Core Softening in Cavernously Weathered Tonalite

Tonalite exhibiting cavernous weathering at Catavina, Baja California, was investigated to determine the factors which contribute to differential hardness within the rock. Soft cores have a high degree of chemical weathering as indicated by kaolinite content. Hematite formed from the leaching of biotite occurs in coatings on rock surfaces, but the hardening effect of the coating is insignificant compared to the core-softening of the interior. The hardness, measured by an abrasion resistance hardness tester, is inversely correlated with kaolinite content in the tonalite. A one-dimensional water flow model was developed for core-softened. cavernously weathered boulders. It indicates that during infiltration and dessication the moisture flux is greatest through the cavern interior wall because of changes in the hydraulic conductivities induced by core softening. Therefore, the cavern interior wall should have the greatest weathering rate in the boulder

RAS isoforms and mutations in cancer at a glance

RAS proteins (KRAS4A, KRAS4B, NRAS and HRAS) function as GDP–GTP-regulated binary on-off switches, which regulate cytoplasmic signaling networks that control diverse normal cellular processes. Gain-of-function missense mutations in RAS genes are found in ∼25% of human cancers, prompting interest in identifying anti-RAS therapeutic strategies for cancer treatment. However, despite more than three decades of intense effort, no anti-RAS therapies have reached clinical application. Contributing to this failure has been an underestimation of the complexities of RAS. First, there is now appreciation that the four human RAS proteins are not functionally identical. Second, with >130 different missense mutations found in cancer, there is an emerging view that there are mutation-specific consequences on RAS structure, biochemistry and biology, and mutation-selective therapeutic strategies are needed. In this Cell Science at a Glance article and accompanying poster, we provide a snapshot of the differences between RAS isoforms and mutations, as well as the current status of anti-RAS drug-discovery efforts

Estimated optical constants of gypsum in the regions of weak absorptions: Application of scattering theories and comparisons to independent measurements

Diffuse reflectance spectra of multiple grain size fractions are used to estimate the optical constants of gypsum over the 0.4–15 μm wavelength region. Two independent scattering theories are used to iteratively determine the imaginary index of refraction from the measured reflectance. We compare the results of these two with each other and with imaginary indices of gypsum reported in the literature. We find that the scattering theory results are more sensitive in the infrared to weak spectral features that are clearly distinguished in the diffuse reflectance spectra. However, we find the scattering results provide a poor determination of the optical constants in the regions of relatively strong absorptions. At visible and near-infrared wavelengths we provide a comparison to the results obtained from analysis of the diffuse reflectance to results obtained from direct transmission measurements of several gypsum crystals having different sample thicknesses. We find the simplest models of the transmission reproduce the observed spectra. The different sample thicknesses for the transmission measurements and different grain sizes in the scattering theories allow evaluation of the imaginary index of refraction over a wide range of values. We find the imaginary index of refraction determined from scattering theories is in remarkable agreement with those obtained from transmission spectra. Different models of the reflectance and transmittance have associated strengths and weaknesses, and we conclude that combining these models provides a more accurate determination of the optical constants of a material when compared to using each separately. We combine the resulting real and imaginary indices of refraction with those reported at infrared wavelengths to provide values covering visual, near-infrared, and infrared wavelengths (0.4–333 μm, 25000–30 cm^(−1))

Human annexin A6 interacts with influenza a virus protein M2 and negatively modulates infection

Copyright © 2012, American Society for Microbiology. All Rights ReservedThe influenza A virus M2 ion channel protein has the longest cytoplasmic tail (CT) among the three viral envelope proteins and is well conserved between different viral strains. It is accessible to the host cellular machinery after fusion with the endosomal membrane and during the trafficking, assembly, and budding processes. We hypothesized that identification of host cellular interactants of M2 CT could help us to better understand the molecular mechanisms regulating the M2-dependent stages of the virus life cycle. Using yeast two-hybrid screening with M2 CT as bait, a novel interaction with the human annexin A6 (AnxA6) protein was identified, and their physical interaction was confirmed by coimmunoprecipitation assay and a colocalization study of virus-infected human cells. We found that small interfering RNA (siRNA)-mediated knockdown of AnxA6 expression significantly increased virus production, while its overexpression could reduce the titer of virus progeny, suggesting a negative regulatory role for AnxA6 during influenza A virus infection. Further characterization revealed that AnxA6 depletion or overexpression had no effect on the early stages of the virus life cycle or on viral RNA replication but impaired the release of progeny virus, as suggested by delayed or defective budding events observed at the plasma membrane of virus-infected cells by transmission electron microscopy. Collectively, this work identifies AnxA6 as a novel cellular regulator that targets and impairs the virus budding and release stages of the influenza A virus life cycle.This work was supported by the Research Fund for the Control of Infectious Disease (project 09080892) of the Hong Kong Government, the Area of Excellence Scheme of the University Grants Committee (grant AoE/M-12/-06 of the Hong Kong Special Administrative Region, China), the French Ministry of Health, the RESPARI Pasteur Network

Independent Validation of the SWMM Green Roof Module

Green roofs are a popular Sustainable Drainage Systems (SuDS) technology. They provide multiple benefits, amongst which the retention of rainfall and detention of runoff are of particular interest to stormwater engineers. The hydrological performance of green roofs has been represented in various models, including the Storm Water Management Model (SWMM). The latest version of SWMM includes a new LID green roof module, which makes it possible to model the hydrological performance of a green roof by directly defining the physical parameters of a green roof’s three layers. However, to date, no study has validated the capability of this module for representing the hydrological performance of an extensive green roof in response to actual rainfall events. In this study, data from a previously-monitored extensive green roof test bed has been utilised to validate the SWMM green roof module for both long-term (173 events over a year) and short-term (per-event) simulations. With only 0.357% difference between measured and modelled annual retention, the uncalibrated model provided good estimates of total annual retention, but the modelled runoff depths deviated significantly from the measured data at certain times (particularly during summer) in the year. Retention results improved (with the difference between modelled and measured annual retention decreasing to 0.169% and the Nash-Sutcliffe Model Efficiency (NSME) coefficient for per-event rainfall depth reaching 0.948) when reductions in actual evapotranspiration due to reduced substrate moisture availability during prolonged dry conditions were used to provide revised estimates of monthly ET. However, this aspect of the model’s performance is ultimately limited by the failure to account for the influence of substrate moisture on actual ET rates. With significant differences existing between measured and simulated runoff and NSME coefficients of below 0.5, the uncalibrated model failed to provide reasonable predictions of the green roof’s detention performance, although this was significantly improved through calibration. To precisely model the hydrological behaviour of an extensive green roof with a plastic board drainage layer, some of the modelling structures in SWMM green roof module require further refinement

Silica coatings in the Ka’u Desert, Hawaii, a Mars analog terrain: A micromorphological, spectral, chemical, and isotopic study

High-silica materials have been observed on Mars, both from orbit by the CRISM spectrometer and in situ by the Spirit rover at Gusev Crater. These observations potentially imply a wet, geologically active Martian surface. To understand silica formation on Mars, it is useful to study analogous terrestrial silica deposits. We studied silica coatings that occur on the 1974 Kilauea flow in the Ka'u Desert, Hawaii. These coatings are typically composed of two layers: a ~10 μm layer of amorphous silica, capped by a ~1 μm layer of Fe-Ti oxide. The oxide coating is composed of ~100 nm spherules, suggesting formation by chemical deposition. Raman spectroscopy indicates altered silica glass as the dominant phase in the silica coating and anatase and rutile as dominant phases in the Fe-Ti coating; jarosite also occurs within the coatings. Oxygen isotopic contents of the coatings were determined by secondary ion mass spectrometry (Cameca 7f and NanoSIMS). The measured values, δ^(18)O_(Fe-Ti) = 14.6 ± 2.1‰, and δ^(18)O_(silica) = 12.1 ± 2.2‰ (relative to SMOW), are enriched in ^(18)O relative to the basalt substrate. The observations presented are consistent with a residual formation mechanism for the silica coating. Acid-sulfate solutions leached away divalent and trivalent cations, leaving a silica-enriched layer behind. Micrometer-scale dissolution and reprecipitation may have also occurred within the coatings. Chemical similarities between the Hawaiian samples and the high-silica deposits at Gusev suggest that the Martian deposits are the product of extended periods of similar acid-sulfate leaching

Carbonate formation on Mars: Latest experiments

Laboratory simulations of Martian CO2 storage address whether carbonate formation could have reduced CO2 pressure from a hypothetical greater than 1 bar to the present 7 mbar in less than or equal to 3 to 4 billion years. This problem is addressed with experiments and analysis designed to verify and improve previous kinetic measurements, reaction mechanisms, and product characterizations, with the goal of improving existing models of Martian CO2 history. A sensitive manometer monitored the pressure drop of CO2 due to uptake by powdered silicate for periods of 3 to 100+ days. Pressure drops for diopside 1 and basalt show rapid short-term (approximately one day) CO2 uptake and considerably slower long-term pressure drops. Curves for diopside 2, olivine 1, and olivine 2 are qualitatively similar to those for diopside 1, whereas quartz and plagioclase show near-zero short-term pressure drops and very slow long-term signals, indistinguishable from a leak (less than 10(exp 11) mol/sq m/s)

Broadening the Impact and Effectiveness of Simulation-Based Curricula for Introductory Statistics

The demands for a statistically literate society are increasing, and the introductory statistics course “Stat 101” remains the primary venue for learning statistics for the majority of high school and undergraduate students. After three decades of very fruitful activity in the areas of pedagogy and assessment, but with comparatively little pressure for rethinking the content of this course, the statistics education community has recently turned its attention to focusing on simulation-based methods, including bootstrapping and permutation tests, to illustrate core concepts of statistical inference within the context of the overall statistical investigative process. This new focus presents an opportunity to address documented shortcomings in the standard Stat 101 course (e.g., seeing the big picture; improving statistical thinking over mere knowledge of procedures). Our group has developed and implemented one of the first cohesive curricula that (a) emphasizes the core logic of inference using simulation-based methods in an intuitive, cyclical, active-learning pedagogy, and (b) emphasizes the overall process of statistical investigations, from asking questions and collecting data through making inferences and drawing conclusions. Improved conceptual understanding and retention of inference and study design that had been observed when using early versions of the curriculum at a single institution, are now being evaluated at dozens of institutions across the country with thousands of students using the fully integrated, stand-alone version of the curriculum. Encouraging preliminary results continue to be observed. We are now leveraging the tremendous national momentum and excitement about the approach to greatly expand implementations of simulation-based curricula by offering workshops around the country to diverse sets of faculty, offering numerous online support structures including: a blog, freely available applets, free instructor materials, earning objective-based instructional videos, free instructor-focused training videos, a listserv, and peer-reviewed publications covering both rationale and assessment results. Many hundreds of instructors have been directly impacted by our workshops and hundreds more through access to the free online materials. We are also in the midst of valuating widespread transferability of the approach across diverse institutions, students, and learning environments and deepening our understanding of how students’ attitudes and conceptual understanding develop using this approach through an assessment project involving concept and attitude inventories with over 10,000 students across 200 different instructors

The dumortierite supergroup. I. A new nomenclature for the dumortierite and holtite groups

Although the distinction between magnesiodumortieite and dumortierite, i.e. Mg vs. Al dominance at the partially vacant octahedral Al1 site, had met current criteria of the IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) for distinguishing mineral species, the distinction between holtite and dumortierite had not, since Al and Si are dominant over Ta and (Sb, As) at the Al1 and two Si sites, respectively, in both minerals. Recent studies have revealed extensive solid solution between Al, Ti, Ta and Nb at Al1 and between Si, As and Sb at the two Si sites or nearly coincident (As, Sb) sites in dumortierite and holtite, further blurring the distinction between the two minerals. This situation necessitated revision in the nomenclature of the dumortierite group. The newly constituted dumortierite supergroup, space group Pnma (no. 62), comprises two groups and six minerals, one of which is the first member of a potential third group, all isostructural with dumortierite. The supergroup, which has been approved by the CNMNC, is based on more specific end-member compositions for dumortierite and holtite, in which occupancy of the Al1 site is critical. (1) Dumortierite group, with Al1 = Al^(3+), Mg^(2+) and 〈, where 〈 denotes cation vacancy. Charge balance is provided by OH substitution for O at the O2, O7 and O10 sites. In addition to dumortierite, endmember composition AlAl_6Bsi_3O_(18), and magnesiodumortierite, endmember composition MgAl_6Bsi_3O_(17)(OH), plus three endmembers, “hydroxydumortierite”, 〈Al_6Bsi_3O_(15)(OH)_3 and two Mg-Ti analogues of dumortierite, (Mg_(0.5)Ti_(0.5))Al_6Bsi_3O_(18) and (Mg_(0.5)Ti_(0.5))Mg_2Al_4Bsi_3O_(16)(OH)_2, none of which correspond to mineral species. Three more hypothetical endmembers are derived by homovalent substitutions of Fe^(3+) for Al and Fe^(2+) for Mg. (2) Holtite group, with Al1 = Ta^(5+), Nb^(5+), Ti^(4+) and 〈. In contrast to the dumortierite group, vacancies serve not only to balance the extra charge introduced by the incorporation of pentavalent and quadrivalent cations for trivalent cations at Al1, but also to reduce repulsion between the highly charged cations. This group includes holtite, endmember composition (Ta_(0.6)〈_(0.4))Al_6Bsi_3O_(18), nioboholite (2012-68), endmember composition (Nb_(0.6)〈_(0.4_)Al_6Bsi_3O_(18), and titanoholtite (2012-69), endmember composition (Ti_(0.75)〈_(0.25))Al_6Bsi_3O_(18). (3) Szklaryite (2012-70) with Al1 = 〈 and an endmember formula 〈Al_6Bas^(3+)_ 3O_(15). Vacancies at Al1 are caused by loss of O at O2 and O7, which coordinate the Al1 with the Si sites, due to replacement of Si^(4+) by As^(3+) and Sb^(3+), and thus this mineral does not belong in either the dumortierite or the holtite group. Although szklaryite is distinguished by the mechanism introducing vacancies at the Al1 site, the primary criterion for identifying it is based on occupancy of the Si/As, Sb sites: (As^(3+) + Sb^(3+)) > Si^(4+) consistent with the dominant-valency rule. A Sb^(3+) analogue to szklaryite is possible