Taming Self-Organization Dynamics to Dramatically Control Porous Architectures

We demonstrate templating of functional materials with unexpected and intricate micro- and nanostructures by controlling the condensation, packing, and evaporation of water droplets on a polymer solution. Spontaneous evaporation of a polymer solution induces cooling of the liquid surface and water microdroplet condensation from the ambient vapor. These droplets pack together and act as a template to imprint an entangled polymer film. This breath figure (BF) phenomenon is an example of self-organization that involves the long-range ordering of droplets. Equilibrium-based analysis provides many insights into contact angles and drop stability of individual drops, but the BF phenomenon remains poorly understood thus far, preventing translation to real applications. Here we investigate the dynamics of this phenomenon to separate out the competing influences and then introduce a modulation scheme to ultimately manipulate the water vapor− liquid equilibrium independently from the solvent evaporation. This approach to BF control provides insights into the mechanism, a rationale for microstructure design, and evidence for the benefits of dynamical control of self-organization systems. We finally present dramatically different porous architectures from this approach reminiscent of microscale Petri dishes, conical flasks, and test tubes.The financial support of Science Foundation Ireland (Grant No. 06/IN.1/I106) and the Australian Research Council grants scheme are gratefully acknowledged.This is the author accepted manuscript. The final version is available from the American Chemical Society via http://dx.doi.org/10.1021/acsnano.5b0608

Stress-Induced Variations in the Stiffness of Micro- and Nanocantilever Beams

The effect of surface stress on the stiffness of cantilever beams remains an outstanding problem in the physical sciences. While numerous experimental studies report significant stiffness change due to surface stress, theoretical predictions are unable to rigorously and quantitatively reconcile these observations. In this Letter, we present the first controlled measurements of stress-induced change in cantilever stiffness with commensurate theoretical quantification. Simultaneous measurements are also performed on equivalent clamped-clamped beams. All experimental results are quantitatively and accurately predicted using elasticity theory. We also present conclusive experimental evidence for invalidity of the longstanding and unphysical axial force model, which has been widely applied to interpret measurements using cantilever beams. Our findings will be of value in the development of micro- and nanoscale resonant mechanical sensors

Antimicrobial activity of daptomycin and selected comparators tested against bloodstream Staphylococcus aureus isolates from hemodialysis patients

Background: Patients on long-term hemodialysis are at a significantly higher risk for catheter-related bloodstream infections (BSI) than the general population. These infections are generally caused by Gram-positive organisms, especially Staphylococcus aureus. in the present study, we evaluated the antimicrobial susceptibility patterns of S. aureus causing BSI in dialysis patients compared to those causing BSI in other patient populations.Methods: the potencies of daptomycin and various comparator agents were evaluated by reference broth microdilution methods for S. aureus bloodstream isolates from dialysis patients (606 strains) in 43 hospitals in North America and Europe. Susceptibility patterns for the dialysis isolate set were compared to those S. aureus causing BSI in other patient populations in the same hospitals and time period.Results: Daptomycin was highly potent against S. aureus causing bacteremia in dialysis patients (MIC(50)/MIC(90), 0.25/0.5 mu g/ml). Vancomycin (MIC(50)/MIC(90), 1/1 mu g/ml) and linezolid (MIC(50)/MIC(90), 2/2 mu g/ml) showed similar potency, and overall susceptibility rates for the three antibiotics were 99.8-100.0% susceptible. Linezolid and vancomycin were four- to eight-fold less potent than daptomycin.Conclusions: the overall susceptibility patterns of S. aureus strains from dialysis patients were very similar to those of non-dialysis patients. (c) 2008 International Society for Infectious Diseases. Published by Elsevier B.V. All rights reserved.Cubist Pharmaceuticals, Inc.AB BIODISKAbbottAPIArpidaAstellasAstraZenecaAvexaBayerbioMerieuxCadenceCempraCerexaChironCornerstoneCubistDaiichiElanElancoEnantaGlaxoSmithKlineJohnson Et Johnson (Ortho McNeil)MerckNovartisOptimerOrdwayOsmoticsPacific BeachPeninsulaPfizerProtezReplidyneSchering-PloughSequoiaShionogiTheravanceTREK DiagnosticsViroPharmaWyethJMI Labs, N Liberty, IA 52317 USAUniversidade Federal de São Paulo, São Paulo, BrazilTufts Univ, Sch Med, Boston, MA 02111 USAUniversidade Federal de São Paulo, São Paulo, BrazilWeb of Scienc

Basic and advanced numerical performances relate to mathematical expertise but are fully mediated by visuospatial skills

Recent studies have highlighted the potential role of basic numerical processing in the acquisition of numerical and mathematical competences. However, it is debated whether high-level numerical skills and mathematics depends specifically on basic numerical representations. In this study mathematicians and nonmathematicians performed a basic number line task, which required mapping positive and negative numbers on a physical horizontal line, and has been shown to correlate with more advanced numerical abilities and mathematical achievement. We found that mathematicians were more accurate compared with nonmathematicians when mapping positive, but not negative numbers, which are considered numerical primitives and cultural artifacts, respectively. Moreover, performance on positive number mapping could predict whether one is a mathematician or not, and was mediated by more advanced mathematical skills. This finding might suggest a link between basic and advanced mathematical skills. However, when we included visuospatial skills, as measured by block design subtest, the mediation analysis revealed that the relation between the performance in the number line task and the group membership was explained by non-numerical visuospatial skills. These results demonstrate that relation between basic, even specific, numerical skills and advanced mathematical achievement can be artifactual and explained by visuospatial processing

Accuracy of three automated systems (MicroScan WalkAway, VITEK, and VITEK 2) for susceptibility testing of Pseudomonas aeruginosa against five broad-spectrum beta-lactam agents

One hundred recent clinical Pseudomonas aeruginosa isolates were used to assess the quantitative (MIC) and qualitative (susceptibility category) accuracies of the MicroScan WalkAway, VITEK, and VITEK 2 automated susceptibility test systems when five-broad spectrum beta-lactams, aztreonam, cefepime, ceftazidime, imipenem, and piperacillin-tazobactam, were tested. Isolates were selected so that the MICs for the isolates over-represented the MICs near the breakpoints to assess precisely the agreement between the results obtained with the automated systems and the results obtained by the reference tests. the categorical and MIC results from the automated systems were compared to the consensus result of three reference methods: broth microdilution, agar dilution, and disk diffusion. the consensus categorical testing (susceptibility and resistance) rates were 47 and 27%, respectively, for aztreonam; 59 and 14%, respectively, for cefepime; 44 and 43%, respectively, for ceftazidime; 71 and 19%, respectively, for imipenem; and 50 and 50%, respectively, for piperacillin-tazobactam. All systems tested exhibited a high, unacceptable level of very major (false-susceptible) errors for piperacillin-tazobactam (19 to 27%). Major (false-resistant) error rates were generally acceptable (0 to 3%), but minor error rates were elevated (8 to 32%) for cefepime (VITEK 2 and VITEK) and for aztreonam (all three systems), leading to consistent trends toward false resistance. Manufacturer reevaluation of these automated systems for the testing of selected beta-lactams with current clinical isolates of P. aeruginosa that exhibit contemporary resistance mechanisms would be prudent to minimize the potential for serious reporting errors.JMI Labs Inc, N Liberty, IA 52317 USAUniversidade Federal de São Paulo, Div Infect Dis, São Paulo, BrazilTufts Univ, Sch Med, Boston, MA 02111 USAUniversidade Federal de São Paulo, Div Infect Dis, São Paulo, BrazilWeb of Scienc

Global assessment of the antimicrobial activity of polymyxin B against 54 731 clinical isolates of Gram-negative bacilli: report from the SENTRY antimicrobial surveillance programme (2001-2004)

In total, 54 731 Gram-negative bacilli isolated worldwide between 2001 and 2004 from diverse sites of infection were tested for susceptibility to polymyxin B by the broth reference microdilution method, with interpretation of results according to CLSI (formerly NCCLS) guidelines. Polymyxin B showed excellent potency and spectrum against 8705 Pseudomonas aeruginosa and 2621 Acinetobacter spp. isolates (MIC50, 98% susceptible) against Citrobacter spp., Escherichia coli and Klebsiella spp., but activity was more variable against Enterobacter spp. (MIC50, 8 mg/L) against Burkholderia cepacia (11.8% susceptible), Serratia spp. (5.4% susceptible), indole-positive Proteus spp. (1.3% susceptible) and Proteus mirabilis (0.7% susceptible).Universidade Federal de São Paulo, Div Infect Dis, BR-04025010 São Paulo, BrazilJMI Labs, N Liberty, IA USATufts Univ, Sch Med, Boston, MA 02111 USAUniversidade Federal de São Paulo, Div Infect Dis, BR-04025010 São Paulo, BrazilWeb of Scienc

Antimicrobial susceptibility of Gram-positive bacteria isolated from European medical centres: results of the Daptomycin Surveillance Programme (2002-2004)

The antimicrobial susceptibility patterns of 9322 contemporary (2002-2004) Gram-positive bacterial isolates collected from 31 medical centres in 14 countries in Europe were evaluated by broth microdilution methods according to CLSI guidelines. the isolates collected comprised Staphylococcus aureus (4842 isolates), coagulase-negative staphylococci (CoNS; 1942 isolates), Enterococcus faecalis (1147 isolates), Enterococcus faecium (391 isolates), beta-haemolytic streptococci (660 isolates) and viridans group streptococci (340 isolates). the organisms were tested against daptomycin and more than 20 comparator agents in Mueller-Hinton broth, supplemented with calcium to 50 mg/L when testing daptomycin. Overall, methicillin (oxacillin) resistance rates were 26.7% and 77.0% for S. aureus (MRSA) and CoNS, respectively, and the vancomycin resistance rate among enterococci was 6.1%. MRSA rates varied from 0.6% in Sweden to 40.2-43.0% in Belgium, Greece, Ireland, the UK and Israel, and VRE rates varied from 0% in Switzerland to 21.2% in Ireland. More than 99.9% of isolates tested were considered susceptible to daptomycin according to breakpoints established by the United States Food and Drug Administration and the CLSI. Daptomycin was active against all Gram-positive species, with the highest MIC being 2, 8, 0.5 and 2 mg/L for staphylococci, enterococci, beta-haemolytic streptococci and viridans group streptococci, respectively. Daptomycin activity was not influenced adversely by resistance to other agents among staphylococci or enterococci. This novel lipopeptide (daptomycin) appears to be an excellent alternative therapeutic option for serious infections caused by multidrug-resistant Gram-positive organisms isolated in Europe.JMI Labs Inc, N Liberty, IA 52317 USAUniversidade Federal de São Paulo, São Paulo, BrazilTufts Univ, Sch Med, Boston, MA 02111 USAUniversidade Federal de São Paulo, São Paulo, BrazilWeb of Scienc