X-ray-diffraction characterization of Pt(111) surface nanopatterning induced by C60 adsorption

Understanding the adsorption mechanisms of large molecules on metal surfaces is a demanding task. Theoretical predictions are difficult because of the large number of atoms that have to be considered in the calculations, and experiments aiming to solve the molecule-substrate interaction geometry are almost impossible with standard laboratory techniques. Here, we show that the adsorption of complex organic molecules can induce perfectly ordered nanostructuring of metal surfaces. We use surface X-ray diffraction to investigate in detail the bonding geometry of C(60) with the Pt(111) surface, and to elucidate the interaction mechanism leading to the restructuring of the Pt(111) surface. The chemical interaction between one monolayer of C(60) molecules and the clean Pt(111) surface results in the formation of an ordered sqrt[13] x sqrt[13]R13.9 degrees reconstruction based on the creation of a surface vacancy lattice. The C(60) molecules are located on top of the vacancies, and 12 covalent bonds are formed between the carbon atoms and the 6 platinum surface atoms around the vacancies. In-plane displacements induced on the platinum substrate are of the order of a few picometres in the top layer, and are undetectable in the deeper layers.     

Fluorescence anisotropy in the frequency domain by an optical microscope

Fluorescence anisotropy decay spectroscopy is a suitable tool for investigating the size and the shape of biological molecules. We coupled this technique to an optical microscope in order to reduce the excitation volume and to allow its application to spatially inhomogeneous samples. Phase modulated measurements of the fluorescence anisotropy decay were performed by feeding an intensity modulated linearly polarized laser beam to the epifluorescence port of a microscope. Here we report the test of the dynamic response of the microscope by comparing the lifetime and fluorescence polarization anisotropy decays obtained in cuvettes in a standard phase modulation fluorometer and on tiny drops on the microscope stage. We show that once a correction factor for the objective depolarization is introduced in the best-fit functions for the data analysis of the decays, the results obtained on the two setups are comparable. Some applications are reported here on long DNA tracts as well on short DNA fragments containing structural anomalies.     

Composition and antimicrobial properties of Sardinian Juniperus essential oils against foodborne pathogens and spoilage microorganisms

In this work, the chemical compositions and antimicrobial properties of Juniperus essential oils and of their main components were determined. Five berry essential oils obtained from different species of Juniperus growing wild in Sardinia were analyzed. The components of the essential oils were identified by gas chromatography-mass spectrometry (GC-MS) analysis. The antimicrobial activities of the oils and their components against food spoilage and pathogenic microorganisms were determined by a broth microdilution method. The GC-MS analysis showed a certain variability in the concentrations of the main constituents of the oils. Alpha-pinene was largely predominant in the oils of the species J. phoenicea subsp. turbinata and J. oxycedrus. Alpha-pinene and myrcene constituted the bulk (67.56%) of the essential oil of J. communis. Significant quantitative differences were observed for myrcene, delta-3-carene, and D-germacrene. The results of the antimicrobial assay show that the oils of J. communis and J. oxycedrus failed to inhibit any of the microorganisms at the highest concentrations tested (MLC > or = 900 microg/ml), while the oils extracted from J. turbinata specimens were active against fungi, particularly against a strain of Aspergillus flavus (an aflatoxin B1 producer). Of the single compounds tested, delta-3-carene was found to possess the broadest spectrum of activity and appeared to contribute significantly to the antifungal activity observed for J. turbinata oils. This activity may be helpful in the prevention of aflatoxin contamination for many foods.     

Effect of CB2 Stimulation on Gene Expression in Pediatric B-Acute Lymphoblastic Leukemia: New Possible Targets

Acute lymphoblastic leukemia type B (B-ALL) is the most common kind of pediatric leukemia, characterized by the clonal proliferation of type B lymphoid stem cells. Important progress in ALL treatments led to improvements in long-term survival; nevertheless, many adverse long-term consequences still concern the medical community. Molecular and cellular target therapies, together with immunotherapy, are promising strategies to overcome these concerns. Cannabinoids, enzymes involved in their metabolism, and cannabinoid receptors type 1 (CB1) and type 2 (CB2) constitute the endocannabinoid system, involved in inflammation, immune response, and cancer. CB2 receptor stimulation exerts anti-proliferative and anti-invasive effects in many tumors. In this study, we evaluated the effects of CB2 stimulation on B-ALL cell lines, SUP-B15, by RNA sequencing, Western blotting, and ELISA. We observe a lower expression of CB2 in SUP-B15 cells compared to lymphocytes from healthy subjects, hypothesizing its involvement in B-ALL pathogenesis. CB2 stimulation reduces the expression of CD9, SEC61G, TBX21, and TMSB4X genes involved in tumor growth and progression, and also negatively affects downstream intracellular pathways. Our findings suggest an antitumor role of CB2 stimulation in B-ALL, and highlight a functional correlation between CB2 receptors and specific anti-tumoral pathways, even though further investigations are needed.     

Transient multiphase CO2 release from high-pressure tanks: Influence of phase changes,viscous heating,and Joule–Thomson effect

In this study, CO₂ free expansion from high-pressure tanks is studied in a transient state while considering the influence of different phenomena—that is, viscous heating, phase transition (solid/liquid/vapour phase), and the Joule–Thomson effect—in an initially supersonic flow. This investigation is performed using computational fluid dynamics (CFD) techniques, comparing the obtained results with some experimental data of the literature with a maximum discrepancy of around 8.5%. In particular, for the first time from the literature, it is observed that, according to the velocity evolution at the outlet, the discharge process is conveniently divided into three here-defined stages: (1) shocking flow, where pressure abruptly decreases with time and flow becomes supersonic, this leading to the condensation of part of CO₂; (2) transition flow, characterized by a sort of constant pressure time trend; and (3) flashing flow, where pressure decreases less abruptly following an asymptotic pattern up to the atmospheric one and flow becomes subsonic. Furthermore, non-equilibrium condensation occurring in the tank, tube, and outlet is observed, finding that the minimum temperature reached by the fluid is around 235 K (−38°C). As well, the non-equilibrium condensation is taken into account in order to give an indication of the amount of liquid CO₂ leaving the outlet in the form of high-speed jet, which can be a serious danger for personnel and surrounding installations. Moreover, we observe an important effect of viscous heating in the early-stage expansion for a relatively short time range, within which the temperature in the tube experiences an abrupt increase of around 210 K (from 170 to 380 K). The same effect in the external room creates a convection flow, pushing CO₂ towards the top. The results of the present work can be used for health, safety, and environment (HSE) management purposes and for a more precise process design related to CO₂ storage and sequestration.