1,243 research outputs found
The Algebra of Non-Local Charges in Non-Linear Sigma Models
We obtain the exact Dirac algebra obeyed by the conserved non-local charges
in bosonic non-linear sigma models. Part of the computation is specialized for
a symmetry group . As it turns out the algebra corresponds to a cubic
deformation of the Kac-Moody algebra. The non-linear terms are computed in
closed form. In each Dirac bracket we only find highest order terms (as
explained in the paper), defining a saturated algebra. We generalize the
results for the presence of a Wess-Zumino term. The algebra is very similar to
the previous one, containing now a calculable correction of order one unit
lower.Comment: 27 pages + figures available via ftp, Plain TeX, IFUSP/P-106
Comparative analysis of SAOCOM and Sentinel-1 data for surface soil moisture retrieval using a change detection method in a semiarid region (Douro River's basin, Spain)
The growing interest in low-frequency SAR for soil parameter retrieval has led to the development of new active L-band satellites, that will provide novel surface soil moisture products and retrieval possibilities; however, due to data unavailability so far, limited applications have investigated the use of change detection models using L-band satellite SAR data. Since July 2020, high revisit time, high-resolution acquisitions by the Satelite Argentino de Observacion COn Microondas (SAOCOM) Argentinian-Italian constellation have become accessible over Europe. Therefore, this research presents an investigation of the potential of multi-temporal L-band SAOCOM-1 for monitoring soil moisture variations underneath low and sparse agricultural vegetation. Moreover, it proposes a procedure for the mitigation of roughness contribution, by exploiting the entropy parameter derived from the dual-polarimetric decomposition. L-band sensitivity to soil moisture has been jointly evaluated in respect of Sentinel-1 C-band data by (1) comparing the temporal profiles of the backscattering coefficient, gamma(0), at VV and VH polarization, with the support of decomposition parameters (entropy and alpha), NDVI and precipitation data; (2) regression analysis with in situ soil moisture measurements, obtained by the REMEDHUS network in the Douro River basin (Spain); 3) evaluating the soil moisture retrievals obtained at C- and L- band using a change detection method. Finally, the effectiveness of the roughness normalization procedure for SAOCOM data has been validated using in situ data. L-band co-polarized gamma(0) has proved to be the best configuration for soil moisture inversion, being relatively insensitive to vegetation, as demonstrated by decomposition results and trend interpretation. Overall, regressions detected an R-2 22% higher at L-band than C-band, with values up to 0.74 for VV ((R) over bar (2)=0.32) and up to 0.47 for the VH band ((R) over bar (2)=0.14). Co-polarized data obtained R-2 on average 62.1% and 74.7% higher for SAOCOM and Sentinel-1. The retrieval models show an ubRMSD of 7.1% for SAOCOM data and 8.3% for Sentinel-1. The application of the proposed roughness normalization procedure to SAOCOM led to an ubRMSD of 6.7% improving the retrieved soil moisture trend by 7.9%. This exploratory analysis demonstrated SAOCOM data potential for soil moisture mapping and would serve as a foundation for more advanced retrieval procedures
A Nonliearly Dispersive Fifth Order Integrable Equation and its Hierarchy
In this paper, we study the properties of a nonlinearly dispersive integrable
system of fifth order and its associated hierarchy. We describe a Lax
representation for such a system which leads to two infinite series of
conserved charges and two hierarchies of equations that share the same
conserved charges. We construct two compatible Hamiltonian structures as well
as their Casimir functionals. One of the structures has a single Casimir
functional while the other has two. This allows us to extend the flows into
negative order and clarifies the meaning of two different hierarchies of
positive flows. We study the behavior of these systems under a hodograph
transformation and show that they are related to the Kaup-Kupershmidt and the
Sawada-Kotera equations under appropriate Miura transformations. We also
discuss briefly some properties associated with the generalization of second,
third and fourth order Lax operators.Comment: 11 pages, LaTex, version to be published in Journal of Nonlinear
Mathematical Physics, has expanded discussio
A combined approach to assess the potential coverage of a multicomponent protein-based vaccine
Meningococcal disease caused by Neisseria meningitidis sero- group B is a public health concern even in developed countries. Despite glycoconjugate vaccines against the other invasive sero- groups (A, C, W135, Y) are already available and successfully introduced in many countries, no vaccine is currently in use for prevention of serogroup B meningitis.
A protein based, multicomponent vaccine (4CMenB) has been developed and proposed for prevention of invasive serogroup B meningococcal disease (MenB). This novel vaccine has been tested in clinical trials and shown to be well tolerated and immunogenic, inducing bactericidal antibodies in infants, adolescents and adults. The high level of genetic and antigenic variability observed in MenB clinical isolates, requires a suitable method to assess the ability of the 4CMenB vaccine to cover genetically diverse menig- ococcal strains and to estimate the potential public health impact. To this purpose the Meningococcal Antigen Typing System (MATS) has been developed and recently described. This method provides a quick and reproducible tool to estimate the level of expression and immunoreactivity of each of the vaccine antigens, in any meningococcal isolate, and it is related to the likelihood that the isolate will be killed by sera from immunized subjects.
A multi-laboratory study involving several European countries, demonstrates that the 4CMenB has the potential to protect against a significant proportion of menB strains circulating in Europe.
The full article is free available on www.jpmh.or
Low-cost wearable multichannel surface EMG acquisition for prosthetic hand control
Prosthetic hand control based on the acquisition
and processing of surface electromyography signals (sEMG) is a
well-established method that makes use of the electric potentials
evoked by the physiological contraction processes of one or more
muscles. Furthermore intelligent mobile medical devices are on
the brink of introducing safe and highly sophisticated systems to
help a broad patient community to regain a considerable amount
of life quality. The major challenges which are inherent in such
integrated system’s design are mainly to be found in obtaining a
compact system with a long mobile autonomy, capable of
delivering the required signal requirements for EMG based
prosthetic control with up to 32 simultaneous acquisition
channels and – with an eye on a possible future exploitation as a
medical device – a proper perspective on a low priced system.
Therefore, according to these requirements we present a wireless,
mobile platform for acquisition and communication of sEMG
signals embedded into a complete mobile control system
structure. This environment further includes a portable device
such as a laptop providing the necessary computational power
for the control and a commercially available robotic handprosthesis.
Means of communication among those devices are
based on the Bluetooth standard. We show, that the developed
low cost mobile device can be used for proper prosthesis control
and that the device can rely on a continuous operation for the
usual daily life usage of a patient
Infections of the upper respiratory tract and counting of leukocytes in volleyball athletes
Submaximal and regular exercise tends to improve the immune response. On the other hand, athletes have a higher incidence of infection of the upper respiratory tract (URTI). The objective of the present study was to correlate the total episodes of URTI with the relative count of circulating neutrophils and lymphocytes in volleyball female athletes, aged 18.92±0.76 years (n=12), within the periods of training. The blood was collected at the end of the periods: Pre-competitive (M1), Competitive-I (M2) and Competitive-II (M3) and the URTI weekly. The athletes participated of 30 weeks of training and competitions. The Pearson correlation coefficient was used, p≤0.05. The results showed moderate to high correlations with 0.8 (p=0.001) and -0.76 (p=0.004) in M1; 0.68 (p=0.014) and -0.59 (p=0.042) in M2; followed by no significant correlations of 0.35 and -0.62 in M3, respectively for neutrophils and lymphocytes when coupled with URTI. The increased number of neutrophils and decreased number of lymphocytes were correlated to URTI and may be useful tools during long time training periods to prevent overload induced immunesuppression
Local structural studies of BaKFeAs using atomic pair distribution function analysis
Systematic local structural studies of BaKFeAs system are
undertaken at room temperature using atomic pair distribution function (PDF)
analysis. The local structure of the BaKFeAs is found to be
well described by the long-range structure extracted from the diffraction
experiments, but with anisotropic atomic vibrations of the constituent atoms
( = ). The crystal unit cell parameters, the
FeAs tetrahedral angle and the pnictogen height above the Fe-plane are seen
to show systematic evolution with K doping, underlining the importance of the
structural changes, in addition to the charge doping, in determining the
properties of BaKFeAs
Micro-scale investigation of carbonation process in partially serpentinized peridotites
The carbonation of ultramafic rocks is, theoretically, the most efficient reaction to trap CO2 irreversibly in
the form of solid carbonates, as predicted by equilibrium thermodynamic calculations. However, the success
of industrial or natural carbonation in large ultramafic aquifers or oceanic ultramafic exposures does not only
rely on the thermodynamic conditions of chemical reactions, but also on their feedback effects on the reactive
surface area and on the local porosity and permeability. In addition, side processes like serpentinization, redox
reactions, abiotic catalytic effects, and biological activity, can be expected in such complex natural system. Their
occurrence and implications on carbon speciation and carbon transfers during hydrothermal alteration of oceanic
peridotites have not been explored yet and requires detailed study of natural and/or experimental carbonation zones.
We have combined petrographic and electron microscopy with SIMS, Raman and FTIR microspectroscopy
on partially serpentinized peridotites drilled during the IODP leg 304 (30
N, MAR) in order to characterize
the mechanisms of peridotite carbonation at the fluid-mineral interface and identify the associated speciation of
carbon (inorganic and organic carbon occurrences). We present first results on zones located close to talc-tremolite
sheared veins in holes 1309B and D. Associations of carbonates, porous phyllosilicates and oxides are observed
in close vicinity of relict olivines that underwent a previous stage of serpentinization. The olivine-carbonate
interface is nanoporous which facilitates mass transfer between fluid and mineral. The phyllosilicate identified as
saponite results from the metasomatic replacement, during the carbonation stage, of previously formed serpentine.
These observations do not favour reaction-induced cracking but rather a transfer-controlled process in an open
system. Among the submicrometric dark clusters widely-distributed in saponite and in serpentine, vibrational
microspectroscopy reveals the presence of various types of organic compounds that tend to be located close to
micrometric sulphides grains.
Those results underline the microscale variability of carbon speciation within hydrothermally altered peridotites. The association of reduced carbon phases with the carbonation texture suggests that CO2 conversion
may not be limited to solid carbonate formation in natural systems and that biological activity and/or abiotic
CO2 reduction, possibly catalyzed by Ni-rich sulphides, can occur contemporaneously. This complex association
of reactions has to be unravelled further to determine the respective contribution of abiotic versus biological
processes and integrate them in carbon transfers modelling through the oceanic lithosphere
Non polynomial conservation law densities generated by the symmetry operators in some hydrodynamical models
New extra series of conserved densities for the polytropic gas model and
nonlinear elasticity equation are obtained without any references to the
recursion operator or to the Lax operator formalism. Our method based on the
utilization of the symmetry operators and allows us to obtain the densities of
arbitrary homogenuity dimensions. The nonpolynomial densities with logarithmics
behaviour are presented as an example. The special attention is paid for the
singular case for which we found new non homogenious solutions
expressed in terms of the elementary functions.Comment: 11 pages, 1 figur
Predicting death from surgery for lung cancer: a comparison of two scoring systems in two European countries
Objectives: Current British guidelines advocate the use of risk prediction scores such as Thoracoscore to estimate mortality prior to radical surgery for non-small cell lung cancer (NSCLC). A recent publication used the National Lung Cancer Audit (NLCA) to produce a score to predict 90 day mortality (NLCA score). The aim of this study is to validate the NLCA score, and compare its performance with Thoracoscore.
Materials and methods: We performed an internal validation using 2858 surgical patients from NLCA and an external validation using 3191 surgical patients from the Danish Lung Cancer Registry (DLCR). We calculated the proportion that died within 90 days of surgery. The discriminatory power of both scores was assessed by a receiver operating characteristic (ROC) and an area under the curve (AUC) calculation.
Results: Ninety day mortality was 5% in both groups. AUC values for internal and external validation of NLCA score and validation of Thoracoscore were 0.68 (95% CI 0.63–0.72), 0.60 (95% CI 0.56–0.65) and 0.60 (95% CI 0.54–0.66) respectively. Post-hoc analysis was performed using NLCA records on 15554 surgical patients to derive summary tables for 30 and 90 day mortality, stratified by procedure type, age and performance status.
Conclusions: Neither score performs well enough to be advocated for individual risk stratification prior to lung cancer surgery. It may be that additional physiological parameters are required; however this is a further project. In the interim we propose the use of our summary tables that provide the real-life range of mortality for lobectomy and pneumonectomy
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