Surface Design for Immobilization of an Antimicrobial Peptide Mimic for Efficient Anti-Biofouling

Microbial surface attachment negatively impacts a wide range of devices from water purification membranes to biomedical implants. Mimics of antimicrobial peptides (AMPs) constituted from poly(N-substituted glycine) „peptoids“ are of great interest as they resist proteolysis and can inhibit a wide spectrum of microbes. We investigate how terminal modification of a peptoid AMP-mimic and its surface immobilization affect antimicrobial activity. We also demonstrate a convenient surface modification strategy for enabling alkyne–azide „click“ coupling on amino-functionalized surfaces. Our results verified that the N- and C-terminal peptoid structures are not required for antimicrobial activity. Moreover, our peptoid immobilization density and choice of PEG tether resulted in a „volumetric“ spatial separation between AMPs that, compared to past studies, enabled the highest AMP surface activity relative to bacterial attachment. Our analysis suggests the importance of spatial flexibility for membrane activity and that AMP separation may be a controlling parameter for optimizing surface anti-biofouling.     

Phosphorescence polarisation of aromatic compounds oriented in stretched polyethylene films

Phosphorescence polarisation measurements are reported for a number of planar aromatic compounds in stretched polyethylene. The phosphorescence is to about 80% polarised perpendicular to the molecular plane. In the in-plane intensity second order Herzberg-Teller coupling terms may be at least competitive with three-center ππ spin-orbit integrals, in agreement with suggestions of Friedrich, Metz and Dörr.     

Seshadi constants via functions on Newton–Okounkov bodies

The aim of this note is to establish a somewhat surprising connection between functions on Newton–Okounkov bodies and Seshadri constants of line bundles on algebraic surfaces.     

Numerical Computation of Dynamical Schwinger-like Pair Production in Graphene

Russian Physics Journal - The density of electron-hole pairs produced in a graphene sample immersed in a homogeneous time-dependent electric field is evaluated. Because low energy charge carriers...     

Thermal lensing, thermal management and transverse mode control in microchip VECSELs

Finite-element analysis is used to explore the practicalities and power-scaling potential of quasi-monolithic microchip vertical-external-cavity surface-emitting lasers: thermal lensing and its implications for transverse mode control are emphasised. A comparison is made between the use of sapphire and diamond heat spreaders. The experimental characterisation of an InGaAs/sapphire microchip VECSEL is presented as an exemplar system and the factors affecting slope efficiency, threshold and output power roll-over are examined. By comparing experimental measurements with the finite-element model, the key role of thermal lensing in transverse mode control is demonstrated. PACS 42.55.Xi; 42.55.Rz; 42.55.Px     

Effects of external electric fields on 1H, 19F,and 14N NMR spectra of 2, 4, 6-trifluoronitrobenzene

When a polar liquid is subjected to an electric field, the dipoles obtain a small average orientation. At sufficiently high field strengths direct spin—spin dipolar and quadrUpolar electric field interactions may modify the NMR spetrum.NMR electric field experiments are reported for the proton, fluorine, and nitrogen NMR spectra of neat 2, 4, 6-trifluoronitrobenzene. The observed alignment values are smaller than those predicted on the basis of Onsager's theory.The ¹⁴N quadrupole coupling constant as been deduced from a comparison of the qUadrupolar and dipolar electric field effects.An upper limit of the absolute value of the anisotropy of the para-¹⁹F chemical shift has been inferred from the absence of a detectable displacement of the resonance on application of an electric field.     

Fluorine chemical shift anisotropy in 1,1-difluoroethene

Chemical shift anisotropies can be determined from NMR in liquid crystalline solutions. In interpreting the experimental data it is customary to assume that the chemical shift is axially symmetric around the bond axis.NMR experiments on 1,1-difluoroethene are reported from which this assumption can be tested. The results confirm axial symmetry of the ¹⁹F chemical shift tensor around the CF bond.