bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of squeeze on electrostatic Trivelpiece-Gould wave damping
Authors: Ashourvan Arash , Dubin Daniel H. E.
Published: May 2014

We present a theory for increased damping of Trivelpiece-Gouid plasma modes on a nonneutral plasma column, due to application of a Debye shielded cylindrically symmetric squeeze potential φ1. We present two models of the effect this has on the plasma modes: a 1D model with only axial dependence, and a 2D model that also keeps radial dependence in the squeezed equilibrium and the mode. We study the models using both analytical and numerical methods. For our analytical studies, we assume that φ1/T≪1, and we treat the Debye shielded squeeze potential as a perturbation in the equilibrium Hamiltonian. Our numerical simulations solve the 1D Vlasov-Poisson system and obtain the frequency and damping rate for a self-consistent plasma mode, making no assumptions as to the size of the squeeze. In both the 1D and 2D models, damping of the mode is caused by Landau resonances at energies En for which the particle bounce frequency ωb(En) and the wave frequency ω satisfy ω=nωb(En). Particles experience a non-sinusoidal wave potential along their bounce orbits due to the squeeze potential. As a result, the squeeze induces bounce harmonics with n > 1 in the perturbed distribution. The harmonics allow resonances at energies En≤T that cause substantial damping, even when wave phase velocities are much larger than the thermal velocity. In the regime ω/k≫T/m (k is the wave number) and T≫φ1, the resonance damping rate has a |φ1|2 dependence. This dependence agrees with the simulations and experimental results.
Time-, frequency-, and wavevector-resolved x-ray diffraction from single molecules
Authors: Bennett Kochise , Biggs Jason D. , Zhang Yu , Dorfman Konstantin E. , Mukamel Shaul
Published: May 2014

Using a quantum electrodynamic framework, we calculate the off-resonant scattering of a broadband X-ray pulse from a sample initially prepared in an arbitrary superposition of electronic states. The signal consists of single-particle (incoherent) and two-particle (coherent) contributions that carry different particle form factors that involve different material transitions. Single-molecule experiments involving incoherent scattering are more influenced by inelastic processes compared to bulk measurements. The conditions under which the technique directly measures charge densities (and can be considered as diffraction) as opposed to correlation functions of the charge-density are specified. The results are illustrated with time- and wavevector-resolved signals from a single amino acid molecule (cysteine) following an impulsive excitation by a stimulated X-ray Raman process resonant with the sulfur K-edge. Our theory and simulations can guide future experimental studies on the structures of nano-particles and proteins.
Density functional theory for carbon dioxide crystal
Authors: Chang Yiwen , Mi Jianguo , Zhong Chongli
Published: May 2014

We present a density functional approach to describe the solid−liquid phase transition, interfacial and crystal structure, and properties of polyatomic CO2. Unlike previous phase field crystal model or density functional theory, which are derived from the second order direct correlation function, the present density functional approach is based on the fundamental measure theory for hard-sphere repulsion in solid. More importantly, the contributions of enthalpic interactions due to the dispersive attractions and of entropic interactions arising from the molecular architecture are integrated in the density functional model. Using the theoretical model, the predicted liquid and solid densities of CO2 at equilibrium triple point are in good agreement with the experimental values. Based on the structure of crystal-liquid interfaces in different planes, the corresponding interfacial tensions are predicted. Their respective accuracies need to be tested.
Behaviour of hydrogen in wide band gap oxides
Authors: Li H. , Robertson J.
Published: May 2014

The defect formation energies and atomic geometries of interstitial hydrogen in its different charge states in a number of wide band gap oxides are calculated by the Heyd, Scuseria, Ernzerhof hybrid functional. As in semiconductors, two behaviours are found, it acts either as an amphoteric defect or as a shallow donor. There are large scale lattice relaxations between the different charge states for the case of the amphoteric defect. Interestingly, we find that the +/− transition level does have a good alignment below the vacuum level, as was found previously for tetrahedral semiconductors.
Improving the accuracy of walking piezo motors
Authors: den Heijer M. , Fokkema V. , Saedi A. , Schakel P. , Rost M. J.
Published: May 2014

Many application areas require ultraprecise, stiff, and compact actuator systems with a high positioning resolution in combination with a large range as well as a high holding and pushing force. One promising solution to meet these conflicting requirements is a walking piezo motor that works with two pairs of piezo elements such that the movement is taken over by one pair, once the other pair reaches its maximum travel distance. A resolution in the pm-range can be achieved, if operating the motor within the travel range of one piezo pair. However, applying the typical walking drive signals, we measure jumps in the displacement up to 2.4 μm, when the movement is given over from one piezo pair to the other. We analyze the reason for these large jumps and propose improved drive signals. The implementation of our new drive signals reduces the jumps to less than 42 nm and makes the motor ideally suitable to operate as a coarse approach motor in an ultra-high vacuum scanning tunneling microscope. The rigidity of the motor is reflected in its high pushing force of 6.4 N.
Injected charge as a cause of the slow dielectric relaxation in thin film Pt/(Ba,Sr)TiO3/Cu structures
Authors: Samoilova Tatyana , Gaidukov Mikhail , Tumarkin Andrey , Gagarin Alexander , Altynnikov Andrey , Kozyrev Andrey
Published: May 2014

Experimental studies of the response of Pt/Ba0.3Sr0.7TiO3/Cu capacitors to switching-off the bias voltage are reported. The remnant capacitance as a function of the bias voltage and the variation of this capacitance with time have been measured and analyzed in terms of the injection model of the space charge origin with consideration for the linear dielectric layer at the Pt/BSTO interface. The energy depths, 0.51 eV, and 0.65 eV, of two trap states controlling the slow (τ ≈ 100 s and τ ≈ 5 × 103 s) space charge relaxation process have been extracted from experiments.
Dynamics of submicron microsphere suspensions observed by dynamic ultrasound scattering techniques in the frequency-domain
Authors: Igarashi Kenta , Norisuye Tomohisa , Kobayashi Keisuke , Sugita Kazuki , Nakanishi Hideyuki , Tran-Cong Miyata Qui
Published: May 2014

Dynamic ultrasound scattering (DSS) techniques have been employed in order to evaluate the dynamics and size of submicron-particles. In addition to the fact that the ultrasound-based techniques could be applied to optically turbid systems, a novel method called frequency-domain DSS allowed us to investigate complex fluid dynamics involving both thermal diffusion and settling of microspheres by recording the time-correlation function at the corresponding spatial length scales. While the particle sizing was successful for silica and polystyrene particles with the hydrodynamics radii down to 100 nm, which was 20 times smaller than the minimal detectable size in the previous DSS studies, coupling of diffusion and sedimentation modes was observed. Since it enables us to quantitatively evaluate the particle motions at the individual scanning windows by a single acquisition, diffusion and sedimentation of submicron particles were simultaneously analyzed at the corresponding scattering vectors where the contribution from sedimentation was neutralized by the density matching.
Temperature-induced unfolding of scrolled graphene and folded graphene
Authors: Yi L. J. , Zhang Y. Y. , Wang C. M. , Chang T. C.
Published: May 2014

Different morphologies of graphene can provide a great potential for applications of graphene-based nano-devices and functional nano-materials. Using molecular dynamic simulations, we show that by altering the temperature, one can induce unfolding of short (length less than ∼50 nm) scrolled or folded graphene to a planar state. The mechanism of these phenomena is that temperature modifies the stability of these unclosed structures. We show in particular that morphology transformation of graphene is not explained by the change of the potential energy of the system, but rather it can be explained by a free energy analysis based on thermal dynamics.
Fatigue damage evaluation of austenitic stainless steel using nonlinear ultrasonic waves in low cycle regime
Authors: Zhang Jianfeng , Xuan Fu-Zhen
Published: May 2014

The interrupted low cycle fatigue test of austenitic stainless steel was conducted and the dislocation structure and fatigue damage was evaluated subsequently by using both transmission electron microscope and nonlinear ultrasonic wave techniques. A “mountain shape” correlation between the nonlinear acoustic parameter and the fatigue life fraction was achieved. This was ascribed to the generation and evolution of planar dislocation structure and nonplanar dislocation structure such as veins, walls, and cells. The “mountain shape” correlation was interpreted successfully by the combined contribution of dislocation monopole and dipole with an internal-stress dependent term of acoustic nonlinearity.
Enhanced refrigerant capacity in two-phase nanocrystalline/amorphous NdPrFe17 melt-spun ribbons
Authors: Sánchez-Valdés C. F. , Ibarra-Gaytán P. J. , Llamazares J. L. Sánchez , Ávalos-Borja M. , Álvarez-Alonso Pablo , Gorria Pedro , Blanco J. A.
Published: May 2014

The magnetocaloric properties of NdPrFe17 melt-spun ribbons composed of nanocrystallites surrounded by an intergranular amorphous phase have been studied. The nanocomposite shows two successive second-order magnetic phase transitions (303 and 332 K), thus giving rise to a remarkable broadening (≈ 84 K) of the full-width at the half-maximum of the magnetic entropy change curve, ΔSM(T), with a consequent enhancement of the refrigerant capacity RC. For a magnetic field change of 2 T, |ΔSMpeak| = 2.1 J kg−1 K−1 and RC = 175 J kg−1. Therefore, the reversible magnetocaloric response together with the one-step preparation process makes these nanostructured Fe-rich alloy ribbons particularly attractive for room temperature magnetic refrigeration.
High efficiency proton beam generation through target thickness control in femtosecond laser-plasma interactions
Authors: Green J. S. , Robinson A. P. L. , Booth N. , Carroll D. C. , Dance R. J. , Gray R. J. , MacLellan D. A. , McKenna P. , Murphy C. D. , Rusby D. , Wilson L.
Published: May 2014

Bright proton beams with maximum energies of up to 30 MeV have been observed in an experiment investigating ion sheath acceleration driven by a short pulse (<50 fs) laser. The scaling of maximum proton energy and total beam energy content at ultra-high intensities of ∼1021 W cm−2 was investigated, with the interplay between target thickness and laser pre-pulse found to be a key factor. While the maximum proton energies observed were maximised for μm-thick targets, the total proton energy content was seen to peak for thinner, 500 nm, foils. The total proton beam energy reached up to 440 mJ (a conversion efficiency of 4%), marking a significant step forward for many laser-driven ion applications. The experimental results are supported by hydrodynamic and particle-in-cell simulations.
The net power output of ideal supercritical organic Rankine cycle with different flow arrangement evaporators
Authors: He Chao , Liu Chao , Gao Hong , Xie Hui , Li Yourong , Wu Shuangying
Published: May 2014

The theoretical models of net power output for ideal supercritical ORC (organic Rankine cycle) with the evaporator of counter flow, parallel flow, and cross flow are, respectively, proposed. The effects of the ratio of heat capacity rates of heat source and working fluid, the number of heat transfer unit, and the ratio of the cycle high and low temperatures on the net power output of ideal supercritical ORC are addressed. The numerical simulation results of ideal supercritical ORC elucidate that the larger rate difference between the heat capacity of working fluids and heat source will help to improve the net power output. The net power output will be kept constant when the number of heat transfer unit reaches a certain value. In addition, supercritical ORC with counter flow evaporator exhibits the largest net power output while one with parallel flow evaporator does the lowest.
Real time drift measurement for colloidal probe atomic force microscope: a visual sensing approach
Authors: Wang Yuliang , Wang Huimin , Bi Shusheng
Published: May 2014

Drift has long been an issue in atomic force microscope (AFM) systems and limits their ability to make long time period measurements. In this study, a new method is proposed to directly measure and compensate for the drift between AFM cantilevers and sample surfaces in AFM systems. This was achieved by simultaneously measuring z positions for beads at the end of an AFM colloidal probe and on sample surface through an off-focus image processing based visual sensing method. The working principle and system configuration are presented. Experiments were conducted to validate the real time drift measurement and compensation. The implication of the proposed method for regular AFM measurements is discussed. We believe that this technique provides a practical and efficient approach for AFM experiments requiring long time period measurement.
Femtosecond measurements of near-infrared pulse induced mid-infrared transmission modulation of quantum cascade lasers
Authors: Cai Hong , Liu Sheng , Lalanne Elaine , Guo Dingkai , Chen Xing , Wang Xiaojun , Choa Fow-Sen , Johnson Anthony M.
Published: May 2014

We temporally resolved the ultrafast mid-infrared transmission modulation of quantum cascade lasers (QCLs) using a near-infrared pump/mid-infrared probe technique at room temperature. Two different femtosecond wavelength pumps were used with photon energy above and below the quantum well (QW) bandgap. The shorter wavelength pump modulates the mid-infrared probe transmission through interband transition assisted mechanisms, resulting in a high transmission modulation depth and several nanoseconds recovery lifetime. In contrast, pumping with a photon energy below the QW bandgap induces a smaller transmission modulation depth but much faster (several picoseconds) recovery lifetime, attributed to intersubband transition assisted mechanisms. The latter ultrafast modulation (>60 GHz) could provide a potential way to realize fast QCL based free space optical communication.
Cell-induced flow-focusing instability in gelatin methacrylate microdroplet generation
Authors: Jung Jinmu , Oh Jonghyun
Published: May 2014

Photo-crosslinkable gelatin methacrylate (GelMa) microspheres are applicable to deliver cells or drugs in biological or biomedical applications. To fabricate GelMa microdroplets, a flow focusing technique with advantages of size control and rapid production was used in a T-junction microfluidic device. Instability played an important role in promoting microdroplet uniformity. 5 wt. % GelMa prepolymer solution mixed with cells affected cell-induced instability. At low flow rate ratio of GelMa to mineral oil below 0.200, stability was maintained regardless of GelMa concentration (5 and 8 wt. %) and cell presence, which led to uniform microdroplet generation. In contrast, instability at high flow rate ratio above 0.200 was worsened by cell presence and unstable jetting length, resulting in the generation of non-uniform cell-laden microdroplets. Therefore, the effect of cell-induced instability on microdroplet generation was minimized at a low flow rate ratio.
Vertical focusing and cell ordering in a microchannel via viscoelasticity: Applications for cell monitoring using a digital holographic microscopy
Authors: Won Seo Kyung , Ran Ha Young , Joon Lee Sang
Published: May 2014

We demonstrate sheath-free vertical concentration and positioning of cells induced by fluid viscoelasticity in a rectangular channel. The high uniformity in depth position and the reduction in cell overlap eliminate out-of-focus blurring and increase detection sensitivity. Additionally, orientational ordering of red blood cells improves the monitoring and counting performance of an optical imaging system. As a proof of concept of vertical focusing and cell ordering, we demonstrate counting and monitoring of red blood cells flowing in a microchannel using phase-contrast holographic microscopy for quantitative phase imaging.
Effect of interfacial structural phase transitions on the coupled motion of grain boundaries: A molecular dynamics study
Authors: Frolov T.
Published: May 2014

In this work, the coupled motion of two different phases of Σ 5(210)[001] grain boundaries was investigated by molecular dynamics simulations of fcc Cu. The effect of interfacial structural phase transitions is shown to have a profound effect on both the shear strength and the nature of the coupled motion. Specifically, the motion of the two different phases is described by ideal coupling factors β⟨100⟩ and β⟨110⟩ that have different magnitudes and even signs. Additionally, the shear strength for the two interfacial phases is observed to differ by up to 40% at the lowest temperatures simulated. The study demonstrates that grain boundary phases transitions may have strong effects on the kinetics of microstructural evolution.
Burrowing behaviour of the northern hopping-mouse (Notomys aquilo): field observations
Authors: Diete Rebecca L. , Meek Paul D. , Dickman Christopher R. , Leung Luke K.-P.
Published: May 2014

We describe burrowing behaviour of the elusive northern hopping-mouse (Notomys aquilo) recorded by camera traps. New burrows were observed at the beginning and end of the wet season on Groote Eylandt, Northern Territory. Initial burrow entrances were open for approximately five days before being back-filled, leaving only a spoil heap with pop holes (burrow entrances) up to 5.3 m away. These results will improve survey techniques for this cryptic, threatened species.
Low-valent Iron Complexes Stabilised by a Bulky Guanidinate Ligand: Synthesis and Reactivity Studies
Authors: Fohlmeister Lea , Jones Cameron
Published: May 2014

A toluene-capped guanidinato iron(i) complex [(Pipiso)Fe(η6-toluene)] (Pipiso = [(DipN)2C(cis-NC5H8Me2-2,6)]–) was prepared by magnesium metal reduction of {[(Pipiso)FeII(µ-Br)]2} in toluene. The reactivity of the closely related FeI–FeI multiply bonded species, {[Fe(μ-Pipiso)]2} towards a range of unsaturated small molecule substrates was investigated, and found to be broadly similar to that of low-valent β-diketiminato iron complexes. That is, its reaction with CO yielded the iron(i) carbonyl complex [(Pipiso)Fe(CO)3], whereas reaction with CO2 formed the same product via an apparent reductive disproportionation of the substrate. In contrast, reaction between {[Fe(μ-Pipiso)]2} and CS2 led to reductive C=S bond cleavage and the isolation of {[(Pipiso)Fe]2(μ-S)(μ-CS)}. Different reactivity was seen with AdN3 (Ad = 1-adamantyl), which was reductively coupled by the iron(i) dimer to give iron(ii) hexaazenyl complex {[(Pipiso)Fe]2(μ-AdN6Ad)}.
Encoding and storage of spatial information in the retrosplenial cortex
Authors: Czajkowski Rafał , Jayaprakash Balaji , Wiltgen Brian , Rogerson Thomas , Guzman-Karlsson Mikael C. , Barth Alison L. , Trachtenberg Joshua T. , Silva Alcino J.
Published: May 2014

Significance

The retrosplenial cortex (RSC) is a key part of a network of brain regions that processes and stores spatial information. However, it is unclear whether the RSC actually encodes or stores spatial information. With time-lapse two-photon in vivo imaging that allowed us to study the immediate early gene c-fos expression in tens of thousands of cells in the RSC, we uncovered repetitive activation of a fraction of cells in this structure during spatial learning. We also showed that RSC inactivation disrupts performance in a spatial task, whereas overexpressing of the transcription factor CREB results in enhanced spatial memory. Silencing the CREB-expressing neurons occluded these memory enhancements. These results demonstrate that the retrosplenial cortex is involved in the formation and storage of spatial information.
Geomechanical behavior of the reservoir and caprock system at the In Salah CO
2
storage project
Authors: White Joshua A. , Chiaramonte Laura , Ezzedine Souheil , Foxall William , Hao Yue , Ramirez Abelardo , McNab Walt
Published: May 2014

Significance

In Salah is one of the largest carbon capture and storage projects to date and has played a central role in demonstrating the feasibility of onshore sequestration of CO
2
in deep saline aquifers. The unique field experience at In Salah provides a valuable case study in managing commercial-scale CO
2
injections. In particular, the current work highlights the importance of geomechanics and integrated monitoring in understanding field behavior and managing storage risk.
Vaccinating captive chimpanzees to save wild chimpanzees
Authors: Warfield Kelly L. , Goetzmann Jason E. , Biggins Julia E. , Kasda Mary Beth , Unfer Robert C. , Vu Hong , Aman M. Javad , Olinger Gene Gerrard , Walsh Peter D.
Published: May 2014

Significance

Although infectious disease is now recognized as a major threat to wild gorillas and chimpanzees, safety fears have stifled the use of a powerful disease control tool, vaccination. To illustrate that safety can be rigorously evaluated before vaccines are used on wild apes, we conducted what is, to our knowledge, the first conservation-oriented vaccine trial on captive chimpanzees. We tested an experimental virus-like particle (VLP) vaccine against Ebola virus, a leading killer of wild apes. Our trial illustrates both the ape conservation value that will be lost if efforts to end vaccine trials on captive chimpanzee are successful and the broader potential that noninfectious VLP vaccines have in other wildlife applications.
Switching brain serotonin with oxytocin
Authors: Mottolese Raphaelle , Redouté Jérôme , Costes Nicolas , Le Bars Didier , Sirigu Angela
Published: May 2014

Significance

Serotonin (5-HT) and oxytocin (OXT) are two neuromodulators involved in human affect and sociality and in disorders like depression and autism. Here we show that these chemical messengers interact in areas of the human brain important for the regulation of emotion-based behavior. By highlighting the role of OXT in the regulation of 5-HT signaling, our findings can lead to novel therapeutic strategies for mental disorders such as social anxiety, depression, and autism.
PHLDA3 is a novel tumor suppressor of pancreatic neuroendocrine tumors
Authors: Ohki Rieko , Saito Kozue , Chen Yu , Kawase Tatsuya , Hiraoka Nobuyoshi , Saigawa Raira , Minegishi Maiko , Aita Yukie , Yanai Goichi , Shimizu Hiroko , Yachida Shinichi , Sakata Naoaki , Doi Ryuichiro , Kosuge Tomoo , Shimada Kazuaki , Tycko Benjamin , Tsukada Toshihiko , Kanai Yae , Sumi Shoichiro , Namiki Hideo , Taya Yoichi , Shibata Tatsuhiro , Nakagama Hitoshi
Published: May 2014

Significance

Pancreatic neuroendocrine tumors (PanNETs) are a rare pathology, and molecular mechanisms underlying their development have not been well defined. This article shows that a two-hit inactivation of the
PHLDA3
gene is required for PanNET development: methylation of the locus and loss of heterozygosity. PHLDA3 functions as a suppressor of PanNETs via repression of Akt activity and downstream Akt-regulated biological processes. In addition, the tumor-suppressing pathway mediated by MEN1, a well known suppressor of PanNETs, is dependent on the pathway mediated by PHLDA3, and inactivation of PHLDA3 and MEN1 cooperatively contribute to PanNET development. A novel PHLDA3-mediated pathway of tumor suppression that is important in the development of PanNETs is demonstrated, and the findings may contribute to personalized medicine of PanNET patients.
IκB kinase-induced interaction of TPL-2 kinase with 14-3-3 is essential for Toll-like receptor activation of ERK-1 and -2 MAP kinases
Authors: Ben-Addi Abduelhakem , Mambole-Dema Agnes , Brender Christine , Martin Stephen R. , Janzen Julia , Kjaer Sven , Smerdon Stephen J. , Ley Steven C.
Published: May 2014

Significance

TPL-2 is a MEK-1/2 kinase that mediates Toll-like receptor activation of ERK-1/2 MAP kinases in macrophages and is critical for TNF induction during inflammation. TPL-2 activation of MEK-1/2 requires release from its associated inhibitor NF-κB1 p105, resulting from p105 proteolysis triggered by the IκB kinase (IKK) complex. Here, we show that IKK phosphorylation of the TPL-2 C terminus induces 14-3-3 association with TPL-2, stimulating its MEK kinase activity, which is essential for TPL-2 activation of ERK-1/2. The 14-3-3 binding to TPL-2 is also indispensible for its induction of TNF, which is regulated independently of ERK-1/2 activation. The IKK complex, a key regulator of NF-κB transcription factors, therefore directly controls two key steps for TPL-2 activation in inflammatory responses.
Genome-wide RNAi screen identifies the Parkinson disease GWAS risk locusSREBF1as a regulator of mitophagy
Authors: Ivatt Rachael M. , Sanchez-Martinez Alvaro , Godena Vinay K. , Brown Stephen , Ziviani Elena , Whitworth Alexander J.
Published: May 2014

Significance

This study presents the first results, to our knowledge, of a whole-genome RNAi screen to identify factors that promote Parkin-mediated mitophagy, which have been validated for conservation across species. Top hits comprise several components of thesterol regulatory element binding transcription factor(SREBF) lipogenesis pathway, and we show that provision of exogenous lipids can promote the mitophagy pathway. BecauseSREBF1has been identified as a risk locus for sporadic Parkinson disease (PD) through genome-wide association studies, the identification ofSREBF1in our screen provides evidence for mechanistic insight into the pathogenesis of sporadic PD. Thus, our functional studies provide the first insight, to our knowledge, into why the master regulator for lipogenesis,SREBF1, may contribute to sporadic PD and further underscore the impact of dysfunctional mitophagy on pathogenesis.
Hedgehog signaling mediates adaptive variation in a dynamic functional system in the cichlid feeding apparatus
Authors: Hu Yinan , Albertson R. Craig
Published: May 2014

Significance

Although evolutionary developmental biology has traditionally focused on linking genes to simple shifts in morphology, adaptation to new environments involves divergence in resource use, which often involves variation in complex functional systems. Thus, for evo-devo research to explain broad evolutionary processes, we must examine more dynamic traits within this context. Here we combine traditional quantitative trait locus mapping, population genetics, and experimental embryology to show how differences in gene expression during larval development lead to adaptive morphological variation in adults. By functional modeling of the skull, we show further how such anatomical shifts in response to genetic variation predict discrete differences in feeding mechanics in African cichlids.
Mechanisms underlying differential effectiveness of memantine and ketamine in rapid antidepressant responses
Authors: Gideons Erinn S. , Kavalali Ege T. , Monteggia Lisa M.
Published: May 2014

Significance

Ketamine is an NMDA receptor (NMDAR) antagonist that elicits rapid antidepressant responses in patients with treatment-resistant depression. However, ketamine can also produce adverse side effects, which raised interest in whether the clinically tolerated NMDAR antagonist memantine can elicit similar fast antidepressant action. Rather surprisingly, clinical data have shown that memantine does not trigger rapid antidepressant effects for reasons that have yet to be elucidated. Here, we reconstitute the ketamine and memantine clinical findings in animal models and, combined with the analysis of synaptic function and subsequent intracellular signaling, demonstrate significant differences between the efficacies of ketamine and memantine on NMDAR-mediated neurotransmission and downstream intracellular signaling. These findings suggest a potential mechanism to explain the earlier clinical observations.
Molecular determinants of Hv1 proton channel inhibition by guanidine derivatives
Authors: Hong Liang , Kim Iris H. , Tombola Francesco
Published: May 2014

Significance

The activity of the Hv1 proton channel has been shown to exacerbate neuronal death after cerebral hypoxia and promote tumor formation by highly metastatic breast cancer cells. Compounds able to inhibit excessive Hv1 activity could find applications as neuroprotective agents in ischemic stroke or anticancer drugs. In this work, we investigate how guanidine derivatives, like 2-guanidinobenzimidazole (2GBI), interact with Hv1 and inhibit proton conduction. We identify the binding site for 2GBI and determine the most likely orientation of the inhibitor inside the channel. We also show that a simple modification of 2GBI eliminates the requirement for the inhibitor to have direct access to the intracellular side of the channel to block the proton current.
Endogenous retrovirus induces leukemia in a xenograft mouse model for primary myelofibrosis
Authors: Triviai Ioanna , Ziegler Marion , Bergholz Ulla , Oler Andrew J. , Stübig Thomas , Prassolov Vladimir , Fehse Boris , Kozak Christine A. , Kröger Nicolaus , Stocking Carol
Published: May 2014

Significance

Immunodeficient mice are important tools to define stem cells that drive malignancies (cancers). Primary myelofibrosis (PMF) is a chronic myeloproliferative neoplasm that can progress to malignant leukemia. In a study to define PMF stem cells in transplanted mice, we observed a high incidence of mouse leukemia. We show that endogenous retrovirus (ERV), whose replication is unrestricted in immunodeficient mice, are pathogenic in the PMF-xenograft microenvironment, likely because of increased numbers of proliferating mouse cells stimulated by PMF-derived cells. Proliferating cells are targets of retroviral transformation and spontaneous mutations, and thus susceptible to leukemia induction. These results substantiate the importance of paracrine mechanisms in PMF disease and expose the presence of replicating ERVs in mice commonly used to model human diseases.
Loss of the death receptor CD95 (Fas) expression by dendritic cells protects from a chronic viral infection
Authors: Varanasi Vineeth , Khan Aly Azeem , Chervonsky Alexander V.
Published: May 2014

Significance

Chronic viral infections evolved to avoid destruction by the immune system. Lymphocytic choriomeningitis virus (LCMV) clone 13, which causes a chronic infection, induces expression of Fas death receptor protein by antigen-presenting cells, such as dendritic cells (DCs). When Fas is ligated by Fas ligand expressed by T cells, DCs die. This event blocks further T-cell activation. To break this mechanism and to sustain antiviral T-cell responses, we used mice that lost Fas from DCs. These animals cleared the infection, whereas Fas-sufficient mice did not. Moreover, a transfer of Fas-negative DCs into infected mice supported the clearance of LCMV infection. Thus, we suggest a novel strategy for stimulation of T cells to achieve the clearance of persistent viruses in infected animals and humans.
Father's brain is sensitive to childcare experiences
Authors: Abraham Eyal , Hendler Talma , Shapira-Lichter Irit , Kanat-Maymon Yaniv , Zagoory-Sharon Orna , Feldman Ruth
Published: May 2014

Significance

Brain, oxytocin, and parenting behavior were measured in primary-caregiving mothers, secondary-caregiving fathers, and primary-caregiving homosexual fathers raising infants without maternal involvement. Parenting integrated functioning of two neural networks: subcortical-paralimbic structures implicated in emotional processing and cortical circuits involved in social understanding. Mothers showed greater activation in the emotional processing network and fathers in the socio-cognitive circuits, which were differentially linked with oxytocin and behavior. Primary-caregiving fathers exhibited high amygdala activation similar to mothers, alongside high superior temporal sulcus (STS) activation comparable to fathers, and functional connectivity between amygdala and STS. Among all fathers, time spent in childcare correlated with amygdala-STS connectivity. Findings describe mechanisms of brain malleability with caregiving experiences in human fathers.
Structural and functional characterization of a conserved pair of bacterial cellulose-oxidizing lytic polysaccharide monooxygenases
Authors: Forsberg Zarah , Mackenzie Alasdair K. , Sørlie Morten , Røhr Åsmund K. , Helland Ronny , Arvai Andrew S. , Vaaje-Kolstad Gustav , Eijsink Vincent G. H.
Published: May 2014

Significance

The discovery of lytic polysaccharide monooxygenases (LPMOs) has profoundly changed our understanding of the enzymatic conversion of recalcitrant polysaccharides, such as cellulose. Although in-depth studies of fungal cellulolytic LPMOs have been reported, the structures and functions of their bacterial counterparts with no detectable sequence similarity remain largely elusive. We present the structures of a conserved pair of bacterial cellulose-active LPMOs supplemented with extensive functional characterization. The structural data allow a thorough comparative assessment of fungal and bacterial LPMOs, providing insight into the structural basis of substrate specificity and the oxidative mechanism (C1/C4 oxidation). Importantly, we show that this LPMO pair acts synergistically when degrading cellulose, a finding that may help explain the occurrence of multiple LPMOs in a single microbe.
PipX, the coactivator of NtcA, is a global regulator in cyanobacteria
Authors: Espinosa Javier , Rodríguez-Mateos Francisco , Salinas Paloma , Lanza Val F. , Dixon Ray , de la Cruz Fernando , Contreras Asuncion
Published: May 2014

Significance

PII, a signal transduction protein involved in nitrogen control in bacteria and plants, and NtcA, the transcriptional nitrogen regulator of cyanobacteria, can form complexes with PIIinteracting protein X (PipX). We demonstrate by a combination of genetic, transcriptomic, and multivariate analyses that PipX is involved in a much wider interaction network affecting nitrogen assimilation, translation, and photosynthesis. Two groups of genes differentially regulated bypipXprovided further insights into the function of NtcA–PipX complexes and an improved definition of the consensus NtcA binding motif. The other four groups suggested the involvement of PipX in NtcA-independent regulatory pathways. Our results pave the way to uncover new regulatory interactions and mechanisms in the control of gene expression in cyanobacteria.
Scalable production of mechanically tunable block polymers from sugar
Authors: Xiong Mingyong , Schneiderman Deborah K. , Bates Frank S. , Hillmyer Marc A. , Zhang Kechun
Published: May 2014

Significance

In recent years there has been extensive research toward the development of sustainable polymeric materials. However, environmentally benign, bioderived polymers still represent a woefully small fraction of plastics and elastomers on the market today. To displace the widely useful oil-based polymers that currently dominate the industry, a bioderived synthetic polymer must be both cost and performance competitive. In this paper we address this challenge by combining the efficient bioproduction of β-methyl-δ-valerolactone with controlled polymerization techniques to produce economically viable block polymer materials with mechanical properties akin to commercially available thermoplastics and elastomers.
Nonequilibrium dynamics and ultraslow relaxation of confined DNA during viral packaging
Authors: Berndsen Zachary T. , Keller Nicholas , Grimes Shelley , Jardine Paul J. , Smith Douglas E.
Published: May 2014

Significance

The high-density packaging of DNA in many viruses is a process that requires the action of powerful molecular motor complexes. Besides being a key step in viral assembly, DNA packaging is a general model for understanding the physics of tightly confined polymers. A fundamental question raised in the literature is whether packaging can be modeled as a quasistatic thermodynamic process, in which the DNA relaxes quickly to equilibrium, or whether it involves nonequilibrium dynamics. In this study, we show that the confined DNA undergoes nonequilibrium dynamics with an extremely long relaxation time and this slows the motor, causes significant heterogeneity in packaging rates of individual viruses, and causes frequent pausing in DNA translocation by the motor.
IL-15.IL-15Rα complex shedding followingtrans-presentation is essential for the survival of IL-15 responding NK and T cells
Authors: Tamzalit Fella , Barbieux Isabelle , Plet Ariane , Heim Julie , Nedellec Steven , Morisseau Sébastien , Jacques Yannick , Mortier Erwan
Published: May 2014

Significance

Interleukin (IL)-15 plays a role in diverse functions of cells involved in the protection against cancer and infections. IL-15 signal is delivered via a mechanism calledtrans-presentation, in which IL-15 expressed at the surface of presenting cells via the membrane-bound IL-15Rα chain, is presented during the interaction with responding cells expressing the transducing receptor. IL-15Rα can be cleaved from the surface of presenting cells and we wondered whether such a mechanism could participate in the regulation of IL-15trans-presentation. By generating an uncleavable form of IL-15Rα, we found an unprecedented cytokine pathway in which the IL-15.IL-15Rα complex cleaved from presenting cells allows responding cells to internalize, store and use IL-15.IL-15Rα complex for their own proliferation and survival.
Accounting for a mirror-image conformation as a subtle effect in protein folding
Authors: Kachlishvili Khatuna , Maisuradze Gia G. , Martin Osvaldo A. , Liwo Adam , Vila Jorge A. , Scheraga Harold A.
Published: May 2014

Significance

Numerous diseases, including neurodegenerative diseases, are caused by misfolding of proteins; therefore, understanding the mechanism by which a protein folds to its native conformation is one of the most important problems of biophysics. This task becomes more complicated for proteins with a high degree of symmetry that, in addition to the native structure, allows the existence of another, energetically competitive conformation with the native one, a native-like “mirror-image” structure, which has not yet been detected experimentally. By investigating one of the representatives of such symmetrical proteins, reasons for formation of the mirror-image conformation are provided.
Pivotal role for the ubiquitin Y59-E51 loop in lysine 48 polyubiquitination
Authors: Chong Robert A. , Wu Kenneth , Spratt Donald E. , Yang Yingying , Lee Chan , Nayak Jaladhi , Xu Ming , Elkholi Rana , Tappin Inger , Li Jessica , Hurwitz Jerard , Brown Brian D. , Chipuk Jerry Edward , Chen Zhijian J. , Sanchez Roberto , Shaw Gary S. , Huang Lan , Pan Zhen-Qiang
Published: May 2014

Significance

Our identification and characterization of the ubiquitin (Ub) Y59-E51 loop have uncovered a pivotal determinant for lysine 48 (K48) linkage-specific Ub chain synthesis catalyzed by Cdc34 E2 Ub-conjugating enzyme. The Ub Y59-E51 loop appears to anchor a Cdc34 E2-engaging zone, allowing the landing of E2 and enabling it to gain access to the receptor K48. These findings will provide a strong starting point for future biochemical and structural studies aiming to elucidate the detailed interactions between Ub and E2/E3 enzymes that produce the K48 linkage. In addition, the observed global impact of the Ub Y59-E51 loop in cellular K48-polyubiquitination and apoptosis will stimulate investigations for exploring new therapeutic strategies to induce cell killing through pharmacological perturbation of K48-polyubiquitination.
I haven’t spoken to him about it
Authors: Schubert Christoph
Published: May 2014

White House press briefings have the function of providing journalists with first-hand information on present activities of the US-American administration. The Press Secretary, currently Jay Carney, mainly draws on indirect reportative evidentialiy, referring to recent utterances by the President. However, owing to the often critical and persistent inquiries by investigative journalists based on counter-evidentiality, the Press Secretary frequently resorts to evasive manoeuvres. Moreover, he commonly refuses to use logical inferencing in his function as a mouthpiece of the government, since speculations might be potentially harmful when given to the press. Thus, the present paper investigates the possibilities and limitations of evidentiality in this interview genre from a discourse-analytical perspective on the basis of an online archive of transcripts.
The risks of uncertainty
Authors: Ponterotto Diane
Published: May 2014

This paper presents an analysis of the forms and functions that a normal conversational strategy likehedgingcan assume in an institutionalized form of discourse — in this case, the courtroom, and particularly, in a specific juridical text-type: the cross-examination of the victim-witness in a rape trial. The study aims to show principally how the defence attorney of the accused exploits thehedgingstrategies of the female victim-witness in order to discredit her testimony and thereby win the case for the defence. By so doing, the argumentation will make two theoretical points. The first point is disciplinary, in that it will demonstrate the powerful contribution of the language sciences to the identification and unveiling of social injustice. The second point is ideological, in that it will show how some areas of Anglo-American institutions continue to reflect a social tendency towards leniency in the face of violence against women.
Evidential and epistemic strategies in Romanian parliamentary debates
Authors: Constantinescu Mihaela-Viorica
Published: May 2014

The paper presents some evidential and epistemic strategies that appear frequently in old and present-day Romanian parliamentary debates. By evidential and epistemic strategy we mean the manipulation of evidential and epistemic markers, either grammaticalized or pragmatic, in order to achieve various interactional and rhetorical aims. We have in view not only encoded evidential and epistemic meanings, but also (interactional) inferentially conveyed evidential and epistemic meanings. Modality can be manipulated in various ways: the usual ranking of evidentials can be reinterpreted for argumentative means: i.e., hearsay can be sometimes rejected, while, in other cases, it can be presented as more reliable than perceptual evidence.
Identification of interacting proteins for calcium-dependent protein kinase 8 by a novel screening system based on bimolecular fluorescence complementation
Authors: Kamimura Mayu , Han Yulong , Kito Nobuki , Che Fang-Sik
Published: May 2014

Protein kinases are key regulators of cell function that constitute one of the largest and most functionally diverse gene families. We developed a novel assay system, based on the bimolecular fluorescence complementation (BiFC) technique in Escherichia coli, for detecting transient interactions such as those between kinases and their substrates. This system detected the interaction between OsMEK1 and its direct target OsMAP1. By contrast, BiFC fluorescence was not observed when OsMAP2 or OsMAP3, which are not substrates of OsMEK1, were used as prey proteins. We also screened for interacting proteins of calcium-dependent protein kinase 8 (OsCPK8), a regulator of plant immune responses, and identified three proteins as interacting molecules of OsCPK8. The interaction between OsCPK8 and two of these proteins (ARF-GEF and peptidyl prolyl isomerase) was confirmed in rice cells by means of BiFC technology. These results indicate that our new assay system has the potential to screen for protein kinase target molecules.
Phylogenetic relationship of Paenibacillus species based on putative replication origin regions and analysis of an yheCD-like sequence found in this region
Authors: Iiyama Kazuhiro , Otao Masahiro , Mori Kazuki , Mon Hiroaki , Lee Jae Man , Kusakabe Takahiro , Tashiro Kousuke , Asano Shin-Ichiro , Yasunaga-Aoki Chisa
Published: May 2014

To determine the phylogenetic relationship among Paenibacillus species, putative replication origin regions were compared. In the rsmG-gyrA region, gene arrangements in Paenibacillus species were identical to those of Bacillus species, with the exception of an open reading frame (orf14) positioned between gyrB and gyrA, which was observed only in Paenibacillus species. The orf14 product was homologous to the endospore-associated proteins YheC and YheD of Bacillus subtilis. Phylogenetic analysis based on the YheCD proteins suggested that Orf14 could be categorized into the YheC group. In the Paenibacillus genome, DnaA box clusters were found in rpmH-dnaA and dnaA-dnaN intergenic regions, known as box regions C and R, respectively; this localization was similar to that observed in B. halodurans. A phylogenetic tree based on the nucleotide sequences of the whole replication origin regions suggested that P. popilliae, P. thiaminolyticus, and P. dendritiformis are closely related species.
Thiol modification by bioactivated polyphenols and its potential role in skin inflammation
Authors: Nakamura Yoshimasa , Ishii Takeshi , Abe Naomi , Murata Yoshiyuki
Published: May 2014

In the present study, we evaluated the modifying behavior of simple phenolic compounds on the sulfhydryl groups of glutathione and proteins. The catechol-type polyphenols, including protocatechuic acid, but neither the monophenols nor O-methylated catechol, can modify the sulfhydryl groups in a phenol oxidase-dependent manner. The possible involvement of polyphenol bioactivation in the enhancement of skin inflammation was also suggested.
Ascorbic acid deficiency decreases hepatic cytochrome P-450, especially CYP2B1/2B2, and simultaneously induces heme oxygenase-1 gene expression in scurvy-prone ODS rats
Authors: Kobayashi Misato , Hoshinaga Yukiko , Miura Natsuko , Tokuda Yuki , Shigeoka Shigeru , Murai Atsushi , Horio Fumihiko
Published: May 2014

The mechanisms underlying the decrease in hepatic cytochrome P-450 (CYP) content in ascorbic acid deficiency was investigated in scurvy-prone ODS rats. First, male ODS rats were fed a diet containing sufficient ascorbic acid (control) or a diet without ascorbic acid (deficient) for 18 days, with or without the intraperitoneal injection of phenobarbital. Ascorbic acid deficiency decreased hepatic microsomal total CYP content, CYP2B1/2B2 protein, and mitochondrial cytochrome oxidase (COX) complex IV subunit I protein, and simultaneously increased heme oxygenase-1 protein in microsomes and mitochondria. Next, heme oxygenase-1 inducers, that is lipopolysaccharide and hemin, were administered to phenobaribital-treated ODS rats fed sufficient ascorbic acid. The administration of these inducers decreased hepatic microsomal total CYP content, CYP2B1/2B2 protein, and mitochondrial COX complex IV subunit I protein. These results suggested that the stimulation of hepatic heme oxygenase-1 expression by ascorbic acid deficiency caused the decrease in CYP content in liver.