bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exploratory Studies to Investigate a Linked Prebiotic Origin of RNA and Coded Peptides
Authors: Borsenberger Vinciane , Crowe Michael A. , Lehbauer Jörg , Raftery Jim , Helliwell Madeleine , Bhutia Kajal , Cox Tony , Sutherland John D. 
Published: March 2004

AbstractAn introduction to the premise that RNA and genetically coded proteins should not be viewed as etiologically discrete entities in the origin of life is presented. This premise follows from the mutual interdependence of RNA and coded proteins in biology and the lack of prebiotically plausible constitutional self‐assembly processes leading to either polymeric species. The RNA : coded peptides subsystem and its informational core, the genetic code, are then analysed retrosynthetically to suggest a (replicative) synthesis involving the intermediacy of aminoacyl‐RNA trimers (cf. Scheme 5). A number of potential candidate aminoacyl‐RNA trimers are identified (23–26; Scheme 6) and a chemical strategy to assess their validity is outlined. Experimental investigation of potential aminoacylation chemistry, nucleobase assembly and phosphate activation rules out three of the trimers but suggests that 26 is worthy of further investigation.
Amphotericin B Covalent Dimers Bearing a Tartarate Linkage
Authors: Matsumori Nobuaki , Masuda Rie , Murata Michio 
Published: March 2004

AbstractAmphotericin B (AmB, 1) is known to assemble together and form an ion channel across biomembranes, by which the drug presumably exerts its antimicrobial activity. To access the whole architecture of this channel assemblage, the understanding of binary interaction between AmB molecules is of prime importance because the dimeric interaction is the basis of the assemblage. In this context, we have recently reported covalently conjugated AmB dimers such as 2 and 3 with a long linker, which show prominent hemolytic potency and ion‐channel activity. To evaluate the effect of the length and hydrophilicity of linker parts on the activity, we prepared new dimers bearing tartarate linkages (4 and 5). Especially, 5 exhibited potent hemolytic activity (EC50, 0.03 μM) surpassing those of AmB, 2, and 3. Measurements of UV and CD spectra of 5 in liposomes indicated that AmB portions of 5 could adopt appropriate arrangements in molecular assemblage in spite of the short linkage, and also indicated that the assemblage formed by 5 appeared more stable than AmB. These short‐tethered dimers are expected to be a promising tool to reveal the mechanism of dimeric interaction in the ion channel formed by AmB.
On‐line identification and damage detection in non‐linear structural systems using a variable forgetting factor approach
Authors: Lin Jeng‐Wen , Betti Raimondo 
Published: March 2004

AbstractThis paper presents an adaptive on‐line identification algorithm based on a newly defined variable forgetting factor approach. At each time step, the proposed methodology, a recursive least‐square (Kalman filter) based algorithm, upgrades the adaptation gain matrix using an adaptive forgetting factor that is expressed as the ratio between the minimum value of the diagonal elements of the adaptation gain matrix and a set of pre‐defined threshold values. This approach requires only acceleration measurements and is particularly robust to the integration errors introduced in determining velocities and displacements. Such an algorithm has been implemented for both parametric and non‐parametric identification studies. For the case of no a priori information on the type of the structural model, an analytical method based on a power series of multivariable polynomial expansions has been introduced. The effectiveness and robustness of the proposed approach has been shown in various numerical simulations, considering the effects of excitation amplitude, of measurement noise, of a priori mass estimation error, and of exact‐, under‐, and over‐parameterization of the structural model. General polynomial‐type non‐linear models such as Duffing and Van der Pole oscillators and Bouc–Wen hysteretic model have been analyzed using the proposed modeling process. The methodology presented in this paper leads to a more accurate and controllable on‐line identification either for the estimation of time‐invariant or time‐varying structural parameters (for damage detection purposes) or for the prediction of the future structural response to dynamic loading. Copyright © 2003 John Wiley & Sons, Ltd.
Optimal design of viscoelastic dampers using eigenvalue assignment
Authors: Lee Sang‐Hyun , Son Dong‐In , Kim Jinkoo , Min Kyung‐Won 
Published: March 2004

AbstractIn this study a procedure for determining the optimum size and location of viscoelastic dampers is proposed using the eigenvalue assignment technique. Natural frequencies and modal damping ratios, required to realize a given target response, are determined first by the convex model. Then the desired dynamic structural properties are realized by optimally distributing the damping and stiffness coefficients of viscoelastic dampers using non‐linear programming based on the gradient of eigenvalues. This optimization method provides information on the optimal location as well as the magnitude of the damper parameters. The proposed procedure is applied to the retrofit of a 10‐story shear frame, and to a three‐dimensional structure with an asymmetric plan. The analysis results confirm that the responses of model structures retrofitted by the proposed method correspond well with the given target response. Copyright © 2003 John Wiley & Sons, Ltd.
Understanding the experience of college graduates during their first year of employment
Authors: Polach Janet L. 
Published: March 2004

AbstractA company's college recruitment practices, as well as its socialization processes for graduates once they
have joined the organization, can be improved when there is understanding of college graduates' experience
during the first year of employment. This study recorded the experiences of eight college graduates who were
employed by a medical device manufacturer in the Midwest. Nine themes common to all participants are identified
and grouped into three categories: work environment, friendship, and performance. Related research on college
graduates and first‐job experiences, Generations X and Y, job expectations, and new‐hire
socialization is also reviewed. Recommendations are offered for consideration by the organization that employs
the study's participants to improve college graduates' experience. Further research implications are
also discussed.
In vitro apatite induction by osteopontin: Interfacial energy for hydroxyapatite nucleation on osteopontin
Authors: Ito Shuichi , Saito Takashi , Amano Kaori 
Published: March 2004

AbstractNoncollagenous phosphoproteins that interact with type I collagen are thought to nucleate the mineral phase to the collagen fibril network of mineralized tissues. We previously reported that a specific dentin phosphoprotein, phosphophoryn, crosslinked to an insoluble substrate such as type I collagen fibrils, was an effective nucleator of apatite. In this study, we investigated the capacity of another phosphoprotein in dentin, osteopontin, for apatite nucleation in vitro. Osteopontin purified from bovine milk was either absorbed to agarose beads or crosslinked to agarose beads. Each preparation was incubated at 37°C in metastable solutions. Apatite was induced by osteopontin that was crosslinked to agarose beads, whereas osteopontin adsorbed to agarose beads failed to induce apatite crystal formation. Using classical nucleation theory, the interfacial energy for hydroxyapatite nucleation on osteopontin crosslinked to agarose beads was determined to be 94.7 ergs/cm2. This value is larger than that for phosphophoryn, though it is similar to that for hydroxyapatite. The present study indicates that osteopontin, like phosphophoryn, has a high potential to induce apatite formation when it is covalently bound to some substrate in vitro, and suggests the possibility that osteopontin bound to type I collagen may induce apatite formation in vivo. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 11–16, 2004
Controlled degradation and macrophage responses of a fluoride‐treated polycaprolactone
Authors: Gough J. E. , Christian P. , Unsworth J. , Evans M. P. , Scotchford C. A. , Jones I. A. 
Published: March 2004

AbstractWe have developed a new bone replacement material based on polycaprolactone (PCL), which can act as a suitable matrix for monomer transfer molding of degradable composites. A boron trifluoride catalyst with glycerol additive was used to produce PCL with a degradation rate that can be altered by treatment with fluoride ions. The effect of cations on the degradation of the polymer and macrophage cell responses are discussed. We found that treatment with fluoride ions reduced the degradation rate. No significant difference between these three fluorides was observed although a general trend was seen where KF‐treated PCL appeared to degrade slower than NaF‐treated PCL which was slower than NH4F‐treated PCL. Variation in solubilities of the salts was observed where the K+ cation had the highest solubility and the Na+ cation had the lowest solubility, which suggests that NaF was able to degrade the polymer more efficiently than the other fluorides. No significant macrophage activation was observed after culture on the polymer surfaces as determined by peroxide and IL‐1β release, whereas some activation occurred after culture in degradation products. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 17–25, 2004
Effects of interleukin‐10 on titanium particle‐induced macrophage transcription factor activation and cytokine expression in vitro
Authors: Wong Neal , Trindade Michael C. D. , Patel Raj , Yaszay Burt , Goodman Stuart B. , Smith R. Lane 
Published: March 2004

AbstractThis study tests the hypothesis that transcription factor activation by exposure of macrophages to titanium particles can be modulated by the addition of the antiinflammatory cytokine, interleukin 10 (IL‐10). The experiments were carried out with primary human monocyte/macrophages that were treated in the presence or absence of IL‐10 with and without exposure to titanium particles. The time course for experiments varied from 1 h–5 h for analysis of nuclear protein and up to 48 h for analysis of cytokine release. Transcription factor translocation to the nucleus was analyzed using electrophoretic gel shift assays and cytokine release was quantified by enzyme‐linked immunosorbent assay. Addition of titanium particles increased release of tumor necrosis factor‐alpha (TNF‐α), interleukin‐6 (IL‐6), and interleukin‐1 beta (IL‐1β). In addition, titantium particle induced translocation of the transcription factors, NF‐κB and NF‐IL6, in the nucleus within 1 h. Treatment of macrophages with IL‐10 prior to exposure to titanium particles decreased translocation of NF‐IL6 but did not significantly alter nuclear levels of NF‐κB. In addition, pretreatment of the cells with IL‐10 decreased particle‐induced cytokine release. These data show that antiinflammatory cytokines may provide a mechanism by which particle‐induced inflammatory response may be modulated in vivo. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 40–46, 2004
Poly(ethylene glycol)‐polyacrylate copolymers modified to control adherent monocyte–macrophage physiology: Interactions with attaching Staphylococcus epidermidis or Pseudomonas aeruginosa bacteria
Authors: Wagner Victoria E. , Bryers James D. 
Published: March 2004

AbstractThe ability of various surface modifications of poly(ethylene glycol)‐graft‐polyacrylate (PEG‐g‐PA) copolymers (tethered adhesion peptides and fragments of monoclonal antibodies) to modulate monocyte–macrophage cell interactions with surface colonizing bacteria is reported. The PEG‐g‐PA copolymers were made to inhibit nonspecific protein and cellular adhesion. The copolymers were then covalently modified with either cell adhesion peptides (YRGDS, YEILDV, or YRGES) or fragments of antibodies to monocyte–macrophage integrin receptors (anti‐VLA4, anti‐β1, anti‐β2, and anti‐CD64), which are known to enhance macrophage adhesion and perhaps modulate their activation. Cytokine expression and phagocytosis response by surface adherent monocyte–macrophages to Stapylococcus epidermidis and Pseudomonas aeruginosa bacteria were quantified. The cytokine expression (interleukins 6 and 1β) of adherent macrophages in response to the modified polymers only and to bacterial challenges were quantified by dynamic ELISA assays. The adherent macrophage phagocytic response (oxidative burst) to various materials is compared to oxidative responses to both opsonized and nonopsonized S. epidermidis and P. aeruginosa bacteria. The efficiency of adherent macrophages to ingest and kill both species was determined using radiolabeled and fluorescent labeled bacterial cell ingestion studies as a function of the PEG‐g‐PA surface modification. Materials modified with adhesion peptides marginally enhanced (2×) macrophage attachment versus controls but, upon bacterial challenges, these materials predisposed adherent macrophages to overexpress proinflammatory cytokines and to exhibit a significant phagocytic response. Conversely, PEG‐g‐PA materials modified by fragments of monoclonal antibodies significantly enhanced (7×) macrophage adhesion but, upon bacterial challenge, “per cell” cytokine expression levels were reduced compared to peptide modified materials. Macrophages adhering to antibody fragment modified surfaces also exhibited sustained enhanced phagocytic response and higher bacterial killing efficiencies when compared with peptide modified materials. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 79–90, 2004
Poly(ethylene glycol) enhances cell motility on protein‐based poly(ethylene glycol)‐polycarbonate substrates: A mechanism for cell‐guided ligand remodeling
Authors: Sharma Ram I. , Kohn Joachim , Moghe Prabhas V. 
Published: March 2004

AbstractThe regulation of cell motility on ligand‐adsorbed poly(ethylene glycol) (PEG)‐based polymeric biomaterials is governed by variables that are not well characterized. In this report, we examined keratinocyte migratory responsiveness to PEG‐variant tyrosine‐derived polycarbonates adsorbed with equivalent levels of the cell adhesion ligand, fibronectin. The equivalently adsorbed ligand adopted differential distributions, confirmed via atomic force microscopy, and the total number of exposed cell‐binding domains (CBD), quantified through immunosorbent fluorometry, varied as a function of PEG concentration. Specifically, the CBD exposure was maximized at 4 mol % PEG and diminished at 8 mol % PEG, suggesting, based on our previous work (Tziampazis et al., Biomaterials 2000;21:511–520), that activation of cell adhesion and motility could be potentially promoted through increased CBD exposure at intermediate levels of PEG. This was confirmed through cell migration studies wherein cell speed values increased from 11 to 22 μm/h as the PEG concentration was increased from 0 to 4 mol %. Unexpectedly, however, high cell motility rates were sustained at 8 mol % PEG despite diminished levels of initial CBD exposure beyond 4 mol % PEG, suggesting that factors other than the initial CBD exposure may additionally have a role in activating cell migration at higher levels of PEG. Through studies of direct ligand mobility, cell‐ligand‐polymer interactions via atomic force microscopy, and CBD variation and integrin receptor roles in ligand remodeling, we offer evidence that cell motility is enhanced by a new mechanism for the regimen of higher PEG concentration: upon cell attachment and spreading, the ligand exhibits greater “slippage” at the polymer interface, and undergoes cell‐engendered remodeling, which further activates cell motility, likely through enhanced exposure of hitherto encrypted sites for cell binding and signaling. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 114–123, 2004
Treatment of bioprosthetic heart valve tissue with long chain alcohol solution to lower calcification potential
Authors: Pathak Chandrashekar P. , Adams Alan K. , Simpson Tom , Phillips Richard E. , Moore Mark A. 
Published: March 2004

AbstractThe use of glutaraldehyde‐treated biological tissue in heart valve substitutes is an important option in the treatment of heart valve disease. These devices have limited durability, in part, because of tissue calcification and subsequent tearing of the valve leaflets. Components thought to induce calcification include lipids, cell remnants, and residual glutaraldehyde. We hypothesized that treatment of glutaraldehyde‐treated bioprosthetic heart valve material using a short and long chain alcohol (LCA) combination, composed of 5% 1,2‐octanediol in an ethanolic buffered solution, would reduce phospholipid content and subsequently lower the propensity of these tissues to calcify in vivo. Phospholipid content of glutaraldehyde‐treated porcine valve leaflets and bovine pericardium was found to be 10.1 ± 4.3 (n = 7) and 3.9 ± 0.48 (n = 2) μg/mg dry tissue, respectively, which was reduced to 0.041 ± 0.06 (n = 7) and 0.21 ± 0.05 (n = 4) μg/mg dry tissue, respectively, after LCA treatment. Calcification potential of the treated tissues was assessed using a rat subcutaneous implant model. After 60 days of implantation, calcium levels were found to be 171 ± 32 (n = 11) and 83 ± 70 (n = 12) mg/g dry weight for glutaraldehyde‐treated porcine leaflets and bovine pericardium, respectively, whereas prior LCA treatment resulted in reduced calcium levels of 1.1 ± 0.6 (n = 12) and 0.82 ± 0.1 (n = 12) mg/g dry weight, respectively. These data, taken together, support the notion that treatment of glutaraldehyde‐treated tissue with a short and long chain alcohol combination will reduce both extractable phospholipids and the propensity for in vivo calcification. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 140–144, 2004
Effect of rapidly resorbable calcium phosphates and a calcium phosphate bone cement on the expression of bone‐related genes and proteins in vitro
Authors: Knabe C. , Berger G. , Gildenhaar R. , Meyer J. , Howlett C. R. , Markovic B. , Zreiqat H. 
Published: March 2004

AbstractThe use of biodegradable bone substitutes is advantageous for alveolar ridge augmentation because it avoids second‐site surgery for autograft harvesting. This study examines the effect of novel, rapidly resorbable calcium phosphates and a calcium phosphate bone cement on the expression of bone‐related genes and proteins by human bone‐derived cells (HBDCs) and compares this behavior to that of tricalciumphosphate (TCP). Test materials were α‐TCP, two materials with a crystalline phase Ca2KNa(PO4)2 and with a small amorphous portion containing either magnesium potassium phosphate (material denominated GB14) or silica phosphate (material denominated GB9), and a calcium phosphate bone cement (material denominated Biocement D). HBDCs were grown on the substrata for 3, 7, 14, and 21 days, counted, and probed for various mRNAs and proteins (type I collagen, osteocalcin, osteopontin, osteonectin, alkaline phosphatase, and bone sialoprotein). All substrates supported continuous cellular growth for 21 days. In the presence of GB14 and Biocement D specimens cell proliferation was reduced and cell differentiation increased. At day 21, the greatest number of cells was found on GB9 expressing significantly higher levels of bone‐related proteins than cells grown on all other surfaces. Because all novel materials facilitated the expression of the osteoblastic phenotype at least as much as TCP and the polystyrene control, these biomaterials can be regarded as excellent candidate bone substitute materials. GB9 induced the highest proliferation and cellular differentiation after 21 days of incubation, suggesting that this material may possess a higher potency for enhancing osteogenesis than TCP. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 145–154, 2004
Evaluating the effectiveness of interactive computer tutorials for an undergraduate mathematical literacy course
Authors: Frith Vera , Jaftha Jacob , Prince Robert 
Published: March 2004

AbstractThis article describes a study of learning when students used interactive spreadsheet‐based computer tutorials in a mathematical literacy course. It foregrounds theories relating to the role of computer technology (and specifically spreadsheets) as a mediator for learning of mathematics. It outlines the application of quantitative methods involving pre‐ and post‐testing of students, both in the computer laboratory and in the lecture sessions, and discusses factors constraining the experimental design and the usefulness of the results. There are indications that the data reveal real differences between the learning experiences in the lecture sessions and the computer laboratories. It appears that in some respects the computer tutorials were more effective in conveying the concepts than the lecture sessions were. A method of analysing and representing the data, that tracks the extent of learning of concepts through the pre‐ and post‐tests, was developed. It allows for the performance of sub‐groups of students to be examined separately. This analysis shows that simple definitions of disadvantage (such as having English as a second language) are inadequate to account for the poor performance of students in the lower quartile.
Impacts of migratory behaviour on population structure in North Sea plaice
Authors: Hunter Ewan , Metcalfe J. D. , Arnold G. P. , Reynolds J. D. 
Published: March 2004

SummaryMigration is widespread among marine fishes, yet little is known about variation in the migration of individuals within localities, and the consequences for spatial population structure. We tested the hypothesis that variation in the migratory behaviour among plaice (Pleuronectes platessaL.) in the North Sea could be explained by large‐scale differences in the speed and directions of the tidal streams, which the fish use as a transport mechanism.We released 752 mature female plaice tagged with electronic data storage tags at eight locations with contrasting tidal flow properties between December 1993 and September 1999.The experiment yielded 20 403 days of data from 145 plaice. Individual tags recorded depth and temperature for up to 512 days. The position of each fish was determined at intervals throughout the liberty period using the tidal location method.The results show that the fish were segregated into three discrete feeding aggregations during the summer non‐breeding season. Two clusters were in warm, thermally mixed water in the eastern and western North Sea, respectively, and one was in deeper, cold, thermally stratified water to the north.In the winter spawning period, fish from all three aggregations mixed together in the southern North Sea, and fish from the eastern and northern subunits spawned in the south‐eastern North Sea. The only fish that left the North Sea were western subunit plaice that visited spawning grounds in the eastern English Channel.Our results re‐affirmed the major role of the tidal streams in the southern North Sea in structuring plaice dispersion, both by providing transport and guidance and by delimiting the extent of distribution due to thermal stratification during the summer. However, plaice from the northern North Sea did not use tidal stream transport.These results confirm the prediction that large‐scale variation in migration behaviour can be explained in part by the tidal guidance and transport mechanisms available. They have also revealed features of spatial dynamics not observed previously from a century of conventional tagging experiments and illustrate how the study of individual fish can successfully define the migratory characteristics of populations.