Development of an improved falling ball viscometer for high-pressure measurements with supercritical CO2

This study presents the development of an improved technique for viscosity measurements under high pressure. The apparatus is based on the principle of the falling ball viscometer, implemented in a high-pressure autoclave fitted with visualisation windows. The originality here is that the balls fall through a tube open at both ends with a diameter slightly greater than that of the balls, allowing a simplified modelling and numerical simulation. A numerical approach has been used for viscosity determination. Calculations have been made with COMSOL Multiphysics^® with the laminar Navier-Stokes model for Newtonian mixtures. It includes the specific hydrodynamic effects without the need for a calibration fluid. However, validation experiments were carried out at atmospheric pressure with dimethylsulfoxide (DMSO) at 298, 308 and 318 K and with cocoa butter at 313 and 353 K, with values of viscosity in the range from 1.4 to 45.4 mPa s. Comparative measurements with literature data have been conducted with cocoa butter saturated with carbon dioxide at 313 and 353 K and for pressures ranging from 0.1 to 25 MPa. At 313 K, viscosity varies from 45.4 mPa s to 3.1 mPa s while at 353 K it varies from 12.4 to 1.9 mPa s. For both isotherms tested, within the range 0-15 MPa, the higher the CO₂ dissolution in the cocoa butter, the lower the viscosity. However, this decrease in viscosity is more pronounced at the lowest temperature. Above 15 MPa the CO₂ dissolution effect on viscosity becomes insignificant, i.e. within the experimental error, due to a counter effect linked with the high hydrostatic pressure. Furthermore, the limits of use of this method have been determined. This technique is revealed as reliable and can therefore be used with other binary systems.     

Silicon Vibrating Wires at Low Temperatures

Nowadays microfabrication techniques originating from micro-electro nics enable to create mechanical objects of micron-size. The field of Micro-Electro-Mechanical devices (MEMs) is continuously expanding, with an amazingly broad range of applications at room temperature. Vibrating objects (torsional oscillators, vibrating wires) widely used at low temperatures to study quantum fluids, can be replaced advantageously by Silicon MEMs. In this letter we report on the study of Silicon vibrating wire devices. A goal-post structure covered with a metal layer is driven at resonance by the Laplace force acting on a current in a magnetic field, while the induced voltage arising from the cut magnetic flux allows to detect the motion. The characteristics of the resonance have been studied from 10 mK to 30 K, in vacuum and in ⁴He gas. In this article, we focus on the results obtained above 1.5 K, in vacuum and gas, and introduce some features observed at lower temperatures. The resonant properties can be quantitatively understood by means of simple models, from the linear regime to a highly non-linear response at strong drives. We demonstrate that the non-linearity is mostly due to the geometry of the vibrators. We also show that in our device the friction mechanisms originate in the metallic layers, and can be fully characterized. The interaction with ⁴He gas is fit to theory without adjustable parameters.      

Measurements and simulation of the Zeeman splitting in NdOCl and Nd:LiYF4

Measurements and simulation of the Zeeman effect in NdOCl and 1%Nd³⁺:LiYF₄ single crystals were carried out. The rare earth local symmetries are C_4v and D_2d respectively. The isomorphism between these two point groups allows discussion on symmetry assignments. The attention is focused on the ⁴G_7/2 and ⁴G_9/2 levels for NdOCl and on the ⁴F_9/2 and ⁴G_7/2 levels for Nd³⁺:LiYF₄, because they are representative of the general splitting behaviour. We have first revisited the simulation of the energy level scheme in order to deal with confident wave functions. In the experimental magnetic field (B) range we have obtained linear, non-linear, undefined crossing and anti-crossing levels. These features depend on the orientation of B, on the irreducible representation and on the transition closeness. The line widths have been the main obstacle in confirming crossing regions, because their average values are 8 cm⁻¹ at liquid helium temperature. The simulations were performed by introducing the magnetic Hamiltonian μ_BB(L+g_eS) in the secular determinant before diagonalisation. A magnetic accidental degeneracy is considered when discussing the crossing and anti-crossing cases.     

Constipation Mitigation by Rhubarb Extract in Middle-Aged Adults Is Linked to Gut Microbiome Modulation: A Double-Blind Randomized Placebo-Controlled Trial

Gut microbiota alterations are intimately linked to chronic constipation upon aging. We investigated the role of targeted changes in the gut microbiota composition in the relief of constipation symptoms after rhubarb extract (RE) supplementation in middle-aged volunteers. Subjects (95% women, average 58 years old) were randomized to three groups treated with RE at two different doses determined by its content of rhein (supplementation of 12.5 mg and 25 mg per day) vs. placebo (maltodextrin) for 30 days. We demonstrated that daily oral supplementation of RE for 30 days was safe even at the higher dose. Stool frequency and consistency, and perceived change in transit problem, transit speed and difficulty in evacuating, investigated by validated questionnaires, were improved in both groups of RE-treated volunteers compared to placebo. Higher abundance of Lachnospiraceae (mainly Roseburia and Agathobacter) only occurred after RE treatment when present at low levels at baseline, whereas an opposite shift in short-chain fatty acid (SCFA) levels was observed in both RE-treated groups (increase) and placebo (decrease). Fecal Lachnospiraceae and SCFA were positively correlated with stool consistency. This study demonstrates that RE supplementation promotes butyrate-producing bacteria and SCFA, an effect that could contribute to relieving chronic constipation in middle-aged persons.     

Examining the alliance using the Psychotherapy Process Q-Set.

The alliance between therapist and patient was investigated using the Psychotherapy Process Q-Set (PQS), an instrument that quantitatively describes therapy sessions in a manner that captures the complexity of the therapy process. More specifically, the PQS was used to examine the treatment processes being assessed by observer ratings on the California Psychotherapy Alliance Scales (CALPAS). Using data from 30 brief psychodynamic psychotherapy treatments (patients aged 20–81 yrs), three PQS factors were found to be associated with alliance: Patient–Therapist Interaction, Patient Capacity/Commitment, and Therapist Countertransference. In multiple regression analyses with scales constructed from these three factors, Patient–Therapist Interaction was found to predict alliance ratings, while the other two aspects of the treatment process did not account for any significant additional variance in the alliance ratings. Results suggest that Patient–Therapist Interaction plays a defining role in the alliance construct, as assessed by the observer version of the CALPAS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Team productivity and contradiction of management policy commitments.

What is the relationship between management consistency of policy and team productivity? "A simulated small industrial plant was the setting for an experiment in which a team of Ss worked together on a manufacturing problem. Their assigned task was to produce different kinds of toys at a profit… . Twenty four-man teams were divided into ten consecutive team pairs, each member of a pair being subjected either to (a) a condition under which the team's expectations of management were contradicted by subsequent events or (b) a condition under which the team's expectations were confirmed. The hypothesis that team productivity would be greater under the confirmation condition was supported by the data. Some theoretical implications of the experiment were suggested." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Removal of organics in water using hydrogen peroxide in presence of ultraviolet light

The optimum conditions for the removal of dissolved organic impurities from water using hydrogen peroxide (50%) followed by ultraviolet irradiation were investigated. The photochemically initiated hydroxyl radical (OH) oxidation reduced the total organic carbon (TOC) content of distilled water samples by about 88% and of tap water by 98%. Extraction with hexane of equal volumes of water samples before and after H₂O₂/u.v. treatment followed by gas chromatographic analysis of the concentrated extracts indicated that about 12% of the electron-capturing, residual organics remained after this treatment. These results support the conclusion drawn from total organic carbon analysis that this simple method yields water nearly free of organic impurities.