144 research outputs found
Correlation function of spin noise due to atomic diffusion
We use paramagnetic Faraday rotation to study spin noise spectrum from
unpolarized Rb vapor in a tightly focused probe beam in the presence of N
buffer gas. We derive an analytical form for the diffusion component of the
spin noise time-correlation function in a Gaussian probe beam. We also obtain
analytical forms for the frequency spectrum of the spin noise in the limit of a
tightly focused or a collimated Gaussian beam in the presence of diffusion. In
particular, we find that in a tightly focused probe beam the spectral lineshape
can be independent of the buffer gas pressure. Experimentally, we find good
agreement between the calculated and measured spin noise spectra for N gas
pressures ranging from 56 to 820 torr.Comment: 6 pages, 4 figure
Femtotesla direct magnetic gradiometer using a single multipass cell
We describe a direct gradiometer using optical pumping with opposite circular
polarization in two Rb atomic ensembles within a single multipass cell.
A far-detuned probe laser undergoes a near-zero paramagnetic Faraday rotation
due to the intrinsic subtraction of two contributions exceeding 3.5 rad from
the highly-polarized ensembles. We develop analysis methods for the direct
gradiometer signal and measure a gradiometer sensitivity of
fT/cm. We also demonstrate that our multipass design, in
addition to increasing the optical depth, provides a fundamental advantage due
to the significantly reduced effect of atomic diffusion on the spin noise
time-correlation, in excellent agreement with theoretical estimate.Comment: 5 pages, 4 figure
Heading errors in all-optical alkali-vapor magnetometers in geomagnetic fields
Alkali-metal atomic magnetometers suffer from heading errors in geomagnetic
fields as the measured magnetic field depends on the orientation of the sensor
with respect to the field. In addition to the nonlinear Zeeman splitting, the
difference between Zeeman resonances in the two hyperfine ground states can
also generate heading errors depending on initial spin polarization. We examine
heading errors in an all-optical scalar magnetometer that uses free precession
of polarized atoms by varying the direction and magnitude of
the magnetic field at different spin polarization regimes. In the high
polarization limit where the lower hyperfine ground state is almost
depopulated, we show that heading errors can be corrected with an analytical
expression, reducing the errors by two orders of magnitude in Earth's field. We
also verify the linearity of the measured Zeeman precession frequency with the
magnetic field. With lower spin polarization, we find that the splitting of the
Zeeman resonances for the two hyperfine states causes beating in the precession
signals and nonlinearity of the measured precession frequency with the magnetic
field. We correct for the frequency shifts by using the unique probe geometry
where two orthogonal probe beams measure opposite relative phases between the
two hyperfine states during the spin precession
Portable magnetometry for detection of biomagnetism in ambient environments
We present a method of optical magnetometry with parts-per-billion resolution
that is able to detect biomagnetic signals generated from the human brain and
heart in Earth's ambient environment. Our magnetically silent sensors measure
the total magnetic field by detecting the free-precession frequency of highly
spin-polarized alkali metal vapor. A first-order gradiometer is formed from two
magnetometers that are separated by a 3 cm baseline. Our gradiometer operates
from a laptop consuming 5 W over a USB port, enabled by state-of-the-art
micro-fabricated alkali vapor cells, advanced thermal insulation, custom
electronics, and laser packages within the sensor head. The gradiometer obtains
a sensitivity of 16 fT/cm/Hz outdoors, which we use to detect neuronal
electrical currents and magnetic cardiography signals. Recording of neuronal
magnetic fields is one of a few available methods for non-invasive functional
brain imaging that usually requires extensive magnetic shielding and other
infractructure. This work demonstrates the possibility of a dense array of
portable biomagnetic sensors that are deployable in a variety of natural
environments
Digital orphans: Data closure and openness in patient- powered networks
This is the author accepted manuscript. The final version is available from Palgrave Macmillan via the DOI in this record.In this paper, we discuss an issue linked to data-sharing regimes in patient-powered, social-media-based networks, namely that most of the data that patient users share are not used to research scientific issues or the patient voice. This is not a trivial issue, as participation in these networks is linked to openness in data sharing, which would benefits fellow patients and contributes to the public good more generally. Patient-powered research networks are often framed as disrupting research agendas and the industry. However, when data that patients share are not accessible for research, their epistemic potential is denied. The problem is linked to the business models of the organisations managing these networks: models centred on controlling patient data tend to close networks with regard to data use. The constraint on research is at odds with the ideals of a sharing, open and supportive epistemic community that networks’ own narratives evoke. This kind of failure can create peculiar scenarios, such as the emergence of the ‘digital orphans’ of Internet research. By pointing out the issue of data use, this paper informs the discussion about the capacity of patient-powered networks to support research participation and the patient voice.We are indebted to the anonymous reviewers and the editor, who with their supportive and constructive comments helped us to better clarify and highlight the argument of the article. We would like to also thank friends and colleagues who have offered valuable comments and suggestions on early drafts of this paper. We would like to especially thank Barbara Prainsack, Sabina Leonelli, Alena Buyx, and David Teira. This research is funded by the European Research Council (ERC) under the European Union’s Seventh Framework Programme (FP7/2007–2013)/ERC grant agreement number 335925, and the German Federal Ministry of Education and Research (grant number 01GP1311
Serum tissue inhibitor of matrix metalloproteinase-1 levels are associated with mortality in patients with malignant middle cerebral artery infarction
Background: In the last years, circulating matrix metalloproteinases (MMP)-9 levels have been associated with functional outcome in ischemic stroke patients. However the prognostic value of circulating levels of tissue inhibitor of matrix metalloproteinases (TIMP)-1 and MMP-10 in functional outcome of ischemic stroke patients has been scarcely studied.
In addition, to our knowledge, serum MMP-9, MMP-10 and TIMP-1 levels in patients with malignant middle cerebral artery infarction (MMCAI) for mortality prediction have not been studied, and these were the objectives of this study.
Methods: This was a multicenter, observational and prospective study carried out in six Spanish Intensive Care Units. We included patients with severe MMCAI defined as Glasgow Coma Scale (GCS) lower than 9. We measured circulating levels of MMP-9, MMP-10, TIMP-1, in 50 patients with severe MMCAI at diagnosis and in 50 healthy subjects. Endpoint was 30-day mortality.
Results: Patients with severe MMCAI showed higher serum levels of MMP-9 (p = 0.001), MMP-10 (p 239 ng/mL are associated with 30-day mortality (OR = 5.82; 95 % CI = 1.37-24.73; P = 0.02) controlling for GCS and age. The area under the curve for TIMP-1 as predictor of
30-day mortality was 0.81 (95 % CI = 0.67-0.91; P < 0.001). We found an association between circulating levels of TIMP-1 and MMP-10 (rho = 0.45; P = 0.001), plasminogen activator inhibitor (PAI)-1 (rho = 0.53; P < 0.001), and tumor necrosis factor (TNF)-alpha (rho = 0.70; P < 0.001).
Conclusions: The most relevant and new findings of our study, were that serum TIMP-1 levels in MMCAI patients were associated with mortality, and could be used as a prognostic biomarker of mortality in MMCAI patients
A survey of clinical features of allergic rhinitis in adults
Background: Allergic rhinitis (AR) has high prevalence and substantial socio-economic burden.
Material/Methods: The study included 35 Italian Centers recruiting an overall number of 3383 adult patients with rhinitis (48% males, 52% females, mean age 29.1, range 18\u201345 years). For each patient, the attending physician had to fill in a standardized questionnaire, covering, in particular, some issues such as the ARIA classification of allergic rhinitis (AR), the results of skin prick test (SPT), the kind of treatment, the response to treatment, and the satisfaction with treatment.
Results: Out of the 3383 patients with rhinitis, 2788 (82.4%) had AR: 311 (11.5%) had a mild intermittent, 229 (8.8%) a mild persistent, 636 (23.5%) a moderate-severe intermittent, and 1518 (56.1%) a moderate-severe persistent form. The most frequently used drugs were oral antihistamines (77.1%) and topical corticosteroids (60.8%). The response to treatment was judged as excellent in 12.2%, good in 41.3%, fair in 31.2%, poor in 14.5%, and very bad in 0.8% of subjects. The rate of treatment dissatisfaction was significantly higher in patients with moderate-to-severe AR than in patients with mild AR (p<0.0001). Indication to allergen immunotherapy (AIT) was significantly more frequent (p<0.01) in patients with severe AR than with mild AR. .
Conclusions: These fndings confirm the appropriateness of ARIA guidelines in classifying the AR patients and the association of severe symptoms with unsuccessful drug treatment. The optimal targeting of patients to be treated with AIT needs to be reassessed
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