Perturbed frequency-selective surfaces fabricated on large thin polymer membranes for multiband infrared applications

The design, fabrication, and characterization of single-screen perturbed frequency-selective surfaces (FSS) at infrared frequencies for single and multiband applications are reported. Single-band FSS based on parallel strips have been perturbed by decreasing the length of every second strip within the array in order to achieve dual band-stop responses. The same principle has been extended to design FSS exhibiting tri- and quadreflection bands. In addition, strip FSSs have been perturbed by replacing every second strip for a metallic ring, resulting in dual-band filters with different polarization responses of the bands. These designs have been fabricated on large thin polyimide membranes using sacrificial silicon wafers. An oxide interlayer between the sacrificial silicon wafer and the polyimide membrane is employed to stop the silicon etching and is wet etched subsequently by a solution of ammonium fluoride and acetic acid that does not attack either the polyimide membrane or the aluminium FSS elements. Fourier transform infrared spectroscopy measurements are presented to validate the predicted responses of the fabricated prototypes.

Turning solid aluminium transparent by intense soft X-ray photoionization

Saturable absorption is a phenomenon readily seen in the optical and infrared wavelengths. It has never been observed in core-electron transitions owing to the short lifetime of the excited states involved and the high intensities of the soft X-rays needed. We report saturable absorption of an L-shell transition in aluminium using record intensities over 10(16)W cm(-2) at a photon energy of 92 eV. From a consideration of the relevant timescales, we infer that immediately after the X-rays have passed, the sample is in an exotic state where all of the aluminium atoms have an L-shell hole, and the valence band has approximately a 9 eV temperature, whereas the atoms are still on their crystallographic positions. Subsequently, Auger decay heats the material to the warm dense matter regime, at around 25 eV temperatures. The method is an ideal candidate to study homogeneous warm dense matter, highly relevant to planetary science, astrophysics and inertial confinement fusion.

pcDNA3.1tdTomato is superior to pDsRed2-N1 for optical fluorescence imaging in the F344/AY-27 rat model of bladder cancer

PURPOSE: Animal models are important for pre-clinical assessment of novel therapies in metastatic bladder cancer. The F344/AY-27 model involves orthotopic colonisation with AY-27 tumour cells which are syngeneic to F344 rats. One disadvantage of the model is the unknown status of colonisation between instillation and sacrifice. Non-invasive optical imaging using red fluorescence reporters could potentially detect tumours in situ and would also reduce the number of animals required for each experiment.

MATERIALS AND METHODS: AY-27 cells were stably transfected with either pDsRed2-N1 or pcDNA3.1tdTomato. The intensity and stability of fluorescence in the resultant AY-27/DsRed2-N1 and AY-27/tdTomato stable cell lines were compared using Xenogen IVIS®200 and Olympus IX51 systems.

RESULTS: AY-27/tdTomato fluorescence intensity was 60-fold brighter than AY-27/DsRed2-N1 and was sustained in AY-27/tdTomato cells following freezing and six subsequent sub-cultures. After sub-cutaneous injection, fluorescence intensity from AY-27/tdTomato cells was threefold stronger than that detected from AY-27/DsRed2-N1 cells. IVIS®200 detected fluorescence from AY-27/tdTomato and AY-27/DsRed2-N1 cells colonising resected and exteriorised bladders, respectively. However, the deep-seated position of the bladder precluded in vivo imaging. Characteristics of AY-27/tdTomato cells in vitro and in tumours colonising F344 rats resembled those of parental AY-27 cells. Tumour transformation was observed in the bladders colonised with AY-27/DsRed2-N1 cells.

CONCLUSIONS: In vivo whole-body imaging of internal red fluorescent animal tumours should use pcDNA3.1tdTomato rather than pDsRed2-N1. Optical imaging of deep-seated organs in larger animals remains a challenge which may require proteins with brighter red or far-red fluorescence and/or alternative approaches.

Abrasive wear resistance of electroless Ni-P coated aluminium after post treatment

Electroless nickel (EN) coatings are recognised for their hardness and wear resistance in automotive and aerospace industries. In this work, electroless Ni–P coatings were deposited on aluminium alloy substrate LM24 (Al–9 wt.% Si alloy) and the effect of post treatment on the wear resistance was studied. The post treatments included heat treatment and lapping with two different surface textures. Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and micro-abrasion tester were used to analyse morphology, structure and abrasive wear resistance of the coatings. Post heat treatment significantly improved the coating density and structure, giving rise to enhanced hardness and wear resistance. Microhardness of electroless Ni–P coatings with thickness of about 15 μm increased due to the formation of Ni3P after heat treatment.