Self-assembled monolayers with biospecific affinity for lactate dehydrogenase for the electroenzymatic oxidation of lactate

Surface modified gold electrodes with high biospecific affinity for NAD(H)-dependent lactate dehydrogenase have been prepared by covalent attachment of several traizine dyes to stepwise functionalized mixed alkanethiol self-assembled monolayers. The biospecific affinity of such ligand-anchored monolayers to bind submonolayer amounts of enzyme was demonstrated from the course of the protein adsorption events monitored by surface plasmon resonance. Electroenzymatic activity measurements of lactate dehydrogenase modified surfaces for the reaction of lactate oxidation, carried out `ex situ¿ at different stages of protein layer growth, allowed the optimization of the preparative procedure to yield reproducible enzymatic electrodes with a low amount of unspecifically bound protein. A short adsorption time, as well as a high concentration of enzyme in the solution used for protein layer growth, led to lactate dehydrogenase-modified gold electrode surfaces with a high electroenzymatic activity arising mainly from biospecifically bound species. The lowest amount of unspecifically adsorbed protein was found for ligand-anchored monolayers prepared from mixed alkanethiol underlayers with an excess of positively charged groups. The lack of electroenzymatic activity shown by lactate dehydrogenase modified electrodes in the absence of soluble coenzyme (NAD+) indicates that none of the investigated ligand-anchored monolayers could provide an efficient electronic pathway from the metal to the active site of the enzyme. Therefore, the monolayers acted just as an anchoring system for lactate dehydrogenase

The Material Culture of Childhood: Problems and Potential in Historical Explanation

The discovery of childhood over the past two centuries, initially by educators, clergy, merchandisers, and sociologists throughout the nineteenth century, and then by childpsychologists, antique dealers, writers, and social historians in the twentieth century, has meant an ever-expanding interest in the role of children and the concept of childhood. Part of this interest has focused on the things of children, on the surviving artifacts of past infancy, childhood and adolescence. Two questions are posed about this interest in extant childhood artifacts: How and why has the material culture of childhood intrigued so many collectors, curators and scholars? What are the problems and possibilities of using such physical evidence in historical explanation? These questions are explored by reviewing how the objects of the child have been collected, exhibited, and interpreted over the past century. The essay's argument and supporting data, while largely drawn from the American historical experience, aims at providing a tentative overview of the topic. Résumé La découverte de la condition de l'enfance au cours des deux derniers siècles, faite d'abord par les éducateurs, les membres du clergé, les spécialistes des techniques marchandes et les sociologues pendant tout le XIXe siècle, puis par les psychologues, les antiquaires, les écrivains et les historiens sociaux, au cours du XXe siècle, a suscité un intérêt sans cesse croissant envers le rôle de l'enfant et le concept de l'enfance. On s'est notamment intéressé aux choses que possédaient les enfants: aux objets des bambins, des enfants et des adolescents d'autrefois, parvenus jusqu'à nous. Cette étude pose deux questions sur l'intérêt manifesté à propos des objets façonnés ayant appartenu aux enfants et qui ont été conservés. On se demande comment et pourquoi la culture matérielle de l'enfance a suscité la curiosité de tant de collectionneurs, de conservateurs et de spécialistes, et on s'interroge aussi sur la nature des problèmes et des possibilités qu'entraîne l'utilisation de ces témoins d'un autre âge pour expliquer le passé. On explore ces questions en étudiant comment les objets que possédaient les enfants d'autrefois ont été collectionnés, exposés et interprétés depuis un siècle. L'étude, dont les raisonnements et les preuves apportées à l'appui sont tirés en majeure partie de l'histoire américaine, vise à donner provisoirement une vue d'ensemble du sujet

A Case Fore Buffer Zones

Golf tournaments are fun and exciting events because they allow for up-close interaction with players, but they also present a risk management concern. Professional golfers are not immune to hitting errant golf shots and a lack of buffer zones often results in spectator injury. The purpose of this paper is to examine how buffer zones can be enhanced or developed to protect patrons. Utilizing data from the PGA Tour, a model was developed to aid in predicting errant tee shots to enhance buffer zones

Large quantum dots with small oscillator strength

We have measured the oscillator strength and quantum efficiency of excitons confined in large InGaAs quantum dots by recording the spontaneous emission decay rate while systematically varying the distance between the quantum dots and a semiconductor-air interface. The size of the quantum dots is measured by in-plane transmission electron microscopy and we find average in-plane diameters of 40 nm. We have calculated the oscillator strength of excitons of that size and predict a very large oscillator strength due to Coulomb effects. This is in stark contrast to the measured oscillator strength, which turns out to be much below the upper limit imposed by the strong confinement model. We attribute these findings to exciton localization in local potential minima arising from alloy intermixing inside the quantum dots.Comment: 4 pages, 3 figures, submitte

Tests of a Novel Design of Resistive Plate Chambers

A novel design of Resistive Plate Chambers (RPCs), using only a single resistive plate, is being proposed. Based on this design, two large size prototype chambers were constructed and were tested with cosmic rays and in particle beams. The tests confirmed the viability of this new approach. In addition to showing an improved single-particle response compared to the traditional 2-plate design, the novel chambers also prove to be suitable for calorimetric applications

Empirical Evaluation of Fair Use Flat Rate Strategies forMobile Internet

The fair use flat rate is a promising tariff concept for the mobile telecommunication industry. Similar to classical flat rates it allows unlimited usage at a fixed monthly fee. Contrary to classical flat rates it limits the access speed once a certain usage threshold is exceeded. Due to the current global roll-out of the LTE (Long Term Evolution) technology and the related economic changes for telecommunication providers, the application of fair use flat rates needs a reassessment. We therefore propose a simulation model to evaluate different pricing strategies and their contribution margin impact. The key input element of the model is provided by socalled discrete choice experiments that allow the estimation of customer preferences. Based on this customer information and the simulation results, the article provides the following recommendations. Classical flat rates do not allow profitable provisioning of mobile Internet access. Instead, operators should apply fair use flat rates with a lower usage threshold of 1 or 3 GB which leads to an improved contribution margin. Bandwidth and speed are secondary and do merely impact customer preferences. The main motivation for new mobile technologies such as LTE should therefore be to improve the cost structure of an operator rather than using it to skim an assumed higher willingness to pay of mobile subscribers

YOU CAN\u27T ALWAYS GET WHAT YOU WANT : EXAMINING EMPLOYEES\u27 PREFERENCES AND JOB SATISFACTION IN AGILE TRANSFORMATIONS

Agile transformations cause fundamental changes to work designs. To better understand resistance to transformations, we shed light on employee preferences and the consequences of team and work organization changes for job satisfaction. We tested two hypotheses on how job satisfaction in agile transformations is influenced by a mismatch of perceived and preferred forms of organizing and a general preference for agile, hybrid, or more traditional forms of organizing. Therefore, we designed the self-stated preference method pairwise comparison-based preference measurement . In summary, we identified team organization as the most important dimension in agile transformations. For requirements engineering, the distance between employee preferences and the perceived status quo was particularly large. Further, we found evidence that a larger distance between team and work organization preferences and perceptions negatively influenced job satisfaction. A relationship between a general preference for one form of organizing and job satisfaction was only weakly supported

A Bit Serial Approach to Massively Parallel Floating Point Operations on an FPGA

In this paper we discuss the pros and cons of bit serial arithmetic for performing mathematical operations for signal processing and scientific computations on an FPGA. We describe our formulation of the architecture for such massively parallel systems, the advantage being that it requires no parallel programming in the traditional sense. We describe a pseudo floating point bit serial circuit which is less complex than full precision floating point and show that it is suitable for many applications. We conclude with several application examples and show that a bit serial implementation can be competitive with a high speed parallel implementation