Aharonov-Bohm oscillations in a mesoscopic ring with a quantum dot

We present an analysis of the Aharonov-Bohm oscillations for a mesoscopic ring with a quantum dot inserted in one of its arms. It is shown that microreversibility demands that the phase of the Aharonov-Bohm oscillations changes {\it abruptly} when a resonant level crosses the Fermi energy. We use the Friedel sum rule to discuss the conservation of the parity of the oscillations at different conductance peaks. Our predictions are illustrated with the help of a simple one channel model that permits the variation of the potential landscape along the ring.Comment: 11 pages, Revtex style, 3 figures under request. Submitted to Phys. Rev. B (rapid communications

Linear response conductance and magneto-resistance of ferromagnetic single-electron transistors

The current through ferromagnetic single-electron transistors (SET's) is considered. Using path integrals the linear response conductance is formulated as a function of the tunnel conductance vs. quantum conductance and the temperature vs. Coulomb charging energy. The magneto-resistance of ferromagnet-normal metal-ferromagnet (F-N-F) SET's is almost independent of the Coulomb charging energy and is only reduced when the transport dwell time is longer than the spin-flip relaxation time. In all-ferromagnetic (F-F-F) SET's with negligible spin-flip relaxation time the magneto-resistance is calculated analytically at high temperatures and numerically at low temperatures. The F-F-F magneto-resistance is enhanced by higher order tunneling processes at low temperatures in the 'off' state when the induced charges vanishes. In contrast, in the 'on' state near resonance the magneto-resistance ratio is a non-monotonic function of the inverse temperature.Comment: 10 pages, 6 figures. accepted for publication in Phys. Rev.

Distribution of the area enclosed by a 2D random walk in a disordered medium

The asymptotic probability distribution for a Brownian particle wandering in a 2D plane with random traps to enclose the algebraic area A by time t is calculated using the instanton technique.Comment: 4 pages, ReVTeX. Phys. Rev. E (March 1999), to be publishe

Adhesion mechanics of graphene membranes

The interaction of graphene with neighboring materials and structures plays an important role in its behavior, both scientifically and technologically. The interactions are complicated due to the interplay between surface forces and possibly nonlinear elastic behavior. Here we review recent experimental and theoretical advances in the understanding of graphene adhesion. We organize our discussion into experimental and theoretical efforts directed toward: graphene conformation to a substrate, determination of adhesion energy, and applications where graphene adhesion plays an important role. We conclude with a brief prospectus outlining open issues.Comment: Review article to appear in special issue on graphene in Solid State Communication

Neuropsychological constraints to human data production on a global scale

Which are the factors underlying human information production on a global level? In order to gain an insight into this question we study a corpus of 252-633 Million publicly available data files on the Internet corresponding to an overall storage volume of 284-675 Terabytes. Analyzing the file size distribution for several distinct data types we find indications that the neuropsychological capacity of the human brain to process and record information may constitute the dominant limiting factor for the overall growth of globally stored information, with real-world economic constraints having only a negligible influence. This supposition draws support from the observation that the files size distributions follow a power law for data without a time component, like images, and a log-normal distribution for multimedia files, for which time is a defining qualia.Comment: to be published in: European Physical Journal

In Situ Measurements of Interstellar Dust

We present the mass distribution of interstellar grains measured in situ by the Galileo and Ulysses spaceprobes as cumulative flux. The derived in situ mass distribution per logarithmic size interval is compared to the distribution determined by fitting extinction measurements. Large grains measured in situ contribute significantly to the overall mass of dust in the local interstellar cloud. The problem of a dust-to-gas mass ratio that contradicts cosmic abundances is discussed.Comment: 4 pages and two figure

Comparison of methods for determining leaf area in tree rows

Accepted versio

Vacuum structure of Toroidal Carbon Nanotubes

Low energy excitations in carbon nanotubes can be described by an effective field theory of two components spinor. It is pointed out that the chiral anomaly in 1+1 dimensions should be observed in a metallic toroidal carbon nanotube on a planar geometry with varying magnetic field. We propose an experimental setup for studying this quantum effect. We also analyze the vacuum structure of the metallic toroidal carbon nanotube including the Coulomb interactions and discuss some effects of external charges on the vacuum.Comment: 10 pages, 11 figure

Women, men and coronary heart disease: a review of the qualitative literature

Aim. This paper presents a review of the qualitative literature which examines the experiences of patients with coronary heart disease. The paper also assesses whether the experiences of both female and male patients are reflected in the literature and summarizes key themes. Background. Understanding patients' experiences of their illness is important for coronary heart disease prevention and education. Qualitative methods are particularly suited to eliciting patients' detailed understandings and perceptions of illness. As much previous research has been 'gender neutral', this review pays particular attention to gender. Methods. Published papers from 60 qualitative studies were identified for the review through searches in MEDLINE, EMBASE, CINAHL, PREMEDLINE, PsychINFO, Social Sciences Citation Index and Web of Science using keywords related to coronary heart disease. Findings. Early qualitative studies of patients with coronary heart disease were conducted almost exclusively with men, and tended to generalize from 'male' experience to 'human' experience. By the late 1990s this pattern had changed, with the majority of studies including women and many being conducted with solely female samples. However, many studies that include both male and female coronary heart disease patients still do not have a specific gender focus. Key themes in the literature include interpreting symptoms and seeking help, belief about coronary 'candidates' and relationships with health professionals. The influence of social roles is important: many female patients have difficulties reconciling family responsibilities and medical advice, while male patients worry about being absent from work. Conclusions. There is a need for studies that compare the experiences of men and women. There is also an urgent need for work that takes masculinity and gender roles into account when exploring the experiences of men with coronary heart disease

Keeping it in the family: Parental influences on young people's attitudes to police

Prior research finds young people are less satisfied with police than their older counterparts. Despite this, our understanding of youth attitudes to police is limited, as most research has focused on adult attitudes to police. This study adds to our understanding by examining the influence of parent–child dynamics on youth attitudes to police. We predict that youth attitudes to police will be influenced by their parents’ attitudes. A survey of 540 school students in South East Queensland reveals that perceived parental attitudes to police are associated with youth attitudes to police. However, this effect is partially mediated by maternal, but not paternal attachment. These findings suggest that youth attitudes to police are not simply influenced by contact with police and delinquency, but that familial context is important. Consequently, our theoretical understanding of youth attitudes to police must move beyond a focus upon police contact and delinquency