Exact solutions for hydrodynamic interactions of two squirming spheres

We provide exact solutions of the Stokes equations for a squirming sphere close to a no-slip surface, both planar and spherical, and for the interactions between two squirmers, in three dimensions. These allow the hydrodynamic interactions of swimming microscopic organisms with confining boundaries, or each other, to be determined for arbitrary separation and, in particular, in the close proximity regime where approximate methods based on point singularity descriptions cease to be valid. We give a detailed description of the circular motion of an arbitrary squirmer moving parallel to a no-slip spherical boundary or flat free surface at close separation, finding that the circling generically has opposite sense at free surfaces and at solid boundaries. While the asymptotic interaction is symmetric under head-tail reversal of the swimmer, in the near field microscopic structure can result in significant asymmetry. We also find the translational velocity towards the surface for a simple model with only the lowest two squirming modes. By comparing these to asymptotic approximations of the interaction we find that the transition from near- to far-field behaviour occurs at a separation of about two swimmer diameters. These solutions are for the rotational velocity about the wall normal, or common diameter of two spheres, and the translational speed along that same direction, and are obtained using the Lorentz reciprocal theorem for Stokes flows in conjunction with known solutions for the conjugate Stokes drag problems, the derivations of which are demonstrated here for completeness. The analogous motions in the perpendicular directions, i.e. parallel to the wall, currently cannot be calculated exactly since the relevant Stokes drag solutions needed for the reciprocal theorem are not available.Comment: 27 pages, 7 figure

Alternative strategies for the extraction of compounds from natural resources

Book of Abstracts of CEB Annual Meeting 2017[Excerpt] Exploitable compounds from natural resources include polysaccharides, proteins and peptides, gum exudates, lipids, polyphenols and other secondary metabolites. Traditional-water extraction (TWE) of polysaccharides is a time-consuming process that requires high solvent and energy consumptions and generates large amounts of waste. Other bioactive compounds are traditionally extracted with organic solvents or mixtures of organic solvents and water, with or without heat. Subcritical water extraction and hydrolysis have been used as an alternative to traditional solvent extraction for many compounds in different matrices (1). Advantages include absence of chemical solvents, lower solvent costs, lower extraction times at moderate operational conditions, resulting in higher quality extracts. Furthermore, water is a solvent with very interesting properties in subcritical conditions. As temperature increases hydrogen bonds break, significantly decreasing the dielectric constant and the polarity, thus increasing solubility of more hydrophobic compounds. On the other hand water ionization increases (thus increasing H+ and OH- ions concentration), meaning that reactions catalysed by acids or bases, like biomass hydrolysis, are accelerated. [...]info:eu-repo/semantics/publishedVersio

Modélisation de l'entretien du paysage par des herbivores en moyenne montagne : une approche multi-agents

L'abandon de l'utilisation des ressources herbagères par l'activité pastorale entraîne un appauvrissement de la diversité écologique et spécifique. A terme, cette évolution se traduit par le déplacement des activités humaines hors de ces zones et à un déséquilibre au niveau du territoire national. Un programme de recherche pluridisciplinaire, dans le cadre d'un Groupement d'intérêt Scientifique, a été mis en place dès 1994 pour élaborer de nouveaux modes de gestion qui concilient production agricole et entretien de l'espace en condition de sous chargement (peu d'animaux par unité de surface). Cet article s'inscrit dans une démarche d'acquisition de méthodes afin d'expérimenter des techniques de gestion de pâturage mixte bovins et chevaux selon une hypothèse de complémentarité entre ces deux espèces. La partie informatique présentée vise à simuler les dynamiques animales, végétales et paysagères futures et, à terme, proposer des protocoles de gestion aptes à répondre à ces nouvelles demandes. L'objectif de la modélisation que nous présentons est de simuler le fonctionnement de l'estive, afin de comprendre l'interaction entre l'évolution de la végétation, les déplacements et les actions des animaux en pâture. Un des modes de simulation utilise un système multi-agents. Le modèle conceptuel de la simulation est en cours de validation, il a été formalisé avec la notation graphique du langage de modélisation unifié (UML) et la version actuelle du logiciel est implémentée avec le langage de programmation Java. Pour suivre et enregistrer les localisations des animaux sur le terrain, ceux-ci sont équipés d'un récepteur satellite GPS (Global Positioning System). L'activité de pâturage des animaux est enregistrée par des colliers Ethosys. / The surrender of herbaceous resources by the grazing activity results in an impoverishment of both ecological and specific diversity. On the long term, this trend imposes the localization of human activities far from these zones and a national imbalance. A multidisciplinary research program was set up in 1994 with the aim of elaborating new ways of management, which would contribute to maintain both the productivity and the opened landscapes within the condition of low grazing pressure. This paper exposes the methods we elaborated in order to test several management techniques of grasslands by mean of cattle and horses within the hypothesis of complementarity between these two species. The computer science part of this paper presents the results of simulations of future dynamic behaviors of the animals, vegetation and landscape, in order to propound some management protocols. The simulator is based on a multi-agent system. The conceptual model, formalized with Unified Modeling Language graphical notation is actually in validation phase and the implementation of the software was done in the Java programming language. The following of the animals in the field was done by means of GPS equipments and the animal activity was recorded by Ethosys equipments

Fluid Structure Interaction of Multiple Flapping Filaments Using Lattice Boltzmann and Immersed Boundary Methods

The problem of flapping filaments in an uniform incoming flow is tackled using a Lattice Boltzmann—Immersed Boundary method. The fluid momentum equations are solved on a Cartesian uniform lattice while the beating filaments are tracked through a series of markers, whose dynamics are functions of the forces exerted by the fluid, the filament flexural rigidity and the tension. The instantaneous wall conditions on the filament are imposed via a system of singular body forces, consistently discretised on the lattice of the Boltzmann equation. We first consider the case of a single beating filament, and then the case of multiple beating filaments in a side-by-side configuration, focussing on the modal behaviour of the whole dynamical systems

Cabergoline therapy for macroprolactinoma during pregnancy: a case report.

Background: We assessed the safety of Cabergoline therapy during pregnancy in a lady with hyperprolactinemia intolerant to Bromocriptine. Case presentation: We report the case of a 31 year old lady who presented to us with uncontrolled hyperprolactinemia. A pituitary Macroadenoma was demonstrated by MRI. Due to intolerance to Bromocriptine, Cabergoline was started. The patient improved and subsequently conceived. MRI in the second trimester demonstrated further reduction in the tumor size. It was decided to continue Cabergoline throughout pregnancy to ensure further reduction in tumor size until delivery and to hold Cabergoline during postpartum period to allow for an adequate interval of breastfeeding. At 37 weeks of gestation, the patient delivered a healthy baby. Conclusion: We were able to safely treat macroprolactinemia in our patient during pregnancy with cabergoline. This case report contributes to the relatively meager data available which advocates the safety of cabergoline therapy in pregnant hyperprolactinemic patients

Xylanase and β-xylosidase production by Aspergillus ochraceus: new perspectives for the application of wheat straw autohydrolysis liquor

The xylanase biosynthesis is induced by its substrate—xylan. The high xylan content in some wastes such as wheat residues (wheat bran and wheat straw) makes them accessible and cheap sources of inducers to be mainly applied in great volumes of fermentation, such as those of industrial bioreactors. Thus, in this work, the main proposal was incorporated in the nutrient medium wheat straw particles decomposed to soluble compounds (liquor) through treatment of lignocellulosic materials in autohydrolysis process, as a strategy to increase and undervalue xylanase production by Aspergillus ochraceus. The wheat straw autohydrolysis liquor produced in several conditions was used as a sole carbon source or with wheat bran. The best conditions for xylanase and β-xylosidase production were observed when A. ochraceus was cultivated with 1% wheat bran added of 10% wheat straw liquor (produced after 15 min of hydrothermal treatment) as carbon source. This substrate was more favorable when compared with xylan, wheat bran, and wheat straw autohydrolysis liquor used separately. The application of this substrate mixture in a stirred tank bioreactor indicated the possibility of scaling up the process to commercial production.This work was supported by Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP/Brazil), Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq/Brazil), National System for Research on Biodiversity (SISBIOTA-Brazil, CNPq 563260/2010-6/FAPESP no. 2010/52322-3), and Fundacao para a Ciencia e a Tecnologia (FCT/Portugal)

Immobilization and application of the recombinant xylanase GH10 of Malbranchea pulchella in the production of xylooligosaccharides from hydrothermal liquor of the eucalyptus (Eucalyptus grandis) wood chips

Xylooligosaccharides (XOS) are widely used in the food industry as prebiotic components. XOS with high purity are required for practical prebiotic function and other biological benefits, such as antioxidant and inflammatory properties. In this work, we immobilized the recombinant endo-1,4-β-xylanase of Malbranchea pulchella (MpXyn10) in various chemical supports and evaluated its potential to produce xylooligosaccharides (XOS) from hydrothermal liquor of eucalyptus wood chips. Values >90% of immobilization yields were achieved from amino-activated supports for 120 min. The highest recovery values were found on Purolite (142%) and MANAE-MpXyn10 (137%) derivatives, which maintained more than 90% residual activity for 24 h at 70 °C, while the free-MpXyn10 maintained only 11%. In addition, active MpXyn10 derivatives were stable in the range of pH 4.0–6.0 and the presence of the furfural and HMF compounds. MpXyn10 derivatives were tested to produce XOS from xylan of various sources. Maximum values were observed for birchwood xylan at 8.6 mg mL−1 and wheat arabinoxylan at 8.9 mg mL−1, using Purolite-MpXyn10. Its derivative was also successfully applied in the hydrolysis of soluble xylan present in hydrothermal liquor, with 0.9 mg mL−1 of XOS after 3 h at 50 °C. This derivative maintained more than 80% XOS yield after six cycles of the assay. The results obtained provide a basis for the application of immobilized MpXyn10 to produce XOS with high purity and other high-value-added products in the lignocellulosic biorefinery field.The authors gratefully acknowledge FAPESP (São Paulo Research Foundation, grants No: 2018/07522-6) and FCT (POCI-01-0145-FEDER-032206)—transnational cooperation project EcoTech, and National Institute of Science and Technology of Bioethanol, INCT, CNPq 465319/2014-9/FAPESP n ◦ 2014/50884- 5) for financial support. Research scholarships were granted to RCA, DA, and JCSS by FAPESP (Grant No: 2020/00081-4, 2020/15510-8, and 2019/21989-7, respectively), to CCVD and VEP by CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Finance Code 001).info:eu-repo/semantics/publishedVersio

The Type and the Position of HNF1A Mutation Modulate Age at Diagnosis of Diabetes in Patients with Maturity-Onset Diabetes of the Young (MODY)-3

OBJECTIVE—The clinical expression of maturity-onset diabetes of the young (MODY)-3 is highly variable. This may be due to environmental and/or genetic factors, including molecular characteristics of the hepatocyte nuclear factor 1-α (HNF1A) gene mutation. RESEARCH DESIGN AND METHODS—We analyzed the mutations identified in 356 unrelated MODY3 patients, including 118 novel mutations, and searched for correlations between the genotype and age at diagnosis of diabetes. RESULTS—Missense mutations prevailed in the dimerization and DNA-binding domains (74%), while truncating mutations were predominant in the transactivation domain (62%). The majority (83%) of the mutations were located in exons 1- 6, thus affecting the three HNF1A isoforms. Age at diagnosis of diabetes was lower in patients with truncating mutations than in those with missense mutations (18 vs. 22 years, P = 0.005). Missense mutations affecting the dimerization/DNA-binding domains were associated with a lower age at diagnosis than those affecting the transactivation domain (20 vs. 30 years, P = 10−4). Patients with missense mutations affecting the three isoforms were younger at diagnosis than those with missense mutations involving one or two isoforms (P = 0.03). CONCLUSIONS—These data show that part of the variability of the clinical expression in MODY3 patients may be explained by the type and the location of HNF1A mutations. These findings should be considered in studies for the search of additional modifier genetic factors

A comparative study of some properties of cassava and tree cassava starch films

Cassava and tree cassava starch films plasticized with glycerol were produced by casting method. Different glycerol contents (30, 35, 40 and 45 wt. % on starch dry basis) were used and the resulting films were fully characterized. Their water barrier and mechanical properties were compared. While increasing glycerol concentration, moisture content, water solubility, water vapour permeability, tensile strength, percent elongation at break and Young's modulus decreased for both cassava and tree cassava films. Tree cassava films presented better values of water vapour permeability, water solubility and percent elongation at break compared to those of cassava films, regardless of the glycerol content