bluuebunny/crossref_metadata_2025 huggingface dataset:
Pressure‐rate product and phase angle as measures of acute inspiratory upper airway obstruction in rhesus monkeys
Authors: Ross Patrick A. , Hammer Jürg , Khemani Robinder , Klein Max , Newth Christopher J.L.
Published: May 2010

Rationale

There are limited validated, objective, and minimally invasive techniques for the bedside evaluation of upper airway obstruction (UAO) in sick infants, despite its frequency in pediatric medicine. Prior techniques include pressure‐rate product (PRP), a product of esophageal pressure and respiratory rate and phase angles (PAs), a measure of asynchrony between ribcage and abdominal respiratory movements in infants with UAO. The purpose of this study is to validate the PRP and compare it to a previously validated PA in rhesus monkeys.

Methods

Calibrated resistors were applied to the inspiratory limb of 10 anesthetized, intubated, and spontaneously breathing rhesus monkeys (weight 8.7 ± 2.5 kg). Airway pressure, respiratory rate, PAs, heart rate, and oxygen saturation were recorded. Obstruction was applied in random order as 0, 5, 20, 200, 500, and 1,000 cmH2O/L/sec for 2‐min periods, the last 15 sec (10–20 breaths) were analyzed for each timeframe.

Results

PA increased significantly at the 200 cmH2O/L/sec level but it reached a plateau above 500 cmH2O/L/sec. PRP rose progressively and was significantly different at all levels of obstruction. Esophageal pressure change was progressively and statistically significantly different from baseline and each other at 200, 500, and 1,000 cmH2O/L/sec (P < 0.001).

Conclusions

In this model of UAO, PRP tracks increasing inspiratory load better than PA. PRP continued to be linear up through the highest inspiratory resistance where the change in PA reached a plateau before the highest load. The assessment of esophageal pressure changes may offer the simplest objective measure of UAO. Pediatr Pulmonol. 2010; 45:639–644. © 2010 Wiley‐Liss, Inc.
Children with corrected or palliated congenital heart disease on home mechanical ventilation
Authors: Edwards Jeffrey D. , Kun Sheila S. , Keens Thomas G. , Khemani Robinder G. , Moromisato David Y.
Published: May 2010

Infants and children with surgically corrected or palliated congenital heart disease (CHD) are at risk for chronic respiratory failure, necessitating home mechanical ventilation (HMV) via tracheostomy. However, very little data exists on this population or their outcomes. We conducted a retrospective chart review of all children with CHD enrolled in the Childrens Hospital Los Angeles HMV program between 1994 and 2009. Data were collected on type of heart lesion, surgeries performed, number of failed extubations, timing of tracheostomy, mortality, length of time on HMV, weaning status, associated co‐morbidities, and Risk Adjusted classification for Congenital Heart Surgery (RACHS‐1) category. Thirty‐five children were identified; six with single ventricle anatomy, who received palliative procedures. Twenty‐three (66%) patients are alive; 8 (23%) living patients have been weaned off HMV. Twelve (34%) patients are deceased. The incidence of mortality for single ventricle patients was 50%, and only one of the surviving children has received final palliation and weaned off HMV. Eight of nine patients (89%) with a RACHS score ≥4 died, and none have been weaned off of HMV. The 5‐year survival for all CHD HMV patients was 68%; 90% for patients with RACHS ≤3; and 12% for patients with score ≥4. Children with more complex lesions, as demonstrated by single ventricle physiology or greater RACHS scores, had higher mortality rates and less success weaning off HMV. This case series suggests that caregivers should give serious consideration to the type of heart defect as they advise families considering HMV in children with CHD. Pediatr Pulmonol. 2010; 45:645–649. © 2010 Wiley‐Liss, Inc.
CMV pneumonia in HIV‐infected ventilated infants
Authors: Goussard P. , Kling S. , Gie R.P. , Nel E.D. , Heyns L. , Rossouw G.J. , Janson J.T.
Published: May 2010

Background

The contributing role of cytomegalovirus (CMV) in infants treated for Pneumocystis jiroveci pneumonia (PJP) is unknown. High dose steroids used in the treatment of PJP may further immunocompromise these infants contributing to the development of CMV pneumonia.

Aim

The aim of this study was to determine the role of CMV pneumonia in infants being ventilated for suspected PJP.

Methods

In this prospective study HIV infected infants being treated with trimethoprim–sulfamethoxazole (TMP/SMX) and ventilated for suspected PJP were included if they had not responded to treatment. Open lung biopsy was performed if there was no improvement in ventilatory requirements.

Results

Twenty‐five HIV positive infants with a mean age of 3.3 months were included. Lung biopsy was performed in 17 (68%) and post‐mortem lung tissue was obtained in 8 (32%). After evaluation of the histology, immunohistochemistry, and viral cultures from lung tissue, the most likely causes of pneumonia were: CMV and PJP dual infection 36% (n = 9), CMV pneumonia 36% (n = 9), and PJP 24% (n = 6). The pp65 test for CMV antigen was falsely negative in 24%. The mean blood CD4 count was 287/µl. There was an association between the CD4 lymphocyte status and the final diagnosis, with the CMV and PJP group (CD4 110/µl) having the lowest CD4 status (P = 0.0128). Pediatric Intensive Care Unit (PICU) mortality was 72% (n = 18) and in hospital mortality 88%.

Conclusion

Of the ventilated infants failing to respond to treatment, 72% had histologically confirmed CMV pneumonia, probably accounting for the high mortality in this cohort. The incidence of CMV disease in HIV infected infants being ventilated for severe pneumonia warrants that ganciclovir is used empirically until CMV disease is excluded. The role of lung biopsy in these circumstances needs to be researched. Pediatr Pulmonol. 2010; 45:650–655. © 2010 Wiley‐Liss, Inc.
Voriconazole inhibition of vitamin A metabolism: Are adverse events increased in cystic fibrosis patients?
Authors: Cheng Matthew Pellan , Paquette Katryn , Lands Larry C. , Ovetchkine Philippe , Théoret Yves , Quach Caroline
Published: May 2010

Background

As Voriconazole is being used more frequently in cystic fibrosis (CF) patients, we aimed to describe the adverse events associated with voriconazole treatment in this population.

Methods

We performed a retrospective cohort study of all children with CF who received voriconazole between September 2006 and August 2008.

Results

Five of six CF patients receiving treatment developed photosensitivity, whereas all six patients reported visual disturbances. We report two clinical cases of particular interest: a 7‐year‐old boy developed striking erythema in the face and upper thorax; a 16‐year‐old girl who reported unexpected visual disturbances, including scotomas and tunneling vision.

Conclusion

Significant adverse effects of voriconazole were noted in all treated CF patients. We speculate that this may be due to suppression of activity of hepatic enzymes involved in all transretinonic acid metabolism coupled with vitamin A supplementation in CF. Consideration should be given to reducing vitamin A supplementation during voriconazole treatment. Pediatr Pulmonol. 2010; 45:661–666. © 2010 Wiley‐Liss, Inc.
Community‐acquired Moraxella catarrhalis pneumonia in previously healthy children
Authors: Sy Magdalena G. , Robinson Joan L.
Published: May 2010

Background

The aim of this study was to determine if Moraxella catarrhalis is a common cause of community acquired pneumonia in children with no chronic medical problems. A secondary goal was to describe the clinical features of children with M. catarrhalis pneumonia.

Methods

A systematic literature search was conducted for (i) case series of pediatric community‐acquired pneumonia (CAP) where one or more diagnostic tests for M. catarrhalis were applied to all cases and (ii) case reports of previously healthy children with proven M. catarrhalis pneumonia.

Results

There were nine case series describing a total of 1,500 children with CAP. The number of children tested and yield was as follows: blood cultures 0/402 (0%); sputum cultures 15/157 (10%); nasopharyngeal, or postnasal cultures 129/521 (25%); sputum or nasopharyngeal cultures 0/74 (0%) (one study allowed either); nucleic acid amplification testing 2/100 (2%); serology 30/976 (3%). There were eight case reports of CAP with M. catarrhalis in previously well children. Children were ages 3 weeks to 7 years of age (median 14 months). Six of 8 (75%) children required mechanical ventilation. All survived.

Conclusion

It is common to detect M. catarrhalis in upper respiratory secretions in children with pneumonia, but bacteremia or seroconversion is rare. There are only eight well‐documented case reports CAP due to M. catarrhalis in previously well children, with there being no distinctive features in the eight cases described to date. This organism is likely a rare cause of CAP in previously healthy children. Pediatr Pulmonol. 2010; 45:674–678. © 2010 Wiley‐Liss, Inc.
Skeletal dysplasias: Evaluation with impulse oscillometry and thoracoabdominal motion analysis
Authors: Rodriguez M.E. , Mackenzie William G. , Ditro Colleen , Miller Thomas L. , Chidekel Aaron , Shaffer Thomas H.
Published: May 2010

Background

Children with skeletal dysplasia (SD) often have pulmonary disease, which can be life threatening. In clinical practice, chest wall and formal respiratory function tests are difficult to perform owing to the small size and cooperation. The objective of this study was to demonstrate distinct thoracopulmonary function patterns in children with SD.

Methods

We conducted a retrospective study reviewing pulmonary function tests from 17 patients with the diagnosis of SD. Three subgroups were studied: Morquio syndrome (MS), metatropic–spondylocostal dysplasia (MSD), and unspecified skeletal dysplasias (SDU). Rib cage contribution to tidal volume excursions (%RC), phase angle (Phθ), phase relation during total breath (PhRTB), respiratory resistance (Rrs5–35 Hz), respiratory reactance (Xrs5–35 Hz), resonant frequency, and their frequency–dependency were analyzed. Values were age‐matched and height‐matched to reference values of healthy subjects.

Results

There was a decrease in %RC and an increase in PhRTB (P < 0.05) in the SD group. %RC differed between subgroups [MS: 46.4 ± 1.8% SE, MSD: 18.4 ± 2.6% SE, SDU: 27.5 ± 5.2% SE (P < 0.05)]; Phθ was within reference values only in MS, which exhibited a decrease in Xrs at 5 Hz (P < 0.05) and an increase in Rrs independent of the frequency. SDU showed a decrease in Xrs at 35 Hz (P < 0.05), no differences were found in Rrs. In MS, a correlation was found between RC and Rrs at all frequencies (r = −0.98, P < 0.01) and between Xrs5–10 and Phθ (r = −0.93, P < 0.05).

Conclusions

Thoracoabdominal dysfunction was associated with altered chest wall reactance at high frequencies in a subgroup of SD patients with abnormal lung reactance and central airway involvement in MS. Pediatr Pulmonol. 2010; 45:679–686. © 2010 Wiley‐Liss, Inc.
Toll‐like receptor 4 Asp299Gly polymorphism in respiratory syncytial virus epidemics
Authors: Löfgren Johan , Marttila Riitta , Renko Marjo , Rämet Mika , Hallman Mikko
Published: May 2010

The respiratory syncytial virus (RSV) antigen serves as ligand for Toll‐like receptor (TLR) 4 that is a transmembrane signaling receptor in macrophages and dendritic cells. According to current evidence single nucleotide polymorphism involving amino acid 299 influences the susceptibility to severe RSV infections. The Asp299Gly allele has been shown to influence the TLR4‐mediated signaling causing conformational change in the extracellular domain that recognizes pathogen‐associated molecular patterns. The aim was to study the association between the TLR4 Asp299Gly polymorphism and the susceptibility to severe RSV bronchiolitis in infants. Altogether 312 cases and 356 controls, selected on the basis place of residence, date of birth, gender, and gestation at birth, were studied. When adjusted for multiple dependent variables, no allele or genotype frequency difference was found between the cases and the controls. Post hoc analysis revealed that during the year 2000 epidemics, the Gly299Gly genotype associated with protection against severe RSV and during 2004 epidemics Gly299Gly genotype and 299Gly allele associated with severe RSV. To conclude, we could not confirm the association of the Gly299 allele with severe RSV. This is consistent with the evidence that the susceptibility to severe RSV infection is principally dependent on environmental and constitutional factors. We propose that the risk of severe RSV infection may additionally depend on the interaction between individual TLR4 genotype and the particular RSV group causing bronchiolitis. Pediatr Pulmonol. 2010; 45:687–692. © 2010 Wiley‐Liss, Inc.
Tracheal gas insufflation with partial liquid ventilation to treat LPS‐induced acute lung injury in juvenile piglets
Authors: Guo Zhong‐Liang , Liang Yong‐Jie , Lu Guo‐Ping , Wang Jun‐Chen , Ren Tao , Zheng Yong‐Hua , Gong Jing‐Yu , Yu Jerry
Published: May 2010

Objectives

Partial liquid ventilation (PLV) with perfluorocarbons (PFC) seems not superior to conventional ventilation clinically. We hypothesized that a combination of continuous tracheal gas insufflation (TGI) with protective strategy of PLV (low dose of PFC, low inflation pressure, moderate inhalation of oxygen and moderate anesthesia) would improve cardiopulmonary function in acute lung injury.

Methods

Twenty‐four healthy juvenile piglets were anesthetized and mechanically ventilated at PEEP of 2 cmH2O with a peak inspiratory pressure of 10 cmH2O and FIO2 of 0.4. The piglets were challenged with lipopolysaccharide and randomly assigned to four groups (n = 6 each): (1) mechanical ventilation alone (MV); (2) PLV with perfluorodecalin (10 ml/kg); (3) TGI with continuous airway flow 2 L/min; and (4) combination of PLV and TGI. The outcome was assessed functionally and histologically.

Results

All treatments except MV improved pH, PaO2/FIO2, PaCO2, ventilation efficacy index (VEI) and tidal volume. Both PLV‐associated treatments also improved heart rate, respiratory rate, pulse contour cardiac output, systemic vascular resistance, dynamic lung compliance, mean airway resistance and mean airway pressure. The combination group resulted in higher PaO2/FIO2, VEI and a better lung histology score than any other treatments.

Conclusions

The new protective strategy may provide a better treatment for sepsis‐induced acute lung injury. Pediatr Pulmonol. 2010; 45:700–707. © 2010 Wiley‐Liss, Inc.
Phosphorus‐Based Nanothermites: A New Generation of Pyrotechnics Illustrated by the Example of n‐CuO/Red P Mixtures
Authors: Comet Marc , Siegert Benny , Schnell Fabien , Pichot Vincent , Ciszek Fabrice , Spitzer Denis
Published: May 2010

The use of aluminium nanoparticles (e.g. Al 50P) with various metallic oxides to prepare superthermites was reported in numerous recent papers. These compositions have exceptional energetic performances, but their fabrication cannot be scaled up due to the difficulty in producing or supplying aluminium nanopowders. The use of red phosphorus as an alternative reducing agent in nanothermite compositions was found to be very promising. Surprisingly, although this substance is a component of many explosive compositions, it was never tested with metallic oxide nanoparticles. In a preliminarily study, the reactivity of different metallic oxides with red phosphorus was screened. These tests led to classify the oxides according to their combustion potential, by ascending order: NiO<Fe2O3 $\rm{ \ll }$ CuO $\rm{ \ll }$ PbO2. The CuO/P mixture possesses an impressive reactivity, and its combustion residues are less hazardous than those formed with PbO2 insofar as lead derivatives are generally more toxic than their copper counterparts. CuO‐based P‐nanothermites were prepared by physically mixing copper(II) oxide nanoparticles with micrometre‐sized red phosphorus particles. The phosphorus content was varied from 16 to 50 wt.‐% in order to investigate the effect of the mass ratio on the reactivity of CuO/P materials. The impact sensitivity of CuO/P nanothermites is moderate (27–39 J), but their friction (<5–8 J) and electrostatic discharge sensitivities (<0.12–0.21 mJ) are extremely high. The combustion of P‐nanothermites (P‐NT) gives droplets of molten copper with a typical fractal structure after cooling down.
Linear Actuation Using Milligram Quantities of CL‐20 and TAGDNAT
Authors: Tappan Alexander S. , Basiliere Marc , Ball J. Patrick , Snedigar Shane , Fischer Gary J. , Salton Jonathan
Published: May 2010

There are numerous applications for small‐scale actuation utilizing pyrotechnics and explosives. In certain applications, especially when multiple actuation strokes are needed, or actuator reuse is required, it is desirable to have all gaseous combustion products with no condensed residue in the actuator cylinder. Toward this goal, we have performed experiments on utilizing milligram quantities of high explosives to drive a millimeter‐diameter actuator with a stroke of 30 mm. Calculations were performed to select proper material quantities to provide 0.5 J of actuation energy. This was performed utilizing the thermochemical code Cheetah to calculate the impetus for numerous propellants and to select quantities based on estimated efficiencies of these propellants at small scales. Milligram quantities of propellants were loaded into a small‐scale actuator and ignited with an ignition increment and hot wire ignition. Actuator combustion chamber pressure was monitored with a pressure transducer and actuator stroke was monitored using a laser displacement meter. Total actuation energy was determined by calculating the kinetic energy of reaction mass motion against gravity. Of the materials utilized, the best performance was obtained with a mixture of 2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane (CL‐20) and bis‐triaminoguanidinium(3,3′dinitroazotriazolate) (TAGDNAT).
Telerehabilitation mediated physiotherapy assessment of ankle disorders
Authors: Russell Trevor G. , Blumke Robert , Richardson Bradley , Truter Piers
Published: May 2010

Background and Purpose. Musculoskeletal injuries are the most common source of chronic pain and disability. The ankle joint is the most common of these injuries and without adequate rehabilitation function can be severely impaired. Access to physiotherapy rehabilitation services can be limited due to geographical remoteness and a shortage of services in rural and remote areas. Telerehabilitation is a potential solution to bridge this service delivery gap. The aim of this study was to determine the criterion validity and reliability of conducting a remote musculoskeletal assessment of the ankle joint complex using telerehabilitation technologies compared with a face‐to‐face assessment. Methods. This study utilized a repeated measures design to assess 15 subjects (mean age 24.5, SD 10.8 years) presenting with ankle pain. Conventional face‐to‐face assessments were compared with assessments performed via a telerehabilitation system. Results. A similar agreement of 93.3% in patho‐anatomical diagnosis and an 80% exact agreement (χ2 = 4.267; p < 0.04) in primary systems diagnosis was found between face‐to‐face and telerehabilitation assessments. Clinical observations were found to have very strong agreement (k = 0.92) for categorical data and significant agreement (93.3% agreement; χ2 = 234.4; p < 0.001) for binary data. A high level of inter‐ and intrarater reliability was found for the telerehabilitation assessments. Conclusions. This study demonstrates the criterion validity and reliability of remote musculoskeletal assessments of the ankle joint complex using telerehabilitation. Copyright © 2010 John Wiley & Sons, Ltd.
Functional dissection of an intrinsically disordered protein: Understanding the roles of different domains of Knr4 protein in protein–protein interactions
Authors: Dagkessamanskaia Adilia , Durand Fabien , Uversky Vladimir N. , Binda Matteo , Lopez Frédéric , El Azzouzi Karim , Francois Jean Marie , Martin‐Yken Hélène
Published: May 2010

Knr4, recently characterized as an intrinsically disordered Saccharomyces cerevisiae protein, participates in cell wall formation and cell cycle regulation. It is constituted of a functional central globular core flanked by a poorly structured N‐terminal and large natively unfolded C‐terminal domains. Up to now, about 30 different proteins have been reported to physically interact with Knr4. Here, we used an in vivo two‐hybrid system approach and an in vitro surface plasmon resonance (BIAcore) technique to compare the interaction level of different Knr4 deletion variants with given protein partners. We demonstrate the indispensability of the N‐terminal domain of Knr4 for the interactions. On the other hand, presence of the unstructured C‐terminal domain has a negative effect on the interaction strength. In protein interactions networks, the most highly connected proteins or “hubs” are significantly enriched in unstructured regions, and among them the transient hub proteins contain the largest and most highly flexible regions. The results presented here of our analysis of Knr4 protein suggest that these large disordered regions are not always involved in promoting the protein–protein interactions of hub proteins, but in some cases, might rather inhibit them. We propose that this type of regions could prevent unspecific protein interactions, or ensure the correct timing of occurrence of transient interactions, which may be of crucial importance for different signaling and regulation processes.
DE‐loop mutations affect β2 microglobulin stability, oligomerization, and the low‐pH unfolded form
Authors: Santambrogio Carlo , Ricagno Stefano , Colombo Matteo , Barbiroli Alberto , Bonomi Francesco , Bellotti Vittorio , Bolognesi Martino , Grandori Rita
Published: May 2010

β2 microglobulin (β2m) is the light chain of class‐I major histocompatibility complex (MHC‐I). Its accumulation in the blood of patients affected by kidney failure leads to amyloid deposition around skeletal joints and bones, a severe condition known as Dialysis Related Amyloidosis (DRA). In an effort to dissect the structural determinants of β2m aggregation, several β2m mutants have been previously studied. Among these, three single‐residue mutations in the loop connecting strands D and E (W60G, W60V, D59P) have been shown to affect β2m amyloidogenic properties, and are here considered. To investigate the biochemical and biophysical properties of wild‐type (w.t.) β2m and the three mutants, we explored thermal unfolding by Trp fluorescence and circular dichroism (CD). The W60G mutant reveals a pronounced increase in conformational stability. Protein oligomerization and reduction kinetics were investigated by electrospray‐ionization mass spectrometry (ESI‐MS). All the mutations analyzed here reduce the protein propensity to form soluble oligomers, suggesting a role for the DE‐loop in intermolecular interactions. A partially folded intermediate, which may be involved in protein aggregation induced by acids, accumulates for all the tested proteins at pH 2.5 under oxidizing conditions. Moreover, the kinetics of disulfide reduction reveals specific differences among the tested mutants. Thus, β2m DE‐loop mutations display long‐range effects, affecting stability and structural properties of the native protein and its low‐pH intermediate. The evidence presented here hints to a crucial role played by the DE‐loop in determining the overall properties of native and partially folded β2m.
The transcription repressor NmrA is subject to proteolysis by three Aspergillus nidulans proteases
Authors: Zhao Xiao , Hume Samantha L. , Johnson Christopher , Thompson Paul , Huang Junyong , Gray Joe , Lamb Heather K. , Hawkins Alastair R.
Published: May 2010

The role of specific cleavage of transcription repressor proteins by proteases and how this may be related to the emerging theme of dinucleotides as cellular signaling molecules is poorly characterized. The transcription repressor NmrA of Aspergillus nidulans discriminates between oxidized and reduced dinucleotides, however, dinucleotide binding has no effect on its interaction with the zinc finger in the transcription activator AreA. Protease activity in A. nidulans was assayed using NmrA as the substrate, and was absent in mycelium grown under nitrogen sufficient conditions but abundant in mycelium starved of nitrogen. One of the proteases was purified and identified as the protein Q5BAR4 encoded by the gene AN2366.2. Fluorescence confocal microscopy showed that the nuclear levels of NmrA were reduced approximately 38% when mycelium was grown on nitrate compared to ammonium and absent when starved of nitrogen. Proteolysis of NmrA occurred in an ordered manner by preferential digestion within a C‐terminal surface exposed loop and subsequent digestion at other sites. NmrA digested at the C‐terminal site was unable to bind to the AreA zinc finger. These data reveal a potential new layer of control of nitrogen metabolite repression by the ordered proteolytic cleavage of NmrA. NmrA digested at the C‐terminal site retained the ability to bind NAD+ and showed a resistance to further digestion that was enhanced by the presence of NAD+. This is the first time that an effect of dinucleotide binding to NmrA has been demonstrated.
Extremal black holes, attractor equations, and harmonic functions
Authors: Mohaupt T. , Waite K.
Published: May 2010

We review the construction of multi‐centered black hole solutions through dimensional reduction over time. This method does not rely on Killing spinor equations or gradient flow equations, but on solving the second order field equations in terms of harmonic functions. The black hole attractor equations are obtained directly from the field equations.
Proton hexality in GUTs and strings
Authors: Förste S.
Published: May 2010

Proton hexality is a discrete symmetry ensuring the stability of the proton under dimension four and five interactions. We discuss the embedding of proton hexality into Grand Unified Theories. This leads naturally to the concept of extra dimensions and string theory. This talk is based on a collaboration with results to be published shortly [1].
The μ‐problem, the NMSSM and string theory
Authors: Ramos‐Sánchez S.
Published: May 2010

We discuss recent developments on the solution of the so‐called supersymmetric μ‐problem in the context of heterotic orbifolds. In particular, an approximate R symmetry can induce an admissible μ‐term in Minkowski vacua of orbifold models with the MSSM spectrum. A natural solution to the μ‐problem is offered by explicitly string derived NMSSMs. These models also ameliorate the fine‐tuning of the MSSM.
Geometric flows and applications
Authors: Petropoulos P.M.
Published: May 2010

I present some applications of geometric flows in string theory and gravity. In some circumstances time evolution in string theory can be approximately identified with Ricci‐flow parametric evolution of spatial sections. In four dimensions, homogeneous, self‐dual, gravitational instantons of general relativity evolve in time exactly as geometric flows of homogeneous three‐manifolds. For non‐relativistic versions of gravity, this property persists in any dimension, under the assumption of detailed‐balance condition.
Facet formation for laser diodes on nonpolar and semipolar GaN
Authors: Rass Jens , Wernicke Tim , Kremzow Raimund , John Wilfred , Einfeldt Sven , Vogt Patrick , Weyers Markus , Kneissl Michael
Published: May 2010

Different technologies have been evaluated in order to create vertical and smooth facets for GaN‐based laser diodes on non‐ and semipolar substrates. Laser assisted scribing and cleaving proved to be a suitable method to create c‐, a‐ and m‐plane facets for devices grown on nonpolar, polar and semipolar GaN planes. The RMS roughness measured by atomic force microscopy was found to be less than 1 nm. Semipolar facets showed tilted or multifaceted cleavage planes. Dry etching using inductively coupled plasma etching (ICP) resulted in vertical facets for devices grown on polar c‐plane GaN, while the facets of semipolar $(11\overline 2 2)$ GaN on sapphire exhibited a slight tilt depending on the crystal orientation. Wet chemical postprocessing of semipolar facets can improve the tilt angle but suffers from a roughening of the facets due to selective dislocation etching. By using a focussed ion beam (FIB) it is possible to create vertical and smooth facets independent of the crystal orientation.
High‐output‐power AlGaN/GaN ultraviolet‐light‐emitting diodes by activation of Mg‐doped p‐type AlGaN in oxygen ambient
Authors: Nagata Kengo , Ichikawa Tomoki , Takeda Kenichiro , Nagamatsu Kentaro , Iwaya Motoaki , Kamiyama Satoshi , Amano Hiroshi , Akasaki Isamu
Published: May 2010

We demonstrated activation annealing of Mg‐doped p‐type Al0.17Ga0.83N in different gases. The hole concentration of Al0.17Ga0.83N annealed in oxygen is higher than that annealed in nitrogen or air. A hole concentration of 1.3 × 1016 cm−3 at room temperature was achieved by annealing in oxygen flow at 900 °C. Secondary ion mass spectroscopy shows that hydrogen dissociation from Mg‐doped Al0.17Ga0.83N is found to be enhanced by annealing in a flow of oxygen, compared with annealing in a flow of nitrogen. We confirmed the effect of activation annealing in oxygen flow on the performance of UV light‐emitting diode (LED). At a DC current of 100 mA, the output power of the LED annealed in oxygen flow at 900 °C is four times higher than that of the LED annealed in nitrogen flow at 800 °C.
Electroluminescence properties of Eu‐doped GaN‐based red light‐emitting diode by OMVPE
Authors: Nishikawa Atsushi , Kawasaki Takashi , Furukawa Naoki , Terai Yoshikazu , Fujiwara Yasufumi
Published: May 2010

We investigated the electroluminescence (EL) properties of europium (Eu)‐doped GaN‐based red light‐emitting diode (LED). Under current injection, the energy transfer from the GaN host material to Eu3+ ions successfully occurred and the red emission from Eu3+ ions was observed with naked eyes under normal lighting conditions at room temperature (RT). The operation voltage was as low as 2.4 V. The dominant peak was observed at a wavelength of 621 nm and its intensity increased with increasing applied voltage. The several peaks beside the main peak appeared with higher injected currents in the EL spectrum. The light output power, which was integrated over the main peak, as a function of injected current shows the saturated behaviour in the high injected current region. As a result, the external quantum efficiency was still lower than the conventional GaN‐based blue and green LEDs at high injected current. However, this result suggests a novel way to realize GaN‐based red LEDs, which leads to realize a monolithic device composed of red, green and blue GaN‐based LEDs for full‐colour display or lighting technology.
In‐clustering effects in InAlN and InGaN revealed by high pressure studies
Authors: Gorczyca I. , Suski T. , Kamińska A. , Staszczak G. , Schenk H. P. D. , Christensen N. E. , Svane A.
Published: May 2010

Electronic band structure calculations of InAlN and InGaN under pressure are presented for two different arrangements of the In atoms, uniform and clustered. The band gap pressure coefficients exhibit strong bowing, and the effect is especially large when indium atoms are clustered. The theoretical results are compared with the results of photoluminescence measurements performed at high hydrostatic pressures on InAlN and InGaN quasi‐bulk epilayers. We discuss the modification of the uppermost valence band due to formation of In clusters which, together with the related lattice relaxations, may be a possible source of the observed phenomena.
Structural properties of MBE AlInN and AlGaInN barrier layers for GaN‐HEMT structures
Authors: Kirste Lutz , Lim Taek , Aidam Rolf , Müller Stefan , Waltereit Patrick , Ambacher Oliver
Published: May 2010

A high‐resolution X‐ray diffraction and X‐ray reflectivity study of the structural properties of AlInN/GaN and AlGaInN/GaN high electron mobility transistor structures deposited by molecular beam epitaxy on metal organic chemical vapor deposition GaN/Al2O3 and GaN/SiC templates is presented. A new AlN/GaN/AlN triple‐interlayer is implemented to improve the interface properties between barrier layer and GaN buffer for a higher mobility of the polarization induced two‐dimensional electron gas. Layer properties and structural parameters like concentration, interface quality, layer thickness, strain and crystalline perfection are analyzed. Best structural properties are achieved for an AlGaInN layer with AlN/GaN/AlN interlayer deposited on a GaN/4H‐SiC (00.1) template.
Fabrication of freestanding 2″‐GaN wafers by hydride vapour phase epitaxy and self‐separation during cooldown
Authors: Lipski Frank , Wunderer Thomas , Schwaiger Stephan , Scholz Ferdinand
Published: May 2010

Using a dielectric mask, structured by optical lithography, freestanding 2″‐GaN wafers were prepared by hydride vapour phase epitaxy (HVPE) and self‐separation during cooldown. The mask was deposited on a GaN template grown on sapphire by metal organic vapour phase epitaxy (MOVPE) and it was shown that the instability of a SiN mask at growth temperature supports the further self‐separation. Testing different mask geometries, a hexagonally shaped pattern with a period of 30 µm and an opening of 3 µm showed best performance. This mask allowed the growth and separation of a full 2″ GaN wafer by utilizing the stress arising during cooldown from thermal mismatch to the substrate. Thickness inhomogenity was below 10% and the samples show good surface morphology.
Fabrication of blue and green non‐polar InGaN/GaN multiple quantum well light‐emitting diodes on LiAlO2(100) substrates
Authors: Liu Bin , Han Ping , Xie Zili , Zhang Rong , Liu Chengxiang , Xiu Xiangqian , Hua Xuemei , Lu Hai , Chen Peng , Zheng Youdou , Zhou Shengming
Published: May 2010

The non‐polar m‐plane InGaN/GaN light‐emitting diodes (LEDs) grown by metal‐organic chemical vapor deposition (MOCVD) on LiAlO2(100) substrates were investigated. The structure of LEDs is composed by GaN p–n junction and five InGaN/GaN multiple quantum wells (MQWs). They emit blue or green light, respectively, with different indium composition of InGaN as active layers in the MQWs. Third‐order satellite peaks are observed in high resolution X‐ray diffraction spectrum, indicating good quantum well interfaces. For 800 × 800 µm2 blue LED device, the output power achieves 3 mW under 200 mA injection current. The electroluminescence (EL) spectra of both non‐polar blue and green InGaN/GaN LEDs show that the EL peak wavelength of LEDs almost saturates at certain position with increasing injection currents. This proves the absence of polarization fields in the active region present in c‐plane structures.
Optically pumped lasing at 300.4 nm in AlGaN MQW structures grown by plasma‐assisted molecular beam epitaxy on c‐Al2O3
Authors: Jmerik V. N. , Mizerov A. M. , Shubina T. V. , Toropov A. A. , Belyaev K. G. , Sitnikova A. A. , Yagovkina M. A. , Kop'ev P. S. , Lutsenko E. V. , Danilchyk A. V. , Rzheutskii N. V. , Yablonskii G. P. , Monemar B. , Ivanov S. V.
Published: May 2010

We have demonstrated optically pumped room‐temperature pulse lasing at 300.4 nm from an AlGaN‐based multiple‐quantum‐well (MQW) structure grown by plasma‐assisted molecular beam epitaxy on a c‐sapphire substrate. The lasing was achieved at the threshold peak power of ∼12 MW/cm2. The MQW structure involved AlGaN/AlN short‐period superlattices to decrease the threading dislocation densities from 1011 down to 109–1010 cm−2. Studies of time‐resolved photoluminescence (TRPL) spectra and cw PL temperature dependences (10–300 K) of different MQW structures, as well as numerical calculations of the optical gain and confinement in the laser structure allowed us to conclude about the optimum design of AlGaN‐based MQW structures for the lower threshold UV lasing.
AlInN HEMT grown on SiC by metalorganic vapor phase epitaxy for millimeter‐wave applications
Authors: Guo Shiping , Gao Xiang , Gorka Daniel , Chung Jinwoork W. , Wang Han , Palacios Tomas , Crespo Antonio , Gillespie James K. , Chabak Kelson , Trejo Manuel , Miller Virginia , Bellot Mark , Via Glen , Kossler Mauricio , Smith Howard , Tomich David
Published: May 2010

In this work we present the epitaxial and device results of AlInN/GaN HEMTs grown on SiC by metalorganic vapor phase epitaxy. High quality AlInN/GaN HEMT structures with sub‐10 nm AlInN barrier were grown with very low Ga background level (<1%). The low Rsh of 215 Ω/sq was obtained with an excellent standard deviation of 1.1% across 3″ wafers. Lehighton RT contactless Hall tests show a high mobility of 1617 cm2/V s and sheet charge density of 1.76 × 1013/cm2. DC characteristics of an AlInN/GaN HEMT with a gate length of 0.1 µm and 25 nm Al2O3 passivation show maximum drain current (IDS,max) of 2.36 A/mm at VGS = 2 V. Gate recessed devices with 0.15 µm gate length and 25 nm Al2O3 passivation resulted in maximum transconductance (gm) of 675 mS/mm, the highest value ever reported in AlInN transistors. Excellent frequency response was obtained. The maximum fT is 86 GHz and fmax is 91.7 GHz.
GaInN‐based LED structures on selectively grown semi‐polar crystal facets
Authors: Scholz Ferdinand , Wunderer Thomas , Feneberg Martin , Thonke Klaus , Chuvilin Andrei , Kaiser Ute , Metzner Sebastian , Bertram Frank , Christen Jürgen
Published: May 2010

In conventional nitride‐based light emitting diodes, huge internal electric fields lead to a reduced overlap of electron and hole wave functions in the active GaInN quantum wells as a consequence of the piezoelectricity of these polar materials. In order to minimize these internal fields while still maintaining the well‐established c‐direction as main epitaxial growth direction for high‐quality low‐defect‐density layers, we have investigated semi‐polar LED structures on the side‐facets of triangular GaN stripes grown by selective area epitaxy. The reduced internal electric field could be confirmed by several spectroscopic methods. We found a strongly facet dependent growth mechanism leading to very flat surfaces on $\{ 1\bar {1}01\}$ facets as opposed to their $\{ 11\bar {2}2\}$ counterparts. An increased indium uptake on semipolar $\{ 1\bar {1}01\}$ facets as compared to conventional c‐plane layers helped to shift the LED emission to longer wave lengths beyond 500 nm in the green spectral range despite the significantly reduced field‐dependent Stark shift.
Impedance measurement for microstructure characterization and internal surface estimation of macroporous silicon
Authors: RoyChaudhuri C. , Jana M. , Bandopadhyay N. R.
Published: May 2010

In this paper, a simple and convenient method based on impedance measurement has been proposed for the first time to evaluate the average porosity, pore radius, and internal surface area of macroporous silicon structure fabricated by electrochemical method. The porosity and the average pore radius have been obtained by developing a geometrical model and applying the generalized effective medium approximation theory to the dc and ac impedance measurement of both unoxidized and thermally oxidized macroporous silicon. The internal surface area per unit volume is then computed from the porosity and the pore radius using the same model. The method has been applied to a wide range of porosity from 30 to 58% fabricated on p‐type <100> silicon with a resistivity of 10–20 Ω cm. Experimental verification of porosity, mean pore radius, and internal surface area have been performed by standard gravimetric technique and by top‐view and cross‐section SEM imaging, respectively. A typical mean pore radius, porosity, and internal surface area of a macroporous silicon sample has been obtained to be 1.52 µm, 54.2%, and 3565.7 cm2/cm3, respectively, from the impedance measurement and 1.5 µm, 55%, and 3666.7 cm2/cm3 from SEM and gravimetric analysis which shows that the results are within 2% of the values obtained by conventional methods. The advantages of this method over the other recently reported techniques for similar characterization have been discussed.
Synthesis and physical properties of cylindrite micro tubes and lamellae
Authors: Kaden Ronny , Wagner Gerald , Sturm Chris , Schmidt‐Grund Rüdiger , von Wenckstern Holger , Prager Andrea , Bente Klaus , Grundmann Marius
Published: May 2010

The natural semiconductor cylindrite FeSn4Pb3Sb2S14 was synthesised by chemical vapour transport (CVT). Crystals with lamellar shape and cylindrical morphology could be deposited on substrates. The endothermic reactions responsible for material transport were simulated by means of thermodynamic modelling. Cylindrite belongs to the class of misfit layered compounds, where its modulated incommensurate crystal structure is based on the regular alternation of two types of layers. The so called T‐ and H‐slab are incommensurately linked. Determined from single crystal XRD measurements, the modulation of atom positions as well as modulation of metal site occupancy of both subsystems are presented. The origin of super structure reflections found in scattering experiments can be clearly explained by a structure model. Based on experimentally determined single crystal XRD data and HRTEM inspections a model is derived to explain the formation of cylindrical architecture of crystals. The specific electrical conductivity of cylindrite improves from 10−2 to 101 Ω−1/m when increasing the atomic ratio Pb/Sb from 1.35 to 1.75. In the same way the Seebeck coefficient S can reach negative values of −730 µV/K indicating n‐type conduction. The band gap energy Eg rises from 0.65 to 1.15 eV with decreasing (Pb + Fe)/(Sn + Sb) from 0.71 to 0.53.

magnified image

TEM bright field image of high magnification demonstrating the continuous bending of (100) layers in a cylindrite cylinder.
Ionized physical vapor deposited Al2O3films: Does subplantation favor formation of α‐Al2O3?
Authors: Sarakinos K. , Music D. , Nahif F. , Jiang K. , Braun A. , Zilkens C. , Schneider J. M.
Published: May 2010

The broad energy distributions of the condensing particles typically encountered in ion assisted vapor deposition techniques are often a drawback when attempting to understand the effect of the energetic bombardment on the film properties. In the current study, a monoenergetic Al+beam generated by a filtered cathodic arc discharge is employed for the deposition of alumina (Al2O3) films at well defined Al+ion energies between 4 eV and 200 eV at a substrate temperature of 720 °C. Structural analysis shows that Al+energies of 40 eV or larger favor the formation of the thermodynamically stable α‐Al2O3phase at the expense of other metastable Al2O3polymorphs. The well defined ion energies are used as input for Monte‐Carlo based simulations of the ion–surface interactions. The results of these simulations reveal that the increase of the Al+ion energy leads to an increase in the fraction of ions subplanted into the growing film. These findings underline the previously not considered role of subsurface processes on the phase formation of ionized physical vapor deposited Al2O3films. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Amelioration of oxidative stress by dandelion extract through CYP2E1 suppression against acute liver injury induced by carbon tetrachloride in sprague‐dawley rats
Authors: Park Chung Mu , Cha Yeon Suk , Youn Hyun Joo , Cho Chung Won , Song Young Sun
Published: May 2010

The protective effects of common dandelion leaf water extract (DLWE) were investigated by carbon tetrachloride (CCl4) induced hepatitis in Sprague‐Dawley rats. The animals were divided into five groups: normal control, DLWE control, CCl4 control, and two DLWE groups (0.5 and 2 g/kg bw). After 1 week of administering corresponding vehicle or DLWE, a single dose of CCl4 (50% CCl4/olive oil; 0.5 mL/kg bw) was administered 24 h before killing in order to produce acute liver injury. The DLWE treatment significantly decreased CCl4‐induced hepatic enzyme activities (AST, ALT and LDH) in a dose dependent manner. Also, the obstructed release of TG and cholesterol into the serum was repaired by DLWE administration. Hepatic lipid peroxidation was elevated while the GSH content and antioxidative enzyme activities were reduced in the liver as a result of CCl4 administration, which were counteracted by DLWE administration. Furthermore, the hepatocytotoxic effects of CCl4 were confirmed by significantly elevated Fas and TNF‐? mRNA expression levels, but DLWE down‐regulated these expressions to the levels of the normal control. Highly up‐regulated cytochrome P450 2E1 was also lowered significantly in the DLWE groups. These results indicate that DLWE has a protective effect against CCl4‐induced hepatic damage with at least part of its effect being attributable to the attenuation of oxidative stress and inflammatory processes resulting from cytochrome P450 activation by CCl4. Copyright © 2010 John Wiley & Sons, Ltd.
Effect of isolated fractions ofHarpagophytum procumbensD.C. (devil's claw) on COX‐1, COX‐2 activity and nitric oxide production on whole‐blood assay
Authors: Anauate Maria Cecilia , Torres Luce Maria , de Mello Suzana Beatriz Veríssimo
Published: May 2010

The present study evaluates the effect of isolated fractions ofHarpagophytum procumbens(devil's claw) on cyclooxygenase (COX‐1 and COX‐2) activities and NO production using a whole blood assay. The activity of COX‐1 was quantified as platelet thromboxane B2production in blood clotting and COX‐2 as prostaglandin E2production in LPS‐stimulated whole blood. Total NO2−/NO3−concentration was determined by Griess reaction in LPS stimulated blood. Assays were performed by incubation of isolated fractions obtained by flash chromatography monitored with HPLC, TLC and identified by1HNMR, containing different amounts of harpagoside with blood from healthy donors. Indomethacin and etoricoxib were the positive controls of COX‐1 and COX‐2 Inhibition. Data shows that fraction containing the highest concentration of harpagoside inhibited indistinctively COX‐1 and COX‐2 (37.2 and 29.5% respectively) activity and greatly inhibited NO production (66%). In contrast the fraction including iridoid pool increased COX‐2 and did not alter NO and COX‐1 activities. The fraction containing cinnamic acid was able to reduce only NO production (67%). Our results demonstrated that the harpagoside fraction is the main responsible for the effect of devils claw on these enzyme activities. However, other components from devil's claw crude extract could antagonize or increase the synthesis of inflammatory mediators. Copyright © 2010 John Wiley & Sons, Ltd.
Individual and combined effects of foods on helicobacter pylori growth
Authors: Keenan Jacqueline I. , Salm Nina , Hampton Mark B. , Wallace Alison J.
Published: May 2010

Eradication of H. pylori can reduce the risk of non‐cardia gastric cancer developing in infected humans. Thus, the consumption of foods that inhibit the growth of these bacteria may provide an alternative to current therapies that include antibiotics, proton pump inhibitors and/or bismuth salts. This study describes a simple broth dilution assay developed to screen a range of foods for their individual and combined effects on H. pylori growth. It was found that foods with measurable anti‐H. pylori activity have an effect greater in combination than the sum of foods tested singly, and that this was most noticeable with a combination of broccoli sprouts and blackcurrant oil. The results suggest that food synergy should be considered in any nutraceutical approach to H. pylori infection. Copyright © 2010 John Wiley & Sons, Ltd.
Xanthone constituents of the fruits of garcinia mangostana with anticomplement activity
Authors: Quan Gui‐Hua , Oh Sei‐Ryang , Kim Jung‐Hee , Lee Hyeong‐Kyu , Kinghorn A. Douglas , Chin Young‐Won
Published: May 2010

Phytochemical investigation of a chloroform‐soluble fraction of the freeze‐dried fruits of Garcinia mangostana (Clusiaceace) with anticomplement activity in the classical pathway led to the identification of five known xanthones. The structures of these compounds were confirmed by interpretation of NMR and MS spectroscopic data. Of the isolates obtained, 1‐isomangostin and garcinone E were found to be active constituents in the anticomplement assay used. Copyright © 2010 John Wiley & Sons, Ltd.