Modeling the Radio Background from the First Black Holes at Cosmic Dawn: Implications for the 21 cm Absorption Amplitude

We estimate the 21 cm Radio Background from accretion onto the first intermediate-mass Black Holes between $z\approx 30$ and $z\approx 16$. Combining potentially optimistic, but plausible, scenarios for black hole formation and growth with empirical correlations between luminosity and radio-emission observed in low-redshift active galactic nuclei, we find that a model of black holes forming in molecular cooling halos is able to produce a 21 cm background that exceeds the Cosmic Microwave Background (CMB) at $z \approx 17$ though models involving larger halo masses are not entirely excluded. Such a background could explain the surprisingly large amplitude of the 21 cm absorption feature recently reported by the EDGES collaboration. Such black holes would also produce significant X-ray emission and contribute to the $0.5-2$ keV soft X-ray background at the level of $\approx 10^{-13}-10^{-12}$ erg sec$^{-1}$ cm$^{-2}$ deg$^{-2}$, consistent with existing constraints. In order to avoid heating the IGM over the EDGES trough, these black holes would need to be obscured by Hydrogen column depths of $N_\text{H} \sim 5 \times 10^{23} \text{cm}^{-2}$. Such black holes would avoid violating contraints on the CMB optical depth from Planck if their UV photon escape fractions were below $f_{\text{esc}} \lesssim 0.1$, which would be a natural result of $N_\text{H} \sim 5 \times 10^{23} \text{cm}^{-2}$ imposed by an unheated IGM.Comment: 10 pages, 7 figures, accepted to ApJ, replacement to match submitted versio

Metallochaperones Are Needed for Mycobacterium tuberculosis and Escherichia coli Nicotinamidase-Pyrazinamidase Activity.

Mycobacterium tuberculosis nicotinamidase-pyrazinamidase (PZAse) is a metalloenzyme that catalyzes conversion of nicotinamide-pyrazinamide to nicotinic acid-pyrazinoic acid. This study investigated whether a metallochaperone is required for optimal PZAse activity. M. tuberculosis and Escherichia coli PZAses (PZAse-MT and PZAse-EC, respectively) were inactivated by metal depletion (giving PZAse-MT-Apo and PZAse-EC-Apo). Reactivation with the E. coli metallochaperone ZnuA or Rv2059 (the M. tuberculosis analog) was measured. This was repeated following proteolytic and thermal treatment of ZnuA and Rv2059. The CDC1551 M. tuberculosis reference strain had the Rv2059 coding gene knocked out, and PZA susceptibility and the pyrazinoic acid (POA) efflux rate were measured. ZnuA (200 μM) achieved 65% PZAse-EC-Apo reactivation. Rv2059 (1 μM) and ZnuA (1 μM) achieved 69% and 34.3% PZAse-MT-Apo reactivation, respectively. Proteolytic treatment of ZnuA and Rv2059 and application of three (but not one) thermal shocks to ZnuA significantly reduced the capacity to reactivate PZAse-MT-Apo. An M. tuberculosis Rv2059 knockout strain was Wayne positive and susceptible to PZA and did not have a significantly different POA efflux rate than the reference strain, although a trend toward a lower efflux rate was observed after knockout. The metallochaperone Rv2059 restored the activity of metal-depleted PZAse in vitro Although Rv2059 is important in vitro, it seems to have a smaller effect on PZA susceptibility in vivo. It may be important to mechanisms of action and resistance to pyrazinamide in M. tuberculosis Further studies are needed for confirmation.IMPORTANCE Tuberculosis is an infectious disease caused by the bacterium Mycobacterium tuberculosis and remains one of the major causes of disease and death worldwide. Pyrazinamide is a key drug used in the treatment of tuberculosis, yet its mechanism of action is not fully understood, and testing strains of M. tuberculosis for pyrazinamide resistance is not easy with the tools that are presently available. The significance of the present research is that a metallochaperone-like protein may be crucial to pyrazinamide's mechanisms of action and of resistance. This may support the development of improved tools to detect pyrazinamide resistance, which would have significant implications for the clinical management of patients with tuberculosis: drug regimens that are appropriately tailored to the resistance profile of a patient's individual strain lead to better clinical outcomes, reduced onward transmission of infection, and reduction of the development of resistant strains that are more challenging and expensive to treat

Assessment of climate change vulnerability of farm households in Pyapon District, a delta region in Myanmar

Sea level rise causes saltwater intrusion and flooding of agricultural land and ultimately threatens the livelihoods of farm households in the delta region of Myanmar. Empirical research on the effects of climate change on the delta's agriculture and an assessment of the vulnerability are becoming necessary. This study explores the vulnerability of farm households to sea level rise using two methods: the Livelihood Vulnerability Index (LVI), which is comprised of 37 indicators, and the Socioeconomic Vulnerability Index (SeVI), which contains 35 indicators. Interviews with 178 farmers were conducted in Bogale, Pyapon and Dedaye Townships in Pyapon District. In addition, 7 focus group discussions were performed, with at least 2 discussions in each Township. Both methods identify Bogale to be the most vulnerable Township, followed by Dedaye and Pyapon Townships. Following the LVI approach, Bogale Township has the highest sensitivity to climate effects and the highest exposure to natural hazards, but also a higher adaptive capacity than the other townships. In contrast using the SeVI approach, Bogale was found to have the highest sensitivity and exposure to natural hazards but the lowest adaptive capacity score. The study found that the climate change adaptation measures taken by the farmers are important to limit vulnerable to the adverse effects of climate change and thus promotion of the adaptive capacity of farmers is important for the delta region of Myanmar

Evaluación del ultrasonido como método complementario en la conservación del queso blanco paisa venezolano

El queso blanco PAISA® se caracteriza por ser un producto estándar apetecible en todo el territorio Venezolano, por su color blanco marfil, fácil rebanabilidad, dureza, su sabor característico a salado – mantequilla y baja acidez. Al ser un producto fresco éstas características sufren modificaciones que se pronuncian en la tercera semana de almacenamiento viéndose limitada su comercialización por los cambios en la firmeza (rebanabilidad) y acidez. Por ello, se estudió el efecto del ultrasonido como método complementario en la conservación de la calidad y extensión de la vida útil del queso Venezolano Paisa. Fueron utilizados 78 bloques de queso empacados al vacío, se sometieron a ocho tratamientos con ultrasonido de alta intensidad (50kHz y 75W), temperaturas (5°C, 10°C y 22°C) y tiempo de exposición (5, 10 y 15 minutos), y una muestra sin tratamiento como testigo. Se evaluó el pH, color interno y externo, textura (TPA), perfil sensorial, coliformes totales y mohos en un lapso de cinco (5) semanas en almacenamiento a 4°C. Resultó que la aplicación del ultrasonido causa inicialmente reducción estadísticamente significativa en el crecimiento de coliformes totales, provoca en el tiempo un efecto positivo en el color interno y externo, en la rebanabilidad, en el olor y sabor ácido, reduciendo la intensidad del sabor. El tratamiento de aplicación de ultrasonido de alta intensidad por diez (10) minutos a temperatura de 5°C supuso una mejora significativa en el tiempo de vida útil del queso blanco Paisa Venezolano, lográndose una mayor aceptación sensorial

Determinación de la respuesta a fatiga de GLARE (Glass Reinforced Laminate) reforzado con nanotubos de carbono

Se investigó la respuesta a fatiga de GLARE (Glass Reinforced Laminate) fabricado con resina epóxica reforzada con nanotubos de carbono (NTC). Para la fabricación del Glare se utilizó Al 2024-T3, fibra de vidrio S2-5433, resina epóxica L20 y endurecedor EPH-161. Se usaron NTC comerciales. Las muestras se prepararon íntegramente en el taller de materiales compuestos de la Empresa Nacional de Aeronáutica (ENAER). Se utilizaron probetas rectangulares de 50 x 140 mm de acuerdo a la norma ASTM E647. Con el fin de reforzar la resina epóxica utilizada, se agregaron NTC en las dosificaciones de 0,5 y 1% en peso. Se determinaron las curvas carga versus número de ciclos utilizándose cinco niveles de carga y tres probetas por cada nivel. Se determinaron las curvas de Paris para cada una de las configuraciones fabricadas, determinándose los coeficientes C y m. La metodología experimental consideró en todos los casos una perforación circular de 7,7 mm de diámetro en el centro de cada probeta, dos entallas ubicadas perpendiculares al eje de aplicación de carga de 2 mm y una pregrieta de 3 mm de longitud. Los resultados se compararon con los resultados obtenidos con GLARE fabricado sin refuerzo a través de ensayos de fatiga, obteniéndose en todos los niveles una mejora en la vida a fatiga

Nematic Films and Radially Anisotropic Delaunay Surfaces

We develop a theory of axisymmetric surfaces minimizing a combination of surface tension and nematic elastic energies which may be suitable for describing simple film and bubble shapes. As a function of the elastic constant and the applied tension on the bubbles, we find the analogues of the unduloid, sphere, and nodoid in addition to other new surfaces.Comment: 15 pages, 18 figure

Gravitational Redshift, Equivalence Principle, and Matter Waves

We review matter wave and clock comparison tests of the gravitational redshift. To elucidate their relationship to tests of the universality of free fall (UFF), we define scenarios wherein redshift violations are coupled to violations of UFF ("type II"), or independent of UFF violations ("type III"), respectively. Clock comparisons and atom interferometers are sensitive to similar effects in type II and precisely the same effects in type III scenarios, although type III violations remain poorly constrained. Finally, we describe the "Geodesic Explorer," a conceptual spaceborne atom interferometer that will test the gravitational redshift with an accuracy 5 orders of magnitude better than current terrestrial redshift experiments for type II scenarios and 12 orders of magnitude better for type III.Comment: Work in progress. 11 page