Testing eccentricity pumping mechanisms to model eccentric long period sdB binaries with MESA

Hot subdwarf-B stars in long-period binaries are found to be on eccentric orbits, even though current binary-evolution theory predicts those objects to be circularised before the onset of Roche-lobe overflow (RLOF). We aim to find binary-evolution mechanisms that can explain these eccentric long-period orbits, and reproduce the currently observed period-eccentricity diagram. Three different processes are considered; tidally-enhanced wind mass-loss, phase-dependent RLOF on eccentric orbits and the interaction between a circumbinary disk and the binary. The binary module of the stellar-evolution code MESA (Modules for Experiments in Stellar Astrophysics) is extended to include the eccentricity-pumping processes. The effects of different input parameters on the final period and eccentricity of a binary-evolution model are tested with MESA. The end products of models with only tidally-enhanced wind mass-loss can indeed be eccentric, but these models need to lose too much mass, and invariably end up with a helium white dwarf that is too light to ignite helium. Within the tested parameter space, no sdBs in eccentric systems are formed. Phase-dependent RLOF can reintroduce eccentricity during RLOF, and could help to populate the short-period part of the period-eccentricity diagram. When phase-dependent RLOF is combined with eccentricity pumping via a circumbinary disk, the higher eccentricities can be reached as well. A remaining problem is that these models favour a distribution of higher eccentricities at lower periods, while the observed systems show the opposite. The models presented here are potentially capable of explaining the period-eccentricity distribution of long-period sdB binaries, but further theoretical work on the physical mechanisms is necessary.Comment: 18 pages, 9 figures, accepted for publication in A&

A compensatory model for simultaneously setting cutting scores for selection-placement-mastery decisions

A method is proposed for optimizing cutting scores for a selection-placement-mastery problem simultaneously. A simultaneous approach has two advantages over separate optimization. First, test scores used in previous decisions can be used as "prior data" in later decisions, increasing the efficiency of the decisions. Then, more realistic utility structures can be defined using final success criteria in utility functions for earlier decisions. An important distinction is made between weak and strong decision rules. Weak rules are allowed to be a function of prior test scores. Conditions for optimal rules to be monotone are presented, and it is shown that optimal weak monotone rules are compensatory by nature. Results from an empirical example of instructional decision making illustrate the differences between simultaneous and separate approaches. Subjects were 71 medical students receiving interactive video or computer-aided instruction

Simultaneous optimization of decisions using a linear utility function

The purpose of this article is to simultaneously optimize decision rules for combinations of elementary decisions. With this approach, rules are found that make more efficient use of the data than could be achieved by optimizing these decisions separately. The framework for the approach is derived from Bayesian decision theory. To illustrate the approach, two elementary decisions (selection and mastery decisions) are combined into a simple decision network. A linear utility structure is assumed. Decision rules are derived both for quota-free and quota-restricted selection-mastery decisions in case of several subpopulations. An empirical example of instructional decision making in an individual study system concludes the article

Syntax of Dutch: Verbs and Verb Phrases. Volume 1

Syntax of Dutch: Verbs and Verb Phrases consists of three volumes. Volume 1 opens with a general introduction to verbs, including a review of various verb classifications and discussions on inflection, tense, mood, modality and aspect. This is followed by a comprehensive discussion of complementation (argument structure and verb frame alternations). Volume 2 continues the discussion of complementation, but is more specifically focused on clausal complements: the reader will find detailed discussions of finite and infinitival argument clauses, complex verb constructions and verb clustering. Volume 3 concludes with a description of adverbial modification and the overall structure of clauses in relation to, e.g., word order (verb placement, wh-movement. extraposition phenomena, scrambling, etc.)

Supplier-contractor collaboration in the construction industry:A taxonomic approach to the literature of the 2000-2009 decade

Purpose – Recent developments in the construction industry resulted in an increased importance of collaboration with and managing of suppliers by prime contractors. The focus of this study is on getting insights into existing knowledge on this topic and the gaps in this knowledge base. The goals of this study are threefold: to verify the current state of, to gain insights into, and to provide suggestions for supplier-contractor research. Design/methodology/approach – The current state of supplier-contractor research in the construction industry is verified through a taxonomic approach to the literature on buyer-supplier research over the last decade (2000-2009). The method followed consists of the following three steps: journal selection, initial article selection and final article selection. Findings – Supplier-contractor research in the construction industry is still a relatively under-researched phenomenon. The major topics discussed in the identified articles are aspects of partnering (conditions, characteristics and barriers/obstacles) and (sub)contracting/procurement issues (practices, selection criteria, performance and characteristics). Research limitations/implications – This study concludes that future research should focus on longitudinal studies, testing organisational barriers to partnering, the benefits of partnering in practice, conditions under which the formation of collaborative relationships between suppliers and contractors takes place, and experiences with this formation process. Practical implications – In practice, contractors do see a need to develop closer and more collaborative relationships with their suppliers. This study highlights the topics that need to be addressed to achieve these goals. Originality/value – This study is a literature overview of relatively scarce research on collaborative relationships between suppliers and contractors in the construction industry

Trade-offs in the value capture of architectural firms

Architectural firms often have difficulty generating profit from their services as they pursue not only commercial but also professional goals. These goals frequently conflict and have to be balanced during the process of value creation and value capture. So far, literature has focused on the interaction between the perceived use value for the customer and the fee that is paid to the firm. To better understand how professional service firms realize their organizational targets, professional value needs to be included. In this study, in-depth interviews with the architects and clients of nine housing projects provide insight into the content and process of value capture by architectural firms. The data reveal strategies by which architects tried to maximize the capture of professional value at the expense of profit or sometimes even their clients’ perceived use value. These trade-offs in value capture confirm the importance of professional value when studying value creation and capture in a professional service context. This paper provides an understanding of how architectural firms struggle to balance competing goals and highlights the importance of well-managed value capture

Taking risks to play it safe: value capture strategies of architectural firms

Project-based firms have to capture value from the projects in which they engage. This can be a challenging process, as firms need to reconcile project goals and organizational goals while attempting to avoid value slippage. Drawing on case-based interviews with architects and clients, this research reveals how architectural firms used the strategies of postponing financial revenues in a project, compensating for loss of financial revenues across projects and rejecting a project to capture value. The study contributes to the literature on project business by showing that firms will sometimes risk or accept slippage of financial value yet counteract the potential slippage of professional value in projects to enhance the overall benefits for the firm. These insights help to advance the research on value capture by project-based firms and can be used by managers to identify and overcome value capture difficulties at project and firm levels

Caenorhabditis elegans as a model system for studying drug induced mitochondrial toxicity

Today HIV-1 infection is recognized as a chronic disease with obligatory lifelong treatment to keep viral titers below detectable levels. The continuous intake of antiretroviral drugs however, leads to severe and even life-threatening side effects, supposedly by the deleterious impact of nucleoside-analogue type compounds on the functioning of the mitochondrial DNA polymerase. For detailed investigation of the yet partially understood underlying mechanisms, the availability of a versatile model system is crucial. We therefore set out to develop the use of Caenorhabditis elegansto study drug induced mitochondrial toxicity. Using a combination of molecular-biological and functional assays, combined with a quantitative analysis of mitochondrial network morphology, we conclude that anti-retroviral drugs with similar working mechanisms can be classified into distinct groups based on their effects on mitochondrial morphology and biochemistry. Additionally we show that mitochondrial toxicity of antiretroviral drugs cannot be exclusively attributed to interference with the mitochondrial DNA polymerase

Synthesis, in vitro and in vivo evaluation of 3β-[18F]fluorocholic acid for the detection of drug-induced cholestasis in mice

Introduction : Drug-induced cholestasis is a liver disorder that might be caused by interference of drugs with the hepatobiliary bile acid transporters. It is important to identify this interference early on in drug development. In this work, Positron Emission Tomography (PET)-imaging with a F-18 labeled bile acid analogue was introduced to detect disturbed hepatobiliary transport of bile acids. Methods : 3 beta-[F-18]fluorocholic acid ([F-18]FCA) was prepared by nucleophilic substitution of a mesylated precursor with [F-18]fluoride, followed by deprotection with sodium hydroxide. Transport of [F-18]FCA was assessed in vitro using CHO-NTCP, HEK-OATP1B1, HEK-OATP1B3 transfected cells and BSEP & MRP2 membrane vesicles. Investigation of [F-18]FCA metabolites was performed with primary mouse hepatocytes. Hepatobiliary transport of [F-18]FCA was evaluated in vivo in wild-type, rifampicin and bosentan pretreated FVB-mice by dynamic mu PET scanning. Results : Radiosynthesis of [F-18] FCA was achieved in a moderate radiochemical yield (8.11-1.94%; non-decay corrected; n = 10) and high radiochemical purity (>99%). FCA was transported by the basolateral bile acid uptake transporters NTCP, OATP1B1 and OATP1B3. For canalicular efflux, BSEP and MRP2 are the relevant bile acid transporters. [F-18]FCA was found to be metabolically stable. In vivo, [F-18]FCA showed fast hepatic uptake (4.5-0.5 min to reach 71.8-1.2% maximum % ID) and subsequent efflux to the gallbladder and intestines (93.3-6.0% ID after 1 hour). Hepatobiliary transport of [F-18]FCA was significantly inhibited by both rifampicin and bosentan. Conclusion : A F-18 labeled bile acid analogue, [F-18]FCA, has been developed that shows transport by NTCP, OATP, MRP2 and BSEP. [F-18]FCA can be used as a probe to monitor disturbed hepatobiliary transport in vivo and accumulation of bile acids in blood and liver during drug development