Towards an analytical theory for charged hard spheres

Ion mixtures require an exclusion core to avoid collapse. The Debye Hueckel theory, where ions are point charges, is accurate only in the limit of infinite dilution. The MSA is the embedding of hard cores into DH, is valid for higher densities. In the MSA the properties of any ionic mixture can be represented by a single screening parameter $\Gamma$. For equal ionic size restricted model is obtained from the Debye parameter $\kappa$. This one parameter representation (BIMSA) is valid for complex and associating systems, such as the general n-polyelectrolytes. The BIMSA is the only theory that satisfies the infinite dilution limit of the DH theory for any chain length. The contact pair distribution function of hard ions mixture is a functional of $\Gamma$ and a small mean field parameter. This yields good agreement with the Monte Carlo (Bresme et al. Phys. Rev. E {\textbf 51} 289 (1995)) .Comment: 6 pages, 1 figur

Solubility of hydrogen in aqueous solutions of sodium and potassium bicarbonate from 293 to 333 K

An experimental study is presented of the hydrogen solubility in aqueous salt solutions containing sodium and potassium bicarbonate from 293 to 333 K. For this purpose, gas consumption measurements have been performed by determining the ultimate pressure decrease in an intensively stirred, high pressure autoclave. Experiments were carried out at salt concentrations up to 1.0 mol kg-1. At higher salt molalities, the hydrogen solubility was too low to be measured reliably. It was demonstrated that the hydrogen solubility followed the well-known Sechenov salt concentration dependence. At 298 K, the Sechenov or salting-out parameters were equal to 0.41 and 0.32 kg mol-1 for sodium and potassium bicarbonate, respectively. Fairly good agreement was obtained with the salting-out parameters predicted by a recently developed empirical estimation method. The concentration ratio of the bicarbonate and carbonate ions showed only a minor influence on the hydrogen solubility. Furthermore, the Sechenov parameter was found to be a weak function of temperature. Virtually the same, linear temperature dependence was observed for both bicarbonate salts studied, i.e. −0.0023 and −0.0024 kg mol-1 K-1 for sodium and potassium bicarbonate, respectively

Towards pain-free diagnosis of skin diseases through multiplexed microneedles: biomarker extraction and detection using a highly sensitive blotting method

Immunodiagnostic microneedles provide a novel way to extract protein biomarkers from the skin in a minimally invasive manner for analysis in vitro. The technology could overcome challenges in biomarker analysis specifically in solid tissue, which currently often involves invasive biopsies. This study describes the development of a multiplex immunodiagnostic device incorporating mechanisms to detect multiple antigens simultaneously, as well as internal assay controls for result validation. A novel detection method is also proposed. It enables signal detection specifically at microneedle tips and therefore may aid the construction of depth profiles of skin biomarkers. The detection method can be coupled with computerised densitometry for signal quantitation. The antigen specificity, sensitivity and functional stability of the device were assessed against a number of model biomarkers. Detection and analysis of endogenous antigens (interleukins 1α and 6) from the skin using the device was demonstrated. The results were verified using conventional enzyme-linked immunosorbent assays. The detection limit of the microneedle device, at ≤10 pg/mL, was at least comparable to conventional plate-based solid-phase enzyme immunoassays

Reduction in ionic permeability of a silicone hydrogel contact lenses after one month of daily wear

[EN] Purpose. To compare the ionic permeability using the ionoflux method of new and worn samples of a silicone hydrogel contact lens material. Methods. An ionoflux experimental setup was established to measure the ionic permeability (NaCl) of soft contact lenses. Samples of a silicone hydrogel lens (Comfilcon A, Coopervision, Pleasanton, CA) with optical powers of -1.00, -1.50 and -4.75 diopters (D) were used in this study. Three samples of each power were measured after being worn for one month on a daily wear basis. Lenses were cleaned and disinfected every night using multipurpose disinfecting solutions. Three samples of new lenses from the same batch and the same optical power were also measured to evaluate the effect of lens wear on the ionic permeability of the lens material. Before measurement, the lenses were equilibrated with a 1 M NaCl solution during one week before of each measurement. Results. Lens power had minimal effect on the ionic permeability of a modern silicone hydrogel contact lens with the -1.00 lens having a 15% lower permeability compared to the other two lenses. After one month of lens wear the apparent ionic permeability for lenses with -1.50 D decreased by 15%. In the case of -1.00 and -4.75 D lenses there was a decrease of 26%. Conclusions. The ionic permeability of silicone hydrogel lenses of different optical powers was not significantly different. Worn lenses present a significant reduction of the ionic permeability after a month of wear. The potential effect this reduction on lens movement and discomfort associated to lens wear should be further evaluated.The authors have no proprietary interest in any of the materials mentioned in this article. This work was funded in part by FEDER through the COMPTETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of projects PTDC/SAU-BEB/098391/2008, PTDC/SAU-BEB/098392/2008 and the Strategic Project PEST-C/FIS/UI607/2011.Ferreira Da Silva, AR.; Compañ Moreno, V.; Gonzalez-Meijome, JM. (2015). Reduction in ionic permeability of a silicone hydrogel contact lenses after one month of daily wear. Materials Research Express. 2(6). https://doi.org/10.1088/2053-1591/2/6/065007S26Yoon, S. C., & Jhon, M. S. (1982). The transport phenomena of some model solutes through postcrosslinked poly(2-hydroxyethyl methacrylate) membranes with different tactic precursors. Journal of Applied Polymer Science, 27(8), 3133-3149. doi:10.1002/app.1982.070270834Yasuda, H., Lamaze, C. E., & Ikenberry, L. D. (1968). Die Makromolekulare Chemie, 118(1), 19-35. doi:10.1002/macp.1968.021180102MURPHY, S., HAMILTON, C., & TIGHE, B. (1988). Synthetic hydrogels: 5. Transport processes in 2-hydroxyethyl methacrylate copolymers. Polymer, 29(10), 1887-1893. doi:10.1016/0032-3861(88)90407-7Nicolson, P. C., & Vogt, J. (2001). Soft contact lens polymers: an evolution. Biomaterials, 22(24), 3273-3283. doi:10.1016/s0142-9612(01)00165-xMonticelli, M. V., Chauhan, A., & Radke, C. J. (2005). The Effect of Water Hydraulic Permeability on the Settling of a Soft Contact Lens on the Eye. Current Eye Research, 30(5), 329-336. doi:10.1080/02713680590934085Guan, L., Jiménez, M. E. G., Walowski, C., Boushehri, A., Prausnitz, J. M., & Radke, C. J. (2011). Permeability and partition coefficient of aqueous sodium chloride in soft contact lenses. Journal of Applied Polymer Science, 122(3), 1457-1471. doi:10.1002/app.33336Cheng, M.-L., & Sun, Y.-M. (2005). Observation of the solute transport in the permeation through hydrogel membranes by using FTIR-microscopy. Journal of Membrane Science, 253(1-2), 191-198. doi:10.1016/j.memsci.2005.01.017CHHABRA, M., PRAUSNITZ, J., & RADKE, C. (2007). A single-lens polarographic measurement of oxygen permeability (Dk) for hypertransmissible soft contact lenses. Biomaterials, 28(30), 4331-4342. doi:10.1016/j.biomaterials.2007.06.024González-Méijome, J. M., López-Alemany, A., Almeida, J. B., & Parafita, M. A. (2009). Surface AFM microscopy of unworn and worn samples of silicone hydrogel contact lenses. Journal of Biomedical Materials Research Part B: Applied Biomaterials, 88B(1), 75-82. doi:10.1002/jbm.b.31153González-Méijome, J. M., López-Alemany, A., Almeida, J. B., & Parafita, M. A. (2008). Dynamic in vitro dehydration patterns of unworn and worn silicone hydrogel contact lenses. Journal of Biomedical Materials Research Part B: Applied Biomaterials, 90B(1), 250-258. doi:10.1002/jbm.b.31279Pozuelo, J., Compañ, V., González-Méijome, J. M., González, M., & Mollá, S. (2014). Oxygen and ionic transport in hydrogel and silicone-hydrogel contact lens materials: An experimental and theoretical study. Journal of Membrane Science, 452, 62-72. doi:10.1016/j.memsci.2013.10.010Wolffsohn, J. S., Hunt, O. A., & Basra, A. K. (2009). Simplified recording of soft contact lens fit. Contact Lens and Anterior Eye, 32(1), 37-42. doi:10.1016/j.clae.2008.12.00

Conductors\u27 Annotated Scores: A Comprehensive Study

Conductors’ annotations have a different nature and goal from those of orchestral musicians. The purpose of this study is to obtain a better understanding of the process of conductors’ annotations based on examined scores[1]collected from professional conductors and supported by a questionnaire answered by twenty-seven participants. Certain questions provided a better understanding of the elements used in conductors’ annotations. For example: Why do some conductors prefer to use symbols, words, numbers, or colors? What kind of annotations are more suitable to specific repertories? Why are reinforcement markings, although redundant, so popular among conductors and why do some conductors consider the score as a document that should not be modified under any circumstances? Analysis of the scores as well as the questionnaire responses show some similarities among conductors’ annotated scores and orchestra musicians’ annotations. However, the utility and nature of the conductors’ annotations are so unique that they resulted in a different outcome from the research of musicians’ annotations used as a reference for this research. Despite the similarities among conductors’ annotations, the study found no clearly defined or standardized process. Rather, the findings include individual solutions annotated by conductors to make the music more readable and to provide a unique, personal specific analysis in order to achieve a better understanding of the piece. Further research emphasizing the annotation process of world-renowned conductors and their practices across an array of works and musical styles should be undertaken as a means of determining their individual approaches to the art and craft of conducting. [1]This study used Tchaikovsky’s Symphony no 5, in E minor, Op.64 as reference instead of an open choice so that some aspects of the analysis could only be compared to the same musical content. However, some conductors sent an annotated score of other work, which the author accepted considering that the focus of this research was the annotations rather than the music itself

Benchmarking the SPARC software program for estimating solubilities of naphthalene and anthracene in organic solvents

The SPARC software program was benchmarked for calculating the solubilities of two representative polyaromatic hydrocarbons (PAHs), naphthalene and anthracene, in a range of organic solvents at various temperatures. Although SPARC was able to reasonably approximate the solubilities of naphthalene in some organic solvents, gross errors were obtained for other solvents. For anthracene, poor prediction performance was observed in all solvents considered. Overall, the results suggest that SPARC is currently not suitable for accurately predicting the solubilities of representative PAHs relevant for the petroleum sector in various organic solvents

Thermodynamic Activity-Based Michaelis Constants

The classical approach towards analysing the influence of co-solvents (i.e., cellular molecules that are chemically inert and do not act as reacting agents) on the Michaelis constants of enzyme-catalysed reactions is empirical. More precisely, reaction kinetics is usually mathematically modelled by fitting empirical parameters to experimental concentration vs. time data. In this chapter, a thermodynamic approach is presented that replaces substrate concentrations by thermodynamic activities of the substrates. This approach allows determining activity-based Michaelis constants. The advantage of such activity-based constants K M a over their concentration-based pendants K M obs is twofold: First, K M a is independent of any co-solvent added (while K M obs is not) as long as it does not directly interfere with the reaction mechanism (e.g., inhibitor or activator). Second, known K M a values allow predictions of Michalis constants for different enzymes and reactions under co-solvent influence. This is demonstrated for a pseudo-one-substrate peptide hydrolysis reaction as well as for more complex two-substrate alcohol dehydrogenase reactions