Single Large Pore Research Articles

Template-free route to fabricate extra-lightweight ceramsite with a single large pore structure

As a lightweight aggregate, single-pore ceramsite is used in the construction industry, which can effectively solve the problems of traditional porous ceramsite with high bulk density, poor thermal insulation performance and easy leakage. However, preparing single-pore ceramsite by template method brings high cost, complicated process, and serious pollution problems. To overcome these challenges, in this work, we used copper tailings (60 wt%) and clay (40 wt%) as raw materials to prepare extra-lightweight single-pore ceramsite by template-free method. By adding 0.7 wt% SiC to the raw material and sintering at 1180 °C for 15 min, the extra-lightweight single pore structure with 200 density class in GB/T 17431.1–2010 can be obtained. Based on the thermodynamics and the sintered morphology, the mechanism of the single-pore structure formed by the pores sealed by the liquid phase is summarized. Template-free method is beneficial to save the preparation cost, simplify the process flow and reduce carbon emissions. As a result, template-free method provides a new, green, economical, and simple way for single-pore ceramsite production.

Nanobowls from Amphiphilic Core–Shell Cyclic Bottlebrush Polymers

Cyclic bottlebrush polymers are macrocycles that contain pendent side-chain polymers on nearly every repeat unit. We leveraged a method to generate cyclic bottlebrush polymers utilizing ring-expansion polymerization (REP) followed by subsequent grafting-from via atom-transfer radical polymerization (ATRP) to produce core–shell cyclic bottlebrush polymers and investigated their self-assembly behavior in water. The bottlebrush polymers were comprised of a cyclic backbone with side chains composed of a hydrophobic polystyrene block and a hydrophilic poly(acrylic acid) block. A two-step morphological transformation from spheres to porous spheres to nanobowls (spheres with a single large pore) was observed with solvent exchange from tetrahydrofuran to water. In contrast, under identical experimental conditions, an analogous linear bottlebrush polymer with a similar backbone and side chain degrees of polymerizations did not aggregate into nanobowls but rather exhibited a porous sphere morphology. These unusual morphologies and their propensities to transform can be attributed to changes in the internal viscosity of the aggregates during the solvent exchange process. Additionally, the rate of solvent exchange was found to influence the propensity for shape transformation to occur.

Hollow Porous Silica Nanosphere with Single Large Pore Opening for Pesticide Loading and Delivery

Hollow porous silica nanospheres (HSNs) have unveiled as a potential carrier for pesticide delivery. However, HSNs mostly suffer from postsynthesis loading process of pesticides because of the tiny...

New tardigrade records for the Baltic states with a description of Minibiotus formosus sp. n. (Eutardigrada, Macrobiotidae).

In sixteen moss, lichen and mixed (moss/lichen) samples, collected from Estonia, Latvia and Lithuania, 291 specimens, 48 simplexes, including one exuvium with 6 eggs, and 8 free-laid eggs of eutardigrades were found. In total, 17 species, together with one new to science, were identified (all are new records for the Baltic states): Astatumen bartosi, Diphascon (Adropion) prorsirostre, D. (Diphascon) bullatum, D. (D.) pingue pingue, D. (D.) recamieri, D. (D.) rugosum, Hypsibius convergens, H. dujardini, H. cf. scabropygus, Isohypsibius ronsisvallei, I. sattleri, Macrobiotus harmsworthi harmsworthi, M. hufelandi hufelandi, Milnesium asiaticum, Milnesium tardigradum tardigradum, Minibiotus formosus sp. n. and Paramacrobiotus richtersi. The new species is most similar to Minibiotus gumersindoi, but differs from it mainly by the presence of two types of cuticular pores, the absence of a triangular or pentagonal arrangement of pores above a single large pore on legs, the presence of granulation on all legs and a different macroplacoid length sequence. In this paper we also provide photographs and morphometrics of H. cf. scabropygus.

A new Early Cretaceous coelacanth from Texas

Coelacanths have a long fossil record spanning from Early Devonian to the present globally, but until now only from Permian and Triassic sediments in Texas. Reported here is a partial skull, including an articulated lower jaw and disarticulated cranial elements, of a new coelacanth fish (Sarcopterygii: Actinistia) from the Early Cretaceous (Albian) of northern Texas. The presence of a single large pore opening for the supraorbital sensory canal, lack of ornamentation of the cheek and opercular bones, the presence of a few large pore openings in the cheekbones (five or less in the lachrymojugal, one in the other cheekbones) and the presence of small teeth are characters placing this specimen within a new clade along with the genera Libys, Ticinepomis and Diplurus. An upturned symphysis, unornamented gular plates whose posterior margins taper to points, and angular with sinuous dorsal edges reaching the same dorsal extent as the dentary are characters that make this specimen morphologically unique among the new clade. This specimen represents a new species here named as Reidus hilli.

Pore Formation in a Binary Giant Vesicle Induced by Cone-Shaped Lipids

We have investigated shape deformations of binary giant unilamellar vesicles (GUVs) composed of cone- and cylinder-shaped lipids. By coupling the spontaneous curvature of lipids with the phase separation, we demonstrated pore opening and closing in GUVs. When the temperature was set below the chain melting transition temperature of the cylinder-shaped lipid, the GUVs burst and then formed a single large pore, where the cone shape lipids form a cap at the edge of the bilayer to stabilize the pore. The pore closed when we increased the temperature above the transition temperature. The pore showed three types of shapes depending on the cone-shaped lipid concentration: simple circular, rolled-rim, and wrinkled-rim pores. These pore shape changes indicate that the distribution of the cone- and cylinder-shaped lipids is asymmetric between the inner and outer leaflets in the bilayer. We have proposed a theoretical model for a two-component membrane with an edge of bilayer where lipids can transfer between two leaflets. Using this model, we have reproduced numerically the observed shape deformations at the rim of pore.

A whole-cell reconstruction of Mallomonas porifera Siver & Wolfe from the Eocene: Implications for the evolution of Chrysophyte cell architecture

Mallomonas porifera was originally described from Middle Eocene lake sediments based on isolated siliceous microfossils and named for the single large pore found centrally on the base plate. Both domeless body and domed scales were described, however it was not known how the scales were positioned on the cell covering nor if the organism possessed bristles. Since the original description, 15 additional sam- ples taken from a long sequence of the sediment core and found to contain M. porifera have been examined, including fractured mudstone sections from each sample. The fractured surfaces were found to contain the remains of whole cells allowing for a detailed description of the siliceous cell covering. Mallomonas porifera contains three types of scales and one bristle morphology arranged in precise positions on the cell. Domed scales are restricted to the anterior of the cell and each is associated with a bristle. The domed scales transition abruptly to domeless body scales that surround the main portion of the cell and are not associated with bristles. The posterior part of the cell covering consists of large triangular-shaped and spine-bearing scales that lack the characteristic large base plate pore found on the other scale types. The relationship of M. porifera to modern taxa within the genus is discussed.

Examining the effect of pore size distribution and shape on flow through unsaturated peat using computed tomography

Abstract. The hydraulic conductivity of unsaturated peat soil is controlled by the air-filled porosity, pore size and geometric distribution as well as other physical properties of peat materials. This study investigates how the size and shape of pores affects the flow of water through peat soils. In this study we used X-ray Computed Tomography (CT), at 45 μm resolution under 5 specific soil-water pressure head levels to provide 3-D, high-resolution images that were used to detect the inner pore structure of peat samples under a changing water regime. Pore structure and configuration were found to be irregular, which affected the rate of water transmission through peat soils. The 3-D analysis suggested that pore distribution is dominated by a single large pore-space. At low pressure head, this single large air-filled pore imparted a more effective flowpath compared to smaller pores. Smaller pores were disconnected and the flowpath was more tortuous than in the single large air-filled pore, and their contribution to flow was negligible when the single large pore was active. We quantify the pore structure of peat soil that affects the hydraulic conductivity in the unsaturated condition, and demonstrate the validity of our estimation of peat unsaturated hydraulic conductivity by making a comparison with a standard permeameter-based method. Estimates of unsaturated hydraulic conductivities were made for the purpose of testing the sensitivity of pore shape and geometry parameters on the hydraulic properties of peats and how to evaluate the structure of the peat and its affects on parameterization. We also studied the ability to quantify these factors for different soil moisture contents in order to define how the factors controlling the shape coefficient vary with changes in soil water pressure head. The relation between measured and estimated unsaturated hydraulic conductivity at various heads shows that rapid initial drainage, that changes the air-filled pore properties, creates a sharp decline in hydraulic conductivity. This is because the large pores readily lose water, the peat rapidly becomes less conductive and the flow path among pores, more tortuous.

Measuring physical and hydraulic properties of peat from X-ray tomography

Organic soils cover a large percentage of the Canadian land mass in the form of peatlands (14%) and other organic terrains, including arctic and alpine tundra and taiga (25%). Sphagnum mosses are the dominant peat-forming species in all of these terrains. Understanding the processes by which this material conducts, retains and redistributes moisture and energy is crucial to the successful development of physically-based methods of measuring and modelling their hydrological response. Sphagnum-peat was sampled from Scotty Creek, in the wetland-dominated zone of discontinuous permafrost near Fort Simpson, Northwest Territories, Canada. Physical properties of the peat samples were measured from standard methods, and X-ray tomographic images of sub-samples were obtained at 5 levels of volumetric moisture content between ∼ 0.4 and 0.7. The volumetric moisture content measured using the tomographic images closely approximated the gravimetric measurements. Properties of the pore spaces were measured in both two and three dimensions. The active porosities measured in 2D and 3D were very similar, and matched closely with values reported in the literature. Specific surface area (3D), however, was larger than the specific perimeter (2D). The 2D analysis suggests a relatively gradual transition from small to large pores; while in 3D, the distribution is dominated by a single large pore space, whose volume and surface area are 3-orders of magnitude larger than the next largest pore, and > 99% of the total inter-particle pore volume. This single, large pore space contains the flow network. This study elucidated the volume and configuration of this network for discrete ranges of soil water pressure that typically occur in the field. The flow network diminished from 17.6% to 9.0% of a sample volume as its volumetric moisture content lowered from 0.65 to 0.42. This volume loss was accommodated by the thinning and disaggregation of moisture films, although as the sample lost moisture, the flow network maintained a relatively even spatial distribution.

Starting electroosmotic flow in an annulus and in a rectangular channel

The initial electroosmotic flow through a small pore or microchannel with annular or rectangular cross section is studied under the Debye-Hückel approximation. Analytical series solutions and their asymptotic behavior for small and large non-dimensional electrokinetic widths are found for these two basic cases. The explicit and accurate solutions are particularly useful for examining various geometric/physical effects on the transient time scales and the flow rates for the transient states. The steady flow rate of the smaller channel may be disproportionately smaller than a reference channel if the electric double layer is thick, but will be in close proportion to the area ratio if the electric double layer is thin. A smaller channel compared to a reference channel has a shorter transient time scale, and the transient flow has characters very different from the steady state if the electric double layer is thin. The total transient flow rate of several smaller pores or channels may exceed largely that of a single large pore or channel with the same total cross section on the transient time scale of the smaller channels. The results have important implications on liquid transport in micropores or channels by pulse voltages or more general time-varying voltages.

Variation of nitrogen solubility and mechanism of pore formation during production of porous Fe–Cr–Mn–Si–C material

Experiments regarding the synthesis of porous metallic materials were performed by dissolution of nitrogen into molten hypereutectic 77Fe–8Cr–6Mn–5Si–4C (wt-%) and hypoeutectic 79Fe–8Cr–6Mn–5Si–2C alloys, and water quenching. A uniform pore distribution was obtained only for the hypereutectic alloy. To study the effect of the alloy composition and microstructure on the pore distribution, the variation of nitrogen solubility during primary solidification was calculated for both alloys, taking into account the phase composition changes. A mechanism of pore formation is proposed. In the hypereutectic alloy, an increasing nitrogen supersaturation in the melt during primary carbide growth is believed to fuel the growth of nucleated N2 pores. The primary M7C3 carbides play an essential role in preventing pore coalescence. In the hypoeutectic alloy, a decreasing nitrogen solubility gap between the austenite dendrites and the liquid does not allow extensive pore growth. The absence of primary carbides favours the formation of a single large pore.

The contradictory effects of pores on fatigue cracking of bone cement

The beneficial effect of porosity reduction on the fatigue life of bone cement has been demonstrated in numerous experimental studies. Clinically, however, it seems that the beneficial effect of porosity reduction of cement around total hip replacement components can only be found in large follow-up studies. Little is known about the actual mechanical effect of a pore on fatigue crack formation in cement mantles. We studied the effect of pores on the crack formation process in a finite element model of a transverse slice of a total hip reconstruction. We created models with a single large pore and models with multiple pores at levels of 2, 4, and 9%. The models were cyclically torque-loaded, causing macrocracks to appear in the cement mantle. In all models, we found that pores acted as microcrack initiators. However, pores could have both a detrimental and a beneficial effect on the macrocrack propagation in the cement mantle. Both effects were seen in the models with a single large pore and in the models with multiple pores. Pores would either accelerate, deviate, or decelerate the macrocrack propagation in the cement mantle. The effect of the pores depended on the location of the pores with respect to the stress intensities in the model, but was independent of the pore size or the level of porosity. The results may explain why the beneficial effect of vacuum mixing is difficult to demonstrate clinically. Stress intensities that are present in a cement mantle in an in vivo situation may overshadow the detrimental effect of a pore, while the beneficial effect may become more pronounced.

Morphology and chemistry of the mandibular gland complex in the primitive termite, Zootermopsis angusticollis (Hagen) (Isoptera : Hodotermitidae)

A pair of cephalic exocrine glands are described in the primitive termite Zootermopsis angusticollis (Hagen) (Isoptera : Hodotermitidae). One of the glands, the accessory mandibular gland, is apparently undescribed and is located ventrally near the mandibular gland. The 2 glands are located on either side of the head and open in a region of intersegmental cuticle between the maxilla and the lateral margins of the head capsule. Together, the 2 glands are termed the mandibular gland complex. The morphology of the 2 glands is described using light microscopy and scanning electron microscopy. The accessory mandibular gland is formed as an invagination of intersegmental cuticle, has the shape of a 3-fingered glove, and empties via a single large pore. The mandibular gland empties via numerous pores into a pore plate which, when folded, becomes a “pocket” or reservoir. Individual accessory mandibular glands were dissected free of intersegmental cuticle and the 2 major components of the secretion of the gland were identified as n-heneicosane and n-tricosane. It is suggested that the secretion of the accessory mandibular gland may function as a recognition pheromone and/or as a spreading agent for the secretion of the mandibular gland.

The correct position of flagellar insertion in Prorocentrum and description of Prorocentrum rhathymum sp. nov. (Pyrrhophyta)

For three Prorocentrum species, P. minimum (Pavillard) Schiller, P. rhathymum sp. nov., and P. triestinum Schiller, we have found that both flagella emerge from a single large pore. This arrangement is contrary to previous observations which suggested they arose from separate pores. Prorocentrum triestinum has only one anterior pore, whereas P. minimum and P. rhathymum sp. nov. have an additional auxiliary pore. The pores in all three species are formed by a series of small plates. The left and right valves on each species can be identified by ornamentation unique to each valve. Prorocentrum rhathymum sp. nov., isolated from the plankton of Cinnamon Bay, Virgin Islands, is described.