Tunable effective g-factor in InAs nanowire quantum dots

We report tunneling spectroscopy measurements of the Zeeman spin splitting in InAs few-electron quantum dots. The dots are formed between two InP barriers in InAs nanowires with a wurtzite crystal structure grown by chemical beam epitaxy. The values of the electron g-factors of the first few electrons entering the dot are found to strongly depend on dot size and range from close to the InAs bulk value in large dots |g^*|=13 down to |g^*|=2.3 for the smallest dots. These findings are discussed in view of a simple model.Comment: 4 pages, 3 figure

What is the influence on water quality in temperate eutrophic lakes of a reduction of planktivorous and benthivorous fish? A systematic review protocol

Background: In lakes that have become eutrophic due to sewage discharges or nutrient runoff from land, problems such as algal blooms and oxygen deficiency often persist even when nutrient supplies have been reduced. One reason is that phosphorus stored in the sediments can exchange with the water. There are indications that the high abundance of phytoplankton, turbid water and lack of submerged vegetation seen in many eutrophic lakes may represent a semi-stable state. For that reason, a shift back to more natural clear-water conditions could be difficult to achieve. In some cases, though, temporary mitigation of eutrophication-related problems has been accomplished through biomanipulation: stocks of zooplanktivorous fish have been reduced by intensive fishing, leading to increased populations of phytoplankton-feeding zooplankton. Moreover, reduction of benthivorous fish may result in lower phosphorus fluxes from the sediments. An alternative to reducing the dominance of planktivores and benthivores by fishing is to stock lakes with piscivorous fish. These two approaches have often been used in combination. The implementation of the EU Water Framework Directive has recently led to more stringent demands for measures against eutrophication, and a systematic review could clarify whether biomanipulation is efficient as a measure of that kind. Methods: The review will examine primary field studies of how large-scale biomanipulation has affected water quality and community structure in eutrophic lakes or reservoirs in temperate regions. Such studies can be based on comparison between conditions before and after manipulation, on comparison between treated and non-treated water bodies, or both. Relevant outcomes include Secchi depth, concentrations of oxygen, nutrients, suspended solids and chlorophyll, abundance and composition of phytoplankton, zooplankton and fish, and coverage of submerged macrophytes.A Systematic review to this article was published on 22 May 2015: ernes, C., Carpenter, S.R., Gårdmark, A. et al. What is the influence of a reduction of planktivorous and benthivorous fish on water quality in temperate eutrophic lakes? A systematic review. Environ Evid 4, 7 (2015). DOI: 10.1186/s13750-015-0032-9Mistr

Minimum detection efficiency for a loophole-free atom-photon Bell experiment

In Bell experiments, one problem is to achieve high enough photodetection to ensure that there is no possibility of describing the results via a local hidden-variable model. Using the Clauser-Horne inequality and a two-photon non-maximally entangled state, a photodetection efficiency higher than 0.67 is necessary. Here we discuss atom-photon Bell experiments. We show that, assuming perfect detection efficiency of the atom, it is possible to perform a loophole-free atom-photon Bell experiment whenever the photodetection efficiency exceeds 0.50.Comment: REVTeX4, 4 pages, 1 figur

Correlation-induced conductance suppression at level degeneracy in a quantum dot

The large, level-dependent g-factors in an InSb nanowire quantum dot allow for the occurrence of a variety of level crossings in the dot. While we observe the standard conductance enhancement in the Coulomb blockade region for aligned levels with different spins due to the Kondo effect, a vanishing of the conductance is found at the alignment of levels with equal spins. This conductance suppression appears as a canyon cutting through the web of direct tunneling lines and an enclosed Coulomb blockade region. In the center of the Coulomb blockade region, we observe the predicted correlation-induced resonance, which now turns out to be part of a larger scenario. Our findings are supported by numerical and analytical calculations.Comment: 5 pages, 4 figure

Analyzing capacitance-voltage measurements of vertical wrapped-gated nanowires

The capacitance of arrays of vertical wrapped-gate InAs nanowires are analyzed. With the help of a Poisson-Schr"odinger solver, information about the doping density can be obtained directly. Further features in the measured capacitance-voltage characteristics can be attributed to the presence of surface states as well as the coexistence of electrons and holes in the wire. For both scenarios, quantitative estimates are provided. It is furthermore shown that the difference between the actual capacitance and the geometrical limit is quite large, and depends strongly on the nanowire material.Comment: 15 pages, 6 Figures included, to appear in Nanotechnolog

Psychiatric symptoms and disorders in HIV infected mine workers in South Africa A retrospective descriptive study of acute first admissions

Objective: The social and living conditions of mine workers in South Africa contribute to a rapid transmission of human immunodeficiency virus (HIV) and other sexually transmitted infections. HIV-associated dementia is a serious condition during HIV disease. Several other psychiatric symptoms and disorders, such as psychosis, secondary mania and depression, have also been associated with clinical HIV infection. We describe the onset of psychiatric symptoms and signs in a group of untreated, HIVinfected male mine workers first admitted for psychiatric treatment at the Rand Mutual Hospital in Johannesburg. Method: Between 1987 and 1997, 38 consecutive cases were admitted, and their files were retrieved for study in 2006. The subjects were 38 black male mine workers admitted acutely for psychiatric care due to psychiatric symptoms, and subsequently diagnosed with HIV infection. The presenting psychiatric symptoms on admission and diagnoses at discharge were compiled for all patients, not to infer causality but to establish the range of symptoms that the clinician has to deal with. Results: The 38 patients presented with a wide range of psychiatric symptoms. The dominating symptoms were those of cognitive deficits, and different psychotic manifestations. 12 of the patients, almost one third of the individuals, were diagnosed with dementia. The patients with dementia exhibited cognitive deficits, and in addition often abnormal behaviour and psychotic symptoms, and several also had symptoms of secondary mania. 5 of the patients presented with delirium. Psychosis, without concurrent dementia, was diagnosed in 5 patients. Bipolar disorder with mania, without concurrent dementia, and major depression was present in 2 patients, respectively. Screening for substance abuse showed that 9 of the patients had ongoing cannabis abuse and 10 had alcohol abuse.  Cannabis-induced psychotic disorder was present in 5 patients. Conclusion: The findings confirm that patients with a new diagnosis of HIV may present with disorders of thought and/or cognition as well as gross behavioural disturbance, and that psychotic symptoms and secondary mania could be manifestations of the clinical onset of HIV/acquired immune deficiency syndrome (AIDS) infection

HIV infection and psychiatric illness

Objective: To review the clinical features and current knowledge on the treatment of psychiatric symptoms and disorders in patients with human immunodeficiency virus (HIV) infection. Method: We searched the PubMed database combining HIV/AIDS with different keywords for psychiatric diagnoses and symptoms (e.g. depression, mania, anxiety, psychosis, dementia, substance abuse) and for psychopharmacological treatment. The years covered by these searches included 1980 to 2008. Results: Patients with HIV infection are at an increased risk of psychiatric illness. Major depressive disorder and subsyndromal depressive symptoms, as well as anxiety disorder and substance abuse are more prevalent among HIV infected individuals than among the general population. HIV-associated neurocognitive disorders (HAND) are common among HIV patients, and HIV-associated dementia (HAD) is a serious condition during the acquired immune deficiency syndrome (AIDS) stage of HIV disease. Secondarymania and psychosis might be the first clinical symptom of HIV dementia. The introduction of highly active anti-retroviral therapy (HAART) has resulted in significant decreases in morbidity and mortality for HIV infected patients. HAART has also decreased the incidence of HAD, but does not give complete protection from this condition. The utility of psychotropic medications in HIV patients has not been studied sufficiently as a basis for guidelines, and more controlled trials are needed. Conclusion: Psychiatric illness is common in HIV infected individuals, and underlines the importance for screening not only for cognitive impairment but also forco morbid mental disease in HIV-positive patients. Further studies of the neuropsychiatric complications during HIV disease and the use of psychotropics under these circumstances are clearly needed. A better understanding of the pathogenesis of HAD is essential to identify additional therapeutic strategies for prevention and treatment of this neurodegenerative disease. Studies are also needed for optimizing effective utilization of antiretrovirals into the CNS. Mania and psychosis secondary to HAD may be used as an indicator to initiate HAART, irrespective of CD4 count. Further research on the utility of HAART in the treatment of such acute neuropsychiatric symptoms associated with HIV infection should be initiated

A Study of Holographic Renormalization Group Flows in d=6 and d=3

We present an explicit study of the holographic renormalization group (RG) in six dimensions using minimal gauged supergravity. By perturbing the theory with the addition of a relevant operator of dimension four one flows to a non-supersymmetric conformal fixed point. There are also solutions describing non-conformal vacua of the same theory obtained by giving an expectation value to the operator. One such vacuum is supersymmetric and is obtained by using the true superpotential of the theory. We discuss the physical acceptability of these vacua by applying the criteria recently given by Gubser for the four dimensional case and find that those criteria give a clear physical picture in the six dimensional case as well. We use this example to comment on the role of the Hamilton-Jacobi equations in implementing the RG. We conclude with some remarks on AdS_4 and the status of three dimensional superconformal theories from squashed solutions of M-theory.Comment: 15 pages, 5 figures, V2: minor change