DC-conductivity of a suspension of insulating particles with internal rotation

We analyse the consequences of Quincke rotation on the conductivity of a suspension. Quincke rotation refers to the spontaneous rotation of insulating particles dispersed in a slightly conducting liquid and subject to a high DC electric field: above a critical field, each particle rotates continuously around itself with an axis pointing in any direction perpendicular to the DC field. When the suspension is subject to an electric field lower than the threshold one, the presence of insulating particles in the host liquid decreases the bulk conductivity since the particles form obstacles to ion migration. But for electric fields higher than the critical one, the particles rotate and facilitate ion migration: the effective conductivity of the suspension is increased. We provide a theoretical analysis of the impact of Quincke rotation on the apparent conductivity of a suspension and we present experimental results obtained with a suspension of PMMA particles dispersed in weakly conducting liquids

Normal Stresses and Interface Displacement: Influence of Viscoelasticity on Enhanced Oil Recovery Efficiency

International audienceOne of chemical Enhanced Oil Recovery (EOR) methods consists in injecting aqueous solutions of polymers into the reservoir in order to improve mobility ratio between the injected fluid and the remaining oil. This "polymer flooding" process is usually only characterized with the low shear viscosity of the injected fluid, even if these aqueous solutions are strongly shear thinning and may show high elastic properties evidenced by normal stresses appearance. In order to study the mechanisms at the interface level, we develop simple model experimentations with the goal of quantifying the influence of viscoelastic properties on fluid displacement in a simple geometry. For this purpose, we propose and characterize a model fluid formulation, for which elastic and viscous effects can be tuned systematically. We study then the displacement of a viscous oil by a Newtonian non elastic, a viscoelastic or a purely shear thinning fluid in a two dimensional flow cell. Observing the shape of the interface between aqueous fluids and displaced oil permits to appreciate viscoelasticity effects on the displacement. Using model geometries and controlled rheology fluids, we show that viscoelastic fluids tend to better displace immiscible liquids than Newtonian fluids and that those effects are closely related to the apparitions of normal stresses independently of shear thinning property or variation of interfacial tension as soon as viscous effects govern the flow

Enhanced displacement of a liquid pushed by a viscoelastic fluid.

International audienceWe consider the displacement, in a rectangular channel, of a Newtonian oil pushed by different types of liquids (Newtonian, shear-thinning, viscoelastic) of slightly higher apparent viscosity. ln the absence of viscoelastic effects the interface between the two fluids becomes sharper at larger velocities, so that the thickness of the lateral film left behind increases with the flow rate. On the contrary, with a viscoelastic fluid, the shape of the interface is almost independent of the velocity so that the thickness of the lateral film is approximately constant. Moreover this thickness decreases when the ratio of normal to tangential stresses increases, suggesting that this effect can be attributed to normal stress differences. A heuristic theoretical approach tends to confirm this statement

Effect of nitrogen fertilization on sorghum for biomass production

ArticleTwo field experiments were carried out in 2005 and 2006 in central Italy in order to evaluate the effects of different nitrogen (N) application rates (0, 50 100 and 150 kg ha-1 ) on flowering date, plant height, biomass production and partitioning (leaves, panicles and stems) and biomass quality of a sorghum hybrid (H133). Sorghum showed a high potential in terms of biomass production without N fertilization (18.5 t ha-1 of d.m. in 2005 and 26.6 t ha-1 of d.m. in 2006). The rate that maximized the biomass production was 100 kg ha-1 of N, increasing the biomass dry weight by 23.8% in 2005 and 18.8% in 2006, with respect to unfertilized sorghum; higher N rates are not advisable in order to avoid increasing fertilization costs and environmental impact without benefit of greater biomass production. The two highest N rates when combined with low water availability appeared to increase the rate of plant development, causing earlier flowering and increasing the percentage of panicles in total biomass. Higher heating value (HHV), lower heating value (LHV) and ash concentration of biomass varied among N rates, with values of HHV and LHV lower for unfertilized sorghum (17.6 and 16.7 MJ kg-1 d.m., respectively) than when N was applied (from 19.0 to 19.7 and from 18.1 to 18.8 MJ kg-1 d.m., respectively); on the contrary, ash concentration was greater for unfertilized sorghum (7.5% d.m.) than for fertilized sorghum (from 5.8 to 6.7% d.m.). This research showed the high potential of sorghum in terms of biomass production also when cultivated with limited irrigation and fertilization inputs. The biomass dry yield obtained by one hectare of sorghum crop without N nitrogen fertilization (i.e. 22.6 t ha-1 of d.m., average of 2005 and 2006 values) produces the same energy, by thermal utilisation, of 9.3 toe, that is equivalent to energy produced by 10,385 L of diesel fuel or 11,097 m3 of methane fuel. This aspect increases the certainty of the energetic and environmental sustainability of sorghum crop

Continuum modeling of micro-particle electrorotation in Couette and Poiseuille flows—The zero spin viscosity limit

A continuum mechanical model is presented to analyze the negative electrorheological responses of a particle-liquid mixture with the suspended micro-particles undergoing Quincke rotation for both Couette and Poiseuille flow geometries by combining particle electromechanics and continuum anti-symmetric/couple stress analyses in the zero spin viscosity limit. We propose a phenomenological polarization relaxation model to incorporate both the micro-particle rotation speed and macro-continuum spin velocity effects on the fluid polarization during non-equilibrium motion. Theoretical predictions of the Couette effective viscosity and Poiseuille flow rate obtained from the present continuum treatment are in good agreement with the experimental measurements reported in current literature.National Science Council (China) (grant no. TMS-094-2-A-029)United States-Israel Binational Science Foundation (grant 2004081

A BIOMECHANICAL STUDY SHOULDER PAIN IN ELITE GYMNASTS

Introduction: Shoulder problems are common in overhead sports like baseball, basketball and volleyball. Although gymnastics consists of overhead activities, there are few studies of shoulder problems in this sport. During 1992-1995 we treated five young competitive gymnasts for shoulder pain. Arthroscopy revealed that all suffered from SLAP-lesions or other labral pathologies although they had never dislocated their shoulders. Since four of these athletes stated that they first became aware of acute shoulder pain during ring exercises in suspension, we decided to make an EMG-study of the shoulder musculature during exercises on the parallel bars and rings. Methods: Three elite gymnasts were investigated with telemetric surface EMG of the pect.maj., deltoid, biceps, triceps, trapezius and lat.dorsi. The gymnasts performed the standard bar and ring program. Results: During the ring exercises in suspension there was a ‘critical phase’ during which muscle activity around the shoulder was very low, leading to great articular stresses at the end of the ‘giant swing’, when their shoulders were suddenly exposed to a load of several times their body weight. EMG of biceps brachii was 67 µV just before the end of the giant swing and increased to 698µV. A similar tenfold increase was found in the other muscles as well. This probably explains the occurrence the SLAP lesions. A very strong pull in the long biceps tendon (before the muscle contracts) could tear loose the superior labrum and cause this socalled SLAP-lesion. Modifications of the rings or the ring exercises might decrease the occurrence of SLAP-lesions. Conclusion: Telemetric EMG analysis of the shoulder musculature during ring exercises provided an explanation for the occurrence of SLAP-lesions in gymnasts

Photochemical and thermal degradation of a naturally occurring dye used in artistic painting. A chromatographic, spectrophotometric and fluorimetric study on saffron

Saffron is a yellow substance which is extracted from the stigmas ofCrocus sativus L. and is used in painting, cooking and medicine. In this paper six components (transandciscrocins) with carotenoid structures were separated from natural saffron by HPLC and were characterised by their absorption and emission spectra. Photochemical and thermal processes which degrade the dye were also investigated. The effect of light promoted thecis⇄transisomerization, while the thermal effect detached the glycosyl moieties

Fabrication and electrokinetic motion of electrically anisotropic Janus droplets in microchannels

This is the peer reviewed version of the following article: Li, M. and Li, D. (2017), Fabrication and electrokinetic motion of electrically anisotropic Janus droplets in microchannels. ELECTROPHORESIS, 38: 287–295 which has been published in final form at http://dx.doi.org/10.1002/elps.201600310. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.This paper presents experimental investigations of the fabrication and the motion of electrically anisotropic Janus droplets in a microchannel under externally applied direct current (DC) electrical field. The fabrication method of the Janus droplets is presented first. To begin, oil droplets are coated uniformly with positively charged nanoparticles in the aluminum oxide nanoparticle suspension. The electrically anisotropic Janus droplets are formed when the nanoparticles are accumulated to one side of the droplets in response to externally applied DC electric field. The surface coverage of the Janus droplets by nanoparticles can be adjusted by controlling the concentration of the nanoparticle suspension. The flow fields around the Janus droplets moving in a microchannel were observed with tracing particles. Finally, the electrokinetic velocity of the Janus droplets in a microchannel was measured. The effects of the strength of the electrical field, the surface coverage of the Janus droplets by nanoparticles, the size of the droplets as well as the electrolyte concentration on the electrokinetic velocity of the Janus droplets were studied.Natural Sciences and Engineering Research Council of Canad

Cardiological Aspects of Feeding and Eating Disorders in Children and Adolescents and Associations with Refeeding Syndrome, Purging Behaviors, and Psychoactive Drugs

Feeding and Eating Disorders (FEDs) constitute a complex spectrum of psychiatric conditions, impacting physical and psychosocial well-being. This retrospective observational study aimed to dissect the electrocardiographic (ECG) alterations in pediatric patients with FEDs, correlating them with clinical factors, treatment modalities, Refeeding Syndrome (RS) and the reversibility of ECG abnormalities post-treatment. Analyzing records from a third level Italian Regional Center for FEDs in children and adolescents, the study encompassed 150 patients meeting the inclusion criteria. Sinus bradycardia was the prevalent ECG alteration, notably in Anorexia Nervosa (AN) restrictive type. Association analyses revealed links between the severity of AN, hormonal imbalances, and amenorrhea and ECG abnormalities. Pharmacological interventions, particularly antipsychotics, exhibited associations with a QT interval prolongation. RS demonstrated significant correlations with potassium and magnesium imbalances, which were linked to specific ECG changes. This study highlighted the reversibility of ECG abnormalities, concomitant with Body Mass Index improvement. This analysis underscores the critical cardiac implications of FEDs, advocating for multidisciplinary interventions and close cardiac monitoring. Early detection and holistic care are imperative in managing patients with FEDs in the developmental age, offering potential reversibility of cardiac alterations post-treatment. These findings underscore the need for prospective studies to validate these observations and delve deeper into cardiac involvement in FEDs