Operating envelope charts for the Langley 0.3-meter transonic cryogenic wind tunnel

To take full advantage of the unique Reynolds number capabilities of the 0.3-meter Transonic Cryogenic Tunnel (0.3-m TCT) at the NASA Langley Research Center, it was designed to accommodate test sections other than the original, octagonal, three-dimensional test section. A 20- by 60-cm two-dimensional test section was installed in 1976 and was extensively used, primarily for airfoil testing, through the fall of 1984. The tunnel was inactive during 1985 so that a new test section and improved high speed diffuser could be installed in the tunnel circuit. The new test section has solid adaptive top and bottom walls to reduce or eliminate wall interference for two-dimensional testing. The test section is 33- by 33-cm in cross section at the entrance and is 142 cm long. In the planning and running of past airfoil tests in the 0.3-m TCT, the use of operating envelope charts have proven very useful. These charts give the variation of total temperature and pressure with Mach number and Reynolds number. The operating total temperature range of the 0.3-m TCT is from about 78 K to 327 K with total pressures ranging from about 17.5 psia to 88 psia. This report presents the operating envelope charts for the 0.3-m TCT with the adaptive wall tes t section installed. They were all generated based on a 1-foot chord model. The Mach numbers vary from 0.1 to 0.95

Temperature dependence of the E2h phonon mode of wurtzite GaN/AlN quantum dots

Raman scattering has been used to study the temperature dependence of the frequency and linewidth of the E2h phonon mode of GaN/AlN quantum dot stacks grown on 6H-SiC. The evolution of the nonpolar phonon mode was analyzed in the temperature range from 80 to 655 K for both quantum dots and barrier materials. The experimental results are interpreted by comparison with a model that takes into account symmetric phonon decay and the different thermal expansions of the constituents of the heterostructure. We find a small increase in the anharmonic parameters of the phonon modes in the heterostructure with respect to [email protected] [email protected] [email protected]

Electronic, vibrational, and thermodynamic properties of ZnS (zincblende and rocksalt structure)

We have measured the specific heat of zincblende ZnS for several isotopic compositions and over a broad temperature range (3 to 1100 K). We have compared these results with calculations based on ab initio electronic band structures, performed using both LDA and GGA exchange- correlation functionals. We have compared the lattice dynamics obtained in this manner with experimental data and have calculated the one-phonon and two-phonon densities of states. We have also calculated mode Grueneisen parameters at a number of high symmetry points of the Brillouin zone. The electronic part of our calculations has been used to investigate the effect of the 3d core electrons of zinc on the spin-orbit splitting of the top valence bands. The effect of these core electrons on the band structure of the rock salt modification of ZnS is also discussed.Comment: 33pages, 16 Figures, submitted to Phys. Rev.

Design and Fabrication of Ultralight Weight, Adjustable Multi-electrode Probes for Electrophysiological Recordings in Mice

The number of physiological investigations in the mouse, mus musculus, has experienced a recent surge, paralleling the growth in methods of genetic targeting for microcircuit dissection and disease modeling. The introduction of optogenetics, for example, has allowed for bidirectional manipulation of genetically-identified neurons, at an unprecedented temporal resolution. To capitalize on these tools and gain insight into dynamic interactions among brain microcircuits, it is essential that one has the ability to record from ensembles of neurons deep within the brain of this small rodent, in both head-fixed and freely behaving preparations. To record from deep structures and distinct cell layers requires a preparation that allows precise advancement of electrodes towards desired brain regions. To record neural ensembles, it is necessary that each electrode be independently movable, allowing the experimenter to resolve individual cells while leaving neighboring electrodes undisturbed. To do both in a freely behaving mouse requires an electrode drive that is lightweight, resilient, and highly customizable for targeting specific brain structures. A technique for designing and fabricating miniature, ultralight weight, microdrive electrode arrays that are individually customizable and easily assembled from commercially available parts is presented. These devices are easily scalable and can be customized to the structure being targeted; it has been used successfully to record from thalamic and cortical regions in a freely behaving animal during natural behavior.Simons FoundationNational Institute of Neurological Disorders and Stroke (U.S.) (NIH Pathway to Independence Career Award)National Institutes of Health (U.S.

Heat Capacity of PbS: Isotope Effects

In recent years, the availability of highly pure stable isotopes has made possible the investigation of the dependence of the physical properties of crystals, in particular semiconductors, on their isotopic composition. Following the investigation of the specific heat ($C_p$, $C_v$) of monatomic crystals such as diamond, silicon, and germanium, similar investigations have been undertaken for the tetrahedral diatomic systems ZnO and GaN (wurtzite structure), for which the effect of the mass of the cation differs from that of the anion. In this article we present measurements for a semiconductor with rock salt structure, namely lead sulfide. Because of the large difference in the atomic mass of both constituents ($M_{\rm Pb}$= 207.21 and ($M_{\rm S}$=32.06 a.m.u., for the natural isotopic abundance) the effects of varying the cation and that of the anion mass are very different for this canonical semiconductor. We compare the measured temperature dependence of $C_p \approx C_v$, and the corresponding derivatives with respect to ($M_{\rm Pb}$ and $M_{\rm S}$), with \textit{\textit{ab initio}} calculations based on the lattice dynamics obtained from the local density approximation (LDA) electronic band structure. Quantitative deviations between theory and experiment are attributed to the absence of spin-orbit interaction in the ABINIT program used for the electronic band structure calculations.Comment: 17 pages including 10 Fig

Low Cost MR Compatible Haptic Stimulation with Application to fMRI Neurofeedback

The most common feedback displays in the fMRI environment are visual, e.g., in which participants try to increase or decrease the level of a thermometer. However, haptic feedback is increasingly valued in computer interaction tasks, particularly for real-time fMRI feedback. fMRI-neurofeedback is a clinical intervention that has not yet taken advantage of this trend. Here we describe a low-cost, user-friendly, MR-compatible system that can provide graded haptic vibrotactile stimulation in an initial application to fMRI neurofeedback. We also present a feasibility demonstration showing that we could successfully set up the system and obtain data in the context of a neurofeedback paradigm. We conclude that vibrotactile stimulation using this low-cost system is a viable method of feedback presentation, and encourage neurofeedback researchers to incorporate this type of feedback into their studies

Pediatric functional magnetic resonance neuroimaging: tactics for encouraging task compliance

<p>Abstract</p> <p>Background</p> <p>Neuroimaging technology has afforded advances in our understanding of normal and pathological brain function and development in children and adolescents. However, noncompliance involving the inability to remain in the magnetic resonance imaging (MRI) scanner to complete tasks is one common and significant problem. Task noncompliance is an especially significant problem in pediatric functional magnetic resonance imaging (fMRI) research because increases in noncompliance produces a greater risk that a study sample will not be representative of the study population.</p> <p>Method</p> <p>In this preliminary investigation, we describe the development and application of an approach for increasing the number of fMRI tasks children complete during neuroimaging. Twenty-eight healthy children ages 9-13 years participated. Generalization of the approach was examined in additional fMRI and event-related potential investigations with children at risk for depression, children with anxiety and children with depression (N = 120). Essential features of the approach include a preference assessment for identifying multiple individualized rewards, increasing reinforcement rates during imaging by pairing tasks with chosen rewards and presenting a visual 'road map' listing tasks, rewards and current progress.</p> <p>Results</p> <p>Our results showing a higher percentage of fMRI task completion by healthy children provides proof of concept data for the recommended tactics. Additional support was provided by results showing our approach generalized to several additional fMRI and event-related potential investigations and clinical populations.</p> <p>Discussion</p> <p>We proposed that some forms of task noncompliance may emerge from less than optimal reward protocols. While our findings may not directly support the effectiveness of the multiple reward compliance protocol, increased attention to how rewards are selected and delivered may aid cooperation with completing fMRI tasks</p> <p>Conclusion</p> <p>The proposed approach contributes to the pediatric neuroimaging literature by providing a useful way to conceptualize and measure task noncompliance and by providing simple cost effective tactics for improving the effectiveness of common reward-based protocols.</p

Mathematical literacy in Plant Physiology undergraduates: results of interventions aimed at improving students' performance

The importance of mathematical literacy in any scientific career is widely recognized. However, various studies report lack of numeracy and mathematical literacy in students from various countries. In the present work we present a detailed study of the mathematical literacy of Spanish undergraduate students of Biology enrolled in a Plant Physiology course. We have performed individual analyses of results obtained during the period 2000-2011, for questions in the examinations requiring and not requiring mathematical skills. Additionally, we present the outcome of two interventions introduced with the aim of helping students improve their prospects for success in the course. Our results confirm previous research showing students' deficiencies in mathematical skills. However, the scores obtained for mathematical questions in the examinations are good predictors of the final grades attained in Plant Physiology, as there are strong correlations at the individual level between results for questions requiring and not requiring mathematical skills. The introduction of a laboratory session devoted to strengthening the application of students' previously acquired mathematical knowledge did not change significantly the results obtained for mathematical questions. Since mathematical abilities of students entering university have declined in recent years, this intervention may have helped to maintain students' performance to a level comparable to that of previous years. The outcome of self-assessment online tests indicates that though Mathematics anxiety is lower than during examinations, the poor results obtained for questions requiring mathematical skills are, at least in part, due to a lack of self-efficacy

Inequality, Fiscal Capacity and the Political Regime: Lessons from the Post-Communist Transition

Using panel data for twenty-seven post-communist economies between 1987-2003, we examine the nexus of relationships between inequality, fiscal capacity (defined as the ability to raise taxes efficiently) and the political regime. Investigating the impact of political reform we find that full political freedom is associated with lower levels of income inequality. Under more oligarchic (authoritarian) regimes, the level of inequality is conditioned by the state’s fiscal capacity. Specifically, oligarchic regimes with more developed fiscal systems are able to defend the prevailing vested interests at a lower cost in terms of social injustice. This empirical finding is consistent with the model developed by Acemoglu (2006). We also find that transition countries undertaking early macroeconomic stabilisation now enjoy lower levels of inequality; we confirm that education fosters equality and the suggestion of Commander et al (1999) that larger countries are prone to higher levels of inequality.http://deepblue.lib.umich.edu/bitstream/2027.42/57211/1/wp831 .pd

Purpose in life predicts better emotional recovery from negative stimuli

Purpose in life predicts both health and longevity suggesting that the ability to find meaning from life’s experiences, especially when confronting life’s challenges, may be a mechanism underlying resilience. Having purpose in life may motivate reframing stressful situations to deal with them more productively, thereby facilitating recovery from stress and trauma. In turn, enhanced ability to recover from negative events may allow a person to achieve or maintain a feeling of greater purpose in life over time. In a large sample of adults (aged 36-84 years) from the MIDUS study (Midlife in the U.S., http://www.midus.wisc.edu/), we tested whether purpose in life was associated with better emotional recovery following exposure to negative picture stimuli indexed by the magnitude of the eyeblink startle reflex (EBR), a measure sensitive to emotional state. We differentiated between initial emotional reactivity (during stimulus presentation) and emotional recovery (occurring after stimulus offset). Greater purpose in life, assessed over two years prior, predicted better recovery from negative stimuli indexed by a smaller eyeblink after negative pictures offset, even after controlling for initial reactivity to the stimuli during the picture presentation, gender, age, trait affect, and other well-being dimensions. These data suggest a proximal mechanism by which purpose in life may afford protection from negative events and confer resilience is through enhanced automatic emotion regulation after negative emotional provocation