5,395 research outputs found
A nickel pyridine-selenolate complex for the photocatalytic evolution of hydrogen from aqueous solutions
Abstract(#br)A nickel pyridine-selenolate complex, [Ni(4,4′-dmbpy)(2-pySe) 2 ] ( 1 , where 4,4′-dmbpy = 4,4′-dimethyl-2,2′-bipyridine, and 2-pySe = pyridine-2-selenolate), has been synthesized, and investigated for photocatalytic production of H 2 from aqueous solution. Electrochemical studies show that the nickel complex 1 can efficiently electrocatalyze H 2 evolution from weakly acidic solutions. Under visible-light irradiation (λ > 420 nm), the complex 1 displays impressive H 2 evolution activity with a TON of 1340 (based on a catalyst) in a noble-metal-free system, which contains fluorescein (Fl) as photosensitizer and triethylamine (TEA) as sacrificial electron donor in acetonitrile-water solution. It should be noted that complex 1 is the rare example of nickel pyridine-selenolate complex as molecular photocatalyst for water reduction
Spectral fluctuations in the interacting boson model
The energy dependence of the spectral fluctuations in the interacting boson
model (IBM) and its connections to the mean-field structures have been analyzed
through adopting two statistical measures, the nearest neighbor level spacing
distribution measuring the chaoticity (regularity) in energy spectra and
the statistics of Dyson and Metha measuring the spectral
rigidity. Specifically, the statistical results as functions of the energy
cutoff have been worked out for different dynamical situations including the
U(5)-SU(3) and SU(3)-O(6) transitions as well as those near the AW arc of
regularity. It is found that most of the changes in spectral fluctuations are
triggered near the stationary points of the classical potential especially for
the cases in the deformed region of the IBM phase diagram. The results thus
justify the stationary point effects from the point of view of statistics. In
addition, the approximate degeneracies in the spectrum on the AW arc is
also revealed from the statistical calculations
Production of squeezed state of single mode cavity field by the coupling of squeezed vacuum field reservoir in nonautonomous case
The dissipative and decoherence properties as well as the asymptotic behavior
of the single mode electromagnetic field interacting with the time-dependent
squeezed vacuum field reservoir are investigated in detail by using the
algebraic dynamical method. With the help of the left and right representations
of the relevant algebra, the dynamical symmetry of the nonautonomous
master equation of the system is found to be . The unique equilibrium
steady solution is found to be the squeezed state and any initial state of the
system is proved to approach the unique squeezed state asymptotically. Thus the
squeezed vacuum field reservoir is found to play the role of a squeezing mold
of the cavity field.Comment: 5 pages, no figure, Revtex
Uncovering the spatial heterogeneity of Ediacaran carbon cycling
Author Posting. © The Author(s), 2016. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Geobiology 15 (2017): 211–224, doi:10.1111/gbi.12222.Records of the Ediacaran carbon cycle (635 to 541 million years ago) include the
Shuram excursion (SE), the largest negative carbonate-carbon isotope excursion in
Earth history (down to -12 ‰). The nature of this excursion remains enigmatic given the
difficulties of interpreting a perceived extreme global decrease in the δ13C of seawater
dissolved inorganic carbon (DIC). Here, we present carbonate and organic carbon
isotope (δ13Ccarb and δ13Corg) records from the Ediacaran Doushantuo Formation along
a proximal-to-distal transect across the Yangtze Platform of South China as a test of the
spatial variation of the SE. Contrary to expectations, our results show that the
magnitude and morphology of this excursion and its relationship with coexisting δ13Corg
are highly heterogeneous across the platform. Integrated geochemical, mineralogical,
petrographic, and stratigraphic evidence indicates that the SE is a primary marine
signature. Data compilations demonstrate that the SE was also accompanied globally by
parallel negative shifts of δ34S of carbonate-associated sulfate (CAS) and increased
87Sr/86Sr ratio and coastal CAS concentration, suggesting elevated continental
weathering and coastal marine sulfate concentration during the SE. In light of these
observations, we propose a heterogeneous oxidation model to explain the high spatial
heterogeneity of the SE and coexisting δ13Corg records of the Doushantuo, with likely
relevance to the SE in other regions. In this model, we infer continued marine redox
stratification through the SE but with increased availability of oxidants (e.g., O2 and
sulfate) limited to marginal near-surface marine environments. Oxidation of limited
spatiotemporal extent provides a mechanism to drive heterogeneous oxidation of
subsurface reduced carbon mostly in shelf areas. Regardless of the mechanism driving
the SE, future models must consider the evidence for spatial heterogeneity in δ13C
presented in this study.We thank the National Key Basic Research Program of China (Grant
2013CB955704) and the State Key R&D project of China (Grant 2016YFA060104) as well
as the NSF-ELT program and the NASA Astrobiology Institute (TWL) for funding
Stress-Induced Epinephrine Enhances Lactate Dehydrogenase A and Promotes Breast Cancer Stem-Like Cells
Chronic stress triggers activation of the sympathetic nervous system and drives malignancy. Using an immunodeficient murine system, we showed that chronic stress–induced epinephrine promoted breast cancer stem-like properties via lactate dehydrogenase A–dependent (LDHA-dependent) metabolic rewiring. Chronic stress–induced epinephrine activated LDHA to generate lactate, and the adjusted pH directed USP28-mediated deubiquitination and stabilization of MYC. The SLUG promoter was then activated by MYC, which promoted development of breast cancer stem-like traits. Using a drug screen that targeted LDHA, we found that a chronic stress–induced cancer stem-like phenotype could be reversed by vitamin C. These findings demonstrated the critical importance of psychological factors in promoting stem-like properties in breast cancer cells. Thus, the LDHA-lowering agent vitamin C can be a potential approach for combating stress-associated breast cancer
Transcription phase, protein characteristics of DEV UL45 and prokaryotic expression, antibody preparation of the UL45 des-transmembrane domain
<p>Abstract</p> <p>Background</p> <p>Some UL45 gene function of Herpesvirus was reported. While there was no any report of the duck enteritis virus (DEV) UL45 protein as yet.</p> <p>Results</p> <p>The UL45 gene and des-transmembrane domain of UL45 (named UL45Δ gene, 295-675bp of UL45) of DEV were amplified by PCR and subcloned into the prokaryotic expression vector pET-32a(+). The constructed recombinant plasmids were transformed into the host strain BL21(DE3) PLysS and induced by IPTG. SDS-PAGE analysis showed the UL45 gene couldn't express while UL45Δ gene was highly expressed. His Purify Kit or salting-out could purify the protein effectively. Using the purified protein to immunize New-Zealand rabbits and produce polyclonal antibody. The agar diffusion reaction showed the titer of antibody was 1:32. Western blot analysis indicated the purified rabbit anti-UL45Δ IgG had a high level of specificity and the UL45 gene was a part of DEV genome. The transcription phase study of UL45 gene showed that expression of UL45 mRNA was at a low level from 0 to 18 h post-infection (pi), then accumulated quickly at 24 h pi and peaked at 42 h pi. It can be detected till 72 h pi. Besides, western blot analysis of purified virion and different viral ingredients showed that the UL45 protein resided in the purified virion and the viral envelope.</p> <p>Conclusions</p> <p>The rabbit anti-UL45Δ IgG was produced successfully and it can serve as a good tool for penetrating studies of the function of DEV UL45 protein. The transcription phase and protein characteristics analysis indicated that DEV UL45 gene was a late gene and UL45 protein may be a viral envelope protein.</p
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