CiteULike: Tag people

The Peter Principle: Why Things Always Go Wrong

Laurence Peter — 2005-09-06T21:35:40-00:00

(23 August 1994)

The Information Commons at Lied Library

J Church — 2005-03-29T21:17:48-00:00

Library Hi Tech, Vol. 20, No. 1. (March 2002), pp. 58-70.

Presents the development of the Information Commons in the new Lied Library at the University of Nevada, Las Vegas, from conceptualization to realization. Discusses the goals of the facility, including the need to create a space that simultaneously supports access, collaboration, and production in scholarly endeavors. Also addresses the impact of the Information Commons concept on patterns of service, and illustrates the challenges in designing Information Commons workstations, including such considerations as user authentication and resources for those with disabilities.

Profile: Robert Tjian

Emily Waltz — 2006-03-08T21:53:06-00:00

Nature Biotechnology, Vol. 24, No. 3. (08 March 2006), pp. 235-235.

Rising to the Challenges of a Catastrophe: The Emergent and Prosocial Behavior following Hurricane Katrina

Havidan Rodriguez — 2008-03-07T06:52:37-00:00

The ANNALS of the American Academy of Political and Social Science, Vol. 604, No. 1. (1 March 2006), pp. 82-101.

Using several data sources including an extensive database of media reports and a series of government documents, but relying primarily on the University of Delaware's Disaster Research Center's field research in the aftermath of Hurricane Katrina, the authors describe the nontraditional behavior that emerged in that catastrophe. They also discuss the prosocial behavior (much of it emergent) that was by far the primary response to this event, despite widespread media reports of massive antisocial behavior. Their study focuses on individual and group reactions in Louisiana during the first three weeks following the hurricane. The authors limit their systematic analyses of emergent behavior to five groupings: hotels, hospitals, neighborhood groups, rescue teams, and the Joint Field Office. Their analysis shows that most of the improvisations undertaken helped in dealing with the various problems that continued to emerge following Katrina. The various social systems and the people in them rose to the demanding challenges of a catastrophe. 10.1177/0002716205284677

Disambiguating Web appearances of people in a social network

Ron Bekkerman — 2006-02-06T17:33:09-00:00

(2005), pp. 463-470.

Disability-free life expectancy of elderly people in a population undergoing demographic and epidemiologic transition.

S Jitapunkul — 2007-03-07T10:05:52-00:00

Age Ageing, Vol. 32, No. 4. (July 2003), pp. 401-405.

BACKGROUND: the major purpose of health and social policy in old age is to increase quality of life of elderly people. In many demographically developing countries, life expectancy is increasing very rapidly, but little information is available on survival free of disability. OBJECTIVES: to determine prevalence and severity of disability among the elderly population and to compare disability-free life expectancy and self-care life expectancy among different age groups and between men and women. DESIGN: a cross-sectional multi-stage random sample survey and routine life tables for Thailand. SETTING: national population of Thailand. SUBJECTS: 4,048 elderly subjects aged 60+ years. RESULTS: prevalence rates (95% CI) of long-term disability and dependency in self-care activities of daily living were 19% (95% CI 17.8, 20.2) and 6.9% (6.1, 7.7) respectively. Rates of disabilities increased with age and women were more disabled than men. The life expectancy and disability-free life expectancy at age 60 for men were 20.3 years and 16.4 years, and for women were 23.9 years and 18.2 years respectively. Self-care life expectancies at age 60, calculated from the prevalence of needing help with basic self-care activities, were 18.6 years and 21.3 years for men and women respectively. Women spent proportionately more of their longer life expectancy in a disabled state than men. Men and women can, respectively, expect that 19% and 24% of their life expectancy at age 60 will be spent in a disabled state, but may expect only about 10% of their life expectancy to be spent unable to manage basic self-care activities of daily living. CONCLUSION: long-term disability is common in old age, affecting a quarter of people over 60 years. However, self-care problems are much less common and suggest that the social and health care consequences of demographic transitions are over-estimated by use of simple questions about limiting long-standing disability. Self-care life expectancy provides a useful monitoring tool for censuses and national disability surveys.

Gis, Organisations and People: A Socio-Technical Approach (GIS for Beginners)

DE Reeve — 2005-11-01T14:27:57-00:00

(31 January 1999)

GIS projects have previously been viewed primarily as technical exercises but these projects have socio-organizational contexts which must be taken into account if they are to succeed. This book presents an overview of the "human" side of GIS, both individual and organizational.

Statistical physics of social dynamics

Claudio Castellano — 2007-10-18T16:28:55-00:00

(17 Oct 2007)

Statistical physics has proven to be a very fruitful framework to describe phenomena outside the realm of traditional physics. The last years have witnessed the attempt by physicists to study collective phenomena emerging from the interactions of individuals as elementary units in social structures. Here we review the state of the art by focusing on three major research lines i.e., opinion, cultural and language dynamics. In addition we discuss other social phenomena, such as crowd behavior, hierarchy formation, human dynamics, social spreading. We highlight the connections between these problems and other, more traditional, topics of statistical physics. We also emphasize the comparison of model results with empirical data from social systems.

Mistakes Were Made (But Not by Me): Why We Justify Foolish Beliefs, Bad Decisions, and Hurtful Acts

Carol Tavris — 2007-10-09T06:38:21-00:00

(07 May 2007)

<div>Why do people dodge responsibility when things fall apart? Why the parade of public figures unable to own up when they screw up? Why the endless marital quarrels over who is right? Why can we see hypocrisy in others but not in ourselves? Are we all liars? Or do we really believe the stories we tell? <br><br>Renowned social psychologists Carol Tavris and Elliot Aronson take a compelling look into how the brain is wired for self-justification. When we make mistakes, we must calm the cognitive dissonance that jars our feelings of self-worth. And so we create fictions that absolve us of responsibility, restoring our belief that we are smart, moral, and right—a belief that often keeps us on a course that is dumb, immoral, and wrong. <br><br>Backed by years of research and delivered in lively, energetic prose, Mistakes Were Made (But Not by Me) offers a fascinating explanation of self-deception—how it works, the harm it can cause, and how we can overcome it.<br><br></div>

Ethnography, Institutions, and the Problematic of the Everyday World

Peter Grahame — 2008-05-28T16:41:31-00:00

Human Studies, Vol. 21, No. 4. (1 October 1998), pp. 347-360.

This essay describes institutional ethnography as a method of inquiry pioneered by Dorothy E. Smith, and introduces a collection of papers which make distinctive contributions to the development of this novel form of investigation. Institutional ethnography is presented as a research strategy which emerges from Smith's wide-ranging explorations of the problematic of the everyday world. Smith's conception of the everyday world as problematic involves a critical departure from the concepts and procedures of more conventional sociologies. She argues for an alternative sociology which begins with the standpoint of the actor in everyday life, rather than from within a professional sociological discourse aligned with the society's ruling institutions. The familiar sociologies of everyday life do not suffice for this purpose, since they deal with local settings and social worlds, but stop short of examining how these are knitted into broader forms of social organization. In contrast, institutional ethnography examines how the scenes of everyday life are shaped by forms of social organization which cannot be fully grasped from within those scenes. The principal tasks of institutional ethnography include describing the coordination of activities in the everyday world, discovering how ideological accounts define those activities in relation to institutional imperatives, and examining the broader social relations in which local sites of activity are embedded. The four papers which follow demonstrate that specific contributions to institutional ethnography can be made in relation to a wide array of topics, methods, and interests.

Interview<br />The 'art' of being Donald Knuth

2008-06-24T15:49:45-00:00

Commun. ACM, Vol. 51, No. 7. (July 2008), pp. 35-39.

Discussing DRAM and CMOS Scaling with Inventor Bob Dennard

2008-04-21T14:48:38-00:00

Design & Test of Computers, IEEE, Vol. 25, No. 2. (2008), pp. 188-191.

This is one of a series of ongoing interviews in IEEE Design & Test with well-known engineers in the electronics industry. In this interview, Ken Wagner talks with IBM Fellow Bob Dennard, the inventor of DRAM. In addition to his foundational work in DRAM, Dennard is also well-known for his work in CMOS process scaling.

A conversation with Tim Bray

Jim Gray — 2005-02-21T14:15:36-00:00

Queue, Vol. 3, No. 1. (February 2005), pp. 20-25.

Julian Schwinger: Nuclear Physics, the Radiation Laboratory, Renormalized QED, Source Theory, and Beyond

KA Milton — 2006-10-18T22:19:38-00:00

(9 Oct 2006)

Julian Schwinger's influence on twentieth century science is profound and pervasive. Of course, he is most famous for his renormalization theory of quantum electrodynamics, for which he shared the Nobel Prize with Richard Feynman and Sin-itiro Tomonaga. But although this triumph was undoubtedly his most heroic work, his legacy lives on chiefly through subtle and elegant work in classical electrodynamics, quantum variational principles, proper-time methods, quantum anomalies, dynamical mass generation, partial symmetry, and more. Starting as just a boy, he rapidly became the pre-eminent nuclear physicist in the late 1930s, led the theoretical development of radar technology at MIT during World War II, and then, soon after the war, conquered quantum electrodynamics, and became the leading quantum field theorist for two decades, before taking a more iconoclastic route during his last quarter century.

An analysis of key principles in Valuing People: implications for supporting people with dementia.

L Forbat — 2006-11-08T13:30:01-00:00

J Intellect Disabil, Vol. 10, No. 3. (September 2006), pp. 249-260.

This article reports an analysis of practitioner and policy implementers' views on implementing the strategy document Valuing People. It is based on empirical data generated from the first phase of a research project that seeks to develop best practice in supporting people with an intellectual disability and dementia.The analysis focuses on how Valuing People's four key principles (choice, independence, rights and inclusion) were drawn on and talked about spontaneously by participants. Each of these four principles has important implications for the provision of services for people with intellectual disabilities and dementia. This article adds to the growing dialogue on service provision for this group.

Effects of different regimens to lower blood pressure on major cardiovascular events in older and younger adults: meta-analysis of randomised trials

Blood — 2008-07-05T14:30:12-00:00

BMJ, Vol. 336, No. 7653. (17 May 2008), pp. 1121-1123.

Objective To quantify the relative risk reductions achieved with different regimens to lower blood pressure in younger and older adults. Design Meta-analyses and meta-regression analyses used to compare the effects on the primary outcome between two age groups (<65 v [≥]65 years). Evidence for an interaction between age and the effects of treatment sought by fitting age as a continuous variable and estimating overall effects across trials. Main outcome measures Primary outcome: total major cardiovascular events. Results 31 trials, with 190 606 participants, were included. The meta-analyses showed no clear difference between age groups in the effects of lowering blood pressure or any difference between the effects of the drug classes on major cardiovascular events (all P[≥]0.24). Neither was there any significant interaction between age and treatment when age was fitted as a continuous variable (all P>0.09). The meta-regressions also showed no difference in effects between the two age groups for the outcome of major cardiovascular events (<65 v [≥]65; P=0.38). Conclusions Reduction of blood pressure produces benefits in younger (<65 years) and older ([≥]65 years) adults, with no strong evidence that protection against major vascular events afforded by different drug classes varies substantially with age. 10.1136/bmj.39548.738368.BE

Extracting Humans from Nature

Kent Redford — 2008-04-28T18:04:34-00:00

Conservation Biology, Vol. 14, No. 5. (2000), pp. 1362-1364.

Conserved to death : Are tropical forests being overprotected from people?

David Wood — 2008-04-28T17:52:12-00:00

Land Use Policy, Vol. 12, No. 2. (April 1995), pp. 115-135.

There are plans to double the area of strictly protected tropical forest. This article suggests that the siting and management of such reserves are based on models of conservation inappropriate to developing countries, and that an ignorance of past and present tropical land use will prevent reserves achieving their major objective of conserving useful biodiversity. Strict preservation could also destroy the indigenous knowledge needed for ecosystem management. Multipurpose management and continued human use of tropical forests is a more effective and sustainable conservation policy for tropical developing countries. Rural communities should be actively and physically involved in the future productive management of tropical forests, rather than being induced or pressured into abandoning their forest heritage.

Conservation Where People Live and Work

James Miller — 2008-05-25T16:50:18-00:00

Conservation Biology, Vol. 16, No. 2. (2002), pp. 330-337.

Abstract: Effective conservation planning requires information from well-designed studies across a spectrum of land uses, ranging from wildlands to highly modified production landscapes and large cities. There is currently a lack of such information about human settlement, even though this is a major source of land-use change with serious implications for biodiversity. Fewer than 6% of the papers in recent volumes of Conservation Biology described work conducted in urban, suburban, or exurban areas or studies in which human settlement was considered explicitly. For a variety of reasons, conservation has tended to focus on lands with a relatively small human presence, often dominated by resource extraction and agriculture. Urbanization is occurring in numerous biodiversity hotspots worldwide, however, and has been identified as a primary cause of declines in many threatened and endangered species. Suburban and exurban growth are affecting biodiversity in many places once thought of as too remote to attract such levels of development. Conservation biologists must address the issue of human settlement to enhance the habitat value of unreserved lands for native species, to increase landscape connectivity between reserves, and to mitigate adverse influences on reserves from adjacent lands. Conservation and restoration of native habitats in densely settled areas also have social and educational value. We therefore suggest a more balanced approach in conservation biology to addressing the effects of human land use through increased attention to areas where people live and work. Conservacion donde la Gente Vive y Trabaja da planeacion eficaz de la conservacion Resumen: La planeacion de una eficaz conservacion requiere de informacion que provenga de estudios bien disenados a lo largo de un amplio espectro de usos del suelo que se enfiende desde tierras silvestres hasta paisajes de produccion altamente modificados y ciudades grandes. Actualmente, existe una carencia de informacion en lo referente a los asentamientos humanos, a pesar de que este factor constituya una fuente importante de cambio del uso del suelo con implicaciones serias para la biodiversidad. Menos de un 6% de los documentos escritos en volumenes recientes de Conservacion Biologica han descrito trabajos realizados en areas urbanas, suburbanas y exurbanas, o son estudios en los cuales los asentamientos humanos fueron considerados explicitamente. Por una variedad de razones, la conservacion ha tendido a enfocarse en tierras con relativamente poca presencia humana, frecuentemente dominada por la extraccion de recursos y la agricultura. Sin embargo, la urbanizacion esta ocurriendo en numerosos sitios importantes para la biodiversidad a nivel mundial y ha sido identificada como la principal causa de disminuciones de muchas especies amenazadas y en peligro de extincion. El crecimiento suburbano y exurbano esta afectando la biodiversidad en muchos lugares que anteriormente eran considerados muy remotos como para que atrajeran estos niveles de desarrollo. Los biologos de la conservacion deben enfrentar el tema de los asentamientos humanos para resaltar el valor del habitat de areas fuera de reservas para especies nativas, para incrementar la conectividad del paisaje entre reservas y mitigar las influencias adversas de zonas aledanas a las reservas. La conservacion y restauracion de habitats nativos en areas densamente pobladas tambien tienen un valor social y educativo. Por lo tanto sugerimos una aproximacion mas balanceada de la conservacian biologica para atacar los efectos del uso humano del suelo poniendo una mayor atencion en las areas donde la gente vive y trabaja.

Parks, protected areas and local populations: New international issues and imperatives

Abbasi — 2008-06-19T14:59:13-00:00

Landscape and Urban Planning, Vol. 19, No. 2. (May 1990), pp. 197-201.

Over the past decade, the protection of natural areas has acquired a new urgency, even as the concepts underlying park protection have undergone significant change and evolution. Several emergent issues have added to this sense of urgency: the recognition that the earth's biological diversity is rapidly being depleted as critical habitats are permanently lost, the increasing rapidity of tropical deforestation, of concern in connection with both biological diversity and climate change due to the "greenhouse effect", and the emergence of concern for sustainable economic development in the Third World. The experience of park managers around the world over this same period has led to new imperatives in accommodating a variety of human needs in park planning and management. A new way of thinking about the goals and objectives of parks in many of the world's nations is emerging, and many experienced observers report that these new concepts are critical if existing parks are to remain protected and if new protected areas are to succeed in achieving their goals. These new concepts and imperatives emerge clearly from the papers on local population interactions with national parks and equivalent reserves presented at the June 1988 Second Symposium on Social Science in Resource Management at the University of Illinois.

Precariousness under the new psychological contract: the effect on trust and the willingness to converse and share knowledge

Rob Sharkie — 2005-04-07T03:48:06-00:00

Knowledge Management Research & Practice, Vol. 3, No. 1. (March 2005), pp. 37-44.

Perceived value of knowledge: the potential informers perception

Ford — 2006-05-14T09:50:44-00:00

Knowledge Management Research & Practice, Vol. 4, No. 1. (February 2006), pp. 3-16.

Knowledge sharing and team trustworthiness: its all about social ties!

Wang — 2006-10-18T02:34:57-00:00

Knowledge Management Research & Practice, Vol. 4, No. 3. (August 2006), pp. 175-186.

The Eighteenth-Century Rediscovery of Alexis Grimou and the Emergence of the Proto-Bohemian Image of the French Artist

George Levitine — 2008-05-21T17:56:57-00:00

Eighteenth-Century Studies, Vol. 2, No. 1. (1968), pp. 58-76.

An Early Black-Music Concert from Spirituals to Swing

James Dugan — 2008-05-21T17:43:14-00:00

The Black Perspective in Music, Vol. 2, No. 2. (1974), pp. 191-207.

Ernst Jünger's Legacy

Elliot Neaman — 2008-03-10T21:38:56-00:00

Nicolas de Staël: In Memoriam

Douglas Cooper — 2008-01-04T23:19:42-00:00

Outside the Parenthesis (Those People Were a Kind of Solution)

Haun Saussy — 2008-06-16T22:06:50-00:00

MLN, Vol. 115, No. 5. (2000), pp. 849-891.

Life Course Factors Associated With Suicidal Behaviors in Young People

Annette Beautrais — 2007-11-14T08:48:11-00:00

American Behavioral Scientist, Vol. 46, No. 9. (1 May 2003), pp. 1137-1156.

This article reviews the major life course factors and processes associated with the development of suicidal behaviors in young people. Key issues examined include (a) the spectrum of suicidal behaviors in young people; (b) changing risks of suicidal behavior during childhood, adolescence, and young adulthood; and (c) key risk and protective factors. It is concluded that suicidal tendencies are frequently the culmination of adverse life course sequences that involve multiple risk factors. Future research priorities include a focus on (a) greater understanding of the role of genetic and biologic factors in the development of suicidal behaviors, (b) exploration of factors that may protect young people against suicidal behaviors, and (c) evaluation of public health and clinical programs designed to minimize risk of suicidal behaviors in young people. 10.1177/0002764202250657

Neighborhood Deprivation, Individual Socioeconomic Status, and Cognitive Function in Older People: Analyses from the English Longitudinal Study of Ageing

Lang — 2008-01-31T12:30:10-00:00

Journal of the American Geriatrics Society, Vol. 56, No. 2. (February 2008), pp. 191-198.

JAMES CLERK MAXWELL AND THE DEMOCRATIC INTELLECT

I Macleod — 2005-01-31T14:51:57-00:00

Civil Engineering and Environmental Systems, Vol. 20, No. 1. (1 January 2002), pp. 23-29.

A study of blind drawing practice: creating graphical information without the visual channel

Hesham Kamel — 2007-03-30T12:01:51-00:00

(2000), pp. 34-41.

People versus Information: The Evolution of Mobile Technology

Richard Harper — 2007-06-06T19:29:49-00:00

Human-Computer Interaction with Mobile Devices and Services (2003), pp. 1-14.

This reports research on users attitudes towards and use of GSM devices and discusses the implications these have for the future evolution of hand-held devices. It argues that current usage patterns suggest that there is unlikely to be a widespread convergence of information accessing devices and person to person communication devices. It also argues that the latter devices and their associated applications could provide much richer opportunities for communication behaviours than is currently available, and that therefore design efforts within the mobile HCI community should focus on this rather than on information use applications.

Growing Up in Poor Neighbourhoods: The Significance of Class and Place in the Extended Transitions of 'Socially Excluded'Young Adults

Robert Macdonald — 2008-03-04T19:01:21-00:00

Sociology, Vol. 39, No. 5. (1 December 2005), pp. 873-891.

Drawing upon qualitative, longitudinal research with socially excluded' young adults from some of England's poorest neighbourhoods, the article explores how locally-embedded, social networks become part of the process whereby poverty and class inequalities are reproduced. Networks of family and friends, rooted in severely de-industrialized locales, supported young people as they carved out transitions to adulthood in adverse circumstances. Examples are given in respect of informants' highly localized housing careers and their longer-term experience of poor work'. Paradoxically, though, while local networks helped in coping with the problems of growing up in poor neighbourhoods and generated a sense of inclusion, the sort of social capital embedded in them served simultaneously to close down opportunities and to limit the possibilities of escaping the conditions of social exclusion. Overall, and contrary to some recent youth sociology, the article stresses the continuing importance of class and place in shaping youth transitions. 10.1177/0038038505058370

Influence of people shadowing on optimal deployment of WLAN access points

M Klepal — 2006-05-19T04:45:52-00:00

Vehicular Technology Conference, 2004. VTC2004-Fall. 2004 IEEE 60th, Vol. 6 (2004), pp. 4516-4520 Vol. 6.

With their low cost and high-speed data rate capabilities, installations of IEEE 802.11-based wireless local area networks (WLANs) are growing exponentially. Although many organizations have started using WLANs, there are still very few tools available that can help the design of WLAN networks. As a result, the current deployment remains ad-hoc in nature. The objective of this work is to develop modeling tools for performance optimization of WLAN networks and WLAN access points. In particular, propagation models are available that can predict the signal strength and interference in a WLAN system by taking into account environment specific parameters such as the structure of the building, presence or absence of stationary obstacles etc. This paper investigates the influence of moving obstacles, such as people, on radio wave propagation inside a building and the effect on received signal quality in a WLAN. Our findings suggest that the presence of moving obstacles seriously affects the performance of the system by introducing heavy variations in the received signal strength.

Controllable Monodisperse Multiple Emulsions

Liang-Yin Chu — 2008-04-17T18:59:41-00:00

Angewandte Chemie International Edition, Vol. 46, No. 47. (2007), pp. 8970-8974.

No Abstract

Molecular Dynamics Simulation of Cage Effect in the Glass Transition of Argon

Sun Yong-Li — 2008-03-01T20:40:20-00:00

Chinese Physics Letters, Vol. 23, No. 10. (2006), pp. 2830-2833.

The glass transition process of argon is studied by molecular dynamics simulations with Lennard-Jones potential. The cage effect appears at about 24 K. The Lindemann length of argon is found to be 0.55 Å. Two relaxation processes are clearly observed near the glass transition temperature, which is in agreement with the mode-coupling theory.

Transient filamentous network structure of a colloidal suspension excited by stepwise electric fields

Yu Tian — 2008-06-11T21:18:17-00:00

Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 75, No. 1. (2007)

Jamming and force networks observed in electrorheological (ER) fluids bear many similarities to those observed in various granular and colloidal systems. We have measured the time evolution (transient stresses) of filamentous networks of colloidal particles in suspensions subjected to continuous tensile strain concomitant with the switching on and off of electric fields. The density of particle chains was found to increase exponentially with the applied tensile strain via a rapid formation of single chains followed by a slower coarsening (aggregation) of the chains. The two processes can be ascribed to the field-induced short-range and long-range interparticle forces, respectively, along with the tensile viscous force.

Direct-Current Nanogenerator Driven by Ultrasonic Waves

Xudong Wang — 2007-07-25T03:43:40-00:00

Science, Vol. 316, No. 5821. (6 April 2007), pp. 102-105.

We have developed a nanowire nanogenerator that is driven by an ultrasonic wave to produce continuous direct-current output. The nanogenerator was fabricated with vertically aligned zinc oxide nanowire arrays that were placed beneath a zigzag metal electrode with a small gap. The wave drives the electrode up and down to bend and/or vibrate the nanowires. A piezoelectric-semiconducting coupling process converts mechanical energy into electricity. The zigzag electrode acts as an array of parallel integrated metal tips that simultaneously and continuously create, collect, and output electricity from all of the nanowires. The approach presents an adaptable, mobile, and cost-effective technology for harvesting energy from the environment, and it offers a potential solution for powering nanodevices and nanosystems. 10.1126/science.1139366

Molecular Theory of Physical Aging in Polymer Glasses

Kang Chen — 2008-03-18T23:12:48-00:00

Physical Review Letters, Vol. 98, No. 16. (2007)

A molecular level theory for the physical aging of polymer glasses is proposed. The nonequilibrium time evolution of the amplitude of long wavelength density fluctuations, and its influence on activated barrier hopping, plays an essential role. The theory predicts temperature-dependent apparent power-law aging of the segmental relaxation time and logarithmic aging of thermodynamiclike properties, in good accord with experiments. A physical origin for the quantitative nonuniversal aspects based on the amplitude of quenched density fluctuations is suggested.

Solvent-Induced DNA Conformational Transition

B Gu — 2008-05-07T23:28:21-00:00

Physical Review Letters, Vol. 100, No. 8. (2008)

Modified water models with scaled charges are used to investigate solvent polarity effects on DNA structure. Several intensive molecular dynamics simulations of the DNA EcoRI dodecamer d(CGCGAATTCGCG) in different model solvents are performed. When the polarity of the solvent molecule decreases, from overpolarized to less polarized, DNA experiences the conformational transitions of constrainedB form(A-B)mixA form. We demonstrate that one important cause of these structure changes is the competition between hydration and direct cation coupling to the free oxygen atoms in the phosphate groups on DNA backbones.

Two-dimensional binary clusters in a hard-wall trap: Structural and spectral properties

Wen Yang — 2008-06-10T20:17:29-00:00

Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 76, No. 4. (2007)

Within the Monte Carlo formalism supplemented by the modified Newton-Raphson optimization technique, we investigated structural and dynamical properties of two-dimensional binary clusters confined in an external hard-wall potential. Two species of differently charged classical particles, interacting through the repulsive Coulomb force are confined in the cluster. Subtle changes in the energy landscape and the stable cluster configurations are investigated as a function of the total number of particles and the relative number of each of the two particle species. The excitation spectrum and the normal modes corresponding to the ground-state configuration of the system are discussed, and the lowest nonzero eigenfrequency as a measure of the stability of the cluster is analyzed. The influence of the particle mass on the eigenfrequencies and eigenmodes are studied, i.e., we study a binary system of particles with different charge and different mass. Several unique features distinct from a monodisperse system are obtained.

Spatially Heterogeneous Dynamics and Dynamic Facilitation in a Model of Viscous Silica

Michael Vogel — 2006-08-01T23:05:33-00:00

Physical Review Letters, Vol. 92, No. 25. (2004)

We perform molecular dynamics simulations to study the structural relaxation dynamics of a model of viscous silica, the prototype of a strong glass former. We find that the melt dynamics are spatially heterogeneous regardless of whether the bulk relaxation is non-Arrhenius or Arrhenius, and cannot be understood as a statistical bondbreaking process. Further, we show that stringlike motion is suppressed by the covalent bondings, yet high particle mobility propagates continuously, supporting the concept of dynamic facilitation emphasized in recent theoretical work.

Anomalous behavior of a single particle falling through a funnel

Yuan Fang — 2008-06-08T23:48:50-00:00

Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 77, No. 4. (2008)

We show several surprising phenomena that occur in an extremely simple system of a single frictionless, inelastic, spherical particle falling under gravity through a symmetric funnel. One might naively expect that particles would fall through funnels with steeper sides more quickly, exert a smaller total impulse on the funnel walls, and lose less energy. However, we show that there are special ranges of angles of the funnel walls for which exactly the opposite occurs. Typically, the particle will experience a sequence of collisions that is highly sensitive to the location at which it enters the funnel and nearby particle trajectories become widely dispersed. However, in the special angular ranges this is not the case and the particle can experience sequences of collisions that have a highly coherent structure. We provide a theoretical analysis that can predict and explain this surprising behavior.

Effective potential between two spheres in a suspension of adhesive rods

Chengyu Zhang — 2008-06-11T14:49:19-00:00

Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 75, No. 4. (2007)

Analytic treatment and Monte Carlo simulations are used to study the effective potential between two spheres in a suspension of rods whose ends can adhere to the surface of the spheres. When only one end of each rod is adhesive the effective potential changes from being attractive to repulsive with enhancing the adherence, but when both ends of each rod are adhesive the effective potential is not a monotonic function of the distance between the two spheres for strong adherence. As the adhesive strength is fixed, the range of the effective potential will increase with increasing the length of the rods. When the adhesive range is much smaller than the diameter of the spheres, its influence on single end adhesion is approximately linear and on two end adhesion is about quadratic. Our results are qualitatively consistent with a recent experimental work.

Crystal nucleation enhanced at the diffuse interface of immiscible polymer blends

Yu Ma — 2008-06-08T18:30:03-00:00

Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 77, No. 6. (2008)

We report dynamic Monte Carlo simulations of immiscible binary polymer blends, which exhibit weakly enhanced crystal nucleation near interfaces between two phase-separated polymers. We found that this enhancement is not accompanied by any preferred crystal orientation, implying its origin is mainly of enthalpic rather than entropic nature. Mean-field theory of polymer blends predicts that for immiscible polymers the melting point of the crystallizable component increases upon dilution in the other component, while it normally decreases for miscible blends. A local dilution is forced to occur at the diffuse interface of immiscible polymers; therefore the melting point of crystallizable polymers rises, which, in turn, enhances the thermodynamic driving force for crystal nucleation near the interface.

Origin of the reduced attracting force between a rotating dielectric particle and a stationary one

WJ Tian — 2008-06-11T22:06:04-00:00

Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 75, No. 2. (2007)

Recently Tao and Lan [Phys. Rev. E. 72, 041508 (2005)] experimentally reported that the rotation of a dielectric particle can reduce significantly the attracting interparticle force between the rotating dielectric particle and a stationary one in argon gas. We develop the Gu-Yu-Hui theory of relaxation [J. Chem. Phys. 116, 24 (2002)] to account for the Tao-Lan observations. Excellent agreement between the theoretical results and the Tao-Lan experimental data shows that the reduction in the attracting interparticle force is due to the effect of charge relaxation. We also show that the relaxation time of touching rotating particles can be accurately determined with the aid of the developed theory, for which, however, the well-known Maxwell-Wagner relaxation time is no longer valid.

Passive Oscillations of Two Tandem Flexible Filaments in a Flowing Soap Film

Lai Jia — 2008-06-08T18:18:59-00:00

Physical Review Letters, Vol. 100, No. 22. (2008)

The passive oscillations of flexible filaments in a flowing soap film were investigated to learn the serial interaction between them. When arranged in tandem, the downstream filament flaps at the same frequency as that of the upstream one, but with a larger amplitude, whereas the upstream one is almost unaffected compared to the single filament case. The data analysis shows the downstream filament indeed extracts energy from the vortex street and receives greater force than the upstream one or a single filament in a uniform flow.

Interactions between a rotating polarized sphere and a stationary one in an electric field

R Tao — 2008-06-11T22:04:59-00:00

Physical Review E (Statistical, Nonlinear, and Soft Matter Physics), Vol. 72, No. 4. (2005)

Precise measurement of the attracting force between two polarized spheres inside an electric field indicates that the rotation of one sphere along the axis perpendicular to the electric field reduces the attracting force between them. The important difference between the experimental results and the existing theory indicated that this reduction is due to several factors. In addition to the reduction of polarization due to the free surface charges, the rotation may also weaken the local field near the rotating sphere, making the main contribution to the reduction of the attracting force. Moreover, the experiment also suggests that the polarization due to the molecular polarizability cannot be ignored.

Spontaneous Formation of Complex Micelles from a Homogeneous Solution

Xuehao He — 2008-05-03T17:52:28-00:00

Physical Review Letters, Vol. 100, No. 13. (2008)

We present an extensive computer simulation study of structure formation in amphiphilic block copolymer solutions after a quench from a homogeneous state. By using a mesoscopic field-based simulation method, we are able to access time scales in the range of a second. A “phase diagram” of final structures is mapped out as a function of the concentration and solvent philicity of the copolymers. A rich spectrum of structures is observed, ranging from spherical and rodlike micelles and vesicles to toroidal and net-cage micelles. The dynamical pathways leading to these structures are analyzed in detail, and possible ways to control the structures are discussed briefly.