22 research outputs found
Stochastically Fluctuating Black-Hole Geometry, Hawking Radiation and the Trans-Planckian Problem
We study the propagation of null rays and massless fields in a black hole
fluctuating geometry. The metric fluctuations are induced by a small
oscillating incoming flux of energy. The flux also induces black hole mass
oscillations around its average value. We assume that the metric fluctuations
are described by a statistical ensemble. The stochastic variables are the
phases and the amplitudes of Fourier modes of the fluctuations. By averaging
over these variables, we obtain an effective propagation for massless fields
which is characterized by a critical length defined by the amplitude of the
metric fluctuations: Smooth wave packets with respect to this length are not
significantly affected when they are propagated forward in time. Concomitantly,
we find that the asymptotic properties of Hawking radiation are not severely
modified. However, backward propagated wave packets are dissipated by the
metric fluctuations once their blue shifted frequency reaches the inverse
critical length. All these properties bear many resemblences with those
obtained in models for black hole radiation based on a modified dispersion
relation. This strongly suggests that the physical origin of these models,
which were introduced to confront the trans-Planckian problem, comes from the
fluctuations of the black hole geometry.Comment: 32 page
Work-related allergy in medical doctors: atopy, exposure to domestic animals, eczema induced by common chemicals and membership of the surgical profession as potential risk factors
Purpose To investigate the risk factors associated with
work-related allergy-like symptoms in medical doctors.
Methods Self-administered questionnaire survey and CAP
test were conducted among medical school students in the
4th grade of their 6-year medical course in 1993â1996 and
1999â2001. Follow-up questionnaires were sent in 2004 to
the graduates. These questionnaires enquired into personal
and family history of allergic diseases, lifestyle, history of
allergy-like symptoms including work-relatedness and
occupational history as medical doctors. Relationships
between allergy-like symptoms and relevant factors were
evaluated by multivariate logistic regression analysis.
Results Of 261 respondents at the follow-up survey, 139
(53.3%) and 54 (20.7%) had a history of any allergy-like
symptoms and any work-related allergy-like symptoms,
respectively. Female gender and family history of allergic
diseases were signiWcantly associated with any allergy-like
symptoms. Personal history of allergic disease, exposure
to domestic animals, eczema caused by rubber gloves,
metallic accessories, or cosmetics during schooling days,
and membership of the surgical profession were signiW-
cant risk factors for work-related allergy-like symptoms.
On the contrary, to work-related allergy-like symptoms,
gender, age, and smoking status were not signiWcantly
related, and consumption of prepared foods was inversely
related.
Conclusions Personal history of atopy and eczema
induced by common goods and the history of keeping
domestic animals may be predictors of work-related
allergy-like symptoms in doctors. After graduation from
medical school, physicians start with exposure to various
allergens and irritants at work, which relate to work-related
allergy-like symptoms, especially for surgeons