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J Weickenmeier, P Saze, C A M Butler, P G Young, A Goriely, E Kuhl
Brain swelling is a serious condition associated with an accumulation of fluid inside the brain that can be caused by trauma, stroke, infection, or tumors. It increases the pressure inside the skull and reduces blood and oxygen supply. To relieve the intracranial pressure, neurosurgeons remove part of the skull and allow the swollen brain to bulge outward, a procedure known as decompressive craniectomy. Decompressive craniectomy has been preformed for more than a century; yet, its effects on the swollen brain remain poorly understood...
December 2017: Journal of Elasticity
M Pourtabrizi, N Shahtahmassebi, A Kompany, S Sharifi
This study is conducted to investigate the effect of nano-droplets concentration and size on linear and nonlinear optical properties of Rhodamine 6G by UV-Vis, spectrofluorometer and Z-Scan techniques. Nano-droplets were prepared by mixture of AOT, n-Decane and Water at three different water to surfactant molar ratios (W = 3, 6.7 and 40) and two dye to water mass ratios (R). At high enough dye concentration, the fluorescence intensity and its red shift depend on the concentration of dye in water nano-droplets (R)...
November 18, 2017: Journal of Fluorescence
Spencer E Szczesny, Tristan P Driscoll, Hsiao-Yun Tseng, Pang-Ching Liu, Su-Jin Heo, Robert L Mauck, Pen-Hsiu G Chao
To fully recapitulate tissue microstructure and mechanics, fiber crimping must exist within biomaterials used for tendon/ligament engineering. Existing crimped nanofibrous scaffolds produced via electrospinning are dense materials that prevent cellular infiltration into the scaffold interior. In this study, we used a sacrificial fiber population to increase the scaffold porosity and evaluated the effect on fiber crimping. We found that increasing scaffold porosity increased fiber crimping and ensured that the fibers properly uncrimped as the scaffolds were stretched by minimizing fiber-fiber interactions...
November 13, 2017: ACS Biomaterials Science & Engineering
Daisuke Furuki, Ken Takiyama
Goal-directed whole-body movements are fundamental in our daily life, sports, music, art, and other activities. Goal-directed movements have been intensively investigated by focusing on simplified movements (e.g., arm-reaching movements or eye movements); however, the nature of goal-directed whole-body movements has not been sufficiently investigated because of the high-dimensional nonlinear dynamics and redundancy inherent in whole-body motion. One open question is how to overcome high-dimensional nonlinear dynamics and redundancy to achieve the desired performance...
November 15, 2017: Scientific Reports
Qitian Ru, Zachary E Loparo, XiaoSheng Zhang, Sean Crystal, Subith Vasu, Peter G Schunemann, Konstantin L Vodopyanov
We report an octave-wide mid-IR spectrum (2.3-4.8 μm) obtained from a subharmonic optical parametric oscillator (OPO) based on a newly developed nonlinear crystal, orientation-patterned gallium phosphide (OP-GaP), which was synchronously pumped by a femtosecond 1560 nm fiber laser. We proved that the octave-wide output is in the form of a single frequency comb. The observed f-to-2f frequency beats, originating directly from the OPO, can be used for self-referencing and phase locking of the pump laser comb with no need for supercontinuum generation...
November 15, 2017: Optics Letters
Gonzalo E Mena, Lauren E Grosberg, Sasidhar Madugula, Paweł Hottowy, Alan Litke, John Cunningham, E J Chichilnisky, Liam Paninski
Simultaneous electrical stimulation and recording using multi-electrode arrays can provide a valuable technique for studying circuit connectivity and engineering neural interfaces. However, interpreting these measurements is challenging because the spike sorting process (identifying and segregating action potentials arising from different neurons) is greatly complicated by electrical stimulation artifacts across the array, which can exhibit complex and nonlinear waveforms, and overlap temporarily with evoked spikes...
November 13, 2017: PLoS Computational Biology
Lucas C Cahill, Michael G Giacomelli, Tadayuki Yoshitake, Hilde Vardeh, Beverly E Faulkner-Jones, James L Connolly, Chi-Kuang Sun, James G Fujimoto
Up to 40% of patients undergoing breast conserving surgery for breast cancer require repeat surgeries due to close to or positive margins. The lengthy processing required for evaluating surgical margins by standard paraffin-embedded histology precludes its use during surgery and therefore, technologies for rapid evaluation of surgical pathology could improve the treatment of breast cancer by reducing the number of surgeries required. We demonstrate real-time histological evaluation of breast cancer surgical specimens by staining specimens with acridine orange (AO) and sulforhodamine 101 (SR101) analogously to hematoxylin and eosin (H&E) and then imaging the specimens with fluorescence nonlinear microscopy (NLM) using a compact femtosecond fiber laser...
November 13, 2017: Laboratory Investigation; a Journal of Technical Methods and Pathology
Andrey Baydin, Halina Krzyzanowska, Rustam Gatamov, Joy Garnett, Norman Tolk
The photoelastic phenomenon has been widely investigated as a fundamental elastooptical property of solids. This effect has been applied extensively to study stress distribution in lattice-mismatched semiconductor heterostructures. GaAs based optoelectronic devices (e.g. solar cells, modulators, detectors, and diodes) used in space probes are subject to damage arising from energetic proton (H(+)) irradiation. For that reason, the effect of proton irradiation on photoelastic coefficients of GaAs is of primary importance to space applied optoelectronics...
November 9, 2017: Scientific Reports
Michael T Barako, Scott G Isaacson, Feifei Lian, Eric Pop, Reinhold H Dauskardt, Kenneth E Goodson, Jesse Tice
Thermal interface materials (TIMs) are essential for managing heat in modern electronics, and nanocomposite TIMs can offer critical improvements. Here, we demonstrate thermally conductive, mechanically compliant TIMs based on dense, vertically aligned copper nanowires (CuNWs) embedded into polymer matrices. We evaluate the thermal and mechanical characteristics of 20-25% dense CuNW arrays with and without polydimethylsiloxane infiltration. The thermal resistance achieved is below 5 mm(2) K W(-1), over an order of magnitude lower than commercial heat sink compounds...
November 20, 2017: ACS Applied Materials & Interfaces
Tobias Tiess, Martin Becker, Manfred Rothhardt, Hartmut Bartelt, Matthias Jäger
We present a fiber-integrated laser enabling independent tuning of two emission wavelengths with a synchronized pulsed emission. The discrete tuning concept comprises a theta cavity fiber laser (TCFL), a fiber Bragg grating (FBG) array as a versatile spectral filter, facilitating tailored tuning ranges, and optical gating to control the emission spectrum. A novel electrical driving scheme uniquely enables independently tunable multi-wavelength emission from a single laser oscillator. Tunable dual-wavelength emission is experimentally investigated with a ytterbium (Yb)-doped TCFL using an FBG array with 11 gratings...
October 30, 2017: Optics Express
Zheng Yan, Mengdi Han, Yan Shi, Adina Badea, Yiyuan Yang, Ashish Kulkarni, Erik Hanson, Mikhail E Kandel, Xiewen Wen, Fan Zhang, Yiyue Luo, Qing Lin, Hang Zhang, Xiaogang Guo, Yuming Huang, Kewang Nan, Shuai Jia, Aaron W Oraham, Molly B Mevis, Jaeman Lim, Xuelin Guo, Mingye Gao, Woomi Ryu, Ki Jun Yu, Bruno G Nicolau, Aaron Petronico, Stanislav S Rubakhin, Jun Lou, Pulickel M Ajayan, Katsuyo Thornton, Gabriel Popescu, Daining Fang, Jonathan V Sweedler, Paul V Braun, Haixia Zhang, Ralph G Nuzzo, Yonggang Huang, Yihui Zhang, John A Rogers
Recent work demonstrates that processes of stress release in prestrained elastomeric substrates can guide the assembly of sophisticated 3D micro/nanostructures in advanced materials. Reported application examples include soft electronic components, tunable electromagnetic and optical devices, vibrational metrology platforms, and other unusual technologies, each enabled by uniquely engineered 3D architectures. A significant disadvantage of these systems is that the elastomeric substrates, while essential to the assembly process, can impose significant engineering constraints in terms of operating temperatures and levels of dimensional stability; they also prevent the realization of 3D structures in freestanding forms...
November 7, 2017: Proceedings of the National Academy of Sciences of the United States of America
Russell Lande, Steinar Engen, Bernt-Erik Sæther
We analyze the stochastic demography and evolution of a density-dependent age- (or stage-) structured population in a fluctuating environment. A positive linear combination of age classes (e.g., weighted by body mass) is assumed to act as the single variable of population size, [Formula: see text], exerting density dependence on age-specific vital rates through an increasing function of population size. The environment fluctuates in a stationary distribution with no autocorrelation. We show by analysis and simulation of age structure, under assumptions often met by vertebrate populations, that the stochastic dynamics of population size can be accurately approximated by a univariate model governed by three key demographic parameters: the intrinsic rate of increase and carrying capacity in the average environment, [Formula: see text] and [Formula: see text], and the environmental variance in population growth rate, [Formula: see text] Allowing these parameters to be genetically variable and to evolve, but assuming that a fourth parameter, [Formula: see text], measuring the nonlinearity of density dependence, remains constant, the expected evolution maximizes [Formula: see text] This shows that the magnitude of environmental stochasticity governs the classical trade-off between selection for higher [Formula: see text] versus higher [Formula: see text] However, selection also acts to decrease [Formula: see text], so the simple life-history trade-off between [Formula: see text]- and [Formula: see text]-selection may be obscured by additional trade-offs between them and [Formula: see text] Under the classical logistic model of population growth with linear density dependence ([Formula: see text]), life-history evolution in a fluctuating environment tends to maximize the average population size...
October 31, 2017: Proceedings of the National Academy of Sciences of the United States of America
Sarah von Pfingsten, David Oliver Broll, Niklas von der Assen, André Bardow
Life cycle assessment (LCA) results are inevitably subject to uncertainties. Since the complete elimination of uncertainties is impossible, LCA results should be complemented by an uncertainty analysis. However, the approaches currently used for uncertainty analysis have some shortcomings: statistical uncertainty analysis via Monte Carlo simulations are inherently uncertain due to their statistical nature and can become computationally inefficient for large systems; analytical approaches use a linear approximation to the uncertainty by a first-order Taylor series expansion and thus, they are only precise for small input uncertainties...
November 10, 2017: Environmental Science & Technology
Horacio G Rotstein
The generation of spiking resonances in neurons (preferred spiking responses to oscillatory inputs) requires the interplay of the intrinsic ionic currents that operate at the subthreshold voltage level and the spiking mechanisms. Combinations of the same types of ionic currents in different parameter regimes may give rise to different types of nonlinearities in the voltage equation (e.g., parabolic- and cubic-like), generating subthreshold (membrane potential) oscillations patterns with different properties...
December 2017: Journal of Computational Neuroscience
G Valenza, H Wendt, K Kiyono, J Hayano, E Watanabe, Y Yamamoto, P Abry, R Barbieri
Multifractal analysis of cardiovascular variability series is an effective tool for the characterization of pathological states associated with congestive heart failure (CHF). Consequently, variations of heartbeat scaling properties have been associated with the dynamical balancing of nonlinear sympathetic/vagal activity. Nevertheless, whether vagal dynamics has multifractal properties yet alone is currently unknown. In this study, we answer this question by conducting multifractal analysis through wavelet leader-based multiscale representations of instantaneous series of vagal activity as estimated from inhomogeneous point process models...
July 2017: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
M Nardelli, A Greco, J Bolea, G Valenza, E P Scilingo, R Bailon
This study reports on the reliability of Lagged Poincaré Plot (LPP) parameters calculated from ultra-short cardiovascular time series (from 30 to 180 seconds). ity (HRV) signals, whereas a few studies have studied nonlinear approaches. Particularly, methods derived from the phase-space theory, especially the ones employing multi-lag analyses, are usually considered to be inaccurate with a low number of samples. Here we propose a comprehensive study about LPP, using both synthetic and real RR series. Specifically, we considered 109 5-minutes HRV series: 60 synthetic series generated through the Integral Pulse Frequency Modulation (IPFM) model and 49 experimental series acquired from healthy subjects during resting-state...
July 2017: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Gerardo Severino, Francesco Giannino, Fabrizio Cartení, Stefano Mazzoleni, Daniel M Tartakovsky
Current models of vegetation pattern formation rely on a system of weakly nonlinear reaction-diffusion equations that are coupled by their source terms. While these equations, which are used to describe a spatiotemporal planar evolution of biomass and soil water, qualitatively capture the emergence of various types of vegetation patterns in arid environments, they are phenomenological and have a limited predictive power. We ameliorate these limitations by deriving the vertically averaged Richards' equation to describe flow (as opposed to "diffusion") of water in partially saturated soils...
October 19, 2017: Bulletin of Mathematical Biology
Andrew P Voorhees, Ning-Jiun Jan, Morgan E Austin, John G Flanagan, Jeremy M Sivak, Richard A Bilonick, Ian A Sigal
Purpose: The purpose of this study was to determine how the architecture of the lamina cribrosa (LC) microstructure, including the shape and size of the lamina pores, influences the IOP-induced deformation of the neural tissues within the LC pores using computational modeling. Methods: We built seven specimen-specific finite element models of LC microstructure with distinct nonlinear anisotropic properties for LC beams and neural tissues based on histological sections from three sheep eyes...
October 1, 2017: Investigative Ophthalmology & Visual Science
Piotr Roztocki, Michael Kues, Christian Reimer, Benjamin Wetzel, Stefania Sciara, Yanbing Zhang, Alfonso Cino, Brent E Little, Sai T Chu, David J Moss, Roberto Morandotti
The on-chip generation of large and complex optical quantum states will enable low-cost and accessible advances for quantum technologies, such as secure communications and quantum computation. Integrated frequency combs are on-chip light sources with a broad spectrum of evenly-spaced frequency modes, commonly generated by four-wave mixing in optically-excited nonlinear micro-cavities, whose recent use for quantum state generation has provided a solution for scalable and multi-mode quantum light sources. Pulsed quantum frequency combs are of particular interest, since they allow the generation of single-frequency-mode photons, required for scaling state complexity towards, e...
August 7, 2017: Optics Express
Niansheng Tang, Sy-Miin Chow, Joseph G Ibrahim, Hongtu Zhu
Many psychological concepts are unobserved and usually represented as latent factors apprehended through multiple observed indicators. When multiple-subject multivariate time series data are available, dynamic factor analysis models with random effects offer one way of modeling patterns of within- and between-person variations by combining factor analysis and time series analysis at the factor level. Using the Dirichlet process (DP) as a nonparametric prior for individual-specific time series parameters further allows the distributional forms of these parameters to deviate from commonly imposed (e...
October 13, 2017: Psychometrika
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