cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Anderson Acceleration for Nonsmooth Fixed Point Problems
Creators: name: Bian, Wei
name: Chen, Xiaojun
Publisher: name: arXiv
Year: 2022
Subjects: subject: Optimization and Control (math.OC)
subject: FOS: Mathematics
subject: F.2.2; G.1.6
subject: 65H10, 68W25

description: We give new convergence results of Anderson acceleration for the composite $\max$ fixed point problem. We prove that Anderson(1) and EDIIS(1) are q-linear convergent with a smaller q-factor than existing q-factors. Moreover, we propose a smoothing approximation of the composite max function in the contractive fixed point problem. We show that the smoothing approximation is a contraction mapping with the same fixed point as the composite $\max$ fixed point problem. Our results rigorously confirm that the nonsmoothness does not affect the convergence rate of Anderson acceleration method when we use the proposed smoothing approximation for the composite $\max$ fixed point problem. Numerical results for constrained minimax problems, complementarity problems and nonsmooth differential equations are presented to show the efficiency and good performance of the proposed Anderson acceleration method with smoothing approximation.
The NIKA 2012-2014 observing campaigns: control of systematic effects and results
Creators: name: Catalano, A.
name: Adam, R.
name: Adane, A.
name: Ade, P.
name: André, P.
name: Beelen, A.
name: Belier, B.
name: Benôit, A.
name: Bideaud, A.
name: Billot, N.
name: Boudou, N.
name: Bourrion, O.
name: Calvo, M.
name: Coiffard, G.
name: Comis, B.
name: D'Addabbo, A.
name: Désert, F. -X.
name: Doyle, S.
name: Goupy, J.
name: Kramer, C.
name: Leclercq, S.
name: Macías-Pérez, J. F.
name: Martino, J.
name: Mauskopf, P.
name: Mayet, F.
name: Monfardini, A.
name: Pajot, F.
name: Pascale, E.
name: Perotto, L.
name: Ponthieu, E. Pointecouteau N.
name: Revéret, V.
name: Ritacco, A.
name: Rodriguez, L.
name: Savini, G.
name: Schuster, K.
name: Sievers, A.
name: Tucker, C.
name: Zylka, R.
Publisher: name: arXiv
Year: 2014
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: The New IRAM KID Array (NIKA) is a dual-band camera operating with frequency multiplexed arrays of Lumped Element Kinetic Inductance Detectors (LEKIDs) cooled to 100 mK. NIKA is designed to observe the intensity and polarisation of the sky at 1.25 and 2.14 mm from the IRAM 30 m telescope. We present the improvements on the control of systematic effects and astrophysical results made during the last observation campaigns between 2012 and 2014.
description: 11 pages, 17 figures, SPIE conference proceeding
Morphodynamics of Active Nematic Fluid Surfaces
Creators: name: Al-Izzi, Sami C.
name: Morris, Richard G.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Biological Physics (physics.bio-ph)
subject: FOS: Physical sciences

description: Morphodynamic equations governing the behaviour of active nematic fluids on deformable curved surfaces are constructed in the large deformation limit. Emphasis is placed on the formulation of objective rates that account for normal deformations whilst ensuring that tangential flows are Eulerian, and the use of the surface derivative (rather than the covariant derivative) in the nematic free energy, which elastically couples local order to out-of-plane bending of the surface. Focusing on surface geometry and its dynamical interplay with the hydrodynamics, several illustrative instabilities are then characterised. These include cases where the role of the Scriven-Love number and its nematic analogue are non-negligible, and where the active nematic forcing can be characterised by an analogue of the Föppl-von-Kármán number. For the former, flows and changes to the nematic texture are coupled to surface geometry by viscous dissipation. This is shown to result in non-trivial relaxation dynamics for a nematic tube. For the latter, the nematic active forcing couples to the surface bending terms of the nematic free energy, resulting in extensile (active ruffling) and contractile (active pearling) instabilities in the tube shape, as well as active bend instabilities in the nematic texture. In comparison to the flat case, such bend instabilities now have a threshold set by the extrinsic curvature of the tube. Finally, we examine a topological defect located on an almost flat surface and show that there exists a steady state where a combination of defect elasticity, activity and non-negligible spin-connection drive a shape change in the surface.
description: 27 pages, 7 figures (Accepted version)
Modulation of integrin antagonist signaling by ligand binding of the heparin-binding domain of vitronectin to the αVβ3 integrin
Creators: name: Clemmons, David R.
name: Maile, Laura A.
name: Veluvolu, Umadevi
name: Sanghani, Ravi
name: Aday, Ariel W.
name: Busby, Walker H.
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2008

description: The interaction between the arginine glycine and aspartic acid motif (RGD) of integrin ligands such as vitronectin and the integrin receptor αVβ3 in mediating cell attachment has been well described. Similarly, the ability of disintegrins, small RGD containing peptides, to inhibit cell attachment and other cellular processes has also been studied extensively. Recently, we characterized a second site of interaction between vitronectin and its integrin partner. We determined that amino acids within the heparin binding domain of vitronectin bind to a cysteine loop (C-loop) region of β3 and that this interaction is required for the positive effects of αVβ3 ligand occupancy on IGF-I signaling in smooth muscle cells. In this study we examine the signaling events activated following ligand binding of disintegrins to the αVβ3 and the ability of these signals to be regulated by binding of the heparin binding domain of vitronectin. We demonstrate that disintegrin ligand binding activates a series of events including the sequential activation of the tyrosine kinases c-Src and Syk. This leads to the activation of calpain and the cleavage of the β3 cytoplasmic tail. Addition of vitronectin or a peptide homologous to the heparin binding domain inhibited activation of this pathway.
Electron Spin Relaxation in Two Polymorphic Structures of GaN
Creators: name: Kang, Nam Lyong
Publisher: name: arXiv
Year: 2014
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: The relaxation process of electron spin in systems of electrons interacting with piezoelectric deformation phonons that are mediated through spin-orbit interactions was interpreted from a microscopic point of view using the formula for the electron spin relaxation times derived by a projection-reduction method. The electron spin relaxation times in two polymorphic structures of GaN were calculated. The piezoelectric material constant for the wurtzite structure obtained by a comparison with a previously reported experimental result was P_pe=1.5 x 10^29 eV/m. The temperature and magnetic field dependence of the relaxation times for both wurtzite and zinc-blende structures were similar, but the relaxation times in zinc-blende GaN were smaller and decreased more rapidly with increasing temperature and magnetic field than that in wurtzite GaN. This study also showed that the electron spin relaxation for wurtzite GaN at low density could be explained by the Elliot-Yafet process but not for zinc-blende GaN in the metallic regime.
Indomethacin promotes adipogenesis of mesenchymal stem cells through a cyclooxygenase independent mechanism
Creators: name: Case, Natasha
name: Styner, Maya
name: Rubin, Janet
name: Sen, Buer
name: Xie, Zhihui
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2010

description: Regulation of mesenchymal stem cell (MSC) lineage selection is important for the generation of bone mass. Inhibition of cyclooxygenase-2 (COX2) may increase adipogenesis at the cost of decreasing osteoprogenitor output. Here we investigated the role of COX2 and its products during MSC differentiation. Indomethacin stimulated adipogenesis (increased aP2, adiponectin and lipid droplets) of CH310T1/2 stem cells as well as marrow-derived MSCs to a degree similar to the PPARγ2 ligand, rosiglitazone. Unlike rosiglitazone, indomethacin significantly upregulated PPARγ2 expression. Indomethacin and the COX2 specific inhibitor celecoxib suppressed PGE2 production, but celecoxib did not induce adipogenesis. As well, addition of PGE2 failed to reverse indomethacin induced adipogenesis, indicating that indomethacin’s effects were prostaglandin independent. In MSCs over-expressing PPARγ2 and RXRα, indomethacin did not increase PPAR-induced transcription, while rosiglitazone and 15d-PGJ2 did (1.7- and 1.3-fold, respectively, P < 0.001). We considered whether indomethacin might directly affect C/EBPβ proximally to PPARγ2 induction. Indomethacin significantly increased C/EBPβ expression and protein within 24 h of addition. These results indicate that indomethacin promotes adipogenesis by increasing C/EBPβ and PPARγ2 expression in a prostaglandin-independent fashion. This effect of indomethacin is pertinent to potential deleterious effects of this commonly used anti-inflammatory drug on bone remodeling and tissue healing.
A fast tree-based method for estimating column densities in Adaptive Mesh Refinement codes Influence of UV radiation field on the structure of molecular clouds
Creators: name: Valdivia, Valeska
name: Hennebelle, Patrick
Publisher: name: arXiv
Year: 2014
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: Context. Ultraviolet radiation plays a crucial role in molecular clouds. Radiation and matter are tightly coupled and their interplay influences the physical and chemical properties of gas. In particular, modeling the radiation propagation requires calculating column densities, which can be numerically expensive in high-resolution multidimensional simulations. Aims. Developing fast methods for estimating column densities is mandatory if we are interested in the dynamical influence of the radiative transfer. In particular, we focus on the effect of the UV screening on the dynamics and on the statistical properties of molecular clouds. Methods. We have developed a tree-based method for a fast estimate of column densities, implemented in the adaptive mesh refinement code RAMSES. We performed numerical simulations using this method in order to analyze the influence of the screening on the clump formation. Results. We find that the accuracy for the extinction of the tree-based method is better than 10%, while the relative error for the column density can be much more. We describe the implementation of a method based on precalculating the geometrical terms that noticeably reduces the calculation time. To study the influence of the screening on the statistical properties of molecular clouds we present the probability distribution function (PDF) of gas and the associated temperature per density bin and the mass spectra for different density thresholds. Conclusions. The tree-based method is fast and accurate enough to be used during numerical simulations since no communication is needed between CPUs when using a fully threaded tree. It is then suitable to parallel computing. We show that the screening for far UV radiation mainly affects the dense gas, thereby favoring low temperatures and affecting the fragmentation.
description: 14 pages, 20 figures
D6.2 – Framework for a European network of agroecological LLs and RIs
Creators: name: Wigboldus, Seerp
name: Hassink, Jan
name: Goris, Margriet
name: Dawson, Andrew
Publisher: name: Zenodo
Year: 2024

description: From early 2022, AE4EU partners embarked on a journey to create a European network in which many agroecology-related networks and associations were invited to participate in co-creating a common purpose and approach to help accelerate agroecological transformations in agriculture and the wider food systems. The journey began by first clarifying the purpose and scope of the network in order for it to be something that would originate from, and cater to, the needs of agroecological grassroots and farmer (representative) groups, and networks where the energy and motivation for leading agroecological transformation is strongest although their potential is not always harnessed as innovations and networks are fragmented. In becoming more connected to other major processes related to agroecological transitions in Europe (such as the current EU partnership on agroecology), their contribution and capacity to accelerate agroecological transformations in Europe will be strengthened. To this end, a process of developing a European agroecology network of networks (NofN) was started.
Upgrade of the ALICE experiment beyond LHC Run 3
Creators: name: Colella, Domenico
name: Collaboration, for the ALICE
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Experiment (hep-ex)
subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences

description: The ALICE Collaboration completed the upgrade of the detector and is now commissioning for the beginning of the data taking during LHC Run 3. In parallel, R&D activities and simulation studies are being performed to define the future of the experiment beyond LHC Run 3. Two detector upgrades are foreseen for the next long shutdown (LS3). The first is the replacement of the three layers of the inner tracking system closest to the beam with a novel vertex detector consisting of curved wafer-scale ultra-thin silicon sensors arranged in perfectly cylindrical layers to improve impact parameter resolution and significantly extend the physics capability for the study of the heavy-flavor production and the low-mass dielectrons. The second upgrade for the LS3 is the addition of a Forward Calorimeter detector at large rapidity consisting of a Si-W electromagnetic calorimeter with pad and pixel readout, that will equip the experiment with unique capabilities to measure small-x gluon distributions via prompt photon production. A proposal of a next-generation heavy-ion experiment for LHC Run 5 is also in preparation and will be discussed. The aim is to perform novel measurements of the electromagnetic and hadronic probes of the QGP, such as the production of multiply-charmed baryons, which have so far been inaccessible, both because of detector performance and luminosity. The concept of the new apparatus foresees an extensive usage of thin silicon sensors for tracking and a modern particle identification system, combining a silicon-based time of flight detector, a RICH detector, an electromagnetic calorimeter and a muon system.
description: 13 pages, 11 figures, 10th International Conference on New Frontiers in Physics (ICNFP 2021), 23 August - 2 September, Kolymbari, Crete, Greece
A spectral element solution of the 2D linearized potential flow radiation problem
Creators: name: Visbech, Jens
name: Engsig-Karup, Allan P.
name: Bingham, Harry B.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Numerical Analysis (math.NA)
subject: Computational Physics (physics.comp-ph)
subject: FOS: Mathematics
subject: FOS: Physical sciences

description: We present a scalable 2D Galerkin spectral element method solution to the linearized potential flow radiation problem for wave induced forcing of a floating offshore structure. The pseudo-impulsive formulation of the problem is solved in the time-domain using a Gaussian displacement signal tailored to the discrete resolution. The added mass and damping coefficients are then obtained via Fourier transformation. The spectral element method is used to discretize the spatial fluid domain, whereas the classical explicit 4-stage 4th order Runge-Kutta scheme is employed for the temporal integration. Spectral convergence of the proposed model is established for both affine and curvilinear elements, and the computational effort is shown to scale with $\mathcal{O}(N^p)$, with $N$ begin the total number of grid points and $p \approx 1$. Temporal stability properties, caused by the spatial resolution, are considered to ensure a stable model. The solver is used to compute the hydrodynamic coefficients for several floating bodies and compare against known public benchmark results. The results are showing excellent agreement, ultimately validating the solver and emphasizing the geometrical flexibility and high accuracy and efficiency of the proposed solver strategy. Lastly, an extensive investigation of non-resolved energy from the pseudo-impulse is carried out to characterise the induced spurious oscillations of the free surface quantities leading to a verification of a proposal on how to efficiently and accurately calculate added mass and damping coefficients in pseudo-impulsive solvers.
Cyclin E in centrosome duplication and reduplication in sea urchin zygotes
Creators: name: Sluder, Greenfield
name: Marzluff, William F.
name: Schnackenberg, Bradley J.
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2008

description: When protein synthesis is completely blocked from before fertilization, the sea urchin zygote arrests in first S phase and the paternal centrosome reduplicates multiple times. However, when protein synthesis is blocked starting in prophase of first mitosis, the zygote divides and the blastomeres arrest in a G1-like state. The centrosome inherited from this mitosis duplicates only once in each blastomere for reasons that are not understood. The late G1 rise in cyclin E/cdk2 kinase activity initiates centrosome duplication in mammalian cells and its activity is needed for centrosome duplication in Xenopus egg extracts. Since the half-time for cyclin E turnover is normally ~1 hour in sea urchin zygotes, the different behaviors of centrosomes during G1 and S phase arrests could be due to differential losses of cyclin E and its associated kinase activities at these two arrest points. To better understand the mechanisms that limit centrosome duplication, we characterize the levels of cyclin E and its associated kinase activity at the S phase and G1 arrest points. We first demonstrate that cyclin E/cdk2 kinase activity is required for centrosome duplication and reduplication in sea urchin zygotes. Next we find that cyclin E levels and cyclin E/cdk2 kinase activities are both constitutively and equivalently elevated during both the S phase and G1 arrests. This indicates that centrosome duplication during the G1 arrest is limited by a block to reduplication under conditions permissive for duplication. The cytoplasmic conditions of S phase, however, abrogate this block to reduplication.
Partially Observable Markov Decision Processes in Robotics: A Survey
Creators: name: Lauri, Mikko
name: Hsu, David
name: Pajarinen, Joni
Publisher: name: arXiv
Year: 2022
Subjects: subject: Robotics (cs.RO)
subject: Artificial Intelligence (cs.AI)
subject: Systems and Control (eess.SY)
subject: FOS: Computer and information sciences
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: Noisy sensing, imperfect control, and environment changes are defining characteristics of many real-world robot tasks. The partially observable Markov decision process (POMDP) provides a principled mathematical framework for modeling and solving robot decision and control tasks under uncertainty. Over the last decade, it has seen many successful applications, spanning localization and navigation, search and tracking, autonomous driving, multi-robot systems, manipulation, and human-robot interaction. This survey aims to bridge the gap between the development of POMDP models and algorithms at one end and application to diverse robot decision tasks at the other. It analyzes the characteristics of these tasks and connects them with the mathematical and algorithmic properties of the POMDP framework for effective modeling and solution. For practitioners, the survey provides some of the key task characteristics in deciding when and how to apply POMDPs to robot tasks successfully. For POMDP algorithm designers, the survey provides new insights into the unique challenges of applying POMDPs to robot systems and points to promising new directions for further research.
description: 20 pages, 10 figures. Author version of paper. Accepted for publication in IEEE Transactions on Robotics
The subnuclear organization of histone gene regulatory proteins and 3′ end processing factors of normal somatic and embryonic stem cells is compromised in selected human cancer cell types
Creators: name: Lian, Jane B.
name: Ghule, Prachi N.
name: Stein, Janet L.
name: Stein, Gary S.
name: van Wijnen, Andre J.
name: Dominski, Zbigniew
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2009

description: Human histone gene expression is controlled at the level of transcription initiation and subsequent 3′end processing to generate non-polyadenylated stem-loop containing histone mRNAs. Transcription is controlled at the G1/S phase transition by the Cyclin E/CDK2 mediated induction of p220NPAT/HiNF-P complexes at subnuclear domains designated Histone Locus Bodies (HLBs) that associate with histone gene clusters. Histone mRNA maturation is mediated by Lsm10 containing U7snRNP complexes. In normal human somatic and embryonic stem cells, the 6p histone locus, the transcription marker p220NPAT and the 3′end processing marker Lsm10 (but not the Cajal Body marker coilin) co-localize, reflecting the assembly of an integrated factory for histone gene expression. Using in situ immuno-fluorescence microscopy and fluorescence in situ hybridization (FISH), we show that this subnuclear organization is compromised in some cancer cell lines. In aneuploid cells, the presence of Histone Locus Bodies correlates with the number of histone gene loci. More importantly, the in situ co-localization of p220NPAT and Lsm10 is disrupted in HeLa S3 cervical carcinoma cells and MCF7 breast adenocarcinoma cells, with most Lsm10 residing in Cajal Bodies. The finding that the subnuclear integration of transcriptional initiation and 3′end processing of histone gene transcripts is deregulated may be causally linked to tumor-related modifications in molecular pathways controlling histone gene expression during the cell cycle.
Study of maximum electron energy of sub-PeV pulsar wind nebulae by multiwavelength modelling
Creators: name: Joshi, Jagdish C.
name: Tanaka, Shuta J.
name: Miranda, Luis Salvador
name: Razzaque, Soebur
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: Recently, the Large High Altitude Air Shower Observatory (LHAASO) reported the discovery of 12 ultrahigh-energy (UHE; $\mathrm{\varepsilon} \ge 100$ TeV) gamma-ray sources located in the Galactic plane. A few of these UHE gamma-ray emitting regions are in spatial coincidence with pulsar wind nebulae (PWNe). We consider a sample of five sources; two of them are LHAASO sources (LHAASO J1908+0621 and LHAASO J2226+6057) and the remaining three are GeV-TeV gamma-ray emitters. In addition, X-rays, radio observations, or upper limits are also available for these objects. We study multiwavelength radiation from these sources by considering a PWN origin, where the emission is powered by the spin-down luminosity of the associated pulsars. In this leptonic emission model, the electron population is calculated at different times under the radiative (synchrotron and inverse-Compton) and adiabatic cooling. We also include the onset of the reverberation phase for the PWN, by assuming radially symmetric expansion. However, in this work, we find that multiwavelength emission can be interpreted before the onset of this phase. The maximum energy of the electrons based on the spectral fit is found to be above 0.1 PeV and close to 1 PeV. For LHAASO J2226+6057, using its observations in radio to UHE gamma-rays, we find that UHE gamma-rays can be interpreted using electrons with maximum energy of 1 PeV. We estimate the upper limits on the minimum Lorentz factor of the electrons and it also infers the minimum value of the pair-multiplicity of charged pairs.
description: 13 pages, 11 figures, Revised version, Accepted for publication in MNRAS, Comments welcome
Optical readout of singlet fission biexcitons with photoluminescence detected magnetic resonance
Creators: name: Joshi, Gajadhar
name: Dill, Ryan D.
name: Thorley, Karl J.
name: Anthony, John E.
name: Reid, Obadiah G.
name: Johnson, Justin C.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Molecular spin systems based on photoexcited triplet pairs formed via singlet fission (SF) are attractive as carriers of quantum information because of their potentially pure and controllable spin polarization, but developing systems that offer optical routes to readout as well as initialization is challenging. Herein, we characterize the electron spin magnetic resonance change in photoluminescence intensity for a tailored organic molecular crystal while sweeping a microwave drive up to 10 GHz in a broadband loop structure. We observe resonant transitions for both triplet and quintet spin sublevel populations showing their optical sensitivity, and revealing zero-field parameters for each. We map the evolution of these spectra in both microwave frequency and magnetic field, producing a pattern of optically-detected magnetic resonance (ODMR) peaks. Fits to this data using a suitable model suggest significant spin polarization in this system with orientation selectivity. Unusual excitation intensity dependence is also observed, which inverts the sign of the ODMR signal for triplet features, but not for quintet. These observations demonstrate optical detection of the spin sublevel population dictated by SF and intermolecular geometry, and provide unique insight into the dynamics of triplet pairs.
description: The following article has been submitted to 'The Journal of Chemical Physics. After it is published, it will be found at this Link
Component on shell actions of supersymmetric 3-brane I. 3-brane in D=6
Creators: name: Bellucci, S.
name: Kozyrev, N.
name: Krivonos, S.
name: Sutulin, A.
Publisher: name: arXiv
Year: 2014
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: In the present and accompanying papers we explicitly construct the on-shell supersymmetric component actions for 3-branes moving in D=6 and in D=8 within the nonlinear realizations framework. In the first paper we apply our schema to construct the action of supersymmetric 3-brane in D=6. It turns out that all ingredients entering the component action can be obtained almost algorithmically by using the nonlinear realizations approach. Within this approach, properly adapted to the construction of on-shell component actions, we pay much attention to broken supersymmetry. Doing so, we were able to write the action in terms of purely geometric objects (vielbeins and covariant derivatives of the physical bosonic components), covariant with respect to broken supersymmetry. It turns out that all terms of the higher orders in the fermions, are hidden inside these covariant derivatives and vielbeins. Moreover, the main part of the component action just mimics its bosonic cousin in which the ordinary space-time derivatives and the bosonic world volume are replaced by their covariant supersymmetric analogs. The Wess-Zumino term in the action, which does not exist in the bosonic case, can be also easily constructed in terms of reduced Cartan forms. Keeping the broken supersymmetry almost explicit, one may write the Ansatz for the component action, fully defined up to two constant parameters. The role of the unbroken supersymmetry is just to fix these parameters.
description: 14 pages, no figures, PACS: 11.30.Pb, 12.60.Jv, 11.25.-w
Two-temperature activity induces liquid-crystal phases inaccessible in equilibrium
Creators: name: Chattopadhyay, Jayeeta
name: Ramaswamy, Sriram
name: Dasgupta, Chandan
name: Maiti, Prabal K.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: In equilibrium hard-rod fluids, and in effective hard-rod descriptions of anisotropic soft-particle systems, the transition from the isotropic (I) phase to the nematic phase (N) is observed above the rod aspect ratio L/D = 3.70 as predicted by Onsager. We examine the fate of this criterion in a molecular dynamics study of a system of soft repulsive spherocylinders rendered active by coupling half the particles to a heat bath at a higher temperature than that imposed on the other half. We show that the system phase separates and self-organizes into various liquid-crystalline phases that are not observed in equilibrium for the respective aspect ratios. In particular, we find a nematic phase for L/D = 3 and a smectic phase for L/D = 2 above a critical activity.
description: 13 pages, 15 figures
On type IIB supergravity action on $M^5 \times X^5$ solutions
Creators: name: Kurlyand, S. A.
name: Tseytlin, A. A.
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: While the 10d type IIB supergravity action evaluated on AdS$_5\times S^5$ solution vanishes, the 5d effective action reconstructed from the equations of motion using $M^5 \times S^5$ compactification ansatz is proportional to the AdS$_5$ volume. The latter is consistent with the conformal anomaly interpretation in AdS/CFT context. We show that this paradox can be resolved if, in the case of $M^5 \times X^5$ topology, the 10d action contains an additional 5-form dependent "topological" term $\int F_{5M} \wedge F_{5X}$. The presence of this term is suggested also by gauge-invariance considerations in the PST formulation of type IIB supergravity action. We show that this term contributes to the 10d action evaluated on the D3-brane solution.
description: 16 pages. v2, v3: references and minor comments added
BRG1 mutations found in human cancer cell lines inactivate Rb-mediated cell-cycle arrest
Creators: name: Weissman, Bernard E.
name: Bartlett, Christopher
name: Orvis, Tess J.
name: Rosson, Gary S.
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2011

description: Eukaryotic organisms package DNA into chromatin for compact storage in the cell nucleus. However, this process promotes transcriptional repression of genes. To overcome the transcriptional repression, chromatin remodeling complexes have evolved that alter the configuration of chromatin packaging of DNA into nucleosomes by histones. The SWI/SNF chromatin remodeling complex uses energy from ATP hydrolysis to reposition nucleosomes and make DNA accessible to transcription factors. Recent studies showing mutations of BRG1, one of 2 mutually exclusive ATPase subunits, in human tumor cell lines and primary tissue samples have implicated a role for its loss in cancer development. While most of the mutations lead to complete loss of BRG1 protein expression, others result in single amino acid substitutions. To better understand the role of these BRG1 point mutations in cancer development, we characterized SWI/SNF function in human tumor cell lines with these mutations in the absence of BRM expression, the other ATPase component. We found that the mutant BRG1 proteins still interacted with the core complex members and appeared at the promoters of target genes. However, while these mutations did not affect CD44 and CDH1 expression, known targets of the SWI/SNF complex, they did abrogate Rb mediated cell cycle arrest. Therefore, our results implicate that these mutations disrupt the de novo chromatin remodeling activity of the complex without affecting the status of existing nucleosome positioning.
Derivation of the fractional porous medium equation from a microscopic dynamics
Creators: name: Cardoso, Pedro
name: De Paula, Renato
name: Gonçalves, Patrícia
Publisher: name: arXiv
Year: 2022
Subjects: subject: Probability (math.PR)
subject: Analysis of PDEs (math.AP)
subject: FOS: Mathematics

description: In this article we derive the fractional porous medium equation for any power of the fractional Laplacian as the hydrodynamic limit of a microscopic dynamics of random particles with long range interactions, but the jump rate highly depends on the occupancy near the sites where the interactions take place.
Second-harmonic generation in subwavelength graphene waveguides
Creators: name: Smirnova, Daria
name: Kivshar, Yuri S.
Publisher: name: arXiv
Year: 2014
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: We suggest a novel approach for generating second-harmonic radiation in subwavelength graphene waveguides. We demonstrate that quadratic phase matching between the plasmonic guided modes of different symmetries can be achieved in a planar double-layer geometry when conductivity of one of the layers becomes spatially modulated. We predict theoretically that, owing to graphene nonlocal conductivity, the second-order nonlinear processes can be actualized for interacting plasmonic modes with an effective grating coupler to allow external pumping of the structure and output of the radiation at the double frequency.
description: 5 pages, 3 figures
Implications of the muon anomalous magnetic moment for the LHC and MUonE
Creators: name: Bhardwaj, Akanksha
name: Englert, Christoph
name: Stylianou, Panagiotis
Publisher: name: arXiv
Year: 2022
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Experiment (hep-ex)
subject: FOS: Physical sciences

description: We consider the anomalous magnetic moment of the muon $a_μ$, which shows a significant deviation from the Standard Model expectation given the recent measurements at Fermilab and BNL. We focus on Standard Model Effective Field Theory (SMEFT) with the aim to identify avenues for the upcoming LHC runs and future experiments such as MUonE. To this end, we include radiative effects to $a_μ$ in SMEFT to connect the muon anomaly to potentially interesting searches at the LHC, specifically Higgs decays into muon pairs and such decays with resolved photons. Our investigation shows that similar to results for concrete UV extensions of the Standard Model, the Fermilab/BNL result can indicate strong coupling within the EFT framework and $a_μ$ is increasingly sensitive to a single operator direction for high scale UV completions. In such cases, there is some complementarity between expected future experimental improvements, yet with considerable statistical challenges to match the precision provided by the recent $a_μ$ measurement.
description: 11 pages, 9 figures; v2 accepted by PRD
Reprogramming the pluripotent cell cycle: Restoration of an abbreviated G1 phase in human induced pluripotent stem (iPS) cells
Creators: name: Stein, Gary S.
name: Qiao, Meng
name: Ghule, Prachi N.
name: Lengner, Christopher J.
name: van Wijnen, Andre J.
name: Dominski, Zbigniew
name: Mandeville, Matthew
name: Stein, Janet L.
name: Lian, Jane B.
name: Medina, Ricardo
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2011

description: Induced pluripotent stem (iPS) cells derived from terminally differentiated human fibroblasts are re-programmed to possess stem cell like properties. However, the extent to which iPS cells exhibit unique properties of the human embryonic stem (hES) cell cycle remains to be established. Human ES cells are characterized by an abbreviated G1 phase (~2.5 h) and accelerated organization of subnuclear domains that mediate the assembly of regulatory machinery for histone gene expression [i.e., histone locus bodies (HLBs)]. We therefore examined cell cycle parameters of iPS cells in comparison to hES cells. Analysis of DNA synthesis (BrdU incorporation), cell cycle distribution (FACS analysis and Ki67 staining) and subnuclear organization of HLBs [immuno-fluorescence microscopy and fluorescence in situ hybridization (FISH)] revealed that human iPS cells have a short G1 phase (~2.5 h) and an abbreviated cell cycle (16–18 h). Furthermore, HLBs are formed and reorganized rapidly after mitosis (within0.5 to 1.5 h). Thus, reprogrammed iPS cells have cell cycle kinetics and dynamic subnuclear organization of regulatory machinery that are principal properties of pluripotent hES cells. Our findings support the concept that the abbreviated cell cycle of hES and iPS cells is functionally linked to pluripotency.
Metaboloepigenetics: Interrelationships between energy metabolism and epigenetic control of gene expression
Creators: name: Bultman, Scott J.
name: Donohoe, Dallas R.
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2012

description: Diet and energy metabolism affect gene expression, which influences human health and disease. Here, we discuss the role of epigenetics as a mechanistic link between energy metabolism and control of gene expression. A number of key energy metabolites including SAM, acetyl-CoA, NAD+, and ATP serve as essential co-factors for many, perhaps most, epigenetic enzymes that regulate DNA methylation, posttranslational histone modifications, and nucleosome position. The relative abundance of these energy metabolites allows a cell to sense its energetic state. And as co-factors, energy metabolites act as rheostats to modulate the activity of epigenetic enzymes and upregulate/downregulate transcription as appropriate to maintain homeostasis.
Matched Quality Evaluation of Temporally Downsampled Videos with Non-Integer Factors
Creators: name: Herglotz, Christian
name: Ramasubbu, Geetha
name: Kaup, André
Publisher: name: arXiv
Year: 2022
Subjects: subject: Image and Video Processing (eess.IV)
subject: FOS: Electrical engineering, electronic engineering, information engineering

description: Recent research has shown that temporal downsampling of high-frame-rate sequences can be exploited to improve the rate-distortion performance in video coding. However, until now, research only targeted downsampling factors of powers of two, which greatly restricts the potential applicability of temporal downsampling. A major reason is that traditional, objective quality metrics such as peak signal-to-noise ratio or more recent approaches, which try to mimic subjective quality, can only be evaluated between two sequences whose frame rate ratio is an integer value. To relieve this problem, we propose a quality evaluation method that allows calculating the distortion between two sequences whose frame rate ratio is fractional. The proposed method can be applied to any full-reference quality metric.
description: Proc. 12th International Conference on Quality of Multimedia Experience (QoMEX)
The power-law TST reaction rate coefficient with tunneling correction
Creators: name: Yin, Cangtao
name: Zhou, Yanjun
name: Du, Jiulin
Publisher: name: arXiv
Year: 2014
Subjects: subject: Chemical Physics (physics.chem-ph)
subject: Statistical Mechanics (cond-mat.stat-mech)
subject: FOS: Physical sciences

description: We study the TST reaction rate for the systems with power-law distributions. We derive the expressions of the reaction rate coefficient with tunneling correction, which strongly depends on the power-law parameter. The numerical results show that a small deviation from one in the parameter can result in a significant change in the rate coefficient, but only cause a small change in the tunneling correction. Thus the tunneling correction is not sensitive to the power-law distributions. As an application example, we take the hydrogen reaction to calculate the power-law reaction rate coefficient with the tunneling correction, the results of which with the parameter slightly different from one are in good agreement with all the experimental studies in temperature range 200~1000K.
description: 12 pages, 4 figures, 2 tables, 25 references
Functors in Lorentzian geometry -- three variations on a theme
Creators: name: Müller, Olaf
Publisher: name: arXiv
Year: 2022
Subjects: subject: Differential Geometry (math.DG)
subject: FOS: Mathematics
subject: 53C50

description: We review three examples of functors from Lorentzian categories and their applications in finiteness results, singularity theorems and boundary constructions. The third example is a novel functor from the category of ordered measure spaces to the category of Lorentzian pre-length spaces in the sense of Kunzinger-Sämann.
description: 15 pages. The article is a contribution to the conference volume of the conference "Singularity theorems, causality and all that; a tribute to Roger Penrose" (2021) and is in large parts an overview article but also contains some new results
Quadrupolar photovoltaic effect in the terahertz range in a two-dimensional spin-3/2 hole system
Creators: name: Farokhnezhad, Mohsen
name: Coish, W. A.
name: Asgari, Reza
name: Culcer, Dimitrie
Publisher: name: arXiv
Year: 2022
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: Other Condensed Matter (cond-mat.other)
subject: FOS: Physical sciences

description: We identify a strong photovoltaic response due to the non-linear optical transition between heavy and light hole sub-bands enabled by T_d-symmetry in a quantum well, which we term the quadrupolar photovoltaic effect (QPE). The photovoltaic current exhibits a strong resonance in the vicinity of the heavy hole-light hole splitting, with a magnitude governed by the momentum relaxation time, which can reach nanoseconds in GaAs holes. Since the heavy hole-light hole splitting can be tuned from a few meV to nearly 100 meV the QPE could serve as the basis for a terahertz photo-detector. We discuss strategies for experimental observation and device applications.
description: 6 pages, 4 figures + Supplement
Computer Simulation of the Early Stages of Self-Assembly and Thermal Decomposition of ZIF-8
Creators: name: Balestra, Salvador R. G.
name: Semino, Rocio
Publisher: name: arXiv
Year: 2022
Subjects: subject: Chemical Physics (physics.chem-ph)
subject: FOS: Physical sciences

description: We employ all-atom well-tempered metadynamics simulations to study the mechanistic details of both the early stages of nucleation and crystal decomposition for the benchmark metal-organic framework ZIF-8. To do so, we developed and validated a force field that reliably models the modes of coordination bonds via a Morse potential functional form and employs cationic and anionic dummy atoms to capture coordination symmetry. We also explored a set of physically relevant collective variables and carefully selected an appropriate subset for our problem at hand. After a rapid increase of the Zn-N connectivity, we observe the evaporation of small clusters in favor of a few large clusters, that lead to the formation of an amorphous highly-connected aggregate. Zn(MIm)42- and Zn(MIm)3- complexes are observed, with lifetimes in the order of a few picoseconds, while larger structures, such as 4-, 5- and 6-membered rings, have substantially longer lifetimes of a few nanoseconds. The free ligands act as ``templating agents'' for the formation of the sodalite cages. ZIF-8 crystal decomposition results in the formation of a vitreous phase. Our findings contribute to a fundamental understanding of MOF's synthesis that paves the way to controlling synthesis products. Furthermore, our developed force field and methodology can be applied to model solution processes that require coordination bond reactivity for other ZIFs besides ZIF-8.
description: 16 pages, 6 figures. This version corresponds to the accepted article, changes were applied in response to the peer-reviewing process. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in The Journal of Chemical Physics and may be found at https://aip.scitation.org/doi/10.1063/5.0128656
The HD5980 multiple system: Masses and evolutionary status
Creators: name: Koenigsberger, Gloria
name: Morrell, Nidia
name: Hillier, D. John
name: Gamen, Roberto
name: Schneider, Fabian R. N.
name: Gonzalez-Jimenez, Nicolas
name: Langer, Norbert
name: Barba, Rodolfo
Publisher: name: arXiv
Year: 2014
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: New spectroscopic observations of the LBV/WR multiple system HD5980 in the Small Magellanic Cloud are used to address the question of the masses and evolutionary status of the two very luminous stars in the 19.3d eclipsing binary system. Two distinct components of the N V 4944 A line are detected in emission and their radial velocity variations are used to derive masses of 61 and 66 Mo, under the assumption that binary interaction effects on this atomic transition are negligible. We propose that this binary system is the product of quasi-chemically homogeneous evolution with little or no mass transfer. Thus, both of these binary stars may be candidates for gamma-ray burst progenitors or even pair instability supernovae. Analysis of the photospheric absorption lines belonging to the third-light object in the system confirm that it consists of an O-type star in a 96.56d eccentric orbit (e=0.82) around an unseen companion. The 5:1 period ratio and high eccentricities of the two binaries suggest that they may constitute a hierarchical quadruple system.
description: 27 pages, 8 tables, 15 figures; accepted AJ
Quantitative Measurements of Cerebral Blood Oxygen Saturation Using Magnetic Resonance Imaging
Creators: name: Lin, Weili
name: An, Hongyu
Publisher: name: The University of North Carolina at Chapel Hill University Libraries
Year: 2000

description: A quantitative estimate of cerebral blood oxygen saturation is of critical importance in the investigation of cerebrovascular disease because of the fact that it could potentially provide information on tissue viability in vivo. In the current study, a multi-echo gradient and spin echo magnetic resonance imaging sequence was used to acquire images from eight normal volunteer subjects. All images were acquired on a Siemens 1.5T Symphony whole-body scanner (Siemens, Erlangen, Germany). A theoretical signal model, which describes the signal dephasing phenomena in the presence of deoxyhemoglobin, was used for postprocessing of the acquired images and obtaining a quantitative measurement of cerebral blood oxygen saturation in vivo. With a region-of-interest analysis, a mean cerebral blood oxygen saturation of 58.4% ± 1.8% was obtained in the brain parenchyma from all volunteers. It is in excellent agreement with the known cerebral blood oxygen saturation under normal physiologic conditions in humans. Although further studies are needed to overcome some of the confounding factors affecting the estimates of cerebral blood oxygen saturation, these preliminary results are encouraging and should open a new avenue for the noninvasive investigation of cerebral oxygen metabolism under different pathophysiologic conditions using a magnetic resonance imaging approach.