Electrostatic depletion forces between planar surfaces

The interaction between two dielectric plates immersed in an electrolyte solution is examined by using a variational perturbation approximation for the grand partition function. This approach differs from previous treatments in that the screening length between the plates is treated as a variational parameter. A key finding is that adjacent to each plate is a layer of ion depletion with thickness given by about one-half of a Bjerrum length. Consequently, for plate-plate separations less than the Bjerrum length, nearly all the electrolyte is excluded from between the plates, and the interaction is given by the sum of a van der Waals interaction and an attractive osmotic depletion force. In contrast to the predictions of previous theories, the interaction between the plates at short range increases with increasing electrolyte concentration and may provide an important contribution to the salt-induced attraction, commonly referred to as salting out. Because the range of the osmotic depletion force is roughly equal to the Bjerrum length, it increases with the square of the valency of the electrolyte. At larger plate-plate separations, the van der Waals interaction is screened as electrolyte enters the space between the plates, leading to an exponential decay of the interactions, as has been previously observed. However, this interaction is slightly stronger than that previously predicted, due to ion depletion from the surface of the interface, also this effect increases with increasing electrolyte concentration

Mathematical models for planning support

In this paper we describe how computer systems can provide planners with active planning support, when these planners are carrying out their daily planning activities. This means that computer systems actively participate in the planning process by automatically generating plans or partial plans. Active planning support by computer systems requires the application of mathematical models and solution techniques. In this paper we describe the modeling process in general terms, as well as several modeling and solution techniques. We also present some background information on computational complexity theory, since most practical planning problems are hard to solve. We also describe how several objective functions can be handled, since it is rare that solutions can be evaluated by just one single objective. Furthermore, we give an introduction into the use of mathematical modeling systems, which are useful tools in a modeling context, especially during the development phases of a mathematical model. We finish the paper with a real life example related to the planning process of the rolling stock circulation of a railway operator

Naar gerichter woonbeleid

De overheid rekent het tot haar taak het eigenwoningbezit te bevorderen en goede en betaalbare huisvesting te garanderen voor lage inkomens. De beleidsinstrumenten om deze doelstellingen te realiseren zijn daarop echter te weinig toegespitst en creëren verstoringen op de woonmarkt

Van bedrijfssparen naar verlofsparen

De afschaffing van het spaarloon is op inhoudelijke gronden wel te verdedigen. Dat de spaarloonfaciliteit plaats maakt voor een nieuwe ingewikkelde levensloopregeling is moeilijker te onderbouwen. Het is beter om de bestaande regelingen te hervormen. Eventueel kunnen ze worden gekoppeld aan een fiscale levensloopregeling die is gebaseerd op de omkeerregel

The Reverend and the Shaykh: Jonathan Edwards, Muḥammad Ibn ʿAbd al-Wahhāb and the encounter of eighteenth-century conservatism in New England and Najd

In many ways, Jonathan Edwards and Muhammad Ibn 'Abd al-Wahhāb are about as far apart as two figures could possibly be. Without minimizing their very real differences, however, this comparative study finds numerous parallels that beckon even the most conservative of Christians and Muslims to take a second look at their own faith, as well as the faith of the other. Encompassing a variety of disciplines, and spanning the globe from North America to the Arabian Gulf, this study examines the major themes in the lives and works of the Reverend and the Shaykh, two traditionalist icons of the eighteenth century in Christianity and Islam. With implications in diverse fields such as politics, law, philosophy, theology, religion, history, warfare, and even gender issues, this research unearths numerous striking parallels in Edwards and Ibn 'Abd al-Wahhāb that have heretofore gone unnoticed or largely ignored. Surprising congruences in their respective contexts, as well as in their conceptions of God, humanity, and the faith of the other, suggest that religious conservatives who revere these figures stand much to gain from a reassessment of long-held views that could lead to wholly new patterns of global engagement

Role of somatostatin receptors in normal and tumoral pituitary corticotropic cells

Normal and tumoral pituitary corticotropic cells express sst2and sst5, of which sst5is the predominantly expressed receptor subtype. Somatostatin (SS) inhibits pituitary adrenocorticotropin hormone (ACTH) secretion in vitro, but the sensitivity to SS is strongly regulated by glucocorticoids. In pathological conditions of a low endogenous cortisol level, i.e. in patients with adrenal insufficiency and in patients with Nelson's syndrome, SS and sst2-preferring SS analogs (SSA), such as octreotide, are able to lower circulating ACTH and cortisol levels. On the other hand, sst2-preferring SSA seem not effective in lowering ACTH and cortisol levels in patients with untreated Cushing's disease (CD), in which circulating cortisol levels are high. This is likely due to the downregulation of sst2receptors by glucocorticoids. sst5receptor expression is more resistant to the inhibitory effect of glucocorticoids. In recent years, novel sst subtype-selective and universal SSA have been developed. In particular, SSA with a high sst5-binding affinity are potent inhibitors of ACTH secretion by pituitary corticotropic adenoma cells. This knowledge has initiated clinical trials evaluating the efficacy of these novel SSA in patients with CD, with the aim to lower circulating ACTH and cortisol levels by targeting multiple ssts on the corticotropic adenoma cells. In this minireview, the effects of SS in the regulation of normal and tumoral ACTH secretion, the role of sst subtypes involved herein, as well as the potentials of novel SSA in the treatment of patients with recurrent or persisting CD are discussed

Medical treatment of Cushing's syndrome: Adrenal-blocking drugs and ketaconazole

Cushing's syndrome is associated with serious morbidity and increased mortality. Irrespective of its cause, i.e. a pituitary adenoma, ectopic ACTH production or an adrenal neoplasia, Cushing's syndrome is primarily treated surgically. However, when surgery is unsuccessful or contraindicated, medical therapy is needed to treat hypercortisolism. The spectrum of available drugs includes adrenal-blocking agents, neuromodulatory drugs and glucocorticoid receptor antagonists. Adrenal blocking drugs suppress adrenal cortisol production via inhibition of steroidogenic enzymes. Ketoconazole and metyrapone are most frequently used for this purpose, but chronic treatment with these drugs can be limited by side effects like hepatotoxicity (ketoconazole) and increased androgen and mineralocorticoid production (metyrapone). Etomidate can be used to rapidly reverse cortisol excess in patients with acute complications of (severe) hypercortisolism like psychosis. In Cushing's disease, combination therapy with drugs that target the corticotropic adenoma, i.e. the universal somatostatin analogue pasireotide and/or the dopamine agonist cabergoline, and low-dose ketoconazole seems a rational approach to achieve biochemical control

Flexible Connections in PESP Models for Cyclic Passenger Railway Timetabling

In this paper we describe how rolling stock and passenger connections in a cyclic railway timetable can be modeled in a flexible way within the model for the Periodic Event Scheduling Problem (PESP). The PESP model was introduced by Serani and Ukovich (1989). Usually, PESP-models assume that the constraints for rolling stock or passenger connections specify in detail which trains should connect with each other. However, the flexibility described in this paper allows the model to choose which trains should connect with each other in a rolling stock or passenger connection. We express the required number of train compositions in terms of the integer cycle variables of the constraint graph. We also describe an abstract framework, demonstrating that, under certain conditions, the extra flexibility can be modeled purely in terms of PESP constraints. The concept of flexible rolling stock and passenger connections is illustrated by an example based on three intercity lines of Netherlands Railways

Crowdsourced Delivery: A Dynamic Pickup and Delivery Problem with Ad-hoc Drivers

The trend towards shorter delivery lead-times reduces operational efficiency and increases transportation costs for internet retailers. Mobile technology, however, creates new opportunities to organize the last-mile. In this paper, we study the concept of crowdsourced delivery that aims to use excess capacity on journeys that already take place to make deliveries. We consider a peer-to-peer platform that automatically creates matches between parcel delivery tasks and ad-hoc drivers. The platform also operates a fleet of backup vehicles to serve the tasks that cannot be served by the ad-hoc drivers. The matching of tasks, drivers and backup vehicles gives rise to a new variant of the dynamic pick-up and delivery problem. We propose a rolling horizon framework and develop an exact solution approach to solve the various subproblems. In order to investigate the potential benefit of crowdsourced delivery, we conduct a wide range of computational experiments. The experiments provide insights into the viability of crowdsourced delivery under various assumptions about the environment and the behavior of the ad-hoc drivers. The results suggest that the use of ad-hoc drivers has the potential to make the last-mile more cost-efficient and can reduce the system-wide vehicle-miles

A Framework for Representation, Validation and Implementation of Database Application Semantics

New application domains in data-processing environments pose new requirements on the methodologies, techniques and tools used to design them. The applications’ semantics should be fully represented at an increasingly high level, and the representation should be subject to rigorous validation and verification. We present a semantic representation framework (including the language, methods and tools) for design of data-processing applications. The new features of the framework include a small number of precisely defined domain-independent concepts, high-level possibilities for describing behavioural semantics (methods and constraints) and the validation and verification tools included in the framework. We present examples of the use of the framework, including the use of its tools