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Although parasites and microbial pathogens are both detrimental to insects, little information is currently available on the mechanism involved in how parasitized hosts balance their immune responses to defend against microbial infections. We addressed this in the present study by comparing the immune response between unparasitized and parasitized pupae of the chrysomelid beetle, Octodonta nipae (Maulik), to Escherichia coli invasion. In an in vivo survival assay, a markedly reduced number of E. coli colony-forming units per microliter was detected in parasitized pupae at 12 and 24 h post-parasitism, together with decreased phagocytosis and enhanced bactericidal activity at 12 h post-parasitism. The effects that parasitism had on the mRNA expression level of selected antimicrobial peptides (AMPs) of O. nipae pupae showed that nearly all transcripts of AMPs examined were highly upregulated during the early and late parasitism stages except defensin 2B, whose mRNA expression level was downregulated at 24 h post-parasitism. Further elucidation on the main maternal fluids responsible for alteration of the primary immune response against E. coli showed that ovarian fluid increased phagocytosis at 48 h post-injection. These results indicated that the enhanced degradation of E. coli in parasitized pupae resulted mainly from the elevated bactericidal activity without observing the increased transcripts of target AMPs. This study contributes to a better understanding of the mechanisms involved in the immune responses of a parasitized host to bacterial infections.
Methane produced from formate is one of the important methanogensis pathways in the rumen. However, quantitative information of CH4 production from formate has been rarely reported. The aim of this study was to characterize the conversion rate (CR) of formic acid into CH4 and CO2 by rumen microorganisms. Ground lucerne hay was incubated with buffered ruminal fluid for 6, 12, 24 and 48 h. Before the incubation, 13C-labeled H13COOH was also supplied into the incubation bottle at a dose of 0, 1.5, 2.2 or 2.9 mg/g of DM substrate. There were no interactions (P>0.05) between dose and incubation time for all variables evaluated. When expressed as an absolute amount (ml in gas sample) or a relative CR (%), both 13CH4 and 13CO2 production quadratically increased (P<0.01) with the addition of H13COOH. The total 13C (13CH4 and 13CO2) CR was also quadratically increased (P<0.01) when H13COOH was added. Moreover, formate addition linearly decreased (P<0.031) the concentrations of NH3-N, total and individual volatile fatty acids (acetate, propionate and butyrate), and quadratically decreased (P<0.014) the populations of protozoa, total methanogens, Methanosphaera stadtmanae, Methanobrevibacter ruminantium M1, Methanobrevibacter smithii and Methanosarcina barkeri. In summary, formate affects ruminal fermentation and methanogenesis, as well as the rumen microbiome, in particular microorganisms which are directly or indirectly involved in ruminal methanogenesis. This study provides quantitative verification for the rapid dissimilation of formate into CH4 and CO2 by rumen microorganisms.
The vast majority of pulsar profiles at meter wavelengths are dominated by core components (Rankin 1983, 1990; Lyne and Manchester 1988), but in the usual polar cap models of pulsar emission, it is difficult to get central beam or “core” radiation. In this paper, we present a calculation for both the “core” and hollow “cone” emission beams, as well as model pulse profiles in an inverse-Compton scattering (ICS) model. Both “core” and hollow “cone” emission beams axe obtained naturally in the calculations. Examples of pulse profiles of pulsars at different radio frequencies are presented.
The theoretical shapes of the pulse profiles agree very satisfactorily with actual observations, which means that the mechanism suggested here may be the actual one.
The physical conditions and locations of the emission regions for core and hollow cone emissions are very important in understanding the mechanism of radio pulsars. We present two related methods in an Inverse-Compton Scattering (ICS) model in this paper, which give a clear scenario for determining the location of the emission regions and are consistent with the results given by Cordes et al. (1984) and Rankin (1990).
An induced-collapse model [hereafter IC model; He et al. (1990)] can overcome the problems of the single star model of SN1987A. According to the IC model, there is a possibility that the SN1987A remnant will be a binary system with two neutron stars, one of them (SK-69 202) will have a strong magnetic field and a high surface temperature which favors detection as an X-ray or γ-ray pulsar. If the surface temperature of the neutron star cools down to T = 107 K, a radio binary pulsar is expected. There is also the possibility that an X-ray or γ-ray pulsar will be observed first, and only later will a radio pulsar will be detected.
A newly formed neutron star is thought to have a short (millisecond) period. In this case, the core emission beam is then very large (Qiao 1992) and is thus very likely to swing in the direction of the Earth.
Four ground-state OH transitions were detected in emission, absorption and maser emission in the Southern Parkes Large-Area Survey in Hydroxyl (SPLASH). We re-observed these OH masers with the Australia Telescope Compact Array to obtain positions with high accuracy (~1 arcsec). According to the positions, we categorised these OH masers into different classes, i.e. star formation, evolved stars, supernova remnants and unknown origin. We found one interesting OH maser source (G336.644-0.695) in the pilot region, which has been studied in detail in Qiao et al. (2016a). In this paper, we present the current stage of the ATCA follow-up for SPLASH and discuss the potential future researches derived from the ATCA data.
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.
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.
Pulsars are among the most highly polarized sources in the universe. The NVSS has cataloged 2 million radio sources with linear polarization measurements, from which we have selected 253 sources, with polarization percentage greater than 25%, as targets for pulsar searches. We believe that such a sample is not biased by selection effects against ultra-short spin or orbit periods. Using the Parkes 64-m telescope, we conducted searches with sample intervals of 50 μs and 80 μs, sensitive to submillisecond pulsars. Unfortunately we did not find any new pulsars.
The pitch angles of the local magnetic field in our Galaxy, previously derived from Rotation Measures (RMs) of pulsars by many authors, are not consistent with each other and with the pitch angles of the local spiral arms. That may be due to the fact that the used pulsar samples are located in different arms in which the directions of the magnetic fields are different. In this paper 2-D and 3-D models for the local magnetic field based on spiral arms are proposed for fitting the RMs of 129 nearby pulsars. In our models the amplitude of the uniform field changes sinusoidally to avoid abrupt reversals, and the directions are parallel or anti-parallel. The best-fitting 2-D model shows that in the Orion arm the strength of the regular field component is 2.4 ± 0.3μG, with its direction towards l = 73° ± 3°. There is a direction reversal in Sagittarius-Carina arm beginning at Drev = 0.3Kpc. The half “wavelength” of the sinusoidal variation is about 1.7 ± 0.4Kpc. The best fitting 3-D model shows that the scale height is only about 0.16 Kpc, which means that the local uniform field is confined in the galactic plane. The strongest regular field in this 3-D model is about 2.8±0.3μG. The results from both, the 2-D model as well as the 3-D model, show that the orientation of the field is in excellent agreement with the spiral arms.
Ground-state OH masers identified in the Southern Parkes Large-Area Survey in Hydroxyl were observed with the Australia Telescope Compact Array to obtain positions with high accuracy (~1 arcsec). We classified these OH masers into evolved star OH maser sites, star formation OH maser sites, supernova remnant OH maser sites, planetary nebula OH maser sites and unknown maser sites using their accurate positions. Evolved star and star formation OH maser sites in the Galactic Centre region (between Galactic longitudes of −5° to +5° and Galactic latitudes of −2° and +2°) were studied in detail to understand their distributions.
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.
It is believed that pulsars are neutron stars or strange stars with crusts. However we suggest here that pulsars may be bare strange stars (i.e., strange stars without crust). Due to rapid rotation and strong emission, young strange stars produced in supernova explosions should be bare when they act as radio pulsars. Because of strong magnetic field, two polar-crusts would shield the polar caps of an accreting strange star. Such a suggestion can be checked by further observations.