Broadband optical ultrafast reflectivity of Si, Ge and GaAs.

Ultrafast optical reflectivity measurements of silicon, germanium, and gallium arsenide have been carried out using an advanced set-up providing intense subpicosecond pulses (35 fs FWHM, [Formula: see text] = 400 nm) as a pump and broadband 340-780 nm ultrafast pulses as a white supercontinuum probe. Measurements have been performed for selected pump fluence conditions below the damage thresholds, that were carefully characterized. The obtained fluence damage thresholds are 30, 20.8, 9.6 mJ/[Formula: see text] for Si, Ge and GaAs respectively. Ultrafast reflectivity patterns show clear differences in the Si, Ge, and GaAs trends both for the wavelength and time dependences. Important changes were observed near the wavelength regions corresponding to the [Formula: see text], [Formula: see text] singularities in the joint density of states, so related to the peculiar band structure of the three systems. For Ge, ultrafast reflectivity spectra were also collected at low temperature (down to 80 K) showing a shift of the characteristic doublet peak around 2.23 eV and a reduction of the recovery times.

Mechanical exfoliation and layer number identification of single crystal monoclinic CrCl3.

After the recent finding that CrI3, displays ferromagnetic order down to its monolayer, extensive studies have followed to pursue new two-dimensional (2D) magnetic materials. In this article, we report on the growth of single crystal CrCl3 in the layered monoclinic phase. The system after mechanical exfoliation exhibits stability in ambient air (the degradation occurs on a time scale at least four orders of magnitude longer than is observed for CrI3). By means of mechanical cleavage and atomic force microscopy (AFM) combined with optical identification, we demonstrate the systematic isolation of single and few layer flakes onto 270 nm and 285 nm SiO2/Si (100) substrates with lateral size larger than graphene flakes isolated with the same method. The layer number identification has been carried with statistically significant data, quantifying the optical contrast as a function of the number of layers for up to six layers. Layer dependent optical contrast data have been fitted within the Fresnel equation formalism determining the real and imaginary part of the wavelength dependent refractive index of the material. A layer dependent (532 nm) micro-Raman study has been carried out down to two layers with no detectable spectral shifts as a function of the layer number and with respect to the bulk.

New insights on metal allergy in total joint arthroplasty.

Metal allergy is an uncommon and not completely understood cause of failure in total joint arthroplasty (TJA). However, either immunopathology neither histologic studies clarified the mechanisms through which the metal ions could lead to the complications related to them. The lack of evidence around this topic also reflects the difficulties to diagnose the MRP in TJA. In fact, the diagnosis is generally based on the exclusion of other causes. Currently, skin-patch testing and lymphocyte transformation test (LTT) are being commonly used to investigate about metal hypersensitivity and a delayed type-IV hypersensitivity is the immuno-histologic response to metals involved in TJA loosening. A review of the recent publications about this topic has been made focusing on immunology, histopathology, and clinics to better understand a still debated topic in orthopedic practice.

Linking flow-stream variability to grain size distribution of suspended sediment from a satellite-based analysis of the Tiber River plume (Tyrrhenian Sea).

Several coastal regions on Earth have been increasingly affected by intense, often catastrophic, flash floods that deliver significant amounts of sediment along shorelines. One of the critical questions related to the impact of these impulsive runoffs is "are flash floods more efficient in delivering non-cohesive sandy sediment along the coasts?" Here we relate flow stages (i.e., from erratic to persistent) to the grain size distribution of the suspended load, by performing a synergic analysis of in-situ river discharge and satellite-retrieved grain size distribution, from 2002 to 2014, covering the 2012 Tiber River (Italy) exceptional flood event. Our analysis shows novel and promising results regarding the capability of remote sensing in characterizing suspended sediment in terms of grain size distribution and reveals that erratic stages favour delivering of non-cohesive sandy sediment more than the persistent stages. This conclusion is supported by numerical simulations and is consistent with previous studies on suspended sediment rating curves.

Two-stage reimplantation in periprosthetic knee infection.

OBJECTIVE: The increasing number of total knee arthroplasties performed yearly worldwide has resulted in a concomitant rise in bacterial infections. Two-stage reimplantation has been reported as the most successful method of treating periprosthetic knee infections. The purpose of this study was to describe all the phases of the two-stage reimplantation and to review the literature regarding the topic. MATERIALS AND METHODS: Most significant and recent papers about the management of periprosthetic knee infection through a two-stage reimplantation protocol were carefully analysed and reviewed. Our personal experience, previously published, with two-stage-reimplantation protocol was also briefly reported. RESULTS: Two-stage reimplantation has been reported as the most successful method of treating periprosthetic knee infections. The strategy of using an antibiotic-loaded cement spacer and intravenous antibiotics with delayed exchange arthroplasty is actually considered the state-of-the-art, with a reported success rate of 88-96%. The two-stage protocol has been reported as a viable option also for patients with a periprosthetic knee infection by multidrug-resistant organisms. On the other hand, open debridement with polyethylene exchange and single-stage reimplantation have been reported effective only in selective case series involving acute infections by low-virulence organisms. CONCLUSIONS: The strategy that involves the use of cement spacer, intravenous antibiotic therapy, and successive revision total knee implantation is nowadays considered the gold standard for the management of the periprosthetic knee infection. This treatment is actually considered the first choice not only for chronic but also for acute infections, especially in the presence of resistant bacteria.

Free electron laser-driven ultrafast rearrangement of the electronic structure in Ti.

High-energy density extreme ultraviolet radiation delivered by the FERMI seeded free-electron laser has been used to create an exotic nonequilibrium state of matter in a titanium sample characterized by a highly excited electron subsystem at temperatures in excess of 10 eV and a cold solid-density ion lattice. The obtained transient state has been investigated through ultrafast absorption spectroscopy across the Ti M2,3-edge revealing a drastic rearrangement of the sample electronic structure around the Fermi level occurring on a time scale of about 100 fs.

Glass polymorphism in amorphous germanium probed by first-principles computer simulations.

The low-density (LDA) to high-density (HDA) transformation in amorphous Ge at high pressure is studied by first-principles molecular dynamics simulations in the framework of density functional theory. Previous experiments are accurately reproduced, including the presence of a well-defined LDA-HDA transition above 8 GPa. The LDA-HDA density increase is found to be about 14%. Pair and bond-angle distributions are obtained in the 0-16 GPa pressure range and allowed us a detailed analysis of the transition. The local fourfold coordination is transformed in an average HDA sixfold coordination associated with different local geometries as confirmed by coordination number analysis and shape of the bond-angle distributions.

Visible light photoactivity of Polypropylene coated Nano-TiO2 for dyes degradation in water.

The use of Polypropylene as support material for nano-TiO2 photocatalyst in the photodegradation of Alizarin Red S in water solutions under the action of visible light was investigated. The optimization of TiO2 pastes preparation using two commercial TiO2, Aeroxide P-25 and Anatase, was performed and a green low-cost dip-coating procedure was developed. Scanning electron microscopy, Atomic Force Microscopy and X-Ray Diffraction analysis were used in order to obtain morphological and structural information of as-prepared TiO2 on support material. Equilibrium and kinetics aspects in the adsorption and successive photodegradation of Alizarin Red S, as reference dye, are described using polypropylene-TiO2 films in the Visible/TiO2/water reactor showing efficient dyes degradation.

Short-range order of compressed amorphous GeSe2.

The structure of amorphous GeSe2 (a-GeSe2) has been studied by means of a combination of two-edges X-ray absorption spectroscopy (XAS) and angle-dispersive X-ray diffraction under pressures up to about 30 GPa. Multiple-edge XAS data-analysis of a-GeSe2 at ambient conditions allowed us to reconstruct and compare the first-neighbor distribution function with previous results obtained by neutron diffraction with isotopic substitution. GeSe2 is found to remain amorphous up to the highest pressures attained, and a reversible 1.5 eV red-shift of the Ge K-edge energy indicating metallization, occurs between 10 GPa and 15 GPa. Two compression stages are identified by XAS structure refinement. First, a decrease of the first-neighbor distances up to about 10 GPa, in the same pressure region of a previously observed breakdown of the intermediate-range order. Second, an increase of the Ge-Se distances, bond disorder, and of the coordination number. This stage is related to a reversible non-isostructural transition involving a gradual conversion from tetra- to octa-hedral geometry which is not yet fully completed at 30 GPa.

Spectrometer for X-ray emission experiments at FERMI free-electron-laser.

A portable and compact photon spectrometer to be used for photon in-photon out experiments, in particular x-ray emission spectroscopy, is presented. The instrument operates in the 25-800 eV energy range to cover the full emissions of the FEL1 and FEL2 stages of FERMI. The optical design consists of two interchangeable spherical varied-lined-spaced gratings and a CCD detector. Different input sections can be accommodated, with/without an entrance slit and with/without an additional relay mirror, that allow to mount the spectrometer in different end-stations and at variable distances from the target area both at synchrotron and at free-electron-laser beamlines. The characterization on the Gas Phase beamline at ELETTRA Synchrotron (Italy) is presented.

Reflectivity enhancement in titanium by ultrafast XUV irradiation.

The study of highly photo-excited matter at solid state density is an emerging field of research, which is benefitting the development of free-electron-laser (FEL) technology. We report an extreme ultraviolet (XUV) reflectivity experiment from a titanium (Ti) sample irradiated with ultrafast seeded FEL pulses at variable incident photon fluence and frequency. Using a Drude formalism we relate the observed increase in reflectivity as a function of the excitation fluence to an increase in the plasma frequency, which allows us to estimate the free electron density in the excited sample. The extreme simplicity of the experimental setup makes the present approach potentially a valuable complementary tool to determine the average ionization state of the excited sample, information of primary relevance for understanding the physics of matter under extreme conditions.

Determination of the ion temperature in a stainless steel slab exposed to intense ultrashort laser pulses.

We present an effective approach to determine the amount of energy absorbed by solid samples exposed to ultrashort laser pulses, thus, retrieving the maximum temperature attained by the ion lattice in the picosecond time scale. The method is based on the pyrometric detection of a slow temperature fluctuation on the rear side of a sample slab associated with absorption of the laser pulse on the front side. This approach, successfully corroborated by theoretical calculations, can provide a robust and practical diagnostic tool for characterization of laser-generated warm dense matter.

Crystalline nucleation in undercooled liquids: a Bayesian data-analysis approach for a nonhomogeneous Poisson process.

A Bayesian data-analysis approach to data sets of maximum undercooling temperatures recorded in repeated melting-cooling cycles of high-purity samples is proposed. The crystallization phenomenon is described in terms of a nonhomogeneous Poisson process driven by a temperature-dependent sample nucleation rate J(T). The method was extensively tested by computer simulations and applied to real data for undercooled liquid Ge. It proved to be particularly useful in the case of scarce data sets where the usage of binned data would degrade the available experimental information.

Depth profiling of melting and metallization in Si(111) and Si(001) surfaces.

An original approach for measuring the depth profile of melting and metallization of the Si(111) and Si(001) surfaces is proposed and applied. The different probing depths of the Auger electron and electron energy loss (EELS) spectroscopies are exploited to study the number of molten and metallic layers within 5-30 Å from the surface up to about 1650 K. Melting is limited to 3 atomic layers in Si(001) in the range 1400-1650 K while the number of molten layers grows much faster (5 layers at about 1500 K) in Si(111) as also indicated by the L(3)-edge shift observed by EELS. The relationship between melting and metallization is briefly discussed.

Localization of the dopant in Ge:Mn diluted magnetic semiconductors by x-ray absorption at the Mn K edge.

A unitary picture of the structural properties of Mn(x)Ge(1-x) diluted alloys fabricated by either ion implantation or molecular beam epitaxy (MBE), at various growth temperatures (from 80 to about 623 K) and few per cent concentrations, is proposed. Analysis is based on synchrotron radiation x-ray absorption spectroscopy at the Mn K edge. When the growth temperature exceeds 330 K, the MBE samples show a high number of precipitated ferromagnetic nanoparticles, mainly Mn(5)Ge(3), nucleated from the previous occupation of interstitial tetrahedral sites. Efficient substitution is observed in the case of MBE samples made by alternate layers of GeMn alloys grown at T ≤ 433 K and undoped Ge thick layers. Similar good dilution properties are obtained by implanting Mn ions at low temperatures (80 K). Possible precursors to preferential mechanisms in the alloy formation are discussed on the basis of the present comparative study.

Meal intake similarly reduces circulating concentrations of octanoyl and total ghrelin in humans.

UNLABELLED: ABSTRACT. Several data show that meal intake and nutritional status regulate circulating ghrelin concentrations in humans. Ghrelin mainly circulates in two different forms: octanoyl and des-octanoyl ghrelin. Most circulating ghrelin is des-octanoyl ghrelin which is considered inactive because it lacks endocrine activity. However, recent evidence suggests that des-octanoyl ghrelin exerts biological activity such as stimulation of adipogenesis, cardiovascular effects and control of cell growth. In healthy humans, although the total ghrelin concentration is known to peak before meals and to be reduced by food intake, no data are available about the octanoyl ghrelin response in the absorptive state. Therefore, after an overnight fast, we compared the effects of a mixed meal ingestion (meal study) or of additional 240 min fasting (control study) on plasma concentrations of octanoyl and total ghrelin in 6 healthy subjects (body mass index: 23 +/- 0.7). At baseline, octanoyl-ghrelin accounted for 3.15 +/- 0.2% of total circulating ghrelin without differences between the two sessions. A similar ratio was maintained in the absorptive state with no differences between the studies and basal values. Compared with control, meal intake significantly suppressed (nadir at 90 min) octanoyl and total ghrelin by 38 +/- 3 and 40 +/- 3% of basal values, respectively. In the meal study, multivariate analysis of variance showed that serum insulin best predicted plasma octanoyl-ghrelin concentrations accounting for 97% of its variation (r2 = -0.97,p = 0.0016). IN CONCLUSION: in healthy humans, octanoyl-ghrelin represents about 3-4% of total circula-ting ghrelin and this ratio is closely maintained in post-absorptive and absorptive states.

Effects of whole-body vibration exercise on the endocrine system of healthy men.

Whole-body vibration is reported to increase muscle performance, bone mineral density and stimulate the secretion of lipolytic and protein anabolic hormones, such as GH and testosterone, that might be used for the treatment of obesity. To date, as no controlled trial has examined the effects of vibration exercise on the human endocrine system, we performed a randomized controlled study, to establish whether the circulating concentrations of glucose and hormones (insulin, glucagon, cortisol, epinephrine, norepinephrine, GH, IGF-1, free and total testosterone) are affected by vibration in 10 healthy men [age 39 +/- 3, body mass index (BMI) of 23.5 +/- 0.5 kg/m2, mean +/- SEM]. Volunteers were studied on two occasions before and after standing for 25 min on a ground plate in the absence (control) or in the presence (vibration) of 30 Hz whole body vibration. Vibration slightly reduced plasma glucose (30 min: vibration 4.59 +/- 0.21, control 4.74 +/- 0.22 mM, p=0.049) and increased plasma norepinephrine concentrations (60 min: vibration 1.29 +/- 0.18, control 1.01 +/- 0.07 nM, p=0.038), but did not change the circulating concentrations of other hormones. These results demonstrate that vibration exercise transiently reduces plasma glucose, possibly by increasing glucose utilization by contracting muscles. Since hormonal responses, with the exception of norepinephrine, are not affected by acute vibration exposure, this type of exercise is not expected to reduce fat mass in obese subjects.

Laparoscopic radical nephrectomy for T1 renal cancer: the gold standard? A comparison of laparoscopic vs open nephrectomy.

OBJECTIVE: To evaluate the complication rate and clinical follow-up of patients treated for T1 renal cancer by open or laparoscopic nephrectomy at the same institution, as this approach appears to be attractive for treating small renal cancers. PATIENTS AND METHODS: Between 1995 and 2002, 39 patients underwent retroperitoneal laparoscopic and 26 transperitoneal open radical nephrectomy for T1 renal cancer (TNM 1997). Variables before during and after surgery, e.g. cancer recurrence, were compared between the groups. RESULTS: There were no differences between the laparoscopic and open groups in age, sex ratio, weight, height, fitness score, operative duration (134 vs 133 min), minor or major complications, tumour diameter, Fuhrman grade or length of follow-up. Patients who underwent laparoscopic surgery had less blood loss (133 vs 357 mL, P < 0.001), less need for transfusion (none vs 150 mL, P = 0.04), a lower consumption of analgesia drugs, and shorter hospitalization (5.5 vs 8.8 days, P < 0.001). With a mean follow-up of 20.4 months there was no recurrence or tumour progression. CONCLUSION: Laparoscopic radical nephrectomy for patients with T1 renal cancer is a safe, reliable procedure that decreases hospitalization time and bleeding, and ensures the same cancer control as open nephrectomy.

Environmental risk factors for type 1 diabetes in Rome and province.

BACKGROUND: In subjects genetically susceptible to type 1 diabetes, exposure to environmental factors during the gestational period, the neonatal period, and the first years of life is thought to play an important role in triggering the immune process leading to beta cell destruction. AIMS: To investigate risk factors for inhabitants of continental Italy. METHODS: A case-control study of 150 type 1 diabetes cases and 750 control subjects (age range 6-18 years) was carried out in Rome and its province, measuring the exposure to environmental risk factors. RESULTS: Three environmental factors were found to occur significantly more in the diabetic group than in the controls. During the mothers' pregnancies, the one risk factor which proved to be higher in diabetics than in controls was maternal infectious disease. During the neonatal period, no risk factors associated with the disease were detected. During early life, eczema and a short duration of breast feeding (less than three months), occurred significantly more in diabetic cases than controls. CONCLUSION: Eczema and breast feeding for less than three months are risk factors for type 1 diabetes in a southern European population. The type, duration, and mode of treatment for infectious diseases during pregnancy need additional investigation as risk factors for type 1 diabetes.