Teoria dei gruppi e simmetrie: il modello a quark

In questa tesi si discutono i principali risultati della teoria dei gruppi per lo studio delle simmetrie e se ne presentano alcuni successi nel contesto della fisica fondamentale. Vengono studiate la teoria di Lie per i gruppi continui, la teoria delle rappresentazioni e la teoria delle algebre di Lie semisemplici, sottolineando gli aspetti più rilevanti di tali teorie in funzione della loro applicazione in fisica. Si studiano due simmetrie approssimate agenti a livello fondamentale: la simmetria di isospin, associata al gruppo SU(2), e la sua naturale generalizzazione in una simmetria associata al gruppo SU(3), accompagnando la trattazione con esempi e illustrazioni grafiche. Concentrando, infine, l'attenzione sul modello a quark, si mostra come sia possibile ricostruire la struttura a quark degli adroni leggeri studiando le simmetrie dell'interazione forte con i soli strumenti forniti dalla teoria dei gruppi

Diagnosing criticality in symmetric and chiral clock models

Quantum clock models are statistical mechanical spin models which may be regarded as a sort of bridge between the one-dimensional quantum Ising model and the one-dimensional quantum XY model. This thesis aims to provide an exhaustive review of these models using both analytical and numerical techniques. We present some important duality transformations which allow us to recast clock models into different forms, involving for example parafermions and lattice gauge theories. Thus, the notion of topological order enters into the game opening new scenarios for possible applications, like topological quantum computing. The second part of this thesis is devoted to the numerical analysis of clock models. We explore their phase diagram under different setups, with and without chirality, starting with a transverse field and then adding a longitudinal field as well. The most important observables we take into account for diagnosing criticality are the energy gap, the magnetisation, the entanglement entropy and the correlation functions

Parámetros edáficos, crecimiento y rendimiento del cultivo de trigo bajo diferentes manejos

Las prácticas de manejo pueden afectar la producción de los cultivos a través de su influencia en la distribución de la materia orgánica, la capacidad de almacenaje de agua del suelo y la dinámica de nutrientes. La experiencia se realizó en la EEA INTA Oliveros durante el ciclo 92/93, sobre un Argiudol ácuico. El objetivo del trabajo fue determinar el efecto del manejo sobre parámetros del suelo y el crecimiento y rendimiento del cultivo de trigo (Triticum aestivum L.) en una rotación trigo/soja (Glycine max (L.) Merr) realizada en forma continua durante 11 años y en una situación proveniente de una pastura antigua. Los tratamientos de labranza fueron: labranza convencional con arado de rejas (LC) y labranza vertical con cincel (LV) en la rotación trigo/soja y labranza convencional con arado de rejas en la situación proveniente de pastura (PC). En los tres tratamientos se aplicó nitrógeno en dosis de 100kg N ha-¹, dejando testigo sin fertilizar (100N y 0N, respectivamente). Se evaluaron propiedades del suelo en superficie (0-21cm), en distintas etapas del cultivo: densidad aparente (DA); porcentaje de agregados estables al benceno, alcohol y agua; porosidad estructural (PE); carbono orgánico total (COT) y humedad volumétrica (HV). Además, se determinó DA y HV a los 21-36cm y 36-70cm de profundidad. La densidad aparente del suelo a los 0-21cm y 21-36 cm de profundidad, fue significativamente mayor en LC (P?0,05) con respecto a LV y PC, en todas las fechas de muestreo. El tratamiento PC presentó en las tres fechas de muestreo un mayor porcentaje de agregados estables al benceno, alcohol, y agua; mayor PE y mayor contenido de COT (P?0,05), con respecto a los tratamientos LC y LV. Se halló una relación inversa entre DA y PE (r²= 0,70). El porcentaje de agregados estables al alcohol se correlacionó positivamente con el COT (r²=0,86). El contenido de humedad en superficie fue significativamente menor (P<0,05) en LC con respecto a LV y PC, en la mayor parte del ciclo del cultivo. A partir de los 21cm de profundidad, PC presentó los valores más elevados de HV. La acumulación de materia seca en LC fue el 45,8%, 64%, 73% y 73% de lo acumulado en PC en las etapas de macollaje, encañazón, antesis y madurez fisiológica, respectivamente; mientras que LV acumuló un 76,7%, 83,4%, 85% y 95% con respecto a PC, en las mismas etapas de crecimiento. El rendimiento del cultivo en LC fue el 73% de lo obtenido en PC (para 100N y 0N); mientras que para LV fue el 85,5% (parcelas 100N) y 93,1% (0N) de lo hallado en PC. La mayor compactación, la inestabilidad de la estructura, la menor acumulación de COT y humedad del suelo que presentó LC, pudieron incidir negativamente en el crecimiento y rendimiento del cultivo.The tillage practices can affect crop production through their influence on distribution of soil organic matter, available water-holding capacity and nutrient dynamics. The experiment was conducted at the EEA INTA Oliveros, during 1992/93 in an Aquic Argiudoll. The aim of the study was to determine the effects of management practices on soil properties and wheat (Triticum aestivum L.) growth and grain yield in a continuous wheat-soybean (Glycine max (L.) Merr) rotation (11 yr.) and a plot coming from a long-term pasture. Tillage treatments were: moldboard plowing (LC) and chisel plowing (LV) in wheat-soybean rotation, and moldboard plowing in the plot coming from pasture (PC), with two levels of nitrogen (0 and 100 kg N ha–1). Soil bulk density (DA); the percentage of stable aggregates to benzene, ethanol and water; structural porosity (PE), total organic carbon (COT), and volumetric water content (HV) in the 0-21cm layer were evaluated during the growing season. Soil bulk density and HV in the 21-36cm and 36-70cm layers were measured. Soil bulk density at 0-21 cm and 21-36 cm depth was significantly higher in LC with respect to LV and PC (P?0.05). The percentage of stable aggregates to pre-treatments with benzene, ethanol and water, PE and COT were significantly higher in PC with respect to LC and LV (P?0.05). Soil bulk density was inversely related to the PE (r2=0.70). The percentage of stable aggregates to ethanol was directly correlated to COT (r2=0.86). Volumetric water content in the top layer was lower in LC than in PC and LV. While PC showed the highest values in the depths of 21-36cm and 36-70cm. Dry matter under LC was 45.8%, 64%, 73% y 73% of that obtained in PC at tillering, stem elongation, anthesis and physiological maturity, respectively. Dry matter under LV was 76.7%, 83.4%, 85% y 95% with respect to PC, in the same growth stages. Grain yield in LC was 73% of that obtained in PC for both levels of N, while grain yield in LV was 85.5% and 93.1% of that obtained in PC for 0 and 100 kg N ha-1; respectively. A negative impact on wheat growth and grain yield could have been due to a greater soil compaction, soil structure instability, lower soil organic carbon and lower soil water content under LC

Parámetros físicos del suelo en condiciones no perturbadas y bajo laboreo

- Se estudió el efecto de dos sistemas de labranza sobre algunas propiedades del suelo y el rendimiento de soja. La experiencia se realizó sobre un Argiudol típico durante 1996. Los tratamientos fueron: siembra directa (SD), labranza vertical (LV) y un control no laboreado (T). Se determinó: densidad del suelo (DS); densidad máxima (DSMAX); compactación relativa (CR); porosidad estructural (PE); carbono orgánico total (COT), humificado (COH) y libre (COL) y humedad gravimétrica (HG). Se realizó el perfil cultural en LV y SD. La DS en SD fue significativamente mayor (P≤0,01) en superficie y en profundidad (1,22 y 1,37 Mg m-3, respectivamente). La PE en superficie fue LV>T>SD, mientras que en profundidad fue T>LV>SD. Hubo relación inversa entre CR y PE (r2 = 0,87). El perfil cultural mostró un 40% de agregados sin porosidad interna en SD. En superficie T presentó mayor COT, COH y COL. La DSMAX se correlacionó negativamente con el COT (r2 = 0,88). Al inicio del cultivo, SD presentó mayor HG (P≤0,01) que LV; en floración LV presentó mayor HG (P≤0,01). Si bien SD presentó mayor COT, COH y COL que LV, la mayor compactación observada en SD pudo incidir negativamente en el rendimiento del cultivo (fue el 50% de LV).The effect of two tillage systems on soil properties and soybean yield was studied. The experiment was carried out on a Typic Argiudoll during 1996. Treatments were: no-tillage (NT), chisel plow (CP) and a control not sown (CNS). Soil bulk density (SBD), maximum bulk density (MAXDB), relative compaction (RC), structural porosity (SP), total organic carbon (TOC), humified organic carbon (HOC), free organic carbon (FOC) and water content were evaluated. Soil profile analysis was performed for both tillage systems. Results of SBD in NT showed significant differences both at surface and in depth (1.22 and 1.37 Mg m-3, respectively). The SP at both sampling depths was in the order CP>CNS>NT and CNS>CP>NT, respectively. RC was inversely related to the SP (r2 = 0.87). Soil profiles showed a 40% of aggregates without internal porosity in NT. TOC, HOC and FOC on surface was higher (P≤0,01) in T as respect NT and CP. MAXBD was negatively correlated to TOC (r2 = 0.88). Water content in NT was higher (P≤0,01) than in CP at the initial stages, while it was higher (P≤0.01) in CP at flowering. Though TOC, HOC and FOC were slightly higher in NT than CP, higher compaction in NT could negatively influence on crop yield (50% lower than CP).Se estudió el efecto de dos sistemas de labranza sobre algunas propiedades del suelo y el rendimiento de soja. La experiencia se realizó sobre un Argiudol típico durante 1996. Los tratamientos fueron: siembra directa (SD), labranza vertical (LV) y un control no laboreado (T). Se determinó: densidad del suelo (DS); densidad máxima (DSMAX); compactación relativa (CR); porosidad estructural (PE); carbono orgánico total (COT), humificado (COH) y libre (COL) y humedad gravimétrica (HG). Se realizó el perfil cultural en LV y SD. La DS en SD fue significativamente mayor (P≤0,01) en superficie y en profundidad (1,22 y 1,37 Mg m-3, respectivamente). La PE en superficie fue LV>T>SD, mientras que en profundidad fue T>LV>SD. Hubo relación inversa entre CR y PE (r2 = 0,87). El perfil cultural mostró un 40% de agregados sin porosidad interna en SD. En superficie T presentó mayor COT, COH y COL. La DSMAX se correlacionó negativamente con el COT (r2 = 0,88). Al inicio del cultivo, SD presentó mayor HG (P≤0,01) que LV; en floración LV presentó mayor HG (P≤0,01). Si bien SD presentó mayor COT, COH y COL que LV, la mayor compactación observada en SD pudo incidir negativamente en el rendimiento del cultivo (fue el 50% de LV)

Fatores associados a proporção de resultados alterados nas mamografias de rastreamento: estudo ecológico

Objetivo: Analisar os fatores associados aproporção de resultados alterados nas mamografias de rastreamento.Métodos: Estudo ecológico, com dados do DATASUS/SISCAN, Atlas Brasil do Desenvolvimento Humano, Fundação SEADE, e Sistema e-Gestor, de 2016 a 2019, de mulheres de 50 a 69 anos dos 645 municípios de São Paulo (Brasil). Variáveis independentes foram associadas ao desfecho: proporção de cobertura insatisfatória de resultados de exames alterados (proporção Breast Imaging Reporting and Data System - BI-RADS® 0, 4 e 5&gt;10% dos exames realizados). Utilizou-se regressão múltipla de Poisson.Resultados: Maior proporção de mamografia de rastreamento (RP=1,20; IC95%: 1,00;1,45), maior porcentagem de pobres (RP=1,20; IC95%: 1,07;1,36), baixa (RP= 1,57; IC95%: 1,38;1,78) e média cobertura de Estratégia Saúde da Família (ESF) (RP=1,30; IC95%: 1,09;1,52) foram associados ao desfecho.Conclusão: Fatores socioeconômicos e de cobertura da ESF medeiam a proporção de mamografias alteradas no serviço público. Portanto, são aspectos importantes no combate ao câncer de mama.Palavras-chave: Neoplasias da mama. Mamografia. Técnicas e procedimentos diagnósticos. Políticas saúde. Estudos ecológicos

Rapid Mathematical Programming for Cooperative Truck Networks

Many biological assays require the ability to isolate and process single cells. Some research fields, such as the characterization of rare cells, the in vitro processing of stem cells, and the study of early stage cell differentiation, call for the additional and typically unmet ability to work with extremely low-count cell populations. In all these cases, efficient single-cell handling must be matched with the ability to work on a limited number of cells with a low cell loss rate. In this paper, we present a platform combining flow-through processing with deterministic (nonstatistical) patterning of cells coming from extremely small cell populations. We describe here modules using dielectrophoresis to control the position of cells flowing in microchannels and to pattern them in open microwells where cells were further analyzed. K562 cells continuously flowing at a speed of up to 100 μm/s were tridimensionally focused, aligned, and patterned inside microwells. A high-patterning yield and low cell loss rate were demonstrated experimentally: 15uL drops, containing an average of 15 cells, were transferred to the microchannel with an 83% yield, and cells were then patterned into microwells with a 100% yield. The deterministic patterning of cells was demonstrated both by isolating single cells in microwells and by creating clusters composed of a predetermined number of cells. Cell proliferation was assessed by easily recovering cells from open microwells, and a growth rate comparable to the control was obtained

COVID-19 Rapid Antigen Test Screening in Patients on Hemodialysis

Introduction. Patients receiving in-center hemodialysis are extremely vulnerable to COVID-19. It is unclear if routine screening of asymptomatic hemodialysis patients is an effective strategy to prevent COVID-19 outbreaks within the dialysis unit. Methods. We conducted a retrospective analysis of in-center hemodialysis patients who underwent bimonthly COVID-19 rapid antigen test screening from February 15(th) to December 26(th), 2021. Nasal rapid antigen testing was performed in all asymptomatic patients. All rapid antigen-positive tests were confirmed by RT-PCR nasopharyngeal swab. Besides universal rapid antigen screening, RT-PCR testing was conducted in all symptomatic patients and contacts of COVID-19 subjects. Results. Overall, 4079 rapid antigen tests were performed in 277 hemodialysis patients on chronic hemodialysis with a mean age of 68.4 +/- 14.6 years. Thirty-eight (0.9%) rapid antigen tests resulted positive. Only five (13.8%) positive-rapid antigen tests were also positive by RT-PCR testing. During the same period, 219 patients regularly screened by rapid antigen tests bimonthly underwent 442 RT-PCR nasopharyngeal swabs for clinical reasons. RT-PCR testing yielded a positive result in 13 (5.9%) patients. The time elapsed between PCR and the negative-rapid antigen test was 7.7 +/- 4.6 days (range 1.8-13.9 days). At the end of the follow-up, 6.4% of the population on in-center hemodialysis contracted COVID-19, and routine rapid antigen tests detected only 5 out of 18 (27.7%) COVID-19 cases. No outbreaks of COVID-19 were identified within the dialysis unit. Conclusion. Bimonthly rapid antigen screening led to the early diagnosis of COVID-19 in less than one-third of cases. The short incubation period of the new SARS-CoV-2 variants makes bimonthly test screening inadequate for an early diagnosis of COVID-19. More frequent tests are probably necessary to improve the utility of COVID-19 nasal rapid antigen test in patients on hemodialysis

Elongation Factor 1 alpha interacts with phospho-Akt in breast cancer cells and regulates their proliferation, survival and motility

BACKGROUND: Akt/PKB is a serine/threonine kinase that has attracted much attention because of its central role in regulating cell proliferation, survival, motility and angiogenesis. Activation of Akt in breast cancer portends aggressive tumour behaviour, resistance to hormone-, chemo-, and radiotherapy-induced apoptosis and it is correlated with decreased overall survival. Recent studies have identified novel tumor-specific substrates of Akt that may provide new diagnostic and prognostic markers and serve as therapeutic targets. This study was undertaken to identify pAkt-interacting proteins and to assess their biological roles in breast cancer cells. RESULTS: We confirmed that one of the pAkt interacting proteins is the Elongation Factor EF1alpha. EF1alpha contains a putative Akt phosphorylation site, but is not phosphorylated by pAkt1 or pAkt2, suggesting that it may function as a modulator of pAkt activity. Indeed, downregulation of EF1alpha expression by siRNAs led to markedly decreased expression of pAkt1 and to less extent of pAkt2 and was associated with reduced proliferation, survival and invasion of HCC1937 cells. Proliferation and survival was further reduced by combining EF1alpha siRNAs with specific pAkt inhibitors whereas EF1alpha downregulation slightly attenuated the decreased invasion induced by Akt inhibitors. CONCLUSION: We show here that EF1alpha is a pAkt-interacting protein which regulates pAkt levels. Since EF1alpha is often overexpressed in breast cancer, the consequences of EF1alpha increased levels for proliferation, survival and invasion will likely depend on the relative concentration of Akt1 and Akt2

Effect of packaging and storage conditions on some quality traits of bovine meat

Packaging is considered one of the most interesting technological aspects of food production and is a constantly evolving subject in food production. The type of packaging is important for the quality and safety of the product and for the visual appearance of the product to be immediately evaluated by consumers. The purpose of this study was to investigate the effect of four different types of modified atmosphere packaging (ATM) and vacuum packaging (VP) currently used by a company in central Italy, on the main qualitative characteristics of beef. For these two traditional and two new solutions with reduced environmental impact and compostable were evaluated. For each type of packaging, two different products were analyzed: steaks and hamburgers. The samples, immediately after production, were transported to the laboratory in refrigerated containers. Several parameters (color, pH, water holding capacity, drip loss, and microbiological characteristics) were evaluated at time 0 and after 7 (T7), 14 (T14) and 21 days (T21) of storage in the dark and at refrigeration temperature (+4°C ± 2°C). The results showed that the two types of packaging have very similar effects on the water-retaining capacity of the steaks. More noticeable differences were recorded by the colorimetric analysis: for both steaks and hamburgers, the products packaged in the traditional packaging appeared brighter and redder than those packaged in the new alternatives. The microbiological analysis of the steaks showed higher values in the “new” packaging. The formation of abundant ropy slime was observed in one of the samples in the “new” modified atmosphere package at T21. The results of this study showed that the technological characteristics (in particular, the color) and the microbiological characteristics of the steaks and hamburgers were better in “old” packaging, with a better appearance and a longer shelf life. The results obtained show how the research for eco-sustainable products for packaging must be addressed, taking into account the effect of the materials on the qualitative and hygienic- sanitary characteristics of the meat.https://www.pagepressjournals.org/index.php/ijfsam2023Paraclinical Science