Statistical Properties of Level Widths and Conductance Peaks in a Quantum Dot

We study the statistics of level widths of a quantum dot with extended contacts in the absence of time-reversal symmetry. The widths are determined by the amplitude of the wavefunction averaged over the contact area. The distribution function of level widths for a two-point contact is evaluated exactly. The distribution resembles closely the result obtained when the wavefunction fluctuates independently at each point, but differs from the one-point case. Analytical calculations and numerical simulations show that the distribution for many-point contacts has a power-law behavior at small level widths. The exponent is given by the number of points in the lead and diverges in the continuous limit. The distribution of level widths is used to determine the distribution of conductance peaks in the resonance regime. At intermediate temperatures, we find that the distribution tends to normal and fluctuations in the height of the peaks are suppressed as the lead size is increased.Comment: 13 pages, RevTeX 3, six uuencoded postscript figures, CMT-ERM-940

Quality of life in primary sclerosing cholangitis: a systematic review.

BACKGROUND: Primary sclerosing cholangitis (PSC) is a rare bile duct and liver disease which can considerably impact quality of life (QoL). As part of a project developing a measure of QoL for people with PSC, we conducted a systematic review with four review questions. The first of these questions overlaps with a recently published systematic review, so this paper reports on the last three of our initial four questions: (A) How does QoL in PSC compare with other groups?, (B) Which attributes/factors are associated with impaired QoL in PSC?, (C) Which interventions are effective in improving QoL in people with PSC?. METHODS: We systematically searched five databases from inception to 1 November 2020 and assessed the methodological quality of included studies using standard checklists. RESULTS: We identified 28 studies: 17 for (A), ten for (B), and nine for (C). Limited evidence was found for all review questions, with few studies included in each comparison, and small sample sizes. The limited evidence available indicated poorer QoL for people with PSC compared with healthy controls, but findings were mixed for comparisons with the general population. QoL outcomes in PSC were comparable to other chronic conditions. Itch, pain, jaundice, severity of inflammatory bowel disease, liver cirrhosis, and large-duct PSC were all associated with impaired QoL. No associations were found between QoL and PSC severity measured with surrogate markers of disease progression or one of three prognostic scoring systems. No interventions were found to improve QoL outcomes. CONCLUSION: The limited findings from included studies suggest that markers of disease progression used in clinical trials may not reflect the experiences of people with PSC. This highlights the importance for clinical research studies to assess QoL alongside clinical and laboratory-based outcomes. A valid and responsive PSC-specific measure of QoL, to adequately capture all issues of importance to people with PSC, would therefore be helpful for clinical research studies

Quantum chaos in a deformable billiard: Applications to quantum dots

We perform a detailed numerical study of energy-level and wavefunction statistics of a deformable quantum billiard focusing on properties relevant to semiconductor quantum dots. We consider the family of Robnik billiards generated by simple conformal maps of the unit disk; the shape of this family of billiards may be varied continuously at fixed area by tuning the parameters of the map. The classical dynamics of these billiards is well-understood and this allows us to study the quantum properties of subfamilies which span the transition from integrability to chaos as well as families at approximately constant degree of chaoticity (Kolmogorov entropy). In the regime of hard chaos we find that the statistical properties of interest are well-described by random-matrix theory and completely insensitive to the particular shape of the dot. However in the nearly-integrable regime non-universal behavior is found. Specifically, the level-width distribution is well-described by the predicted $\chi^2$ distribution both in the presence and absence of magnetic flux when the system is fully chaotic; however it departs substantially from this behavior in the mixed regime. The chaotic behavior corroborates the previously predicted behavior of the peak-height distribution for deformed quantum dots. We also investigate the energy-level correlation functions which are found to agree well with the behavior calculated for quasi-zero-dimensional disordered systems.Comment: 25 pages (revtex 3.0). 16 figures are available by mail or fax upon request at [email protected]

Identification and evaluation of observational measures for the assessment and/or monitoring of level of consciousness in adult palliative care patients: A systematic review for I-CAN-CARE.

BACKGROUND: The use of observational measures to assess palliative care patients' level of consciousness may improve patient care and comfort. However, there is limited knowledge regarding the validity and reliability of these measures in palliative care settings. AIM: To identify and evaluate the psychometric performance of observational level of consciousness measures used in palliative care. DESIGN: Systematic review; PROSPERO registration: CRD42017073080. DATA SOURCES: We searched six databases until November 2018, using search terms combining subject headings and free-text terms. Psychometric performance for each identified tool was appraised independently by two reviewers following established criteria for developing and evaluating health outcome measures. RESULTS: We found 35 different levels of consciousness tools used in 65 studies. Only seven studies reported information about psychometric performance of just eight tools. All other studies used either ad hoc measures for which no formal validation had been undertaken (n = 21) or established tools mainly developed and validated in non-palliative care settings (n = 37). The Consciousness Scale for Palliative Care and a modified version of the Richmond Agitation-Sedation Scale received the highest ratings in our appraisal, but, since psychometric evidence was limited, no tool could be assessed for all psychometric properties. CONCLUSION: An increasing number of studies in palliative care are using observational measures of level of consciousness. However, only a few of these tools have been tested for their psychometric performance in that context. Future research in this area should validate and/or refine the existing measures, rather than developing new tools

Weak-Localization and Integrability in Ballistic Cavities

We demonstrate the existence of an interference contribution to the average magnetoconductance, G(B), of ballistic cavities and use it to test the semiclassical theory of quantum billiards. G(B) is qualitatively different for chaotic and regular cavities, an effect explained semiclassically by the differing classical distribution of areas. The magnitude of G(B) is poorly explained by the semiclassical theory of coherent backscattering (elastic enhancement factor)-- correlations beyond time-reversed pairs of trajectories must be included-- but is in agreement with random matrix theory.Comment: 12 pages + 3 figures, revtex, hub-92-w

Aharonov-Bohm effect and resonances in the circular quantum billiard with two leads

We calculate the conductance through a circular quantum billiard with two leads and a point magnetic flux at the center. The boundary element method is used to solve the Schrodinger equation of the scattering problem, and the Landauer formula is used to calculate the conductance from the transmission coefficients. We use two different shapes of leads, straight and conic, and find that the conductance is affected by lead geometry, the relative positions of the leads and the magnetic flux. The Aharonov-Bohm effect can be seen from shifts and splittings of fluctuations. When the flux is equal to (h/2e) and the angle between leads is 180 degree, the conductance tends to be suppressed to zero in the low energy range due to the Aharonov-Bohm effect.Comment: LaTeX2e, 8 pages, 6 figures, submitted to Phys. Rev. B (Two references added. A discussion on discrete symmetries removed.