Different resol phenol–formaldehyde prepolymer resins have been synthesized with different Formaldehyde/Phenol (F/P) ratios or different catalysts and characterized by
13C NMR spectroscopy in ...solution. A fast quantitative measuring protocol is proposed based on the use of chromium(III)acetylacetonate as a relaxation agent. APT (attached proton test) and DEPT (distortionless enhancement by polarisation transfer) spectra were acquired to enable proper resonance assignments, especially in the regions with severe signal overlap. Equations are presented in which the methylene bridges (MB), the methylol groups (MG) and the dimethylene ether bridges (DMEB) of resol resins are quantitatively taken into account. Important structural factors determined quantitatively for resol prepolymer resins are the F/P ratio after reaction, the degree of polymerization (
n), the number average molecular weight (
M
n) and the content of free
ortho and
para positions.
The anterior jaw bones are often considered relatively safe surgical sites. Nonetheless, the increasing rate of surgical interventions in that area, such as oral implant placement and bone grafting, ...has highlighted the potential risks and has raised the reported complications. A careful documentation of all anatomic variations in anterior jaw bone neurovascularization has thus become necessary. The present report attempts to revisit jaw bone neurovascularization, addressing typical anatomic appearances and variations. We summarize the results of various microanatomical studies carried out by high-resolution magnetic resonance imaging (HR-MRI) of the human anterior jaw bones. These studies reveal that edentulous and dentate anterior jaws present significant variation in the occurrence of the mandibular incisive canal and genial spinal foramina, as well as the maxillary nasopalatine canal. All of these canal structures contain a neurovascular bundle, whose diameter may be large enough to cause clinically significant trauma. A careful presurgical radiographic analysis of the anterior jaw bones is therefore advised.
A qualitative and quantitative study of the curing behaviour of a high-ortho novolac resin with paraformaldehyde under different conditions is reported. The extent of cure by means of the ...formaldehyde/phenol ratio, the degree of conversion, and the characterization of the final structure after curing are determined based on quantitative
13C solid-state nuclear magnetic resonance with cross polarization and magic angle spinning. The
T
1H relaxation time is measured as a probe to follow the evolution of cure. In conjunction Fourier transform–Raman spectroscopy is proposed as a qualitative tool to follow the degree of crosslinking in this high-ortho novolac.
17 alpha-Boldenone (17 alpha-BOL) and/or 17 beta-boldenone (17 beta-BOL) appear occasionally in fecal matter of cattle. In addition to 17 alpha-BOL, a whole array of boldenone related substances can ...be found in the same samples. In vitro experiments with microsomal liver preparations and isolated hepatocytes combined with the excretion profiles found in urine and feces samples of in vivo experiments made it possible to identify several metabolites of 17 beta-BOL in 17 beta-BOL positive feces samples. In one animal treated with 17 beta-BOL, no 17 beta-BOL or its metabolites were present before treatment and most of these compounds disappeared gradually in time after the treatment was stopped. It is not clear what the origin is of 17 alpha-BOL and boldenone metabolites in samples screened routinely for the abuse of anabolic steroids and considered to be 'negative' because of the absence of 17 beta-BOL since other workers showed some evidence that 17 alpha-BOL can be of endogenous origin. However, in our hands, most of these 17 alpha-BOL positive samples, obtained during routinely performed screenings of cattle, contained large amounts of delta 4-androstene-3,17-dione (AED), which normally is absent from routinely screened negative samples. Furthermore, AED was absent in all samples obtained from the animals treated with 17 beta-BOL. We have no direct evidence that 17 alpha-BOL or 17 beta-BOL is of endogenous origin.
The influence of octanedithiol (ODT) on the film morphology of PCPDTBT:PCBM (1:2) blends processed from solutions in chlorobenzene was studied by chemical shift selective carbon-13 solid-state NMR ...relaxation experiments. A close contact between PCBM and PCPDTBT is demonstrated for PCPDTBT:PCBM films processed with as well as without ODT, i.e. the dimensions of the substructures in the PCBM rich and polymer rich domains are smaller than 10
nm. The PCBM organization is shown to be reduced towards very small and weakly organized clusters. The main difference of processing the active film in the presence of ODT can be found in the ability of the polymer to improve its chain packing towards a state that closely resembles this of pure PCPDTBT. This difference in physical interaction between the polymer chains can explain the improved power conversion efficiency and the EQE red-shift of solar cells processed with ODT.
Display omitted
► Solid-state NMR was used to study the influence of ODT on PCPDTBT:PCBM morphology. ► A close contact between PCBM and PCPDTBT is demonstrated in every case (w/ or w/o ODT). ► The dimensions of the PCBM and PCPDTBT substructures are smaller than 10
nm. ► The PCBM is organized into very small and weakly organized clusters. ► The ODT improves polymer chain packing towards this of pure PCPDTBT.
A modified starch (high-amylose, crystalline and resistant starch) was evaluated as an alternative excipient to microcrystalline cellulose for pellets prepared via extrusion/spheronisation. ...Theophylline anhydrous (25%, w/w) was used as a model drug. A binder was necessary to obtain an acceptable yield and the addition of sorbitol improved the surface properties of the pellets. A surface response design with three formulation variables (binder, sorbitol and water level) and one process variable (spheronisation speed) was used to optimise the process and to evaluate pellet yield, sphericity (aspect ratio and two-dimensional shape factor,
e
R), size (mean Feret diameter), friability and disintegration properties. Mixer torque rheometry and solid-state NMR revealed a significant influence of sorbitol on wet mass consistency and pellet properties. A high pellet yield (>90%), acceptable sphericity (AR
<
1.2), low friability (<0.01%), fast disintegration (<10
min) and complete drug release in less than 20
min for all formulations, demonstrated the potential of this modified starch in formulations intended for extrusion/spheronisation.
PDF
