A new look at the problem of gauge invariance in quantum field theory

Quantum field theory is assumed to be gauge invariant. However it is well known that when certain quantities are calculated using perturbation theory the results are not gauge invariant. The non-gauge invariant terms have to be removed in order to obtain a physically correct result. In this paper we will examine this problem and determine why a theory that is supposed to be gauge invariant produces non-gauge invariant results.Comment: Accepted by Physica Scripta. 27 page

Carrier extraction circuit

Feedback loop extracts demodulated reference signals from IF input and feeds signal back to demodulator. Since reference signal is extracted directly from carrier, no separate reference need be transmitted. Circuit obtains coherent carrier from balanced or unbalanced four-phase signal of varying characteristics

Advanced ceramic material for high temperature turbine tip seals

Forty-one material systems were evaluated for potential use in turbine blade tip seal applications at 1370 C. Both ceramic blade tip inserts and abradable ceramic tip shoes were tested. Hot gas erosion, impact resistance, thermal stability, and dynamic rub performance were the criteria used in rating the various materials. Silicon carbide and silicon nitride were used, both as blade tips and abradables. The blade tip inserts were fabricated by hot pressing while low density and honeycomb abradables were sintered or reaction bonded

Ground-based measurements of O3, NO2, OClO, and BrO during the 1987 Antarctic ozone depletion event

Near-ultraviolet absorption spectroscopy in the wavelength range from 330 to 370 nm was used to measure O3, NO2, OClO, and BrO at McMurdo Station (78S) during 1987. Visible absorption measurements of O3, NO2, and OClO were also obtained using the wavelength range from about 403 to 453 nm. These data are described and compared to observations obtained in 1986. It is shown that comparisons of observations in the two wavelength ranges provide a sensitive measure of the altitude where the bulk of atmospheric absorption takes place

Antibiotics for trachoma.

BACKGROUND: Trachoma is the world's leading infectious cause of blindness. In 1997 the World Health Organization (WHO) launched an Alliance for the Global Elimination of Trachoma by the year 2020, based on the 'SAFE' strategy (surgery, antibiotics, facial cleanliness and environmental improvement). OBJECTIVES: To assess the evidence supporting the antibiotic arm of the SAFE strategy by assessing the effects of antibiotics on both active trachoma (primary objective) and on Chlamydia trachomatis (C. trachomatis) infection of the conjunctiva (secondary objective). SEARCH STRATEGY: We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2010, Issue 11), MEDLINE (January 1950 to December 2010), EMBASE (January 1980 to December 2010), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com) (December 2010) and ClinicalTrials.gov (www.clinicaltrials.gov) (December 2010). We used the Science Citation Index to look for articles that cited the included studies. We searched the reference lists of identified articles and we contacted authors and experts for details of further relevant studies. There were no language or date restrictions in the search for trials. The electronic databases were last searched on 12 December 2010. SELECTION CRITERIA: We included randomised trials that satisfied either of two criteria: (a) trials in which topical or oral administration of an antibiotic was compared to placebo or no treatment in people or communities with trachoma, (b) trials in which a topical antibiotic was compared with an oral antibiotic in people or communities with trachoma. A subdivision of particular interest was trials in which topical tetracycline or chlortetracycline and oral azithromycin were compared with each other, or in which one of these treatments was compared with placebo or no treatment, as these are the two WHO recommended antibiotics. We considered individually randomised and cluster-randomised trials separately. DATA COLLECTION AND ANALYSIS: Two authors independently assessed trial quality and extracted data. We contacted investigators for missing data. Where appropriate, the effect estimates from the individual studies (risk ratios) were pooled using a random-effects model. MAIN RESULTS: A total of 14 trials randomised individuals with trachoma to oral antibiotic, topical antibiotic, both, or control (no treatment or placebo) and were eligible for inclusion in this review (n = 3587). Overall, the quality of the evidence provided from these trials was low. Nine of the trials compared antibiotic treatment to control. Most of the studies found a beneficial effect of treatment on active trachoma and ocular chlamydial infection at three and 12 months follow up. There was considerable clinical and statistical heterogeneity between trials, which meant that it was difficult to reliably estimate the size of the treatment effect. It is likely to be in the region of a 20% relative risk reduction. Seven of the 14 trials compared the effectiveness of oral and topical antibiotics. There was no consistent evidence as to whether oral or topical antibiotics were more effective, although one trial suggested that a single dose of oral azithromycin was significantly more effective than unsupervised use of topical tetracyclineA further eight trials assessed the effectiveness of community-based treatment. In five trials antibiotic treatment was compared to no (or delayed) treatment (57 communities), and in three trials oral antibiotic was compared to topical treatment (12 communities). The quality of the evidence provided by these trials was variable but at least one trial was considered to provide high quality evidence. There was evidence that community-based antibiotic treatment reduced the prevalence of active trachoma and ocular infection 12 months after single-dose treatment. There was some evidence that oral azithromycin was more effective than topical tetracycline as a community treatment. Data on adverse effects were not consistently reported however there were no reported serious adverse events associated with treatment with oral azithromycin or topical tetracycline; in one sample survey of 671 people treated with azithromycin between 10% and 15% experienced gastrointestinal adverse effects (nausea or vomiting, or both). AUTHORS' CONCLUSIONS: Antibiotic treatment reduces the risk of active trachoma and ocular chlamydial infection in people infected with C. trachomatis, but we do not know for certain the size of the treatment effect in individuals. Mass antibiotic treatment with single-dose oral azithromycin reduces the prevalence of active trachoma and ocular infection in communities

Visible and near-ultraviolet spectroscopy at Thule AFB (76.5 N) from January 28 - February 15, 1988

Near-ultraviolet and visible spectrographs identical to those employed at McMurdo Station, Antarctica (77.8 S) during the austral spring seasons of 1986 and 1987 were used to study the stratosphere above Thule, Greenland (76.5 N) during early spring, 1988. Observations were carried out both at night using the direct moon as a light source, and during the day by collecting the scattered light from the zenith sky when solar zenith angles were less than about 94.5 degrees. Excellent meteorological conditions prevailed in the troposphere and stratosphere at Thule. Surface weather was extremely clear over most of the period, facilitating measurements of the direct light from the moon. The lower stratospheric arctic polar vortex was located very near Thule throughout the observing period, and temperature at the 30 mbar level were typically below -80 C above Thule, according to the National Meteorological Center daily analyses. Thus conditions were favorable for polar stratospheric cloud formation above Thule. Total column ozone abundances were about 350 to 400 Dobson units, and did not suggest a clear temporal trend over the observing period. Stratospheric nitrogen dioxide measurements were complicated by the presence of a large component of tropospheric pollution on many occasions. Stratospheric nitrogen dioxide could be identified on most days using the absorption in the scattered light from the zenith sky, which greatly enhances the stratospheric airmass while suppressing the tropospheric contribution. These measurements suggest that the total vertical column abundance of nitrogen dioxide present over Thule in February was extremely low, sometimes as low as 3 x 10 to the 14th per sq cm. The abundance of nitrogen dioxide increased systemically from about 3 x 10 to the 14th in late January to 1.0 x 10 to the 15th per sq cm in mid-February, perhaps because of photolysis of N2O5 in the upper part of the stratosphere, near 25 to 35 km

The Molecular Interstellar Medium in Ultraluminous Infrared Galaxies

We present CO observations of a large sample of ultraluminous IR galaxies out to z = 0.3. Most of the galaxies are interacting, but not completed mergers. All but one have high CO(1-0) luminosities, log(Lco [K-km/s-pc^2]) = 9.92 +/- 0.12. The dispersion in Lco is only 30%, less than that in the FIR luminosity. The integrated CO intensity correlates Strongly with the 100 micron flux density, as expected for a black body model in which the mid and far IR radiation are optically thick. We use this model to derive sizes of the FIR and CO emitting regions and the enclosed dynamical masses. Both the IR and CO emission originate in regions a few hundred parsecs in radius. The median value of Lfir/Lco = 160 Lsun/(K-km/s-pc^2), within a factor of two of the black body limit for the observed FIR temperatures. The entire ISM is a scaled up version of a normal galactic disk with densities a factor of 100 higher, making even the intercloud medium a molecular region. Using three different techniques of H2 mass estimation, we conclude that the ratio of gas mass to Lco is about a factor of four lower than for Galactic molecular clouds, but that the gas mass is a large fraction of the dynamical mass. Our analysis of CO emission reduces the H2 mass from previous estimates of 2-5e10 Msun to 0.4-1.5e10 Msun, which is in the range found for molecular gas rich spiral galaxies. A collision involving a molecular gas rich spiral could lead to an ultraluminous galaxy powered by central starbursts triggered by the compression of infalling preexisting GMC's.Comment: 34 pages LaTeX with aasms.sty, 14 Postscript figures, submitted to ApJ Higher quality versions of Figs 2a-f and 7a-c available by anonymous FTP from ftp://sbast1.ess.sunysb.edu/solomon/

Masses, luminosities and dynamics of galactic molecular clouds

Star formation in galaxies takes place in molecular clouds and the Milky Way is the only galaxy in which it is possible to resolve and study the physical properties and star formation activity of individual clouds. The masses, luminosities, dynamics, and distribution of molecular clouds, primarily giant molecular clouds in the Milky Way are described and analyzed. The observational data sets are the Massachusetts-Stony Brook CO Galactic Plane Survey and the IRAS far IR images. The molecular mass and infrared luminosities of glactic clouds are then compared with the molecular mass and infrared luminosities of external galaxies

Application of remote sensing to state and regional problems

The methods and procedures used, accomplishments, current status, and future plans are discussed for each of the following applications of LANDSAT in Mississippi: (1) land use planning in Lowndes County; (2) strip mine inventory and reclamation; (3) white-tailed deer habitat evaluation; (4) remote sensing data analysis support systems; (5) discrimination of unique forest habitats in potential lignite areas; (6) changes in gravel operations; and (7) determining freshwater wetlands for inventory and monitoring. The documentation of all existing software and the integration of the image analysis and data base software into a single package are now considered very high priority items

Transient Random Walks in Random Environment on a Galton-Watson Tree

We consider a transient random walk $(X_n)$ in random environment on a Galton--Watson tree. Under fairly general assumptions, we give a sharp and explicit criterion for the asymptotic speed to be positive. As a consequence, situations with zero speed are revealed to occur. In such cases, we prove that $X_n$ is of order of magnitude $n^{\Lambda}$, with $\Lambda \in (0,1)$. We also show that the linearly edge reinforced random walk on a regular tree always has a positive asymptotic speed, which improves a recent result of Collevecchio \cite{Col06}