1,290 research outputs found
Reduction of Coxiella burnetii prevalence by vaccination of goats and sheep, the Netherlands
Recently, the number of human Q fever cases in the Netherlands increased dramatically. In response to this increase, dairy goats and dairy sheep were vaccinated against Coxiella burnetii. All pregnant dairy goats and dairy sheep in herds positive for Q fever were culled. We identified the effect of vaccination on bacterial shedding by small ruminants. On the day of culling, samples of uterine fluid, vaginal mucus, and milk were obtained from 957 pregnant animals in 13 herds. Prevalence and bacterial load were reduced in vaccinated animals compared with unvaccinated animals. These effects were most pronounced in animals during their first pregnancy. Results indicate that vaccination may reduce bacterial load in the environment and human exposure to C. burnetii
Zin in leven in de gloria?
Afscheidsredes PThU Kampen d.d. 4 november 2011.
Bevat: L.J. van de Brom, God schept ons een zinvolle ruimte : de metafoor van de eigenzinnige tuinman (p. 3-23) en E.R. Jonker, Leren leven in de gloria : vormen, beschaven, geloven (p. 24-47)
Myocardial blood flow under general anaesthesia with sevoflurane in type 2 diabetic patients: a pilot study
BACKGROUND: In type 2 diabetic patients, cardiac events in the perioperative period may be associated with diminished myocardial vasomotor function and endothelial dysfunction. The influence of sevoflurane anaesthesia on myocardial endothelial dysfunction in type 2 diabetic mellitus is investigated in this pilot study. METHODS: Six males with type 2 diabetes mellitus and eight healthy controls were included. Using myocardial contrast echocardiography, myocardial blood flow (MBF) was measured at rest, during adenosine-induced hyperaemia (endothelium-independent vasodilation) and after sympathetic stimulation by the cold pressor test (endothelium-dependent vasodilation). Measurements were performed before and after induction of sevoflurane anaesthesia. RESULTS: Sevoflurane anaesthesia decreased resting MBF in diabetics but not in controls (P = 0.03), while baseline MBF did not differ between diabetics and controls. Without anaesthesia, adenosine-induced hyperaemia increased MBF in both groups compared to resting values. Adenosine combined with sevoflurane resulted in a lower hyperaemic MBF in both groups compared to no anaesthesia. Differences in MBF in response to adenosine before and after sevoflurane administration were larger in diabetic patients, however not statistically significant in this pilot group (P = 0.08). Myocardial blood flow parameters after the cold pressor test were not different between groups. CONCLUSION: These pilot data in type 2 diabetic patients show that sevoflurane anaesthesia decreases resting myocardial blood flow compared to healthy controls. Further, we observed a trend towards a lower endothelium-independent vasodilation capacity in diabetic patients under sevoflurane anaesthesia. Endothelium-dependent vasodilation was not affected by sevoflurane in diabetic patients. These data provide preliminary insight into myocardial responses in type 2 diabetic patients under general anaesthesia. TRIAL REGISTRATION: http://www.clinicialtrials.gov, NCT0086680
Giant enhancement of photodissociation of polar dimers in electric fields
We explore the photodissociation of polar dimers in static electric fields in
the cold regime using the example of the LiCs molecule. A giant enhancement of
the differential cross section is found for laboratory electric field
strengths, and analyzed with varying rovibrational bound states, continuum
energies as well as field strengths.Comment: 6 pages, 6 figure
High-bias stability of monatomic chains
For the metals Au, Pt and Ir it is possible to form freely suspended
monatomic chains between bulk electrodes. The atomic chains sustain very large
current densities, but finally fail at high bias. We investigate the breaking
mechanism, that involves current-induced heating of the atomic wires and
electromigration forces. We find good agreement of the observations for Au
based on models due to Todorov and coworkers. The high-bias breaking of atomic
chains for Pt can also be described by the models, although here the parameters
have not been obtained independently. In the limit of long chains the breaking
voltage decreases inversely proportional to the length.Comment: 7 pages, 5 figure
Shot-noise suppression by Fermi and Coulomb correlations in ballistic conductors
We investigate the injection of degenerate Fermi-Dirac electrons into a
multimode ballistic conductor under the space-charge limited regime. The
nonequilibrium current fluctuations were found to be suppressed by both Coulomb
and Fermi correlations. We show that the Fermi shot-noise suppression factor is
limited below by the value 2kT/epsilon_F, where T is the temperature and
epsilon_F the Fermi energy of the injected electrons. The Coulomb noise
suppression factor may attain much lower values epsilon_F/2qU, because of its
dependence on the applied bias U >> kT/q. The asymptotic behaviour of the
overall shot-noise suppression factor in a high degenerate limit was found to
be kT/qU, independently of the material parameters.Comment: 8 pages, 4 figures, minor changes, published versio
Direct link between Coulomb blockade and shot noise in a quantum coherent structure
We analyze the current-voltage characteristic of a quantum conduction channel
coupled to an electromagnetic environment of arbitrary frequency-dependent
impedance. In the weak blockade regime the correction to the ohmic behavior is
directly related to the channel current fluctuations vanishing at perfect
transmission in the same way as shot noise. This relation can be generalized to
describe the environmental Coulomb blockade in a generic mesoscopic conductor
coupled to an external impedance, as the response of the latter to the current
fluctuations in the former.Comment: 12 pages, 2 figures, submitted to Phys. Rev. Let
Shot noise suppression at room temperature in atomic-scale Au junctions
Shot noise encodes additional information not directly inferable from simple
electronic transport measurements. Previous measurements in atomic-scale metal
junctions at cryogenic temperatures have shown suppression of the shot noise at
particular conductance values. This suppression demonstrates that transport in
these structures proceeds via discrete quantum channels. Using a high frequency
technique, we simultaneously acquire noise data and conductance histograms in
Au junctions at room temperature and ambient conditions. We observe noise
suppression at up to three conductance quanta, with possible indications of
current-induced local heating and noise in the contact region at high
biases. These measurements demonstrate the quantum character of transport at
room temperature at the atomic scale. This technique provides an additional
tool for studying dissipation and correlations in nanodevices.Comment: 15 pages, 4 figures + supporting information (6 pages, 6 figures
Observation of Supershell Structure in Alkali Metal Nanowires
Nanowires are formed by indenting and subsequently retracting two pieces of
sodium metal. Their cross-section gradually reduces upon retraction and the
diameters can be obtained from the conductance. In previous work we have
demonstrated that when one constructs a histogram of diameters from large
numbers of indentation-retraction cycles, such histograms show a periodic
pattern of stable nanowire diameters due to shell structure in the conductance
modes. Here, we report the observation of a modulation of this periodic
pattern, in agreement with predictions of a supershell structure.Comment: Phys. Rev. Lett., in prin
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