We modeled the radio non-detection of two Type Ia supernovae (SNe), SN 2011fe and SN 2014J, considering synchrotron emission from the interaction between SN ejecta and the circumstellar medium. For ...ejecta whose outer parts have a power-law density structure, we compare synchrotron emission with radio observations. Assuming that 20% of the bulk shock energy is being shared equally between electrons and magnetic fields, we found a very low-density medium around both the SNe. A less tenuous medium with particle density ∼1 cm−3, which could be expected around both SNe, can be estimated when the magnetic field amplification is less than that presumed for energy equipartition. This conclusion also holds if the progenitor of SN 2014J was a rigidly rotating white dwarf (WD) with a main-sequence (MS) or red giant companion. For a He star companion, or a MS for SN 2014J, with 10% and 1% of bulk kinetic energy in magnetic fields, we obtain mass-loss rates of and for a wind velocity of 100 . The former requires a mass accretion efficiency of >99% onto the WD, but is less restricted for the latter case. However, if the tenuous medium is due to a recurrent nova, it is difficult from our model to predict synchrotron luminosities. Although the formation channels of SNe 2011fe and 2014J are not clear, the null detection in radio wavelengths could point toward a low amplification efficiency for magnetic fields in SN shocks.
We perform hydrodynamical simulations of the interaction between supernova (SN) ejecta and circumstellar medium (CSM) for SN 1993J and SN 2011dh, and calculate the radio and X-ray emissions expected ...from the shocked gas at late epochs (t). Considering the ejecta structure from multi-group radiation hydrodynamics simulation, we find that the observed rapid drop in radio and X-ray light curves of SN 1993J at t > 3000 days may be due to a change in the mass-loss rate ( ) ∼6500 yr prior to the explosion of the SN. The exact epoch scales inversely with the assumed wind velocity of vw = 10 . The progenitor of this SN very likely belonged to a binary system, where, during its evolution, the primary had transferred material to the secondary. It is argued in this paper that the change in can happen because of a change in the mass accretion efficiency ( ) of the companion star. It is possible that before ∼6500 (vw/10 )−1 yr prior to the explosion, was high, and thus the CSM was tenuous, which causes the late-time downturn in fluxes. In the case of SN 2011dh, the late-time evolution is found to be consistent with a wind medium with /vw = 4 × 10−6 /10 . It is difficult from our analysis to predict whether the progenitor of this SN had a binary companion; however, if future observations show a similar decrease in radio and X-ray fluxes, then this would give strong support to a scenario where both SNe had undergone a similar kind of binary evolution before explosion.
We perform hydrodynamical simulations of the interaction between supernova (SN) ejecta and circumstellar medium (CSM) for SN 1993J and SN 2011dh, and calculate the radio and X-ray emissions expected ...from the shocked gas at late epochs (t). Considering the ejecta structure from multi-group radiation hydrodynamics simulation, we find that the observed rapid drop in radio and X-ray light curves of SN 1993J at t > 3000 days may be due to a change in the mass-loss rate ((M)over dot) similar to 6500 yr prior to the explosion of the SN. The exact epoch scales inversely with the assumed wind velocity of nu(w) = 10 km s(-1). The progenitor of this SN very likely belonged to a binary system, where, during its evolution, the primary had transferred material to the secondary. It is argued in this paper that the change in (M)over dot can happen because of a change in the mass accretion efficiency (eta) of the companion star. It is possible that before similar to 6500. (nu(w)/10 km s(-1))(-1) yr prior to the explosion, eta was high, and thus the CSM was tenuous, which causes the late-time downturn in fluxes. In the case of SN. 2011dh, the late-time evolution is found to be consistent with a wind medium with (M)over dot/nu(w) = 4 x 10(-6) M-circle dot yr(-1)/10 km s(-1). It is difficult from our analysis to predict whether the progenitor of this SN had a binary companion; however, if future observations show a similar decrease in radio and X-ray fluxes, then this would give strong support to a scenario where both SNe had undergone a similar kind of binary evolution before explosion.
The antioxidant potential of silk protein sericin from the non-mulberry tropical tasar silkworm Antheraea mylitta cocoon has been assessed and compared with that of the mulberry silkworm, Bombyx ...mori. Skin fibroblast cell line (AH927) challenged with hydrogen peroxide served as the positive control for the experiment Our results showed that the sericin obtained from tasar cocoons offers protection against oxidative stress and cell viability is restored to that of control on pre-incubation with the sericin. Fibroblasts pre-incubated with non-mulberry sericin had significantly lower levels of catalase, lactate dehydrogenase and malondialdehyde activity when compared to untreated ones. This report indicates that the silk protein sericin from the non-mulberry tropical tasar silkworm, A. mylitta can serve as a valuable antioxidant.
Molecular Phylogeny of Silk Producing Insects Based on Internal Transcribed Spacer DNA1 Mahendran, Botlagunta (Indian Institute of Technology, Kharagpur, India); Ghosh, Sudip K. (Indian Institute of Technology, Kharagpur, India); Kundu, Subhas C. (Indian Institute of Technology, Kharagpur, India), E-mail: kundu@hijli.iitkgp.ernet.in
BMB Reports,
09/2006, Letnik:
39, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Silk moths are the best studied silk secreting insects and belong to the families Bombycidae and Saturniidae. The phylogenetic relationship between eleven silk producing insects was analyzed using ...the complete DNA sequence of the internal transcribed spacer DNA 1 locus. The PCR amplification and sequence analysis showed variation in length ranging from 138 bp (Antheraea polyphemus) to 911 bp (Hyalopora cecropia). Microsatellite sequences were found and was be used to distinguish Saturniidae and Bombycidae members.
Efficacy of nano-hydroxyapatite prepared by an aqueous solution combustion technique in healing bone defects of goat Kumar Nandi, Samit (West Bengal University of Animal and Fishery Sciences, Kolkata, India); Kundu, Biswanath (Central Glass and Ceramic Research Institute, Kolkata, India), E-mail: biswa_kundu@rediffmail.com; Kumar Ghosh, Samir (Central Glass and Ceramic Research Institute, Kolkata, India) ...
Journal of veterinary science,
06/2008, Letnik:
9, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The present study was undertaken to evaluate porous hydroxyapatite (HAp), the powder of which was prepared by a novel aqueous solution combustion technique, as a bone substitute in healing bone ...defects in vivo, as assessed by radiologic and histopathologic methods, oxytetracycline labeling, and angiogenic features in Bengal goat. Bone defects were created in the diaphysis of the radius and either not filled (group Ⅰ) or filled with a HAp strut (group Ⅱ). The radiologic study in group Ⅱ showed the presence of unabsorbed implants which acted as a scaffold for new bone growth across the defect, and the quality of healing of the bone defect was almost indistinguishable from the control group, in which the defect was more or less similar, although the newly formed bony tissue was more organized when HAp was used. Histologic methods showed complete normal ossification with development of Haversian canals and well-defined osteoblasts at the periphery in group Ⅱ, whereas the control group had moderate fibro-collagenization and an adequate amount of marrow material, fat cells, and blood vessels. An oxytetracycline labeling study showed moderate activity of new bone formation with crossing-over of new bone trabeculae along with the presence of resorption cavities in group Ⅱ, whereas in the control group, the process of new bone formation was active from both ends and the defect site appeared as a homogenous non-fluoroscent area. Angiograms of the animals in the control group showed uniform angiogenesis in the defect site with establishment of trans-transplant angiogenesis, whereas in group Ⅱ there was complete trans-transplant shunting of blood vessel communication. Porous HAp ceramic prepared by an aqueous combustion technique promoted bone formation over the defect, confirming their biologic osteoconductive property.
Biomaterials of either natural or synthetic origin are used to fabricate implantable devices, as carriers for bioactive molecules or as substrates to facilitate tissue regeneration. For the design of ...medical devices it is fundamental to use materials characterized by non-immunogenicity, biocompatibility, slow and/or controllable biodegradability, non-toxicity, and structural integrity. The success of biomaterial-derived biodevices tends to be based on the biomimetic architecture of the materials. Recently, proteins from natural precursors that are essentially structural and functional polymers, have gained popularity as biomaterials. The silks produced by silkworms or spiders are of particular interest as versatile protein polymers. These form the basis for diverse biomedical applications that exploit their unique biochemical nature, biocompatibility and high mechanical strength. This review discusses and summarizes the latest advances in the engineering of silk-based biomaterials, focusing specifically on the fabrication of diverse bio-mimetic structures such as films, hydrogels, scaffolds, nanofibers and nanoparticles; their functionalization and potential for biomedical applications.
The “holobiont” concept, defined as the collective contribution of the eukaryotic and prokaryotic counterparts to the multicellular organism, introduces a complex definition of individuality enabling ...a new comprehensive view of human evolution and personalized characteristics. Here, we provide snapshots of the evolving microbial-host associations and relations during distinct milestones across the lifespan of a human being. We discuss the current knowledge of biological symbiosis between the microbiome and its host and portray the challenges in understanding these interactions and their potential effects on human physiology, including microbiome-nervous system inter-relationship and its relevance to human variation and individuality.
Host-microbe associations vary and evolve during the lifespans of human beings. This review provides insights into symbiotic relationships between the microbiome and its human host in the context of physiology and aging.
The safety, affordability, and impressive electrochemical performance of many Zn-ion batteries (ZIBs) has recently triggered an overwhelming literature surge. As is typical for a new area, initial ...enthusiasm and high expectations have now been replaced by a more measured period of research that reaches deep into the underlying factors controlling electrochemical properties. Rather than battery metrics, this review focuses on fundamental aspects of the chemistry of ZIBs that are the least understood and on which there has been progress over the last few years. We provide guidance for future research regarding (1) the significant challenge of proton/Zn2+ co-intercalation in aqueous media, (2) limitations to conversion chemistry that often accompanies ZIB electrochemistry, (3) positive aspects of facile Zn2+ (de)intercalation in nonaqueous electrolytes and organic cathode materials, (4) the desolvation penalty at electrode-electrolyte interfaces, (5) solutions for controlling Zn dendritic growth, and (6) suggested electrochemistry protocols for the field.
Display omitted
Looming concerns of climate change and the prospects of sustainable energy resources, such as solar and wind, have entered the global spotlight, triggering the hunt for reliable, low-cost electrochemical energy storage. Among the various options, lithium-ion batteries (LIBs) are currently the most attractive candidates because of their high energy density and foothold in the marketplace. However, many factors (expense, safety, and lifetime) will likely limit their large-scale applications and dictate against their use in stationary electrochemical energy storage (grid, mini-grids, telecommunication stations, etc.) wherein low cost and durability are more of a concern than weight. Alternative battery technologies are thus of considerable current interest. These include Zn-ion batteries (that utilize a Zn metal negative electrode), which offer greater safety, environmental friendliness, and affordability compared with their Li-ion cousins.
There has been an explosion of research in this field over the past few years—resulting in a plethora of publications—but clarity on the fundamental aspects of Zn-battery function in both aqueous and non-aqueous media is yet to be achieved. In this review, we provide a broad yet balanced overview of the field, insights into important progress made to date, key challenges to be overcome in future research, and perspectives on the many open questions remaining. In particular, we critically analyze the problem of proton co-intercalation in aqueous media and address the challenges it imposes on the practical implementation of Zn-ion technology for large-scale applications. We question whether Zn-ion intercalation (i.e., diffusion in the bulk) or pseudocapacitive behavior underlies some ultra-high rates that have been reported in aqueous electrolytes and note that the surprisingly good performance of some cathode materials in non-aqueous cells bodes well for future development.
Zn-ion batteries are frequently cited with promising metrics for a myriad of applications including stationary storage. However, fundamental aspects of their chemistry, which may hinder commercialization, have been largely overlooked in the recent literature. In this review, we focus on these aspects and provide guidance for future research, including the challenge of proton/Zn2+ co-intercalation, fast rate-testing protocols and Zn dendritic growth in aqueous electrolytes, limitations of non-aqueous electrolytes, and an evaluation of potential cathode candidates.
PDF
