bluuebunny/crossref_metadata_2025 huggingface dataset:
Pea leaf weevil herbivory on pea seedlings: effects on growth response and yield
Authors: Williams Livy , Schotzko D. J. , O'Keeffe L. E.
Published: April 2011

Field experiments were conducted to determine growth and yield responses of Pisum sativum L. to defoliation by adult Sitona lineatus (L.). Seedlings grown under conventional (moldboard plowed) and conservation (chisel plowed) tillage treatments were infested for a 1‐week period with 0, 1 and 8 weevils per plant at two times: at 75% field emergence and 1 week later. After the early infestation, defoliation for the control, low and high weevil densities was about 0, 15 and 50%, respectively, while defoliation after the late infestation was about 0, 10 and 35%. An undercompensatory growth response was observed in one experiment after seedlings were subjected to moderate levels of early defoliation. Exact compensation was observed in two experiments after early infestations of low and high Sitona densities. Sitona defoliation reduced the number of pods per plant and pod length in two experiments. However, seed biomass was never significantly reduced. Averaged over all experiments, reduction in seed biomass due to high Sitona densities was 10 and 5% for early and late infestations, respectively. Tillage treatments did not affect Pisum compensatory growth response, although yield components were sometimes greater in conservation tillage than in conventional tillage, possibly due to slightly greater soil moisture in the conservation tillage plots.
Plant oils as grain protectants against infestations of Cryptolestes pusillus and Rhyzopertha dominica in stored grain
Authors: Obeng‐Ofori D.
Published: April 2011

Plant oils (cottonseed, soybean, corn, groundnut and palm) at different dosages were evaluated in the laboratory for their ability to suppress the populations of Cryptolestes pusillus and Rhyzopertha dominica in maize and sorghum. Exposure of adults of both beetle species to grains treated with 10 ml/kg of the different oils induced 100% mortality within 24 h. A dose of 5 ml/kg of each oil significantly decreased the progeny produced by R. dominica. Complete protection was achieved on grains treated with 10 ml/kg. These oils also repelled the adults of both species. Percentage weight loss caused by R. dominica in grains treated with 5 ml/kg and 10 ml/kg levels were significantly lower than in untreated grains. Oil treatment did not affect the germination of, or water absorption by, maize and sorghum grains compared with untreated grains. The potential use of plant oils in the management of insect pests in traditional grain storage is discussed.
Toxicity of Bacillus thuringiensisδ‐ endotoxins toward the potato aphid in an artificial diet bioassay
Authors: Walters Frederick S. , English Leigh H.
Published: April 2011

Recent investigations indicated that Bacillus thuringiensis delta‐endotoxins (DET) possess aphidicidal activity in an artificial diet bioassay. Crystalline preparations of CryIIA, CryIIIA and CryIVD solubilized in a slightly alkaline sucrose/amino acid diet clearly imparted toxicity toward adults of potato aphid, Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae) after 4–5 days of continuous feeding. No obvious feeding deterrence was noted in these assays, as copious honeydew was produced and aphids often died in a feeding position. CryIIIA which was solubilized in aphid diet, but filtered to remove spores or crystalline toxin lacked aphidicidal activity. Spores from an acrystalliferous strain (EG2205) were not toxic by themselves at 7.75 × 105 spores/ml aphid diet, but did restore toxicity to the filtered CryIIIA solution. Therefore, low levels of spores may be very effective in concert with DET for aphicidal activity. Results also clearly demonstrated that a suspension of crystalline CryIIIA alone, without spores, exhibited toxicity. Therefore, DET may be more toxic to the aphids when imbibed as a fine suspension, perhaps indicating the need for slow solubilization into the aphid midgut.
Genetic variation in chrysanthemum for resistance to Frankliniella occidentalis
Authors: de Jager C. M. , Butôt R. P. T. , Klinkhamer P. G. L. , de Jong T. J. , Wolff K. , van der Meijden E.
Published: April 2011

In a choice‐experiment, 42 chrysanthemum cultivars were screened for resistance to Frankliniella occidentalis (Pergande). Oviposition preference, two types of feeding damage and thrips numbers per flower were recorded as measures of resistance. A large genetic variation in thrips resistance was found among the cultivars screened. The amount of feeding damage was strongly determined by oviposition preference. Besides, a positive correlation was found between the oviposition preference in non‐flowering chrysanthemums (number of eggs) and flowering chrysanthemums (number of thrips per flower). Thrips feeding on young, developing tissues, causes growth damage because affected cells are unable to expand and leaves become distorted. Thrips feeding on older, expanded leaves causes cells to become filled with air, resulting in ‘silver’ damage. The amounts of growth‐ and ‘silver’ damage were negatively correlated suggesting that thrips chose either young or older leaves to feed on. The order of resistance among cultivars did not change during the experiment. In order to get more insight in resistance mechanisms the influence of some plant‐ and flower characters on resistance was examined. The plant characters height, number of leaves, flower production and flower weight were all negatively correlated with resistance. It is suggested that tall chrysanthemum cultivars with many and large flowers may invest less in defence than smaller cultivars, and therefore are more damaged by thrips.
CONTRAST ENHANCED SONOGRAPHIC ASSESSMENT OF FEEDING VESSELS AS A DISCRIMINATOR BETWEEN MALIGNANT VS. BENIGN FOCAL SPLENIC LESIONS
Authors: Taeymans Olivier , Penninck Dominique
Published: April 2011

Contrast‐enhanced sonography was conducted in 17 confirmed focal splenic lesions (five malignant, 12 benign). Relative echogenicity changes were used for subjective interpretation of lesion perfusion. A rapid influx of contrast agent, resulting in an increased relative echogenicity of the lesion, followed by a rapid clearance of contrast agent was referred to as early washin/early washout. There were 6/12 benign, and 3/5 malignant lesions characterized by early washin/early washout. Therefore, sensitivity, specificity, and accuracy for this parameter in differentiating malignant from benign lesions was 60%, 50%, and 53%, respectively. There were 2/12 benign, and 2/5 malignant lesions with persistent hypoperfusion throughout all phases. Therefore, sensitivity, specificity, and accuracy for malignancy using this criterion were 40%, 83%, and 71%, respectively. However, none of the benign and all malignant lesions were characterized by tortuous and persistently visible feeding vessels. This suggests that interpretation of splenic lesions cannot be performed accurately on the basis of echogenicity or persistent hypoperfusion, but that assessment of vascular tortuosity may be helpful in discriminating between a malignant vs. benign focal splenic lesion.
Junctional adhesion molecules are required for melanoma cell lines transendothelial migration in vitro
Authors: Ghislin Stephanie , Obino Dorian , Middendorp Sandrine , Boggetto Nicole , Alcaide‐Loridan Catherine , Deshayes Frederique
Published: April 2011

One of the main steps of metastasis is extravasation, a phenomenon well described in lymphocytes but remaining to be fully uncovered for melanoma. Junctional adhesion molecules (JAMs) control the transendothelial migration of leukocytes. To date, the role of the JAM proteins, notably JAM‐A and JAM‐C, has not been examined in melanoma. Here, we compared two melanoma tumor cell lines, A375 and SLM8 cells, the A375 cell line being four times more efficient than the SLM8 cells in the crossing of the endothelial monolayer. We show evidence of the differential expression of JAM‐A and JAM‐C in these cell lines with JAM‐C mainly expressed in the A375 cell line, and JAM‐A detected preferentially in the SLM8 cells. To further dissect the respective roles of these proteins, we used both siRNA and blocking antibodies to decrease JAM‐A and JAM‐C expression.
Instability and Chaos of a Flexible Rotor Ball Bearing System: An Investigation on the Influence of Rotating Imbalance and Bearing Clearance
Authors: Gupta T. C. , Gupta K. , Sehgal D. K.
Published: April 2011

In this paper, a horizontal flexible rotor supported on two deep groove ball bearings is theoretically investigated for instability and chaos. The system is biperiodically excited. The two sources of excitation are rotating imbalance and self excitation due to varying compliance effect of ball bearing. A generalized Timoshenko beam finite element (FE) formulation, which can be used for both flexible and rigid rotor systems with equal effectiveness, is developed. The novel scheme proposed in the literature to analyze quasiperiodic response is coupled with the existing nonautonomous shooting method and is thus modified; the shooting method is used to obtain a steady state quasiperiodic solution. The eigenvalues of monodromy matrix provide information about stability and nature of bifurcation of the quasiperiodic solution. The maximum value of the Lyapunov exponent is used for quantitative measure of chaos in the dynamic response. The effect of three parameters, viz., rotating unbalance, bearing clearance, and rotor flexibility, on an unstable and chaotic behavior of a horizontal flexible rotor is studied. Interactive effects between the three parameters are examined in detail in respect of rotor system instability and chaos, and finally the range of parameters is established for the same.
Topological Phase Transition and Texture Inversion in a Tunable Topological Insulator
Authors: Xu Su-Yang , Xia Y. , Wray L. A. , Jia S. , Meier F. , Dil J. H. , Osterwalder J. , Slomski B. , Bansil A. , Lin H. , Cava R. J. , Hasan M. Z.
Published: April 2011

Two types of bulk insulator are realized in the same family of compounds through chemical doping.
Directed Culturing of Microorganisms Using Metatranscriptomics
Authors: Bomar Lindsey , Maltz Michele , Colston Sophie , Graf Joerg
Published: April 2011

The vast majority of bacterial species remain uncultured, and this severely limits the investigation of their physiology, metabolic capabilities, and role in the environment. High-throughput sequencing of RNA transcripts (RNA-seq) allows the investigation of the diverse physiologies from uncultured microorganisms in their natural habitat. Here, we report the use of RNA-seq for characterizing the metatranscriptome of the simple gut microbiome from the medicinal leech
Hirudo verbana
and for utilizing this information to design a medium for cultivating members of the microbiome. Expression data suggested that a
Rikenella
-like bacterium, the most abundant but uncultured symbiont, forages on sulfated- and sialated-mucin glycans that are fermented, leading to the secretion of acetate. Histological stains were consistent with the presence of sulfated and sialated mucins along the crop epithelium. The second dominant symbiont,
Aeromonas veronii
, grows in two different microenvironments and is predicted to utilize either acetate or carbohydrates. Based on the metatranscriptome, a medium containing mucin was designed, which enabled the cultivation of the
Rikenella
-like bacterium. Metatranscriptomes shed light on microbial metabolism
in situ
and provide critical clues for directing the culturing of uncultured microorganisms. By choosing a condition under which the desired organism is rapidly proliferating and focusing on highly expressed genes encoding hydrolytic enzymes, binding proteins, and transporters, one can identify an organism’s nutritional preferences and design a culture medium.

IMPORTANCE
The number of prokaryotes on the planet has been estimated to exceed 10
30
cells, and the overwhelming majority of them have evaded cultivation, making it difficult to investigate their ecological, medical, and industrial relevance. The application of transcriptomics based on high-throughput sequencing of RNA transcripts (RNA-seq) to microorganisms in their natural environment can provide investigators with insight into their physiologies under optimal growth conditions. We utilized RNA-seq to learn more about the uncultured and cultured symbionts that comprise the relatively simple digestive-tract microbiome of the medicinal leech. The expression data revealed highly expressed hydrolytic enzymes and transporters that provided critical clues for the design of a culture medium enabling the isolation of the previously uncultured
Rikenella
-like symbiont. This directed culturing method will greatly aid efforts aimed at understanding uncultured microorganisms, including beneficial symbionts, pathogens, and ecologically relevant microorganisms, by facilitating genome sequencing, physiological characterization, and genetic manipulation of the previously uncultured microbes.
GROUND-STATE CORRELATION ENTROPY IN THE ONE- AND TWO-DIMENSIONAL XXZ MODEL
Authors: YOU WEN-LONG , LU WEN-LONG
Published: April 2011

In this paper, we study quantum phase transitions in both the one- (1D) and two-dimensional (2D) spin 1/2 XXZ models by a two-site correlation entropy. We show that the behavior of the correlation entropy is related to the ground-state symmetries and low-lying excitations of these systems. Therefore, the anomalies and minimum behaviors of the correlation entropy can signal the quantum phase transition points in the ground state of both models.
EFFECT OF JUMP LENGTH OF ELECTRON AND CATION DISTRIBUTION STUDY OF Co1-xZnxFe2-xAlxO4
Authors: ALONE S. T. , KADAM R. H. , SHIRSATH SAGAR E. , JADHAV K. M.
Published: April 2011

The zinc and aluminum co-substituted cobalt ferrite of the series Co 1-x Zn x Fe 2-x Al x O 4 were prepared by wet chemical co-precipitation method. The variation of lattice constant and jump length of electron of wet and annealed samples was studied. The variation of lattice constant and jump length of electron of wet and annealed wet samples shows that it increases up to x=0.2 thereafter x>0.2 it decreases in both the cases. In the present work the values of tetrahedral and octahedral bond length (dAx) and (dBx), shared tetrahedral and octahedral edge was also studied. The cationic distribution is calculated on the basis X-ray diffraction method. The cation distribution estimated from X-ray intensity ratio calculations suggest that, Zn 2+ ions occupies only tetrahedral (A) site whereas Al 3+ ions occupies both tetrahedral (A) and octahedral [B] sites.
STRUCTURE AND PHOTOLUMINESCENT PROPERTIES OF SiCO THIN-FILMS DOPED WITH Al PREPARED BY DUAL MAGNETRON SPUTTERING
Authors: ZHOU JICHENG , ZHENG XUQIANG , SHI ZHIJIE , ZHAO BAOXING , LIU FU , LI YOUZHEN
Published: April 2011

SiCO thin-films doped with aluminum (Al) prepared by alternate deposition of SiC and Al thin layers using Ar and O 2 as sputtering gas were deposited on n- Si substrates. The as-deposited thin-films were annealed under 600°C in nitrogen ambient. The thin-films have been characterized by atomic force microscopy, energy dispersive spectrometer, X-ray diffraction, fourier transform infrared spectroscopy, and photoluminescence spectra. The results showed that the introduction of Al promotes the formation of Si — C bonds, but hinders amorphous SiC to further transform to crystalline SiC . The doped Al would react with SiO x in the thin-films to form more Si particles which strongly affect the optical properties. After Al doped, there presented a seven times of enhancement emission band centered around 412 nm, which is ascribed to nanostructure Si -related defect centers embedded in the SiCO thin-films. The obtained results are expected to have important applications in modern optoelectronic devices.
FANO-TYPE SPIN-FLIP MESOSCOPIC TRANSPORT THROUGH AN AHARONOV–BOHM INTERFEROMETER RESPONDED BY AC MAGNETIC FIELDS
Authors: GAO HE , ZHAO HONG-KANG
Published: April 2011

We have investigated the mesoscopic transport properties of an Aharonov–Bohm (AB) interferometer composed of a direct tunneling path and a resonant tunneling path incorporating a quantum dot (QD). The QD is perturbed by a rotating magnetic field (RMF) and an oscillating magnetic field (OMF). The nonresonant tunneling (NRT) path takes significant role in the spin and charge currents, and the Fano profiles display in the currents due to the modification of NRT strength. The spin current exhibits completely different behaviors as the source–drain bias eV = 0 and eV≠0. The spin current is symmetric versus gate voltage when the source–drain bias eV = 0; however, it becomes asymmetric Fano-line shape resulting from the interference effect when eV≠0. The OMF induced photon-assisted tunneling is quite different from the ones induced by the oscillating electric field and RMF. The tunnel currents vary dramatically with the evolution of the AB magnetic flux, and the Fano-type spin and charge currents are adjusted by OMF, RMF, AB flux, gate voltage, the source–drain bias, as well as the NRT strength to generate novel Fano-type photon-assisted spin and charge currents.
INVESTIGATION OF THE PERTURBED VIRIAL EQUATIONS WITH ARBITRARY TEMPERATURE-DEPENDENT SECOND AND THIRD VIRIAL COEFFICIENTS
Authors: TIAN JIANXIANG
Published: April 2011

In this paper, the perturbed virial equations of state with temperature-dependent virial coefficients are constructed using the Carnahan–Starling (CS) hard sphere equation as reference. Considering the second virial coefficient, some critical properties are interaction-independent and the critical packing factor is in the range of that of real fluids. But the critical compressibility factor and the liquid–vapor equilibrium properties disagree with experiments. When both the second and the third virial coefficient are considered, the critical properties are interaction-dependent but are out of the range of experimental results of real fluids. As a conclusion, the fourth virial coefficients are required for further consideration.
Reducing the switching activity of test sequences under transparent-scan
Authors: Pomeranz Irith , Reddy Sudhakar M.
Published: April 2011

Transparent-scan is a test application scheme for scan circuits. It provides unique opportunities for test compaction that do not exist with the standard test application scheme. We show that it also provides unique opportunities for reducing the power dissipation of a scan-based test set. After translating a standard scan-based test set into a transparent-scan sequence, we apply two operations for reducing the power dissipation of the sequence. The first operation attempts to remove a test vector that causes high power dissipation. The second operation attempts to replace a scan clock cycle with a functional clock cycle, or a functional clock cycle with a scan clock cycle, in order to reduce the power dissipation. Both operations are implemented such that they reduce the power dissipation without reducing the fault coverage. We also consider a third operation that attempts to complement arbitrary values in the transparent-scan sequence in order to further reduce the power dissipation.
IWGS 2010 workshop report
Authors: Ali Mohamed , Hoel Erik , Shahabi Cyrus
Published: April 2011

The ACM SIGSPATIAL International Workshop on Geostreaming (IWGS) was held for the first time in conjunction with the 18th ACM SIGSPATIAL International Conference on Advances in Geographic Information Systems (ACM SIGSPATIAL GIS 2010). The workshop has been a successful event that attracted participants from both academia and industry. The workshop addressed topics that are at the intersection of data streaming and geospatial systems. The workshop fostered an environment where geospatial researchers can benefit from the advances in geosensing technologies and data streaming systems.
Current Collectors for Rechargeable Li-Air Batteries
Authors: Veith Gabriel M. , Dudney Nancy J.
Published: April 2011

Here we report the negative influence of porous nickel foam for use as current collectors in rechargeable Li-air batteries. Uncoated nickel foam promotes the decomposition of LiPF6-organic carbonate electrolytes under normal charging conditions reported for rechargeable Li-air cells. Partially coating the Ni reduces the extent of electrolyte decomposition. We have identified Ni-free porous carbon supports as more appropriate cathode current collectors.
Ascorbic acid regulates osterix expression in osteoblasts by activation of prolyl hydroxylase and ubiquitination-mediated proteosomal degradation pathway
Authors: Xing Weirong , Pourteymoor Sheila , Mohan Subburaman
Published: April 2011

Mouse genetic studies reveal that ascorbic acid (AA) is essential for osteoblast (OB) differentiation and that osterix (Osx) was a key downstream target of AA action in OBs. To determine the molecular pathways for AA regulation of Osx expression, we evaluated if AA regulates Osx expression by regulating production and/or actions of local growth factors and extracellular matrix (ECM) proteins. Inhibition of actions of IGFs by inhibitory IGFBP-4, BMPs by noggin, and ECM-mediated integrin signaling by RGD did not block AA effects on Osx expression in OBs. Furthermore, blockade of components of MAPK signaling pathway had no effect on AA-induced Osx expression. Because AA is required for prolyl hydroxylase domain (PHD) activity and because PHD-induced prolyl-hydroxylation targets proteins to proteosomal degradation, we next tested if AA effect on Osx expression involves activation of PHD to hydroxylate and induce ubiquitin-proteosome-mediated degradation of transcriptional repressor(s) of Osx gene. Treatment of OBs with dimethyloxallyl glycine and ethyl 3, 4-dihydroxybenzoate, known inhibitors of PHD, completely blocked AA effect on Osx expression and OB differentiation. Knockdown of PHD2 expression by Lentivirus-mediated shRNA abolished AA-induced Osx induction and alkaline phosphatase activity. Furthermore, treatment of OBs with MG115, inhibitor of proteosomal degradation, completely blocked AA effects on Osx expression. Based on these data, we conclude that AA effect on Osx expression is mediated via a novel mechanism that involves PHD2 and proteosomal degradation of a yet to be identified transcriptional repressor that is independent of BMP, IGF-I, or integrin-mediated signaling in mouse OBs.
Pregnant and Nonpregnant Women in Cape Town, South Africa: Drug Use, Sexual Behavior, and the Need for Comprehensive Services
Authors: Jones Hendrée E. , Browne Felicia A. , Myers Bronwyn J. , Carney Tara , Ellerson Rachel Middlesteadt , Kline Tracy L. , Poulton Winona , Zule William A. , Wechsberg Wendee M.
Published: April 2011

The multiple risks associated with methamphetamine use are of serious concern for women. These risks and consequences are magnified during pregnancy. This secondary analysis of a parent study compared 26 pregnant to 356 nonpregnant women in Cape Town, South Africa, on selected demographic, psychosocial, and HIV-risk domains to identify their treatment service needs. Proportionally, more pregnant than nonpregnant women are using methamphetamine,P=.01, although a very high rate of women used methamphetamine. Women reported similar monthly rates of sexual intercourse, but pregnant women were significantly less likely to report condom use,P<.0001, maintaining their risky behavior. Both groups reported elevated Center for Epidemiological Studies Depression Scale CES-D means, suggesting a need for depression treatment. Results demonstrate a pervasive need for women's comprehensive treatment, regardless of pregnancy status. Moreover, findings support the urgent need for women-focused and pregnancy-specific treatment services for methamphetamine use. Finally, a job-skills training/employment component focus is suggested.
A Therapeutic and Diagnostic Dilemma: Granular Cell Tumor of the Breast
Authors: Pergel Ahmet , Yucel Ahmet Fikret , Karaca A. Serdar , Aydin Ibrahim , Sahin Dursun Ali , Demirbag Nilgun
Published: April 2011

Six to eight percent of granular cell tumors are seen in the breast. Although mostly benign, they rarely have malignant features clinically and radiologically reminding of breast cancer. This may lead to a potential misdiagnosis of breast carcinoma and overtreatment of patients. The final diagnosis is made by immunohistochemical examination. We performed excisional biopsy on a patient who was diagnosed to have a breast mass. The histopathological examination of the mass revealed granular cell tumor.
Reliability and Validity of an Instrument to Measure Quality of Life in the Dysarthric Speaker
Authors: Piacentini Valentina , Zuin Annalisa , Cattaneo Davide , Schindler Antonio
Published: April 2011

Objective: To develop a tool to measure quality of life (QOL) in the dysarthric speaker (QOL-DyS). Patients and Method: The study consisted of two phases: scale development and item reduction (phase 1), and reliability and validity analysis (phase 2). The 100-item ‘Dysarthria from the Point of View of the Dysarthric Patient’ questionnaire was used for item development; the data from 50 dysarthric patients were measured for internal consistency and the 40-item QOL-DyS was developed. A second group of 50 dysarthric patients and 30 control participants were recruited for phase 2. Internal consistency and test-retest reliability were analyzed through Cronbach’s α coefficient and intraclass correlation coefficient (ICC), respectively. The scores obtained from the pathological and the control group were compared using the Mann-Whitney test. Finally, the correlation between the QOL-DyS and dysarthria severity was assessed using the Spearman test. Results: An excellent internal consistency (α = 0.90) and test-retest reliability (ICC = 0.98, 95% CI: 0.97–0.99) were found; the score difference between the dysarthric and control groups was significant (p < 0.001). The QOL-DyS scores correlated positively with the severity of dysarthria (r = 0.43). Conclusion: The QOL-DyS is a reliable and valid tool to assess QOL in patients with dysarthria.
Erythropoietin: A Hormone with Multiple Functions
Authors: Lombardero Matilde , Kovacs Kalman , Scheithauer Bernd W.
Published: April 2011

Erythropoietin (EPO), the main hemopoietic hormone synthesized by the kidney as well as by the liver in fetal life, is implicated in mammalian erythropoiesis. Production and secretion of EPO and the expression of its receptor (EPO-R) are regulated by tissue oxygenation. EPO and EPO-R, expressed in several tissues, exert pleiotropic activities and have different effects on nonhemopoietic cells. EPO is a cytokine with antiapoptotic activity and plays a potential neuroprotective and cardioprotective role against ischemia. EPO is also involved in angiogenesis, neurogenesis, and the immune response. EPO can prevent metabolic alterations, neuronal and vascular degeneration, and inflammatory cell activation. Consequently, EPO may be of therapeutic use for a variety of disorders. Many tumors express EPO and/or EPO-R, but the action of EPO on tumor cells remains controversial. It has been suggested that EPO promotes the proliferation and survival of cancer cells expressing EPO-R. On the other hand, other reports have concluded that EPO-R plays no role in tumor progression. This review provides a detailed insight into the nonhemopoietic role of EPO and its mechanism(s) of action which may lead to a better understanding of its potential therapeutic value in diverse clinical settings.
Sensitivity of ENSO to Stratification in a Recharge–Discharge Conceptual Model
Authors: Thual Sulian , Dewitte Boris , An Soon-Il , Ayoub Nadia
Published: April 2011

El Niño–Southern Oscillation (ENSO) is driven by large-scale ocean–atmosphere interactions in the equatorial Pacific and is sensitive to change in the mean state. Whereas conceptual models of ENSO usually consider the depth of the thermocline to be influential on the stability of ENSO, the observed changes in the depth of the 20°C isotherm are rather weak, on the order of approximately 5 m over the last decades. Conversely, change in stratification that affects both the intensity and sharpness of the thermocline can be pronounced. Here, the two-strip conceptual model of An and Jin is extended to include three parameters (i.e., the contribution of the first three baroclinic modes) that account for the main characteristics of the mean thermocline vertical structure.

A stability analysis of the model is carried out that indicates that the model sustains a lower ENSO mode when the high-order baroclinic modes (M2 and M3) are considered. The sensitivity of the model solution to the coupling efficiency further indicates that, in the weak coupling regime, the model allows for several ocean basin modes at low frequency. The latter can eventually merge into a low-frequency and unstable mode representative of ENSO as the coupling efficiency increases. Also, higher baroclinic modes project more energy onto the ocean dynamics for the same input of wind forcing. Therefore, in this study’s model, a shallower, yet more intense mean thermocline may still sustain a strong (i.e., unstable) and low-frequency ENSO mode. Sensitivity tests to the strength of the two dominant feedbacks (thermocline vs zonal advection) indicate that the presence of high-order baroclinic modes favors the bifurcation from a low-frequency regime to a higher-frequency regime when the zonal advective feedback is enhanced.

It is suggested that the proposed formalism can be used to interpret and measure the sensitivity of coupled general circulation models to climate change.
The Direct Effects of Principal–Student Discussions on Eighth Grade Students’ Gains in Reading Achievement
Authors: Silva Jack P. , White George P. , Yoshida Roland K.
Published: April 2011

Purpose: School effectiveness and instructional leadership research over the past 30 years has largely concluded that principal effects on student achievement are small and indirect. It has been assumed that the principal effect is important but mediated through other school factors. Findings: This experimental study found that one-on-one discussions between a principal and a nonproficient student that focused on the student’s 2008 reading score and a goal for his or her 2009 reading score had a direct and significant effect on the student’s subsequent reading achievement gains on a state reading test. Students in the experimental condition who held discussions with a principal prior to the state reading test showed reading gains significantly larger than students in the control condition who had their discussions after the state reading test. The randomly assigned participants (20 in the experimental condition and 21 in the control condition) were 41 of the 66 eighth grade students who made up the entire nonproficient population of a large suburban middle school. Student achievement gains were calculated as the difference between the predicted versus actual reading percentile score as reported by the state’s value-added system of assessment. Conclusions: The results of this study provide the first steps in investigating the potential benefits to principals who seek the most immediate and direct ways to improve student achievement to meet the leadership imperatives of No Child Left Behind. Future research should investigate the principal–student discussion effects on students of different genders, grade levels, and communities.
Dietary Digital Diaries
Authors: Staiano Amanda E. , Baker Christina M. , Calvert Sandra L.
Published: April 2011

Obesogenic environments promote excessive caloric and fat intake. A total of 23 low-income, African American adolescents digitally photographed their lunchtime food environment at a school buffet during summer camp. Depicted food was coded for nutritional content on the platescape (own plate or others’ plates) and the tablescape (open buffet). Students digitally depicted high-caloric and high-fat content, particularly students who had higher baseline waist-to-hip ratio. Students who included higher caloric and fat content in their digital diaries gained more weight over the 4-week program than those who did not. Digital photography connects adolescents’ perceived food environment with weight gain, revealing the environmental cues that promote excessive caloric and fat intake. Digital photography can also identify adolescents with problematic eating behaviors that increase risk for obesity.
The Influence of Fibre Properties on the Properties of Glass-Fibre-Reinforced Polyamide 6,6
Authors: Thomason J. L.
Published: April 2011

We discuss the effect of fibre strength and diameter on the balance of mechanical properties of glass reinforced polyamide 6,6. The results show that the elastic properties of injection moulded short glass fibre reinforced polyamide 6,6 are not strongly influenced by fibre diameter in the 10-17 micron range. The ultimate properties of these composites (strength and Izod impact) showed a clear dependence on fibre diameter and the presence of high strength S-2 glass® fibres. Tensile elongation, tensile and flexural strength, and unnotched Izod impact all decreased significantly over the 10-17 micron diameter range. Notched Izod impact showed a small but significant increase over the same range. Addition of 20% w/w of S-2 glass® to the 17 micron E-glass resulted in an 8% improvement in the fibre contribution to composite strength.
Characterization of Mode II Delamination Growth in Glass/Epoxy Composite Cylinders
Authors: Ozdil F. , Carlsson L. A. , Li X.
Published: April 2011

Delamination growth in filament wound composite cylinders has been characterized for shear (mode II) loading. Beam specimens were machined from cylinders with embedded aluminum films to define an initial delamination. The specimens were machined so that the delamination was at one end, and the beam axis parallel to the cylinder axis. Analysis of compliance and energy release rate of beam specimens configured in ENF mode II loading was performed based on a formulation for cylindrical shear-deformable shells. The contribution from residual thermal stress to the energy release rate was examined, but found negligible for the [±θ]n (n = 6 and 12) glass/epoxy specimens under consideration (θ = 30°, 55° and 85°). Contoured loading bars and supports were prepared for experimental ENF testing of beams with curved cross-section machined from composite cylinders. The experimental compliance data were in close agreement with predictions over the ranges of crack lengths, beam thicknesses, and ply angles examined. The mode II fracture toughness increased with increased angle θ at the ±θ interface.
Design and Analysis of Composite Pipe Joints under Tensile Loading
Authors: Yang Chihdar
Published: April 2011

Composite pipe has been used in transporting corrosive fluid in many chemical processes in the petrochemical and pulp and paper industries. More recently, composite pipe has further gained its importance in the offshore oil and gas industry due to its light-weight, corrosion resistance, and the new invention of Tension Leg Platforms (TLPs) for deep-water oil and gas exploration and production. Despite the fact that it has been estimated that there is one joint for every four feet of composite pipe installed for marine applications, the joints are the weakest link in a composite piping system. In order to understand the mechanical behavior and to provide analytical design tools for composite pipe joints, an analytical model was developed based on the first-order laminated anisotropic plate theory. In this developed model, a three-component joint system consisted of coupling, adhesive, and pipe was used to model different types of composite pipe joints such as adhesive-bonded socket joints, butt-and-strap joints, and heat-activated coupling joints. Results obtained from the developed model including adhesive peel stress and shear stress distributions were compared with finite element models. Good correlations were found. With this developed model, the influence of joint length and coupling design on the joint performance was determined.
Measurement of Residual Stresses in Layered Composites by Compliance Method
Authors: Ersoy Nuri , Vardar Oktem
Published: April 2011

Macroscopic residual stresses in layered composites were investigated by paying particular attention to implement a reliable experimental technique for the measurement of through-the-thickness residual stresses in layered composite plates. Residual stresses in (010/9010) S APC-2 laminate have been measured by two experimental techniques, i.e., by layer removal method, and by compliance method. The latter has been successfully employed up to date for the measurement of residual stresses in isotropic materials and the authors propose an extension of the method's use to layered orthotropic composites. The data obtained by the layer removal and compliance methods are compared to the results obtained by a numerical model developed by other researchers. There is an excellent agreement between the experimental data obtained by the layer removal and compliance methods and the results predicted by the model. The layer removal and compliance methods are also compared in terms of accuracy and practicality.
Time-Resolved Impact Response and Damage of Fiber-Reinforced Composite Laminates
Authors: Park S. W. , Zhou M. , Veazie D. R.
Published: April 2011

An experimental technique for time-resolved characterization of the mechanical response and induced damage of fiber-reinforced composite laminates during low-velocity, transverse impact is presented. The configuration uses a three-point bend fixture in a split Hopkinson pressure bar (SHPB) apparatus for controlled loading and real-time diagnosis. The full histories of contact force, displacement and energy absorption of the specimen during impact are measured. The materials analyzed are IM7/K3B, a graphite-fiber polyimide-matrix composite, and S2 glass/5250-4, a glass-fiber bismaleimide-matrix composite. Experiments conducted characterize the responses of the materials over a range of impact energy. The initial peak force sustained by the specimen is found to be constant over the range of impact energy studied. A monotonic relation is observed between the amount of energy absorbed by the specimens and the post-impact tensile strength of the materials. For the same amount of energy dissipated through damage, the glass fiber composite retains a higher percentage of its tensile strength than the graphite-fiber composite. Postmortem X-ray radiography and ultrasonic tests are used to assess the extent and effects of damage. The mean square amplitude of the transverse vibratory response of an impacted specimen decreases with increasing impact-induced damage quantified in terms of dissipated energy. A similar correlation is observed between the through-thickness wave speed of an impacted specimen and the dissipated energy.
Progressive Fatigue Damage Modeling of Composite Materials, Part II: Material Characterization and Model Verification
Authors: Shokrieh Mahmood M. , Lessard Larry B.
Published: April 2011

To validate the fatigue progressive damage model, developed in the first part of this paper, an experimental program was conducted using graphite/epoxy AS4/3501-6 material. As the input for the model, the material properties (residual stiffness, residual strength and fatigue life) of unidirectional AS4/3501-6 graphite/epoxy material are fully characterized under tension and compression, for fiber and matrix directions, and under in-plane and out-of-plane shear in static and fatigue loading conditions. An extensive experimental program, by using standard experimental techniques, is performed for this purpose. Some of the existing standard testing methods are necessarily modified and improved. To evaluate the progressive fatigue damage model, fatigue behaviour of pin/bolt-loaded composite laminates is simulated as a complicated example. The model is validated by conducting an experimental program on pin/bolt-loaded composite laminates and by comparison with experimental results from other authors. Different capabilities of the model are examined by conducting different types of experiments. The comparison between the analytical results and the experiments shows the successful simulation capability of the model.
Optimization of Coating Layers in the Design of Ceramic Fiber Reinforced Metal Matrix Composites
Authors: Doghri I. , Jansson S. , Leckie F. A. , Lemaitre J.
Published: April 2011

The potential of using coating layers to reduce thermal stresses in the matrix of composites with a mismatch in coefficients of thermal expansion (CTE) of fiber and matrix is investigated. Two thermoelastic solutions based on a 3-cylinder model are developed and a comprehensive sensitivity study is conducted. It is shown that the performance of the layer can be defined by the product of its CTE and thickness, and that a compensating layer with a sufficiently high CTE can reduce the thermal stresses in the matrix significantly. A practical procedure offering a window of coating layer candidates is proposed. Easy-to-use contours of matrix stress reduction factors are produced.
Application of PEEK Coatings to C/PEEK Substrates by Plasma-Spray Process
Authors: Strait L. H. , Jamison R. D.
Published: April 2011

This article describes the development of a method for applying PEEK coatings to C/PEEK substrates by plasma spraying. Uniform, well-bonded PEEK coatings have been achieved using this technology. The process temperature is a critical parameter. "Hotter" coatings exhibit less porosity and better adhesion than "colder" coatings. No significant degradation of the PEEK has been observed as a result of the plasma-spray process as verified by DSC and TGA. Use of a plasma postheat cycle improves the uniformity and surface finish of the coating by reducing the number of unmelted PEEK particles on the surface of the coating. Use of a plasma preheat cycle provides a 52% increase in tensile bond strength of the coating. Plasma and reactive gas surface treatments do not appear to have any significant effect on bond strength when used in conjunction with a plasma preheat cycle. The optimized plasma-spray parameters developed in this study produce PEEK coatings 0.254 to 0.381 mm thick which are black in color and exhibit a moderate degree of porosity which is evenly distributed. Individual pores are isolated rather than interconnected and do not vary in size or distribution with substrate thickness, postheating, or annealing. No interface is visible between the PEEK coating and the C/PEEK substrate at magnifications up to 500 x. Tensile bond strengths of 13.37 ± 0.83 MPa have been measured on 3.175 mm thick C/PEEK substrates and similar tests on 12.7 mm thick C/PEEK substrates have yielded values of 24.28 + 0.65 MPa. The as-sprayed PEEK coatings are essentially amorphous and require an annealing treatment in order to ensure a reasonable degree of crystallinity. This treatment does not affect the bond strength of the coating.
Fatigue Notch Sensitivity of Glass Woven Fabric Composites Having a Circular Hole under Tension/Torsion Biaxial Loading
Authors: Fujii Toru , Shiina Toru , Okubo Kazuya
Published: April 2011

Fatigue notch sensitivity of woven fabric composites having a circular hole under tension/torsion biaxial loading was investigated. In-phase (proportional) biaxial stress was applied to tubular specimens. A fatigue notch factor was used to evaluate the fatigue notch sensitivity. The experimental results revealed that the fatigue notch factor was approximately linear with respect to a parameter; cos (tan-' ce) for any fatigue life (a is biaxiality ratio of combined stress). The fatigue notch factor decreased with an increase in fatigue life in the case where the shear stress component was relatively small. However, in the case where the shear stress component was large, it increased with an increase in fatigue life. Under pure torsion loading, fatigue damage did not progress along the principal axis. It grew along both longitudinal and transverse fiber bundles.

An empirical equation which can easily predict the fatigue notch factor at any arbitrary fatigue life under biaxial loading was proposed. Unknown variables in this equation are determined by fatigue tests under uniaxial tensile and pure torsion loadings.
Non-Newtonian Constitutive Relationships for Hyperconcentrated Fiber Suspensions
Authors: Pipes R. Byron , Coffin Douglas W. , Shuler Stephen F. , Šimáček Pavel
Published: April 2011

Previously developed relationships for the prediction of the effective Newtonian viscosities of collimated, discontinuous fiber suspensions have been recently extended to include non-Newtonian behavior by incorporating the Carreau constitutive relation for the matrix fluid viscosity [9]. A new class of suspensions termed "hyperconcentrated" are defined here and illustrated to be that class for which these relationships are appropriate. The predictions for the influence of strain rate on the primary anisotropic viscosities of these suspensions are also presented. The predictions are compared to Binding's results [12] for a fiber suspension consisting of polypropylene with 25 volume percent glass fibers. Both axial elongational viscosity and shearing viscosity predictions developed for shear thinning polymers show excellent agreement with experimental results over ranges in strain rate of 100 to 102 s-1 and 101 to 103 s-l, respectively. Utilizing the Carreau model to describe the behavior of the matrix fluid, decreases in the range of strain rate where Newtonian behavior dominates the suspension response are predicted for both the elongational and shearing viscosities when compared to the shearing viscosity of the matrix fluid.
A Numerical and Experimental Study of Delaminated Layered Composites
Authors: Mukherjee Yu Xie , Gulrajani Sunil N. , Mukherjee Subrata , Netravali Anil N.
Published: April 2011

This paper describes the development of a finite element-based computer model for the determination of stress fields and energy release rates around a delamination in a layered composite. The model is fully three-dimensional. Each layer of a composite material is modelled as homogeneous and orthotropic. The basic finite elements are isoparametric 20-noded bricks with collapsed, prismatic quarter-point elements around the delamination front. Contact theory is used to prevent interpenetration between the faces of a delamination. The modified crack closure method is used to calculate the energy release rates around a delamination.

Preliminary experiments are performed to study the growth of a delamination between the layers of a two-layer laminate-one epoxy and the other graphite/epoxy. Initial results from the experiments and numerical simulations are shown to be consistent.
Deformation Induced Degradation of Thermal Conductivity in Cracked Solids
Authors: Tzou Da Yu
Published: April 2011

The present work studies the overall (effective) thermal conductivity in solid media with a variable microcrack density. For a solid undergoing continuous straining, the self-consistent model is used to describe the evolution of microcrack density in the strain history. While the model established by Budiansky and O'Connell is implemented for the degradation of the load-bearing capacity due to microcracks, the micromechanical model established by Tzou and Chen is used to relate the microcrack density to strains. Degradation of thermal conductivity is then obtained by the analytical result obtained by Tzou in the same self-consistent framework.