367 research outputs found
Supernova-Remnant Origin of Cosmic Rays?
It is thought that Galactic cosmic ray (CR) nuclei are gradually accelerated
to high energies (up to ~300 TeV/nucleon, where 1TeV=10^12eV) in the expanding
shock-waves connected with the remnants of powerful supernova explosions.
However, this conjecture has eluded direct observational confirmation^1,2 since
it was first proposed in 1953 (ref. 3). Enomoto et al.^4 claim to have finally
found definitive evidence that corroborates this model, proposing that the
very-high-energy, TeV-range, gamma-rays from the supernova remnant (SNR) RX
J1713.7-3946 are due to the interactions of energetic nuclei in this region.
Here we argue that their claim is not supported by the existing multiwavelength
spectrum of this source. The search for the origin(s) of Galactic cosmic ray
nuclei may be closing in on the long-suspected supernova-remnant sources, but
it is not yet over.Comment: 4 pages, 1 Figur
The Extraordinary X-ray Light Curve of the Classical Nova V1494 Aquilae (1999 #2) in Outburst: The Discovery of Pulsations and a "Burst"
V1494 Aql (Nova Aql 1999 No. 2) was discovered on 2 December 1999. We
obtained Chandra ACIS-I spectra on 15 April and 7 June 2000 which appear to
show only emission lines. Our third observation, on 6 August, showed that its
spectrum had evolved to that characteristic of a Super Soft X-ray Source. We
then obtained Chandra LETG+HRC-S spectra on 28 September (8 ksec) and 1 October
(17 ksec). We analyzed the X-ray light curve of our grating observations and
found both a short time scale ``burst'' and oscillations. Neither of these
phenomena have previously been seen in the light curve of a nova in outburst.
The ``burst'' was a factor of 10 rise in X-ray counts near the middle of the
second observation, and which lasted about 1000 sec; it exhibited at least two
peaks, in addition to other structure. Our time series analysis of the combined
25 ksec observation shows a peak at 2500 s which is present in independent
analyses of both the zeroth order image and the dispersed spectrum and is not
present in similar analyses of grating data for HZ 43 and Sirius B. Further
analyses of the V1494 Aql data find other periods present which implies that we
are observing non-radial g+ modes from the pulsating, rekindled white dwarf.Comment: ApJ accepte
Is the Supernova Remnant RX J1713.7-3946 a Hadronic Cosmic Ray Accelerator ?
The non-thermal supernova remnant RX J1713.7-3946 (G347.3-0.5) has recently
been shown to be a site of cosmic ray (CR) electron acceleration to TeV
energies (Muraishi et al. 2000). Here we present evidence that this remnant is
also accelerating CR nuclei. Such nuclei can interact with ambient interstellar
gas to produce high energy gamma-rays via the decay of neutral pions. We
associate the unidentified EGRET GeV gamma- ray source 3EG J1714-3857 with a
massive (~3*10 5 Mo) and dense (~500 nucleons cm -3) molecular cloud
interacting with RX J1713.7-3946. Direct evidence for such interaction is
provided by observations of the lowest two rotational transitions of CO in the
cloud; as in other clear cases of interaction, the CO(J=2-1)/CO(J=1-0) ratio is
significantly enhanced. Since the cloud is of low radio and X-ray brightness,
CR electrons cannot be responsible for the bulk of its GeV emission there. A
picture thus emerges where both electrons and nuclei are being accelerated by
the SNR: whereas the CR electrons dominate the local non-thermal radio, X-ray
and TeV emission, the shock accelerated CR protons and ions (hadrons) are
revealed through their interactions in the adjacent massive cloud. Such a
scenario had been anticipated by Aharonian, Drury and Volk (1994).Comment: 15 pages, 2 low-resolution figures, submitted to ApJL Aug 10, 2001;
this version includes referee's suggestion
Impact of dispersion media and carrier type on spray-dried proliposome powder formulations loaded with beclomethasone dipropionate for their pulmonary drug delivery via a next generation impactor
Drug delivery via aerosolization for localized and systemic effect is a non-invasive approach to achieving pulmonary targeting. The aim of this study was to prepare spray-dried proliposome (SDP) powder formulations to produce carrier particles for superior aerosolization performance, assessed via a next generation impactor (NGI) in combination with a dry powder inhaler. SDP powder formulations (F1-F10) were prepared using a spray dryer, employing five different types of lactose carriers (Lactose monohydrate (LMH), lactose microfine (LMF), lactose 003, lactose 220 and lactose 300) and two different dispersion media. The first dispersion medium was comprised of water and ethanol (50:50% v/v ratio), and the second dispersion medium comprised wholly of ethanol (100%). In the first dispersion medium, the lipid phase (consisting of Soya phosphatidylcholine (SPC as phospholipid) and Beclomethasone dipropionate (BDP; model drug) were dissolved in ethanol and the lactose carrier in water, followed by spray drying. Whereas in second dispersion medium, the lipid phase and lactose carrier were dispersed in ethanol only, post spray drying. SDP powder formulations (F1-F5) possessed significantly smaller particles (2.89 ± 1.24-4.48 ± 1.20 μm), when compared to SDP F6-F10 formulations (10.63 ± 3.71-19.27 ± 4.98 μm), irrespective of lactose carrier type via SEM (scanning electron microscopy). Crystallinity of the F6-F10 and amorphicity of F1-F15 formulations were confirmed by XRD (X-ray diffraction). Differences in size and crystallinity were further reflected in production yield, where significantly higher production yield was obtained for F1-F5 (74.87 ± 4.28-87.32 ± 2.42%) then F6-F10 formulations (40.08 ± 5.714-54.98 ± 5.82%), irrespective of carrier type. Negligible differences were noted in terms of entrapment efficiency, when comparing F1-F5 SDP formulations (94.67 ± 8.41-96.35 ± 7.93) to F6-F10 formulations (78.16 ± 9.35-82.95 ± 9.62). Moreover, formulations F1-F5 demonstrated significantly higher fine particle fraction (FPF), fine particle dose (FPD) and respirable fraction (RF) (on average of 30.35%, 890.12 μg and 85.90%) when compared to counterpart SDP powder formulations (F6-F10). This study has demonstrated that when a combination of water and ethanol was employed as dispersion medium (formulations F1-F5), superior formulation properties for pulmonary drug delivery were observed, irrespective of carrier type employed
PHP48 COST SENSITIVENESS AND PHYSICIAN TREATMENT CHOICES
Objectives To explore the relationship between nodule count and lung cancer probability in baseline low-dose CT lung cancer screening. Materials and Methods Included were participants from the NELSON trial with at least one baseline nodule (3392 participants [45% of screen-group], 7258 nodules). We determined nodule count per participant. Malignancy was confirmed by histology. Nodules not diagnosed as screen-detected or interval cancer until the end of the fourth screening round were regarded as benign. We compared lung cancer probability per nodule count category. Results 1746 (51.5%) participants had one nodule, 800 (23.6%) had two nodules, 354 (10.4%) had three nodules, 191 (5.6%) had four nodules, and 301 (8.9%) had > 4 nodules. Lung cancer in a baseline nodule was diagnosed in 134 participants (139 cancers; 4.0%). Median nodule count in participants with only benign nodules was 1 (Inter-quartile range [IQR]: 1–2), and 2 (IQR 1–3) in participants with lung cancer (p = NS). At baseline, malignancy was detected mostly in the largest nodule (64/66 cancers). Lung cancer probability was 62/1746 (3.6%) in case a participant had one nodule, 33/800 (4.1%) for two nodules, 17/354 (4.8%) for three nodules, 12/191 (6.3%) for four nodules and 10/301 (3.3%) for > 4 nodules (p = NS). Conclusion In baseline lung cancer CT screening, half of participants with lung nodules have more than one nodule. Lung cancer probability does not significantly change with the number of nodules. Baseline nodule count will not help to differentiate between benign and malignant nodules. Each nodule found in lung cancer screening should be assessed separately independent of the presence of other nodules
Reduced Lung-Cancer Mortality with Volume CT Screening in a Randomized Trial
BACKGROUND There are limited data from randomized trials regarding whether volume-based, low-dose computed tomographic (CT) screening can reduce lung-cancer mortality among male former and current smokers. METHODS A total of 13,195 men (primary analysis) and 2594 women (subgroup analyses) between the ages of 50 and 74 were randomly assigned to undergo CT screening at T0 (baseline), year 1, year 3, and year 5.5 or no screening. We obtained data on cancer diagnosis and the date and cause of death through linkages with national registries in the Netherlands and Belgium, and a review committee confirmed lung cancer as the cause of death when possible. A minimum follow-up of 10 years until December 31, 2015, was completed for all participants. RESULTS Among men, the average adherence to CT screening was 90.0%. On average, 9.2% of the screened participants underwent at least one additional CT scan (initially indeterminate). The overall referral rate for suspicious nodules was 2.1%. At 10 years of follow-up, the incidence of lung cancer was 5.58 cases per 1000 personyears in the screening group and 4.91 cases per 1000 person-years in the control group; lung-cancer mortality was 2.50 deaths per 1000 person-years and 3.30 deaths per 1000 person-years, respectively. The cumulative rate ratio for death from lung cancer at 10 years was 0.76 (95% confidence interval [CI], 0.61 to 0.94; P = 0.01) in the screening group as compared with the control group, similar to the values at years 8 and 9. Among women, the rate ratio was 0.67 (95% CI, 0.38 to 1.14) at 10 years of follow-up, with values of 0.41 to 0.52 in years 7 through 9. CONCLUSIONS In this trial involving high-risk persons, lung-cancer mortality was significantly lower among those who underwent volume CT screening than among those who underwent no screening. There were low rates of follow-up procedures for results suggestive of lung cancer. (Funded by the Netherlands Organization of Health Research and Development and others; NELSON Netherlands Trial Register number, NL580.)
CHANDRA/VLA Follow-up of TeV J2032+4131, the Only Unidentified TeV Gamma-ray Source
The HEGRA Cherenkov telescope array group recently reported a steady and
extended unidentified TeV gamma-ray source lying at the outskirts of Cygnus
OB2. This is the most massive stellar association known in the Galaxy,
estimated to contain ~2600 OB type members alone. It has been previously argued
that the large scale shocks and turbulence induced by the multiple interacting
supersonic winds from the many young stars in such associations may play a role
in accelerating Galactic cosmic rays. Indeed, Cyg OB2 also coincides with the
non-variable MeV-GeV range unidentified EGRET source, 3EG 2033+4118. We report
on the near-simultaneous follow-up observations of the extended TeV source
region with the CHANDRA X-ray Observatory and the Very Large Array (VLA) radio
telescope obtained in order to explore this possibility. Analysis of the CO,
HI, and IRAS 100 micron emissions shows that the TeV source region coincides
with an outlying sub-group of powerful OB stars which have evacuated or
destroyed much of the ambient atomic, molecular and dust material, and which
may be related to the very high-energy emissions. An interesting SNR-like
structure is also revealed near the TeV source region in the CO, HI and radio
emission maps. Applying a numerical simulation which accurately tracks the
radio to gamma-ray emission from primary hadrons as well as primary and
secondary e+/-, we find that the broadband spectrum of the TeV source region
favors a predominantly nucleonic - rather than electronic - origin of the
high-energy flux, though deeper X-ray and radio observations are needed to
confirm this. A very reasonable, ~0.1%, conversion efficiency of Cyg OB2's
extreme stellar wind mechanical luminosity to nucleonic acceleration to ~PeV
(10^15 eV) energies is sufficient to explain the multifrequency emissions.Comment: ApJ accepte
Suicide in cancer patients in South East England from 1996 to 2005: a population-based study
BACKGROUND: Studies from around the world have shown that suicide risk is increased in cancer patients, but no previous detailed analysis has been carried out in England
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