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Cliff C Kerr, Salvador Dura-Bernal, Tomasz G Smolinski, George L Chadderdon, David P Wilson
When standard optimization methods fail to find a satisfactory solution for a parameter fitting problem, a tempting recourse is to adjust parameters manually. While tedious, this approach can be surprisingly powerful in terms of achieving optimal or near-optimal solutions. This paper outlines an optimization algorithm, Adaptive Stochastic Descent (ASD), that has been designed to replicate the essential aspects of manual parameter fitting in an automated way. Specifically, ASD uses simple principles to form probabilistic assumptions about (a) which parameters have the greatest effect on the objective function, and (b) optimal step sizes for each parameter...
2018: PloS One
Alison G Abraham, Long Zhang, Keri Calkins, Adrienne Tin, Andrew Hoofnagle, Frank J Palella, Michelle M Estrella, Lisa P Jacobson, Mallory D Witt, Lawrence A Kingsley, Todd T Brown
OBJECTIVE: Despite effective antiretroviral therapy (HAART) and durable viral suppression, many HIV-infected individuals still do not achieve CD4+ cell count (CD4) normalization. Vitamin D has immunoregulatory functions, including inducing the development of T cells, and higher levels may improve CD4 rebound. DESIGN: Longitudinal study of men from the Multicenter AIDS Cohort Study who virally suppressed following HAART initiation and had pre- and post-HAART 25[OH]D and 1,25[OH]2D measurements and repeated measures of CD4...
March 15, 2018: AIDS
Guy G Marcus, Dae-Jeong Kim, Jacob A Tutmaher, Jose A Rodriguez-Rivera, Jonas Okkels Birk, Christof Niedermeyer, Hannoh Lee, Zachary Fisk, Collin L Broholm
We report the discovery of a field driven transition from a single-q to multi-q spin density wave (SDW) in the tetragonal heavy fermion compound CeAuSb_{2}. Polarized along c, the sinusoidal SDW amplitude is 1.8(2)μ_{B}/Ce for T≪T_{N}=6.25(10)  K with a wave vector q_{1}=(η,η,1/2) [η=0.136(2)]. For H∥c, harmonics appearing at 2q_{1} evidence a striped magnetic texture below μ_{∘}H_{1}=2.78(1)  T. Above H_{1}, these are replaced by coupled harmonics at q_{1}+q_{2}=(2η,0,0)+c^{*} until μ_{∘}H_{2}=5...
March 2, 2018: Physical Review Letters
Qingwang Xue, Chunxue Liu, Xia Li, Li Dai, Huaisheng Wang
Various fluorescent sensing systems for miRNAs detection have been developed. But they mostly contain enzymatic amplification reactions and label procedures. The strict reaction conditions of tool enzymes and the high cost of labeling limit their potential applications, especially in complex biological matrix. Here we have addressed the difficult problems and report a strategy for label-free fluorescent DNA dendrimers based on enzyme-free nonlinear hybridization chain reaction (HCR)-mediated multiple G-quadruplex for simple, sensitive and selective detection of miRNAs with low-background signal...
March 16, 2018: Bioconjugate Chemistry
Kara Pham, Emma Turian, Kai Liu, Shuwang Li, John Lowengrub
We consider the nonlinear dynamics of an avascular tumor at the tissue scale using a two-fluid flow Stokes model, where the viscosity of the tumor and host microenvironment may be different. The viscosities reflect the combined properties of cell and extracellular matrix mixtures. We perform a linear morphological stability analysis of the tumors, and we investigate the role of nonlinearity using boundary-integral simulations in two dimensions. The tumor is non-necrotic, although cell death may occur through apoptosis...
March 15, 2018: Journal of Mathematical Biology
Alejandra Nieto, Holger Roehl
There has been a growing interest in recent years in the assessment of suitable vial/stopper combinations for storage and shipment of frozen drug products. Considering that the glass transition temperature (Tg) of butyl rubber stoppers used in Container Closure Systems (CCS) is between -55°C to -65°C, a storage or shipment temperature of a frozen product below the Tg of the rubber stopper, may require special attention, since below the Tg the rubber becomes more plastic-like and loses its elastic (sealing) characteristics...
March 15, 2018: PDA Journal of Pharmaceutical Science and Technology
Zhen Tian, Jingqi Yuan, Xiang Zhang, Lei Kong, Jingcheng Wang
The coordinated control system (CCS) serves as an important role in load regulation, efficiency optimization and pollutant reduction for coal-fired power plants. The CCS faces with tough challenges, such as the wide-range load variation, various uncertainties and constraints. This paper aims to improve the load tacking ability and robustness for boiler-turbine units under wide-range operation. To capture the key dynamics of the ultra-supercritical boiler-turbine system, a nonlinear control-oriented model is developed based on mechanism analysis and model reduction techniques, which is validated with the history operation data of a real 1000 MW unit...
March 12, 2018: ISA Transactions
Mengli Xiao, Yongbo Zhang, Huimin Fu, Zhihua Wang
High-precision navigation algorithm is essential for the future Mars pinpoint landing mission. The unknown inputs caused by large uncertainties of atmospheric density and aerodynamic coefficients as well as unknown measurement biases may cause large estimation errors of conventional Kalman filters. This paper proposes a derivative-free version of nonlinear unbiased minimum variance filter for Mars entry navigation. This filter has been designed to solve this problem by estimating the state and unknown measurement biases simultaneously with derivative-free character, leading to a high-precision algorithm for the Mars entry navigation...
March 12, 2018: ISA Transactions
Joseph R Cendagorta, Zlatko Bačić, Mark E Tuckerman
We introduce a scheme for approximating quantum time correlation functions numerically within the Feynman path integral formulation. Starting with the symmetrized version of the correlation function expressed as a discretized path integral, we introduce a change of integration variables often used in the derivation of trajectory-based semiclassical methods. In particular, we transform to sum and difference variables between forward and backward complex-time propagation paths. Once the transformation is performed, the potential energy is expanded in powers of the difference variables, which allows us to perform the integrals over these variables analytically...
March 14, 2018: Journal of Chemical Physics
Junhao Liang, Anwarud Din, Tianshou Zhou
While many physical or chemical systems can be modeled by nonlinear Langevin equations (LEs), dynamical analysis of these systems is challenging in the cases of moderate and strong noise. Here we develop a linear approximation scheme, which can transform an often intractable LE into a linear set of binomial moment equations (BMEs). This scheme provides a feasible way to capture nonlinear behaviors in the sense of probability distribution and is effective even when the noise is moderate or big. Based on BMEs, we further develop a noise reduction technique, which can effectively handle tough cases where traditional small-noise theories are inapplicable...
March 14, 2018: Journal of Chemical Physics
Ondřej Novák, Peter R Krogen, Tobias Kroh, Tomáš Mocek, Franz X Kärtner, Kyung-Han Hong
We report on a femtosecond ∼8.5  μm, ∼2  μJ source based on the intrapulse difference-frequency generation (DFG) of 2.1 μm pulses in an AgGaSe2 (AGSe) crystal. Compared to the conventional ∼0.8 or 1 μm near-infrared (IR) pulses, a ∼2  μm driver for intrapulse DFG can provide more efficient conversion into the wavelengths longer than 5 μm due to a lower quantum defect and is more suitable for the non-oxide nonlinear crystals that have a relatively low bandgap energy. Using 26 fs, 2...
March 15, 2018: Optics Letters
Can Cihan, Abdullah Muti, Isinsu Baylam, Askin Kocabas, Umit Demirbas, Alphan Sennaroglu
We report, to the best of our knowledge, the shortest femtosecond pulses generated from a Kerr-lens mode-locked (KLM) Alexandrite laser operating near 750 nm. The Alexandrite gain medium was pumped with a continuous-wave (cw), 532 nm laser, and the performance of both the short and extended resonators was investigated. The use of an extended cavity eliminated the multi-wavelength spectral instabilities observed during the cw operation of the short cavity. Furthermore, since the repetition rate of the Alexandrite laser was reduced from 107 to 5...
March 15, 2018: Optics Letters
Rai Kou, Taiki Hatakeyama, Jason Horng, Ji-Hun Kang, Yuan Wang, Xiang Zhang, Feng Wang
Mid-infrared light provides numerous unexpected opportunities in scientific discoveries because this wavelength region covers the fingerprints of various molecular vibrational resonances. However, the light generation efficiency and bandwidth have been a long-standing bottleneck which has limited the development so far. Moreover, the light source that can be integrated with other components such as wavelength filters, detectors, and electronics, will be the key factor toward the future practical applications...
March 15, 2018: Optics Letters
Qiulin Zhang, Bofang Zheng, Chester Shu
We proposed a novel scheme for realizing Kramers-Kronig detection by utilizing the narrow-band and high-gain characteristic of stimulated Brillouin scattering. At the receiver, the weak virtual carrier located at the edge of the signal spectrum is Brillouin amplified by the output of a slave laser, which is injection locked by a weak pump seed provided by the transmitter. More than a 2.7-dB optical signal-to-noise ratio sensitivity improvement is experimentally obtained compared with the traditional virtual carrier assisted scheme after an 80-km transmission...
March 15, 2018: Optics Letters
Alan Sugarman
No abstract text is available yet for this article.
February 2018: Journal of the American Psychoanalytic Association
David Müller, Andreas Otto, Günter Radons
We show that the output of systems with time-varying delay can exhibit a new kind of chaotic behavior characterized by laminar phases, which are periodically interrupted by irregular bursts. Within each laminar phase the output intensity remains almost constant, but its level varies chaotically from phase to phase. In scalar systems, the periodic dynamics of the lengths and the chaotic dynamics of the intensity levels can be understood and also tuned via two one-dimensional maps, which can be deduced from the nonlinearity of the delay equation and from the delay variation, respectively...
February 23, 2018: Physical Review Letters
Y Wang, S Subhankar, P Bienias, M Łącki, T-C Tsui, M A Baranov, A V Gorshkov, P Zoller, J V Porto, S L Rolston
We report on the experimental realization of a conservative optical lattice for cold atoms with a subwavelength spatial structure. The potential is based on the nonlinear optical response of three-level atoms in laser-dressed dark states, which is not constrained by the diffraction limit of the light generating the potential. The lattice consists of a one-dimensional array of ultranarrow barriers with widths less than 10 nm, well below the wavelength of the lattice light, physically realizing a Kronig-Penney potential...
February 23, 2018: Physical Review Letters
Zhaoxiang Liu, Jinping Yao, Jinming Chen, Bo Xu, Wei Chu, Ya Cheng
The generation of laserlike narrow bandwidth emissions from nitrogen molecular ions (N_{2}^{+}) generated in intense near- and mid infrared femtosecond laser fields has aroused much interest because of the mysterious physics underlying such a phenomenon. Here, we perform a pump-probe measurement on the nonlinear interaction of rotational quantum wave packets of N_{2}^{+} generated in midinfrared (e.g., at a wavelength centered at 1580 nm) femtosecond laser fields with an ultrashort probe pulse whose broad spectrum overlaps both P- and R-branch rotational transition lines between the electronic states N_{2}^{+}(B^{2}Σ_{u}^{+},v^{'}=0) and N_{2}^{+}(X^{2}Σ_{g}^{+},v=0)...
February 23, 2018: Physical Review Letters
P Wiegmann
We develop the quantum hydrodynamics of inner waves in the bulk of fractional quantum Hall states. We show that the inelastic light scattering by inner waves is a sole effect of the gravitational anomaly. We obtain the formula for the oscillator strength or mean energy of optical absorption expressed solely in terms of an independently measurable static structure factor. The formula does not explicitly depend on a model interaction potential.
February 23, 2018: Physical Review Letters
Timothy J Proctor, Paul A Knott, Jacob A Dunningham
We introduce a general model for a network of quantum sensors, and we use this model to consider the following question: When can entanglement between the sensors, and/or global measurements, enhance the precision with which the network can measure a set of unknown parameters? We rigorously answer this question by presenting precise theorems proving that for a broad class of problems there is, at most, a very limited intrinsic advantage to using entangled states or global measurements. Moreover, for many estimation problems separable states and local measurements are optimal, and can achieve the ultimate quantum limit on the estimation uncertainty...
February 23, 2018: Physical Review Letters
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