A supressor mutation in Escherichia coli

Nutritionally deficient mutant strains of bacteria (auxotrophs) are often capable of undergoing "reversion," giving rise to strains having the wild type nutritional state (prototrophs). It is usually impossible to determine whether the prototrophs are true back-mutants, or whether the wild phenotype is restored by the action of an independent suppressor mutation. An auxotroph requiring histidine was isolated from strain B/r of Escherichia coli (which grows well on minimal medium) after ultraviolet irradiation and layering(1). Some time later, the histidineless strain was irradiated with ultraviolet and subjected to penicillin screening(2,3) Among the mutants isolated was one requiring serine or glycine in addition to histidine. This diauxotroph, strain M2, was thus characterized by two growth factor requirements acquired separately and serially, presumably by two mutational steps

Nonlinearities and Parametric Amplification in Superconducting Coplanar Waveguide Resonators

Experimental investigations of the nonlinear properties of superconducting niobium coplanar waveguide resonators are reported. The nonlinearity due to a current dependent kinetic inductance of the center conductor is strong enough to realize bifurcation of the nonlinear oscillator. When driven with two frequencies near the threshold for bifurcation, parametric amplification with a gain of +22.4 dB is observed.Comment: 4 pages, 5 figures, 1 table. In version 2: Added appendix with model description and fits to measurements. Minor corrections and rephrasin

In situ anticaries efficacy of dentifrices with different formulations – A pooled analysis of results from three randomized clinical trials

Objectives Data generated from three similar in situ caries crossover studies presented the opportunity to conduct a pooled analysis to investigate how dentifrice formulations with different fluoride salts and combinations at concentrations of 1400–1450 ppm F, different abrasive systems and in some cases, carbomer (Carb), affect enamel caries lesion remineralization and fluoridation. Methods Subjects continuously wore modified partial dentures holding two gauze-covered partially-demineralized human enamel specimens for 14 days and brushed 2×/day with their assigned dentifrice: Study 1: sodium fluoride (NaF)/Carb/silica, NaF/silica, NaF + monofluorophosphate (MFP)/chalk; Study 2: NaF/Carb/silica, NaF + MFP/dical, amine fluoride (AmF)/silica; Study 3: NaF/Carb/silica, NaF + stannous fluoride (SnF2)/silica/hexametaphosphate (HMP). All studies included Placebo (0 ppm F) and/or dose-response controls (675 ppm F as NaF [675F-NaF]) ±Carb. Specimens were evaluated for percentage surface microhardness recovery (SMHR) and enamel fluoride uptake (EFU). Results All 1400–1450 ppm F dentifrices except NaF + SnF2/silica/HMP provided significantly greater lesion remineralization than Placebo (p < 0.0001): differences in SMHR ranged from 17.46% (NaF + MFP/dical) to 26.66% (AmF/silica). For EFU (back-transformed log EFU), all 1400–1450 ppm F dentifrices gave significant fluoride uptake compared to Placebo (p < 0.0001): increases in EFU ranged from 4.95 μg F/cm2 (NaF + SnF2/silica/HMP) to 16.32 μg F/cm2 (NaF/carb/silica). Dentifrices containing NaF or AmF as sole fluoride source provided the greatest remineralization and fluoridation; Carb addition did not alter fluoride efficacy; some excipients appeared to interfere with the cariostatic action of fluoride. Treatments were generally well-tolerated with ≤4 treatment-related adverse events per study. Conclusion Commercially available fluoride dentifrices varied greatly in their ability to remineralize and fluoridate early caries lesions. Clinical significance Fluoride dentifrices are the most impactful anticaries modality worldwide. While clinical caries trials have not consistently shown the superiority of one formulation over another, these findings using a sensitive in situ caries model indicated that dentifrices containing NaF or AmF as the sole fluoride source provided the greatest remineralization and fluoridation benefits

“completación dual concéntrica con bomba electrosumergible y flujo natural de un pozo en el oriente ecuatoriano para revestimiento de 9-5/8” y liner de 7”

Este proyecto tiene como finalidad mostrar una alternativa para el diseño de una Completación Dual Concéntrica con Bomba Electrosumergible y Flujo Natural para revestimiento de 9 5/8” y liner de 7”. Se procede a estudiar las propiedades de las rocas y fluidos del campo, se explica los tipos de yacimientos y se estudia brevemente los tipos de empuje presentes. Se realiza una explicación sobre las Completaciones Duales y se describe las herramientas usadas en nuestra completación, así como el equipo electrosumergible y el ensamblaje para producir por flujo natural. Se muestra el diseño de nuestra Completación Dual Concéntrica para revestimiento de 9 5/8” y Liner 7” con el respectivo análisis técnico y procedimiento operacional, además detallamos los cálculos de las profundidades de la completación dual de nuestro pozo ESPOL FEV-01. Se explica el estudio económico de la Completación Dual llegando a evaluar la rentabilidad de nuestro diseño, presentando las respectivas conclusiones y recomendaciones de una alternativa eficaz en la Completación de pozos en el Oriente Ecuatoriano.ESPO

Reflexiones desde la Ciencia Política en torno a la intervención social

Este trabajo presenta las tareas desempeñadas en el espacio de una beca de Iniciación a la Investigación en el Proyecto: &quot;Intervención social y procesos sociales: un estudio sobre la territorialidad, desterritorialidad y politicidad en la ciudad de Paraná&quot; , evaluado y aprobado por el Consejo Superior en septiembre de 2015 (Res. CS N°230/15). La problemática se fue configurando desde los interrogantes surgidos durante el desarrollo de investigaciones anteriores del equipo de investigación, en las que la cuestión de la intervención social fue uno de los ejes teóricos centrales. Se considera la relación entre la intervención social y los procesos sociales que generaron formas organizativas alrededor de determinados intereses materiales y simbólicos en espacios particulares, constituyendo politicidades también particulares. Así, las intervenciones sociales de cuño netamente neoliberal expresada en políticas focalizadas privilegiaron el territorio. Las diversificaciones de las políticas sociales hoy (universales, selectivas y focalizadas) dan cuenta de cierto cambio de la intervención social. Esta situación nos lleva a indagar la relación social-procesos sociales para conocer las características que adquieren los espacios, formatos organizativos y la politicidad actual en la ciudad de Paraná. Este es el espacio de inserción y experiencia como becaria que intento transmitir.Fil: Frank, Judit Evelyn. Universidad Nacional de Entre Río

Multicolor 3D Orbital Tracking

Feedback-based single-particle tracking (SPT) is a powerful technique for investigating particle behavior with very high spatiotemporal resolution. The ability to follow different species and their interactions independently adds a new dimension to the information available from SPT. However, only a few approaches have been expanded to multiple colors and no method is currently available that can follow two differently labeled biomolecules in 4 dimensions independently. In this proof-of-concept paper, the new modalities available when performing 3D orbital tracking with a second detection channel are demonstrated. First, dual-color tracking experiments are described studying independently diffusing particles of different types. For interacting particles where their motion is correlated, a second modality is implemented where a particle is tracked in one channel and the position of the second fluorescence species is monitored in the other channel. As a third modality, 3D orbital tracking is performed in one channel while monitoring its spectral signature in a second channel. This last modality is used to successfully readout accurate Forster Resonance Energy Transfer (FRET) values over time while tracking a mobile particle