bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Characteristics of a Magnetically Levitated Impeller in a Centrifugal Blood Pump
Authors: Asama Junichi , Shinshi Tadahiko , Hoshi Hideo , Takatani Setsuo , Shimokohbe Akira
Published: April 2007

Abstract:  Centrifugal blood pumps that employ hybrid active/passive magnetic bearings to support noncontact impellers have been developed in order to reduce bearing wear, pump size, the power consumption of the active magnetic bearing, and blood trauma. However, estimates made at the design stage of the vibration of the impeller in the direction of passive suspension during pump operation were inaccurate, because the influence of both the pumping fluid and the rotation of the impeller on the dynamic characteristics was not fully recognized. The purpose of this study is to investigate the dynamic characteristics in a fluid of a magnetically levitated rotating impeller by measuring both the frequency response to sinusoidal excitation of the housing over a wide frequency range and the displacement due to input of a pulsatile flow during left ventricular (LV) assist. The excitation tests were conducted under conditions in which the impeller was levitated in either air or water, and with or without rotation. The experimental and analytical results indicate that vibration of the impeller due to the external force in water was decreased, compared with that in air due to the hydraulic force of water. The axial resonant frequency rose quadratically with rotational speed, and the tilt mode had two resonant frequencies while rotating due to the gyroscopic effect. With the pump inserted into a mock systemic circulatory loop, the dynamic stability of the impeller when pulsatile pressure was applied during LV assist was verified experimentally. The amplitudes of vibration in response to the pulsatile flow in the passively constrained directions were considerably smaller in size than the dimensions of initial gaps between the impeller and the pump housing.
A Nonsurgical Technique for Blood Access in Extracorporeal Affinity Adsorption of Antibodies in Rats
Authors: Mårtensson Linda , Nilsson Rune , Sjögren Hans‐Olov , Strand Sven‐Erik , Tennvall Jan
Published: April 2007

Abstract:  Monoclonal antibodies for targeting cytotoxic conjugates to tumor cells are currently being evaluated together with extracorporeal affinity adsorption. The aim of the adsorption was to reduce undesired side effects in normal organs and to increase the tumor‐to‐normal tissue ratios. This technique is also applicable to several other therapeutic areas such as immune‐mediated disorders, that is, autoimmunity, allergy, and transplantation rejection. We describe an improved technique for extracorporeal affinity adsorption of radiolabeled biotinylated antibodies in rats. Blood access is established through the tail artery and tail vein, without surgical insertion of permanent catheters. This technique is simple, does not require surgery, and causes only minimal stress to the animals. In addition, experiments can be carried out on several animals simultaneously. This new technique is of considerable benefit for studying extracorporeal affinity adsorption in rats, as experiments can be carried out with negligible anatomical and physiological interventions, compared to previously used techniques.
The Discovery of a New Drug Class for the Acute Treatment of Migraine
Authors: Humphrey Patrick P.A.
Published: April 2007

The history of the scientific ideas and events that led to the discovery of sumatriptan is outlined with personal reminiscences about individuals who influenced the approach. The development of sumatriptan revolutionized the acute treatment of migraine and led to the availability of a number of other triptans. The anti‐migraine effects of all the triptans are mediated via 5‐HT1B, and possibly 5‐HT1Dreceptors, which transduce their effects via G; proteins. This suggests that agonists at other Giprotein‐coupled receptor types appropriately located (eg, somatostatin sst2, adenosine A1) should be examined for their effects on the trigeminovascular system, Studies on such receptor targets may provide insight into a novel approach towards the design of new anti‐migraine drugs.
Current Trends in Migraine Prophylaxis
Authors: Ramadan Nabih M.
Published: April 2007

A variety of drugs from diverse pharmacological classes are in use for migraine prevention. Traditionally, they have been discovered by serendipity. Examples include β‐adrenergic blockers, anticonvulsants, tricyclic antidepressants, and serotonin receptor antagonists. The mechanisms of action of migraine preventive drugs are multiple but it is postulated that they converge on two targets: (1) inhibition of cortical excitation; (2) restoring nociceptive dysmodulation. The antiepileptic drugs (e.g., topiramate, valproate, gabapentin), calcium channel blockers such as verapamil, and inhibitors of cortical spreading depression are some examples of drugs that reduce neuronal hyperexcitability. On the other hand, modulators of the serotonergic and adrenergic systems and cholinergic enhancing drugs may restore descending nociceptive inhibition and play a role in migraine prevention. To date, Level 1 evidence and clinical experience favor the use of the antidepressant amitriptyline, the anticonvulsants divalproex and topiramate, and the β‐adrenergic blockers propranolol, timolol and metoprolol as first line migraine preventive drugs. The evidence for others (e.g., verapamil) is not as strong. Migraine preventive drugs have varying degrees of adverse effects, some of which could be limiting, and their efficacy should balanced with their risks of adverse effects, patients' expectations and desires, and compliance. It is hoped that future migraine preventive drugs target migraine mechanisms more specifically, which could well enhance the therapeutic index.
Once‐Daily Cefepime Versus Ceftriaxone for Nursing Home–Acquired Pneumonia
Authors: Paladino Joseph A. , Eubanks David A. , Adelman Martin H. , Schentag Jerome J.
Published: April 2007

OBJECTIVES: To compare once‐daily intramuscular cefepime with ceftriaxone controls.

DESIGN: Double‐blind study.

SETTING: Six skilled nursing facilities.

PARTICIPANTS: Residents aged 60 and older with nursing home–acquired pneumonia.

INTERVENTION: Cultures were obtained, and patients were randomized to cefepime or ceftriaxone 1 g intramuscularly every 24 hours.

MEASUREMENTS: Clinical success: cure or improvement. Cure was defined as complete resolution of all symptoms and signs of pneumonia or a return to the patient's baseline state. Improvement was defined as clear improvement but incomplete resolution of all pretherapy symptoms or signs or incomplete return to the patient's usual baseline status. Safety and pharmacoeconomics were also assessed.

RESULTS: Sixty‐nine patients were randomized; 61 were evaluable: (32 to cefepime, 29 ceftriaxone). Patients were predominately female (76%). They had a mean age±standard deviation of 85±6, with a mean 5.8±1.9 comorbidities; they had age‐appropriate renal dysfunction, with a mean estimated creatinine clearance of 35±7 mL/min. Clinical success occurred in 78% of cefepime‐ and 66% of ceftriaxone‐treated patients (P=.39). Fifty‐seven patients (93%) were switched to oral antibiotics after 3 days. Antibiotic‐related adverse events occurred in 5% of patients. Seven patients (11.5%) were hospitalized. The overall mortality rate was 8%. Mean antibiotic costs were $117±40 for cefepime‐ and $215±68 for ceftriaxone‐treated patients (P<.001). Cost‐effectiveness analysis of total costs showed that cefepime would cost $597 and ceftriaxone $1,709 per expected successfully treated patient. One‐ and two‐way sensitivity analyses using a generic price for ceftriaxone and improving its comparative efficacy revealed that the results were robust.

CONCLUSIONS: Once‐daily cefepime was a cost‐effective alternative to ceftriaxone for the treatment of elderly nursing home residents who developed pneumonia and did not require hospitalization.
Systemic Markers of Inflammation and Cognitive Decline in Old Age
Authors: Schram Miranda T. , Euser Sjoerd M. , De Craen Anton J. M. , Witteman Jacqueline C. , Frölich Marijke , Hofman Albert , Jolles Jelle , Breteler Monique M. B. , Westendorp Rudi G. J.
Published: April 2007

OBJECTIVES: To investigate whether higher circulating levels of C‐reactive protein (CRP), interleukin‐6 (IL‐6), and α1‐antichymotrypsin (ACT) are associated with worse cognitive function and decline in old age.

DESIGN: Two independent population‐based cohort studies.

SETTING: The Rotterdam Study (mean follow‐up 4.6 years) and the Leiden 85‐plus Study (maximal follow‐up 5 years).

PARTICIPANTS: Three thousand eight hundred seventy‐four individuals, mean age 72, from the Rotterdam Study, and 491 individuals, all aged 85, from the Leiden 85‐plus Study.

MEASUREMENTS: Both studies assessed global cognition, executive function, and memory. Linear regression analyses were used in the current study to investigate the associations between inflammatory markers and cognitive function and decline.

RESULTS: In the Rotterdam Study, higher levels of CRP and IL‐6 were cross‐sectionally associated with worse global cognition and executive function (P<.05). ACT was not associated with cognitive function. In the Leiden 85‐plus Study, estimates were similar for CRP, although not statistically significant. Higher IL‐6 levels were related to a steeper annual decline in memory function in the longitudinal analysis in the Leiden 85‐plus Study (P<.05). The effect of higher IL‐6 levels on global and memory function decline was stronger in apolipoprotein E (APOE) ɛ4 carriers (P‐interaction=.01) than in those who were not (P‐interaction=.05). In the Rotterdam Study, higher IL‐6 levels were related to a steeper annual decline in global cognition in APOE ɛ4 carriers only.

CONCLUSION: Systemic markers of inflammation are only moderately associated with cognitive function and decline and tend to be stronger in carriers of the APOE ɛ4 allele. Systemic markers of inflammation are not suitable for risk stratification.
Quality of Life Among Implantable Cardioverter‐Defibrillator Recipients in the Primary Prevention Therapeutic Era
Authors: GROENEVELD PETER W. , MATTA MARY A. , SUH JANICE J. , YANG FEIFEI , SHEA JUDY A.
Published: April 2007

Background: Although patients receiving implantable cardioverter‐defibrillators (ICDs) for primary prevention of sudden cardiac death are the fastest growing segment of the ICD recipient population, the quality‐of‐life (QOL) effects of the ICD among primary prevention patients are not well understood. The purpose of this study was to measure and compare the health‐related QOL among primary and secondary prevention ICD recipients, and to determine predictive factors for high or low QOL in each group.

Methods: Forty‐five primary prevention and 75 secondary prevention ICD recipients receiving routine care in electrophysiology clinics within the University of Pennsylvania Health System were assessed using several well‐validated general and ICD‐specific QOL instruments.

Results: Between primary and secondary prevention patients, there were no significant differences in EuroQol 5D (medians: 0.84 vs 0.84, P = 0.71), Health Utilities Index (medians: 0.88 vs 0.85, P = 0.95), Short Form‐12 aggregate physical summary (means: 45 vs 46, P = 0.64), and Short Form‐12 aggregate mental summary (means: 46 vs 47, P = 0.93) scores. Both primary and secondary prevention patients viewed their devices favorably according to the Florida Patient Acceptance Survey scale, with no significant differences between group means (80 vs 83, P = 0.71). However, substantial fractions of both primary and secondary prevention recipients had particular concerns about lifting (40%), sexual activity (19%), and driving (14%).

Conclusions: QOL does not significantly differ between primary prevention and secondary prevention ICD recipients. Device recipients had comparable QOL to published, nationwide QOL estimates among non‐ICD patients of similar age. The ICD was highly acceptable to most primary and secondary prevention patients.
Electromagnetic Interference from Wireless Video‐Capsule Endoscopy on Implantable Cardioverter‐Defibrillators
Authors: DUBNER SERGIO , DUBNER YAEL , RUBIO HORACIO , GOLDIN ERAN
Published: April 2007

Objectives: The purpose of this study was to evaluate potential interference between the Pill‐cam™ video‐capsule and implanted cardio‐defibrillators (ICD) in both in vitro and in vivo test environments.

Methods: Phase I consisted of in vitro testing utilized 6 ICD models. Each was placed in a saline gel bath in conjunction with a tool designed to emit the same wave length as the Pill‐Cam™ (the Test Cap). Tests were performed at both the manufacturer's nominal and most sensitive settings with the test probe placed at 1, 5, 10, and 15 cm from three different points. There were emissions of 10‐, 30‐, and 60‐ second duration at each location. Phase II was the in vivo study utilizing patients with implanted ICDs for standard clinical reasons who were undergoing evaluation with the Test Cap.

Results: In Phase I, 864 tests were performed involving the 6 ICDs. There was totally normal behavior in 5 of the devices. The Biotronik Belos (Berlin, Germany) demonstrated oversensing and delivery of inappropriate therapy. In phase II, 6 patients underwent a total number of 288 tests (48 in each patient). There were 4 men and 2 women, mean age 61 (33–77) and none demonstrated any adverse interactions.

Conclusions: In patients with devices identical to those evaluated that showed no interference, the use of the Pill‐Cam is safe. However, in patients with a Biotronik Belos ICD (or any other nontested ICD) the use of the Pill‐Cam should be done only in‐hospital, after suspended ICD therapy and in conjunction with close monitoring.
Adaptive Bi‐Atrial Pacing Improves the Maintenance of Sinus Rhythm
Authors: BACIK BRADLEY M. , MULLER DAVID , CORBISIERO RAFFAELE
Published: April 2007

Introduction: Multiple pacing modalities have been shown to individually decrease atrial fibrillation (AF) burden and relieve symptoms of AF. This investigation retrospectively evaluated whether a combination of bi‐atrial pacing with dynamic atrial overdrive (DAO) AF suppression would further decrease AF burden as compared to AF suppression (DAO) alone.

Methods and Results: A total of 33 patients were retrospectively evaluated. Patients (n = 16) were identified from the Deborah Heart and Lung Center pacemaker database with DAO programmed on at time of implantation. Patients (n = 17) were identified with bi‐atrial pacing leads in right atrium and mid to distal coronary sinus who also had DAO programmed on at the time of implant. Evaluation of interrogated pacing data revealed Percent Time in Mode Switch (18.2%± 7.2% vs 0.59%± 0.08%) to be significantly lower (P = 0.014) in the bi‐atrial paced group. In addition, there were less mode switches per day (MSPD) in the bi‐atrial paced group (0.62 ± 0.43 MSPD) versus control (4.40 ± 3.24 MSPD) (P = 0.06).

Conclusion: Bi‐atrial pacing while used in conjunction with an adaptive pacing suppression algorithm (DAO) may successfully be used to inhibit PAF.
A Nonfluoroscopic Approach for Electrophysiology and Catheter Ablation Procedures Using a Three‐Dimensional Navigation System
Authors: TUZCU VOLKAN
Published: April 2007

Background: Three‐dimensional (3D) electroanatomical navigation systems decrease the fluoroscopy time of electrophysiology and ablation procedures. The aim of this study was to assess the safety and efficacy of a complete nonfluoroscopic approach for electrophysiologic studies and right‐sided catheter ablations for supraventricular tachycardia in patients with normal cardiac anatomy using a 3D, surface electrode‐based navigation system (NavX™, St. Jude Medical, St. Paul, MN, USA).

Methods and Results: Electrophysiologic studies were performed in 26 consecutive cases (12.7 ± 7.5 years) using NavX™ without fluoroscopy. The procedure time was 98.7 ± 49.7 minutes. Nonfluoroscopic catheter ablations were performed in 24 of 28 consecutive patients. Cryoablation was used in 23 of 24. The procedure time was 193.5 ± 80 minutes. The coronary sinus access was obtained in 32.1 ± 12 (range: 15–60) seconds. No complications occurred. All patients (n = 19) who underwent cryoablation for right‐sided arrhythmia substrates with conventional fluoroscopic guidance in addition to NavX™ were used as a control group (10.1 ± 5.2 years). Catheter ablation success rate of the control group (16/19, 84%) was not significantly different compared to the patients who underwent ablation without fluoroscopy (22/24, 92%). The procedure time was also not significantly different between the two groups (P = NS).

Conclusion: This study demonstrates that nonfluoroscopic electrophysiologic studies and right‐sided catheter ablations for supraventricular tachycardia can be safely and effectively performed in the majority of patients with normal cardiac anatomy using NavX™. Further studies will be necessary in order to establish the potential utility of NavX™ in eliminating or decreasing radiation exposure for other electrophysiology procedures.
Radiofrequency Ablation of the Ventricular Tachycardia with Arrhythmogenic Right Ventricular Cardiomyopathy Using Non‐contact Mapping
Authors: YAO YAN , ZHANG SHU , HE DING SHENG , ZHANG KUIJUN , HUA WEI , CHU JIANMIN , PU JIELIN , CHEN KEPING , WANG FANGZHENG , CHEN XIN
Published: April 2007

Background: Intracardiac non‐contact mapping provides a rapid and accurate isopotential mapping that facilitates catheter ablation of the ventricular tachyarrhythmias in arrhythmogenic right ventricular cardiomyopathy (ARVC).

Methods: Thirty‐two consecutive patients (26 men and 6 women, mean 37.2 ± 13.8 years) were treated with ablation. Fourteen patients had a history of syncope/pre‐syncope. Two patients had an implantable cardiac defibrillator (ICD) previously implanted.

Results: There were 67 ventricular tachycardias (VTs) induced in the 32 patients. The average VT rate was 210 ± 32.2 (130–310) bpm. There were 42 episodes of VT that had a heart rate ≥200 bpm and 24 of the 32 patients (75%) had ≥2 morphologies of VT. Regional ablation was applied by targeting the earliest VT activation sites under the guidance of non‐contact mapping. Acute success was achieved in 84.4% (27/32) patients, and significant improvement was seen in 15.6% (5/32) patients as evidenced by a slower rate of VT. None of the patients experienced syncope/pre‐syncope or sudden death during the 28.6 ± 16 (9–72) month follow‐up. There were no complications of the procedure. At the end of follow‐up, 81.3% of the patients were free of VT without medication while the rest of the patients achieved a modified success.

Conclusions: The rapid ventricular tachyarrhythmias in ARVC patients can be abolished or improved significantly by regional RF catheter ablation under the guidance of non‐contact mapping. There was no sudden cardiac arrest or death in those patients without ICD implantation. Delayed efficacy may occur in some patients after ablation.
Demonstration of Ventricular Myocardial Extensions into the Pulmonary Artery and Aorta Beyond the Ventriculo‐Arterial Junction
Authors: HASDEMİR CAN , AKTAS SAFİYE , GOVSA FİGEN , AKTAS EKİN O. , KOCAK AYTAC , BOZKAYA YASEMİN T. , DEMİRBAS MUGE I. , ULUCAN CEM , OZDOGAN ONER , KAYİKCİOGLU MERAL , CAN LEVENT H. , PAYZİN SERDAR
Published: April 2007

Background: A subgroup of outflow tract (OT) ventricular tachycardias (VT) originate from the aortic sinuses or the main stem of the pulmonary artery. The anatomic substrate for these tachycardias is unknown. The aim of this study was to investigate the presence of ventricular myocardial extensions (VME) into the pulmonary artery (PA) and aorta (Ao) beyond the ventriculo‐arterial junction (VAJ) and determine the anatomical and histological characteristics of these muscle extensions.

Methods: Ninety‐five consecutive human hearts obtained at autopsy were studied. Longitudinal strips of tissue containing each cusp, aortic, and pulmonary artery walls and left and right ventricular outflow tracts were excised and histologically analyzed. Anatomical measurements, including length and thickness of VMEs, obtained at autopsy, were made.

Results: VMEs beyond the VAJ were found in 21 of 95 (22%) patients studied. VMEs were found in 16 of 95 PAs (17%) and 7 of 95 Aos (7%) were examined. VMEs were located within the adventitia in 23 (88%) and on the epicardial surface in three (12%). The majority of VMEs were in continuity with the underlying ventricular OT muscle tissue. Myocellular hypertrophy and fibrosis were present in 19 (73%) and fatty tissue between the layers of VME in 18 (69%). Clinical data were available in 14 of 21 patients with positive VME. None of the patients (clinical data available group) had history of cardiac disease or signs or symptoms (palpitations or syncope) of cardiac disease.

Conclusions: VMEs into the PA and Ao beyond the VAJ are relatively common. It seems that their mere presence does not predispose to OT VTs. There are probably intrinsic arrhythmogenic properties in tissues specific to these regions in those patients who develop OT VTs.
A Left‐Sided Accessory Pathway Revisited with Remote Retrograde Magnetic Navigation
Authors: THORNTON ANDREW S. , JORDAENS LUC
Published: April 2007

Accessory pathways can be ablated with a high success rate. Occasionally, recurrences appear after successful procedures, sometimes shortly after the end of the procedure. We describe a successful ablation using remote magnetic navigation of a single catheter using stored vectors after recurrence of accessory pathway conduction while the patient was still in the electrophysiology laboratory.
Value of Pacemaker Atrial Diagnostic Data in Patients with Paroxysmal Atrial Fibrillation: An Opportunity to Improve Rates of Warfarin Utilization
Authors: KIM MICHAEL H. , TROHMAN RICHARD G. , CHRISTIANSEN SARA , HARSCH MANYA R. , KINSER KEN , REITER MICHAEL J. , PFEIFFER JULIE
Published: April 2007

Atrial diagnostic data within implantable devices provide an opportunity to assess the frequency and quantity of atrial fibrillation (AF) episodes (AF burden) and its impact on appropriate warfarin anticoagulation. Cardiologists were given clinical scenarios to review with different types of pacemaker diagnostic data in an elderly patient with risk factors for stroke. AF specific data was associated with increased warfarin utilization, but only at intermediate rates. Potential reasons and clinical implications are discussed.
Cox Regression Methods for Two‐Stage Randomization Designs
Authors: Lokhnygina Yuliya , Helterbrand Jeffrey D.
Published: April 2007

Summary Two‐stage randomization designs (TSRD) are becoming increasingly common in oncology and AIDS clinical trials as they make more efficient use of study participants to examine therapeutic regimens. In these designs patients are initially randomized to an induction treatment, followed by randomization to a maintenance treatment conditional on their induction response and consent to further study treatment. Broader acceptance of TSRDs in drug development may hinge on the ability to make appropriate intent‐to‐treat type inference within this design framework as to whether an experimental induction regimen is better than a standard induction regimen when maintenance treatment is fixed. Recently Lunceford, Davidian, and Tsiatis (2002, Biometrics58, 48–57) introduced an inverse probability weighting based analytical framework for estimating survival distributions and mean restricted survival times, as well as for comparing treatment policies at landmarks in the TSRD setting. In practice Cox regression is widely used and in this article we extend the analytical framework of Lunceford et al. (2002) to derive a consistent estimator for the log hazard in the Cox model and a robust score test to compare treatment policies. Large sample properties of these methods are derived, illustrated via a simulation study, and applied to a TSRD clinical trial.
Time‐Varying Coefficient Models for the Analysis of Air Pollution and Health Outcome Data
Authors: Lee Duncan , Shaddick Gavin
Published: April 2007

SummaryIn this article a time‐varying coefficient model is developed to examine the relationship between adverse health and short‐term (acute) exposure to air pollution. This model allows the relative risk to evolve over time, which may be due to an interaction with temperature, or from a change in the composition of pollutants, such as particulate matter, over time. The model produces a smooth estimate of these time‐varying effects, which are not constrained to follow a fixed parametric form set by the investigator. Instead, the shape is estimated from the data using penalized natural cubic splines. Poisson regression models, using both quasi‐likelihood and Bayesian techniques, are developed, with estimation performed using an iteratively re‐weighted least squares procedure and Markov chain Monte Carlo simulation, respectively. The efficacy of the methods to estimate different types of time‐varying effects are assessed via a simulation study, and the models are then applied to data from four cities that were part of the National Morbidity, Mortality, and Air Pollution Study.
Modeling Maternal–Infant HIV Transmission in the Presence of Breastfeeding with an Imperfect Test
Authors: Gupte N. , Brookmeyer R. , Bollinger R. , Gray G.
Published: April 2007

Summary An important public health question is to determine the probabilities of perinatal HIV transmission and when it occurs, whether antepartum, intrapartum, or postpartum through breastfeeding. However, this is a difficult problem because the presence of HIV infection in an infant can only be ascertained through viral assays in the postpartum period. We propose a model that simultaneously estimates the risks of antepartum, intrapartum, and postpartum transmissions together with the sensitivity of the screening tests for HIV infection. The model allows estimating of infectivity through breast milk during postpartum periods. The methods are illustrated on a South African randomized clinical trial of extended AZT versus a short course of nevirapine in infants whose mothers had no access to antenatal antiretroviral therapy.
Low Loss Dielectrics in the Ca(B′1/2Nb1/2)O3 [B′=Lanthanides, Y] System
Authors: Abdul Khalam L. , Sebastian M. T.
Published: April 2007

The Ca(B′1/2Nb1/2)O3 [B′=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Yb, and In] complex perovskites have been prepared by conventional solid‐state ceramic route. The structure and microstructure of the ceramics have been characterized by X‐ray diffraction and scanning electron microscopy methods. The ceramics have dielectric constant (ɛr) in the range 23–32, normalized Q‐factor (Qu×f) 11 000–38 000 GHz and temperature coefficient of resonant frequency (τf) −43–5.2 ppm/°C. The microwave dielectric properties of Ca(B′1/2Nb1/2)O3 ceramics are found to depend on the ionic radii of B′‐site elements and tolerance factor (t). The substitution of Ba2+ and Sr2+ for Ca2+ resulted a phase transition in Ca(B′1/2Nb1/2)O3 ceramics. The (Ca0.05Ba0.95) (Y1/2Nb1/2)O3 has τf close to zero (1.2 ppm/°C) with ɛr=35 and Qu×f=48 500 GHz and is proposed as a useful material for base station applications. Dielectric properties of the Ca(B′1/2Nb1/2)O3 ceramics were tailored by the addition of TiO2 and CaTiO3.
Modification of MgAl2O4 Microwave Dielectric Ceramics by Zn Substitution
Authors: Zheng Chang Wei , Wu Shu Ya , Chen Xiang Ming , Song Kai Xin
Published: April 2007

MgAl2O4 microwave dielectric ceramics were modified by Zn substitution for Mg, and their dielectric characteristics were evaluated, along with their structures. Dense (Mg1−xZnx)Al2O4 ceramics were obtained by sintering at 1550°–1650°C in air for 3 h, and the (Mg1−xZnx)Al2O4 solid solution was determined in the entire composition range. With Zn substitution for Mg, the dielectric constant ɛ of MgAl2O4 just varied from 7.90 to 8.56, while the Q×f value had significantly improved up to a maximal value of 106 000 GHz at x=1.0. Moreover, the τf of MgAl2O4 ceramics had declined from −73 to −63 ppm/°C.
Use of Genetic Algorithm to Determine the Kinetic Model of Solid‐State Reactions
Authors: Maitra S. , Pal A. J. , Bandyopadhyay N. , Das S. , Pal Jayita
Published: April 2007

Solid‐state reactions take place by different rate‐controlling heterogeneous processes. To find the appropriate kinetic model for a particular solid‐state reaction, a genetic algorithm‐based simulation technique was carried out using DTA data with a fitness function, and a computer program was developed for the same. The process was applied to the decomposition reactions of limestone and magnesite samples. It was observed that both the decomposition reactions mostly followed the Avrami–Erofeev kinetics model.
Microwave Dielectric Properties of Sintered Alumina Using Nano‐Scaled Powders of α Alumina and TiO2
Authors: Huang Cheng‐Liang , Wang Jun‐Jie , Huang Chi‐Yuen
Published: April 2007

The microstructure and the microwave dielectric properties of nano‐scaled α alumina (α‐Al2O3) ceramics with various added amounts of nano‐scaled TiO2 have been investigated. The sintering temperature of nano‐scaled α alumina can be effectively lowered by increasing the TiO2 content. The Q×f values of nano‐scaled α alumina could be tremendously boosted by adding an appropriate amount of TiO2. However, introducing excessive TiO2 into the alumina ceramics would instead lead to a decrease in the Q×f values. The phases of TiO2 and Al2TiO5 co‐existed at 1350°C, and the maximum Q×f value appeared right after the eradication of TiO2 phase at 1400°C. Consequently, increasing the TiO2 content to 0.5 wt% yielded a Q×f value of 680 000 GHz (measured at 14 GHz) for nano‐scaled α alumina prepared at 1400°C for duration of 4 h. In addition, a very low loss tangent (tan δ) of 2 × 10−5 was also obtained at 14 GHz. The τf value is strongly correlated to the compositions and can be controlled through the existing phases. In fact, τf could be adjusted to near zero by adding 8 wt% TiO2 to α alumina ceramics. A dielectric constant (ɛr) of 10.81, a high Q×f value of 338 000 GHz (measured at 14 GHz), and a temperature coefficient of resonant frequency (τf) of 1.3 ppm/°C were obtained for nano‐scaled α alumina with 8 wt% TiO2 sintered at 1350°C for 4 h. Sintered ceramic samples were also characterized by X‐ray diffraction and scanning electron microscopy.
Process Window of BaTiO3–Ni Ferroelectric–Ferromagnetic Composites
Authors: Huang Yung‐Ching , Chen Shiu‐Sheng , Tuan Wei‐Hsing
Published: April 2007

Experimental study and thermodynamic analysis are conducted to identify a process window for the preparation of BaTiO3–Ni ferroelectric–ferromagnetic composites. A tiny amount of Ni solutes (<0.5 mol%) can play a key role in the preparation of the composites. The Ni solute acts as an acceptor that enhances the reduction resistance of BaTiO3. Owing to the presence of Ni acceptors, dense BaTiO3–Ni composites can be prepared by sintering above 1330°C in an atmosphere of 1 Pa oxygen partial pressure.
Phase Transitions and Electrical Properties of (Na1−xKx)(Nb1−ySby)O3 Lead‐Free Piezoelectric Ceramics With a MnO2 Sintering Aid
Authors: Lin Dunmin , Kwok Kin Wing , Tian Huyong , Chan Helen Wong Lai‐wa
Published: April 2007

Lead‐free piezoelectric ceramics (Na1−xKx)(Nb1−ySby)O3+z mol% MnO2 have been prepared by a conventional solid‐state sintering technique. Our results reveal that Sb5+ diffuses into the K0.5Na0.5NbO3 lattices to form a solid solution with a single‐phase orthorhombic perovskite structure. The partial substitution of Sb5+ for B‐site ion Nb5+ decreases the paraelectric cubic‐ferroelectric tetragonal phase transition (Tc) and the ferroelectric tetragonal‐ferroelectric orthorhombic phase transition (TO–F), and retains strong ferroelectricity. A small amount of MnO2 is enough to improve the densification of the ceramics. The co‐effects of MnO2 doping and Sb substitution lead to significant improvements in ferroelectric and piezoelectric properties. The ceramics with x=0.45–0.525, y=0.06–0.08, and z=0.5–1 exhibit excellent ferroelectric and piezoelectric properties: d33=163–204 pC/N, kP=0.47–0.51, kt=0.46–0.52, ɛ=640–1053, tan δ=1.3–3.0%, Pr=18.1–22.6 μC/cm2, Ec=0.72–0.98 kV/mm, and TC=269°–314°C.
Synthesis and Mechanism of Ferroelectric Potassium Tantalate Niobate Nanoparticles by the Solvothermal and Hydrothermal Processes
Authors: Wei Nian , Zhang Duan‐Ming , Han Xiang‐Yun , Yang Feng‐Xia , Zhong Zhi‐Cheng , Zheng Ke‐Yu
Published: April 2007

High‐purity KTa0.3Nb0.7O3 nanoparticles have been successfully synthesized by hydrothermal and solvothermal methods. The KOH concentration and the solvent composition have significant effects on the final products. The synthesis mechanism was discussed. X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy investigations show that the typical samples solvothermally synthesized are nanosized, well crystallized, and single crystalline. The KTa0.3Nb0.7O3 shows a pseudo‐cubic to tetragonal transition with increasing crystallite size. It is believed that supercritical isopropanol plays an important role in synthesizing KTa0.3Nb0.7O3 nanoparticles under milder conditions than the hydrothermal route. The present solvothermal method provides a new potential route for synthesizing ferroelectric potassium tantalate niobate material.
Load‐Dependent Transition in Sliding Wear Properties of TiCN–WC–Ni Cermets
Authors: Manoj Kumar B. V. , Basu Bikramjit , Kalin Mitjan , Vizintin Joze
Published: April 2007

The present investigation aims at evaluating the sliding wear behavior of TiCN–20 wt%Ni cermets, containing varying amounts of WC (5–25 wt%) against 100Cr6 steel at different loads (5, 20, and 50 N). The dominant wear mechanisms were established by using surface topography analysis (Stylus profilometry), scanning electron microscopy, and X‐ray diffraction. The steady‐state coefficient of friction varies over a wide range: 0.73–0.27 at different loads for the investigated cermets. The volumetric wear loss of the cermets in general increases with load, while the wear rate varies in the order of 10−7 mm3·(N·m)−1. The worn surface characterization reveals that a transition in wear mechanism occurs from abrasion and mild tribo‐oxidation at low loads to the formation of a dense tribo‐oxide layer, containing oxides of Fe and Ti (essentially Fe9TiO15) at high loads. Efforts have been made to discuss the possible reaction pathways to explain the formation of the tribochemical layer. The addition of WC to TiCN–Ni‐based cermets results in increased abrasion at low loads and severe fracture of the tribo‐oxide layer at high loads.
Zinc Titanate Nanofibers for the Detoxification of Chemical Warfare Simulants
Authors: Ramaseshan Ramakrishnan , Ramakrishna Seeram
Published: April 2007

Fabrication of a novel ceramic nanofiber system viz. zinc titanate using the well‐known electrospinning technology with polyvinylpyrrolidone as a binder is reported. Use of zinc titanates as reactive sorbents to detoxify chemical warfare agents is hypothesized and proved. The zinc titanate nanofibers are tested against simulants of nerve and mustard agents and show satisfactory destructive activity. The extent of detoxification is measured using GC‐MS analysis. The products of reaction of zinc titanate against the simulants are identified and are found to be relatively harmless. The possibility of replacement of conventional‐activated carbon by electrospun ceramic nanofibers for face masks and protective clothing is proposed.
Effect of Liquid‐Phase Sintering on the Breakdown Strength of Barium Titanate
Authors: Young A. , Hilmas G. , Zhang S. C. , Schwartz R. W.
Published: April 2007

A glass used to liquid‐phase sinter BaTiO3 was developed and its properties were tested to determine the feasibility of using this glass to aid densification behavior. Glass was added to pure BaTiO3 powder and pressed into dimpled pellets with glass contents varying from 4 to 20 vol%. The breakdown strength was measured and compared with pure BaTiO3 and two commercially available dielectric materials. Liquid‐phase sintering increased the breakdown strength of pure BaTiO3 for all the compositions tested. The breakdown strength of the samples containing 20 vol% glass additions was increased by a factor of 2.8 compared with pure BaTiO3.
Strength Measurement of Ceramic Spheres Using a Diametrally Compressed “C‐Sphere” Specimen
Authors: Wereszczak Andrew A. , Kirkland Timothy P. , Jadaan Osama M.
Published: April 2007

A “C‐sphere” specimen geometry was conceived and developed to measure failure stress of bearing‐grade silicon nitride (Si3N4) balls caused by tension at the ball's surface. The induced method of fracture also allows for the study of surface‐located strength‐limiting flaws in ceramic spheres. A slot is machined into the balls to a set depth to produce the C‐sphere geometry. A simple, monotonically increasing uniaxial compressive force produces an increasing tensile stress at the C sphere's outer surface that ultimately initiates fracture. The strength is determined using a combination of failure load, C‐sphere geometry, and finite element analysis. Additionally, the stress field was used to determine the effective areas and effective volumes of a C‐sphere as a function of Weibull modulus. To demonstrate this new specimen, C‐sphere flexure strength distributions were determined for three commercially available bearing‐grade Si3N4 materials (NBD200, SN101C, and TSN‐03NH), and differences among their characteristic strengths and Weibull moduli were found.
Increased bone formation to unstable nano rough titanium implants
Authors: Meirelles Luiz , Arvidsson Anna , Albrektsson Tomas , Wennerberg Ann
Published: April 2007

Abstract: Early bone response to cylindrical smooth titanium implants (Sa=0.1 μm) inserted into the rabbit tibia was compared in a stable and nonstable regime. Surface roughness parameters were calculated from measurements obtained with optical interferometry and atomic force microscopy. Contrary to our hypothesis, the nonstable implant showed higher bone to metal contact and increased bone area in the endosteal region compared with the stable implant after 4 weeks of healing. Bone area measurements in the cortical region revealed similar values. Primitive woven bone was found in close contact with both implants, but significantly more with the nonstable implant. Finding more bone‐to‐implant contact (BIC) need not necessarily indicate that unstable implants were more strongly integrated. Primitive bone stage development observed indicates less strong implant anchorage than could be expected from BIC percentage alone. Stable implant design used in this study is a reliable model to evaluate submicron and nanostructures in vivo, as implant stability was achieved in the absence of microirregularaties.
Identification of type I interferon‐associated inflammation in the pathogenesis of cutaneous lupus erythematosus opens up options for novel therapeutic approaches
Authors: Wenzel Joerg , Tüting Thomas
Published: April 2007

Abstract:  Cutaneous lupus erythematosus (CLE) is one of the most common dermatological autoimmune disorders worldwide. Recently, several studies provided evidence for a pathogenic role of type I interferons (IFNs) in this disease. Plasmacytoid dendritic cells are major type I IFN producers in CLE skin lesions. Type I IFNs are able to induce the expression of several proinflammatory chemokines, including CXCL9 and 10, and enhance the cytotoxic capacity of infiltrating cells. Additionally, adhesion molecules and chemokine receptors, such as intercellular adhesion molecule‐1, cutaneous lymphocyte antigen, E‐selectin, CCR4 and CXCR3, are involved in the recruitment of potentially autoreactive lymphocytes into the skin. Here, we review the role of type I IFNs, adhesion molecules and chemokine receptors in CLE and discuss options for novel therapeutic approaches.
AFMK, a melatonin metabolite, attenuates X‐ray‐induced oxidative damage to DNA, proteins and lipids in mice
Authors: Manda Kailash , Ueno Megumi , Anzai Kazunori
Published: April 2007

Abstract:  Antioxidant function of melatonin is well established. However, N1‐acetyl‐N2‐formyl‐5‐methoxykynuramine (AFMK), a melatonin metabolite is a sparingly investigated biogenic amine, especially in relation to its in vivo antioxidant function. We have evaluated the oxidative damage to biomolecules (DNA, protein and lipid) induced by X‐irradiation in C57BL mice and the prophylactic action of AFMK. The extent of DNA damage was analyzed by single‐cell gel electrophoresis in cerebral cortex and serum 8‐hydroxydeoxyguanosine (8‐OHdG) levels by enzyme‐linked immunosorbent assay. Oxidative modification of protein and lipid was measured in the terms of carbonyl content and 4‐HAE + MDA (4‐hydroxyalkenal + malondialdehyde) status of brain cortex. Radiation exposure dramatically augmented the level of 8‐OHdG in serum as well as DNA migration in the comet tail. AFMK pretreatment significantly inhibited DNA damage. In addition, radiation‐induced augmentation of protein carbonyl content and HAE + MDA was ameliorated by AFMK pretreatment. Whole‐body exposure of mice to X‐irradiation also reduced the level of brain sulfhydryl contents (protein‐bound sulfhydryl, total sulfhydryl, and nonprotein sulfhydryl) which were significantly protected by AFMK. Radiation‐induced decline in the total antioxidant capacity of plasma was significantly reversed in AFMK pretreated mice. Moreover, AFMK showed a very high level of in vitro hydroxyl radical scavenging potential which was measured by an electron spin resonance (ESR) study of the 2‐hydroxy‐5,5‐dimethyl‐1‐pyrrolineN‐oxide (DMPO‐OH) adduct. IC50 values resulting from ESR analysis was 338.08 nm. The present study indicate that AFMK is a potent antioxidant in both in vivo and in vitro systems.
Elevation of Amniotic Fluid Macrophage Colony‐Stimulating Factor in Normotensive Pregnancies That Delivered Small‐For‐Gestational‐Age Infants
Authors: Hayashi Masatoshi , Zhu Kun , Sagesaka Toshiaki , Fukasawa Ichio , Inaba Noriyuki
Published: April 2007

Problem

Macrophage colony‐stimulating factor (M‐CSF) promotes placental growth and maintenance. We evaluated whether amniotic fluid M‐CSF levels were altered in normotensive pregnancies that produced small‐for‐gestational‐age (SGA) infants arising from unknown factors.

Method of study

This study enrolled 68 Japanese women experiencing normotensive pregnancies with single fetuses. Of these pregnancies, 22 delivered SGA infants arising from unknown factors (SGA group); one delivered an SGA infant with intestinal obstruction. The other 45 were women who delivered appropriate‐for‐gestational‐age (AGA) infants (AGA group). They were selected as controls. Amniotic fluid was collected and the M‐CSF levels were compared between the two groups. The M‐CSF level was determined by enzyme‐linked immunosorbent assay method.

Results

Amniotic fluid M‐CSF concentrations were 6525 pg/mL (median) in the SGA group and 4790 pg/mL in the AGA group; the concentrations were significantly higher in the SGA group than in the AGA group. The M‐CSF concentrations in the woman who delivered an SGA infant with intestinal obstruction showed very high values (24290 pg/mL).

Conclusion

We demonstrated a significant increase in amniotic fluid M‐CSF levels in the SGA group. Excessive concentrations of M‐CSF in amniotic fluid via amniotic membranes may be highly related to immunological abnormalities contributing to low birth weight of neonates.
Fabrication of Al‐Added TiN Materials by the Combination of Double Self‐Propagating High‐Temperature Synthesis and Pulsed Electric‐Current Pressure Sintering
Authors: Nakane Shingo , Hikawa Sho , Endo Takaya , Kato Masaki , Hirota Ken , Miyauchi Hiroya , Hioki Tadashi
Published: April 2007

Crystalline phases of Al‐added TiN, denoted as (Ti1−xAlx)Ny(0≤x≤0.10, 0.8<y<1.0), prepared from a mixture of Ti and Al powders by self‐propagating high‐temperature synthesis (SHS) in a nitrogen atmosphere, have been investigated. By repeating SHS twice, in the region of 0.0<x≤0.02 cubic (Ti1−xAlx)Nysolid solutions, and in the region of 0.0297% of theoretical) by pulsed electric‐current pressure sintering. With increasing Al addition, the optimum sintering temperatures were lowered, followed by reduction of grain size. Their mechanical properties, that is, three‐point bending strength σb, Vickers hardnessHv, and fracture toughnessKICwere evaluated as a function of Al content.
Performance of English Language Learners as a Subgroup in Large‐Scale Assessment: Interaction of Research and Policy
Authors: Abedi Jamal , Gándara Patricia
Published: April 2007

Factors that contribute to the performance gap between subgroups and mainstream students deserve special attention. Different subgroups are faced with different sets of challenges. To understand and control for factors leading to the performance gap between subgroups and mainstream students one must clearly understand the issues specific to each subgroup. This paper focuses on assessment and performance issues for English language learner (ELL) students as a subgroup. Identifying factors affecting the performance gap between ELL and non‐ELL students may help gain insight into assessment issues for other subgroups of students as well as strengthen assessment of this group.
OPTIMIZATION OF CAROTENE RECOVERY FROM HYDROLYZED PALM OLEIN IN ADSORPTION COLUMN CHROMATOGRAPHY USING RESPONSE SURFACE METHODOLOGY
Authors: YOU L. L. , ABDULLAH M. A. , QUEK S. Y. , BAHARIN B. S.
Published: April 2007

Response Surface Methodology (RSM) for optimization of carotene recovery from hydrolyzed palm olein (HCPOlein) in adsorption chromatography was carried out. The level and interaction of three independent variables was investigated: column temperature (50 to 60C), oil loading (25 to 200 g), and mobile phase flow rate (6 to 60 mL/min). Based on the response as percentage of carotene recovery from 50 g of HP‐20 adsorbent, the optimum conditions were achieved at 200 g of oil loading, column temperature at 55C, and flow rate at 33 mL/min. Up to 98% of carotene recovery was obtained under these conditions. Interaction of oil‐oil, oil‐flow rate and flow rate‐flow rate could enhance the percentage of carotene recovery. However, oil and flow rate as single factors could significantly reduce percentage of carotene recovery. Oil loading as a single factor could positively influence the amount of carotene adsorbed. However, flow rate as a single factor and oil‐oil interaction could negatively influence the amount of carotene adsorbed. The mean of difference (MD) of the experimental and predicted data for percentage of carotene recovery and the amount of carotene adsorbed were very small, −0.0067 and 0.0133, respectively. The probability (P) value showed no significant lack‐of‐fit for both equations in this model.
THE PAN‐HEATING STABILITY OF AN EXPELLER EXPRESSED SOYBEAN OIL
Authors: COSCIONE ALINE R. , OSIDACZ PATRICIA C. , KIATSRICHART SUDATIP , ARTZ WILLIAM E.
Published: April 2007

The relative stability of an expeller expressed, physically refined soybean oil (EE‐SBO, iodine value = 126.6) was compared to a low‐linolenic acid soybean oil (LL‐SBO, iodine value = 120.9) using pan frying. Physicochemical analyses, including free fatty acid analysis, the dielectric constant (Food Oil Sensor), and the Lovibond color were completed. High performance size exclusion chromatography was used to quantify the amount of polymeric triacylglycerol formed in the oil samples during heating. Oil samples were heated as thin films on a teflon‐coated frying pan at ∼ 180C to a target endpoint of ≥ 20% polymer. The endpoint, as determined by high performance size exclusion chromatography, was reached after 10 min of heating for the EE‐SBO (23.8% polymer) and 12 min for the LL‐SBO (24.9% polymer) sample. Although the iodine value suggests that LL‐SBO should have an oxidative stability comparable to EE‐SBO, the results from the physicochemical analyses indicated that the EE‐SBO was approximately 20% more stable than the LL‐SBO.