Unusually stable liquid foams

Obtaining stable liquid foams is an important issue in view of their numerous applications. In some of these, the liquid foam in itself is of interest, in others, the liquid foam acts as a precursor for the generation of solid foam. In this short review, we will make a survey of the existing results in the area. This will include foams stabilised by surfactants, proteins and particles. The origin of the stability is related to the slowing down of coarsening, drainage or coalescence, and eventually to their arrest. The three effects are frequently coupled and in many cases, they act simultaneously and enhance one another. Drainage can be arrested if the liquid of the foam either gels or solidifies. Coalescence is slowed down by gelified foam films, and it can be arrested if the films become very thick and/or rigid. These mechanisms are thus qualitatively easy to identify, but they are less easy to model in order to obtain quantitative predictions. The slowing down of coarsening requests either very thick or small films, and its arrest was observed in cases where the surface compression modulus was large. The detail of the mechanisms at play remains unclear.     

A Microcalorimetric Study on the Role of Moisture in Photolysis of Nifedipine Powder

A well-known photolabile substance, nifedipine, was used as a sample material to test self-constructed irradiation cells and demonstrate their usefulness in photostability studies. The devices were made as accessories for a commercial isothermal microcalorimeter. Several powder samples containing various amounts of moisture were irradiated with monochromatic light as a scan measurement from 700 to 280 nm, and the heat flow evolved in the photodegradation of nifedipine was determined. According to the results, light does not affect the nifedipine molecule directly, but the photodegradation is a result of the combined effects of moisture and light. This revised version was published online in August 2006 with corrections to the Cover Date.     

Calculations of millimeter wave depolarization due to melting layer and rain

A model for calculating the total depolarization due to the melting layer and rain is proposed under the assumption that oblate spheroidal melting particles and raindrops have the same orientation. The melting layer is composed of the melting particles which are made up from the mixture of ice, air and water. The specific attenuation and the specific phase shift both for the melting layer and for rain are given in the power lawaR ^b form for the rain rates 0≤R≤12.5 mm/h and the parameters are tabled over the frequency range of 1–100 GHz. Using the model, the numerical calculation of the depolarization is possible for three drop size distributions.     

Anomalous polarization of Raman scattering spectra from porous silicon

A violation of the polarization selection rules for Raman scattering is observed in porous silicon. This effect is caused by a weak disorientation of the quasi-one-dimensional silicon wires, with the crystal structure of the wires themselves and the macroscopic homogeneity of the material in optical experiments remaining intact. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 2, 95–100 (25 January 1998)     

Convex-transitivity and function spaces

It is shown that if X is a convex-transitive Banach space and 1p<∞, then L^p([0,1],X) and are convex-transitive. Here is the closed linear span of the simple functions in the Bochner space L^∞([0,1],X). If H is an infinite-dimensional Hilbert space and C₀(L) is convex-transitive, then C₀(L,H) is convex-transitive. Some new fairly concrete examples of convex-transitive spaces are provided.     

On the existence of Nash equilibria in large games

We study the existence of Nash equilibria in games with an infinite number of players. We show that there exists a Nash equilibrium in mixed strategies in all normal form games such that pure strategy sets are compact metric spaces and utility functions are continuous. The player set can be any nonempty set.     

Configurable Data Memory for Multimedia Processing

In modern multimedia applications, memory bottleneck can be alleviated with special stride data accesses. Data elements in stride access can be retrieved in parallel with parallel memories, in which the idea is to increase memory bandwidth with several memory modules working in parallel and feed the processor with only necessary data. Arbitrary stride access capability with interleaved memories is described in previous research where the skewing scheme is changed at run time according to the currently used stride. This paper presents the improved schemes which are adapted to parallel memories. The proposed novel parallel memory implementation allows conflict free accesses with all the constant strides which has not been possible in prior application specific parallel memories. Moreover, the possible access locations are unrestricted and the accessed data element count equals to the number of memory modules. Timing and area estimates are given for Altera Stratix FPGA and 0.18 micrometer CMOS process with memory module count from 2 to 32. The FPGA results show 129 MHz clock frequency for a system with 16 memory modules when read and write latencies are 3 and 2 clock cycles, respectively. The complexity of the proposed system is shown to be a trade-off between application specific and highly configurable parallel memory system.     

Polarisation independence of amplitude scintillation

Otung and Evans presented some results of slant path scintillation measurements from Sparsholt (UK) which indicate that tropospheric scintillation is dependent on polarisation angle. However, results from Kirkkonummi (Finland), Lessive (Belgium) and Darmstadt (Germany), which are presented, do not show any significant polarisation dependence. The theoretical basis given by Otung and Evans is studied further, showing that tropospheric scintillation is not expected to be significantly influenced by polarisation angle     

Thiolation and Cell‐Penetrating Peptide Surface Functionalization of Porous Silicon Nanoparticles for Oral Delivery of Insulin

During the last decades, advanced oral delivery systems to enhance the intestinal absorption of widely applicable proteins and peptides, particularly insulin, have been developed. Here, chitosan‐conjugated undecylenic acid‐modified thermally hydrocarbonized porous silicon nanoparticles (CSUn NPs) are used, which promote the mucoadhesion and cellular interactions, thus boosting the intestinal permeability of insulin. Then, to further potentiate the mucoadhesion and permeability enhancement of chitosan‐modified NPs, the surface of the NPs is further modified with either l ‐cysteine (CYS‐CSUn NPs) or a cell‐penetrating peptide (CPP‐CSUn NPs). CYS‐CSUn and CPP‐CSUn NPs show 17‐ and 12‐fold increase in the apparent permeability of insulin across cellular intestinal cells, respectively, with significant enhancement in the cellular interactions. The insulin uptake mechanism pathways in intestinal cells from the developed NPs are also unraveled, which demonstrates major involvement of active transport process and electrostatic interactions, along with adsorptive and clathrin‐mediated endocytic pathways. Moreover, after oral administration in diabetic rats, CYS‐CSUn NPs show 1.86‐ and 2.03‐fold increase in the relative bioavailability of insulin, as compared to empty NPs and oral insulin solution, respectively. In conclusion, this study presents l ‐cysteine modified CSUn NPs as a promising strategy with the ability to overcome the multiple barriers for oral delivery of insulin.     

Use of thermoanalytical methods in quantification of drug load in mesoporous silicon microparticles

Summary Thermally carbonised mesoporous silicon microparticles were produced and loaded with two active pharmaceutical ingredients, ibuprofen and antipyrine. By combining the results measured with TG and DSC, reliable estimations for the degrees of the drug loads were obtained. To distinguish the drug adsorbed on the surfaces of the microparticles from that absorbed into the pores, the principle of thermoporometry on the DSC measurements was employed. According to the principle, the drug held in the capillaries of porous material has a depressed melting temperature because of the higher pressure of the drug in cavities with a curved interface. On the other hand, the drug located on the external surface of the microparticles exhibits the normal melting of bulk drug. The loading degrees obtained with the thermoanalytical methods (31 and 26 mass&percnt; for ibuprofen and antipyrine, respectively) were comparable with the results obtained with helium pycnometry (the corresponding values were 33 and 28 mass&percnt;). Nitrogen sorption studies were not reliable for quantitative determinations due to the inability of nitrogen to penetrate in all pores, which might be blocked by the drug on the surface of the microparticles.