747 research outputs found

    Evolution of Synchrotron X-rays in Supernova Remnants

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    A systematic study of the synchrotron X-ray emission from supernova remnants (SNRs) has been conducted. We selected a total of 12 SNRs whose synchrotron X-ray spectral parameters are available in the literature with reasonable accuracy, and studied how their luminosities change as a function of radius. It is found that the synchrotron X-ray luminosity tends to drop especially when the SNRs become larger than ~5 pc, despite large scatter. This may be explained by the change of spectral shape caused by the decrease of the synchrotron roll-off energy. A simple evolutionary model of the X-ray luminosity is proposed and is found to reproduce the observed data approximately, with reasonable model parameters. According to the model, the total energy of accelerated electrons is estimated to be 10^(47-48) ergs, which is well below the supernova explosion energy. The maximum energies of accelerated electrons and protons are also discussed.Comment: 6 pages, 2 figures, ApJ, in pres

    Construction of Artificial Viral Capsids Encapsulating Short DNAs via Disulfide Bonds and Controlled Release of DNAs by Reduction

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    To construct an artificial viral capsid encapsulated short single-stranded DNA, a β-annulus peptide conjugated with ssDNA through a disulfide bond at the N-terminus (DNA-SS-β-Annulus) was synthesized. The DNA-SS-β-Annulus conjugate self-assembled into spherical structures ranging in the size of 36–60 nm. ssDNA was released from the capsids via the reduction of disulfide bonds

    Effects of environmental factors on life cycle regulation in Lasius japonicus Santschi (Formicidae)

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    This study investigated environmental factors that regulate oviposition by queens and colony development in Lasius japonicus Santschi. Newly mated queens were collected from fields in Okayama, Japan. All queens died within 50 days at 30 °C, whereas all or most of the queens survived at lower temperatures. At 25 °C, many pupae were observed approximately 1 month after the onset of oviposition. Diapause in either queens or workers was not induced at 25 °C. At 20 °C, many larvae did not pupate, indicating that larval diapause was induced. At 15 °C, hatching was not recorded and eggs disappeared. Low temperatures may induce reproductive diapause in queens. There were no significant differences between long-day (LD 16:8 h) and short-day (LD 12:12 h) conditions at any temperature. Under outdoor conditions, when summer temperature was moderate in 2005, queens started their nuptial flights in June, and pupation was recorded three times. However, when summer temperature was high in 2006, pupation occurred 1–2 times before winter, with queens making their nuptial flights as late as mid-July. Eggs and pupae disappeared in most colonies before the arrival of winter. Only queens, adult workers, and larvae were observed during winter. The present study showed that queens of L. japonicus founded and developed their colonies for as long as environmental conditions remained favorable, by responding to changes in temperature

    Open-field scale-model experiments of fire whirls over L-shaped line fires

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    This paper presents the results of open-field scale-model experiments of fire-whirl formation over line fires. L-shaped line fires were burned in crosswinds, and the processes of fire-whirl formation were observed. The flame height was measured using an image-processing technique, while two-dimensional velocity components were measured at two different locations using ultrasonic anemometers. Two tests were selected for comparison: test A, in which intense fire whirls repeatedly formed, and test B, in which no whirls were observed. In test A, the wind flow was bent by the fire plume, creating swirling flows near the burning area, thereby forming fire whirls. On the other hand, the crosswind in test B was too fast to be affected by the fire plume. These results confirmed the existence of critical wind velocity to form intense fire whirls. The critical wind velocity, approximately 1 m/s, agreed with the scaling law on the critical wind velocity which was previously developed based on similar experiments of a smaller scale

    Purification and Properties of Hyaluronidase (EC 4. 2. 2. 1) from an Oral Strain of Propionibacterium acnes

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    From a culture supernatant of P. acnes isolated from a lesion of periodontal disease, hyaluronidase was purified to homogeneity by the sequential procedures including ammonium sulfate precipitation, carboxy methy-cellulose column chromatography, and Sephadex G-100 gel filtration. Specific activity increased 1,027 fold and the recovery of the enzymatic activity was 12.4%. Molecular weight was determined to be 67,000 and isoelectric point was 7.2. Optimal pH for the activity was found at 5.5. The enzyme was inactivated by heating at 60℃ for 10 min. The purified hyaluronidase degraded hyaluronic acid, chondroitin, chondroitin sulfate A and chondroitin sulfate C. From the degradation products of these substrates, unsaturated disaccharides were detected by paper chromatography. When the rate of reaction of this enzyme against hyaluronic acid is supposed to be 100%, the corresponding values against chondroitin, chondroitin sulfate A, and C were 47%, 8%, and 8%, respectively. No degradation by this enzyme of heparin and heparan sulfate was demonstrated

    Encapsulation of mRNA into Artificial Viral Capsids via Hybridization of a β-Annulus-dT20 Conjugate and the Poly(A) Tail of mRNA

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    Messenger RNA (mRNA) drugs have attracted considerable attention as promising tools with many therapeutic applications. The efficient delivery of mRNA drugs using non-viral materials is currently being explored. We demonstrate a novel concept where mCherry mRNA bearing a poly(A) tail is encapsulated into capsids co-assembled from viral β-annulus peptides bearing a 20-mer oligothymine (dT20) at the N-terminus and unmodified peptides via hybridization of dT20 and poly(A). Dynamic light scattering measurements and transmission electron microscopy images of the mRNA-encapsulated capsids show the formation of spherical assemblies of approximately 50 nm. The encapsulated mRNA shows remarkable ribonuclease resistance. Further, modification by a cell-penetrating peptide (His16) on the capsid enables the intracellular expression of mCherry of encapsulated mRNA
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