3D FEM Modelling of a Deep Excavation Case Considering Small-Strain Stiffness of Soil and Thermal Shrinkage of Concrete

A typical top-down deep excavation project in Shanghai was carefully monitored during the construction process. This case history was back-analysed with a complex 3D FEM numerical model in ABAQUS to investigate the influence of different modelling procedures. The model considered the detailed construction procedures and structural information. The calculations included the small-strain stiffness of the soil and thermal shrinkage of the concrete beams and slabs. The small-strain stiffness is modelled with a multi-surface soil model developed at Oxford which has been implemented into ABAQUS. The diaphragm wall was modelled as an anisotropic linear elastic material to represent the effect of the joints in the wall. The beam and slabs were modelled as a linear elastic material and including the shrinkage of concrete. The numerical results captured the main excavation behavior and agreed well with the field measurements. Two sets of calculations were conducted to investigate the influence of soil models and thermal shrinkage on the computed excavation behavior. The results showed that small-strain soil stiffness is crucial to capture the excavation behavior and the thermal shrinkage of concrete should not be neglected in deep excavation problem

Ichthyological Bulletin of the J.L.B. Smith Institute of Ichthyology; No. 56

A neotype for Clarias gariepinus (Burchell, 1822) is designated and described. Data from 41 specimens from the type locality are also presented. The geographical distribution of the species is discussed.Rhodes University Libraries (Digitisation

Taming Ambident Triazole Anions: Regioselective Ion-Pairing Catalyzes Direct N-Alkylation with Atypical Regioselectivity

Controlling the regioselectivity of ambident nucleophiles toward alkylating agents is a fundamental problem in heterocyclic chemistry. Unsubstituted triazoles are particularly challenging, often requiring inefficient stepwise protection–deprotection strategies and prefunctionalization protocols. Herein we report on the alkylation of archetypal ambident 1,2,4-triazole, 1,2,3-triazole, and their anions, analyzed by in situ ¹H/¹⁹F NMR, kinetic modeling, diffusion-ordered NMR spectroscopy, X-ray crystallography, highly correlated coupled-cluster computations [CCSD­(T)-F12, DF-LCCSD­(T)-F12, DLPNO-CCSD­(T)], and Marcus theory. The resulting mechanistic insights allow design of an organocatalytic methodology for ambident control in the <i>direct</i> N-alkylation of unsubstituted triazole anions. Amidinium and guanidinium receptors are shown to act as strongly coordinating phase-transfer organocatalysts, shuttling triazolate anions into solution. The intimate ion pairs formed in solution retain the reactivity of liberated triazole anions but, by virtue of highly regioselective ion pairing, exhibit alkylation selectivities that are completely inverted (1,2,4-triazole) or substantially enhanced (1,2,3-triazole) compared to the parent anions. The methodology allows direct access to 4-alkyl-1,2,4-triazoles (<i>rr</i> up to 94:6) and 1-alkyl-1,2,3-triazoles (<i>rr</i> up to 99:1) in one step. Regioselective ion pairing acts in effect as a noncovalent in situ protection mechanism, a concept that may have broader application in the control of ambident systems

Expansion of the ligand knowledge base for chelating P,P-donor ligands (LKB-PP)

[Image: see text] We have expanded the ligand knowledge base for bidentate P,P- and P,N-donor ligands (LKB-PP, Organometallics2008, 27, 1372–1383) by 208 ligands and introduced an additional steric descriptor (nHe(8)). This expanded knowledge base now captures information on 334 bidentate ligands and has been processed with principal component analysis (PCA) of the descriptors to produce a detailed map of bidentate ligand space, which better captures ligand variation and has been used for the analysis of ligand properties

Tertiary time: The precariat's dilemma

Progressive politics has always been about the struggle to reduce social inequities and inequalities. What takes priority depends on the type of society we live in. Today people in rich countries live in societies that are tertiary, not industrial, in that what they do is largely covered by “services.” In a tertiary society, one iniquitous form of inequality is control of time. Time is a key asset. But we do not have a conceptualization of tertiary time. We must rectify that so as to develop a progressive politics of time

Occultation Modeling for Radiation Obstruction Effects on Spacecraft Systems

A geometric occultation model has been developed to determine line-of-sight obstruction of radiation sources expected for different NASA space exploration mission designs. Example applications includes fidelity improvements for surface lighting conditions, radiation pressure, thermal and power subsystem modeling. The model makes use of geometric two dimensional shape primitives to most effectively model space vehicles. A set of these primitives is used to represent three dimensional obstructing objects as a two dimensional outline from the perspective of an observing point of interest. Radiation sources, such as the Sun or a Moon's albedo is represented as a collection of points, each of which is assigned a flux value to represent a section of the radiation source. Planetary bodies, such as a Martian moon, is represented as a collection of triangular facets which are distributed in spherical height fields for optimization. These design aspects and the overall model architecture will be presented. Specific uses to be presented includes a study of the lighting condition on Phobos for a possible future surface mission, and computing the incident flux on a spacecraft's solar panels and radiators from direct and reflected solar radiation subject to self-shadowing or shadowing by third bodies

Seasonal Patterns in Stable Isotope and Fatty Acid Profiles of Southern Stingrays (Hypanus americana) at Stingray City Sandbar, Grand Cayman

Ecotourism opportunities in the marine environment often rely heavily on provisioning to ensure the viewing of cryptic species by the public. However, intentional feeding of wildlife can impact numerous aspects of an animals’ behavior and ecology. Southern stingrays (Hypanus americana) provisioned at Stingray City Sandbar (SCS) in Grand Cayman have altered diel activity patterns and decreased measures of health. This study looked at seasonal changes in stable isotope (SI) and fatty acid (FA) profiles of provisioned stingrays at SCS. Plasma δ15N was higher in male stingrays (11.86 ± 1.71‰) compared to females (10.70 ± 1.71‰). Lower values for δ15N in males and females were measured in October during low tourist season, suggesting stingrays may be forced to rely on native prey items to supplement the decreased amount of provisioned squid available during this time. Plasma FA profiles were significantly different between sexes and across sampling time points, with FAs 22:6n3, 16:0, 20:5n3, 18:1n3C, 18:0 and 18:1n9T contributing to dissimilarity scores between groups. Dietary FAs primarily contributed to differences between males and females lending further evidence to differences in foraging patterns at SCS, likely due to intraspecific competition. Further, canonical analysis of principal coordinates (CAP) analysis of FA profiles suggest similar diets during peak tourist season and differences in diet between males and females during the low season. This study demonstrates alterations in feeding ecology in stingrays at SCS which is of critical importance for effective management of the SCS aggregation

Supplemental Feeding for Ecotourism Reverses Diel Activity and Alters Movement Patterns and Spatial Distribution of the Southern Stingray, Dasyatis americana

Southern stingrays, Dasyatis americana, have been provided supplemental food in ecotourism operations at Stingray City Sandbar (SCS), Grand Cayman since 1986, with this site becoming one of the world’s most famous and heavily visited marine wildlife interaction venues. Given expansion of marine wildlife interactive tourism worldwide, there are questions about the effects of such activities on the focal species and their ecosystems. We used a combination of acoustic telemetry and tag-recapture efforts to test the hypothesis that human-sourced supplemental feeding has altered stingray activity patterns and habitat use at SCS relative to wild animals at control sites. Secondarily, we also qualitatively estimated the population size of stingrays supporting this major ecotourism venue. Tag-recapture data indicated that a population of at least 164 stingrays, over 80% female, utilized the small area at SCS for prolonged periods of time. Examination of comparative movements of mature female stingrays at SCS and control sites revealed strong differences between the two groups: The fed animals demonstrated a notable inversion of diel activity, being constantly active during the day with little movement at night compared to the nocturnally active wild stingrays; The fed stingrays utilized significantly (