Morphology and structure of the 1999 lava flows at Mount Cameroon Volcano (West Africa) and their bearings on the emplacement dynamics of volume-limited flows

The morphology and structure of the 1999 lava flows at Mount Cameroon volcano are documented and discussed in relation to local and source dynamics. Structures are analysed qualitatively and more detailed arguments are developed on the processes of levee formation and systematic links between flow dynamics and levee-channel interface geometry. The flows have clear channels bordered by four main types of levees: initial, accretionary, rubble and overflow levees. Thermally immature pahoehoe lava units with overflow drapes define the proximal zone, whereas rubble and accretionary levees are common in the distal region bordering thermally mature aa clinker or blocky aa flow channels. Pressure ridges, squeeze-ups and pahoehoe ropes are the prevalent compressive structures. Standlines displayed on clinkery breccias are interpreted to represent levee-channel interactions in response to changing flow levels. These data complement previous knowledge on lava flow morphology, thus far dominated by Etnean and Hawaiian examples

Twinning-mediated formability in Mg alloys

Mg alloys are promising candidates for automotive applications due to their low density and high specific strength. However, their widespread applications have not been realized mainly because of poor formability at room temperature, arising from limited number of active deformation systems and strong basal texture. It has been recently shown that Mg-Zn-Ca alloys have excellent stretch formability, which has been ascribed to their weak basal texture. However, the distribution of basal poles is orthotropic, which might result in anisotropy during deformation and have adverse effect on formability. Here, we show that tension twinning is mainly responsible for enhanced formability of Mg-Zn-Ca alloys. We found that tension twinning is quite active during both uniaxial deformation and biaxial deformation of Mg-Zn-Ca alloy even under the stress conditions unfavourable for the formation of tensile twins. Our results provide new insights into the development of Mg alloys having high formability.112514Ysciescopu

Volcanic Ash from the 1999 Eruption of Mount Cameroon Volcano: Characterization and Implications to Health Hazards

Volcanic ash from the 1999 eruption of Mount Cameroon volcano has been characterized for its particle size and shape (by scanning electron microscopy, SEM), and mineralogy (by X-ray diffractometry, XRD). Also the total fluorine (F) content of the ash was determined by the selective ion electrode method. The results show that the Mount Cameroon ash particles have a variety of shapes including fibrous, rounded, subrounded, irregular, angular, eleongated and bladed. All the ash samples have a significant proportion (~ 30%) of ash < 4 ƒÊm in size and thisis classified in occupational medicine as 'thoracic' and 'respirable' ash that is considered harmful to health. The XRD patterns show that the ash contains plagioclase feldspar, enstatite, augite and chromite, which, if fine enough may cause irritation of the respiratory tract, but they are relatively insoluble in the alveolar region. The ash lacks free silica, the main mineral in volcanic ash responsible for causing silicosis. The F concentration in the ash ranges from 46 ƒÊg/ g to 189ƒÊg/g. This is high considering that the lethal dose of F is set internationally at ~ 100ƒÊg/g. This study forms the basis for a long term monitoring of volcanic ash risk and possible mitigation measures of the Mount Cameroon volcano.Keywords: volcanic ash, Mt. Cameroon, health hazardsCendre de Volcan de L'Eruption de 1999 du Mont Cameroun: Caracterisation et Implications aux Risques Sanitaires.La cendre de volcan de l'eruption de 1999 du mont Cameroun a ete caracterisee pour la dimension et la forme de ces particules (en utilisant la microscopie electronique a balayant, SEM), et mineralogie (diffractometrie a rayon X, XRD). En outre toute la teneur en fluor (F) de la cendre a ete determinee par la methode selective d'electrode d'ion. Les resultats prouvent que les particules de cendre du mont Cameroun ont une variete de formes comprenant : les fibreux, les arrondies, les sous arrondies, les irreguliers, les angulaires et les ovales. Tous les echantillons de cendreont une proportion significative de (~ 30 %) de cendre ayant la taille < 4 m et ceci est classifie dans la medecine du travail comme la cendre 'thoracique' et 'respirable' qui est consideree nocif a la sante. Les modeles de XRD montre que la cendre contient le feldspath de plagioclase, l'enstatite, l'augite et la chromite qui, s'ils sont assez fins, peuvent produire l'irritation de la cavite nasale mais sont relativement insolubles dans la region d'aveolaire. La cendre manque de la silice libre, qui est le minerai principal de la cendre volcanique responsable d'engendrer la silicose. La concentration de F dans la cendre s'echelonne de 189 g/g. Ceci est eleve considerant que la dose mortelle de F est place internationalement aux environs de ~ 100 g/g. Cette etude forme la base pour une surveillance a long terme du risque volcanique et des mesures possibles de reduction du volcan de mont Cameroun.Mots cles : cendre de volcan, Mont Cameroun, risques sanitaire

Medium-Term Exposure to Traffic-Related Air Pollution and Markers of Inflammation and Endothelial Function

Bac k g r o u n d: Exposure to traffic-related air pollution (TRAP) contributes to increased cardiovascular risk. Land-use regression models can improve exposure assessment for TRAP. Objectives: We examined the association between medium-term concentrations of black carbon (BC) estimated by land-use regression and levels of soluble intercellular adhesion molecule-1 (sICAM-1) and soluble vascular cell adhesion molecule-1 (sVCAM-1), both markers of inflammatory and endothelial response. Me t h o d s: We studied 642 elderly men participating in the Veterans Administration (VA) Normative Aging Study with repeated measurements of sICAM‑1 and sVCAM‑1 during 1999–2008. Daily estimates of BC exposure at each geocoded participant address were derived using a validated spatiotemporal model and averaged to form 4-, 8-, and 12-week exposures. We used linear mixed models to estimate associations, controlling for confounders. We examined effect modification by statin use, obesity, and diabetes. Re s u l t s: We found statistically significant positive associations between BC and sICAM‑1 for averages of 4, 8, and 12 weeks. An interquartile-range increase in 8-week BC exposure (0.30 μg/m3) was associated with a 1.58 % increase in sICAM‑1 (95 % confidence interval, 0.18–3.00%). Overall association

Genomic structure and alterations of homeobox gene CDX2 in colorectal carcinomas

Expression of CDX2, a caudal-related homeobox gene, was found to be decreased in colorectal carcinomas. Heterozygous null mutant mice as to Cdx2 develop multiple intestinal adenomatous polyps. To clarify the role of CDX2 in colorectal carcinogenesis, we determined its genomic structure, and searched for mutations of CDX2 in 49 sporadic colorectal carcinomas and ten hereditary non-polyposis colorectal cancers (HNPCC) without microsatellite instability. None of them exhibited a mutation. We further examined 19 HNPCC carcinomas with microsatellite instability for mutations in a (G)7 repeat site within CDX2. One of them (5.3%) exhibited one G insertion. Loss of heterozygosity was observed in 2 of the 20 (10%) informative sporadic carcinomas, and in one of the three (33.3%) informative HNPCC cancers. These data indicate that CDX2 may play only a minor role in colorectal carcinogenesis. © 1999 Cancer Research Campaig

Preferential Paths of Air-water Two-phase Flow in Porous Structures with Special Consideration of Channel Thickness Effects.

Accurate understanding and predicting the flow paths of immiscible two-phase flow in rocky porous structures are of critical importance for the evaluation of oil or gas recovery and prediction of rock slides caused by gas-liquid flow. A 2D phase field model was established for compressible air-water two-phase flow in heterogenous porous structures. The dynamic characteristics of air-water two-phase interface and preferential paths in porous structures were simulated. The factors affecting the path selection of two-phase flow in porous structures were analyzed. Transparent physical models of complex porous structures were prepared using 3D printing technology. Tracer dye was used to visually observe the flow characteristics and path selection in air-water two-phase displacement experiments. The experimental observations agree with the numerical results used to validate the accuracy of phase field model. The effects of channel thickness on the air-water two-phase flow behavior and paths in porous structures were also analyzed. The results indicate that thick channels can induce secondary air flow paths due to the increase in flow resistance; consequently, the flow distribution is different from that in narrow channels. This study provides a new reference for quantitatively analyzing multi-phase flow and predicting the preferential paths of immiscible fluids in porous structures