Report on the Field Work of the Polish Spitsbergen Expedition, Summer 1970

With the support of the Commission of Geophysical Expeditions of the Polish Academy of Sciences and in collaboration with the Geophysical Department of the Polish Academy of Sciences the Geographical Institute of the University of Wroclaw organized in 1970 a scientific summer expedition to Spitsbergen. It operated in the Hornsund Fiord region where previous Polish investigations (1957-1962) had been carried out. The expedition's principal aims were to make detailed glaciological and geomorphological studies in the Hornsund region in connection with previous research. At the same time the expedition members carried out repairs and maintenance work of the installation and equipment within the premises of the Polish Station in Hornsund. ... The main part of the expedition research was concerned with glaciological, geomorphological and to some extent geophysical work performed on the Werenskiold Glacier (which terminates on land) and on the Hans Glacier (which flows into the fiord) and in their immediate vicinity. ... The work included: climatological and glacio-meteorological research, glaciological investigations, hydrological and hydrographical measurements and observations, and glaciomorphological and geomorphological research. The principal purpose of the climatological and glacio-meteorological investigations was to establish how climatic conditions arise on the periglacial tundra in the Hornsund Base vicinity, and on the Werenskiold Glacier and vicinity. ... Because of the close link between the process of glacier ablation and the energetic processes in the atmosphere, special attention was given to the study of the course of the parameters of radiation and heat balances in the ground air layer. ... The quickly retreating Werenskiold Glacier snout creates particularly favourable conditions for glacio-morphological and geomorphological studies mainly because of the abundance of the freshly uncovered forms and due to a great diversity of geomorphic problems. The main aim of these investigations in the 1970 season was to mark the character of changes on the map of the marginal zone of the Werenskiold Glacier in the scale 1:7,500. ... At the Arie Glacier forefield detailed geomorphological and geological studies were undertaken which resulted in constructing a map of the region in the scale 1:10,000. Besides making several pits and exposures, ten rock and morainic samples were taken from the region for laboratory examination. The process of dead ice ablation under the morainic cover and without it and the process of melting-out and translocation of the rock surface material on the distal slopes of the Hans Glacier lateral moraine underwent careful observation and measurements. For comparison the ablation of the active part of the Hans Glacier near its end was measured. Five samples were taken for further analysis in Poland. Observations and measurements regarding the development and distribution of the block covers on the ridges of the Fugleberget. Ariekammen, Skodefjellet and Rotjesfiellet mountains were also made as well as observations of rock forms on raised sea beaches in the vicinity of the Hornsund Base. The geophysical investigations concerned glaciological problems to a considerable degree. The natural tremors of the Hans Glacier were studied on the basis of microseismographic recordings taken with the help of a vertical seismograph. ... Since this summary report was written, the Geographical Institute of the University of Wroclaw sent another expedition to Spitsbergen, in the summer of 1971. The report on that expedition with some preliminary results of the work done during the two summers will appear in a future issue of Arctic. ..

A Time-Orbiting Potential Trap for Bose-Einstein Condensate Interferometry

We describe a novel atom trap for Bose-Einstein condensates of 87Rb to be used in atom interferometry experiments. The trap is based on a time-orbiting potential waveguide. It supports the atoms against gravity while providing weak confinement to minimize interaction effects. We observe harmonic oscillation frequencies omega_x, omega_y, omega_z as low as 2 pi times (6.0,1.2,3.3) Hz. Up to 2 times 10^4 condensate atoms have been loaded into the trap, at estimated temperatures as low as 850 pK. We anticipate that interferometer measurement times of 1 s or more should be achievable in this device.Comment: 9 pages, 3 figure

Concentrated solar thermoelectric generators

Solar thermoelectric generators (STEGs) are solid state heat engines that generate electricity from concentrated sunlight. In this paper, we develop a novel detailed balance model for STEGs and apply this model to both state-of-the-art and idealized materials. This model uses thermoelectric compatibility theory to provide analytic solutions to device efficiency in idealized materials with temperature-dependent properties. The results of this modeling allow us to predict maximum theoretical STEG efficiencies and suggest general design rules for STEGs. With today's materials, a STEG with an incident flux of 100 kW m^(−2) and a hot side temperature of 1000 °C could achieve 15.9% generator efficiency, making STEGs competitive with concentrated solar power plants. Future developments will depend on materials that can provide higher operating temperatures or higher material efficiency. For example, a STEG with zT = 2 at 1500 °C would have an efficiency of 30.6%

Effective thermal conductivity in thermoelectric materials

Thermoelectric generators (TEGs) are solid state heat engines that generate electricity from a temperature gradient. Optimizing these devices for maximum power production can be difficult due to the many heat transport mechanisms occurring simultaneously within the TEG. In this paper, we develop a model for heat transport in thermoelectric materials in which an “effective thermal conductivity” (κ_eff) encompasses both the one dimensional steady-state Fourier conduction and the heat generation/consumption due to secondary thermoelectric effects. This model is especially powerful in that the value of κeff does not depend upon the operating conditions of the TEG but rather on the transport properties of the TE materials themselves. We analyze a variety of thermoelectric materials and generator designs using this concept and demonstrate that κ_(eff) predicts the heat fluxes within these devices to 5% of the exact value

Relating Use of Effective Responsive, Structure, and Non-Directive Control Vegetable Parenting Practices to Subscales from the Model of Goal Directed Behavior

Parents may positively influence children’s vegetable consumption through effective vegetable parenting practices (VPP). Research has demonstrated three dimensions of effective VPP: Effective Responsiveness, Structure, and Non-Directive Control, but there is limited research investigating each separately. This study presents the modeling of Effective Responsive, Structure, and Non-Directive Control VPP using constructs from the Model of Goal Directed Vegetable Parenting Practices (MGDVPP). Parents (n=307) completed a survey on demographics, MGDVPP constructs, and effective VPP. Block regression modeling tested three models: one for each dimension of effective VPP as the dependent variable. Independent variables included validated subscales representing MGDVPP constructs: Intention, Desire, Perceived Barriers, Autonomy, Relatedness, Self-Efficacy, Habit, Anticipated Emotions, Perceived Behavioral Control, Attitudes, and Norms. Participants were racially diverse, and a majority was female, of higher socioeconomic status, and with a male child. Effective Responsive VPP was positively related to a Habit subscale. Effective Structure VPP was positively related to a Barrier, two Habit, and an Attitude subscales. Effective Non-Directive Control VPP was positively related to being a high school or GED graduate, having younger children, a Habit, and two Intentions subscales, and negatively related to an Intentions and a Perceived Behavioral Control subscales. The adjusted R2 for the Effective Responsive, Structure, and Non-Directive Control VPP models were 0.432, 0.310, and 0.515, respectively. This was the first study to relate constructs from a theoretical model to effective VPP dimensions. Research is needed to longitudinally assess the MGDVPP and test its utility in vegetable-related interventions

Probing the inter-layer exciton physics in a MoS2_2/MoSe2_2/MoS2_2 van der Waals heterostructure

Stacking atomic monolayers of semiconducting transition metal dichalcogenides (TMDs) has emerged as an effective way to engineer their properties. In principle, the staggered band alignment of TMD heterostructures should result in the formation of inter-layer excitons with long lifetimes and robust valley polarization. However, these features have been observed simultaneously only in MoSe$_2$/WSe$_2$ heterostructures. Here we report on the observation of long lived inter-layer exciton emission in a MoS$_2$/MoSe$_2$/MoS$_2$ trilayer van der Waals heterostructure. The inter-layer nature of the observed transition is confirmed by photoluminescence spectroscopy, as well as by analyzing the temporal, excitation power and temperature dependence of the inter-layer emission peak. The observed complex photoluminescence dynamics suggests the presence of quasi-degenerate momentum-direct and momentum-indirect bandgaps. We show that circularly polarized optical pumping results in long lived valley polarization of inter-layer exciton. Intriguingly, the inter-layer exciton photoluminescence has helicity opposite to the excitation. Our results show that through a careful choice of the TMDs forming the van der Waals heterostructure it is possible to control the circular polarization of the inter-layer exciton emission.Comment: 19 pages, 3 figures. Just accepted for publication in Nano Letters (http://pubs.acs.org/doi/10.1021/acs.nanolett.7b03184