1,984 research outputs found
Piperazine-2,3,5,6-tetraÂone
The molÂecule of the title compound, C4H2N2O4, is located around an inversion center and the four O atoms are in the 2,3,5,6-positions of the piperazine ring. In the crystal, bifurcated NâHâŻO hydrogen bonds link the molÂecules into a corrugated layer parallel to (101)
The chloride channel cystic fibrosis transmembrane conductance regulator (CFTR) controls cellular quiescence by hyperpolarizing the cell membrane during diapause in the crustacean Artemia
Cellular quiescence, a reversible state in which growth, proliferation, and other cellular activities are arrested, is important for self-renewal, differentiation, development, regeneration, and stress resistance. However, the physiological mechanisms underlying cellular quiescence remain largely unknown. In the present study, we used embryos of the crustacean Artemia in the diapause stage, in which these embryos remain quiescent for prolonged periods, as a model to explore the relationship between cell-membrane potential (V-mem) and quiescence. We found that V-mem is hyperpolarized and that the intracellular chloride concentration is high in diapause embryos, whereas V-mem is depolarized and intracellular chloride concentration is reduced in postdiapause embryos and during further embryonic development. We identified and characterized the chloride ion channel protein cystic fibrosis transmembrane conductance regulator (CFTR) of Artemia (Ar-CFTR) and found that its expression is silenced in quiescent cells of Artemia diapause embryos but remains constant in all other embryonic stages. Ar-CFTR knockdown and GlyH-101-mediated chemical inhibition of Ar-CFTR produced diapause embryos having a high V-mem and intracellular chloride concentration, whereas control Artemia embryos released free-swimming nauplius larvae. Transcriptome analysis of embryos at different developmental stages revealed that proliferation, differentiation, and metabolism are suppressed in diapause embryos and restored in postdiapause embryos. Combined with RNA sequencing (RNA-Seq) of GlyH-101-treated MCF-7 breast cancer cells, these analyses revealed that CFTR inhibition down-regulates the Wnt and Aurora Kinase A (AURKA) signaling pathways and up-regulates the p53 signaling pathway. Our findings provide insight into CFTR-mediated regulation of cellular quiescence and V-mem in the Artemia model
Geometric density of states of electronic structures for local responses: Phase information from the amplitudes of STM measurement
Electronic band structures underlie the physical properties of crystalline
materials, their geometrical exploration renovates the conventional cognition
and brings about novel applications. Inspired by geometry phases, we introduce
a geometric amplitude named as the geometric density of states (GDOS) dictated
by the differential curvature of the constant-energy contour. The GDOS
determines the amplitude of the real-space Green's function making it attain
the ultimate expression with transparent physics. The local responses of
crystalline materials are usually formulated by the real-space Green's
function, so the relevant physics should be refreshed by GDOS. As an example of
local responses, we suggest using scanning tunneling microscopy (STM) to
characterize the surface states of three-dimensional topological insulator
under an in-plane magnetic field. The GDOS favors the straightforward
simulation of STM measurement without resorting to Fourier transform of the
real-space measurement, and also excavates the unexplored potential of STM
measurement to extract the phase information of wavefunction through its
amplitude, i.e., the spin and curvature textures. Therefore, the proposed GDOS
deepens the understanding of electronic band structures and is indispensable in
local responses, and it should be universal for any periodic systems.Comment: 6 pages, 2 figure
Distribution of Spectral Lags in Gamma Ray Bursts
Using the data acquired in the Time To Spill (TTS) mode for long gamma-ray
bursts (GRBs) collected by the Burst and Transient Source Experiment on board
the Compton Gamma Ray Observatory (BATSE/CGRO), we have carefully measured
spectral lags in time between the low (25-55 keV) and high (110-320 keV) energy
bands of individual pulses contained in 64 multi-peak GRBs. We find that the
temporal lead by higher-energy gamma-ray photons (i.e., positive lags) is the
norm in this selected sample set of long GRBs. While relatively few in number,
some pulses of several long GRBs do show negative lags. This distribution of
spectral lags in long GRBs is in contrast to that in short GRBs. This apparent
difference poses challenges and constraints on the physical mechanism(s) of
producing long and short GRBs. The relation between the pulse peak count rates
and the spectral lags is also examined. Observationally, there seems to be no
clear evidence for systematic spectral lag-luminosity connection for pulses
within a given long GRB.Comment: 20 pages, 4 figure
Identification of essential genes in human lymphopoiesis
Objective. Pesticide self-poisoning accounts for one-third of suicides worldwide, but few studies have investigated the national epidemiology of pesticide suicide in countries where it is a commonly used method. We investigated trends in pesticide suicide, and factors associated with such trends, in Taiwan, a rapidly developing East Asian country. Methods. We conducted an ecological study using graphical approaches and Spearman's correlation coefficients to examine trends in pesticide suicide (19872010) in Taiwan in relation to pesticide sales, bans on selected pesticides, the proportion of the workforce involved in agriculture and unemployment. We compared pesticide products banned by the Taiwanese government with products that remained on the market and pesticides that accounted for the most poisoning deaths in Taiwan. Results. Age-standardised rates of pesticide suicide showed a 67% reduction from 7.7 per 100,000 (42% of all suicides) in 1987 to 2.5 per 100,000 (12% of all suicides) in 2010, in contrast to a 69% increase in suicide rates by other methods. Pesticide poisoning was the most commonly used method of suicide in 1987 but had become the third most common method by 2010. The reduction was paralleled by a 66% fall in the workforce involved in agriculture but there was no strong evidence for its association with trends in pesticide sales, bans on selected pesticide products or unemployment. The bans mostly post-dated the decline in pesticide suicides; furthermore, they did not include products (e.g. paraquat) that accounted for most deaths and were mainly restricted to selected high-strength formulated products whilst their equivalent low-strength products were not banned. Conclusions. Access to pesticides, indicated by the size of agricultural workforce, appears to influence trends in pesticide suicide in Taiwan. Targeted bans on pesticides should focus on those products that account for most deaths. © 2012 Informa Healthcare USA, Inc.postprin
Current reversals and metastable states in the infinite Bose-Hubbard chain with local particle loss
We present an algorithm which combines the quantum trajectory approach to
open quantum systems with a density-matrix renormalization group scheme for
infinite one-dimensional lattice systems. We apply this method to investigate
the long-time dynamics in the Bose-Hubbard model with local particle loss
starting from a Mott-insulating initial state with one boson per site. While
the short-time dynamics can be described even quantitatively by an equation of
motion (EOM) approach at the mean-field level, many-body interactions lead to
unexpected effects at intermediate and long times: local particle currents far
away from the dissipative site start to reverse direction ultimately leading to
a metastable state with a total particle current pointing away from the lossy
site. An alternative EOM approach based on an effective fermion model shows
that the reversal of currents can be understood qualitatively by the creation
of holon-doublon pairs at the edge of the region of reduced particle density.
The doublons are then able to escape while the holes move towards the
dissipative site, a process reminiscent---in a loose sense---of Hawking
radiation
Giant 2D Skyrmion Topological Hall Effect with Ultrawide Temperature Window and Low-Current Manipulation in 2D Room-Temperature Ferromagnetic Crystals
The discovery and manipulation of topological Hall effect (THE), an abnormal
magnetoelectric response mostly related to the Dzyaloshinskii-Moriya
interaction (DMI), are promising for next-generation spintronic devices based
on topological spin textures such as magnetic skyrmions. However, most
skyrmions and THE are stabilized in a narrow temperature window either below or
over room temperature with high critical current manipulation. It is still
elusive and challenging to achieve large THE with both wide temperature window
till room temperature and low critical current manipulation. Here, by using
controllable, naturally-oxidized, sub-20 and sub-10 nm 2D van der Waals
room-temperature ferromagnetic Fe3GaTe2-x crystals, robust 2D THE with
ultrawide temperature window ranging in three orders of magnitude from 2 to 300
K is reported, combining with giant THE of ~5.4 micro-ohm cm at 10 K and ~0.15
micro-ohm cm at 300 K which is 1-3 orders of magnitude larger than that of all
known room-temperature 2D skyrmion systems. Moreover, room-temperature
current-controlled THE is also realized with a low critical current density of
~6.2*10^5 A cm^-2. First-principles calculations unveil natural
oxidation-induced highly-enhanced 2D interfacial DMI reasonable for robust
giant THE. This work paves the way to room-temperature, electrically-controlled
2D THE-based practical spintronic devices
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