Closed-cycle gas flow system for cooling of high Tc d.c. SQUID magnetometers

A high Tc.d.c SQUID based magnetometer for magnetocardiography is currently under development at the University of Twente. Since such a magnetometer should be simple to use, the cooling of the system can be realized most practically by means of a cryocooler. A closed-cycle gas flow cooling system incorporating such a cooler has been designed, constructed and tested. The aimed resolution of the magnetometer is 0.1 pT Hz−1/2. The required operating temperature for the SQUIDs is 30 to about 77 K with a stability of 2 × 10−4 K Hz−1/2. After a cool-down time of 1–2 h, a stationary cooling power of at least 0.2 W is required. In the design, helium gas is cooled by a Leybold Heraeus RG 210 cryocooler, transported through a gas line, and subsequently passed through a heat exchanger on which SQUIDs can be installed. The lowest obtainable SQUID heat exchanger temperature is 31 ± 2 K. This can be reached in roughly 2–3 h with an optimal mass flow with respect to the cooling power of 6 × 10−6 kg s−1. At this mass flow the cooling power at the SQUID heat exchanger is 0.2 W at 42 K and roughly 1.2 W at 77 K. A temperature stability of 0.05 K was measured at a SQUID heat exchanger temperature of 54 K and a mass flow of 3 × 10kg s−5. The experience gained with this large cooling system will be used in the design of a smaller configuration cooling system, incorporating miniature Stirling cryocoolers. In this paper the design and the construction of the present closed-cycle system are described and test results are presented.\ud \u

Investigating the Development of the Internal and External Service Tasks of Non-executive Directors: The Case of the Netherlands (1997-2005)

During the last decade, globalization and liberalization of financial markets, changing societal expectations and corporate governance scandals have increased the attention for the fiduciary duties of non-executive directors. In this context, recent corporate governance reform initiatives have emphasized the control task and independence of non-executive directors. However, little attention has been paid to their impact on the external and internal service tasks of non-executive directors. Therefore, this paper investigates how the service tasks of non-executive directors have evolved in the Netherlands. Data on corporate governance at the top-100 listed companies in the Netherlands between 1997 and 2005 show that the emphasis on non-executive directors’ external service task has shifted to their internal service task, i.e. from non-executive directors acting as boundary spanners to non-executive directors providing advice and counseling to executive directors. This shift in board responsibilities affects non-executive directors’ ability to generate network benefits through board relationships and has implications for non-executive directors’ functional requirements.

Monitoring the Dutch Phytophtora infestans population for virulence against new R-genes

New possibilities offered by marker assisted breeding and GMO breeding have sparked renewed international efforts to breed for durable potato late blight resistance. Phytophthora infestans is however known for its adaptability, a trait confirmed by recent discoveries on the structure of the P. infestans genome. One of the possibilities to enhance the durability of newly introduced host resistance is to monitor the pathogen population for virulence to new R genes, prior to - and after their introduction. The late blight control strategy should be adapted accordingly. The Dutch P. infestans population was monitored during the growing seasons 2006 – 2008. P. infestans isolates were collected from blighted production fields and from bait fields in which R gene containing potato clones were grown without fungicide protection. A selection of the P. infestans isolates collected were characterized for virulence to a range of new R genes using a detached leaf bio-assay. Virulence for all single R genes tested was found. When we focus on R genes Rpi-blb1 and Rpi-blb2, no virulence was found in 2006. One Rpi-blb1 virulent isolate was found in 2007. Another 2007 isolate was found to be virulent to Rpi-blb2. Depending on the genetic background in which Rpi-blb1 was placed 13 or 21 isolates were virulent in 2008. Depending on the genetic background in which Rpi-blb2 was placed 4 or 11 isolates were virulent in 2008. One isolate was found to infect the stacked Rpi-blb1 and Rpi-blb2 resistance genes in a detached leaf assay. From these findings it is recommended that monitoring systems should be part of future potato late blight control strategies. The resulting information on the dynamics of virulence within the local P. infestans population can then be used to enhance the durability of newly introduced host resistanc

Boards of Directors’ Contribution to Strategy: A Literature Review and Research Agenda

Manuscript Type: Literature review.Research Question/Issue: Over the last four decades, research on the relationship between boards of directors and strategy has proliferated. Yet to date there is little theoretical and empirical agreement regarding the question of how boards of directors contribute to strategy. This review assesses the extant literature by highlighting emerging trends and identifying several avenues for future research.Research Findings/Insights: Using a content-analysis of 150 articles published in 23 manage-ment journals until 2007, we describe and analyze how research on boards of directors and strategy has evolved over time. We illustrate how topics, theories, settings and sources of data interact and influence insights about board-strategy relationships during three specific periods.Theoretical/Academic Implications: Our study illustrates that research on boards of directors and strategy evolved from normative and structural approaches to behavioral and cognitive approaches. Our results encourage future studies (i) to examine the impact of institutional and context-specific factors on the (expected) contribution of boards to strategy, and (ii) to apply alternative methods to fully capture the impact of board processes and dynamics on strategy-making.Practical/Policy Implications: The increasing interest in boards of directors’ contribution to strategy echoes a movement towards more strategic involvement of boards of directors. However, best governance practices and the emphasis on board independence and control may hinder the board contribution to the strategic decision-making. Our study invites investors and policy-makers to consider the requirements for an effective strategic task when they nominee board members and develop new regulations.boards of directors;contribution to strategy;literature review

Active noise compensation for multichannel magnetocardiography in an unshielded environment

A multichannel high-T/sub c/-SQUID-based heart scanner for unshielded environments is under development, Outside a magnetically shielded room, sensitive SQUID measurements are possible using gradiometers. However, it is difficult to realize large-baseline gradiometers in high-T/sub c/ materials, Therefore, the authors developed two active noise compensation techniques. In the Total Field Compensation technique, a Helmholtz type coil set is placed around the sensors. One magnetometer is used as a zero detector controlling the compensation current through the coil set. For Individual Flux Compensation, the reference signal is sent to the separate SQUIDs (or their flux transformer circuits) to compensate the local environmental noise fluxes, The latter technique was tested on low-T/sub c/ rf-SQUID magnetometers, each sensor set to a field resolution SQUID magnetometers, i.e. 0.1 pT/sub RMS///spl radic/Hz. The authors were able to suppress the environmental disturbances to such an extent that magnetocardiograms could be recorded in an ordinary environment. Here the two suppression techniques are described and experimental results are presente

Price-based control of electrical power systems

In this chapter we present the price-based control as a suitable approach to solve some of the challenging problems facing future, market-based power sys tems. On the example of economically optimal power balance and transmission network congestion control, we present how global objectives and constraints can in real-time be translated into time-varying prices which adequately reflect the cur rent state of the physical system. Furthermore, we show how the price signals can be efficiently used for control purposes. Becoming the crucial control signals, the timevarying prices are employed to optimally shape, coordinate and synchronize local, profit-driven behaviors of producers/consumers to mutually reinforce and guarantee global objectives and constraints. The main focus in the chapter is on exploiting specific structural properties of the global system constraints in the synthesis of price-based controllers. The global constraints arise from sparse and highly struc tured power flow equations. Preserving this structure in the controller synthesis implies that the devised solutions can be implemented in a distributed fashion

Strategische vernieuwing in Nederlandse non-profit organisaties

Strategische vernieuwing in ondernemingen staat hoog op de agenda van managers en onderzoekers. De aandacht voor nonprofit-organisaties in dit verband is echter beperkt. Zo is er weinig bekend over de mate, de oorzaken en de implicaties van strategische vernieuwing. Dit artikel gaat in op dit thema. Met behulp van een enquête en twee casestudies wordt voor het eerst de vernieuwingsdynamiek van Nederlandse nonprofit-organisaties in kaart gebracht. De resultaten laten zien dat strategische vernieuwing door nonprofit-organisaties leidt tot een hoger prestatieniveau. Druk vanuit het management en/ of bestuur en druk vanuit de sociale omgeving blijken belangrijke determinanten voor de mate van strategische vernieuwin

De adviserende rol van commissarissen in het licht van de code Tabaksblat: Minder overlappende commissariaten meer interne verantwoordelijkheden

Van oudsher bestaan de hoofdverantwoordelijkheden van de raad van commissarissen uit het houden van toezicht op het beleid van de raad van bestuur en het bijstaan van de raad van bestuur door het geven van advies en het dienen als klankbord. Op het eerste gezicht lijken deze beide hoofdverantwoordelijkhedenmet elkaar te conflicteren: voor toezicht is namelijk onafhankelijkheid noodzakelijk, terwijl voor advisering een zekere mate van betrokkenheid noodzakelijk is (VanManen enVan der Reijden, 2005;Huse, 2007). In de praktijk worstelen commissarissen dan ookmet dit vraagstuk. Temeer doordat het wettelijk raamwerk in Nederland geen duidelijke oplossing aandraagt

PRIMET Version 1.0, manual and technical description; a decision support system for assessing pesticide risks in the Tropics to man, environment and trade

Pesticide exposure via for instance spray drift or runoff to surface water, accumulation in the topsoil, and leaching to groundwater potentially affects organisms in water and soil and might also pose risks to humans via dietary exposure, in case they consume contaminated aquatic products like groundwater, macrophytes and fish. To estimate these risks at the household level the PRIMET Decision Support System was developed. PRIMET runs with a minimum of input data and is developed to be used in developing countries. The risk assessment is expressed in Exposure Toxicity Ratio’s which are calculated by dividing the predicted exposure by the safe concentration. This report provides a mathematical description of the processes incorporated into PRIMET and a user manual. PRIMET is freely available at www.primet.wur.n

Boards of Directors’ Contribution to Strategy: A Literature Review and Research Agenda

Manuscript Type: Literature review. Research Question/Issue: Over the last four decades, research on the relationship between boards of directors and strategy has proliferated. Yet to date there is little theoretical and empirical agreement regarding the question of how boards of directors contribute to strategy. This review assesses the extant literature by highlighting emerging trends and identifying several avenues for future research. Research Findings/Insights: Using a content-analysis of 150 articles published in 23 manage-ment journals until 2007, we describe and analyze how research on boards of directors and strategy has evolved over time. We illustrate how topics, theories, settings and sources of data interact and influence insights about board-strategy relationships during three specific periods. Theoretical/Academic Implications: Our study illustrates that research on boards of directors and strategy evolved from normative and structural approaches to behavioral and cognitive approaches. Our results encourage future studies (i) to examine the impact of institutional and context-specific factors on the (expected) contribution of boards to strategy, and (ii) to apply alternative methods to fully capture the impact of board processes and dynamics on strategy-making. Practical/Policy Implications: The increasing interest in boards of directors’ contribution to strategy echoes a movement towards more strategic involvement of boards of directors. However, best governance practices and the emphasis on board independence and control may hinder the board contribution to the strategic decision-making. Our study invites investors and policy-makers to consider the requirements for an effective strategic task when they nominee board members and develop new regulations