7,724 research outputs found
Recommended from our members
The transcriptome of retinal Müller glial cells
Müller glial cells are the major type of glia in the mammalian retina. To identify the molecular machinery that defines Müller glial cell identity and function, single cell gene expression profiling was performed on Affymetrix microarrays. Identification of a cluster of genes expressed at high levels suggests a Müller glia core transcriptome, which likely underlies many of the functions of Müller glia. Expression of components of the cell cycle machinery and the Notch pathway, as well as of growth factors, chemokines, and lipoproteins might allow communication between Müller glial cells and the neurons that they support, including modulation of neuronal activity. This approach revealed a set of transcripts that were not previously characterized in (Müller) glia; validation of the expression of some of these genes was performed by in situ hybridization. Genes expressed exclusively by Müller glia were identified as novel markers. In addition, a novel BAC transgenic mouse that expresses Cre in Müller glia cells was generated. The molecular fingerprint of Müller glia provides a foundation for further studies of Müller glia development and function in normal and diseased states
Incorporation of μ3-CO3 into an MnIII/MnIV Mn12 cluster: {[(cyclam)MnIV(μ-O)2MnIII(H2O)(μ-OH)]6(μ3-CO3)2}Cl8·24H2O
The centrosymmetric title cluster, hexaaquadi-μ3-carbonato-hexacyclamhexa-μ2-hydroxido-dodeca-μ2-oxido-hexamanganese(IV)hexamanganese(III) octachloride tetracosahydrate, [Mn12(CO3)2O12(OH)6(C10H24N4)6(H2O)6]Cl8·24H2O, has two μ3-CO3 groups that not only bridge octahedrally coordinated MnIII ions but also act as acceptors to two different kinds of hydrogen bonds. The carbonate anion is planar within experimental error and has an average C—O distance of 1.294 (4) Å. The crystal packing is stabilized by O—H⋯Cl, O—H⋯O, N—H⋯Cl and N—H⋯O hydrogen bonds. Two of the four independent chloride ions are disordered over five positions, and eight of the 12 independent water molecules are disordered over 21 positions
Inclusive and Direct Photons in S + Au Central Collisions at 200A GeV/c
A hadron and string cascade model, JPCIAE, which is based on LUND string
model, PYTHIA event generator especially, is used to study both inclusive
photon production and direct photon production in 200A GeV S + Au central
collisions. The model takes into account the photon production from the
partonic QCD scattering process, the hadronic final-state interaction, and the
hadronic decay and deals with them consistently. The results of JPCIAE model
reproduce successfully both the WA93 data of low p_T inclusive photon
distribution and the WA80 data of transverse momentum dependent upper limit of
direct photon. The photon production from different decay channels is
investigated for both direct and inclusive photons. We have discussed the
effects of the partonic QCD scattering and the hadronic final-state interaction
on direct photon production as well.Comment: 6 pages with 5 figure
Phase transition in the rich-get-richer mechanism due to finite-size effects
The rich-get-richer mechanism (agents increase their ``wealth'' randomly at a
rate proportional to their holdings) is often invoked to explain the Pareto
power-law distribution observed in many physical situations, such as the degree
distribution of growing scale free nets. We use two different analytical
approaches, as well as numerical simulations, to study the case where the
number of agents is fixed and finite (but large), and the rich-get-richer
mechanism is invoked a fraction r of the time (the remainder of the time wealth
is disbursed by a homogeneous process). At short times, we recover the Pareto
law observed for an unbounded number of agents. In later times, the (moving)
distribution can be scaled to reveal a phase transition with a Gaussian
asymptotic form for r < 1/2 and a Pareto-like tail (on the positive side) and a
novel stretched exponential decay (on the negative side) for r > 1/2.Comment: 9 pages, 1 figure, code and data included with source. Update
corrects typos, adds journal-re
Field dependence of magnetization reversal by spin transfer
We analyse the effect of the applied field (Happl) on the current-driven
magnetization reversal in pillar-shaped Co/Cu/Co trilayers, where we observe
two different types of transition between the parallel (P) and antiparallel
(AP) magnetic configurations of the Co layers. If Happl is weaker than a rather
small threshold value, the transitions between P and AP are irreversible and
relatively sharp. For Happl exceding the threshold value, the same transitions
are progressive and reversible. We show that the criteria for the stability of
the P and AP states and the experimentally observed behavior can be precisely
accounted for by introducing the current-induced torque of the spin transfer
models in a Landau-Lifschitz-Gilbert equation. This approach also provides a
good description for the field dependence of the critical currents
One-Shot Unsupervised Cross-Domain Detection
Despite impressive progress in object detection over the last years, it is
still an open challenge to reliably detect objects across visual domains.
Although the topic has attracted attention recently, current approaches all
rely on the ability to access a sizable amount of target data for use at
training time. This is a heavy assumption, as often it is not possible to
anticipate the domain where a detector will be used, nor to access it in
advance for data acquisition. Consider for instance the task of monitoring
image feeds from social media: as every image is created and uploaded by a
different user it belongs to a different target domain that is impossible to
foresee during training. This paper addresses this setting, presenting an
object detection algorithm able to perform unsupervised adaption across domains
by using only one target sample, seen at test time. We achieve this by
introducing a multi-task architecture that one-shot adapts to any incoming
sample by iteratively solving a self-supervised task on it. We further enhance
this auxiliary adaptation with cross-task pseudo-labeling. A thorough benchmark
analysis against the most recent cross-domain detection methods and a detailed
ablation study show the advantage of our method, which sets the
state-of-the-art in the defined one-shot scenario
Two-photon NADH imaging exposes boundaries of oxygen diffusion in cortical vascular supply regions
Oxygen transport imposes a possible constraint on the brain's ability to sustain variable metabolic demands, but oxygen diffusion in the cerebral cortex has not yet been observed directly. We show that concurrent two-photon fluorescence imaging of endogenous nicotinamide adenine dinucleotide (NADH) and the cortical microcirculation exposes well-defined boundaries of tissue oxygen diffusion in the mouse cortex. The NADH fluorescence increases rapidly over a narrow, very low pO2 range with a p50 of 3.4±0.6 mm Hg, thereby establishing a nearly binary reporter of significant, metabolically limiting hypoxia. The transient cortical tissue boundaries of NADH fluorescence exhibit remarkably delineated geometrical patterns, which define the limits of tissue oxygen diffusion from the cortical microcirculation and bear a striking resemblance to the ideal Krogh tissue cylinder. The visualization of microvessels and their regional contribution to oxygen delivery establishes penetrating arterioles as major oxygen sources in addition to the capillary network and confirms the existence of cortical oxygen fields with steep microregional oxygen gradients. Thus, two-photon NADH imaging can be applied to expose vascular supply regions and to localize functionally relevant microregional cortical hypoxia with micrometer spatial resolution
Non-Equilibrium in Adsorbed Polymer Layers
High molecular weight polymer solutions have a powerful tendency to deposit
adsorbed layers when exposed to even mildly attractive surfaces. The
equilibrium properties of these dense interfacial layers have been extensively
studied theoretically. A large body of experimental evidence, however,
indicates that non-equilibrium effects are dominant whenever monomer-surface
sticking energies are somewhat larger than kT, a common case. Polymer
relaxation kinetics within the layer are then severely retarded, leading to
non-equilibrium layers whose structure and dynamics depend on adsorption
kinetics and layer ageing. Here we review experimental and theoretical work
exploring these non-equilibrium effects, with emphasis on recent developments.
The discussion addresses the structure and dynamics in non-equilibrium polymer
layers adsorbed from dilute polymer solutions and from polymer melts and more
concentrated solutions. Two distinct classes of behaviour arise, depending on
whether physisorption or chemisorption is involved. A given adsorbed chain
belonging to the layer has a certain fraction of its monomers bound to the
surface, f, and the remainder belonging to loops making bulk excursions. A
natural classification scheme for layers adsorbed from solution is the
distribution of single chain f values, P(f), which may hold the key to
quantifying the degree of irreversibility in adsorbed polymer layers. Here we
calculate P(f) for equilibrium layers; we find its form is very different to
the theoretical P(f) for non-equilibrium layers which are predicted to have
infinitely many statistical classes of chain. Experimental measurements of P(f)
are compared to these theoretical predictions.Comment: 29 pages, Submitted to J. Phys.: Condens. Matte
- …