Kwantitatieve bemonstering van benthos en bodem voorafgaand aan zandsuppleties bij Texel (nulmeting)

Dit rapport beschrijft een kwantitatieve inventarisatie (nulmeting) van de bodemfauna (benthos) en de bodemsamenstelling (sediment) nabij de noordwest punt van Texel, voorafgaand aan suppletiewerken van Rijkswaterstaat in 2009. Dit betreft een vooroeversuppletie van 1.300.000 kubieke meter zand bij de Eierlandse dam bij Texe

Swelling of 9 polymers commonly employed for solvent-resistant nanofiltration membranes: A comprehensive dataset

The presence of a solvent in a dense polymeric nanofiltration membrane layer can affect the macromolecular dynamics of the polymer material and the mobility of the solvent penetrant molecules. In addition, even the affinity of the swollen material for the solvent molecules can be distinct from that of the pure polymer material. These effects can substantially affect the membrane's performance. This paper provides sorption and swelling data of 9 thin polymer films that are commonly used for organic solvent nanofiltration (P84, Matrimid, PEI, PAN, PES, PSf, PEBAX, PTMSP, PDMS) swollen by 10 common solvents (hexane, toluene, dichloromethane, ethyl acetate, methyl ethyl ketone, acetone, isopropanol, ethanol, methanol, water). The paper describes the swelling dynamics during short-term solvent exposure (0–8 h), assesses the stability upon long-term solvent exposure (up to 2 months), and provides quantitative data on the solvent volume fractions inside the swollen layers. Among the surprising findings are the glubbery behavior of PTMSP and the completely different response of PES and PSf to toluene exposure. The results of this work demonstrate three crucial findings relevant to organic solvent nanofiltration membranes and other applications: 1. For many polymers, the swelling changes over long timescales of up to 2 months and longer. Results obtained on short timescales do however not always allow for direct extrapolation to longer time scales.2. Structural similarity of polymers does not guarantee similar swelling behavior.3. Swelling behavior of solvents cannot be solely explained by classifying solvents into aprotic, polar aprotic and polar protic solvents.The results of this work can aid in constructing transport models and can help predicting polymer-solvent compatibility and membrane performance in OSN applications

The Functions of RNA-Dependent RNA Polymerases in Arabidopsis

One recently identified mechanism that regulates mRNA abundance is RNA silencing, and pioneering work in Arabidopsis thaliana and other genetic model organisms helped define this process. RNA silencing pathways are triggered by either self-complementary fold-back structures or the production of double-stranded RNA (dsRNA) that gives rise to small RNAs (smRNAs) known as microRNAs (miRNAs) or small-interfering RNAs (siRNAs). These smRNAs direct sequence-specific regulation of various gene transcripts, repetitive sequences, viruses, and mobile elements via RNA cleavage, translational inhibition, or transcriptional silencing through DNA methylation and heterochromatin formation. Early genetic screens in Arabidopsis were instrumental in uncovering numerous proteins required for these important regulatory pathways. Among the factors identified by these studies were RNA-dependent RNA polymerases (RDRs), which are proteins that synthesize siRNA-producing dsRNA molecules using a single-stranded RNA (ssRNA) molecule as a template. Recently, a growing body of evidence has implicated RDR-dependent RNA silencing in many different aspects of plant biology ranging from reproductive development to pathogen resistance. Here, we focus on the specific functions of the six Arabidopsis RDRs in RNA silencing, their ssRNA substrates and resulting RDR-dependent smRNAs, and the numerous biological functions of these proteins in plant development and stress responses