Unoccupied electronic states of 2D Si on Ag-3-Si(111).

Optimizing substrate characterization to grow 2D Si layers on surfaces is a major issue toward the development of synthesis techniques of the promising silicene. We have used inverse photoemission spectroscopy (IPES) to study the electronic band structure of an ordered 2D Si layer on the3×3-Ag/Si(111) surface (3-Ag). Exploiting the large upwards band bending of the3-Ag substrate, we could investigate the evolution of the unoccupied surface and interface states in most of the Si band gap. In particular, thek∥-dispersion of the3-Ag free-electron-likeS1surface state measured by IPES, is reported for the first time. Upon deposition of ∼1 ML Si on3-Ag maintained at ∼200 °C, the interface undergoes a metal-insulator transition with the complete disappearance of theS1state. The latter is replaced by a higher-lying stateU0with a minimum at 1.0 eV aboveEF. The origin of this new state is discussed in terms of various Si 2D structures including silicene.

Prevalence of less severe hypercortisolism in fractured patients admitted in an outpatient clinic for metabolic bone diseases.

PURPOSE: To evaluate the prevalence of less severe hypercortisolism (LSH) in fractured patients, and its association with hypertension, hyperglicemia, dyslipidemia, and obesity. METHOD: From July 2015 to October 2018 we enrolled all fractured patients admitted in our outpatient center for metabolic bone diseases, after exclusion of patients with secondary osteoporosis apart from diabetes and taking drugs known to affect bone metabolism. In all enrolled patients we collected data regarding gonadal status, history of diabetes, high blood pressure, dyslipidemia, and measured blood pressure, lipid profile, fasting glycaemia. Bone mass was measured with DXA at lumbar spine and femoral neck and the presence of fractures was evaluated with X-ray of thoracic and lumbar spine. All patients performed twice, 1 mg overnight dexametasone suppression test (DST) and, as confirmatory, 2day low-dose DST for diagnosing hypercortisolism. RESULTS: We enrolled 101 fractured patients (75 females, 26 males), aged 65 ± 10.3 years. Five out of 101 (5.0%) patients were diagnosed as LSH. Fifty-five (54.5%) out of 101 were hypertensive, 57 (56.4%) dyslipidemic, 17 (16.8%) hyperglicaemic, 28(27.7%) obese patients. LSH tended to be associated to blood hypertension [5/5 vs 50/96 (Fisher exact test, p = 0.06) hypertensive patients]. Four out five LSH patients were hypogonadic. CONCLUSIONS: Our study confirms that a nonnegligible percentage of fractured subjects actually presents an unrecognized hypercortisolism. Accordingly, regardless of age, we suggest to screen for hypercortisolism all patients with established osteoporosis and in particular hypertensive subjects.

Hidden hypercortisolism: a too frequently neglected clinical condition.

PURPOSE: Classic Cushing's syndrome (CS) is a severe disease characterized by central obesity, hypertension, easy bruising, striae rubrae, buffalo hump, proximal myopathy and hypertricosis. However, several CS cases have also been reported with unusual or camouflaged manifestations. In recent years, several authors investigated the prevalence of "hidden hypercortisolism" (HidHyCo) among subjects affected with bone fragility, hypertension and type 2 diabetes mellitus (DM2). The prevalence of the HidHyCo is estimated to be much higher than that of classic CS. However, similarly to classic CS, HidHyCo is known to increase the risk of fractures, cardiovascular disease and mortality. METHODS: We reviewed all published cases of unusual presentations of hypercortisolism and studies specifically assessing the HidHyCo prevalence in diabetic, osteoporotic and hypertensive patients. RESULTS: We found 49 HidHyCo cases, in whom bone fragility, hypertension and diabetes were the presenting manifestations of an otherwise silent hypercortisolism. Amongst these cases, 34.7%, 32.7%, 6.1% and 19.0%, respectively, had bone fragility, hypertension, DM2 or hypertension plus DM2 as the sole clinical manifestations of HidHyCo. Overall, 25% of HidHyCo cases were of pituitary origin, and bone fragility was the very prevalent first manifestation among them. In population studies, it is possible to estimate that 1-4% of patients with apparent primary osteoporosis has a HidHyCo and the prevalence of this condition among diabetics ranges between 3.4 and 10%. CONCLUSION: These data indicate that patients with resistant or suddenly worsening hypertension or DM2 or unexplainable bone fragility should be screened for HidHyCo using the most recently approved sensitive cut-offs.

Peculiar covalent bonding of C60/6H-SiC(0 0 0 1)-(3 × 3) probed by photoelectron spectroscopy.

High resolution photoemission with synchrotron radiation was used to study the interface formation of a thin layer of C60 on 6H-SiC(0 0 0 1)-(3 × 3), characterized by protruding Si-tetramers. The results show that C60 is chemisorbed by orbital hybridization between the highest-occupied molecular orbital (HOMO) and the p z orbital of Si adatom at the apex of the tetramers. The covalent nature of the bonding was inferred from core level as well as valence band spectra. The Si 2p spectra reveal that a large fraction (at least 45%) of the Si adatoms remain unbound despite the reactive character of the associated dangling bonds. This is consistent with a model in which each C60 is attached to the substrate through a single covalent C60-Si bond. A binding energy shift of the core levels associated with sub-surface Si or C atoms indicates a decrease of the SiC band bending caused by a charge transfer from the C60 molecules to the substrate via the formation of donor-like interface states.

Advanced photoelectric effect experiment beamline at Elettra: A surface science laboratory coupled with Synchrotron Radiation.

We report the main characteristics of the advanced photoelectric effect experiments beamline, operational at Elettra storage ring, featuring a fully independent double branch scheme obtained by the use of chicane undulators and able to keep polarization control in both linear and circular mode. The paper describes the novel technical solutions adopted, namely, (a) the design of a quasiperiodic undulator resulting in optimized suppression of higher harmonics over a large photon energy range (10-100 eV), (b) the thermal stability of optics under high heat load via cryocoolers, and (c) the end station interconnected setup allowing full access to off-beam and on-beam facilities and, at the same time, the integration of users' specialized sample growth chambers or modules.

Interface dipole formation of different ZnPcCl(8) phases on Ag(111) observed by Kelvin probe force microscopy.

Recently, we investigated the adsorption of octachloro zinc phthalocyanine (ZnPcCl(8)) on Ag(111) by scanning tunneling microscopy. Compared to the standard phthalocyanine, halogenated phthalocyanine molecules show a much more complex binding behavior, which results in the formation of three different structural phases. These phases follow from the ordering process with the formation of 8, 4 and 0 intermolecular hydrogen-halogen bonds (Abel et al 2006 ChemPhysChem 7 82). In the present work we investigate these phases by Kelvin probe force microscopy in order to quantitatively deduce the electric interface barrier of the first monolayer. Our measurements reveal that the binding behavior does not only affect the structural ordering but also the interface dipole formation, which leads to different work functions. The fact that we observe interface barriers of opposite signs between ordered and disordered molecular layers underlines the importance of exactly knowing the molecular arrangement at the interface when assembling organic molecule devices.

Standardization of PSA measures: a reappraisal and an experience with WHO calibration of Beckman Coulter Access Hybritech total and free PSA.

Prostate-specific antigen (PSA) is the serum biomarker most widely used in prostate diseases. Since there is significant variation in PSA results among non-equimolar assays, the 90:10 ratio of complexed PSA to free PSA (the Stanford standard) was proposed as standardization; this became the basis for the PSA mass standards WHO 96/670 for tPSA and 96/668 for fPSA. Nevertheless, recent publications underlined the lack of interchangeability between different commercial assays, all claimed to be equimolar and calibrated to the WHO standard. Importantly, the WHO calibration yields about 16-20% lower PSA results. Manufacturers that have chosen to calibrate existing assays to the mass value of WHO 96/760 have introduced a significant negative bias compared to the Hybritech assay calibration; this bias is transferred to clinical evaluation if the cutoff of 4 ng/mL, clinically validated for the Hybritech assay, is maintained with the WHO calibration. Beckman Coulter recently provided the option of calibrating the Access Hybritech PSA and Free PSA assays to the WHO standard introducing a different clinical cutoff. Using two different reagent lots, we tested about 200 routine patients for tPSA and fPSA with both calibrations; we also calculated the f/tPSA ratio with both calibrated methods. Moreover, we verified the analytical sensitivity and inter- and intra-assay variability. In accordance with the claim of the manufacturer, the results obtained with the WHO calibration showed a negative bias of about 25% and, as expected, no significant difference was found for % f/tPSA. The same bias was found when retesting samples of the External Quality Assessment Scheme of the Institute of Clinical Physiology of the National Research Council in Pisa. Based on this experience we decided for the moment to keep the Hybritech calibration, in order to avoid cutoff changes during patient follow-up. Moreover, we have started to provide information to clinicians aimed at the alignment of our results with the WHO standardization.

Phase separation in potassium-doped ZnPc thin films.

In this study synchrotron radiation was used to investigate the electronic properties of a thin film of zinc-phthalocyanine (ZnPc) deposited on Si(001)-2x1 and progressively doped with K atoms. The molecular orientation was probed by angular-dependent x-ray absorption spectroscopy and the molecules were found to lie with the macrocycle plane roughly perpendicular to the surface. The evolution of the electronic properties of the film was then followed by measuring the photoemission spectra upon in situ evaporation of K atoms on the pristine ZnPc film. The results show that doping proceeds through charge donation from the K atoms to the molecular units whose lowest unoccupied molecular orbital (LUMO) becomes progressively filled. Despite the fact that the LUMO spectral weight increases as the stoichiometry x in the K(x)ZnPc compound varies from about 1 to 4 (as determined by core level photoemission), no detectable density of states was observed at the Fermi level, showing that the film remains insulating for all the investigated stoichiometries. On the other hand the C 1s spectra, which appear merely broadened at the earliest stages of doping (x approximately 1), clearly develop two distinct components when x exceeds 2, suggesting that the charge state is not the same for all the molecules. At the same time, the modification of the valence band points towards the coexistence of two distinct phases with x=2 and x=4.

The clinical relevance of antinuclear antibodies in connective tissue diseases.

Detection of antinuclear antibodies (ANA) is of growing relevance in the management of connective tissue diseases (CTD). ANA are useful diagnostic tools, since most CTD have a peculiar ANA profile, characterized either by restricted specificities, abnormally high titers, or both. Furthermore, the study of the intimate structure and function of nuclear antigens, and of their corresponding antibodies may provide important insights to understand both origin and pathogenesis of CTD. Finally, the more or less close association of ANA levels and/or specificity with certain signs or symptoms of CTD is of increasing help to the clinician in the correct monitoring and management of CTD.