9,327 research outputs found
On the turbulent energy cascade in anisotropic magnetohydrodynamic turbulence
The problem of the occurrence of an energy cascade for Alfv\'enic turbulence
in solar wind plasmas was hystorically addressed by using phenomenological
arguments based to the weakness of nonlinear interactions and the anisotropy of
the cascade in wave vectors space. Here, this paradox is reviewed through the
formal derivation of a Yaglom relation from anisotropic Magnetohydrodynamic
equation. The Yaglom relation involves a third-order moment calculated from
velocity and magnetic fields and involving both Els\"asser vector fields, and
is particularly useful to be used as far as spacecraft observations of
turbulence are concerned
Charge and Magnetic Flux Correlations in Chern-Simons Theory with Fermions
Charge and magnetic flux bearing operators are introduced in Chern-Simons
theory both in its pure form and when it is coupled to fermions. The magnetic
flux creation operator turns out to be the Wilson line. The euclidean
correlation functions of these operators are shown to be local and are
evaluated exactly in the pure case and through an expansion in the inverse
fermion mass whenever these are present. Physical states only occur in the
presence of fermions and consist of composite charge-magnetic flux carrying
states which are in general anyonic. The large distance behavior of the
correlation functions indicates the condensation of charge and magnetic flux.Comment: Latex, 17 page
Determining the prevalence of malnutritionin hospitalised paediatric patients
Aim. To determine the prevalence of malnutrition in hospitalised paediatric patients at Red Cross War Memorial Children’s Hospital. Method. A 1-day cross-sectional survey was completed in all medical and surgical wards and some specialist outpatient clinics. Results. A total of 227 children participated in the study. Thirty-five per cent of patients were moderately malnourished (b -2 z-score), of whom 70% had no road to health card with them. Thirty-four per cent of children under 60 months of age received supplements in addition to a normal ward diet, 7.8% were enterally fed and less than 1% were parenterally fed. Almost 14% of children were found to be overweight/ obese, which is higher than the national average of 6%. The prevalence of HIV infection on the day of the audit was 18% across all age groups compared with the Western Cape antenatal prevalence of 15.7% (2005). Conclusion. The overall prevalence of undernutrition was 34%, which is comparable with similar studies. However, the proportion of overweight children (14%) was greater than the national average. In view of the level of malnutrition seen, a nutrition risk-screening tool, identifying risk factors for malnutrition such as food access and vulnerability, should be developed. The tool should be used to assess nutrition status and risk during the course of hospitalisation, in addition to planning appropriate nutrition care plan interventions for discharge
Prevalence of bacterial contamination of powdered infant feeds in a hospital enviroment
Background. The study arose as part of a best-practice nutrition model regarding the introduction of ready-to-use (RTU) infant feeds in place of powdered infant feeds (PIFs) as a standard formula for infants under the age of 1 year who are unable to be breastfed. Internationally and locally there is grave concern regarding the safety and efficacy of mixing PIFs, especially in a hospital setting, and the resultant bacterial contamination causing enteric infections, especially in premature, immunocompromised and sick infants.
Objective. To evaluate the prevalence of bacterial contamination of PIFs given to infants at Red Cross War Memorial Children’s Hospital, Cape Town.
Methods. Quantitative levels of bacterial contamination were determined and were expressed as colony-forming units (CFUs) per millilitre of sample. Aliquots of milk were inoculated onto agar, and the milk samples were then incubated at 25o C overnight (N = 10), 30o C overnight (N = 48) and 30o C for 6 hours (N = 34). Post-incubation milk samples were cultured again. Contamination was defined as any positive culture before administration (i.e. pre incubation) or > 102 CFU/ ml after administration (i.e. post incubation).
Results. Fifty samples of PIFs (N = 82) were contaminated pre incubation, with 25/82 samples (30.4%) being heavily contaminated (≥ 104 CFU/ml). Post incubation, 43/92 samples (46.7%) were contaminated with > 102 CFU/ml. The acidified PIFs appeared to have some bactericidal effect against some of the organisms, but not all.
Conclusions. RTU infant feeds are sterile and are recommended for use in all hospitalised infants. The results of this study indicate that even when milk is prepared in a controlled environment there is significant bacterial contamination of PIFs post production. As RTU feeds are now readily available in South Africa every attempt should be made to use a sterile RTU system for hospitalised infant
Sulle orme del consumatore affinity analysis e knowledge visualization per il processo decisionale
L\u2019articolo analizza i reali comportamenti di acquisto dell\u2019acquirente all\u2019interno del punto vendita e individua i pattern latenti pi\uf9 significativi attraverso un\u2019analisi di affinit\ue0 di 128.364 scontrini estratti da un dataset di 715.662 transazioni effettuate in un anno. Lo studio individua le strutture associative pi\uf9 ricorrenti relativamente alla singola merceologia. Attraverso la tecnica della Market Basket Analysis \ue8 stato possibile individuare le categorie merceologiche che creano \u201cpoli d\u2019attrazione\u201d sul punto vendita stimolando acquisti di altre categorie. In particolar modo, applicando le regole associative sul punto vendita \ue8 stato possibile identificare le \u201caree calde\u201d e le \u201caree fredde\u201d. L\u2019articolo evidenzia quindi alcune riflessioni sulle strategie che possono adottare gli store manager
Number statistics for -ensembles of random matrices: applications to trapped fermions at zero temperature
Let be the probability that a
-ensemble of random matrices with confining potential
has eigenvalues inside an interval of the real
line. We introduce a general formalism, based on the Coulomb gas technique and
the resolvent method, to compute analytically for large . We show that this probability scales for large
as , where is the Dyson index of the
ensemble. The rate function , independent of ,
is computed in terms of single integrals that can be easily evaluated
numerically. The general formalism is then applied to the classical
-Gaussian (), -Wishart () and
-Cauchy () ensembles. Expanding the rate function
around its minimum, we find that generically the number variance exhibits a non-monotonic behavior as a function of the size
of the interval, with a maximum that can be precisely characterized. These
analytical results, corroborated by numerical simulations, provide the full
counting statistics of many systems where random matrix models apply. In
particular, we present results for the full counting statistics of zero
temperature one-dimensional spinless fermions in a harmonic trap.Comment: 34 pages, 19 figure
Duality, Quantum Skyrmions and the Stability of an SO(3) Two-Dimensional Quantum Spin-Glass
Quantum topological excitations (skyrmions) are analyzed from the point of
view of their duality to spin excitations in the different phases of a
disordered two-dimensional, short-range interacting, SO(3) quantum magnetic
system of Heisenberg type. The phase diagram displays all the phases, which are
allowed by the duality relation. We study the large distance behavior of the
two-point correlation function of quantum skyrmions in each of these phases
and, out of this, extract information about the energy spectrum and
non-triviality of these excitations. The skyrmion correlators present a
power-law decay in the spin-glass(SG)-phase, indicating that these quantum
topological excitations are gapless but nontrivial in this phase. The SG phase
is dual to the AF phase, in the sense that topological and spin excitations are
respectively gapless in each of them. The Berezinskii-Kosterlitz-Thouless
mechanism guarantees the survival of the SG phase at , whereas the AF
phase is washed out to T=0 by the quantum fluctuations. Our results suggest a
new, more symmetric way of characterizing a SG-phase: one for which both the
order and disorder parameters vanish, namely , ,
where is the spin and is the topological excitation operators.Comment: 10 pages, 1 figur
A Rational Approach to the Ecological Transition in the Cruise Market: Technologies and Design Compromises for the Fuel Switch
Supporting policies to achieve a green revolution and ecological transition is a global trend. Although the maritime transport of goods and people can rightly be counted among the least polluting sectors, much can be done to further reduce its environmental footprint. Moreover, to boost the ecological transition of vessels, a whole series of international regulations and national laws have been promulgated. Among these, the most impactful on both design and operational management of ships concern the containment of air-polluting emissions in terms of GHG, NOx, SOx and PM. To address this challenge, it might seem that many technologies already successfully used in other transport sectors could be applied. However, the peculiar characteristics of ships make this statement not entirely true. In fact, technological solutions recently adopted, for example, in the automotive sector must deal with the large size of vessels and the consequent large amount of energy necessary for their operation. In this paper, with reference to the case study of a medium/large-sized passenger cruise ship, the use of different fuels (LNG, ammonia, hydrogen) and technologies (internal combustion engines, fuel cells) for propulsion and energy generation on board will be compared. By imposing the design constraint of not modifying the payload and the speed of the ship, the criticalities linked to the use of one fuel rather than another will be highlighted. The current limits of application of some fuels will be made evident, with reference to the state of maturity of the relevant technologies. Furthermore, the operational consequences in terms of autonomy reduction will be presented. The obtained results underline the necessity for shipowners and shipbuilders to reflect on the compromises required by the challenges of the ecological transition, which will force them to choose between reducing payload or reducing performance
Inflammatory markers as prognostic factors of survival in patients affected by hepatocellular carcinoma undergoing transarterial chemoembolization
Transarterial chemoembolization (TACE) is a good choice for hepatocellular carcinoma (HCC) treatment when surgery and liver transplantation are not feasible. Few studies reported the value of prognostic factors influencing survival after chemoembolization. In this study, we evaluated whether preoperative inflammatory factors such as neutrophil to lymphocyte ratio and platelet to lymphocyte ratio affected our patient survival when affected by hepatocellular carcinoma. Methods. We retrospectively evaluated a total of 72 patients with hepatocellular carcinoma that underwent TACE. We enrolled patients with different etiopathogeneses of hepatitis and histologically proven HCC not suitable for surgery. The overall study population was dichotomized in two groups according to the median NLR value and was analyzed also according to other prognostic factors. Results. The global median overall survival (OS) was 28 months. The OS in patients with high NLR was statistically significantly shorter than that in patients with low NLR. The following pretreatment variables were significantly associated with the OS in univariate analyses: age, Child-Pugh score, BCLC stage, INR, and NLR. Pretreated high NLR was an independently unfavorable factor for OS. Conclusion. NLR could be considered a good prognostic factor of survival useful to stratify patients that could benefit from TACE treatment
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