An Experimental Setup for Combined In-Vacuo Raman Spectroscopy and Cavity-Interferometry Measurements on TMDC Nano-resonators

Experimental Mechanics - Nanoelectromechanical (NEMS) systems fabricated using atomically thin materials have low mass and high stiffness and are thus ideal candidates for force and mass sensing...     

Influence of substrate temperature and N2/Ar flow ratio on the stoichiometry,structure and hardness of TaNx coatings deposited by DC reactive sputtering

The effect of substrate temperature and N2/Ar flow ratio on the stoichiometry, structure and hardness of TaN_x coatings prepared on (111) Si substrates by DC reactive sputtering was investigated. For the structural, chemical and morphological analysis, X‐ray diffraction (XRD), Auger electron scanning and atomic force microscopy were respectively used. Hardness values of thin films were determined using the work of indentation model from nanoindentation measurements. TaN stoichiometric coatings were obtained for samples deposited at room temperature. The stoichiometric TaN phase was not obtained by increasing the temperature up to 773 K, even when increasing the N₂/Ar flow ratio. Even when a saturation in nitrogen content was achieved, nitrogen vacancies are still present in those samples. For coatings prepared at 773 K and low N₂/Ar flow ratio, a phase mixture between TaN_x and cubic α‐Ta was observed, while a cubic structure δ‐TaN was formed by increasing the N₂/Ar flow ratio. A maximum in hardness and (38 GPa) was obtained for the sample deposited at 773 K and a N₂/Ar flow ratio of 0.2, which presented a δ‐TaN cubic crystalline structure and a roughness value of 1.6 nm. Copyright © 2015 John Wiley & Sons, Ltd.     

Analysis of Non-innocence of Phosphaquinodimethane Ligands when Charge and Aromaticity Come into Play

Several phosphaquinodimethanes and their M(CO)₅ complexes (M=Cr, Mo, W) and model derivatives have been theoretically investigated regarding the quest of non-innocence. Computed structural and electronic properties of the P-Me/NH₂ substituted phosphaquinodimethanes and tungsten complexes revealed an interesting non-innocent ligand behaviour for the radical anion complexes with distonic ion character and a strong rearomatization of the middle phenyl ring. The latter was further probed taking also geometric aromaticity (HOMA) and quinoid distortion parameters (HOMQc) into account, as well as NICS(1). Furthermore, the effect of the P-substitution was investigated for real (or plausible) complexes and their free ligands focusing on the resulting aromaticity at the middle phenyl ring and vertical one-electron redox processes. The best picture of ligand engagement in redox changes was provided by representing NICS(1) values versus HOMA and the new geometric distortion parameter HOMQc8.     

Effectiveness of Photodynamic Therapy in Elimination of HPV‐16 and HPV‐18 Associated with CIN I in Mexican Women

This study aimed to determine the effectiveness of photodynamic therapy (PDT), using δ‐aminolevulinic acid (5‐ALA), in the elimination of premalignant cervical lesions in Mexican patients with human papillomavirus (HPV) infection and/or cervical intraepithelial neoplasia (CIN). Thirty women diagnosed with CIN I and/or positive for HPV participated in the study. Topical 6% 5‐ALA in gel form was applied to the uterine cervix; after 4 h, the lesion area was irradiated with a light dose of 200 J cm^?2 at 635 nm. This procedure was performed three times at 48‐h intervals. Clinical follow‐up was performed at 3, 6, and 12 months after the initial PDT administration, by colposcopy, cervical cytology, histopathological analysis, polymerase chain reaction, and hybrid capture. Of HPV‐infected patients without evidence of CIN I, 80% cleared the infection, while HPV associated with CIN I was eliminated in 83% of patients (P < 0.05). At 12 months, CIN I had regressed in 57% of patients, although this response was not statistically significant. PDT using 6% 5‐ALA is concluded to be effective in eliminating HPV infection associated or not with CIN I.     

Dynamic compression-shear response of brittle materials with specimen recovery

A new configuration for compression-shear soft-recovery experiments is presented. This technique is used to investigate various failure mechanisms during dynamic multiaxial loading of an Al₂O₃/SiC nanocomposite and TiB₂. Velocity profiles of the target surface are measured with a variable sensitivity displacement interferometer, yielding normal and transverse velocity-time histories. A dynamic shear stress of approximately 280 MPa is obtained, in the Al₂O₃/SiC nanocomposite, for an imposed axial stress of about 3.45 GPa on a 540 m thick sample. This dynamic shear stress is well below the value predicted by elastic wave propagation theory. This could be the result of stress-induced damage and inelasticity in the bulk of the sample or inelasticity on the sample surface due to frictional sliding. To gain further insight into the possible failure mechanisms, an investigation of compression-shear recovery techniques, with simultaneous trapping of longitudinal and lateral release waves, is conducted.     

A Novel Fluid Structure Interaction Experiment to Investigate Deformation of Structural Elements Subjected to Impulsive Loading

This paper presents a novel experimental methodology for the study of dynamic deformation of structures under underwater impulsive loading. The experimental setup simulates fluid–structure interactions (FSI) encountered in various applications of interest. To generate impulsive loading similar to blast, a specially designed flyer plate impact experiment was designed and implemented. The design is based on scaling analysis to achieve a laboratory scale apparatus that can capture essential features in the deformation and failure of large scale naval structures. In the FSI setup, a water chamber made of a steel tube is incorporated into a gas gun apparatus. A scaled structure is fixed at one end of the steel tube and a water piston seals the other end. A flyer plate impacts the water piston and produces an exponentially decaying pressure history in lieu of explosive detonation. The pressure induced by the flyer plate propagates and imposes an impulse to the structure (panel specimen), which response elicits bubble formation and water cavitations. Calibration experiments and numerical simulations proved the experimental setup to be functional. A 304 stainless steel monolithic plate was tested and analyzed to assess its dynamic deformation behavior under impulsive loading. The experimental diagnostic included measurements of flyer impact velocity, pressure wave history in the water, and full deformation fields by means of shadow moiré and high speed photography.     

Estimation of Temperatures in Geothermal Wells During Circulation and Shut-in in the Presence of Lost Circulation

The estimation of temperatures in and around a geothermal well during circulation, and during shut-in conditions in the presence of lost circulation is presented in this work. Estimated temperatures are compared with temperature logs measured during drilling stoppages. Temperatures were estimatted using a computer code specifically developed to account for the transient convective heat transfer due to lost circulation in the rock surrounding a well. This feature of the present code is important since wellbore simulators normally consider the heat transfer process in the rock as a merely conductive problem. The code is capable of accounting for these losses at any point in the well and application was made to the study of two Mexican geothermal wells(well LV-3 from the Las Tres Vírgenes field and well EAZ-2 from the Los Azufres field). The results show that the effect of lost circulation on the shut-in temperature profiles can be modelled satisfactorily. Research is under way to improve the present methodology.