Continuous Avalanche Segregation of Granular Mixtures in Thin Rotating Drums

We study segregation of granular mixtures in the continuous avalanche regime (for frequencies above ~ 1 rpm) in thin rotating drums using a continuum theory for surface flows of grains. The theory predicts profiles in agreement with experiments only when we consider a flux dependent velocity of flowing grains. We find the segregation of species of different size and surface properties, with the smallest and roughest grains being found preferentially at the center of the drum. For a wide difference between the species we find a complete segregation in agreement with experiments. In addition, we predict a transition to a smooth segregation regime - with an power-law decay of the concentrations as a function of radial coordinate - as the size ratio between the grains is decreased towards one.Comment: 4 pages, 4 figures, http://polymer.bu.edu/~hmaks

Biculturals in International Business Negotiations: Moving away from the single culture paradigm

Article publication date: 24 March 2023Purpose – Biculturals possess higher cultural intelligence than monocultural individuals. This study explores biculturals’ key factors and attributes and how their cultural knowledge and identification influence International Business Negotiations (IBNs) and help their firms outperform others. Design/methodology/approach – Data were collected from semi-structured interviews with 35 bicultural senior managers in Lebanon. Findings – The findings highlight three essential qualities and behaviors that allow biculturals to act as a bridge between the parties during IBN: adaptability, cultural frame switching (CFS) and creativity. Originality/value – This study explores the notion of bicultural personnel using their understanding of multiple cultures to be innovative, avoid groupthink and generate new creative ideas that help overcome stalemates during IBNs.Priyan Khakhar, Hussain Gulzar Ramma, Vijay Pereir

Synthesis of p-benzohydroquinone-1, 3, 5-C<SUB>3</SUB><SUP>13 </SUP>

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Size Segregation of Granular Matter in Silo Discharges

We present an experimental study of segregation of granular matter in a quasi-two dimensional silo emptying out of an orifice. Size separation is observed when multi-sized particles are used with the larger particles found in the center of the silo in the region of fastest flow. We use imaging to study the flow inside the silo and quantitatively measure the concentration profiles of bi-disperse beads as a function of position and time. The angle of the surface is given by the angle of repose of the particles, and the flow occurs in a few layers only near the top of this inclined surface. The flowing region becomes deeper near the center of the silo and is confined to a parabolic region centered at the orifice which is approximately described by the kinematic model. The experimental evidence suggests that the segregation occurs on the surface and not in the flow deep inside the silo where velocity gradients also are present. We report the time development of the concentrations of the bi-disperse particles as a function of size ratios, flow rate, and the ratio of initial mixture. The qualitative aspects of the observed phenomena may be explained by a void filling model of segregation.Comment: 6 pages, 10 figures (gif format), postscript version at http://physics.clarku.edu/~akudrolli/nls.htm

DNA resection in eukaryotes: deciding how to fix the break

DNA double-strand breaks are repaired by different mechanisms, including homologous recombination and nonhomologous end-joining. DNA-end resection, the first step in recombination, is a key step that contributes to the choice of DSB repair. Resection, an evolutionarily conserved process that generates single-stranded DNA, is linked to checkpoint activation and is critical for survival. Failure to regulate and execute this process results in defective recombination and can contribute to human disease. Here, I review recent findings on the mechanisms of resection in eukaryotes, from yeast to vertebrates, provide insights into the regulatory strategies that control it, and highlight the consequences of both its impairment and its deregulation

Patterns and Collective Behavior in Granular Media: Theoretical Concepts

Granular materials are ubiquitous in our daily lives. While they have been a subject of intensive engineering research for centuries, in the last decade granular matter attracted significant attention of physicists. Yet despite a major efforts by many groups, the theoretical description of granular systems remains largely a plethora of different, often contradicting concepts and approaches. Authors give an overview of various theoretical models emerged in the physics of granular matter, with the focus on the onset of collective behavior and pattern formation. Their aim is two-fold: to identify general principles common for granular systems and other complex non-equilibrium systems, and to elucidate important distinctions between collective behavior in granular and continuum pattern-forming systems.Comment: Submitted to Reviews of Modern Physics. Full text with figures (2Mb pdf) avaliable at http://mti.msd.anl.gov/AransonTsimringReview/aranson_tsimring.pdf Community responce is appreciated. Comments/suggestions send to [email protected]

DNA End Resection Controls the Balance between Homologous and Illegitimate Recombination in Escherichia coli

Even a partial loss of function of human RecQ helicase analogs causes adverse effects such as a cancer-prone Werner, Bloom or Rothmund-Thompson syndrome, whereas a complete RecQ deficiency in Escherichia coli is not deleterious for a cell. We show that this puzzling difference is due to different mechanisms of DNA double strand break (DSB) resection in E. coli and humans. Coupled helicase and RecA loading activities of RecBCD enzyme, which is found exclusively in bacteria, are shown to be responsible for channeling recombinogenic 3′ ending tails toward productive, homologous and away from nonproductive, aberrant recombination events. On the other hand, in recB1080/recB1067 mutants, lacking RecBCD’s RecA loading activity while preserving its helicase activity, DSB resection is mechanistically more alike that in eukaryotes (by its uncoupling from a recombinase polymerization step), and remarkably, the role of RecQ also becomes akin of its eukaryotic counterparts in a way of promoting homologous and suppressing illegitimate recombination. The sickly phenotype of recB1080 recQ mutant was further exacerbated by inactivation of an exonuclease I, which degrades the unwound 3′ tail. The respective recB1080 recQ xonA mutant showed poor viability, DNA repair and homologous recombination deficiency, and very increased illegitimate recombination. These findings demonstrate that the metabolism of the 3′ ending overhang is a decisive factor in tuning the balance of homologous and illegitimate recombination in E. coli, thus highlighting the importance of regulating DSB resection for preserving genome integrity. recB mutants used in this study, showing pronounced RecQ helicase and exonuclease I dependence, make up a suitable model system for studying mechanisms of DSB resection in bacteria. Also, these mutants might be useful for investigating functions of the conserved RecQ helicase family members, and congruently serve as a simpler, more defined model system for human oncogenesis

Hydraulic resistance of rigid polyurethane foams. III. Effect of variation of the concentration of catalysts on foam structure and properties

Water blown rigid polyurethane foams are made using dibutyltin dilaurate and triethanol amine as catalysts. The rate of carbon dioxide generation due to the reaction of isocyanate with water and the rate of polymerization are varied by changing the relative proportion of the catalysts keeping the total catalyst concentration fixed. The foams have densities in the range of 134 to 164 kg/m(3). Foams are characterized for hydraulic resistance, "closed cell content," and compressive modulus. A cell window is the lamella of the foam material that separates two adjacent cells. A strut is generated where three windows of three different cells meet. The cell window area and strut width of the foam cells are measured by optical microscopy. It is found that cell window area and strut width decrease and the respective distribution becomes narrower as the proportion of dibutyltin dilaurate in the total amount of the catalysts is increased. The hydraulic resistance and hence threshold pressure of the foams increases with increase in the proportion of dibutyltin dilaurate. The maximum threshold pressure of 1.81 MPa is observed for the foam made with dibutyltin dilaurate alone. (C) 2004

Culture and business networks: International business negotiations with Arab managers

The Arab world is an important economic region due to its natural resources, geographic location and political influence. However, limited attention has been paid to researching and understanding the way business is conducted in this region. We address this gap by exploring the key socio-economic, cultural and political factors that influence the negotiation process between Arab and non-Arab managers. Semi-structured interviews were conducted with 30 Arab managers in Lebanon with experience in international business. The findings of the study show that: Arab negotiators place emphasis on building relationships and use referent power (wasta); the political uncertainty influences the bargaining power of the Arab negotiators and political volatility in the country influences the Arab managers' use of time during negotiations. © 2012 Elsevier Ltd