1,502 research outputs found
Homo- and Heteroleptic Copper(I) Complexes with Diazabutadiene Ligands: Synthesis, Solution- and Solid-State Structural Studies
The preparation of novel copper(I) complexes of diazabutadiene (DAB) ligands with aliphatic backbones is reported. [Cu(DABR)2](BF4), [Cu(DABR)(NCMe)2](BF4) and [CuCl(DABR)] are easily synthesised and air-stable. These complexes, which remain scarce in the literature, have been fully characterised, and their behaviour both in the solid state as well as in solution has been studied by means of X-ray crystallography, NMR and UV/Vis spectroscopy
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A global atmospheric electricity monitoring network for climate and geophysical research
The Global atmospheric Electric Circuit (GEC) is a fundamental coupling network of the climate system connecting electrically disturbed weather regions with fair weather regions across the planet. The GEC sustains the fair weather electric field (or potential gradient, PG) which is present globally and can be measured routinely at the surface using durable instrumentation such as modern electric field mills, which are now widely deployed internationally. In contrast to lightning or magnetic fields, fair weather PG cannot be measured remotely. Despite the existence of many PG datasets (both contemporary and historical), few attempts have been made to coordinate and integrate these fragmented surface measurements within a global framework. Such a synthesis is important elvinin order to fully study major influences on the GEC such as climate variations and space weather effects, as well as more local atmospheric electrical processes such as cloud electrification, lightning initiation, and dust and aerosol charging.
The GloCAEM (Global Coordination of Atmospheric Electricity Measurements) project has brought together experts in atmospheric electricity to make the first steps towards an effective global network for atmospheric electricity monitoring, which will provide data in near real time. Data from all sites are available in identically-formatted files, at both one second and one minute temporal resolution, along with meteorological data (wherever available) for ease of interpretation of electrical measurements. This work describes the details of the GloCAEM database and presents what is likely to be the largest single analysis of PG data performed from multiple datasets at geographically distinct locations. Analysis of the diurnal variation in PG from all 17 GloCAEM sites demonstrates that the majority of sites show two daily maxima, characteristic of local influences on the PG, such as the sunrise effect. Data analysis methods to minimise such effects are presented and recommendations provided on the most suitable GloCAEM sites for the study of various scientific phenomena. The use of the dataset for a further understanding of the GEC is also demonstrated, in particular for more detailed characterization of day-to-day global circuit variability. Such coordinated effort enables deeper insight into PG phenomenology which goes beyond single-location PG measurements, providing a simple measurement of global thunderstorm variability on a day-to-day timescale. The creation of the GloCAEM database is likely to enable much more effective study of atmospheric electricity variables than has ever been possible before, which will improve our understanding of the role of atmospheric electricity in the complex processes underlying weather and climate
A differential method for bounding the ground state energy
For a wide class of Hamiltonians, a novel method to obtain lower and upper
bounds for the lowest energy is presented. Unlike perturbative or variational
techniques, this method does not involve the computation of any integral (a
normalisation factor or a matrix element). It just requires the determination
of the absolute minimum and maximum in the whole configuration space of the
local energy associated with a normalisable trial function (the calculation of
the norm is not needed). After a general introduction, the method is applied to
three non-integrable systems: the asymmetric annular billiard, the many-body
spinless Coulombian problem, the hydrogen atom in a constant and uniform
magnetic field. Being more sensitive than the variational methods to any local
perturbation of the trial function, this method can used to systematically
improve the energy bounds with a local skilled analysis; an algorithm relying
on this method can therefore be constructed and an explicit example for a
one-dimensional problem is given.Comment: Accepted for publication in Journal of Physics
Angiotensin II induced inflammation in the kidney and in the heart of double transgenic rats
BACKGROUND: We are investigating a double transgenic rat (dTGR) model, in which rats transgenic for the human angiotensinogen and renin genes are crossed. These rats develop moderately severe hypertension but die of end-organ cardiac and renal damage by week 7. The heart shows necrosis and fibrosis, whereas the kidneys resemble the hemolytic-uremic syndrome vasculopathy. Surface adhesion molecules (ICAM-1 and VCAM-1) are expressed early on the endothelium, while the corresponding ligands are found on circulating leukocytes. Leukocyte infiltration in the vascular wall accompanies PAI-1, MCP-1, iNOS and Tissue Factor expression. Furthermore we show evidence that Ang II causes the upregulation of NF-{kappa}B in our model. METHODS: We started PDTC-treatment on four weeks old dTGR (200 mg/kg sc) and age-matched SD rats. Blood-pressure- and albuminuria- measurements were monitored during the treatment period (four weeks). The seven weeks old animals were killed, hearts and kidneys were isolated and used for immunohistochemical-and electromobility shift assay analysis. RESULTS: Chronic treatment with the antioxidant PDTC decreased blood pressure (162 plus minus 8 vs. 190 plus minus 7 mm Hg, p = 0.02). Cardiac hypertrophy index was significantly reduced (4.90 plus minus 0.1 vs. 5.77 plus minus 0.1 mg/g, p < 0.001) compared to dTGR. PDTC reduced 24 h albuminuria by 85 % (2.7 plus minus 0.5 vs. 18.0 plus minus 3.4 mg/d, p < 0.001) and prevented death significantly. Vascular injury was ameliorated in small renal and cardiac vessels. PDTC inhibited NF-{kappa}B binding activity in heart and kidney. Immunohistochemical analysis shows increased expression of the p65 NF-{kappa}B subunit in the endothelium, smooth muscles cells of damaged small vessels, infiltrated cells, glomeruli, tubuli and collecting ducts of dTGR. PDTC markedly reduced the immunoreactivity of p65. CONCLUSION: Our data show that inhibition of NF-{kappa}B by PDTC markedly reduces inflammation, iNOS expression in the dTGR most likely leading to decreased cytotoxicity, and cell proliferation. Thus, NF-{kappa}B activation plays an important role in ANG II-induced end-organ damage
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The intensification of metallic layered phenomena above thunderstorms through the modulation of atmospheric tides
We present a multi-instrument experiment to study the effects of tropospheric thunderstorms on the mesopause region and the lower ionosphere. Sodium (Na) lidar and ionospheric observations by two digital ionospheric sounders are used to study the variation in the neutral metal atoms and metallic ions above thunderstorms. An enhanced ionospheric sporadic E layer with a downward tidal phase is observed followed by a subsequent intensification of neutral Na number density with an increase of 600 cm−3 in the mesosphere. In addition, the Na neutral chemistry and ion-molecule chemistry are considered in a Na chemistry model to simulate the dynamical and chemical coupling processes in the mesosphere and ionosphere above thunderstorms. The enhanced Na layer in the simulation obtained by using the ionospheric observation as input is in agreement with the Na lidar observation. We find that the intensification of metallic layered phenomena above thunderstorms is associated with the atmospheric tides, as a result of the troposphere-mesosphere-ionosphere coupling
Evolution of cooperation driven by zealots
Recent experimental results with humans involved in social dilemma games
suggest that cooperation may be a contagious phenomenon and that the selection
pressure operating on evolutionary dynamics (i.e., mimicry) is relatively weak.
I propose an evolutionary dynamics model that links these experimental findings
and evolution of cooperation. By assuming a small fraction of (imperfect)
zealous cooperators, I show that a large fraction of cooperation emerges in
evolutionary dynamics of social dilemma games. Even if defection is more
lucrative than cooperation for most individuals, they often mimic cooperation
of fellows unless the selection pressure is very strong. Then, zealous
cooperators can transform the population to be even fully cooperative under
standard evolutionary dynamics.Comment: 5 figure
Solar science with the Atacama Large Millimeter/submillimeter Array - A new view of our Sun
The Atacama Large Millimeter/submillimeter Array (ALMA) is a new powerful
tool for observing the Sun at high spatial, temporal, and spectral resolution.
These capabilities can address a broad range of fundamental scientific
questions in solar physics. The radiation observed by ALMA originates mostly
from the chromosphere - a complex and dynamic region between the photosphere
and corona, which plays a crucial role in the transport of energy and matter
and, ultimately, the heating of the outer layers of the solar atmosphere. Based
on first solar test observations, strategies for regular solar campaigns are
currently being developed. State-of-the-art numerical simulations of the solar
atmosphere and modeling of instrumental effects can help constrain and optimize
future observing modes for ALMA. Here we present a short technical description
of ALMA and an overview of past efforts and future possibilities for solar
observations at submillimeter and millimeter wavelengths. In addition, selected
numerical simulations and observations at other wavelengths demonstrate ALMA's
scientific potential for studying the Sun for a large range of science cases.Comment: 73 pages, 21 figures ; Space Science Reviews (accepted December 10th,
2015); accepted versio
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Co-occurrences of substance use and other potentially addictive behaviors: epidemiological results from the Psychological and Genetic Factors of the Addictive Behaviors (PGA) Study
Background and aims: Changes in the nomenclature of addictions suggest a significant shift in the conceptualization of addictions, where non-substance related behaviors can also be classified as addictions. A large amount of data provides empirical evidence that there are overlaps of different types of addictive behaviors in etiology, phenomenology, and in the underlying psychological and biological mechanisms. Our aim was to investigate the co-occurrences of a wide range of substance use and behavioral addictions.
Methods: The present epidemiological analysis was carried out as part of the Psychological and Genetic Factors of the Addictive Behaviors (PGA) Study, where data were collected from 3,003 adolescents and young adults (42.6% males; mean age 21 years). Addictions to psychoactive substances and behaviors were rigorously assessed.
Results: Data is provided on lifetime occurrences of the assessed substance uses, their co-occurrences, the prevalence estimates of specific behavioral addictions , and co-occurrences of different substance use and potentially addictive behaviors. Associations were found between (i) smoking and problematic Internet use, exercising, eating disorders, and gambling (ii) alcohol consumption and problematic Internet use, problematic online gaming, gambling, and eating disorders, and (iii) cannabis use and problematic online gaming and gambling.
Conclusions: The results suggest a large overlap between the occurrence of these addictions and behaviors and underlies the importance of investigating the possible common psychological, genetic and neural pathways. These data further support concepts such as the Reward Deficiency Syndrome and the component model of addictions that propose a common phenomenological and etiological background of different addictive and related behaviors
An Overview of the 2014 ALMA Long Baseline Campaign
A major goal of the Atacama Large Millimeter/submillimeter Array (ALMA) is to
make accurate images with resolutions of tens of milliarcseconds, which at
submillimeter (submm) wavelengths requires baselines up to ~15 km. To develop
and test this capability, a Long Baseline Campaign (LBC) was carried out from
September to late November 2014, culminating in end-to-end observations,
calibrations, and imaging of selected Science Verification (SV) targets. This
paper presents an overview of the campaign and its main results, including an
investigation of the short-term coherence properties and systematic phase
errors over the long baselines at the ALMA site, a summary of the SV targets
and observations, and recommendations for science observing strategies at long
baselines. Deep ALMA images of the quasar 3C138 at 97 and 241 GHz are also
compared to VLA 43 GHz results, demonstrating an agreement at a level of a few
percent. As a result of the extensive program of LBC testing, the highly
successful SV imaging at long baselines achieved angular resolutions as fine as
19 mas at ~350 GHz. Observing with ALMA on baselines of up to 15 km is now
possible, and opens up new parameter space for submm astronomy.Comment: 11 pages, 7 figures, 2 tables; accepted for publication in the
Astrophysical Journal Letters; this version with small changes to
affiliation
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