Non equilibrium optical properties in semiconductors from first--principles: a combined theoretical and experimental study of bulk silicon

The calculation of the equilibrium optical properties of bulk silicon by using the Bethe--Salpeter equation solved in the Kohn--Sham basis represents a cornerstone in the development of an ab--initio approach to the optical and electronic properties of materials. Nevertheless calculations of the {\em transient} optical spectrum using the same efficient and successful scheme are scarce. We report, here, a joint theoretical and experimental study of the transient reflectivity spectrum of bulk silicon. Femtosecond transient reflectivity is compared to a parameter--free calculation based on the non--equilibrium Bethe--Salpeter equation. By providing an accurate description of the experimental results we disclose the different phenomena that determine the transient optical response of a semiconductor. We give a parameter--free interpretation of concepts like bleaching, photo--induced absorption and stimulated emission, beyond the Fermi golden rule. We also introduce the concept of optical gap renormalization, as a generalization of the known mechanism of band gap renormalization. The present scheme successfully describes the case of bulk silicon, showing its universality and accuracy.Comment: 14 pages, 13 figure

Resonant optical control of the structural distortions that drive ultrafast demagnetization in Cr2_2O3_3

We study how the color and polarization of ultrashort pulses of visible light can be used to control the demagnetization processes of the antiferromagnetic insulator Cr$_2$O$_3$. We utilize time-resolved second harmonic generation (SHG) to probe how changes in the magnetic and structural state evolve in time. We show that, varying the pump photon-energy to excite either localized transitions within the Cr or charge transfer states, leads to markedly different dynamics. Through a full polarization analysis of the SHG signal, symmetry considerations and density functional theory calculations, we show that, in the non-equilibrium state, SHG is sensitive to {\em both} lattice displacements and changes to the magnetic order, which allows us to conclude that different excited states couple to phonon modes of different symmetries. Furthermore, the spin-scattering rate depends on the induced distortion, enabling us to control the timescale for the demagnetization process. Our results suggest that selective photoexcitation of antiferromagnetic insulators allows fast and efficient manipulation of their magnetic state.Comment: 7 pages, 5 figure

Effects of natural compounds on microbial safety and sensory quality of Fior di Latte cheese, a typical Italian cheese.

This work presents a preliminary study to assess the efficiency of plant essential oils as natural food preservatives in Fior di Latte cheese. Selected compounds were directly dissolved into Fior di Latte brine. Packaged Fior di Latte samples were stored at 10 degrees C for about 6 d. The cell loads of spoilage and useful microorganisms were monitored to calculate the microbial acceptability limit. Results show that some tested compounds were not acceptable by the panel from a sensorial point of view. Most compounds did not affect the microbial acceptability limit value to a great extent, and only a few such as lemon, sage, and thyme markedly prolonged the microbial acceptability limit of the investigated fresh cheese. Moreover, the above active agents exerted an inhibitory effect on the microorganisms responsible for spoilage without affecting the dairy microflora

Shelf life of Stracciatella cheese under modified-atmosphere packaging

The aim of this work is to evaluate the shelf life of Stracciatella cheese packaged in a protective atmosphere, using 4 different CO(2):N(2):O(2) gas mixtures [50:50:0 (M1), 95:5:0 (M2), 75:25:0 (M3), and 30:65:5 (M4) vol/vol] and stored at 8 degrees C. Cheese in traditional tubs and under vacuum were used as the controls. Results showed that the modified-atmosphere packaging, in particular M1 and M2, delayed microbial growth of spoilage bacteria, without affecting the dairy microflora, and prolonged the sensorial acceptability limit

Risk factors for incident depression in patients at first acute coronary syndrome

The association between depression and acute coronary syndrome (ACS) is well-established and the first seems to impact meaningfully on cardiac prognosis. Nonetheless only a few studies have evaluated the relationship between incident depression, defined as new cases in patients with no history of depression, and ACS. Therefore the aim of this study is to analyse the risk factors of incident depression in a sample of patients who were presenting their first ACS. 304 consecutive patients were recruited. The presence of major (MD) and minor (md) depression was assessed with the Primary Care Evaluation of Mental Disorders (PRIME-MD), whereas its severity was evaluated with the Hospital Anxiety and Depression Scale (HADS). Evaluations were collected both at baseline and at 1, 2, 4, 6, 9 and 12 month follow ups. Out of 304 subjects (80.6% males), MD was diagnosed in 15 (4.9%) and md in 25 patients (8.2%). At baseline risk factors for a post-ACS depressive disorder were being women (MD only), widowed (md only) and having mild anhedonic depressive symptoms few days after the ACS. Clinicians should keep in mind these variables when facing a patient at his/her first ACS, given the detrimental effect of depression on cardiac prognosis

Acute fluctuating neurological deficits after pulmonary vein isolation: unmasking a rare complication due to spontaneous spinal subdural bleeding: a case report

Background Pulmonary vein isolation (PVI) is becoming the therapy of choice for symptomatic paroxysmal drug-refractory atrial fibrillation (AF). The most frequently reported complications are vascular complications (1.4%). Bleeding complications of the central nervous system have rarely been described. We report a case of spontaneous spinal bleed after PVI. Case summary A 68-year-old woman with a 2-year history of highly symptomatic paroxysmal AF (EHRA 3) was referred for a PVI redo procedure. A high-density mapping showed pulmonary vein reconnection of all pulmonary veins successfully isolated by radiofrequency ablation. During the entire procedure, the patient had sinus rhythm with an ACT around 300 s. No intraprocedural and peri-procedural complications occurred. Four hours after haemostasis, the anticoagulation clotting time (ACT) was 110 s and rivaroxaban (20 mg) was reinitiated. In the following hours, the patient developed fluctuating neurological lower limb symptoms. A lumbar magnetic resonance imaging showed a subdural spinal haematic collection with an associated epidural component from L3 to S2 exerting compression over the dural sheath. A conservative treatment approach was adopted with progressive recovery of sensorial and motor deficits. After 5 months, the patient still presented residual lower limb motor deficits necessitating the support of a walking stick. Discussion We describe the first case of a spontaneous spinal bleeding following PVI. Given the gradual diffusion of PVI to treat AF in more clinically complex patients with a larger range of comorbidities, particular consideration should be given to seek predisposing bleeding factors in order to assess the risk for neurological complications

Macrospin dynamics in antiferromagnets triggered by sub-20 femtosecond injection of nanomagnons

The understanding of how the sub-nanoscale exchange interaction evolves in macroscale correlations and ordered phases of matter, such as magnetism and superconductivity, requires to bridging the quantum and classical worlds. This monumental challenge has so far only been achieved for systems close to their thermodynamical equilibrium. Here we follow in real time the ultrafast dynamics of the macroscale magnetic order parameter in the Heisenberg antiferromagnet KNiF 3 triggered by the impulsive optical generation of spin excitations with the shortest possible nanometre wavelength and femtosecond period. Our magneto-optical pump-probe experiments also demonstrate the coherent manipulation of the phase and amplitude of these femtosecond nanomagnons, whose frequencies are defined by the exchange energy. These findings open up opportunities for fundamental research on the role of short-wavelength spin excitations in magnetism and strongly correlated materials; they also suggest that nanospintronics and nanomagnonics can employ coherently controllable spin waves with frequencies in the 20 THz domain

Exciton-phonon coupling strength in single-layer MoSe2 at room temperature

Single-layer transition metal dichalcogenides are at the center of an ever increasing research effort both in terms of fundamental physics and applications. Exciton-phonon coupling plays a key role in determining the (opto)electronic properties of these materials. However, the exciton-phonon coupling strength has not been measured at room temperature. Here, we develop two-dimensional micro-spectroscopy to determine exciton-phonon coupling of single-layer MoSe2. We detect beating signals as a function of waiting time T, induced by the coupling between the A exciton and the A'1 optical phonon. Analysis of two-dimensional beating maps combined with simulations provides the exciton-phonon coupling. The Huang-Rhys factor of ~1 is larger than in most other inorganic semiconductor nanostructures. Our technique offers a unique tool to measure exciton-phonon coupling also in other heterogeneous semiconducting systems with a spatial resolution ~260 nm, and will provide design-relevant parameters for the development of optoelectronic devices

Major gaps in the information provided to patients before implantation of cardioverter defibrillators: a prospective patient European evaluation

AIMS: Information provided to patients prior to implantable cardioverter-defibrillator (ICD) insertion and their participation in the decision-making process are crucial for understanding ICD function and accepting this lifelong therapy. The aim of this study is to evaluate the extent to which different aspects related to ICD and quality of life were transmitted to patients prior to ICD implantation. METHODS AND RESULTS: Prospective, multicenter European study with an online questionnaire initiated by the European Heart Rhythm Association. The questionnaire was filled-in directly and personally by the ICD patients who were invited to participate. A total of 1809 patients (majority in their 40s-70s, with 624 women, 34.5%) from 10 European countries participated in the study. The median time from first ICD implantation was 5 years (interquartile range 2-10). Overall, 1155 patients (71.5%) felt optimally informed at the time of device implantation, however many respondents received no information about ICD-related complications (n = 801, 49.6%), driving restrictions (n = 718, 44.5%), and possibility of end-of-life ICD deactivation (n = 408, 25.4%). Of note, women were less frequently involved in the decision-making process than men (47.3% vs. 55.9%, P = 0.003) and reported to be less often optimally informed before ICD implantation than men (61.2% vs. 76.8%, P < 0.001). More women mentioned the desire to have learned more about ICD therapy and the benefit/risk balance (45.4% vs. 33.7% of men; P < 0.001). CONCLUSIONS: This patient-based evaluation provides alarming findings on the lack of information provided to patients prior ICD implantation, particularly for women