Network Contraction Research Articles

Contratto di rete e turismo: la collaborazione aziendale come driver della competitività del settore e del territorio. Un’analisi delle prime esperienze

This work deals with the theme of businesses networks in the tourist sector through the network contract (Italian Law. n. 33 of 9th April 2009 and subsequent modifications). Furthermore it develops several preliminary reflections that have emerged from an analysis of current literature and from empirical research on the role of the network contract in sustaining the competitiveness of small and medium-sized enterprises in the tourist sector and at the same time in valorizing the territory. The paper is made up of two main parts. The first presents the theoretical framework focused on forms of inter-firm collaboration which include the network contract. The second part presents the results of the first exploratory investigation into network contracts drawn up in the tourist sector in February 2013 with the aim of identifying, on the basis of the objectives shared by companies, its potential in the tourist sphere and its possible impact on the social and economic fabric of local society. The initial results highlight that today the network contract is not yet widely used in the tourist sector, although recent signs of growth indicate a development in the future. The objectives followed through this tool of inter-firm collaboration are mainly geared towards marketing strategies, integration in the tourist industry, internationalization and promoting the territory which all open up new spaces for economic, social and environmental growth.

Self-Protection Mechanism For Wireless Sensor Networks

Because of the widespread use of wireless sensor networks in many applications, and due to the nature of the specifications of these networks (WSN) in terms of wireless communication, the network contract specifications, and published it in difficult environments. All this leads to the network exposure to many types of external attacks. Therefore, the protection of these networks from external attacks is considered the one of the most important researches at this time. In this paper we investigated the security in wireless sensor networks, Limitations of WSN, Characteristic Values for some types of attacks, and have been providing protection mechanism capable of detecting and protecting wireless sensor networks from a wide range of attacks.

Actomyosin sliding is attenuated in contractile biomimetic cortices.

Myosin II motors embedded within the actin cortex generate contractile forces to modulate cell shape in essential behaviors, including polarization, migration, and division. In sarcomeres, myosin II-mediated sliding of antiparallel F-actin is tightly coupled to myofibril contraction. By contrast, cortical F-actin is highly disordered in polarity, orientation, and length. How the disordered nature of the actin cortex affects actin and myosin movements and resultant contraction is unknown. Here we reconstitute a model cortex in vitro to monitor the relative movements of actin and myosin under conditions that promote or abrogate network contraction. In weakly contractile networks, myosin can translocate large distances across stationary F-actin. By contrast, the extent of relative actomyosin sliding is attenuated during contraction. Thus actomyosin sliding efficiently drives contraction in actomyosin networks despite the high degree of disorder. These results are consistent with the nominal degree of relative actomyosin movement observed in actomyosin assemblies in nonmuscle cells.

Temporary streams in a peatland catchment: pattern, timing, and controls on stream network expansion and contraction

ABSTRACTIn peatlands, poorly maintained baseflows mean that network expansion during storm events can be rapid and pronounced, resulting in large changes in catchment connectivity. This has implications for the timing and magnitude of material fluxes from these environments, understanding of which is becoming increasingly important due to peatlands' significance as global carbon stores. In this study, electrical resistance (ER) technology has been used to create sensors capable of detecting the presence and absence of flow in ephemeral portions of the channel network. These sensors provide data on the patterns of network variation in the Upper North Grain research catchment, a small peatland headwater in the South Pennines, UK. Networks of around 40 sensors were deployed in autumn 2007 and summer 2008, giving a total of almost four months of high‐resolution monitoring data. Drainage density in the catchment was found to vary between 1.4 and 30.0 km/km2, suggesting significant differences in connectivity between the expanded and contracted networks. Water table depth was identified as the key factor determining the temporal pattern of streamflow at both the site‐ and catchment‐wide scales. Spatially, network expansion and contraction occurred in a disjointed manner, following a similar pattern between events, suggesting that localized controls are important for flow generation. Spatial controls on flow generation relate to local water table levels, and include drainage area, local dissection, channel slope and gully morphology. The importance of water table as the key control on catchment connectivity suggests that potential future change in catchment water tables, associated with projected climate change or with peatland restoration by rewetting, will modify the frequency of full catchment connectivity. Copyright © 2014 John Wiley & Sons, Ltd.

The multiple faces of leukocyte interstitial migration

Spatiotemporal control of leukocyte dynamics within tissues is critical for successful innate and adaptive immune responses. Homeostatic trafficking and coordinated infiltration into and within sites of inflammation and infection rely on signaling in response to extracellular cues that in turn controls a variety of intracellular protein networks regulating leukocyte motility, migration, chemotaxis, positioning, and cell-cell interaction. In contrast to mesenchymal cells, leukocytes migrate in an amoeboid fashion by rapid cycles of actin polymerization and actomyosin contraction, and their migration in tissues is generally referred to as low adhesive and nonproteolytic. The interplay of actin network expansion, contraction, and adhesion shapes the exact mode of amoeboid migration, and in this review, we explore how leukocyte subsets potentially harness the same basic biomechanical mechanisms in a cell-type-specific manner. Most of our detailed understanding of these processes derives from in vitro migration studies in three-dimensional gels and confined spaces that mimic geometrical aspects of physiological tissues. We summarize these in vitro results and then critically compare them to data from intravital imaging of leukocyte interstitial migration in mouse tissues. We outline the technical challenges of obtaining conclusive mechanistic results from intravital studies, discuss leukocyte migration strategies in vivo, and present examples of mode switching during physiological interstitial migration. These findings are also placed in the context of leukocyte migration defects in primary immunodeficiencies. This overview of both in vitro and in vivo studies highlights recent progress in understanding the molecular and biophysical mechanisms that shape robust leukocyte migration responses in physiologically complex and heterogeneous environments.

Characterizing ephemeral streams in a southern Ontario watershed using electrical resistance sensors

Ephemeral streams are small headwater streams that only experience streamflow in response to a precipitation event. Due to their highly complex and dynamic spatial and temporal nature, ephemeral streams have been difficult to monitor and are in general poorly understood. This research implemented an extensive network of electrical resistance sensors to monitor three ephemeral streams within the same small headwater catchment in Southern Ontario, Canada. The results suggest that the most common patterns of network expansion and contraction in the studied streams are incomplete coalescence and disintegration, respectively. Binary logistic regression analysis of the primary controls on ephemeral streamflow showed only weak Nagelkerke R2 values, suggesting that there are more complex processes at work in these ephemeral streams. A comparison of all three streams suggests that even ephemeral streams within the same subwatershed may experience differences in network expansion and contraction and may be dominated by different spatial and temporal controls. Copyright © 2013 John Wiley & Sons, Ltd.

Traction Force Microscopy Based on an Active Cable Network Model

Generation of mechanical force is essential for the function of tissue cells, for example during migration, wound healing or rigidity sensing. The traction field of adherent cells can be measured on soft elastic substrates using traction force microscopy (TFM). However, mathematical reconstruction of traction fields effectively requires inversion of the long-ranged elastic equations and therefore is an ill-posed inverse problem. Moreover measurement of the traction pattern alone does not tell us how force is distributed inside the cell. To improve the robustness, resolution and scope of conventional TFM, we have developed a new procedure called model-based TFM (MBTFM). We estimate the distribution of intracellular tension from elastic substrate data by minimizing the difference between the experimentally measured displacement field and the predictions of a detailed theoretical model based on active cable networks. Previously this type of model has been successfully used to predict cell shapes on micropatterned substrates. For MBTFM, we consider not only active network contraction, but also contributions of various types of contractile bundles modeled as contractile one-dimensional line element embedded into the network. Subsequent computer simulations of network contraction and parameter optimization allow us to estimate the most likely distribution of tension over various contractile structures and adhesion sites.

The Juridical Nature of Distribution (Network) Contracts from the Polish Perspective

OER Osteuropa Recht , Seite 143 - 163

Promoting SME cooperative aggregations: main criteria and contractual models

Collaboration is considered an effective solution to improve business strategies. However, small and medium enterprises (SMEs) often lack common principles and common forms of contractual coordination. Several policies implemented by the EU have addressed the set-up of a comprehensive SME policy framework, but European institutions seem to have focused more on organisational devices to conduct business activities rather than on contractual forms of coordination. In April 2009, Italy adopted a law in network contract to promote the development of inter-firm cooperation strategies to foster enterprises’ innovation and growth. Even if this law represents a novelty in Europe and may offer new challenges and hints, it still presents some lacks in its formulation. The current research aims at presenting the Italian law for network contract and a comparison with other models of SME aggregations adopted in EU countries. A formal model to support the design of an SME network was proposed, by providing both an ontology-based model to help the definition of the contract in a structured way, and a basic workflow to identify the important phases of the network design, i.e. the feasibility study and the negotiation.

Shear dilatancy in marginal solids

Shearing stresses can change the volume of a material via a nonlinear effect known as shear dilatancy. We calculate the elastic dilatancy coefficient of soft sphere packings and random spring networks, two canonical models of marginal solids close to their rigidity transition. We predict a dramatic enhancement of dilatancy near rigidity loss in both materials, with a surprising distinction: while packings expand under shear, networks contract. We show that contraction in networks is due to the destabilizing influence of increasing hydrostatic or uniaxial loads, which is counteracted in packings by the formation of new contacts.

Scheduling Model for Rehabilitation of Distribution Networks Using MINLP

AbstractScheduling of the rehabilitation activities of water main networks depends mainly on available budget and planning time. Other factors such as network reliability, criticality, location, contract size, and rehabilitation method(s) affect the optimization of the scheduling process. This paper presents a method for optimized scheduling of rehabilitation work for water distribution networks. The method utilizes unsupervised neural networks (UNNs) and mixed-integer nonlinear programming (MINLP) and performs the scheduling in two stages. In the first stage, UNNs are used to cluster water mains into groups according to locations and rehabilitation methods of water mains. In the second stage, MINLP is used to determine the number of rehabilitation contract packages and the generation of optimized scheduling of these packages considering network reliability, criticality, contract size, and planning time. In order to demonstrate the essential features of the developed method, a case study was analyzed and ...

The Network Contract

This paper studies costs and benefits of firm networks, and related industrial policies, with a focus on the recently introduced in the Italian legislation. Incentives to networks creation could be useful to foster future mergers, but may prove ineffective as a substitute for firms' growth. The network contract is a comparatively more flexible instrument, but its potential is hindered by the indeterminacy of its contents: some standardization would be beneficial. The contract adds to a plethora of incentives that distort firms' choices. Members of a network contract have often a pre-established relationship, and are located in classical marshallian industrial districts. One novel aspect is that sometimes partner firms are located in faraway regions. Probit regressions show: i) the probability of entering a network contract increases with firm's size and growth; this shows that the network does not seem to be the solution to small size problems; ii) the degree of leverage does not discriminate between firms in networks and the others.

The Network Contract and its Influence on Strategic Decision of Internationalization

This paper analyzes a new legislative instrument designed to support inter-firm cooperation (the “network contract” - a tool introduced by the Italian government to sustain corporate competitiveness in 2009) - to see whether this type of formal cooperation represents a relevant driver of change in a firm’s strategic orientation regarding internationalization. Results indicate that the network contract is a flexible instrument used by Italian SMEs to achieve different strategies of growth and long-term objectives. The authors found that internationalization does not represent the main goal of firms participating in network contracts, however there are a few firms that have increased their business activity abroad after joining the network. At the same time, firms with a previous history of internationalization do not seem to have changed their approach regarding the international dimension. Consequently, the network contract does not represent the most suitable tool for promoting internationalization among domestic firms, although internationalization may emerge as a by-product of inter-firm relationships.

F-actin buckling coordinates contractility and severing in a biomimetic actomyosin cortex

Here we develop a minimal model of the cell actomyosin cortex by forming a quasi-2D cross-linked filamentous actin (F-actin) network adhered to a model cell membrane and contracted by myosin thick filaments. Myosin motors generate both compressive and tensile stresses on F-actin and consequently induce large bending fluctuations, which reduces their effective persistence length to <1 μm. Over a large range of conditions, we show the extent of network contraction corresponds exactly to the extent of individual F-actin shortening via buckling. This demonstrates an essential role of buckling in breaking the symmetry between tensile and compressive stresses to facilitate mesoscale network contraction of up to 80% strain. Portions of buckled F-actin with a radius of curvature ~300 nm are prone to severing and thus compressive stresses mechanically coordinate contractility with F-actin severing, the initial step of F-actin turnover. Finally, the F-actin curvature acquired by myosin-induced stresses can be further constrained by adhesion of the network to a membrane, accelerating filament severing but inhibiting the long-range transmission of the stresses necessary for network contractility. Thus, the extent of membrane adhesion can regulate the coupling between network contraction and F-actin severing. These data demonstrate the essential role of the nonlinear response of F-actin to compressive stresses in potentiating both myosin-mediated contractility and filament severing. This may serve as a general mechanism to mechanically coordinate contractility and cortical dynamics across diverse actomyosin assemblies in smooth muscle and nonmuscle cells.

Transmission Rights to the Electrical Transmission Grid in the Post Liberalization Era

The electric power industry has been consistently moving away from vertically integrated, centrally regulated system towards a market-based, competitively organized industry. There remain unfulfilled requirements for institutional reform. In this paper, we confront existing and developing congestion management techniques in conjunction with the principal problems of electricity reform. The approaches adopted vary across countries in terms of market and system operation, property rights, and investment incentives. A number of key concepts emerge as central to the organization of the grid, including locational marginal pricing, transmission capacity rights, and compensation for wire ownership. Nonetheless, a set of core, generalizable problems in congestion management with regard to congestion pricing and market power abuse remain. Endowing network operations, contract networks, and financial transmission rights are considered. Contract networks entail the market allocation of long-term capacity rights for transmission. An alternative approach involves endowing a network operator with joint match-making and dispatch responsibilities. This approach involves considerable centralization and network oversight. The indirect implementation of transmission rights has not been proven to remove the chief difficulties. A final and more elaborate market mechanism, namely financial transmission rights, which involves the joint trading of energy and transmission capacity, has been showcased. In this paper, we describe the principal strategic management issues in the electrical transmission grid. Secondly, we highlight the principal policy options in conjunction with the described strategic management issues. Lastly, we explicate the current situation involving congestion management towards a pan-European power grid. The challenges ahead are discussed.

The Network and Capital Allocation in the Italian Companies

Pursuant to paragraph 4-ter, letter c), of the law no.122 of July 30, 2010, in the network contract the institute of common fund is now optional for the parties: where envisaged, transfer of capital may be realized by means of allocation of assets to any one specific business pursuant to art.2447–bis of the Civil Code. This way companies may have accounting and real separation of part of their assets intended to meet the network requirements, but nevertheless maintain the ownership of the aforementioned assets. However, as for the application of the above-mentioned regulations, difficulties arise with reference to the extensibility of the legal institute in question to Ltd.s: if several considerations lead to support its inadmissibility, nonetheless it is not unfounded the possibility of extending the use of assets allocation for the participation in a network contract at least to Ltd.s with abundance of assets comparable to that of the joint-stock companies.

ESRD Networks

Established by Federal law in 1978, the ESRD Networks are regional nonprofit organizations that contract with the Centers for Medicare and Medicaid Services to provide quality oversight services to chronic dialysis facilities. The governing bodies and medical review boards of each network are populated by volunteer professionals and patients. The medical review boards drive the quality agenda for each network, addressing specific local barriers to improvement. The network contract deliverables are defined by the Centers for Medicare and Medicaid Services in a scope of work document (SOW) that is generally revised with each 3-year contracting cycle. The current SOW has not been revised since the implementation of the new Conditions for Coverage for dialysis facilities in 2008 or the implementation of a bundled payment system and quality incentive program for dialysis providers in 2011. The future success of the ESRD Network Program will depend upon adequate funding, data accessibility to drive rapid-cycle quality improvement efforts, and partnerships with other stakeholder groups to address the continuum of care of patients with CKD. The Forum of ESRD Networks has developed a strategic plan that aligns the priorities of the networks with the National Quality Strategy. The integration of these objectives into the next SOW will augment the relevance of the network program to the ESRD stakeholder community as the networks move from a task-oriented approach to a system-improvement approach to quality oversight.

Reti D’Impresa, Performance E Assetti Banca-Impresa

A salient feature of the Italian economy is its high reliance on small firms and local productive systems. For this reason, a relevant policy question is how the Italian production system can deal with the growing competition in global markets. The literature suggests that Italian economic system needs new mechanisms that help a coordination of all the phases of the production process, thereby fostering the development of economies of scale that are external to firms. In the last few years, Italy introduced a law about the network contract, to stimulate strategic cooperation among the firms in some specific areas, like innovation, internationalization and distribution. Subsequently, enterprise networks have started to emerge throughout the country. The aim of this paper is to make a first assessment on the impact of enterprise networks participation on firms’ performance. The results show that enterprise network participation has a positive effect on firms’ performance.

A Computational Approach to the Real Option Management of Network Contracts for Natural Gas Pipeline Transport Capacity

Commodity merchants use real option models to manage their operations. A central element of such a model is its underlying operating policy. We focus on network contracts for the transport capacity of natural gas pipelines, specific energy conversion assets. Practitioners commonly manage these contracts as portfolios of spread options. Although computationally fast, we show that this approach in general is heuristic because of the suboptimality of its operating policy. We propose a different computationally efficient real option approach based on an optimal operating policy, integrating linear optimization and Monte Carlo simulation. We use our approach to benchmark the spread option approach in a numerical study based on market data and realistic instances. We find that our approach can substantially improve on the contract valuations computed by the spread option approach, especially for contracts with flexibility in their allowed capacity usage. We also show that the optimal operating policy of contracts with this flexibility is of the greedy type, whereas the one of contracts without it in general is not. However, we observe that greedy optimization yields a near-optimal operating policy for the latter type of contracts with a substantially reduced computational effort. A version of our model was recently implemented by a major international energy trading company. Our model can also be employed to efficiently estimate the contract value sensitivities (the “Greeks”), which merchants use for financial hedging purposes. Potentially, our work has wider significance for the merchant management of other commodity conversion assets with payoffs determined by solving capacity constrained optimization models.

Signatures of sea level changes on tidal geomorphology: Experiments on network incision and retreat

How do tidal networks respond to changes in relative mean sea level (RMSL)? The question on whether the morphological features of a tidal landscape retain signatures of past environmental forcings, or are in equilibrium with current ones, is critical to our prediction of the fate of residual tidal landforms. In the case of tidal networks, the issue is quite relevant owing to their fundamental role on landscape eco‐morphodynamic evolution. Here we explore the response of tidal networks to cyclic variations in RMSL triggering tidal prism changes on the basis of laboratory experiments carried out in a synthetic lagoonal environment. A decrease in the tidal prism leads to network retreat and contraction of channel cross sections. Conversely, an increase in the tidal prism promotes network re‐incision and re‐expansion of channel cross sections: Network retreat and expansion tend to occur within the same planar blueprint. Our results show that the drainage density of tidal channels is linearly related to the landscape‐forming prism, although this relation is speculated to hold with reasonable approximation as a statistical tendency rather than as a pointwise, instantaneous adaptation. Changes in tidal prism rapidly influence network efficiency in draining the intertidal platform and the related transport of water, sediments, nutrients and pollutants. This bears important consequences for quantitative predictions of the long‐term ecomorphological adaptation of the tidal landscape to RMSL changes.