Release Properties of Pressurized Microgel Templated Capsules

Direction‐specific release induced through osmotic pressure inside giant microcapsules is realized and monitored at high and low concentrations of encapsulated polymer. A clear correlation between the release kinetics upon opening the shell and encapsulated polymer concentration is observed. This has been independently confirmed by shell opening via nanoindentation and laser radiation. To quantify these observations, the internal pressure of the capsules is determined by analysis of mechanical tests performed via colloidal probe AFM. As expected, larger amounts of encapsulated material lead to increased internal pressures and enhanced release kinetics. The results show how drug release can be accelerated by encapsulation of osmotic pressure generating species. Such pressurized capsules systems show large ejection velocities and are envisioned as an inexpensive biolistic transfection device for in vitro applications.     

Bacterial siderophores promote dissolution of UO2 under reducing conditions

Tetravalent actinides are often considered environmentally immobile due to their strong hydrolysis and formation of sparingly soluble oxide phases. However, biogenic ligands commonly found in the soil environment may increase their solubility and mobility. We studied the adsorption and dissolution kinetics of UO2 in the presence of a microbial siderophore, desferrioxamine-B (DFO-B), under reducing conditions. Using batch and continuous flow stirred tank reactors (CFSTR),we found that DFO-B increases the solubility of UIV and accelerates UO2 dissolution rates through a ligand-promoted dissolution mechanism. DFO-B adsorption to UO2 followed a Langmuir-type isotherm. The maximum adsorbed DFO-B concentrations were 3.3 micromol m(-2) between pH 3 and 8 and declined above pH 8. DFO-B dissolved UO2 at a DFO-B surface-saturated net rate of 64 nmol h(-1) m(-2) (pH 7.5, l = 0.01 M) according to the first-order rate equation R = kL[Lads], with a rate coefficient kL of 0.019 h(-1). Even at very low siderophore concentrations (e.g. 1 microM), net dissolution rates (16 nmol h(-1) m(-2), pH 7.5, l = 0.01 M) were substantially greater than net proton-promoted dissolution rates (3 nmol h(-1) m(-2), pH 7-7.5, l = 0.01 M). Interestingly, adding dissolved FeIII had negligible effects on DFO-B-promoted UO2 dissolution rates, despite its potential as a competitor for DFO-B and as an oxidant of UIV. Our results suggest that strong organic ligands could influence the environmental mobility of tetravalent actinides and should be considered in predictions for nuclear waste storage and remediation strategies.     

A density dependent dispersion correction

Density functional approximations fail to provide an accurate treatment of weak interactions. More recent, but not readily available functionals can lead to significant improvements. A simple alternative to correct for the missing weak interactions is to add, a posteriori, an atom pair-wise dispersion correction. We here present a density dependent dispersion correction, dDXDM, which dramatically improves the performance of popular functionals (e.g., PBE-dDXDM or B3LYP-dDXDM) for a set of 145 systems featuring both inter- and intramolecular interactions. Whereas the highly parameterized M06-2X functional, the long-range corrected LC-BLYP and the fully non-local van der Waals density functional rPW86-W09 also lead to improved results as compared to standard DFT methods, the enhanced performance of dDXDM remains the most impressive.     

Free volume distribution at the Teflon AF/silicon interfaces probed by a slow positron beam

We performed positron annihilation lifetime spectroscopy experiments at Teflon AF^®/silicon interfaces as function of the positron implantation energy to determine the free volume hole size distribution in the interfacial region and to investigate the width of the interphase. While no interphase was detected in very short chained solvent-free, thermally evaporated Teflon AF^®, an interphase of some tens of nm in extension was observed for high molecular weight spin-coated Teflon AF^® films. Influences of the native oxide layer on the data evaluation could be ruled out.     

Origin of Work Function Modification by Ionic and Amine‐Based Interface Layers

Work function modification by polyelectrolytes and tertiary aliphatic amines is found to be due to the formation of a net dipole at the electrode interface, induced by interaction with its own image dipole in the electrode. In polyelectrolytes differences in size and side groups between the moving ions lead to differences in approach distance towards the surface. These differences determine magnitude and direction of the resulting dipole. In tertiary aliphatic amines the lone pairs of electrons are anticipated to shift towards their image when close to the interface rather than the nitrogen nuclei, which are sterically hindered by the alkyl side chains. Data supporting this model is from scanning Kelvin probe microscopy, used to determine the work function modification by thin layers of such materials on different substrates. Both reductions and increases in work function by different materials are found to follow a general mechanism. Work function modification is found to only take place when the work function modification layer (WML) is deposited on conductors or semiconductors. On insulators no effect is observed. Additionally, the work function modification is independent of the WML thickness or the substrate work function in the range of 3 to 5 eV. Based on these results charge transfer, doping, and spontaneous dipole orientation are excluded as possible mechanisms. This understanding of the work function modification by polyelectrolytes and amines facilitates design of new air‐stable and solution‐processable WMLs for organic electronics.     

Network Virtualization: A Viable Path Towards the Future Internet

New technologies as well as new ways of using network services are rapidly changing the Internet’s landscape. These developments will have far-reaching implications for the architecture of the networks of the future. However, the current Internet design is plagued with a number of fundamental limitations, which makes its use as the sole basis for the networking applications of the future questionable. We believe that the Future Internet must allow the co-existence of diverse network designs and paradigms, both new and old, to remain open to innovation and meet the challenges of the future. In this paper, we propose to use network virtualization, embedded in an architectural framework, to achieve this goal and to lay the foundation for the deployment of novel concepts such as content-centric networking.

Estradiol (E2) Improves Glucose-Stimulated Insulin Secretion and Stabilizes GDM Progression in a Prediabetic Mouse Model

Female New Zealand obese (NZO) mice are an established model of preconceptional (pc.) prediabetes that progresses as gestational diabetes mellitus (GDM) during gestation. It is known that NZO mice show improvement in insulin sensitivity and glucose-stimulated insulin secretion (GSIS) during gestation in vivo. The latter is no longer detectable in ex vivo perifusion experiments in isolated islets of Langerhans, suggesting a modulation by extrapancreatic factors. Here, we demonstrated that plasma 17β-estradiol (E2) levels increased markedly in NZO mice during gestation. The aim of this work was to determine whether these increased E2 levels are responsible for the improvement in metabolism during gestation. To achieve this goal, we examined its effects in isolated islets and primary hepatocytes of both NZO and metabolically healthy NMRI mice. E2 increased GSIS in the islets of both strains significantly. Hepatic glucose production (HGP) failed to be decreased by insulin in NZO hepatocytes but was reduced by E2 in both strains. Hepatocytes of pregnant NZO mice showed significantly lower glucose uptake (HGU) compared with NMRI controls, whereby E2 stimulation diminished this difference. Hepatocytes of pregnant NZO showed reduced glycogen content, increased cyclic adenosine monophosphate (cAMP) levels, and reduced AKT activation. These differences were abolished after E2 stimulation. In conclusion, our data indicate that E2 stabilizes and prevents deterioration of the metabolic state of the prediabetic NZO mice. E2 particularly increases GSIS and improves hepatic glucose utilization to a lower extent.     

Role of Serotonin (5-HT) in GDM Prediction Considering Islet and Liver Interplay in Prediabetic Mice during Gestation

Gestational diabetes (GDM) is characterized by a glucose tolerance disorder. This may first appear during pregnancy or pre-exist before conception as a form of prediabetes, but there are few data on the pathogenesis of the latter subtype. Female New Zealand obese (NZO) mice serve as a model for this subpopulation of GDM. It was recently shown that GDM is associated with elevated urinary serotonin (5-hydroxytryptamine, 5-HT) levels, but the role of the biogenic amine in subpopulations with prediabetes remains unclear. 5-HT is synthesized in different tissues, including the islets of Langerhans during pregnancy. Furthermore, 5-HT receptors (HTRs) are expressed in tissues important for the regulation of glucose homeostasis, such as liver and pancreas. Interestingly, NZO mice showed elevated plasma and islet 5-HT concentrations as well as impaired glucose-stimulated 5-HT secretion. Incubation of isolated primary NZO islets with 5-HT revealed an inhibitory effect on insulin and glucagon secretion. In primary NZO hepatocytes, 5-HT aggravated hepatic glucose production (HGP), decreased glucose uptake (HGU), glycogen content, and modulated AKT activation as well as cyclic adenosine monophosphate (cAMP) increase, indicating 5-HT downstream modulation. Treatment with an HTR2B antagonist reduced this 5-HT-mediated deterioration of the metabolic state. With its strong effect on glucose metabolism, these data indicate that 5-HT is already a potential indicator of GDM before conception in mice.