bluuebunny/crossref_metadata_2025 huggingface dataset:
Negative regulation of activated α2 integrins during thrombopoiesis
Authors: Zou Zhiying , Schmaier Alec A. , Cheng Lan , Mericko Patricia , Dickeson S. Kent , Stricker Thomas P. , Santoro Samuel A. , Kahn Mark L.
Published: March 2009

Circulating platelets exhibit rapid signaling and adhesive responses to collagen that facilitate hemostasis at sites of vessel injury. Because platelets are anuclear, their collagen receptors must be expressed by megakaryocytes, platelet precursors that arise in the collagen-rich environment of the bone marrow. Whether and how megakaryocytes regulate collagen adhesion during their development in the bone marrow are unknown. We find that surface expression of activated, but not wild-type, α2 integrins in hematopoietic cells in vivo results in the generation of platelets that lack surface α2 receptors. Culture of hematopoietic progenitor cells ex vivo reveals that surface levels of activated, but not wild-type, α2 integrin receptors are rapidly down-regulated during cell growth on collagen but reach wild-type levels when cells are grown in the absence of collagen. Progenitor cells that express activated α2 integrins are normally distributed in the bone marrow in vivo and exhibit normal migration across a collagen-coated membrane ex vivo. This migration is accompanied by rapid down-regulation of activated surface integrins. These studies identify ligand-dependent removal of activated α2 receptors from the cell surface as a mechanism by which integrin function can be negatively regulated in hematopoietic cells during migration between the adhesive environment of the bone marrow and the nonadhesive environment of the circulating blood.
EBV-associated mononucleosis does not induce long-term global deficit in T-cell responsiveness to IL-15
Authors: Giron-Michel Julien , Menard Fanny , Negrini Simone , Devocelle Aurore , Azzarone Bruno , Besson Caroline
Published: March 2009

It has been reported that infectious mononucleosis (IM)–symptomatic primary Epstein-Barr virus infection produces a global down-regulation of interleukin-15 receptor-α (IL-15Rα) on T cells and natural killer cells associated with a defective IL-15 responsiveness that lasts for many years after the disease episode. In contrast with these results, our data indicate that, in the T-cell compartment derived from remote IM subjects, there is no quantitative or qualitative defect in the expression of the IL-15Rα chain and no deficit in T-cell responsiveness to IL-15. We observed efficient signal transduction, survival, and proliferation even in response to low IL-15 concentrations. These data are relevant and shed new light on the immune long-term response in IM subjects because they contradict the hypothesis that defects in Epstein-Barr virus–host immune balance may be correlated with a long-lasting global deficit in T-cell responsiveness to IL-15.
RNAslider: a faster engine for consecutive windows folding and its application to the analysis of genomic folding asymmetry
Authors: Horesh Yair , Wexler Ydo , Lebenthal Ilana , Ziv-Ukelson Michal , Unger Ron
Published: March 2009

Background

Scanning large genomes with a sliding window in search of locally stable RNA structures is a well motivated problem in bioinformatics. Given a predefined window size L and an RNA sequence S of size N (L < N), the consecutive windows folding problem is to compute the minimal free energy (MFE) for the folding of each of the L-sized substrings of S. The consecutive windows folding problem can be naively solved in O(NL3) by applying any of the classical cubic-time RNA folding algorithms to each of the N-L windows of size L. Recently an O(NL2) solution for this problem has been described.

Results

Here, we describe and implement an O(NLψ(L)) engine for the consecutive windows folding problem, where ψ(L) is shown to converge to O(1) under the assumption of a standard probabilistic polymer folding model, yielding an O(L) speedup which is experimentally confirmed. Using this tool, we note an intriguing directionality (5'-3' vs. 3'-5') folding bias, i.e. that the minimal free energy (MFE) of folding is higher in the native direction of the DNA than in the reverse direction of various genomic regions in several organisms including regions of the genomes that do not encode proteins or ncRNA. This bias largely emerges from the genomic dinucleotide bias which affects the MFE, however we see some variations in the folding bias in the different genomic regions when normalized to the dinucleotide bias. We also present results from calculating the MFE landscape of a mouse chromosome 1, characterizing the MFE of the long ncRNA molecules that reside in this chromosome.

Conclusion

The efficient consecutive windows folding engine described in this paper allows for genome wide scans for ncRNA molecules as well as large-scale statistics. This is implemented here as a software tool, called RNAslider, and applied to the scanning of long chromosomes, leading to the observation of features that are visible only on a large scale.
Id2 promotes the invasive growth of MCF-7 and SKOV-3 cells by a novel mechanism independent of dimerization to basic helix-loop-helix factors
Authors: Meng Yuanguang , Gu Chenglei , Wu Zhiqiang , Zhao Yali , Si Yiling , Fu Xiaobing , Han Weidong
Published: March 2009

Background

Inhibitor of differentiation 2 (Id2) is a critical factor for cell proliferation and differentiation in normal vertebrate development. Most of the biological function of Id2 has been ascribed to its helix-loop-helix motif. Overexpression of Id2 is frequently observed in various human tumors, but its role for invasion potential in tumor cells is dispute. We aimed to reveal the role of Id2 in invasion potential in poorly invasive and estrogen receptor α (ERα)-positive MCF-7 and SKOV-3 cancer cells.

Methods

MCF-7 and SKOV-3 cells were stably transfected with the wild-type, degradation-resistant full-length or helix-loop-helix (HLH)-deleted Id2, respectively. Protein levels of Id2 and its mutants and E-cadherin were determined by western blot analysis and mRNA levels of Id2 and its mutants were determined by RT-PCR. The effects of Id2 and its mutants on cell proliferation were determined by [3H]-thymidine incorporation assay and the 3- [4, 5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) dye method. The in vitro invasion potential of cells was evaluated by Transwell assay. Cell motility was assessed by scratch wound assay. The promoter activity of E-cadherin was determined by cotransfection and luciferase assays.

Results

Ectopic transfection of the wild-type Id2 markedly increased the protein and mRNA expression of Id2 in MCF-7 and SKOV-3 cells; the protein level but not mRNA level was further increased by transfection with the degradation-resistant Id2 form. The ectopic expression of Id2 or its mutants did not alter proliferation of either MCF-7 or SKOV-3 cells. Transfection of the wild-type Id2 significantly induced the invasion potential and migratory capacity of cells, which was further augmented by transfection with the degradation-resistant full-length or HLH-deleted Id2. E-cadherin protein expression and transactivation of the proximal E-cadherin promoter were markedly suppressed by the degradation-resistant full-length or HLH-deleted Id2 but not wild-type Id2. Ectopic expression of E-cadherin in MCF-7 and SKOV-3 cells only partially blunted the invasion potential induced by the degradation-resistant HLH-deleted Id2.

Conclusion

Overexpression of Id2 in ERα-positive epithelial tumor cells indeed increases the cells' invasive potential through a novel mechanism independent of dimerization to basic helix-loop-helix factors. E-cadherin contributes only in part to Id2-induced cell invasion when Id2 is accumulated to a higher level in some specific cell types.
Ultrafast and memory-efficient alignment of short DNA sequences to the human genome
Authors: Langmead Ben , Trapnell Cole , Pop Mihai , Salzberg Steven L
Published: March 2009

Bowtie is an ultrafast, memory-efficient alignment program for aligning short DNA sequence reads to large genomes. For the human genome, Burrows-Wheeler indexing allows Bowtie to align more than 25 million reads per CPU hour with a memory footprint of approximately 1.3 gigabytes. Bowtie extends previous Burrows-Wheeler techniques with a novel quality-aware backtracking algorithm that permits mismatches. Multiple processor cores can be used simultaneously to achieve even greater alignment speeds. Bowtie is open source http://bowtie.cbcb.umd.edu.
Benefits of the induced polarization geoelectric method to hydrocarbon exploration
Authors: Veeken Paul C. , Legeydo Peter J. , Davidenko Yuri A. , Kudryavceva Elena O. , Ivanov Sergei A. , Chuvaev Anton
Published: March 2009

Delineation of hydrocarbon prospective areas is an important issue in petroleum exploration. The geoelectric method helps to identify attractive areas and reduces the overall drilling risk. For this purpose, induced polarization (IP) effects are mapped caused by the presence of epigenetic pyrite microcrystals in sedimentary rocks. These crystals occur in a shallow halo-shaped mineralogical alteration zone, often overlying a deeper-seated hydrocarbon accumulation. Local enrichment in pyrite results from reducing geochemical conditions below an impermeable layer. The imperfect top seal of the accumulation permits minor amounts of hydrocarbons to escape and migrate through the overlying rocks to shallower levels. During migration, hydro-carbons encounter an impermeable barrier, forming an altera-tion zone. Induced polarization logging and coring in wells confirm this working model. Geoelectric surveying visual-izes anomalies in electric potential difference measured be-tween receiver electrodes. The differentially normalized method (DNME) inverts the registered decay in potential differences, establishing a depth model constrained by seismic and petro-physical data. Diagnostic geoelectric attributes are proposed, giving a better grip on chargeability and resistivity distribution. Acquisition and processing parameters are adjusted to the target depth. Encouraging results are obtained in deeper [Formula: see text] as well as in very shallow water. Onshore, a grounded current transmitter is used. Geoelectric surveys cover different geologic settings with varying target depths. The success ratio for predicting hydrocarbon occurrences is high. So far, 40 successful wells have been drilled in Russia on mapped geoelectric anomalies. Out of 126 wells, the method produced satisfactory results in all but two cases. The technique reduces the risk attached to new hydrocarbon prospects and allows better ranking at a reasonable cost.
A passive seismic survey over a gas field: Analysis of low-frequency anomalies
Authors: Saenger Erik H. , Schmalholz Stefan M. , Lambert Marc-A. , Nguyen Tung T. , Torres Arnaud , Metzger Sabrina , Habiger Robert M. , Müller Tamara , Rentsch Susanne , Méndez-Hernández Efraín
Published: March 2009

Passive seismic low-frequency (from approximately [Formula: see text]) data have been acquired at several locations around the world. Spectra calculated from these data, acquired over fields with known hydrocarbon accumulations, show common spectral anomalies. Verification of whether these anomalies are common to only a few, many, or all hydrocarbon reservoirs can be provided only if more and detailed results are reported. An extensive survey was carried out above a tight gas reservoir and an adjacent exploration area in Mexico. Data from several hundred stations with three-component broadband seismometers distributed over approximately [Formula: see text] were used for the analysis. Severalhydrocarbon reservoir-related microtremor attributes were calculated, and mapped attributes were compared with known gas intervals, with good agreement. Wells drilled after the survey confirm a predicted high hydrocarbon potential in the exploration area. A preliminary model was developed to explain the source mechanism of those microtremors. Poroelastic effects caused by wave-induced fluid flow and oscillations of different fluid phases are significant processes in the low-frequency range that can modify the omnipresent seismic background spectrum. These processes only occur in partially saturated rocks. We assume that hydrocarbon reservoirs are partially saturated, whereas the surrounding rocks are fully saturated. Our real data observations are consistent with this conceptual model.
High Prevalence of Reduced Fecundity in Men with Congenital Adrenal Hyperplasia
Authors: Reisch Nicole , Flade Linda , Scherr Michael , Rottenkolber Marietta , Pedrosa Gil Francesco , Bidlingmaier Martin , Wolff Hans , Schwarz Hans-Peter , Quinkler Marcus , Beuschlein Felix , Reincke Martin
Published: March 2009

Context: Testicular adrenal rest tumors (TARTs) are regarded to contribute to the high prevalence of subfertility in males with congenital adrenal hyperplasia (CAH).

Objectives: Our objectives were to evaluate reduced fecundity and its possible causes in well-controlled adult males with CAH, and to investigate diagnostic tools for improved treatment monitoring with respect to fertility outcomes.

Design: In a cross-sectional study at the Department of Endocrinology at the University Hospital München, Germany, 22 adult male CAH patients (15 salt wasting and seven simple virilizing, age 19–48 yr) were clinically assessed according to their hormonal control. We performed testicular ultrasound (22 of 22), magnetic resonance imaging (18 of 22), and a semen analysis (19 of 22) in the participants.

Results: All patients had a pathological semen analysis. TART prevalence was 10 of 22 (eight salt wasting, two simple virilizing). Poor therapy control was present in five patients, and all five had TARTs. Of the other 17 well-controlled patients with normal or suppressed adrenal androgens and 17-hydroxyprogesterone levels, five presented with TARTs. There was a significant correlation between sperm concentration and functional testicular volume (r = 0.70; P = 0.002), TART volume (r = −0.70; P = 0.036), as well as inhibin B levels (r = 0.75; P < 0.0001), respectively. In several men, hormonal control parameters suggested hypogonadism, with glucocorticoid overtreatment as a relevant factor for poor semen quality.

Conclusions: Poor semen parameters are common in male CAH patients. TARTs, most likely reflecting undertreatment, as well as inhibin B are important indicators of fecundity. On the other hand, long-term glucocorticoid overtreatment also seems to contribute to low semen quality.
Differential trafficking of Src, Lyn, Yes and Fyn is specified by the state of palmitoylation in the SH4 domain
Authors: Sato Izumi , Obata Yuuki , Kasahara Kousuke , Nakayama Yuji , Fukumoto Yasunori , Yamasaki Takahito , Yokoyama Kazunari K. , Saito Takashi , Yamaguchi Naoto
Published: March 2009

Src-family tyrosine kinases (SFKs), which participate in a variety of signal transduction events, are known to localize to the cytoplasmic face of the plasma membrane through lipid modification. Recently, we showed that Lyn, an SFK member, is exocytosed to the plasma membrane via the Golgi region along the secretory pathway. We show here that SFK trafficking is specified by the palmitoylation state. Yes is also a monopalmitoylated SFK and is biosynthetically transported from the Golgi pool of caveolin to the plasma membrane. This pathway can be inhibited in the trans-Golgi network (TGN)-to-cell surface delivery by temperature block at 19°C or dominant-negative Rab11 GTPase. A large fraction of Fyn, a dually palmitoylated SFK, is directly targeted to the plasma membrane irrespective of temperature block of TGN exit. Fyn(C6S), which lacks the second palmitoylation site, is able to traffic in the same way as Lyn and Yes. Moreover, construction of Yes(S6C) and chimeric Lyn or Yes with the Fyn N-terminus further substantiates the importance of the dual palmitoylation site for plasma membrane targeting. Taken together with our recent finding that Src, a nonpalmitoylated SFK, is rapidly exchanged between the plasma membrane and late endosomes/lysosomes, these results suggest that SFK trafficking is specified by the palmitoylation state in the SH4 domain.
Rail lubrication and its impact on the wheel/rail system
Authors: Fröhling R , de Koker J , Amade M
Published: March 2009

As the effectiveness of Transnet Freight Rail's current hi-rail lubrication strategy cannot be adequately quantified, an investigation into the level of surface protection between application cycles was initiated. Influencing factors such as the tracking performance of rolling stock, the number and type of locomotives and wagons in a train, axle load, train speed, and the coefficient of friction on the gauge face have, thus, been considered. After a brief literature review of international experiences with respect to friction management, a detailed description is given of the tests that were conducted by Transnet Freight Rail. Conclusions from these tests indicate that the increase in rail gauge face temperature on the high rail is dominated by the duration and the magnitude of the flange forces.
Evaluation of Potential Interaction Between Vinorelbine and Clarithromycin
Authors: Yano Ryoichi , Tani Daisuke , Watanabe Kyohei , Tsukamoto Hitoshi , Igarashi Toshiaki , Nakamura Toshiaki , Masada Mikio
Published: March 2009

Background:

Myelotoxicity, a major toxicity of vinorelbine, may be related to the degree of one's exposure to vinorelbine. In theory, clarithromycin has the potential to alter vinorelbine's pharmacokinetics by inhibiting CYP3A and/or P-glycoprotein; this may result in massive exposure to vinorelbine and severe toxicity. To date, macrolide–vinorelbine drug interactions have not been reported.

Objective:

To estimate the clinical risk of a interaction between vinorelbine and clarithromycin.

Methods:

In a retrospective cohort study, we searched computerized medical records of patients who had been administered vinorelbine in the University of Fukui Hospital. The study cohort was defined as all patients with non–small-cell lung cancer who received vinorelbine between May 30, 2003, and January 31, 2008. The treatment courses were classified according to whether or not clarithromycin was concomitantly administered with vinorelbine. Nadir neutrophil counts were recorded as the major outcomes. Vinorelbine–clarithromycin interaction was defined as a significant increase in the risk of severe neutropenia when the 2 drugs were administered concomitantly.

Results:

A total of 12 (63.2%) and 11 (27.5%) episodes of grade 3/4 neutropenia occurred among the patients who were and were not administered clarithromycin, respectively. The incidence of grade 4 neutropenia was higher in the group administered clarithromycin than in those who did not receive it (31.6% vs 2.5%; p = 0.0033). Vinorelbine dose, concomitant clarithromycin administration, and female sex were significantly correlated with severe neutropenia, with unadjusted odds ratios of 0.07 (95% CI 0.01 to 0.59), 4.52 (95% CI 1.41 to 14.45), and 4.55 (95% CI 1.39 to 14.29), respectively.

Conclusions:

Compared with patients who are administered vinorelbine alone, patients who are administered clarithromycin during chemotherapy with vinorelbine are at a higher risk for severe neutropenia. Physicians should educate their patients about this interaction. If possible, clarithromycin administration should be avoided in patients who will undergo chemotherapy with vinorelbine in the near future. However, further prospective pharmacokinetic studies are required to confirm this interaction.
Coronary Vasospasm and Atrial Fibrillation Associated with Ondansetron Therapy
Authors: Havrilla Pamela L , Kane-Gill Sandra L , Verrico Margaret M , Seybert Amy L , Reis Steven E
Published: March 2009

Objective:

To provide further evidence of cardiovascular adverse effects of ondansetron, including new-onset atrial fibrillation, ST segment elevation, and chest pain subsequent to ondansetron administration, and to review cardiovascular adverse events related to several 5-hydroxytryptamine type 3 (5-HT3) receptor antagonists.

Case Summary:

A 51-year-old male with an uncomplicated past medical history was admitted for an elective inguinal hernia repair and septoplasty. His maintenance medications were discontinued prior to surgery. After a second 4-mg dose of intravenous ondansetron was administered, he developed nausea and diaphoresis. His electrocardiograph revealed new-onset atrial fibrillation and inferolateral ST segment elevation with ST segment alternans. During emergent cardiac catheterization, no obstructive coronary artery disease was evident. The patient's heart rhythm was electrically converted to normal sinus rhythm. During 3 years of follow-up, he has had no return of chest pain or hypotension.

Discussion:

Although considered a safe class of medications by many clinicians, several of the 5-HT3 receptor antagonists have been associated with serious cardiovascular effects. Three case reports described cardiac dysrhythmias and 9 documented coronary vasospasm and chest pain, possibly resulting from ondansetron. This is the first reported case of a combination of hypotension, atrial fibrillation, ST segment elevation, and chest pain following ondansetron administration after elective surgery in a healthy adult male with a nonconfounding medication profile. The Naranjo probability scale indicated that ondansetron was the probable cause of these cardiovascular events.

Conclusions:

This case report supports the concern regarding cardiovascular adverse effects of ondansetron. Clinicians should be aware of cardiovascular adverse reactions that may be associated with intravenous ondansetron and monitor for electrocardiographic changes as indicated. Further investigation is needed to delineate the actual incidence of cardiovascular effects associated with ondansetron and whether the intravenous rate of administration is a contributing factor.
Frequency and Distribution of Nerves in Scrapie-affected and Unaffected Peyer's Patches and Lymph Nodes
Authors: McGovern G. , Martin S. , González L. , Witz J. , Jeffrey M.
Published: March 2009

Transmission of sheep scrapie and some other prion diseases, including variant Creutzfeldt-Jakob disease of man, probably occurs via the oral route. A disease-associated variant of the host-coded prion protein (PrPd) accumulates in germinal center follicles of lymphoid tissues, including Peyer's patches of the gut, where it can be detected before its accumulation in the central nervous system. To investigate the potential role of lymphoid tissue nerves in neuroinvasion, we used immunohistochemical methods to study the frequency and distribution of nerves and PrPd accumulation in Peyer's patches and other lymphoid tissues from scrapie-affected and unaffected sheep. Nerves were infrequently found in secondary follicles of Peyer's patches, but never in germinal centers of the other lymphoid tissues tested. No differences in the frequency or distribution of nerves were found in relation to the presence or absence of PrPd accumulation. PrPd accumulation and nerves were only infrequently present together in Peyer's patches. These results suggest that, even if amplification of infectivity in lymphoid tissues facilitates neuroinvasion, nerves within lymph nodes and germinal centers of Peyer's patches do not play a primary role in transport of infectivity to the central nervous system. However, sheep between 2 and 4 months of age had significantly more nerve fibers within follicles than older groups. It is therefore possible that a general increase in nerve density of the intestine during early phases of life may contribute to an increased susceptibility of young animals to oral prion infection.
Effects of 4-n-Octylphenol on the Induction of Mammary Tumors Induced by 7,12-Dimethylbenz[a]anthracene in Rats
Authors: Kawaguchi H. , Umekita Y. , Yoshida H.
Published: March 2009

We previously reported that a neonatal administration of diethylstilbestrol or 17β-estradiol affected the mammary carcinogenesis induced by 7,12-dimethylbenz[a]anthracene (DMBA) in rats. The aim of this present study was to investigate the effects of 4- n-octylphenol (OP), a weak estrogenic disruptor, on the induction of mammary carcinomas (MC) and benign proliferative lesions (PL) induced by DMBA in rats. All female rats were administered at 0, 0.1, 10, 100, and 1,000 μg OP once at birth, given 10 mg DMBA at 50 days after birth, and thereafter underwent necropsy at 351 days after birth. All male rats were given 10 mg DMBA at 28, 42, and 56 days after birth, and 0, 10, 100, and 1,000 ppm OP fed from day 70-153; they underwent necropsy at 153 days after birth. Neonatal single administration of OP in female rats showed no effects such as persistent estrus, anovulatory ovaries, or PL. A slight increase in numbers of rats with MC occurred at the highest dosage. Feeding a large dose of OP for a long period in male rats induced atrophy of testes and slightly increased numbers of affected MC but not increased numbers of males while it showed no effects on PL. These results suggested that administration of a large dose of OP for a long period may have had a minimal effect on mammary carcinogenesis in male rats.
Modern Stone Cladding, Design and Installation of Exterior Dimension Stone Systems
Authors: Lewis MD
Published: March 2009

Description

Shows you how to select, design, and install stone cladding systems for exterior walls. New engineering applications as well as recognized industry practices are explained extensively to help you make objective and rational decisions.

Section I, Introduction to Modern Stone Cladding and Section II, Precedents to Modern Stone Cladding discuss the history of stone as it evolved into modern thin, non-load bearing cladding.

Section III, Determining Responsible Design Values and Section IV, The Future of Stone outline a variable-based design procedure analogous to load-and-resistance factor design.

Section V, Guide Specification for Stone Systems advises owners, architects, engineers, and contractors about the specialty of modern stonework.
Manual on Coating and Lining Methods for Cooling Water Systems in Power Plants
Authors: Monday JC , Shugart TB , Tamayo JA
Published: March 2009

Description

The only book of its kind to address coating technology specifically for power plant applications and their unique problems. This single volume contains the latest information on:

• Corrosion and erosion problems

• Remedies

• Inspection

• Testing

• Case histories

• Degradation of equipment

• Design tools to implement technology and test data

• Application of ASTM test methods and standards

• and New technology.
Materials and Mechanics Analyses of Durability Tests for High-Temperature Polymer Matrix Composites
Authors: McManus HL , Cunningham RA
Published: March 2009

Models of the environmentally-induced degradation of composite materials and the effect of this degradation on composite laminate behavior are presented. Although the models are not sufficiently mature for predictive design use, they provide insights into the mechanisms of degradation of composite materials. The models are used to study test methods frequently used to assess composite durability, including weight loss, shrinkage, and mechanical property degradation testing. It is found that even simple tests of material undergoing environmentally induced degradation are difficult to interpret. In particular, the spatial non-uniformity of degradation converts originally simple specimens into complex structures with non-uniform chemical and mechanical states. Consideration of this complexity is vital to the full understanding of the results of such tests.
Two-Dimensional Moisture Diffusion in Hybrid Composite Components
Authors: Zaffaroni G
Published: March 2009

A thermodynamics formulation for two-dimensional (2-D) diffusion in hybrid composite is discussed. The model had been transferred in a computer code and the validation is assessed here through the comparison with the analytical solution in the case where Fick's law is adequate (2-D, only 1 material) and with the experimental measurements in some simple cases (1-D, more than 1 material). An example of the use of the computer code is presented.
High Temperature and Environmental Effects on the Durability of Ti-6AI-4V/FM5 Adhesive Bonded System
Authors: Parvatareddy H , Pasricha A , Dillard DA , Holmes B , Dillard JG
Published: March 2009

A fracture mechanics based approach using wedge and double cantilever beam (DCB) specimens is being used to evaluate the durability of a titanium/adhesive system. The adhesive used was a polyimide, developed by NASA Langley Research Center, modified and supplied by Cytec Engineered Materials, Inc., and designated as FM5. Prior to bonding, the adherend surfaces were pretreated by one of two surface pretreatments: phenylethynyl trimethyl silane or chromic acid anodization.

Samples were aged at one of three different temperatures, 150, 177, and 204°C, all of which are well below the (250°C) glass transition temperature (Tg) of the adhesive. Aging was also carried out in one of three different environments, ambient atmospheric air and reduced air pressures of 2 psi air (13.8 KPa) and 0.2 psi air (1.38 KPa), for several months. Samples aged for different times were then tested to evaluate both static and fatigue properties. Results obtained thus far indicate that the greatest loss in strength occurs after aging in air at the highest aging temperature of 204°C. Strain energy release rate G values obtained from the static DCB tests dropped by 10 to 20% after aging for periods of up to 6 months.

Solvent uptake tests were conducted on neat FM5 resin in several common organic solvents followed by tensile tests to evaluate both saturated and residual properties. Strain energy release rate values were also computed from wedge tests of samples immersed in the different solvents for several days. Results showed the FM5 resin to be quite solvent resistant.
Long-Term Isothermal Aging Effects on Carbon Fabric-Reinforced PMR-15 Composites: Compression Strength
Authors: Bowles KJ , Roberts GD , Kamvouris JE
Published: March 2009

A study was conducted to determine the effects of long-term isothermal thermo-oxidative aging on the compressive properties of T-650-35 fabric reinforced PMR-15 composites. The temperatures that were studied were 204, 260, 288, 316, and 343°C. Specimens of different geometries were evaluated. Cut edge-to-surface ratios of 0.03 to 0.89 were fabricated and aged. Aging times extended to a period in excess of 15 000 h for the lower temperature runs.

The unaged and aged specimens were tested in compression in accordance with Test Method for Compressive Properties of Rigid Plastics (ASTM D 695). Both thin and thick (prism) specimens were tested. Three specimens were tested at each time/temperature/geometry condition. The failure modes appeared to be initiated by fiber kinking with longitudinal, interlaminar splitting.

In general, it appears that the thermo-oxidative degradation of the compression strength of the composite material may occur by both thermal (time-dependent) and oxidative (weight-loss) mechanisms. Both mechanisms appear to be specimen-thickness dependent.
Physical and Chemical Aging Effects in PMR-15 Neat Resin
Authors: Kamvouris JE , Roberts GD , Pereira JM , Rabzak C
Published: March 2009

The objective of this study was to determine whether a shifting approach can be used to account for both chemical and physical effects during long-term aging of high temperature polyimide thermoset polymers, such as the commercial material PMR-15. Stress relaxation curves measured after aging at 316°C for times up to 800 h could be shifted to form a master curve. The horizontal shift factors were found to increase with increasing aging time, consistent with a reduction in molecular mobility that occurs as a result of either physical aging or increased cross-linking. There was a correlation between the vertical shift factors and cure related chemical changes that cause Tg to increase and mass to decrease. Aging effects were partially reversed by heating the aged specimen above its glass transition temperature, indicating that a large portion of the aging is physical in nature. Specimens aged in nitrogen had a larger reversible component than specimens aged in air.
Behavioral Studies of Contaminant Effects on Aquatic Invertebrates: A Review of Russian Investigations
Authors: Nepomnyashchikh VA , DeLonay VA , Little EE
Published: March 2009

Studies by Russian scientists have documented significant alterations and impairment of critical behavioral functions in aquatic organisms following exposure to environmental contaminants. Behavioral responses disrupted by sublethal exposure to toxicants are intimately involved in habitat selection, foraging, competition, predator-prey relationships, and reproduction, and are essential to survival. Behavioral responses of benthic invertebrates have received considerable study in Russia. A range of invertebrate taxa have been studied, including leeches, insects, molluscs, plankton, and crustaceans. In addition, aquatic invertebrates exhibit a large number of behavioral responses which are sensitive to contaminant exposure and are easily quantified. Standardized behavioral methodologies for measuring contaminant effects are being developed.
A Novel Method for the Measurement of Noticeability of Package Information
Authors: Buckley P
Published: March 2009

This paper presents a method that enables package design elements to be manipulated systematically while giving the graphic design quality of commmercially available products. The presentation method was developed to give the timing and exposure accuracy of tachistoscopic methods without the need for very brief exposure times.

Essentially, a commercially available package is photographed onto 35-mm slide film at a viewing distance of 600 mm, scanned into an Apple Macintosh, retouched using Adobe Photoshop—a graphic design/retouch program, and output to 35-mm slide film. Design variations are presented on a tachistoscope such that the time taken to detect the design element of interest is recorded in thousandths of a second.

This method has been used to investigate the effects of package information position, size and surround presence, and package size, shape, orientation, and package information load (or clutter) on the noticeability of food label health and nutrition claims (e.g., low fat, high fiber). The potential of this technique and variations on it as a cost-effective package information testing tool are numerous.
Mechanical Damping in the Martensitic Phase of Cu-Al-Ni Crystals
Authors: Kustov SB , Humbeeck JV , Hurtado I , Golyandin SN , De Batist R
Published: March 2009

Amplitude and frequency dependences of intrinsic damping have been studied in copper-aluminum-nickel (Cu-Al-Ni) single crystals in the martensitic state after different heat treatments. The measurements of intrinsic damping were performed by resonant and forced oscillation techniques in a range from infra-to ultrasonic frequencies. The conclusion is drawn that during aging in β-phase (200°C) the behavior of the pinning obstacles in the martensitic state at room temperature changes from highly mobile and forming atmospheres around the mobile defects, presumably dislocations, to rather immobile and homogeneously distributed in the bulk of the crystal. Observed regularities of the amplitude-dependent intrinsic damping do not correspond to the breakaway model of amplitude-dependent internal friction both for quenched and aged specimens. In contrast to the generally accepted point of view, a notable frequency dependence of the amplitude-dependent damping is revealed, especially in the case of quenched specimens. Short-range pinning points are considered as basic obstacles for dislocation motion in the quenched specimens. Two types of obstacles are supposed to form the amplitude frequency spectra of damping for the aged specimens: purely hysteretic or athermal, due to the presence of γ-precipitates, and thermally activated due to the existence of short-range pinning points.
Damping Due to Grain Boundary Sliding in Zirconia and Alumina
Authors: Lakki A , Schaller R
Published: March 2009

Low-frequency mechanical spectroscopy measurements were performed in fine-grained zirconia and alumina. In both cases, anelastic relaxation phenomena at high temperature (>1200 K) have been observed, which are found to be in close correlation with the creep behavior. More precisely, a more or less resolved mechanical loss peak is obtained, superimposed on a mechanical loss background and accompanied by a decrease in the shear modulus. Creep deformation in these materials occurs mainly by accommodated grain boundary sliding and the anelastic deformation seems to be related to local grain-sliding motion. In the case of zirconia, the mechanical loss spectra consist of a mechanical loss peak which continuously evolves into an exponential background. This behavior can be described in terms of a model of grain boundary sliding, lubricated by an intergranular amorphous phase, the viscosity of which may thus be estimated. The transition from peak to background could then give an account for the onset of microcreep in these materials. Effectively, the activation energy values as obtained for the spectra are in close agreement with the corresponding values obtained by creep tests, and also the same dependence on grain size is found. The spectra in alumina are similar to those in zirconia, but show a complex dependence on the grain size, and the activation energy values are higher than those determined by creep tests. In order to account for all the features of the observed spectra, a description of the grain boundary sliding mechanism in terms of motion of grain boundary dislocations is needed.
Effect of Crystalline and Magnetic Structure on Magnetomechanical Damping of Fe-Cr-Based Alloys
Authors: Chudakov IB , Golovin IS
Published: March 2009

The results of magnetic and structural investigations of binary and complex alloyed iron-chromium (Fe-Cr)-based high-damping alloys (HDA) have been generalized on the basis of recent data obtained with the authors' participation. Alloys have been tested in the high damping state as well as in the state with a strongly suppressed intrinsic damping capacity. An internal friction method, different mechanical tests, transmission electron microscopy, X-ray scattering, diffraction and refraction of neutrons in the range of small angles, magnetic hysteresis loops, and magnetostriction investigations have all been used. The combination of the last three methods allows us to reveal information concerning magnetic domain structure in the bulk samples. Relaxation and hysteresis internal friction effects in applied magnetic fields allow us to obtain information about interstitial redistributions and dislocation mobility. The increase of annealing temperature of cold-worked alloys leads to the nonmonotonic increase of damping capacity due to magnetomechanical damping (MMD). Simultaneously, a strong structural modification as well as modifications of the magnetic domain structure take place. For a reasonable interpretation of the high intrinsic damping capacity, both aforementioned structures have to be considered.

The magnetic domain structure of Fe-Cr HDAs fundamentally differs in the high damping state and after heat treatment which decreases damping capacity. A good correlation between average magnetic domain size in the bulk of material (obtained by the neutron refraction method) and the specific damping capacity (Ψ) has been obtained. This correlation represents a maximum for Ψ in the average domain size of about 8 μm for different binary and additionally alloyed Fe-Cr alloys. This domain structure may be realized for various alloys with the help of different heat treatments. Therefore the damping capacity of Fe-Cr-based alloys fundamentally depends on the type and parameters of the magnetic domain structure and its interaction with crystalline lattice imperfections in an applied stress.
Amplitude-Dependent Damping in YBCO Ceramics Between 6.5 K and 290 K
Authors: Kardashev BK , Golyandin SN , Kustov SB , Nikanorov SP , Devos P , Cornelis J , De Batist R
Published: March 2009

Nonlinear acoustic effects in yttrium-barium-copper-oxygen (YBCO) ceramics with different grain sizes were investigated by means of the piezoelectric ultrasonic composite oscillator technique (PUCOT) at frequencies of about 100 kHz, corresponding to longitudinal resonance vibration. It has been shown that the acoustic parameters (decrement and resonance frequency) exhibit hysteretic behavior at temperatures in the range between 6.5 K and 290 K. Irreversible changes occurring in these acoustic parameters during measurements of their amplitude dependence at 6.5 K were found to disappear as a result of thermal annealing at 65 K. Furthermore, an unusual crossover behavior in the amplitude dependent damping curves obtained at low temperatures has been observed for the first time. This crossover effect depends strongly on grain size and disappears at temperatures above 100 K; it has never been, so far, observed at room temperature. It appears that the crossover effect is related to an unusual time dependence of the nonlinear damping: at high vibration amplitudes, the decrement decreases, simultaneously with a decrease of the resonance frequency, that is, an increase of the Young's modulus defect. This observation can be understood by considering separately the effects of high-amplitude vibration on the acoustic parameters at both low and high strain amplitude.

Analysis of the results suggests that the hysteretic phenomena observed in YBCO ceramics may be ascribed to crystal dislocations vibrating in the internal stress fields of various types of point defects, some of which remain mobile down to liquid helium temperature. High-amplitude excitation introduces (quasi-permanent) changes in the microstructure, that is, in the dislocation-pinning point configuration, which are responsible for the enhanced dissipation of mechanical energy and thus for the crossover effect.

Finally, some preliminary results of magnetomechanical measurements are presented, demonstrating the usefulness of the PUCOT for studying the relationship between the magnetic properties and the stress-induced structural modifications occurring in YBCO ceramics.
Amplitude-Dependent Material Damping—Old Beliefs and New Facts: Working Toward a Synthesizing Model
Authors: Gelli D , Olzi E
Published: March 2009

A study is underway to achieve a reasonably general model for amplitude-dependent material damping. This paper illustrates the conclusions we have reached so far.

Conventional, firmly held convictions, not corroborated by subsequently produced experimental evidence, are listed and discussed. The main phenomenological features of the experimental results and the aspects common to many instances are briefly outlined. Interesting similarities between dislocation damping and other damping sources are pointed out. A line of interpretation of the updated phenomenology in the framework of a “moties-pinners” model is suggested. The prospect of an “equivalent pinned string” of a generic moty is also advanced. Lastly, some fractal features of the amplitude-dependent damping are cited.
A Review of the Physical Metallurgy and Damping Characteristics of High Damping Cu-Mn Alloys
Authors: Laddha S , Van Aken DC
Published: March 2009

This paper reviews the physical metallurgy and damping characteristics of copper-manganese (Cu-Mn) alloys. Many of the examples given in this paper are based upon the authors' experimental investigations of an alloy with nominal composition (composition in weight percent) of 48Cu-48Mn-1.5Al-0.27 Si-0.072Sn-0.028C-0.05Er. The results for this material were obtained in a bending mode, and the reported strain amplitudes represent the maximum surface strain imposed. Damping in these materials is very sensitive to heat treatment and carbon content. Recent work has shown that carbon in solid solution is detrimental to the damping capacity and results in a strain aging behavior and subsequent loss of damping capacity when stored at room temperature. Copper-manganese alloys can lose more than 50% of their damping capacity during room temperature storage. The role of erbium in the stabilization of the damping capacity is explained in the context of the physical metallurgy of the Cu-Mn system.
Snoek Relaxation in Ternary Body-Centered-Cubic Alloys
Authors: Numakura H , Koiwa M
Published: March 2009

Experimental and theoretical studies on the effect of substitutional solutes on the Snoek relaxation of interstitial solutes in body-centered-cubic (bcc) metals are reviewed. The presence of a small amount of alloying element (M) gives rise to additional components, which often lead to a complex damping spectrum. The origin of the effect is the interaction between the substitutional and interstitial solute atoms, or s-i interaction. Experimental findings on the s-i interaction in Fe-M-(C, N) and (V, Nb, Ta)-M-(O, N) systems are presented, and theoretical studies on the relaxation mechanism are summarized. Recent advances in experiment and theory are briefly described, followed by suggestions for future studies.
Football Fields and Facilities: Safety Guideline Concerns
Authors: Mittelstaedt AH
Published: March 2009

Football fields, known to most people as the pro/college stadium or the local field at the park or school grounds, are used at many levels of proficiency by players of all ages. Little attention is given to the differences imposed by variations in skill, size, training, equipment, and other human factors. Studies are being undertaken by the National and American Football Leagues, universities, the medical profession, and Players Association, as well as the National Federation of State High School Athletics Association, the National Athletic Trainers Association, and others. These organizations are studying factors such as physical conditioning, developmental and physical characteristics of players, types of training and scrimmaging, types of plays, defensive and offensive motions, blocks, tackles, interceptions, other techniques, protective devices, and other aspects of the game. There is no question that there is a cause-and-effect relationship between the players' performance, equipment, the facilities, and the injuries. It must be acknowledged that regardless of the surface, facility, or equipment, football has inherent risks. This paper addresses those aspects of the football field surface and other appurtenances that may be the cause of injury.
The Sports Turf Management Research Program at Michigan State University
Authors: Rogers JN , Stier JC , Crum JR , Krick TM , Vanini JT
Published: March 2009

The turfgrass program at Michigan State University has recently dedicated and focused its research on sports turf management. There are three major areas of research: (1) the indoor turfgrass project, (2) the use of crumb rubber from used tires, and (3) management of high sand-based root zone athletic fields. The indoor turf project stemmed from the 1994 World Cup Soccer Matches involving the installation and maintenance of a portable turfgrass system in the Pontiac Silverdome in Pontiac, Michigan. The majority of the research for this project was completed in a 600-m2 dome constructed on the Michigan State University campus specifically for this project. The crumb rubber project was initiated in 1990 and nine experiments were used to investigate the incorporation of crumb rubber from used tires into the soil profile and at the turf-soil interface of turf systems to improve turfgrass wear tolerance and reduce soil compaction. The sand-based root zone turf project was initiated in 1992 to investigate establishment and management scenarios specific to these areas. A 334-m2 field was constructed to investigate these practices. Initial studies dealt with the establishment of either Kentucky bluegrass (Poa pratensis L.) or perennial ryegrass (Lolium perenne L.) with different fertilizer management regimes.