Atmospheric fluctuations below 0.1 Hz during drift-scan solar diameter measurements

Measurements of the power spectrum of the seeing in the range 0.001-1 Hz have been performed in order to understand the criticity of the transits' method for solar diameter monitoring.Comment: 3 pages, 3 figures, proc. of the Fourth French-Chinese meeting on Solar Physics Understanding Solar Activity: Advances and Challenges, 15 - 18 November, 2011 Nice, Franc

Vapor etching to avoid micro-masking by gas-bubbles in wet release of MEMS

We report on the formation of gas bubbles during the release of MEMS devices using buffered oxide etch. Several approaches to mitigate the problem are proposed and tested together with a qualitative study of the phenomenon. The chemical reaction behind such phenomenon and the influence of defects and topography is discussed. Finally, a comparison with the HF-vapor release technique is shown

Strutture anatomiche craniofacciali: correlazioni tra cefalometria in proiezione laterolaterale e posteroanteriore = Cranio-facial structures: correlations between cephalometry in latero-lateral and postero-anterior projection

Scopo del lavoro. Lo scopo di questo lavoro consiste nel valutare se esiste una relazione fra dimensioni lineari di alcune strutture anatomiche craniofacciali in proiezione laterolaterale e posteroanteriore. Materiali e metodi. Sono stati presi in considerazione i tracciati cefalometrici condotti sulle teleradiografie del cranio in proiezione laterolaterale e posteroanteriore di 100 pazienti che si sono presentati al Reparto di Ortognatodonzia dell\u2019Universit\ue0 degli Studi di Milano. Sulla teleradiografia del cranio in proiezione laterolaterale sono state considerate le dimensioni lineari della base cranica (S-N), del mascellare superiore (SNP-A) e della mandibola (GO-ME); sulla proiezione posteroanteriore sono state analizzate una distanza rilevata a livello della base cranica (PASdx-PASsx), una del mascellare superiore (MXdx-MXsin) e una mandibolare (GOdx-GOsx). Risultati. L\u2019analisi delle dimensioni lineari di alcune strutture anatomiche craniofacciali in proiezione laterolaterale e posteroanteriore consente di individuare una relazione tra le strutture considerate. Tuttavia le teleradiografie del cranio in proiezione laterolaterale e posteroanteriore forniscono una rappresentazione bidimensionale di una struttura tridimensionale. Conclusioni. \uc8 possibile individuare una relazione lineare fra le misure delle stesse strutture anatomiche in due proiezioni diverse. I dati ottenuti sono considerati significativi a livello del mascellare superiore e della mandibola, non per la relazione PASdx-PASsx e S-N. Infatti questi valori non rappresentano le stesse strutture anatomiche, bens\uec sono solo misure di controllo fra strutture diverse.Aim of the work. The aim of this work consists in evaluating the relationship between linear dimensions of some craniofacial structures in lateral and frontal vision. Materials and methods. Cephalometric tracings done on lateral and frontal radiography of 100 patient of the Orthodontic Department (University of Milan) were analyzeded. On lateral teleradiographs, the linear dimension of cranial base (S-N), maxilla (SNP-A) and mandible (GO-ME) were considered. On frontal tracing the same measurement were performed at a definite distance from: cranial base (PASdx-PASsx), maxillary bone (MXdx-MXsin) and mandibular bone (GOdx-GOsx). Results. The analysis of linear dimensions of some anatomic cranio-facial structures in lateral and frontal projection allows to individuate their relationship. However, lateral and frontal radiographs gave a bidimensional representation of a tridimensional structure. Conclusions. it is possible to individuate a linear relationship between the measures of the same anatomic structures in two different projections. Data obtained are significative for the upper maxilla and lower jaw, but not for PASdx-PASsx and S-N. In fact, these values don\u2019t represent the same anatomic structures but they are control values among different structures

CO2 Adsorption in a Robust Iron(III) Pyrazolate-Based MOF: Molecular-Level Details and Frameworks Dynamics From Powder X-ray Diffraction Adsorption Isotherms

Understanding adsorption processes at the molecular level, with multi-technique approaches, is nowadays at the frontier of porous materials research. In this work it is shown that with a proper data treatment, in situ high-resolution powder X-ray diffraction (HR-PXRD) at variable temperature and gas pressure can reveal atomic details of the accommodation sites, the framework dynamics as well as thermodynamic information (isosteric heat of adsorption) of the CO2 adsorption process in the robust iron(III) pyrazolate-based MOF Fe2(BDP)3 [H2BDP = 1,4-bis(1H-pyrazol-4-yl)benzene]. Highly reliable "HR-PXRD adsorption isotherms" can be constructed from occupancy values of CO2 molecules. The "HR-PXRD adsorption isotherms" accurately match the results of conventional static and dynamic gas sorption experiments and Monte Carlo simulations. These results are indicative of the impact of the molecular-level behavior on the bulk properties of the system under study and of the potential of the presented multi-technique approach to understand adsorption processes in metal-organic frameworks

Quantum Poincare Recurrences for Hydrogen Atom in a Microwave Field

We study the time dependence of the ionization probability of Rydberg atoms driven by a microwave field, both in classical and in quantum mechanics. The quantum survival probability follows the classical one up to the Heisenberg time and then decays algebraically as P(t) ~ 1/t. This decay law derives from the exponentially long times required to escape from some region of the phase space, due to tunneling and localization effects. We also provide parameter values which should allow to observe such decay in laboratory experiments.Comment: revtex, 4 pages, 4 figure

Electrode-dependent asymmetric conduction mechanisms in K0.5Na0.5NbO3 micro-capacitors

The ultimate performance of devices employing lead-free piezoelectrics is determined not only by the intrinsic properties of the piezo, but also by processes and materials employed to create the electric contacts. In this paper, we investigate the impact of different metallic electrodes with increasing chemical reactivity (Pt, Ni, Ti, Cr), on the asymmetric behavior of the leakage current in M/K0.5Na0.5NbO3/Pt(111) micro-capacitors, where M stands for the top metallic electrode. For all electrodes we found a marked leakage asymmetry that we ascribed to the presence of a Schottky-like rectifying junction at the M/K0.5Na0.5NbO3/Pt(111) bottom interface, while the corresponding junction at the top interface is deeply affected by the creation of oxygen vacancies due to oxygen scavenging during the growth of the top metallic electrodes, leading to an almost ohmic top contact. The leakage increases with the reactivity of the electrodes, while the asymmetry decreases, thus suggesting that the creation of the top metal/K0.5Na0.5NbO3 interface generates oxygen vacancies diffusing down to the bottom interface and impacting on the rectifying behavior of the Schottky-like junction. Noteworthy, this asymmetric conduction can reflect in an asymmetric piezoelectric and ferroelectric behavior, as a sizable portion of the applied voltage drops across the rectifying junction in reverse bias, thus hampering symmetric bipolar operation, especially in leaky materials

Mercury clathration-driven phase transition in a luminescent bipyrazolate metal-organic framework: a multitechnique investigation

Mercury is one of the most toxic heavy metals. By virtue of its triple bond, the novel ligand 1,2-bis(1H-pyrazol-4-yl)ethyne (H2BPE) was expressly designed and synthesized to devise metal-organic frameworks (MOFs) exhibiting high chemical affinity for mercury. Two MOFs, Zn(BPE) and Zn(BPE)·nDMF [interpenetrated i-Zn and noninterpenetrated ni-Zn·S, respectively; DMF = dimethylformamide], were isolated as microcrystalline powders. While i-Zn is stable in water for at least 15 days, its suspension in HgCl2 aqueous solutions prompts its conversion into HgCl2@ni-Zn. A multitechnique approach allowed us to shed light onto the observed HgCl2-triggered i-Zn-to-HgCl2@ni-Zn transformation at the molecular level. Density functional theory calculations on model systems suggested that HgCl2 interacts via the mercury atom with the carbon-carbon triple bond exclusively in ni-Zn. Powder X-ray diffraction enabled us to quantify the extent of the i-Zn-to-HgCl2@ni-Zn transition in 100-5000 ppm HgCl2 (aq) solutions, while X-ray fluorescence and inductively coupled plasma-mass spectrometry allowed us to demonstrate that HgCl2 is quantitatively sequestered from the aqueous phase. Irradiating at 365 nm, an intense fluorescence is observed at 470 nm for ni-Zn·S, which is partially quenched for i-Zn. This spectral benchmark was exploited to monitor in real time the i-Zn-to-HgCl2@ni-Zn conversion kinetics at different HgCl2 (aq) concentrations. A sizeable fluorescence increase was observed, within a 1 h time lapse, even at a concentration of 5 ppb. Overall, this comprehensive investigation unraveled an intriguing molecular mechanism, featuring the disaggregation of a water-stable MOF in the presence of HgCl2 and the self-assembly of a different crystalline phase around the pollutant, which is sequestered and simultaneously quantified by means of a luminescence change. Such a case study might open the way to new-conception strategies to achieve real-time sensing of mercury-containing pollutants in wastewaters and, eventually, pursue their straightforward and cost-effective purification

Quantum Poincar\'e Recurrences

We show that quantum effects modify the decay rate of Poincar\'e recurrences P(t) in classical chaotic systems with hierarchical structure of phase space. The exponent p of the algebraic decay P(t) ~ 1/t^p is shown to have the universal value p=1 due to tunneling and localization effects. Experimental evidence of such decay should be observable in mesoscopic systems and cold atoms.Comment: revtex, 4 pages, 4 figure

Unprecedented chemical and thermal stability of MOFs with exposed metal sites

n/