Anomalous quantum chaotic behavior in nanoelectromechanical structures

It is predicted that for sufficiently strong electron-phonon coupling an anomalous quantum chaotic behavior develops in certain types of suspended electro-mechanical nanostructures, here comprised by a thin cylindrical quantum dot (billiard) on a suspended rectangular dielectric plate. The deformation potential and piezoelectric interactions are considered. As a result of the electron-phonon coupling between the two systems the spectral statistics of the electro-mechanic eigenenergies exhibit an anomalous behavior. If the center of the quantum dot is located at one of the symmetry axes of the rectangular plate, the energy level distributions correspond to the Gaussian Orthogonal Ensemble (GOE), otherwise they belong to the Gaussian Unitary Ensemble (GUE), even though the system is time-reversal invariant.Comment: 4 pages, pdf forma

Quantum chaos in nanoelectromechanical systems

We present a theoretical study of the electron-phonon coupling in suspended nanoelectromechanical systems (NEMS) and investigate the resulting quantum chaotic behavior. The phonons are associated with the vibrational modes of a suspended rectangular dielectric plate, with free or clamped boundary conditions, whereas the electrons are confined to a large quantum dot (QD) on the plate's surface. The deformation potential and piezoelectric interactions are considered. By performing standard energy-level statistics we demonstrate that the spectral fluctuations exhibit the same distributions as those of the Gaussian Orthogonal Ensemble (GOE) or the Gaussian Unitary Ensemble (GUE), therefore evidencing the emergence of quantum chaos. That is verified for a large range of material and geometry parameters. In particular, the GUE statistics occurs only in the case of a circular QD. It represents an anomalous phenomenon, previously reported for just a small number of systems, since the problem is time-reversal invariant. The obtained results are explained through a detailed analysis of the Hamiltonian matrix structure.Comment: 14 pages, two column

Change & Maintaining Change in School Cafeterias: Economic and Behavioral-Economic Approaches to Increasing Fruit and Vegetable Consumption

Developing a daily habit of consuming fruits and vegetables (FV) in children is an important public-health goal. Eating habits acquired in childhood are predictive of adolescent and adult dietary patterns. Thus, healthy eating patterns developed early in life can protect the individual against a number of costly health deficits and may reduce the prevalence of obesity. At present, children in the United States (US) under-consume FV despite having access to them through the National School Lunch Program. Because access is an obstacle to developing healthy eating habits, particularly in low-income households, targeting children’s FV consumption in schools has the advantage of near-universal FV availability among more than 30 million US children. This chapter reviews economic and behavioral-economic approaches to increasing FV consumption in schools. Inclusion criteria include objective measurement of FV consumption (e.g., plate waste measures) and minimal demand characteristics. Simple but effective interventions include (a) increasing the variety of vegetables served, (b) serving sliced instead of whole fruits, (c) scheduling lunch after recess, and (d) giving children at least 25 minutes to eat. Improving the taste of FV and short-term incentivizing consumption of gradually increasing amounts can produce large increases in consumption of these foods. Low-cost game-based incentive program may increase the practicality of the latter strategy

MALNUTRITION AND LABORATORY MARKERS IN GERIATRIC PATIENTS. A COMPARISON OF NEUROLOGIC-PSYCHIATRIC, INTERNAL AND TRAUMA SURGICAL DISEASES

Objectives: There is minimal information on malnutrition in neurologic-psychiatric patients compared to internal and trauma-surgical patients. The aim of the present study was to explore if there is a correlation of these different disease groups with the nutritional assessment and biochemical markers. Design: Cross - sectional study. Setting and Participants: The study was done in a department of geriatric medicine with subspecialisation in neurologic diseases and stroke unit. 338 patients (m / f = 136 / 202, mean age 81.4 +/- 7.3 years) were evaluated. Measurements: The nutritional status was evaluated by using the short form of the Mini Nutritional Assessment (MNA-SF) and seven biochemical markers (hemoglobin, iron, ferritin, vitamin B 12, folic acid, albumin and cholinesterase) were measured. Results: There were 74 (22%) patients with MNA <= 7 points (malnutrition), 148 (44%) patients with an MNA 8 - 11 points (risk of malnutrition) and 116 (34%) patients with an MNA = 12 points (good nutritional status). The mean MNA score of the three major disease groups trauma-surgery, internal medicine and neurology-psychiatry was 9.1 +/- 3.2 vs. 9.9 +/- 3.1 vs. 10.0 +/- 2.8 (p=0.236). There were significant differences of laboratory markers between the disease groups. A deficit of albumin, cholinesterase and hemoglobin was found more often in trauma-surgical and internal patients than in neurological-psychiatric patients (albumin: 21.4%, 15.7%, 5.3%; p=0.001; cholinesterase 16.7%, 16.9%, 6.3%; p=0.007; hemoglobin 78.6%, 61.4%, 50.0%; p=0.002). Conclusions: Following Mini Nutritional Assessment, the additional measurement of albumin, cholinesterase and hemoglobin allowed a more precise grading of malnutrition. There were significant differences between the disease groups. A deficit of albumin, cholinesterase and hemoglobin was found more often in multimorbid trauma-surgical and internal patients than in neurologic-psychiatric patients

Photochemistry of Transition Metal Complexes Induced by Outer-Sphere Charge Transfer Excitation

The intermolecular (outer sphere, OS) interaction of a reducing and an oxidizing metal complex generates a new optical transition involving charge transfer (CT) from the electron donor to the acceptor. OS CT transitions are classified according to the redox site (metal or ligand). Generally, the interaction between donor and acceptor is facilitated by ion pairs consisting of an oxidizing complex cation and a reducing complex anion. There are also ion pairs which are composed of a metal complex and an organic counter ion as electron donor or acceptor. In addition, the review includes examples of OS CT interaction which do not involve ion pairs at all. — A short introduction into the theory is followed by the discussion of the spectroscopy of OS CT of transition metal complexes. Finally, photoreactions induced by OS CT transitions are reviewed. The optical transfer is frequently followed by a rapid back electron transfer which regenerates the starting complexes. In many cases the primary products are kinetically labile and substitution reactions compete successfully with back electron transfer. As a result stable redox products may be formed. As an alternative, the substitution can be followed by back electron transfer. Product formation appears then as a substitution of the starting complexes. The various possibilities are illustrated by appropriate examples