bluuebunny/crossref_metadata_2025 huggingface dataset:
Common Metabolic Profile in Infants Indicating Impaired Cobalamin Status Responds to Cobalamin Supplementation
Authors: Bjørke-Monsen Anne-Lise , Torsvik Ingrid , Sætran Hege , Markestad Trond , Ueland Per Magne
Published: July 2008

OBJECTIVE. A metabolic profile consistent with impaired cobalamin status is prevalent in breastfed infants. We investigated whether this profile reflects immature organ systems or impaired cobalamin status.

METHODS. In a single-center, randomized, placebo-controlled trial, we studied 107 six-week-old infants. The infants were randomly assigned to receive either an intramuscular injection of 400 μg of cobalamin or no intervention. Concentrations of cobalamin and folate in serum and total homocysteine, methylmalonic acid, and cystathionine in plasma were determined at enrollment and at the age of 4 months.

RESULTS. There were no significant differences between the intervention group (n = 54) and the control group (n = 53) in the concentrations of any vitamin marker at baseline (6 weeks). At 4 months, the supplement-treated infants had a 75% higher median serum cobalamin level and remarkable reductions in median plasma total homocysteine (from 7.46 to 4.57 μmol/L) and methylmalonic acid (from 0.58 to 0.20 μmol/L) levels, whereas levels of both metabolites were essentially unchanged during the follow-up period in the control group.

CONCLUSIONS. Cobalamin supplementation changed all markers of impaired cobalamin status (low cobalamin, high total homocysteine, and high methylmalonic acid levels) toward a profile observed in cobalamin-replete older children and adults. Therefore, the high total homocysteine and methylmalonic acid levels reported for a large fraction of infants reflect not immature metabolism but rather insufficient cobalamin levels to fully sustain cobalamin-dependent reactions fully.
School Food Environments and Policies in US Public Schools
Authors: Finkelstein Daniel M. , Hill Elaine L. , Whitaker Robert C.
Published: July 2008

OBJECTIVE. The purpose of this study was to describe school food environments and policies in US public schools and how they vary according to school characteristics.

METHODS. We analyzed cross-sectional data from the third School Nutrition and Dietary Assessment study by using a nationally representative sample of 395 US public schools in 129 school districts in 38 states. These 2005 data included school reports of foods and beverages offered in the National School Lunch Program and on-site observations, in a subsample of schools, of competitive foods and beverages (those sold in vending machines and a la carte and that are not part of the National School Lunch Program). Seventeen factors were used to characterize school lunches, competitive foods, and other food-related policies and practices. These factors were used to compute the food environment summary score (0 [least healthy] to 17 [most healthy]) of each school.

RESULTS. There were vending machines in 17%, 82%, and 97% of elementary, middle, and high schools, respectively, and a la carte items were sold in 71%, 92%, and 93% of schools, respectively. Among secondary schools with vending and a la carte sales, these sources were free of low-nutrient energy-dense foods or beverages in 15% and 21% of middle and high schools, respectively. The food environment summary score was significantly higher (healthier) in the lower grade levels. The summary score was not associated with the percentage of students that was certified for free or reduced-price lunches or the percentage of students that was a racial/ethnic minority.

CONCLUSIONS. As children move to higher grade levels, their school food environments become less healthy. The great majority of US secondary schools sell items a la carte in the cafeteria and through vending machines, and these 2 sources often contain low-nutrient, energy-dense foods and beverages, commonly referred to as junk food.
Child Versus Adult Research: The Gap in High-Quality Study Design
Authors: Martinez-Castaldi Carolina , Silverstein Michael , Bauchner Howard
Published: July 2008

OBJECTIVE. The objective of this study was to determine whether there were differences in study design and purpose between published child- and adult-focused clinical research.

METHODS. We reviewed all articles published in the New England Journal of Medicine, Journal of the American Medical Association, Annals of Internal Medicine, Pediatrics, Archives of Internal Medicine, and Archives of Adolescent and Pediatric Medicine during the first 3 months of 2005 and assessed each study's design and purpose. We compared articles focused on adults with those focused on children.

RESULTS. We included 370 original research reports in our analysis (New England Journal of Medicine, n = 46; Journal of the American Medical Association, n = 60; Annals of Internal Medicine, n = 27; Pediatrics, n = 130; Archives of Internal Medicine, n = 73; Archives of Adolescent and Pediatric Medicine, n = 34), of which 189 included only adults as subjects and 181 only children. Among adult studies, compared with child studies, there were more randomized, controlled trials (23.8% vs 8.8%) and systematic reviews (10.6% vs 1.7%) and fewer cross sectional studies (16.9% vs 40.9%). Study purposes also varied, with studies of therapies constituting 38.1% of adult studies, compared with 17.7% of child studies. In contrast, epidemiological studies, defined as studies describing the prevalence or incidence of diseases or risk factors or showing associations between risk factors and diseases, constituted 6.4% of adult studies, compared with 26.5% of child studies.

CONCLUSIONS. In 6 leading generalist and specialist journals, studies involving adults were significantly more likely than child studies to be randomized, controlled trials, systematic reviews, or studies of therapies. If such studies are to be viewed as the highest possible quality of evidence, then this difference has implications for quality of care for children and for funding and future directions in clinical research involving children.
Countywide School-Based Influenza Immunization: Direct and Indirect Impact on Student Absenteeism
Authors: Davis Mollie M. , King James C. , Moag Lauren , Cummings Ginny , Magder Laurence S.
Published: July 2008

OBJECTIVE. Live attenuated influenza vaccine was given to 5319 (44%) of the 12090 students enrolled in public elementary schools in Carroll County, Maryland, during the fall of 2005. We examined the impact of this community-based intervention on countywide student absenteeism during the subsequent influenza outbreak.

METHODS. This study used existing, anonymous information: census data, community influenza tests, and public school absenteeism data. The intervention group was Carroll County, years 2005–2006. The control group included Carroll County, years 2001–2005, and adjacent Frederick County, years 2001–2006. Weekly student absenteeism was determined during baseline influenza-free periods and influenza outbreak periods for all of the public schools.

RESULTS. The absolute change in absenteeism during the influenza outbreak periods over baseline in elementary schools was 0.61% for the intervention group and 1.79% for the control group. Similarly, the change in absenteeism during the influenza outbreak period over baseline for high schools was 0.32% for the intervention group and 1.80% for the control group. Although not statistically significant, trends in middle schools were similar.

CONCLUSIONS. Countywide school-based influenza vaccination was associated with reduced absenteeism during an influenza outbreak. The data suggest not only a direct impact on elementary schools but also an indirect impact on high schools. School-based programs provide an efficient method of providing influenza vaccination to children, and protection may extend to unvaccinated community members. Additional research is needed to determine whether school-based vaccination of children reduces morbidity and mortality associated with influenza outbreaks.
Adverse Medical Outcomes of Early Newborn Screening Programs for Phenylketonuria
Authors: Brosco Jeffrey P. , Sanders Lee M. , Seider Michael I. , Dunn Angela C.
Published: July 2008

OBJECTIVE. Despite the success of current newborn screening programs, some critics have argued that in the 1960s hundreds of children with false-positive results for phenylketonuria suffered death or disability from treatment with restrictive diets. Medically adverse outcomes after false-positive results may be a reason to be cautious when expanding current newborn screening programs. We sought to determine if newborn screening programs for phenylketonuria before 1980 led to adverse medical outcomes in children with false-positive results.

PATIENTS AND METHODS. We examined the history of newborn screening programs for phenylketonuria in the United States. We reviewed the historical scholarship, conducted a systematic search for medical adverse outcomes, and interviewed key participants in the history of newborn screening programs.

RESULTS. We found no population-based studies of early screening programs for phenylketonuria. One author reported 2 infants treated with restrictive diets after false-positive results for phenylketonuria who were developmentally delayed, and there is unpublished evidence of 4 additional cases of inappropriate treatment, although adverse outcomes were not documented. There were also 4 published reports of adverse medical outcomes after treating children with phenylketonuria variants, as screening for phenylketonuria revealed infants with intermediate or transiently high levels of phenylalanine.

CONCLUSIONS. We found little evidence of death or disability that resulted from the inappropriate treatment of well children who were falsely identified by early newborn screening programs. Because the first decade of newborn screening typically reveals diagnostic and therapeutic complexity, systematic follow-up of screened populations and rapid dissemination of results may reduce morbidity/mortality rates.
Death, Child Abuse, and Adverse Neurological Outcome of Infants After an Apparent Life-Threatening Event
Authors: Bonkowsky Joshua L. , Guenther Elisabeth , Filloux Francis M. , Srivastava Rajendu
Published: July 2008

OBJECTIVES. Apparent life-threatening events in infants constitute a significant challenge for health care providers. Apparent life-threatening event evaluation and management are poorly defined, and outcomes have not been clearly determined. Our objectives were to characterize short- and long-term risks for death, child abuse, and abnormal neurological outcomes of infants after an apparent life-threatening event and to identify clinical features that are predictive of these outcomes.

METHODS. We collected data from infants ages birth to 12 months of age who were hospitalized after an apparent life-threatening event during a 5-year time period. Patients were evaluated for subsequent death, child abuse, or adverse neurological outcome (chronic epilepsy or developmental delay).

RESULTS. A total of 471 patients met inclusion criteria and were followed an average of 5.1 years. Two patients died after developing chronic epilepsy and severe developmental delay. Fifty-four (11%) patients were diagnosed as being a victim of child abuse, but only 2 were identified at initial presentation. There were 23 (4.9%) patients with adverse neurological outcomes, including 17 (3.6%) with chronic epilepsy and 14 (3.0%) with developmental delay. Of those who developed chronic epilepsy, 71% returned within 1 month of the initial apparent life-threatening event with a second event. Neurological evaluation at the time of the apparent life-threatening event had low yield for predicting those who would develop chronic epilepsy.

CONCLUSIONS. Infants who suffer an apparent life-threatening event are at risk for subsequent child abuse and adverse neurological outcomes. Deaths were uncommon and only occurred in the setting of severe developmental delay and seizure disorders. Neurological evaluation during hospitalization for a first apparent life-threatening event is of low yield, but close follow-up is essential.
Effect of Long-term Corticosteroid Use on Bone Mineral Density in Children: A Prospective Longitudinal Assessment in the Childhood Asthma Management Program (CAMP) Study
Authors: Kelly H. William , Van Natta Mark L. , Covar Ronina A. , Tonascia James , Green Rebecca P. , Strunk Robert C. ,   for the CAMP Research Group
Published: July 2008

OBJECTIVE. Systemic corticosteroids are known to induce osteoporosis and increase the risk for fractures in adults and children. Inhaled corticosteroids have been shown to increase the risk for osteoporosis and fractures in adults at risk; however, long-term prospective studies of children to assess risks of multiple short courses of oral corticosteroids and chronic inhaled corticosteroids have not been performed. Thus, we assessed the effects of multiple short courses of oral corticosteroids and long-term inhaled corticosteroids on bone mineral accretion over a period of years.

METHODS. This was a cohort follow-up study for a median of 7 years of children who had mild-to-moderate asthma and initially were randomly assigned into the Childhood Asthma Management Program trial. Serial dual-energy radiograph absorptiometry scans of the lumbar spine for bone mineral density were performed for all patients. Annual bone mineral accretion was calculated for 531 boys and 346 girls who had asthma and were aged 5 to 12 years at baseline (84% of the initial cohort).

RESULTS. Oral corticosteroid bursts produced a dosage-dependent reduction in bone mineral accretion (0.052, 0.049, and 0.046 g/cm2 per year) and an increase in risk for osteopenia (10%, 14%, and 21%) for 0, 1 to 4, and ≥5 courses, respectively, in boys but not girls. Cumulative inhaled corticosteroid use was associated with a small decrease in bone mineral accretion in boys but not girls but no increased risk for osteopenia.

CONCLUSIONS. Multiple oral corticosteroid bursts over a period of years can produce a dosage-dependent reduction in bone mineral accretion and increased risk for osteopenia in children with asthma. Inhaled corticosteroid use has the potential for reducing bone mineral accretion in male children progressing through puberty, but this risk is likely to be outweighed by the ability to reduce the amount of oral corticosteroids used in these children.
Intranasal Budesonide Treatment for Children With Mild Obstructive Sleep Apnea Syndrome
Authors: Kheirandish-Gozal Leila , Gozal David
Published: July 2008

OBJECTIVES. Intranasal corticosteroids have been advanced as a nonsurgical therapeutic alternative for pediatric obstructive sleep apnea syndrome, particularly for patients with mild disease, and aims at reducing the size of hypertrophic adenotonsillar tissue.

METHODS. Of 71 possible candidates, 62 children with polysomnographically diagnosed mild obstructive sleep apnea syndrome were recruited onto a double-blind, randomized, crossover trial of intranasal budesonide (32 μg per nostril at bedtime) or placebo for 6 weeks followed by an additional 6-week treatment in the alternative treatment arm after allowing for a 2-week washout period. Polysomnographic assessment and radiographs for assessment of adenoid size were performed after completion of each phase.

RESULTS. There were significant improvements in both polysomnographic measures (sleep latency, slow-wave sleep, and rapid-eye-movement sleep), in the magnitude of respiratory disturbance (apnea/hypopnea index, nadir pulse oxygen saturation), and in adenoid size among the 48 children who completed the treatment phase compared with 32 children who received placebo in their initial arm, with normalization of sleep measures in 54.1% of the treated children. Furthermore, discontinuation of treatment for 8 weeks for 25 children revealed a sustained duration of the initial treatment effect.

CONCLUSIONS. A 6-week treatment with intranasal budesonide effectively reduced the severity of mild obstructive sleep apnea syndrome and the magnitude of the underlying adenoidal hypertrophy, and this effect persisted for at least 8 weeks after cessation of therapy. These findings justify the use of topical steroids as the initial therapeutic option in otherwise healthy children with mild obstructive sleep apnea.
Shyness and Timidity in Young Adults Who Were Born at Extremely Low Birth Weight
Authors: Schmidt Louis A. , Miskovic Vladimir , Boyle Michael H. , Saigal Saroj
Published: July 2008

OBJECTIVE. Recent studies have noted personality differences among adult survivors of very preterm birth, including higher neuroticism and cautiousness and lower extraversion. We attempted to replicate and extend these recent studies by examining personality characteristics across multiple components of personality that traditionally define personality structure in a birth cohort of young adults born at extremely low birth weight (501–1000 g), the smallest and most at-risk infants.

PARTICIPANTS AND METHODS. We assessed 71 (76% of the original birth cohort) extremely low birth weight and 83 (74% of the original cohort) term normal birth weight young adults by using well-validated personality measures, indexing 4 traditional components of personality: temperament (Cheek and Buss shyness and sociability and Eysenck neuroticism and extraversion), motivation (Carver and White behavioral inhibition and behavioral activation), cognitive and affective (Coopersmith self-esteem and University of California, Los Angeles, loneliness), and socialization (Eysenck psychoticism and lie). All of the participants were right-handed and free of neurosensory and psychiatric impairments.

RESULTS. Extremely low birth weight adults reported significantly higher shyness, behavioral inhibition, and socialization (a measure of prosocial behavior defined by risk aversion and adherence to societal mores) and lower sociability and emotional well-being than their normal birth weight counterparts, replicating and extending the findings of previous studies.

CONCLUSIONS. Young adults who were born at extremely low birth weight and without major impairments are more cautious, shy, and risk aversive and less extraverted than their normal birth weight counterparts, possibly placing them at risk for future psychiatric and emotional problems.
Special Health Care Needs Among Children in the Child Welfare System
Authors: Ringeisen Heather , Casanueva Cecilia , Urato Mathew , Cross Theodore
Published: July 2008

OBJECTIVE. The aim of this study was to determine levels of special health care need among children in the child welfare system and how these needs may affect children's functioning.

METHODS. Data were from the National Survey of Child and Adolescent Well-being, a national probability study of children investigated for child maltreatment. The sample consisted of 5496 children aged 0 to 15 years at baseline. For analysis, we used descriptive statistics to determine special health care needs and children's functioning from baseline to 3-year follow-up. Logistic regression was used to examine correlates of special health care needs.

RESULTS. At any point in the study period, approximately one third of the children were identified as having special health care needs. Overall, across 3 years of follow-up data, 50.3% of the children were identified as having special health care needs. Boys were significantly more likely than girls to have had special health care needs, and children aged 0 to 2 years at baseline were significantly less likely to have had special health care needs than older children. Adopted and foster children were significantly more likely to have had special health care needs than children never placed out of the home. The most commonly reported type of chronic health condition was asthma. The most commonly reported type of special need was a learning disability.

CONCLUSIONS. Special health care needs are prevalent among children in the child welfare system. Many children with special health care needs have cognitive, language, adaptive, social, or behavioral functional impairments. Mechanisms are needed to ensure that this vulnerable population has access to and receives coordinated health and related social services.
Lamotrigine in Breast Milk and Nursing Infants: Determination of Exposure
Authors: Newport D. Jeffrey , Pennell Page B. , Calamaras Martha R. , Ritchie James C. , Newman Melanee , Knight Bettina , Viguera Adele C. , Liporace Joyce , Stowe Zachary N.
Published: July 2008

OBJECTIVE. Although lamotrigine use during pregnancy has substantially increased over the past decade secondary to accumulated reproductive safety data, systematic data on lamotrigine during breastfeeding remains sparse. We sought to characterize the determinants of lamotrigine concentrations in breast milk and nursing-infant plasma.

PATIENTS AND METHODS. Women who enrolled in a prospective investigation of perinatal medication pharmacokinetics, were treated with lamotrigine, and chose to continue lamotrigine while breastfeeding were included in the analysis. Breast milk samples were collected via breast pump from foremilk to hindmilk from a single breast to determine the excretion gradient and serial samples over 24 hours to determine the time course of excretion. Paired maternal/infant plasma samples were also collected. Lamotrigine concentrations in all of the samples were determined by using high-performance liquid chromatography with ultraviolet detection. Statistical analyses of breast milk and infant plasma concentrations and their determinants were conducted.

RESULTS. Thirty women and their nursing infants participated in the study, providing a total of 210 breast milk samples. The mean milk/plasma ratio was 41.3%. There was a nonsignificant trend for higher lamotrigine concentrations in breast milk 4 hours after the maternal dose. Infant plasma concentrations were 18.3% of maternal plasma concentrations. The theoretical infant lamotrigine dose was 0.51 mg/kg per day, and the relative infant lamotrigine dose was 9.2%. Mild thrombocytosis was present in 7 of 8 infants at the time of serum sampling. No other adverse events were observed or reported in the breastfed infants.

CONCLUSIONS. Consistent with previous investigations of medications in breast milk, the lamotrigine milk/plasma ratio is highly variable. The rate of lamotrigine excretion into human breast milk is similar to that observed with other antiepileptic drugs. These data expand the extant literature on lamotrigine in breastfeeding and demonstrate relatively comparable nursing-infant exposure to lamotrigine compared with other antiepileptic drugs.
Protecting Public Trust in Immunization
Authors: Cooper Louis Z. , Larson Heidi J. , Katz Samuel L.
Published: July 2008

Public trust in the safety and efficacy of vaccines is one key to the remarkable success of immunization programs within the United States and globally. Allegations of harm from vaccination have raised parental, political, and clinical anxiety to a level that now threatens the ability of children to receive timely, full immunization. Multiple factors have contributed to current concerns, including the interdependent issues of an evolving communications environment and shortfalls in structure and resources that constrain research on immunization safety (immunization-safety science). Prompt attention by public health leadership to spreading concern about the safety of immunization is essential for protecting deserved public trust in immunization.
Lipid Screening and Cardiovascular Health in Childhood
Authors: Daniels Stephen R. , Greer Frank R. ,   and the Committee on Nutrition
Published: July 2008

This Clinical Report was retired May 2012.

This clinical report replaces the 1998 policy statement from the American Academy of Pediatrics on cholesterol in childhood, which has been retired. This report has taken on new urgency given the current epidemic of childhood obesity with the subsequent increasing risk of type 2 diabetes mellitus, hypertension, and cardiovascular disease in older children and adults. The approach to screening children and adolescents with a fasting lipid profile remains a targeted approach. Overweight children belong to a special risk category of children and are in need of cholesterol screening regardless of family history or other risk factors. This report reemphasizes the need for prevention of cardiovascular disease by following Dietary Guidelines for Americans and increasing physical activity and also includes a review of the pharmacologic agents and indications for treating dyslipidemia in children.
Heat generation associated with pressure-induced infiltration in a nanoporous silica gel
Authors: Han Aijie , Punyamurtula Venkata K. , Qiao Yu
Published: July 2008

As a liquid moves in the nanopores of a silica gel, because of the hysteresis of sorption behavior, significant energy dissipation can take place. Through a calometric measurement, the characteristics of associated heat generation are investigated. The temperature variation increases with the mass of silica gel, which consists of a reversible part and an irreversible part. The residual temperature change is about 30% to 60% of the maximum temperature increase and can be accumulated as multiple loading cycles are applied.
Nonhydrolytic sol-gel synthesis: Microstructural and morphological study on nickel ferrite nanocrystals coated with oleic acid
Authors: Yin H. , Chow G.M.
Published: July 2008

Nickel ferrite nanostructured particles coated with chemisorbed oleic acid were successfully synthesized by nonhydrolytic sol-gel method. By varying the composition of metal precursors, two microstructures were obtained, i.e., dispersed nanocrystals (9.7 ± 1.8 nm) and submicron aggregates (152 ± 21 nm) consisted of many nanocrystals (8.1 ± 1.3 nm). Because oleic acid could form complex with iron (III) ions, but not with nickel (II), increasing the concentration of iron precursor consumed more oleic acid and led to insufficient oleic acid coating on particle surface. Strong intercrystallite interaction was induced from less protected nanocrystals, and aggregation thus occurred between different crystallites.
High-strength Cu–Zr binary alloy with an ultrafine eutectic microstructure
Authors: Kim Kyou-Hyun , Ahn Jae-Pyoung , Lee Jae-Hoon , Lee Jae-Chul
Published: July 2008

In this study, we synthesized Cu–Zr binary alloys reinforced with an ultrafine eutectic microstructure. The alloys consisted of alternating layers of a hard superlattice phase and a ductile Cu phase with a very fine interlamellar spacing of ∼60 nm. The superlattice phase enhanced the strength of the alloys while the laminated composite structure helped improve their plasticity, making their mechanical properties comparable to those of the earlier reported high strength alloys. This paper discusses the fundamental microstructural aspects that influence the mechanical properties of these alloys.
Controlling the shape of Al/Ni multilayer foils using variations in stress
Authors: Knepper Robert , Fritz Gregory , Weihs Timothy P.
Published: July 2008

Al/Ni multilayer foils were sputter-deposited with an in-plane residual stress state that was altered midway through the thickness of the foils by changing the bilayer spacing. The difference in stress between the top and bottom halves of the foil caused these systems to curl when they were removed from their substrates. As predicted, the radius of curvature increased linearly as the difference in stress between the upper and lower halves decreased and as foil thickness increased, demonstrating the ability to fabricate layered foils with specific curvatures. Unexpectedly, however, the radii of curvature of all the free-standing foils decreased with time after removal from their substrates, suggesting that a time-dependent relaxation mechanism was operating. An explanation based on stress driven, time-dependent deformation is offered to explain the relaxation, and an elasticity-based curvature model is presented for comparison with the measured steady state curvatures.
Reaction kinetics in the combustion synthesis of Al–Ir–Ni intermetallic compounds
Authors: Cai Kai , Ode Machiko , Murakami Hideyuki
Published: July 2008

The combustion synthesis of Al50Ir48Ni2 (at.%) was conducted at different heating rates in both a differential scanning calorimetry (DSC) chamber and a vacuum furnace. It was found that a higher heating rate, a sufficient amount of reactant powder, and effective control of the heat loss facilitated the complete reaction and resulted in combusted single IrAl phase products. Otherwise, multiphase products containing IrAl, unreacted Ir, and Al3Ir were synthesized. The reactions involved in different processes were discussed in terms of the thermal competition between heat generation and loss during the reaction. All ignition temperatures were below 773 K, indicating that the combustion reaction occurs at the solid–solid state. With increasing heating rate, the ignition temperature increased while the product density decreased.
Structure evolution of ZrB2–SiC during the oxidation in air
Authors: Zhang Xing-Hong , Hu Ping , Han Jie-Cai
Published: July 2008

The structure evolution and oxidation behavior of ZrB2–SiC composites in air from room temperature to ultrahigh temperature were investigated using furnace testing, arc jet testing, and thermal gravimetric analysis (TGA). The oxide structure changed with the increasing temperature. SiC content has no apparent influence on the evolution of structure during the oxidation of ZrB2–SiC below 1600 °C. However, the evolution of structure for ZrB2–SiC above 1800 °C was significantly affected by the SiC content. The formation of the SiC depleted layer in the ZrB2–SiC system not only depends on the surrounding conditions of pressure and temperature but also on the structure distribution of the SiC in the ZrB2 matrix. The apparent recrystallization of the ZrO2 occurred above 1800 °C. The SiC content should be controlled at ∼16% in the ZrB2–SiC system for the ultrahigh-temperature application. The mechanisms of the structure evolution during oxidation in air were also analyzed.
Influence of heterogeneities with different length scale on the plasticity of Fe-base ultrafine eutectic alloys
Authors: Park Jin Man , Kim Do Hyang , Kim Ki Buem , Lee Min Ha , Kim Won Tae , Eckert Jürgen
Published: July 2008

The evolution of microstructure and its influence on the mechanical properties of high-strength ultrafine eutectic Fe–(Ti, Zr)–(B, Co) alloys has been studied. The addition of B or Co improves the room temperature compressive plasticity from 1% to ∼8.5% or ∼14%, respectively, due to the formation of a heterogeneous microstructure with distinctly different length scales, which can delay the propagation of shear bands and promotes the activation of multiple shear bands.
Electromigration-induced Pb and Sn whisker growth in SnPb solder stripes
Authors: Wei C.C. , Liu P.C. , Chen Chih , Tu K.N.
Published: July 2008

Electromigration at 5 × 104 A/cm2 and 100 °C was conducted to grow composite Pb/Sn whiskers from SnPb solders, in which a Pb whisker grows first and then a whisker of Sn grows. In some cases, small Sn islands are embedded in Pb whiskers. The diameter of a composite whisker is <1 μm, which is much smaller than that of spontaneous Sn whisker growth on leadframes. The growth orientation of Pb whiskers was in the [110], [1¯11], and [112] directions. This investigation proposes that compressive stress generated by electromigration at the anode provides the force driving whisker growth. Therefore, accelerated tests of whisker growth at higher temperatures using electromigration are feasible.
Mechanism of the interfacial reaction between cation-deficient La0.56Li0.33TiO3 and metallic lithium at room temperature
Authors: Yang Kai-Yun , Leu Ing-Chi , Fung Kuan-Zong , Hon Min-Hsiung , Hsu Ming-Chi , Hsiao Yu-Jen , Wang Moo-Chin
Published: July 2008

We used x-ray diffractometry (XRD), x-ray photoelectron spectrometry (XPS), and secondary-ion mass spectrometry (SIMS) to investigate the mechanism of the interfacial room-temperature (RT) chemical reaction between cation-deficient La0.56Li0.33TiO3 solid electrolytes and metallic lithium anodes in all-solid-state lithium batteries. A stoichiometric mixture of La2O3, Li2CO3, and TiO2 powders was calcined at 1250 °C for 8 h to obtain a single perovskite structure of La0.56Li0.33TiO3. When this La0.56Li0.33TiO3 sample and lithium were placed in contact at room temperature for 24 h, the phase of the La0.56Li0.33TiO3 remained unchanged. The XPS results indicate that 12% of the tetravalent Ti4+ ions were converted into trivalent Ti3+ ions. The valence conversion and degree of conversion were limited by the structural rigidity of the host crystal. Our SIMS analysis suggests the existence of a local electric field near the contact surface and indicates that the 6Li+ isotope ions were inserted into the specimen through the effect of this field. The change in the electrical properties of La0.56Li0.33TiO3 supports this mechanism for the interfacial reaction. The ionic conductivities of the grain and total grain boundary decreased and increased, respectively, after the insertion of Li+, and the total electronic conductivity increased as a result of the presence of intervalence electron hopping between mixed Ti3+/Ti4+ states. The mechanism of the lithium-activated RT interfacial reaction is associated with the reduction of Ti4+ transition metal ions from tetravalent to trivalent states and the local-electric-field-induced Li+ insertion into La3+/Li+-site vacancies of La0.56Li0.33TiO3.
Influence of Environmental Factors on Seed Germination and Seedling Emergence of American Sloughgrass (Beckmannia syzigachne)
Authors: Rao Na , Dong Liyao , Li Jun , Zhang Hongjun
Published: July 2008

The influence of environmental factors on seed germination and seedling emergence of American sloughgrass was studied in laboratory and greenhouse conditions. The optimum temperature for seed germination was 10 C and light was not necessary. Seed germination was sensitive to osmotic potential and completely inhibited at an osmotic potential of −0.6 MPa, but it was quite tolerant to salinity: germination occurred even at 160 mM NaCl (36%). More than 80% of seeds germinated at pH values ranging between 4 and 10. Seedling emergence was highest when seeds were placed on the soil surface (91%) but declined with burial depth. Few (3%) seedlings emerged when seeds were planted at a depth of 5 cm. Information gained in this study will lead to a better understanding of the requirements for American sloughgrass germination and emergence.
A Hydrothermal Seedling Emergence Model for Giant Ragweed (Ambrosia trifida)
Authors: Schutte Brian J. , Regnier Emilie E. , Harrison S. Kent , Schmoll Jerron T. , Spokas Kurt , Forcella Frank
Published: July 2008

Late-season giant ragweed emergence in Ohio crop fields complicates decisions concerning the optimum time to implement control measures. Our objectives were to develop a hydrothermal time emergence model for a late-emerging biotype and validate the model in a variety of locations and burial environments. To develop the model, giant ragweed seedlings were counted and removed weekly each growing season from 2000 to 2003 in a fallow field located in west central Ohio. Weather data, soil characteristics and geographic location were used to predict soil thermal and moisture conditions with the Soil Temperature and Moisture Model (STM2). Hydrothermal time (θHT) initiated March 1 and base values were extrapolated from the literature (Tb= 2 C, ψb= −10 MPa). Cumulative percent emergence initially increased rapidly and reached 60% of maximum by late April (approximately 400 θHT), leveled off for a period in May, and increased again at a lower rate before concluding in late July (approximately 2,300 θHT). The period in May when few seedlings emerged was not subject to soil temperatures or water potentials less than the θHTbase values. The biphasic pattern of emergence was modeled with two successive Weibull models that were validated in 2005 in a tilled and a no-tillage environment and in 2006 at a separate location in a no-tillage environment. Root-mean-square values for comparing actual and model predicted cumulative emergence values ranged from 8.0 to 9.5%, indicating a high degree of accuracy. This experiment demonstrated an approach to emergence modeling that can be used to forecast emergence on a local basis according to weed biotype and easily obtainable soil and weather data.
Factors Affecting Germination of Coolatai Grass (Hyparrhenia hirta)
Authors: Chejara Vinod K. , Kristiansen Paul , Whalley Ralph D. B. , Sindel Brian M. , Nadolny Christopher
Published: July 2008

Coolatai grass is an invasive, perennial grass from Africa and the Middle East that has infested large areas of northern New South Wales, Australia, and also occurs in other Australian states. An understanding of the seed germination ecology of Coolatai grass can assist in predicting its potential distribution and developing effective management strategies. The effects of various environmental factors on Coolatai grass seed germination were investigated in a series of laboratory experiments. The effect of diurnal alternating temperatures (5–45 C) with a 12-h photoperiod were examined on a thermogradient plate. Seed germination occurred at almost all temperature combinations from 5 to 45 C. At moderate temperatures the speed of seed germination was very high; at 30/20 C more than 80% of seeds were germinated within 12 h. Germination was slightly enhanced by the presence of light, but length of photoperiod did not affect germination. Germination at neutral pH was over 90%, and declined to 65% at acidic (pH 4) and alkaline (pH 10) pH levels. Germination was completely inhibited at an osmotic stress of −0.55 MPa or greater and was reduced by 50% at −0.37 MPa. Greater germination in relatively dry soil conditions compared with native species may contribute to the establishment of this species in the field. Results indicate that Coolatai grass seeds can germinate over a wide range of diurnal temperatures, light regimes, pH levels, and under marginal water stress. These characteristics help explain the successful invasion of Coolatai grass and provide evidence that this species is capable of establishing in many parts of Australia.
Selection of a Barley Yield Model Using Information–Theoretic Criteria
Authors: Jasieniuk Marie , Taper Mark L. , Wagner Nicole C. , Stougaard Robert N. , Brelsford Monica , Maxwell Bruce D.
Published: July 2008

Empirical models of crop–weed competition are integral components of bioeconomic models, which depend on predictions of the impact of weeds on crop yields to make cost-effective weed management recommendations. Selection of the best empirical model for a specific crop–weed system is not straightforward, however. We used information–theoretic criteria to identify the model that best describes barley yield based on data from barley–wild oat competition experiments conducted at three locations in Montana over 2 yr. Each experiment consisted of a complete addition series arranged as a randomized complete block design with three replications. Barley was planted at 0, 0.5, 1, and 2 times the locally recommended seeding rate. Wild oat was planted at target infestation densities of 0, 10, 40, 160, and 400 plants m−2. Twenty-five candidate yield models were used to describe the data from each location and year using maximum likelihood estimation. Based on Akaike's Information Criterion (AIC), a second-order small-sample version ofAIC(AICc), and the Bayesian Information Criterion (BIC), most data sets supported yield models with crop density (Dc), weed density (Dw), and the relative time of emergence of the two species (T) as variables, indicating that all variables affected barley yield in most locations.AIC,AICc, andBICselected identical best models for all but one data set. In contrast, the Information Complexity criterion,ICOMP, generally selected simpler best models with fewer parameters. For data pooled over years and locations,AIC,AICc, andBICstrongly supported a single best model with variablesDc,Dw,T, and a functional form specifying both intraspecific and interspecific competition.ICOMPselected a simpler model withDcandDwonly, and a functional form specifying interspecific, but no intraspecific, competition. The information–theoretic approach offers a rigorous, objective method for choosing crop yield and yield loss equations for bioeconomic models.
Cover-Crop Systems Affect Weed Communities in a California Vineyard
Authors: Baumgartner Kendra , Steenwerth Kerri L. , Veilleux Lissa
Published: July 2008

Vineyard weed communities were examined under four dormant-season cover-crop systems representative of those used in the north-coastal grape-growing region of California: no-till annuals (ANoT) (rose clover, soft brome, zorro fescue), no-till perennials (PNoT) (blue wildrye, California brome, meadow barley, red fescue, yarrow), tilled annual (AT) (triticale), and a no-cover-crop tilled control (NoCT). Treatments were carried out for 3 yr in the interrows of a wine grape vineyard. Glyphosate was used to control weeds directly beneath the vines, in the intrarows. Treatments significantly impacted weed biomass, community structure, and species diversity in the interrows. Orthogonal contrasts showed that tillage, and not the presence of a cover crop, impacted interrow weed biomass. Distance-based redundancy analyses (db-RDA) revealed significant effects of the cover-crop systems and of tillage on weed community structure in the interrows. For scarlet pimpernel and spiny sowthistle, the combination of ANOVA and orthogonal contrasts confirmed their association with the tilled treatments, as revealed by db-RDA. This same approach identified the association between California burclover and the no-till treatments. Our findings of no significant effects of the cover-crop systems on weed biomass, community structure, or diversity in the intrarows demonstrate that the impacts the cover-crop management systems had on the interrows did not carry over to adjacent intrarows. In addition, the fact that the cover crops did not affect vine yield, growth, or nutrition relative to the no-cover-crop control suggests that cover crops are likely to minimize soil erosion from winter rains, which is the primary purpose of vineyard cover cropping in northern California, without adversely affecting vine health or weed control.
Growth and Reproduction of Benghal Dayflower (Commelina benghalensis) in Response to Drought Stress
Authors: Webster Theodore M. , Grey Timothy L.
Published: July 2008

Greenhouse experiments were conducted to evaluate growth and reproduction of Benghal dayflower in response to daily (nondrought stress) and weekly (drought stress) irrigation. With daily irrigation, Benghal dayflower plants added one leaf per plant each week during the initial 6 wk of growth and then increased leaf number eightfold between the intervals of 6 and 10 wk after planting (WAP) and 10 and 15 WAP. By 15 WAP each plant had in excess of 400 leaves. Benghal dayflower plant height increased 2.4 cm wk−1 between 5 and 14 WAP, increasing eightfold during this interval, while plant width increased 20-fold. Aerial spathe formation began between 7 and 8 WAP, with 26 spathes maturing (containing seeds ready for dispersal) each week beginning at 11 WAP. In another study, the influence of duration of drought stress at intervals between 7 and 56 d on early growth and development of cotton and Benghal dayflower was evaluated. Benghal dayflower aboveground biomass was 3.5 times greater than cotton. There was an inverse linear relationship between aboveground biomass and duration of drought stress for cotton and Benghal dayflower, though there was a more rapid decline for Benghal dayflower. A final study evaluated Benghal dayflower response to weekly moisture regimes that approximated 13, 25, 50, and 100% of soil field capacity. Benghal dayflower aerial spathes were 4.6 times more numerous than subterranean spathes. Rate of seed production decreased in a linear manner with decreasing water volume, however, rate of subterranean seed production was less affected by water volume than was aerial seed production. These data indicate that Benghal dayflower thrives under high soil moisture regimes, but that drought stress inhibits growth and reproduction. Cotton appears to be more drought tolerant than Benghal dayflower. Judicious water use in cotton cropping systems in the southeastern United States could be an important component of multiple-tactic Benghal dayflower management program.
Seed Persistence in the Field May Be Predicted by Laboratory-Controlled Aging
Authors: Long Rowena L. , Panetta F. Dane , Steadman Kathryn J. , Probert Robin , Bekker Renée M. , Brooks Simon , Adkins Steve W.
Published: July 2008

Weed management is complicated by the presence of soil seed banks. The complexity of soil–seed interactions means that seed persistence in the field is often difficult to measure, let alone predict. Field trials, although accurate in their context, are time-consuming and expensive to conduct for individual species. Some ex situ techniques for estimating seed life expectancy have been proposed, but these fail to simulate the environmental complexity of the field. Also, it has been questioned whether techniques such as the controlled aging test (CAT) are useful indicators of field persistence. This study aimed to test the validity of the standard CAT (seed aging at 45 C and 60% relative humidity) in use at the Royal Botanic Gardens, Kew, U.K., for predicting field seed-persistence. Comparison of seed persistence and CAT data for 27 northwest European species suggested a significant positive correlation of 0.31. Subsequently, 13 species of emerging and common weeds of Queensland were assessed for their seed longevity using the CAT. The seed longevity data of these species in the CAT were linked with field seed-persistence data according to three broad seed-persistence categories: < 1 yr, 1 to 3 yr, and > 3 yr. We discuss the scope for using the CAT as a tool for rapid assignment of species to these categories. There is a need for further studies that compare predictions of seed persistence based on the CAT with seed persistence in the field for a larger range of species and environments.
Germination Ecology of Two Troublesome Asteraceae Species of Rainfed Rice: Siam Weed (Chromolaena odorata) and Coat Buttons (Tridax procumbens)
Authors: Chauhan Bhagirath S. , Johnson David E.
Published: July 2008

Siam weed and coat buttons are among the most troublesome Asteraceae weed species of rainfed rice. The influence of various environmental factors on seed germination and seedling emergence of these weeds was determined. Germination response of both species was greater at the warmer fluctuating temperatures (30/20 and 35/25 C) than at the colder temperatures (25/15 C). Light stimulated germination in both species; however, some seeds still germinated in the dark. Both species were moderately tolerant of salt and water stress, but Siam weed tolerated more stresses than coat buttons. At the soil surface, Siam weed and coat buttons emergence was 75 and 76%, respectively, but this declined rapidly with increasing soil depths. Neither species emerged from depths exceeding 3 cm. Seedling emergence and seedling dry matter of both species were greatly reduced with the addition of crop residue to the soil surface at rates equivalent to 4 to 6 t ha−1. The information gained in this study will be used to facilitate development of effective weed control programs.