In situ synthesis of size-controlled, stable silver nanoparticles within ultrashort peptide hydrogels and their anti-bacterial properties

We have developed a silver-releasing biomaterial with promising potential for wound healing applications. The material is made of ultrashort peptides which can self-assemble in water to form hydrogels. Silver nanoparticles (Ag NPs) were synthesized in situ within the biomaterial, using only UV irradiation and no additional chemical reducing agents. The synthetic strategy allows precise control of the nanoparticle size, with the network of peptide fibers preventing aggregation of Ag NPs. The biomaterial shows increased mechanical strength compared to the hydrogel control. We observed a sustained release of Ag NPs over a period of 14 days. This is a crucial prerequisite for effective anti-bacterial therapy. The ability to inhibit bacterial growth was tested using different bacterial strains, namely gram-negative Escherichia coli and Pseudomonas aeruginosa and gram-positive Staphylococcus aureus. Inhibition of bacterial growth was observed for all strains. The best results were obtained for Pseudomonas aeruginosa which is known for exhibiting multidrug resistance. Biocompatibility studies on HDFa cells, using Ag NP-containing hydrogels, did not show any significant influence on cell viability. We propose this silver-releasing hydrogel as an excellent biomaterial with great potential for applications in wound healing due to its low silver content, sustained silver nanoparticle release and biocompatibility

Growth control of GaAs nanowires using pulsed laser deposition with arsenic over pressure

Using pulsed laser ablation with arsenic over pressure, the growth conditions for GaAs nanowires have been systematically investigated and optimized. Arsenic over pressure with As$_2$ molecules was introduced to the system by thermal decomposition of polycrystalline GaAs to control the stoichiometry and shape of the nanowires during growth. GaAs nanowires exhibit a variety of geometries under varying arsenic over pressure, which can be understood by different growth processes via vapor-liquid-solid mechanism. Single-crystal GaAs nanowires with uniform diameter, lengths over 20 $\mu$m, and thin surface oxide layer were obtained and can potentially be used for further electronic characterization

Risiko von Infektionen unter einer Behandlung mit Tumornekrosefaktor-α-Inhibitoren

Zusammenfassung: Tumornekrosefaktor-α (TNF) ist ein Zytokin, welches bei der Aktivierung von Entzündungszellen essenziell ist. Es ist bei der Granulombildung und -erhaltung im Rahmen von chronischen Infektionen beteiligt. Bei entzündlichen Prozessen kann sich die exzessive Produktion von TNF jedoch für den Patienten nachteilig auswirken. So spielt TNF eine wichtige Rolle bei der Entzündung chronischer Autoimmunkrankheiten. Medikamente zur Hemmung von TNF (Etanercept, Infliximab, Adalimumab) werden bei verschiedenen entzündlichen rheumatischen und autoimmunen Krankheiten mit Erfolg eingesetzt. Patienten unter einer Anti-TNF-Therapie haben ein erhöhtes Risiko, an Tuberkulose zu erkranken. Die Datenlage für andere infektiöse Erkrankungen ist weniger gut dokumentiert. Es gibt etliche anekdotische Fallberichte über die Assoziation von TNF-Hemmern und Infektionskrankheiten wie Histoplasmose, Listeriose, Kokzidioidomykose, Candidiasis und Aspergillose. Sie weisen auf eine erhöhte Infektionsanfälligkeit bei Patienten unter einer Anti-TNF-Therapie hin. In dieser Übersichtsarbeit erörtern wir zuerst die Bedeutung von TNF allgemein und spezifisch für die Infektionsabwehr, beschreiben kurz die Unterschiede der verfügbaren TNF-Hemmer und gehen im Detail die klinischen Daten durch, welche auf das erhöhte Infektionsrisiko unter einer Anti-TNF-Therapie hinweise

Anomalous magnetotransport in (Y1−x_{1-x}Gdx_{x})Co2_{2} alloys: interplay of disorder and itinerant metamagnetism

New mechanism of magnetoresistivity in itinerant metamagnets with a structural disorder is introduced basing on analysis of experimental results on magnetoresistivity, susceptibility, and magnetization of structurally disordered alloys (Y$_{1-x}$Gd$_{x}$)Co$_{2}$. In this series, YCo$_{2}$ is an enhanced Pauli paramagnet, whereas GdCo$_{2}$ is a ferrimagnet (T$_{\rm c}$=400 K) with Gd sublattice coupled antiferromagnetically to the itinerant Co-3d electrons. The alloys are paramagnetic for $x < 0.12$. Large positive magnetoresistivity has been observed in the alloys with magnetic ground state at temperatures T$<$T$_{\rm c}$. We show that this unusual feature is linked to a combination of structural disorder and metamagnetic instability of itinerant Co-3d electrons. This new mechanism of the magnetoresistivity is common for a broad class of materials featuring a static magnetic disorder and itinerant metamagnetism.Comment: 7 pages 7 figure

Comparison of the COBE FIRAS and DIRBE Calibrations

We compare the independent FIRAS and DIRBE observations from the COBE in the wavelength range 100-300 microns. This cross calibration provides checks of both data sets. The results show that the data sets are consistent within the estimated gain and offset uncertainties of the two instruments. They show the possibility of improving the gain and offset determination of DIRBE at 140 and 240 microns.Comment: Accepted for publication in the Astrophysical Journal 11 pages, plus 3 figures in separate postscript files. Figure 3 has three part

Effect of spin orbit scattering on the magnetic and superconducting properties of nearly ferromagnetic metals: application to granular Pt

We calculate the effect of scattering on the static, exchange enhanced, spin susceptibility and show that in particular spin orbit scattering leads to a reduction of the giant moments and spin glass freezing temperature due to dilute magnetic impurities. The harmful spin fluctuation contribution to the intra-grain pairing interaction is strongly reduced opening the way for BCS superconductivity. We are thus able to explain the superconducting and magnetic properties recently observed in granular Pt as due to scattering effects in single small grains.Comment: 9 pages 3 figures, accepted for publication in Phys. Rev. Letter

Rotational 3D Printing of Sensor Devices using Reactive Ink Chemistries

This paper charts progress in three key areas of a project supported by both UK government and UK industry to manufacture novel sensor devices using rotary 3D printing technology and innovative ink chemistries; (1) the development of an STL file slicing algorithm that returns constant Z height 2D contour data at a resolution that matches the given print head setup, allowing digital images to be generated of the correct size without the need for scaling; (2) the development of image transformation algorithms which allow images to be printed at higher resolutions using tilted print heads and; (3) the formulation of multi part reaction inks which combine and react on the substrate to form solid material layers with a finite thickness. A Direct Light Projection (DLP) technique demonstrated the robustness of the slice data by constructing fine detailed three dimensional test pieces which were comparable to identical parts built in an identical way from slice data obtained using commercial software. Material systems currently under investigation include plaster, stiff polyamides and epoxy polymers and conductive metallic’s. Early experimental results show conductivities of silver approaching 1.42x105 Siemens/m.Mechanical Engineerin

Measurements of elastohydrodynamic film thickness, wear and tempering behavior of high pressure oxygen turbopump bearings

The reusable design of the Space Shuttle requires a target life of 7.5 hours for the turbopumps of the Space Shuttle main engine (SSME). This large increase from the few hundred seconds required in single-use rockets has caused various problems with the bearings of the turbopumps. The berings of the high pressure oxygen turbopump (HPOTP) were of particular concern because of wear, spalling, and cage failures at service time well below the required 7.5 hours. Lubrication and wear data were developed for the bearings. Since the HPOTP bearings operate in liquid oxygen, conventional liquid lubricants cannot be applied. Therefore, solid lubricant coatings and lubricant transfer from the polytetrafluorethylene (FTFE) cage were the primary lubrication approaches for the bearings. Measurements were made using liquid nitrogen in a rolling disk machine to determine whether usable elastohydrodynamic films could be generated to assist in the bearing lubrication