Explosive Gas Blast: The Expansion of Detonation Products in Vacuum

A series of 0.2- to 3-gm HNS charges were detonated in vacuums of 10^−3 to 10^−5 Torr. The resultant freely expanding, detonation product, gas blast achieves terminal velocities of 8 to 12 km/sec within 3 to 5 µsec after the detonation wave arrives at the free surface. Measured pressure profiles display rise times to maximum stagnation (``reflected shock'') pressure varying from ~30 µsec, 20-cm away from a 2.6-gm charge, to ~185 µsec, 127-cm away from 0.2-gm charge at 10−5 Torr. Rise times were generally shorter at 10−3 and 10−4 Torr; the 10−5 Torr values agree with numerical calculations. Using cube root scaling of charge mass, the observed peak reflected pressure as a function of range may be represented by p = 6.5 x 10^5 (bar) r'^-3.5, where r[prime] the ratio of the range to the equivalent charge radius

Local Bulletin of Earthquakes in the Southern California Region 1 January 1963 to 31 December 1966

The Local Bulletin of the Pasadena Seismological Laboratory has been issued regularly since the beginning of 1934, and the present Bulletin covers the four-year period from 1 January 1963 to 31 December 1966

Improving aerobic capacity in healthy older adults does not necessarily lead to improved cognitive performance.

The effects of aerobic exercise training in a sample of 85 older adults were investigated. Ss were assigned randomly to either an aerobic exercise group, a nonaerobic exercise (yoga) group, or a waiting-list control group. Following 16 weeks of the group-specific protocol, all of the older Ss received 16 weeks of aerobic exercise training. The older adults demonstrated a significant increase in aerobic capacity (cardiorespiratory fitness). Performance on reaction-time tests of attention and memory retrieval was slower for the older adults than for a comparison group of 24 young adults, and there was no improvement in the older adults ' performance on these tests as a function of aerobic exercise training. Results suggest that exercise-related changes in older adults ' cognitive performance are due either to extended periods of training or to cohort differences between physically active and sedentary individuals. Several parameters of cardiovascular functioning (e.g., maxi-mal heart rate, cardiac output, and left ventricular ejection fraction during exercise) typically exhibit a decline during later adulthood, even in the absence of overt coronary diseas

Note and Comment

Unliquidated Tort Claims as Provable Debts in Bankruptcy; May a State, in the Exercise of its Police Power, Regulate Insurace Rates?; Interest upon Legacies which are not Payable Until Legatee Attains Certain Age; Validity of a Classification of Banks Based Upon the Amount of Their Average Annual Deposit

Microwave and Millimeter Wave Techniques

Contains reports on two research projects.Joint Services Electronics Program (Contract DAAG29-78-C-0020)National Science Foundation (Grant AST77-26896

Extension of BrdU-dye analysis of DNA replication and sister chromatid exchange formation to in vivo systems : (in vivo, BrdU-dye, DNA replication, sister chromatid exchange)

BrdU-dye methodology was initially developed in tissue culture. Wide application of the technique for cytogenetic studies of DNA structure, replication and repair followed. Although the need for parallel in vivo studies was apparent, technical difficulties delayed the establishment of highly relevant BrdU-dye methods in intact mammals. Recently, BrdU-dye methods were adapted to in vivo rodent systems and the potential for diverse analyses of chromosome structure and function, comparable to those of in vitro analyses, demonstrated. In addition, the unique suitability of in vivo systems for studying replication kinetics and sister chromatid exchange formation in multiple tissues, inclusive of both somatic and germ cells, was shown. New in vivo protocols under development offer methodological simplicity and convenience of implementation. In vivo BrdU-dye techniques should thus afford an attractive alternative to in vitro systems for many cytogenetic studies.JAMES W. ALLEN, CHARLES F. SHULER, AND SAMUEL A. LATT, Clinical Genetics Division, Mental Retardation Program, Children's Hospital Medical Center and the Department of Pediatrics, Harvard Medical School, Boston, Massachusetts

Effects of CYP46A1 inhibition on long-term-depression in hippocampal slices ex vivo and 24S-hydroxycholesterol levels in mice in vivo

The manipulation of cholesterol and its metabolites has been hypothesized to be therapeutically beneficial for mood disorders, neurodegenerative disorders, and epilepsies. A major regulator of cholesterol clearance and turnover in the central nervous system is CYP46A1, a brain enriched enzyme responsible for metabolism of cholesterol into 24S-hydroxycholesterol. Inhibition of this enzyme may negatively modulate NMDARs as 24S-hydroxycholesterol was shown to enhance NMDAR function. In addition, alterations of local cholesterol or other changes mediated by CYP46A1 activity could have important influences on central nervous system function. Here we demonstrate that humans and mice display brain region specific and similar CYP46A1 and 24S-hydroxycholesterol distribution. Treatment with distinct classes of CYP46A1 inhibitors led to central 24S-hydroxycholesterol reductio