Physical Bond Research Articles

Mother Is a Verb: An Unconventional History by Sarah Knott

Reviewed by: Mother Is a Verb: An Unconventional History by Sarah Knott Susan E. Klepp Sarah Knott. Mother Is a Verb: An Unconventional History. New York: Sarah Crichton Books, Farrar, Straus and Giroux, 2019. viii + 306 pp. Ill. $27.00 (9780374213589). Sarah Knott's book on motherhood, mothering, and the early stages of childrearing challenges the traditional conventions of historical analysis—conventions that were largely established in Germany in the nineteenth century. History, real history, is written by experts whose deep knowledge of particular men and events [End Page 141] is tested through the dispassionate arguments of other experts in order to reach conclusions that help move human knowledge ever closer to universal truths. Stylistically, the formality of the prose, the complex sentences, and the Latinate vocabulary signal the seriousness of the historical enterprise. Like the sciences, history is an academic discipline. Knott has written a book that is perhaps more suited to our own times: to email and tweets, to informality, to diversity of opinion and experience, to a focus on the self, and to despair over ever reaching some shared vision of an identifiable truth. So sentence fragments, slang, and short paragraphs that shift abruptly from one subject to another confound a simple, linear chronology and leave conclusions and meaning to the reader. Sources are rather lightly footnoted, previous scholarship is mostly unquestioned, and there is no index. Women are not only present but central to the narrative. Rather than borrowing from scientific discourse, Knott presents a seemingly artless, casual, living-in-the-moment prose style that combines her personal memoir, written in the mode of a Joycean stream of consciousness, with an appreciation of the specific "historical circumstances" that refute "false universals" (pp. 83–84). But Knott's approach turns out to be artful and carefully plotted, not artless or haphazard. Two chronologies are seamlessly intertwined. One is Knott's lived experience as she and her husband decide to have a child. Miscarriage and then another pregnancy follow, then birth, breastfeeding, sleep deprivation, sickness, love, worries, and more. Her second pregnancy and another child complete this narrative. Weaning ends both the book and the physical bond that embodies Knott's maternity. The second chronology provides the historical framework for Knott's personal experiences. Here the focus is on the English-speaking world of women in Britain and North America. From the late eighteenth century to the present large families, frequent pregnancies, and long experience with rearing infants have been giving way to smaller families and fewer births. Formal education and career options for women compete uneasily with childbearing and childrearing. These tensions are accompanied by the anxieties of inexperience, an ignorance heightened by the hectoring of medical and self-proclaimed experts. Driving the methodological choices Knott makes is the limited archival record on or by women. Before the seventeenth century there is virtually nothing in the archive authored by women. Even after literacy becomes more widespread, there is little on some topics. Not surprisingly, almost no woman takes to her pen to record contractions, crowning, and birth as they happen. Surprisingly, neither do the sources give much insight on "the basic question—What is the history of knowing what to do, what is the history of uncertainties felt or dispelled?" (pp. 172–73). To highlight the diversity of reproductive and personal experience, ethnographic anecdotes are interspersed within these chronologies. Examples of birthing practices among Native Americans, African Americans, British factory operatives, immigrants, aristocrats, lesbian, and single mothers are among those populating these pages, but so fleeting are their appearances that it often seems that these diverse mothers appear to have no history. [End Page 142] The book is a good read and should appeal to undergraduates and the interested public. Scholars who specialize in women, fertility, family, birthing, baby care, and mothering will find little that is unfamiliar in their areas of specialization, but will benefit from the juxtaposition of a wide range of ideas and practices. Given the abundance of detail and interpretation, the author's decision to avoid "maternal mortality, infant loss, or forced relinquishment" (p. 17) is curious, and the book says nothing of the too frequent violence against women and infants. I would...

Physicochemical, cytotoxicity, and biological properties of calcium silicate-based root canal sealers: A literature review

The aim of this study was to evaluate the main calcium silicate-based root canal sealers (bioceramic-based root canal sealers) currently used in endodontic field as well as their specific characteristics and to compare with other conventional sealers. A review of the literature was made to evaluate numerous investigations covering different properties of these materials. The properties of interest were physical properties, bond strength, pH, radiopacity, solubility, setting and working time, dimensional changes, flow, calcium ion release, biocompatibility, antimicrobial activity, sealing ability, adhesion, and cytotoxicity. The outcome of these studies of bioceramic-based sealers revealed favorable biological and physicochemical properties along with comparative investigations of other agents. It was concluded that bioceramic-based sealers, in spite of drawbacks of some, were found to be attractive due to their bioactivity, dimensional stability, and acceptable physicochemical properties in comparison with other conventional sealers.

Coordination bonding in dicopper and dichromium tetrakis(μ-acetato)-diaqua complexes: Nature, strength, length, and topology.

Geometry optimization, energetics, electronic structure, and topology of electron density of dicopper (I) and dichromium (II) tetrakis(μ-acetato)-diaqua complexes are studied focusing on the metal-metal interactions. The performance of broken symmetry (BS) single-determinant ab initio (Hartree-Fock, Møller-Plesset perturbation theory to the second and third orders, coupled clusters singles and doubles) and density functional theory (BLYP, B3LYP, B3LYP-D3, B2PLYP, MPW2PLYP) methods is compared to multideterminant ab initio (CASSCF, NEVPT2) methods as well as to the multipole model of charge density from a single-crystal X-ray diffraction experiment (Herich et al., Acta Cryst. 2018, B74, 681-692). In vacuo DFT geometry optimizations (improper axial water ligand orientation) are compared against the periodic ones. The singlet state is found to be energetically preferred. J coupling of (I) becomes underestimated for all ab initio methods used, when compared to experiment. It is concluded that the strength of the direct M─M interactions correlates closely with the J coupling magnitude at a given level of theory. The double potential well character of (II) and of the dehydrated form of (II) are considered with respect to the Cr─Cr distance. The physical effective bond order of the metal-metal interaction is small (below 0.1 e) in (I) and moderate (0.4 e) in (II). The CASSCF results overestimate the electron density of the metal-metal bond critical point by 20% and 50% in (I) and (II), respectively, when compared to the multipole model. © 2019 Wiley Periodicals, Inc.

Tradisi Uang Pelangkah Pernikahan Dalam Adat Betawi di Tinjau Dari Hukum Islam di Kecamatan Babelan Kabupaten Bekasi

Marriage is a physical and mental bond between a man and a woman as husband and wifewith the aim of forming a happy and eternal family or household based on the Supreme Lordship.In the custom of marriage in the people of Babelan District, Bekasi Regency, there is a customthat if someone wants to get married but there is an older brother who is not married, then thatperson must wait for his brother to marry first or can marry before his brother on condition that theperson who wants to step over his brother must give something in the form of money or goods to herbrother. According to traditional leaders, the stepper is required to maintain a good relationship withhis brother. However, if the stepper was burdensome or prevented his younger sibling from gettingmarried, the traditional leader revealed that this was not justified because the stepper could not beasked for a certain nominal value or certain items, only the awareness of his younger sibling. Inline with the opinion of traditional leaders, clerical figures reveal that stepping may be applied onthe basis of the rules of العادة مُحَكَّمة , but this is not a necessity.. Primary data sources were obtainedfrom interviews and secondary data sources were obtained from books, magazines, journals, etc.The type of research used in this research is the type of field research (Field Research). The researchapproach carried out by the author uses descriptive qualitative. Data collection is done by theauthor to get and understand the picture and the existing reality, the writer uses data collectiontechniques by interview, observation and documents. From the data that has been collected, then thewriter analyzes using descriptive method. Based on the research data, the authors conclude that thetradition of stepping marriage money can be preserved because the tradition of stepping marriagemoney is not only a symbol of national identity, but also as a form of respect for older siblings whowill be stepped over and as a guardian of good family relations. Although it must be preserved, theremust be filtering and adjustments to fiqh so that there is no conflict between adat and fiqh. Some ofthe problems with stepping customs that must be filtered and adapted to fiqh include the prohibitionof marriage from older siblings to younger siblings who wish to marry. Barring his younger siblingfrom marrying is not justified in custom and in fiqh it can be forbidden because it can cause a lotof harm. In addition, things that are burdensome and troublesome for a person to get married mustalso be eliminated. The brother who is going to be stepped over must be able to accept whatever theyounger siblings give as a permit application to marry. Should not impose the ability of the youngersibling and must not burden the request of the younger sibling.

Evaluation and modeling of mechanical behaviors of thermosetting polymer under monotonic and cyclic tensile tests

A nonlinear elastic-inelastic model for a thermosetting polymer is proposed based on the molecular chain network theory. In the proposed model, the bond of the polymer chain is divided into physical and chemical bonds, and the physical bond is allowed to separate and recombine during the deformation. The decrease in the rigidity and increase in the inelastic strain are related to the development of the physical bond density to represent the characteristic deformation behavior of the polymer. A rate-form large deformation constitutive equation is then formulated based on the updated Lagrangian method. Additionally, deformation behaviors of the epoxy under monotonic and cyclic tensile tests were evaluated by experimental and computational studies. The experimental results of the monotonic tensile test displayed a gradual transition from elastic to inelastic deformation, strain softening behavior after the macroscopic yielding stress, and an increase in the initial slope and the macroscopic yielding stresses with an increasing strain rate. The computational model can represent such characteristics by controlling the development of the physical bond density. In a cyclic test, a decrease in the rigidity and an increase in the residual strain with increasing cycles were observed even in a small strain range. Such inelastic deformation depended on the strain rate and the given upper stress in the cyclic test. Further, the proposed model successfully reproduced such nonlinear behavior in the cyclic test.

A polymerization scenario of the liquid–liquid transition of GeI4

SnI4 and GeI4 have been shown to exhibit similar polyamorphic nature. We examine the microscopic nature of the liquid–liquid transition in GeI4 by conducting an isothermal–isobaric molecular dynamics simulation for the system composed of rigid tetrahedral molecules. The model allows us to semiquantitatively discuss the structural properties of liquid GeI4 below 1 GPa. We define a physical bond between the nearest intermolecular iodine sites satisfying the conditions of forming the metallic I2 bond. We then focus on the formation of molecular clusters in dynamic networks of the bonds. The clusters are mainly formed by molecules whose nearest pairs are in edge-to-edge, face-to-edge, and vertex-to-edge orientations. The clusters grow as pressure increases, and the onset of percolation is observed below 1 GPa. The finite-size scaling analysis for the percolation probability identifies that the threshold pressure is GPa for the present model, which is near the extension of the boundary between the two liquid phases. We thus speculate that the liquid–liquid transition of GeI4 is attained by polymerization, i.e. percolation of molecular networks. The same percolation scenario with a slight modification such as introducing a bootstrap mechanism is expected to apply to the transition in liquid SnI4.

Mechanical Properties and Reinforcement Mechanisms of Carbon Nanotube Composites with Amine Functional Groups Based on Molecular Dynamics

This study successfully used the concept of molecular dynamics to explore multi-walled carbon nanotubes (MWNTs) with amine functional groups and subsequently applied these to macromolecular materials to construct a novel MWCNT-reinforced macromolecular composite. Nanoscale tensile simulations were performed to examine the reinforcing phenomena of the nanocomposite composed of functional group-based MWNTs and subsequently explore the reinforcement mechanisms involved. The reinforcement mechanism of a nanocomposite made only of MWNTs and macromolecular materials stems from the interfacial energy between the MWNTs and macromolecular material. The interfacial energy is supplied by the Van der Waals force between the MWNTs and macromolecules and is considered a physical bond. By contrast, the interfacial energy between the novel macromolecular composite with amine functional groups was supplied by the chemical bond between the functional groups on the surface of the MWNTs and macromolecular materials. The interfacial binding force of a chemical bond is stronger than that of a physical bond. Therefore, a nanocomposite composed of functional group-based MWNTs can provide greater strength.

Energetic nitrocellulose coating: effective way to decrease sensitivity and modify surface property of HMX particles

ABSTRACTModifying the surface properties of energetic materials has theoretical and practical significance in the field of their application. In this paper, irregular cyclotetramethylene tetranitramine (HMX) particles were successfully coated by energetic nitrocellulose (NC), leading to the uniform NC-coated HMX particles. As coating materials, energetic (NC was chosen to decrease the sensitivity and modify the surface property of HMX particles, in order to expand their application furthermore. Scanning electron microscopy, laser particle size analysis, energy dispersive spectrometer, and Fourier-transform infrared (FT-IR) spectra were utilized to investigate the morphology, size, and coating quality of NC-coated HMX particles. These results indicated the effective preparation of composites structure. Moreover, the thermal behaviors of NC-coated HMX particles were investigated by simultaneous thermogravimetric and differential scanning calorimetry analysis, coupled with FT-IR and mass spectroscopy. These results showed that NC did not induce chemical properties change of HMX, only physical hydrogen bond was formed in the coating process. Finally, the friction sensitivity, impact sensitivity, and surface properties NC-coated HMX were investigated, and the results suggested that NC-coated HMX particles had better safety and depicted stronger interaction with the binder matrix than original HMX, owing to the stability of NC on the outer layer.

Research on 5-fluorouracil as a drug carrier materials with its in vitro release properties on organic modified magadiite

The magadiite (MAG) was modified by cetyltrimethyl ammonium-Bromide (CTAB) and then further modified by Chitosan (CS) which is called organic modified-magadiite as magadiite-cetyltrimethyl ammonium bromide (MAG-CTAB) and magadiite-cetyltrimethyl ammonium bromide-Chitosan (MAG-CTAB-CS), respectively, in this research study. The MAG, MAG-CTAB, and MAG-CTAB-CS were used as 5-Fluorouracil (5-FU) drug carrier materials; the drug carrier's materials were marked as magadiite-5-Fluorouracil (MAG/5-FU), magadiite-cetyltrimethyl ammonium bromide-5-Fluorouracil (MAG-CTAB/5-FU), and magadiite-cetyltrimethyl ammonium bromide-Chitosan (MAG-CTAB-CS/5-FU). X-ray diffraction(XRD, Flourier transform infrared spectrometry (FTIR) and scanning electron microscopy (SEM) results were shown that 5-Fluorouracil was combined with carrier materials through physical apparent adsorption, ion exchange, chemical bond, hydrogen bond, and electrostatic interaction. The drug carriers in vitro release behavior in simulated gastric fluids (SGF，pH = 1.35) and intestinal fluids (SIF，pH = 7.40) were investigated. The drug loading capacity and accumulated release ration were as follows the order: MAG-CTAB-CS/5-FU > MAG-CTAB/5-FU > MAG/5-FU. The drug loading capacity of MAG-CTAB-CS/5-FU was 162.29 mg/g, 48 h later the drug accumulated release ratio was 61.24%, and the release amount was 97.52 mg/g for 24 h. Korsmeyer-Peppas model and First order model were found to be suitable to describe the vitro release behavior of 5-Fluorouracil. This would be an economically viable and efficient method for the preparation of advanced drug delivery system.

Effects of Water Immersion on the Adhesion between Adhesive Layer and Concrete Block

The effectiveness of load transfer in the CFRP‐adhesive‐concrete system highly relies on the integrity of the interfacial bond between adhesive layer and concrete. In the present paper, the effects of water immersion on the mode I fracture energy of the adhesion between CFRP adhesive and concrete were investigated experimentally and numerically. Four‐point bending test was conducted to measure the mode I fracture energy of the interfacial layer between adhesive and concrete. The moisture content distribution and the hygrothermal stress were determined by using the finite element method (FEM). The mode I fracture energy was found decreasing with increasing immersion time. The difference between the mode I fracture energy at 2 weeks and 4 weeks is rare. The failure mode of the four‐point bending test specimen shifts from concrete failure to interfacial debonding. The moisture content at the adhesive/concrete interface reaches equilibrium after 2 weeks of water immersion. The hygrothermal stress between adhesive and concrete is smaller than the tensile strength of concrete. Deterioration of the physical bond leads to the degradation of bonding strength. The reduction of the mode I fracture energy is more severe than that of the mode II fracture energy.

Performance of oxygen/argon plasma-treated steel fibres in cement mortar

Steel fibres are used widely to control initiation and growth of cracks in concrete. However, the bond between steel fibres and the cement matrix in steel fibre-reinforced concrete (SFRC) is almost always purely physical. A viable approach to reduce cracking in fibre-reinforced concrete is to supplement the physical bond between fibres and cement matrix with a relatively uniform chemical bond along the fibres' surface. However, despite the promising results reported for other types of fibres, little attention has been paid to chemical surface treatment of steel fibres to improve their ability to bond with concrete. In this study, an oxygen/argon plasma treatment process is investigated as a potential technique to improve the bond between steel fibres and a cementitious matrix. Several variations in treatment parameters are made in order to identify the optimal treatment conditions. The results of X-ray Photoelectron Spectroscopy and surface energy measurements confirm that plasma treatment can significantly increase the fibres’ surface energy and consequently the strength of the fibre-cement bond. The improved bond between steel fibres and concrete is confirmed by the results of fibre pull-out tests, as well as the reduced average crack size observed in restrained drying shrinkage tests. Moreover, the results indicate considerable decrease in the volume of permeable voids in SFRC due to plasma treatment of steel fibres.

AKIBAT HUKUM PEMBATALAN PERKAWINAN KARENA WALI NIKAH YANG TIDAK BERHAK TERHADAP KEDUDUKAN ANAK DAN HARTA BERSAMA MENURUT HUKUM ISLAM

Marriage is a physical and spiritual bond between man and woman who become husband and wife creating the happy and eternal family in the name of God Almighty. To conduct a marriage, the prospective groom and bride must meet marriage terms and conditions, or else the marriage itself may be cancelled. The cancellation of marriage is one way of breaking the bond which requirements and principles are flawed. In the provisions of article 71 letter (e), the Islamic law compilation decrales that the marriage held without an authorized guardian will result on abolishment or be considered never exist. Neverthless, the cancelled marriage does not abolish the parental obligation of the children. The child remains legitimate and they are under their parents responsibility. Meanwhile, in the case of shared assets, in Islamic law, husband and wife can choose to use the method of Ash Sulh (negotiation),‘Urf (customary law), and the last option is Qadha (justice).

Investigation of hydrogen adsorption on zeolites A, X and Y using statistical physics formalism

Abstract By means of the grand canonical ensemble and using statistical physics, experimental adsorption isotherms of hydrogen on three adsorbents (zeolite A, X and Y) at T = 77 K have been best fitted with a developed monolayer model with one type of sites. Exploiting some simplifying hypotheses, the model analytical expression of this model was established involving three physicochemical parameters with which we can describe the adsorption process at a microscopic level. These characteristic parameters are: the number of hydrogen molecules per site n, the receptor site density Nm and the energetic parameter P1/2 which are all deduced from the experimental data by numerical simulation. The evolution of these parameters was investigated of different types of zeolite and different type of exchanged cations. Our fitting results revealed that the hydrogen adsorption surface for each zeolite is homogeneous with physical bond energies. Finally, the thermo-dynamical potential functions which govern the adsorption process such as internal energy Eint, free enthalpy of Gibbs Ga and entropy Sa are derived by statistical physics derivation from the adopted model.

Effects of micrometre-sized graphite flake to reinforce the performances of poly(lactic acid) thermoplastic biocomposites

Biocomposites of poly(lactic acid) (PLA) and micrometre-sized graphite (GP) flake powder with 0–30 wt% GP contents have been prepared using extrusion moulding followed by compression moulding. The pure PLA and PLA-GP composites (PGC) have been examined by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy (RS), X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), transmission electron microscopy (TEM), mechanical and micromechanical testing, differential thermal analysis (DTA) and thermogravimetric analysis (TGA). FTIR spectra confirm the physical bond formation between GP and PLA. RS distinguishes the D-band spectra of pure PLA and PGC. XRD shows a partially crystalline structure in the PLA. SEM and TEM exhibit a clear dispersion of GP particles in PLA matrix at lower loading and aggregates at higher loading. With an increase of filler content, the tensile and flexural strengths decrease, but the Young’s and tangent moduli are observed to increase by 58% and 77%, respectively. These increments represent an increase in the stiffness of the materials and are found to be consistent with the theoretical values. A decrease in microhardness with increase in filler content is also observed. Both the DTA and TGA reveal an increased thermal stability of the composites.

A novel iron ore pelletization for increased strength under ambient conditions

A novel ambient condition production of superior strength, non-abrasive, non-sticky iron ore pellets devoid of undesirable fines under the compression stress of 4 kN is presented. Interfacial bond between epoxy and iron oxide imparts high strength as opposed to physical bond in the conventional pellets. The pellets show high compression strength of 4 kN, without heat treatment compared to the industry requirement (2.5 kN) of an indurated pellet processed at 1200–1350 °C. Pelletization and iron ore reduction are accompanied by great reduction in energy and carbon dioxide emission. Enhanced rate and degree of iron ore reduction are due to secondary reactions involving carbon dioxide and the volatiles. Pellets reduced at 1550 °C show carbon dissolution up to 4 wt%, high porosity, low sulphur and slag levels. Silica fillers in the resin impart high mechanical strength to the crosslinked epoxy-iron oxide network facilitating mass transfer of off-gases at the interface enhancing the reduction rate and the degree of reduction. Utilising biorenewable or recycled resin, will make this process sustainable, cleaner and cost-effective reducing the landfill burden.

The role of mechanical, chemical and physical bonds in metal-ceramic bond strength

Purpose: A review regarding the mechanisms of metal-ceramic join is presented. Design/methodology/approach: The impact of the air-abrasion parameters on the mechanical bond strength of the ceramic crowns was discussed. The presence of opaque on the chemical bond was analysed. Research of the influence of the difference in the coefficient of thermal expansion values on the metal-ceramic bond was included. The methods of testing the bond strength were analysed. Findings: The metal substructure-dental ceramic bond strength is affected by all types of bond. In bond strength, 3-point bending test and shear test are mainly used. Created samples simulate the ceramic crowns veneered on one side. The role of physical bond on ceramic crowns veneered around metal substructure is unknown. Research limitations/implications: The prosthetic restorations with the ceramic surrounding whole the metal substructure are commonly used. The impact of shrinkage in the cylindrical deposition of the ceramic on metal substructure should be analysed. Practical implications: Numerical analysis and FEM simulation can be helpful in the analysis of the physical bond between the metal substructure and the dental ceramic around it. Originality/value: The impact of the type of the bond to metal-ceramic bond strength is presented, taking into account the cognitive gap in the influence of the coefficient of thermal expansion on the cylindrical placement of ceramic on the substructure.

Effects of magnesium oxide on carbonic acid resistance of oil well cement

This paper presents the results of an experimental study on the effects of magnesium oxide additive on the performance of oil well cement under a high-pressure high-temperature (HPHT) carbonic acid environment. Magnesium oxide (MgO) is a well-known expanding agent that improves sealing performance of cement. However, the performance of MgO-based cement has not been tested in a carbonic acid environment. Therefore, to investigate the impact of MgO on carbonic acid resistance of cement, two cement slurry formulations: Class H cement with 35% silica (baseline or HS) and baseline cement with MgO (HSMG) were compared after exposure to an acidic environment. To evaluate their performance, cylindrical cores and shear bond strengths (SBS) samples were prepared and aged in HPHT autoclave containing brine (2% sodium chloride solution) saturated with mixed gas containing CH4 and CO2. Six aging tests were conducted varying CO2 concentration, temperature, and pressure. After aging for 14 days at constant pressure and temperature, the samples were recovered, and their physical (bond and compressive strength, porosity and permeability) and mineralogical composition were measured and compared with those of unaged samples. The results suggest that addition of 5% MgO reduces the carbonation of cement and could potentially prolong the operational life of cement by protecting its binding components (calcium hydroxide and calcium silicate hydrate).

Suppression of shrinkage porosity in laser-joining of CFRP and steel using a laser surface modification process “Surfi-Sculpt ®”

The emergence of shrinkage porosity is a significant issue in the laser joining of carbon fiber reinforced polymer (CFRP) and steel. The joining process uses laser heating to melt a thermoplastic CFRP matrix in contact with a metal substrate to create a physical bond upon cooling. During the cooling process, melted CFRP at different location has different solidification rate, leading to the shrinkage porosity in the CFRP. In this study, the laser Surfi-Sculpt® is used to prevent the formation of shrinkage porosity in CFRP. The effects of the morphology characteristics (protrusion height and density) on shrinkage porosity are investigated, and the thermal distribution and history during the joining is simulated to examine mechanism of shrinkage porosity suppression. The results show that formation of shrinkage porosity can be suppressed with the laser Surfi-Sculpt®, which is attributed to the change of heat conduction path. The protrusions conduct the heat from the interior of melted zone to steel, decreasing the heat accumulation at the interface and suppressing the formation of shrinkage porosity. After adopting this technique, the porosity can be reduced from 7.13% to 1.26% and the shear strength of the joint increases from 9.3 MPa to 30.8 MPa.

Physical Properties, Film Thickness, and Bond Strengths of Resin-Modified Glass Ionomer Cements According to Their Delivery Method.

To determine the effect of changing the dispensing or mixing method of resin-modified glass ionomer (RMGI) cements on their water sorption, solubility, film thickness, and shear bond strength. Disc-shaped specimens of RMGI cements (RelyX: Luting [handmix], Luting Plus [clicker-handmix], Luting Plus [automix], GC: Fuji PLUS [capsule-automix], FujiCEM 2 [automix], [n=10]) were prepared according to ISO standard 4049 for water sorption and solubility tests. Furthermore, the percentage of mass change, percentage of solubility, and percentage of water absorbed was also determined. Film thickness was measured according to ISO standard 9917-2; the mean of 5 measurements for each cement was calculated. Shear bond strength for each cement was determined according to ISO standard 29022 before and after thermocycling at 20,000 cycles, temperatures 5 to 55°C with a 15-second dwell time (n=10/subgroup). Two- and one-way ANOVA were used to analyze data for statistical significance (p < 0.05). Water sorptions of the RMGI cements were in close range (214-250 μg/mm3 ) with no statistical differences between counterparts (p > 0.05). RelyX Luting Plus (clicker-handmix) displayed lower solubility than its handmix and automix counterparts (p < 0.05). Film thickness of RelyX cements was significantly different (p < 0.05). RelyX Luting Plus (automix) had the lowest film thickness (19 μm) compared to its handmix (48 μm) and clicker-handmix (117 μm) counterparts (p < 0.05). GC Fuji PLUS (capsule-automix, 22 μm) was significantly lower than the automix version (GC FujiCEM 2, 127 μm) (p < 0.05). Shear bond strength of RelyX Luting Plus (automix) was significantly lower than its handmix and clicker-handmix versions (p < 0.05). GC Fuji PLUS (capsule-automix) was significantly higher than GC FujiCEM 2 (automix) (p < 0.05). The binary interaction of the two independent variables (dispensing/mixing method and thermocycling) was significant for the shear bond strengths of the GC cements only (p < 0.05). Change in the dispensing/mixing method of RMGI cement from the same brand may have an effect on its physical properties, in addition to its film thickness and shear bond strength. Newer, easier, and faster cement delivery systems are not necessarily better. Clinical outcomes of these differences are yet to be confirmed.

Dispersion and stability of graphene nanoplatelet in water and its influence on cement composites

Cement nanocomposites were fabricated by slight modification of existing casting method to introduce graphene nanoplatelet (GNP) into cement paste. Dispersant dosage and ultrasonication time were varied to seek the optimum dispersion effectiveness. The stability of sonicated GNPs in suspension was assessed quantitatively by light absorbance over time and results suggested that 1 h of sonication and 15% of surfactant was sufficient to produce a 1% GNP suspension that remains stable for 6 h. Particle strengthening effect was obtained through the strong physical bond at the graphene interface, which was reflected by the doubling of the hardness. Mercury intrusion testing indicated that GNP could reduce the effective porosity and refine the critical pore diameter, particularly at the concentration of 1% GNP where reductions of 37% and 30% on the effective porosity and critical pore diameter were found respectively.