Atomic-scale 3D imaging of individual dopant atoms in an oxide semiconductor.

The physical properties of semiconductors are controlled by chemical doping. In oxide semiconductors, small variations in the density of dopant atoms can completely change the local electric and magnetic responses caused by their strongly correlated electrons. In lightly doped systems, however, such variations are difficult to determine as quantitative 3D imaging of individual dopant atoms is a major challenge. We apply atom probe tomography to resolve the atomic sites that donors occupy in the small band gap semiconductor Er(Mn,Ti)O3 with a nominal Ti concentration of 0.04 at. %, map their 3D lattice positions, and quantify spatial variations. Our work enables atomic-level 3D studies of structure-property relations in lightly doped complex oxides, which is crucial to understand and control emergent dopant-driven quantum phenomena.

Functional electronic inversion layers at ferroelectric domain walls.

Ferroelectric domain walls hold great promise as functional two-dimensional materials because of their unusual electronic properties. Particularly intriguing are the so-called charged walls where a polarity mismatch causes local, diverging electrostatic potentials requiring charge compensation and hence a change in the electronic structure. These walls can exhibit significantly enhanced conductivity and serve as a circuit path. The development of all-domain-wall devices, however, also requires walls with controllable output to emulate electronic nano-components such as diodes and transistors. Here we demonstrate electric-field control of the electronic transport at ferroelectric domain walls. We reversibly switch from resistive to conductive behaviour at charged walls in semiconducting ErMnO3. We relate the transition to the formation-and eventual activation-of an inversion layer that acts as the channel for the charge transport. The findings provide new insight into the domain-wall physics in ferroelectrics and foreshadow the possibility to design elementary digital devices for all-domain-wall circuitry.

Polysaccharides from the red seaweed Gracilaria dura (Gracilariales, Rhodophyta).

The yield and physical and chemical properties of agars from Gracilaria dura (C. Agardh) J. Agardh, harvested in Thau lagoon (Mediterranean sea, France), were investigated. The agar yield ranged from 32% to 35%. Gel strength of agar ranged from 263 to 600 g cm(-2), with the maximum observed in October. A positive correlation was found between agar yield and gel strength (r = 0.82; P < 0.01). The gelling temperature followed the same pattern of gel strength and also showed higher value in October (43 degrees C). The nitrogen content varied from 1.04+/-0.60% (June) to 4.70+/-0.01% (October). A positive correlation was noted between nitrogen content and gel strength (r = 0.77; P < 0.05). The 3,6-anhydrogalactose content ranged from 0.70 to 0.84 and showed monthly significant differences (P < 0.05). There was a positive correlation between 3,6-anhydrogalactose content and gel strength. The values of sulfate content were relatively constant during the studied period and no significant differences were observed. The relative high gel strength indicates that this species may be considered as source of agar for commercial use.

Effects of season on the yield and quality of agar from Gracilaria species (Gracilariaceae, Rhodophyta).

The effect of season on yield and physical properties of agars extracted from Gracia gracilis and G. bursa-pastoris were determined. The agar yield from G. gracilis was maximum during spring (30%) and minimum during autumn (19%). In G. bursa-pastoris, the agar yield was greatest in summer (36%) and lowest in winter (23%). Agar yield from G. bursa-pastoris was positively correlated with temperature (r=0.94; P<0.01) and salinity (r=0.97; P<0.01) and negatively with nitrogen content (r=-0.93; P<0.01). Agar gel strengths fluctuated from 229 to 828 gcm(-2) and 23 to 168 gcm(-2) for G. gracilis and G. bursa-pastoris, respectively. The gelling temperature showed significant seasonal variation for both species. Chemical analysis of agar from the two seaweeds indicated variation in 3,6-anhydrogalactose and sulfate content (P<0.01). Furthermore, there was an inverse correlation between the two chemical variables. In general, agar extracted from G. gracilis possessed better qualities than agar extracted from G. bursa-pastoris and can be considered a candidate for industrial use.

Effect of controlled kappa-casein hydrolysis on rheological properties of acid milk gels.

An experimental method based on the controlled chymosin-induced kappa-casein hydrolysis of milk was proposed to modify micellar reactivity. Milk samples with a degree of kappa-casein hydrolysis of 19, 35, and 51% were obtained. The physicochemical properties of partially converted casein micelles were determined. The net negative charge of casein micelles was reduced with increasing degree of kappa-casein hydrolysis and a small but significant decrease in hydrodynamic diameter and micellar hydration were noted. Dynamic low amplitude oscillatory rheology was used to monitor the rheological properties of acid milk gels (GDL) made with partially chymosin-hydrolyzed milks in comparison with those of strictly acid and rennet gels. An increase in the gelation pH value was observed with increasing the degree of kappa-casein hydrolysis. The moduli values (G' and G'') reached 2 h after the point of gel were, for all degrees of hydrolysis tested, significantly higher than those of strictly rennet and acid gels. Comparison of changes in delta G'/delta t with time indicated differences in gel formation that could be related to the increased values of G' obtained for acid gel made with chymosin-treated milk. At a given time after gelation (2 h), increasing the degree of kappa-casein hydrolysis in milk led also to an increase in the loss tangent and the serum holding capacity of acid milk gels suggesting a correlation between these two parameters.

Prick tests to aeroallergens: is it possible simply to wipe the device between tests?

BACKGROUND: Improperly performed skin prick tests (SPT) can lead to wrong allergy diagnosis and incorrect treatment. To overcome false-positive results it is recommended to change the puncture device between each test, although very few studies have examined the real drawbacks (false-positives) and advantages (time and cost savings) of using only one device. METHODS: Two groups of 20 patients with rhinitis or asthma, sensitized to either house-dust mites or grass pollens, had successive serial SPT to 9% codeine phosphate and the relevant allergen using the same needle or lancet, wiped between each test. RESULTS: With both the needle and the lancet, there were 12.5-67.5% false-positive results using the house-dust mite or grass pollen allergen extracts, respectively. There were no false-positive results with the 9% codeine phosphate. CONCLUSIONS: Our study shows that this technique is not reliable as it provoked an unacceptable number of false-positive results.

The meaning of mobility for residents and staff in long-term care facilities.

BACKGROUND: Although the physical and psychological effects of decreased mobility have been documented, little is known about what it means to be mobile from the institutionalized elders' perspective. Even less is known about nurses' perceptions regarding institutionalized elders' mobility and about mobility enhancing strategies. AIM: The purpose of this study was to generate knowledge about the phenomenon of mobility from both the nurses' and institutionalized elders' perspective. DESIGN: An exploratory qualitative design was used. Focus groups with residents and nursing staff were conducted in three long-term care facilities in a large metropolitan city in 1998. Ethical approval was received from the ethics committees in all three facilities prior to study implementation. Twenty long-term care facility residents and 15 nursing staff participated in the study. METHODS: A trained facilitator used an interview guide to moderate discussions in which residents' and nurses' opinions and feelings about mobility were solicited. The group responses were tape recorded, transcribed and coded. The codes reflected major concepts or abstractions of the data and emerged from the participants' verbal responses to the research questions. FINDINGS: Both groups identified mobility as being pivotal to the residents' quality of life and well-being. The residents viewed mobility as a means of freedom, choice and independence, and they made great efforts to maintain their mobility. The nurses also valued the importance of mobility and assisted the residents through preparatory care, environmental modifications and encouragement. Factors that related to the residents' willingness to be mobile, environmental barriers and the impact of waiting were compared between the two groups. CONCLUSION: Mobility involves more than the movement from one point to another. The nature of the assistive nurse-client relationship and the resident's subjective perspective must become central to understanding the meaning of mobility for residents in a long-term care facility.

In-vitro comparative study of buccal mucoadhesive performance of different polymeric films.

A comparison of the buccal mucoadhesive performance of different polymeric films was carried out using texture analyzer TA-XT2i. A large range of putative polymers differing in their chemical nature, molecular structure as well as hydration status was used. The used polymeric films were classified in rank order of buccal mucoadhesive performance, namely carbopol 971P>polycarbophil>Carrrageenan type lambda > Sodium carboxymethylcellulose. Swelling state as well as tensile strength of the used polymeric films was used as measuring parameters of mucoadhesive interaction. These two approaches gave two opposite orders of performance between CMC and Carrrageenan type lambda after a contact time of 15 min. However the measurement of the viscoelastic moduli of the hydrogels gave the same ranking order of mucoadhesive performance after the same contact time. In reference to the previous works, we noted the importance of the molecular weight, the density of charges, the composition of which the chains of molecules are capable to arrange themselves in a network like form, thus those which are characterized by a tan delta<1 (i.e network formation), are those which develop the best synergism with the mucus because of the reinforcement of an established link. The goal of this study is to assess the buccal mucoadhesive performance aiming to optimize the design of drug delivery via buccal mucoadhesive polymeric films

Addressing ethical issues in geriatrics and long-term care: ethics education at the Baycrest Centre for Geriatric Care.

An innovative program in ethics education exists at Baycrest Centre for Geriatric Care. This program can serve as a helpful model for long-term care and geriatric care facilities seeking to implement formal training programs in bioethics. Various aspects of the ethics education program are examined. In addition to describing the role of the ethics committee and research ethics board, consideration is given to case consultations, ethics rounds, the training of junior physicians and medical students, grand rounds and the planning of conferences and guest lectures. With regard to educational content in bioethics, health law, professional guidelines and the principlist approach of Beauchamp and Childress are used to explore the ethical dimensions of particular cases. Given the clinical context of the educational initiatives, the pedagogical approach is predominately case-based. While the bioethics literature emphasizes the patient-physician relationship, ethics education at Baycrest recognizes the importance of multiple professions. Physicians, nurses, social workers, speech pathologists, nutritionists and other health care providers are involved in ethical deliberation and education.

Rheological behavior of drug suspensions in Gelucire mixtures and proxyphylline release from matrix hard gelatin capsules.

Mixtures of Gelucires 50/02 and 50/13 showing different hydrophilic-lipophilic balances (HLB) and of proxyphylline were used to prepare suspensions at a concentration of 25% and to manufacture extended release hard gelatin capsules by cooling. The rheological behaviors of Gelucire mixtures with and without drug were determined by adjustment of the rheograms to the Ostwald power-law and by statistical assessment of the flow index. Pure Gelucire mixtures were very slightly shear thickening whereas proxyphylline suspensions had a thixotropic shear thinning behavior. These rheological behaviors can be explained by the chemical composition and by the ratio of the two Gelucires used. Extended release of proxyphylline was obtained with all these mixtures. Drug release increased with Gelucire mixture HLB owing to higher erosion. A viscosity-release relationship was found and allowed, with these two Gelucires of extreme HLB and viscosities, to define the formulations which will give an optimal drug release, by the determination of their suspension viscosity. Modeling of dissolution kinetics has generally shown the predominance of surface erosion of the plugs relative to drug diffusion inside the matrix. This was confirmed by the better linearization of percentage released, according to Hixson-Crowell as compared with Higuchi.

Rheology of polyol behenates and drug release from matrix monolithic capsules.

Three polyol behenates with similar melting points (MP) and different hydrophilic-lipophilic balances (HLB) were studied (MP/HLB: 70/02, 63/05 and 57/13). After melting at MP+30 degrees C, the rheological behaviour of behenates was determined by adjustment of the rheograms to the Ostwald power-law and by statistical assessment of the flow index. Behenates showed slight shear thickening. This shear thickening increased when HLB of behenates decreased. This behaviour accounted for a reorganization of the particles under the shear, which became easier when the proportion of the polyethylene glycol chains in the wax decreased. Proxyphylline was used to prepare suspensions at a concentration of 25% in the melted behenates, and to manufacture monolithic capsules by cooling. The suspensions had a shear-thinning behaviour with or without thixotropy. Colloidal particles and aggregates formed in these suspensions directly influenced the rheological properties, as observation of solidified suspensions by scanning electron microscopy confirmed. Extended release of proxyphylline was obtained with the three waxes. Behenates 63/05 and 70/02 gave inert matrices and released drug very slowly. Hydrodispersible behenate 57/13 swelled and made up a kind of hydrophilic matrix that released proxyphylline more quickly, due to slight erosion. In the three cases, the release mechanism was basically diffusional in nature.

Effect of formulation on the rheology of theophylline compound suspensions in Gelucires.

The theophylline derivatives, etofylline, diprophylline and proxyphylline, which exhibit increasing aqueous solubility, were used to prepare suspensions in seven saturated polyglycolyzed glycerides (Gelucires) characterized by their rising hydrophilic-lipophilic balance (HLB). Drug concentration was set at 25% w/w and the production temperature was set at the Gelucire melting point plus 30 degrees C in order to obtain suitable suspensions. Various formulation factors were studied. Ostwald flow indices revealed that the suspensions had a thixotropic shear-thinning behaviour and a relative viscosity which increased as drug aqueous solubility rose and Gelucire HLB decreased. These rheological properties could be explained by the chemical composition of Gelucires and drugs used. A microstructure was proposed for the liquid suspension such that colloidal particles and aggregates formed in these suspensions directly influenced the observed rheological properties. Observation of solidified suspensions by scanning electron microscopy confirmed this hypothesis. Moreover, a correlation between the relative viscosity of drug suspensions on the one hand and drug concentration, drug solubility and Gelucire HLB on the other allowed for the calculation of the required concentration of each theophylline derivative in each Gelucire to obtain a given viscosity.

Rheological behaviour of saturated polyglycolysed glycerides.

Seven saturated polyglycolysed glycerides (Gelucires) of melting points varying from 42 to 53 degrees C and hydrophilic-lipophilic balance values from 2 to 14 were selected. Their rheological behaviour was determined by adjustment of the flow curves to the Ostwald power-law and by statistical assessment of the flow index. The flow of Gelucires was slightly shear thickening. This shear thickening rose when the temperature and the lipophilic specificity of the Gelucire increased. This behaviour accounted for a reorganization of the particles under the shear which became easier when the temperature increased and when the degree of condensation of the polyethylene glycol chains decreased with lipophilicity of the Gelucires.

[Determination of micro-quantities of serum lithium by atomic absorption spectrophotometry. Significance and applications]. / Détermination de micro-quantités de lithium sérique par spectrophotométrie d'absorption atomique. Intérêt et applications.

The dilution of serum and the ionic components having an usual effect upon the lithium assay is examined about their influences in the determination of lithium microquantities. These are discussed according to the technique selected as well as the normal ionic variations that may be come across in serums. The method was applied to determination of serum lithium rate in a group of old subjects. The got lithium distribution is unsymmetrical at lower rates and no influence of age or sex was obvious.

[A simple hemolytic plate method for complement activity estimation (author's transl)]. / Application de l'immuno-hémolyse radiale au dosage courant du complément sérique.

The previous single radial haemolysis method is simplified for complement activity assay in human serums. The proceeding a "one point" test is described. This new technique is remarkable by its simplicity and rapidity. A study of the precision shows tha possibility of to make use of this simple "one point" hemolytic plate method.

[A study of the single radial haemolysis optimization for complement haemolytic activity assay (author's transl)]. / Etude de l'optimisation du test d'immunohemolyse radiale applique au dosage du complement total.

The experimental conditions for single radial haemolysis are analysed in order to optimize the haemolytic plate method for the assay of human total complement. The amount of haemolytic antibody used for sensitization of red cells, the concentration of sensitized sheep erythrocytes, the thickness of agarose layer, and the diameters of wells all exercise an influence on the area of haemolysis. The effects of these parameters are investigated with a view to obtaining the clearest reading and greatest sensitivity of the haemolytic activity plate method, and at the same time verifying the validity of the assay and the precision of the human serum haemolytic titres. This work reports the optimal experimental requirements with regard to the factors studied for minimizing the sources of error in complement haemolytic plate assay.