Comparison of E-test with broth microdilution and disk diffusion for susceptibility testing of coryneform bacteria

The susceptibilities of 135 coryneform bacteria isolated from clinical samples to ampicillin (AMP), cephalothin (CR), cefoxitin (FOX), cefotaxime (CTX), erythromycin (E), ciprofioxacin (CIP), tetracycline (TE), amikacin (AK), vancomycin (VA), and rifampin (R) were determined by disk diffusion, broth microdilution, and the E-test. The following species (number of isolates in parentheses) were included: Corynebacterium urealyticum (30), Corynebacterium minutissimum (20), coryneform CDC group ANF-1 (20), Corynebacterium striatum (20), Corynebacterium jeikeium (15), coryneform CDC group 12 (8), Listeria monocytogenes (7), Corynebacterium xerosis (5), and other coryneform bacteria (10). Agreement within one twofold dilution between the E-test and broth microdilution was 31% (VA), 64% (AK), 71% (CTX), 77% (FOX and CIP), 79% (TE), 84% (AMP), 87% (E), and 88% (CR and R). For the 1,350 combinations of microorganisms and antimicrobial agents, 85 (6.3%) discrepancies in interpretive category were found (4.2% minor, 1.2% major, and 0.9% very major). Seventy (5.1%) disagreements in interpretive category were found between disk diffusion and the E-test (3.8% minor, 0.4% major, and 0.9% very major), and 85 (6.3%) disagreements were found between microdilution (reference method) and disk diffusion (4.2% minor, 0.5% major, and 1.5% very major). MICs obtained with the E-test were highly reproducible. No category discrepancy was observed for VA, despite quantitative results. Considering interpretive categories, there is a good overall agreement between the three methods studied here, but further evaluation of current methodologies for susceptibility testing is required when considering coryneform bacteria and determination of quantitative activity of antimicrobial agents

Impacto de las competencias gerenciales en las empresas del sector privado

El trabajo de grado describe algunas de las competencias gerenciales más importantes y el impacto en empresas del sector privadoThis graduate work describes some of the most important managment skills and the impact in the private secto

Determinación teórica y experimental de diagramas de interacción de esfuerzos en estructuras de fábrica y aplicación al análisis de construcciones históricas

Se propone una metodología de análisis para construcciones históricas de fábrica basada en el Método de los Estados Límite, haciendo uso de diagramas de interacción de esfuerzos, de forma similar a la práctica habitual en hormigón estructural o acero, pero incorporando las peculiaridades mecánicas del material estudiado. La tesis presenta la construcción teórica de los diagramas y la campaña experimental desarrollada para el contraste de la teoría. Se muestran los resultados de ensayos sobre probetas y muretes de fábrica de ladrillo sometidas a distintas combinaciones de esfuerzos planos, axil, momento y cortante. En los ensayos se detecta un fenómeno no recogido anteriormente en la literatura, consistente en una significativa sobre resistencia de la fábrica sometida a axiles excéntricos en su plano. Se presentan estudios numéricos de micromodelo que aclaran la naturaleza del fenómeno. Se incluyen tres ejemplos de aplicación de las técnicas propuestas a casos reales desarrollados sobre construcciones históricas de fábrica: La Catedral de Palma de Mallorca, el refuerzo y la ampliación de un puente de bóvedas del s. XIX en La Coruña y una cúpula barroca colapsada en 2000 en Zaragoza

Good Predictions and Bad Policies

Relatively little has been said on economic policy by participants in the debate on the realisticness of assumptions in economic models. What has been said is that a `Friedmanian´ methodology which accepts unrealistic assumptions and is only concerned with correct predictions is appropriate from the perspective of a practical economist who is in charge of designing policy. This paper tries to show that this is not true. Even if a model provides very accurate predictions of an event, its ability to provide valid explanations is determined by the realisticness of its underlying assumptions. Different assumptions yield different explanations and unrealistic assumptions tend to provide no explanation at all. There is a strong relation between the way a phenomenon is explained and understood and the actions that are consequently recommended. Therefore, a model based on unrealistic assumptions is not a reliable source of advice on policy.Milton Friedman, unrealistic assumptions, economic policy, economic models, instrumentalism.

Inverting Singlet and Triplet Excited States using Strong Light-Matter Coupling

In organic microcavities, hybrid light-matter states can form with energies that differ from the bare molecular excitation energies by nearly 1 eV. A timely question, given recent advances in the development of thermally activated delayed fluorescence materials, is whether strong light-matter coupling can be used to invert the ordering of singlet and triplet states and, in addition, enhance reverse intersystem crossing (RISC) rates. Here, we demonstrate a complete inversion of the singlet lower polariton and triplet excited states. We also unambiguously measure the RISC rate in strongly-coupled organic microcavities and find that, regardless of the large energy level shifts, it is unchanged compared to films of the bare molecules. This observation is a consequence of slow RISC to the lower polariton due to the delocalized nature of the state across many molecules and an inability to compete with RISC to the dark exciton reservoir, which occurs at a rate comparable to that in bare molecules

Triplet harvesting in the polaritonic regime: a variational polaron approach

We explore the electroluminescence efficiency for a quantum mechanical model of a large number of molecular emitters embedded in an optical microcavity. We characterize the circumstances under which a microcavity enhances harvesting of triplet excitons via reverse intersystem-crossing (R-ISC) into singlet populations that can emit light. For that end, we develop a time-local master equation in a variationally optimized frame which allows for the exploration of the population dynamics of chemically relevant species in different regimes of emitter coupling to the condensed phase vibrational bath and to the microcavity photonic mode. For a vibrational bath that equilibrates faster than R-ISC (in emitters with weak singlet-triplet mixing), our results reveal that significant improvements in efficiencies with respect to the cavity-free counterpart can be obtained for strong coupling of the singlet exciton to a photonic mode, as long as the singlet to triplet exciton transition is within the inverted Marcus regime; under these circumstances, we show the possibility to overcome the detrimental delocalization of the polariton states across a macroscopic number of molecules. On the other hand, for a vibrational bath that equilibrates slower than R-ISC (i.e., emitters with strong singlet-triplet mixing), we find that while enhancemnents in photoluminiscence can be obtained via vibrational relaxation into polaritons, this only occurs for small number of emitters coupled to the photon mode, with delocalization of the polaritons across many emitters eventually being detrimental to electroluminescence efficiency. These findings provide insight on the tunability of optoelectronic processes in molecular materials due to weak and strong light-matter coupling

Relaxation oscillations, pulses, and travelling waves in the diffusive Volterra delay-differential equation

The diffusive Volterra equation with discrete or continuous delay is studied in the limit of long delays using matched asymptotic expansions. In the case of continuous delay, the procedure was explicitly carried out for general normalized kernels of the form Sigma/sub n=p//sup N/ g/sub n/(t/sup n//T/sup n+1/)e/sup -t/T/, pges2, in the limit in which the strength of the delayed regulation is much greater than that of the instantaneous one, and also for g/sub n/=delta/sub n2/ and any strength ratio. Solutions include homogeneous relaxation oscillations and travelling waves such as pulses, periodic wavetrains, pacemakers and leading centers, so that the diffusive Volterra equation presents the main features of excitable media

Lenguaje y funciones ejecutivas en niños con desórdenes en el desarrollo del lenguaje

La evidencia indica que los niños con desórdenes o alteraciones en el desarrollo del lenguaje (DDL; denominados previamente TEL) presentan, además de sus dificultades con el lenguaje, un desempeño inferior en variadas tareas cognitivas; entre ellas, en tareas de funciones ejecutivas. No obstante, la evidencia no es concluyente e incluso contradictoria. El propósito de esta ponencia es triple: (1) revisar y discutir la evidencia sobre las funciones ejecutivas en niños con DDL; (2) presentar datos originales sobre funciones ejecutivas en niños con DDL, de acuerdo con dos modelos: (a) modelo multifactorial (funciones ejecutivas de cambio o flexibilidad, inhibición y actualización o memoria de trabajo) y (b) funciones ejecutivas según la dicotomía de funciones frías y cálidas, es decir, aquellas que incluyen o no la participación de factores afectivos y motivacionales; (3) discutir las implicancias hacia la evaluación y la intervención respecto a estos temas en el marco de la relación entre el lenguaje y la cognición en niños con DDL.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech