The context-dependence of mutations: a linkage of formalisms

Defining the extent of epistasis - the non-independence of the effects of mutations - is essential for understanding the relationship of genotype, phenotype, and fitness in biological systems. The applications cover many areas of biological research, including biochemistry, genomics, protein and systems engineering, medicine, and evolutionary biology. However, the quantitative definitions of epistasis vary among fields, and its analysis beyond just pairwise effects remains obscure in general. Here, we show that different definitions of epistasis are versions of a single mathematical formalism - the weighted Walsh-Hadamard transform. We discuss that one of the definitions, the backgound-averaged epistasis, is the most informative when the goal is to uncover the general epistatic structure of a biological system, a description that can be rather different from the local epistatic structure of specific model systems. Key issues are the choice of effective ensembles for averaging and to practically contend with the vast combinatorial complexity of mutations. In this regard, we discuss possible approaches for optimally learning the epistatic structure of biological systems.Comment: 6 pages, 3 figures, supplementary informatio

Manipulation of Spherical Droplets on a Liquid Platform Using Thermal Gradients

In the recent years, there has been a growing interest in droplet-based (digital) microfluidics for which, reliable means of droplet manipulation are required. In this study we demonstrate thermal actuation of droplets on liquid platforms, which is ideal for biochemical microsystems and lab-on-chip applications because droplets can be transported with high speed, good control and minimal thermal loading as compared to using conventional solid substrates. In addition, other disadvantages of using solid surfaces such as evaporation, contamination, pinning, hysteresis and irreversibility of droplet motion are avoided. Based on the theoretical development and measurements, a silicon-based droplet transportation platform was developed with embedded Titanium micro heaters. A shallow liquid pool of inert liquid (FC-43) served as the carrier liquid. Heaters were interfaced with control electronics and driven through a computer graphical user interface. By creating appropriate spatio-temporal thermal gradient maps, transport of droplets on predetermined pathways was successfully demonstrated with high level of robustness, speed and reliability. The video shows normal imaging of droplet manipulation accompanied by the corresponding infrared thermal imaging showing the spatio-temporal temperature maps and the outline of the drop as it moves towards hot spots.Comment: 63rd APS - Division of Fluid Dynamics - 201

Low elevation angle KU-band satellite measurements at Austin, Texas

At low elevation angles, the propagation of satellite signals is affected by precipitation as well as by inhomogeneties of the refractive index. Whereas precipitation causes fades for relatively small percentages of time, the refractive index variability causes scintillations which can be observed for most of the time. An experiment is now under way in Austin, Texas, in which the right hand circularly polarized 12 GHz beacon of INTELSAT-V/F10 is observed at a 5.8 deg elevation angle, along with the radiometric sky temperature, rainfall rate, humidity, pressure, temperature, and wind speed and direction. The objective of these measurements is to accumulate a database over a period of 2 years and to analyze the probabilities and dynamical behavior of the signal variations in relation to the meteorological parameters. The hardware and software used for the data acquisition and analysis is described and the results from the first year of measurements are presented

Chronic Neck Pain and Neck Muscle Strength

INTRODUCTION: Neck pain is one of the most common musculoskeletal disorders, with an estimated 1-year prevalence of 31.4% to 35.6% of adults in the general population. The course of neck pain is characterized by exacerbations and remissions and only a small part of the patients experience complete resolution of their symptoms within 1 year. A substantial proportion of the neck pain patients will thus develop chronic neck pain. The definition of chronic pain differs between studies, in terms of either 3 or 6 months duration of complaints. Nevertheless, the estimates of their one year prevalence in the general population are similar: 8.7% to 17.8% for the 3-months definition, and 8% to 13.8% for the 6-months definition. OBJECTIVES: There is not much scientific evidence to support the standard treatments of neck pain (including things like hot and cold packs, ultrasound and massage.) The aim of this study is to assess the neck muscle strength in chronic neck pain patients and in control group and compare the difference in these two groups. This study will give an idea of the difference if at all present in neck muscle strength in these two groups. This also may give an indication of the necessity to improve the neck muscles in the neck pain group. MATERIAL AND METHOD: In this study we assessed the cervical spine muscle strength in persons with chronic neck pain and in control group without history of neck pain. With this data the strength of the neck muscles are compared and the difference in muscle strength is found out. SELECTION OF THE SUBJECTS: It is well known that the acute pain inhibits the muscle contraction. In this study only patient who is totally pain free is taken up for the study. These are the patients who have chronic pain for more than six months and they are in remission during the evaluation. They should not have any organic lesion, fracture, infection, post operative problems. From all the persons consent to join in the study is received. METHODOLOGY: Isometric neck muscle strength is assessed in sitting posture. A spring balance [Pic – 6] was mounted on a stand and the height is fixed. According to the height of the subject the stool height is adjusted. SUMMARY: • Neck muscles are weaker in Chronic Neck Pain patients. • Neck extensors are more than two times stronger than flexors. • In the control group the neck muscles are stronger in the active group. The sedentary people in the control group have weaker muscles. • The lateral flexors are stronger on the left side. CONCLUSION: 1. In Chronic Neck Pain patients due to their weak neck muscles the protection to the cervical spine is less to prevent further injury during stressful situations. So they require regular and specific neck muscle strengthening exercise to prevent recurrence of symptom. These specific cervical exercises strengthen the spinal muscles and provide better support by spinal bracing. 2. The role of cervical brace is also important. They may be used in situations where the person with chronic neck pain is subjected to prolonged stresses as in occupation or while traveling. 3. The sedentary people in the control group were found to have weaker muscles. Are they prone to neck pain? Only long term study can prove this aspect of finding. Follow up - All the Chronic Neck Pain patients were given a program of exercise. The neck pain feed back form is also given to them. Follow up in future will confirm the usefulness of the exercise in preventing frequent recurrences

Divergent Reactions to Convergent Strategies: Investor Beliefs and Analyst Reactions During Technological Change

An important outcome of technological change is industry “convergence,” as a new technology spurs competition between established firms from different industries. We study the reactions of securities analysts, as important sources of institutional pressures for firms, to the similar product/market strategies undertaken by firms from different prior industries responding to industry convergence. Our empirical setting is the convergence between the wireline telecommunications and cable television industries in the period following the advent of voice over Internet protocol technology. Controlling for firm financial performance and capabilities, we find that analysts were consistently more positive toward the cable firms than toward the wireline telecom firms. Our findings further show that this divergence in reactions arises from differences in existing investor expectations and preferences concerning how firms create value; stocks owned by investors with a greater preference for growth receive more positive reactions than those owned by investors with a greater preference for margins. However, this divergence in reactions shrinks over time as convergence unfolds and as investors shift their shareholdings in response to misalignment between their preferences and firms\u27 strategic changes. Reactions from analysts—reflecting inertial expectations of investors—may persist for a time despite changes to firms\u27 strategies, thus creating challenges for some firms in responding to technological change and industry convergence while legitimating and enabling similar responses from their competitors

Droplets on liquid surfaces: Dual equilibrium states and their energy barrier

Floating aqueous droplets were formed at oil-air interface, and two stable configurations of (i) non-coalescent droplet and (ii) cap/bead droplet were observed. General solutions for energy and force analysis were obtained for both configurations and were shown to be in good agreement with the experimental observations. The energy barrier obtained for transition from configuration (i) to configuration (ii) was correlated to the droplet release height and the probability of non-coalescent droplet formation

Discrete Droplet Manipulation on Liquid Platforms using Thermal Gradients

AbstractManipulation of droplet motion on the free surface of an liquid platform using thermal gradient has been studied. Two distinct motion mechanisms were observed. Droplets that remain spherical are propelled from cold to warm region and those which break up into a sessile lens move in the opposite direction. Driving forces acting on the droplet due to interfacial-tension gradients arising from induced thermal gradients were analyzed using theoretical models. By adopting a liquid platform, limitations associated with previously-reported capillary-based mechanisms, which used chemical/thermally-patterned solid substrates, are overcome to make the proposed scheme suitable for droplet-based bio-chemical lab on chips: minimal droplet temperature fluctuation (<5°C); avoiding droplet-pinning and contact-angle hysteresis allow for higher transport speeds (~4 mm/sec) and no evaporative losses or contaminations

Effect of laminar velocity profile variation on mixing in microfluidic devices: The sigma micromixer

The effect of the laminar velocity profile and its variation on mixing phenomena at the reduced scale is studied. It is shown that the diffusive mass flux between two miscible streams, flowing laminar in a microchannel, is enhanced if the velocity at their diffusion interface is increased. Based on this idea, an in-plane passive micromixing concept is proposed and implemented in a working device (sigma micromixer). This mixer shows considerable mixing performance by periodically varying the flow velocity profile, such that the maximum of the profile coincides with the transversely progressing diffusion fronts repeatedly throughout the mixing channel

Droplet actuation on a liquid layer due to thermocapillary motion: Shape effect

In the thermocapillary migration of droplets on the free surface of immiscible liquids, we observe that the lens-shaped drops move from warm toward cooler regions while spherical drops move in the opposite direction. We explain this dual behavior using an analysis of surface deformation and velocity profiles of thin liquid layers subject to a lateral thermal gradient. Liquid platforms allow thermocapillary transport of drops with higher migration speeds than solid substrates and lower internal temperature fluctuation. Such conditions may be exploited in biochemical microsystems where droplet evaporation, contamination, and surface pinning need to be avoided