370 research outputs found

    A Theory of Common Dealing with the Internet as an Innovative Distribution Channel

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    After the emergence of the Internet, an interesting question arises that what is its impact on the firms’ channel and pricing strategies. This paper applies game theory to study the strategic interactions between rational manufacturers, retailers, and consumers, and it generates the following results: 1. The presence of the Internet allows imperfectly competitive manufacturers to better coordinate their pricing, targeting, and channel strategies, thereby minimizing the agency costs involved in common dealing at the traditional outlets, which in turn enhances the manufacturers’ profits. 2. Exclusive dealing may and may not become more prevalent in the presence of the Internet. It all depends on the ratio of the population of switchers to the entire population of consumers. 3. The presence of the Internet allows a monopolistic manufacturer to screen consumers by serving different people at different outlets. Screening is less effective, however, in the case of imperfect competition. 4. A dynamic adjustment process is obtained which describes how a manufacturer should optimally change his channel and pricing strategies when the population of the Internet purchasers grows over time

    Dosimetric verification of vmat dose distribution with DELTA4 Phantom

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    Radiation Oncology, has changed a great deal, undergoing an innovation and technical development; there has been an evolution from conformal radiotherapy techniques (3D-CRT), through advanced modalities like intensity-modulated radiation therapy (IMRT) and next volumetric modulated arc therapy (VMAT). VMAT technique requires a dedicated QA (Quality Assurance) procedure for dosimetric verification of a planned dose distribution to check for the agreement between a dose distribution calculated by the Treatment Planning System (TPS) and the corresponding measured dose distribution. Since November 2010, in Radiation Therapy Department of “V. Fazzi” hospital in Lecce (Italy), 257 patients were treated with VMAT and the corresponding dose distribution were verified with the Delta4 diode array phantom. Parameters used in the comparison between calculated e measured dose are the dose agreement (DA), the distance to agreement (DTA) and the -index. The phantom measurements closely match the planned dose distributions in high and low dose-gradient region

    Atomistic modelling studies of fluorite- and perovskite-based oxide materials

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    Fast oxide-ion and proton conductors are the subject of considerable research due to their technological applications in sensors, ceramic membranes and solid oxide fuel cells (SOFCs). This thesis describes the use of computer modelling techniques to study point defects, dopants and clustering effects in fluorite-and perovskitetype ion conductors with potential SOFC applications. Bi2O3 related phases are being developed with the objective of high oxide-ion conductivities at lower operating temperatures than 1000°C, as in current generation SOFC electrolytes. Doped Bi2O3 phases have shown promise as materials capable of accomplishing this goal. First, the Y-doped phase, Bi3YO6, has been investigated including the ordering of intrinsic vacancies. The defect and dopant characteristics of Bi3YO6 have been examined and show that a highly mobile oxygen sub-lattice exists in this material. A preliminary structural modelling study of a new Re-doped Bi2O3 phase was also undertaken. A comprehensive investigation of the proton-conducting perovskites BaZrO3, BaPrO3 and BaThO3 is then presented. Our results suggest that intrinsic atomic disorder in BaZrO3 and BaThO3 is unlikely, but reduction of Pr4+ in BaPrO3 is favourable. The water incorporation energy is found to be less exothermic for BaZrO3 than for BaPrO3 and BaThO3, but in all cases the results suggest that the proton concentration would decrease with increasing temperature, in accord with experimental data. The high binding energies for all the dopant-OH pair clusters in BaPrO3 and BaThO3 suggest strong proton trapping effects. Finally, a study of multiferroic BiFeO3 is presented, in which the defect, dopant and migration properties of this highly topical phase are investigated. The reduction process involving the formation of oxygen vacancies and Fe2+ is the most favourable redox process. In addition, the results suggest that oxide-ion migration is anisotropic within this system.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

    L’evoluzione tecnologica in Radioterapia: modulazione volumetrica del fascio ed Adaptavtive Radiation Therapy

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    Le innovazioni in radioterapia sono volte all’aumento del gradiente di dose tra neoplasia e tessuto sano attraverso un miglioramento sia dell’erogazione del fascio sia del controllo dell’errore. La più importante novità nel delivering è la modulazione volumetrica della intensità del fascio. La novità nel controllo dell’errore è rappresentata dalla Adaptative Radiation Therapy (ART), che prevede l’adattamento della distribuzione di dose ad un target mobile o deformabile, seguendo il movimento d’organo (IGRT) e la deformazione e cambio di volume di tumore e degli organi a rischio. La posizione iniziale del target viene riprodotta attraverso il movimento del lettino, il movimento elettronico del fascio, il movimento del braccio dell’acceleratore e la modifica dell’apertura del collimatore. La ART off line individua e corregge errori sistematici che possono avere origine in diverse fasi del processo e si propagano fino alla fine dello stesso, presentandosi in modo identico e ricorrente in ciascuna frazione attraverso il monitoraggio (IGRT) del posizionamento del paziente durante le prime frazioni, allo scopo di adattare i margini di trattamento e/o i piani di trattamento per le restanti sedutesu base individuale. La ART on line corregge errori random (di “esecuzione”), che possono variare di giorno in giorno, poiché si possono presentare in modo diverso per ciascuna frazione del trattamento, attraverso il monitoraggio (IGRT) del posizionamento del paziente durante tutte le frazioni per la misura e la correzione giornaliera degli errori di setup del paziente

    Multi-Species Genomics-Enabled Selection for Improving Agroecosystems Across Space and Time

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    Plant breeding has been central to global increases in crop yields. Breeding deserves praise for helping to establish better food security, but also shares the responsibility of unintended consequences. Much work has been done describing alternative agricultural systems that seek to alleviate these externalities, however, breeding methods and breeding programs have largely not focused on these systems. Here we explore breeding and selection strategies that better align with these more diverse spatial and temporal agricultural systems

    SARS-CoV-2 serological profile in healthcare professionals of a Southern Italy hospital

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    Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the first coronavirus that has caused a pandemic. Assessing the prevalence of anti-SARS-CoV-2 in healthcare worker groups offers a unique opportunity to study the correlation between seroconversion and immunization because of their occupational exposure and a higher risk of contagion. The study enrolled 3242 asymptomatic employees of “Policlinico Riuniti”, Foggia. After the first screening, we collected sequential serum samples for up to 23 weeks from the same subjects. In order to perform a longitudinal follow-up study and get information about the titration of IgG levels, we analyzed data from subjects (33) with at least two consecutive serological IgG—positive tests; 62 (1.9%; 95% CI: 1.4–2.3) tested positive for at least one anti-SARS-CoV-2 antibody. The seroprevalence was lower in the high-risk group 1.4% (6/428; 95% CI: 0.5–2.6) vs. the intermediate-risk group 2.0% (55/2736; 95% CI: 1.5–2.5). Overall, within eight weeks, we detected a mean reduction of –17% in IgG levels. Our data suggest a reduction of about 9.27 AU/mL every week (R2 = 0.35, p = 0.0003). This study revealed the prevalence of SARS-CoV-2 antibodies among Foggia’s hospital healthcare staff (1.9%). Moreover, the IgG level reduction suggests that the serological response fades fast in asymptomatic infections

    Identification of na\uefve HCV-1 patients with chronic hepatitis who may benefit from dual therapy with peg-interferon and ribavirin

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    Background & Aims The pool of HCV genotype 1 patients likely to be cured by peg-interferon and ribavirin remains to be quantified. Methods In 1045 patients treated with peg-interferon and ribavirin, two therapeutic strategies were confronted: the first one evaluated only baseline variables associated with sustained virological response (SVR), and the second one included the rapid virologic response (RVR) in addition to baseline predictors. An 80% SVR rate was the threshold to retain a strategy as clinically relevant. Results Overall, 414 patients (39.6%) attained SVR. In the first strategy, the hierarchy of features independently associated with SVR was IL28B CC genotype (OR 5.082; CI 3.637-7.101), low (80% SVR threshold. Only 26.6% of no-RVR patients attained SVR. Among the 255 RVR patients, the likelihood of SVR was 61.8% in those with unfavorable predictors, 80% in the presence of a single predictor, and 100% when both predictors were present. By using this model, 200 patients (19.1%) were predicted to have an 80% chance of being cured with dual therapy. Conclusions A consistent subset of na\uefve HCV-1 patients, identified by some baseline characteristics and RVR, may benefit from dual treatment with peg-interferon and ribavirin. \ua9 2013 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved

    Epidemiological and virological investigation of a Norovirus outbreak in a resort in Puglia, Italy

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    <p>Abstract</p> <p>Background</p> <p>This paper describes the third large outbreak of Norovirus (NoV) gastroenteritis reported in the Southern Italy region of Puglia.</p> <p>Methods</p> <p>A matched case control study was conducted, on 19 July 2005, for investigating risk factors, using a structured questionnaire on food consumption. A multivariate analysis was conducted to estimate the adjusted Odds Ratios. Laboratory and environmental investigation were also performed.</p> <p>Results</p> <p>On the day of the study 41 cases were identified and 41 controls were enrolled. Controls were matched for age and gender. The mean age of the cases was 26 years old, and 58% were female. The clinical pattern of the disease was characterised by the presence of diarrhoea (95%), vomiting (70%), abdominal pain (51%) and fever (32%). Of the 41 cases included in the study, the majority (65%) were residents of Northern Italian regions. No food samples were available for testing. The matched univariate analysis revealed that cases were more likely to have consumed raw mussels, eggs or ice cubes made of tap water than controls. In the multivariate conditional logistic regression analysis, having eaten raw mussels or ice became more strongly associated with illness.</p> <p>All of the 20 faecal samples collected were tested for NoVs. Eighteen stools (90% of total examined) were positive by RT-PCR, and sequence analysis performed onto 3 samples confirmed the presence of a GGII NoV. No test specific for NoV was performed on water or food samples.</p> <p>Conclusion</p> <p>The most likely hypothesis supported by the findings of the epidemiological investigation was that illness was associated with raw mussels and ice, made with tap water. These hypothesis could not be confirmed by specific microbiologic testing for NoV in food or ice. The lack of clear knowledge of NoV as a major causative agent of epidemic outbreaks of gastroenteritis in Italy is due to the absence of timely reporting of the cases to the local public health offices and the uncommon practice of saving clinical samples for virological analysis after bacteriological testing.</p

    Impact of Chronic Lung Disease on Very Low Birth Weight infants: a collaborative study of the Italian Group of Neonatal Pneumology

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    Objective. To evaluate the incidence and risk factors for chronic lung disease in a population of very low birth weight infants. Methods. In a prospective multicentric trial all very low birth weight infants (&lt; 1500 g) accepted in 36 Italian Neonatal Intensive care units were studied from February 89 to January 99. For each patient were recorded maternal history, perinatal events, respiratory disease, infections, patent ductus arteriosus, retinopathy of prematurity, intraventricular haemorrhage and final outcome. Logistic regression analysis was performed in a multivariate assessment of risk factors for chronic lung disease. Results. In the study were included 1634 patients: 1387 infants survived beyond 36 weeks and 6.9% of them still oxygen dependent. The incidence of chronic lung disease was higher among babies with a gestational age of &lt; 28 weeks and weight \ub2 1000 g. The multivariate analysis showed that low birth weight, respiratory distress syndrome, persistent ductus arteriosus and sepsis were the main risk factors. Conclusions. In our study the incidence of chronic lung disease was relatively lo
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