The illitization reaction in a thick K-bentonite bed located in upper Cretaceous marine shale in the Montana disturbed belt was studied by X-ray diffraction, chemical analysis, and thermal ...gravimetric analysis. Modeling of the experimental XRD patterns from oriented clay specimens in air-dried and glycolated states shows that at each sample location in the bentonite bed a mixture of R0 illite-smectite (I-S) and R1 I-S coexist. Each of these phases in all samples consists of the same or similar content of illite and expandable layers independent on location in the bed. In particular, the illite content in the R0 I-S and the R1 I-S from the <0.5 µm fractions is equal to 30 and 62%, respectively. The main difference between the samples at different locations is the different weight concentrations of the coexisting I-S phases. The R1 I-S content decreases progressively from the lower and upper contacts of the bed to its center. The reverse trend was observed for the R0 I-S. The layer unit-cell parameter b increases from samples located near the middle of the bed toward samples near the bed margins. The DTG patterns of the samples contain two endothermic maxima at about 640 and 470°C, corresponding to cis-vacant (cv) illite and trans-vacant (tv) smectite layers coexisting in the R1 I-S and R0 I-S. Analysis of the crystal-chemical features of the R1 I-S and R0 I-S shows that, in the middle of the bed, both phases are characterized by the lowest octahedral Mg and the highest tetrahedral Al contents. In the structural formula of the R1 I-S, the tetrahedral Al content is significantly higher than the (K+Na) content independent of sample location. In contrast, tetrahedral Al in the R0 I-S located near the bed boundaries is lower compared with (K+Na) content. To account for the crystal-chemical features of the coexisting I-S, a first assumption is that the initial volcanic ash was altered into tv smectite having a homogeneous Al-rich composition throughout the bed. Second, along with K, the active role in illitization was controlled by Mg. Mineralogical zonation of the K-bentonite is explained by the progressive migration of K from the margins toward the bed center with the associated decrease of K cations in the pore fluids. However, the decrease in K concentration was accompanied by a successive increase in R0 I-S content, but not a progressive decrease in illite layer content in a single I-S phase. The main role of Mg was to redistribute octahedral and tetrahedral Al in the 2:1 layers of the R0 I-S and R1 I-S in such a way that the amount of Al in the tetrahedral sheets increased at the expense of the substitution of Mg for Al in the octahedral sheet of the 2:1 layers in the initial smectite. These results demonstrate a new insight into mineralogical sequences of intermediate members of smectite illitization. Instead of a statistically homogeneous and continuous reaction associated with the increase of illite layers in I-S and the simultaneous increase of order of the layer stacking sequence, the illitization reaction in the thick K-bentonite consists of the formation of a physical mixture of two I-S having a contrasting content of layer types and their distribution. Factors responsible for the formation of the coexisting R0 I-S and R1 I-S are discussed.
The current work is the first audit study to experimentally investigate bias toward people who use they/them pronouns in real-life circumstances, extending prior survey and experimental scenario ...work. Four hundred and sixty-six authors (62.30% perceived as female identifying and 37.70% perceived as male identifying as coded by independent raters) of recently published empirical psychology articles were contacted with a request for a copy of their recent work. The content of the emails was identical except the email signature was randomly assigned to include she/her, he/him, they/them, or no pronouns. The primary dependent variable was whether or not emails were responded to. As hypothesized, emails from requesters with they/them pronouns were less likely to be responded to overall than all other conditions. However, also consistent with hypotheses, this effect was moderated by the perceived gender of the author. Authors who were perceived as female responded at similar rates regardless of the pronouns in the requester’s email. Authors who were perceived as male were less likely to respond to emails from requesters with they/them pronouns than all other conditions. This work finds that people who use they/them pronouns experience bias in real-world situations due solely to their gender pronouns. This clear demonstration of gender bias even in a low-stakes educational setting highlights the need to further investigate and dismantle prejudice regarding gender diversity in academia. (PsycInfo Database Record (c) 2024 APA, all rights reserved) (Source: journal abstract)
A multi-cycle heating and cooling thermogravimetric (TG) method was used to study the kinetic behavior of partially dehydroxylated illite, aluminoceladonite, and dioctahedral smectite samples. The ...method consists of consecutive heating cycles separated by intervals of cooling to room temperature, with the maximum cycle temperatures (MCTs) set incrementally higher in each consecutive cycle. In the studied samples, dehydroxylation of each portion of the initial OH groups follows the kinetics of a homogeneous zero-order reaction in each heating cycle. The activation energies (Ea) were calculated in terms of this model for separate heating cycles of each sample with regression coefficients R2≥0.999. A zero-order reaction determined at each heating cycle indicates that at each stage of partial dehydroxylation, there is no formation of an intermediate phase and the reaction is probably the direct transformation of the original layers into completely dehydroxylated layers. The Wyoming montmorillonite and illite consisting of cis-vacant (cv) layers had the highest Ea values (53-55 kcal/mol). In the samples consisting of trans-vacant (tv) layers and having almost the same octahedral cation composition the maximum Ea values varied from 45 to 30 kcal/mol and the Ea of each sample in this group are similar over a wide range of the DT. For the samples consisting of a mixture of cv and tv illite structures, a bimodal distribution of the Ea values exists with increasing MCT and DT. The maximum Ea values for dehydroxylation of the tv and cv illite structures are different. The activation energies from the tv aluminoceladonite and Otay tv montmorillonite samples have similar maximum Ea values (39.4 to 41.8 kcal/mol), but the variation in Ea with DT has a skewed bell-like distribution that is probably related to a heterogeneous octahedral cation composition of the 2:1 layers. The Ea values calculated for the mineral structures in this study are compared with those published and the main factors controlling the Ea variation at different stages of the partial dehydroxylation are discussed.
The reactive growth of ultrathin Fe oxide films on Ru(0001) has been studied and characterized using low-energy electron microscopy, diffraction, and laterally resolved spectroscopies. Under exposure ...to molecular oxygen at 900 K, we observed the growth of a bicomponent film composed of micrometer-sized flat triangular Fe3O4 (magnetite) islands on a FeO (wüstite) wetting layer. Subsequent oxidation using NO2 at 600 K resulted in the chemical transformation of the initially grown film to a Fe2O3 composition but still in bicomponent form. The triangular magnetite islands evolve to γ-Fe2O3 (maghemite), and the surrounding layer is converted to α-Fe2O3 (hematite). The evolution of both members of the bicomponent iron oxide films, wüstite to hematite and magnetite to maghemite, can be understood by considering that both are topotactic transformations occurring by the diffusion of iron in octahedral sites to react with oxygen on the film’s surface.
Thermal analysis experiments in the environment of an extremely low water vapor concentration provide insight into the first steps of the rehydration mechanism in smectite when completely dehydrated ...and the interlayer region is collapsed. The relative structural and compositional controls on dehydration and rehydration reactions are compared from a well-characterized suite of samples that vary with respect to chemical composition, octahedral and tetrahedral substitution, octahedral cation site vacancy, and degree of dehydroxylation. Techniques including multi-cycle heating-cooling thermogravimetric analysis and nitrogen gas adsorption on various smectite samples preheated at different temperatures followed by rehydration at ambient conditions were used to characterize the interaction of water molecules with completely dehydrated montmorillonite, beidellite, and nontronite smectite types. Beidellite with high-Al3+ tetrahedral substitution results in electrostatically undersaturated basal oxygen atoms that exert strong repulsion between the tetrahedral sheets of adjacent 2:1 layers. The interlayer region of dehydrated or dehydroxylated beidellite is capable of being spontaneously rehydrated even in low water vapor environments. In completely dehydrated montmorillonite and nontronite, the external surface area of the crystallites is a primary control on water adsorption at low humidity when the molecules form a shell around the exchangeable cations present on external surfaces. The potential of montmorillonite and nontronite to reopen a collapsed interlayer is significantly lower than beidellite because of their crystal-chemical features that result in 2:1 layer and interlayer cation attraction. With increasing water vapor partial pressure, the hydration potential of interlayer cations provokes a reopening of the interlayer. In a dehydroxylated nontronite, the undersaturated residual oxygen atom strongly bonds the interlayer cation within the ditrigonal ring of the tetrahedral sheet, resulting in a permanent interlayer collapse. The specific surface area calculated from a conventional N2 gas adsorption measurement using the BET model represents the external surface area of a dehydrated smectite crystallite and can be converted into the mean crystallite thickness. The mean crystallite thickness of a completely dehydrated smectite increases with an increase in preheating temperature.
•A metastable network of dislocations forms on a Cu monolayer on Ru(0001).•We observe the dislocation-covered region evolution by low-energy electron microscopy.•We characterize the dislocation ...network by low-energy electron diffraction.•The decay time of the dislocated regions follows an Arrhenius law.•The dislocation density changes as fast as adatom diffusion allows.
We have used low-energy electron microscopy (LEEM) to study how misfit dislocations evolve in the first atomic layer of Cu deposited on Ru(0001). At equilibrium the Cu islands are pseudomorphic and dislocation-free. However, the islands develop dislocation networks as they grow during deposition. These dislocations are metastable: after deposition ceases, the dislocated area shrinks as adatoms ejected from the network travel to the Cu-island edges. We analyze the dislocation decay rate and find no evidence of a significant energetic barrier for Cu adatoms to exchange with the dislocated phases. Instead, the metastable film's decay is consistent with adatom diffusion being the rate-limiting factor. A small barrier for changing misfit-dislocation density has a consequence – as a film's chemical environment changes during catalysis, its dislocation density can rapidly respond.
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Rehydroxylation of the previously dehydroxylated dioctahedral 2:1 layer clay mineral occurs preferentially in specific sites within the former octahedral sheet. The rehydroxylation of dehydroxylated ...Al-rich and Al,Mg-rich 2:1 layers occurs as trans-vacant (tv) structural arrangements, regardless of whether the initial structure was tv or cis-vacant (cv). In nontronite (Fe-rich 2:1 layer clay), the dehydroxylate pseudo-cv structure is probably directly reconstructed into the rehydroxylated cv structure without migration of octahedral cations. Rehydroxylation occurs preferentially in the R3+-Or-R3+ former octahedral structural arrangements (Or=residual oxygen) over R2+-Or-R (R=R3+ or R2+=Al3+, Fe3+ or Mg2+, Fe2+). In the case of the R2+ octahedral substitution, the interlayer cation is attracted to the electrostatically undersaturated residual oxygen of the R2+-Or-R arrangement, which blocks the ability of water molecules to pass through the ditrigonal cavity and rehydroxylate the previously dehydroxylated local arrangement. The pyrophyllite-like type of octahedral R3+-Or-R3+ arrangements, formed due to the lack of tetrahedral substitution and resulting in the absence of interlayer cations, is thus favored for rehydroxylation over the mica-like R3+-Or-R3+ arrangements where Al occurs in the tetrahedral sheet. The valence of the interlayer cation and the charge density of the 2:1 layer clay mineral, which controls the interlayer cation content, also affect the degree of rehydroxylation. Dehydroxylated 2:1 layer minerals with a high-rehydroxylation potential, including beidellite and illite, use all the adsorbed water molecules that persist above 200°C for rehydroxylation; the water vapor from the ambient environment also becomes a source of H2O molecules for rehydroxylation. The high demand for water molecules to use for rehydroxylation results in a noticeable gain of mass in the temperature interval between 200 and 350°C even during heating.
Gender non-binary people identify as neither exclusively men nor exclusively women. The current work represents some of the first quantitative investigations into stereotypes and prejudice directed ...towards gender non-binary people. In Study 1, 238 cisgender women and 156 cisgender men indicated how they thought cisgender men, cisgender women, gender non-binary people, and binary transgender people were perceived by American society on measures of competence, warmth, identity invalidation, and prejudice. In Study 2, 264 cisgender women and 151 cisgender men indicated how they personally perceived cisgender men, cisgender women, gender non-binary people, and binary transgender people on the same stereotyping and prejudice measures. In Study 3, 206 women and 283 men indicated how they personally perceived either men, women, or gender non-binary people on similar measures. Across all three studies and consistent with hypotheses, gender non-binary people were perceived as less competent, as having less valid identities, and as more likely to experience prejudice than men and women (
p
s < .05). Perceptions of warmth were inconsistent across the three studies. In Studies 1 and 2, gender non-binary people were perceived as more competent but as having less valid identities than binary transgender people. Study 3 did not include the binary transgender comparison but added new measures including one regarding perceptions of mental wellbeing and found gender non-binary people were perceived as having worse mental wellbeing than men and women (
p
s < .001). Identifying stereotypes surrounding gender non-binary people is an important first step in being able to reduce the bias they face. This work underscores the importance of research on the experiences of gender non-binary people specifically, as opposed to studying their experiences solely within larger umbrella identities such as transgender and gender non-conforming people (TGNC).
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