Degree Of Packing Research Articles

Effective Reduction of Cement Content in Pavement Concrete Mixtures Based on Theoretical and Experimental Particle Packing Methods

The effective reduction of cement content in pavement concrete without compromising its fresh, mechanical, and durability properties can lead to more economical and sustainable pavement engineering. Because a reduction in cement content in concrete can be achieved by improving the particle packing of aggregates, this study attempted to improve a practical mix design procedure based on both theoretical and experimental particle packing methods. In this study, optimum aggregate blends were first identified using the Modified Toufar Model, which indicated good correlation with the experimental packing results based on a combined void content test. The Modified Box Test was then used to evaluate the fresh concrete performance and to justify the effectiveness of cement reduction. The results indicated that cement content could be reduced by up to 56 kg/m3 from the reference mix with the optimum aggregate gradation. The results from hardened concrete tests, such as compressive strength, flexural strength, and resistivity, confirmed that concrete properties were not compromised by the reduced cement content. Freeze-thaw resistance was improved with up to an 11% increase in the relative dynamic modulus at 300 freeze-thaw cycles. The optimum mixes also demonstrated reduced shrinkages, with a 12%–20% reduced strain at 180 days of free shrinkage and a delayed cracking age based on the restrained shrinkage test. Based on the laboratory test results, an improved mixture design procedure aided by the particle packing degree and the minimum excess paste-to-aggregates volume ratio is presented.

Electromechanical properties of fibers produced from randomly oriented SWCNT films by wet pulling technique

We examined a fiber formation from pristine and modified single-walled carbon nanotube (SWCNT) films using a recently developed wet pulling technique. Crucial phenomena in the wet pulling process are a folding of a solvent soaked SWCNT film due to the liquid surface tension and fiber densification during the solvent evaporation. It is shown that electrical characteristics of the as-produced fibers are determined by the type of the liquid employed in their formation, which defines the SWCNT packing degree. The obtained specific strength (0.6–0.8 N/tex), toughness (up to 127 J/g) and specific conductivity (0.5–1.2 kS·m2/kg) are in many cases comparable with published data for fibers produced by more resource-consuming methods. These, in combination with the simplicity of our method and high piezoresistive gauge factor of 14 (for untwisted fibers at a 1% elongation), make SWCNT fibers promising components in future applications of stretchable electronics and robotics.

Kinetic Frustration Effects on Dense Two-Dimensional Packings of Convex Particles and Their Structural Characteristics.

The study of hard-particle packings is of fundamental importance in physics, chemistry, cell biology, and discrete geometry. Much of the previous work on hard-particle packings concerns their densest possible arrangements. By contrast, we examine kinetic effects inevitably present in both numerical and experimental packing protocols. Specifically, we determine how changing the compression/shear rate of a two-dimensional packing of noncircular particles causes it to deviate from its densest possible configuration, which is always periodic. The adaptive shrinking cell (ASC) optimization scheme maximizes the packing fraction of a hard-particle packing by first applying random translations and rotations to the particles and then isotropically compressing and shearing the simulation box repeatedly until a possibly jammed state is reached. We use a stochastic implementation of the ASC optimization scheme to mimic different effective time scales by varying the number of particle moves between compressions/shears. We generate dense, effectively jammed, monodisperse, two-dimensional packings of obtuse scalene triangle, rhombus, curved triangle, lens, and "ice cream cone" (a semicircle grafted onto an isosceles triangle) shaped particles, with a wide range of packing fractions and degrees of order. To quantify these kinetic effects, we introduce the kinetic frustration index K, which measures the deviation of a packing from its maximum possible packing fraction. To investigate how kinetics affect short- and long-range ordering in these packings, we compute their spectral densities χ̃V(k) and characterize their contact networks. We find that kinetic effects are most significant when the particles have greater asphericity, less curvature, and less rotational symmetry. This work may be relevant to the design of laboratory packing protocols.

A methodology for the effective use of materials in concrete paving block

For a long time, concrete paving blocks have been broadly utilized in different countries as a specialized problem-solving technique to provide pavement in areas where, traditional forms of construction were less robust due to several drawbacks. Low maintenance, ease of placing and evacuation and quick use after installation make it best fit for various utilizations where the conventional pavement technologies are not practical or desirable. So there emerges a dynamic enthusiasm for the concepts of the mix design process for the development of concrete paving blocks arises. This paper aims to develop an optimized mix design for concrete paver blocks for medium traffic as per relevant codes, considering quality and economy. To maximise the particle packing density of concrete, the packing density approach was used here. The method of packing density receipt maximises the concrete material packing density by selecting the perfect measure of different aggregates to fill the voids, allowing a denser and firmer structure. The higher degree of particle packing contributes to minimum voids, maximum density, and thus fewer cement and water demands, leading ideal medium traffic design.

Effect of cobalt doping on structural parameters, cation distribution and magnetic properties of nickel ferrite nanocrystals

Here, thermal heat treatment method has been used for the synthesis of PVP capped nickel ferrite (NiFe2O4) and cobalt doped nickel (Ni0.5Co0.5Fe2O4) spinel ferrite nanocrystals with the aim of investigating the effect of Co doping on the structural and magnetic properties of NiFe2O4 nanocrystals. XRD analysis confirms the formation of a pure form of FCC nanocrystals of spinel ferrite type, where the average crystallite size has been found to be approximately 17 nm and 19 nm respectively for nickel ferrite (NF) and cobalt doped nickel ferrite (CNF) from XRD. Again, HRTEM study gives the average size for NF and CNF as 20 nm and 25 nm respectively. Further, SAED pattern indicates the polycrystallinity of both the sample, whereas EDX analysis confirms the presence of expected elements in the sample. From XRD data analysis different structural parameters such as lattice spacing, lattice constant, tetrahedral and octahedral ionic radii, oxygen position parameter, average cation radius per molecule, ionic packing coefficients (Pa, Pb), the degree of ionic packing (α), vacancy parameter (β), hopping lengths, and bond lengths etc. have been calculated for both nickel and cobalt doped nickel ferrite nanocrystals. Further, obtained cation distribution for NF and CNF nanocrystals from their XRD pattern analysis shows huge change in the distribution as a result of doping. In addition, FTIR spectral analysis also confirms the phase purity of both the samples. Magnetic characterization shows the improvement of different magnetic parameters due to cobalt doping on nickel, thereby making CNF nanocrystals suitable for different application purposes.

Processes of structure formation and paste matrix hydration with multilayer carbon nanotubes additives

The creation of high-strength materials with targeted structure formation and hydration to obtain building composites with a given set of properties represents a relevant area of the modern construction sector. This paper investigates promising nanomodifying additives i.e. multilayer carbon nanotubes along with an effective method to obtain a comprehensive nanomodifying additive through pre-ultrasonic dispersion of MWCNT globules of varying dispersive capacity in an isopropyl alcohol medium. The comprehensive nanomodifying additive obtained is characterized by high stability as well as a uniform distribution of carbon nanotubes in the additive. The Structure software package developed by the authors was used to study the structure of paste matrix at the mesastructural level. The modification of paste matrix by means of the developed comprehensive nanostructure additive reduces the crack length index to 113% with the crack length ratio and the crack shape ratio going down to 61% and 34%, respectively. The increase in the strength and durability of the compositions modified by the developed comprehensive nanomodifying additive is due to a more complete filling of the intergranular void with newly formed structures in the form of C-S-H (I), tobermorite and gel phases which enhance the degree of packing and density of the composite under examination. However, the share of nano - and micropores goes up by 1.21 and 1.31 times, respectively, while the share of meso - and macropores decreases by 1.51 and 5.25 times.

Redox-Driven In Situ Helix Reversal of Graphene-Based Hydrogels.

Controlling the handedness of dynamic helical nanostructures of supramolecular assemblies by external stimuli is of great fundamental significance with appealing morphology-dependent applications. Significantly, access to in situ chirality transformation of dynamic multistimuli-responsive systems can provide channels for real-time monitoring of the transfer processes in biological systems. However, efforts to achieve helix inversion in an all-gel-state and to comprehend the phenomena at a molecular scale are scarce. Herein, we introduce an example of supramolecular hydrogel in which graphene oxide (GO) incorporation leads to opposite helicity of the l-phenylalanine derivative (LPFEG) upon UV irradiation. The gelator modulates different degrees of packing that are responsible for the initial construction of right-handed nanofibers in GO surfaces and for the change in helix to preferred left-handedness in RGO surfaces caused by GO reduction. Specifically, LPFEG shows a mixture of right- and left-handed nanofibers with an appropriate exposure to UV light. A thermal-reversible transformation of chirality is also discovered in the supramolecular assemblies, allowing a dynamic and invertible flip of helicity upon heating and cooling. The morphology transformation makes the hybrid an ideal candidate for application in a precisely controlled drug delivery process. It can unexpectedly serve as a photosensitizer and a carrier for enantioselective absorption of specific chiral drugs enantiomer (l-dopa and S-naproxen sodium) and also exhibit on-demand drug release due to the helix reversal induced by light irradiation. Our results illustrate how the surface reactivity can direct the helical organization of adsorbed fibers, which in turn provide control over enantioselective absorption of chiral drug enantiomers, further giving rise to on-demand drug release due to handedness inversion upon UV irradiation.

Experimental and Ab Initio Studies of Intrinsic Defects in "Antizeolite" Borates with a Ba12(BO3)66+ Framework and Their Influence on Properties.

The porous Ba12(BO3)66+ framework of the so-called "antizeolite" borates with channels along the c axis is capable of accommodating various guest anionic groups, e.g. [BO3]3-, [F2]2-, [F4]4-, and [(Li,Na)F4]3-. Taking as an example the Ba12(BO3)6[BO3][LiF4] crystal, we put forward the argument that the optical properties of "antizeolite" borates are strongly influenced by the degree of channel packing with anionic groups and, correspondingly, by the conjugated intrinsic defects. With the use of optical, electron-spin resonance, Raman spectroscopy, and ab initio calculations, it was shown that intrinsic defects largely impact the absorption of light in the visible and UV regions (the color of the bulk crystals can change from colorless to dark brown), absorption-edge position, dichroism, and other optical properties. The change in the optical absorption in the visible range is caused by the appearance of new states in the electronic structure inside the band gap, which are associated mainly with the presence of single and double F centers-fluorine vacancies that capture electrons-in [□F4]4-, [F2]2-, and [LiF4]3- groups. The formation of F centers in the [F2]2- group is the most energetically favorable. It has been found that Ba12(BO3)6[BO3][LiF4] crystals are optically active gyrotropic with an isotropic point at 499 nm at 300 K and are of interest for practical application as narrow-band light filters.

Utilisation of Ultra-High Performance Fiber Reinforced Concrete(UHPFRC) for Retroffiting – a Review

Retrofitting has become a proven method for improving the load carrying capacity of existing concrete structural elements subjected to high mechanical loading, ageing or aggressive environments. Ultra-High Performance Fiber Reinforced Concrete (UHPFRC)is a relatively new generation of cement-based retrofitting material with a very high compressive strength and low permeability attributed to its tightly packed microstructure, also displaying excellent bonding ability with normal structural concrete. It has the potential to eliminate various problems caused by other retrofitting methods like FRPs or externally bonded steel plates as a result of the mismatch of stiffness with parent concrete. This study presents an overview of UHPFRC focusing on its properties, design, applications and challenges. The performance of UHPFRC concrete mix is greatly influenced by the type and degree of packing of its constituents in the cementitious matrix, necessitating the need for optimisation. Strength properties are very much higher when compared to that of conventional concrete alongside with increased durability aspects. The retrofitting technique showed an enhancement in the load carrying capacity of deteriorated structures. Therefore, UHPFRC can be considered as a practical solution to improve the sustainability of buildings and other infrastructural components. However, as a retrofit, there are some concerns regarding the loss of ductility. This broadens the need for methods to improve its ductility. This paper presents the state-of-art review of existing literature that deals with the retrofitting/rehabilitation of structures using UHPFRC. Altogether, the paper aims to expand the awareness regarding UHPFRC which was otherwise hindered, owing to limited design codes.

Too packed for existence? More-than-subjective land-use issues in pockets of local order: the case of land-use conflict in Swedish Lapland

ABSTRACT Time geography has been applied to study geographical situations characterised by intertwining temporal and spatial aspects. The availability of space for the conduct of land-use activities as temporal-action sequences can be investigated using time geography. The present study utilises time geography to examine how geography matters in the context of a contested mining proposal in Swedish Lapland, namely the case of reindeer herding in Gállok. The time-geographic notion of “packing” that denotes time–space compactness is utilised to investigate the room to manoeuvre available for reindeer herding. The theoretical entry lies in the idea that maximum nearness in human society has to do with the manner in which activities are organised in space and time. This is embraced by the time-geographic concept of the pocket of local order. The article reviews discussion in the literature of the notion of packing and discusses the organisation of reindeer herding as land use in the case studied. The study examines how space and time may matter in detail, as well as how the concept of the pocket of local order can be utilised to assess this and to detect the prevailing degree of packing. It suggests that such dependences represent more-than-subjective preconditions of operational character in land use. The study contributes to understanding of how the successful conduct of the business of land use may depend on the ability to maintain organisational coherence in a temporal–spatial sense.

General and adaptive synthesis protocol for high-quality organosilane self-assembled monolayers as tunable surface chemistry platforms for biochemical applications.

The controlled modification of surface properties represents a pervasive requirement to be fulfilled when developing new technologies. In this paper, we propose an easy-to-implement protocol for the functionalization of glass with self-assembled monolayers (SAMs). The adaptivity of the synthesis route was demonstrated by the controlled anchoring of thiol, amino, glycidyloxy, and methacrylate groups onto the glass surface. The optimization of the synthetic pathway was mirrored by extremely smooth SAMs (approximately 150 pm roughness), layer thickness comparable to the theoretical molecule length, absence of silane islands along the surface, quasi-unitary degree of packing, and tailored wettability and charge. The functionalization kinetics of two model silanes, 3-mercapto- and 3-amino-propyltrimethoxysilane, was determined by cross-comparing x-ray photoelectron spectroscopy and time of flight secondary ion mass spectrometry data. Our SAMs with tailored physicochemical attributes will be implemented as supports for the crystallization of pharmaceuticals and biomolecules in upcoming studies. Here, the application to a small molecule drug model, namely aspirin, was discussed as a proof of concept.

Towards a Deeper Understanding of Creep and Physical Aging Behavior of the Emulsion Polymer Isocyanate.

Information of the relaxation behaviors of polymer film is crucial to judge the durability of emulsion polymer isocyanate (EPI) as a structural adhesive for bonding timber-based products. A sequence of tensile creep tests and free volume evaluation of the cured EPI adhesive films during isothermal condition were carried out by dynamic mechanical analysis and positron annihilation lifetime spectroscopy, respectively. It is the first time to explore the creep response and physical aging of the EPI film, as well as associated microstructural evolution. The results indicate that the creep characteristics of the glassy EPI coating intimately depend upon the crosslinker and elapsed time, and the ideal momentary creep master curve can be constructed in terms of modified horizontal shifting method. Furthermore, the relaxation process is found to be dominated by vacancy diffusion mechanism. In addition, increasing the polymeric isocyanate content can significantly enhance the resistance to creep deformation of EPI films, but also accelerate the physical aging process. Due to a higher packing degree of pure polymer films, the EPI films with aqueous emulsified isocyanate exhibit much better relaxation resistance compared to that with general isocyanate crosslinker.

Effect of Aggregate Packing on Strength of Reactive Powder Concrete: Modeling and Experimental Evaluation

This research investigates the effects of aggregate packing degree on the strength of Reactive Powder Concrete (RPC) mixtures on the basis of the Toufar model. To optimize the packing degree of sand for strength development of RPC, various sand blends with the combination of different fraction size were used. In addition, 10 different blends that showed best packing degree were chosen to investigate the compressive strength of RPC. It was found that experimental verification results conform to Toufar model calculations. The test result shows that packing degree had a significant effect on the strength of RPC: Mixtures with higher packing degree can achieve higher compressive strength. Furthermore, Results indicate the Toufar model can predict packing degree of aggregate blends.

Gold nanoparticles interacting with synthetic lipid rafts: an AFM investigation

Inorganic nanoparticles (NPs) represent promising examples of engineered nanomaterials, providing interesting biomedical solutions in several fields, like therapeutics and diagnostics. Despite the extensive number of investigations motivated by their remarkable potential for nanomedicinal applications, the interactions of NPs with biological interfaces are still poorly understood. The effect of NPs on living organisms is mediated by biological barriers, such as the cell plasma membrane, whose lateral heterogeneity is thought to play a prominent role in NPs adsorption and uptake pathways. In particular, biological membranes feature the presence of rafts, that is segregated lipid micro and/or nanodomains in the so-called liquid ordered phase (Lo ), immiscible with the surrounding liquid disordered phase (Ld ). Rafts are involved in various biological functions and act as sites for the selective adsorption of materials on the membrane. Indeed, the thickness mismatch present along their boundaries generates energetically favourable conditions for the adsorption of NPs. Despite its clear implications in NPs internalisation processes and cytotoxicity, a direct proof of the selective adsorption of NPs along the rafts' boundaries is still missing to date. Here we use multicomponent supported lipid bilayers (SLBs) as reliable synthetic models, reproducing the nanometric lateral heterogeneity of cell membranes. After being characterised by atomic force microscopy (AFM) and neutron reflectivity (NR), multidomain SLBs are challenged by prototypical inorganic nanoparticles, that is citrated gold nanoparticles (AuNPs), under simplified and highly controlled conditions. By exploiting AFM, we demonstrate that AuNPs preferentially target lipid phase boundaries as adsorption sites. The herein reported study consolidates and extends the fundamental knowledge on NPs-membrane interactions, which constitute a key aspect to consider when designing NPs-related biomedical applications. LAY DESCRIPTION: Inorganic nanoparticles (NPs) represent promising examples of engineered nanomaterials, offering interesting biomedical solutions in multiple fields like therapeutics and diagnostics. Despite being extensively investigated due to their remarkable potential for nanomedicinal applications, the interaction of NPs with biological systems is in several cases still poorly understood. The interaction of NPs with living organisms is mediated by biological barriers, such as the cell plasma membrane. Supported lipid bilayers (SLBs) represent suitable synthetic membrane models for studying the physicochemical properties of natural interfaces and their interaction with inorganic nanomaterials under simplified and controlled conditions. Recently, multicomponent SLBs were developed in order to mimic the lateral heterogeneity of most biological membranes. In particular, biological membranes feature the presence of rafts, that is segregated lipid micro and/or nanodomains, enriched in cholesterol, sphingomyelin, saturated glycerophospholipids and glycosphingolipids: these lipids segregate in the so-called liquid-ordered phase (Lo ), characterised by a high molecular packing degree, which promotes the phase separation from the surrounding liquid-crystalline (disordered, Ld ) phase, where the intermolecular mobility is increased. Rafts are thought to participate in the formation and targeting of nano-sized biogenic lipid vesicles and are also actively involved in multiple membrane processes. Indeed, Lo -Ld phase boundaries represent high energy areas, providing active sites for the preferential adsorption of external material. The selective adsorption of NPs along the phase boundaries of rafted membranes has been theorised and indirectly probed by different research groups; however, a direct proof of this phenomenon is still missing to date. We herein exploit atomic force microscopy (AFM) to directly visualise the preferential adsorption of gold nanoparticles (AuNPs) along the phase boundaries of multicomponent SLBs (previously characterised by neutron reflectivity), obtained from synthetic vesicles containing both an Ld and an Lo phase. The quantitative localisation and morphometry of AuNPs adsorbed on the SLB reveal important information on their interaction with the lipid matrix and directly prove the already theorised differential NPs-lipid interaction at the phase boundaries. The presented results could help the development of future NP-based applications, involving NPs adsorption on membranes with nanoscale phase segregations.

A critical examination of the influence of material characteristics and extruder geometry on 3D printing of cementitious binders

Extrusion pressure-displacement tests on cementitious pastes with multiple starting materials and differing particle packing, subjected to different extrusion geometries are reported. The steady state extrusion pressure (equivalent to extrusion yield stress) and the deadzone length (static zone of material buildup at die entry) are determined from the pressure-displacement response to characterize the extrudability and/or printability. A unique “geometric ratio” is used to account for the effects of barrel-die geometry on paste extrusion. The ratio of extrusion yield stress (25–75 kPa) to the measured shear yield stress (50–300 Pa), the deadzone length, and the measured-to-designed filament volume at a given flow rate (print speed) are found to remain relatively invariant with geometric ratio for mixtures with high degree of microstructural packing, and thus better extrudability and shape stability. This paper marries materials- and process-related issues and, could pave the way for test methods for 3D printable mixture qualification.

Genesis and taphonomic biases of Quaternary tank deposits of northeastern Brazil

A taphonomic comparison among ten Quaternary tank deposits bearing megafauna remains in northeastern Brazil allowed the identification of four regional-scale taphonomic aspects controlled by climate seasonality: differential preservation of mega-mammal bones, poor physical integrity, spatial resolution (local) and time averaging (104 years). Sedimentary aspects, such as the high degree of packing of fossiliferous layer, indicate conditions of low clastic detrital sediment input in arid conditions. The correlation among geochronological data of tank deposits and paleoclimatic curves of northeastern Brazil suggest that the climate was arid/semi-arid characterized by seasonality between dry and rainy periods. Thus, we postulate the succession of the two paleoenvironmental and paleoecological scenarios during the late Quaternary affecting the formation of fossiliferous tank deposits: (i) the intensity and duration of arid periods led animals to search for water and food, and consequently, concentration and death near these water sources; and (ii) in the rainy season, carcasses, disarticulated and fragmented bones around these water sources were transported and accumulated through high-energy tractive flows, reworking previously buried skeletal material.

Fluorocarbon versus hydrocarbon organosilicon surfactants for wettability alteration: A molecular dynamics approach

This paper presents a theoretical model based on molecular dynamics to represent and explain the experimental measurements of water droplet contact angles on fluorocarbon and hydrocarbon organosilicon surfactants of different chain lengths. In addition to the contact angles, we evaluated the distribution of the surfactants on the surface (surface density, packing degree, density profile, and coating thickness) and the interaction energies (surfactant–surfactant, surfactant–water, and water–water) to better understand the effect generated by the differences in the molecular structure of the surfactants. We found that the surface densities of the fluorocarbon surfactants were lower than those of hydrocarbon surfactants. This is because fluorocarbon chains are more rigid and because the attractive interaction energy between CF chains is less than that between CH chains because the fluorine–fluorine repulsive electrostatic interactions are stronger than the corresponding hydrogen–hydrogen interactions. The wettability alteration resulted from the modified surface–water interactions. The initial state was hydrophilic (water angle contact of 24°), produced by the high interaction energy between water and the silica surface. Upon application of surfactant, the surface–water interaction energies were considerably lowered, generating hydrophobic surfaces, with water angles contact between 87° and 99°.

In Situ Biological Transmutation of Catalytic Lactic Acid Waste into Calcium Lactate in a Readily Processable Three-Dimensional Fibrillar Structure for Bone Tissue Engineering.

A bioinspired three-dimensional (3D) fibrous structure possesses biomimicry, valuable functionality, and performance to scaffolding in tissue engineering. In particular, an electrospun fibrous mesh has been studied as a scaffold material in various tissue regeneration applications. We produced a low-density 3D polycaprolactone/lactic acid (LA) fibrous mesh (3D-PCLS) via the novel lactic-assisted 3D electrospinning technique exploiting the catalytic properties of LA as we reported previously. In the study, we demonstrated a strategy of recycling the LA component to synthesize the osteoinductive biomolecules in situ, calcium lactate (CaL), thereby forming a 3D bioactive PCL/CaL fibrous scaffold (3D-SCaL) for bone tissue engineering. The fiber morphology of 3D-PCLS and its packing degree could have been tailored by modifying the spinning solution and the collector design. 3D-SCaL demonstrated successful conversion of CaL from LA and exhibited the significantly enhanced biomineralization capacity, cell infiltration and proliferation rate, and osteoblastic differentiation in vitro with two different cell lines, MC3T3-e1 and bone marrow stem cells. In conclusion, 3D-SCaL proves to be a highly practical and accessible strategy using a variety of polymers to produce 3D fibers as a potential candidate for future regenerative medicine and tissue engineering applications.

A taphofacies interpretation of shell concentrations and their relationship with petrophysics: A case study of Barremian-Aptian coquinas in the Itapema Formation, Santos Basin-Brazil

The Itapema Formation in the Santos Basin is described as a carbonate coquina interval, a type of sedimentary rock composed mainly by shells and their fragments. These rocks have different textural characteristics related to depositional and diagenetic processes, which influence the pore system and consequently the permeability. Understanding how the different facies are distributed and their relationship with petrophysics is essential to preview the quality of a reservoir. In this study, we classify the shell beds of the Itapema Formation through taphonomic characteristics, applying the concept of taphofacies, where taphonomic patterns such as orientation of shells, degree of packing, fragmentation of shells, abrasion, rounding, and sorting (type of grains) are used to differentiate shell concentrations. Six taphofacies (Tf-1 to Tf-6) were described in a core interval of 12 m, which corresponds to the Itapema Formation. Taphofacies Tf-1 and Tf-2 are well-sorted and unsorted grainstones/rudstones with parallel-oriented and densely packed shells with a braded valves. Taphofacies Tf-3 and Tf-4 are well-sorted and unsorted grainstones/rudstones with oblique oriented shells, generally well-preserved but often with high shell dissolution. Taphofacies Tf-5 and Tf-6 are well-sorted and unsorted grainstones/rudstones with randomly oriented shells and densely packed deposits. In general, all the well-sorted taphofacies are composed mainly of shells and their fragments, do not show mud matrix or even shell fragments smaller than 0.2 mm, the size of valves varies from 0.5 to 5 mm and shell fragments are the smallest components. The unsorted taphofacies contain grains smaller than 0.2 mm, most of them peloids, and very small shell fragments. Through the analysis of thin sections, x-ray tomography (CT), high resolution tomography (H-CT) and Nuclear Magnetic Resonance (NMR) it was possible to quantify the porosity in the described taphofacies and classify them according to Choquette and Pray (1970) and Ahr (2008). In well-sorted taphofacies primary pores are preserved; the total porosity varies from 9% to 21% in thin sections, and mainly consists of interparticle, intraparticle, and moldic pores and vugs. The control of porosity varies from depositional to hybrid 1, according to Ahr (2008), and pores are generally connected. In unsorted taphofacies, preserved primary porosity is uncommon and most pores are moldic and vugs. The total porosity in this facies varies from 2 to 15%, although almost all values are between 10% and 15%. The control of porosity varies from hybrid 1 to diagenetic, based on Ahr (2008), and the connectivity varies. Despite these textural differences between well-sorted and unsorted taphofacies, in general, the porosity is good and varies between 10% and 25%. The permeability in well-sorted taphofacies varies from 0.3 to 8 D, the high values being associated with a connected porous system, whereas in unsorted taphofacies the permeability varies from 0.01 to 0.4 D due to the occurrence of isolated vugs and moldic pores. The well-sorted coquinas were interpreted as deposits influenced by storm-induced currents and waves where the energy was sufficient to winnow the finer grains and preserve the primary pores. The taphonomic characteristics indicate tempestites to shoreface deposits, whereas in unsorted taphofacies the energy was not sufficient to remove finer grains generally associated with distal tempestites and backshore deposits. • Shell concentration (coquinas) pore types and petrophysics. • Taphofacies interpretation and their relationship with porosity and permeability. • Porosity control in carbonate coquina deposits. • Permeability distribution in carbonate coquinas reservoir.

Reduced magnetization curves of Ising nanoparticles with high critical temperature

ABSTRACTThe magnetic properties (phase diagram, the thermal variations of magnetization and the reduced magnetization curve) in graphene-like Ising nanoparticles are examined by the effective-field theory with correlations. The effects of surface exchange interaction JS on the magnetic properties are discussed. When JS is larger than the critical value JSC, a nanoparticle with high critical temperature is possible. The value of JSC depends on the shape and the degree of structural packing of the nanoparticle. It is found that there exist two types of reduced magnetization curves for a nanoparticle with JS > JSC.