A regioselectivity switch in Pd-catalyzed hydroallylation of alkynes.

By exploiting the reactivity of a vinyl-Pd species, we control the regioselectivity in hydroallylation of alkynes under Pd-hydride catalysis. A monophosphine ligand and carboxylic acid combination promotes 1,5-dienes through a pathway involving isomerization of alkynes to allenes. In contrast, a bisphosphine ligand and copper cocatalyst favor 1,4-dienes via a mechanism that involves transmetalation. Our study highlights how to access different isomers by diverting a common organometallic intermediate

Design of a New Cascade Reaction for the Construction of Complex Acyclic Architecture: The Tandem Acyl-Claisen Rearrangement

Tandem or domino reactions have long been established as powerful chemical tools for the rapid formation of complex cyclic and polycyclic architecture. Surprisingly, however, relatively few tandem strategies have been directed toward the production of acyclic structural motifs despite significant advances in the area of acyclic stereocontrol. In our recent study, we reported the development of the acyl-Claisen rearrangement, a catalytic [3,3]-bond reorganization that allows the stereoselective synthesis of α,β-disubstituted-γ,δ-unsaturated carbonyls. In this communication, we outline the development of the tandem acyl-Claisen reaction, a highly stereoselective three-component coupling that enables the rapid construction of complex acyclic systems in the context of 2,3,6-trisubstituted-1,7-dioxoheptane architecture (eq 1). This versatile cascade sequence is conducted by using simple allyl diamines and acid chlorides, chemicals that are widely available in a diverse range of structural formats. As such, we expect this tandem reaction to be of broad utility to a number of chemical fields that employ molecule construction including natural product and parallel medicinal agent synthesis

Azimuthal anisotropy in Au+Au collisions at sqrtsNN = 200 GeV

The results from the STAR Collaboration on directed flow (v_1), elliptic flow (v_2), and the fourth harmonic (v_4) in the anisotropic azimuthal distribution of particles from Au+Au collisions at sqrtsNN = 200 GeV are summarized and compared with results from other experiments and theoretical models. Results for identified particles are presented and fit with a Blast Wave model. Different anisotropic flow analysis methods are compared and nonflow effects are extracted from the data. For v_2, scaling with the number of constituent quarks and parton coalescence is discussed. For v_4, scaling with v_2^2 and quark coalescence is discussed.Comment: 26 pages. As accepted by Phys. Rev. C. Text rearranged, figures modified, but data the same. However, in Fig. 35 the hydro calculations are corrected in this version. The data tables are available at http://www.star.bnl.gov/central/publications/ by searching for "flow" and then this pape

Azimuthal anisotropy and correlations at large transverse momenta in p+pp+p and Au+Au collisions at sNN\sqrt{s_{_{NN}}}= 200 GeV

Results on high transverse momentum charged particle emission with respect to the reaction plane are presented for Au+Au collisions at $\sqrt{s_{_{NN}}}$= 200 GeV. Two- and four-particle correlations results are presented as well as a comparison of azimuthal correlations in Au+Au collisions to those in $p+p$ at the same energy. Elliptic anisotropy, $v_2$, is found to reach its maximum at $p_t \sim 3$ GeV/c, then decrease slowly and remain significant up to $p_t\approx 7$ -- 10 GeV/c. Stronger suppression is found in the back-to-back high-$p_t$ particle correlations for particles emitted out-of-plane compared to those emitted in-plane. The centrality dependence of $v_2$ at intermediate $p_t$ is compared to simple models based on jet quenching.Comment: 4 figures. Published version as PRL 93, 252301 (2004

Coronary computed tomography angiography investigation of the association between left main coronary artery bifurcation angle and risk factors of coronary artery disease

To explore the association between the left main coronary artery bifurcation angle and common atherosclerotic risk factors with regard to the development of coronary artery disease (CAD) using coronary computed tomography angiography (CCTA). A retrospective review of 196 CCTA cases (129 males, 67 females, mean age 58 ± 10.5 years) was conducted. The bifurcation angle between the left anterior descending (LAD) and left circumflex (LCx) was measured on two-dimensional (2D) and three-dimensional (3D) reconstructed images and the type of plaque and degree of lumen stenosis was assessed to determine the disease severity. An association between bifurcation angle and patient risk factors [gender, body mass index (BMI), hypertension, cholesterol, diabetes, smoking and family history] of CAD was also assessed to demonstrate the relationship between these variables. The mean bifurcation angle between the LAD and LCx was 79.40° ± 22.97°, ranging from 35.5° to 178°. Gender and BMI were found to have significant associations with bifurcation angle. Males were at 2.07-fold greater risk of having a >80° bifurcation angle and developing CAD than females (P = 0.003), and patients with high BMI (>25 kg/m2) were 2.54-fold more likely to have a >80° bifurcation angle than patients with a normal BMI (P = 0.001) and thus were at greater risk of developing CAD. There is a direct relationship between the left main coronary artery bifurcation angle and patient gender and BMI. Measurement of the bifurcation angle should be incorporated into clinical practice to identify patients at high risk of developing CAD

A diverse view of science to catalyse change:Valuing diversity leads to scientific excellence, the progress of science and, most importantly, it is simply the right thing to do. we must value diversity not only in words, but also in actions

No abstract available.publishe

A diverse view of science to catalyse change

Valuing diversity leads to scientific excellence, the progress of science and, most importantly, it is simply the right thing to do. We must value diversity not only in words, but also in actions

Step by step: reconstruction of terrestrial animal movement paths by dead-reckoning

Background: Research on wild animal ecology is increasingly employing GPS telemetry in order to determine animal movement. However, GPS systems record position intermittently, providing no information on latent position or track tortuosity. High frequency GPS have high power requirements, which necessitates large batteries (often effectively precluding their use on small animals) or reduced deployment duration. Dead-reckoning is an alternative approach which has the potential to ‘fill in the gaps’ between less resolute forms of telemetry without incurring the power costs. However, although this method has been used in aquatic environments, no explicit demonstration of terrestrial dead-reckoning has been presented.Results: We perform a simple validation experiment to assess the rate of error accumulation in terrestrial dead-reckoning. In addition, examples of successful implementation of dead-reckoning are given using data from the domestic dog Canus lupus, horse Equus ferus, cow Bos taurus and wild badger Meles meles.Conclusions: This study documents how terrestrial dead-reckoning can be undertaken, describing derivation of heading from tri-axial accelerometer and tri-axial magnetometer data, correction for hard and soft iron distortions on the magnetometer output, and presenting a novel correction procedure to marry dead-reckoned paths to ground-truthed positions. This study is the first explicit demonstration of terrestrial dead-reckoning, which provides a workable method of deriving the paths of animals on a step-by-step scale. The wider implications of this method for the understanding of animal movement ecology are discussed