bluuebunny/crossref_metadata_2025 huggingface dataset:
Immersion Scald Burns and the Ability of Young Children to Climb Into a Bathtub
Authors: Allasio David , Fischer Howard
Published: May 2005

Introduction. Immersion scald burns in children are often suspicious for neglect or abuse. The history that a child climbed into a tub previously filled with hot water by the parent is common. The child's ability to climb into such a tub is a major factor in determining the reliability of the history.

Methods. A standard bathtub was installed in an examination room at a pediatric clinic in a children's hospital. Foam mats were placed in and outside of the tub. Toy boats were placed in the back of the tub. Children were selected if they were between 10 and 18 months of age, born at term, and had no past or present medical condition that could be expected to have affected their fine or gross motor or central nervous system development and had a normal Denver Developmental Screening Test within the past 3 months. The parent placed the child in a standing position with the child holding onto the front of the tub. Parents encouraged the child to climb into the tub and get the toys. The child's efforts were videotaped. Children were allowed 5 minutes to climb, depending on their attention span and tolerance.

Results. Of 176 children in the study, 62 (35%) climbed into the tub. One fourth climbed in head first, and the rest climbed in sideways.

Conclusions. Our study may have underestimated children's climbing abilities because of the absence of a shower curtain to help with balance and the distracting presence of strangers. The diagnosis of abuse is in part based on a described mechanism being inconsistent with the observed pattern of injury. This has severe repercussions for the child and his or her family. Our study brings into question previously held beliefs that these injuries could only be sustained by direct immersion.
Influence of Gender, Race, and Ethnicity on Suspected Fatty Liver in Obese Adolescents
Authors: Schwimmer Jeffrey B. , McGreal Nancy , Deutsch Reena , Finegold Milton J. , Lavine Joel E.
Published: May 2005

Objectives. Fatty liver is a common cause of liver disease in children. However, the epidemiology of pediatric fatty liver is limited to single-center case series of nonalcoholic fatty liver disease (NAFLD). Obesity and insulin resistance are major established risk factors for NAFLD. The role of gender, race, and ethnicity on the prevalence of fatty liver in obese children is unknown.

Methods. We recruited obese 12th-grade participants from the Child and Adolescent Trial for Cardiovascular Health in California, Louisiana, Minnesota, and Texas. Serum samples were collected at school when the participants were well. Alanine aminotransferase (ALT) was measured by kinetic enzymatic assay, and ALT >40 U/L was defined as abnormal. Causes of abnormal ALT other than NAFLD were excluded by serum testing.

Results. A total of 127 obese students (73 female, 54 male) had a mean BMI of 35.2 kg/m2. Unexplained ALT elevation was present in 23% of participants overall. The mean ALT for participants with normal values was 28 U/L and for participants with an abnormal ALT was 56 U/L. Abnormal ALT was significantly more prevalent in boys (44%) than in girls (7%). The prevalence of abnormal ALT differed significantly by race and ethnicity (Hispanic: 36%; white: 22%; black: 14%). Serum ALT value was significantly predicted by the combination of gender, race/ethnicity, and BMI. After controlling for gender and BMI, Hispanic ethnicity significantly predicted greater ALT than black race.

Conclusions. In a national, school-based sample of obese adolescents, boys were 6 times more likely than girls to have an unexplained elevated ALT. Given that participants were well and causes of chronic liver disease were excluded, we speculate that obese adolescent boys have an increased prevalence of fatty liver compared with obese adolescent girls. This population-based study also supports the hypothesis that NAFLD is more common in Hispanic adolescents. These findings have implications for both disease screening and studies of fatty liver pathophysiology.
An Evaluation of the Motion Picture Association of America’s Treatment of Violence in PG-, PG-13–, and R-Rated Films
Authors: Jenkins Lucille , Webb Theresa , Browne Nick , Afifi A.A. , Kraus Jess
Published: May 2005

Objective. The purpose of this study was to determine whether the Motion Picture Association of America’s ratings system distinguishes among the 3 primary rating categories (PG, PG-13, and R) with respect to violence based on a study of the 100 top-grossing films of 1994.

Methods. The Motion Picture Association of America assigns age-based ratings for every film that is released in the United States accompanied by the reasons for the rating. A data abstraction instrument was designed to code each act of violence within the sample of 100 films. A series of Poisson regression models were used to examine the association among rating, seriousness of violence, and primary reason for the rating assignment.

Results. The total average number of violent acts within each film by rating category increased from PG (14) to PG-13 (20) to R (32). However, using results from the Poisson models, it is clear that the rating does not predict the frequency of violence in films. For all 3 rating categories, the predicted number of violent acts is almost identical for films with violence as a primary descriptor and films with the highest level of seriousness (R = 62.4 acts, PG-13 = 55.2 acts, and PG = 56.1 acts). The regression analysis shows that the rating does not predict the frequency of violence that occurs in films.

Conclusions. Frequency of violence alone is not the most important criterion for the assignment of rating. The content descriptors and average seriousness of films are better measures of the violence than rating assignment.
Assessment of Perinatal Hepatitis B and Rubella Prevention in New Hampshire Delivery Hospitals
Authors: Bascom Susan , Miller Stephanie , Greenblatt Jesse
Published: May 2005

Objective. To evaluate current performance on recommended perinatal hepatitis B and rubella prevention practices in New Hampshire.

Methods. Data were extracted from 2021 paired mother-infant records for the year 2000 birth cohort in New Hampshire's 25 delivery hospitals. Assessment was done on the following: prenatal screening for hepatitis B and rubella, administration of the hepatitis B vaccine birth dose to all infants, administration of hepatitis B immune globulin to infants who were born to hepatitis B surface antigen-positive mothers, rubella immunity, and administration of in-hospital postpartum rubella vaccine to rubella nonimmune women.

Results. Prenatal screening rates for hepatitis B (98.8%) and rubella (99.4%) were high. Hepatitis B vaccine birth dose was administered to 76.2% of all infants. All infants who were born to hepatitis B surface antigen-positive mothers also received hepatitis B immune globulin. Multivariate logistic regression showed that the month of delivery and infant birth weight were independent predictors of hepatitis B vaccination. The proportion of infants who were vaccinated in January and February 2000 (48.5% and 67.5%, respectively) was less than any other months, whereas the proportion who were vaccinated in December 2000 (88.2%) was the highest. Women who were born between 1971 and 1975 had the highest rate of rubella nonimmunity (9.5%). In-hospital postpartum rubella vaccine administration was documented for 75.6% of nonimmune women.

Conclusion. This study documents good compliance in New Hampshire's birthing hospitals with national guidelines for perinatal hepatitis B and rubella prevention and highlights potential areas for improvement.
Affect and Sexual Behavior in Adolescents: A Review of the Literature and Comparison of Momentary Sampling With Diary and Retrospective Self-Report Methods of Measurement
Authors: Shrier Lydia A. , Shih Mei-Chiung , Beardslee William R.
Published: May 2005

Objective. Assessment of mental health is important in understanding sexual risk behavior in adolescents, yet few studies have examined how affect is directly related to sexual behavior. Momentary sampling (MS) methods permit real-time assessment of affect in relation to specific events and embed the collected data in the context of the respondent's moment-to-moment life. The objectives of this study were to review the literature on affect and sexual behavior and to compare the feasibility and acceptability of MS with diaries and retrospective self-report as a means of collecting temporally relevant data on affect and sexual behavior in adolescents.

Methods. Sexually active, nondepressed adolescent outpatients who were aged 15 to 18 years were randomly assigned to a schedule of the 3 methods of data collection for 2 weeks each. All participants completed a retrospective self-report by interview at the end of each 2-week period. In the diary arm, participants completed twice-daily paper-and-pencil diary cards, which were returned by mail. In the MS arm, participants used 2-way pagers to respond to several random pages per day. Primary outcomes included rates of completion (diaries vs MS reports) and the participants' tolerance of and preferences for the methods. A secondary outcome was the agreement in means for positive and negative affect and in report of days on which substance use and sexual activity occurred. Associations of affect with contextual factors and with sexual activity were also explored in the MS arm.

Results. Ten youths completed 30 of 30 retrospective self-reports (100%, 3 per participant, by design), 254 of 280 diaries (91%; mean: 25.4 per participant), and 442 of 600 MS reports (74%; mean: 44.2 per participant). Most participants preferred the MS method to the diaries or retrospective self-report. Affect scores and reports of sexual activity and substance use were correlated among the methods. Measured with MS, affect was found to differ by location, companionship, and thoughts when paged; notably, positive affect was highest when participants reported thoughts about sex. There was no difference in affect before versus after coitus.

Conclusions. The results of this study suggest that MS in adolescents is feasible and preferred and provides contextual, temporally relevant, event-level data on affect and sexual activity that are not readily measured with traditional methods. Future research using MS methods will be important in increasing our understanding of the link between affect and sexual behavior and inform the development of improved risk reduction interventions for adolescents.
Comparison of Parent and Child Reports of Emotional Trauma Symptoms in Pediatric Outpatient Settings
Authors: Shemesh Eyal , Newcorn Jeffrey H. , Rockmore Lori , Shneider Benjamin L. , Emre Sukru , Gelb Bruce D. , Rapaport Robert , Noone Sally A. , Annunziato Rachel , Schmeidler James , Yehuda Rachel
Published: May 2005

Objective. Exposure to emotionally traumatic events is common among children who are treated in pediatric medical care settings, and it is important to recognize the emotional reactions that children might develop as a response to the trauma. Practitioners sometimes rely on parental reports of the child's emotional reactions, but these reports may be biased by the parent's own posttraumatic symptoms. Understanding the differences between parent and child reports of the child's emotional symptoms is essential to guide proper diagnosis and care. This study evaluated discrepancies in parental versus child reports of the child's emotional trauma symptoms in pediatric medical care settings.

Methods. We enrolled children and adolescents (age: 8–19) who had not previously received a diagnosis of a psychiatric disorder and were treated in pediatric specialty care clinics at Mount Sinai Medical Center in New York. We used the UCLA posttraumatic stress reaction index, child, adolescent, and parent versions, to evaluate child and parent reports of symptoms of posttraumatic stress disorder (PTSD) in the child. The Impact of Event Scale was used to evaluate the parents' own posttraumatic symptoms. We conducted a “best estimate” psychiatric diagnostic procedure to determine whether the child met diagnostic criteria for PTSD and evaluated the association between the diagnostic status (as determined by the “best estimate” procedure) and the results of the questionnaires.

Results. A total of 115 patients and parents consented to the study, and 76 completed the evaluation. Sixty-four percent of the parents identified the child's traumatic experience as their own most traumatic experience, too. The child's self-report of PTSD symptoms was significantly correlated with the diagnosis of PTSD in the child. In contrast, parents' reports of their child's PTSD symptoms were not significantly associated with the child's diagnosis. Parents' own posttraumatic symptoms were associated with parental reports of the child's overall PTSD symptoms (correlation coefficient: 0.283).

Conclusions. When a child is emotionally traumatized, the parent's own posttraumatic stress may influence his or her report and interpretation of the child's symptoms. Clinicians who evaluate children and adolescents for PTSD in medical care settings should directly seek the child's report and should not rely exclusively on parental reports. Parental reports of a child's PTSD symptoms can offer insights into the parent's own level of posttraumatic stress.
Early-Onset Group B Streptococcal Disease in the Era of Maternal Screening
Authors: Puopolo Karen M. , Madoff Lawrence C. , Eichenwald Eric C.
Published: May 2005

Background. With the widespread implementation of intrapartum antibiotic prophylaxis (IAP), the rate of early-onset neonatal sepsis and meningitis caused by Streptococcus agalactiae (group B streptococcus [GBS]) has decreased dramatically, especially in term infants. However, cases of GBS disease continue to occur despite IAP and incur significant morbidity and mortality. Inaccurate screening results, improper implementation of IAP, or antibiotic failure all may contribute to persistent disease.

Objective. To determine if clinical, procedural, or microbiologic factors influenced persistent early-onset GBS disease (EOGBS) cases in a single large maternity service after the institution of a screening-based protocol for IAP.

Methods. Retrospective review of all cases of culture-proven EOGBS at the Brigham and Women's Hospital (Boston, MA) from 1997 to 2003. Serotyping and surface protein analyses were performed on available disease isolates.

Results. A total of 67260 infants were live-born during this period. Twenty-five cases of EOGBS (0.37 of 1000 live births) were identified. The overall incidence of EOGBS progressively decreased with different approaches to IAP. Of the 25 cases identified after institution of a screening-based protocol, 17 (68%) occurred in term infants (1 death), and 8 (32%) occurred in preterm infants (3 deaths). Among the mothers of term infants, 14 of 17 (82%) had been screened GBS negative; 1 was GBS unknown. More than half of the mothers of term infants who had screened GBS negative (8 of 14) had intrapartum risk factors for neonatal infection but did not receive antibiotics before delivery. Ten of the 17 term infants were evaluated for infection because of clinical signs of illness, and the remainder were evaluated because of intrapartum sepsis risk factors. Of the mothers of preterm infants, by the time of delivery 3 of 8 had been documented as GBS positive, 2 of 8 had been documented GBS negative, and 3 of 8 remained unknown. Only 1 of 25 women received adequate IAP, but the isolate was resistant to the administered antibiotic (clindamycin). Antibiotic resistance was not a factor in any other case, and no dominant serovariant was identified among tested isolates. Procedural errors (lack of recognition of documented GBS colonization or failure to evaluate infants at risk for sepsis) were identified in 4 cases.

Conclusions. The majority of the remaining cases of EOGBS occurred in infants whose mothers screened negative for GBS colonization. Even in the setting of a maternal GBS-screening program, efforts to evaluate and treat infants with intrapartum clinical risk factors for early-onset sepsis remain important. Until effective vaccines against GBS are available for clinical use, development and implementation of rapid and sensitive techniques for screening for GBS status and antibiotic susceptibility at presentation may help prevent additional cases of invasive GBS disease.
Cost-Effectiveness of Conjugate Meningococcal Vaccination Strategies in the United States
Authors: Shepard Colin W. , Ortega-Sanchez Ismael R. , Scott R. Douglas , Rosenstein Nancy E. ,   and the ABCs Team
Published: May 2005

Context. The US Food and Drug Administration approved a meningococcal conjugate A/C/Y/W-135 vaccine (MCV-4) for use in persons aged 11 to 55 years in January, 2005; licensure for use in younger age groups is expected in 2 to 4 years.

Objective. To evaluate and compare the projected health and economic impact of MCV-4 vaccination of US adolescents, toddlers, and infants.

Design. Cost-effectiveness analysis from a societal perspective based on data from Active Bacterial Core Surveillance (ABCs) and other published and unpublished sources. Sensitivity analyses in which key input measures were varied over plausible ranges were performed.

Setting and Patients. A hypothetical 2003 US population cohort of children 11 years of age and a 2003 US birth cohort.

Interventions. Hypothetical routine vaccination of adolescents (1 dose at 11 years of age), toddlers (1 dose at 1 year of age), and infants (3 doses at 2, 4, and 6 months of age). Each vaccination scenario was compared with a “no-vaccination” scenario.

Main Outcome Measures. Meningococcal cases and deaths prevented, cost per case prevented, cost per life-year saved, and cost per quality-adjusted life-year saved.

Results. Routine MCV-4 vaccination of US adolescents (11 years of age) would prevent 270 meningococcal cases and 36 deaths in the vaccinated cohort over 22 years, a decrease of 46% in the expected burden of disease. Before program costs are counted, adolescent vaccination would reduce direct disease costs by $18 million and decrease productivity losses by $50 million. At a cost per vaccination (average public-private price per dose plus administration fees) of $82.50, adolescent vaccination would cost society $633000 per meningococcal case prevented and $121000 per life-year saved. Key variables influencing results were disease incidence, case-fatality ratio, and cost per vaccination. The cost-effectiveness of toddler vaccination is essentially equivalent to adolescent vaccination, whereas infant vaccination would be much less cost-effective.

Conclusions. Routine MCV-4 vaccination of US children would reduce the burden of disease in vaccinated cohorts but at a relatively high net societal cost. The projected cost-effectiveness of adolescent vaccination approaches that of recently adopted childhood vaccines under conditions of above-average meningococcal disease incidence or at a lower cost per vaccination.
Synthesis and Thermal Analyses of TiO2-Derived Nanotubes Prepared by the Hydrothermal Method
Authors: Suzuki Yoshikazu , Yoshikawa Susumu
Published: May 2005

TiO2-derived nanotubes were prepared by hydrothermal treatment of TiO2 powder in NaOH aqueous solution. High-temperature x-ray diffraction (HT-XRD) andthermogravimetry-differential thermal analysis (TG-DTA) demonstrated the formation of TiO2 (B) phase (a metastable polymorph of titanium dioxide) from the nanotubes under heating at ∼800 °C, which indicates the as-prepared nanotubes should be composed of layered titanate, most probably as H2Ti3O7·nH2O (n < 3). Dehydration behavior and phase transformation confirmed by the HT-XRD study have suggested reliable reaction path and have well-solved the contradictions on the nanotube-formation mechanism among previous studies.
Doped Self-Aligned Metallization for Solar Cells
Authors: Addo Ernest A. , Shah S. Ismat , Opila Robert , Barnett Allen M. , Allison Kevin , Sulima Oleg
Published: May 2005

Metal contacts using doped self-aligning metallization to [100] and [111] p-type silicon were investigated. Contacts formed in this manner allow the formation of a pn-junction and provide front metallization for photovoltaic applications. Formulated screen-printable thick films were annealed above Ag/Si eutectic temperature of 830 °C. The annealing process resulted in a junction depth of 0.3–1.1 μm with improved Ag/Si metal contacts due to the reduction of parasitic native oxide layer via the use of a wetting agent. The technique inhibits shunts (high conductivity paths through the solar cell pn-junction caused by excessive metal penetration) due to limited solubility of Ag in Si. The technique also reduces series resistance (a parasitic resistance due to surface states that also limit solar cell performance) due to a robust thermal processing window. The use of magnesium (Mg) as a wetting agent in the thick film Ag matrix was explored. We observed a correlation between increased wetting and improved dark saturation current J02 in the absence of a pre-existing junction.
Effects of Properties and Growth Parameters of Doped and Undoped Silicon Oxide Films on Wear Behavior During Chemical Mechanical Planarization Process
Authors: Sikder A.K. , Kumar Ashok , Thagella S. , Yota Jiro
Published: May 2005

Understanding the tribological, mechanical, and structural properties of an inorganic and organic dielectric layer in the chemical mechanical planarization (CMP) process is crucial for successful evaluation and implementation of these materials with copper metallization. Polishing behaviors of different carbon- and fluorine-doped silicon dioxide (SiO2) low dielectric constant materials in CMP process are discussed in this paper. Films were deposited using both chemical vapor deposition and spin-on method. Carbon and fluorine incorporation in the Si–O network weaken the mechanical integrity of the structure and behave differently in slurry selective to SiO2 films. Mechanical properties of the films were measured using depth-sensing nanoindentation technique, and it was found that undoped SiO2 film has the highest and spin-on carbon-doped oxide films have the lowest hardness and modulus values. Wear behavior of the doped SiO2 is studied in a typical SiO2 CMP environment, and results are analyzed and compared with those of the undoped SiO2 films. Coefficient of friction and acoustic emission signals have significant effect on the polishing behavior. Surface of the films are investigated before and after polishing using atomic force microscopy. Roughness and section analysis of the films after polishing show the variation in wear mechanism. Validation of Preston’s equation is discussed in this study. Additionally, different wear mechanisms are presented, and a two body abrasion model is proposed for the softer films.
Electronic Superstructures Observed by Scanning Tunneling Microscopy on Graphene Sheet in Vicinity of Nano-Defects of Ir(111) Substrate
Authors: Waqar Z. , Makarenko I.V. , Titkov A.N. , Gall N.R. , Rutkov E.V. , Tontegode A.Ya. , Dumas Ph.
Published: May 2005

Two-dimensional electronic and atomic superstructures (SS) on monolayer graphite (graphene) grown on a clean Ir(111) surface were observed near substrate nano-defect sites by scanning tunneling microscopy. These SS were found rotated 30° with respect to the undistorted areas (away from defects sites) of the graphene layer with a periodicity of and a(a = 2.46 Å)decay over a distance of few nanometers away from the defects. The observed SS were not due to real surface reconstruction, rather they just had an electronic nature.
Transmission Electron Microscopy and X-ray Diffraction Investigation of the Microstructure of Nanoscale Multilayer TiAlN/VN Grown by Unbalanced Magnetron Deposition
Authors: Luo Q. , Lewis D.B. , Hovsepian P.Eh. , Münz W-D.
Published: May 2005

Cubic NaCl-B1 structured multilayer TiAlN/VN with a bi-layer thickness of approximately 3 nm and atomic ratios of (Ti+Al)/V = 0.98 to 1.15 and Ti/V = 0.55 to 0.61 were deposited by unbalanced magnetron sputtering at substrate bias voltages between -75 and -150 V. In this paper, detailed transmission electron microscopy and x-ray diffraction revealed pronounced microstructure changes depending on the bias. At the bias -75 V, TiAlN/VN followed a layer growth model led by a strong (110) texture to form a T-type structure in the Thornton structure model of thin films, which resulted in a rough growth front, dense columnar structure with inter-column voids, and low compressive stress of -3.8 GPa. At higher biases, the coatings showed a typical Type-II structure following the strain energy growth model, characterized by the columnar structure, void-free column boundaries, smooth surface, a predominant (111) texture, and high residual stresses between -8 and -11.5 GPa.
Spherical Nanoindentations and Kink Bands in Ti3SiC2
Authors: Murugaiah A. , Barsoum M.W. , Kalidindi S.R. , Zhen T.
Published: May 2005

We report for the first time on load versus depth-of-indentation response of Ti3SiC2 surfaces loaded with a 13.5 μm spherical tipped diamond indenter up to loads of 500 mN. Using orientation imaging microscopy, two groups of crystals were identified; one in which the basal planes were parallel to, and the other normal to, the surface. When the load-penetration depth curves were converted to stress-strain curves the following was apparent: when the surfaces were loaded normal to the c axis, the response at the lowest loads was linear elastic—well described by a modulus of 320 GPa—followed by a clear yield point at approximately 4.5 GPa. And while the first cycle was slightly open, the next 4 on the same location were significantly harder, almost indistinguishable, and fully reversible. At the highest loads (500 mN) pop-ins due to delaminations between basal planes were observed. When pop-ins were not observed the indentations, for the most part, left no trace. When the load was applied parallel to the c axis, the initial response was again linear elastic (modulus of 320 GPa) followed by a yield point of approximately 4 GPa. Here again significant hardening was observed between the first and subsequent cycles. Each cycle resulted in some strain, but no concomitant increase in yield points. This orientation was even more damage tolerant than the orthogonal direction. This response was attributed to the formation of incipient kink bands that lead to the formation of regular kink bands. Remarkably, these dislocation-based mechanisms allow repeated loading of Ti3SiC2 without damage, while dissipating significant amounts of energy per unit volume, Wd, during each cycle. The values of Wd measured herein were in excellent agreement with corresponding measurements in simple compression tests reported earlier, confirming that the same mechanisms continue to operate even at the high (≈9 GPa) stress levels typical of the indentation experiments.
Etching of Zirconium Oxide, Hafnium Oxide, and Hafnium Silicates in Dilute Hydrofluoric Acid Solutions
Authors: Lowalekar Viral , Raghavan Srini
Published: May 2005

Oxides and silicates of zirconium and hafnium are actively being considered and tested to replace SiO2 as the gate material. Though these materials have the high-dielectric constant (k ∼ 20–25) needed to provide a larger equivalent oxide thickness, they are very refractory and difficult to etch by wet and dry methods. In this paper, work done on wet etching of ZrO2, HfO2, and HfSixOy in dilute hydrofluoric acid (HF) solutions is presented and discussed. Experiments were done on various high-k films deposited by metalorganic chemical vapor deposition. It was found that the as-deposited high-k films can be dissolved with a good selectivity over SiO2 in dilute HF solutions, but heat-treated high-k films are difficult to etch with good selectivity over SiO2 under the same conditions.
Degradation of AlN Powder in Aqueous Environments
Authors: Krnel Kristoffer , Dražič Goran , Kosmač Tomaž
Published: May 2005

The reactivity of AlN powder in an aqueous environment was studied by measuring the pH and the temperature during the hydrolysis of the powder at room and elevated temperatures. The influences of the powder concentration and the starting pH of the slurry were also investigated. The results of the measurements at room temperature show that there is an incubation time before the start of the AlN hydrolysis reactions. Once this incubation time is over, the pH and the temperature of the slurry start to increase, indicating the onset of the reactions. A higher starting temperature not only speeds up the reaction of the AlN powder with water, but it also shortens the incubation time. In addition, the starting temperature influences the morphology of the reaction product: at temperatures below 60 °C, the final product of the hydrolysis is crystalline Al(OH)3, whereas at higher temperatures (above 60 °C), crystalline AlOOH is formed. At very low pH values (pH = 1), the reaction of AlN powder with water is prevented (i.e., the incubation time is very long), whereas in an alkaline environment, the incubation time is approximately the same as in distilled water, but the reaction is accelerated.
Thermodynamic Evaluation of the Interface Stability Between Selected Metal Oxides and Co
Authors: Yang Ying , Ladwig Peter F. , Chang Y. Austin , Liu Feng , Pant Bharat. B. , Schultz Allan E.
Published: May 2005

For an interface to be considered thermodynamically stable, the phases in contact must be in equilibrium with each other (connected by a stable tie-line) and have negligible mutual solubility on the phase diagram. The stability of Co based magnetic tunnel junctions (MTJs), with Co/MxO1-x/Co structures (M = Al, Gd, Hf, La, Mg, Si, Ti, Ta, Y and Zr), were evaluated with regard to these two conditions. Specifically, low temperature ternary isothermal phase diagrams were calculated and evaluated for the Co–M–O systems. All of these systems have at least one oxide in equilibrium with Co and thus have at least one thermodynamically stable tunnel barrier candidate for use in Co based MTJs. In light of the assumptions made in this analysis, along with the uncertainty in applying bulk enthalpy data to thin films, the current evaluation of interfacial stability serves as a first step in identifying suitable stable tunneling barrier materials in MTJs for detailed study.
Micro-Indentation of Aluminum Processed by Equal Channel Angular Extrusion
Authors: Yang Fuqian , Peng Lingling , Okazaki Kenji
Published: May 2005

The near-surface deformation of equal-channel angular extruded (ECAE) pure aluminum was investigated using the micro-indentation technique. Compared with fully annealed Al samples, there is a distinguishable difference in the indentation deformation. The unloading slope of the ECAE deformed Al after a short unloading period was found to be less than that of the annealed samples due to plastic recovery. Work hardening was observed, which depended on the history of local deformation. A new relationship between the plastic energy dissipated in the indentation and the applied load was derived, which is supported by the experimental results.
Redox and Electrocatalytic Activity of Ni Ion-Implanted Ti
Authors: Pham M.T. , Maitz M.F. , Reuther H. , Richter E. , Matz W. , Muecklich A. , Shevchenko N. , Prokert F.
Published: May 2005

Ni-Ti surface alloy was prepared by ion-implanting Ni into Ti. The surface film was amorphous having a Ni surface content of 10–40 at.%. The material was compared with a Ni-Ti bulk alloy (44.08:55.9) regarding their redox and electrocatalytic behavior in NaOH by cyclic voltammetry. The surface was characterized by x-ray photoelectron spectroscopy, x-ray and electron diffraction, transmission electron microscopy, and atomic force microscopy. The ion-implanted material revealed an enhanced activity toward the redox conversion of Ni(OH)2 ↔ NiOOH and the anodic oxidation of glucose. The effect is discussed considering the enhanced generation of active Ni surface sites from amorphous Ni and the stabilization of higher valence Ni by Ti.
Paper 1: “Cement as a Thermoelectric Material,” [J. Mater. Res. 15, 2844-2848 (2000)] And Paper 2: “Rectifying and Thermocouple Junctions Based on Portland Cement,” J. Mater. Res. 16, 1989-1993 (2001)]
Authors: Wen Sihai , Chung D.D.L.
Published: May 2005

In the two papers listed above, the conversion of the Seebeck coefficient (relative to copper) to the absolute thermoelectric power was done by using the wrong sign of the absolute thermoelectric power of copper (2.34 μV/°C). The corrected tables are shown below for both papers. The correction means that plain cement paste is slightly p-type rather than slightly n-type. In addition, it means that cement pastes with carbon fibers are more p-type and those with steel fibers are less n-type than reported. Note in Table III of Paper 2 that all cement pastes are p-type except for paste (ii). Note in Table IV of Paper 2 that all cement junctions are pn-junctions (rather than some being nn+-junctions).
Atomic structures of nonequilibrium alloys in an immiscible Co–Ag system
Authors: Guo H.B. , Liu B.X.
Published: May 2005

A Co–Ag potential in the form of TB-SMA (the second moment approximation of the tight-binding scheme) is derived based on some ab initio calculated physical properties. Applying the derived potential, molecular dynamics simulations reveal that a Co-/Ag-based solid solution retains its atomic homogeneity up to a critical ratio of9 Ag/12 Co at.%, over which the Ag/Co solute atoms begin to segregate. Correspondingly, a cage-like configuration is proposed to have 1 Ag/Co atom isotropically surrounded by 9 Co/7 Ag atoms for the homogeneous solid solution. Moreover, when the solute atoms exceed 12 Ag/18 Co at.%, the solid solution turns into an amorphous phase with inhomogeneous atomic structure.
Tree-like Ag nanostructures based on monolithic mesoporous silica
Authors: Kan Caixia , Cai Weiping , Hofmeister Herbert
Published: May 2005

A novel tree-like nanostructured Ag crystal, with stems, branches, and leaves, has been synthesized by pre-forming Au seeds, soaking, and annealing, based on monolithic mesoporous silica. The obtained Ag nanotrees are of single-crystal nature and statistically symmetrical in geometry. Further experiments revealed that the interconnected channels of the porous silica, heating at low temperature, and the pre-formed Au seeds are crucial to form such structure. Its formation can be attributed to the low nucleation rate and preferentially unidirectional diffusion of Ag atoms to the Au seeds along interconnected channels. This nanostructured material is of great potential to be building blocks for assembling some mini-functional devices of the next generation. The current study is also of importance in studying the diffusion mechanism of single-crystal formation, and especially in improving our understanding of the underlying physical structure of both natural and synthetic porous materials.
Fe-based bulk metallic glasses with diameter thickness larger than one centimeter
Authors: Ponnambalam V. , Poon S. Joseph , Shiflet Gary J.
Published: May 2005

Fe–Cr–Mo–(Y,Ln)–C–B bulk metallic glasses (Ln are lanthanides) with maximum diameter thicknesses reaching 12 mm have been obtained by casting. The high glass formability is attained despite a low reduced glass transition temperature of 0.58. The inclusion of Y/Ln is motivated by the idea that elements with large atomic sizes can destabilize the competing crystalline phase, enabling the amorphous phase to be formed. It is found that the role of Y/Ln as a fluxing agent is relatively small in terms of glass formability enhancement. The obtained bulk metallic glasses are non-ferromagnetic and exhibit high elastic moduli of approximately 180–200 GPa and microhardness of approximately 13 GPa.
Synthesis of Al2O3/AlN composite powders by plasma processed Al2O3with various additives
Authors: Boey F.Y.C. , Zhao X.L. , Tok A.I.Y.
Published: May 2005

A novel method was developed to produce Al2O3/AlN composite powders. The composite powders were synthesized by the direct nitridation of Al2O3using various additives by plasma processed with two different types of gas (Ar/N2and N2plasma). The effects of these two different plasma gases and additives on the formation of the Al2O3/AlN composites were studied. The x-ray diffraction results in the composite powders showed that the cubic AlN was converted to the major phase while transient γ–Al2O3was the minor phase when the composite powder was fully melted using nitrogen as the sole working gas. In contrast, the main phase was still α–Al2O3when the composite powder was not well melted using the mixture of argon and nitrogen as the working gas. Carbon was found as an effective conversion additive to increase the cubic AlN of this composite powder up to 49 vol%. The reaction mechanism of forming this composite powder was also analyzed.
Growth of cubic boron nitride films on tungsten carbide substrates by direct current jet plasma chemical vapor deposition
Authors: Yu J. , Matsumoto S.
Published: May 2005

Cubic boron nitride (cBN) film was deposited on Co-containing WC substrates by dc jet plasma chemical vapor deposition from an Ar–N2–BF3–H2 gas system. The formation of cobalt nitrides was observed at interface, and the hindrance of Co on cBN growth was demonstrated. Growth temperature and etching treatment of the substrate before deposition influenced the cBN growth greatly. At 1050 °C, cBN films were obtained on etched substrates but not on unetched substrates. At 1090 °C, cBN films were not obtained even on etched substrates. At 960 °C, cBN films deposited even on unetched substrate but the films always peeled off after exposing to air. The film quality of cBN deposited at 960 °C is better than that deposited at 1050 °C.
Effects of heat-treatment on the spectroscopic and electrochemical properties of a mixed manganese/vanadium oxide film prepared by electrodeposition
Authors: Nakayama Masaharu , Tanaka Akihiro , Konishi Sayaka , Ogura Kotaro
Published: May 2005

Thin films of mixed manganese (mainly 4+) and vanadium (5+) oxides deposited electrochemically on a platinum substrate have been heat-treated under vacuum at various temperatures between 25 and 400 °C. Electron spin resonance and x-ray photoelectron spectroscopy revealed that the reductive formation of Mn2+ occurs at 300 °C only in the presence of vanadium within the film. This phenomenon can be regarded as a result of electron transfer from V4+ ions generated thermally to neighboring Mn sites. Voltammetric response of the heat-treated Mn/V oxide film in borate solution was enhanced with increasing the number of potential cycles, and the steady-state current was much larger than that of pure manganese oxide. Vanadate ions were diffused from the film to maintain the charge balance during the repetition cycles. The resultant porous structure can allow easier mass transport of protons to electrically conductive Mn oxide surface, offering the improved charge–discharge performance of the electrode.
Changes in structures and electrical conduction mechanisms of chemical vapor deposited Ta2O5 thin films by annealing under O3 atmosphere with ultraviolet light radiation
Authors: Eom Dail , Jeon In Sang , No Sang Yong , Hwang Cheol Seong , Kim Hyeong Joon
Published: May 2005

The electrical conduction mechanisms of approximately 8-nm-thick Ta2O5 films grown by metalorganic chemical vapor deposition were investigated by measuring the current density–voltage characteristics at various temperatures. The Ta2O5 films were grown in two steps with or without intermittent annealing at 450 °C under an O3 atmosphere with ultraviolet light radiation (UV-O3 treatment). High-resolution transmission electron microscopy of the films after post-deposition annealing at 750 °C under an O2 atmosphere showed that the intermittent UV-O3 treatment improved the crystallization of the film during post-annealing. Auger electron spectroscopy of the variously treated samples showed that the improvement in crystallization was due to the increase in the oxygen concentration of the Ta2O5 films by the UV-O3 treatment. The Ta2O5 film without the UV-O3 treatment mostly exhibited a Poole–Frenkel conduction behavior with the electron trap level of 0.62 eV from the conduction band edge. The whole layer UV-O3 treated Ta2O5 films also showed a Poole–Frenkel conduction behavior with an almost identical electron trap level and a reduced density. The partially UV-O3 treated Ta2O5 films exhibited a direct tunneling behavior in a relatively low voltage region by the tunneling through the thin (∼3.8 nm) UV-O3 treated surface layer. However, these films showed a Poole–Frenkel conduction behavior in the high-voltage region. In general, the UV-O3 treatment was an efficient method to reduce the leakage current of the high-dielectric Ta2O5 films.
Factors inducing degradation of properties after long-term oxidation of Si3N4–MoSi2electroconductive composites
Authors: Medri V. , Bellosi A.
Published: May 2005

The effects of heat treatments on strength and electrical conductivity after 100 h in air up to 1500 °C were evaluated on hot-pressed Si3N4–35 vol% MoSi2composite. The long-term oxidation involves microstructural changes at the material surface and subsurface, such as the formation of oxide scales and of a multilayered microstructure. AtT⩾ 1200 °C, a glassy silicate phase is formed, which embeds cristobalite grains and highly textured Y2Si2O7crystals. At the same time, MoSi2, assisted by oxygen, reacts with Si3N4forming Mo5Si3, Si2N2O, and SiO2. The decrease of the room temperature flexural strength reached about 25% in the samples exposed at 1000 °C for 100 h, compared to the as-produced materials. On the contrary, after treatments at higher temperatures, the strength decrease is lower at 1500 °C, the residual strength is 836 ± 62 MPa with a strength decrease of about 8%. The surface oxide scale is an insulator and, consequently, the electrical resistivity of the composite rises from 10-3to 107–109Ωcm.
Etching to obtain atomically flat 6H–SiC (000-1) surface after annealing in nitrogen ambient
Authors: Harada Masashi , Nagano Takayuki , Shibata Noriyoshi
Published: May 2005

The etching process of the 6H–SiC(000-1) surface was investigated to obtain a flat surface by removing scratches due to polishing. An atomically flat surface with a step-terrace structure without scratches has been obtained by removing the graphite layer grown on the substrate after annealing in N2 at a temperature of 1900 °C for 6 h. The step height corresponds to that of a 6H–SiC unit cell. In contrast, a rough surface was observed on the Si face, 6H–SiC (0001), using the same process as for the C face.
Thermal analysis and optical transition of Yb3+, Er3+ co-doped lead–germanium–tellurite glasses
Authors: Yang Zhongmin , Xu Shiqing , Yang Jianhu , Hu Lili , Jiang Zhonghong
Published: May 2005

In this article, we present a study of a new glass system: lead–germanium–tellurite glasses in the form of 0.05K2O–0.1ZnO–0.1BaO–0.2PbO–xGeO2–(0.55 - x)TeO2 with x = 0.1, 0.2, 0.3, 0.4, 0.5, and 0.55. Differential temperature analysis of this glass system shows that increasing GeO2 content raises the glass transition temperature (Tg) and suppresses the crystallization tendency in a large temperature range from Tg to the glass melting temperature. The maximum vibrational frequency is intermediate between germanate and fluoride glasses, in the range of 750 cm−1 to 820 cm−1. Subsequently, Optical absorption, photoluminescence, and upconversion fluorescence were measured for Yb3+, Er3+ co-doped lead–tellurium–germanate glasses. It was found that the full width at half-maximum of the fluorescence spectrum at 1534 nm decreases and the measured radiative lifetime increases with the replacement of TeO2 by GeO2. Excitation at 976 nm into the glass system leads to an intense green emission and a relatively weak red emission. With the addition of GeO2, the increase of red fluorescence and the decrease of green emission in intensity are due to the increase of nonradiative transition rates between the 4S3/2 and 4F9/2 states of Er3+ ions. The quadratic dependence of the green and red emissions on excitation power indicates that two-photon absorption process occurs in this glass system excited at 976 nm.
Energy dissipated during spherical indentation
Authors: Malzbender Jürgen
Published: May 2005

A relationship is derived for spherical indentation relating the dissipated energy to the ratio of hardness to elastic modulus and the ratio of indentation depth to radius. The result agrees with recent findings obtained on the basis of scaling relationships in combination with finite element simulations. Furthermore, relationships are given for hardness, elastic modulus and contact area, which permit a determination of these properties independent of the strain hardening characteristics and independent of pileup and sink-in.
Effects of substrate on determination of hardness of thin films by nanoscratch and nanoindentation techniques
Authors: Tayebi Noureddine , Polycarpou Andreas A. , Conry Thomas F.
Published: May 2005

A comparative study on the effects of the substrate on the determination of hardness of thin films by the use of the nanoscratch and nanoindentation techniques was conducted. Gold films deposited on fused quartz substrates and silicon dioxide films deposited on aluminum substrates with variant film thicknesses were investigated. These two systems correspond to a soft film on a hard substrate and a hard film on a soft substrate, respectively. The effect of substrate interaction on the measurement of hardness using the nanoscratch technique was found to be less pronounced compared to that of the nanoindentation technique due to: (i) the lower normal loads applied to achieve the penetration depths that occur at higher loads when using the nanoindentation method; (ii) the direct imaging of the residual deformation profile that is used in the nanoscratch technique, which allows for the effects of pileup or sink-in to be taken into account, whereas in the nanoindentation technique the contact area is estimated from the load-displacement data, which does not include such effects; and (iii) the account of elastic recovery of the plastically deformed surfaces from scratch tests. The film thickness did not appear to have any effect on the hardness of Au and SiO2 films obtained from nanoscratch data. This observation allowed, for the case of SiO2 films, the determination of the “free substrate effect region” and the derivation of an empirical relationship that relates the composite hardness of the film/substrate system to the contact-depth-to-film-thickness ratio, even when the indenter penetrates into the substrate. Such findings can allow for the determination of the intrinsic hardness of ultrathin hard films (∼1–5 nm thick), where the substrate effect is unavoidable.
Temperature-dependent ferroelectric properties of (Pb0.75La0.25)TiO3 thin films
Authors: Zhang S.T. , Li J.P. , Chen Y.F. , Liu Z.G. , Ming N.B.
Published: May 2005

Polycrystalline (Pb0.75La0.25)TiO3 (PLT25) thin films have been fabricated on Pt/Ti/SiO2/Si substrates by pulsed laser deposition. The room-temperature structures and dielectric properties are studied by x-ray diffraction, scanning electron microscopy, and HP4294A impedance/phase analyzer. The temperature-dependent ferroelectric properties are systematically investigated by using a RT66A ferroelectric tester combined with a temperature-controllable vacuum chamber. For well-saturated hysteresis loops, with the temperature decrease from 295 to 97 K, the coercive field (Ec) and remanent polarization (Pr) increase and the saturated polarization (Ps) is almost temperature-independent. However, this is not the case for the unsaturated hysteresis loops. Temperature-dependent fatigue-resistance of the PLT25 films is also experimentally established: after 2.22 × 109 switching cycles, the nonvolatile polarizationdecreases 38% when measured at room-temperature and it decreases 15% at 97 K. The nature and population of point defects and their effects on the subtle variations of the Ec, Ps, Pr, and fatigue-resistance against temperature are discussed in detail.