Omniphobic “RF Paper” Produced by Silanization of Paper with Fluoroalkyltrichlorosilanes

The fabrication and properties of “fluoroalkylated paper” (“R^F paper”) by vapor‐phase silanization of paper with fluoroalkyl trichlorosilanes is reported. R^F paper is both hydrophobic and oleophobic: it repels water (θ_app^H2^O>140°), organic liquids with surface tensions as low as 28 mN m^‐1, aqueous solutions containing ionic and non‐ionic surfactants, and complex liquids such as blood (which contains salts, surfactants, and biological material such as cells, proteins, and lipids). The propensity of the paper to resist wetting by liquids with a wide range of surface tensions correlates with the length and degree of fluorination of the organosilane (with a few exceptions in the case of methyl trichlorosilane‐treated paper), and with the roughness of the paper. R^F paper maintains the high permeability to gases and mechanical flexibility of the untreated paper, and can be folded into functional shapes (e.g., microtiter plates and liquid‐filled gas sensors). When impregnated with a perfluorinated oil, R^F paper forms a “slippery” surface (paper slippery liquid‐infused porous surface, or “paper SLIPS“) capable of repelling liquids with surface tensions as low as 15 mN m^‐1. The foldability of the paper SLIPS allows the fabrication of channels and flow switches to guide the transport of liquid droplets.     

Single-electrolyte isotachophoresis using a nanochannel-induced depletion zone

Isotachophoretic separations are triggered at the border of a nanochannel-induced ion-depleted zone. This depletion zone acts as a terminating electrolyte and is created by concentration polarization over the nanochannel. We show both continuous and discrete sample injections as well as separation of up to four analytes. Continuous injection of a spacer compound was used for selective analyte elution. Zones were kept focused for over one hour, while shifting less than 700 μm. Moreover, zones could be deliberately positioned in the separation channel and focusing strength could be precisely tuned employing a three-point voltage actuation scheme. This makes depletion zone isotachophoresis (dzITP) a fully controllable single-electrolyte focusing and separation technique. For on-chip electrokinetic methods, dzITP sets a new standard in terms of versatility and operational simplicity.     

Steel Quality Improvement Potentials in the Continuous Casting Process Using State of the Art Refractory Flow Control Systems

In the continuous casting process for high quality steel grades, activities are mainly focused on avoiding reoxidation and promoting non-metallic inclusion removal during steel transfer from the ladle through the tundish to the mould. In this paper, methods to effectively control flow from the tundish to the continuous casting mould are described and specific state of the art refractory solutions are also introduced.     

Bottom-gated epitaxial graphene

High-quality epitaxial graphene on silicon carbide (SiC) is today available in wafer size. Similar to exfoliated graphene, its charge carriers are governed by the Dirac-Weyl Hamiltonian and it shows excellent mobilities. For many experiments with graphene, in particular for surface science, a bottom gate is desirable. Commonly, exfoliated graphene flakes are placed on an oxidized silicon wafer that readily provides a bottom gate. However, this cannot be applied to epitaxial graphene as the SiC provides the source material out of which graphene grows. Here, we present a reliable scheme for the fabrication of bottom-gated epitaxial graphene devices, which is based on nitrogen (N) implantation into a SiC wafer and subsequent graphene growth. We demonstrate working devices in a broad temperature range from 6 to 300 K. Two gating regimes can be addressed, which opens a wide engineering space for tailored devices by controlling the doping of the gate structure.     

Towards ready-to-use 3-D scaffolds for regenerative medicine: adhesion-based cryopreservation of human mesenchymal stem cells attached and spread within alginate–gelatin cryogel scaffolds

Cultivation and proliferation of stem cells in three-dimensional (3-D) scaffolds is a promising strategy for regenerative medicine. Mesenchymal stem cells with their potential to differentiate in various cell types, cryopreserved adhesion-based in fabricated scaffolds of biocompatible materials can serve as ready-to-use transplantation units for tissue repair, where pores allow a direct contact of graft cells and recipient tissue without further preparation. A successful cryopreservation of adherent cells depends on attachment and spreading processes that start directly after cell seeding. Here, we analyzed different cultivation times (0.5, 2, 24 h) prior to adhesion-based cryopreservation of human mesenchymal stem cells within alginate–gelatin cryogel scaffolds and its influence on cell viability, recovery and functionality at recovery times (0, 24, 48 h) in comparison to non-frozen control. Analysis with confocal laser scanning microscopy and scanning electron microscopy indicated that 2 h cultivation time enhanced cryopreservation success: cell number, visual cell contacts, membrane integrity, motility, as well as spreading were comparable to control. In contrast, cell number by short cultivation time (0.5 h) reduced dramatically after thawing and expanded cultivation time (24 h) decreased cell viability. Our results provide necessary information to enhance the production and to store ready-to-use transplantation units for application in bone, cartilage or skin regenerative therapy.     

Epoxide and thiirane toxicity in vitro with the ciliates Tetrahymena pyriformis: structural alerts indicating excess toxicity

The 48 h toxicity of 18 organic narcotics, 13 epoxides, and 2 thiiranes toward the ciliates Tetrahymena pyriformis was determined in terms of 50% growth inhibition EC(50). Nominal EC(50) was corrected for volatilization and sorption to quantify the freely dissolved compound fraction in solution. The derived baseline narcosis model served to evaluate toxicity enhancements T(e) as ratios of narcosis-predicted over experimental EC(50) values. Among the nine heterocycles with aliphatic side chains that include two thiiranes, three compounds yielded T(e) > 10, suggesting their covalent binding at nucleophilic protein sites such as -OH, -NHR, and -SH through S(N)2-type ring-opening. As a general trend of this group, T(e) decreases with increasing alkyl group size. Moreover, four of the six nonaliphatic epoxides exerted substantial excess toxicities with T(e) > 10, which could be rationalized by ring-opening activation through negative inductive effect, benzylic stabilization, and phenyl ring H-bonding. By contrast, 1,2 substituted epoxides showed narcosis-level toxicity, despite the opportunity of side-chain Schiff-base formation with protein amino groups. The resulting structural alerts enable an in silico screening of epoxides and thiiranes for their potential to exert excess toxicity. Note that observed differences in T(e) sensitivity between ciliates, bacteria and fish should be taken into account when designing in vitro alternatives to fish toxicity studies.     

Porous SiC Ceramics Derived from Tailored Wood-Based Fiberboards

Specific modification of properties such as porosity and pore size of engineered wood-based source material enables the custom design of porous wood-derived SiC that is produced by carbothermal reduction between the carbonized wood-based material and an infiltrated silica sol. In contrast to bulk wood, the anisotropic shrinkage of the source material is less distinctive and can be controlled. Furthermore, the obtained structural properties of the material are isotropic. Material processing and properties of the wood-derived ceramic material are described in this paper.     

Social environment and reproduction in female European rabbits (Oryctolagus cuniculus): Benefits of the presence of litter sisters.

The authors investigated in an observational study the consequences of the presence of litter sisters on the social interactions and on reproductive performance of young female European rabbits (Oryctolagus cuniculus) from a population living under seminatural conditions. In early winter, when all young females were settled in a social group, they were characterized by the presence or absence of litter sisters in their groups. Females with litter sisters in their groups displayed significantly more positive social interaction with females of their social group compared to females without sisters, whereas this difference was mainly due to the high frequency of positive social interactions among the respective sisters. Such differences between the females of both categories were already apparent during the animals' juvenile phase, before the females integrated into a particular group: females which later had litter sisters in their group showed more positive social behavior than females which later no longer had litter sisters. During their first breeding season, females with litter sisters present generally started to breed earlier by an average of 14 days. A more favorable social environment might have possibly facilitated the earlier onset of breeding in females with present litter sisters by attenuating the negative consequences of stress. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modular specification and verification of XTP

The transfer protocol framework supports the formal specification and verification of data transfer protocols. It consists of generic specification modules and theorems. Compositions of specification module instances result in well-structured specifications which describe a protocol, the medium used, and the service provided by means of TLA formulas. The protocol verification is based on the proof of the logical implication between protocol and service specification. Due to the modular structuring of the specifications, this proof can be decomposed into a set of subimplications which correspond directly to theorems of the framework. Therefore, the development of formal specifications as well as the protocol verification can be reduced to the instantiation and arrangement of framework elements. The flexibility of the framework opens its application for a broad spectrum of data transfer protocols. We outline the principles of the framework and concentrate on its application to the high-speed transfer protocol XTP. Because of the framework support, the formal modeling and analysis of this modern and function-rich protocol was manageable and identifies deficiencies of the current protocol definition clearly.