Lattice vibration modes and electron-phonon interactions in monolayer vs. bilayer of transition metal dichalcogenides.

Transition metal dichalcogenides are at the center of intense scientific activity due to their promising applications, as well as the growing interest in basic research related to their electronic and dielectric properties. The layered structure of single-(ML) and two-layer (2ML) samples presents exciting features for light-matter interaction, electron transport, and electronic and optoelectronic applications. Lattice vibrations and electron-phonon interactions are essential for studying the above mentioned topics. Phonon spectra in ML and 2ML of MoX2 and WX2 (X = S, Se, and Te) families are studied using first principles calculations. A comprehensive analysis of the two-dimensional optical-phonon dispersion laws is performed, and the results illustrate the main differences between ML and 2ML for each considered semiconductor. Taking advantage of ab initio calculations, a generalization of the phenomenological Born-Huang dielectric model for long-wavelength vibrational modes around the Γ-point of the Brillouin zone (BZ) in 2ML structures is implemented. Explicit expressions are derived for the optical phonon dispersion of in-plane and out-of-plane normal modes. The set of characteristic parameters describing each long-wavelength optical branch is resolved from a direct comparison with the exact dispersion laws provided using the first principles calculations. The long-range electron-phonon Pekar-Fröhlich (PF) interaction and intra-valley electron scattering rates at the K-point of the BZ via E' (LO) and Eul longitudinal optical oscillations are examined for the ML and 2ML structures, respectively. The non-local macroscopic screening and the coupling between the in-plane electric field and longitudinal optical mechanical oscillation, profoundly affect the PF Hamiltonian and the carrier inverse relaxation time.

First-principles based Monte Carlo modeling of the magnetization of oxygen-deficient Fe-substituted SrTiO3.

Transition-metal (TM) substituted SrTiO3 has attracted much attention because its magnetism and/or ferroelectricity can be tuned via cation substitution, point defects, strain and/or oxygen deficiency. For example, Goto et al. [Phys. Rev. Applied, 7, 024006 (2017)] reported the magnetization of SrTi1-xFexO3-δ (STF) grown under different oxygen pressures and on various substrates. Here, we use hybrid density functional theory to calculate the effects of different oxygen vacancy (VO) states in STF on the magnetization for a variety of Fe cation arrangements. The magnetic states of the cations associated with the VO ground-states for x = {0.125, 0.25} are used within a Monte Carlo model for collinear magnetism to simulate the spontaneous magnetization. Our model captures several experimental features of STF, i.e., an increase in magnetization for small δ up to a maximum of ∼0.35µB per formula unit at an intermediate number of vacancies, with a slower decrease in magnetization with an increasing number of vacancies. Our approach gives insight into the relation between vacancy concentration and the oxygen pressure required to maximize the magnetization.

Flat bands and gaps in twisted double bilayer graphene.

We present electronic structure calculations of twisted double bilayer graphene (TDBG): a tetralayer graphene structure composed of two AB-stacked graphene bilayers with a relative rotation angle between them. Using first-principles calculations, we find that TDBG is semiconducting with a band gap that depends on the twist angle, that can be tuned by an external electric field. The gap is consistent with TDBG symmetry and its magnitude is related to surface effects, driving electron transfer from outer to inner layers. The surface effect competes with an energy upshift of localized states at inner layers, giving rise to the peculiar angle dependence of the band gap, which reduces at low angles. For these low twist angles, the TDBG develops flat bands, in which electrons in the inner layers are localized at the AA regions, as in twisted bilayer graphene.

Effect of companion presence on maternal satisfaction during neuraxial catheter placement for labor analgesia: a randomized clinical trial.

BACKGROUND: Neuraxial labor analgesia is frequently achieved after placing an epidural catheter under sterile conditions. There is no consensus on the risk versus benefit of allowing a parturient's companion to remain during the procedure. We sought to assess the effect of the presence of a companion on maternal satisfaction and anxiety during neuraxial catheter placement for labor analgesia. METHODS: Healthy nulliparous parturients planning to receive neuraxial labor analgesia after admission to labor, and who had a companion with them at the time of interview, were randomized to having a companion present or not present in the labor and delivery room during neuraxial catheter placement. Participants completed questionnaires to assess maternal anxiety, pain catastrophizing and health literacy. Satisfaction was scored on 5-point Likert scale (1- highly dissatisfied, 2- dissatisfied, 3- neutral, 4- satisfied, 5- highly satisfied). RESULTS: A total of 143 participants completed the study. The Wilcoxon-Mann-Whitney odds ratio for a random pair of satisfaction scores for a woman with her companion present compared with companion not present was 1.93 (95% CI 1.30 to 2.81, P=0.001). Anxiety scores were decreased following the procedure (P=0.39) in both groups. Eighty-nine percent of women randomized to companion not present would have preferred to have a companion present (P <0.001) compared with only one with their companion present who would have preferred her companion to be not present (P=0.99). CONCLUSION: Maternal satisfaction can be improved with the presence of a companion in the labor and delivery room at the time of neuraxial catheter placement for labor analgesia.

Correlation between oxyhaemoglobin saturation by pulse oximetry and partial pressure of oxygen in patients with acute respiratory failure. / Correlación entre la saturación de oxihemoglobina por pulsioximetría y la presión arterial de oxígeno en pacientes con insuficiencia respiratoria aguda.

OBJECTIVES: To ascertain the correlation between the partial pressure of oxygen (PaO2) and oxyhaemoglobin saturation by pulse oximetry (SpO2) in patients who were admitted to the emergency department with suspected acute respiratory failure. MATERIAL AND METHODS: A prospective, observational multicentre study was conducted in the emergency departments of 3 Spanish hospitals. RESULTS: The study included 166 patients who presented mean±standard deviation PaO2, SpO2 and fraction of inspired oxygen (FiO2) values of 61.64±17.3mmHg, 87.61±8.8% and 0.28±0.15%, respectively. The median PaO2/FiO2 and SpO2/FiO2 ratios were 256.6 and 359.2, respectively. The correlation between PaO2/FiO2 and the SpO2/FiO2 was 0.745 (P<.001). CONCLUSIONS: The SpO2/FiO2 ratio can be used to calculate PaO2/FiO2 and determine the oxygenation state of patients with acute respiratory failure.

A Lower Baseline CD4/CD8 T-Cell Ratio Is Independently Associated with Immunodiscordant Response to Antiretroviral Therapy in HIV-Infected Subjects.

We explored if baseline CD4/CD8 T-cell ratio is associated with immunodiscordant response to antiretroviral therapy in HIV-infected subjects. Comparing immunodiscordant and immunoconcordant subjects matched by pretreatment CD4 counts, we observed a lower pretreatment CD4/CD8 T-cell ratio in immunodiscordant subjects. Furthermore, pretreatment CD4/CD8 T-cell ratio, but not CD4 counts, correlated with the main immunological alterations observed in immunodiscordants, including increased regulatory T-cell (Treg) frequency and T-cell turnover-related markers. Then, in a larger cohort, only baseline CD4/CD8 T-cell ratio was independently associated with immunodiscordance, after adjusting by the viral CXCR4-tropic HIV variants. Our results suggest that the CD4/CD8 T-cell ratio could be an accurate biomarker of the subjacent immunological damage triggering immunodiscordance.

Increased risk of non-AIDS-related events in HIV subjects with persistent low CD4 counts despite cART in the CoRIS cohort.

The aim was to analyze clinical complications in HIV-infected subjects who persistently maintain low CD4 levels despite virological response to cART in the Spanish CoRIS cohort. The main inclusion criteria were CD4 counts <200cells/mm(3) at cART-initiation and at least 2years under cART achieving a viral load <500copies/mL. Those patients with CD4 counts <250cells/mm(3) 2years after cART were classified as the Low-CD4 group, and clinical events were collected from this time-point. Poisson regression models were used to calculate incidence rate ratios of death, AIDS-defining events, serious non-AIDS-defining events (NAE) and of each specific NAE category (non-AIDS-defining malignancies (non-ADM), cardiovascular, kidney- and liver-related events). Of 9667 patients in the cohort, a total of 1128 met the criteria and 287 (25.4%) were classified in the Low-CD4 group. A higher risk of death (aIRR: 4.71; 95% CI: 1.88-11.82; p-value=0.001) and of non-ADM were observed in this group (aIRR: 2.23; 95% CI: 1.07-4.63; p=0.03). Our results stress the need to control accelerated aging in this population to counter their increased risk of non-AIDS-defining diseases, particularly cancer, and are consistent with the concept that clinical complications are potentially affected by genetics and lifestyle.

[Cardiac arrest at induction of a patient with thyrotoxicosis. Have you thought of anaphylaxis?]. / Arrêt cardiaque à l'induction d'un patient en thyrotoxicose. Avez-vous pensé à l'anaphylaxie ?

We report the occurrence of cardiac arrest shortly after the anaesthetic induction for thyroidectomy in a patient with decompensated thyrotoxicosis associated with taking amiodarone. After investigation, it was revealed that the cardiac arrest was linked to an anaphylactic reaction to suxamethonium. This accident, unrelated to hyperthyroidism, reminds us of the relative frequency and severity of anaphylactic reactions related to curare. This event, in the context of severe cardiac insufficiency, due to an amiodarone-associated thyrotoxicosis, is described here for the first time. Its diagnosis requires to remain consistent. Its support must be in compliance with the recommendations of learned societies of anaesthesia.

[Nodular alveolar pattern of presentation for amiodarone pulmonary toxicity]. / Patrón alveolar nodular como forma de presentación de la toxicidad pulmonar por amiodarona.

Amiodarone is a triiodinated antiarrhythmic drug that accumulates in alveolar macrophages. Its use is limited by its high rate of associated pulmonary toxicity, estimated at 5-7%. Radiologic findings for pulmonary toxicity caused by amiodarone are unspecific and varied. The most common finding is subpleural reticular-type interstitial thickening, predominately in the bases of the lungs. However, the presence of parenchymal nodules is an uncommon presentation. We report the case of a woman treated with amiodarone that presented multiple nodular lesions at plain-film radiography and high-resolution CT that were compatible with pulmonary toxicity caused by amiodarone at pathologic examination.

Patrón alveolar nodular como forma de presentación de la toxicidad pulmonar por amiodarona / Nodular alveolar pattern of presentation for amiodarone pulmonary toxicity

La amiodarona es un antiarrítmico triyodado que se deposita en los macrófagos alveolares, cuyo uso se ve limitado por su toxicidad pulmonar que presenta una incidencia estimada del 5-7%. Los hallazgos radiológicos de la toxicidad pulmonar por amiodarona son inespecíficos y variados, siendo el más frecuente un engrosamiento intersticial de tipo reticular subpleural de predominio en bases. La presencia de nódulos parenquimatosos es, sin embrago, una forma infrecuente de presentación de esta entidad. Exponemos el caso de una mujer en tratamiento con amiodarona que presentaba en la radiología simple de tórax y tomografía computarizada (TC) de alta resolución múltiples lesiones nodulares cuyo posterior estudio anatomopatológico confirmaba su compatibilidad con toxicidad pulmonar por amiodarona

Amiodarone is a triiodinated antiarrhythmic drug that accumulates in alveolar macrophages. Its use is limited by its high rate of associated pulmonary toxicity, estimated at 5-7%. Radiologic findings for pulmonary toxicity caused by amiodarone are unspecific and varied. The most common finding is subpleural reticular-type interstitial thickening, predominately in the bases of the lungs. However, the presence of parenchymal nodules is an uncommon presentation. We report the case of a woman treated with amiodarone that presented multiple nodular lesions at plain-film radiography and high-resolution CT that were compatible with pulmonary toxicity caused by amiodarone at pathologic examination

[Systemic embolism after reversion to sinusal rhythm of persistent atrial flutter]. / Embolismo sistémico tras reversión a ritmo sinusal del aleteo auricular persistente.

BACKGROUND: The incidence of embolism in atrial flutter has been underestimated in the routine clinical practice. PATIENTS AND METHODS: In this study the incidence of thromboembolic events after restoration of sinus rhythm (by catheter ablation or cardioversion) was compared in two groups of consecutive patients, with a different anticoagulation protocol. A total of 169 patients were evaluated. A first retrospective analysis of 79 non anticoagulated patients (group I). A second prospective group of 90 patients who were treated with an anticoagulation protocol (group II) similar to that for patients with atrial fibrillation. All had typical atrial flutter of at least one month's duration before the procedure. RESULTS: The mean age of patients in group I was 61 12 years and the mean left ventricular ejection fraction was 57 6%. Patients in group II had a mean age of 61 10 years and the mean left ventricular ejection fraction was 56 9%. No differences were observed regarding prevalence of structural cardiopathy, arterial hypertension, diabetes mellitus, left ventricular dysfunction, atrial size or atrial fibrillation between the two groups of patients. Four patients in the retrospective analysis (5%) had an embolic event associated with the procedure, compared with 0 (0%) in the group of patients treated with the anticoagulation protocol. The efficient anticoagulation was associated with a lower risk of thromboembolic events (p < 0.05). CONCLUSIONS: The incidence of embolic events after reversion to sinusal rhythm of persistent atrial flutter can be decreased. These patients should follow the same recommendations of anticoagulation that apply for patients with persistent atrial fibrillation that are going to be reverted to sinus rhythm.

Embolismo sistémico tras reversión a ritmo sinusaldel aleteo auricular persistente / Systemic embolism after reversion to sinusal rhythm of persistent atrial flutter

Pacientes y métodos. En este estudio se compara la incidencia de eventos tromboembólicos después de restaurar el ritmo sinusal (por ablación con catéter o cardioversión) en dos grupos consecutivos de pacientes con un protocolo de anticoagulación diferente. Se evaluaron 169 pacientes. Un primer análisis retrospectivo de 79 pacientes no anticoagulados (grupo I). Un segundo grupo prospectivo de 90 pacientes se trató con un protocolo de anticoagulación (grupo II) similar al de los pacientes con fibrilación auricular. Todos presentaban aleteo auricular típico de al menos un mes de duración antes del procedimiento. Resultados. Grupo I: la edad media fue 61ñ12 años y la fracción de eyección ventricular izquierda media de 57 ñ 6 por ciento. Grupo II: tuvo una edad media 61 ñ 10 años y fracción de eyección ventricular izquierda media de 56 ñ 9 por ciento. No hubo ninguna diferencia en la prevalencia de cardiopatía estructural, hipertensión arterial, diabetes mellitus, disfunción ventricular izquierda, tamaño auricular o fibrilación auricular entre los dos grupos de pacientes. Cuatro pacientes del análisis retrospectivo (5 por ciento) presentaron un episodio embólico asociado con el procedimiento, comparado con 0 (0 por ciento) de los pacientes tratados con un protocolo de anticoagulación. La anticoagulación eficaz se asoció con un menor riesgo de tromboembolismo (p < 0,05). Conclusiones. Es posible reducir la incidencia de eventos embólicos después de la reversión a ritmo sinusal del aleteo auricular persistente. Estos pacientes deben seguir las mismas recomendaciones de anticoagulación que los pacientes con fibrilación auricular persistente que van a ser revertidos a ritmo sinusal (AU)

Fiebre y adenopatías cervicales / Fever and cervical lymph node enlargement

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137Cs and 210Po dose assessment from marine food in Cienfuegos Bay (Cuba).

One part of Radiological Monitoring Programme in central Cuba (1991-1995) was dedicated to study the background levels of natural and anthropogenic radioactivity in Cienfuegos Bay in the vicinity of the first Cuban nuclear power station under construction. 210Po and 137Cs concentrations in fish, molluscs and crustaceans collected in Cienfuegos Bay were determined and the committed effective doses (CED) were calculated for two population groups inhabiting this region. The highest values of 210Po concentrations were found in crustaceans, but significant accumulation was also observed in fish and molluscs. The mean 137Cs concentrations in organisms are several times lower with respect to 210Po, a situation that characterises the regions affected by the global fallout only. Values of CED from the consumption of crustaceans and molluscs are very low both from 210Po and 137Cs. The mean individual dose from 210Po in the seafood consumed varies from 39 microSv for general populations to 2802 microSv for the "critical group" consuming 320 kg of fish per year. The dose from 137Cs is negligible.

Hiponatremia grave asociada al uso de fluoxetina en el anciano

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[Toxic food infection caused by Shigella flexneri in a military unit]. / Toxi-infection alimentaire à Shigella flexneri dans une collectivité militaire.

Food borne disease outbreaks have increased in France, but outbreaks caused by Shigella are rare, accounting for only 73 cases (1.62%) in 1993. We report a food borne outbreak of Shigella flexneri strain 3 infection in a fire fighting unit in Paris between July 13th and 17th 1995. Forty of the 127 firemen suffered symptoms including acute diarrhea (80%), fever (50%) and blood and mucus in stools (1 case, 2.5%). Epidemiological investigation generated an unimodal epidemic curve suggesting a single source of contamination with no secondary cases. The median incubation period was between 43 hours 30 minutes and 51 hours 30 minutes. This is consistent with food borne Shigella infection. Statistical analysis of a case-control study implicated a mixed salad containing frozen shellfish from Asia (shrimps and mussels), served at lunch and dinner on July 13th 1995. Shigella was not detected in this salad by microbiological methods. However, inoculation with as little as 100 organisms can cause symptoms. There was low-level contamination with Escherichia coli (940 cfu/g) due to cross-contamination. Shigella flexneri strain 3 was isolated from 11 of 18 stool cultures, but was never isolated from cultures of stools provided by the cooks. All isolates had identical antibiotic resistance profiles. They were resistant to ampicillin and ticarcillin, moderately sensitive to amoxicillin-clavulanic acid, highly sensitive to aminosides, erythromycin and quinolones. This identical pattern in all isolates suggests a common source of contamination. Plasmid-based multiple resistance is common in this organism. Therefore, antibiotics should only be given to patients with evident clinical signs of infection. Treatment was symptom-based in all but 4 patients, who had acute diarrhea and were treated with ciprofloxacin. This antibiotic is well tolerated, has rapid bactericidal action and significantly reduces the duration of the symptoms and excretion of Shigella, thus preventing secondary contamination with this highly infectious bacterium. Thus, food borne outbreaks of Shigella can occur in countries with a high standard of living because of the increase in mass catering (e.g. fast food restaurants) and importation of foodstuffs from developing countries with endemic shigellosis. This is a public health problem because of the morbidity and absenteeism due to illness, particularly when the patients are firemen responsible for emergency management.