62 research outputs found
Integration of external and internal dosimetry in Switzerland
Individual monitoring regulations in Switzerland are based on the ICRP60 recommendations. The annual limit of 20 mSv for the effective dose applies to the sum of external and internal radiation. External radiation is monitored monthly or quarterly with TLD, DIS or CR-39 dosemeters by 10 approved external dosimetry services and reported as Hp(10) and Hp(0.07). Internal monitoring is done in two steps. At the workplace, simple screening measurements are done frequently in order to recognise a possible incorporation. If a nuclide dependent activity threshold is exceeded then one of the seven approved dosimetry services for internal radiation does an incorporation measurement to assess the committed effective dose E50. The dosimetry services report all the measured or assessed dose values to the employer and to the National Dose Registry. The employer records the annually accumulated dose values into the individual dose certificate of the occupationally exposed person, both the external dose Hp(10) and the internal dose E50 as well as the total effective dose E = Hp(10)+E50. Based on the national dose registry an annual report on the dosimetry in Switzerland is published which contains the statistics for the total effective dose, as well as separate statistics for external and internal exposur
Field effects on the statistical behavior of the molecular conductance in a single molecular junction in aqueous solution
Green function techniques in the treatment of quantum transport at the molecular scale
The theoretical investigation of charge (and spin) transport at nanometer
length scales requires the use of advanced and powerful techniques able to deal
with the dynamical properties of the relevant physical systems, to explicitly
include out-of-equilibrium situations typical for electrical/heat transport as
well as to take into account interaction effects in a systematic way.
Equilibrium Green function techniques and their extension to non-equilibrium
situations via the Keldysh formalism build one of the pillars of current
state-of-the-art approaches to quantum transport which have been implemented in
both model Hamiltonian formulations and first-principle methodologies. We offer
a tutorial overview of the applications of Green functions to deal with some
fundamental aspects of charge transport at the nanoscale, mainly focusing on
applications to model Hamiltonian formulations.Comment: Tutorial review, LaTeX, 129 pages, 41 figures, 300 references,
submitted to Springer series "Lecture Notes in Physics
Vibration induced memory effects and switching in ac-driven molecular nanojunctions
We investigate bistability and memory effects in a molecular junction weakly
coupled to metallic leads with the latter being subject to an adiabatic
periodic change of the bias voltage. The system is described by a simple
Anderson-Holstein model and its dynamics is calculated via a master equation
approach. The controlled electrical switching between the many-body states of
the system is achieved due to polaron shift and Franck-Condon blockade in the
presence of strong electron-vibron interaction. Particular emphasis is given to
the role played by the excited vibronic states in the bistability and
hysteretic switching dynamics as a function of the voltage sweeping rates. In
general, both the occupation probabilities of the vibronic states and the
associated vibron energy show hysteretic behaviour for driving frequencies in a
range set by the minimum and maximum lifetimes of the system. The consequences
on the transport properties for various driving frequencies and in the limit of
DC-bias are also investigated.Comment: 15 pages, 20 figures, published versio
Cardiovascular mortality and exposure to extremely low frequency magnetic fields: a cohort study of Swiss railway workers
<p>Abstract</p> <p>Background</p> <p>Exposure to intermittent magnetic fields of 16 Hz has been shown to reduce heart rate variability, and decreased heart rate variability predicts cardiovascular mortality. We examined mortality from cardiovascular causes in railway workers exposed to varying degrees to intermittent 16.7 Hz magnetic fields.</p> <p>Methods</p> <p>We studied a cohort of 20,141 Swiss railway employees between 1972 and 2002, including highly exposed train drivers (median lifetime exposure 120.5 μT-years), and less or little exposed shunting yard engineers (42.1 μT-years), train attendants (13.3 μT-years) and station masters (5.7 μT-years). During 464,129 person-years of follow up, 5,413 deaths were recorded and 3,594 deaths were attributed to cardio-vascular diseases. We analyzed data using Cox proportional hazards models.</p> <p>Results</p> <p>For all cardiovascular mortality the hazard ratio compared to station masters was 0.99 (95%CI: 0.91, 1.08) in train drivers, 1.13 (95%CI: 0.98, 1.30) in shunting yard engineers, and 1.09 (95%CI: 1.00, 1.19) in train attendants.Corresponding hazard ratios for arrhythmia related deaths were 1.04 (95%CI: 0.68, 1.59), 0.58 (95%CI: 0.24, 1.37) and 1.30 (95%CI: 0.87, 1.93) and for acute myocardial infarction 1.00 (95%CI: 0.73, 1.36), 1.56 (95%CI: 1.04, 2.32), and 1.14 (95%CI: 0.85, 1.53). The hazard ratio for arrhythmia related deaths per 100 μT-years of cumulative exposure was 0.94 (95%CI: 0.71, 1.24) and 0.91 (95%CI: 0.75, 1.11) for acute myocardial infarction.</p> <p>Conclusion</p> <p>This study provides evidence against an association between long-term occupational exposure to intermittent 16.7 Hz magnetic fields and cardiovascular mortality.</p
Bias-induced conductance switching in single molecule junctions containing a redox-active transition metal complex
Single-Molecule Electrochemical Transistor Utilizing a Nickel-Pyridyl Spinterface
Using a scanning tunnelling microscope
break-junction technique,
we produce 4,4′-bipyridine (44BP) single-molecule junctions
with Ni and Au contacts. Electrochemical control is used to prevent
Ni oxidation and to modulate the conductance of the devices via nonredox
gatingthe first time this has been shown using non-Au contacts.
Remarkably the conductance and gain of the resulting Ni-44BP-Ni electrochemical
transistors is significantly higher than analogous Au-based devices.
Ab-initio calculations reveal that this behavior arises because charge
transport is mediated by spin-polarized Ni <i>d</i>-electrons,
which hybridize strongly with molecular orbitals to form a “spinterface”.
Our results highlight the important role of the contact material for
single-molecule devices and show that it can be varied to provide
control of charge and spin transport
Collectively Induced Quantum-Confined Stark Effect in Monolayers of Molecules Consisting of Polar Repeating Units
Integration of external and internal dosimetry in Switzerland
Individual monitoring regulations in Switzerland are based on the ICRP60 recommendations. The annual limit of 20 mSv for the effective dose applies to the sum of external and internal radiation. External radiation is monitored monthly or quarterly with TLD, DIS or CR-39 dosemeters by 10 approved external dosimetry services and reported as H(p)(10) and H(p)(0.07). Internal monitoring is done in two steps. At the workplace, simple screening measurements are done frequently in order to recognise a possible incorporation. If a nuclide dependent activity threshold is exceeded then one of the seven approved dosimetry services for internal radiation does an incorporation measurement to assess the committed effective dose E(50). The dosimetry services report all the measured or assessed dose values to the employer and to the National Dose Registry. The employer records the annually accumulated dose values into the individual dose certificate of the occupationally exposed person, both the external dose H(p)(10) and the internal dose E(50) as well as the total effective dose E = H(p)(10)+E(50). Based on the national dose registry an annual report on the dosimetry in Switzerland is published which contains the statistics for the total effective dose, as well as separate statistics for external and internal exposure
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