Brookhaven College

About: Brookhaven College is a education organization based out in Farmers Branch, Texas, United States. It is known for research contribution in the topics: Catalysis & Beam (structure). The organization has 1331 authors who have published 950 publications receiving 19400 citations.

Overlapping neuronal circuits in addiction and obesity: evidence of systems pathology

Abstract: Drugs and food exert their reinforcing effects in part by increasing dopamine (DA) in limbic regions, which has generated interest in understanding how drug abuse/addiction relates to obesity. Here, we integrate findings from positron emission tomography imaging studies on DA's role in drug abuse/addiction and in obesity and propose a common model for these two conditions. Both in abuse/addiction and in obesity, there is an enhanced value of one type of reinforcer (drugs and food, respectively) at the expense of other reinforcers, which is a consequence of conditioned learning and resetting of reward thresholds secondary to repeated stimulation by drugs (abuse/addiction) and by large quantities of palatable food (obesity) in vulnerable individuals (i.e. genetic factors). In this model, during exposure to the reinforcer or to conditioned cues, the expected reward (processed by memory circuits) overactivates the reward and motivation circuits while inhibiting the cognitive control circuit, resulting in an inability to inhibit the drive to consume the drug or food despite attempts to do so. These neuronal circuits, which are modulated by DA, interact with one another so that disruption in one circuit can be buffered by another, which highlights the need of multiprong approaches in the treatment of addiction and obesity.

A new intermolecular interaction: unconventional hydrogen bonds with element-hydride bonds as proton acceptor.

Abstract: This Account describes a new type of intermolecular interaction, the H‚‚‚H or dihydrogen bond, which operates between a conventional hydrogen bond donor such as an NH or OH bond as the weak acid component and an element-hydride bond as the weak base component, where the element in question can be a transition metal or boron. The interaction, which involves a close approach of protonic and hydridic hydrogens, has been characterized by crystallography, including neutron diffraction, and by physical and theoretical methods. These interactions occur in the so-called second or outer coordination sphere of a metal complex, as distinct from the first or inner sphere of the ligands directly bound to the metal. Taube1 has drawn attention to the importance of the outer solvent sphere in certain electron transfer processes, but otherwise very little is known about the structure and energetics of the outer sphere, and little attention2 has been given to the possibility of its control and organization. By selectively stabilizing the transition state, such interactions might be capable of accelerating specific reactions and so provide a general strategy with useful applications in catalysis. Conventional hydrogen bonds are formed between a proton donor, such as an OH or NH group, and a proton acceptor, such as an oxygen or nitrogen lone pair,3 but in all such cases a nonbonding electron pair acts as the weak base component. In rare cases, π-bonds4 and even metal atoms in metal complexes5 have also been shown to act as weak proton acceptors. A wide variety of element-hydrogen σ bonds, such as B-H and M-H (M ) transition metal), act as unexpectedly efficient hydrogen bond acceptors toward conventional proton donors, such as O-H and N-H groups. The resulting E-H‚‚‚H-X systems have close H‚‚‚H contacts (1.75-1.9 Å) and they have therefore been termed “H‚‚‚H or dihydrogen bonds”.6 Their heats of interaction are substantial (3-7 kcal mol-1) and lie in the range found for conventional H-bonds. Both interand intramolecular versions have been identified, and a number of reactions involving these new H-bonds have also been found. A significant feature of the work has been the close cooperation among synthetic, physical, crystallographic, and theoretical approaches.

Light Harvesting and Utilization by Phytoplankton

Abstract: Application d'un modele theorique a l'analyse des relations photosynthese-irradiance chez 3 especes marines phytoplanctoniques

Electroweak radiative corrections to tau decay.

Abstract: An analysis of electroweak radiative corrections to \ensuremath{\tau} decays is presented. Precise predictions for leptonic and some hadronic decay rates are given. The total hadronic decay width is shown to be relatively enhanced by 2.36% due mainly to short-distance loop effects. Implications for the extraction of ${\ensuremath{\Lambda}}_{\mathrm{MS}\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}$ from the \ensuremath{\tau} lifetime or leptonic branching ratios are discussed. (MS\ifmmode\bar\else\textasciimacron\fi{} denotes the modified minimal-subtraction scheme.)