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James Lim, David J Ing, Joachim Rosskopf, Jan Jeske, Jared H Cole, Susana F Huelga, Martin B Plenio
We investigate how correlated fluctuations affect oscillatory features in rephasing and non-rephasing two-dimensional (2D) electronic spectra of a model dimer system. Based on a beating map analysis, we show that non-secular environmental couplings induced by uncorrelated fluctuations lead to oscillations centered at both cross- and diagonal-peaks in rephasing spectra as well as in non-rephasing spectra. Using an analytical approach, we provide a quantitative description of the non-secular effects in terms of the Feynman diagrams and show that the environment-induced mixing of different inter-excitonic coherences leads to oscillations in the rephasing diagonal-peaks and non-rephasing cross-peaks...
January 14, 2017: Journal of Chemical Physics
Milan K Hazra, Biman Bagchi
Valuable dynamical and structural information about neat liquid DMSO at ambient conditions can be obtained through a study of low frequency vibrations in the far infrared (FIR), that is, terahertz regime. For DMSO, collective excitations as well as single molecule stretches and bends have been measured by different kinds of experiments such as OHD-RIKES and terahertz spectroscopy. In the present work, we investigate the intermolecular vibrational spectrum of DMSO through three different computational techniques namely (i) the far-infrared spectrum obtained through the Fourier transform of total dipole moment auto-time correlation function, (ii) from the Fourier transform of the translational and angular velocity time autocorrelation functions, and (iii) a quenched normal mode analysis of the parent liquid at 300 K...
January 14, 2017: Journal of Chemical Physics
Jin-Jin Ding, Yao Wang, Hou-Dao Zhang, Rui-Xue Xu, Xiao Zheng, YiJing Yan
We revisit Caldeira-Leggett's quantum master equation representing mixed quantum-classical theory, but with limited applications. Proposed is a Fokker-Planck quantum master equation theory, with a generic bi-exponential correlation function description on semiclassical Brownian oscillators' environments. The new theory has caustic terms that bridge between the quantum description on primary systems and the semiclassical or quasi-classical description on environments. Various parametrization schemes, both analytical and numerical, for the generic bi-exponential environment bath correlation functions are proposed and scrutinized...
January 14, 2017: Journal of Chemical Physics
Hiroshi Yoke, Chikako Shingyoji
Oscillatory bending movement of eukaryotic flagella is powered by orchestrated activity of dynein motor proteins that hydrolyze ATP and produce microtubule sliding. Although the ATP concentration within a flagellum is kept uniform at a few mmol l(-1) level, sliding activities of dyneins are dynamically coordinated along the flagellum in accordance with the phase of bending waves. Thus, at the organellar level the dynein not only generates force for bending but also modulates its motile activity by responding to bending of the flagellum...
January 13, 2017: Journal of Experimental Biology
John Kealy, Sean Commins, John P Lowry
Non-competitive NMDA receptor antagonists are known to induce psychosis-like symptoms in rodents. Administration of such compounds cause behavioural effects such as memory impairment and hyperlocomotion. Additionally, drugs such as phencyclidine (PCP), ketamine and MK-801 all cause distinctive increases in striatal local field potential (LFP) in the high frequency oscillation (HFO) band in the power spectrum (140-180 Hz). Amperometric sensors provide a means to measure tissue oxygen (tO2; a BOLD-like signal) in the brains of freely-moving rats while simultaneously acquiring LFP using the same electrode...
January 10, 2017: Neuropharmacology
David Druzd, Olga Matveeva, Louise Ince, Ute Harrison, Wenyan He, Christoph Schmal, Hanspeter Herzel, Anthony H Tsang, Naoto Kawakami, Alexei Leliavski, Olaf Uhl, Ling Yao, Leif Erik Sander, Chien-Sin Chen, Kerstin Kraus, Alba de Juan, Sophia Martina Hergenhan, Marc Ehlers, Berthold Koletzko, Rainer Haas, Werner Solbach, Henrik Oster, Christoph Scheiermann
Lymphocytes circulate through lymph nodes (LN) in search for antigen in what is believed to be a continuous process. Here, we show that lymphocyte migration through lymph nodes and lymph occurred in a non-continuous, circadian manner. Lymphocyte homing to lymph nodes peaked at night onset, with cells leaving the tissue during the day. This resulted in strong oscillations in lymphocyte cellularity in lymph nodes and efferent lymphatic fluid. Using lineage-specific genetic ablation of circadian clock function, we demonstrated this to be dependent on rhythmic expression of promigratory factors on lymphocytes...
January 6, 2017: Immunity
Kathrin J Mohler, Bernhard J Bohn, Ming Yan, Gwénaëlle Mélen, Theodor W Hänsch, Nathalie Picqué
We extend the technique of multiplex coherent Raman spectroscopy with two femtosecond mode-locked lasers to oscillators of a pulse repetition frequency of 1 GHz. We demonstrate a spectra of liquids, which span 1100  cm<sup>-1</sup> of Raman shifts. At a resolution of 6  cm<sup>-1</sup>, their measurement time may be as short as 5 μs for a refresh rate of 2 kHz. The waiting period between acquisitions is improved 10-fold compared to previous experiments with two lasers of 100-MHz repetition frequencies...
January 15, 2017: Optics Letters
Émeric Mercier, Lionel Weicker, Delphine Wolfersberger, Deborah M Kane, Marc Sciamanna
We experimentally report the sequence of bifurcations destabilizing and restabilizing a laser diode with phase-conjugate feedback when the feedback rate is increased. Specifically, we successively observe the initial steady state, undamped relaxation oscillations, quasi-periodicity, chaos, and oscillating solutions at harmonics up to 13 times the external cavity frequency but also the restabilization to a steady state. The experimental results are qualitatively well reproduced by a model that accounts for the time the light takes to penetrate the phase-conjugate mirror...
January 15, 2017: Optics Letters
Chun-Ting Lin, Shou-Chih Chiang, Che-Hao Li, Hou-Tzu Huang, Chi-Hsiang Lin, Bo-Jiun Lin
This Letter presents a V-band gapless orthogonal frequency division multiplexing (OFDM) RoF system at 60 GHz employing a power detector to support vector signal down-conversion. Additional RF tone is generated and transmitted from a central station to replace the local oscillator at a wireless receiver for power detector down-conversion. To enhance the spectrum efficiency, the gap between the OFDM signal and the RF tone is not needed. However, the down-converted signal will suffer signal-to-signal interference (SSBI)...
January 15, 2017: Optics Letters
Miguel Angel Fernández-González, Daniel Rivero, Cristina García-Iriepa, Diego Sampedro, Luis Manuel Frutos
Control of absorption spectra in chromophores is a fundamental aspect of many photochemical and photophysical processes as it constitutes the first step of the global photoinduced process. Here we explore the use of mechanical forces to modulate the light absorption process. Specifically, we develop a computational formalism for determining the type of mechanical forces permitting a global tuning of the absorption spectrum. This control extends to the excitation wavelength, absorption bands overlap and oscillator strength...
January 12, 2017: Journal of Chemical Theory and Computation
Jeremy B Clark, Florent Lecocq, Raymond W Simmonds, José Aumentado, John D Teufel
Quantum fluctuations of the electromagnetic vacuum produce measurable physical effects such as Casimir forces and the Lamb shift. They also impose an observable limit-known as the quantum backaction limit-on the lowest temperatures that can be reached using conventional laser cooling techniques. As laser cooling experiments continue to bring massive mechanical systems to unprecedentedly low temperatures, this seemingly fundamental limit is increasingly important in the laboratory. Fortunately, vacuum fluctuations are not immutable and can be 'squeezed', reducing amplitude fluctuations at the expense of phase fluctuations...
January 11, 2017: Nature
Matthew Andrew, Julia M Yeomans, Dmitri O Pushkin
We introduce a solvable Lagrangian model for droplet bouncing. The model predicts that, for an axisymmetric drop, the contact time decreases to a constant value with increasing Weber number, in qualitative agreement with experiments, because the system is well approximated as a simple harmonic oscillator. We introduce asymmetries in the velocity, initial droplet shape, and contact line drag acting on the droplet and show that asymmetry can often lead to a reduced contact time and lift-off in an elongated shape...
January 12, 2017: Soft Matter
Freek van Ede, Marcel Niklaus, Anna C Nobre
: Although working memory is generally considered a highly dynamic mnemonic store, popular laboratory tasks used to understand its psychological and neural mechanisms (such as change detection and continuous reproduction) often remain relatively "static," involving the retention of a set number of items throughout a shared delay interval. In the current study, we investigated visual working memory in a more dynamic setting, and assessed the following: (1) whether internally guided temporal expectations can dynamically and reversibly prioritize individual mnemonic items at specific times at which they are deemed most relevant; and (2) the neural substrates that support such dynamic prioritization...
January 11, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
Jonathan Daume, Thomas Gruber, Andreas K Engel, Uwe Friese
: It has been suggested that cross-frequency phase-amplitude coupling (PAC), particularly in temporal brain structures, serves as a neural mechanism for coordinated working memory storage. In this magnetoencephalography study, we show that during visual working memory maintenance, temporal cortex regions, which exhibit enhanced PAC, interact with prefrontal cortex via enhanced low-frequency phase synchronization. Healthy human participants were engaged in a visual delayed match-to-sample task with pictures of natural objects...
January 11, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
Theresa Wildegger, Freek van Ede, Mark W Woolrich, Celine R Gillebert, Anna Christina Nobre
Preparatory modulations of cortical alpha-band oscillations are a reliable index of the voluntary allocation of covert spatial attention. It is currently unclear whether attentional cues containing information about a target's identity (such as its visual orientation), in addition to its location, might additionally shape preparatory alpha modulations. Here, we explore this question by directly comparing spatial and feature-based attention in the same visual detection task while recording brain activity using magneto-encephalography (MEG)...
January 11, 2017: Journal of Neurophysiology
Romain Gibeaux, Antonio Z Politi, Peter Philippsen, François Nédélec
Multinucleated cells are important in many organisms but the mechanisms governing the movements of nuclei sharing a common cytoplasm are not understood. In the hyphae of the plant pathogenic fungus Ashbya gossypii, nuclei move back and forth, occasionally bypassing each other, and, preventing the formation of nuclear clusters, this is essential for genetic stability. These movements depend on cytoplasmic microtubules emanating from the nuclei, that are pulled by dynein motors anchored at the cortex. Using 3D stochastic simulations with parameters constrained by the literature, we predict the cortical anchors density from the characteristics of nuclear movements...
January 11, 2017: Molecular Biology of the Cell
Mallory A Ballinger, Christine Schwartz, Matthew T Andrews
During hibernation, thirteen-lined ground squirrels (Ictidomys tridecemlineatus) regularly cycle between bouts of torpor and interbout arousal (IBA).  Most of the brain is electrically quiescent during torpor, but regains activity quickly upon arousal to IBA resulting in extreme oscillations in energy demand during hibernation.  We predicted increased functional capacity of brain mitochondria during hibernation compared to spring to accommodate the variable energy demands of hibernation.  To address this hypothesis, we examined mitochondrial bioenergetics in the ground squirrel brain across three time points: spring (SP), torpor (TOR), and IBA...
January 11, 2017: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
Shujuan Geng, Weidong Zhou
We analyze the neurodynamics attributed by a model proposed by Wendling and co-workers (2002) [Wendling, F., Bartolomei, F., Bellanger, J.J. & Chauvel, P. (2002) Epileptic fast activity can be explained by a model of impaired GABAergic dendritic inhibition. Eur. J. Neurosci., 15, 1499.] to explain several different types of electroencephalographic activities. We could find three principal types of steady states when the system parameters change slowly: (i) the model produce a constant output when it is under a state of stable equilibrium point with a constant input...
January 11, 2017: Journal of Integrative Neuroscience
Sreerama Chaitanya Sridhara, Sílvia Carvalho, Ana Rita Grosso, Lina Marcela Gallego-Paez, Maria Carmo-Fonseca, Sérgio Fernandes de Almeida
Genomic instability is frequently caused by nucleic acid structures termed R-loops that are formed during transcription. Despite their harmful potential, mechanisms that sense, signal, and suppress these structures remain elusive. Here, we report that oscillations in transcription dynamics are a major sensor of R-loops. We show that pausing of RNA polymerase II (RNA Pol II) initiates a signaling cascade whereby the serine/arginine protein kinase 2 (SRPK2) phosphorylates the DDX23 helicase, culminating in the suppression of R-loops...
January 10, 2017: Cell Reports
Giovanna Mollo, Piers L Cornelissen, Rebecca E Millman, Andrew W Ellis, Elizabeth Jefferies
The "hub and spoke model" of semantic representation suggests that the multimodal features of objects are drawn together by an anterior temporal lobe (ATL) "hub", while modality-specific "spokes" capture perceptual/action features. However, relatively little is known about how these components are recruited through time to support object identification. We used magnetoencephalography to measure neural oscillations within left ATL, lateral fusiform cortex (FC) and central sulcus (CS) during word-picture matching at different levels of specificity (employing superordinate vs...
2017: PloS One
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