107 research outputs found
Towards T1-limited magnetic resonance imaging using Rabi beats
Two proof-of-principle experiments towards T1-limited magnetic resonance
imaging with NV centers in diamond are demonstrated. First, a large number of
Rabi oscillations is measured and it is demonstrated that the hyperfine
interaction due to the NV's 14N can be extracted from the beating oscillations.
Second, the Rabi beats under V-type microwave excitation of the three hyperfine
manifolds is studied experimentally and described theoretically.Comment: 6 pages, 8 figure
Ion-induced sulfuric acid-ammonia nucleation drives particle formation in coastal Antarctica
Formation of new aerosol particles from trace gases is a major source of cloud condensation nuclei (CCN) in the global atmosphere, with potentially large effects on cloud optical properties and Earth's radiative balance. Controlled laboratory experiments have resolved, in detail, the different nucleation pathways likely responsible for atmospheric new particle formation, yet very little is known from field studies about the molecular steps and compounds involved in different regions of the atmosphere. The scarcity of primary particle sources makes secondary aerosol formation particularly important in the Antarctic atmosphere. Here, we report on the observation of ion-induced nucleation of sulfuric acid and ammonia-a process experimentally investigated by the CERN CLOUD experiment-as a major source of secondary aerosol particles over coastal Antarctica. We further show that measured high sulfuric acid concentrations, exceeding 10(7) molecules cm(-3), are sufficient to explain the observed new particle growth rates. Our findings show that ion-induced nucleation is the dominant particle formation mechanism, implying that galactic cosmic radiation plays a key role in new particle formation in the pristine Antarctic atmosphere.Peer reviewe
Serum osteoprotegerin level, carotid-femoral pulse wave velocity and cardiovascular survival in haemodialysis patients
BACKGROUND: Osteoprotegerin (OPG) is a marker and regulator of
arterial calcification, and it is related to cardiovascular
survival in haemodialysis patients. The link between OPG and
aortic stiffening--a consequence of arterial calcification--has
not been previously evaluated in this population, and it is not
known whether OPG-related mortality risk is mediated by arterial
stiffening. METHODS: At baseline, OPG and aortic pulse wave
velocity (PWV) were measured in 98 chronic haemodialysis
patients who were followed for a median of 24 months. The
relationship between OPG and PWV was assessed by multivariate
linear regression. The role of PWV in mediating OPG related
cardiovascular mortality was evaluated by including both OPG and
PWV in the same survival model. RESULTS: At baseline mean
(standard deviation) PWV was 11.2 (3.3) m/s and median OPG
(interquartile range) was 11.1 (7.5-15.9) pmol/L. There was a
strong, positive, linear relationship between PWV and lnOPG (P =
0.009, model R(2) = 0.540) independent of covariates. During
follow-up 23 patients died of cardiovascular causes. In separate
univariate survival models both PWV and lnOPG were related to
cardiovascular mortality [hazard ratios 1.31 (1.14-1.50) and
8.96 (3.07-26.16), respectively]. When both PWV and lnOPG were
entered into the same model, only lnOPG remained significantly
associated with cardiovascular mortality [hazard ratio 1.11
(0.93-1.33) and 7.18 (1.89-27.25), respectively). CONCLUSION: In
haemodialysis patients OPG is strongly related to PWV and OPG
related cardiovascular mortality risk is, in part, mediated by
increased PWV
Exploring haemodynamics of haemodialysis using extrema points analysis model
Background: Haemodialysis is a form of renal replacement therapy used to treat
patients with end stage renal failure. It is becoming more appreciated that
haemodialysis patients exhibit higher rates of multiple end organ damage
compared to the general population. There is also a strong emerging evidence that
haemodialysis itself causes circulatory stress. We aimed at examining
haemodynamic patterns during haemodialysis using a new model and test that
model against a normal control.
Methods: We hypothesised that blood pressures generated by each heart beat
constantly vary between local peaks and troughs (local extrema), the frequency and
amplitude of which is regulated to maintain optimal organ perfusion. We also
hypothesised that such model could reveal multiple haemodynamic aberrations
during HD. Using a non-invasive cardiac output monitoring device (Finometer®) we
compared various haemodynamic parameters using the above model between a
haemodialysis patient during a dialysis session and an exercised normal control after
comparison at rest.
Results: Measurements yielded 29,751 data points for each haemodynamic
parameter. Extrema points frequency of mean arterial blood pressure was higher in
the HD subject compared to the normal control (0.761Hz IQR 0.5-0.818 vs 0.468Hz
IQR 0.223-0.872, P < 0.0001). Similarly, extrema points frequency of systolic blood
pressure was significantly higher in haemodialysis compared to normal. In contrary,
the frequency of extrema points for TPR was higher in the normal control compared
to HD (0.947 IQR 0.520-1.512 vs 0.845 IQR 0.730-1.569, P < 0.0001) with significantly
higher amplitudes.
Conclusion: Haemodialysis patients potentially exhibit an aberrant haemodynamic
behaviour characterised by higher extrema frequencies of mean arterial blood
pressure and lower extrema frequencies of total peripheral resistance. This, in
theory, could lead to higher variation in organ perfusion and may be detrimental to vulnerable vascular beds
Effects of the Veterinary Pharmaceutical Ivermectin in Indoor Aquatic Microcosms
The effects of the parasiticide ivermectin were assessed in plankton-dominated indoor microcosms. Ivermectin was applied once at concentrations of 30, 100, 300, 1000, 3000, and 10,000 ng/l. The half-life (dissipation time 50%; DT50) of ivermectin in the water phase ranged from 1.1 to 8.3 days. The lowest NOECcommunity that could be derived on an isolated sampling from the microcosm study by means of multivariate techniques was 100 ng/l. The most sensitive species in the microcosm study were the cladocerans Ceriodaphnia sp. (no observed effect concentration, NOEC = 30 ng/l) and Chydorus sphaericus (NOEC = 100 ng/l). The amphipod Gammarus pulex was less sensitive to ivermectin, showing consistent statistically significant reductions at the 1000-ng/l treatment level. Copepoda taxa decreased directly after application of ivermectin in the highest treatment but had already recovered at day 20 posttreatment. Indirect effects (e.g., increase of rotifers, increased primary production) were observed at the highest treatment level starting only on day 13 of the exposure phase. Cladocera showed the highest sensitivity to ivermectin in both standard laboratory toxicity tests as well as in the microcosm study. This study demonstrates that simple plankton-dominated test systems for assessing the effects of ivermectin can produce results similar to those obtained with large complex outdoor systems
Toxicity of Sediment-Associated Pesticides to Chironomus dilutus and Hyalella azteca
Two hundred sediment samples were collected and their toxicity evaluated to aquatic species in a previous study in the agriculturally dominated Central Valley of California, United States. Pyrethroid insecticides were the main contributors to the observed toxicity. However, mortality in approximately one third of the toxic samples could not be explained solely by the presence of pyrethroids in the matrices. Hundreds of pesticides are currently used in the Central Valley of California, but only a few dozen are analyzed in standard environmental monitoring. A significant amount of unexplained sediment toxicity may be due to pesticides that are in widespread use that but have not been routinely monitored in the environment, and even if some of them were, the concentrations harmful to aquatic organisms are unknown. In this study, toxicity thresholds for nine sediment-associated pesticides including abamectin, diazinon, dicofol, fenpropathrin, indoxacarb, methyl parathion, oxyfluorfen, propargite, and pyraclostrobin were established for two aquatic species, the midge Chironomus dilutus and the amphipod Hyalella azteca. For midges, the median lethal concentration (LC50) of the pesticides ranged from 0.18 to 964 μg/g organic carbon (OC), with abamectin being the most toxic and propargite being the least toxic pesticide. A sublethal growth endpoint using average individual ash-free dry mass was also measured for the midges. The no–observable effect concentration values for growth ranged from 0.10 to 633 μg/g OC for the nine pesticides. For the amphipods, fenpropathrin was the most toxic, with an LC50 of 1–2 μg/g OC. Abamectin, diazinon, and methyl parathion were all moderately toxic (LC50s 2.8–26 μg/g OC). Dicofol, indoxacarb, oxyfluorfen, propargite, and pyraclostrobin were all relatively nontoxic, with LC50s greater than the highest concentrations tested. The toxicity information collected in the present study will be helpful in decreasing the frequency of unexplained sediment toxicity in agricultural waterways
Ultrafast electronic read-out of diamond NV centers coupled to graphene
Nonradiative transfer processes are often regarded as loss channels for an
optical emitter1, since they are inherently difficult to be experimentally
accessed. Recently, it has been shown that emitters, such as fluorophores and
nitrogen vacancy centers in diamond, can exhibit a strong nonradiative energy
transfer to graphene. So far, the energy of the transferred electronic
excitations has been considered to be lost within the electron bath of the
graphene. Here, we demonstrate that the trans-ferred excitations can be
read-out by detecting corresponding currents with picosecond time resolution.
We electrically detect the spin of nitrogen vacancy centers in diamond
electronically and con-trol the nonradiative transfer to graphene by electron
spin resonance. Our results open the avenue for incorporating nitrogen vacancy
centers as spin qubits into ultrafast electronic circuits and for harvesting
non-radiative transfer processes electronically
Prediction and measurement of the size-dependent stability of fluorescence in diamond over the entire nanoscale
Fluorescent defects in non-cytotoxic diamond nanoparticles are candidates for
qubits in quantum computing, optical labels in biomedical imaging and sensors
in magnetometry. For each application these defects need to be optically and
thermodynamically stable, and included in individual particles at suitable
concentrations (singly or in large numbers). In this letter, we combine
simulations, theory and experiment to provide the first comprehensive and
generic prediction of the size, temperature and nitrogen-concentration
dependent stability of optically active NV defects in nanodiamonds.Comment: Published in Nano Letters August 2009 24 pages, 6 figure
Rhinovirus illnesses during infancy predict subsequent childhood wheezing
Background: The contribution of viral respiratory infections during infancy to the development of subsequent wheezing and/ or allergic diseases in early childhood is not established. Objective: To evaluate these relationships prospectively from birth to 3 years of age in 285 children genetically at high risk for developing allergic respiratory diseases. Methods: By using nasal lavage, the relationship of timing, severity, and etiology of viral respiratory infections during infancy to wheezing in the 3rd year of life was evaluated. In addition, genetic and environmental factors that could modify risk of infections and wheezing prevalence were analyzed. Results: Risk factors for 3rd year wheezing were passive smoke exposure (odds ratio [OR] 5 2.1), older siblings (OR 5 2.5), allergic sensitization to foods at age 1 year (OR 5 2.0), any moderate to severe respiratory illness without wheezing during infancy (OR 5 3.6), and at least 1 wheezing illness with respiratory syncytial virus (RSV; OR 5 3.0), rhinovirus (OR 5 10) and/or non-rhinovirus/RSV pathogens (OR 5 3.9) during infancy. When viral etiology was considered, 1st-year wheezing illnesses caused by rhinovirus infection were the strongest predictor of subsequent 3rd year wheezing (OR 5 6.6; P < .0001). Moreover, 63% of infants who wheezed during rhinovirus seasons continued to wheeze in the 3rd year of life, compared with only 20% of all other infants (OR 5 6.6; P < .0001). Conclusion: In this population of children at increased risk of developing allergies and asthma, the most significant risk factor for the development of preschool childhood wheezing is the occurrence of symptomatic rhinovirus illnesses during infancy that are clinically and prognostically informative based on their seasonal nature. (J Allergy Clin Immunol 2005;116:571-7.
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