Asymptotic analysis of multi-phase-field models: A thorough consideration of junctions.

The solutions of multi-phase-field models exhibit boundary layer behavior not only along the binary interfaces but also at the common contacts of three or more phases, i.e., junctions. Hence, to completely determine the asymptotic behavior of a multi-phase-field model, the inner analysis of both types of layers has to be carried out, whereas, traditionally, the junctions part is ignored. This is remedied in the current work for a phase-field model of simple grain growth in two spatial dimensions. Since the junction neighbourhoods are fundamentally different from those of the binary interfaces, pertinent matching conditions had to be derived from scratch, which is also accomplished in a detailed manner. The leading-order matching analysis of the junctions exposed the restrictions present on the interfacial arrangement at the common meeting point, while the next-to-the-leading one uncovered the law governing the instantaneous motion of the latter. In particular, it is predicted for the considered model that the Young's law is always satisfied at a triple point, whether or not it is at rest. Surprisingly, the mobilities and the curvatures of the involving interfaces as well as the driving forces on the them do not affect this result. However, they do play a significant role in determining the instantaneous velocity of the junction point. The study has opened up many new directions for future research.

Asymptotic analysis of multi-phase-field models: A thorough consideration of binary interfaces.

Although multi-phase-field models are applied extensively to simulate various pattern formations, their asymptotic analysis is not typically performed at a level of rigor common to their scalar counterparts. Most of the time, arguments given, such as for the justification of the selection of the bulk phases or the phasal composition of the interfaces between them, are only heuristic in nature. In particular, the reduction of the multi-phase-field models to two-phase ones, so as to ascertain the dynamical laws captured by them, can only be termed as hand waving, at best. It is also common to land the starting point of the analysis directly at a point where the binary interfaces have already formed and continue therefrom with the prediction of their instantaneous evolution. However, exactly how a given initial filling transitions to a state characterized by the presence of bulk phases separated by internal layers, and with what distribution, is rarely addressed. Moreover, a detailed and systematic study, focused on the numerical realization of the asymptotics predicted laws, has never been reported before for multi-phase-field models. In the current article, endorsing against these undesirabilities of the common presentations, a full-fledged asymptotic analysis of a multi-grain-growth phase-field model is put forth and numerically verified. However, the consideration is only limited to the analysis of binary interfaces; that of junctions (triple points, quadruple points, etc.) is deferred to a later work.

Multiphase-field model for surface diffusion and attachment kinetics in the grand-potential framework.

Grand-potential based multiphase-field model is extended to include surface diffusion. Diffusion is elevated in the interface through a scalar degenerate term. In contrast to the classical Cahn-Hilliard-based formulations, the present model circumvents the related difficulties in restricting diffusion solely to the interface by combining two second-order equations, an Allen-Cahn-type equation for the phase field supplemented with an obstacle-type potential and a conservative diffusion equation for the chemical potential or composition evolution. The sharp interface limiting behavior of the model is deduced by means of asymptotic analysis. A combination of surface diffusion and finite attachment kinetics is retrieved as the governing law. Infinite attachment kinetics can be achieved through a minor modification of the model, and with a slight change in the interpretation, the same model handles the cases of pure substances and alloys. Relations between model parameters and physical properties are obtained which allow one to quantitatively interpret simulation results. An extensive study of thermal grooving is conducted to validate the model based on existing theories. The results show good agreement with the theoretical sharp-interface solutions. The obviation of fourth-order derivatives and the usage of the obstacle potential make the model computationally cost-effective.

Treatment of landfill leachate by hybrid precipitation/microfiltration/nanofiltration process.

This paper describes a promising method to treat stabilized landfill leachate. Such method consists of a combination of chemical precipitation processes, a cost-effective technique with high potential to remove contaminants with foulant nature, microfiltration aimed at removing the produced precipitate and nanofiltration (NF) for final polishing. This study was carried out on a bench unit comprising a precipitation reactor associated with a submerged hollow-fiber microfiltration membrane module and a flat NF membrane cell operated in batch and continuous mode with a treating capacity of 0.1 L h(-1). Combining these processes yielded a clear and colorless permeate and proved to be very efficient at removing organic and inorganic matter. The results showed the importance of membrane processes to ensure treated landfill leachate quality. Also the precipitation associated with microfiltration as a pretreatment process is able to guarantee low membrane fouling due to the significant retention of humic substances which are known for their high potential to cause NF membrane fouling.

Assessment of annual whole-body occupational radiation exposure in education, research and industrial sectors in Ghana (2000-09).

Institutions in the education, research and industrial sectors in Ghana are quite few in comparison to the medical sector. Occupational exposure to radiation in the education, research and industrial sectors in Ghana have been analysed for a 10 y period between 2000 and 2009, by extracting dose data from the database of the Radiation Protection Institute, Ghana Atomic Energy Commission. Thirty-four institutions belonging to the three sectors were monitored out of which ∼65% were in the industrial sector. During the 10 y study period, monitored institutions ranged from 18 to 23 while the exposed workers ranged from 246 to 156 between 2000 and 2009. Annual collective doses received by all the exposed workers reduced by a factor of 2 between 2000 and 2009. This is seen as a reduction in annual collective doses in education/research and industrial sectors by ∼39 and ∼62%, respectively, for the 10 y period. Highest and least annual collective doses of 182.0 man mSv and 68.5 man mSv were all recorded in the industrial sector in 2000 and 2009, respectively. Annual average values for dose per institution and dose per exposed worker decreased by 49 and 42.9%, respectively, between 2000 and 2009. Average dose per exposed worker for the 10 y period was least in the industrial sector and highest in the education/research sector with values 0.6 and 3.7 mSv, respectively. The mean of the ratio of annual occupationally exposed worker (OEW) doses for the industrial sector to the annual OEW doses for the education/research sector was 0.67, a suggestion that radiation protection practices are better in the industrial sector than they are in the education/research sector. Range of institutional average effective doses within the education/research and industrial sectors were 0.059-6.029, and 0.110-2.945 mSv, respectively. An average dose per all three sectors of 11.87 mSv and an average dose per exposed worker of 1.12 mSv were realised for the entire study period. The entire study period had 187 instances in which exposed workers received individual annual doses >1 mSv, with exposed workers in the education/research sector primarily receiving most of this individual dose.

Response of blood pressure to maximum exercise in hypertensive patients under different therapeutic programs.

OBJECTIVE: To evaluate the behavior of blood pressure during exercise in patients with hypertension controlled by frontline antihypertension drugs. METHODS: From 979ergometric tests we retrospectively selected 49 hypertensive patients (19 males). The age was 53+/-12 years old and normal range rest arterial pressure (< or = 140/90 mmHg) all on pharmacological monotherapy. There were 12 on beta blockers; 14 on calcium antagonists, 13 on diuretics and 10 on angiotensin converting enzyme inhibitor. Abnormal exercise behavior of blood pressure was diagnosed if anyone of the following criteria was detected: peak systolic pressure above 220 mmHg, raising of systolic pressure > or = 10 mmHg/MET; or increase of diastolic pressure greater than 15 mmHg. RESULTS: Physiologic response of arterial blood pressure occurred in 50% of patients on beta blockers, the best one (p<0.05), in 36% and 31% on calcium antagonists and on diuretics, respectively, and in 20% on angiotensin converting enzyme inhibitor, the later the least one (p<0.05). CONCLUSION: Beta-blockers were more effective than calcium antagonists, diuretics and angiotensin-converting enzyme inhibitors in controlling blood pressure during exercise, and angiotensin converting enzyme inhibitors the least effective drugs.

Molecular characterization of methicillin-resistant Staphylococcus aureus (MRSA) in a university hospital in Italy.

The molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) in a university hospital in Italy was studied in a five-month period in 1996, during which all S. aureus isolated were collected. All MRSA isolates (95) and a sample of methicillin-susceptible S. aureus (20) were typed with a variety of phenotypic and genotypic methods. Clonal identities were determined by pulsed-field gel electrophoresis (PFGE) of chromosomal SmaI digests and, for MRSA isolates, by probing ClaI digests with a mecA probe and a Tn554 probe. Overall, MRSA represented 32.3% of all isolates, with very high percentages from the intensive care units (adult and neonatal). PFGE after restriction with SmaI resolved genomic DNA of 95 MRSA strains into 26 major PFGE patterns. The use of southern blot hybridization of ClaI genomic digests with mecA and Tn554 allowed us a significant increase in discrimination, differentiating at least 32 different clones. Two major clones, however, each sharing common ClaI-mecA and Tn554 type and PFGE pattern as well as a common resistance phenotype, represented more than 50% of all MRSA isolates. The recovery of these two clones in the majority of the isolates of adult and neonatal intensive care units, respectively, is indicative of typical nosocomial outbreaks and clonal spread. It is concluded that intensive care units are major areas requiring preventative interventions.

Efficacy and safety of teicoplanin in gram-positive pulmonary infections.

Teicoplanin is a new antibiotic obtained from a culture filtrate of Actinoplanes teichomyceticus with potent activity against aerobic and anaerobic gram-positive bacteria and having a high affinity for healthy or inflamed bronchial mucosa and pulmonary parenchyma. To investigate the efficacy and safety of this drug, we selected 13 patients suffering from lower respiratory tract infections caused by gram-positive organisms. Pathogens isolated from sputum or bronchial aspirate were: 8 Staphylococcus aureus, 1 Staphylococcus epidermidis, 3 Streptococcus pneumoniae and 1 Streptococcus species. We began treatment as monotherapy at the dosage of 400 mg daily (200 mg x 2) I.M. only after microbiological evaluation. 11 patients (84.6%) were clinically and bacteriologically cured, 1 (7.7%) showed definite clinical improvement but persistence of causative agent and 1 (7.7%) failed to respond. The mean treatment period was 8.3 days. No major adverse effect was observed. We conclude that teicoplanin is a very efficacious and well-tolerated antibiotic for therapy of gram-positive pulmonary infections.

Microbiological profile of teicoplanin.

The in-vitro antibacterial activity of teicoplanin, a new glycopeptide antibiotic, previously named teichomycin A2, was tested against 258 gram-positive anaerobic bacterial strains, recently clinically isolated, by measuring the minimum inhibitory concentrations. Comparisons were made with other drugs, clindamycin, rifampicin, netilmicin, enoxacin, vancomycin, widely utilized for the treatment of bacterial infections. Teicoplanin was very active against the tested species and showed the highest activity against all the tested strains, with a geometric mean of MICs, a MIC 50 and MIC 90 of 0.125, 0.12 and 0.5 microg/ml, respectively.

Evaluation of pefloxacin activity against recent clinical isolates.

The in-vitro antibacterial activity of pefloxacin, a new quinolone carboxylic acid, was tested against 1140 bacterial strains, recently clinically isolated, by measuring the minimum inhibitory concentrations. Comparisons were made with other quinolones (enoxacin, norfloxacin, flumekin, oxolinic acid, pipemidic acid) and other drugs (piperacillin, cefotaxime, ceftazidime, gentamicin, tobramycin, amikacin) widely used for the treatment of bacterial infections. Pefloxacin was very active against the tested species and was the most active drug against all the bacterial strains, with a geometric mean of MICs, a MIC 50 and MIC 90 of 0.27, 0.12 and 4 microg/ml respectively.

Jejunal bacterial overgrowth and intestinal permeability in children with immunodeficiency syndromes.

Seventeen paediatric patients with immunodeficiency syndromes (10 with selective IgA deficiency, four with panhypogammaglobulinaemia, and three with selective T cell deficiency) were investigated for bacterial overgrowth of the small intestine and gut permeability to macromolecules. Five of 12 patients showed viable bacterial counts of more than 2 x 10(5)/ml in jejunal fluid. Bacterial overgrowth was also confirmed indirectly by breath hydrogen determination, which was higher than 10 ppm in four of the five patients with positive jejunal culture. Gut permeability to lactulose and L-rhamnose was abnormal in 16 of the 17 immunodeficient patients, who also had higher mean urinary excretion ratios than control subjects-mean (SD) values were 0.216 (0.160) and 0.029 (0.002), respectively. These studies indicate that bacterial overgrowth of the small intestine is a common feature in immunodeficient patients, regardless of the immunological abnormality. Moreover, these patients have an increased gut permeability to macromolecules.

Evaluation of ciprofloxacin's activity against recent clinical isolates.

The in vitro antibacterial activity of ciprofloxacin, a new quinoline carboxylic acid, was tested against 1671 recently clinically isolated bacterial strains, by measuring the minimum inhibitory concentrations (MIC). Comparisons were made with other quinolones: nalidixic acid, norfloxacin, and other drugs: piperacillin, cefoxitin, cefotetan, ceftazidime, tobramycin, rifampin, tetracycline, chloramphenicol. Ciprofloxacin was very active against the tested species and was the most active drug against all the bacterial strains, with a geometric mean, a MIC50 and MIC90 of 0.27, 0.12 and 2 micrograms/ml, respectively.

Effectiveness of single daily intraperitoneal administration of aztreonam and cefuroxime in the treatment of peritonitis in continuous ambulatory peritoneal dialysis (CAPD).

To discover if the management of peritonitis in continuous ambulatory peritoneal dialysis (CAPD) may be effectively simplified by single daily i.p. administration of aztreonam (A) and cefuroxime (C), 10 adult CAPD patients (pts) with peritonitis were trained to start the following treatment procedure: a) sterile collection of dialysate effluent for cultures; b) 4 rapid in-and-out exchanges with antibiotic free dialysate; c) addition of 2 g C and 2 g A to a 2-L exchange for 6-h dwell time (the same dosage was repeated once a day in the overnight exchange); d) routine CAPD exchanges. Concentrations of C and A were measured in dialysate and serum of the patients 2, 12, 18, and 21-23 h after the i.p. administration: C remained within therapeutic range in all samples, while serum and dialysate A levels fell below such range 16 h after the i.p. administration. Seventeen peritonitis episodes occurred during the observation period (12 months): initial dialysate cultures grew Staph. aureus in 6 episodes, Staph epidermidis in 6, Pseudomonas aer. in 2, Streptococcus faecalis in 1, Citrobacter in 1, and Candida in 1. All patients but 1 (with Candida-positive culture) responded to this treatment with no relapse in 2 months. We conclude that once a day i.p. administration of 2 g aztreonam plus 2 g of cefuroxime is an effective and simple way of treating CAPD pts with gram-positive and gram-negative peritonitis.

Evaluation of in vitro activity of teicoplanin against recent clinical isolates.

The in vitro antibacterial activity of teicoplanin, a new glycopeptide antibiotic, previously named teichomycin A2, has been compared to that of five other chemoantibiotics: netilmicin, clindamycin, rifampicin, enoxacin and vancomycin. The minimum inhibitory concentration (MIC) values against 588 gram-positive strains, 561 facultative aerobes and 27 anaerobes, recently isolated from clinical specimens, were evaluated. Teicoplanin showed the highest activity against all the tested strains, with a geometrical mean of the MICs (GMM), a MIC50 and MIC90 of 0.123, 0.12 and 0.5 micrograms/ml respectively.

Comparative evaluation of the new Titertek Enterobac Rapid Automated System (TTE-RAS) for identification of members of the family Enterobacteriaceae.

The Titertek Enterobac Rapid Automated System (TTE-RAS; Flow Laboratories, SpA, Milan, Italy), a new semiautomated system for the identification of members of the family Enterobacteriaceae, was compared with the API 20E system (API System P.A., Montalieu Vercieu, France) by using 284 clinically isolated strains that were previously identified by conventional methods. Six strains from the American Type Culture Collection (Rockville, Md.) were included to evaluate the reproducibility of identification by both systems. Correct identifications at the species level were 93.7% with TTE-RAS and 96.1% with API 20E. Although some of the features of the TTE-RAS data base were not satisfactory, we consider this new miniaturized system to be a very valuable tool for the rapid identification of the most frequently isolated opportunistic bacteria.

[Bactericidal and potent antiadhesive activity of sulbenicillin]. / Studio dell'attivita battericida di sulbenicillina e del suo potere antiaderente.

Sulbenicillin, a wide broad spectrum penicillin, is active against a lot of gram positive and gram negative bacteria. The AA. studied the activity of this molecule against urinary infections causing germs, by evaluating two parameters: his antiadhesive capability and the Killing curves, in comparison with mezlocillin and piperacillin. An inhibition in adhesive capability of test-germs, due to sulbenicillin was obtained. Furthermore, resulting Killing curves showed more rapidity in action for sulbenicillin than for the two others molecules, versus resistant germs, like P. aeruginosa and S. faecalis.