Damping-limited modulation bandwidths up to 40 GHz in undoped short-cavity In/sub 0.35/Ga/sub 0.65/As-GaAs multiple-quantum-well lasers

We demonstrate record direct modulation bandwidths from MBE-grown In/sub 0.35/Ga/sub 0.65/As-GaAs multiple-quantum-well lasers with undoped active regions and with the upper and lower cladding layers grown at different growth temperatures. Short-cavity ridge waveguide lasers achieve CW direct modulation bandwidths up to 40 GHz for 6/spl times/130 /spl mu/m/sup 2/ devices at a bias current of 155 mA, which is the damping limit for this structure. We further demonstrate large-signal digital modulation up to 20 Gb/s (limited by the measurement setup) and linewidth enhancement factors of 1.4 at the lasing wavelength at threshold of /spl sim/1.1 /spl mu/m for these devices.     

Evidence for localized and discrete roles for enkephalins during memory formation in the chick.

This study examined effects on memory formation produced by [Leu]enkephalin and [Met]enkephalin administration in 2 regions of the 2-day-old chick brain involved in memory formation: the intermediate medial hyperstriatum ventrale (IMHV) and the lobus parolfactorius (LPO). Basal concentrations of endogenous [Leu]enkephalin and [Met]enkephalin were determined for 5 brain regions, and effects of 1-trial peck-avoidance training on enkephalin concentrations were examined in the IMHV and LPO. [Leu]enkephalin was amnestic when administered in the IMHV but not in the LPO. In contrast, [Met]enkephalin may be amnestic when administered in the LPO but not in the IMHV. Training decreased [Met]enkephalin concentration in the LPO but not in the IMHV. Training had no effect on [Leu]enkephalin concentration in either the IMHV or the LPO. Thus, amnestic effects of [Leu]- or [Met]enkephalin administration are brain-region specific. Regional activity of endogenous [Met]enkephalin during memory formation is consistent with localized amnestic effects produced by [Met]enkephalin administration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual pattern integration in psychiatric patients.

Tested 32 psychiatric inpatients (approximate mean age 23 yrs) with a modification of C. Eriksen and J. Collins's visual pattern integration test (1967). Ss were divided into schizophrenic and nonschizophrenic groups and were compared with 20 hospital staff and 20 college students. The visual pattern integration functions of schizophrenics were found to be different from those of college students, but no other group differences were found. Among the inpatients, no correlations were found between visual pattern integration and premorbid adjustment, symptomatology, or various clinical/demographic factors. The one group difference appears to be the result of variables such as age and task motivation. It is concluded that icon-processing abnormalities, as represented by visual pattern integration deficits, cannot account for posticonic abnormalities found in schizophrenics. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The final tribute of E. G. Boring to G. T. Fechner: Concerning the date October 22, 1850.

E. G. Boring, the preeminent historian of experimental psychology, wrote a letter shortly before his death in 1968 concerning G. T. Fechner's first insight into the fundamental principle of psychophysics on October 22, 1850. The celebration of that date at Harvard, more or less annually, and the establishment there of the first chair of psychophysics are recounted in the letter and interwoven with Boring's own birthday (October 23). The letter is published here as a minor contribution to the centennial of Fechner's death (November 18, 1887). That event was scheduled for celebration at Leipzig University by a three-day symposium in June devoted to Fechner's founding of psychophysics and, hence, of experimental psychology. Boring's later skepticism about the validity of certain landmark dates in scientific history was meant to deemphasize the contribution of the individual and to strengthen the role of the impersonal Zeitgeist. But it appears that this skepticism may have arisen, in part, from Boring's recognition of his subjectivity in playfully confounding Fechner's date of insight with his own birthday. Overgeneralization may have followed the fun. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Design, synthesis, and application of particle-based fluorescence resonance energy transfer sensors for carbohydrates and glycoproteins

This paper describes the development of novel particle-based fluorescence resonance energy transfer (FRET) sensors to quantify the concentration and monitor the binding affinity of carbohydrates and glycoproteins to lectins, which are carbohydrate binding proteins. The sensing approach is based on FRET between fluorescein (donor)-labeled lectin molecules, adsorbed on the surface of micrometric polymeric beads, and polymeric dextran molecules labeled with Texas Red (acceptor). The FRET efficiency of the donor-acceptor pair decreases in the presence of carbohydrates or glycoproteins that compete with the Texas Red-labeled dextran molecules on the lectinic binding sites. The inhibitory effect is concentration and time dependent. The sensing technique enables the discrimination between carbohydrates and glycoproteins based on their binding affinity to the FRET sensing particles as well as quantitative analysis of carbohydrates and glycoproteins in aqueous samples. In the future, the newly developed sensors could enable screening glycoprotein-based drugs for their binding affinity toward selective receptors.     

Direct contact with enriched environment is required to alter cerebral weights in rats.

To test the relative effectiveness of direct vs indirect interaction with an enriched environment, 2 experiments were conducted with Berkeley S1 rats. Some Ss were housed in groups of 12 in large enriched condition (EC) cages while littermate "observer" (OC) Ss were placed singly in small wire-mesh cages within EC. A 3rd group was housed singly in an impoverished condition (IC) where stimulation was minimal. After 30 days, Ss were killed and the brains dissected. In both experiments the usual pattern of EC-IC differences in brain weights appeared, whereas OC showed no significant differences from IC. On measures of exploratory behavior taken during the last 2 days of Exp II, IC fell significantly below EC, and OC was somewhat below IC. Thus EC differed from both IC and OC in brain and in behavior. Active contact with an enriched environment appears necessary for development of EC effects. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

G. Stanley Hall vis-à-vis William James.

Suggests that the article by J. C. McCullers (see record 1970-10077-001) on G. Stanley Hall's influence is misleading; Hall has not been forgotten. The author comments on Hall's place as a founder and 1st president of the American Psychological Association, on the comparison of W. James with Hall, and notes that it is time that Hall's importance be more fittingly assessed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Softening temperature of glassy polymers as affected by residual stresses

Heat deflection temperature and Vicat softening point of polystyrene and polymethylmethacrylate with various thermal histories were measured. Surface residual stresses were characterized by liquid crazing. Residual stress profiles across the sample thickness were also measured. It is suggested that the softening behavior of glassy polymers is affected by the state of the residual stresses in addition to the traditionally accepted free volume approach.     

Copper delivery by metallochaperone proteins

Copper is an essential element in all living organisms, serving as a cofactor for many important proteins and enzymes. Metallochaperone proteins deliver copper ions to specific physiological partners by direct protein-protein interactions. The Atx1-like chaperones transfer copper to intracellular copper transporters, and the CCS chaperones shuttle copper to copper,zinc superoxide dismutase. Crystallographic studies of these two copper chaperone families have provided insights into metal binding and target recognition by metallochaperones and have led to detailed molecular models for the copper transfer mechanism.