Deterioration of Iowa Highway Concrete Pavements: A Petrographic Study, HR-1065, 1999

Major highway concrete pavements in Iowa have exhibited premature deterioration attributed to effects of ettringite formation, alkali-silica expansive reactions, and to frost attack, or some combination of them. These pavements were constructed in the mid- 1980s as non-reinforced, dual-lane, roads ranging in thickness between 200 mm and 300 mm, with skewed joints reinforced with dowels. Deterioration was initially recognized with a darkening of joint regions, which occurred for some pavements as soon as four years after construction. Pavement condition ranges from severe damage to none, and there appeared to be no unequivocal materials or processing variables correlated with failure. Based upon visual examinations, petrographic evaluation, and application of materials models, the deterioration of concrete highway pavements in Iowa appear related to a freeze-thaw failure of the coarse aggregate and the mortar. Crack patterns sub-parallel to the concrete surface transecting the mortar fraction and the coarse aggregate are indicative of freeze-thaw damage of both the mortar and aggregate. The entrained air void system was marginal to substandard, and filling of some of the finer-sized voids by ettringite appears to have further degraded the air void system. The formation of secondary ettringite within the entrained air voids probably reflects a relatively high degree of concrete saturation causing the smaller voids to be filled with pore solution when the concrete freezes. Alkali-silica reaction (ASR) affects some quartz and shale in the fine aggregate, but is not considered to be a significant cause of the deterioration. Delayed ettringite formation was not deemed likely as no evidence of a uniform paste expansion was observed. The lack of field-observed expansion is also evidence against the ASR and DEF modes of deterioration. The utilization of fly ash does not appear to have affected the deterioration as all pavements with or without fly ash exhibiting substantial damage also exhibit significant filling of the entrained air void system, and specimens containing fly ash from sound pavements do not have significant filling. The influence of the mixture design, mixing, and placing must be evaluated with respect to development of an adequate entrained air void system, concrete homogeneity, longterm drying shrinkage, and microcracking. A high-sand mix may have contributed to the difficult mixture characteristics noted upon placement and exacerbate concrete heterogeneity problems, difficulty in developing an adequate entrained air void system, poor consolidation potential, and increased drying shrinkage and cracking. Finally, the availability of moisture must also be considered, as the secondary precipitation of ettringite in entrained air voids indicates they were at least partially filled with pore solution at times. Water availability at the base of the slabs, in joints, and cracks may have provided a means for absorbing water to a point of critical saturation.

Portland Cement Concrete Curing Compound Performance Phase I and Phase II, MLR-02-03, 2003

Testing the efficiency of Portland Cement Concrete (PCC) curing compounds is currently done following Test Method Iowa 901-D, May 2002. Concrete test specimens are prepared from mortar materials and are wet cured 5 hours before the curing compound is applied. All brands of curing compound submitted to the Iowa Department of Transportation are laboratory tested for comparative performance under the same test conditions. These conditions are different than field PCC paving conditions. Phase I tests followed Test Method Iowa 901-D, but modified the application amounts of the curing compound. Test results showed that the application of two coats of one-half thickness each increased efficiency compared to one full thickness coat. Phase II tests also used the modified application amounts, used a concrete mix (instead of a mortar mix) and applied curing compound a few minutes after molding. Measurements of losses, during spraying of the curing compound, were noted and were found to be significant. Test results showed that application amounts, testing techniques, concrete specimen mix design and spray losses do influence the curing compound efficiency. The significance of the spray losses indicates that the conventional test method being used (Iowa 901 D) should be revised.

Optimization and Management of Materials in Earthwork Construction, TR-501, 2010

As a result of forensic investigations of problems across Iowa, a research study was developed aimed at providing solutions to identified problems through better management and optimization of the available pavement geotechnical materials and through ground improvement, soil reinforcement, and other soil treatment techniques. The overall goal was worked out through simple laboratory experiments, such as particle size analysis, plasticity tests, compaction tests, permeability tests, and strength tests. A review of the problems suggested three areas of study: pavement cracking due to improper management of pavement geotechnical materials, permeability of mixed-subgrade soils, and settlement of soil above the pipe due to improper compaction of the backfill. This resulted in the following three areas of study: (1) The optimization and management of earthwork materials through general soil mixing of various select and unsuitable soils and a specific example of optimization of materials in earthwork construction by soil mixing; (2) An investigation of the saturated permeability of compacted glacial till in relation to validation and prediction with the Enhanced Integrated Climatic Model (EICM); and (3) A field investigation and numerical modeling of culvert settlement. For each area of study, a literature review was conducted, research data were collected and analyzed, and important findings and conclusions were drawn. It was found that optimum mixtures of select and unsuitable soils can be defined that allow the use of unsuitable materials in embankment and subgrade locations. An improved model of saturated hydraulic conductivity was proposed for use with glacial soils from Iowa. The use of proper trench backfill compaction or the use of flowable mortar will reduce the potential for developing a bump above culverts.

Seal properties of TachoSil: in vitro hemodynamic measurements.

Fibrin glue products and collagen patches are frequently used as a sealing product, preventing surgical side bleedings. This is especially true in the field of cardiovascular surgery, where increasing numbers of patients are being operated with antiplatelet and anticoagulation therapy. The aim of this report was, in an in vitro hemodynamic setting, to examine the sealant properties of the TachoSil (Nycomed Pharma, Linz, Austria) patch. Burst pressure and normal force of 15 TachoSil sealed defects were measured. This was determined in a closed hydraulic system. Mean burst pressure load for a 5-mm defect was 69+/-11.4 mmHg; for a 7-mm defect was 63+/-16 mmHg; and, 62+/-16 mmHg for the defect with a diameter of 10 mm (P>0.05). The mean calculated normal force was as follows: 0.91+/-0.15 N for the 5 mm defect, 6.5+/-1.6 N for the 7 mm, and 8.1+/-0.75 N for the 10 mm defect. The TachoSil patch has the capability to seal small defects. However, at the larger defects the seal character was significantly reduced. These results suggest that the device may be a good alternative for hemostasis for small defects. The capacity to curtail or stop hemorrhage at the larger defects is unlikely.

Maintenance and Design of Steel Abutment Piles in Iowa Bridges, TR-622, 2014

Soil consolidation and erosion caused by roadway runoff have exposed the upper portions of steel piles at the abutments of numerous bridges, leaving them susceptible to accelerated corrosion rates due to the abundance of moisture, oxygen, and chlorides at these locations. This problem is compounded by the relative inaccessibility of abutment piles for close-up inspection and repair. The objective of this study was to provide bridge owners with recommendations for effective methods of addressing corrosion of steel abutment piles in existing and future bridges A review of available literature on the performance and protection of steel piles exposed to a variety of environments was performed. Eight potential coating systems for use in protecting existing and/or new piles were selected and subjected to accelerated corrosion conditions in the laboratory. Two surface preparation methods were evaluated in the field and three coating systems were installed on three piles at an existing bridge where abutment piles had been exposed by erosion. In addition, a passive cathodic protection (CP) system using sacrificial zinc anodes was tested in the laboratory. Several trial flowable mortar mixes were evaluated for use in conjunction with the CP system. For existing abutment piles, application of a protective coating system is a promising method of mitigating corrosion. Based on its excellent performance in accelerated corrosion conditions in the laboratory on steel test specimens with SSPC-SP3, -SP6, and -SP10 surface preparations, glass flake polyester is recommended for use on existing piles. An alternative is epoxy over organic zinc rich primer. Surface preparation of existing piles should include abrasive blast cleaning to SSPC-SP6. Although additional field testing is needed, based on the results of the laboratory testing, a passive CP system could provide an effective means of protecting piles in existing bridges when combined with a pumped mortar used to fill voids between the abutment footing and soil. The addition of a corrosion inhibitor to the mortar appears to be beneficial. For new construction, shop application of thermally sprayed aluminum or glass flake polyester to the upper portion of the piles is recommended.

Stable masking by H-2Dd cis ligand limits Ly49A relocalization to the site of NK cell/target cell contact.

Ly49A is an inhibitory receptor, which counteracts natural killer (NK) cell activation on the engagement with H-2D(d) (D(d)) MHC class I molecules (MHC-I) on target cells. In addition to binding D(d) on apposed membranes, Ly49A interacts with D(d) ligand expressed in the plane of the NK cells' membrane. Indeed, multivalent, soluble MHC-I ligand binds inefficiently to Ly49A unless the NK cells' D(d) complexes are destroyed. However, it is not known whether masked Ly49A remains constitutively associated with cis D(d) also during target cell interaction. Alternatively, it is possible that Ly49A has to be unmasked to significantly interact with its ligand on target cells. These two scenarios suggest distinct roles of Ly49A/D(d) cis interaction for NK cell function. Here, we show that Ly49A contributes to target cell adhesion and efficiently accumulates at synapses with D(d)-expressing target cells when NK cells themselves lack D(d). When NK cells express D(d), Ly49A no longer contributes to adhesion, and ligand-driven recruitment to the cellular contact site is strongly reduced. The destruction of D(d) complexes on NK cells, which unmasks Ly49A, is necessary and sufficient to restore Ly49A adhesive function and recruitment to the synapse. Thus, cis D(d) continuously sequesters a considerable fraction of Ly49A receptors, preventing efficient Ly49A recruitment to the synapse with D(d)+ target cells. The reduced number of Ly49A receptors that can functionally interact with D(d) on target cells explains the modest inhibitory capacity of Ly49A in D(d) NK cells. This property renders Ly49A NK cells more sensitive to react to diseased host cells.

Clinical effectiveness of direct class II restorations: a meta-analysis.

Purpose: More than five hundred million direct dental restorations are placed each year worldwide. In about 55% of the cases, resin composites or compomers are used, and in 45% amalgam. The longevity of posterior resin restorations is well documented. However, data on resin composites that are placed without enamel/dentin conditioning and resin composites placed with self-etching adhesive systems are missing. Material and Methods: The database SCOPUS was searched for clinical trials on posterior resin composites without restricting the search to the year of publication. The inclusion criteria were: (1) prospective clinical trial with at least 2 years of observation; (2) minimum number of restorations at last recall = 20; (3) report on dropout rate; (4) report of operative technique and materials used; (5) utilization of Ryge or modified Ryge evaluation criteria. For amalgam, only those studies were included that directly compared composite resin restorations with amalgam. For the statistical analysis, a linear mixed model was used with random effects to account for the heterogeneity between the studies. P-values under 0.05 were considered significant. Results: Of the 373 clinical trials, 59 studies met the inclusion criteria. In 70% of the studies, Class II and Class I restorations had been placed. The overall success rate of composite resin restorations was about 90% after 10 years, which was not different from that of amalgam. Restorations with compomers had a significantly lower longevity. The main reason for replacement were bulk fractures and caries adjacent to restorations. Both of these incidents were infrequent in most studies and accounted only for about 6% of all replaced restorations after 10 years. Restorations with macrofilled composites and compomer suffered significantly more loss of anatomical form than restorations with other types of material. Restorations that were placed without enamel acid etching and a dentin bonding agent showed significantly more marginal staining and detectable margins compared to those restorations placed using the enamel-etch or etch-and-rinse technique; restorations with self-etching systems were between the other groups. Restorations with compomer suffered significantly more chippings (repairable fracture) than restorations with other materials, which did not statistically differ among each other. Restorations that were placed with a rubber-dam showed significantly fewer material fractures that needed replacement, and this also had a significant effect on the overall longevity. Conclusion: Restorations with hybrid and microfilled composites that were placed with the enamel-etching technique and rubber-dam showed the best overall performance; the longevity of these restorations was similar to amalgam restorations. Compomer restorations, restorations placed with macrofilled composites, and resin restorations with no-etching or self-etching adhesives demonstrated significant shortcomings and shorter longevity.

A study of the effects of PVAC on works of art on paper and wood: pH and colour change

This paper presents the preliminary findings of pH and colour measurements carried out on artworks on paperand on wood that had been treated with a poly(vinyl acetate) (PVAC) based adhesive in the 1980s. In both cases, areas treated with PVAC proved to be less acidic than untreated areas. Contrary to expectations, the conservation treatments have not, as yet, increased acidity levels in the objects under study. Colour measurements of the works on paper showed that those that had been backed with a cotton fabric using a mixture of methylcellulose and PVAC were less yellow than those from the same print run that had not been backed. This finding suggests that the backing somehow prevented the natural degradation of the support. In view of these preliminary results, further research is clearly needed. This study forms part of a broader ongoing project to assess the role of PVAC in the conservation of a range of cultural assets.

A study of the effects of PVAC on works of art on paper and wood: pH and colour change

This paper presents the preliminary findings of pH and colour measurements carried out on artworks on paperand on wood that had been treated with a poly(vinyl acetate) (PVAC) based adhesive in the 1980s. In both cases, areas treated with PVAC proved to be less acidic than untreated areas. Contrary to expectations, the conservation treatments have not, as yet, increased acidity levels in the objects under study. Colour measurements of the works on paper showed that those that had been backed with a cotton fabric using a mixture of methylcellulose and PVAC were less yellow than those from the same print run that had not been backed. This finding suggests that the backing somehow prevented the natural degradation of the support. In view of these preliminary results, further research is clearly needed. This study forms part of a broader ongoing project to assess the role of PVAC in the conservation of a range of cultural assets.

Redefining dropping out in online higher education: a case study from the UOC

In recent years, studies into the reasons for dropping out of higher education (including online education) have been undertaken with greater regularity, parallel to the rise in the relative weight of this type of education, compared with brick-and-mortar education. However, the work invested in characterising the students who drop out of education, compared with those who do not, appears not to have had the same relevance as that invested in the analysis of the causes. The definition of dropping out is very sensitive to the context. In this article, we reach a purely empirical definition of student dropping out, based on the probability of not continuing a specific academic programme following several consecutive semesters of "theoretical break". Dropping out should be properly defined before analysing its causes, as well as comparing the drop-out rates between the different online programmes, or between online and on-campus ones. Our results show that there are significant differences among programmes, depending on their theoretical extension, but not their domain of knowledge.

Development of Craniofacial Bone Defect Reconstruction Implant Based on Fibre-Reinforced Composite with Photopolymerisable Resin Systems. Experimental studies in vitro and in vivo.

Reconstruction of defects in the craniomaxillofacial (CMF) area has mainly been based on bone grafts or metallic fixing plates and screws. Particularly in the case of large calvarial and/or craniofacial defects caused by trauma, tumours or congenital malformations, there is a need for reliable reconstruction biomaterials, because bone grafts or metallic fixing systems do not completely fulfill the criteria for the best possible reconstruction methods in these complicated cases. In this series of studies, the usability of fibre-reinforced composite (FRC) was studied as a biostable, nonmetallic alternative material for reconstructing artificially created bone defects in frontal and calvarial areas of rabbits. The experimental part of this work describes the different stages of the product development process from the first in vitro tests with resin-impregnated fibrereinforced composites to the in vivo animal studies, in which this FRC was tested as an implant material for reconstructing different size bone defects in rabbit frontal and calvarial areas. In the first in vitro study, the FRC was polymerised in contact with bone or blood in the laboratory. The polymerised FRC samples were then incubated in water, which was analysed for residual monomer content by using high performance liquid chromatography (HPLC). It was found that this in vitro polymerisation in contact with bone and blood did not markedly increase the residual monomer leaching from the FRC. In the second in vitro study, different adhesive systems were tested in fixing the implant to bone surface. This was done to find an alternative implant fixing system to screws and pins. On the basis of this study, it was found that the surface of the calvarial bone needed both mechanical and chemical treatments before the resinimpregnated FRC could be properly fixed onto it. In three animal studies performed with rabbit frontal bone defects and critical size calvarial bone defect models, biological responses to the FRC implants were evaluated. On the basis of theseevaluations, it can be concluded that the FRC, based on E-glass (electrical glass) fibres forming a porous fibre veil enables the ingrowth of connective tissues to the inner structures of the material, as well as the bone formation and mineralization inside the fibre veil. Bone formation could be enhanced by using bioactive glass granules fixed to the FRC implants. FRC-implanted bone defects healed partly; no total healing of defects was achieved. Biological responses during the follow-up time, at a maximum of 12 weeks, to resin-impregnated composite implant seemed to depend on the polymerization time of the resin matrix of the FRC. Both of the studied resin systems used in the FRC were photopolymerised and the heat-induced postpolymerisation was used additionally.

Tarkkuusannostelulaitteen kehittäminen

Prosessiteollisuuden aloilla, kuten lasin raaka-ainelaitoksissa ja laasti- ja tasoitetehtaissa, prosessin onnistumisen kannalta jauhemaisten raaka-aineiden tarkka annostelu on avainasemassa. Diplomityön tarkoituksena oli kehittää olemassa olevan idean pohjalta uusi materiaalin annostelulaite jauhemaisille ja fluidisoituville aineille. Tavoitteena oli suunnitella annostelulaite toimivalle prototyyppiasteelle ja saamaan siitä informaatiota materiaalilaboratoriossa tehtävien annostuskokeiden avulla. Työssä tarkasteltiin aluksi yleisesti jauhemaisen aineen ominaisuuksia ja ongelmia, tyypillisiä annostelulaitteita ja annostustarkkuuteen ja punnitustarkkuuteen vaikuttavia tekijöitä. Varsinainen laitekehitys eteni tyypillisen tuotekehitystyön mukaisesti. Annostuslaite kattaa laaj an dynaamisen toiminta-alueen eli massavirran säätömandollisuus on samalla toimilaitteella aikaisempia annostelulaitteita laajempi. Laite soveltuu erittäin tarkkaan annostukseen hyvin lyhyellä annostusajalla. Hyvät ja luotettavat annostusjärjestelmät myötävaikuttavat merkittävästi koko tehdaskaupan saamiseen, koska asiakas säästää työvoimakustannuksissa ja laatukustannuksissa. Kehittämällä jauhemaisten aineiden annostusta saadaan tekninen etumatka kilpailijoihin nähden.

A support system for evaluating a suitable joining method in the production of sheet metal goods

This report illustrates a comparative study of various joining methods involved in sheet metal production. In this report it shows the selection of joining methods, which includes comparing the advantages and disadvantages of a method over the other ones and choosing the best method for joining. On the basis of various joining process from references, a table is generated containing set of criterion that helps in evaluation of various sheet metal joining processes and in selecting the most suitable process for a particular product. Three products are selected and a comprehensive study of the joining methods is analyzed with the help of various parameters. The table thus is the main part of the analysis process of this study and can be advanced with the beneficial results. It helps in a better and easy understanding and comparing the various methods, which provides the foundation of this study and analysis. The suitability of the joining method for various types of cases of different sheet metal products can be tested with the help of this table. The sections of the created table display the requirements of manufacturing. The important factor has been considered and given focus in the table, as how the usage of these parameters is important in percentages according to particular or individual case. The analysis of the methods can be extended or altered by changing the parameters according to the constraint. The use of this table is demonstrated by pertaining the cases from sheet metal production.

Effect of water contamination on the shear bond strength of five orthodontic adhesives

Objectives: To evaluate the shear bond strength and site of failure of brackets bonded to dry and wet enamel. Study design: 50 teeth were divided into ten groups of 5 teeth each (10 surfaces). In half the groups enamel was kept dry before bonding, and in the other half distilled water was applied to wet the surface after etching. The following groups were established: 1)Acid/Transbond-XT (dry/wet) XT; 2) Transbond Plus Self Etching Primer (TSEP)/Transbond-XT paste (dry/wet); 3) Concise (dry), Transbond MIP/Concise (wet), 4) FujiOrtho-LC (dry/wet); 5) SmartBond (dry/wet). Brackets were bonded to both buccal and lingual surfaces. Specimens were stored in distilled water (24 hours at 37ºC) and thermocycled. Brackets were debonded using a Universal testing machine (cross-head speed 1 mm/min). Failure sites were classified using a stereomicroscope. Results: No significant differences in bond strength were detected between the adhesives under wet and dry conditions except for Smart- Bond, whose bond strength was significantly lower under dry conditions. For all the adhesives most bond failures were of mixed site location except for Smartbond, which failed at the adhesive-bracket interface. Conclusions: Under wet conditions the bonding capacity of the adhesives tested was similar than under dry conditions, with the exception of SmartBond which improved under wet conditions

Terässiilojen mitoitusohjelman kehittäminen

Siiloja käytetään jauhemaisten ja rakeisten aineiden varastointiin ja annosteluun maataloudessa sekä mm. lasi-, laasti- ja tasoiteteollisuudessa. Tällaiset laitokset toimitetaan usein kokonaistoimituksina, joissa tavanomaisten teräsrakenteiden kustannusvaikutus voi olla jopa 30 % koko toimituksen arvosta. Niinpä osaltaan siilojen tehokkaalla mitoituksella ja erilaisiarakenneratkaisuja vertailemalla voidaan alentaa toimitusten kokonaiskustannuksia. Tässä diplomityössä perehdyttiin siilojen rakenteisiin ja niiden lujuustekniseen mitoitukseen etenkin tuentaratkaisujen osalta. Mitoituksen osalta työssä perehdyttiin pääasiassa uusiin Eurooppalaisiin standardeihin SFS-EN 1991-4 ja SFS-EN 1993-4-1. Niiden mukaan määritetään mitoituskuormat sekä tehdään lujuustekninen mitoitus. Työn tuloksena laadittiin Microsoft Excel -pohjainen mitoitusohjelma, jolla voidaan nopeasti mitoittaa siilojen olennaisimmat teräsrakenteet. Ohjelmalla voidaan määrittää mitoitus koskien siilon lieriön ja kartion seinämiä sekä tuentaratkaisuja. Ohjelma nopeuttaa erityisesti tarjousvaiheen suunnittelua ja antaa pohjan varsinaiselle siilojen yksityiskohtaiselle mitoittamiselle ja suunnittelulle.