Observations of the globular clusters NGC 6388 and M 15 were carried out by the H.E.S.S. array of Cherenkov telescopes for a live time of 27.2 and 15.2 hours respectively. No gamma-ray signal is ...found at the nominal target position of NGC 6388 and M 15. In the primordial formation scenario, globular clusters are formed in a dark matter halo and dark matter could still be present in the baryon-dominated environment of globular clusters. This opens the possibility of observing a dark matter self-annihilation signal. The dark matter content of the globular clusters NGC 6388 and M 15 is modelled taking into account the astrophysical processes that can be expected to influence the dark matter distribution during the evolution of the globular cluster: the adiabatic contraction of dark matter by baryons, the adiabatic growth of a black hole in the dark matter halo and the kinetic heating of dark matter by stars. 95% confidence level exclusion limits on the dark matter particle velocity-weighted annihilation cross section are derived for these dark matter haloes. In the TeV range, the limits on the velocity-weighted annihilation cross section are derived at the 10-25 cm3 s-1 level and a few 10-24 cm3 s-1 for NGC 6388 and M 15 respectively.
S locus glycoprotein (SLG) and S locus receptor kinase (SRK) cDNAs were isolated from an S allele present in a number of self-compatible Brassica napus lines. This A10 allele did not segregate with ...self-incompatibility in crosses involving other self-incompatible B. napus lines. The SLG-A10 cDNA was found to contain an intact open reading frame and was predicted to encode an SLG protein with sequence similarities to those previously associated with phenotypically strong self-incompatibility reactions. SLG-A10 transcripts were detected in the developing stigma at steady state levels even higher than those detected for SLG alleles linked with self-incompatibility. Analysis of the corresponding SRK-A10 cDNA showed that it was very similar to other S locus receptor kinase genes and was expressed predominantly in the stigma. However, a 1-bp deletion was detected in the SRK gene toward the 3′ end of the SLG homology domain. This deletion would lead to premature termination of translation and the production of a truncated SRK protein. The A10 allele was determined to represent a B. oleracea S allele based on its segregation pattern with the B. oleracea S24 allele when both these alleles were present in the same B. napus background. These results suggest that a functional SRK gene is required for Brassica self-incompatibility.
In this paper it is suggested that the double-averaged (in temporal and in spatial domains) momentum equations should be used as a natural basis for the hydraulics of rough-bed open-channel flows, ...especially with small relative submergence. The relationships for the vertical distribution of the total stress for the simplest case of 2D, steady, uniform, spatially averaged flow over a rough bed with flat free surface are derived. These relationships explicitly include the form-induced stresses and form drag as components of the total stress. Using this approach, we define three types of rough-bed flows: (1) Flow with high relative submergence; (2) flow with small relative submergence; and (3) flow over a partially inundated rough bed. The relationships for the double-averaged velocity distribution and hydraulic resistance for all three flow types are derived and compared with measurements where possible. The double-averaged turbulent and form-induced intensities and stresses for the case of regular spherical-segment-type roughness show the dominant role of the double-averaged turbulence stresses and form drag in momentum transfer in the near-bed region.
Detection of Gamma Rays from a Starburst Galaxy Acero, F; Akhperjanian, A.G; Anton, G ...
Science (American Association for the Advancement of Science),
11/2009, Letnik:
326, Številka:
5956
Journal Article
Recenzirano
Odprti dostop
Starburst galaxies exhibit in their central regions a highly increased rate of supernovae, the remnants of which are thought to accelerate energetic cosmic rays up to energies of approximately 10¹⁵ ...electron volts. We report the detection of gamma rays--tracers of such cosmic rays--from the starburst galaxy NGC 253 using the High Energy Stereoscopic System (H.E.S.S.) array of imaging atmospheric Cherenkov telescopes. The gamma-ray flux above 220 billion electron volts is F = (5.5 ± 1.0stat ± 2.8sys) x 10⁻¹³ cm⁻² s⁻¹, implying a cosmic-ray density about three orders of magnitude larger than that in the center of the Milky Way. The fraction of cosmic-ray energy channeled into gamma rays in this starburst environment is five times as large as that in our Galaxy.
Ocean tides around New Zealand Walters, Roy A.; Goring, Derek G.; Bell, Rob G.
New Zealand journal of marine and freshwater research,
20/9/1/, Letnik:
35, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The distribution of amplitude and phase for eight ocean tidal constituents (M
2
, S
2
, N
2
, K
2
, K
1
, O
1
, P
1
, Q
1
) is presented as tidal maps for the New Zealand area. The distribution was ...calculated using a barotropic tidal model driven by TOPEX/ Poseidon data on the outer ocean boundaries. The maps exhibit the known features of the tides in this area such as a complete rotation of the semi-diurnal tides around New Zealand and the reduced spring-neap variations on the east coast. They also point out several new features for which there are few or no observations, such as diurnal trapped waves and shelf waves. A comparison of the model results with observations shows that sea level errors are within 0.1 m in amplitude and 10° in phase for the largest constituents at all locations, including sites where the data are of low quality and where the geometry is not adequately resolved. For locations where the geometry is adequately represented and the observations are of high quality, sea level errors are within 0.02 m in amplitude and 7° in phase. These results represent the most accurate and highest resolution calculations of tides and currents yet attained for this area.
Recent theoretical predictions of the lowest very high energy (VHE) luminosity of SN 1006 are only a factor 5 below the previously published H.E.S.S. upper limit, thus motivating further in-depth ...observations of this source. Deep observations at VHE energies (above 100 GeV) were carried out with the High Energy Stereoscopic System (H.E.S.S.) of Cherenkov Telescopes from 2003 to 2008. More than 100 hours of data have been collected and subjected to an improved analysis procedure. Observations resulted in the detection of VHE gamma-rays from SN 1006. The measured gamma-ray spectrum is compatible with a power-law, the flux is of the order of 1% of that detected from the Crab Nebula, and is thus consistent with the previously established H.E.S.S. upper limit. The source exhibits a bipolar morphology, which is strongly correlated with non-thermal X-rays. Because the thickness of the VHE-shell is compatible with emission from a thin rim, particle acceleration in shock waves is likely to be the origin of the gamma-ray signal. The measured flux level can be accounted for by inverse Compton emission, but a mixed scenario that includes leptonic and hadronic components and takes into account the ambient matter density inferred from observations also leads to a satisfactory description of the multi-wavelength spectrum.
The yeast two-hybrid system was used to further characterize the interactions between the Brassica S receptor kinase (SRK) and three putative substrates, ARC1 and the two thioredoxin h proteins, THL1 ...and THL2. Interactions were generally detectable with kinase domains of both Class I and Class II SRKs. Chimeric constructs were made between the SRK910 kinase domain and the non-interacting Arabidopsis RLK5 kinase domain. Only one chimeric construct, SRR2, interacted with THL1 and THL2, while none of the chimeras were able to interact with ARC1. SRR2 is largely made up of RLK5 kinase domain with the N-terminal end being derived from the SRK910 kinase domain and was the only chimeric construct that retained kinase activity. Deletion or substitution of a conserved cysteine at the N-terminal end of the SRK910 kinase domain resulted in loss of interaction with THL1 and THL2, while the addition of this cysteine to a related receptor kinase, SFR1, conferred the ability to interact with the thioredoxin h proteins. In addition, substitution of the cysteines in the THL1 active site abolished the interaction. Lastly, the two Arabidopsis thioredoxin h clones most closely related to THL1 and THL2 were found to interact with the SRK kinase domains. Thus, the nature of the interaction of the thioredoxin h clones with SRK involves the reducing activity of these proteins and is restricted to the class of thioredoxin h proteins which have the variant CPPC active site.
The Peru tsunami of 23 June 2001 arrived at New Zealand's east coast 16.5 h after generation, having travelled c. 8000 km across the Pacific Ocean. All the sea level recorders on the east coast ...recorded waves, but the response was highly variable, with the greatest response in Lyttelton Harbour, where the water fell by 26 cm, then rose over the next hour to peak at 30 cm. None of the recorders on the west coast felt the tsunami. The time scale of the waves was between 2 and 20 min and they persisted for more than 20 h after the first waves arrived, before starting to slowly decay. In some places, like Pegasus Bay, the tsunami excited local seiche, but these waves quickly dissipated. Analysis of data collected at 1-min intervals, instead of the standard 5-min intervals, indicated that information is lost when sampling tsunami at 5-min intervals.
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