bluuebunny/crossref_metadata_2025 huggingface dataset:
Large-scale reprogramming of cranial neural crest gene expression by retinoic acid exposure
Authors: Williams Sarah S. , Mear John P. , Liang Hung-Chi , Potter S. Steven , Aronow Bruce J. , Colbert Melissa C.
Published: October 2004

Although retinoic acid (RA), the active form of vitamin A, is required for normal embryonic growth and development, it is also a powerful teratogen. Infants born to mothers exposed to retinoids during pregnancy have a 25-fold increased risk for malformations, nearly exclusively of cranial neural crest-derived tissues. To characterize neural crest cell responses to RA, we exposed murine crest cultures to teratogenic levels of RA and subjected their RNA to microarray-based gene expression profile analysis using Affymetrix MG-U74Av2 GeneChips. RNAs were isolated from independent cultures treated with 10−6M RA for 6, 12, 24, or 48 h. Statistical analyses of gene expression profile data facilitated identification of the 205 top-ranked differentially regulated genes whose expression was reproducibly changed by RA over time. Cluster analyses of these genes across the independently treated sample series revealed distinctive kinetic patterns of altered gene expression. The largest group was transiently affected within the first 6 h of exposure, representing early responding genes. Group 2 showed sustained induction by RA over all times, whereas group 3 was characterized by the suppression of a time-dependent expression increase normally seen in untreated cells. Additional patterns demonstrated time-dependent increased or decreased expression among genes not normally regulated to a significant extent. Gene function analysis revealed that more than one-third of all RA-regulated genes were associated with developmental regulation, including both canonical and noncanonical Wnt signaling pathways. Multiple genes associated with cell adhesion and cell cycle regulation, recognized targets for the biological effects of RA, were also affected. Taken together, these results support the hypothesis that the teratogenic effects of RA derive from reprogramming gene expression of a host of genes, which play critical roles during embryonic development regulating pathways that determine subsequent differentiation of cranial neural crest cells.
Metacognitive Strategy Use in Reading of Gifted High Achieving and Gifted Underachieving Middle School Students in New York City
Authors: Berkowitz Esther , Cicchelli Terry
Published: October 2004

High achieving and underachieving gifted New York City adolescent students were compared in their use of metacognitive reading strategies. A stratified sample was used to identify extreme groups of achievers, 5 consistent high achievers and 5 consistent underachievers. Data were collected from three sources: (a) the Metacognitive Awareness of Reading Strategies Inventory (MARSI; Mokhtari & Reichard, 2002), (b) think-aloud protocols, and (c) interviews. While no significant differences were noted, frequency of strategy use, particularly in monitoring, made clear that the gifted high achievers were more homogeneous and the gifted underachievers were more heterogeneous strategy users. Further research on metacognitive reading strategy use of high and underachieving gifted middle school students may include the following: (a) using a multidimensional perspective to identify gifted urban students, and (b) examining metacognitive reading strategy use in other academic content areas related to students’ interest. Optimistically, this research should be encouraged in working with urban adolescent students.
School Finance
Authors: Reyes Augustina H. , Rodriguez Gloria M.
Published: October 2004

School finance drives policy and practice in public education, yet most citizens and some practitioners know very little about how their schools are funded. The purpose of this article is to address the financial issues related to urban schools and the challenge of balancing expectations of higher levels of education with the values of equity, efficiency, and economic growth. Section 1 discusses the social context of school finance in the United States, including urban education issues. This section will discuss equity issues in the context of the history of school finance litigation in the United States. Section 1 will also show how the school funds are spent. Section 2 will discuss traditional funding structures and state funding policies. Section 3 will discuss decentralization and site-based budgeting, including the use of charters, vouchers, and contracts. The conclusion will explore how restructuring school budgeting can improve instruction and student performance.
Fear of Crime in Italy
Authors: Miceli Renato , Roccato Michele , Rosato Rosalba
Published: October 2004

The aim of this study is to examine the spread and determinants of fear of crime in Italy. A secondary analysis was performed on the 1995 Italian National Statistics Institute data (Italian representative sample: 19,785 participants). In addition, data from official judicial statistics were analyzed. Main results are as follows: (a) fear of crime correlates with crime spread; (b) fear of crime is more widespread than crime itself; (c) the best predictors of fear of crime are urbanization, degradation of residential areas, and residence in Northeastern Italy; (d) criminal victimization exerts a minor influence on fear of crime; and (e) sociodemographic variables under investigation exert little influence on fear of crime. These results are discussed in reference to international literature, and possible subsequent lines of research are suggested.
Patterns of Psychological Acculturation in Adult and Adolescent Moroccan Immigrants Living in the Netherlands
Authors: Stevens Gonneke W. J. M. , Pels Trees V. M. , Vollebergh Wilma A. M. , Crijnen Alfons A. M.
Published: October 2004

Psychological acculturation patterns within a Moroccan adult and adolescent population in the Netherlands were determined through latent class analysis. The Psychological Acculturation Scale (PAS) was adapted, and strong psychometric properties were demonstrated. We found Dutch and Moroccan Psychological Acculturation Subscales (D-PAS; M-PAS). Three classes with similar patterns of acculturation were revealed for both populations. One class showed medium scores on the D-PAS and M-PAS items and one class revealed a pattern with high scores on the M-PAS and medium to high scores on the D-PAS items. The third class was characterized by low scores on the D-PAS and high scores on the M-PAS items. These acculturation classes were shown to be meaningful constructs and yield detailed information about acculturation.
Adolescent Self-Esteem in Cross-Cultural Perspective
Authors: Farruggia Susan P. , Chen Chuansheng , Greenberger Ellen , Dmitrieva Julia , Macek Petr
Published: October 2004

Theorists and researchers have raised the question of whether self-esteem has similar meanings and correlates in individualistic and collectivist cultures. This study examined the cross-cultural equivalence of the Rosenberg Self-Esteem Scale in four countries and compared its association with parental warmth and acceptance and depressed mood. Participants were 11th graders in the United States ( n = 422), the Czech Republic ( n = 490), China ( n = 502), and Korea ( n = 497). Cross-cultural similarities in the factor structure of the self-esteem scale and in the relations of self-esteem to other variables were more striking than cross-cultural differences. Across cultures, parental warmth was significantly related to both positive and negative self-image, each of which in turn was related significantly to depressive symptomatology. There was little evidence for the hypothesis that self-esteem would more strongly mediate the relation between parental warmth and adolescent depressive symptoms in the more individualistic(as opposed to collectivist) cultures.
Icelanders’ and U.S. Nationals’ Expectations about Counseling
Authors: ÆGisdóTtir StefanÍA , Gerstein Lawrence H.
Published: October 2004

This study compared counseling expectations of Icelandic and U.S. college students, investigated counseling expectations as a function of sex, and explored the relationship between counseling expectations and Holland’s typology. It was discovered that the Icelandic students expected greater expertise from the counselor than did the U.S. students and the U.S. students expected the counseling conditions to be more facilitative than did the Icelandic students. Also, women, as compared with men, expected counseling to be more facilitative of change and expected to be more personally committed to the counseling process, whereas men expected more counselor expertise. A canonical correlation analysis revealed a significant relationship between counseling expectations and Holland’s Social and Realistic personality types for the U.S. students and Holland’s Social type for the Icelandic students.
Racial Democracy in the Americas
Authors: PeñA Yesilernis , Sidanius Jim , Sawyer Mark
Published: October 2004

The “racial democracy” (Iberian exceptionalism) thesis claims that racial prejudice in Latin America is not only lower than that found in the United States but is essentially absent altogether. We explored the plausibility of this thesis by the use of both explicit and implicit prejudice measures among Blacks and Whites from the United States and three Caribbean nations. In general, the results showed significant racial prejudice against Blacks and in favor of Whites in all four nations. African Americans were the only participants not to show significant implicit prejudice either in favor of or against Blacks. In addition, North Americans (i.e., participants from the United States) displayed lower implicit and explicit racial prejudice than participants in each of the three Latino nations. Overall, the results clearly contradicted the thesis of racial democracy and suggest that Latin America may not be nearly as egalitarian as some have argued.
Gunslinger School Administrators
Authors: Eisinger Peter K. , Hula Richard C.
Published: October 2004

Educators, political leaders, and the public in the United States share a broad consensus that school systems in the larger urban areas are not meeting the educational needs of the children they are charged to serve. The result has been a virtual explosion in alternative reform strategies. In one fascinating example, some cities have consciously decided to recruit a school CEO or superintendent whose professional backgrounds lie entirely outside of the sphere of public education. We liken these education outsiders, these nontraditional school system leaders, to the “gunslinger” of American frontier mythology, the stranger, like Shane, who rides into town and solves a menacing problem that the townsfolk cannot manage themselves. This article explores the gunslinger phenomenon in public education leadership by describing it, specifying the conditions under which cities resort to this sort of reform, and exploring its implications for public education.
W/Righting History
Authors: Brandon Lavada Taylor
Published: October 2004

An avid supporter of oral history, educator historian Carter G. Woodson maintained that an understanding of the past would enlighten present generations. Illuminating Woodson’s spirit and philosophy, this article is written to investigate oral history as a theory and practice used to problematize traditional assumptions of history while licensing urban African American learners to become authors and constructors of knowledge. In so doing, the piece highlights educative possibilities of oral history as a pedagogical approach with urban African American students.
Normative Meanings of Experiences for a Spectrum of Tourism Places
Authors: Snepenger David , Murphy Leann , Snepenger Mary , Anderson Wythe
Published: October 2004

Within a tourism system, some places have a predominantly tourism clientele, other places cater to both tourists and locals, and still others focus on locals and only incidentally tourists. These places may be viewed as a spectrum with different demand structures. This article investigates how a community with a large tourism economy defined the normative meanings of experiences for the spectrum. Three places represented the spectrum: Yellowstone National Park, the downtown shopping district, and big-box stores. A quasi-experimental design of community residents assessed consumption, hedonic, utilitarian, and social meanings for the places while controlling for background characteristics. The high-, mixed-, and low-tourism-demand places differed on meanings. Correlation analysis indicated that some of the places shared meanings, whereas others did not. Discriminant analysis predicted the correct place 86% of the time based on the meanings. The article concludes by discussing some recommendations for future research.
Predicting Attitude Extremity: The Interactive Effects of Schema Development and the Need to Evaluate and Their Mediation by Evaluative Integration
Authors: Federico Christopher M.
Published: October 2004

Research on attitude extremity suggests that schemas containing more information about a particular attitude domain are more likely to be associated with extreme attitudes toward objects in that domain when perceivers’ responses toward features of the domain are evaluatively integrated. The present study argues that a high need to evaluate may play an important role in determining when schema development will be associated with the integrated responses to different domain features necessary for extremity. Consistent with this argument, data from a nationally representative survey of political attitudes indicated that the need to evaluate was associated with increased extremity across two different indices of the latter; that it moderated the relationships between schema development (in the form of political expertise), on one hand, and increased extremity and integration, on the other; and that the moderating effects of the need to evaluate vis-à-vis extremity were mediated by integration.
The Swimsuit Becomes Us All: Ethnicity, Gender, and Vulnerability to Self-Objectification
Authors: Hebl Michelle R. , King Eden B. , Lin Jean
Published: October 2004

Self-objectification theory posits and past research has found that Caucasian women’s body image is negatively affected by a stigma of obesity and sociocultural norm of thinness that leads women to self-focus from a critical external perspective. However, research in this area is limited by its methodology and the restricted demographic composition of its study participants. The current study tested 176 men and 224 women of Caucasian, African American, Hispanic, and Asian American descent in a situation that induced a state of self-objectification (e.g., wearing a one-piece Speedo bathing suit) or that served as a control condition (e.g., wearing a sweater). Contrary to previous research, when put in a self-objectifying situation, men and women of every ethnicity experienced negative outcomes (e.g., lower math performance) that parallel those previously found for Caucasian women.
Tracking the Timecourse of Social Perception: The Effects of Racial Cues on Event-Related Brain Potentials
Authors: Ito Tiffany A. , Thompson Erin , Cacioppo John T.
Published: October 2004

Event-related potentials were used to track social perception processes associated with viewing faces of racial ingroup and outgroup members. Activity associated with three distinct processes was detected. First, peaking at approximately 170 ms, faces were distinguished from nonface stimuli. Second, peaking at approximately 250 ms, ingroup members were differentiated from outgroup members, with a larger component suggesting greater attention to ingroup members. This effect may reflect the spontaneous application of a deeper level of processing to ingroup members. Third, peaking at approximately 520 ms, evaluative differentiation of ingroup and outgroup members occurred, with greater ingroup bias displayed by those with higher levels of prejudice on an explicit measure. Together, the results demonstrate the promise of using neural processes to track the presence, timing, and degree of activation of components relevant to social perception, prejudice, and stereotyping.
Partially Observed Mixtures of IRT Models: An Extension of the Generalized Partial-Credit Model
Authors: Von Davier Matthias , Yamamoto Kentaro
Published: October 2004

The generalized partial-credit model (GPCM) is used frequently in educational testing and in large-scale assessments for analyzing polytomous data. Special cases of the generalized partial-credit model are the partial-credit model—or Rasch model for ordinal data—and the two-parameter logistic (2PL) model. This article extends the GPCM to the class of discrete mixture distribution models. The developments presented here extend models such as the mixed Rasch model and dichotomous multiparameter item response theory (IRT) mixture models. In addition, the model proposed here allows estimation of multigroup models with partially missing grouping information. An application of the proposed partially observed mixture IRT model to a sparse matrix sample of item responses from a national large-scale assessment program is also presented.
Factors Influencing the Mantel and Generalized Mantel-Haenszel Methods for the Assessment of Differential Item Functioning in Polytomous Items
Authors: Wang Wen-Chung , Su Ya-Hui
Published: October 2004

Eight independent variables (differential item functioning [DIF] detection method, purification procedure, item response model, mean latent trait difference between groups, test length, DIF pattern, magnitude of DIF, and percentage of DIF items) were manipulated, and two dependent variables (Type I error and power) were assessed through simulations. Results showed that it was the average signed area between the two item characteristic curves of the reference and focal groups rather than the percentage of DIF items in the test that determined the Type I error of the Mantel and generalized Mantel-Haenszel (GMH) methods. As long as the average signed area approached zero, both methods maintained control over their Type I error, even when the percentage of DIF items was very high (e.g., 40%). The Mantel yielded higher power than the GMH under all but the balanced DIF patterns. The two-stage Mantel is recommended if a single method is to be used.
Designing a Data and Safety Monitoring Plan
Authors: Slimmer Lynda , Andersen Burton
Published: October 2004

Evidence-based nursing practice is now the expected standard of care intensifying the need to conduct clinical research studies to investigate the efficacy of nursing interventions. To ensure that the urgency to document such efficacy does not compromise human participant safety, government research funding agencies are advocating special procedures to protect individuals who voluntarily participate in research studies. The National Institutes of Health application for clinical trial funding requires a data and safety monitoring plan (DSMP) to enhance human participant safety and clinical research integrity. This article describes an approach to developing a DSMP that includes a study risk assessment and a monitoring design based on that assessment.
Knowledge, Attitudes, and Predictors of Advance Directive Discussions of Registered Nurses
Authors: Lipson Amy R. , Hausman Alice J. , Higgins Patricia A. , Burant Christopher J.
Published: October 2004

The purpose of this study was to describe nurses’ knowledge, attitudes, and experiences regarding advance directives. A secondary purpose was to examine predictors of advance directive discussions between nurses and patients. Seven-hundred and nineteen respondents, randomly selected from a list of registered nurses in the state of Ohio, completed mailed questionnaires. Descriptive t test, chi-square, and logistic regression statistics were used in the data analyses. The respondents were knowledgeable and possessed positive attitudes about advance directives. Higher self-perceived confidence in advance directive discussion skills and the experience of caring for at least one patient with a current advance directive were found to be significant predictors of advance directive discussions. These findings suggest that experience with advance directives documents is critical for nurses’ comfort and that developing interventions to further nurses’ confidence in their discussion skills may increase advance directive discussions.
The Johnson-Neyman Procedure as an Alternative to ANCOVA
Authors: D’Alonzo Karen T.
Published: October 2004

ANCOVA is a widely used statistical procedure that is particularly useful in analyzing data from experimental designs. There are, however, a number of assumptions that must be tested before proceeding with the ANCOVA. Of particular concern is the assumption of homogeneity of regression slopes (HOS). When the HOS assumption has been violated, the researcher needs to look for an alternative approach to the ANCOVA. The Johnson-Neyman procedure (J-N) is presented as such an alternative. Although the calculations for the procedure are somewhat tedious and are not currently a standard feature of statistical software packages, an alternative approach using SAS syntax codes is presented.
“Workers Wanted”
Authors: Rodriguez Nestor
Published: October 2004

Employers play central roles in the social incorporation of immigrant labor but have usually received only scant attention in research literature. From the importation of contract Mexican workers from 1942 to 1964 to the present employment of foreign-born workers in primary and secondary labor markets, employers have played critical functions in recruiting foreign-born labor into the U.S. economy. Directly and indirectly, the U.S. government has supported these functions. The future likely holds a continuation of temporary governmental policies for the recruitment of skilled and unskilled foreign-born labor as well as a continuation of employer attraction to this labor.
Patent Activity and Financial Performance of Publicly Traded Companies in the U.S. Pharmaceutical Industry: The Role of Local Economic Conditions
Authors: MacPherson Alan , Boasson Vigdis
Published: October 2004

This article looks at the spatial distribution of patent activity among publicly traded companies in the U.S. pharmaceutical industry. Data for two time periods show that patent introductions tend to favor the Northeast. Significant locational variations are uncovered in the innovation performance of firms in this industry. These variations are hypothesized to reflect the localized economic conditions that characterize Porter’s model of competitive advantage (the diamond paradigm). Our analysis suggests that patent counts respond positively to the degree of spatially concentrated production (density of competition). Furthermore, findings suggest that local business conditions play an important role in the innovation and financial performance of U.S. pharmaceutical companies.
Traditional Chinese Medicine: Ancient Holistic Healing
Authors: Barbaso-Schwartz Alma
Published: October 2004

This article introduces the philosophy of traditional Chinese medicine (TCM) and discusses the concepts of yin-yang balance, qi (energy or life force), and the five elements—wood, fire, earth, metal and water—in relation to health and healing. In addition to qi, an overview of jing (essence) and shen (spirit) are presented in this article. The effects of one’s emotions on health and specific organs are detailed within this article, identifying the emotion and its correlative effect on the organ(s) involved and TCM approaches to harmonizing the effects of these emotions on health.
The Excess Burden of the Social Security Payroll Tax
Authors: Liu Liqun , Rettenmaier Andrew J.
Published: October 2004

The conventional measure of the excess burden of a discrete increase in the rate of either a labor income tax or an excise tax is typically represented by a trapezoid in the supply/demand framework. This article adopts an alternative view of the incremental excess burden due to Mayshar and finds that the excess burden of a discrete increase in the rate of either a labor tax or an excise tax is represented by a triangle plus a rectangle, which is smaller than the conventional trapezoid for labor income taxes but larger than it for excise taxes. The new measure indicates an excess burden for U.S. social security tax (in the labor market alone) that is 10 to 50 percent of what is captured by the traditional trapezoid.
Promotion’s Limited Impact in the 2000 Sydney Olympics
Authors: Eastman Susan Tyler , Billings Andrew C.
Published: October 2004

Lower-than-expected ratings made the 2000 Sydney Olympics an unusual promotional platform and led the National Broadcasting Company (NBC) to alter its on-air plans for marketing its fall 2000 prime-time schedule while the event was proceeding. This study assessed the impact of the prime-time promos carried in the 2000 Games on post-Olympics program ratings. A comparison of before-and-after difference scores for each promoted program showed that only one-quarter of its promoted programs rose in the ratings after the event, half stayed flat, and one-third went down, despite NBC’s having the top-rated shows at the time. Ten factors were identified that potentially affected the promos’ collective impact. From a theoretical perspective, the findings suggested two new variables that might be incorporated in salience theory and from a practical perspective, suggested that NBC’s unusual promotional practices led to too little exposure time and repetition for effective promotion.
Structural Change and Cobalt Fixation in the Hydrothermally Synthesized Zeolite Phases from a Si–Al–Co Hydrous Oxide
Authors: Nagase Takako , Chatterjee Abhijit , Tanaka Alfred P , Tanco Margot L , Tazaki Kazue
Published: October 2004

A series of Co-zeolite samples were synthesized at 170–200 °C, controlling the reaction between a Si–Al–Co hydrous oxide and NaOH solution. With increase of the reaction time, and NaOH concentration, synthesized phase changed in the sequence of MOR, PHI, and ANA with Na. The results of chemical analysis and FT-IR spectra of each phases showed that NaOH concentration in the initial slurry and the architecture of zeolite affected Co fixation in the zeolite structure.
Practical Synthesis of Optically Active Fluorine-substituted α-Phenylethylamines by Retardation of Hydrogenolytic Cleavage at Benzylic Position
Authors: Kanai Masatomi , Yasumoto Manabu , Kuriyama Yokusu , Inomiya Kenjin , Katsuhara Yutaka , Higashiyama Kimio , Ishii Akihiro
Published: October 2004

High regioselectivity in hydrogenolysis of bis(α-methylbenzyl)amines having a fluorine atom on aromatic ring results from retardation of hydrogenolytic cleavage at benzylic position of fluorine-substituted aromatic ring.
Bi(OTf)3-[Bmim]PF6: A novel and Recyclable Catalytic System for the Diasteroselective Synthesis of Cis-fused Pyrano and Furanobenzopyrans
Authors: Yadav J S , Reddy B V S , Reddy P Narayana
Published: October 2004

The Stereoselective one-pot synthesis of cis-fused pyrano and furanobenzopyrans has been developed from o-hydroxybenzaldehydes, aromatic amines, and cyclic enol ethers in the presence of Bi(OTf)3 in air- and moisture-stable ionic liquid, [bmim]PF6 under mild conditions. The recovered ionic liquid containing Bi(OTf)3 can be reused three to five subsequent runs with only a gradual decrease in activity. The recovery of catalyst is facilitated by its hydrophobic nature of [bmim]PF6.
Evidence for Two Competing Mechanisms in Regeneration of 2-(2,4-Dinitrobenzyl)pyridine from its Enamine Tautomer
Authors: Kira Nobuhiro , Takahashi Toru , Ohga Yasushi , Asano Tsutomu
Published: October 2004

Kinetic effects of pressure on the title reaction were studied. The reaction was insensitive to a change in pressure at 0.1 MPa, however, it was accelerated by an increase in pressure at P > 100 MPa, showing the existence of two reaction routes with and without solvent participation. Viscosity-induced retardations observed in highly viscous media supported intervention of solvent molecules at high pressures.
UV–vis Absorption Spectra of Powdered Materials: Direct Measurements by Optical Waveguide Spectroscopy
Authors: Ogawa Keiichiro , Harada Jun , Fujiwara Toshikatsu , Takahashi Hiromi
Published: October 2004

UV–vis absorption spectra of powders of naphthalene and salicylideneaniline were obtained using optical waveguide spectroscopy. It is demonstrated that the optical waveguide spectroscopy is an excellent method for the measurement of UV–vis absorption spectra of powdered materials as they are, without any treatment.
Paraneoplastic antibodies coexist and predict cancer, not neurological syndrome
Authors: Pittock Sean J. , Kryzer Thomas J. , Lennon Vanda A.
Published: October 2004

We investigated coexisting autoantibodies in sera of 553 patients with a neurological presentation and one or more paraneoplastic neuronal nuclear or cytoplasmic autoantibodies: antineuronal nuclear autoantibody type 1 (ANNA‐1), ANNA‐2, ANNA‐3; Purkinje cell cytoplasmic autoantibody type 1 (PCA‐1), PCA‐2; and CRMP‐5–immunoglobulin G or amphiphysin–immunoglobulin G. Except for PCA‐1, which occurred alone, 31% of sera had more than one of these autoantibodies. In addition, 25% of sera had neuronal calcium channel (P/Q‐type or N‐type), potassium channel, ganglionic acetylcholine receptor, muscle acetylcholine receptor, or striational antibodies. The autoantibody profiles observed in patients with paraneoplastic disorders imply the targeting of multiple onconeural antigens and predict the patient's neoplasm, but not a specific neurological syndrome. Ann Neurol 2004
Modification of lignin–polyethylene blends with high lignin content using ethylene–vinylacetate copolymer as modifier
Authors: Alexy Pavol , Košíková Božena , Crkonová Gabriela , Gregorová Adriána , Martiš Pavol
Published: October 2004

Blending of polyethylene with lignin in concentrations > 20 wt % yielded blends with relatively low mechanical properties. A new method, based on modification of polyethylene with ethylene–vinylacetate (EVA) copolymer, was developed for the preparation of polyethylene blends containing about 30 wt % lignin with acceptable strength properties. The addition of 10 wt % EVA caused an increase of tensile strength about twice and elongation at break about 13 times compared to those of the corresponding nonmodified samples. The optimization of lignin–polyethylene–EVA blend composition was based on a regression equation, which was obtained as output from an experimental design. The prepared composite material with 33.6 wt % lignin showed acceptable processing and mechanical properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1855–1860, 2004
Particle features of a poly(methyl methacrylate) resin prepared by a new emulsion polymerization process
Authors: Bao Yong‐Zhong , Huang Zhi‐Ming , Weng Zhi‐Xue
Published: October 2004

A new emulsion polymerization process, in which water acted as the dispersed phase and a mixture of methyl methacrylate (MMA) and cyclohexane acted as the continuous phase, was applied to the preparation of a poly(methyl methacrylate) (PMMA) resin. The primary (latex) particles were formed in the early stage of polymerization and coagulated as the polymerization conversion increased. Scanning electron micrographs showed that the final PMMA particles were porous and composed of loosely aggregated primary particles. The porosity characterized by cold di(2‐ethylhexyl) phthalate absorption increased as the water/oil and cyclohexane/MMA mass ratios increased. The PMMA primary particles were smaller than the primary particles in the PMMA resin prepared by suspension polymerization in the presence of cyclohexane. Because of the phase composition of the reaction system, the solubility of PMMA in a mixture of cyclohexane and MMA, and the particle morphology of PMMA, a particle formation mechanism, including the formation, growth, and coagulation of primary particles in dispersed water droplets, was proposed. The primary particles formed mainly through a homogeneous nucleation mechanism and increased in size as MMA diffused from the oil phase to the water phase to the primary particles. The coagulation of the primary particles occurred because of the lower colloidal stability and the space limitations of the primary particles. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1905–1911, 2004
Independent control of lower critical solution temperature and swelling behavior with pH for poly(N‐isopropylacrylamide‐co‐maleic acid)
Authors: Weiss‐Malik Rachael A. , Solis Francisco J. , Vernon Brent L.
Published: October 2004

Polymer solutions that gel in response to changes in temperature and pH are of interest for various forms of drug delivery, and it is desirable to increase swelling for diffusion‐controlled release without bringing the lower critical solution temperature (LCST) above 37°C. N‐isopropylacrylamide (NIP) was polymerized with maleic acid (MAc), a diprotic acid, and acrylic acid (AAc), a monoprotic acid, to compare swelling and temperature response with changes in pH. For samples with equal acid contents and almost identical LCST responses to pH, poly(N‐isopropylacrylamide‐co‐maleic acid) (pNIP MAc) demonstrated greater swelling than poly(N‐isopropylacrylamide‐co‐acrylic acid) (pNIP AAc). The LCST increase for MAc occurred at a pH corresponding to the deprotonation of almost all of the first acid groups. Further increases in pH led to the deprotonation of the second COOH and only served to increase the charge concentration at a given location. These results provide strong support for the theory that LCST results largely from uninterrupted chain lengths of NIP and that swelling results from the actual charge density of acid groups along the chain. Because the use of a diprotic acid copolymer allows swelling to be decoupled from LCST, pNIP MAc may be an appropriate candidate for pH‐sensitive drug‐delivery applications. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2110–2116, 2004
Surface and thermal characteristics of rubber‐modified aromatic polyamide
Authors: Park Young‐Wook , Lee Dong‐Sung
Published: October 2004

Polyamide/epoxysilane (coupling agent) composites were reacted with poly(dimethylsiloxane) (PDMS), a condensation product of diethoxydimethylsilane (DEDMS), by a sol–gel process. Polyamide–PDMS nanocomposites were obtained. The existence of the condensation product of DEDMS and the reaction between the epoxy group and the polyamide were confirmed with Fourier transform infrared, attenuated total reflection, and wide‐scanning X‐ray photoelectron spectroscopy. Atomic force microscopy and contact‐angle measurements showed that the surface properties of polyamide were greatly improved by the addition of PDMS. The pyrolysis temperature of polyamide with PDMS was approximately 400°C, and the pyrolysis temperature was similar to that of pure polyamide. Also, the char contents increased with the addition of PDMS. The glass‐transition temperature of polyamide with or without PDMS was approximately 140°C according to differential scanning calorimetry. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1947–1955, 2004
Preparation of silica‐filled poly(2‐hydroxymethyl methacrylate) nanocomposites cured by photoirradiation during the sol–gel process
Authors: Lin Dar‐Jong , Chen Ching‐Chung , Su Yi‐Che , Huang Shu‐Hui , Cheng Liao‐Ping
Published: October 2004

The sol–gel process was used to prepare a photosensitive inorganic–organic composite, silica/poly(2‐hydroxymethyl methacrylate). Its nanoscale morphology was observed with field emission scanning electron microscopy at high magnifications (e.g., 160,000×). The size of the particles in the nanocomposite synthesized under various preparation conditions fell in the range of 20–50 nm. The effects of the pH, reactant composition, and solvent content in the reaction mixture on the thermal and mechanical properties of the nanocomposite were studied with thermogravimetric analysis, dynamic mechanical analysis, and thermomechanical analysis. The thermal stability of the synthesized nanocomposite could generally be improved by an increase in the molar ratio of the inorganic component, a reduction in the reaction pH, or an increase in the solvent content. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1927–1935, 2004
Influence of temperature changes on crystallization of an ethylene–propylene random copolymer
Authors: Raimo Maria
Published: October 2004

Unconventional procedures were used to crystallize an ethylene/propylene copolymer (E/P), with the aim of investigating the effect of temperature changes on crystallization kinetics and spherulitic morphology. The solidification process of specimens crystallizing under isothermal conditions was cyclically stopped for a while, by increasing the temperature, and afterward reestablished by cooling at the original temperature. The resulting morphology characterized by rings within spherulites was compared to that obtained by continuous isothermal crystallization. The different temperature dependencies of the thermal expansion coefficients of liquid and solid phases account for the presence of rings within spherulites grown in a temperature field. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2008–2013, 2004
Study of plasma polymerization of dichloromethane on cotton and polyester fabrics
Authors: Jahagirdar C. J. , Tiwari L. B.
Published: October 2004

Dichloromethane (DCM) was polymerized on cotton and polyester fabrics in nonequilibrium low‐temperature plasma for different durations and the effects obtained were discussed. The modified cotton and polyester fabrics were dyed with Reactive Red HE 8BI and C.I. Disperse Red 364 dyes, respectively. The relative color strength of polymerized dyed fabrics was measured and compared with that of untreated dyed fabrics. The color parameters of polymerized fabrics were evaluated by the CIE system of color measurement, with standard illuminant D65 and 10° standard observer, by a Dataflash 100 color measurement spectrophotometer equipped with Colortools QC 1.3 color quality control software. The chemical structures of untreated and polymerized fabrics were studied by attenuated total reflectance–infrared spectroscopy. The presence of free radicals, attributed to the polymerization, was measured by electron spin resonance spectroscopy. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2014–2021, 2004
Alloying of poly(vinyl chloride) to reduce plasticizer migration
Authors: Thomas N. L.
Published: October 2004

Concern over the migration of low molecular weight plasticizer from flexible poly(vinyl chloride) (PVC) used in toys and medical products has spearheaded the commercialization of a number of plasticizing polymers. In this study the plasticizing behavior of an ethylene/vinyl acetate/carbon monoxide terpolymer (Elvaloy® from DuPont) was investigated. Blends of PVC, Elvaloy 742, and dioctyl phthalate (DOP) were processed on a twin‐roll mill and compression molded into plaques. These materials were characterized in terms of their hardness, glass‐transition temperature (Tg), clarity, mechanical properties, and plasticizer migration behavior. The ratios of PVC/DOP/Elvaloy investigated were determined by experimental design. Using this approach it was possible to model the results and produce contour plots to map out the properties of a wide range of formulations. It was confirmed that Elvaloy 742 is compatible with PVC and has a plasticizing effect: this was demonstrated both in terms of a reduction in Shore A hardness and a reduction in Tg. Plasticizer migration was reduced in proportion to the amount of liquid plasticizer replaced. Plasticizing with Elvaloy gave an improvement in tear strength. However, at constant hardness there was no improvement in tensile strength from replacing DOP with Elvaloy. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2022–2031, 2004
Metallization of crosslinked epoxy resins derived from diglycidyl ethers of poly(ethylene glycol) and bisphenol a by reduction of polymer‐incorporated cobalt ion
Authors: Shibata Mitsuhiro , Kuribayashi Masamichi , Uda Takayasu
Published: October 2004

The surface of the blend films of poly(ethylene glycol) diglycidyl ether (PEG‐E) and bisphenol A diglycidyl ether (BPA‐E) cured with 5‐(2,5‐dioxotetrahydrofuryl)‐3‐methyl‐3‐cyclohexene‐1,2‐dicarboxylic acid anhydride at 200°C for 5 h was metallized by the reduction of polymer‐incorporated cobalt acetate with aqueous sodium borohydride at 20–50°C. Although the cured films of PEG‐E/BPA‐E, weight ratio 100/0–80/20, were successfully metallized, the blend ratio 60/40 did not afford a metallized film by this reduction method. The glass transition temperature (Tg) of the cured resin measured by dynamic viscoelastic analysis rose with an increase of BPA‐E content. The difficulty of surface metallization in the case of blend ratio 60/40 is related to the hindrance of migration of cobalt ion due to the restriction of molecular chain motion. Electron probe microanalysis and X‐ray photoelectron spectroscopy measurement revealed that the cobalt ion that was homogeneously distributed in the inner part of the film before reduction migrated to both sides of the film and then was reduced to pure metal by the reduction treatment. The X‐ray diffraction analysis of the reduced films revealed that the generated cobalt was almost amorphous. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2164–2169, 2004
Neural tube defect rates before and after food fortification with folic acid
Authors: Mills James L. , Signore Caroline
Published: October 2004

BACKGROUND

Since 1998, enriched cereal grains sold in the United States have been fortified with folic acid, to reduce the incidence of neural tube defects (NTDs). The Centers for Disease Control and Prevention (CDC) recently reported that NTD rates have decreased 26% since fortification, but that additional effort is needed to achieve the national goal of a 50% reduction. However, accurate determination of NTD rates requires counting antenatally detected cases; the CDC study noted that the number of prenatally diagnosed cases was likely underestimated.

METHODS AND RESULTS

We examined studies from the United States and Canada that compared rates of NTDs before and after very similar fortification programs were instituted in each country. U.S. studies had incomplete ascertainment of prenatally diagnosed NTD cases, and as a result, underreported the number of NTDs prevented. Canadian studies, in which ascertainment was more complete, showed decreases in NTD rates up to 54%.

CONCLUSIONS

There is a strong correlation between the completeness of ascertainment and the percentage decrease in NTD rates. Studies that identify cases best show that folic acid fortification is preventing around 50% of NTDs. The percentage of NTDs that are folate‐preventable in the United States is uncertain, but is probably 50–60%. Thus, we may be quite close to achieving the optimum level of protection at current fortification levels. Birth Defects Research (Part A), 2004. Published 2004 Wiley‐Liss, Inc.
Structural analysis of amyloid β peptide fragment (25–35) in different microenvironments
Authors: Shanmugam Ganesh , Jayakumar Rajadas
Published: October 2004

Amyloid β (Aβ) peptides are one of the classes of amphiphilic molecules that on dissolution in aqueous solvents undergo interesting conformational transitions. These conformational changes are known to be associated with their neuronal toxicity. The mechanism of structural transition involved in the monomeric Aβ to toxic assemblage is yet to be understood at the molecular level. Early results indicate that oriented molecular crowding has a profound effect on their assemblage formation. In this work, we have studied how different microenvironments affect the conformational transitions of one of the active amyloid β‐peptide fragments (Aβ25–35). Spectroscopic techniques such as CD and Fourier transform infrared spectroscopy were used. It was observed that a stored peptide concentrates on dissolution in methanol adopts a minor α‐helical conformation along with unordered structures. On changing the methanol concentration in the solvated film form, the conformation switches to the antiparallel β‐sheet structure on the hydrophilic surface, whereas the peptide shows transition from a mixture of helix and unordered structure into predominantly a β‐sheet with minor contribution of helix structure on the hydrophobic surface. Our present investigations indicate that the conformations induced by the different surfaces dictate the gross conformational preference of the peptide concentrate. © 2004 Wiley Periodicals, Inc. Biopolymers (Pept Sci), 2004
Stacking and hydrogen bonding: DNA cooperativity at melting
Authors: Morozov Vladimir F. , Badasyan Artem V. , Grigoryan Arsen V. , Sahakyan Mihran A. , Mamasakhlisov Yevgeni Sh
Published: October 2004

By taking into account base–base stacking interactions we improve the Generalized Model of Polypeptide Chain (GMPC). Based on a one‐dimensional Potts‐like model with many‐particle interactions, the GMPC describes the helix–coil transition in both polypeptides and polynucleotides. In the framework of the GMPC we show that correctly introduced nearest‐neighbor stacking interactions against the background of hydrogen bonding lead to increased stability (melting temperature) and, unexpectedly, to decreased cooperativity (maximal correlation length). The increase in stability is explained as due to an additional stabilizing interaction (stacking) and the surprising decrease in cooperativity is seen as a result of mixing of contributions of hydrogen bonding and stacking. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004
Protein conformational transitions coupled to binding in molecular recognition of unstructured proteins: Hierarchy of structural loss from all‐atom Monte Carlo simulations of p27Kip1 unfolding–unbinding and structural determinants of the binding mechanism
Authors: Verkhivker Gennady M.
Published: October 2004

Conformational transitions coupled to binding are studied for the p27Kip1 protein which undergoes a functional disorder–to–order folding transition during tertiary complex formation with the phosphorylated cyclin A–cyclin‐dependent kinase 2 (Cdk2) binary complex. Temperature–induced Monte Carlo simulations of p27Kip1 unfolding–unbinding carried out from the crystal structure of the tertiary complex have revealed a systematic trend in the hierarchy of structural loss for p27Kip1 and a considerable difference in mobility of p27Kip1 secondary structure elements. The most persistent interactions of p27Kip1 at the intermolecular interface during unfolding–unbinding simulations are formed by β‐hairpin and β–strand that on average maintain their structural integrity considerably longer than other p27Kip1 elements. We have found that the ensemble of unfolded p27Kip1 conformations is characterized by transitions between mostly unbound, collapsed conformations and entropically favorable p27Kip1 conformations, which are weakly bound to the cyclin A side of the binary complex. The results of this study are consistent with the experimental evidence pointing to this region of the intermolecular interface as a potential initiation docking site during binding reaction and may reconcile conflicting experimental hypotheses on the recognition of substrate recruitment motifs. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004
Ladungsdichtewellen: Elektrische Leitfähigkeit
Authors: Tremel Wolfgang , Finckh E. Wolfgang
Published: October 2004

Die physikalischen Eigenschaften von Verbindungen werden im wesentlichen durch deren Aufbau bestimmt. Die Eigenschaften der Elemente sind nur insoweit wichtig, als sie den strukturellen Aufbau und damit die Bildung einer bestimmten Verbindung überhaupt erst ermöglichen. Hier, in der Untersuchung und systematischen Veränderung der Substanzeigenschaften liegt die eigentliche Schnittstelle von Chemie und Physik – der Chemiker muss allerdings neben der Synthese, die sein eigentliches Handwerk ist, noch die Grundlagen der Physik so weit beherrschen, dass er die relevanten Fragestellungen erfasst. Umgekehrt muss der Physiker eine gewisse Stoffkenntnis besitzen, um ein Gespür dafür bekommen, welche Verbindung oder Verbindungsgruppe die von ihm gewünschten Eigenschaften besitzen könnte.