297 research outputs found
Quadexciton cascade and fine structure splitting of the triexciton in a single quantum dot
We report the properties of emission lines associated with the cascaded
recombination of a quadexciton in single GaAlAs/AlAs quantum dots, studied by
means of polarization-resolved photoluminescence and single-photon correlation
experiments. It is found that photons which are emitted in a double-step 4X-3X
process preserve their linear polarization, similarly to the case of conserved
polarization of correlated photons in the 2X-X cascade. In contrast, an
emission of either co-linear or cross-linear pairs of photons is observed for
the 3X-2X cascade. Each emission line associated with the quadexciton cascade
shows doublet structure in the polarization-resolved photoluminescence
experiment. The maximum splitting is seen when the polarization axis is chosen
along and perpendicular to the [110] crystallographic direction. This effect is
ascribed to the fine structure splitting of the exciton and triexciton states
in the presence of an anisotropic confining potential of ae dot. We also show
that the splitting in the triexciton state surpasses that in the exciton state
by a factor up to eight and their ratio scales with the energy distance between
the 3X and X emission lines, thus, very likely, with a lateral size and/or a
composition of the dot.Comment: submitted to Physical Review
Hypertrophic reversed palmaris longus muscle: a cadaveric finding
Variations of the forearm musculature are vastly described in the literature. The palmaris longus muscle is one of the most variable structures of the human body. It usually arises from the medial epicondyle of the humerus and inserts itself into the palmar aponeurosis. Anatomy textbooks and recent papers state that this muscle may act as a weak wrist flexor. The present work aims to report an anatomical variation where the palmaris longus muscle was abnormally hypertrophied and was completely fleshy throughout the whole forearm. Anatomical variations of the palmaris longus may induce symptoms of neurovascular bundle compression, especially of the median nerve. The palmaris longus muscle may be used in tendon graft or muscle graft, due to its lack of apparent function. Furthermore, it is one of the anatomical landmarks for local anaesthesia procedures. (Folia Morphol 2018; 77, 2: 403–405
Trajectories of Delinquency and Parenting Styles
We investigated trajectories of adolescent delinquent development using data from the Pittsburgh Youth Study and examined the extent to which these different trajectories are differentially predicted by childhood parenting styles. Based on self-reported and official delinquency seriousness, covering ages 10–19, we identified five distinct delinquency trajectories differing in both level and change in seriousness over time: a nondelinquent, minor persisting, moderate desisting, serious persisting, and serious desisting trajectory. More serious delinquents tended to more frequently engage in delinquency, and to report a higher proportion of theft. Proportionally, serious persistent delinquents were the most violent of all trajectory groups. Using cluster analysis we identified three parenting styles: authoritative, authoritarian (moderately supportive), and neglectful (punishing). Controlling for demographic characteristics and childhood delinquency, neglectful parenting was more frequent in moderate desisters, serious persisters, and serious desisters, suggesting that parenting styles differentiate non- or minor delinquents from more serious delinquents
New England Medical Center Posterior Circulation Stroke Registry II. Vascular Lesions
Among 407 New England Medical Center Posterior Circulation Registry (NEMC-PCR) patients, the extracranial (ECVA) and intracranial vertebral arteries (ICVA) were the commonest sites of severe occlusive disease followed by the basilar artery (BA). Severe occlusive lesions were found in >1 large artery in 148 patients; 134 had unilateral or bilateral severe disease at one arterial location. Single arterial site occlusive disease occurred most often in the ECVA (52 patients, 15 bilateral) followed by the ICVA (40 patients, 12 bilateral) and the BA (46 patients). Involvement of the ICVAs and the BA was very common and some patients also had ECVA lesions. Hypertension, smoking, and coronary and peripheral vascular disease were most prevalent in patients with extracranial disease while diabetes and hyperlipidemia were more common when occlusive lesions were only intracranial. Intra-arterial embolism was the most common mechanism of brain infarction in patients with ECVA and ICVA occlusive disease. ICVA occlusive lesions infrequently caused infarction limited to the proximal territory (medulla and posterior inferior cerebellum). BA lesions most often caused infarcts limited to the middle posterior circulation territory (pons and anterior inferior cerebellum). Posterior cerebral artery occlusive lesions were predominantly embolic. Penetrating artery disease caused mostly pontine and thalamic infarcts. Prognosis was poorest in patients with BA disease. The best prognosis surprisingly was in patients who had multiple arterial occlusive lesions; they often had position-sensitive transient ischemic attacks during months or years
Flanker performance in female college students with ADHD: a diffusion model analysis
Attention-deficit hyperactivity disorder (ADHD) is characterized by poor adaptation to environmental demands, which leads to various everyday life problems. The present study had four aims: (1) to compare performance in a flanker task in female college students with and without ADHD (N = 39) in a classical analyses of reaction time and error rate and studying the underlying processes using a diffusion model, (2) to compare the amount of focused attention, (3) to explore the adaptation of focused attention, and (4) to relate adaptation to psychological functioning. The study followed a 2-between (group: ADHD vs. control) Ă— 2-within (flanker conflict: incongruent vs. congruent) Ă— 2-within (conflict frequency: 20 vs. 80 %) design. Compared to a control group, the ADHD group displayed prolonged response times accompanied by fewer errors in a flanker task. Results from the diffusion model analyses revealed that the members of the ADHD group showed deficits in non-decisional processes (i.e., higher non-decision time) and leaned more toward accuracy than participants without ADHD (i.e., setting higher boundaries). The ADHD group showed a more focused attention and less adaptation to the task conditions which is related to psychological functioning. Deficient non-decisional processes and poor adaptation are in line with theories of ADHD and presumably typical for the ADHD population, although this has not been shown using a diffusion model. However, we assume that the cautious strategy of trading speed of for accuracy is specific to the subgroup of female college students with ADHD and might be interpreted as a compensation mechanism
The Relationship Between Parenting and Delinquency: A Meta-analysis
This meta-analysis of 161 published and unpublished manuscripts was conducted to determine whether the association between parenting and delinquency exists and what the magnitude of this linkage is. The strongest links were found for parental monitoring, psychological control, and negative aspects of support such as rejection and hostility, accounting for up to 11% of the variance in delinquency. Several effect sizes were moderated by parent and child gender, child age, informant on parenting, and delinquency type, indicating that some parenting behaviors are more important for particular contexts or subsamples. Although both dimensions of warmth and support seem to be important, surprisingly very few studies focused on parenting styles. Furthermore, fewer than 20% of the studies focused on parenting behavior of fathers, despite the fact that the effect of poor support by fathers was larger than poor maternal support, particularly for sons. Implications for theory and parenting are discussed
- …