a spatial working memory task performed without sedation. No diffusion differences could be found with DTI, in line with the reported paucity of anatomical abnormalities. This study is the first to demonstrate functional MRI abnormalities in TBE patients that bears similarity to other patient groups with diffuse neuronal damage. Copyright © 2015 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.

Investigations of Turbulent Transport Channels in Gyrokinetic Simulations

NASA Astrophysics Data System (ADS)

Dimits, A. M.; Candy, J.; Guttenfelder, W.; Holland, C.; Howard, N.; Nevins, W. M.; Wang, E.

2014-10-01

Magnetic-field stochasticity arises due to microtearing perturbations, which can be driven linearly or nonlinearly (in cases where they are linearly stable), even at very modest values of the plasma beta. The resulting magnetic-flutter contribution may or may not be a significant component of the overall electron (particle and thermal) transport. Investigations of the effect of ExB flow shear on electron-drift magnetic-flutter diffusion coefficient Dedr (r ,v||) using perturbed magnetic fields from simulations, using the GYRO code, of ITG turbulence show a significant effect for electrons with parallel velocities v|| surprisingly far from the resonant velocity. We further examine changes in the radial dependence of this diffusion coefficient vs. v|| and which resonant magnetic-field perturbations are important to the values and radial structure of Dedr. The resulting electron transport fluxes are compared with the simulation results. Improvements over in treating the ambipolar field in the relationship between the magnetic (or drift) diffusion coefficients and the transport have been made in these comparisons. Prepared for US DOE by LLNL under Contract DE-AC52-07NA27344, by GA under Contract DE-FG03-95ER54309, and by PPPL under Contract DE-AC02-09CH11466.

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

Krelowski, J.; Galazutdinov, G.; Kolos, R., E-mail: jacek@astri.uni.torun.pl, E-mail: runizag@gmail.com, E-mail: robert.kolos@ichf.edu.pl

The recent assignment of two broad diffuse interstellar bands (DIBs) near 4882 and 5450 A to the propadienylidene (l-C{sub 3}H{sub 2}) molecule is examined using a statistically meaningful sample of targets. Our spectra clearly show that the strength ratio of two broad DIBs is strongly variable, contrary to what should be observed if both features are due to l-C{sub 3}H{sub 2}, since the proposed transitions are lifetime broadened and start from the same level. Moreover, even in directions where the 4882 DIB and 5450 DIB are strong, the third expected l-C{sub 3}H{sub 2} band, in the 5165-5185 A region, ismore » absent. Another puzzling characteristic of l-C{sub 3}H{sub 2} as the proposed carrier of both broad diffuse bands is its column density of several 10{sup 14} cm{sup -2}, inferred from the equivalent width of the 5450 DIB. This value is one order of magnitude higher than N(CH) toward the same objects and two to three orders of magnitude higher than N(H{sub 2}CCC), measured at radio frequencies in absorption, for comparable samples of the diffuse medium. We conclude that the proposed identification of broad DIBs is unjustified.« less

A Qualitative Analysis and Comparison of the Educational Technology Diffusion and Attitudes toward Adopting Computing Technologies, of the Ministry of Education, Principals/Vice-Principals, and Teachers, in Jamaican Public Primary and Secondary Schools

ERIC Educational Resources Information Center

White, Kerry-Ann

2012-01-01

Given the lack of computer diffusion studies in the Caribbean, and coupled with the necessity to understand Jamaica in efforts to get a clearer global representation of the digital divide, this study takes an exploratory approach and examines the differences of the computer technology adoption and diffusion attitudes and viewpoints between the…

Diffusional dynamics of an active rhodamine-labeled 1,4-dihydropyridine in sarcolemmal lipid multibilayers.

PubMed Central

Mason, R P; Chester, D W

1989-01-01

A "membrane bilayer pathway" model, involving ligand partition into the bilayer, lateral diffusion, and receptor binding has been invoked to describe the 1,4-dihydropyridine (DHP) calcium channel antagonist receptor binding mechanism. In an earlier study (Chester et al. 1987. Biophys. J. 52:1021-1030), the diffusional component of this model was examined using an active fluorescence labeled DHP calcium channel antagonist, nisoldipine-lissamine rhodamine B (Ns-R), in purified cardiac sarcolemmal (CSL) lipid multibilayers. Diffusion coefficient measurements on membrane-bound drug and phospholipid at maximum bilayer hydration yielded similar values (3.8 x 10(-8) cm2/s). However, decreases in bilayer hydration resulted in dramatically reduced diffusion coefficient values for both probes with substantially greater impact on Ns-R diffusion. These data suggested that hydration dependent diffusional differences could be a function of relative probe location along the bilayer normal. In this communication, we have addressed the relative effect of the rhodamine substituent on Ns-R diffusion complex by examining the diffusional dynamics of free rhodamine B under the same conditions used to evaluate Ns-R complex and phospholipid diffusion. X-ray diffraction studies were performed to determine the Ns-R location in the membrane and model the CSL lipid bilayer profile structure to give a rationale for the differences in probe diffusional dynamics as a function of interbilayer water space. PMID:2611332

Lagrangian Statistics of Slightly Buoyant Droplets in Isotropic Turbulence

NASA Astrophysics Data System (ADS)

Gopalan, Balaji; Malkiel, Edwin; Katz, Joseph

2006-11-01

This project examines the dynamics of slightly buoyant diesel droplets in isotropic turbulence using high speed in-line digital Holographic PIV. A cloud of droplets with specific gravity of 0.85 is injected into the central portion of an isotropic turbulence facility. The droplet trajectories are measured in a 50x50x50 mm̂3 sample volume using high speed in-line digital holography. An automated program has been developed to obtain accurate time history of droplet velocities. Data analysis determines the PDF of velocity and acceleration in three dimensions. The time histories enable us to calculate the three dimensional Lagrangian velocity autocorrelation function, and from them the diffusion coefficients. Due to buoyancy the vertical diffusion time scale exceeds the horizontal one by about 65% .The diffusion coefficients vary between 2.8 cm̂2/sec in the horizontal direction to 5.5 cm̂2/sec in the vertical direction. For droplets with size varying from 2 to 11 Kolmogorov scales there are no clear trends with size. The variations of diffusion rates for different turbulent intensities and the effect of finite window size are presently examined. For shorter time scales, when the diffusion need not be Fickian the three dimensional trajectories can be used to calculate the generalized dispersion tensor and measure the time elapsed for diffusion to become Fickian.

Reaction diffusion in the nickel-chromium-aluminum and cobalt-chromium-aluminum systems

NASA Technical Reports Server (NTRS)

Levine, S. R.

1977-01-01

The effects of MCrAl coating-substrate interdiffusion on oxidation life and the general mutliphase, multicomponent diffusion problem were examined. Semi-infinite diffusion couples that had sources representing coatings and sinks representing gas turbine alloys were annealed at 1,000, 1,095, 1,150, or 1,205 C for as long as 500 hours. The source and sink aluminum and chromium contents and the base metal (cobalt or nickel) determined the parabolic diffusion rate constants of the couples and predicted finite coating lives. The beta source strength concept provided a method (1) for correlating beta recession rate constants with composition; (2) for determining reliable average total, diffusion, and constitutional activation energies; and (3) for calculating interdiffusion coefficients.

Minority carrier diffusion and defects in InGaAsN grown by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Kurtz, Steven R.; Klem, J. F.; Allerman, A. A.; Sieg, R. M.; Seager, C. H.; Jones, E. D.

2002-02-01

To gain insight into the nitrogen-related defects of InGaAsN, nitrogen vibrational mode spectra, Hall mobilities, and minority carrier diffusion lengths are examined for InGaAsN (1.1 eV band gap) grown by molecular beam epitaxy (MBE). Annealing promotes the formation of In-N bonding, and lateral carrier transport is limited by large scale (≫mean free path) material inhomogeneities. Comparing solar cell quantum efficiencies with our earlier results for devices grown by metalorganic chemical vapor deposition (MOCVD), we find significant electron diffusion in the MBE material (reversed from the hole diffusion in MOCVD material), and minority carrier diffusion in InGaAsN cannot be explained by a "universal," nitrogen-related defect.

Simulation of atomic diffusion in the Fcc NiAl system: A kinetic Monte Carlo study

DOE PAGES

Alfonso, Dominic R.; Tafen, De Nyago

2015-04-28

The atomic diffusion in fcc NiAl binary alloys was studied by kinetic Monte Carlo simulation. The environment dependent hopping barriers were computed using a pair interaction model whose parameters were fitted to relevant data derived from electronic structure calculations. Long time diffusivities were calculated and the effect of composition change on the tracer diffusion coefficients was analyzed. These results indicate that this variation has noticeable impact on the atomic diffusivities. A reduction in the mobility of both Ni and Al is demonstrated with increasing Al content. As a result, examination of the pair interaction between atoms was carried out formore » the purpose of understanding the predicted trends.« less

Highly Sensitive Measurements of 222Rn Diffusion and Emanation

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

Zuzel, Grzegorz

Highly sensitive techniques for determination of the 222Rn emanation from solids and diffusion through different membranes are presented. 222Rn and its daughters are measured via the alpha decays in special proportional counters at the absolute sensitivity of {approx}30 {mu}Bq. Radon diffusion can be measured at the level of {approx}10-13 cm2/s. Several samples were examined, e.g. stainless steel, teflon, various gaskets (emanation and diffusion measurements) and tanks. A combination of measurements of the 222Rn diffusion and emanation of thin nylon foils (used in the Borexino experiment) allowed the determination of 226Ra in the materials of interest at the level of {approx}10-12more » g/g 238U-equivalent.« less

The role of boundary variability in polycrystalline grain-boundary diffusion

NASA Astrophysics Data System (ADS)

Moghadam, M. M.; Rickman, J. M.; Harmer, M. P.; Chan, H. M.

2015-01-01

We investigate the impact of grain-boundary variability on mass transport in a polycrystal. More specifically, we perform both numerical and analytical studies of steady-state diffusion in prototypical microstructures in which there is either a discrete spectrum of grain-boundary activation energies or else a complex distribution of grain-boundary character, and hence a continuous spectrum of boundary activation energies. An effective diffusivity is calculated for these structures using simplified multi-state models and, for the case of a continuous spectrum, employing experimentally obtained grain-boundary energy data. We identify different diffusive regimes for these cases and quantify deviations from Arrhenius behavior using effective medium theory. Finally, we examine the diffusion kinetics of a simplified model of an interfacial layering (i.e., complexion) transition.

Paratesticular fibrous pseudotumor: a report of five cases and literature review.

PubMed

Zhang, Zhicheng; Yang, Jun; Li, Mingchao; Cai, Wei; Liu, Qingquan; Wang, Tao; Guo, Xiaolin; Wang, Shaogang; Liu, Jihong; Ye, Zhangqun

2014-12-01

Paratesticular fibrous pseudotumor is a rare benign tumor that originates from intrascrotal tissue, such as tunica vaginalis, epididymis, or spermatic cord. Five cases of fibrous pseudotumor in our hospital were reviewed retrospectively, and the clinical manifestations were analyzed. Three cases of unilateral nodules, comprising one case located in the tunica vaginalis and two cases located in the epididymis, underwent local excision of the unilateral nodule. Two cases of diffuse incrassation in the tunica vaginalis underwent right radical orchiectomy. Postoperative pathological examination showed that all were fibrous pseudotumors. An average follow-up of 26 months showed uneventful results without recurrence for all patients. Fibrous pseudotumor is not a neoplasm but a reactive fibrous inflammatory hyperplasia. Definitive diagnosis requires pathological examination. Radical orchiectomy should be avoided when possible, and local excision should be performed because of the lack of obvious evidence of potential malignancy.

Antigen size and charge in immune complex glomerulonephritis. II. Passive induction of immune deposits with dextran-anti-dextran immune complexes.

PubMed Central

Isaacs, K. L.; Miller, F.

1983-01-01

Utilizing dextrans of restricted sizes (10,000, 70,000, 500,000 daltons), modified with regard to charge (neutral, polycationic, polyanionic) and an anti-dextran murine IgA myeloma, W3129, the authors have examined a model that may be used in the study of the combined effect of size and charge on renal deposition of immune complexes. Polycationic DEAE dextran complexes, using the 10,000 dalton antigen, showed a mesangiocapillary pattern of deposition. The other antigens showed focal to diffuse mesangial localization of varying degree. This indicates the potential usefulness of this system in examining the factors important in glomerular immune injury. The relevance to other observations, importance of polysaccharide antigens, and role in circulating versus in situ or "planted" immune complex models are considered. Images Figure 3 Figure 4 Figure 5 Figure 6 PMID:6190406

A Study on the Characteristics of Design Variables for IRSS Diffuser

NASA Astrophysics Data System (ADS)

Cho, Yong-Jin; Ko, Dae-Eun

2017-11-01

In modern naval ships, infrared signature suppression systems (IRSS) are installed to decrease the temperature of waste gas generated in propulsion engine and the metallic surface temperature of heated exhaust pipes. Generally, IRSS is composed of eductor, mixing tube, and diffuser. Diffuser serves to reduce the temperature by creating an air film using the pressure difference between internal gas and external air. In this study, design variables were selected by analyzing the diffuser and the characteristics of design variables that affect the performance of diffuser were examined using Taguchi experiment method. For the diffuser performance analysis, a heat flow analysis technique established in previous research was used. The IRSS performance evaluation was carried out based on the average area value of the metal surface temperature and the temperature of the exhaust gas at the outlet of the diffuser, which are variables directly related to the intensity of infrared signature in naval ships. It was verified that the exhaust gas temperature is greatly affected by changes in the diameter of the diffuser outlet, and the metal surface temperature of diffuser is greatly affected by changes in the number of diffuser rings.

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

Cognitive Severity-Specific Neuronal Degenerative Network in Charcoal Burning Suicide-Related Carbon Monoxide Intoxication

PubMed Central

Chen, Nai-Ching; Huang, Chi-Wei; Huang, Shu-Hua; Chang, Wen-Neng; Chang, Ya-Ting; Lui, Chun-Chung; Lin, Pin-Hsuan; Lee, Chen-Chang; Chang, Yen-Hsiang; Chang, Chiung-Chih

2015-01-01

Abstract While carbon monoxide (CO) intoxication often triggers multiple intraneuronal immune- or inflammatory-related cascades, it is not known whether the pathological processes within the affected regions evolve equally in the long term. To understand the neurodegenerative networks, we examined 49 patients with a clinical diagnosis of CO intoxication related to charcoal burning suicide at the chronic stage and compared them with 15 age- and sex-matched controls. Reconstructions of degenerative networks were performed using T1 magnetic resonance imaging, diffusion-tensor imaging, and fluorodeoxyglucose positron emission tomography (PET). Tract-specific fractional anisotropy (FA) quantification of 11 association fibers was performed while the clinical significance of the reconstructed structural or functional networks was determined by correlating them with the cognitive parameters. Compared with the controls, the patients had frontotemporal gray matter (GM) atrophy, diffuse white matter (WM) FA decrement, and axial diffusivity (AD) increment. The patients were further stratified into 3 groups based on the cognitive severities. The spatial extents within the frontal-insular-caudate GM as well as the prefrontal WM AD increment regions determined the cognitive severities among 3 groups. Meanwhile, the prefrontal WM FA values and PET signals also correlated significantly with the patient's Mini-Mental State Examination score. Frontal hypometabolic patterns in PET analysis, even after adjusted for GM volume, were highly coherent to the GM atrophic regions, suggesting structural basis of functional alterations. Among the calculated major association bundles, only the anterior thalamic radiation FA values correlated significantly with all chosen cognitive scores. Our findings suggest that fronto-insular-caudate areas represent target degenerative network in CO intoxication. The topography that occurred at a cognitive severity-specific level at the chronic phase suggested the clinical roles of frontal areas. Although changes in FA are also diffusely distributed, different regional changes in AD suggested unequal long-term compensatory capacities among WM bundles. As such, the affected WM regions showing irreversible changes may exert adverse impacts to the interconnected GM structures. PMID:25984663

Hydrograph variances over different timescales in hydropower production networks

NASA Astrophysics Data System (ADS)

Zmijewski, Nicholas; Wörman, Anders

2016-08-01

The operation of water reservoirs involves a spectrum of timescales based on the distribution of stream flow travel times between reservoirs, as well as the technical, environmental, and social constraints imposed on the operation. In this research, a hydrodynamically based description of the flow between hydropower stations was implemented to study the relative importance of wave diffusion on the spectrum of hydrograph variance in a regulated watershed. Using spectral decomposition of the effluence hydrograph of a watershed, an exact expression of the variance in the outflow response was derived, as a function of the trends of hydraulic and geomorphologic dispersion and management of production and reservoirs. We show that the power spectra of involved time-series follow nearly fractal patterns, which facilitates examination of the relative importance of wave diffusion and possible changes in production demand on the outflow spectrum. The exact spectral solution can also identify statistical bounds of future demand patterns due to limitations in storage capacity. The impact of the hydraulic description of the stream flow on the reservoir discharge was examined for a given power demand in River Dalälven, Sweden, as function of a stream flow Peclet number. The regulation of hydropower production on the River Dalälven generally increased the short-term variance in the effluence hydrograph, whereas wave diffusion decreased the short-term variance over periods of <1 week, depending on the Peclet number (Pe) of the stream reach. This implies that flow variance becomes more erratic (closer to white noise) as a result of current production objectives.

Diffusion of aromatic hydrocarbons in hierarchical mesoporous H-ZSM-5 zeolite

DOE PAGES

Bu, Lintao; Nimlos, Mark R.; Robichaud, David J.; ...

2018-02-08

Hierarchical mesoporous zeolites exhibit higher catalytic activities and longer lifetime compared to the traditional microporous zeolites due to improved diffusivity of substrate molecules and their enhanced access to the zeolite active sites. Understanding diffusion of biomass pyrolysis vapors and their upgraded products in such materials is fundamentally important during catalytic fast pyrolysis (CFP) of lignocellulosic biomass, since diffusion makes major contribution to determine shape selectivity and product distribution. However, diffusivities of biomass relevant species in hierarchical mesoporous zeolites are poorly characterized, primarily due to the limitations of the available experimental technology. In this work, molecular dynamics (MD) simulations are utilizedmore » to investigate the diffusivities of several selected coke precursor molecules, benzene, naphthalene, and anthracene, in hierarchical mesoporous H-ZSM-5 zeolite. The effects of temperature and size of mesopores on the diffusivity of the chosen model compounds are examined. The simulation results demonstrate that diffusion within the microspores as well as on the external surface of mesoporous H-ZSM-5 dominates only at low temperature. At pyrolysis relevant temperatures, mass transfer is essentially conducted via diffusion along the mesopores. Additionally, the results illustrate the heuristic diffusion model, such as the extensively used Knudsen diffusion, overestimates the diffusion of bulky molecules in the mesopores, thus making MD simulation a powerful and compulsory approach to explore diffusion in zeolites.« less

Innovation Diffusion: Implications for Evaluation

ERIC Educational Resources Information Center

Ashley, Shena R.

2009-01-01

Whether looking at the spread and adoption of an intervention across a community, across multiple units, or within a single unit, an understanding of diffusion theory can help evaluators uncover patterns and impacts that might otherwise be overlooked. The theory alerts evaluators to examine why uptake of an intervention appeared different in…

A Cross-Age Study of Student Understanding of the Concept of Diffusion.

ERIC Educational Resources Information Center

Westbrook, Susan L.; Marek, Edmund A.

1991-01-01

Examines seventh grade life science students, tenth grade biology students, and college zoology students for understanding of the concept of diffusion. Describes the differences among the grade levels in sound or partial understanding, misconceptions, and no understanding. Discusses the effect of developmental level on understanding. (KR)

What Drives the Diffusion of Inclusionary Zoning?

ERIC Educational Resources Information Center

Meltzer, Rachel; Schuetz, Jenny

2010-01-01

Social scientists offer competing theories on what explains the policymaking process. These typically include economic rationalism, political competition or power struggles, and policy imitation of the kind that diffuses across spatially proximate neighbors. In this paper, we examine the factors that have influenced a recent local policy trend in…

The Diffusion Of An Innovation: A Case Study Of One Social Studies Program.

ERIC Educational Resources Information Center

Hahn, Carole L.

1985-01-01

Examined what factors were important in the diffusion and adoption of the new social studies program, Toward a Better World. Survey results indicate that media advertisements were ineffective persuaders, while interpersonal communication sources appeared to be more important. Includes tables and references. (TRS)

Spatial Resolution, Grayscale, and Error Diffusion Trade-offs: Impact on Display System Design

NASA Technical Reports Server (NTRS)

Gille, Jennifer L. (Principal Investigator)

1996-01-01

We examine technology trade-offs related to grayscale resolution, spatial resolution, and error diffusion for tessellated display systems. We present new empirical results from our psychophysical study of these trade-offs and compare them to the predictions of a model of human vision.

Interdiffusion and Intrinsic Diffusion in the Mg-Al System

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

Brennan, Sarah; Bermudez, Katrina; Sohn, Yong Ho

2012-01-01

Solid-to-solid diffusion couples were assembled and annealed to examine the diffusion between pure Mg (99.96%) and Al (99.999%). Diffusion anneals were carried out at 300 , 350 , and 400 C for 720, 360, and 240 hours, respectively. Optical and scanning electron microscopes were utilized to identify the formation of the intermetallic phases, -Al12Mg17 and -Al3Mg2 and absence of the -phase in the diffusion couples. Thicknesses of the -Al12Mg17 and -Al3Mg2 phases were measured and the parabolic growth constants were calculated to determine the activation energies for the growth, 165 and 86 KJ/mole, respectively. Concentration profiles were determined with electronmore » microprobe analysis using pure elemental standards. Composition-dependent interdiffusion coefficients in Mg-solid solution, -Al12Mg17 and - Al3Mg2 and Al-solid solutions were calculated based on the Boltzmann-Matano analysis. Average effective interdiffusion coefficients for each phase were also calculated, and the magnitude was the highest for the -Al3Mg2 phase, followed by -Al12Mg17, Al-solid solution and Mg-solid solution. Intrinsic diffusion coefficients based on Huemann s analysis (e.g., marker plane) were determined for the ~38 at.% Mg in the -Al3Mg2 phase. Activation energies and the pre-exponential factors for the inter- and intrinsic diffusion coefficients were calculated for the temperature range examined. The -Al3Mg2 phase was found to have the lowest activation energies for growth and interdiffusion among all four phases studied. At the marker location in the -Al3Mg2 phase, the intrinsic diffusion of Al was found to be faster than that of Mg. Extrapolations of the impurity diffusion coefficients in the terminal solid solutions were made and compared to the available self- and impurity diffusion data from literature. Thermodynamic factor, tracer diffusion coefficients and atomic mobilities at the marker plane composition were approximated using available literature values of Mg activity in the -Al3Mg2 phase.« less

Early detection of response to radiation therapy in patients with brain malignancies using conventional and high b-value diffusion-weighted magnetic resonance imaging.

PubMed

Mardor, Yael; Pfeffer, Raphael; Spiegelmann, Roberto; Roth, Yiftach; Maier, Stephan E; Nissim, Ouzi; Berger, Raanan; Glicksman, Ami; Baram, Jacob; Orenstein, Arie; Cohen, Jack S; Tichler, Thomas

2003-03-15

To study the feasibility of using diffusion-weighted magnetic resonance imaging (DWMRI), which is sensitive to the diffusion of water molecules in tissues, for detection of early tumor response to radiation therapy; and to evaluate the additional information obtained from high DWMRI, which is more sensitive to low-mobility water molecules (such as intracellular or bound water), in increasing the sensitivity to response. Standard MRI and DWMRI were acquired before and at regular intervals after initiating radiation therapy for 10 malignant brain lesions in eight patients. One week posttherapy, three of six responding lesions showed an increase in the conventional DWMRI parameters. Another three responding lesions showed no change. Four nonresponding lesions showed a decrease or no change. The early change in the diffusion parameters was enhanced by using high DWMRI. When high DWMRI was used, all responding lesions showed increase in the diffusion parameter and all nonresponding lesions showed no change or decrease. Response was determined by standard MRI 7 weeks posttherapy. The changes in the diffusion parameters measured 1 week after initiating treatment were correlated with later tumor response or no response (P <.006). This correlation was increased to P <.0006 when high DWMRI was used. The significant correlation between changes in diffusion parameters 1 week after initiating treatment and later tumor response or no response suggests the feasibility of using DWMRI for early, noninvasive prediction of tumor response. The ability to predict response may enable early termination of treatment in nonresponding patients, prevent additional toxicity, and allow for early changes in treatment.

Determination of the effect of lipophilicity on the in vitro permeability and tissue reservoir characteristics of topically applied solutes in human skin layers.

PubMed

Cross, Sheree E; Magnusson, Beatrice M; Winckle, Gareth; Anissimov, Yuri; Roberts, Michael S

2003-05-01

In order to establish the relationship between solute lipophilicity and skin penetration (including flux and concentration behavior), we examined the in vitro penetration and membrane concentration of a series of homologous alcohols (C2-C10) applied topically in aqueous solutions to human epidermal, full-thickness, and dermal membranes. The partitioning/distribution of each alcohol between the donor solution, stratum corneum, viable epidermis, dermis, and receptor phase compartments was determined during the penetration process and separately to isolated samples of each tissue type. Maximum flux and permeability coefficients are compared for each membrane and estimates of alcohol diffusivity are made based on flux/concentration data and also the related tissue resistance (the reciprocal of permeability coefficient) for each membrane type. The permeability coefficient increased with increasing lipophilicity to alcohol C8 (octanol) with no further increase for C10 (decanol). Log vehicle:stratum corneum partition coefficients were related to logP, and the concentration of alcohols in each of the tissue layers appeared to increase with lipophilicity. No difference was measured in the diffusivity of smaller more polar alcohols in the three membranes; however, the larger more lipophilic solutes showed slower diffusivity values. The study showed that the dermis may be a much more lipophilic environment than originally believed and that distribution of smaller nonionized solutes into local tissues below a site of topical application may be estimated based on knowledge of their lipophilicity alone.

Immunohistochemical characterization of prototypical endometrial clear cell carcinoma--diagnostic utility of HNF-1β and oestrogen receptor.

PubMed

Hoang, Lien N; Han, Guangming; McConechy, Melissa; Lau, Sherman; Chow, Christine; Gilks, C Blake; Huntsman, David G; Köbel, Martin; Lee, Cheng-Han

2014-03-01

The great majority of ovarian clear cell carcinomas have a hepatocyte nuclear factor 1 homeobox B (HNF-1β)-positive and oestrogen receptor (ER)-negative immunoprofile. However, the pattern of HNF-1β and ER immunostaining in clear cell carcinomas of the endometrium and the usefulness of this panel in distinguishing clear cell carcinoma from other histological types of endometrial carcinoma have yet to be well defined. We examined the immunostaining patterns of HNF-1β, ER and p53 in 15 morphologically classic pure endometrial clear cell carcinomas, and compared these patterns with 15 endometrioid and 15 serous carcinomas of the endometrium. We observed the presence of diffuse (>70%) moderate to strong nuclear HNF-1β staining and negative ER staining in 14 of 15 clear cell carcinomas, with the remaining case showing both diffuse strong nuclear HNF-1β staining and focal ER staining. In comparison, only one of 15 serous carcinomas and none of 15 endometrioid carcinomas showed a combination of diffuse moderate to strong HNF-1β nuclear staining and negative ER staining. Aberrant p53 immunostaining was observed in five of 15 (33%) clear cell carcinomas. Overall, our findings demonstrate that, similarly to the situation for the ovary, a diagnostic panel of HNF-1β and ER may be considered for separating clear cell carcinoma from endometrioid and serous carcinoma of the endometrium. © 2013 John Wiley & Sons Ltd.

Effect of SiN x diffusion barrier thickness on the structural properties and photocatalytic activity of TiO2 films obtained by sol-gel dip coating and reactive magnetron sputtering.

PubMed

Ghazzal, Mohamed Nawfal; Aubry, Eric; Chaoui, Nouari; Robert, Didier

2015-01-01

We investigate the effect of the thickness of the silicon nitride (SiN x ) diffusion barrier on the structural and photocatalytic efficiency of TiO2 films obtained with different processes. We show that the structural and photocatalytic efficiency of TiO2 films produced using soft chemistry (sol-gel) and physical methods (reactive sputtering) are affected differentially by the intercalating SiN x diffusion barrier. Increasing the thickness of the SiN x diffusion barrier induced a gradual decrease of the crystallite size of TiO2 films obtained by the sol-gel process. However, TiO2 obtained using the reactive sputtering method showed no dependence on the thickness of the SiN x barrier diffusion. The SiN x barrier diffusion showed a beneficial effect on the photocatalytic efficiency of TiO2 films regardless of the synthesis method used. The proposed mechanism leading to the improvement in the photocatalytic efficiency of the TiO2 films obtained by each process was discussed.

Dynamics and diffusion mechanism of low-density liquid silicon

DOE PAGES

Shen, B.; Wang, Z. Y.; Dong, F.; ...

2015-11-05

A first-order phase transition from a high-density liquid to a low-density liquid has been proposed to explain the various thermodynamic anomies of water. It also has been proposed that such liquid–liquid phase transition would exist in supercooled silicon. Computer simulation studies show that, across the transition, the diffusivity drops roughly 2 orders of magnitude, and the structures exhibit considerable tetrahedral ordering. The resulting phase is a highly viscous, low-density liquid silicon. Investigations on the atomic diffusion of such a novel form of liquid silicon are of high interest. Here we report such diffusion results from molecular dynamics simulations using themore » classical Stillinger–Weber (SW) potential of silicon. We show that the atomic diffusion of the low-density liquid is highly correlated with local tetrahedral geometries. We also show that atoms diffuse through hopping processes within short ranges, which gradually accumulate to an overall random motion for long ranges as in normal liquids. There is a close relationship between dynamical heterogeneity and hopping process. We point out that the above diffusion mechanism is closely related to the strong directional bonding nature of the distorted tetrahedral network. Here, our work offers new insights into the complex behavior of the highly viscous low density liquid silicon, suggesting similar diffusion behaviors in other tetrahedral coordinated liquids that exhibit liquid–liquid phase transition such as carbon and germanium.« less

Symmetrical and overloaded effect of diffusion in information filtering

NASA Astrophysics Data System (ADS)

Zhu, Xuzhen; Tian, Hui; Chen, Guilin; Cai, Shimin

2017-10-01

In physical dynamics, mass diffusion theory has been applied to design effective information filtering models on bipartite network. In previous works, researchers unilaterally believe objects' similarities are determined by single directional mass diffusion from the collected object to the uncollected, meanwhile, inadvertently ignore adverse influence of diffusion overload. It in some extent veils the essence of diffusion in physical dynamics and hurts the recommendation accuracy and diversity. After delicate investigation, we argue that symmetrical diffusion effectively discloses essence of mass diffusion, and high diffusion overload should be published. Accordingly, in this paper, we propose an symmetrical and overload penalized diffusion based model (SOPD), which shows excellent performances in extensive experiments on benchmark datasets Movielens and Netflix.

Hemoglobin diffusion and the dynamics of oxygen capture by red blood cells.

PubMed

Longeville, Stéphane; Stingaciu, Laura-Roxana

2017-09-05

Translational diffusion of macromolecules in cell is generally assumed to be anomalous due high macromolecular crowding of the milieu. Red blood cells are a special case of cells filled quasi exclusively (95% of the dry weight of the cell) with an almost spherical protein: hemoglobin. Hemoglobin diffusion has since a long time been recognized as facilitating the rate of oxygen diffusion through a solution. We address in this paper the question on how hemoglobin diffusion in the red blood cells can help the oxygen capture at the cell level and hence to improve oxygen transport. We report a measurement by neutron spin echo spectroscopy of the diffusion of hemoglobin in solutions with increasing protein concentration. We show that hemoglobin diffusion in solution can be described as Brownian motion up to physiological concentration and that hemoglobin diffusion in the red blood cells and in solutions at similar concentration are the same. Finally, using a simple model and the concentration dependence of the diffusion of the protein reported here, we show that hemoglobin concentration observed in human red blood cells ([Formula: see text]330 g.L -1 ) corresponds to an optimum for oxygen transport for individuals under strong activity.

Mapping immune cell infiltration using restricted diffusion MRI.

PubMed

Yeh, Fang-Cheng; Liu, Li; Hitchens, T Kevin; Wu, Yijen L

2017-02-01

Diffusion MRI provides a noninvasive way to assess tissue microstructure. Based on diffusion MRI, we propose a model-free method called restricted diffusion imaging (RDI) to quantify restricted diffusion and correlate it with cellularity. An analytical relation between q-space signals and the density of restricted spins was derived to quantify restricted diffusion. A phantom study was conducted to investigate the performance of RDI, and RDI was applied to an animal study to assess immune cell infiltration in myocardial tissues with ischemia-reperfusion injury. Our phantom study showed a correlation coefficient of 0.998 between cell density and the restricted diffusion quantified by RDI. The animal study also showed that the high-value regions in RDI matched well with the macrophage infiltration areas in the H&E stained slides. In comparison with diffusion tensor imaging (DTI), RDI exhibited its outperformance to detect macrophage infiltration and delineate inflammatory myocardium. RDI can be used to reveal cell density and detect immune cell infiltration. RDI exhibits better specificity than the diffusivity measurement derived from DTI. Magn Reson Med 77:603-612, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Hemoglobin diffusion and the dynamics of oxygen capture by red blood cells

DOE PAGES

Longeville, Stéphane; Stingaciu, Laura-Roxana

2017-09-05

Translational diffusion of macromolecules in cell is generally assumed to be anomalous due high macromolecular crowding of the milieu. Red blood cells are a special case of cells filled quasi exclusively (95% of the dry weight of the cell) with an almost spherical protein: hemoglobin. Hemoglobin diffusion has since a long time been recognized as facilitating the rate of oxygen diffusion through a solution. We address in this paper the question on how hemoglobin diffusion in the red blood cells can help the oxygen capture at the cell level and hence to improve oxygen transport. We report a measurement bymore » neutron spin echo spectroscopy of the diffusion of hemoglobin in solutions with increasing protein concentration. We show that hemoglobin diffusion in solution can be described as Brownian motion up to physiological concentration and that hemoglobin diffusion in the red blood cells and in solutions at similar concentration are the same. Finally, using a simple model and the concentration dependence of the diffusion of the protein reported here, we show that hemoglobin concentration observed in human red blood cells (≃330 g.L -1) corresponds to an optimum for oxygen transport for individuals under strong activity.« less

Hemoglobin diffusion and the dynamics of oxygen capture by red blood cells

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

Longeville, Stéphane; Stingaciu, Laura-Roxana

Translational diffusion of macromolecules in cell is generally assumed to be anomalous due high macromolecular crowding of the milieu. Red blood cells are a special case of cells filled quasi exclusively (95% of the dry weight of the cell) with an almost spherical protein: hemoglobin. Hemoglobin diffusion has since a long time been recognized as facilitating the rate of oxygen diffusion through a solution. We address in this paper the question on how hemoglobin diffusion in the red blood cells can help the oxygen capture at the cell level and hence to improve oxygen transport. We report a measurement bymore » neutron spin echo spectroscopy of the diffusion of hemoglobin in solutions with increasing protein concentration. We show that hemoglobin diffusion in solution can be described as Brownian motion up to physiological concentration and that hemoglobin diffusion in the red blood cells and in solutions at similar concentration are the same. Finally, using a simple model and the concentration dependence of the diffusion of the protein reported here, we show that hemoglobin concentration observed in human red blood cells (≃330 g.L -1) corresponds to an optimum for oxygen transport for individuals under strong activity.« less

Analysis of diffusion in curved surfaces and its application to tubular membranes

PubMed Central

Klaus, Colin James Stockdale; Raghunathan, Krishnan; DiBenedetto, Emmanuele; Kenworthy, Anne K.

2016-01-01

Diffusion of particles in curved surfaces is inherently complex compared with diffusion in a flat membrane, owing to the nonplanarity of the surface. The consequence of such nonplanar geometry on diffusion is poorly understood but is highly relevant in the case of cell membranes, which often adopt complex geometries. To address this question, we developed a new finite element approach to model diffusion on curved membrane surfaces based on solutions to Fick’s law of diffusion and used this to study the effects of geometry on the entry of surface-bound particles into tubules by diffusion. We show that variations in tubule radius and length can distinctly alter diffusion gradients in tubules over biologically relevant timescales. In addition, we show that tubular structures tend to retain concentration gradients for a longer time compared with a comparable flat surface. These findings indicate that sorting of particles along the surfaces of tubules can arise simply as a geometric consequence of the curvature without any specific contribution from the membrane environment. Our studies provide a framework for modeling diffusion in curved surfaces and suggest that biological regulation can emerge purely from membrane geometry. PMID:27733625

Stochastic mechanics of reciprocal diffusions

NASA Astrophysics Data System (ADS)

Levy, Bernard C.; Krener, Arthur J.

1996-02-01

The dynamics and kinematics of reciprocal diffusions were examined in a previous paper [J. Math. Phys. 34, 1846 (1993)], where it was shown that reciprocal diffusions admit a chain of conservation laws, which close after the first two laws for two disjoint subclasses of reciprocal diffusions, the Markov and quantum diffusions. For the case of quantum diffusions, the conservation laws are equivalent to Schrödinger's equation. The Markov diffusions were employed by Schrödinger [Sitzungsber. Preuss. Akad. Wiss. Phys. Math Kl. 144 (1931); Ann. Inst. H. Poincaré 2, 269 (1932)], Nelson [Dynamical Theories of Brownian Motion (Princeton University, Princeton, NJ, 1967); Quantum Fluctuations (Princeton University, Princeton, NJ, 1985)], and other researchers to develop stochastic formulations of quantum mechanics, called stochastic mechanics. We propose here an alternative version of stochastic mechanics based on quantum diffusions. A procedure is presented for constructing the quantum diffusion associated to a given wave function. It is shown that quantum diffusions satisfy the uncertainty principle, and have a locality property, whereby given two dynamically uncoupled but statistically correlated particles, the marginal statistics of each particle depend only on the local fields to which the particle is subjected. However, like Wigner's joint probability distribution for the position and momentum of a particle, the finite joint probability densities of quantum diffusions may take negative values.

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.

Optimal Network Modularity for Information Diffusion

NASA Astrophysics Data System (ADS)

Nematzadeh, Azadeh; Ferrara, Emilio; Flammini, Alessandro; Ahn, Yong-Yeol

2014-08-01

We investigate the impact of community structure on information diffusion with the linear threshold model. Our results demonstrate that modular structure may have counterintuitive effects on information diffusion when social reinforcement is present. We show that strong communities can facilitate global diffusion by enhancing local, intracommunity spreading. Using both analytic approaches and numerical simulations, we demonstrate the existence of an optimal network modularity, where global diffusion requires the minimal number of early adopters.

Primary lymphoma of appendix presenting as acute appendicitis: A case report.

PubMed

Caristo, Giuseppe; Griseri, Guido; Fornaro, Rosario; Langone, Antonio; Franceschi, Angelo; Errigo, Veronica; Ferrari, Cecilia; Casaccia, Marco; Frascio, Marco; Schirru, Angelo

2018-05-07

Primary lymphomas of appendix are extremely rare tumors. The incidence is 0.015% of all gastrointestinal lymphomas. We present a case of a 75 year-old male patient who presented with acute abdominal pain in the lower right quadrant and fever. The patient received laparotomic appendectomy. The definitive histopathological examination revealed the presence of diffuse large cell B-lymphoma of the appendix. The neoplasms of appendix usually manifest clinically with sign and symptoms of acute appendicitis from luminal obstruction (30-50%). Preoperative diagnosis is difficult and often occurs through histopathological examination. Primary appendiceal lymphoma is rare and there are no clear guidelines for therapy. Primary surgical resection followed by post-operative chemotherapy showed high efficacy. The histopathological examination of all appendectomy is essential. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

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.

Relative Roles of Gap Junction Channels and Cytoplasm in Cell-to-Cell Diffusion of Fluorescent Tracers

NASA Astrophysics Data System (ADS)

Safranyos, Richard G. A.; Caveney, Stanley; Miller, James G.; Petersen, Nils O.

1987-04-01

Intercellular (tissue) diffusion of molecules requires cytoplasmic diffusion and diffusion through gap junctional (or cell-to-cell) channels. The rates of tissue and cytoplasmic diffusion of fluorescent tracers, expressed as an effective diffusion coefficient, De, and a cytoplasmic diffusion coefficient, Dcyt, have been measured among the developing epidermal cells of a larval beetle, Tenebrio molitor L., to determine the contribution of the junctional channels to intercellular diffusion. Tracer diffusion was measured by injecting fluorescent tracers into cells and quantitating the rate of subsequent spread into adjacent cells. Cytoplasmic diffusion was determined by fluorescence photobleaching. These experiments show that gap junctional channels constitute approximately 70-80% of the total cell-to-cell resistance to the diffusion of organic tracers at high concentrations in this tissue. At low concentrations, however, the binding of tracer to cytoplasm slows down the cytoplasmic diffusion, which may limit intercellular diffusion.

On modeling pressure diffusion in non-homogeneous shear flows

NASA Technical Reports Server (NTRS)

Demuren, A. O.; Rogers, M. M.; Durbin, P.; Lele, S. K.

1996-01-01

New models are proposed for the 'slow and 'rapid' parts of the pressure diffusive transport based on the examination of DNS databases for plane mixing layers and wakes. The model for the 'slow' part is non-local, but requires the distribution of the triple-velocity correlation as a local source. The latter can be computed accurately for the normal component from standard gradient diffusion models, but such models are inadequate for the cross component. More work is required to remedy this situation.

Fluorescence correlation spectroscopy diffusion laws in the presence of moving nanodomains

NASA Astrophysics Data System (ADS)

Šachl, Radek; Bergstrand, Jan; Widengren, Jerker; Hof, Martin

2016-03-01

It has been shown by means of simulations that spot variation fluorescence correlation spectroscopy (sv-FCS) can be used for the identification and, to some extent, also characterization of immobile lipid nanodomains in model as well as cellular plasma membranes. However, in these simulations, the nanodomains were assumed to be stationary, whereas they actually tend to move like the surrounding lipids. In the present study, we investigated how such domain movement influences the diffusion time/spot-size dependence observed in FCS experiments, usually referred to as ‘diffusion law’ analysis. We show that domain movement might mask the effects of the ‘anomalous’ diffusion characteristics of membrane lipids or proteins predicted for stationary domains, making it difficult to identify such moving nanodomains by sv-FCS. More specifically, our simulations indicate that (i) for domains moving up to a factor of 2.25 slower than the surrounding lipids, such impeded diffusion cannot be observed and the diffusion behaviour of the proteins or lipids is indistinguishable from that of freely diffusing molecules, i.e. nanodomains are not detected; (ii) impeded protein/lipid diffusion behaviour can be observed in experiments where the radii of the detection volume are similar in size to the domain radii, the domain diffusion is about 10 times slower than that of the lipids, and the probes show a high affinity to the domains; and (iii) presence of nanodomains can only be reliably detected by diffraction limited sv-FCS when the domains move very slowly (about 200 times slower than the lipid diffusion). As nanodomains are expected to be in the range of tens of nanometres and most probes show low affinities to such domains, sv-FCS is limited to stationary domains and/or STED-FCS. However, even for that latter technique, diffusing domains smaller than 50 nm in radius are hardly detectable by FCS diffusion time/spot-size dependencies.

The experimental study of matching between centrifugal compressor impeller and diffuser

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

Tamaki, H.; Nakao, H.; Saito, M.

1999-01-01

the centrifugal compressor for a marine use turbocharger with its design pressure ratio of 3.2 was tested with a vaneless diffuser and various vaned diffusers. Vaned diffusers were chosen to cover impeller operating range as broad as possible. The analysis of the static pressure ratio in the impeller and the diffusing system, consisting of the diffuser and scroll, showed that there were four possible combinations of characteristics of impeller pressure ratio and diffusing system pressure ratio. The flow rate, Q{sub P}, where the impeller achieved maximum static pressure ratio, was surge flow rate of the centrifugal compressor determined by themore » critical flow rate. In order to operate the compressor at a rate lower than Q{sub P}, the diffusing system, whose pressure recovery factor was steep negative slope near Q{sub P}, was needed. When the diffuser throat area was less than a certain value, the compressor efficiency deteriorated; however, the compressor stage pressure ratio was almost constant. In this study, by reducing the diffuser throat area, the compressor could be operated at a flow rate less than 40% of its design flow rate. Analysis of the pressure ratio in the impeller and diffusing systems at design and off-design speeds showed that the irregularities in surge line occurred when the component that controlled the negative slope on the compressor stage pressure ratio changed.« less

Hydrodynamically induced fluid transfer and non-convective double-diffusion in microgravity sliding solvent diffusion cells

NASA Technical Reports Server (NTRS)

Pollmann, Konrad W.; Stodieck, Louis S.; Luttges, Marvin W.

1994-01-01

Microgravity can provide a diffusion-dominated environment for double-diffusion and diffusion-reaction experiments otherwise disrupted by buoyant convection or sedimentation. In sliding solvent diffusion cells, a diffusion interface between two liquid columns is achieved by aligning two offset sliding wells. Fluid in contact with the sliding lid of the cavities is subjected to an applied shear stress. The momentum change by the start/stop action of the well creates an additional hydrodynamical force. In microgravity, these viscous and inertial forces are sufficiently large to deform the diffusion interface and induce hydrodynamic transfer between the wells. A series of KC-135 parabolic flight experiments were conducted to characterize these effects and establish baseline data for microgravity diffusion experiments. Flow visualizations show the diffusion interface to be deformed in a sinusoidal fashion following well alignment. After the wells were separated again in a second sliding movement, the total induced liquid transfer was determined and normalized by the well aspect ratio. The normalized transfer decreased linearly with Reynolds number from 3.3 to 4.0% (w/v) for Re = 0.4 (Stokes flow) to a minimum of 1.0% for Re = 23 to 30. Reynolds numbers that provide minimum induced transfers are characterized by an interface that is highly deformed and unsuitable for diffusion measurements. Flat diffusion interfaces acceptable for diffusion measurements are obtained with Reynolds numbers on the order of 7 to 10. Microgravity experiments aboard a sounding rocket flight verified counterdiffusion of different solutes to be diffusion dominated. Ground control experiments showed enhanced mixing by double-diffusive convection. Careful selection of experimental parameters improves initial conditions and minimizes induced transfer rates.

Water diffusion in silicate glasses: the effect of glass structure

NASA Astrophysics Data System (ADS)

Kuroda, M.; Tachibana, S.

2016-12-01

Water diffusion in silicate melts (glasses) is one of the main controlling factors of magmatism in a volcanic system. Water diffusivity in silicate glasses depends on its own concentration. However, the mechanism causing those dependences has not been fully understood yet. In order to construct a general model for water diffusion in various silicate glasses, we performed water diffusion experiments in silica glass and proposed a new water diffusion model [Kuroda et al., 2015]. In the model, water diffusivity is controlled by the concentration of both main diffusion species (i.e. molecular water) and diffusion pathways, which are determined by the concentrations of hydroxyl groups and network modifier cations. The model well explains the water diffusivity in various silicate glasses from silica glass to basalt glass. However, pre-exponential factors of water diffusivity in various glasses show five orders of magnitude variations although the pre-exponential factor should ideally represent the jump frequency and the jump distance of molecular water and show a much smaller variation. Here, we attribute the large variation of pre-exponential factors to a glass structure dependence of activation energy for molecular water diffusion. It has been known that the activation energy depends on the water concentration [Nowak and Behrens, 1997]. The concentration of hydroxyls, which cut Si-O-Si network in the glass structure, increases with water concentration, resulting in lowering the activation energy for water diffusion probably due to more fragmented structure. Network modifier cations are likely to play the same role as water. With taking the effect of glass structure into account, we found that the variation of pre-exponential factors of water diffusivity in silicate glasses can be much smaller than the five orders of magnitude, implying that the diffusion of molecular water in silicate glasses is controlled by the same atomic process.

First-principles investigation of diffusion and defect properties of Fe and Ni in Cr2O3

NASA Astrophysics Data System (ADS)

Rak, Zs.; Brenner, D. W.

2018-04-01

Diffusion of Fe and Ni and the energetics of Fe- and Ni-related defects in chromium oxide (α-Cr2O3) are investigated using first-principles Density Functional Theory calculations in combination with the climbing-image nudged elastic band method. The orientations of the spin magnetic moments of the migrating ions are taken into account and their effects on migration barriers are examined. Several possible diffusion pathways were explored through interstitial and vacancy mechanisms, and it was found that the principal mode of ion transport in Cr2O3 is via vacancies. Both interstitial- and vacancy-mediated diffusions are anisotropic, with diffusion being faster in the z-direction. The energetics of defect formation indicates that the Ni-related defects are less stable than the Fe-related ones. This is consistent with Ni-diffusion being faster than Fe-diffusion. The results are compared with previous theoretical and experimental data and possible implications in corrosion control are discussed.

Diffusion processes of fragmentary information on scale-free networks

NASA Astrophysics Data System (ADS)

Li, Xun; Cao, Lang

2016-05-01

Compartmental models of diffusion over contact networks have proven representative of real-life propagation phenomena among interacting individuals. However, there is a broad class of collective spreading mechanisms departing from compartmental representations, including those for diffusive objects capable of fragmentation and transmission unnecessarily as a whole. Here, we consider a continuous-state susceptible-infected-susceptible (SIS) model as an ideal limit-case of diffusion processes of fragmentary information on networks, where individuals possess fractions of the information content and update them by selectively exchanging messages with partners in the vicinity. Specifically, we incorporate local information, such as neighbors' node degrees and carried contents, into the individual partner choice, and examine the roles of a variety of such strategies in the information diffusion process, both qualitatively and quantitatively. Our method provides an effective and flexible route of modulating continuous-state diffusion dynamics on networks and has potential in a wide array of practical applications.

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

On the anisotropic advection-diffusion equation with time dependent coefficients

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

Hernandez-Coronado, Hector; Coronado, Manuel; Del-Castillo-Negrete, Diego B.

The advection-diffusion equation with time dependent velocity and anisotropic time dependent diffusion tensor is examined in regard to its non-classical transport features and to the use of a non-orthogonal coordinate system. Although this equation appears in diverse physical problems, particularly in particle transport in stochastic velocity fields and in underground porous media, a detailed analysis of its solutions is lacking. In order to study the effects of the time-dependent coefficients and the anisotropic diffusion on transport, we solve analytically the equation for an initial Dirac delta pulse. Here, we discuss the solutions to three cases: one based on power-law correlationmore » functions where the pulse diffuses faster than the classical rate ~t, a second case specically designed to display slower rate of diffusion than the classical one, and a third case to describe hydrodynamic dispersion in porous media« less

On the anisotropic advection-diffusion equation with time dependent coefficients

DOE PAGES

Hernandez-Coronado, Hector; Coronado, Manuel; Del-Castillo-Negrete, Diego B.

2017-02-01

The advection-diffusion equation with time dependent velocity and anisotropic time dependent diffusion tensor is examined in regard to its non-classical transport features and to the use of a non-orthogonal coordinate system. Although this equation appears in diverse physical problems, particularly in particle transport in stochastic velocity fields and in underground porous media, a detailed analysis of its solutions is lacking. In order to study the effects of the time-dependent coefficients and the anisotropic diffusion on transport, we solve analytically the equation for an initial Dirac delta pulse. Here, we discuss the solutions to three cases: one based on power-law correlationmore » functions where the pulse diffuses faster than the classical rate ~t, a second case specically designed to display slower rate of diffusion than the classical one, and a third case to describe hydrodynamic dispersion in porous media« less

Ion radial diffusion in an electrostatic impulse model for stormtime ring current formation

NASA Technical Reports Server (NTRS)

Chen, Margaret W.; Schulz, Michael; Lyons, Larry R.; Gorney, David J.

1992-01-01

Two refinements to the quasi-linear theory of ion radial diffusion are proposed and examined analytically with simulations of particle trajectories. The resonance-broadening correction by Dungey (1965) is applied to the quasi-linear diffusion theory by Faelthammar (1965) for an individual model storm. Quasi-linear theory is then applied to the mean diffusion coefficients resulting from simulations of particle trajectories in 20 model storms. The correction for drift-resonance broadening results in quasi-linear diffusion coefficients with discrepancies from the corresponding simulated values that are reduced by a factor of about 3. Further reductions in the discrepancies are noted following the averaging of the quasi-linear diffusion coefficients, the simulated coefficients, and the resonance-broadened coefficients for the 20 storms. Quasi-linear theory provides good descriptions of particle transport for a single storm but performs even better in conjunction with the present ensemble-averaging.

Molecules in motion: influences of diffusion on metabolic structure and function in skeletal muscle.

PubMed

Kinsey, Stephen T; Locke, Bruce R; Dillaman, Richard M

2011-01-15

Metabolic processes are often represented as a group of metabolites that interact through enzymatic reactions, thus forming a network of linked biochemical pathways. Implicit in this view is that diffusion of metabolites to and from enzymes is very fast compared with reaction rates, and metabolic fluxes are therefore almost exclusively dictated by catalytic properties. However, diffusion may exert greater control over the rates of reactions through: (1) an increase in reaction rates; (2) an increase in diffusion distances; or (3) a decrease in the relevant diffusion coefficients. It is therefore not surprising that skeletal muscle fibers have long been the focus of reaction-diffusion analyses because they have high and variable rates of ATP turnover, long diffusion distances, and hindered metabolite diffusion due to an abundance of intracellular barriers. Examination of the diversity of skeletal muscle fiber designs found in animals provides insights into the role that diffusion plays in governing both rates of metabolic fluxes and cellular organization. Experimental measurements of metabolic fluxes, diffusion distances and diffusion coefficients, coupled with reaction-diffusion mathematical models in a range of muscle types has started to reveal some general principles guiding muscle structure and metabolic function. Foremost among these is that metabolic processes in muscles do, in fact, appear to be largely reaction controlled and are not greatly limited by diffusion. However, the influence of diffusion is apparent in patterns of fiber growth and metabolic organization that appear to result from selective pressure to maintain reaction control of metabolism in muscle.

Measurement of distributions of temperature and wavelength-dependent emissivity of a laminar diffusion flame using hyper-spectral imaging technique

NASA Astrophysics Data System (ADS)

Liu, Huawei; Zheng, Shu; Zhou, Huaichun; Qi, Chaobo

2016-02-01

A generalized method to estimate a two-dimensional (2D) distribution of temperature and wavelength-dependent emissivity in a sooty flame with spectroscopic radiation intensities is proposed in this paper. The method adopts a Newton-type iterative method to solve the unknown coefficients in the polynomial relationship between the emissivity and the wavelength, as well as the unknown temperature. Polynomial functions with increasing order are examined, and final results are determined as the result converges. Numerical simulation on a fictitious flame with wavelength-dependent absorption coefficients shows a good performance with relative errors less than 0.5% in the average temperature. What’s more, a hyper-spectral imaging device is introduced to measure an ethylene/air laminar diffusion flame with the proposed method. The proper order for the polynomial function is selected to be 2, because every one order increase in the polynomial function will only bring in a temperature variation smaller than 20 K. For the ethylene laminar diffusion flame with 194 ml min-1 C2H4 and 284 L min-1 air studied in this paper, the 2D distribution of average temperature estimated along the line of sight is similar to, but smoother than that of the local temperature given in references, and the 2D distribution of emissivity shows a cumulative effect of the absorption coefficient along the line of sight. It also shows that emissivity of the flame decreases as the wavelength increases. The emissivity under wavelength 400 nm is about 2.5 times as much as that under wavelength 1000 nm for a typical line-of-sight in the flame, with the same trend for the absorption coefficient of soot varied with the wavelength.

Global and Regional Brain Non-Gaussian Diffusion Changes in Newly Diagnosed Patients with Obstructive Sleep Apnea.

PubMed

Tummala, Sudhakar; Palomares, Jose; Kang, Daniel W; Park, Bumhee; Woo, Mary A; Harper, Ronald M; Kumar, Rajesh

2016-01-01

Obstructive sleep apnea (OSA) patients show brain structural injury and functional deficits in autonomic, affective, and cognitive regulatory sites, as revealed by mean diffusivity (MD) and other imaging procedures. The time course and nature of gray and white matter injury can be revealed in more detail with mean kurtosis (MK) procedures, which can differentiate acute from chronic injury, and better show extent of damage over MD procedures. Our objective was to examine global and regional MK changes in newly diagnosed OSA, relative to control subjects. Two diffusion kurtosis image series were collected from 22 recently-diagnosed, treatment-naïve OSA and 26 control subjects using a 3.0-Tesla MRI scanner. MK maps were generated, normalized to a common space, smoothed, and compared voxel-by-voxel between groups using analysis of covariance (covariates; age, sex). No age or sex differences appeared, but body mass index, sleep, neuropsychologic, and cognitive scores significantly differed between groups. MK values were significantly increased globally in OSA over controls, and in multiple localized sites, including the basal forebrain, extending to the hypothalamus, hippocampus, thalamus, insular cortices, basal ganglia, limbic regions, cerebellar areas, parietal cortices, ventral temporal lobe, ventrolateral medulla, and midline pons. Multiple sites, including the insular cortices, ventrolateral medulla, and midline pons showed more injury over previously identified damage with MD procedures, with damage often lateralized. Global mean kurtosis values are significantly increased in obstructive sleep apnea (OSA), suggesting acute tissue injury, and these changes are principally localized in critical sites mediating deficient functions in the condition. The mechanisms for injury likely include altered perfusion and hypoxemia-induced processes, leading to acute tissue changes in recently diagnosed OSA. © 2016 Associated Professional Sleep Societies, LLC.

Stimulated echo diffusion tensor imaging (STEAM-DTI) with varying diffusion times as a probe of breast tissue.

PubMed

Teruel, Jose R; Cho, Gene Y; Moccaldi Rt, Melanie; Goa, Pål E; Bathen, Tone F; Feiweier, Thorsten; Kim, Sungheon G; Moy, Linda; Sigmund, Eric E

2017-01-01

To explore the application of diffusion tensor imaging (DTI) for breast tissue and breast pathologies using a stimulated-echo acquisition mode (STEAM) with variable diffusion times. In this Health Insurance Portability and Accountability Act-compliant study, approved by the local institutional review board, eight patients and six healthy volunteers underwent an MRI examination at 3 Tesla including STEAM-DTI with several diffusion times ranging from 68.5 to 902.5 ms. A DTI model was fitted to the data for each diffusion time, and parametric maps of mean diffusivity, fractional anisotropy, axial diffusivity, and radial diffusivity were computed for healthy fibroglandular tissue (FGT) and lesions. The median value of radial diffusivity for FGT was fitted to a linear decay to obtain an estimation of the surface-to-volume ratio, from which the radial diameter was calculated. For healthy FGT, radial diffusivity presented a linear decay with the square root of the diffusion time resulting in a range of estimated radial diameters from 202 to 496 µm, while axial diffusivity presented a nearly time-independent diffusion. Residual fat signal was reduced at longer diffusion times due to the shorter T1 of fat. Residual fat signal to the overall signal in the healthy volunteers' FGT was found to range from 2.39% to 2.55% (shortest mixing time), and from 0.40% to 0.51% (longest mixing time) for the b500 images. The use of variable diffusion times may provide an in vivo noninvasive tool to probe diffusion lengths in breast tissue and breast pathology, and might aid by improving fat suppression at longer diffusion times. 2 J. Magn. Reson. Imaging 2017;45:84-93. © 2016 International Society for Magnetic Resonance in Medicine.

Diffusion behavior of lipid vesicles in entangled polymer solutions.

PubMed Central

Cao, X; Bansil, R; Gantz, D; Moore, E W; Niu, N; Afdhal, N H

1997-01-01

Dynamic light scattering was used to follow the tracer diffusion of phospholipid/cholesterol vesicles in aqueous polyacrylamide solutions and compared with the diffusive behavior of polystyrene (PS) latex spheres of comparable diameters. Over the range of the matrix concentration examined (Cp = 0.1-10 mg/ml), the diffusivities of the PS spheres and the large multilamellar vesicles exhibited the Stokes-Einstein (SE) relation, while the diffusivity of the unilamellar vesicles did not follow the increase of the solution's viscosity caused by the presence of the matrix molecules. The difference between the diffusion behaviors of unilamellar vesicles and hard PS spheres of similar size is possibly due to the flexibility of the lipid bilayer of the vesicles. The unilamellar vesicles are capable of changing their shape to move through the entangled polymer solution so that the hindrance to their diffusion due to the presence of the polymer chains is reduced, while the rigid PS spheres have little flexibility and they encounter greater resistance. The multilamellar vesicles are less flexible, thus their diffusion is similar to the hard PS spheres of similar diameter. Images FIGURE 2 PMID:9336189

Study of Solid-State Diffusion of Bi in Polycrystalline Sn Using Electron Probe Microanalysis

NASA Astrophysics Data System (ADS)

Delhaise, André M.; Perovic, Doug D.

2018-03-01

Current lead-free solders such as SAC305 exhibit degradation in microstructure, properties, and reliability. Current third-generation alloys containing bismuth (Bi) demonstrate preservation of strength after aging; this is accompanied by homogenization of the Bi precipitates in the tin (Sn) matrix, driven via solid-state diffusion. This study quantifies the diffusion of Bi in Sn. Diffusion couples were prepared by mating together polished samples of pure Sn and Bi. Couples were annealed at one of three temperatures, viz. 85°C for 7 days, 100°C for 2 days, or 125°C for 1 day. After cross-sectioning the couples to examine the diffusion microstructure and grain size, elemental analysis was performed using electron probe microanalysis. For this study, it was assumed that the diffusivity of Bi in Sn is concentration dependent, therefore inverse methods were used to solve Fick's non-steady-state diffusion equation. In addition, Darken analysis was used to extract the impurity diffusivity of Bi in Sn at each temperature, allowing estimation of the Arrhenius parameters D 0 and k A.

Performance of a contact textile-based light diffuser for photodynamic therapy.

PubMed

Khan, Tania; Unternährer, Merthan; Buchholz, Julia; Kaser-Hotz, Barbara; Selm, Bärbel; Rothmaier, Markus; Walt, Heinrich

2006-03-01

Medical textiles offer a unique contact opportunity that could provide value-added comfort, reliability, and safety for light or laser-based applications. We investigated a luminous textile diffuser for use in photodynamic therapy. Textile diffusers are produced by an embroidery process. Plastic optical fibers are bent and sewn into textile to release light by macrobending. A reflective backing is incorporated to improve surface homogeneity, intensity, and safety. Clonogenic assay (MCF-7 cells) and trypan blue exclusion (NuTu19 cells) tests were performed in vitro using 0.1μg/ml m-THPC with three textile diffusers and a standard front lens diffuser. Heating effects were studied in solution and on human skin. PDT application in vivo was performed with the textile diffuser on equine sarcoids (three animals, 50mW/cm(2), 10-20J) and eight research animals. Lastly, computer simulations were performed to see how the textile diffuser might work on a curved object. At low fluency rate, there is a trend for the textile diffuser to have lower survival rates than the front lens diffuser for both cell lines. The textile diffuser was observed to retain more heat over a long period (>1min). All animals tolerated the treatments well and showed similar initial reactions. The simulations showed a likely focusing effect in a curved geometry. The initial feasibility and application using a textile-based optical diffuser has been demonstrated. Possibilities that provide additional practical advantages of the textile diffuser are discussed.

GALACTIC WINDS DRIVEN BY ISOTROPIC AND ANISOTROPIC COSMIC-RAY DIFFUSION IN DISK GALAXIES

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

Pakmor, R.; Pfrommer, C.; Simpson, C. M.

2016-06-20

The physics of cosmic rays (CRs) is a promising candidate for explaining the driving of galactic winds and outflows. Recent galaxy formation simulations have demonstrated the need for active CR transport either in the form of diffusion or streaming to successfully launch winds in galaxies. However, due to computational limitations, most previous simulations have modeled CR transport isotropically. Here, we discuss high-resolution simulations of isolated disk galaxies in a 10{sup 11} M {sub ⊙} halo with the moving-mesh code Arepo that include injection of CRs from supernovae, advective transport, CR cooling, and CR transport through isotropic or anisotropic diffusion. Wemore » show that either mode of diffusion leads to the formation of strong bipolar outflows. However, they develop significantly later in the simulation with anisotropic diffusion compared to the simulation with isotropic diffusion. Moreover, we find that isotropic diffusion allows most of the CRs to quickly diffuse out of the disk, while in the simulation with anisotropic diffusion, most CRs remain in the disk once the magnetic field becomes dominated by its azimuthal component, which occurs after ∼300 Myr. This has important consequences for the gas dynamics in the disk. In particular, we show that isotropic diffusion strongly suppresses the amplification of the magnetic field in the disk compared to anisotropic or no diffusion models. We therefore conclude that reliable simulations which include CR transport inevitably need to account for anisotropic diffusion.« less

Determination of the zincate diffusion coefficient and its application to alkaline battery problems

NASA Technical Reports Server (NTRS)

May, C. E.; Kautz, Harold E.

1978-01-01

The diffusion coefficient for the zincate ion at 24 C was found to be 9.9 X 10 to the minus 7th power squared cm per sec + or - 30 percent in 45 percent potassium hydroxide and 1.4 x 10 to the minus 7 squared cm per sec + or - 25 percent in 40 percent sodium hydroxide. Comparison of these values with literature values at different potassium hydroxide concentrations show that the Stokes-Einstein equation is obeyed. The diffusion coefficient is characteristic of the zincate ion (not the cation) and independent of its concentration. Calculations with the measured value of the diffusion coefficient show that the zinc concentration in an alkaline zincate half cell becomes uniform throughout in tens of hours by diffusion alone. Diffusion equations are derived which are applicable to finite size chambers. Details and discussion of the experimental method are also given.

Modified chloride diffusion model for concrete under the coupling effect of mechanical load and chloride salt environment

NASA Astrophysics Data System (ADS)

Lei, Mingfeng; Lin, Dayong; Liu, Jianwen; Shi, Chenghua; Ma, Jianjun; Yang, Weichao; Yu, Xiaoniu

2018-03-01

For the purpose of investigating lining concrete durability, this study derives a modified chloride diffusion model for concrete based on the odd continuation of boundary conditions and Fourier transform. In order to achieve this, the linear stress distribution on a sectional structure is considered, detailed procedures and methods are presented for model verification and parametric analysis. Simulation results show that the chloride diffusion model can reflect the effects of linear stress distribution of the sectional structure on the chloride diffusivity with reliable accuracy. Along with the natural environmental characteristics of practical engineering structures, reference value ranges of model parameters are provided. Furthermore, a chloride diffusion model is extended for the consideration of multi-factor coupling of linear stress distribution, chloride concentration and diffusion time. Comparison between model simulation and typical current research results shows that the presented model can produce better considerations with a greater universality.

Determination of the zincate diffusion coefficient and its application to alkaline battery problems

NASA Technical Reports Server (NTRS)

May, C. E.; Kautz, H. E.

1978-01-01

The diffusion coefficient for the zincate ion at 24 C was found to be 9.9 x 10 to the -7th power sq cm/sec + or - 30% in 45% potassium hydroxide and 1.4 x 10 to the -7th power sq cm/sec + or - 25% in 40% sodium hydroxide. Comparison of these values with literature values at different potassium hydroxide concentrations show that the Stokes-Einstein equation is obeyed. The diffusion coefficient is characteristic of the zincate ion (not the cation) and independent of its concentration. Calculations with the measured value of the diffusion coefficient show that the zinc concentration in an alkaline zincate half-cell becomes uniform throughout in tens of hours by diffusion alone. Diffusion equations are derived which are applicable to finite-size chambers. Details and discussion of the experimental method are also given.

Inter-Diffusion in the Presence of Free Convection

NASA Technical Reports Server (NTRS)

Gupta, Prabhat K.

1999-01-01

Because of their technological importance, establishment of the precise values of interdiffusion coefficients is important in multicomponent fluid systems. Such values are not available because diffusion is influenced by free convection due to compositionally induced density variations. In this project, earth based diffusion experiments are being performed in a viscous fluid system PbO-SiO2 at temperatures between 500-1000 C. This system is chosen because it shows a large variation in density with small changes in composition and is expected to show a large free convection effect. Infinite diffusion couples at different temperatures and times are being studied with different orientations with respect to gravity. Composition fields will be measured using an Electron Microprobe Analyzer and will be compared with the results of a complementary modeling study to extract the values of the true diffusion coefficient from the measured diffusion profiles.

Turing pattern dynamics and adaptive discretization for a super-diffusive Lotka-Volterra model.

PubMed

Bendahmane, Mostafa; Ruiz-Baier, Ricardo; Tian, Canrong

2016-05-01

In this paper we analyze the effects of introducing the fractional-in-space operator into a Lotka-Volterra competitive model describing population super-diffusion. First, we study how cross super-diffusion influences the formation of spatial patterns: a linear stability analysis is carried out, showing that cross super-diffusion triggers Turing instabilities, whereas classical (self) super-diffusion does not. In addition we perform a weakly nonlinear analysis yielding a system of amplitude equations, whose study shows the stability of Turing steady states. A second goal of this contribution is to propose a fully adaptive multiresolution finite volume method that employs shifted Grünwald gradient approximations, and which is tailored for a larger class of systems involving fractional diffusion operators. The scheme is aimed at efficient dynamic mesh adaptation and substantial savings in computational burden. A numerical simulation of the model was performed near the instability boundaries, confirming the behavior predicted by our analysis.

Lifetime of Major Histocompatibility Complex Class-I Membrane Clusters Is Controlled by the Actin Cytoskeleton

PubMed Central

Lavi, Yael; Gov, Nir; Edidin, Michael; Gheber, Levi A.

2012-01-01

Lateral heterogeneity of cell membranes has been demonstrated in numerous studies showing anomalous diffusion of membrane proteins; it has been explained by models and experiments suggesting dynamic barriers to free diffusion, that temporarily confine membrane proteins into microscopic patches. This picture, however, comes short of explaining a steady-state patchy distribution of proteins, in face of the transient opening of the barriers. In our previous work we directly imaged persistent clusters of MHC-I, a type I transmembrane protein, and proposed a model of a dynamic equilibrium between proteins newly delivered to the cell surface by vesicle traffic, temporary confinement by dynamic barriers to lateral diffusion, and dispersion of the clusters by diffusion over the dynamic barriers. Our model predicted that the clusters are dynamic, appearing when an exocytic vesicle fuses with the plasma membrane and dispersing with a typical lifetime that depends on lateral diffusion and the dynamics of barriers. In a subsequent work, we showed this to be the case. Here we test another prediction of the model, and show that changing the stability of actin barriers to lateral diffusion changes cluster lifetimes. We also develop a model for the distribution of cluster lifetimes, consistent with the function of barriers to lateral diffusion in maintaining MHC-I clusters. PMID:22500754

Diffusion, Viscosity and Crystal Growth in Microgravity

NASA Technical Reports Server (NTRS)

Myerson, Allan S.

1996-01-01

The diffusivity of TriGlycine Sulfate (TGS), Potassium Dihydrogen Phosphate (KDP), Ammonium Dihydrogen Phosphate (ADF) and other compounds of interest to microgravity crystal growth, in supersaturated solutions as a function of solution concentration, 'age' and 'history was studied experimentally. The factors that affect the growth of crystals from water solutions in microgravity have been examined. Three non-linear optical materials have been studied, potassium dihydrogen phosphate (KDP), ammonium dihydrogen phosphate (ADP) and triglycine sulfate (TGC). The diffusion coefficient and viscosity of supersaturated water solutions were measured. Also theoretical model of diffusivity and viscosity in a metastable state, model of crystal growth from solution including non-linear time dependent diffusivity and viscosity effect and computer simulation of the crystal growth process which allows simulation of the microgravity crystal growth were developed.

Tubulointerstitial nephritis and uveitis syndrome associated with hyperthyroidism.

PubMed

Ebihara, Itaru; Hirayama, Kouichi; Usui, Joichi; Seki, Masanori; Higuchi, Fujiko; Oteki, Takaaki; Kobayashi, Masaki; Yamagata, Kunihiro

2006-09-01

We report a 17-year-old male patient with tubulointerstitial nephritis and uveitis (TINU) associated with hyperthyroidism. He presented with a 2-month history of fatigue, loss of appetite, low-grade fever, and a 12-kg weight loss when he was admitted to our hospital. He had iritis, which was complicated by fibrin in the anterior chamber, diagnosed by slit-lamp examination. On laboratory examinations, deteriorated renal function (blood urea nitrogen level was 25.9 mg/dl and creatinine level was 2.82 mg/dl) and elevated urinary levels of N-acetyl-beta-D-glucosaminidase (33.1 U/l) and beta2-microglobulin (78,600 microg/l) were observed. Serum thyroid-stimulating hormone (TSH) was undetectable, at less than 0.01 microIU/ml, and free triiodothyronine and free thyroxine were elevated, up to 5.23 pg/ml and 2.85 ng/dl, respectively. The titers of antithyroglobulin and antithyroid microsomal and TSH-receptor antibodies were not elevated. Abdominal and thyroidal ultrasonography showed evident bilateral enlargement of the kidneys and diffuse enlargement of the thyroid gland. Iodine-123 scintigraphy showed low uptake in the thyroid gland. The biopsied renal specimen showed mild edema and severe diffuse infiltration of mononuclear cells and few eosinophils in the interstitium, without any glomerular or vascular abnormalities. Based on the clinical features and pathological findings, a diagnosis of TINU syndrome with associated hyperthyroidism was made. Treatment was started with 30 mg/day of prednisolone. The iritis disappeared, and the patient's clinical status improved remarkably. This case suggests the possibility of thyroid dysfunction in some patients with TINU syndrome, and we believe thyroid function should be measured in all TINU patients. Moreover, histopathological diagnosis of the thyroid glands before treatment is necessary for TINU patients with thyroid dysfunction.

[A case report of early-onset Alzheimer's disease with multiple psychotic symptoms, finally diagnosed as APPV717I mutation by genetic testing].

PubMed

Ishimaru, Takashi; Ochi, Shinichiro; Matsumoto, Teruhisa; Yoshida, Taku; Abe, Masao; Toyota, Yasutaka; Fukuhara, Ryuji; Tanimukai, Satoshi; Ueno, Shu-ichi

2013-01-01

It is difficult to confirm a diagnosis of early-onset Alzheimer's disease (EOAD) because patients sometimes have non-specific cortical features, such as psychiatric symptoms, executive functional impairment, and pyramidal symptoms, along with typical symptoms, such as recent memory impairment and disorientation. We encountered a patient with multiple psychotic symptoms, finally diagnosed with EOAD on genetic testing. A right-handed sixty-year-old man, whose mother was suspected of having dementia, developed memory impairment at the age of fifty, disorientation at the age of fifty-six, and both visual hallucination and dressing apraxia at the age of fifty-nine. After admission to a psychiatric hospital for treatment, his symptoms disappeared with antipsychotic medication. However, his ADL were declining and so he was referred to our university hospital. He had frontal lobe symptoms, pyramidal signs, and extrapyramidal signs with severe dementia. Neuropsychological examinations were not possible because of sedation. On brain MRI, he showed diffuse atrophy of the cerebral cortex and hippocampus. HMPO-SPECT showed hypoperfusion of cerebral cortices diffusely. We decided to perform genetic testing because he had both family and alcohol abuse histories. He showed EOAD with V717I mutation of the amyloid precursor protein gene. After the discontinuation of antipsychotics, excessive sedation and extrapyramidal signs disappeared. A dose of 10 mg of donepezil was effective to improve motivation and activity, and his mini mental examination score was calculable after recovery. The case supports usefulness of applying genetic testing for Alzheimer's disease to patients with early onset dementia, even when they do not have a family history.

Diffusion weighted imaging with background body signal suppression / T2 image fusion in magnetic resonance mammography for breast cancer diagnosis.

PubMed

Nechifor-Boilă, I A; Bancu, S; Buruian, M; Charlot, M; Decaussin-Petrucci, M; Krauth, J-S; Nechifor-Boilă, A C; Borda, A

2013-01-01

Dynamic Contrast-Enhanced Magnetic Resonance Mammography (DCE-MRM) represents the most sensitive examination for breast cancer (BC) diagnosis. However literature data reports very inhomogeneous specificity. The aim of our study was to evaluate the clinical efficiency of a new MRM technique - diffusion weighted imaging with background body signal suppression T2 image fusion in BC diagnosis, compared to DCE-MRM. We retrospectively analyzed 50 consecutive DCE-MRM examinations with DWIBS sequence from the archives of the Department of Radiology, Lyon Sud Hospital, (02.2010- 02.2011), summing up to 64 breast lesions. Fusions were created using the Osirix software from the DWIBS images (b=1000 s mm2) and their T2 correspondents. Interpretation was performed using an adapted BI-RADS system. The final histopathological examination or a minimum 6-months follow-up served as gold standard. Out of the 64 examined breast lesions, 35(54.7%) were classified as malignant by DCE-MRM and 24(37.5%) cases by DWIBS T2, respectively. Thus the DWIBS T2 fusion had a Sensitivity of 62.5%(95%CI:35.4-84.8) and a Specificity of 70.8%(95%CI:55.9-83.3) while DCE-MRM had a higher Sensitivity: 87.5%(95%CI:61.6-98.4) but a lower Specificity: 56.2%(95%CI:41.1-70.5). DWIBS T2 fusion is an innovative MRM technique, with a specificity superior to DCE-MRM, showing a large potential for improving the clinical efficiency of classical MRM. Celsius.

Diffusion coefficients of water in biobased hydrogel polymer matrices by nuclear magnetic resonance imaging

USDA-ARS?s Scientific Manuscript database

The diffusion coefficient of water in biobased hydrogels were measured utilizing a simple NMR method. This method tracks the migration of deuterium oxide through imaging data that is fit to a diffusion equation. The results show that a 5 wt% soybean oil based hydrogel gives aqueous diffusion of 1.37...

Relativistic diffusive motion in random electromagnetic fields

NASA Astrophysics Data System (ADS)

Haba, Z.

2011-08-01

We show that the relativistic dynamics in a Gaussian random electromagnetic field can be approximated by the relativistic diffusion of Schay and Dudley. Lorentz invariant dynamics in the proper time leads to the diffusion in the proper time. The dynamics in the laboratory time gives the diffusive transport equation corresponding to the Jüttner equilibrium at the inverse temperature β-1 = mc2. The diffusion constant is expressed by the field strength correlation function (Kubo's formula).

Theoretical examination of effective oxygen diffusion coefficient and electrical conductivity of polymer electrolyte fuel cell porous components

NASA Astrophysics Data System (ADS)

Inoue, Gen; Yokoyama, Kouji; Ooyama, Junpei; Terao, Takeshi; Tokunaga, Tomomi; Kubo, Norio; Kawase, Motoaki

2016-09-01

The reduction of oxygen transfer resistance through porous components consisting of a gas diffusion layer (GDL), microporous layer (MPL), and catalyst layer (CL) is very important to reduce the cost and improve the performance of a PEFC system. This study involves a systematic examination of the relationship between the oxygen transfer resistance of the actual porous components and their three-dimensional structure by direct measurement with FIB-SEM and X-ray CT. Numerical simulations were carried out to model the properties of oxygen transport. Moreover, based on the model structure and theoretical equations, an approach to the design of new structures is proposed. In the case of the GDL, the binder was found to obstruct gas diffusion with a negative effect on performance. The relative diffusion coefficient of the MPL is almost equal to that of the model structure of particle packing. However, that of CL is an order of magnitude less than those of the other two components. Furthermore, an equation expressing the relative diffusion coefficient of each component can be obtained with the function of porosity. The electrical conductivity of MPL, which is lower than that of the carbon black packing, is considered to depend on the contact resistance.

3D-CFD analysis of diffusion and emission of VOCs in a FLEC cavity.

PubMed

Zhu, Q; Kato, S; Murakami, S; Ito, K

2007-06-01

This study is performed as a part of research that examines the emission and diffusion characteristics of volatile organic compounds (VOCs) from indoor building materials. In this paper, the flow field and the emission field of VOCs from the surface of building materials in a Field and Laboratory Emission Cell (FLEC) cavity are examined by 3D Computational Fluid Dynamics (CFD) analysis. The flow field within the FLEC cavity is laminar. With a total flow of 250 ml/min, the air velocity near the test material surface ranges from 0.1 to 4.5 cm/s. Three types of emission from building materials are studied here: (i) emission phenomena controlled by internal diffusion, (ii) emission phenomena controlled by external diffusion, and (iii) emission phenomena controlled by mixed diffusion (internal + external diffusion). In the case of internal diffusion material, with respect to the concentration distribution in the cavity, the local VOC emission rate becomes uniform and the FLEC works well. However, in the case of evaporation type (external diffusion) material, or mixed type materials (internal + external diffusion) when the resistance to transporting VOCs in the material is small, the FLEC is not suitable for emission testing because of the thin FLEC cavity. In this case, the mean emission rate is restricted to a small value, since the VOC concentration in the cavity rises to the same value as the surface concentration through molecular diffusion within the thin cavity, and the concentration gradient normal to the surface becomes small. The diffusion field and emission rate depend on the cavity concentration and on the Loading Factor. That is, when the testing material surface in the cavity is partially sealed to decrease the Loading Factor, the emission rate become higher with the decrease in the exposed area of the testing material. The flow field and diffusion field within the FLEC cavity are investigated by CFD method. After presenting a summary of the velocity distributed over the surface of test material and the emission properties of different type materials in FLEC, the paper pointed out that there is a bias in the airflow inside the FLEC cavity but do not influence the result of test emission rate, and the FLEC method is unsuitable for evaporation type materials in which the mass transfer of the surface controls the emission rate.

Inter-diffusion analysis of joint interface of tungsten-rhenium couple

NASA Astrophysics Data System (ADS)

Hua, Y. F.; Li, Z. X.; Zhang, X.; Du, J. H.; Huang, C. L.; Du, M. H.

2011-09-01

The tungsten-rhenium couple was prepared by using glow plasma physical vapor deposition (PVD) on the isotropic fine grained graphite (IG) substrates. Diffusion anneals of the tungsten-rhenium couple were conducted at the temperature from 1100 °C to 1400 °C to investigate the inter-diffusion behaviors. The results showed that the thickness of the inter-diffusion zone increased with increasing annealing temperature. The relationship between the inter-diffusion coefficient and the annealing temperature accorded with the Arrhenius manner. The value of inter-diffusion activation energies was 189 kJ/mole (1.96 eV). The service time of tungsten-rhenium multilayer diffusion barrier was limited by the inter-diffusion for rhenium and tungsten rather than the diffusion of carbon in rhenium.

Diffusing Innovations: Adoption of Serious Educational Games by K-12 Science Teachers

ERIC Educational Resources Information Center

Vallett, David; Annetta, Leonard; Lamb, Richard; Bowling, Brandy

2014-01-01

Innovation is a term that has become widely used in education; especially as it pertains to technology infusion. Applying the corporate theory of diffusing innovation to educational practice is an innovation in itself. This mixed-methods study examined 38 teachers in a science educational gaming professional development program that provided…

White Matter Microstructure in Subjects with Attention-Deficit/Hyperactivity Disorder and Their Siblings

ERIC Educational Resources Information Center

Lawrence, Katherine E.; Levitt, Jennifer G.; Loo, Sandra K.; Ly, Ronald; Yee, Victor; O'Neill, Joseph; Alger, Jeffry; Narr, Katherine L.

2013-01-01

Objective: Previous voxel-based and regions-of-interest (ROI)-based diffusion tensor imaging (DTI) studies have found above-normal mean diffusivity (MD) and below-normal fractional anisotropy (FA) in subjects with attention-deficit/hyperactivity disorder (ADHD). However, findings remain mixed, and few studies have examined the contribution of ADHD…

The Diffusion of the Learning Pyramid Myths in Academia: An Exploratory Study

ERIC Educational Resources Information Center

Letrud, Kåre; Hernes, Sigbjørn

2016-01-01

This article examines the diffusion and present day status of a family of unsubstantiated learning-retention myths, some of which are referred to as "the learning pyramid". We demonstrate through an extensive search in academic journals and field-specific encyclopaedias that these myths are indeed widely publicised in academia and that…

An Assessment of Social Diffusion in the Respecting Choices Advance Care Planning Program

ERIC Educational Resources Information Center

Moorman, Sara M.; Carr, Deborah; Kirchhoff, Karin T.; Hammes, Bernard J.

2012-01-01

This study examines the potential social diffusion effects of the Respecting Choices advance care planning program administered in La Crosse, Wisconsin, since 1991. The program produces educational materials for patients, trains facilitators to help patients prepare for end of life, and ensures that advance directives are connected to patients'…

Controlled Release Drug Delivery via Polymeric Microspheres: A Neat Application of the Spherical Diffusion Equation

ERIC Educational Resources Information Center

Ormerod, C. S.; Nelson, M.

2017-01-01

Various applied mathematics undergraduate skills are demonstrated via an adaptation of Crank's axisymmetric spherical diffusion model. By the introduction of a one-parameter Heaviside initial condition, the pharmaceutically problematic initial mass flux is attenuated. Quantities germane to the pharmaceutical industry are examined and the model is…

Preliminary engineering report for design of a subscale ejector/diffuser system for high expansion ratio space engine testing

NASA Technical Reports Server (NTRS)

Wojciechowski, C. J.; Kurzius, S. C.; Doktor, M. F.

1984-01-01

The design of a subscale jet engine driven ejector/diffuser system is examined. Analytical results and preliminary design drawings and plans are included. Previously developed performance prediction techniques are verified. A safety analysis is performed to determine the mechanism for detonation suppression.

DIFFUSION OF MAGNESIUM AND MICROSTRUCTURES IN Mg+ IMPLANTED SILICON CARBIDE

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

Jiang, Weilin; Edwards, Danny J.; Jung, Hee Joon

2014-08-28

Following our previous reports [ 1- 3], further isochronal annealing (2 hrs.) of the monocrystalline 6H-SiC and polycrystalline CVD 3C-SiC was performed at 1573 and 1673 K in Ar environment. SIMS data indicate that observable Mg diffusion in 6H-SiC starts and a more rapid diffusion in CVD 3C-SiC occurs at 1573 K. The implanted Mg atoms tend to diffuse deeper into the undamaged CVD 3C-SiC. The microstructure with Mg inclusions in the as-implanted SiC has been initially examined using high-resolution STEM. The presence of Mg in the TEM specimen has been confirmed based on EDS mapping. Additional monocrystalline 3C-SiC samplesmore » have been implanted at 673 K to ion fluence 3 times higher than the previous one. RBS/C analysis has been performed before and after thermal annealing at 1573 K for 12 hrs. Isothermal annealing at 1573 K is being carried out and Mg depth profiles being measured. Microstructures in both the as-implanted and annealed samples are also being examined using STEM.« less

Numerical investigation of rotating stall in centrifugal compressor with vaned and vaneless diffuser

NASA Astrophysics Data System (ADS)

Halawa, Taher; Alqaradawi, Mohamed; Gadala, Mohamed S.; Shahin, Ibrahim; Badr, Osama

2015-06-01

This study presents a numerical simulation of the stall and surge in a centrifugal compressor and presents a descriptionof the stall development in two different cases. The first case is for a compressor with vaneless diffuser and the second is for a compressor with vaned diffuser of the vane island shape. The main aim of this study is to compare the flow characteristics and behavior for the two compressors near the surge operating condition and provide further understanding of the diffuser role when back flow occurs at surge. Results showed that for a locationnear the diffuser entrance, the amplitude of the static pressure fluctuations for the vaneless diffuser case is higher than that for the vaned diffuser case near surge condition. These pressure fluctuations in the case of the vaneless diffuser appear with a gradual decrease of the mean pressure value as a part of the surge cycle. While for the case of the vaned diffuser, the pressure drop during surge occurs faster than the case of the vaneless diffuser. Also, results indicated that during surge in the case of vaneless diffuser, there is a region with low velocity and back flow that appears as a layer connecting all impeller passages near shroud surface and this layer develops in size with time. On the other hand, for the case of vaned diffuser during surge, the low velocity regions appear in random locations in some passages and these regions expand with time towards the shroud surface. Results showed that during stall, the impeller passages are exposed to identical impact from stall cells in the case of vaneless diffuser while the stall effect varies from passage to another in the case of the vaned diffuser.

Diffusion with social reinforcement: The role of individual preferences

NASA Astrophysics Data System (ADS)

Tur, Elena M.; Zeppini, Paolo; Frenken, Koen

2018-02-01

The debate on diffusion in social networks has traditionally focused on the structure of the network to understand the efficiency of a network in terms of diffusion. Recently, the role of social reinforcement has been added to the debate, as it has been proposed that simple contagions diffuse better in random networks and complex contagions diffuse better in regular networks. In this paper, we show that individual preferences cannot be overlooked: complex contagions diffuse better in regular networks only if the large majority of the population is biased against adoption.

Neutral evolution in a biological population as diffusion in phenotype space: reproduction with local mutation but without selection.

PubMed

Lawson, Daniel John; Jensen, Henrik Jeldtoft

2007-03-02

The process of "evolutionary diffusion," i.e., reproduction with local mutation but without selection in a biological population, resembles standard diffusion in many ways. However, evolutionary diffusion allows the formation of localized peaks that undergo drift, even in the infinite population limit. We relate a microscopic evolution model to a stochastic model which we solve fully. This allows us to understand the large population limit, relates evolution to diffusion, and shows that independent local mutations act as a diffusion of interacting particles taking larger steps.

Correlation Structure of Fractional Pearson Diffusions.

PubMed

Leonenko, Nikolai N; Meerschaert, Mark M; Sikorskii, Alla

2013-09-01

The stochastic solution to a diffusion equations with polynomial coefficients is called a Pearson diffusion. If the first time derivative is replaced by a Caputo fractional derivative of order less than one, the stochastic solution is called a fractional Pearson diffusion. This paper develops an explicit formula for the covariance function of a fractional Pearson diffusion in steady state, in terms of Mittag-Leffler functions. That formula shows that fractional Pearson diffusions are long range dependent, with a correlation that falls off like a power law, whose exponent equals the order of the fractional derivative.

Counter-extrapolation method for conjugate interfaces in computational heat and mass transfer.

PubMed

Le, Guigao; Oulaid, Othmane; Zhang, Junfeng

2015-03-01

In this paper a conjugate interface method is developed by performing extrapolations along the normal direction. Compared to other existing conjugate models, our method has several technical advantages, including the simple and straightforward algorithm, accurate representation of the interface geometry, applicability to any interface-lattice relative orientation, and availability of the normal gradient. The model is validated by simulating the steady and unsteady convection-diffusion system with a flat interface and the steady diffusion system with a circular interface, and good agreement is observed when comparing the lattice Boltzmann results with respective analytical solutions. A more general system with unsteady convection-diffusion process and a curved interface, i.e., the cooling process of a hot cylinder in a cold flow, is also simulated as an example to illustrate the practical usefulness of our model, and the effects of the cylinder heat capacity and thermal diffusivity on the cooling process are examined. Results show that the cylinder with a larger heat capacity can release more heat energy into the fluid and the cylinder temperature cools down slower, while the enhanced heat conduction inside the cylinder can facilitate the cooling process of the system. Although these findings appear obvious from physical principles, the confirming results demonstrates the application potential of our method in more complex systems. In addition, the basic idea and algorithm of the counter-extrapolation procedure presented here can be readily extended to other lattice Boltzmann models and even other computational technologies for heat and mass transfer systems.

Frontal white matter changes and aggression in methamphetamine dependence.

PubMed

Lederer, Katharina; Fouche, Jean-Paul; Wilson, Don; Stein, Dan J; Uhlmann, Anne

2016-02-01

Chronic methamphetamine (MA) use can lead to white matter (WM) changes and increased levels of aggression. While previous studies have examined WM abnormalities relating to cognitive impairment, associations between WM integrity and aggression in MA dependence remain unclear. Diffusion Tensor Imaging (DTI) was used to investigate WM changes in 40 individuals with MA dependence and 40 matched healthy controls. A region of interest (ROI) approach using tract based spatial statistics (TBSS) in FSL was performed. We compared fractional anisotropy (FA), mean diffusivity (MD), parallel diffusivity (λ║) and perpendicular diffusivity (λ┴) in WM tracts of the frontal brain. A relationship of WM with aggression scores from the Buss & Perry Questionnaire was investigated. Mean scores for anger (p < 0.001), physical aggression (p = 0.032) and total aggression (p = 0.021) were significantly higher in the MA group relative to controls. ROI analysis showed increased MD (U = 439.5, p = 0.001) and λ┴ (U = 561.5, p = 0.021) values in the genu of the corpus callosum, and increased MD (U = 541.5, p = 0.012) values in the right cingulum in MA dependence. None of the WM changes were significantly associated with aggression scores. This study provides evidence of frontal WM changes and increased levels of aggression in individuals with MA dependence. The lack of significant associations between WM and aggressive behaviour may reflect methodological issues in measuring such behaviour, or may indicate that the neurobiology of aggression is not simply correlated with WM damage but is more complex.

Hydrolytic degradation and morphologic study of poly-p-dioxanone.

PubMed

Lin, H L; Chu, C C; Grubb, D

1993-02-01

The in vitro hydrolytic degradation of 2-0 size PDS monofilament suture was studied for the purpose of revealing its morphologic structure and degradation mechanism. The sutures were immersed in phosphate buffer of pH 7.44 for up to 120 days at 37 degrees C. These hydrolyzed sutures were examined by the changes in tensile properties, weight, thermal properties, x-ray diffraction structure, surface morphology, and dye diffusion phenomena. It was found that hydrolysis had significant effects on the change of PDS fiber morphology and properties. Hydrolysis, however, had no significant effect on overall molecular orientation of the fiber until the very late stage. PDS suture fibers retained their skeleton throughout the earlier periods of hydrolysis concurrent with mass and tensile strength losses. PDS sutures exhibited an absorption delay of 120 days. Both heat of fusion and melting point exhibited a maximum function of hydrolysis time. Hydrolysis of PDS suture fibers proceeded through two stages: random scission of chain segments located in the amorphous regions of microfibrils and intermicrofibrillar space, followed by stepwise scission of chain segments located in the crystalline regions of microfibrils. Dye diffusion data showed that the passage along the longitudinal direction of the fiber was relatively easier than the lateral direction as evident in the diffusion coefficient, activation energy, and flexibility of chain segments. Swiss-cheese model of fiber structure appears to describe the observed dye diffusion phenomena and their dependence on hydrolysis time and dying temperature.

Cuticular gas exchange by Antarctic sea spiders.

PubMed

Lane, Steven J; Moran, Amy L; Shishido, Caitlin M; Tobalske, Bret W; Woods, H Arthur

2018-04-25

Many marine organisms and life stages lack specialized respiratory structures, like gills, and rely instead on cutaneous respiration, which they facilitate by having thin integuments. This respiratory mode may limit body size, especially if the integument also functions in support or locomotion. Pycnogonids, or sea spiders, are marine arthropods that lack gills and rely on cutaneous respiration but still grow to large sizes. Their cuticle contains pores, which may play a role in gas exchange. Here, we examined alternative paths of gas exchange in sea spiders: (1) oxygen diffuses across pores in the cuticle, a common mechanism in terrestrial eggshells, (2) oxygen diffuses directly across the cuticle, a common mechanism in small aquatic insects, or (3) oxygen diffuses across both pores and cuticle. We examined these possibilities by modeling diffusive oxygen fluxes across all pores in the body of sea spiders and asking whether those fluxes differed from measured metabolic rates. We estimated fluxes across pores using Fick's law parameterized with measurements of pore morphology and oxygen gradients. Modeled oxygen fluxes through pores closely matched oxygen consumption across a range of body sizes, which means the pores facilitate oxygen diffusion. Furthermore, pore volume scaled hypermetrically with body size, which helps larger species facilitate greater diffusive oxygen fluxes across their cuticle. This likely presents a functional trade-off between gas exchange and structural support, in which the cuticle must be thick enough to prevent buckling due to external forces but porous enough to allow sufficient gas exchange. © 2018. Published by The Company of Biologists Ltd.

Resistance is futile: but it is slowing the pace of EHR adoption nonetheless.

PubMed

Ford, Eric W; Menachemi, Nir; Peterson, Lori T; Huerta, Timothy R

2009-01-01

The purpose of this study is to reassess the projected rate of Electronic Health Record (EHR) diffusion and examine how the federal government's efforts to promote the use of EHR technology have influenced physicians' willingness to adopt such systems. The study recreates and extends the analyses conducted by Ford et al. (1) The two periods examined come before and after the U.S. Federal Government's concerted activity to promote EHR adoption. Meta-analysis and bass modeling are used to compare EHR diffusion rates for two distinct periods of government activity. Very low levels of government activity to promote EHR diffusion marked the first period, before 2004. In 2004, the President of the United States called for a "Universal EHR Adoption" by 2014 (10 yrs), creating the major wave of activity and increased awareness of how EHRs will impact physicians' practices. EHR adoption parameters--external and internal coefficients of influence--are estimated using bass diffusion models and future adoption rates are projected. Comparing the EHR adoption rates before and after 2004 (2001-2004 and 2001-2007 respectively) indicate the physicians' resistance to adoption has increased during the second period. Based on current levels of adoption, less than half the physicians working in small practices will have implemented an EHR by 2014 (47.3%). The external forces driving EHR diffusion have grown in importance since 2004 relative to physicians' internal motivation to adopt such systems. Several national forces are likely contributing to the slowing pace of EHR diffusion.

Temporally resolved electrocardiogram-triggered diffusion-weighted imaging of the human kidney: correlation between intravoxel incoherent motion parameters and renal blood flow at different time points of the cardiac cycle.

PubMed

Wittsack, Hans-Jörg; Lanzman, Rotem S; Quentin, Michael; Kuhlemann, Julia; Klasen, Janina; Pentang, Gael; Riegger, Caroline; Antoch, Gerald; Blondin, Dirk

2012-04-01

To evaluate the influence of pulsatile blood flow on apparent diffusion coefficients (ADC) and the fraction of pseudodiffusion (F(P)) in the human kidney. The kidneys of 6 healthy volunteers were examined by a 3-T magnetic resonance scanner. Electrocardiogram (ECG)-gated and respiratory-triggered diffusion-weighted imaging (DWI) and phase-contrast flow measurements were performed. Flow imaging of renal arteries was carried out to quantify the dependence of renal blood flow on the cardiac cycle. ECG-triggered DWI was acquired in the coronal plane with 16 b values in the range of 0 s/mm(2) and 750 s/mm(2) at the time of minimum (MIN) (20 milliseconds after R wave) and maximum renal blood flow (MAX) (197 ± 24 milliseconds after R wave). The diffusion coefficients were calculated using the monoexponential approach as well as the biexponential intravoxel incoherent motion model and correlated to phase-contrast flow measurements. Flow imaging showed pulsatile renal blood flow depending on the cardiac cycle. The mean flow velocity at MIN was 45 cm/s as compared with 61 cm/s at MAX. F(p) at MIN (0.29) was significantly lower than at MAX (0.40) (P = 0.001). Similarly, ADC(mono), derived from the monoexponential model, also showed a significant difference (P < 0.001) between MIN (ADC(mono) = 2.14 ± 0.08 × 10(-3) mm(2)/s) and MAX (ADC(mono) = 2.37 ± 0.04 × 10(-3) mm(2)/s). The correlation between renal blood flow and F(p) (r = 0.85) as well as ADC(mono) (r = 0.67) was statistically significant. Temporally resolved ECG-gated DWI enables for the determination of the diffusion coefficients at different time points of the cardiac cycle. ADC(mono) and FP vary significantly among acquisitions at minimum (diastole) and maximum (systole) renal blood flow. Temporally resolved ECG-gated DWI might therefore serve as a novel technique for the assessment of pulsatility in the human kidney.

On common noise-induced synchronization in complex networks with state-dependent noise diffusion processes

NASA Astrophysics Data System (ADS)

Russo, Giovanni; Shorten, Robert

2018-04-01

This paper is concerned with the study of common noise-induced synchronization phenomena in complex networks of diffusively coupled nonlinear systems. We consider the case where common noise propagation depends on the network state and, as a result, the noise diffusion process at the nodes depends on the state of the network. For such networks, we present an algebraic sufficient condition for the onset of synchronization, which depends on the network topology, the dynamics at the nodes, the coupling strength and the noise diffusion. Our result explicitly shows that certain noise diffusion processes can drive an unsynchronized network towards synchronization. In order to illustrate the effectiveness of our result, we consider two applications: collective decision processes and synchronization of chaotic systems. We explicitly show that, in the former application, a sufficiently large noise can drive a population towards a common decision, while, in the latter, we show how common noise can synchronize a network of Lorentz chaotic systems.

PCNA appears in two populations of slow and fast diffusion with a constant ratio throughout S-phase in replicating mammalian cells.

PubMed

Zessin, Patrick J M; Sporbert, Anje; Heilemann, Mike

2016-01-13

DNA replication is a fundamental cellular process that precedes cell division. Proliferating cell nuclear antigen (PCNA) is a central scaffold protein that orchestrates DNA replication by recruiting many factors essential for the replication machinery. We studied the mobility of PCNA in live mammalian cells using single-particle tracking in combination with photoactivated-localization microscopy (sptPALM) and found two populations. The first population which is only present in cells with active DNA replication, showed slow diffusion and was found to be located in replication foci. The second population showed fast diffusion, and represents the nucleoplasmic pool of unbound PCNA not involved in DNA replication. The ratio of these two populations remained constant throughout different stages of S-phase. A fraction of molecules in both populations showed spatially constrained mobility. We determined an exploration radius of ~100 nm for 13% of the slow-diffusing PCNA molecules, and of ~600 nm for 46% of the fast-diffusing PCNA molecules.

Atypical presentations of subacute sclerosing panencephalitis in two neurologically handicapped cases.

PubMed

Demir, E; Ozcelik, A; Arhan, E; Serdaroglu, A; Gucuyener, K

2009-08-01

Subacute sclerosing panencephalitis (SSPE) is a neurodegenerative disorder caused by persistent measles infection. Here, we report two neurologically handicapped cases presenting with atypical features of SSPE. Patient 1 who had mild mental retardation manifested acute encephalopathy with partial seizures and hemiplegia, mimicking encephalitis. He showed a fulminant course without myoclonia or a periodic electroencephalogram complex. Although SSPE is usually associated with an increased diffusion pattern, diffusion-weighted imaging of our patient showed decreased diffusion in the right hippocampus. Patient 2 with infantile hemiparesis presented with secondary generalized seizures, followed by asymettrical myoclonias involving the side contralateral to the hemiparesis. A periodic electroencephalogram complex was absent on the previously damaged brain regions. Our findings show that preexisting neurological disorders may modify the clinical or electrophysiological findings of SSPE, leading to atypical presentations. SSPE should be considered in the differential diagnosis of acute encephalopathy with lateralizing signs or unidentified seizures. Decreased diffusion resolution in diffusion-weighted-imaging may correlate with rapid clinical progression in SSPE. Georg Thieme Verlag KG Stuttgart New York.

Optical absorption characteristics in the assessment of powder phosphor-based x-ray detectors: from nano- to micro-scale.

PubMed

Liaparinos, P F

2015-11-21

X-ray phosphor-based detectors have enormously improved the quality of medical imaging examinations through the optimization of optical diffusion. In recent years, with the development of science and technology in the field of materials, improved powder phosphors require structural and optical properties that contribute to better optical signal propagation. The purpose of this paper was to provide a quantitative and qualitative understanding of the optical absorption characteristics in the assessment of powder phosphor-based detectors (from nano- scale up to micro-scale). Variations on the optical absorption parameters (i.e. the light extinction coefficient [Formula: see text] and the percentage probability of light absorption p%) were evaluated based on Mie calculations examining a wide range of light wavelengths, particle refractive indices and sizes. To model and assess the effects of the aforementioned parameters on optical diffusion, Monte Carlo simulation techniques were employed considering: (i) phosphors of different layer thickness, 100 μm (thin layer) and 300 μm (thick layer), respectively, (ii) light extinction coefficient values, 1, 3 and 6 μm(-1), and (iii) percentage probability of light absorption p% in the range 10(-4)-10(-2). Results showed that the [Formula: see text] coefficient is high for phosphor grains in the submicron scale and for low light wavelengths. At higher wavelengths (above 650 nm), optical quanta follow approximately similar depths until interaction for grain diameter 500 nm and 1 μm. Regarding the variability of the refractive index, high variations of the [Formula: see text] coefficient occurred above 1.6. Furthermore, results derived from Monte Carlo modeling showed that high spatial resolution phosphors can be accomplished by increasing the [Formula: see text] parameter. More specifically, the FWHM was found to decrease (i.e. higher resolution): (i) 4.8% at 100 μm and (ii) 9.5%, at 300 μm layer thickness. This study attempted to examine the role of the optical absorption parameters on optical diffusion studies. A significant outcome of the present investigation was that the improvement of phosphor spatial resolution without decreasing the light collection efficiency too much can be better achieved by increasing the parameter [Formula: see text] rather than the parameter p%.

The species-area relationship and evolution.

PubMed

Lawson, Daniel; Jensen, Henrik Jeldtoft

2006-08-07

Models relating to the species-area curve usually assume the existence of species, and are concerned mainly with ecological timescales. We examine an individual-based model of co-evolution on a spatial lattice based on the tangled nature model in which species are emergent structures, and show that reproduction, mutation and dispersion by diffusion, with interaction via genotype space, produces power-law species-area relations as observed in ecological measurements at medium scales. We find that long-lasting co-evolutionary habitats form, allowing high diversity levels in a spatially homogenous system.

Bovine Progressive Degenerative Myeloencephalopathy (Weaver Syndrome) in Brown Swiss Cattle in Canada: A Literature Review and Case Report

PubMed Central

Baird, John D.; Sarmiento, Ulla M.; Basrur, Parvathi K.

1988-01-01

A 15-month-old purebred Brown Swiss heifer was presented because of posterior paresis and ataxia. Histopathological examination of the brain and spinal cord showed evidence of a mild diffuse degenerative myeloencephalopathy. The most severe degenerative lesions were located in the white matter of the thoracic spinal cord. We believe this to be the first documented case of bovine progressive degenerative myeloencephalopathy (“weaver syndrome”) in Canada. ImagesFigure 1.Figure 2., Figure 3., Figure 4.Figure 5. PMID:17423028

Fifty years of sociological leadership at Social Science and Medicine.

PubMed

Timmermans, Stefan; Tietbohl, Caroline

2018-01-01

In this review article, we examine some of the conceptual contributions of sociology of health and illness over the past fifty years. Specifically, we focus on research dealing with medicalization, the management of stigma, research on adherence and compliance, and patient-doctor interaction. We show how these themes that originated within sociology, diffused in other disciplines. Sociology in Social Science and Medicine started as an applied research tradition but morphed into a robust, stand-alone social science tradition. Copyright © 2017 Elsevier Ltd. All rights reserved.

Spring 2014 Internship Diffuser Data Analysis

NASA Technical Reports Server (NTRS)

Laigaie, Robert T.; Ryan, Harry M.

2014-01-01

J-2X engine testing on the A-2 test stand at the NASA John C. Stennis Space Center (SSC) has recently concluded. As part of that test campaign, the engine was operated at lower power levels in support of expanding the use of J-2X to other missions. However, the A-2 diffuser was not designed for engine testing at the proposed low power levels. To evaluate the risk of damage to the diffuser, computer simulations were created of the rocket engine exhaust plume inside the 50ft long, water-cooled, altitude-simulating diffuser. The simulations predicted that low power level testing would cause the plume to oscillate in the lower sections of the diffuser. This can possibly cause excessive vibrations, stress, and heat transfer from the plume to the diffuser walls. To understand and assess the performance of the diffuser during low power level engine testing, nine accelerometers and four strain gages were installed around the outer surface of the diffuser. The added instrumentation also allowed for the verification of the rocket exhaust plume computational model. Prior to engine hot-fire testing, a diffuser water-flow test was conducted to verify the proper operation of the newly installed instrumentation. Subsequently, two J-2X engine hot-fire tests were completed. Hot-Fire Test 1 was 11.5 seconds in duration, and accelerometer and strain data verified that the rocket engine plume oscillated in the lower sections of the diffuser. The accelerometers showed very different results dependent upon location. The diffuser consists of four sections, with Section 1 being closest to the engine nozzle and Section 4 being farthest from the engine nozzle. Section 1 accelerometers showed increased amplitudes at startup and shutdown, but low amplitudes while the diffuser was started. Section 3 accelerometers showed the opposite results with near zero G amplitudes prior to and after diffuser start and peak amplitudes to +/- 100G while the diffuser was started. Hot-Fire Test 1 strain gages showed different data dependent on section. Section 1 strains were small, and were in the range of 50 to 150 microstrain, which would result in stresses from 1.45 to 4.35 ksi. The yield stress of the material, A-285 Grade C Steel, is 29.7 ksi. Section 4 strain gages showed much higher values with strains peaking at 1600 microstrain. This strain corresponds to a stress of 46.41 ksi, which is in excess of the yield stress, but below the ultimate stress of 55 to 75 ksi. The decreased accelerations and strain in Section 1, and the increased accelerations and strain in Sections 3 and 4 verified the computer simulation prediction of increased plume oscillations in the lower sections of the diffuser. Hot-Fire Test 2 ran for a duration of 125 seconds. The engine operated at a slightly higher power level than Hot-Fire Test 1 for the initial 35 seconds of the test. After 35 seconds the power level was lowered to Hot-Fire Test 1 levels. The acceleration and strain data for Hot-Fire Test 2 was similar during the initial part of the test. However, just prior to the engine being lowered to the Hot-Fire Test 1 power level, the strain gage data in Section 4 showed a large decrease to strains near zero microstrain from their peak at 1500 microstrain. Future work includes further strain and acceleration data analysis and evaluation.

Normal development of human brain white matter from infancy to early adulthood: a diffusion tensor imaging study.

PubMed

Uda, Satoshi; Matsui, Mie; Tanaka, Chiaki; Uematsu, Akiko; Miura, Kayoko; Kawana, Izumi; Noguchi, Kyo

2015-01-01

Diffusion tensor imaging (DTI), which measures the magnitude of anisotropy of water diffusion in white matter, has recently been used to visualize and quantify parameters of neural tracts connecting brain regions. In order to investigate the developmental changes and sex and hemispheric differences of neural fibers in normal white matter, we used DTI to examine 52 healthy humans ranging in age from 2 months to 25 years. We extracted the following tracts of interest (TOIs) using the region of interest method: the corpus callosum (CC), cingulum hippocampus (CGH), inferior longitudinal fasciculus (ILF), and superior longitudinal fasciculus (SLF). We measured fractional anisotropy (FA), apparent diffusion coefficient (ADC), axial diffusivity (AD), and radial diffusivity (RD). Approximate values and changes in growth rates of all DTI parameters at each age were calculated and analyzed using LOESS (locally weighted scatterplot smoothing). We found that for all TOIs, FA increased with age, whereas ADC, AD and RD values decreased with age. The turning point of growth rates was at approximately 6 years. FA in the CC was greater than that in the SLF, ILF and CGH. Moreover, FA, ADC and AD of the splenium of the CC (sCC) were greater than in the genu of the CC (gCC), whereas the RD of the sCC was lower than the RD of the gCC. The FA of right-hemisphere TOIs was significantly greater than that of left-hemisphere TOIs. In infants, growth rates of both FA and RD were larger than those of AD. Our data show that developmental patterns differ by TOIs and myelination along with the development of white matter, which can be mainly expressed as an increase in FA together with a decrease in RD. These findings clarify the long-term normal developmental characteristics of white matter microstructure from infancy to early adulthood. © 2015 S. Karger AG, Basel.