A novel device for in situ study of gas adsorption under rotation.

The effect of rotation on adsorption kinetics of CO2 on activated carbon (AC) is studied using a novel rotation device. The device consists of a rotating cylindrical cell with inner dimensions of 4.5 cm radius and 1 mm height, while it operates at 5000 and 8000 rpm. Various cases of the CO2/AC system are examined under a rotation field: in particular, (a) solid at vacuum, (b) gas without solid, (c) gas/solid at a non-equilibrium state of the adsorption process, and (d) gas/solid near an equilibrium state of the adsorption process. Micro-fragmentation of solid particles is observed at 8000 rpm but not at 5000 rpm; the latter is then chosen as the preferable speed for the rest of the experiments. During rotation of the gas, a well is noticed at the pressure curve, the size of which is in accordance with theoretical predictions of the behavior of a spinning gas. Rotation at an early stage of the adsorption process can suppress the filling time of a rotating storage reservoir to half of its value. Rotation near the equilibrium point reveals an enhanced adsorption capacity of the solid. The physics behind these phenomena are discussed with the aid of N2-adsorption porosimetry and scanning electron microscopy measurements.

Hydroxyapatite Crystal Thickness and Buckling Phenomenon in Bone Nanostructure During Mechanical Tests.

An investigation of bone samples taken from the left ulna of New Zealand white rabbits, with and without stresses and hysteresis loop, was undertaken using Small Angle X-ray Scattering technique. The purpose of this study is to investigate the nanostructural changes in the mean size of hydroxyapatite crystals thickness (T) during different mechanical conditions. The experiments were performed using bone samples aged 2 and 4 weeks, with and without strontium ranelate treatment, after compressive load and hysteresis loop. We did not observe any clear effects of strontium ranelate on the bones since the MANOVA test for epiphysis and diaphysis were found. On the other hand, a significant difference appears in epiphysis between 2 and 4 weeks. Furthermore, a reduction in the mean size of hydroxyapatite crystal thickness was observed when the loading pressure force increased, due to the buckling phenomenon. A return of memory points in the elastic region of the bone was observed. The significance of these results lays on the development of nanoproducts, with properties that are closer to the actual bone structure.

Kidney stone nano-structure - Is there an opportunity for nanomedicine development?

BACKGROUND: Kidney stone analysis techniques are well-established in the field of materials characterization and provide information for the chemical composition and structure of a sample. Nanomedicine, on the other hand, is a field with an increasing rate of scientific research, a big budget and increasingly developing market. The key scientific question is if there is a possibility for the development of a nanomedicine to treat kidney stones. MAJOR CONCLUSIONS: The main calculi characterization techniques such as X-ray Diffraction and Fourier Transform Infrared Spectroscopy can provide information about the composition of a kidney stone but not for its nanostructure. On the other hand, Small Angle X-ray Scattering and Nitrogen Porosimetry can show the nanostructural parameters of the calculi. The combination of the previously described parameters can be used for the development of nano-drugs for the treatment of urolithiasis, while no such nano-drugs exist yet. GENERAL SIGNIFICANCE: In this study, we focus on the most well-known techniques for kidney stone analysis, the urolithiasis management and the search for possible nanomedicine for the treatment of kidney stone disease. We combine the results from five different analysis techniques in order to represent a three dimensional model and we propose a hypothetical nano-drug with gold nanoparticles. This article is part of a Special Issue entitled "Recent Advances in Bionanomaterials" Guest Editor: Dr. Marie-Louise Saboungi and Dr. Samuel D. Bader.

A framework for health-related nanomaterial grouping.

BACKGROUND: Nanotechnology has been in the limelight since its emergence and its products affect everyday lives. Nanomaterials are characterized by features such as size and shape, thus rendering their possible number essentially unlimited, which in turn makes them difficult to study and categorize regarding possible dangers. This work suggests that grouping could allow studying them with limited testing efforts without endangering safety. METHODS: Initially, the materials are identified and grouped according to their applications in health/medicine, as well as on their environmentally-friendly potential. The materials are then categorized using various toxicity classification methods to identify those with highest risks and group them with others that demonstrate similar behavior. RESULTS: The materials studied show promising uses in diagnostics, drug delivery, biosensors, water purification, oil spill cleaning, emission control and other fields. The toxicity risk assessment shows that the majority pose little to moderate risk, however there are certain materials that can be extremely hazardous or even cause death under specific circumstances. A risk mitigation plan was also developed. CONCLUSIONS: Nanomaterials applications, including drug delivery, cancer treatment, waste treatment, solar energy generation etc. can be very beneficiary, but at the same time, these materials can be extremely harmful or even cause death, thus making the need to prioritize research on high risk materials crucial. A clear regulatory framework that addresses both benefits and risks and communicates that information effectively should play an important part in European and worldwide efforts. GENERAL SIGNIFICANCE: The risk analysis validated the impression that there is limited research on nanomaterial toxicity risks, which calls for a more organized approach. The framework outlined in this work can be utilized by researchers as well as government bodies, in order to form regulatory policies and adopt a universally accepted labeling system. This article is part of a Special Issue entitled "Recent Advances in Bionanomaterials" Guest Editor: Dr. Marie-Louise Saboungi and Dr. Samuel D. Bader.

Small-angle X-ray scattering studies of adsorption in Vycor glass.

Porous Vycor is examined by measuring CH(2)Br(2) adsorption in situ with small-angle X-ray scattering. When a class of pores fills with condensed vapors of this particular adsorbate it ceases to act as scatterer and only the remaining empty pores produce a measurable intensity. By determining a number of scattering curves at various relative pressure loadings details on the structure of the glass as well as on the adsorption/desorption mechanism are obtained. Pore chord length and specific surface area are estimated from Porod tangent analysis to 78 A and 108 m(2)/g. Comparison of the results with those reported for N(2) and Ar adsorption is also given. The role of network effects on the shape of the hysteresis loop is considered and the pore-blocking hypothesis is verified from the scattering spectra. The pore connectivity is calculated to 5.6. The X-ray data are further treated with the inverse Fourier transformation technique. Pore-size distributions are extracted and weighed against the prediction of the Kelvin equation.

The Kelvin equation.

The capillary condensation/evaporation process is studied in conjunction with small angle X-ray scattering measurements. The scattering data are analyzed with the indirect Fourier transformation technique and the results are compared with the predictions of the Kelvin equation. It is found that the Kelvin equation is obeyed by menisci with mean radius of curvature as low as 40 A. For smaller radii, in particular from 40 to 30 A, the two methods differ by approximately 25%. Broekhoff and de Boer analysis may improve the prediction. The hysteresis region of an adsorption step is presented schematically.