Decoherence in quantum dots due to real and virtual transitions: a non-perturbative calculation

We investigate theoretically acoustic phonon induced decoherence in quantum dots. We calculate the dephasing of fundamental (interband or intraband) optical transitions due to real and virtual transitions with higher energy levels. Up to two acoustic phonon processes (absorption and/or emission) are taken into account simultaneously in a non-perturbative manner. An analytic expression of acoustic phonon induced broadening is given as a function of the electron-phonon matrix elements and is physically interpreted. The theory is applied to the dephasing of intersublevel transitions in self-assembled quantum dots.Comment: 8 pages, 4 figure

Revisiting the Naturalness Problem -- Who is afraid of quadratic divergences? --

It is widely believed that quadratic divergences severely restrict natural constructions of particle physics models beyond the standard model (SM). Supersymmetry provides a beautiful solution, but the recent LHC experiments have excluded large parameter regions of supersymmetric extensions of the SM. It will now be important to reconsider whether we have been misinterpreting the quadratic divergences in field theories. In this paper, we revisit the problem from the viewpoint of the Wilsonian renormalization group and argue that quadratic divergences, which can always be absorbed into a position of the critical surface, should be simply subtracted in model constructions. Such a picture gives another justification to the argument that the scale invariance of the SM, except for the soft-breaking terms, is an alternative solution to the naturalness problem. It also largely broadens possibilities of model constructions beyond the SM since we just need to take care of logarithmic divergences, which cause mixings of various physical scales and runnings of couplings.Comment: 22 pages, 6 figures, version published in Phys. Rev.

Growth Mechanism of Helicoidal Nickel Whiskers

NICKEL whiskers obtained by reduction of the iodide of the metal can be classified into two categories : (i) rectilinear whiskers (ii) helicoidal whiskers In general, these whiskers are formed by a stacking of small idiomorphic crystals. The law governing such stackings was determined theoretically in a previous investigation .1,2 It was shown that they were formed from nickel iodide in fusion and that the theory of dendritic growth was quite true for rectilinear whiskers ; the axes of growth are of low indices ( , ---100> ) and the conditions required for dendritic growth as described by Papapetrou3 are fulfilled. Rectilinear whiskers without branches are obtained, because one of the directions of dendritic growth is favoured and the development takes place only in that direction. This paper presents a study of the growth mechanisms of helicoidal whiskers

Growth Mechanism of Helicoidal Nickel Whiskers

Nickel whiskers obtained by reduction of the iodide of the metal can be classified into two categories:- - Rectilinear whiskers - Spiral whiskers Rectilinear whiskers without branches are obtained because one of the directions of dendritic growth is favoured and the development takes place only in that direction

Efficacy of using life design-based counselling for an emerging adult who had suffered parental neglect

This article reports on the value of life design-based counselling for an emerging adult who had experienced parental (emotional) neglect and was now ready to embark on a career. Purposive sampling was used to select an emerging adult who had experienced parental neglect and had entered the workplace stage. Such research in South African education contexts is limited. A QUAL + quan design was used to gather and analyse the data. An intrinsic, descriptive, exploratory intervention case study involving a single individual was the basis of the research. Thematic data analysis (in combination with ATLAS.ti) was conducted to analyse the data, that is, look for themes and subthemes in the data. The intervention enhanced the participant’s career resilience and career adaptability. Exploring her life story for themes and patterns helped her gain new insight into the meaning of her experiences. The intervention enabled her to enter a new chapter in her life from a position of strength and an improved sense of self. Longitudinal studies on the long-term effects of life design-based interventions on groups of emerging adults who had experienced different kinds of parental neglect are needed to determine the longer-term value of the kind of intervention described in this article

C57BL/6 life span study: age-related declines in muscle power production and contractile velocity

Quantification of key outcome measures in animal models of aging is an important step preceding intervention testing. One such measurement, skeletal muscle power generation (force * velocity), is critical for dynamic movement. Prior research focused on maximum power (P max), which occurs around 30-40 % of maximum load. However, movement occurs over the entire load range. Thus, the primary purpose of this study was to determine the effect of age on power generation during concentric contractions in the extensor digitorum longus (EDL) and soleus muscles over the load range from 10 to 90 % of peak isometric tetanic force (P 0). Adult, old, and elderly male C57BL/6 mice were examined for contractile function (6-7 months old, 100 % survival; ~24 months, 75 %; and ~28 months, 50 % P 0). The shape of the force-velocity curve also changed with age (a/P 0 increased). In addition, there were prolonged contraction times to maximum force and shifts in the distribution of the myosin light and heavy chain isoforms in the EDL. The results demonstrate that age-associated difficulty in movement during challenging tasks is likely due, in addition to overall reduced force output, to an accelerated deterioration of power production and contractile velocity under heavily loaded conditions.R01 AG017768 - NIA NIH HHS; F31 AG044108 - NIA NIH HHS; T32 AG029796 - NIA NIH HHS; R01 EY15313 - NEI NIH HHS; R01 EY015313 - NEI NIH HH

Polaron relaxation in self-assembled quantum dots: Breakdown of the semi-classical model

We calculate the lifetime of conduction band excited states in self-assembled quantum dots by taking into account LO-phonon-electron interaction and various anharmonic phonon couplings. We show that polaron relaxation cannot be accurately described by a semi-classical model. The contributions of different anharmonic decay channels are shown to depend strongly on the polaron energy. We calculate the energy dependence of polaron lifetime and compare our results to available experimental measurements of polaron decay time in InAs/GaAs quantum dots.Comment: 5 pages, 4 figure, accepted for publication in Phys. Rev. B (Rapid Com.

Cantu syndrome–associated SUR2 (ABCC9) mutations in distinct structural domains result in KATP channel gain-of-function by differential mechanisms

The complex disorder Cantu syndrome (CS) arises from gainof-function mutations in either KCNJ8 or ABCC9, the genes encoding the Kir6.1 and SUR2 subunits of ATP-sensitive potassium (KATP) channels, respectively. Recent reports indicate that such mutations can increase channel activity by multiple molecular mechanisms. In this study, we determined the mechanism by which KATP function is altered by several substitutions in distinct structural domains of SUR2: D207E in the intracellular L0-linker and Y985S, G989E, M1060I, and R1154Q/R1154W in TMD2. We engineered substitutions at their equivalent positions in rat SUR2A (D207E, Y981S, G985E, M1056I, and R1150Q/R1150W) and investigated functional consequences using macroscopic rubidium (86Rb-) efflux assays and patchclamp electrophysiology. Our results indicate that D207E increases KATP channel activity by increasing intrinsic stability of the open state, whereas the cluster of Y981S/G985E/M1056I substitutions, as well as R1150Q/R1150W, augmented Mg-nucleotide activation. We also tested the responses of these channel variants to inhibition by the sulfonylurea drug glibenclamide, a potential pharmacotherapy for CS. None of the D207E, Y981S, G985E, or M1056I substitutions had a significant effect on glibenclamide sensitivity. However, Gln and Trp substitution at Arg-1150 significantly decreased glibenclamide potency. In summary, these results provide additional confirmation that mutations in CS-Associated SUR2 mutations result in KATP gain-of-function. They help link CS genotypes to phenotypes and shed light on the underlying molecular mechanisms, including consequences for inhibitory drug sensitivity, insights that may inform the development of therapeutic approaches to manage CS