41 research outputs found
Beyond quantum microcanonical statistics
Descriptions of molecular systems usually refer to two distinct theoretical
frameworks. On the one hand the quantum pure state, i.e. the wavefunction, of
an isolated system which is determined to calculate molecular properties and to
consider the time evolution according to the unitary Schr\"odinger equation. On
the other hand a mixed state, i.e. a statistical density matrix, is the
standard formalism to account for thermal equilibrium, as postulated in the
microcanonical quantum statistics. In the present paper an alternative
treatment relying on a statistical analysis of the possible wavefunctions of an
isolated system is presented. In analogy with the classical ergodic theory, the
time evolution of the wavefunction determines the probability distribution in
the phase space pertaining to an isolated system. However, this alone cannot
account for a well defined thermodynamical description of the system in the
macroscopic limit, unless a suitable probability distribution for the quantum
constants of motion is introduced. We present a workable formalism assuring the
emergence of typical values of thermodynamic functions, such as the internal
energy and the entropy, in the large size limit of the system. This allows the
identification of macroscopic properties independently of the specific
realization of the quantum state. A description of material systems in
agreement with equilibrium thermodynamics is then derived without constraints
on the physical constituents and interactions of the system. Furthermore, the
canonical statistics is recovered in all generality for the reduced density
matrix of a subsystem
Music Teacher Education at a Liberal Arts College
In 2012, a committee at a small Midwestern liberal arts college, Lake Forest College, embarked on a journey to create a music education teacher licensure major. Drawing from narrative inquiry, this article reports how the dean of faculty, education department chair, music department chair, and assistant professor of music/music education coordinator collaborated on a curricular creation. Findings from this process included (a) the created music education major, (b) each participant’s rationale for wanting the new music education major, (c) valued components of the music education major, and (d) unique elements of a music education major at a liberal arts college. Implications from this experience could be valuable for music education programs at small liberal arts colleges, those involved in university/school partnerships such as professional development schools, and those looking to advocate for their music education programs across campus
Monte-Carlo sampling of energy-constrained quantum superpositions in high-dimensional Hilbert spaces
Recent studies into the properties of quantum statistical ensembles in
high-dimensional Hilbert spaces have encountered difficulties associated with
the Monte-Carlo sampling of quantum superpositions constrained by the energy
expectation value. A straightforward Monte-Carlo routine would enclose the
energy constrained manifold within a larger manifold, which is easy to sample,
for example, a hypercube. The efficiency of such a sampling routine decreases
exponentially with the increase of the dimension of the Hilbert space, because
the volume of the enclosing manifold becomes exponentially larger than the
volume of the manifold of interest. The present paper explores the ways to
optimise the above routine by varying the shapes of the manifolds enclosing the
energy-constrained manifold. The resulting improvement in the sampling
efficiency is about a factor of five for a 14-dimensional Hilbert space. The
advantage of the above algorithm is that it does not compromise on the rigorous
statistical nature of the sampling outcome and hence can be used to test other
more sophisticated Monte-Carlo routines. The present attempts to optimise the
enclosing manifolds also bring insights into the geometrical properties of the
energy constrained manifold itself.Comment: 9 pages, 7 figures, accepted for publication in European Physical
Journal
Measurement of the front-end dead-time of the LHCb muon detector and evaluation of its contribution to the muon detection inefficiency
A method is described which allows to deduce the dead-time of the front-end
electronics of the LHCb muon detector from a series of measurements performed
at different luminosities at a bunch-crossing rate of 20 MHz. The measured
values of the dead-time range from 70 ns to 100 ns. These results allow to
estimate the performance of the muon detector at the future bunch-crossing rate
of 40 MHz and at higher luminosity
Cold non-ischemic heart preservation with continuous perfusion prevents early graft failure in orthotopic pig-to-baboon xenotransplantation
Background Successful preclinical transplantations of porcine hearts into baboon recipients are required before commencing clinical trials. Despite years of research, over half of the orthotopic cardiac xenografts were lost during the first 48 hours after transplantation, primarily caused by perioperative cardiac xenograft dysfunction (PCXD). To decrease the rate of PCXD, we adopted a preservation technique of cold non-ischemic perfusion for our ongoing pig-to-baboon cardiac xenotransplantation project. Methods Fourteen orthotopic cardiac xenotransplantation experiments were carried out with genetically modified juvenile pigs (GGTA1- KO/hCD46/hTBM) as donors and captive-bred baboons as recipients. Organ preservation was compared according to the two techniques applied: cold static ischemic cardioplegia (IC; n = 5) and cold non-ischemic continuous perfusion (CP; n = 9) with an oxygenated albumin-containing hyperoncotic cardioplegic solution containing nutrients, erythrocytes and hormones. Prior to surgery, we measured serum levels of preformed anti-non-Gal-antibodies. During surgery, hemodynamic parameters were monitored with transpulmonary thermodilution. Central venous blood gas analyses were taken at regular intervals to estimate oxygen extraction, as well as lactate production. After surgery, we measured troponine T and serum parameters of the recipient's kidney, liver and coagulation functions. Results In porcine grafts preserved with IC, we found significantly depressed systolic cardiac function after transplantation which did not recover despite increasing inotropic support. Postoperative oxygen extraction and lactate production were significantly increased. Troponin T, creatinine, aspartate aminotransferase levels were pathologically high, whereas prothrombin ratios were abnormally low. In three of five IC experiments, PCXD developed within 24 hours. By contrast, all nine hearts preserved with CP retained fully preserved systolic function, none showed any signs of PCXD. Oxygen extraction was within normal ranges; serum lactate as well as parameters of organ functions were only mildly elevated. Preformed anti-non-Gal-antibodies were similar in recipients receiving grafts from either IC or CP preservation. Conclusions While standard ischemic cardioplegia solutions have been used with great success in human allotransplantation over many years, our data indicate that they are insufficient for preservation of porcine hearts transplanted into baboons: Ischemic storage caused severe impairment of cardiac function and decreased tissue oxygen supply, leading to multi-organ failure in more than half of the xenotransplantation experiments. In contrast, cold non-ischemic heart preservation with continuous perfusion reliably prevented early graft failure. Consistent survival in the perioperative phase is a prerequisite for preclinical long-term results after cardiac xenotransplantation
Influence of Capping on the Atomistic Arrangement in Palladium Nanoparticles at Room Temperature
Mass spectrometry-based untargeted proteomics for the assessment of food authenticity: The case of farmed versus wild-Type salmon
Diet composition and social environment determine food consumption, phenotype and fecundity in an omnivorous insect
Nutrition is the single most important factor for individual's growth and reproduction. Consequently, the inability to reach the nutritional optimum imposes severe consequences for animal fitness. Yet, under natural conditions, organisms may face a mixture of stressors that can modulate the effects of nutritional asymmetry. For instance, stressful environments caused by intense interaction with conspecifics. Here, we subjected the house cricket Acheta domesticus to (i) either of two types of diet that have proved to affect cricket performance and (ii) simultaneously manipulated their social environment throughout their complete life cycle. We aimed to track sex-specific consequences for multiple traits during insect development throughout all life stages. Both factors affected critical life-history traits with potential population-level consequences: diet composition induced strong effects on insect development time, lifespan and fitness, while the social environment affected the number of nymphs that completed development, food consumption and whole-body lipid content. Additionally, both factors interactively determined female body mass. Our results highlight that insects may acquire and invest resources in a different manner when subjected to an intense interaction with conspecifics or when isolated. Furthermore, while only diet composition affected individual reproductive output, the social environment would determine the number of reproductive females, thus indirectly influencing population performance
Multivalued Logic at the Nanoscale
Molecular and nanostructured systems for logic processing are typically characterized by more than two internal states. The implementation of multivalued logic is thus a natural strategy to minimize storing space, to reduce the burden of interconnections and to enhance the complexity of the logic processing. We discuss the application of multivalued logic at the nanoscale by considering different physical implementations of multivalued processing. Unconventional hardware such as molecular electronic states have been used to implement multivalued decision trees and decomposition of logic functions in base five. We discuss an all-optical set-up where the dynamics of molecular states excited by a sequence of laser pulses realizes an unprecedented density of logic processing through the parallelism inherent in the quantum dynamical evolution. Moreover, the search for low energy computing devices that can be interfaced with the conventional CMOS technology led to the design of several multivalued logic schemes in solid state nanostructures. We report in detail a possible implementation of a ternary full-addition in quantum dots embedded in a solid state matrix