LD泵浦的声光调Q腔内倍频激光器

研制成用ＬＤ泵浦的声光调Ｑ的Ｎｄ：ＹＶＯ４－ＫＴＰ腔内倍频激光器，得到了ＴＥＭ００模、频率高达１００ｋＨｚ的稳定的５３２ｕｍ绿激光脉冲系列输出，阈值泵浦功率为２７ｍＷ；在连续５７０ｍＷ的泵浦功率下，绿激光脉冲的峰值功率达１１００Ｗ，脉宽为４．６ｕｓ；输出功率稳定，在±５℃的工作温度变化下，输出功率变化小于±２％。此种器件可望得到广泛的应用。     

Interaction Between a Linearly Polarized Electromagnetic Plane and a Double Spherical Shell

An exact solution inside, outside, and within two arbitrary concentric spherical shells is presented for an impinging monochromatic linearly polarized electromagnetic wave. Specifically, the solution was found for a double-shell spherical acrylic plastic enclosure irradiated with 2450-MHz microwaves. The enclosure is used as an environmentally controlled exposure chamber for experimental animals during microwave irradiation. The analysis shows that an air foamed material, such as styrofoam, would be a better material than either Plexiglas or Teflon, provided it is sufficiently durable.     

Methane detection with a narrow-band source at 3.4 µm based on a Nd:YAG pump laser and a combination of stimulated Raman scattering and difference frequency mixing

We report the characterization of a 10-Hz pulsed, narrow-band source that is coincident with a fundamental ν(3) rovibrational absorption of methane at 3.43 μm. To generate this midinfrared wavelength, an injection-seeded 1.06-μm Nd:YAG laser is difference frequency mixed with first Stokes light generated in a high-pressure methane cell (1.06 ? 1.54 μm) to result in light at a wavelength of 3.43 μm, that is, the ν(1) Raman active frequency of methane (~2916.2 cm(-1)). With a modest-energy Nd:YAG laser (200 mJ), a few millijoules of this midinfrared energy can be generated with a pulse width of ~7 ns (FWHM). The methane ν(1) frequency can be pressure tuned over 8-32 atm (corresponding to ~13 GHz) and scanned across part of the ν(3)P(10) rovibrational level of methane, resulting in a peak measured methane absorption coefficient of 4.2 cm(-1) atm(-1).     

Measuring hydraulic properties of geotextiles after installation damage

Since geotextiles have been progressively incorporated into coastal protection structures, the influence of installation damage on them has been the primary concern. During installation/construction, geotextiles are repeatedly subjected to high mechanical stresses which often exceed service stress. It is therefore vital to evaluate the mechanical and hydraulic damage and determine the consequences of these damages to better develop criteria for selection of suitable products. As these damages could reduce the material's mechanical strength and hydraulic efficiency, or in the severest form of damage, puncturing, would end the separation function. The properties investigated in this paper include the permittivity and apparent opening size (AOS) of geotextiles. Generally, the greater the drop energy of armour units applied to geotextiles, the greater the potential for damage. Findings show that the residual permittivity could increase significantly, 45% during installation. The preliminary design of coastal structures will be optimised as engineers and designers can better estimate the amount of damage on geotextiles upon installation.     

Micromachined multichannel systems for the measurement of cellular metabolism

Using living cells as the biological recognition element in a biosensor has two important advantages: cell receptors provide functional rather than structural specificity, and the cells provide second messenger pathways that amplify the receptor/ligand binding events. Cellular responses can be detected by measuring extracellular acidification with a silicon sensor. By using silicon micromachining technology, we can integrate the fluidic pathways and chambers for immobilizing cells with the silicon sensor. We describe a multichannel chip in which each channel is etched into the surface, and has its own flow of tissue-culture medium past the cells. Measurements have been made on adherent cells in which a muscarinic acetylcholine receptor is transfected. Responses to the agonist carbachol are shown.     

The design of a family of high-current switches with over-currentand over-temperature protection

This paper describes the design and manufacture of a family of five high-current, high-voltage dc switches with over-current and over-temperature protection. The capacity of the switches ranged from 5 A, 163 V to 100 A, 400 V. Steps were taken to achieve stability in over-current and over-temperature trip thresholds with changes in supply voltage and ambient temperature. A small physical size was achieved, and the design of a ceramic and Kovar package is described. Difficulties arose in measuring circuit parameters while testing performance due to induced magnetic and electric noise, and solutions to these difficulties are discussed. In addition, difficulties achieving some of the design goals and subsequent solutions are described. Thick-film hybrid circuit processing was the chosen technology for circuit fabrication. Thermal management was a major area of design emphasis, and the use of aluminum nitride substrates in some of the networks offered a solution in maintaining output FET junction temperatures at a safe level. Suggestions for improvements are offered. It is clear that switching of many tens of kilowatts of power at high voltages with over-temperature and over-current protection is obtainable in a small package at a reasonable cost     

Glutathione and catalase provide overlapping defenses for protection against hydrogen peroxide in the yeast Saccharomyces cerevisiae

Glutathione (GSH) is an abundant and ubiquitous low-molecular-weight thiol which has proposed roles in many cellular processes including protection against the deleterious effects of reactive oxygen species. Our experiments have addressed the role of GSH in protection against hydrogen peroxide in the yeast Saccharomyces cerevisiae, and have shown that GSH and catalase provide overlapping defense systems. GSH appears to be the primary antioxidant for protection against hydrogen peroxide since mutants lacking GSH (gsh1) or glutathione reductase (glr1) are sensitive, whereas, strains lacking catalase A (cta1) or catalase T (ctt1) are unaffected in resistance to this oxidant. Furthermore, following treatment with hydrogen peroxide, the levels of oxidized, protein-bound and extracellular GSH were all increased at the expense of intracellular GSH. However, there are two lines of evidence that indicate catalases are required in the absence of GSH; firstly, strains that lack both catalase A and T accumulate increased levels of oxidized glutathione following treatment with hydrogen peroxide; and secondly, deletion of catalase genes exacerbates the hydrogen peroxide sensitivity of glr1 and gsh1 mutants.     

The robust beauty of improper linear models in decision making.

Proper linear models are those in which predictor variables are given weights such that the resulting linear composite optimally predicts some criterion of interest; examples of proper linear models are standard regression analysis, discriminant function analysis, and ridge regression analysis. Research summarized in P. Meehl's (1954) book on clinical vs statistical prediction and research stimulated in part by that book indicate that when a numerical criterion variable (e.g., graduate GPA) is to be predicted from numerical predictor variables, proper linear models outperform clinical intuition. Improper linear models are those in which the weights of the predictor variables are obtained by some nonoptimal method. The present article presents evidence that even such improper linear models are superior to clinical intuition when predicting a numerical criterion from numerical predictors. In fact, unit (i.e., equal) weighting is quite robust for making such predictions. The application of unit weights to decide what bullet the Denver Police Department should use is described; some technical, psychological, and ethical resistances to using linear models in making social decisions are considered; and arguments that could weaken these resistances are presented. (50 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

In defense of rigorous evaluation.

Comments on Sikes and Cleveland's (see record 1969-07237-001) article on a program to improve the social relationships between police and community. If verbal labels are ignored, the modal response for both police and community is on the negative side of the scale. Not using more rigorous procedures leaves the results of their evaluation ambiguous. (0 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)