407 research outputs found
Threshold feedback control for a collective flashing ratchet: threshold dependence
We study the threshold control protocol for a collective flashing ratchet. In
particular, we analyze the dependence of the current on the values of the
thresholds. We have found analytical expressions for the small threshold
dependence both for the few and for the many particle case. For few particles
the current is a decreasing function of the thresholds, thus, the maximum
current is reached for zero thresholds. In contrast, for many particles the
optimal thresholds have a nonzero finite value. We have numerically checked the
relation that allows to obtain the optimal thresholds for an infinite number of
particles from the optimal period of the periodic protocol. These optimal
thresholds for an infinite number of particles give good results for many
particles. In addition, they also give good results for few particles due to
the smooth dependence of the current up to these threshold values.Comment: LaTeX, 10 pages, 7 figures, improved version to appear in Phys. Rev.
Integrated optics for astronomical interferometry. I. Concept and astronomical applications
We propose a new instrumental concept for long-baseline optical single-mode
interferometry using integrated optics which were developed for
telecommunication. Visible and infrared multi-aperture interferometry requires
many optical functions (spatial filtering, beam combination, photometric
calibration, polarization control) to detect astronomical signals at very high
angular resolution. Since the 80's, integrated optics on planar substrate have
become available for telecommunication applications with multiple optical
functions like power dividing, coupling, multiplexing, etc. We present the
concept of an optical / infrared interferometric instrument based on this new
technology. The main advantage is to provide an interferometric combination
unit on a single optical chip. Integrated optics are compact, provide
stability, low sensitivity to external constrains like temperature, pressure or
mechanical stresses, no optical alignment except for coupling, simplicity and
intrinsic polarization control. The integrated optics devices are inexpensive
compared to devices that have the same functionalities in bulk optics. We think
integrated optics will fundamentally change single-mode interferometry.
Integrated optics devices are in particular well-suited for interferometric
combination of numerous beams to achieve aperture synthesis imaging or for
space-based interferometers where stability and a minimum of optical alignments
are wished.Comment: 11 pages, 8 figures, accpeted by Astronomy and Astrophysics
Supplement Serie
Lymphome intravasculaire : à propos de deux observations autopsiques et revue de la littérature
Intravacular large B-cell lymphoma (LIV) is a rare entity individualized in the WHO classification since 2001 as a subtype of extranodal diffuse large B-cell lymphoma. We report two autopsic cases of LIV: a 77-year-old woman presenting with fever, dyspnea, antehypophyseal failure and a 54-year-old man presenting with fever, weight-loss, night-sweats and encephalopathy. They died respectively 10 and 7 months after the beginning of symptoms, without diagnosis. Neither infectious disease nor lymphomatous proliferation had been identified. From these two cases and our literature review, we insist on the importance of histopathological diagnosis on biopsy for this rare pathology which clinical diagnosis remains difficult
Toxicological study and efficacy of blank and paclitaxel-loaded lipid nanocapsules after i.v. administration in mice
PURPOSE: Lipid nanocapsules (LNCs) are solvent-free drug nanocarriers permitting entrapment of paclitaxel and increasing its antitumoural effect in animal models after i.v. injection. The tolerance and efficacy of LNCs after repeated dose i.v. administration were assessed in mice. The maximum tolerated dose (MTD) and 50 percent lethal dose (LD50) were studied.METHODS: Paclitaxel-loaded LNC formulation was given i.v. at the dose of 12 mg/kg per day for 5 consecutive days in comparison with blank LNCs and saline. Histological examination, complete blood counts and biochemical quantification were performed after a recovery of 7 days. Growth of NCI-H460 subcutaneous xenografts in nude mice receiving one of the aforementioned schedules was assessed. MTD and LD50 were determined by Irwin test. RESULTS: No mortality was observed in repeated injections studies. Histological studies revealed no lesions and no accumulation of lipids. Blood studies were normal. The tumoural growth was significantly reduced in the group treated by paclitaxel-loaded LNCs. The MTDs/LD50s of Taxol, paclitaxel-loaded LNCs and blank LNCs were 12/19.5, 96/216 and above 288/288 mg/kg, respectively. CONCLUSIONS: This study demonstrates that a five-day i.v. injection schedule of paclitaxel-loaded LNC dispersions induces no histological or biochemical abnormalities in mice and improves paclitaxel efficacy and therapeutic index in comparison with Taxol
The interferometric baselines and GRAVITY astrometric error budget
GRAVITY is a new generation beam combination instrument for the VLTI. Its
goal is to achieve microarsecond astrometric accuracy between objects separated
by a few arcsec. This accuracy on astrometric measurements is the most
important challenge of the instrument, and careful error budget have been
paramount during the technical design of the instrument. In this poster, we
will focus on baselines induced errors, which is part of a larger error budget.Comment: SPIE Meeting 2014 -- Montrea
Practical application and clinical impact of the WHO histopathological criteria on bone marrow biopsy for the diagnosis of essential thrombocythemia versus prefibrotic primary myelofibrosis
Aims: To evaluate the feasibility of the histopathological diagnosis of prefibrotic–early primary myelofibrosis (PM) as described in the World Health Organization (WHO) classification and to evaluate the clinical implications of prefibrotic–early PM in a series of patients previously diagnosed as having essential thrombocythemia (ET) according to the Polycythemia Vera Study Group criteria.
Methods and results: WHO criteria were applied to bone marrow biopsy specimens by two pathologists who then reclassified 127 cases as 102 ET (80.3%), 18 prefibrotic–early PM (14.2%) and seven fibrotic PM (5.5%). In 45 cases (35%), the final diagnosis was only reached by consensus. The megakaryocytic criteria that best discriminated between ET and prefibrotic–early PM were an increased nucleo–cytoplasmic ratio, presence of cloudlike nuclei, hyperchromatic-dysplastic nuclei, paratrabecular megakaryocytes and tight clusters. A histological score discriminated between ET (score ≤3) and PM (score ≥6), but 21 cases showed an intermediate ambiguous score. No significant differences were observed at diagnosis and at follow-up (median time 93 months) for thrombosis, major haemorrhage, laboratory data, transformation into overt myeloid metaplasia and survival.
Conclusions: The distinction between ET and prefibrotic–early PM is impaired by subjectivity in pathological practice and is of questionable clinical relevance, at least when considering individual patients
Characterization of integrated optics components for the second generation of VLTI instruments
Two of the three instruments proposed to ESO for the second generation
instrumentation of the VLTI would use integrated optics for beam combination.
Several design are studied, including co-axial and multi-axial recombination.
An extensive quantity of combiners are therefore under test in our
laboratories. We will present the various components, and the method used to
validate and compare the different combiners. Finally, we will discuss the
performances and their implication for both VSI and Gravity VLTI instruments.Comment: SPIE Astronomical Instrumentation 2008 in Marseille, France --
Equation (7) update
Depinning of kinks in a Josephson-junction ratchet array
We have measured the depinning of trapped kinks in a ratchet potential using
a fabricated circular array of Josephson junctions. Our ratchet system consists
of a parallel array of junctions with alternating cell inductances and
junctions areas. We have compared this ratchet array with other circular
arrays. We find experimentally and numerically that the depinning current
depends on the direction of the applied current in our ratchet ring. We also
find other properties of the depinning current versus applied field, such as a
long period and a lack of reflection symmetry, which we can explain
analytically.Comment: to be published in PR
Combination of blood tests for significant fibrosis and cirrhosis improves the assessment of liver-prognosis in chronic hepatitis C
BACKGROUND: Recent longitudinal studies have emphasised the prognostic value of noninvasive tests of liver fibrosis and cross-sectional studies have shown their combination significantly improves diagnostic accuracy.
AIM: To compare the prognostic accuracy of six blood fibrosis tests and liver biopsy, and evaluate if test combination improves the liver-prognosis assessment in chronic hepatitis C (CHC).
METHODS: A total of 373 patients with compensated CHC, liver biopsy (Metavir F) and blood tests targeting fibrosis (APRI, FIB4, Fibrotest, Hepascore, FibroMeter) or cirrhosis (CirrhoMeter) were included. Significant liver-related events (SLRE) and liver-related deaths were recorded during follow-up (started the day of biopsy).
RESULTS: During the median follow-up of 9.5 years (3508 person-years), 47 patients had a SLRE and 23 patients died from liver-related causes. For the prediction of first SLRE, most blood tests allowed higher prognostication than Metavir F [Harrell C-index: 0.811 (95% CI: 0.751-0.868)] with a significant increase for FIB4: 0.879 [0.832-0.919] (P = 0.002), FibroMeter: 0.870 [0.812-0.922] (P = 0.005) and APRI: 0.861 [0.813-0.902] (P = 0.039). Multivariate analysis identified FibroMeter, CirrhoMeter and sustained viral response as independent predictors of first SLRE. CirrhoMeter was the only independent predictor of liver-related death. The combination of FibroMeter and CirrhoMeter classifications into a new FM/CM classification improved the liver-prognosis assessment compared to Metavir F staging or single tests by identifying five subgroups of patients with significantly different prognoses.
CONCLUSIONS: Some blood fibrosis tests are more accurate than liver biopsy for determining liver prognosis in CHC. A new combination of two complementary blood tests, one targeted for fibrosis and the other for cirrhosis, optimises assessment of liver-prognosis
Age-related delay in information accrual for faces: Evidence from a parametric, single-trial EEG approach
Background: In this study, we quantified age-related changes in the time-course of face processing
by means of an innovative single-trial ERP approach. Unlike analyses used in previous studies, our
approach does not rely on peak measurements and can provide a more sensitive measure of
processing delays. Young and old adults (mean ages 22 and 70 years) performed a non-speeded
discrimination task between two faces. The phase spectrum of these faces was manipulated
parametrically to create pictures that ranged between pure noise (0% phase information) and the
undistorted signal (100% phase information), with five intermediate steps.
Results: Behavioural 75% correct thresholds were on average lower, and maximum accuracy was
higher, in younger than older observers. ERPs from each subject were entered into a single-trial
general linear regression model to identify variations in neural activity statistically associated with
changes in image structure. The earliest age-related ERP differences occurred in the time window
of the N170. Older observers had a significantly stronger N170 in response to noise, but this age
difference decreased with increasing phase information. Overall, manipulating image phase
information had a greater effect on ERPs from younger observers, which was quantified using a
hierarchical modelling approach. Importantly, visual activity was modulated by the same stimulus
parameters in younger and older subjects. The fit of the model, indexed by R2, was computed at
multiple post-stimulus time points. The time-course of the R2 function showed a significantly slower
processing in older observers starting around 120 ms after stimulus onset. This age-related delay
increased over time to reach a maximum around 190 ms, at which latency younger observers had
around 50 ms time lead over older observers.
Conclusion: Using a component-free ERP analysis that provides a precise timing of the visual
system sensitivity to image structure, the current study demonstrates that older observers
accumulate face information more slowly than younger subjects. Additionally, the N170 appears to
be less face-sensitive in older observers
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