Solid-state laser spectral narrowing using a volumetric photothermal refractive Bragg grating cavity mirror

Dramatic spectral narrowing of two normally broadband lasers, Ti:sapphire and Cr:LiSAF, was achieved by simply replacing the output mirror with a reflective, volumetric Bragg grating recorded in photothermal refractive glass. The output power of each laser was unchanged from that obtained using dielectric coated output mirrors with the same output coupling as the Bragg grating while spectral brightness increased by 3 orders of magnitude.     

Effect of oxalate test dose size on absolute and percent oxalate absorption

The purpose of this pilot study was to establish the dependence or independence of oxalate absorption on the quantity of the test dose of sodium oxalate over a range of test doses corresponding to physiological dietary oxalate intake values. Gastrointestinal oxalate absorption was measured with the [13C2]oxalate absorption test. Six healthy volunteers were always tested under standardized dietary conditions with 63 mg dietary oxalate and 800 mg dietary calcium per day. The volunteers were tested thrice each with sodium oxalate test doses of 25, 50, 200, and 600 mg. Additionally, 1000 mg sodium oxalate was applied once to three of these volunteers. The oxalate absorption of the six volunteers tested under the standardized conditions with 50 mg sodium [13C2]oxalate was 7.2 +/- 2.62 % (mean +/- SD), similar to the 120 volunteers tested previously: 8.0 +/- 4.4 % (mean +/- SD). The tests with sodium [13C2]oxalate doses in the range 25-1000 mg revealed similar percent oxalate absorption values. In conclusion, in healthy volunteers, the amount of oxalate absorbed in the gastrointestinal tract increased proportionally with the higher test doses of oxalate. However, percent oxalate absorption remained unchanged with test doses in the dose range of physiological dietary oxalate intakes.     

The Effects of Different Superplasticizers and Water-to-Cement Ratios on the Hydration of Gray Cement Using T2-NMR

In the present work, we compare the influence introduced by the variation of water-to-cement ratio and the presence of different superplasticizers on the hydration process of gray cement using the low-field nuclear magnetic resonance relaxometry. The stages of hydration are identified and a relationship between the ettringite formation during hydration process and the transverse relaxation time is established. It is also demonstrated that the addition of small amounts of superplasticizer in the cement paste significantly expands the dormant period while the hardening period is reduced. On the other side, the increase in the water-to-cement ratio has little influence on the dormant period but can instead increase the porosity of the sample and consequently reduce its strength.     

Monitoring the synthesis of new polymer nanocomposites based on different polyhedral oligomeric silsesquioxanes using Raman spectroscopy

The kinetic behavior of the urethane dimethacrylate (UDMA) copolymerized and reinforced by different concentrations of polyhedral oligomeric silsesquioxane (POSS) with methacrylic groups was studied through Raman spectroscopy. UDMA‐POSS networks have been synthesized with three different types of POSS, two monofunctional POSS (1‐propylmethacrylate)‐heptaisobutyl substituted (HISO‐POSS) and heptacyclopentyl‐octasiloxan‐1‐yloxy) dimethylsilyl] propyl methacrylate (CPENTYL‐POSS) and one octafunctional POSS‐methacryl substituted (MA‐POSS). In order to show the influence of POSS on the final conversion, the hybrid systems were cured using three types of initiators which decompose at different temperatures: azobisisobutyronitrile (AIBN) (65 °C), benzoyl peroxide (BP) (80 °C) and di‐tert‐butyl peroxide (DTBP) (120 °C). The structure of the hybrid's surface was investigated by X‐ray photoelectron spectroscopy (XPS) and the T_g values were calculated from dynamic mechanical analysis (DMA) tests. Copyright © 2009 John Wiley & Sons, Ltd.     

Enhancement of single‑photon emission from nitrogen‑vacancy centers with TiN/(Al,Sc)N hyperbolic metamaterial

The broadband enhancement of single‑photon emission from nitrogen‐vacancy centers in nanodiamonds coupled to a planar multilayer metamaterial with hyperbolic dispersion is studied experimentally. The metamaterial is fabricated as an epitaxial metal/dielectric superlattice consisting of CMOS‐compatible ceramics: titanium nitride (TiN) and aluminum scandium nitride (Al_xSc_1‐xN). It is demonstrated that employing the metamaterial results in significant enhancement of collected single‑photon emission and reduction of the excited‐state lifetime. Our results could have an impact on future CMOS‐compatible integrated quantum sources.

     

Regular patterns stabilize auditory streams

The auditory system continuously parses the acoustic environment into auditory objects, usually representing separate sound sources. Sound sources typically show characteristic emission patterns. These regular temporal sound patterns are possible cues for distinguishing sound sources. The present study was designed to test whether regular patterns are used as cues for source distinction and to specify the role that detecting these regularities may play in the process of auditory stream segregation. Participants were presented with tone sequences, and they were asked to continuously indicate whether they perceived the tones in terms of a single coherent sequence of sounds (integrated) or as two concurrent sound streams (segregated). Unknown to the participant, in some stimulus conditions, regular patterns were present in one or both putative streams. In all stimulus conditions, participants' perception switched back and forth between the two sound organizations. Importantly, regular patterns occurring in either one or both streams prolonged the mean duration of two-stream percepts, whereas the duration of one-stream percepts was unaffected. These results suggest that temporal regularities are utilized in auditory scene analysis. It appears that the role of this cue lies in stabilizing streams once they have been formed on the basis of simpler acoustic cues.     

Cr∶Nd∶GSGG晶体1.061 μm受激发射截面随温度变化特性研究

测量了Cr∶Nd∶GSGG晶体从 - 70℃到 +80℃温度下的荧光发射光谱和荧光寿命 ,计算了该晶体在不同温度下 1 .0 61 μm受激发射截面 ,获得在此温度变化范围内受激发射截面随温度的线性变化关系     

Photooxidation of Histidine by 3,3′,4,4′-Benzophenone Tetracarboxylic Acid in Aqueous Solution: Time-Resolved and Field-Dependent CIDNP Study

The photooxidation reaction between 3,3′,4,4′-benzophenone tetracarboxylic acid (TCBP) and l-histidine (His) has been investigated in neutral aqueous solution using the technique of chemically induced dynamic nuclear polarization (CIDNP). Relative values of ¹³C isotropic hyperfine couplings in the TCBP and His radicals were obtained from the ¹³C-time-resolved CIDNP spectrum, recorded during the photoreaction of TCBP with His at natural abundance of the magnetic isotope ¹³C. Good agreement was found for the hyperfine coupling constants of the TCBP ketyl radical calculated using methods of density functional theory, and those obtained from the ¹³C-time-resolved CIDNP spectrum. The mechanism of the quenching reaction of triplet-excited TCBP by His in neutral aqueous solution was established. ¹H CIDNP field dependencies for the photoreaction of TCBP with His were obtained and the g-factor of the histidyl radical was found.     

High-pressure phase transition of Bi2Fe4O9

The high-pressure behaviour of Bi2Fe4O9 was analysed by in situ powder and single-crystal x-ray diffraction and Raman spectroscopy. Pressures up to 34.3(8) GPa were generated using the diamond anvil cell technique. A reversible phase transition is observed at approximately 6.89(6) GPa and the high-pressure structure is stable up to 26.3(1) GPa. At higher pressures the onset of amorphization is observed. The crystal structures were refined from single-crystal data at ambient pressure and pressures of 4.49(2), 6.46(2), 7.26(2) and 9.4(1) GPa. The high-pressure structure is isotypic to the high-pressure structure of Bi2Ga4O9. The lower phase transition pressure of Bi2Fe4O9 with respect to that of Bi2Ga4O9 (16 GPa) confirms the previously proposed strong influence of cation substitution on the high-pressure stability and the misfit of Ga3+ and Fe3+ in tetrahedral coordination at high pressure. A fit of a second-order Birch–Murnaghan equation of state to the p–V data results in K0 = 74(3) GPa for the low-pressure phase and K0 = 79(2) GPa for the high-pressure phase. The mode Grüneisen parameters were obtained from Raman-spectroscopic measurements.