bluuebunny/crossref_metadata_2025 huggingface dataset:
The Akt isoforms are present at distinct subcellular locations
Authors: Santi Stacey A. , Lee Hoyun
Published: December 2009

Akt is involved in the regulation of diverse cellular functions such as cell proliferation, energy metabolism, and apoptosis. Although three Akt isoforms are known, the function of each isoform is poorly understood. To gain a better understanding of each Akt isoform, we examined the subcellular localization and expression of each isoform in transformed and nontransformed cells. Akt1 was localized in the cytoplasm, which is in agreement with the currently accepted model that cytoplasmic Akt is translocated and activated at the inner leaflet of the plasma membrane. Interestingly, HEK-293 and HEK-293T cells contained Akt1 in the nucleus and cytoplasm, respectively, suggesting that SV40 T-antigen plays a crucial role in the cytoplasmic localization and activation of Akt1 in HEK-293T. Akt2 was colocalized with the mitochondria, while Akt3 was localized in both the nucleus and nuclear membrane. The subcellular localization of the Akt isoforms was not substantially altered in response to ionizing radiation or EGF. Furthermore, the ablation of one Akt isoform by small interfering RNA (siRNA) did not alter the subcellular location of the remaining isoforms, suggesting that the major function of one isoform is not compensated for by other isoforms. Together, our data support the notion that Akt2 and Akt3 are regulated at the mitochondrial and nuclear membranes, respectively. The mitochondrial localization of Akt2 raises the possibility that this isoform may be involved in both glucose-based energy metabolism and suppression of apoptosis, two Akt functions previously identified with anti-pan-Akt antibodies.
The 24-hour respiratory quotient predicts energy intake and changes in body mass
Authors: Longo Kenneth A. , Charoenthongtrakul Soratree , Giuliana Derek J. , Govek Elizabeth K. , McDonagh Thomas , DiStefano Peter S. , Geddes Brad J.
Published: December 2009

To define the relationship between the respiratory quotient (RQ) and energy intake (EI) and to determine the impact of spontaneous locomotor activity (LMA) in the development of diet-induced obesity (DIO), we fed C57BL/6 mice a high-fat diet (HFD) for either 4 days or 17 wk and analyzed them using indirect calorimetry. Importantly, changes in body mass during calorimetry (Δ Mb) significantly covaried with RQ and EI; adjusting the data for Δ Mb permitted an analysis of the energy-balanced state. The 24-h RQ strongly predicted 24-h EI, and the slope of this relationship was diet dependent (HFD or chow) but independent of the HFD feeding period. Early-stage DIO was characterized by dark-period hyperphagia and fat storage, offset by greater light-period lipid oxidation; later stage DIO mice had a milder hyperphagia and lower substrate flexibility. Consequently, whereas 24-h RQ equaled the food quotient of the HFD in both early- and late-stage DIO, the range of RQ values was negatively correlated with, and mostly explained by, 24-h EI only in late-stage DIO. Lean and early-stage DIO mice had similar LMA values that were reduced in late-stage DIO. However, LMA significantly explained variance in total energy expenditure (EE) in only early-stage DIO mice. This indicated that the link between LMA and EE was a transient adaptive response to early DIO, whereas the later loss of LMA did not explain body weight gain in C57BL/6 DIO mice.
Spectral and Temporal Modulation Tradeoff in the Inferior Colliculus
Authors: Rodríguez Francisco A. , Read Heather L. , Escabí Monty A.
Published: December 2009

The cochlea encodes sounds through frequency-selective channels that exhibit low-pass modulation sensitivity. Unlike the cochlea, neurons in the auditory midbrain are tuned for spectral and temporal modulations found in natural sounds, yet the role of this transformation is not known. We report a distinct tradeoff in modulation sensitivity and tuning that is topographically ordered within the central nucleus of the inferior colliculus (CNIC). Spectrotemporal receptive fields (STRFs) were obtained with 16-channel electrodes inserted orthogonal to the isofrequency lamina. Surprisingly, temporal and spectral characteristics exhibited an opposing relationship along the tonotopic axis. For low best frequencies (BFs), units were selective for fast temporal and broad spectral modulations. A systematic progression was observed toward slower temporal and finer spectral modulation sensitivity at high BF. This tradeoff was strongly reflected in the arrangement of excitation and inhibition and, consequently, in the modulation tuning characteristics. Comparisons with auditory nerve fibers show that these trends oppose the pattern imposed by the peripheral filters. These results suggest that spectrotemporal preferences are reordered within the tonotopic axis of the CNIC. This topographic organization has profound implications for the coding of spectrotemporal features in natural sounds and could underlie a number of perceptual phenomena.
Twin Pregnancy Presenting as a Praevia Complete Hydatidiform Mole and Coexisting Fetus Complicated by a Placental Abscess
Authors: Suri S. , Davies M. , Jauniaux E.
Published: December 2009

Background: A twin pregnancy consisting of a complete hydatidiform mole and a coexisting normal fetus (CMCF) is a rare and challenging condition when diagnosed prenatally and is associated with major obstetric complications. Case Report: We present a case of CMCF in which the molar component presented as a major placenta praevia at 19 weeks, and which was complicated by a placental abscess with maternal septicaemia from 26 weeks. An emergency caesarean section, performed at 28 weeks’ gestation due to severe maternal septicaemia, resulted in the delivery of a live male infant. Despite the molar mass being praevia, the delivery was not complicated by extensive haemorrhage. Conclusion: This is only the second case of CMCF complicated by a molar praevia and the first complicated by a placental abscess. We believe that the 2 conditions are linked and that the absence of normal fetal membranes surrounding the molar mass enabled secondary colonization by vaginal bacteria. Therefore, we recommend that immediate antibiotic treatment is initiated in cases of CMCF presenting as a praevia when maternal and/or fetal symptoms of infection develop.
Radiological-Pathological Comparison in a Case of Conjoined Gnatho-Thoracopagus Twins
Authors: Salmaso Roberto , Manara Renzo , Fassan Matteo , Severino Maria Savina , Visentin Silvia , Macchi Veronica , Cosmi Erich
Published: December 2009

Background: Conjoined twins may present an extremely wide range of complex congenital malformations. Because of the increasing number of attempts to separate them surgically, profound knowledge is needed of this abnormality spectrum. Case: Ultrasonographic, radiological (X-ray, computed tomography and magnetic resonance imaging) and pathological findings of gnatho-thoracopagus conjoined twins at 18 weeks of gestation are reported, focusing on clinical topographic correlations. Conclusions: High-resolution imaging techniques may provide useful information for surgery or autopsy planning of cases with complex congenital malformations.
Chorioamnionitis and Intrauterine Fetal Death after Second-Trimester Amniocentesis
Authors: Vigliani Marguerite
Published: December 2009

We report an intrauterine fetal death that occurred less than 24 h after transabdominal amniocentesis. Chorioamnionitis was confirmed by amniotic fluid culture which showed multiple enteric organisms and postmortem examination of the fetus that showed Clostridium perfringens. The patient was treated with intravenous broad-spectrum antibiotics and uterine evacuation and her condition rapidly improved. Intra-amniotic infection after amniocentesis requires a high index of suspicion and prompt aggressive treatment with broad spectrum antibiotics and uterine evacuation to prevent maternal sepsis-related morbidity and mortality.
Maternal Plasma Fibronectin and Advanced Oxidative Protein Products for the Prediction of Preeclampsia in High Risk Pregnancies: A Prospective Cohort Study
Authors: Dane Cem , Buyukasik Hasan , Dane Banu , Yayla Murat
Published: December 2009

Objective: To determine whether maternal plasma fibronectin and advanced oxidative protein products (AOPP) can be used for the prediction of preeclampsia in high-risk women. Study Design: One hundred pregnant women at high risk of preeclampsia were enrolled in this prospective cohort study. Maternal plasma total fibronectin and AOPP levels were measured at 19–25 weeks of gestation. AOPP levels were also measured in 23 normal non-pregnant women. After delivery, the pregnant cohort was assigned to either the normotensive or preeclamptic group depending on their clinical course. Results: Among the 78 pregnant women who completed the study, 19 (24.3%) developed preeclampsia between 36 and 39 (36.8 ± 1.0) weeks of gestation. AOPP levels, which are significantly higher in normotensive pregnant women compared to nonpregnant controls (42.55 ± 15.94 vs. 27.95 ± 10.5; p = 0.0001) were not significantly different between normotensive and preeclamptic women (42.55 ± 15.94 vs. 47.45 ± 14.19 μM; p = 0.23). Plasma fibronectin levels were significantly higher in women who continued to develop preeclampsia rather than remain normotensive (383.68 ± 19.07 vs. 227.65 ± 97.39; p < 0.0001). ROC curve analysis shows that total fibronectin ≥360 mg/l is predictive for the development of preeclampsia. The sensitivity, specificity, positive and negative predictive values are 57, 92, 73 and 85%, respectively, with a likelihood ratio of 7.38. Conclusion: Second trimester plasma concentrations of AOPP are not altered in women that develop pre-eclampsia later in pregnancy. However, total fibronectin levels are significantly increased and may be used to predict the onset of clinical symptoms of preeclampsia.
An Experimental Model of Fetal Growth Restriction Based on Selective Ligature of Uteroplacental Vessels in the Pregnant Rabbit
Authors: Eixarch E. , Figueras F. , Hernández-Andrade E. , Crispi F. , Nadal A. , Torre I. , Oliveira S. , Gratacós E.
Published: December 2009

Introduction: To describe an animal model of growth restriction based on selective ligature of uteroplacental vessels in the pregnant rabbit. Material and Methods: Two experimental protocols (+21 and +25 days of gestation) with three groups were defined: controls, mild (20–30%) and severe (40–50%) uteroplacental vessel ligature. Fetuses were delivered 120 h after the procedure by cesarean section. Biometrical measurements were carried out. Brains were obtained and glial response and cell proliferation were studied by S100β and Ki-67 immunohistochemistry. Results: Mortality rate and biometrical restriction increased across experimental groups according to the time and severity of the procedure. S100β expression was significantly higher in the severe reduction group at 25 days. Ki-67 expression was significantly higher in the mild reduction group at 21 days and in the severe reduction group at 25 days. Discussion: Selective ligature of uteroplacental vessels in the pregnant rabbit results in a gradual model of growth restriction in terms of mortality, biometrical restriction and histological brain changes.
Timing of Group B Streptococcus Screening in Pregnancy: A Systematic Review
Authors: Valkenburg-van den Berg Arijaan W. , Houtman-Roelofsen Rebecca L. , Oostvogel Paul M. , Dekker Friedo W. , Dörr P. Joep , Sprij Arwen J.
Published: December 2009

Background: Group B streptococcus (GBS) is an important cause of neonatal sepsis. Guidelines advise to collect cultures at 35–37 weeks’ gestation and to administer intrapartum antibiotic prophylaxis in case of GBS-positive cultures, as well as in all preterm deliveries. Improved effectiveness of antenatal cultures might help to further decrease GBS early-onset disease. Objective: To determine the best timing of antenatal cultures, which may help establish optimal prevention of perinatal GBS infection in both term and preterm neonates. Methods: PubMed and EMBASE databases were searched for relevant articles published from 1966 to February 2009. Nine articles were included. Information about study features and predictive values of antenatal cultures were abstracted. Results: Positive predictive values for antenatal GBS cultures ranged from 43 to 100% (mean 69%) and negative predictive values from 80 to 100% (mean 94%). GBS cultures collected in late pregnancy had high positive predictive values for colonization during delivery. The negative predictive value was high and relatively constant regardless of GA. Conclusions: This systematic review confirms recommendations to screen pregnant women for colonization of GBS at 35–37 weeks’ gestation, but one should be aware of the limitations of screening, with 6% of GBS carriers remaining undetected in antenatal cultures.
Middle-Molecule Clearance at 20 and 35 ml/kg/h in Continuous Venovenous Hemodiafiltration
Authors: Hofmann C.L. , Fissell W.H.
Published: December 2009

Background: Of 5 clinical trials testing dose response of continuous renal replacement therapy (CRRT) in acute kidney injury, 2 showed a benefit, 2 showed none, and 1 appeared equivocal. However, blood-membrane interactions may dominate macromolecule transport in continuous venovenous hemodiafiltration, reducing the impact of dose adjustment. The dosing arms in the Acute Renal Failure Trial Network (ATN) study may have delivered similar clearances for middle molecules. Methods: We simulated the 2 CRRT doses in the ATN study using a synthetic polydisperse macromolecular probe in bovine blood. Clearance of tracers between 10 and 100 kDa molecular weight was measured during 6 h of therapy. Results: Middle-molecule clearance differed by less than 2 ml/min between the 2 dosing arms. Conclusion: The CRRT prescription used in the ATN study appears to have achieved dose separation for small molecules while holding middle-molecule clearance nearly constant. This may explain the outcome difference between the ATN study and earlier studies, and suggests subsequent trial designs.
Growth Hormone Internalization in Mitochondria Decreases Respiratory Chain Activity
Authors: Ardail Dominique , Debon Aude , Perret-Vivancos Cécile , Biol-N’Garagba Marie-Claire , Krantic Slavika , Lobie Peter E. , Morel Gérard
Published: December 2009

Growth hormone (GH) is a signaling molecule regulating cell proliferation, differentiation and metabolism via activation of specific cell surface receptors and subsequent triggering of signal transduction pathways. This is associated with GH/GH receptor internalization and accumulation of GH in several subcellular compartments, including mitochondria. To assess the functional relevance of such mitochondrial accumulation, we first confirmed the occurrence of mitochondrial GH uptake ex vivo as early as 10 min after 125I-GH injection to the rats. We next showed that intact 125I-GH accumulates in mitochondrial fractions in vitro in a specific, rapid and saturable manner with an apparent affinity (Kd) of 1.44 nM. At the electron-microscopic level, immunoreactive GH density within mitochondria increased after in vitro hormone incubation, without any modification of the sub-mitochondrial distribution pattern. The presence of GH in the inter-membrane space and at the inner membrane seen by electron microscopy was confirmed by SDS-PAGE and autoradiography after mitochondrial fractioning thus suggesting the involvement of GH in the respiration control. To test this hypothesis further, we performed polarographic and spectrophotometric assays on isolated mitochondria. These assays pointed to a direct, selective and dose-dependent effect of GH on the inhibition of succinate dehydrogenase and cytochrome C oxidase activities. The latter inhibition was in contrast with indirect, GH receptor-initiated stimulation of cytochrome C oxidase activity observed in GH-treated whole BRL cells transfected to express this receptor. Altogether, these data show that GH is specifically imported in mitochondria, where it operates a direct metabolic effect, independently of cell surface receptors and signal transduction.
Microsurgical and Stereotactic Radiofrequency Amygdalohippocampectomy for the Treatment of Mesial Temporal Lobe Epilepsy: Different Volume Reduction, Similar Clinical Seizure Control
Authors: Malikova Hana , Vojtech Zdenek , Liscak Roman , Prochazka Tomas , Vymazal Josef , Mareckova Iva , Kalina Miroslav , Dbaly Vladimir , Keller Jiri , Vladyka Vilibald
Published: December 2009

We compared stereotactic radiofrequency amygdalohippocampectomy (SAHE) with microsurgical amygdalohippocampectomy (AHE) in a group of 33 patients with mesial temporal lobe epilepsy in terms of hippocampal and amygdalar volume reductions and clinical outcome. In 23 subjects treated by SAHE, the hippocampal volume decreased by 58.0% (20.0; median, quartile range), with p = 10–4, and the amygdalar volume decreased by 55.2% (23.8), with p = 10–4. Two years after SAHE, 74% of patients were classified as class I, 22% as class II and 4% as class III. In 10 subjects treated by AHE, 83.5% (11.2) of the hippocampal and 53.1% (53.9) of the amygdalar volumes were removed (p = 0.05 and p = 0.005, respectively). Two years after the operation, 50% of the subjects were classified as class I, 30% as class II and 10% as class III and IV. To conclude, SAHE leads to a similar reduction of the amygdalar volume but to a significantly lower reduction of the hippocampal volume than AHE. The clinical outcome of SAHE is comparable with that of AHE.
Spontaneous Cranial Osteomyelitis in an Otherwise Healthy Ten-Year-Old Male
Authors: Arnold Paul M. , Govindan Sushant , Anderson Karen K.
Published: December 2009

Frontal bone osteomyelitis is a relatively rare entity, particularly in the otherwise healthy pediatric population. Most cases trace their origins to either previous frontal sinusitis or trauma. In children, three origins for cranial osteomyelitis appear to dominate: Pott’s puffy tumor, skull base osteomyelitis secondary to ear infection, or post-surgical complications. However, on extremely rare occasions, risk factors or etiology may not be ascertained. We present a case of spontaneous frontal bone osteomyelitis in a ten-year-old African-American male with no previous history of cranial surgeries, frontal sinusitis, or major trauma.
Functional Abdominal Pain in Childhood: From Etiology to Maladaptation
Authors: Schulte Ilva Elena , Petermann Franz , Noeker Meinolf
Published: December 2009

Objective: To review the extant literature on functional abdominal pain in childhood through the lens of the developmental psychopathology perspective and to systematize research results by means of a two-stage pathway model in which the emergence of functional abdominal pain and its potential transition into a somatoform adjustment disorder is outlined. Methods: Using electronic searches for published studies and previous reviews about functional abdominal pain. Results: An association of functional abdominal pain with internalizing symptoms, poor well-being of family members, major life events and daily stressors is found. The impact of stress on pain seems to be moderated by the children’s coping style and their perceived competence and self-efficacy to manage the pain experience. There is evidence for the influence of modeling and operant mechanisms on pain experiences. A new term, ‘somatoform adjustment disorder’, and its relation to functional abdominal pain is discussed. Conclusions: It seems that those children with functional abdominal pain who cannot adapt to the pain indeed run the risk of developing a somatoform adjustment disorder.
Vasoactive Intestinal Peptide Improves the Survival and Development of Caprine Preantral Follicles after in vitro Tissue Culture
Authors: Bruno J.B. , Celestino J.J.H. , Lima-Verde I.B. , Matos M.H.T. , Lima L.F. , Name K.P.O. , Araújo V.R. , Saraiva M.V.A. , Martins F.S. , Campello C.C. , Silva J.R.V. , Báo S.N. , Figueiredo J.R.
Published: December 2009

The aim of this study was to evaluate the effect of vasoactive intestinal peptide (VIP)on the survival, activation and growth of goat preantral follicles after in vitro culture. The ovarian cortex was divided into small pieces and one fragment was immediately fixed (control). The remaining fragments were cultured in vitro for 1 or 7 days at 39°C and 5% CO2, in supplemented minimum essential medium (MEM+) with or without different concentrations of VIP (1, 10, 50, 100 or 200 ng/ml). Noncultured (fresh control) and cultured ovarian fragments were processed for histological analysis and transmission electron microscopy. Follicles were classified as primordial or developing, and as normal or degenerated. Our findings indicate that when compared with control, addition of all concentrations of VIP except 200 ng/ml resulted in similar percentages of normal preantral follicles after 1 and 7 days of culture. Culture of ovarian cortex tissue for 1 and 7 days increased the percentage of follicular activation in all treatments when compared with control, except with 1 ng/ml of VIP after 1 day. However, no difference was observed between VIP-treated and MEM+-treated follicles. In addition, after 7 days of culture, the highest follicular and oocyte diameters were observed in follicles cultured with 10 ng/ml VIP relative to MEM+ alone. Transmission electron microscopy showed ultrastructural integrity of follicles after 7 days of culture in 10 ng/ml VIP. In conclusion, this study demonstrates that VIP maintains follicular integrity and stimulates caprine preantral follicle growth.
Konzentrationsmessungen verschiedener Proteolyse- und Gefäßfaktoren im Plasma und Plazentaextrakt bei Schwangeren mit HELLP-Syndrom, Prä-/Eklampsie und hochpathologischen Dopplerflußbefunden
Authors: Kolben M. , Lopens A. , Bläser J. , Huber A. , Frank M. , Wilhelm O. , Wilhelm S. , Schneider K.T.M. , Ulm K. , Tschesche H. , Schmitt M. , Graeff H.
Published: December 2009

Fragestellung: Bei der Entstehung der PrÄeklampsie spielt die StÖrung der Trophoblastinvasion eine wichtige Rolle. Aus diesem Grunde haben wir verschiedene an der Invasion beteiligte Faktoren bei Gestationserkrankungen untersucht. Methoden: Bei Schwangeren mit HELLP-Syndrom (n = 18), Pr-Ä/Eklampsie (n = 21) und hochpathologischen Dopplerbefunden (hpD) (n = 13) wurden im Plasma und Plazentaextrakt uPA, uPA-Rezeptor, tPA, PAI-1, MMP-8, MMP-9, TIMP-1, Thrombomodulin und Angiogenin mittels ELISA gemessen. Ergebnisse: In alien drei Gruppen war PAI-1 im Plasma erhÖht (p < 0,05), bei HELLP-Syndrom auch tPA und TIMP-1. Im Plazentaextrakt war MMP-9 bei Pr-Ä/Eklampsie erniedrigt. Schlußfolgerungen: Die StÖrung der plazentaren Implantations- und UmbauvorgÄnge bei Gestationserkrankungen spiegelt sich in KonzentrationsverÄnderungen einiger an diesen Prozessen beteiligter Faktoren wider.
Where Does the Iberian Peninsula Moisture Come From? An Answer Based on a Lagrangian Approach
Authors: Gimeno Luis , Nieto Raquel , Trigo Ricardo M. , Vicente-Serrano Sergio M. , López-Moreno Juan Ignacio
Published: December 2009

This study investigated the main sources of moisture in the atmosphere over the Iberian Peninsula (IP) at annual and seasonal scales using FLEXPART, a powerful new 3D Lagrangian diagnosis method that identifies the humidity contributions to the moisture budget of a region. This method can identify moisture sources at lower cost and with greater accuracy than standard isotopic content methods. The results are based on back-tracking analysis of all air masses residing over the IP in the 5-yr period from 2000 to 2004. The results show that the two most important moisture source regions affecting the IP are in a tropical–subtropical North Atlantic corridor that extends from the Gulf of Mexico to the IP, and the IP itself and the surrounding Mediterranean. The importance of these two source areas varies throughout the year, and also with respect to different climatic regions inside the IP. The former source region is the dominant moisture source for the entire IP during winter and in western regions throughout the year, whereas the latter source region dominates the moisture supply to the IP in summer and in the eastern Mediterranean region of the IP throughout the year. The results also demonstrate that winter precipitation in the IP is influenced by both atmospheric instability that forces air masses to rise, and the supply of moisture from the tropical–subtropical North Atlantic corridor on a daily scale and a seasonal basis. Thus, a combination of high (low) moisture supply from the North Atlantic corridor and high (low) atmospheric instability appears to be responsible for the most recent wet (dry) winter in the IP.
Social Capital Worldwide: Potential for Democratization or Stabilizer of Authoritarian Rule?
Authors: Roßteutscher Sigrid
Published: December 2009

The notion of social capital has gained enthusiastic support from nongovernmental organizations, intergovernmental confederations, and supranational bodies such as the European Union, the World Bank, and the United Nations. They all believe that social capital might be a potent aid for democratization, for repairing defective democracies, and for undermining authoritarian regimes. This article examines whether social capital has such positive effects in countries where democracy is not yet established. Does social capital help in a country’s move toward democratization, or is the link between democracy and social capital more dubious? Does social capital even contribute to the stabilization of nondemocratic regimes? This article analyzes 70 countries that participated in the third wave of the World Values Survey. The results are clear: Social capital functions as a stabilizer of authoritarian rule. Its effects are mainly negative. Social trust, in particular, might be a “key resource for the market economy and democratic politics” (Stolle, 2003, p. 19). In nondemocratic contexts, however, it appears to throw a spanner in the works of democratization. Social participation and trust, specifically, increase the stability of nondemocratic leadership by generating popular support, by suppressing regime-threatening forms of protest activity, and by nourishing undemocratic ideals of governance.
Erosive Wear Performance Analysis of Jute-Epoxy-SiC Hybrid Composites
Authors: Alok Kumar Jha  , Mantry Sisir , Satapathy Alok , Patnaik Amar
Published: December 2009

The present article reports the solid particle erosion response of a new class of multi-component composite system consisting of epoxy resin reinforced with jute—fiber and SiC particles derived from a bio-resource like rice husk. Erosion trials are carried out at various test conditions. For this, an air jet type erosion test rig and Taguchi’s orthogonal arrays are used. Significant control factors influencing the erosion wear rate are identified. This article also presents the development of a theoretical model for estimating erosion damage caused by solid particle impact on the composites. The model is based upon conservation of particle kinetic energy and relates the erosion rate with some of the material properties and test conditions. The theoretical results are compared and are found to be in good agreement with the experimental values.
Tensile Properties of Hildegardia Fibers Reinforced Polypropylene Biocomposites
Authors: Xiaoyan Li  , Jun Zhang  , Jiaosong He  , Jeevan Prasad Reddy D. , Varada Rajulu A.
Published: December 2009

Biocomposites of Hildegardia/polypropylene (PP) were prepared. The effect of fiber loading and the compatibilizer on the tensile properties of these composites was studied. The interfacial bonding between the fibers and the matrix was examined using the fractographs. Using diffuse reflectance Fourier transform infrared spectra, the established bonding between the fibers and PP was investigated.
Electroerosion Resistance Performance of the Electroformed Cu-Graphite Composites
Authors: Pingmei Ming  , Di Zhu  , Yongbin Zeng  , Yangyang Hu
Published: December 2009

Cu—graphite composites, which combine with two kinds of commonly used electro-discharge machining (EDM) electrode materials, were prepared using the co-electroforming technique in an acid sulfate bath. To obtain an optimum combination of copper and graphite in the composites with an excellent electroerosion resistance performance, the effect of electrodeposition conditions, such as graphite bath content, current density, stirring rate, and electrolyte temperature, on the tool-electrode wear were investigated using micro-EDM experiments, and the functional relation of the tool-electrode wear ratio (t) and volume content percent of embedded graphite particles (s) in the composites was further developed. In comparison with the electroformed pure copper, the co-electroformed Cu-20.6vol% graphite EDM macro-scale electrode showed considerably better electroerosion resistance performance, mainly resulting from its optimal volume fraction ratio combination of copper with an excellent heat-transfer character, and graphite with an extremely high melting point, while the UV-LIGA electroformed Cu-20.6vol% graphite micro-feature EDM electrode exhibited much worse electroerosion resistance behavior, primarily owing to its rougher surfaces, lower strength, looser texture, and various deposition drawbacks.
Social-Class Differences in Summer Learning Between Kindergarten and First Grade: Model Specification and Estimation
Authors: Burkam David T. , Ready Douglas D. , Lee Valerie E. , LoGerfo Laura F.
Published: December 2009

Sociologists suggest that children from socially advantaged families continue to learn during the summer, whereas children from disadvantaged families learn either little or lose ground. This disparity in summer learning is hypothesized to result from differential participation in educationally beneficial summer activities. In this article, we test this theory with current and nationally representative data, the Early Childhood Longitudinal Study—Kindergarten Cohort. We examine how children's socioeconomic status (SES) is associated with their learning of literacy, mathematics, and general knowledge over the summer between kindergarten and the first grade. We also explore whether social-background differences in learning are explained by differential participation rates in summer activities. Our analytic models adjust for discrepancies between the timing of assessments and the timing of schools closing for the summer and opening in the fall. Much of the observed gain results from time in school. Nonetheless, social stratification characterizes summer learning between kindergarten and the first grade, with higher-SES children learning more. However, these social-background differences are only modestly explained by the activities in which children participate during the summer months.
School Choice, Magnet Schools, and the Liberation Model: An Empirical Study
Authors: Archbald Douglas A.
Published: December 2009

The rapid growth of magnet schools in the 1980s introduced the first widely adopted form of public school choice in the United States. Magnet-based choice is supported as a way to expand school choice for parents, bring innovation through specialty schools and programs, and promote voluntary forms of racial integration. Some contend that this form of public school choice is especially helpful to lower-income parents who are trapped in inferior inner-city schools, while others claim that magnet schools may worsen stratification among schools by family income. The study presented here used a large national data set to examine relationships between magnet-based school choice and income-based stratification in school districts. It did not find a difference between school districts with magnet-based school choice and school districts without school choice. Implications for other forms of school choice are discussed.
Education and Gender Egalitarianism: The Case of China
Authors: Shu Xiaoling
Published: December 2009

This study examined Chinese attitudes toward women's careers, marriage rights, sexual freedom, and the importance of having sons using a 1991 national sample of individuals and community-level data and through a series of nested multilevel models. Education influences gender attitudes in multiple ways at both the micro- and macrolevels. Better-educated individuals hold more egalitarian gender attitudes, and this positive effect of individual education is larger for women than for men, indicating a strong empowerment effect for women. Egalitarian gender attitudes trickle down through education, as individuals in communities with high education are socialized toward more egalitarian attitudes. Community education has a larger effect toward the egalitarian direction on the attitude toward the importance of having sons than on the attitude toward women's marriage rights, indicating that change in the latter attitude occurred earlier and has now spread via education. These findings show that education is a vehicle of socialization that is used by both the domestic power elite (the Communist Party) and the Western culture.
Tracking, Students' Effort, and Academic Achievement
Authors: Carbonaro William
Published: December 2009

This study examined the links among students' effort, tracking, and students' achievement. It found that students in higher tracks exert substantially more effort than do students in lower tracks. These differences in effort are largely explained by differences in prior effort and achievement, as well as students' experiences in their classes. Students' effort is strongly related to students' learning, and track differences in students' effort account for a modest portion of track differences in students' learning. Finally, the effect of students' effort on students' learning is roughly the same, regardless of the track in which a student is placed.
High School Exit Examinations and High School Dropout in Texas and Florida, 1971–2000
Authors: Warren Robert Warren , Jenkins Krista N.
Published: December 2009

In this article, the authors ask whether state high school exit examinations are associated with high school dropout rates and racial/ethnic and socioeconomic inequalities in high school dropout rates in Florida and Texas. Using data from the 1968–2000 October Current Population Surveys, they first consider the 1971–2000 graduating classes and use a measure of whether students left school without obtaining any high school credential as the outcome variable. They next consider the 1991–2000 graduating classes and use a measure that classifies students who obtained general equivalency diplomas as dropouts as the outcome variable. In neither case did the authors find evidence that state high school exit examinations are independently associated with higher dropout rates or greater inequalities in dropout rates.
Double Disadvantage or Blessing in Disguise? Understanding the Relationship Between College Major and Employment Sector
Authors: Roksa Josipa
Published: December 2009

Although college graduates earn substantial labor market rewards, not all college degrees are rewarded equally. Graduates who majored in female-dominated fields earn substantially lower incomes than do graduates who majored in male-dominated fields. Income differentials that are associated with different types of college majors are extensively noted but poorly understood. This article advances the previous literature by examining how college major affects the labor market outcomes of college graduates through its relationship with employment sector. The results show that graduates of female-dominated fields are disproportionately employed in public and nonprofit organizations, which offer lower monetary rewards but facilitate access to professional and managerial positions. Notably, college major and employment sector interact in ways that reduce income penalties and enhance the occupational location of graduates of female-dominated fields who work in public and nonprofit settings. These findings highlight the importance of considering organizational context in the study of labor market outcomes, particularly when examining the gendered character of educational credentials and occupations.
Lessons from the Cold War: Military Service and College Education
Authors: MacLean Alair
Published: December 2009

Since World War II, the federal government has provided funds to pay for the education of veterans through the GI bill. Yet, these funds were unavailable from 1955 to 1965. This article considers four potentially overlapping hypotheses to describe the effect of military service on veterans' educational attainment in the absence of government funding. Military service may have (1) reproduced civilian status defined by social background, (2) reflected the process of selection on the basis of individual characteristics, (3) changed men's educational trajectories by providing a positive turning point, or (4) disrupted the educational portion of the transition to adulthood. The results indicate that veterans who were drafted were less likely than were nonveterans and veterans who were not drafted to go on to college, which is consistent with the disruption hypothesis, and that military service diverted academically ambitious men from their plans for higher education. Thus, military service disrupted some men's educational trajectories, but may also be described as a turning point with negative, rather than positive, consequences for the pursuit of higher education.
Coloring Outside the Lines: Racial Segregation in Public Schools and Their Attendance Boundaries
Authors: Saporito Salvatore , Sohoni Deenesh
Published: December 2009

Scholars have debated whether students' enrollment in private schools changes levels of racial segregation across urban school districts. The authors examine this issue by comparing the actual racial composition of schools with the racial composition of school-aged children living in the corresponding attendance areas. They do so by linking maps of school attendance boundaries with 2000 census data, the Common Core of Data, and the Private School Survey for the 22 largest U.S. school districts. The results show that public schools would be less racially segregated if all children living in a school district attended their neighborhood schools. In addition, private, magnet, and charter schools contribute to overall racial segregation within many school districts. The effects are particularly striking for segregation between white and Hispanic children. Finally, a few school districts with desegregation policies have succeeded in reducing racial segregation. The analyses contribute to debates regarding recent proposals to eliminate desegregation programs while simultaneously expanding “free-market” educational reforms that promote students' mobility across public, private, and charter schools.
The End of Affirmative Action in Washington State and Its Impact on the Transition from High School to College
Authors: Brown Susan K. , Hirschman Charles
Published: December 2009

Changes in affirmative action policies in some states create possibilities for “natural experiments” to observe the effect of public policy on racial and ethnic inequality in American society. This study measured the impact of Initiative 200, a ballot measure that eliminated affirmative action in Washington State, on the transition from high school to college. As of 1999, the year after I-200 passed, the proportion of minority high school seniors who went to college in Washington State decreased temporarily. The impact of I-200 was registered almost entirely at the University of Washington, the flagship public institution in the state. This decrease, however, stemmed less from changes in minority admission rates than from declines in application rates. Affirmative action programs may provide a signal of an institutional “welcoming environment” that serves as a counterweight to the normal reluctance of prospective students to apply to institutions that may be perceived as intimidating. Although the impact of I-200 was short-lived, significant racial and ethnic differences remain in the transition from high school to college.
Effects of Sibship Structure Revisited: Evidence from Intrafamily Resource Transfer in Taiwan
Authors: Chu C. Y. Cyrus , Xie Yu , Yu Ruoh-rong
Published: December 2009

Numerous studies have consistently found negative effects of sibship size on educational outcomes. Three main explanations of these effects have been offered in the literature: (1) the dilution of family resources, (2) a changing intellectual environment in the family for each succeeding sibling, and (3) unobserved selectivity at the family level. In this article, the authors propose a fourth explanation as an extension of the resource-dilution hypothesis: In a traditional or transitional society where resources from all family members are pooled together, families may sacrifice the educational opportunities of older (female) siblings and use their remittance to compensate the family expenses, particularly when there are younger siblings. With analyses of data from the Panel Study of Family Dynamics (PSFD), the authors found empirical evidence to support this explanation. In particular, they found that the negative effects of sibship size are the strongest for girls with younger brothers and sisters who are spaced apart from them. They interpret this unusual high-order interaction involving sibship size, gender, density, and seniority within the context of Taiwan's patriarchal culture, in which families typically favor boys over girls.
Making It Through the First Year of College: The Role of Students' Economic Resources, Employment, and Living Arrangements
Authors: Bozick Robert
Published: December 2009

Using data from the Beginning Postsecondary Students Longitudinal Study of 1996, this article explores the effect of economic resources on the paid work experiences and living arrangements of first-year college students. Students from low-income families are more likely to work for school-related expenses and to live at home during the first year of college—cost-saving strategies that, in some cases, impede their chances of continuing into the second year. Students who work more than 20 hours a week and who live at home are more likely to leave school during the first year than are those who work 20 hours a week or less and who reside on campus. Employment and living arrangements both play a strong role in shaping the transition to college, beyond background characteristics and academic preparation.
Student Engagement, Peer Social Capital, and School Dropout Among Mexican American and Non-Latino White Students
Authors: Ream Robert K. , Rumberger Russell W.
Published: December 2009

Policy makers are especially concerned about persistently high dropout rates among U.S. Latinos, the largest minority population in the United States. This study used a national longitudinal database to show that the behavioral and social aspects of schooling are dynamically linked in the process of school completion and dropout among Mexican American and non-Latino white adolescents. In contrast to the tendency of academically disengaged students to develop street-oriented friendships, students who are involved in school tend to befriend others who also make schooling a priority. Thus, student engagement influences competing friendship networks in a manner that contributes to the completion of school. Furthermore, engagement behaviors and school-oriented friendship networks have the potential to reduce dropout rates. To their social and educational detriment, however, Mexican American students appear to be less engaged in unorganized academic endeavors and formally sponsored extracurricular activities than are white students. The results of this study support policies that combine targeted educational and social reforms to bolster school completion among Mexican origin youths.
How African American Is the Net Black Advantage? Differences in College Attendance Among Immigrant Blacks, Native Blacks, and Whites
Authors: Bennett Pamela R. , Lutz Amy
Published: December 2009

Previous research has shown that although a smaller proportion of black high school graduates than white high school graduates attend college, black high school graduates are more likely than white high school graduates to attend college net of differences in socioeconomic family background and academic performance. Yet, the overrepresentation of black immigrants in selective colleges and theoretical work on immigrant incorporation raises the question of whether this net black advantage is very African American. Using data from the National Education Longitudinal Study of 1988, logistic regression, and propensity score analysis, the authors investigated whether the net black advantage reflects the educational trajectories of immigrant rather than native blacks. They found dual, yet distinct, cases of the net black advantage, such that native blacks are more likely than are comparable whites to attend all types of colleges, whereas immigrant blacks are only more likely than similar whites to attend selective colleges. The theoretical and social stratification implications of the findings are explored.
The Downside of Social Closure: Brokerage, Parental Influence, and Delinquency Among African American Boys
Authors: Mangino William
Published: December 2009

Building on the literature that stresses the social capital advantages of open and diffuse social networks, this article shows that African American boys who are a social bridge across two or more large but cohesive peer groups are less delinquent than are their counterparts who are members of a single peer group. Statistical interaction terms reveal that this decrease in delinquency can be attributed to the increased influence of parents among social bridges. The article concludes that the network form of the adolescent society, independent of its composition, conditions the parent-child relationship.
UNESCO and the Associated Schools Project: Symbolic Affirmation of World Community, International Understanding, and Human Rights
Authors: Suárez David F. , Ramirez Francisco O. , Koo Jeong-Woo
Published: December 2009

The UNESCO Associated Schools Project emphasizes world community, human rights, and international understanding. This article investigates the emergence and global diffusion of the project from 1953 to 2001, estimating the influence of national, regional, and world characteristics on the likelihood of a country adopting a UNESCO school. It also addresses the effects of national linkages to the international human rights regime. The results reveal that adoption rates are positively influenced by stronger national links to the human rights regime throughout the period and that various measures of the density of global society influence adoption, particularly after the institutionalization of human rights. Finally, the results demonstrate that democratic countries and nations with more expanded educational systems tend to adopt a UNESCO school before the period of human rights institutionalization. The implications of these findings are discussed in relation to the literature on the global environment and the diffusion of innovations in education.