bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Novel A2AAdenosine Receptor Agonist ATL 313 onClostridium difficileToxin A-Induced Murine Ileal Enteritis
Authors: Cavalcante I. C. , Castro M. V. , Barreto A. R. F. , Sullivan G. W. , Vale M. , Almeida P. R. C. , Linden J. , Rieger J. M. , Cunha F. Q. , Guerrant R. L. , Ribeiro R. A. , Brito G. A. C.
Published: April 2006

Clostridium difficileis a spore-forming, anaerobic, gram-positive bacillus that releases two main virulence factors: toxins A and B. Toxin A plays an important pathogenic role in antibiotic-induced diarrhea and pseudomembranous colitis, a condition characterized by intense mucosal inflammation and secretion. Agonist activity at A2Aadenosine receptors attenuates inflammation and damage in many tissues. This study evaluated the effects of a new selective A2Aadenosine receptor agonist (ATL 313) on toxin A-induced injury in murine ileal loops. ATL 313 (0.5 to 5 nM) and/or the A2Aadenosine receptor antagonist (ZM241385; 5 nM) or phosphate-buffered saline (PBS) were injected into ileal loops immediately prior to challenge with toxin A (1 to 10 μg/loop) or PBS. Intestinal fluid volume/length and weight/length ratios were calculated 3 h later. Ileal tissues were collected for the measurement of myeloperoxidase, adenosine deaminase activity, tumor necrosis factor alpha (TNF-α) production, histopathology, and detection of cell death by the TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling) method. Toxin A significantly increased volume/length and weight/length ratios in a dose-dependent fashion. ATL 313 treatment significantly (P< 0.05) reduced toxin A-induced secretion and edema, prevented mucosal disruption, and neutrophil infiltration as measured by myeloperoxidase activity. ATL 313 also reduced the toxin A-induced TNF-α production and adenosine deaminase activity and prevented toxin A-induced cell death. These protective effects of ATL 313 were reversed by ZM241385. In conclusion, the A2Aadenosine receptor agonist, ATL 313, reduces tissue injury and inflammation in mice with toxin A-induced enteritis. The finding of increased ileal adenosine deaminase activity following the administration of toxin A is new and might contribute to the pathogenesis of the toxin A-induced enteritis by deaminating endogenous adenosine.
Brucella abortus
Rough Mutants Induce Macrophage Oncosis That Requires Bacterial Protein Synthesis and Direct Interaction with the Macrophage
Authors: Pei Jianwu , Turse Joshua E. , Wu Qingmin , Ficht Thomas A.
Published: April 2006

Previous studies suggest that smooth
Brucella
organisms inhibit macrophage apoptosis. In contrast, necrotic cell death of macrophages infected with rough
Brucella
organisms in vitro has been reported, which may in part explain the failure of some rough organisms to thrive. To characterize these potential macrophage killing mechanisms, J774.A1 murine macrophages were infected with
Brucella abortus
S2308-derived rough mutant CA180. Electron microscopic analysis and polyethylene glycol protection assays revealed that the cells were killed as a result of necrosis and oncosis. This killing was shown to be unaffected by treatment with carbenicillin, an inhibitor of bacterial cell wall biosynthesis and, indirectly, replication. In contrast, chloramphenicol treatment of macrophages infected at multiplicities of infection exceeding 10,000 prevented cell death, despite internalization of large numbers of bacteria. Similarly, heat-killed and gentamicin-killed CA180 did not induce cytopathic effects in the macrophage. These results suggested that killing of infected host cells requires active bacterial protein synthesis. Cytochalasin D treatment revealed that internalization of the bacteria was necessary to initiate killing. Transwell experiments demonstrated that cell death is not mediated by a diffusible product, including tumor necrosis factor alpha and nitric oxide, but does require direct contact between host and pathogen. Furthermore, macrophages preinfected with
B. abortus
S2308 or pretreated with
B. abortus
O polysaccharide did not prevent rough CA180-induced cell death. In conclusion,
Brucella
rough mutant infection induces necrotic and oncotic macrophage cell death that requires bacterial protein synthesis and direct interaction of bacteria with the target cells.
Outer Membrane Protein A of
Escherichia coli
O157:H7 Stimulates Dendritic Cell Activation
Authors: Torres Alfredo G. , Li Yongguo , Tutt Christopher B. , Xin Lijun , Eaves-Pyles Tonyia , Soong Lynn
Published: April 2006

Outer membrane protein A (OmpA) is located in the membrane of
Escherichia coli
and other gram-negative bacteria and plays a multifunctional role in bacterial physiology and pathogenesis. In enterohemorrhagic
E. coli
(EHEC), especially serotype O157:H7, OmpA interacts with cultured human intestinal cells and likely acts as an important component to stimulate the immune response during infection. To test this hypothesis, we analyzed the effect of EHEC OmpA on cytokine production by dendritic cells (DCs) and on DC migration across polarized intestinal epithelial cells. OmpA induced murine DCs to secrete interleukin-1 (IL-1), IL-10, and IL-12 in a dose-dependent manner, and this effect was independent of Toll-like receptor 4. Although DCs displayed differential responses to EHEC OmpA and OmpA-specific antibodies enhanced DC cytokine secretion, we cannot discard that other EHEC surface elements were likely to be involved. While OmpA was required for bacterial binding to polarized Caco-2 cells, it was not needed for the induction of cytokine production by Caco-2 cells or for human DC migration across polarized cells.
Characterization of the Opsonic and Protective Activity against
Staphylococcus aureus
of Fully Human Monoclonal Antibodies Specific for the Bacterial Surface Polysaccharide Poly-
N
-Acetylglucosamine
Authors: Kelly-Quintos Casie , Cavacini Lisa A. , Posner Marshall R. , Goldmann Donald , Pier Gerald B.
Published: April 2006

Carbohydrate antigens are important targets of the immune system in clearing bacterial pathogens. Although the immune system almost exclusively uses antibodies in response to foreign carbohydrates, there is still much to learn about the role of different epitopes on the carbohydrate as targets of protective immunity. We examined the role of acetyl group-dependent and -independent epitopes on the staphylococcal surface of polysaccharide poly-
N
-acetylated glucosamine (PNAG) by use of human monoclonal antibodies (MAbs) specific for such epitopes. We utilized hybridoma technology to produce fully human immunoglobulin G2 (IgG2) MAbs from B cells of an individual post-
Staphylococcus aureus
infection and cloned the antibody variable regions to produce an IgG1 form of each original MAb. Specificity and functionality of the purified MAbs were tested in vitro using enzyme-linked immunosorbent assays, complement deposition, and opsonophagocytic assays. We found that a MAb (MAb F598) that bound the best to nonacetylated or backbone epitopes on PNAG had superior complement deposition and opsonophagocytic activity compared to two MAbs that bound optimally to PNAG that was expressed with a native level (>90%) of
N
-acetyl groups (MAbs F628 and F630). Protection of mice against lethality due to
S. aureus
strains Mn8 and Reynolds further showed that the backbone-specific MAb had optimal protective efficacy compared with the acetate-specific MAbs. These results provide evidence for the importance of epitope specificity in inducing the optimal protective antibody response to PNAG and indicate that MAbs to the deacetylated form of PNAG could be immunotherapeutic agents for preventing or treating staphylococcal infections.
In Vivo Activation of Naive CD4+T Cells in Nasal Mucosa-Associated Lymphoid Tissue following Intranasal Immunization with RecombinantStreptococcus gordonii
Authors: Medaglini Donata , Ciabattini Annalisa , Cuppone Anna Maria , Costa Caterina , Ricci Susanna , Costalonga Massimo , Pozzi Gianni
Published: April 2006

The antigen-specific primary activation of CD4+T cells was studied in vivo by adoptive transfer of ovalbumin-specific transgenic T cells (KJ1-26+CD4+) following intranasal immunization with recombinantStreptococcus gordonii. A strain ofS. gordoniiexpressing on its surface a model vaccine antigen fused to the ovalbumin (OVA) peptide from position 323 to 339 was constructed and used to study the OVA-specific T-cell activation in nasal mucosa-associated lymphoid tissue (NALT), lymph nodes, and spleens of mice immunized by the intranasal route. The recombinant strain, but not the wild type, activated the OVA-specific CD4+T-cell population in the NALT (89% of KJ1-26+CD4+T cells) just 3 days following immunization. In the cervical lymph nodes and in the spleen, the percentage of proliferating cells was initially low, but it reached the peak of activation at day 5 (90%). This antigen-specific clonal expansion of KJ1-26+CD4+T cells after intranasal immunization was obtained with live and inactivated recombinant bacteria, and it indicates that the NALT is the site of antigen-specific T-cell priming.
Modulation of the Triggering Receptor Expressed on the Myeloid Cell Type 1 Pathway in Murine Septic Shock
Authors: Gibot Sébastien , Buonsanti Cecilia , Massin Frédéric , Romano Michele , Kolopp-Sarda Marie-Nathalie , Benigni Fabio , Faure Gilbert C. , Béné Marie-Christine , Panina-Bordignon Paola , Passini Nadia , Lévy Bruno
Published: April 2006

The triggering receptor expressed on myeloid cell type 1 (TREM-1) is a cell surface molecule that has been identified on both human and murine polymorphonuclear neutrophils and mature monocytes. The activation of TREM-1 in the presence of microbial components amplifies the inflammatory response and may be responsible for the hyperresponsiveness observed during the initial stage of sepsis. To investigate the effect of the modulation of the TREM-1 pathway during experimental murine sepsis, we used analogue synthetic peptides derived from the extracellular moiety of TREM-1. The TREM-1 ligand was expressed on both peritoneal and peripheral neutrophils during experimental peritonitis in mice. The TREM-1 peptides inhibited the recognition by TREM-1 of its ligand and protected endotoxinic mice from death. In septic rats, the TREM-1 peptides improved the hemodynamic status, attenuated the development of lactic acidosis, modulated the production of such proinflammatory cytokines as tumor necrosis factor alpha and interleukin-1β, and improved survival. The protective effect of these peptides on arterial pressure could partly be explained by a decreased production of nitric oxide. These data suggest that in vivo modulation of TREM-1 might be a suitable therapeutic tool for the treatment of sepsis.
Bordetella pertussisInhibition of Interleukin-12 (IL-12) p70 in Human Monocyte-Derived Dendritic Cells Blocks IL-12 p35 through Adenylate Cyclase Toxin-Dependent Cyclic AMP Induction
Authors: Spensieri Fabiana , Fedele Giorgio , Fazio Cecilia , Nasso Maria , Stefanelli Paola , Mastrantonio Paola , Ausiello Clara Maria
Published: April 2006

Bordetella pertussis, the causative agent of whooping cough, possesses an array of virulence factors, including adenylate cyclase toxin (ACT), relevant in the establishment of infection. Here we better define the impact of cyclic AMP (cAMP) intoxication due to the action of ACT on dendritic cell (DC)-driven immune response, by infecting monocyte-derived DC (MDDC) with an ACT-deficientB. pertussismutant (ACT−18HS19) or its parental strain (WT18323). Both strains induced MDDC maturation and antigen-presenting cell functions; however, only ACT−18HS19 infected MDDC-induced production of interleukin-12 (IL-12) p70. Gene expression analysis of the IL-12 cytokine family subunits revealed that both strains induced high levels of p40 (protein chain communal to IL-12 p70 and IL-23) as well as p19, a subunit of IL-23. Conversely only ACT−18HS19 infection induced consistent transcription of IL-12 p35, a subunit of IL-12 p70. Addition of the cAMP analogousd-butyril-cAMP (d-cAMP) abolished IL-12 p70 production and IL-12 p35 expression in ACT−18HS19-infected MDDC. ACT−18HS19 infection induced the expression of the transcription factors interferon regulatory factor 1 (IRF-1) and IRF-8 and of beta interferon, involved in IL-12 p35 regulation, and the expression of these genes was inhibited byd-cAMP addition and in WT18323-infected MDDC. The concomitant expression of IL-12 p70 and IL-23 allowed ACT−18HS19 to trigger a more pronounced T helper 1 polarization compared to WT18323. The present study suggests that ACT-dependent cAMP induction leads to the inhibition of pathways ultimately leading to IL-12 p35 production, thus representing a mechanism forB. pertussisto escape the host immune response.
Mucosal Adjuvant Properties of theShigellaInvasin Complex
Authors: Kaminski Robert W. , Turbyfill K. Ross , Oaks Edwin V.
Published: April 2006

TheShigellainvasin complex (Invaplex) is an effective mucosal vaccine capable of protecting againstShigellachallenge in animal models. The major antigenic constituents of Invaplex are the Ipa proteins and lipopolysaccharide. The cell-binding capacity of the Ipa proteins prompted the investigation into the adjuvanticity of Invaplex. Using ovalbumin (OVA) as a model antigen, intranasal immunization with OVA combined with Invaplex was found to enhance anti-OVA serum immunoglobulin G (IgG) and IgA responses and induce OVA-specific mucosal antibody responses at sites located both proximal and distal to the immunization site. The immune responses induced with OVA and Invaplex were comparable in both magnitude and duration to the immune responses induced after immunization with OVA and cholera toxin. The OVA-specific immune response was characterized by high levels of serum IgG1 and increased production of interleukin-4 (IL-4), IL-5, or IL-10 from lymphoid cells of immunized animals, suggesting a Th2 response. In addition to enhancing the immunogenicity of OVA, Invaplex-specific immune responses were also induced, indicating the potential for the development of a combination vaccine consisting of Invaplex and other immunogens. Preexisting Invaplex-specific immunity did not interfere with the capacity to enhance the immunogenicity of a second, unrelated vaccine antigen, suggesting that Invaplex could be used as a mucosal adjuvant in multiple vaccine regimens.
Cytokine mRNA Expression inMycobacteriam ulcerans-Infected Human Skin and Correlation with Local Inflammatory Response
Authors: Phillips R. , Horsfield C. , Mangan J. , Laing K. , Etuaful S. , Awuah P. , Nyarko K. , Osei-Sarpong F. , Butcher P. , Lucas S. , Wansbrough-Jones M.
Published: April 2006

Cytokine mRNA expression in biopsies ofMycobacterium ulcerans-infected human tissue was investigated using real-time PCR, and the findings were correlated with the clinical stages of disease and histopathologies. A broad range of cytokine mRNAs were detected in 16 early nodules and 28 late-stage ulcers, including those for the Th1 cytokines tumor necrosis factor alpha (TNF-α) and gamma interferon (IFN-γ) and the Th2 cytokine interleukin 10 (IL-10). IFN-γ was strongly expressed in both nodules and ulcers, suggesting that a Th1 response begins early in the disease. There was a significantly higher expression of IL-8 and other proinflammatory cytokines in results from 32 biopsies with neutrophilia than in those from 12 biopsies without acute inflammation. Ten tissue samples containing granulomas showed high mRNA expression for IFN-γ, IL-1β, IL-12p35, IL-12p40, IL-15, and TNF-α relative to 34 tissue samples without granulomas. These results suggest that the human immune response toM. ulceransis similar to that seen with some other mycobacteria despite the presence of the toxin mycolactone in the tissues.
The Anti-
Candida
Vaccine Based on the Recombinant N-Terminal Domain of Als1p Is Broadly Active against Disseminated Candidiasis
Authors: Ibrahim Ashraf S. , Spellberg Brad J. , Avanesian Valentina , Fu Yue , Edwards John E.
Published: April 2006

We have previously shown that vaccination with a vaccine based on the recombinant N-terminal domain of Als1p (rAls1p-N) protected BALB/c mice against disseminated infection caused by a single strain of
Candida albicans
(A. S. Ibrahim, B. J. Spellberg, V. Avenissian, Y. Fu, S. G. Filler, and J. E. Edwards, Jr., Infect. Immun.
73:
999-1005, 2005, and B. J. Spellberg, A. S. Ibrahim, V. Avenissian, S. G. Filler, C. Myers, Y. Fu, and J. E. Edwards, Jr., Infect. Immun.
73:
6191-6193, 2005). Here we show that the rAls1p-N vaccine also improves survival of outbred mice from disseminated candidiasis and that it is active against multiple virulent strains of
C. albicans
and non-
C. albicans
spp.
Requirement of Histidine Kinases HP0165 and HP1364 for Acid Resistance in
Helicobacter pylori
Authors: Loh John T. , Cover Timothy L.
Published: April 2006

In this study, we investigated a potential requirement of two-component signal transduction systems for acid resistance in
Helicobacter pylori
. In comparison to a wild-type strain, isogenic strains with null mutations in either HP0165 or HP1364 histidine kinases were impaired in their ability to grow at pH 5.0. The growth of complemented mutant strains was similar to that of the wild-type strain.
H. pylori
DNA array analyses and transcriptional reporter assays indicated that acid-responsive gene transcription was altered in the HP0165 and HP1364 null mutant strains compared to the parental wild-type strain. These results indicate that intact HP0165 and HP1364 histidine kinases are required for acid resistance in
H. pylori
.
Role of the Histone-Like Nucleoid Structuring Protein in Colonization, Motility, and Bile-Dependent Repression of Virulence Gene Expression in
Vibrio cholerae
Authors: Ghosh Amalendu , Paul Kalidas , Chowdhury Rukhsana
Published: April 2006

Bile-mediated repression of virulence gene expression is relieved in a
Vibrio cholerae hns
mutant. The mutant also exhibited reduced motility due to lower
flrA
expression, higher in vivo production of the virulence factors, and lower colonization efficiency. The colonization defect of the mutant was due to low FlrA production.
Methanocaldococcus jannaschii
Uses a Modified Mevalonate Pathway for Biosynthesis of Isopentenyl Diphosphate
Authors: Grochowski Laura L. , Xu Huimin , White Robert H.
Published: April 2006

Archaea have been shown to produce isoprenoids from mevalonate; however, genome analysis has failed to identify several genes in the mevalonate pathway on the basis of sequence similarity. A predicted archaeal kinase, coded for by the MJ0044 gene, was associated with other mevalonate pathway genes in the archaea and was predicted to be the “missing” phosphomevalonate kinase. The MJ0044-derived protein was tested for phosphomevalonate kinase activity and was found not to catalyze this reaction. The MJ0044 gene product was found to phosphorylate isopentenyl phosphate, generating isopentenyl diphosphate. Unlike other known kinases associated with isoprene biosynthesis,
Methanocaldococcus jannaschii
isopentenyl phosphate kinase is predicted to be a member of the aspartokinase superfamily.
Selenium Is Involved in Regulation of Periplasmic Hydrogenase Gene Expression in
Desulfovibrio vulgaris
Hildenborough
Authors: Valente Filipa M. A. , Almeida Cláudia C. , Pacheco Isabel , Carita João , Saraiva Lígia M. , Pereira Inês A. C.
Published: April 2006

Desulfovibrio vulgaris
Hildenborough is a good model organism to study hydrogen metabolism in sulfate-reducing bacteria. Hydrogen is a key compound for these organisms, since it is one of their major energy sources in natural habitats and also an intermediate in the energy metabolism. The
D. vulgaris
Hildenborough genome codes for six different hydrogenases, but only three of them, the periplasmic-facing [FeFe], [FeNi]
1
, and [FeNiSe] hydrogenases, are usually detected. In this work, we studied the synthesis of each of these enzymes in response to different electron donors and acceptors for growth as well as in response to the availability of Ni and Se. The formation of the three hydrogenases was not very strongly affected by the electron donors or acceptors used, but the highest levels were observed after growth with hydrogen as electron donor and lowest with thiosulfate as electron acceptor. The major effect observed was with inclusion of Se in the growth medium, which led to a strong repression of the [FeFe] and [NiFe]
1
hydrogenases and a strong increase in the [NiFeSe] hydrogenase that is not detected in the absence of Se. Ni also led to increased formation of the [NiFe]
1
hydrogenase, except for growth with H
2
, where its synthesis is very high even without Ni added to the medium. Growth with H
2
results in a strong increase in the soluble forms of the [NiFe]
1
and [NiFeSe] hydrogenases. This study is an important contribution to understanding why
D. vulgaris
Hildenborough has three periplasmic hydrogenases. It supports their similar physiological role in H
2
oxidation and reveals that element availability has a strong influence in their relative expression.
Identification and Functional Characterization of theLactococcus lactisCodY-Regulated Branched-Chain Amino Acid Permease BcaP (CtrA)
Authors: den Hengst Chris D. , Groeneveld Maarten , Kuipers Oscar P. , Kok Jan
Published: April 2006

Transcriptome analyses have previously revealed that a gene encoding the putative amino acid transporter CtrA (YhdG) is one of the major targets of the pleiotropic regulator CodY inLactococcus lactisandBacillus subtilis. The role ofctrAinL. lactiswas further investigated with respect to both transport activity as well as CodY-mediated regulation. CtrA is required for optimal growth in media containing free amino acids as the only amino acid source. Amino acid transport studies showed thatctrAencodes a secondary amino acid transport system that is specific for branched-chain amino acids (BCAAs) (isoleucine, leucine, and valine) and methionine, which is in disagreement with its previously proposed function (a cationic amino acid transporter), which was assigned based on homology. We propose to rename CtrA BcaP, for branched-chain amino acid permease. BcaP is a member of a group of conserved transport systems, as homologs are widely distributed among gram-positive bacteria. Deletion ofbcaPresulted in the loss of most of the BCAA uptake activity ofL. lactis, indicating that BcaP is the major BCAA carrier of this organism. Deletion ofbcaPtogether with a second (putative) BCAA permease, encoded bybrnQ, further reduced the viability of the strain. DNA microarray analysis showed that deletion ofbcaPpredominantly affects genes belonging to the regulons of the transcriptional regulator CodY, which is involved in global nitrogen metabolism and needs BCAAs for its activation, and of CmbR, which is involved in sulfur amino acid metabolism.
Myocardial Structure and Function Differ in Systolic and Diastolic Heart Failure
Authors: van Heerebeek Loek , Borbély Attila , Niessen Hans W.M. , Bronzwaer Jean G.F. , van der Velden Jolanda , Stienen Ger J.M. , Linke Wolfgang A. , Laarman Gerrit J. , Paulus Walter J.
Published: April 2006

Background—

To support the clinical distinction between systolic heart failure (SHF) and diastolic heart failure (DHF), left ventricular (LV) myocardial structure and function were compared in LV endomyocardial biopsy samples of patients with systolic and diastolic heart failure.

Methods and Results—

Patients hospitalized for worsening heart failure were classified as having SHF (n=22; LV ejection fraction (EF) 34±2%) or DHF (n=22; LVEF 62±2%). No patient had coronary artery disease or biopsy evidence of infiltrative or inflammatory myocardial disease. More DHF patients had a history of arterial hypertension and were obese. Biopsy samples were analyzed with histomorphometry and electron microscopy. Single cardiomyocytes were isolated from the samples, stretched to a sarcomere length of 2.2 μm to measure passive force (F
passive
), and activated with calcium-containing solutions to measure total force. Cardiomyocyte diameter was higher in DHF (20.3±0.6 versus 15.1±0.4 μm,
P
<0.001), but collagen volume fraction was equally elevated. Myofibrillar density was lower in SHF (36±2% versus 46±2%,
P
<0.001). Cardiomyocytes of DHF patients had higher F
passive
(7.1±0.6 versus 5.3±0.3 kN/m
2
;
P
<0.01), but their total force was comparable. After administration of protein kinase A to the cardiomyocytes, the drop in F
passive
was larger (
P
<0.01) in DHF than in SHF.

Conclusions—

LV myocardial structure and function differ in SHF and DHF because of distinct cardiomyocyte abnormalities. These findings support the clinical separation of heart failure patients into SHF and DHF phenotypes.
Stiffness Contribution of Various Wood Fibers to Composite Materials
Authors: Neagu R. Cristian , Gamstedt E. Kristofer , Berthold Fredrik
Published: April 2006

Wood pulp fibers can serve as useful reinforcement of plastics for increased stiffness. To assess the potential of various wood fibers as reinforcement, a method has been developed to determine the contribution of the fibers to the elastic properties of the composite. A micromechanical composite model and classical laminate mechanics are used to relate the elastic properties of the fibers to the elastic properties of the composite. A large variety of composites made of various wood pulp fibers in an epoxy vinyl ester matrix was manufactured. From the tensile test results of the composites, the contributing Young’s moduli of the fibers in the longitudinal direction are back-calculated and summarized. One finding is that there is an optimum in fiber stiffness as a function of lignin content. It is also found that industrially pulped hardwood fibers have higher stiffness than the corresponding softwood fibers. One example is kraft-cooked Norway spruce fiber, for which a Young’s modulus of 40 GPa is found. The effects of hornification, prehydrolysis, and sulfite processing are also investigated. The results indicate that mild defibration process should be used, that does not damage the cell wall structure so that the inherent high stiffness of the native fibers can be retained. It can be concluded that the proposed method works well to rank the wood fiber candidates in terms of their contribution to the composite stiffness.
A Computational Procedure for the Determination of Fracture Parameters at Interfacial Contact Cracks in Composite Laminates
Authors: Penado F. Ernesto
Published: April 2006

This article presents a method to calculate the fracture parameters at interfacial cracks in laminated composites. Depending on the applied loading and crack length, a contact region may develop that changes the nature of the resulting stress intensity factors and energy release rates with respect to the open crack. A combined analytical and numerical model based on frictionless contact is used to eliminate the overlapping of the crack faces where applicable to obtain the correct results. In cases where the contact region is very small, an approximate method to obtain the fracture parameters is derived by consideration of the J-integral. The laminates studied include cross-ply and angle-ply laminates in three-point bending containing a central delamination. The present results are compared with results in the literature obtained by the virtual crack closure integral technique for the special case of cross-ply laminates and a close agreement is found. In addition, results are given for the extent of the contact zone as well as Mode I and II stress intensity factors and energy release rates as a function of the lamination angle. Overall, the method used provides an effective way to analyze interfacial cracks and delaminations in composite plates in cylindrical bending subjected to transverse loads or low velocity impacts.
Use of Artificial Neural Network for Prediction of Mechanical Properties of α-Al2O3 Particulate-reinforced Al–Si10Mg Alloy Composites Prepared by using Stir Casting Process
Authors: Altinkok Necat
Published: April 2006

In this article, the tensile strength, hardening behavior, and density properties of different α-Al2O3 particle size (μm)-reinforced metal matrix composites (MMCs), produced by using stir casting process, are predicted by designing a backpropagation (BP) neural network that used gradient-descent learning algorithm. Artificial neural network (ANN) is an intelligent technique that can solve nonlinear problems by learning from the samples. Therefore, some experimental samples are prepared at first to train the ANN to provide (to estimate) tensile strength, hardening behavior, and density properties of the MMCs produced for any given α-Al2O3 particle size (μm). The most important point is that after the ANN has been trained using some experimental samples, it gives approximately correct outputs for some of the experimental inputs that have not been used in the training. First, to prepare the training and test (checking) set of the network, some results are experimentally obtained and recorded in a file on a computer. In the experiments, α-Al2O3 particles are supplied commercially. α-Al2O3 ceramic powder of a varying particle size of 10 vol% is prepared, and then this ceramic powder with different α-Al2O3 particle sizes is added to Al–Si10Mg alloy in melt condition by stir casting process. The effect of reinforced particle size on the tensile strength, hardness resistance, and density properties of α-Al2O3-reinforced MMCs have been investigated. Mechanical tests reveal that tensile strength and hardness resistance of the α-Al2O3 ceramic powder composites decrease with increasing reinforced α-Al2O3 particle size. Then, neural network is trained using the prepared training set, also known as the learning set. In the preparation of the ANN training module, the aim of the use of the model is to predict the tensile strength, hardening behavior, and density properties for any given α-Al2O3 particle size by using some experimental results. Different α-Al2O3 particle sizes (μm) are used as the input, and tensile strength, hardening behavior, and density properties are used as outputs in the neural network training module. The tensile strength, hardening behavior, and density properties of the produced MMCs are estimated for different α-Al2O3 particle sizes using neural network efficiently instead of time-consuming experimental processes. At the end of the training process, the test data are used to check the system accuracy. Simulation results confirm the feasibility of this approach and show a good agreement with experimental results for a wide range of MMCs produced.
Prediction of the Thermal Conductivity of the Constituents of Fiber-Reinforced Composite Laminates: Voids Effect
Authors: Al-Sulaiman Faleh A. , Al-Nassar Yaagoub N. , Mokheimer Esmail M. A.
Published: April 2006

There are inherent difficulties in the direct measurement of the thermal conductivity of fibers. The need to determine the thermal conductivity of fibers for design purposes has been the motivation of the present work. Four empirical formulas are developed to predict the thermal conductivities of fiberreinforced composite laminates (FRCLs) and their constituents. Two of these models utilize the parallel and series thermal models of composite walls in predicting the thermal conductivity of the fibers. The models are tested at different fiber-to-resin volume ratios (30/70, 45/55, 50/50, 60/40, and 75/25) and various fiber-to-resin thermal conductivity ratios (0.5, 1, 2, 3, 4, and 5). These ranges indicate the physically possible fiber to resin volume thermal conductivity ratios including the extreme possible cases. The effect of the air void volume ratio on the thermal conductivity of the composite laminates is investigated. The range of the investigated void fractions also represent the practical ranges. The predicted thermal conductivity of the fiber can be accurately predicted throughout the spectrum via three models. The first model is a first-order formula (R 2 = 0.9148) based on the parallel series structure of the constituents within the composite laminate. The second model is a second-order formula (R 2 = 0.9308) which is also based on the parallel series structure of the constituents. A third model is developed to predict the fiber thermal conductivity as a direct function of the composite thermal conductivity and other composite constituents and volume ratios. This correlation has a coefficient of determination (R 2 = 0.9632). A fourth model is developed to predict the effective thermal conductivity of the laminate. The effective thermal conductivity of the FRCL is predicted with very high accuracy (R 2 = 0.9948). Another use of these models is to determine the fiber to resin volume ratio or air void volume fraction (if all thermal conductivities of fiber, resin, and laminate are known).
Evaluating Shear Rigidity of Woven Fabrics
Authors: Zheng Jiaming , Komatsu Takuya , Yazaki Yoshihiko , Takatera Masayuki , Inui Shigeru , Shimizu Yoshio
Published: April 2006

A new shear tester of woven fabrics based on the trellis shear model is described. The tester can be used to carry out shear deformation experiments under quite low tensile stresses. The values of shear rigidity tested on the new tester were compared with those tested on the uniaxial tensile tester and the KES (Kawabata’s Evaluation System) instrument. The results confirm that the tester is more feasible and effective for measuring shear behavior in a natural state. This study establishes a foundation for constructing a universal instrument that can be used to measure shear deformation under any conditions.
Torque in Worsted Wool Yarns
Authors: Mitchell P. , Naylor G. R. S. , Phillips D. G.
Published: April 2006

A direct technique developed for measuring yarn torque is explored for the case of worsted wool yarns. The technique balances the torque in a yarn hank against a wire of known torsional rigidity. It is shown that this technique gives a reliable measure of the torque per strand independent of the size of the hank. The torque per strand was found to be linearly dependent on the applied external tension and a finite torque exists even at zero applied tension. This leads to the concept of resolving the torque into two components, (a) the torque due to the applied tension and (b) the intrinsic torque that exists in the untensioned yarn. The torque due to the applied tension does not depend on the yarn history but only on yarn geometric factors such as the yarn twist and linear density. By comparison the intrinsic torque depends on factors such as the level of yarn set as well as the twist and linear density. These components of torque due to tension and intrinsic torque are shown to be consistent with literature models and lead to estimates of yarn specific volume, yarn packing fraction and relative fiber relaxation moduli after steaming.
Activated Peroxide for Enzymatic Control of Wool Shrinkage Part II: Wool and Other Fiber-type Fabrics
Authors: Cardamone Jeanette M.
Published: April 2006

In Part I we investigated the mechanism for bleaching wool with activated peroxide in the pretreatment step of the chemoenzymatic ARS process for whitening, biopolishing, and shrinkage prevention of wool. Here in Part II we report on applying the process to wool woven and knit fabrics of various constructions and fabric weights and to woven fabrics of other fiber compositions. The contribution of relaxation shrinkage to overall shrinkage that includes felting shrinkage is pronounced in wool fabrics, especially knits. The ARS process is specific for controlling felting shrinkage to provide dimensional stability in machine washing and drying. When applied to acetate, cotton, nylon, polyester, viscose, 62% wool/38% cotton, and a wool/Nomex blend the process was most effective for controlling the shrinkage of acetate, cotton, nylon, viscose, and wool/cotton blend. We treated wool, cotton, and viscose at pH 11.5, 30°C for 30 minutes with individual components used in ARS pretreatment: dicyandiamide (DD), gluconic acid (GA), alkali (NaOH), and hydrogen peroxide (H2O2), and subsequently applied the enzyme treatment. We found that NaOH imparted a mercerizing effect to cotton and viscose and shrinkage was limited to less than 1%. Only the combination of DD/GA/NaOH/H2O2 imparted highest whiteness to wool, cotton, and viscose. When pretreatment utilizing activated DD peroxide was followed by enzyme applied at pH 8–9, 45°C for 40 minutes, the wool fabrics became dimensionally stable and biopolished for itch-free comfort.
Resilience in Children
Authors: Condly Steven J.
Published: April 2006

In spite of the most adverse circumstances, some children manage to survive and even thrive, academically and socially, into adulthood. A complex array of individual, family, and community factors has been identified that best explains resilience and lays the foundation for programs and interventions targeted at fostering the development and maintenance of resilience in at-risk youth. The literature is reviewed to identify and explain those factors, discuss their mutual interaction, and explain their implications for the creation of programs designed to support resilience in school-aged children.
Fascists or Revolutionaries? Left and Right Politics of the Rural Poor
Authors: Anderson Leslie E.
Published: April 2006

This article compares rural support for authoritarian populism in the new democracies in western Europe and Latin America. Literature on mass-based peasant revolutions sees the rural poor as revolutionaries, but an earlier, Marxist view saw them as counter-revolutionary. What can we expect of rural people in new democracies? The article examines four cases of rural support for authoritarian populism and contrasts them with patterns of peasant leftism. Two factors explain the difference: (1) background factors (economic and social relations, the nature of land tenure) and (2) foreground factors (political leadership, organizational style, and rhetoric). The article considers these conclusions for the contemporary international context and draws implications for democratization today.
Beyond visual conventions: Rethinking the design of tactile diagrams
Authors: Thompson Leanne , Chronicle Edward
Published: April 2006

This article reviews the debate over the comprehension of two-dimensional microcapsule tactile pictures portraying three-dimensional information through the use of perspective and visual drawing conventions. It is proposed that three-dimensional haptic object recognition and its relationship to visual object recognition can inform the design of two-dimensional tactual displays. Experimental work is discussed which validates the use of such information in informing the design of 2-D tactile pictures.
Motion Planning of Multi-Limbed Robots Subject to Equilibrium Constraints: The Free-Climbing Robot Problem
Authors: Bretl Timothy
Published: April 2006

This paper addresses the problem of planning the motion of a multilimbed robot in order to “free-climb” vertical rock surfaces. Freeclimbing only relies on frictional contact with the surfaces rather than on special fixtures or tools like pitons. It requires strength, but more importantly it requires deliberate reasoning: not only must the robot decide how to adjust its posture to reach the next feature without falling, it must plan an entire sequence of steps, where each one might have future consequences. In this paper, this process of reasoning is broken into manageable pieces by decomposing a freeclimbing robot's configuration space into manifolds associated with each state of contact between the robot and its environment. A multistep planning framework is presented that decides which manifolds to explore by generating a candidate sequence of hand and foot placements first. A one-step planning algorithm is then described that explores individual manifolds quickly. This algorithm extends the probabilistic roadmap approach to better handle the interaction between static equilibrium and the topology of closed kinematic chains. It is assumed throughout this paper that a set of potential contact points has been presurveyed. Validation with real hardware was done with a four-limbed robot called LEMUR (developed by the Mechanical and Robotic Technologies Group at NASA–JPL). Using the planner presented in this paper, LEMUR free-climbed an indoor, near-vertical surface covered with artificial rock features.
Knotting/Unknotting Manipulation of Deformable Linear Objects
Authors: Wakamatsu Hidefumi , Arai Eiji , Hirai Shinichi
Published: April 2006

Here, we propose a planning method for knotting/unknotting of deformable linear objects. First, we propose a topological description of the state of a linear object. Second, transitions between these states are defined by introducing four basic operations. Then, possible sequences of crossing state transitions, i.e. possible manipulation processes, can be generated once the initial and the objective states are given. Third, a method for determining grasping points and their directions of movement is proposed to realize derived manipulation processes. Our proposed method indicated that it is theoretically possible for any knotting manipulation of a linear object placed on a table to be realized by a one-handed robot with three translational DOF and one rotational DOF. Furthermore, criteria for evaluation of generated plans are introduced to reduce the candidates of manipulation plans. Fourth, a planning method for tying knots tightly is established because they fulfill their fixing function by tightening them. Finally, we report knotting/unknotting manipulation performed by a vision-guided system to demonstrate the usefulness of our approach.
Plastic Zones and Residual Stresses of Metal Reinforced Composite Laminated Rectangular Plates with a Hole under In-Plane Loading
Authors: Şahin Ömer Sinan
Published: April 2006

The nonlinear stress analysis and the spread of plastic zones in layered woven steel fiber-reinforced thermoplastic-matrix laminated rectangular plates are examined using the Finite element method and the first-order shear deformation theory for small deformations. Composite structures consisting of woven Cr–Ni wire as the fiber and F2.12 low-density polyethylene as the thermoplastic matrix are manufactured by hot-press molding. The mechanical properties are experimentally determined. The effect of aspect ratio of rectangular plate and antisymmetric structure is investigated. It is assumed that the laminated plates are subjected to in-plane uniform loads. Loading is gradually increased from the yield point of the plate as 0.01MPa at each load step. Load steps are chosen as 300, 350, and 400 iterations. Residual stresses and expansion of plastic zone have been presented by means of tables and figures.
Performance of Alkali-resistant Glass Fiber Reinforced Concrete
Authors: Ghugal Yuwaraj M. , Deshmukh Santosh B.
Published: April 2006

This article deals with the results of an experimental investigation on the glass fiber modified properties of structural concrete. Alkali-resistant glass fibers are used in this investigation. The effects of these fibers on workability, density, and on various strengths of M20 grade concrete are studied. Fiber content varies from 0.5 to 4.5% by weight of cement. The various strengths considered for investigation are compressive strength, flexural strength, split tensile strength, and bond strength. Cubes of 150 mm for compressive and bond strengths, cylinders of 150 mm diameter 300 mm length for split tensile strength, beams of 100 × 100 × 500 mm for flexural strength are cast. All the specimens are water cured and tested after 28 days. Workability of wet mix is found to be reduced with increased fiber content. Ductility of concrete is found to increase in glass fiber reinforced concrete (GFRC) as observed from the study of load-deflection behavior. New expressions for various strengths are proposed. Results of elastic constants obtained by various methods and newly proposed expressions are presented. A significant improvement in the various strengths is observed due to inclusion of glass fibers in the concrete. Optimum fiber content is found to be strength dependent.
Tensile Properties of Glass Fiber Knitted Fabric Reinforced Polypropylene Composite Made from GF/PP Commingled Yarn Affected by Prestretching
Authors: Zaixia Fan , Zhangyu  , Yanmo Chen , Hairu Long
Published: April 2006

The effects of prestretching of rib 1: 1 knitted fabric preform on the tensile properties of GF/PP composites are investigated in this study. The preform is made from GF/PP commingled yarn. As far as tensile stiffness and tensile strength are concerned, there is a critical value of prestretch ratio. An increase in the prestretch ratio within the range of this critical value increases both the tensile stiffness and the tensile strength. If the prestretch ratio goes beyond this critical value and continues to increase, both tensile stiffness and tensile strength display a tendency of slight decrease because of the break of more glass fibers. The failure strain of the composites decreases with the increase of the prestretch ratio because of the decrease of the stretchability of the knitted reinforcements.
Transient Temperature Distribution in Composites with Layers of Functionally Graded Materials (FGMs)
Authors: Agarwal Bhupesh , Upadhyay P. C. , Banta Larry , Lyons Donald
Published: April 2006

Solution to the non-homogeneous problem of transient heat conduction in a composite medium consisting of a number of parallel layers of functionally graded materials (FGMs) is presented. A generalized program (algorithm) is developed which can be used to obtain the time-dependent temperature profile through laminates having discrete layers of FGMs. It can also be used in case of continuously graded FGM layers by discretizing and replacing them with a reasonably chosen number of sublayers. Working of the algorithm is demonstrated through the solution obtained for the transient response of a thermal barrier coating (TBC) system.
Effects of Hydrothermal Aging on Mechanical Behavior of Sub-zero Weathered GFRP Composites
Authors: Mula S. , Bera T. , Ray P. K. , Ray B. C.
Published: April 2006

Sub-zero weathered GFRP (glass fiber reinforced plastics) composites were aged in water at 60 C for different conditioning times to study fluid sorption kinetics under the influence of a thermal gradient. The effect of subsequent freezing of the conditioned samples on the retention of prior thermal history has been investigated. The variation in mechanical properties during the aging process was studied. One batch of the hydrothermally conditioned specimens was further subjected to sub-zero treatment at 20 C temperature. The samples which were subsequently frozen showed higher interlaminar shear strength (ILSS) initially, although this trend was reversed after a certain conditioning period. Thus, the present study aims to evaluate the mechanical behavior of polymer composites under the influence of extreme and complex conditions.
Building a New World
Authors: Gudmundsdottir Maria , Chesla Catherine A.
Published: April 2006

The goal of this interpretive phenomenological study is to describe and understand significant habits and practices developed by families bereaved from the sudden and unexpected loss of their children. Data were primarily collected through the interviewing of 15 family members in seven families. At least four interviews were conducted with each family. Family members were interviewed both together and separately. The analysis of the data illuminated the development of significant and meaningful family practices. These practices acknowledged the death of the children, integrated their loss into the everyday lives of these families, allowed for continuing connection, and were of utter importance as they contributed to family healing.