bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of School-Based Smoking-Cessation Interventions for Self-Described Adolescent Smokers
Authors: Joffe Alain , McNeely Clea , Colantuoni Elizabeth , An Ming-Wen , Wang Weiwei , Scharfstein Daniel
Published: July 2009

OBJECTIVE: The goal was to compare the efficacy of school-based, multisession, group smoking-cessation interventions versus a single group session in increasing quit rates among adolescent smokers.

METHODS: Eight schools were assigned randomly to use 1 of 2 group smoking-cessation programs previously shown to increase quit rates among adolescents (Not on Tobacco [NOT] or Kickin' Butts). We reformatted the programs to twice-weekly 25- to 30-minute sessions delivered during lunch periods. Smoking status was assessed at end of program (EOP) and 1, 3, 6, and 12 months later. Self-reported quit status was confirmed with salivary cotinine levels.

RESULTS: A total of 407 students (56% black and 52% female; mean age: 16 years) participated. Kickin' Butts participants were no more likely to quit than control subjects. In the conservative analysis (students with missing follow-up data classified as smokers), NOT participants were 1.92 times (95% confidence interval [CI]: 1.09–3.40 times) more likely to self-report quitting at 1 month. In the Bayesian analysis (missing follow-up data imputed by using all available data), NOT participants were significantly more likely than control subjects to self-report quitting at EOP (relative risk [RR]: 1.26 [95% CI: 1.10–1.43]), 1 month (RR: 2.07 [95% CI: 1.68–2.56]), and 12 months (RR: 1.58 [95% CI: 1.22–2.04]). Cotinine-confirmed quit rates were significantly greater among NOT participants, compared with control subjects, at EOP and 1 month.

CONCLUSIONS: The reformatted NOT program had a modest effect on adolescents interested in quitting. Kickin' Butts, as reformatted for this project, did not have any effect on quit rates.
Onset of Breast and Pubic Hair Development and Menses in Urban Chinese Girls
Authors: Ma Hua-Mei , Du Min-Lian , Luo Xiao-Ping , Chen Shao-Ke , Liu Li , Chen Rui-Min , Zhu Cheng , Xiong Feng , Li Tang , Wang Wei , Liu Ge-Li ,   on behalf of the Pubertal Study Group of the Society of Pediatric Endocrinology and Genetic Disease, Chinese Medical Association
Published: July 2009

OBJECTIVES: To determine the current prevalence and mean ages of onset of pubertal characteristics in healthy urban Chinese girls.

METHODS: A cross-sectional study of sexual maturation of healthy Chinese girls was conducted in 9 representative cities of the eastern, western, southern, and northern parts and central region of China between 2003 and 2005. At examination, stages of breast and pubic hair development were rated on girls 3 through 19.83 years of age, and height and weight were also recorded. Data on menses were collected by the status quo method. Probit analysis was used to calculate the median age and 95% confidence interval (CI) for onset of breast and pubic hair development and menarche.

RESULTS: Data were analyzed for 20654 apparently healthy girls. At age 8 years, 19.57% of these girls had evidence of breast development. The median ages of onset of Tanner stages 2 and 3 for breast development were 9.20 (95% CI: 9.06–9.32) years and 10.37 (95% CI: 10.28–10.45) years, respectively. The median ages of onset of Tanner stages 2 and 3 for pubic hair development were 11.16 (95% CI: 11.03–11.29) years and 12.40 (95% CI: 12.25–12.55) years, respectively. Menses occurred at 12.27 years (95% CI: 12.16–12.39).

CONCLUSIONS: These data suggest that urban Chinese girls are actually experiencing earlier breast development than currently used norms. The up-to-date reference for normal pubertal development in urban Chinese girls needs to be established for the purpose of determining precocious puberty or pubertal delay.
Reforming Procedural Skills Training for Pediatric Residents: A Randomized, Interventional Trial
Authors: Gaies Michael G. , Morris Shaine A. , Hafler Janet P. , Graham Dionne A. , Capraro Andrew J. , Zhou Jing , Landrigan Christopher P. , Sandora Thomas J.
Published: July 2009

BACKGROUND: Pediatric housestaff are required to learn basic procedural skills and demonstrate competence during training. To our knowledge, an evidenced-based procedural skills curriculum does not exist.

OBJECTIVE: To create, implement, and evaluate a modular procedural skills curriculum for pediatric residents.

METHODS: A randomized, controlled trial was performed. Thirty-eight interns in the Boston Combined Residency Program who began their training in 2005 were enrolled and randomly assigned. Modules were created to teach residents bag-mask ventilation, venipuncture, peripheral intravenous catheter (PIV) insertion, and lumbar puncture skills. The curriculum was administered to participants in the intervention group during intern orientation. Interns in the control group learned procedural skills by usual methods. Subjects were evaluated by using a structured objective assessment on simulators immediately after the intervention and 7 months later. Success in performing live-patient procedures was self-reported by subjects. The primary outcome was successful performance of the procedure on the initial assessment. Secondary outcomes included checklist and knowledge examination scores, live-patient success, and qualitative assessment of the curriculum.

RESULTS: Participants in the intervention group performed PIV placement more successfully than controls (79% vs 35%) and scored significantly higher on the checklist for PIV placement (81% vs 61%) and lumbar puncture (77% vs 68%) at the initial assessment. There were no differences between groups at month 7, and both groups demonstrated declining skills. There were no statistically significant differences in success on live-patient procedures. Those in the intervention group scored significantly higher on knowledge examinations.

CONCLUSIONS: Participants in the intervention group were more successful performing certain simulated procedures than controls when tested immediately after receiving the curriculum but demonstrated declining skills thereafter. Future efforts must emphasize retraining, and residents must have sufficient opportunities to practice skills learned in a formal curriculum.
Probiotic Effects on Cold and Influenza-Like Symptom Incidence and Duration in Children
Authors: Leyer Gregory J. , Li Shuguang , Mubasher Mohamed E. , Reifer Cheryl , Ouwehand Arthur C.
Published: July 2009

OBJECTIVE: Probiotic consumption effects on cold and influenza-like symptom incidence and duration were evaluated in healthy children during the winter season.

METHODS: In this double-blind, placebo-controlled study, 326 eligible children (3–5 years of age) were assigned randomly to receive placebo (N = 104), Lactobacillus acidophilus NCFM (N = 110), or L acidophilus NCFM in combination with Bifidobacterium animalis subsp lactis Bi-07 (N = 112). Children were treated twice daily for 6 months.

RESULTS: Relative to the placebo group, single and combination probiotics reduced fever incidence by 53.0% (P = .0085) and 72.7% (P = .0009), coughing incidence by 41.4% (P = .027) and 62.1% (P = .005), and rhinorrhea incidence by 28.2% (P = .68) and 58.8% (P = .03), respectively. Fever, coughing, and rhinorrhea duration was decreased significantly, relative to placebo, by 32% (single strain; P = .0023) and 48% (strain combination; P < .001). Antibiotic use incidence was reduced, relative to placebo, by 68.4% (single strain; P = .0002) and 84.2% (strain combination; P < .0001). Subjects receiving probiotic products had significant reductions in days absent from group child care, by 31.8% (single strain; P = .002) and 27.7% (strain combination; P < .001), compared with subjects receiving placebo treatment.

CONCLUSION: Daily dietary probiotic supplementation for 6 months was a safe effective way to reduce fever, rhinorrhea, and cough incidence and duration and antibiotic prescription incidence, as well as the number of missed school days attributable to illness, for children 3 to 5 years of age.
Acquired Microcephaly: Causes, Patterns, Motor and IQ Effects, and Associated Growth Changes
Authors: Baxter Peter Stuart , Rigby Alan Steven , Rotsaert Marianne Hélène Elise Pascale Dominique , Wright Ingram
Published: July 2009

OBJECTIVES: The goals were to identify and to classify causes and growth patterns of acquired (or progressive) microcephaly and to look for hypothesized correlations between causes, growth patterns, and developmental quotient/IQ.

METHODS: Fifty-one children (24 boys), 0.7 to 11.3 years of age, with early occipitofrontal circumference measurements above and later ones below the second percentile (SD: −2.03) were studied through retrospective note and growth chart review, with formal assessments of developmental quotient or IQ (n = 34).

RESULTS: Causes were classifiable into 5 groups as follows: idiopathic, familial, syndromic, symptomatic, and mixed. Four patterns of head growth were identified, as follows: type A, initial decrease from the normal range to below the second percentile, followed by growth below and parallel to the second percentile; type B, continued decrease away from the second percentile; type C, decrease below the normal range, with partial later recovery; type D, insufficient data. For 12 children, there were accompanying decreases in weight percentiles and for 5 of these in height percentiles as well. Infants with lower head circumference z scores at the end of the study also had lower z scores for final weight and final length. There was no correlation between causal group and growth pattern. Developmental quotient/IQ values were mostly <100 and did not correlate with head circumference z score, cause, or pattern.

CONCLUSIONS: The classification of causal groups and growth patterns should aid clinical management. Neither cause nor pattern predicted outcomes. The associations with poor weight gain and body growth deserve further study.
Meta-Analysis of Neurobehavioral Outcomes in Very Preterm and/or Very Low Birth Weight Children
Authors: Aarnoudse-Moens Cornelieke Sandrine Hanan , Weisglas-Kuperus Nynke , van Goudoever Johannes Bernard , Oosterlaan Jaap
Published: July 2009

OBJECTIVE: Sequelae of academic underachievement, behavioral problems, and poor executive function (EF) have been extensively reported for very preterm (≤33 weeks' gestation) and/or very low birth weight (VLBW) (≤1500 g) children. Great variability in the published results, however, hinders the field in studying underlying dysfunctions and developing intervention strategies. We conducted a quantitative meta-analysis of studies published between 1998 and 2008 on academic achievement, behavioral functioning, and EF with the aim of providing aggregated measures of effect size for these outcome domains.

METHODS: Suitable for inclusion were 14 studies on academic achievement, 9 studies on behavioral problems, and 12 studies on EF, which compared a total of 4125 very preterm and/or VLBW children with 3197 term-born controls. Combined effect sizes for the 3 outcome domains were calculated in terms of Cohen's d. Q-test statistics were performed to test homogeneity among the obtained effect sizes. Pearson's correlation coefficients were calculated to examine the impact of mean birth weight and mean gestational age, as well as the influence of mean age at assessment on the effect sizes for academic achievement, behavioral problems, and EF.

RESULTS: Combined effect sizes show that very preterm and/or VLBW children score 0.60 SD lower on mathematics tests, 0.48 SD on reading tests, and 0.76 SD on spelling tests than term-born peers. Of all behavioral problems stacked, attention problems were most pronounced in very preterm and/or VLBW children, with teacher and parent ratings being 0.43 to 0.59 SD higher than for controls, respectively. Combined effect sizes for parent and teacher ratings of internalizing behavior problems were small (<0.28) and for externalizing behavior problems negligible (<0.09) and not significant. Combined effect sizes for EF revealed a decrement of 0.57 SD for verbal fluency, 0.36 SD for working memory, and 0.49 SD for cognitive flexibility in comparison to controls. Mean age at assessment was not correlated with the strength of the effect sizes. Mathematics and reading performance, parent ratings of internalizing problems, teacher ratings of externalizing behavior, and attention problems, showed strong and positive correlations with mean birth weight and mean gestational age (all r values > 0.51).

CONCLUSIONS: Very preterm and/or VLBW children have moderate-to-severe deficits in academic achievement, attention problems, and internalizing behavioral problems and poor EF, which are adverse outcomes that were strongly correlated to their immaturity at birth. During transition to young adulthood these children continue to lag behind term-born peers.
Incidence of Gastrointestinal Symptoms in Children With Autism: A Population-Based Study
Authors: Ibrahim Samar H. , Voigt Robert G. , Katusic Slavica K. , Weaver Amy L. , Barbaresi William J.
Published: July 2009

OBJECTIVE: To determine whether children with autism have an increased incidence of gastrointestinal symptoms compared with matched control subjects in a population-based sample.

DESIGN/METHODS: In a previous study including all of the residents of Olmsted County, Minnesota, aged <21 years between 1976 and 1997, we identified 124 children who fulfilled criteria on the basis of Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, for a research diagnosis of autism. Two matched control subjects were identified for each case subject. Through the Rochester Epidemiology Project, all medical diagnoses, are indexed for computerized retrieval. Gastrointestinal diagnoses before 21 years of age were grouped into 5 categories: (1) constipation; (2) diarrhea; (3) abdominal bloating, discomfort, or irritability; (4) gastroesophageal reflux or vomiting; and (5) feeding issues or food selectivity. The cumulative incidence of each category was calculated by using the Kaplan-Meier method. Cox proportional hazards models were fit to estimate the risk ratios (case subjects versus control subjects) and corresponding 95% confidence intervals.

RESULTS: Subjects were followed to median ages of 18.2 (case subjects) and 18.7 (control subjects) years. Significant differences between autism case and control subjects were identified in the cumulative incidence of constipation (33.9% vs 17.6%) and feeding issues/food selectivity (24.5% vs 16.1). No significant associations were found between autism case status and overall incidence of gastrointestinal symptoms or any other gastrointestinal symptom category.

CONCLUSIONS: As constipation and feeding issues/food selectivity often have a behavioral etiology, data suggest that a neurobehavioral rather than a primary organic gastrointestinal etiology may account for the higher incidence of these gastrointestinal symptoms in children with autism.
Insulin Resistance and Oxidative Stress in Children Born Small and Large for Gestational Age
Authors: Chiavaroli Valentina , Giannini Cosimo , D'Adamo Ebe , de Giorgis Tommaso , Chiarelli Francesco , Mohn Angelika
Published: July 2009

OBJECTIVE: Our aim was to evaluate the effect of BW and obesity on oxidative stress and IR in prepubertal SGA and LGA children compared with appropriate-for-gestational-age (AGA) children.

METHODS: We performed a cross-sectional study comparing oxidative stress and IR in 103 children categorized into 6 groups according to BW (26 SGA, 15 AGA, and 16 LGA normal-weight children) and obesity (15 SGA, 15 AGA, and 16 LGA obese children). Indexes of IR (HOMA-IR, G/I) and the marker of oxidative stress (urinary isoprostanes) were evaluated.

RESULTS: Homeostasis Model Assessment was higher in both normal-weight SGA and LGA children than in normal-weight AGA children (all P ≤ .02). Furthermore, a difference was detected between obese SGA and obese LGA subjects compared with normal-weight SGA (all P ≤ .0007) and LGA (all P ≤ .01) children, respectively. The G/I ratio was lower in the 3 obese groups than normal-weight AGA (all P ≤ .009) and normal-weight SGA children (all P ≤ .02). Furthermore, a difference was detected between obese SGA and obese LGA children compared with normal-weight LGA children (all P ≤ .0002). Isoprostane levels were higher in both normal-weight SGA and LGA children than in normal-weight AGA children (all P ≤ .002). Moreover, both obese SGA and LGA children showed higher levels than obese AGA children (all P ≤ .01) and in comparison to the 3 normal-weight groups (all P ≤ .04).

CONCLUSION: Increased IR and oxidative stress are already present in prepubertal normal-weight SGA and LGA children with a continuous alteration in relation to obesity, suggesting that BW and adiposity represent 2 independent risk factors for degenerative diseases.
Erythropoietin Improved Neurologic Outcomes in Newborns With Hypoxic-Ischemic Encephalopathy
Authors: Zhu Changlian , Kang Wenqing , Xu Falin , Cheng Xiuyong , Zhang Zhan , Jia Liting , Ji Ling , Guo Xiaoyan , Xiong Hong , Simbruner George , Blomgren Klas , Wang Xiaoyang
Published: July 2009

OBJECTIVE: The purpose of this study was to evaluate the efficacy and safety of erythropoietin in neonatal hypoxic-ischemic encephalopathy (HIE), by using a randomized, prospective study design.

METHODS: A total of 167 term infants with moderate/severe HIE were assigned randomly to receive either erythropoietin (N = 83) or conventional treatment (N = 84). Recombinant human erythropoietin, at either 300 U/kg (N = 52) or 500 U/kg (N = 31), was administered every other day for 2 weeks, starting <48 hours after birth. The primary outcome was death or disability. Neurodevelopmental outcomes were assessed at 18 months of age.

RESULTS: Complete outcome data were available for 153 infants. Nine patients dropped out during treatment, and 5 patients were lost to follow-up monitoring. Death or moderate/severe disability occurred for 35 (43.8%) of 80 infants in the control group and 18 (24.6%) of 73 infants in the erythropoietin group (P = .017) at 18 months. The primary outcomes were not different between the 2 erythropoietin doses. Subgroup analyses indicated that erythropoietin improved long-term outcomes only for infants with moderate HIE (P = .001) and not those with severe HIE (P = .227). No negative hematopoietic side effects were observed.

CONCLUSION: Repeated, low-dose, recombinant human erythropoietin treatment reduced the risk of disability for infants with moderate HIE, without apparent side effects.
Pedestrian Safety
Authors:   Committee on Injury, Violence, and Poison Prevention
Published: July 2009

This Policy Statement was reaffirmed August 2013 and May 2019.

Each year, approximately 900 pediatric pedestrians younger than 19 years are killed. In addition, 51000 children are injured as pedestrians, and 5300 of them are hospitalized because of their injuries. Parents should be warned that young children often do not have the cognitive, perceptual, and behavioral abilities to negotiate traffic independently. Parents should also be informed about the danger of vehicle back-over injuries to toddlers playing in driveways. Because posttraumatic stress syndrome commonly follows even minor pedestrian injury, pediatricians should screen and refer for this condition as necessary. The American Academy of Pediatrics supports community- and school-based strategies that minimize a child's exposure to traffic, especially to high-speed, high-volume traffic. Furthermore, the American Academy of Pediatrics supports governmental and industry action that would lead to improvements in vehicle design, driver manuals, driver education, and data collection for the purpose of reducing pediatric pedestrian injury.
Forgoing Medically Provided Nutrition and Hydration in Children
Authors: Diekema Douglas S. , Botkin Jeffrey R. ,   Committee on Bioethics
Published: July 2009

This Clinical Report was reaffirmed January 2014 and June 2024.

There is broad consensus that withholding or withdrawing medical interventions is morally permissible when requested by competent patients or, in the case of patients without decision-making capacity, when the interventions no longer confer a benefit to the patient or when the burdens associated with the interventions outweigh the benefits received. The withdrawal or withholding of measures such as attempted resuscitation, ventilators, and critical care medications is common in the terminal care of adults and children. In the case of adults, a consensus has emerged in law and ethics that the medical administration of fluid and nutrition is not fundamentally different from other medical interventions such as use of ventilators; therefore, it can be forgone or withdrawn when a competent adult or legally authorized surrogate requests withdrawal or when the intervention no longer provides a net benefit to the patient. In pediatrics, forgoing or withdrawing medically administered fluids and nutrition has been more controversial because of the inability of children to make autonomous decisions and the emotional power of feeding as a basic element of the care of children. This statement reviews the medical, ethical, and legal issues relevant to the withholding or withdrawing of medically provided fluids and nutrition in children. The American Academy of Pediatrics concludes that the withdrawal of medically administered fluids and nutrition for pediatric patients is ethically acceptable in limited circumstances. Ethics consultation is strongly recommended when particularly difficult or controversial decisions are being considered.
Learning Disabilities, Dyslexia, and Vision
Authors:   American Academy of Pediatrics, Section on Ophthalmology, Council on Children with Disabilities,   American Academy of Ophthalmology,   American Association for Pediatric Ophthalmology and Strabismus,   American Association of Certified Orthoptists
Published: July 2009

Learning disabilities, including reading disabilities, are commonly diagnosed in children. Their etiologies are multifactorial, reflecting genetic influences and dysfunction of brain systems. Learning disabilities are complex problems that require complex solutions. Early recognition and referral to qualified educational professionals for evidence-based evaluations and treatments seem necessary to achieve the best possible outcome. Most experts believe that dyslexia is a language-based disorder. Vision problems can interfere with the process of learning; however, vision problems are not the cause of primary dyslexia or learning disabilities. Scientific evidence does not support the efficacy of eye exercises, behavioral vision therapy, or special tinted filters or lenses for improving the long-term educational performance in these complex pediatric neurocognitive conditions. Diagnostic and treatment approaches that lack scientific evidence of efficacy, including eye exercises, behavioral vision therapy, or special tinted filters or lenses, are not endorsed and should not be recommended.
Aerosol infection of calves with Histophilus somni
Authors: Jánosi Katalin , Stipkovits László , Glávits Róbert , Molnár Tamás , Makrai László , Gyuranecz Miklós , Varga János , Fodor László
Published: July 2009

The purpose of this study was to develop and evaluate an aerosol infection method withHistophilus somnithat closely resembles the natural way of infection of calves. Another aim was to compare the virulence of twoH. somnistrains by collecting clinical and postmortem data of experimentally infected and control animals. Seventeen conventionally reared 3-month-old calves were divided into three groups. Two groups of six animals each were exposed to suspensions containingH. somnion three consecutive days using a vaporiser mask. The third group of five animals was used as control. The data of individual clinical examination were recorded daily. All animals were exterminated, and gross pathology of all lungs was evaluated on the 15th day after the first infection. BothH. somnistrains caused an increase of rectal temperature, respiratory signs, decrease of weight gain, and severe catarrhal bronchopneumonia in both infected groups. Although some chronic lesions were detected in the lungs of the control animals as well, the histopathological findings in the infected and control groups were different.H. somniwas recultured from all lungs in the challenged groups but it could not be reisolated or detected by PCR examination in the control group. This is the first paper on aerosol challenge of calves withH. somniusing repeated infection and verified by detailed pathological, bacteriological and histopathological examination. The infection method proved to be successful. There was no difference in the virulence of the twoH. somnistrains used in the trial.
First report of the simultaneous occurrence of choroid plexus papilloma and meningioma in a dog
Authors: Espino Luciano , Suarez Maruska , Santamarina German , Vila Mónica , Miño Natalia , Lopez-Peña Mónica
Published: July 2009

A 7-year-old spayed female English Cocker Spaniel was examined because of a 1-week history of lethargy, stumbling over objects and circling, and the presence of two tonic-clonic generalised seizures two days before presentation. The neurological signs suggested a lesion involving the right forebrain. Computed tomography revealed the presence of two intracranial masses, one located inside the right lateral ventricle and the other located in the right frontal lobe attached to the falx cerebri. Because of the poor prognosis, the owner refused to continue with the therapy and the dog was euthanised. On postmortem examination one mass was diagnosed histologically as a meningioma and the other as a papilloma of the choroid plexus. Information in the veterinary literature on multiple malignancies affecting the central nervous system is very limited. To the best of the authors’ knowledge, the association of meningioma and choroid plexus papilloma has never been reported either in the human or in the veterinary medical literature.
Effects of surface charging treatment on outer and inner surfaces of a nanoporous carbon
Authors: Lu Weiyi , Han Aijie , Kim Taewan , Lim Hyuck , Qiao Yu
Published: July 2009

As the outer surface of a nanoporous carbon is treated with 16-mercaptohexadecanoic acid, the carbon particles can form a stable suspension in water. When the water phase is compressed, the liquid infiltration behavior in the nanopores becomes significantly different from that of untreated material, suggesting that the inner surface is also modified. After the treatment, the infiltration pressure does not decrease. Therefore, the surface-chain configurations at the inner and outer surfaces must be different, which explains the variations in infiltration pressure and volume.
Microstructural properties and formation mechanisms of GaN nanorods grown on Al2O3 (0001) substrates
Authors: Lee Kyu H. , Lee Jeong Y. , Kwon Y.H. , Kang Tae W. , Kim Dong H. , Lee D.U. , Kim Taewhan
Published: July 2009

X-ray diffraction patterns, scanning electron microscopy images, and transmission electron microscopy images showed that one-dimensional GaN nanorods with [0001]-oriented single-crystalline wurtzite structures were grown on Al2O3 (0001) substrates by hydride vapor-phase epitaxy without a catalyst. The tip morphology of the GaN nanorods became flat with increasing temperature difference between the gas mixing and the substrate zones. The gas mixing temperature significantly affected the formation of the nanorods, and the substrate temperature influenced the morphology and the strain of the GaN nanorods near the GaN/Al2O3 heterointerface. The strain and the stress existing in the GaN layer near the heterointerface were decreased with increasing growth rate. The formation mechanisms of the GaN nanorods grown on the Al2O3 (0001) substrates are described on the basis of the experimental results.
The location and effects of Si in (Ti1–xSix)Ny thin films
Authors: Flink Axel , Beckers Manfred , Sjölén Jacob , Larsson Tommy , Braun Slawomir , Karlsson Lennart , Hultman Lars
Published: July 2009

(Ti1–xSix)Ny (0 ≤ x ≤ 0.20; 0.99 ≤ y(x) ≤ 1.13) thin films deposited by arc evaporation have been investigated by analytical transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and nanoindentation. Films with x ≤ 0.09 are single-phase cubic (Ti,Si)N solid solutions with a dense columnar microstructure. Films with x > 0.09 have a featherlike microstructure consisting of cubic TiN:Si nanocrystallite bundles separated by metastable SiNz with coherent-to-semicoherent interfaces and a dislocation density of as much as 1014 cm−2 is present. The films exhibit retained composition and hardness between 31 and 42 GPa in annealing experiments to 1000 °C due to segregation of SiNz to the grain boundaries. During annealing at 1100–1200 °C, this tissue phase thickens and transforms to amorphous SiNz. At the same time, Si and N diffuse out of the films via the grain boundaries and TiN recrystallize.
Electropulsing-induced phase transformations in a Zn–Al-based alloy
Authors: Zhu Yaohua , To Sandy , Lee Wing B. , Liu Xingming , Jiang Yanbin , Tang Guoyi
Published: July 2009

Microstructural changes and phase transformations of an electropulsing-treated (EPT) ZA22 alloy wire were studied using scanning electron microscopy and transmission electron-microscopy techniques. Two stages of phase transformation were detected in the EPT alloy: (i) quenching from the as furnace-cooled (FC) state to the final stable state and (ii) up-quenching from the final stable state back to the as FC state through two reverse phase transformations: T′ + η → α + ε and η′T + ε + α → η′FC. Electropulsing accelerated phase transformation tremendously. It was at least 1200 times faster than the aging process. The mechanism of the electropulsing-induced phase transformations is discussed from the point of view of Gibbs free energy and electropulsing kinetics.
Preparation and visible-light photocatalyst activity of nanometric-sized TiO2-xNy powders from a two-microemulsion process
Authors: Yang Wein-Duo , Lin Wen-Chung , Yang Chunhui , Chung Zen-Ja , Huang I-Lun
Published: July 2009

Nanometric-sized nitrogen-doped titanium oxide (TiO2-xNy) powders were synthesized by the two-microemulsion technology. The dried precursor precipitate was characterized by differential thermal analysis/thermogravimetric analysis, Raman spectroscopy, transmission electron microscopy, Brunauer-Emmet-Teller, and x-ray photoelectron spectrometer (XPS), and the mechanisms for the evolution of TiO2-xNy powders in this process were proposed and discussed in the context of the microstructure. It shows that a higher pH value solution results in obtaining a small size and much more homogeneous TiO2-xNy powder after calcinations. The powder prepared from a solution of pH 10–11 and calcined at 500 °C has a particle size of ∼4–6 nm with a specific surface area of 160 m2/g and exhibits a pure phase of anatase containing ∼5 mol% of N evidenced by XPS. However, the nanometric-sized TiO2-xNy powder shows the photocatalytic degradation of methylene blue solution effectively by exposing the powders in aqueous solution under visible light.
Experimental investigation and thermodynamic calculation in the Ag–Bi–Ni and Cu–Bi–Ni systems
Authors: Gao Feng , Wang Cuiping , Liu X.J. , Takaku Yoshikazu , Ohnuma I. , Ishida Kiyohito
Published: July 2009

The phase equilibria at 300, 400, 500, and 600 °C in the Ag–Bi–Ni system and 300, 400, and 500 °C in the Cu–Bi–Ni system were experimentally determined by metallography and electron probe microanalysis on equilibrated alloys and diffusion couples. Differential scanning calorimetry was used to measure the temperatures of phase transformations. All the experimental results show that the solubilities of the ternary elements of the binary intermetallic compounds in the Ag–Bi–Ni system are limited. However, the binary intermetallic compounds have some solubilities of the ternary elements in the Cu–Bi–Ni system. No ternary intermetallic compound was found in the Ag–Bi–Ni and Cu–Bi–Ni systems. On the basis of the determined results, the phase equilibria in the Ag–Bi–Ni and Cu–Bi–Ni systems were thermodynamically assessed, and reasonable agreement between the calculated results and experimental data was obtained.
Free-volume dependent pressure sensitivity of Zr-based bulk metallic glass
Authors: Dubach Alban , Eswar Prasad K. , Raghavan Rejin , Löffler Jorg F. , Michler Johann , Ramamurty Upadrasta
Published: July 2009

Instrumented indentation experiments on a Zr-based bulk metallic glass (BMG) in as-cast, shot-peened and structurally relaxed conditions were conducted to examine the dependence of plastic deformation on its structural state. Results show significant differences in hardness, H, with structural relaxation increasing it and shot peening markedly reducing it, and slightly changed morphology of shear bands around the indents. This effect is in contrast to uniaxial compressive yield strength, σy, which remains invariant with the change in the structural state of the alloys investigated. The plastic constraint factor, C = H/σy, of the relaxed BMG increases compared with that of the as-cast glass, indicating enhanced pressure sensitivity upon annealing. In contrast, C of the shot-peened layer was found to be similar to that observed in crystalline metals, indicating that severe plastic deformation could eliminate pressure sensitivity. Microscopic origins for this result, in terms of shear transformation zones and free volume, are discussed.
Morphological evolution of calcium apatites from nanorods to hollow spheres mediated by acetic acid
Authors: Hui Junfeng , Fan Daidi
Published: July 2009

Hydroxyapatite (HAp) and brushite (DCPD) are two important compounds of the calcium apatite family with excellent bioactivity and osteoconductive properties in vivo. This work aimed to investigate the stability of HAp nanorods synthesized by the hydrothermal method in acetic acid aqueous solution. The results illuminated that HAp nanorods were converted into hollow nanospheres, and it was found that the concentration and amount of the acetic acid and the reaction time significantly affected the degree of the morphological evolution. Transmission electron microscope, high-resolution transmission electron microscope, and x-ray diffraction were performed for characterizing the samples.
Surface stability and electronic structure of hydrogen- and fluorine-terminated diamond surfaces: A first-principles investigation
Authors: Sen Fatih G. , Qi Yue , Alpas Ahmet T.
Published: July 2009

The effect of fluorine termination on the stability and bonding structure of diamond (111) surfaces were studied using first-principles calculations and compared with hydrogen termination by creating mixed F- and H-containing diamond surfaces. Surface F atoms, similar to H, formed sp3-type bonding with C atoms, which resulted in a more stable 1 × 1 configuration. The surface phase diagram built showed that the F-terminated surface was more stable in a larger-phase space than H termination, because of the formation of strong ionic C–F bonds and the development of attractive forces between F atoms, resulting in close packing of large F atoms. Hence, the F-terminated diamond surface was more chemically inert. A large repulsive force was required to bring two F-terminated surfaces together, because of the negative charge on F atoms, resulting in reduced adhesion tendency between two F-terminated diamond surfaces compared with H-terminated surfaces.
Phase configuration, nanostructure, and mechanical behaviors in Ti-B-C-N thin films
Authors: Lu Yonghao , Wang Junping , Shen Yaogen , Sun Dongbai
Published: July 2009

A series of Ti-B-C-N thin films were deposited on Si (100) at 500 °C by incorporation of different amounts of N into Ti-B-C using reactive unbalanced dc magnetron sputtering in an Ar-N2 gas mixture. The effect of N content on phase configuration, nanostructure evolution, and mechanical behaviors was studied by x-ray diffraction, x-ray photoelectron spectroscopy, Raman spectroscopy, high-resolution transmission electron microscopy, and microindentation. It was found that the pure Ti-B-C was two-phased quasi-amorphous thin films comprising TiCx and TiB2. Incorporation of a small amount of N not only dissolved into TiCx but also promoted growth of TiCx nano-grains. As a result, nanocomposite thin films of nanocrystalline (nc-) TiCx(Ny) (x + y < 1) embedded into amorphous (a-) TiB2 were observed until nitrogen fully filled all carbon vacancy lattice (at that time x + y = 1). Additional increase of N content promoted formation of a-BN at the cost of TiB2, which produced nanocomposite thin films of nc-Ti(Cx,N1-x) embedded into a-(TiB2, BN). Formation of BN also decreased nanocrystalline size. Both microhardness and elastic modulus values were increased with an increase of N content and got their maximums at nanocomposite thin films consisting of nc-Ti(Cx,N1-x) and a-TiB2. Both values were decreased after formation of BN. Residual compressive stress value was successively decreased with an increase of N content. Enhancement of hardness was attributed to formation of nanocomposite structure and solid solution hardening.
Preparation and enhancement of second-order nonlinearity of hybrid PMMA/SiO2 glass with Sb2S3 nanocrystals
Authors: Liu Qiming , Zhou Wei , Lu Xinmiao , Hu Ting , Zhao Xiujian
Published: July 2009

Bulk hybrid polymethyl methacrylate (PMMA)/SiO2 glass with Sb2S3 nanocrystals was prepared by the sol-gel process. We tried to minimize the quantity of water as much as possible in tetraethyl orthosilicate (TEOS) hydrolyzing, prepolymerized the organic monomers, mixed inorganic precursors, and prepolymerized organic monomers under a noncosolvent condition to reduce possible volume shrinkage. A silane coupling agent, which hydrolyzed simultaneously with TEOS, was introduced into the system to improve the miscibility of the organic and inorganic materials. The maximum dopant of Sb2S3 was 9 wt% in our experiments. The second-harmonic generation was observed in the hybrid PMMA/SiO2 glasses with electron-beam poling. Second-harmonic intensity increased with increase of accelerating voltage, current, and the content of Sb2S3 nanocrystals. The maximum χ2 in our study, as large as 1.64 p.m./V, was obtained under the optimized poling condition conducted at 25 kV, 20 nA, and 10 min. It was indicated from the thermally stimulated depolarization current measurements that the nonlinear layer was located in the thin 10-μm irradiated surface of the glass.
Fabrication and characterization of novel bicrystalline ZnO nanowires
Authors: Zhuang Huizhao , Wang Dexiao , Shen Jiabing , Xue Chengshan , Zhang Xiaokai , Liu Hang
Published: July 2009

Two types of novel bicrystalline ZnO nanowires have been synthesized by a thermal evaporation method. The morphology and microstructure of the nanowires have been extensively investigated. One type of the nanowires has agg twin boundary extending down its entire length with twinning plane and the zone axis. The other type is those nanowires with twin crystal-single crystal junction. The twin defects in the Sn-Zn alloy droplets in the initial growth process are proposed for interpreting the growth of these two kinds of bicrystalline nanowires.
Formation mechanism of Sn-patch between SnAgCu solder and Ti/Ni(V)/Cu under bump metallization
Authors: Wang Kai-Jheng , Tsai Yan-Zuo , Duh Jenq-Gong , Shih Toung-Yi
Published: July 2009

An Sn-patch formed in Ni(V)-based under bump metallization during reflow and aging. To elucidate the evolution of the Sn-patch, the detailed compositions and microstructure in Sn–Ag–Cu and Ti/Ni(V)/Cu joints were analyzed by a field emission electron probe microanalyzer (EPMA) and transmission electron microscope (TEM), respectively. There existed a concentration redistribution in the Sn-patch, and its microstructure also varied with aging. The Sn-patch consisted of crystalline Ni and an amorphous Sn-rich phase after reflow, whereas V2Sn3 formed with amorphous an Sn-rich phase during aging. A possible formation mechanism of the Sn-patch was proposed.
Preparation and characterization of polypyrrole/TiO2 nanocomposite and its photocatalytic activity under visible light irradiation
Authors: Li Shengying , Chen Mingkai , He Lijun , Xu Fei , Zhao Guohu
Published: July 2009

A simple and convenient method for preparing visible light response photocatalyst polypyrrole/TiO2 (PPy/TiO2) nanocomposite was developed. The products were characterized by x-ray diffraction, transmission electron microscopy, atomic force microscopy, ultraviolet-visible, and Fourier transform infrared techniques. The results indicated that the nanohybrid was composed of anatase TiO2 and PPy and exhibited an enhanced visible light-capturing ability. Average diameters of TiO2 and PPy/TiO2 were 18 and 35 nm, respectively. The photocatalytic activity of the nanocomposite was evaluated by the degradation of methyl orange under visible light irradiation. In the presence of PPy/TiO2 nanocomposite, the degradation efficiency of methyl orange of 95.54% could be obtained under visible light irradiation within 120 min. The apparent rate constant was 2.19 × 10−2, which was better than that Degussa P25 nano-TiO2. The sensitization mechanism of PPy/TiO2 photocatalyst was discussed briefly.
Luminescent properties of Y2O3:Eu3+ nanophosphor prepared from urea added precursor using flame spray pyrolysis
Authors: Seok Lee Jae , Kim Se Jin , Kim Tae Kon , Singh Rajiv K. , Ranade Madhav B.
Published: July 2009

Y2O3:Eu3+ nanophosphor was synthesized by flame spray pyrolysis (FSP) from urea added nitrate based liquid precursor. In this study, urea serves as fuel and subsequently provides additional heat in the flame zone during the synthesis of phosphor particles. The end product shows cubic phase Y2O3:Eu3+ nanophosphor successfully prepared by FSP without heat treatment. The influence of synthesis conditions such as different mol of urea and nitrate source materials in aqueous solution, and doping concentration on luminescent properties, were investigated. The characteristics of nanophosphor such as crystallinity and morphology under various experiments of conditions were carried out by x-ray diffraction (XRD) and field emission-scanning electron microscopy (FE-SEM). The particle size of product was found to be in the range of 20–30 nm from transmission electron microscopy (TEM). In photoluminescence (PL) properties, Y2O3:Eu3+ nanophosphor emitted red light with a peak wavelength of 609 nm when excited with 398 nm wavelength photons.
Epitaxial CoSi2 formation using an oxynitride buffer layer
Authors: Lee Jaesang , Lee Keunwoo , Kim Dongock , Park Taeyong , Kim Honggyu , Jeon Hyeongtag
Published: July 2009

We investigated the epitaxial growth of CoSi2 (100) on an Si (100) substrate using a modified oxide mediated epitaxy (OME) method to overcome the disadvantages of the OME method. These disadvantages are sensitivity of Co films to contamination by oxygen and the need for reiterating the film growth process to obtain thicker films. To solve these problems, nitrogen atoms were incorporated into chemically grown oxide (SiOx) by NH3 plasma treatment prior to the deposition of a Co film on the oxynitride buffer layer using the metal organic chemical vapor deposition (MOCVD) method. Subsequently, ex situ rapid thermal annealing was performed to grow Co-silicide at a temperature between 400 °C and 700 °C for 1 min. The results show that the diffusion of Co was effectively controlled by the oxynitride buffer layer without the formation of additional SiOx in between Co and Si. Our findings indicate that by using an oxynitride buffer layer, CoSi2 films can be grown epitaxially despite the fact that the initial Co film was exposed to oxygen.
Rapid synthesis of bulk Ti2AlC by self-propagating high temperature combustion synthesis with a pseudo–hot isostatic pressing process
Authors: Bai Yuelei , He Xiaodong , Li Yibin , Zhu Chuncheng , Zhang Sam
Published: July 2009

In this study, the dense polycrystalline Ti2AlC was synthesized by self-propagating high-temperature combustion synthesis with the pseudo–hot isostatic pressing process (SHS/PHIP). The resultant phase purity is highly dependent on the mol ratio of raw powders. The Ti2AlC was densified by applying pressure after the SHS reaction. The resultant sample mainly contains typical plate-like nonstoichiometric Ti2AlCx (x = 0.69) with grain size of ∼6 µm. The sample shows the Vickers hardness of 5.5 GPa, highest flexural strength of 431 MPa, compressive strength of 1033 MPa, and fracture toughness of 6.5 MPa·m1/2. No indentation cracks in Ti2AlCx were observed, indicative of a damage material nature. The reaction mechanism for the formation of SHS/PHIP-derived Ti2AlC is also discussed based on differential thermal analysis and x-ray diffraction results.
Dehydrogenation/rehydrogenation mechanism in aluminum destabilized lithium borohydride
Authors: Yu Xuebin , Xia Guanglin , Guo Zaiping , Liu Huakun
Published: July 2009

LiBH4/Al mixtures with various mol ratios were prepared by ball milling. The hydrogen storage properties of the mixtures were evaluated by differential scanning calorimetry/thermogravimetry analyses coupled with mass spectrometry measurements. The phase compositions and chemical state of elements for the LiBH4/Al mixtures before and after hydrogen desorption and absorption reactions were assessed via powder x-ray diffraction, infrared spectroscopy, and x-ray photoelectron spectroscopy. Dehydrogenation results revealed that LiBH4could react with Al to form AlB2and AlLi compounds with a two-step decomposition, resulting in improved dehydrogenation. The rehydrogenation experiments were investigated at 600 °C with various H2pressure. It was found that intermediate hydride was formed firstly at a low H2pressure of 30 atm, while LiBH4could be reformed completely after increasing the pressure to 100 atm. Absorption/desorption cycle results showed that the dehydrogenation temperature increased and the hydrogen capacity degraded with the increase of cycle numbers.
Preparation and characterization of conducting nylon 6 fibers
Authors: Saritha Chandran A. , Narayanankutty Sunil K.
Published: July 2009

Conducting nylon 6 fibers were prepared by in situ polymerization of aniline on to the fiber surface, after providing a chemical etching treatment to the fibers using chromic acid. The properties of the etched and polyaniline (PANI) coated fibers were evaluated using scanning electron microscopy, x-ray photoelectron spectroscopy, infrared spectroscopy, x-ray diffraction, thermogravimetry, and differential scanning calorimetry. Though the etching process caused a marginal decline in the mechanical properties of the fiber, it provided a reasonably rough surface for PANI adhesion and enhanced the conductivity of the fiber. The conductivity increased from 4.22 × 10−2 to 3.72 × 10−1 S/cm at an etching time of 4 h.