Preformed Cavities Research Articles

Hydraulic gradient analysis on embankment dam foundation associated with internal erosion

Internal erosion is susceptible to occur in conditions where there are cracks or pre-formed cavities at the interface between the dam foundation and embankment. The initiation of internal erosion is related to the critical gradient (Ic ) and hydraulic gradient (Ixy ) at a certain position. The addition of repair materials in foundation improvement will change the total head, especially on the dam foundation, so the value of the hydraulic gradient will also change simultaneously from upstream to downstream. This study examines the value of the hydraulic gradient (Ixy ) at certain points on the dam foundation under the condition of foundation with and without improvement. Several scenarios were simulated using Geostudio Seep/W software to get an estimated value of the hydraulic gradient. The upstream blanket foundation improvement method increases the hydraulic gradient in the upstream zone when compared to the curtain grouting method, thereby increasing the potential for internal erosion in a related area. Increasing the depth of curtain grouting from 25 m to 35 m does not significantly reduce the value of the hydraulic gradient in the dam foundation. Research results can be used for analysis to improve design and construction, and as a reference for similar dams.

Adaptive Binding of Alkyl Glycosides by Nonpeptidic Helix Bundles in Water: Toward Artificial Glycolipid Binding Proteins.

Amphipathic water-soluble helices formed from synthetic peptides or foldamers are promising building blocks for the creation of self-assembled architectures with non-natural shapes and functions. While rationally designed artificial quaternary structures such as helix bundles have been shown to contain preformed cavities suitable for guest binding, there are no examples of adaptive binding of guest molecules by such assemblies in aqueous conditions. We have previously reported a foldamer 6-helix bundle that contains an internal nonpolar cavity able to bind primary alcohols as guest molecules. Here, we show that this 6-helix bundle can also interact with larger, more complex guests such as n-alkyl glycosides. X-ray diffraction analysis of co-crystals using a diverse set of guests together with solution and gas-phase studies reveals an adaptive binding mode whereby the apo form of the 6-helix bundle undergoes substantial conformational change to accommodate the hydrocarbon chain in a manner reminiscent of glycolipid transfer proteins in which the cavity forms upon lipid uptake. The dynamic nature of the self-assembling and molecular recognition processes reported here marks a step forward in the design of functional proteomimetic molecular assemblies.

Cucurbiturils mimicked by low polarizability solvents with pre-formed cavities: an empirical model to predict hydrocarbon selectivity.

Relative binding affinities of a series of nine rigid hydrocarbons towards the cavity formed by a portion of the inner wall of cucurbit[8]uril (CB[8]) and a positive auxiliary guest were determined by competitive 19F NMR titrations in deuterium oxide. The corresponding free binding energies were corrected by the hydrocarbon computed solvation energies to obtain their free energies of transfer from the gas phase to the CB[8]/auxiliary guest cavity. These energies correlate linearly with the hydrocarbon static polarizabilities, thereby suggesting that the selectivity is driven, perhaps exclusively, by dispersive interactions between the hydrocarbons and the tailor-made cavity, regardless of the degree of unsaturation of the guests. The free energies of transfer also correlate linearly with the energy released upon introduction of the hydrocarbon into a pre-formed cavity extruded from a solvent (benzene) selected to mimic the polarity and polarizability of the CB[8]/auxiliary probe cavity – and this, with a unity slope. Among other features, this empirical model also accurately predicts the relative binding affinities of various rigid hydrocarbons to CB[6] and CB[7], as well as noble gases to CB[5], when the macrocycles are mimicked with pre-formed cavities in perfluorohexane or perfluorohexane/benzene mixtures, both being notoriously non-polar and non-polarizable environments.

Computational study (MM and DFT) on the conformations of some aromatic crown ether rotaxane macrocycles

We examined the preferred conformations of several aromatic crown ether macrocycles containing dibenzo (DB24C8 (1), BMP25C8 (2), BPP34C10 (3)), dinaphtho (2/3DN30C10 (4), 1/5DN38C10 (5)), diphenyl phenanthroline (6) or isophthalamide (7) groups in order to elucidate their preferred conformations and to test the performance of computational methods (molecular mechanics and DFT) in the description of the building blocks of some mechanically interlocked molecules. An exhaustive search for low energy conformations was carried out. The analyses of the geometries of the low-energy conformations of 1–7 revealed that all they have either preformed cavities for adopting substrates, or due to the high flexibility and easy deformability of the macrorings, they have the potential to allow threading of an axle-like molecular component as a slippage step in the formation of a rotaxane structure. Unexpectedly, for one of the macrorings, 4, the geometries of the low-energy conformations differ significantly from the representative conformations of prima facie conformationally similar macrocycles. Contributions from the vibrational entropy term reorder the steric energy lists of conformations in some cases (1, 2, 4, 6), compensating relative steric energies up to 0.9 kcal mol−1. Cluster analysis of the molecular conformations was performed with examining the dependence of the results on the number of torsions for the clustering and the characteristic threshold distances, defining the clustering. All conformations with relative steric energies not exceeding 2.0 kcal mol−1 were examined also with the DFT method (M06-2X functional). In some cases (1 and 2) conformations with relative steric energies ca. 2.0 kcal mol−1 are with the lowest total energies in the corresponding DFT energy lists. These are conformations where the aromatic fragments are facing each other at short distance, ca. 5 Å. We are inclined to conclude that in such cases the DFT models used enhance the dispersion interactions at short distances.

Neuroprotective Properties of Xenon.

Xenon is a rare noble gas that was introduced into clinical practice more than 70 years ago. Xenon's clinical properties are predicated by its ability to fit into preformed cavities of macromolecules thereby altering their biological functions. One such action targets the NMDA-subtype of the glutamate receptors thereby inhibiting its excitatory action. As the glutamate receptors are pivotal for both anesthesia and acute neurological injury, its clinical use has included both general anesthesia as well as neuroprotection. In this manuscript, the efficacy and safety of xenon in clinical trials that address both the anesthetic and neuroprotective applications are discussed. Because of the clinical safety of this chemically inert monatomic gas, the lack of an alternative for neuroprotection, and encouraging phase 2 trial data, a multinational pivotal randomized clinical trial (XePOHCAS) has been launched to assess the utility of xenon for patients that have been successfully resuscitated following an out of hospital cardiac arrest but still remain comatose, indicating ongoing neurological ischemic-perfusion injury. If successful, the trial will herald a new era of treatments for previously intractable conditions such as traumatic brain injury, ischemic and hemorrhagic strokes, and anesthetic-induced developmental neurotoxicity.

<i>Euryglossina</i> (<i>Euryglossina</i>) <i>perpusilla</i> (Hymenoptera: Colletidae: Euryglossinae) nesting in pre-formed cavities in <i>Banksia attenuata</i> (Proteaceae)

This article reports observations of nesting by Euryglossina (Euryglossina) perpusilla Cockerell, 1910 in preformed cavities in a Banksia attenuata tree in an urban bushland remnants.

Exploring nest structures of acorn dwelling ants with X-ray microtomography and surface-based three-dimensional visibility graph analysis.

The physical spaces within which organisms live affect their biology and in many cases can be considered part of their extended phenotype. The nests of social insect societies have a fundamental impact on their ability to function as complex superorganisms. Ants in many species excavate elaborate subterranean nests, but others inhabit relatively small pre-formed cavities within rock crevices and hollow seeds. Temnothorax ants, which often nest within acorns, have become a model system for studying collective decision making. While these ants have demonstrated remarkable degrees of rationality and consistent precision with regard to their nest choices, never before has the fine scale internal architecture and spatial organization of their nests been investigated. We used X-ray microtomography to record high-resolution three-dimensional (3D) scans of Temnothorax colonies within their acorns. These data were then quantified using image segmentation and surface-based 3D visibility graph analysis, a new computational methodology for analysing spatial structures. The visibility graph analysis method integrates knowledge from the field of architecture with the empirical study of animal-built structures, thus providing the first methodological cross-disciplinary synergy of these two research areas. We found a surprisingly high surface area and degree of spatial heterogeneity within the acorn nests. Specific regions, such as those associated with the locations of queens and brood, were significantly more conducive to connectivity than others. From an architect's point of view, spatial analysis research has never focused on all-surface 3D movement, as we describe within ant nests. Therefore, we believe our approach will provide new methods for understanding both human design and the comparative biology of habitat spaces.This article is part of the theme issue 'Interdisciplinary approaches for uncovering the impacts of architecture on collective behaviour'.

Twin-tunnelling-induced changes to clay stiffness

Tunnels used for transportation in urban environments are often constructed in pairs. Projects in which tunnels are constructed sequentially and within close proximity are referred to as ‘twin tunnelling’. Case studies and recent research indicate that the prediction of settlements for such schemes cannot be determined using existing simple methods derived from consideration of a single tunnel. To establish the reasons for the observed variation in settlements, a series of centrifuge tests was undertaken on various twin-tunnel arrangements in overconsolidated clay. The tests consisted of preformed cavities from which a specific quantity of supporting fluid could be drained, with precision, creating a predetermined magnitude of tunnelling volume loss. Data were obtained for surface and subsurface displacements, changes in pore-water pressure near the tunnels and the support pressure within the tunnels. The systematic use of cavity contraction models was found to be an informative method of explaining the observations. Use of an elastic–perfectly plastic cavity contraction model coupled with observations from the experiments enabled the shear stiffness of the clay around the tunnel to be described. Further analysis demonstrated a reduction in shear stiffness of the soil prior to and during the second tunnel excavation, explaining the increase in volume loss observed in that event.

Thickness-dependent in-plane thermal conductivity of suspended MoS2 grown by chemical vapor deposition.

The in-plane thermal conductivities of suspended monolayer, bilayer, and multilayer MoS2 films were measured in vacuum by using non-invasive Raman spectroscopy. The samples were prepared by chemical vapor deposition (CVD) and transferred onto preformed cavities on a Au-coated SiO2/Si substrate. The measured thermal conductivity (13.3 ± 1.4 W m-1 K-1) of the suspended monolayer MoS2 was below the previously reported value of 34.5 ± 4 W m-1 K-1. We demonstrate that this discrepancy arises from the experimental conditions that differ from vacuum conditions and small absorbance. The measured in-plane thermal conductivity of the suspended MoS2 films increased in proportion to the number of layers, reaching 43.4 ± 9.1 W m-1 K-1 for the multilayer MoS2, which explicitly follows the Fuchs-Sondheimer suppression function. The increase in the thermal conductivity with the number of MoS2 layers is explained by the reduced phonon boundary scattering. We also observe that the Fuchs-Sondheimer model works for the thickness-dependent thermal conductivity of MoS2 down to 10 nm in thickness at room temperature, yielding a phonon mean free path of 17 nm for bulk.

Florida Carpenter Ants

Carpenter ants are in the genus Camponotus, in which up to over 900 species have been described worldwide. They get their common name, “carpenter ant,” because some species excavate nests in wood. Carpenter ants are sometimes called bulldog ants or bull ants. However, not all species in the genus Camponotus are true carpenter ants because some nest in preformed cavities or in soil. This 5-page fact sheet was originally published as part of Pests in and around the Florida Home, and was written by R. J. Vazquez, P. G. Koehler, R. M. Pereira, J. Warner, and R. H. Scheffrahn, and published by the UF Department of Entomology and Nematology, October 2013.

Variation and decomposition of the partial molar volume of small gas molecules in different organic solvents derived from molecular dynamics simulations

The partial molar volumes, V(i), of the gas solutes H2, CO, and CO2, solvated in acetone, methanol, heptane, and diethylether are determined computationally in the limit of infinite dilution and standard conditions. Solutions are described with molecular dynamics simulations in combination with the OPLS-aa force field for solvents and customized force field for solutes. V(i) is determined with the direct method, while the composition of V(i) is studied with Kirkwood-Buff integrals (KBIs). Subsequently, the amount of unoccupied space and size of pre-formed cavities in pure solvents is determined. Additionally, the shape of individual solvent cages is analyzed. Calculated V(i) deviate only 3.4 cm(3) mol(-1) (7.1%) from experimental literature values. Experimental V(i) variations across solutions are reproduced qualitatively and also quantitatively in most cases. The KBI analysis identifies differences in solute induced solvent reorganization in the immediate vicinity of H2 (<0.7 nm) and solvent reorganization up to the third solvation shell of CO and CO2 (<1.6 nm) as the origin of V(i) variations. In all solutions, larger V(i) are found in solvents that exhibit weak internal interactions, low cohesive energy density and large compressibility. Weak internal interactions facilitate solvent displacement by thermal solute movement, which enhances the size of solvent cages and thus V(i). Additionally, attractive electrostatic interactions of CO2 and the solvents, which do not depend on internal solvent interactions only, partially reversed the V(i) trends observed in H2 and CO solutions where electrostatic interactions with the solvents are absent. More empty space and larger pre-formed cavities are found in solvents with weak internal interactions, however, no evidence is found that solutes in any considered solvent are accommodated in pre-formed cavities. Individual solvent cages are found to be elongated in the negative direction of solute movement. This wake behind the moving solute is more pronounced in case of mobile H2 and in solvents with weaker internal interactions. However, deviations from a spherical solvent cage shape do not influence solute-solvent radial distribution functions after averaging over all solvent cage orientations and hence do not change V(i). Overall, the applied methodology reproduces V(i) and its variations reliably and the used V(i) decompositions identify the underlying reasons behind observed V(i) variations.

Trapping of electromagnetic radiation in self-generated and preformed cavities

AbstractLaser light trapping in cavities in near-critical density plasmas is studied by two-dimensional particle-in-cell simulation. The laser ponderomotive force can create in the plasma a vacuum cavity bounded by a thin overcritical-density wall. The laser light is self-consistently trapped as a half-cycle electromagnetic wave in the form of an oscillon-caviton structure until it is slowly depleted through interaction with the cavity wall. When the near-critical density plasma contains a preformed cavity, laser light can become a standing wave in the latter. The trapped light is characterized as multi-peak structure. The overdense plasma wall around the self-generated and preformed cavities induced by the laser ponderomotive force is found to be crucial for pulse trapping. Once this wall forms, the trapped pulse can hardly penetrate.

Endoscopic Management of Orbital and Frontal Sinus Fractures

Endoscopic Management of Orbital and Frontal Sinus Fractures

Stretched Cavity‐Assisted Molding of Micrometer and Submicrometer Photopolymerized Hydrogel Particles

Stretched cavity-assisted molding of particles is a novel method that can produce monodisperse submicrometer hydrogel particles (see image) loaded with a model protein drug, fluorescein-isothiocyanate-conjugated bovine serum albumin. The method avoids agitation, solvents, and high-energy input by forming the particles inside preformed cavities. This method has the potential to be generalized to prepare multilayered or targeted particles containing fragile drugs for the pharmaceutical industry.

The Tropical Ant Mosaic in a Primary Bornean Rain Forest

ABSTRACTIn primary lowland rain forest in Brunei Darussalam, we studied arboreal ant communities to evaluate whether densities and spacing of spatially territorial taxa along 2.9 km of well‐studied trails are consistent with existence of a continuous mosaic of dominant ants. A median intercolony distance of 24.5 m, about twice or less distances over which colonies of most included species regularly ranged, suggested a relatively continuous mosaic. Despite relying on nesting sites in preformed plant cavities, carpenter ants contributed &gt; 70 percent of mapped colonies. Most belonged to the Camponotus (Colobopsis) cylindricus (COCY) complex, including SE Asia's ‘exploding’ ants. Their lack of aggression against certain Polyrhachis species was associated with interspecific territory sharing by members of the two groups, and with a dominance‐discovery trade‐off. Experimental approaches yielded evidence for two putative contributors to positive association. Larger‐bodied Polyrhachis parasitize food‐finding abilities of smaller, more populous Camponotus workers, and the two taxa cooperate in territorial defense. Highly territorial and predatory weaver ants (Oecophylla smaragdina) were an important component of the ant mosaic in primary forest, second only to codominant COCY and Polyrhachis taxa. Members of the genus Crematogaster were significantly associated with Oecophylla in baiting censuses and regularly monopolized near‐nest baits to the exclusion of weaver ants. Litter ant abundances differed between territories of Oecophylla and less predatory COCY species, but direction of difference was inconsistent over time. The densely packed mosaic of spatially territorial, and differentially predatory, taxa in Bornean rain forest likely contributes to spatial variation in ant effects on plant and arthropod communities.

The selection of building material for wall construction by ants

Building by ants often involves excavation, but Temnothorax albipennis colonies build walls in preformed cavities. To do this they need to choose and retrieve building material. Thus, building in T. albipennis can be analysed, in part, from the perspective of a foraging strategy. We gave ant colonies a choice between large and small sand grains that were available at three different distances. From theoretical considerations, we expected ant colonies to maximize the amount of material collected per unit time and therefore to choose large grains exclusively. Instead, they always chose grains of both sizes. Such partial preferences can be explained in terms of the mechanical benefits of constructing walls as a mixture of two grain sizes. Barricades composed of two grain sizes can be more resilient than walls made from a single grain size, as estimated in terms of angles of maximum stability and packing densities. Thus, foraging decisions need to be analysed in the broader context of how collected material is utilized. Here partial foraging preferences can have direct benefits: different choices by different foragers and even individual ‘error’ proneness might contribute to the collective good.

« Aspergillus » et système respiratoire

Aspergillus is the first causative organism of respiratory mycosis. It causes a variety of clinical presentations, of different pathophysiological mechanisms that depend mainly on the host's local and general predisposing factors and on environmental factors. Aspergilloma consists of masses of fungal mycelia in preformed lung cavities. Invasive pulmonary aspergillosis is a severe and commonly fatal acute infectious disease in immunocompromised patients. Chronic necrotizing aspergillosis is a subacute pulmonary infection in mildly immunocompromised patients with chronic lung disease. Allergic bronchopulmonary aspergillosis is a hypersensitivity reaction to Aspergillus which affects patients with asthma or cystic fibrosis. These last years showed both an increasing incidence of aspergillosis and the development of radiological and mycological diagnostic methods and new antifungal therapy.

Nesting and nest trees of stingless bees (Apidae: Meliponini) in lowland dipterocarp forests in Sabah, Malaysia, with implications for forest management

Nesting habits of highly social stingless bees (Meliponini) were studied in lowland dipterocarp forests in Sabah, Borneo. A total of 275 nests of 12 species of bees were located. All nests were closely associated with living (91.5%) or dead (8.5%) trees, either within pre-formed cavities in the trunk (cavity nests) or situated in or under the tree base (base nests). Species of bees differed in nesting habit. The majority of species (seven) were cavity nesters, but the majority of nests (81%) were base nests. Nests were often aggregated (mean of 1.94 nests/nest tree), with up to eight colonies and three species in a single tree. Nest trees were mostly large to very large (86.1% above 60 cm dbh) commercial timber trees; 47.3% of nest trees were dipterocarps. According to visual inspection nest trees were of significantly lower expected timber quality then randomly chosen control trees. Taking into account information on tree species, size and expected timber quality, we estimated that 34.0 or 42.6% of nest trees were potential harvest trees, depending on harvesting regulations (reduced impact logging (RIL) versus conventional). Lower percentages under RIL guidelines were mostly due to size restrictions that protect very large trees (>120 cm dbh). Harvesting is likely to kill bee colonies associated with the respective tree. Therefore, and because meliponine colonies are long-lived and have low fecundity, direct impact from logging may have lasting effects on bee populations. Harvesting guidelines that retain high proportions of large and hollow trees should be promoted in order to preserve meliponine pollination in sustainable forest management.

Biology and Immature Stages of the Bee Tribe Tetrapediini (Hymenoptera: Apidae)

Tetrapedia diversipes Klug is herein reported for the first time to be the host of the cleptoparasite Coelioxoides waltheriae Ducke. Because these two genera had been previously recognized as sister taxa [A. Roig-Alsina. 1990. Coelioxoides Cresson, a parasitic genus of Tetrapediini (Hymenoptera: Apoidea). Journal of the Kansas Entomological Society 63: 279–287], the authors wished to learn to what extent biological information and immature stages reflected this relationship. Tetrapedia diversipes normally nests in holes in wood such as old beetle burrows, and it was induced to use trap nests for this study. Many aspects of the nesting behavior of females of this species are described, including the following: diurnal flight period; sleeping habits; nest structure; nest provisioning; egg placement; and sequence of nest construction, provisioning, and oviposition. Eggs produced by this species are categorized as “giant” (K. Iwata and S.F. Sakagami. 1966. Gigantism and dwarfism in bee eggs in relation to the mode of life, with notes on the number of ovarioles. Japanese Journal of Ecology 16: 4–16). Its first instar was discovered to be pharate within the chorion while the following four instars actively feed. Defecation starts early in the last larval stadium. Females use floral oils both in nest construction and in provisioning, and they carry pollen, oil, and soil with their scopae. The biology of T. diversipes was compared with that of other species in the genus and then compared with that of other apines that are known to nest in preformed cavities and that provision nests with pollen and floral oils.The host-nest searching behavior of Coelioxoides waltheriae is described. The cleptoparasite introduces its egg into the closed cell of the host shortly after cell closure. This egg is characterized as “small” (Iwata and Sakagami, ibid.) and has a very short incubation period. The highly modified first instar immediately feeds on the host egg and grows remarkably fast on the host yolk. This species has only four instars.Rates of development of the host and cleptoparasite are compared. Both have four ovarioles per ovary. Eggs, first instars, last larval instars, and pupae of host and cleptoparasite are taxonomically described and compared. In conclusion, the immatures of Coelioxoides and Tetrapedia are quite distinct from those of other known apids. While these two genera are probably sister genera based on the similarities identified by Roig-Alsina (op. cit.) and by this study, they are quite different from one another based on features of the eggs, first instars, and pupae.

On the effect of time-dependent deformations on the behaviour of patch-repaired reinforced concrete short columns

This paper reports the results of an experimental study of the effect of time-dependent deformations (such as shrinkage and creep) of concrete repair materials on the ability of patch repairs to contribute to the structural function of reinforced concrete short columns. Prior to repair, strain measurements were taken from loaded columns with preformed cavities; cavity depths varied between columns. One polymeric and one polymer-modified concrete repair material were used for repair, all repairs being performed under zero load. After repair, the distribution of strain was measured from columns subjected to axial service load and from similar columns observed under zero load. Test results indicate that in the short term both the repair materials assist the repaired column to carry load, but in the long term the contribution of the polymer-modified material is reduced substantially while that of the polymeric material is sustained. It is observed that shrinkage of the repair material can induce bending in the repaired column and that this bending increases with patch repair cavity depth. Within the repaired zone, bending strain distributions were linear which would suggest that conventional methods of structural analysis are appropriate for such members.