Search

We investigate the orthorhombic distortion and the structural dynamics of epitaxial MnAs layers on GaAs(001) using static and time-resolved x-ray diffraction. Laser-induced intensity oscillations of Bragg reflections allow us to identify the optical phonon associated with orthorhombic distortion and to follow its softening along the path towards an undistorted phase of hexagonal symmetry. The frequency of this mode falls in the THz range, in agreement with recent calculations. Incomplete softening suggests that the β-γ transformation deviates from a purely second-order displacive transition.

The intense research effort investigating magnetic skyrmions and their applications for spintronics has yielded reports of more exotic objects including the biskyrmion, which consists of a bound pair of counter-rotating vortices of magnetization. Biskyrmions have been identified only from transmission electron microscopy images and have not been observed by other techniques, nor seen in simulations carried out under realistic conditions. Here, quantitative Lorentz transmission electron microscopy, X-ray holography, and micromagnetic simulations are combined to search for biskyrmions in MnNiGa, a material in which they have been reported. Only type-I and type-II magnetic bubbles are found and images purported to show biskyrmions can be explained as type-II bubbles viewed at an angle to their axes. It is not the magnetization but the magnetic flux density resulting from this object that forms the counter-rotating vortices., (© 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Chirality in condensed matter has recently become a topic of the utmost importance because of its significant role in the understanding and mastering of a large variety of new fundamental physical mechanisms. Versatile experimental approaches, capable to reveal easily the exact winding of order parameters, are therefore essential. Here we report x-ray resonant magnetic scattering as a straightforward tool to reveal directly the properties of chiral magnetic systems. We show that it can straightforwardly and unambiguously determine the main characteristics of chiral magnetic distributions: i.e., its chiral nature, the quantitative winding sense (clockwise or counterclockwise), and its type, i.e., Néel [cycloidal] or Bloch [helical]. This method is model independent, does not require a priori knowledge of the magnetic parameters, and can be applied to any system with magnetic domains ranging from a few nanometers (wavelength limited) to several microns. By using prototypical multilayers with tailored magnetic chiralities driven by spin-orbit-related effects at Co|Pt interfaces, we illustrate the strength of this method.

The SOLEIL synchrotron radiation source is regularly operated in special filling modes dedicated to pump-probe experiments. Among others, the low-α mode operation is characterized by shorter pulse duration and represents the natural bridge between 50 ps synchrotron pulses and femtosecond experiments. Here, the capabilities in low-α mode of the experimental set-ups developed at the TEMPO beamline to perform pump-probe experiments with soft X-rays based on photoelectron or photon detection are presented. A 282 kHz repetition-rate femtosecond laser is synchronized with the synchrotron radiation time structure to induce fast electronic and/or magnetic excitations. Detection is performed using a two-dimensional space resolution plus time resolution detector based on microchannel plates equipped with a delay line. Results of time-resolved photoelectron spectroscopy, circular dichroism and magnetic scattering experiments are reported, and their respective advantages and limitations in the framework of high-time-resolution pump-probe experiments compared and discussed.

Spintronic devices currently rely on magnetization control by external magnetic fields or spin-polarized currents. Developing temperature-driven magnetization control has potential for achieving enhanced device functionalities. Recently, there has been much interest in thermally induced magnetisation switching (TIMS), where the temperature control of intrinsic material properties drives a deterministic switching without applying external fields. TIMS, mainly investigated in rare-earth-transition-metal ferrimagnets, has also been observed in epitaxial Fe/MnAs/GaAs(001), where it stems from a completely different physical mechanism. In Fe/MnAs temperature actually modifies the surface dipolar fields associated with the MnAs magnetic microstructure. This in turn determines the effective magnetic field acting on the Fe overlayer. In this way one can reverse the Fe magnetization direction by performing thermal cycles at ambient temperatures. Here we use element selective magnetization measurements to demonstrate that various magnetic configurations of the Fe/MnAs/GaAs(001) system are stabilized predictably by acting on the thermal cycle parameters and on the presence of a bias field. We show in particular that the maximum temperature reached during the cycle affects the final magnetic configuration. Our findings show that applications are possible for fast magnetization switching, where local temperature changes are induced by laser excitations.

Thin film magnetization reversal without applying external fields is an attractive perspective for applications in sensors and devices. One way to accomplish it is by fine-tuning the microstructure of a magnetic substrate via temperature control, as in the case of a thin Fe layer deposited on a MnAs/GaAs(001) template. This work reports a time-resolved resonant scattering study exploring the magnetic and structural properties of the Fe/MnAs system, using a 100 fs optical laser pulse to trigger local temperature variations and a 100 fs x-ray free-electron laser pulse to probe the induced magnetic and structural dynamics. The experiment provides direct evidence that a single optical laser pulse can reverse the Fe magnetization locally. It reveals that the time scale of the magnetization reversal is slower than that of the MnAs structural transformations triggered by the optical pulse, which take place after a few picoseconds already.

THE PURPOSE OF THIS STUDY WAS THE QUALITATIVE AND QUANTITATIVE ANALYSIS OF FLAVONOIDS FROM ROBINIA PSEUDOACACIA USING TWO DIFFERENT TECHNIQUES OF ANALYSIS: Thin Layer Chromatography (TLC) and TLC coupled with photo-densitometry. The results obtained by chromatographic analysis showed a higher concentration of flavonoids in flowers than in leaves. The flowers harvested in the plains have a higher concentration of hyperoside (0.9 mg/mL) compared with the flowers collected from the hills (0.54 mg/mL). The leaves are richer in ruthoside (0.98 mg/mL) compared with the flowers.

We present the first single-shot images of ferromagnetic, nanoscale spin order taken with femtosecond x-ray pulses. X-ray-induced electron and spin dynamics can be outrun with pulses shorter than 80 fs in the investigated fluence regime, and no permanent aftereffects in the samples are observed below a fluence of 25 mJ/cm(2). Employing resonant spatially muliplexed x-ray holography results in a low imaging threshold of 5 mJ/cm(2). Our results open new ways to combine ultrafast laser spectroscopy with sequential snapshot imaging on a single sample, generating a movie of excited state dynamics.

We present a method for imaging magnetic domains via x-ray Fourier transform holography at linearly polarized sources. Our approach is based on the separation of holographic mask and sample and on the Faraday rotation induced on the reference wave. We compare images of perpendicular magnetic domains obtained with either linearly or circularly polarized x-rays and discuss the relevance of this method to future experiments at free-electron laser and high-harmonic-generation sources., (© 2012 Optical Society of America)

Introduction: Transabdominal routes for surgery entail general anaesthesia with its inherent risks and complications (prolonged hospital stay, abdominal incisions that may be difficult in obese patients). Minimally invasive procedures require shorter hospitalization, have shorter recovery periods, less postoperative discomfort, and lower morbidity and complications. The purpose of this study was to use a porcine model to determine the feasibility and the safety of organ resection (oophorectomy and tubectomy)., Materials and Methods: 10 Big White pigs between 25-30 kg underwent transgastric ooforectomy. The first 5 cases were performed in a hybrid procedure (laparoscopic-NOTES) in order to have a better control and supervise the maneuvers done by the mobile endoscope and to guide in the abdominal cavity., Results: Adnexectomy was possible in all ten experiments. Full operative time (from starting endoscopy to complete gastrectomy closing) was 180 min to 270 min. The gastric defect closing was the most difficult manoever lasting from 10 min with OTSC clips to 100 using endoloops and clips. The animals have tolerated well the experiments and there have been no remarkable incidents during our 10 experments. In only one case a bleeding from gastotomy required electric coagulation., Conclusion: Transgastric ooforectomy in an experimental model is a procedure that requires advanced laparoscopical and endoscopical skills. Our early results are promissing. Its application in humans needs further confirmation of the method.

Introduction: Initially considered experimental, liver transplantation (LT) has become the treatment of choice for the patients with end-stage liver diseases., Material and Methods: Between April 2000 and October 2009, 200 LTs (10 reLTs) were performed in 190 patients, this study being retrospective. There were transplanted 110 men and 80 women, 159 adults and 31 children with the age between 1 and 64 years old (mean age--39.9). The main indication in the adult group was represented by viral cirrhosis, while the pediatric series the etiology was mainly glycogenosis and biliary atresia. There were performed 143 whole graft LTs, 46 living donor LTs, 6 split LTs, 4 reduced LTs and one domino LT RESULTS: The postoperative survival was 90% (170 patients). The patient and graft one-year and five-year survivals were 76.9%, 73.6% and 71%, 68.2%, respectively. The early complications occurred in 127 patients (67%). The late complications were recorded in 71 patients (37.3%). The intraoperative and early postoperative mortality rate was 9.5% (18 patients)., Conclusions: The Romanian liver transplantation program from Fundeni includes all types of current surgical techniques and the results are comparable with those from other international centers.

A gamma-ray source with an intense component around the giant dipole resonance for photonuclear absorption has been obtained via bremsstrahlung of electron bunches driven by a 10-TW tabletop laser. 3D particle-in-cell simulation proves the achievement of a nonlinear regime leading to efficient acceleration of several sequential electron bunches per each laser pulse. The rate of the gamma-ray yield in the giant dipole resonance region (8

The morphotype of 40 children with cryptorchidism (18 bilateral, 22 unilateral), selected by complex endocrine examination, was assessed in relation to age and clinical form of cryptorchidism. The morphotype was established on the basis of 9 anthropometric parameters (weight, stature, pube-ground distance, a-a, thr-thr, thoracic, abdominal, hips and cephalic circumferences). The malformed lot consists of 28 children with common and 12 with symptome cryptorchidism (5 adiposogenital, 3 male Turner's syndrome and 3 with gonadal dysgenesis). In the child with symptom cryptorchidism, the morphogram reveals, irrespective of age, a morphotype which corresponds in point of absolute dimensions and proportions, to the somatotype in which cryptorchidism as a symptome is included. The child with common cryptorchidism has irrespective of age, a normal or short stature and is underweight. Compared to the stature, the head is small, the lower limbs are short, the trunk is long and the hips are well developed. In our series of common cryptorchid child, the most marked statural deficit was found between 11 and 15 years as well as under the age of 6.

The reproductive ability of 150 men occupationally exposed to lead were studied by clinical and toxicological analysis. Subjects were divided into four groups: lead-poisoned workmen (23) and those showing a moderate (42), slight (35), or physiologic absorption (50). Findings show that (1) Lead poisoning as well as moderate increased absorption of lead decrease the fertile ability of men. An increased frequency of asthenospermia, hypospermia, and teratospermia have objectified the decrease. (2) Slight increased or physiologic absorption of lead do not significantly influence the fertile ability of workmen. (3) Hypofertility induced by lead is due, perhaps, to its direct toxic effect on the gonads, as no interference with the hypothalamopituitary axis were evidenced.

Age-related somatic variability studied by 15 anthropometric parameters was assessed in 278 subjects (138 boys and 140 girls) aged between 5 and 20 years. Of these, 30% had simple obesity, 10.0% obesity associated with hypothyroidism, 10.0% obesity with diabetes, 25% obesity with adrenocortical reaction, 23.5% functional adiposo-genital syndrome and 1.5% Cushing's syndrome. The peculiarities related to the somatic development as a whole, the degree of bone development, and adiposity are interpreted in the main clinical forms of obesity, on the basis of the morphogram.

The somatotype of 92 children with sexual structural anomalies of whom 28 with female Turner's syndrome, 22 with Klinefelter's syndrome, 20 with adreno-genital syndrome, 14 with hypospadias, 2 with Reinfenstein's syndrome and 6 with feminizing testis was established on the basis of biometric and genetically determined morphologic characteristics (dermatoglyphics, pigment complex). A morphogram utilizing 12 anthropometric and 5 dermatoglyphic parameters was constructed; it can be used in phenotypical differentiation of the anatomo-clinical variants of structural anomalies of the genitalia and gonads. The 12 anthropometric parameters were: weight, stature, height of the head + neck segment, the sternum-symphysis distance, length of arms and legs, the biacromial and bitrochanterian diameters, the circumference of the thorax, abdomen, hips and head. The dermatoglyphic parameters were: the digital delta index, TFRC, a-b ridge count, the ATD angle and the A line obliquity. For longitudinal assessment of the phenotype of children with structural anomalies of genitalia and gonads, the authors propose utilization of the percentile diagrams regarding weight, stature, pubes to floor distance, and the biacromial and bitrochanterian diameters.

Long-term variation (21-30 days) in the gonadotropic hormones level and testosterone was followed up in Klinefelter's syndrome (chromatine positive). Clinically, the authors followed up the development of the androgen-dependent target tissues before and after administration of 400 mg testosterone/month for 6 months. It was also found a fluctuation in the gonadotropic hormones secretion on a 21-30-day trial which differs from that of the normal adult male. We noticed a great variability of the androgen-dependent structures development in one and the same subject or in different subjects, and a low response to the action of big and prolonged doses of testosterone. The authors interpret these findings as a decrease in the sensitivity of the androgen-dependent target structures (hypothalamus and peripheral tissues) induced genetically and fundamenting the concept of the existence of a receptivity pathology.

The incidence of chromosome aberrations was studied by peripheral blood incubation (52 hr, the last 4 hr in the presence of Colcemid) using a modification of the Evans' technique in twenty-two men exposed to either vapors of metallic mercury (Group I) or organic mercury (Group II). Mercury concentrations of the work areas frequently exceeded the Maximum Allowable Concentrations in the past. During the year proceding the investigation, mercury values ranged between 0.15 and 0.44 mg/m3. None of the investigated men were poisoned, but all had had repeated increased mercury absorption with urinary eliminations reaching 890 microgram/l and 896 microgram/l for subjects in Groups I and II, respectively. The incidence of chromosome aberrations was significantly higher (P less than .001) in subjects exposed to mercury as compared with a control group (ten subjects) of a similar mean age. There was no statistical difference in the incidence of chromosome aberrations between men belonging to Groups I and II. Although an increase of both chromatid gaps and breaks was noticed in exposed men, the incidence did not significantly differ from controls. No chromatid interchanges were recorded and no difference between exposed and control subjects was noticed concerning the frequency of aneuploid or polyploid cells.