An integral gated mode single photon detector at telecom wavelengths

We demonstrate an integral gated mode single photon detector at telecom wavelengths. The charge number of an avalanche pulse rather than the peak current is monitored for single-photon detection. The transient spikes in conventional gated mode operation are canceled completely by integrating, which enables one to improve the performance of single photon detector greatly with the same avalanche photodiode. This method has achieved a detection efficiency of 29.9% at the dark count probability per gate equal to 5.57E-6/gate (1.11E-6/ns) at 1550nm.Comment: word to PDF, 3 pages with 4 figure

Satellite-Based Assessment of Possible Dust Aerosols Semi-Direct Effect on Cloud Water Path over East Asia

The semi-direct effects of dust aerosols are analyzed over eastern Asia using 2 years (June 2002 to June 2004) of data from the Clouds and the Earth s Radiant Energy System (CERES) scanning radiometer and MODerate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite, and 18 years (1984 to 2001) of International Satellite Cloud Climatology Project (ISCCP) data. The results show that the water path of dust-contaminated clouds is considerably smaller than that of dust-free clouds. The mean ice water path (IWP) and liquid water path (LWP) of dusty clouds are less than their dust-free counterparts by 23.7% and 49.8%, respectively. The long-term statistical relationship derived from ISCCP also confirms that there is significant negative correlation between dust storm index and ISCCP cloud water path. These results suggest that dust aerosols warm clouds, increase the evaporation of cloud droplets and further reduce cloud water path, the so-called semi-direct effect. The semi-direct effect may play a role in cloud development over arid and semi-arid areas of East Asia and contribute to the reduction of precipitation

Dicamba Retention in Commercial Sprayers Following Triple Rinse Cleanout Procedures, and Soybean Response to Contamination Concentrations

The commercial launch of dicamba‐tolerant (DT) crops has resulted in increased dicamba usage and a high number of dicamba off‐target movement complaints on sensitive soybeans (Glycine max L.). Dicamba is a synthetic auxin and low dosages as 0.028 g ae ha−1 can induce injury on sensitive soybean. Tank contamination has been identified as one of the sources for unintended sensitive crop exposure. The labels of new dicamba formulations require a triple rinse cleanout procedure following applications. Cleanout efficacy might vary based on the sprayer type and procedure followed. This study was performed to quantify dicamba retention in commercial sprayers and assess the risk for crop injury from remaining contaminants. The results indicate triple rinse with water was comparable to cleanout procedures utilizing ammonium, commercial tank cleaners, and glyphosate in rinses. Dicamba contaminants in final rinsates resulted in \u3c15% visual injury and no yield response when applied to sensitive soybeans at R1 stage. A survey of 25 agricultural sprayers demonstrated a cleanout efficacy of 99.996% by triple rinsing with water following applications of dicamba at 560 g ae ha−1, with concentrations of less than 1 ug mL−1 detected rinsates from the fourth rinse. A dose response experiment predicted dosages causing 5% visual injury and the yield losses were 0.1185 and 2.8525 g ae ha−1. However, symptomology was observed for all tested dosages, including the rate as low as 0.03 g ae ha−1. The results from this study suggest triple rinsing with sufficient amount of water (≥10% of tank volume) is adequate for the removal of dicamba residues from sprayers to avoid sensitive soybean damage. This study can provide producers with confidence in cleanout procedures following dicamba applications, and aid in minimizing risk for off‐target movement through tank contamination

A living cell quartz crystal microbalance biosensor for continuous monitoring of cytotoxic responses of macrophages to single-walled carbon nanotubes

<p>Abstract</p> <p>Background</p> <p>Numerous engineered nanomaterials (ENMs) exist and new ENMs are being developed. A challenge to nanotoxicology and environmental health and safety is evaluating toxicity of ENMs before they become widely utilized. Cellular assays remain the predominant test platform yet these methods are limited by using discrete time endpoints and reliance on organic dyes, vulnerable to interference from ENMs. Label-free, continuous, rapid response systems with biologically meaningful endpoints are needed. We have developed a device to detect and monitor in real time responses of living cells to ENMs. The device, a living cell quartz crystal microbalance biosensor (QCMB), uses macrophages adherent to a quartz crystal. The communal response of macrophages to treatments is monitored continuously as changes in crystal oscillation frequency (Δf). We report the ability of this QCMB to distinguish benign from toxic exposures and reveal unique kinetic information about cellular responses to varying doses of single-walled carbon nanotubes (SWCNTs).</p> <p>Results</p> <p>We analyzed macrophage responses to additions of Zymosan A, polystyrene beads (PBs) (benign substances) or SWCNT (3-150 μg/ml) in the QCMB over 18 hrs. In parallel, toxicity was monitored over 24/48 hrs using conventional viability assays and histological stains to detect apoptosis. In the QCMB, a stable unchanging oscillation frequency occurred when cells alone, Zymosan A alone, PBs alone or SWCNTs without cells at the highest dose alone were used. With living cells in the QCMB, when Zymosan A, PBs or SWCNTs were added, a significant decrease in frequency occurred from 1-6 hrs. For SWCNTs, this Δf was dose-dependent. From 6-18 hrs, benign substances or low dose SWCNT (3-30 μg/ml) treatments showed a reversal of the decrease of oscillation frequency, returning to or exceeding pre-treatment levels. Cell recovery was confirmed in conventional assays. The lag time to see the Δf reversal in QCMB plots was linearly SWCNT-dose dependent. Lastly, the frequency never reversed at high dose SWCNT (100-150 μg/ml), and apoptosis/necrosis was documented in conventional 24 and 48 hr-assays.</p> <p>Conclusion</p> <p>These data suggest that the new QCMB detects and provides unique information about peak, sub-lethal and toxic exposures of living cells to ENMs before they are detected using conventional cell assays.</p

Mummified precocial bird wings in mid-Cretaceous Burmese amber

Our knowledge of Cretaceous plumage is limited by the fossil record itself: compression fossils surrounding skeletons lack the finest morphological details and seldom preserve visible traces of colour, while discoveries in amber have been disassociated from their source animals. Here we report the osteology, plumage and pterylosis of two exceptionally preserved theropod wings from Burmese amber, with vestiges of soft tissues. The extremely small size and osteological development of the wings, combined with their digit proportions, strongly suggests that the remains represent precocial hatchlings of enantiornithine birds. These specimens demonstrate that the plumage types associated with modern birds were present within single individuals of Enantiornithes by the Cenomanian (99 million years ago), providing insights into plumage arrangement and microstructure alongside immature skeletal remains. This finding brings new detail to our understanding of infrequently preserved juveniles, including the first concrete examples of follicles, feather tracts and apteria in Cretaceous avialans

Interaction of serum vitamin B12 and folate with MTHFR genotypes on risk of ischemic stroke

ObjectiveWe evaluated the interaction of serum folate and vitamin B12 with methylenetetrahydrofolate reductase (MTHFR) C677T genotypes on the risk of first ischemic stroke and on the efficacy of folic acid treatment in prevention of first ischemic stroke.MethodsA total of 20,702 hypertensive adults were randomized to a double-blind treatment of daily enalapril 10 mg and folic acid 0.8 mg or enalapril 10 mg alone. Participants were followed up every 3 months.ResultsMedian values of folate and B12 concentrations at baseline were 8.1 ng/mL and 280.2 pmol/L, respectively. Over a median of 4.5 years, among those not receiving folic acid, participants with baseline serum B12 or serum folate above the median had a significantly lower risk of first ischemic stroke (hazard ratio [HR], 0.74; 95% confidence interval [CI], 0.57-0.96), especially in those with MTHFR 677 CC genotype (wild-type) (HR, 0.49; 95% CI, 0.31-0.78). Folic acid treatment significantly reduced the risk of first ischemic stroke in participants with both folate and B12 below the median (2.3% in enalapril-folic acid group vs 3.6% in enalapril-only group; HR, 0.62; 95% CI, 0.46-0.86), particularly in MTHFR 677 CC carriers (1.6% vs 4.9%; HR, 0.24; 95% CI, 0.11-0.55). However, TT homozygotes responded better with both folate and B12 levels above the median (HR, 0.28; 95% CI, 0.10-0.75).ConclusionsThe risk of first ischemic stroke was significantly higher in hypertensive patients with low levels of both folate and B12. Effect of folic acid treatment was greatest in patients with low folate and B12 with the CC genotype, and with high folate and B12 with the TT genotype

The new model of fitting the spectral energy distributions of Mkn 421 and Mkn 501

The spectral energy distribution (SED) of TeV blazars has a double-humped shape that is usually interpreted as Synchrotron Self Compton (SSC) model. The one zone SSC model is used broadly but cannot fit the high energy tail of SED very well. It need bulk Lorentz factor which is conflict with the observation. Furthermore one zone SSC model can not explain the entire spectrum. In the paper, we propose a new model that the high energy emission is produced by the accelerated protons in the blob with a small size and high magnetic field, the low energy radiation comes from the electrons in the expanded blob. Because the high and low energy photons are not produced at the same time, the requirement of large Doppler factor from pair production is relaxed. We present the fitting results of the SEDs for Mkn 501 during April 1997 and Mkn 421 during March 2001 respectively.Comment: 5 pages, 1 figures, 1table. accepted for publication in Sciences in China --

Double Trouble of Air Pollution by Anthropogenic Dust

With urbanization worldwide in recent decades, anthropogenic dust (AD) emissions due to heavy urban construction and off-road vehicle use have been increasing. Its perturbations on urban air pollution at the global scale are still unclear. Based on observations, we found that a high urban AD optical depth is often accompanied by severe non-dust aerosol optical depth in the planetary boundary layer (PBL), both magnitudes even comparable. To investigate the causes, an AD emission inventory constrained by satellite retrievals is implemented in a global climate model. The results show that AD-induced surface radiative cooling of up to -15.9 +/- 4.0 W m(-2) regionally leads to reduced PBL height, which deteriorates non-dust pollution, especially over India and northern China, in addition to the tremendous direct AD contribution to pollutants. The estimated global total premature mortality due to AD is 0.8 million deaths per year and is more severe in populous regions.Peer reviewe

Recent glitches detected in the Crab pulsar

From 2000 to 2010, monitoring of radio emission from the Crab pulsar at Xinjiang Observatory detected a total of nine glitches. The occurrence of glitches appears to be a random process as described by previous researches. A persistent change in pulse frequency and pulse frequency derivative after each glitch was found. There is no obvious correlation between glitch sizes and the time since last glitch. For these glitches $\Delta\nu_{p}$ and $\Delta\dot{\nu}_{p}$ span two orders of magnitude. The pulsar suffered the largest frequency jump ever seen on MJD 53067.1. The size of the glitch is $\sim$ 6.8 $\times 10^{-6}$ Hz, $\sim$ 3.5 times that of the glitch occured in 1989 glitch, with a very large permanent changes in frequency and pulse frequency derivative and followed by a decay with time constant $\sim$ 21 days. The braking index presents significant changes. We attribute this variation to a varying particle wind strength which may be caused by glitch activities. We discuss the properties of detected glitches in Crab pulsar and compare them with glitches in the Vela pulsar.Comment: Accepted for publication in Astrophysics & Space Scienc

Antimicrobial Constituents from Machaerium Pers.: Inhibitory Activities and Synergism of Machaeriols and Machaeridiols against Methicillin-Resistant Staphylococcus aureus, Vancomycin-Resistant Enterococcus faecium, and Permeabilized Gram-Negative Pathogens

Two new epimeric bibenzylated monoterpenes machaerifurogerol (1a) and 5-epi-machaerifurogerol (1b), and four known isoflavonoids (+)-vestitol (2), 7-O-methylvestitol (3), (+)-medicarpin (4), and 3,8-dihydroxy-9-methoxypterocarpan (5) were isolated from Machaerium Pers. This plant was previously assigned as Machaerium multiflorum Spruce, from which machaeriols A-D (6-9) and machaeridiols A-C (10-12) were reported, and all were then re-isolated, except the minor compound 9, for a comprehensive antimicrobial activity evaluation. Structures of the isolated compounds were determined by full NMR and mass spectroscopic data. Among the isolated compounds, the mixture 10 + 11 was the most active with an MIC value of 1.25 μg/mL against methicillin-resistant Staphylococcus aureus (MRSA) strains BAA 1696, -1708, -1717, -33591, and vancomycin-resistant Enterococcus faecium (VRE 700221) and E. faecalis (VRE 51299) and vancomycin-sensitive E. faecalis (VSE 29212). Compounds 6-8 and 10-12 were found to be more potent against MRSA 1708, and 6, 11, and 12 against VRE 700221, than the drug control ciprofloxacin and vancomycin. A combination study using an in vitro Checkerboard method was carried out for machaeriols (7 or 8) and machaeridiols (11 or 12), which exhibited a strong synergistic activity of 12 + 8 (MIC 0.156 and 0.625 µg/mL), with \u3e32- and \u3e8-fold reduction of MIC\u27s, compared to 12, against MRSA 1708 and -1717, respectively. In the presence of sub-inhibitory concentrations on polymyxin B nonapeptide (PMBN), compounds 10 + 11, 11, 12, and 8 showed activity in the range of 0.5-8 µg/mL for two strains of Acinetobacter baumannii, 2-16 µg/mL against Pseudomonas aeruginosa PAO1, and 2 µg/mL against Escherichia coli NCTC 12923, but were inactive (MIC \u3e 64 µg/mL) against the two isolates of Klebsiella pneumoniae