Altered white matter tract property related to impaired focused attention, sustained attention, cognitive impulsivity and vigilance in attention-deficit/hyperactivity disorder

PubMed Central

Chiang, Huey-Ling; Chen, Yu-Jen; Lo, Yu-Chun; Tseng, Wen-Yih Isaac; Gau, Susan Shur-Fen

2015-01-01

Background The neural substrate for clinical symptoms and neuropsychological performance in individuals with attention-deficit/hyperactivity disorder (ADHD) has rarely been studied and has yielded inconsistent results. We sought to compare the microstructural property of fibre tracts associated with the prefrontal cortex and its association with ADHD symptoms and a wide range of attention performance in youth with ADHD and healthy controls. Methods We assessed youths with ADHD and age-, sex-, handedness-, coil- and intelligence-matched controls using the Conners’ Continuous Performance Test (CCPT) for attention performance and MRI. The 10 target tracts, including the bilateral frontostriatal tracts (caudate to dorsolateral prefrontal cortex, ventrolateral prefrontal cortex and orbitofrontal cortex), superior longitudinal fasciculus (SLF) and cingulum bundle were reconstructed using diffusion spectrum imaging tractography. We computed generalized fractional anisotropy (GFA) values to indicate tract-specific microstructural property. Results We included 50 youths with ADHD and 50 healthy controls in our study. Youths with ADHD had lower GFA in the left frontostriatal tracts, bilateral SLF and right cingulum bundle and performed worse in the CCPT than controls. Furthermore, alteration of the right SLF GFA was most significantly associated with the clinical symptom of inattention in youths with ADHD. Finally, youths with ADHD had differential association patterns of the 10 fibre tract GFA values with attention performance compared with controls. Limitations Ten of the youths with ADHD were treated with methylphenidate, which may have long-term effects on microstructural property. Conclusion Our study highlights the importance of the SLF, cingulum bundle and frontostriatal tracts for clinical symptoms and attention performance in youths with ADHD and demonstrates the involvement of different fibre tracts in attention performance in these individuals. PMID:25871496

Altered white matter tract property related to impaired focused attention, sustained attention, cognitive impulsivity and vigilance in attention-deficit/ hyperactivity disorder.

PubMed

Chiang, Huey-Ling; Chen, Yu-Jen; Lo, Yu-Chun; Tseng, Wen-Yih I; Gau, Susan S

2015-09-01

The neural substrate for clinical symptoms and neuropsychological performance in individuals with attention-deficit/hyperactivity disorder (ADHD) has rarely been studied and has yielded inconsistent results. We sought to compare the microstructural property of fibre tracts associated with the prefrontal cortex and its association with ADHD symptoms and a wide range of attention performance in youth with ADHD and healthy controls. We assessed youths with ADHD and age-, sex-, handedness-, coil- and intelligence-matched controls using the Conners' Continuous Performance Test (CCPT) for attention performance and MRI. The 10 target tracts, including the bilateral frontostriatal tracts (caudate to dorsolateral prefrontal cortex, ventrolateral prefrontal cortex and orbitofrontal cortex), superior longitudinal fasciculus (SLF) and cingulum bundle were reconstructed using diffusion spectrum imaging tractography. We computed generalized fractional anisotropy (GFA) values to indicate tract-specific microstructural property. We included 50 youths with ADHD and 50 healthy controls in our study. Youths with ADHD had lower GFA in the left frontostriatal tracts, bilateral SLF and right cingulum bundle and performed worse in the CCPT than controls. Furthermore, alteration of the right SLF GFA was most significantly associated with the clinical symptom of inattention in youths with ADHD. Finally, youths with ADHD had differential association patterns of the 10 fibre tract GFA values with attention performance compared with controls. Ten of the youths with ADHD were treated with methylphenidate, which may have long-term effects on microstructural property. Our study highlights the importance of the SLF, cingulum bundle and frontostriatal tracts for clinical symptoms and attention performance in youths with ADHD and demonstrates the involvement of different fibre tracts in attention performance in these individuals.

Projecting diffusion along the normal bundle of a plane curve

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

Valero-Valdés, Carlos; Herrera-Guzmán, Rafael

2014-05-15

The purpose of this paper is to provide new formulas for the effective diffusion coefficient of a generalized Fick-Jacob's equation obtained by projecting the two-dimensional diffusion equation along the normal directions of an arbitrary curve on the plane.

Enhanced field emission properties of carbon nanotube bundles confined in SiO2 pits

NASA Astrophysics Data System (ADS)

Lim, Yu Dian; Grapov, Dmitry; Hu, Liangxing; Kong, Qinyu; Tay, Beng Kang; Labunov, Vladimir; Miao, Jianmin; Coquet, Philippe; Aditya, Sheel

2018-02-01

It has been widely reported that carbon nanotubes (CNTs) exhibit superior field emission (FE) properties due to their high aspect ratios and unique structural properties. Among the various types of CNTs, random growth CNTs exhibit promising FE properties due to their reduced inter-tube screening effect. However, growing random growth CNTs on individual catalyst islands often results in spread out CNT bundles, which reduces overall field enhancement. In this study, significant improvement in FE properties in CNT bundles is demonstrated by confining them in microfabricated SiO2 pits. Growing CNT bundles in narrow (0.5 μm diameter and 2 μm height) SiO2 pits achieves FE current density of 1-1.4 A cm-2, which is much higher than for freestanding CNT bundles (76.9 mA cm-2). From the Fowler Nordheim plots, confined CNT bundles show a higher field enhancement factor. This improvement can be attributed to the reduced bundle diameter by SiO2 pit confinement, which yields bundles with higher aspect ratios. Combining the obtained outcomes, it can be conclusively summarized that confining CNTs in SiO2 pits yields higher FE current density due to the higher field enhancement of confined CNTs.

Effect of fabricated density and bamboo species on physical-mechanical properties of bamboo fiber bundle reinforced composites

Treesearch

Jiulong Xie; Jinqiu Qi; Tingxing Hu; Cornelis F. De Hoop; Chung Yun Hse; Todd F. Shupe

2016-01-01

Bamboo stems were subjected to a mechanical treatment process for the extraction of bamboo fiber bundles. The fiber bundles were used as reinforcement for the fabrication of high-performance composites with phenolic resins as matrix. The influence of fabricated density and bamboo species on physical–mechanical properties of bamboo fiber bundle reinforced composites (...

Cations Modulate Actin Bundle Mechanics, Assembly Dynamics, and Structure.

PubMed

Castaneda, Nicholas; Zheng, Tianyu; Rivera-Jacquez, Hector J; Lee, Hyun-Ju; Hyun, Jaekyung; Balaeff, Alexander; Huo, Qun; Kang, Hyeran

2018-04-12

Actin bundles are key factors in the mechanical support and dynamic reorganization of the cytoskeleton. High concentrations of multivalent counterions promote bundle formation through electrostatic attraction between actin filaments that are negatively charged polyelectrolytes. In this study, we evaluate how physiologically relevant divalent cations affect the mechanical, dynamic, and structural properties of actin bundles. Using a combination of total internal reflection fluorescence microscopy, transmission electron microscopy, and dynamic light scattering, we demonstrate that divalent cations modulate bundle stiffness, length distribution, and lateral growth. Molecular dynamics simulations of an all-atom model of the actin bundle reveal specific actin residues coordinate cation-binding sites that promote the bundle formation. Our work suggests that specific cation interactions may play a fundamental role in the assembly, structure, and mechanical properties of actin bundles.

Characterization of active hair-bundle motility by a mechanical-load clamp

NASA Astrophysics Data System (ADS)

Salvi, Joshua D.; Maoiléidigh, Dáibhid Ó.; Fabella, Brian A.; Tobin, Mélanie; Hudspeth, A. J.

2015-12-01

Active hair-bundle motility endows hair cells with several traits that augment auditory stimuli. The activity of a hair bundle might be controlled by adjusting its mechanical properties. Indeed, the mechanical properties of bundles vary between different organisms and along the tonotopic axis of a single auditory organ. Motivated by these biological differences and a dynamical model of hair-bundle motility, we explore how adjusting the mass, drag, stiffness, and offset force applied to a bundle control its dynamics and response to external perturbations. Utilizing a mechanical-load clamp, we systematically mapped the two-dimensional state diagram of a hair bundle. The clamp system used a real-time processor to tightly control each of the virtual mechanical elements. Increasing the stiffness of a hair bundle advances its operating point from a spontaneously oscillating regime into a quiescent regime. As predicted by a dynamical model of hair-bundle mechanics, this boundary constitutes a Hopf bifurcation.

Fused oblique incidence reflectometry and confocal fluorescence microscopy

NASA Astrophysics Data System (ADS)

Risi, Matthew D.; Rouse, Andrew R.; Gmitro, Arthur F.

2011-03-01

Confocal microendoscopy provides real-time high resolution cellular level images via a minimally invasive procedure, but relies on exogenous fluorophores, has a relatively limited penetration depth (100 μm) and field of view (700 μm), and produces a high rate of detailed information to the user. A new catheter based multi-modal system has been designed that combines confocal imaging and oblique incidence reflectometry (OIR), which is a non-invasive method capable of rapidly extracting tissue absorption, μa, and reduced scattering, μ's, spectra from tissue. The system builds on previous developments of a custom slit-scan multi-spectral confocal microendoscope and is designed to rapidly switch between diffuse spectroscopy and confocal fluorescence imaging modes of operation. An experimental proof-of-principle catheter has been developed that consists of a fiber bundle for traditional confocal fluorescence imaging and a single OIR source fiber which is manually redirected at +/- 26 degrees. Diffusely scattered light from each orientation of the source fiber is collected via the fiber bundle, with a frame of data representing spectra collected at a range of distances from the OIR source point. Initial results with intralipid phantoms show good agreement to published data over the 550-650 nm spectral range. We successfully imaged and measured the optical properties of rodent cardiac muscle.

Actin-binding proteins sensitively mediate F-actin bundle stiffness

NASA Astrophysics Data System (ADS)

Claessens, Mireille M. A. E.; Bathe, Mark; Frey, Erwin; Bausch, Andreas R.

2006-09-01

Bundles of filamentous actin (F-actin) form primary structural components of a broad range of cytoskeletal processes including filopodia, sensory hair cell bristles and microvilli. Actin-binding proteins (ABPs) allow the cell to tailor the dimensions and mechanical properties of the bundles to suit specific biological functions. Therefore, it is important to obtain quantitative knowledge on the effect of ABPs on the mechanical properties of F-actin bundles. Here we measure the bending stiffness of F-actin bundles crosslinked by three ABPs that are ubiquitous in eukaryotes. We observe distinct regimes of bundle bending stiffness that differ by orders of magnitude depending on ABP type, concentration and bundle size. The behaviour observed experimentally is reproduced quantitatively by a molecular-based mechanical model in which ABP shearing competes with F-actin extension/compression. Our results shed new light on the biomechanical function of ABPs and demonstrate how single-molecule properties determine mesoscopic behaviour. The bending mechanics of F-actin fibre bundles are general and have implications for cytoskeletal mechanics and for the rational design of functional materials.

FADTTSter: accelerating hypothesis testing with functional analysis of diffusion tensor tract statistics

NASA Astrophysics Data System (ADS)

Noel, Jean; Prieto, Juan C.; Styner, Martin

2017-03-01

Functional Analysis of Diffusion Tensor Tract Statistics (FADTTS) is a toolbox for analysis of white matter (WM) fiber tracts. It allows associating diffusion properties along major WM bundles with a set of covariates of interest, such as age, diagnostic status and gender, and the structure of the variability of these WM tract properties. However, to use this toolbox, a user must have an intermediate knowledge in scripting languages (MATLAB). FADTTSter was created to overcome this issue and make the statistical analysis accessible to any non-technical researcher. FADTTSter is actively being used by researchers at the University of North Carolina. FADTTSter guides non-technical users through a series of steps including quality control of subjects and fibers in order to setup the necessary parameters to run FADTTS. Additionally, FADTTSter implements interactive charts for FADTTS' outputs. This interactive chart enhances the researcher experience and facilitates the analysis of the results. FADTTSter's motivation is to improve usability and provide a new analysis tool to the community that complements FADTTS. Ultimately, by enabling FADTTS to a broader audience, FADTTSter seeks to accelerate hypothesis testing in neuroimaging studies involving heterogeneous clinical data and diffusion tensor imaging. This work is submitted to the Biomedical Applications in Molecular, Structural, and Functional Imaging conference. The source code of this application is available in NITRC.

Ab initio density functional theory investigation of electronic properties of semiconducting single-walled carbon nanotube bundles

NASA Astrophysics Data System (ADS)

Moradian, Rostam; Behzad, Somayeh; Azadi, Sam

2008-09-01

By using ab initio density functional theory we investigated the structural and electronic properties of semiconducting (7, 0), (8, 0) and (10, 0) carbon nanotube bundles. The energetic and electronic evolutions of nanotubes in the bundling process are also studied. The effects of inter-tube coupling on the electronic dispersions of semiconducting carbon nanotube bundles are demonstrated. Our results show that the inter-tube coupling decreases the energy gap in semiconducting nanotubes. We found that bundles of (7, 0) and (8, 0) carbon nanotubes have metallic feature, while (10, 0) bundle is a semiconductor with an energy gap of 0.22 eV. To clarify our results the band structures of isolated and bundled nanotubes are compared.

The challenge of mapping the human connectome based on diffusion tractography.

PubMed

Maier-Hein, Klaus H; Neher, Peter F; Houde, Jean-Christophe; Côté, Marc-Alexandre; Garyfallidis, Eleftherios; Zhong, Jidan; Chamberland, Maxime; Yeh, Fang-Cheng; Lin, Ying-Chia; Ji, Qing; Reddick, Wilburn E; Glass, John O; Chen, David Qixiang; Feng, Yuanjing; Gao, Chengfeng; Wu, Ye; Ma, Jieyan; Renjie, H; Li, Qiang; Westin, Carl-Fredrik; Deslauriers-Gauthier, Samuel; González, J Omar Ocegueda; Paquette, Michael; St-Jean, Samuel; Girard, Gabriel; Rheault, François; Sidhu, Jasmeen; Tax, Chantal M W; Guo, Fenghua; Mesri, Hamed Y; Dávid, Szabolcs; Froeling, Martijn; Heemskerk, Anneriet M; Leemans, Alexander; Boré, Arnaud; Pinsard, Basile; Bedetti, Christophe; Desrosiers, Matthieu; Brambati, Simona; Doyon, Julien; Sarica, Alessia; Vasta, Roberta; Cerasa, Antonio; Quattrone, Aldo; Yeatman, Jason; Khan, Ali R; Hodges, Wes; Alexander, Simon; Romascano, David; Barakovic, Muhamed; Auría, Anna; Esteban, Oscar; Lemkaddem, Alia; Thiran, Jean-Philippe; Cetingul, H Ertan; Odry, Benjamin L; Mailhe, Boris; Nadar, Mariappan S; Pizzagalli, Fabrizio; Prasad, Gautam; Villalon-Reina, Julio E; Galvis, Justin; Thompson, Paul M; Requejo, Francisco De Santiago; Laguna, Pedro Luque; Lacerda, Luis Miguel; Barrett, Rachel; Dell'Acqua, Flavio; Catani, Marco; Petit, Laurent; Caruyer, Emmanuel; Daducci, Alessandro; Dyrby, Tim B; Holland-Letz, Tim; Hilgetag, Claus C; Stieltjes, Bram; Descoteaux, Maxime

2017-11-07

Tractography based on non-invasive diffusion imaging is central to the study of human brain connectivity. To date, the approach has not been systematically validated in ground truth studies. Based on a simulated human brain data set with ground truth tracts, we organized an open international tractography challenge, which resulted in 96 distinct submissions from 20 research groups. Here, we report the encouraging finding that most state-of-the-art algorithms produce tractograms containing 90% of the ground truth bundles (to at least some extent). However, the same tractograms contain many more invalid than valid bundles, and half of these invalid bundles occur systematically across research groups. Taken together, our results demonstrate and confirm fundamental ambiguities inherent in tract reconstruction based on orientation information alone, which need to be considered when interpreting tractography and connectivity results. Our approach provides a novel framework for estimating reliability of tractography and encourages innovation to address its current limitations.

Recognition of white matter bundles using local and global streamline-based registration and clustering.

PubMed

Garyfallidis, Eleftherios; Côté, Marc-Alexandre; Rheault, Francois; Sidhu, Jasmeen; Hau, Janice; Petit, Laurent; Fortin, David; Cunanne, Stephen; Descoteaux, Maxime

2018-04-15

Virtual dissection of diffusion MRI tractograms is cumbersome and needs extensive knowledge of white matter anatomy. This virtual dissection often requires several inclusion and exclusion regions-of-interest that make it a process that is very hard to reproduce across experts. Having automated tools that can extract white matter bundles for tract-based studies of large numbers of people is of great interest for neuroscience and neurosurgical planning. The purpose of our proposed method, named RecoBundles, is to segment white matter bundles and make virtual dissection easier to perform. This can help explore large tractograms from multiple persons directly in their native space. RecoBundles leverages latest state-of-the-art streamline-based registration and clustering to recognize and extract bundles using prior bundle models. RecoBundles uses bundle models as shape priors for detecting similar streamlines and bundles in tractograms. RecoBundles is 100% streamline-based, is efficient to work with millions of streamlines and, most importantly, is robust and adaptive to incomplete data and bundles with missing components. It is also robust to pathological brains with tumors and deformations. We evaluated our results using multiple bundles and showed that RecoBundles is in good agreement with the neuroanatomical experts and generally produced more dense bundles. Across all the different experiments reported in this paper, RecoBundles was able to identify the core parts of the bundles, independently from tractography type (deterministic or probabilistic) or size. Thus, RecoBundles can be a valuable method for exploring tractograms and facilitating tractometry studies. Copyright © 2017 Elsevier Inc. All rights reserved.

In-Depth Analysis of the Structure and Properties of Two Varieties of Natural Luffa Sponge Fibers

PubMed Central

Chen, Yuxia; Su, Na; Zhang, Kaiting; Zhu, Shiliu; Zhao, Lei; Fang, Fei; Ren, Linyan; Guo, Yong

2017-01-01

The advancement in science and technology has led to luffa sponge (LS) being widely used as a natural material in industrial application because of its polyporous structure and light texture. To enhance the utility of LS fibers as the reinforcement of lightweight composite materials, the current study investigates their water absorption, mechanical properties, anatomical characteristics and thermal performance. Hence, moisture regain and tensile properties of LS fiber bundles were measured in accordance with American Society for Testing and Materials (ASTM) standards while their structural characteristics were investigated via microscopic observation. Scanning electron microscopy (SEM) was used to observe the surface morphology and fractured surface of fiber bundles. The test results show that the special structure where the phloem tissues degenerate to cavities had a significant influence on the mechanical properties of LS fiber bundles. Additionally, the transverse sectional area occupied by fibers in a fiber bundle (SF), wall thickness, ratio of wall to lumen of fiber cell, and crystallinity of cellulose had substantial impact on the mechanical properties of LS fiber bundles. Furthermore, the density of fiber bundles of LS ranged within 385.46–468.70 kg/m3, significantly less than that of jute (1360.40 kg/m3) and Arenga engleri (950.20 kg/m3). However, LS fiber bundles demonstrated superior specific modulus than Arenga engleri. PMID:28772838

Diffusion Tensor Imaging of Incentive Effects in Prospective Memory after Pediatric Traumatic Brain Injury

PubMed Central

Wilde, Elisabeth A.; Bigler, Erin D.; Chu, Zili; Yallampalli, Ragini; Oni, Margaret B.; Wu, Trevor C.; Ramos, Marco A.; Pedroza, Claudia; Vásquez, Ana C.; Hunter, Jill V.; Levin, Harvey S.

2011-01-01

Abstract Few studies exist investigating the brain-behavior relations of event-based prospective memory (EB-PM) impairments following traumatic brain injury (TBI). To address this, children with moderate-to-severe TBI performed an EB-PM test with two motivational enhancement conditions and underwent concurrent diffusion tensor imaging (DTI) at 3 months post-injury. Children with orthopedic injuries (OI; n = 37) or moderate-to-severe TBI (n = 40) were contrasted. Significant group differences were found for fractional anisotropy (FA) and apparent diffusion coefficient for orbitofrontal white matter (WM), cingulum bundles, and uncinate fasciculi. The FA of these WM structures in children with TBI significantly correlated with EB-PM performance in the high, but not the low motivation condition. Regression analyses within the TBI group indicated that the FA of the left cingulum bundle (p = 0.003), left orbitofrontal WM (p < 0.02), and left (p < 0.02) and right (p < 0.008) uncinate fasciculi significantly predicted EB-PM performance in the high motivation condition. We infer that the cingulum bundles, orbitofrontal WM, and uncinate fasciculi are important WM structures mediating motivation-based EB-PM responses following moderate-to-severe TBI in children. PMID:21250917

Microheterogeneity of actin gels formed under controlled linear shear.

PubMed

Cortese, J D; Frieden, C

1988-10-01

The diffusion coefficients and fluorescence polarization properties of actin subjected to a known shear have been determined both during and after polymerization, using a modification of a cone-plate Wells-Brookfield rheometer that allows monitoring of samples with an epifluorescence microscope. Fluorescence polarization and fluorescence photobleaching recovery experiments using rhodamine-labeled actin as a tracer showed that under conditions of low shear (shear rates of 0.05 s-1), a spatial heterogeneity of polymerized actin was observed with respect to fluorescence intensity and the diffusion coefficients with actin mobility becoming quite variable in different regions of the sample. In addition, complex changes in fluorescence polarization were noted after stopping the shear. Actin filaments of controlled length were obtained using plasma gelsolin (gelsolin/actin molar ratios of 1:50 to 1:300). At ratios of 1:50, neither spatial heterogeneity nor changes in polarization were observed on subjecting the polymerized actin to shear. At ratios of approximately 1:100, a decrease on the intensity of fluorescence polarization occurs on stopping the shear. Longer filaments exhibit spatial micro-heterogeneity and complex changes in fluorescence polarization. In addition, at ratios of 1:100 or 1:300, the diffusion coefficient decreases as the total applied shear increased. This behavior is interpreted as bundling of filaments aligned under shear. We also find that the F-actin translational diffusion coefficients decrease as the total applied shear increases (shear rates between 0.05 and 12.66 s-1), as expected for a cumulative process. When chicken gizzard filamin was added to gelsolin-actin filaments (at filamin/actin molar ratios of 1:300 to 1:10), a similar decrease in the diffusion coefficients was observed for unsheared samples. Spatial microheterogeneity might be related to the effects of the shear field in the alignment of filaments, and the balance between a three-dimensional network and a microheterogeneous system (containing bundles or anisotropic phases) appears related to both shear and the presence of actin-binding proteins.

Chemisorption and Diffusion of H on a Graphene Sheet and Single-Wall Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Srivastava, Deepak; Dzegilenko, Fedor; Menon, Madhu

2000-01-01

Recent experiments on hydrogen storage in single wall nanotubes and nanotube bundles have reported large fractional weight of stored molecular hydrogen which are not in agreement with theoretical estimates based of simulation of hydrogen storage by physisorption mechanisms. Hydrogen storage in catalytically doped nanotube bundles indicate that atomic H might undergo chemisorption changing the basic nature of the storage mechanism under investigation by many groups. Using a generalized tight-binding molecular dynamics (GTBMD) method for reactive C-H dynamics, we investigate chemisorption and diffusion of atomic H on graphene sheet and C nanotubes. Effective potential energy surfaces (EPS) for chemisorption and diffusion are calculated for graphene sheet and nanotubes of different curvatures. Analysis of the activation barriers and quantum rate constants, computed via wave-packet dynamics method, will be discussed in this presentation.

Fiberprint: A subject fingerprint based on sparse code pooling for white matter fiber analysis.

PubMed

Kumar, Kuldeep; Desrosiers, Christian; Siddiqi, Kaleem; Colliot, Olivier; Toews, Matthew

2017-09-01

White matter characterization studies use the information provided by diffusion magnetic resonance imaging (dMRI) to draw cross-population inferences. However, the structure, function, and white matter geometry vary across individuals. Here, we propose a subject fingerprint, called Fiberprint, to quantify the individual uniqueness in white matter geometry using fiber trajectories. We learn a sparse coding representation for fiber trajectories by mapping them to a common space defined by a dictionary. A subject fingerprint is then generated by applying a pooling function for each bundle, thus providing a vector of bundle-wise features describing a particular subject's white matter geometry. These features encode unique properties of fiber trajectories, such as their density along prominent bundles. An analysis of data from 861 Human Connectome Project subjects reveals that a fingerprint based on approximately 3000 fiber trajectories can uniquely identify exemplars from the same individual. We also use fingerprints for twin/sibling identification, our observations consistent with the twin data studies of white matter integrity. Our results demonstrate that the proposed Fiberprint can effectively capture the variability in white matter fiber geometry across individuals, using a compact feature vector (dimension of 50), making this framework particularly attractive for handling large datasets. Copyright © 2017 Elsevier Inc. All rights reserved.

Ab initio density functional theory investigation of structural and electronic properties of silicon carbide nanotube bundles

NASA Astrophysics Data System (ADS)

Moradian, Rostam; Behzad, Somayeh; Chegel, Raad

2008-10-01

By using ab initio density functional theory the structural and electronic properties of isolated and bundled (8,0) and (6,6) silicon carbide nanotubes (SiCNTs) are investigated. Our results show that for such small diameter nanotubes the inter-tube interaction causes a very small radial deformation, while band splitting and reduction of the semiconducting energy band gap are significant. We compared the equilibrium interaction energy and inter-tube separation distance of (8,0) SiCNT bundle with (10,0) carbon nanotube (CNT) bundle where they have the same radius. We found that there is a larger inter-tube separation and weaker inter-tube interaction in the (8,0) SiCNT bundle with respect to (10,0) CNT bundle, although they have the same radius.

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

PubMed

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

2015-12-15

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

Mechanical properties and cellular response of novel electrospun nanofibers for ligament tissue engineering: Effects of orientation and geometry.

PubMed

Pauly, Hannah M; Kelly, Daniel J; Popat, Ketul C; Trujillo, Nathan A; Dunne, Nicholas J; McCarthy, Helen O; Haut Donahue, Tammy L

2016-08-01

Electrospun nanofibers are a promising material for ligamentous tissue engineering, however weak mechanical properties of fibers to date have limited their clinical usage. The goal of this work was to modify electrospun nanofibers to create a robust structure that mimics the complex hierarchy of native tendons and ligaments. The scaffolds that were fabricated in this study consisted of either random or aligned nanofibers in flat sheets or rolled nanofiber bundles that mimic the size scale of fascicle units in primarily tensile load bearing soft musculoskeletal tissues. Altering nanofiber orientation and geometry significantly affected mechanical properties; most notably aligned nanofiber sheets had the greatest modulus; 125% higher than that of random nanofiber sheets; and 45% higher than aligned nanofiber bundles. Modifying aligned nanofiber sheets to form aligned nanofiber bundles also resulted in approximately 107% higher yield stresses and 140% higher yield strains. The mechanical properties of aligned nanofiber bundles were in the range of the mechanical properties of the native ACL: modulus=158±32MPa, yield stress=57±23MPa and yield strain=0.38±0.08. Adipose derived stem cells cultured on all surfaces remained viable and proliferated extensively over a 7 day culture period and cells elongated on nanofiber bundles. The results of the study suggest that aligned nanofiber bundles may be useful for ligament and tendon tissue engineering based on their mechanical properties and ability to support cell adhesion, proliferation, and elongation. Copyright © 2016 Elsevier Ltd. All rights reserved.

A stochastic method for Brownian-like optical transport calculations in anisotropic biosuspensions and blood

NASA Astrophysics Data System (ADS)

Miller, Steven

1998-03-01

A generic stochastic method is presented that rapidly evaluates numerical bulk flux solutions to the one-dimensional integrodifferential radiative transport equation, for coherent irradiance of optically anisotropic suspensions of nonspheroidal bioparticles, such as blood. As Fermat rays or geodesics enter the suspension, they evolve into a bundle of random paths or trajectories due to scattering by the suspended bioparticles. Overall, this can be interpreted as a bundle of Markov trajectories traced out by a "gas" of Brownian-like point photons being scattered and absorbed by the homogeneous distribution of uncorrelated cells in suspension. By considering the cumulative vectorial intersections of a statistical bundle of random trajectories through sets of interior data planes in the space containing the medium, the effective equivalent information content and behavior of the (generally unknown) analytical flux solutions of the radiative transfer equation rapidly emerges. The fluxes match the analytical diffuse flux solutions in the diffusion limit, which verifies the accuracy of the algorithm. The method is not constrained by the diffusion limit and gives correct solutions for conditions where diffuse solutions are not viable. Unlike conventional Monte Carlo and numerical techniques adapted from neutron transport or nuclear reactor problems that compute scalar quantities, this vectorial technique is fast, easily implemented, adaptable, and viable for a wide class of biophotonic scenarios. By comparison, other analytical or numerical techniques generally become unwieldy, lack viability, or are more difficult to utilize and adapt. Illustrative calculations are presented for blood medias at monochromatic wavelengths in the visible spectrum.

Hexagonally Ordered Arrays of α-Helical Bundles Formed from Peptide-Dendron Hybrids

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

Barkley, Deborah A.; Rokhlenko, Yekaterina; Marine, Jeannette E.

Combining monodisperse building blocks that have distinct folding properties serves as a modular strategy for controlling structural complexity in hierarchically organized materials. We combine an α-helical bundle-forming peptide with self-assembling dendrons to better control the arrangement of functional groups within cylindrical nanostructures. Site-specific grafting of dendrons to amino acid residues on the exterior of the α-helical bundle yields monodisperse macromolecules with programmable folding and self-assembly properties. The resulting hybrid biomaterials form thermotropic columnar hexagonal mesophases in which the peptides adopt an α-helical conformation. Bundling of the α-helical peptides accompanies self-assembly of the peptide-dendron hybrids into cylindrical nanostructures. The bundle stoichiometrymore » in the mesophase agrees well with the size found in solution for α-helical bundles of peptides with a similar amino acid sequence.« less

Flexible ex vivo phantoms for validation of diffusion tensor tractography on a clinical scanner.

PubMed

Watanabe, Makoto; Aoki, Shigeki; Masutani, Yoshitaka; Abe, Osamu; Hayashi, Naoto; Masumoto, Tomohiko; Mori, Harushi; Kabasawa, Hiroyuki; Ohtomo, Kuni

2006-11-01

The aim of this study was to develop ex vivo diffusion tensor (DT) flexible phantoms. Materials were bundles of textile threads of cotton, monofilament nylon, rayon, and polyester bunched with spiral wrapping bands and immersed in water. DT images were acquired on a 1.5-Tesla clinical magnetic resonance scanner using echo planar imaging sequences with 15 motion probing gradient directions. DT tractography with seeding and a line-tracking method was carried out by software originally developed on a PC-based workstation. We observed relatively high fractional anisotropy on the polyester phantom and were able to reconstruct tractography. Straight tracts along the bundle were displayed when it was arranged linearly. It was easy to bend arcuately or bifurcate at one end; and tracts followed the course of the bundle, whether it was curved or branched and had good agreement with direct visual observation. Tractography with the other fibers was unsuccessful. The polyester phantom revealed a diffusion anisotropic structure according to its shape and would be utilizable repeatedly under the same conditions, differently from living central neuronal system. It would be useful to validate DT sequences and to optimize an algorithm or parameters of DT tractography software. Additionally, the flexibility of the phantom would enable us to model human axonal projections.

Global and Targeted Pathway Impact of Gliomas on White Matter Integrity Based on Lobar Localization.

PubMed

Ormond, David R; D'Souza, Shawn; Thompson, John A

2017-09-07

Primary brain tumors comprise 28% of all tumors and 80% of malignant tumors. Pathophysiology of high-grade gliomas includes significant distortion of white matter architecture, necrosis, the breakdown of the blood brain barrier, and increased intracranial pressure. Diffusion tensor imaging (DTI), a diffusion weighted imaging technique, can be used to assess white matter architecture. Use of DTI as a non-invasive pathophysiological tool to analyze glioma impact on white matter microstructure has yet to be fully explored. Preliminary assessment of DTI tractography was done as a measure of intracranial tumor impact on white matter architecture. Specifically, we addressed three questions: 1) whether glioma differentially affects local white matter structure compared to metastasis, 2) whether glioma affects tract integrity of major white matter bundles, 3) whether glioma lobe localization affects tract integrity of different white matter bundles. In this study, we retrospectively investigated preoperative DTI scans from 24 patients undergoing tumor resection. Fiber tractography was estimated using a deterministic fiber tracking algorithm in DSI (diffusion spectrum imaging) Studio. The automatic anatomical labeling (AAL) atlas was used to define the left and right (L/R)   hemisphere regions of interest (ROI). In addition, the John Hopkins University (JHU) White Matter Atlas was used to auto-segment major white matter bundle ROIs. For all tracts derived from ROI seed targets, we computed the following parameters: tract number, tract length, fractional anisotropy (FA), axial diffusivity (AD), mean diffusivity (MD), and radial diffusivity (RD). The DTI tractography analysis revealed that white matter integrity in the hemisphere ipsilateral to intracranial tumor was significantly compromised compared to the control contralateral hemisphere. No differences were observed between high vs low-grade gliomas, however, gliomas induced significantly greater white matter degradation than metastases. In addition, targeted analysis of major white matter bundles important for sensory/motor function (i.e., corticospinal tract and superior longitudinal fasciculus) revealed tract-parameter specific susceptibility due to the presence of the tumor. Finally, major tract bundles were differentially affected based on lobar localization of the glioma. These DTI-based tractographic analyses complement findings from gross histopathological examination of glioma impact on neural tissue. Global and focal white matter architecture, ipsilateral to glioma, shows higher rates of degradation or edema - based on DTI tractographic metrics - in comparison to normal brain or metastases. Gliomas, which arise in the parietal lobe, also have a higher negative impact (potentially due to increased edema) on white matter integrity of the superior longitudinal fasciculus(SLF) than those which arise in the frontal lobe. Future studies will focus on using preoperative and postoperative tractography to predict functional deficits following resective surgery.

Fiber optic spectroscopic digital imaging sensor and method for flame properties monitoring

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

Zelepouga, Serguei A; Rue, David M; Saveliev, Alexei V

2011-03-15

A system for real-time monitoring of flame properties in combustors and gasifiers which includes an imaging fiber optic bundle having a light receiving end and a light output end and a spectroscopic imaging system operably connected with the light output end of the imaging fiber optic bundle. Focusing of the light received by the light receiving end of the imaging fiber optic bundle by a wall disposed between the light receiving end of the fiber optic bundle and a light source, which wall forms a pinhole opening aligned with the light receiving end.

Oblique incidence reflectometry: optical models and measurements using a side-viewing gradient index lens-based endoscopic imaging system

NASA Astrophysics Data System (ADS)

Wall, R. Andrew; Barton, Jennifer K.

2014-06-01

A side-viewing, 2.3-mm diameter oblique incidence reflectometry endoscope has been designed to obtain optical property measurements of turbid samples. Light from a single-mode fiber is relayed obliquely onto the tissue with a gradient index lens-based distal optics assembly and the resulting diffuse reflectance profile is imaged and collected with a 30,000 element, 0.72 mm clear aperture fiber bundle. Sampling the diffuse reflectance in two-dimensions allows for fitting of the reflected intensity profile to a well-known theoretical model, permitting the extraction of both absorption and reduced scattering coefficients of the tissue sample. Models and measurements of the endoscopic imaging system are presented in tissue phantoms and in vivo mouse colon, verifying the endoscope's capabilities to accurately measure effective attenuation coefficient and differentiate diseased from normal colon.

Carbon Nanotubules: Building Blocks for Nanometer-Scale Engineering

NASA Technical Reports Server (NTRS)

Sinnott, Susan B.

1999-01-01

The proposed work consisted of two projects: the investigation of fluid permeation and diffusion through ultrafiltration membranes composed of carbon nanotubules and the design and study of molecular transistors composed of nanotubules. The progress made on each project is summarized and also discussion about additional projects, one of which is a continuation of work supported by another grant, is included. The first project was Liquid Interactions within a Nanotubule Membrane. The second was the design of nanometer-scale hydrocarbon electronic devices. The third was the investigation of Mechanical properties of Nanotubules and Nanotubule bundles. The fourth project was to investigate the growth mechanisms of Carbon Nanotubules.

Comparative assessment of therapeutic response to physiotherapy with or without botulinum toxin injection using diffusion tensor tractography and clinical scores in term diplegic cerebral palsy children.

PubMed

Chaturvedi, Saurabh K; Rai, Yogita; Chourasia, Ankita; Goel, Puneet; Paliwal, Vimal K; Garg, Ravindra K; Rathore, Ram Kishore S; Pandey, Chandra M; Gupta, Rakesh K

2013-08-01

The present study was to compare the effects of combined therapy [botulinum (BTX) plus physiotherapy] with physiotherapy alone using diffusion tensor imaging (DTI) derived fractional anisotropy (FA) values of motor and sensory fiber bundles and clinical grade of the disability to see the value of BTX in term children with spastic diplegic cerebral palsy (CP). Clinically diagnosed 36 children participated in the study. All these children were born at term, and had no history of seizures. The study was randomly categorized into two groups: group I (n=18) - physiotherapy alone and group II (n=18) - physiotherapy plus BTX injection. Quantitative diffusion tensor tractography on all these children was performed on motor and sensory fiber bundles on baseline as well as after 6months of therapy. Motor function and clinical grades were also measured by gross motor function measures (GMFM) scale on both occasions. We observed significant change in FA value in motor and sensory fiber bundle as well as in GMFM scores at 6months compared to baseline study in both the groups. However, delta change and relative delta change in FA values of sensory and motor fiber bundle as well as GMFM score between group I and group II was statistically insignificant. We conclude that addition of BTX to physiotherapy regimen does not influence the outcome at 6months with similar insult in children with term diplegic spastic CP. This information may influence management of diplegic CP especially in developing countries, where BTX is beyond the reach of these children. Copyright © 2012 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

Effects of inter-tube coupling on the electro-optical properties of silicon carbide nanotube bundles studied by density functional theory

NASA Astrophysics Data System (ADS)

Behzad, Somayeh

2015-09-01

The electronic and optical properties of bundled armchair and zigzag silicon carbide nanotubes (SiCNTs) are investigated by using density functional theory. The effects of inter-tube coupling on the electronic dispersions of SiCNT bundles are demonstrated. It was found that the band structure of (6, 0) SiCNT bundle shows metallic feature. The calculated dielectric functions of the armchair and zigzag bundles are similar to that of the isolated tubes, except for the appearance of broadened peaks, small shifts of peak positions about 0.1 eV and increasing of peak intensities. For (6, 0) SiCNT with smaller radius, by considering interband and interaband transitions, the band structure coupling causes an extra peak at low energies.

Design and validation of a diffuse reflectance and spectroscopic microendoscope with poly(dimethylsioxane)-based phantoms

PubMed Central

Greening, Gage J.; Powless, Amy J.; Hutcheson, Joshua A.; Prieto, Sandra P.; Majid, Aneeka A.; Muldoon, Timothy J.

2015-01-01

Many cases of epithelial cancer originate in basal layers of tissue and are initially undetected by conventional microendoscopy techniques. We present a bench-top, fiber-bundle microendoscope capable of providing high resolution images of surface cell morphology. Additionally, the microendoscope has the capability to interrogate deeper into material by using diffuse reflectance and broadband diffuse reflectance spectroscopy. The purpose of this multimodal technique was to overcome the limitation of microendoscopy techniques that are limited to only visualizing morphology at the tissue or cellular level. Using a custom fiber optic probe, high resolution surface images were acquired using topical proflavine to fluorescently stain non-keratinized epithelia. A 635 nm laser coupled to a 200 μm multimode fiber delivers light to the sample and the diffuse reflectance signal was captured by a 1 mm image guide fiber. Finally, a tungsten-halogen lamp coupled to a 200 μm multimode fiber delivers broadband light to the sample to acquire spectra at source-detector separations of 374, 729, and 1051 μm. To test the instrumentation, a high resolution proflavine-induced fluorescent image of resected healthy mouse colon was acquired. Additionally, five monolayer poly(dimethylsiloxane)-based optical phantoms with varying absorption and scattering properties were created to acquire diffuse reflectance profiles and broadband spectra. PMID:25983372

Design and validation of a diffuse reflectance and spectroscopic microendoscope with poly(dimethylsiloxane)-based phantoms

NASA Astrophysics Data System (ADS)

Greening, Gage J.; Powless, Amy J.; Hutcheson, Joshua A.; Prieto, Sandra P.; Majid, Aneeka A.; Muldoon, Timothy J.

2015-03-01

Many cases of epithelial cancer originate in basal layers of tissue and are initially undetected by conventional microendoscopy techniques. We present a bench-top, fiber-bundle microendoscope capable of providing high resolution images of surface cell morphology. Additionally, the microendoscope has the capability to interrogate deeper into material by using diffuse reflectance and broadband diffuse reflectance spectroscopy. The purpose of this multimodal technique was to overcome the limitation of microendoscopy techniques that are limited to only visualizing morphology at the tissue or cellular level. Using a custom fiber optic probe, high resolution surface images were acquired using topical proflavine to fluorescently stain non-keratinized epithelia. A 635 nm laser coupled to a 200 μm multimode fiber delivers light to the sample and the diffuse reflectance signal was captured by a 1 mm image guide fiber. Finally, a tungsten-halogen lamp coupled to a 200 μm multimode fiber delivers broadband light to the sample to acquire spectra at source-detector separations of 374, 729, and 1051 μm. To test the instrumentation, a high resolution proflavine-induced fluorescent image of resected healthy mouse colon was acquired. Additionally, five monolayer poly(dimethylsiloxane)-based optical phantoms with varying absorption and scattering properties were created to acquire diffuse reflectance profiles and broadband spectra.

Application of neuroanatomical features to tractography clustering.

PubMed

Wang, Qian; Yap, Pew-Thian; Wu, Guorong; Shen, Dinggang

2013-09-01

Diffusion tensor imaging allows unprecedented insight into brain neural connectivity in vivo by allowing reconstruction of neuronal tracts via captured patterns of water diffusion in white matter microstructures. However, tractography algorithms often output hundreds of thousands of fibers, rendering subsequent data analysis intractable. As a remedy, fiber clustering techniques are able to group fibers into dozens of bundles and thus facilitate analyses. Most existing fiber clustering methods rely on geometrical information of fibers, by viewing them as curves in 3D Euclidean space. The important neuroanatomical aspect of fibers, however, is ignored. In this article, the neuroanatomical information of each fiber is encapsulated in the associativity vector, which functions as the unique "fingerprint" of the fiber. Specifically, each entry in the associativity vector describes the relationship between the fiber and a certain anatomical ROI in a fuzzy manner. The value of the entry approaches 1 if the fiber is spatially related to the ROI at high confidence; on the contrary, the value drops closer to 0. The confidence of the ROI is calculated by diffusing the ROI according to the underlying fibers from tractography. In particular, we have adopted the fast marching method for simulation of ROI diffusion. Using the associativity vectors of fibers, we further model fibers as observations sampled from multivariate Gaussian mixtures in the feature space. To group all fibers into relevant major bundles, an expectation-maximization clustering approach is employed. Experimental results indicate that our method results in anatomically meaningful bundles that are highly consistent across subjects. Copyright © 2012 Wiley Periodicals, Inc., a Wiley company.

Real-Time Dynamics of Emerging Actin Networks in Cell-Mimicking Compartments

PubMed Central

Deshpande, Siddharth; Pfohl, Thomas

2015-01-01

Understanding the cytoskeletal functionality and its relation to other cellular components and properties is a prominent question in biophysics. The dynamics of actin cytoskeleton and its polymorphic nature are indispensable for the proper functioning of living cells. Actin bundles are involved in cell motility, environmental exploration, intracellular transport and mechanical stability. Though the viscoelastic properties of actin-based structures have been extensively probed, the underlying microstructure dynamics, especially their disassembly, is not fully understood. In this article, we explore the rich dynamics and emergent properties exhibited by actin bundles within flow-free confinements using a microfluidic set-up and epifluorescence microscopy. After forming entangled actin filaments within cell-sized quasi two-dimensional confinements, we induce their bundling using three different fundamental mechanisms: counterion condensation, depletion interactions and specific protein-protein interactions. Intriguingly, long actin filaments form emerging networks of actin bundles via percolation leading to remarkable properties such as stress generation and spindle-like intermediate structures. Simultaneous sharing of filaments in different links of the network is an important parameter, as short filaments do not form networks but segregated clusters of bundles instead. We encounter a hierarchical process of bundling and its subsequent disassembly. Additionally, our study suggests that such percolated networks are likely to exist within living cells in a dynamic fashion. These observations render a perspective about differential cytoskeletal responses towards numerous stimuli. PMID:25785606

Mechanism of Interaction between the General Anesthetic Halothane and a Model Ion Channel Protein, II: Fluorescence and Vibrational Spectroscopy Using a Cyanophenylalanine Probe

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

Liu, J.; Strzalka, J; Tronin, A

2009-01-01

We demonstrate that cyano-phenylalanine (PheCN) can be utilized to probe the binding of the inhalational anesthetic halothane to an anesthetic-binding, model ion channel protein hbAP-PheCN. The Trp to PheCN mutation alters neither the a-helical conformation nor the 4-helix bundle structure. The halothane binding properties of this PheCN mutant hbAP-PheCN, based on fluorescence quenching, are consistent with those of the prototype, hbAP1. The dependence of fluorescence lifetime as a function of halothane concentration implies that the diffusion of halothane in the nonpolar core of the protein bundle is one-dimensional. As a consequence, at low halothane concentrations, the quenching of the fluorescencemore » is dynamic, whereas at high concentrations the quenching becomes static. The 4-helix bundle structure present in aqueous detergent solution and at the air-water interface, is preserved in multilayer films of hbAP-PheCN, enabling vibrational spectroscopy of both the protein and its nitrile label (-CN). The nitrile groups' stretching vibration band shifts to higher frequency in the presence of halothane, and this blue-shift is largely reversible. Due to the complexity of this amphiphilic 4-helix bundle model membrane protein, where four PheCN probes are present adjacent to the designed cavity forming the binding site within each bundle, all contributing to the infrared absorption, molecular dynamics (MD) simulation is required to interpret the infrared results. The MD simulations indicate that the blue-shift of -CN stretching vibration induced by halothane arises from an indirect effect, namely an induced change in the electrostatic protein environment averaged over the four probe oscillators, rather than a direct interaction with the oscillators. hbAP-PheCN therefore provides a successful template for extending these investigations of the interactions of halothane with the model membrane protein via vibrational spectroscopy, using cyano-alanine residues to form the anesthetic binding cavity.« less

Electrostatic interaction between stereocilia: II. Influence on the mechanical properties of the hair bundle.

PubMed

Dolgobrodov, S G; Lukashkin, A N; Russell, I J

2000-12-01

This paper is based on our model [Dolgobrodov et al., 2000. Hear. Res., submitted for publication] in which we examine the significance of the polyanionic surface layers of stereocilia for electrostatic interaction between them. We analyse how electrostatic forces modify the mechanical properties of the sensory hair bundle. Different charge distribution profiles within the glycocalyx are considered. When modelling a typical experiment on bundle stiffness measurements, applying an external force to the tallest row of stereocilia shows that the asymptotic stiffness of the hair bundle for negative displacements is always larger than the asymptotic stiffness for positive displacements. This increase in stiffness is monotonic for even charge distribution and shows local minima when the negative charge is concentrated in a thinner layer within the cell coat. The minima can also originate from the co-operative effect of electrostatic repulsion and inter-ciliary links with non-linear mechanical properties. Existing experimental observations are compared with the predictions of the model. We conclude that the forces of electrostatic interaction between stereocilia may influence the mechanical properties of the hair bundle and, being strongly non-linear, contribute to the non-linear phenomena, which have been recorded from the auditory periphery.

Decreased white matter integrity in fronto-occipital fasciculus bundles: relation to visual information processing in alcohol-dependent subjects.

PubMed

Bagga, Deepika; Sharma, Aakansha; Kumari, Archana; Kaur, Prabhjot; Bhattacharya, Debajyoti; Garg, Mohan Lal; Khushu, Subash; Singh, Namita

2014-02-01

Chronic alcohol abuse is characterized by impaired cognitive abilities with a more severe deficit in visual than in verbal functions. Neuropathologically, it is associated with widespread brain structural compromise marked by gray matter shrinkage, ventricular enlargement, and white matter degradation. The present study sought to increase current understanding of the impairment of visual processing abilities in alcohol-dependent subjects, and its correlation with white matter microstructural alterations, using diffusion tensor imaging (DTI). To that end, a DTI study was carried out on 35 alcohol-dependent subjects and 30 healthy male control subjects. Neuropsychological tests were assessed for visual processing skills and deficits were reported as raw dysfunction scores (rDyS). Reduced FA (fractional anisotropy) and increased MD (mean diffusivity) were observed bilaterally in inferior and superior fronto-occipital fasciculus (FOF) fiber bundles. A significant inverse correlation in rDyS and FA values was observed in these fiber tracts whereas a positive correlation of these scores was found with the MD values. Our results suggest that FOF fiber bundles linking the frontal lobe to occipital lobe might be related to visual processing skills. This is the first report of an alteration of the white matter microstructure of FOF fiber bundles that might have functional consequences for visual processing in alcohol-dependent subjects who exhibit no neurological complications. Copyright © 2014 Elsevier Inc. All rights reserved.

Deformation quantization with separation of variables of an endomorphism bundle

NASA Astrophysics Data System (ADS)

Karabegov, Alexander

2014-01-01

Given a holomorphic Hermitian vector bundle E and a star-product with separation of variables on a pseudo-Kähler manifold, we construct a star product on the sections of the endomorphism bundle of the dual bundle E∗ which also has the appropriately generalized property of separation of variables. For this star product we prove a generalization of Gammelgaard's graph-theoretic formula.

Electronic structure and optical properties of boron nitride nanotube bundles from first principles

NASA Astrophysics Data System (ADS)

Behzad, Somayeh

2015-06-01

The electronic and optical properties of bundled armchair and zigzag boron nitride nanotubes (BNNTs) are investigated by using density functional theory. Owing to the inter-tube coupling, the dispersions along the tube axis and in the plane perpendicular to the tube axis of BNNT bundles are significantly varied, which are characterized by the decrease of band gap, the splitting of the doubly degenerated states, the expansions of valence and conduction bands. The calculated dielectric functions of the armchair and zigzag bundles are similar to that of the isolated tubes, except for the appearance of broadened peaks, small shifts of peak positions about 0.1 eV and increasing of peak intensities.

Nanomorphology Characteristics of Thermally Annealed Pre Encapsulated P3HT:PCBM Thin Films Using Atomic Force Microscopy

DTIC Science & Technology

2014-10-30

fib- rils aggregate in bundles with the fullerene as the anneal- ing temperature increases. This bundle formation or grain features could indicate a...the diffusion lengths of charge carriers (∼10 nm). Past work on these fullerene networks have shown that trap distribution in devices is broader for...aver- age distance between polymer and fullerene molecules. The size of crystallites perhaps reach an upper limit in the range of 150 "C; beyond this

On the force-velocity relationship of a bundle of rigid bio-filaments

NASA Astrophysics Data System (ADS)

Perilli, Alessia; Pierleoni, Carlo; Ciccotti, Giovanni; Ryckaert, Jean-Paul

2018-03-01

In various cellular processes, bio-filaments like F-actin and F-tubulin are able to exploit chemical energy associated with polymerization to perform mechanical work against an obstacle loaded with an external force. The force-velocity relationship quantitatively summarizes the nature of this process. By a stochastic dynamical model, we give, together with the evolution of a staggered bundle of Nf rigid living filaments facing a loaded wall, the corresponding force-velocity relationship. We compute the evolution of the model in the infinite wall diffusion limit and in supercritical conditions (monomer density reduced by critical density ρ^ 1>1 ), and we show that this solution remains valid for moderate non-zero values of the ratio between the wall diffusion and the chemical time scales. We consider two classical protocols: the bundle is opposed either to a constant load or to an optical trap setup, characterized by a harmonic restoring force. The constant load case leads, for each F value, to a stationary velocity Vs t a t(F ;Nf,ρ^ 1 ) after a relaxation with characteristic time τmicro(F). When the bundle (initially taken as an assembly of filament seeds) is subjected to a harmonic restoring force (optical trap load), the bundle elongates and the load increases up to stalling over a characteristic time τOT. Extracted from this single experiment, the force-velocity VO T(F ;Nf,ρ^ 1 ) curve is found to coincide with Vs t a t(F ;Nf,ρ^ 1 ) , except at low loads. We show that this result follows from the adiabatic separation between τmicro and τOT, i.e., τmicro ≪ τOT.

Bundles over nearly-Kahler homogeneous spaces in heterotic string theory

NASA Astrophysics Data System (ADS)

Klaput, Michael; Lukas, Andre; Matti, Cyril

2011-09-01

We construct heterotic vacua based on six-dimensional nearly-Kahler homogeneous manifolds and non-trivial vector bundles thereon. Our examples are based on three specific group coset spaces. It is shown how to construct line bundles over these spaces, compute their properties and build up vector bundles consistent with supersymmetry and anomaly cancelation. It turns out that the most interesting coset is SU(3)/U(1)2. This space supports a large number of vector bundles which lead to consistent heterotic vacua, some of them with three chiral families.

Thermal Characterization of Carbon Fiber-Reinforced Carbon Composites

NASA Astrophysics Data System (ADS)

Macias, J. D.; Bante-Guerra, J.; Cervantes-Alvarez, F.; Rodrìguez-Gattorno, G.; Arés-Muzio, O.; Romero-Paredes, H.; Arancibia-Bulnes, C. A.; Ramos-Sánchez, V.; Villafán-Vidales, H. I.; Ordonez-Miranda, J.; Li Voti, R.; Alvarado-Gil, J. J.

2018-04-01

Carbon fiber-reinforced carbon (C/C) composites consist in a carbon matrix holding carbon or graphite fibers together, whose physical properties are determined not only by those of their individual components, but also by the layer buildup and the material preparation and processing. The complex structure of C/C composites along with the fiber orientation provide an effective means for tailoring their mechanical, electrical, and thermal properties. In this work, we use the Laser Flash Technique to measure the thermal diffusivity and thermal conductivity of C/C composites made up of laminates of weaved bundles of carbon fibers, forming a regular and repeated orthogonal pattern, embedded in a graphite matrix. Our experimental data show that: i) the cross-plane thermal conductivity remains practically constant around (5.3 ± 0.4) W·m-1 K-1, within the temperature range from 370 K to 1700 K. ii) The thermal diffusivity and thermal conductivity along the cross-plane direction to the fibers axis is about five times smaller than the corresponding ones in the laminates plane. iii) The measured cross-plane thermal conductivity is well described by a theoretical model that considers both the conductive and radiative thermal contributions of the effective thermal conductivity.

Cross-Linker Unbinding and Self-Similarity in Bundled Cytoskeletal Networks

NASA Astrophysics Data System (ADS)

Lieleg, O.; Bausch, A. R.

2007-10-01

The macromechanical properties of purely bundled in vitro actin networks are not only determined by the micromechanical properties of individual bundles but also by molecular unbinding events of the actin-binding protein (ABP) fascin. Under high mechanical load the network elasticity depends on the forced unbinding of individual ABPs in a rate dependent manner. Cross-linker unbinding in combination with the structural self-similarity of the network enables the introduction of a concentration-time superposition principle—broadening the mechanically accessible frequency range over 8 orders of magnitude.

Frequent coexistence of Lewy bodies and neurofibrillary tangles in the same neurons of patients with diffuse Lewy body disease.

PubMed

Iseki, E; Marui, W; Kosaka, K; Uéda, K

1999-04-09

We examined the frequency of neurons with coexistent Lewy bodies (LB) and neurofibrillary tangles (NFT) in diffuse Lewy body disease brains, by a double-immunostaining method using MDV2 and Human tau. Double-positive neurons were frequently observed in the limbic areas. These neurons mostly revealed the feature of intermingled MDV2- and Human tau-positive substances. Immunoelectron microscopically, the MDV2-positive components were not in continuity with the MDV2-negative paired helical filaments (PHF). The MDV2-positive LB were surrounded by the small PHF bundles, frequently accompanied by the randomly oriented PHF within LB. In the intermingled neurons, MDV2-positive non-filamentous components without LB were found among the large PHF bundles. These non-filamentous components may represent the early stage of LB formation.

Cortico-Cortical, Cortico-Striatal, and Cortico-Thalamic White Matter Fiber Tracts Generated in the Macaque Brain via Dynamic Programming

PubMed Central

Lal, Rakesh M.; An, Michael; Poynton, Clare B.; Li, Muwei; Jiang, Hangyi; Oishi, Kenichi; Selemon, Lynn D.; Mori, Susumu; Miller, Michael I.

2013-01-01

Abstract Probabilistic methods have the potential to generate multiple and complex white matter fiber tracts in diffusion tensor imaging (DTI). Here, a method based on dynamic programming (DP) is introduced to reconstruct fibers pathways whose complex anatomical structures cannot be resolved beyond the resolution of standard DTI data. DP is based on optimizing a sequentially additive cost function derived from a Gaussian diffusion model whose covariance is defined by the diffusion tensor. DP is used to determine the optimal path between initial and terminal nodes by efficiently searching over all paths, connecting the nodes, and choosing the path in which the total probability is maximized. An ex vivo high-resolution scan of a macaque hemi-brain is used to demonstrate the advantages and limitations of DP. DP can generate fiber bundles between distant cortical areas (superior longitudinal fasciculi, arcuate fasciculus, uncinate fasciculus, and fronto-occipital fasciculus), neighboring cortical areas (dorsal and ventral banks of the principal sulcus), as well as cortical projections to the hippocampal formation (cingulum bundle), neostriatum (motor cortical projections to the putamen), thalamus (subcortical bundle), and hippocampal formation projections to the mammillary bodies via the fornix. Validation is established either by comparison with in vivo intracellular transport of horseradish peroxidase in another macaque monkey or by comparison with atlases. DP is able to generate known pathways, including crossing and kissing tracts. Thus, DP has the potential to enhance neuroimaging studies of cortical connectivity. PMID:23879573

Warps, grids and curvature in triple vector bundles

NASA Astrophysics Data System (ADS)

Flari, Magdalini K.; Mackenzie, Kirill

2018-06-01

A triple vector bundle is a cube of vector bundle structures which commute in the (strict) categorical sense. A grid in a triple vector bundle is a collection of sections of each bundle structure with certain linearity properties. A grid provides two routes around each face of the triple vector bundle, and six routes from the base manifold to the total manifold; the warps measure the lack of commutativity of these routes. In this paper we first prove that the sum of the warps in a triple vector bundle is zero. The proof we give is intrinsic and, we believe, clearer than the proof using decompositions given earlier by one of us. We apply this result to the triple tangent bundle T^3M of a manifold and deduce (as earlier) the Jacobi identity. We further apply the result to the triple vector bundle T^2A for a vector bundle A using a connection in A to define a grid in T^2A . In this case the curvature emerges from the warp theorem.

Study on parameters affecting the mechanical properties of dry fiber bundles during continuous composite manufacturing processes

NASA Astrophysics Data System (ADS)

Maier, A.; Schledjewski, R.

2016-07-01

For continuous manufacturing processes mechanical preloading of the fibers occurs during the delivery of the fibers from the spool creel to the actual manufacturing process step. Moreover preloading of the dry roving bundles might be mandatory, e.g. during winding, to be able to produce high quality components. On the one hand too high tensile loads within dry roving bundles might result in a catastrophic failure and on the other hand the part produced under too low pre-tension might have low quality and mechanical properties. In this work, load conditions influencing mechanical properties of dry glass fiber bundles during continuous composite manufacturing processes were analyzed. Load conditions, i.e. fiber delivery speed, necessary pre-tension and other effects of the delivery system during continuous fiber winding, were chosen in process typical ranges. First, the strain rate dependency under static tensile load conditions was investigated. Furthermore different free gauge lengths up to 1.2 m, interactions between fiber points of contact regarding influence of sizing as well as impregnation were tested and the effect of twisting on the mechanical behavior of dry glass fiber bundles during the fiber delivery was studied.

From cell differentiation to cell collectives: Bacillus subtilis uses division of labor to migrate.

PubMed

van Gestel, Jordi; Vlamakis, Hera; Kolter, Roberto

2015-04-01

The organization of cells, emerging from cell-cell interactions, can give rise to collective properties. These properties are adaptive when together cells can face environmental challenges that they separately cannot. One particular challenge that is important for microorganisms is migration. In this study, we show how flagellum-independent migration is driven by the division of labor of two cell types that appear during Bacillus subtilis sliding motility. Cell collectives organize themselves into bundles (called "van Gogh bundles") of tightly aligned cell chains that form filamentous loops at the colony edge. We show, by time-course microscopy, that these loops migrate by pushing themselves away from the colony. The formation of van Gogh bundles depends critically on the synergistic interaction of surfactin-producing and matrix-producing cells. We propose that surfactin-producing cells reduce the friction between cells and their substrate, thereby facilitating matrix-producing cells to form bundles. The folding properties of these bundles determine the rate of colony expansion. Our study illustrates how the simple organization of cells within a community can yield a strong ecological advantage. This is a key factor underlying the diverse origins of multicellularity.

Progressive Assessment of Ischemic Injury to White Matter Using Diffusion Tensor Imaging: A Preliminary Study of a Macaque Model of Stroke.

PubMed

Zhang, Xiaodong; Yan, Yumei; Tong, Frank; Li, Chun-Xia; Jones, Benjamin; Wang, Silun; Meng, Yuguang; Muly, E Chris; Kempf, Doty; Howell, Leonard

2018-01-01

Previous Diffusion Tensor Imaging (DTI) studies have demonstrated the temporal evolution of stroke injury in grey matter and white matter can be characterized by DTI indices. However, it still remains not fully understood how the DTI indices of white matter are altered progressively during the hyperacute (first 6 hours) and acute stage of stroke (≤ 1 week). In the present study, DTI was employed to characterize the temporal evolution of infarction and white matter injury after stroke insult using a macaque model with permanent ischemic occlusion. Permanent middle cerebral artery (MCA) occlusion was induced in rhesus monkeys (n=4, 10-21 years old). The brain lesion was examined longitudinally with DTI during the hyperacute phase (2-6 hours, n=4), 48 hours (n=4) and 96 hours (n=3) post-occlusion. Cortical infarction was seen in all animals. The Mean Diffusivity (MD) in lesion regions decreased substantially at the first time point (2 hours post stroke) (35%, p <0.05, compared to the contralateral side) and became pseudo-normalized at 96 hours. In contrast, evident FA reduction was seen at 48 hours (39%, p <0.10) post-stroke. MD reduction in white matter bundles of the lesion area was much less than that in the grey matter during the hyper-acute phase but significant change was observed 4 hours (4.2%, p < 0.05) post stroke . Also, MD pseudonormalisation was seen at 96 hours post stroke. There was a significant correlation between the temporal changes of MD in white matter bundles and those in whole lesion areas during the entire study period. Meanwhile, no obvious fractional anisotropy (FA) changes were seen during the hyper-acute phase in either the entire infarct region or white matter bundles. Significant FA alteration was observed in entire lesion areas and injured white matter bundles 48 and 96 hours post stroke. The stroke lesion in grey matter and white matter was validated by pathological findings. The temporal evolution of ischemic injury to the grey matter and white matter from 2 to 96 hours after stroke onset was characterized using a macaque model and DTI. Progressive MD changes in white matter bundles are seen from hyperacute phase to acute phase after permanent MCA occlusion and temporally correlated with the MD changes in entire infarction regions. MD reduction in white matter bundles is mild in comparison with that in the grey matter but significant and progressive, indicating it may be useful to detect early white matter degeneration after stroke.

Application of liquid-liquid interactions with single-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Wang, Randy Kai-Wei

This study covers three important research topics related to the application of liquid-liquid interaction with single-walled carbon nanotubes (SWNTs). The first topic describes the removal of SWNT bundles from liquid suspensions of nanotubes. The key to this work includes the use of liquid-liquid interfaces to trap the SWNT bundles due to the free energy change of the system during the process. SWNTs pack into crystalline ropes that form bundles due to strong van der Waals attraction. Bundling diminishes mechanical and electronic properties because it could interrupt the electronic structure of the nanotubes. Also, the electronic devices based on as-grown nanotubes, which contains a mixture of individual nanotubes and nanotube bundles, make the electrical response unpredictable. We developed a new simple process to remove bundles by liquid-liquid interaction. SWNTs bundles are trapped at the interface because bundles stabilize the emulsions. Eliminating the use of ultracentrifugation to remove SWNT bundles enables large-scale production with reduced production costs and time savings. The second topic presented the swelling effect of the surfactant layer surrounding SWNTs with nonpolar solvents. Solvatochromic shifts in the absorbance and fluorescence spectra are observed when surfactant-stabilized aqueous SWNT suspensions are mixed with immiscible organic solvents. When aqueous surfactant-suspended SWNTs are mixed with certain solvents, the spectra closely match the peaks for SWNTs dispersed in only that solvent. These spectral changes suggest the hydrophobic region of the micelle surrounding SWNTs swells with the organic solvent when mixed. The solvatochromic shifts of the aqueous SWNT suspensions are reversible once the solvent evaporates. However, some surfactant-solvent systems show permanent changes to the fluorescence emission intensity after exposure to the organic solvent. The intensity of some large diameter SWNT (n, m) types increase by more than 175%. These differences are attributed to surfactant reorganization, which can improve nanotube coverage, resulting in decreased exposure to quenching mechanisms from the aqueous phase. The third topic describes the further study of the solvatochromism of the SWNTs. Since SWNTs are encapsulated with microenvironments of nonpolar solvents, it provides a new method to measure the photophysical properties of nanotubes in environments with known properties. Fluorescence and absorbance spectra of SWNTs show solvatochromic shifts in 16 nonpolar solvents, which are proportional to the solvent induction polarization. The photophysical properties of SWNTs were used to determine the relationship between the longitudinal polarizability and other nanotube properties, alpha11,|| ∝ 1/(R2E11 3). (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)

An applied investigation of kenaf-based fiber/polymer composites as potential lightweight materials for automotive components

NASA Astrophysics Data System (ADS)

Du, Yicheng

Natural fibers have the potential to replace glass fibers in fiber-reinforced composite applications. However, the natural fibers' intrinsic properties cause these issues: (1) the mechanical property variation; (2) moisture uptake by natural fibers and their composites; (3) lack of sound, cost-effective, environment-friendly fiber-matrix compounding processes; (4) incompatibility between natural fibers and polymer matrices; and (5) low heat-resistance of natural fibers and their composites. This dissertation systematically studied the use of kenaf bast fiber bundles, obtained via a mechanical retting method, as a light-weight reinforcement material for fiber-reinforced thermoset polymer composites for automotive applications. Kenaf bast fiber bundle tensile properties were tested, and the effects of locations in the kenaf plant, loading rates, retting methods, and high temperature treatments and their durations on kenaf bast fiber bundle tensile properties were evaluated. A process has been developed for fabricating high fiber loading kenaf bast fiber bundle-reinforced unsaturated polyester composites. The generated composites possessed high elastic moduli and their tensile strengths were close to specification requirements for glass fiber-reinforced sheet molding compounds. Effects of fiber loadings and lengths on resultant composite's tensile properties were evaluated. Fiber loadings were very important for composite tensile modulus. Both fiber loadings and fiber lengths were important for composite tensile strengths. The distributions of composite tensile, flexural and impact strengths were analyzed. The 2-parameter Weibull model was found to be the most appropriate for describing the composite strength distributions and provided the most conservative design values. Kenaf-reinforced unsaturated polyester composites were also proved to be more cost-effective than glass fiber-reinforced SMCs at high fiber loadings. Kenaf bast fiber bundle-reinforced composite's water absorption properties were tested. Surface-coating and edge-sealing significantly reduced composite water resistance properties. Encapsulation was a practical method to improve composite water resistance properties. The molding pressure and styrene concentrations on composite and matrix properties were evaluated. Laser and plasma treatment improved fiber-to-matrix adhesion.

The very good property for parabolic vector bundles over curves

NASA Astrophysics Data System (ADS)

Soibelman, Alexander

2018-06-01

The purpose of this note is to extend Beilinson and Drinfeld's "very good" property to moduli stacks of parabolic vector bundles on curves of genuses g = 0 and g = 1. Beilinson and Drinfeld show that for g > 1 a trivial parabolic structure is sufficient for the moduli stacks to be "very good." We give a sufficient condition on the parabolic structure for this property to hold in the case of nontrivial parabolic structure.

Diffusion of myosin light chain kinase on actin: A mechanism to enhance myosin phosphorylation rates in smooth muscle.

PubMed

Hong, Feng; Brizendine, Richard K; Carter, Michael S; Alcala, Diego B; Brown, Avery E; Chattin, Amy M; Haldeman, Brian D; Walsh, Michael P; Facemyer, Kevin C; Baker, Josh E; Cremo, Christine R

2015-10-01

Smooth muscle myosin (SMM) light chain kinase (MLCK) phosphorylates SMM, thereby activating the ATPase activity required for muscle contraction. The abundance of active MLCK, which is tightly associated with the contractile apparatus, is low relative to that of SMM. SMM phosphorylation is rapid despite the low ratio of MLCK to SMM, raising the question of how one MLCK rapidly phosphorylates many SMM molecules. We used total internal reflection fluorescence microscopy to monitor single molecules of streptavidin-coated quantum dot-labeled MLCK interacting with purified actin, actin bundles, and stress fibers of smooth muscle cells. Surprisingly, MLCK and the N-terminal 75 residues of MLCK (N75) moved on actin bundles and stress fibers of smooth muscle cell cytoskeletons by a random one-dimensional (1-D) diffusion mechanism. Although diffusion of proteins along microtubules and oligonucleotides has been observed previously, this is the first characterization to our knowledge of a protein diffusing in a sustained manner along actin. By measuring the frequency of motion, we found that MLCK motion is permitted only if acto-myosin and MLCK-myosin interactions are weak. From these data, diffusion coefficients, and other kinetic and geometric considerations relating to the contractile apparatus, we suggest that 1-D diffusion of MLCK along actin (a) ensures that diffusion is not rate limiting for phosphorylation, (b) allows MLCK to locate to areas in which myosin is not yet phosphorylated, and (c) allows MLCK to avoid getting "stuck" on myosins that have already been phosphorylated. Diffusion of MLCK along actin filaments may be an important mechanism for enhancing the rate of SMM phosphorylation in smooth muscle. © 2015 Hong et al.

Coulomb explosion: a novel approach to separate single-walled carbon nanotubes from their bundle.

PubMed

Liu, Guangtong; Zhao, Yuanchun; Zheng, Kaihong; Liu, Zheng; Ma, Wenjun; Ren, Yan; Xie, Sishen; Sun, Lianfeng

2009-01-01

A novel approach based on Coulomb explosion has been developed to separate single-walled carbon nanotubes (SWNTs) from their bundle. With this technique, we can readily separate a bundle of SWNTs into smaller bundles with uniform diameter as well as some individual SWNTs. The separated SWNTs have a typical length of several microns and form a nanotree at one end of the original bundle. More importantly, this separating procedure involves no surfactant and includes only one-step physical process. The separation method offers great conveniences for the subsequent individual SWNT or multiterminal SWNTs device fabrication and their physical properties studies.

Load sharing in the growth of bundled biopolymers

PubMed Central

Wang, Ruizhe; Carlsson, A. E.

2014-01-01

To elucidate the nature of load sharing in the growth of multiple biopolymers, we perform stochastic simulations of the growth of biopolymer bundles against obstacles under a broad range of conditions and varying assumptions. The obstacle motion due to thermal fluctuations is treated explicitly. We assume the “Perfect Brownian Ratchet” (PBR) model, in which the polymerization rate equals the free-filament rate as soon as the filament-obstacle distance exceeds the monomer size. Accurate closed-form formulas are obtained for the case of a rapidly moving obstacle. We find the following: (1) load sharing is usually sub-perfect in the sense that polymerization is slower than for a single filament carrying the same average force; (2) the sub-perfect behavior becomes significant at a total force proportional to the logarithm or the square root of the number of filaments, depending on the alignment of the filaments; (3) for the special case of slow barrier diffusion and low opposing force, an enhanced obstacle velocity for an increasing number of filaments is possible; (4) the obstacle velocity is very sensitive to the alignment of the filaments in the bundle, with a staggered alignment being an order of magnitude faster than an unstaggered one at forces of only 0.5 pN per filament for 20 filaments; (5) for large numbers of filaments, the power is maximized at a force well below 1 pN per filament; (6) for intermediate values of the obstacle diffusion coefficient, the shape of the force velocity relation is very similar to that for rapid obstacle diffusion. PMID:25489273

Load sharing in the growth of bundled biopolymers.

PubMed

Wang, Ruizhe; Carlsson, A E

2014-11-01

To elucidate the nature of load sharing in the growth of multiple biopolymers, we perform stochastic simulations of the growth of biopolymer bundles against obstacles under a broad range of conditions and varying assumptions. The obstacle motion due to thermal fluctuations is treated explicitly. We assume the "Perfect Brownian Ratchet" (PBR) model, in which the polymerization rate equals the free-filament rate as soon as the filament-obstacle distance exceeds the monomer size. Accurate closed-form formulas are obtained for the case of a rapidly moving obstacle. We find the following: (1) load sharing is usually sub-perfect in the sense that polymerization is slower than for a single filament carrying the same average force; (2) the sub-perfect behavior becomes significant at a total force proportional to the logarithm or the square root of the number of filaments, depending on the alignment of the filaments; (3) for the special case of slow barrier diffusion and low opposing force, an enhanced obstacle velocity for an increasing number of filaments is possible; (4) the obstacle velocity is very sensitive to the alignment of the filaments in the bundle, with a staggered alignment being an order of magnitude faster than an unstaggered one at forces of only 0.5 pN per filament for 20 filaments; (5) for large numbers of filaments, the power is maximized at a force well below 1 pN per filament; (6) for intermediate values of the obstacle diffusion coefficient, the shape of the force velocity relation is very similar to that for rapid obstacle diffusion.

Multilayered phantoms with tunable optical properties for a better understanding of light/tissue interactions

NASA Astrophysics Data System (ADS)

Roig, Blandine; Koenig, Anne; Perraut, François; Piot, Olivier; Vignoud, Séverine; Lavaud, Jonathan; Manfait, Michel; Dinten, Jean-Marc

2015-03-01

Light/tissue interactions, like diffuse reflectance, endogenous fluorescence and Raman scattering, are a powerful means for providing skin diagnosis. Instrument calibration is an important step. We thus developed multilayered phantoms for calibration of optical systems. These phantoms mimic the optical properties of biological tissues such as skin. Our final objective is to better understand light/tissue interactions especially in the case of confocal Raman spectroscopy. The phantom preparation procedure is described, including the employed method to obtain a stratified object. PDMS was chosen as the bulk material. TiO2 was used as light scattering agent. Dye and ink were adopted to mimic, respectively, oxy-hemoglobin and melanin absorption spectra. By varying the amount of the incorporated components, we created a material with tunable optical properties. Monolayer and multilayered phantoms were designed to allow several characterization methods. Among them, we can name: X-ray tomography for structural information; Diffuse Reflectance Spectroscopy (DRS) with a homemade fibered bundle system for optical characterization; and Raman depth profiling with a commercial confocal Raman microscope for structural information and for our final objective. For each technique, the obtained results are presented and correlated when possible. A few words are said on our final objective. Raman depth profiles of the multilayered phantoms are distorted by elastic scattering. The signal attenuation through each single layer is directly dependent on its own scattering property. Therefore, determining the optical properties, obtained here with DRS, is crucial to properly correct Raman depth profiles. Thus, it would be permitted to consider quantitative studies on skin for drug permeation follow-up or hydration assessment, for instance.

Dimerization and actin-bundling properties of villin and its role in the assembly of epithelial cell brush borders.

PubMed

George, Sudeep P; Wang, Yaohong; Mathew, Sijo; Srinivasan, Kamalakkannan; Khurana, Seema

2007-09-07

Villin is a major actin-bundling protein in the brush border of epithelial cells. In this study we demonstrate for the first time that villin can bundle actin filaments using a single F-actin binding site, because it has the ability to self-associate. Using fluorescence resonance energy transfer, we demonstrate villin self-association in living cells in microvilli and in growth factor-stimulated cells in membrane ruffles and lamellipodia. Using sucrose density gradient, size-exclusion chromatography, and matrix-assisted laser desorption ionization time-of-flight, the majority of villin was identified as a monomer or dimer. Villin dimers were also identified in Caco-2 cells, which endogenously express villin and Madin-Darby canine kidney cells that ectopically express villin. Using truncation mutants of villin, site-directed mutagenesis, and fluorescence resonance energy transfer, an amino-terminal dimerization site was identified that regulated villin self-association in parallel conformation as well as actin bundling by villin. This detailed analysis describes for the first time microvillus assembly by villin, redefines the actin-bundling function of villin, and provides a molecular mechanism for actin bundling by villin, which could have wider implications for other actin cross-linking proteins that share a villin-like headpiece domain. Our study also provides a molecular basis to separate the morphologically distinct actin-severing and actin-bundling properties of villin.

Geometrical and Mechanical Properties Control Actin Filament Organization

PubMed Central

Ennomani, Hajer; Théry, Manuel; Nedelec, Francois; Blanchoin, Laurent

2015-01-01

The different actin structures governing eukaryotic cell shape and movement are not only determined by the properties of the actin filaments and associated proteins, but also by geometrical constraints. We recently demonstrated that limiting nucleation to specific regions was sufficient to obtain actin networks with different organization. To further investigate how spatially constrained actin nucleation determines the emergent actin organization, we performed detailed simulations of the actin filament system using Cytosim. We first calibrated the steric interaction between filaments, by matching, in simulations and experiments, the bundled actin organization observed with a rectangular bar of nucleating factor. We then studied the overall organization of actin filaments generated by more complex pattern geometries used experimentally. We found that the fraction of parallel versus antiparallel bundles is determined by the mechanical properties of actin filament or bundles and the efficiency of nucleation. Thus nucleation geometry, actin filaments local interactions, bundle rigidity, and nucleation efficiency are the key parameters controlling the emergent actin architecture. We finally simulated more complex nucleation patterns and performed the corresponding experiments to confirm the predictive capabilities of the model. PMID:26016478

Biological natural retting for determining the hierarchical structuration of banana fibers.

PubMed

Gañán, Piedad; Zuluaga, Robin; Velez, Juan Manuel; Mondragon, Iñaki

2004-10-20

Extraction processes of natural fibers can be performed by different procedures that include mechanical, chemical and biological methods. Each method presents different advantages or drawbacks according to the amount of fiber produced or the quality and properties of fiber bundles obtained. In this study, biological natural retting was satisfactorily used for obtaining banana fibers from plant bunches. However, the most important contribution of this work refers to the description of the hierarchical microstructural ordering present in banana fiber bundles in both bundle surface and inner region. The chemical composition of banana fiber bundles has been evaluated by FTIR spectroscopy. Through exposure time, the fiber bundle configuration presents small variations in composition. The main changes are related to hemicellulose and pectins as they conform the outer walls of the bundle. Hierarchical helicoidal ordering in the bundle surface as well as orientation on the longitudinal axis of the bundle were observed by optical microscopy (OM) and scanning electron microscopy (SEM) for 3-4 microm surface fibers and 10-15 microm inner elementary fibers, respectively. With increasing exposure time, fiber bundle walls lose integrity, as reflected in their mechanical behavior.

Dipy, a library for the analysis of diffusion MRI data.

PubMed

Garyfallidis, Eleftherios; Brett, Matthew; Amirbekian, Bagrat; Rokem, Ariel; van der Walt, Stefan; Descoteaux, Maxime; Nimmo-Smith, Ian

2014-01-01

Diffusion Imaging in Python (Dipy) is a free and open source software project for the analysis of data from diffusion magnetic resonance imaging (dMRI) experiments. dMRI is an application of MRI that can be used to measure structural features of brain white matter. Many methods have been developed to use dMRI data to model the local configuration of white matter nerve fiber bundles and infer the trajectory of bundles connecting different parts of the brain. Dipy gathers implementations of many different methods in dMRI, including: diffusion signal pre-processing; reconstruction of diffusion distributions in individual voxels; fiber tractography and fiber track post-processing, analysis and visualization. Dipy aims to provide transparent implementations for all the different steps of dMRI analysis with a uniform programming interface. We have implemented classical signal reconstruction techniques, such as the diffusion tensor model and deterministic fiber tractography. In addition, cutting edge novel reconstruction techniques are implemented, such as constrained spherical deconvolution and diffusion spectrum imaging (DSI) with deconvolution, as well as methods for probabilistic tracking and original methods for tractography clustering. Many additional utility functions are provided to calculate various statistics, informative visualizations, as well as file-handling routines to assist in the development and use of novel techniques. In contrast to many other scientific software projects, Dipy is not being developed by a single research group. Rather, it is an open project that encourages contributions from any scientist/developer through GitHub and open discussions on the project mailing list. Consequently, Dipy today has an international team of contributors, spanning seven different academic institutions in five countries and three continents, which is still growing.

Dipy, a library for the analysis of diffusion MRI data

PubMed Central

Garyfallidis, Eleftherios; Brett, Matthew; Amirbekian, Bagrat; Rokem, Ariel; van der Walt, Stefan; Descoteaux, Maxime; Nimmo-Smith, Ian

2014-01-01

Diffusion Imaging in Python (Dipy) is a free and open source software project for the analysis of data from diffusion magnetic resonance imaging (dMRI) experiments. dMRI is an application of MRI that can be used to measure structural features of brain white matter. Many methods have been developed to use dMRI data to model the local configuration of white matter nerve fiber bundles and infer the trajectory of bundles connecting different parts of the brain. Dipy gathers implementations of many different methods in dMRI, including: diffusion signal pre-processing; reconstruction of diffusion distributions in individual voxels; fiber tractography and fiber track post-processing, analysis and visualization. Dipy aims to provide transparent implementations for all the different steps of dMRI analysis with a uniform programming interface. We have implemented classical signal reconstruction techniques, such as the diffusion tensor model and deterministic fiber tractography. In addition, cutting edge novel reconstruction techniques are implemented, such as constrained spherical deconvolution and diffusion spectrum imaging (DSI) with deconvolution, as well as methods for probabilistic tracking and original methods for tractography clustering. Many additional utility functions are provided to calculate various statistics, informative visualizations, as well as file-handling routines to assist in the development and use of novel techniques. In contrast to many other scientific software projects, Dipy is not being developed by a single research group. Rather, it is an open project that encourages contributions from any scientist/developer through GitHub and open discussions on the project mailing list. Consequently, Dipy today has an international team of contributors, spanning seven different academic institutions in five countries and three continents, which is still growing. PMID:24600385

Delay Discounting and Frontostriatal Fiber Tracts: A Combined DTI and MTR Study on Impulsive Choices in Healthy Young Adults

PubMed Central

Peper, Jiska S.; Mandl, René C.W.; Braams, Barbara R.; de Water, Erik; Heijboer, Annemieke C.; Koolschijn, P. Cédric M.P.; Crone, Eveline A.

2013-01-01

Delay discounting, a measure of impulsive choice, has been associated with decreased control of the prefrontal cortex over striatum responses. The anatomical connectivity between both brain regions in delaying gratification remains unknown. Here, we investigate whether the quality of frontostriatal (FS) white matter tracts can predict individual differences in delay-discounting behavior. We use tract-based diffusion tensor imaging and magnetization transfer imaging to measure the microstructural properties of FS fiber tracts in 40 healthy young adults (from 18 to 25 years). We additionally explored whether internal sex hormone levels affect the integrity of FS tracts, based on the hypothesis that sex hormones modulate axonal density within prefrontal dopaminergic circuits. We calculated fractional anisotropy (FA), mean diffusivity (MD), longitudinal diffusivity, radial diffusivity (RD), and magnetization transfer ratio (MTR), a putative measure of myelination, for the FS tract. Results showed that lower integrity within the FS tract (higher MD and RD and lower FA), predicts faster discounting in both sexes. MTR was unrelated to delay-discounting performance. In addition, testosterone levels in males were associated with a lower integrity (higher RD) within the FS tract. Our study provides support for the hypothesis that enhanced structural integrity of white matter fiber bundles between prefrontal and striatal brain areas is associated with better impulse control. PMID:22693341

From single muscle fiber to whole muscle mechanics: a finite element model of a muscle bundle with fast and slow fibers.

PubMed

Marcucci, Lorenzo; Reggiani, Carlo; Natali, Arturo N; Pavan, Piero G

2017-12-01

Muscles exhibit highly complex, multi-scale architecture with thousands of muscle fibers, each with different properties, interacting with each other and surrounding connective structures. Consequently, the results of single-fiber experiments are scarcely linked to the macroscopic or whole muscle behavior. This is especially true for human muscles where it would be important to understand of how skeletal muscles disorders affect patients' life. In this work, we developed a mathematical model to study how fast and slow muscle fibers, well characterized in single-fiber experiments, work and generate together force and displacement in muscle bundles. We characterized the parameters of a Hill-type model, using experimental data on fast and slow single human muscle fibers, and comparing experimental data with numerical simulations obtained from finite element (FE) models of single fibers. Then, we developed a FE model of a bundle of 19 fibers, based on an immunohistochemically stained cross section of human diaphragm and including the corresponding properties of each slow or fast fiber. Simulations of isotonic contractions of the bundle model allowed the generation of its apparent force-velocity relationship. Although close to the average of the force-velocity curves of fast and slow fibers, the bundle curve deviates substantially toward the fast fibers at low loads. We believe that the present model and the characterization of the force-velocity curve of a fiber bundle represents the starting point to link the single-fiber properties to those of whole muscle with FE application in phenomenological models of human muscles.

Efficient global fiber tracking on multi-dimensional diffusion direction maps

NASA Astrophysics Data System (ADS)

Klein, Jan; Köhler, Benjamin; Hahn, Horst K.

2012-02-01

Global fiber tracking algorithms have recently been proposed which were able to compute results of unprecedented quality. They account for avoiding accumulation errors by a global optimization process at the cost of a high computation time of several hours or even days. In this paper, we introduce a novel global fiber tracking algorithm which, for the first time, globally optimizes the underlying diffusion direction map obtained from DTI or HARDI data, instead of single fiber segments. As a consequence, the number of iterations in the optimization process can drastically be reduced by about three orders of magnitude. Furthermore, in contrast to all previous algorithms, the density of the tracked fibers can be adjusted after the optimization within a few seconds. We evaluated our method for diffusion-weighted images obtained from software phantoms, healthy volunteers, and tumor patients. We show that difficult fiber bundles, e.g., the visual pathways or tracts for different motor functions can be determined and separated in an excellent quality. Furthermore, crossing and kissing bundles are correctly resolved. On current standard hardware, a dense fiber tracking result of a whole brain can be determined in less than half an hour which is a strong improvement compared to previous work.

Thermodynamic properties Ar films on the surface of a bundle of carbon nanotubes

NASA Astrophysics Data System (ADS)

Cole, Milton; Gatica, Silvina

2005-03-01

We employ canonical Monte Carlo simulations to explore the properties of an Argon film adsorbed on the external surface of a bundle of carbon nanotubes. The study is concerned primarily with three properties: specific heat, differential heat of adsorption, and Ar-Ar correlation functions. These measurable functions exhibit information about the dependence of film structure on coverage and temperature. Our results are intended to stimulate further experimental studies of this system and analogous systems involving other gases on nanotube bundles. One of the more interesting general results is that the specific heat is typically larger than might have been expected. Particularly remarkable outcome from the correlation function studies include the reduced longitudinal correlations in the groove and striped phases as T rises above 60 K. These results would be amenable to testing by diffraction experiments.

Automated retinofugal visual pathway reconstruction with multi-shell HARDI and FOD-based analysis.

PubMed

Kammen, Alexandra; Law, Meng; Tjan, Bosco S; Toga, Arthur W; Shi, Yonggang

2016-01-15

Diffusion MRI tractography provides a non-invasive modality to examine the human retinofugal projection, which consists of the optic nerves, optic chiasm, optic tracts, the lateral geniculate nuclei (LGN) and the optic radiations. However, the pathway has several anatomic features that make it particularly challenging to study with tractography, including its location near blood vessels and bone-air interface at the base of the cerebrum, crossing fibers at the chiasm, somewhat-tortuous course around the temporal horn via Meyer's Loop, and multiple closely neighboring fiber bundles. To date, these unique complexities of the visual pathway have impeded the development of a robust and automated reconstruction method using tractography. To overcome these challenges, we develop a novel, fully automated system to reconstruct the retinofugal visual pathway from high-resolution diffusion imaging data. Using multi-shell, high angular resolution diffusion imaging (HARDI) data, we reconstruct precise fiber orientation distributions (FODs) with high order spherical harmonics (SPHARM) to resolve fiber crossings, which allows the tractography algorithm to successfully navigate the complicated anatomy surrounding the retinofugal pathway. We also develop automated algorithms for the identification of ROIs used for fiber bundle reconstruction. In particular, we develop a novel approach to extract the LGN region of interest (ROI) based on intrinsic shape analysis of a fiber bundle computed from a seed region at the optic chiasm to a target at the primary visual cortex. By combining automatically identified ROIs and FOD-based tractography, we obtain a fully automated system to compute the main components of the retinofugal pathway, including the optic tract and the optic radiation. We apply our method to the multi-shell HARDI data of 215 subjects from the Human Connectome Project (HCP). Through comparisons with post-mortem dissection measurements, we demonstrate the retinotopic organization of the optic radiation including a successful reconstruction of Meyer's loop. Then, using the reconstructed optic radiation bundle from the HCP cohort, we construct a probabilistic atlas and demonstrate its consistency with a post-mortem atlas. Finally, we generate a shape-based representation of the optic radiation for morphometry analysis. Copyright © 2015 Elsevier Inc. All rights reserved.

The improvement of wave-absorbing ability of silicon carbide fibers by depositing boron nitride coating

NASA Astrophysics Data System (ADS)

Ye, Fang; Zhang, Litong; Yin, Xiaowei; Liu, Yongsheng; Cheng, Laifei

2013-04-01

This work investigated electromagnetic wave (EMW) absorption and mechanical properties of silicon carbide (SiC) fibers with and without boron nitride (BN) coating by chemical vapor infiltration (CVI). The dielectric property and EM shielding effectiveness of SiC fiber bundles before and after being coated by BN were measured by wave guide method. The EM reflection coefficient of SiC fiber laminates with and without BN coating was determined by model calculation and NRL-arc method, respectively. Tensile properties of SiC fiber bundles with and without BN coating were tested at room temperature. Results show that SiC fibers with BN coating had a great improvement of EMW absorbing property because the composites achieved the impedance matching. BN with the low permittivity and dielectric loss contributed to the enhancive introduction and reduced reflection of EMW. The tensile strength and Weibull modulus of SiC fiber bundles coated by BN increased owing to the decrease of defects in SiC fibers and the protection of coating during loading.

Nanomechanics of Pectin-Linked β-Lactoglobulin Nanofibril Bundles.

PubMed

Loveday, Simon M; Gunning, A Patrick

2018-06-14

Nanofibrils of β-lactoglobulin can be assembled into bundles by site-specific noncovalent cross-linking with high-methoxyl pectin (Hettiarachchi et al. Soft Matter 2016, 12, 756). Here we characterized the nanomechanical properties of bundles using atomic force microscopy and force spectroscopy. Bundles had Gaussian cross sections and a mean height of 17.4 ± 1.4 nm. Persistence lengths were calculated using image analysis with the mean-squared end-to-end model. The relationship between the persistence length and the thickness had exponents of 1.69-2.30, which is consistent with previous reports for other fibril types. In force spectroscopy experiments, the bundles stretched in a qualitatively different manner to fibrils, and some of the force curves were consistent with peeling fibrils away from bundles. The flexibility of pectin-linked nanofibril bundles is likely to be tunable by modulating the stiffness and length of fibrils and the ratio of pectin to fibrils, giving rise to a wide range of structures and functionalities.

From Cell Differentiation to Cell Collectives: Bacillus subtilis Uses Division of Labor to Migrate

PubMed Central

van Gestel, Jordi; Vlamakis, Hera; Kolter, Roberto

2015-01-01

The organization of cells, emerging from cell–cell interactions, can give rise to collective properties. These properties are adaptive when together cells can face environmental challenges that they separately cannot. One particular challenge that is important for microorganisms is migration. In this study, we show how flagellum-independent migration is driven by the division of labor of two cell types that appear during Bacillus subtilis sliding motility. Cell collectives organize themselves into bundles (called “van Gogh bundles”) of tightly aligned cell chains that form filamentous loops at the colony edge. We show, by time-course microscopy, that these loops migrate by pushing themselves away from the colony. The formation of van Gogh bundles depends critically on the synergistic interaction of surfactin-producing and matrix-producing cells. We propose that surfactin-producing cells reduce the friction between cells and their substrate, thereby facilitating matrix-producing cells to form bundles. The folding properties of these bundles determine the rate of colony expansion. Our study illustrates how the simple organization of cells within a community can yield a strong ecological advantage. This is a key factor underlying the diverse origins of multicellularity. PMID:25894589

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.

N-acetyl-aspartate levels correlate with intra-axonal compartment parameters from diffusion MRI.

PubMed

Grossman, Elan J; Kirov, Ivan I; Gonen, Oded; Novikov, Dmitry S; Davitz, Matthew S; Lui, Yvonne W; Grossman, Robert I; Inglese, Matilde; Fieremans, Els

2015-09-01

Diffusion MRI combined with biophysical modeling allows for the description of a white matter (WM) fiber bundle in terms of compartment specific white matter tract integrity (WMTI) metrics, which include intra-axonal diffusivity (Daxon), extra-axonal axial diffusivity (De||), extra-axonal radial diffusivity (De┴), axonal water fraction (AWF), and tortuosity (α) of extra-axonal space. Here we derive these parameters from diffusion kurtosis imaging to examine their relationship to concentrations of global WM N-acetyl-aspartate (NAA), creatine (Cr), choline (Cho) and myo-Inositol (mI), as measured with proton MR spectroscopy ((1)H-MRS), in a cohort of 25 patients with mild traumatic brain injury (MTBI). We found statistically significant (p<0.05) positive correlations between NAA and Daxon, AWF, α, and fractional anisotropy; negative correlations between NAA and De,┴ and the overall radial diffusivity (D┴). These correlations were supported by similar findings in regional analysis of the genu and splenium of the corpus callosum. Furthermore, a positive correlation in global WM was noted between Daxon and Cr, as well as a positive correlation between De|| and Cho, and a positive trend between De|| and mI. The specific correlations between NAA, an endogenous probe of the neuronal intracellular space, and WMTI metrics related to the intra-axonal space, combined with the specific correlations of De|| with mI and Cho, both predominantly present extra-axonally, corroborate the overarching assumption of many advanced modeling approaches that diffusion imaging can disentangle between the intra- and extra-axonal compartments in WM fiber bundles. Our findings are also generally consistent with what is known about the pathophysiology of MTBI, which appears to involve both intra-axonal injury (as reflected by a positive trend between NAA and Daxon) as well as axonal shrinkage, demyelination, degeneration, and/or loss (as reflected by correlations between NAA and De┴, AWF, and α). Copyright © 2015 Elsevier Inc. All rights reserved.

Nanostructured Composites: Effective Mechanical Property Determination of Nanotube Bundles

NASA Technical Reports Server (NTRS)

Saether, E.; Pipes, R. B.; Frankland, S. J. V.

2002-01-01

Carbon nanotubes naturally tend to form crystals in the form of hexagonally packed bundles or ropes that should exhibit a transversely isotropic constitutive behavior. Although the intratube axial stiffness is on the order of 1 TPa due to a strong network of delocalized bonds, the intertube cohesive strength is orders of magnitude less controlled by weak, nonbonding van der Waals interactions. An accurate determination of the effective mechanical properties of nanotube bundles is important to assess potential structural applications such as reinforcement in future composite material systems. A direct method for calculating effective material constants is developed in the present study. The Lennard-Jones potential is used to model the nonbonding cohesive forces. A complete set of transverse moduli are obtained and compared with existing data.

Mode-field adapter for tapered-fiber-bundle signal and pump combiners.

PubMed

Koška, Pavel; Baravets, Yauhen; Peterka, Pavel; Bohata, Jan; Písařík, Michael

2015-02-01

We report on a novel mode-field adapter that is proposed to be incorporated inside tapered fused-fiber-bundle pump and signal combiners for high-power double-clad fiber lasers. Such an adapter allows optimization of signal-mode-field matching on the input and output fibers. Correspondingly, losses of the combiner signal branch are significantly reduced. The mode-field adapter optimization procedure is demonstrated on a combiner based on commercially available fibers. Signal wavelengths of 1.55 and 2 μm are considered. The losses can be further improved by using specially designed intermediate fiber and by dopant diffusion during splicing as confirmed by preliminary experimental results.

Molecular dynamics calculations suggest a conduction mechanism for the M2 proton channel from influenza A virus

PubMed Central

Khurana, Ekta; Peraro, Matteo Dal; DeVane, Russell; Vemparala, Satyavani; DeGrado, William F.; Klein, Michael L.

2009-01-01

The M2 protein of the influenza A virus is activated by low endosomal pH and performs the essential function of proton transfer into the viral interior. The resulting decrease in pH within the virion is essential for the uncoating and further replication of the viral genetic material. The x-ray crystal [Stouffer AL, et al. (2008) Nature 451:596–599] and solution NMR [Schnell JR, Chou JJ (2008) Nature 451:591–595] structures of the transmembrane region of the M2 homo-tetrameric bundle both revealed pores with narrow constrictions at one end, leaving a question as to how protons enter the channel. His-37, which is essential for proton-gating and selective conduction of protons, lies in the pore of the crystallographic and NMR structures. Here, we explore the different protonation states of the His-37 residues of the M2 bundle in a bilayer using molecular dynamics (MD) simulations. When the His-37 residues are neutral, the protein prefers an Openout-Closedin conformation in which the channel is open to the environment on the outside of the virus but closed to the interior environment of the virus. Diffusion of protons into the channel from the outside of the virus and protonation of His-37 residues in the tetramer stabilizes an oppositely gated Closedout-Openin conformation. Thus, protons might be conducted through a transporter-like mechanism, in which the protein alternates between Openout-Closedin and Closedout-Openin conformations, and His-37 is protonated/deprotonated during each turnover. The transporter-like mechanism is consistent with the known properties of the M2 bundle, including its relatively low rate of proton flux and its strong rectifying behavior. PMID:19144924

Ab initio density functional theory investigation of crystalline bundles of polygonized single-walled silicon carbide nanotubes

NASA Astrophysics Data System (ADS)

Moradian, Rostam; Behzad, Somayeh; Chegel, Raad

2008-11-01

By using ab initio density functional theory, the structural characterizations and electronic properties of two large-diameter (13, 13) and (14, 14) armchair silicon carbide nanotube (SiCNT) bundles are investigated. Full structural optimizations show that the cross sections of these large-diameter SiCNTs in the bundles have a nearly hexagonal shape. The effects of inter-tube coupling on the electronic dispersions of large-diameter SiCNT bundles are demonstrated. By comparing the band structures of the triangular lattices of (14, 14) SiCNTs with nearly hexagonal and circular cross sections we found that the polygonization of the tubes in the bundle leads to a further dispersion of the occupied bands and an increase in the bandgap by 0.18 eV.

Ab initio density functional theory investigation of crystalline bundles of polygonized single-walled silicon carbide nanotubes.

PubMed

Moradian, Rostam; Behzad, Somayeh; Chegel, Raad

2008-11-19

By using ab initio density functional theory, the structural characterizations and electronic properties of two large-diameter (13, 13) and (14, 14) armchair silicon carbide nanotube (SiCNT) bundles are investigated. Full structural optimizations show that the cross sections of these large-diameter SiCNTs in the bundles have a nearly hexagonal shape. The effects of inter-tube coupling on the electronic dispersions of large-diameter SiCNT bundles are demonstrated. By comparing the band structures of the triangular lattices of (14, 14) SiCNTs with nearly hexagonal and circular cross sections we found that the polygonization of the tubes in the bundle leads to a further dispersion of the occupied bands and an increase in the bandgap by 0.18 eV.

Contribution of actin filaments to the global compressive properties of fibroblasts.

PubMed

Ujihara, Yoshihiro; Nakamura, Masanori; Miyazaki, Hiroshi; Wada, Shigeo

2012-10-01

Actin filaments are often regarded as tension-bearing components. Here, we examined the effects of actin filaments on global compressive properties of cells experimentally and numerically. Fibroblasts were harvested from the patellar tendon of a mature Japanese white rabbit and treated with cytochalasin D to depolymerize the actin filaments. Intact cells and cells with disrupted actin filaments were subjected to the compressive tests. Each floating cell was held between the cantilever and compressive plates and compressed by moving the compressive plate with a linear actuator to obtain a load-deformation curve under quasi-static conditions. The experimental results demonstrated that the initial stiffness of a cell with disrupted actin filaments decreased by 51%. After the experiments, we simulated the compressive test of cells with/without bundles of actin filaments. A bundle of actin filaments was modeled as a tension-bearing component that generates a force based on Hooke's law only when it was elongated. By contrast, if it was shortened, it was assumed to exert no force. The computational results revealed that the alignment of bundles of actin filaments significantly affected the cell stiffness. In addition, the passive reorientation of bundles of actin filaments perpendicular to the compression induced an increase in the resistance to the vertical elongation of a cell and thereby increased the cell stiffness. These results clearly indicated that bundles of actin filaments contribute to the compressive properties of a cell, even if they are tension-bearing components. Copyright © 2012 Elsevier Ltd. All rights reserved.

Method of bundling rods so as to form an optical fiber preform

DOEpatents

Kliner, Dahv A. V. [San Ramon, CA; Koplow, Jeffery P [Washington, DC

2004-03-30

The present invention provides a simple method for fabricating fiber-optic glass preforms having complex refractive index configurations and/or dopant distributions in a radial direction with a high degree of accuracy and precision. The method teaches bundling together a plurality of glass rods of specific physical, chemical, or optical properties and wherein the rod bundle is fused in a manner that maintains the cross-sectional composition and refractive-index profiles established by the position of the rods.

Negative hair-bundle stiffness betrays a mechanism for mechanical amplification by the hair cell.

PubMed

Martin, P; Mehta, A D; Hudspeth, A J

2000-10-24

Hearing and balance rely on the ability of hair cells in the inner ear to sense miniscule mechanical stimuli. In each cell, sound or acceleration deflects the mechanosensitive hair bundle, a tuft of rigid stereocilia protruding from the cell's apical surface. By altering the tension in gating springs linked to mechanically sensitive transduction channels, this deflection changes the channels' open probability and elicits an electrical response. To detect weak stimuli despite energy losses caused by viscous dissipation, a hair cell can use active hair-bundle movement to amplify its mechanical inputs. This amplificatory process also yields spontaneous bundle oscillations. Using a displacement-clamp system to measure the mechanical properties of individual hair bundles from the bullfrog's ear, we found that an oscillatory bundle displays negative slope stiffness at the heart of its region of mechanosensitivity. Offsetting the hair bundle's position activates an adaptation process that shifts the region of negative stiffness along the displacement axis. Modeling indicates that the interplay between negative bundle stiffness and the motor responsible for mechanical adaptation produces bundle oscillation similar to that observed. Just as the negative resistance of electrically excitable cells and of tunnel diodes can be embedded in a biasing circuit to amplify electrical signals, negative stiffness can be harnessed to amplify mechanical stimuli in the ear.

Monoubiquitination Inhibits the Actin Bundling Activity of Fascin*

PubMed Central

Lin, Shengchen; Lu, Shuang; Mulaj, Mentor; Fang, Bin; Keeley, Tyler; Wan, Lixin; Hao, Jihui; Muschol, Martin; Sun, Jianwei; Yang, Shengyu

2016-01-01

Fascin is an actin bundling protein that cross-links individual actin filaments into straight, compact, and stiff bundles, which are crucial for the formation of filopodia, stereocillia, and other finger-like membrane protrusions. The dysregulation of fascin has been implicated in cancer metastasis, hearing loss, and blindness. Here we identified monoubiquitination as a novel mechanism that regulates fascin bundling activity and dynamics. The monoubiquitination sites were identified to be Lys247 and Lys250, two residues located in a positive charge patch at the actin binding site 2 of fascin. Using a chemical ubiquitination method, we synthesized chemically monoubiquitinated fascin and determined the effects of monoubiquitination on fascin bundling activity and dynamics. Our data demonstrated that monoubiquitination decreased the fascin bundling EC50, delayed the initiation of bundle assembly, and accelerated the disassembly of existing bundles. By analyzing the electrostatic properties on the solvent-accessible surface of fascin, we proposed that monoubiquitination introduced steric hindrance to interfere with the interaction between actin filaments and the positively charged patch at actin binding site 2. We also identified Smurf1 as a E3 ligase regulating the monoubiquitination of fascin. Our findings revealed a previously unidentified regulatory mechanism for fascin, which will have important implications for the understanding of actin bundle regulation under physiological and pathological conditions. PMID:27879315

Steady-state stiffness of utricular hair cells depends on macular location and hair bundle structure.

PubMed

Spoon, Corrie; Moravec, W J; Rowe, M H; Grant, J W; Peterson, E H

2011-12-01

Spatial and temporal properties of head movement are encoded by vestibular hair cells in the inner ear. One of the most striking features of these receptors is the orderly structural variation in their mechanoreceptive hair bundles, but the functional significance of this diversity is poorly understood. We tested the hypothesis that hair bundle structure is a significant contributor to hair bundle mechanics by comparing structure and steady-state stiffness of 73 hair bundles at varying locations on the utricular macula. Our first major finding is that stiffness of utricular hair bundles varies systematically with macular locus. Stiffness values are highest in the striola, near the line of hair bundle polarity reversal, and decline exponentially toward the medial extrastriola. Striolar bundles are significantly more stiff than those in medial (median: 8.9 μN/m) and lateral (2.0 μN/m) extrastriolae. Within the striola, bundle stiffness is greatest in zone 2 (106.4 μN/m), a band of type II hair cells, and significantly less in zone 3 (30.6 μN/m), which contains the only type I hair cells in the macula. Bathing bundles in media that break interciliary links produced changes in bundle stiffness with predictable time course and magnitude, suggesting that links were intact in our standard media and contributed normally to bundle stiffness during measurements. Our second major finding is that bundle structure is a significant predictor of steady-state stiffness: the heights of kinocilia and the tallest stereocilia are the most important determinants of bundle stiffness. Our results suggest 1) a functional interpretation of bundle height variability in vertebrate vestibular organs, 2) a role for the striola in detecting onset of head movement, and 3) the hypothesis that differences in bundle stiffness contribute to diversity in afferent response dynamics.

Steady-state stiffness of utricular hair cells depends on macular location and hair bundle structure

PubMed Central

Spoon, Corrie; Moravec, W. J.; Rowe, M. H.; Grant, J. W.

2011-01-01

Spatial and temporal properties of head movement are encoded by vestibular hair cells in the inner ear. One of the most striking features of these receptors is the orderly structural variation in their mechanoreceptive hair bundles, but the functional significance of this diversity is poorly understood. We tested the hypothesis that hair bundle structure is a significant contributor to hair bundle mechanics by comparing structure and steady-state stiffness of 73 hair bundles at varying locations on the utricular macula. Our first major finding is that stiffness of utricular hair bundles varies systematically with macular locus. Stiffness values are highest in the striola, near the line of hair bundle polarity reversal, and decline exponentially toward the medial extrastriola. Striolar bundles are significantly more stiff than those in medial (median: 8.9 μN/m) and lateral (2.0 μN/m) extrastriolae. Within the striola, bundle stiffness is greatest in zone 2 (106.4 μN/m), a band of type II hair cells, and significantly less in zone 3 (30.6 μN/m), which contains the only type I hair cells in the macula. Bathing bundles in media that break interciliary links produced changes in bundle stiffness with predictable time course and magnitude, suggesting that links were intact in our standard media and contributed normally to bundle stiffness during measurements. Our second major finding is that bundle structure is a significant predictor of steady-state stiffness: the heights of kinocilia and the tallest stereocilia are the most important determinants of bundle stiffness. Our results suggest 1) a functional interpretation of bundle height variability in vertebrate vestibular organs, 2) a role for the striola in detecting onset of head movement, and 3) the hypothesis that differences in bundle stiffness contribute to diversity in afferent response dynamics. PMID:21918003

Increased dermal collagen bundle alignment in systemic sclerosis is associated with a cell migration signature and role of Arhgdib in directed fibroblast migration on aligned ECMs

PubMed Central

Lafyatis, Robert; Burkly, Linda C.

2017-01-01

Systemic sclerosis (SSc) is a devastating disease affecting the skin and internal organs. Dermal fibrosis manifests early and Modified Rodnan Skin Scores (MRSS) correlate with disease progression. Transcriptomics of SSc skin biopsies suggest the role of the in vivo microenvironment in maintaining the pathological myofibroblasts. Therefore, defining the structural changes in dermal collagen in SSc patients could inform our understanding of fibrosis pathogenesis. Here, we report a method for quantitative whole-slide image analysis of dermal collagen from SSc patients, and our findings of more aligned dermal collagen bundles in diffuse cutaneous SSc (dcSSc) patients. Using the bleomycin-induced mouse model of SSc, we identified a distinct high dermal collagen bundle alignment gene signature, characterized by a concerted upregulation in cell migration, adhesion, and guidance pathways, and downregulation of spindle, replication, and cytokinesis pathways. Furthermore, increased bundle alignment induced a cell migration gene signature in fibroblasts in vitro, and these cells demonstrated increased directed migration on aligned ECM fibers that is dependent on expression of Arhgdib (Rho GDP-dissociation inhibitor 2). Our results indicate that increased cell migration is a cellular response to the increased collagen bundle alignment featured in fibrotic skin. Moreover, many of the cell migration genes identified in our study are shared with human SSc skin and may be new targets for therapeutic intervention. PMID:28662216

Ag-Modified In2O3/ZnO Nanobundles with High Formaldehyde Gas-Sensing Performance

PubMed Central

Fang, Fang; Bai, Lu; Song, Dongsheng; Yang, Hongping; Sun, Xiaoming; Sun, Hongyu; Zhu, Jing

2015-01-01

Ag-modified In2O3/ZnO bundles with micro/nano porous structures have been designed and synthesized with by hydrothermal method continuing with dehydration process. Each bundle consists of nanoparticles, where nanogaps of 10–30 nm are present between the nanoparticles, leading to a porous structure. This porous structure brings high surface area and fast gas diffusion, enhancing the gas sensitivity. Consequently, the HCHO gas-sensing performance of the Ag-modified In2O3/ZnO bundles have been tested, with the formaldehyde-detection limit of 100 ppb (parts per billion) and the response and recover times as short as 6 s and 3 s, respectively, at 300 °C and the detection limit of 100 ppb, response time of 12 s and recover times of 6 s at 100 °C. The HCHO sensing detect limitation matches the health standard limitation on the concentration of formaldehyde for indoor air. Moreover, the strategy to synthesize the nanobundles is just two-step heating and easy to scale up. Therefore, the Ag-modified In2O3/ZnO bundles are ready for industrialization and practical applications. PMID:26287205

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

Wen, Zhigang, E-mail: xh168688@126.com; State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083; Department of Chemistry and Chemical Engineering, Qiannan Normal College for Nationalities, Duyun 558000

SnO{sub 2} nanorod bundles were synthesized by hydrothermal method. Field-emission scanning electron microscopy and transmission electron microscopy images showed that the as-prepared flowerlike SnO{sub 2} nanorod bundles consist of tetragonal nanorods with size readily tunable. Their electrochemical properties and application as anode for lithium-ion battery were evaluated by galvanostatic discharge–charge testing and cycle voltammetry. SnO{sub 2} nanorod flowers possess improved discharge capacity of 694 mA h g{sup −1} up to 40th cycle at 0.1 C. - Highlights: ► The flowerlike SnO{sub 2} nanorod bundles were synthesized by hydrothermal method. ► SnO{sub 2} nanorod bundles with tunable size by controlling concentrationmore » of SnCl{sub 4}. ► A probable formation mechanism of SnO{sub 2} nanorod bundles has been proposed.« less

Gross, Arthroscopic, and Radiographic Anatomies of the Anterior Cruciate Ligament: Foundations for Anterior Cruciate Ligament Surgery.

PubMed

Irarrázaval, Sebastián; Albers, Marcio; Chao, Tom; Fu, Freddie H

2017-01-01

The anterior cruciate ligament (ACL) is one of the more studied structures in the knee joint. It is not a tubular structure, but is much narrower in its midsubstance and broader at its ends, producing an hourglass shape. The ACL is composed of 2 functional bundles, the anteromedial and posterolateral bundles, that are named for their location of insertion on the anterior surface of the tibial plateau. Although the relative contribution in terms of total cross-sectional area of the ACL has been noted to be equal in regards to each bundle, dynamically these bundles demonstrate different properties for knee function. Copyright © 2016 Elsevier Inc. All rights reserved.

Improvements to Wire Bundle Thermal Modeling for Ampacity Determination

NASA Technical Reports Server (NTRS)

Rickman, Steve L.; Iannello, Christopher J.; Shariff, Khadijah

2017-01-01

Determining current carrying capacity (ampacity) of wire bundles in aerospace vehicles is critical not only to safety but also to efficient design. Published standards provide guidance on determining wire bundle ampacity but offer little flexibility for configurations where wire bundles of mixed gauges and currents are employed with varying external insulation jacket surface properties. Thermal modeling has been employed in an attempt to develop techniques to assist in ampacity determination for these complex configurations. Previous developments allowed analysis of wire bundle configurations but was constrained to configurations comprised of less than 50 elements. Additionally, for vacuum analyses, configurations with very low emittance external jackets suffered from numerical instability in the solution. A new thermal modeler is presented allowing for larger configurations and is not constrained for low bundle infrared emissivity calculations. Formulation of key internal radiation and interface conductance parameters is discussed including the effects of temperature and air pressure on wire to wire thermal conductance. Test cases comparing model-predicted ampacity and that calculated from standards documents are presented.

Stiff muscle fibers in calf muscles of patients with cerebral palsy lead to high passive muscle stiffness.

PubMed

Mathewson, Margie A; Chambers, Henry G; Girard, Paul J; Tenenhaus, Mayer; Schwartz, Alexandra K; Lieber, Richard L

2014-12-01

Cerebral palsy (CP), caused by an injury to the developing brain, can lead to alterations in muscle function. Subsequently, increased muscle stiffness and decreased joint range of motion are often seen in patients with CP. We examined mechanical and biochemical properties of the gastrocnemius and soleus muscles, which are involved in equinus muscle contracture. Passive mechanical testing of single muscle fibers from gastrocnemius and soleus muscle of patients with CP undergoing surgery for equinus deformity showed a significant increase in fiber stiffness (p<0.01). Bundles of fibers that included their surrounding connective tissues showed no stiffness difference (p=0.28).). When in vivo sarcomere lengths were measured and fiber and bundle stiffness compared at these lengths, both fibers and bundles of patients with CP were predicted to be much stiffer in vivo compared to typically developing (TD) individuals. Interestingly, differences in fiber and bundle stiffness were not explained by typical biochemical measures such as titin molecular weight (a giant protein thought to impact fiber stiffness) or collagen content (a proxy for extracellular matrix amount). We suggest that the passive mechanical properties of fibers and bundles are thus poorly understood. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Impaired diffusion tensor imaging findings in the corpus callosum and cingulum may underlie impaired learning and memory abilities in systemic lupus erythematosus.

PubMed

Shapira-Lichter, I; Weinstein, M; Lustgarten, N; Ash, E; Litinsky, I; Aloush, V; Anouk, M; Caspi, D; Hendler, T; Paran, D

2016-10-01

Memory impairment is prevalent in systemic lupus erythematosus (SLE); however, its pathogenesis is unknown. In a previous functional magnetic resonance imaging (fMRI) study we demonstrated altered brain activity dynamics and less brain deactivation in patients with SLE as compared with healthy controls, when performing a learning and memory task. Our findings localized this impairment to the default mode network (DMN), and particularly to its anterior medial prefrontal cortex node. In addition, altered networking of the hippocampal subsystem of the DMN was seen in patients with SLE when performing this task, as well as atrophy of the left hippocampus. The present study aimed to search for a structural substrate for the altered recruitment pattern observed in fMRI studies using diffusion tensor imaging (DTI). Using DTI, we characterized brain diffusivity in 10 patients with SLE and nine healthy controls. Two tracts associated with the DMN were reconstructed: the corpus callosum (CC) and the cingulum bundle. The CC was segmented according to the Witelson segmentation scheme and the cingulum was segmented into superior and descending bundles. A significant increase in mean diffusivity (MD) was seen in patients with SLE without neuropsychiatric SLE (NPSLE) as compared with healthy controls in all five segments of the CC (segment 1: p = 0.043; segment 2: p = 0.005; segment 3: p = 0.003; segment 4: p = 0.012; segment 5: p = 0.023) as well as in the descending portion of the left cingulum bundle (p = 0.026). Increased MD values in the CC and the left cingulum may indicate impaired organization/reduced integrity of these tracts, which may underlie the abnormal pattern of brain activity recruitment of the DMN observed during a verbal learning and memory task. Taking into account the central role of the left hippocampus in verbal memory, the abnormal integrity of the left cingulum may contribute to the reduced performance of patients with SLE on verbal memory tasks. © The Author(s) 2016.

Brill-Noether theory for vector bundles on projective curves

NASA Astrophysics Data System (ADS)

Ballico, E.

1998-11-01

In this paper we will study the Brill-Noether theory of vector bundles on a smooth projective curve X. As usual in papers on this topic we are mainly interested in stable or at least semistable bundles. Let Wkr, d(X) be the scheme of all stable vector bundles E on X with rank (E)=r, deg (E)=d and h0(X, E)[gt-or-equal, slanted]k+1. For a survey of the main known results, see the introduction of [6]. The referee has pointed out that the results in [6] were improved by V. Mercat in [14]; he proved that Wkr, d(X) is non-empty for d<2r if and only if k+1[less-than-or-eq, slant]r+(d[minus sign]r)/g. If X has general moduli the more interesting existence theorem was proved in [19]. However, in this paper we are mainly interested in very special curves X, e.g. the hyperelliptic or the bielliptic curves. We work over an algebraically closed base field K. In Section 5 we will assume char (K)=0. In Section 1 we will give some theorems of Clifford's type. In Section 2 we will construct several stable bundles with certain properties. Here the main tool is an operation (the +elementary transformation) which sends a vector bundle E on X to another vector bundle E[prime prime or minute] with rank (E[prime prime or minute])=rank (E) and deg (E[prime prime or minute])=deg (E)+1 (see Section 2 for its definition and its elementary properties). Using the +elementary transformations in Section 3 we will prove the following existence theorem which covers the case of a ‘small’ number of sections.

Biomechanics of selected arborescent and shrubby monocotyledons

PubMed Central

Haushahn, Tobias; Fink, Samuel; Speck, Thomas

2016-01-01

Main aims of the study are a deepened understanding of the mechanically relevant (ultra-)structures and the mechanical behaviour of various arborescent and shrubby monocotyledons and obtaining the structure–function relationships of different structurally conspicuous parts in Dracaena marginata stems. The stems of five different “woody” monocotyledon species were dissected and the mechanical properties of the most noticeable tissues in the five monocotyledons and, additionally, of individual vascular bundles in D. marginata, were tested under tensile stress. Results for Young’s moduli and density of these tissues were assessed as well as the area, critical strain, Young’s modulus and tensile strength of the vascular bundles in Dracaena marginata. These analyses allowed for generating a model for the mechanical interaction of tissues and vascular bundles of the stem in D. marginata as well as filling major “white spots” in property charts for biological materials. Additionally we shortly discuss the potential significance of such studies for the development of branched and unbranched bio-inspired fibre-reinforced materials and structures with enhanced properties. PMID:28144511

Tract-based analysis of white matter integrity in psychotic and nonpsychotic bipolar disorder.

PubMed

Ji, Andrew; Godwin, Douglass; Rutlin, Jerrel; Kandala, Sridhar; Shimony, Joshua S; Mamah, Daniel

2017-02-01

At least 50% of individuals with bipolar disorder (BD) present with psychosis during their lifetime. Psychotic symptoms have sometimes been linked to specific genetic and phenotypic markers. This study aims to explore potential differences between bipolar disorder subtypes by measuring white matter integrity of the brain and relationships with clinical measures. Diffusion tensor imaging and clinical measures were acquired from 102 participants, grouped as psychotic bipolar disorder (PBD) (n=48), non-psychotic bipolar disorder (NBD) (n=24), and healthy controls (n=30). We utilized a powerful, automated tool (TRACULA: Tracts Constrained by Underlying Anatomy) to analyze the fractional anisotropy (FA) and mean diffusivity (MD) of 18 white matter tracts. Decreased FA in numerous tracts was observed in bipolar disorder groups compared to healthy controls: bilateral cingulum-cingulate gyrus bundles, corticospinal tracts, and superior longitudinal fasciculi as well as the right hemisphere cingulum-angular bundle. Only left uncinate fasciculus FA differed between PBD and NPBD groups. We found no group differences in MD. Positive symptoms correlated with FA in the superior (inversely) and inferior (directly) longitudinal fasciculi. Negative symptoms directly correlated with mean FA of the corticospinal tract and cingulum-angular bundle. Neurotropic, mood-stabilizing medication prescribed for individuals with BD may interact with measures of white matter integrity in our BD participants. Our results indicate decreased white matter coherence in BD. Minimal differences in white matter FA between PBD and NPBD participants suggest related underlying neurobiology. Copyright © 2016 Elsevier B.V. All rights reserved.

Prenatal exposure to maternal and paternal depressive symptoms and white matter microstructure in children.

PubMed

El Marroun, Hanan; Zou, Runyu; Muetzel, Ryan L; Jaddoe, Vincent W; Verhulst, Frank C; White, Tonya; Tiemeier, Henning

2018-04-01

Prenatal maternal depression has been associated with multiple problems in offspring involving affect, cognition, and neuroendocrine functioning. This suggests that prenatal depression influences neurodevelopment. However, the underlying neurodevelopmental mechanism remains unclear. We prospectively assessed whether maternal depressive symptoms during pregnancy and at the child's age 3 years are related to white matter microstructure in 690 children. The association of paternal depressive symptoms with childhood white matter microstructure was assessed to evaluate genetic or familial confounding. Parental depressive symptoms were measured using the Brief Symptom Inventory. In children aged 6-9 years, we used diffusion tensor imaging to assess white matter microstructure characteristics including fractional anisotropy (FA) and mean diffusivity (MD). Exposure to maternal depressive symptoms during pregnancy was associated with higher MD in the uncinate fasciculus and to lower FA and higher MD in the cingulum bundle. No associations of maternal depressive symptoms at the child's age of 3 years with white matter characteristics were observed. Paternal depressive symptoms also showed a trend toward significance for a lower FA in the cingulum bundle. Prenatal maternal depressive symptoms were associated with higher MD in the uncinate fasciculus and the cingulum bundle. These structures are part of the limbic system, which is involved in motivation, emotion, learning, and memory. As paternal depressive symptoms were also related to lower FA in the cingulum, the observed effect may partly reflect a genetic predisposition and shared environmental family factors and to a lesser extent a specific intrauterine effect. © 2018 Wiley Periodicals, Inc.

Cotton properties: relative humidity and its effect on flat bundle strength elongation and fracture morphology

USDA-ARS?s Scientific Manuscript database

The effects of the relative humidity (RH) of testing conditions on stelometer cotton flat bundle strength and elongation measurements, and on the morphology of fiber fractures will be discussed in this talk. We observed a trend for stelometer strength and elongations measurements. Testing in conditi...

Synthesis, characterization, and growth mechanism of motifs of ultrathin cobalt-substituted NaFeSi 2O 6 nanowires

DOE PAGES

Lewis, Crystal S.; Moronta, Dominic; Terban, Maxwell W.; ...

2017-12-12

In this report, we have synthesized and structurally characterized nanowire bundles of cobalt-substituted pyroxenes, similar to the crystal structure of aegirine (i.e. Co-substituted XYSi 2O 6 with X and Y referring to metallic elements such as but not limited to Co, Na, and Fe), using a readily scalable hydrothermal technique. We then propose a growth mechanism for these bundles, based on detailed time and temperature dependent studies as well as complementary control experiments, particularly reactions in the absence of either 3-aminopropyltriethoxysilane (APTES) or sodium hydroxide (NaOH), via a transmission electron microscopy visualization study. Moreover, these nanowire bundles were probed formore » their magnetic properties and chemical composition using superconducting quantum interference device (SQUID) measurements, X-ray diffraction, and pair distribution function analysis, respectively. Specifically, SQUID measurement observations highlighted that these bundles evince (i) unique and interesting super-paramagnetic properties at 5 K that are consistent with that of our previously published ~2 nm ultra-small nanoparticles as well as (ii) paramagnetic behavior at 300 K.« less

Field emission properties of a DWCNT bundle and a single MWCNT

NASA Astrophysics Data System (ADS)

Fujishige, Masatsugu; Wongwiriyapan, Winadda; Muramatsu, Hiroyuki; Takeuchi, Kenji; Arai, Susumu

2018-02-01

The field emission properties of a bundle of double-walled carbon nanotubes (DWCNTs) and a single multiwalled carbon nanotube (MWCNT) were investigated. A DWCNT bundle or a single MWCNT was attached to the head of sharpened tip of tungsten by electrophoresis; the tungsten tip was dipped into a drop of a carbon nanotube/1,2-dichloroethane suspension on a stainless plate, and a high-frequency AC voltage (20 V peak to peak with a frequency of 15 MHz) was applied between the tungsten tip and the stainless steel plate. The turn-on fields of the DWCNT and MWCNT tips for 1 nA/cm2 were 0.05 and 0.48 V/μm, respectively. From the Fowler-Nordheim plots, the field enhancement factor (β) of the tips was estimated to be 109,600 (DWCNT) and 6780 (MWCNT). The present DWCNT emitter is characterized by a very small turn-on field and large β. The field emission performance is discussed in terms of the sizes of the bundle of DWCNTs and a single MWCNT.

Synthesis, characterization, and growth mechanism of motifs of ultrathin cobalt-substituted NaFeSi 2O 6 nanowires

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

Lewis, Crystal S.; Moronta, Dominic; Terban, Maxwell W.

In this report, we have synthesized and structurally characterized nanowire bundles of cobalt-substituted pyroxenes, similar to the crystal structure of aegirine (i.e. Co-substituted XYSi 2O 6 with X and Y referring to metallic elements such as but not limited to Co, Na, and Fe), using a readily scalable hydrothermal technique. We then propose a growth mechanism for these bundles, based on detailed time and temperature dependent studies as well as complementary control experiments, particularly reactions in the absence of either 3-aminopropyltriethoxysilane (APTES) or sodium hydroxide (NaOH), via a transmission electron microscopy visualization study. Moreover, these nanowire bundles were probed formore » their magnetic properties and chemical composition using superconducting quantum interference device (SQUID) measurements, X-ray diffraction, and pair distribution function analysis, respectively. Specifically, SQUID measurement observations highlighted that these bundles evince (i) unique and interesting super-paramagnetic properties at 5 K that are consistent with that of our previously published ~2 nm ultra-small nanoparticles as well as (ii) paramagnetic behavior at 300 K.« less

Monoubiquitination Inhibits the Actin Bundling Activity of Fascin.

PubMed

Lin, Shengchen; Lu, Shuang; Mulaj, Mentor; Fang, Bin; Keeley, Tyler; Wan, Lixin; Hao, Jihui; Muschol, Martin; Sun, Jianwei; Yang, Shengyu

2016-12-30

Fascin is an actin bundling protein that cross-links individual actin filaments into straight, compact, and stiff bundles, which are crucial for the formation of filopodia, stereocillia, and other finger-like membrane protrusions. The dysregulation of fascin has been implicated in cancer metastasis, hearing loss, and blindness. Here we identified monoubiquitination as a novel mechanism that regulates fascin bundling activity and dynamics. The monoubiquitination sites were identified to be Lys 247 and Lys 250 , two residues located in a positive charge patch at the actin binding site 2 of fascin. Using a chemical ubiquitination method, we synthesized chemically monoubiquitinated fascin and determined the effects of monoubiquitination on fascin bundling activity and dynamics. Our data demonstrated that monoubiquitination decreased the fascin bundling EC 50 , delayed the initiation of bundle assembly, and accelerated the disassembly of existing bundles. By analyzing the electrostatic properties on the solvent-accessible surface of fascin, we proposed that monoubiquitination introduced steric hindrance to interfere with the interaction between actin filaments and the positively charged patch at actin binding site 2. We also identified Smurf1 as a E3 ligase regulating the monoubiquitination of fascin. Our findings revealed a previously unidentified regulatory mechanism for fascin, which will have important implications for the understanding of actin bundle regulation under physiological and pathological conditions. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Constrained ripple optimization of Tokamak bundle divertors

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

Hively, L.M.; Rome, J.A.; Lynch, V.E.

1983-02-01

Magnetic field ripple from a tokamak bundle divertor is localized to a small toroidal sector and must be treated differently from the usual (distributed) toroidal field (TF) coil ripple. Generally, in a tokamak with an unoptimized divertor design, all of the banana-trapped fast ions are quickly lost due to banana drift diffusion or to trapping between the 1/R variation in absolute value vector B ..xi.. B and local field maxima due to the divertor. A computer code has been written to optimize automatically on-axis ripple subject to these constraints, while varying up to nine design parameters. Optimum configurations have lowmore » on-axis ripple (<0.2%) so that, now, most banana-trapped fast ions are confined. Only those ions with banana tips near the outside region (absolute value theta < or equal to 45/sup 0/) are lost. However, because finite-sized TF coils have not been used in this study, the flux bundle is not expanded.« less

Investigating Musical Disorders with Diffusion Tensor Imaging: a Comparison of Imaging Parameters

PubMed Central

Loui, Psyche; Schlaug, Gottfried

2009-01-01

The Arcuate Fasciculus (AF) is a bundle of white matter traditionally thought to be responsible for language function. However, its role in music is not known. Here we investigate the connectivity of the AF using Diffusion Tensor Imaging (DTI) and show that musically tone-deaf individuals, who show impairments in pitch discrimination, have reduced connectivity in the AF relative to musically normal-functioning control subjects. Results were robust to variations in imaging parameters and emphasize the importance of brain connectivity in para-linguistic processes such as music. PMID:19673766

Ab initio density functional theory investigation of Li-intercalated silicon carbide nanotube bundles

NASA Astrophysics Data System (ADS)

Moradian, Rostam; Behzad, Somayeh; Chegel, Raad

2009-06-01

We present the results of ab initio density functional theory calculations on the energetic, and geometric and electronic structure of Li-intercalated ( 6,6) silicon carbide nanotube (SiCNT) bundles. Our results show that intercalation of lithium leads to the significant changes in the geometrical structure. The most prominent effect of Li intercalation on the electronic band structure is a shift of the Fermi energy which occurs as a result of charge transfer from lithium to the SiCNTs. All the Li-intercalated ( 6,6) SiCNT bundles are predicted to be metallic representing a substantial change in electronic properties relative to the undoped bundle, which is a wide band gap semiconductor. Both inside of the nanotube and the interstitial space are susceptible for intercalation. The present calculations suggest that the SiCNT bundle is a promising candidate for the anode material in battery applications.

Heterotic line bundle models on elliptically fibered Calabi-Yau three-folds

NASA Astrophysics Data System (ADS)

Braun, Andreas P.; Brodie, Callum R.; Lukas, Andre

2018-04-01

We analyze heterotic line bundle models on elliptically fibered Calabi-Yau three-folds over weak Fano bases. In order to facilitate Wilson line breaking to the standard model group, we focus on elliptically fibered three-folds with a second section and a freely-acting involution. Specifically, we consider toric weak Fano surfaces as base manifolds and identify six such manifolds with the required properties. The requisite mathematical tools for the construction of line bundle models on these spaces, including the calculation of line bundle cohomology, are developed. A computer scan leads to more than 400 line bundle models with the right number of families and an SU(5) GUT group which could descend to standard-like models after taking the ℤ2 quotient. A common and surprising feature of these models is the presence of a large number of vector-like states.

Mutational Analyses of HAMP Helices Suggest a Dynamic Bundle Model of Input-Output Signaling in Chemoreceptors

PubMed Central

Zhou, Qin; Ames, Peter; Parkinson, John S.

2009-01-01

SUMMARY To test the gearbox model of HAMP signaling in the E. coli serine receptor, Tsr, we generated a series of amino acid replacements at each residue of the AS1 and AS2 helices. The residues most critical for Tsr function defined hydrophobic packing faces consistent with a 4-helix bundle. Suppression patterns of helix lesions conformed to the the predicted packing layers in the bundle. Although the properties and patterns of most AS1 and AS2 lesions were consistent with both proposed gearbox structures, some mutational features specifically indicate the functional importance of an x-da bundle over an alternative a-d bundle. These genetic data suggest that HAMP signaling could simply involve changes in the stability of its x-da bundle. We propose that Tsr HAMP controls output signals by modulating destabilizing phase clashes between the AS2 helices and the adjoining kinase control helices. Our model further proposes that chemoeffectors regulate HAMP bundle stability through a control cable connection between the transmembrane segments and AS1 helices. Attractant stimuli, which cause inward piston displacements in chemoreceptors, should reduce cable tension, thereby stabilizing the HAMP bundle. This study shows how transmembrane signaling and HAMP input-output control could occur without the helix rotations central to the gearbox model. PMID:19656294

Cambial variations of Piper (Piperaceae) in Taiwan.

PubMed

Yang, Sheng-Zehn; Chen, Po-Hao

2017-12-01

Cambial variations in lianas of Piperaceae in Taiwan have not been studied previously. The stem anatomy of seven Piper species from Taiwan was examined to document cambial variations and better distinguish the species when leaves are absent. A key for the seven species is provided, based on the internal stem anatomy. The seven Piper species climb via adventitious roots, and in cross section, the stems were generally eccentric and oblate, although a transversely elliptic stem was found in P. kadsura (Choisy) Ohwi and P. sintenense Hatus. A cambial variant with secondary growth of external primary vascular bundles and xylem in plates was observed in all species except Piper betle L., which developed another cambium variant with xylem furrowed deeply by parenchyma proliferation. The sclerenchymatous ring surrounding the medullary vascular bundles was always continuous except in P. betle, where it was discontinuous. Mucilage canals varied from absent to present in the center of the pith, or present in the pith and inner cortex. Different sizes of vessels dispersed throughout the stem were ring or diffuse porous. The numbers of medullary and peripheral vascular bundles were distinctive and the widths of rays were noticeably different in each species. Differences in the growth rate of the medullary vascular bundles produced two development types of vascular bundles, although in both types, the peripheral vascular bundles gradually lengthen and become separated from each other by wide rays. We documented the internal stem anatomy of six previously unstudied species of Piper, including three endemic species, P. kwashoense Hayata, P. sintenense, and P. taiwanense Lin and Lu, and found that P. betle had deeply furrowed xylem, which had not been reported for the species before. The descriptions and photographs of seven Piper species will also provide a basis for further morphological studies.

Alteration of architecture of MoO₃ nanostructures on arbitrary substrates: growth kinetics, spectroscopic and gas sensing properties.

PubMed

Illyaskutty, Navas; Sreedhar, Sreeja; Sanal Kumar, G; Kohler, Heinz; Schwotzer, Matthias; Natzeck, Carsten; Pillai, V P Mahadevan

2014-11-21

MoO3 nanostructures have been grown in thin film form on five different substrates by RF magnetron sputtering and subsequent annealing; non-aligned nanorods, aligned nanorods, bundled nanowires, vertical nanorods and nanoslabs are formed respectively on the glass, quartz, wafer, alumina and sapphire substrates. The nanostructures formed on these substrates are characterized by AFM, SEM, GIXRD, XPS, micro-Raman, diffuse reflectance and photoluminescence spectroscopy. A detailed growth model for morphology alteration with respect to substrates has been discussed by considering various aspects such as surface roughness, lattice parameters and the thermal expansion coefficient, of both substrates and MoO3. The present study developed a strategy for the choice of substrates to materialize different types MoO3 nanostructures for future thin film applications. The gas sensing tests point towards using these MoO3 nanostructures as principal detection elements in gas sensors.

Accessory factors promote AlfA-dependent plasmid segregation by regulating filament nucleation, disassembly, and bundling

PubMed Central

Polka, Jessica K.; Kollman, Justin M.; Mullins, R. Dyche

2014-01-01

In bacteria, some plasmids are partitioned to daughter cells by assembly of actin-like proteins (ALPs). The best understood ALP, ParM, has a core set of biochemical properties that contributes to its function, including dynamic instability, spontaneous nucleation, and bidirectional elongation. AlfA, an ALP that pushes plasmids apart in Bacillus, relies on a different set of underlying properties to segregate DNA. AlfA elongates unidirectionally and is not dynamically unstable; its assembly and disassembly are regulated by a cofactor, AlfB. Free AlfB breaks up AlfA bundles and promotes filament turnover. However, when AlfB is bound to the centromeric DNA sequence, parN, it forms a segrosome complex that nucleates and stabilizes AlfA filaments. When reconstituted in vitro, this system creates polarized, motile comet tails that associate by antiparallel filament bundling to form bipolar, DNA-segregating spindles. PMID:24481252

Plant trait-based models identify direct and indirect effects of climate change on bundles of grassland ecosystem services

PubMed Central

Lamarque, Pénélope; Lavorel, Sandra; Mouchet, Maud; Quétier, Fabien

2014-01-01

Land use and climate change are primary causes of changes in the supply of ecosystem services (ESs). Although the consequences of climate change on ecosystem properties and associated services are well documented, the cascading impacts of climate change on ESs through changes in land use are largely overlooked. We present a trait-based framework based on an empirical model to elucidate how climate change affects tradeoffs among ESs. Using alternative scenarios for mountain grasslands, we predicted how direct effects of climate change on ecosystems and indirect effects through farmers’ adaptations are likely to affect ES bundles through changes in plant functional properties. ES supply was overall more sensitive to climate than to induced management change, and ES bundles remained stable across scenarios. These responses largely reflected the restricted extent of management change in this constrained system, which was incorporated when scaling up plot level climate and management effects on ecosystem properties to the entire landscape. The trait-based approach revealed how the combination of common driving traits and common responses to changed fertility determined interactions and tradeoffs among ESs. PMID:25225382

Plant trait-based models identify direct and indirect effects of climate change on bundles of grassland ecosystem services.

PubMed

Lamarque, Pénélope; Lavorel, Sandra; Mouchet, Maud; Quétier, Fabien

2014-09-23

Land use and climate change are primary causes of changes in the supply of ecosystem services (ESs). Although the consequences of climate change on ecosystem properties and associated services are well documented, the cascading impacts of climate change on ESs through changes in land use are largely overlooked. We present a trait-based framework based on an empirical model to elucidate how climate change affects tradeoffs among ESs. Using alternative scenarios for mountain grasslands, we predicted how direct effects of climate change on ecosystems and indirect effects through farmers' adaptations are likely to affect ES bundles through changes in plant functional properties. ES supply was overall more sensitive to climate than to induced management change, and ES bundles remained stable across scenarios. These responses largely reflected the restricted extent of management change in this constrained system, which was incorporated when scaling up plot level climate and management effects on ecosystem properties to the entire landscape. The trait-based approach revealed how the combination of common driving traits and common responses to changed fertility determined interactions and tradeoffs among ESs.

Joint Multi-Fiber NODDI Parameter Estimation and Tractography Using the Unscented Information Filter

PubMed Central

Reddy, Chinthala P.; Rathi, Yogesh

2016-01-01

Tracing white matter fiber bundles is an integral part of analyzing brain connectivity. An accurate estimate of the underlying tissue parameters is also paramount in several neuroscience applications. In this work, we propose to use a joint fiber model estimation and tractography algorithm that uses the NODDI (neurite orientation dispersion diffusion imaging) model to estimate fiber orientation dispersion consistently and smoothly along the fiber tracts along with estimating the intracellular and extracellular volume fractions from the diffusion signal. While the NODDI model has been used in earlier works to estimate the microstructural parameters at each voxel independently, for the first time, we propose to integrate it into a tractography framework. We extend this framework to estimate the NODDI parameters for two crossing fibers, which is imperative to trace fiber bundles through crossings as well as to estimate the microstructural parameters for each fiber bundle separately. We propose to use the unscented information filter (UIF) to accurately estimate the model parameters and perform tractography. The proposed approach has significant computational performance improvements as well as numerical robustness over the unscented Kalman filter (UKF). Our method not only estimates the confidence in the estimated parameters via the covariance matrix, but also provides the Fisher-information matrix of the state variables (model parameters), which can be quite useful to measure model complexity. Results from in-vivo human brain data sets demonstrate the ability of our algorithm to trace through crossing fiber regions, while estimating orientation dispersion and other biophysical model parameters in a consistent manner along the tracts. PMID:27147956

Joint Multi-Fiber NODDI Parameter Estimation and Tractography Using the Unscented Information Filter.

PubMed

Reddy, Chinthala P; Rathi, Yogesh

2016-01-01

Tracing white matter fiber bundles is an integral part of analyzing brain connectivity. An accurate estimate of the underlying tissue parameters is also paramount in several neuroscience applications. In this work, we propose to use a joint fiber model estimation and tractography algorithm that uses the NODDI (neurite orientation dispersion diffusion imaging) model to estimate fiber orientation dispersion consistently and smoothly along the fiber tracts along with estimating the intracellular and extracellular volume fractions from the diffusion signal. While the NODDI model has been used in earlier works to estimate the microstructural parameters at each voxel independently, for the first time, we propose to integrate it into a tractography framework. We extend this framework to estimate the NODDI parameters for two crossing fibers, which is imperative to trace fiber bundles through crossings as well as to estimate the microstructural parameters for each fiber bundle separately. We propose to use the unscented information filter (UIF) to accurately estimate the model parameters and perform tractography. The proposed approach has significant computational performance improvements as well as numerical robustness over the unscented Kalman filter (UKF). Our method not only estimates the confidence in the estimated parameters via the covariance matrix, but also provides the Fisher-information matrix of the state variables (model parameters), which can be quite useful to measure model complexity. Results from in-vivo human brain data sets demonstrate the ability of our algorithm to trace through crossing fiber regions, while estimating orientation dispersion and other biophysical model parameters in a consistent manner along the tracts.

Shape analysis of the cingulum, uncinate and arcuate fasciculi in patients with bipolar disorder

PubMed Central

Sun, Zhong Yi; Houenou, Josselin; Duclap, Delphine; Sarrazin, Samuel; Linke, Julia; Daban, Claire; Hamdani, Nora; d’Albis, Marc-Antoine; Le Corvoisier, Philippe; Guevara, Pamela; Delavest, Marine; Bellivier, Frank; Almeida, Jorge; Versace, Amelia; Poupon, Cyril; Leboyer, Marion; Phillips, Mary; Wessa, Michèle; Mangin, Jean-François

2017-01-01

Background Abnormal maturation of brain connectivity is supposed to underlie the dysfunctional emotion regulation in patients with bipolar disorder (BD). To test this hypothesis, white matter integrity is usually investigated using measures of water diffusivity provided by MRI. Here we consider a more intuitive aspect of the morphometry of the white matter tracts: the shape of the fibre bundles, which is associated with neurodevelopment. We analyzed the shape of 3 tracts involved in BD: the cingulum (CG), uncinate fasciculus (UF) and arcuate fasciculus (AF). Methods We analyzed diffusion MRI data in patients with BD and healthy controls. The fibre bundles were reconstructed using Q-ball–based tractography and automated segmentation. Using Isomap, a manifold learning method, the differences in the shape of the reconstructed bundles were visualized and quantified. Results We included 112 patients and 82 controls in our analysis. We found the left AF of patients to be further extended toward the temporal pole, forming a tighter hook than in controls. We found no significant difference in terms of shape for the left UF, the left CG or the 3 right fasciculi. However, in patients compared with controls, the ventrolateral branch of the left UF in the orbitofrontal region had a tendency to be larger, and the left CG of patients had a tendency to be smaller in the frontal lobe and larger in the parietal lobe. Limitations This was a cross-sectional study. Conclusion Our results suggest neurodevelopmental abnormalities in the left AF in patients with BD. The statistical tendencies observed for the left UF and left CG deserve further study. PMID:28234596

Shape analysis of the cingulum, uncinate and arcuate fasciculi in patients with bipolar disorder.

PubMed

Sun, Zhong Yi; Houenou, Josselin; Duclap, Delphine; Sarrazin, Samuel; Linke, Julia; Daban, Claire; Hamdani, Nora; d'Albis, Marc-Antoine; Le Corvoisier, Philippe; Guevara, Pamela; Delavest, Marine; Bellivier, Frank; Bellivier, Frank; Almeida, Jorge; Versace, Amelia; Poupon, Cyril; Leboyer, Marion; Phillips, Mary; Wessa, Michèle; Mangin, Jean-François

2017-01-01

Abnormal maturation of brain connectivity is supposed to underlie the dysfunctional emotion regulation in patients with bipolar disorder (BD). To test this hypothesis, white matter integrity is usually investigated using measures of water diffusivity provided by MRI. Here we consider a more intuitive aspect of the morphometry of the white matter tracts: the shape of the fibre bundles, which is associated with neurodevelopment. We analyzed the shape of 3 tracts involved in BD: the cingulum (CG), uncinate fasciculus (UF) and arcuate fasciculus (AF). We analyzed diffusion MRI data in patients with BD and healthy controls. The fibre bundles were reconstructed using Q-ball-based tractography and automated segmentation. Using Isomap, a manifold learning method, the differences in the shape of the reconstructed bundles were visualized and quantified. We included 112 patients and 82 controls in our analysis. We found the left AF of patients to be further extended toward the temporal pole, forming a tighter hook than in controls. We found no significant difference in terms of shape for the left UF, the left CG or the 3 right fasciculi. However, in patients compared with controls, the ventrolateral branch of the left UF in the orbitofrontal region had a tendency to be larger, and the left CG of patients had a tendency to be smaller in the frontal lobe and larger in the parietal lobe. This was a cross-sectional study. Our results suggest neurodevelopmental abnormalities in the left AF in patients with BD. The statistical tendencies observed for the left UF and left CG deserve further study.

Preoperative automated fibre quantification predicts postoperative seizure outcome in temporal lobe epilepsy.

PubMed

Keller, Simon S; Glenn, G Russell; Weber, Bernd; Kreilkamp, Barbara A K; Jensen, Jens H; Helpern, Joseph A; Wagner, Jan; Barker, Gareth J; Richardson, Mark P; Bonilha, Leonardo

2017-01-01

Approximately one in every two patients with pharmacoresistant temporal lobe epilepsy will not be rendered completely seizure-free after temporal lobe surgery. The reasons for this are unknown and are likely to be multifactorial. Quantitative volumetric magnetic resonance imaging techniques have provided limited insight into the causes of persistent postoperative seizures in patients with temporal lobe epilepsy. The relationship between postoperative outcome and preoperative pathology of white matter tracts, which constitute crucial components of epileptogenic networks, is unknown. We investigated regional tissue characteristics of preoperative temporal lobe white matter tracts known to be important in the generation and propagation of temporal lobe seizures in temporal lobe epilepsy, using diffusion tensor imaging and automated fibre quantification. We studied 43 patients with mesial temporal lobe epilepsy associated with hippocampal sclerosis and 44 healthy controls. Patients underwent preoperative imaging, amygdalohippocampectomy and postoperative assessment using the International League Against Epilepsy seizure outcome scale. From preoperative imaging, the fimbria-fornix, parahippocampal white matter bundle and uncinate fasciculus were reconstructed, and scalar diffusion metrics were calculated along the length of each tract. Altogether, 51.2% of patients were rendered completely seizure-free and 48.8% continued to experience postoperative seizure symptoms. Relative to controls, both patient groups exhibited strong and significant diffusion abnormalities along the length of the uncinate bilaterally, the ipsilateral parahippocampal white matter bundle, and the ipsilateral fimbria-fornix in regions located within the medial temporal lobe. However, only patients with persistent postoperative seizures showed evidence of significant pathology of tract sections located in the ipsilateral dorsal fornix and in the contralateral parahippocampal white matter bundle. Using receiver operating characteristic curves, diffusion characteristics of these regions could classify individual patients according to outcome with 84% sensitivity and 89% specificity. Pathological changes in the dorsal fornix were beyond the margins of resection, and contralateral parahippocampal changes may suggest a bitemporal disorder in some patients. Furthermore, diffusion characteristics of the ipsilateral uncinate could classify patients from controls with a sensitivity of 98%; importantly, by co-registering the preoperative fibre maps to postoperative surgical lacuna maps, we observed that the extent of uncinate resection was significantly greater in patients who were rendered seizure-free, suggesting that a smaller resection of the uncinate may represent insufficient disconnection of an anterior temporal epileptogenic network. These results may have the potential to be developed into imaging prognostic markers of postoperative outcome and provide new insights for why some patients with temporal lobe epilepsy continue to experience postoperative seizures. © The Author (2016). Published by Oxford University Press on behalf of the Guarantors of Brain.

Preoperative automated fibre quantification predicts postoperative seizure outcome in temporal lobe epilepsy

PubMed Central

Keller, Simon S; Glenn, G Russell; Weber, Bernd; Kreilkamp, Barbara A K; Jensen, Jens H; Helpern, Joseph A; Wagner, Jan; Barker, Gareth J; Richardson, Mark P; Bonilha, Leonardo

2017-01-01

Abstract Approximately one in every two patients with pharmacoresistant temporal lobe epilepsy will not be rendered completely seizure-free after temporal lobe surgery. The reasons for this are unknown and are likely to be multifactorial. Quantitative volumetric magnetic resonance imaging techniques have provided limited insight into the causes of persistent postoperative seizures in patients with temporal lobe epilepsy. The relationship between postoperative outcome and preoperative pathology of white matter tracts, which constitute crucial components of epileptogenic networks, is unknown. We investigated regional tissue characteristics of preoperative temporal lobe white matter tracts known to be important in the generation and propagation of temporal lobe seizures in temporal lobe epilepsy, using diffusion tensor imaging and automated fibre quantification. We studied 43 patients with mesial temporal lobe epilepsy associated with hippocampal sclerosis and 44 healthy controls. Patients underwent preoperative imaging, amygdalohippocampectomy and postoperative assessment using the International League Against Epilepsy seizure outcome scale. From preoperative imaging, the fimbria-fornix, parahippocampal white matter bundle and uncinate fasciculus were reconstructed, and scalar diffusion metrics were calculated along the length of each tract. Altogether, 51.2% of patients were rendered completely seizure-free and 48.8% continued to experience postoperative seizure symptoms. Relative to controls, both patient groups exhibited strong and significant diffusion abnormalities along the length of the uncinate bilaterally, the ipsilateral parahippocampal white matter bundle, and the ipsilateral fimbria-fornix in regions located within the medial temporal lobe. However, only patients with persistent postoperative seizures showed evidence of significant pathology of tract sections located in the ipsilateral dorsal fornix and in the contralateral parahippocampal white matter bundle. Using receiver operating characteristic curves, diffusion characteristics of these regions could classify individual patients according to outcome with 84% sensitivity and 89% specificity. Pathological changes in the dorsal fornix were beyond the margins of resection, and contralateral parahippocampal changes may suggest a bitemporal disorder in some patients. Furthermore, diffusion characteristics of the ipsilateral uncinate could classify patients from controls with a sensitivity of 98%; importantly, by co-registering the preoperative fibre maps to postoperative surgical lacuna maps, we observed that the extent of uncinate resection was significantly greater in patients who were rendered seizure-free, suggesting that a smaller resection of the uncinate may represent insufficient disconnection of an anterior temporal epileptogenic network. These results may have the potential to be developed into imaging prognostic markers of postoperative outcome and provide new insights for why some patients with temporal lobe epilepsy continue to experience postoperative seizures. PMID:28031219

* Hierarchically Structured Electrospun Scaffolds with Chemically Conjugated Growth Factor for Ligament Tissue Engineering.

PubMed

Pauly, Hannah M; Sathy, Binulal N; Olvera, Dinorath; McCarthy, Helen O; Kelly, Daniel J; Popat, Ketul C; Dunne, Nicholas J; Haut Donahue, Tammy Lynn

2017-08-01

The anterior cruciate ligament (ACL) of the knee is vital for proper joint function and is commonly ruptured during sports injuries or car accidents. Due to a lack of intrinsic healing capacity and drawbacks with allografts and autografts, there is a need for a tissue-engineered ACL replacement. Our group has previously used aligned sheets of electrospun polycaprolactone nanofibers to develop solid cylindrical bundles of longitudinally aligned nanofibers. We have shown that these nanofiber bundles support cell proliferation and elongation and the hierarchical structure and material properties are similar to the native human ACL. It is possible to combine multiple nanofiber bundles to create a scaffold that attempts to mimic the macroscale structure of the ACL. The goal of this work was to develop a hierarchical bioactive scaffold for ligament tissue engineering using connective tissue growth factor (CTGF)-conjugated nanofiber bundles and evaluate the behavior of mesenchymal stem cells (MSCs) on these scaffolds in vitro and in vivo. CTGF was immobilized onto the surface of individual nanofiber bundles or scaffolds consisting of multiple nanofiber bundles. The conjugation efficiency and the release of conjugated CTGF were assessed using X-ray photoelectron spectroscopy, assays, and immunofluorescence staining. Scaffolds were seeded with MSCs and maintained in vitro for 7 days (individual nanofiber bundles), in vitro for 21 days (scaled-up scaffolds of 20 nanofiber bundles), or in vivo for 6 weeks (small scaffolds of 4 nanofiber bundles), and ligament-specific tissue formation was assessed in comparison to non-CTGF-conjugated control scaffolds. Results showed that CTGF conjugation encouraged cell proliferation and ligament-specific tissue formation in vitro and in vivo. The results suggest that hierarchical electrospun nanofiber bundles conjugated with CTGF are a scalable and bioactive scaffold for ACL tissue engineering.

The evaluation of energy efficiency of convective heat transfer surfaces in tube bundles

NASA Astrophysics Data System (ADS)

Grigoriev, B. A.; Pronin, V. A.; Salohin, V. I.; Sidenkov, D. V.

2017-11-01

When evaluating the effectiveness of the heat exchange surfaces in the main considered characteristics such as heat flow (Q, Watt), the power required for pumps (N, Watt), and surface area of heat transfer (F, m2). The most correct comparison provides a comparison “ceteris paribus”. Carried out performance comparison “ceteris paribus” in-line and staggered configurations of bundles with a circular pipes can serve as a basis for the development of physical models of flow and heat transfer in tube bundles with tubes of other geometric shapes, considering intertubular stream with attached eddies. The effect of longitudinal and transverse steps of the pipes on the energy efficiency of different configurations would take into account by mean of physical relations between the structure of shell side flow with attached eddies and intensity of transfer processes of heat and momentum. With the aim of energy-efficient placement of tubes, such an approach opens up great opportunities for the synthesis of a plurality of tubular heat exchange surfaces, in particular, the layout of the twisted and in-line-diffuser type with a drop-shaped pipes.

Simultaneous 3D tracking of passive tracers and microtubule bundles in an active gel

NASA Astrophysics Data System (ADS)

Fan, Yi; Breuer, Kenneth S.; Fluids Team

Kinesin-driven microtubule bundles generate a spontaneous flow in unconfined geometries. They exhibit properties of active matter, including the emergence of collective motion, reduction of apparent viscosity and consumption of local energy. Here we present results from 3D tracking of passive tracers (using Airy rings and 3D scanning) synchronized with 3D measurement of the microtubule bundles motion. This technique is applied to measure viscosity variation and collective flow in a confined geometry with particular attention paid to the self-pumping system recently reported by Wu et al. (2016). Results show that the viscosity in an equilibrium microtubule network is around half that of the isotropic unbundled microtubule solution. Cross-correlations of the active microtubule network and passive tracers define a neighborhood around microtubule bundles in which passive tracers are effectively transported. MRSEC NSF.

In situ Raman study on single- and double-walled carbon nanotubes as a function of lithium insertion.

PubMed

Kim, Yoong Ahm; Kojima, Masahito; Muramatsu, Hiroyuki; Umemoto, Souichiro; Watanabe, Takaaki; Yoshida, Kazuto; Sato, Keigo; Ikeda, Takuya; Hayashi, Takuya; Endo, Morinobu; Terrones, Mauricio; Dresselhaus, Mildred S

2006-05-01

We investigated the electrochemical lithium ion (Li(+)) insertion/desertion behavior on highly pure and bundled single- and double-walled carbon nanotubes (SWNTs and DWNTs) using an in situ Raman technique. In general, two storage sites could host Li(+) in SWNT and DWNT bundles when varying an external potential: a) the outer surface sites, and b) the interstitial spaces within the bundles. The most sensitive changes in the tangential mode (TM) of the Raman spectra upon doping with Li(+) can be divided into two regions. The first region was found from 2.8 to 1.0 V (the coverage of Li(+) on the outer surface of a bundled nanotube) and was characterized by the loss of resonant conditions via partial charge transfer, where the G(+) line of the SWNT and the TM of the outer tube of DWNTs experienced a highly depressed intensity, but remained almost constant in frequency. The appearance of a Breit-Wigner-Fano (BWF) profile provided strong evidence of metallic inner tubes within DWNTs. The second region was observed when the applied potentials ranged from 0.9 to 0 V and was characterized by Li(+) diffusion into the interstitial sites of the bundled nanotube material. This phenomenon invoked a large downshift of the G(-) band in SWNTs, and a small downshift of the TM of the inner tube of DWNTs caused by expansion of the C--C bonds due to the charge transferred to the nanotubes, and the disappearance of the BWF profile through the screening effect of the interstitial Li(+) layers.

Role of the node in controlling traffic of cadmium, zinc, and manganese in rice

PubMed Central

Yamaguchi, Noriko; Ishikawa, Satoru; Abe, Tadashi; Baba, Koji; Terada, Yasuko

2012-01-01

Heavy metals are transported to rice grains via the phloem. In rice nodes, the diffuse vascular bundles (DVBs), which enclose the enlarged elliptical vascular bundles (EVBs), are connected to the panicle and have a morphological feature that facilitates xylem-to-phloem transfer. To find a mechanism for restricting cadmium (Cd) transport into grains, the distribution of Cd, zinc (Zn), manganese (Mn), and sulphur (S) around the vascular bundles in node I (the node beneath the panicle) of Oryza sativa ‘Koshihikari’ were compared 1 week after heading. Elemental maps of Cd, Zn, Mn, and S in the vascular bundles of node I were obtained by synchrotron micro-X-ray fluorescence spectrometry and electron probe microanalysis. In addition, Cd K-edge microfocused X-ray absorption near-edge structure analyses were used to identify the elements co-ordinated with Cd. Both Cd and S were mainly distributed in the xylem of the EVB and in the parenchyma cell bridge (PCB) surrounding the EVB. Zn accumulated in the PCB, and Mn accumulated around the protoxylem of the EVB. Cd was co-ordinated mainly with S in the xylem of the EVB, but with both S and O in the phloem of the EVB and in the PCB. The EVB in the node retarded horizontal transport of Cd toward the DVB. By contrast, Zn was first stored in the PCB and then efficiently transferred toward the DVB. Our results provide evidence that transport of Cd, Zn, and Mn is differentially controlled in rice nodes, where vascular bundles are functionally interconnected. PMID:22291135

Cellular target of weak magnetic fields: ionic conduction along actin filaments of microvilli.

PubMed

Gartzke, Joachim; Lange, Klaus

2002-11-01

The interaction of weak electromagnetic fields (EMF) with living cells is a most important but still unresolved biophysical problem. For this interaction, thermal and other types of noise appear to cause severe restrictions in the action of weak signals on relevant components of the cell. A recently presented general concept of regulation of ion and substrate pathways through microvilli provides a possible theoretical basis for the comprehension of physiological effects of even extremely low magnetic fields. The actin-based core of microfilaments in microvilli is proposed to represent a cellular interaction site for magnetic fields. Both the central role of F-actin in Ca2+ signaling and its polyelectrolyte nature eliciting specific ion conduction properties render the microvillar actin filament bundle an ideal interaction site for magnetic and electric fields. Ion channels at the tip of microvilli are connected with the cytoplasm by a bundle of microfilaments forming a diffusion barrier system. Because of its polyelectrolyte nature, the microfilament core of microvilli allows Ca2+ entry into the cytoplasm via nonlinear cable-like cation conduction through arrays of condensed ion clouds. The interaction of ion clouds with periodically applied EMFs and field-induced cation pumping through the cascade of potential barriers on the F-actin polyelectrolyte follows well-known physical principles of ion-magnetic field (MF) interaction and signal discrimination as described by the stochastic resonance and Brownian motor hypotheses. The proposed interaction mechanism is in accord with our present knowledge about Ca2+ signaling as the biological main target of MFs and the postulated extreme sensitivity for coherent excitation by very low field energies within specific amplitude and frequency windows. Microvillar F-actin bundles shielded by a lipid membrane appear to function like electronic integration devices for signal-to-noise enhancement; the influence of coherent signals on cation transduction is amplified, whereas that of random noise is reduced.

From Biological Cilia to Artificial Flow Sensors: Biomimetic Soft Polymer Nanosensors with High Sensing Performance

NASA Astrophysics Data System (ADS)

Asadnia, Mohsen; Kottapalli, Ajay Giri Prakash; Karavitaki, K. Domenica; Warkiani, Majid Ebrahimi; Miao, Jianmin; Corey, David P.; Triantafyllou, Michael

2016-09-01

We report the development of a new class of miniature all-polymer flow sensors that closely mimic the intricate morphology of the mechanosensory ciliary bundles in biological hair cells. An artificial ciliary bundle is achieved by fabricating bundled polydimethylsiloxane (PDMS) micro-pillars with graded heights and electrospinning polyvinylidenefluoride (PVDF) piezoelectric nanofiber tip links. The piezoelectric nature of a single nanofiber tip link is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Rheology and nanoindentation experiments are used to ensure that the viscous properties of the hyaluronic acid (HA)-based hydrogel are close to the biological cupula. A dome-shaped HA hydrogel cupula that encapsulates the artificial hair cell bundle is formed through precision drop-casting and swelling processes. Fluid drag force actuates the hydrogel cupula and deflects the micro-pillar bundle, stretching the nanofibers and generating electric charges. Functioning with principles analogous to the hair bundles, the sensors achieve a sensitivity and threshold detection limit of 300 mV/(m/s) and 8 μm/s, respectively. These self-powered, sensitive, flexible, biocompatibale and miniaturized sensors can find extensive applications in navigation and maneuvering of underwater robots, artificial hearing systems, biomedical and microfluidic devices.

From Biological Cilia to Artificial Flow Sensors: Biomimetic Soft Polymer Nanosensors with High Sensing Performance.

PubMed

Asadnia, Mohsen; Kottapalli, Ajay Giri Prakash; Karavitaki, K Domenica; Warkiani, Majid Ebrahimi; Miao, Jianmin; Corey, David P; Triantafyllou, Michael

2016-09-13

We report the development of a new class of miniature all-polymer flow sensors that closely mimic the intricate morphology of the mechanosensory ciliary bundles in biological hair cells. An artificial ciliary bundle is achieved by fabricating bundled polydimethylsiloxane (PDMS) micro-pillars with graded heights and electrospinning polyvinylidenefluoride (PVDF) piezoelectric nanofiber tip links. The piezoelectric nature of a single nanofiber tip link is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Rheology and nanoindentation experiments are used to ensure that the viscous properties of the hyaluronic acid (HA)-based hydrogel are close to the biological cupula. A dome-shaped HA hydrogel cupula that encapsulates the artificial hair cell bundle is formed through precision drop-casting and swelling processes. Fluid drag force actuates the hydrogel cupula and deflects the micro-pillar bundle, stretching the nanofibers and generating electric charges. Functioning with principles analogous to the hair bundles, the sensors achieve a sensitivity and threshold detection limit of 300 mV/(m/s) and 8 μm/s, respectively. These self-powered, sensitive, flexible, biocompatibale and miniaturized sensors can find extensive applications in navigation and maneuvering of underwater robots, artificial hearing systems, biomedical and microfluidic devices.

Exploring the Early Organization and Maturation of Linguistic Pathways in the Human Infant Brain.

PubMed

Dubois, Jessica; Poupon, Cyril; Thirion, Bertrand; Simonnet, Hina; Kulikova, Sofya; Leroy, François; Hertz-Pannier, Lucie; Dehaene-Lambertz, Ghislaine

2016-05-01

Linguistic processing is based on a close collaboration between temporal and frontal regions connected by two pathways: the "dorsal" and "ventral pathways" (assumed to support phonological and semantic processing, respectively, in adults). We investigated here the development of these pathways at the onset of language acquisition, during the first post-natal weeks, using cross-sectional diffusion imaging in 21 healthy infants (6-22 weeks of age) and 17 young adults. We compared the bundle organization and microstructure at these two ages using tractography and original clustering analyses of diffusion tensor imaging parameters. We observed structural similarities between both groups, especially concerning the dorsal/ventral pathway segregation and the arcuate fasciculus asymmetry. We further highlighted the developmental tempos of the linguistic bundles: The ventral pathway maturation was more advanced than the dorsal pathway maturation, but the latter catches up during the first post-natal months. Its fast development during this period might relate to the learning of speech cross-modal representations and to the first combinatorial analyses of the speech input. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Transduction channels' gating can control friction on vibrating hair-cell bundles in the ear.

PubMed

Bormuth, Volker; Barral, Jérémie; Joanny, Jean-François; Jülicher, Frank; Martin, Pascal

2014-05-20

Hearing starts when sound-evoked mechanical vibrations of the hair-cell bundle activate mechanosensitive ion channels, giving birth to an electrical signal. As for any mechanical system, friction impedes movements of the hair bundle and thus constrains the sensitivity and frequency selectivity of auditory transduction. Friction is generally thought to result mainly from viscous drag by the surrounding fluid. We demonstrate here that the opening and closing of the transduction channels produce internal frictional forces that can dominate viscous drag on the micrometer-sized hair bundle. We characterized friction by analyzing hysteresis in the force-displacement relation of single hair-cell bundles in response to periodic triangular stimuli. For bundle velocities high enough to outrun adaptation, we found that frictional forces were maximal within the narrow region of deflections that elicited significant channel gating, plummeted upon application of a channel blocker, and displayed a sublinear growth for increasing bundle velocity. At low velocity, the slope of the relation between the frictional force and velocity was nearly fivefold larger than the hydrodynamic friction coefficient that was measured when the transduction machinery was decoupled from bundle motion by severing tip links. A theoretical analysis reveals that channel friction arises from coupling the dynamics of the conformational change associated with channel gating to tip-link tension. Varying channel properties affects friction, with faster channels producing smaller friction. We propose that this intrinsic source of friction may contribute to the process that sets the hair cell's characteristic frequency of responsiveness.

Transduction channels’ gating can control friction on vibrating hair-cell bundles in the ear

PubMed Central

Bormuth, Volker; Barral, Jérémie; Joanny, Jean-François; Jülicher, Frank; Martin, Pascal

2014-01-01

Hearing starts when sound-evoked mechanical vibrations of the hair-cell bundle activate mechanosensitive ion channels, giving birth to an electrical signal. As for any mechanical system, friction impedes movements of the hair bundle and thus constrains the sensitivity and frequency selectivity of auditory transduction. Friction is generally thought to result mainly from viscous drag by the surrounding fluid. We demonstrate here that the opening and closing of the transduction channels produce internal frictional forces that can dominate viscous drag on the micrometer-sized hair bundle. We characterized friction by analyzing hysteresis in the force–displacement relation of single hair-cell bundles in response to periodic triangular stimuli. For bundle velocities high enough to outrun adaptation, we found that frictional forces were maximal within the narrow region of deflections that elicited significant channel gating, plummeted upon application of a channel blocker, and displayed a sublinear growth for increasing bundle velocity. At low velocity, the slope of the relation between the frictional force and velocity was nearly fivefold larger than the hydrodynamic friction coefficient that was measured when the transduction machinery was decoupled from bundle motion by severing tip links. A theoretical analysis reveals that channel friction arises from coupling the dynamics of the conformational change associated with channel gating to tip-link tension. Varying channel properties affects friction, with faster channels producing smaller friction. We propose that this intrinsic source of friction may contribute to the process that sets the hair cell’s characteristic frequency of responsiveness. PMID:24799674

Scintillator-fiber charged particle track-imaging detector

NASA Technical Reports Server (NTRS)

Binns, W. R.; Israel, M. H.; Klarmann, J.

1983-01-01

A scintillator-fiber charged-particle track-imaging detector was developed using a bundle of square cross section plastic scintillator fiber optics, proximity focused onto an image intensified charge injection device (CID) camera. The tracks of charged particle penetrating into the scintillator fiber bundle are projected onto the CID camera and the imaging information is read out in video format. The detector was exposed to beams of 15 MeV protons and relativistic Neon, Manganese, and Gold nuclei and images of their tracks were obtained. Details of the detector technique, properties of the tracks obtained, and preliminary range measurements of 15 MeV protons stopping in the fiber bundle are presented.

White matter correlates of cognitive domains in normal aging with diffusion tensor imaging.

PubMed

Sasson, Efrat; Doniger, Glen M; Pasternak, Ofer; Tarrasch, Ricardo; Assaf, Yaniv

2013-01-01

The ability to perform complex as well as simple cognitive tasks engages a network of brain regions that is mediated by the white matter fiber bundles connecting them. Different cognitive tasks employ distinctive white matter fiber bundles. The temporal lobe and its projections subserve a variety of key functions known to deteriorate during aging. In a cohort of 52 healthy subjects (ages 25-82 years), we performed voxel-wise regression analysis correlating performance in higher-order cognitive domains (executive function, information processing speed, and memory) with white matter integrity, as measured by diffusion tensor imaging (DTI) fiber tracking in the temporal lobe projections [uncinate fasciculus (UF), fornix, cingulum, inferior longitudinal fasciculus (ILF), and superior longitudinal fasciculus (SLF)]. The fiber tracts were spatially registered and statistical parametric maps were produced to spatially localize the significant correlations. Results showed that performance in the executive function domain is correlated with DTI parameters in the left SLF and right UF; performance in the information processing speed domain is correlated with fractional anisotropy (FA) in the left cingulum, left fornix, right and left ILF and SLF; and the memory domain shows significant correlations with DTI parameters in the right fornix, right cingulum, left ILF, left SLF and right UF. These findings suggest that DTI tractography enables anatomical definition of region of interest (ROI) for correlation of behavioral parameters with diffusion indices, and functionality can be correlated with white matter integrity.

Myofiber Architecture of the Human Atria as Revealed by Submillimeter Diffusion Tensor Imaging.

PubMed

Pashakhanloo, Farhad; Herzka, Daniel A; Ashikaga, Hiroshi; Mori, Susumu; Gai, Neville; Bluemke, David A; Trayanova, Natalia A; McVeigh, Elliot R

2016-04-01

Accurate knowledge of the human atrial fibrous structure is paramount in understanding the mechanisms of atrial electric function in health and disease. Thus far, such knowledge has been acquired from destructive sectioning, and there is a paucity of data about atrial fiber architecture variability in the human population. In this study, we have developed a customized 3-dimensional diffusion tensor magnetic resonance imaging sequence on a clinical scanner that makes it possible to image an entire intact human heart specimen ex vivo at submillimeter resolution. The data from 8 human atrial specimens obtained with this technique present complete maps of the fibrous organization of the human atria. The findings demonstrate that the main features of atrial anatomy are mostly preserved across subjects although the exact location and orientation of atrial bundles vary. Using the full tractography data, we were able to cluster, visualize, and characterize the distinct major bundles in the human atria. Furthermore, quantitative characterization of the fiber angles across the atrial wall revealed that the transmural fiber angle distribution is heterogeneous throughout different regions of the atria. The application of submillimeter diffusion tensor magnetic resonance imaging provides an unprecedented level of information on both human atrial structure, as well as its intersubject variability. The high resolution and fidelity of this data could enhance our understanding of structural contributions to atrial rhythm and pump disorders and lead to improvements in their targeted treatment. © 2016 American Heart Association, Inc.

Leading non-Gaussian corrections for diffusion orientation distribution function.

PubMed

Jensen, Jens H; Helpern, Joseph A; Tabesh, Ali

2014-02-01

An analytical representation of the leading non-Gaussian corrections for a class of diffusion orientation distribution functions (dODFs) is presented. This formula is constructed from the diffusion and diffusional kurtosis tensors, both of which may be estimated with diffusional kurtosis imaging (DKI). By incorporating model-independent non-Gaussian diffusion effects, it improves on the Gaussian approximation used in diffusion tensor imaging (DTI). This analytical representation therefore provides a natural foundation for DKI-based white matter fiber tractography, which has potential advantages over conventional DTI-based fiber tractography in generating more accurate predictions for the orientations of fiber bundles and in being able to directly resolve intra-voxel fiber crossings. The formula is illustrated with numerical simulations for a two-compartment model of fiber crossings and for human brain data. These results indicate that the inclusion of the leading non-Gaussian corrections can significantly affect fiber tractography in white matter regions, such as the centrum semiovale, where fiber crossings are common. 2013 John Wiley & Sons, Ltd.

Leading Non-Gaussian Corrections for Diffusion Orientation Distribution Function

PubMed Central

Jensen, Jens H.; Helpern, Joseph A.; Tabesh, Ali

2014-01-01

An analytical representation of the leading non-Gaussian corrections for a class of diffusion orientation distribution functions (dODFs) is presented. This formula is constructed out of the diffusion and diffusional kurtosis tensors, both of which may be estimated with diffusional kurtosis imaging (DKI). By incorporating model-independent non-Gaussian diffusion effects, it improves upon the Gaussian approximation used in diffusion tensor imaging (DTI). This analytical representation therefore provides a natural foundation for DKI-based white matter fiber tractography, which has potential advantages over conventional DTI-based fiber tractography in generating more accurate predictions for the orientations of fiber bundles and in being able to directly resolve intra-voxel fiber crossings. The formula is illustrated with numerical simulations for a two-compartment model of fiber crossings and for human brain data. These results indicate that the inclusion of the leading non-Gaussian corrections can significantly affect fiber tractography in white matter regions, such as the centrum semiovale, where fiber crossings are common. PMID:24738143

Modeling of chemical vapor infiltration for ceramic composites reinforced with layered, woven fabrics

NASA Technical Reports Server (NTRS)

Chung, Gui-Yung; Mccoy, Benjamin J.

1991-01-01

A homogeneous model is developed for the chemical vapor infiltration by one-dimensional diffusion into a system of layered plies consisting of woven tows containing bundles of filaments. The model predictions of the amount of deposition and the porosity of the sample as a function of time are compared with the predictions of a recent nonhomogeneous model with aligned holes formed by the weave. The nonhomogeneous model allows for diffusion through the aligned holes, into the spaces between plies, and into the gaps around filaments; i.e., three diffusion equations apply. Relative to the nonhomogeneous results, the homogeneous model underestimates the amount of deposition, since the absence of holes and spaces allows earlier occlusion of gaps around filaments and restricts the vapor infiltration.

Diffusing wave spectroscopy studies of gelling systems

NASA Astrophysics Data System (ADS)

Horne, David S.

1991-06-01

The recognition that the transmission of light through a concentrated, opaque system can be treated as a diffusion process has extended the application of photon correlation techniques to the study of particle size, mobility and interactions in such systems. Solutions of the photon diffusion equation are sensitive to the boundary conditions imposed by the geometry of the scattering apparatus. The apparatus, incorporating a bifurcated fiber optic bundle for light transmission between source, sample and detector, takes advantage of the particularly simple solution for a back-scattering configuration. Its ability to measure particle size using monodisperse polystyrene latices and to respond to concentration dependent particle interactions in a study of casein micelle mobility in skim and concentrated milks is demonstrated. Finally, the changes in dynamic light scattering behavior occurring during colloidal gel formation are described and discussed.

An Exploration of Human Well-Being Bundles as Identifiers of Ecosystem Service Use Patterns

PubMed Central

Biggs, Reinette; Reyers, Belinda

2016-01-01

We take a social-ecological systems perspective to investigate the linkages between ecosystem services and human well-being in South Africa. A recent paper identified different types of social-ecological systems in the country, based on distinct bundles of ecosystem service use. These system types were found to represent increasingly weak direct feedbacks between nature and people, from rural “green-loop” communities to urban “red-loop” societies. Here we construct human well-being bundles and explore whether the well-being bundles can be used to identify the same social-ecological system types that were identified using bundles of ecosystem service use. Based on national census data, we found three distinct well-being bundle types that are mainly characterized by differences in income, unemployment and property ownership. The distribution of these well-being bundles approximates the distribution of ecosystem service use bundles to a substantial degree: High levels of income and education generally coincided with areas characterised by low levels of direct ecosystem service use (or red-loop systems), while the majority of low well-being areas coincided with medium and high levels of direct ecosystem service use (or transition and green-loop systems). However, our results indicate that transformations from green-loop to red-loop systems do not always entail an immediate improvement in well-being, which we suggest may be due to a time lag between changes in the different system components. Using human well-being bundles as an indicator of social-ecological dynamics may be useful in other contexts since it is based on socio-economic data commonly collected by governments, and provides important insights into the connections between ecosystem services and human well-being at policy-relevant sub-national scales. PMID:27695120

An Exploration of Human Well-Being Bundles as Identifiers of Ecosystem Service Use Patterns.

PubMed

Hamann, Maike; Biggs, Reinette; Reyers, Belinda

2016-01-01

We take a social-ecological systems perspective to investigate the linkages between ecosystem services and human well-being in South Africa. A recent paper identified different types of social-ecological systems in the country, based on distinct bundles of ecosystem service use. These system types were found to represent increasingly weak direct feedbacks between nature and people, from rural "green-loop" communities to urban "red-loop" societies. Here we construct human well-being bundles and explore whether the well-being bundles can be used to identify the same social-ecological system types that were identified using bundles of ecosystem service use. Based on national census data, we found three distinct well-being bundle types that are mainly characterized by differences in income, unemployment and property ownership. The distribution of these well-being bundles approximates the distribution of ecosystem service use bundles to a substantial degree: High levels of income and education generally coincided with areas characterised by low levels of direct ecosystem service use (or red-loop systems), while the majority of low well-being areas coincided with medium and high levels of direct ecosystem service use (or transition and green-loop systems). However, our results indicate that transformations from green-loop to red-loop systems do not always entail an immediate improvement in well-being, which we suggest may be due to a time lag between changes in the different system components. Using human well-being bundles as an indicator of social-ecological dynamics may be useful in other contexts since it is based on socio-economic data commonly collected by governments, and provides important insights into the connections between ecosystem services and human well-being at policy-relevant sub-national scales.

PASSIVE MECHANICAL PROPERTIES AND RELATED PROTEINS CHANGE WITH BOTULINUM NEUROTOXIN A INJECTION OF NORMAL SKELETAL MUSCLE

PubMed Central

Thacker, Bryan E.; Tomiya, Akihito; Hulst, Jonah B.; Suzuki, Kentaro P.; Bremner, Shannon N.; Gastwirt, Randy F.; Greaser, Marion L.; Lieber, Richard L.; Ward, Samuel R.

2011-01-01

Summary The effects of botulinum neurotoxin A on the passive mechanical properties of skeletal muscle have not been investigated, but may have significant impact in the treatment of neuromuscular disorders including spasticity. Single fiber and fiber bundle passive mechanical testing was performed on rat muscles treated with botulinum neurotoxin A. Myosin heavy chain and titin composition of single fibers was determined by gel electrophoresis. Muscle collagen content was determined using a hydroxyproline assay. Neurotoxin-treated single fiber passive elastic modulus was reduced compared to control fibers (53.00 kPa versus 63.43 kPa). Fiber stiffness and slack sarcomere length were also reduced compared to control fibers and myosin heavy chain composition shifted from faster to slower isoforms. Average titin molecular weight increased 1.77% after treatment. Fiber bundle passive elastic modulus increased following treatment (168.83 kPa versus 75.14 kPa). Bundle stiffness also increased while collagen content per mass of muscle tissue increased 38%. Injection of botulinum neurotoxin A produces an effect on the passive mechanical properties of normal muscle that is opposite to the changes observed in spastic muscles. PMID:21853457

Biomechanics and functional morphology of a climbing monocot

PubMed Central

Hesse, Linnea; Wagner, Sarah T.; Neinhuis, Christoph

2016-01-01

Plants with a climbing growth habit possess unique biomechanical properties arising from adaptations to changing loading conditions connected with close attachment to mechanical supports. In monocot climbers, mechanical adaptation is restricted by the absence of a bifacial vascular cambium. Flagellaria indica was used to investigate the mechanical properties and adaptations of a monocot climber that, uniquely, attaches to the surrounding vegetation via leaf tendrils. Biomechanical methods such as three-point bending and torsion tests were used together with anatomical studies on tissue development, modification and distribution. In general, the torsional modulus was lower than the bending modulus; hence, torsional stiffness was less than flexural stiffness. Basal parts of mature stems showed the greatest stiffness while that of more apical stem segments levelled off. Mechanical properties were modulated via tissue maturation processes mainly affecting the peripheral region of the stem. Peripheral vascular bundles showed a reduction in the amount of conducting tissue while the proportion and density of the bundle sheath increased. Furthermore, adjacent bundle sheaths merged resulting in a dense ring of fibrous tissue. Although F. indica lacks secondary cambial growth, the climbing habit is facilitated by a complex interaction of tissue maturation and attachment. PMID:26819259

Passive mechanical properties and related proteins change with botulinum neurotoxin A injection of normal skeletal muscle.

PubMed

Thacker, Bryan E; Tomiya, Akihito; Hulst, Jonah B; Suzuki, Kentaro P; Bremner, Shannon N; Gastwirt, Randy F; Greaser, Marion L; Lieber, Richard L; Ward, Samuel R

2012-03-01

The effects of botulinum neurotoxin A on the passive mechanical properties of skeletal muscle have not been investigated, but may have significant impact in the treatment of neuromuscular disorders including spasticity. Single fiber and fiber bundle passive mechanical testing was performed on rat muscles treated with botulinum neurotoxin A. Myosin heavy chain and titin composition of single fibers was determined by gel electrophoresis. Muscle collagen content was determined using a hydroxyproline assay. Neurotoxin-treated single fiber passive elastic modulus was reduced compared to control fibers (53.00 kPa vs. 63.43 kPa). Fiber stiffness and slack sarcomere length were also reduced compared to control fibers and myosin heavy chain composition shifted from faster to slower isoforms. Average titin molecular weight increased 1.77% after treatment. Fiber bundle passive elastic modulus increased following treatment (168.83  kPa vs. 75.14 kPa). Bundle stiffness also increased while collagen content per mass of muscle tissue increased 38%. Injection of botulinum neurotoxin A produces an effect on the passive mechanical properties of normal muscle that is opposite to the changes observed in spastic muscles. Copyright © 2011 Orthopaedic Research Society.

Multimodal fiber-probe spectroscopy as a clinical tool for diagnosing and classifying biological tissues

NASA Astrophysics Data System (ADS)

Cicchi, Riccardo; Anand, Suresh; Fantechi, Riccardo; Giordano, Flavio; Gacci, Mauro; Conti, Valerio; Nesi, Gabriella; Buccoliero, Anna Maria; Carini, Marco; Guerrini, Renzo; Pavone, Francesco Saverio

2017-07-01

An optical fiber probe for multimodal spectroscopy was designed, developed and used for tissue diagnostics. The probe, based on a fiber bundle with optical fibers of various size and properties, allows performing spectroscopic measurements with different techniques, including fluorescence, Raman, and diffuse reflectance, using the same probe. Two visible laser diodes were used for fluorescence spectroscopy, a laser diode emitting in the NIR was used for Raman spectroscopy, and a fiber-coupled halogen lamp for diffuse reflectance. The developed probe was successfully employed for diagnostic purposes on various tissues, including brain and bladder. In particular, the device allowed discriminating healthy tissue from both tumor and dysplastic tissue as well as to perform tumor grading. The diagnostic capabilities of the method, determined using a cross-validation method with a leave-one-out approach, demonstrated high sensitivity and specificity for all the examined samples, as well as a good agreement with histopathological examination performed on the same samples. The obtained results demonstrated that the multimodal approach is crucial for improving diagnostic capabilities with respect to what can be obtained from individual techniques. The experimental setup presented here can improve diagnostic capabilities on a broad range of tissues and has the potential of being used clinically for guiding surgical resection in the near future.

Mesoscopic structure of neuronal tracts from time-dependent diffusion

PubMed Central

Burcaw, Lauren M.; Fieremans, Els; Novikov, Dmitry S.

2015-01-01

Interpreting brain diffusion MRI measurements in terms of neuronal structure at a micrometer level is an exciting unresolved problem. Here we consider diffusion transverse to a bundle of fibers, and show theoretically, as well as using Monte Carlo simulations and measurements in a phantom made of parallel fibers mimicking axons, that the time dependent diffusion coefficient approaches its macroscopic limit slowly, in a (lnt)/t fashion. The logarithmic singularity arises due to short range disorder in the fiber packing. We identify short range disorder in axonal fibers based on histological data from the splenium, and argue that the time dependent contribution to the overall diffusion coefficient from the extra-axonal water dominates that of the intra-axonal water. This dominance may explain the bias in measuring axon diameters in clinical settings. The short range disorder is also reflected in the linear frequency dependence of the diffusion coefficient measured with oscillating gradients, in agreement with recent experiments. Our results relate the measured diffusion to the mesoscopic structure of neuronal tissue, uncovering the sensitivity of diffusion metrics to axonal arrangement within a fiber tract, and providing an alternative interpretation of axonal diameter mapping techniques. PMID:25837598

Mesoscopic structure of neuronal tracts from time-dependent diffusion.

PubMed

Burcaw, Lauren M; Fieremans, Els; Novikov, Dmitry S

2015-07-01

Interpreting brain diffusion MRI measurements in terms of neuronal structure at a micrometer level is an exciting unresolved problem. Here we consider diffusion transverse to a bundle of fibers, and show theoretically, as well as using Monte Carlo simulations and measurements in a phantom made of parallel fibers mimicking axons, that the time dependent diffusion coefficient approaches its macroscopic limit slowly, in a (ln t)/t fashion. The logarithmic singularity arises due to short range disorder in the fiber packing. We identify short range disorder in axonal fibers based on histological data from the splenium, and argue that the time dependent contribution to the overall diffusion coefficient from the extra-axonal water dominates that of the intra-axonal water. This dominance may explain the bias in measuring axon diameters in clinical settings. The short range disorder is also reflected in the asymptotically linear frequency dependence of the diffusion coefficient measured with oscillating gradients, in agreement with recent experiments. Our results relate the measured diffusion to the mesoscopic structure of neuronal tissue, uncovering the sensitivity of diffusion metrics to axonal arrangement within a fiber tract, and providing an alternative interpretation of axonal diameter mapping techniques. Copyright © 2015 Elsevier Inc. All rights reserved.

[From Brownian motion to mind imaging: diffusion MRI].

PubMed

Le Bihan, Denis

2006-11-01

The success of diffusion MRI, which was introduced in the mid 1980s is deeply rooted in the powerful concept that during their random, diffusion-driven movements water molecules probe tissue structure at a microscopic scale well beyond the usual image resolution. The observation of these movements thus provides valuable information on the structure and the geometric organization of tissues. The most successful application of diffusion MRI has been in brain ischemia, following the discovery that water diffusion drops at a very early stage of the ischemic event. Diffusion MRI provides some patients with the opportunity to receive suitable treatment at a very acute stage when brain tissue might still be salvageable. On the other hand, diffusion is modulated by the spatial orientation of large bundles of myelinated axons running in parallel through in brain white matter. This feature can be exploited to map out the orientation in space of the white matter tracks and to visualize the connections between different parts of the brain on an individual basis. Furthermore, recent data suggest that diffusion MRI may also be used to visualize rapid dynamic tissue changes, such as neuronal swelling, associated with cortical activation, offering a new and direct approach to brain functional imaging.

Reinforcement of single-walled carbon nanotube bundles by intertube bridging

NASA Astrophysics Data System (ADS)

Kis, A.; Csányi, G.; Salvetat, J.-P.; Lee, Thien-Nga; Couteau, E.; Kulik, A. J.; Benoit, W.; Brugger, J.; Forró, L.

2004-03-01

During their production, single-walled carbon nanotubes form bundles. Owing to the weak van der Waals interaction that holds them together in the bundle, the tubes can easily slide on each other, resulting in a shear modulus comparable to that of graphite. This low shear modulus is also a major obstacle in the fabrication of macroscopic fibres composed of carbon nanotubes. Here, we have introduced stable links between neighbouring carbon nanotubes within bundles, using moderate electron-beam irradiation inside a transmission electron microscope. Concurrent measurements of the mechanical properties using an atomic force microscope show a 30-fold increase of the bending modulus, due to the formation of stable crosslinks that effectively eliminate sliding between the nanotubes. Crosslinks were modelled using first-principles calculations, showing that interstitial carbon atoms formed during irradiation in addition to carboxyl groups, can independently lead to bridge formation between neighbouring nanotubes.

The best features of diamond nanothread for nanofibre applications

NASA Astrophysics Data System (ADS)

Zhan, Haifei; Zhang, Gang; Tan, Vincent B. C.; Gu, Yuantong

2017-03-01

Carbon fibres have attracted interest from both the scientific and engineering communities due to their outstanding physical properties. Here we report that recently synthesized ultrathin diamond nanothread not only possesses excellent torsional deformation capability, but also excellent interfacial load-transfer efficiency. Compared with (10,10) carbon nanotube bundles, the flattening of nanotubes is not observed in diamond nanothread bundles, which leads to a high-torsional elastic limit that is almost three times higher. Pull-out tests reveal that the diamond nanothread bundle has an interface transfer load of more than twice that of the carbon nanotube bundle, corresponding to an order of magnitude higher in terms of the interfacial shear strength. Such high load-transfer efficiency is attributed to the strong mechanical interlocking effect at the interface. These intriguing features suggest that diamond nanothread could be an excellent candidate for constructing next-generation carbon fibres.

Neural substrates of behavioral variability in attention deficit hyperactivity disorder: based on ex-Gaussian reaction time distribution and diffusion spectrum imaging tractography.

PubMed

Lin, H-Y; Gau, S S-F; Huang-Gu, S L; Shang, C-Y; Wu, Y-H; Tseng, W-Y I

2014-06-01

Increased intra-individual variability (IIV) in reaction time (RT) across various tasks is one ubiquitous neuropsychological finding in attention deficit hyperactivity disorder (ADHD). However, neurobiological underpinnings of IIV in individuals with ADHD have not yet been fully delineated. The ex-Gaussian distribution has been proved to capture IIV in RT. The authors explored the three parameters [μ (mu), σ (sigma), τ (tau)] of an ex-Gaussian RT distribution derived from the Conners' continuous performance test (CCPT) and their correlations with the microstructural integrity of the frontostriatal-caudate tracts and the cingulum bundles. We assessed 28 youths with ADHD (8-17 years; 25 males) and 28 age-, sex-, IQ- and handedness-matched typically developing (TD) youths using the CCPT, Wechsler Intelligence Scale for Children, 3rd edition and magnetic resonance imaging (MRI). Microstructural integrity, indexed by generalized fractional anisotropy (GFA), was measured by diffusion spectrum imaging tractrography on a 3-T MRI system. Youths with ADHD had larger σ (s.d. of Gaussian distribution) and τ (mean of exponential distribution) and reduced GFA in four bilateral frontostriatal tracts. With increased inter-stimulus intervals of CCPT, the magnitude of greater τ in ADHD than TD increased. In ADHD youths, the cingulum bundles and frontostriatal integrity were associated with three ex-Gaussian parameters and with μ (mean of Gaussian distribution) and τ, respectively; while only frontostriatal GFA was associated with μ and τ in TD youths. Our findings suggest the crucial role of the integrity of the cingulum bundles in accounting for IIV in ADHD. Involvement of different brain systems in mediating IIV may relate to a distinctive pathophysiological processing and/or adaptive compensatory mechanism.

In vivo measurements of optical properties of human muscles with visible and near infrared reflectance spectroscopy

NASA Astrophysics Data System (ADS)

Wang, Chiao Yi; Yu, Ting Wen; Sung, Kung Bin

2018-02-01

Estimating optical properties of tissues is a crucial step to model photon migration in tissue, facilitate the design of the probe geometry, better interpret data measured from tissue and predict photon energy distributions in tissue for various diagnostic and therapeutic applications. Diffuse reflectance spectroscopy (DRS) using visible and near-infrared light is a well-known method for estimating optical properties of tissues. For estimating optical properties of muscles, most existing researches have used integrating spheres for ex-vivo measurements. However, due to inter-subject variability and sitespecific conditions, an in-vivo approach can provide more accurate estimations of muscle absorption and scattering coefficients, which is important for the tomographic reconstruction of changes in the absorption or fluorescence in tissue. In this study, we used DRS with wavelengths between 600 nm and 800 nm and a fiber bundle with source-to-detector separations in the range of 0.18-0.35 cm to quantify wavelength-dependent scattering and absorption coefficients of human muscles in vivo with an inverse Monte Carlo model. Reflectance spectra were measured on the neck and the upper arm of one volunteer. After calibrating spectra with tissue phantoms made of Intralipid and India ink, we estimated scattering and absorption coefficients of muscles. The results are compared to those measured ex vivo in the literature.

Stochastic reservoir simulation for the modeling of uncertainty in coal seam degasification

PubMed Central

Karacan, C. Özgen; Olea, Ricardo A.

2018-01-01

Coal seam degasification improves coal mine safety by reducing the gas content of coal seams and also by generating added value as an energy source. Coal seam reservoir simulation is one of the most effective ways to help with these two main objectives. As in all modeling and simulation studies, how the reservoir is defined and whether observed productions can be predicted are important considerations. Using geostatistical realizations as spatial maps of different coal reservoir properties is a more realistic approach than assuming uniform properties across the field. In fact, this approach can help with simultaneous history matching of multiple wellbores to enhance the confidence in spatial models of different coal properties that are pertinent to degasification. The problem that still remains is the uncertainty in geostatistical simulations originating from the partial sampling of the seam that does not properly reflect the stochastic nature of coal property realizations. Stochastic simulations and using individual realizations, rather than E-type, make evaluation of uncertainty possible. This work is an advancement over Karacan et al. (2014) in the sense of assessing uncertainty that stems from geostatistical maps. In this work, we batched 100 individual realizations of 10 coal properties that were randomly generated to create 100 bundles and used them in 100 separate coal seam reservoir simulations for simultaneous history matching. We then evaluated the history matching errors for each bundle and defined the single set of realizations that would minimize the error for all wells. We further compared the errors with those of E-type and the average realization of the best matches. Unlike in Karacan et al. (2014), which used E-type maps and average of quantile maps, using these 100 bundles created 100 different history match results from separate simulations, and distributions of results for in-place gas quantity, for example, from which uncertainty in coal property realizations could be evaluated. The study helped to determine the realization bundle that consisted of the spatial maps of coal properties, which resulted in minimum error. In addition, it was shown that both E-type and the average of realizations that gave the best match for invidual approximated the same properties resonably. Moreover, the determined realization bundle showed that the study field initially had 151.5 million m3 (cubic meter) of gas and 1.04 million m3 water in the coal, corresponding to Q90 of the entire range of probability for gas and close to Q75 for water. In 2013, in-place fluid amounts decreased to 138.9 million m3 and 0.997 million m3 for gas and water, respectively. PMID:29563647

Digital image correlation-aided mechanical characterization of the anteromedial and posterolateral bundles of the anterior cruciate ligament.

PubMed

Mallett, Kaitlyn F; Arruda, Ellen M

2017-07-01

The anterior cruciate ligament (ACL) is one of the most commonly injured soft tissue structures in the articular knee joint, often requiring invasive surgery for patients to restore pre-injury knee kinematics. There is a pressing need to understand the role of the ACL in knee function, in order to select proper replacements. Digital image correlation (DIC), a non-contact full field displacement measurement technique, is an established tool for evaluating non-biological materials. The application of DIC to soft tissues has been in the nascent stages, largely due to patterning challenges of such materials. The ACL is notoriously difficult to mechanically characterize, due to the complex geometry of its two bundles and their insertions. This paper examines the use of DIC to determine the tensile mechanical properties of the AM and PL bundles of ovine ACLs in a well-known loading state. Homogenous loading in the mid-substance of the bundles provides for accurate development of stress/strain curves using DIC. Animal to animal variability is reduced, and the bundles are stiffer than previously thought when tissue-level strains are accurately measured. The anterior cruciate ligament (ACL), a major stabilizing ligament of the articular knee joint, is one of the most commonly injured soft tissue structures in the knee. Often, invasive surgery is required to restore pre-injury knee kinematics, and there are several long-term consequences of ACL reconstructions, including early-onset osteoarthritis. The role of the ACL in knee stability and motion has received much attention in the biomechanics community. This paper examines the use of a non-contact full-field displacement measurement technique, digital image correlation, to determine the tensile mechanical properties of the ACL. The focus of this work is to investigate the intrinsic mechanical properties of the ACL, as new knowledge in these areas will aid clinicians in selecting ACL replacements. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Prostate tissue ablation with MRI guided transurethral therapeutic ultrasound and intraoperative assessment of the integrity of the neurovascular bundle

NASA Astrophysics Data System (ADS)

Sammet, Steffen; Partanen, Ari; Yousuf, Ambereen; Wardrip, Craig; Niekrasz, Marek; Antic, Tatjana; Razmaria, Aria; Sokka, Sham; Karczmar, Gregory; Oto, Aytekin

2017-03-01

OBJECTIVES: Evaluation of the precision of prostate tissue ablation with MRI guided therapeuticultrasound by intraoperative objective assessment of the neurovascular bundle in canines in-vivo. METHODS: In this ongoing IACUC approved study, eight male canines were scanned in a clinical 3T Achieva MRI scanner (Philips) before, during, and after ultrasound therapy with a prototype MR-guided ultrasound therapy system (Philips). The system includes a therapy console to plan treatment, to calculate real-time temperature maps, and to control ultrasound exposures with temperature feedback. Atransurethral ultrasound applicator with eight transducer elements was used to ablate canine prostate tissue in-vivo. Ablated prostate tissue volumes were compared to the prescribed target volumes to evaluate technical effectiveness. The ablated volumes determined by MRI (T1, T2, diffusion, dynamic contrast enhanced and 240 CEM43 thermal dose maps) were compared to H&E stained histological slides afterprostatectomy. Potential nerve damage of the neurovascular bundle was objectively assessed intraoperativelyduring prostatectomy with a CaverMap Surgical Aid nerve stimulator (Blue Torch Medical Technologies). RESULTS: Transurethral MRI -guided ultrasound therapy can effectively ablate canine prostate tissue invivo. Coronal MR-imaging confirmed the correct placement of the HIFU transducer. MRI temperature maps were acquired during HIFU treatment, and subsequently used for calculating thermal dose. Prescribed target volumes corresponded to the 240 CEM43 thermal dose maps during HIFU treatment in all canines. Ablated volumes on high resolution anatomical, diffusion weighted, and contrast enhanced MR images matched corresponding histological slides after prostatectomy. MRI guidance with realtime temperature monitoring showed no damage to surrounding tissues, especially to the neurovascular bundle (assessed intra-operatively with a nerve stimulator) or to the rectum wall. CONCLUSIONS: Our study demonstrates the effectiveness and precision of transurethral ultrasound ablation of prostatic tissue in canines with MRI monitoring and guidance. The canine prostate is an excellent model for the human prostate with similar anatomical characteristics and diseases. MRI guidance with real-time, intraoperative temperature monitoring reduces the risk of damaging critical surrounding anatomical structures in ultrasound therapy of the prostate.

From Biological Cilia to Artificial Flow Sensors: Biomimetic Soft Polymer Nanosensors with High Sensing Performance

PubMed Central

Asadnia, Mohsen; Kottapalli, Ajay Giri Prakash; Karavitaki, K. Domenica; Warkiani, Majid Ebrahimi; Miao, Jianmin; Corey, David P.; Triantafyllou, Michael

2016-01-01

We report the development of a new class of miniature all-polymer flow sensors that closely mimic the intricate morphology of the mechanosensory ciliary bundles in biological hair cells. An artificial ciliary bundle is achieved by fabricating bundled polydimethylsiloxane (PDMS) micro-pillars with graded heights and electrospinning polyvinylidenefluoride (PVDF) piezoelectric nanofiber tip links. The piezoelectric nature of a single nanofiber tip link is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Rheology and nanoindentation experiments are used to ensure that the viscous properties of the hyaluronic acid (HA)-based hydrogel are close to the biological cupula. A dome-shaped HA hydrogel cupula that encapsulates the artificial hair cell bundle is formed through precision drop-casting and swelling processes. Fluid drag force actuates the hydrogel cupula and deflects the micro-pillar bundle, stretching the nanofibers and generating electric charges. Functioning with principles analogous to the hair bundles, the sensors achieve a sensitivity and threshold detection limit of 300 mV/(m/s) and 8 μm/s, respectively. These self-powered, sensitive, flexible, biocompatibale and miniaturized sensors can find extensive applications in navigation and maneuvering of underwater robots, artificial hearing systems, biomedical and microfluidic devices. PMID:27622466

Enhancing the efficiency of lithium intercalation in carbon nanotube bundles using surface functional groups.

PubMed

Xiao, Shiyan; Zhu, Hong; Wang, Lei; Chen, Liping; Liang, Haojun

2014-08-14

The effect of surface functionalization on the ability and kinetics of lithium intercalation in carbon nanotube (CNT) bundles has been studied by comparing the dynamical behaviors of lithium (Li) ions in pristine and -NH2 functionalized CNTs via ab initio molecular dynamics simulations. It was observed that lithium intercalation has been achieved quickly for both the pristine and surface functionalized CNT bundle. Our calculations demonstrated for the first time that CNT functionalization improved the efficiency of lithium intercalation significantly at both low and high Li ion density. Moreover, we found that keeping the nanotubes apart with an appropriate distance and charging the battery at a rational rate were beneficial to achieve a high rate of lithium intercalation. Besides, the calculated adsorption energy curves indicated that the potential wells in the system of -NH2 functionalized CNT were deeper than that of the pristine CNT bundle by 0.74 eV, and a third energy minimum with a value of 2.64 eV existed at the midpoint of the central axis of the nanotube. Thus, it would be more difficult to remove Li ions from the nanotube interior after surface functionalization. The barrier for lithium diffusion in the interior of the nanotube is greatly decreased because of the surface functional groups. Based on these results, we would suggest to "damage" the nanotube by introducing defects at its sidewall in order to improve not only the capacity of surface functionalized CNTs but also the efficiency of lithium intercalation and deintercalation processes. Our results presented here are helpful in understanding the mechanism of lithium intercalation into nanotube bundles, which may potentially be applied in the development of CNT based electrodes.

Inter-individual differences in audio-motor learning of piano melodies and white matter fiber tract architecture.

PubMed

Engel, Annerose; Hijmans, Brenda S; Cerliani, Leonardo; Bangert, Marc; Nanetti, Luca; Keller, Peter E; Keysers, Christian

2014-05-01

Humans vary substantially in their ability to learn new motor skills. Here, we examined inter-individual differences in learning to play the piano, with the goal of identifying relations to structural properties of white matter fiber tracts relevant to audio-motor learning. Non-musicians (n = 18) learned to perform three short melodies on a piano keyboard in a pure audio-motor training condition (vision of their own fingers was occluded). Initial learning times ranged from 17 to 120 min (mean ± SD: 62 ± 29 min). Diffusion-weighted magnetic resonance imaging was used to derive the fractional anisotropy (FA), an index of white matter microstructural arrangement. A correlation analysis revealed that higher FA values were associated with faster learning of piano melodies. These effects were observed in the bilateral corticospinal tracts, bundles of axons relevant for the execution of voluntary movements, and the right superior longitudinal fasciculus, a tract important for audio-motor transformations. These results suggest that the speed with which novel complex audio-motor skills can be acquired may be determined by variability in structural properties of white matter fiber tracts connecting brain areas functionally relevant for audio-motor learning. Copyright © 2013 Wiley Periodicals, Inc.

White matter and schizophrenia: A meta-analysis of voxel-based morphometry and diffusion tensor imaging studies.

PubMed

Vitolo, Enrico; Tatu, Mona Karina; Pignolo, Claudia; Cauda, Franco; Costa, Tommaso; Ando', Agata; Zennaro, Alessandro

2017-12-30

Voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) are the most implemented methodologies to detect alterations of both gray and white matter (WM). However, the role of WM in mental disorders is still not well defined. We aimed at clarifying the role of WM disruption in schizophrenia and at identifying the most frequently involved brain networks. A systematic literature search was conducted to identify VBM and DTI studies focusing on WM alterations in patients with schizophrenia compared to control subjects. We selected studies reporting the coordinates of WM reductions and we performed the anatomical likelihood estimation (ALE). Moreover, we labeled the WM bundles with an anatomical atlas and compared VBM and DTI ALE-scores of each significant WM tract. A total of 59 studies were eligible for the meta-analysis. WM alterations were reported in 31 and 34 foci with VBM and DTI methods, respectively. The most occurred WM bundles in both VBM and DTI studies and largely involved in schizophrenia were long projection fibers, callosal and commissural fibers, part of motor descending fibers, and fronto-temporal-limbic pathways. The meta-analysis showed a widespread WM disruption in schizophrenia involving specific cerebral circuits instead of well-defined regions. Copyright © 2017 Elsevier B.V. All rights reserved.

White matter tractography by means of Turboprop diffusion tensor imaging.

PubMed

Arfanakis, Konstantinos; Gui, Minzhi; Lazar, Mariana

2005-12-01

White matter fiber-tractography by means of diffusion tensor imaging (DTI) is a noninvasive technique that provides estimates of the structural connectivity of the brain. However, conventional fiber-tracking methods using DTI are based on echo-planar image acquisitions (EPI), which suffer from image distortions and artifacts due to magnetic susceptibility variations and eddy currents. Thus, a large percentage of white matter fiber bundles that are mapped using EPI-based DTI data are distorted, and/or terminated early, while others are completely undetected. This severely limits the potential of fiber-tracking techniques. In contrast, Turboprop imaging is a multiple-shot gradient and spin-echo (GRASE) technique that provides images with significantly fewer susceptibility and eddy current-related artifacts than EPI. The purpose of this work was to evaluate the performance of fiber-tractography techniques when using data obtained with Turboprop-DTI. All fiber pathways that were mapped were found to be in agreement with the anatomy. There were no visible distortions in any of the traced fiber bundles, even when these were located in the vicinity of significant magnetic field inhomogeneities. Additionally, the Turboprop-DTI data used in this research were acquired in less than 19 min of scan time. Thus, Turboprop appears to be a promising DTI data acquisition technique for tracing white matter fibers.

Preform For Producing An Optical Fiber And Method Therefor

DOEpatents

Kliner, Dahv A. V.; Koplow, Jeffery P.

2004-08-10

The present invention provides a simple method for fabricating fiber-optic glass preforms having complex refractive index configurations and/or dopant distributions in a radial direction with a high degree of accuracy and precision. The method teaches bundling together a plurality of glass rods of specific physical, chemical, or optical properties and wherein the rod bundle is fused in a manner that maintains the cross-sectional composition and refractive-index profiles established by the position of the rods.

Preform For Producing An Optical Fiber And Method Therefor

DOEpatents

Kliner, Dahv A. V.; Koplow, Jeffery P.

2005-04-19

The present invention provides a simple method for fabricating fiber-optic glass preforms having complex refractive index configurations and/or dopant distributions in a radial direction with a high degree of accuracy and precision. The method teaches bundling together a plurality of glass rods of specific physical, chemical, or optical properties and wherein the rod bundle is fused in a manner that maintains the cross-sectional composition and refractive-index profiles established by the position of the rods.

Nanostructured optical fibre arrays for high-density biochemical sensing and remote imaging.

PubMed

Deiss, F; Sojic, N; White, D J; Stoddart, P R

2010-01-01

Optical fibre bundles usually comprise a few thousand to tens of thousands of individually clad glass optical fibres. The ordered arrangement of the fibres enables coherent transmission of an image through the bundle and therefore enables analysis and viewing in remote locations. In fused bundles, this architecture has also been used to fabricate arrays of various micro to nano-scale surface structures (micro/nanowells, nanotips, triangles, etc.) over relatively large areas. These surface structures have been used to obtain new optical and analytical capabilities. Indeed, the imaging bundle can be thought of as a "starting material" that can be sculpted by a combination of fibre drawing and selective wet-chemical etching processes. A large variety of bioanalytical applications have thus been developed, ranging from nano-optics to DNA nanoarrays. For instance, nanostructured optical surfaces with intrinsic light-guiding properties have been exploited as surface-enhanced Raman scattering (SERS) platforms and as near-field probe arrays. They have also been productively associated with electrochemistry to fabricate arrays of transparent nanoelectrodes with electrochemiluminescent imaging properties. The confined geometry of the wells has been loaded with biosensing materials and used as femtolitre-sized vessels to detect single molecules. This review describes the fabrication of high-density nanostructured optical fibre arrays and summarizes the large range of optical and bioanalytical applications that have been developed, reflecting the versatility of this ordered light-guiding platform.

Polymer-based doping control for performance enhancement of wet-processed short-channel CNTFETs

NASA Astrophysics Data System (ADS)

Hartmann, Martin; Schubel, René; Claus, Martin; Jordan, Rainer; Schulz, Stefan E.; Hermann, Sascha

2018-01-01

The electrical transport properties of short-channel transistors based on single-walled carbon nanotubes (CNT) are significantly affected by bundling along with solution processing. We report that especially high off currents of CNT transistors are not only related to the incorporation of metallic CNTs but also to the incorporation of CNT bundles. By applying device passivation with poly(4-vinylpyridine), the impact of CNT bundling on the device performance can be strongly reduced due to increased gate efficiency as well as reduced oxygen and water-induced p-type doping, boosting essential field-effect transistor performance parameters by several orders of magnitude. Moreover, this passivation approach allows the hysteresis and threshold voltage of CNT transistors to be tuned.

The counterbend dynamics of cross-linked filament bundles and flagella

PubMed Central

Coy, Rachel

2017-01-01

Cross-linked filament bundles, such as in cilia and flagella, are ubiquitous in biology. They are considered in textbooks as simple filaments with larger stiffness. Recent observations of flagellar counterbend, however, show that induction of curvature in one section of a passive flagellum instigates a compensatory counter-curvature elsewhere, exposing the intricate role of the diminutive cross-linking proteins at large scales. We show that this effect, a material property of the cross-linking mechanics, modifies the bundle dynamics and induces a bimodal L2 − L3 length-dependent material response that departs from the Euler–Bernoulli theory. Hence, the use of simpler theories to analyse experiments can result in paradoxical interpretations. Remarkably, the counterbend dynamics instigates counter-waves in opposition to driven oscillations in distant parts of the bundle, with potential impact on the regulation of flagellar bending waves. These results have a range of physical and biological applications, including the empirical disentanglement of material quantities via counterbend dynamics. PMID:28566516

Comparative transduction mechanisms of hair cells in the bullfrog uticulus. 2: Sensitivity and response dynamics to hair bundle displacement

NASA Technical Reports Server (NTRS)

Baird, Richard A.

1994-01-01

The present study was motivated by an interest in seeing whether hair cell types in the bullfrog utriculus might differ in their voltage responses to hair bundle displacement. Particular interest was in assessing the contributions of two factors to the responses of utricular hair cells. First, interest in examining the effect of hair bundle morphology on the sensitivity of hair cells to natural stimulation was motivated by the observation that vestibular hair cells, unlike many auditory hair cells, are not free-standing but rather linked to an accessory cupular or otolithic membrane via the tip of their kinocilium. Interest also laid in examining the contribution, if any, of adaptation to the response properties of utricular hair cells. Hair cells in auditory and vibratory inner ear endorgans adapt to maintained displacements of their hair bundles, sharply limiting their low frequency sensitivity. This adaptation is mediated by a shift in the displacement-response curve (DRC) of the hair cell along the displacement axis. Observations suggest that the adaptation process occurs within the hair bundle and precedes mechanoelectric transduction. Recent observations of time-dependent changes in hair bundle stiffness are consistent with this conclusion. Adaptation would be expected to be most useful in inner ear endorgans in which hair cells are subject to large static displacements that could potentially saturate their instantaneous response and compromise their sensitivity to high frequency stimulation. The adaptation process also permits hair cells to maintain their sensory hair bundle in the most sensitive portion of their DRC. In vestibular otolith organs in which static sensitivity is desirable, any adaptation process in the hair cells may be undesirable. The rate and extent of the decline of the voltage responses was measured of utricular hair cells to step and sinusoidal hair bundle displacements. Then for similar resting potentials and response amplitudes, the voltage responses of individual hair cells were compared to both hair bundle displacement and intracellular current.

Adsorption site analysis of impurity embedded single-walled carbon nanotube bundles

USGS Publications Warehouse

Agnihotri, S.; Mota, J.P.B.; Rostam-Abadi, M.; Rood, M.J.

2006-01-01

Bundle morphology and adsorptive contributions from nanotubes and impurities are studied both experimentally and by simulation using a computer-aided methodology, which employs a small physisorbed probe molecule to explore the porosity of nanotube samples. Grand canonical Monte Carlo simulation of nitrogen adsorption on localized sites of a bundle is carried out to predict adsorption in its accessible internal pore volume and on its external surface as a function of tube diameter. External adsorption is split into the contributions from the clean surface of the outermost nanotubes of the bundle and from the surface of the impurities. The site-specific isotherms are then combined into a global isotherm for a given sample using knowledge of its tube-diameter distribution obtained by Raman spectroscopy. The structural parameters of the sample, such as the fraction of open-ended nanotubes and the contributions from impurities and nanotube bundles to total external surface area, are determined by fitting the experimental nitrogen adsorption data to the simulated isotherm. The degree of closure between experimental and calculated adsorption isotherms for samples manufactured by two different methods, to provide different nanotube morphology and contamination level, further strengthens the validity and resulting interpretations based on the proposed approach. The average number of nanotubes per bundle and average bundle size, within a sample, are also quantified. The proposed method allows for extrapolation of adsorption properties to conditions where the purification process is 100% effective at removing all impurities and opening access to all intrabundle adsorption sites. ?? 2006 Elsevier Ltd. All rights reserved.

Anionic poly(amino acid)s dissolve F-actin and DNA bundles, enhance DNase activity, and reduce the viscosity of cystic fibrosis sputum.

PubMed

Tang, Jay X; Wen, Qi; Bennett, Andrew; Kim, Brian; Sheils, Catherine A; Bucki, Robert; Janmey, Paul A

2005-10-01

Bundles of F-actin and DNA present in the sputum of cystic fibrosis (CF) patients but absent from normal airway fluid contribute to the altered viscoelastic properties of sputum that inhibit clearance of infected airway fluid and exacerbate the pathology of CF. Previous strategies to remove these filamentous aggregates have focused on DNase to enzymatically depolymerize DNA to constituent monomers and gelsolin to sever F-actin to small fragments. The high densities of negative surface charge on DNA and F-actin suggest that the bundles of these filaments, which alone exhibit a strong electrostatic repulsion, may be stabilized by multivalent cations such as histones, antimicrobial peptides, and other positively charged molecules prevalent in airway fluid. This study reports that bundles of DNA or F-actin formed after addition of histone H1 or lysozyme are efficiently dissolved by soluble multivalent anions such as polymeric aspartate or glutamate. Addition of poly-aspartate or poly-glutamate also disperses DNA and actin-containing bundles in CF sputum and lowers the elastic moduli of these samples to levels comparable to those obtained after treatment with DNase I or gelsolin. Addition of poly-aspartic acid also increased DNase activity when added to samples containing DNA bundles formed with histone H1. When added to CF sputum, poly-aspartic acid significantly reduced the growth of bacteria, suggesting activation of endogenous antibacterial factors. These findings suggest that soluble multivalent anions have potential alone or in combination with other mucolytic agents to selectively dissociate the large bundles of charged biopolymers that form in CF sputum.

Risk of Revision Was Not Reduced by a Double-bundle ACL Reconstruction Technique: Results From the Scandinavian Registers.

PubMed

Aga, Cathrine; Kartus, Jüri-Tomas; Lind, Martin; Lygre, Stein Håkon Låstad; Granan, Lars-Petter; Engebretsen, Lars

2017-10-01

Double-bundle anterior cruciate ligament (ACL) reconstruction has demonstrated improved biomechanical properties and moderately better objective outcomes compared with single-bundle reconstructions. This could make an impact on the rerupture rate and reduce the risk of revisions in patients undergoing double-bundle ACL reconstruction compared with patients reconstructed with a traditional single-bundle technique. The National Knee Ligament Registers in Scandinavia provide information that can be used to evaluate the revision outcome after ACL reconstructions. The purposes of the study were (1) to compare the risk of revision between double-bundle and single-bundle reconstructions, reconstructed with autologous hamstring tendon grafts; (2) to compare the risk of revision between double-bundle hamstring tendon and single-bundle bone-patellar tendon-bone autografts; and (3) to compare the hazard ratios for the same two research questions after Cox regression analysis was performed. Data collection of primary ACL reconstructions from the National Knee Ligament Registers in Denmark, Norway, and Sweden from July 1, 2005, to December 31, 2014, was retrospectively analyzed. A total of 60,775 patients were included in the study; 994 patients were reconstructed with double-bundle hamstring tendon grafts, 51,991 with single-bundle hamstring tendon grafts, and 7790 with single-bundle bone-patellar tendon-bone grafts. The double-bundle ACL-reconstructed patients were compared with the two other groups. The risk of revision for each research question was detected by the risk ratio, hazard ratio, and the corresponding 95% confidence intervals. Kaplan-Meier analysis was used to estimate survival at 1, 2, and 5 years for the three different groups. Furthermore, a Cox proportional hazard regression model was applied and the hazard ratios were adjusted for country, age, sex, meniscal or chondral injury, and utilized fixation devices on the femoral and tibial sides. There were no differences in the crude risk of revision between the patients undergoing the double-bundle technique and the two other groups. A total of 3.7% patients were revised in the double-bundle group (37 of 994 patients) versus 3.8% in the single-bundle hamstring tendon group (1952 of 51,991; risk ratio, 1.01; 95% confidence interval (CI), 0.73-1.39; p = 0.96), and 2.8% of the patients were revised in the bone-patellar tendon-bone group (219 of the 7790 bone-patellar tendon-bone patients; risk ratio, 0.76; 95% CI, 0.54-1.06; p = 0.11). Cox regression analysis with adjustment for country, age, sex, menisci or cartilage injury, and utilized fixation device on the femoral and tibial sides, did not reveal any further difference in the risk of revision between the single-bundle hamstring tendon and double-bundle hamstring tendon groups (hazard ratio, 1.18; 95% CI, 0.85-1.62; p = 0.33), but the adjusted hazard ratio showed a lower risk of revision in the single-bundle bone-patellar tendon-bone group compared with the double-bundle group (hazard ratio, 0.62; 95% CI, 0.43-0.90; p = 0.01). Comparisons of the graft revision rates reported separately for each country revealed that double-bundle hamstring tendon reconstructions in Sweden had a lower hazard ratio compared with the single-bundle hamstring tendon reconstructions (hazard ratio, 1.00 versus 1.89; 95% CI, 1.09-3.29; p = 0.02). Survival at 5 years after index surgery was 96.0% for the double-bundle group, 95.4% for the single-bundle hamstring tendon group, and 97.0% for the single-bundle bone-patellar tendon-bone group. Based on the data from all three national registers, the risk of revision was not influenced by the reconstruction technique in terms of using single- or double-bundle hamstring tendons, although national differences in survival existed. Using bone-patellar tendon-bone grafts lowered the risk of revision compared with double-bundle hamstring tendon grafts. These findings should be considered when deciding what reconstruction technique to use in ACL-deficient knees. Future studies identifying the reasons for graft rerupture in single- and double-bundle reconstructions would be of interest to understand the findings of the present study. Level III, therapeutic study.

Scintillator-fiber charged-particle track-imaging detector

NASA Technical Reports Server (NTRS)

Binns, W. R.; Israel, M. H.; Klarmann, J.

1983-01-01

A scintillator-fiber charged-particle track-imaging detector has been developed using a bundle of square cross-section plastic scintillator fiber optics, proximity focused onto an image intensified Charge Injection Device (CID) camera. Detector to beams of 15 MeV protons and relativistic Neon, Manganese, and Gold nuclei have been exposed and images of their tracks are obtained. This paper presents details of the detector technique, properties of the tracks obtained, and range measurements of 15 MeV protons stopping in the fiber bundle.

Hemangiopericytoma in the eyelid of a horse.

PubMed

Serena, A; Joiner, K S; Schumacher, J

2006-07-01

Hemangiopericytoma (HP) is a well-recognized neoplasm arising from vascular pericytes that has been reported only in the dog and man. In this study, we describe a 14-year-old female Arabian horse that was presented for surgical excision of a 2-cm-diameter expansile subcuticular mass in the right lower eyelid. Histologically, the mass consisted of loosely arranged interlacing streams and storiform bundles of spindle cells that often formed distinct whorls around a central capillary and bundles of collagen (Antoni A-like pattern). Immunohistochemical analysis revealed strong diffuse cytoplasmic immunoreactivity for vimentin and focal immunoreactivity for smooth muscle actin, whereas neoplastic cells did not stain for Factor VIII-related antigen, Glial fibrillary acidic protein (GFAP), or S100. On the basis of histomorphology and immunohistochemical reactivity, the present tumor was diagnosed as HP. To our knowledge, this is the first report describing a HP in a horse.

Modes of failure in disordered solids

NASA Astrophysics Data System (ADS)

Roy, Subhadeep; Biswas, Soumyajyoti; Ray, Purusattam

2017-12-01

The two principal ingredients determining the failure modes of disordered solids are the strength of heterogeneity and the length scale of the region affected in the solid following a local failure. While the latter facilitates damage nucleation, the former leads to diffused damage—the two extreme natures of the failure modes. In this study, using the random fiber bundle model as a prototype for disordered solids, we classify all failure modes that are the results of interplay between these two effects. We obtain scaling criteria for the different modes and propose a general phase diagram that provides a framework for understanding previous theoretical and experimental attempts of interpolation between these modes. As the fiber bundle model is a long-standing model for interpreting various features of stressed disordered solids, the general phase diagram can serve as a guiding principle in anticipating the responses of disordered solids in general.

Optimized mode-field adapter for low-loss fused fiber bundle signal and pump combiners

NASA Astrophysics Data System (ADS)

Koška, Pavel; Baravets, Yauhen; Peterka, Pavel; Písařík, Michael; Bohata, Jan

2015-03-01

In our contribution we report novel mode field adapter incorporated inside bundled tapered pump and signal combiner. Pump and signal combiners are crucial component of contemporary double clad high power fiber lasers. Proposed combiner allows simultaneous matching to single mode core on input and output. We used advanced optimization techniques to match the combiner to a single mode core simultaneously on input and output and to minimalize losses of the combiner signal branch. We designed two arrangements of combiners' mode field adapters. Our numerical simulations estimates losses in signal branches of optimized combiners of 0.23 dB for the first design and 0.16 dB for the second design for SMF-28 input fiber and SMF-28 matched output double clad fiber for the wavelength of 2000 nm. The splice losses of the actual combiner are expected to be even lower thanks to dopant diffusion during the splicing process.

Review of Recent Developments on Using an Off-Lattice Monte Carlo Approach to Predict the Effective Thermal Conductivity of Composite Systems with Complex Structures

PubMed Central

Gong, Feng; Duong, Hai M.; Papavassiliou, Dimitrios V.

2016-01-01

Here, we present a review of recent developments for an off-lattice Monte Carlo approach used to investigate the thermal transport properties of multiphase composites with complex structure. The thermal energy was quantified by a large number of randomly moving thermal walkers. Different modes of heat conduction were modeled in appropriate ways. The diffusive heat conduction in the polymer matrix was modeled with random Brownian motion of thermal walkers within the polymer, and the ballistic heat transfer within the carbon nanotubes (CNTs) was modeled by assigning infinite speed of thermal walkers in the CNTs. Three case studies were conducted to validate the developed approach, including three-phase single-walled CNTs/tungsten disulfide (WS2)/(poly(ether ether ketone) (PEEK) composites, single-walled CNT/WS2/PEEK composites with the CNTs clustered in bundles, and complex graphene/poly(methyl methacrylate) (PMMA) composites. In all cases, resistance to heat transfer due to nanoscale phenomena was also modeled. By quantitatively studying the influencing factors on the thermal transport properties of the multiphase composites, it was found that the orientation, aggregation and morphology of fillers, as well as the interfacial thermal resistance at filler-matrix interfaces would limit the transfer of heat in the composites. These quantitative findings may be applied in the design and synthesis of multiphase composites with specific thermal transport properties. PMID:28335270

Intrauterine device for laser light diffusion and method of using the same

DOEpatents

Tadir, Yona; Berns, Michael W.; Svaasand, Lars O.; Tromberg, Bruce J.

1995-01-01

An improved device for delivery of photoenergy from a light source, such as a laser, into a uterine cavity for photodynamic therapy is comprised of a plurality of optic fibers, which are bundled together and inserted into the uterine cavity by means of a uterine cannula. The cannula is positioned within the uterine cavity at a preferred location and then withdrawn thereby allowing the plurality of optic fibers to splay or diverge one from the other within the cavity. Different portions of the distal tip of the optic fiber is provided with a light diffusing tip, the remainder being provided with a nondiffusing tip portion. The fiber optic shape, as well as the segment which is permitted to actively diffuse light through the tip, is selected in order to provide a more uniform exposure intensity of the photo energy or at least sufficient radiation directed to each segment of the uterine walls.

Intrauterine device for laser light diffusion and method of using the same

DOEpatents

Tadir, Y.; Berns, M.W.; Svaasand, L.O.; Tromberg, B.J.

1995-12-26

An improved device for delivery of photoenergy from a light source, such as a laser, into a uterine cavity for photodynamic therapy is comprised of a plurality of optic fibers, which are bundled together and inserted into the uterine cavity by means of a uterine cannula. The cannula is positioned within the uterine cavity at a preferred location and then withdrawn thereby allowing the plurality of optic fibers to splay or diverge one from the other within the cavity. Different portions of the distal tip of the optic fiber is provided with a light diffusing tip, the remainder being provided with a nondiffusing tip portion. The fiber optic shape, as well as the segment which is permitted to actively diffuse light through the tip, is selected in order to provide a more uniform exposure intensity of the photo energy or at least sufficient radiation directed to each segment of the uterine walls. 5 figs.

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

Design of Multishell Sampling Schemes with Uniform Coverage in Diffusion MRI

PubMed Central

Caruyer, Emmanuel; Lenglet, Christophe; Sapiro, Guillermo; Deriche, Rachid

2017-01-01

Purpose In diffusion MRI, a technique known as diffusion spectrum imaging reconstructs the propagator with a discrete Fourier transform, from a Cartesian sampling of the diffusion signal. Alternatively, it is possible to directly reconstruct the orientation distribution function in q-ball imaging, providing so-called high angular resolution diffusion imaging. In between these two techniques, acquisitions on several spheres in q-space offer an interesting trade-off between the angular resolution and the radial information gathered in diffusion MRI. A careful design is central in the success of multishell acquisition and reconstruction techniques. Methods The design of acquisition in multishell is still an open and active field of research, however. In this work, we provide a general method to design multishell acquisition with uniform angular coverage. This method is based on a generalization of electrostatic repulsion to multishell. Results We evaluate the impact of our method using simulations, on the angular resolution in one and two bundles of fiber configurations. Compared to more commonly used radial sampling, we show that our method improves the angular resolution, as well as fiber crossing discrimination. Discussion We propose a novel method to design sampling schemes with optimal angular coverage and show the positive impact on angular resolution in diffusion MRI. PMID:23625329

A probabilistic atlas of human brainstem pathways based on connectome imaging data.

PubMed

Tang, Yuchun; Sun, Wei; Toga, Arthur W; Ringman, John M; Shi, Yonggang

2018-04-01

The brainstem is a critical structure that regulates vital autonomic functions, houses the cranial nerves and their nuclei, relays motor and sensory information between the brain and spinal cord, and modulates cognition, mood, and emotions. As a primary relay center, the fiber pathways of the brainstem include efferent and afferent connections among the cerebral cortex, spinal cord, and cerebellum. While diffusion MRI has been successfully applied to map various brain pathways, its application for the in vivo imaging of the brainstem pathways has been limited due to inadequate resolution and large susceptibility-induced distortion artifacts. With the release of high-resolution data from the Human Connectome Project (HCP), there is increasing interest in mapping human brainstem pathways. Previous works relying on HCP data to study brainstem pathways, however, did not consider the prevalence (>80%) of large distortions in the brainstem even after the application of correction procedures from the HCP-Pipeline. They were also limited in the lack of adequate consideration of subject variability in either fiber pathways or region of interests (ROIs) used for bundle reconstruction. To overcome these limitations, we develop in this work a probabilistic atlas of 23 major brainstem bundles using high-quality HCP data passing rigorous quality control. For the large-scale data from the 500-Subject release of HCP, we conducted extensive quality controls to exclude subjects with severe distortions in the brainstem area. After that, we developed a systematic protocol to manually delineate 1300 ROIs on 20 HCP subjects (10 males; 10 females) for the reconstruction of fiber bundles using tractography techniques. Finally, we leveraged our novel connectome modeling techniques including high order fiber orientation distribution (FOD) reconstruction from multi-shell diffusion imaging and topography-preserving tract filtering algorithms to successfully reconstruct the 23 fiber bundles for each subject, which were then used to calculate the probabilistic atlases in the MNI152 space for public release. In our experimental results, we demonstrate that our method yielded anatomically faithful reconstruction of the brainstem pathways and achieved improved performance in comparison with an existing atlas of cerebellar peduncles based on HCP data. These atlases have been publicly released on NITRIC (https://www.nitrc.org/projects/brainstem_atlas/) and can be readily used by brain imaging researchers interested in studying brainstem pathways. Copyright © 2017 Elsevier Inc. All rights reserved.

Biophotonics of skin: method for correction of deep Raman spectra distorted by elastic scattering

NASA Astrophysics Data System (ADS)

Roig, Blandine; Koenig, Anne; Perraut, François; Piot, Olivier; Gobinet, Cyril; Manfait, Michel; Dinten, Jean-Marc

2015-03-01

Confocal Raman microspectroscopy allows in-depth molecular and conformational characterization of biological tissues non-invasively. Unfortunately, spectral distortions occur due to elastic scattering. Our objective is to correct the attenuation of in-depth Raman peaks intensity by considering this phenomenon, enabling thus quantitative diagnosis. In this purpose, we developed PDMS phantoms mimicking skin optical properties used as tools for instrument calibration and data processing method validation. An optical system based on a fibers bundle has been previously developed for in vivo skin characterization with Diffuse Reflectance Spectroscopy (DRS). Used on our phantoms, this technique allows checking their optical properties: the targeted ones were retrieved. Raman microspectroscopy was performed using a commercial confocal microscope. Depth profiles were constructed from integrated intensity of some specific PDMS Raman vibrations. Acquired on monolayer phantoms, they display a decline which is increasing with the scattering coefficient. Furthermore, when acquiring Raman spectra on multilayered phantoms, the signal attenuation through each single layer is directly dependent on its own scattering property. Therefore, determining the optical properties of any biological sample, obtained with DRS for example, is crucial to correct properly Raman depth profiles. A model, inspired from S.L. Jacques's expression for Confocal Reflectance Microscopy and modified at some points, is proposed and tested to fit the depth profiles obtained on the phantoms as function of the reduced scattering coefficient. Consequently, once the optical properties of a biological sample are known, the intensity of deep Raman spectra distorted by elastic scattering can be corrected with our reliable model, permitting thus to consider quantitative studies for purposes of characterization or diagnosis.

Atlas-guided cluster analysis of large tractography datasets.

PubMed

Ros, Christian; Güllmar, Daniel; Stenzel, Martin; Mentzel, Hans-Joachim; Reichenbach, Jürgen Rainer

2013-01-01

Diffusion Tensor Imaging (DTI) and fiber tractography are important tools to map the cerebral white matter microstructure in vivo and to model the underlying axonal pathways in the brain with three-dimensional fiber tracts. As the fast and consistent extraction of anatomically correct fiber bundles for multiple datasets is still challenging, we present a novel atlas-guided clustering framework for exploratory data analysis of large tractography datasets. The framework uses an hierarchical cluster analysis approach that exploits the inherent redundancy in large datasets to time-efficiently group fiber tracts. Structural information of a white matter atlas can be incorporated into the clustering to achieve an anatomically correct and reproducible grouping of fiber tracts. This approach facilitates not only the identification of the bundles corresponding to the classes of the atlas; it also enables the extraction of bundles that are not present in the atlas. The new technique was applied to cluster datasets of 46 healthy subjects. Prospects of automatic and anatomically correct as well as reproducible clustering are explored. Reconstructed clusters were well separated and showed good correspondence to anatomical bundles. Using the atlas-guided cluster approach, we observed consistent results across subjects with high reproducibility. In order to investigate the outlier elimination performance of the clustering algorithm, scenarios with varying amounts of noise were simulated and clustered with three different outlier elimination strategies. By exploiting the multithreading capabilities of modern multiprocessor systems in combination with novel algorithms, our toolkit clusters large datasets in a couple of minutes. Experiments were conducted to investigate the achievable speedup and to demonstrate the high performance of the clustering framework in a multiprocessing environment.

Nanomechanics modeling of carbon nanotubes interacting with surfaces in various configurations

NASA Astrophysics Data System (ADS)

Wu, Yu-Chiao

Carbon nanotubes (CNTs) have been widely used as potential components in reported nanoelectromechanical (NEM) devices due to their excellent mechanical and electrical properties. This thesis models the experiments by the continuum mechanics in two distinct scenarios. In the first situation, measurements are made of CNT configurations after manipulations. Modeling is then used to determine the interfacial properties during the manipulation which led to the observed configuration. This technique is used to determine the shear stress between a SWNT bundle and other materials. During manipulation, a SWNT bundle slipped on two micro-cantilevers. According to the slack due to the slippage after testing and the device configuration, the shear stress between a SWNT bundle and other materials can be determined. In another model, the work of adhesion was determined on two accidentally fabricated devices. Through the configuration of two SWNT adhered bundles and the force-distance curves measured by an atomic force microscope (AFM), modeling was used to determine the work of adhesion between two bundles and the shear stress at the SWNT-substrate interface. In the second situation, modeling is used in a more traditional fashion to make theoretical predictions as to how a device will operate. Using this technique, the actuation mechanism of a single-trench SWNT-based switch was investigated. During the actuation, the deflection-induced tension causes the SWNT bundle to slip on both platforms and to be partially peeled from two side recessed electrodes. These effects produce a slack which reduces the threshold voltages subsequent to the first actuation. The result shows excellent agreement between the theory and the measurement. Furthermore, the operation of a double-trenched SWNT-based switch was investigated. A slack is produced in the 1st actuated trench region by the slip and peeling effects. This slack reduces the 2nd actuation voltage in the neighbor trench. Finally, the adhesive slip process at the SWNT-substrate interface was simulated. The result shows that the force for slip of a SWNT remains constant for lengths less than about 240 nm. Beyond that length, increasing the contact length causes increase the force for slippage. This phenomenon agrees well with reported experiments.

Mechanical properties of sensory hair bundles are reflected in their Brownian motion measured with a laser differential interferometer.

PubMed Central

Denk, W; Webb, W W; Hudspeth, A J

1989-01-01

By optically probing with a focused, low-power laser beam, we measured the spontaneous deflection fluctuations of the sensory hair bundles on frog saccular hair cells with a sensitivity of about 1 pm/square root of Hz. The preparation was illuminated by two orthogonally polarized laser beams separated by only about 0.2 microns at their foci in the structure under investigation. Slight movement of the object from one beam toward the other caused a change of the phase difference between the transmitted beams and an intensity modulation at the detector where the beams interfered. Maintenance of the health of the cells and function of the transduction mechanism were occasionally confirmed by measuring the intracellular resting potential and the sensitivity of transduction. The root-mean-square (rms) displacement of approximately 3.5 nm at a hair bundle's tip suggests a stiffness of about 350 microN/m, in agreement with measurements made with a probe attached to a bundle's tip. The spectra resemble those of overdamped harmonic oscillators with roll-off frequencies between 200 and 800 Hz. Because the roll-off frequencies depended strongly on the viscosity of the bathing medium, we conclude that hair-bundle motion is mainly damped by the surrounding fluid. PMID:2787510

Characterizing Brain Structures and Remodeling after TBI Based on Information Content, Diffusion Entropy

PubMed Central

Fozouni, Niloufar; Chopp, Michael; Nejad-Davarani, Siamak P.; Zhang, Zheng Gang; Lehman, Norman L.; Gu, Steven; Ueno, Yuji; Lu, Mei; Ding, Guangliang; Li, Lian; Hu, Jiani; Bagher-Ebadian, Hassan; Hearshen, David; Jiang, Quan

2013-01-01

Background To overcome the limitations of conventional diffusion tensor magnetic resonance imaging resulting from the assumption of a Gaussian diffusion model for characterizing voxels containing multiple axonal orientations, Shannon's entropy was employed to evaluate white matter structure in human brain and in brain remodeling after traumatic brain injury (TBI) in a rat. Methods Thirteen healthy subjects were investigated using a Q-ball based DTI data sampling scheme. FA and entropy values were measured in white matter bundles, white matter fiber crossing areas, different gray matter (GM) regions and cerebrospinal fluid (CSF). Axonal densities' from the same regions of interest (ROIs) were evaluated in Bielschowsky and Luxol fast blue stained autopsy (n = 30) brain sections by light microscopy. As a case demonstration, a Wistar rat subjected to TBI and treated with bone marrow stromal cells (MSC) 1 week after TBI was employed to illustrate the superior ability of entropy over FA in detecting reorganized crossing axonal bundles as confirmed by histological analysis with Bielschowsky and Luxol fast blue staining. Results Unlike FA, entropy was less affected by axonal orientation and more affected by axonal density. A significant agreement (r = 0.91) was detected between entropy values from in vivo human brain and histologically measured axonal density from post mortum from the same brain structures. The MSC treated TBI rat demonstrated that the entropy approach is superior to FA in detecting axonal remodeling after injury. Compared with FA, entropy detected new axonal remodeling regions with crossing axons, confirmed with immunohistological staining. Conclusions Entropy measurement is more effective in distinguishing axonal remodeling after injury, when compared with FA. Entropy is also more sensitive to axonal density than axonal orientation, and thus may provide a more accurate reflection of axonal changes that occur in neurological injury and disease. PMID:24143186

Characterizing brain structures and remodeling after TBI based on information content, diffusion entropy.

PubMed

Fozouni, Niloufar; Chopp, Michael; Nejad-Davarani, Siamak P; Zhang, Zheng Gang; Lehman, Norman L; Gu, Steven; Ueno, Yuji; Lu, Mei; Ding, Guangliang; Li, Lian; Hu, Jiani; Bagher-Ebadian, Hassan; Hearshen, David; Jiang, Quan

2013-01-01

To overcome the limitations of conventional diffusion tensor magnetic resonance imaging resulting from the assumption of a Gaussian diffusion model for characterizing voxels containing multiple axonal orientations, Shannon's entropy was employed to evaluate white matter structure in human brain and in brain remodeling after traumatic brain injury (TBI) in a rat. Thirteen healthy subjects were investigated using a Q-ball based DTI data sampling scheme. FA and entropy values were measured in white matter bundles, white matter fiber crossing areas, different gray matter (GM) regions and cerebrospinal fluid (CSF). Axonal densities' from the same regions of interest (ROIs) were evaluated in Bielschowsky and Luxol fast blue stained autopsy (n = 30) brain sections by light microscopy. As a case demonstration, a Wistar rat subjected to TBI and treated with bone marrow stromal cells (MSC) 1 week after TBI was employed to illustrate the superior ability of entropy over FA in detecting reorganized crossing axonal bundles as confirmed by histological analysis with Bielschowsky and Luxol fast blue staining. Unlike FA, entropy was less affected by axonal orientation and more affected by axonal density. A significant agreement (r = 0.91) was detected between entropy values from in vivo human brain and histologically measured axonal density from post mortum from the same brain structures. The MSC treated TBI rat demonstrated that the entropy approach is superior to FA in detecting axonal remodeling after injury. Compared with FA, entropy detected new axonal remodeling regions with crossing axons, confirmed with immunohistological staining. Entropy measurement is more effective in distinguishing axonal remodeling after injury, when compared with FA. Entropy is also more sensitive to axonal density than axonal orientation, and thus may provide a more accurate reflection of axonal changes that occur in neurological injury and disease.

Modelling the development and arrangement of the primary vascular structure in plants.

PubMed

Cartenì, Fabrizio; Giannino, Francesco; Schweingruber, Fritz Hans; Mazzoleni, Stefano

2014-09-01

The process of vascular development in plants results in the formation of a specific array of bundles that run throughout the plant in a characteristic spatial arrangement. Although much is known about the genes involved in the specification of procambium, phloem and xylem, the dynamic processes and interactions that define the development of the radial arrangement of such tissues remain elusive. This study presents a spatially explicit reaction-diffusion model defining a set of logical and functional rules to simulate the differentiation of procambium, phloem and xylem and their spatial patterns, starting from a homogeneous group of undifferentiated cells. Simulation results showed that the model is capable of reproducing most vascular patterns observed in plants, from primitive and simple structures made up of a single strand of vascular bundles (protostele), to more complex and evolved structures, with separated vascular bundles arranged in an ordered pattern within the plant section (e.g. eustele). The results presented demonstrate, as a proof of concept, that a common genetic-molecular machinery can be the basis of different spatial patterns of plant vascular development. Moreover, the model has the potential to become a useful tool to test different hypotheses of genetic and molecular interactions involved in the specification of vascular tissues.

Microscopic Analysis of Bacterial Motility at High Pressure

PubMed Central

Nishiyama, Masayoshi; Sowa, Yoshiyuki

2012-01-01

The bacterial flagellar motor is a molecular machine that converts an ion flux to the rotation of a helical flagellar filament. Counterclockwise rotation of the filaments allows them to join in a bundle and propel the cell forward. Loss of motility can be caused by environmental factors such as temperature, pH, and solvation. Hydrostatic pressure is also a physical inhibitor of bacterial motility, but the detailed mechanism of this inhibition is still unknown. Here, we developed a high-pressure microscope that enables us to acquire high-resolution microscopic images, regardless of applied pressures. We also characterized the pressure dependence of the motility of swimming Escherichia coli cells and the rotation of single flagellar motors. The fraction and speed of swimming cells decreased with increased pressure. At 80 MPa, all cells stopped swimming and simply diffused in solution. After the release of pressure, most cells immediately recovered their initial motility. Direct observation of the motility of single flagellar motors revealed that at 80 MPa, the motors generate torque that should be sufficient to join rotating filaments in a bundle. The discrepancy in the behavior of free swimming cells and individual motors could be due to the applied pressure inhibiting the formation of rotating filament bundles that can propel the cell body in an aqueous environment. PMID:22768943

Bundle-sheath leakiness in C4 photosynthesis: a careful balancing act between CO2 concentration and assimilation.

PubMed

Kromdijk, Johannes; Ubierna, Nerea; Cousins, Asaph B; Griffiths, Howard

2014-07-01

Crop species with the C4 photosynthetic pathway are generally characterized by high productivity, especially in environmental conditions favouring photorespiration. In comparison with the ancestral C3 pathway, the biochemical and anatomical modifications of the C4 pathway allow spatial separation of primary carbon acquisition in mesophyll cells and subsequent assimilation in bundle-sheath cells. The CO2-concentrating C4 cycle has to operate in close coordination with CO2 reduction via the Calvin-Benson-Bassham (CBB) cycle in order to keep the C4 pathway energetically efficient. The gradient in CO2 concentration between bundle-sheath and mesophyll cells facilitates diffusive leakage of CO2. This rate of bundle-sheath CO2 leakage relative to the rate of phosphoenolpyruvate carboxylation (termed leakiness) has been used to probe the balance between C4 carbon acquisition and subsequent reduction as a result of environmental perturbations. When doing so, the correct choice of equations to derive leakiness from stable carbon isotope discrimination (Δ(13)C) during gas exchange is critical to avoid biased results. Leakiness responses to photon flux density, either short-term (during measurements) or long-term (during growth and development), can have important implications for C4 performance in understorey light conditions. However, recent reports show leakiness to be subject to considerable acclimation. Additionally, the recent discovery of two decarboxylating C4 cycles operating in parallel in Zea mays suggests that flexibility in the transported C4 acid and associated decarboxylase could also aid in maintaining C4/CBB balance in a changing environment. In this paper, we review improvements in methodology to estimate leakiness, synthesize reports on bundle-sheath leakiness, discuss different interpretations, and highlight areas where future research is necessary. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

A nano-microstructured artificial-hair-cell-type sensor based on topologically graded 3D carbon nanotube bundles

NASA Astrophysics Data System (ADS)

Yilmazoglu, O.; Yadav, S.; Cicek, D.; Schneider, J. J.

2016-09-01

A design for a unique artificial-hair-cell-type sensor (AHCTS) based entirely on 3D-structured, vertically aligned carbon nanotube (CNT) bundles is introduced. Standard microfabrication techniques were used for the straightforward micro-nano integration of vertically aligned carbon nanotube arrays composed of low-layer multi-walled CNTs (two to six layers). The mechanical properties of the carbon nanotube bundles were intensively characterized with regard to various substrates and CNT morphology, e.g. bundle height. The CNT bundles display excellent flexibility and mechanical stability for lateral bending, showing high tear resistance. The integrated 3D CNT sensor can detect three-dimensional forces using the deflection or compression of a central CNT bundle which changes the contact resistance to the shorter neighboring bundles. The complete sensor system can be fabricated using a single chemical vapor deposition (CVD) process step. Moreover, sophisticated external contacts to the surroundings are not necessary for signal detection. No additional sensors or external bias for signal detection are required. This simplifies the miniaturization and the integration of these nanostructures for future microsystem set-ups. The new nanostructured sensor system exhibits an average sensitivity of 2100 ppm in the linear regime with the relative resistance change per micron (ppm μm-1) of the individual CNT bundle tip deflection. Furthermore, experiments have shown highly sensitive piezoresistive behavior with an electrical resistance decrease of up to ˜11% at 50 μm mechanical deflection. The detection sensitivity is as low as 1 μm of deflection, and thus highly comparable with the tactile hair sensors of insects, having typical thresholds on the order of 30-50 μm. The AHCTS can easily be adapted and applied as a flow, tactile or acceleration sensor as well as a vibration sensor. Potential applications of the latter might come up in artificial cochlear systems. In particular, the stable mechanical bending of the sensor up to 90° opens up unique application opportunities.

Direct electrical and mechanical characterization of in situ generated DNA between the tips of silicon nanotweezers (SNT).

PubMed

Karsten, Stanislav L; Kumemura, Momoko; Jalabert, Laurent; Lafitte, Nicolas; Kudo, Lili C; Collard, Dominique; Fujita, Hiroyuki

2016-05-24

Previously, we reported the application of micromachined silicon nanotweezers (SNT) integrated with a comb-drive actuator and capacitive sensors for capturing and mechanical characterization of DNA bundles. Here, we demonstrate direct DNA amplification on such a MEMS structure with subsequent electrical and mechanical characterization of a single stranded DNA (ssDNA) bundle generated between the tips of SNT via isothermal rolling circle amplification (RCA) and dielectrophoresis (DEP). An in situ generated ssDNA bundle was visualized and evaluated via electrical conductivity (I-V) and mechanical frequency response measurements. Colloidal gold nanoparticles significantly enhanced (P < 0.01) the electrical properties of thin ssDNA bundles. The proposed technology allows direct in situ synthesis of DNA with a predefined sequence on the tips of a MEMS sensor device, such as SNT, followed by direct DNA electrical and mechanical characterization. In addition, our data provides a "proof-of-principle" for the feasibility of the on-chip label free DNA detection device that can be used for a variety of biomedical applications focused on sequence specific DNA detection.

Geometry of matrix product states: Metric, parallel transport, and curvature

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

Haegeman, Jutho, E-mail: jutho.haegeman@gmail.com; Verstraete, Frank; Faculty of Physics and Astronomy, University of Ghent, Krijgslaan 281 S9, 9000 Gent

2014-02-15

We study the geometric properties of the manifold of states described as (uniform) matrix product states. Due to the parameter redundancy in the matrix product state representation, matrix product states have the mathematical structure of a (principal) fiber bundle. The total space or bundle space corresponds to the parameter space, i.e., the space of tensors associated to every physical site. The base manifold is embedded in Hilbert space and can be given the structure of a Kähler manifold by inducing the Hilbert space metric. Our main interest is in the states living in the tangent space to the base manifold,more » which have recently been shown to be interesting in relation to time dependence and elementary excitations. By lifting these tangent vectors to the (tangent space) of the bundle space using a well-chosen prescription (a principal bundle connection), we can define and efficiently compute an inverse metric, and introduce differential geometric concepts such as parallel transport (related to the Levi-Civita connection) and the Riemann curvature tensor.« less

Mass Transport Through Carbon Nanotube-Polystyrene Bundles

NASA Astrophysics Data System (ADS)

Lin, Rongzhou; Tran, Tuan

2016-05-01

Carbon nanotubes have been widely used as test channels to study nanofluidic transport, which has been found to have distinctive properties compared to transport of fluids in macroscopic channels. A long-standing challenge in the study of mass transport through carbon nanotubes (CNTs) is the determination of flow enhancement. Various experimental investigations have been conducted to measure the flow rate through CNTs, mainly based on either vertically aligned CNT membranes or individual CNTs. Here, we proposed an alternative approach that can be used to quantify the mass transport through CNTs. This is a simple method relying on the use of carbon nanotube-polystyrene bundles, which are made of CNTs pulled out from a vertically aligned CNT array and glued together by polystyrene. We experimentally showed by using fluorescent tagging that the composite bundles allowed measureable and selective mass transport through CNTs. This type of composite bundle may be useful in various CNT research areas as they are simple to fabricate, less likely to form macroscopic cracks, and offer a high density of CNT pores while maintaining the aligned morphology of CNTs.

Fabrication of an ideal nanoring from a black phosphorus nanoribbon upon movable bundling carbon nanotubes

NASA Astrophysics Data System (ADS)

Cai, Kun; Shi, Jiao; Liu, Lingnan; Qin, Qing H.

2017-09-01

As a low dimensional material, black phosphorus (BP) continues to attract much attention from researchers due to its excellent electric properties. In particular, the one-dimensional material, in the form of a ring or tube formed from BP, has been extensively studied and found to be a perfect semiconductor. But the BP ring has never been reported in laboratories. To form an ideal ring from a rectangular BP ribbon, we choose a carbon nanotube (CNT) bundle to attract the ribbon and move one or more CNTs in the bundle to induce the unsaturated ends of the BP ribbon to become covalently bonded. Numerical experiments are applied to BP ribbons with lengths either equal to, shorter, or longer than the perimeter of the CNT bundle, to investigate the formation of a BP ring. Experiments show that if one end of the BP ribbon is attracted by a CNT, moving the other CNTs away endows the ribbon with high probability of forming an ideal ring. The conclusions drawn from these results will benefit future in situ experiments involving forming a ring from a BP ribbon.

Electrostatic interaction between stereocilia: I. Its role in supporting the structure of the hair bundle.

PubMed

Dolgobrodov, S G; Lukashkin, A N; Russell, I J

2000-12-01

This paper provides theoretical estimates for the forces of electrostatic interaction between adjacent stereocilia in auditory and vestibular hair cells. Estimates are given for parameters within the measured physiological range using constraints appropriate for the known geometry of the hair bundle. Stereocilia are assumed to possess an extended, negatively charged surface coat, the glycocalyx. Different charge distribution profiles within the glycocalyx are analysed. It is shown that charged glycocalices on the apical surface of the hair cells can support spatial separation between adjacent stereocilia in the hair bundles through electrostatic repulsion between stereocilia. The charge density profile within the glycocalyx is a crucial parameter. In fact, attraction instead of repulsion between adjacent stereocilia will be observed if the charge of the glycocalyx is concentrated near the membrane of the stereocilia, thereby making this type of charge distribution unlikely. The forces of electrostatic interaction between stereocilia may influence the mechanical properties of the hair bundle and, being strongly non-linear, contribute to the non-linear phenomena that have been recorded from the periphery of the auditory and vestibular systems.

Numerical implementation of complex orthogonalization, parallel transport on Stiefel bundles, and analyticity

NASA Astrophysics Data System (ADS)

Avitabile, Daniele; Bridges, Thomas J.

2010-06-01

Numerical integration of complex linear systems of ODEs depending analytically on an eigenvalue parameter are considered. Complex orthogonalization, which is required to stabilize the numerical integration, results in non-analytic systems. It is shown that properties of eigenvalues are still efficiently recoverable by extracting information from a non-analytic characteristic function. The orthonormal systems are constructed using the geometry of Stiefel bundles. Different forms of continuous orthogonalization in the literature are shown to correspond to different choices of connection one-form on the Stiefel bundle. For the numerical integration, Gauss-Legendre Runge-Kutta algorithms are the principal choice for preserving orthogonality, and performance results are shown for a range of GLRK methods. The theory and methods are tested by application to example boundary value problems including the Orr-Sommerfeld equation in hydrodynamic stability.

Weavability of dry polymer powder towpreg

NASA Technical Reports Server (NTRS)

Hugh, Maylene K.; Marchello, Joseph M.; Maiden, Janice R.; Johnston, Norman J.

1993-01-01

Carbon fiber yarns (3k, 6k, 12k) were impregnated with LARC (tm) thermoplastic polyimide dry powder. Parameters for weaving these yarns were established. Eight-harness satin fabrics were successfully woven from each of the three classes of yarns and consolidated into test specimens to determine mechanical properties. It was observed that for optimum results warp yarns should have flexural rigidities between 10,000 and 100,000 mg-cm. Tow handling minimization, low tensioning, and tow bundle twisting were used to reduce fiber breakage, the separation of filaments, and tow-to-tow abrasion. No apparent effect of tow size or twist was observed on either tension or compression modulus. However, fiber damage and processing costs favor the use of 12k yarn bundles versus 3k or 6k yarn bundles in the weaving of powder-coated towpreg.

Electro-mechanical response of a 3D nerve bundle model to mechanical loads leading to axonal injury.

PubMed

Cinelli, I; Destrade, M; Duffy, M; McHugh, P

2017-07-01

Axonal damage is one of the most common pathological features of traumatic brain injury, leading to abnormalities in signal propagation for nervous systems. We present a 3D fully coupled electro-mechanical model of a nerve bundle, made with the finite element software Abaqus 6.13-3. The model includes a real-time coupling, modulated threshold for spiking activation and independent alteration of the electrical properties for each 3-layer fibre within the bundle. Compression and tension are simulated to induce damage at the nerve membrane. Changes in strain, stress distribution and neural activity are investigated for myelinated and unmyelinated nerve fibres, by considering the cases of an intact and of a traumatized nerve membrane. Results show greater changes in transmitting action potential in the myelinated fibre.

Resolving power for the diffusion orientation distribution function.

PubMed

Jensen, Jens H; Helpern, Joseph A

2016-08-01

The diffusion orientation distribution function (dODF) is primarily used for white matter fiber tractography. Here the resolving power of the dODF is investigated for a simple diffusion model of two intersecting axonal fiber bundles. The resolving power for the dODF is evaluated using the Sparrow criterion. This is determined for the exact dODF and also for q-space imaging (QSI), q-ball, and kurtosis approximations. Based on theoretical and numerical calculations, the resolving power is found to depend on the eigenvalues of the diffusion model and on the degree of radial weighting for the dODF. The resolving powers of the QSI and q-ball dODFs improve with increased b-value. The kurtosis dODF has a resolving power similar to that of the exact dODF. The dODFs, whether exact or approximate, have finite resolving powers that limit their sensitivity to fiber crossings. The resolving powers for the different dODFs considered here provide convenient benchmarks for assessing and comparing their performance. Magn Reson Med 76:679-688, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Dual-modality smartphone endoscope for cervical pre-cancer detection (Conference Presentation)

NASA Astrophysics Data System (ADS)

Hong, Xiangqian; Yu, Bing

2017-02-01

Early detection is the key to the prevention of cervical cancer. There is an urgent need for a portable, affordable, and easy-to-use device for cervical pre-cancer detection, especially in low-resource settings. We have developed a dual-modality fiber-optic endoscope system (SmartME) that integrates high-resolution fluorescence imaging (FLI) and quantitative diffuse reflectance spectroscopy (DRS) onto a smartphone platform. The SmartME consists of a smartphone, a miniature fiber-optic endoscope, a phone attachment containing imaging optics, and a smartphone application (app). FLI is obtained by painting the tissue with a contrast agent (e.g., proflavine), illuminating the tissue and collecting its fluorescence images through an imaging bundle that is coupled to the phone camera. DRS is achieved by using a white LED, attaching additional source and detection fibers to the imaging bundle, and converting the phone camera into a spectrometer. The app collects images/spectra and transmits them to a remote server for analysis to extract the tissue parameters, including nuclear-to-cytoplasm ratio (calculated from FLI), concentrations of oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb) as well as scattering (measured by DRS). These parameters can be used to detect cervical dysplasia. Our preliminary studies have demonstrated that the SmartME can clearly visualize the nuclei in living cells and in vivo biological samples, with a high spatial resolution of 3.1μm. The device can also measure tissue absorption and scattering properties with comparable accuracy to those of a benchtop DRS system. The SmartME has great potential to provide a compact, affordable, and `smart' solution for early detection of neoplastic changes in cervix.

An analytical fiber bundle model for pullout mechanics of root bundles

NASA Astrophysics Data System (ADS)

Cohen, D.; Schwarz, M.; Or, D.

2011-09-01

Roots in soil contribute to the mechanical stability of slopes. Estimation of root reinforcement is challenging because roots form complex biological networks whose geometrical and mechanical characteristics are difficult to characterize. Here we describe an analytical model that builds on simple root descriptors to estimate root reinforcement. Root bundles are modeled as bundles of heterogeneous fibers pulled along their long axes neglecting root-soil friction. Analytical expressions for the pullout force as a function of displacement are derived. The maximum pullout force and corresponding critical displacement are either derived analytically or computed numerically. Key model inputs are a root diameter distribution (uniform, Weibull, or lognormal) and three empirical power law relations describing tensile strength, elastic modulus, and length of roots as functions of root diameter. When a root bundle with root tips anchored in the soil matrix is pulled by a rigid plate, a unique parameter, ?, that depends only on the exponents of the power law relations, dictates the order in which roots of different diameters break. If ? < 1, small roots break first; if ? > 1, large roots break first. When ? = 1, all fibers break simultaneously, and the maximum tensile force is simply the roots' mean force times the number of roots in the bundle. Based on measurements of root geometry and mechanical properties, the value of ? is less than 1, usually ranging between 0 and 0.7. Thus, small roots always fail first. The model shows how geometrical and mechanical characteristics of roots and root diameter distribution affect the pullout force, its maximum and corresponding displacement. Comparing bundles of roots that have similar mean diameters, a bundle with a narrow variance in root diameter will result in a larger maximum force and a smaller displacement at maximum force than a bundle with a wide diameter distribution. Increasing the mean root diameter of a bundle without changing the distribution's shape increases both the maximum force and corresponding displacement. Estimates of the maximum pullout forces for bundles of 100 roots with identical diameter distribution for different species range from less than 1 kN for barley (Hordeum vulgare) to almost 16 kN for pistachio (Pistacia lentiscus). The model explains why a commonly used assumption that all roots break simultaneously overpredicts the maximum pullout force by a factor of about 1.6-2. This ratio may exceed 3 for diameter distributions that have a large number of small roots like the exponential distribution.

Cotton fiber properties: relative humidity and its effect on flat bundle strength, elongation, and fracture morphology

USDA-ARS?s Scientific Manuscript database

It is well known that cotton fibers readily exchange moisture content with their surrounding atmosphere. As moisture exchange progresses, several physical properties of the fiber are significantly affected. In this study, the effects of relative humidity (RH), a factor that affects the atmospheric m...

Multiscale mechanics of the lateral pressure effect on enhancing the load transfer between polymer coated CNTs.

PubMed

Yazdandoost, Fatemeh; Mirzaeifar, Reza; Qin, Zhao; Buehler, Markus J

2017-05-04

While individual carbon nanotubes (CNTs) are known as one of the strongest fibers ever known, even the strongest fabricated macroscale CNT yarns and fibers are still significantly weaker than individual nanotubes. The loss in mechanical properties is mainly because the deformation mechanism of CNT fibers is highly governed by the weak shear strength corresponding to sliding of nanotubes on each other. Adding polymer coating to the bundles, and twisting the CNT yarns to enhance the intertube interactions are both efficient methods to improve the mechanical properties of macroscale yarns. Here, we perform molecular dynamics (MD) simulations to unravel the unknown deformation mechanism in the intertube polymer chains and also local deformations of the CNTs at the atomistic scale. Our results show that the lateral pressure can have both beneficial and adverse effects on shear strength of polymer coated CNTs, depending on the local deformations at the atomistic scale. In this paper we also introduce a bottom-up bridging strategy between a full atomistic model and a coarse-grained (CG) model. Our trained CG model is capable of incorporating the atomistic scale local deformations of each CNT to the larger scale collect behavior of bundles, which enables the model to accurately predict the effect of lateral pressure on larger CNT bundles and yarns. The developed multiscale CG model is implemented to study the effect of lateral pressure on the shear strength of straight polymer coated CNT yarns, and also the effect of twisting on the pull-out force of bundles in spun CNT yarns.

Self-assembly of hierarchically ordered structures in DNA nanotube systems

NASA Astrophysics Data System (ADS)

Glaser, Martin; Schnauß, Jörg; Tschirner, Teresa; Schmidt, B. U. Sebastian; Moebius-Winkler, Maximilian; Käs, Josef A.; Smith, David M.

2016-05-01

The self-assembly of molecular and macromolecular building blocks into organized patterns is a complex process found in diverse systems over a wide range of size and time scales. The formation of star- or aster-like configurations, for example, is a common characteristic in solutions of polymers or other molecules containing multi-scaled, hierarchical assembly processes. This is a recurring phenomenon in numerous pattern-forming systems ranging from cellular constructs to solutions of ferromagnetic colloids or synthetic plastics. To date, however, it has not been possible to systematically parameterize structural properties of the constituent components in order to study their influence on assembled states. Here, we circumvent this limitation by using DNA nanotubes with programmable mechanical properties as our basic building blocks. A small set of DNA oligonucleotides can be chosen to hybridize into micron-length DNA nanotubes with a well-defined circumference and stiffness. The self-assembly of these nanotubes to hierarchically ordered structures is driven by depletion forces caused by the presence of polyethylene glycol. This trait allowed us to investigate self-assembly effects while maintaining a complete decoupling of density, self-association or bundling strength, and stiffness of the nanotubes. Our findings show diverse ranges of emerging structures including heterogeneous networks, aster-like structures, and densely bundled needle-like structures, which compare to configurations found in many other systems. These show a strong dependence not only on concentration and bundling strength, but also on the underlying mechanical properties of the nanotubes. Similar network architectures to those caused by depletion forces in the low-density regime are obtained when an alternative hybridization-based bundling mechanism is employed to induce self-assembly in an isotropic network of pre-formed DNA nanotubes. This emphasizes the universal effect inevitable attractive forces in crowded environments have on systems of self-assembling soft matter, which should be considered for macromolecular structures applied in crowded systems such as cells.

Lung volumes: measurement, clinical use, and coding.

PubMed

Flesch, Judd D; Dine, C Jessica

2012-08-01

Measurement of lung volumes is an integral part of complete pulmonary function testing. Some lung volumes can be measured during spirometry; however, measurement of the residual volume (RV), functional residual capacity (FRC), and total lung capacity (TLC) requires special techniques. FRC is typically measured by one of three methods. Body plethysmography uses Boyle's Law to determine lung volumes, whereas inert gas dilution and nitrogen washout use dilution properties of gases. After determination of FRC, expiratory reserve volume and inspiratory vital capacity are measured, which allows the calculation of the RV and TLC. Lung volumes are commonly used for the diagnosis of restriction. In obstructive lung disease, they are used to assess for hyperinflation. Changes in lung volumes can also be seen in a number of other clinical conditions. Reimbursement for measurement of lung volumes requires knowledge of current procedural terminology (CPT) codes, relevant indications, and an appropriate level of physician supervision. Because of recent efforts to eliminate payment inefficiencies, the 10 previous CPT codes for lung volumes, airway resistance, and diffusing capacity have been bundled into four new CPT codes.

Assessment of Ablative Therapies in Swine: Response of Respiratory Diaphragm to Varying Doses.

PubMed

Singal, Ashish; Mattison, Lars M; Soule, Charles L; Ballard, John R; Rudie, Eric N; Cressman, Erik N K; Iaizzo, Paul A

2018-03-28

Ablation is a common procedure for treating patients with cancer, cardiac arrhythmia, and other conditions, yet it can cause collateral injury to the respiratory diaphragm. Collateral injury can alter the diaphragm's properties and/or lead to respiratory dysfunction. Thus, it is important to understand the diaphragm's physiologic and biomechanical properties in response to ablation therapies, in order to better understand ablative modalities, minimize complications, and maximize the safety and efficacy of ablative procedures. In this study, we analyzed physiologic and biomechanical properties of swine respiratory diaphragm muscle bundles when exposed to 5 ablative modalities. To assess physiologic properties, we performed in vitro tissue bath studies and measured changes in peak force and baseline force. To assess biomechanical properties, we performed uniaxial stress tests, measuring force-displacement responses, stress-strain characteristics, and avulsion forces. After treating the muscle bundles with all 5 ablative modalities, we observed dose-dependent sustained reductions in peak force and transient increases in baseline force-but no consistent dose-dependent biomechanical responses. These data provide novel insights into the effects of various ablative modalities on the respiratory diaphragm, insights that could enable improvements in ablative techniques and therapies.

Atlas-Guided Cluster Analysis of Large Tractography Datasets

PubMed Central

Ros, Christian; Güllmar, Daniel; Stenzel, Martin; Mentzel, Hans-Joachim; Reichenbach, Jürgen Rainer

2013-01-01

Diffusion Tensor Imaging (DTI) and fiber tractography are important tools to map the cerebral white matter microstructure in vivo and to model the underlying axonal pathways in the brain with three-dimensional fiber tracts. As the fast and consistent extraction of anatomically correct fiber bundles for multiple datasets is still challenging, we present a novel atlas-guided clustering framework for exploratory data analysis of large tractography datasets. The framework uses an hierarchical cluster analysis approach that exploits the inherent redundancy in large datasets to time-efficiently group fiber tracts. Structural information of a white matter atlas can be incorporated into the clustering to achieve an anatomically correct and reproducible grouping of fiber tracts. This approach facilitates not only the identification of the bundles corresponding to the classes of the atlas; it also enables the extraction of bundles that are not present in the atlas. The new technique was applied to cluster datasets of 46 healthy subjects. Prospects of automatic and anatomically correct as well as reproducible clustering are explored. Reconstructed clusters were well separated and showed good correspondence to anatomical bundles. Using the atlas-guided cluster approach, we observed consistent results across subjects with high reproducibility. In order to investigate the outlier elimination performance of the clustering algorithm, scenarios with varying amounts of noise were simulated and clustered with three different outlier elimination strategies. By exploiting the multithreading capabilities of modern multiprocessor systems in combination with novel algorithms, our toolkit clusters large datasets in a couple of minutes. Experiments were conducted to investigate the achievable speedup and to demonstrate the high performance of the clustering framework in a multiprocessing environment. PMID:24386292

Weak reversible cross links may decrease the strength of aligned fiber bundles.

PubMed

Nabavi, S Soran; Hartmann, Markus A

2016-02-21

Reversible cross-linking is an effective strategy to specifically tailor the mechanical properties of polymeric materials that can be found in a variety of biological as well as man-made materials. Using a simple model in this paper the influence of weak, reversible cross-links on the mechanical properties of aligned fiber bundles is investigated. Special emphasis in this analysis is put on the strength of the investigated structures. Using Monte Carlo methods two topologies of cross-links exceeding the strength of the covalent backbone are studied. Most surprisingly only two cross-links are sufficient to break the backbone of a multi chain system, resulting in a reduced strength of the material. The found effect crucially depends on the ratio of inter- to intra-chain cross-links and, thus, on the grafting density that determines this ratio.

Stochastic reservoir simulation for the modeling of uncertainty in coal seam degasification

USGS Publications Warehouse

Karacan, C. Özgen; Olea, Ricardo A.

2015-01-01

The study helped to determine the realization bundle that consisted of the spatial maps of coal properties, which resulted in minimum error. In addition, it was shown that both E-type and the average of realizations that gave the best match for invidual approximated the same properties resonably. Moreover, the determined realization bundle showed that the study field initially had 151.5 million m3 (cubic meter) of gas and 1.04 million m3 water in the coal, corresponding to Q90 of the entire range of probability for gas and close to Q75 for water. In 2013, in-place fluid amounts decreased to 138.9 million m3 and 0.997 million m3 for gas and water, respectively.

Auditory Mechanics of the Tectorial Membrane and the Cochlear Spiral

PubMed Central

Gavara, Núria; Manoussaki, Daphne; Chadwick, Richard S.

2012-01-01

Purpose of review This review is timely and relevant since new experimental and theoretical findings suggest that cochlear mechanics from the nanoscale to the macroscale are affected by mechanical properties of the tectorial membrane and the spiral shape. Recent findings Main tectorial membrane themes covered are i) composition and morphology, ii) nanoscale mechanical interactions with the outer hair cell bundle, iii) macroscale longitudinal coupling, iv) fluid interaction with inner hair cell bundles, v) macroscale dynamics and waves. Main cochlear spiral themes are macroscale low-frequency energy focusing and microscale organ of Corti shear gain. Implications Findings from new experimental and theoretical models reveal exquisite sensitivity of cochlear mechanical performance to tectorial membrane structural organization, mechanics, and its positioning with respect to hair bundles. The cochlear spiral geometry is a major determinant of low frequency hearing. Suggestions are made for future research directions. PMID:21785353

Single Molecule Stepping and Structural Dynamics of Myosin X

PubMed Central

Sun, Yujie; Sato, Osamu; Ruhnow, Felix; Arsenault, Mark E.; Ikebe, Mitsuo; Goldman, Yale E.

2010-01-01

Myosin X is an unconventional myosin with puzzling motility properties. We studied the motility of dimerized myosin X using single molecule fluorescence techniques – polTIRF, FIONA, and Parallax to measure rotation angles and 3-dimensional position of the molecule during its walk. It was found that Myosin X steps processively in a hand-over-hand manner following a left-handed helical path along both single actin filaments and bundles. Its step size and velocity are smaller on actin bundles than individual filaments, suggesting myosin X often steps onto neighboring filaments in a bundle. The data suggest that a previously postulated single α-helical domain mechanically extends the 3-IQ motif lever arm and either the neck-tail hinge or the tail is flexible. These structural features, in conjunction with the membrane and microtubule binding domains, enable myosin X to perform multiple functions on varied actin structures in cells. PMID:20364131

Neuropsychological Correlates of Diffusion Tensor Imaging in Schizophrenia

PubMed Central

Nestor, Paul G.; Kubicki, Marek; Gurrera, Ronald J.; Niznikiewicz, Margaret; Frumin, Melissa; McCarley, Robert W.; Shenton, Martha E.

2009-01-01

Patients with schizophrenia (n = 41) and healthy comparison participants (n = 46) completed neuropsychological measures of intelligence, memory, and executive function. A subset of each group also completed magnetic resonance diffusion tensor imaging (DTI) studies (fractional anisotropy and cross-sectional area) of the uncinate fasciculus (UF) and cingulate bundle (CB). Patients with schizophrenia showed reduced levels of functioning across all neuropsychological measures. In addition, selective neuropsychological–DTI relationships emerged. Among patients but not controls, lower levels of declarative–episodic verbal memory correlated with reduced left UF, whereas executive function errors related to performance monitoring correlated with reduced left CB. The data suggested abnormal DTI patterns linking declarative–episodic verbal memory deficits to the left UF and executive function deficits to the left CB among patients with schizophrenia. PMID:15506830

A solar dynamo surface wave at the interface between convection and nonuniform rotation

NASA Technical Reports Server (NTRS)

Parker, E. N.

1993-01-01

A simple dynamo surface wave is presented to illustrate the basic principles of a dynamo operating in the thin layer of shear and suppressed eddy diffusion beneath the cyclonic convection in the convection zone of the sun. It is shown that the restriction of the shear delta(Omega)/delta(r) to a region below the convective zone provides the basic mode with a greatly reduced turbulent diffusion coefficient in the region of strong azimuthal field. The dynamo takes on the character of a surface wave tied to the lower surface z = 0 of the convective zone. There is a substantial body of evidence suggesting a fibril state for the principal flux bundles beneath the surface of the sun, with fundamental implications for the solar dynamo.

Selective damage to cochlear efferents by the choline neurotoxin ethylcholine mustard aziridinium ion (AF64A) in the chinchilla.

PubMed

Smith, D W; Mount, R J; Callahan, J W

1989-10-01

The cholinotoxin ethylcholine mustard aziridinium ion (AF64A) was diluted in artificial perilymph to concentrations ranging from 10-100 microM, injected unilaterally into the bulla of chinchillas, and allowed to passively diffuse across the round window membrane. Following 21-day survival, the animals were sacrificed and ears removed and embedded in epoxy for histological evaluation under both light and transmission electron microscopy. At 10 microM concentration, selective degeneration of efferent fibers was observed in the efferent terminals on outer hair cells (OHC), tunnel radial fibers, tunnel spiral bundle, and the inner spiral bundle. Serial sections of the middle turn of an animal at 10 microM concentrations showed normal efferent terminals on approximately 50% of OHCs. At the higher concentrations non-specific damage was seen in OHCs, afferents, and some supporting cells. These data suggest that low doses AF64A produces selective damage to cochlear efferent terminals and fibers in the chinchilla.

Design of a dynamic optical tissue phantom to model extravasation pharmacokinetics

NASA Astrophysics Data System (ADS)

Zhang, Jane Y.; Ergin, Aysegul; Andken, Kerry Lee; Sheng, Chao; Bigio, Irving J.

2010-02-01

We describe an optical tissue phantom that enables the simulation of drug extravasation from microvessels and validates computational compartmental models of drug delivery. The phantom consists of a microdialysis tubing bundle to simulate the permeable blood vessels, immersed in either an aqueous suspension of titanium dioxide (TiO2) or a TiO2 mixed agarose scattering medium. Drug administration is represented by a dye circulated through this porous microdialysis tubing bundle. Optical pharmacokinetic (OP) methods are used to measure changes in the absorption coefficient of the scattering medium due to the arrival and diffusion of the dye. We have established particle sizedependent concentration profiles over time of phantom drug delivery by intravenous (IV) and intra-arterial (IA) routes. Additionally, pharmacokinetic compartmental models are implemented in computer simulations for the conditions studied within the phantom. The simulated concentration-time profiles agree well with measurements from the phantom. The results are encouraging for future optical pharmacokinetic method development, both physical and computational, to understand drug extravasation under various physiological conditions.

Tug of war in motility assay experiments

NASA Astrophysics Data System (ADS)

Hexner, Daniel; Kafri, Yariv

2009-09-01

The dynamics of two groups of molecular motors pulling in opposite directions on a rigid filament is studied theoretically. To this end we first consider the behavior of one set of motors pulling in a single direction against an external force using a new mean-field approach. Based on these results we analyze a similar setup with two sets of motors pulling in opposite directions in a tug of war in the presence of an external force. In both cases we find that the interplay of fluid friction and protein friction leads to a complex phase diagram where the force-velocity relations can exhibit regions of bistability and spontaneous symmetry breaking. Finally, motivated by recent work, we turn to the case of motility assay experiments where motors bound to a surface push on a bundle of filaments. We find that, depending on the absence or the presence of bistability in the force-velocity curve at zero force, the bundle exhibits anomalous or biased diffusion on long-time and large-length scales.

Centrifugal Deposited Au-Pd Core-Shell Nanoparticle Film for Room-Temperature Optical Detection of Hydrogen Gas.

PubMed

Song, Han; Luo, Zhijie; Liu, Mingyao; Zhang, Gang; Peng, Wang; Wang, Boyi; Zhu, Yong

2018-05-06

In the present work, centrifugal deposited Au-Pd core-shell nanoparticle (NP) film was proposed for the room-temperature optical detection of hydrogen gas. The size dimension of 44, 48, 54, and 62 nm Au-Pd core-shell nanocubes with 40 nm Au core were synthesized following a solution-based seed-mediated growth method. Compared to a pure Pd NP, this core-shell structure with an inert Au core could decrease the H diffusion length in the Pd shell. Through a modified centrifugal deposition process, continues film samples with different core-shell NPs were deposited on 10 mm diameter quartz substrates. Under various hydrogen concentration conditions, the optical response properties of these samples were characterized by an intensity-based optical fiber bundle sensor. Experimental results show that the continues film that was composed of 62 nm Au-Pd core-shell NPs has achieved a stable and repeatable reflectance response with low zero drift in the range of 4 to 0.1% hydrogen after a stress relaxation mechanism at first few loading/unloading cycles. Because of the short H diffusion length due to the thinner Pd shell, the film sample composed of 44 nm Au-Pd NPs has achieved a dramatically decreased response/recovery time to 4 s/30 s. The experiments present the promising prospect of this simple method to fabricate optical hydrogen sensors with controllable high sensitivity and response rate at low cost.

Calculation of single chain cellulose elasticity using fully atomistic modeling

Treesearch

Xiawa Wu; Robert J. Moon; Ashlie Martini

2011-01-01

Cellulose nanocrystals, a potential base material for green nanocomposites, are ordered bundles of cellulose chains. The properties of these chains have been studied for many years using atomic-scale modeling. However, model predictions are difficult to interpret because of the significant dependence of predicted properties on model details. The goal of this study is...

Metaplectic-c Quantomorphisms

NASA Astrophysics Data System (ADS)

Vaughan, Jennifer

2015-03-01

In the classical Kostant-Souriau prequantization procedure, the Poisson algebra of a symplectic manifold (M,ω) is realized as the space of infinitesimal quantomorphisms of the prequantization circle bundle. Robinson and Rawnsley developed an alternative to the Kostant-Souriau quantization process in which the prequantization circle bundle and metaplectic structure for (M,ω) are replaced by a metaplectic-c prequantization. They proved that metaplectic-c quantization can be applied to a larger class of manifolds than the classical recipe. This paper presents a definition for a metaplectic-c quantomorphism, which is a diffeomorphism of metaplectic-c prequantizations that preserves all of their structures. Since the structure of a metaplectic-c prequantization is more complicated than that of a circle bundle, we find that the definition must include an extra condition that does not have an analogue in the Kostant-Souriau case. We then define an infinitesimal quantomorphism to be a vector field whose flow consists of metaplectic-c quantomorphisms, and prove that the space of infinitesimal metaplectic-c quantomorphisms exhibits all of the same properties that are seen for the infinitesimal quantomorphisms of a prequantization circle bundle. In particular, this space is isomorphic to the Poisson algebra C^∞(M).

Rheological alteration of erythrocytes exposed to carbon nanotubes.

PubMed

Heo, Yujin; Li, Cheng-Ai; Kim, Duckjong; Shin, Sehyun

2017-01-01

Single-walled carbon nanotubes (SWNTs) have been increasingly used in a variety of biomedical applications, such as in vivo delivery of drugs and tumor imaging. Potential exposure of SWNTs to human red blood cells (RBCs) may cause serious toxicity including alteration of mechanical properties of cells. The present study investigated the cellular response to exposure of SWNTs with measuring rheological characteristics of RBCs, including hemolysis, deformability, aggregation, and morphological changes. RBCs were exposed to two different dispersion-state samples (i.e. individual SWNTs and bundled SWNTs) in chitosan hydroxyphenyl acetamide (CHPA) solutions. The concentrations of SWNTs were carefully chosen to avoid any hemorheological alterations due to hemolysis. Rheological characteristics were measured using microfluidic-laser diffractometry and aggregometry. Our results show that the bundled SWNTs had higher hemolytic activity than did the individual SWNTs. RBC aggregation apparently decreased as the concentration of SWNTs or incubation time increased. Additionally, bundled SWNTs caused significant alterations in the shape and fusion of RBCs. In conclusion, bundled SWNTs were found to be more toxic than individual SWNTs. These results provide important insights into the interactions between RBCs and SWNTs and will facilitate assessment of the risk of nanomaterial toxicity of blood.

Cytoskeletal mechanics: Structure and Dynamics

NASA Astrophysics Data System (ADS)

Bausch, Andreas

2008-03-01

The actin cytoskeleton, a dynamic network of semiflexible filaments and associated regulatory proteins, is responsible for the extraordinary viscoelastic properties of cells. Especially for cellular motility the controlled self assembly to defined structures and the dynamic reorganization on different time scales are of outstanding importance. A prominent example for the controlled self assembly are actin bundles: in many cytoskeletal processes cells rely on the tight control of the structural and mechanical properties of the actin bundles. Using an in vitro model system we show that size control relies on a mismatch between the helical structure of individual actin filaments and the packing symmetry within bundles. While such self assembled structure may evoke the picture of a static network the contrary is the case: the cytoskeleton is highly dynamic and a constant remodeling takes place in vivo. Such dynamic reorganization of the cytoskeleton relies on the non-static nature of single actin/ABP bonds. Here, we study the thermal and forced unbinding events of individual ABP in such in vitro networks. The binding kinetics of the transient crosslinkers determines the mechanical response of such networks -- in the linear as well in the non-linear regime. These effects are important prerequisites for the high adaptability of cells and at the same time might be the molecular mechanism employed by them for mechanosensing.

Optical Coherence Tomographic Comparison of Cuban Epidemic and Leber’s Hereditary Optic Neuropathy

PubMed Central

Santiesteban-Freixas, Rosaralis; Pola-Alvarado, Lester; Columbie-Garbey, Yannara; Gonzalez-Quevedo, Alina; Juvier-Riesgo, Tamara; Hernandez-Echevarria, Odelaisys; Hedges, Thomas R.; Mendoza-Santiesteban, Carlos

2015-01-01

Abstract Following the epidemic of optic and peripheral neuropathy, which occurred in Cuba between 1991 and 1993, a number of patients have been re-evaluated, including testing with optical coherence tomography (OCT) and electrophysiology. At the same time, a number of patients with Leber’s hereditary optic neuropathy have also been evaluated. The purpose of this study was to detect residual loss of retinal nerve fibre layer (RNFL) in patients who suffered Cuban epidemic optic neuropathy (CEON), and to compare these findings with those in patients with Leber’s hereditary optic neuropathy (LHON). Optical coherence tomography as well as clinical examinations were performed on 11 patients diagnosed with CEON 15 years following the epidemic and 14 patients with LHON. OCT in CEON patients showed thinning of the RNFL in the temporal sector and normal thickness in other quadrants. However, patients with chronic LHON had more diffuse RNFL loss throughout the retina. OCT findings corresponded with clinical findings in CEON and LHON. There was drop out of the papillomacular bundle in both diseases. Two patients in the acute stages of LHON and three LHON carriers showed thinning of the temporal RNFL only. This is the first report of OCT in CEON that shows residual damage in the papillomacular bundle compared with chronic LHON where there is more diffuse and progressive loss of the RNFL. The importance of OCT for the diagnosis and evaluation of similar optic neuropathies is emphasised. PMID:27928368

Apparent Fibre Density: a novel measure for the analysis of diffusion-weighted magnetic resonance images.

PubMed

Raffelt, David; Tournier, J-Donald; Rose, Stephen; Ridgway, Gerard R; Henderson, Robert; Crozier, Stuart; Salvado, Olivier; Connelly, Alan

2012-02-15

This article proposes a new measure called Apparent Fibre Density (AFD) for the analysis of high angular resolution diffusion-weighted images using higher-order information provided by fibre orientation distributions (FODs) computed using spherical deconvolution. AFD has the potential to provide specific information regarding differences between populations by identifying not only the location, but also the orientations along which differences exist. In this work, analytical and numerical Monte-Carlo simulations are used to support the use of the FOD amplitude as a quantitative measure (i.e. AFD) for population and longitudinal analysis. To perform robust voxel-based analysis of AFD, we present and evaluate a novel method to modulate the FOD to account for changes in fibre bundle cross-sectional area that occur during spatial normalisation. We then describe a novel approach for statistical analysis of AFD that uses cluster-based inference of differences extended throughout space and orientation. Finally, we demonstrate the capability of the proposed method by performing voxel-based AFD comparisons between a group of Motor Neurone Disease patients and healthy control subjects. A significant decrease in AFD was detected along voxels and orientations corresponding to both the corticospinal tract and corpus callosal fibres that connect the primary motor cortices. In addition to corroborating previous findings in MND, this study demonstrates the clear advantage of using this type of analysis by identifying differences along single fibre bundles in regions containing multiple fibre populations. Copyright © 2011 Elsevier Inc. All rights reserved.

Plant 115-kDa actin-filament bundling protein, P-115-ABP, is a homologue of plant villin and is widely distributed in cells.

PubMed

Yokota, Etsuo; Vidali, Luis; Tominaga, Motoki; Tahara, Hiroshi; Orii, Hidefumi; Morizane, Yosuke; Hepler, Peter K; Shimmen, Teruo

2003-10-01

In many cases, actin filaments are arranged into bundles and serve as tracks for cytoplasmic streaming in plant cells. We have isolated an actin-filament bundling protein, which is composed of 115-kDa polypeptide (P-115-ABP), from the germinating pollen of lily, Lilium longiflorum [Nakayasu et al. (1998) BIOCHEM: Biophys. Res. Commun. 249: 61]. P-115-ABP shared similar antigenicity with a plant 135-kDa actin-filament bundling protein (P-135-ABP), a plant homologue of villin. A full-length cDNA clone (ABP115; accession no. AB097407) was isolated from an expression cDNA library of lily pollen by immuno-screening using antisera against P-115-ABP and P-135-ABP. The amino acid sequence of P-115-ABP deduced from this clone showed high homology with those of P-135-ABP and four villin isoforms of Arabidopsis thaliana (AtVLN1, AtVLN2, AtVLN3 and AtVLN4), especially AtVLN4, indicating that P-115-ABP can also be classified as a plant villin. The P-115-ABP isolated biochemically from the germinating lily pollen was able to arrange F-actin filaments with uniform polarity into bundles and this bundling activity was suppressed by Ca2+-calmodulin (CaM), similar to the actin-filament bundling properties of P-135-ABP. The P-115-ABP type of plant villin was widely distributed in plant cells, from algae to land plants. In root hair cells of Hydrocharis dubia, this type of plant villin was co-localized with actin-filament bundles in the transvacuolar strands and the sub-cortical regions. Microinjection of the antiserum against P-115-ABP into living root hair cells caused the disappearance of transvaculor strands and alteration of the route of cytoplasmic streaming. In internodal cells of Chara corallina in which the P-135-ABP type of plant villin is lacking, the P-115-ABP type showed co-localization with actin-filament cables anchored on the intracellular surface of chloroplasts. These results indicated that plant villins are widely distributed and involved in the organization of actin filaments into bundles throughout the plant kingdom.

Distribution of radiodense contrast medium after perineural injection of the palmar and palmar metacarpal nerves (low 4-point nerve block): an in vivo and ex vivo study in horses.

PubMed

Nagy, A; Bodò, G; Dyson, S J; Compostella, F; Barr, A R S

2010-09-01

Evidence-based information is limited on distribution of local anaesthetic solution following perineural analgesia of the palmar (Pa) and palmar metacarpal (PaM) nerves in the distal aspect of the metacarpal (Mc) region ('low 4-point nerve block'). To demonstrate the potential distribution of local anaesthetic solution after a low 4-point nerve block using a radiographic contrast model. A radiodense contrast medium was injected subcutaneously over the medial or the lateral Pa nerve at the junction of the proximal three-quarters and distal quarter of the Mc region (Pa injection) and over the ipsilateral PaM nerve immediately distal to the distal aspect of the second or fourth Mc bones (PaM injection) in both forelimbs of 10 mature horses free from lameness. Radiographs were obtained 0, 10 and 20 min after injection and analysed subjectively and objectively. Methylene blue and a radiodense contrast medium were injected in 20 cadaver limbs using the same techniques. Radiographs were obtained and the limbs dissected. After 31/40 (77.5%) Pa injections, the pattern of the contrast medium suggested distribution in the neurovascular bundle. There was significant proximal diffusion with time, but the main contrast medium patch never progressed proximal to the mid-Mc region. The radiological appearance of 2 limbs suggested that contrast medium was present in the digital flexor tendon sheath (DFTS). After PaM injections, the contrast medium was distributed diffusely around the injection site in the majority of the limbs. In cadaver limbs, after Pa injections, the contrast medium and the dye were distributed in the neurovascular bundle in 8/20 (40%) limbs and in the DFTS in 6/20 (30%) of limbs. After PaM injections, the contrast and dye were distributed diffusely around the injection site in 9/20 (45%) limbs and showed diffuse and tubular distribution in 11/20 (55%) limbs. Proximal diffusion of local anaesthetic solution after a low 4-point nerve block is unlikely to be responsible for decreasing lameness caused by pain in the proximal Mc region. The DFTS may be penetrated inadvertently when performing a low 4-point nerve block.

Measurement and simulation of myoplasmic calcium transients in mouse slow-twitch muscle fibres.

PubMed

Hollingworth, Stephen; Kim, Michele M; Baylor, Stephen M

2012-02-01

Bundles of intact fibres from soleus muscles of adult mice were isolated by dissection and one fibre within a bundle was micro-injected with either furaptra or mag-fluo-4, two low-affinity rapidly responding Ca(2+) indicators. Fibres were activated by action potentials to elicit changes in indicator fluorescence (ΔF), a monitor of the myoplasmic free Ca(2+) transient ([Ca(2+)]), and changes in fibre tension. All injected fibres appeared to be slow-twitch (type I) fibres as inferred from the time course of their tension responses. The full-duration at half-maximum (FDHM) of ΔF was found to be essentially identical with the two indicators; the mean value was 8.4 ± 0.3 ms (±SEM) at 16°C and 5.1 ± 0.3 ms at 22°C. The value at 22°C is about one-third that reported previously in enzyme-dissociated slow-twitch fibres that had been AM-loaded with mag-fluo-4: 12.4 ± 0.8 ms and 17.2 ± 1.7 ms. We attribute the larger FDHM in enzyme-dissociated fibres either to an alteration of fibre properties due to the enzyme treatment or to some error in the measurement of ΔF associated with AM loading. ΔF in intact fibres was simulated with a multi-compartment reaction-diffusion model that permitted estimation of the amount and time course of Ca(2+) release from the sarcoplasmic reticulum (SR), the binding and diffusion of Ca(2+) in the myoplasm, the re-uptake of Ca(2+) by the SR Ca(2+) pump, and Δ[Ca(2+)] itself. In response to one action potential at 16°C, the following estimates were obtained: 107 μm for the amount of Ca(2+) release; 1.7 ms for the FDHM of the release flux; 7.6 μm and 4.9 ms for the peak and FDHM of spatially averaged Δ[Ca(2+)]. With five action potentials at 67 Hz, the estimated amount of Ca(2+) release is 186 μm. Two important unknown model parameters are the on- and off-rate constants of the reaction between Ca(2+) and the regulatory sites on troponin; values of 0.4 × 10(8) m(-1) s(-1) and 26 s(-1), respectively, were found to be consistent with the ΔF measurements.

Myopodin is an F-actin bundling protein with multiple independent actin-binding regions.

PubMed

Linnemann, Anja; Vakeel, Padmanabhan; Bezerra, Eduardo; Orfanos, Zacharias; Djinović-Carugo, Kristina; van der Ven, Peter F M; Kirfel, Gregor; Fürst, Dieter O

2013-02-01

The assembly of striated muscle myofibrils is a multistep process in which a variety of proteins is involved. One of the first and most important steps in myofibrillogenesis is the arrangement of thin myofilaments into ordered I-Z-I brushes, requiring the coordinated activity of numerous actin binding proteins. The early expression of myopodin prior to sarcomeric α-actinin, as well as its binding to actin, α-actinin and filamin indicate an important role for this protein in actin cytoskeleton remodelling with the precise function of myopodin in this process yet remaining to be resolved. While myopodin was previously described as a protein capable of cross-linking actin filaments into thick bundles upon transient transfections, it has remained unclear whether myopodin alone is capable of bundling actin, or if additional proteins are involved. We have therefore investigated the in vitro actin binding properties of myopodin. High speed cosedimentation assays with skeletal muscle actin confirmed direct binding of myopodin to F-actin and showed that this interaction is mediated by at least two independent actin binding sites, found in all myopodin isoforms identified to date. Furthermore, low-speed cosedimentation assays revealed that not only full length myopodin, but also the fragment containing only the second binding site, bundles microfilaments in the absence of accessory proteins. Ultrastructural analysis demonstrated that this bundling activity resembled that of α-actinin. Biochemical experiments revealed that bundling was not achieved by myopodin's ability to dimerize, indicating the presence of two individual F-actin binding sites within the second binding segment. Thus full length myopodin contains at least three F-actin binding sites. These data provide further understanding of the mechanisms by which myopodin contributes to actin reorganization during myofibril assembly.

Compressive force generation by a bundle of living biofilaments

NASA Astrophysics Data System (ADS)

Ramachandran, Sanoop; Ryckaert, Jean-Paul

2013-08-01

To study the compressional forces exerted by a bundle of living stiff filaments pressing on a surface, akin to the case of an actin bundle in filopodia structures, we have performed particulate molecular dynamics simulations of a grafted bundle of parallel living (self-assembling) filaments, in chemical equilibrium with a solution of their constitutive monomers. Equilibrium is established as these filaments, grafted at one end to a wall of the simulation box, grow at their chemically active free end, and encounter the opposite confining wall of the simulation box. Further growth of filaments requires bending and thus energy, which automatically limit the populations of longer filaments. The resulting filament sizes distribution and the force exerted by the bundle on the obstacle are analyzed for different grafting densities and different sub- or supercritical conditions, these properties being compared with the predictions of the corresponding ideal confined bundle model. In this analysis, non-ideal effects due to interactions between filaments and confinement effects are singled out. For all state points considered at the same temperature and at the same gap width between the two surfaces, the force per filament exerted on the opposite wall appears to be a function of a rescaled free monomer density hat{ρ }_1^eff. This quantity can be estimated directly from the characteristic length of the exponential filament size distribution P observed in the size domain where these grafted filaments are not in direct contact with the wall. We also analyze the dynamics of the filament contour length fluctuations in terms of effective polymerization (U) and depolymerization (W) rates, where again it is possible to disentangle non-ideal and confinement effects.

Stimulus dependent properties of mammalian cochlear hair cell mechanoelectrical transduction

NASA Astrophysics Data System (ADS)

Scharr, A. L.; Ricci, Anthony

2018-05-01

Cochlear hair cell stereocilia move semi-independently, shaping the force transfer to mechanoelectrical transduction (MET) channels, as indicated by the MET current response. Semi-independent movement of stereocilia was evoked by stimulating inner hair cell (IHC) bundles from acutely dissected rat cochlea with stiff probes ranging in size from 1 to 10 µm. MET current responses were recorded using whole-cell patch-clamp electrophysiology. Small probes directly displaced stereocilia they contacted, and recruited adjacent stereocilia depending on stimulus magnitude. We inferred that the recruitment of stereocilia resulted in less uniform and less synchronous movement. Step displacements using smaller probes resulted in smaller current responses (from 1 nA for large probes to 0.3 nA for small, p <.0001), slower rate of current activation, as measured from the linear portion (from 4 nA/ms to 1 nA/ms, p <.0001), slower time constants of adaptation, as measured from double exponential fits from peak to steady state current (fast component: from 0.6 to 1.2 ms, p =.004; slow component: from 8 ms to 12 ms, p =.001) and less complete adaptation (from 95% to 30%, p <.0001). These results indicate that the mechanical properties of less coherent bundles greatly affect force transfer to MET channels as indicated by the electrical response of the cell. Thus, outer hair cells (OHCs), with their bundles embedded in the tectorial membrane, may exhibit synchronous MET activation and therefore time-dependent adaptation where fast adaptation provides a high pass filter. Hair cells with free standing bundles, like inner hair cells (IHC), may exhibit more asynchronous MET activation and adaptation, in which case adaptation would not provide this additional filter.

Genes and spleens: property, contract, or privacy rights in the human body?

PubMed

Rao, Radhika

2007-01-01

This article compares three frameworks for legal regulation of the human body. Property law systematically favors those who use the body to create commercial products. Yet contract and privacy rights cannot compete with the property paradigm, which alone affords a complete bundle of rights enforceable against the whole world. In the face of researchers' property rights, the theoretical freedom to contract and the meager interest in privacy leave those who supply body parts vulnerable to exploitation.

Subcortical pathways serving cortical language sites: initial experience with diffusion tensor imaging fiber tracking combined with intraoperative language mapping.

PubMed

Henry, Roland G; Berman, Jeffrey I; Nagarajan, Srikantan S; Mukherjee, Pratik; Berger, Mitchel S

2004-02-01

The combination of mapping functional cortical neurons by intraoperative cortical stimulation and axonal architecture by diffusion tensor MRI fiber tracking can be used to delineate the pathways between functional regions. In this study the authors investigated the feasibility of combining these techniques to yield connectivity associated with motor speech and naming. Diffusion tensor MRI fiber tracking provides maps of axonal bundles and was combined with intraoperative mapping of eloquent cortex for a patient undergoing brain tumor surgery. Tracks from eight stimulated sites in the inferior frontal cortex including mouth motor, speech arrest, and anomia were generated from the diffusion tensor MRI data. The regions connected by the fiber tracking were compared to foci from previous functional imaging reports on language tasks. Connections were found between speech arrest, mouth motor, and anomia sites and the SMA proper and cerebral peduncle. The speech arrest and a mouth motor site were also seen to connect to the putamen via the external capsule. This is the first demonstration of delineation of subcortical pathways using diffusion tensor MRI fiber tracking with intraoperative cortical stimulation. The combined techniques may provide improved preservation of eloquent regions during neurological surgery, and may provide access to direct connectivity information between functional regions of the brain.

Subcortical pathways serving cortical language sites: initial experience with diffusion tensor imaging fiber tracking combined with intraoperative language mapping

PubMed Central

Henry, Roland G.; Berman, Jeffrey I.; Nagarajan, Srikantan S.; Mukherjee, Pratik; Berger, Mitchel S.

2014-01-01

The combination of mapping functional cortical neurons by intraoperative cortical stimulation and axonal architecture by diffusion tensor MRI fiber tracking can be used to delineate the pathways between functional regions. In this study the authors investigated the feasibility of combining these techniques to yield connectivity associated with motor speech and naming. Diffusion tensor MRI fiber tracking provides maps of axonal bundles and was combined with intraoperative mapping of eloquent cortex for a patient undergoing brain tumor surgery. Tracks from eight stimulated sites in the inferior frontal cortex including mouth motor, speech arrest, and anomia were generated from the diffusion tensor MRI data. The regions connected by the fiber tracking were compared to foci from previous functional imaging reports on language tasks. Connections were found between speech arrest, mouth motor, and anomia sites and the SMA proper and cerebral peduncle. The speech arrest and a mouth motor site were also seen to connect to the putamen via the external capsule. This is the first demonstration of delineation of subcortical pathways using diffusion tensor MRI fiber tracking with intraoperative cortical stimulation. The combined techniques may provide improved preservation of eloquent regions during neurological surgery, and may provide access to direct connectivity information between functional regions of the brain. PMID:14980564

White matter changes after stroke in type 2 diabetic rats measured by diffusion magnetic resonance imaging.

PubMed

Ding, Guangliang; Chen, Jieli; Chopp, Michael; Li, Lian; Yan, Tao; Davoodi-Bojd, Esmaeil; Li, Qingjiang; Davarani, Siamak Pn; Jiang, Quan

2017-01-01

Diffusion-related magnetic resonance imaging parametric maps may be employed to characterize white matter of brain. We hypothesize that entropy of diffusion anisotropy may be most effective for detecting therapeutic effects of bone marrow stromal cell treatment of ischemia in type 2 diabetes mellitus rats. Type 2 diabetes mellitus was induced in adult male Wistar rats. These rats were then subjected to 2 h of middle cerebral artery occlusion, and received bone marrow stromal cell (5 × 10 6 , n = 8) or an equal volume of saline (n = 8) via tail vein injection at three days after middle cerebral artery occlusion. Magnetic resonance imaging was performed on day one and then weekly for five weeks post middle cerebral artery occlusion. The diffusion metrics complementarily permitted characterization of axons and axonal myelination. All six magnetic resonance imaging diffusion metrics, confirmed by histological measures, demonstrated that bone marrow stromal cell treatment significantly (p < 0.05) improved magnetic resonance imaging diffusion indices of white matter in type 2 diabetes mellitus rats after middle cerebral artery occlusion compared with the saline-treated rats. Superior to the fractional anisotropy metric that provided measures related to organization of neuronal fiber bundles, the entropy metric can also identify microstructures and low-density axonal fibers of cerebral tissue after stroke in type 2 diabetes mellitus rats. © The Author(s) 2015.

White matter changes after stroke in type 2 diabetic rats measured by diffusion magnetic resonance imaging

PubMed Central

Ding, Guangliang; Chen, Jieli; Chopp, Michael; Li, Lian; Yan, Tao; Davoodi-Bojd, Esmaeil; Li, Qingjiang; Davarani, Siamak PN

2015-01-01

Diffusion-related magnetic resonance imaging parametric maps may be employed to characterize white matter of brain. We hypothesize that entropy of diffusion anisotropy may be most effective for detecting therapeutic effects of bone marrow stromal cell treatment of ischemia in type 2 diabetes mellitus rats. Type 2 diabetes mellitus was induced in adult male Wistar rats. These rats were then subjected to 2 h of middle cerebral artery occlusion, and received bone marrow stromal cell (5 × 106, n = 8) or an equal volume of saline (n = 8) via tail vein injection at three days after middle cerebral artery occlusion. Magnetic resonance imaging was performed on day one and then weekly for five weeks post middle cerebral artery occlusion. The diffusion metrics complementarily permitted characterization of axons and axonal myelination. All six magnetic resonance imaging diffusion metrics, confirmed by histological measures, demonstrated that bone marrow stromal cell treatment significantly (p < 0.05) improved magnetic resonance imaging diffusion indices of white matter in type 2 diabetes mellitus rats after middle cerebral artery occlusion compared with the saline-treated rats. Superior to the fractional anisotropy metric that provided measures related to organization of neuronal fiber bundles, the entropy metric can also identify microstructures and low-density axonal fibers of cerebral tissue after stroke in type 2 diabetes mellitus rats. PMID:26685128

Statistical spatio-temporal properties of the Laser MegaJoule speckle

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

Le Cain, A.; Sajer, J. M.; Riazuelo, G.

2012-10-15

This paper investigates a statistical model to describe the spatial and temporal properties of hot spots generated by the superimposition of multiple laser beams. In the context of the Laser MegaJoule design, we introduce the formula for contrasts, trajectories and velocities of the speckle pattern. Single bundle of four beams, two-cones and three-cones configurations are considered. Statistical properties of the speckle in the zone where all the beams overlap are studied with different configurations of polarizations. These properties are shown to be very different from the case of one single bundle of four beams. The configuration of polarization has onlymore » a slight effect in the two-cones or three cones configuration. Indeed, the impact of the double polarization smoothing is reduced in the area in which all the beams overlap, while it is much more significant when they split. Moreover, the size of the hot-spots decreases as the number of laser beams increases, but we show that their velocity decreases. As a matter of fact, the maximal velocity of hot spots is found to be only about 10{sup -5} of the velocity of light and the integrated contrast is about 15% when the beams overlap.« less

Tailoring the structure of aligned carbon nanotube bundle by reactive polymer for strengthening its surface interaction with thermosets and the excellent properties of the hybrid thermosets

NASA Astrophysics Data System (ADS)

Guan, Qingbao; Yuan, Li; Zhang, Yi; Gu, Aijuan; Liang, Guozheng

2018-05-01

Aligned carbon nanotube bundles (ACNTB) with multi-level hierarchical structures were tailored by reactive polymer vinyl-terminated polyphenylene ether (PPE) for the excellent integrated property of bismaleimide-triazine (BT) resin. The PPE-tailored ACNTB (ACNTB@PPE) has increased strength for the penetration of PPE into porous ACNTB strengthening the interaction between each CNT. The strong interaction at the interface of ACNTB@PPE and BT matrix can be created owing to the reaction of the vinyl group in PPE on the surface of ACNTB and maleimide group in BT. BT with 2% ACNTB@PPE composite shows the optimal flexural strength, fracture toughness and tensile strength, which are 88%, 115% and 77% higher than those of BT, respectively. The introduction of ACNTB@PPE slightly enhances the thermal property of BT. ACNTB@PPE can significantly improve the flame retardancy of BT composites. As compared to individual ACNTB, ACNTB@PPE effectively improves the integrated property of BT composites mainly due to the chemical interaction at the interface of ACNTB@PPE and BT matrix and the increased interaction between each CNT.

Liquid crystalline composites toward organic photovoltaic application (Conference Presentation)

NASA Astrophysics Data System (ADS)

Shimizu, Yo; Sosa-Vargas, Lydia; Shin, Woong; Higuchi, Yumi; Itani, Hiromichi; Kawano, Koki; Dao, Quang Duy; Fujii, Akihiko; Ozaki, Masanori

2017-02-01

Liquid crystalline semiconductor is an interesting category of organic electronic materials and also has been extensively studied in terms of "Printed Electronics". For the wider diversity in research toward new applications, one can consider how to use a combination of miscibility and phase separation in liquid crystals. Here we report discotic liquid crystals in making a composite of which structural order is controlled in nano-scale toward photovoltaic applications. Discotic columnar LCs were studied on their resultant molecular order and carrier transport properties. Liquid crystals of phthalocyanine and its analogues which exhibit columnar mesomorphism with high carrier mobility (10-1 cm2/Vs) were examined with making binary phase diagrams and the correlation to carrier transport properties by TOF measurements was discussed. The shape-analogues in chemical structure shows a good miscibility even for the different lattice-type of columnar arrangement and the carrier mobility is mostly decrease except for a case of combination with a metal-free and the metal complex. For the mixtures with non-mesogenic C60 derivatives, one sees a phase-separated structure due to its immiscibility, though the columnar order is remained in a range of component ratio.Especially, in a range of the ratio, it was observed the phase separated C60 derivatives are fused into the matrix of columnar bundles, indicating C60 derivatives could be diffused in columnar arrays in molecular level.

Volume illustration of muscle from diffusion tensor images.

PubMed

Chen, Wei; Yan, Zhicheng; Zhang, Song; Crow, John Allen; Ebert, David S; McLaughlin, Ronald M; Mullins, Katie B; Cooper, Robert; Ding, Zi'ang; Liao, Jun

2009-01-01

Medical illustration has demonstrated its effectiveness to depict salient anatomical features while hiding the irrelevant details. Current solutions are ineffective for visualizing fibrous structures such as muscle, because typical datasets (CT or MRI) do not contain directional details. In this paper, we introduce a new muscle illustration approach that leverages diffusion tensor imaging (DTI) data and example-based texture synthesis techniques. Beginning with a volumetric diffusion tensor image, we reformulate it into a scalar field and an auxiliary guidance vector field to represent the structure and orientation of a muscle bundle. A muscle mask derived from the input diffusion tensor image is used to classify the muscle structure. The guidance vector field is further refined to remove noise and clarify structure. To simulate the internal appearance of the muscle, we propose a new two-dimensional example based solid texture synthesis algorithm that builds a solid texture constrained by the guidance vector field. Illustrating the constructed scalar field and solid texture efficiently highlights the global appearance of the muscle as well as the local shape and structure of the muscle fibers in an illustrative fashion. We have applied the proposed approach to five example datasets (four pig hearts and a pig leg), demonstrating plausible illustration and expressiveness.

Spatially resolved, diffuse reflectance imaging for subsurface pattern visualization toward development of a lensless imaging platform: phantom experiments

NASA Astrophysics Data System (ADS)

Schelkanova, Irina; Pandya, Aditya; Saiko, Guennadi; Nacy, Lidia; Babar, Hannan; Shah, Duoaud; Lilge, Lothar; Douplik, Alexandre

2016-01-01

A portable, spatially resolved, diffuse reflectance lensless imaging technique based on the charge-coupled device or complementary metal-oxide semiconductor sensor directly coupled to the fiber optic bundle is proposed for visualization of subsurface structures such as superficial microvasculature in the epithelium. We discuss an experimental method for emulating a lensless imaging setup via raster scanning a single fiber-optic cable over a microfluidic phantom containing periodic hemoglobin absorption contrast. To evaluate the ability of the technique to recover information about the subsurface linear structures, scattering layers formed of the Sylgard® 184 Silicone Elastomer and titanium dioxide were placed atop the microfluidic phantom. Thickness of the layers ranged from 0.2 to 0.7 mm, and the values of the reduced scattering coefficient (μs‧) were between 0.85 and 4.25 mm-1. The results demonstrate that fiber-optic, lensless platform can be used for two-dimensional imaging of absorbing inclusions in diffuse reflectance mode. In these experiments, it was shown that diffuse reflectance imaging can provide sufficient spatial sampling of the phantom for differentiation of 30 μm structural features of the embedded absorbing pattern inside the scattering media.

Simulation studies of self-organization of microtubules and molecular motors.

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

Jian, Z.; Karpeev, D.; Aranson, I. S.

We perform Monte Carlo type simulation studies of self-organization of microtubules interacting with molecular motors. We model microtubules as stiff polar rods of equal length exhibiting anisotropic diffusion in the plane. The molecular motors are implicitly introduced by specifying certain probabilistic collision rules resulting in realignment of the rods. This approximation of the complicated microtubule-motor interaction by a simple instant collision allows us to bypass the 'computational bottlenecks' associated with the details of the diffusion and the dynamics of motors and the reorientation of microtubules. Consequently, we are able to perform simulations of large ensembles of microtubules and motors onmore » a very large time scale. This simple model reproduces all important phenomenology observed in in vitro experiments: Formation of vortices for low motor density and raylike asters and bundles for higher motor density.« less

Confocal microendoscopy: Characterization of imaging bundles, fluorescent contrast agents, and early clinical results

NASA Astrophysics Data System (ADS)

Udovich, Joshua Anthony

Ovarian cancer is the fifth leading cause of cancer related deaths among women. Early detection improves the chances of survival following diagnosis, and new imaging modalities have the potential to reduce deaths due to this disease. The confocal microendoscope (CME) is a non-destructive in-vivo imaging device for visualization of the ovaries that operates in real-time. Two components of the CME system are evaluated in this paper, and initial results from an ongoing clinical trial are presented. Fiber-optic imaging bundles are used in the CME imaging catheter to relay images over distances of up to 20 feet. When detecting fluorescent signals from investigated tissue, any fluorescence in the system can potentially reduce contrast in images. The emission and transmission properties of three commercially available fiber optic imaging bundles were evaluated. Emission maps of fluorescence from bundles were generated at multiple excitation wavelengths to determine the profile and amount of fluorescence present in bundles manufactured by Sumitomo, Fujikura, and Schott. Results are also presented that show the variation of transmittance as a function of illumination angle in these bundles. Users of high-resolution fiber-optic imaging bundles should be aware of these properties and take them into account during system design. Contrast is improved in images obtained with the CME through the application of topical dyes. Acridine orange (AO) and SYTO 16 are two fluorescent stains that are used to show the size, shape, and distribution of cell nuclei. Unfortunately, little is known about the effects of these dyes on living tissues. This study was undertaken to evaluate the effects of dye treatment on peritoneal tissues in mice. Seventy-five Balb/c mice were split into five groups of fifteen and given peritoneal injections of dye or saline. The proportions of negative outcomes for the control and test groups were compared using confidence intervals and the Fisher's exact test. No significant difference was determined between the groups. These data provide preliminary results on determining the effect of these dyes on living tissues. Preliminary results of a clinical trial are presented showing in-vivo use of the CME for imaging of the ovaries. This is the first portion of a two part study to demonstrate the clinical diagnosis potential of the CME system. A mobile version of the bench-top CME was modified to be used in the clinic. Fluorescein sodium is used as an initial contrast agent in these studies to demonstrate fluorescence imaging. Twenty patients were successfully imaged, and results of this study have allowed progression to a clinical validation study showing the diagnostic capabilities of the CME.

Controlling diameter distribution of catalyst nanoparticles in arc discharge.

PubMed

Li, Jian; Volotskova, Olga; Shashurin, Alexey; Keidar, Michael

2011-11-01

It is demonstrated that the diameter distribution of catalyst nanoparticles in arc discharge can be controlled by a magnetic field. The magnetic field affects the arc shape, shortens the diffusing time of the catalyst nanoparticles through the nucleation zone, and consequentially reduces the average diameters of nanoparticles. The average diameter is reduced from about 7.5 nm without magnetic field to about 5 nm is the case of a magnetic field. Decrease of the catalyst nanoparticle diameter with magnetic field correlates well with decrease in the single-wall carbon nanotube and their bundles diameters.

Relating microstructure to rheology of a bundled and cross-linked F-actin network in vitro

NASA Astrophysics Data System (ADS)

Shin, J. H.; Gardel, M. L.; Mahadevan, L.; Matsudaira, P.; Weitz, D. A.

2004-06-01

The organization of individual actin filaments into higher-order structures is controlled by actin-binding proteins (ABPs). Although the biological significance of the ABPs is well documented, little is known about how bundling and cross-linking quantitatively affect the microstructure and mechanical properties of actin networks. Here we quantify the effect of the ABP scruin on actin networks by using imaging techniques, cosedimentation assays, multiparticle tracking, and bulk rheology. We show how the structure of the actin network is modified as the scruin concentration is varied, and we correlate these structural changes to variations in the resultant network elasticity.

A physiological basis for variation in the contractile properties of isolated rat heart.

PubMed Central

Lin, L E; McClellan, G; Weisberg, A; Winegrad, S

1991-01-01

1. The maximum Ca(2+)-activated force, maximum velocity of unloaded shortening and both Ca(2+)- and actin-activated ATPase activities of myosin have been measured in detergent-skinned preparations of isolated bundles of rat right ventricle after exposure of the intact tissue to different conditions of superfusion, mechanical activity and temperature. 2. Maximum Ca(2+)-activated force per unit cross-sectional area decreases with increasing cross-sectional area, and, in the absence of electrical stimulation, with the duration of superfusion. Maximum velocity of unloaded shortening is not influenced by these differences. 3. Actin-activated ATPase activity of myosin decreases as cross-sectional area increases and duration of superfusion increases, but the extent of the decrease in enzymatic activity is less than that of developed force. Ca(2+)-activated ATPase activity is independent of these differences. 4. Actin-activated ATPase activity in cryostatic sections of quickly frozen tissue is not uniform across the transverse section. In thin bundles, it is highest in the centre and lowest at the edge of the section, which correspond, respectively, to the centre and the surface of the tissue bundle. Exposure of the tissue section to 1 microM-cyclic AMP increases the actin-activated ATPase activity of myosin with the largest increase in activity occurring at or near the surface of the bundle. 5. Ca(2+)-activated ATPase activity of myosin is uniform across the transverse section and is not changed by cyclic AMP. 6. Electrical stimulation, elevated Ca2+ concentration in the superfusion medium, or isoprenaline partially or completely reverse the decline in maximum Ca(2+)-activated force produced by prolonged superfusion of the bundle before its skinning. 7. These observations are similar in many ways to those made on frog skeletal muscles by Elzinga, Howarth, Rull, Wilson & Woledge (1989a). An explanation based on the existence of a physiological mechanism for regulating the properties of force generators is proposed. Regulation of the attachment of the cross-bridge to an actin filament may be the basis for the regulatory mechanism. Images Fig. 4 Fig. 7 PMID:1667804

Biomechanical characterization of double-bundle femoral press-fit fixation techniques.

PubMed

Ettinger, M; Haasper, C; Hankemeier, S; Hurschler, C; Breitmeier, D; Krettek, C; Jagodzinski, M

2011-03-01

Press-fit fixation of patellar tendon bone anterior cruciate ligament autografts is an interesting technique because no hardware is necessary. To date, no biomechanical data exist describing an implant-free double-bundle press-fit procedure. The purpose of this study was to characterize the biomechanical properties of three double-bundle press-fit fixations. In a controlled laboratory study, the patellar-, quadriceps- and hamstring tendons of 10 human cadavers (age: 49.2 ± 18.5 years) were used. An inside out press-fit fixation with a knot in the semitendinosus and gracilis tendons (SG) combined with an additional bone block, with two quadriceps tendon bone block grafts (QU) was compared with press-fit fixation of two bone patellar tendon bone block (PT) grafts in 30 porcine femora. Constructs were cyclically stretched and then loaded until failure. Maximum load to failure, stiffness and elongation during failure testing and cyclical loading were investigated. The maximum load to failure was 703 ± 136 N for SG fixation, 632 ± 130 N for QU and 656 ± 127 N for PT fixation. Stiffness of the constructs averaged 138 ± 26 N/mm for SG, 159 ± 74 N/mm for QU, and 154 ± 50 N/mm for PT fixation. Elongation during initial cyclical loading was 1.2 ± 1.4 mm for SG, 2.0 ± 1.4 mm for QU, and 1.0 ± 0.6 mm for PT (significantly larger for PT and QU between the first 5 cycles compared with cycles 15-20th, P < 0.01). All investigated double-bundle fixation techniques were equal in terms of maximum load to failure, stiffness, and elongation. Unlike with single-bundle press-fit fixation techniques that have been published, no difference was observed between pure tendon combined with an additional bone block and tendon bone grafts. All techniques exhibited larger elongation during initial cyclical loading. All three press-fit fixation techniques that were investigated exhibit comparable biomechanical properties. Preconditioning of the constructs is critical.

Diffusion and bulk flow in phloem loading: A theoretical analysis of the polymer trap mechanism for sugar transport in plants

NASA Astrophysics Data System (ADS)

Dölger, Julia; Rademaker, Hanna; Liesche, Johannes; Schulz, Alexander; Bohr, Tomas

2014-10-01

Plants create sugar in the mesophyll cells of their leaves by photosynthesis. This sugar, mostly sucrose, has to be loaded via the bundle sheath into the phloem vascular system (the sieve elements), where it is distributed to growing parts of the plant. We analyze the feasibility of a particular loading mechanism, active symplasmic loading, also called the polymer trap mechanism, where sucrose is transformed into heavier sugars, such as raffinose and stachyose, in the intermediary-type companion cells bordering the sieve elements in the minor veins of the phloem. Keeping the heavier sugars from diffusing back requires that the plasmodesmata connecting the bundle sheath with the intermediary cell act as extremely precise filters, which are able to distinguish between molecules that differ by less than 20% in size. In our modeling, we take into account the coupled water and sugar movement across the relevant interfaces, without explicitly considering the chemical reactions transforming the sucrose into the heavier sugars. Based on the available data for plasmodesmata geometry, sugar concentrations, and flux rates, we conclude that this mechanism can in principle function, but that it requires pores of molecular sizes. Comparing with the somewhat uncertain experimental values for sugar export rates, we expect the pores to be only 5%-10% larger than the hydraulic radius of the sucrose molecules. We find that the water flow through the plasmodesmata, which has not been quantified before, contributes only 10%-20% to the sucrose flux into the intermediary cells, while the main part is transported by diffusion. On the other hand, the subsequent sugar translocation into the sieve elements would very likely be carried predominantly by bulk water flow through the plasmodesmata. Thus, in contrast to apoplasmic loaders, all the necessary water for phloem translocation would be supplied in this way with no need for additional water uptake across the plasma membranes of the phloem.

Bundle Sheath Diffusive Resistance to CO2 and Effectiveness of C4 Photosynthesis and Refixation of Photorespired CO2 in a C4 Cycle Mutant and Wild-Type Amaranthus edulis1

PubMed Central

Kiirats, Olavi; Lea, Peter J.; Franceschi, Vincent R.; Edwards, Gerald E.

2002-01-01

A mutant of the NAD-malic enzyme-type C4 plant, Amaranthus edulis, which lacks phosphoenolpyruvate carboxylase (PEPC) in the mesophyll cells was studied. Analysis of CO2 response curves of photosynthesis of the mutant, which has normal Kranz anatomy but lacks a functional C4 cycle, provided a direct means of determining the liquid phase-diffusive resistance of atmospheric CO2 to sites of ribulose 1,5-bisphosphate carboxylation inside bundle sheath (BS) chloroplasts (rbs) within intact plants. Comparisons were made with excised shoots of wild-type plants fed 3,3-dichloro-2-(dihydroxyphosphinoyl-methyl)-propenoate, an inhibitor of PEPC. Values of rbs in A. edulis were 70 to 180 m2 s−1 mol−1, increasing as the leaf matured. This is about 70-fold higher than the liquid phase resistance for diffusion of CO2 to Rubisco in mesophyll cells of C3 plants. The values of rbs in A. edulis are sufficient for C4 photosynthesis to elevate CO2 in BS cells and to minimize photorespiration. The calculated CO2 concentration in BS cells, which is dependent on input of rbs, was about 2,000 μbar under maximum rates of CO2 fixation, which is about six times the ambient level of CO2. High re-assimilation of photorespired CO2 was demonstrated in both mutant and wild-type plants at limiting CO2 concentrations, which can be explained by high rbs. Increasing O2 from near zero up to ambient levels under low CO2, resulted in an increase in the gross rate of O2 evolution measured by chlorophyll fluorescence analysis in the PEPC mutant; this increase was simulated from a Rubisco kinetic model, which indicates effective refixation of photorespired CO2 in BS cells. PMID:12376660

Diffusion and bulk flow in phloem loading: a theoretical analysis of the polymer trap mechanism for sugar transport in plants.

PubMed

Dölger, Julia; Rademaker, Hanna; Liesche, Johannes; Schulz, Alexander; Bohr, Tomas

2014-10-01

Plants create sugar in the mesophyll cells of their leaves by photosynthesis. This sugar, mostly sucrose, has to be loaded via the bundle sheath into the phloem vascular system (the sieve elements), where it is distributed to growing parts of the plant. We analyze the feasibility of a particular loading mechanism, active symplasmic loading, also called the polymer trap mechanism, where sucrose is transformed into heavier sugars, such as raffinose and stachyose, in the intermediary-type companion cells bordering the sieve elements in the minor veins of the phloem. Keeping the heavier sugars from diffusing back requires that the plasmodesmata connecting the bundle sheath with the intermediary cell act as extremely precise filters, which are able to distinguish between molecules that differ by less than 20% in size. In our modeling, we take into account the coupled water and sugar movement across the relevant interfaces, without explicitly considering the chemical reactions transforming the sucrose into the heavier sugars. Based on the available data for plasmodesmata geometry, sugar concentrations, and flux rates, we conclude that this mechanism can in principle function, but that it requires pores of molecular sizes. Comparing with the somewhat uncertain experimental values for sugar export rates, we expect the pores to be only 5%-10% larger than the hydraulic radius of the sucrose molecules. We find that the water flow through the plasmodesmata, which has not been quantified before, contributes only 10%-20% to the sucrose flux into the intermediary cells, while the main part is transported by diffusion. On the other hand, the subsequent sugar translocation into the sieve elements would very likely be carried predominantly by bulk water flow through the plasmodesmata. Thus, in contrast to apoplasmic loaders, all the necessary water for phloem translocation would be supplied in this way with no need for additional water uptake across the plasma membranes of the phloem.

Reduced graphene oxide-supported TiO2 fiber bundles with mesostructures as anode materials for lithium-ion batteries.

PubMed

Zhen, Mengmeng; Zhu, Xiaohe; Zhang, Xiao; Zhou, Zhen; Liu, Lu

2015-10-05

Although the synthesis of mesoporous materials is well established, the preparation of TiO2 fiber bundles with mesostructures, highly crystalline walls, and good thermal stability on the RGO nanosheets remains a challenge. Herein, a low-cost and environmentally friendly hydrothermal route for the synthesis of RGO nanosheet-supported anatase TiO2 fiber bundles with dense mesostructures is used. These mesostructured TiO2 -RGO materials are used for investigation of Li-ion insertion properties, which show a reversible capacity of 235 mA h g(-1) at 200 mA g(-1) and 150 mA h g(-1) at 1000 mA g(-1) after 1000 cycles. The higher specific surface area of the new mesostructures and high conductive substrate (RGO nanosheets) result in excellent lithium storage performance, high-rate performance, and strong cycling stability of the TiO2 -RGO composites. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Carbon Nanotube Networks Reinforced by Silver Nanowires with Improved Optical Transparency and Conductivity

NASA Astrophysics Data System (ADS)

Martine, Patricia; Fakhimi, Azin; Lin, Ling; Jurewicz, Izabela; Dalton, Alan; Zakhidov, Anvar A.; Baughman, Ray H.

2015-03-01

We have fabricated highly transparent and conductive free-standing nanocomposite thin film electrodes by adding silver nanowires (AgNWs) to dry-spun Multiwall Carbon Nanotube (MWNT) aerogels. This nanocomposite exhibits desirable properties such as high optical transmittance, excellent flexibility and enhanced electrical conductivity. The incorporation of the AgNWs to the MWNT aerogels was accomplished by using a spray coating method. The optical transparency and sheet resistance of the nanocomposite was tuned by adjusting the concentration of AgNWs, back pressure and nozzle distance of the spray gun to the MWNT aerogel during deposition. As the solvent evaporated, the aerogel MWNT bundles densified via surface tension which caused the MWNT bundles to collapse. This adjustable process was responsible in forming well defined apertures that increased the nanocomposite's transmittance up to 90 percent. Via AgNWs percolation and random interconnections between separate MWNT bundles in the aerogel matrix, the sheet resistance decreased from 1 K ohm/sq to less than 100 ohm/sq. Alan G. MacDiarmid NanoTech Institute

The helix bundle: A reversible lipid binding motif

PubMed Central

Narayanaswami, Vasanthy; Kiss, Robert S.; Weers, Paul M.M.

2009-01-01

Apolipoproteins are the protein components of lipoproteins that have the innate ability to inter convert between a lipid-free and a lipid-bound form in a facile manner, a remarkable property conferred by the helix bundle motif. Composed of a series of four or five amphipathic α-helices that fold to form a helix bundle, this motif allows the en face orientation of the hydrophobic faces of the α-helices in the protein interior in the lipid-free state. A conformational switch then permits helix-helix interactions to be substituted by helix-lipid interactions upon lipid binding interaction. This review compares the apolipoprotein high resolution structures and the factors that trigger this switch in insect apolipophorin III and the mammalian apolipoproteins, apolipoprotein E and apolipoprotein A-I, pointing out the commonalities and key differences in the mode of lipid interaction. Further insights into the lipid bound conformation of apolipoproteins are required to fully understand their functional role under physiological conditions. PMID:19770066

Selective Oxidation of Amorphous Carbon Layers without Damaging Embedded Single Wall Carbon Nanotube Bundles

NASA Astrophysics Data System (ADS)

Choi, Young Chul; Lim, Seong Chu

2013-11-01

Single wall carbon nanotubes (SWCNTs) were synthesized by arc discharge, and then purified by selective oxidation of amorphous carbon layers that were found to encase SWCNT bundles and catalyst metal particles. In order to remove selectively the amorphous carbon layers with SWCNTs being intact, we have systematically investigated the thermal treatment conditions; firstly, setting the temperature by measuring the activation energies of SWCNTs and amorphous carbon layers, and then, secondly, finding the optimal process time. As a consequence, the optimal temperature and time for the thermal treatment was found to be 460 °C and 20 min, respectively. The complete elimination of surrounding amorphous carbon layers makes it possible to efficiently disperse the SWCNT bundles, resulting in high absorbance of SWCNT-ink. The SWCNTs which were thermal-treated at optimized temperature (460 °C) and duration (20 min) showed much better crystallinity, dispersibility, and transparent conducting properties, compared with as-synthesized and the nanotubes thermal-treated at different experimental conditions.

The pH sensibility of actin-bundling LIM proteins is governed by the acidic properties of their C-terminal domain.

PubMed

Moes, Danièle; Hoffmann, Céline; Dieterle, Monika; Moreau, Flora; Neumann, Katrin; Papuga, Jessica; Furtado, Angela Tavares; Steinmetz, André; Thomas, Clément

2015-08-19

Actin-bundling Arabidopsis LIM proteins are subdivided into two subfamilies differing in their pH sensitivity. Widely-expressed WLIMs are active under low and high physiologically-relevant pH conditions, whereas pollen-enriched PLIMs are inactivated by pH values above 6.8. By a domain swapping approach we identified the C-terminal (Ct) domain of PLIMs as the domain responsible for pH responsiveness. Remarkably, this domain conferred pH sensitivity to LIM proteins, when provided "in trans" (i.e., as a single, independent, peptide), indicating that it operates through the interaction with another domain. An acidic 6xc-Myc peptide functionally mimicked the Ct domain of PLIMs and efficiently inhibited LIM actin bundling activity under high pH conditions. Together, our data suggest a model where PLIMs are regulated by an intermolecular interaction between their acidic Ct domain and another, yet unidentified, domain. Copyright © 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Molecular modeling of polymers 16. Gaseous diffusion in polymers: a quantitative structure-property relationship (QSPR) analysis.

PubMed

Patel, H C; Tokarski, J S; Hopfinger, A J

1997-10-01

The purpose of this study was to identify the key physicochemical molecular properties of polymeric materials responsible for gaseous diffusion in the polymers. Quantitative structure-property relationships, QSPRs were constructed using a genetic algorithm on a training set of 16 polymers for which CO2, N2, O2 diffusion constants were measured. Nine physicochemical properties of each of the polymers were used in the trial basis set for QSPR model construction. The linear cross-correlation matrices were constructed and investigated for colinearity among the members of the training sets. Common water diffusion measures for a limited training set of six polymers was used to construct a "semi-QSPR" model. The bulk modulus of the polymer was overwhelmingly found to be the dominant physicochemical polymer property that governs CO2, N2 and O2 diffusion. Some secondary physicochemical properties controlling diffusion, including conformational entropy, were also identified as correlation descriptors. Very significant QSPR diffusion models were constructed for all three gases. Cohesive energy was identified as the main correlation physicochemical property with aqueous diffusion measures. The dominant role of polymer bulk modulus on gaseous diffusion makes it difficult to develop criteria for selective transport of gases through polymers. Moreover, high bulk moduli are predicted to be necessary for effective gas barrier materials. This property requirement may limit the processing and packaging features of the material. Aqueous diffusion in polymers may occur by a different mechanism than gaseous diffusion since bulk modulus does not correlate with aqueous diffusion, but rather cohesive energy of the polymer.

The shape of strings to come: How topological defects twist, bend, and wrinkle filament bundles

NASA Astrophysics Data System (ADS)

Bruss, Isaac; Grason, Gregory

2015-03-01

Topological defects are crucial to the thermodynamics and structure of condensed matter systems. For instance, when incorporated into crystalline membranes like graphene, 5- and 7-fold disclinations produce conical- and saddle-like geometries respectively. A recently discovered mapping between the inter-filament spacing within a deformed bundle and the metric properties of curved surfaces, suggests previously unexplored parallels between the two, specifically in regards to how 2D patterning promotes 3D shape transitions. This discovery is poised to describe the structure of a host of filamentous materials-both biological and microfabricated-that exhibit distinctive shapes and packings. Motivated by the filamentous analogs to the conical and saddles shapes found in thin membranes, we investigate for the first time the interplay between defects in the cross section of a bundle and its global structure, using a combination of continuum elasticity theory and numerical simulation of cohesive bundles with a fixed packing topology. Focusing primarily on the instability response to disclinations, we predict a host of new equilibria structures, some of which are without direct parallel to the analogous membrane, including torsional wrinkling, radial kinking, and helical winding. Center for Hierarchical Manufacturing-CMMI 10-25020, NSF CAREER Award-DMR 09-55760, & UMass MRSEC.

Biomechanical differences of the anterior and posterior bands of the ulnar collateral ligament of the elbow.

PubMed

Jackson, Timothy J; Jarrell, Shelby E; Adamson, Gregory J; Chung, Kyung Chil; Lee, Thay Q

2016-07-01

The main purpose of this study was to examine the functional characteristics of the anterior and posterior bands of the anterior bundle of the ulnar collateral ligament (UCL). Six cadaveric elbows were tested using a digital tracking system to measure the strain in the anterior band and posterior band of the anterior bundle of the UCL throughout a flexion/extension arc. The specimens were then placed in an Instron materials testing machine and loaded to failure to determine yield load and ultimate load of the UCL. The posterior band showed a linear increase in strain with increasing degrees of elbow flexion while the anterior band showed minimal change in strain throughout. The bands showed similar strain at yield load and ultimate load, demonstrating similar intrinsic properties. The anterior band of the anterior bundle of the UCL shows an isometric strain pattern through elbow range of motion, while the posterior band shows an increasing strain pattern in higher degrees of elbow flexion. Both bands show similar strain in a load to failure model, indicating insertion point, not intrinsic differences, of the bands determine the function of the anterior bundle of the UCL. This demonstrates a biomechanical rationale for UCL reconstructions using single point anatomical insertion points.

Structure based computational assessment of channel properties of assembled ORF-8a from SARS-CoV.

PubMed

Hsu, Hao-Jen; Lin, Meng-Han; Schindler, Christina; Fischer, Wolfgang B

2015-02-01

ORF 8a is a short 39 amino acid bitopic membrane protein encoded by severe acute respiratory syndrome causing corona virus (SARS-CoV). It has been identified to increase permeability of the lipid membrane for cations. Permeability is suggested to occur due to the assembly of helical bundles. Computational models of a pentameric assembly of 8a peptides are generated using the first 22 amino acids, which include the transmembrane domain. Low energy structures reveal a hydrophilic pore mantled by residues Thr-8, and -18, Ser-11, Cys-13, and Arg-22. Potential of mean force (PMF) profiles for mono (Na(+) , K(+) , Cl(-) ) and divalent (Ca(2+) ) ions along the pore are calculated. The data support experimental findings of a weak cation selectivity of the channel. Calculations on 8a are compared to data derived for a pentameric bundle consisting of the M2 helices of the bacterial pentameric ligand gated ion channel GLIC (3EHZ). PMF curves of both, bundles 8a and M2, show sigmoidal shaped profiles. In comparison to the data for the M2-GLIC model, data of the 8a bundle show lower amplitude of the PMF values between maximum and minimum and less discrimination amongst ions. © 2014 Wiley Periodicals, Inc.

Synthesis and magnetic properties of bundled and dispersed Co{sub 3}O{sub 4} nanowires

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

Zhang, B.B.; Wang, P.F.; Xu, J.C.

Highlights: • Co{sub 3}O{sub 4} nanowires possessed the same diameter and the different interwires distance. • All samples possessed antiferromagnetism and superparamagnetism at high temperature. • The exchange bias effect was observed at low temperature. • The surface spin coupling restrained the surface effect of magnetic nanostructures. - Abstract: The magnetic Co{sub 3}O{sub 4} nanowires were synthesized using the templates of SBA-15, and then the well-dispersed nanowires (D-wires) were separated from the bundled ordered nanowires (B-wires) with the centrifugal technique. TEM images indicated that D-wires were highly dispersed Co{sub 3}O{sub 4} nanowires and B-wires existed in bundles. All samples possessedmore » the antiferromagnetism and superparamagnetism at high temperature. After revealing the intrinsic magnetic properties of Co{sub 3}O{sub 4} nanowires with D-wires, the magnetic behavior of B-wires was discussed in detail, and then the magnetic interaction between neighboring nanowires could be deduced. The exchange bias effect from the body Co{sub 3}O{sub 4} antiferromagnetism and surface ferromagnetism was observed at low temperature. The magnetization of B-wires was higher than that of D-wires, which was attributed to the constraint of the surface spin coupling between the neighboring nanowires to the surface affect of nanostructures.« less

Visualizing heterogeneity of photosynthetic properties of plant leaves with two-photon fluorescence lifetime imaging microscopy.

PubMed

Iermak, Ievgeniia; Vink, Jochem; Bader, Arjen N; Wientjes, Emilie; van Amerongen, Herbert

2016-09-01

Two-photon fluorescence lifetime imaging microscopy (FLIM) was used to analyse the distribution and properties of Photosystem I (PSI) and Photosystem II (PSII) in palisade and spongy chloroplasts of leaves from the C3 plant Arabidopsis thaliana and the C4 plant Miscanthus x giganteus. This was achieved by separating the time-resolved fluorescence of PSI and PSII in the leaf. It is found that the PSII antenna size is larger on the abaxial side of A. thaliana leaves, presumably because chloroplasts in the spongy mesophyll are "shaded" by the palisade cells. The number of chlorophylls in PSI on the adaxial side of the A. thaliana leaf is slightly higher. The C4 plant M. x giganteus contains both mesophyll and bundle sheath cells, which have a different PSI/PSII ratio. It is shown that the time-resolved fluorescence of bundle sheath and mesophyll cells can be analysed separately. The relative number of chlorophylls, which belong to PSI (as compared to PSII) in the bundle sheath cells is at least 2.5 times higher than in mesophyll cells. FLIM is thus demonstrated to be a useful technique to study the PSI/PSII ratio and PSII antenna size in well-defined regions of plant leaves without having to isolate pigment-protein complexes. Copyright © 2016 Elsevier B.V. All rights reserved.

Metabolite pools and carbon flow during C4 photosynthesis in maize: 13CO2 labeling kinetics and cell type fractionation.

PubMed

Arrivault, Stéphanie; Obata, Toshihiro; Szecówka, Marek; Mengin, Virginie; Guenther, Manuela; Hoehne, Melanie; Fernie, Alisdair R; Stitt, Mark

2017-01-01

Worldwide efforts to engineer C 4 photosynthesis into C 3 crops require a deep understanding of how this complex pathway operates. CO 2 is incorporated into four-carbon metabolites in the mesophyll, which move to the bundle sheath where they are decarboxylated to concentrate CO 2 around RuBisCO. We performed dynamic 13 CO 2 labeling in maize to analyze C flow in C 4 photosynthesis. The overall labeling kinetics reflected the topology of C 4 photosynthesis. Analyses of cell-specific labeling patterns after fractionation to enrich bundle sheath and mesophyll cells revealed concentration gradients to drive intercellular diffusion of malate, but not pyruvate, in the major CO 2 -concentrating shuttle. They also revealed intercellular concentration gradients of aspartate, alanine, and phosphenolpyruvate to drive a second phosphoenolpyruvate carboxykinase (PEPCK)-type shuttle, which carries 10-14% of the carbon into the bundle sheath. Gradients also exist to drive intercellular exchange of 3-phosphoglycerate and triose-phosphate. There is rapid carbon exchange between the Calvin-Benson cycle and the CO 2 -concentrating shuttle, equivalent to ~10% of carbon gain. In contrast, very little C leaks from the large pools of metabolites in the C concentration shuttle into respiratory metabolism. We postulate that the presence of multiple shuttles, alongside carbon transfer between them and the Calvin-Benson cycle, confers great flexibility in C 4 photosynthesis. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Left bundle branch block, an old-new entity.

PubMed

Breithardt, Günter; Breithardt, Ole-Alexander

2012-04-01

Left bundle branch block (LBBB) is generally associated with a poorer prognosis in comparison to normal intraventricular conduction, but also in comparison to right bundle branch block which is generally considered to be benign in the absence of an underlying cardiac disorder like congenital heart disease. LBBB may be the first manifestation of a more diffuse myocardial disease. The typical surface ECG feature of LBBB is a prolongation of QRS above 0.11 s in combination with a delay of the intrinsic deflection in leads V5 and V6 of more than 60 ms and no septal q waves in leads I, V5, and V6 due to the abnormal septal activation from right to left. LBBB may induce abnormalities in left ventricular performance due to abnormal asynchronous contraction patterns which can be compensated by biventricular pacing (resynchronization therapy). Asynchronous electrical activation of the ventricles causes regional differences in workload which may lead to asymmetric hypertrophy and left ventricular dilatation, especially due to increased wall mass in late-activated regions, which may aggravate preexisting left ventricular pumping performance or even induce it. Of special interest are patients with LBBB and normal left ventricular dimensions and normal ejection fraction at rest but who may present with an abnormal increase in pulmonary artery pressure during exercise, production of lactate during high-rate pacing, signs of ischemia on myocardial scintigrams (but no coronary artery narrowing), and abnormal ultrastructural findings on myocardial biopsy. For this entity, the term latent cardiomyopathy had been suggested previously.

Biomechanical Comparison of Five Posterior Cruciate Ligament Reconstruction Techniques.

PubMed

Nuelle, Clayton W; Milles, Jeffrey L; Pfeiffer, Ferris M; Stannard, James P; Smith, Patrick A; Kfuri, Mauricio; Cook, James L

2017-07-01

No surgical technique recreates native posterior cruciate ligament (PCL) biomechanics. We compared the biomechanics of five different PCL reconstruction techniques versus the native PCL. Cadaveric knees ( n  = 20) were randomly assigned to one of five reconstruction techniques: Single bundle all-inside arthroscopic inlay, single bundle all-inside suspensory fixation, single bundle arthroscopic-assisted open onlay (SB-ONL), double bundle arthroscopic-assisted open inlay (DB-INL), and double bundle all-inside suspensory fixation (DB-SUSP). Each specimen was potted and connected to a servo-hydraulic load frame for testing in three conditions: PCL intact, PCL deficient, and PCL reconstructed. Testing consisted of a posterior force up to 100 N at a rate of 1 N/s at four knee flexion angles: 10, 30, 60, and 90 degrees. Three material properties were measured under each condition: load to 5 mm displacement, maximal displacement, and stiffness. Data were normalized to the native PCL, compared across techniques, compared with all PCL-intact knees and to all PCL-deficient knees using one-way analysis of variance. For load to 5 mm displacement, intact knees required significantly ( p  < 0.03) more load at 30 degrees of flexion than all reconstructions except the DB-SUSP. At 60 degrees of flexion, intact required significantly ( p  < 0.01) more load than all others except the SB-ONL. At 90 degrees, intact, SB-ONL, DB-INL, and DB-SUSP required significantly more load ( p  < 0.05). Maximal displacement testing showed the intact to have significantly ( p  < 0.02) less laxity than all others except the DB-INL and DB-SUSP at 60 degrees. At 90 degrees the intact showed significantly ( p  < 0.01) less laxity than all others except the DB-SUSP. The intact was significantly stiffer than all others at 30 degrees ( p  < 0.03) and 60 degrees ( p  < 0.01). Finally, the intact was significantly ( p  < 0.05) stiffer than all others except the DB-SUSP at 90 degrees. No technique matched the exact properties of the native PCL, but the double bundle reconstructions more closely recreated the native biomechanics immediately after implantation, with the DB-SUSP coming closest to the native ligament. This study contributes new data for consideration in PCL reconstruction technique choice. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Purification and Properties of Mesophyll and Bundle Sheath Cell α-Glucan Phosphorylases from Zea mays L. 1

PubMed Central

Mateyka, Christian; Schnarrenberger, Claus

1988-01-01

Two major α-glucan phosphorylases (I and II) from leaves of the C4 plant corn (Zea mays L.) were previously shown to be compartmented in mesophyll and bundle sheath cells, respectively (C Mateyka, C Schnarrenberger 1984 Plant Sci Lett 36: 119-123). The two enzymes were separated by chromatography on DEAE-cellulose and purified to homogeneity by affinity chromatography on immobilized starch, according to published procedures, as developed for the cytosol and chloroplast phosphorylase from the C3 plant spinach. The two α-glucan phosphorylases have their pH optimum at pH 7. The specificity for polyglucans was similar for soluble starch and amylopectin, however, differed for glycogen (Km = 16 micrograms per milliliter for the mesophyll cell and 250 micrograms per milliliter for the bundle sheath cell phosphorylase). Maltose, maltotriose, and maltotetraose were not cleaved by either phosphorylase. If maltopentaose was used as substrate, the rate was about twice as high with the bundle sheath cell phosphorylase, than with the mesophyll cell phosphorylase. The phosphorylase I showed a molecular mass of 174 kilodaltons and the phosphorylase II of 195 kilodaltons for the native enzyme and of 87 and of 53 kilodaltons for the SDS-treated proteins, respectively. Specific antisera raised against mesophyll cell phosphorylase from corn leaves and against chloroplast phosphorylase from spinach leaves implied high similarity for the cytosol phosphorylase of the C3 plant spinach with mesophyll cell phosphorylase of the C4 plant corn and of chloroplast phosphorylase of spinach with the bundle sheath cell phosphorylase of corn. Images Fig. 2 Fig. 7 PMID:16665923

Fascin- and α-Actinin-Bundled Networks Contain Intrinsic Structural Features that Drive Protein Sorting.

PubMed

Winkelman, Jonathan D; Suarez, Cristian; Hocky, Glen M; Harker, Alyssa J; Morganthaler, Alisha N; Christensen, Jenna R; Voth, Gregory A; Bartles, James R; Kovar, David R

2016-10-24

Cells assemble and maintain functionally distinct actin cytoskeleton networks with various actin filament organizations and dynamics through the coordinated action of different sets of actin-binding proteins. The biochemical and functional properties of diverse actin-binding proteins, both alone and in combination, have been increasingly well studied. Conversely, how different sets of actin-binding proteins properly sort to distinct actin filament networks in the first place is not nearly as well understood. Actin-binding protein sorting is critical for the self-organization of diverse dynamic actin cytoskeleton networks within a common cytoplasm. Using in vitro reconstitution techniques including biomimetic assays and single-molecule multi-color total internal reflection fluorescence microscopy, we discovered that sorting of the prominent actin-bundling proteins fascin and α-actinin to distinct networks is an intrinsic behavior, free of complicated cellular signaling cascades. When mixed, fascin and α-actinin mutually exclude each other by promoting their own recruitment and inhibiting recruitment of the other, resulting in the formation of distinct fascin- or α-actinin-bundled domains. Subdiffraction-resolution light microscopy and negative-staining electron microscopy revealed that fascin domains are densely packed, whereas α-actinin domains consist of widely spaced parallel actin filaments. Importantly, other actin-binding proteins such as fimbrin and espin show high specificity between these two bundle types within the same reaction. Here we directly observe that fascin and α-actinin intrinsically segregate to discrete bundled domains that are specifically recognized by other actin-binding proteins. Copyright © 2016 Elsevier Ltd. All rights reserved.

Possible structural abnormality of the brainstem in unipolar depressive illness: a transcranial ultrasound and diffusion tensor magnetic resonance imaging study.

PubMed

Steele, J D; Bastin, M E; Wardlaw, J M; Ebmeier, K P

2005-11-01

Most empirically derived antidepressants increase monoamine levels. The nuclei of cells synthesising these monoamines are located in the brainstem, and projection tracts such as the medial forebrain bundle reach virtually all other brain areas. Two studies of unipolar depressive illness using transcranial ultrasound have reported reduced echogenicity of the brainstem midline in unipolar depressed patients. This may be consistent with disruption of white matter tracts, including the medial forebrain bundle, and it has been suggested that the effect of such disruption could be reversed by antidepressants. To replicate these findings in a group of unipolar depressed patients and controls. Fifteen unipolar depressed patients and 15 controls were studied using transcranial ultrasound imaging and diffusion tensor magnetic resonance imaging (DT-MRI). No difference in echogenicity of the brainstem midline of unipolar depressed patients was found. A possible trend (Cohen's d = 0.39) in the direction of previous studies was found. Although the echogenicity of the brainstem midline of the control group was found to be similar to previous reports, there was no reduction in the patient group. Additionally, no structural abnormality of the brainstem was identified using DT-MRI. While these data do not replicate the findings of previous studies reporting a significant reduction in the echogenicity of the brainstem midline in unipolar depressed patients, the ultrasound investigation indicated that there may be a trend in this direction. Given the importance of identifying the causes of depressive illness, it is important that other groups attempt similar studies.

Robust fiber clustering of cerebral fiber bundles in white matter

NASA Astrophysics Data System (ADS)

Yao, Xufeng; Wang, Yongxiong; Zhuang, Songlin

2014-11-01

Diffusion tensor imaging fiber tracking (DTI-FT) has been widely accepted in the diagnosis and treatment of brain diseases. During the rendering pipeline of specific fiber tracts, the image noise and low resolution of DTI would lead to false propagations. In this paper, we propose a robust fiber clustering (FC) approach to diminish false fibers from one fiber tract. Our algorithm consists of three steps. Firstly, the optimized fiber assignment continuous tracking (FACT) is implemented to reconstruct one fiber tract; and then each curved fiber in the fiber tract is mapped to a point by kernel principal component analysis (KPCA); finally, the point clouds of fiber tract are clustered by hierarchical clustering which could distinguish false fibers from true fibers in one tract. In our experiment, the corticospinal tract (CST) in one case of human data in vivo was used to validate our method. Our method showed reliable capability in decreasing the false fibers in one tract. In conclusion, our method could effectively optimize the visualization of fiber bundles and would help a lot in the field of fiber evaluation.

Concurrent white matter bundles and grey matter networks using independent component analysis.

PubMed

O'Muircheartaigh, Jonathan; Jbabdi, Saad

2018-04-15

Developments in non-invasive diffusion MRI tractography techniques have permitted the investigation of both the anatomy of white matter pathways connecting grey matter regions and their structural integrity. In parallel, there has been an expansion in automated techniques aimed at parcellating grey matter into distinct regions based on functional imaging. Here we apply independent component analysis to whole-brain tractography data to automatically extract brain networks based on their associated white matter pathways. This method decomposes the tractography data into components that consist of paired grey matter 'nodes' and white matter 'edges', and automatically separates major white matter bundles, including known cortico-cortical and cortico-subcortical tracts. We show how this framework can be used to investigate individual variations in brain networks (in terms of both nodes and edges) as well as their associations with individual differences in behaviour and anatomy. Finally, we investigate correspondences between tractography-based brain components and several canonical resting-state networks derived from functional MRI. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Node-controlled allocation of mineral elements in Poaceae.

PubMed

Yamaji, Naoki; Ma, Jian Feng

2017-10-01

Mineral elements taken up by the roots will be delivered to different organs and tissues depending on their requirements. In Poaceae, this selective distribution is mainly mediated in the nodes, which have highly developed and fully organized vascular systems. Inter-vascular transfer of mineral elements from enlarged vascular bundles to diffuse vascular bundles is required for their preferential distribution to developing tissues and reproductive organs. A number of transporters involved in this inter-vascular transfer processes have been identified mainly in rice. They are localized at the different cell layers and form an efficient machinery within the node. Furthermore, some these transporters show rapid response to the environmental changes of mineral elements at the protein level. In addition to the node-based transporters, distinct nodal structures including enlarged xylem area, folded plasma membrane of xylem transfer cells and presence of an apoplastic barrier are also required for the efficient inter-vascular transfer. Manipulation of node-based transporters will provide a novel breeding target to improve nutrient use efficiency, productivity, nutritional value and safety in cereal crops. Copyright © 2017 Elsevier Ltd. All rights reserved.

Microstructure Imaging of Crossing (MIX) White Matter Fibers from diffusion MRI

PubMed Central

Farooq, Hamza; Xu, Junqian; Nam, Jung Who; Keefe, Daniel F.; Yacoub, Essa; Georgiou, Tryphon; Lenglet, Christophe

2016-01-01

Diffusion MRI (dMRI) reveals microstructural features of the brain white matter by quantifying the anisotropic diffusion of water molecules within axonal bundles. Yet, identifying features such as axonal orientation dispersion, density, diameter, etc., in complex white matter fiber configurations (e.g. crossings) has proved challenging. Besides optimized data acquisition and advanced biophysical models, computational procedures to fit such models to the data are critical. However, these procedures have been largely overlooked by the dMRI microstructure community and new, more versatile, approaches are needed to solve complex biophysical model fitting problems. Existing methods are limited to models assuming single fiber orientation, relevant to limited brain areas like the corpus callosum, or multiple orientations but without the ability to extract detailed microstructural features. Here, we introduce a new and versatile optimization technique (MIX), which enables microstructure imaging of crossing white matter fibers. We provide a MATLAB implementation of MIX, and demonstrate its applicability to general microstructure models in fiber crossings using synthetic as well as ex-vivo and in-vivo brain data. PMID:27982056

Validity of the Electrodiffusion Model for Calculating Conductance of Simple Ion Channels.

PubMed

Pohorille, Andrew; Wilson, Michael A; Wei, Chenyu

2017-04-20

We examine the validity and utility of the electrodiffusion (ED) equation, i.e., the generalized Nernst-Planck equation, to characterize, in combination with molecular dynamics, the electrophysiological behavior of simple ion channels. As models, we consider three systems-two naturally occurring channels formed by α-helical bundles of peptaibols, trichotoxin, and alamethicin, and a synthetic, hexameric channel, formed by a peptide that contains only leucine and serine. All these channels mediate transport of potassium and chloride ions. Starting with equilibrium properties, such as the potential of mean force experienced by an ion traversing the channel and diffusivity, obtained from molecular dynamics simulations, the ED equation can be used to determine the full current-voltage dependence with modest or no additional effort. The potential of mean force can be obtained not only from equilibrium simulations, but also, with comparable accuracy, from nonequilibrium simulations at a single voltage. The main assumptions underlying the ED equation appear to hold well for the channels and voltages studied here. To expand the utility of the ED equation, we examine what are the necessary and sufficient conditions for Ohmic and nonrectifying behavior and relate deviations from this behavior to the shape of the ionic potential of mean force.

Specific compartmental analysis of cartilage status in double-bundle ACL reconstruction patients: a comparative study using pre- and postoperative MR images.

PubMed

Lee, Yong Seuk; Jeong, Yu Mi; Sim, Jae Ang; Kwak, Ji Hoon; Kim, Kwang Hee; Nam, Shin Woo; Lee, Beom Koo

2013-03-01

The purpose of this study was to evaluate the changes in the site-specific cartilage status after a double-bundle ACL reconstruction using preoperative and follow-up MR images. Thirty-six knees that underwent a double-bundle ACL reconstruction from 2001 to 2009 with the available preoperative and follow-up magnetic resonance imaging were included. Patients with a meniscal injury were compared with those without a meniscal injury. The cartilage morphology was classified using a 6-grade scale [from 0 = normal thickness and signal, to 6 = diffuse full-thickness loss (>75 % of the region)]. The changes in cartilage status were evaluated at 14 sites. Cartilage changes were observed in all sites and were classified according to the site and degree of change. The majority of changes were grade 0 and 1, which accounted for 68 and 16.8 % of changes, respectively. The patella medial facet and anterolateral and centromedial femoral regions showed significantly more cartilage loss than the posteromedial, centrolateral, anterolateral, and anteromedial tibial regions. No significance was observed between the knees with or without combined injuries (n.s.). On the other hand, knees with or without combined injuries showed a different pattern of cartilage change, as demonstrated by different levels of grade change at sites. The change in cartilage status was minimal after a double-bundle ACL reconstruction. The patella medial facet, lateral femur anterior region, and medial femur central region showed significantly more cartilage loss than the medial tibia posterior, lateral tibia central, lateral tibia anterior, and medial tibia anterior regions. The presence of a combined injury did not affect the cartilage status changes, even though it was underpowered and too short term to assess the influence of the meniscal injury. Case series, Level IV.

Adaptive focus for deep tissue using diffuse backscatter

NASA Astrophysics Data System (ADS)

Kress, Jeremy; Pourrezaei, Kambiz

2014-02-01

A system integrating high density diffuse optical imaging with adaptive optics using MEMS for deep tissue interaction is presented. In this system, a laser source is scanned over a high density fiber bundle using Digital Micromirror Device (DMD) and channeled to a tissue phantom. Backscatter is then collected from the tissue phantom by a high density fiber array of different fiber type and channeled to CMOS sensor for image acquisition. Intensity focus is directly verified using a second CMOS sensor which measures intensity transmitted though the tissue phantom. A set of training patterns are displayed on the DMD and backscatter is numerically fit to the transmission intensity. After the training patterns are displayed, adaptive focus is performed using only the backscatter and fitting functions. Additionally, tissue reconstruction and prediction of interference focusing by photoacoustic and optical tomographic methods is discussed. Finally, potential NIR applications such as in-vivo adaptive neural photostimulation and cancer targeting are discussed.

Fiber tracking of brain white matter based on graph theory.

PubMed

Lu, Meng

2015-01-01

Brain white matter tractography is reconstructed via diffusion-weighted magnetic resonance images. Due to the complex structure of brain white matter fiber bundles, fiber crossing and fiber branching are abundant in human brain. And regular methods with diffusion tensor imaging (DTI) can't accurately handle this problem. the biggest problems of the brain tractography. Therefore, this paper presented a novel brain white matter tractography method based on graph theory, so the fiber tracking between two voxels is transformed into locating the shortest path in a graph. Besides, the presented method uses Q-ball imaging (QBI) as the source data instead of DTI, because QBI can provide accurate information about multiple fiber crossing and branching in one voxel using orientation distribution function (ODF). Experiments showed that the presented method can accurately handle the problem of brain white matter fiber crossing and branching, and reconstruct brain tractograhpy both in phantom data and real brain data.

A peptide hormone required for Casparian strip diffusion barrier formation in Arabidopsis roots.

PubMed

Nakayama, Takuya; Shinohara, Hidefumi; Tanaka, Mina; Baba, Koki; Ogawa-Ohnishi, Mari; Matsubayashi, Yoshikatsu

2017-01-20

Plants achieve mineral ion homeostasis by means of a hydrophobic barrier on endodermal cells called the Casparian strip, which restricts lateral diffusion of ions between the root vascular bundles and the soil. We identified a family of sulfated peptides required for contiguous Casparian strip formation in Arabidopsis roots. These peptide hormones, which we named Casparian strip integrity factor 1 (CIF1) and CIF2, are expressed in the root stele and specifically bind the endodermis-expressed leucine-rich repeat receptor kinase GASSHO1 (GSO1)/SCHENGEN3 and its homolog, GSO2. A mutant devoid of CIF peptides is defective in ion homeostasis in the xylem. CIF genes are environmentally responsive. Casparian strip regulation is not merely a passive process driven by root developmental cues; it also serves as an active strategy to cope with adverse soil conditions. Copyright © 2017, American Association for the Advancement of Science.

Diffusion Tensor Tractography Reveals Disrupted Structural Connectivity during Brain Aging

NASA Astrophysics Data System (ADS)

Lin, Lan; Tian, Miao; Wang, Qi; Wu, Shuicai

2017-10-01

Brain aging is one of the most crucial biological processes that entail many physical, biological, chemical, and psychological changes, and also a major risk factor for most common neurodegenerative diseases. To improve the quality of life for the elderly, it is important to understand how the brain is changed during the normal aging process. We compared diffusion tensor imaging (DTI)-based brain networks in a cohort of 75 healthy old subjects by using graph theory metrics to describe the anatomical networks and connectivity patterns, and network-based statistic (NBS) analysis was used to identify pairs of regions with altered structural connectivity. The NBS analysis revealed a significant network comprising nine distinct fiber bundles linking 10 different brain regions showed altered white matter structures in young-old group compare with middle-aged group (p < .05, family-wise error-corrected). Our results might guide future studies and help to gain a better understanding of brain aging.

Single-shot polarimetry imaging of multicore fiber.

PubMed

Sivankutty, Siddharth; Andresen, Esben Ravn; Bouwmans, Géraud; Brown, Thomas G; Alonso, Miguel A; Rigneault, Hervé

2016-05-01

We report an experimental test of single-shot polarimetry applied to the problem of real-time monitoring of the output polarization states in each core within a multicore fiber bundle. The technique uses a stress-engineered optical element, together with an analyzer, and provides a point spread function whose shape unambiguously reveals the polarization state of a point source. We implement this technique to monitor, simultaneously and in real time, the output polarization states of up to 180 single-mode fiber cores in both conventional and polarization-maintaining fiber bundles. We demonstrate also that the technique can be used to fully characterize the polarization properties of each individual fiber core, including eigen-polarization states, phase delay, and diattenuation.

Studying microstructure and microstructural changes in plant tissues by advanced diffusion magnetic resonance imaging techniques

PubMed Central

Morozov, Darya; Tal, Iris; Pisanty, Odelia; Shani, Eilon

2017-01-01

Abstract As sessile organisms, plants must respond to the environment by adjusting their growth and development. Most of the plant body is formed post-embryonically by continuous activity of apical and lateral meristems. The development of lateral adventitious roots is a complex process, and therefore the development of methods that can visualize, non-invasively, the plant microstructure and organ initiation that occur during growth and development is of paramount importance. In this study, relaxation-based and advanced diffusion magnetic resonance imaging (MRI) methods including diffusion tensor (DTI), q-space diffusion imaging (QSI), and double-pulsed-field-gradient (d-PFG) MRI, at 14.1 T, were used to characterize the hypocotyl microstructure and the microstructural changes that occurred during the development of lateral adventitious roots in tomato. Better contrast was observed in relaxation-based MRI using higher in-plane resolution but this also resulted in a significant reduction in the signal-to-noise ratio of the T2-weighted MR images. Diffusion MRI revealed that water diffusion is highly anisotropic in the vascular cylinder. QSI and d-PGSE MRI showed that in the vascular cylinder some of the cells have sizes in the range of 6–10 μm. The MR images captured cell reorganization during adventitious root formation in the periphery of the primary vascular bundles, adjacent to the xylem pole that broke through the cortex and epidermis layers. This study demonstrates that MRI and diffusion MRI methods allow the non-invasive study of microstructural features of plants, and enable microstructural changes associated with adventitious root formation to be followed. PMID:28398563

Carbon nanotube conditioning: ab initio simulations of the effect of defects and doping on the electronic properties of carbon nanotube systems.

NASA Astrophysics Data System (ADS)

Soto, Matias; Barrera, Enrique

Using carbon nanotubes for electrical conduction applications at the macroscale has proven to be a difficult task, mainly, due to defects and impurities present, and lack of uniform electronic properties in synthesized carbon nanotube bundles. Some researchers have suggested that growing only metallic armchair nanotubes and arranging them with an ideal contact length could lead to the ultimate electrical conductivity; however, such recipe presents too high of a cost to pay. A different route and the topic of this work is to learn to manage the defects, impurities, and the electronic properties of carbon nanotubes present, so that the electrical conduction of a bundle or even wire may be enhanced. We used density functional theory calculations to study the effect of defects and doping on the electronic structure of metallic, semi-metal and semiconducting carbon nanotubes in order to gain a clear picture of their properties. Additionally, using dopants to increase the conductance across a junction between two carbon nanotubes was studied for different configurations. Finally, interaction potentials obtained via first-principles calculations were generalized by developing mathematical models for the purpose of running simulations at a larger length scale using molecular dynamics. Partial funding was received from CONACyT Scholarship 314419.

A Tangent Bundle Theory for Visual Curve Completion.

PubMed

Ben-Yosef, Guy; Ben-Shahar, Ohad

2012-07-01

Visual curve completion is a fundamental perceptual mechanism that completes the missing parts (e.g., due to occlusion) between observed contour fragments. Previous research into the shape of completed curves has generally followed an "axiomatic" approach, where desired perceptual/geometrical properties are first defined as axioms, followed by mathematical investigation into curves that satisfy them. However, determining psychophysically such desired properties is difficult and researchers still debate what they should be in the first place. Instead, here we exploit the observation that curve completion is an early visual process to formalize the problem in the unit tangent bundle R(2) × S(1), which abstracts the primary visual cortex (V1) and facilitates exploration of basic principles from which perceptual properties are later derived rather than imposed. Exploring here the elementary principle of least action in V1, we show how the problem becomes one of finding minimum-length admissible curves in R(2) × S(1). We formalize the problem in variational terms, we analyze it theoretically, and we formulate practical algorithms for the reconstruction of these completed curves. We then explore their induced visual properties vis-à-vis popular perceptual axioms and show how our theory predicts many perceptual properties reported in the corresponding perceptual literature. Finally, we demonstrate a variety of curve completions and report comparisons to psychophysical data and other completion models.

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

Iyer, Ajai, E-mail: ajai.iyer@aalto.fi; Etula, Jarkko; Liu, Xuwen

Single walled carbon nanotube networks (SWCNTNs) were coated by tetrahedral amorphous carbon (ta-C) to improve the mechanical wear properties of the composite film. The ta-C deposition was performed by using pulsed filtered cathodic vacuum arc method resulting in the generation of C+ ions in the energy range of 40–60 eV which coalesce to form a ta-C film. The primary disadvantage of this process is a significant increase in the electrical resistance of the SWCNTN post coating. The increase in the SWCNTN resistance is attributed primarily to the intrinsic stress of the ta-C coating which affects the inter-bundle junction resistance between themore » SWCNTN bundles. E-beam evaporated carbon was deposited on the SWCNTNs prior to the ta-C deposition in order to protect the SWCNTN from the intrinsic stress of the ta-C film. The causes of changes in electrical resistance and the effect of evaporated carbon thickness on the changes in electrical resistance and mechanical wear properties have been studied.« less

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.

Visualization of Fiber Structurein the Left and Right Ventricleof a Human Heart

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

Rohmer, Damien; Sitek, Arkadiusz; Gullberg, Grant T.

2006-07-12

The human heart is composed of a helical network of musclefibers. Anisotropic least squares filtering followed by fiber trackingtechniques were applied to Diffusion Tensor Magnetic Resonance Imaging(DTMRI) data of the excised human heart. The fiber configuration wasvisualized by using thin tubes to increase 3-dimensional visualperception of the complex structure. All visualizations were performedusing the high-quality ray-tracing software POV-Ray. The fibers are shownwithin the left and right ventricles. Both ventricles exhibit similarfiber architecture and some bundles of fibers are shown linking right andleft ventricles on the posterior region of the heart.

High-pressure homogenization associated hydrothermal process of palygorskite for enhanced adsorption of Methylene blue

NASA Astrophysics Data System (ADS)

Zhang, Zhifang; Wang, Wenbo; Wang, Aiqin

2015-02-01

Palygorskite (PAL) was modified by a high-pressure homogenization assisted hydrothermal process. The effects of modification on the morphology, structure and physicochemical properties of PAL were systematically investigated by Field-emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FTIR), Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD) and Zeta potential analysis techniques, and the adsorption properties were systematically evaluated using Methylene blue (MB) as the model dye. The results revealed that the crystal bundles were disaggregated and the PAL nanorods became more even after treated via associated high-pressure homogenization and hydrothermal process, and the crystal bundles were dispersed as nanorods. The intrinsic crystal structure of PAL was remained after hydrothermal treatment, and the pore size calculated by the BET method was increased. The adsorption properties of PAL for MB were evidently improved (from 119 mg/g to 171 mg/g) after modification, and the dispersion of PAL before hydrothermal reaction is favorable to the adsorption. The desorption evaluation confirms that the modified PAL has stronger affinity with MB, which is benefit to fabricate a stable organic-inorganic hybrid pigment.

Carbon Nanotube Conditioning: Ab Initio Simulations of the Effect of Interwall Interaction, Defects And Doping on the Electronic Properties of Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Castillo, Matias Soto

Using carbon nanotubes for electrical conduction applications at the macroscale has been shown to be a difficult task for some time now, mainly, due to defects and impurities present, and lack of uniform electronic properties in synthesized carbon nanotube bundles. Some researchers have suggested that growing only metallic armchair nanotubes and arranging them with an ideal contact length could lead to the ultimate electrical conductivity; however, such recipe presents too high of a cost to pay. A different route is to learn to manage the defects, impurities, and the electronic properties of carbon nanotubes present in bundles grown by current state-of-the-art reactors, so that the electrical conduction of a bundle or even wire may be enhanced. In our work, we have used first-principles density functional theory calculations to study the effect of interwall interaction, defects and doping on the electronic structure of metallic, semi-metal and semiconducting single- and double-walled carbon nanotubes in order to gain a clear picture of their properties. The electronic band gap for a range of zigzag single-walled carbon nanotubes with chiral indices (5,0) - (30,0) was obtained. Their properties were used as a stepping stone in the study of the interwall interaction in double-walled carbon nanotubes, from which it was found that the electronic band gap depends on the type of inner and outer tubes, average diameter, and interwall distance. The effect of vacancy defects was also studied for a range of single-walled carbon nanotubes. It was found that the electronic band gap is reduced for the entire range of zigzag carbon nanotubes, even at vacancy defects concentrations of less than 1%. Finally, interaction potentials obtained via first-principles calculations were generalized by developing mathematical models for the purpose of running simulations at a larger length scale using molecular dynamics of the adsorption doping of diatomic iodine. An ideal adsorption site was found using a stochastic approach and with an adsorption energy higher than other values in the literature.

On the concept of a filtered bundle

NASA Astrophysics Data System (ADS)

Bruce, Andrew James; Grabowska, Katarzyna; Grabowski, Janusz

We present the notion of a filtered bundle as a generalization of a graded bundle. In particular, we weaken the necessity of the transformation laws for local coordinates to exactly respect the weight of the coordinates by allowing more general polynomial transformation laws. The key examples of such bundles include affine bundles and various jet bundles, both of which play fundamental roles in geometric mechanics and classical field theory. We also present the notion of double filtered bundles which provide natural generalizations of double vector bundles and double affine bundles. Furthermore, we show that the linearization of a filtered bundle — which can be seen as a partial polarization of the admissible changes of local coordinates — is well defined.

Bundle Data Approach at GES DISC Targeting Natural Hazards

NASA Technical Reports Server (NTRS)

Shie, Chung-Lin; Shen, Suhung; Kempler, Steven J.

2015-01-01

Severe natural phenomena such as hurricane, volcano, blizzard, flood and drought have the potential to cause immeasurable property damages, great socioeconomic impact, and tragic loss of human life. From searching to assessing the Big, i.e., massive and heterogeneous scientific data (particularly, satellite and model products) in order to investigate those natural hazards, it has, however, become a daunting task for Earth scientists and applications researchers, especially during recent decades. The NASA Goddard Earth Sciences Data and Information Service Center (GES DISC) has served Big Earth science data, and the pertinent valuable information and services to the aforementioned users of diverse communities for years. In order to help and guide our users to online readily (i.e., with a minimum effort) acquire their requested data from our enormous resource at GES DISC for studying their targeted hazard event, we have thus initiated a Bundle Data approach in 2014, first targeting the hurricane event topic. We have recently worked on new topics such as volcano and blizzard. The bundle data of a specific hazard event is basically a sophisticated integrated data package consisting of a series of proper datasets containing a group of relevant (knowledge--based) data variables readily accessible to users via a system-prearranged table linking those data variables to the proper datasets (URLs). This online approach has been developed by utilizing a few existing data services such as Mirador as search engine; Giovanni for visualization; and OPeNDAP for data access, etc. The online Data Cookbook site at GES DISC is the current host for the bundle data. We are now also planning on developing an Automated Virtual Collection Framework that shall eventually accommodate the bundle data, as well as further improve our management in Big Data.

"Bundle Data" Approach at GES DISC Targeting Natural Hazards

NASA Astrophysics Data System (ADS)

Shie, C. L.; Shen, S.; Kempler, S. J.

2015-12-01

Severe natural phenomena such as hurricane, volcano, blizzard, flood and drought have the potential to cause immeasurable property damages, great socioeconomic impact, and tragic loss of human life. From searching to assessing the "Big", i.e., massive and heterogeneous scientific data (particularly, satellite and model products) in order to investigate those natural hazards, it has, however, become a daunting task for Earth scientists and applications researchers, especially during recent decades. The NASA Goddard Earth Sciences Data and Information Service Center (GES DISC) has served "Big" Earth science data, and the pertinent valuable information and services to the aforementioned users of diverse communities for years. In order to help and guide our users to online readily (i.e., with a minimum effort) acquire their requested data from our enormous resource at GES DISC for studying their targeted hazard/event, we have thus initiated a "Bundle Data" approach in 2014, first targeting the hurricane event/topic. We have recently worked on new topics such as volcano and blizzard. The "bundle data" of a specific hazard/event is basically a sophisticated integrated data package consisting of a series of proper datasets containing a group of relevant ("knowledge-based") data variables readily accessible to users via a system-prearranged table linking those data variables to the proper datasets (URLs). This online approach has been developed by utilizing a few existing data services such as Mirador as search engine; Giovanni for visualization; and OPeNDAP for data access, etc. The online "Data Cookbook" site at GES DISC is the current host for the "bundle data". We are now also planning on developing an "Automated Virtual Collection Framework" that shall eventually accommodate the "bundle data", as well as further improve our management in "Big Data".

A materials perspective of Martyniaceae fruits: Exploring structural and micromechanical properties.

PubMed

Horbens, Melanie; Eder, Michaela; Neinhuis, Christoph

2015-12-01

Several species of the plant family Martyniaceae are characterised by unique lignified capsules with hook-shaped extensions that interlock with hooves and ankles of large mammals to disperse the seeds. The arrangement of fruit endocarp fibre tissues is exceptional and intriguing among plants. Structure-function-relationships of these slender, curved, but mechanically highly stressed fruit extensions are of particular interest that may inspire advanced biomimetic composite materials. In the present study, we analyse mechanical properties and fracture behaviour of the hook-shaped fruit extensions under different load conditions. The results are correlated with calculated stress distributions, the specific cell wall structure, and chemical composition, providing a detailed interpretation of the complex fruit tissue microstructure. At the cell wall level, both a large microfibril angle and greater strain rates resulted in Young's moduli of 4-9 GPa, leading to structural plasticity. Longitudinally arranged fibre bundles contribute to a great tensile strength. At the tissue level, transversely oriented fibres absorb radial stresses upon bending, whereas cells encompass and pervade longitudinal fibre bundles, thus, stabilise them against buckling. During bending and torsion, microcracks between axial fibre bundles are probably spanned analogous to a circular anchor. Our study fathoms a highly specialized plant structure, substantiating former assumptions about epizoochory as dispersal mode. While the increased flexibility allows for proper attachment of fruits during dynamical locomotion, the high strength and stability prevent a premature failure due to heavy loads exerted by the animal. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Braided nanofibrous scaffold for tendon and ligament tissue engineering.

PubMed

Barber, John G; Handorf, Andrew M; Allee, Tyler J; Li, Wan-Ju

2013-06-01

Tendon and ligament (T/L) injuries present an important clinical challenge due to their intrinsically poor healing capacity. Natural healing typically leads to the formation of scar-like tissue possessing inferior mechanical properties. Therefore, tissue engineering has gained considerable attention as a promising alternative for T/L repair. In this study, we fabricated braided nanofibrous scaffolds (BNFSs) as a potential construct for T/L tissue engineering. Scaffolds were fabricated by braiding 3, 4, or 5 aligned bundles of electrospun poly(L-lactic acid) nanofibers, thus introducing an additional degree of flexibility to alter the mechanical properties of individual scaffolds. We observed that the Young's modulus, yield stress, and ultimate stress were all increased in the 3-bundle compared to the 4- and 5-bundle BNFSs. Interestingly, acellular BNFSs mimicked the normal tri-phasic mechanical behavior of native tendon and ligament (T/L) during loading. When cultured on the BNFSs, human mesenchymal stem cells (hMSCs) adhered, aligned parallel to the length of the nanofibers, and displayed a concomitant realignment of the actin cytoskeleton. In addition, the BNFSs supported hMSC proliferation and induced an upregulation in the expression of key pluripotency genes. When cultured on BNFSs in the presence of tenogenic growth factors and stimulated with cyclic tensile strain, hMSCs differentiated into the tenogenic lineage, evidenced most notably by the significant upregulation of Scleraxis gene expression. These results demonstrate that BNFSs provide a versatile scaffold capable of supporting both stem cell expansion and differentiation for T/L tissue engineering applications.

Anatomy of the anterior cruciate ligament with regard to its two bundles.

PubMed

Petersen, Wolf; Zantop, Thore

2007-01-01

The anterior cruciate ligament (ACL) consists of two major fiber bundles, namely the anteromedial and posterolateral bundle. When the knee is extended, the posterolateral bundle (PL) is tight and the anteromedial (AM) bundle is moderately lax. As the knee is flexed, the femoral attachment of the ACL becomes a more horizontal orientation; causing the AM bundle to tighten and the PL bundle to relax. There is some degree of variability for the femoral origin of the anterome-dial and posterolateral bundle. The anteromedial bundle is located proximal and anterior in the femoral ACL origin (high and deep in the notch when the knee is flexed at 90 degrees ); the posterolateral bundle starts in the distal and posterior aspect of the femoral ACL origin (shallow and low when the knee is flexed at 90 degrees ). In the frontal plane the anteromedial bundle origin is in the 10:30 clock position and the postero-lateral bundle origin in the 9:30 clock position. At the tibial insertion the ACL fans out to form the foot region. The anteromedial bundle insertion is in the anterior part of the tibial ACL footprint, the posterolateral bundle in the posterior part. While the anteromedial bundle is the primary restraint against anterior tibial translation, the posterolateral bundle tends to stabilize the knee near full extension, particularly against rotatory loads.

A fast bilinear structure from motion algorithm using a video sequence and inertial sensors.

PubMed

Ramachandran, Mahesh; Veeraraghavan, Ashok; Chellappa, Rama

2011-01-01

In this paper, we study the benefits of the availability of a specific form of additional information—the vertical direction (gravity) and the height of the camera, both of which can be conveniently measured using inertial sensors and a monocular video sequence for 3D urban modeling. We show that in the presence of this information, the SfM equations can be rewritten in a bilinear form. This allows us to derive a fast, robust, and scalable SfM algorithm for large scale applications. The SfM algorithm developed in this paper is experimentally demonstrated to have favorable properties compared to the sparse bundle adjustment algorithm. We provide experimental evidence indicating that the proposed algorithm converges in many cases to solutions with lower error than state-of-art implementations of bundle adjustment. We also demonstrate that for the case of large reconstruction problems, the proposed algorithm takes lesser time to reach its solution compared to bundle adjustment. We also present SfM results using our algorithm on the Google StreetView research data set.

Atypical Frontal-Striatal-Thalamic Circuit White Matter Development in Pediatric Obsessive Compulsive Disorder

PubMed Central

Fitzgerald, Kate D.; Liu, Yanni; Reamer, Elyse N.; Taylor, Stephan F.; Welsh, Robert C.

2015-01-01

Objective Atypical development of frontal-striatal-thalamic circuitry (FSTC) has been hypothesized to underlie the early course of obsessive-compulsive disorder (OCD); however, the development of FSTC white matter tracts remains to be studied in young patients. Method To address this gap, we scanned 36 patients with pediatric OCD compared to 27 healthy controls, aged 8 to 19 years, with diffusion tensor imaging (DTI) to measure fractional anisotropy (FA), an index of white matter coherence. Tract-based spatial statistics (TBSS) were used to test differential effects of age on FA, across the whole brain, in those with OCD compared to healthy youth, followed by analyses in a priori regions of interest (anterior corpus callosum, anterior cingulum bundle and anterior limb of the internal capsule [ALIC]) to further characterize developmental differences between groups. Results Patients with OCD showed more pronounced age-related increases in FA than controls in regions of interest, as well as several other white matter tracts. In patients, greater FA in anterior cingulum bundle correlated with more severe symptoms after controlling for age. Conclusions Our findings support theories of atypical FSTC maturation in pediatric OCD by providing the first evidence for altered trajectories of white matter development in anterior corpus callosum, anterior cingulum bundle, and ALIC in young patients. Steeper age-related increases of FA in these and other select white matter tracts in OCD, compared to healthy controls, may derive from an early delay in white matter development and/or prolonged white matter growth, but confirmation of these possibilities awaits longitudinal work. PMID:25440312

CFD modeling of turbulent mixing through vertical pressure tube type boiling water reactor fuel rod bundles with spacer-grids

NASA Astrophysics Data System (ADS)

Verma, Shashi Kant; Sinha, S. L.; Chandraker, D. K.

2018-05-01

Numerical simulation has been carried out for the study of natural mixing of a Tracer (Passive scalar) to describe the development of turbulent diffusion in an injected sub-channel and, afterwards on, cross-mixing between adjacent sub-channels. In this investigation, post benchmark evaluation of the inter-subchannel mixing was initiated to test the ability of state-of-the-art Computational Fluid Dynamics (CFD) codes to numerically predict the important turbulence parameters downstream of a ring type spacer grid in a rod-bundle. A three-dimensional Computational Fluid Dynamics (CFD) tool (STAR-CCM+) was used to model the single phase flow through a 30° segment or 1/12th of the cross segment of a 54-rod bundle with a ring shaped spacer grid. Polyhedrons were used to discretize the computational domain, along with prismatic cells near the walls, with an overall mesh count of 5.2 M cell volumes. The Reynolds Stress Models (RSM) was tested because of RSM accounts for the turbulence anisotropy, to assess their capability in predicting the velocities as well as mass fraction of potassium nitrate measured in the experiment. In this way, the line probes are located in the different position of subchannels which could be used to characterize the progress of the mixing along the flow direction, and the degree of cross-mixing assessed using the quantity of tracer arriving in the neighbouring sub-channels. The predicted dimensionless mixing scalar along the length, however, was in good agreement with the measurements downstream of spacers.

Anatomy of the Limbic White Matter Tracts as Revealed by Fiber Dissection and Tractography.

PubMed

Pascalau, Raluca; Popa Stănilă, Roxana; Sfrângeu, Silviu; Szabo, Bianca

2018-05-01

The limbic tracts are involved in crucial cerebral functions such as memory, emotion, and behavior. The complex architecture of the limbic circuit makes it harder to approach compared with other white matter networks. Our study aims to describe the 3-dimensional anatomy of the limbic white matter by the use of 2 complementary study methods, namely ex vivo fiber dissection and in vivo magnetic resonance imaging-based tractography. Three fiber dissection protocols were performed using blunt wooden instruments and a surgical microscope on formalin-fixed brains prepared according to the Klingler method. Diffusion tensor imaging acquisitions were done with a 3-Tesla magnetic resonance scanner on patients with head and neck pathology that did not involve the brain. Fiber tracking was performed with manually selected regions of interest. Cingulum, fornix, the anterior thalamic peduncle, the accumbofrontal bundle, medial forebrain bundle, the uncinate fasciculus, the mammillothalamic tract, ansa peduncularis, and stria terminalis were dissected and fiber tracked. For each tract, location, configuration, segmentation, dimensions, dissection and tractography particularities, anatomical relations, and terminations are described. The limbic white matter tracts were systematized as 2 concentric rings around the thalamus. The inner ring is formed by fornix, mammillothalamic tract, ansa peduncularis, stria terminalis, accumbofrontal fasciculus, and medial forebrain bundle and anterior thalamic peduncle, and the outer ring is formed by the cingulum and uncinate fasciculus. This paper proposes a fiber-tracking protocol for the limbic tracts inspired and validated by fiber dissection findings that can be used routinely in the clinical practice. Copyright © 2018 Elsevier Inc. All rights reserved.

Gas phase synthesis of non-bundled, small diameter single-walled carbon nanotubes with near-armchair chiralities

NASA Astrophysics Data System (ADS)

Mustonen, K.; Laiho, P.; Kaskela, A.; Zhu, Z.; Reynaud, O.; Houbenov, N.; Tian, Y.; Susi, T.; Jiang, H.; Nasibulin, A. G.; Kauppinen, E. I.

2015-07-01

We present a floating catalyst synthesis route for individual, i.e., non-bundled, small diameter single-walled carbon nanotubes (SWCNTs) with a narrow chiral angle distribution peaking at high chiralities near the armchair species. An ex situ spark discharge generator was used to form iron particles with geometric number mean diameters of 3-4 nm and fed into a laminar flow chemical vapour deposition reactor for the continuous synthesis of long and high-quality SWCNTs from ambient pressure carbon monoxide. The intensity ratio of G/D peaks in Raman spectra up to 48 and mean tube lengths up to 4 μm were observed. The chiral distributions, as directly determined by electron diffraction in the transmission electron microscope, clustered around the (n,m) indices (7,6), (8,6), (8,7), and (9,6), with up to 70% of tubes having chiral angles over 20°. The mean diameter of SWCNTs was reduced from 1.10 to 1.04 nm by decreasing the growth temperature from 880 to 750 °C, which simultaneously increased the fraction of semiconducting tubes from 67% to 80%. Limiting the nanotube gas phase number concentration to ˜105 cm-3 prevented nanotube bundle formation that is due to collisions induced by Brownian diffusion. Up to 80% of 500 as-deposited tubes observed by atomic force and transmission electron microscopy were individual. Transparent conducting films deposited from these SWCNTs exhibited record low sheet resistances of 63 Ω/□ at 90% transparency for 550 nm light.

Surfactant-free solvothermal synthesis of Hydroxyapatite nested bundles for the effective photodegradation of cationic dyes

NASA Astrophysics Data System (ADS)

Reeta Mary, I.; Sonia, S.; Navadeepthy, D.; Mangalaraj, D.; Viswanathan, C.; Ponpandian, N.

2018-05-01

In this study, hydroxyapatite nested bundles (HNBs) were successfully constructed from nanosticks as nanoscale building blocks via a facile, solvothermal process without using any surfactant. The fabricated HNBs were structurally analyzed using X-ray diffraction and Fourier transform infrared spectroscopy, which confirmed the purity of the HNBs. The surface characteristics were determined by field emission scanning electron microscopy and Brunauer-Emmett-Teller analysis, and the optical characteristics by ultraviolet (UV)-visible spectroscopy. The synthesized HNBs were tested to determine their activity during the degradation of methylene blue, methylene violet, and rhodamine B via photocatalysis under UV irradiation. The degradation efficiency of HNBs and the rate of degradation can be explained based on the properties of the HNBs and cationic dyes.

Brownian dynamics simulation of sickle hemoglobin bundle formation

NASA Astrophysics Data System (ADS)

Liu, Ya; Gunton, James; Chakrabarti, Amit

2010-03-01

The physical properties of biopolymer fibers, such as their stability and degree of aggregation, are implicated in many diseases, including sickle cell anemia. The natural chirality of protofilaments plays a crucial role in the formation of sickle hemoglobin fiber which leads to the permanent blockage of microvessels. We use Brownian dynamics to investigate the kinetics of fiber aggregation. The geometrical helical structure and chirality of the filaments are modeled by anisotropic patch-like interactions. We present the kinetics of fiber formation and study the possibility of a finite critical fiber bundle size. We compare our results with various experimental and theoretical results. This work is supported by grants from the NSF and the G. Harold and Leila Y. Mathers Foundation.

Dynamical boson stars.

PubMed

Liebling, Steven L; Palenzuela, Carlos

2017-01-01

The idea of stable, localized bundles of energy has strong appeal as a model for particles. In the 1950s, John Wheeler envisioned such bundles as smooth configurations of electromagnetic energy that he called geons , but none were found. Instead, particle-like solutions were found in the late 1960s with the addition of a scalar field, and these were given the name boson stars . Since then, boson stars find use in a wide variety of models as sources of dark matter, as black hole mimickers, in simple models of binary systems, and as a tool in finding black holes in higher dimensions with only a single Killing vector. We discuss important varieties of boson stars, their dynamic properties, and some of their uses, concentrating on recent efforts.

Investigation of BCF-12 Plastic Scintillating Coherent Fiber Bundle Timing Properties

DTIC Science & Technology

2012-03-22

spread in transit time. The shape of the voltage pulse produced at the anode of a PM following a scin - tillation event depends on the time constant of...Choong, G. Hull, and B.W. Reutter. “ Scin - tillator Non-Proportionality: Present Understanding and Future Challenges”. Nuclear Science, IEEE

Joint brain connectivity estimation from diffusion and functional MRI data

NASA Astrophysics Data System (ADS)

Chu, Shu-Hsien; Lenglet, Christophe; Parhi, Keshab K.

2015-03-01

Estimating brain wiring patterns is critical to better understand the brain organization and function. Anatomical brain connectivity models axonal pathways, while the functional brain connectivity characterizes the statistical dependencies and correlation between the activities of various brain regions. The synchronization of brain activity can be inferred through the variation of blood-oxygen-level dependent (BOLD) signal from functional MRI (fMRI) and the neural connections can be estimated using tractography from diffusion MRI (dMRI). Functional connections between brain regions are supported by anatomical connections, and the synchronization of brain activities arises through sharing of information in the form of electro-chemical signals on axon pathways. Jointly modeling fMRI and dMRI data may improve the accuracy in constructing anatomical connectivity as well as functional connectivity. Such an approach may lead to novel multimodal biomarkers potentially able to better capture functional and anatomical connectivity variations. We present a novel brain network model which jointly models the dMRI and fMRI data to improve the anatomical connectivity estimation and extract the anatomical subnetworks associated with specific functional modes by constraining the anatomical connections as structural supports to the functional connections. The key idea is similar to a multi-commodity flow optimization problem that minimizes the cost or maximizes the efficiency for flow configuration and simultaneously fulfills the supply-demand constraint for each commodity. In the proposed network, the nodes represent the grey matter (GM) regions providing brain functionality, and the links represent white matter (WM) fiber bundles connecting those regions and delivering information. The commodities can be thought of as the information corresponding to brain activity patterns as obtained for instance by independent component analysis (ICA) of fMRI data. The concept of information flow is introduced and used to model the propagation of information between GM areas through WM fiber bundles. The link capacity, i.e., ability to transfer information, is characterized by the relative strength of fiber bundles, e.g., fiber count gathered from the tractography of dMRI data. The node information demand is considered to be proportional to the correlation between neural activity at various cortical areas involved in a particular functional mode (e.g. visual, motor, etc.). These two properties lead to the link capacity and node demand constraints in the proposed model. Moreover, the information flow of a link cannot exceed the demand from either end node. This is captured by the feasibility constraints. Two different cost functions are considered in the optimization formulation in this paper. The first cost function, the reciprocal of fiber strength represents the unit cost for information passing through the link. In the second cost function, a min-max (minimizing the maximal link load) approach is used to balance the usage of each link. Optimizing the first cost function selects the pathway with strongest fiber strength for information propagation. In the second case, the optimization procedure finds all the possible propagation pathways and allocates the flow proportionally to their strength. Additionally, a penalty term is incorporated with both the cost functions to capture the possible missing and weak anatomical connections. With this set of constraints and the proposed cost functions, solving the network optimization problem recovers missing and weak anatomical connections supported by the functional information and provides the functional-associated anatomical subnetworks. Feasibility is demonstrated using realistic diffusion and functional MRI phantom data. It is shown that the proposed model recovers the maximum number of true connections, with fewest number of false connections when compared with the connectivity derived from a joint probabilistic model using the expectation-maximization (EM) algorithm presented in a prior work. We also apply the proposed method to data provided by the Human Connectome Project (HCP).

A Tractography Comparison between Turboprop and Spin-Echo Echo-Planar Diffusion Tensor Imaging

PubMed Central

Gui, Minzhi; Peng, Huiling; Carew, John D.; Lesniak, Maciej S.; Arfanakis, Konstantinos

2008-01-01

The development of accurate, non-invasive methods for mapping white matter fiber-tracts is of critical importance. However, fiber-tracking is typically performed on diffusion tensor imaging (DTI) data obtained with echo-planar-based imaging techniques (EPI), which suffer from susceptibility-related image artifacts, and image warping due to eddy-currents. Thus, a number of white matter fiber-bundles mapped using EPI-based DTI data are distorted and/or terminated early. This severely limits the clinical potential of fiber-tracking. In contrast, Turboprop-MRI provides images with significantly fewer susceptibility and eddy-current-related artifacts than EPI. The purpose of this work was to compare fiber-tracking results obtained from DTI data acquired with Turboprop-DTI and EPI-based DTI. It was shown that, in brain regions near magnetic field inhomogeneities, white matter fiber-bundles obtained with EPI-based DTI were distorted and/or partially detected, when magnetic susceptibility-induced distortions were not corrected. After correction, residual distortions were still present and several fiber-tracts remained partially detected. In contrast, when using Turboprop-DTI data, all traced fiber-tracts were in agreement with known anatomy. The inter-session reproducibility of tractography results was higher for Turboprop than EPI-based DTI data in regions near field inhomogeneities. Thus, Turboprop may be a more appropriate DTI data acquisition technique for tracing white matter fibers near regions with significant magnetic susceptibility differences, as well as in longitudinal studies of such fibers. However, the intra-session reproducibility of tractography results was higher for EPI-based than Turboprop DTI data. Thus, EPI-based DTI may be more advantageous for tracing fibers minimally affected by field inhomogeneities. PMID:18621131

A tractography comparison between turboprop and spin-echo echo-planar diffusion tensor imaging.

PubMed

Gui, Minzhi; Peng, Huiling; Carew, John D; Lesniak, Maciej S; Arfanakis, Konstantinos

2008-10-01

The development of accurate, non-invasive methods for mapping white matter fiber-tracts is of critical importance. However, fiber-tracking is typically performed on diffusion tensor imaging (DTI) data obtained with echo-planar-based imaging techniques (EPI), which suffer from susceptibility-related image artifacts, and image warping due to eddy-currents. Thus, a number of white matter fiber-bundles mapped using EPI-based DTI data are distorted and/or terminated early. This severely limits the clinical potential of fiber-tracking. In contrast, Turboprop-MRI provides images with significantly fewer susceptibility and eddy-current-related artifacts than EPI. The purpose of this work was to compare fiber-tracking results obtained from DTI data acquired with Turboprop-DTI and EPI-based DTI. It was shown that, in brain regions near magnetic field inhomogeneities, white matter fiber-bundles obtained with EPI-based DTI were distorted and/or partially detected, when magnetic susceptibility-induced distortions were not corrected. After correction, residual distortions were still present and several fiber-tracts remained partially detected. In contrast, when using Turboprop-DTI data, all traced fiber-tracts were in agreement with known anatomy. The inter-session reproducibility of tractography results was higher for Turboprop than EPI-based DTI data in regions near field inhomogeneities. Thus, Turboprop may be a more appropriate DTI data acquisition technique for tracing white matter fibers near regions with significant magnetic susceptibility differences, as well as in longitudinal studies of such fibers. However, the intra-session reproducibility of tractography results was higher for EPI-based than Turboprop DTI data. Thus, EPI-based DTI may be more advantageous for tracing fibers minimally affected by field inhomogeneities.

Functional Analysis of Corn Husk Photosynthesis[W][OA

PubMed Central

Pengelly, Jasper J.L.; Kwasny, Scott; Bala, Soumi; Evans, John R.; Voznesenskaya, Elena V.; Koteyeva, Nuria K.; Edwards, Gerald E.; Furbank, Robert T.; von Caemmerer, Susanne

2011-01-01

The husk surrounding the ear of corn/maize (Zea mays) has widely spaced veins with a number of interveinal mesophyll (M) cells and has been described as operating a partial C3 photosynthetic pathway, in contrast to its leaves, which use the C4 photosynthetic pathway. Here, we characterized photosynthesis in maize husk and leaf by measuring combined gas exchange and carbon isotope discrimination, the oxygen dependence of the CO2 compensation point, and photosynthetic enzyme activity and localization together with anatomy. The CO2 assimilation rate in the husk was less than that in the leaves and did not saturate at high CO2, indicating CO2 diffusion limitations. However, maximal photosynthetic rates were similar between the leaf and husk when expressed on a chlorophyll basis. The CO2 compensation points of the husk were high compared with the leaf but did not vary with oxygen concentration. This and the low carbon isotope discrimination measured concurrently with gas exchange in the husk and leaf suggested C4-like photosynthesis in the husk. However, both Rubisco activity and the ratio of phosphoenolpyruvate carboxylase to Rubisco activity were reduced in the husk. Immunolocalization studies showed that phosphoenolpyruvate carboxylase is specifically localized in the layer of M cells surrounding the bundle sheath cells, while Rubisco and glycine decarboxylase were enriched in bundle sheath cells but also present in M cells. We conclude that maize husk operates C4 photosynthesis dispersed around the widely spaced veins (analogous to leaves) in a diffusion-limited manner due to low M surface area exposed to intercellular air space, with the functional role of Rubisco and glycine decarboxylase in distant M yet to be explained. PMID:21511990

Probabilistic vs. deterministic fiber tracking and the influence of different seed regions to delineate cerebellar-thalamic fibers in deep brain stimulation.

PubMed

Schlaier, Juergen R; Beer, Anton L; Faltermeier, Rupert; Fellner, Claudia; Steib, Kathrin; Lange, Max; Greenlee, Mark W; Brawanski, Alexander T; Anthofer, Judith M

2017-06-01

This study compared tractography approaches for identifying cerebellar-thalamic fiber bundles relevant to planning target sites for deep brain stimulation (DBS). In particular, probabilistic and deterministic tracking of the dentate-rubro-thalamic tract (DRTT) and differences between the spatial courses of the DRTT and the cerebello-thalamo-cortical (CTC) tract were compared. Six patients with movement disorders were examined by magnetic resonance imaging (MRI), including two sets of diffusion-weighted images (12 and 64 directions). Probabilistic and deterministic tractography was applied on each diffusion-weighted dataset to delineate the DRTT. Results were compared with regard to their sensitivity in revealing the DRTT and additional fiber tracts and processing time. Two sets of regions-of-interests (ROIs) guided deterministic tractography of the DRTT or the CTC, respectively. Tract distances to an atlas-based reference target were compared. Probabilistic fiber tracking with 64 orientations detected the DRTT in all twelve hemispheres. Deterministic tracking detected the DRTT in nine (12 directions) and in only two (64 directions) hemispheres. Probabilistic tracking was more sensitive in detecting additional fibers (e.g. ansa lenticularis and medial forebrain bundle) than deterministic tracking. Probabilistic tracking lasted substantially longer than deterministic. Deterministic tracking was more sensitive in detecting the CTC than the DRTT. CTC tracts were located adjacent but consistently more posterior to DRTT tracts. These results suggest that probabilistic tracking is more sensitive and robust in detecting the DRTT but harder to implement than deterministic approaches. Although sensitivity of deterministic tracking is higher for the CTC than the DRTT, targets for DBS based on these tracts likely differ. © 2017 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Regionally-Specific Diffusion Tensor Imaging in Mild Cognitive Impairment and Alzheimer’s Disease

PubMed Central

Mielke, M.M.; Kozauer, N.A.; Chan, K.C.G.; George, M.; Toroney, J.; Zerrate, M.; Bandeen-Roche, K.; Wang, M-C; vanZijl, P.; Pekar, J.J.; Mori, S.; Lyketsos, C.G.; Albert, M.

2009-01-01

Background Diffusion tensor imaging (DTI) studies have shown significant cross-sectional differences among normal controls (Bozzali et al., 2002), mild cognitive impairment (Robbins et al.) and Alzheimer’s disease (AD) patients in several fiber tracts in the brain, but longitudinal assessment is needed. Methods We studied 75 participants (25 NC, 25 amnestic MCI, and 25 mild AD) at baseline and 3 months later, with both imaging and clinical evaluations. Fractional anisotropy (Bozzali et al., 2002) was analyzed in regions of interest (ROIs) in: (1) fornix, (2) cingulum bundle, (3) splenium, and (4) cerebral peduncles. Clinical data included assessments of clinical severity and cognitive function. Cross-sectional and longitudinal differences in FA, within each ROI, were analyzed with generalized estimating equations (GEE). Results Cross-sectionally, AD patients had lower FA than NC (p<0.05) at baseline and 3 months in the fornix and anterior portion of the cingulum bundle. Compared to MCI, AD cases had lower FA (p<0.05) in these regions and the splenium at 0 and 3 months. Both the fornix and anterior cingulum correlated across all clinical cognitive scores; lower FA in these ROIs corresponded to worse performance. Over the course of 3 months, when the subjects were clinically stable, the ROIs were also largely stable. Conclusions Using DTI, findings indicate FA is decreased in specific fiber tracts among groups of subjects that vary along the spectrum from normal to AD, and that this measure is stable over short periods of time. The fornix is a predominant outflow tract of the hippocampus and may be an important indicator of AD progression. PMID:19457371

Kernel Regression Estimation of Fiber Orientation Mixtures in Diffusion MRI

PubMed Central

Cabeen, Ryan P.; Bastin, Mark E.; Laidlaw, David H.

2016-01-01

We present and evaluate a method for kernel regression estimation of fiber orientations and associated volume fractions for diffusion MR tractography and population-based atlas construction in clinical imaging studies of brain white matter. This is a model-based image processing technique in which representative fiber models are estimated from collections of component fiber models in model-valued image data. This extends prior work in nonparametric image processing and multi-compartment processing to provide computational tools for image interpolation, smoothing, and fusion with fiber orientation mixtures. In contrast to related work on multi-compartment processing, this approach is based on directional measures of divergence and includes data-adaptive extensions for model selection and bilateral filtering. This is useful for reconstructing complex anatomical features in clinical datasets analyzed with the ball-and-sticks model, and our framework’s data-adaptive extensions are potentially useful for general multi-compartment image processing. We experimentally evaluate our approach with both synthetic data from computational phantoms and in vivo clinical data from human subjects. With synthetic data experiments, we evaluate performance based on errors in fiber orientation, volume fraction, compartment count, and tractography-based connectivity. With in vivo data experiments, we first show improved scan-rescan reproducibility and reliability of quantitative fiber bundle metrics, including mean length, volume, streamline count, and mean volume fraction. We then demonstrate the creation of a multi-fiber tractography atlas from a population of 80 human subjects. In comparison to single tensor atlasing, our multi-fiber atlas shows more complete features of known fiber bundles and includes reconstructions of the lateral projections of the corpus callosum and complex fronto-parietal connections of the superior longitudinal fasciculus I, II, and III. PMID:26691524

Atypical age-dependency of executive function and white matter microstructure in children and adolescents with autism spectrum disorders.

PubMed

Martínez, Kenia; Merchán-Naranjo, Jessica; Pina-Camacho, Laura; Alemán-Gómez, Yasser; Boada, Leticia; Fraguas, David; Moreno, Carmen; Arango, Celso; Janssen, Joost; Parellada, Mara

2017-11-01

Executive function (EF) performance is associated with measurements of white matter microstructure (WMS) in typical individuals. Impaired EF is a hallmark symptom of autism spectrum disorders (ASD) but it is unclear how impaired EF relates to variability in WMS. Twenty-one male youth (8-18 years) with ASD and without intellectual disability and twenty-one typical male participants (TP) matched for age, intelligence quotient, handedness, race and parental socioeconomic status were recruited. Five EF domains were assessed and several DTI-based measurements of WMS [fractional anisotropy (FA), mean diffusivity (MD) and radial diffusivity (RD)] were estimated for eighteen white matter tracts. The ASD group had lower scores for attention (F = 8.37, p = 0.006) and response inhibition (F = 13.09, p = 0.001). Age-dependent changes of EF performance and WMS measurements were present in TP but attenuated in the ASD group. The strongest diagnosis-by-age effect was found for forceps minor, left anterior thalamic radiation and left cingulum angular bundle (all p's ≤ 0.002). In these tracts subjects with ASD tended to have equal or increased FA and/or reduced MD and/or RD at younger ages while controls had increased FA and/or reduced MD and/or RD thereafter. Only for TP individuals, increased FA in the left anterior thalamic radiation was associated with better response inhibition, while reduced RD in forceps minor and left cingulum angular bundle was related to better problem solving and working memory performance respectively. These findings provide novel insight into the age-dependency of EF performance and WMS in ASD, which can be instructive to cognitive training programs.

White matter abnormalities in Gulf War veterans with posttraumatic stress disorder: A pilot study.

PubMed

Bierer, Linda M; Ivanov, Iliyan; Carpenter, David M; Wong, Edmund W; Golier, Julia A; Tang, Cheuk Y; Yehuda, Rachel

2015-01-01

Gulf War veterans were exposed to environmental toxins not present in other combat theaters resulting in a unique biological signature that only partially resembles that seen in other combat veterans with PTSD. Thus it is important to determine if brain abnormalities seen in non-Gulf War veterans with PTSD are also present in Gulf War veterans. In this pilot study, diffusion tensor imaging (DTI) tractography was used to assess the ultra-structural integrity of fronto-limbic white matter connections in Gulf War veterans with and without PTSD. The effects of chronic multisymptom illness on DTI measures was also evaluated. Subjects were 20 previously studied Gulf War veterans on whom MRIs had been obtained. Mean diffusivity (MD) and fractional anisotropy (FA) were determined for left and right cingulum bundle by DTI tractography and compared in separate analyses for 12 veterans with, and 8 without PTSD. The effect of chronic multisymptom illness and it's interaction with PTSD, were similarly investigated using multivariate ACOVA. Partial correlations were used to test the associations of both DTI indices with PTSD severity and plasma cortisol, controlling for whole brain volume. Significantly lower MD was demonstrated in the right cingulum bundle among Gulf War veterans with PTSD. There were no significant differences in MD or FA in the left cingulum bundle. The presence of chronic multisymptom illness significantly attenuated the PTSD associated decrement in right cingulum MD. Clinician and self-rated PTSD symptom severity scores were significantly associated with reduced MD and increased FA in the right cingulum. Similar associations were observed for 8am plasma cortisol in a subset of participants. The preliminary findings indicate increased structural integrity - supporting enhanced connectivity - between right amygdala and anterior cingulate cortex in PTSD. This effect was strongest among Gulf War veterans without chronic multisymptom illness. The association of both MD and FA in the right cingulum with PTSD severity, and with heightened glucocorticoid responsivity, suggests that these DTI findings are a reflection of current PTSD illness expression. Although based on a small sample, these microstructural observations are consistent with a functional model suggesting increased amygdala responsivity in association with anterior cingulate modulation in PTSD. Copyright © 2014. Published by Elsevier Ltd.

Diffusion Tensor Imaging of Normal-Appearing White Matter as Biomarker for Radiation-Induced Late Delayed Cognitive Decline

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

Chapman, Christopher H., E-mail: chchap@umich.edu; Nagesh, Vijaya; Sundgren, Pia C.

Purpose: To determine whether early assessment of cerebral white matter degradation can predict late delayed cognitive decline after radiotherapy (RT). Methods and Materials: Ten patients undergoing conformal fractionated brain RT participated in a prospective diffusion tensor magnetic resonance imaging study. Magnetic resonance imaging studies were acquired before RT, at 3 and 6 weeks during RT, and 10, 30, and 78 weeks after starting RT. The diffusivity variables in the parahippocampal cingulum bundle and temporal lobe white matter were computed. A quality-of-life survey and neurocognitive function tests were administered before and after RT at the magnetic resonance imaging follow-up visits. Results:more » In both structures, longitudinal diffusivity ({lambda}{sub Double-Vertical-Line }) decreased and perpendicular diffusivity ({lambda}{sub Up-Tack }) increased after RT, with early changes correlating to later changes (p < .05). The radiation dose correlated with an increase in cingulum {lambda}{sub Up-Tack} at 3 weeks, and patients with >50% of cingula volume receiving >12 Gy had a greater increase in {lambda}{sub Up-Tack} at 3 and 6 weeks (p < .05). The post-RT changes in verbal recall scores correlated linearly with the late changes in cingulum {lambda}{sub Double-Vertical-Line} (30 weeks, p < .02). Using receiver operating characteristic curves, early cingulum {lambda}{sub Double-Vertical-Line} changes predicted for post-RT changes in verbal recall scores (3 and 6 weeks, p < .05). The neurocognitive test scores correlated significantly with the quality-of-life survey results. Conclusions: The correlation between early diffusivity changes in the parahippocampal cingulum and the late decline in verbal recall suggests that diffusion tensor imaging might be useful as a biomarker for predicting late delayed cognitive decline.« less

Lamellar and fibre bundle mechanics of the annulus fibrosus in bovine intervertebral disc.

PubMed

Vergari, Claudio; Mansfield, Jessica; Meakin, Judith R; Winlove, Peter C

2016-06-01

The intervertebral disc is a multicomposite structure, with an outer fibrous ring, the annulus fibrosus, retaining a gel-like core, the nucleus pulposus. The disc presents complex mechanical behaviour, and it is of high importance for spine biomechanics. Advances in multiscale modelling and disc repair raised a need for new quantitative data on the finest details of annulus fibrosus mechanics. In this work we explored inter-lamella and inter-bundle behaviour of the outer annulus using micromechanical testing and second harmonic generation microscopy. Twenty-one intervertebral discs were dissected from cow tails; the nucleus and inner annulus were excised to leave a ring of outer annulus, which was tested in circumferential loading while imaging the tissue's collagen fibres network with sub-micron resolution. Custom software was developed to determine local tissue strains through image analysis. Inter-bundle linear and shear strains were 5.5 and 2.8 times higher than intra-bundle strains. Bundles tended to remain parallel while rotating under loading, with large slipping between them. Inter-lamella linear strain was almost 3 times the intra-lamella one, but no slipping was observed at the junction between lamellae. This study confirms that outer annulus straining is mainly due to bundles slipping and rotating. Further development of disc multiscale modelling and repair techniques should take into account this modular behaviour of the lamella, rather than considering it as a homogeneous fibre-reinforced matrix. The intervertebral disc is an organ tucked between each couple of vertebrae in the spine. It is composed by an outer fibrous layer retaining a gel-like core. This organ undergoes severe and repeated loading during everyday life activities, since it is the compliant component that gives the spine its flexibility. Its properties are affected by pathologies such as disc degeneration, a major cause of back pain. In this article we explored the micromechanical behaviour of the disc's outer layer using second harmonic generation, a technique which allowed us to visualize, with unprecedented detail, how bundles of collagen fibres slide relative to each other when loaded. Our results will help further the development of new multiscale numerical models and repairing techniques. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Development of a Human Brain Diffusion Tensor Template

PubMed Central

Peng, Huiling; Orlichenko, Anton; Dawe, Robert J.; Agam, Gady; Zhang, Shengwei; Arfanakis, Konstantinos

2009-01-01

The development of a brain template for diffusion tensor imaging (DTI) is crucial for comparisons of neuronal structural integrity and brain connectivity across populations, as well as for the development of a white matter atlas. Previous efforts to produce a DTI brain template have been compromised by factors related to image quality, the effectiveness of the image registration approach, the appropriateness of subject inclusion criteria, the completeness and accuracy of the information summarized in the final template. The purpose of this work was to develop a DTI human brain template using techniques that address the shortcomings of previous efforts. Therefore, data containing minimal artifacts were first obtained on 67 healthy human subjects selected from an age-group with relatively similar diffusion characteristics (20–40 years of age), using an appropriate DTI acquisition protocol. Non-linear image registration based on mean diffusion-weighted and fractional anisotropy images was employed. DTI brain templates containing median and mean tensors were produced in ICBM-152 space and made publicly available. The resulting set of DTI templates is characterized by higher image sharpness, provides the ability to distinguish smaller white matter fiber structures, contains fewer image artifacts, than previously developed templates, and to our knowledge, is one of only two templates produced based on a relatively large number of subjects. Furthermore, median tensors were shown to better preserve the diffusion characteristics at the group level than mean tensors. Finally, white matter fiber tractography was applied on the template and several fiber-bundles were traced. PMID:19341801

Development of a human brain diffusion tensor template.

PubMed

Peng, Huiling; Orlichenko, Anton; Dawe, Robert J; Agam, Gady; Zhang, Shengwei; Arfanakis, Konstantinos

2009-07-15

The development of a brain template for diffusion tensor imaging (DTI) is crucial for comparisons of neuronal structural integrity and brain connectivity across populations, as well as for the development of a white matter atlas. Previous efforts to produce a DTI brain template have been compromised by factors related to image quality, the effectiveness of the image registration approach, the appropriateness of subject inclusion criteria, and the completeness and accuracy of the information summarized in the final template. The purpose of this work was to develop a DTI human brain template using techniques that address the shortcomings of previous efforts. Therefore, data containing minimal artifacts were first obtained on 67 healthy human subjects selected from an age-group with relatively similar diffusion characteristics (20-40 years of age), using an appropriate DTI acquisition protocol. Non-linear image registration based on mean diffusion-weighted and fractional anisotropy images was employed. DTI brain templates containing median and mean tensors were produced in ICBM-152 space and made publicly available. The resulting set of DTI templates is characterized by higher image sharpness, provides the ability to distinguish smaller white matter fiber structures, contains fewer image artifacts, than previously developed templates, and to our knowledge, is one of only two templates produced based on a relatively large number of subjects. Furthermore, median tensors were shown to better preserve the diffusion characteristics at the group level than mean tensors. Finally, white matter fiber tractography was applied on the template and several fiber-bundles were traced.

Verification of the FBR fuel bundle-duct interaction analysis code BAMBOO by the out-of-pile bundle compression test with large diameter pins

NASA Astrophysics Data System (ADS)

Uwaba, Tomoyuki; Ito, Masahiro; Nemoto, Junichi; Ichikawa, Shoichi; Katsuyama, Kozo

2014-09-01

The BAMBOO computer code was verified by results for the out-of-pile bundle compression test with large diameter pin bundle deformation under the bundle-duct interaction (BDI) condition. The pin diameters of the examined test bundles were 8.5 mm and 10.4 mm, which are targeted as preliminary fuel pin diameters for the upgraded core of the prototype fast breeder reactor (FBR) and for demonstration and commercial FBRs studied in the FaCT project. In the bundle compression test, bundle cross-sectional views were obtained from X-ray computer tomography (CT) images and local parameters of bundle deformation such as pin-to-duct and pin-to-pin clearances were measured by CT image analyses. In the verification, calculation results of bundle deformation obtained by the BAMBOO code analyses were compared with the experimental results from the CT image analyses. The comparison showed that the BAMBOO code reasonably predicts deformation of large diameter pin bundles under the BDI condition by assuming that pin bowing and cladding oval distortion are the major deformation mechanisms, the same as in the case of small diameter pin bundles. In addition, the BAMBOO analysis results confirmed that cladding oval distortion effectively suppresses BDI in large diameter pin bundles as well as in small diameter pin bundles.

Basic concepts of MR imaging, diffusion MR imaging, and diffusion tensor imaging.

PubMed

de Figueiredo, Eduardo H M S G; Borgonovi, Arthur F N G; Doring, Thomas M

2011-02-01

MR image contrast is based on intrinsic tissue properties and specific pulse sequences and parameter adjustments. A growing number of MRI imaging applications are based on diffusion properties of water. To better understand MRI diffusion-weighted imaging, a brief overview of MR physics is presented in this article followed by physics of the evolving techniques of diffusion MR imaging and diffusion tensor imaging. Copyright © 2011. Published by Elsevier Inc.

In vivo quantification of demyelination and recovery using compartment-specific diffusion MRI metrics validated by electron microscopy.

PubMed

Jelescu, Ileana O; Zurek, Magdalena; Winters, Kerryanne V; Veraart, Jelle; Rajaratnam, Anjali; Kim, Nathanael S; Babb, James S; Shepherd, Timothy M; Novikov, Dmitry S; Kim, Sungheon G; Fieremans, Els

2016-05-15

There is a need for accurate quantitative non-invasive biomarkers to monitor myelin pathology in vivo and distinguish myelin changes from other pathological features including inflammation and axonal loss. Conventional MRI metrics such as T2, magnetization transfer ratio and radial diffusivity have proven sensitivity but not specificity. In highly coherent white matter bundles, compartment-specific white matter tract integrity (WMTI) metrics can be directly derived from the diffusion and kurtosis tensors: axonal water fraction, intra-axonal diffusivity, and extra-axonal radial and axial diffusivities. We evaluate the potential of WMTI to quantify demyelination by monitoring the effects of both acute (6weeks) and chronic (12weeks) cuprizone intoxication and subsequent recovery in the mouse corpus callosum, and compare its performance with that of conventional metrics (T2, magnetization transfer, and DTI parameters). The changes observed in vivo correlated with those obtained from quantitative electron microscopy image analysis. A 6-week intoxication produced a significant decrease in axonal water fraction (p<0.001), with only mild changes in extra-axonal radial diffusivity, consistent with patchy demyelination, while a 12-week intoxication caused a more marked decrease in extra-axonal radial diffusivity (p=0.0135), consistent with more severe demyelination and clearance of the extra-axonal space. Results thus revealed increased specificity of the axonal water fraction and extra-axonal radial diffusivity parameters to different degrees and patterns of demyelination. The specificities of these parameters were corroborated by their respective correlations with microstructural features: the axonal water fraction correlated significantly with the electron microscopy derived total axonal water fraction (ρ=0.66; p=0.0014) but not with the g-ratio, while the extra-axonal radial diffusivity correlated with the g-ratio (ρ=0.48; p=0.0342) but not with the electron microscopy derived axonal water fraction. These parameters represent promising candidates as clinically feasible biomarkers of demyelination and remyelination in the white matter. Copyright © 2016 Elsevier Inc. All rights reserved.

Mesoscale mechanics of twisting carbon nanotube yarns.

PubMed

Mirzaeifar, Reza; Qin, Zhao; Buehler, Markus J

2015-03-12

Fabricating continuous macroscopic carbon nanotube (CNT) yarns with mechanical properties close to individual CNTs remains a major challenge. Spinning CNT fibers and ribbons for enhancing the weak interactions between the nanotubes is a simple and efficient method for fabricating high-strength and tough continuous yarns. Here we investigate the mesoscale mechanics of twisting CNT yarns using full atomistic and coarse grained molecular dynamics simulations, considering concurrent mechanisms at multiple length-scales. To investigate the mechanical response of such a complex structure without losing insights into the molecular mechanism, we applied a multiscale strategy. The full atomistic results are used for training a coarse grained model for studying larger systems consisting of several CNTs. The mesoscopic model parameters are updated as a function of the twist angle, based on the full atomistic results, in order to incorporate the atomistic scale deformation mechanisms in larger scale simulations. By bridging across two length scales, our model is capable of accurately predicting the mechanical behavior of twisted yarns while the atomistic level deformations in individual nanotubes are integrated into the model by updating the parameters. Our results focused on studying a bundle of close packed nanotubes provide novel mechanistic insights into the spinning of CNTs. Our simulations reveal how twisting a bundle of CNTs improves the shear interaction between the nanotubes up to a certain level due to increasing the interaction surface. Furthermore, twisting the bundle weakens the intertube interactions due to excessive deformation in the cross sections of individual CNTs in the bundle.

Study on bubbly flow behavior in natural circulation reactor by thermal-hydraulic simulation tests with SF6-Gas and ethanol liquid

NASA Astrophysics Data System (ADS)

Kondo, Yoshiyuki; Suga, Keishi; Hibi, Koki; Okazaki, Toshihiko; Komeno, Toshihiro; Kunugi, Tomoaki; Serizawa, Akimi; Yoneda, Kimitoshi; Arai, Takahiro

2009-02-01

An advanced experimental technique has been developed to simulate two-phase flow behavior in a light water reactor (LWR). The technique applies three kinds of methods; (1) use of sulfur-hexafluoride (SF6) gas and ethanol (C2H5OH) liquid at atmospheric temperature and a pressure less than 1.0MPa, where the fluid properties are similar to steam-water ones in the LWR, (2) generation of bubble with a sintering tube, which simulates bubble generation on heated surface in the LWR, (3) measurement of detailed bubble distribution data with a bi-optical probe (BOP), (4) and measurement of liquid velocities with the tracer liquid. This experimental technique provides easy visualization of flows by using a large scale experimental apparatus, which gives three-dimensional flows, and measurement of detailed spatial distributions of two-phase flow. With this technique, we have carried out experiments simulating two-phase flow behavior in a single-channel geometry, a multi-rod-bundle one, and a horizontal-tube-bundle one on a typical natural circulation reactor system. Those experiments have clarified a) a flow regime map in a rod bundle on the transient region between bubbly and churn flow, b) three-dimensional flow behaviour in rod-bundles where inter-subassembly cross-flow occurs, c) bubble-separation behavior with consideration of reactor internal structures. The data have given analysis models for the natural circulation reactor design with good extrapolation.

Electro-mechanical response of a 3D nerve bundle model to mechanical loads leading to axonal injury.

PubMed

Cinelli, I; Destrade, M; Duffy, M; McHugh, P

2018-03-01

Traumatic brain injuries and damage are major causes of death and disability. We propose a 3D fully coupled electro-mechanical model of a nerve bundle to investigate the electrophysiological impairments due to trauma at the cellular level. The coupling is based on a thermal analogy of the neural electrical activity by using the finite element software Abaqus CAE 6.13-3. The model includes a real-time coupling, modulated threshold for spiking activation, and independent alteration of the electrical properties for each 3-layer fibre within a nerve bundle as a function of strain. Results of the coupled electro-mechanical model are validated with previously published experimental results of damaged axons. Here, the cases of compression and tension are simulated to induce (mild, moderate, and severe) damage at the nerve membrane of a nerve bundle, made of 4 fibres. Changes in strain, stress distribution, and neural activity are investigated for myelinated and unmyelinated nerve fibres, by considering the cases of an intact and of a traumatised nerve membrane. A fully coupled electro-mechanical modelling approach is established to provide insights into crucial aspects of neural activity at the cellular level due to traumatic brain injury. One of the key findings is the 3D distribution of residual stresses and strains at the membrane of each fibre due to mechanically induced electrophysiological impairments, and its impact on signal transmission. Copyright © 2017 John Wiley & Sons, Ltd.

Cocowood Fibrovascular Tissue System—Another Wonder of Plant Evolution

PubMed Central

González, Oswaldo M.; Nguyen, Khoi A.

2016-01-01

The coconut palm (Cocos nucifera L.) stem tissue (referred to as cocowood in this study) is a complex fibrovascular system that is made up of fibrovascular bundles embedded into a parenchymatous ground tissue. The complex configuration of fibrovascular bundles along with the non-uniform distribution of the material properties likely allow senile coconut stems to optimize their biomechanical performance per unit mass (i.e., mechanical efficiency) and grow into tall, slender, and very flexible plants with minimum resources of biomass and water. For the first time, to the best of the authors' knowledge, this paper examines, from the integral (i.e., stem structure) and macroscopic (i.e., tissue structure) levels of hierarchy, the characteristic triple helix formation depicted by the fibrovascular bundles within the monocotyledon cocowood. The natural course of the tangential orientation of the axial fibrovascular bundles is mapped for the whole cocowood structure by quantifying 264 cocowood discs, corresponding to 41 senile coconut palms estimated to be >70 years old. The observed variations were modeled in this paper by simple equations that partially enabled characterization of the cocowood fibrovascular tissue system. Furthermore, 11 finite element analyses (FEA) were performed over a three dimensional (3D) finite element (FE) model resembling a characteristic coconut palm stem of 25 m in height to analyze the biomaterial reactions produced by the progressive deviation of the tangential fibrovascular bundles on the cocowood mechanical response (i.e., on the material compressive strength and the bending stiffness). The analyses in this study were carried out for the critical wind speed of 23 m/s (i.e., Gale tornado according to the Fujita tornado scale). For each analysis, the characteristic average maxima degree of orientation of the cocowood fibrovascular bundles was varied from 0° to 51°. The acquired results provided a deep understanding of the cocowood optimum fibrovascular tissue system that denotes the natural evolution of the material through millions of years. The knowledge advanced from this study may also serve as concept generators for innovative biomimetic applications to improve current engineered wood products. PMID:27555849

Signal detection by active, noisy hair bundles

NASA Astrophysics Data System (ADS)

O'Maoiléidigh, Dáibhid; Salvi, Joshua D.; Hudspeth, A. J.

2018-05-01

Vertebrate ears employ hair bundles to transduce mechanical movements into electrical signals, but their performance is limited by noise. Hair bundles are substantially more sensitive to periodic stimulation when they are mechanically active, however, than when they are passive. We developed a model of active hair-bundle mechanics that predicts the conditions under which a bundle is most sensitive to periodic stimulation. The model relies only on the existence of mechanotransduction channels and an active adaptation mechanism that recloses the channels. For a frequency-detuned stimulus, a noisy hair bundle's phase-locked response and degree of entrainment as well as its detection bandwidth are maximized when the bundle exhibits low-amplitude spontaneous oscillations. The phase-locked response and entrainment of a bundle are predicted to peak as functions of the noise level. We confirmed several of these predictions experimentally by periodically forcing hair bundles held near the onset of self-oscillation. A hair bundle's active process amplifies the stimulus preferentially over the noise, allowing the bundle to detect periodic forces less than 1 pN in amplitude. Moreover, the addition of noise can improve a bundle's ability to detect the stimulus. Although, mechanical activity has not yet been observed in mammalian hair bundles, a related model predicts that active but quiescent bundles can oscillate spontaneously when they are loaded by a sufficiently massive object such as the tectorial membrane. Overall, this work indicates that auditory systems rely on active elements, composed of hair cells and their mechanical environment, that operate on the brink of self-oscillation.

Reaction-diffusion systems coupled at the boundary and the Morse-Smale property

NASA Astrophysics Data System (ADS)

Broche, Rita de Cássia D. S.; de Oliveira, Luiz Augusto F.

We study an one-dimensional nonlinear reaction-diffusion system coupled on the boundary. Such system comes from modeling problems of temperature distribution on two bars of same length, jointed together, with different diffusion coefficients. We prove the transversality property of unstable and stable manifolds assuming all equilibrium points are hyperbolic. To this end, we write the system as an equation with noncontinuous diffusion coefficient. We then study the nonincreasing property of the number of zeros of a linearized nonautonomous equation as well as the Sturm-Liouville properties of the solutions of a linear elliptic problem.

Crossed Module Bundle Gerbes; Classification, String Group and Differential Geometry

NASA Astrophysics Data System (ADS)

Jurčo, Branislav

We discuss nonabelian bundle gerbes and their differential geometry using simplicial methods. Associated to any crossed module there is a simplicial group NC, the nerve of the 1-category defined by the crossed module and its geometric realization |NC|. Equivalence classes of principal bundles with structure group |NC| are shown to be one-to-one with stable equivalence classes of what we call crossed module gerbes bundle gerbes. We can also associate to a crossed module a 2-category C'. Then there are two equivalent ways how to view classifying spaces of NC-bundles and hence of |NC|-bundles and crossed module bundle gerbes. We can either apply the W-construction to NC or take the nerve of the 2-category C'. We discuss the string group and string structures from this point of view. Also a simplicial principal bundle can be equipped with a simplicial connection and a B-field. It is shown how in the case of a simplicial principal NC-bundle these simplicial objects give the bundle gerbe connection and the bundle gerbe B-field.

Hyperedge bundling: Data, source code, and precautions to modeling-accuracy bias to synchrony estimates.

PubMed

Wang, Sheng H; Lobier, Muriel; Siebenhühner, Felix; Puoliväli, Tuomas; Palva, Satu; Palva, J Matias

2018-06-01

It has not been well documented that MEG/EEG functional connectivity graphs estimated with zero-lag-free interaction metrics are severely confounded by a multitude of spurious interactions (SI), i.e., the false-positive "ghosts" of true interactions [1], [2]. These SI are caused by the multivariate linear mixing between sources, and thus they pose a severe challenge to the validity of connectivity analysis. Due to the complex nature of signal mixing and the SI problem, there is a need to intuitively demonstrate how the SI are discovered and how they can be attenuated using a novel approach that we termed hyperedge bundling. Here we provide a dataset with software with which the readers can perform simulations in order to better understand the theory and the solution to SI. We include the supplementary material of [1] that is not directly relevant to the hyperedge bundling per se but reflects important properties of the MEG source model and the functional connectivity graphs. For example, the gyri of dorsal-lateral cortices are the most accurately modeled areas; the sulci of inferior temporal, frontal and the insula have the least modeling accuracy. Importantly, we found the interaction estimates are heavily biased by the modeling accuracy between regions, which means the estimates cannot be straightforwardly interpreted as the coupling between brain regions. This raise a red flag that the conventional method of thresholding graphs by estimate values is rather suboptimal: because the measured topology of the graph reflects the geometric property of source-model instead of the cortical interactions under investigation.

Anatomical approach to permanent His bundle pacing: Optimizing His bundle capture.

PubMed

Vijayaraman, Pugazhendhi; Dandamudi, Gopi

2016-01-01

Permanent His bundle pacing is a physiological alternative to right ventricular pacing. In this article we describe our approach to His bundle pacing in patients with AV nodal and intra-Hisian conduction disease. It is essential for the implanters to understand the anatomic variations of the His bundle course and its effect on the type of His bundle pacing achieved. We describe several case examples to illustrate our anatomical approach to permanent His bundle pacing in this article. Copyright © 2016 Elsevier Inc. All rights reserved.

Age Related Changes in Topological Properties of Brain Functional Network and Structural Connectivity.

PubMed

Shah, Chandan; Liu, Jia; Lv, Peilin; Sun, Huaiqiang; Xiao, Yuan; Liu, Jieke; Zhao, Youjin; Zhang, Wenjing; Yao, Li; Gong, Qiyong; Lui, Su

2018-01-01

Introduction: There are still uncertainties about the true nature of age related changes in topological properties of the brain functional network and its structural connectivity during various developmental stages. In this cross- sectional study, we investigated the effects of age and its relationship with regional nodal properties of the functional brain network and white matter integrity. Method: DTI and fMRI data were acquired from 458 healthy Chinese participants ranging from age 8 to 81 years. Tractography was conducted on the DTI data using FSL. Graph Theory analyses were conducted on the functional data yielding topological properties of the functional network using SPM and GRETNA toolbox. Two multiple regressions were performed to investigate the effects of age on nodal topological properties of the functional brain network and white matter integrity. Result: For the functional studies, we observed that regional nodal characteristics such as node betweenness were decreased while node degree and node efficiency was increased in relation to increasing age. Perversely, we observed that the relationship between nodal topological properties and fasciculus structures were primarily positive for nodal betweenness but negative for nodal degree and nodal efficiency. Decrease in functional nodal betweenness was primarily located in superior frontal lobe, right occipital lobe and the global hubs. These brain regions also had both direct and indirect anatomical relationships with the 14 fiber bundles. A linear age related decreases in the Fractional anisotropy (FA) value was found in the callosum forceps minor. Conclusion: These results suggests that age related differences were more pronounced in the functional than in structural measure indicating these measures do not have direct one-to-one mapping. Our study also indicates that the fiber bundles with longer fibers exhibited a more pronounced effect on the properties of functional network.

Plasmonic Gold Decorated MWCNT Nanocomposite for Localized Plasmon Resonance Sensing

PubMed Central

Ozhikandathil, J.; Badilescu, S.; Packirisamy, M.

2015-01-01

The synergism of excellent properties of carbon nanotubes and gold nanoparticles is used in this work for bio-sensing of recombinant bovine growth hormones (rbST) by making Multi Wall Carbon Nanotubes (MWCNT) locally optically responsive by augmenting it optical properties through Localized Surface Plasmon Resonance (LSPR). To this purpose, locally gold nano particles decorated gold–MWCNT composite was synthesized from a suspension of MWCNT bundles and hydrogen chloroauric acid in an aqueous solution, activated ultrasonically and, then, drop-casted on a glass substrate. The slow drying of the drop produces a “coffee ring” pattern that is found to contain gold–MWCNT nanocomposites, accumulated mostly along the perimeter of the ring. The reaction is studied also at low-temperature, in the vacuum chamber of the Scanning Electron Microscope and is accounted for by the local melting processes that facilitate the contact between the bundle of tubes and the gold ions. Biosensing applications of the gold–MWCNT nanocomposite using their LSPR properties are demonstrated for the plasmonic detection of traces of bovine growth hormone. The sensitivity of the hybrid platform which is found to be 1 ng/ml is much better than that measuring with gold nanoparticles alone which is only 25 ng/ml. PMID:26282187

Micro/Nanomechanical characterization of multi-walled carbon nanotubes reinforced epoxy composite.

PubMed

Cui, Peng; Wang, Xinnan; Tangpong, X W

2012-11-01

In this paper, the mechanical properties of 1 wt.% multi-walled carbon nanotubes (MWCNTs) reinforced epoxy nanocomposites were characterized using a self-designed micro/nano three point bending tester that was on an atomic force microscope (AFM) to in situ observe MWCNTs movement on the sample surface under loading. The migration of an individual MWCNT at the surface of the nanocomposite was tracked to address the nanomechanical reinforcing mechanism of the nanocomposites. Through morphology analysis of the nanocomposite via scanning electron microscopy, AFM, and digital image correlation technique, it was found that the MWCNTs agglomerate and the bundles were the main factors for limiting the bending strength of the composites. The agglomeration/bundle effect was included in the Halpin-Tsai model to account for the elastic modulus of the nanocomposites.

Physical characterization of functionalized spider silk: electronic and sensing properties

PubMed Central

Steven, Eden; Park, Jin Gyu; Paravastu, Anant; Lopes, Elsa Branco; Brooks, James S; Englander, Ongi; Siegrist, Theo; Kaner, Papatya; Alamo, Rufina G

2011-01-01

This work explores functional, fundamental and applied aspects of naturally harvested spider silk fibers. Natural silk is a protein polymer where different amino acids control the physical properties of fibroin bundles, producing, for example, combinations of β-sheet (crystalline) and amorphous (helical) structural regions. This complexity presents opportunities for functional modification to obtain new types of material properties. Electrical conductivity is the starting point of this investigation, where the insulating nature of neat silk under ambient conditions is described first. Modification of the conductivity by humidity, exposure to polar solvents, iodine doping, pyrolization and deposition of a thin metallic film are explored next. The conductivity increases exponentially with relative humidity and/or solvent, whereas only an incremental increase occurs after iodine doping. In contrast, iodine doping, optimal at 70 °C, has a strong effect on the morphology of silk bundles (increasing their size), on the process of pyrolization (suppressing mass loss rates) and on the resulting carbonized fiber structure (that becomes more robust against bending and strain). The effects of iodine doping and other functional parameters (vacuum and thin film coating) motivated an investigation with magic angle spinning nuclear magnetic resonance (MAS-NMR) to monitor doping-induced changes in the amino acid-protein backbone signature. MAS-NMR revealed a moderate effect of iodine on the helical and β-sheet structures, and a lesser effect of gold sputtering. The effects of iodine doping were further probed by Fourier transform infrared (FTIR) spectroscopy, revealing a partial transformation of β-sheet-to-amorphous constituency. A model is proposed, based on the findings from the MAS-NMR and FTIR, which involves iodine-induced changes in the silk fibroin bundle environment that can account for the altered physical properties. Finally, proof-of-concept applications of functionalized spider silk are presented for thermoelectric (Seebeck) effects and incandescence in iodine-doped pyrolized silk fibers, and metallic conductivity and flexibility of micron-sized gold-sputtered silk fibers. In the latter case, we demonstrate the application of gold-sputtered neat spider silk to make four-terminal, flexible, ohmic contacts to organic superconductor samples. PMID:27877440

Search for Ultra-High-Energy Neutrinos with AMANDA-II

NASA Astrophysics Data System (ADS)

Ackermann, M.; Adams, J.; Ahrens, J.; Andeen, K.; Auffenberg, J.; Bai, X.; Baret, B.; Barwick, S. W.; Bay, R.; Beattie, K.; Becka, T.; Becker, J. K.; Becker, K.-H.; Beimforde, M.; Berghaus, P.; Berley, D.; Bernardini, E.; Bertrand, D.; Besson, D. Z.; Blaufuss, E.; Boersma, D. J.; Bohm, C.; Bolmont, J.; Böser, S.; Botner, O.; Bouchta, A.; Braun, J.; Burgess, T.; Castermans, T.; Chirkin, D.; Christy, B.; Clem, J.; Cowen, D. F.; D'Agostino, M. V.; Davour, A.; Day, C. T.; De Clercq, C.; Demirörs, L.; Descamps, F.; Desiati, P.; de Vries-Uiterweerd, G.; DeYoung, T.; Diaz-Velez, J. C.; Dreyer, J.; Dumm, J. P.; Duvoort, M. R.; Edwards, W. R.; Ehrlich, R.; Eisch, J.; Ellsworth, R. W.; Evenson, P. A.; Fadiran, O.; Fazely, A. R.; Filimonov, K.; Finley, C.; Foerster, M. M.; Fox, B. D.; Franckowiak, A.; Franke, R.; Gaisser, T. K.; Gallagher, J.; Ganugapati, R.; Geenen, H.; Gerhardt, L.; Goldschmidt, A.; Goodman, J. A.; Gozzini, R.; Griesel, T.; Groß, A.; Grullon, S.; Gunasingha, R. M.; Gurtner, M.; Ha, C.; Hallgren, A.; Halzen, F.; Han, K.; Hanson, K.; Hardtke, D.; Hardtke, R.; Hasegawa, Y.; Hauschildt, T.; Heise, J.; Helbing, K.; Hellwig, M.; Herquet, P.; Hill, G. C.; Hodges, J.; Hoffman, K. D.; Hommez, B.; Hoshina, K.; Hubert, D.; Hughey, B.; Hülß, J.-P.; Hulth, P. O.; Hultqvist, K.; Hundertmark, S.; Inaba, M.; Ishihara, A.; Jacobsen, J.; Japaridze, G. S.; Johansson, H.; Joseph, J. M.; Kampert, K.-H.; Kappes, A.; Karg, T.; Karle, A.; Kawai, H.; Kelley, J. L.; Kiryluk, J.; Kislat, F.; Kitamura, N.; Klein, S. R.; Klepser, S.; Kohnen, G.; Kolanoski, H.; Köpke, L.; Kowalski, M.; Kowarik, T.; Krasberg, M.; Kuehn, K.; Kuwabara, T.; Labare, M.; Laihem, K.; Landsman, H.; Lauer, R.; Leich, H.; Leier, D.; Liubarsky, I.; Lundberg, J.; Lünemann, J.; Madsen, J.; Maruyama, R.; Mase, K.; Matis, H. S.; McCauley, T.; McParland, C. P.; Meagher, K.; Meli, A.; Messarius, T.; Mészáros, P.; Miyamoto, H.; Montaruli, T.; Morey, A.; Morse, R.; Movit, S. M.; Münich, K.; Nahnhauer, R.; Nam, J. W.; Nießen, P.; Nygren, D. R.; Olivas, A.; Ono, M.; Patton, S.; Pérez de los Heros, C.; Piegsa, A.; Pieloth, D.; Pohl, A. C.; Porrata, R.; Pretz, J.; Price, P. B.; Przybylski, G. T.; Rawlins, K.; Razzaque, S.; Redl, P.; Resconi, E.; Rhode, W.; Ribordy, M.; Rizzo, A.; Robbins, S.; Robbins, W. J.; Roth, P.; Rothmaier, F.; Rott, C.; Roucelle, C.; Rutledge, D.; Ryckbosch, D.; Sander, H.-G.; Sarkar, S.; Satalecka, K.; Schlenstedt, S.; Schmidt, T.; Schneider, D.; Schultz, O.; Seckel, D.; Semburg, B.; Seo, S. H.; Sestayo, Y.; Seunarine, S.; Silvestri, A.; Smith, A. J.; Song, C.; Spiczak, G. M.; Spiering, C.; Stamatikos, M.; Stanev, T.; Stezelberger, T.; Stokstad, R. G.; Stoufer, M. C.; Stoyanov, S.; Strahler, E. A.; Straszheim, T.; Sulanke, K.-H.; Sullivan, G. W.; Sumner, T. J.; Swillens, Q.; Taboada, I.; Tarasova, O.; Tepe, A.; Thollander, L.; Tilav, S.; Tluczykont, M.; Toale, P. A.; Tosi, D.; Turčan, D.; van Eijndhoven, N.; Vandenbroucke, J.; Van Overloop, A.; Viscomi, V.; Vogt, C.; Voigt, B.; Wagner, W.; Walck, C.; Waldmann, H.; Waldenmaier, T.; Walter, M.; Wang, Y.-R.; Wendt, C.; Wiebusch, C. H.; Wiedemann, C.; Wikström, G.; Williams, D. R.; Wischnewski, R.; Wissing, H.; Woschnagg, K.; Xu, X. W.; Yodh, G.; Yoshida, S.; Zornoza, J. D.; IceCube Collaboration

2008-03-01

A search for diffuse neutrinos with energies in excess of 105 GeV is conducted with AMANDA-II data recorded between 2000 and 2002. Above 107 GeV, the Earth is essentially opaque to neutrinos. This fact, combined with the limited overburden of the AMANDA-II detector (roughly 1.5 km), concentrates these ultra-high-energy neutrinos at the horizon. The primary background for this analysis is bundles of downgoing, high-energy muons from the interaction of cosmic rays in the atmosphere. No statistically significant excess above the expected background is seen in the data, and an upper limit is set on the diffuse all-flavor neutrino flux of E2Φ90% CL < 2.7 × 10-7 GeV cm-2 s-1 sr-1 valid over the energy range of 2 × 105 to 109 GeV. A number of models that predict neutrino fluxes from active galactic nuclei are excluded at the 90% confidence level.

In vitro determination of the mechanical and chemical properties of a fibre orthodontic retainer.

PubMed

Silvestrini-Biavati, Armando; Angiero, Francesca; Gibelli, Francesca; Signore, Antonio; Benedicenti, Stefano

2012-12-01

The aim of this study was to analyse, in vitro, the chemical and mechanical properties of a new fibre retainer, Everstick, comparing its characteristics with the requirements for an orthodontic retainer. Chemical analysis was used to examine seven fibre bundles exposed to a photocuring lamp and then to different acids and resistance to corrosion by artificial saliva fortified with plaque acids. The mechanical properties examined were tensile strength and resistance to flexural force. Ten fibre samples were tested for each mechanical analysis and the mean value and standard deviation were calculated. Wilcoxon signed rank test was used to evaluate change in weight after treatment in each group. To determine changes over time between the groups for each acid considered separately, both repeated measures analysis of variance (ANOVA) on original data and on rank transformed data were used. If the results were different, ANOVA on rank-transformed data was considered. Acetic acid was found to be the most corrosive and caused the most substance loss: both pure and at the salivary pH value. Hydrofluoric acid was the most damaging. For all acids analysed in both groups (lactic, formic, acetic, propionic), changes after treatment were statistically different between two groups (P < 0.001 for lactic, acetic, propionic; P = 0.004 for formic acid).The mean Young's modulus value was 68 510 MPa. Deformation before the fibre separated into its constituent elements (glass fibre and composite) was 3.9 per cent, stress to rupture was 1546 MPa, and resistance to bending was 534 MPa. The deflection produced over a length of 12 mm was 1.4 mm. The fibre bundle was attacked by acids potentially present in the oral cavity; the degree of aggressiveness depending on the acid concentration. To preserve fibre bundles long term, careful plaque control is necessary, especially in the interproximal spaces, to avoid acid formation. The tested product was found to be sufficiently strong to oppose flexural and occlusal forces.

Effects of Atomic-Scale Structure on the Fracture Properties of Amorphous Carbon - Carbon Nanotube Composites

NASA Technical Reports Server (NTRS)

Jensen, Benjamin D.; Wise, Kristopher E.; Odegard, Gregory M.

2015-01-01

The fracture of carbon materials is a complex process, the understanding of which is critical to the development of next generation high performance materials. While quantum mechanical (QM) calculations are the most accurate way to model fracture, the fracture behavior of many carbon-based composite engineering materials, such as carbon nanotube (CNT) composites, is a multi-scale process that occurs on time and length scales beyond the practical limitations of QM methods. The Reax Force Field (ReaxFF) is capable of predicting mechanical properties involving strong deformation, bond breaking and bond formation in the classical molecular dynamics framework. This has been achieved by adding to the potential energy function a bond-order term that varies continuously with distance. The use of an empirical bond order potential, such as ReaxFF, enables the simulation of failure in molecular systems that are several orders of magnitude larger than would be possible in QM techniques. In this work, the fracture behavior of an amorphous carbon (AC) matrix reinforced with CNTs was modeled using molecular dynamics with the ReaxFF reactive forcefield. Care was taken to select the appropriate simulation parameters, which can be different from those required when using traditional fixed-bond force fields. The effect of CNT arrangement was investigated with three systems: a single-wall nanotube (SWNT) array, a multi-wall nanotube (MWNT) array, and a SWNT bundle system. For each arrangement, covalent bonds are added between the CNTs and AC, with crosslink fractions ranging from 0-25% of the interfacial CNT atoms. The SWNT and MWNT array systems represent ideal cases with evenly spaced CNTs; the SWNT bundle system represents a more realistic case because, in practice, van der Waals interactions lead to the agglomeration of CNTs into bundles. The simulation results will serve as guidance in setting experimental processing conditions to optimize the mechanical properties of CNT composites.

Microstructural and Compositional Features of the Fibrous and Hyaline Cartilage on the Medial Tibial Plateau Imply a Unique Role for the Hopping Locomotion of Kangaroo

PubMed Central

He, Bo; Wu, Jian Ping; Xu, Jiake; Day, Robert E.; Kirk, Thomas Brett

2013-01-01

Hopping provides efficient and energy saving locomotion for kangaroos, but it results in great forces in the knee joints. A previous study has suggested that a unique fibrous cartilage in the central region of the tibial cartilage could serve to decrease the peak stresses generated within kangaroo tibiofemoral joints. However, the influences of the microstructure, composition and mechanical properties of the central fibrous and peripheral hyaline cartilage on the function of the knee joints are still to be defined. The present study showed that the fibrous cartilage was thicker and had a lower chondrocyte density than the hyaline cartilage. Despite having a higher PG content in the middle and deep zones, the fibrous cartilage had an inferior compressive strength compared to the peripheral hyaline cartilage. The fibrous cartilage had a complex three dimensional collagen meshwork with collagen bundles parallel to the surface in the superficial zone, and with collagen bundles both parallel and perpendicular to the surface in the middle and deep zones. The collagen in the hyaline cartilage displayed a typical Benninghoff structure, with collagen fibres parallel to the surface in the superficial zone and collagen fibres perpendicular to the surface in the deep zone. Elastin fibres were found throughout the entire tissue depth of the fibrous cartilage and displayed a similar alignment to the adjacent collagen bundles. In comparison, the elastin fibres in the hyaline cartilage were confined within the superficial zone. This study examined for the first time the fibrillary structure, PG content and compressive properties of the central fibrous cartilage pad and peripheral hyaline cartilage within the kangaroo medial tibial plateau. It provided insights into the microstructure and composition of the fibrous and peripheral hyaline cartilage in relation to the unique mechanical properties of the tissues to provide for the normal activities of kangaroos. PMID:24058543

Microstructural and compositional features of the fibrous and hyaline cartilage on the medial tibial plateau imply a unique role for the hopping locomotion of kangaroo.

PubMed

He, Bo; Wu, Jian Ping; Xu, Jiake; Day, Robert E; Kirk, Thomas Brett

2013-01-01

Hopping provides efficient and energy saving locomotion for kangaroos, but it results in great forces in the knee joints. A previous study has suggested that a unique fibrous cartilage in the central region of the tibial cartilage could serve to decrease the peak stresses generated within kangaroo tibiofemoral joints. However, the influences of the microstructure, composition and mechanical properties of the central fibrous and peripheral hyaline cartilage on the function of the knee joints are still to be defined. The present study showed that the fibrous cartilage was thicker and had a lower chondrocyte density than the hyaline cartilage. Despite having a higher PG content in the middle and deep zones, the fibrous cartilage had an inferior compressive strength compared to the peripheral hyaline cartilage. The fibrous cartilage had a complex three dimensional collagen meshwork with collagen bundles parallel to the surface in the superficial zone, and with collagen bundles both parallel and perpendicular to the surface in the middle and deep zones. The collagen in the hyaline cartilage displayed a typical Benninghoff structure, with collagen fibres parallel to the surface in the superficial zone and collagen fibres perpendicular to the surface in the deep zone. Elastin fibres were found throughout the entire tissue depth of the fibrous cartilage and displayed a similar alignment to the adjacent collagen bundles. In comparison, the elastin fibres in the hyaline cartilage were confined within the superficial zone. This study examined for the first time the fibrillary structure, PG content and compressive properties of the central fibrous cartilage pad and peripheral hyaline cartilage within the kangaroo medial tibial plateau. It provided insights into the microstructure and composition of the fibrous and peripheral hyaline cartilage in relation to the unique mechanical properties of the tissues to provide for the normal activities of kangaroos.

Double-bundle anterior cruciate ligament reconstruction is superior to single-bundle reconstruction in terms of revision frequency: a study of 22,460 patients from the Swedish National Knee Ligament Register.

PubMed

Svantesson, Eleonor; Sundemo, David; Hamrin Senorski, Eric; Alentorn-Geli, Eduard; Musahl, Volker; Fu, Freddie H; Desai, Neel; Stålman, Anders; Samuelsson, Kristian

2017-12-01

Studies comparing single- and double-bundle anterior cruciate ligament (ACL) reconstructions often include a combined analysis of anatomic and non-anatomic techniques. The purpose of this study was to compare the revision rates between single- and double-bundle ACL reconstructions in the Swedish National Knee Ligament Register with regard to surgical variables as determined by the anatomic ACL reconstruction scoring checklist (AARSC). Patients from the Swedish National Knee Ligament Register who underwent either single- or double-bundle ACL reconstruction with hamstring tendon autograft during the period 2007-2014 were included. The follow-up period started with primary ACL reconstruction, and the outcome measure was set as revision surgery. An online questionnaire based on the items of the AARSC was used to determine the surgical technique implemented in the single-bundle procedures. These were organized into subgroups based on surgical variables, and the revision rates were compared with the double-bundle ACL reconstruction. Hazard ratios (HR) with 95% confidence interval (CI) was calculated and adjusted for confounders by Cox regression. A total of 22,460 patients were included in the study, of which 21,846 were single-bundle and 614 were double-bundle ACL reconstruction. Double-bundle ACL reconstruction had a revision frequency of 2.0% (n = 12) and single-bundle 3.2% (n = 689). Single-bundle reconstruction had an increased risk of revision surgery compared with double-bundle [adjusted HR 1.98 (95% CI 1.12-3.51), p = 0.019]. The subgroup analysis showed a significantly increased risk of revision surgery in patients undergoing single-bundle with anatomic technique using transportal drilling [adjusted HR 2.51 (95% CI 1.39-4.54), p = 0.002] compared with double-bundle ACL reconstruction. Utilizing a more complete anatomic technique according to the AARSC lowered the hazard rate considerably when transportal drilling was performed but still resulted in significantly increased risk of revision surgery compared with double-bundle ACL reconstruction [adjusted HR 1.87 (95% CI 1.04-3.38), p = 0.037]. Double-bundle ACL reconstruction is associated with a lower risk of revision surgery than single-bundle ACL reconstruction. Single-bundle procedures performed using transportal femoral drilling technique had significantly higher risk of revision surgery compared with double-bundle. However, a reference reconstruction with transportal drilling defined as a more complete anatomic reconstruction reduces the risk of revision surgery considerably. III.

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

Sun, Shibin; College of Electromechanical Engineering, Qingdao University of Science and Technology, Qingdao 266061; Chang, Xueting, E-mail: xuetingchang@yahoo.cn

Cobalt-doped tungsten oxide mesocrystals with different morphologies have been successfully generated using a solvothermal method with tungsten hexachloride and cobalt chloride salts as precursors. The resulting mesocrystals were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Brunauer-Emmet-Teller analysis of nitrogen sorptometer, and UV-vis diffuse reflectance spectroscopy. The photocatalytic properties of the cobalt-doped tungsten oxide mesocrystals were evaluated on the basis of their ability to degrade methyl orange in an aqueous solution under simulated sunlight irradiation. Results showed that the cobalt doping had obvious effect on the morphologies of the final products, and lenticular and blocky cobalt-dopedmore » tungsten oxide mesocrystals could be obtained with 1.0 wt.% and 2.0 wt.% cobalt doping, respectively. The cobalt-doped tungsten oxides exhibited superior photocatalytic activities to that of the undoped tungsten oxide. - Graphical abstract: Schematic illustrations of the growth of the bundled nanowires, lenticular mesocrystals, and blocky mesocrystals. Highlights: Black-Right-Pointing-Pointer Co-doped W{sub 18}O{sub 49} mesocrystals were synthesized using a solvothermal method. Black-Right-Pointing-Pointer The Co doping has obvious effect on the morphology of the final mesocrystals. Black-Right-Pointing-Pointer The Co-doped W{sub 18}O{sub 49} exhibited superior photocatalytic activity to the undoped W{sub 18}O{sub 49}.« less

Optically addressed and submillisecond response phase only liquid crystal spatial light modulator

NASA Astrophysics Data System (ADS)

Zhao, Xiangjie; Duan, Jiazhu; Zhang, Dayong; Luo, Yongquan

2014-10-01

Liquid crystal based phase only spatial light modulator has attracted many research interests since last decades because of its superior advantage. Until now the liquid crystal spatial light modulator has been applied in many fields, but the response speed of nematic LC limited its further application. In this paper, an optically addressed phase only LC spatial light modulator was proposed based on polymer network liquid crystal. Morphology effect on the light scattering of PNLC was studied, which was mainly consisted of fiber and fiber bundles. The morphology nearly determined the light scattering and electro-optical property. Due to the high threshold voltage, to address the PNLC phase modulator was also concerned. Optical addressing method was proposed, in which BSO crystal was selected to replace one of the glass substrate. The response speed of PNLC was so fast that the reorientation of liquid crystal director will follow the change of effective voltage applied on LC layer, which was related with the voltage signal and especially with electron transport of photo-induced carriers due to diffusion and drift. The on state dynamic response of phase change was investigated. Based on this device, beam steering was also achieved by loading 488nm laser strip on the optical addressed phase only spatial light modulator.

A Comprehensive Reanalysis of the Distal Iliotibial Band: Quantitative Anatomy, Radiographic Markers, and Biomechanical Properties.

PubMed

Godin, Jonathan A; Chahla, Jorge; Moatshe, Gilbert; Kruckeberg, Bradley M; Muckenhirn, Kyle J; Vap, Alexander R; Geeslin, Andrew G; LaPrade, Robert F

2017-09-01

The qualitative anatomy of the distal iliotibial band (ITB) has previously been described. However, a comprehensive characterization of the quantitative anatomic, radiographic, and biomechanical properties of the Kaplan fibers of the deep distal ITB has not yet been established. It is paramount to delineate these characteristics to fully understand the distal ITB's contribution to rotational knee stability. Purpose/Hypothesis: There were 2 distinct purposes for this study: (1) to perform a quantitative anatomic and radiographic evaluation of the distal ITB's attachment sites and their relationships to pertinent osseous and soft tissue landmarks, and (2) to quantify the biomechanical properties of the deep (Kaplan) fibers of the distal ITB. It was hypothesized that the distal ITB has definable parameters concerning its anatomic attachments and consistent relationships to surgically pertinent landmarks with correlating plain radiographic findings. In addition, it was hypothesized that the biomechanical properties of the Kaplan fibers would support their role as important restraints against internal rotation. Descriptive laboratory study. Ten nonpaired, fresh-frozen human cadaveric knees (mean age, 61.1 years; range, 54-65 years) were dissected for anatomic and radiographic purposes. A coordinate measuring device quantified the attachment areas of the distal ITB to the distal femur, patella, and proximal tibia and their relationships to pertinent bony landmarks. A radiographic analysis was performed by inserting pins into the attachment sites of relevant anatomic structures to assess their location relative to pertinent bony landmarks with fluoroscopic guidance. A further biomechanical assessment of 10 cadaveric knees quantified the load to failure and stiffness of the Kaplan fibers' insertion on the distal femur after a preconditioning protocol. Two separate deep (Kaplan) fiber bundles were identified with attachments to 2 newly identified femoral bony prominences (ridges). The proximal and distal bundles inserted on the distal femur 53.6 mm (95% CI, 50.7-56.6 mm) and 31.4 mm (95% CI, 27.3-35.5 mm) proximal to the lateral epicondyle, respectively. The centers of the bundle insertions were 22.5 mm (95% CI, 19.1-25.9 mm) apart. The total insertion area of the distal ITB on the proximal tibia was 429.1 mm 2 (95% CI, 349.2-509.1 mm 2 ). A distinct capsulo-osseous layer of the distal ITB was also identified that was intimately related to the lateral knee capsule. Its origin was in close proximity to the lateral gastrocnemius tubercle, and it inserted on the proximal tibia at the lateral tibial tubercle between the fibular head and the Gerdy tubercle. Radiographic analysis supported the quantitative anatomic findings. The mean maximum load during pull-to-failure testing was 71.3 N (95% CI, 41.2-101.4 N) and 170.2 N (95% CI, 123.6-216.8 N) for the proximal and distal Kaplan bundles, respectively. The most important finding of this study was that 2 distinct deep bundles (Kaplan fibers) of the distal ITB were identified. Each bundle of the deep layer of the ITB was associated with a newly identified distinct bony ridge. Radiographic analysis confirmed the measurements previously recorded and established reproducible landmarks for the newly described structures. Biomechanical testing revealed that the Kaplan fibers had a strong attachment to the distal femur, thereby supporting a role in rotational knee stability. The identification of 2 distinct deep fiber (Kaplan) attachments clarifies the function of the ITB more definitively. The results also support the role of the ITB in rotatory knee stability because of the fibers' vectors and their identified maximum loads. These findings provide the anatomic and biomechanical foundation needed for the development of reconstruction or repair techniques to anatomically address these deficiencies in knee ligament injuries.

The behavioral economics of will in recovery from addiction.

PubMed

Monterosso, John; Ainslie, George

2007-09-01

Behavioral economic studies demonstrate that rewards are discounted proportionally with their delay (hyperbolic discounting). Hyperbolic discounting implies temporary preference for smaller rewards when they are imminent, and this concept has been widely considered by researchers interested in the causes of addictive behavior. Far less consideration has been given to the fact that systematic preference reversal also predicts various self-control phenomena, which may also be analyzed from a behavioral economic perspective. Here we summarize self-control phenomena predicted by hyperbolic discounting, particularly with application to the field of addiction. Of greatest interest is the phenomenon of choice bundling, an increase in motivation to wait for delayed rewards that can be expected to result from making choices in whole categories. Specifically, when a person's expectations about her own future behavior are conditional upon her current behavior, the value of these expectations is added to the contingencies for the current behavior, resulting in reduced impulsivity. Hyperbolic discounting provides a bottom-up basis for the intuitive learning of choice bundling, the properties of which match common descriptions of willpower. We suggest that the bundling effect can also be discerned in the advice of 12-step programs.

Actin assembly factors regulate the gelation kinetics and architecture of F-actin networks.

PubMed

Falzone, Tobias T; Oakes, Patrick W; Sees, Jennifer; Kovar, David R; Gardel, Margaret L

2013-04-16

Dynamic regulation of the actin cytoskeleton is required for diverse cellular processes. Proteins regulating the assembly kinetics of the cytoskeletal biopolymer F-actin are known to impact the architecture of actin cytoskeletal networks in vivo, but the underlying mechanisms are not well understood. Here, we demonstrate that changes to actin assembly kinetics with physiologically relevant proteins profilin and formin (mDia1 and Cdc12) have dramatic consequences on the architecture and gelation kinetics of otherwise biochemically identical cross-linked F-actin networks. Reduced F-actin nucleation rates promote the formation of a sparse network of thick bundles, whereas increased nucleation rates result in a denser network of thinner bundles. Changes to F-actin elongation rates also have marked consequences. At low elongation rates, gelation ceases and a solution of rigid bundles is formed. By contrast, rapid filament elongation accelerates dynamic arrest and promotes gelation with minimal F-actin density. These results are consistent with a recently developed model of how kinetic constraints regulate network architecture and underscore how molecular control of polymer assembly is exploited to modulate cytoskeletal architecture and material properties. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Actin Assembly Factors Regulate the Gelation Kinetics and Architecture of F-actin Networks

PubMed Central

Falzone, Tobias T.; Oakes, Patrick W.; Sees, Jennifer; Kovar, David R.; Gardel, Margaret L.

2013-01-01

Dynamic regulation of the actin cytoskeleton is required for diverse cellular processes. Proteins regulating the assembly kinetics of the cytoskeletal biopolymer F-actin are known to impact the architecture of actin cytoskeletal networks in vivo, but the underlying mechanisms are not well understood. Here, we demonstrate that changes to actin assembly kinetics with physiologically relevant proteins profilin and formin (mDia1 and Cdc12) have dramatic consequences on the architecture and gelation kinetics of otherwise biochemically identical cross-linked F-actin networks. Reduced F-actin nucleation rates promote the formation of a sparse network of thick bundles, whereas increased nucleation rates result in a denser network of thinner bundles. Changes to F-actin elongation rates also have marked consequences. At low elongation rates, gelation ceases and a solution of rigid bundles is formed. By contrast, rapid filament elongation accelerates dynamic arrest and promotes gelation with minimal F-actin density. These results are consistent with a recently developed model of how kinetic constraints regulate network architecture and underscore how molecular control of polymer assembly is exploited to modulate cytoskeletal architecture and material properties. PMID:23601318

The behavioral economics of will in recovery from addiction

PubMed Central

Monterosso, John; Ainslie, George

2007-01-01

Behavioral economic studies demonstrate that rewards are discounted proportionally with their delay (hyperbolic discounting). Hyperbolic discounting implies temporary preference for smaller rewards when they are imminent, and this concept has been widely considered by researchers interested in the causes of addictive behavior. Far less consideration has been given to the fact that systematic preference reversal also predicts various self-control phenomena, which may also be analyzed from a behavioral economic perspective. Here we summarize self-control phenomena predicted by hyperbolic discounting, particularly with application to the field of addiction. Of greatest interest is the phenomenon of choice bundling, an increase in motivation to wait for delayed rewards that can be expected to result from making choices in whole categories. Specifically, when a person’s expectations about her own future behavior are conditional upon her current behavior, the value of these expectations is added to the contingencies for the current behavior, resulting in reduced impulsivity. Hyperbolic discounting provides a bottom-up basis for the intuitive learning of choice bundling, the properties of which match common descriptions of willpower. We suggest that the bundling effect can also be discerned in the advice of 12-step programs. PMID:17034958

Moisture separator reheater with round tube bundle

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

Byerley, W. M.

1984-11-27

A moisture separator reheater having a central chamber with cylindrical wall protions and a generally round tube bundle, the tube bundle having arcuate plates disposed on each side of the bundle which form a wrapper on each side of the bundle and having a tongue and groove juncture between the wrapper and cylindrical wall portions to provide a seal therebetween and a track for installing and removing the tube bundle from the central chamber.

["Habitual" left branch block alternating with 2 "disguised" bracnch block].

PubMed

Lévy, S; Jullien, G; Mathieu, P; Mostefa, S; Gérard, R

1976-10-01

Two cases of alternating left bundle branch block and "masquerading block" (with left bundle branch morphology in the stnadard leads and right bundle branch block morphology in the precordial leads) were studied by serial tracings and his bundle electrocardiography. In case 1 "the masquerading" block was associated with a first degree AV block related to a prolongation of HV interval. This case is to our knowledge the first cas of alternating bundle branch block in which his bundle activity was recorded in man. In case 2, the patient had atrial fibrilation and His bundle recordings were performed while differents degrees of left bundle branch block were present: The mechanism of the alternation and the concept of "masquerading" block are discussed. It is suggested that this type of block represents a right bundle branch block associated with severe lesions of the "left system".

Bundled payments in orthopedic surgery.

PubMed

Bushnell, Brandon D

2015-02-01

As a result of reading this article, physicians should be able to: 1. Describe the concept of bundled payments and the potential applications of bundled payments in orthopedic surgery. 2. For specific situations, outline a clinical episode of care, determine the participants in a bundling situation, and define care protocols and pathways. 3. Recognize the importance of resource utilization management, quality outcome measurement, and combined economic-clinical value in determining the value of bundled payment arrangements. 4. Identify the implications of bundled payments for practicing orthopedists, as well as the legal issues and potential future directions of this increasingly popular alternative payment method. Bundled payments, the idea of paying a single price for a bundle of goods and services, is a financial concept familiar to most American consumers because examples appear in many industries. The idea of bundled payments has recently gained significant momentum as a financial model with the potential to decrease the significant current costs of health care. Orthopedic surgery as a field of medicine is uniquely positioned for success in an environment of bundled payments. This article reviews the history, logistics, and implications of the bundled payment model relative to orthopedic surgery. Copyright 2015, SLACK Incorporated.

Location-dependent correlation between tissue structure and the mechanical behaviour of the urinary bladder.

PubMed

Morales-Orcajo, Enrique; Siebert, Tobias; Böl, Markus

2018-05-25

The mechanical properties of the urinary bladder wall are important to understand its filling-voiding cycle in health and disease. However, much remains unknown about its mechanical properties, especially regarding regional heterogeneities and wall microstructure. The present study aimed to assess the regional differences in the mechanical properties and microstructure of the urinary bladder wall. Ninety (n=90) samples of porcine urinary bladder wall (ten samples from nine different locations) were mechanically and histologically analysed. Half of the samples (n=45) were equibiaxially tested within physiological conditions, and the other half, matching the sample location of the mechanical tests, was frozen, cryosectioned, and stained with Picro-Sirius red to differentiate smooth muscle cells, extracellular matrix, and fat. The bladder wall shows a non-linear stress-stretch relationship with hysteresis and softening effects. Regional differences were found in the mechanical response and in the microstructure. The trigone region presents higher peak stresses and thinner muscularis layer compared to the rest of the bladder. Furthermore, the ventral side of the bladder presents anisotropic characteristics, whereas the dorsal side features perfect isotropic behaviour. This response matches the smooth muscle fibre bundle orientation within the tunica muscularis. This layer, comprising approximately 78% of the wall thickness, is composed of two fibre bundle arrangements that are cross-oriented, one with respect to the other, varying the angle between them across the organ. That is, the ventral side presents a 60°/120° cross-orientation structure, while the muscle bundles were oriented perpendicular in the dorsal side. In the present study, we demonstrate that the mechanical properties and the microstructure of the urinary bladder wall are heterogeneous across the organ. The mechanical properties and the microstructure of the urinary bladder wall within nine specific locations matching explicitly the mechanical and structural variations have been examined. On the one hand, the results of this study contribute to the understanding of bladder mechanics and thus to their functional understanding of bladder filling and voiding. On the other hand, they are relevant to the fields of constitutive formulation of bladder tissue, whole bladder mechanics, and bladder-derived scaffolds i.e., tissue-engineering grafts. Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Diffusion-weighted imaging of mucinous carcinoma of the breast: evaluation of apparent diffusion coefficient and signal intensity in correlation with histologic findings.

PubMed

Woodhams, Reiko; Kakita, Satoko; Hata, Hirofumi; Iwabuchi, Keiichi; Umeoka, Shigeaki; Mountford, Carolyn E; Hatabu, Hiroto

2009-07-01

The purposes of this study were to compare the apparent diffusion coefficient (ADC) of mucinous carcinoma of the breast with that of other breast tumors and to analyze correlations between signal intensity on diffusion-weighted images and the histologic features of mucinous carcinoma. Two hundred seventy-six patients with 277 lesions, including 15 mucinous carcinomas (13 pure type, two mixed type), 204 other malignant tumors, and 58 benign lesions, were examined with 1.5-T MRI at b values of 0 and 1,500 s/mm(2). The correlations between cellularity and ADC, homogeneity of signal intensity on diffusion-weighted images, and histopathologic findings were analyzed. The difference was statistically significant (p < 0.05). The mean ADC of mucinous carcinoma (1.8 +/- 0.4 x 10(-3) mm(2)/s) was statistically higher than that of benign lesions (1.3+/- 0.3 x 10(-3) mm(2)/s) and other malignant tumors (0.9 +/- 0.2 x 10(-3) mm(2)/s) (p < 0.001). The ADC of pure type mucinous carcinoma (1.8 +/- 0.3 x 10(-3) mm(2)/s) was higher than that of mixed type mucinous carcinoma (1.2 +/- 0.2 x 10(-3) mm(2)/s) (p < 0.001) and other histologic types (p > 0.05). The correlation between mean cellularity and the ADC of mucinous carcinoma was significant (rho(s) = -0.754; p = 0.001). The homogeneity of signal intensity on diffusion-weighted images correlated with the homogeneity of histologic structures of mucinous carcinoma (p < 0.001; kappa = 0.826). Mucinous carcinoma can be clearly differentiated from other breast tumors on the basis of ADC. The low signal intensity of mucinous carcinoma on diffusion-weighted images appears to reflect the presence of mucin and low cellularity. High signal intensity on diffusion-weighted images may reflect the presence of fibrovascular bundles, increased cell density, or a combination of these features.

White matter damage in primary progressive aphasias: a diffusion tensor tractography study.

PubMed

Galantucci, Sebastiano; Tartaglia, Maria Carmela; Wilson, Stephen M; Henry, Maya L; Filippi, Massimo; Agosta, Federica; Dronkers, Nina F; Henry, Roland G; Ogar, Jennifer M; Miller, Bruce L; Gorno-Tempini, Maria Luisa

2011-10-01

Primary progressive aphasia is a clinical syndrome that encompasses three major phenotypes: non-fluent/agrammatic, semantic and logopenic. These clinical entities have been associated with characteristic patterns of focal grey matter atrophy in left posterior frontoinsular, anterior temporal and left temporoparietal regions, respectively. Recently, network-level dysfunction has been hypothesized but research to date has focused largely on studying grey matter damage. The aim of this study was to assess the integrity of white matter tracts in the different primary progressive aphasia subtypes. We used diffusion tensor imaging in 48 individuals: nine non-fluent, nine semantic, nine logopenic and 21 age-matched controls. Probabilistic tractography was used to identify bilateral inferior longitudinal (anterior, middle, posterior) and uncinate fasciculi (referred to as the ventral pathway); and the superior longitudinal fasciculus segmented into its frontosupramarginal, frontoangular, frontotemporal and temporoparietal components, (referred to as the dorsal pathway). We compared the tracts' mean fractional anisotropy, axial, radial and mean diffusivities for each tract in the different diagnostic categories. The most prominent white matter changes were found in the dorsal pathways in non-fluent patients, in the two ventral pathways and the temporal components of the dorsal pathways in semantic variant, and in the temporoparietal component of the dorsal bundles in logopenic patients. Each of the primary progressive aphasia variants showed different patterns of diffusion tensor metrics alterations: non-fluent patients showed the greatest changes in fractional anisotropy and radial and mean diffusivities; semantic variant patients had severe changes in all metrics; and logopenic patients had the least white matter damage, mainly involving diffusivity, with fractional anisotropy altered only in the temporoparietal component of the dorsal pathway. This study demonstrates that both careful dissection of the main language tracts and consideration of all diffusion tensor metrics are necessary to characterize the white matter changes that occur in the variants of primary progressive aphasia. These results highlight the potential value of diffusion tensor imaging as a new tool in the multimodal diagnostic evaluation of primary progressive aphasia.

Quantitative study of bundle size effect on thermal conductivity of single-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Feng, Ya; Inoue, Taiki; An, Hua; Xiang, Rong; Chiashi, Shohei; Maruyama, Shigeo

2018-05-01

Compared with isolated single-walled carbon nanotubes (SWNTs), thermal conductivity is greatly impeded in SWNT bundles; however, the measurement of the bundle size effect is difficult. In this study, the number of SWNTs in a bundle was determined based on the transferred horizontally aligned SWNTs on a suspended micro-thermometer to quantitatively study the effect of the bundle size on thermal conductivity. Increasing the bundle size significantly degraded the thermal conductivity. For isolated SWNTs, thermal conductivity was approximately 5000 ± 1000 W m-1 K-1 at room temperature, three times larger than that of the four-SWNT bundle. The logarithmical deterioration of thermal conductivity resulting from the increased bundle size can be attributed to the increased scattering rate with neighboring SWNTs based on the kinetic theory.

Deformation behavior and mechanical analysis of vertically aligned carbon nanotube (VACNT) bundles

NASA Astrophysics Data System (ADS)

Hutchens, Shelby B.

Vertically aligned carbon nanotubes (VACNTs) serve as integral components in a variety of applications including MEMS devices, energy absorbing materials, dry adhesives, light absorbing coatings, and electron emitters, all of which require structural robustness. It is only through an understanding of VACNT's structural mechanical response and local constitutive stress-strain relationship that future advancements through rational design may take place. Even for applications in which the structural response is not central to device performance, VACNTs must be sufficiently robust and therefore knowledge of their microstructure-property relationship is essential. This thesis first describes the results of in situ uniaxial compression experiments of 50 micron diameter cylindrical bundles of these complex, hierarchical materials as they undergo unusual deformation behavior. Most notably they deform via a series of localized folding events, originating near the bundle base, which propagate laterally and collapse sequentially from bottom to top. This deformation mechanism accompanies an overall foam-like stress-strain response having elastic, plateau, and densification regimes with the addition of undulations in the stress throughout the plateau regime that correspond to the sequential folding events. Microstructural observations indicate the presence of a strength gradient, due to a gradient in both tube density and alignment along the bundle height, which is found to play a key role in both the sequential deformation process and the overall stress-strain response. Using the complicated structural response as both motivation and confirmation, a finite element model based on a viscoplastic solid is proposed. This model is characterized by a flow stress relation that contains an initial peak followed by strong softening and successive hardening. Analysis of this constitutive relation results in capture of the sequential buckling phenomenon and a strength gradient effect. This combination of experimental and modeling approaches motivates discussion of the particular microstructural mechanisms and local material behavior that govern the non-trivial energy absorption via sequential, localized buckle formation in the VACNT bundles.

Spinal surgery: variations in health care costs and implications for episode-based bundled payments.

PubMed

Ugiliweneza, Beatrice; Kong, Maiying; Nosova, Kristin; Huang, Kevin T; Babu, Ranjith; Lad, Shivanand P; Boakye, Maxwell

2014-07-01

Retrospective, observational. To simulate what episodes of care in spinal surgery might look like in a bundled payment system and to evaluate the associated costs and characteristics. Episode-based payment bundling has received considerable attention as a potential method to help curb the rise in health care spending and is being investigated as a new payment model as part of the Affordable Care Act. Although earlier studies investigated bundled payments in a number of surgical settings, very few focused on spine surgery, specifically. We analyzed data from MarketScan. Patients were included in the study if they underwent cervical or lumbar spinal surgery during 2000-2009, had at least 2-year preoperative and 90-day postoperative follow-up data. Patients were grouped on the basis of their diagnosis-related group (DRG) and then tracked in simulated episodes-of-care/payment bundles that lasted for the duration of 30, 60, and 90 days after the discharge from the index-surgical hospitalization. The total cost associated with each episode-of-care duration was measured and characterized. A total of 196,918 patients met our inclusion criteria. Significant variation existed between DRGs, ranging from $11,180 (30-day bundle, DRG 491) to $107,642 (30-day bundle, DRG 456). There were significant cost variations within each individual DRG. Postdischarge care accounted for a relatively small portion of overall bundle costs (range, 4%-8% in 90-day bundles). Total bundle costs remained relatively flat as bundle-length increased (total average cost of 30-day bundle: $33,522 vs. $35,165 for 90-day bundle). Payments to hospitals accounted for the largest portion of bundle costs (76%). There exists significant variation in total health care costs for patients who undergo spinal surgery, even within a given DRG. Better characterization of impacts of a bundled payment system in spine surgery is important for understanding the costs of index procedure hospital, physician services, and postoperative care on potential future health care policy decision making. N/A.

Nurses' perceptions of a pressure ulcer prevention care bundle: a qualitative descriptive study.

PubMed

Roberts, Shelley; McInnes, Elizabeth; Wallis, Marianne; Bucknall, Tracey; Banks, Merrilyn; Chaboyer, Wendy

2016-01-01

Pressure ulcer prevention is a critical patient safety indicator for acute care hospitals. An innovative pressure ulcer prevention care bundle targeting patient participation in their care was recently tested in a cluster randomised trial in eight Australian hospitals. Understanding nurses' perspectives of such an intervention is imperative when interpreting results and translating evidence into practice. As part of a process evaluation for the main trial, this study assessed nurses' perceptions of the usefulness and impact of a pressure ulcer prevention care bundle intervention on clinical practice. This qualitative descriptive study involved semi-structured interviews with nursing staff at four Australian hospitals that were intervention sites for a cluster randomised trial testing a pressure ulcer prevention care bundle. Four to five participants were purposively sampled at each site. A trained interviewer used a semi-structured interview guide to question participants about their perceptions of the care bundle. Interviews were digitally recorded, transcribed and analysed using thematic analysis. Eighteen nurses from four hospitals participated in the study. Nurses' perceptions of the intervention are described in five themes: 1) Awareness of the pressure ulcer prevention care bundle and its similarity to current practice; 2) Improving awareness, communication and participation with the pressure ulcer prevention care bundle; 3) Appreciating the positive aspects of patient participation in care; 4) Perceived barriers to engaging patients in the pressure ulcer prevention care bundle; and 5) Partnering with nursing staff to facilitate pressure ulcer prevention care bundle implementation. Overall, nurses found the care bundle feasible and acceptable. They identified a number of benefits from the bundle, including improved communication, awareness and participation in pressure ulcer prevention care among patients and staff. However, nurses thought the care bundle was not appropriate or effective for all patients, such as those who were cognitively impaired. Perceived enablers to implementation of the bundle included facilitation through effective communication and dissemination of evidence about the care bundle; strong leadership and ability to influence staff behaviour; and simplicity of the care bundle.

MOX fuel assembly design

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

Reese, A.P.; Crowther, R.L. Jr.

1992-02-18

This patent describes improvement in a boiling water reactor core having a plurality of vertically upstanding fuel bundles; each fuel bundle containing longitudinally extending sealed rods with fissile material therein; the improvement comprises the fissile material including a mixture of uranium and recovered plutonium in rods of the fuel bundle at locations other than the corners of the fuel bundle; and, neutron absorbing material being located in rods of the fuel bundle at rod locations adjacent the corners of the fuel bundles whereby the neutron absorbing material has decreased shielding from the plutonium and maximum exposure to thermal neutrons formore » shaping the cold reactivity shutdown zone in the fuel bundle.« less

Toward a better understanding of the savant brain.

PubMed

Corrigan, Neva M; Richards, Todd L; Treffert, Darold A; Dager, Stephen R

2012-08-01

The objectives of this study are to investigate the neuroanatomy, regional brain connectivity, and neurochemistry of a prodigious artistic savant; to place these findings within the context of existing neuroimaging literature of savant syndrome; and to discuss the utility of newer imaging modalities to extend our current understanding of mechanisms underlying savant skills. High-resolution magnetic resonance (MR) imaging, J-resolved MR spectroscopy, and diffusion tensor imaging data were acquired during a single scanning session for a 63-year-old male autistic savant with prodigious artistic skills. Regional and compartmental brain volumes, N-acetyl aspartate, choline, creatine, glutamate and γ-aminobutyric acid concentrations, fractional anisotropy values, and white matter bundle volumes as well as axial, radial, and mean diffusivities were calculated. No gross anatomical differences were observed. By morphological assessment, cerebral volume (1362 mL) was larger than normative literature values for adult males. The corpus callosum was intact and did not exhibit abnormal structural features. The right cerebral hemisphere was 1.9% larger than the left hemisphere; the right amygdala and right caudate nuclei were 24% and 9.9% larger, respectively, compared with the left side. In contrast, the putamen was 8.3% larger on the left side. Fractional anisotropy was increased on the right side as compared with the left for 4 of the 5 bilateral regions studied (the amygdala, caudate, frontal lobe, and hippocampus). Fiber tract bundle volumes were larger on the right side for the amygdala, hippocampus, frontal lobe, and occipital lobe. Both the left and the right hippocampi had substantially increased axial and mean diffusivities as compared with those of a comparison sample of nonsavant adult males. The corpus callosum and left amygdala also exhibited high axial, radial, and mean diffusivities. MR spectroscopy revealed markedly decreased γ-aminobutyric acid and glutamate in the parietal lobe. Although examination of brain gross morphometry demonstrated no clinically remarkable abnormalities, utilization of conventional as well as newer MR imaging technologies revealed several atypical structural and chemical features that may be involved in the special skills of this prodigious savant. The multimodal imaging approach presented in this study is suitable for the evaluation of larger samples of savants with a diverse range of talents to investigate common brain features that may underlie the exceptional cognitive capabilities characteristic of savant syndrome. Given the high co-occurrence of the two syndromes, elucidating the underlying neurophysiologic basis of savant syndrome may also lead to a better understanding of autism spectrum disorder. Copyright © 2012 Elsevier Inc. All rights reserved.

Polycation induced actin bundles.

PubMed

Muhlrad, Andras; Grintsevich, Elena E; Reisler, Emil

2011-04-01

Three polycations, polylysine, the polyamine spermine and the polycationic protein lysozyme were used to study the formation, structure, ionic strength sensitivity and dissociation of polycation-induced actin bundles. Bundles form fast, simultaneously with the polymerization of MgATP-G-actins, upon the addition of polycations to solutions of actins at low ionic strength conditions. This indicates that nuclei and/or nascent filaments bundle due to attractive, electrostatic effect of polycations and the neutralization of repulsive interactions of negative charges on actin. The attractive forces between the filaments are strong, as shown by the low (in nanomolar range) critical concentration of their bundling at low ionic strength. These bundles are sensitive to ionic strength and disassemble partially in 100 mM NaCl, but both the dissociation and ionic strength sensitivity can be countered by higher polycation concentrations. Cys374 residues of actin monomers residing on neighboring filaments in the bundles can be cross-linked by the short span (5.4Å) MTS-1 (1,1-methanedyl bismethanethiosulfonate) cross-linker, which indicates a tight packing of filaments in the bundles. The interfilament cross-links, which connect monomers located on oppositely oriented filaments, prevent disassembly of bundles at high ionic strength. Cofilin and the polysaccharide polyanion heparin disassemble lysozyme induced actin bundles more effectively than the polylysine-induced bundles. The actin-lysozyme bundles are pathologically significant as both proteins are found in the pulmonary airways of cystic fibrosis patients. Their bundles contribute to the formation of viscous mucus, which is the main cause of breathing difficulties and eventual death in this disorder. Copyright © 2011 Elsevier B.V. All rights reserved.

Post-natal molecular adaptations in anteromedial and posterolateral bundles of the ovine anterior cruciate ligament: one structure with two parts or two distinct ligaments?

PubMed

Huebner, Kyla D; O'Brien, Etienne J O; Heard, Bryan J; Chung, May; Achari, Yamini; Shrive, Nigel G; Frank, Cyril B

2012-01-01

The human anterior cruciate ligament (ACL) is a composite structure of two anatomically distinct bundles: an anteromedial (AM) and posterolateral (PL) bundles. Tendons are often used as autografts for surgical reconstruction of ACL following severe injury. However, despite successful surgical reconstruction, some people experience re-rupture and later development of osteoarthritis. Understanding the structure and molecular makeup of normal ACL is essential for its optimal replacement. Reportedly the two bundles display different tensions throughout joint motion and may be fundamentally different. This study assessed the similarities and differences in ultrastructure and molecular composition of the AM and PL bundles to test the hypothesis that the two bundles of the ACL develop unique characteristics with maturation. ACLs from nine mature and six immature sheep were compared. The bundles were examined for mRNA and protein levels of collagen types I, III, V, and VI, and two proteoglycans. The fibril diameter composition of the two bundles was examined with transmission electron microscopy. Maturation does alter the molecular and structural composition of the two bundles of ACL. Although the PL band appears to mature slower than the AM band, no significant differences were detected between the bundles in the mature animals. We thus reject our hypothesis that the two ACL bundles are distinct. The two anatomically distinct bundles of the sheep ACL can be considered as two parts of one structure at maturity and material that would result in a structure of similar functionality can be used to replace each ACL bundle in the sheep.

Mean Green operators of deformable fiber networks embedded in a compliant matrix and property estimates

NASA Astrophysics Data System (ADS)

Franciosi, Patrick; Spagnuolo, Mario; Salman, Oguz Umut

2018-04-01

Composites comprising included phases in a continuous matrix constitute a huge class of meta-materials, whose effective properties, whether they be mechanical, physical or coupled, can be selectively optimized by using appropriate phase arrangements and architectures. An important subclass is represented by "network-reinforced matrices," say those materials in which one or more of the embedded phases are co-continuous with the matrix in one or more directions. In this article, we present a method to study effective properties of simple such structures from which more complex ones can be accessible. Effective properties are shown, in the framework of linear elasticity, estimable by using the global mean Green operator for the entire embedded fiber network which is by definition through sample spanning. This network operator is obtained from one of infinite planar alignments of infinite fibers, which the network can be seen as an interpenetrated set of, with the fiber interactions being fully accounted for in the alignments. The mean operator of such alignments is given in exact closed form for isotropic elastic-like or dielectric-like matrices. We first exemplify how these operators relevantly provide, from classic homogenization frameworks, effective properties in the case of 1D fiber bundles embedded in an isotropic elastic-like medium. It is also shown that using infinite patterns with fully interacting elements over their whole influence range at any element concentration suppresses the dilute approximation limit of these frameworks. We finally present a construction method for a global operator of fiber networks described as interpenetrated such bundles.

Long-term diffuse phosphorus pollution dynamics under the combined influence of land use and soil property variations.

PubMed

Huang, Haobo; Ouyang, Wei; Wu, Haotian; Liu, Hongbin; Andrea, Critto

2017-02-01

Analyses of the spatial-temporal distribution of diffuse pollution in agricultural regions are essential to the sustained management of water resources. Although nutrients, such as phosphorus fertilizers, can promote crop growth while improving soil fertility, excessive nutrient inputs can produce diffuse pollution, which may results in water quality degradation. The objective of this paper is to employ the SWAT (Soil and Water Assessment Tool) to estimate diffuse P effects on temporal and spatial distributions for a typical agricultural watershed and to identify the conjunct and independent influences of long-term land use and soil properties variation on diffuse P. With the validated model, the four-period simulation results (from 1979 to 2009) indicate that land use changes from agricultural development increased diffuse P yields. However, regarding updated soil properties, no significant differences of P yield were found between 1979 and 2009, demonstrating that impact of the cropland expansion were naturalized with soil property variations. An F-test was employed to assess the essentiality of all of the variables examined during the simulation period, and the test results indicated that diffuse P loading was more sensitive to soil properties than to land use. Before the P pollution control project about the land use optimization planning, it is more effective to distinguish the impacts of land use and soil properties. Copyright © 2016 Elsevier B.V. All rights reserved.

Statistical variances of diffusional properties from ab initio molecular dynamics simulations

NASA Astrophysics Data System (ADS)

He, Xingfeng; Zhu, Yizhou; Epstein, Alexander; Mo, Yifei

2018-12-01

Ab initio molecular dynamics (AIMD) simulation is widely employed in studying diffusion mechanisms and in quantifying diffusional properties of materials. However, AIMD simulations are often limited to a few hundred atoms and a short, sub-nanosecond physical timescale, which leads to models that include only a limited number of diffusion events. As a result, the diffusional properties obtained from AIMD simulations are often plagued by poor statistics. In this paper, we re-examine the process to estimate diffusivity and ionic conductivity from the AIMD simulations and establish the procedure to minimize the fitting errors. In addition, we propose methods for quantifying the statistical variance of the diffusivity and ionic conductivity from the number of diffusion events observed during the AIMD simulation. Since an adequate number of diffusion events must be sampled, AIMD simulations should be sufficiently long and can only be performed on materials with reasonably fast diffusion. We chart the ranges of materials and physical conditions that can be accessible by AIMD simulations in studying diffusional properties. Our work provides the foundation for quantifying the statistical confidence levels of diffusion results from AIMD simulations and for correctly employing this powerful technique.

Nonabelian Bundle Gerbes, Their Differential Geometry and Gauge Theory

NASA Astrophysics Data System (ADS)

Aschieri, Paolo; Cantini, Luigi; Jurčo, Branislav

2005-03-01

Bundle gerbes are a higher version of line bundles, we present nonabelian bundle gerbes as a higher version of principal bundles. Connection, curving, curvature and gauge transformations are studied both in a global coordinate independent formalism and in local coordinates. These are the gauge fields needed for the construction of Yang-Mills theories with 2-form gauge potential.

Microstructural abnormalities of the brain white matter in attention-deficit/hyperactivity disorder

PubMed Central

Chen, Lizhou; Huang, Xiaoqi; Lei, Du; He, Ning; Hu, Xinyu; Chen, Ying; Li, Yuanyuan; Zhou, Jinbo; Guo, Lanting; Kemp, Graham J.; Gong, Qiyong

2015-01-01

Background Attention-deficit/hyperactivity disorder (ADHD) is an early-onset neurodevelopmental disorder with multiple behavioural problems and executive dysfunctions for which neuroimaging studies have reported a variety of abnormalities, with inconsistencies partly owing to confounding by medication and concurrent psychiatric disease. We aimed to investigate the microstructural abnormalities of white matter in unmedicated children and adolescents with pure ADHD and to explore the association between these abnormalities and behavioural symptoms and executive functions. Methods We assessed children and adolescents with ADHD and healthy controls using psychiatric interviews. Behavioural problems were rated using the revised Conners’ Parent Rating Scale, and executive functions were measured using the Stroop Colour-Word Test and the Wisconsin Card Sorting test. We acquired diffusion tensor imaging data using a 3 T MRI system, and we compared diffusion parameters, including fractional anisotropy (FA) and mean, axial and radial diffusivities, between the 2 groups. Results Thirty-three children and adolescents with ADHD and 35 healthy controls were included in our study. In patients compared with controls, FA was increased in the left posterior cingulum bundle as a result of both increased axial diffusivity and decreased radial diffusivity. In addition, the averaged FA of the cluster in this region correlated with behavioural measures as well as executive function in patients with ADHD. Limitations This study was limited by its cross-sectional design and small sample size. The cluster size of the significant result was small. Conclusion Our findings suggest that white matter abnormalities within the limbic network could be part of the neural underpinning of behavioural problems and executive dysfunction in patients with ADHD. PMID:25853285

In-situ polymerisation of fully bioresorbable polycaprolactone/phosphate glass fibre composites: In vitro degradation and mechanical properties.

PubMed

Chen, Menghao; Parsons, Andrew J; Felfel, Reda M; Rudd, Christopher D; Irvine, Derek J; Ahmed, Ifty

2016-06-01

Fully bioresorbable composites have been investigated in order to replace metal implant plates used for hard tissue repair. Retention of the composite mechanical properties within a physiological environment has been shown to be significantly affected due to loss of the integrity of the fibre/matrix interface. This study investigated phosphate based glass fibre (PGF) reinforced polycaprolactone (PCL) composites with 20%, 35% and 50% fibre volume fractions (Vf) manufactured via an in-situ polymerisation (ISP) process and a conventional laminate stacking (LS) followed by compression moulding. Reinforcing efficiency between the LS and ISP manufacturing process was compared, and the ISP composites revealed significant improvements in mechanical properties when compared to LS composites. The degradation profiles and mechanical properties were monitored in phosphate buffered saline (PBS) at 37°C for 28 days. ISP composites revealed significantly less media uptake and mass loss (p<0.001) throughout the degradation period. The initial flexural properties of ISP composites were substantially higher (p<0.0001) than those of the LS composites, which showed that the ISP manufacturing process provided a significantly enhanced reinforcement effect than the LS process. During the degradation study, statistically higher flexural property retention profiles were also seen for the ISP composites compared to LS composites. SEM micrographs of fracture surfaces for the LS composites revealed dry fibre bundles and poor fibre dispersion with polymer rich zones, which indicated poor interfacial bonding, distribution and adhesion. In contrast, evenly distributed fibres without dry fibre bundles or polymer rich zones, were clearly observed for the ISP composite samples, which showed that a superior fibre/matrix interface was achieved with highly improved adhesion. Copyright © 2015 Elsevier Ltd. All rights reserved.

Bundled payment fails to gain a foothold In California: the experience of the IHA bundled payment demonstration.

PubMed

Ridgely, M Susan; de Vries, David; Bozic, Kevin J; Hussey, Peter S

2014-08-01

To determine whether bundled payment could be an effective payment model for California, the Integrated Healthcare Association convened a group of stakeholders (health plans, hospitals, ambulatory surgery centers, physician organizations, and vendors) to develop, through a consensus process, the methods and means of implementing bundled payment. In spite of a high level of enthusiasm and effort, the pilot did not succeed in its goal to implement bundled payment for orthopedic procedures across multiple payers and hospital-physician partners. An evaluation of the pilot documented a number of barriers, such as administrative burden, state regulatory uncertainty, and disagreements about bundle definition and assumption of risk. Ultimately, few contracts were signed, which resulted in insufficient volume to test hypotheses about the impact of bundled payment on quality and costs. Although bundled payment failed to gain a foothold in California, the evaluation provides lessons for future bundled payment initiatives. Project HOPE—The People-to-People Health Foundation, Inc.

Double-bundle ACL reconstruction can improve rotational stability.

PubMed

Yagi, Masayoshi; Kuroda, Ryosuke; Nagamune, Kouki; Yoshiya, Shinichi; Kurosaka, Masahiro

2007-01-01

Double-bundle anterior cruciate ligament (ACL) reconstruction reproduces anteromedial and posterolateral bundles, and thus has theoretical advantages over conventional single-bundle reconstruction in controlling rotational torque in vitro. However, its superiority in clinical practice has not been proven. We analyzed rotational stability with three reconstruction techniques in 60 consecutive patients who were randomly divided into three groups (double-bundle, anteromedial single-bundle, posterolateral single-bundle). In the reconstructive procedure, the hamstring tendon was harvested and used as a free tendon graft. Followup examinations were performed 1 year after surgery. Anteroposterior laxity of the knee was examined with a KT-1000 arthrometer, whereas rotatory instability, as elicited by the pivot shift test, was assessed using a new measurement system incorporating three-dimensional electromagnetic sensors. Routine clinical evaluations, including KT examination, demonstrated no differences among the three groups. However, using the new measurement system, patients with double-bundle ACL reconstruction showed better pivot shift control of complex instability than patients with anteromedial and posterolateral single-bundle reconstruction.

Influence of diffuse reflectance measurement accuracy on the scattering coefficient in determination of optical properties with integrating sphere optics (a secondary publication).

PubMed

Horibe, Takuro; Ishii, Katsunori; Fukutomi, Daichi; Awazu, Kunio

2015-12-30

An estimation error of the scattering coefficient of hemoglobin in the high absorption wavelength range has been observed in optical property calculations of blood-rich tissues. In this study, the relationship between the accuracy of diffuse reflectance measurement in the integrating sphere and calculated scattering coefficient was evaluated with a system to calculate optical properties combined with an integrating sphere setup and the inverse Monte Carlo simulation. Diffuse reflectance was measured with the integrating sphere using a small incident port diameter and optical properties were calculated. As a result, the estimation error of the scattering coefficient was improved by accurate measurement of diffuse reflectance. In the high absorption wavelength range, the accuracy of diffuse reflectance measurement has an effect on the calculated scattering coefficient.

Force-Induced Unravelling of DNA Origami.

PubMed

Engel, Megan C; Smith, David M; Jobst, Markus A; Sajfutdinow, Martin; Liedl, Tim; Romano, Flavio; Rovigatti, Lorenzo; Louis, Ard A; Doye, Jonathan P K

2018-05-31

The mechanical properties of DNA nanostructures are of widespread interest as applications that exploit their stability under constant or intermittent external forces become increasingly common. We explore the force response of DNA origami in comprehensive detail by combining AFM single molecule force spectroscopy experiments with simulations using oxDNA, a coarse-grained model of DNA at the nucleotide level, to study the unravelling of an iconic origami system: the Rothemund tile. We contrast the force-induced melting of the tile with simulations of an origami 10-helix bundle. Finally, we simulate a recently-proposed origami biosensor, whose function takes advantage of origami behaviour under tension. We observe characteristic stick-slip unfolding dynamics in our force-extension curves for both the Rothemund tile and the helix bundle and reasonable agreement with experimentally observed rupture forces for these systems. Our results highlight the effect of design on force response: we observe regular, modular unfolding for the Rothemund tile that contrasts with strain-softening of the 10-helix bundle which leads to catastropic failure under monotonically increasing force. Further, unravelling occurs straightforwardly from the scaffold ends inwards for the Rothemund tile, while the helix bundle unfolds more nonlinearly. The detailed visualization of the yielding events provided by simulation allows preferred pathways through the complex unfolding free-energy landscape to be mapped, as a key factor in determining relative barrier heights is the extensional release per base pair broken. We shed light on two important questions: how stable DNA nanostructures are under external forces; and what design principles can be applied to enhance stability.

Thin-film diffusion brazing of titanium alloys

NASA Technical Reports Server (NTRS)

Mikus, E. B.

1972-01-01

A thin film diffusion brazing technique for joining titanium alloys by use of a Cu intermediate is described. The method has been characterized in terms of static and dynamic mechanical properties on Ti-6Al-4V alloy. These include tensile, fracture toughness, stress corrosion, shear, corrosion fatigue, mechanical fatigue and acoustic fatigue. Most of the properties of titanium joints formed by thin film diffusion brazing are equal or exceed base metal properties. The advantages of thin film diffusion brazing over solid state diffusion bonding and brazing with conventional braze alloys are discussed. The producibility advantages of this process over others provide the potential for producing high efficiency joints in structural components of titanium alloys for the minimum cost.

Quantifying the transport properties of lipid mesophases by theoretical modelling of diffusion experiments

NASA Astrophysics Data System (ADS)

Antognini, Luca M.; Assenza, Salvatore; Speziale, Chiara; Mezzenga, Raffaele

2016-08-01

Lyotropic Liquid Crystals (LLCs) are a class of lipid-based membranes with a strong potential for drug-delivery employment. The characterization and control of their transport properties is a central issue in this regard, and has recently prompted a notable volume of research on the topic. A promising experimental approach is provided by the so-called diffusion setup, where the drug molecules diffuse from a feeding chamber filled with water to a receiving one passing through a LLC. In the present work we provide a theoretical framework for the proper description of this setup, and validate it by means of targeted experiments. Due to the inhomogeneity of the system, a rich palette of different diffusion dynamics emerges from the interplay of the different time- and lengthscales thereby present. Our work paves the way to the employment of diffusion experiments to quantitatively characterize the transport properties of LLCs, and provides the basic tools for device diffusion setups with controlled kinetic properties.

Intraluminal laser speckle rheology using an omni-directional viewing catheter

PubMed Central

Wang, Jing; Hosoda, Masaki; Tshikudi, Diane M.; Hajjarian, Zeinab; Nadkarni, Seemantini K.

2016-01-01

A number of disease conditions in luminal organs are associated with alterations in tissue mechanical properties. Here, we report a new omni-directional viewing Laser Speckle Rheology (LSR) catheter for mapping the mechanical properties of luminal organs without the need for rotational motion. The LSR catheter incorporates multiple illumination fibers, an optical fiber bundle and a multi-faceted mirror to permit omni-directional viewing of the luminal wall. By retracting the catheter using a motor-drive assembly, cylindrical maps of tissue mechanical properties are reconstructed. Evaluation conducted in a test phantom with circumferentially-varying mechanical properties demonstrates the capability of the LSR catheter for the accurate mechanical assessment of luminal organs. PMID:28101407

Numerical Simulations on the Laser Spot Welding of Zirconium Alloy Endplate for Nuclear Fuel Bundle Assembly

NASA Astrophysics Data System (ADS)

Satyanarayana, G.; Narayana, K. L.; Boggarapu, Nageswara Rao

2018-03-01

In the nuclear industry, a critical welding process is joining of an end plate to a fuel rod to form a fuel bundle. Literature on zirconium welding in such a critical operation is limited. A CFD model is developed and performed for the three-dimensional non-linear thermo-fluid analysis incorporating buoyancy and Marnangoni stress and specifying temperature dependent properties to predict weld geometry and temperature field in and around the melt pool of laser spot during welding of a zirconium alloy E110 endplate with a fuel rod. Using this method, it is possible to estimate the weld pool dimensions for the specified laser power and laser-on-time. The temperature profiles will estimate the HAZ and microstructure. The adequacy of generic nature of the model is validated with existing experimental data.

Heat Transfer Analysis in Wire Bundles for Aerospace Vehicles

NASA Technical Reports Server (NTRS)

Rickman, S. L.; Iamello, C. J.

2016-01-01

Design of wiring for aerospace vehicles relies on an understanding of "ampacity" which refers to the current carrying capacity of wires, either, individually or in wire bundles. Designers rely on standards to derate allowable current flow to prevent exceedance of wire temperature limits due to resistive heat dissipation within the wires or wire bundles. These standards often add considerable margin and are based on empirical data. Commercial providers are taking an aggressive approach to wire sizing which challenges the conventional wisdom of the established standards. Thermal modelling of wire bundles may offer significant mass reduction in a system if the technique can be generalized to produce reliable temperature predictions for arbitrary bundle configurations. Thermal analysis has been applied to the problem of wire bundles wherein any or all of the wires within the bundle may carry current. Wire bundles present analytical challenges because the heat transfer path from conductors internal to the bundle is tortuous, relying on internal radiation and thermal interface conductance to move the heat from within the bundle to the external jacket where it can be carried away by convective and radiative heat transfer. The problem is further complicated by the dependence of wire electrical resistivity on temperature. Reduced heat transfer out of the bundle leads to higher conductor temperatures and, hence, increased resistive heat dissipation. Development of a generalized wire bundle thermal model is presented and compared with test data. The steady state heat balance for a single wire is derived and extended to the bundle configuration. The generalized model includes the effects of temperature varying resistance, internal radiation and thermal interface conductance, external radiation and temperature varying convective relief from the free surface. The sensitivity of the response to uncertainties in key model parameters is explored using Monte Carlo analysis.

78 FR 76987 - Adjustment of Determination of Compulsory License Rates for Mechanical and Digital Phonorecords

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-20

... service bundles, music bundles, paid locker services, and purchased content locker services. The technical... downloads, limited offerings, mixed service bundles, music bundles, paid locker services, and purchased...

Characterization of chronic vocal fold scarring in a rabbit model.

PubMed

Rousseau, Bernard; Hirano, Shigeru; Chan, Roger W; Welham, Nathan V; Thibeault, Susan L; Ford, Charles N; Bless, Diane M

2004-03-01

The purpose of the current study was to assess the histologic and rheologic properties of the scarred vocal fold lamina propria during a chronic phase of wound repair in a rabbit model. Eighteen rabbit larynges were scarred using a procedure that involved stripping the vocal fold lamina propria down to the thyroarytenoid muscle, using 3-mm microforceps. The approximate dimension of injury to the vocal fold was 3 x 1.5 x 0.5 mm [length x width x depth]. At 6 months postoperatively, histologic analysis of the scarred and control lamina propria in eight of these rabbits was completed for collagen, procollagen, elastin, and hyaluronic acid. Compared with control samples, scarred tissue samples revealed fragmented and disorganized elastin fibers. Additionally, collagen was significantly increased, organized, and formed thick bundles in the scarred vocal fold lamina propria. Measurements of the viscoelastic shear properties of the scarred and control lamina propria in the remaining 10 rabbits revealed increased elastic shear modulus (G') in 8 of 10 scarred samples and increased dynamic viscosity (eta') in 9 of 10 scarred samples. Although rheologic differences were not statistically significant, they revealed that on average, scarred samples were stiffer and more viscous than the normal controls. Histologic data are interpreted as indicating that by 6 months postinjury, the scarred rabbit vocal fold has reached a mature phase of wound repair, characterized by an increased, organized, and thick bundle collagen matrix. Rheologic data are interpreted as providing support for the potential role of increased, thick bundle collagen, and a disorganized elastin network on shear stiffness and dynamic viscosity in the chronic vocal fold scar. Based on these results, a 6-month postoperative time frame is proposed for future studies of chronic vocal fold scarring using the rabbit animal model.

Cost-Effectiveness of a Central Venous Catheter Care Bundle

PubMed Central

Halton, Kate A.; Cook, David; Paterson, David L.; Safdar, Nasia; Graves, Nicholas

2010-01-01

Background A bundled approach to central venous catheter care is currently being promoted as an effective way of preventing catheter-related bloodstream infection (CR-BSI). Consumables used in the bundled approach are relatively inexpensive which may lead to the conclusion that the bundle is cost-effective. However, this fails to consider the nontrivial costs of the monitoring and education activities required to implement the bundle, or that alternative strategies are available to prevent CR-BSI. We evaluated the cost-effectiveness of a bundle to prevent CR-BSI in Australian intensive care patients. Methods and Findings A Markov decision model was used to evaluate the cost-effectiveness of the bundle relative to remaining with current practice (a non-bundled approach to catheter care and uncoated catheters), or use of antimicrobial catheters. We assumed the bundle reduced relative risk of CR-BSI to 0.34. Given uncertainty about the cost of the bundle, threshold analyses were used to determine the maximum cost at which the bundle remained cost-effective relative to the other approaches to infection control. Sensitivity analyses explored how this threshold alters under different assumptions about the economic value placed on bed-days and health benefits gained by preventing infection. If clinicians are prepared to use antimicrobial catheters, the bundle is cost-effective if national 18-month implementation costs are below $1.1 million. If antimicrobial catheters are not an option the bundle must cost less than $4.3 million. If decision makers are only interested in obtaining cash-savings for the unit, and place no economic value on either the bed-days or the health benefits gained through preventing infection, these cost thresholds are reduced by two-thirds. Conclusions A catheter care bundle has the potential to be cost-effective in the Australian intensive care setting. Rather than anticipating cash-savings from this intervention, decision makers must be prepared to invest resources in infection control to see efficiency improvements. PMID:20862246

Cost-effectiveness of a central venous catheter care bundle.

PubMed

Halton, Kate A; Cook, David; Paterson, David L; Safdar, Nasia; Graves, Nicholas

2010-09-17

A bundled approach to central venous catheter care is currently being promoted as an effective way of preventing catheter-related bloodstream infection (CR-BSI). Consumables used in the bundled approach are relatively inexpensive which may lead to the conclusion that the bundle is cost-effective. However, this fails to consider the nontrivial costs of the monitoring and education activities required to implement the bundle, or that alternative strategies are available to prevent CR-BSI. We evaluated the cost-effectiveness of a bundle to prevent CR-BSI in Australian intensive care patients. A Markov decision model was used to evaluate the cost-effectiveness of the bundle relative to remaining with current practice (a non-bundled approach to catheter care and uncoated catheters), or use of antimicrobial catheters. We assumed the bundle reduced relative risk of CR-BSI to 0.34. Given uncertainty about the cost of the bundle, threshold analyses were used to determine the maximum cost at which the bundle remained cost-effective relative to the other approaches to infection control. Sensitivity analyses explored how this threshold alters under different assumptions about the economic value placed on bed-days and health benefits gained by preventing infection. If clinicians are prepared to use antimicrobial catheters, the bundle is cost-effective if national 18-month implementation costs are below $1.1 million. If antimicrobial catheters are not an option the bundle must cost less than $4.3 million. If decision makers are only interested in obtaining cash-savings for the unit, and place no economic value on either the bed-days or the health benefits gained through preventing infection, these cost thresholds are reduced by two-thirds. A catheter care bundle has the potential to be cost-effective in the Australian intensive care setting. Rather than anticipating cash-savings from this intervention, decision makers must be prepared to invest resources in infection control to see efficiency improvements.

Adhering to a national surgical care bundle reduces the risk of surgical site infections

PubMed Central

Hopmans, Titia E. M.; Soetens, Loes C.; Wille, Jan C.; Geerlings, Suzanne E.; Vos, Margreet C.; van Benthem, Birgit H. B.; de Greeff, Sabine C.

2017-01-01

Background In 2008, a bundle of care to prevent Surgical Site Infections (SSIs) was introduced in the Netherlands. The bundle consisted of four elements: antibiotic prophylaxis according to local guidelines, no hair removal, normothermia and ‘hygiene discipline’ in the operating room (i.e. number of door movements). Dutch hospitals were advised to implement the bundle and to measure the outcome. This study’s goal was to assess how effective the bundle was in reducing SSI risk. Methods Hospitals assessed whether their staff complied with each of the bundle elements and voluntary reported compliance data to the national SSI surveillance network (PREZIES). From PREZIES data, we selected data from 2009 to 2014 relating to 13 types of surgical procedures. We excluded surgeries with missing (non)compliance data, and calculated for each remaining surgery with reported (non)compliance data the level of compliance with the bundle (that is, being compliant with 0, 1, 2, 3, or 4 of the elements). Subsequently, we used this level of compliance to assess the effect of bundle compliance on the SSI risk, using multilevel logistic regression techniques. Results 217 489 surgeries were included, of which 62 486 surgeries (29%) had complete bundle reporting. Within this group, the SSI risk was significantly lower for surgeries with complete bundle compliance compared to surgeries with lower compliance levels. Odds ratios ranged from 0.63 to 0.86 (risk reduction of 14% to 37%), while a 13% risk reduction was demonstrated for each point increase in compliance-level. Sensitivity analysis indicated that due to analysing reported bundles only, we probably underestimated the total effect of implementing the bundle. Conclusions This study demonstrated that adhering to a surgical care bundle significantly reduced the risk of SSIs. Reporting of and compliance with the bundle compliance can, however, still be improved. Therefore an even greater effect might be achieved. PMID:28877223

Regional white matter development in very preterm infants: perinatal predictors and early developmental outcomes.

PubMed

Rogers, Cynthia E; Smyser, Tara; Smyser, Christopher D; Shimony, Joshua; Inder, Terrie E; Neil, Jeffrey J

2016-01-01

Preterm infants are at risk for white matter (WM) injury and adverse neurodevelopmental outcomes. Serial diffusion tensor magnetic resonance imaging data were obtained from very preterm infants (N = 78) born <30 wk gestation imaged up to four times from 26-42 wk postmenstrual age. Slopes were calculated for fractional anisotropy (FA) and mean diffusivity (MD) within regions of interest for infants with ≥2 scans (N = 50). Sixty-five children underwent neurodevelopmental testing at 2 y of age. FA slope for the posterior limb of the internal capsule was greater than other regions. The anterior limb of the internal capsule (ALIC), corpus callosum, and optic radiations demonstrated greater FA slope with increasing gestational age. Infants with patent ductus arteriosus had lower FA slope in the ALIC. MD slope was lower with prolonged ventilation or lack of antenatal steroids. At 2 y of age, lower motor scores were associated with lower FA in the left but higher FA in the right inferior temporal lobe at term-equivalent age. Better social-emotional competence was related to lower FA in the left cingulum bundle. This study demonstrates regional variability in the susceptibility/sensitivity of WM maturation to perinatal factors and relationships between altered diffusion measures and developmental outcomes in preterm neonates.

Lexical bundles in an advanced INTOCSU writing class and engineering texts: A functional analysis

NASA Astrophysics Data System (ADS)

Alquraishi, Mohammed Abdulrahman

The purpose of this study is to investigate the functions of lexical bundles in two corpora: a corpus of engineering academic texts and a corpus of IEP advanced writing class texts. This study is concerned with the nature of formulaic language in Pathway IEPs and engineering texts, and whether those types of texts show similar or distinctive formulaic functions. Moreover, the study looked into lexical bundles found in an engineering 1.26 million-word corpus and an ESL 65000-word corpus using a concordancing program. The study then analyzed the functions of those lexical bundles and compared them statistically using chi-square tests. Additionally, the results of this investigation showed 236 unique frequent lexical bundles in the engineering corpus and 37 bundles in the pathway corpus. Also, the study identified several differences between the density and functions of lexical bundles in the two corpora. These differences were evident in the distribution of functions of lexical bundles and the minimal overlap of lexical bundles found in the two corpora. The results of this study call for more attention to formulaic language at ESP and EAP programs.

Polarizability of Six-Helix Bundle and Triangle DNA Origami and Their Escape Characteristics from a Dielectrophoretic Trap.

PubMed

Gan, Lin; Camacho-Alanis, Fernanda; Ros, Alexandra

2015-12-15

DNA nanoassemblies, such as DNA origamis, hold promise in biosensing, drug delivery, nanoelectronic circuits, and biological computing, which require suitable methods for migration and precision positioning. Insulator-based dielectrophoresis (iDEP) has been demonstrated as a powerful migration and trapping tool for μm- and nm-sized colloids as well as DNA origamis. However, little is known about the polarizability of origami species, which is responsible for their dielectrophoretic migration. Here, we report the experimentally determined polarizabilities of the six-helix bundle origami (6HxB) and triangle origami by measuring the migration times through a potential landscape exhibiting dielectrophoretic barriers. The resulting migration times correlate to the depth of the dielectrophoretic potential barrier and the escape characteristics of the origami according to an adapted Kramer's rate model, allowing their polarizabilities to be determined. We found that the 6HxB polarizability is larger than that of the triangle origami, which correlates with the variations in charge density of both origamis. Further, we discuss the orientation of both origami species in the dielectrophoretic trap and discuss the influence of diffusion during the escape process. Our study provides detailed insight into the factors contributing to the migration through dielectrophoretic potential landscapes, which can be exploited for applications with DNA and other nanoassemblies based on dielectrophoresis.

Dual effect of pseudorabies virus growth factor (PRGF) displayed on actin cytoskeleton.

PubMed

Urbancíková, M; Vozárová, G; Lesko, J; Golais, F

1999-10-01

Pseudorabies virus growth factor (PRGF) was shown to possess transforming activity as well as transformation repressing activity in in vitro systems. In order to better understand these phenomena we studied actin cytoskeleton and its alterations induced by PRGF using normal human fibroblasts VH-10 and transformed cell line HeLa. For specific detection of filamentous actin cells were stained with phalloidin conjugated with fluorescein isothiocyanate (FITC)-phalloidin. PRGF was applied to VH-10 cells for various length of time from 10 min up to 48 h. The effect was very fast and changes in actin filament composition could be detected already after 10 min. In comparison to untreated cells the staining of treated cells was more diffuse and a number of actin microfilaments in individual stress fibers became reduced. After 30 min thick short actin bundles appeared in the perinuclear region. A 24-h exposure resulted in a large reduction of actin bundles. After additional 24 h a partial restoration of actin cytoskeleton in cells was observed. In transformed HeLa cells PRGF induced opposite process than in normal cells: the number of filamentous actin structures increased. We hypothesise that PRGF may act as a transcription-like factor and may initiate changes in gene expression which consequently result in actin cytoskeleton alterations.

Correlation properties of interstellar dust: Diffuse interstellar bands

NASA Technical Reports Server (NTRS)

Somerville, W. B.

1989-01-01

Results are presented from a research program in which an attempt was made to establish the physical nature of the interstellar grains, and the carriers of the diffuse interstellar bands, by comparing relations between different observed properties; the properties used include the extinction in the optical and ultraviolet (including wavelength 2200 and the far-UV rise), cloud density, atomic depletions, and strengths of the diffuse bands. Observations and also data from literature were used, selecting particularly sight-lines where some observed property was found to have anomalous behavior.

Role of insulin receptor and insulin signaling on αPS2CβPS integrins' lateral diffusion.

PubMed

Mainali, Dipak; Syed, Aleem; Arora, Neha; Smith, Emily A

2014-12-01

Integrins are ubiquitous transmembrane receptors with adhesion and signaling properties. The influence of insulin receptor and insulin signaling on αPS2CβPS integrins' lateral diffusion was studied using single particle tracking in S2 cells before and after reducing the insulin receptor expression or insulin stimulation. Insulin signaling was monitored by Western blotting for phospho-Akt expression. The expression of the insulin receptor was reduced using RNA interference (RNAi). After insulin receptor RNAi, four significant changes were measured in integrin diffusion properties: (1) there was a 24% increase in the mobile integrin population, (2) 14% of the increase was represented by integrins with Brownian diffusion, (3) for integrins that reside in confined zones of diffusion, there was a 45% increase in the diameter of the confined zone, and (4) there was a 29% increase in the duration integrins spend in confined zones of diffusion. In contrast to reduced expression of the insulin receptor, which alters integrin diffusion properties, insulin stimulation alone or insulin stimulation under conditions of reduced insulin receptor expression have minimal effects on altering the measured integrin diffusion properties. The differences in integrin diffusion measured after insulin receptor RNAi in the presence or absence of insulin stimulation may be the result of other insulin signaling pathways that are activated at reduced insulin receptor conditions. No change in the average integrin diffusion coefficient was measured for any conditions included in this study.

Gelation And Mechanical Response of Patchy Rods

NASA Astrophysics Data System (ADS)

Kazem, Navid; Majidi, Carmel; Maloney, Craig

We perform Brownian Dynamics simulations to study the gelation of suspensions of attractive, rod-like particles. We show that details of the particle-particle interactions can dramatically affect the dynamics of gelation and the structure and mechanics of the networks that form. If the attraction between the rods is perfectly smooth along their length, they will collapse into compact bundles. If the attraction is sufficiently corrugated or patchy, over time, a rigid space spanning network forms. We study the structure and mechanical properties of the networks that form as a function of the fraction of the surface that is allowed to bind. Surprisingly, the structural and mechanical properties are non-monotonic in the surface coverage. At low coverage, there are not a sufficient number of cross-linking sites to form networks. At high coverage, rods bundle and form disconnected clusters. At intermediate coverage, robust networks form. The elastic modulus and yield stress are both non-monotonic in the surface coverage. The stiffest and strongest networks show an essentially homogeneous deformation under strain with rods re-orienting along the extensional axis. Weaker, clumpy networks at high surface coverage exhibit relatively little re-orienting with strong non-affine deformation. These results suggest design strategies for tailoring surface interactions between rods to yield rigid networks with optimal properties. National Science Foundation and the Air Force Office of Scientific Research.

Microstructure and Tensile Properties of BN/SiC Coated Hi-Nicalon, and Sylramic SiC Fiber Preforms. Revised

NASA Technical Reports Server (NTRS)

Bhatt, Ramakrishna T.; Chen, Yuan L.; Morscher, Gregory N.

2002-01-01

Batch to batch and within batch variations, and the influence of fiber architecture on room temperature physical and tensile properties of BN/SiC coated Hi-Nicalon and Sylramic SiC fiber preform specimens were determined. The three fiber architectures studied were plain weave (PW), 5-harness satin (5HS), and 8-harness satin (8HS). Results indicate that the physical properties vary up to 10 percent within a batch, and up to 20 percent between batches of preforms. Load-reload (Hysteresis) and acoustic emission methods were used to analyze damage accumulation occurring during tensile loading. Early acoustic emission activity, before observable hysteretic behavior, indicates that the damage starts with the formation of nonbridged tunnel cracks. These cracks then propagate and intersect the load bearing "0 deg" fibers giving rise to hysteretic behavior. For the Hi-Nicalon preform specimens, the onset of "0 deg" bundle cracking stress and strain appeared to be independent of the fiber architecture. Also, the "0 deg" fiber bundle cracking strain remained nearly the same for the preform specimens of both fiber types. TEM analysis indicates that the CVI BN interface coating is mostly amorphous and contains carbon and oxygen impurities, and the CVI SiC coating is crystalline. No reaction exists between the CVI BN and SiC coating.

Microstructure and Tensile Properties of BN/SiC Coated Hi-Nicalon, and Sylramic SiC Fiber Preforms

NASA Technical Reports Server (NTRS)

Bhatt, Ramakrishna T.; Chen, Yuan L.; Morscher, Gregory N.

2001-01-01

Batch to batch and within batch variations, and the influence of fiber architecture on room temperature physical and tensile properties of BN/SiC coated Hi-Nicalon and Sylramic SiC fiber preform specimens were determined. The three fiber architectures studied were plain weave (PW), 5-harness satin (5HS) and 8-harness satin (8HS) Results indicate that the physical properties vary up to 10 percent within a batch, and up to 20 percent between batches of preforms. Load-reload (Hysteresis) and acoustic emission methods were used to analyze damage accumulation occurring during tensile loading. Early acoustic emission activity, before observable hysteretic behavior, indicates that the damage starts with the formation of nonbridged tunnel cracks. These cracks then propagate and intersect the load bearing "0" fibers giving rise to hysteretic behavior, For the Hi-Nicalon preform specimens, the onset of "0" bundle cracking stress and strain appeared to be independent of the fiber architecture. Also, the "0" fiber bundle cracking strain remained nearly the same for the preform specimens of both fiber types. Transmission Electron Microscope (TEM) analysis indicates that the Chemical Vapor Infiltration (CVI) Boron Nitride (BN) interface coating is mostly amorphous and contains carbon and oxygen impurities, and the CVI SiC coating is crystalline. No reaction exists between the CVI BN and SiC coating.

Roles of silica and lignin in horsetail (Equisetum hyemale), with special reference to mechanical properties

NASA Astrophysics Data System (ADS)

Yamanaka, Shigeru; Sato, Kanna; Ito, Fuyu; Komatsubara, Satoshi; Ohata, Hiroshi; Yoshino, Katsumi

2012-02-01

This research deals with detailed analyses of silica and lignin distribution in horsetail with special reference to mechanical strength. Scanning electron images of a cross-section of an internode showed silica deposited densely only around the outer epidermis. Detailed histochemical analyses of lignin showed no lignin deposition in the silica-rich outer internodes of horsetail, while a characteristic lignin deposition was noticed in the vascular bundle in inner side of internodes. To analyze the structure of horsetail from a mechanical viewpoint, we calculated the response of a model structure of horsetail to a mechanical force applied perpendicularly to the long axis by a finite element method. We found that silica distributed in the outer epidermis may play the major structural role, with lignin's role being limited ensuring that the vascular bundle keep waterproof. These results were in contrast to more modern tall trees like gymnosperms, for which lignin provides mechanical strength. Lignin has the advantage of sticking to cellulose, hemicellulose, and other materials. Such properties make it possible for plants containing lignin to branch. Branching of tree stems aids in competing for light and other atmospheric resources. This type of branching was impossible for ancient horsetails, which relied on the physical properties of silica. From the evolutional view points, over millennia in trees with high lignin content, true branching, and many chlorophyll-containing leaves developed.

The effect of ultrasonic processing of multi-wall carbon nanotubes on properties of elastomeric compositions on the basis of synthetic isoprene rubber

NASA Astrophysics Data System (ADS)

Mitryaeva, N. S.; Myshlyavtsev, A. V.; Akimenko, S. S.

2017-08-01

The paper studies the effect of ultrasonic processing on the vulcanizing, physical, mechanical and electrophysical properties of elastomeric compositions based on synthetic isoprene rubber. Microscopic studies of multi-wall carbon nanotubes samples before and after ultrasonic processing are carried out. Due to the research, the applied ultrasonic processing method provides splitting of bundles formed from multi-wall carbon nanotubes. This results in elastomeric material with increased strength and high electrical conductivity with a low concentration of nanofiller.

Stimulation of hair cells with ultraviolet light

NASA Astrophysics Data System (ADS)

Azimzadeh, Julien B.; Fabella, Brian A.; Hudspeth, A. J.

2018-05-01

Hair bundles are specialized organelles that transduce mechanical inputs into electrical outputs. To activate hair cells, physiologists have resorted to mechanical methods of hair-bundle stimulation. Here we describe a new method of hair-bundle stimulation, irradiation with ultraviolet light. A hair bundle illuminated by ultraviolet light rapidly moves towards its tall edge, a motion typically associated with excitatory stimulation. The motion disappears upon tip-link rupture and is associated with the opening of mechanotransduction channels. Hair bundles can be induced to move sinusoidally with oscillatory modulation of the stimulation power. We discuss the implications of ultraviolet stimulation as a novel hair-bundle stimulus.

Formation and structural organization of the egg-sperm bundle of the scleractinian coral Montipora capitata

NASA Astrophysics Data System (ADS)

Padilla-Gamiño, J. L.; Weatherby, T. M.; Waller, R. G.; Gates, R. D.

2011-06-01

The majority of scleractinian corals are hermaphrodites that broadcast spawn their gametes separately or packaged as egg-sperm bundles during spawning events that are timed to the lunar cycle. The egg-sperm bundle is an efficient way of transporting gametes to the ocean surface where fertilization takes place, while minimizing sperm dilution and maximizing the opportunity for gamete encounters during a spawning event. To date, there are few studies that focus on the formation and structure of egg-sperm bundle. This study explores formation, ultrastructure, and longevity of the egg-sperm bundle in Montipora capitata, a major reef building coral in Hawai`i. Our results show that the egg-sperm bundle is formed by a mucus layer secreted by the oocytes. The sperm package is located at the center of each bundle, possibly reflecting the development of male and female gametes in different mesenteries. Once the egg-sperm bundle has reached the ocean surface, it breaks open within 10-35 min, depending on the environmental conditions (i.e., wind, water turbulence). Although the bundle has an ephemeral life span, the formation of an egg-sperm bundle is a fundamental part of the reproductive process that could be strongly influenced by climate change and deterioration of water quality (due to anthropogenic effects) and thus requires further investigation.

Robust Mapping of Incoherent Fiber-Optic Bundles

NASA Technical Reports Server (NTRS)

Roberts, Harry E.; Deason, Brent E.; DePlachett, Charles P.; Pilgrim, Robert A.; Sanford, Harold S.

2007-01-01

A method and apparatus for mapping between the positions of fibers at opposite ends of incoherent fiber-optic bundles have been invented to enable the use of such bundles to transmit images in visible or infrared light. The method is robust in the sense that it provides useful mapping even for a bundle that contains thousands of narrow, irregularly packed fibers, some of which may be defective. In a coherent fiber-optic bundle, the input and output ends of each fiber lie at identical positions in the input and output planes; therefore, the bundle can be used to transmit images without further modification. Unfortunately, the fabrication of coherent fiber-optic bundles is too labor-intensive and expensive for many applications. An incoherent fiber-optic bundle can be fabricated more easily and at lower cost, but it produces a scrambled image because the position of the end of each fiber in the input plane is generally different from the end of the same fiber in the output plane. However, the image transmitted by an incoherent fiber-optic bundle can be unscrambled (or, from a different perspective, decoded) by digital processing of the output image if the mapping between the input and output fiber-end positions is known. Thus, the present invention enables the use of relatively inexpensive fiber-optic bundles to transmit images.

A new compression format for fiber tracking datasets.

PubMed

Presseau, Caroline; Jodoin, Pierre-Marc; Houde, Jean-Christophe; Descoteaux, Maxime

2015-04-01

A single diffusion MRI streamline fiber tracking dataset may contain hundreds of thousands, and often millions of streamlines and can take up to several gigabytes of memory. This amount of data is not only heavy to compute, but also difficult to visualize and hard to store on disk (especially when dealing with a collection of brains). These problems call for a fiber-specific compression format that simplifies its manipulation. As of today, no fiber compression format has yet been adopted and the need for it is now becoming an issue for future connectomics research. In this work, we propose a new compression format, .zfib, for streamline tractography datasets reconstructed from diffusion magnetic resonance imaging (dMRI). Tracts contain a large amount of redundant information and are relatively smooth. Hence, they are highly compressible. The proposed method is a processing pipeline containing a linearization, a quantization and an encoding step. Our pipeline is tested and validated under a wide range of DTI and HARDI tractography configurations (step size, streamline number, deterministic and probabilistic tracking) and compression options. Similar to JPEG, the user has one parameter to select: a worst-case maximum tolerance error in millimeter (mm). Overall, we find a compression factor of more than 96% for a maximum error of 0.1mm without any perceptual change or change of diffusion statistics (mean fractional anisotropy and mean diffusivity) along bundles. This opens new opportunities for connectomics and tractometry applications. Copyright © 2014 Elsevier Inc. All rights reserved.

Surface-based brain morphometry and diffusion tensor imaging in schizoaffective disorder.

PubMed

Landin-Romero, Ramón; Canales-Rodríguez, Erick J; Kumfor, Fiona; Moreno-Alcázar, Ana; Madre, Mercè; Maristany, Teresa; Pomarol-Clotet, Edith; Amann, Benedikt L

2017-01-01

The profile of grey matter abnormalities and related white-matter pathology in schizoaffective disorder has only been studied to a limited extent. The aim of this study was to identify grey- and white-matter abnormalities in patients with schizoaffective disorder using complementary structural imaging techniques. Forty-five patients meeting Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition criteria and Research Diagnostic Criteria for schizoaffective disorder and 45 matched healthy controls underwent structural-T1 and diffusion magnetic resonance imaging to enable surface-based brain morphometry and diffusion tensor imaging analyses. Analyses were conducted to determine group differences in cortical volume, cortical thickness and surface area, as well as in fractional anisotropy and mean diffusivity. At a threshold of p = 0.05 corrected, all measures revealed significant differences between patients and controls at the group level. Spatial overlap of abnormalities was observed across the various structural neuroimaging measures. In grey matter, patients with schizoaffective disorder showed abnormalities in the frontal and temporal lobes, striatum, fusiform, cuneus, precuneus, lingual and limbic regions. White-matter abnormalities were identified in tracts connecting these areas, including the corpus callosum, superior and inferior longitudinal fasciculi, anterior thalamic radiation, uncinate fasciculus and cingulum bundle. The spatial overlap of abnormalities across the different imaging techniques suggests widespread and consistent brain pathology in schizoaffective disorder. The abnormalities were mainly detected in areas that have commonly been reported to be abnormal in schizophrenia, and to some extent in bipolar disorder, which may explain the clinical and aetiological overlap in these disorders.

Comparative fiber property and transcriptome analyses reveal key genes potentially related to high fiber strength in cotton (Gossypium hirsutum L.) line MD52ne

USDA-ARS?s Scientific Manuscript database

Background: Individual fiber strength is an important quality attribute that greatly influences the strength of the yarn spun from cotton fibers. Fiber strength is usually measured from bundles of fibers due to the difficulty of reliably measuring strength from individual cotton fibers. However, bun...

Topological T-duality, automorphisms and classifying spaces

NASA Astrophysics Data System (ADS)

Pande, Ashwin S.

2014-08-01

We extend the formalism of Topological T-duality to spaces which are the total space of a principal S1-bundle p:E→W with an H-flux in H3(E,Z) together with an automorphism of the continuous-trace algebra on E determined by H. The automorphism is a ‘topological approximation’ to a gerby gauge transformation of spacetime. We motivate this physically from Buscher’s Rules for T-duality. Using the Equivariant Brauer Group, we connect this problem to the C∗-algebraic formalism of Topological T-duality of Mathai and Rosenberg (2005). We show that the study of this problem leads to the study of a purely topological problem, namely, Topological T-duality of triples (p,b,H) consisting of isomorphism classes of a principal circle bundle p:X→B and classes b∈H2(X,Z) and H∈H3(X,Z). We construct a classifying space R for triples in a manner similar to the work of Bunke and Schick (2005). We characterize R up to homotopy and study some of its properties. We show that it possesses a natural self-map which induces T-duality for triples. We study some properties of this map.

Functional Single-Walled Carbon Nanotubes and Nanoengineered Networks for Organic- and Perovskite-Solar-Cell Applications.

PubMed

Barbero, David R; Stranks, Samuel D

2016-11-01

Carbon nanotubes have a variety of remarkable electronic and mechanical properties that, in principle, lend them to promising optoelectronic applications. However, the field has been plagued by heterogeneity in the distributions of synthesized tubes and uncontrolled bundling, both of which have prevented nanotubes from reaching their full potential. Here, a variety of recently demonstrated solution-processing avenues is presented, which may combat these challenges through manipulation of nanoscale structures. Recent advances in polymer-wrapping of single-walled carbon nanotubes (SWNTs) are shown, along with how the resulting nanostructures can selectively disperse tubes while also exploiting the favorable properties of the polymer, such as light-harvesting ability. New methods to controllably form nanoengineered SWNT networks with controlled nanotube placement are discussed. These nanoengineered networks decrease bundling, lower the percolation threshold, and enable a strong enhancement in charge conductivity compared to random networks, making them potentially attractive for optoelectronic applications. Finally, SWNT applications, to date, in organic and perovskite photovoltaics are reviewed, and insights as to how the aforementioned recent advancements can lead to improved device performance provided. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A compressed sensing approach for resolution improvement in fiber-bundle based endomicroscopy

NASA Astrophysics Data System (ADS)

Dumas, John P.; Lodhi, Muhammad A.; Bajwa, Waheed U.; Pierce, Mark C.

2018-02-01

Endomicroscopy techniques such as confocal, multi-photon, and wide-field imaging have all been demonstrated using coherent fiber-optic imaging bundles. While the narrow diameter and flexibility of fiber bundles is clinically advantageous, the number of resolvable points in an image is conventionally limited to the number of individual fibers within the bundle. We are introducing concepts from the compressed sensing (CS) field to fiber bundle based endomicroscopy, to allow images to be recovered with more resolvable points than fibers in the bundle. The distal face of the fiber bundle is treated as a low-resolution sensor with circular pixels (fibers) arranged in a hexagonal lattice. A spatial light modulator is located conjugate to the object and distal face, applying multiple high resolution masks to the intermediate image prior to propagation through the bundle. We acquire images of the proximal end of the bundle for each (known) mask pattern and then apply CS inversion algorithms to recover a single high-resolution image. We first developed a theoretical forward model describing image formation through the mask and fiber bundle. We then imaged objects through a rigid fiber bundle and demonstrate that our CS endomicroscopy architecture can recover intra-fiber details while filling inter-fiber regions with interpolation. Finally, we examine the relationship between reconstruction quality and the ratio of the number of mask elements to the number of fiber cores, finding that images could be generated with approximately 28,900 resolvable points for a 1,000 fiber region in our platform.

Understanding nurses' views on a pressure ulcer prevention care bundle: a first step towards successful implementation.

PubMed

Chaboyer, Wendy; Gillespie, Brigid M

2014-12-01

To explore nurses' views of the barriers and facilitators to the use of a newly devised patient-centred pressure ulcer prevention care bundle. Given pressure ulcer prevention strategies are not implemented consistently, the use of a pressure ulcer care bundle may improve implementation given bundles generally assist in standardising care. A quality improvement project was undertaken after a pressure ulcer prevention care bundle was developed and pilot-tested. Short, conversational interviews with nurse explored their views of a patient-centred pressure ulcer care bundle. Interviews were audio-taped and transcribed. Inductive content analysis was used to analyse the transcripts. A total of 20 nurses were interviewed. Five categories with corresponding subcategories emerged from the analysis. They were increasing awareness of pressure ulcer prevention, prompting pressure ulcer prevention activities, promoting active patient participation, barriers to using a pressure ulcer prevention care bundle and enabling integration of the pressure ulcer prevention care bundle into routine practice. Benefits of using a patient-centred pressure ulcer prevention care bundle may include prompting patients and staff to implement prevention strategies and promote active patient participation in care. The success of the care bundle relied on both patients' willingness to participate and nurses' willingness to incorporate it into their routine work. A patient-centred pressure ulcer prevention care bundle may facilitate more consistent implementation of pressure ulcer prevention strategies and active patient participation in care. © 2014 John Wiley & Sons Ltd.

Stokes-polarimetry imaging of tissue

NASA Astrophysics Data System (ADS)

Wu, Paul J.

A novel Stokes-polarimetry imaging system and technique was developed to quantify fully the polarization properties of light remitted from tissue. The uniqueness of the system and technique is established in the incident polarization. Here, the diffuse illumination is varied and controlled with the intention to improve the visibility of tissue structures. Since light retains some polarization even after multiple-scattering events, the polarization of remitted light depends upon the interactions within the material. Differentiation between tissue structures is accomplished by two-dimensional mapping of the imaged area using metrics such as the degree of linear polarization, degree of circular polarization, ellipticity, and Stokes parameters. While Stokes-polarimetry imaging can be applied to a variety of tissues and conditions, this thesis focuses on tissue types associated with the disease endometriosis. The current standard in diagnosing endometriosis is visual laparoscopy with tissue biopsy. The documented correlation between laparoscopy inspection and histological confirmation of suspected lesions was at best 67%. Endometrial lesions vary greatly in their appearance and depth of infiltration. Although laparoscopy permits tissue to be assessed by color and texture, to advance beyond the state-of-the-art, a new imaging modality involving polarized light was investigated; in particular, Stokes-polarimetry imaging was used to determine the polarization signature of light that interacted with tissue. Basic science studies were conducted on rat tails embedded within turbid gelatin. The purpose of these experiments was to determine how identification of sub-surface structures could be improved. Experimental results indicate image contrast among various structures such as tendon, soft tissue and intervertebral discs. Stokes-polarimetry imaging experiments were performed on various tissues associated with endometriosis to obtain a baseline characterization for each tissue type. Structures such as birefringent collagen, smooth-muscle fiber-bundles, and nerve bundles were visualized that were otherwise not observable with unpolarized light imaging. Finally, a study of cutaneous scars indicated the feasibility of using Stokes-polarimetry imaging in the detection of atypical tissue. A relationship between incident linear polarization angle and skin anatomy was determined so as to obtain maximum contrast between scar tissue and normal skin.

Mechanical Overstimulation of Hair Bundles: Suppression and Recovery of Active Motility

PubMed Central

Kao, Albert; Meenderink, Sebastiaan W. F.; Bozovic, Dolores

2013-01-01

We explore the effects of high-amplitude mechanical stimuli on hair bundles of the bullfrog sacculus. Under in vitro conditions, these bundles exhibit spontaneous limit cycle oscillations. Prolonged deflection exerted two effects. First, it induced an offset in the position of the bundle. Recovery to the original position displayed two distinct time scales, suggesting the existence of two adaptive mechanisms. Second, the stimulus suppressed spontaneous oscillations, indicating a change in the hair bundle’s dynamic state. After cessation of the stimulus, active bundle motility recovered with time. Both effects were dependent on the duration of the imposed stimulus. External calcium concentration also affected the recovery to the oscillatory state. Our results indicate that both offset in the bundle position and calcium concentration control the dynamic state of the bundle. PMID:23505461

Influence of knee flexion angle and transverse drill angle on creation of femoral tunnels in double-bundle anterior cruciate ligament reconstruction using the transportal technique: Three-dimensional computed tomography simulation analysis.

PubMed

Choi, Chong Hyuk; Kim, Sung-Jae; Chun, Yong-Min; Kim, Sung-Hwan; Lee, Su-Keon; Eom, Nam-Kyu; Jung, Min

2018-01-01

The purpose of this study was to find appropriate flexion angle and transverse drill angle for optimal femoral tunnels of anteromedial (AM) bundle and posterolateral (PL) bundle in double-bundle ACL reconstruction using transportal technique. Thirty three-dimensional knee models were reconstructed. Knee flexion angles were altered from 100° to 130° at intervals of 10°. Maximum transverse drill angle (MTA), MTA minus 10° and 20° were set up. Twelve different tunnels were determined by four flexion angles and three transverse drill angles for each bundle. Tunnel length, wall breakage, inter-tunnel communication and graft-bending angle were assessed. Mean tunnel length of AM bundle was >30mm at 120° and 130° of flexion in all transverse drill angles. Mean tunnel length of PL bundle was >30mm during every condition. There were ≥1 cases of wall breakage except at 120° and 130° of flexion with MTA for AM bundle. There was no case of wall breakage for PL bundle. Considering inter-tunnel gap of >2mm without communication and obtuse graft-bending angle, 120° of flexion and MTA could be recommended as optimal condition for femoral tunnels of AM and PL bundles. Flexion angle and transverse drill angle had combined effect on femoral tunnel in double-bundle ACL reconstruction using transportal technique. Achieving flexion angle of 120° and transverse drill angle close to the medial femoral condyle could be recommended as optimal condition for femoral tunnels of AM and PL bundles to avoid insufficient tunnel length, wall breakage, inter-tunnel communication and acute graft-bending angle. Copyright © 2017 Elsevier B.V. All rights reserved.

Filament formation of the Escherichia coli actin-related protein, MreB, in fission yeast.

PubMed

Srinivasan, Ramanujam; Mishra, Mithilesh; Murata-Hori, Maki; Balasubramanian, Mohan K

2007-02-06

Proteins structurally related to eukaryotic actins have recently been identified in several prokaryotic organisms. These actin-like proteins (MreB and ParM) and the deviant Walker A ATPase (SopA) play a key role in DNA segregation and assemble into polymers in vitro and in vivo. MreB also plays a role in cellular morphogenesis. Whereas the dynamic properties of eukaryotic actins have been extensively characterized, those of bacterial actins are only beginning to emerge. We have established the fission yeast Schizosaccharomyces pombe as a cellular model for the functional analysis of the Escherichia coli actin-related protein MreB. We show that MreB organizes into linear bundles that grow in a symmetrically bidirectional manner at 0.46 +/- 0.03 microm/min, with new monomers and/or oligomers being added along the entire length of the bundle. Organization of linear arrays was dependent on the ATPase activity of MreB, and their alignment along the cellular long axis was achieved by sliding along the cortex of the cylindrical part of the cell. The cell ends appeared to provide a physical barrier for bundle elongation. These experiments provide new insights into the mechanism of assembly and organization of the bacterial actin cytoskeleton.

Structural plasticity of 4-α-helical bundles exemplified by the puzzle-like molecular assembly of the Rop protein

PubMed Central

Amprazi, Maria; Kotsifaki, Dina; Providaki, Mary; Kapetaniou, Evangelia G.; Fellas, Georgios; Kyriazidis, Ioannis; Pérez, Javier; Kokkinidis, Michael

2014-01-01

The dimeric Repressor of Primer (Rop) protein, a widely used model system for the study of coiled-coil 4-α-helical bundles, is characterized by a remarkable structural plasticity. Loop region mutations lead to a wide range of topologies, folding states, and altered physicochemical properties. A protein-folding study of Rop and several loop variants has identified specific residues and sequences that are linked to the observed structural plasticity. Apart from the native state, native-like and molten-globule states have been identified; these states are sensitive to reducing agents due to the formation of nonnative disulfide bridges. Pro residues in the loop are critical for the establishment of new topologies and molten globule states; their effects, however, can be in part compensated by Gly residues. The extreme plasticity in the assembly of 4-α-helical bundles reflects the capacity of the Rop sequence to combine a specific set of hydrophobic residues into strikingly different hydrophobic cores. These cores include highly hydrated ones that are consistent with the formation of interchain, nonnative disulfide bridges and the establishment of molten globules. Potential applications of this structural plasticity are among others in the engineering of bio-inspired materials. PMID:25024213

The Mechanical Properties of Hydrated Intermediate Filaments: Insights from Hagfish Slime Threads

PubMed Central

Fudge, Douglas S.; Gardner, Kenn H.; Forsyth, V. Trevor; Riekel, Christian; Gosline, John M.

2003-01-01

Intermediate filaments (IFs) impart mechanical integrity to cells, yet IF mechanics are poorly understood. It is assumed that IFs in cells are as stiff as hard α-keratin, F-actin, and microtubules, but the high bending flexibility of IFs and the low stiffness of soft α-keratins suggest that hydrated IFs may be quite soft. To test this hypothesis, we measured the tensile mechanics of the keratin-like threads from hagfish slime, which are an ideal model for exploring the mechanics of IF bundles and IFs because they consist of tightly packed and aligned IFs. Tensile tests suggest that hydrated IF bundles possess low initial stiffness (Ei = 6.4 MPa) and remarkable elasticity (up to strains of 0.34), which we attribute to soft elastomeric IF protein terminal domains in series with stiffer coiled coils. The high tensile strength (180 MPa) and toughness (130 MJ/m3) of IF bundles support the notion that IFs lend mechanical integrity to cells. Their long-range elasticity suggests that IFs may also allow cells to recover from large deformations. X-ray diffraction and congo-red staining indicate that post-yield deformation leads to an irreversible α→β conformational transition in IFs, which leads to plastic deformation, and may be used by cells as a mechanosensory cue. PMID:12944314

Actin-induced dimerization of palladin promotes actin-bundling

PubMed Central

Vattepu, Ravi; Yadav, Rahul; Beck, Moriah R

2015-01-01

A subset of actin binding proteins is able to form crosslinks between two or more actin filaments, thus producing structures of parallel or networked bundles. These actin crosslinking proteins interact with actin through either bivalent binding or dimerization. We recently identified two binding sites within the actin binding domain of palladin, an actin crosslinking protein that plays an important role in normal cell adhesion and motility during wound healing and embryonic development. In this study, we show that actin induces dimerization of palladin. Furthermore, the extent of dimerization reflects earlier comparisons of actin binding and bundling between different domains of palladin. On the basis of these results we hypothesized that actin binding may promote a conformational change that results in dimerization of palladin, which in turn may drive the crosslinking of actin filaments. The proximal distance between two actin binding sites on crosslinking proteins determines the ultrastructural properties of the filament network, therefore we also explored interdomain interactions using a combination of chemical crosslinking experiments and actin cosedimentation assays. Limited proteolysis data reveals that palladin is less susceptible to enzyme digestion after actin binding. Our results suggest that domain movements in palladin are necessary for interactions with actin and are induced by interactions with actin filaments. Accordingly, we put forth a model linking the structural changes to functional dynamics. PMID:25307943

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

Hughes, Michael John; McConnaughhay, Johnie Franklin

A combustor includes a tube bundle that extends radially across at least a portion of the combustor. The tube bundle includes an upstream surface axially separated from a downstream surface, and a plurality of tubes extend from the upstream surface through the downstream surface to provide fluid communication through the tube bundle. A barrier extends radially inside the tube bundle between the upstream and downstream surfaces, and a baffle extends axially inside the tube bundle between the upstream surface and the barrier.

Sampling system and method

DOEpatents

Decker, David L; Lyles, Brad F; Purcell, Richard G; Hershey, Ronald Lee

2014-05-20

An apparatus and method for supporting a tubing bundle during installation or removal. The apparatus includes a clamp for securing the tubing bundle to an external wireline. The method includes deploying the tubing bundle and wireline together, The tubing bundle is periodically secured to the wireline using a clamp.

Fiber-bundle-basis sparse reconstruction for high resolution wide-field microendoscopy.

PubMed

Mekhail, Simon Peter; Abudukeyoumu, Nilupaer; Ward, Jonathan; Arbuthnott, Gordon; Chormaic, Síle Nic

2018-04-01

In order to observe deep regions of the brain, we propose the use of a fiber bundle for microendoscopy. Fiber bundles allow for the excitation and collection of fluorescence as well as wide field imaging while remaining largely impervious to image distortions brought on by bending. Furthermore, their thin diameter, from 200-500 µ m, means their impact on living tissue, though not absent, is minimal. Although wide field imaging with a bundle allows for a high temporal resolution since no scanning is involved, the largest criticism of bundle imaging is the drastically lowered spatial resolution. In this paper, we make use of sparsity in the object being imaged to up sample the low resolution images from the fiber bundle with compressive sensing. We take each image in a single shot by using a measurement basis dictated by the quasi-crystalline arrangement of the bundle's cores. We find that this technique allows us to increase the resolution of a typical image taken through a fiber bundle.

Equilibrium polyelectrolyte bundles with different multivalent counterion concentrations

NASA Astrophysics Data System (ADS)

Sayar, Mehmet; Holm, Christian

2010-09-01

We present the results of molecular-dynamics simulations on the salt concentration dependence of the formation of polyelectrolyte bundles in thermodynamic equilibrium. Extending our results on salt-free systems we investigate here deficiency or excess of trivalent counterions in solution. Our results reveal that the trivalent counterion concentration significantly alters the bundle size and size distribution. The onset of bundle formation takes place at earlier Bjerrum length values with increasing trivalent counterion concentration. For the cases of 80%, 95%, and 100% charge compensation via trivalent counterions, the net charge of the bundles decreases with increasing size. We suggest that competition among two different mechanisms, counterion condensation and merger of bundles, leads to a nonmonotonic change in line-charge density with increasing Bjerrum length. The investigated case of having an abundance of trivalent counterions by 200% prohibits such a behavior. In this case, we find that the difference in effective line-charge density of different size bundles diminishes. In fact, the system displays an isoelectric point, where all bundles become charge neutral.

Overhead electric power transmission line jumpering system for bundles of five or more subconductors

DOEpatents

Winkelman, Paul F.

1982-01-01

Jumpering of electric power transmission lines at a dead end tower. Two transmission line conductor bundles each contain five or more spaced apart subconductors (5) arranged in the shape of a cylinder having a circular cross section. The ends of each bundle of subconductors are attached with insulators to a dead end tower (1). Jumpering allows the electric current to flow between the two bundles of subconductors using jumper buses, internal jumper conductors, and external jumper conductors. One or more current collecting jumper buses (37) are located inside each bundle of subconductors with each jumper bus being attached to the end of a subconductor. Small-diameter internal jumper conductors (33) are located in the inherently electrically shielded area inside each bundle of subconductors with each subconductor (except ones having an attached jumper bus) having one internal jumper conductor connected between that subconductor's end and a jumper bus. Large-diameter external jumper conductors (9) are located outside each bundle of subconductors with one or more external jumper conductors being connected between the jumper buses in one bundle of subconductors and the jumper buses in the other bundle.

Comparison of computational results of the SABRE LMFBR pin bundle blockage code with data from well-instrumented out-of-pile test bundles (THORS bundles 3A and 5A)

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

Dearing, J.F.

The Subchannel Analysis of Blockages in Reactor Elements (SABRE) computer code, developed by the United Kingdom Atomic Energy Authority, is currently the only practical tool available for performing detailed analyses of velocity and temperature fields in the recirculating flow regions downstream of blockages in liquid-metal fast breeder reactor (LMFBR) pin bundles. SABRE is a subchannel analysis code; that is, it accurately represents the complex geometry of nuclear fuel pins arranged on a triangular lattice. The results of SABRE computational models are compared here with temperature data from two out-of-pile 19-pin test bundles from the Thermal-Hydraulic Out-of-Reactor Safety (THORS) Facility atmore » Oak Ridge National Laboratory. One of these bundles has a small central flow blockage (bundle 3A), while the other has a large edge blockage (bundle 5A). Values that give best agreement with experiment for the empirical thermal mixing correlation factor, FMIX, in SABRE are suggested. These values of FMIX are Reynolds-number dependent, however, indicating that the coded turbulent mixing correlation is not appropriate for wire-wrap pin bundles.« less

Characterization of midrib vascular bundles of selected medicinal species in Rubiaceae

NASA Astrophysics Data System (ADS)

Nurul-Syahirah, M.; Noraini, T.; Latiff, A.

2016-11-01

An anatomical study was carried out on mature leaves of five selected medicinal species of Rubiaceae from Peninsular Malaysia. The chosen medicinal species were Aidia densiflora, Aidia racemosa, Chasallia chartacea, Hedyotis auricularia and Ixora grandifolia. The objective of this study is to determine the taxonomic value of midrib anatomical characteristics. Leaves samples were collected from Taman Paku Pakis, Universiti Kebangsaan Malaysia, Bangi, Selangor and Kledang Saiong Forest Reserve, Perak, Malaysia. Leaves samples then were fixed in spirit and acetic acid (3:1), the midrib parts then were sectioned using sliding microtome, cleared using Clorox, stained in Safranin and Alcian blue, mounted in Euparal and were observed under light microscope. Findings in this study have shown all species have collateral bundles. The midrib vascular bundles characteristics that can be used as tool to differentiate between species or genus are vascular bundles system (opened or closed), shape and arrangement of main vascular bundles, presence of both additional and medullary vascular bundles, position of additional vascular bundles, shape of medullary vascular bundles, presence of sclerenchyma cells ensheathed the vascular bundles. As a conclusion, midrib anatomical characteristics can be used to identify and discriminate medicinal plants species studied in the Rubiaceae.

Metabolite diffusion up to very high b in the mouse brain in vivo: Revisiting the potential correlation between relaxation and diffusion properties.

PubMed

Ligneul, Clémence; Palombo, Marco; Valette, Julien

2017-04-01

To assess the potential correlation between metabolites diffusion and relaxation in the mouse brain, which is of importance for interpreting and modeling metabolite diffusion based on pure geometry, irrespective of relaxation properties (multicompartmental relaxation or surface relaxivity). A new diffusion-weighted magnetic resonance spectroscopy sequence is introduced, dubbed "STE-LASER," which presents several nice properties, in particular the absence of cross-terms with selection gradients and a very clean localization. Metabolite diffusion is then measured in a large voxel in the mouse brain at 11.7 Tesla using a cryoprobe, resulting in excellent signal-to-noise ratio, up to very high b-values under different echo time, mixing time, and diffusion time combinations. Our results suggest that the correlation between relaxation and diffusion properties is extremely small or even nonexistent for metabolites in the mouse brain. The present work strongly supports the interpretation and modeling of metabolite diffusion primarily based on geometry, irrespective of relaxation properties, at least under current experimental conditions. Magn Reson Med 77:1390-1398, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

High-Pressure Transport Properties Of Fluids: Theory And Data From Levitated Drops At Combustion-Relevant Temperatures

NASA Technical Reports Server (NTRS)

Bellan, Josette; Harstad, Kenneth; Ohsaka, Kenichi

2003-01-01

Although the high pressure multicomponent fluid conservation equations have already been derived and approximately validated for binary mixtures by this PI, the validation of the multicomponent theory is hampered by the lack of existing mixing rules for property calculations. Classical gas dynamics theory can provide property mixing-rules at low pressures exclusively. While thermal conductivity and viscosity high-pressure mixing rules have been documented in the literature, there is no such equivalent for the diffusion coefficients and the thermal diffusion factors. The primary goal of this investigation is to extend the low pressure mixing rule theory to high pressures and validate the new theory with experimental data from levitated single drops. The two properties that will be addressed are the diffusion coefficients and the thermal diffusion factors. To validate/determine the property calculations, ground-based experiments from levitated drops are being conducted.

Brain Volume, Connectivity, and Neuropsychological Performance in Mild Traumatic Brain Injury: The Impact of Post-Traumatic Stress Disorder Symptoms.

PubMed

Lopez, Katherine C; Leary, Jacob B; Pham, Dzung L; Chou, Yi-Yu; Dsurney, John; Chan, Leighton

2017-01-01

Post-traumatic stress disorder (PTSD) is commonly associated with mild traumatic brain injury (mTBI). To better understand their relationship, we examined neuroanatomical structures and neuropsychological performance in a sample of individuals with mTBI, with and without PTSD symptoms. Thirty-nine subjects with mTBI were dichotomized into those with (n = 12) and without (n = 27) significant PTSD symptoms based on scores on the PTSD Checklist. Using a region-of-interest approach, fronto-temporal volumes, fiber bundles obtained by diffusion tensor imaging, and neuropsychological scores were compared between the two groups. After controlling for total intracranial volume and age, subjects with mTBI and PTSD symptoms exhibited volumetric differences in the entorhinal cortex, an area associated with memory networks, relative to mTBI-only patients (F = 4.28; p = 0.046). Additionally, subjects with PTSD symptoms showed reduced white matter integrity in the right cingulum bundle (axial diffusivity, F = 6.04; p = 0.020). Accompanying these structural alterations, mTBI and PTSD subjects also showed impaired performance in encoding (F = 5.98; p = 0.019) and retrieval (F = 7.32; p = 0.010) phases of list learning and in tests of processing speed (Wechsler Adult Intelligence Scale Processing Speed Index, F = 12.23; p = 0.001; Trail Making Test A, F = 5.56; p = 0.024). Increased volume and white matter disruptions in these areas, commonly associated with memory functions, may be related to functional disturbances during cognitively demanding tasks. Differences in brain volume and white matter integrity between mTBI subjects and those with mTBI and co-morbid PTSD symptoms point to neuroanatomical differences that may underlie poorer recovery of mTBI subjects who experience PTSD symptoms. These findings support theoretical models of PTSD and its relationship to learning deficits.

Progressive levels of physical dependence to tobacco coincide with changes in the anterior cingulum bundle microstructure.

PubMed

Huang, Wei; DiFranza, Joseph R; Kennedy, David N; Zhang, Nanyin; Ziedonis, Douglas; Ursprung, Sanouri; King, Jean A

2013-01-01

The tobacco withdrawal syndrome indicates the development of neurophysiologic dependence. Clinical evidence indicates that neurophysiologic dependence develops through a set sequence of symptom presentation that can be assessed with a new 3-item survey measure of wanting, craving, and needing tobacco, the Level of Physical Dependence (PD). This study sought to determine if advancing neurophysiologic dependence as measured by the Level of PD correlates with characteristics of white matter structure measured by Fractional Anisotropy (FA). Diffusion-MRI based FA and diffusion tensor imaging probabilistic tractography were used to evaluate 11 smokers and 10 nonsmokers. FA was also examined in relation to two additional measures of dependence severity, the Hooked on Nicotine Checklist (HONC), and the Fagerström Test for Nicotine Dependence (FTND). Among smokers, FA in the left anterior cingulate bundle (ACb) correlated negatively with the Level of PD (r = -0.68, p = 0.02) and HONC scores (r = -0.65, p = 0.03), but the correlation for the FTND did not reach statistical significance (r = -49, p = 0.12). With advancing Levels of PD, the density of streamlines between the ACb and precuneus increased (r = -0.67, p<0.05) and those between the ACb and white matter projecting to the superior-frontal cortex (r = -0.86, p = 0.0006) decreased significantly. The correlations between neural structure and both the clinical Level of PD survey measure and the HONC suggest that the Level of PD and the HONC may reflect the microstructural integrity of white matter, as influenced by tobacco abuse. Given that the Level of PD is measuring a sequence of symptoms of neurophysiologic dependence that develops over time, the correlation between the Level of PD and neural structure suggests that these features might represent neuroplastic changes that develop over time to support the development of neurophysiologic dependence.

Comparative transduction mechanisms of hair cells in the bullfrog utriculus. 1: Responses to intracellular current

NASA Technical Reports Server (NTRS)

Baird, Richard A.

1994-01-01

Hair cells in the bullfrog sacculus are specifically adapted to sense small-amplitude, high-frequency linear accelerations. These hair cells display many properties that are undesirable or inappropriate for hair cells that must provide static gravity sensitivity. This study resulted in part due to an interest in seeing how the transduction mechanisms of hair cells in a gravity-sensing otolith endorgan would differ from those in the bullfrog sacculus. The bullfrog utriculus is an appropriate model for these studies, because its structure is representative of higher vertebrates in general and its function as a sensor of static gravity and dynamic linear acceleration is well known. Hair cells in the bullfrog utriculus, classifiable as Type 2 by cell body and synapse morphology, differ markedly in hair bundle morphology from those in the bullfrog sacculus. Moreover, the hair bundle morphologies of utricular hair cells, unlike those in the sacculus, differ in different membrane regions.

Heat transfer in laminar flow along circular rods in infinite square arrays

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

Kim, J.H.; Li, W.H.

1988-02-01

The need to understand heat transfer characteristics over rods or tube bundles often arises in the design of compact heat exchangers and safety analysis of nuclear reactors. In particular, the fuel bundles of typical light water nuclear reactors are composed of a large number of circular rods arranged in square array pattern. The purpose of the present study is to analyze heat transfer characteristics of flow in such a multirod geometric configuration. The analysis given here will follow as closely as possible the method of Sparrow et al. who analyzed a similar problem for circular cylinders arranged in an equilateralmore » triangular array. The following major assumptions are made in the present analysis: (1) Flow is fully developed laminar flow paralleled to the axis of rods. (2) The axial profile of the surface heat flux to the fluid is uniform.(3) Thermodynamic properties are assumed constant.« less

Solid friction between soft filaments.

PubMed

Ward, Andrew; Hilitski, Feodor; Schwenger, Walter; Welch, David; Lau, A W C; Vitelli, Vincenzo; Mahadevan, L; Dogic, Zvonimir

2015-06-01

Any macroscopic deformation of a filamentous bundle is necessarily accompanied by local sliding and/or stretching of the constituent filaments. Yet the nature of the sliding friction between two aligned filaments interacting through multiple contacts remains largely unexplored. Here, by directly measuring the sliding forces between two bundled F-actin filaments, we show that these frictional forces are unexpectedly large, scale logarithmically with sliding velocity as in solid-like friction, and exhibit complex dependence on the filaments' overlap length. We also show that a reduction of the frictional force by orders of magnitude, associated with a transition from solid-like friction to Stokes's drag, can be induced by coating F-actin with polymeric brushes. Furthermore, we observe similar transitions in filamentous microtubules and bacterial flagella. Our findings demonstrate how altering a filament's elasticity, structure and interactions can be used to engineer interfilament friction and thus tune the properties of fibrous composite materials.

Solid friction between soft filaments

NASA Astrophysics Data System (ADS)

Ward, Andrew; Hilitski, Feodor; Schwenger, Walter; Welch, David; Lau, A. W. C.; Vitelli, Vincenzo; Mahadevan, L.; Dogic, Zvonimir

2015-06-01

Any macroscopic deformation of a filamentous bundle is necessarily accompanied by local sliding and/or stretching of the constituent filaments. Yet the nature of the sliding friction between two aligned filaments interacting through multiple contacts remains largely unexplored. Here, by directly measuring the sliding forces between two bundled F-actin filaments, we show that these frictional forces are unexpectedly large, scale logarithmically with sliding velocity as in solid-like friction, and exhibit complex dependence on the filaments’ overlap length. We also show that a reduction of the frictional force by orders of magnitude, associated with a transition from solid-like friction to Stokes’s drag, can be induced by coating F-actin with polymeric brushes. Furthermore, we observe similar transitions in filamentous microtubules and bacterial flagella. Our findings demonstrate how altering a filament’s elasticity, structure and interactions can be used to engineer interfilament friction and thus tune the properties of fibrous composite materials.

Mechanical splitting of microtubules into protofilament bundles by surface-bound kinesin-1

DOE PAGES

VanDelinder, Virginia; Adams, Peter G.; Bachand, George D.

2016-12-21

The fundamental biophysics of gliding microtubule (MT) motility by surface-tethered kinesin-1 motor proteins has been widely studied, as well as applied to capture and transport analytes in bioanalytical microdevices. In these systems, phenomena such as molecular wear and fracture into shorter MTs have been reported due the mechanical forces applied on the MT during transport. In the present work, we show that MTs can be split longitudinally into protofilament bundles (PFBs) by the work performed by surface-bound kinesin motors. We examine the properties of these PFBs using several techniques (e.g., fluorescence microscopy, SEM, AFM), and show that the PFBs continuemore » to be mobile on the surface and display very high curvature compared to MT. Further, higher surface density of kinesin motors and shorter kinesin-surface tethers promote PFB formation, whereas modifying MT with GMPCPP or higher paclitaxel concentrations did not affect PFB formation.« less

Continuum mechanical model for cross-linked actin networks with contractile bundles

NASA Astrophysics Data System (ADS)

Ferreira, J. P. S.; Parente, M. P. L.; Natal Jorge, R. M.

2018-01-01

In the context of a mechanical approach to cell biology, there is a close relationship between cellular function and mechanical properties. In recent years, an increasing amount of attention has been given to the coupling between biochemical and mechanical signals by means of constitutive models. In particular, on the active contractility of the actin cytoskeleton. Given the importance of the actin contraction on the physiological functions, this study propose a constitutive model to describe how the filamentous network controls its mechanics actively. Embedded in a soft isotropic ground substance, the network behaves as a viscous mechanical continuum, comprised of isotropically distributed cross-linked actin filaments and actomyosin bundles. Trough virtual rheometry experiments, the present model relates the dynamics of the myosin motors with the network stiffness, which is to a large extent governed by the time-scale of the applied deformations/forces.

Solid friction between soft filaments

DOE PAGES

Ward, Andrew; Hilitski, Feodor; Schwenger, Walter; ...

2015-03-02

Any macroscopic deformation of a filamentous bundle is necessarily accompanied by local sliding and/or stretching of the constituent filaments. Yet the nature of the sliding friction between two aligned filaments interacting through multiple contacts remains largely unexplored. Here, by directly measuring the sliding forces between two bundled F-actin filaments, we show that these frictional forces are unexpectedly large, scale logarithmically with sliding velocity as in solid-like friction, and exhibit complex dependence on the filaments’ overlap length. We also show that a reduction of the frictional force by orders of magnitude, associated with a transition from solid-like friction to Stokes’s drag,more » can be induced by coating F-actin with polymeric brushes. Furthermore, we observe similar transitions in filamentous microtubules and bacterial flagella. In conclusion, our findings demonstrate how altering a filament’s elasticity, structure and interactions can be used to engineer interfilament friction and thus tune the properties of fibrous composite materials.« less

Folding and stability of helical bundle proteins from coarse-grained models.

PubMed

Kapoor, Abhijeet; Travesset, Alex

2013-07-01

We develop a coarse-grained model where solvent is considered implicitly, electrostatics are included as short-range interactions, and side-chains are coarse-grained to a single bead. The model depends on three main parameters: hydrophobic, electrostatic, and side-chain hydrogen bond strength. The parameters are determined by considering three level of approximations and characterizing the folding for three selected proteins (training set). Nine additional proteins (containing up to 126 residues) as well as mutated versions (test set) are folded with the given parameters. In all folding simulations, the initial state is a random coil configuration. Besides the native state, some proteins fold into an additional state differing in the topology (structure of the helical bundle). We discuss the stability of the native states, and compare the dynamics of our model to all atom molecular dynamics simulations as well as some general properties on the interactions governing folding dynamics. Copyright © 2013 Wiley Periodicals, Inc.

Inhomogeneity of block copolymers at the interface of an immiscible polymer blend

NASA Astrophysics Data System (ADS)

Ryu, Ji Ho; Kim, YongJoo; Lee, Won Bo

2018-04-01

We present the effects of structure and stiffness of block copolymers on the interfacial properties of an immiscible homopolymer blend. Diblock and two-arm grafted copolymers with variation in stiffness are modeled using coarse-grained molecular dynamics to compare the compatibilization efficiency, i.e., reduction of interfacial tension. Overall, grafted copolymers are located more compactly at the interface and show better compatibilization efficiency than diblock copolymers. In addition, an increase in the stiffness for one of the blocks of the diblock copolymers causes unusual inhomogeneous interfacial coverage due to bundle formation. However, an increase in the stiffness for one of blocks of the grafted copolymers prevents the bundle formation due to the branched chain. As a result, homogeneous interfacial coverage of homopolymer blends is realized with significant reduction of interfacial tension which makes grafted copolymer a better candidate for the compatibilizer of immiscible homopolymer blend.

Evidence for two populations of hair bundles in the sea anemone, Nematostella vectensis.

PubMed

Menard, Shelcie S; Watson, Glen M

2017-06-01

Cytochalasin D (CD) was employed to disrupt F-actin within stereocilia of anemone hair bundles. CD treatment decreases the abundance of hair bundles (by 85%) while significantly impairing predation. The remaining hair bundles are 'CD-resistant.' Surprisingly, the morphology and F-actin content of resistant hair bundles are comparable to those of untreated controls. However, the resistant hair bundles fail to respond normally to the N-acetylated sugar, NANA, by elongating. Instead, they remain at resting length. Immediately after CD treatment, when only CD-resistant hair bundles are present, nematocyst discharge is normal into targets touched to tentacles in the absence of vibrations (i.e., baseline) but fails to increase normally in the presence of nearby vibrations at 56Hz, a key frequency. After CD treatment, the abundance of hair bundles recovers to control levels within three hours. At 2h after CD treatment, when CD-resistant and CD-sensitive hair bundles are both present, but a full-recovery is not yet complete, somewhat enhanced discharge of nematocysts occurs into targets touched to tentacles in the presence of nearby vibrations at 56Hz (at least as compared to the response of CD-treated animals to contact with test probes in the absence of vibrations). Additionally, at 2h after CD-treatment, prey capture recovers to normal. Thus, two populations of hair bundles may be present on tentacles of sea anemones: those that are CD-resistant and those that are CD-sensitive. The functions of these hair bundles may be distinct. Copyright © 2017 Elsevier Inc. All rights reserved.

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.

Computational Study of the Blood Flow in Three Types of 3D Hollow Fiber Membrane Bundles

PubMed Central

Zhang, Jiafeng; Chen, Xiaobing; Ding, Jun; Fraser, Katharine H.; Ertan Taskin, M.; Griffith, Bartley P.; Wu, Zhongjun J.

2013-01-01

The goal of this study is to develop a computational fluid dynamics (CFD) modeling approach to better estimate the blood flow dynamics in the bundles of the hollow fiber membrane based medical devices (i.e., blood oxygenators, artificial lungs, and hemodialyzers). Three representative types of arrays, square, diagonal, and random with the porosity value of 0.55, were studied. In addition, a 3D array with the same porosity was studied. The flow fields between the individual fibers in these arrays at selected Reynolds numbers (Re) were simulated with CFD modeling. Hemolysis is not significant in the fiber bundles but the platelet activation may be essential. For each type of array, the average wall shear stress is linearly proportional to the Re. For the same Re but different arrays, the average wall shear stress also exhibits a linear dependency on the pressure difference across arrays, while Darcy′s law prescribes a power-law relationship, therefore, underestimating the shear stress level. For the same Re, the average wall shear stress of the diagonal array is approximately 3.1, 1.8, and 2.0 times larger than that of the square, random, and 3D arrays, respectively. A coefficient C is suggested to correlate the CFD predicted data with the analytical solution, and C is 1.16, 1.51, and 2.05 for the square, random, and diagonal arrays in this paper, respectively. It is worth noting that C is strongly dependent on the array geometrical properties, whereas it is weakly dependent on the flow field. Additionally, the 3D fiber bundle simulation results show that the three-dimensional effect is not negligible. Specifically, velocity and shear stress distribution can vary significantly along the fiber axial direction. PMID:24141394

Histological analysis of the structural composition of ankle ligaments.

PubMed

Rein, Susanne; Hagert, Elisabet; Schneiders, Wolfgang; Fieguth, Armin; Zwipp, Hans

2015-02-01

Various ankle ligaments have different structural composition. The aim of this study was to analyze the morphological structure of ankle ligaments to further understand their function in ankle stability. One hundred forty ligaments from 10 fresh-frozen cadaver ankle joints were dissected: the calcaneofibular, anterior, and posterior talofibular ligaments; the inferior extensor retinaculum, the talocalcaneal oblique ligament, the canalis tarsi ligament; the deltoid ligament; and the anterior tibiofibular ligament. Hematoxylin-eosin and Elastica van Gieson stains were used for determination of tissue morphology. Three different morphological compositions were identified: dense, mixed, and interlaced compositions. Densely packed ligaments, characterized by parallel bundles of collagen, were primarily seen in the lateral region, the canalis tarsi, and the anterior tibiofibular ligaments. Ligaments with mixed tight and loose parallel bundles of collagenous connective tissue were mainly found in the inferior extensor retinaculum and talocalcaneal oblique ligament. Densely packed and fiber-rich interlacing collagen was primarily seen in the areas of ligament insertion into bone of the deltoid ligament. Ligaments of the lateral region, the canalis tarsi, and the anterior tibiofibular ligaments have tightly packed, parallel collagen bundles and thus can resist high tensile forces. The mixed tight and loose, parallel oriented collagenous connective tissue of the inferior extensor retinaculum and the talocalcaneal oblique ligament support the dynamic positioning of the foot on the ground. The interlacing collagen bundles seen at the insertion of the deltoid ligament suggest that these insertion areas are susceptible to tension in a multitude of directions. The morphology and mechanical properties of ankle ligaments may provide an understanding of their response to the loads to which they are subjected. © The Author(s) 2015.

Hexavalent chromium-induced differential disruption of cortical microtubules in some Fabaceae species is correlated with acetylation of α-tubulin.

PubMed

Eleftheriou, Eleftherios P; Adamakis, Ioannis-Dimosthenis S; Michalopoulou, Vasiliki A

2016-03-01

The effects of hexavalent chromium [Cr(VI)] on the cortical microtubules (MTs) of five species of the Fabaceae family (Vicia faba, Pisum sativum, Vigna sinensis, Vigna angularis, and Medicago sativa) were investigated by confocal laser scanning microscopy after immunolocalization of total tubulin with conventional immunofluorescence techniques and of acetylated α-tubulin with the specific 6-11B-1 monoclonal antibody. Moreover, total α-tubulin and acetylated α-tubulin were quantified by Western immunoblotting and scanning densitometry. Results showed the universality of Cr(VI) detrimental effects to cortical MTs, which proved to be a sensitive and reliable subcellular marker for monitoring Cr(VI) toxicity in plant cells. However, a species-specific response was recorded, and a correlation of MT disturbance with the acetylation status of α-tubulin was demonstrated. In V. faba, MTs were depolymerized at the gain of cytoplasmic tubulin background and displayed low α-tubulin acetylation, while in P. sativum, V. sinensis, V. angularis, and M. sativa, MTs became bundled and changed orientation from perpendicular to oblique or longitudinal. Bundled MTs were highly acetylated as determined by both immunofluorescence and Western immunoblotting. Tubulin acetylation in P. sativum and M. sativa preceded MT bundling; in V. sinensis it followed MT derangement, while in V. angularis the two phenomena coincided. Total α-tubulin remained constant in all treatments. Should acetylation be an indicator of MT stabilization, it is deduced that bundled MTs became stabilized, lost their dynamic properties, and were rendered inactive. Results of this report allow the conclusion that Cr(VI) toxicity disrupts MTs and deranges the MT-mediated functions either by depolymerizing or stabilizing them.

Metabolite diffusion up to very high b in the mouse brain in vivo: Revisiting the potential correlation between relaxation and diffusion properties

PubMed Central

Ligneul, Clémence; Palombo, Marco

2016-01-01

Purpose To assess the potential correlation between metabolites diffusion and relaxation in the mouse brain, which is of importance for interpreting and modeling metabolite diffusion based on pure geometry, irrespective of relaxation properties (multicompartmental relaxation or surface relaxivity). Methods A new diffusion‐weighted magnetic resonance spectroscopy sequence is introduced, dubbed “STE‐LASER,” which presents several nice properties, in particular the absence of cross‐terms with selection gradients and a very clean localization. Metabolite diffusion is then measured in a large voxel in the mouse brain at 11.7 Tesla using a cryoprobe, resulting in excellent signal‐to‐noise ratio, up to very high b‐values under different echo time, mixing time, and diffusion time combinations. Results Our results suggest that the correlation between relaxation and diffusion properties is extremely small or even nonexistent for metabolites in the mouse brain. Conclusion The present work strongly supports the interpretation and modeling of metabolite diffusion primarily based on geometry, irrespective of relaxation properties, at least under current experimental conditions. Magn Reson Med 77:1390–1398, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made. PMID:27018415

Characterizing molecular probes for diffusion measurements in the brain

PubMed Central

Kaur, Gurjinder; Hrabetova, Sabina; Guilfoyle, David N.; Nicholson, Charles; Hrabe, Jan

2008-01-01

Brain diffusion properties are at present most commonly evaluated by magnetic resonance (MR) diffusion imaging. MR cannot easily distinguish between the extracellular and intracellular signal components, but the older technique of Real-Time Iontophoresis (RTI) detects exclusively extracellular diffusion. Interpretation of the MR results would therefore benefit from auxiliary RTI measurements. This requires a molecular probe detectable by both techniques. Our aim was to specify a minimum set of requirements that such a diffusion probe should fulfill and apply it to two candidate probes: the cation tetramethylammonium (TMA+), used routinely in the RTI experiments, and the anion hexafluoroantimonate (SbF6−). Desirable characteristics of a molecular diffusion probe include predictable diffusion properties, stability, minimum interaction with cellular physiology, very slow penetration into the cells, and sufficiently strong and selective MR and RTI signals. These properties were evaluated using preparations of rat neocortical slices under normal and ischemic conditions, as well as solutions and agarose gel. While both molecules can be detected by MR and RTI, neither proved an ideal candidate. TMA+ was very stable but it penetrated into the cells and accumulated there within tens of minutes. SbF6− did not enter the cells as readily but it was not stable, particularly in ischemic tissue and at higher temperatures. Its presence also resulted in a decreased extracellular volume. These probe properties help to interpret previously published MR data on TMA+ diffusion and might play a role in other diffusion experiments obtained with them. PMID:18466980

Translating Pressure Ulcer Prevention Into Intensive Care Nursing Practice: Overlaying a Care Bundle Approach With a Model for Research Implementation.

PubMed

Tayyib, Nahla; Coyer, Fiona

This article reports on the development and implementation process used to integrate a care bundle approach (a pressure ulcer [PU] prevention bundle to improve patients' skin integrity in intensive care) and the Ottawa Model of Research Use (OMRU). The PU prevention care bundle demonstrated significant reduction in PU incidence, with the OMRU model providing a consolidated framework for the implementation of bundled evidence in an effective and consistent manner into daily clinical nursing practice.

Diffusion, swelling, cross linkage study and mechanical properties of ZnO doped PVA/NaAlg blend polymer nanocomposite

NASA Astrophysics Data System (ADS)

Guruswamy, B.; Ravindrachary, V.; Shruthi, C.; Hegde, Shreedatta; Sagar, Rohan N.

2018-04-01

ZnO nano particles were synthesized using a chemical precipitation method. Pure and ZnO nano particle doped PVA-NaAlg blend composite films were prepared using solution casing method. Structural information of these composites was studied using FTIR. Diffusion kinetics of these polymer blend composite were studied using Flory-Huggins theory. Using these diffusion studies, cross-linking density and swelling properties of the films were analyzed. Mechanical properties of these composite are also studied.

The Plasticity of the Superior Longitudinal Fasciculus as a Function of Musical Expertise: A Diffusion Tensor Imaging Study

PubMed Central

Oechslin, Mathias S.; Imfeld, Adrian; Loenneker, Thomas; Meyer, Martin; Jäncke, Lutz

2009-01-01

Previous neuroimaging studies have demonstrated that musical expertise leads to functional alterations in language processing. We utilized diffusion tensor imaging (DTI) to investigate white matter plasticity in musicians with absolute pitch (AP), relative pitch and non-musicians. Using DTI, we analysed the fractional anisotropy (FA) of the superior longitudinal fasciculus (SLF), which is considered the most primary pathway for processing and production of speech and music. In association with different levels of musical expertise, we found that AP is characterized by a greater left than right asymmetry of FA in core fibres of the SLF. A voxel-based analysis revealed three clusters within the left hemisphere SLF that showed significant positive correlations with error rates only for AP-musicians in an AP-test, but not for musicians without AP. We therefore conclude that the SLF architecture in AP musicians is related to AP acuity. In order to reconcile our observations with general aspects of development of fibre bundles, we introduce the Pioneer Axon Thesis, a theoretical approach to formalize axonal arrangements of major white matter pathways. PMID:20161812

Connectome imaging for mapping human brain pathways

PubMed Central

Shi, Y; Toga, A W

2017-01-01

With the fast advance of connectome imaging techniques, we have the opportunity of mapping the human brain pathways in vivo at unprecedented resolution. In this article we review the current developments of diffusion magnetic resonance imaging (MRI) for the reconstruction of anatomical pathways in connectome studies. We first introduce the background of diffusion MRI with an emphasis on the technical advances and challenges in state-of-the-art multi-shell acquisition schemes used in the Human Connectome Project. Characterization of the microstructural environment in the human brain is discussed from the tensor model to the general fiber orientation distribution (FOD) models that can resolve crossing fibers in each voxel of the image. Using FOD-based tractography, we describe novel methods for fiber bundle reconstruction and graph-based connectivity analysis. Building upon these novel developments, there have already been successful applications of connectome imaging techniques in reconstructing challenging brain pathways. Examples including retinofugal and brainstem pathways will be reviewed. Finally, we discuss future directions in connectome imaging and its interaction with other aspects of brain imaging research. PMID:28461700

Search for Ultra-High-Energy Neutrinos with AMANDA-II

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

Ackermann, M.; Bernardini, E.; Adams, J.

2008-03-10

A search for diffuse neutrinos with energies in excess of 10{sup 5} GeV is conducted with AMANDA-II data recorded between 2000 and 2002. Above 10{sup 7} GeV, the Earth is essentially opaque to neutrinos. This fact, combined with the limited overburden of the AMANDA-II detector (roughly 1.5 km), concentrates these ultra-high-energy neutrinos at the horizon. The primary background for this analysis is bundles of downgoing, high-energy muons from the interaction of cosmic rays in the atmosphere. No statistically significant excess above the expected background is seen in the data, and an upper limit is set on the diffuse all-flavor neutrinomore » flux of E{sup 2}{phi}{sub 90%CL} < 2.7 x 10{sup -7} GeV cm{sup -2} s{sup -1} sr{sup -1} valid over the energy range of 2 x 10{sup 5} to 10{sup 9} GeV. A number of models that predict neutrino fluxes from active galactic nuclei are excluded at the 90% confidence level.« less

Search for Ultra High-Energy Neutrinos with AMANDA-II

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

IceCube Collaboration; Klein, Spencer; Ackermann, M.

2007-11-19

A search for diffuse neutrinos with energies in excess of 10{sup 5} GeV is conducted with AMANDA-II data recorded between 2000 and 2002. Above 10{sup 7} GeV, the Earth is essentially opaque to neutrinos. This fact, combined with the limited overburden of the AMANDA-II detector (roughly 1.5 km), concentrates these ultra high-energy neutrinos at the horizon. The primary background for this analysis is bundles of downgoing, high-energy muons from the interaction of cosmic rays in the atmosphere. No statistically significant excess above the expected background is seen in the data, and an upper limit is set on the diffuse all-flavormore » neutrino flux of E{sup 2} {Phi}{sub 90%CL} < 2.7 x 10{sup -7} GeV cm{sup -2}s{sup -1} sr{sup -1} valid over the energy range of 2 x 10{sup 5} GeV to 10{sup 9} GeV. A number of models which predict neutrino fluxes from active galactic nuclei are excluded at the 90% confidence level.« less

Two-particle problem in comblike structures

NASA Astrophysics Data System (ADS)

Agliari, Elena; Cassi, Davide; Cattivelli, Luca; Sartori, Fabio

2016-05-01

Encounters between walkers performing a random motion on an appropriate structure can describe a wide variety of natural phenomena ranging from pharmacokinetics to foraging. On homogeneous structures the asymptotic encounter probability between two walkers is (qualitatively) independent of whether both walkers are moving or one is kept fixed. On infinite comblike structures this is no longer the case and here we deepen the mechanisms underlying the emergence of a finite probability that two random walkers will never meet, while one single random walker is certain to visit any site. In particular, we introduce an analytical approach to address this problem and even more general problems such as the case of two walkers with different diffusivity, particles walking on a finite comb and on arbitrary bundled structures, possibly in the presence of loops. Our investigations are both analytical and numerical and highlight that, in general, the outcome of a reaction involving two reactants on a comblike architecture can strongly differ according to whether both reactants are moving (no matter their relative diffusivities) or only one is moving and according to the density of shortcuts among the branches.

Field Emission Study of Carbon Nanotubes: High Current Density from Nanotube Bundle Arrays

NASA Technical Reports Server (NTRS)

Bronikowski, Micheal J.; Manohara, Harish M.; Siegel, Peter H.; Hunt, Brian D.

2004-01-01

We have investigated the field emission behavior of lithographically patterned bundles of multiwalled carbon nanotubes arranged in a variety of array geometries. Such arrays of nanotube bundles are found to perform significantly better in field emission than arrays of isolated nanotubes or dense, continuous mats of nanotubes, with the field emission performance depending on the bundle diameter and inter-bundle spacing. Arrays of 2-micrometers diameter nanotube bundles spaced 5 micrometers apart (edge-to-edge spacing) produced the largest emission densities, routinely giving 1.5 to 1.8 A/cm(sup 2) at approximately 4 V/micrometer electric field, and greater than 6 A/cm(sup 2) at 20 V/micrometers.

National Partnership for Maternal Safety: Consensus Bundle on Safe Reduction of Primary Cesarean Births-Supporting Intended Vaginal Births.

PubMed

Lagrew, David C; Low, Lisa Kane; Brennan, Rita; Corry, Maureen P; Edmonds, Joyce K; Gilpin, Brian G; Frost, Jennifer; Pinger, Whitney; Reisner, Dale P; Jaffer, Sara

2018-03-01

Cesarean births and associated morbidity and mortality have reached near epidemic proportions. The National Partnership for Maternal Safety under the guidance of the Council on Patient Safety in Women's Health Care responded by developing a patient safety bundle to reduce the number of primary cesarean births. Safety bundles outline critical practices to implement in every maternity unit. This National Partnership for Maternity Safety bundle, as with other bundles, is organized into four domains: Readiness, Recognition and Prevention, Response, and Reporting and Systems Learning. Bundle components may be adapted to individual facilities, but standardization within an institution is advised. Evidence-based resources and recommendations are provided to assist implementation.

Matrix remodeling between cells and cellular interactions with collagen bundle

NASA Astrophysics Data System (ADS)

Kim, Jihan; Sun, Bo

When cells are surrounded by complex environment, they continuously probe and interact with it by applying cellular traction forces. As cells apply traction forces, they can sense rigidity of their local environment and remodel the matrix microstructure simultaneously. Previous study shows that single human carcinoma cell (MDA-MB-231) remodeled its surrounding extracellular matrix (ECM) and the matrix remodeling was reversible. In this study we examined the matrix microstructure between cells and cellular interaction between them using quantitative confocal microscopy. The result shows that the matrix microstructure is the most significantly remodeled between cells consisting of aligned, and densified collagen fibers (collagen bundle)., the result shows that collagen bundle is irreversible and significantly change micromechanics of ECM around the bundle. We further examined cellular interaction with collagen bundle by analyzing dynamics of actin and talin formation along with the direction of bundle. Lastly, we analyzed dynamics of cellular protrusion and migrating direction of cells along the bundle.

Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction With a Free Quadriceps Tendon Autograft.

PubMed

Caterev, Sergiu; Nistor, Dan Viorel; Todor, Adrian

2016-10-01

Anatomic double-bundle anterior cruciate ligament (ACL) reconstruction aims to restore the 2 functional bundles of the ACL in an attempt to better reproduce the native biomechanics of the injured knee and promote long-term knee health. However, this concept is not fully accepted and is not performed on a standard basis. In addition, the superiority of this technique over the conventional single-bundle technique has been questioned, especially the long-term clinical results. One of the down sides of the double-bundle reconstruction is the complexity of the procedure, with increased risks, operative time, and costs compared with the single-bundle procedure. Also, the revision procedure, if necessary, is more challenging. We propose a technique that has some advantages over the traditional double-bundle procedure, using a single femoral tunnel, 2 tibial tunnels, and a free quadriceps tendon autograft.

Synchronization of Spontaneous Active Motility of Hair Cell Bundles

PubMed Central

Zhang, Tracy-Ying; Ji, Seung; Bozovic, Dolores

2015-01-01

Hair cells of the inner ear exhibit an active process, believed to be crucial for achieving the sensitivity of auditory and vestibular detection. One of the manifestations of the active process is the occurrence of spontaneous hair bundle oscillations in vitro. Hair bundles are coupled by overlying membranes in vivo; hence, explaining the potential role of innate bundle motility in the generation of otoacoustic emissions requires an understanding of the effects of coupling on the active bundle dynamics. We used microbeads to connect small groups of hair cell bundles, using in vitro preparations that maintain their innate oscillations. Our experiments demonstrate robust synchronization of spontaneous oscillations, with either 1:1 or multi-mode phase-locking. The frequency of synchronized oscillation was found to be near the mean of the innate frequencies of individual bundles. Coupling also led to an improved regularity of entrained oscillations, demonstrated by an increase in the quality factor. PMID:26540409

A Fundamental Study of the Electromagnetic Properties of Advanced Composite Materials

DTIC Science & Technology

1978-07-01

MKDC), Space and Missile Systems Organization (SAMSO). Aeronautical System Division (ASD), Electronic Systems Division ( ESD ), Air Force Avionics...discussions, the work reported involved only one fiber type--Thornel T300 as used in Narmco 5208 pre-preg tapes . Individual graphite fibers have radii... teflon coated tweezers to separate individual fibers from the bundle. Microscopic observation and a steady hand during this procedure improved the

Exploring Differential Bundle Functioning in Mathematics by Gender: The Effect of Hierarchical Modelling

ERIC Educational Resources Information Center

Ong, Yoke Mooi; Williams, Julian; Lamprianou, Iasonas

2013-01-01

Researchers interested in exploring substantive group differences are increasingly attending to bundles of items (or testlets): the aim is to understand how gender differences, for instance, are explained by differential performances on different types or bundles of items, hence differential bundle functioning (DBF). Some previous work has…

Universal fiber-optic C.I.E. colorimeter

DOEpatents

Kronberg, James W.

1992-01-01

Apparatus for color measurements according to the C.I.E. system comprises a first fiber optic cable for receiving and linearizing light from a light source, a lens system for spectrally displaying the linearized light and focusing the light on one end of a trifurcated fiber optic assembly that integrates and separates the light according to the three C.I.E. tristimulus functions. The separated light is received by three photodiodes and electronically evaluated to determine the magnitude of the light corresponding to the tristimulus functions. The fiber optic assembly is made by forming, at one end, a bundle of optic fibers to match the contours of one of the tristimulus functions, encapsulating that bundle, adding a second bundle that, together with the first bundle, will match the contours of the first plus one other tristimulus function, encapsulating that second bundle, then adding a third bundle which together with the first and second bundles, has contours matching the sum of all three tristimulus functions. At the other end of the assembly the three bundles are separated and aligned with their respective photodiodes.

Implementing a Daily Maintenance Care Bundle to Prevent Central Line-Associated Bloodstream Infections in Pediatric Oncology Patients.

PubMed

Duffy, Elizabeth A; Rodgers, Cheryl C; Shever, Leah L; Hockenberry, Marilyn J

2015-01-01

Eliminating central line-associated bloodstream infection (CLABSI) is a national priority. Central venous catheter (CVC) care bundles are composed of a series of interventions that, when used together, are effective in preventing CLABSI. A CVC daily maintenance care bundle includes procedural guidelines for hygiene, dressing changes, and access as well as specific timeframes. Failure to complete one of the components of the care bundle predisposes the patient to a bloodstream infection. A nurse-led multidisciplinary team implemented and, for six months, sustained a daily maintenance care bundle for pediatric oncology patients. This quality improvement project focused on nursing staffs' implementation of the daily maintenance care bundle and the sustainment of the intervention. The project used a pre-post program design to evaluate outcomes of CVC daily maintenance care bundle compliancy and CLABSI. A statistically significant increase between the pre- and post-assessments of the compliance was noted with the CVC daily maintenance care bundle. CLABSI infection rates decreased during the intervention. Strategies to implement practice change and promote sustainability are discussed. © 2015 by Association of Pediatric Hematology/Oncology Nurses.

National Partnership for Maternal Safety: Consensus Bundle on Severe Hypertension During Pregnancy and the Postpartum Period.

PubMed

Bernstein, Peter S; Martin, James N; Barton, John R; Shields, Laurence E; Druzin, Maurice L; Scavone, Barbara M; Frost, Jennifer; Morton, Christine H; Ruhl, Catherine; Slager, Joan; Tsigas, Eleni Z; Jaffer, Sara; Menard, M Kathryn

2017-08-01

Complications arising from hypertensive disorders of pregnancy are among the leading causes of preventable severe maternal morbidity and mortality. Timely and appropriate treatment has the potential to significantly reduce hypertension-related complications. To assist health care providers in achieving this goal, this patient safety bundle provides guidance to coordinate and standardize the care provided to women with severe hypertension during pregnancy and the postpartum period. This is one of several patient safety bundles developed by multidisciplinary work groups of the National Partnership for Maternal Safety under the guidance of the Council on Patient Safety in Women's Health Care. These safety bundles outline critical clinical practices that should be implemented in every maternity care setting. Similar to other bundles that have been developed and promoted by the Partnership, the hypertension safety bundle is organized into four domains: Readiness, Recognition and Prevention, Response, and Reporting and Systems Learning. Although the bundle components may be adapted to meet the resources available in individual facilities, standardization within an institution is strongly encouraged. This commentary provides information to assist with bundle implementation.

Microtubule bundling plays a role in ethylene-mediated cortical microtubule reorientation in etiolated Arabidopsis hypocotyls.

PubMed

Ma, Qianqian; Sun, Jingbo; Mao, Tonglin

2016-05-15

The gaseous hormone ethylene is known to regulate plant growth under etiolated conditions (the 'triple response'). Although organization of cortical microtubules is essential for cell elongation, the underlying mechanisms that regulate microtubule organization by hormone signaling, including ethylene, are ambiguous. In the present study, we demonstrate that ethylene signaling participates in regulation of cortical microtubule reorientation. In particular, regulation of microtubule bundling is important for this process in etiolated hypocotyls. Time-lapse analysis indicated that selective stabilization of microtubule-bundling structures formed in various arrays is related to ethylene-mediated microtubule orientation. Bundling events and bundle growth lifetimes were significantly increased in oblique and longitudinal arrays, but decreased in transverse arrays in wild-type cells in response to ethylene. However, the effects of ethylene on microtubule bundling were partially suppressed in a microtubule-bundling protein WDL5 knockout mutant (wdl5-1). This study suggests that modulation of microtubule bundles that have formed in certain orientations plays a role in reorienting microtubule arrays in response to ethylene-mediated etiolated hypocotyl cell elongation. © 2016. Published by The Company of Biologists Ltd.

Abnormal Q waves in right sided chest leads provoked by onset of right bundle-branch block in patients with anteroseptal infarction.

PubMed Central

Rosenbaum, M B; Girotti, L A; Lázzari, J O; Halpern, M S; Elizari, M V

1982-01-01

In five cases of anteroseptal myocardial infarction complicated by intermittent right bundle-branch block, the onset of right bundle-branch block provoked the appearance of abnormal Q waves in leads V1 and V2, whereas a small initial R wave was present in the same leads during normal conduction. The intermittency of the conduction disturbance indicated that the Q waves were "right bundle-branch block dependent". It was also apparent that right bundle-branch block shifted the electrical location of the infarct towards the right, and made it look much larger. Right bundle-branch block dependent Q waves may arise during the acute stage of an anterior infarct suggesting, fallaciously, that an acute extension has occurred, or during the chronic stage, leading to the erroneous supposition that a new infarct had developed. The abnormal Q waves anteroseptal infarction complicated by fixed right bundle-branch block, though obviously related to the infarct, may be dependent on the right bundle-branch block. PMID:7059400

Influence of fiber packing structure on permeability

NASA Technical Reports Server (NTRS)

Cai, Zhong; Berdichevsky, Alexander L.

1993-01-01

The study on the permeability of an aligned fiber bundle is the key building block in modeling the permeability of advanced woven and braided preforms. Available results on the permeability of fiber bundles in the literature show that a substantial difference exists between numerical and analytical calculations on idealized fiber packing structures, such as square and hexagonal packing, and experimental measurements on practical fiber bundles. The present study focuses on the variation of the permeability of a fiber bundle under practical process conditions. Fiber bundles are considered as containing openings and fiber clusters within the bundle. Numerical simulations on the influence of various openings on the permeability were conducted. Idealized packing structures are used, but with introduced openings distributed in different patterns. Both longitudinal and transverse flow are considered. The results show that openings within the fiber bundle have substantial effect on the permeability. In the longitudinal flow case, the openings become the dominant flow path. In the transverse flow case, the fiber clusters reduce the gap sizes among fibers. Therefore the permeability is greatly influenced by these openings and clusters, respectively. In addition to the porosity or fiber volume fraction, which is commonly used in the permeability expression, another fiber bundle status parameter, the ultimate fiber volume fraction, is introduced to capture the disturbance within a fiber bundle.

Accuracy of Shack-Hartmann wavefront sensor using a coherent wound fibre image bundle

NASA Astrophysics Data System (ADS)

Zheng, Jessica R.; Goodwin, Michael; Lawrence, Jon

2018-03-01

Shack-Hartmannwavefront sensors using wound fibre image bundles are desired for multi-object adaptive optical systems to provide large multiplex positioned by Starbugs. The use of a large-sized wound fibre image bundle provides the flexibility to use more sub-apertures wavefront sensor for ELTs. These compact wavefront sensors take advantage of large focal surfaces such as the Giant Magellan Telescope. The focus of this paper is to study the wound fibre image bundle structure defects effect on the centroid measurement accuracy of a Shack-Hartmann wavefront sensor. We use the first moment centroid method to estimate the centroid of a focused Gaussian beam sampled by a simulated bundle. Spot estimation accuracy with wound fibre image bundle and its structure impact on wavefront measurement accuracy statistics are addressed. Our results show that when the measurement signal-to-noise ratio is high, the centroid measurement accuracy is dominated by the wound fibre image bundle structure, e.g. tile angle and gap spacing. For the measurement with low signal-to-noise ratio, its accuracy is influenced by the read noise of the detector instead of the wound fibre image bundle structure defects. We demonstrate this both with simulation and experimentally. We provide a statistical model of the centroid and wavefront error of a wound fibre image bundle found through experiment.

Spatial confinement of active microtubule networks induces large-scale rotational cytoplasmic flow

PubMed Central

Suzuki, Kazuya; Miyazaki, Makito; Takagi, Jun; Itabashi, Takeshi; Ishiwata, Shin’ichi

2017-01-01

Collective behaviors of motile units through hydrodynamic interactions induce directed fluid flow on a larger length scale than individual units. In cells, active cytoskeletal systems composed of polar filaments and molecular motors drive fluid flow, a process known as cytoplasmic streaming. The motor-driven elongation of microtubule bundles generates turbulent-like flow in purified systems; however, it remains unclear whether and how microtubule bundles induce large-scale directed flow like the cytoplasmic streaming observed in cells. Here, we adopted Xenopus egg extracts as a model system of the cytoplasm and found that microtubule bundle elongation induces directed flow for which the length scale and timescale depend on the existence of geometrical constraints. At the lower activity of dynein, kinesins bundle and slide microtubules, organizing extensile microtubule bundles. In bulk extracts, the extensile bundles connected with each other and formed a random network, and vortex flows with a length scale comparable to the bundle length continually emerged and persisted for 1 min at multiple places. When the extracts were encapsulated in droplets, the extensile bundles pushed the droplet boundary. This pushing force initiated symmetry breaking of the randomly oriented bundle network, leading to bundles aligning into a rotating vortex structure. This vortex induced rotational cytoplasmic flows on the length scale and timescale that were 10- to 100-fold longer than the vortex flows emerging in bulk extracts. Our results suggest that microtubule systems use not only hydrodynamic interactions but also mechanical interactions to induce large-scale temporally stable cytoplasmic flow. PMID:28265076

Reducing hospital-acquired pressure ulcers using bundle methodology in pediatric and neonatal patients receiving extracorporeal membrane oxygenation therapy: An integrative review and call to action.

PubMed

Courtwright, Suzanne E; Mastro, Kari A; Preuster, Christa; Dardashti, Navid; McGill, Sandra; Madelon, Myrlene; Johnson, Donna

2017-10-01

This review focuses on identifying (1) evidence of the effectiveness of care bundle methodology to reduce hospital-acquired pressure ulcers (HAPUs) in pediatric and neonatal patients receiving extracorporeal membrane oxygenation (ECMO) therapy and (2) barriers to implementing HAPU care bundles in this at-risk population. An integrative review was conducted and reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A search of the scientific literature was performed. Studies included were published between January 2011 and February 2016. A total of seven articles met inclusion criteria. Data were extracted from each published article and analyzed to identify common themes, specifically bundle methodology and barriers to implementing HAPU bundles, in this population. There is limited research on effectiveness of care bundle methodology in reducing HAPUs in children, and no research specific to its effectiveness in pediatric or neonatal ECMO patients. No research was identified studying barriers to implementation of HAPU care bundles in this population. Nurses are well poised to test innovative strategies to prevent HAPUs. Nurses should consider implementing and testing bundle methodology to reduce HAPU in this at-risk population, and conduct research to identify any barriers to implementing this strategy. There is literature to support the use of nurses as unit-based skin care champions to facilitate teamwork and reliable use of the bundle, both critical components to the success of bundle methodology. © 2017 Wiley Periodicals, Inc.

Generating a Simulated Fluid Flow Over an Aircraft Surface Using Anisotropic Diffusion

NASA Technical Reports Server (NTRS)

Rodriguez, David L. (Inventor); Sturdza, Peter (Inventor)

2013-01-01

A fluid-flow simulation over a computer-generated aircraft surface is generated using a diffusion technique. The surface is comprised of a surface mesh of polygons. A boundary-layer fluid property is obtained for a subset of the polygons of the surface mesh. A pressure-gradient vector is determined for a selected polygon, the selected polygon belonging to the surface mesh but not one of the subset of polygons. A maximum and minimum diffusion rate is determined along directions determined using a pressure gradient vector corresponding to the selected polygon. A diffusion-path vector is defined between a point in the selected polygon and a neighboring point in a neighboring polygon. An updated fluid property is determined for the selected polygon using a variable diffusion rate, the variable diffusion rate based on the minimum diffusion rate, maximum diffusion rate, and angular difference between the diffusion-path vector and the pressure-gradient vector.

Sustained Reduction of Ventilator-Associated Pneumonia Rates Using Real-Time Course Correction With a Ventilator Bundle Compliance Dashboard.

PubMed

Talbot, Thomas R; Carr, Devin; Parmley, C Lee; Martin, Barbara J; Gray, Barbara; Ambrose, Anna; Starmer, Jack

2015-11-01

The effectiveness of practice bundles on reducing ventilator-associated pneumonia (VAP) has been questioned. To implement a comprehensive program that included a real-time bundle compliance dashboard to improve compliance and reduce ventilator-associated complications. DESIGN Before-and-after quasi-experimental study with interrupted time-series analysis. SETTING Academic medical center. In 2007 a comprehensive institutional ventilator bundle program was developed. To assess bundle compliance and stimulate instant course correction of noncompliant parameters, a real-time computerized dashboard was developed. Program impact in 6 adult intensive care units (ICUs) was assessed. Bundle compliance was noted as an overall cumulative bundle adherence assessment, reflecting the percentage of time all elements were concurrently in compliance for all patients. The VAP rate in all ICUs combined decreased from 19.5 to 9.2 VAPs per 1,000 ventilator-days following program implementation (P<.001). Bundle compliance significantly increased (Z100 score of 23% in August 2007 to 83% in June 2011 [P<.001]). The implementation resulted in a significant monthly decrease in the overall ICU VAP rate of 3.28/1,000 ventilator-days (95% CI, 2.64-3.92/1,000 ventilator-days). Following the intervention, the VAP rate decreased significantly at a rate of 0.20/1,000 ventilator-days per month (95% CI, 0.14-0.30/1,000 ventilator-days per month). Among all adult ICUs combined, improved bundle compliance was moderately correlated with monthly VAP rate reductions (Pearson correlation coefficient, -0.32). A prevention program using a real-time bundle adherence dashboard was associated with significant sustained decreases in VAP rates and an increase in bundle compliance among adult ICU patients.

High-resolution imaging of the retinal nerve fiber layer in normal eyes using adaptive optics scanning laser ophthalmoscopy.

PubMed

Takayama, Kohei; Ooto, Sotaro; Hangai, Masanori; Arakawa, Naoko; Oshima, Susumu; Shibata, Naohisa; Hanebuchi, Masaaki; Inoue, Takashi; Yoshimura, Nagahisa

2012-01-01

To conduct high-resolution imaging of the retinal nerve fiber layer (RNFL) in normal eyes using adaptive optics scanning laser ophthalmoscopy (AO-SLO). AO-SLO images were obtained in 20 normal eyes at multiple locations in the posterior polar area and a circular path with a 3-4-mm diameter around the optic disc. For each eye, images focused on the RNFL were recorded and a montage of AO-SLO images was created. AO-SLO images for all eyes showed many hyperreflective bundles in the RNFL. Hyperreflective bundles above or below the fovea were seen in an arch from the temporal periphery on either side of a horizontal dividing line to the optic disc. The dark lines among the hyperreflective bundles were narrower around the optic disc compared with those in the temporal raphe. The hyperreflective bundles corresponded with the direction of the striations on SLO red-free images. The resolution and contrast of the bundles were much higher in AO-SLO images than in red-free fundus photography or SLO red-free images. The mean hyperreflective bundle width around the optic disc had a double-humped shape; the bundles at the temporal and nasal sides of the optic disc were narrower than those above and below the optic disc (P<0.001). RNFL thickness obtained by optical coherence tomography correlated with the hyperreflective bundle widths on AO-SLO (P<0.001) AO-SLO revealed hyperreflective bundles and dark lines in the RNFL, believed to be retinal nerve fiber bundles and Müller cell septa. The widths of the nerve fiber bundles appear to be proportional to the RNFL thickness at equivalent distances from the optic disc.

High-resolution imaging of retinal nerve fiber bundles in glaucoma using adaptive optics scanning laser ophthalmoscopy.

PubMed

Takayama, Kohei; Ooto, Sotaro; Hangai, Masanori; Ueda-Arakawa, Naoko; Yoshida, Sachiko; Akagi, Tadamichi; Ikeda, Hanako Ohashi; Nonaka, Atsushi; Hanebuchi, Masaaki; Inoue, Takashi; Yoshimura, Nagahisa

2013-05-01

To detect pathologic changes in retinal nerve fiber bundles in glaucomatous eyes seen on images obtained by adaptive optics (AO) scanning laser ophthalmoscopy (AO SLO). Prospective cross-sectional study. Twenty-eight eyes of 28 patients with open-angle glaucoma and 21 normal eyes of 21 volunteer subjects underwent a full ophthalmologic examination, visual field testing using a Humphrey Field Analyzer, fundus photography, red-free SLO imaging, spectral-domain optical coherence tomography, and imaging with an original prototype AO SLO system. The AO SLO images showed many hyperreflective bundles suggesting nerve fiber bundles. In glaucomatous eyes, the nerve fiber bundles were narrower than in normal eyes, and the nerve fiber layer thickness was correlated with the nerve fiber bundle widths on AO SLO (P < .001). In the nerve fiber layer defect area on fundus photography, the nerve fiber bundles on AO SLO were narrower compared with those in normal eyes (P < .001). At 60 degrees on the inferior temporal side of the optic disc, the nerve fiber bundle width was significantly lower, even in areas without nerve fiber layer defect, in eyes with glaucomatous eyes compared with normal eyes (P = .026). The mean deviations of each cluster in visual field testing were correlated with the corresponding nerve fiber bundle widths (P = .017). AO SLO images showed reduced nerve fiber bundle widths both in clinically normal and abnormal areas of glaucomatous eyes, and these abnormalities were associated with visual field defects, suggesting that AO SLO may be useful for detecting early nerve fiber bundle abnormalities associated with loss of visual function. Copyright © 2013 Elsevier Inc. All rights reserved.

The vertical occipital fasciculus: a century of controversy resolved by in vivo measurements.

PubMed

Yeatman, Jason D; Weiner, Kevin S; Pestilli, Franco; Rokem, Ariel; Mezer, Aviv; Wandell, Brian A

2014-12-02

The vertical occipital fasciculus (VOF) is the only major fiber bundle connecting dorsolateral and ventrolateral visual cortex. Only a handful of studies have examined the anatomy of the VOF or its role in cognition in the living human brain. Here, we trace the contentious history of the VOF, beginning with its original discovery in monkey by Wernicke (1881) and in human by Obersteiner (1888), to its disappearance from the literature, and recent reemergence a century later. We introduce an algorithm to identify the VOF in vivo using diffusion-weighted imaging and tractography, and show that the VOF can be found in every hemisphere (n = 74). Quantitative T1 measurements demonstrate that tissue properties, such as myelination, in the VOF differ from neighboring white-matter tracts. The terminations of the VOF are in consistent positions relative to cortical folding patterns in the dorsal and ventral visual streams. Recent findings demonstrate that these same anatomical locations also mark cytoarchitectonic and functional transitions in dorsal and ventral visual cortex. We conclude that the VOF is likely to serve a unique role in the communication of signals between regions on the ventral surface that are important for the perception of visual categories (e.g., words, faces, bodies, etc.) and regions on the dorsal surface involved in the control of eye movements, attention, and motion perception.

Implementation of a post-cardiac arrest care bundle including therapeutic hypothermia and hemodynamic optimization in comatose patients with return of spontaneous circulation after out-of-hospital cardiac arrest: a feasibility study.

PubMed

Walters, Elizabeth Lea; Morawski, Kyle; Dorotta, Ihab; Ramsingh, Davinder; Lumen, Kelly; Bland, David; Clem, Kathleen; Nguyen, H Bryant

2011-04-01

Patients who present to the emergency department (ED) with return of spontaneous circulation after cardiac arrest generally have poor outcomes. Guidelines for treatment can be complicated and difficult to implement. This study examined the feasibility of implementing a care bundle including therapeutic hypothermia (TH) and early hemodynamic optimization for comatose patients with return of spontaneous circulation after out-of-hospital cardiac arrest. The study included patients over a 2-year period in the ED and intensive care unit of an academic tertiary-care medical center. The first year (prebundle) provided a historical control, followed by a prospective observational period of bundle implementation during the second year. The bundle elements included (a) TH initiated; (b) central venous pressure/central venous oxygen saturation monitoring in 2 h; (c) target temperature in 4 h; (d) central venous pressure greater than 12 mmHg in 6 h; (e) MAP greater than 65 mmHg in 6 h; (f) central venous oxygen saturation greater than 70% in 6 h; (g) TH maintained for 24 h; and (h) decreasing lactate in 24 h. Fifty-five patients were enrolled, 26 patients in the prebundle phase and 29 patients in the bundle phase. Seventy-seven percent of bundle elements were completed during the bundle phase. In-hospital mortality in bundle compared with prebundle patients was 55.2% vs. 69.2% (P = 0.29). In the bundle patients, those patients who received all elements of the care bundle had mortality 33.3% compared with 60.9% in those receiving some of the bundle elements (P = 0.22). Bundle patients tended to achieve good neurologic outcome compared with prebundle patients, Cerebral Performance Category 1 or 2 in 31 vs. 12% patients, respectively (P = 0.08). Our study demonstrated that a post-cardiac arrest care bundle that incorporates TH and early hemodynamic optimization can be implemented in the ED and intensive care unit collaboratively and can achieve similar clinical benefits compared with those observed in previous clinical trials.

Working Toward Nanotube Composites

NASA Technical Reports Server (NTRS)

Arepalli, Sivaram; Nikolaev, Pavel; Gorelik, Olga; Hadjiev, Victor G.; Scott, Carl D.; Files, Bradley S.

2001-01-01

One of the most attractive applications of single-wall carbon nanotubes (SWNT) is found in the area of structural materials. Nanotubes have a unique combination of high strength, modulus, and elongation to failure, and therefore have potential to significantly enhance the mechanical properties of today's composites. This is especially attractive for the aerospace industry looking for any chance to save weight. This is why NASA has chosen to tackle this difficult application of SWNT. Nanotube properties differ significantly from that of conventional carbon fibers, and a whole new set of problems, including adhesion and dispersion in the adhesive polymer matrix, must be resolved in order to engineer superior composite materials. From recent work on a variety of applications it is obvious that the wide range of research in nanotubes will lead to advances in physics, chemistry, and engineering. However, the possibility of ultralightweight structures is what causes dreamers to really get excited. One of the important issues in composite engineering is aspect ratio of the fibers, since it affects load transfer in composites. Nanotube length was a gray area for years, since they are formed in bundles, making it impossible to monitor individual nanotube length. Even though bundles are observed to be tens and hundreds of microns long, they can be built of relatively short tubes weakly bound by Van der Waals forces. Nanotube length can be affected by subsequent purification and ultrasound processing, which has been necessary in order to disperse nanotubes and introduce them into a polymer matrix. Some calculations show that nanotubes with 10(exp 5) aspect ratio may be necessary to achieve good load transfer. We show here that nanotubes produced in our laser system are as much as tens of microns long and get cut into lengths of hundreds of nanometers during ultrasound processing. Nanotube length was measured by AFM on pristine nanotube specimens as well, as after sonication. In each case great care was taken to measure individual nanotubes, rather than bundles. Pristine nanotubes were collected on quartz substrates placed directly in the laser oven and exposed for 0.5 s. This results in an equal mix of bundles and individual nanotubes. Nanotube length measurements were limited practically by the lateral span of the AFM scanner, but nanotube length is certainly in excess of 20 micrometers.

Effect of heat treatment and diffusion welding conditions on the structure and properties of porous material workpieces made of titanium fibers

NASA Astrophysics Data System (ADS)

Kollerov, M. Yu.; Shlyapin, S. D.; Gusev, D. E.; Senkevich, K. S.; Runova, Yu. E.

2015-11-01

The effect of the diffusion welding conditions on the structure and properties of a porous material (PM) made of titanium fibers is studied. It is shown that the use of fibers produced by melt quenching and then joined to form workpieces or articles by diffusion welding can be a promising trend in the production of PMs for medicine applications. A change in the solidification rate of fibers and their contact substantially affects the mechanical properties of PM workpieces. As the diffusion welding temperature of both sheet and cylindrical workpieces increases, the strength of PM increases and the plasticity of PM decreases.

Generating a Simulated Fluid Flow over a Surface Using Anisotropic Diffusion

NASA Technical Reports Server (NTRS)

Rodriguez, David L. (Inventor); Sturdza, Peter (Inventor)

2016-01-01

A fluid-flow simulation over a computer-generated surface is generated using a diffusion technique. The surface is comprised of a surface mesh of polygons. A boundary-layer fluid property is obtained for a subset of the polygons of the surface mesh. A gradient vector is determined for a selected polygon, the selected polygon belonging to the surface mesh but not one of the subset of polygons. A maximum and minimum diffusion rate is determined along directions determined using the gradient vector corresponding to the selected polygon. A diffusion-path vector is defined between a point in the selected polygon and a neighboring point in a neighboring polygon. An updated fluid property is determined for the selected polygon using a variable diffusion rate, the variable diffusion rate based on the minimum diffusion rate, maximum diffusion rate, and the gradient vector.

ELMOD1 Stimulates ARF6-GTP Hydrolysis to Stabilize Apical Structures in Developing Vestibular Hair Cells.

PubMed

Krey, Jocelyn F; Dumont, Rachel A; Wilmarth, Philip A; David, Larry L; Johnson, Kenneth R; Barr-Gillespie, Peter G

2018-01-24

Sensory hair cells require control of physical properties of their apical plasma membranes for normal development and function. Members of the ADP-ribosylation factor (ARF) small GTPase family regulate membrane trafficking and cytoskeletal assembly in many cells. We identified ELMO domain-containing protein 1 (ELMOD1), a guanine nucleoside triphosphatase activating protein (GAP) for ARF6, as the most highly enriched ARF regulator in hair cells. To characterize ELMOD1 control of trafficking, we analyzed mice of both sexes from a strain lacking functional ELMOD1 [roundabout ( rda )]. In rda/rda mice, cuticular plates of utricle hair cells initially formed normally, then degenerated after postnatal day 5; large numbers of vesicles invaded the compromised cuticular plate. Hair bundles initially developed normally, but the cell's apical membrane lifted away from the cuticular plate, and stereocilia elongated and fused. Membrane trafficking in type I hair cells, measured by FM1-43 dye labeling, was altered in rda/rda mice. Consistent with the proposed GAP role for ELMOD1, the ARF6 GTP/GDP ratio was significantly elevated in rda/rda utricles compared with controls, and the level of ARF6-GTP was correlated with the severity of the rda/rda phenotype. These results suggest that conversion of ARF6 to its GDP-bound form is necessary for final stabilization of the hair bundle. SIGNIFICANCE STATEMENT Assembly of the mechanically sensitive hair bundle of sensory hair cells requires growth and reorganization of apical actin and membrane structures. Hair bundles and apical membranes in mice with mutations in the Elmod1 gene degenerate after formation, suggesting that the ELMOD1 protein stabilizes these structures. We show that ELMOD1 is a GTPase-activating protein in hair cells for the small GTP-binding protein ARF6, known to participate in actin assembly and membrane trafficking. We propose that conversion of ARF6 into the GDP-bound form in the apical domain of hair cells is essential for stabilizing apical actin structures like the hair bundle and ensuring that the apical membrane forms appropriately around the stereocilia. Copyright © 2018 the authors 0270-6474/18/380843-15$15.00/0.

On the properties of a bundle of flexible actin filaments in an optical trap.

PubMed

Perilli, Alessia; Pierleoni, Carlo; Ciccotti, Giovanni; Ryckaert, Jean-Paul

2016-06-28

We establish the statistical mechanics framework for a bundle of Nf living and uncrosslinked actin filaments in a supercritical solution of free monomers pressing against a mobile wall. The filaments are anchored normally to a fixed planar surface at one of their ends and, because of their limited flexibility, they grow almost parallel to each other. Their growing ends hit a moving obstacle, depicted as a second planar wall, parallel to the previous one and subjected to a harmonic compressive force. The force constant is denoted as the trap strength while the distance between the two walls as the trap length to make contact with the experimental optical trap apparatus. For an ideal solution of reactive filaments and free monomers at fixed free monomer chemical potential μ1, we obtain the general expression for the grand potential from which we derive averages and distributions of relevant physical quantities, namely, the obstacle position, the bundle polymerization force, and the number of filaments in direct contact with the wall. The grafted living filaments are modeled as discrete Wormlike chains, with F-actin persistence length ℓp, subject to discrete contour length variations ±d (the monomer size) to model single monomer (de)polymerization steps. Rigid filaments (ℓp = ∞), either isolated or in bundles, all provide average values of the stalling force in agreement with Hill's predictions Fs (H)=NfkBTln(ρ1/ρ1c)/d, independent of the average trap length. Here ρ1 is the density of free monomers in the solution and ρ1c its critical value at which the filament does not grow nor shrink in the absence of external forces. Flexible filaments (ℓp < ∞) instead, for values of the trap strength suitable to prevent their lateral escape, provide an average bundle force and an average trap length slightly larger than the corresponding rigid cases (few percents). Still the stalling force remains nearly independent on the average trap length, but results from the product of two strongly L-dependent contributions: the fraction of touching filaments ∝〈L〉(O.T.) (2) and the single filament buckling force ∝〈L〉(O.T.) (-2).

Effects of TiB2 Particle and Short Fiber Sizes on the Microstructure and Properties of TiB2-Reinforced Composite Coatings

NASA Astrophysics Data System (ADS)

Lin, Yinghua; Yao, Jianhua; Wang, Liang; Zhang, Qunli; Li, Xueqiao; Lei, Yongping; Fu, Hanguang

2018-03-01

In this study, particle and short fiber-reinforced titanium matrix composite coatings are prepared via laser in situ technique using (0.5 and 50 μm) TiB2 and Ti powder as cladding materials. The microstructure and properties of the composite coatings are studied, and the changing mechanism of the microstructure is discussed. The results reveal that particle agglomeration is prone to appear with using fine TiB2 particles. Decomposition of the particles preferentially occurs with using coarse TiB2 particles. The cracks and pores on the surface of the coating are formed at a lower laser energy density. With the increase in the laser energy density, cracking on the surface of the coating diminishes, but the coating exhibits depression behavior. The depression extent of the coating using fine TiB2 particle as the reinforcement is much less than that of the coating using coarse TiB2 particle. Moreover, the size of the aggregate and the tendency of cracking can be reduced with the increase in Ti addition. Meanwhile, short TiB fiber bundles are formed by the diffusion mechanism of rod aggregate, and randomly oriented TiB short fibers are formed mainly by the dissolution-precipitation mechanism of fine TiB2 particles. Moreover, the growth of short TiB fibers can be in an alternating manner between B27 and Bf structures. The micro-hardness and wear resistance of the coatings are evidently higher than that of the titanium alloy substrate. The wear resistance of the large size TiB2 coating is higher than that of the small size TiB2 coating under the condition of low load.

Electrical properties associated with wide intercellular clefts in rabbit Purkinje fibres.

PubMed Central

Colatsky, T J; Tsien, R W

1979-01-01

1. Rabbit Purkinje fibres were studied using micro-electrode recordings of electrical activity or a two-micro-electrode voltage clamp. Previous morphological work had suggested that these preparations offer structural advantages for the analysis of ionic permeability mechanisms. 2. Viable preparations could be obtained consistently by exposure to a K glutamate Tyrode solution during excision and recovery. In NaCl Tyrode solution, the action potential showed a large overshoot and fully developed plateau, but no pacemaker depolarization at negative potentials. 3. The passive electrical properties were consistent with morphological evidence for the accessibility of cleft membranes within the cell bundle. Electrotonic responses to intracellular current steps showed the behaviour expected for a simple leaky capacitative cable. Capacitative current transients under voltage clamp were changed very little by an eightfold reduction in the external solution conductivity. 4. Slow current changes attributable to K depletion were small compared to those found in other cardiac preparations. The amount of depletion was close to that predicted by a cleft model which assumed free K diffusion in 1 micron clefts. 5. Step depolarizations over the plateau range of potentials evoked a slow inward current which was resistant to tetrodotoxin but blocked by D600. 6. Strong depolarizations to potentials near 0 mV elicited a transient outward current and a slowly activating late outward current. Both components resembled currents found in sheep or calf Purkinje fibres. 7. These experiments support previous interpretations of slow plateau currents in terms of genuine permeability changes. The rabbit Purkinje fibre may allow various ionic channels to be studied with relatively little interference from radial non-uniformities in membrane potential or ion concentration. Images Fig. 7 PMID:469754

Specific features of defect and mass transport in concentrated fcc alloys

DOE PAGES

Osetsky, Yuri N.; Béland, Laurent K.; Stoller, Roger E.

2016-06-15

We report that diffusion and mass transport are basic properties that control materials performance, such as phase stability, solute decomposition and radiation tolerance. While understanding diffusion in dilute alloys is a mature field, concentrated alloys are much less studied. Here, atomic-scale diffusion and mass transport via vacancies and interstitial atoms are compared in fcc Ni, Fe and equiatomic Ni-Fe alloy. High temperature properties were determined using conventional molecular dynamics on the microsecond timescale, whereas the kinetic activation-relaxation (k-ART) approach was applied at low temperatures. The k-ART was also used to calculate transition states in the alloy and defect transport coefficients.more » The calculations reveal several specific features. For example, vacancy and interstitial defects migrate via different alloy components, diffusion is more sluggish in the alloy and, notably, mass transport in the concentrated alloy cannot be predicted on the basis of diffusion in its pure metal counterparts. Lastly, the percolation threshold for the defect diffusion in the alloy is discussed and it is suggested that this phenomenon depends on the properties and diffusion mechanisms of specific defects.« less

White matter damage in primary progressive aphasias: a diffusion tensor tractography study

PubMed Central

Galantucci, Sebastiano; Tartaglia, Maria Carmela; Wilson, Stephen M.; Henry, Maya L.; Filippi, Massimo; Agosta, Federica; Dronkers, Nina F.; Henry, Roland G.; Ogar, Jennifer M.; Miller, Bruce L.

2011-01-01

Primary progressive aphasia is a clinical syndrome that encompasses three major phenotypes: non-fluent/agrammatic, semantic and logopenic. These clinical entities have been associated with characteristic patterns of focal grey matter atrophy in left posterior frontoinsular, anterior temporal and left temporoparietal regions, respectively. Recently, network-level dysfunction has been hypothesized but research to date has focused largely on studying grey matter damage. The aim of this study was to assess the integrity of white matter tracts in the different primary progressive aphasia subtypes. We used diffusion tensor imaging in 48 individuals: nine non-fluent, nine semantic, nine logopenic and 21 age-matched controls. Probabilistic tractography was used to identify bilateral inferior longitudinal (anterior, middle, posterior) and uncinate fasciculi (referred to as the ventral pathway); and the superior longitudinal fasciculus segmented into its frontosupramarginal, frontoangular, frontotemporal and temporoparietal components, (referred to as the dorsal pathway). We compared the tracts’ mean fractional anisotropy, axial, radial and mean diffusivities for each tract in the different diagnostic categories. The most prominent white matter changes were found in the dorsal pathways in non-fluent patients, in the two ventral pathways and the temporal components of the dorsal pathways in semantic variant, and in the temporoparietal component of the dorsal bundles in logopenic patients. Each of the primary progressive aphasia variants showed different patterns of diffusion tensor metrics alterations: non-fluent patients showed the greatest changes in fractional anisotropy and radial and mean diffusivities; semantic variant patients had severe changes in all metrics; and logopenic patients had the least white matter damage, mainly involving diffusivity, with fractional anisotropy altered only in the temporoparietal component of the dorsal pathway. This study demonstrates that both careful dissection of the main language tracts and consideration of all diffusion tensor metrics are necessary to characterize the white matter changes that occur in the variants of primary progressive aphasia. These results highlight the potential value of diffusion tensor imaging as a new tool in the multimodal diagnostic evaluation of primary progressive aphasia. PMID:21666264

Turkish and Native English Academic Writers' Use of Lexical Bundles

ERIC Educational Resources Information Center

Öztürk, Yusuf; Köse, Gül Durmusoglu

2016-01-01

Lexical bundles such as "on the other hand" and "as a result of" are extremely common and important in academic discourse. The appropriate use of lexical bundles typical of a specific academic discipline is important for writers and the absence of such bundles may not sound fluent and native-like. Recent studies (e.g. Adel…

Verification of a neutronic code for transient analysis in reactors with Hex-z geometry

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

Gonzalez-Pintor, S.; Verdu, G.; Ginestar, D.

Due to the geometry of the fuel bundles, to simulate reactors such as VVER reactors it is necessary to develop methods that can deal with hexagonal prisms as basic elements of the spatial discretization. The main features of a code based on a high order finite element method for the spatial discretization of the neutron diffusion equation and an implicit difference method for the time discretization of this equation are presented and the performance of the code is tested solving the first exercise of the AER transient benchmark. The obtained results are compared with the reference results of the benchmarkmore » and with the results provided by PARCS code. (authors)« less

Localization and physical properties experiments conducted by Spirit at Gusev crater

USGS Publications Warehouse

Arvidson, R. E.; Anderson, R.C.; Bartlett, P.; Bell, J.F.; Blaney, D.; Christensen, P.R.; Chu, P.; Crumpler, L.; Davis, K.; Ehlmann, B.L.; Fergason, R.; Golombek, M.P.; Gorevan, S.; Grant, J. A.; Greeley, R.; Guinness, E.A.; Haldemann, A.F.C.; Herkenhoff, K.; Johnson, J.; Landis, G.; Li, R.; Lindemann, R.; McSween, H.; Ming, D. W.; Myrick, T.; Richter, L.; Seelos, F.P.; Squyres, S. W.; Sullivan, R.J.; Wang, A.; Wilson, Jim

2004-01-01

The precise location and relative elevation of Spirit during its traverses from the Columbia Memorial station to Bonneville crater were determined with bundle-adjusted retrievals from rover wheel turns, suspension and tilt angles, and overlapping images. Physical properties experiments show a decrease of 0.2% per Mars solar day in solar cell output resulting from deposition of airborne dust, cohesive soil-like deposits in plains and hollows, bright and dark rock coatings, and relatively weak volcanic rocks of basaltic composition. Volcanic, impact, aeolian, and water-related processes produced the encountered landforms and materials.

Localization and physical properties experiments conducted by Spirit at Gusev Crater.

PubMed

Arvidson, R E; Anderson, R C; Bartlett, P; Bell, J F; Blaney, D; Christensen, P R; Chu, P; Crumpler, L; Davis, K; Ehlmann, B L; Fergason, R; Golombek, M P; Gorevan, S; Grant, J A; Greeley, R; Guinness, E A; Haldemann, A F C; Herkenhoff, K; Johnson, J; Landis, G; Li, R; Lindemann, R; McSween, H; Ming, D W; Myrick, T; Richter, L; Seelos, F P; Squyres, S W; Sullivan, R J; Wang, A; Wilson, J

2004-08-06

The precise location and relative elevation of Spirit during its traverses from the Columbia Memorial station to Bonneville crater were determined with bundle-adjusted retrievals from rover wheel turns, suspension and tilt angles, and overlapping images. Physical properties experiments show a decrease of 0.2% per Mars solar day in solar cell output resulting from deposition of airborne dust, cohesive soil-like deposits in plains and hollows, bright and dark rock coatings, and relatively weak volcanic rocks of basaltic composition. Volcanic, impact, aeolian, and water-related processes produced the encountered landforms and materials.

Coupling and Elastic Loading Affect the Active Response by the Inner Ear Hair Cell Bundles

PubMed Central

Strimbu, Clark Elliott; Fredrickson-Hemsing, Lea; Bozovic, Dolores

2012-01-01

Active hair bundle motility has been proposed to underlie the amplification mechanism in the auditory endorgans of non-mammals and in the vestibular systems of all vertebrates, and to constitute a crucial component of cochlear amplification in mammals. We used semi-intact in vitro preparations of the bullfrog sacculus to study the effects of elastic mechanical loading on both natively coupled and freely oscillating hair bundles. For the latter, we attached glass fibers of different stiffness to the stereocilia and observed the induced changes in the spontaneous bundle movement. When driven with sinusoidal deflections, hair bundles displayed phase-locked response indicative of an Arnold Tongue, with the frequency selectivity highest at low amplitudes and decreasing under stronger stimulation. A striking broadening of the mode-locked response was seen with increasing stiffness of the load, until approximate impedance matching, where the phase-locked response remained flat over the physiological range of frequencies. When the otolithic membrane was left intact atop the preparation, the natural loading of the bundles likewise decreased their frequency selectivity with respect to that observed in freely oscillating bundles. To probe for signatures of the active process under natural loading and coupling conditions, we applied transient mechanical stimuli to the otolithic membrane. Following the pulses, the underlying bundles displayed active movement in the opposite direction, analogous to the twitches observed in individual cells. Tracking features in the otolithic membrane indicated that it moved in phase with the bundles. Hence, synchronous active motility evoked in the system of coupled hair bundles by external input is sufficient to displace large overlying structures. PMID:22479461

Prevalence of Split Nerve Fiber Layer Bundles in Healthy People Imaged with Spectral Domain Optical Coherence Tomography.

PubMed

Gür Güngör, Sirel; Akman, Ahmet; Sarıgül Sezenöz, Almila; Tanrıaşıkı, Gülşah

2016-12-01

The presence of retinal nerve fiber layer (RNFL) split bundles was recently described in normal eyes scanned using scanning laser polarimetry and by histologic studies. Split bundles may resemble RNFL loss in healthy eyes. The aim of our study was to determine the prevalence of nerve fiber layer split bundles in healthy people. We imaged 718 eyes of 359 healthy persons with the spectral domain optical coherence tomography in this cross-sectional study. All eyes had intraocular pressure of 21 mmHg or less, normal appearance of the optic nerve head, and normal visual fields (Humphrey Field Analyzer 24-2 full threshold program). In our study, a bundle was defined as 'split' when there is localized defect not resembling a wedge defect in the RNFL deviation map with a symmetrically divided RNFL appearance on the RNFL thickness map. The classification was performed by two independent observers who used an identical set of reference examples to standardize the classification. Inter-observer consensus was reached in all cases. Bilateral superior split bundles were seen in 19 cases (5.29%) and unilateral superior split was observed in 15 cases (4.16%). In 325 cases (90.52%) there was no split bundle. Split nerve fiber layer bundles, in contrast to single nerve fiber layer bundles, are not common findings in healthy eyes. In eyes with normal optic disc appearance, especially when a superior RNFL defect is observed in RNFL deviation map, the RNLF thickness map and graphs should also be examined for split nerve fiber layer bundles.

LED lamp or bulb with remote phosphor and diffuser configuration with enhanced scattering properties

DOEpatents

Tong, Tao; Le Toquin, Ronan; Keller, Bernd; Tarsa, Eric; Youmans, Mark; Lowes, Theodore; Medendorp, Jr., Nicholas W; Van De Ven, Antony; Negley, Gerald

2014-11-11

An LED lamp or bulb is disclosed that comprises a light source, a heat sink structure and an optical cavity. The optical cavity comprises a phosphor carrier having a conversions material and arranged over an opening to the cavity. The phosphor carrier comprises a thermally conductive transparent material and is thermally coupled to the heat sink structure. An LED based light source is mounted in the optical cavity remote to the phosphor carrier with light from the light source passing through the phosphor carrier. A diffuser dome is included that is mounted over the optical cavity, with light from the optical cavity passing through the diffuser dome. The properties of the diffuser, such as geometry, scattering properties of the scattering layer, surface roughness or smoothness, and spatial distribution of the scattering layer properties may be used to control various lamp properties such as color uniformity and light intensity distribution as a function of viewing angle.

Computational imaging through a fiber-optic bundle

NASA Astrophysics Data System (ADS)

Lodhi, Muhammad A.; Dumas, John Paul; Pierce, Mark C.; Bajwa, Waheed U.

2017-05-01

Compressive sensing (CS) has proven to be a viable method for reconstructing high-resolution signals using low-resolution measurements. Integrating CS principles into an optical system allows for higher-resolution imaging using lower-resolution sensor arrays. In contrast to prior works on CS-based imaging, our focus in this paper is on imaging through fiber-optic bundles, in which manufacturing constraints limit individual fiber spacing to around 2 μm. This limitation essentially renders fiber-optic bundles as low-resolution sensors with relatively few resolvable points per unit area. These fiber bundles are often used in minimally invasive medical instruments for viewing tissue at macro and microscopic levels. While the compact nature and flexibility of fiber bundles allow for excellent tissue access in-vivo, imaging through fiber bundles does not provide the fine details of tissue features that is demanded in some medical situations. Our hypothesis is that adapting existing CS principles to fiber bundle-based optical systems will overcome the resolution limitation inherent in fiber-bundle imaging. In a previous paper we examined the practical challenges involved in implementing a highly parallel version of the single-pixel camera while focusing on synthetic objects. This paper extends the same architecture for fiber-bundle imaging under incoherent illumination and addresses some practical issues associated with imaging physical objects. Additionally, we model the optical non-idealities in the system to get lower modelling errors.

75 FR 51668 - Optional Mail Preparation Standards for Flat-Size Mailpieces in FSS Zones

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-23

... bundles of six or more addressed pieces each, subject to these standards: * * * * * [Revise item b of 13.2... combination. Mailers will then prepare bundles of uniform size from the pieces in the pool. Bundles must be... this option may be applied to the top piece of each bundle, unless otherwise required to be placed on...

Recognizing asymmetry in pseudo-symmetry; structural insights into the interaction between amphipathic α-helices and X-bundle proteins.

PubMed

Haddad, John Faissal; Yang, Yidai; Yeung, Sylvain; Couture, Jean-François

2017-11-01

An α-helix bundle is a small and compact protein fold always composed of more than 2 α-helices that typically run nearly parallel or antiparallel to each other. The repertoire of arrangements of α-helix bundle is such that these domains bind to a myriad of molecular entities including DNA, RNA, proteins and small molecules. A special instance of α-helical bundle is the X-type in which the arrangement of two α-helices interact at 45° to form an X. Among those, some X-helix bundle proteins bind to the hydrophobic section of an amphipathic α-helix in a seemingly orientation and sequence specific manner. In this review, we will compare the binding mode of amphipathic α-helices to X-helix bundle and α-helical bundle proteins. From these structures, we will highlight potential regulatory paradigms that may control the specific interactions of X-helix bundle proteins to amphipathic α-helices. This article is part of a Special Issue entitled: Biophysics in Canada, edited by Lewis Kay, John Baenziger, Albert Berghuis and Peter Tieleman. Copyright © 2017 Elsevier B.V. All rights reserved.

Muscle architecture of the elongated nose in the Asian elephant (Elephas maximus).

PubMed

Endo, H; Hayashi, Y; Komiya, T; Narushima, E; Sasaki, M

2001-05-01

The architecture of the M. caninus in the elongated nose was examined in the Asian elephant (Elephas maximus). The following complicated musculature of the M. caninus was observed in the proximal and distal regions of the nose: (1) Proximal region: In the superficial layer, the longitudinal bundles are confirmed in the dorsal part, and the obliquely-oriented ones in the ventral part. In the middle layer, some bundles run ventro-distally, while other ones represent longitudinally-oriented running. The deep layer consists of complicated architecture of many bundles. Some muscle bundles run medio-laterally, while the others extend proximo-distally in this space. (2) Distal region: In the dorsal part of the M. caninus, the bundles run at deep-superficial direction, while in the ventral part the bundles are longitudinally arranged. The bundles run at lateral direction near the septum of the nasal conduits. The N. facialis and N. infraorbitalis send many branches in the lateral area of the M. caninus in the trunk. This muscle architecture of multi-oriented bundles and well-developed innervation to them suggest that they enable the elongated nose to act as a refined manipulator in the Asian elephant.

The impact of a ventilator bundle on preventing ventilator-associated pneumonia: a multicenter study.

PubMed

Eom, Joong Sik; Lee, Mi-Suk; Chun, Hee-Kyung; Choi, Hee Jung; Jung, Sun-Young; Kim, Yeon-Sook; Yoon, Seon Jin; Kwak, Yee Gyung; Oh, Gang-Bok; Jeon, Min-Hyok; Park, Sun-Young; Koo, Hyun-Sook; Ju, Young-Su; Lee, Jin Seo

2014-01-01

For prevention of ventilator-associated pneumonia (VAP), a bundle approach was applied to patients receiving mechanical ventilation in intensive care units. The incidence of VAP and the preventive efficacy of the VAP bundle were investigated. A quasi-experimental study was conducted in adult intensive care units of 6 university hospitals with similar VAP rates. We implemented the VAP bundle between March 2011 and June 2011, then compared the rate of VAP after implementation of the VAP bundle with the rate in the previous 8 months. Our ventilator bundle included head of bed elevation, peptic ulcer disease prophylaxis, deep venous thrombosis prophylaxis, and oral decontamination with chlorhexidine 0.12%. Continuous aspiration of subglottic secretions was an option. Implementation of the VAP bundle reduced the VAP rate from a mean of 4.08 cases per 1,000 ventilator-days to 1.16 cases per 1,000 ventilator-days. The incidence density ratio (rate) was 0.28 (95% confidence interval, 0.275-0.292). Implementing the appropriate VAP bundle significantly decreased the incidence of VAP in patients with mechanical ventilation. Copyright © 2014 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Mosby, Inc. All rights reserved.

Using Perturbation Theory to Reduce Noise in Diffusion Tensor Fields

PubMed Central

Bansal, Ravi; Staib, Lawrence H.; Xu, Dongrong; Laine, Andrew F.; Liu, Jun; Peterson, Bradley S.

2009-01-01

We propose the use of Perturbation theory to reduce noise in Diffusion Tensor (DT) fields. Diffusion Tensor Imaging (DTI) encodes the diffusion of water molecules along different spatial directions in a positive-definite, 3 × 3 symmetric tensor. Eigenvectors and eigenvalues of DTs allow the in vivo visualization and quantitative analysis of white matter fiber bundles across the brain. The validity and reliability of these analyses are limited, however, by the low spatial resolution and low Signal-to-Noise Ratio (SNR) in DTI datasets. Our procedures can be applied to improve the validity and reliability of these quantitative analyses by reducing noise in the tensor fields. We model a tensor field as a three-dimensional Markov Random Field and then compute the likelihood and the prior terms of this model using Perturbation theory. The prior term constrains the tensor field to be smooth, whereas the likelihood term constrains the smoothed tensor field to be similar to the original field. Thus, the proposed method generates a smoothed field that is close in structure to the original tensor field. We evaluate the performance of our method both visually and quantitatively using synthetic and real-world datasets. We quantitatively assess the performance of our method by computing the SNR for eigenvalues and the coherence measures for eigenvectors of DTs across tensor fields. In addition, we quantitatively compare the performance of our procedures with the performance of one method that uses a Riemannian distance to compute the similarity between two tensors, and with another method that reduces noise in tensor fields by anisotropically filtering the diffusion weighted images that are used to estimate diffusion tensors. These experiments demonstrate that our method significantly increases the coherence of the eigenvectors and the SNR of the eigenvalues, while simultaneously preserving the fine structure and boundaries between homogeneous regions, in the smoothed tensor field. PMID:19540791

Tokyo Guidelines 2018: management bundles for acute cholangitis and cholecystitis.

PubMed

Mayumi, Toshihiko; Okamoto, Kohji; Takada, Tadahiro; Strasberg, Steven M; Solomkin, Joseph S; Schlossberg, David; Pitt, Henry A; Yoshida, Masahiro; Gomi, Harumi; Miura, Fumihiko; Garden, O James; Kiriyama, Seiki; Yokoe, Masamichi; Endo, Itaru; Asbun, Horacio J; Iwashita, Yukio; Hibi, Taizo; Umezawa, Akiko; Suzuki, Kenji; Itoi, Takao; Hata, Jiro; Han, Ho-Seong; Hwang, Tsann-Long; Dervenis, Christos; Asai, Koji; Mori, Yasuhisa; Huang, Wayne Shih-Wei; Belli, Giulio; Mukai, Shuntaro; Jagannath, Palepu; Cherqui, Daniel; Kozaka, Kazuto; Baron, Todd H; de Santibañes, Eduardo; Higuchi, Ryota; Wada, Keita; Gouma, Dirk J; Deziel, Daniel J; Liau, Kui-Hin; Wakabayashi, Go; Padbury, Robert; Jonas, Eduard; Supe, Avinash Nivritti; Singh, Harjit; Gabata, Toshifumi; Chan, Angus C W; Lau, Wan Yee; Fan, Sheung Tat; Chen, Miin-Fu; Ker, Chen-Guo; Yoon, Yoo-Seok; Choi, In-Seok; Kim, Myung-Hwan; Yoon, Dong-Sup; Kitano, Seigo; Inomata, Masafumi; Hirata, Koichi; Inui, Kazuo; Sumiyama, Yoshinobu; Yamamoto, Masakazu

2018-01-01

Management bundles that define items or procedures strongly recommended in clinical practice have been used in many guidelines in recent years. Application of these bundles facilitates the adaptation of guidelines and helps improve the prognosis of target diseases. In Tokyo Guidelines 2013 (TG13), we proposed management bundles for acute cholangitis and cholecystitis. Here, in Tokyo Guidelines 2018 (TG18), we redefine the management bundles for acute cholangitis and cholecystitis. Critical parts of the bundles in TG18 include the diagnostic process, severity assessment, transfer of patients if necessary, and therapeutic approach at each time point. Observance of these items and procedures should improve the prognosis of acute cholangitis and cholecystitis. Studies are now needed to evaluate the dissemination of these TG18 bundles and their effectiveness. Free full articles and mobile app of TG18 are available at: http://www.jshbps.jp/modules/en/index.php?content_id=47. Related clinical questions and references are also included. © 2017 Japanese Society of Hepato-Biliary-Pancreatic Surgery.

Hair-bundle proteomes of avian and mammalian inner-ear utricles

PubMed Central

Wilmarth, Phillip A.; Krey, Jocelyn F.; Shin, Jung-Bum; Choi, Dongseok; David, Larry L.; Barr-Gillespie, Peter G.

2015-01-01

Examination of multiple proteomics datasets within or between species increases the reliability of protein identification. We report here proteomes of inner-ear hair bundles from three species (chick, mouse, and rat), which were collected on LTQ or LTQ Velos ion-trap mass spectrometers; the constituent proteins were quantified using MS2 intensities, which are the summed intensities of all peptide fragmentation spectra matched to a protein. The data are available via ProteomeXchange with identifiers PXD002410 (chick LTQ), PXD002414 (chick Velos), PXD002415 (mouse Velos), and PXD002416 (rat LTQ). The two chick bundle datasets compared favourably to a third, already-described chick bundle dataset, which was quantified using MS1 peak intensities, the summed intensities of peptides identified by high-resolution mass spectrometry (PXD000104; updated analysis in PXD002445). The mouse bundle dataset described here was comparable to a different mouse bundle dataset quantified using MS1 intensities (PXD002167). These six datasets will be useful for identifying the core proteome of vestibular hair bundles. PMID:26645194

A collagen and elastic network in the wing of the bat.

PubMed

Holbrook, K A; Odland, G F

1978-05-01

Bundles of collagen fibrils, elastic fibres and fibroblasts are organized into a network that lies in the plane of a large portion of the bat wing. By ultrastructural (TEM and SEM) and biochemical analyses it was found that individual bundles of the net are similar to elastic ligaments. Although elastic fibres predominate, they are integrated and aligned in parallel with small bundles of collagen. A reticulum of fibroblasts, joined by focal junctions, forms a cellular framework throughout each bundle. Because of the unique features of the fibre bundles of the bat's wing, in particular their accessibility, and the parallel alignment of the collagen fibrils and elastic fibres in each easily isolatable fibre bundle, they should prove a most valuable model for connective tissue studies, particularly for the study of collagen-elastin interactions.

Analysis of the Proteome of Hair-Cell Stereocilia by Mass Spectrometry

PubMed Central

Krey, Jocelyn F.; Wilmarth, Philip A.; David, Larry L.; Barr-Gillespie, Peter G.

2017-01-01

Characterization of proteins that mediate mechanotransduction by hair cells, the sensory cells of the inner ear, is hampered by the scarcity of these cells and their sensory organelle, the hair bundle. Mass spectrometry, with its high sensitivity and identification precision, is the ideal method for determining which proteins are present in bundles and what proteins they interact with. We describe here the isolation of mouse hair bundles, as well as preparation of bundle-protein samples for mass spectrometry. We also describe protocols for data-dependent (shotgun) and parallel-reaction-monitoring (targeted) mass spectrometry that allow us to identify and quantify proteins of the hair bundle. These sensitive methods are particularly useful for comparing proteomes of wild-type and mice with deafness mutations affecting hair-bundle proteins. (120 words; maximum 250) PMID:28109437

Interpolation of orientation distribution functions in diffusion weighted imaging using multi-tensor model.

PubMed

Afzali, Maryam; Fatemizadeh, Emad; Soltanian-Zadeh, Hamid

2015-09-30

Diffusion weighted imaging (DWI) is a non-invasive method for investigating the brain white matter structure and can be used to evaluate fiber bundles. However, due to practical constraints, DWI data acquired in clinics are low resolution. This paper proposes a method for interpolation of orientation distribution functions (ODFs). To this end, fuzzy clustering is applied to segment ODFs based on the principal diffusion directions (PDDs). Next, a cluster is modeled by a tensor so that an ODF is represented by a mixture of tensors. For interpolation, each tensor is rotated separately. The method is applied on the synthetic and real DWI data of control and epileptic subjects. Both experiments illustrate capability of the method in increasing spatial resolution of the data in the ODF field properly. The real dataset show that the method is capable of reliable identification of differences between temporal lobe epilepsy (TLE) patients and normal subjects. The method is compared to existing methods. Comparison studies show that the proposed method generates smaller angular errors relative to the existing methods. Another advantage of the method is that it does not require an iterative algorithm to find the tensors. The proposed method is appropriate for increasing resolution in the ODF field and can be applied to clinical data to improve evaluation of white matter fibers in the brain. Copyright © 2015 Elsevier B.V. All rights reserved.