23 research outputs found
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
Malnutrition and Frailty. A Comparison of neurological with internal and trauma surgery with neurological and trauma Illnesses
Analysis of Electrolysis Reactions of Metal Complexes Using On-Line Electrospray Ionization Mass Spectrometry with a Compact Electrolytic Flow-Through Cell
Detection of Ligand-Substitution Intermediates in the Photoreactions of Bis(2,2′-bipyridine)butanediamineruthenium(II) Complex Using Electrospray Ionization Mass Spectrometry
Baltic cod genetic diversity in SD 25 predicted by stock structure and oxygen situation: A different perspective on the cod ageing problem?
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