Noise exposure and auditory thresholds of German airline pilots: a cross-sectional study

Objective: The cockpit workplace of airline pilots is a noisy environment. This study examines the hearing thresholds of pilots with respect to ambient noise and communication sound. Methods: The hearing of 487 German pilots was analysed by audiometry in the frequency range of 125 Hz–16 kHz in varying age groups. Cockpit noise (free-field) data and communication sound (acoustic manikin) measurements were evaluated.Results The ambient noise levels in cockpits were found to be between 74 and 80 dB(A), and the sound pressure levels under the headset were found to be between 84 and 88 dB(A).The left–right threshold differences at 3, 4 and 6 kHz show evidence of impaired hearing at the left ear, which worsens by age.In the age groups 40/=40 years the mean differences at 3 kHz are 2/3 dB, at 4 kHz 2/4 dB and at 6 kHz 1/6 dB.In the pilot group which used mostly the left ear for communication tasks (43 of 45 are in the older age group) the mean difference at 3?kHz is 6?dB, at 4 kHz 7 dB and at 6 kHz 10 dB. The pilots who used the headset only at the right ear also show worse hearing at the left ear of 2 dB at 3 kHz, 3 dB at 4 kHz and at 6 kHz. The frequency-corrected exposure levels under the headset are 7–11 dB(A) higher than the ambient noise with an averaged signal-to-noise ratio for communication of about 10 dB(A). Conclusions: The left ear seems to be more susceptible to hearing loss than the right ear. Active noise reduction systems allow for a reduced sound level for the communication signal below the upper exposure action value of 85 dB(A) and allow for a more relaxed working environment for pilots

Description of atomic excitations in heavy-ion reactions

Excitations of the atomic shell in heavy-ion collisions are influenced by the presence of a nuclear reaction. In the present Rapid Communication we point out the equivalence between a semiclassical description based on the nuclear autocorrelation function with an earlier model which employs a distribution of reaction times f(T). For the example of U+U collisions, results of coupled-channel calculations for positron creation and K-hole excitations are discussed for two schematic reaction models

Comment on "New atomic mechanism for positron production in heavy-ion collisoins"

A Comment on the Letter by W. Lichten and A. Robatino, Phys. Rev. Lett. 54, 781 (1985). See Also: W. Lichten and A. Robatino, New atomic mechanism for positron production in heavy-ion collisions, Phys. Rev. Lett. 54, 781 (1985). http://prola.aps.org/abstract/PRL/v54/i8/p781_

Theory of positron production in heavy-ion collisions

Collisions of very heavy ions at energies close to the Coulomb barrier are discussed as a unique tool to study the behavior of the electron-positron field in the presence of strong external electromagnetic fields. To calculate the excitation processes induced by the collision dynamics, a semiclassical model is employed and adapted to describe the field-theoretical many-particle system. An expansion in the adiabatic molecular basis is chosen. Energies and matrix elements are calculated using the monopole approximation. In a supercritical (Z1+Z2≳173) quasiatomic system the 1s level joins the antiparticle continuum and becomes a resonance, rendering the neutral vacuum state unstable. Several methods of treating the corresponding time-dependent problem are discussed. A projection-operator technique is introduced for a fully dynamical treatment of the resonance. Positron excitation rates in s1/2 and p1/2 states are obtained by numerical solution of the coupled-channel equations and are compared with results from first- plus second-order perturbation theory. Calculations are performed for subcritical and supercritical collisions of Pb-Pb, Pb-U, U-U, and U-Cf. Strong relativistic deformations of the wave functions and the growing contributions from inner-shell bound states lead to a very steep Z dependence of positron production. The results are compared with available data from experiments done at GSI. Correlations between electrons and positrons are briefly discussed

Gaussian, exponential, and power-law decay of time-dependent correlation functions in quantum spin chains

Dynamic spin correlation functions $$ for the 1D $S=1/2$ $XX$ model $H = -J\Sigma_i \{S_i^x S_{i+1}^x + S_i^y S_{i+1}^y \}$ are calculated exactly for finite open chains with up to N=10000 spins. Over a certain time range the results are free of finite-size effects and thus represent correlation functions of an infinite chain (bulk regime) or a semi-infinite chain (boundary regime). In the bulk regime, the long-time asymptotic decay as inferred by extrapolation is Gaussian at $T=\infty$, exponential at $0 < T < \infty$, and power-law $(\sim t^{-1/2})$ at T=0, in agreement with exact results. In the boundary regime, a power-law decay obtains at all temperatures; the characteristic exponent is universal at T=0 $(\sim t^{-1})$ and at $0 < T < \infty$ $(\sim t^{-3/2})$, but is site-dependent at $T=\infty$. In the high-temperature regime $(T/J \gg 1)$ and in the low-temperature regime $(T/J \ll 1)$, crossovers between different decay laws can be observed in $<S_i^x (t)S_j^x>$. Additional crossovers are found between bulk-type and boundary-type decay for $i=j$ near the boundary, and between space-like and time-like behavior for $i \neq j$.Comment: 9 pages, 8 figures appended as uuencoded compressed postscript fil

Data-driven Modeling and Coordination of Large Process Structures

In the engineering domain, the development of complex products (e.g., cars) necessitates the coordination of thousands of (sub-)processes. One of the biggest challenges for process management systems is to support the modeling, monitoring and maintenance of the many interdependencies between these sub-processes. The resulting process structures are large and can be characterized by a strong relationship with the assembly of the product; i.e., the sub-processes to be coordinated can be related to the different product components. So far, sub-process coordination has been mainly accomplished manually, resulting in high efforts and inconsistencies. IT support is required to utilize the information about the product and its structure for deriving, coordinating and maintaining such data-driven process structures. In this paper, we introduce the COREPRO framework for the data-driven modeling of large process structures. The approach reduces modeling efforts significantly and provides mechanisms for maintaining data-driven process structures

Positron production in crossed beams of bare uranium nuclei

Positron creation in crossed-beam collisions of high-energy, fully stripped heavy ions is investigated within the coupled-channel formalism. In comparison with fixed-target collisions of highly stripped heavy-ion projectiles positron production probabilities are enhanced by more than one order of magnitude. The increase results from the possibility to excite electrons from the negative energy continuum into all bound states. The positron spectrum is shifted towards higher energies because of the absence of electron screening. Rutherford scattering as well as nuclear collisions with time delay are investigated. We also discuss the filling of empty bound states by electrons from pair-production processes

Dr. Max Dornbusch zum 80. Geburtstag

Unter Bezugnahme auf bisherige Laudationes für Dr. Max Dornbusch (u. a. Erz 1997, Liedel 1997, Müller 1997, Wendt 1997, Müller 2012) soll hier zur Vollendung des 80. Lebensjahres eine Würdigung seines besonderen Engagements als Natur- und Artenschützer erfolgen

Prof. Dr. Peter Hentschel zum Andenken (23.03.1933 - 26.01.2002)

Peter Hentschel verstarb am 26. Januar 2002 nach schwerer Krankheit. Wir alle, die ihn näher kannten, trauern sehr über seinen allzu frühen Tod. Wie bereits zu seinem 65. Geburtstag dargestellt (Reichhoff & Schönbrodt 1998, in dieser Zeitschrift), war sein Leben von sowohl haupt- als auch ehrenamtlich engagierten Tätigkeiten für den Naturschutz und insbesondere die Landschaftsforschung und -planung gekennzeichnet

Vogel-Beringer tagten in der Vogelschutzwarte Steckby

Am 23. Februar 2002 tagten in der Staatlichen Vogelschutzwarte Steckby des Landesamtes für Umweltschutz Sachsen-Anhalt die 50 ehrenamtlichen Vogelberinger des Landes. Sie sind mit Genehmigung des Ministeriums für Raumordnung, Landwirtschaft und Umwelt des Landes Sachsen-Anhalt zugleich als Mitarbeiter der Vogelwarte Hiddensee an Forschungsprogrammen der europaweit koordinierenden Dachorganisation EURING (The European Union for Bird Ringing) tätig