Observation of Gravitational Waves from a Binary Black Hole Merger

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0 × 10−21. It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410þ160 −180 Mpc corresponding to a redshift z ¼ 0.09þ0.03 −0.04 . In the source frame, the initial black hole masses are 36þ5 −4M⊙ and 29þ4 −4M⊙, and the final black hole mass is 62þ4 −4M⊙, with 3.0þ0.5 −0.5M⊙c2 radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger

Arsenic Contamination of Groundwater in Indus River Basin of Pakistan

Arsenic (As) contamination of drinking water from groundwater sources is an issue of public health concern in many parts of the world, including South Asia. The presence of As in groundwater of Pakistan was reported around the city of Karachi as early as 1997. Widespread occurrences of As are reported in groundwater through a number of subsequent studies in the provinces of Punjab and Sindh, the two most populated provinces in the Indus River basin of Pakistan and thereby emerged as an issue of public health concern. These studies have revealed that concentrations of As are elevated by a factor of 10–250 as compared to the WHO drinking water guideline. Both natural and anthropogenic processes have been primarily indicated as cause for elevated As concentration in groundwater. An increasing number of studies also show evidence that irrigation with As contaminated groundwater is associated with elevated As concentrations in agricultural products. The future research should therefore focus on the detailed understanding of the complexities of the geological and hydrogeological setting of Pakistan and to outline the sources of As and the mechanisms of transport to the Indus basin aquifers

Fast and Inexpensive Detection of Total and Extractable Element Concentrations in Aquatic Sediments Using Near-Infrared Reflectance Spectroscopy (NIRS)

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