9 research outputs found
BeppoSAX Observations of Unprecedented Synchrotron Activity in the BL Lac Object Mkn 501
The BL Lac object Mkn 501, one of the only three extragalactic sources (with
Mkn 421 and 1ES 2344+514) so far detected at TeV energies, was observed with
the BeppoSAX satellite on 7, 11, and 16 April 1997 during a phase of high
activity at TeV energies, as monitored with the Whipple, HEGRA and CAT
Cherenkov telescopes. Over the whole 0.1-200 keV range the spectrum was
exceptionally hard (alpha =< 1, with F_nu ~ nu^{-alpha}) indicating that the
X-ray power output peaked at (or above) ~100 keV. This represents a shift of at
least two orders of magnitude with respect to previous observations of Mkn 501,
a behavior never seen before in this or any other blazar. The overall X-ray
spectrum hardens with increasing intensity and, at each epoch, it is softer at
larger energies. The correlated variability from soft X-rays to the TeV band
points to models in which the same population of relativistic electrons
produces the X-ray continuum via synchrotron radiation and the TeV emission by
inverse Compton scattering of the synchrotron photons or other seed photons.
For the first time in any blazar the synchrotron power is observed to peak at
hard X-ray energies. The large shift of the synchrotron peak frequency with
respect to previous observations of Mkn 501 implies that intrinsic changes in
the relativistic electron spectrum caused the increase in emitted power. Due to
the very high electron energies, the inverse Compton process is limited by the
Klein-Nishina regime. This implies a quasi-linear (as opposed to quadratic)
relation of the variability amplitude in the TeV and hard X-ray ranges (for the
SSC model) and an increase of the inverse Compton peak frequency smaller than
that of the synchrotron peak frequency.Comment: 11 pages, Latex, 4 Postscript figures, to appear in The Astrophysical
Journal Letter
Actual role of the bronchography in the diagnosis of bronchogenic carcinoma: a retrospective analysis
The diagnostic score of bronchography in the diagnosis of malignant lung disease is assessed in a group of 210 patients who underwent bronchography. Its diagnostic sensitivity is compared with that of the 'diagnostic triad' (bronchoscopy, papanicolaou-test, transbronchial biopsy) individually and collectively. The classical bronchographic signs of malignancy are reviewed and a sign is described that is highly suggestive for a diagnosis of malignant lesion at the periphery of the lung field. A review of the possible differential diagnosis is given. A comparison is made between the (diagnostic) accuracy of bronchography and the results obtained at percutaneous biopsy of lung lesions, including the possible complication of both methods. The final conclusion is that bronchography is still of value as a diagnostic aid in the early detection of lung cancer.SCOPUS: NotDefined.jinfo:eu-repo/semantics/publishe
Percutaneous cricothyroid bronchography
A simple technique for cricothyroid bronchography using a disposal needle and catheter set is described. This has been used by the authors in over 380 examinations, giving excellent filling of the bronchial tree and proving to be well tolerated by all patients. Serious complications have been rare; since side effects were seen in about 1.8% of cases, of which 0.5% were due to lack of experience. The other 1.3% of complications were minor, necessitating simple treatment or no treatment at all.SCOPUS: NotDefined.jinfo:eu-repo/semantics/publishe
VALEUR DE LA RADIOGRAPHIE STANDARD DU THORAX DANS L'EVALUATION DE LA PRESSION CAPILLAIRE PULMONAIRE
The authors correlated the capillary pressures predicted by analysis of the erect standard thorax view with the catheterization findings in 63 patients. A capillary pressure schedule is proposed, based on radiological identification of apical vascular redistribution and interstitial and alveolar edema. Good correlation was established in 80% of cases for pressure values between 12 and 30 mmHg. Patients presenting vascular redistribution and radiological evidence of pulmonary arterial hypertension are considered separately. Plain chest film would seem to be a valuable diagnostic aid in predicting pulmonary capillary pressures.SCOPUS: ar.jinfo:eu-repo/semantics/publishe