分类: 生物学 >> 生物物理学 >> 神经科学 提交时间: 2016-05-11
摘要: Hypoxic preconditioning (HPC) elicits resistance to more drastic subsequent insults, which potentially provide neuroprotective therapeutic strategy, but the underlying mechanisms remain to be fully elucidated. Here, we examined the effects of HPC on synaptic ultrastructure in olfactory bulb of mice. Mice underwent up to five cycles of repeated HPC treatments, and hypoxic tolerance was assessed with a standard gasp reflex assay. As expected, HPC induced an increase in tolerance time. To assess synaptic responses, Western blots were used to quantify protein levels of representative markers for glia, neuron, and synapse, and transmission electron microscopy was used to examine synaptic ultrastructure and mitochondrial density. HPC did not significantly alter the protein levels of astroglial marker (GFAP), neuron-specific markers (GAP43, Tuj-1, and OMP), synaptic number markers (synaptophysin and SNAP25) or the percentage of excitatory synapses versus inhibitory synapses. However, HPC significantly affected synaptic curvature and the percentage of synapses with presynaptic mitochondria, which showed concomitant change pattern. These findings demonstrate that HPC is associated with changes in synaptic ultrastructure. (C) 2014 Wiley Periodicals, Inc.
分类: 物理学 >> 核物理学 提交时间: 2016-09-13
摘要: A silicon pixel detector with fine pitch size of 19x19 um, developed base on SOI (silicon on insulator) technology, was tested under the illumination of infrared laser pulses. As an alternative way to particle beam tests, the laser pulses were tuned to very short duration and small transverse profile to simulate the tracks of MIPs (minimum ionization particles) in silicon. Hit cluster sizes were measured with focused laser pulses propagating through the SOI detector perpendicular to its surface and most of the induced charge was found to be collected inside the seed pixel. For the first time, the signal amplitude as a function of the applied bias voltage was measured for this SOI detector, deepening understanding of its depletion characteristics.
分类: 物理学 >> 核物理学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: In radiotherapy, the energy of the rays used could be larger than 10 MeV, which would potentially activate stable nucleus into a radioactive one. The induced reactions on some of the human essential elements are studied to show the probability of changes of nuclei. The Talys1.4 toolkit was adopted as the theoretical model for calculation. The reactions investigated include the (, n) and (, p) channels for the stable Na, Mg, Cl, K, Ca, and Fe isotopes, with the incident energy of ranging from 1 to 30 MeV. It was found that the cross sections for the reactions are very low, and the maximum cross section is no larger than 100 mb. By considering the threshold energy of the channel, the half-life time of the residue nucleus, and the percentage of the element accounting for the weight and its importance in the body, it is suggested to track the radioactive nuclei 22Na, 41Ca, and 42,43K after therapy. The results might be useful for medical diagnosis and disease treatment.
提交时间: 2017-05-02
摘要: Development of novel biocompatible nanomaterials has provided insights into their potential biomedical applications. Bulk fabrication of the nanomaterials in the form of coatings remains challenging. Here, we report hydroxyapatite [HA]/graphene-nanosheet
分类: 物理学 >> 核物理学 提交时间: 2022-01-21 合作期刊: 《Nuclear Science and Techniques》
摘要: Configurational information entropy (CIE) theory was employed to determine the neutron skin thickness of neutron-rich calcium isotopes. The nuclear density distributions and fragment cross-sections in 350 MeV/u 40-60Ca + 9Be projectile fragmentation reactions were calculated using a modified statistical abrasion-ablation model. CIE quantities were determined from the nuclear density, isotopic, mass, and charge distributions. The linear correlations between the CIE determined using the isotopic, mass, and charge distributions and the neutron skin thickness of the projectile nucleus show that CIE provides new methods to extract the neutron skin thickness of neutron-rich nuclei.
分类: 物理学 >> 核物理学 提交时间: 2021-12-31
摘要: Configurational information entropy (CIE) theory was employed to determine the neutron skin thickness of neutron-rich calcium isotopes. The nuclear density distributions and fragment cross-sections in 350 MeV/u 40060Ca + 9Be projectile fragmentation reactions were calculated using a modified statistical abrasion-ablation model. CIE quantities were determined from the nuclear density, isotopic, mass, and charge distributions. The linear correlations between the CIE determined using the isotopic, mass, and charge distributions and the neutron skin thickness of the projectile nucleus show that CIE provides new methods to extract the neutron skin thickness of neutron-rich nuclei.
分类: 物理学 >> 地球物理学、天文学和天体物理学 提交时间: 2024-01-09 合作期刊: 《Research in Astronomy and Astrophysics》
摘要: In this paper, we study five luminous supernovae (LSNe) Ibc (SN 2009ca, ASASSN-15mj, SN 2019omd, SN 2002ued, and SN 2021bmf) whose peak absolute magnitudes Mpeak are ≈ −19.5 to −21 mag by fitting their multi-band light curves (LCs) with different energy source models. We find that SN 2009ca might be powered by the 56Ni model since the required 56Ni mass (0.56 M⊙) is comparable to those of energetic SNe Ic, while the rest four SNe cannot be accounted for the 56Ni model since their derived 56Ni masses are ≳1 M⊙ or the ratios of the 56Ni mass to the ejecta mass are larger than 0.2. This indicates that some LSNe might be powered by 56Ni decay, while most of them need additional energy sources. We then use the magnetar plus 56Ni model and the fallback plus 56Ni model to fit the LCs of the four LSNe that cannot be explained by the 56Ni model, finding that the two models can account for the four SNe, and the derived parameters are comparable to those of LSNe or superluminous SNe in the literature, if they were (mainly) powered by magnetars or fallback. We suggest that the magnetar plus 56Ni model is more reasonable than the fallback plus 56Ni model, since the validity of the fallback plus 56Ni model depends on the value of accretion efficiency (η) and favors a large η value, and the magnetar plus 56Ni model yields smaller χ2/dof values. It should be pointed out that, however, the fallback plus 56Ni model is still a promising model that can account for the four SNe in our sample as well as other LSNe.
提交时间: 2017-05-02
摘要: Here we report aluminum-alumina composite coatings fabricated by flame spraying for potential marine applications against both corrosion and wear. Microstructure examination suggested dense coating structures and the evenly distributed alumina splats form
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Titania-hydroxyapatite (HA) nanocomposites were fabricated by wet chemical synthesis approach. HA exhibited crystallographic orientation of nucleation on nano titania particle, forming the composite particles with titania being partially enwrapped with HA. Microstructural characterization by high res- olution transmission electron microscopy revealed coherent interfacial bond of (110) and (222) planes of HA crystal with (101) plane of anatase. The HA layer promoted significantly recruitment of Escherichia coli bacteria onto the titania-based particles for subsequent photocatalytic killing. Less extent of enwrapping of HA on titania particle, as accomplished by increasing the aging time of HA suspension, gave rise to better capability of photocatalytic degradation of methylene blue and sterilization of the bacteria. The novel HA-enwrapped titania powder shows great potential for environmental applications.
分类: 地球科学 >> 空间物理学 提交时间: 2016-05-12
摘要: The largest geomagnetic storms of solar cycle 24 so far occurred on 2015 March 17 and June 22 with D-st minima of -223 and -195 nT, respectively. Both of the geomagnetic storms show a multi-step development. We examine the plasma and magnetic field characteristics of the driving coronal mass ejections (CMEs) in connection with the development of the geomagnetic storms. A particular effort is to reconstruct the in situ structure using a Grad-Shafranov technique and compare the reconstruction results with solar observations, which gives a larger spatial perspective of the source conditions than one-dimensional in situ measurements. Key results are obtained concerning how the plasma and magnetic field characteristics of CMEs control the geomagnetic storm intensity and variability: (1) a sheath-ejecta-ejecta mechanism and a sheath-sheath-ejecta scenario are proposed for the multi-step development of the 2015 March 17 and June 22 geomagnetic storms, respectively;(2) two contrasting cases of how the CME flux-rope characteristics generate intense geomagnetic storms are found, which indicates that a southward flux-rope orientation is not a necessity for a strong geomagnetic storm;and (3) the unexpected 2015 March 17 intense geomagnetic storm resulted from the interaction between two successive CMEs plus the compression by a high-speed stream from behind, which is essentially the "perfect storm" scenario proposed by Liu et al. (i.e., a combination of circumstances results in an event of unusual magnitude), so the "perfect storm" scenario may not be as rare as the phrase implies.
分类: 物理学 >> 核物理学 提交时间: 2016-09-13
摘要: As the main tracking detector of BESIII, the drift chamber works for accurate measurements of the tracking and the momentum of the charged particles decayed from the reaction of BEPCII e+ and e-. After operation six years, the drift chamber is suffering from aging problems due to huge beam related background. The gains of the cells in the first ten layers experience an obvious decrease, reaching a maximum of about 29% for the first layer cells. Two calculation methods for the gains change (Bhabha events and accumulated charges with 0.3% aging ratio for inner chamber cells) get almost the same results. For the Malter effect encountered by the inner drift chamber in Jan., 2012, about 0.2% water vapor was added to MDC gas mixture to solve this cathode aging problem. These results provide an important reference for MDC operation high voltage setting and the upgrade of the inner drift chamber.
分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: The X-ray diffraction beamline developed at Shanghai Synchrotron Radiation Facility (SSRF)is located at the BL14B1 bending magnet port of the 3.5 GeV storage ring. The beamline optics is based on a collimating mirror, a sagittally focused double crystal monochromator and a focusing mirror. Photon flux of 4.43�1011 phs/s at 10 keV is obtained. The primary instrument equipped in the experimental end-station is a Huber 5021 six-cycle diffractometer. BL14B1 is a general purpose X-ray diffraction beamline and focused on material science, condensed matter physics and other relevant fields looking for structural information.
分类: 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间: 2016-05-12
摘要: The lipid droplet (LD) is a cellular organelle that stores neutral lipids in cells and has been linked with metabolic disorders. Caenorhabditis elegans has many characteristics which make it an excellent animal model for studying LDs. However, unlike in mammalian cells, no LD structure-like/resident proteins have been identified in C. elegans, which has limited the utility of this model for the study of lipid storage and metabolism. Herein based on three lines of evidence, we identified that MDT-28 and DHS-3 previously identified in C. elegans LD proteome were two LD structure-like/resident proteins. First, MDT-28 and DHS-3 were found to be the two most abundant LD proteins in the worm. Second, the proteins were specifically localized to LDs and we identified the domains responsible for this targeting in both proteins. Third and most importantly, the depletion of MDT-28 induced LD clustering while DHS-3 deletion reduced triacylglycerol content (TAG). We further characterized the proteins finding that MDT-28 was ubiquitously expressed in the intestine, muscle, hypodermis, and embryos, whereas DHS-3 was expressed mainly in intestinal cells. Together, these two LD structure-like/resident proteins provide a basis for future mechanistic studies into the dynamics and functions of LDs in C. elegans. (C) 2015 Elsevier B.V. All rights reserved.