Search results for "scanning"
showing 10 items of 1808 documents
The comparison of seven different methods to quantify the amorphous content of spray dried lactose
2006
The purpose of this work was to verify the usefulness, advantages and disadvantages of seven methods that are widely used to detect, and quantify the amorphous contents in pharmaceutical solids. Here, StepScan DSC, a type of modulated temperature calorimetry method, was applied for the first time to quantify amorphicity. The comparison of the analytical methods was undertaken with real (non-artificial) test samples, i.e. spray-dried lactose samples with various degrees of crystallinity. In these samples, it was essential that the amorphous and the crystalline portions are not present as separate particles, which is the case when physical (artificial) mixtures of totally amorphous and totall…
Effects of Ethanol to Water Ratio in Feed Solution on the Crystallinity of Spray-Dried Lactose
2002
In the present study, the effects of ethanol to water ratio in feed solution on the physical properties of spray-dried alpha-lactose monohydrate were evaluated. Crystallinity of the spray-dried lactose was determined by isothermal microcalorimetry (IMC) and by differential scanning calorimetry (DSC). Water content of the spray-dried lactose was determined by thermogravimetric analysis and the surface area was evaluated by Brunauer, Emmett, and Teller (BET) method. The crystallinity of spray-dried lactose varied from 0% to 100%, depending on the ratio of ethanol to water in the feed solution. Lactose spray dried from pure ethanol was 100% crystalline and contained hydrate water. Lactose spra…
Micro-Raman characterization of graphene grown on SiC(000-1)
2014
Graphene (Gr) was grown on the C face of 4H-SiC under optimized conditions (high annealing temperatures ranging from 1850 to 1950°C in Ar ambient at 900 mbar) in order to achieve few layers of Gr coverage. Several microscopy techniques, including optical microscopy (OM), ?Raman spectroscopy, atomic force microscopy (AFM) and atomic resolution scanning transmission electron microscopy (STEM) have been used to extensively characterize the lateral uniformity of the as-grown layers at different temperatures. ?Raman analysis provided information on the variation of the number of layers, of the stacking-type, doping and strain.
Local Time-Dependent Charging in a Perovskite Solar Cell
2016
Efficient charge extraction within solar cells explicitly depends on the optimization of the internal interfaces. Potential barriers, unbalanced charge extraction, and interfacial trap states can prevent cells from reaching high power conversion efficiencies. In the case of perovskite solar cells, slow processes happening on time scales of seconds cause hysteresis in the current-voltage characteristics. In this work, we localized and investigated these slow processes using frequency-modulation Kelvin probe force microscopy (FM-KPFM) on cross sections of planar methylammonium lead iodide (MAPI) perovskite solar cells. FM-KPFM can map the charge density distribution and its dynamics at intern…
Use of a collagen/elastin-membrane for the tissue engineering of dermis.
1999
In an experimental model in rats, xenogeneic membranes consisting of processed native collagen and elastin were grafted to serve as a template for the formation of a neo-dermis, while in vitro-cultured autogeneic keratinocytes were applied on top of this to restore an epidermis. The process of tissue reconstruction and the digestion of the grafted membrane components were analysed by histological and immunohistochemical methods as well as electron microscopy. Approximately 3 weeks post grafting the membranes were completely vascularised and colonized by different types of cells. After 6 weeks, the collagenous fibres of the graft were mostly replaced by newly formed collagenous texture, wher…
Influence of cryogenic grinding on properties of a self-emulsifying formulation
2003
Abstract Recently, self-emulsifying drug delivery systems (SEDDS) have been developed as a method to deliver lipophilic drugs. Gelucire® 44/14 is an excipient, from the lauroyl macrogolglycerides family, producing a fine oil-in-water emulsion when introduced into an aqueous phase under gentle agitation as SEDDS, improving thereby solubility of poorly water-soluble drugs and their bioavailability. The aims of this study were to process Gelucire® 44/14 into a powder by cryogenic grinding to produce solid oral dosage forms and to investigate influence of this process on different properties of a formulation made of Gelucire® 44/14 and ketoprofen (90/10). Cryogenic grinding produced Gelucire® 4…
Colonic drug delivery: influence of cross-linking agent on pectin beads properties and role of the shell capsule type.
2006
For colonic delivery, pectin beads obtained by ionotropic gelation method have been already reported as an interesting approach. This study investigated the influence of the cross-linking agent (calcium or zinc) and the type of shell capsule used (classical or enteric capsules) on pectin beads properties and on their performance to target the colon (in vitro dissolution studies with subsequent pH change to mimic overall gastro-intestinal tract). Zinc pectinate beads seemed to be relatively similar to calcium's ones in morphological point, except on the surface aspect. When beads were introduced in classical hard capsules, ketoprofen release was not significantly different between CPG and ZP…
Miscibility and properties of linear poly(l-lactide)/branched poly(l-lactide) copolyester blends
2006
Abstract Polymer blends consisting of linear poly( l -lactide) (PLLA) and different proportions of dendritic PLLA-based copolyesters ( hb -PLLA) characterized by different degrees of branching (DB) were obtained in melt. The solid-state properties of poly( l -lactide)s and their blends were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), atomic force microscopy (AFM) and stress–strain measurements. DSC and DMA methods proved miscibility of PLLA/ hb -PLLA blends for the studied composition range. AFM indicated that no phase separation occurs in PLLA/ hb -PLLA blends and that PLLA and hb -PLLA cocrystallize in one single lamellae type. The mechanica…
Comparison of two melting range analysis methods with lactitol monohydrate
2001
Abstract In pharmacopoeia, the melting point is determined by a standard method with a melting point instrument. The melting point can also be determined with differential scanning calorimetry (DSC). In this study, the standard method and DSC method are compared for determining the melting range of lactitol monohydrate. The effect of initial temperature, grinding, and drying on the melting range of different lactitol monohydrate samples was studied by a melting point instrument. The melting point and melting enthalpy of the stable form of lactitol monohydrate was identified by DSC. The statistical analysis of the results is based on a t-test. All studied variables had a small effect on the …
Scanning electrochemical microscopy as a probe of Ag+ binding kinetics at Langmuir phospholipid monolayers
2005
A new method has been developed for measuring local adsorption rates of metal ions at interfaces based on scanning electrochemical microscopy (SECM). The technique is illustrated with the example of Ag+ binding at Langmuir phospholipid monolayers formed at the water/air interface. Specifically, an inverted 25 microm diameter silver disc ultramicroelectrode (UME) was positioned in the subphase of a Langmuir trough, close to a dipalmitoyl phosphatidic acid (DPPA) monolayer, and used to generate Ag+ via Ag electro-oxidation. The method involved measuring the transient current-time response at the UME when the electrode was switched to a potential to electrogenerate Ag+. Since the Ag+/Ag couple…