Leadership training

Thesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 1984.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH.Bibliography: leaf [51].by Thomas A. Stokes.M.C.P

Generation of two-color polarization-entangled optical beams with a self-phase-locked two-crystal Optical Parametric Oscillator

A new device to generate polarization-entangled light in the continuous variable regime is introduced. It consists of an Optical Parametric Oscillator with two type-II phase-matched non-linear crystals orthogonally oriented, associated with birefringent elements for adjustable linear coupling. We give in this paper a theoretical study of its classical and quantum properties. It is shown that two optical beams with adjustable frequencies and well-defined polarization can be emitted. The Stokes parameters of the two beams are entangled. The principal advantage of this setup is the possibility to directly generate polarization entangled light without the need of mixing four modes on beam splitters as required in current experimental setups. This device opens new directions for the study of light-matter interfaces and generation of multimode non-classical light and higher dimensional phase space

Capillary micromechanics: Measuring the elasticity of microscopic soft objects

We present a simple method for accessing the elastic properties of microscopic deformable particles. This method is based on measuring the pressure-induced deformation of soft particles as they are forced through a tapered glass microcapillary. It allows us to determine both the compressive and the shear modulus of a deformable object in one single experiment. Measurements on a model system of poly-acrylamide microgel particles exhibit excellent agreement with measurements on bulk gels of identical composition. Our approach is applicable over a wide range of mechanical properties and should thus be a valuable tool for the characterization of a variety of soft and biological materials

Strain-induced kinetics of intergrain defects as the mechanism of slow dynamics in the nonlinear resonant response of humid sandstone bars

A closed-form description is proposed to explain nonlinear and slow dynamics effects exhibited by sandstone bars in longitudinal resonance experiments. Along with the fast subsystem of longitudinal nonlinear displacements we examine the strain-dependent slow subsystem of broken intergrain and interlamina cohesive bonds. We show that even the simplest but phenomenologically correct modelling of their mutual feedback elucidates the main experimental findings typical for forced longitudinal oscillations of sandstone bars, namely, (i) hysteretic behavior of a resonance curve on both its up- and down-slopes, (ii) linear softening of resonant frequency with increase of driving level, and (iii) gradual recovery (increase) of resonant frequency at low dynamical strains after the sample was conditioned by high strains. In order to reproduce the highly nonlinear elastic features of sandstone grained structure a realistic non-perturbative form of strain potential energy was adopted. In our theory slow dynamics associated with the experimentally observed memory of peak strain history is attributed to strain-induced kinetic changes in concentration of ruptured inter-grain and inter-lamina cohesive bonds causing a net hysteretic effect on the elastic Young's modulus. Finally, we explain how enhancement of hysteretic phenomena originates from an increase in equilibrium concentration of ruptured cohesive bonds that are due to water saturation.Comment: 5 pages, 3 figure

Depression, anxiety, pain and quality of life in people living with chronic hepatitis C: A systematic review and meta-analysis

Objectives: Individuals infected with hepatitis C virus (HCV) can develop extrahepatic conditions which may have a significant impact on life expectancy and quality of life. We conducted a systematic review to assess the causal relationship between HCV and extrahepatic conditions and the impact of HCV upon health-related quality of life of people in the UK. / Methods: HCV advocacy groups identified conditions that they thought most important to research, and the perspectives of various stakeholders informed the scope of the review. A comprehensive literature search of a range of electronic databases and websites was undertaken. Screening, quality assessment and data extraction were conducted using specialist software. The key criterion for inclusion in a synthesis was a study’s testing of the association between HCV and either quality of life or conditions specified as important by advocacy groups: depression, anxiety or painful conditions. Other criteria relating to study populations, measures and matching of study groups were also applied. Two reviewers assessed included studies, with disagreements resolved by a third reviewer where necessary. Studies were assessed for methodological quality using standardised appraisal tools. Metaanalyses were performed. Based on the consistency and sufficiency of research evidence, the findings were graded as strong, promising, tentative or inconclusive. / Results: 71 studies were included in the review’s syntheses. All studies were judged to be at a moderate or high risk of bias. Only two UK studies met our inclusion criteria. / Quality of life: Evidence from 22 studies indicates that people with HCV have worse quality of life than ‘general’ or ‘healthy’ populations; meta-analysis of nine studies indicated\ud that the physical (PCS) and mental health (MCS) domains of quality of life on the Health-Related Quality of Life Scale were both statistically and clinically worse among HCV-infected people (PCS: MD 5.54, 95% CI 3.73-7.35, MCS: MD 3.81, 95% CI 1.97-5.64). Evidence from seven included studies suggests that people co-infected with HCV and HIV have worse quality of life than individuals with HIV only; metaanalysis of five studies indicated that both the physical and mental health domains of quality of life were significantly worse among people who were co-infected (PCS: MD 2.57, 95% CI 1.08-4.06, MCS: MD 1.88, 95% CI 0.06-3.69). / Depression and anxiety: Evidence from 22 studies indicates that depression and anxiety are more severe, and depression is more common among people with HCV compared to those without it. Meta-analysis of 12 studies identified the severity of depression in people with HCV to be significantly greater than in those without HCV (Mean difference 0.98, 95% CI 0.43-1.53). Meta-analysis of nine studies identified the severity of clinical anxiety to be significantly greater among people with HCV (Mean difference 0.47, 95% CI 0.09-0.86). Meta-analysis of seven studies identified participants with HCV to be approximately three times more likely to be depressed compared to those without HCV (OR 2.77, 95% CI 1.62-4.74). No statistically significant evidence that anxiety is more common among people with HCV was found. / Pain: Evidence was appraised from 26 studies on painful conditions. A meta-analysis of four studies indicates that people with HCV are 17% more likely to suffer from arthralgia than those without HCV (RR 1.17, 95% CI 1.04-1.31). A meta-analysis of five studies suggested that people with HCV are significantly more likely to suffer from fibromyalgia; key differences across the studies in terms of the health status (co-morbidities) of HCV patients and comparison groups mean it is not possible to quantify the increased risk attributable to HCV. Other studies, including those on arthritis, were not amenable to meta-analysis. / Conclusions: Evidence suggests an association between HCV infection and depression, anxiety, fibromyalgia, arthralgia and health-related quality of life. However, the evidence was graded as ‘promising’ or ‘tentative’ rather than ‘strong’. More high-quality research on the association between HCV and these conditions is needed

Sexual health promotion and contraceptive services in local authorities: a systematic review of economic evaluations 2010-2015

Background Since 2013, health commissioners in England’s local authorities have been responsible for sexual health services, including contraception, HIV testing, STI testing and treatment, health education and specialist sexual health services. Effective commissioning requires information to indicate which interventions may, or may not, be cost-effective. However, current UK guidance and recent research on the cost-effectiveness of sexual health services provides patchy and fragmented evidence. This study aims systematically to review the evidence available on the cost-effectiveness of OECD-based interventions relevant to UK local authority-commissioned sexual health services. Methods Key informants, bibliographic database searches and reference lists of guidance documents and included studies were searched for potentially relevant research. Guided by key stakeholders, we sought economic evaluations of sexual health interventions within the responsibility of local authorities, and focused in the UK, on contraception and on health promotion, published between 2010 and 2015 in English. Eligible studies were full economic evaluations based in an OECD country. Studies were classified using a specifically developed tool and assessed for methodological risk of bias using one of three design-specific assessment tools. Descriptive frequencies of codes were analysed to provide a ‘map’ of research that informed stakeholder discussions to focus the subsequent synthesis. The characteristics of studies, quality ratings and cost outcomes from each included study were extracted into tables and findings summarised narratively. Studies were assessed for their relative cost-saving or cost-effectiveness according to NICE guidance. Results In total, 17,705 references were screened; of these, 29 met our inclusion criteria and were included in the synthesis. Nine studies were undertaken in the UK; the remainder were US based. Fifteen studies examined the economics of contraception and 14 evaluated health promotion. Overall, studies were of medium methodological quality. In general, economic evaluations of contraception reported cost-effectiveness or cost savings for ulipristal acetate (UPA) as emergency contraception, long-acting reversible contraceptives (LARCs) for regular, post-natal and post-abortion contraception, and targeting to high risk groups; none, however, reported costs per quality-adjusted life year (QALY) within NICE thresholds. Economic evaluations of sexual health promotion interventions indicated more mixed results. Only three interventions were found to be cost-effective according to the NICE thresholds for HIV or sexually transmitted infection (STI) outcomes: nurse-led rapid testing and tailored counselling; condom negotiations skills training for female sex workers; and a teacher-led STI prevention and skills training intervention. UK studies focused on health promotion and contraception, and supported the above findings. In general, there has been a reasonable amount of economic research into sexual health interventions since 2010, and these support current NICE sexual health guidance. Abstract Sexual health promotion and contraceptive services in local authorities: a systematic review of economic evaluations 2010-2015 vi Conclusions The broad nature of the research question posed in this systematic review resulted in the inclusion of a dataset very diverse in terms of populations, interventions, outcomes and types of economic evaluation designs. In considering the cost-effectiveness of these strategies in relation to their own commissioning climate, policy and decision makers should consider carefully the fit between their context and that of individual studies. Use of longer-term outcomes in trials used in economic evaluations would strengthen estimates of effects such as QALYs, as would the routine use of longitudinal cohort data

Forces between clustered stereocilia minimize friction in the ear on a subnanometre scale

The detection of sound begins when energy derived from acoustic stimuli deflects the hair bundles atop hair cells. As hair bundles move, the viscous friction between stereocilia and the surrounding liquid poses a fundamental challenge to the ear's high sensitivity and sharp frequency selectivity. Part of the solution to this problem lies in the active process that uses energy for frequency-selective sound amplification. Here we demonstrate that a complementary part involves the fluid-structure interaction between the liquid within the hair bundle and the stereocilia. Using force measurement on a dynamically scaled model, finite-element analysis, analytical estimation of hydrodynamic forces, stochastic simulation and high-resolution interferometric measurement of hair bundles, we characterize the origin and magnitude of the forces between individual stereocilia during small hair-bundle deflections. We find that the close apposition of stereocilia effectively immobilizes the liquid between them, which reduces the drag and suppresses the relative squeezing but not the sliding mode of stereociliary motion. The obliquely oriented tip links couple the mechanotransduction channels to this least dissipative coherent mode, whereas the elastic horizontal top connectors stabilize the structure, further reducing the drag. As measured from the distortion products associated with channel gating at physiological stimulation amplitudes of tens of nanometres, the balance of forces in a hair bundle permits a relative mode of motion between adjacent stereocilia that encompasses only a fraction of a nanometre. A combination of high-resolution experiments and detailed numerical modelling of fluid-structure interactions reveals the physical principles behind the basic structural features of hair bundles and shows quantitatively how these organelles are adapted to the needs of sensitive mechanotransduction.Comment: 21 pages, including 3 figures. For supplementary information, please see the online version of the article at http://www.nature.com/natur

Using Voice Coils to Actuate Modular Soft Robots: Wormbot, an Example

In this study, we present a modular worm-like robot, which utilizes voice coils as a new paradigm in soft robot actuation. Drive electronics are incorporated into the actuators, providing a significant improvement in self-sufficiency when compared with existing soft robot actuation modes such as pneumatics or hydraulics. The body plan of this robot is inspired by the phylum Annelida and consists of three-dimensional printed voice coil actuators, which are connected by flexible silicone membranes. Each electromagnetic actuator engages with its neighbor to compress or extend the membrane of each segment, and the sequence in which they are actuated results in an earthworm-inspired peristaltic motion. We find that a minimum of three segments is required for locomotion, but due to our modular design, robots of any length can be quickly and easily assembled. In addition to actuation, voice coils provide audio input and output capabilities. We demonstrate transmission of data between segments by high-frequency carrier waves and, using a similar mechanism, we note that the passing of power between coupled coils in neighboring modules—or from an external power source—is also possible. Voice coils are a convenient multifunctional alternative to existing soft robot actuators. Their self-contained nature and ability to communicate with each other are ideal for modular robotics, and the additional functionality of sound input/output and power transfer will become increasingly useful as soft robots begin the transition from early proof-of-concept systems toward fully functional and highly integrated robotic systems

Twirling and Whirling: Viscous Dynamics of Rotating Elastica

Motivated by diverse phenomena in cellular biophysics, including bacterial flagellar motion and DNA transcription and replication, we study the overdamped nonlinear dynamics of a rotationally forced filament with twist and bend elasticity. Competition between twist injection, twist diffusion, and writhing instabilities is described by a novel pair of coupled PDEs for twist and bend evolution. Analytical and numerical methods elucidate the twist/bend coupling and reveal two dynamical regimes separated by a Hopf bifurcation: (i) diffusion-dominated axial rotation, or twirling, and (ii) steady-state crankshafting motion, or whirling. The consequences of these phenomena for self-propulsion are investigated, and experimental tests proposed.Comment: To be published in Physical Review Letter