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Achieving strong filler/matrix interactions is essential in the design and manufacturing of composite systems. Molecular dynamics simulation has played a vital role in the investigation of interfacial behavior by predicting the mechanical properties of polymer-based composites. There has been, however, a big gap for clearly establishing a correlation between simulations and experiments because of limitations in size and time scale. Herein, a comparative analysis on the interfacial adhesion behavior of the short glass fiber and dental resin matrix is performed combining the atomistic simulations and single fiber/microdroplet pull-out tests in micro-scale. The interfacial shear strength is measured at the molecular level by applying the scale factor on the glass fiber, and the simulations are compared with the experimental results of the pull-out tests. The enhanced reinforcement effects induced by the surface modification via silane coupling agents grafting on the glass fibers are verified in both studies. Moreover, the mechanical properties and dynamic behavior of the dental composites under the longitudinal and transverse tension loadings are examined with quantifying the free volume changes. The findings of this research provide the optimized design guidelines to precisely predict the mechanical performances of the short fiber reinforced dental composites via molecular dynamics simulations and experiments.

The influence of interfacial shear strength (IFSS) between processed short S-glass fibers (250 and 350 μm in length, 5 μm in diameter) and the dental resin (a mixture of urethane dimethacrylate and triethylene glycol dimethacrylate monomers) on the mechanical properties has been studied experimentally. The surface profile of short S-glass fibers was modified using a selective atomic level metal etching process and simple silanization process to enhance the interfacial properties. The S-glass fibers were etched in acid solutions to increase the surface roughness and selectively remove Al3+ and Mg2+ ions, which promoted the mechanical and chemical interfacial bonding reactions. The single glass fiber tensile and microdroplet pull-out tests were performed to investigate the effects of interfacial properties on the flexural strength of the resultant composites. The surface modified S-glass fibers showed an increase of 11-40% in IFSS compared to untreated glass fibers. Composites reinforced with 350 μm length glass fibers (AR-70), which were treated in piranha solution for 4 h, showed the highest improvement in overall mechanical properties, flexural strength (34.2%), modulus (9.7%), and breaking energy (51.9%), compared to the untreated fiber-reinforced composites. The modified Lewis-Nielsen equation was developed using the effective fiber length factor to accurately predict the modulus of the short fiber-reinforced composites and validated with experimental results.

Interfacial bonding between fibre and matrix is most critical to obtain enhanced mechanical properties of the resulting composites. Here we present a new surface tailoring method of selective wet etching and organosilicon monomers (3-(Trimethoxysilyl) propyl methacrylate, TMSPMA) deposition process on the short S-Glass fibre as a reinforcing material, resulting in increased mechanical retention and strong chemical bonding between glass fibres and polymer resin (a mixture of triethylene glycol dimethacrylate (TEGDMA) and urethane dimethacrylate (UDMA) monomers). The effect of surface modification on fibre matrix interfacial strength was investigated through microdroplet tests. An S-Glass fibre treated with piranha solution (a mixture of H 2 O 2 and H 2 SO 4 ) for 24 hours followed by TMSPMA surface silanization shows highest increase up to 39.6% in interfacial shear strength (IFSS), and critical fibre length could be reduced from 916.0 µm to 432.5 µm. We find the optimal surface treatment condition in that the flexural strength of dental composites reinforced by the S-Glass fibres enhanced up to 22.3% compared to the composites without fibre surface treatments. The significant elevation in strength is attributed to changes in the surface roughness of glass fibres at atomic scale, specifically by providing the multiplied spots of the chemical bridge and nano-mechanical interlocking. The findings offer a new strategy for advanced tailoring of short S-Glass fibres to maximise the mechanical properties of biomedical and dental composites.

Traditional polymerisation shrinkage (PS) measurement systems measure average PS of dental composites, but the true local PS varies along the length and breadth of the composite. The PS depends on the curing light intensity distribution, resultant degree of conversion (DOC) and the curing rate. In this paper, optical fibre Bragg grating (FBG) sensing based technology is used to measure the linear post-gel PS at multiple locations within dental composite specimens, and is correlated with DOC and curing rate. A commercial dental composite is used, and its post-gel PS and DOC are mapped using embedded fibre Bragg grating sensors at different curing conditions. The distance between the curing lamp and the composite specimen is varied which resulted in different intensity distribution across the specimen. The effect of curing light intensity distribution on PS, curing rate and DOC are investigated for demonstrating a relationship among them. It is demonstrated that FBG sensing method is an effective method to accurately profiling post-gel PS across the specimen.

While it is apparent that rare variation can play an important role in the genetic architecture of autism spectrum disorders (ASDs), the contribution of common variation to the risk of developing ASD is less clear. To produce a more comprehensive picture, we report Stage 2 of the Autism Genome Project genome-wide association study, adding 1301 ASD families and bringing the total to 2705 families analysed (Stages 1 and 2). In addition to evaluating the association of individual single nucleotide polymorphisms (SNPs), we also sought evidence that common variants, en masse, might affect the risk. Despite genotyping over a million SNPs covering the genome, no single SNP shows significant association with ASD or selected phenotypes at a genome-wide level. The SNP that achieves the smallest P-value from secondary analyses is rs1718101. It falls in CNTNAP2, a gene previously implicated in susceptibility for ASD. This SNP also shows modest association with age of word/phrase acquisition in ASD subjects, of interest because features of language development are also associated with other variation in CNTNAP2. In contrast, allele scores derived from the transmission of common alleles to Stage 1 cases significantly predict case status in the independent Stage 2 sample. Despite being significant, the variance explained by these allele scores was small (Vm < 1%). Based on results from individual SNPs and their en masse effect on risk, as inferred from the allele score results, it is reasonable to conclude that common variants affect the risk for ASD but their individual effects are modest.

Qualitative researchers, by the very nature of their endeavours, are likely to undertake projects which involve exploration into the intimate crevices of people’s lives. Feminist research further plumbs the depths of such exploration into the lives and experiences of women. Frequently such research will involve topics considered to be of a sensitive nature because of the threats that they pose to the research participants’ emotional, spiritual and psychic integrity. Whereas one of the basic tenets of feminist research is that the participants should not be exposed to harm, it should follow that a feminist research method such as memory-work must not be deleterious. While the focus of this paper is a discussion of some of the issues which I uncovered during the use of memory-work into the social construction of women’s sexuality in the 1960s, I also refer to issues which arose during my initial attempt to use memory-work as part of a larger project which investigated the meaning of losing a baby to adoption (Farrar, 2000).

Qualitative researchers, by the very nature of their endeavours, are likely to undertake projects which involve exploration into the intimate crevices of people’s lives. Feminist research further plumbs the depths of such exploration into the lives and experiences of women. Frequently such research will involve topics considered to be of a sensitive nature because of the threats that they pose to the research participants’ emotional, spiritual and psychic integrity. Whereas one of the basic tenets of feminist research is that the participants should not be exposed to harm, it should follow that a feminist research method such as memory-work must not be deleterious. While the focus of this paper is a discussion of some of the issues which I uncovered during the use of memory-work into the social construction of women’s sexuality in the 1960s, I also refer to issues which arose during my initial attempt to use memory-work as part of a larger project which investigated the meaning of losing a baby to adoption (Farrar, 2000).

It is well documented that ocean swell arrives at the U.S. Pacific coast especially southern California, from the Southern Ocean during the Northern Hemisphere summer. This swell can have a major impact on sand transport in the littoral zone as it shoals and breaks on the beach. Hindcast wave information for this region does not contain this component of the wave climate. This report describes a method by which this swell can be included in future wave hindcasts. Buoy wave measurements are analyzed to identify and characterize swell from the Southern Hemisphere. The Wave Information Study wave model WISWAVE 2.0 is used to hindcast swell from a hypothetical storm in the Southern Hemisphere as well as actual storms during the summers of 1988 and 1989. Hindcast results are compared to theory and measurements. Swell heights calculated by the model tend to be higher than those determined from measurements. Differences are attributed to loss of swell energy during propagation through the south Pacific islands not represented in the model and possibly to inaccurate wind speeds and directions over the Southern Ocean. Despite differences, the approach is considered practical if model results are calibrated to measurements.

Twenty years of hindcast significant height, peak period, and mean direction wave information is summarized for 35 North Pacific locations in four data products: (1) percent occurrence tables; (2) Wave rose diagrams; (3) Mean and largest H sub s and 20-year statistics tables; Return period table. Brief descriptions and examples for each product are also provided.

Twenty years of hindcast significant height, peak period, and mean direction wave information is summarized for 53 North Pacific locations in four data products: a. Percent occurrence tables. b. Wave rose diagrams. c. Mean and largest H sub s (Significant wave height) and 20-year statistics tables. d. Return period table. Brief descriptions and examples for each data product are provided also. Keywords: North Pacific Ocean; Ocean waves; Wind waves statistical data.

Supersedes AD-425 208.

Supersedes AD-483 735.

In order to develop titanium alloys with higher ductilities and 0.1% yield strengths in the range of 190,000 to 240,000 psi and usable ductility in the range from 240,000 to 260,000 psi, a total of 57 eight-pound and 2 ten-pound ingots were investigated. Eight alloys which showed promising properties in the 190,000-240,000 psi range as 8 lb. ingots were remelted as 80 lb. ingots for further evaluation as bar, plate and sheet material. Tensile tests at room temperature and -40F impact tests were performed on the bar stock and the plate for the eight ingots. In addition, elevated and low temperature impact, as well as smooth and notch bar tests, were performed on the 1/2 inch bar for the most promising heat treatments. The sheet material was tested at room temperature with the most promising heat treatments being tested at -320F, +400F, +600F, with some of the alloys being tested at +800F and 1000F as well. In addition, limited welding tests were run on the sheet. (Author)

In order to develop titanium alloys with higher ductilities and 0.1% yield strengths in the range of 190,000 to 240,000 psi and usable ductility in the range from 240,000 to 260,000 psi, 30 eight pound ingots were investigated and an additional 26 eight pound ingots are now being evaluated. Four alloys which showed promising properties in the 190,000-240,000 psi range as 8 Lb. ingots were remelted as 80 Lb. ingots for further evaluation as bar, plate and sheet material. Tensile tests at room temperature and -40F impact tests have been completed for three of the alloys at different heat treatments and the data is tabulated in this report. (Author)

In order to develop titanium alloys with higher ductilities and 0.1% yield strengths in the range of 190,000 to 240,000 psi and usable ductility in the range from 240,000 to 260,000 psi, a total of 53 eight-pound ingots were investigated. An additional 3 eight-lb. iodide Ti base ingots are being prepared. Four alloys which showed promising properties in the 190,000-240,000 psi range as 8-lb. ingots were remelted as 80-lb. ingots for further evaluation as bar, plate and sheet material. Tensile tests at room temperature and -40 F impact tests were completed on the bar stock and the plate for the four ingots, and welding tests were conducted on the sheet material. Elevated and low temperature tests on the bar stock were completed and the data are included. The compositions of four additional alloys to be evaluated as 80-lb. ingots were selected and preparation of the ingots was begun. (Author)