Observing the intrinsic linewidth of a quantum-cascade laser: beyond the Schawlow-Townes limit

A comprehensive investigation of the frequency-noise spectral density of a free-running mid-infrared quantum-cascade laser is presented for the first time. It provides direct evidence of the leveling of this noise down to a white noise plateau, corresponding to an intrinsic linewidth of a few hundred Hz. The experiment is in agreement with the most recent theory on the fundamental mechanism of line broadening in quantum-cascade lasers, which provides a new insight into the Schawlow-Townes formula and predicts a narrowing beyond the limit set by the radiative lifetime of the upper level.Comment: 4 pages, 4 figure

Protein kinase C epsilon is required for macrophage activation and defense against bacterial infection

Imperial Cancer Research Fund, and grants FEDER 2FD-1997-1432 from Comisión Interministerial de Ciencia y Tecnología (CICYT) and PM98-0120 from Dirección General de Enseñanza Superior e Investigación Científica, Spain. F. Otto was supported by Deutsche Forschungsgemeinschaft grant Ot 134/1-1

Primary gas thermometry by means of laser-absorption spectroscopy: Determination of the Boltzmann constant

We report on a new optical implementation of primary gas thermometry based on laser absorption spectrometry in the near infrared. The method consists in retrieving the Doppler broadening from highly accurate observations of the line shape of the R(12) $\nu_{1} + 2 \nu_{2}^{\phantom{1}0} + \nu_{3}$ transition in CO$_{2}$ gas at thermodynamic equilibrium. Doppler width measurements as a function of gas temperature, ranging between the triple point of water and the gallium melting point, allowed for a spectroscopic determination of the Boltzmann constant with a relative accuracy of $\sim1.6\times10^{-4}$.Comment: Submitted to Physical Review Letter

Self-trapping in B-doped amorphous Si: Intrinsic origin of low acceptor efficiency

We have used ab initio simulations to study the doping efficiency of amorphous semiconductors, in particular of B-doped amorphous Si. We have found that even in the optimum case of substitutional doping in dangling-bond free amorphous Si the holes provided by B atoms do not behave as free carriers. Instead, they are trapped into regions with locally distorted bond angles. Thus, the effective activation energy for hole conduction turns to be the hole binding energy to these traps. In the case of high B concentration, the trap states move deeper in the gap and the binding energy and spatial localization of holes increase. In addition, B atoms have lower energies for shorter bond lengths, configurations favored in the vicinity of these traps

Absorption line shape recovery beyond the detection bandwidth limit: application to the precision spectroscopic measurement of the Boltzmann constant

22 pagesInternational audienceA theoretical model of the influence of detection bandwidth properties on observed line shapes in laser absorption spectroscopy is described. The model predicts artificial frequency shifts, extra broadenings and line asymmetries which must be taken into account in order to obtain accurate central frequencies and other spectroscopic parameters. This reveals sources of systematic effects most probably underestimated so far potentially affecting spectroscopic measurements. This may impact many fields of research, from atmospheric and interstellar physics to precision spectroscopic measurements devoted to metrological applications, tests of quantum electrodynamics or other fundamental laws of nature. Our theoretical model is validated by linear absorption experiments performed on H2O and NH3 molecular lines recorded by precision laser spectroscopy in two distinct spectral regions, near- and mid-infrared. Possible means of recovering original line shape parameters or experimental conditions under which the detection bandwidth has a negligible impact, given a targeted accuracy, are proposed. Particular emphasis is put on the detection bandwidth adjustments required to use such high-quality molecular spectra for a spectroscopic determination of the Boltzmann constant at the 1 ppm level of accuracy

The nuclear receptor LXRα controls the functional specialization of splenic macrophages.

Macrophages are professional phagocytic cells that orchestrate innate immune responses and have considerable phenotypic diversity at different anatomical locations. However, the mechanisms that control the heterogeneity of tissue macrophages are not well characterized. Here we found that the nuclear receptor LXRα was essential for the differentiation of macrophages in the marginal zone (MZ) of the spleen. LXR-deficient mice were defective in the generation of MZ and metallophilic macrophages, which resulted in abnormal responses to blood-borne antigens. Myeloid-specific expression of LXRα or adoptive transfer of wild-type monocytes restored the MZ microenvironment in LXRα-deficient mice. Our results demonstrate that signaling via LXRα in myeloid cells is crucial for the generation of splenic MZ macrophages and identify an unprecedented role for a nuclear receptor in the generation of specialized macrophage subsets

El correo electrónico en la consulta de Parkinson: ¿soluciones a un clic? // Use of e-mail for Parkinson's disease consultations: Are answers just a clic away?

INTRODUCCION: La problemática de los trastornos del movimiento (TM) es compleja y la duración y frecuencia de las consultas presenciales puede estar limitada por problemas de espacio y tiempo. Analizamos el funcionamiento de un servicio de atención por correo electrónico institucional para médicos de Atención Primaria (MAP) y pacientes en la Unidad de Trastornos del Movimiento (UTM). METODOS: Se revisaron retrospectivamente los correos electrónicos enviados y recibidos en un periodo de 4 meses, un año tras su implantación. La dirección se proporcionaba en consulta y mediante sesiones informativas a los MAP del área. Se analizaron datos clínicos y demográficos de los pacientes, tipo de interlocutor, número de consultas, motivo y actuaciones derivadas de ellas. RESULTADOS: Del 1 de enero al 30 de abril de 2015 se recibieron 137 correos de 63 pacientes (43% varones; edad 71 ± 10,5 años) diagnosticados de enfermedad de Parkinson (76%), parkinsonismos atípicos (10%) y otros (14%), y se enviaron 116 respuestas. En 20 casos (32%) fueron redactados por el paciente, en 38 (60%) por sus familiares y en 5 (8%) por MAP. Los motivos de consulta fueron clínicos en 50 casos (80%): deterioro clínico (16; 32%), nuevos síntomas (14; 28%), efectos secundarios o dudas sobre medicación (20; 40%). Como consecuencia, se adelantó una cita programada en 9 casos (14%), mientras que el resto se solucionaron por correo electrónico. En 13 (20%), el motivo de consulta fue burocrático: relacionado con citas (11, 85%) y solicitud de informe (2, 15%). La satisfacción fue generalizada, sin constituir una sobrecarga asistencial excesiva para los facultativos responsables. CONCLUSIONES: La implantación de una consulta por correo electrónico es factible en UTM, facilita la comunicación médico-paciente y la continuidad asistencial con Atención Primaria. // INTRODUCTION: The clinical problems of patients with movement disorders (MD) are complex, and the duration and frequency of face-to-face consultations may be insufficient to meet their needs. We analysed the implementation of an e-mail-based query service for our MD unit's patients and their primary care physicians (PCPs). METHODS: We retrospectively reviewed all consecutive emails sent and received over a period of 4 months, one year after implementation of the e-mail inquiry system. All patients received the during consultations, and PCPs, during scheduled informative meetings. We recorded and later analysed the profile of the questioner, patients’ demographic and clinical data, number of queries, reason for consultation, and actions taken. RESULTS: From 1 January 2015 to 30 April 2015, the service received 137 emails from 63 patients (43% male, mean age 71 ± 10.5) diagnosed with Parkinson's disease (76%), atypical parkinsonism (10%), and others (14%); 116 responses were sent. Twenty (32%) emails were written by patients, 38 (60%) by their caregivers, and 5 (8%) by their PCPs. The reasons for consultation were clinical in 50 cases (80%): 16 (32%) described clinical deterioration, 14 (28%) onset of new symptoms, and 20 (40%) side effects or concerns about medications. In 13 cases (20%), the query was bureaucratic: 11 were related to appointments (85%) and 2 were requests for clinical reports (15%). In response, new appointments were scheduled in 9 cases (14%), while the rest of the questions were answered by email. Patients were satisfied overall and the additional care burden on specialists was not excessive. CONCLUSIONS: Implementing an e-mail-based consultation system is feasible in MD units. It facilitates both communication between neurologists and patients and continued care in the primary care setting

Antibiotic-induced perturbations in gut microbial diversity influences neuro-inflammation and amyloidosis in a murine model of Alzheimer’s disease

Severe amyloidosis and plaque-localized neuro-inflammation are key pathological features of Alzheimer’s disease (AD). In addition to astrocyte and microglial reactivity, emerging evidence suggests a role of gut microbiota in regulating innate immunity and influencing brain function. Here, we examine the role of the host microbiome in regulating amyloidosis in the APP(SWE)/PS1(ΔE9) mouse model of AD. We show that prolonged shifts in gut microbial composition and diversity induced by long-term broad-spectrum combinatorial antibiotic treatment regime decreases Aβ plaque deposition. We also show that levels of soluble Aβ are elevated and that levels of circulating cytokine and chemokine signatures are altered in this setting. Finally, we observe attenuated plaque-localised glial reactivity in these mice and significantly altered microglial morphology. These findings suggest the gut microbiota community diversity can regulate host innate immunity mechanisms that impact Aβ amyloidosis

The Nuclear Receptor LXR Limits Bacterial Infection of Host Macrophages through a Mechanism that Impacts Cellular NAD Metabolism

Macrophages exert potent effector functions against invading microorganisms but constitute, paradoxically, a preferential niche for many bacterial strains to replicate. Using a model of infection by Salmonella Typhimurium, we have identified a molecular mechanism regulated by the nuclear receptor LXR that limits infection of host macrophages through transcriptional activation of the multifunctional enzyme CD38. LXR agonists reduced the intracellular levels of NAD+ in a CD38-dependent manner, counteracting pathogen-induced changes in macrophage morphology and the distribution of the F-actin cytoskeleton and reducing the capability of non-opsonized Salmonella to infect macrophages. Remarkably, pharmacological treatment with an LXR agonist ameliorated clinical signs associated with Salmonella infection in vivo, and these effects were dependent on CD38 expression in bone-marrow-derived cells. Altogether, this work reveals an unappreciated role for CD38 in bacterial-host cell interaction that can be pharmacologically exploited by activation of the LXR pathway

Equilibrium shapes and energies of coherent strained InP islands

The equilibrium shapes and energies of coherent strained InP islands grown on GaP have been investigated with a hybrid approach that has been previously applied to InAs islands on GaAs. This combines calculations of the surface energies by density functional theory and the bulk deformation energies by continuum elasticity theory. The calculated equilibrium shapes for different chemical environments exhibit the {101}, {111}, {\=1\=1\=1} facets and a (001) top surface. They compare quite well with recent atomic-force microscopy data. Thus in the InP/GaInP-system a considerable equilibration of the individual islands with respect to their shapes can be achieved. We discuss the implications of our results for the Ostwald ripening of the coherent InP islands. In addition we compare strain fields in uncapped and capped islands.Comment: 10 pages including 6 figures. Submitted to Phys. Rev. B. Related publications can be found at http://www.fhi-berlin.mpg.de/th/paper.htm