Flat Bands and Giant Light-Matter Interaction in Hexagonal Boron Nitride.

Dispersionless energy bands in k space are a peculiar property gathering increasing attention for the emergence of novel electronic, magnetic, and photonic properties. Here, we explore the impact of electronic flat bands on the light-matter interaction. The van der Waals interaction between the atomic layers of hexagonal boron nitride induces flat bands along specific lines of the Brillouin zone. The macroscopic degeneracy along these lines leads to van Hove singularities with divergent joint density of states, resulting in outstanding optical properties of the excitonic states. For the direct exciton, we report a giant oscillator strength with a longitudinal-transverse splitting of 420 meV, a record value, confirmed by our ab initio calculations. For the fundamental indirect exciton, flat bands result in phonon-assisted processes of exceptional efficiency, that compete with direct absorption in reflectivity, and that make the internal quantum efficiency close to values typical of direct band gap semiconductors.

Genetic characterization of an almond germplasm collection and volatilome profiling of raw and roasted kernels.

Almond is appreciated for its nutraceutical value and for the aromatic profile of the kernels. In this work, an almond collection composed of 96 Sicilian accessions complemented with 10 widely cultivated cultivars was phenotyped for the production of volatile organic compounds using a proton-transfer time-of-flight mass spectrometer and genotyped using the Illumina Infinium®18 K Peach SNP array. The profiling of the aroma was carried out on fresh and roasted kernels enabling the detection of 150 mass peaks. Sixty eight, for the most related with sulfur compounds, furan containing compounds, and aldehydes formed by Strecker degradation, significantly increased during roasting, while the concentration of fifty-four mass peaks, for the most belonging to alcohols and terpenes, significantly decreased. Four hundred and seventy-one robust SNPs were selected and employed for population genetic studies. Structure analysis detected three subpopulations with the Sicilian accessions characterized by a different genetic stratification compared to those collected in Apulia (South Italy) and the International cultivars. The linkage-disequilibrium (LD) decay across the genome was equal to r2 = 0.083. Furthermore, a high level of collinearity (r2 = 0.96) between almond and peach was registered confirming the high synteny between the two genomes. A preliminary application of a genome-wide association analysis allowed the detection of significant marker-trait associations for 31 fresh and 33 roasted almond mass peaks respectively. An accurate genetic and phenotypic characterization of novel germplasm can represent a valuable tool for the set-up of marker-assisted selection of novel cultivars with an enhanced aromatic profile.

Value of three-dimensional volume rendering images in the assessment of the centrality index for preoperative planning in patients with renal masses.

AIM: To evaluate the precision of the centrality index (CI) measurement on three-dimensional (3D) volume rendering technique (VRT) images in patients with renal masses, compared to its standard measurement on axial images. MATERIALS AND METHODS: Sixty-five patients with renal lesions underwent contrast-enhanced multidetector (MD) computed tomography (CT) for preoperative imaging. Two readers calculated the CI on two-dimensional axial images and on VRT images, measuring it in the plane that the tumour and centre of the kidney were lying in. Correlation and agreement of interobserver measurements and inter-method results were calculated using intraclass correlation (ICC) coefficients and the Bland-Altman method. Time saving was also calculated. RESULTS: The correlation coefficients were r=0.99 (p<0.05) and r=0.99 (p<0.05) for both the CI on axial and VRT images, with an ICC of 0.99, and 0.99, respectively. Correlation between the two methods of measuring the CI on VRT and axial CT images was r=0.99 (p<0.05). The two methods showed a mean difference of -0.03 (SD 0.13). Mean time saving per each examination with VRT was 45.5%. CONCLUSIONS: The present study showed that VRT and axial images produce almost identical values of CI, with the advantages of greater ease of execution and a time saving of almost 50% for 3D VRT images. In addition, VRT provides an integrated perspective that can better assist surgeons in clinical decision making and in operative planning, suggesting this technique as a possible standard method for CI measurement.

Predictors of progression in patients presenting with minor subcortical stroke.

OBJECTIVES: Early neurological worsening is common in minor subcortical strokes (SS) and may lead to a poor outcome. We aimed to describe clinical and imaging features associated with progression. MATERIAL AND METHODS: Consecutive patients with SS were divided into progressive and non-progressive. Progression was defined as an increase of NIHSS motor score ≥ 1 point within 72 h from onset. Vascular risk factors and imaging features (vascular territory, size and number of slices in which the lesion was visible, the presence of leukoaraiosis) were compared in the two groups. We investigated potential independent determinants of progression using stepwise logistic regression. RESULTS: Thirty of 94 patients (31.9%) underwent progression. The distribution of vascular risk factors did not differ significantly between the two groups. Increasing number of risk factors was associated with a higher risk of progression (OR 2.2; 95% CI 1.1-4.5). Patients who progressed were more likely to have a lesion ≥ 15 mm in diameter (P = 0.004) or a lesion visible ≥ 3 slices (P = 0.007). After logistic regression stepwise adjustment for all the considered potential determinants, diameter ≥ 15 mm and severe leukoaraiosis proved to be independently associated with neurological worsening (OR = 6.3, 95% CI 2.0-19.6 and OR = 5.9, 95% CI 1.3-25.7, respectively). CONCLUSION: In a series of consecutive SS, early neurological worsening was associated with a high vascular risk profile, a larger infarct size and the presence of severe leukoaraiosis. Based on the knowledge that extensive microvascular changes are a feature of severe leukoaraiosis, we hypothesize that stroke progression could be promoted through an impaired compensatory flow in the penumbral area.

[Coarctation of the aorta with aortic arch hypoplasia in newborn with partial trisomy 11q associated to 4q interstitial deletion]. / Coartazione aortica con ipoplasia dell'arco in una neonata con trisomia parziale 11q associata a delezione interstiziale 4q.

This article reports the case of newborn with multiple dimorphisms (microcephaly, hypertelorism, wide and flat nasal bridge, small nose, long philtrum, microretrognathia, malformed and low-set ears, short neck, redundant nuchal skin, genital anomalies), admitted in the hospital after two days from delivery for torpor, poor food and cyanosis. Babies were affected, at color-Doppler echocardiography, by coarctation of the aorta (CoA) with aortic arch hypoplasia. CoA is often associated to genetic and environmental factors that interact frequently. In this study the anamnestic absence of teratogen noxae and the presence of facial and genital anomalies suggest a genetic study to provide appropriate genetic information to parents. G-banding chromosomic analysis revealed a 46, XX der 4t(4;11) karyotype with partial 11q trisomy confirmed with FISH chromosome painting 4;11 and with FISH subtelomere specific 4(p/q)11(p/q). These techniques showed that derivative chromosome 4 was constituted by chromosome 4 with partial deletion in the q35 region and by 11q21 translocation. This rare anomaly is often inherited by an unbalanced segregation of a balanced translocation, present in one of the two parents. In the present study, the father carried a t(4q;11q) balanced translocation. A CGH-array analysis was executed to the child for the breakpoints definition. As 11q trisomy cases reported in literature are still few, this case can contribute to improve our knowledge on the genotype-phenotype correlation in this rare genetic anomaly.

Double excitations in finite systems.

Time-dependent density-functional theory (TDDFT) is widely used in the study of linear response properties of finite systems. However, there are difficulties in properly describing excited states, which have double- and higher-excitation characters, which are particularly important in molecules with an open-shell ground state. These states would be described if the exact TDDFT kernel were used; however, within the adiabatic approximation to the exchange-correlation (xc) kernel, the calculated excitation energies have a strict single-excitation character and are fewer than the real ones. A frequency-dependent xc kernel could create extra poles in the response function, which would describe states with a multiple-excitation character. We introduce a frequency-dependent xc kernel, which can reproduce, within TDDFT, double excitations in finite systems. In order to achieve this, we use the Bethe-Salpeter equation with a dynamically screened Coulomb interaction W(omega), which can describe these excitations, and from this we obtain the xc kernel. Using a two-electron model system, we show that the frequency dependence of W does indeed introduce the double excitations that are instead absent in any static approximation of the electron-hole screening.

Linear plasmon dispersion in single-wall carbon nanotubes and the collective excitation spectrum of graphene.

We have measured a strictly linear pi plasmon dispersion along the axis of individualized single-wall carbon nanotubes, which is completely different from plasmon dispersions of graphite or bundled single-wall carbon nanotubes. Comparative ab initio studies on graphene-based systems allow us to reproduce the different dispersions. This suggests that individualized nanotubes provide viable experimental access to collective electronic excitations of graphene, and it validates the use of graphene to understand electronic excitations of carbon nanotubes. In particular, the calculations reveal that local field effects cause a mixing of electronic transitions, including the "Dirac cone," resulting in the observed linear dispersion.

Anomalous angular dependence of the dynamic structure factor near Bragg reflections: graphite.

The electron energy-loss function of graphite is studied for momentum transfers q beyond the first Brillouin zone. We find that near Bragg reflections the spectra can change drastically for very small variations in q. The effect is investigated by means of first principle calculations in the random phase approximation and confirmed by inelastic x-ray scattering measurements of the dynamic structure factor S(q, omega). We demonstrate that this effect is governed by crystal local field effects and the stacking of graphite. It is traced back to a strong coupling between excitations at small and large momentum transfers.

[Accidental ethyl alcohol intoxication in a 30-day-old infant. Clinical findings and neurological follow-up]. / Intossicazione accidentale da alcol etilico in un lattante di 30 giorni. Quadro clinico e follow-up neurologico.

Fetus damages due to alcohol abuse in pregnancy, fetal alcohol syndrome (FAS), are widely documented in the literature, whereas short and long term clinical signs of acute alcohol intoxication in newborn babies are poorly described. In our study we describe the case of a 30-day-old newborn baby erroneously fed with 70 mL of white wine in place of the water for milk dilution. The baby clinical features were torpor, tremors, slight fever without metabolic anomalies typical of classic acute alcohol intoxication such as hypoglycemia, hypothermia, metabolic acidosis and coma. Periodical follow-up a 2, 3, 6 and 12 months were performed in order to evaluate neuromotor development using Bayley Scales of Infant Development II, for children between 1 and 42 months old. The results showed normal psychomotor development in our patient.

[Normal urinary levels of telopeptide aminoterminal (NTx) of type I collagen in healthy term newborns and infants in the first month of life]. / Livelli normali urinari di telopeptide amino terminale (NTx) del collagene di tipo I in neonati a termine e lattanti sani nei primi tre mesi di vita.

The Authors have studied urinary aminoterminal telopeptide of type I collagen (NTx), a bone catabolism marker of recent determination, by an enzyme-linked immunoassorbent assay (OSTEOMARK) in 80 urine samples of term healthy infants in the first 3 months of life. Highly significant variations have been compared in the whole period studied (P = 0.000). Levels of NTx increase significantly from 1 to 7 days of life, reaching a plateau that is kept until 45th day and then significantly decrease until 90th day, when, however, they result higher than the values reported in literature concerning older ages. The Authors conclude that even this bone catabolism marker is influenced, in the first week of life, by the particular phenomenology linked to the neonatal adaptation, and that, subsequently, shows a trend strictly linked to the bone turnover modifications throughout the faster stage of the growth.

Gastric colonization as a consequence of stress ulcer prophylaxis: a prospective, randomized trial.

STUDY OBJECTIVE: To evaluate gastric alkalization and bacterial colonization in critically ill patients receiving stress ulcer prophylaxis with gastric tube feeds, sucralfate, intermittent intravenous cimetidine, or continuous intravenous cimetidine. DESIGN; Prospective, randomized, unblinded trial. SETTING: Medical and surgical intensive care units of a large university-affiliated, tertiary care community hospital. PATIENTS: Fifty-three evaluable critically ill patients with respiratory failure requiring mechanical ventilation. INTERVENTIONS: Patients not receiving nasogastric tube feeds were randomized to sucralfate 1 g every 6 hours, cimetidine 300 mg by intravenous bolus every 8 hours, or cimetidine 900 mg by continuous intravenous infusion/24 hours. Gastric samples were obtained daily for pH and culture. MEASUREMENTS AND MAIN RESULTS: Patients with respiratory failure and a high mortality rate had a mean gastric pH of 1.96 +/- 1.5 at study entry. There were no significant differences in gastric pH or gastric colonization among the three arms. Fourteen patients (26%) developed gastric colonization, which was statistically significant but poorly correlated with gastric alkalinity (r2=0.08, p<0.043). CONCLUSION: Gastric luminal pH was unchanged regardless of which method was used for stress ulcer prophylaxis. Bacterial colonization was increasingly likely in patients with a persistent alkaline gastric environment.

A comparison of four severity-adjusted models to predict mortality after coronary artery bypass graft surgery.

OBJECTIVE: To assess the validity of four severity-adjusted models to predict mortality following coronary artery bypass graft surgery by using an independent surgical database. DESIGN: A prospective observational study wherein predicted mortality for each patient was obtained by using four different published severity-adjusted models. SETTING: A university-affiliated teaching community hospital. PATIENTS: Eight hundred sixty-eight consecutive patients who underwent coronary artery bypass graft surgery without accompanying valve or aneurysm repair during the period from 1991 to 1993. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Predicted mortality rates for each model were obtained by averaging individual patient predictions and were compared with actual morality rates. We assessed the accuracy of overall prediction for the total series, as well as compared individual patient predictions created by each model. The discrimination of models was assessed with receiver operating characteristic curves and the Hosmer-Lemeshow goodness-of-fit statistic. RESULTS: The observed crude mortality rate was 3.7%. The predicted mortality rate ranged from 2.8% to 9.2%, despite relatively good discrimination by the models (area under the receiver operating characteristic curve, 0.70 to 0.74). The individual patient mortality predicted by different models varied by as much as a ninefold difference. CONCLUSIONS: The currently used coronary artery bypass graft predictive models, although generally accurate, have significant shortcomings and should be used with caution. The predicted mortality rate following coronary artery bypass graft surgery varied by a factor of 3.3 from lowest to highest, making the choice of model a critical factor when assessing outcome. The use of these models for individual patient risk estimations is risky because of the marked discrepancies in individual predictions created by each model.

Evaluation of right ventricular function during aortic operations.

The simultaneous measurements of mixed venous oxygen saturation (SvO2) and right ventricular ejection fraction (RVEF) have now made it possible to precisely define and correlate the various hemodynamic changes that occur during abdominal aortic operations. Twenty-five patients undergoing infrarenal abdominal aortic aneurysm repair were examined with a pulmonary artery catheter capable of continuously measuring SvO2 and RVEF. With aortic clamping, significant reductions in cardiac index, stroke volume index, and right ventricular end-diastolic volume index (RVEDVI) were noted, while RVEF remained unchanged. Following unclamping of the aorta, a significant reduction in SvO2 occurred, accompanied by an increase in mean pulmonary artery pressure and in pulmonary vascular resistance. Despite the increase in afterload, RVEDVI and RVEF did not change after unclamping. These preliminary data suggest that right ventricular function is preserved during abdominal aortic aneurysm repair.

Continuous monitoring of mixed venous oxygen saturation during aortic operations.

OBJECTIVE: To systematically analyze the changes in mixed venous oxygen saturation (delta SvO2) during aortic operations with tube, aortobi-iliac, and aortobifemoral grafts. DESIGN: Survey of consecutive patients. SETTING: Teaching community hospital. PATIENTS: Thirty-one patients (22 male, 9 female, mean age 67 +/- 10 yrs), undergoing elective operations for aortic aneurysms (n = 25) and aortoiliac occlusive disease (n = 6). INTERVENTIONS: SvO2 was recorded throughout the operation. Cardiac output, mean pulmonary arterial pressure, arterial oxygen saturation (SaO2), and arterial pH were measured before and immediately after the unclamping of the aortic graft. RESULTS: In all patients, unclamping the aorta resulted in a marked reduction of mean SvO2, with no change in the cardiac output or SaO2. The unclamping of tube grafts was associated with a significant reduction in arterial pH (p less than .01) and in SvO2 (p less than .001), when compared with unclamping of bifurcation grafts. A significant (p less than .05) increase in mean pulmonary arterial pressure was observed after unclamping the aorta in patients with tube grafts. Despite a longer clamp time, unclamping the second limb of a bifurcation graft resulted in a smaller delta SvO2, when compared with that observed after unclamping the first limb (12% vs. 6%; p less than .01). The delta SvO2 after unclamping limb II was only 2% in aortobifemoral grafts and 9% in aortobi-iliac grafts. CONCLUSIONS: Reperfusion via extensive pelvic and lumbar collaterals in patients with aortoiliac occlusive disease reduces the delta SvO2 after aortic unclamping. Monitoring the changes in SvO2 during different types of aortic reconstruction helps to define precisely the physiologic alterations that occur in the course of these operations.

Nosocomial respiratory tract colonization and infection with aminoglycoside-resistant Acinetobacter calcoaceticus var anitratus: epidemiologic characteristics and clinical significance.

During the period July 1983 through December 1984, aminoglycoside-resistant Acinetobacter calcoaceticus var anitratus (ACA) were isolated from 98 patients in a university hospital. Eighty-seven percent of patients (85/98) acquired aminoglycoside-resistant ACA in the intensive care unit (ICU) and 92% (90/98) of all initial isolates were from sputum. ICU patients with respiratory colonization/infection with aminoglycoside-resistant ACA were compared with matched ICU controls with other gram-negative rods in sputum. Compared with controls, the duration of ICU stay prior to colonization/infection with aminoglycoside-resistant ACA was significantly longer for cases (14.7 days v 5.9 days, P = 0.002). Although exposures to devices and procedures were not significantly different for the two groups, cases received respiratory therapy significantly longer than did controls (14.7 days v 6.6 days, P = 0.006). Prior to isolation of aminoglycoside-resistant ACA in sputum, cases received more cephalosporins than did controls (1.9 v 1.2, P = 0.018); aminoglycoside usage in the two groups was comparable but cases tended to have received aminoglycoside for longer durations before colonization/infection than had controls (9.0 days v 6.1 days, P = 0.08). Following sputum isolation of ACA, 6 of 22 cases developed ACA bacteremia compared with bacteremia in 2 of 22 controls. We conclude that factors predisposing to colonization/infection with aminoglycoside-resistant ACA were extended ICU care, prolonged respiratory therapy, and prior therapy with cephalosporins and aminoglycoside. In addition, ACA may be a more common cause of secondary bacteremia than previously appreciated.

Nosocomial pulmonary infection: possible etiologic significance of bacterial adhesion to endotracheal tubes.

Biomaterials are essential for life support and monitoring of critically ill patients, but their use increases the risk of nosocomial infection. Of the various plastics used for life support and monitoring devices, polyvinylchloride is one to which bacteria most readily adhere. Through the use of qualitative culture techniques and scanning and transmission electron microscopy, we studied the surfaces of polyvinylchloride endotracheal tubes removed from 25 ICU patients, to determine if bacterial adhesion to those tubes was sufficient to provide a possible source for repeated contamination of the tracheobronchial tree. Of the surfaces studied, 16% were partially covered and 84% were completely covered by an amorphous bacteria-containing matrix. Some biofilm-enclosed bacterial aggregates projected from the matrix into the lumen of the tube. The mechanism by which endotracheal tubes repeatedly inoculate the lungs of intubated patients may prove to be dislodgment of such aggregates by suction apparatus.

[Pathology of alcoholism. Experiences and treatment possibilities]. / Patologia alcool-correlata. Esperienze e possibilità operative.

In the present study, the state of art of alcohol-related pathology is described, and the most credited etiological theories reviewed. An effort has been made to apply theory to the daily practice of the health practitioner and the social worker, who operate in the field. Particular emphasis has been given to the experience in the County of Dolo, Italy, where alcohol-related problems have been successfully dealt with by the Alcoholism Unit of the local General Hospital.