Studying Spin-Orbit Dynamics using Measurements of the Proton's Polarized Gluon Asymmetry

Measurements involving the gluon spin density, Delta G=G++ - G+-, can play an important role in the quantitative understanding of proton structure. To demonstrate this, we show that the shape of the gluon asymmetry, A(x,t)=Delta G(x,t)/G(x,t), contains significant dynamical information about non-perturbative spin-orbit effects. It is instructive to use a separation A(x,t)=A_0^epsilon(x)+epsilon(x,t), where A_0^epsilon(x) is an approximately scale-invariant form that can be calculated within a given factorization prescription from the measured distributions Delta q(x,t), q(x,t) and G(x,t). Applying this separation with the J_z=1/2 sum rule provides a convenient way to determine the total amount of orbital angular momentum generated by mechanisms associated with confinement and chiral dynamics. The results are consistent with alternate non-perturbative approaches to the determination of orbital angular momentum in the proton. Our studies help to specify the accuracy that future measurements should achieve to constrain theoretical models for nucleon structure.Comment: 24 pages, 3 figure

Simulation of Hot-Carrier Dynamics and Terahertz Emission in Laser-Excited Metallic Bilayers

We present a multiscale model that simulates optically induced spin currents in metallic bilayer structures that emit terahertz radiation after optical pulse excitation. We describe hot-electron transport in a metallic bilayer by a Boltzmann transport equation, which is solved numerically by a particle-in-cell approach. Optical excitation and propagation effects are taken into account by our determining the emitted terahertz waves from the excited-carrier dynamics. We apply this approach to an Fe/Pt bilayer and show in detail how microscopic scattering effects and transport determine the emitted signal. The versatility of the approach presented here allows it to be readily adapted to a wide spectrum of spintronic-terahertz-emitter designs. As an example, we show how the terahertz generation efficiency, defined as the output-power-to-input-power ratio, can be increased and optimized with use of serially stacked layers in conjunction with terahertz antireflective coatings. We derive an analytical expression for the terahertz emission of a single layer that allows us to determine the relationship between the emitted field and the current profile that generates it.German Science Foundation [SFB/TRR 173 Spin+X]; Graduate School of Excellence MAINZ (Excellence Initiative) [DFG/GSC 266]; [SFB/TRR 173]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Modification of spintronic terahertz emitter performance through defect engineering

Spintronic ferromagnetic/non-magnetic heterostructures are novel sources for the generation of THz radiation based on spin-to-charge conversion in the layers. The key technological and scientific challenge of THz spintronic emitters is to increase their intensity and frequency bandwidth. Our work reveals the factors to engineer spintronic Terahertz generation by introducing the scattering lifetime and the interface transmission for spin polarized, non-equilibrium electrons. We clarify the influence of the electron-defect scattering lifetime on the spectral shape and the interface transmission on the THz amplitude, and how this is linked to structural defects of bilayer emitters. The results of our study define a roadmap of the properties of emitted as well as detected THz-pulse shapes and spectra that is essential for future applications of metallic spintronic THz emitters.Comment: 33 pages, 13 figure

Gas6 Increases Myelination by Oligodendrocytes and Its Deficiency Delays Recovery following Cuprizone-Induced Demyelination

Multiple sclerosis (MS) is a complex demyelinating disease of the central nervous system. Current research has shown that at least in some cases, the primary insult in MS could be directed at the oligodendrocyte, and that the earliest immune responses are primarily via innate immune cells. We have identified a family of receptor protein tyrosine kinases, known as the TAM receptors (Tyro3, Axl and Mertk), as potentially important in regulating both the oligodendrocyte and immune responses. We have previously shown that Gas6, a ligand for the TAM receptors, can affect the severity of demyelination in mice, with a loss of signalling via Gas6 leading to decreased oligodendrocyte survival and increased microglial activation during cuprizone-induced demyelination. We hypothesised TAM receptor signalling would also influence the extent of recovery in mice following demyelination. A significant effect of the absence of Gas6 was detected upon remyelination, with a lower level of myelination after 4 weeks of recovery in comparison with wild-type mice. The delay in remyelination was accompanied by a reduction in oligodendrocyte numbers. To understand the molecular mechanisms that drive the observed effects, we also examined the effect of exogenous Gas6 in in vitro myelination assays. We found that Gas6 significantly increased myelination in a dose-dependent manner, suggesting that TAM receptor signalling could be directly involved in myelination by oligodendrocytes. The reduced rate of remyelination in the absence of Gas6 could thus result from a lack of Gas6 at a critical time during myelin production after injury. These findings establish Gas6 as an important regulator of both CNS demyelination and remyelination

Evidence of sound production by spawning lake trout (Salvelinus namaycush) in lakes Huron and Champlain

Two sounds associated with spawning lake trout (Salvelinus namaycush) in lakes Huron and Champlain were characterized by comparing sound recordings with behavioral data collected using acoustic telemetry and video. These sounds were named “growls” and “snaps” and were heard on lake trout spawning reefs, but not on a nonspawning reef, and were more common at night than during the day. Growls also occurred more often during the spawning period than the prespawning period, while the trend for snaps was reversed. In a laboratory flume, sounds occurred when male lake trout were displaying spawning behaviors: growls when males were quivering and parallel swimming and snaps when males moved their jaw. Combining our results with the observation of possible sound production by spawning splake (Salvelinus fontinalis × Salvelinus namaycush hybrid) provides rare evidence for spawning-related sound production by a salmonid or any other fish in the superorder Protacanthopterygii. Further characterization of these sounds could be useful for lake trout assessment, restoration, and control

Sub-3mm spatial resolution from a large monolithic LaBr3 (Ce) scintillator

Abstract A Compton camera prototype for ion beam range monitoring via prompt (< 1 ns) gamma detection in hadron therapy is being developed and characterized at the Medical Physics Department of LMU Munich. The system consists of a large (50x50x30 mm3) monolithic LaBr3(Ce) scintillation crystal as absorber component to detect the multi-MeV Compton scattered photons, together with a stack of 6 double-sided silicon strip detectors (DSSSD) acting as scatterer component. Key ingredient of the γ-source reconstruction is the determination of the γ-ray interaction position in the scintillator, which is read out by a 256-fold segmented multi-anode photomultiplier tube (PMT). From simulations an angular resolution of about 1.5o for the photon source reconstruction can be expected for the energy range around 3 – 5 MeV, provided that a spatial resolution of 3 mm can be reached in the absorbing scintillator [1]. Therefore, particular effort was dedicated to characterize this latter property as a function of the γ-ray energy. Intense, tightly collimated 137Cs and 60Co photon sources were used for 2D irradiation scans (step size 0.5 mm) as prerequisite for studying the performance of the "k-Nearest-Neighbors" algorithm developed at TU Delft [2] (together with its variant "Categorical Average Pattern", CAP) and extending its applicability into the energy range beyond the original 511 keV. In this paper we present our most recent interaction position analysis in the absorbing scintillator, leading to a considerably improved value for the spatial resolution: systematic studies were performed as a function of the k-NN parameters and the PMT segmentation. A trend of improving spatial resolution with increasing photon energy was confirmed, resulting in the realization of the presently optimum spatial resolution of 2.9(1) mm @1.3 MeV, thus reaching the design specifications of the Compton camera absorber. The specification goal was reached also for a reduced PMT segmentation of 8x8 anode segments (each with 6x6 mm2 active area), thus allowing to reduce the complexity of the signal processing while preserving the performance

Spinodal Decomposition in a Binary Polymer Mixture: Dynamic Self Consistent Field Theory and Monte Carlo Simulations

We investigate how the dynamics of a single chain influences the kinetics of early stage phase separation in a symmetric binary polymer mixture. We consider quenches from the disordered phase into the region of spinodal instability. On a mean field level we approach this problem with two methods: a dynamical extension of the self consistent field theory for Gaussian chains, with the density variables evolving in time, and the method of the external potential dynamics where the effective external fields are propagated in time. Different wave vector dependencies of the kinetic coefficient are taken into account. These early stages of spinodal decomposition are also studied through Monte Carlo simulations employing the bond fluctuation model that maps the chains -- in our case with 64 effective segments -- on a coarse grained lattice. The results obtained through self consistent field calculations and Monte Carlo simulations can be compared because the time, length, and temperature scales are mapped onto each other through the diffusion constant, the chain extension, and the energy of mixing. The quantitative comparison of the relaxation rate of the global structure factor shows that a kinetic coefficient according to the Rouse model gives a much better agreement than a local, i.e. wave vector independent, kinetic factor. Including fluctuations in the self consistent field calculations leads to a shorter time span of spinodal behaviour and a reduction of the relaxation rate for smaller wave vectors and prevents the relaxation rate from becoming negative for larger values of the wave vector. This is also in agreement with the simulation results.Comment: Phys.Rev.E in prin

Comparative Single-Cell Analysis of Different E. coli Expression Systems during Microfluidic Cultivation

Binder D, Probst C, Grünberger A, et al. Comparative Single-Cell Analysis of Different E. coli Expression Systems during Microfluidic Cultivation. PLoS one. 2016;11(8): e0160711.Recombinant protein production is mostly realized with large-scale cultivations and monitored at the level of the entire population. Detailed knowledge of cell-to-cell variations with respect to cellular growth and product formation is limited, even though phenotypic heterogeneity may distinctly hamper overall production yields, especially for toxic or difficult-to-express proteins. Unraveling phenotypic heterogeneity is thus a key aspect in understanding and optimizing recombinant protein production in biotechnology and synthetic biology. Here, microfluidic single-cell analysis serves as the method of choice to investigate and unmask population heterogeneities in a dynamic and spatiotemporal fashion. In this study, we report on comparative microfluidic single-cell analyses of commonly used E. coli expression systems to uncover system-inherent specifications in the synthetic M9CA growth medium. To this end, the PT7lac/LacI, the PBAD/AraC and the Pm/XylS system were systematically analyzed in order to gain detailed insights into variations of growth behavior and expression phenotypes and thus to uncover individual strengths and deficiencies at the single-cell level. Specifically, we evaluated the impact of different system-specific inducers, inducer concentrations as well as genetic modifications that affect inducer-uptake and regulation of target gene expression on responsiveness and phenotypic heterogeneity. Interestingly, the most frequently applied expression system based on E. coli strain BL21(DE3) clearly fell behind with respect to expression homogeneity and robustness of growth. Moreover, both the choice of inducer and the presence of inducer uptake systems proved crucial for phenotypic heterogeneity. Conclusively, microfluidic evaluation of different inducible E. coli expression systems and setups identified the modified lacY-deficient PT7lac/LacI as well as the Pm/XylS system with conventional m-toluic acid induction as key players for precise and robust triggering of bacterial gene expression in E. coli in a homogeneous fashion

Bidirectional Psychoneuroimmune Interactions in the Early Postpartum Period Influence Risk of Postpartum Depression

More than 500,000 U.S. women develop postpartum depression (PPD) annually. Although psychosocial risks are known, the underlying biology remains unclear. Dysregulation of the immune inflammatory response and the hypothalamic–pituitary–adrenal (HPA) axis are associated with depression in other populations. While significant research on the contribution of these systems to the development of PPD has been conducted, results have been inconclusive. This is partly because few studies have focused on whether disruption in the bidirectional and dynamic interaction between the inflammatory response and the HPA axis together influence PPD. In this study, we tested the hypothesis that disruption in the inflammatory-HPA axis bidirectional relationship would increase the risk of PPD. Plasma pro- and anti-inflammatory cytokines were measured in women during the 3rd trimester of pregnancy and on Days 7 and 14, and Months 1, 2, 3, and 6 after childbirth. Saliva was collected 5 times the day preceding blood draws for determination of cortisol area under the curve (AUC) and depressive symptoms were measured using the Edinburgh Postpartum Depression Survey (EPDS). Of the 152 women who completed the EPDS, 18% were depressed according to EDPS criteria within the 6 months postpartum. Cortisol AUC was higher in symptomatic women on Day 14 (p = .017). To consider the combined effects of cytokines and cortisol on predicting symptoms of PPD, a multiple logistic regression model was developed that included predictors identified in bivariate analyses to have an effect on depressive symptoms. Results indicated that family history of depression, day 14 cortisol AUC, and the day 14 IL8/IL10 ratio were significant predictors of PPD symptoms. One unit increase each in the IL8/IL10 ratio and cortisol AUC resulted in 1.50 (p = 0.06) and 2.16 (p = 0.02) fold increases respectively in the development of PPD. Overall, this model correctly classified 84.2% of individuals in their respective groups. Findings suggest that variability in the complex interaction between the inflammatory response and the HPA axis influence the risk of PPD