Characterization of internal structure of hydrated agar and gelatin matrices by cryo‐SEM

There has been a considerable interest in recent years in developing polymer gel matrices for many important applications such as 2DE for quantization and separation of a variety of proteins and drug delivery system to control the release of active agents. However, a well‐defined knowledge of the ultrastructures of the gels has been elusive. In this study, we report the characterization of two different polymers used in 2DE: Gelatin, a naturally occurring polymer derived from collagen (protein) and agar, a polymer of polysaccharide (sugar) origin. Low‐temperature SEM is used to examine the internal structure of these gels in their frozen natural hydrated states. Results of this study show that both polymers have an array of hollow cells that resembles honeycomb structures. While agar pores are almost circular, the corresponding Gaussian curve is very broad exhibiting a range of radii from nearly 370 to 700 nm. Gelatin pores are smaller and more homogeneous reflecting a narrower distribution from nearly 320 to 650 nm. Overall, these ultrastructural findings could be used to correlate with functions of the polymers.     

Dynamic SIMS analysis of cryo-prepared biological and geological specimens

The modification of a dynamic magnetic sector secondary ion mass spectrometry (SIMS) instrument to permit the analysis of frozen biological and geological samples is described. The SIMS instrument used for this study combines SIMS analysis with the generation of ion-induced secondary electron images, allowing direct superposition of the SIMS image onto the image of cellular structures. Secondary ion maps have been acquired with sub-micron resolution, permitting the characterisation of sub-cellular elemental distributions in plant cells and human fibroblast cells, as well as the distribution of chemical impurities at grain boundaries in polar ice samples. This cryo-preparation technique clearly extends the applicability of SIMS analysis to a wide range of samples.     

Marine environment compatible antireflection coating with nanotop layer on silicon optics

Antireflection coating on silicon optics have crucial importance in thermal device working in 3.6–4.9 μm wavelength region. When the thermal device is used in marine environment, the optics face harsh saline weather condition compared to normal field environment. This deteriorates coated optics and to improve mechanical strength of the coating, a nanotop layer on the antireflection coating has been developed. In this paper a study has been carried out to improve marine environment compatibility by employing a nanolayer on the top of antireflection coating on silicon optics. Optimac synthesis method was used to design the multilayer stack on the substrate with germanium and IR-F625 as high/low refractive index respectively and the layer number was restricted to four layers. The top nanolayer was 60 ± 2 nm thick hafnium dioxide layer developed with ion assisted deposition (End–Hall) on the optics during coating process. The deposition of multilayer coating was carried out inside the coating plant fitted with cryo pump and residual gas analyzer. The evaporation was carried out at high vacuum (2–6 × 10⁻⁶ mbar) using electron beam gun and layer thicknesses were measured with crystal monitor. The average transmission achieved was 97% in the spectral band of 3.6–4.9 μm with a hardness of 9.7 GPa on the coated optics.     

Periodic minimal surface organizations of the lipid bilayer at the lung surface and in cubic cytomembrane assemblies

The existence of infinite periodic lipid bilayer structures in biological systems was first demonstrated in cell membrane assemblies. Such periodicity is only possible in symmetric bilayers, and their occurrence is discussed here in relation to the asymmetry of cell membranes in vivo. A periodic membrane conformation in the prolamellar body of plants corresponds to a dormant state without photosynthesis. A similar reversible formation of a dormant state has also been observed in the mitochondria of the amoeba Chaos. In these cases the energy production has become insufficient to maintain the membrane asymmetry. Formation of membranes that are symmetric over the bilayer is proposed to be a principal mechanism behind formation of cubic membrane systems.     

Sucrose cryo‐protection facilitates imaging of whole eye sections by MALDI mass spectrometry

Sucrose is used as a cryo‐preservation agent on large mammalian eyes post formalin fixation and is shown to reduce freezing artefacts allowing the collection of 12‐µm thick sections from these large aqueous samples. The suitability of this technique for use in MALDI imaging experiments is demonstrated by the acquisition of the first images of lipid distributions within whole sagittal porcine eye sections. Copyright © 2012 John Wiley & Sons, Ltd.     

A Study of the Emulsified Microemulsion by SAXS,Cryo‐TEM,SD‐NMR,and Electrical Conductivity

A water‐in‐oil microemulsion was further dispersed in an aqueous phase containing Pluronic F127 as a steric stabilizer, to form a specific type of double emulsion termed emulsified microemulsion (EME). The inner microemulsion phase was made from glycerol‐monooleate (GMO), R(+)‐limonene, ethanol and glycerol. SAXS (small x‐ray scattering), PGSE‐NMR (pulse gradient spin echo‐NMR), electrical conductivity, and cryo‐TEM (cryogenic‐transmission electron microscopy) imaging techniques were used to confirm the existence of inner W/O nano‐droplets after second emulsification step and upon EME aging. Spherical globules of EME without long‐range internal order were observed by the SAXS measurements and the cryo‐TEM images. The average globule size of about 200–300 nm remained intact for at least 6 months.     

Cryo‐XPS study of xanthate adsorption on pyrite

The adsorption of xanthate on pyrite has been extensively studied. However, the adsorption mechanisms remain a subject of controversy. Formation of both dixanthogen and metal‐xanthate complexes has been suggested. In this study, both room temperature X‐ray photoelectron spectroscopy (XPS) (RT‐XPS) and liquid nitrogen temperature XPS (Cryo‐XPS) were used to study interactions between pyrite and xanthate. While dixanthogen was not detected by RT‐XPS, it was successfully identified through C1s and S 2p peaks using Cryo‐XPS. The impact of pH and copper activation on adsorption of xanthate on pyrite was also investigated. It was found that at low pH, dixanthogen is the dominant species of xanthate adsorption on pyrite. At high pH, metal‐xanthate complexes were found to be prevalent on pyrite surfaces, which are responsible for the surface hydrophobicity. Copper activation showed a significant effect on xanthate adsorption on Cu‐activated pyrite, resulting in mostly the formation of Cu‐xanthate complexes rather than dixanthogen, mainly in the form of Cu(I)‐isopropyl xanthate complex (CuIPX). Copyright © 2012 John Wiley & Sons, Ltd.