Synchrotron Radiation for Detecting Movement of a Volatile Soil Liquid

Heat and volatile liquid transport in soils are physically coupled processes. Soil water movement driven by thermal gradients has received considerable attention both experimentally and via models. This is appropriate since the thermal regime of underground electric power cables, pipelines, agricultural soils, and nuclear-waste repositories influences their ability to function effectively. However, available experimental liquid concentration data are of relatively low resolution, generally about one measurement per cm. By using synchrotron x rays we were able to nondestructively obtain high (50 μm) spatial resolution, time-lapsed data for the thermally driven movement of dibromomethane (DBM) in soil. Under repeated temperature cycling during a 22 h period, DBM movement within a sealed, 25-mm-long quartz sand (D50 = 0.25?mm) soil column was highly repeatable. About four complete scans of the column were completed each hour. Average DBM vol?% within the column as a whole was 4.0 and the porosity was 0.31. Measurements of DBM concentration at the same position and equivalent times during different cycles usually differed by less than 0.2 vol?%. Experimental data of this precision will permit better comparison with detailed model predictions.     

SHORT METHODS FOR CHEMICAL ANALYSIS OF GLASS*

Analytical methods have been developed which shorten the time required for the determination of many of the constituents found in glass. These short methods have been worked into a procedure for the routine chemical analysis of container and sheet glasses. The determination of SiO₂, BaO, SO₃, R₂O₃, CaO, MgO, B₂O₃, Na₂O, and K₂O percentages on several samples can be made in a single day. Most of the experimental work has been done on Bureau of Standards glass No. 128, but results from several other glasses are included. Particular care has been taken to discover interfering substances and to eliminate errors from this source. The accuracy is comparable with that obtained from the use of umpire methods.     

Physical, chemical and energy aspects of underground hydrogen storage

Large scale energy storage is becoming an important consideration as we turn more towards nuclear power and the utilization of renewable sources such as solar energy. Underground storage of hydrogen in aquifers has been suggested as an inexpensive method of providing the required energy storage. With this theme in mind, the losses associated with gas storage in aquifers are discussed. These losses include physical leakage of gas, loss of gas through underground chemical reactions and the energy requirements associated with storing and recovering the gas.

Although underground storage of hydrogen appears a most promising solution to the problem of large scale energy storage it is shown that much work remains to be done to confirm this. For example, better estimates of hydrogen diffusion through water saturated porous media are required.     

Yield Strengths of Biaxially Textured Metallic Substrates (Ni and its Alloys) Determined Using a Simplified Test Method

A simple testing method is used to compare the yield strengths (YS) of biaxially textured metallic substrates (Ni and its alloys) presently under development for YBa₂Cu₃O_7−x coated conductors. This method is based on a retired ASTM D3379 tensile test standard method that was originally recommended for single filament materials. Several common textured substrates, such as Ni, Ni-3at.%W, and Ni-5at.%W, procured from different manufacturers, were tested using this method, and the data were compared with the values reported in the literature. A new alloy substrate (constantan (Cu55-Ni44-Mn1wt.%)) that is biaxially textured in-house was also tested using this method, and the YS data were compared with those of other substrates. For the substrates used in this study, the data obtained using this method indicated that Ni substrates have YS of ∼52 MPa, Ni-3at.%W substrates have YS of ∼106 MPa, Ni-5at.%W substrates have YS 163 MPa, and Cu55-Ni44-Mn1 wt.% substrates have YS of 74 MPa.     

Design and synthesis of a series of potent and orally bioavailable noncovalent thrombin inhibitors that utilize nonbasic groups in the P1 position

As part of an ongoing effort to prepare therapeutically useful orally active thrombin inhibitors, we have synthesized a series of compounds that utilize nonbasic groups in the P1 position. The work is based on our previously reported lead structure, compound 1, which was discovered via a resin-based approach to varying P1. By minimizing the size and lipophilicity of the P3 group and by incorporating hydrogen-bonding groups on the N-terminus or on the 2-position of the P1 aromatic ring, we have prepared a number of derivatives in this series that exhibit subnanomolar enzyme potency combined with good in vivo antithrombotic and bioavailability profiles. The oxyacetic amide compound 14b exhibited the best overall profile of in vitro and in vivo activity, and crystallographic studies indicate a unique mode of binding in the thrombin active site.