bluuebunny/crossref_metadata_2025 huggingface dataset:
Expression of interleukin-1 (IL-1) ligands system in the most common endometriosis-associated ovarian cancer subtypes
Authors: Keita Mamadou , Bessette Paul , Pelmus Manuella , Ainmelk Youssef , Aris Aziz
Published: January 2010

Objectives

Endometrioid carcinoma of the ovary is one of the most types of epithelial ovarian cancer associated to endometrioisis. Endometrioid tumors as well as endometriotic implants are characterized by the presence of epithelial cells, stromal cells, or a combination of booth, that resemble the endometrial cells, suggesting a possible endometrial origin of these tumors. Pro-inflammatory cytokines, including interleukin-1 (IL-1) have been reported to be involved in both endometriosis and ovarian carcinogenesis. The major objective of this study was to determine the level expression of IL-1 ligands system (IL-1α, IL-1β and IL-1RA) in the most common subtypes of ovarian cancer cells compared to endometrial cells.

Methods

We used primary endometrial cells, endometrial cell line RL-952 and different subtypes of epithelial ovarian cancer cell lines including TOV-112D (endometrioid), TOV-21G (clear cell) and OV-90 (serous). Immunofluorescence and real-time PCR analysis were used respectively for detecting IL-1 ligands at the levels of cell-associated protein and mRNA. Soluble IL-1 ligands were analyzed by ELISA.

Results

We demonstrated that IL-1 ligands were expressed by all endometriosis-associated ovarian cancer subtypes and endometrial cells. In contrast to other cancer ovarian cells, endometrioid cells exhibit a specific decrease of cell-associated IL-1RA expression and its soluble secretion.

Conclusion

Endometrioid ovarian cancer exhibits an alteration in the expression of IL-1RA, a key protector against tumorogenic effects of IL-1. This alteration evokes the same alteration observed in endometriotic cells in previous studies. This suggests a possible link between the endometrium, the tissue ectopic endometriosis and endometrioid ovarian cancer.
Characterization of X-Linked SNP genotypic variation in globally distributed human populations
Authors: Casto Amanda M , Li Jun Z , Absher Devin , Myers Richard , Ramachandran Sohini , Feldman Marcus W
Published: January 2010

Background

The transmission pattern of the human X chromosome reduces its population size relative to the autosomes, subjects it to disproportionate influence by female demography, and leaves X-linked mutations exposed to selection in males. As a result, the analysis of X-linked genomic variation can provide insights into the influence of demography and selection on the human genome. Here we characterize the genomic variation represented by 16,297 X-linked SNPs genotyped in the CEPH human genome diversity project samples.

Results

We found that X chromosomes tend to be more differentiated between human populations than autosomes, with several notable exceptions. Comparisons between genetically distant populations also showed an excess of X-linked SNPs with large allele frequency differences. Combining information about these SNPs with results from tests designed to detect selective sweeps, we identified two regions that were clear outliers from the rest of the X chromosome for haplotype structure and allele frequency distribution. We were also able to more precisely define the geographical extent of some previously described X-linked selective sweeps.

Conclusions

The relationship between male and female demographic histories is likely to be complex as evidence supporting different conclusions can be found in the same dataset. Although demography may have contributed to the excess of SNPs with large allele frequency differences observed on the X chromosome, we believe that selection is at least partially responsible. Finally, our results reveal the geographical complexities of selective sweeps on the X chromosome and argue for the use of diverse populations in studies of selection.
Zapotec Time, Alphabetic Writing, and the Public Sphere
Authors: Tavárez David
Published: January 2010

In this essay, I analyze a sample drawn from a corpus of about 107 alphabetic texts that were produced in a clandestine manner by Zapotec ritual specialists in northern Oaxaca, Mexico, during the second half of the seventeenth century. I argue that these texts represent an unusual appropriation of the Latin alphabet and of European literacy practices by local indigenous intellectuals. This development led to the inception of a novel textual genre, the biyee, an alphabetic, pluralistic, multilayered rendering of the Zapotec 260-day divinatory calendar. I also contend that, as they moved along social networks, these calendars mapped out literate modes of transmission of cosmological knowledge that linked individual specialists with both collective spheres and individual social spaces. In the end, the circulation of these texts provided an essential core for the reproduction of a clandestine public sphere.
Reflections on What Writing Means, Beyond What It “Says”: The Political Economy and Semiotics of Graphic Pluralism in the Americas
Authors: Bender Margaret
Published: January 2010

Graphic representation is linked to meaning at a number of levels, among them those of orthographic system, text, and individual character. This essay explores the range of possible meanings of “the graphic” at these different levels, particularly in terms of political economy, language ideology, and multileveled semiotic functioning. As the illustrations discussed here suggest, writing and other forms of graphic representation powerfully connect the ideological and material cultural realms, and their patterns of use (including production, distribution, circulation, and consumption) reveal and enact social relationships and inequalities. The author reminds readers that to fully explore the rich implications of the graphic, scholars must expand their investigations beyond writing's capacity to represent spoken language and also investigate the iconic and indexical dimensions of graphic semiotic functioning.
QUEER THEORY AND NATIVE STUDIES
Authors: Smith Andrea
Published: January 2010

Queer studies highlights the importance of developing analyses that go beyond identity and representational politics. For Native studies in particular, queer theory points to the possibility of going beyond representing the voices of Native peoples, a project that can quickly become co-opted into providing Native commodities for consumption in the multicultural academic-industrial complex. The subjectless critique of queer theory can assist Native studies in critically interrogating how it could unwittingly re-create colonial hierarchies even within projects of decolonization. This critique also sheds light on how Native peoples function within the colonial imaginary—including the colonial imaginary of scholars and movements that claim to be radical. At the same time, Native studies can build on queer of color critique's engagement with subjectless critique. In the move to go “postidentity,” queer theory often reinstantiates a white supremacist, settler colonialism by disappearing the indigenous peoples colonized in this land who become the foils for the emergence of postcolonial, postmodern, diasporic, and queer subjects. With respect to Native studies, even queer of color critique does not necessarily mark how identities are shaped by settler colonialism. Thus a conversation between Native studies and queer theory is important, because the logics of settler colonialism and decolonization must be queered in order to properly speak to the genocidal present that not only continues to disappear indigenous peoples but reinforces the structures of white supremacy, settler colonialism, and heteropatriarchy that affect all peoples.
SUSPICIONING
Authors: Womack Craig
Published: January 2010

“Suspicioning” examines the silences that surround issues of same-sex desire in and out of the poetry of Joy Harjo.
VISIBLE SEXUALITIES OR INVISIBLE NATIONS
Authors: Tatonetti Lisa
Published: January 2010

This essay examines the construction of Two-Spirit identity in three contemporary narrative films, Big Eden, Johnny Greyeyes, and The Business of Fancydancing, arguing that, despite each story's focus on a queer Native protagonist, by their conclusions each film fractures Two-Spirit identities. Whereas Big Eden elides indigenous identity, Johnny Greyeyes and The Business of Fancydancing segregate indigeneity from queer sexuality, thereby relegating queerness entirely to off-reservation spaces. As this essay demonstrates, when the films' protagonists cross reservation lines, they literally leave behind their queer lovers and figuratively abandon all that those lovers represent when the storylines turn nearly exclusively to familial and cultural ties. As a result, such films suggest that the boundaries of nation in indigenous contexts are constructed and maintained by the heteronormative gaze and that Two-Spirit people are therefore forced to choose between sexual and national affiliations. This theme of division, in which indigenous affiliations with tribe and nation are split from expressions of queer sexuality, demonstrates how contemporary representations of Two-Spirit identities in narrative film continue to mirror the ongoing legacy of settler colonialism. In the case of Big Eden, Indian people, and thus any potential for actual Two-Spirit erotics, vanish completely under the weight of colonial desires; in the case of Johnny Greyeyes, though the aftermath of settler violence is both highlighted and healed by invoking a Two-Spirit relationship, articulations of Two-Spirit desire are bounded by the walls of the prison; and, finally, in the case of The Business of Fancydancing, regulating settler logics, which long degraded and denied Two-Spirit cosmologies, are replicated and, in fact, reinvigorated by deploying a gay imaginary that rests on dominant constructions of queerness.
Role of PIN-mediated auxin efflux in apical hook development ofArabidopsis thaliana
Authors: Žádníková Petra , Petrášek Jan , Marhavý Peter , Raz Vered , Vandenbussche Filip , Ding Zhaojun , Schwarzerová Kateřina , Morita Miyo T. , Tasaka Masao , Hejátko Jan , Van Der Straeten Dominique , Friml Jiří , Benková Eva
Published: January 2010

The apical hook of dark-grown Arabidopsis seedlings is a simple structure that develops soon after germination to protect the meristem tissues during emergence through the soil and that opens upon exposure to light. Differential growth at the apical hook proceeds in three sequential steps that are regulated by multiple hormones, principally auxin and ethylene. We show that the progress of the apical hook through these developmental phases depends on the dynamic, asymmetric distribution of auxin, which is regulated by auxin efflux carriers of the PIN family. Several PIN proteins exhibited specific, partially overlapping spatial and temporal expression patterns, and their subcellular localization suggested auxin fluxes during hook development. Genetic manipulation of individual PIN activities interfered with different stages of hook development, implying that specific combinations of PIN genes are required for progress of the apical hook through the developmental phases. Furthermore, ethylene might modulate apical hook development by prolonging the formation phase and strongly suppressing the maintenance phase. This ethylene effect is in part mediated by regulation of PIN-dependent auxin efflux and auxin signaling.
STIMPY mediates cytokinin signaling during shoot meristem establishment in Arabidopsis seedlings
Authors: Skylar Anna , Hong Fangxin , Chory Joanne , Weigel Detlef , Wu Xuelin
Published: January 2010

The establishment of the primary meristems through proliferation after germination is essential for plant post-embryonic development. Cytokinins have long been considered a key regulator of plant cell division. Here we show that cytokinins are essential for early seedling development of Arabidopsis. Loss of cytokinin perception leads to a complete failure of meristem establishment and growth arrest after germination. We also present evidence that cytokinin signaling is involved in activation of the homeobox gene STIMPY (STIP or WOX9) expression in meristematic tissues, which is essential for maintaining the meristematic fate. Cytokinin-independent STIP expression is able to partially compensate for the shoot apical meristem growth defects in mutants that cannot sense cytokinin. These findings identify a new branch of the cytokinin signaling network, linking cytokinin to the process of meristem and seedling establishment.
Digital nature of the immediate-early transcriptional response
Authors: Stevense Michelle , Muramoto Tetsuya , Müller Iris , Chubb Jonathan R.
Published: January 2010

Stimulation of transcription by extracellular signals is a major component of a cell's decision making. Yet the quantitative relationship between signal and acute transcriptional response is unclear. One view is that transcription is directly graded with inducer concentration. In an alternative model, the response occurs only above a threshold inducer concentration. Standard methods for monitoring transcription lack continuous information from individual cells or mask immediate-early transcription by measuring downstream protein expression. We have therefore used a technique for directly monitoring nascent RNA in living cells, to quantify the direct transcriptional response to an extracellular signal in real time, in single cells. At increasing doses of inducer, increasing numbers of cells displayed a transcriptional response. However, over the same range of doses, the change in cell response strength, measured as the length, frequency and intensity of transcriptional pulses, was small, with considerable variation between cells. These data support a model in which cells have different sensitivities to developmental inducer and respond in a digital manner above individual stimulus thresholds. Biased digital responses may be necessary for certain forms of developmental specification. Limiting bias in responsiveness is required to reduce noise in positional signalling.
Inactivation of sestrin 2 induces TGF-β signaling and partially rescues pulmonary emphysema in a mouse model of COPD
Authors: Wempe Frank , De-Zolt Silke , Koli Katri , Bangsow Thorsten , Parajuli Nirmal , Dumitrascu Rio , Sterner-Kock Anja , Weissmann Norbert , Keski-Oja Jorma , von Melchner Harald
Published: January 2010

Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality worldwide. Cigarette smoking has been identified as one of the major risk factors and several predisposing genetic factors have been implicated in the pathogenesis of COPD, including a single nucleotide polymorphism (SNP) in the latent transforming growth factor (TGF)-β binding protein 4 (Ltbp4)-encoding gene. Consistent with this finding, mice with a null mutation of the short splice variant of Ltbp4 (Ltbp4S) develop pulmonary emphysema that is reminiscent of COPD. Here, we report that the mutational inactivation of the antioxidant protein sestrin 2 (sesn2) partially rescues the emphysema phenotype of Ltbp4S mice and is associated with activation of the TGF-β and mammalian target of rapamycin (mTOR) signal transduction pathways. The results suggest that sesn2 could be clinically relevant to patients with COPD who might benefit from antagonists of sestrin function.
The regulatory protein RraA modulates RNA-binding and helicase activities of the E. coli RNA degradosome
Authors: Górna Maria W. , Pietras Zbigniew , Tsai Yi-Chun , Callaghan Anastasia J. , Hernández Helena , Robinson Carol V. , Luisi Ben F.
Published: January 2010

The Escherichia coli endoribonuclease RNase E is an essential enzyme having key roles in mRNA turnover and the processing of several structured RNA precursors, and it provides the scaffold to assemble the multienzyme RNA degradosome. The activity of RNase E is inhibited by the protein RraA, which can interact with the ribonuclease's degradosome-scaffolding domain. Here, we report that RraA can bind to the RNA helicase component of the degradosome (RhlB) and the two RNA-binding sites in the degradosome-scaffolding domain of RNase E. In the presence of ATP, the helicase can facilitate the exchange of RraA for RNA stably bound to the degradosome. Our data suggest that RraA can affect multiple components of the RNA degradosome in a dynamic, energy-dependent equilibrium. The multidentate interactions of RraA impede the RNA-binding and ribonuclease activities of the degradosome and may result in complex modulation and rerouting of degradosome activity.
Variational Conditions Under the Constant Rank Constraint Qualification
Authors: Lu Shu
Published: January 2010

This paper studies solution properties of a parametric variational condition under the constant rank constraint qualification (CRCQ), and properties of its underlying set. We start by showing that if the CRCQ holds at a point in a fixed set, then there exists a one-to-one correspondence between the collection of nonempty faces of the normal cone to the set at that point and the collection of active index sets at points nearby. We then study the behavior of the Euclidean projector, and prove under the CRCQ that the set of multipliers associated with the Euclidean projection is locally a continuous multifunction. Following that, we apply the degree theory to a localized normal map, to show that the combination of the CRCQ and the so-called strong coherent orientation condition suffices for the parametric variational condition to have a locally unique, continuous solution, which is selected from finitely many C1 functions. Applications of this result under additional assumptions extend or recover some earlier results on parametric variational inequalities.
On the One-Dimensional Optimal Switching Problem
Authors: Bayraktar Erhan , Egami Masahiko
Published: January 2010

We explicitly solve the optimal switching problem for one-dimensional diffusions by directly using the dynamic programming principle and the excessive characterization of the value function. The shape of the value function and the smooth fit principle then can be proved using the properties of concave functions.
Memory Loss Property for Products of Random Matrices in the Max-Plus Algebra
Authors: Merlet Glenn
Published: January 2010

Products of random matrices in the max-plus algebra are used as models of a wide range of discrete event systems, including train or queueing networks, job shops, timed digital circuits, or parallel processing systems. Several mathematical models such as timed event graph or task-resources models also lead to max-plus products of matrices.

Some stability and computability results, such as convergence of waiting times to a unique stationary regime or limit theorems for the throughput, have been proved under the so-called memory loss property (MLP).

When the random matrices are i.i.d., we prove that this property is generic in the following sense: if it is not fulfilled, the support of the common law of the random matrices is included in a union of finitely many affine hyperplanes.
Sharing the Cost of a Capacity Network
Authors: Bogomolnaia Anna , Holzman Ron , Moulin Hervé
Published: January 2010

We consider a communication network where each pair of users requests a connection guaranteeing a certain capacity. The cost of building capacity is identical across pairs. Efficiency is achieved by any maximal cost spanning tree. We construct cost sharing methods ensuring standalone core stability, monotonicity of one's cost share in one's capacity requests, and continuity in everyone's requests. We define a solution for simple problems where each pairwise request is zero or one, and extend it piecewise linearly to all problems. The uniform solution obtains if we require one's cost share to be weakly increasing in everyone's capacity request. In the solution, we propose, on the contrary, one's cost share is weakly decreasing in other agents' requests. The computational complexity of both solutions is polynomial in the number of users. The uniform solution admits a closed form expression, and is the analog of a popular solution for the minimal cost spanning tree problem.
Approximation Algorithms for Combinatorial Auctions with Complement-Free Bidders
Authors: Dobzinski Shahar , Nisan Noam , Schapira Michael
Published: January 2010

In a combinatorial auction m heterogenous indivisible items are sold to n bidders. This paper considers settings in which the valuation functions of the bidders are known to be complement free (a.k.a. subadditive). We provide several approximation algorithms for the social-welfare maximization problem in such settings. First, we present a logarithmic upper bound for the case that the access to the valuation functions is via demand queries. For the weaker value queries model we provide a tight O(√m) approximation. Unlike the other algorithms we present, this algorithm is also incentive compatible. Finally, we present two approximation algorithms for the more restricted class of XOS valuations: A simple deterministic algorithm that provides an approximation ratio of two and an optimal e/(e −1) approximation achieved via randomized rounding. We also present optimal lower bounds for both the demand oracles model and the value oracles model.
Legal Aspects of Surgical Practice
Authors: Hadfield Lisa
Published: January 2010

A 45-year-old lorry driver has been a patient under your care, having sustained multiple trauma that includes a closed head injury with bilateral frontal and temporal lobe contusions. His physical recovery is reasonable but he has problems with concentration and impairment of short-term memory. He tells you that despite a blackout he has returned to work as he is desperate for money to pay his mortgage, which is in arrears. You have already informed him of his duty to tell the DVLA about the change in his medical history and have told him he should not drive due to the blackout. During the consultation you reiterate this. You subsequently learn that he continues to drive his articulated lorry.
Laparoscopic simulator performance: Harrier fighter pilots versus medical and non-medical undergraduates
Authors: Tsim P , Carty H-M , Baxendale B , Ferguson E , Maxwell-Armstrong CA
Published: January 2010

There is increasing use of simulation in medical training, including laparoscopic surgery. This is a situation likely to increase as the number of hours spent in direct surgical training reduces as a result of the European Working Time Directive and the consequently decreased length of training. New skills are required by laparoscopic surgeons, including overcoming altered depth perception, translating 2D images into 3D anatomy, and familiarisation with laparoscopic instruments. These skills must be mastered in addition to those required by open surgeons: no transfer has been found between open surgical and new laparoscopic skills.
Practitioner research in social work: a knowledge review
Authors: Mitchell Fiona , Lunt Neil , Shaw Ian
Published: January 2010

This article reports what may be the first systematic mapping and review of practitioner research studies in social work. We reflect on the difficulties of identifying such studies and outline the review and mapping processes adopted in the study. The paper categorises the kinds of research undertaken, drawing on a recently developed framework; it also reports and assesses the research against its contribution to knowledge, its methodological standards and its pursuit of due ethical research process. Finally, the paper explores what is known regarding the utility of the research, its contribution to capacity building and its value for people, and closes with a discussion of the issues raised by the review.
A web-based tool for adjusting costs to a specific target currency and price year
Authors: Shemilt Ian , James Thomas , Marcello Morciano
Published: January 2010

Objective:

To develop a web-based tool to automate the adjustment of estimates of costs drawn from previously published or unpublished studies to a specified target currency and price year.

Methods:

A web-based tool was programmed using C#, utilising GDP deflator index values and Purchasing Power Parities conversion rates produced by the International Monetary Fund and the Organisation for Economic Co-operation and Development.

Results:

Version 1.0 is available at http://eppi.ioe.ac.uk/costconversion/default.aspx

Conclusions:

The tool can be used as a first-line approach to cost adjustment in non-healthcare applications and as an optional approach in healthcare applications when use of more sophisticated methods is not feasible.
Setting the research agenda for health services management practice: who decides?
Authors: Davies Stephen
Published: January 2010

The value of research to society depends not only on its intrinsic quality but also on topic selection. Because it is difficult to assess objectively the value of topic selection, research funders develop transparent processes for research needs assessment and prioritisation. In this paper, these processes are analysed for one publicly funded research commissioner in England, paying attention to the positioning of the programme within national institutions and with discussion of some historical antecedents. The dynamics between interest groups with a stake in the programme are identified. Different strategies for balancing stakeholder interests are described and their relative merits discussed. The conclusion is that no one strategy can be effective in isolation and a mixed approach is needed.
Compressive Strength of Small Concrete Specimens Confined with Fiberglass Laminates
Authors: Larralde J
Published: January 2010

Portland cement concrete, like most granular materials, exhibits an increase in compressive strength when subjected to confinement. This characteristic is advantageously used in the design of reinforced concrete columns, for instance, in which the load capacity is considerably increased when the column is properly confined with stirr-ups or spiral reinforcement. Recently, exterior reinforcement in the form of fiberglass composite wrapping has been used to retrofit or repair concrete columns. Wrapping with fiberglass composites increases the capacity of columns to withstand axial as well as eccentric loading. This paper presents comparative test results of small concrete specimens subjected to axial loading and tested under unconfined conditions and confined conditions produced by fiberglass composite wrapping. The test results show a considerable increase in the compressive strength and an increase in the toughness in the fiberglass confined specimens.
Durability Findings from Case Studies of Marine Concrete Structures
Authors: Mackechnie JR , Alexander MG
Published: January 2010

The marine environment provides a severe durability test for reinforced concrete structures and deterioration may occur rapidly unless structures are correctly designed and built. Existing specifications for concrete do not appear to be effective in ensuring satisfactory durability performance in the marine environment and many structures require repairs during their design lives. From a survey of over 20 marine concrete structures along the Cape coast of South Africa, a number of observations are made regarding deterioration of marine concrete. Issues such as cover to reinforcement, concrete type, site practice, corrosion of reinforcement, and suitability of repairs are discussed and recommendations are made for improving concrete durability. Findings from the survey indicated that current specifications and construction practice were inadequate and could not guarantee concrete durability.
Thermal Properties of Commercially Available High-Strength Concretes
Authors: Van Geem MG , Gajda J , Dombrowski K
Published: January 2010

This paper summarizes the thermal properties of commercially available high-strength concretes. Five concretes with anticipated compressive strengths in the range of 10 000 to 20 000 psi (69 to 138 MPa) were tested. W/C ratios ranged from 0.26 to 0.43; water-to-total cementitious material ratios ranged from 0.22 to 0.32. The concretes, containing either no mineral admixtures, silica fume only, or both fly ash and silica fume, were delivered by a ready-mix supplier for laboratory testing.

Tests covered by this paper include thermal conductivity, thermal diffusivity, specific heat, and drying rates. Thermal conductivity was measured using a guarded hot plate (ASTM C 177) at 85, 300, and 700°F (30, 150, and 370°C). Thermal conductivity was also measured using the hot-wire method (ASTM C 1113) at 70, 300, 570, 840, 1110, 1380, and 1830°F (25, 150, 300, 450, 600, 750, and 1000°C). Thermal diffusivity was measured, using the guarded hot plate apparatus, at 95, 250, and 500°F (35, 120, and 250°C). Thermal diffusivity was also measured using a dynamic radial heat flow method continuously from 210 to 1830°F (100 to 1000°C). Thermal properties at high temperatures differed depending on the method used. Specific heat was measured on saturated concrete at ambient temperatures. Rates of drying for initially moist cured specimens were determined by oven-drying thermal conductivity specimens at 150, 185, and 220°F (65, 85, and 105°C) prior to thermal testing. Mass loss was measured at temperatures up to 1740°F (950°C) at heating rates of 4, 36, and 90°F (2, 20, and 50°C) per minute.
Abrasion Resistance of Surface-Treated Concrete
Authors: Sadegzadeh M , Kettle RJ
Published: January 2010

This paper describes a laboratory study of surface treatments on the abrasion resistance of concrete. A test method based on rotating steel wheels running in a circular path was adopted to assess the abrasion resistance. The reported data are from a series of tests performed on relatively large slabs so that power trowelling and finishing could be used to produce the test surfaces. These slabs were used to assess the effects of various treatments on abrasion resistance, including both liquid surface treatments and dry shake surface treatments.

Concrete liquid hardeners were more effective in improving the abrasion resistance of mixes with low water-cement ratios rather than those with high water-cement ratios. Proper curing, however, of the concrete slabs was more effective in improving the abrasion resistance than the application of concrete liquid hardeners. Penetrating sealing and hardening treatments significantly increased the abrasion resistance of all types of concrete mixes. The abrasion resistance obtained by the use of penetrating sealer and hardener treatments ranked highest when compared with other air-cured specimen slabs. The application of these treatments reduced the influence of concrete mix design on the abrasion resistance of the slab.
Test Methods for Rapid-Hardening Magnesium Phosphate-Based Cements
Authors: Popovics S , Rajendran N
Published: January 2010

This paper describes several different test methods that were used for rapid-hardening cements. The term “rapid-hardening cement” is defined in this paper as a hydraulic binder that can develop at least 2000-psi (15-MPa) compressive strength within 2 h under normal conditions. Due to the special nature of these cements, it is questionable whether the conventional methods are suitable for testing them. The quickness of setting and the very rapid strength development may cause a need for special testing procedures. Furthermore, unlike the standard portland cements, these materials come as a mixture of sand and cement.

The conclusion is that many of the applied ASTM methods, perhaps with modifications, can provide useful information about the technically important properties of these rapid-hardening cements. This paves the way toward a more uniform testing and the eventual standardization of test methods for these special cements and mortars of increasing popularity. Though this paper describes only magnesium phosphate (MP)-based cements, the conclusions of the paper apply to most of the rapid-hardening hydraulic binders.
Trade-Off of Gradation and Cost Requirements in Aggregate Blending
Authors: Easa SM
Published: January 2010

Existing aggregate blending methods can be used to provide the optimum proportions based on either gradation or cost requirements. The purpose of this paper is to present an analytical method that allows a trade-off between gradation and cost requirements in determining the optimum proportions. Only three aggregates are considered, but the method can be extended to any number of aggregates. The method provides the entire feasible region of proportions that satisfies the gradation specification limits along with the mean deviation and cost of every point in that region. The mean deviation can be based on mid-point specifications or the maximum density gradation curve. The optimum proportions for the minimum mean deviation, minimum cost, or a trade-off between the two are determined. The method was applied to two examples of aggregate blending. The first example illustrates the trade-off analysis of gradation and cost requirements, and the second example illustrates a special advantage of the method. In addition to considering both gradation and cost requirements, the method has other advantages. Unlike existing methods, this method automatically eliminates negative solutions and can handle any type of the cost function of aggregates.
Durability of Concrete
Authors: Rodway LE
Published: January 2010

The durability of concrete is obviously a complex topic. This paper deals with an overview in four parts: The first part consists of durability as affected by more than 200 individual separate items involved in its constituent materials; the effect of practical matters in preparing and handling concrete aggregates; cement storage and handling and construction techniques; the physical properties of the hardened concrete; nature of exposure of the concrete; and finally the types of loading to which concrete is exposed. Second, examples of durability of nonstructural exposed concrete are given in terms of resistance to freeze-thaw forces in relation to air-void characteristics of normal concrete. Third, an example of nondurable, load bearing structural concrete is illustrated along with the causes of distress and method of repair. Finally, a recent example of a high strength structural concrete bridge deck containing a superplasticizer is presented in terms of its durability characteristics. Detailed data on each of these four classifications has been referenced to facilitate a more in-depth study by those parties who may have an interest in one or more of those topics.
The Determination of Specific Gravity Using the Siphon-Can Method
Authors: Black RW
Published: January 2010

Current methods of determining the specific gravity, moisture content, and absorption of concrete aggregates (ASTM Test Method for Specific Gravity and Absorption of Coarse Aggregate [C 127], ASTM Test Method for Specific Gravity and Absorption of Fine Aggregate [C 128], and ASTM Test Method for Total Moisture Content of Aggregate by Drying [C 566]) are slow and dependent upon subjective “end-point” determinations as well as requiring elaborate and cumbersome equipment. Presented here is a method using simple equipment, the siphon can, to accomplish all three tests. This technique has an objective “end-point” and statistical error of measurement one-quarter that of ASTM C 127 or C 128. Derivation of formulae and method of application are discussed. The use of this technique in routine concrete production can result in large savings to concrete producers.
Effect of Cement Replacement, Content, and Type on the Durability Performance of Fly Ash Concrete in the Middle East
Authors: Rasheeduzzafar  , Al-Mana A , Haneef M , Maslehuddin M
Published: January 2010

The low durability of concrete construction in the Middle East caused by corrosion of reinforcement, sulfate attack, environmental cracking, and aggregate-cement reactivity necessitates that mix design techniques be formulated to yield dense and impervious concrete with as little heat of hydration as possible; it should also have enhanced resistance to salt attack and possible cement-aggregate reactivity. These objectives present fly ash as a potentially useful admixture from the standpoint of improving the durability of concrete construction in the aggressive service environment of the Gulf seaboard.

This investigation presents data on the strength, general quality, and durability performance of fly-ash portland-cement concrete against sulfate/chloride attack. The variables used for this study are fly ash additions as cement replacement from 0 to 40%, cement factors of 300, 360 and 450 kg/m3 (500, 600, and 750 lb/yd3) and tricalcium aluminate (C3A) phase ranging from 0 to 9.5%. Results show that 20% replacement by fly as shows the best performance in terms of rate of strength gain, ultimate strength, absorptive characteristics, and resistance to sulfate/chloride attack. The strength gain is superior in lean mixes, and the effect of fly ash addition on sulfate resistance of concrete is more pronounced for higher C3A cements. An increase in the cement factor without attendant changes in water/cement ratio does not necessarily provide better durability performance.
Some Laboratory Experiments on the Inhibitor Effect of Sodium Nitrite on Reinforcement Corrosion
Authors: Andrade C , Alonso C , González JA
Published: January 2010

The summary of several years of research about the inhibitor effect of NO2− on the corrosion of reinforcement is presented. Their inhibitor effect has been studied using galvanostatic and potentiodynamic polarization curves, and we have measured the corrosion rates using the polarization resistance method (linear polarization). Verification has been done by this last technique Rp, that the NO2− in concrete, if it is used in sufficient proportion, is a complete inhibitor when the Cl− is added during the mixing (for example, mixing with seawater, calcium chloride (CaCl2) as an accelerator inhibitor). Insufficient amounts of NO2− have never provoked more corrosion in our experiments in concrete. The presence of NO2− always have produced a beneficial effect. The NO2− are also beneficial in carbonated concrete, suppressing or at least reducing the attacked area and the corrosion rate of the reinforcements.
Shrinkage and Creep of Concrete Containing 50% Lignite Fly Ash at High Temperatures
Authors: Nasser KW , Al-Manaseer AA
Published: January 2010

This paper investigates the influence of high temperature on the shrinkage and creep of unsealed and sealed concrete containing 50% Saskatchewan lignite fly ash and 50% Type I portland cement. Concrete was tested at six different temperatures between 70 and 450°F (21 and 232°C) and under three stress levels of 750, 1200, and 1500 psi (5.2, 8.3, and 10.3 MPa). The tests were made on 3 by 9-in. (75 by 225mm) concrete cylinders, and shrinkage and creep were measured for a maximum period of 112 days.

It was found that the shape of the shrinkage and the creep time curves were similar at both normal and elevated temperatures.

Test results also showed that shrinkage and creep of unsealed specimens decreased with a rise in temperature from 70 to 350°F (21 to 177°C) and then increased with a further rise in temperature. Creep of sealed specimens was found to increase with a rise in temperature from 70 to 160°F (21 to 71°C) and then to decrease with a further rise in temperature. Shrinkage and creep of unsealed specimens were nearly the same as those of plain concrete at the age of 112 days and at temperatures of 70 to 450°F (21 to 232°C).
KC8A3: X-Ray Diffraction Characterization of the Compound and Comparison with NC8A3 and C3A
Authors: Gebhardt RF
Published: January 2010

The X-ray diffraction pattern of KC8A3 has been determined in detail. Comparison of the KC8A3 data with new and previous X-ray diffraction data on NC8A3 and C3A shows it to be a distinctly different phase bearing close structural similarities to the other aluminates in portland cement clinker. The progression from cubic C3A to tetragonal KC8A3 to orthorhombic NC8A3 with only minor shifts in cell parameters suggests the possibility of solid solution between respective adjacent pairs in production clinkers.
Effect of Different Admixtures on the Strength of Sulphur Concrete
Authors: Czarnecki B , Gillott JE
Published: January 2010

The strength of sulphur concrete is affected by factors such as type of aggregate, aggregate particle shape and texture, amount of sulphur binder in the mix, and type of admixture used. The density of this concrete is also affected by these factors. Some of these concretes perform poorly in moist conditions, as shown by loss of more than 30% strength. Increased amounts of sulphur binder adversely affect the strength of concrete; however, loss of strength of such mixes upon immersion in water is smaller. Type of aggregate influences the strength of concrete, but no correlation was found between the petrography and mineralogy of aggregates and the strength of concrete; the strongest aggregate did not always produce the strongest concrete.

Four types of admixtures were employed: glycerin, crude oil, and two types of silanes. Glycerin and crude oil generally decreased the strength of sulphur concrete. Silane admixtures act as adhesion promoters and are capable of rendering the concrete hydrophobic. Concretes made with aggregates that were pretreated with silanes generally showed a dramatic increase in strength under both dry and wet conditions.
Drying Shrinkage of Glass Fiber Reinforced Concrete
Authors: Al-Obaid YF
Published: January 2010

Experimental tests have been carried out on the shrinkage behavior of glass fiber reinforced concrete. Reinforcing concrete by mixing in fiber is one method for preventing cracks occurring due to drying shrinkage. The tests performed show that shrinkage strain is decreased with the increase of the fiber content. A three-dimensional finite-element analysis was carried out on samples tested in the laboratory. The analytical results produced show good agreement with those obtained from the experimental results.
Observations of Healing of Cracks in High-Strength Lightweight Concrete
Authors: Mor A , Monteiro PJM , Hester WT
Published: January 2010

Some favorable properties of lightweight aggregate concrete are shown to originate from its internal structure, which combines relatively flexible aggregate with more rigid cement paste matrix. Scanning electron microscopy (SEM) was used to analyze the cracking pattern which developed under cyclic loading. The cracks appear to originate in the hard brittle matrix and progress into the aggregate. At low load levels, some cracks seem to deflect and lose energy as they penetrate the aggregates, with many never emerging from the other side or emerging as thinner cracks.

A process of healing of cracks through the formation of new products appears to restore integrity and enhance strength of a previously cracked concrete which was allowed to rest for a long period after cracking. Micrographs of the healed cracks are presented.
Effect of Coarse Aggregate on the Behavior of Normal and High-Strength Concretes
Authors: Ezeldin AS , Aitcin P-C
Published: January 2010

The effect of four coarse aggregate types on the compressive strength, flexural strength, and flexural strength/compressive strength ratio of normal- and high-strength concrete are reported. With normal-strength concrete mixtures, it was found that the coarse aggregate type did not greatly influence the mechanical properties. However, the high-strength concrete mixtures containing the limestone aggregate produced higher compressive strength than the concrete mixtures containing either gravel or granite aggregates. The flexural behavior of high-strength concrete was not affected by the aggregate type. Also, the experimental results did not show a conclusive influence of the aggregate type on the variation of flexural strength/compressive strength ratio.
Crushed Tile Coarse Aggregate Concrete
Authors: Khaloo AR
Published: January 2010

This paper investigates the potential of crushed tiles as coarse aggregate in concrete. Test results of bulk, saturated surface dry (SSD) and apparent specific gravities, bulk unit weight, water absorption, resistance to abrasion, percent of voids and grading (performed as per ASTM standards) on two types of crushed tiles were compared with the results of conventional crushed stone aggregate. Also included are results from tests on concrete cylinders under uniaxial compression, split tension, and beams under flexure to determine the influence of variables of test age on concrete strength, type of tiles, and ratio of volume of crushed tile to the total volume of coarse aggregate in concrete. Recommendations for use of crushed tile as coarse aggregates in concrete are given.
A Latex-Modified Concrete Overlay on Plain-Jointed Concrete Pavement
Authors: Glauz DL
Published: January 2010

A latex-modified concrete overlay was placed on Interstate 5 in Northern California at a Strategic Highway Research Program SPS-6 test site. The objective of the test was to evaluate a potentially lower cost latex overlay system. The cost of the overlay would be reduced by eliminating surface prewetting and the wet burlap cure. The test section was placed 300-m long across three lanes. Unusual features of the overlay were: (1) it was placed on a dry substrate, (2) latex content was 43% higher than conventional practice, (3) cure was by curing compound rather than wet burlap, and (4) it was on a plain jointed portland cement concrete pavement. Bond to the substrate was very good. Curing compound provided an adequate curing membrane when applied at the proper rate. The system was evaluated annually. To date, the only problem has been at the joints, which present a serious problem for a bonded overlay. Delaminations or spalls have occurred at most of the transverse joints. The objective was met although the system is not suitable for use on jointed pavements.

A latex-modified concrete overlay can be placed on a dry substrate and bond well. It can also be cured successfully with a curing compound that conforms to Specification for Liquid Membrane-Forming Compounds for Curing Concrete (ASTM C 309), Type 2, Class B. This type of overlay is not suitable for a jointed pavement without careful attention to the joint detail.
Precision of Tests for Assessment of the Deicer Salt Scaling Resistance of Concrete
Authors: Marchand J , Pleau R , Pigeon M
Published: January 2010

Some aspects of the variability of Test Method for Scaling Resistance of Concrete Surfaces Exposed to Deicing Chemicals (ASTM C 672) measurements are discussed in this paper. The influence of the operator's subjectivity on the visual rating is studied. The relationship between the visual rating and the cumulated mass of scaled-off particles is also analyzed. From a statistical analysis of several hundred different concrete mixtures, the variability of the test method is estimated for various types of concrete considering only the cumulated mass of scaled-off particles. Using the same statistical analysis, the precision of ASTM C 672 is finally compared to that of the Canadian brine immersion test (Precast Concrete Paving Blocks, CAN/CSA A231.2 M85) designed to assess the deicer salt scaling resistance of precast concrete elements.
Durability of Reinforced Lightweight Mortars with Corrosion Inhibitors
Authors: Batis G , Kouloumbi N , Katsiamboulas A
Published: January 2010

The aim of this experimental work is the examination of the performance of reinforced mortar specimens containing Greek fine-pumice aggregates together with corrosion inhibitors (sodium nitrite or sodium benzoate or iron oxides) added in order to lower the corrosion rate of steel reinforcement in a chloride environment. The durability of the specimen was evaluated by measuring the corrosion potential and the mass loss time dependence of the steel rebar, the carbonation depth, the porosity, and the compressive strength of the specimens. Correlation of the above results revealed that the corrosion inhibitors examined have a protective effect on the steel, while the changes of the mechanical strength of the relative lightweight mortars are not significant compared to the practical needs. The most efficient inhibitor was sodium nitrite in both concentrations examined, that is, 2 and 5%.