Injection-seeded single-longitudinal-mode Ti:Sapphire laser with no active stabilization

We report on the first injection-seeded nanosecond Ti:Sapphire laser that demonstrates a stable single-longitudinal-mode operation with no feedback loop for active cavity stabilization. The short cavity generates 6-mJ transform-limited pulses at a wavelength of 807 nm and with a slope efficiency of 43%. An intracavity dispersive prism makes a novel cavity design for injection-seeded lasers and provides pre-selection of the emission wavelength. In support of these experiments, we perform numerical simulations that include extra cavity losses. The simulation results are in good agreement with the outcome of the experiment and reveal the formation scenario of the laser mode.

Clinical application of a gadolinium-based capsule as an MRI contrast agent in slow transit constipation diagnostics

BACKGROUND

As a traditional method for the assessment of colon dynamics, radio-opaque markers (ROMs) are limited in clinical use because of their ionizing radiation. We compared the accuracy and applicability of gadolinium-based capsules with ROMs in the measurement of colon dynamics in healthy controls and slow transit constipation (STC) patients.

METHODS

Seven patients with STC and nine healthy controls under a normal diet orally consumed ROMs and gadolinium-based capsules simultaneously. All subjects underwent X-ray and magnetic resonance imaging (MRI). Healthy control images were acquired at 12, 24, and 48 h, and STC patient images were acquired at 24, 48, and 72 h. The scores based on the position of the labeling capsules and ROMs in the colon and the colon transit times (CTTs) in the two groups were compared.

KEY RESULTS

The CTTs obtained via the ROMs were 34.7±17.4 and 67.3±6.5 h in the healthy controls and STC patients, respectively (P<.05). The CTTs obtained via MRI were 30.9±15.9 and 74.1±7.2 h in the healthy controls and STC patients, respectively (P<.05). The CTTs of the STC patients were significantly longer than the healthy controls. The correlation (r_s ) between the scores based on the position of the labeling capsule and ROMs in the healthy group and the STC patients was .880 (P<.05) and .889 (P<.05), respectively.

CONCLUSIONS AND INFERENCES

As a MRI contrast label, gadolinium-based capsules exhibit results comparable to ROMs in colon motility measurements.

NUDT15 polymorphisms are better than thiopurine S-methyltransferase as predictor of risk for thiopurine-induced leukopenia in Chinese patients with Crohn's disease

BACKGROUND

Thiopurine-induced leukopenia is the most common dangerous adverse event in Asians. NUDT15 R139C was recently proposed to be a promising biomarker for leukopenia with thiopurine therapy in Asians, but this has not been replicated in the Chinese population.

AIM

To investigate the influence of NUDT15 R139C, thiopurine S-methyltransferase (TPMT), 6-TGN and 6-MMPR on thiopurine-induced leukopenia in Chinese patients with Crohn's disease.

METHODS

Clinical and epidemiological characteristics were reviewed from medical records. NUDT15 R139C and TPMT were genotyped. 6-TGN/6-MMPR concentrations were measured with high-performance liquid chromatography (HPLC).

RESULTS

A total of 253 patients were included, 65 (25.7%) of whom experienced leukopenia. The median follow-up with thiopurine treatment was 38.0 weeks (range, 1-192 weeks). NUDT15 R139C was strongly associated with the incidence of leukopenia (70.2% mutation vs. 12.8% wild type; P=8.61×10^-19 ; odds ratio, 10.80; 95% CI, 5.89-19.83). However, TPMT genotype was not found to be correlated with the incidence of leukopenia (P = 0.44). In subgroup of NUDT15 wild type, there was significant difference of 6TGN concentration between patients with and without leukopenia (413.0 (174.2-831.4) vs. 279.7 (77.3-666.9) pmol/8 × 10⁸ RBC, P = 0.0055). In contrast, no association was found in patients with NUDT15 R139C variant alleles (P = 0.26). 6-MMPR was not correlated with leukopenia (P = 0.84).

CONCLUSIONS

In Chinese patients, it is strongly recommended to detect NUDT15 genotype rather than TPMT before initiating thiopurine drugs. 6TGN concentration should be routinely monitored in CD patients with NUDT15 wild type. As for CT genotype, starting at low dose and careful monitoring for leukopenia and 6TGN levels is recommended.

Coherent transfer of optical orbital angular momentum in multi-order Raman sideband generation

Experimental results from the generation of Raman sidebands using optical vortices are presented. By generating two sets of sidebands originating from different locations in a Raman-active crystal, one set containing optical orbital angular momentum and the other serving as a reference, Young's double slit experiment was simultaneously realized for each sideband. The interference between the two sets of sidebands was used to determine the helicity and topological charge in each order. Topological charges in all orders were found to be discrete and follow selection rules predicted by a cascaded Raman process.

Energy transfer between laser filaments in liquid methanol

We demonstrate energy exchange between two filament-forming femtosecond laser beams in liquid methanol. Our results are consistent with those of previous works documenting coupling between filaments in air; in addition, we identify an unreported phenomenon in which the direction of energy exchange oscillates at increments in the relative pulse delay equal to an optical period (2.6 fs). Energy transfer from one filament to another may be used in remote sensing and spectroscopic applications utilizing femtosecond laser filaments in water and air.

Pulse-shaper-assisted phase control of a coherent broadband spectrum of Raman sidebands

We report pulse-shaper-assisted phase control of a broad spectrum, aiming to synthesize nonsinusoidal waveforms. We first generate multiple-order coherent Raman sidebands by focusing two laser beams into a piece of diamond. Then we combine five sidebands into a single beam by using a prism. Our setup allows for both coarse, manual phase adjustments and fine tuning of the spectral phases. A flat spectral phase across these five frequency-separated sub-bands is achieved, which implies generation of two to three optical-cycle pulses.

Measurements and a model of the outer hair cell hydraulic conductivity

The hydraulic conductivity of the cochlear outer hair cell (OHC) is central to the maintenance of the positive intracellular pressure necessary for its function as the cochlear amplifier. A mathematical model of osmotic water transport across the OHC membrane is formulated. The model relates the OHC hydraulic conductivity, Lp, to the rate of volume change in response to osmotic stimuli. Lp is evaluated from osmotic experiments in which isolated OHCs are exposed to an hypotonic solution. The rate of volume increase in response to the hypotonic challenge was determined by a morphometric analysis of video images of cells. Lp was found to be about 10(-14) m s-1 Pa-1 or equivalently, Pf approximately 10(-4) cm s-1. This is on the low side of values reported for different lipid bilayers and is 2 orders of magnitude lower than the hydraulic conductivity of red blood cells. The relation of the low OHC hydraulic conductivity to the composition and morphology of its membranes is discussed.

The ratio of elastic moduli of cochlear outer hair cells derived from osmotic experiments

Outer hair cells (OHCs) were subjected to three different hypo-osmotic challenges which induced shape changes in OHCs. The longitudinal and circumferential strains, epsilon z and epsilon c, respectively, were extracted from a morphometric analysis of video images of the cells. A value of epsilon z/epsilon c = -0.72 was obtained and was found to be independent of the applied osmotic gradient. Using an elastic isotropic membrane model for the OHC lateral wall, the ratio of the elastic shear modulus mu to the elastic area expansion modulus K was calculated yielding a value of 0.054. The contribution of this ratio to OHC mechanics is discussed.

Preliminary study of the distribution of the toxic elements As, Cd, and Hg in human hair and tissues by RNAA

In order to study the relationships between trace element concentrations of hair and internal body burdens, a radiochemical NAA technique has been used for determination of the elements As, Cd, and Hg in autopsy samples of liver, kidney-cortex, lung, and hair from 24 male persons who died by accident. High significant positive correlations were observed between the As concentration in hair and in kidney-cortex, and between Cd and Zn concentrations in kidney-cortex. The contents of Cd, both for lung and kidney-cortex, were related to the smoking habits of the subjects.

Study of correlation of Se content in human hair and internal organs by INAA

The correlations of essential element Se between human hair and kidney-cortex, liver, and lung from the same subjects were investigated by instrumental neutron activation analysis, using the reaction 76Se (n, gamma) 77mSe, for 24 Chinese autopsies. The concentration of Se is higher in kidney-cortex (2.04-5.36 mg/kg) than in liver (0.73-2.29), lung (0.50-1.85), and hair (0.37-1.43). It is important to know that there are significant relationships of Se concentration between hair and the other three internal organs. The correlation coefficient by linear regression analysis are 0.639, 0.570, and 0.635 for liver, lung, and kidney-cortex, respectively; and the P values are all less than 0.01 for the three tissues.