ORMOCHALCs: organically modified chalcogenide polymers for infrared optics.

A novel method combining elemental sulfur and selenium was developed, yielding crystalline sulfur-selenium compounds. The compounds were melted, and an organic comonomer added. Once the organic comonomer was consumed, the viscous compound was vitrified and allowed to cool yielding organic-inorganic hybrid polymers that are termed Organically Modified Chalcogenide (ORMOCHALC) polymers.

Optimizing average power in low quantum defect lasers.

Waste heat generation is a generic problem in high-power solid-state laser systems. One way to reduce heat loading while improving efficiency is to reduce the laser's quantum defect. This paper presents a simple analysis of low quantum defect laser materials. In these laser materials, the effects of fluorescent cooling and weak loss processes should not be ignored. Simple expressions are developed for efficiency and heating in a steady-state purely radiative material. These expressions are then extended to include weak losses and fluorescence reabsorption. Evaluation of these relations using ytterbium-doped YAG is used to illustrate several optimization schemes and the impact of realistic losses.

Diode pumped yellow dysprosium lasers.

First operation of the 4F9/2 → 6H13/2 laser transition in dysprosium doped yttrium aluminum garnet is reported. Efficient room temperature operation at 583 nm was obtained using 447 nm GaN diode lasers pumps. Gaussian single-mode operation was demonstrated with a non-optimized slope efficiency of 12%. Millisecond pulsed operation generated 150 mW with power limited by the pump diodes' brightness.

Glutamate-stimulated peroxynitrite production in a brain-derived endothelial cell line is dependent on N-methyl-D-aspartate (NMDA) receptor activation.

There is accumulating and convincing evidence indicating a role for glutamate in the pathogenesis of the human demyelinating disease multiple sclerosis (MS). Studies in experimental autoimmune encephalomyelitis (EAE), the animal model of MS, demonstrate that pharmacological inhibition of specific glutamate receptors suppresses neurological symptoms and prevents blood-brain barrier (BBB) breakdown. The mechanisms through which glutamate influences BBB function during EAE remain unclear. Glutamate triggers the production of nitric oxide and superoxide, which can lead to the formation of peroxynitrite (ONOO(-)). Recent studies have implicated ONOO(-) in the loss of neurovascular integrity during EAE. We propose that glutamate contributes to BBB breakdown via the actions of ONOO(-). The present investigation examined glutamate-induced ONOO(-) formation in the b.End3 brain-derived endothelial cell line. b.End3 cells were incubated with a concentration range of glutamate and ONOO(-) production was assessed over time. Results showed a concentration- and time-dependent increase in ONOO(-) levels in glutamate-treated cells that were suppressed by selective and non-selective inhibitors of ONOO(-)-mediated reactions. Specific activation of b.End3-associated NMDA receptors also resulted in a concentration-dependent increase in ONOO(-) production. The ability of b.End3 cells to respond to the presence of glutamate was confirmed through the detection of NMDA receptor immnuoreactivity in cell extracts. In addition, the use of the NMDA receptor antagonists MK-801 and memantine reduced glutamate-mediated ONOO(-) generation from b.End3 cells. The data reinforce the important relationship between glutamate and the NMDA receptor, positioned at neurovascular sites, which may be of particular relevance to the pathogenesis of demyelinating disease.

Lock-in holography using optically addressed multiple-quantum-well spatial light modulators.

Perpendicular-field multiple-quantum-well optically addressed spatial light modulators have a response that saturates at high writing intensity. This limits the diffraction efficiency of low-fringe-visibility holograms. This effect is suppressed by use of the ability of these structures to subtract images rapidly. The modulator is exposed to a hologram with a spatially uniform beam, which is incoherent with the hologram, superimposed on top of it. Pulsing the hologram synchronously with the device drive voltage but leaving the uniform beam constant in time can build up the diffraction to large values even when the fringe visibility is low.

Personality counts for a lot: predictors of mental and physical health of spouse caregivers in two disease groups.

The purpose of this study were to examine the influence of personality on mental and physical health of spouse caregivers and to determine whether there were differences in such influences depending on disease context. The disease contexts compared were Alzheimer's disease (AD) and Parkinson's disease (PD; with no coexisting dementia)--both chronic, degenerative diseases of later life. It was predicted that personality would be related to mental and physical health, directly and indirectly, and that AD caregivers would have higher levels of perceived stress and worse mental and physical health outcomes. Participants in the study were 175 caregivers (88 AD; 87 PD) living at home with their ill spouses. The data provided an excellent fit to the hypothesized model of the relationships between personality, disease group, social support, perceived stress, and mental and physical health. Seventy-eight percent of the variance in mental health was accounted for and 35% of the variance in physical health was explained. Personality had significant direct and indirect effects on mental health and significant indirect effects on physical health. As predicted, AD caregivers had significantly worse mental health than PD caregivers; however, AD caregivers had better physical health than PD caregivers, controlling for other variables in the model. These results are discussed in relation to the existing caregiving and behavioral medicine literature. Future research should include different domains of personality--states and longer term self-regulatory processes in addition to traits--to advance models of caregiving processes further.

Amount of care given and caregiving satisfaction: a latent growth curve analysis.

We examined the wear-and-tear hypothesis using data from 4 annual interviews with 130 (128 White) middle-aged daughters caring for their physically impaired, elderly mothers. We formulated a latent growth curve model hypothesizing that increases in the amount of care given by daughters caused a decrease in caregiving satisfaction, independent of caregiving duration. We found considerable individual variability and change in both caregiving satisfaction and the amount of care given in univariate latent growth curve analyses. Contrary to the wear-and-tear hypothesis, a multivariate latent growth curve analysis revealed duration of caregiving had no effect on either initial caregiving satisfaction or change in satisfaction. An elaborated wear-and-tear model was supported, however. The mechanism for decline in satisfaction is an increase in the amount of care given.

Transient thermal lens in a ZnGeP(2) crystal.

The first observations, to the authors' knowledge, of transient thermal lensing in a ZnGeP(2) crystal achieved with 2.09-µm laser excitation of 800-µs, 70-mJ pulses at 30 Hz and by burst-mode Q-switched pumping are presented. The laser power transmitted through an aperture was approximated by an adiabatic model with currently accepted values for the thermal properties of ZnGeP(2) and corresponded to focal-length changes from infinity to 10 cm during each 800-µs pulse. Similar results were seen when the crystal was operated as an optical parametric oscillator. This transient thermal lens severely limits ZnGeP(2) as a material for use in optical parametric oscillators for these modulated, high-power operating conditions.

High-average-power operation of a Q-switched diode-pumped holmium laser.

We have investigated high-peak- and high-average-power operation of diode-pumped, thulium-sensitized, holmium 2.1-microm lasers. Free-running laser powers of 14 W at 29 Hz have been demonstrated with 2.6% electrical efficiency. Q-switched operation produced average powers in excess of 11 W in a burst of short pulses. Preliminary optical parametric oscillator frequency conversion of the holmium laser to 4 microm is also reported.

Diode-pumped 1.34-microm Nd(3+):YAlO(3) laser.

We have pumped Nd(3+):YAlO(3) lasers with a 40-stripe, 500-mW, 807-nm diode laser. Maximum output powers at 1.34 microm of 26 mW multimode and 20 mW in a single transverse mode were achieved. The several longitudinal modes had a total spectral width of ~0.4 nm.