588 research outputs found
A method for the detection of clouds using AVHRR infrared observations
A method is proposed for cloud detection over sea using a single infrared channel of a high spatial resolution satellite radiometer. The method combines a spatial coherence test and an absolute threshold test for the temperature field. The threshold for the second test is automatically determined by a histogram analysis of data which were preselected by the coherence test. The coherence test used differs from the classical standard deviation test in the way of the test value computation: the weight of the pixel to be investigated is increased. A simulation shows that under conditions of low cloud cover this makes the proposed coherence test more sensitive than the standard deviation test. When applied to real data the test was also found to be very sensitive compared with visible and IR threshold tests. Cloud cover obtained by the whole method is finally compared with that resulting from the visible and IR histogram analysis procedure of Phulpin et al. This comparison indicates a high reliability of the proposed method
Frequency, syndrome specificity, influence of disease activity, long-term course, association with AQP4-IgG, and origin
Background Antibodies to myelin oligodendrocyte glycoprotein (MOG-IgG) have
been suggested to play a role in a subset of patients with neuromyelitis
optica and related disorders. Objective To assess (i) the frequency of MOG-IgG
in a large and predominantly Caucasian cohort of patients with optic neuritis
(ON) and/or myelitis; (ii) the frequency of MOG-IgG among AQP4-IgG-positive
patients and vice versa; (iii) the origin and frequency of MOG-IgG in the
cerebrospinal fluid (CSF); (iv) the presence of MOG-IgG at disease onset; and
(v) the influence of disease activity and treatment status on MOG-IgG titers.
Methods 614 serum samples from patients with ON and/or myelitis and from
controls, including 92 follow-up samples from 55 subjects, and 18 CSF samples
were tested for MOG-IgG using a live cell-based assay (CBA) employing full-
length human MOG-transfected HEK293A cells. Results MOG-IgG was detected in 95
sera from 50 patients with ON and/or myelitis, including 22/54 (40.7%)
patients with a history of both ON and myelitis, 22/103 (21.4%) with a history
of ON but no myelitis and 6/45 (13.3%) with a history of longitudinally
extensive transverse myelitis but no ON, and in 1 control patient with
encephalitis and a connective tissue disorder, all of whom were negative for
AQP4-IgG. MOG-IgG was absent in 221 further controls, including 83 patients
with AQP4-IgG-seropositive neuromyelitis optica spectrum disorders and 85 with
multiple sclerosis (MS). MOG-IgG was found in 12/18 (67%) CSF samples from
MOG-IgG-seropositive patients; the MOG-IgG-specific antibody index was
negative in all cases, indicating a predominantly peripheral origin of CSF
MOG-IgG. Serum and CSF MOG-IgG belonged to the complement-activating IgG1
subclass. MOG-IgG was present already at disease onset. The antibodies
remained detectable in 40/45 (89%) follow-up samples obtained over a median
period of 16.5 months (range 0–123). Serum titers were higher during attacks
than during remission (p < 0.0001), highest during attacks of simultaneous
myelitis and ON, lowest during acute isolated ON, and declined following
treatment. Conclusions To date, this is the largest cohort studied for IgG to
human full-length MOG by means of an up-to-date CBA. MOG-IgG is present in a
substantial subset of patients with ON and/or myelitis, but not in classical
MS. Co-existence of MOG-IgG and AQP4-IgG is highly uncommon. CSF MOG-IgG is of
extrathecal origin. Serum MOG-IgG is present already at disease onset and
remains detectable in the long-term course. Serum titers depend on disease
activity and treatment status
Evolution of a Bose-condensed gas under variations of the confining potential
We discuss the dynamic properties of a trapped Bose-condensed gas under
variations of the confining field and find analytical scaling solutions for the
evolving coherent state (condensate). We further discuss the characteristic
features and the depletion of this coherent state.Comment: 4 pages, no postscript figure
Probing dipolar effects with condensate shape oscillation
We discuss the low energy shape oscillations of a magnetic trapped atomic
condensate including the spin dipole interaction. When the nominal isotropic
s-wave interaction strength becomes tunable through a Feshbach resonance (e.g.
as for Rb atoms), anisotropic dipolar effects are shown to be detectable
under current experimental conditions [E. A. Donley {\it et al.}, Nature {\bf
412}, 295 (2001)].Comment: revised version, submitte
Moment of Inertia and Superfluidity of a Trapped Bose Gas
The temperature dependence of the moment of inertia of a dilute Bose gas
confined in a harmonic trap is determined. Deviations from the rigid value, due
to the occurrence of Bose-Einstein condensation, reveal the superfluid
behaviour of the system. In the noninteracting gas these deviations become
important at temperatures of the order of . The role of
interactions is also discussed.Comment: 10 pages, REVTEX, 1 figure attached as postscript fil
The 198Au beta-half-life in the metal Au revisited
The half-life of the beta-decay of 198Au has been measured for room
temperature and 12 K. The resulting values of T(RT) = 2.684 +- 0.004 d and T(12
K) = 2.687 +- 0.005 d agree well within statistical uncertainties. An evidence
for a temperature dependence of the half-life was not observed.Comment: accepted for publication in Eur. Phys. J.
RF Feedback and Detuning Studies for the BESSY Variable Pulse Length Storage Ring Higher Harmonic SC Cavities
For the feasibility of the BESSY VSR upgrade project of BESSY II two higher harmonic systems at a factor of 3 and 3.5 of the ring s RF fundamental of 500 MHz will be installed in the ring. Operating in continuous wave at high average accelerating field of 20 MV m and phased at zerocrossing, the superconducting cavities have to be detuned within tight margins to ensure stable operation and lowpower consumption at a loaded Q of 5 107. The field variation of the cavities is mainly driven by the repetitive transient beam loading of the envisaged complex bunch fill pattern in the ring. Within this work combined LLRF cavity and longitudinal beam dynamics simulation will demonstrate the limits for stable operation, especially the coupling between synchrotron oscillation and RF feedback settings. Further impact by beam current decay and top up injection shots are being simulate
Epidemiology, clinical presentation, radiological and laboratory features, treatment responses, and long-term outcome
Background A subset of patients with neuromyelitis optica spectrum disorders
(NMOSD) has been shown to be seropositive for myelin oligodendrocyte
glycoprotein antibodies (MOG-IgG). Objective To describe the epidemiological,
clinical, radiological, cerebrospinal fluid (CSF), and electrophysiological
features of a large cohort of MOG-IgG-positive patients with optic neuritis
(ON) and/or myelitis (n = 50) as well as attack and long-term treatment
outcomes. Methods Retrospective multicenter study. Results The sex ratio was
1:2.8 (m:f). Median age at onset was 31 years (range 6-70). The disease
followed a multiphasic course in 80% (median time-to-first-relapse 5 months;
annualized relapse rate 0.92) and resulted in significant disability in 40%
(mean follow-up 75 ± 46.5 months), with severe visual impairment or functional
blindness (36%) and markedly impaired ambulation due to paresis or ataxia
(25%) as the most common long-term sequelae. Functional blindness in one or
both eyes was noted during at least one ON attack in around 70%. Perioptic
enhancement was present in several patients. Besides acute tetra-/paraparesis,
dysesthesia and pain were common in acute myelitis (70%). Longitudinally
extensive spinal cord lesions were frequent, but short lesions occurred at
least once in 44%. Fourty-one percent had a history of simultaneous ON and
myelitis. Clinical or radiological involvement of the brain, brainstem, or
cerebellum was present in 50%; extra-opticospinal symptoms included
intractable nausea and vomiting and respiratory insufficiency (fatal in one).
CSF pleocytosis (partly neutrophilic) was present in 70%, oligoclonal bands in
only 13%, and blood-CSF-barrier dysfunction in 32%. Intravenous
methylprednisolone (IVMP) and long-term immunosuppression were often
effective; however, treatment failure leading to rapid accumulation of
disability was noted in many patients as well as flare-ups after steroid
withdrawal. Full recovery was achieved by plasma exchange in some cases,
including after IVMP failure. Breakthrough attacks under azathioprine were
linked to the drug-specific latency period and a lack of cotreatment with oral
steroids. Methotrexate was effective in 5/6 patients. Interferon-beta was
associated with ongoing or increasing disease activity. Rituximab and
ofatumumab were effective in some patients. However, treatment with rituximab
was followed by early relapses in several cases; end-of-dose relapses occurred
9-12 months after the first infusion. Coexisting autoimmunity was rare (9%).
Wingerchuk’s 2006 and 2015 criteria for NMO(SD) and Barkhof and McDonald
criteria for multiple sclerosis (MS) were met by 28%, 32%, 15%, 33%,
respectively; MS had been suspected in 36%. Disease onset or relapses were
preceded by infection, vaccination, or pregnancy/delivery in several cases.
Conclusion Our findings from a predominantly Caucasian cohort strongly argue
against the concept of MOG-IgG denoting a mild and usually monophasic variant
of NMOSD. The predominantly relapsing and often severe disease course and the
short median time to second attack support the use of prophylactic long-term
treatments in patients with MOG-IgG-positive ON and/or myelitis
Macroscopic Quantum Tunneling of a Bose Condensate
We study, by means of a variational method, the stability of a condensate in
a magnetically trapped atomic Bose gas with a negative scattering length and
find that the condensate is unstable in general. However, for temperatures
sufficiently close to the critical temperature the condensate turns out to be
metastable. For that case we determine in the usual WKB approximation the decay
rate of the condensate due to macroscopic quantum fluctuations. When
appropriate, we also calculate the decay rate due to thermal fluctuations. An
important feature of our approach is that (nonsingular) phase fluctuations of
the condensate are taken into account exactly.Comment: Invited paper for the Journal of Statistical Physic
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