The Osmotic Coefficient of Rod-like Polyelectrolytes: Computer Simulation, Analytical Theory, and Experiment

The osmotic coefficient of solutions of rod-like polyelectrolytes is considered by comparing current theoretical treatments and simulations to recent experimental data. The discussion is restricted to the case of monovalent counterions and dilute, salt-free solutions. The classical Poisson-Boltzmann solution of the cell model correctly predicts a strong decrease in the osmotic coefficient, but upon closer look systematically overestimates its value. The contribution of ion-ion-correlations are quantitatively studied by MD simulations and the recently proposed DHHC theory. However, our comparison with experimental data obtained on synthetic, stiff-chain polyelectrolytes shows that correlation effects can only partly explain the discrepancy. A quantitative understanding thus requires theoretical efforts beyond the restricted primitive model of electrolytes.Comment: 16 pages, 2 figure

Tear fluid biomarkers in ocular and systemic disease: potential use for predictive, preventive and personalised medicine

In the field of predictive, preventive and personalised medicine, researchers are keen to identify novel and reliable ways to predict and diagnose disease, as well as to monitor patient response to therapeutic agents. In the last decade alone, the sensitivity of profiling technologies has undergone huge improvements in detection sensitivity, thus allowing quantification of minute samples, for example body fluids that were previously difficult to assay. As a consequence, there has been a huge increase in tear fluid investigation, predominantly in the field of ocular surface disease. As tears are a more accessible and less complex body fluid (than serum or plasma) and sampling is much less invasive, research is starting to focus on how disease processes affect the proteomic, lipidomic and metabolomic composition of the tear film. By determining compositional changes to tear profiles, crucial pathways in disease progression may be identified, allowing for more predictive and personalised therapy of the individual. This article will provide an overview of the various putative tear fluid biomarkers that have been identified to date, ranging from ocular surface disease and retinopathies to cancer and multiple sclerosis. Putative tear fluid biomarkers of ocular disorders, as well as the more recent field of systemic disease biomarkers, will be shown

Neutral and Charged Polymers at Interfaces

Chain-like macromolecules (polymers) show characteristic adsorption properties due to their flexibility and internal degrees of freedom, when attracted to surfaces and interfaces. In this review we discuss concepts and features that are relevant to the adsorption of neutral and charged polymers at equilibrium, including the type of polymer/surface interaction, the solvent quality, the characteristics of the surface, and the polymer structure. We pay special attention to the case of charged polymers (polyelectrolytes) that have a special importance due to their water solubility. We present a summary of recent progress in this rapidly evolving field. Because many experimental studies are performed with rather stiff biopolymers, we discuss in detail the case of semi-flexible polymers in addition to flexible ones. We first review the behavior of neutral and charged chains in solution. Then, the adsorption of a single polymer chain is considered. Next, the adsorption and depletion processes in the many-chain case are reviewed. Profiles, changes in the surface tension and polymer surface excess are presented. Mean-field and corrections due to fluctuations and lateral correlations are discussed. The force of interaction between two adsorbed layers, which is important in understanding colloidal stability, is characterized. The behavior of grafted polymers is also reviewed, both for neutral and charged polymer brushes.Comment: a review: 130 pages, 30 ps figures; final form, added reference

Unified Homogenization Theory for Magnetoinductive and Electromagnetic Waves in Split Ring Metamaterials

A unified homogenization procedure for split ring metamaterials taking into account time and spatial dispersion is introduced. The procedure is based on two coupled systems of equations. The first one comes from an approximation of the metamaterial as a cubic arrangement of coupled LC circuits, giving the relation between currents and local magnetic field. The second equation comes from macroscopic Maxwell equations, and gives the relation between the macroscopic magnetic field and the average magnetization of the metamaterial. It is shown that electromagnetic and magnetoinductive waves propagating in the metamaterial are obtained from this analysis. Therefore, the proposed time and spatially dispersive permeability accounts for the characterization of the complete spectrum of waves of the metamaterial. Finally, it is shown that the proposed theory is in good quantitative and qualitative agreement with full wave simulations.Comment: 4 pages, 3 figure

Pheromone communication in the model organism Nasonia vitripennis (Hymenoptera: Pteromalidae)

In insects chemical communication is an important channel to exchange information between and within species. Pheromones serve as transmitter for communication within species and are involved in the whole repertoire of insect behaviour. The focus of this doctoral thesis is on sex pheromones in the model organism Nasonia vitripennis (Hymenoptera: Pteromalidae), a haplodiploid parasitoid wasp. Males attract virgin females by deposits of a male sex pheromone: a mixture of (4R,5R)- and (4R,5S)-5-hydroxy-4-decanolide (HDL) and 4-methylquinazoline (4-MeQ) as a minor synergetic component. It has been shown that the HDL amount correlates with the functional fertility of males and works as a quality indicator for the females. During courtship males elicit females` receptivity by the release of a second pheromone, a so-called “aphrodisiac” that is not identified yet. In this doctoral thesis the influence of nutritional fatty acids on the male HDL titre was investigated and in the course of these experiments two new steps of HDL biosynthesis were identified. Furthermore the influence of the male body size on the HDL titre and on the mating success was analysed. Finally a new effect of the aphrodisiac in precopulatory courtship was revealed. Two fatty acids, namely linoleic acid (LA) and oleic acid (OA) could be identified as precursors for HDL biosynthesis. It was shown that N. vitripennis, as the first insect in the order Hymenoptera, is able to convert OA into LA, an ability known only from a few other animals before. LA is commonly biosynthesized from OA under involvement of a ∆12-desaturase. Two putative Nasonia genes, with the highest sequence homology to other insect ∆12-desaturase genes were expressed successfully in competent yeast cells. However none of the two genes could be determined as ∆12-desaturase gene. Nasonia females preferred hosts artificially enriched in OA and LA for oviposition. The male offspring developing in these hosts had higher sperm amounts and produced and released a higher amount of HDL and were able to attract more virgin females than males from hosts poor in OA and LA. Females of haplodiploid species are not able to produce sons of high reproductive success by choosing an attractive male. The results of this doctoral thesis demonstrate that females of haplodiploid parasitoids can increase the reproductive success by choosing hosts with high amounts of sex pheromone precursors for oviposition. Hosts were fed with different tissues of beef in order to simulate the variability of host quality on a cadaver, a natural habitat of Nasonia. The fatty acid compositions of the hosts were different and very similar to the one of their diet. Therefore parasitoid females supposedly also have the choice between hosts of different nutritional value in the field. Male body size was supposed to be a further factor influencing the HDL titre. Chemical analyses showed that large males are able to produce and release higher pheromone deposits than small males. However, in direct competition for a female the mating success of a large male and a small male did not differ, because of the high agility of small males. During courtship of Nasonia a second pheromone becomes important. When performing precopulatory courtship, males release a so-called “aphrodisiac” from an oral gland that elicits females` receptivity. It has been shown that simultaneously the “aphrodisiac” causes a behavioural switch in the females. A few minutes after coming in contact with the aphrodisiac, females` attraction to HDL was switched off, even without copulation and sperm transfer. This shows that a pheromone can inactivate the attractive effect of another pheromone. The results of this doctoral thesis provide new, exciting insights into pheromone communication of insects. Results showed that the diet of the hosts can influence the reproductive success of the male offspring. Hosts ingest primary nutrients from their diet that function as pheromone precursors of the parasitoids. Females are able to choose hosts with a high amount of sex pheromone precursors with the effect that their sons developing in these hosts have a high sex pheromone titre. Further results have shown that the body size can be positively correlated with sexual signalling; however mating success can be independent of body size in direct mate competition. Finally a new example of interaction of two sex pheromones was demonstrated: the inactivation of a pheromone with another pheromone

Overcoming the Marine Corps program managers' expenditure reporting delays

Marine Corps program managers at MARCORSYSCOM have a genuine need for timely and accurate expenditure reporting information in order to achieve effective planhing and budgeting for future programs. Since expenditures are not always recorded accurately during the reporting process, program managers experience delays.http://archive.org/details/overcomingmarine1094531404NANAU.S. Marine Corps (U.S.M.C.) author