Near Infrared Spectroscopy of High Redshift Active Galactic Nuclei. II. Disappearing Narrow Line Regions and the Role of Accretion

We present new near infrared spectroscopic measurements for 29 luminous high-z quasars and use the data to discuss the size and other properties of the NLRs in those sources. The high resolution spectra have been used to carefully model the Fe II blends and to provide reliable [O III], Fe II and Hb measurements. We find that about 2/3 of all high luminosity sources show strong [O III] lines while the remaining objects show no or very weak such line. While weak [O III] emitters are also found among lower luminosity AGN, we argue that the implications for very high luminosity objects are different. In particular, we suggest that the averaging of these two populations in other works gave rise to claims of a Baldwin relationship in [O III] which is not confirmed by our data. We also argue that earlier proposed relations of the type R_NLR \propto L_[O III]^{1/2}, where R_NLR is the NLR radius, are theoretically sound yet they must break down for R_NLR exceeding a few kpc. This suggests that the NLR properties in luminous sources are different from those observed in nearby AGN. In particular, we suggest that some sources lost their very large, dynamically unbound NLR while others are in a phase of violent star-forming events that produce a large quantity of high density gas in the central kpc. This gas is ionized and excited by the central radiation source and its spectroscopic properties may be different from those observed in nearby, lower luminosity NLRs. We also discuss the dependence of EW(Hb) and Fe II/Hb on L, M_BH, and accretion rate for a large sample of AGNs. The strongest dependence of the two quantities is on the accretion rate and the Fe II/Hb correlation is probably due to the EW(Hb) dependence on accretion rate. We show the most extreme values measured so far of Fe II/Hb and address its correlation with EW([O III]).Comment: 10 pages (emulateapj), 9 figures. Accepted by Ap

Solving the mechanistic mystery of RGP blending - Removal versus redistribution

The effect of blending a rigid gas permeable (RGP) contact lens was studied, specifically concentrating upon whether the process removes lens material or if it simply redistributes it. The masses of RGP lenses were measured both before and after blending, and then analysis was performed to determine if material had been removed. Findings indicate that blending a contact lens does indeed remove lens material. This was found to be true with both silicon acrylate and fluorosilicon acrylate lenses

Mms22p protects Saccharomyces cerevisiae from DNA damage induced by topoisomerase II

The cleavage reaction of topoisomerase II, which creates double-stranded DNA breaks, plays a central role in both the cure and initiation of cancer. Therefore, it is important to understand the cellular processes that repair topoisomerase II-generated DNA damage. Using a genome-wide approach with Saccharomyces cerevisiae, we found that Δmre11, Δxrs2, Δrad50, Δrad51, Δrad52, Δrad54, Δrad55, Δrad57 and Δmms22 strains were hypersensitive to etoposide, a drug that specifically increases levels of topoisomerase II-mediated DNA breaks. These results confirm that the single-strand invasion pathway of homologous recombination is the major pathway that repairs topoisomerase II-induced DNA damage in yeast and also indicate an important role for Mms22p. Although Δmms22 strains are sensitive to several DNA-damaging agents, little is known about the function of Mms22p. Δmms22 cultures accumulate in G(2)/M, and display an abnormal cell cycle response to topoisomerase II-mediated DNA damage. MMS22 appears to function outside of the single-strand invasion pathway, but levels of etoposide-induced homologous recombination in Δmms22 cells are lower than wild-type. MMS22 is epistatic with RTT101 and RTT107, genes that encode its protein binding partners. Finally, consistent with a role in DNA processes, Mms22p localizes to discrete nuclear foci, even in the absence of etoposide or its binding partners

Interpreting Tuberculin Skin Tests in a Population With a High Prevalence of HIV, Tuberculosis, and Nonspecific Tuberculin Sensitivity

Understanding the epidemiology and clinical course of tuberculosis is hampered by the absence of a perfect test for latent tuberculosis infection. The tuberculin skin test (TST) is widely used but suffers poor specificity in those receiving the bacille Calmette-Guérin vaccine and poor sensitivity in individuals with human immunodeficiency virus (HIV) infections. TST responses for a target population in Harare, Zimbabwe (HIV prevalence, 21%), recruited in 2005–2006, were interpreted by using a separate calibration population in Harare, for which interferon-gamma release assays (enzyme-linked immunosorbent spot (ELISpot)) results were also known. Statistical fitting of the responses in the calibration population allowed computation of the probability that an individual in the target population with a given TST and HIV result would have tested ELISpot positive. From this, estimates of the prevalence of tuberculosis infection, and optimal TST cutpoints to minimize misdiagnosis, were computed for different assumptions about ELISpot performance. Different assumptions about the sensitivity and specificity of ELISpot gave a 40%–57% prevalence of tuberculosis infection in the target population (including HIV-infected individuals) and optimal TST cutpoints typically in the 10 mm–20 mm range. However, the optimal cutpoint for HIV-infected individuals was consistently 0 mm. This calibration method may provide a valuable tool for interpreting TST results in other populations

Nursing and community rates of Mycobacterium tuberculosis infection among students in Harare, Zimbabwe.

BACKGROUND: African hospitals have experienced major increases in admissions for tuberculosis, but they are ill-equipped to prevent institutional transmission. We compared institutional rates and community rates of tuberculin skin test (TST) conversion in Harare, Zimbabwe. METHODS: We conducted a cohort study of TST conversion 6, 12, and 18 months into training among 159 nursing and 195 polytechnic school students in Harare. Students had negative TST results (induration diameter, or =10 mm) per 100 person-years (95% confidence interval [CI], 14.2-26.2 conversions per 100 person-years), and polytechnic school students experienced 6.0 (95% CI, 3.5-10.4) conversions per 100 person-years. The rate of difference was 13.2 conversions (95% CI, 6.5-20.0) per 100 person-years. With a more stringent definition of conversion (increase in the induration diameter of > or =10 mm to at least 15 mm), which is likely to increase specificity but decrease sensitivity, conversion rates were 12.5 and 2.8 conversions per 100 person-years in nursing and polytechnic school students, respectively (rate difference, 9.7 conversions per 100 person-years; 95% CI, 4.5-14.8 conversions per 100 person-years). Nursing students reportedly nursed 20,868 inpatients with tuberculosis during 315 person-years of training. CONCLUSIONS: Both groups had high TST conversion rates, but the extremely high rates among nursing students imply high occupational exposure to Mycobacterium tuberculosis. Intense exposure to inpatients with tuberculosis was reported during training. Better prevention, surveillance, and management of institutional M. tuberculosis transmission need to be supported as part of the international response to the severe human immunodeficiency virus infection epidemic and health care worker crisis in Africa

The Hubble Constant from (CLASS) Gravitational Lenses

One of the main objectives of the Cosmic Lens All-Sky Survey (CLASS) collaboration has been to find gravitational lens (GL) systems at radio wavelengths that are suitable for the determination of time delays between image pairs. The survey is now near completion and at least 18 GL systems have been found. Here, I will discuss our efforts to measure time delays from several of these systems with the ultimate aim of constraining the Hubble Constant (H0). Thus far three CLASS GL systems (i.e. B0218+357, B1600+434 and B1608+656) have yielded measurements of time delays, from which values of H0=60-70 km/s/Mpc have been estimated. Although most GL systems give similar values of H0, statistical and systematic uncertainties are still considerable. To reduce these uncertainties, I will shortly mention two monitoring programs that we are undertaking to (re)measure time delays in 15 CLASS GL systems and address several important issues for the near future.Comment: 4 pages, no figures; based on a talk given at the "The OzLenz Workshop" in Melbourne (Au), 2000 dec. 4-6; to appear in PAS

Provider-initiated symptom screening for tuberculosis in Zimbabwe: diagnostic value and the effect of HIV status.

OBJECTIVE: To assess the diagnostic value of provider-initiated symptom screening for tuberculosis (TB) and how HIV status affects it. METHODS: We performed a secondary analysis of randomly selected participants in a community-based TB-HIV prevalence survey in Harare, Zimbabwe. All completed a five-symptom questionnaire and underwent sputum TB culture and HIV testing. We calculated the sensitivity, specificity, and positive and negative predictive values of various symptoms and used regression analysis to investigate the relationship between symptoms and TB disease. FINDINGS: We found one or more symptoms of TB in 21.2% of 1858 HIV-positive (HIV+) and 9.9% of 7121 HIV-negative (HIV-) participants (P or = 2 weeks' duration, any symptom and a positive sputum culture had sensitivities of 48%, 81% and 65%, respectively; in HIV- participants, the sensitivities were 45%, 71% and 74%, respectively. Symptoms had a similar sensitivity and specificity in HIV+ and HIV- participants, but in HIV+ participants they had a higher positive and a lower negative predictive value. CONCLUSION: Even smear-positive TB may be missed by provider-initiated symptom screening, especially in HIV+ individuals. Symptom screening is useful for ruling out TB, but better TB diagnostics are urgently needed for resource-poor settings

Multiband optical polarimetry of BL Lac objects with the Nordic Optical Telescope

Optical polarization of seven selected BL Lac objects in UBVRI bands was studied with the Nordic Optical Telescope from December 10-14, 1999. Two of them, 3C 66A and PKS 0735+178, were monitored for 4 nights for a total integration time of 4.75 and 5.5 hours, respectively. Other objects (1Jy 0138-097, H 0414+009, PKS 0823-223, OJ287 and BL Lac) were observed sparsely during the run. Apart from PKS 0823-223 (more polarized than observed in the past), the sources show levels of flux and polarization consistent with results at previous epochs. 3C 66A and PKS 0735+178 were intensively observed during December 11 and 12 and exhibited variability of polarization, both on internight and intranight time scales. Wavelength dependence of polarization has been investigated, as well as circular polarization. The results are discussed within the standard model for BL Lacs.Comment: 11 pages, 7 figures, accepted to Astronomy & Astrophysic

Ultraviolet and Multiwavelength Variability of the Blazar 3C 279: Evidence for Thermal Emission

The gamma-ray blazar 3C 279 was monitored on a nearly daily basis with IUE, ROSAT and EGRET for three weeks between December 1992 and January 1993. During this period, the blazar was at a historical minimum at all wavelengths. Here we present the UV data obtained during the above multiwavelength campaign. A maximum UV variation of ~50% is detected, while during the same period the X-ray flux varied by no more than 13%. At the lowest UV flux level the average spectrum in the 1230-2700 A interval is unusually flat for this object (~1). The flattening could represent the lowest energy tail of the inverse Compton component responsible for the X-ray emission, or could be due to the presence of a thermal component at ~20000 K possibly associated with an accretion disk. The presence of an accretion disk in this blazar object, likely observable only in very low states and otherwise hidden by the beamed, variable synchrotron component, would be consistent with the scenario in which the seed photons for the inverse Compton mechanism producing the gamma-rays are external to the relativistic jet. We further discuss the long term correlation of the UV flux with the X-ray and gamma-ray fluxes obtained at various epochs. All UV archival data are included in the analysis. Both the X- and gamma-ray fluxes are generally well correlated with the UV flux, approximately with square root and quadratic dependences, respectively.Comment: 22 pages, Latex, 7 PostScript figures, to appear in The Astrophysical Journa

Examining Dehydration and Hypoxic Stress in Wheat Plants Using a Porous Tube Plant Nutrient Delivery System Developed for Microgravity

The Porous Tube Plant Nutrient Delivery System (PTPNDS) was designed for NASA to grow plants in microgravity of space. The system utilizes a controlled fluid loop to supply nutrients and water to plant roots growing on a ceramic surface moistened by capiflary action. A PTPNDS test bed was developed and utilizing remote sensing systems, spectral analyses procedures, gas-exchange, and fluorescence measurements, we examined differences in plant water status for wheat plants (Triticum aestivum, cv. Perigee) grown in a modified growth chamber during the summers of 2003 and 2004. Some differences in plant performance were detectable in the gas-exchange and fluorescence measurements. For instance, in both years the plants grown with the most available water had the lowest rates of photosynthesis and exhibited higher proportions of non-photochemical quenching particularly under low light levels. In addition, small differences in mean leaf water content between treatments were detected using spectral reflectance analyses