835 research outputs found
Excited electronic states of MnO4−:Challenges for wavefunction and density functional response theories
AbstractThe lowest excited electronic states of the permanganate ion MnO4− are calculated using a hierarchy of coupled cluster response approaches, as well as time-dependent density functional theory. It is shown that while full linear response coupled cluster with singles and doubles (or higher) performs well, that permanganate represents a stern test for approximate coupled cluster response models, and that problems can be traced to very large orbital relaxation effects. TD-DFT is reasonably robust although errors around 0.6eV are still observed. In order to further investigate the strong correlations prevalent in the electronic ground state large-scale RASSCF calculations were also performed. Again very large orbital relaxation in the correlated wavefunction is observed. Although the system can qualitatively be described by a single configuration, multi-reference diagnostic values show that care must be taken in this and similar metal complexes
Germ-Line Gene Editing and Congressional Reaction in Context: Learning From Almost 50 Years of Congressional Reactions to Biomedical Breakthroughs
On December 18, 2015, President Obama signed into law a policy rider forestalling the therapeutic modification of the human germ line. The rider, motivated by the science’s potential unethical ends, is only the most recent instance in which the legislature cut short the ongoing national conversation on the acceptability of a developing science. This essay offers historical perspective on what bills were proposed and passed surrounding four other then-developing scientific breakthroughs—Recombinant DNA, in vitro fertilization, Cloning, Stem Cells—to better analyze how Congress is, and should, regulate this exciting and promising science
Dilution effects on magnesium efflux from the rumen
Factors affecting magnesium absorption from the rumen are integrally
involved in grass tetany because most of the absorbed Mg passes through
the rumen wall. Recent work has shown that ruminal Mg absorption occurs
by a sodium-linked active transport following saturation kinetics. The dilution
effects on Mg absorption were evaluated by a dynamic simulation of Mg
flow in the rumen. As several factors in the rumen influence Mg availability,
a simple rumen submodel was developed to predict rumen parameters (fiber
content, microbial mass, liquid dilution rate, particulate passage rate) for
different conditions. Cation-exchange capacity of fiber and the microbial
mass as well as insoluble Mg complex formation reduce the available Mg
pool for absorption in the model. Preliminary results for 500 kg cattle grazing
crested wheatgrass (DMI = 1.2 % BW / day), indicate that efficiency of
magnesium absorption from the rumen was greatly affected by liquid dilution
rate. Without considering insoluble Mg precipitate formation, the efficiency
of Mg absorption from the rumen ranged from .41 to .31 as the rumen liquid
fractional passage rate varied from .08/h to .14/h. Factors affecting the
rumen liquid dilution rate include rumen water holding capacity, saliva
secretion, rumen osmolarity, and water intake from drinking and eating.
Kinetic factors may be responsible for the poor efficiency of absorption of
Mg under conditions when rumen liquid dilution rates are high
Cabinet-Makers' Awareness and Usage of Rainforest Cabinet Timbers in Queensland
This paper reports findings of surveys into the usage of, and attitudes to, rainforest cabinet timbers by cabinet-makers in Queensland, Australia. In determining policies to promote growing of native rainforest trees on private land, it is necessary to know the market requirements for various cabinet species. The species most in demand by cabinet-makers are identified in this paper. Suitability and availability are found to be important determinants of cabinet-maker demand for timber. The species being planted in north Queensland are not a close match with those predicted by cabinet-makers to be in greatest demand in the future
Structural and biophysical characterization of bacillus thuringiensis insecticidal proteins Cry34Ab1 and Cry35Ab1
Bacillus thuringiensis strains are well known for the production of insecticidal proteins upon sporulation and these proteins are deposited in parasporal crystalline inclusions. The majority of these insect-specific toxins exhibit three domains in the mature toxin sequence. However, other Cry toxins are structurally and evolutionarily unrelated to this three-domain family and little is known of their three dimensional structures, limiting our understanding of their mechanisms of action and our ability to engineer the proteins to enhance their function. Among the non-three domain Cry toxins, the Cry34Ab1 and Cry35Ab1 proteins from B. thuringiensis strain PS149B1 are required to act together to produce toxicity to the western corn rootworm (WCR) Diabrotica virgifera virgifera Le Conte via a pore forming mechanism of action. Cry34Ab1 is a protein of ∼14 kDa with features of the aegerolysin family (Pfam06355) of proteins that have known membrane disrupting activity, while Cry35Ab1 is a ∼44 kDa member of the toxin_10 family (Pfam05431) that includes other insecticidal proteins such as the binary toxin BinA/BinB. The Cry34Ab1/Cry35Ab1 proteins represent an important seed trait technology having been developed as insect resistance traits in commercialized corn hybrids for control of WCR. The structures of Cry34Ab1 and Cry35Ab1 have been elucidated to 2.15 Å and 1.80 Å resolution, respectively. The solution structures of the toxins were further studied by small angle X-ray scattering and native electrospray ion mobility mass spectrometry. We present here the first published structure from the aegerolysin protein domain family and the structural comparisons of Cry34Ab1 and Cry35Ab1 with other pore forming toxins
Progressive transformation of a flux rope to an ICME
The solar wind conditions at one astronomical unit (AU) can be strongly
disturbed by the interplanetary coronal mass ejections (ICMEs). A subset,
called magnetic clouds (MCs), is formed by twisted flux ropes that transport an
important amount of magnetic flux and helicity which is released in CMEs. At 1
AU from the Sun, the magnetic structure of MCs is generally modeled neglecting
their expansion during the spacecraft crossing. However, in some cases, MCs
present a significant expansion. We present here an analysis of the huge and
significantly expanding MC observed by the Wind spacecraft during 9 and 10
November, 2004. After determining an approximated orientation for the flux rope
using the minimum variance method, we precise the orientation of the cloud axis
relating its front and rear magnetic discontinuities using a direct method.
This method takes into account the conservation of the azimuthal magnetic flux
between the in- and out-bound branches, and is valid for a finite impact
parameter (i.e., not necessarily a small distance between the spacecraft
trajectory and the cloud axis). Moreover, using the direct method, we find that
the ICME is formed by a flux rope (MC) followed by an extended coherent
magnetic region. These observations are interpreted considering the existence
of a previous larger flux rope, which partially reconnected with its
environment in the front. These findings imply that the ejected flux rope is
progressively peeled by reconnection and transformed to the observed ICME (with
a remnant flux rope in the front part).Comment: Solar Physics (in press
The Five Factor Model of personality and evaluation of drug consumption risk
The problem of evaluating an individual's risk of drug consumption and misuse
is highly important. An online survey methodology was employed to collect data
including Big Five personality traits (NEO-FFI-R), impulsivity (BIS-11),
sensation seeking (ImpSS), and demographic information. The data set contained
information on the consumption of 18 central nervous system psychoactive drugs.
Correlation analysis demonstrated the existence of groups of drugs with
strongly correlated consumption patterns. Three correlation pleiades were
identified, named by the central drug in the pleiade: ecstasy, heroin, and
benzodiazepines pleiades. An exhaustive search was performed to select the most
effective subset of input features and data mining methods to classify users
and non-users for each drug and pleiad. A number of classification methods were
employed (decision tree, random forest, -nearest neighbors, linear
discriminant analysis, Gaussian mixture, probability density function
estimation, logistic regression and na{\"i}ve Bayes) and the most effective
classifier was selected for each drug. The quality of classification was
surprisingly high with sensitivity and specificity (evaluated by leave-one-out
cross-validation) being greater than 70\% for almost all classification tasks.
The best results with sensitivity and specificity being greater than 75\% were
achieved for cannabis, crack, ecstasy, legal highs, LSD, and volatile substance
abuse (VSA).Comment: Significantly extended report with 67 pages, 27 tables, 21 figure
Homophily and Contagion Are Generically Confounded in Observational Social Network Studies
We consider processes on social networks that can potentially involve three
factors: homophily, or the formation of social ties due to matching individual
traits; social contagion, also known as social influence; and the causal effect
of an individual's covariates on their behavior or other measurable responses.
We show that, generically, all of these are confounded with each other.
Distinguishing them from one another requires strong assumptions on the
parametrization of the social process or on the adequacy of the covariates used
(or both). In particular we demonstrate, with simple examples, that asymmetries
in regression coefficients cannot identify causal effects, and that very simple
models of imitation (a form of social contagion) can produce substantial
correlations between an individual's enduring traits and their choices, even
when there is no intrinsic affinity between them. We also suggest some possible
constructive responses to these results.Comment: 27 pages, 9 figures. V2: Revised in response to referees. V3: Ditt
Dose-Ranging Effect of Adjunctive Oral Cannabidiol vs Placebo on Convulsive Seizure Frequency in Dravet Syndrome A Randomized Clinical Trial
Question Is adjunctive cannabidiol at doses of 10 and 20 mg/kg/d
superior to placebo in reducing convulsive seizure frequency in
patients with Dravet syndrome?
Findings This double-blind clinical trial randomized 199 children
with Dravet syndrome to cannabidiol (10 or 20 mg/kg/d) or
matched placebo for 14 weeks. Convulsive seizure frequency
compared with baseline was reduced by 48.7% in the 10-mg/kg/d
cannabidiol group and 45.7% in the 20-mg/kg/d cannabidiol
group vs 26.9% in the placebo group.
Meaning Both doses of adjunctive cannabidiol were similarly
efficacious in reducing convulsive seizures associated with Dravet
syndrome
- …