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91.
Why do new technology-based firms (NTBFs) cooperate? Starting from Teece's [Teece, D.J., 1986. Profiting from technological innovation: implications for integration, collaboration, licensing, and public policy. Research Policy 15, 285-305] conceptual framework and taking advantage of subsequent literature on alliance formation in the resource and competence-based tradition and in the social structure perspective, we derive an empirical model that aims at highlighting the inducements and obstacles that these firms face in alliance formation according to firm-specific characteristics and the nature of the alliance. In particular, a distinction is made between exploitative commercial alliances and explorative technological alliances. The econometric estimates, based on a large sample of Italian young high-tech firms that are observed from 1994 to 2003, provide strong evidence supporting two key intuitions of Teece's work. First, the “combination of specialized complementary assets” appears to be a key driver of the formation of exploitative commercial alliances by NTBFs. More specifically, patent holding affects positively the likelihood to establish commercial alliances, but this propensity is found to rapidly decrease with firm size, suggesting that as long as NTBFs become larger and possess specialized commercial assets their urge for commercial alliances diminishes. Second, following the parallelism set forth by Teece between search for alliance partners and access to external financing, the analysis indicates that potentially beneficial alliances may not take place because of the high transaction costs faced by smaller NTBFs. In this respect, our results clearly support the view that sponsor institutions as public research organizations, venture and corporate venture capitalists may sensibly reduce these costs and that their role crucially depends on both the identity of the sponsor and the type of alliance.  相似文献   
92.
Vividness and controllability of relaxing and energizing imagery by efficient and less efficient imagers.  相似文献   
93.

Introduction:

The activities involving phlebotomy, a critical task for obtaining diagnostic blood samples, are poorly studied as regards the major sources of errors and the procedures related to laboratory quality control. The aim of this study was to verify the compliance with CLSI documents of clinical laboratories from South America and to assess whether teaching phlebotomists to follow the exact procedure for blood collection by venipuncture from CLSI/NCCLS H03-A6 - Procedures for the Collection of Diagnostic Blood Specimens by Venipuncture might improve the quality of the process.

Materials and methods:

A survey was sent by mail to 3674 laboratories from South America to verify the use of CLSI documents. Thirty skilled phlebotomists were trained with the CLSI H03-A6 document to perform venipuncture procedures for a period of 20 consecutive working days. The overall performances of the phlebotomists were further compared before and after the training program.

Results:

2622 from 2781 laboratories that did answer our survey used CLSI documents to standardize their procedures and process. The phlebotomists’ training for 20 days before our evaluation completely eliminated non-conformity procedures for: i) incorrect friction of the forearm, during the cleaning of the venipuncture site to ease vein location; ii) incorrect sequence of vacuum tubes collection; and iii) inadequate mixing of the blood in primary vacuum tubes containing anticoagulants or clot activators. Unfortunately the CLSI H03-A6 document does not caution against both unsuitable tourniquet application time (i.e., for more than one minute) and inappropriate request to clench the fist repeatedly. These inadequate procedures were observed for all phlebotomists.

Conclusion:

We showed that strict observance of the CLSI H03-A6 document can remarkably improve quality, although the various steps for collecting diagnostic blood specimens are not a gold standard, since they may still permit errors. Tourniquet application time and forearm clench should be verified by all quality laboratory managers in the services. Moreover, the procedure for collecting blood specimens should be revised to eliminate this source of laboratory variability and safeguard the quality.  相似文献   
94.
Constrained control for stochastic linear systems is generally a difficult task due to the possible infeasibility of state constraints. In this paper, we focus on a finite control horizon and propose a design methodology where the constrained control problem is formulated as a chance-constrained optimization problem depending on some parameter. This parameter can be tuned so as to decide the appropriate trade-off between control cost minimization and state constraints satisfaction. An approximate solution is computed via a randomized algorithm. Precise guarantees about its feasibility for the original chance-constrained problem are provided. A numerical example shows the efficacy of the proposed methodology.  相似文献   
95.
Kleinbergs HITS algorithm (Kleinberg 1999), which was originally developed in a Web context, tries to infer the authoritativeness of a Web page in relation to a specific query using the structure of a subgraph of the Web graph, which is obtained considering this specific query. Recent applications of this algorithm in contexts far removed from that of Web searching (Bacchin, Ferro and Melucci 2002, Ng et al. 2001) inspired us to study the algorithm in the abstract, independently of its particular applications, trying to mathematically illuminate its behaviour. In the present paper we detail this theoretical analysis. The original work starts from the definition of a revised and more general version of the algorithm, which includes the classic one as a particular case. We perform an analysis of the structure of two particular matrices, essential to studying the behaviour of the algorithm, and we prove the convergence of the algorithm in the most general case, finding the analytic expression of the vectors to which it converges. Then we study the symmetry of the algorithm and prove the equivalence between the existence of symmetry and the independence from the order of execution of some basic operations on initial vectors. Finally, we expound some interesting consequences of our theoretical results.Supported in part by a grant from the Italian National Research Council (CNR) research project Technologies and Services for Enhanced Content Delivery.  相似文献   
96.
There is currently a growing interest in control of stretching of DNA inside nanoconfined regions due to the possibility to analyze and manipulate single biomolecules for applications such as DNA mapping and barcoding, which are based on stretching the DNA in a linear fashion. In the present work, we couple Finite Element Methods and Monte Carlo simulations in order to study the conformation of DNA molecules confined in nanofluidic channels with neutral and charged walls. We find that the electrostatic forces become more and more important when lowering the ionic strength of the solution. The influence of the nanochannel cross section geometry is also studied by evaluating the DNA elongation in square, rectangular, and triangular channels. We demonstrate that coupling electrostatically interacting walls with a triangular geometry is an efficient way to stretch DNA molecules at the scale of hundreds of nanometers. The paper reports experimental observations of λ-DNA molecules in poly(dimethylsiloxane) nanochannels filled with solutions of different ionic strength. The results are in good agreement with the theoretical predictions, confirming the crucial role of the electrostatic repulsion of the constraining walls on the molecule stretching.  相似文献   
97.
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