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We present polarimetric observations of the 4 ground-state transitions of OH, toward a sample of maser-emitting planetary nebulae (PNe) using the Australia Telescope Compact Array. This sample includes confirmed OH-emitting PNe, confirmed and candidate H2O-maser-emitting PNe. Polarimetric observations provide information related to the magnetic field of these sources. Maser-emitting PNe are very young PNe and magnetic fields are a key ingredient in the early evolution and shaping process of PNe. Our preliminary results suggest that magnetic field strengths may change very rapidly in young PNe.
Many observations have been reported in the field of X-ray pulsars, but the mechanism for X-ray emission is not well understood. The X-ray spectra can not be simply described in terms of blackbody or thermal bremsstralung. The high-energy cutoff could be due to cyclotron absorption in high (≧1012 Gauss) magnetic fields. For the lower energy it can be fitted by a power law with energy index α.
In strong magnetic field near pulsar's surface, the quantum effect for electrons is quite complicated. The classical approximation may lose resonance feature, which gives much smaller cross-section.
In this paper, we performed numerical integrations to get the total cross-section and the power spectrum of single electron. Thus considering the resonance, the inverse Compton scattering could be an efficient mechanism in strong magnetic fields. We have carefully calculated the power spectrum of single electron travelling through the isotropic thermal fields.
Our calculations show that the cross section of the inverse Compton scattering in strong magnetic fields may be larger than that of Thompson scattering by sevaral orders of magnitude in the case of polar cap surface of pulsars. We can also see that when the energy of e± exceeds a certain value, their energy loss caused by the inverse Compton scattering may be larger than the energy gain from electric field in the inner gap, which implies that the e± could not be accelerated to γ = 106. Meanwhile, the electrostatic forces acting on the electrons will be balanced by the radiative pressure if temperature T > 108 K.
It is beleived that the surface temperarure for most of pulsars is less than 106 K, in that case the ions of iron can not be emitted from the surface of pulsars. However, the temperarure at the polar cap can be increased to 3×106 through the bombardment of electrons to the polar cap according to R-S model. This quasi-equilibrium state by self-regulating must make the coherent radio emission unstable on the contrary.
We describe the performance of the Boolardy Engineering Test Array, the prototype for the Australian Square Kilometre Array Pathfinder telescope. Boolardy Engineering Test Array is the first aperture synthesis radio telescope to use phased array feed technology, giving it the ability to electronically form up to nine dual-polarisation beams. We report the methods developed for forming and measuring the beams, and the adaptations that have been made to the traditional calibration and imaging procedures in order to allow BETA to function as a multi-beam aperture synthesis telescope. We describe the commissioning of the instrument and present details of Boolardy Engineering Test Array’s performance: sensitivity, beam characteristics, polarimetric properties, and image quality. We summarise the astronomical science that it has produced and draw lessons from operating Boolardy Engineering Test Array that will be relevant to the commissioning and operation of the final Australian Square Kilometre Array Path telescope.
A new death line for radio pulsars is presented in this paper within the framework of vacuum gap and inverse Compton scattering (ICS) induced pair production process. The 8.5s period pulsar PSR J2144-3933 is located above the death line without any additional assumptions. An “appearance line” instead of the so-called “Hubble line”, is also presented in this paper. Both of those two lines fit observations well.
Combing the data of all the 10 rotation-powered pulsars that have measurements of relative phase of radio and X-ray pulses, we report here the behavior of radio/X-ray phase offset. We find that the radio/X-ray offset of normal pulsars does not show the trend of increase with increasing pulsar period as the radio/gamma-ray offset exhibits. The offset of millisecond pulsars is generally much less than that of the normal pulsars. Such phenomenon should also be taken into account by the high energy models for pulsars.
Although pulsars can radiate electromagnetic wave from radio to gamma ray bands, we still have no a united model to understand the multi-band emission. In this paper the effort for a joint model is presented. The inverse Compton scattering (ICS) and a second acceleration process near the null surface are involved to account for the radio and the gama-ray emission, respectively. Various kind of pulse profiles and other observational properties can be reproduced.
We developed a rapidly-gelling chitosan sponge crosslinked with Guanosine 5'-Diphosphate (GDP). GDP has not been previously explored as an anionic crosslinker, and it was used in this application since the nucleoside guanosine has been shown to improve remyelination in situ, and thus its presence in the sponge composition was hypothesized to induce Oligodendrocyte Progenitor Cells' (OPC) differentiation. In addition to the chemical composition tailored to target OPCs, the developed chitosan sponge possesses a wide range of desirable physicochemical properties such as: rapid gelation, high porosity with interconnected pores, moduli of elasticity resembling that of soft tissue and cytocompatibility with many cell types. Moreover, protein encapsulation into the sponges was possible with high encapsulation efficiencies (e.g. BMP-7 and NT-3). In this study, BDNF was encapsulated in the chitosan sponges with an encapsulation efficiency greater than 80% and a sustained release over a 16-day period was achieved. We demonstrate here for the first time, the attachment of human fetal OPCs to the sponges and their differentiation after 12 days of culture. Overall, this newly-introduced injectable sponge is a promising therapeutic modality that can be used to enhance remyelination post-spinal cord injuries.
Previous studies showed that monochromatic green light stimuli during embryogenesis accelerated posthatch body weight (BW) and pectoral muscle growth of broilers. In this experiment, we further investigated the morphological and molecular basis of this phenomenon. Fertile broiler eggs (Arbor Acres, n=880) were pre-weighed and randomly assigned to 1 of the 2 incubation treatment groups: (1) dark condition (control group), and (2) monochromatic green light group (560 nm). The monochromatic lighting systems sourced from light-emitting diode lamps and were equalized at the intensity of 15 lx at eggshell level. The dark condition was set as a commercial control from day 1 until hatching. After hatch, 120 male 1-day-old chicks from each group were housed under incandescent white light with an intensity of 30 lx at bird-head level. No effects of light stimuli during embryogenesis on hatching time, hatchability, hatching weight and bird mortality during the feeding trial period were observed in the present study. Compared with the dark condition, the BW, pectoral muscle weight and myofiber cross-sectional areas were significantly greater on 7-day-old chicks incubated under green light. Green light also increased the satellite cell mitotic activity of pectoral muscle on 1- and 3-day-old birds. In addition, green light upregulated MyoD, myogenin and myostatin mRNA expression in late embryos and/ or newly hatched chicks. These data suggest that stimulation with monochromatic green light during incubation promote muscle growth by enhancing proliferation and differentiation of satellite cells in late embryonic and newly hatched stages. Higher expression of myostatin may ultimately help prevent excessive proliferation and differentiation of satellite cells in birds incubated under green light.
A new inverse Compton scattering scheme for production of high-energy Gamma-ray sources is proposed in which a Giga-electronvolt (GeV) electron beam is injected into a thermal hohlraum. It is found that by increasing the hohlraum background temperature, the scattered photons experience kinematic pileup, resulting in more monochromatic spectrum and smaller scattering angle. When a relativistic electron beam with energy 1 GeV and charge 10nC is injected into a 0.5 keV hohlraum, 80% of the scattered photons have energy above 0.5 GeV.
Acceptor (Mg)-doped AlGaN/GaN heterostructures were grown via MOVPE and compared to similarly doped GaN standard films grown in the same reactor. Chemical analysis of the films, via secondary ion mass spectrometry (SIMS), revealed comparable Mg concentrations of ∼2×1019 atoms/cm3 in all films. The Mg-doped GaN standard sample had a sheet conductance of 7-μS compared to a sheet conductance of 20-μS for an AlGaN/GaN heterostructure. The sheet conductance of the AlGaN/GaN heterostructures was higher due to piezoelectric acceptor doping and modulation doping effects in addition to conventional Mg acceptor doping.
We report dye-sensitized solar cells using low cost carbon nanoparticles as an alternative to platinum as a counter-electrode catalyst for triiodide reduction. The counter carbon-electrode was deposited onto fluorine-doped tin oxide (FTO) by spin coating from an aqueous colloidal suspension of the blend of carbon nanoparticles and TiO2 nanocrystals. DSSC devices were fabricated using a stable Ru complex dye (Z-907) as the sensitizer. The cells based on carbon-nanoparticle counter electrode were made and then compared with those cells from platinum counter electrode at similar fabrication conditions. The results have shown that the device performance in terms of short circuit current density (Jsc), open circuit voltage (Voc) and energy conversion efficiency (η) from the cells based on carbon nanoparticle counter electrode were comparable to those from platinum counter-electrode devices. The carbon nanoparticle based cells have achieved an overall energy conversion efficiency of 5.55% under one sun AM 1.5 illumination (100 mW/cm2). The carbon nanoparticles showed significant potential as a low cost alternative to the current widely-used platinum.
The β-3 adrenergic receptor (ADRB3) is a G-protein coupled receptor involved in regulating lipolysis, as part of homeostatic regulation. In this study, South African Mutton Merino and Shanxi Dam Line were used to study the distribution and quantification of ADRB3 in adipose (subcutaneous, omental, retroperitoneal, mesenteric and perirenal fat) and non-adipose (heart, liver, spleen, lung and kidney) tissues of sheep. The protein was determined by immunohistochemical technique and by mRNA abundance via real-time polymerase chain reaction. ADRB3 was detected in all studied tissues with abundance in adipose tissues higher than in non-adipose tissues (P < 0.001). For adipose tissues, greater expression was found in deep deposits such as great omental and retroperitoneal fat than in subcutaneous fat (P < 0.05). Significant differences (P < 0.05) both for mRNA and for protein expression also existed between the two sheep flocks. These findings are consistent with the known function of ADRB3 in mediating lipolysis and homeostasis in adipose tissues.
A case-control study was conducted in Linxian, Henan Province in China to explore potential risk factors for hepatitis C virus (HCV) infection unassociated with injection drug use. One hundred and ninety-two persons (41·7% male, 95·8% aged >60 years) were recruited from an earlier cohort. Of these, 48 were HCV positive and 144 HCV negative. Residence in a plain region and 3–10 injections in a health setting per year were significantly associated with HCV in both univariate and multivariate analysis (P<0·01). In rural China, the geographic distribution of HCV infection was heterogeneous and associated with injections in a health setting, a pattern which differed from the epidemics in injection drug users in urban cities.
We report an extremely rare case of malignant triton tumour.
Case report and review of the world literature concerning malignant triton tumour and heredity.
We present the case of a 47-year-old woman who underwent a lateral rhinotomy surgical resection of a malignant triton tumour of the right paranasal sinuses, a rare location for this tumour. Thereafter, she received adjuvant radiotherapy. The prognosis for this group of tumours is poor. Radical surgical excision of the tumour followed by radiation therapy must be the treatment of choice.
To our knowledge, this is a rare report in the world literature of malignant triton tumour. This case indicates that malignant triton tumour of the paranasal sinuses is a rare disease which otolaryngologists should be aware of, and one which should be included in the differential diagnosis of malignant lesions involving the sinonasal tract.
This paper reports on our observing campaign of faint satellites performed at the National Time Service Center and Sheshan station of SHAO from 1994 up to today. In the past few years due to benefit from using a large size CCD and the publication of the modern catalogues (UCAC2), a series of observations of faint satellites were obtained by us. Moreover the work of improving the orbit of Phoebe via numerical fit to the observations over a century is also presented.
The polynomial-fit method is applied to remove the uneven background of a satellite when it is near a bright primary object. Detailed analysis of this method is given. Some useful conclusions are drawn from the results of simulated data.
Using geometrically constrained specimens, the plastic flow behaviors of the as-cast and the relaxed Zr52.5Cu17.9Ni14.6Al10.0Ti5.0 bulk metallic glass in the dynamic compression were investigated. Both alloys exhibit a significant plasticity in the dynamic compression. The plastic deformation in both alloys is still inhomogeneous, which is characterized by the serrated plastic flow and the formation of shear bands. Free volumes affect the shear banding and the plastic flow. The reduced free volume results in the deviation of the shear banding direction from the maximum shear stress. The relaxed alloy exhibits the obvious stress overshoot, which is consistent with the theoretical prediction using a free volume model.