Broad-band multisection electrooptic modulators

A general solution has been derived for expressing the conversion of power from a base frequency to a modulation sideband using a multisection electrooptic modulator. The objective is to obtain broadband frequency modulation of a laser by the use of multiple collinear electrooptic crystals with microwave power levels well below the breakdown threshold. It is found that segmented structures lead to greater bandwidths, which increase with the number of modular sections. This is achieved by adjusting the phases of microwaves between sections to maximize the single-sideband conversion efficiency. It is shown that a 10.6-μm CO₂ laser modulator with six geometrically identical CdTe sections can potentially achieve a 3-dB bandwidth of nearly 6 GHz using a 10-kW traveling-wave tube operating at 16-GHz center frequency     

Pasteurella multocida toxin is a mitogen for bone cells in primary culture

The effect of recombinant Pasteurella multocida toxin (PMT) on primary cultures of embryonic chick bone-derived osteoblastic cells was investigated. It was found that PMT was a potent mitogen for primary derived chicken osteoblasts. The toxin stimulated DNA synthesis and cell proliferation in quiescent osteoblasts at the first passage and accelerated cell growth in subconfluent cultures. Cell viability was not affected by PMT, even at relatively high concentrations. Osteoblast numbers increased in a dose-dependent manner in response to PMT. Intracellular inositol phosphates were elevated in response to PMT, but no elevation in cyclic AMP (cAMP) levels was evident. Indeed, PMT inhibited cAMP elevation in osteoblasts in response to cholera toxin at a stage before other PMT-mediated events take place. In addition to increased cell turnover, PMT down-regulated the expression of several markers of osteoblast differentiation. Both alkaline phosphatase and type I collagen were reduced, but osteonectin was not affected. The in vitro deposition of mineral in cultures of primary osteoblasts and osteoblast-like osteosarcoma cells was also inhibited by the presence of PMT. This suggests that PMT interferes with differentiation at a preosteoblastic stage.     

Quantum effects in cyclotron resonance using a CW hydrogen-cyanide laser

A submillimeter resonance spectrometer has been developed, which employs a molecular gas laser as a source of radiation. Cyclotron resonance measurements of the quantum effects in the valence bands in germanium were taken with the use of a CW HCN laser. It is shown that the use of CW instead of pulsed lasers helps to avoid resonance line broadening and permits extensive quantitative results suitable for theoretical analysis to be recorded. The purpose of pursuing these methods to acquire detailed data on quantum transitions in semiconductors is to collect the information needed to design and develop a tunable submillimeter maser based on cyclotron resonance transitions.     

Quantum noise VII: The rate equations and amplitude noise in lasers

In this paper we start from our Quantum Noise IV model of a homogenously broadened maser and specialize to the case in which the number of photons and the population difference are the slowest changing variables. In spite of the high coherence of the system, we find that by eliminating all other variables adiabatically we obtain the usual rate equations plus a set of noise sources with precisely those moments appropriate to shot noise. Thus we justify McCumber's model for amplitude noise in a laser, and after making a quasi-linear approximation obtain his amplitude spectrum. Comparison with exact calculations of Hempstead and Lax for the rotating wave van der Pol oscillator suggests that quasi-linear methods are accurate except within a factor 10 (in photon number) of threshold.     

Quantum noise IX: Quantum Fokker-Planck solution for laser noise

A dynamic correspondence is set up between the density matrix of the electromagnetic field and an associated classical function. Means of one and two time quantum operators are shown to be obtainable from the corresponding averages of the associated classical random problem. When all atomic response rates are fast compared to photon rates, the equation of motion is obtained for the field density matrix. The associated classical problem is shown to obey a Fokker-Planck equation. Over a broad region that includes the threshold region, the Fokker-Planck equation is reduced to that for the rotating-wave van der Pol oscillator for which exact numerical solutions have been previously obtained by Hempstead and Lax.     

Adult day care: Psychological practice and evaluation.

The unnecessary institutionalization of frail adults most often occurs when emotional factors exhaust the relationship between the caretaker and the frail adult. 14 60–93 yr olds with diagnoses of depression, chronic schizophrenia, or organic brain syndrome participated in a program that attempted to remediate depression and enrich affective involvement with caretakers. The program met twice weekly for 6 hrs and provided an intervention structured around familylike relationships, group psychotherapy, and task activity. Salient themes for the group were family relations, fear of institutionalization, and grief. Analysis of pre- and posttest scores on the Life Satisfaction Index (Form A), Mental Status Questionnaire, and the Self-Rating Depression Scale showed a reduction in depression, improved life satisfaction, increased knowledge of community resources, and a broader range of community activities. The role of psychology in adult daycare and the usefulness of linking evaluation to service delivery are discussed. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)