The effective hydrodynamic radius of single DNA-grafted colloids as measured by fast Brownian motion analysis

Optical tweezers accomplished with fast position detection enable one to carry out Brownian motion analysis of single DNA-grafted (grafting density: ∼1000 molecules per particle, molecular weight: 4000 bp) colloids in media of varying NaCl concentration. By that the effective hydrodynamic radius of the colloid under study is determined and found to be strongly dependent on the conformation of the grafted DNA chains. Our results compare well both with recent measurements of the pair interaction potential between DNA-grafted colloids (Kegler et al. Phys Rev Lett 2008; 100:118302) and with microfluidic studies (Gutsche et al. Microfluid Nanofluid 2006; 2:381-386). The observed scaling of the brush height with the ion concentration is in full accord with the theoretical predictions by Pincus, Zhulina, Birshtein and Borisov.     

Altruism on American Television: Examining the Amount of, and Context Surrounding, Acts of Helping and Sharing

Using a representative sample of television content featuring 2,227 programs across different genres and 18 different channels, the frequency and context of altruistic actions were content analyzed. A social cognitive theory approach was taken to guide the selection of contextual variables. The results showed that 73% of the programs in the sample featured instances of helping/sharing at a rate of 2.92 incidents per hour. Further, the actions were most likely to be initiated by adult White males and many acts were depicted in a humorous, realistic, and rewarding context. In terms of channel differences, shows on children's basic cable featured not only the highest proportion of programs with one or more instances of altruism but also the highest rate per hour (4.02 acts). Differences in contextual features and channel type are discussed in terms of social cognitive theory below.     

Cognitive and learning difficulties and how they affect access to IT systems

In October 2005, the IBM Human Ability and Accessibility Center and T.J. Watson Research Center hosted a symposium on “cognitive and learning difficulties and how they affect access to IT systems”. The central premise of the symposium was the recognition that cognitive and learning difficulties have a profound impact on a person’s ability to interact with information technology (IT) systems, but that little support is currently being offered by those systems. By bringing together internationally renowned experts from a variety of different, but complementary, research fields, the symposium aimed to provide a complete overview of the issues related to this topic. This paper summarises the discussions and findings of the symposium.     

Interactions of Fibroblasts with Different Morphologies Made of an Engineered Spider Silk Protein

Spider silk has been investigated for decades due to the intriguing mechanical and also biomedical properties of the silk fibers. Previously, it has been shown that recombinant silk proteins can also be processed into other morphologies. Here, we characterized scaffolds made of the recombinant spider silk protein eADF4(C16) concerning their surface interactions with fibroblasts. Studies of BALB/3T3 cells on hydrogels and films made of eADF4(C16) showed low cell adhesion without observable duplication. Electro‐spun non‐woven scaffolds made of eADF4(C16), however, enabled both their adhesion and proliferation. Since eADF4(C16) lacks specific motifs for cell attachment, fibroblasts cannot generate focal adhesions with the material's surface, and, therefore, other cell–interface interactions such as topographical anchorage or cell attachment mediated by adhesion of extracellular matrix proteins are discussed in this paper. On non‐woven meshes protrusion of filopodia and/or lamellipodia between individual fibers increase the surface contact area, which depends on the diameter of the fibers of the non‐woven meshes. In contrast, at flat (film) or microstructured surfaces (hydrogels) such interactions seem to be precluded.     

Novel TTLL5 Variants Associated with Cone-Rod Dystrophy and Early-Onset Severe Retinal Dystrophy

Variants of the TTLL5 gene, which encodes tubulin tyrosine ligase-like family member five, are a rare cause of cone dystrophy (COD) or cone-rod dystrophy (CORD). To date, only a few TTLL5 patients have been clinically and genetically described. In this study, we report five patients harbouring biallelic variants of TTLL5. Four adult patients presented either COD or CORD with onset in the late teenage years. The youngest patient had a phenotype of early onset severe retinal dystrophy (EOSRD). Genetic analysis was performed by targeted next generation sequencing of gene panels and assessment of copy number variants (CNV). We identified eight variants, of which six were novel, including two large multiexon deletions in patients with COD or CORD, while the EOSRD patient harboured the novel homozygous p.(Trp640*) variant and three distinct USH2A variants, which might explain the observed rod involvement. Our study highlights the role of TTLL5 in COD/CORD and the importance of large deletions. These findings suggest that COD or CORD patients lacking variants in known genes may harbour CNVs to be discovered in TTLL5, previously undetected by classical sequencing methods. In addition, variable phenotypes in TTLL5-associated patients might be due to the presence of additional gene defects.     

An on-line contingency filtering scheme for dynamic securityassessment

This paper describes the philosophy and development of a contingency screening system for the selection and ranking of dynamic security assessment. The most severe cases are identified and ranked high on the contingency list for more exact analysis. The nonsevere cases are filtered out of the list. In the proposed system, a cascade of more restrictive filters is developed based on the sparse transient energy function method     

Efficient Modular Synthesis of Isomeric Mono‐ and Bispyridyl[2.2]paracyclophanes by Palladium‐Catalyzed Cross‐ Coupling Reactions

Pyridyl‐substituted [2.2]paracyclophanes build a multifunctional structural motif that is useful in material chemistry, catalysis and for luminescent structures. Nonetheless, there is still a lack of general methods for the synthesis of these structures tolerating easily accessible bromides as well as different isomeric pyridyl groups. Hence the coupling of functionalized [2.2]paracyclophanes with various substituted and functionalized pyridyl derivatives was achieved using Stille, Suzuki and Kumada coupling conditions. Hereby the Stille coupling of a [2.2]paracyclophane is presented as a versatile reaction for the formation of heteromeric [2.2]paracyclophane‐containing biaryl structures.

     

Influence of nutrition level on digestibility in high yielding cows and effects on energy evaluation systems

The objective of the study was to determine the effect of nutrition level (NL, multiples of maintenance energy requirement) on the digestibility of nutrients for dairy cows regarding the energy supply of the animal. The digestion of nutrients and energy was investigated in two trials using lactating dairy cows. The NL varied from 2.7 to 5.0 using diets similar composition. In addition, sheep were given the same feed with a NL of 1.4. Digestibility of dry matter (DM) and all specific measures of dietary components declined significantly as NL increased. Digestibility of energy decreased by 4.1% for each increase in NL. The metabolizable energy, the ability to metabolize energy (metabolizable energy/gross energy), and the content of net energy for lactation (NE(L)) per kilogram of DM intake were calculated for NL from 1 to 6 on the basis of these relationships and as well as the gross energy, methane energy, and urine energy. Accordingly the NEL content declined by 0.11 MJ/kg of DM intake or 1.6% as the NL increased by one unit. It means that the NE(L) requirement above the maintenance requirement increased by 0.07 MJ of NE(L) per kilogram of fat-corrected milk, if the NL increased by one unit.     

Drag reduction by DNA-grafting for single microspheres in a dilute λ-DNA solution

The fluid resistance of single micrometre-sized blank and DNA-grafted polystyrene microspheres under shear flow is compared in purified water and dilute λ-DNA solutions by means of optical tweezers experiments with a high spatial (±4 nm) and temporal (±0.2 ms) resolution. The measurement results show that the drag experienced by a colloid in a dilute λ-DNA solution (molecular weight of 48,502 bp per molecule, radius of gyration of 0.5 μm) is significantly decreased if the microsphere bears a grafted DNA brush. This newly discovered drag reduction effect is studied for different parameters, comprising the molecular weight of the grafted DNA molecules (250 bp, 1000 bp and 4000 bp), the concentration of the λ-DNA solution (11, 17 and 23 μg ml^?1, all being significantly smaller than the critical entanglement concentration c¹), the microsphere core diameter (2 μm, 3 μm and 6 μm) as well as the flow speed of the medium (10–50 μm s^?1). The maximum extent of the drag reduction is found to amount to (60 ± 20)% compared to the λ-DNA-induced contribution on the drag acting on blank colloids. We propose a theoretical explanation of this effect based on the combination of the dynamic density functional theory of Rauscher and co-workers [Rauscher M. J. Phys.: Condens. Matter 2010;22:364109] and the stagnation length theory of polymer brushes, as it was established by Kim, Lobaskin et al. [Kim et al. Macromolecules 2008;42(10):3650–3655]. In particular, the solution of the Stokes equation (i.e., the Navier–Stokes equation for creeping flow) for the studied system yields a numerical prediction that is found to be in full accord with our experimental results within measurement uncertainty.