bluuebunny/crossref_metadata_2025 huggingface dataset:
Precise determination of the erythema response of human skin to ultraviolet radiation and quantification of effects of protectors
Authors: Healy Zachary R. , Dinkova‐Kostova Albena T. , Wehage Scott L. , Thompson Richard E. , Fahey Jed W. , Talalay Paul
Published: January 2009

Background: We describe highly reproducible methods for quantifying the erythema response of precisely selected areas (spots) of human skin to graded doses of ultraviolet radiation (UVR). These methods have permitted evaluation of the efficacy of protectors, such as sulforaphane from crucifers, that defend cells through induction of cytoprotective (phase 2) genes.

Methods: Spots on the back were precisely located by opaque, adhesive, vinyl templates provided with 16 circular, 2.0 cm diameter occludable windows. Doses (100–800 mJ/cm2) of narrow‐band (311 nm) UVR were administered, and the erythema index (a*) was measured with a chromometer on treated and control areas, before and after radiation.

Results: Daily variations in basal a* values of each spot were much smaller than the differences of a* values among spots of one individual, or those of corresponding spots among different individuals. The increments in erythema responses to UVR (Δa*) were similar despite large variations of basal a* of spots. The most appropriate measure of UVR‐evoked erythema is therefore the Δa* value for each spot, which is an independent observational entity. Δa* was proportional to UVR dose, and independent of spot location. To evaluate effectiveness of protectors against UVR damage we paired horizontally adjacent spots for treatment and controls. Vertical or random spot pairing did not provide significantly higher consistency. Protective efficacy against UVR erythema is appropriately expressed as percent reduction in Δa* values upon treatment with inducers.

Conclusions: The protection of skin against UVR damage can be quantified precisely from changes in erythema index (Δa*) obtained with a chromometer.
Neurocognitive variation in smoking behavior and withdrawal: genetic and affective moderators
Authors: Evans D. E. , Park J. Y. , Maxfield N. , Drobes D. J.
Published: January 2009

A burgeoning literature suggests that attentional factors are associated with smoking behavior (e.g. direct nicotine effects and smoking withdrawal). This study examined differences in attentional processing between nonsmokers, satiated smokers and overnight nicotine‐deprived smokers by comparing the amplitude of the P300 (P3) component of the event‐related brain potential (ERP) elicited during a go–nogo task. We also examined the moderating effects of a common dopamine receptor genotype and state negative affect (SNA) on this ERP index of attention. Nonsmokers relative to smokers had greater nogo P3 amplitude. Carrying the A1 allele at the dopamine receptor D2 (DRD2) Taq1A polymorphism site moderated the effects of withdrawal on nogo P3 amplitude, suggesting the A1 allele is a vulnerability marker for withdrawal‐related attentional deficits. Increased SNA also predicted attenuated P3 amplitude among deprived smokers. These findings suggest that DRD2 status and SNA moderate the effects of smoking status and withdrawal on neurocognitive variation during attentional processing. This research contributes to a better understanding of the role of individual differences and attentional processing in smoking behavior.
Cardiorespiratory fitness and body mass index values in 9‐year‐old rural Norwegian children
Authors: Resaland GK , Mamen A , Anderssen SA , Andersen LB
Published: January 2009

Aim: To describe cardiorespiratory fitness and body mass index (BMI) values in a representative population of 9‐year‐old Norwegian children in two rural communities and compare present values with previous findings.

Methods: Two hundred and fifty‐nine 9‐year‐old children were invited, and 256 participated in this study. Maximal oxygen uptake was directly measured during a continuous progressive treadmill protocol. Body mass and height were also measured.

Results: The mean ± SD relative maximal oxygen uptake was 52.8 ± 6.5 for boys and 46.9 ± 7.2 mL/kg/min for girls. Eight percent of the boys and 16.8% of the girls were classified as overweight, and 1.6% of the boys and 6.9% of the girls as obese. Mean age, body mass, height and Ponderal index were not significantly different between sexes. Girls had a higher BMI than boys (p = 0.05).

Conclusion: Compared to earlier Norwegian studies, children's BMI values seem to have increased substantially. This increase is most pronounced in girls. When assessing these differences using the PI, this increase is less marked. Comparing maximal oxygen uptake data with that in earlier Nordic studies, there is no evidence that fitness has declined among 9‐year olds. However, the limitations of the few earlier studies make reliable comparisons difficult.
ADPase activity of recombinantly expressed thermotolerant ATPases may be caused by copurification of adenylate kinase of Escherichia coli
Authors: Chen Baoyu , Sysoeva Tatyana A. , Chowdhury Saikat , Guo Liang , Nixon B. Tracy
Published: January 2009

Except for apyrases, ATPases generally target only the γ‐phosphate of a nucleotide. Some non‐apyrase ATPases from thermophilic microorganisms are reported to hydrolyze ADP as well as ATP, which has been described as a novel property of the ATPases from extreme thermophiles. Here, we describe an apparent ADP hydrolysis by highly purified preparations of the AAA+ ATPase NtrC1 from an extremely thermophilic bacterium, Aquifex aeolicus. This activity is actually a combination of the activities of the ATPase and contaminating adenylate kinase (AK) from Escherichia coli, which is present at 1/10 000 of the level of the ATPase. AK catalyzes conversion of two molecules of ADP into AMP and ATP, the latter being a substrate for the ATPase. We raise concern that the observed thermotolerance of E. coli AK and its copurification with thermostable proteins by commonly used methods may confound studies of enzymes that specifically catalyze hydrolysis of nucleoside diphosphates or triphosphates. For example, contamination with E. coli AK may be responsible for reported ADPase activities of the ATPase chaperonins from Pyrococcus furiosus, Pyrococcus horikoshii, Methanococcus jannaschii and Thermoplasma acidophilum; the ATP/ADP‐dependent DNA ligases from Aeropyrum pernix K1 and Staphylothermus marinus; or the reported ATP‐dependent activities of ADP‐dependent phosphofructokinase of P. furiosus. Purification methods developed to separate NtrC1 ATPase from AK also revealed two distinct forms of the ATPase. One is tightly bound to ADP or GDP and able to bind to Q but not S ion exchange matrixes. The other is nucleotide‐free and binds to both Q and S ion exchange matrixes.
Expression of Helicobacter pylori CagA domains by library‐based construct screening
Authors: Angelini Alessandro , Tosi Tommaso , Mas Philippe , Acajjaoui Samira , Zanotti Giuseppe , Terradot Laurent , Hart Darren J.
Published: January 2009

Highly pathogenic strains of Helicobacter pylori use a type IV secretion system to inject the CagA protein into human gastric cells. There, CagA associates with the inner side of the membrane and is tyrosine‐phosphorylated at EPIYA motifs by host kinases. The phosphorylation triggers a series of interactions between CagA and human proteins that result in a dramatic change of cellular morphology. Structural and functional analyses of the protein have proved difficult, due to the proteolytically sensitive nature of the recombinant protein. To circumvent these difficulties, we applied ESPRIT, a library‐based construct screening method, to generate a comprehensive set of 5′‐randomly deleted gene fragments. Screening of 18 432 constructs for soluble expression resulted in a panel of 40 clones, which were further investigated by large‐scale purification. Two constructs of approximately 25 and 33 kDa were particularly soluble and were purified to near homogeneity. CagA fragments larger than 40 kDa were prone to heavy proteolysis at the C‐terminus, with a favoured cleavage site near the first EPIYA motif. Thus, these well‐expressed recombinant constructs isolated are likely to be similar to those observed following natural proteolysis in human cells, and open the way for structural and functional studies requiring large amounts of purified material.
A neomorphic sgs3 allele stabilizing miRNA cleavage products reveals that SGS3 acts as a homodimer
Authors: Elmayan Taline , Adenot Xavier , Gissot Lionel , Lauressergues Dominique , Gy Isabelle , Vaucheret Hervé
Published: January 2009

The putative RNA‐binding protein SUPPRESSOR OF GENE SILENCING 3 (SGS3) protects RNA from degradation before transformation into dsRNA by the RNA‐dependent RNA polymerase RDR6 during plant post‐transcriptional gene silencing and trans‐acting small interfering (siRNA) pathways. In this study, we show that SGS3 acts as a homodimer, and that the point mutation sgs3‐3 impairs post‐transcriptional gene silencing in a dominant‐negative manner through the formation of SGS3/sgs3‐3 heterodimers. Unlike complete‐loss‐of‐function sgs3 mutants, which are impaired in the accumulation of both micro RNA‐directed TAS cleavage products and mature trans‐acting siRNAs, the sgs3‐3 mutant overaccumulates TAS cleavage products and exhibits slightly reduced trans‐acting siRNA accumulation. Together, these results suggest that sgs3‐3 is a neomorphic allele that shows increased RNA protective activity, resulting in decreased RNA processing by downstream post‐transcriptional gene silencing and trans‐acting siRNA pathway components.
Accessory active site residues of Streptomyces sp. N174 chitosanase
Authors: Lacombe‐Harvey Marie‐Ève , Fukamizo Tamo , Gagnon Julie , Ghinet Mariana G. , Dennhart Nicole , Letzel Thomas , Brzezinski Ryszard
Published: January 2009

The chitosanase from Streptomyces sp. N174 (CsnN174) is an inverting glycoside hydrolase belonging to family 46. Previous studies identified Asp40 as the general base residue. Mutation of Asp40 into glycine revealed an unexpectedly high residual activity. D40G mutation did not affect the stereochemical mechanism of catalysis or the mode of interaction with substrate. To explain the D40G residual activity, putative accessory catalytic residues were examined. Mutation of Glu36 was highly deleterious in a D40G background. Possibly, the D40G mutation reconfigured the catalytic center in a way that allowed Glu36 to be positioned favorably to perform catalysis. Thr45 was also found to be essential. Thr45 is thought to orientate the nucleophilic water molecule in a position to attack the glycosidic link. The finding that expression of heterologous CsnN174 in Escherichia coli protects cells against the antimicrobial effect of chitosan, allowed the selection of active chitosanase variants after saturation mutagenesis. Thr45 could be replaced only by serine, indicating the importance of the hydroxyl group. The newly identified accessory catalytic residues, Glu36 and Thr45 are located on a three‐strand β sheet highly conserved in GH19, 22, 23, 24 and 46, all members of the ‘lysozyme superfamily’. Structural comparisons reveal that each family has its catalytic residues located among a small number of critical positions in this β sheet. The position of Glu36 in CsnN174 is equivalent to general base residue in GH19 chitinases, whereas Thr45 is located similarly to the catalytic residue Asp52 of GH22 lysozyme. These examples reinforce the evolutionary link among these five GH families.
Data‐driven homology modelling of P‐glycoprotein in the ATP‐bound state indicates flexibility of the transmembrane domains
Authors: Stockner Thomas , de Vries Sjoerd J. , Bonvin Alexandre M. J. J. , Ecker Gerhard F. , Chiba Peter
Published: January 2009

Human P‐glycoprotein is an ATP‐binding cassette transporter that plays an important role in the defence against potentially harmful molecules from the environment. It is involved in conferring resistance against cancer therapeutics and plays an important role for the pharmacokinetics of drugs. The lack of a high resolution structure of P‐glycoprotein has hindered its functional understanding and represents an obstacle for structure based drug development. The homologous bacterial exporter Sav1866 has been shown to share a common architecture and overlapping substrate specificity with P‐glycoprotein. The structure of Sav1866 suggests that helices in the transmembrane domains diverge at the extracytoplasmic face, whereas cross‐link information and a combination of small angle X‐ray scattering and cryo‐electron crystallography data indicate that helices 6 and 12 of P‐glycoprotein are closer in P‐glycoprotein than in the crystal structure of Sav1866. Using homology modelling, we present evidence that the protein possesses intrinsic structural flexibility to allow cross‐links to occur between helices 6 and 12 of P‐glycoprotein, thereby reconciling crystallographic models with available experimental data from cross‐linking.
Amyloid‐β protofibril levels correlate with spatial learning in Arctic Alzheimer’s disease transgenic mice
Authors: Lord Anna , Englund Hillevi , Söderberg Linda , Tucker Stina , Clausen Fredrik , Hillered Lars , Gordon Marcia , Morgan Dave , Lannfelt Lars , Pettersson Frida E. , Nilsson Lars N. G.
Published: January 2009

Oligomeric assemblies of amyloid‐β (Aβ) are suggested to be central in the pathogenesis of Alzheimer’s disease because levels of soluble Aβ correlate much better with the extent of cognitive dysfunctions than do senile plaque counts. Moreover, such Aβ species have been shown to be neurotoxic, to interfere with learned behavior and to inhibit the maintenance of hippocampal long‐term potentiation. The tg‐ArcSwe model (i.e. transgenic mice with the Arctic and Swedish Alzheimer mutations) expresses elevated levels of Aβ protofibrils in the brain, making tg‐ArcSwe a highly suitable model for investigating the pathogenic role of these Aβ assemblies. In the present study, we estimated Aβ protofibril levels in the brain and cerebrospinal fluid of tg‐ArcSwe mice, and also assessed their role with respect to cognitive functions. Protofibril levels, specifically measured with a sandwich ELISA, were found to be elevated in young tg‐ArcSwe mice compared to several transgenic models lacking the Arctic mutation. In aged tg‐ArcSwe mice with considerable plaque deposition, Aβ protofibrils were approximately 50% higher than in younger mice, whereas levels of total Aβ were exponentially increased. Young tg‐ArcSwe mice showed deficits in spatial learning, and individual performances in the Morris water maze were correlated inversely with levels of Aβ protofibrils, but not with total Aβ levels. We conclude that Aβ protofibrils accumulate in an age‐dependent manner in tg‐ArcSwe mice, although to a far lesser extent than total Aβ. Our findings suggest that increased levels of Aβ protofibrils could result in spatial learning impairment.
Improvement in Quality of Sexual Life in Female Partners of Men with Erectile Dysfunction Treated with Sildenafil Citrate: Findings of the Index of Sexual Life (ISL) in a Couple Study
Authors: Chevret-Méasson Marie , Lavallée Emmanuel , Troy Sylvie , Arnould Benoit , Oudin Séverine , Cuzin Beatrice
Published: January 2009

Introduction

Women’s quality of sexual life is strongly impaired by erectile dysfunction (ED). Women’s involvement in ED treatment is important for compliance and long-term efficacy but remains difficult. The Index of Sexual Life (ISL), specific of the quality of sexual life of women with ED partners, is used here to assess the impact of ED treatment on female partners.

Aim

The study explored in a context close to routine clinical practice the effect of sildenafil citrate (Viagra®; Pfizer, New York, NY, USA) treatment on women’s quality of sexual life, in parallel with men’s ED evaluations.

Methods

This prospective, open-labeled clinical trial was performed in France in 2006. Sexologists and andrologists recruited 67 volunteer couples for a 14-week sildenafil citrate treatment of male partners, without sex therapy in parallel.

Main Outcome Measures

Women’s quality of sexual life using ISL, and men’s ED using International Index of Erectile Function (IIEF) and Self-Esteem And Relationship (SEAR) were assessed at baseline and at the end of the study. Satisfaction for treatment was measured using Erectile Dysfunction Inventory of Treatment Satisfaction (EDITS) and EDITS Partner.

Results

The ISL sexual life satisfaction score was low at baseline (12.3), and increased by 8.3 during the study (P < 0.0001). Women were 79.0% to be responders according to ISL assessment. The other ISL dimensions also improved. The final ISL sexual life satisfaction score was dependant on women’s age and final IIEF scores. The observed correlations between the ISL sexual life satisfaction dimension and the IIEF erectile function dimension, and the SEAR confidence dimension confirmed our assumptions. Both partners were highly satisfied with the treatment.

Conclusion

Women satisfaction with their sex life was improved by ED treatment (sildenafil citrate). Couple global caring seemed to amplify the well-known effect of ED treatment for men. The ISL could be a useful tool to help women in their partner’s treatment and to integrate ED treatment in a couple approach.
Scoring Correspondence in Outcomes Related to Erectile Dysfunction Treatment on a 4-Point Scale (SCORE-4)
Authors: Cappelleri Joseph C. , Bushmakin Andrew G. , Symonds Tara , Schnetzler Gabriel
Published: January 2009

Introduction

The Erection Hardness Score (EHS), a validated single-item patient-reported outcome (PRO), may provide a simple method to capture erectile dysfunction (ED) symptoms and to monitor treatment outcome.

Aim

To map the relationship between the EHS, which was used as the anchor, and other validated PROs: International Index of Erectile Function (IIEF), Quality of Erection Questionnaire (QEQ), Sexual Experience Questionnaire (SEX-Q), and Self-Esteem and Relationship questionnaire (SEAR).

Methods

Data were from a trial of flexible-dose sildenafil (50 or 100 mg) in 209 men with ED.

Main Outcome Measures

A mixed-effects repeated-measures model with EHS as a categorical explanatory variable and each of the other PROs, as a separate dependent variable, was applied to analyze the longitudinal data from randomization to the end of the 10-week, double-blind, placebo-controlled phase and the 6-week open-label phase. EHS data, which were generated at each sexual encounter (event), were averaged per patient over the same recall period that preceded administration of the other PRO questionnaires.

Results

Scores on all domains of the IIEF and SEX-Q, as well as the SEAR total score and SEAR Sexual Relationship domain, discriminated on all EHS categories. The QEQ total score discriminated on all EHS categories except EHS 1 and EHS 2. Although the model did not impose any functional relationship between PRO score and EHS, an approximately linear relationship existed between the EHS and all other PROs, which was especially pronounced for those PROs that were more directly related to erectile quality or function.

Conclusions

The relationship between discrete EHS categories and PRO scores demonstrates the close correspondence of erectile hardness with erectile function (IIEF), erection quality (QEQ), overall sexual experience (SEX-Q), and ED-related psychosocial factors (SEAR) in men with ED.
Extraction and Microencapsulation of Khat: Effects on Sexual Motivation and Estradiol Level in Female Rats
Authors: Aziz Hesham Abdul , Peh Kok Khiang , Tan Yvonne Tze Fung
Published: January 2009

Introduction

Khat (Catha edulis) is an evergreen tree/shrub that is thought to affect sexual motivation or libido. Its positive effect on sexual desire is more frequently observed in females than in males and occurs when khat is chewed. Thus, khat’s effects on sexual behavior may depend on the release mode of its active constituent.

Aim

This study aimed to investigate the effect of dried khat alkaloids on the sexual motivation and estradiol levels of female rats, with special emphasis on the importance of the sustained release effect.

Methods

Dried khat leaves were extracted and isolated. The alkaloids in khat extract were identified and calculated using thin layer chromatography and high-performance liquid chromatography. The isolated khat extract was microencapsulated using a phase separation coacervation method. The morphology, particle size, yield, drug loading, and entrapment efficiency were evaluated. The in vitro release and stability of alkaloids in khat extract and in khat extract microcapsules were determined. The effect of khat extract microcapsules and varying doses of khat extract on sexual motivation in female rats were investigated. Additionally, estradiol levels, vaginal secretions and vaginal pH were determined.

Main Outcome Measures

The differences in the effect of khat extract and khat extract microcapsules on sexual motivation, vaginal secretion and estradiol levels in female rats were compared.

Results

Cathine and norephedrine were identified in the isolated khat extract at composition of 81.3% and 17.2%, respectively. Among the formulations studied, khat extract microcapsules of formulation 2:3:5 (containing a ratio of khat extract to ovalbumin to gelatin of 2:3:5) were found to exhibit higher yield, loading, and entrapment efficiency. Khat extract microcapsules showed sustained in vitro release and were more stable than khat extract. In addition, khat extract microcapsules enhanced sexual motivation, increased vaginal secretions, and upregulated estradiol level in female rats.

Conclusion

The sustained release of alkaloids from dried khat has significantly enhanced the sexual motivation and increased the estradiol level of female rats. Thus the release of dried khat alkaloids from microcapsules might be an effective means of enhancing the libido in females.
SYNTHESIS: Evolutionary ecology of microbial wars: within‐host competition and (incidental) virulence
Authors: Brown Sam P. , Fredrik Inglis R. , Taddei François
Published: January 2009

Invading an occupied niche is a formidable ecological challenge, and one of particular human importance in the context of food‐borne microbial pathogens. We discuss distinct categories of invader‐triggered environmental change that facilitate invasion by emptying their niche of competitors. Evidence is reviewed that gut bacteria use such strategies to manipulate their environment (via bacteriocins, temperate phage viruses or immuno‐manipulation) at the expense of their competitors are reviewed. The possible virulence implications of microbial warfare among multiple co‐infecting strains are diverse. Killing competitors can reduce virulence by reducing overall microbial densities, or increase virulence if for example the allelopathic mechanism involves immuno‐manipulation. Finally, we place microbial anti‐competitor strategies in a social evolution framework, highlighting how costly anti‐competitor strategies can be understood as examples of microbial spite. We conclude by discussing other invasive species that have also developed such proactive strategies of invasion.
SYNTHESIS: Plastic parasites: sophisticated strategies for survival and reproduction?
Authors: Reece Sarah E. , Ramiro Ricardo S. , Nussey Daniel H.
Published: January 2009

Adaptive phenotypic plasticity in life history traits, behaviours, and strategies is ubiquitous in biological systems. It is driven by variation in selection pressures across environmental gradients and operates under constraints imposed by trade‐offs. Phenotypic plasticity has been thoroughly documented for multicellular taxa, such as insects, birds and mammals, and in many cases the underlying selective pressures are well understood. Whilst unicellular parasites face many of the same selective pressures and trade‐offs, plasticity in their phenotypic traits has been largely overlooked and remains poorly understood. Here, we demonstrate that evolutionary theory, developed to explain variation observed in the life‐history traits of multicellular organisms, can be applied to parasites. Though our message is general – we can expect the life‐histories of all parasites to have evolved phenotypic plasticity – we focus our discussion on malaria parasites. We use an evolutionary framework to explain the trade‐offs that parasites face and how plasticity in their life history traits will be expressed according to changes in their in‐host environment. Testing whether variation in parasites traits is adaptive will provide new and fundamental insights into the basic biology of parasites, their epidemiology and the processes of disease during individual infections.
The dental patient with special needs: a review of indications for treatment under general anesthesia
Authors: Dougherty Nancy
Published: January 2009

General anesthesia (GA) can play an important role in the facilitation of dental treatment for individuals who present with challenging behaviors. This article presents a review of the literature discussing indications for the utilization of GA in the treatment of dental patients with special needs.
Numerical-Experimental Study and Solutions to Reduce the Dwell-Time Threshold for Fusion-Free Consecutive Injections in a Multijet Solenoid-Type CR System
Authors: Catania Andrea E. , Ferrari Alessandro , Spessa Ezio
Published: January 2009

In “multijet” common rail (CR) diesel injection systems, when two consecutive injection current pulses approach each other, a merging of the two injections into a single one can occur. Such an “injection fusion” causes an undesired excessive amount of injected fuel, worsening both fuel consumption and particulate emissions. In order to avoid this phenomenon, lower limits to the dwell-time values are introduced in the control unit maps by a conservatively overestimated threshold, which reduces the flexibility of multiple-injection management. The injection fusion occurrence is mainly related to the time delay between the electrical signal to the solenoid and the nozzle opening and closure. The dwell-time fusion threshold was found to strongly decrease particularly with the nozzle closure delay. A functional dependence of the nozzle opening and closure delays on the solenoid energizing time and nominal rail pressure was experimentally assessed, and the injection temporal duration was correlated to the energizing time and rail pressure. A multijet CR injection-system mathematical model that was previously developed, including thermodynamics of liquids, fluid dynamics, mechanics of subsystems, and electromagnetism equations, was applied to better understand the cause and effect relationships for nozzle opening and closure delays. In particular, numerical results on the time histories of delivery- and control-chamber pressures, pilot- and needle-valve lifts, and mass flow rates through Z and A holes were obtained and analyzed to highlight the dependence of nozzle opening and closure delays on injector geometric features, physical variables, and valve dynamics. The nozzle closure delay was shown to strongly depend on the needle dynamics. Parametric numerical tests were carried out to identify configurations useful for minimizing the nozzle closure delay. Based on the results of these tests, a modified version of a commercial electroinjector was built, so as to achieve effectively lower nozzle closure delays and very close sequential injections without any fusion between them.
Compliant Hybrid Journal Bearings Using Integral Wire Mesh Dampers
Authors: Ertas Bugra H.
Published: January 2009

The following work presents a new type of hybrid journal bearing developed for enabling oil-free operation of high performance turbomachinery. The new design integrates compliant hydrostatic-hydrodynamic partitioned bearing pads with two flexibly mounted integral wire mesh dampers. The primary aim of the new bearing configuration was to maximize the load-carrying capacity and effective damping levels while maintaining adequate compliance to misalignment and variations in rotor geometry. The concept of operation is discussed along with the description of the bearing design. Several experiments using room temperature air as the working fluid were performed that demonstrate proof of concept, which include lift-off tests, bearing load tests, and rotordynamic characterization tests. The experiments demonstrate stable operation to 40,000 rpm (2.8×106 DN) of a 2.750 in. (70 mm) diameter bearing. In addition to the experimental results, an analytical model is presented for the compliant bearing system. The aeroelastic theory couples the steady state numerical solution of the compressible Reynolds flow equation with a flexible structure possessing translational and rotational compliance. This was achieved by formulating a fluid-structure force balance for each partitioned bearing pad while maintaining a global mass flow balance through the hydrostatic restrictors and bearing lands. Example numerical results for pad pressure profile, film thickness, torque, and leakage are shown.
Assessment of Different Actuator Concepts for Acoustic Boundary Control of a Premixed Combustor
Authors: Bothien Mirko R. , Moeck Jonas P. , Paschereit Christian Oliver
Published: January 2009

In the design process, new burners are generally tested in combustion test rigs. With these experiments, computational fluid dynamics, and finite element calculations, the burners’ performance in the full-scale engine is sought to be predicted. Especially, information about the thermoacoustic behavior and the emissions is very important. As the thermoacoustics strongly depend on the acoustic boundary conditions of the system, it is obvious that test rig conditions should match or be close to those of the full-scale engine. This is, however, generally not the case. Hence, if the combustion process in the test rig is stable at certain operating conditions, it may show unfavorable dynamics at the same conditions in the engine. In previous works, the authors introduced an active control scheme, which is able to mimic almost arbitrary acoustic boundary conditions. Thus, the test rig properties can be tuned to correspond to those of the full-scale engine. The acoustic boundary conditions were manipulated using woofers. In the present study, proportional valves are investigated regarding their capabilities of being used in the control scheme. It is found that the test rig impedance can be tuned equally well. In contrast to the woofers, however, the valves could be used in industrial applications, as they are more robust and exhibit more control authority. Additionally, the control scheme is further developed and used to tune the test rig at discrete frequencies. This exhibits certain advantages compared with the case of control over a broad frequency band.
Foreign Object Damage in an Oxide/Oxide Composite at Ambient Temperature
Authors: Choi Sung R. , Alexander Donald J. , Kowalik Robert W.
Published: January 2009

Foreign object damage behavior of an oxide/oxide (N720/AS) ceramic matrix composite was determined at ambient temperature using impact velocities ranging from 100 m/s to 400 m/s by 1.59 mm diameter steel-ball projectiles. Two different support configurations of target specimens were used: fully supported and partially supported. The degree of post-impact strength degradation increased with increasing impact velocity and was greater in a partially supported configuration than in a fully supported one. For the fully supported configuration, frontal contact stress played a major role in generating composite damage, while for the partially supported case, both frontal contact and backside flexure stresses were the combined sources of damage generation. The oxide/oxide composite was able to survive high energy (∼1.3 J) impacts without complete structural failure. The degree of relative post-impact strength degradation of the oxide/oxide composite was similar to that of an advanced SiC/SiC composite observed from a previous study, regardless of the type of specimen support. Like the SiC/SiC composite, impact-damage tolerance was greater in the oxide/oxide than in monolithic silicon nitride ceramics for impact velocities >300 m/s.
A General Purpose Test Facility for Evaluating Gas Lubricated Journal Bearings
Authors: Ertas B. , Drexel M. , Van Dam J. , Hallman D.
Published: January 2009

The present work describes the detailed design and operational capabilities of a general purpose test facility developed to evaluate the dynamics and performance of gas lubricated journal bearings. The component level test facility was developed to serve as an initial tollgate test platform for certifying gas lubricated journal bearings into aircraft engine applications. A rotating test rig was engineered to test 70–120 mm diameter bearings at 40,000–80,000 rpm and 1200°F. The test rig described in this paper possesses design elements that enable the simultaneous application of dynamic and static load profiles of up to 1000 lb while monitoring and measuring the bearing torque. This capability allows for the characterization of several critical metrics such as bearing lift off speed characteristics, load capacity, and frequency dependent rotordynamic force coefficients. This paper discusses the functionality of the test facility and presents sample test measurements from several experiments.
Experimental Study on Laser-Induced Ignition of Swirl-Stabilized Kerosene Flames
Authors: Moesl Klaus G. , Vollmer Klaus G. , Sattelmayer Thomas , Eckstein Johannes , Kopecek Herbert
Published: January 2009

Conventional ignition systems of aeroengines are an integral part of the combustion chamber’s structure. Due to this hardware-related constraint, the ignition spark has to be generated in the quench zone of the combustion chamber, which is far from the optimum regarding thermo- and aerodynamics. An improved ignitability of the fuel-air mixture can be found in the central zone of the combustor, where higher local equivalence ratios prevail and where mixing is favorable for a smooth ignition. It would be a major advancement in aeroengine design to position the ignition kernel in these zones. A laser system is able to ignite the fuel-air mixture at almost any location inside of the combustion chamber. Commercial laser systems are under development, which can replace conventional spark plugs in internal combustion engines and gas turbines. This study was conducted to evaluate the applicability of laser ignition in liquid-fueled aeroengines. Ignition tests were performed with premixed natural gas and kerosene to evaluate the different approaches of laser and spark plug ignition. The experiments were carried out on a generic test rig with a well-investigated swirler, allowing sufficient operational flexibility for parametric testing. The possibility of the free choice of the laser’s focal point is the main advantage of laser-induced ignition. Placing the ignition kernel at the spray cone’s shear layer or at favorable locations in the recirculation zone could significantly increase the ignitability of the system. Consequently, the laser ignition of atomized kerosene was successfully tested down to a global equivalence ratio of 0.23. Furthermore, the laser outperformed the spark plug at ignition locations below axial distances of 50 mm from the spray nozzle.
Losses in High Speed Permanent Magnet Machines Used in Microturbine Applications
Authors: Huynh Co , Zheng Liping , Acharya Dipjyoti
Published: January 2009

High speed permanent magnet (PM) machines are used in microturbine applications due to their compactness, robust construction, and high efficiency characteristics. These machines are integrated with the turbines and rotate at the same speeds. This paper discusses in detail the losses in high speed PM machines. A typical PM machine designed for microturbine application is presented with its detailed loss calculations. Various loss verification methods are also discussed.
Real-Time Self-Learning Optimization of Diesel Engine Calibration
Authors: Malikopoulos Andreas A. , Assanis Dennis N. , Papalambros Panos Y.
Published: January 2009

Compression ignition engine technologies have been advanced in the past decade to provide superior fuel economy and high performance. These technologies offer increased opportunities for optimizing engine calibration. Current engine calibration methods rely on deriving static tabular relationships between a set of steady-state operating points and the corresponding values of the controllable variables. While the engine is running, these values are being interpolated for each engine operating point to coordinate optimal performance criteria, e.g., fuel economy, emissions, and acceleration. These methods, however, are not efficient in capturing transient engine operation designated by common driving habits, e.g., stop-and-go driving, rapid acceleration, and braking. An alternative approach was developed recently, which makes the engine an autonomous intelligent system, namely, one capable of learning its optimal calibration for both steady-state and transient operating points in real time. Through this approach, while the engine is running the vehicle, it progressively perceives the driver’s driving style and eventually learns to operate in a manner that optimizes specified performance criteria. The major challenge to this approach is problem dimensionality when more than one controllable variable is considered. In this paper, we address this problem by proposing a decentralized learning control scheme. The scheme is evaluated through simulation of a diesel engine model, which learns the values of injection timing and variable geometry turbocharging vane position that optimize fuel economy and pollutant emissions over a segment of the FTP-75 driving cycle.
Effect on plasma and etch-rate uniformity of controlled phase shift between rf voltages applied to powered electrodes in a triode capacitively coupled plasma reactor
Authors: Sung Dougyong , Jeong Sangmin , Park Youngmin , Volynets Vladimir N. , Ushakov Andrey G. , Kim Gon-Ho
Published: January 2009

The influence of the phase shift between rf voltages applied to the powered electrodes on plasma parameters and etch characteristics was studied in a very high-frequency (VHF) capacitively coupled plasma (CCP) triode reactor. rf voltages at 100MHz were simultaneously applied to the top and bottom electrodes having a controlled phase shift between them, which could be varied between 0° and 360°. Several plasma and process characteristics were measured as a function of the phase shift: (i) radial profiles of plasma-emission intensity, (ii) line-of-sight averaged plasma-emission intensity, and (iii) radial profiles of blanket SiO2 etching rate over a 300mm wafer. Radial profiles of plasma emission were obtained using the scanning optical probe. It has been shown that all the measured characteristics strongly depend on the phase shift: (i) plasma-emission intensity is minimal at phase shift equal to 0° and maximal at 180° for all radial positions, while the emission radial profile changes from bell-shaped distribution with considerable nonuniformity at 0° to a much more flattened distribution at 180°; (ii) line-of-sight averaged plasma-emission intensity shows a similar dependence on the phase shift with minimum and maximum at 0° and 180°, respectively; and (iii) the etch-rate radial profile at 180° shows a much better uniformity as compared to that at 0°. Some of these results can be qualitatively explained by the redistribution of plasma currents that flow between the electrodes and also from the electrodes to the grounded wall with the phase shift. We suggest that the phase-shift effect can be used to improve the plasma and etch-rate spatial uniformity in VHF-CCP triode reactors.
Tritium gas flow dynamics through the source and transport system of the Karlsruhe tritium neutrino experiment
Authors: Malyshev O. B. , Day Chr. , Luo X. , Sharipov F.
Published: January 2009

The source and transport system of the Karlsruhe tritium neutrino experiment (KATRIN) must provide a significant reduction in tritium flow and gas density. It comprises a 10 m long windowless source tube, where the tritium gas is injected, followed by a differential pumping system and a cryogenic pumping system. The primary challenge of the analysis is that the gas flow changes from a viscous flow regime inside the source tube to a transitional flow regime at the first pumping stage, and to a molecular flow regime at the remaining stages of the differential pumping system and further downstream. A strong molecular beaming effect must be considered. This article presents the results of calculations of gas density and flow for the complete source and differential pumping system. It is shown that a total flow-rate reduction factor of 1.4×10−8 can be attained, which is one of the prerequisites to achieve extreme-high vacuum conditions in the spectrometers used in the downstream end of the experiment.
Second-order resonant ZnO-based film bulk acoustic resonator devices and thermal techniques to improve their resonant characteristics
Authors: Mai Linh , Pham Van-Su , Yoon Giwan
Published: January 2009

In this article, the authors describe a novel fabrication technique of ZnO-based film bulk acoustic resonator (FBAR) devices using a new type of multilayered Bragg reflector with very thin chromium (Cr) layers additionally formed between silicon dioxide (SiO2) and tungsten (W) layers. Each Cr layer is considered to enhance the adhesion between the SiO2 and W layers. The fabricated FBAR devices are shown to operate at the frequency range of 2.7–3.0 GHz, along with good return loss as well as high Q factors. Furthermore, various thermal treatments are performed to further improve the resonant characteristics of the FBAR devices, and also their effects on the device characteristics are investigated. At the second-order resonant frequency, excellent resonant characteristics are observed in terms of high return loss and good figure of merit. This feasibility study indicates that the novel fabrication technique can be useful for future broadband mobile worldwide interoperability for microwave access applications.
Nanocomposite TiSiN coatings deposited by large area filtered arc deposition
Authors: Cheng Y. H. , Browne T. , Heckerman B.
Published: January 2009

Nanocomposite TiSiN coatings were successfully synthesized at a temperature and N2 partial pressure of 350 °C and 0.02 Pa, respectively, from TiSi alloy targets with Si content of 20 at. % by using a large area filtered arc deposition technique. Scanning electron microscopy, x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) were used to investigate the surface morphology, crystalline structure, grain size, composition, and bonding structure of the deposited coatings. Nanoindentation was used to characterize the mechanical properties of the deposited coatings. It was found that adding Si into TiN coatings reduces the grain size significantly from 16.9 to 5.8 nm, changes the orientation from (111) to (220) preferred orientation, and increases the hardness and Young’s modulus from 33 and 376 GPa to 51 and 449 GPa, respectively. XPS and XRD results show that the Si/Ti atomic ratio in the coatings is 0.17 and the deposited TiSiN coatings consist of nanosized TiN grains encapsulated by amorphous Si3N4 layer, corresponding to the superhigh hardness of the TiSiN coatings. The high plasma density, ion energy, and ion reactivity of the filtered cathodic arc plasma contribute to the formation of the nanocomposite TiSiN coatings at low temperature and low N2 partial pressure.
Commissioning of modulator‐based IMRT with XiO treatment planning system
Authors: Oguchi Hiroshi , Obata Yasunori
Published: January 2009

This article describes the procedures for correction of the modulator thickness and commissioning of the XiO treatment planning system (TPS) for modulator‐based intensity modulated radiation therapy (M‐IMRT). This modulator manufacturing system adopts a method in which the modulator is milled using a floor‐type computer‐aided numerical control milling machine (CNC‐mill) with modulator data calculated by XiO TPS. XiO TPS uses only effective attenuation coefficients (EAC) for modulator thickness calculation. This article describes a modified method for assessing modulator thickness. A two‐dimensional linear attenuation array was used to correct the modulator thickness calculated by XiO. Narrow‐beam geometry was used for measuring the linear attenuation coefficient (LAC) at off‐axis positions (OAP) for varying brass thicknesses. An equation for the two‐dimensional LAC ratio (2D‐LACR) can be used to calculate the corrected modulator thickness. It is assumed that the broad beam EAC of a small field varies with the brass thickness and the OAP distance in the same way as that of LACR, so the two‐dimensional EAC (2D‐EAC) is equal to the EAC corrected using the LACR. The dose distribution was evaluated for three geometric patterns and one clinical case on low energy x ray with a large field size . The results using the proposed correction method of modulator thickness showed a good agreement between the measured dose distributions and the dose distributions calculated by TPS with the correction. Hence, the method is effective to improve the accuracy of M‐IMRT in XiO TPS. An important problem for the brass modulator is the milling condition, such as the drill diameter and the cutting pitch size. It is necessary to improve the accuracy of M‐IMRT for the “softening” and “hardening” effects of the beam to be considered in dose calculation in patients and the modulator profile design.
Reducing the sensitivity of IMPT treatment plans to setup errors and range uncertainties via probabilistic treatment planning
Authors: Unkelbach Jan , Bortfeld Thomas , Martin Benjamin C. , Soukup Martin
Published: January 2009

Treatment plans optimized for intensity modulated proton therapy (IMPT) may be very sensitive to setup errors and range uncertainties. If these errors are not accounted for during treatment planning, the dose distribution realized in the patient may by strongly degraded compared to the planned dose distribution. The authors implemented the probabilistic approach to incorporate uncertainties directly into the optimization of an intensity modulated treatment plan. Following this approach, the dose distribution depends on a set of random variables which parameterize the uncertainty, as does the objective function used to optimize the treatment plan. The authors optimize the expected value of the objective function. They investigate IMPT treatment planning regarding range uncertainties and setup errors. They demonstrate that incorporating these uncertainties into the optimization yields qualitatively different treatment plans compared to conventional plans which do not account for uncertainty. The sensitivity of an IMPT plan depends on the dose contributions of individual beam directions. Roughly speaking, steep dose gradients in beam direction make treatment plans sensitive to range errors. Steep lateral dose gradients make plans sensitive to setup errors. More robust treatment plans are obtained by redistributing dose among different beam directions. This can be achieved by the probabilistic approach. In contrast, the safety margin approach as widely applied in photon therapy fails in IMPT and is neither suitable for handling range variations nor setup errors.