3,141 research outputs found
Upper Limits on the Extragalactic Background Light from the Gamma-Ray Spectra of Blazars
The direct measurement of the extragalactic background light (EBL) is
difficult at optical to infrared wavelengths because of the strong foreground
radiation originating in the Solar System. Very high energy (VHE, E100 GeV)
gamma rays interact with EBL photons of these wavelengths through pair
production. In this work, the available VHE spectra from six blazars are used
to place upper limits on the EBL. These blazars have been detected over a range
of redshifts and a steepening of the spectral index is observed with increasing
source distance. This can be interpreted as absorption by the EBL. In general,
knowledge of the intrinsic source spectrum is necessary to determine the
density of the intervening EBL. Motivated by the observed spectral steepening
with redshift, upper limits on the EBL are derived by assuming that the
intrinsic spectra of the six blazars are . Upper limits are
then placed on the EBL flux at discrete energies without assuming a specific
spectral shape for the EBL. This is an advantage over other methods since the
EBL spectrum is uncertain.Comment: 33 pages, 14 figures, accepted by Ap
Shortened Lung Clearance Index is a repeatable and sensitive test in children and adults with cystic fibrosis
BACKGROUND: Lung clearance index (LCI) derived from sulfur hexafluoride (SF6) multiple breath washout (MBW) is a sensitive measure of lung disease in people with cystic fibrosis (CF). However, it can be time-consuming, limiting its use clinically. AIM: To compare the repeatability, sensitivity and test duration of LCI derived from washout to 1/30th (LCI1/30), 1/20th (LCI1/20) and 1/10th (LCI1/10) to 'standard' LCI derived from washout to 1/40th initial concentration (LCI1/40). METHODS: Triplicate MBW test results from 30 clinically stable people with CF and 30 healthy controls were analysed retrospectively. MBW tests were performed using 0.2% SF6 and a modified Innocor device. All LCI end points were calculated using SimpleWashout software. Repeatability was assessed using coefficient of variation (CV%). The proportion of people with CF with and without abnormal LCI and forced expiratory volume in 1 s (FEV1) % predicted was compared. Receiver operating characteristic (ROC) curve statistics were calculated. Test duration of all LCI end points was compared using paired t tests. RESULTS: In people with CF, LCI1/40 CV% (p=0.16), LCI1/30 CV%, (p=0.53), LCI1/20 CV% (p=0.14) and LCI1/10 CV% (p=0.25) was not significantly different to controls. The sensitivity of LCI1/40, LCI1/30 and LCI1/20 to the presence of CF was equal (67%). The sensitivity of LCI1/10 and FEV1% predicted was lower (53% and 47% respectively). Area under the ROC curve (95% CI) for LCI1/40, LCI1/30, LCI1/20, LCI1/10 and FEV1% predicted was 0.89 (0.80 to 0.97), 0.87 (0.77 to 0.96), 0.87 (0.78 to 0.96), 0.83 (0.72 to 0.94) and 0.73 (0.60 to 0.86), respectively. Test duration of LCI1/30, LCI1/20 and LCI1/10 was significantly shorter compared with the test duration of LCI1/40 in people with CF (p<0.0001) equating to a 5%, 9% and 15% time saving, respectively. CONCLUSIONS: In this study, LCI1/20 was a repeatable and sensitive measure with equal diagnostic performance to LCI1/40. LCI1/20 was shorter, potentially offering a more feasible research and clinical measure
Draft Genome Sequences of 15 Isolates of Listeria monocytogenes Serotype 1/2a, Subgroup ST204
Listeria monocytogenes sequence type 204 (ST204) strains have been isolated from a range of food, environmental, and clinical sources in Australia. This study describes the draft genome sequences of 15 isolates collected from meat and dairy associated sources
Recommended from our members
Histone-DNA contacts in structure/function relationships of nucleosomes as revealed by crosslinking
The magnitude of the problem of understanding the structure/function relationships of eukaryotic chromosomes can be appreciated from the fact that the human diploid genome contains more than 2 meters of DNA packaged into 46 chromosomes, each at metaphase being several microns in length. Each chromatid of a chromosome contains a single DNA molecule several centimeters in length. In addition to the DNA, chromosomes contain an equal weight of histones and an equal weight of non-histone chromosomal proteins. These histones are the major chromosomal structural proteins. The non-histone chromosomal proteins are involved in the DNA processes of transcription and replication, in chromosome organization and in nuclear architecture. Polytene chromosomes with their bands and interbands and puffs of active genetic loci provide visual evidence for long range order as do the bands and interbands of mammalian metaphase chromosomes. The gentle removal of histones and all but the most tightly bound 2--3% of non-histone proteins from metaphase chromosomes revealed by electron microscopy a residual protein scaffold constraining a halo of DNA loops extending out from the scaffold
Reallocation of Responsibilities and/or Financing for Selected Municipal Services to the State: A Municipal Finance Alternative
This report recommends that the administration and/or financing of a selected group of public services be shifted from municipalities to the state government in Massachusetts.
Several criteria are used to identify local functions and local fiscal responsibilities which are more suitable for state than local financing. The first criterion is the efficiency of delivery of the service: for some functions, such as solid waste disposal, technology makes it more costly per capita to provide the service separately through individual municipalities than to operate regionally-based waste disposal facilities. The second criterion is the degree to which residents of the service area are agreed as to the quantity or quality of the service to be provided. The greatest degree of consensus can always be found at the lowest jurisdictional level, but this report argues that for the services selected for shifting, state financing will not result in service levels too different from any one municipality\u27s preferences. For example, there is not likely to be much dispute among municipal officials as to correctional institution standards. Third, the report recommends shifting services which have significant spill-in or spill-out characteristics; that is, when municipally-financed, they benefit or adversely affect residents of other local jurisdictions which have no voice in their delivery, on the one hand; and on the other hand, services with these characteristics involve costs without commensurate benefits to the responsible jurisdiction and eventually generate taxpayer resistance which forces severe reductions in service levels. Vocational education and transportation are two good examples of this phenomenon. The fourth criterion is that the area taxed to provide any service which effects a redistribution of services or cash (e.g. health and hospitals, veterans\u27 assistance) should include enough persons in both groups to make redistribution worthwhile: enough of those we wish to redistribute from and enough of those we wish to redistribute to. A great many municipalities in Massachusetts are somewhat internally homogeneous with respect to income; that is, the incomes of residents of any one community are likely to cluster. This tendency inhibits the provision of services with redistributive objectives which might significantly change the relative inequality of opportunity or well-being.
In addition, the report notes that over-dependence on the local property tax has both inefficient and inequitable consequences which can be somewhat alleviated by any kind or measure of property tax relief
- …