Enhancing space transportation: The NASA program to develop electric propulsion

The NASA Office of Aeronautics, Exploration, and Technology (OAET) supports a research and technology (R and T) program in electric propulsion to provide the basis for increased performance and life of electric thruster systems which can have a major impact on space system performance, including orbital transfer, stationkeeping, and planetary exploration. The program is oriented toward providing high-performance options that will be applicable to a broad range of near-term and far-term missions and vehicles. The program, which is being conducted through the Jet Propulsion Laboratory (JPL) and Lewis Research Center (LeRC) includes research on resistojet, arcjets, ion engines, magnetoplasmadynamic (MPD) thrusters, and electrodeless thrusters. Planning is also under way for nuclear electric propulsion (NEP) as part of the Space Exploration Initiative (SEI)

Conformational Dynamics of metallo-β-lactamase CcrA during Catalysis Investigated by Using DEER Spectroscopy

Previous crystallographic and mutagenesis studies have implicated the role of a position-conserved hairpin loop in the metallo-β-lactamases in substrate binding and catalysis. In an effort to probe the motion of that loop during catalysis, rapid-freeze-quench double electron–electron resonance (RFQ-DEER) spectroscopy was used to interrogate metallo-β-lactamase CcrA, which had a spin label at position 49 on the loop and spin labels (at positions 82, 126, or 233) 20–35 Å away from residue 49, during catalysis. At 10 ms after mixing, the DEER spectra show distance increases of 7, 10, and 13 Å between the spin label at position 49 and the spin labels at positions 82, 126, and 233, respectively. In contrast to previous hypotheses, these data suggest that the loop moves nearly 10 Å away from the metal center during catalysis and that the loop does not clamp down on the substrate during catalysis. This study demonstrates that loop motion during catalysis can be interrogated on the millisecond time scale

Quantum key distribution with higher-order alphabets using spatially-encoded qudits

We propose and demonstrate a quantum key distribution scheme in higher-order $d$-dimensional alphabets using spatial degrees of freedom of photons. Our implementation allows for the transmission of 4.56 bits per sifted photon, while providing improved security: an intercept-resend attack on all photons would induce an error rate of 0.47. Using our system, it should be possible to send more than a byte of information per sifted photon.Comment: 4 pages, 5 figures. Replaced with published versio

Caste- and development-associated gene expression in a lower termite

BACKGROUND: Social insects such as termites express dramatic polyphenism (the occurrence of multiple forms in a species on the basis of differential gene expression) both in association with caste differentiation and between castes after differentiation. We have used cDNA macroarrays to compare gene expression between polyphenic castes and intermediary developmental stages of the termite Reticulitermes flavipes. RESULTS: We identified differentially expressed genes from nine ontogenic categories. Quantitative PCR was used to quantify precise differences in gene expression between castes and between intermediary developmental stages. We found worker and nymph-biased expression of transcripts encoding termite and endosymbiont cellulases; presoldier-biased expression of transcripts encoding the storage/hormone-binding protein vitellogenin; and soldier-biased expression of gene transcripts encoding two transcription/translation factors, two signal transduction factors and four cytoskeletal/muscle proteins. The two transcription/translation factors showed significant homology to the bicaudal and bric-a-brac developmental genes of Drosophila. CONCLUSIONS: Our results show differential expression of regulatory, structural and enzyme-coding genes in association with termite castes and their developmental precursor stages. They also provide the first glimpse into how insect endosymbiont cellulase gene expression can vary in association with the caste of a host. These findings shed light on molecular processes associated with termite biology, polyphenism, caste differentiation and development and highlight potentially interesting variations in developmental themes between termites, other insects, and higher animals

Space Launch System Liftoff and Transition Aerodynamic Characterization in the NASA Langley 14- by 22-Foot Subsonic Wind Tunnel

A 1.75% scale force and moment model of the Space Launch System was tested in the NASA Langley Research Center 14- by 22-Foot Subsonic Wind Tunnel to quantify the aerodynamic forces that will be experienced by the launch vehicle during its liftoff and transition to ascent flight. The test consisted of two parts: the first was dedicated to measuring forces and moments for the entire range of angles of attack (0deg to 90deg) and roll angles (0 deg. to 360 deg.). The second was designed to measure the aerodynamic effects of the liftoff tower on the launch vehicle for ground winds from all azimuthal directions (0 deg. to 360 deg.), and vehicle liftoff height ratios from 0 to 0.94. This wind tunnel model also included a set of 154 surface static pressure ports. Details on the experimental setup, and results from both parts of testing are presented, along with a description of how the wind tunnel data was analyzed and post-processed in order to develop an aerodynamic database. Finally, lessons learned from experiencing significant dynamics in the mid-range angles of attack due to steady asymmetric vortex shedding are presented

The Influence of Superpositional Wave Function Oscillations on Shor's Quantum Algorithm

We investigate the influence of superpositional wave function oscillations on the performance of Shor's quantum algorithm for factorization of integers. It is shown that the wave function oscillations can destroy the required quantum interference. This undesirable effect can be routinely eliminated using a resonant pulse implementation of quantum computation, but requires special analysis for non-resonant implementations.Comment: 4 pages, NO figures, revte

Genetic changes in beef cow traits following selection for calving ease

One approach to reducing calving difficulty is to select heifers with higher breeding value for calving ease. Calving ease is often associated with lower birth weight and that may result in other possible effects on lifetime productivity. Females from experimental select and control calving ease lines within each of the seven populations were compared. Random samples of 720 heifers from lines selected for better calving ease breeding values and 190 heifers from control lines selected for average birth weights were followed through four parities. Select and control lines within the same population were selected to achieve similar yearling weight breeding values. Weights of sampled heifers in select lines were 2.6 kg (P \u3c 0.01) lighter at birth but not different from control lines at weaning. Select lines had significantly shorter hip height, lighter mature weight, and greater calving success at second parity. Their calves were born significantly earlier with lighter weights and less assistance. Significant interactions with parity showed fewer calves assisted and greater calf survival to weaning as heifers but negligible differences with control lines in later parities. Steer progeny sampled from these dams in select lines (n = 204) were not different from steers in control lines (n = 91) for hot carcass weight but had significantly greater fat depth. Two production systems were compared considering the seven populations as replicates. The systems differed in selection history of females (select and control lines) and the use of bulls within their lines as young cows, but used the same bulls in both lines as older cows. Cows were culled after single unsuccessful breeding and kept for up to four parities. Select line cows tended (P ≤ 0.10) to wean more calves and stay in the herd longer. They were assisted significantly fewer times at calving and had greater calf weight gain to weaning when evaluated over their herd life. Mature weights were lighter in select lines, but marketable cow weight from the systems was nearly identical. Control lines did have more marketable young cow weight and select lines older cow weight. Weaned calf weight per heifer starting the system was significantly greater for the select heifer system due to greater survival of calves from heifers and greater calving success at second parity. No important unfavorable effects of genetic differences in calving ease were identified in this experiment

A randomized comparative effectiveness study of Healthy Directions 2—A multiple risk behavior intervention for primary care

Objective: To evaluate the effectiveness of the Healthy Directions 2 (HD2) intervention in the primary care setting. Methods: HD2 was a cluster randomized trial (conducted 3/09–11/11). The primary sampling unit was provider (n = 33), with secondary sampling of patients within provider (n = 2440). Study arms included: 1) usual care (UC); 2) HD2—a patient self-guided intervention targeting 5 risk behaviors; and 3) HD2 plus 2 brief telephone coaching calls (HD2 + CC). The outcome measure was the proportion of participants with a lower multiple risk behavior (MRB) score by follow-up. Results: At baseline, only 4% of the participants met all behavioral recommendations. Both HD2 and HD2 + CC led to improvements in MRB score, relative to UC, with no differences between the two HD2 conditions. Twenty-eight percent of the UC participants had improved MRB scores at 6 months, vs. 39% and 43% in HD2 and HD2 + CC, respectively (ps ≤ .001); results were similar at 18 months (p ≤ .05). The incremental cost of one risk factor reduction in MRB score was $310 for HD2 and$450 for HD2 + CC. Conclusions: Self-guided and coached intervention conditions had equivalent levels of effect in reducing multiple chronic disease risk factors, were relatively low cost, and thus are potentially useful for routine implementation in similar health settings

Dynamics of a Quantum Control-Not Gate for an Ensemble of Four-Spin Molecules at Room Temperature

We investigate numerically a single-pulse implementation of a quantum Control-Not (CN) gate for an ensemble of Ising spin systems at room temperature. For an ensemble of four-spin ``molecules'' we simulate the time-evolution of the density matrix, for both digital and superpositional initial conditions. Our numerical calculations confirm the feasibility of implementation of quantum CN gate in this system at finite temperature, using electromagnetic $\pi$-pulse.Comment: 7 pages 3 figure