Shake-up Processes in a Low-Density Two-Dimensional Electron Gas: Spin-Dependent Transitions to Higher Hole Landau Levels

A theory of shake-up processes in photoabsorption of an interacting low-density two-dimensional electron gas (2DEG) in strong magnetic fields is presented. In these processes, an incident photon creates an electron-hole pair and, because of Coulomb interactions, simultaneously excites one particle to higher Landau levels (LL's). In this work, the spectra of correlated charged spin-singlet and spin-triplet electron-hole states in the first hole LL and optical transitions to these states (i.e., shake-ups to the first hole LL) are studied. Our results indicate, in particular, the presence of optically-active three-particle quasi-discrete states in the exciton continuum that may give rise to surprisingly sharp Fano resonances in strong magnetic fields. The relation between shake-ups in photoabsorption of the 2DEG and in the 2D hole gas (2DHG), and shake-ups of isolated negative X^- and positive X^+ trions are discussed.Comment: 8 pages, 8 figures. References updated, one figure added (Fig. 6). Accepted in Phys. Rev.

Penumbral Rescue by normobaric O = O administration in patients with ischemic stroke and target mismatch proFile (PROOF): Study protocol of a phase IIb trial.

Oxygen is essential for cellular energy metabolism. Neurons are particularly vulnerable to hypoxia. Increasing oxygen supply shortly after stroke onset could preserve the ischemic penumbra until revascularization occurs. PROOF investigates the use of normobaric oxygen (NBO) therapy within 6 h of symptom onset/notice for brain-protective bridging until endovascular revascularization of acute intracranial anterior-circulation occlusion. Randomized (1:1), standard treatment-controlled, open-label, blinded endpoint, multicenter adaptive phase IIb trial. Primary outcome is ischemic core growth (mL) from baseline to 24 h (intention-to-treat analysis). Secondary efficacy outcomes include change in NIHSS from baseline to 24 h, mRS at 90 days, cognitive and emotional function, and quality of life. Safety outcomes include mortality, intracranial hemorrhage, and respiratory failure. Exploratory analyses of imaging and blood biomarkers will be conducted. Using an adaptive design with interim analysis at 80 patients per arm, up to 456 participants (228 per arm) would be needed for 80% power (one-sided alpha 0.05) to detect a mean reduction of ischemic core growth by 6.68 mL, assuming 21.4 mL standard deviation. By enrolling endovascular thrombectomy candidates in an early time window, the trial replicates insights from preclinical studies in which NBO showed beneficial effects, namely early initiation of near 100% inspired oxygen during short temporary ischemia. Primary outcome assessment at 24 h on follow-up imaging reduces variability due to withdrawal of care and early clinical confounders such as delayed extubation and aspiration pneumonia. ClinicalTrials.gov: NCT03500939; EudraCT: 2017-001355-31

Oscillator strengths of dark charged excitons at low electron filling factors

By direct absorption spectroscopy and comparison to photoluminescence (PL), we investigate negatively charged excitons in dilute two-dimensional electron systems at temperatures down to T = 40 mK in the regime of the fractional quantum Hall effect. At very low temperatures, for filling factor nu<1/3, an additional excitation appears in the PL spectrum, between the well-known singlet and triplet excitons. The observation of a similar excitation by PL was reported very recently [G. Yusa et al., Phys. Rev. Lett. 87, 216402 (2001)], and the excitation was assigned, in spite of the PL intensity similar to that of the neutral exciton, to be due to a dark triplet exciton. By comparing PL and direct absorption spectra in optically thin samples at T<100 mK, we can identify the new excitation indeed as a "dark" mode, since we find that the oscillator strength is much smaller than those of the "bright" modes

Optical Probing of a Fractionally Charged Quasihole in an Incompressible Liquid

In photoluminescence spectroscopy of a low-mobility two-dimensional electron gas subjected to a quantizing magnetic field, we observe an anomaly around nu= (1/3) at a very low temperature (0.1 K) and an intermediate electron density (0.9×1011 cm–2). The anomaly is explained as due to perturbation of the incompressible liquid at the Laughlin state due to close proximity of a localized charged exciton which creates a fractionally charged quasihole in the liquid. The anomaly of ~2 meV can be destroyed by applying a small thermal energy of ~0.2 meV that is enough to close the quasihole energy gap

Acta Psychiatr. Scand.

Evidence based on controlled studies is still limited for treatment strategies that prevent recurrence of suicide attempts. Findings from observational as well as meta-analytic studies strongly suggest that lithium may have suicide-protective properties. Patients with a recent suicide attempt in the context of an affective spectrum disorder (n = 167) were treated with either lithium or placebo during a 12-month period. Survival analysis showed no significant difference of suicidal acts between lithium and placebo-treated individuals (adjusted hazard ratio 0.517; 95% CI 0.18-1.43). However, post hoc analysis revealed that all completed suicides had occurred in the placebo group accounting for a significant difference in incidence rates (P = 0.049). Results indicate that lithium treatment might be effective in reducing the risk of completed suicide in adult patients with affective disorders. Our findings contribute to the growing body of evidence suggesting a specific antisuicidal effect of lithium

Adjunctive lithium treatment in the prevention of suicidal behavior in patients with depression and comorbid personality disorders

Objective. Patients with both major depression and personality disorders have a high risk of suicidal behavior. Lithium is meant to have anti-suicidal properties in patients with affective disorders. The anti-suicidal effect of lithium in patients with affective disorders and comorbid personality disorders has not been investigated yet. Methods. A post-hoc analysis of a subsample of patients with depression and comorbid personality disorder (PD) and a recent suicide attempt (n = 19) from the prospective, placebo-controlled lithium intervention study (N = 167), was conducted. Results. Three patients in the lithium group (n = 8) and two patients in the placebo group (n = 11) presented a suicide attempt throughout the course of the study. No differences related to suicidal behavior could be detected between the placebo group and the group with lithium intervention. Conclusions. On the basis of the small sample size, among patients with comorbid PD, lithium does not seem to have an effect on suicidal behavior in contrast to patients with affective disorders without comorbid PD