38 research outputs found

    Multi-wavelength Stellar Polarimetry of the Filamentary Cloud IC5146: I. Dust Properties

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    We present optical and near-infrared stellar polarization observations toward the dark filamentary clouds associated with IC5146. The data allow us to investigate the dust properties (this paper) and the magnetic field structure (Paper II). A total of 2022 background stars were detected in RcR_{c}-, ii'-, HH-, and/or KK-bands to AV25A_V \lesssim 25 mag. The ratio of the polarization percentage at different wavelengths provides an estimate of λmax\lambda_{max}, the wavelength of peak polarization, which is an indicator of the small-size cutoff of the grain size distribution. The grain size distribution seems to significantly change at AVA_V \sim 3 mag, where both the average and dispersion of PRc/PHP_{R_c}/P_{H} decrease. In addition, we found λmax\lambda_{max} \sim 0.6-0.9 μ\mum for AV>2.5A_V>2.5 mag, which is larger than the \sim 0.55 μ\mum in the general ISM, suggesting that grain growth has already started in low AVA_V regions. Our data also reveal that polarization efficiency (PE Pλ/AV\equiv P_{\lambda}/A_V) decreases with AVA_V as a power-law in RcR_c-, ii'-, and KK-bands with indices of -0.71±\pm0.10, -1.23±\pm0.10 and -0.53±\pm0.09. However, HH-band data show a power index change; the PE varies with AVA_V steeply (index of -0.95±\pm0.30) when AV<2.88±0.67A_V < 2.88\pm0.67 mag but softly (index of -0.25±\pm0.06) for greater AVA_V values. The soft decay of PE in high AVA_V regions is consistent with the Radiative Aligned Torque model, suggesting that our data trace the magnetic field to AV20A_V \sim 20 mag. Furthermore, the breakpoint found in HH-band is similar to the AVA_V where we found the PRc/PHP_{R_c}/P_{H} dispersion significantly decreased. Therefore, the flat PE-AVA_V in high AVA_V regions implies that the power index changes result from additional grain growth.Comment: 31 pages, 17 figures, and 3 tables; accepted for publication in Ap

    Automated Design of Genetic Toggle Switches with Predetermined Bistability

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    Synthetic biology aims to rationally construct biological devices with required functionalities. Methods that automate the design of genetic devices without post-hoc adjustment are therefore highly desired. Here we provide a method to predictably design genetic toggle switches with predetermined bistability. To accomplish this task, a biophysical model that links ribosome binding site (RBS) DNA sequence to toggle switch bistability was first developed by integrating a stochastic model with RBS design method. Then, to parametrize the model, a library of genetic toggle switch mutants was experimentally built, followed by establishing the equivalence between RBS DNA sequences and switch bistability. To test this equivalence, RBS nucleotide sequences for different specified bistabilities were <i>in silico</i> designed and experimentally verified. Results show that the deciphered equivalence is highly predictive for the toggle switch design with predetermined bistability. This method can be generalized to quantitative design of other probabilistic genetic devices in synthetic biology

    Suppression of Rap1 Impairs Cardiac Myofibrils and Conduction System in Zebrafish

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    <div><p>Numerous studies have revealed that Rap1 (Ras-proximate-1 or Ras-related protein 1), a small GTPase protein, plays a crucial role in mediating cAMP signaling in isolated cardiac tissues and cell lines. However, the involvement of Rap1 in the cardiac development <em>in vivo</em> is largely unknown. By injecting anti-sense morpholino oligonucleotides to knock down Rap1a and Rap1b in zebrafish embryos, and in combination with time-lapsed imaging, <em>in situ</em> hybridization, immunohistochemistry and transmission electron microscope techniques, we seek to understand the role of Rap1 in cardiac development and functions. At an optimized low dose of mixed <em>rap1a</em> and <em>rap1b</em> morpholino oligonucleotides, the heart developed essentially normally until cardiac contraction occurred. Morphant hearts showed the myocardium defect phenotypes, most likely due to disrupted myofibril assembly and alignment. <em>In vivo</em> heart electrocardiography revealed prolonged P-R interval and QRS duration, consistent with an adherens junction defect and reduced Connexons in cardiac myocytes of morphants. We conclude that a proper level of Rap1 is crucial for heart morphogenesis and function, and suggest that Rap1 and/or their downstream factor genes are potential candidates for genetic screening for human heart diseases.</p> </div

    Ultra-structural changes of cell junctions and sarcomeres in Rap1 knock-down zebrafish heart.

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    <p>Transmission electronic scan revealed that the myofibril units, regularly organized into hexagonal lattices with thick (green arrow) and thin (yellow arrows) filaments (A) with adherens junctions (AJs) along the membrane of adjacent cardiac myocytes (B). In <i>rap1</i>MO heart, thick filaments (green arrow) number was not markablely changed but thin filaments (yellow arrows) number was significantly and statistically reduced (A' and D), and less myofibrils attached to AJs (arrows in B and B'), with lager space between the membrane of adjacent cardiac myocytes (B'). Antibody against Connexin 43 stained a significantly and statistically less GJ signal (arrowheads in C and C') in <i>rap1</i>MO cardiomyocytes at 3 dpf, compared to a normal heart (C, C', and E). Scale bar, 50 nm in A and A'; 350 nm in B and B'; 50 µm in C and C'. Columns and error bars in D and E showed mean±S.D. n = 9 in filaments experiment (D) for each group, and n = 10 in C×43 antibody staining experiment (E) for each group. Unpaired two-tailed t-test was used to test the significance between two columns in each group in D. *** in statistic graph represent p<0.001 in the t-test.</p

    Summary of ECG features.

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    <p>Note: Data was shown as mean ± S.D. P value was calculated by unpaired two-tailed t test.</p

    Evaluation of genome-wide susceptibility loci for high myopia in a Han Chinese population

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    <p><i>Purpose</i>: High myopia (HM) is a common cause of visual impairment worldwide. Previous genome-wide association studies have reported that seven single nucleotide polymorphisms (SNPs), including rs1254319, rs3138144, rs12205363, rs17648524, rs7829127, rs1656404, and rs7084402, are associated with HM in Caucasians. The aim of this study was to investigate the association of these SNPs in Han Chinese.</p> <p><i>Methods</i>: SNPs were genotyped by SNaPshot method in a Chinese cohort composed of 830 HM patients and 1140 controls.</p> <p><i>Results</i>: Rs17648524 (C/G) and rs7084402 (A/G) were significantly associated with HM (<i>p</i> = 3.0 × 10<sup>−3</sup>, OR = 0.43; <i>p</i> = 3.7 × 10<sup>−2</sup>, OR = 1.25, respectively). The association of rs17648524 was also observed under the heterozygous model (CG vs. GG, <i>p</i> = 7.0 × 10<sup>−3</sup>, OR = 0.43) and the dominant model (CC + CG vs. GG, <i>p</i> = 4.0 × 10<sup>−3</sup>, OR = 0.42). The association of rs7084402 was found under the homozygous model (GG vs. AA, <i>p</i> = 4.0 × 10<sup>−2</sup>, OR = 1.56) and the dominant model (GG+ AG vs. AA, <i>p</i> = 3.8 × 10<sup>−2</sup>, OR = 1.41). Another SNP, rs7829127 (A/G), was found to be significantly associated with HM under the heterozygous model (AG vs. AA, <i>p</i> = 4.6 × 10<sup>−2</sup>, OR = 0.67). Furthermore, the associations of rs17648524 and rs7084402 with HM were gender-specific, with significance observed only in females but not in males. As for the other four SNPs, no associations were detected under these genetic models.</p> <p><i>Conclusions</i>: Our findings suggested rs17648524 (intronic <i>RBFOX1</i> gene) and rs7084402 (7.5kb 5′ of the <i>BICC1</i> gene) showed gender-specific associations with high myopia in the Han Chinese.</p