A faint galaxy redshift survey to B=24

Using the multislit LDSS-2 spectrograph on the {\it William Herschel Telescope} we have completed a redshift survey in the magnitude range $22.5<B< 24$ which has produced 73 redshifts representing a 73\% complete sample uniformly-selected from four deep fields at high Galactic latitude. The survey extends out to $z>1$ and includes the highest redshift galaxy ($z=1.108$) yet discovered in a field sample. The median redshift, \zmed=0.46, and form of the redshift distribution constitute compelling evidence against simple luminosity evolution as an explanation of the large excess of faint galaxies ($\simeq\times$2--4 no-evolution) seen in this magnitude range. Rather we identify the excess population as blue objects with $z\sim 0.4$ and $B$\, luminosities similar to local $L^*$ galaxies indicating a dramatic decrease in the density of such objects over the last Hubble time, confirming the trends found in brighter redshift surveys. We also find a marked absence of {\it very} low redshift galaxies ($z<$0.1) at faint limits, severely constraining any significant steepening of the local field galaxy luminosity function at low luminosities.Comment: uuencoded compressed postscript. The preprint are also available at URL http://www.ast.cam.ac.uk/preprint/PrePrint.htm

Metal-Coated Defect-Core Photonic Crystal Fiber for THz Propagation

Modal solutions for metal-coated defect-core photonic crystal fiber (PCF) with a central air-hole have been obtained by using a full-vectorial finite element method to model the guidance of THz waves. It has been shown that the surface plasmon modes can couple with the defect-core PCF mode to form supermodes, with potential for sensing applications

The Star Formation History of the Hubble Sequence: Spatially Resolved Colour Distributions of Intermediate Redshift Galaxies in the Hubble Deep Field

We analyse the spatially resolved colours of distant galaxies of known redshift in the Hubble Deep Field, using a new technique based on matching resolved four-band internal colour data to the predictions of evolutionary synthesis models. We quantify the relative age, dispersion in age, ongoing star-formation rate, star-formation history, and dust content of these galaxies. To demonstrate the potential of the method, we study the near-complete sample of 32 I ~ 0.5 studied by Bouwens et al (1997). The dispersion of the internal colours of a sample of 0.4<z<1 early-type field galaxies in the HDF indicates that ~40% [4/11] show evidence of star formation which must have occurred within the past third of their ages at the epoch of observation. For a sample of well-defined spirals, we similarly exploit the dispersion in colour to analyse the relative histories of bulge and disc stars, in order to resolve the current controversy regarding the ages of galactic bulges. Dust and metallicity gradients are ruled out as major contributors to the colour dispersions we observe in these systems. The median ages of bulge stars are found to be signicantly older than those in galactic discs, and exhibit markedly different star-formation histories. This result is inconsistent with a secular growth of bulges from disc instabilities, but consistent with gradual disc formation by accretion of gas onto bulges, as predicted by hierarchical theories. We extend our technique in order to discuss the star formation history of the entire Bouwens et al sample in the context of earlier studies concerned with global star formation histories.Comment: 8 colour postscript figures plus LaTeX source; submitted to MNRAS. Uses the mnras.sty LaTeX style fil

Impact of graphene oxide and highly reduced graphene oxide on cement based composites

This study examines and compares the performance of two specific forms of graphene nanomaterials in the cement based composite, namely graphene oxide (GO) and reduced graphene oxide (rGO). A typical forms of GO with the average C:O ratio of 54:46 and a rGO with the average C:O ratio of 82:18 were used in the cement based paste composites. rGO was treated with superplasticizer to improve its dispersibility in water. Both GO and rGO were used as 0.02, 0.04, 0.06 wt% of cement. The effect of GO and rGO on workability, early age hydration, microstructure, mechanical and transport properties was determined. Different characteristics of GO and rGO such as molecular structure, functional groups, d spacing, size and physical strength influenced the properties of the cement based composites. The workability and final setting time of composite gradually decreased compared to 100% PC (control) with higher dosages of GO up to 0.06 wt% (of cement), which is due to the dominant oxygen functional groups and the hydrophilic nature of GO. To the contrary, the workability and final setting time increased in the rGO composites compared to the control mix due to the almost hydrophobic nature of rGO and the presence of superplasticiser. The XRD and TGA quantification of the hydration products shows that GO composites have a greater content of Ca(OH)2 and C-S-H compared to rGO composites measured at 1, 7 and 28 days. Micropores (smaller than ∼10 µm) in GO composites were observed to be filled with calcium silicate hydrate (C-S-H) gel and crystalline compounds. Random pore filling nature was observed in rGO composites and ettringite was more common element in those pores. Meso and gel pores

Localizing gravitational wave sources with optical telescopes and combining electromagnetic and gravitational wave data

Neutron star binaries, which are among the most promising sources for the direct detection of gravitational waves (GW) by ground based detectors, are also potential electromagnetic (EM) emitters. Gravitational waves will provide a new window to observe these events and hopefully give us glimpses of new astrophysics. In this paper, we discuss how EM information of these events can considerably improve GW parameter estimation both in terms of accuracy and computational power requirement. And then in return how GW sky localization can help EM astronomers in follow-up studies of sources which did not yield any prompt emission. We discuss how both EM source information and GW source localization can be used in a framework of multi-messenger astronomy. We illustrate how the large error regions in GW sky localizations can be handled in conducting optical astronomy in the advance detector era. We show some preliminary results in the context of an array of optical telescopes called BlackGEM, dedicated for optical follow-up of GW triggers, that is being constructed in La Silla, Chile and is expected to operate concurrent to the advanced GW detectors.Comment: 8 pages, 8 figures, Proceeding for Sant Cugat Forum for Astrophysic

A Study of Knowledge Attitude and Practice Regarding HIV/AIDS among Adolescents

Introduction: In this world of 7.2 billion people, 1.2 billion live in India and out of these, 243 million, i.e., 20.9% of the population are adolescents, between 10 and 19 years, as per 2011. This makes India the world’s largest adolescent-living country. As per WHO, HIV is the second leading cause of death among adolescents. In Dist. Bathinda, 99,595 people were tested out of which 1339, i.e., 1.34% were found to be positive till February 2014. Hence school education has been described as a ‘social vaccine,’ and it can serve as a powerful preventive tool. In India, there is a wide gap between the inputs in the HIV/AIDS curriculum for schools and the actual education that is imparted.Materials and Methods: A cross-sectional study was conducted among adolescents (14 to 19 years) in three randomly chosen co-educational schools in Bathinda. Adolescents from 14 to 19 years in randomly chosen schools were included in the study. A pre-designed, pre-structured, pre-tested questionnaire was introduced to the participants by the interviewer in English and Hindi. Privacy of the schools and the participants was maintained by not mentioning their names anywhere in the study. Data was collected regarding knowledge, attitude and prevalence regarding HIV/AIDS.Results: A total of 401 adolescents were enrolled in our study out of which 282 were males and 119 females. Almost all the adolescents, i.e., 99.8% had heard about the term HIV/AIDS. 74.8% had TV and 61.6% internet as their source of information. A large number, i.e., 85.3% adolescents (87.6% male adolescents and 79.8% female adolescents) knew that sexual contact could be the mode of transmission of HIV/AIDS. A large number, i.e., 71.82% (80.14% males and 52.1% females) knew that HIV/AIDS could be prevented by using condoms. 52 adolescents had history of previous sexual exposure out of whom 48 used condoms during the last sexual contact. The association was significant between the knowledge and practice regarding the use of condom (highly significant: p<0.01).Conclusion: Thus this study reveals that still much has to be done towards imparting information about HIV/AIDS among adolescents, which could be done through many ways, like involving them in various activities at health centers as and when any IEC activities are carried out. Moreover schools and parents should also involve themselves and impart them more information regarding the disease. Mothers play an important role in providing more information to girl adolescents. Thus a collective effort is needed so as to have a bright future of these adolescents

A universal GRB photon energy-peak luminosity relation

The energetics and emission mechanism of GRBs are not well understood. Here we demonstrate that the instantaneous peak flux or equivalent isotropic peak luminosity, L_iso ergs s^-1, rather than the integrated fluence or equivalent isotropic energy, E_iso ergs, underpins the known high-energy correlations. Using new spectral/temporal parameters calculated for 101 bursts with redshifts from BATSE, BeppoSAX, HETE-II and Swift we describe a parameter space which characterises the apparently diverse properties of the prompt emission. We show that a source frame characteristic-photon-energy/peak luminosity ratio, K_z, can be constructed which is constant within a factor of 2 for all bursts whatever their duration, spectrum, luminosity and the instrumentation used to detect them. The new parameterization embodies the Amati relation but indicates that some correlation between E_peak and E_iso follows as a direct mathematical inference from the Band function and that a simple transformation of E_iso to L_iso yields a universal high energy correlation for GRBs. The existence of K_z indicates that the mechanism responsible for the prompt emission from all GRBs is probably predominantly thermal.Comment: Submitted to Ap

Reduced major axis approach for correcting GPM/GMI radiometric biases to coincide with radiative transfer simulation

Correcting radiometric biases is crucial prior to the use of satellite observations in a physically based retrieval or data assimilation system. This study proposes an algorithm - RARMA (Radiometric Adjustment using Reduced Major Axis) for correcting the radiometric biases so that the observed radiances coincide with the simulation of a radiative transfer modeL The RARMA algorithm is a static bias correction algorithm, which is developed using the reduced major axis (RMA) regression approach, NOAA\u27s Community Radiative Transfer Model (CRTM) has been used as the basis of radiative transfer simulation for adjusting the observed radiometric biases. The algorithm is experimented and applied to the recently launched Global Precipitation Measurement (GPM) mission\u27s GPM Microwave Imager (GMI), Experimental results demonstrate that radiometric biases are apparent in the GMI instrument, The RARMA algorithm has been able to correct such radiometric biases and a significant reduction of observation residuals is revealed while assessing the performance of the algorithm, The experiment is currently tested on clear scenes and over the ocean surface, where, surface emissivity is relatively easier to model. with the help of a microwave emissivity model (FASTEM-5)

Integration Of TRMM Rainfall In Numerical Model For Pesticide Prediction In Subtropical Climate

Rain gauge data in developing countries are usually very limited, which constrains most of the hydrological modelling applications. The satellite based rainfall estimates could be a promising choice and hence can be used as a surrogate to ground-based rainfall. However, the usefulness of these products needs to be evaluated for hydrological application such as for pesticide predictions. The present study compares the contaminant transport simulation with the utilization of Tropical Rainfall Measuring Mission (TRMM) rainfall compared with rain gauge data from the field site. Through this study, transport trends of the pesticide, Thiram, a dithiocarbamate, at different time and depth in the fields under real field conditions for the wheat crop were compared to the numerical simulations using HYDRUS- 1D with the input of daily rainfall from the TRMM. The daily rainfall from TRMM has been utilized to simulate the pesticide concentration up to 60 cm vertical soil profile with the intervals of 15 cm. The simulated soil moisture content using ground based rainfall and TRMM derived rainfall measurements indicate an agreeable goodness of fit between the both. The overall analysis reveals that TRMM rainfall is promising for soil pesticide prediction in absence of ground based measurements of soil pesticide. Further, comparison of the model to measured field data of pesticides movement indicates that the modelling approach can provide reliable and useful estimates of the mass flux of water and non-volatile pesticide in vadose zone. Thus, the satellite-based rainfall products could also be useful for policy makers and planners while controlling inappropriate pesticide application under saturated and deficit soil moisture conditions