Single-mode interband cascade laser based on V-coupled cavity with 210†nm wavelength tuning range near 3†µm.

Interband cascade lasers (ICLs) are efficient and compact mid-infrared (3-5 µm) light sources with many applications. By enhancing the coupling coefficient and using a type-I ICL wafer, single-mode ICLs were demonstrated based on V-coupled cavity with significantly extended tuning range and with a side mode suppression ratio (SMSR) exceeding 35 dB in continuous wave operation near 3 µm. A V-coupled cavity ICL exhibited a wavelength tuning up to 67 nm at a fixed temperature, and the total tuning range exceeds 210 nm when the heat sink temperature is adjusted from 80 to 180 K. The realization of single-mode in such a wide temperature range with a tuning range exceeding 210 nm verified the advantage of V-coupled cavity ICLs for effective detection of multiple gas species. This is very different from the conventional distributed feedback (DFB) laser where the single-mode operation is restricted to a narrow temperature range, in which the match between the gain peak and the DFB grating period determined wavelength is required. Another V-coupled cavity ICL is tuned over 120 nm from 2997.56 nm to 3117.50 nm with the heat-sink temperature varied from 210 K to 240 K, over 100 K higher than the previously reported maximum operating temperature for V-coupled cavity ICLs.

Mid-infrared widely tunable single-mode interband cascade lasers based on V-coupled cavities.

We demonstrate widely tunable single-mode V-coupled-cavity lasers emitting at wavelengths near 3 µm based on a type-II interband cascade (IC) structure. The mode selection is achieved using a half-wave V-coupler designed for the IC structure in the mid-infrared range. The laser waveguides and cavity structure are deeply etched in a single etching step, without any grating. By changing the injection current at a fixed heat-sink temperature, a tuning range over 35 nm can be achieved with a side-mode suppression-ratio up to 28 dB. The tuning range can be extended to 60 nm when combined with the adjustments of the heat-sink temperature.

[Research on the relationship between environmental chemical pollutant exposure and epigenetics].

Environmental chemical pollutants are increasing, which brings various harms to human health. Epigenetics may be an important medium between exposure to environmental chemical contaminants and adverse health effects. Many environmental chemical pollutant exposures can regulate gene expression and promote disease occurrence and development through epigenetic mechanisms. This review outlines the mechanisms of epigenetics and the latest research advances in exposure and epigenetics of several environmental chemical substances (heavy metal arsenic, bisphenol A, dioctyl phthalate and benzene). To further understand and study the relationship between environmental chemical pollutant exposures and epigenetics in order to elucidate the mechanisms of disease occurrence and development.

Ammonium concentration of spent medium provides a noninvasive assessment of embryonic developmental potential in IVF.

BACKGROUND: Currently, morphological criteria are used to select embryos for transfer in in vitro fertilization (IVF)-embryo transfer. However, the implantation rate is only about 30%, indicating a need for a more efficient method of selecting high-quality embryos. This study investigated the relationship between medium ammonium concentration and IVF implantation rates and evaluated the possibility of using ammonium concentration to provide an objective, noninvasive, and simple means of assessment of embryo viability. METHODS: On day 3 after fertilization, we sampled the spent medium bathing embryos obtained from patients undergoing IVF or intracytoplasmic sperm injection (ICSI) at the Reproductive Medical Center of Sun Yat-sen Memorial Hospital, between September 2010 and January 2012. The concentration of ammonium was determined using a dry chemistry system. RESULTS: The ammonium concentration increased significantly during the period of culture of all embryos, but the increase was significantly greater in the group that, subsequently, did not achieve pregnancy (P < .001). An receiver-operating characteristic (ROC) curve indicated that ammonium concentration was highly predictive of embryo implantation failure (area under ROC curve = 0.838). Failure to achieve implantation had a predictive sensitivity of 71% and specificity of 79.6%. The accuracy of prediction of successful or failed implantation was 75.4%. In both IVF and ICSI, the embryo implantation rate decreased significantly as the medium ammonium concentration increased (P < .05). CONCLUSION: Measurement of the ammonium concentration in the spent medium may provide a new research direction for exploring a simple, rapid, and low-cost method for reliable prediction of embryo implantation with high sensitivity and specificity.

Enzymatic properties of the 20S proteasome in wheat endosperm and its biochemical characteristics after seed imbibition.

The 20S proteasome from wheat (Triticum aestivum L., Yangmai 158) endosperm was purified to apparent homogeneity by three sequential centrifugations and gradient PAGE (GPAGE). The purified 20S proteasome clearly cleaved peptidyl-arylamide bonds in the model synthetic substrates Z-GGL-AMC and Z-GGR-AMC, which are used to reflect chymotrypsin-like and trypsin-like activity, respectively. For both substrates, the optimum pH was 8.0, but the optimum temperatures for chymotrypsin-like and trypsin-like activity were 55 degrees C and 37 degrees C, respectively. Both enzyme activities were clearly inhibited by MG115 and PMSF. Polyubiquitinated proteins remained constant from 0 to 7 days after seed imbibition, but caseinolytic activity and the amount of the 20S proteasome associated with the aleurone layer decreased from 1 to 2 days after imbibition (DAI), then increased from 2 to 4 DAI, and reached a maximum at 4 DAI that was retained until 7 DAI. An increase was seen in the mRNA level of the beta5 subunit of the 20S proteasome from 2 DAI, and caseinolytic activity and the amount of the 20S proteasome increased from 3 DAI onwards. In addition, the main storage proteins of the wheat endosperm could not be hydrolyzed by the 20S proteasome. The evidence suggests that the main role of the 20S proteasome may not be to degrade massive proteins of the wheat endosperm after seed imbibition.

Lethality toxicities induced by metal exposure during development in nematode Caenorhabditis elegans.

Lethality changes were investigated during development in 4 h metal exposed Caenorhabditis elegans. Exposure to examined metals caused severe lethality toxicities in L1- and L2-larvae, in L3-larvae exposed to examined metals at concentrations of 50 and 100 microM and to Pb, Hg, and Cr at the concentration of 2.5 microM, in L4-larvae exposed to examined metals at concentrations of 50 and 100 microM, and in adults exposed to Pb, Hg, and Cr at the concentration of 100 microM. Moreover, the lethality toxicities induced by Pb and Hg in L1 larvae for 4 h could be largely comparable to those in young adults for 24 h.

Exposure to lead and mercury in young larvae induces more severe deficits in neuronal survival and synaptic function than in adult nematodes.

In the present study, we investigated the possibly neurotoxic effects of metal (Pb and Hg) exposure at different developmental stages on neuronal loss in the GABAergic nervous system and synaptic functions in the nematode Caenorhabditis elegans. Our data suggest that neuronal survival in GABAergic neurons and cholinergic transmission were relatively stable during development in nematodes. Moreover, neurodegeneration, as shown by the neuronal loss and dorsal/ventral cord gaps, was more severely induced by Pb and Hg exposure at the L1 through L3 larval stages than at the L4 larval and young-adult stages. Similarly, pre- and postsynaptic functions were more severely impaired by Pb and Hg exposure at the L1 through L3 larval stages than at the L4 larval and young-adult stages. Furthermore, both aldicarb and levamisole resistance were significantly correlated with neuronal loss, dorsal cord gap, and ventral cord gap in Pb- and Hg-exposed nematodes, suggesting that neuronal survival was noticeably correlated with synaptic function in metal-exposed nematodes during development. Therefore, younger (L1-L3) larvae show more sensitivity to neurotoxicity of neuronal survival and synaptic function than L4 larvae and young adult nematodes.

Dual interband cascade laser based trace-gas sensor for environmental monitoring.

The development of an interband cascade laser (ICL) based spectroscopic trace-gas sensor for the simultaneous detection of two atmospheric trace gases is reported. The sensor performance was evaluated using two ICLs capable of targeting formaldehyde (H2CO) and ethane (C2H6). Minimum detection limits of 3.5 ppbV for H2CO and 150 pptV for C2H6 was demonstrated with a 1 s integration time. The sensor was deployed for field measurements of H2CO, and laboratory quantification of both formaldehyde and ethane are reported. A cross comparison of the atmospheric concentration data for H2CO with data collected by a collocated commercial H2CO sensor employing Hantzsch reaction based fluorometric detection was performed. These results show excellent agreement between these two different approaches for trace-gas quantification. In addition, laboratory experiments for dual gas quantification show accurate, fast response with no crosstalk between the two gas channels.

Aircraft and balloon in situ measurements of methane and hydrochloric acid using interband cascade lasers.

Aircraft and balloon in situ measurements of CH4 and HCl using cw distributed feedback (DFB) interband cascade (IC) lasers are reported. In the stratosphere and upper troposphere, sensitivity toward CH4 and HCl is better than 10 ppbv (1 s) and 90 pptv (50 s), respectively. These are the first flight measurements of trace gas-phase species using cw DFB IC lasers.