Efficient high-speed direct modulation in p-doped In/sub 0.35/Ga/sub 0.65/As/GaAs multiquantum well lasers

The authors demonstrate p-type modulation-doped strained-layer In/sub 0.35/Ga/sub 0.65/As/GaAs multiquantum well lasers which achieve a 3 dB direct modulation bandwidth of 20 GHz at a low CW drive current of 50 mA in a simple 3*200 mu m/sup 2/ mesa structure. For the same device dimensions, a modulation bandwidth of 30 GHz was measured at a CW drive current of 114 mA. This is the highest direct modulation bandwidth reported for any semiconductor laser.<>     

The identity and idiodynamics of the multiple personality "Sally Beauchamp": A confirmatory supplement.

By an exhaustive reconstruction, the real life identity of Sally Beauchamp, the classic case of multiple personality investigated by Morton Prince and reported in his 1906 book, has been established. On that new basis, important biographical events previously unrecognized have been discovered and related to the dissociation process. The split appears to have begun as a defensive substitute for a conscious recognition of a death in the family toward which the patient had a sense of guilty complicity. This supplementary article adds further evidence for the reconstruction. The new aspect concerns the kind of weather that appears invariably to have occurred at the time of the patient's major dissociation crises. It is shown that an overcast sky, followed by rain, prevailed at the time of her first crisis on the occasion of the death of an infant brother, on June 7, 1880, when she was seven years old. The same type of weather occurred during the two subsequent dissociation crises: June 7, 1893, and June 7, 1899. This gloomy weather was apparently a vital aspect of the imprinting. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of temporal summation in age-related long-term potentiation-induction deficits

Hippocampal long-term potentiation (LTP) is reduced in aged relative to young F-344 rats when peri-threshold stimulation protocols (several stimulus pulses at 100-200 Hz) are used. The present study was designed to examine the possibility that this LTP-induction deficit is caused by a reduced overlap of Schaffer-collateral inputs onto CA1 pyramidal cells (input cooperativity). This reduced input cooperativity would decrease the levels of postsynaptic depolarization during LTP induction, which might account for the age-related LTP deficit. Both behavioral data (Morris Water Maze) and electrophysiological data (intracellular recordings from hippocampal slices) were collected from adult and aged F-344 rats. To counter the effects of reduced input cooperativity, stimulus intensities were adjusted to elicit baseline excitatory postsynaptic potentials (EPSPs) of equivalent amplitude in aged and young rats. Contrary to expectations, however, an age-related LTP-induction deficit was still observed. Further evaluation of the electrophysiological data revealed that temporal summation of multiple EPSPs during high-frequency stimulation was impaired in the aged rats. Thus, despite the equalization across age groups of the baseline EPSP amplitudes, the cells of aged rats were less depolarized during the LTP-inducing stimulation than were those of young rats. This reduced total depolarization was not an artifact of the higher stimulus intensity used on aged animals, nor was it caused by a failure of aged rats' CA1 afferents to follow high-frequency stimulation. The present data therefore suggest that there is a deficit in the ability of aged rats' synapses to provide the sustained depolarization necessary to active the LTP-induction cascade.     

Phosphorylation of the cytoplasmic domain of E-selectin is regulated during leukocyte-endothelial adhesion

E-selectin, a selectin expressed on activated vascular endothelium, supports rolling and stable adhesion of leukocytes at sites of inflammation. Previously, we have reported that leukocyte adhesion to cultured endothelial cells induces association of the cytoplasmic domain of E-selectin with cytoskeletal elements, suggesting that outside-in signaling may occur during E-selectin-mediated adhesion. To investigate this potential signaling function of E-selectin, HUVEC activated with recombinant human IL-1beta (10 U/ml, 4 h) were labeled with [32P]orthophosphate, and E-selectin was immunoprecipitated using mAb H18/7. Autoradiography revealed constitutive phosphorylation of E-selectin in these cells and time-dependent dephosphorylation following adhesion of HL-60 cells. Cross-linking of cell surface E-selectin using H18/7 and a polyclonal secondary Ab induced E-selectin dephosphorylation, as did adhesion of beads coated with recombinant P-selectin glycoprotein ligand-1 (PSGL-1), an E-selectin ligand. Using adenoviral vector-mediated transfection in HUVEC of a tail-less E-selectin and phosphoamino acid analysis, we documented phosphorylation occurring exclusively within the cytoplasmic domain and involving serine residues. Additional experiments using a series of cytoplasmic domain mutants of E-selectin expressed in COS-7 cells localized the regions that were constitutively phosphorylated. Preincubation with okadaic acid and sodium vanadate abrogated adhesion-induced dephosphorylation of E-selectin. Thus, E-selectin, which is constitutively phosphorylated in cytokine-activated human endothelial cells, undergoes an enzymatically regulated dephosphorylation following leukocyte adhesion. This process appears to be triggered by multivalent ligand binding and/or cross-linking of cell surface E-selectin. Ligand-dependent regulation of the phosphorylation of E-selectin's cytoplasmic domain provides additional evidence for a transmembrane signaling function of this molecule during leukocyte-endothelial interactions.     

Bunch length measurement of picosecond electron beams from a photoinjector using coherent transition radiation

The bunch length of an electron beam derived from the UCLA Saturnus photoinjector has been measured using a 45° CTR foil. The sudden change of electrons boundary conditions cause them to radiate (transition radiation) with the spectral power entirely dependent upon the degree of coherency, which strongly relates to the beam size. A polarizing Michelson interferometer allowed measurement of the auto-correlation of the coherent transition radiation signal. An analysis method was developed to compensate for undetected low-frequency radiation and systematically extract the bunch length information for a specific beam model. This analysis allowed observation of pulse lengthening due to the space charge, as well as compression with the variation of the RF injection phase. The hypothesis of a satellite beam has been also tested using this analysis.