Atomic hydrogen maser active oscillator cavity and bulb design optimization

The performance characteristics and reliability of the active oscillator atomic hydrogen maser depend upon oscillation parameters which characterize the interaction region of the maser, the resonant cavity and atom storage bulb assembly. With particular attention to use of the cavity frequency switching servo (1) to reduce cavity pulling, it is important to maintain high oscillation level, high atomic beam flux utilization efficiency, small spin exchange parameter and high cavity quality factor. It is also desirable to have a small and rigid cavity and bulb structure and to minimize the cavity temperature sensitivity. Curves for a novel hydrogen maser cavity configuration which is partially loaded with a quartz dielectric cylinder and show the relationships between cavity length, cavity diameter, bulb size, dielectric thickness, cavity quality factor, filling factor and cavity frequency temperature coefficient are presented. The results are discussed in terms of improvement in maser performance resulting from particular design choices

Boeing 747 aircraft with large external pod for transporting outsize cargo

The effect on structural arrangement, system weight, and range performance of the cargo pod payload carrying capability was determined to include either the bridge launcher or a spacelab module on a Boeing 747 aircraft. Modifications to the carrier aircraft and the installation time required to attach the external pod to the 747 were minimized. Results indicate that the increase in pod size was minimal, and that the basic 747 structure was adequate to safely absorb the load induced by ground or air operation while transporting either payload

A study of high-altitude manned research aircraft employing strut-braced wings of high-aspect-ratio

The effect of increased wing aspect ratio of subsonic aircraft on configurations with and without strut bracing. Results indicate that an optimum cantilever configuration, with a wing aspect ratio of approximately 26, has a 19% improvement in cruise range when compared to a baseline concept with a wing aspect ratio of approximately 10. An optimum strut braced configuration, with a wing aspect ratio of approximately 28, has a 31% improvment in cruise range when compared to the same baseline concept. This improvement is mainly due to the estimated reduction in wing weight resulting from use of lifting struts. All configurations assume the same mission payload and fuel. The drag characteristics of the wings are enhanced with the use of laminar flow airfoils. A method for determining the extent of attainable natural laminar flow, and methods for preliminary structural design and for aerodynamic analysis of wings lifting struts are presented

Two-Bit Gates are Universal for Quantum Computation

A proof is given, which relies on the commutator algebra of the unitary Lie groups, that quantum gates operating on just two bits at a time are sufficient to construct a general quantum circuit. The best previous result had shown the universality of three-bit gates, by analogy to the universality of the Toffoli three-bit gate of classical reversible computing. Two-bit quantum gates may be implemented by magnetic resonance operations applied to a pair of electronic or nuclear spins. A ``gearbox quantum computer'' proposed here, based on the principles of atomic force microscopy, would permit the operation of such two-bit gates in a physical system with very long phase breaking (i.e., quantum phase coherence) times. Simpler versions of the gearbox computer could be used to do experiments on Einstein-Podolsky-Rosen states and related entangled quantum states.Comment: 21 pages, REVTeX 3.0, two .ps figures available from author upon reques

Immobilization of Clover-trapped White-tailed Deer, Odocoileus virginianus, with Medetomidine and Ketamine, and Antagonism with Atipamezole

We evaluated the effectiveness of immobilizing Clover-trapped White-tailed Deer (Odocoileus virginanus) with medetomidine hydrochloride (HCl) and ketamine HCl during winter and summer by monitoring immobilization intervals and vital signs. In winter, we captured deer in Clover traps in 1 4-ha research enclosure for relocation to another on-site enclosure (n = 5). In summer, we captured free-ranging deer in Clover traps to attach radio-collars (n = 4). We administered an estimated 0.055 mg/kg medetomidine HCl and 2.5 mg/kg ketamine HCl to adult (> 1.5 years of age) deer and 0.06 mg/kg medetomidine HCl and 2.5 mg/kg ketamine HCl to subadult (< 1.5 years of age) deer. We used an intramuscular injection of atipamezole HCl as the antagonist at a rate of 0.275 mg/kg for adults and 0.3 mg/kg for subadults > 30 minutes post-induction. Mean induction time in winter was 11.2 minutes (SE = 2.5, range = 5.4 - 24.2) and 6.5 minutes (SE = 0.8, range = 6.2 - 7.5) in summer. After atipamezole HCl injection, the mean time to walking was 17.1 minutes (SE = 3.5, range = 7.5 - 41.5 minutes) in winter and 11.3 minutes (SE = 3.8, range = 4.7 - 13.5) in summer. Rectal temperature was relatively constant throughout immobilization; however rectal temperatures of 5 deer (n = 3 in winter; n = 2 in summer) exceeded 40oC, a sign of hyperthermia. Respiration rate and pulse rate peaked at about 20 minutes post-medetomidine HCl and ketamine HCl injection, then generally declined thereafter. No mortalities were observed in our study. Medetomidine HCl and ketamine HCl doses for Clover-trapped White-tailed Deer provided satisfactory induction times, sufficient level of anesthesia for short-distance relocation or radio-collar attachment, and were effectively reversed with an IM injection of atipamezole HCl

Tracking Canada Geese Near Airports: Using Spatial Data to Better Inform Management

The adaptation of birds to urban environments has created direct hazards to air transportation with the potential for catastrophic incidents. Bird–aircraft collisions involving Canada geese (Branta canadensis; goose) pose greater risks to aircraft than many bird species due to their size and flocking behavior. However, information on factors driving movements of geese near airports and within aircraft arrival/departure areas for application to management are limited. To address this need, we deployed 31 neck collar-mounted global positioning system transmitters on Canada geese near Midway International Airport in Chicago, Illinois, USA during November 2015 to February 2016. We used the movement data obtained to model environmental and behavioral factors influencing the intersection of goose movements (i.e., transition from 1 location to another) with air operations areas (i.e., aircraft flight paths). Of 3,008 goose movements recorded, 821 intersected a 3-km buffer around the airport representing U.S. Federal Aviation Administration recommended distances from wildlife attractants, and 399 intersected flight paths for approaching and landing aircraft. The effects of weather (i.e., snow cover, temperature, wind speed) on the probability of geese flying varied with different air operation areas while certain habitat resources greatly increased the probability of intersection. For example, the juxtaposition of foraging (railyards with spilled grain) and loafing areas (rooftops) near the airport led to a higher probability of movements intersecting important air operations areas. The average altitude of flying geese was 29.8 m above the ground, resulting in the greatest risk of collision being within 0.5 km of the end of runways. We suggest airport goose collision mitigation management actions, such as reducing habitat resources near the airport and using focused nonlethal harassment or physical modifications, when guided by animal movement data, may further mitigate bird-strike risks

Mitigation Translocation of Red-Tailed Hawks to Reduce Raptor–Aircraft Collisions

Translocation of problematic individual animals is commonly used to reduce human–wildlife conflicts, especially to reduce the presence or abundance of raptors within airport environments, where they pose a risk to safe aircraft operations. Although this method has strong public support, there have been no scientific evaluations of its efficacy or to determine which factors might influence the return of translocated birds to the airport. We conducted a study to determine which biological and logistical factors might influence the return of red-tailed hawks (Buteo jamaicensis) translocated from Chicago’s O’Hare International Airport (ORD) during 2010–2013. We live-captured and translocated red-tailed hawks various distances from the ORD airfield and monitored for returning birds. We found the odds of hawk return increased by 2.36 (95% CI=0.99–5.70) times for older birds (\u3e1 yr of age) relative to younger birds (≤1yr of age). Odds of hawk return went up 4.10 (95% CI=0.75–22.2) times when translocations were conducted during the breeding season relative to the non-breeding season. The odds of hawk return increased 11.94 (95% CI=3.29–43.38) times for each subsequent translocation event involving the same hawk. The cost of 1 translocation event to the release sites that were 81, 121, 181, and 204 km from ORD was $213,$284, $362, and$426, respectively. Management programs that use release sites 80 km from the airport minimize translocation events to include only younger birds during the non-breeding season, and undertake only 1 translocation event for an individual hawk would increase program efficacy and greatly reduce program implementation costs. The decision matrix regarding the use of a raptor trapping and translocation program involves a variety of biological, logistical, economic, and sociopolitical variables. This study represents an important first step in providing a scientific foundation for informing such management decisions

Spatial and Time Distribution of Dairy Cattle Manure in an Intensive Pasture System

This study determined distribution of feces and urine from dairy cattle managed in a rotationally grazed pasture. Lactating Holsteins (n=18) and Jerseys (n=18) were grazed on a .74 ha endophyte-free fescue (Festuca arundinacea)/white clover (Trifolium repens) pasture. All cows were constantly observed for 24 h 6 times over 12 mo. Cows had access to about 54% of the paddock during the first grazing period (12 h) and had access to the entire paddock during the second grazing period (8 h). Data included: (1) all feces and urine events from eight cows, observed while in the pasture, feed area, milking parlor or in transit; and (2) all urine and feces events on pasture for all 36 cows each grazing period. After each grazing period, urine (marked with color coded flags) and feces were surveyed and mapped. Data were transformed and then analyzed using statistical software. Percentages of the manure events were highly correlated with time spent in each area (r= .99). Feces and urine (estimated at .12 m2 and .36 m2, respectively) from the six 24-hr observations covered 10% of the total paddock. Within a 30-m radius of the water tank, spatial density of feces and urine from the warm season observations (July, August, September) were significantly greater than concentrations during the cool season observations (December, February, and April). Pasture systems can potentially reduce manure handling and storage requirements proportional to the time cows are kept on pasture. Manure on pasture was relatively evenly distributed over multiple grazing periods

Studies of h/e Aharonov-Bohm Photovoltaic Oscillations in Mesoscopic Au Rings

We have investigated a mesoscopic photovoltaic (PV) effect in micron-size Au rings in which a dc voltage Vdc is generated in response to microwave radiation. The effect is due to the lack of inversion symmetry in a disordered system. Aharonov-Bohm PV oscillations with flux period h/e have been observed at low microwave intensities for temperatures ranging from 1.4 to 13 K. For moderate microwave intensities the h/e PV oscillations are completely quenched providing evidence that the microwaves act to randomize the phase of the electrons. Studies of the temperature dependence of Vdc also provide evidence of the dephasing nature of the microwave field. A complete theoretical explanation of the observed behavior seems to require a theory for the PV effect in a ring geometry.Comment: 10 pages (RevTex twocolumn style), 8 figures-2 pages (one postscript file) To be published in Phys. Rev.

Filtering of spin currents based on ballistic ring

Quantum interference effects in rings provide suitable means for controlling spin at mesoscopic scales. Here we apply such a control mechanism to the spin-dependent transport in a ballistic quasi one dimensional ring patterned in two dimensional electron gases (2DEGs). The study is essentially based on the {\it natural} spin-orbit (SO) interactions, one arising from the laterally confining electric field {($\beta$ term) and the other due to to the quantum-well potential that confines electrons in the 2DEG (conventional Rashba SO interaction or $\alpha$ term).} We focus on single-channel transport and solve analytically the spin polarization of the current. As an important consequence of the presence of spin splitting, we find the occurrence of spin dependent current oscillations. We analyze %the effects of disorder by discussing the transport in the presence of one non-magnetic obstacle in the ring. We demonstrate that a spin polarized current can be induced when an unpolarized charge current is injected in the ring, by focusing on the central role that the presence of the obstacle plays.Comment: 9 pages, 7 figures, PACS numbers: 72.25.-b, 72.20.My, 73.50.Jt, accepted for publication in J. Phys. - Cond. Ma