Isomers of the C84 fullerene: A theoretical consideration within energetic,structural, and topological approaches

Currently, there is no common conception on the stability and achievability of fullerene isomers under the arc-discharge synthesis conditions. Different approaches operate with energetic, structural, and topological parameters of the fullerene molecules to explain why some fullerene isomers are more preferable than the others. In the present work, we have selected the most appropriate approaches based on topological roundness, information entropy, nuclear volumes, and sphericities and compared their predictions with the relevant experimental data on the C₈₄ fullerene isomers (obeying the isolated pentagon rule) and density functional theory estimates of their stability. We have found that the molecules of most stable (and most abundant) C₈₄ isomers have the minimal extremal roundness, maximal sphericity, and largest volume and vice versa. In the case of the information entropy, no correlation is observed. Interestingly, the found correlation between the volume and the stability of the C₈₄ isomers is unexpectedly inverse, i.e. more stable C₈₄ isomers have larger inner cavities inside, though traditionally large volume is associated with instability of hollow framework molecules. We assume that the large volumes allows enhancing the sphericity of the fullerene cages as we found the last one favoring the stability and the unstable C₈₄ fullerene cages having low volumes are far from the spherical shape. We think that the results obtained may be extrapolated to other fullerene isomeric sets and contribute to the understanding the grounds of the interconnection in the triad “topology – structure – energy” underlying structural chemistry.     

A comparison of least squares and maximum likelihood methods using sine fitting in ADC testing

ADC test methods require the best possible reconstruction of the input signal of the ADC under test from the acquired, therefore erroneous, ADC output data. The commonly used least squares (LS) fit and the recently introduced maximum likelihood (ML) estimation are competing methods. This paper presents a simulation-based comparative study of these estimation methods with the goal to investigate the behavior of both methods and to determine their limits. Two alternative algorithms for the calculation of the maximum likelihood fit are considered (gradient-based minimization and differential evolution). The main finding is that while for low-INL (linear) ADCs the two methods (LS and ML) give similar results, for practical (almost always nonlinear) ADCs ML is definitely better.     

Pre‐insulated pipe mains for district heating

A method developed by co‐operative research in Hungary differs from many other ‘pipe‐in‐the‐pipe’ systems; it uses a special joint to couple the prefabricated insulated pipe sections and includes many sub‐systems which can be built into the pipe casing, such as a separate mains line for high‐temperature media. A built‐in electric indicator precisely locates any possible fault area in service.     

Monotectic Al/Cd alloys with homogeneously dispersed Cd-droplets stabilized by strontium aluminide precipitates

Al-rich Al–Sr alloys contain dispersed Al₄Sr precipitates in the Al-matrix. When melted and emulsified together with a smaller volume of Cd, Cd-rich droplets are formed (being immiscible with the Al-rich liquid). The Al₄Sr precipitates prefer the Al/Cd interface, stabilizing the Cd droplets in the Al-matrix. The contact angle of the Cd-rich liquid on Al₄Sr intermetallic phase under the Al-rich liquid alloy is about 90°, being ideal for emulsion stabilization. In this way, Al/Cd monotectic alloys can be produced with homogeneously dispersed Cd particles. The key to the success of this process is the in-situ formation of strontium aluminide precipitates stabilizing the Cd droplets in the liquid Al/Cd emulsion.     

Outflow properties of silos: The effect of arching

Engineers working on the field of agriculture, food- or pharmaceutical industry or in the architecture frequently meet problems arising from the special properties of granular assemblies. Storing large amount of particulate raw materials is mostly made by using large containers, called silos. The design of such large silos is far not an easy problem. The outflow properties are one of the most important parameters of silo design. The constant discharge rate of silos differs from the discharge rate of containers filled with liquids. In case of fluids, the flowing velocity and discharge rate changes with fluid level. In case of granular materials, the velocity is constant (independent of the filling level of silo). There are methods used for the determination of silo discharge rate, but these are mostly experimental without physical explanation of the phenomenon. In this paper we demonstrate that the constant discharge rate is caused by the formation and collapse of arches in the bin. Based on this assumption, we derive an equation for determining the discharge rate. Using the same arching hypothesis we derive the equations describing the velocity distribution at silo outlets. The usability of our new approach is demonstrated by experimental investigations.     

Attachment and proliferation of human osteoblast-like cells (MG-63) on laser-ablated titanium implant material

Demand is increasing for shortening the long (3–6 months) osseointegration period to rehabilitate patients' damaged chewing apparatus in as short a time as possible. For dental implants, as for biomaterials in general, the bio- and osseointegration processes can be controlled at molecular and cellular levels by modification of the implant surface. One of the most promising of such surface modifications is laser ablation, as demonstrated by our previous results [46]. Commercially pure (CP4) sand-blasted, acid-etched titanium disks (Denti® System Ltd., Hungary) were irradiated with a KrF excimer laser (248 nm, fluence 0.4 J/cm², FWHM 18 ns, 2000 pulses), or with a Nd:YAG laser (532 nm, 1.3 J/cm², 10 ns, 200 pulses) then examined by SEM, AFM, and XPS. In vitro attachment (24 h) and proliferation (72 h) of MG-63 osteoblast cells were investigated via dimethylthiazol-diphenyl tetrazolium bromide (MTT), alamarBlue (AB) assays alkaline phosphatase quantification (ALP) and SEM. SEM and AFM revealed significant changes in morphology and roughness. XPS confirmed the presence of TiO₂ on each sample; after Nd:YAG treatment a reduced state of Ti (Ti^3 +) was also observed. MTT, AB and ALP measurements detected an increase in the number of cells between the 24- and 72 hour observations; however, laser treatment did not affect cell attachment and proliferation significantly.     

Comparison of directly compressed vitamin B12 tablets prepared from micronized rotary-spun microfibers and cast films

Fiber-based dosage forms are potential alternatives of conventional dosage forms from the point of the improved extent and rate of drug dissolution. Rotary-spun polymer fibers and cast films were prepared and micronized in order to direct compress after homogenization with tabletting excipients. Particle size distribution of powder mixtures of micronized fibers and films homogenized with tabletting excipients were determined by laser scattering particle size distribution analyzer. Powder rheological behavior of the mixtures containing micronized fibers and cast films was also compared. Positron annihilation lifetime spectroscopy was applied for the microstructural characterization of micronized fibers and films. The water-soluble vitamin B₁₂ release from the compressed tablets was determined. It was confirmed that the rotary spinning method resulted in homogeneous supramolecularly ordered powder mixture, which was successfully compressed after homogenization with conventional tabletting excipients. The obtained directly compressed tablets showed uniform drug release of low variations. The results highlight the novel application of micronized rotary-spun fibers as intermediate for further processing reserving the original favorable powder characteristics of fibrous systems.     

The Form of Sulfur Impurity in Neutron Irradiated Commercial C60

Abstract

By using SEM, SAED, HRTEM and XPD it was found that the unexpectedly high sulphur impurity in some commercial C₆₀ product readily reacts with C₆₀, during neutron irradiation producing the compound C₆₀S₁₆ ⁽³⁾ that can be regarded as a stable collecting form of the original undefined sulphur impurities.     

A novel cyclic RGD-containing peptide polymer improves serum-free adhesion of adipose tissue-derived mesenchymal stem cells to bone implant surfaces

Seeding of bone implants with mesenchymal stem cells (MSCs) may promote osseointegration and bone regeneration. However, implant material surfaces, such as titanium or bovine bone mineral, fail to support rapid and efficient attachment of MSCs, especially under serum-free conditions that may be desirable when human applications or tightly controlled experiments are envisioned. Here we demonstrate that a branched poly[Lys(Ser_i-DL-Ala_m)] polymer functionalized with cyclic arginyl-glycyl-aspartate, when immobilized by simple adsorption to tissue culture plastic, surgical titanium alloy (Ti6Al4V), or Bio-Oss^® bovine bone substitute, significantly accelerates serum-free adhesion and enhances seeding efficiency of human adipose tissue-derived MSCs. Moreover, when exposed to serum-containing osteogenic medium, MSCs survived and differentiated on the peptide-coated scaffolds. In summary, the presented novel polypeptide conjugate can be conveniently used for coating various surfaces, and may find applications whenever quick and efficient seeding of MSCs is required to various scaffolds in the absence of serum.