Rapid calculation of the efficiency of self-terminating four-level Q-switched lasers.

We have developed a simple approach to deriving the efficiency of Q-switched four-level lasers, valid even for arbitrarily long lower laser level lifetimes. By eliminating time dependence from the calculation, numerical solutions can be obtained very rapidly. Its threshold and limiting slope efficiency values provide useful estimates for free-running pulsed four-level lasers as well as Q-switched.

Enhanced mid-infrared emission of Pr ions in solids through a "3-for-1" excitation process - quantified.

Evidence is presented that a "three-for-one" process based on two cross-relaxations between Pr ions efficiently populates the mid-infrared-emitting H manifold in a Pr-doped low-maximum-phonon-energy host. The concentration dependence of infrared fluorescence spectra and lifetimes of polycrystalline Pr:KPbCl initially excited to the F manifolds indicate that the 3500-5500-nm fluorescence becomes strongly favored over shorter-wavelength infrared emission bands in the higher-concentration sample. The strong concentration dependence of the F and H manifold lifetimes suggests that both of these decay by cross-relaxation processes, resulting in more than one ion excited to H for each ion initially excited to F.

Pr:RbPbCl: temperature dependent spectra, dynamics and three-for-one excitation: erratum.

We present an erratum regarding the contents of Table 1.

Pr:RbPbCl: temperature dependent spectra, dynamics and three-for-one excitation.

The temperature dependence of the absorption, fluorescence, and fluorescence lifetimes of states relevant to short-wave-infrared and mid-infrared laser operation have been measured in Pr:RbPbCl. The 3600-5500-nm fluorescence grows strongly with temperature, and at room temperature represents the large majority of the observed photon flux. Intra-ionic decay processes cannot explain this dominance, but a combination of two cross-relaxation processes provides good agreement with the data.

Co-precipitation of rare-earth-doped YO and MgO nanocomposites for mid-infrared solid-state lasers.

Mid-infrared, solid-state laser materials face three main challenges: (1) need to dissipate heat generated in lasing; (2) luminescence quenching by multiphonon relaxation; and (3) trade-off in high thermal conductivity and small maximum phonon energy. We are tackling these challenges by synthesizing a ceramic nanocomposite in which multiple phases will be incorporated into the same structure. The undoped majority species, MgO, will be the main carrier of high thermal conductivity, and the minority species, Er:YO, will have low maximum phonon energy.

Vestibular-somatosensory convergence in head movement control during locomotion after long-duration space flight.

Space flight causes astronauts to be exposed to adaptation in both the vestibular and body load-sensing somatosensory systems. The goal of these studies was to examine the contributions of vestibular and body load-sensing somatosensory influences on vestibular mediated head movement control during locomotion after long-duration space flight. Subjects walked on a motor driven treadmill while performing a gaze stabilization task.

Resonantly diode-pumped Ho3+:Y2O3 ceramic 2.1 µm laser.

We report what is believed to be the first laser operation based on Ho3+-doped Y2O3. The Ho3+:Y2O3 ceramic was resonantly diode-pumped at ~1.93 µm to produce up to 2.

Efficient resonantly pumped tape cast composite ceramic Er:YAG laser at 1645 nm.

Laser operation of a composite ceramic Er:YAG rod is demonstrated at 1645 nm with a slope efficiency of 56.9% under resonant pumping at 1532.3 nm.

Temperature dependence of a diode-pumped cryogenic Er:YAG laser.

We report the laser performance of resonantly diode-pumped Er:YAG from liquid nitrogen temperature to above room temperature. Relative to incident pump power, the best performance was observed at approximately 160 K. Spectroscopy and modeling show that this is due primarily to the changing efficiency of diode pump absorption as the absorption lines broaden with temperature.

Ultralow quantum-defect eye-safe Er:Sc2O3 laser.

Resonantly pumped Er(3+):Sc(2)O(3) laser operation is achieved with a quantum defect (QD) of 1.5% at liquid nitrogen temperature. The laser, in-line pumped at 1535 nm, operated at 1558 nm with a slope efficiency of over 45%.

Concentration quenching in fine-grained ceramic Nd:YAG.

We have studied the concentration dependent fluorescence decay kinetics of ceramic Nd:YAG, to resolve inconsistencies in the previous literature. Our data indicate that earlier reports of single exponential lifetimes even at Nd concentrations of a few percent were due to the effects of long-pulse excitation. Under short-pulse excitation the fluorescence decay is nonexponential for concentrations greater than about 1% atomic.

Ultrahigh-gain bulk solid-state stimulated Brillouin scattering phase-conjugation material.

We report what is believed to be the first observation of phase conjugation by stimulated Brillouin scattering (SBS) in TeO2 single crystal. The observed very low threshold for phase-conjugate mirror (PCM) formation, high PCM reflectivities in this initial experiment, and commercial availability of material hold promise for a host of practical applications in the near future. The resultant steady-state gain parameter, approximately 100 cm/GW, is to our knowledge the largest ever reported for any SBS material.

Adaptation of neuromuscular activation patterns during treadmill walking after long-duration space flight.

The precise neuromuscular control needed for optimal locomotion, particularly around heel strike and toe off, is known to he compromised after short duration (8- to 15-day) space flight. We hypothesized here that longer exposure to weightlessness would result in maladaptive neuromuscular activation during postflight treadmill walking. We also hypothesized that space flight would affect the ability of the sensory-motor control system to generate adaptive neuromuscular activation patterns in response to changes in visual target distance during postflight treadmill walking.

Effects of adaptation of vestibulo-ocular reflex function on manual target localization.

The goal of the present study was to determine if adaptive modulation of vestibulo-ocular reflex (VOR) function is associated with commensurate alterations in manual target localization. To measure the effects of adapted VOR on manual responses we developed the Vestibular-Contingent Pointing Test (VCP). In the VCP test, subjects pointed to a remembered target following passive whole body rotation in the dark.

Using factor analysis to identify neuromuscular synergies during treadmill walking.

Neuroscientists are often interested in grouping variables to facilitate understanding of a particular phenomenon. Factor analysis is a powerful statistical technique that groups variables into conceptually meaningful clusters, but remains underutilized by neuroscience researchers presumably due to its complicated concepts and procedures. This paper illustrates an application of factor analysis to identify coordinated patterns of whole-body muscle activation during treadmill walking.

Sertraline-associated syndrome of inappropriate antidiuretic hormone: case report and review of the literature.

Selective serotonin reuptake inhibitors have gained widespread use in the treatment of depression. A 78-year-old woman became hyponatremic 3 days after being treated with sertraline and was subsequently diagnosed with the syndrome of inappropriate antidiuretic hormone (SIADH). She became symptomatic, but experienced rapid resolution of the laboratory and clinical abnormalities associated with SIADH on discontinuing sertraline and receiving fluid restriction, hypertonic saline, and demeclocycline.

Frasier syndrome.

Objective: To present the case of a 17-year-old girl with primary amenorrhea and a history of hypertension since age 13 years.

Methods: The patient's clinical, laboratory, and radiologic data were summarized, and features of Frasier syndrome and Drash syndrome were compared.

Results: The patient's weight was 126 kg, height was 185 cm, and blood pressure was 150/100 mm Hg.

Savings, remittances, and return migration.

"We use a data set of immigrants to West Germany to simultaneously study both savings and remittances which we relate to individual characteristics, economic variables, migration experiences and remigration plans. Section 2 discusses the basic hypotheses and explains the data. Section 3 presents the empirical study and Section 4 summarizes.

The demographics of labour turnover: a comparison of ordinal probit and censored count data models.

The authors use date collected in 1977 on unemployed residents of West Germany aged 15-54 years old to compare two statistical models used to analyze labor market mobility. "Two classes of statistical models seem appropriate for this type of analysis, the ordinal probit model assuming a latent continuous variable behind the observables, and the count data approach with prominent members as the Poisson and the negative binomial model..