bluuebunny/crossref_metadata_2025 huggingface dataset:
Children’s life world as a perspective on their citizenship: The case of the Finnish Children’s Parliament
Authors: Tuukkanen Terhi , Kankaanranta Marja , Wilska Terhi-Anna
Published: August 2012

The latest childhood studies present children’s citizenship as a process of engaging in matters related to children themselves in their everyday lives. However, only a few studies have been conducted on what those issues are and what they actually tell about children’s citizenship. This study explores the nature of children’s participation and citizenship by adopting a life world perspective. The aim is to examine what kind of issues children want to participate in and influence. The data are drawn from an online discussion in the Finnish Children’s Parliament. Altogether 61 children participated in the discussion, with 566 postings. The analysis of the children’s online discussion shows that children comment mainly on issues that directly impact their lives, such as school. However, they also want to engage in issues that are global in nature, such as children’s general well-being.
Preparation of poly(vinyl chloride)/copper nanocomposite films with reduced bacterial adhesion
Authors: Becerra Abraham , Rodríguez-Llamazares Saddys , Carrasco Claudia , Díaz-Visurraga Judith , Riffo Carla , Mondaca M. A.
Published: August 2012

Films of poly(vinyl chloride)/copper (Cu) nanocomposites exhibiting reduced bacterial adhesion were prepared by film-casting method. Cu nanoparticles (NPs) synthesized using polyol method and stabilized with poly( N-vinyl-2-pyrrolidone) (PVP) at different Cu/PVP molar ratio were previously characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD) and ultraviolet–visible spectroscopy. Zero valent Cu NPs with average diameter of 4 nm were obtained. The nanocomposite films with low and high Cu content were prepared with Cu NPs obtained from Cu/PVP molar ratio of 7.2, 45 and 270. XRD patterns of PVC/Cu nanocomposite films did not show peaks associated at copper oxide and other impurities. Scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy Cu-mapping revealed a homogenous distribution of Cu NPs agglomerates in nanocomposite films prepared with Cu NPs obtained from Cu/PVP ratio of 7.2 and high Cu content, while TEM images of this nanocomposite film with low Cu content showed well-dispersed and distributed Cu NPs in PVC matrix. The films prepared with Cu NPs obtained from Cu/PVP ratio of 270 showed a vertical phase separation, where PVP was segregated to the free surface. SEM images revealed a reduced Escherichia coli adhesion to PVC/Cu nanocomposite films after 4 days of incubation with respect to plasticized PVC.
Analysis of and mathematical model insight into loop formation in colonoscopy
Authors: Cheng Wu Bin , Moser Michael AJ , Kanagaratnam Sivaruban , Zhang Wen Jun
Published: August 2012

The colonoscope is an important tool in the diagnosis and management of diseases of the colon; yet its design has not changed appreciably since it was first introduced to clinical practice 40 years ago. One of the ongoing challenges with this device is that the natural shape of the colon predisposes to loop formation by the scope during the examination. The result of this looping is that further insertion of the scope results in a larger loop size without any advancement of the tip of the scope. Looping thus causes pain in the patient, risks perforation of the colon, and results in incomplete examinations. In this article, loop formation is analyzed in terms of frictional force state and Kirchhoff’s slender rod model in order to better understand the generic principle of loop formation. Next, a mathematical model of deformation of the colon with respect to external manipulation involving a number of variables involved in loop formation is constructed. Finally, a model of the motion of the scope relative to the colon when looping occurs is presented. The model has clinical significance for prediction of advancement of the tip of the scope when looping occurs. The mathematical model was then validated and verified using data available from the literature. Our models are an important starting point in the development of a novel device to overcome loop formation and result in increased patient comfort and an improved completion rate for colonoscopy procedures.
Formation, succession and landscape history of Central-European summit raised bogs: A multiproxy study from the Hrubý Jeseník Mountains
Authors: Dudová Lydie , Hájková Petra , Buchtová Hana , Opravilová Vĕra
Published: August 2012

Central-European raised bogs, developed on mountain summits, are specific ecosystems of high conservation importance, but their history remains largely unknown. Pollen, macrofossils, testate amoebae and peat characteristics were analysed in a peat sequence of the Vozka bog (Hrubý Jeseník Mountains, Eastern Sudetes, Czech Republic). Past water chemistry and water-table depths were reconstructed by transfer functions calibrated from recent testate amoeba data and long-term environmental averages. Peat initiation started in the middle Holocene (approximately 4200 bc) by the process of paludification, resembling the development of Atlantic blanket bogs. Around 100 bc the vegetation changed from Eriophorum vaginatum-poor fen to the ombrotrophic-bog vegetation similar to the recent situation. A hiatus in peat sequence was revealed between ad 1320 and 1954. It can be explained either by human activities, or by an extreme drought causing decomposition of previously accumulated peat. Local bog development was largely independent of landscape development inferred from pollen records. In the middle Holocene, mixed spruce-elm-hazel woodland was recorded close to the treeline. During 2400–800 bc a gradual transition to mixed spruce-fir woodlands with admixture of beech took place, and from approximately 800 bc spruce and fir became dominant. The major human impact started approximately ad 1230 and was connected with settlement and mining in the foothills.
Representations of Executives on Rural Markets
Authors: Sridhar Guda
Published: August 2012

Rural market as a construct has been widely debated, viewed from multiple dimensions and operationalized in more than one way. However, such operationalization of the construct has been a work of academics trying to manipulate the social world drawn from several theories with significant rigour. The earlier operationalizations had very little flavour of the practitioner’s angle. Unless the practitioners’ viewpoints are embedded into the operationalization; the relevance of defining rural markets would be incomplete. In this paper, we attempt to address this concern by considering the way executives represent the rural markets in their daily lives. We developed a scale using the social representations approach and sought responses from over 200 executives. Out of the cluster solutions we received from the executive representations, we observed that there were several overlaps of what rural markets are among the different executives. This article is a preliminary attempt to understand rural markets and serves the purpose for taking up more related studies in future.
Perceptions on Banking Service in Rural India: An Empirical Study
Authors: Bapat Dhananjay
Published: August 2012

The purpose of this paper is to assess the level of banking penetration in a sample village and to find the relationship between bank accounts and related factors, such as, occupation, income and asset-holding status. The findings indicate that 75.2 per cent of the respondents have bank accounts and 26.7 per cent of the respondents avail credit facilities. Two-thirds of the respondents have inclination to avail credit facilities for dairy and for other business activities. Using chi square analysis, significant relationships were established between bank account and relevant factors, such as, occupation, income and asset-holding pattern. While using logistic regression, we find that having a bank account has a significant correlation with income. The findings provide practical implications for bankers in terms of providing banking services in rural areas. The existing gap in credit facilities offers manifold opportunities to bankers for providing various credit facilities. Since the findings indicate that majority of the respondents show an inclination for availing credit for dairy activities, suggestions are offered for tapping potential customers. The article offers not only valuable suggestions to bankers and academicians but also to the government and policy bodies for designing and monitoring financial inclusion targets.
Octonion structural response vector and potential structural damage identification method
Authors: Tang Liqun , Luo Xu , Liu Zejia , Liu Yiping , He Tinghui , Fang Daining
Published: August 2012

A promising method based on octonion structural response vector is proposed for the identification of structural damages according to the database acquired via long-term structural health monitoring. An octonion structural response vector consists of eight elements: seven for structural responses, including normalized static strains at specific positions and natural frequencies of a structure, and one for null. For a perfect structure the octonion structural response vector is a point in the phase plane, whereas for developing damages in the structure the octonion structural response vector manifests itself as a definite trajectory in the phase plane. Therefore, the development of damages in a structure could be investigated by analyzing the trajectory of octonion structural response vector obtained from the data of a long-term structural health monitoring or scheduled routine structural examinations. To demonstrate the implementation of this octonion structural response vector-based method, a two-dimensional numerical model of a simply-supported beam was built with crack-like damages of given location and depth. The octonion structural response vector of the beam corresponding to each state of damages was calculated to draw the trajectory related to the developing damages in the phase plane. The results show that the trajectories are significantly different for different devolvement of damages, even when the damages are in good symmetry. It indicates that the octonion structural response vector-based method recommended in the article could be effective to identify damages of structures using data of structures from long-term structural health monitoring or routine scheduled examinations.
Applicability of small-scale models in prediction flutter pressure of delaminated composite beam-plates
Authors: Yazdi Ali A , Rezaeepazhand Jalil
Published: August 2012

In this study, the flutter pressure of delaminated composite beam-plates subjected to supersonic flow is investigated using similitude theory. An analytical investigation based on the direct use of the governing equations of the systems is undertaken to derive the necessary scaling laws and similarity conditions. The method presented herein has already been shown to be effective in the design of scaled down models for buckling and vibration response of laminated composite shells and panels. In this study, the flutter pressures of the prototypes are predicted by projecting the flutter pressure of the model using the derived scaling law. Based on the result of this study, for flutter of delaminated composite beam-plates, based on structural similitude, set of scaling laws can be found, which are used to develop design rules for small-scale models. For prototypes with the same material properties and stacking sequence as the prototype, distorted models with different delamination length and depth than those of the prototype can predict the behavior of the prototypes, accurately.
Ranolazine-Induced Postrepolarization Refractoriness Suppresses Induction of Atrial Flutter and Fibrillation in Anesthetized Rabbits
Authors: Aidonidis Isaac , Doulas Konstantinos , Hatziefthimiou Apostolia , Tagarakis Georgios , Simopoulos Vassilios , Rizos Ioannis , Tsilimingas Nikolaos , Molyvdas Paschalis-Adam
Published: August 2012

Ranolazine (Ran) is a novel anti-ischemic agent with electrophysiologic properties mainly attributed to the inhibition of late Na+ current and atrial-selective early Na+ current. However, there are only limited data regarding its efficacy and mechanism of action against atrial flutter (Afl) and atrial fibrillation (AF) in intact animals. Therefore, we aimed to investigate the electrophysiologic mechanism of Ran in a rabbit model of inducible atrial tachyarrhythmias elicited by acetylcholine (ACh). Arrhythmias were produced in 19 rabbits by rapid atrial burst pacing during control, after intravenous ACh and after Ran + ACh administration. Recording of right atrial monophasic action potentials (MAPs) and programmed stimulation were utilized to determine the duration of atrial repolarization at various cycle lengths and voltage levels of action potential, including 75% of total MAP duration (MAPD75), effective refractory period (ERP), and postrepolarization refractoriness (PRR = ERP − MAPD75) prior to and after Ran. Control stimulation yielded no arrhythmias or maximal nonsustained runs of Afl/AF. Upon ACh, 17 of 19 rabbits exhibited sustained Afl and AF as well as mixed forms of Afl/AF, while 2 animals revealed none or short runs of nonsustained arrhythmias and were excluded from the study. High-frequency burst pacing during the first 30 minutes after Ran + ACh failed to induce any arrhythmia in 13 of 17 rabbits (76%), while 2 animals displayed sustained Afl/AF and 2 other animals nonsustained Afl/AF. At basic stimulation cycle length of 250 milliseconds, Ran prolonged baseline atrial ERP (80 ± 8 vs 120 ± 9 milliseconds, P < .001) much more than MAPD75 (65 ± 7 vs 85 ± 7 milliseconds, P < .001), leading to atrial PRR which was more pronounced after Ran compared with control measurements (35 ± 11 vs 15 ± 10 milliseconds, P < .001). This in vivo study demonstrates that Ran exerts antiarrhythmic activity by suppressing inducibility of ACh-mediated Afl/AF in intact rabbits. Its action may predominantly be related to a significant increase in atrial PRR, resulting in depressed electrical excitability and impediment of arrhythmia initiation.
Blacks’ and Whites’ Experiences of Neighborhood Racial and Ethnic Diversity
Authors: Wagmiller Robert L.
Published: August 2012

The racial and ethnic diversity of American cities has increased sharply in recent decades. This study uses a unique longitudinal, cohort-comparison research design to investigate changes over the past three decades in the diversity and multigroup integration of Blacks’ and Whites’ neighborhoods between early and early middle adulthood. This study finds that the neighborhoods in which recent cohorts of Blacks and Whites reside are both more diverse and more integrated than were the neighborhoods of earlier cohorts. Although even in the most recent cohorts Blacks’ neighborhoods are more diverse and integrated than Whites’ neighborhoods, overall levels of racial and ethnic diversity and integration for Whites and Blacks are converging. However, the types of diversity and integration Whites and Blacks experience in their neighborhoods remain very different.
Non-communicable diseases: Harnessing the current opportunities
Authors: Sørensen Jane Brandt , Demaio Alessandro , Østergaard Lise Rosendal , Nielsen Karoline Kragelund , Bygbjerg I.B. Christian , De Courten Maximilian
Published: August 2012

Non-communicable diseases (NCDs) are receiving growing attention, which brings a unique opportunity to utilise solutions available to address them. These diseases are largely preventable; proven, cost-effective interventions are available; and when NCDs emerge, means exist to treat them, prevent complications, and to improve quality of life. Yet, there is a lack in progress in responding effectively to NCDs, and the current discussion and research focus predominantly on challenges rather than the opportunities, which this paper outlines.
Luminance coefficients of road surfaces for low angles of illumination
Authors: Köhler S , Neumann C
Published: August 2012

This paper describes research on forward and backward light reflection of road surfaces for typical vehicle-related illumination and observation conditions. The aim is to improve luminance simulation in order to include quality criteria of headlamp light distributions that correspond to visual perception under night driving conditions. Measurements were performed under full scale conditions instead of the usual laboratory tests. Traffic safety requires tests under dry and wet conditions. The experimental data can be described by luminance coefficient-based models. Due to its fixed geometry, backward reflection can be covered with a single luminance coefficient. For forward reflection an angular dependent reflection model is described with which headlamp light distributions can be improved for their impact on automatically detected oncoming traffic even under wet conditions.
Impact of daylight illumination on reducing patient length of stay in hospital after coronary artery bypass graft surgery
Authors: Joarder AR , Price ADF
Published: August 2012

In this research, a field investigation was done with 263 coronary artery bypass graft (CABG) surgery patients to identify the impact of daylight exposure on patient length of stay (LoS) in hospital. Lighting data were collected by installing sensors inside in-patient rooms, and were used to develop a multiple linear regression (MLR) model to explore the relationship between daylight intensity and patient LoS in the presence of other environmental (i.e. provision of outdoor view and room status) and clinical (i.e. mean arterial pressure, heart rate and diabetes mellitus) variables. The coefficient estimates of the developed MLR model suggest that while holding the other explanatory variables constant, the patient LoS reduced by 7.3 hours per 100 lx increase of daylight inside in-patient rooms.
Impact of Fall-Related Behaviors as Risk Factors for Falls Among the Elderly Patients With Dementia in a Geriatric Facility in Japan
Authors: Suzuki Mizue , Kurata Sadami , Yamamoto Emiko , Makino Kumiko , Kanamori Masao
Published: August 2012

The purpose of this study was to clarify potential fall-related behaviors as fall risk factors that may predict the potential for falls among the elderly patients with dementia at a geriatric facility in Japan. This study was conducted from April 2008 to May 2009. A baseline study was conducted in April 2008 to evaluate Mini-Mental State Examination, Physical Self-Maintenance Scale, fall-related behaviors, and other factors. For statistical analysis, paired t test and logistic analysis were used to compare each item between fallers and nonfallers. A total of 135 participants were followed up for 1 year; 50 participants (37.04%) fell during that period. Results of multiple logistic regression analysis showed that the total score for fall-related behaviors was significantly related to falls. It was suggested that 11 fall-related behaviors may be effective indicators to predict falls among the elderly patients with dementia.
Toward a More Nuanced Perception of Alzheimer’s Disease
Authors: Van Gorp Baldwin , Vercruysse Tom , Van den Bulck Jan
Published: August 2012

Starting point of this study was the assumption that Alzheimer’s disease is made worse for the person who has the disease by the negative regard in which the illness is held by society. The aim was to test by means of a campaign advertisement whether more nuanced counterframes could have an impact while remaining credible and comprehensible to the public. A sample of thousand people living in Belgium evaluated the campaign in an experimental design. This revealed that all the versions tested achieved a high average evaluation. The ad in which the heading referred to the fear of death and degeneration was judged to be most attention-grabbing, easier to understand, and more credible than the alternative heading with the idea that someone with Alzheimer’s could still enjoy playing cards. Together, these findings provided a basis for the use of counterframes to generating a more nuanced image of Alzheimer’s disease.
Meta-analysis of effect sizes reported at multiple time points: A multivariate approach
Authors: Trikalinos Thomas A , Olkin Ingram
Published: August 2012

Background

Many comparative studies report results at multiple time points. Such data are correlated because they pertain to the same patients, but are typically meta-analyzed as separate quantitative syntheses at each time point, ignoring the correlations between time points.

Purpose

To develop a meta-analytic approach that estimates treatment effects at successive time points and takes account of the stochastic dependencies of those effects.

Methods

We present both fixed and random effects methods for multivariate meta-analysis of effect sizes reported at multiple time points. We provide formulas for calculating the covariance (and correlations) of the effect sizes at successive time points for four common metrics (log odds ratio, log risk ratio, risk difference, and arcsine difference) based on data reported in the primary studies. We work through an example of a meta-analysis of 17 randomized trials of radiotherapy and chemotherapy versus radiotherapy alone for the postoperative treatment of patients with malignant gliomas, where in each trial survival is assessed at 6, 12, 18, and 24 months post randomization. We also provide software code for the main analyses described in the article.

Results

We discuss the estimation of fixed and random effects models and explore five options for the structure of the covariance matrix of the random effects. In the example, we compare separate (univariate) meta-analyses at each of the four time points with joint analyses across all four time points using the proposed methods. Although results of univariate and multivariate analyses are generally similar in the example, there are small differences in the magnitude of the effect sizes and the corresponding standard errors. We also discuss conditional multivariate analyses where one compares treatment effects at later time points given observed data at earlier time points.

Limitations

Simulation and empirical studies are needed to clarify the gains of multivariate analyses compared with separate meta-analyses under a variety of conditions.

Conclusions

Data reported at multiple time points are multivariate in nature and are efficiently analyzed using multivariate methods. The latter are an attractive alternative or complement to performing separate meta-analyses.
Electroacupuncture at Zusanli Rescues the Enteric Neuronal Loss in the Stomach of Diabetic Rats
Authors: Hu Min , Du Fan , Liu Shi
Published: August 2012

The purpose of this study was to investigate the effects of electroacupuncture at Zusanli acupoint on the enteric neuropathy in diabetic rats. Sprague–Dawley rats were divided into different groups depending on the total electroacupuncture span and frequency. The expression of nitric oxide synthase (nNOS), choline acetyltransferase (CHAT), protein gene product 9.5 (PGP9.5), and doublecortin was significantly decreased in the diabetic group compared with the control group. Long-term electroacupuncture at Zusanli with either high frequency or low frequency could increase the expression levels of nNOS, CHAT, PGP9.5, and doublecortin, and the increase was greater in the high-frequency group. But no obvious changes were seen in the short-term electroacupuncture groups. These results suggest that electroacupuncture at Zusanli can restore the deficiency of enteric neurons in diabetes partly but a comparative long duration of stimuli (6 weeks) is required. The increase of doublecortin may be involved in this positive process.
Effect of test temperature on fracture toughness of modified 9Cr–1Mo steel
Authors: Shashank Dutt B , Nani Babu M , Venugopal S , Sasikala G , Bhaduri A K
Published: August 2012

The quasi-static fracture behaviour ( J– R curves) of modified 9Cr–1Mo (P91) steel was studied. The J– R curves were established at 298, 653, 823 and 893 K, and fracture toughness J0·2 at 0·2 mm of crack extension was determined. The value of ∼ J0·2 at 653 K was lower compared to that at 298 K followed by increases in J0·2 values at 823 and 893 K. The decrease in J0·2 at 653 K can be attributed to the influence of dynamic strain aging. At 893 K, a significantly higher (more than 200) J0·2 was observed, since plastic deformation of the net section, rather than crack growth, occurred in this condition.
Analysis of change in microstructure and properties during high temperature processing of ultralow C and high Nb microalloyed steel
Authors: Xu Y B , Yu Y M , Xiao B L , Liu Z Y , Wang G D
Published: August 2012

To further improve the strength and toughness, the advanced thermomechanical controlled processing has been applied in the development of an ultralow C and high Nb bearing steel. In the present investigation, the effects of processing parameters, consisting of the coiling and starting temperatures in non-recrystallisation region, on the final microstructure and mechanical properties of this steel have been studied by tensile, Charpy impact tests, optical microscopy and transmission electron microscopy. Results indicate that the acicular ferrite dominated microstructure can be greatly refined in grain size with decreasing the starting temperature of finishing rolling. However, for high Nb steels, the too low starting temperature would promote the formation of high temperature transformation products and consequently make against the improvement of mechanical properties. In addition, the optimum temperature window of finishing rolling is found to be also related to alloying levels of austenite stabilising elements. At the high starting temperature of finishing rolling, the precipitation strength contribution increases with increasing coiling temperature. However, the increase in strain accumulation associated with low temperature processing greatly reduces the sensitivity of the precipitation strength contribution to coiling temperature.
Effects of inclusions on formation of acicular ferrite and propagation of crack in high strength low alloy steel weld metal
Authors: Jiang Q L , Li Y J , Wang J , Zhang L
Published: August 2012

High strength low alloy steel was welded by gas shielded arc welding process without preheating. Microstructural characteristics of the weld metal, morphology of inclusions and crack propagation paths were investigated by means of optical microscopy and scanning electron microscopy. The chemical composition of the inclusion and element distribution across the inclusion were analysed via energy dispersive spectroscopy system. Results indicated relatively large inclusions with diameters of about 0·6–0·8 μm are much more effective in providing nucleation sites for acicular ferrite transformation and refining the microstructure within austenite grain than small ones with diameters of about 0·3–0·5 μm. When the main crack tip encountered inclusion, more crack paths would be initiated from the interface between inclusion and acicular ferrite plates.
Design of 10Cr martensitic steels for improved creep resistance in power plant applications
Authors: Sachadel U A , Morris P F , Clarke P D
Published: August 2012

The drive to increase the efficiency of fossil fired power generation to reduce CO2 emissions and to conserve energy resources has led Tata Steel to design new 10Cr martensitic compositions for use at temperatures of 620°C and above with creep properties superior to steel 92 (9Cr, 0·5Mo, and 2W), which is the best currently available steel of this type. In the new alloys, the chromium content was set at 10 to ensure the required oxidation resistance. The long term creep performance of steels with this level of chromium has been limited by the precipitation of Z phase nitrogen rich particles. These form at the expense of vanadium rich MN precipitates that are vital for long term creep strength. Compositions have been designed with the aim of suppressing or delaying Z phase formation. The principles underlying the new steel chemistries are discussed, and a detailed explanation is given of the role of heat treatment in optimising creep rupture strength at temperatures in excess of 600°C. The new steel compositions are based on published work supplemented by thermodynamic calculations to optimise the heat treatment cycle, to produce a fully martensitic microstructure and to maximise the stable nanoprecipitates that are essential to maximise creep rupture life.
Synthesis and growth mechanism of NbC–SiC micro/nanowire by carbothermal reduction
Authors: Li Q , Xiao H N , Hu J L , Guo W M , Qiu Y T
Published: August 2012

NbC–SiC micro/nanowires (MNWs) with NbC content varying from 5 to 20 mol.- were synthesised at 1600–1800°C via carbothermal reduction utilising silica sol, niobium pentoxide powder and carbon black as starting materials. The synthesis process and growth mechanism of NbC–SiC system were investigated. Results show that the morphology of the synthesised products mainly appears as curve shaped microwires or nanowires. The crystalline consists of both SiC and NbC phases which doped with each other by substitution and interstitial reactions in solid solution. NbC–SiC MNWs were developed by vapour–liquid–solid mechanism according to the existence of liquid droplet phase in the tip at reaction temperature. β-SiC twin crystal growing along [112] direction was formed in the stem, and NbC polycrystal was dissociated from Nb–Si liquid phase. The varied concentration of Nb and Si in the Nb–Si liquid phase could be a significant reason for the curved growth of NbC–SiC MNWs.
Tazzoliite: a new mineral with a pyrochlore-related structure from the Euganei Hills, Padova, Italy
Authors: Cámara F. , Nestola F. , Bindi L. , Guastoni A. , Zorzi F. , Peruzzo L. , Pedron D.
Published: August 2012

Tazzoliite, ideally Ba2CaSr0.5Na0.5Ti2Nb3SiO17[PO2(OH)2]0.5, is a new mineral (IMA 2011-018) from Monte delle Basse, Euganei Hills, Galzignano Terme, Padova, Italy. It occurs as lamellar pale orange crystals, which are typically a few m m thick and up to 0.4 mm long, closely associated with a diopsidic pyroxene and titanite. Tazzoliite is transparent. It has a white streak, a pearly lustre, is not fluorescent and has a hardness of 6 (Mohs' scale). The tenacity is brittle and the crystals have a perfect cleavage along {010}. The calculated density is 4.517 g cm–3. Tazzoliite is biaxial (–) with 2Vmeas of ~50º, it is not pleochroic and the average refractive index is 2.04. No twinning was observed. Electronmicroprobe analyses gave the following chemical formula: (Ba1.93Ca1.20Sr0.52Na0.25Fe0.102+)Σ4 (Nb2.88Ti2.05Ta0.07Zr0.01V0.015+)Σ5.02SiO17[(P0.13Si0.12S0.07)Σ0.32O0.66(OH)0.66][F0.09(OH)0.23]Σ0.32.

Tazzoliite is orthorhombic, space group Fmmm, with unit-cell parameters a = 7.4116(3), b = 20.0632(8), c = 21.4402(8) Å, V = 3188.2(2) Å3 and Z = 8. The crystal structure, obtained from single-crystal X-ray diffraction data, was refined to R1(F2) = 0.063. It consists of a framework of Nb(Ti) octahedra and BaO7 polyhedra sharing apexes or edges, and Si tetrahedra sharing apexes with Nb(Ti) octahedra and BaO7 polyhedra. The structure, which is related to the pyrochlore structure, contains three Nb(Ti) octahedra: two are Nb dominant and one is Ti dominant. Chains of A2O8 polyhedra [A2 being occupied by Sr(Ca, Fe)] extend along [100] and are surrounded by Nb octahedra. Channels formed by six Nb(Ti) octahedra and two tetrahedra, or four A1O8(OH) polyhedra (A1 being occupied by Ba), alternate along [100]. The channels are partially occupied by [PO2(OH)2] in two possible mutually exclusive positions, alternating with fully occupied A3O7 polyhedral pairs [A3 being occupied by Ca(Na)]. The seven strongest X-ray powder diffraction lines [d in Å (I/I0) (hkl)] are: 3.66 (60) (044), 3.16 (30) (153), 3.05 (100) (204), 2.98 (25) (240), 2.84 (50) (064), 1.85 (25) (400) and 1.82 (25) (268). Raman spectra of tazzoliite were collected in the range 150–3700 cm–1 and confirm the presence of OH groups. Tazzoliite is named in honour of Vittorio Tazzoli in recognition of his contributions to the fields of mineralogy and crystallography.
Refinement of the crystal structure of zoned philipsbornite–hidalgoite from the Tsumeb mine, Namibia, and hydrogen bonding in the D2+G3+3(T5+O4)(TO3OH)(OH)6 alunite structures
Authors: Cooper M. A. , Hawthorne F. C.
Published: August 2012

The crystal structure of zoned philipsbornite – hidalgoite, hexagonal (rhombohedral), Rm , Z = 3: a = 7.1142(4), c = 17.0973(9) A ˚ , V = 749.4(1) Å3, from the Tsumeb mine, Namibia, has been refined to R1 = 1.68% for 301 unique reflections collected on a Bruker D8 three-circle diffractometer equipped with a rotating-anode generator, multilayer optics and an APEX-II CCD detector. Chemical analysis by electron microprobe showed zoned crystals with a rim enriched in S and Fe relative to the core. The core composition is SO3 3.31, As2O5 30.57, Al2O3 23.05, FeO 1.44, PbO 33.94, H2Ocalc 9.58, total 101.79 wt.%, corresponding to Pb0.982+(Al2.92Fe0.132+)(AsO4)[(As0.72S0.27)O3.14(OH)0.85](OH)6; and the rim composition is SO3 8.88, As2O5 22.63, Al2O3 22.90, FeO 2.57, PbO 34.91, H2Ocalc 9.27, total 101.16 wt.%, corresponding to Pb0.992+(Al2.85Fe0.232+)(AsO4)[(As0.25S0.70)O3.30(OH)0.50](OH)6. Philipsbornite – hidalgoite has the alunite-type structure, sheets of corner-sharing octahedra, decorated on top and bottom by [(As,S)O4] and (AsO3OH) tetrahedra, that are linked into a three-dimensional structure by [12]-coordinated Pb2+ cations and hydrogen bonds. A new hydrogen-bonding scheme for the D2+G33+(T5+O4)(TO3OH)(OH)6 minerals is proposed.
Alcaparrosaite, K3Ti4+Fe3+(SO4)4O(H2O)2, a new hydrophobic Ti4+ sulfate from Alcaparrosa, Chile
Authors: Kampf A. R. , Mills S. J. , Housley R. M. , Williams P. A. , Dini M.
Published: August 2012

Alcaparrosaite, ideally K3Ti4+Fe3+(SO4)4O(H2O)2, is a new mineral from the Alcaparrosa mine, Cerritos Bayos, El Loa Province, Antofagasta, Chile (IMA2011-024). The mineral occurs on and intergrown with coquimbite, and is also associated with ferrinatrite, krausite, pertlikite, pyrite, tamarugite and voltaite. It is a relatively early phase which forms during the oxidation of pyritic masses under increasingly arid conditions. Alcaparrosaite crystallizes from hyperacidic solutions in a chemical environment that is consistent with its association with coquimbite. It occurs as pale yellow blades and tapering prisms up to 4 mm in length, flattened on {010} and elongated along [100]. The observed crystal forms are {010}, {110}, {1.13.0} and {021}. The mineral is transparent and has a white streak, vitreous lustre, Mohs hardness of about 4, brittle tenacity, conchoidal fracture and no cleavage. The measured and calculated densities are 2.80(3) and 2.807 g cm–3, respectively. It is optically biaxial (+) with α = 1.643(1), β = 1.655(1), γ = 1.680(1) (white light), 2Vmeas = 70(2)° and 2Vcalc = 70.3°. The mineral exhibits strong parallel dispersion, r < v. The optical orientation is X = b; Y^c = 27° in the obtuse angle β. No pleochroism was observed. Electron-microprobe analyses (average of 4) provided: Na2O 0.32, K2O 20.44, Fe2O3 11.58, TiO2 11.77, P2O50.55, SO347.52, H2O 5.79 (calc); total 97.97 wt.%. The empirical formula (based on 19 O) is (K2.89Na0.07)Σ2.96Ti0.984+Fe0.973+(S0.99P0.01O4)4O0.72(OH)0.28(H2O)2. The mineral is hydrophobic, insoluble in cold and hot water, very slowly soluble in acids and decomposes slowly in bases. Alcaparrosaite is monoclinic, C2/c, with the cell parameters a = 7.55943(14), b = 16.7923(3), c = 12.1783(9) Å, β = 94.076(7)°, V = 1542.01(12) Å3 and Z = 4. The eight strongest lines in the X-ray powder diffraction pattern [dobs in A ˚ (Irel) (hkl)] are 6.907 (41) (021,110); 3.628 (34) (023,13); 3.320 (32) (02); 3.096 (100) (202,33,150); 3.000 (40) (51); 2.704 (38) (23,152); 1.9283 (30) (55); 1.8406 (31) (53,06). In the structure of alcaparrosaite (R1 = 2.57% for 1725 Fo > 4σF), Ti4+ and Fe3+, in roughly equal amounts, occupy the same octahedrally coordinated site. Octahedra are linked into dimers by corner sharing. The SO4 tetrahedra link the dimers into chains parallel to [001] and link the chains into undulating sheets parallel to {010}. The sheets link via 10- and 11-coordinated K atoms in the interlayer region. The structure shares some features with that of goldichite.
Further developments in the structure topology of the astrophyllite-group minerals
Authors: Sokolova E.
Published: August 2012

The structure topology and crystal chemistry have been considered for ten astrophyllite-group minerals that contain the HOH layer, a central trioctahedral (O) sheet and two adjacent (H) sheets of [5]- and [6]-coordinated D polyhedra and the astrophyllite (T4O12) ribbons. The HOH layer is characterized by a planar cell with a ∼5.4, b ∼11.9 A ˚ and a^b ∼103°. The ideal composition of the O sheet is Fe72+ (astrophyllite) or Mn72+(kupletskite). All structures consist of an HOH layer and an I (intermediate) block that consists of atoms between two HOH layers. In the astrophyllite group, there are two types of structures based on the type of linkage of HOH layers: (1) HOH layers link directly where they share common vertices of D octahedra, and (2) HOH layers do not link directly via polyhedra of the H sheets. The type-1 structure occurs in astrophyllite, niobophyllite, nalivkinite, tarbagataite, kupletskite, niobokupletskite and kupletskite-(Cs); the type-2 structure occurs in magnesioastrophyllite, sveinbergeite and devitoite. The general formulae for the eight astrophyllite-group minerals (astrophyllite, niobophyllite, nalivkinite, tarbagataite, kupletskite, niobokupletskite, kupletskite-(Cs), magnesioastrophyllite) and for the extended astrophyllite group including devitoite and sveinbergeite are A2BC7D2T8O26(OH)4X0–1 and A2pBrC7D2(T4O12)2IXD2OXA4OXDnP, respectively, where C and D are cations of the O and H sheets, C =[6](Fe2+, Mn, Fe3+, Na, Mg, Zn) at the M(1–4) sites; D = [6,5](Ti, Nb, Zr, Fe3+); T = Si, minor Al; A2pBrI is the composition of the I block where p = 1,2; r = 1,2; A = K, Cs, Li, Ba, H2O, ☐; B = Na, Ca, Ba, H2O, ☐; I represents the composition of the central part of the I block, excluding peripheral layers of the form A2B; X = O, OH, F and H2O; n = 0, 1, 2. Two topological issues have been considered: (1) the pattern of sizes of the M octahedra in the O sheet, M(1) > M(2) > M(3) > M(4) and (2) different topologies of the HOH layer in magnesioastrophyllite and all other structures of the astrophyllite group.
Hereroite and vladkrivovichevite: two novel lead oxychlorides from the Kombat mine, Namibia
Authors: Turner R. , Siidra O. I. , Rumsey M. S. , Krivovichev S. V. , Stanley C. J. , Spratt J.
Published: August 2012

Two new lead oxychloride minerals, hereroite [Pb32(O, ☐)21](AsO4)2((Si,As,V,Mo)O4)2Cl10 and vladkrivovichevite [Pb32O18][Pb4Mn2O]Cl14(BO3)8·2H2O occur in association with asisite, damaraite, kombatite, sahlinite, copper, quartz, barysilite, Mn silicates and a number of Mn oxyhydroxide minerals on a specimen from the Kombat mine in Namibia. The minerals formed as late-stage products of hydrothermal reworking of primary sulfide minerals.

Hereroite is monoclinic, C2/c with a = 23.14(1), b = 22.65(1), c = 12.39(1) Å, β = 102.00(5)°, V = 6351.6(41) Å3 from powder-diffraction data and a = 23.139(4), b = 22.684(4), c = 12.389(2) Å, β = 102.090(3)°, V = 6358.8(18) Å3 from single-crystal data. It is bright orange, with white streak and adamantine lustre. It is brittle with no observed parting or cleavage and has a conchoidal fracture. The calculated density is 8.15 g cm–3. The mean refractive index in air at 589 nm is 2.38. The six strongest reflections in the X-ray powder diffraction pattern [d in Å, (I), (hkl)] are as follows: 2.982(100)(51); 2.795(47)(80); 1.986(24)(8); 1.641(24)(11..); 3.512(23)(61); 3.901(21)(511). Hereroite is named for the Herero people, one of the indigenous tribal groupings in the region where the Kombat mine is located.

Vladkrivovichevite is orthorhombic, Pmmn with a = 12.87(5), b = 27.7(4), c = 11.46(3) Å, V = 4080.1(5) Å3, from powder-diffraction data and a = 12.759(1), b = 27.169(4), c = 11.515(1) Å, V = 3992.0(9) Å3, Z = 2, from single-crystal data. It is pale greenish yellow, with white streak and adamantine lustre. It is brittle with no observed parting or cleavage and has a conchoidal fracture. The calculated density is 7.40 g cm–3. The mean refractive indices in air at 589 nm are 2.30 and 2.34. The six strongest reflections in the X-ray powder diffraction pattern [d in Å, (I), (hkl)] are as follows: 2.860(100)(370); 2.733(84)(073); 3.707(49)(073); 3.068(37)(401); 2.075(32)(473); 1.601(32)(3.14.3). Vladkrivovichevite is named in honour of Prof. Dr Vladimir Gerasimovich Krivovichev (b. 24.04.1946), Head of the Department of Mineralogy, Geological Faculty, St Petersburg State University.

The crystal structures of hereroite and vladkrivovichevite consist of alternating litharge-like O – Pb double layers and chlorine sheets and both are structurally related to other layered lead oxychlorides. In hereroite, tetrahedral AsO4 and (Si, As, V, Mo)O4 groups locate in defects within the O – Pb block, which combines square 'symesite-type' and double-square 'kombatite-type' cavities in its crystal structure. The structure of vladkrivovichevite is based on O – Pb derivative blocks with the interlayer occupied by Cl– anions and oxocentred OPb4Mn2 octahedra whose eight triangular faces are capped by triangular borate anions, BO33–.
Tripuhyite and schafarzikite: two of the ultimate sinks for antimony in the natural environment
Authors: Leverett P. , Reynolds J. K. , Roper A. J. , Williams P. A.
Published: August 2012

Studies of the stability of the oxides schafarzikite, FeSb2O4, and tripuhyite, FeSbO4, have been undertaken to clarify the roles these secondary minerals may have in determining the dispersion of antimony in oxidizing environments. Solubilities were determined at 298.15 K in aqueous HNO3, and these data were used to calculate values of ΔGfϴat the same temperature. The derived ΔGfϴ(s, 298.15 K) values for FeSb2O4and FeSbO4are – 959.4±4.3 and – 836.8±2.2 kJ mol–1, respectively. These results have been compared with electrochemically derived data, extrapolated from 771–981 K. The present study shows conclusively that although the mobility of Sb above the water table is limited by simple Sb(III) and Sb(V) oxides and stibiconite-group minerals, depending upon the prevailing redox potential and pH, tripuhyite is an important ultimate sink for Sb in the supergene environment. It is highly insoluble even in strongly acidic conditions and its anomalous stability at ambient temperatures causes the common mineral goethite, FeOOH, to react to form tripuhyite at activities of Sb(OH)5(aq) as low as 10–11. The comparatively limited numbers of reported occurrences of tripuhyite in the supergene zone are almost certainly due to the fact that its physical properties, especially colour and habit, are remarkably similar to those of goethite. In contrast, the small number of reported occurrences of schafarzikite can be related to its decomposition to tripuhyite as redox potentials rise at the top of the supergene zone and the fact that it decomposes to sénarmontite, Sb2O3, in acidic conditions, releasing Fe2+ions into solution. In general, the findings confirm the immobility of Sb in near-surface conditions. Geochemical settings favouring the formation of the above minerals have been assessed using the results of the present study and data from the literature.
Carbon dioxide in pollucite, a feldspathoid with the ideal composition (Cs, Na)16Al16Si32O96·nH2O
Authors: Bellatreccia F. , Ventura G. Della , Gatta G. D. , Guidi M. Cestelli , Harley S.
Published: August 2012

We report a single-crystal Fourier-transform infrared (FTIR) study of a sample of pollucite from Maine, USA. Prior to our work, the sample had been characterized by single-crystal X-ray diffraction, neutron diffraction and electron-probe microanalysis. It is cubic Ia3d, with a crystal-chemical formula Na1.93(Cs10.48Rb0.31K0.04)Σ=10.83(Al14.45Si33.97)Σ=48.42O96·3.92H2O, and an H2O content, determined by thermogravimetric analysis, of 1.6 wt.%. The single-crystal FTIR spectrum has a doublet of intense bands at 3670 and 3589 cm–1, which are assigned to the ν3 and ν1 stretching modes of the H2O molecule, respectively. A very intense and sharp peak at 1620 cm–1 is assigned to the ν2 bending vibration. In the near-infrared region there is a relatively intense peak at 5270 cm–1, which is assigned to a combination (ν2 + ν3) mode of H2O, and a weak but well defined doublet at 7118 and 6831 cm–1, which is assigned to the first overtones of the fundamental stretching modes. A relatively weak but extremely sharp peak at 2348 cm–1 shows that the pollucite contains CO2 molecules in structural cavities. Mapping the sample using FTIR indicates that both H2O and CO2 are homogeneously distributed. Secondary ion mass spectrometry yielded an average CO2 content of 0.09±0.02 wt.%. On the basis of this value, we determined the integrated molar absorption coefficient for the spectroscopic analysis of CO2 in pollucite to be εiCO2 = 11,000±3000 l mol–1 cm–2; the linear molar absorption coefficient for the same integration range is εlCO2 = 1600±500 l mol–1 cm–1.
The high-pressure monazite-to-scheelite transformation in CaSeO4
Authors: Crichton W. A. , Merlini M. , Müller H. , Chantel J. , Hanfland M.
Published: August 2012

The high-pressure monazite – scheelite structure transition has been observed at P >4.57 GPa in CaSeO4 by synchrotron X-ray powder diffraction. It is a first-order transition with a 4.5% volume change and is severely hindered kinetically. Scheelite-type CaSeO4 remains to a maximum experimental pressure of 42.2 GPa and no (002) reflection, specifically indicative of a subgroup transition to a fergusonite-type structure, is observed. Scheelite-type CaSeO4 remains at ambient conditions, where the tetragonal unit cell has parameters of a = 5.04801(11) c = 11.6644(5) Å and V = 297.21(3) Å3 with Dcalc = 4.090 g cm–3. The diffraction pattern of the recovered material was refined in space group I41/a to Rp = 0.98%, wRp = 1.91%, GoF = 0.59, RFobs = 5.04%, wRFobs = 4.27%. The oxygen is located on the general 16f site at (0.2578(8) 0.3699(14) 0.5755(4)) and shares four identical bonds with Se (4a: ½ ½ ½) at 1.644(5) Å. The Ca (4b: 0, 0, ½) is eight-coordinated via O at 4 × 2.440(6) Å and 4 × 2.504(5) Å. This is further evidence of the dissimilarity of sulfate and selenate at high pressure and temperature conditions and the closer resemblance of the selenates to the orthophosphates, arsenates and vanadates, where this type of transition sequence has been described.
The relative strength of perovskite and post-perovskite NaCoF3
Authors: Dobson D. P. , McCormack R. , Hunt S. A. , Ammann M. W. , Weidner D. , Li L , Wang L.
Published: August 2012

Stable perovskite and metastable post-perovskite NaCoF3 were deformed in pure-shear geometry in a deformation-DIA press with radiographic monitoring of the sample strain. In isothermal experiments where there was no transformation, post-perovskite was found to be 5 times weaker than perovskite. In temperature-ramping experiments where post-perovskite transformed to perovskite during the deformation experiment the initial post-perovskite sample was 5–10 times weaker than perovskite under comparable conditions and their strengths converged during the transformation, being equal on completion of the transformation. These results confirm recent findings which show that postperovskite is weaker than perovskite, regardless of the prior history of the sample.