Many-Body Signatures of Collective Decay in Atomic Chains.

Fully inverted atoms placed at exactly the same location synchronize as they deexcite, and light is emitted in a burst (known as "Dicke's superradiance"). We investigate the role of finite interatomic separation on correlated decay in mesoscopic chains and provide an understanding in terms of collective jump operators. We show that the superradiant burst survives at small distances, despite Hamiltonian dipole-dipole interactions. However, for larger separations, competition between different jump operators leads to dephasing, suppressing superradiance. Collective effects are still significant for arrays with lattice constants of the order of a wavelength, and lead to a photon emission rate that decays nonexponentially in time. We calculate the two-photon correlation function and demonstrate that emission is correlated and directional, as well as sensitive to small changes in the interatomic distance. These features can be measured in current experimental setups, and are robust to realistic imperfections.

Spin-optomechanical coupling between light and a nanofiber torsional mode.

Light that carries linear or angular momentum can interact with a mechanical object, giving rise to optomechanical effects. In particular, a photon can transfer its intrinsic angular momentum to an object when the object either absorbs the photon or changes the photon polarization, as in an action/reaction force pair. Here, we demonstrate resonant driving of torsional mechanical modes of a single-mode tapered optical nanofiber using spin angular momentum. The nanofiber torsional mode spectrum is characterized by polarimetry, showing narrow natural resonances (Q≈2,000). By sending amplitude-modulated light through the nanofiber, we resonantly drive individual torsional modes as a function of the light polarization. By varying the input polarization to the fiber, we find the largest amplification of a mechanical oscillation (>35 dB) is observed when driving the system with light containing longitudinal spin on the nanofiber waist. These results present optical nanofibers as a platform suitable for quantum spin-optomechanics experiments.

Trypanosoma cruzi Detection in Colombian Patients with a Diagnosis of Esophageal Achalasia.

Achalasia is a motility disorder of the esophagus that might be secondary to a chronic Trypanosoma cruzi infection. Several studies have investigated esophageal achalasia in patients with Chagas disease (CD) in Latin America, but no related studies have been performed in Colombia. The goals of the present study were to determine the presence of anti-T. cruzi antibodies in patients with esophageal achalasia who visited a referral hospital in Bogotá, Colombia, and to detect the presence of the parasite and its discrete typing units (DTUs). This cross-sectional study was conducted in adult patients (18-65 years old) who were previously diagnosed with esophageal achalasia and from whom blood was drawn to assess antibodies against T. cruzi using four different serological tests. Trypanosoma cruzi DNA was detected by conventional polymerase chain reaction (cPCR) and quantitative polymerase chain reaction (qPCR). In total, 38 patients, with an average age of 46.6 years (standard deviation of ±16.2) and comprising 16 men and 22 women, were enrolled. Five (13.15%) patients were found to be positive for anti-T. cruzi antibodies by indirect immunofluorescence assay (IFA), and two patients who were negative according to IFA were reactive by both enzyme-linked immunosorbent assay and immunoblot (5.3%). Parasite DNA was detected in two of these seven patients by cPCR and in one of these by qPCR. The parasite DTU obtained was TcI. In summary, this study identified T. cruzi in Colombian patients with esophageal achalasia, indicating that digestive compromise could also be present in patients with chronic CD.

Dynamics of trapped atoms around an optical nanofiber probed through polarimetry.

The evanescent field outside an optical nanofiber (ONF) can create optical traps for neutral atoms. We present a non-destructive method to characterize such trapping potentials. An off-resonance linearly polarized probe beam that propagates through the ONF experiences a slow axis of polarization produced by trapped atoms on opposite sides along the ONF. The transverse atomic motion is imprinted onto the probe polarization through the changing atomic index of refraction. By applying a transient impulse, we measure a time-dependent polarization rotation of the probe beam that provides both a rapid and non-destructive measurement of the optical trapping frequencies.

Una mirada rápida al control de calidad interno en el quehacer diario del laboratorio de microbiología / A quick look at internal quality control in the daily routine of the microbiology laboratory

Resumen: el laboratorio de microbiología es un sistema complejo que implica muchos pasos para cada actividad, requiere de diversas personas y cuyos resultados analíticos generados deben ser lo más exactos posible. De no ser así, las consecuencias se pueden volver muy significativas, entre ellas, la realización de procedimientos innecesarios al paciente, los retrasos en la obtención de un resultado correcto y la ejecución de pruebas diagnósticas adicionales que se podían evitar. Estas consecuencias incrementan los gastos, tanto en términos económicos como en tiempo y esfuerzos del personal. La mayoría de las técnicas analíticas implican diversos procedimientos que están sujetos a cierto grado de imprecisión y posibilidad de error. Por tal razón, es importante la realización de un control de calidad interno que asegure que los productos finales o valores analíticos, que son producidos por un laboratorio, sean lo suficientemente fiables y adecuados para la finalidad que persiguen. De esta manera, un laboratorio microbiológico debe evaluar y documentar el desempeño de todos los aspectos de sus procedimientos, que incluye la calidad de la muestra, la eficiencia de los reactivos y antisueros, las coloraciones, los medios de cultivo, el funcionamiento de instrumentos o equipos, las cepas de referencia y la verificación o validación de los resultados obtenidos. El objetivo de este manuscrito es presentar una revisión bibliográfica sobre algunos elementos del laboratorio de microbiología susceptibles de control de calidad interno, como parte integral del trabajo diario del personal que labora en este. (AU)

Abstract: The microbiology laboratory is a complex system, which involves many steps for each activity and different people, and where analytical results must be as accurate as possible. If the results are inaccurate, the consequences can be significant, including the performance of unnecessary procedures, delays in obtaining a proper result and implementation additional diagnostic tests that could be avoided. These consequences increase spending both economics terms as time and efforts of the staff. Most analytical techniques involve several procedures that are subject to some degree of imprecision and possibility of error. Therefore, it's important to apply an internal quality control that ensure that finished products or analytical values which are produced by a laboratory are sufficiently reliable and appropriate to the objective pursued. In this way, a microbiological laboratory must assess and document the performance of all aspects of its procedures that includes the quality of the sample, the efficiency of reagents and antisera, the staining, the culture media, the operation of instruments or equipment, the strains of reference, and the verification or validation of the results obtained. The aim of this manuscript is to present a literature review about some elements of microbiology laboratory that are susceptible of internal quality control, as an integral part of the daily work of the staff working in this one. (AU)