Network Contraction Research Articles

Microgel Particles as a Matrix for Polymerization: A Study of Poly(N-isopropylacrylamide)-Poly(N-methylpyrrole) Dispersions

Poly(N-isopropylacrylamide) (PNIPAM) microgel particles dispersed in water have been used as a matrix for the polymerization of a hydrophobic monomer, N-methylpyrrole (MPy). The presence of poly(MPy) (PMPy) within the dried composite particles has been confirmed using electron paramagnetic resonance (EPR) measurements which show a characteristic free-radical signal at g=2.007. Electron microscopy data (TEM) show that the composite PNIPAM-xPMPy particles have a “raspberry-like” morphology. (The value for x represents the volume percent of MPy added during synthesis with respect to the total microgel volume.) PCS data indicate that PMPy occupies the majority of the collapsed composite particle volume. The maximum value of x consistent with colloid stability for PNIPAM-xPMPy dispersions is 4.5%. Higher values of x result in coagulation due to interparticle bridging by PMPy. Variable temperature PCS measurements of the PNIPAM-xPMPy dispersions have been used to study the thermally induced collapse of the composite particles. The extent of collapse becomes less with increasing values for x. The embedded PMPy particles restrict the extent of PNIPAM network contraction. The stability of the PNIPAM-4.5PMPy dispersions was investigated by means of turbidity measurements using aqueous 0.1 M NaCl solution. The upper critical flocculation temperatures (UCFT) for PNIPAM and PNIPAM-4.5PMPy dispersions were identical (38–39°C). The flocculation observed was found to be fully reversible. The composite dispersion stability in the absence of salt was attributed to electrosteric stabilization afforded by the PNIPAM matrix. These results indicate that PNIPAM microgel particles may have application as a matrix for the polymerization of hydrophobic monomers in water.

Ionic transport crossover in mixed conducting chalcogenide glasses detected by 125Te-Mössbauer spectroscopy

125Te-Mössbauer spectroscopy has been used to verify whether the observed ionic transport crossover for the Ag–As–Se–Te glasses with a silver content of 15 at.% at approximately equimolar Se/Te ratio is accompanied by variations in the hyperfine interaction parameters produced by corresponding changes in the microstructural organization of the glass network. We found that an unusual decrease of the quadrupole splitting with decreasing tellurium fraction, r=Te/(Se+Te)<0.5, is caused by the combined effect of increasing Te–Ag(As) interatomic distances and a non-random substitution of multiple Se sites by Te with a preferential occupation of those with at least one Ag nearest neighbour. The latter process leads also to a step-like decrease in the isomer shift at r⩽0.35. The assumed expansion of the glass network at smaller r and the contrasting network contraction for the Te-rich glasses are consistent with the ionic transport crossover.

Discrete transparent boundary conditions for general Schrödinger-type equations

Quantum many-body systems (QMBs) are some of the most challenging physical systems to simulate numerically. Methods involving approximations for tensor network (TN) contractions have proven to be viable alternatives to algorithms such as quantum Monte Carlo or simulated annealing. However, these methods are cumbersome, difficult to implement, and often have significant limitations in their accuracy and efficiency when considering systems in more than one dimension. In this paper, we explore the exact computation of TN contractions on two-dimensional geometries and present a heuristic improvement of TN contraction that reduces the computing time, the amount of memory, and the communication time. We run our algorithm for the Ising model using memory optimized x1.32x large instances on Amazon Web Services (AWS) Elastic Compute Cloud (EC2). Our results show that cloud computing is a viable alternative to supercomputers for this class of scientific applications.

Separation of propulsive and adhesive traction stresses in locomoting keratocytes.

Strong, actomyosin-dependent, pinching tractions in steadily locomoting (gliding) fish keratocytes revealed by traction imaging present a paradox, since only forces perpendicular to the direction of locomotion are apparent, leaving the actual propulsive forces unresolved. When keratocytes become transiently "stuck" by their trailing edge and adopt a fibroblast-like morphology, the tractions opposing locomotion are concentrated into the tail, leaving the active pinching and propulsive tractions clearly visible under the cell body. Stuck keratocytes can develop approximately 1 mdyn (10,000 pN) total propulsive thrust, originating in the wings of the cell. The leading lamella develops no detectable propulsive traction, even when the cell pulls on its transient tail anchorage. The separation of propulsive and adhesive tractions in the stuck phenotype leads to a mechanically consistent hypothesis that resolves the traction paradox for gliding keratocytes: the propulsive tractions driving locomotion are normally canceled by adhesive tractions resisting locomotion, leaving only the pinching tractions as a resultant. The resolution of the traction pattern into its components specifies conditions to be met for models of cytoskeletal force production, such as the dynamic network contraction model (Svitkina, T.M., A.B. Verkhovsky, K.M. McQuade, and G.G. Borisy. 1997. J. Cell Biol. 139:397-415). The traction pattern associated with cells undergoing sharp turns differs markedly from the normal pinching traction pattern, and can be accounted for by postulating an asymmetry in contractile activity of the opposed lateral wings of the cell.

Ownership decisions in plural contractual systems

A substantial body of research employs agency theory and transaction costs analysis to explain ownership decisions in distribution channels. Agency theory identifies factors that prompt firms to favor behavior‐based contracting over outcome‐based agreements. Transaction cost economics is a complementary framework which maintains that the organizational form in a location should be the one that economizes on production and transaction costs. Prior research illustrates that independent variables (e.g. proximity to highways, dedicated assets) outlined in these theories provide a partial explanation for ownership decisions. Nevertheless, scant research has analyzed whether factors outlined in agency theory and transaction cost analysis are employed by executives when making ownership decisions. The purpose of this study is to investigate managerial rationales underlying plural contractual networks.

Environs of Russian cities: A case study of Moscow

WE HAD NOT YET EMBARKED ON OUR RESEARCH,2 but a kind of terminological drama was already unfolding. In fact, the conflict is barely hidden in the title of this article, for which we took pains to avoid the use of the word 'suburb'. That this word has, nevertheless, surfaced as early as the epigraph, which is a translation from Russian, only underscores our quandary. The attempt to avoid the term 'suburb' derived, quite simply, from our personal acquaintance with rural-urban fringes both in Russia and in the USA, arguably the most suburban nation of the world. Although we had not done significant research on suburbia in the West, it was clear to us from the outset of this analysis that the American suburb and the Russian prigorod evoke different mental associations. This is so despite being locational and direct lexical counterparts of each other, according to any Russian-English or English-Russian dictionary. While 'suburb' implies the outgrowth or extension of an urban realm, its intrusion into the countryside and the ensuing re-implantation of typically urban amenities in a more rarefied residential setting, prigorod suggests the countryside itself, but a countryside impacted by its close proximity to a city, with 'impacted' often meaning gentrified. Also, whereas suburbia typically develops from a central city outward, large groups of people 'ejecting' themselves from the corporate limits of a city, a Russian prigorod largely develops inward: on the one hand, a rural settlement network contracts;3 on the other, the rural people move closer to a city to take advantage of its broader range and higher level of opportunities and quality of services. A restrictive policy governing residence permits (the infamous propiska) in large cities and the lasting absence of a real estate market have created a peculiar barrier effect at the city line. Prigorod has thus become a stepping stone to a city, not out of it as in the West. Paradoxically, the fact that Russian cities used to expand outward, as do all cities of the world, does not seem to change the nature of the situation: typically Russians simply extend a city line, and Western-style suburbia does not take shape. Only most recently, around the largest cities of Russia, has the situation begun to change somewhat. Reflecting on the above distinctions-which by no means exhaust the subject-

Information Technologies within the Cancer Information Service: Factors Related to Innovation Adoption

Background.This collaborative study, conducted by members of the Cancer Information Service Research Consortium Team for Evaluation and Audit Methods and the Network Analysis Advisory Board, is part of a larger project that evaluates the impact of communication structure on innovation within the contractual network of the Cancer Information Service (CIS). This study examines four different technological innovations with respect to the characteristics of relative advantage, compatibility, observability, complexity, trialability, adaptability, riskiness, disadvantage, computer knowledge, and acceptance.Methods.Data were gathered from self-report questionnaires completed in May 1995 by organizational members (n= 82) within the National Cancer Institute's CIS, a geographically dispersed federal government health information program.Results.Paired comparisonttests found that organizational members rate contrasting dimensions of an innovation differentially, depending on the nature of the specific technology. For example, significantly lower levels of riskiness were reported for computerization for communication (e.g., e-mail) than for computerization for telephone service or outreach. In addition, computerization for office management had significantly lower levels of riskiness than computerization for telephone service or outreach. With respect to complexity, computerization for communication had significantly lower ratings than did outreach. In terms of observability and trialability, computerization for communication had significantly lower ratings than for telephone service. With respect to relative advantage, computerization for office management had significantly lower ratings than all other areas of computerization. In terms of computer knowledge, ratings were significantly higher for communication than for all other areas of computerization. No significant differences were found between contrasting innovations for adaptability or acceptance.Conclusions.Results suggest that organizational members rate contrasting dimensions of an innovation differentially, depending on the nature of the specific innovation. Managers can employ this information as a diagnostic tool to evaluate the fit of an innovation, anticipate problems arising as a result of innovation, and modify innovations to reflect the changes that stakeholders deem necessary. Computerization efforts such as this one are at the cutting edge of efforts to improve the dissemination of information to the public. These efforts can result in considerable improvements in public health.

Contrasting Attributes of Preventive Health Innovations

This research employed diffusion of innovations theory to contrast three different preventive health interventions by their innovation attributes. The authors gathered self-report data from organizational members within a new organizational form, the contractual network of the Cancer Information Service, a geographically dispersed federal government health information program. Innovation attributes were rated differentially, depending on the nature of the specific intervention, suggesting important theoretical and policy implications.

The Role of a Conference in Integrating a Contractual Network of Health Services Organizations

The conference can be seen as a key strategic tool to be used in linking a diverse array of participants, through communicative processes, to achieve the level of integration required by new organi...

Health system integration: a means to an end.

The creation of integrated firms and contractual networks in health care often is a precondition for other forms of integration that could actually lower costs and improve quality of care. Although different types of integration activities are leading to innovations in the production of services and the care of populations, the continued influence of the "old" indemnity insurance/fee-for-service system creates important obstacles to those integration activities. If creation of integrated firms and contractual networks races ahead of other forms of integration, it could produce uncompetitive markets that reduce pressures to integrate in ways that can cut costs and improve quality of care. Purchasers' actions could play a major role in determining the future of various integration activities.

Vertical integration and organizational networks in health care.

This paper documents the growing linkages between primary care-centered medical groups and specialists and between physicians and hospitals under managed care. We evaluate the two alternative forms of organizational coordination: "vertical integration," based on unified ownership, and "virtual integration," based on contractual networks. Excess capacity and the need for investment capital are major short-term determinants of these vertical versus virtual integration decisions in health care. In the longer term, the principal determinants are economies of scale, risk-bearing ability, transaction costs, and the capacity for innovation in methods of managing care.

'Health law 2000': the legal system and the changing health care market.

The failure of national health reform confirmed in many ways the conservative nature of the American legal system. Legislatures, regulatory agencies, and courts usually find themselves in a reactive posture, responding to groups and individuals aggrieved by changing circumstances. The rapid transformation of the U.S. health care system through managed care presents an extreme example of this phenomenon, involving billions of dollars, millions of lives, and thousands of existing laws. Over the next few years the legal system will face a host of difficult issues deriving from the integration of health care financing and delivery, and the consolidation of fragmented providers into large corporations and contractual networks. What emerges may be neither logical nor consistent but no doubt will reflect the intricate interplay of societal and individual interests in health care.

Influence of Viscoelasticity and Permeability on the Stress Response of Silica Gel

This review examines the chemical and physical factors that control the response of silica gel to stimuli such as aging, heating, mechanical deformation, and drying. When the liquid phase is chemically aggressive, the gel exhibits spontaneous shrinkage (syneresis) and viscoelasticity; in an inert medium, the network of the gel is purely elastic. The rate of the responses to mechanical loads and changes in temperature depends on the permeability, as well as the modulus, of the network. The properties of the gel change by orders of magnitude as the network contracts during drying, and this has a dramatic effect on the drying stresses.

Noncompetition Agreements in Bankruptcy: Covenants (Maybe) Not to Compete

A struggling young soap opera actress is offered a role on a prime time show on another network.1 Unfortunately, she has over two years left on her network contract, and that contract contains a noncompetition clause: if she terminates the contract, she cannot appear on any competing network for six months. However, just as opportunity is packing its bags, the actress talks to her attorney, who tells her that she can get around the restriction in her contract by, of all things, filing for bankruptcy. Under current case law, whether the attorney is a hero or a heel depends in large measure on where the bankruptcy petition is filed.2 Whether bankruptcy should offer such an escape is the subject of this Comment. It examines whether and when bankruptcy should defeat a nondebtor's right to enforce a covenant not to compete against an individual debtor.3 The current treatment of covenants not to compete in bankruptcy law is at best a tricky, and at worst an incoherent, business. The issue of bankruptcy's effect on covenants not to compete arises most frequently when a trustee rejects an executory contract4 under ? 365 of the Bankruptcy Code (the

Mammary epithelial reorganization on extracellular matrix is mediated by cell surface galactosyltransferase

When plated at appropriate densities in serum-free media, the COMMA-D mammary epithelial cell line rapidly reorganizes into multicellular spheres on the basement membrane matrix derived from Engelbreth-Holm-Swarm murine tumor. Using time-lapse videomicroscopy, four stages of reorganization were discerned during the first 24 h of culture. In the first few hours, cells attached to the matrix, elongated, migrated, and formed chains. In the next 6 h, chains of cells linked together in anastomosing networks. In the period between 8 and 18 h postplating, the networks contracted, resulting in dense cords radiating from central aggregates. During the final 6 h, the cords were drawn into the aggregates, which condensed further into spheres. The events occurring during mammary epithelial cell reorganization on the matrix were shown to be mediated by cell surface β-1,4-galactosyltransferase (GalTase), a receptor that binds N-acetylglucosamine residues on glycosylated proteins. GalTase activity was evident at the surface of cells cultured on reconstituted matrix for 3 h but was absent from cells on glass. The protein α-lactalbumin (α-LA) inhibits the association of GalTase with N-acetylglucosamine. α-LA present from the beginning of culture on reconstituted matrix had no effect on cell attachment but caused concentration-dependent inhibition of the first two steps of reorganization, i.e., cell elongation and network formation, which then interfered with subsequent events. These observations were replicated using polyclonal antibodies to GalTase. Reorganization was impaired when α-LA was added during the first two stages but no effect was observed when it was added during the last two stages. Cells cultured on plastic, which lack surface GalTase activity, were unperturbed by incubation with α-LA. Thus certain events (cell elongation and network elaboration) during mammary epithelial cell reorganization on reconstituted matrix are GalTase dependent, while others (attachment, network contraction, and compaction) are not. The functional and temporal specificity of GalTase involvement indicates that GalTase mediates cell-matrix, but not cell-cell, interactions during epithelial morphogenetic events in culture.

Privity and the concept of a network contract

‘English law, having committed itself to a rather technical and schematic doctrine of contract, in application takes a practical approach, often at the cost of forcing the facts to fit uneasily into the marked slots of offer, acceptance and consideration. Although the context of these remarks was the necessity to analyse the complex of relations between the parties involved in a carriage of goods by sea- cargo owners, carriers, stevedores, and so on- into classical offer and acceptance, with identifiable consideration, this was not, as such, the root of Lord Wilberforce's difficulty. Rather, the source of the problem was the notoriously inconvenient doctrine of privity of contract which, in The Eurymedon, prevented the negligent stevedores from being able to rely straightforwardly upon the time limit provisions in the contract of carriage.

Government data network contract goes to sophos

Government data network contract goes to sophos

A newsletter evaluation using the Title Rating Method.

The Title Rating Method is used to measure readership interests and predict readership topics for future issues, in message ideas. This methodology was used to plan types of articles in a newsletter published through the Cancer Communication Network contract. This article describes evaluation results of the newsletter for health professionals, North Carolina Cancergram. Retrospective and prospective titles were assigned to seven categories: psychosocial, treatment, drugs, nursing issues, rehabilitation, education, and detection. Interest in the titles in each category was evaluated according to five occupational groups: nurses, pharmacists, physicians, allied health, and others. The rank order of most popular to least popular categories was: drugs, treatment, education, psychosocial, rehabilitation, detection, and nursing issues. The most popular article overall across occupational groups was an article directed primarily to physicians, "Informing the patient requires honesty, sensitivity." The readership was primarily white, female, over 35 years of age with a college degree or higher. Most of the readership work in a health related setting although 67.6 percent of the respondents spent less than ten percent of their time working with cancer patients. This is in keeping with the intent of the publication to reach health professionals outside the Cancer Center.

Drainage density changes during rainfall

AbstractObservations of stream behaviour during rainfall indicate that previous notions of a simple expanding and contracting network need review and refinement. In a small rural catchment near Armidale, N.S.W. changes in flowing stream length during rainfall have been depicted on flow length graphs which indicate a varied network response to similar rainfall amounts. Channel flow phenomena include discontinuous flow, the generation of flow points within the channel and movement of water downslope from saturated depression sources. Localized physical controls have a significant effect on stream growth which is a sensitive indicator of the catchment response to rainfall. During rapid changes in stream length total flowing length and discharge are highly correlated. A model of the pattern of network expansion and contraction involves several phases of flow contraction.

The Life History of Merocystis Kathae in the Whelk, Buccinum undatum

1. The life history of Merocystis kathae shows that development follows a seasonal course. The youngest stages may appear in the kidney any time between March and June. Growth proceeds and sexual differentiation takes place but mature gametes are not found until November, when the first stages of sporogony also make their appearance. Mature spores containing sporozoites are formed in January and become increasingly common up to May. Degenerating stages of spores are common in summer.2. The smallest parasites within the cells of the kidney are about 10μ. Growth occurs in the intracellular condition. The karyosome is complex, and contains a chromatinic body; in older parasites no chromatin reaction is given by the nucleus outside the karyosome.3. Sexual differentiation is not perceptible until growth is almost complete.4. In the female the intrakaryosomic body emerges, though a large karyosomic remnant remains until after fertilisation. Very fine granules of chromatin reappear in the nucleus, and form a fine network, which incorporates the intrakaryosomic body, and later forms the characteristic prefertilisation ‘cobweb’ nucleus. This network contracts in the mature macrogamete. Meantime the parasite has become free of its host cell, and the cytoplasm stains more intensely.5. In the male, the elongated karyosome breaks down, generally completely, leaving the centrally placed chromatin body surrounded by a ring (in sectional view), of deeply stained material containing granules of chromatin, into which the central body passes as in the female. The male is released from the host cell, and, as in the female an alteration of the cytoplasmic staining occurs.6. The nucleus, in the male parasite, moves to the surface, and undergoes repeated divisions until approximately 32 nuclei are formed. Cleavage of the cytoplasm brings about the formation of uninucleate cytomeres; within each of these are produced many nuclei, which lie near the surface, and finally become the microgametes.7. After the macrogamete is fertilised, a thick membrane is formed outside the zygote. The nucleus assumes the characteristic spindle shape and subsequently divides.8. Nuclear divisions proceed, until finally a great number of cone-shaped nuclei are found on the surface. This becomes folded and the nuclei sink in, and each is surrounded by a portion of cytoplasm to form a sporoblast. A single nuclear division then occurs, and the two nuclei elongate to form sporozoites each with a small cytoplasmic body.9. Nuclear divisions are mitotic, but the longitudinal splitting of the chromosomes occurs without contraction. It is probable that ‘amitotic’ appearances are due to the incomplete incorporation of these long chromosomes at the telophase poles, and the multipolar divisions to the subsequent division of such ‘amitotic’ resting nuclei. Six chromosomes can be seen at the anaphase poles, but each is looped back so that it is V or J shaped. This chromosome number is characteristic of the divisions of both microgametogenesis and sporogony.10. There is good evidence that, as in other Coccidia, reduction division occurs in the zygote, and that this is therefore the only diploid phase.