Gabor-QR decomposition for image encoding

A new approach to Gabor transformation based on the QR decomposition, with potential applications to image sequence encoding, is proposed. This Gabor-QR scheme computes the exact Gabor coefficients by solving a system of linear equations Ax=b, which is more efficient than iterative schemes, and less complicated than other matrix-based methods. Experimental results from image encoding are presented.<>     

Effect of pindolol on hormone secretion and body temperature: partial agonist effects

Pindolol has been shown to be a partial agonist at 5-HT1A receptors in preclinical studies. It has also been reported to inhibit the effects of other 5-HT1A partial agonists such as ipsapirone and buspirone on hormone secretion and body temperature in man, indicating its antagonist action at 5-HT1A receptors in man. To determine if pindolol has 5-HT1A agonist as well as antagonist effects in man, pindolol, 30 mg, p.o. and placebo, were given single blind in random order to 23 normal men with indwelling venous catheters and its effects on hormone secretion and body temperature noted. Pindolol significantly increased basal plasma cortisol concentrations, whereas it decreased plasma prolactin (PRL) concentrations and body temperature. The increase in plasma cortisol due to pindolol suggests a 5-HT1A agonist action and is consistent with a 5-HT1A partial agonist mechanism in man whereas the PRL effects are consistent with an antagonist action at 5-HT1A receptors. The effects of pindolol on plasma cortisol concentration and body temperature were significantly negatively correlated. Furthermore, these results indicate significant differences in the 5-HT1A-dependent regulation of PRL and the hypothalamo-pituitary-adrenal (HPA) axis and body temperature, and suggest that human basal PRL secretion is tonically stimulated by 5-HT1A mechanism whereas the HPA axis and body temperature are not. Since rodent studies suggest differences in 5-HT1A receptor sensitivity between males and females, the results reported here need to be replicated in females. These differences in the effect of pindolol are discussed in terms of receptor reserve theory.     

Screw-fastened joints for thermal contact at low temperatures

Electrical resistance measurements at 4.2 K on simple screw-fastened joints between two pieces of bare copper, between two pieces of gold-plated copper, and between two pieces of silver indicate the potential usefulness of such joints for thermal contact down to millikelvin temperatures.     

Temporal relationship between progestin and luteinizing hormone concentrations in pseudopregnant rats treated with prostaglandin-F2 alpha

The temporal changes in progesterone (delta 4P), 20 alpha-dihydroprogesterone (20 alpha-DHP) and luteinizing hormone (LH) concentrations in pseudopregnant (PSP) rats after treatment with a single subcutaneous Silastic-PVP tube containing 600 micrograms PGF2 alpha were correlated. Progesterone levels fell and LH levels rose significantly 2h after initiation of treatment, while 20 alpha-DHP levels were found to increase significantly 12h after treatment. Since the changes in delta 4P and LH concentrations occurred concurrently, it seems that the increase in LH levels could have been due to a direct effect of PGF2 alpha on the ovary causing a reduction in delta 4P and thus a negative feedback effect on LH release. Alternatively, PGF2 alpha might exert a direct effect on LH secretion at the hypothalamic-pituitary level.     

Generation and quenching of intensity pulsations in semiconductor lasers coupled to external cavities

The behavior of self-pulsing and nonpulsing lasers coupled to external cavities is investigated experimentally and theoretically. We investigate the dependence of the pulsation characteristics on the external cavity length using a saturable absorber model for self-pulsing lasers. It was found that quenching of self-pulsation occurs only for a certain limited range of external cavity length, and the frequencies of external-cavity induced pulsations lies within a certain range determined by the coupling coefficient. Small-signal analysis allows these ranges to be derived analytically. Hitherto, complex pulsation phenomena can be explained very intuitively by interpreting the combined laser-external cavity system as a microwave oscillator with a limited gain band and discrete mode structure.     

Iron silicide thin film formation at low temperatures

The rate kinetics of the formation of compound phases from thin layers of 1000–1500 Å α-Fe deposited onto single-crystal Si have been studied by MeV ⁴He⁺ backscattering spectrometry. Si is observed to dissolve into the thin α-Fe layer before compound formation. A compound layer of FeSi is produced at about 450°C and FeSi₂ formation begins at about 550°C. The (100) surface of Si is slightly more reactive than the (111) surface. An inert diffusion marker of implanted Xe was used to investigate the relative movement of the two species.X-ray diffractometry identifies the structure of the compound species as identical to bulk FeSi and FeSi₂. The compounds formed on both (111) n-Si and (100) n-Si are apparently polycrystalline and untextured.