A Discrete Elements Study of the Frictional Behavior of Fault Gouges.

A series of discrete elements simulations is presented for the study of fault gouges' frictional response. The gouge is considered to have previously undergone ultra-cataclastic flow and long-time consolidation loading. We explore the effect of different particle characteristics such as size, polydispersity, and also shearing velocities on gouge's response under the conditions met in the seismogenic zone. Monte-Carlo analyses suggest that the local stick-slip events disappear when averaging over a large number of numerical samples. Moreover, the apparent material frictional response remains almost unaffected by the spatial randomness of particles' position and by the particle's size distribution. On the contrary, the mean particle size controls the formation and thickness of the observed shear bands, which appear after the peak friction is met. Furthermore, the apparent friction evolution fits well to an exponential decay law with slip, which involves a particle size dependent critical slip distance. For the studied conditions and depth, the shearing velocity is found to play a secondary role on the apparent frictional response of the gouge, which highlights the importance of analyses involving multiphysics for studying the rheology of fault gouges. Besides improving the understanding of the underlying physics of the problem, the above findings are also useful for deriving pertinent constitutive models in the case of modeling with continuum theories.

Ongoing epidemic of blaVIM-1-positive Klebsiella pneumoniae in Athens, Greece: a prospective survey.

OBJECTIVES: To determine the current frequency and study the characteristics of VIM-1-producing Klebsiella pneumoniae isolates from bloodstream infections in Greek hospitals. METHODS: All blood isolates of K. pneumoniae were prospectively collected during 2004-06 in three teaching hospitals located in Athens. MICs of antibiotics were determined by the Etest. Extended-spectrum- (ESBL) and metallo-beta-lactamase (MBL) production was examined by clavulanate- and EDTA-based techniques, respectively. Isolates were typed by PFGE of XbaI-digested genomic DNA. Detection of bla(VIM-1) and mapping of the VIM-1-encoding integrons were performed by PCR and sequencing. Beta-lactamase activities were analysed by IEF and imipenem hydrolysis was assessed by spectrophotometry. VIM-1-encoding plasmids were transferred to Escherichia coli by conjugation and transformation and characterized by Inc/rep typing and RFLP. RESULTS: Sixty-seven (37.6%) of 178 K. pneumoniae blood isolates were bla(VIM-1)-positive (VPKP); 77.8% of these were from ICUs. All VPKP isolates were multidrug-resistant. The MICs of carbapenems for VPKP varied from the susceptible range to high-level resistance overlapping with those of MBL-negative isolates. The EDTA-imipenem synergy methods had reduced sensitivity in detecting VPKP isolates when the MICs were in the susceptible range. ESBL production was common among VPKP isolates (n = 45, 67.2%) as indicated by resistance to aztreonam and confirmed by a clavulanate-based double-disc synergy test. The responsible ESBL was always an SHV-5-type enzyme as indicated by IEF. PFGE identified eight clusters (A-H) of VPKP isolates with related (>80%) patterns, as well as four unique types. Both inter-hospital spread of several clones and genotypic similarities among susceptible, ESBL-positive and VPKP isolates were also observed. Location of bla(VIM-1) and expression of VIM-1 were studied in 12 isolates representing the eight PFGE clusters. In all isolates, bla(VIM-1) was part of a class 1 integron that also carried aacA4, dhfrI, aadA and sulI. In eight isolates (clusters C, D, G and H), the bla(VIM-1) integron was located in transferable IncN plasmids. A cluster F isolate carried a VIM-1-encoding, self-transferable plasmid that was not typeable by Inc/rep typing. VIM-1-encodingreplicons were not identified in three isolates (PFGE clusters A, B and E). VPKP isolates exhibited differences in imipenem-hydrolysing activities which, however, were not correlated with the respective carbapenem MICs. CONCLUSIONS: A multiclonal epidemic of bla(VIM-1)-carrying K. pneumoniae is under way in the majorhospitals in Greece. Microorganisms producing both VIM-1 and SHV-5 constitute the prevalent multidrug-resistant population of K. pneumoniae in this setting.

Elective intracoronary Micro-Stent II implantation without quantitative coronary angiography or intravascular ultrasound guidance and without subsequent anticoagulation: short- and long-term results.

Intracoronary stenting has been shown to reduce acute closure and restenosis rate in patients treated with coronary angioplasty. The use of high inflation pressures and intravascular ultrasound guidance allowed the substitution of anticoagulants with antiplatelet agents but increased the cost. The aim of this study was to investigate the effectiveness, safety, and long-term outcome of the elective implantation of a relatively new type of stent (Micro-Stent II), without the use of quantitative coronary angiography or intravascular ultrasound guidance and without subsequent anticoagulation. The study included 361 patients who underwent elective microstent implantation. Stent expansion was performed at 8 atm followed by higher inflation pressure at 14-20 atm. Heparin was given intraarterially only once immediately after the arterial sheath insertion. Ticlopidine was started at least 48 hours before the procedure and continued for 1 month while aspirin was continued indefinitely. All patients were followed up for 12.9 +/- 3.6 months. Short term outcome (first month): Stent implantation was successfully achieved in 361 of 366 patients (98.6%). Seven patients (1.9%) were excluded from the study and received anticoagulants because of a suboptimal result. In total, 423 stents were implanted. There was no subacute thrombosis, but acute vessel closure occurred in one patient (0.3%). Non-Q wave myocardial infarction occurred in six patients (1.7%), Q wave myocardial infarction occurred in one patient (0.3%), and only one death (0.3%) of nonischemic origin was reported. No major peripheral vascular complications were observed. Late results: Q or non-Q wave infarction occurred in 13 patients (3.6%), 26 patients (7.2%) underwent a repeat angioplasty, eight patients (2.2%) underwent coronary artery bypass grafting, and four patients (1.1%) died. Overall, 284 patients (78.7%) were free of symptoms, while 77 (21.3%) had recurrent coronary ischemia. In conclusion, Micro-Stent II implantation without quantitative coronary angiography or intravascular ultrasound guidance and without anticoagulation was found to be effective, safe, and with good long-term outcome.

First report of Cryptococcus laurentii meningitis and a fatal case of Cryptococcus albidus cryptococcaemia in AIDS patients.

We report the first case of Cryptococcus laurentii meningitis and a rare case of Cryptococcus albidus cryptococcaemia in AIDS patients. Both infections were treated with amphotericin B and flucytosine. The C. laurentii meningitis was controlled after 2 weeks of treatment with no evidence of infection 20 months later. The patient with C. albidus cryptococcaemia, despite the amphotericin B/flucytosine combination therapy, died on the 14th day of treatment. The minimum inhibitory concentrations (MICs) for C. laurentii, as determined by Etest on RPMI 1640 agar, were 0.25 microg ml(-1) of amphotericin B, 1.25 microg ml(-1) flucytosine, 4 microg ml(-1) fluconazole, 0.50 microg ml(-1) itraconazole and 1.0 microg ml(-1) of ketoconazole. The MIC of amphotericin B for C. albidus was 0.5 microg ml(-1), flucytosine 1.25 microg ml(-1), fluzonazole 4 microg ml(-1), itraconazole 0.5 microg ml(-1) and ketonazole 0.25 microg ml(-1). The agreement of the amphotericin B MIC values obtained in antibiotic medium 3 by the broth microdilution method, with those obtained on casitone medium by Etest, was within a two-dilution range for both isolates. C. laurentii may cause meningitis and may also involve the lungs in AIDS patients.

Postanginal sepsis syndrome with metastatic lung abscess in a young man.

A postanginal Sepsis Syndrome with metastatic lung abscess caused by Fusobacterium necrophorumin a 25-year-old previously healthy man is described. The incomplete and ineffective antibiotic treatment at onset of angina ended progressively in septicaemia and metastatic infections in a 3-week time period. The early parenteral use of Metronidazole based only on the clinical picture, the Gram stain findings and the strict anaerobic feature of the blood isolate in parallel with the long-term antibiotic treatment were possibly the main reasons for the good outcome of this serious infection.