Newly Determined Explosion Center of Tycho's Supernova and the Implications for Proposed Ex-Companion Stars of the Progenitor

`Star G', near the center of the supernova remnant of Tycho's SN1572, has been claimed to be the ex-companion star of the exploding white dwarf, thus pointing to the progenitor being like a recurrent nova. This claim has been controversial, but there have been no confident proofs or disproofs. Previously, no has seriously addressed the question as to the exact explosion site in 1572. We now provide accurate measures of the supernova position by two radically different methods. Our first method is to use the 42 measured angular distances between the supernova in 1572 and bright nearby stars, with individual measures being as good as 84 arc-seconds, and all resulting in a position with a 1-$\sigma$ error radius of 39 arc-seconds (including systematic uncertainties). Our second method is to use a detailed and realistic expansion model for 19 positions around the edge of the remnant, where the swept-up material has measured densities, and we determine the center of expansion with a chi-square fit to the 19 measured radii and velocities. This method has a 1-$\sigma$ error radius of 7.5 arc-seconds. Both measures are substantially offset from the geometric center, and both agree closely, proving that neither has any significant systematic errors. Our final combined position for the site of the 1572 explosion is J2000 $\alpha$=0h 25m 15.36s, $\delta=64^{\circ} 8' 40.2"$, with a 7.3 arc-second 1-sigma uncertainty. Star G is rejected at the 8.2-$\sigma$ confidence level. Our new position lies mostly outside the region previously searched for ex-companion stars.Comment: to be published in Ap

Ex-companions of Supernovae Progenitors

Supernovae (SNe) are titanic explosions that end the life of stars. Fast expanding ejecta can create brightness that is comparable to the entire luminosity of the host galaxy for weeks. Eventually, the ejecta run into the ambient medium, creating the so-called supernova remnant (SNR) that fades away in ~ 10,000 years. SNe come from two completely different mechanisms. The Type Ia SNe (SNIa) are powered by thermonuclear runaway when a white dwarf (WD) in a binary system accretes enough mass from a companion star. The Core Collapse supernovae (CCSNe) are massive stars that run out of fuel at the end of their lives and collapse. The basic scenario for SNIa is well established, but the type of the binary system containing the WD is the long-debated \u27Type Ia Progenitor Problem\u27. (1) Searching for an ex-companion within a SNIa SNR would directly solve this problem as a binary system including two WDs should leave nothing behind, while others should leave a non-degenerate star near the site of the explosion. One of the results from this thesis is the determination of the explosion site of Tycho\u27s SN (SN 1572). From this, I reject popular ex-companion candidates, e.g. Tycho star \u27G\u27 and a few other ones as they are too far away from the explosion site I determined. (2) Another attempt to address this problem is carried out by studying a rare kind of Type Ia SNe. Detailed photometric and spectral analysis indicates that ASASSN-14dc resembles features from the so-called SN Ia-CSM, in which, a SNIa explodes inside of dense Hydrogen-rich Circumstellar Material (CSM). The origin of the CSM brings serious questions to the traditional views of SNIa formation as none of them can comfortably explain the derived mass and distribution of the CSM. A recent realization of a particular model might solve a lot of puzzles around this rare class of SNIa. (3) CCSNe are known to be massive stars that rapidly evolve off the main sequence and soon explode. Nearly 80% of such stars have one or more massive companion stars, and these companions will survive the SN event with nearly the same luminosity in most cases. Interestingly, there is a runaway O-type star, Muzzio 10, that sits just 18\u27\u27 to the north of PSR B1509-58 in SNR G320.4-01.2. This makes Muzzio 10 a remarkable object for an ex-companion candidate. I will present the result from using HST and Chandra to measure both the O star and the pulsar\u27s proper motion and to see whether they came from the same spot

Expressive-VC: Highly Expressive Voice Conversion with Attention Fusion of Bottleneck and Perturbation Features

Voice conversion for highly expressive speech is challenging. Current approaches struggle with the balancing between speaker similarity, intelligibility and expressiveness. To address this problem, we propose Expressive-VC, a novel end-to-end voice conversion framework that leverages advantages from both neural bottleneck feature (BNF) approach and information perturbation approach. Specifically, we use a BNF encoder and a Perturbed-Wav encoder to form a content extractor to learn linguistic and para-linguistic features respectively, where BNFs come from a robust pre-trained ASR model and the perturbed wave becomes speaker-irrelevant after signal perturbation. We further fuse the linguistic and para-linguistic features through an attention mechanism, where speaker-dependent prosody features are adopted as the attention query, which result from a prosody encoder with target speaker embedding and normalized pitch and energy of source speech as input. Finally the decoder consumes the integrated features and the speaker-dependent prosody feature to generate the converted speech. Experiments demonstrate that Expressive-VC is superior to several state-of-the-art systems, achieving both high expressiveness captured from the source speech and high speaker similarity with the target speaker; meanwhile intelligibility is well maintained

Preparation Process of Alkali-extracted Polysaccharides from Abalone Viscera and Its Repair Activity against H2O2 Oxidative Damage in L929 Cells

Objective: The extraction process of alkali-extracted abalone viscera polysaccharides (Aavp) was optimized, and the preventive and repair effects of purified Aavp on H2O2 oxidative damage on L929 cells were studied to provide a reference for the development and application of Aavps. Methods: Crude Aavp was obtained by hot alkali extraction followed by alcohol precipitation, and its extraction process was optimized by the response surface method. The preventive and repair abilities of H2O2 oxidative damage on L929 cells were analyzed. Resulst: The optimum extraction conditions of crude Aavps were as follows: Solid-liquid ratio of 1:150 g/mL, extraction time of 2 h, and extraction temperature of 70 ℃. Under these optimal conditions, the yield of crude Aavp was 8.57%. In the prevention test of H2O2 oxidative damage on L929 cells, different doses of purified Aavp (20, 50 and 100 μg/mL) had a significant preventive effect on L929 cell oxidative damage (P<0.001) but did not show a dose effect. The cell survival rate of the middle dose group (50 μg/mL) was the highest (71.94%±3.08%), which was slightly better than the positive control vitamin E group but not significant. In the repair test, different doses of purified Aavp (20, 50 and 100 μg/mL) had a significant repair effect on the oxidative damage of L929 cells (P<0.001) and showed a dose effect. In contrast, the cell survival rate of the high-dose group (100 μg/mL) was the highest (90.93%±1.17%), slightly higher than that of the positive control vitamin E group (87.96%±3.05%). The results showed that purified Aavp showed an excellent preventive and repair effect on H2O2 oxidative damage in L929 cells. Conclusion: Aavp has an ability to repair H2O2 oxidative damage of L929 cells

Isolation, Purification, Structure Characterization and Antioxidant Activity of Alkali-extracted Polysaccharide from Abalone Viscera

Objective: Alkali-extracted polysaccharides from Abalone viscera (Aavp) were isolated and purified. The structure and antioxidant activity of Aavp were studied, which would provide a reference for developing and applying polysaccharides. Methods: The crude alkali-extracted polysaccharide was prepared by hot alkali extraction and alcohol precipitation. After the purification of DEAE sepharose fast flow and sephacryl S-400 HR, the purified polysaccharide was obtained and subjected to the structural analysis and antioxidant activity assay, such as Gas chromatography (GC), high-performance liquid chromatography (HPLC), infrared spectroscopy (IR), and thermogravimetric analyzer (TGA), etc. Result: Four kinds of components (Aavp Ia, Aavp Ib, Aavp IIa, and Aavp IIb) were obtained from the crude polysaccharide. Because of the highest yield, Aavp IIa was selected for further structural analysis. Aavp IIa was composed of xylose and galactose, with a relative molecular weight of 166513 Da. IR characterized the α-glycosidic bond configuration. The composition of Aavp IIa was possible as follows: The molar percentage of the galactose 1→4 glycosidic bond was 11.81%, the galactose 1→3 glycosidic bond was 34.14%, and the galactose 1→2 glycosidic bond was 10.14%. The molar percentage of the xylose 1→3 glycosidic bond was 33.85%, and the 1→2 and 1→4 glycosidic bond was 10.06%. Thermogravimetric analysis showed that Aavp IIa was broken and decomposed at 226.4~332.6 °C, and the thermal weight loss rate was 43.65%. Antioxidant experiments showed that Aavp IIa had a scavenging rate of 85.89% for superoxide anion radicals and 62.17% for DPPH radicals, respectively, presenting a certain antioxidant activity. Conclusion: Aavp is a heteropolysaccharide with specific antioxidant activity

Virtual Planning and 3D printing modeling for mandibular reconstruction with fibula free flap

This study was to evaluate the use of virtual planning and 3D printing modeling in mandibular reconstruction and compare the operation time and surgical outcome of this technique with conventional method. Between 2014 and 2017, 15 patients underwent vascularized fibula flap mandibular reconstruction using virtual planning and 3D printing modeling. Titanium plates were pre-bent using the models and cutting guides were used for osteotomies. 15 patients who underwent mandibular reconstruction using fibula flap without aid of virtual planning and 3D printing models were selected as control group. The operation time was recorded and compared in two groups. Accuracy of reconstruction was measured by superimposing the preoperative image onto the postoperative image of mandible. The selected bony landmark, distance and angle were measured. The mean total operation time and reconstruction time were 1.60±0.37 and 5.54±0.50 hours in computer-assisted group, respectively; These were 2.58±0.45 and 6.54±0.70 hours in conventional group, respectively. Both operation time and reconstruction time were shorter in computer-assisted group. The difference between the preoperative and postoperative intercondylar distances, intergonial angle distances, anteroposterior distances and gonial angles were 2.92±1.15 and 4.48±1.41mm, 2.93±1.19 and 4.79±1.48mm, 4.31±1.24 and 5.61±1.41mm, 3.85±1.68° and 5.88±2.12° in the computer-assisted and conventional group, respectively. The differences between the preoperative and postoperative mandible is smaller in the computer-assisted group. Virtual planning and 3D printing modeling have the potential to increase mandibular reconstruction accuracy and reduce operation time. we believe that this technology for mandibular reconstruction in selected patients will become a used method and improve the quality of reconstruction

Anisotropic elastic constants calculation of stainless steel cladded layers of pressure vessel steel plate

Cladding stainless steel layer on the inner surface of ferrite pressure vessel is a common method to improve the corrosion resistance and save the economic cost. However, the movement of heat source and temperature gradient in the process of cladded welding will lead to the anisotropy of cladded layer material. When measuring the residual stress of pressure vessel steel plate with stainless steel cladded layers (SSCL) by contour method, it is necessary to know the elastic mechanical properties of stainless steel cladded layers accurately. The assumption of transversely isotropy (TI) was employed, and the relationship between the material compliance matrix and the elastic modulus of transversely isotropic material was utilized. Based on the elastic modulus of each cladded layer and the whole steel plate from the longitudinal direction (0°) until the transverse direction (90°) measured by the experiment, the independent constants S11, S13, S33 and S44 in the compliance matrix of each cladded layer and the whole steel plate were obtained by regression analysis method. Furthermore, by using the relationship between the independent constants of the stiffness matrix of the transversely isotropic material and the single crystal material, the independent constant S12 in the compliance matrix of each stainless steel cladded layer and the whole steel plate were obtained. And then the independent constants of the stiffness matrix of each cladded layer and the whole steel plate were acquired. Hence, a method for calculating the anisotropic elastic constants of the stainless steel cladded layer and the whole steel plate was proposed. The results will provide material data support for measuring residual stress of pressure vessel steel plate with stainless steel cladded layers by contour method

Direct transformation of-alkane into all-conjugated polyene via cascade dehydrogenation

Selective C(sp$^{3}$) −H activation is of fundamental importance in processing alkane feedstocks to produce high-value-added chemical products. By virtue of an on-surface synthesis strategy, we report selective cascade dehydrogenation of n-alkane molecules under surface constraints, which yields monodispersed all-trans conjugated polyenes with unprecedented length controllability. We are also able to demonstrate the generality of this concept for alkyl-substituted molecules with programmable lengths and diverse functionalities, and more importantly its promising potential in molecular wiring