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Atomic clocks, which lock the frequency of an oscillator to the extremely stable quantized energy levels of atoms, are essential for navigation applications such as deep space exploration

We have used VSOP space very long baseline interferometry observations to measure the brightness temperature distribution of a well-defined sub-set of the Pearson-Readhead sample of extragalactic radio sources. VLBI which is restricted to Earth-diameter baselines is not generally sensitive to emitting regions with brightness temperatures greater than approximately $10^{12}$ K, coincidentally close to theoretical estimates of brightness temperature limits, $10^{11} - 10^{12}$ K. We find that a significant proportion of our sample have brightness temperatures greater than $10^{12}$ K; many have unresolved components on the longest baselines, and some remain completely unresolved. These observations begin to bridge the gap between the extended jets seen with ground-based VLBI and the microarcsecond structures inferred from intraday variability, evidenced here by the discovery of a relationship between intraday variability and VSOP-measured brightness temperature, likely due to the effects of relativistic beaming. Also, lower limits on jet Lorentz factors, estimated from space VLBI observations, are starting to challenge numerical simulations that predict low Lorentz factor jets., 4 pages + 1 figure, ApJ letters, accepted

The Jet Propulsion Laboratory (JPL) is a participant in the VSOP Space VLBI mission, an extensive international collaboration led by Japan's Institute of Space and Astronautical Science (ISAS). The JPL effort is funded by the U.S. National Aeronautics and Space Administration (NASA). To obtain data from the orbital element of the VSOP mission, the Japanese HALCA satellite, the Deep Space Network (DSN) of JPL has built a new set of three 11-meter tracking stations in California, Spain, and Australia. These stations have supported over 1000 HALCA passes during the first year of operation, and supply science, telemetry, and Doppler data for the mission. JPL is using the Doppler data to estimate the satellite orbital parameters that are needed by the tracking stations and VLBI data correlators. The DSN also modified their three 70-meter antennas to provide ground VLBI observing support for the mission. In addition to operational support, JPL has had significant involvement in the mission planning and scientific support aspects of the mission, including mission design, international data flow, scientific scheduling, and data analysis during in-orbit checkout. JPL has also aided the scientific community in the use of VSOP by developing a user software package, writing a guide for proposers, and establishing a proposer help desk.

We present VLBI observations at 5 GHz of 11 GHz Peaked Spectrum (GPS) or candidate GPS sources. Two of them belong to the complete sample defined by Stanghellini et al. (1998) (the GPS 1 Jy sample), while the others are selected from a heterogeneous list compiled by O'Dea et al. (1991). Morphologies of the sources presented here are similar to those found in Stanghellini et al. (1997) and in the small Compact Steep Spectrum (CSS) sources studied by Dallacasa et al. (1995). Our results strengthen the evidence that GPS quasars tend to have core-jet or complex morphology and GPS galaxies tend to be compact symmetric objects (CSO).

The Russian Academy of Sciences and Federal Space Agency, together with the participation of many international organizations, worked toward the launch of the RadioAstron orbiting space observatory with its onboard 10-m reflector radio telescope from the Baikonur cosmodrome on July 18, 2011. Together with some of the largest ground-based radio telescopes and a set of stations for tracking, collecting, and reducing the data obtained, this space radio telescope forms a multi-antenna ground-space radio interferometer with extremely long baselines, making it possible for the first time to study various objects in the Universe with angular resolutions a million times better than is possible with the human eye. The project is targeted at systematic studies of compact radio-emitting sources and their dynamics. Objects to be studied include supermassive black holes, accretion disks, and relativistic jets in active galactic nuclei, stellar-mass black holes, neutron stars and hypothetical quark stars, regions of formation of stars and planetary systems in our and other galaxies, interplanetary and interstellar plasma, and the gravitational field of the Earth. The results of ground-based and inflight tests of the space radio telescope carried out in both autonomous and ground-space interferometric regimes are reported. The derived characteristics are in agreement with the main requirements of the project. The astrophysical science program has begun., 54 pages, 11 figures; published by Astronomicheskij Zhurnal (in Russian) and Astronomy Reports (in English)

Using high-resolution radio imaging with VLBI techniques, the TANAMI program has been observing the parsec-scale radio jets of southern (declination south of -30{\deg}) gamma-ray bright AGN simultaneously with Fermi/LAT monitoring of their gamma-ray emission. We present the radio and gamma-ray properties of the TANAMI sources based on one year of contemporaneous TANAMI and Fermi/LAT data. A large fraction (72%) of the TANAMI sample can be associated with bright gamma-ray sources for this time range. Association rates differ for different optical classes with all BL Lacs, 76% of quasars and just 17% of galaxies detected by the LAT. Upper limits were established on the gamma-ray flux from TANAMI sources not detected by LAT. This analysis led to the identification of three new Fermi sources whose detection was later confirmed. The gamma-ray and radio luminosities are related by $L_\gamma \propto L_r^{0.89+-0.04}$. The brightness temperatures of the radio cores increase with the average gamma-ray luminosity, and the presence of brightness temperatures above the inverse Compton limit implies strong Doppler boosting in those sources. The undetected sources have lower gamma/radio luminosity ratios and lower contemporaneous brightness temperatures. Unless the Fermi/LAT-undetected blazars are strongly gamma-ray-fainter than the Fermi/LAT-detected ones, their gamma-ray luminosity should not be significantly lower than the upper limits calculated here., Comment: 12 pages, 11 figures, 3 tables, Accepted for publication in Astronomy & Astrophysics

The Southern Hemisphere VLBI Experiment (SHEVE) program is aimed at producing high-resolution images of southern radio sources. The radio telescopes of the present SHEVE array are described below and some recent results presented.

Maps with high dynamic range are presented of a well-defined sample of powerful core-dominated radio sources, all of which have 5-GHz core flux densities >1 Jy. The maps were made at a frequency of 1.64 GHz from combined VLA and B configuration data. A novel technique for producing high dynamic range maps of variable sources from data taken at different epochs is described. It is found that, on average, BL Lac objects are not more core-dominated than the quasars in the sample. This provides no support for the view that BL Lacs are those quasars seen at such small angles to the line of sight that their relativistically beamed core emission swamps that from other components. The results are consistent with most BL Lac objects being the beamed cores of low-luminosity (FRI) radio galaxies

ac susceptibility measurements of superconducting ${\mathrm{K}}_{3}$${\mathrm{C}}_{60}$ powders in magnetic fields to 30 T yield a roughly linear ${\mathit{H}}_{\mathit{c}2}$(T) curve extending up to the highest experimental fields. Samples prepared by two different methods give -${\mathit{dH}}_{\mathit{c}2}$/dT=2.14\ifmmode\pm\else\textpm\fi{}0.08 T/K, with ${\mathit{T}}_{\mathit{c}}$=18.7 K. The observed ${\mathit{H}}_{\mathit{c}2}$ at low temperatures exceeds the ${\mathit{H}}_{\mathit{c}2}$(T) curve from the standard theory by Werthamer-Helfand-Hohenberg. We discuss the role of flux motion and evidence for enhancement of ${\mathit{H}}_{\mathit{c}2}$ by intrinsic mechanisms such as strong coupling, Fermi surface anisotropy, and/or granularity of the samples.

Five experiments were conducted to demonstrate the feasibility of using lactic fermentation to preserve and recover the nutrients from broiler carcasses. When either 7.5% or 10% glucose was fermented with whole chopped carcasses, and Enterobacter-free, acidic (pH 4.2) silage was produced when incubated at 37°C. Tests of fermentability of a variety of carbohydrate sources showed glucose and sucrose were fermented readily and equally by gut lactobacilli. Cornmeal and cornstarch were fermented, but less efficiently (33%) than sugars. Complex carbohydrates (cellulose) were not fermented at all. All cornmeal and glucose based fermentations produced satisfactory results (pH 4.2). Combinations of carbohydrates that provided 10-20% of fermentable carbohydrate in the mixture also gave good results. A variety of industrial carbohydrate byproducts supported vigorous fermentation of carcasses. On a sugar content basis, nondelactosed whey, molasses, and condensed brewers solubles fermented broiler carcasses equally well. Acid production and pathogen destruction proceeded rapidly when incubated at 37-41°C. Broiler silage maintained a consistent pH (4.2 or less) when stored for 45 days at ambient temperatures, and had a nutrient content that made it suitable for reprocessing and refeeding.

The purpose of this study was to understand the reasons why some UK military personnel refused the anthrax vaccination. Data were collected from 5,302 members of the UK Armed Forces who had been deployed to Iraq since 2003 and had been offered the anthrax vaccination. As part of a larger questionnaire, information was collected on acceptance or refusal of the vaccination. Twenty-eight percent of participants refused the anthrax vaccination; of these 51% indicated that they refused vaccination because of concern that it was being offered voluntarily. Reasons differed between those deployed during the war-fighting phase in Iraq, who were concerned about being supplied with insufficient or unclear information (75% vs. 66%), and those involved on subsequent deployments, who felt that there was no longer a risk that biological weapons would be used against them (61% vs. 43%). Thus, refusal rates were related to perception of the threat. In addition, our results indicated the importance of providing individuals with relevant information to aid them in making decisions to receive the anthrax vaccination or not. The findings provide evidence that for some people, the policy to increase confidence in the anthrax vaccination program may have led to a decrease in levels of trust.

Despite a rich phenomenology, gamma-ray bursts (GRBs) are divided into two classes based on their duration and spectral hardness -- the long-soft and the short-hard bursts. The discovery of afterglow emission from long GRBs was a watershed event, pinpointing their origin to star forming galaxies, and hence the death of massive stars, and indicating an energy release of about 10^51 erg. While theoretical arguments suggest that short GRBs are produced in the coalescence of binary compact objects (neutron stars or black holes), the progenitors, energetics, and environments of these events remain elusive despite recent localizations. Here we report the discovery of the first radio afterglow from a short burst, GRB 050724, which unambiguously associates it with an elliptical galaxy at a redshift, z=0.257. We show that the burst is powered by the same relativistic fireball mechanism as long GRBs, with the ejecta possibly collimated in jets, but that the total energy release is 10-1000 times smaller. More importantly, the nature of the host galaxy demonstrates that short GRBs arise from an old (>1 Gyr) stellar population, strengthening earlier suggestions, and providing support for coalescing compact object binaries as the progenitors., Accepted to Nature; revisions include broad-band afterglow model

High angular resolution images of extragalactic radio sources are being made with the Highly Advanced Laboratory for Communications and Astronomy (HALCA) satellite and ground-based radio telescopes as part of the Very Long Baseline Interferometry (VLBI) Space Observatory Programme (VSOP). VSOP observations at 1.6 and 5 gigahertz of the milli–arc-second–scale structure of radio quasars enable the quasar core size and the corresponding brightness temperature to be determined, and they enable the motions of jet components that are close to the core to be studied. Here, VSOP images of the gamma-ray source 1156+295, the quasar 1548+056, the ultraluminous quasar 0014+813, and the superluminal quasar 0212+735 are presented and discussed.

We are using the VSOP space VLBI mission to observe a complete sample of Pearson-Readhead survey sources at 4.8 GHz to determine core brightness temperatures and pc-scale jet properties. To date we have imaged 27 of the 31 objects in our sample. Our preliminary results show that the majority of objects contain strong core components that remain unresolved on baselines of 30,000 km. The brightness temperatures of several cores significantly exceed 1012 K, which is indicative of highly relativistically beamed emission. We also find that core brightness temperature is correlated with intraday variability in compact AGNs.

Tissues from five chickens from each of 44 flocks affected with "spiking mortality" were examined histologically. Tissues from these chickens were characterized by: multifocal necrosis of hepatocytes with congestion and blood lake formation; severe lymphocyte necrosis in the bursal medulla, thymic cortex, and gut-associated lymphoid tissues; acute necrotic vasculitis in the alimentary serosa and liver; rickets; and air-sac disease in survivors. No specific etiology was identified in sections examined.

THE synthesis of macroscopic amounts of C60 and C70 (fullerenes)1 has stimulated a variety of studies on their chemical and physical properties2,3. We recently demonstrated that C60 and C70 become conductive when doped with alkali metals4. Here we describe low-temperature studies of potassium-doped C60 both as films and bulk samples, and demonstrate that this material becomes superconducting. Superconductivity is demonstrated by microwave, resistivity and Meissner-effect measurements. Both polycrystalline powders and thin-film samples were studied. A thin film showed a resistance transition with an onset temperature of 16 K and essentially zero resistance near 5 K. Bulk samples showed a well-defined Meissner effect and magnetic-field-dependent microwave absorption beginning at 18 K. The onset of superconductivity at 18 K is the highest yet observed for a molecular superconductor.

We have been observing the sub-parsec-scale radio jet in the nucleus of Centaurus A, the closest active radio galaxy, at 8.4 GHz over the last 6 years with the SHEVE array and most recently with the VLBA at 8.4 and 22.2 GHz. In this paper we will review the results of these observations and give a brief summary of our interpretation, concentrating on the evolution of the sub-parsec-scale jet structure with time; subluminal component motions and rapid short timescale evolution. A full description of this work is soon to be published in a major journal article.

We have undertaken VLBI observations of 8 Southern Hemisphere EGRET radio sources. Using our data as well as data obtained from the literature we have examined the difference in radio properties between gamma-ray loud and gamma-ray quiet radio sources. In particular, we find no evidence that gamma-ray loud radio sources lie preferentially in sources with straight radio jets as has been suggested.

PKS 1934–638 is an archetypal GPS source, peaking at 1.4 GHz and exhibits almost no flux density variability. VLBI images at frequencies of .843, 2.3, 4.8, & 8.4 were made with the southern hemisphere VLBI array and they reveal that the source is a 42 mas compact double. There is no detectable change in separation over the last 20 years, yielding an upper limit of ~ 0.03c ± 0.2c on any expansion velocity. The spectral shapes of the two components are remarkably similar, despite indications of finer structure on longer baselines. Magnetic field calculations indicate fields of a few mGauss and the results are consistent with equipartition.

On February 12, 1997 the world’s first dedicated VLBI spacecraft, HALCA, was successfully launched as the space borne element of the VSOP mission. This paper describes the calibration observations that have been undertaken so far with this spacecraft.

We report the results of a 5 GHz southern hemisphere VLBI survey of compact extragalactic radio sources. These observations were undertaken with the SHEVE array plus Shanghai station in November 1992. A sample of 22 sources was observed and images of 20 of them were obtained. Of the 20 sources imaged, 15 showed core-jet structure, one had a two-sided jet and 4 had only single compact cores. Eleven of the 16 core-jet (including one two-sided jet) sources show some evidence of bent jets. No compact doubles were found. A comparison with previous images and the temporal variability of the radio flux density showed evidence for superluminal motion in 4 of the sources. Five sources were high energy (>100 MeV) gamma-ray sources. Statistical analysis showed the dominance of highly polarized quasars among the detected gamma-ray sources, which emphasizes the importance of beaming effect in the gamma-ray emission., 39 pages including 7 ps figures and 5 tables, Latex, to appear in AJ

We present high-resolution very long baseline interferometry images of three southern radio sources that the Energetic Gamma-Ray Experiment Telescope (EGRET), on board the Compton Gamma Ray Observatory, has identified as greater than 100 MeV gamma-ray sources. These are the first results in a continuing program of VLBI observations of southern EGRET identifications. For two of these sources, PKS 0208-512 (at 4.851 GHz) and PKS 0537-441 (at 4.851 and 8.418 GHz), the images represent first-epoch observations. For the remaining lower redshift object, PKS 0521-365, we present images from three epochs at 4.851 GHz and an image from one further epoch at 8.418 GHz, spanning approximately 1 yr. We discuss the need for further extensive VLBI observations of EGRET-identified radio sources.

The distribution of apparent misalignment between the position angle of VLBI and VLA scale jets in coredominated radio sources shows an unexpected bimodal form with one peak close to 0° and the other near 90°. We find that this misalignment distribution implies that there are two populations of core-dominated radio sources. The aligned population can be explained by sources with straight VLBI jets and small, randomly oriented, intrinsic bends between parsec and kiloparsec scales. In contrast the misaligned sources must have parsec-scale jets which are curved into low-pitch (i.e., gently curving) helices

A new class of electrode materials for high energy density, rechargeable batteries based on topochemical reactions of lithium and transition metal compounds is evolving. The physical and structural properties relevant to the ability of transition metal oxides with framework structures to topochemically incorporate lithium are discussed. Perovskite-related structures are particularly attractive hosts for lithium.

Nineteen poultry anaphage (dehydrated cage layer excreta) samples were collected from various locations within the United States, and different models of dehydration machines. These samples were analyzed microbiologically for their microbial population and classifications. The results showed that the average microbial population was 466,900 per gram of poultry anaphage. The most frequent isolates were Bacillus and Streptococcus. Two of the nineteen samples showed no microbial population (one was processed by microwave dryer and the other was dehydrated by a dryer equipped with a sterilization unit).

The performance of the Advanced Circuit Program (ACP) circuits described by D. H. Chung and J. A. Palmieri can be improved by replacing the coupling resistor with a pair of tunnel diodes. The low impedance and power gain properties of the tunnel diode increase the fan-power and provide better control of signal levels. In addition, the improved rise times increase circuit speeds to the extent that delays of less than 1 nsec per logic function have been demonstrated. Since the tunnel diode pair can be designed to perform AND, OR, or majority logic functions, the logic flexibility of these circuits is greater than that of the resistor-coupled circuits. The design techniques which lead to a consistent set of logic circuits and to binary full adders are discussed. The very fast rise times generated by the tunnel diode pair require the use of transmission lines as the interconnection medium. The techniques used to minimize the effects of noise and reflections on circuit performance are discussed.

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IT is of fundamental importance in the study of quasars to understand whether or not their continuum emission is isotropic, because this affects the overall energy budget and can also help to distinguish between the different models proposed for their central regions1. The reported small range of emission-line equivalent widths in quasars have earlier been used to argue against a relativistically beamed or anisotropic continuum2,3. Here we use recent spectroscopic observations of 46 radio-loud quasars to show that the equivalent width of the [O III] 5,007-A emission line is strongly anticorrelated with the degree of radio core prominence R, which has been found to be a statistical indicator of orientation relative to the line of sight4–6. This observed anticorrelation shows that the quasar continuum is anisotropic and provides important evidence in favour of relativistic-beaming unified schemes4,7,8. We also show that the strength of the [O III] emission line is independent of R, consistent with unified schemes.

This report contains the results of a study sponsored by the U.S. Nuclear Regulatory Commission (NRC) of removable surface contamination on radioactive materials transportation containers. The purpose of the study is to provide information to the NRC during their review of existing regulations. Data was obtained from both industry and literature on three major topics: 1) radiation doses, 2) economic costs, and 3) contamination frequencies. Containers for four categories of radioactive materials are considered including radiopharmaceuticals, industrial sources, nuclear fuel cycle materials, and low-level radioactive waste. Assumptions made in this study use current information to obtain realistic yet conservative estimates of radiation dose and economic costs. Collective and individual radiation doses are presented for each container category on a per container basis. Total doses, to workers and the public, are also presented for spent fuel cask and low-level waste drum decontamination. Estimates of the additional economic costs incurred by lowering current limits by factors of 10 and 100 are presented. Current contamination levels for each category of container are estimated from the data collected. The information contained in this report is designed to be useful to the NRC in preparing their recommendations for new regulations.

Liver hemorrhages characteristic of those seen in Fatty Liver-Hemorrhagic Syndrome were not observed in livers having less than 4.0 g. lipid per liver or weighing less than 30 g. wet weight. However, liver size and lipid level per se were not the definitive causes of the hemorrhaging because birds without hemorrhages had liver weights and lipid values equal to or greater than those with hemorrhages. Incorporation of lipotropic vitamins (B12, E, choline, inositol) into the diet of laying chickens did not significantly (P > 0.01) reduce their liver lipid content. Increasing the dietary level of protein, vitamin B12, vitamin E, choline, inositol, selenium and/or cobalt did not prevent the occurrence of liver hemorrhages. Liver lipid was significantly (P > 0.01) reduced by feeding a low energy diet; and no liver hemorrhages were observed.

We present high-resolution radio observations of the second Galactic superluminal radio source GRO1655-40, which was detected as an X-ray transient on 1994 July 27. Our radio radio images reveal two components moving away from each other at an angular speed of 65±5 mas/day, corresponding to superluminal motion (υ/c = 1.4 ± 0.4) at the estimated distance of 3–5 kpc. The 12-day delay between the X-ray and radio outbursts suggests that the ejection of material at relativistic speeds occurs during a stable phase of accretion onto a black hole, which follows an unstable phase with a high accretion rate. A complete description and discussion of these observations can be found in Tingay et al 1995 (Nature, 374, pp 141–143).

A sub-parsec scale radio counterjet has been detected in the nucleus of the closest radio galaxy, Centaurus A (NGC 5128), with VLBI imaging at 2.3 and 8.4 GHz. This is one of the first detections of a VLBI counterjet and provides new constraints on the kinematics of the radio jets emerging from the nucleus of Cen A. A bright, compact core is seen at 8.4 GHz, along with a jet extending along P.A. 51 degrees. The core is completely absorbed at 2.3 GHz. Our images show a much wider gap between the base of the main jet and the counterjet at 2.3 GHz than at 8.4 GHz and also that the core has an extraordinarily inverted spectrum. These observations provide evidence that the innermost 0.4-0.8 pc of the source is seen through a disk or torus of ionized gas which is opaque at low frequencies due to free-free absorption., 3 pages, 2 postscript figures, scheduled for publication in August 1, 1996 issue of Ap.J. Letters

Centaurus A (NGC 5128) is the nearest giant radio galaxy. It is a Fanaroff-Riley type 1 (low luminosity) radio source, but the compact radio source in the nucleus is strong enough that VLBI imaging has been possible with both the SHEVE array and the VLBA at several frequencies. These observations have detected a sub-parsec scale counterjet. This shows that jet formation in at least some FR I sources is intrinsically two-sided over very small distances and the radio jets in Centaurus A are probably only moderately relativistic. We also find evidence that the center of activity in Centaurus A is partially obscured by a disk or torus of dense plasma.

THE recent report1 of superconductivity in Nd1,85Ce0.15CuO4 is the first example of a high-transition-temperature (high– Tc) super-conductor with electrons as the charge carriers and a formal copper oxidation state of less than +2. All previously characterized copper oxide superconductors are hole-doped, and the copper is formally oxidized. Here we show that substitution of fluorine for oxygen in T′-phase Nd2CuO4 provides an alternative route to achieving formal reduction of copper, electron conductivity and superconductivity at temperatures as high as 27 K. This result is unusual, because anionic rather than cationic substitution gives rise to the superconductivity.

Oxide superconductors in the system Tl2Ba2Can–1CunO4+2n (ref. 1) have transition temperatures (Tc) above 100 K, increasing with n. So far, stacking sequences up to n = 3 have been found in small crystals, and sequences with n > 3 have been seen in electron microscopy studies1. For large n, the stoichiometry of Tl2Ba2Can–1CunO4+2n approaches CaCuO2, a structure expected to consist only of CuO2 planes separated by Ca atoms. By analogy with Tl2Ba2Can–1CunO4+2n, the unit cell of this hypothetical phase is expected to be tetragonal with a = 3.86 A. Such a compound is not known in the Ca–Cu–O system, but Roth2 recently reported that small amounts of Sr on the Ca site can stabilize this simple structure. Here we report the growth of small single crystals of this phase, with composition (Ca0.86Sr0.14)CuO2, and their characterization by single-crystal X-ray diffraction. The crystals are tetragonal with space group P4/mmm, and the structure contains planar [CuO2]∞ layers separated by Ca and Sr atoms. The structure is a simple defect perovskite with ordered oxygen vacancies and can be regarded as the n = ∞ parent of the A2B2Can–1CunO4+2n (A = Bi, Tl; B = Sr, Ba) superconductors.