EFFECT OF SURFACE RESISTOR LOADING ON HIGH-IMPEDANCE SURFACE RADAR ABSORBER RETURN LOSS AND BANDWIDTH

A simple method for the selection of the appropriate choice of surface-mounted loading resistor required for a thin radar absorber based on a high-impedance surface (HIS) principle is demonstrated. The absorber consists of a HIS, (artificial magnetic ground plane), thickness 0.03 lambda(0) surface-loaded resistive-elements interconnecting a textured surface of square patches. The properties of absorber are characterized under normal incident using a parallel plate waveguide measurement technique over the operating frequency range of 2.6-3.95 GHz. We show that for this arrangement return loss and bandwidth are insensitive to +/- 2% tolerance variations in surface resistor values about the value predicted using the method elaborated in this letter, and that better than -28 dB at 3.125 GHz reflection loss can be obtained with an effective working bandwidth of up to 11% at -10 dB reflection loss. (C) 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1733-1775, 2009; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/mop.24454

Effect of hydrophobic nanopatches within an ionic surface on the structure of liquids

The structures of liquid water and isopropanol have been studied as a function of the size of a hydrophobic patch present in a model hydrophilic surface via molecular dynamics simulations. A significant anisotropy extending into the first few solvent layers is found over the patch which suggests implications for many real-world systems in which nanoscale heterogeneity is found.

Direct evidence showing the effect of root surface iron plaque on arsenite and arsenate uptake into rice (Oryza sativa) roots

The present study aimed to investigate the effects of root surface iron plaque on the uptake kinetics of arsenite and arsenate by excised roots of rice (Oryza sativa) seedlings. The results demonstrated that the presence of iron plaque enhanced arsenite and decreased arsenate uptake. Arsenite and arsenate uptake kinetics were adequately fitted by the Michaelis-Menten function in the absence of plaque, but produced poor fits to this function in the presence of plaque. Phosphate in the uptake solution did not have a significant effect on arsenite uptake irrespective of the presence of iron plaque; however phosphate had a significant effect on arsenate uptake. Without iron plaque, phosphate inhibited arsenate uptake. The presence of iron plaque diminished the effect of phosphate on arsenate uptake, possibly through a combined effect of arsenate desorption from iron plaque.

Effect of the surface water layer on the optical signal in apertureless scanning near field optical microscopy

Optical signals measured in apertureless scanning near field optical microscopy (ASNOM) under ambient conditions are found to be affected significantly by the thin water layer absorbed on the surface under investigation, the presence of which is detected through measurements of the shear force experienced by the tip. This water layer also results in a large hysteresis between optical signals measured during approach and withdrawal of the tip to the sample surface. The role of this effect in ASNOM is anticipated to be significant, with the possibility of resultant topographically induced artefacts for ASNOM involving intermittent contact of tip and sample, but also providing a potential mechanism for nanoscale optical resolution.

In situ FTIR studies of the effect of temperature on the adsorption and electrooxidation of CO at the Ru(0001) electrode surface

The adsorption and electrooxidation of CO at a Ru(0001) electrode in perchloric acid solution have been investigated as a function of temperature, potential and time using in situ FTIR spectroscopy. This builds upon and extends previous work on the same system carried out at room temperature. As was observed at room temperature, both linear (CO) and 3-fold-hollow (CO) binding CO adsorbates (bands at 2000-2045 cm and 1768-1805 cm, respectively) were detected on the Ru(0001) electrode at 10°C and 50°C. However, the temperature of the Ru(0001) electrode had a significant effect upon the structure and behavior of the CO adlayer. At 10°C, the in-situ FTIR data showed that the adsorbed CO species still remain in rather compact islands up to ca. 1100 mV vs Ag/AgCl as the CO oxidation reaction proceeds, with oxidation occurring only at the boundaries between the CO and active surface oxide/hydroxide domains. However, the IR data collected at 50°C strongly suggest that the adsorbed CO species are present as relatively looser and weaker structures, which are more easily electro-oxidized. The temperature-, potential-, and coverage-dependent relaxation and compression of the CO adlayer at low coverages are also discussed.

Integration of design of experiment, surface response methodology and multi-layer validation to predict the effect of blanching on colour of tomato juice

Response surface methodology was used to develop models to predict the effect of tomato cultivar, juice pH, blanching temperature and time on colour change of tomato juice after blanching. The juice from three tomato cultivars with adjusted pH levels ranging from 3.9 to 4.6 were blanched at temperatures from 60-100 °C for 1-5 min using the central composite design (CCD). The colour change was assessed by calculating the redness (a/b) and total colour change (∆E) after measuring the Hunter L, a and b values. Developed models for both redness and ∆E were significant (p<0.0001) with satisfactory coefficient of determination (R2 = 0.99 and 0.97) and low coefficient of variation (CV% = 1.89 and 7.23), respectively. Multilevel validation that was implemented revealed that the variation between the predicted and experimental values obtained for redness and ∆E were within the acceptable error range of 7.3 and 22.4%, respectively

A comparison of gold nanoparticle surface co-functionalization approaches using Polyethylene Glycol (PEG) and the effect on stability, non-specific protein adsorption and internalization

To create clinically useful gold nanoparticle (AuNP) based cancer therapeutics it is necessary to co-functionalize the AuNP surface with a range of moieties; e.g. Polyethylene Glycol (PEG), peptides and drugs. AuNPs can be functionalized by creating either a mixed monolayer by attaching all the moieties directly to the surface using thiol chemistry, or by binding groups to the surface by means of a bifunctional polyethylene glycol (PEG) linker. The linker methodology has the potential to enhance bioavailability and the amount of functional agent that can be attached. While there is a large body of published work using both surface arrangements independently, the impact of attachment methodology on stability, non-specific protein adsorption and cellular uptake is not well understood, with no published studies directly comparing the two most frequently employed approaches. This paper compares the two methodologies by synthesizing and characterizing PEG and Receptor Mediated Endocytosis (RME) peptide co-functionalized AuNPs prepared using both the mixed monolayer and linker approaches. Successful attachment of both PEG and RME peptide using the two methods was confirmed using Dynamic Light Scattering, Fourier Transform Infrared Spectroscopy and gel electrophoresis. It was observed that while the 'as synthesized' citrate capped AuNPs agglomerated under physiological salt conditions, all the mixed monolayer and PEG linker capped samples remained stable at 1M NaCl, and were stable in PBS over extended periods. While it was noted that both functionalization methods inhibited non-specific protein attachment, the mixed monolayer samples did show some changes in gel electrophoresis migration profile after incubation with fetal calf serum. PEG renders the AuNP stable in-vivo however, studies with MDA-MB-231 and MCF 10A cell lines indicated that functionalization with PEG, blocks cellular uptake. It was observed that co-functionalization with RME peptide using both the mixed monolayer and PEG linker methods greatly enhanced cellular internalization compared to PEG capped AuNPs.

Effect of calcium-modulating cyclophilin ligand on human immunodeficiency virus type 1 particle release and cell surface expression of Tetherin

The HIV-1 accessory protein Vpu enhances virus particle release by counteracting a host factor that retains virions at the cell surface of infected cells. It was recently demonstrated that cellular protein BST2/CD317/Tetherin restricts HIV-1 release in a Vpu-dependent manner. CAML was also proposed to be involved in this process. We investigated whether CAML is involved in Tetherin cell-surface expression. Here, we show that CAML over-expression in permissive Cos-7 cells or CAML depletion in restrictive HeLa cells has no effect on HIV-1 release nor on Tetherin surface expression, indicating that CAML is not required for Tetherin-mediated restriction of HIV-1 release.