Particle motion in Stokes flow near a plane fluid-fluid interface. Part 1. Slender body in a quiescent fluid

The present study examines the motion of a slender body in the presence of a plane fluid–fluid interface with an arbitrary viscosity ratio. The fluids are assumed to be at rest at infinity, and the particle is assumed to have an arbitrary orientation relative to the interface. The method of analysis is slender-body theory for Stokes flow using the fundamental solutions for singularities (i.e. Stokeslets and potential doublets) near a flat interface. We consider translation and rotation, each in three mutually orthogonal directions, thus determining the components of the hydrodynamic resistance tensors which relate the total hydrodynamic force and torque on the particle to its translational and angular velocities for a completely arbitrary translational and angular motion. To illustrate the application of these basic results, we calculate trajectories for a freely rotating particle under the action of an applied force either normal or parallel to a flat interface, which are relevant to particle sedimentation near a flat interface or to the processes of particle capture via drop or bubble flotation

Using molecular mechanics to predict bulk material properties of fibronectin fibers

The structural proteins of the extracellular matrix (ECM) form fibers with finely tuned mechanical properties matched to the time scales of cell traction forces. Several proteins such as fibronectin (Fn) and fibrin undergo molecular conformational changes that extend the proteins and are believed to be a major contributor to the extensibility of bulk fibers. The dynamics of these conformational changes have been thoroughly explored since the advent of single molecule force spectroscopy and molecular dynamics simulations but remarkably, these data have not been rigorously applied to the understanding of the time dependent mechanics of bulk ECM fibers. Using measurements of protein density within fibers, we have examined the influence of dynamic molecular conformational changes and the intermolecular arrangement of Fn within fibers on the bulk mechanical properties of Fn fibers. Fibers were simulated as molecular strands with architectures that promote either equal or disparate molecular loading under conditions of constant extension rate. Measurements of protein concentration within micron scale fibers using deep ultraviolet transmission microscopy allowed the simulations to be scaled appropriately for comparison to in vitro measurements of fiber mechanics as well as providing estimates of fiber porosity and water content, suggesting Fn fibers are approximately 75% solute. Comparing the properties predicted by single molecule measurements to in vitro measurements of Fn fibers showed that domain unfolding is sufficient to predict the high extensibility and nonlinear stiffness of Fn fibers with surprising accuracy, with disparately loaded fibers providing the best fit to experiment. This work shows the promise of this microstructural modeling approach for understanding Fn fiber properties, which is generally applicable to other ECM fibers, and could be further expanded to tissue scale by incorporating these simulated fibers into three dimensional network models

RNAase III-Type Enzyme Dicer Regulates Mitochondrial Fatty Acid Oxidative Metabolism in Cardiac Mesenchymal Stem Cells

Cardiac mesenchymal stem cells (C-MSC) play a key role in maintaining normal cardiac function under physiological and pathological conditions. Glycolysis and mitochondrial oxidative phosphorylation predominately account for energy production in C-MSC. Dicer, a ribonuclease III endoribonuclease, plays a critical role in the control of microRNA maturation in C-MSC, but its role in regulating C-MSC energy metabolism is largely unknown. In this study, we found that Dicer knockout led to concurrent increase in both cell proliferation and apoptosis in C-MSC compared to Dicer floxed C-MSC. We analyzed mitochondrial oxidative phosphorylation by quantifying cellular oxygen consumption rate (OCR), and glycolysis by quantifying the extracellular acidification rate (ECAR), in C-MSC with/without Dicer gene deletion. Dicer gene deletion significantly reduced mitochondrial oxidative phosphorylation while increasing glycolysis in C-MSC. Additionally, Dicer gene deletion selectively reduced the expression of β-oxidation genes without affecting the expression of genes involved in the tricarboxylic acid (TCA) cycle or electron transport chain (ETC). Finally, Dicer gene deletion reduced the copy number of mitochondrially encoded 1,4-Dihydronicotinamide adenine dinucleotide (NADH): ubiquinone oxidoreductase core subunit 6 (MT-ND6), a mitochondrial-encoded gene, in C-MSC. In conclusion, Dicer gene deletion induced a metabolic shift from oxidative metabolism to aerobic glycolysis in C-MSC, suggesting that Dicer functions as a metabolic switch in C-MSC, which in turn may regulate proliferation and environmental adaptation

Quantum Speed Limit for Perfect State Transfer in One Dimension

The basic idea of spin chain engineering for perfect quantum state transfer (QST) is to find a set of coupling constants in the Hamiltonian, such that a particular state initially encoded on one site will evolve freely to the opposite site without any dynamical controls. The minimal possible evolution time represents a speed limit for QST. We prove that the optimal solution is the one simulating the precession of a spin in a static magnetic field. We also argue that, at least for solid-state systems where interactions are local, it is more realistic to characterize the computation power by the couplings than the initial energy.Comment: 5 pages, no figure; improved versio

The packing of granular polymer chains

Rigid particles pack into structures, such as sand dunes on the beach, whose overall stability is determined by the average number of contacts between particles. However, when packing spatially extended objects with flexible shapes, additional concepts must be invoked to understand the stability of the resulting structure. Here we study the disordered packing of chains constructed out of flexibly-connected hard spheres. Using X-ray tomography, we find long chains pack into a low-density structure whose mechanical rigidity is mainly provided by the backbone. On compaction, randomly-oriented, semi-rigid loops form along the chain, and the packing of chains can be understood as the jamming of these elements. Finally we uncover close similarities between the packing of chains and the glass transition in polymers.Comment: 11 pages, 4 figure

Guanxi, IT Systems, and Innovation Capability: The Moderating Role of Proactiveness

In Chinese exporting, small and medium-sized companies (SMEs) need to be innovative to develop a competitive advantage. This research explored how these organizations can use two resources: 1) guanxi with customers, distributors, suppliers, and government officials; and 2) IT systems to enhance their innovation capabilities and new product performance. The moderating role of an organization’s proactiveness with respect to new product development is also examined. The resource-based view provides the theoretical support for the research. A conceptual model is developed and tested using survey data gathered from 210 Chinese SMEs in manufacturing industries that were analyzed using SmartPLS 2.0. Results show that IT systems are positively related to innovation capability. The relationship between guanxi and innovation capability is significant for firms that exhibit high levels of proactiveness but not when proactiveness is low

TABOT TRADITION AND ACCULTURATIVE RELIGIOUS TRADITION OF THE BENGKULU COMMUNITY

Abstract: This article aims to explain the Tabot tradition and its cultural construction with the Bengkulu people as a minority group. The Tabot tradition experienced a kind of acculturation process in which two or more cultures met and made contact. Using Berry’s acculturation theory with a qualitative approach and ethnographic methods, this study resulted in a finding that the Tabut tradition resulted from a process of cultural acculturation between different religious and cultural contacts. In its journey, the Tabot is no longer a non-formal tradition but has become a local Bengkulu community organisation with the formation of the Tabot Harmony Family (KKT). The strategy chosen by KKT is to maintain its cultural and community heritage is integration. In this context, integration means maintaining the original culture and cultural contact.Keywords: Tabot, religious-cultural traditions, local Islam, acculturation Abstrak: Artikel ini bertujuan untuk menjelaskan adat Tabut dan konstruksi budayanya dengan masyarakat Bengkulu sebagai sebuah kelompok minoritas. Adat Tabut mengalami semacam proses akulturasi di mana dua atau lebih budaya bertemu dan melakukan kontak. Menggunakan teori akulturasi Berry dengan pendekatan kualitatif dan metode etnografi, penelitian ini menghasilkan sebuah temuan bahwa Tabut adalah hasil dari proses akulturasi budaya antara kontak agama dan budaya yang berbeda. Dalam perjalanannya, Tabut bukan lagi sebuah adat tradisi non-formal, melainkan telah menjadi sebuah organisasi masyarakat lokal Bengkulu dengan terbentuknya Keluarga Kerukunan Tabut (KKT). Strategi yang dipilih KKT ialah untuk mempertahankan warisan budaya dan komunitasnya adalah integrasi. Dalam konteks ini, integrasi berarti mempertahankan budaya asli dan tetap melakukan kontak budaya.Kata Kunci: Tabot, Tradisi agama-budaya, Islam lokal, Akulturas