Room temperature electron spin relaxation in GaInNAs multiple quantum wells at 1.3 mu m

The authors report a direct measurement of electron spin relaxation in GaInNAs semiconductor multiple quantum wells at room temperature. Multiple quantum wells of widths 5.8, 7, and 8 nm exhibiting excitonic absorption around 1.3 mu m have been studied. Spin relaxation times were found to increase with well width in the range of 77-133 ps. The spin relaxation time dependence on first electron confinement energy suggests the Elliot-Yafet mechanism [A. Tackeuchi , Physica B 272, 318 (1999)] as the dominant relaxation process. (c) 2006 American Institute of Physics.</p

Quantum noise induced entanglement and chaos in the dissipative quantum model of brain

We discuss some features of the dissipative quantum model of brain in the frame of the formalism of quantum dissipation. Such a formalism is based on the doubling of the system degrees of freedom. We show that the doubled modes account for the quantum noise in the fluctuating random force in the system-environment coupling. Remarkably, such a noise manifests itself through the coherent structure of the system ground state. The entanglement of the system modes with the doubled modes is shown to be permanent in the infinite volume limit. In such a limit the trajectories in the memory space are classical chaotic trajectories.Comment: 14 page

Nitrogen-enhanced indium segregation in (Ga,In)(N,As)/GaAs multiple quantum wells grown by molecular-beam epitaxy

Transmission electron microscopy (TEM) is used to determine the composition of quaternary (Ga,In)(N,As) quantum wells (QWs). Through a combined analysis of the chemically sensitive (002) dark-field (DF) images and the lattice-resolving high-resolution TEM images, the local distributions of nitrogen and indium in the growth direction are determined. In particular, we are able to directly detect the existence of indium segregation in (Ga,In)(N,As) QWs. A comparison with the indium distribution profile in the nitrogen-free (In,Ga)As QWs, grown under similar conditions, revealed that incorporating N into the alloy enhanced indium segregation

Laboratorio online: tutoring e vantaggi per lo studente universitario

Il presente lavoro nasce con l’intento di realizzare una ricerca che ha come obiettivo principale quello di analizzare la funzione del tutoring e dei laboratori online su un gruppo di matricole frequentanti il primo anno del Corso di Laurea di Scienze dell’Educazione dell’Università di Cagliari. In tali attività, ruolo cruciale è svolto dal tutor online che funge da facilitatore e contribuisce a chiarire e a raggiungere il conseguimento degli obiettivi educativi e delle interazioni. Il tutor induce lo sviluppo di apprendimento autonomo dei singoli discenti, facendo leva sulla loro curiosità, individuando il loro bisogni formativi, formulando obiettivi compatibili con le loro possibilità e identificando le risorse per loro più adeguate. Partendo da questi presupposti ci siamo chiesti quale sia stata la soddisfazione generale sul ruolo del tutor e l’efficacia del laboratorio in termini di percezione dell’aumento delle proprie abilità di problem solving, dell’autostima, della motivazione, del locus of control e delle competenze informatiche. In generale, si può affermare che l’esperienza del laboratorio di didattica si è rivelata positiva e ha rappresentato un elemento di supporto per gli studenti che vi hanno partecipato

Identification of transcriptional and metabolic programs related to mammalian cell size

SummaryBackgroundRegulation of cell size requires coordination of growth and proliferation. Conditional loss of cyclin-dependent kinase 1 in mice permits hepatocyte growth without cell division, allowing us to study cell size in vivo using transcriptomics and metabolomics.ResultsLarger cells displayed increased expression of cytoskeletal genes but unexpectedly repressed expression of many genes involved in mitochondrial functions. This effect appears to be cell autonomous because cultured Drosophila cells induced to increase cell size displayed a similar gene-expression pattern. Larger hepatocytes also displayed a reduction in the expression of lipogenic transcription factors, especially sterol-regulatory element binding proteins. Inhibition of mitochondrial functions and lipid biosynthesis, which is dependent on mitochondrial metabolism, increased the cell size with reciprocal effects on cell proliferation in several cell lines.ConclusionsWe uncover that large cell-size increase is accompanied by downregulation of mitochondrial gene expression, similar to that observed in diabetic individuals. Mitochondrial metabolism and lipid synthesis are used to couple cell size and cell proliferation. This regulatory mechanism may provide a possible mechanism for sensing metazoan cell size

Use of training with BCI (Brain Computer Interface) in the management of impulsivity

Impulsivity represents one of the risk factors strongly related to dependent behavior in subjects with a diagnosis of substance dependence. The risk appetite, in particular, represents a construct connected with other components such as jumping to conclusion and risk taking.There are several forms of treatment used with subjects who have problems related to impulsivity. A good part of these is aimed at subjects with ADHD (Attention Deficit Hyperactivity Disorder), in the form of training or exercises implemented on software. This work aims to evaluate the use of training for concentration, attention and meditation on reducing risk appetite. The experimental design, of a pre-post type, involves assessing the risk appetite before and after training, to be carried out in six sessions over two weeks. The comparison between the experimental group and the control groups showed significant efficacy in reducing the levels of impulsivity in subjects with addiction.This work represents a pilot study on the possible use of meditation, concentration, and training exercises and demonstrates how these can be considered as excellent forms of training for the reduction of impulsiveness and risk appetite, showing their feasibility in the contexts of intervention and cure for addictions

The composition of the perinatal intestinal microbiota in horse

The establishment of the intestinal microbiota is critical for the digestive and immune systems. We studied the early development of the rectal microbiota in horse, a hindgut fermenter, from birth until 7 days of age, by qPCR and 16S rRNA gene amplicon sequencing. To evaluate initial sources of the foal microbiota, we characterised dam fecal, vaginal and oral microbiotas. We utilised an amplicon sequence variant (ASV) pipeline to maximise resolution and reproducibility. Stringent ASV filtering based on prevalence and abundance in samples and controls purged contaminants while preserving intestinal taxa. Sampled within 20 minutes after birth, rectal meconium contained small amounts of diverse bacterial DNA, with a profile closer to mare feces than mouth. 24 hours after birth, rectum was colonised by Firmicutes and Proteobacteria, some foals dominated by single genera. At day 7, the rectal genera were still different from adult feces. The mare vaginal microbiota contributed to 24 h and 7 day microbiotas. It contained few lactobacilli, with Corynebacterium, Porphyromonas, Campylobacter and Helcococcus as the most abundant genera. In the oral mucosa, Gemella was extremely abundant. Our observations indicate that bacteria or bacterial components are present in the intestine immediately after birth, but the newborn microbiota changes rapidly.Peer reviewe

Band offsets at the GaInP/GaAs heterojunction

We have measured current–voltage curves and the temperature dependence of the zero bias conductance for a p -type Be-doped GaInP/GaAs heterojunction grown by the molecular beam epitaxy method. We have determined the valence band offset ΔEν from both measurements and find it to be 310 meV within 5% of accuracy. Similarly, we find for an n -type Si-doped sample that the conduction band offset ΔEC is 95 meV. First-principles calculations have been carried out for the atomic and electronic structures of the interfaces. For the thermodynamically favored interfaces, the valence band offset is found not to be sensitive to atomic relaxations at the interface. The calculated values are in good agreement with the experiments.Peer reviewe