Stress Tuning of Laser Crystals

The topic of stress tunable laser crystals is addressed in this study with the purpose of determining the piezo-optic coefficients of a new laser material. This data was collected using a quadruple pass birefringence technique because of its high degree of sensitivity relative to the other methods examined including fringe shift analysis using a Mach-Zender interferometer. A green He-Ne laser was passed through a light chopper and Glan-Thompson prism before entering a crystal of Erbium doped Yttrium Aluminum Garnet (Er:YAG) (used in order to validate the experimental technique). The Er:YAG crystal is mounted in a press mechanism and the laser is quadruple passed through test specimen before being returned through the prism and the orthogonally polarized portion of the beam measured with a optical sensor. At a later stage, the Er:YAG crystal was replaced with a new crystal in order to determine the piezo-optic coefficients of this uncharacterized material. The applied load was monitored with the use of a 50 lb. load cell placed in line with the press. Light transmission readings were taken using a lock-in amplifier while load cell measurements were taken with a voltmeter from a 5 volt, 0.5 amp power supply. Despite the fact that an effective crystal press damping system was developed, size limitations precluded the use of the complete system. For this reason, data points were taken only once per full turn so as to minimize the effect of non uniform load application on the collected data. Good correlation was found in the transmission data between the experimentally determined Er:YAG and the previously known peizo-optic constants of non-doped crystal with which it was compared. The variation which was found between the two could be accounted for by the aforementioned presence of Erbium in the experimental sample (for which exact empirical data was not known). The same test procedure was then carried out on a Yttrium Gallium Aluminum garnet (YGAG) for the purpose of establishing values of its unknown piezo-optic constant tensor using experimentally collected transmission data. Significant variation between the piezo-optic constants of YAG and YGAG crystals was found however, the excellent data correlation of separate experimental runs carried out on the YGAG sample demonstrates the validity of these results. The data collected during the stressing of the YGAG was of high quality, however the amount of data collected was somewhat limited by a fracture of YGAG specimen which undoubted altered the crystalline lattice structure and hence precluded any further testing

Thermodynamic properties of argon from the triple point to 300 K at pressures to 1000 atmospheres

Thermodynamic property data for argo

Photostop: production of zero-velocity molecules by photodissociation in a molecular beam

Photostop is an accessible technique capable of producing atoms or molecules at a standstill in the laboratory frame. Starting with a NO2/Xe molecular beam with a mean velocity of 415 m s-1 and a longitudinal translational temperature of 6 K, NO2 molecules are photodissociated to yield NO(X [image omitted]) fragments with a recoil speed equal to the molecular beam speed. The fraction of NO fragments that recoil opposite to the molecular beam are produced with a 6 K longitudinal velocity distribution centred at zero. The NO molecules are allowed to 'evaporate' from the probe volume by waiting for 1

Rotational energy transfer in collisions between CO(X¹Σ⁺, v=2, J=0, 1,4, and 6) and He at temperatures from 294 to 15 K

Infrared-vacuum ultraviolet double resonance experiments have been implemented in the ultracold environment provided by a Cinétique de Réaction en Ecoulement Supersonique Uniforme apparatus. With this technique rate coefficients of two kinds have been measured for rotational energy transfer in collisions between CO and He: (a) those for total removal from the selected rotational states J = 0, 1, 4, and 6 in the vibronic state X 1+, v = 2, and (b) those for transfer between selected initial and specific final states. Using different Laval nozzles, results have been obtained at several different temperatures: 294, 149, 63, 27, and 15 K. The thermally averaged cross sections for total removal by collisions with He show only slight variations both with initial rotational state and with temperature. The variation of state-to-state rate coefficients with J show several general features: (i) a decrease with increasing J; (ii) a propensity to favor odd J over even J; and (iii) at lower temperatures, the distribution of rate coefficients against J becomes narrower, and decreases in J are increasingly favored over increases in J, a preference which is most strongly seen for higher initial values of J. The results are shown to be in remarkably good agreement with those obtained in ab initio scattering calculations by Dalgarno and co-workers [Astrophys. J. 571, 1015 (2002)]

A study of the effectiveness of a phonetic and activity approach to the teaching of spelling in grade four,

Includes appendices. Thesis (M.A.)--Boston Universit

Neonatal mortality in NHS maternity units by timing and mode of birth: a retrospective linked cohort study

OBJECTIVES: To compare neonatal mortality in English hospitals by time of day and day of the week according to care pathway. DESIGN: Retrospective cohort linking birth registration, birth notification and hospital episode data. SETTING: National Health Service (NHS) hospitals in England. PARTICIPANTS: 6 054 536 liveborn singleton births from 2005 to 2014 in NHS maternity units in England. MAIN OUTCOME MEASURES: Neonatal mortality. RESULTS: After adjustment for confounders, there was no significant difference in the odds of neonatal mortality attributed to asphyxia, anoxia or trauma outside of working hours compared with working hours for spontaneous births or instrumental births. Stratification of emergency caesareans by onset of labour showed no difference in mortality by birth timing for emergency caesareans with spontaneous or induced onset of labour. Higher odds of neonatal mortality attributed to asphyxia, anoxia or trauma out of hours for emergency caesareans without labour translated to a small absolute difference in mortality risk. CONCLUSIONS: The apparent 'weekend effect' may result from deaths among the relatively small numbers of babies who were coded as born by emergency caesarean section without labour outside normal working hours. Further research should investigate the potential contribution of care-seeking and community-based factors as well as the adequacy of staffing for managing these relatively unusual emergencies

Trap induced broadening in a potential hydrogen lattice clock

We consider the potential use of optical traps for precision measurements in atomic hydrogen (H). Using an implicit summation method, we calculate the atomic polarisability, the rates of elastic/inelastic scattering and the ionisation rate in the wavelength range (395–1000) nm. We extend previous work to predict three new magic wavelengths for the 1S–2S transition. At the magic wavelengths, the 1S–2S transition is unavoidably and significantly broadened due to trap-induced ionisation associated with the high intensity required to trap the 1S state. However, we also find that this effect is partially mitigated by the low mass of H, which increases the trap frequency, enabling Lamb–Dicke confinement in shallow lattices. We find that a H optical lattice clock, free from the motional systematics which dominate in beam experiments, could operate with an intrinsic linewidth of the order of 1 kHz. Trap-induced losses are shown not to limit measurements of other transitions

Efficacy of Terramycin® 200 for Fish (Oxytetracycline Dihydrate) for the Skeletal Marking of Rainbow Trout

In 2009, we conducted a study to evaluate the efficacy of Terramycin® 200 for Fish (TM200; 44.1% active oxytetracycline dihydrate) administered in feed at a target dosage of 3.75 g/100 lbs fish/day for 10 days for the skeletal (fluorescent) marking of fingerling rainbow trout (Oncorhynchus mykiss). The in-life phase of the study was conducted indoors at a mean water temperature of 10.3 ºC and comprised a 1-day acclimation period (no feed administered), 10-day treatment period (TM200-treated feed fed to six treated tanks; nontreated control feed fed to three control tanks), and 22-day post-treatment period (control feed administered to all tanks). At the end of the posttreatment period, all fish were collected and individually frozen. One month later, all fish were thawed, and two vertebrae were extracted from each fish. Each vertebra extracted was cleaned and then evaluated under ultraviolet light and a dissecting scope for the presence and quality of a fluorescent mark. All vertebrae extracted from TM200-treated fish (n = 120) had clearly visible marks, whereas no vertebrae extracted from control fish (n = 60) were marked. Consequently, in this study, TM200 administered in feed at a target dosage of 3.75 g OTC/100 lbs fish/d for 10 day was effective for the skeletal (fluorescent) marking of fingerling rainbow trout. Results will be used to support a U.S. approval of an expanded skeletal marking claim for TM200

The MAGSORB process for bulk separation of carbon dioxide

During the sixth quarter of this program, work continued on the preparation of homogeneous batches of sorbent. It had previously been found that there was not consistent agreement between the Mg/K ratios calculated from the amounts of reagents used and the ratios determined by chemical analysis using atomic absorption spectrometry. In our investigation of the causes of these inconsistencies, we also found that there was an unacceptably high variation in the Mg/K ratio among the individual sorbent pellets. This quarter, sorbent pellets that had shown excessive variation in the Mg/K ratio were ground and the powder mixed to produce a uniform material. This material was then pelletized with a compaction device and the pellets checked for composition and reactivity. Although this procedure produced pellets with consistent Mg/K ratios, thermobalance tests showed reduced reactivity