44 research outputs found
Refined Structure of Metastable Ice XVII from Neutron Diffraction Measurements
The structure of the recently identified metastable ice XVII, obtained by
release of hydrogen from the C DO-H compound (filled ice), has been
accurately measured by neutron powder diffraction. The diffraction pattern is
indexed with a hexagonal cell and can be refined with space group so
to obtain accurate values of the oxygen and deuterium positions. The values of
the lattice constants at three temperatures between 25 to 100 K are reported,
and their behavior is compared with that of ice Ih. Ice XVII is a porous solid
that, if exposed to H gas, may adsorb a substantial amount of it.
Monitoring this effect at a constant temperature of 50 K, we have observed that
the two lattice constants show opposite behavior, increases and
decreases, with the volume showing a linear increase. At temperatures higher
than 130 K the metastability of this form of porous ice is lost and the sample
transforms into ice Ih
In situ Raman and neutron spectroscopy of complex hydrides
The search of suitable hydrides for hydrogen storage can benefit from Raman and neutron spectroscopy, especially when it is possible to exploit these diagnostic techniques in situ, that is, in controlled conditions of gas pressure and temperature. In this way it is possible to observe and monitor phase transitions or sample chemical decomposition. In our laboratory we have studied the vibrational spectrum of several complex hydride compounds both at cryogenic temperature (15 K) and during or after thermal treatment at high temperature (up to 600 K), in a controlled atmosphere. In particular, in this talk I will present the results of the characterization of bulk samples of Mg(BH4)2 and AlH3 where the proportions of the different phases can be changed by different thermal treatments. Additionally, both Raman and neutron spectra of Na3AlH6, recorded at low temperature, have disclosed the presence of low frequency lattice modes, that have been compared with computational results
Quantum calculation of inelastic neutron scattering spectra of a hydrogen molecule inside a nanoscale cavity based on rigorous treatment of the coupled translation-rotation dynamics
We present a quantum methodology for the calculation of the inelastic neutron scattering (INS) spectra of an molecule confined in a nanoscale cavity. Our approach incorporates the coupled five-dimensional translation-rotation (TR) energy levels and wave functions of the guest molecule. The computed INS spectra are highly realistic and reflect in full the complexity of the coupled TR dynamics on the anisotropic potential energy surfaces of the confining environment. Utilizing this methodology, we simulate the INS spectra of - and -H in the small cage of the structure II clathrate hydrate and compare them with the experimental data
Crystal structure of solid Oxygen at high pressure and low temperature
Results of X-ray diffraction experiments on solid oxygen at low temperature
and at pressures up to 10 GPa are presented.A careful sample preparation and
annealing around 240 K allowed to obtain very good diffraction patterns in the
orthorhombic delta-phase. This phase is stable at low temperature, in contrast
to some recent data [Y. Akahama et al., Phys. Rev. B64, 054105 (2001)], and
transforms with decreasing pressure into a monoclinic phase, which is
identified as the low pressure alpha-phase. The discontinuous change of the
lattice parameters, and the observed metastability of the alpha-phase
increasing pressure suggest that the transition is of the first order.Comment: 4 pages with three figure
Bubbles and outflows: the novel JWST/NIRSpec view of the z=1.59 obscured quasar XID2028
Quasar feedback in the form of powerful outflows is invoked as a key
mechanism to quench star formation in galaxies, although direct observational
evidence is still scarce and debated. Here we present Early Release Science
JWST NIRSpec IFU observations of the z=1.59 prototypical obscured quasar
XID2028: this target represents a unique test case to study QSO feedback at the
peak epoch of AGN-galaxy co-evolution thanks to its existing extensive
multi-wavelength coverage and massive and extended outflow detected both in the
ionised and molecular components. With the unprecedented sensitivity and
spatial resolution of JWST, the NIRSpec dataset reveals a wealth of structures
in the ionised gas kinematics and morphology previously hidden in the
seeing-limited ground-based data. In particular, we find evidence of
interaction between the interstellar medium of the galaxy and the QSO-driven
outflow and radio jet, which is producing an expanding bubble from which the
fast and extended wind detected in previous observations is emerging. The new
observations confirm the complex interplay between the AGN jet/wind and the ISM
of the host galaxy, highlighting the role of low luminosity radio jets in AGN
feedback, and showcase the new window opened by NIRSpec on the detailed study
of feedback at high redshift.Comment: 12 pages, 11 figures, submitted to A&A. Comments welcom
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Predictive significance of circulating histones in hepatocellular carcinoma patients treated with sorafenib
Background: Predictive biomarkers for advanced hepatocellular carcinoma are lacking. EZH2 drives sorafenib resistance through H3K27me3 and is counteracted by SETD2, which catalyzes H3K36me3. The authors tested the predictive power of circulating H3K27me3 and H3K36me3 in advanced hepatocellular carcinoma patients treated with sorafenib. Methods: A total of 80 plasma samples were tested for histone variants by ELISA. Changes from baseline to best response or progressive disease were correlated with patient survival. Results: A higher EZH2/SETD2 ratio predicted worse prognosis in this setting. H3K27me3 and H3K36me3 decreased from baseline to best response. The H3K27me3/H3K36me3 ratio increased from baseline to progressive disease. Higher ratios at best response were associated with shorter progression-free survival. Conclusion: The authors suggest that circulating H3K27me3/H3K36me3 ratio level acts as a predictive biomarker for sorafenib treatment outcomes in patients with advanced hepatocellular carcinoma