3,882 research outputs found
A Mechanistic Study of Hydroboration of 1-Octene with 1,3,2-Dithiaborolane and 1,3,2-Dithiaborinane. Part 1. Synthesis and Kinetic Studies
Alkylthioboranes 1,3,2-dithiaborolane and 1,3,2-dithiaborinane have been synthesized from the reaction of BH3·SMe2 with 1,2-ethanedithiol and 1,3-propanedithiol, respectively. These heterocyclic boranes disproportionated significantly during their synthesis. The rate constants, and the enthalpies and entropies of the hydroboration reaction of 1-octene with 1,3,2-dithiaborolane and 1,3,2-dithiaborinane have been investigated, and we have shown that hydroboration with these boranes is slow and proceeds via an associative mechanism.Keywords: Hydroboration, disproportionation, boranes, transition statesPDF and Supplementry file attache
A Mechanistic Study of Hydroboration of 1-Octene with 1,3,2-Dithiaborolane and 1,3,2-Dithiaborinane. Part 2. A DFT Study of Disproportionation and Hydroboration
The hydroboration reactions of propene with 1,3,2-dithiaborolane and 1,3,2-dithiaborinane in their ground states have been studied using density functional theory (DFT) at the B3LYP/3-21+G and B3LYP/6-31+G(d) levels. Hydroboration and disproportionation transition states have been determined and activation energies for these transition states were compared. It has been shown that hydroboration reactions require slightly higher activation energies than disproportionation, and yield thermodynamically more stable products.Keywords: Hydroboration, disproportionation, DFT, transition states, potential energy surfacePDF and Supplementry file attache
Localization of the human dihydrolipoamide dehydrogenase gene (DLD) to 7q31→q32
The gene for human dihydrolipoamide dehydrogenase (DLD) has been localized to the long arm of chromosome 7, within bands q31→q32, by gel-blot hybridization analysis with DNA from a panel of somatic cell hybrids containing various portions of human chromosome 7.published_or_final_versio
Predicting the behaviour of near-critical and supercritical alcohols at microwave frequencies: Validation of molecular dynamic simulations as a tool that can substitute for measurements under extreme experimental conditions
Equilibrium and non-equilibrium molecular dynamic simulations, predicting the dielectric properties of near-critical and supercritical methanol and ethanol at microwave frequencies have been carried out. The autocorrelation functions of the dielectric relaxation, show dependency on the slow component at the near-critical region for both alcohols. At the supercritical region, two competing relaxation mechanisms are observed, related to the large breakdown of the hydrogen-bonding network and the degree of clustering between the molecules. This approach closely matches experimental data at microwave frequencies and identical temperature and pressure conditions, validating the predictions of how the molecular structure and dynamics manifest themselves into the complex permittivity and dielectric relaxation behaviour. Thus, introducing a modelling-based solution to deliver accurate dielectric property values for materials at supercritical conditions for “a priori” screening of solvents, whilst removing the need to overcome engineering and safety challenges associated with the development of experimental equipment to practically generate such data
Combining Multicolor FISH with Fluorescence Lifetime Imaging for Chromosomal Identification and Chromosomal Sub Structure Investigation
Understanding the structure of chromatin in chromosomes during normal and diseased state of cells is still one of the key challenges in structural biology. Using DAPI staining alone together with Fluorescence lifetime imaging (FLIM), the environment of chromatin in chromosomes can be explored. Fluorescence lifetime can be used to probe the environment of a fluorophore such as energy transfer, pH and viscosity. Multicolor FISH (M-FISH) is a technique that allows individual chromosome identification, classification as well as assessment of the entire genome. Here we describe a combined approach using DAPI as a DNA environment sensor together with FLIM and M-FISH to understand the nanometer structure of all 46 chromosomes in the nucleus covering the entire human genome at the single cell level. Upon DAPI binding to DNA minor groove followed by fluorescence lifetime measurement and imaging by multiphoton excitation, structural differences in the chromosomes can be studied and observed. This manuscript provides a blow by blow account of the protocol required to perform M-FISH-FLIM of whole chromosomes
Entanglement generation outside a Schwarzschild black hole and the Hawking effect
We examine the Hawking effect by studying the asymptotic entanglement of two
mutually independent two-level atoms placed at a fixed radial distance outside
a Schwarzschild black hole in the framework of open quantum systems. We treat
the two-atom system as an open quantum system in a bath of fluctuating
quantized massless scalar fields in vacuum and calculate the concurrence, a
measurement of entanglement, of the equilibrium state of the system at large
times, for the Unruh, Hartle-Hawking and Boulware vacua respectively. We find,
for all three vacuum cases, that the atoms turn out to be entangled even if
they are initially in a separable state as long as the system is not placed
right at the even horizon. Remarkably, only in the Unruh vacuum, will the
asymptotic entanglement be affected by the backscattering of the thermal
radiation off the space-time curvature. The effect of the back scatterings on
the asymptotic entanglement cancels in the Hartle-Hawking vacuum case.Comment: 15 pages, no figures, Revte
Black Holes in Modified Gravity (MOG)
The field equations for Scalar-Tensor-Vector-Gravity (STVG) or modified
gravity (MOG) have a static, spherically symmetric black hole solution
determined by the mass with two horizons. The strength of the gravitational
constant is where is a parameter. A regular
singularity-free MOG solution is derived using a nonlinear field dynamics for
the repulsive gravitational field component and a reasonable physical
energy-momentum tensor. The Kruskal-Szekeres completion of the MOG black hole
solution is obtained. The Kerr-MOG black hole solution is determined by the
mass , the parameter and the spin angular momentum . The
equations of motion and the stability condition of a test particle orbiting the
MOG black hole are derived, and the radius of the black hole photosphere and
the shadows cast by the Schwarzschild-MOG and Kerr-MOG black holes are
calculated. A traversable wormhole solution is constructed with a throat
stabilized by the repulsive component of the gravitational field.Comment: 14 pages, 3 figures. Upgraded version of paper to match published
version in European Physics Journal
Topology of supersymmetric N=1, D=4 supergravity horizons
All supersymmetric N=1, D=4 supergravity horizons have toroidal or spherical
topology, irrespective of whether the black hole preserves any supersymmetry.Comment: 17 pages, latex. Alterations to introduction and section 3.
The dynamics of apparent horizons in Robinson-Trautman spacetimes
We present an alternative scheme of finding apparent horizons based on
spectral methods applied to Robinson-Trautman spacetimes. We have considered
distinct initial data such as representing the spheroids of matter and the
head-on collision of two non-rotating black holes. The evolution of the
apparent horizon is presented. We have obtained in some cases a mass gap
between the final Bondi and apparent horizon masses, whose implications were
briefly commented in the light of the thermodynamics of black holes.Comment: 9 pages, 7 figure
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