Self-consistent field theory for obligatory coassembly

We present a first-order model for obligatory coassembly of block copolymers via an associative driving force in a nonselective solvent, making use of the classical self-consistent field (SCF) theory. The key idea is to use a generic associative driving force to bring two polymer blocks together into the core of the micelle and to employ one block of the copolymer(s) to provide a classical stopping mechanism for micelle formation. The driving force is generated by assuming a negative value for the relevant short-range Flory-Huggins interaction parameter. Hence, the model may be adopted to study micellization via H bonding, acceptor-donor interactions, and electrostatic interactions. Here, we limit ourselves to systems that resemble experimental ones where the mechanism of coassembly is electrostatic attraction leading to charge compensation. The resulting micelles are termed complex coacervate core micelles (CCCMs). We show that the predictions are qualitatively consistent with a wide variety of experimentally observed phenomena, even though the model does not yet account for the charges explicitly. For example, it successfully mimics the effect of salt on CCCMs. In the absence of salt CCCMs are far more stable than in excess salt, where the driving force for self-assembly is screened. The main limitations of the SCF model are related to the occurrence of soluble complexes, i.e., soluble, charged particles that coexist with the CCCM

Advances in the management of obesity in dogs

This article gives a short overview of the management of obesity in dogs and tells you more about the recent introduction of anti-obesity drugs. It is the authors’ opinion that no weight control programme in a veterinary practice can succeed without the active help of veterinary nurses. This article will help you understand the important principles underlying such a programme and answer some questions about setting up such a programme in a practice

Optimisation of two-stage screw expanders for waste heat recovery applications

It has previously been shown that the use of two-phase screw expanders in power generation cycles can achieve an increase in the utilisation of available energy from a low temperature heat source when compared with more conventional single-phase turbines. However, screw expander efficiencies are more sensitive to expansion volume ratio than turbines, and this increases as the expander inlet vapour dryness fraction decreases. For singlestage screw machines with low inlet dryness, this can lead to under expansion of the working fluid and low isentropic efficiency for the expansion process. The performance of the cycle can potentially be improved by using a two-stage expander, consisting of a low pressure machine and a smaller high pressure machine connected in series. By expanding the working fluid over two stages, the built-in volume ratios of the two machines can be selected to provide a better match with the overall expansion process, thereby increasing efficiency for particular inlet and discharge conditions. The mass flow rate though both stages must however be matched, and the compromise between increasing efficiency and maximising power output must also be considered. This research uses a rigorous thermodynamic screw machine model to compare the performance of single and two-stage expanders over a range of operating conditions. The model allows optimisation of the required intermediate pressure in the two- stage expander, along with the rotational speed and built-in volume ratio of both screw machine stages. The results allow the two-stage machine to be fully specified in order to achieve maximum efficiency for a required power output

The influence of long-term inputs of catch crops and cereal straw on yield, protein composition and technological quality of a spring and a winter wheat

Under conditions of restricted nitrogen (N) input such as in organic farming systems, crop N uptake must rely on N mineralised from applied animal manure, crop residues and native soil organic matter. Scarcity of N may impede the production of quality grain for bread production, and input and retention of N in soil are therefore important parameters for soil fertility. Toretain N in the crop-soilsystem, catch crops may be grown in breaks between main crops where they provide a significant sink for N mineralised in late summer and autumn (Thomsen, 2005). In corporation of straw may likewise retain mineralised N by microbial immobilisation (Christensen, 1986) and will also directly add to the N mineralisation potential when the N supplied in the straw accumulates (Thomsen & Christensen, 2004). Under northern European conditions, winter wheat may generally be of lower quality than spring wheat, but winter wheat has a higher yield potential. When the N uptake is mainly based on N mineralised from either applied or indigenous soil organic matter, however, this may even out the quality difference between winter and spring wheat as the longer growing season of winter wheat may boost its N utilisation. Growing conditions are highly important for protein quantity whereas main lygenetic factors influence protein composition (Amesetal., 1999; Luoetal., 2000). Wheat grain proteins have been classified as albumins, globulins, gliadins and glutenins on the basis of their solubility (Osborne, 1907). Reverse-phase (RP) high performance liquid chromatography (HPLC) allows the quantitative determination of these different flour protein groups together with single proteins (α5-, α1,2-, α-, γc-type gliadins, x- and γ-type high (HMW) and low (LMW) molecular weights subunits of glutenin) (Wieser & Seilmeier, 1998). The proteins can also be divided into polymers (glutenins) or monomers (gliadins, albumins, globulins) based on their aggregating properties. The polymeric proteins are critical for governing wheat flour processing properties, and their quantity and size distribution reliably measured by size-exclusion (SE) HPLC techniques have been shown to be important indicators of baking quality (Dachkevitch & Autran, 1989; Bateyetal., 1991). The aim of this study was to examine whether wheat yield and baking quality determined by chromatographic techniques together with rheological and chemical quality measurements could be improved by combining agronomic strategies consisting of wheat cultivars and long-term organic matter inputs. The variables tested were (A) a winter wheat and a spring wheat cultivar, (B) three catch crop strategies and (C) four straw incorporation rates

DFT Study on Structural and Mechanical Properties of Single-walled Carbon and Boron Nitride Nanotubes Functionalized with Carbenes

This paper presents quantum chemistry study on structural and mechanical properties of a series of single-walled carbon nanotubes (SWCNTs) and boron nitride nanotubes (BNNTs) functionalized with carbenes. At the PBE/SVP level, the obtained data on pristine nanotubes are in good accordance with the results of previous experimental and theoretical studies. The calculations show that carbenes functionalization, in general, distorts both SWNCTs and BNNTs frameworks, but there exists the difference between ‘axial’ and ‘circumferential’ functionalization. It turns out that in both cases elastic properties diminish with increasing concentration of adsorbents, however, the functionalized SWCNTs and BNNTs remain strong enough to be suitable for reinforcement of composites

A DFT Study on Electronic and Structural Properties of Graphene Nanoribbons

We carry out quantum chemistry calculations on armchair graphene nanoribbons (AGNRs) using density-functional theory. PVE/SVP results for the dependence of energies of the highest occupied (HOMO) and lowest unoccupied molecular orbitals (LUMO) as well as energy gaps on AGNR widths and lengths are presented. We compare the HOMO and LUMO energies of a series of AGNRs with those energies of fullerene C60 and its soluble derivative, PCBM, to ascertain whether it is possible to use such AGNRs as electron acceptors in organic solar cells. The influence of Stone-Wales defects embedded in the frameworks of AGNRs on their electronic properties is also studied

Application of Riccati-Bessel functions in light scattering

Riccati-Bessel functions, written as combinations of amplitude and phase functions, have been used to re-express Mie theory. This leads to a simple physical explanation of the scattered phase angle as the sum of a phase shift arising from the optical path difference across the particle radius and an interfacial phase difference at the surface of the particle. The mathematical properties of the different phase angles are examined in detail by treating the order as a continuous variable

The role of pollen morphology in plant systematic

Bascd on an invi tcd add ress to the V Palynological Symposium of APLE,Córdoba 27-29 Scptember !984A short historical background t o the s ub ject is g iven . The role of pol len morphology as a taxonomic char acter i s discussed a nd vari ous approaches to the study of pol len are considerad and describe d . The importance of studying the whole polleo grain and i ts potent ial contribut i on to the understand i ng of t he overall biology of the p l ant is emphasized . Exampl es illustrating these points are drawn f rom a number of groups. For example in t he sub family Papilionoideae (Leguminosae ) the exine stratification and apertura structure are shown to be more significant characters for distinguishi ng tri bal and gener ic categori es while ornamentati on i s of more importanc e at speci f ic leve! . The apparent adapta tion of ex i n e characters for bird poll i nation and the potential signifi cance of poll enki tt in t he f amily are discussed. The necessity to establ ish a l arge pollen data base espec i al ly i n t he large tropical plant fami l i es of economic i mportance is emphas i zed . The value of such a data base in understanding structural and f unct i onal homology is demonstrated in Papi l ionoideae and i t s i mpor tance in the i nterpretati on of t he fossil record in Palmae is outl ined . The value of pollen morphology in groups like Restionales 1 which ha ve ver y reduced macromorphologi cal character s 1 i s shown. The very uniform pol len mor phol ogy of t he smal l fami ly Mori ngaceae i s used as an example of how useful information can be deduced f rom data o f this kind. Mandragora (Solanaceae) with crypt oaperturate pollen exemplified how structure can be properly i nterpre ted by r esorting to a wide range of techniques for prepar ation and study . Recent advances in techniques for study of pollen de vel opment and compara ti ve ontogeny and f unctional roles of pollen are considered bri efly . Pollen of sorne representatives of the tri be Vicieae (Papilionoideae ) are illustrated to show the var~ation in exine ornamentation and stratification and to emphasise the need for more TEM in t his group. An extensive bibliography in included.Se da una breve revis i ón del tema . morfología polínica como carácter taxonómico , diversos aspectos del estudio del pol en . Se Se d i scute el papel de l a cons i der ando y descr ibi endo resalta la importancia de l estudio del grano de polen como un todo ún i co y su potencia l contribución al entendimiento de La biologia de las plantas . Se dan ejempl os que i lustran est os aspectos en una serie de grupos vegetales . Por ejemplo , en Papilionoideae (Legwninosac ) la estratificación de l a o;:üna y la estruc tura de l as ape rturas son los caracteres mas significativos para l a segregación de las ca tegorías tribales y genéricas , mien tras que la ornamentación es de mayor importancia a nivel espec ífico. Se discute también la adaptaci ón aparente de los caracteres de la exina para la pol i nización por pájaros y e l signi f i cado po tenc ial del pollen-kitt en la familia. Se resalta la necesidad de establecer una adecuada base de datos polinices en las grandes familias tropical es de importancia económica . Se demuestra en Papilionoideac el valor de tal base de datos en el entend imiento de las homologías es tructura l es y funcionales 1 y se subraya su importanc1a en la interpretación de l os restos fósi les de Palmae . Se muestra el valor de l a morfología en grupos como Restionales 1 que tiene muy reduc idos caracteres macromorfológicos . La muy uniforme morfología pol í nica de la pequeña fami l ia Moringaceae se usa como ejemplo de como se puede deducir úti l i nformación de datos de est e tipo . Mandragora (Solanaccae) con polen criptoaperturado ejempl i fica como la estructura puede ser interpretada con el empleo de un buen número de técnicas de preparación y es tudio . También se cons ideran recientes avances en técni cas de estudio para el mejor entendimi ento de la ontogenia comparada y la funcionalidad del polen . Se ilustra el pol en de algunos representantes de la tri bu Vicieae {Papilionoideae ) para mostrar la variación en la ornamentación y estratifi cación de la ex ina y para resaltar la necesidad de mas estudios a TEM en este grupo . Se incluye una extensa bi bliografía

Structural and Mechanical Properties of Fluorinated SWCNTs: a DFT Study

This paper presents a study on structural and mechanical properties of a series of fluorinated armchair single-walled carbon nanotubes (SWCNTs) by using density functional theory. At the PBE / SVP level, the data obtained compare well with experimental and theoretical studies. The results show that fluorination, in general, distort SWNCTs framework, but there exists the difference between ‘axial’ and ‘circumferential’ functionalization. It turns out that elastic properties diminish with increasing concentration of adsorbents, however, the fluorinated SWCNTs remain strong enough to be suitable for reinforcement of composites