Cobalt-Catalyzed Hydroacylative Dimerization of Allenes Leading to Skipped Dienes.

A cobalt-diphosphine catalyst has been found to promote a selective 1:2 coupling reaction between aldehydes and allenes to form ß,δ-dialkylidene ketones, featuring skipped diene moieties, with high regioselectivities and stereoselectivities. The reaction is distinct from previously reported, rhodium-catalyzed aldehyde-allene 1:2 coupling to afford ß,γ-dialkylidene ketones bearing 1,3-diene moieties. The present hydroacylative dimerization involves a unique allene/allene oxidative cyclization mode to form a C1-C2 linkage between the allene molecules.

Completely Solvent-free Protocols to Access Phase-Pure, Metastable Metal Halide Perovskites and Functional Photodetectors from the Precursor Salts.

Mechanochemistry is a green, solid-state, re-emerging synthetic technique that can rapidly form complex molecules and materials without exogenous heat or solvent(s). Herein, we report the application of solvent-free mechanochemical ball milling for the synthesis of metal halide perovskites, to overcome problems with solution-based syntheses. We prepared phase-pure, air-sensitive CsSnX3 (X = I, Br, Cl) and its mixed halide perovskites by mechanochemistry for the first time by reactions between cesium and tin(II) halides. Notably, we report the sole examples where metastable, high-temperature phases like cubic CsSnCl3, cubic CsPbI3, and trigonal FAPbI3 were accessible at ambient temperatures and pressures without post-synthetic processing. The perovskites can be prepared up to "kilogram scales." Lead-free, all-inorganic photodetector devices were fabricated using the mechanosynthesized CsSnBr1.5Cl1.5 under solvent-free conditions and showed 10-fold differences between on-off currents. We highlight an essentially solvent-free, general approach to synthesize metastable compounds and fabricate photodetectors from commercially available precursors.

Dynamic light scattering by using self-mixing interferometry with a laser diode.

The power spectrum of the laser intensity is studied when optical feedback in a laser diode is used as a sensing configuration for dynamic light-scattering experiments. We present a theory that relates the power spectrum obtained from standard dynamic light-scattering theory to the intensity power spectrum of the laser. This theory provides a concise description of this sensing technique, also known as self-mixing interferometry, when it is applied to Doppler shift and line-broadening measurements of the backscattered field.

Efficient 2.96 microm dysprosium-doped fluoride fibre laser pumped with a Nd:YAG laser operating at 1.3 microm.

A quasi-continuous wave Dy(3+)-doped ZBLAN fibre laser pumped by a ~1.3 microm Nd:YAG laser and operating at 2.96 microm with an emission linewidth of ~14 nm (FWHM) has been demonstrated. The (6)H(15/2) ? (6)H(9/2), (6)F(11/2) absorption band of Dy(3+)-doped ZBLAN centred at 1.3 microm has been used to pump the (6)H(13/2) ? (6)H(15/2) laser transition. For a 60 cm fibre length, a threshold of 0.5 W and a slope efficiency of ~20% with respect to the absorbed pump power was measured. The experimental slope efficiency was ~45% of the Stokes efficiency limit. The high efficiency relates to low pump ESA losses and an optimised output coupling as compared with previous demonstrations.

Possible therapeutic use of vasodilator iontophoresis.

BACKGROUND: Investigation into the effects of a novel vasodilator delivery method (for the eventual treatment of scleroderma related digital ulceration) on healthy controls is reported. When Raynaud's phenomenon (episodic cold-induced colour changes of the fingers) occurs in the context of scleroderma, it can be extremely severe, leading to ulceration and sometimes gangrene. The current treatment of choice for scleroderma-related critical digital ischaemia and/or ulceration is intravenous prostanoid therapy, necessitating hospitalisation. However, iloprost is often poorly tolerated and may be ineffective. METHODS: This study utilises a newly designed iontophoresis chamber which has the potential to allow a therapeutic, rather than diagnostic application for vasodilatory iontophoresis. Ten healthy controls underwent whole finger iontophoresis with 1% acetylcholine chloride for 2 min at 100 microA. Iontophoresis with varying treatment times and currents was carried out on a subset of subjects to determine the effect on perfusion increase. RESULTS: A significant increase in perfusion following iontophoresis was found, compared to the adjacent, untreated finger (P < 0.001). Maximum increase as a percentage from baseline, mean [SD] = 100 [66]%. Both treatment time and current have an approximately linear relationship with perfusion increase. CONCLUSIONS: Iontophoresis of the whole finger administers drugs locally with no systemic effects and warrants further investigation as a therapy.

Lateralisation of nociceptive processing in the human brain: a functional magnetic resonance imaging study.

Nociceptive processing within the human brain takes place within two distinct and parallel systems: the lateral and medial pain systems. Current knowledge indicates that the lateral system is involved in processing the sensory-discriminative aspects of pain, and that the medial system is involved in processing the affective-motivational aspects of pain. Hemispheric differences in brain activation (lateralisation) during nociceptive processing were studied to further clarify the division of function between the lateral and medial pain systems. Hemispheric lateralisation was studied by applying painful CO(2) laser stimuli of 3-s duration sequentially to the left and right medial lower calves of five normal right-handed human subjects. The resultant brain activity was measured using 3-T functional magnetic resonance imaging, by determining significant changes in blood oxygen level dependent (BOLD) signal and applying a general linear modelling approach. Volumes of interest were defined for the primary and secondary somatosensory cortices (SI and SII), the insular cortex, and the thalamus, on individual subjects' high-resolution structural scans. Hemispheric lateralisation was quantified by comparing the level of activation between brain hemispheres within each volume of interest. In SII, no significant hemispheric difference in activation was detected. In the insula, activation was significantly greater in the left hemisphere than the right. In both SI and the thalamus, activation in response to painful stimulation was significantly greater in the hemisphere contralateral to the stimulus, which is consistent with these areas being involved in processing the sensory-discriminative aspects of pain.

Comparison of red and green laser doppler imaging of blood flow.

BACKGROUND AND OBJECTIVES: Laser Doppler imaging (LDI) of perfusion has been performed with a novel green wavelength (532 nm) for comparison with a HeNe laser (633 nm), the aim being validation of the green laser wavelength as a research tool. STUDY DESIGN/MATERIALS AND METHODS: The effect of wavelength and power on images was investigated and perfusion response following both finger occlusion and local heating of the dorsum were examined as reproducible stimuli for clinical studies. RESULTS: The most striking difference between red and green LDI is the absence of veins on green LDI, which are seen with red LDI. Differences have been quantified using vein LDI profiles. Differences were found between blood flow responses imaged by red and green LDI (3 and 5 mW, respectively) for occlusion and heat stimuli. Results are discussed in the context of light penetration. CONCLUSIONS: Red and green wavelengths appear to image different components of the microcirculation.

Comparison of thermography and laser Doppler imaging in the assessment of Raynaud's phenomenon.

The main objective of the study was to compare the techniques of thermographic and laser Doppler imaging in the assessment of digital blood flow. Thermography measures surface temperature; laser Doppler measures microciculatory flow. Seventeen healthy control subjects and 40 patients with Raynaud's phenomenon (7 primary, 33 secondary to systemic sclerosis) underwent a 20-min acclimatization period at 23 degrees C. Thermographic and then laser Doppler images were taken of the dorsal aspect of both hands, and the procedure was repeated at a room temperature of 30 degrees C. Three regions/values of interest from each hand were chosen for analysis: the dorsum of the hand, the tip of the middle finger, and the "gradient" between these. Thermographic and laser Doppler results correlated poorly. For example, correlations between techniques for the gradient value were as follows: left hand 23 degrees C, r = 0.61; right hand 23 degrees C, r = 0.64; left hand 30 degrees C, r = 0.47; right hand 30 degrees C, r = 0.48. One explanation for these findings is that laser Doppler imaging is more sensitive to blood flow changes and therefore more likely to show inhomogeneities than the highly damped temperature response. Therefore one technique cannot substitute for another.

High-peak-power operation of a Q-switched Tm3+-doped silica fiber laser operating near 2 microm.

A peak output power of greater than 4.1 kW and a pulse duration at FWHM of 150 ns have been obtained in a Q-switched Tm3+-doped silica fiber laser in the wavelength region near 2 microm when the laser was pumped with a Nd:YAG laser operating at 1.319 microm. An acousto-optic modulator was used as a Q-switching element and operated at repetition rates of as much as 30 kHz. A core diameter of 17 microm was used to increase the laser gain volume, permitting high-pump-power absorption and an output of high pulse energy and peak power. Stimulated Brillouin scattering was directly observed in the output pulse, and as much as 10 orders of stimulated Brillouin scattering was recorded. This is the first report to the authors' knowledge of high-peak-power operation of a Tm3+-fiber laser.

Sequence lasing in a gain-switched Yb3+,Er(3+)-doped silica double-clad fiber laser.

Experimental results relating to the gain-switched operation of a double-clad Yb3+,Er(3+)-doped silica fiber laser that is pulse pumped with the output from a flash-lamp-pumped Ti:sapphire laser are presented. For all the configurations of the fiber laser that we studied, the 2F5/2-->2F7/2 laser transition of the Yb3+ ion lased prior to laser emission from the 4I13/2-->4I15/2 transition of the Er3+ ion. To the best of our knowledge, this is the first reported operation of sequence lasing in the Yb3+,Er(3+)-codoped system. This succession of laser pulses deduced from the measurements of this investigation is a consequence of both the short intense pump pulse and the short 900-nm wavelength of the pump that does not overlap with any important excited-state absorption transitions. We believe that the predominant interionic interaction during the course of the pump pulse is the double-energy transfer to the Er3+ ion acting twice from the 2F5/2 energy level of the Yb3+ donor ion. A maximum total output of 1.65 mJ is obtained (1.38 mJ from the 2F5/2-->2F7/2 transition of Yb3+ and 0.27 mJ from the 4I13/2-->4I15/2 transition of Er3+) from a nonoptimized configuration of the fiber laser. The wavelength of the output from the fiber laser was measured to vary approximately linearly with fiber length from 1040 to 1046 nm for the Yb(3+)-based laser and 1535 to 1541 nm for the Er(3+)-based laser.