M. van Vliet

The information market: its basic concepts and its challenges

This paper discusses the concept of information market. The authors of this paper have been involved in several aspects of information retrieval research. In continuing this research tradition we now take a wider perspective on this field and re-position it as a market where demand for information meets supply for information. The paper starts by exploring the notion of a market in general and is followed by a specialization of these considerations in the information market, where we will also position some of the existing work.

Hydrogen bonding in the template-directed oligomerization of a pyrimidine nucleotide analogue

We have studied the oligomerization of an activated, achiral nucleotide analogue related to the pyrimidine barbituric acid in the absence and in the presence of a complementary, pyrophosphate-linked oligomer. Although no template-directed catalysis of the oligomerization was observed with water as solvent, catalysis of the oligomerization was demonstrated in a mixture of dimethylformamide with water. Poly(U) also stimulated the oligomerization, but was less effective than the analogue. Environments in which similar effects may be observed, and some potential implications for prebiotic chemistry, are discussed.

An achiral (oligo)nucleotide analog

An achiral nucleotide analog based on barbituric acid has been synthesized. The analog, which is 5,5-di(2-phosphoethyl)barbituric acid, undergoes extensive oligomerization in aqueous solution, when activated, to produce pyrophosphate-linked chains. In contrast to a number of other bisphosphorylated nucleoside analogs which have been studied, the compound has little tendency to cyclize. The possible prebiotic implications are discussed.

Value and the information market

In this paper we explore how (micro)economic theory can be used to analyze and model the exchange of information on the Web. More specifically, we consider searchers for information who engage in transactions on the Web. Searchers will engage in web transactions only if they gain something in such a transaction. To this end we develop a formal model for markets, based on the notions of value and transaction. This model enables us to examine transactions on an information market. In this market we have a dual view on transactions, creating a dichotomy of transactors and transactands.

Predictors of short-term and long-term mortality in critically ill patients admitted to the intensive care unit following allogeneic stem cell transplantation

Historically, the mortality of patients admitted to the ICU after allogeneic stem cell transplantation (alloSCT) is high. Advancements in transplantation procedures, infectious monitoring and supportive care may have improved the outcome. This study aimed to determine short-term and long-term mortality after ICU admission of patients after alloSCT and to identify prognostic clinical and transplantation-related determinants present at ICU admission for long-term outcome. A multicenter cohort study was performed to determine 30-day and 1-year mortality within 2 years following alloSCT. A total of 251 patients were included. The 30-day and 1-year mortality was 55% and 80%, respectively. Platelet count <25 × 109/L (OR: 2.26, CI: 1.02–5.01) and serum bilirubin >19 μmol/L (OR: 2.47 CI: 1.08–5.65) at admission, other donor than a HLA-matched-related or HLA-matched-unrelated donor (OR: 4.59, CI: 1.49–14.1) and vasoactive medication within 24 h (OR: 2.35, CI: 1.28–4.31) were associated with increased 30-day mortality. Other donor than a HLA-matched-related or HLA-matched-unrelated donor (OR: 1.9, CI: 1.13–3.19), serum bilirubin >77 (OR: 2.05, CI: 1.28–3.30) and vasoactive medication within 24 h (OR: 1.65, CI: 1.12–2.43) were associated with increased 1-year mortality. Neutropenia was associated with decreased 30-day and 1-year mortality (OR: 0.29, CI: 0.14–0.59 and OR: 0.70, CI: 0.48–0.98). Myeloablative conditioning and T cell-depleted transplantation were not associated with increased mortality.

Chirality and the First Self-Replicating Molecules

It seems certain that the first self-replicating RNA molecules did not arise by spontaneous chemical synthesis in some prebiotic “soup.” A possible explanation for their origin is that self-replication first developed in another, “nucleic acid-like,” system which was not based on D-ribose and that RNA was formed at a later stage in evolution. One possibility for such a system, based on the non-chiral reduced sugar pentaerythritol, has recently been proposed (Schwartz, 1993). Preliminary results with the first of a series of model compounds designed to test this proposal are reported.