Compact frequency standard based on an intracavity sample of cold cesium atoms

We have demonstrated the possibility for a compact frequency standard based on a sample of cold cesium atoms. In a cylindrical microwave cavity, the atoms are cooled and interrogated during a free expansion and then detected. The operation of this experiment is different from conventional atomic fountains since all the steps are sequentially performed in the same position of space. In this paper we report the analysis of a Ramsey pattern observed to present a (47±5) Hz linewidth and a stability of (5±0.5)x10-13τ-1/2 for an integration time longer than 100 s. Some of the main limitations of the standard are analyzed. This present report demonstrates considerable improvement of our previous work [J. Opt. Soc. Am. B 25, 909 (2008)] where the atoms were in a free space and not inside a microwave cavity.FAPESPCNPqCAPESFAPESP-CNR

Effects of Post-compaction Residual Lateral Stress and Electrolyte Concentration on Swelling Pressures of a Compacted Bentonite

The effects of post-compaction residual lateral stress and salt concentration in the hydrating fluid on swelling pressures of compacted MX80 bentonite is brought out in this paper. In order to release the residual lateral stresses, following the static compaction process during preparation of specimens, compacted bentonite specimens were extruded from the specimen rings and then inserted back prior to testing them for swelling pressures in isochoric condition. The swelling pressure tests were carried out at several dry densities of the bentonite with distilled water and solutions of NaCl (0.1 and 1.0 M) as the hydrating fluids. With water, the test results showed that specimens that underwent extrusion and insertion processes exhibited about 10–15 % greater swelling pressures as compared to the specimens those that were compacted and tested. The influence of saline solutions was found to reduce the swelling pressure of the bentonite, but their impact was less significant at high compaction dry densities

Assessment of Sulphate and Iron Contamination and Seasonal Variations in the Water Resources of a Damodar Valley Coalfield, India: A Case Study

The aim of the present study was to assess the sulphate (SO2−4 ) and iron (Fe) contamination and seasonal variations in the water resources (groundwater, surface water, and mine water) of the West Bokaro coalfield region, India. One hundred and twenty-four water resources samples were collected from the coalfield during the post- and pre-monsoon seasons. The concentrations of SO2−4 were determined using ion chromatography and Fe concentrations were analyzed using inductively coupled plasma mass spectrometry. A statistical analysis was used to easily understand the seasonal variations of the elements in the water resources of the area. The concentrations of SO2−4 and Fe in the water resources were higher in the pre-monsoon season than in the post-monsoon season, irrespective of location. The water resources of the coalfield were contaminated with high concentrations of SO2−4 and Fe, and would require suitable treatment before drinking, domestic and industrial uses