bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Approach of Mathematical Analysis of Structure of Graphene as a Potential Material for Composites
Authors: Jaroniek Mieczysław , Czechowski Leszek , Kaczmarek Łukasz , Warga Tomasz , Kubiak Tomasz
Published: November 2019

The new analysis of a simplified plane model of single-layered graphene is presented in this work as a potential material for reinforcement in ultralight and durable composites. However, owing to the clear literature discrepancies regarding the mechanical properties of graphene, it is extremely difficult to conduct any numerical analysis to design parts of machines and devices made of composites. Therefore, it is necessary to first systemize the analytical and finite element method (FEM) calculations, which will synergize mathematical models, used in the analysis of mechanical properties of graphene sheets, with the very nature of the chemical bond. For this reason, the considered model is a hexagonal mesh simulating the bonds between carbon atoms in graphene. The determination of mechanical properties of graphene was solved using the superposition method and finite element method. The calculation of the graphene tension was performed for two main directions of the graphene arrangement: armchair and zigzag. The computed results were verified and referred to articles and papers in the accessible literature. It was stated that in unloaded flake of graphene, the equilibrium of forces exists; however, owing to changes of inter-atom distance, the inner forces occur, which are responsible for the appearance of strains.
Prediction of Effective Strain Distribution in Two-Pass Drawn Wire
Authors: Lee Sang-Kon , Lee In-Kyu , Lee Sung-Min , Lee Sung-Yun
Published: November 2019

In the multi-pass wire drawing process, the diameter of a wire is decreased by continuously passing it through progressively smaller drawing dies. Although the deformation depends on the process variables, in most wire drawing processes, the wire deformation is concentrated on the surface by its direct contact with the drawing dies, causing a nonlinear distribution of radial direction effective strain from the center to the surface. In this study, a new model for predicting this effective strain in two-pass drawn wire was derived based on the upper bound method, and a finite element analysis and drawing experiment were conducted to validate its effectiveness. The proposed model offers a promising approach to determining and thus controlling the strain in multi-pass drawn wire.
The Effect of Exposure on the Autogenous Self-Healing of Ordinary Portland Cement Mortars
Authors: Rajczakowska Magdalena , Habermehl-Cwirzen Karin , Hedlund Hans , Cwirzen Andrzej
Published: November 2019

Exposure conditions are critical for the autogenous self-healing process of Portland cement based binder matrixes. However, there is still a significant lack of fundamental knowledge related to this factor. The aim of this paper was to investigate and understand the effects of various potentially applicable curing solutions on the efficiency of the crack closure occurring both superficially and internally. Four groups of exposures were tested, including exposure with different water immersion regimes, variable temperatures, application of chemical admixtures, and use of solutions containing micro particles. The self-healing process was evaluated externally, at the surface of the crack, and internally, at different crack depths with the use of optical and scanning electron microscopes (SEM). The phase identification was done with an energy dispersive spectrometer combined with the SEM. The results showed very limited self-healing in all pure water-based exposures, despite the application of different cycles, temperatures, and water volumes. The addition of a phosphate-based retarding admixture demonstrated the highest crack closure, both internally and externally. The highest strength recovery and a very good crack closure ratio was achieved in water exposure containing micro silica particles. The main phase observed on the surface was calcium carbonate, and internally, calcium silicate hydrate, calcium carbonate, and calcium phosphate compounds. Phosphate ions were found to contribute to the filling of the crack, most likely by preventing the formation of a dense shell composed of hydration phases on the exposed areas by crack unhydrated cement grains as well as by the additional precipitation of calcium and phosphate-based compounds. The micro sized silica particles presumably served as nucleation sites for the self-healing products growth. Changes in the chemical composition of the self-healing material were observed with a distance from the surface of the specimen.
Using 445 nm and 970 nm Lasers on Dental Implants—An In Vitro Study on Change in Temperature and Surface Alterations
Authors: Malmqvist Sebastian , Liljeborg Anders , Qadri Talat , Johannsen Gunnar , Johannsen Annsofi
Published: November 2019

The aim of this study was to evaluate the safety of using a 445 nm laser on dental implants by comparing it with a laser with 970 nm wavelength. Two models, a pig mandible and glass ionomer cement, were used to evaluate the temperature increase in dental implants during laser irradiation with both wavelengths. Temperature was measured every second at four different places on the dental implants. Different power settings, effects of water cooling, distance of the laser fibre to the dental implant and continuous comparison to a pulsed laser beam were tested. Surface alterations on titanium discs after laser irradiation for 4 min at 2.0 W, were analysed in a scanning electron microscope (SEM). The maximum temperature and time to reach each of the thresholds were comparable between the 445 nm and 970 nm lasers. Neither the 445 nm nor the 970 nm wavelength showed any signs of surface alterations on the titanium discs. Using a 445 nm laser on dental implants is as safe as using a 970 nm laser, in terms of temperature increase and surface alterations. Applying a generous amount of cooling water and irradiating in short intervals is important when using lasers on dental implants.
ACTH-dependent Hypercortisolemia in a Patient with a Pituitary Microadenoma and an Atypical Carcinoid Tumour of the Thymus
Authors: Baranowska-Jurkun Angelika , Szychlińska Magdalena , Matuszewski Wojciech , Modzelewski Robert , Bandurska-Stankiewicz Elżbieta
Published: November 2019

Cushing’s syndrome (CS) is a set of clinical symptoms which occur as a result of hypercortisolemia. Endogenous ACTH-dependent CS related to an ectopic ACTH-secreting tumour constitutes 12%–17% of CS cases and is one of the most common causes of paraneoplastic syndromes. This study presents a case of a 31 year-old man with diabetes, hypertension, rosacea, purple stretch marks and hypokalemia. Findings of diagnostic procedures include high concentrations of cortisol and ACTH, pituitary microadenoma and a tumour in the anterior mediastinum. Dynamic hormone tests determined the source of excess hormone secretion and ectopic ACTH-dependent CS was diagnosed. Due to increasing symptoms of superior vena cava syndrome, an emergency resection of almost the whole tumour was performed, with only a small part of the upper pole left because of the proximity of large vessels and a risk of damaging them. On the basis of histopathological tests, an atypical carcinoid tumour of the thymus was identified. Immediately after the surgical procedure, there was a significant reduction of clinical and laboratory traits of hypercortisolemia, yet, during the 46 weeks of postoperative observation, despite chemotherapy, the progression of residual masses of the tumour occurred with metastases and increased hormone indices. The presented case shows and discusses the differentiation of ACTH-dependent hypercortisolemia and its causes, difficulties in surgical therapy and chemotherapy, as well as prognosis for atypical carcinoid of the thymus, which is a rare disease.
Narcolepsy in Children and Adults: A Guide to Improved Recognition, Diagnosis and Management
Authors: Morse Anne Marie
Published: November 2019

Narcolepsy is a rare condition that affects children and adults, and commonly has an onset in childhood. Time to appropriate diagnosis frequently is at least a decade. Unrecognized or misdiagnosed symptoms of narcolepsy contribute to increased morbidity, disability and socioeconomic liability in these patients. Delays in diagnosis may be related to variability in presentation in childhood, lack of familiarity with symptoms or appropriate diagnostic testing or misdiagnosis with accidental introduction of treatment that may modify or mask narcolepsy features. Improved awareness about the diagnosis and tailored therapies improve clinical and socioeconomic outcomes by reducing time to effective treatment. Application of effective treatment results in long-term benefits by improving clinical outcomes, potentially enabling improved education, increased employment opportunity, and improved work productivity and quality of life. This review provides a comprehensive stepwise approach to improve knowledge and comfort for recognition of symptoms, diagnostic strategies and management considerations of narcolepsy in children and adults.
Investigation of NbC/TiC Heterogeneous Nucleation Interface by First-Principles and Experimental Methods
Authors: Dong Jianhong , Hou Dejian , Li Jin-Yan , Huang Rui
Published: November 2019

The mechanism of the heterogeneous nucleation of NbC on TiC precipitates was investigated systematically in this paper. The interfacial properties of NbC (100)/TiC (100), NbC (110)/TiC (110), and NbC (111)/TiC (111) interfaces were studied by first-principles calculations. The results showed that the NbC (111)/TiC (111) interface with the Nb–C bond is the most stable one, and the stability of interfaces with the C–Ti, Nb–Ti, and C–C bonds decreases in turn. The interface of the Nb/C-terminated and Third Layer (TL) stacking sequence (NCTL) has the largest adhesion work (10.15 J/m2) and the smallest equilibrium interface spacing (1.290 Å). In the range of low niobium (Nb) chemical potential and high carbon (C) chemical potential, the nucleation of NbC on TiC precipitates takes precedence over the epitaxy growth in the coherent relationship of [ 1 1 ¯ 0 ] ( 111 ) NbC / / [ 1 1 ¯ 0 ] ( 111 ) TiC , while the nucleation of NbC on TiC precipitates is prior to the epitaxy growth in the coherent relationship of [ 001 ] ( 100 ) NbC / / [ 001 ] ( 100 ) TiC in the range of high niobium (Nb) chemical potential and low carbon (C) chemical potential. Besides, the characteristics of heterogeneous nucleation precipitates in Nb–Ti microalloyed steels were analyzed by transmission electron microscopy (TEM). The orientation relationship between the (Ti, Nb) C and (Nb, Ti) C precipitates follows [ 1 1 ¯ 0 ] ( 111 ) ( Nb ,   TiC ) / / [ 1 1 ¯ 0 ] ( 111 ) ( Ti ,   Nb ) C , which is consistent with the calculated result.
Influence of HIP Treatment on Mechanical Properties of Ti6Al4V Scaffolds Prepared by L-PBF Process
Authors: Liu Lili , Zheng Huade , Deng Chunlin
Published: November 2019

To improve biocompatibility and mechanical compatibility, post-treatment is necessary for porous scaffolds of bone tissue engineering. Hot isostatic pressing (HIP) is introduced into post-treatment of metal implants to enhance their mechanical properties by eliminating residual stress and pores. Additionally, oxide film formed on the material surface can be contributed to improve its biocompatibility. Ti6Al4V porous scaffolds fabricated by laser-powder bed fusion (L-PBF) process is studied in this paper, their mechanical properties are measured by pressure test, and the macroscopic surface morphology and microstructure are observed by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). After HIP treatment, an oxide layer of 0.8 μm thickness forms on the surface of Ti6Al4V porous scaffolds and the microstructure of Ti6Al4V transforms from α’ phase to α + β dual-phase, as expected. However, the pressure test results of Ti6Al4V porous scaffolds show a definitely different variation trend of mechanical properties from solid parts, unexpectedly. Concerning Ti6Al4V porous scaffolds, the compression stiffness and critical stress improves clearly using HIP treatment, and the fracture morphology shows obvious brittle fracture. Both the strengthening and brittleness transition of Ti6Al4V porous scaffolds result from the formation of an oxide layer and an oxygen atom diffusion layer. The critical stress of Ti6Al4V porous scaffolds can be calculated by fully considering these two strengthening layers. To obtain a porous scaffold with specific mechanical properties, the effect of post-treatment should be considered during structural design.
Phytochemical Composition and Bioactive Effects of Salvia africana, Salvia officinalis ‘Icterina’ and Salvia mexicana Aqueous Extracts
Authors: Afonso Andrea F. , Pereira Olívia R. , Fernandes Ângela , Calhelha Ricardo C. , Silva Artur M. S. , Ferreira Isabel C.F.R. , Cardoso Susana M.
Published: November 2019

In the present study, aqueous extracts of Salvia africana, Salvia officinalis ‘Icterina’ and Savia mexicana origin were screened for their phenolic composition and for antibacterial, antioxidant, anti-inflammatory and cytotoxic properties. The three aqueous extracts contained distinct phenolic compounds, with S. africana presenting the highest total levels (231.6 ± 7.5 μg/mg). Rosmarinic acid was the dominant phenolic compound in all extracts, yet that of S. africana origin was characterized by the present of yunnaneic acid isomers, which overall accounted for about 40% of total phenolics. In turn, S. officinalis ‘Icterina’ extract presented glycosidic forms of apigenin, luteolin and scuttelarein, and the one obtained from S. mexicana contained several simple caffeic acid derivatives. S. africana aqueous extract exhibited high antioxidant potential in four methods, namely the DPPH• (2,2-diphenyl-1-picrylhydrazyl) scavenging ability, iron-reducing power, inhibition of β-carotene bleaching and of thiobarbituric acid reactive substances (TBARS), for which EC50 values were equal or only 1.3–3.1 higher than those of the standard compounds. Moreover, this extract was able to lower the levels of nitric oxide (NO) production in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages (EC50 = 47.8 ± 2.1 μg/mL). In addition, the three sage aqueous extracts showed promising cytotoxic effect towards hepatocellular HepG2, cervical HeLa, and breast carcinoma cells MCF-7. Overall this study highlights the potential of three little-exploited Salvia species, with commercial value for applications in food or pharmaceutical industries.
The Application of Ferric Chloride-Lignin Sulfonate as Shale Inhibitor in Water-Based Drilling Fluid
Authors: Zhang Rongjun , Gao Long , Duan Wenguang , Hu Weimin , Du Weichao , Gu Xuefan , Zhang Jie , Chen Gang
Published: November 2019

A series of ferric chloride-lignin sulfonate (FCLS) was prepared from ferric chloride and lignin sulfonate to be used as shale inhibitor. The swelling rate of clay with FCLS-2 (w/w = 0.3%) decreased to 41.9%. Compared with control, FCLS-2 displayed high inhibitive ability against the hydrating and swelling processes of clay. Thus, the swelling degree of samples with FCLS-2 was much lower than that of the control, as well as the mud ball was more stable in FCLS-2 solution. Essentially, these excellent performances in inhibitor were assigned to the hydrogen bonding, electrostatic interaction and anchoring between FCLS-2 and other components. In addition, FCLS-2 has good compatibility with other common drilling fluid additives, and it can reduce the viscosity of systems, regardless of the room temperature or high temperature.
Hydrophilic Interaction Chromatography Coupled with Charged Aerosol Detection for Simultaneous Quantitation of Carbohydrates, Polyols and Ions in Food and Beverages
Authors: Pitsch Johannes , Weghuber Julian
Published: November 2019

Here, we report an accurate and versatile method for the simultaneous determination of 17 sugars (arabinose, erythrose, fructose, galactose, glucose, isomaltulose, lactose, lyxose, maltose, maltotriose, mannose, raffinose, rhamnose, ribose, sucrose, sorbose and xylose), seven polyols (erythritol, inositol, lactitol, maltitol, mannitol, sorbitol and xylitol), five ions (K+, Br−, Cl−, NO3− and SO42−) and the pseudosaccharide acarbose. For compound separation, hydrophilic interaction chromatography (HILIC) coupled to a corona charged aerosol detector (CAD) was used. The method was validated for linearity, precision, reproducibility, retention factor and optimal injection volume. Standards were measured in the range of 1–1000 mg L−1 and showed good intraday and interday repeatability, as well as precision (relative standard deviation (RSD) < 5%). The LODs and LOQs for the 30 analytes were in the range of 0.032–2.675 mg L−1 and 0.107–8.918 mg L−1, respectively. This method exhibited correlation coefficients of at least R2 > 0.97 for all analytes. The method was tested in 24 food and beverage samples to validate the separation efficiency and sensitivity in natural food matrices and to show the practicability of its use for routine food analysis.
A Switch between Antioxidant and Prooxidant Properties of the Phenolic Compounds Myricetin, Morin, 3′,4′-Dihydroxyflavone, Taxifolin and 4-Hydroxy-Coumarin in the Presence of Copper(II) Ions: A Spectroscopic, Absorption Titration and DNA Damage Study
Authors: Jomová Klaudia , Hudecova Lenka , Lauro Peter , Simunkova Miriama , Alwasel Saleh H. , Alhazza Ibrahim M. , Valko Marian
Published: November 2019

The beneficial effects of polyphenols, predominantly in the context of oxidative stress-related diseases such as cancer, cardiovascular diseases and neurological conditions including Alzheimer’s and Parkinson’s diseases, have been documented by a number of papers and reviews. The antioxidant/prooxidant properties of phenolic compounds are related mainly to the number and positions of hydroxyl groups and to their redox metal (Cu, Fe) chelating capacity. In this work we studied structurally distinct phenolic molecules such as myricetin, morin, 3′,4′-dihydroxy-flavone, taxifolin and 4-hydroxycoumarin, either alone or as interacting with Cu2+ ions. EPR and UV-Vis spectroscopy confirmed that the effective binding of cupric ions to phenolic compounds requires the presence of the 3-OH and 4-CO groups on the flavonoid C ring and unsaturated C2-C3 bond of the C-ring, which permits through-conjugation with the B-ring. An ABTS assay revealed that radical scavenging activities of phenolic compounds are related to their number of hydroxyl groups, planarity of the molecular skeleton, extent of delocalization and they decrease in the order: myricetin > morin > 3′,4′-dihydroxyflavone ~ 4-hydroxy coumarin > taxifolin. Absorption titrations indicate that copper ions can modulate the DNA binding affinity of flavonoids via the formation of their Cu-chelates. Gel electrophoresis measurements indicated that the protective effect of the phenolic compounds decreases in the order: 3′,4′-dihydroxyflavone > 4-OH coumarin > morin > taxifolin ~ myricetin. This can be explained by the fact that myricetin, taxifolin and morin form stable Cu(II) complexes capable of causing DNA damage via interaction with DNA and ROS formation via the Fenton reaction. Application of ROS scavengers revealed the formation of singlet oxygen, superoxide and hydroxyl radicals and their concerted synergistic effect on the DNA. The overall results suggest that the most pronounced DNA damage has been observed for flavonoids containing higher number of hydroxyl groups (including 3-OH group of the C ring), such as myricetin (six hydroxyl groups), morin and taxifolin (five hydroxyl groups) in the presence of Cu(II) ions. The proposed mechanism of action by which Cu(II) complexes of myricetin, morin and taxifolin interact with DNA predispose these substances to act as potential anticancer agents. The anticancer activity of phenolic compounds can be explained by their moderate prooxidant properties, which can boost ROS formation and kill cancer cells. Alternatively, slight prooxidant properties may activate antioxidant systems, including antioxidant enzymes and low molecular antioxidants such as glutathione and thus act as preventive anticancer agents.
Synthesis and Comparative Structure–Activity Study of Carbohydrate-Based Phenolic Compounds as α-Glucosidase Inhibitors and Antioxidants
Authors: Machida Shota , Mukai Saki , Kono Rina , Funato Megumi , Saito Hiroaki , Uchiyama Taketo
Published: November 2019

Twenty-one natural and unnatural phenolic compounds containing a carbohydrate moiety were synthesized and their structure–activity relationship (SAR) was evaluated for α-glucosidase inhibition and antioxidative activity. Varying the position of the galloyl unit on the 1,5-anhydro-d-glucitol (1,5-AG) core resulted in changes in the α-glucosidase inhibitory activity and notably, particularly strong activity was demonstrated when the galloyl unit was present at the C-2 position. Furthermore, increasing the number of the galloyl units significantly affected the α-glucosidase inhibition, and 2,3,4,6-tetra-galloyl-1,5-AG (54) and 2,3,4,6-tetra-galloyl-d-glucopyranose (61) exhibited excellent activities, which were more than 13-fold higher than the α-glucosidase inhibitory activity of acertannin (37). Moreover, a comparative structure-activity study suggested that a hemiacetal hydroxyl functionality in the carbohydrate core and a biaryl bond of the 4,6-O-hexahydroxydiphenoyl (HHDP) group, which are components of ellagitannins including tellimagrandin I, are not necessary for the α-glucosidase inhibitory activity. Lastly, the antioxidant activity increased proportionally with the number of galloyl units.
Lignin Nanoparticle-Coated Celgard Separator for High-Performance Lithium–Sulfur Batteries
Authors: Zhang Zengyao , Yi Shun , Wei Yuejia , Bian Huiyang , Wang Ruibin , Min Yonggang
Published: November 2019

Tremendous efforts have been made toward the development of lithium–sulfur (Li–S) batteries as one of the most reasonable solutions to the rapidly increasing demand for portable electronic devices and electric vehicles, owing to their high cost-efficiency and theoretical energy density. However, the shuttle effect caused by soluble polysulfides is generally considered to be an insurmountable challenge, which can significantly reduce the battery lifecycle and sulfur utilization. Here, we report a lignin nanoparticle-coated Celgard (LC) separator to alleviate this problem. The LC separator enables abundant electron-donating groups and is expected to induce chemical binding of polysulfides to hinder the shuttle effect. When a sulfur-containing commercially available acetylene black (approximately 73.8 wt% sulfur content) was used as the cathode without modification, the Li–S battery with the LC separator presented much enhanced cycling stability over that with the Celgard separator for over 500 cycles at a current density of 1 C. The strategy demonstrated in this study is expected to provide more possibilities for the utilization of low-cost biomass-derived nanomaterials as separators for high-performance Li–S batteries.
Powdered Activated Carbon Exacerbates Fouling in MBR Treating Olive Mill Wastewater
Authors: Ran Noya , Gilron Jack , Sharon-Gojman Revital , Herzberg Moshe
Published: November 2019

Membrane fouling is a major obstacle in membrane bioreactors (MBRs) that treat wastewater. The addition of powdered activated carbon (PAC) is commonly suggested as a way to improve the MBR wastewater treatment process with respect to membrane fouling and effluent quality. Integrating the PAC addition into the MBR may also improve the stability of the acclimated microbial community for biodegrading the recalcitrant organic compounds that can also enhance membrane fouling. In this study, the ability of the MBR-PAC system to decrease membrane fouling was evaluated. Two pilot-scale reactors were operated: one reactor was supplemented with suspended PAC, and one was operated under similar conditions, without PAC. The feed to the reactors comprised domestic and olive oil mill wastewater. Surprisingly, the permeate flux and the membrane permeability decreased faster in the MBR supplemented with PAC compared to the control reactor. Corroborating these MBR fouling results, soluble microbial products (SMPs), originating from the PAC-supplemented reactor, were found to be more adhesive to an ultrafiltration membrane mimetic surface (polyether sulfone) as analyzed in a quartz crystal microbalance with dissipation monitoring (QCM-D). While the PAC had almost no effect on the dissolved organic carbon in the MBR, it altered the molecular weight distribution of the organic molecules in the SMP as observed with gel permeation chromatography: The fractions of 577–789 kDa and the one bigger than 4 × 103 kDa, were elevated and reduced, respectively, by the addition of PAC. A biofilm formation analysis using a confocal laser scanning microscopy showed a higher amount of biofilm on the membrane taken from the PAC reactor, but this membrane showed no traces of PAC particles when analyzed with a scanning electron microscope (SEM). Taken together, altering the composition of the dissolved organic matter in the MBR by PAC addition promoted its adhesion to the membrane, induced biofilm formation, and more prominently, decreased membrane permeability.
Particle-Based Workflow for Modeling Uncertainty of Reactive Transport in 3D Discrete Fracture Networks
Authors: Vu Phuong Thanh , Ni Chuen-Fa , Li Wei-Ci , Lee I-Hsien , Lin Chi-Ping
Published: November 2019

Fractures are major flow paths for solute transport in fractured rocks. Conducting numerical simulations of reactive transport in fractured rocks is a challenging task because of complex fracture connections and the associated nonuniform flows and chemical reactions. The study presents a computational workflow that can approximately simulate flow and reactive transport in complex fractured media. The workflow involves a series of computational processes. Specifically, the workflow employs a simple particle tracking (PT) algorithm to track flow paths in complex 3D discrete fracture networks (DFNs). The PHREEQC chemical reaction model is then used to simulate the reactive transport along particle traces. The study illustrates the developed workflow with three numerical examples, including a case with a simple fracture connection and two cases with a complex fracture network system. Results show that the integration processes in the workflow successfully model the tetrachloroethylene (PCE) and trichloroethylene (TCE) degradation and transport along particle traces in complex DFNs. The statistics of concentration along particle traces enables the estimations of uncertainty induced by the fracture structures in DFNs. The types of source contaminants can lead to slight variations of particle traces and influence the long term reactive transport. The concentration uncertainty can propagate from parent to daughter compounds and accumulate along with the transport processes.
Euthanasia in the case of dementia: a survey among Flemish GPs
Authors: Cleemput Jasper , Schoenmakers Birgitte
Published: November 2019

Background

In Belgium law prohibits euthanasia at the end stage of dementia when patients are no longer able to formulate their will. The number of applications for euthanasia based on dementia is low, but patients and their relatives are searching for access to euthanasia.

Aim

This study assessed the opinions of GPs facing requests for euthanasia in patients with dementia.

Design & setting

A cross-sectional survey was performed in general practice. Flemish GPs were invited by email to participate in the study.

Method

GPs were reached through the regional GP association and the online survey was open for 4 weeks. The data were then anonymised, analysed, and interpreted. The outcome of interest addresses opinions of Flemish GPs regarding euthanasia in patients with dementia.

Results

A total of 113/308 doctors participated. It was found that 69% agreed that euthanasia in patients without dementia is more acceptable than in patients with dementia. When patients with dementia had concomitant diseases, 59% stated that euthanasia was more acceptable than when patients were ‘healthy’. It was also found that 56% agreed the euthanasia law needs adjustments towards patients with dementia. Legal adjustments were supported more by GPs of a younger generation. Non-religious doctors were twice as likely to be in favour of legal adjustments than their religious colleagues; 51% believed that the ability of patients to repeat their will is essential; while 72% of GPs feared pressure from relatives to follow the declaration of will.

Conclusion

The Belgian GP has an open attitude towards euthanasia for patients with dementia. There was a willingness to perform euthanasia as the stage of dementia worsened and in cases of terminal conditions. Debate, education, and experience will influence opinion and the legislation process.
Growth structure in Ceylon zircon
Authors: Sahama Thure Georg
Published: November 2019

This paper deals with zircon from the gem bearing gravels of the Ratnapura area in southwestern Ceylon.

The zircon crystals are prismatic in habit, mostly 1-2 cm long, with the dominating forms {100} and {101}. When cut centrally parallel to the c-axis and polished, the crystals exhibit invariably a concentric growth structure simulating a sectoral zoning. Microprobe analyses indicate that this growth structure represents no chemical zoning proper but structural banding.

A method was developed to estimate the density of a single band inside a banded crystal by measuring its birefringence under the microscope. With the exception of the lowest birefringences, the following empirical equation was applied :

density = 4.078 + 10.678 x birefringence.

The densities of the successive bands were estimated using this equation. It was found that the visible growth structure reflects mainly a variation in the degree of the radiation damage. In some crystals the density decreases from core to margin. Other crystals show an opposite trend.

The variation in the degree of order within a single crystal is apparently due to irregularity in the convective flow of the crystallizing medium.
Effect of isomorphous iron on the crystal growth of sphalerite
Authors: Minceva-Stefanova Jordana
Published: November 2019

Le changement de l'habitus, ainsi que les particularités générales morphologiques de la blende sont considérés séparément pour la blende ne contenant aucun fer isomorphe et pour celle qui en contient. Ce qui est important dans le deuxième cas, c'est la quantité de fer isomorphe et le mode de sa répartition au cours de la croissance des cristaux.

Des considérations structurales originales concernant le développement d'un habitus tétraédrique sous l'influence du fer isomorphe sont argumentées. La présence du fer isomorphe conditionne une différence entre les vitesses de croissance des deux tétraèdres en retardant la croissance des faces tétraédriques à une tranche externe d'atomes Zn. Ainsi, les cristaux de blende riches en fer isomorphe ont toujours des dimensions relativement petites. Leur croissance ultérieure n'est possible que par trois ou quatre mécanismes différents, envisagés brièvement.
New investigation techniques for minerals ?
Authors: Janot Christian
Published: November 2019

General notions of Mössbauer spectroscopy positron annihilation and extended X-ray absorption fine structure are given. Topics in these techniques are briefly described with emphasis on actual or potential applications to mineral science. Particular attention is payed to investigation of poorly crystallized or amorphous materials.
Thermochemistry of silicate solid solutions
Authors: Newton Robert Chaffer , Wood Bernard J. , Kleppa Ole J.
Published: November 2019

Les résultats expérimentaux déduits d'équilibres de phases et de méthodes cristallographiques telles que la diffraction des rayons X par des monocristaux et la spectrométrie de résonance Mössbauer utilisés conjointement avec des valeurs d'enthalpie de mélange obtenues par calorimétrie de dissolution permettent dans certains cas une compréhension thermodynamique complète de systèmes d'oxydes. Des résultats expérimentaux déduits de chaleurs de dissolution dans l'acide fluorhydrique et d'équilibres entre ions alcalins ont ainsi permis une meilleure compréhension de la thermodynamique des feldspaths de sodium et de potassium. Des modèles thermodynamiques valables pour les clinopyroxènes, exempts de fer, basés sur la diopside ont pu être établis en utilisant des données obtenues par calorimétrie de dissolution en bain d'oxydes et par des expériences d'équilibres de phases à hautes température et pression. L'étude par effet Mössbauer d'omphacites naturelles préalablement chauffées et la calorimétrie de dissolution en bain d'oxydes de jadéite˗diopside synthétiques permettent d'élaborer un modèle réciproque de mélange du système CaMgSi₂O₆-NaAlSi₂O₆.

Les trois séries de clinopyroxènes à base de CaMgSi₂O₆ (diopside) avec CaAl₂SiO₆ (CaTs), NaAlSi₂O₆ (jadéite) et Mg₂Si₂O₆ (clinoenstatite) sont toutes effectivement des solutions régulières (symétriques) dont le paramètre WH est de l'ordre de 4 à 8 kcal. Le dernier système a une solution solide limitée du fait de la difficulté d'échange des ions sur les sites M1. Bien connu thermochimiquement, le solvus à haute température présente un grand intérêt en géothermométrie.

Une entropie d'excès (non configurationnelle) importante a été déduite de données calorimétriques et d'équilibres de phases pour les feldspaths alcalins et les grenats Ca-Mg ; dans ce dernier cas des mesures de chaleurs spécifiques à basse température confirment ce fait. Le mécanisme semble être la substitution d'ions de tailles très différentes sur un large site ionique.

Les mesures d'enthalpie de mélange de plagioclases synthétiques, de forme structurale haute température, combinées à des expériences hydrothermales d'échange d'ions alcalins confirment la prédiction du modèle structural dans lequel les tétraèdres d'aluminium ne se joignent pas. Le modèle proposé conduit à des valeurs d'activités valables dans un large domaine de température et de pression.

Les résultats expérimentaux obtenus antérieurement par dissolution dans l'acide fluorhydrique de plagioclases, d'olivines et de mélilites ne sont pas en bon accord avec les mesures récentes.
Spectres X du silicium, de l'aluminium et du magnésium dans divers minéraux
Authors: Pitault Bernard , Belin-Ferré Esther , Sénémaud Christiane
Published: November 2019

Energy shifts of SiKα, AlKα and MgKα emission lines from seven natural silicates and two oxides have been measured comparatively to the pure element. The results are discussed ; an attempt is made to correlate the measurements to the surrounding of each element in the compound.
Stabilité de différents polytypes de micas dioctaédriques en fonction des potentiels partiels sur les atomes
Authors: Soboleva Svetlana V. , Mineeva Rimma M.
Published: November 2019

L'étude des valeurs de l'énergie électrostatique est menée en vue de déterminer la stabilité relative de polytypes 1M et 2M₁ des micas de composition dioctaédrique. Les auteurs ont analysé la direction des vecteurs O — H dans différents modèles réels et hypothétiques et mis en évidence le rôle prépondérant de l'interaction existant entre le cation interlamellaire K et le proton du réseau octaédrique. On a évalué différents types d'interaction intra- et interlamellaires (répartition ordonnée des cations, répulsion cationique, gaufrage des atomes de base du réseau tétraédrique, etc...) dans les structures des polytypes dioctaédriques 1M et 2M₁.
Applications of 200 kV analytical electron microscopy to the study of fine textures of minerals
Authors: Morimoto Nobuo , Kitamura Masao
Published: November 2019

On a utilisé un microscope électronique analytique à 200 kV (Hitachi-700H) pour l'analyse chimique quantitative avec une résolution spatiale de quelques centaines d'angströms. On a montré que pour les échantillons d'épaisseur inférieure à 1µm, il existe, à 200 kV, une relation linéaire entre l'intensité du rayonnement X caractéristique et l'intensité totale. L'inconvénient d'une tension de 200 kV par rapport à une tension de 100 kV pour l'analyse, est une faible diminution du rapport signal/bruit et l'affaiblissement du rayonnement X caractéristique pour les éléments légers. Cependant, la microscopie électronique à 200 kV permet l'observation d'une plus grande surface.

On a utilisé le microscope électronique analytique à 200 kV pour l'étude des textures fines de minéraux telles que les textures d'exsolution dans les pyroxènes, les bords kélyphitiques autour du grenat et des matériaux synthétiques fabriqués à haute température et haute pression. Les résultats démontrent l'intérêt de la microscopie électronique analytique à 200 kV pour l'étude des textures fines des minéraux.
Étude des défauts dans les minéraux par M.E.T.
Authors: Gandais Madeleine , Willaime Christian
Published: November 2019

La caractérisation des défauts présents dans les minéraux est une étape essentielle dans la connaissance des relations entre défauts et genèse cristalline. La microscopie électronique par transmission permet cette caractérisation. On indique le principe des méthodes « à deux faisceaux » et « à faisceau faible », en précisant leurs limites d'application.
A study of fine textures of Bushveld augite by 200 kV analytical electron microscopy
Authors: Kitamura Masao , Yasuda Masayo , Morimoto Nobuo
Published: November 2019

Fine textures of Bushveld augite (SA-1019) have been studied by a 200 kV analytical electron microscope. Compositional differences were detected among the « 001 » pigeonite lamellae with different orientations of interface and thickness in the augite. Based on the results, the cooling process of the augite has been discussed. The stacking faults parallel to (100) in the « 001 » pigeonite lamellae have been characterized to be twinning of pigeonite in a unit cell scale, as proposed by Champness and Copley (1976). The morphological change of the interface between the pigeonite lamellae and augite host has been explained on the basis of the phase change of pigeonite to augite and hypersthene.
The application of the scanning electron microscope in gossan research
Authors: Nickel Ernest Henry
Published: November 2019

Le microscope électronique à balayage est très utile pour l'étude des chapeaux de fer, surtout quand il est employé dans le mode électron rétrodiffusé/vide léger. Les minerais de chapeaux de fer, étant formés d'éléments de numéro atomique élevé, sont facilement identifiables avec cet appareil, et la présence ou l'absence de tels minéraux sert de guide pour l'évaluation des chapeaux de fer et fournit l'information aidant à l'interprétation de la solution chimique durant le procédé de formation de ces chapeaux de fer.
Crystallisation of pigeonite and olivine from liquids in synthetic systems and in natural samples
Authors: Biggar Gordon
Published: November 2019

Les limites des champs de stabilité de l'olivine et des pyroxènes sub-calciques (pigeonite, orthopyroxène, protopyroxène) sont examinées dans plusieurs systèmes contenant quelques-uns des oxydes

MgO — SiO₂ — Al₂O₃ — Fe₂O₃ — FeO — CaO — Na₂O.

De nouvelles données expérimentales dans le système

SiO₂ — Al₂O₃ — MgO — FeO — CaO,

à savoir aux compositions de liquides en équilibre avec olivine et pigeonite, sont présentées et la variation du rapport Fe : Mg du liquide lors de la cristallisation est documentée. Quelques-unes des compositions étudiées cristallisent aussi un peu d'augite. Le comportement d'échantillons naturels avec seulement des traces d'autres oxydes présents, est comparé aux données relatives aux systèmes synthétiques. D'importantes variations dans les champs de stabilité des olivines et pyroxènes sont notées.
Studies of the orthoamphiboles. I. The Mössbauer and infrared spectra of holmquistite
Authors: Law Anthony D. , Whittaker Eric James William
Published: November 2019

Un échantillon de l'orthoamphibole lithique holmquistite a été examiné par spectroscopic Mössbauer, et son spectre infrarouge dans l'intervalle d'absorption d'hydroxyle (3 800-3 500 cm⁻¹) a été déterminé. Les résultats qualitatifs et quantitatifs sont présentés, et les occupations des sites sont confrontées à celles de précédentes mesures aux rayons X.
Crystal chemistry and paragenetic trends of silicate minerals
Authors: Kostov Ivan
Published: November 2019

A general tendency of consecutive crystallization of silicate minerals according to their structure type, viz. from isometric resp. pseudoisometric, to axial and planar, is discerned with decrease of temperature and increase of mobile constituents notwithstanding the peculiarities of the geological processes. The modification of the habits of the corresponding minerals outlines a second order tendency of successive crystallization depending on changes in external factors like supersaturation, rate of crystallization, impurities, etc.
Studies of the orthoamphiboles. II. Hydroxyl spectra of anthophyllites
Authors: Law Anthony D.
Published: November 2019

Les spectres infrarouges de plusieurs anthophyllites ont été mesurés dans la région de la vibration de valence du groupement OH (3 800-3  500 cm⁻¹). Les bandes principales présentent une structure hyperfine jusqu'ici inconnue.
Dolomitisation, chloritisation et talcification de la formation viséenne à faciès griotte dans la région de Puebla de Lillo (Boñar, Espagne)
Authors: Hardy Michel , Ildefonse Jean-Pierre
Published: November 2019

Dans la région de Puebla de Lillo, le calcaire viséen à faciès griotte a subi successivement une dolomitisation et une talcification. Le calcaire griotte est constitué d'une fraction quartzo-illitique et d'une fraction calcitique. Lors de la dolomitisation la calcite se transforme en dolomite et la fraction quartzo-illitique est remplacée par des chlorites de deux types (clinochlores et ripidolites), témoignant d'un apport de magnésium.

La talcification pseudomorphose les dolomies chloriteuses et s'effectue en deux étapes :

La première étape, qui consiste en un remplacement de la phase chloriteuse par l'association talc + chlorite, nécessite un apport de silicium. Les éléments libérés par cette transformation permettent la cristallisation de nouvelles chlorites (clinochlores et ripidolites).

La deuxième étape qui correspond à la transformation à volume constant de dolomite en talc nécessite un apport conjoint de silicium et de magnésium.

La talcification est interprétée comme une redistribution locale des éléments après dissolution des roches siliceuses et des roches magnésiennes à proximité des gîtes de talc.
« Coalingite » from the Woodsreef serpentinite Barraba, New South Wales, Australia
Authors: Hamilton John D. , Beermann Eberhardt
Published: November 2019

Un minéral qui, selon sa structure et sa composition, est voisin du groupe pyroauritique des hydroxycarbonates a été identifié comme le produit d'une altération profonde dans la serpentinite de Woodsreef, à Barraba, New South Wales. Des concentrations en ce minéral qui s'élèvent jusqu'à 10 % ont été déterminées dans le matériau de la roche-mère de la section septentrionale de ce gisement. Des filons de chrysotile à fibres croisées, qui se trouvent en abondance partout dans la roche ultrabasique, contiennent également l'élément sous la forme d'agglomérés cristallins relativement purs, distribués par des zones d'altération en lentille associées à des intercalations de brucite secondaire. La magnétite constitue l'impureté principale de ces agglomérés.

Dans les spécimens à main les cristaux sont d'une couleur rousse-brune. Sous la lumière polarisée, les sections de clivage 001 sont jaune citron. Les sections marginales sont pléochroïques, d'incolores à jaune citron. Le minéral est uniaxe négatif avec ω = 1,595 et ε = 1,580. Les sections marginales sont lentes en longueur. La densité est de 2,37-2,38 g/cm³. La formule de constitution, calculée à partir des résultats d'une analyse chimique et thermique, est Mg₁₀,₁₇ Fe³⁺₁,₈₂ (CO₃)₀,₉ (OH)₂₄ 2,31 H₂O.

L'analyse à la transformée de Fourier des données de la diffraction non rationnelle des rayons X 001 révèle que la structure est un système irrégulier mais parfaitement dispersé, contenant à environ 70 % d'unités de couche de coalingite et 30 % d'unités de couche de coalingite-K, selon la définition de Pastor-Rodriguez et Taylor (1971). Les déviations observées de la composition idéale de la coalingite que montre le spécimen de Woodsreef sont expliquées en fonction de ce modèle à structure mixte, qui demande 10 % de moins de couches intermédiaires carbonate-eau que ne le fait l'élément terminal à couche de brucite double pure.
Natural occurrences in the systems PbS — Bi2S3 — Sb2S3 and PbS — Sb2S3 from Vall de Ribes, Eastern Pyrenees, Spain
Authors: Ayora Ibañez Carlos , Phillips Roy
Published: November 2019

Minerals in the systems PbS — Bi₂S₃ — Sb₂S₃ and PbS — Sb₂S₃ (with no Bi) have been found in As and Sb veins, probably related to a late-Hercynian granitic intrusion. The minerals have been examined by reflected light microscopy and analysed by electron micro-probe. Paragenesis and petrographical relationships among vein minerals have been established. A particular group of minerals, Pb — Bi — Sb sulphosalts, have been found related to native gold grains. Chemical compositions and possible stability relationships have been stated. Because of the small size of the grains (less than 0.3 mm), no crystallographic determinations have been possible in minerals of the PbS — Bi₂S₃ — Sb₂S₃ system. Variation in the proportions of major and minor elements with distance to a possible mineralizing focus have been observed. Some possible geochemical relationships among sulphosalts and other vein ore minerals have been found.
Some characteristics of uranium oxides in China
Authors: Xu Guoqing , Wang Aizhen , Gu Qifang , Zhang Jingyi , Zhang Zhaoming , Huang Yuzhu
Published: November 2019

Avec les données analytiques de soixante dix sept échantillons de plusieurs dizaines de gisements et d'indices de minerais d'uranium en Chine, on étudie les propriétés chimiques, les dimensions de maille et la réflectance des oxydes d'uranium.

On présente les propriétés chimiques d'oxydes d'uranium de différents types de gisements de minerais d'uranium, et l'influence des divers âges et encaissants de la minéralisation sur la composition des oxydes d'uranium. L'influence de facteurs tels que la température de minéralisation, la composition de l'encaissant et l'environnement géochimique sur la composition des oxydes d'uranium est évidente. Le plomb dans les oxydes d'uranium protérozoïques est relativement enrichi par la désintégration d'éléments radioactifs.

Les dimensions de maille présentent une corrélation positive avec les âges de minéralisation, les températures de formation, et la concentration en terres rares et plomb, et une corrélation négative avec le coefficient d'oxydation. La grandeur de la maille est liée à la teneur en CaO par la relation exponentielle a₀ = 5,399 exp (0,0059/CaO %). Le facteur dont l'influence est la plus importante est la température de minéralisation. La taille du rayon ionique des éléments substitués à U⁴⁺ et l'autooxydation de U⁴⁺ durant le processus de désintégration sont de moindre importance.

La réflectance ne dépend pas de la teneur en CaO et SiO₂. La réflectance a une corrélation positive avec la grandeur de la maille et négative avec le coefficient d'oxydation. La relation entre la réflectance et la teneur en PbO suit la loi logarithmique R = 14,2573 + 2,9126 log PbO %.
On normalized symbols for identification of mineral species
Authors: Kuo Tsung-Shan
Published: November 2019

On propose, pour l'identification des minéraux, une standardisation binominale comprenant le nom de l'espèce suivi d'un symbole normalisé. Il s'agit d'un système à huit positions : symétrie, composition, dureté, densité, indices de réfraction, habitus, clivage, macles. Chaque caractère diagnostique a une position déterminée et est représenté par des lettres ou des nombres ou une combinaison des deux.

Chaque symbole est expliqué et des exemples sont proposés. Ces symboles permettent la standardisation, l'unification, la correspondance, la classification et la comparaison des données sur les minéraux sous une forme condensée et sont donc d'un usage facile pour l'identification par ordinateur.