Direct application of UNIFAC activity coefficient computer programs to the calculation of solvent activities and .chi.-parameters for polymer solutions

Application of UNIFAC computer calculations to polymer solutions does not seem to make sense because of the value of the solvent activity: close to 1.000 over a considerable range of concentrations (up to 90% of polymer). A simple procedure is proposed to calculate solvent activity coefficients, and thus X-parameters, such that the easily available UNIFAC computer programs may be applied directly, without any modification

Transport in nanofluidic systems: a review of theory and applications

In this paper transport through nanochannels is assessed, both of liquids and of dissolved molecules or ions. First, we review principles of transport at the nanoscale, which will involve the identification of important length scales where transitions in behavior occur. We also present several important consequences that a high surface-to-volume ratio has for transport. We review liquid slip, chemical equilibria between solution and wall molecules, molecular adsorption to the channel walls and wall surface roughness. We also identify recent developments and trends in the field of nanofluidics, mention key differences with microfluidic transport and review applications. Novel opportunities are emphasized, made possible by the unique behavior of liquids at the nanoscale

The Failure of Local and Federal Prosecutors to Curb Police Brutality

Although police departments across the country have attempted to ameliorate the hostility between police officers and the cumminity, through careful screening of applicants, minority recruitment, and community policing, police brutality remains a problem within our urban cities. This Essay will first argue that police brutality is largely ignored. Second, it will examine the obstacles facing local and federal prosecutors in obtaining convictions. Then it will compare the advantages and disadvantages of delegating primary responsibility for these cases to the state versus the federal level. Finally, it will argue that, although there are obstacles and advantages for both local and federal prosecutors, ultimately justice is best seved when police brutality is primarily pursued by local prosecutors

Quantification of dynamics of soil-borne pathogens and their consequences for yield in crop rotations

In The Netherlands crop rotation experiments were performed that required a continuation over many years so that long term effects of treatments and rotations may build up. Usually, analysis of variance is performed on within year data or on data from the final years when treatment/rotation effects are maximal. In this thesis the scope is on rotation experiments in the presence of soil-borne pathogens. Instead of estimating the mean densities of these pathogens and the mean yields of the crops over the whole duration of the experiment, dynamics of the pathogens and yield were registered yearly. Two types of dynamical models were applied. In the first model the dependence of the final  (end of the season) pathogen density upon the initial density was represented by a monotonically rising function. The model was applied to an experiment on the dynamics of Pratylenchus penetrans in vegetable crops. In the second model with a Ricker type of functional relation between initial and final pathogen densities, the dynamics of Globodera pallida on 6 cultivars of potato was studied. In both models the pathogen density tended to a stable steady state in the long term. For this steady state an economic evaluation of crop rotations was made. In a third study potato tuber yield was predicted taking into account the presence of three nematode species and the fungus V. dahliae. Also the effect of abiotic factors such as pH and the P content of the soil were taken in consideration. Based on information theory the results of a large class of feasible models was combined by using a suitable method of averaging values of parameters of the different models. Moreover, this method also ranks the predictors with respect to their predictive power. In a fourth study, optimum designs of experiments on pathogen dynamics and yield loss were derived for one of the cultivars already tested in the second study. Furthermore, a measure for the efficiency of a design was introduced so that designs can be compared.&nbsp

Observation of anomalous Hanle spin precession lineshapes resulting from interaction with localized states

It has been shown recently that in spin precession experiments, the interaction of spins with localized states can change the response to a magnetic field, leading to a modified, effective spin relaxation time and precession frequency. Here, we show that also the shape of the Hanle curve can change, so that it cannot be fitted with the solutions of the conventional Bloch equation. We present experimental data that shows such an effect arising at low temperatures in epitaxial graphene on silicon carbide with localized states in the carbon buffer layer. We compare the strength of the effect between materials with different growth methods, epitaxial growth by sublimation and by chemical vapor deposition. The presented analysis gives information about the density of localized states and their coupling to the graphene states, which is inaccessible by charge transport measurements and can be applied to any spin transport channel that is coupled to localized states.Comment: 6 pages, 6 figure

Factoranalyse voor het verklaren van opbrengst- en gehalteverschillen tussen percelen cichorei : factoranalyse uitgevoerd op de I-top databestanden van de jaren 2003, 2004, 2005 en 2006

In de cichoreiteelt wordt sinds 2003 gewerkt met het teeltregistratiesysteem I-top. In dit systeem wordt geregistreerd hoe de teelt op de diverse percelen wordt uitgevoerd. Het doel van het systeem is om inzicht te krijgen in de teeltfactoren die met name de wortelopbrengst, het inulinegehalte en de inuline-opbrengst van de cichorei bepalen. Op basis van dit inzicht kan de teeltadvisering verbeterd worden, terwijl daarnaast ook vastgesteld kan worden aan welke factoren eventueel extra onderzoek nodig is. In het onderzoek dat in dit rapport beschreven wordt is een factoranalyse uitgevoerd op de databestanden van de jaren 2003 t/m 2006. Met behulp van een factoranalyse kan inzicht verkregen worden in de samenhang tussen de variabelen die in de datasets aanwezig zij

Morse theory on spaces of braids and Lagrangian dynamics

In the first half of the paper we construct a Morse-type theory on certain spaces of braid diagrams. We define a topological invariant of closed positive braids which is correlated with the existence of invariant sets of parabolic flows defined on discretized braid spaces. Parabolic flows, a type of one-dimensional lattice dynamics, evolve singular braid diagrams in such a way as to decrease their topological complexity; algebraic lengths decrease monotonically. This topological invariant is derived from a Morse-Conley homotopy index and provides a gloablization of `lap number' techniques used in scalar parabolic PDEs. In the second half of the paper we apply this technology to second order Lagrangians via a discrete formulation of the variational problem. This culminates in a very general forcing theorem for the existence of infinitely many braid classes of closed orbits.Comment: Revised version: numerous changes in exposition. Slight modification of two proofs and one definition; 55 pages, 20 figure