Dielectric breakdown induced by picosecond laser pulses

The damage thresholds of transparent optical materials were investigated. Single picosecond pulses at 1.06 microns, 0.53 microns and 0.35 microns were obtained from a mode locked Nd-YAG oscillator-amplifier-frequency multiplier system. The pulses were Gaussian in space and time and permitted the determination of breakdown thresholds with a reproducibility of 15%. It was shown that the breakdown thresholds are characteristic of the bulk material, which included nine alkali halides, five different laser host materials, KDP, quartz, sapphire and calcium fluoride. The extension of the damage data to the ultraviolet is significant, because some indication was obtained that two- and three-photon absorption processes begin to play a role in determining the threshold. Throughout the visible region of the spectrum the threshold is still an increasing function of frequency, indicating that avalanche ionization is the dominant factor in determining the breakdown threshold. This was confirmed by a detailed study of the damage morphology with a high resolution microscope just above the threshold. The influence of self focusing is discussed, and evidence for beam distortion below the power threshold for complete self focusing is presented, confirming the theory of Marburger

Assessment of the effect of esterified propoxylated glycerol (EPG) on the status of fat-soluble vitamins and select water-soluble nutrients following dietary administration to humans for 8weeks

AbstractThis double-blind, randomized, controlled study assessed the effect of esterified propoxylated glycerol (EPG) on fat-soluble vitamins and select nutrients in human subjects. For 8weeks, 139 healthy volunteers consumed a core diet providing adequate caloric and nutrient intakes. The diet included items (spread, muffins, cookies, and biscuits) providing EPG (10, 25, and 40g/day) vs. margarine alone (control). EPG did not significantly affect circulating retinol, α-tocopherol, or 25-OH D2, but circulating β-carotene and phylloquinone were lower in the EPG groups, and PIVKA-II levels were higher; 25-OH D3 increased but to a lesser extent than the control. The effect might be related to EPG acting as a lipid “sink” during gastrointestinal transit. No effects were seen in secondary endpoint measures (physical exam, clinical pathology, serum folate, RBC folate, vitamin B12, zinc, iron, calcium, phosphorus, osteocalcin, RBP, intact PTH, PT, PTT, cholesterol, HDL-C, LDL-C, triglycerides). Gastrointestinal adverse events (gas with discharge; diarrhea; oily spotting; oily evacuation; oily stool; liquid stool; soft stool) were reported more frequently by subjects receiving 25 or 40g/day of EPG. In general, the incidence and duration of these symptoms correlated directly with EPG dietary concentration. The results suggest 10g/day of EPG was reasonably well tolerated

Anisotropic infrared response of vanadium dioxide microcrystals

Vanadium dioxide (VO2) undergoes a phase transition at a temperature of 340 K between an insulating monoclinic M-1 phase and a conducting rutile phase. Accurate measurements of possible anisotropy of the electronic properties and phonon features of VO2 in the insulating monoclinic M-1 and metallic rutile phases are a prerequisite for understanding the phase transition in this correlated system. Recently, it has become possible to grow single domain untwinned VO2 microcrystals, which makes it possible to investigate the true anisotropy of VO2. We performed polarized transmission infrared micro-spectroscopy on these untwinned microcrystals in the spectral range between 200 cm(-1) and 6000 cm(-1) and have obtained the anisotropic phonon parameters and low frequency electronic properties in the insulating monoclinic M-1 and metallic rutile phases. We have also performed ab initio GGA+U total energy calculations of phonon frequencies for both phases. We find our measurements and calculations to be in good agreement. DOI: 10.1103/PhysRevB.87.11512

Communication: Observation of local-bender eigenstates in acetylene

We report the observation of eigenstates that embody large-amplitude, local-bending vibrational motion in acetylene by stimulated emission pumping spectroscopy via vibrational levels of the S1 state involving excitation in the non-totally symmetric bending modes. The N[subscript b] = 14 level, lying at 8971.69 cm[superscript −1] (J = 0), is assigned on the basis of degeneracy due to dynamical symmetry breaking in the local-mode limit. The level pattern for the N[subscript b] = 16 level, lying at 10 218.9 cm[superscript−1], is consistent with expectations for increased separation of ℓ = 0 and 2 vibrational angular momentum components. Increasingly poor agreement between our observations and the predicted positions of these levels highlights the failure of currently available normal mode effective Hamiltonian models to extrapolate to regions of the potential energy surface involving large-amplitude displacement along the acetylene ⇌ vinylidene isomerization coordinateUnited States. Dept. of Energy. Office of Basic Energy Sciences. Chemical Sciences Geosciences and Biosciences Division (Award No. DE-FG0287ER13671

Fourteen years' experience with 501 subcoronary Ross procedures: Surgical details and results

ObjectiveDuring the past decade the Ross procedure using the full root has become the predominant surgical technique. However, progressive autograft dilatation and eventual failure remain a concern. Here we report on the surgical techniques and results of the subcoronary technique over a 14-year period.MethodsA total of 501 patients (mean age, 44.9 ± 12.9 years; 117 female; 384 male) were operated on from June 1994 to December 2007. The follow-up database, with a completeness of 98.2%, was closed on December 2008, comprising of 2931 patient-years with a mean follow-up of 5.9 ± 3.6 years (range, 0.1–14.1 years).ResultsSurgical details are presented. Early and late mortality were 0.4% (n = 2) and 4% (n = 20), respectively, valve-related mortality was 1.2% (n = 6), whereas the overall survival did not differ from that of the normal population. Neurologic events occurred in 22 patients, major bleeding in 9, autograft endocarditis in 8, and homograft endocarditis in 10. Freedom from autograft and homograft reoperation was 91.9% at 10 years. For the majority of patients, hemodynamics was excellent and no root dilatation was observed.ConclusionsMidterm results after the original subcoronary Ross procedure are excellent, including normal survival and low risk of valve-related morbidity. Longer-term results are necessary for continuous judgment of the subcoronary technique

Studies for a Photon Collider at the ILC

One option at the International Linear Collider is to convert the electron beams into high energy photon beams by Compton scattering a few millimetres in front of the interaction region. Selected physics channels for this option have been analysed and technical issues have been studied. So far no showstoppers for this option have been found.Comment: V2: Minor changes, accepted by NI