Iuliacumite: A Novel Chemical Short-Range Order in a Two-Dimensional Wurtzite Single Monolayer InAs1-xSbx Shell on InAs Nanowires.

A chemical short-range order is found in single monolayer InAs1-xSbx shells, which inherit a wurtzite structure from the underlying InAs nanowire, instead of crystallizing in the energetically preferred zincblende structure. The chemical order is characterized by an anticorrelation ordering vector in the ⟨112̅0⟩ direction and arises from strong Sb-Sb repulsive interactions along the atomic chains in the ⟨112̅0⟩ direction.

Interpretable machine learning for inferring the phase boundaries in a nonequilibrium system.

Still under debate is the question of whether machine learning is capable of going beyond black-box modeling for complex physical systems. We investigate the generalizing and interpretability properties of learning algorithms. To this end, we use supervised and unsupervised learning to infer the phase boundaries of the active Ising model, starting from an ensemble of configurations of the system. We illustrate that unsupervised learning techniques are powerful at identifying the phase boundaries in the control parameter space, even in situations of phase coexistence. It is demonstrated that supervised learning with neural networks is capable of learning the characteristics of the phase diagram, such that the knowledge obtained at a limited set of control variables can be used to determine the phase boundaries across the phase diagram. In this way, we show that properly designed supervised learning provides predictive power to regions in the phase diagram that are not included in the training phase of the algorithm. We stress the importance of introducing interpretability methods in order to perform a physically relevant classification of the phases with deep learning.

Determination of the Pole Position of the Lightest Hybrid Meson Candidate.

Mapping states with explicit gluonic degrees of freedom in the light sector is a challenge, and has led to controversies in the past. In particular, the experiments have reported two different hybrid candidates with spin-exotic signature, π_{1}(1400) and π_{1}(1600), which couple separately to ηπ and η^{'}π. This picture is not compatible with recent Lattice QCD estimates for hybrid states, nor with most phenomenological models. We consider the recent partial wave analysis of the η^{(')}π system by the COMPASS Collaboration. We fit the extracted intensities and phases with a coupled-channel amplitude that enforces the unitarity and analyticity of the S matrix. We provide a robust extraction of a single exotic π_{1} resonant pole, with mass and width 1564±24±86 and 492±54±102 MeV, which couples to both η^{(')}π channels. We find no evidence for a second exotic state. We also provide the resonance parameters of the a_{2}(1320) and a_{2}^{'}(1700).

Composition modulation by twinning in InAsSb nanowires.

We observe a composition modulated axial heterostructure in zincblende (ZB) InAs0.90Sb0.10 nanowires initiated by pseudo-periodic twin boundaries using scanning tunneling microscopy. The twin boundaries exhibit four planes with reduced Sb concentration due to a lower Sb incorporation during lateral overgrowth of a 4H wurtzite as compared to a ZB stacking sequence. We anticipate that this leads to compositional band offsets in addition to known structural band offsets present between 4H and ZB polytypes, changing the band alignment from type II to type I.

Estimation of π-π Electronic Couplings from Current Measurements.

The π-π interactions between organic molecules are among the most important parameters for optimizing the transport and optical properties of organic transistors, light-emitting diodes, and (bio-) molecular devices. Despite substantial theoretical progress, direct experimental measurement of the π-π electronic coupling energy parameter t has remained an old challenge due to molecular structural variability and the large number of parameters that affect the charge transport. Here, we propose a study of π-π interactions from electrochemical and current measurements on a large array of ferrocene-thiolated gold nanocrystals. We confirm the theoretical prediction that t can be assessed from a statistical analysis of current histograms. The extracted value of t ≈35 meV is in the expected range based on our density functional theory analysis. Furthermore, the t distribution is not necessarily Gaussian and could be used as an ultrasensitive technique to assess intermolecular distance fluctuation at the subangström level. The present work establishes a direct bridge between quantum chemistry, electrochemistry, organic electronics, and mesoscopic physics, all of which were used to discuss results and perspectives in a quantitative manner.

NanoARPES of twisted bilayer graphene on SiC: absence of velocity renormalization for small angles.

The structural and electronic properties of twisted bilayer graphene (TBG) on SiC(000) grown by Si flux-assisted molecular beam epitaxy were investigated using scanning tunneling microscopy (STM) and angle-resolved photoelectron spectroscopy with nanometric spatial resolution. STM images revealed a wide distribution of twist angles between the two graphene layers. The electronic structure recorded in single TBG grains showed two closely-spaced Dirac π bands associated to the two stacked layers with respective twist angles in the range 1-3°. The renormalization of velocity predicted in previous theoretical calculations for small twist angles was not observed.

On the mechanical and electronic properties of thiolated gold nanocrystals.

We present a quantitative exploration, combining experiment and simulation, of the mechanical and electronic properties, as well as the modifications induced by an alkylthiolated coating, at the single nanoparticle (NP) level. We determined the response of the NPs to external pressure in a controlled manner using an atomic force microscope tip. We found a strong reduction in their Young's modulus, as compared to bulk gold, and a significant influence of strain on the electronic properties of the alkylthiolated NPs. Electron transport measurements of tiny molecular junctions (NP/alkylthiol/CAFM tip) show that the effective tunnelling barrier through the adsorbed monolayer strongly decreases by increasing the applied load, which translates in a remarkable and unprecedented increase in the tunnel current. These observations are successfully explained using simulations based on the finite element analysis (FEA) and first-principles calculations that permit one to consider the coupling between the mechanical response of the system and the electric dipole variations at the interface.

Narrowing the length distribution of Ge nanowires.

Synthesis of nanostructures of uniform size is fundamental because the size distribution directly affects their physical properties. We present experimental data demonstrating a narrowing effect on the length distribution of Ge nanowires synthesized by the Au-catalyzed molecular beam epitaxy on Si substrates. A theoretical model is developed that is capable of describing this puzzling behavior. It is demonstrated that the direction of the diffusion flux of sidewall adatoms is size dependent and has a major effect on the growth rate of differently sized nanowires. We also show that there exists a fundamental limitation on the maximum nanowire length that can be achieved by molecular beam epitaxy where the direction of the beam is close to the growth axis.

Efficient photogeneration of charge carriers in silicon nanowires with a radial doping gradient.

by performing electrodeless time-resolved microwave conductivity measurements, the efficiency of charge carrier generation, their mobility, and the decay kinetics on photoexcitation were studied in arrays of Si nanowires grown by the vapor-liquid-solid mechanism. Large enhancements in the magnitude of the photoconductance and charge carrier lifetime are found depending on the incorporation of impurities during the growth. They are explained by the internal electric field that builds up, due to higher doped sidewalls, as revealed by detailed analysis of the nanowire morphology and chemical composition.

Multifocal intraparietal activation during discrimination of action intention in observed tool grasping.

The way we grasp an object varies depending on how we want to use that object, and this knowledge can be used to predict the object-related behavior of others. In this study, we assessed the neural correlates that determine the action intention of another person based on observed prehensile movements. Fourteen right-handed volunteers watched video clips of a person performing right-handed transitive grasping gestures that were either aimed at displacing or using a tool-object. Clips showing the grasping and displacement of neutral shapes served as a control condition. By discrimination of the actor's intention, three roughly symmetrical foci were activated in the anterior, middle, and caudal segments of the intraparietal sulci, and in the fusiform gyri and parts of the lateral occipital complex. Anterior intraparietal activation has been associated with the representation of object goals (object specific), and the present findings extend its involvement to functional goals (use-specific). Activation in the middle intraparietal region during intention discrimination was very similar to the activation elicited in a saccadic localizer task, suggesting a relation with spatial attention and eye movements. The caudal intraparietal region has been related with visuospatial guidance of reaching, and its activation during action intention discrimination indicates that the visuospatial properties of the observed reaching movement contribute to understanding of actions. As these parietal regions are strongly linked with motor behavior, our results appear to support the motor simulation hypothesis for action understanding with the preferential recruitment of the mirror-neuron system. This could at least be the case when no contextual information other than the visual properties of the movement is provided to discriminate the intention of an observed hand action.

Dynamic behavior of amplitude detection Kelvin force microscopy in ultrahigh vacuum.

The acquisition rate of all scanning probe imaging techniques with feedback control is limited by the dynamic response of the control loops. Performance criteria are the control loop bandwidth and the output signal noise power spectral density. Depending on the acceptable noise level, it may be necessary to reduce the sampling frequency below the bandwidth of the control loop. In this work, the frequency response of a vacuum Kelvin force microscope with amplitude detection (AM-KFM) using a digital signal processing (DSP) controller is characterized and optimized. Then, the main noise source and its impact on the output signal is identified. A discussion follows on how the system design can be optimized with respect to output noise. Furthermore, the interaction between Kelvin and distance control loop is studied, confirming the beneficial effect of KFM on topography artefact reduction in the frequency domain. The experimental procedure described here can be generalized to other systems and allows to locate the performance limitations.

Kelvin force microscopy at the second cantilever resonance: an out-of-vacuum crosstalk compensation setup.

We investigate the gap-voltage control loop in a Kelvin force microscopy setup with simultaneous non-contact topography imaging. The Kelvin controller electrostatically excites the second resonance of the cantilever at about 6.3 times the first resonance frequency and adjusts the DC component of the gap voltage to cancel the oscillation amplitude at this frequency, while the non-contact topography imaging is based on a frequency control loop that maintains a constant frequency of the mechanically excited first resonance of the cantilever by adjusting the tip-sample separation. Due to the self-excitation of the first resonance in our setup, it has to be considered that the electrostatic excitation at the second resonance frequency is applied to a closed feedback loop and cannot be considered as a simple superposition to the oscillation at the first resonance frequency. In particular, special care has to be taken about internal capacitive crosstalk between the tip bias and the cantilever deflection output signal. It is shown that such a coupling cannot be corrected by subtraction of a constant offset at the demodulator output since the crosstalk is sent into the self-excitation loop and is multiplied by the closed loop transfer function. We present a circuit that actively compensates, outside the vacuum environment, the internal crosstalk by adding to the deflection output a dephased fraction of the electrostatic excitation signal.

Direct evidence for shallow acceptor states with nonspherical symmetry in GaAs.

We investigate the energy and symmetry of Zn and Be dopant-induced acceptor states in GaAs using cross-sectional scanning tunnelling microscopy (STM) and spectroscopy at low temperatures. The ground and first excited states are found to have a nonspherical symmetry. In particular, the first excited acceptor state has a T(d) symmetry. Its major contribution to the STM empty-state images allows us to explain the puzzling triangular shaped contrast observed in the empty-state STM images of acceptor impurities in III-V semiconductors.

[Prospective controlled study comparing laparoscopy and the Shouldice technique in the treatment of unilateral inguinal hernia]. / Etude prospective contrôlée comparant laparoscopie et Shouldice dans le traitement de la hernie inguinale unilatérale.

Between October 1992 and September 1994, 70 patients presenting with primary unilateral hernia were randomly assigned to either a transabdominal preperitoneal laparoscopic (group L) repair (n = 35) with a 3 x 5 inch polypropylene mesh or a conventional Shouldice repair (group S) (n = 35). The series consisted of 60 men and 10 women, with a median age of 56 years and a BMI of 24. We used the Nyhus classification; there were 25 type 2, 24 type 3a and 21 type 3b hernias. Preoperative characteristics of both groups were equivalent. When comparing group L to group S, we noted a similar operative time (65 +/- 20 min) and a similar postoperative hospital stay (3.8 +/- 1.3 days). The postoperative pain that was evaluated on a visual analogue scale (score from 0 to 10) was lower in group L. On the first and third postoperative day, the mean score was 3.4 +/- 1.5 and 1.3 +/- 1.4 in (group L compared) to 5.3 +/- 1.9 (p < 0.001) and 2.8 +/- 1.8 (p < 0.005) in group S. Significant morbidity occurred in 7 patients of group L: 3 seromas and 4 cases of orchitis, and in 5 patients of group S: 1 wound abcess, 2 cases of chronic neuralgia and 2 cases of orchitis. We recorded a quicker return to home activities in group L: 6 +/- 2 versus 10 +/- 4 days (p < 0.05) in group S but time off work was similar in both groups (30 +/- 9 days). All patients were evaluated in April 1996: the median follow-up was 30 months (range: 19-42 months). We recorded 1 recurrence in group L and 3 in group S. Statistical analysis revealed that the recurrence rate, for patients older than 50 and presenting with type 3 hernia, was higher in group S (3/14 = 21%) than in group L (0/13 = 0%). In conclusion, compared to Shouldice repair, laparoscopic herniorrhaphy is associated with less postoperative pain, a quicker return to everyday activities and an equivalent postoperative morbidity. In our series, the recurrence rate was even lower for patients older than 50 with type 3 hernia.

Prospective analysis of 192 consecutive cholecystectomies: a comparative study between laparoscopy and laparotomy.

The hospital records of all the patients who underwent cholecystectomy because of specific biliary symptoms, between October 1990 and March 1993, were prospectively analyzed. The series consisted of 192 patients (159 women and 33 men), the mean age was 56 years and the mean body mass index was 26. Indication for surgery was uncomplicated gallstones in 113, common bile duct stones in 28 and cholecystitis in 51 patients. In those groups, respectively 94 (83%), 16 (57%) and 23 (45%) patients had a laparoscopic cholecystectomy. In total, laparoscopic cholecystectomy was successfully performed in 127 (95%) of the 133 patients in whom it was attempted. When compared with laparotomy, laparoscopic cholecystectomy was associated with shorter operative time: 88 +/- 41 min. (Mean +/- SD) versus 132 +/- 64 min. (p < 0,001), shorter postoperative hospital stay: 5 +/- 3 days versus 13 +/- 7 days (p < 0.001) and reduced cost of hospitalization: 103.301 +/- 51.062 BF versus 186.931 +/- 113.651 BF (p < 0.001). We noted an equivalent perioperative morbidity incidence in the two groups. The advantages of laparoscopy compared to laparotomy were recorded whatever the indication for cholecystectomy was. Therefore, with the increasing experience of surgeons and the improving quality of laparoscopic instruments, we think that laparoscopy can be considered for all patients requiring cholecystectomy.

Once-daily dosing of a new ultrasustained-release theophylline preparation.

Theophylline plasma levels and profiles were evaluated in patients with chronic obstructive pulmonary disease during once-daily dosing of an ultrasustained-release theophylline preparation (Theo-1; capsules filled with microgranules containing 400 mg anhydrous theophylline). In a first study, 6 patients received a single morning dose of 800 mg (a) in the fasting state, and (b) with a protein-fat-rich breakfast in a random order, and the systemic theophylline availability was evaluated for 48 h. No significant differences were found either in Cmax (a: 7.0 +/- 3.2 micrograms/ml; b: 7.6 +/- 2.6 micrograms/ml), or in Tmax (a: 11.7 +/- 6.1 h; b: 10.2 +/- 3.6 h). Elimination half-life was in a 11.4 +/- 4.4 h and in b 12.9 +/- 4.8 h (p less than 0.05). In a second study, the steady-state theophylline levels were measured during a 24-hour dosage interval on day 8 after intake of 800 mg at 8 a.m. in 16 patients and at 8 p.m. in 11 patients. Plateau-shaped plasma concentration-time curves were obtained, with small fluctuations between the peak (Cmax) and trough (Cmin) levels: [100(Cmax-Cmin)/Cmin] was 83 +/- 40% after morning dose, and 54 +/- 26% after evening dose (p less than 0.05). Cmax was 12 +/- 5 and 11 +/- 4 micrograms/ml, respectively (NS). Tmax was 9 +/- 3 and 11 +/- 3 h, respectively (NS). The FDA fluctuation for the 37 patients was 48 +/- 20%. In a third study, the dose-plasma concentration relationship was evaluated in steady state in 6 patients receiving 400, 800 and 1,200 mg for 3 days each. The trough plasma concentrations were 2.6 +/- 0.9, 6.2 +/- 2.1 and 10.2 +/- 3.1 micrograms/ml, respectively. Six hours after drug intake the plasma levels were 5.0 +/- 1.6, 10.6 +/- 2.5 and 15.4 +/- 4.2 micrograms/ml, respectively; and 12 h after drug intake, 4.9 +/- 1.4, 11.6 +/- 2.4 and 14.5 +/- 3.7 micrograms/ml, respectively. In conclusion, we found in these studies that with once-daily dosing of the ultrasustained-release preparation Theo-1, plateau-shaped 24-hour theophylline plasma levels could be achieved. The relationship between daily dosage and theophylline plasma levels was linear intraindividually but showed an important interindividual variation. No consistent interference by food intake was found and no serious side effects occurred within therapeutic plasma levels.

[Haematic pseudo-cysts of the adrenal. About three cases (author's transl)]. / Les pseudo-kystes hématiques de la surrénale. A propos de 3 observations.

The authors report 3 cases of haematic cysts of the adrenal, discovered in young adults (3 female), presenting with lumbar or lumbo-abdominal pain, sometimes violent, and accompanied by fever. In each cases there was a palpable swelling in the hypochondrium and lumbar fossa. In two cases severe anaemia reflected the amount of haemorrhage which had taken place. IVU with a prolonged vascular nephrotomography time with several views and echotomography confirmed the diagnosis, avoiding the need for aortography whenever possible. The size of the cysts was such that adrenalectomy was necessary in two cases and the extent of adhesions required simultaneous nephrectomy. This is followed by a review of the literature, the dominant features being: the prevalence of haematic cysts which account for 40% of adrenal cysts, the absence of specificity of clinical symptoms and signs and the importance of radiological examinations, and finally the usual absence of any cause even though trauma may sometimes be possible.