Kinetic study of an on-chip isocyanate derivatization reaction by on-line nano-esi ms

A high-throughput method is presented for the study of reaction kinetics by nano- electrospray ionization mass spectrometry (nano-ESI MS). The reaction of propyl isocyanate (2), benzyl isocyanate (3), and toluene-2,4-diisocyanate (4) with 4-nitro-7- piperazino-2,1,3-benzoxadiazole (NBDPZ) (1) to yield the corresponding urea derivatives (5) was carried out in a continuous flow glass microchip. Real-time monitoring of the reactions was done by nano-ESI MS. Rate constants of 1.6 ␣ 104 M-1 min-1, 5.2 ␣ 104 M-1 min-1, and 2.5 ␣ 104 M-1 min-1 were determined for isocyanate 2, 3 and 4, respectively

Een gedreven buitenstaander: J.H. van 't Hoff de eerste Nobelprijswinnaar voor Scheikunde

This dissertation presents a new perspective on the life, work and character of the Dutch physical chemist Jacobus Henricus van ’t Hoff, first recipient of the Nobel Prize in Chemistry, and one of the most important and colourful scientists in Dutch history. The image of Van ’t Hoff that emerges from the research presented in this dissertation is that of someone with a strong drive to make a name in science, who nonetheless always remained an outsider. The only major biography was already published in 1912, and was rather uncritical, if not heroizing. Therefore, it was high time for a new one, covering all insights gained over the past hundred years into his scientific research, his personal life and their mutual influence. Public and family archives have delivered a wealth of previously unknown (personal) documents, letters, diaries etc. which to a large extent had never been studied before. They offer previously unknown insights into the character of Van ‘t Hoff and shed new light on the interaction between the personality and scientific work of this leading chemist of the nineteenth century. Apart from these biographical aspects the biography also covers more general historical issues like the internationalisation of science at the end of the nineteenth century, the founding of the new discipline of physical chemistry in the same period, and the changing relationship between education and research in Dutch universities and abroad.Stichting Fysische Chemie Utrecht; Amsterdams Universiteitsfonds; Van ’t Hoff Fonds, AmsterdamHistory of Scienc

Performance of TCP with multiple Priority Classes

We consider the dimensioning problem for Internet access links carrying TCP traffic with two priority classes. To this end, we study the behaviour of TCP at the flow level described by a multiple-server Processor Sharing (PS) queueing model with two customer classes, where the customers represent flows generated by downloading Internet objects; the sojourn times represent the object transfer times. We present closed-form expressions for the mean sojourn times for high-priority customers and approximate expressions for the mean sojourn times of low-priority customers. The accuracy of the model is demonstrated by comparing results based on the PS model with "real" TCP simulation results obtained by the well-known Network Simulator. The experimental results demonstrate that the model-based results are highly accurate when the mean object size is at least 10 IP-packets, and the loss rate is negligible

Gravitation Physics at BGPL

We report progress on a program of gravitational physics experiments using cryogenic torsion pendula undergoing large-amplitude torsion oscillation. This program includes tests of the gravitational inverse square law and of the weak equivalence principle. Here we describe our ongoing search for inverse-square-law violation at a strength down to $10^{-5}$ of standard gravity. The low-vibration environment provided by the Battelle Gravitation Physics Laboratory (BGPL) is uniquely suited to this study.Comment: To be published in The Proceedings of the Francesco Melchiorri Memorial Conference as a special issue of New Astronomy Review

A differential viscosity detector for use in miniaturized chemical separation systems

Abstract—In this paper, we present a micromachined differential viscosity detector suitable for integration into an on-chip hydro-dynamic chromatography system. The general design, however, is applicable to any liquid chromatography system that is used for separation of polymers. The micromachined part of the detector consists of a fluidic Wheatstone bridge and a low hydraulic capaci-tance pressure sensor of which the pressure sensing is based on op-tical detection of a membrane deflection. The stand-alone sensor shows a resolution in specific viscosity of 3 10 3, in which spe-cific viscosity is defined as the increase in viscosity by a sample, relative to the baseline viscosity of a solvent. [0947] Index Terms—Microfluidics, viscometer, viscosity detection