Coexistence of pressure-induced structural phases in bulk black phosphorus: a combined x-ray diffraction and Raman study up to 18 GPa

We report a study of the structural phase transitions induced by pressure in bulk black phosphorus by using both synchrotron x-ray diffraction for pressures up to 12.2 GPa and Raman spectroscopy up to 18.2 GPa. Very recently black phosphorus attracted large attention because of the unique properties of fewlayers samples (phosphorene), but some basic questions are still open in the case of the bulk system. As concerning the presence of a Raman spectrum above 10 GPa, which should not be observed in an elemental simple cubic system, we propose a new explanation by attributing a key role to the non-hydrostatic conditions occurring in Raman experiments. Finally, a combined analysis of Raman and XRD data allowed us to obtain quantitative information on presence and extent of coexistences between different structural phases from ~5 up to ~15 GPa. This information can have an important role in theoretical studies on pressure-induced structural and electronic phase transitions in black phosphorus

Single-crystal diffraction at the high-pressure Indo-Italian beamline Xpress at Elettra, Trieste

In this study the first in situ high-pressure single-crystal X-ray diffraction experiments at Xpress, the Indo-Italian beamline of the Elettra synchrotron, Trieste (Italy), are reported. A description of the beamline experimental setup and of the procedures for single-crystal centring, data collection and processing, using diamond anvil cells, are provided. High-pressure experiments on a synthetic crystal of clinoenstatite (MgSiO3), CaCO3 polymorphs and a natural sample of leucophoenicite [Mn7Si3O12(OH)2] validated the suitability of the beamline experimental setup to: (i) locate and characterize pressure-induced phase transitions; (ii) solve ab initio the crystal structure of high-pressure polymorphs; (iii) perform fine structural analyses at the atomic scale as a function of pressure; (iv) disclose complex symmetry and structural features undetected using conventional X-ray sources

Carrier-envelope shearing and isolated attosecond pulse generation

Conical Bessel-like pulses allow control of the propagation velocity of the main intensity peak.With few-cycle pulses, this leads to a controllable shearing effect with respect to the carrier-phase oscillation and a consequent variation of the instantaneous intensity during propagation. Numerical simulations highlight how this intensity modulation directly controls the atomic dipole phase in the process of high-order harmonic generation and isolates either the long or the short electron-trajectory contributions. We identify a propagation regime in which the harmonic field takes the form of an isolated pulse of 300 as duratio

Vitiligo: What’s old, what’s new

Vitiligo is an acquired pigmentary disorder afflicting 0.5-2% of the world population for both sexes and all races with a capricious and unpredictable course. It has a complex etiology and varies in its manifestation, progression and response to treatment. Even if the precise aetiology and pathobiology of the disease are complex and still debated, recent evidence supports that vitiligo is a T CD8+ cell-mediated autoimmune disease triggered by oxidative stress. To date no clinical, biological and histological criteria allow us to establish the prognosis with certainty. The choice of the best therapy for adult and childhood vitiligo is based on various factors, such as the patient’s age, psychological condition and expectations, distribution and extension of skin lesions, type of vitiligo (stable or not) and availability and cost of therapeutic options. Since vitiligo has a deep psychological impact on patients and their quality of life, treating the disease is very important. As dermatologists, we have important goals in the treatment of vitiligo patients: stabilization of the disease progression, repigmentation of the lesions and especially the persistence of the aforementioned repigmentation. Although several medical and surgical therapeutic options have been proposed, no definite cure has yet been developed and the long-term persistence of repigmentation is unpredictable. We review the different therapeutic options with particular attention on the recurrence rate

From grape berries to wines: Drought impacts on key secondary metabolites

Aim: We aimed to study the impact of water deficit on the concentration of key flavour and phenolic secondary metabolites of wines. Methods and results: A drought-stress field trial was conducted on Vitis vinifera cv. Merlot and Tocai Friulano for two seasons. Fully irrigated (C) and deficit irrigated (D) grapes were microvinified and the resulting wines were analysed to determine the concentrations of anthocyanins, tannins, and free and glycosidically-bound Volatile Organic Compounds (VOCs). A descriptive sensory test was undertaken on the same wines. Water stressed grapes produced wines with higher concentrations of anthocyanins in Merlot and of free and glycosidically-bound monoterpenes in Tocai Friulano. Both cultivars displayed higher amounts of glycosidically-bound C13-norisoprenoids. Conclusions: Previously observed drought-induced compositional changes to the grapes were transfered to the wines, with an increase in polyphenols and VOCs. However, the timing and the duration of the water stress in the field only heavily impacted the final wine composition with major metabolic modification when the severe water deficit started early (at approximately 40 days after anthesis) and lasted over the entire season until harvest. Significance and impact of the study: This study highlights the positive role of a controlled water deficit on the composition of the wines in terms of secondary metabolites

In-orbit background of X-ray microcalorimeters and its effects on observations

Methods.There are no experimental data about the background experienced by microcalorimeters in the L2 orbit, and thus the particle background levels were calculated by means of Monte Carlo simulations: we considered the original design configuration and an improved configuration aimed to reduce the unrejected background, and tested them in the L2 orbit and in the low Earth orbit, comparing the results with experimental data reported by other X-ray instruments.To show the results obtainable with the improved configuration we simulated the observation of a faint, high-redshift, point source (F[0.5-10 keV]~6.4E-16 erg cm-2 s-1, z=3.7), and of a hot galaxy cluster at R200 (Sb[0.5-2 keV]=8.61E-16 erg cm-2 s-1 arcmin-2,T=6.6 keV). Results.First we confirm that implementing an active cryogenic anticoincidence reduces the particle background by an order of magnitude and brings it close to the required level.The implementation and test of several design solutions can reduce the particle background level by a further factor of 6 with respect to the original configuration.The best background level achievable in the L2 orbit with the implementation of ad-hoc passive shielding for secondary particles is similar to that measured in the more favorable LEO environment without the passive shielding, allowing us to exploit the advantages of the L2 orbit.We define a reference model for the diffuse background and collect all the available information on its variation with epoch and pointing direction.With this background level the ATHENA mission with the X-IFU instrument is able to detect ~4100 new obscured AGNs with F>6.4E-16 erg cm-2 s-1 during three years, to characterize cluster of galaxies with Sb(0.5-2 keV)>9.4E-16 erg cm-2 s-1 sr-1 on timescales of 50 ks (500 ks) with errors <40% (<12%) on metallicity,<16% (4.8%) on temperature,2.6% (0.72%) on the gas density, and several single-element abundances.Comment: the PDF has poor quality, it will be improved in the futur

Degeneracija aksona i esteraza povezana s neuropatskim djelovanjem organofosfornih spojeva - pregled

This brief review summarises recent observations which suggest a possible mechanism for organophosphateinduced delayed neuropathy (OPIDN). Neuropathy target esterase (NTE) has been shown to deacylate endoplasmic reticulum (ER) membrane phosphatidylcholine (PtdCho). Raised levels of PtdCho are present in the brains of swiss cheese/NTE mutant Drosophila together with abnormal membrane structures, axonal and dendritic degeneration and neural cell loss. Similar vacuolated pathology is found in the brains of mice with brain-specific deletion of the NTE gene and, in old age, these mice show clinical and histopathological features of neuropathy resembling those in wild-type mice chronically dosed with tri-ortho-cresylphosphate. It is suggested that OPIDN results from the loss of NTE’s phospholipase activity which in turn causes ER malfunction and perturbation of axonal transport and glial-axonal interactions.Ovim se kratkim pregledom razmatraju nedavna opažanja koja upućuju na mogući mehanizam odgođene neuropatije uzrokovane organofosfatima (engl. organophosphate-induced delayed neuropathy, krat. OPIDN). Za esterazu povezanu s neuropatskim djelovanjem organofosfornih spojeva (engl. neuropathy target esterase, krat. NTE) dokazano je da deacilira fosfatidilkolin (PtdCho) membrane endoplazmatskog retikuluma (ER). Povišene razine PtdCho prisutne su u mozgu swiss cheese/NTE mutanta mušice Drosophila uz abnormalne membranske strukture, degeneraciju aksona i dendrita te gubitak neurona. Slična je vakuolarna patologija zamijećena u mozgu miševa u kojih je obrisan NTE gen u mozgu te koji u starijoj dobi pokazuju kliničke i histopatološke znakove neuropatije koja je slična onoj u običnih miševa kronično tretiranih tri-ortho-krezilfosfatom. Odgođena neuropatija uzrokovana organofosfatima mogla bi biti posljedicom prestanka djelovanja fosfolipaze NTE, što potom uzrokuje zatajenje endoplazmatskog retikuluma i smetnje u prijenosu signala putem aksona te interakcije između glija i aksona

Protective role of the dynamin inhibitor Dynasore against the cholesterol-dependent cytolysin of Trueperella pyogenes

The virulence of many Gram-positive bacteria depends on cholesterol-dependent cytolysins (CDCs), which form pores in eukaryotic cell plasma membranes. Pyolysin (PLO) from Trueperella pyogenes provided a unique opportunity to explore cellular responses to CDCs because it does not require thiol activation. Sublytic concentrations of PLO stimulated phosphorylation of MAPK ERK and p38 in primary stromal cells, and induced autophagy as determined by protein light-chain 3B cleavage. Although, inhibitors of MAPK or autophagy did not affect PLO-induced cytolysis. However, 10 μM 3-hydroxynaphthalene-2-carboxylic acid-(3,4-dihydroxybenzylidene)-hydrazide (Dynasore), a dynamin guanosine 5′-triphosphatase inhibitor, protected stromal cells against PLO-induced cytolysis as determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay (85 ± 17% versus 50 ± 9% cell viability), measuring extracellular ATP, and kinetic assays. This was a generalized mechanism because Dynasore also protected HeLa cells against streptolysin O. Furthermore, the effect was reversible, with stromal cell sensitivity to PLO restored within 30 minutes of Dynasore removal. The protective effect of Dynasore was not conferred by dynamin inhibition, induction of ERK phosphorylation, or Dynasore binding to PLO. Rather, Dynasore reduced cellular cholesterol and disrupted plasma membrane lipid rafts, similar to positive control methyl-β-cyclodextrin. Dynasore is a tractable tool to explore the complexity of cholesterol homeostasis in eukaryotic cells and to develop strategies to counter CDCs.—Preta, G., Lotti, V., Cronin, J. G., and Sheldon, I. M. Protective role of the dynamin inhibitor Dynasore against the cholesterol-dependent cytolysin of Trueperella pyogenes