Analysis of the Inner Fluid-Dynamics of Scroll Compressors and Comparison between CFD Numerical and Modelling Approaches

Scroll compressors are widely adopted machines in both refrigeration systems and heat pumps. However, their efficiency is basically poor and constitutes the main bottleneck for improving the overall system performance. In fact, due to the complex machine fluid dynamics, scroll design is mainly based on theoretical and/or semi-empirical approaches. Designs strategies that do not guarantee an in-depth analysis of the machine behavior can be supplemented with a Computation Fluid Dynamics (CFD) approach. To this purpose, in the present work, the scroll compressor inner fluid dynamics is numerically analyzed in detail using two CFD software and two different modelling strategies for the axial gap. The analysis of the fluid evolution within the scroll wraps reveals unsteady phenomena developing during the suction and discharge phases, amplified by the axial clearance with negative impact on the main fluid flow (e.g., 1213% of average mass flow rate for an axial gap of 30 \ub5) and on the scroll performance (e.g., +26% of average absorbed power for an axial gap of 30 \ub5). In terms of accuracy, the k-" offers good performance on the estimation of average quantities but proves to be inadequate for capturing the complexity of the unsteady phenomena caused by the axial gap (e.g., 1219% of the absorbed power in case of perfect tip seal). The need for considering specific geometric details in design procedures is highlighted, and guidelines on the choice of the most suitable numerical model are provided depending on the analysis need

Systematic review of the literature and evidence-based recommendations for antibiotic prophylaxis in trauma : results from an italian consensus of experts

Antibiotic prophylaxis is frequently administered in severe trauma. However, the risk of selecting resistant bacteria, a major issue especially in critical care environments, has not been sufficiently investigated. The aim of the present study was to provide guidelines for antibiotic prophylaxis for four different trauma-related clinical conditions, taking into account the risks of antibiotic-resistant bacteria selection, thus innovating previous guidelines in the field

Elevated creatine kinase activity in primary hepatocellular carcinoma

BACKGROUND: Inconsistent findings have been reported on the occurrence and relevance of creatine kinase (CK) isoenzymes in mammalian liver cells. Part of this confusion might be due to induction of CK expression during metabolic and energetic stress. METHODS: The specific activities and isoenzyme patterns of CK and adenylate kinase (AdK) were analysed in pathological liver tissue of patients undergoing orthotopic liver transplantation. RESULTS: The brain-type, cytosolic BB-CK isoenzyme was detected in all liver specimens analysed. Conversely, CK activity was strongly increased and a mitochondrial CK (Mi-CK) isoenzyme was detected only in tissue samples of two primary hepatocellular carcinomas (HCCs). CONCLUSION: The findings do not support significant expression of CK in normal liver and most liver pathologies. Instead, many of the previous misconceptions in this field can be explained by interference from AdK isoenzymes. Moreover, the data suggest a possible interplay between p53 mutations, HCC, CK expression, and the growth-inhibitory effects of cyclocreatine in HCC. These results, if confirmed, could provide important hints at improved therapies and cures for HCC

Treatment of Acute Hypercalcemia.

Acute hypercalcemia is a life-threatening rather rare condition. This condition may represent an acute decompensation of a pre-existing hypercalcemia, or may be acute at the first instance of the electrolyte disturbance. Hypercalcemic patients can present with a broad spectrum of symptoms, but most of them are mild and non-specific. Hypercalcemia affects a group of organs, which are considered together as a syndrome. The supportive care and ABC assessment are the first step to preserve vital functions. Severity index criteria should be considered at admission: severe dehydratation, mental status alteration, renal impairment, cardiac arrhythmias, ionized calcium level, nausea or vomiting, low social level. The neurological status and the main parameters (arterial blood pressure, cardiac pulses, oxygen saturation, temperature) must be monitored in all patients. Five keystones in the treatment of the hypercalcemic crisis should be considered: (1) Restore normovolemia to prevent renal impairment, (2) Restore renal function and enhance renal excretion of calcium, (3) Dialysis, (4) Inhibit osteoclastic bone resorption, and (5) Reduce intestinal calcium absorption. Currently, bisphosphonates are the drugs of choice in most of the patients after adequate hydration, while non-bisphosphonates drugs, such as calcitonin, gallium nitrate and mithramycin, are now rarely used. It is pivotal to recognize and treat the disease, according to evidence-based guidelines. At the same time, a short diagnostic program should be started to focus to the appropriate treatment of the underlying disease

Randomized trial of combination therapy in relapser or non-responder HCV patients

The combination of interferon (IFN) and ribavirin (RIBA) has efficacy in previously non-responder (NR) or relapser (REL) HCV patients. However, the effect of increased dose of IFN associated with RIBA is not known. The aim of this study was to evaluate different IFN dose in combination with RIBA in NR or REL patients.We randomised 102 patients with biopsy-proven chronic HCV hepatitis to receive either 3 or 5 MU of recombinant IFN three times a week and RIBA (1000-1200 mg/die) for 6 months and followed for additional 6 months. Patients with cirrhosis were excluded from the study. The treatment was stopped at 4 months for cases with abnormal ALT levels and HCV-RNA positivity. The patients with undetectable HCV-RNA and normal ALT at the end of the treatment were defined as complete responders (CR), and those with the same state the end of follow-up were defined as long-term responders (LTR). There were 52 non-responders and 58 relapsers to prior IFN treatment. Mean age and histological severity of liver disease was comparable in the four groups. Four patients (4%) dropped out because skin lesions or severe anaemia. A large fraction of patients (68 cases, 64 %) developed mild anaemia but therapy was not discontinued. Full follow-up data are available on 102 cases. IFN 3 MU 3 times a week End of treatment End follow-up 25 previous NR 4 CR (16%) 21 NR (84%) 4 LTR (16%) 25 previous REL 15 CR (60%) 10 NR (40%) 12 LTR (46%) IFN 5 MU 3 times a week 27 previous NR 18 CR (66%) 9 NR (33%) 12 LTR (44%) 25 previous REL 22 CR (88%) 3 NR (12%) 17 LTR (68%) There was a statistically significant difference between previous REL and NR either at the end of the treatment and of the follow-up. There was difference between previous REL subjects randomised to receive 3 or 5 MU at the end of the therapy but not at the end of the follow-up. On the contrary, in previous NR an increased dose of IFN obtained a statistically (p<0.03) improvement of responses. Interestingly, a fraction (10-40%) of previous REL became NR at the combination therapy, this could indicate the appearance of viral quasispecies or genotypes highly resistant to antiviral drugs. In conclusions, when used in combination with RIBA, 5MU of IFN is able to enhance the response rate compared with 3MU, especially in previous NR. In NR or REL cases after combination therapy, new therapeutical approaches are needed