1,490 research outputs found
An associated partial skeleton of Jainosaurus cf. septentrionalis (Dinosauria: Sauropoda) from the Late Cretaceous of Chhota Simla, Central India
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86940/1/j.1475-4983.2011.01087.x.pd
An Interview on Leadership with Al Carey, CEO, PepsiCo Beverages
Paul T. Barrett, PhD, CPA, is dean and professor of business for the College of Business and Economics, Longwood University, Farmville, VA 23909.
James C. Haug, DBA, is associate professor of management, Longwood University, College of Business and Economics, Farmville, VA 23909.
John N. Gaskins, PhD, currently serves as associate professor of marketing and retailing, Longwood University, College of Business and Economics, Farmville, VA 23909
Spontaneous Transfer Of Chirality In An Atropisomerically Enriched Two-Axis System
One of the most well-recognized stereogenic elements in a chiral molecule is an sp(3)-hybridized carbon atom that is connected to four different substituents. Axes of chirality can also exist about bonds with hindered barriers of rotation; molecules containing such axes are known as atropisomers(1). Understanding the dynamics of these systems can be useful, for example, in the design of single-atropisomer drugs(2) or molecular switches and motors(3). For molecules that exhibit a single axis of chirality, rotation about that axis leads to racemization as the system reaches equilibrium. Here we report a two-axis system for which an enantioselective reaction produces four stereoisomers (two enantiomeric pairs): following a catalytic asymmetric transformation, we observe a kinetically controlled product distribution that is perturbed from the system\u27s equilibrium position. As the system undergoes isomerization, one of the diastereomeric pairs drifts spontaneously to a higher enantiomeric ratio. In a compensatory manner, the enantiomeric ratio of the other diastereomeric pair decreases. These observations are made for a class of unsymmetrical amides that exhibits two asymmetric axes-one axis is defined through a benzamide substructure, and the other axis is associated with differentially N,N-disubstituted amides. The stereodynamics of these substrates provides an opportunity to observe a curious interplay of kinetics and thermodynamics intrinsic to a system of stereoisomers that is constrained to a situation of partial equilibrium
Estimation of cortical magnification from positional error in normally sighted and amblyopic subjects
yesWe describe a method for deriving the linear cortical
magnification factor from positional error across the
visual field. We compared magnification obtained from
this method between normally sighted individuals and
amblyopic individuals, who receive atypical visual input
during development. The cortical magnification factor
was derived for each subject from positional error at
32 locations in the visual field, using an established
model of conformal mapping between retinal and
cortical coordinates. Magnification of the normally
sighted group matched estimates from previous
physiological and neuroimaging studies in humans,
confirming the validity of the approach. The estimate
of magnification for the amblyopic group was
significantly lower than the normal group: by 4.4 mm
deg 1 at 18 eccentricity, assuming a constant scaling
factor for both groups. These estimates, if correct,
suggest a role for early visual experience in establishing
retinotopic mapping in cortex. We discuss the
implications of altered cortical magnification for
cortical size, and consider other neural changes that
may account for the amblyopic results
A temperate palaeodiversity peak in Mesozoic dinosaurs and evidence for Late Cretaceous geographical partitioning
Aimâ Modern biodiversity peaks in the tropics and declines poleward, a pattern that is potentially driven by climate. Although this latitudinal biodiversity gradient (LBG) also characterizes the marine invertebrate fossil record, distributions of ancient terrestrial faunas are poorly understood. This study utilizes data on the dinosaur fossil record to examine spatial patterns in terrestrial biodiversity throughout the Mesozoic.\ud
Locationâ We compiled data on fossil occurrences across the globe.\ud
Methodsâ We compiled a comprehensive dataset of Mesozoic dinosaur genera (738), including birds. Following the utilization of sampling standardization techniques to mediate for the uneven sampling of the fossil record, we constructed latitudinal patterns of biodiversity from this dataset.\ud
Resultsâ The dominant group of Mesozoic terrestrial vertebrates did not conform to the modern LBG. Instead, dinosaur diversity was highest at temperate palaeolatitudes throughout the 160 million year span of dinosaurian evolutionary history. Latitudinal diversity correlates strongly with the distribution of land area. Late Cretaceous sauropods and ornithischians exhibit disparate LBGs.\ud
Main conclusionsâ The continuity of the palaeotemperate peak in dinosaur diversity indicates a diminished role for climate on the Mesozoic LBG; instead, dinosaur diversity may have been driven by the amount of land area among latitudinal belts. There is no evidence that the tropics acted as a cradle for dinosaur diversity. Geographical partitioning among major clades of herbivorous dinosaurs in the Late Cretaceous may result from the advanced stages of continental fragmentation and/or differing responses to increasing latitudinal climatic zonation. Our results suggest that the modern-day LBG on land was only established 30 million years ago, following a significant post-Eocene recalibration, potentially related to increased seasonality
Pseudospectral Calculation of the Wavefunction of Helium and the Negative Hydrogen Ion
We study the numerical solution of the non-relativistic Schr\"{o}dinger
equation for two-electron atoms in ground and excited S-states using
pseudospectral (PS) methods of calculation. The calculation achieves
convergence rates for the energy, Cauchy error in the wavefunction, and
variance in local energy that are exponentially fast for all practical
purposes. The method requires three separate subdomains to handle the
wavefunction's cusp-like behavior near the two-particle coalescences. The use
of three subdomains is essential to maintaining exponential convergence. A
comparison of several different treatments of the cusps and the semi-infinite
domain suggest that the simplest prescription is sufficient. For many purposes
it proves unnecessary to handle the logarithmic behavior near the
three-particle coalescence in a special way. The PS method has many virtues: no
explicit assumptions need be made about the asymptotic behavior of the
wavefunction near cusps or at large distances, the local energy is exactly
equal to the calculated global energy at all collocation points, local errors
go down everywhere with increasing resolution, the effective basis using
Chebyshev polynomials is complete and simple, and the method is easily
extensible to other bound states. This study serves as a proof-of-principle of
the method for more general two- and possibly three-electron applications.Comment: 23 pages, 20 figures, 2 tables, Final refereed version - Some
references added, some stylistic changes, added paragraph to matrix methods
section, added last sentence to abstract
A Far Ultraviolet Study of the Nova-like V794 Aquilae
We present a spectral analysis of the dereddened FUSE and HST/STIS spectra
separately and combined together assuming E(B-V)=0.1 & 0.2. Overall, we find
that the model fits are in much better agreement with the dereddened spectra
when E(B-V) is large, as excess emission in the longer wavelengths render the
slope of the observed spectra almost impossible to fit, unless E(B-V)=0.2 .
The best fit accretion disk model is obtained for E(B-V)=0.2 . A single white
dwarf model leads to a rather hot temperature (30,000K < Twd < 55,000K
depending on the assumptions) but does not provide a fit as good as the
accretion disk model. A combination of a white dwarf plus a disk does not lead
to a better fit. The same best fit disk model is consistently obtained when
fitting the FUSE and HST/STIS spectra individually and when combined together,
implying therefore that the disk model is the best fit not only in the least
chi2 sense, but also as a consistent solution across a large wavelength span of
observation. This is not the case with the single white dwarf model fitting
which leads to a different (and therefore inconsistent) temperature for each
different spectrum FUSE, STIS and FUSE+STIS
A randomised controlled trial of cognitive behavioural treatment for obsessive compulsive disorder in children and adolescents
Cognitive behaviour therapy (CBT) for young people with obsessive compulsive disorder (OCD) has become the treatment of first choice. However, the literature is largely based on studies emphasising exposure and response prevention. In this study, we report on a randomised controlled trial of CBT for young people carried out in typical outpatient clinic conditions which focused on cognitions. A randomised controlled trial compares 10 sessions of manualised cognitive behavioural treatment with a 12-week waiting list for adolescents and children with OCD. Assessors were blind to treatment allocation. 21 consecutive patients with OCD aged between 9 and 18 years were recruited. The group who received treatment improved more than a comparison group who waited for 3 months. The second group was treated subsequently using the same protocol and made similar gains. In conclusion, CBT can be delivered effectively to young people with OCD in typical outpatient settings
Deterministic delivery of externally cold and precisely positioned single molecular ions
We present the preparation and deterministic delivery of a selectable number
of externally cold molecular ions. A laser cooled ensemble of Mg^+ ions
subsequently confined in several linear Paul traps inter-connected via a
quadrupole guide serves as a cold bath for a single or up to a few hundred
molecular ions. Sympathetic cooling embeds the molecular ions in the
crystalline structure. MgH^+ ions, that serve as a model system for a large
variety of other possible molecular ions, are cooled down close to the Doppler
limit and are positioned with an accuracy of one micrometer. After the
production process, severely compromising the vacuum conditions, the molecular
ion is efficiently transfered into nearly background-free environment. The
transfer of a molecular ion between different traps as well as the control of
the molecular ions in the traps is demonstrated. Schemes, optimized for the
transfer of a specific number of ions, are realized and their efficiencies are
evaluated. This versatile source applicable for broad charge-to-mass ratios of
externally cold and precisely positioned molecular ions can serve as a
container-free target preparation device well suited for diffraction or
spectroscopic measurements on individual molecular ions at high repetition
rates (kHz).Comment: 11 pages, 8 figure
The polyAT, intronic IVS11-6 and Lys939Gln XPC polymorphisms are not associated with transitional cell carcinoma of the bladder
Chemical carcinogens from cigarette smoking and occupational exposure are risk factors for bladder transitional cell carcinoma (TCC). The Xeroderma Pigmentosum Group C (XPC) gene is essential for repair of bulky adducts from carcinogens. The Xeroderma Pigmentosum Group C gene polymorphisms may alter DNA repair capacity (DRC), thus giving rise to genetic predisposition to bladder cancer. Recent studies have demonstrated linkage disequilibrium between three polymorphisms in the XPC gene (polyAT, IVS11-6 and Lys939Gln) and these have been shown to influence the DRC, as well as to be associated with bladder cancer risk. We analysed all three XPC polymorphisms in 547 bladder TCC patients and 579 cancer-free controls to investigate the association between these polymorphisms and bladder cancer susceptibility, and we also attempted to assess geneâenvironmental interactions. We confirmed strong linkage disequilibrium among the polymorphisms (Lewontin's DâČ>0.99). Using logistic regression adjusting for smoking, occupational and family history, neither the heterozygote nor the homozygote variants of these polymorphisms were associated with increased bladder cancer risk (adjusted odds ratio [95% confidence interval] for heterozygote 0.82 [0.63â1.07], 0.82 [0.63â1.08] and 0.83 [0.63â1.08] for PolyAT, IVS11-6 and Lys939Gln, respectively and homozygote variant, 0.98 [0.68â1.42], 0.99 [0.69â1.43] and 1.01 [0.70â1.46]). Moreover, we did not find any significant interaction between these XPC polymorphisms and environmental exposure to cigarette smoking and occupational carcinogens
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