A simple approach to sensor discovery and fabrication on self-assembled monolayers on glass

Self-assembled monolayers (SAMs) on glass were used as a platform to sequentially deposit fluorophores and small molecules for ion sensing. The preorganization provided by the surface avoids the need for complex receptor design, allowing for a combinatorial approach to sensing systems based on small molecules. The resulting libraries are easily measured and show varied responses to a series of both cations and anions. This technology is transferable from the macro- to the microscale both via microcontact printing (microCP), where the fluorophore is printed onto a glass surface, and via direct attachment of the fluorophore to microchannel walls. The ease of miniaturization of this technology may make the generation of a wide variety of simple yet efficient microarrays possible.     

Growth and characterization of Nd-doped SBN single crystal fibers

The growth from ceramic pedestals of single crystal fibers of strontium barium niobate (SBN), doped with different Nd concentrations, was studied. High-quality fibers were grown for Nd doping levels of up to 4.2 at.%, and doping levels as high as 9.9 at.% were reached. No signs of core effects were observed, even for the highest concentration samples. The emission spectra of Nd³⁺ ions in the fibers did not differ from those obtained from bulk SBN crystals, showing very broad bands due to the typical disorder of the crystallographic tungsten-bronze structure. Fluorescence quenching was clearly observed for Nd doping levels above 2 at.%. PACS 81.10.Fq; 78.55.-m     

Design and synthesis of two pyrazole libraries based on o-hydroxyacetophenones

Two new solid-phase syntheses of substituted pyrazoles are described. The first includes supporting an o-hydroxyacetophenone on Merrifield resin, Vilsmeier-Haack formylation on the methyl group and cyclization with a substituted hydrazine to afford a pyrazole ring with two diversity centers. The second starts from o-hydroxyacetophenone supported on Wang resin, which undergoes a Claisen condensation with a carboxylic acid ester to yield a 1,3-dicarbonyl compound that cyclizes to a pyrazole using a hydrazine. Both methods have been used to synthesize two small pyrazole libraries.     

Smooth Linearization for a Saddle on Banach Spaces

As a continuation of a previous work on linearization of class C¹ of diffeomorphisms and flows in infinite dimensions near a fixed point, in this work we deal with the case of a saddle point with some non-resonance restrictions for the linear part. Our result can be seen as an extension of results by Hartman [Boletin de la Sociedad Matematica Mexicana 5(2), 220–241 (1960)] and Aronson, Belitskii and Zhuzhoma [Introduction to the Qualitative Theory of Dynamical systems on surfaces, AMS Transl. Math. Monog. vol.153, pp. 268–277 (1996)] in dimension two. We also present an application to a system of nonlinear wave equations.AMS Subject Classifications: Primary: 35B05, 34G20. Secondary: 35B40, 34D05.Dedicated to Professor Shui-Nee Chow on the occasion of his 60th birthday     

Ultrasonic inspection of batters for on-line process monitoring

A new method for on-line batter monitoring using ultrasound techniques is presented. Air or gas incorporation is done during the beating process which produces bubbles in the mixture. The density and the compressibility of the batter vary as a function of mixing time and are quality index of batter. Traditionally, a batter sample of a fixed volume is removed and weighted in order to determine its density. This is a time consuming process. Batters are air filled mixtures of high viscosity which do not support significant transmission of ultrasound. For this reason conventional ultrasonic density sensors for liquids are not suitable for this application. Therefore, a special transducer has been developed. The sensor was constructed using a piezoelectric ceramic at the fundamental frequency of 1 MHz. Instead of measuring density, in this work, changes in compressibility in batters are monitored by measuring the acoustic impedance of the batter. Main advantage of this novel approach is that changes in acoustic impedance are easier to detect than changes in density especially when air incorporation is in small quantities. Experimental results on different liquids and batters with different gas contents are presented and discussed.     

Effect of non-significant proportional bias in the final measurement uncertainty

The trueness of an analytical method can be assessed by calculating the proportional bias of the method in terms of apparent recovery. If the apparent recovery does not differ significantly from one, the analytical method has not a significant bias. If this is the case, the bias is neglected and the uncertainty associated with this bias is included in the uncertainty budget of results. However, when assessing trueness there is always a probability of incorrectly concluding that the proportional bias is not significant. Therefore, the uncertainty of results may be underestimated. In this paper, we study how non-significant bias affects the uncertainty of analytical results. Moreover, we study how to avoid the underestimation of uncertainty by including the non-significant bias calculated in the uncertainty budget. To answer these questions, we have used the Monte-Carlo method to simulate the process of estimating the apparent recovery of a biased analytical method and, subsequently, the future results this method provides. The results of the simulation show that non-significant bias may underestimate the uncertainty of analytical results when bias contributes in more than 20% to the overall uncertainty. Uncertainty is specially underestimated when bias contributes in more than 50% to the overall uncertainty.     

Phase transitions in unstable cancer cell populations

The dynamics of cancer evolution is studied by means of a simple quasispecies model involving cells displaying high levels of genetic instability. Both continuous, mean-field and discrete, bit-string models are analysed. The string model is simulated on a single-peak landscape. It is shown that a phase transition exists at high levels of genetic instability, thus separating two phases of slow and rapid growth. The results suggest that, under a conserved level of genetic instability the cancer cell population will be close to the threshold level. Implications for therapy are outlined.Received: 22 April 2003, Published online: 22 September 2003PACS: 87.10.+e Biological physics: General theory and mathematical aspects - 87.23.Kg Dynamics of evolution - 87.23.-n Ecology and evolution - 89.75.Fb Structures and organization in complex systems     

Anomalous behavior of ideal Fermi gas below two dimensions

Normal behavior of the thermodynamic properties of a Fermi gas in d > 2 dimensions, integer or not, means monotonically increasing or decreasing of its specific heat, chemical potential or isothermal sound velocity, all as functions of temperature. However, for 0 < d < 2 dimensions these properties develop a "hump" (or "trough") which increases (or deepens) as d? 0 d\rightarrow 0 . Though not the phase transition signaled by the sharp features ("cusp" or "jump") in those properties for the ideal Bose gas in d > 2 (known as the Bose-Einstein condensation), it is nevertheless an intriguing structural anomaly which we exhibit in detail.     

Classification of Dansgaard–Oeschger climatic cycles by the application of similitude signal processing

In this work we have performed a detailed analysis, using signal processing tools, to study time series of data (temperature proxy) extracted from the GRIP ice-core records and we relate it with the evolution of atmospheric CO₂ within the last glacial period. Our method is based in considering the warm periods known as Dansgaard–Oeschger (D/O) events and posterior returns to the cold stage as a climatic cycle. After the warming phase, D/O events relax to the initial cold state in three different ways, what gives rise to three classes of cycles. Also, the Younger/Dryas–Bolling/Allerod (Y/D–B/A) cycle corresponds to one of the classes obtained. We have found that all cycles start with identical warming phases which seem completely unrelated to variations in CO₂ concentration. We discuss on the consequences for global climatology of such steady pattern of cycles.