Giant thermopower and figure of merit in single-molecule devices

We present a study of the thermopower $S$ and the dimensionless figure of merit $ZT$ in molecules sandwiched between gold electrodes. We show that for molecules with side groups, the shape of the transmission coefficient can be dramatically modified by Fano resonances near the Fermi energy, which can be tuned to produce huge increases in $S$ and $ZT$. This shows that molecules exhibiting Fano resonances have a high efficiency of thermoelectric cooling which is not present for conventional un-gated molecules with only delocalized states along their backbone.Comment: 4 pages, 4 figure

Space shuttle: Low speed aerodynamic characteristics of the McDonnell Douglas space shuttle booster. Douglas Long Beach, low speed, wind tunnel test results

Low speed aerodynamic characteristics of McDonnell Douglas scale model space shuttle booste

Scalar Top Quark Studies with Various Visible Energies

The precision determination of scalar top quark properties will play an important role at a future International Linear Collider (ILC). Recent and ongoing studies are discussed for different experimental topologies in the detector. First results are presented for small mass differences between the scalar top and neutralino masses. This corresponds to a small expected visible energy in the detector. An ILC will be a unique accelerator to explore this scenario. In addition to finding the existence of light stop quarks, the precise measurement of their properties is crucial for testing their impact on the dark matter relic abundance and the mechanism of electroweak baryogenesis. Significant sensitivity for mass differences down to 5 GeV are obtained. The simulation is based on a fast and realistic detector simulation. A vertex detector concept of the Linear Collider Flavor Identification (LCFI)collaboration, which studies pixel detectors for heavy quark flavour identification, is implemented in the simulations for c-quark tagging. The study extends simulations for large mass differences (large visible energy) for which aspects of different detector simulations, the vertex detector design, and different methods for the determination of the scalar top mass are discussed. Based on the detailed simulations we study the uncertainties for the dark matter density predictions and their estimated uncertainties from various sources. In the region of parameters where stop-neutralino co-annihilation leads to a value of the relic density consistent with experimental results, as precisely determined by the Wilkinson Microwave Anisotropy Probe (WMAP), the stop-neutralino mass difference is small and the ILC will be able to explore this region efficiently.Comment: 11 pages, 11 figures, presented at SUSY'0

Anatomy of a catchment: the relation of physical attributes of the Plynlimon catchments to variations in hydrology and water status

International audienceThe Plynlimon headwater catchments in mid-Wales have been a landmark study of water resources in the UK uplands for over 30 years. The main physical features of the catchments have been digitised as the basis for linking new model developments and process understanding. Examples are given of how the main physical attributes are related to land management, hydrology and water quality. These data are also being used to provide insights into catchment processes that may underpin the development of new research. This work is particularly relevant given the need for the assessment of water status under the Water Framework Directive. The paper presents hypothetical management scenarios for the catchments, to show how ecological status may be improved, for example, by selectively restructuring areas of commercial forest. Keywords: Plynlimon, GIS, catchment study, forestry, hydrology, WF

Quantitative Analysis of Heavy Metals in Children’s Toys and Jewelry: A Multi-Instrument, Multi-Technique Exercise in Analytical Chemistry and Public Health

For most chemistry curricula, laboratory-based activities in quantitative and instrumental analysis continue to be an important aspect of student development/training, one that can be more effective if conceptual understanding is delivered through an inquiry-based process relating the material to relevant issues of public interest and student career trajectories. Laboratory experiences that actively engage students in this manner can be difficult to identify and execute. A special topics, project-based laboratory module is presented here that utilizes multiple techniques and instruments to investigate toxic metal content (lead, cadmium, and arsenic) in children’s toys and toy jewelry. The module effectively illustrates a considerable number of fundamental and advanced quantitative analysis principles including sample digestion, Beer–Lambert law, calibration curve, and standard addition analyses, as well as instrumental analysis considerations of atomic absorption spectroscopy including atomization efficiency (e.g., flames vs furnaces), matrix modifiers, and nondestructive spectroscopy. Module effectiveness stems from the illustration of critical chemical analysis principles in the context of projects with student-directed hypotheses and experimental results that are clearly relevant to the interface of basic science, medicine, and public health: primary career interests for a significant number of undergraduates in the physical and life sciences