Propagative Oscillations in Codirectional Polariton Waveguide Couplers.

We report on novel exciton-polariton routing devices created to study and purposely guide light-matter particles in their condensate phase. In a codirectional coupling device, two waveguides are connected by a partially etched section that facilitates tunable coupling of the adjacent channels. This evanescent coupling of the two macroscopic wave functions in each waveguide reveals itself in real space oscillations of the condensate. This Josephson-like oscillation has only been observed in coupled polariton traps so far. Here, we report on a similar coupling behavior in a controllable, propagative waveguide-based design. By controlling the gap width, channel length, or propagation energy, the exit port of the polariton flow can be chosen. This codirectional polariton device is a passive and scalable coupler element that can serve in compact, next generation logic architectures.

Collective fluid dynamics of a polariton condensate in a semiconductor microcavity.

Semiconductor microcavities offer unique systems in which to investigate the physics of weakly interacting bosons. Their elementary excitations, polaritons-mixtures of excitons and photons-can accumulate in macroscopically degenerate states to form various types of condensate in a wide range of experimental configurations, under either incoherent or coherent excitation. Condensates of polaritons have been put forward as candidates for superfluidity, and the formation of vortices as well as elementary excitations with linear dispersion are actively sought as evidence to support this. Here, using a coherent excitation triggered by a short optical pulse, we have created and set in motion a macroscopically degenerate state of polaritons that can be made to collide with a variety of defects present in the microcavity. Our experiments show striking manifestations of a coherent light-matter packet, travelling at high speed (of the order of one per cent of the speed of light) and displaying collective dynamics consistent with superfluidity, although one of a highly unusual character as it involves an out-of-equilibrium dissipative system. Our main results are the observation of a linear polariton dispersion accompanied by diffusionless motion; flow without resistance when crossing an obstacle; suppression of Rayleigh scattering; and splitting into two fluids when the size of the obstacle is comparable to the size of the wave packet. This work opens the way to the investigation of new phenomenology of out-of-equilibrium condensates.

Transcranial Doppler ultrasound in the diagnosis of brain death. Is it useful or does it delay the diagnosis?

Transcranial Doppler ultrasound is able to demonstrate cerebral circulatory arrest associated to brain death, being especially useful in sedated patients, or in those in which complete neurological exploration is not possible. Transcranial Doppler ulstrasound is a portable, noninvasive and high-availability technique. Among its limitations, mention must be made of the absence of acoustic windows and false-negative cases. In patients clinically diagnosed with brain death, with open skulls or with anoxia as the cause of death, cerebral blood flow can be observed by ultrasound, since cerebral circulatory arrest is not always synchronized to the clinical diagnosis. The diagnostic rate is therefore time-dependent, and this fact that must be recognized in order to avoid delays in death certification. Despite its limitations, transcranial Doppler ulstrasound helps solve common diagnostic problems, avoids the unnecessary consumption of resources, and can optimize organ harvesting for transplantation.

Build up of off-diagonal long-range order in microcavity exciton-polaritons across the parametric threshold.

We report an experimental study of the spontaneous spatial and temporal coherence of polariton condensates generated in the optical parametric oscillator configuration, below and at the parametric threshold, and as a function of condensate area. Above the threshold we obtain very long coherence times (up to 3 ns) and a spatial coherence extending over the entire condensate (40 µm). The very long coherence time and its dependence on condensate area and pump power reflect the suppression of polariton-polariton interactions by an effect equivalent to motional narrowing.

Clinico-radiological related to early brain death factors.

OBJECTIVE: To identify clinical and radiological factors associated to early evolution to brain death (BD), defined as occurring within the first 24 h. DESIGN: A retrospective cohort study was made covering the period 2015-2017. SETTING: An adult Intensive Care Unit (ICU). PATIENTS/METHODS: Epidemiological, clinical and imaging (CT scan) parameters upon admission to the ICU in patients evolving to BD. RESULTS: A total of 166 patients with BD (86 males, mean age 62.7 years) were analyzed. Primary cause: intracerebral hemorrhage 42.8%, subarachnoid hemorrhage 18.7%, traumatic brain injury 17.5%, anoxia 9%, stroke 7.8%, other causes 4.2%. Epidemiological data: arterial hypertension 50%, dyslipidemia 34%, smoking 33%, antiplatelet medication 21%, alcoholism 19%, anticoagulant therapy 15%, diabetes 15%. The Glasgow Coma Score (GCS) upon admission was 3 in 68.8% of the cases in early BD versus in 38.2% of the cases in BD occurring after 24 h (p = 0.0001). Eighty-five patients presented supratentorial hematomas with a volume of 90.9 ml in early BD versus 82.7 ml in BD > 24 h (p = 0.54). The mean midline shift was 10.7 mm in early BD versus 7.8 mm in BD > 24 h (p = 0.045). Ninety-one patients presented ventriculomegaly and 38 additionally ependymal transudation (p = 0.021). Thirty-six patients with early BD versus 24 with BD > 24 h presented complete effacement of basal cisterns (p = 0.005), sulcular effacement (p = 0.013), loss of cortico-subcortical differentiation (p = 0.0001) and effacement of the suprasellar cistern (p = 0.005). The optic nerve sheath measurements showed no significant differences between groups. CONCLUSIONS: Early BD (>24 h) was associated to GCS < 5, midline shift, effacement of the basal cisterns, cerebral sulci and suprasellar cistern, and ependymal transudation.

Motion of spin polariton bullets in semiconductor microcavities.

The dynamics of optical switching in semiconductor microcavities in the strong coupling regime is studied by using time- and spatially resolved spectroscopy. The switching is triggered by polarized short pulses which create spin bullets of high polariton density. The spin packets travel with speeds of the order of 10(6) m/s due to the ballistic propagation and drift of exciton polaritons from high to low density areas. The speed is controlled by the angle of incidence of the excitation beams, which changes the polariton group velocity.

Onset and dynamics of vortex-antivortex pairs in polariton optical parametric oscillator superfluids.

We study, both theoretically and experimentally, the occurrence of topological defects in polariton superfluids in the optical parametric oscillator (OPO) regime. We explain in terms of local supercurrents the deterministic behavior of both the onset and dynamics of vortex-antivortex pairs generated by perturbing the system with a pulsed probe. Using a generalized Gross-Pitaevskii equation, including photonic disorder, pumping and decay, we elucidate the reason why topological defects form in couples and can be detected by direct visualizations in multishot OPO experiments.

Effect of interactions on vortices in a nonequilibrium polariton condensate.

We demonstrate the creation of vortices in a macroscopically occupied polariton state formed in a semiconductor microcavity. A weak external laser beam carrying orbital angular momentum (OAM) is used to imprint a vortex on the condensate arising from the polariton optical parametric oscillator (OPO). The vortex core radius is found to decrease with increasing pump power, and is determined by polariton-polariton interactions. As a result of OAM conservation in the parametric scattering process, the excitation consists of a vortex in the signal and a corresponding antivortex in the idler of the OPO. The experimental results are in good agreement with a theoretical model of a vortex in the polariton OPO.

Polariton condensates put in motion.

We present several examples of the interesting phenomenology shown by a moving polariton condensate in semiconductor microcavities. The superfluid behavior is probed by colliding the polariton condensate against physical obstacles in the form of natural defects of the sample, demonstrating a clear suppression of scattering when the speed of the flow lies below the critical velocity. At higher velocities Cerenkov-like shock waves around the defect and disruption of the condensate are also observed.

Clinico-radiological related to early brain death factors. / Factores clínico-radiológicos asociados con muerte encefálica precoz.

OBJECTIVE: To identify clinical and radiological factors associated to early evolution to brain death (BD), defined as occurring within the first 24 hours. DESIGN: A retrospective cohort study was made covering the period 2015-2017. SETTING: An adult Intensive Care Unit (ICU). PATIENTS/METHODS: Epidemiological, clinical and imaging (CT scan) parameters upon admission to the ICU in patients evolving to BD. RESULTS: A total of 166 patients with BD (86 males, mean age 62.7 years) were analyzed. Primary cause: intracerebral hemorrhage 42.8%, subarachnoid hemorrhage 18.7%, traumatic brain injury 17.5%, anoxia 9%, stroke 7.8%, other causes 4.2%. Epidemiological data: arterial hypertension 50%, dyslipidemia 34%, smoking 33%, antiplatelet medication 21%, alcoholism 19%, anticoagulant therapy 15%, diabetes 15%. The Glasgow Coma Score (GCS) upon admission was 3 in 68.8% of the cases in early BD versus in 38.2% of the cases in BD occurring after 24 h (p = 0.0001). Eighty-five patients presented supratentorial hematomas with a volume of 90.9 ml in early BD versus 82.7 ml in BD >24 h (p = 0.54). The mean midline shift was 10.7 mm in early BD versus 7.8 mm in BD >24 h (p = 0.045). Ninety-one patients presented ventriculomegaly and 38 additionally ependymal transudation (p = 0.021). Thirty-six patients with early BD versus 24 with BD >24 h presented complete effacement of basal cisterns (p = 0.005), sulcular effacement (p = 0.013), loss of cortico-subcortical differentiation (p = 0.0001) and effacement of the suprasellar cistern (p = 0.005). The optic nerve sheath measurements showed no significant differences between groups. CONCLUSIONS: Early BD (>24 h) was associated to GCS < 5, midline shift, effacement of the basal cisterns, cerebral sulci and suprasellar cistern, and ependymal transudation.

[Meningitis/Encephalitis diagnosis in ICU using Multiplex PCR system: Is it time of change?] / Diagnóstico de meningitis/encefalitis en UCI con sistema de PCR múltiple. ¿Es tiempo de cambio?

OBJECTIVE: To evaluate the clinical impact of Meningitis/Encephalitis FilmArray® panel for the diagnosis of cerebral nervous system infection and to compare the results (including time for diagnosis) with those obtained by conventional microbiological techniques. METHODS: A prospective observational study in an Intensive Care Unit of adults from a tertiary hospital was carried out. Cerebrospinal fluid from all patients was taken by lumbar puncture and assessed by the meningitis/encephalitis FilmArray® panel ME, cytochemical study, Gram, and conventional microbiological cultures. RESULTS: A total of 21 patients admitted with suspicion of Meningitis/Encephalitis. Median age of patients was 58.4 years (RIQ 38.1-67.3), median APACHE II 18 (RIQ 12-24). Median stay in ICU and median hospital stay was 4 (RIQ 2-6) and 17 days (RIQ 14-28), respectively. The overall mortality was 14.3%. A final clinical diagnosis of meningitis or encephalitis was established in 16 patients, obtaining the etiological diagnosis in 12 of them (75%). The most frequent etiology was Streptococcus pneumoniae (8 cases). FilmArray® allowed etiological diagnosis in 3 cases in which the culture had been negative, and the results led to changes in the empirical antimicrobial therapy in 7 of 16 cases (43.8%). FilmArray® yielded a global sensitivity and specificity of 100% and 90%, respectively. The median time to obtain results from the latter and conventional culture (including antibiogram) was 2.9 hours (RIQ 2.1-3.8) and 45.1 hours (RIQ 38.9-58.7), respectively. CONCLUSIONS: The Meningitis/Encephalitis FilmArray® panel was able to establish the etiologic diagnosis faster than conventional methods. Also, it achieved a better sensitivity and led to prompt targeted antimicrobial therapy.

Polariton and spin dynamics in semiconductor microcavities under non-resonant excitation.

Semiconductor microcavities offer an ideal scenario to study strong radiation-matter interactions. In this paper we review the temporal dynamics of polaritons in II-VI and III-V based microcavities under non-resonant excitation conditions. We present evidence of final-state stimulated scattering and discuss the spin-dependent emission, which exhibits a remarkably rich behaviour.

Factores clínico-radiológicos asociados con muerte encefálica precoz / Clinico-radiological related to early brain death factors

Objective: To identify clinical and radiological factors associated to early evolution to brain death (BD), defined as occurring within the first 24 h. Design A retrospective cohort study was made covering the period 2015−2017. Setting An adult Intensive Care Unit (ICU).Patients/methodsEpidemiological, clinical and imaging (CT scan) parameters upon admission to the ICU in patients evolving to BD. Results A total of 166 patients with BD (86 males, mean age 62.7 years) were analyzed. Primary cause: intracerebral hemorrhage 42.8%, subarachnoid hemorrhage 18.7%, traumatic brain injury 17.5%, anoxia 9%, stroke 7.8%, other causes 4.2%. Epidemiological data: arterial hypertension 50%, dyslipidemia 34%, smoking 33%, antiplatelet medication 21%, alcoholism 19%, anticoagulant therapy 15%, diabetes 15%. The Glasgow Coma Score (GCS) upon admission was 3 in 68.8% of the cases in early BD versus in 38.2% of the cases in BD occurring after 24 h (p = 0.0001). Eighty-five patients presented supratentorial hematomas with a volume of 90.9 ml in early BD versus 82.7 ml in BD > 24 h (p = 0.54). The mean midline shift was 10.7 mm in early BD versus 7.8 mm in BD > 24 h (p = 0.045). Ninety-one patients presented ventriculomegaly and 38 additionally ependymal transudation (p = 0.021). Thirty-six patients with early BD versus 24 with BD > 24 h presented complete effacement of basal cisterns (p = 0.005), sulcular effacement (p = 0.013), loss of cortico-subcortical differentiation (p = 0.0001) and effacement of the suprasellar cistern (p = 0.005). The optic nerve sheath measurements showed no significant differences between groups.ConclusionsEarly BD (>24 h) was associated to GCS < 5, midline shift, effacement of the basal cisterns, cerebral sulci and suprasellar cistern, and ependymal transudation (AU)

Objetivo: Identificar los factores clínico-radiológicos que se asocian a evolución precoz a muerte encefálica (ME), definida esta como la ocurrida en ≤24 horas Diseño Estudio de cohortes retrospectivo desde 2015 hasta 2017, ambos incluidos. Ámbito Servicio de Medicina Intensiva (SMI) de adultos.Pacientes y métodoAnálisis de variables clínico-epidemiológicas y de la TC craneal de ingreso en pacientes con evolución a ME. Resultados Se analizaron 166 ME, 86 varones, edad media 62,7 años, 42,8% hemorragia intracerebral, 18,7% HSA, 17,5% TCE, 7,8% ictus isquémico, 9% anoxia y 4,2% otras causas; 50% HTA, 34% dislipemia, 33% tabaquismo, 21% antiagregación, 19% enolismo. El 15% anticoagulación, 15% diabetes. El GCS fue tres en el 68,8% en ME precoz frente 38,2% en ME >24 h (p 0,0001); 85 hematoma supratentorial (90,9 mL en ME precoz vs. 82,7 mL ME tardía, p 0,54); 12 hematoma infratentorial. Desplazamiento medio de línea media 10,7 mm en ME precoz vs. 7,8 mm en ME tardía (p 0,045); 91 pacientes ventriculomegalia y 38 trasudado periependimario (p 0,021). Borramiento completo de cisternas basales 36 en ME precoz frente a 24 en ME tardía (p 0,005), borramiento de surcos (p 0,013), pérdida de diferenciación córtico-subcortical (p 0,0001) y ausencia de cisterna supraselar (p 0,005). La medición de la vaina del nervio óptico no mostró diferencias significativas entre los dos grupos.ConclusionesSe asoció con ME ≤ 24 horas el GCS < 5, el desplazamiento de línea media, la pérdida de diferenciación córtico-subcortical, el borramiento de surcos, el borramiento completo de cisternas basales, de la cisterna supraselar y la presencia de trasudado periependimario (AU)

Infectious complications related to external ventricular shunt. Incidence and risk factors. / Complicaciones infecciosas relacionadas con el drenaje ventricular externo. Incidencia y factores de riesgo.

OBJECTIVE: Infectious complications related to external ventricular shunt (ICREVS) are a main problem in neurocritical intensive care units (ICU). The aim of the review is to assess the incidence of ICREVS and to analyse factors involved. METHODS: Retrospective analysis, adult polyvalent ICU in a third level reference hospital. Patients carrying external ventricular shunt (DVE) were included. Those patients with central nervous system infection diagnosed prior DVE placement were excluded. RESULTS: 87 patients were included with 106 DVE. Most common admittance diagnosis was subarachnoid haemorrhage (49.4%). 31 patients with 32 DVE developed an ICREVS. Infection rate is 19.5 per 1000 days of shunt for ICREVS and 14 per 1000 days for ventriculitis. 31.6% of the patients developed ICREVS and 25.3% ventriculitis. Patients who developed ICREVS presented higher shunt manipulations (2.0 ± 0.6 vs. 3.26 ± 1.02, p=0.02), shunt repositioning (0.1 ± 0.1 vs. 0.2 ± 0.1) and ICU and hospital stay (29.8 ± 4.9 vs 49.8 ± 5.2, p<0.01 y 67.4 ± 18.8 vs. 108.9 ± 30.2, p=0.02. Those DVE with ICREVS were placed for longer not only at infection diagnosis but also at removal (12.6 ± 2.1 vs. 18.3 ± 3.6 and 12.6 ± 2.1 vs. 30.4 ± 7.3 days, p<0.01). No difference in mortality was found. CONCLUSIONS: One out of three patients with a DVE develops an infection. The risk factors are the number of manipulations, repositioning and the permanency days. Patients with ICREVS had a longer ICU and hospital average stay without an increase in mortality.

[Visitation policy, design and comfort in Spanish intensive care units]. / Política de visitas, diseño y confortabilidad en las unidades de cuidados intensivos españolas.

OBJECTIVE: To determine the design and comfort in the Intensive Care Units (ICUs), by analysing visiting hours, information, and family participation in patient care. DESIGN: Descriptive, multicentre study. SETTING: Spanish ICUs. METHODS: A questionnaire e-mailed to members of the Spanish Society of Intensive Care Medicine, Critical and Coronary Units (SEMICYUC), subscribers of the Electronic Journal Intensive Care Medicine, and disseminated through the blog Proyecto HU-CI. RESULTS: A total of 135 questionnaires from 131 hospitals were analysed. Visiting hours: 3.8% open 24h, 9.8% open daytime, and 67.7% have 2 visits a day. Information: given only by the doctor in 75.2% of the cases, doctor and nurse together in 4.5%, with a frequency of once a day in 79.7%. During weekends, information is given in 95.5% of the cases. Information given over the phone 74.4%. Family participation in patient care: hygiene 11%, feeding 80.5%, physiotherapy 17%. Personal objects allowed: mobile phone 41%, computer 55%, sound system 77%, and television 30%. Architecture and comfort: all individual cubicles 60.2%, natural light 54.9%, television 7.5%, ambient music 12%, clock in the cubicle 15.8%, environmental noise meter 3.8%, and a waiting room near the ICU 68.4%. CONCLUSIONS: Visiting policy is restrictive, with a closed ICU being the predominating culture. On average, technological communication devices are not allowed. Family participation in patient care is low. The ICU design does not guarantee privacy or provide a desirable level of comfort.