bluuebunny/crossref_metadata_2025 huggingface dataset:
Research ethics – a widening of the scope and extrapolation into the future
Authors: RIIS P.
Published: August 2009

Abstract. Until recently, the concept of research ethics covered only the safety of, and the respect for, the research subject, i.e. the trial patient and the healthy volunteer. The reason was obviously that human research subjects are the most vulnerable of all key persons involved in biomedical research, and the fact that this vulnerability was made tragically visible through the atrocities of World War II.

Not in any way to detract importance from this part of research ethics these years experience a widening of the conceptual scope, involving not only the researcher and his or her honesty but also society as a whole, not just duties and rights considered unilaterally but bilaterally. And further, including perspectives as science freedom and a given generation's responsibility for its global fellow‐men and for future generations.
Sex Steroid Levels in XY Males and Sex‐Reversed XX Males, of Rainbow Trout (Oncorhynchus mykiss), During the Reproductive Cycle
Authors: Espinosa E , Josa A , Gil L , González N
Published: August 2009

Contents

In this study, the annual cycle of the gonadal steroids testosterone (T), 11‐ketotestosterone (11‐KT), 17β‐oestradiol (E2) and 17α, 20β‐dihydroxy‐4‐pregnen‐3‐one (DHP) was determined using radioimmunoassay and then compared, for XY males (n = 35) and sex‐reversed XX males (n = 27) rainbow trout, to establish possible endocrinology differences. Both in XY males and sex‐reversed XX males, significant correlation was shown between body weight and T (r = 0.5046 and 0.34078, respectively; p < 0.0001) or KT (r = 0.52494 and 0.43545, respectively; p < 0.0001) concentrations. Plasma androgen levels in XY and sex‐reversed XX males were similar and showed an intense seasonal variation. The highest levels for T and 11‐KT were detected from December to April with a peak in January (51.67 ± 5.11 and 61.95 ± 4.25 ng/ml, for XY males and 57.1 ± 5.82 and 59.27 ± 4.84 ng/ml, respectively, for XX males). In addition, there was a positive correlation (p < 0.0001) between T and 11‐KT levels for XY males (r = 0.7533) and sex‐reversed XX males (r = 0.6019). Concentrations of DHP in XY males also showed seasonal variation with a peak in February (25.18 ± 12.99 ng/ml). However, DHP levels in sex‐reversed XX males were undetectable (<0.1 ng/ml) over the year. Levels of E2 were undetectable through the year in both groups of trout. In conclusion, the androgenic and oestrogenic profiles of sex‐reversed XX males were similar to those observed in XY males. The only difference in the annual gonadal steroid cycle between XY and sex‐reversed XX males was in the DHP profile.
Chlorhexidine prevents hypochlorous acid‐induced inactivation of α1‐antitrypsin
Authors: Montecucco F , Bertolotto M , Ottonello L , Pende A , Dapino P , Quercioli A , Mach F , Dallegri F
Published: August 2009

1. Chlorhexidine digluconate has been used as a topical antiseptic in the treatment of acne vulgaris and periodontitis. The acute phase of these diseases involves neutrophilic infiltration. Neutrophil activation and recruitment to inflammatory sites are crucial in both protection against bacterial infection and the induction of hystotoxic damage. Activated neutrophils release several enzymes, including elastase and myeloperoxidase (MPO), which contribute to tissue injury via direct toxic actions, the generation of oxidants and inactivation of protective factors, such as α1‐antitrypsin (α1‐AT). In the present study, we investigated whether chlorhexidine can modulate neutrophil‐mediated histotoxicity.

2. Human primary neutrophils were isolated from healthy donors. Inactivation of α1‐AT by neutrophils or hypochlorous acid (HOCl) was evaluated by spectrophotometry and sodium dodecyl sulphate–polyacrylamide gel electrophoresis analysis of its capacity to complex with porcine pancreatic elastase (PPE). Neutrophil generation of HOCl, superoxide anion and MPO release were assessed spectrophometrically.

3. Chlorhexidine (0, 0.5, 1, 5 and 10 μmol/L) dose‐dependently prevented HOCl‐induced inactivation of α1‐AT and reduced HOCl recovery from phorbol myristate acetate (PMA)‐treated human neutrophils, but did not inhibit superoxide anion and MPO release. Chlorhexidine directly inhibited HOCl recovery from neutrophils and HOCl‐induced inactivation of α1‐AT in a cell‐free assay. Accordingly, chlorhexidine reversed HOCl‐mediated inhibition of α1‐AT capacity to complex with PPE.

4. These data suggest that chlorhexidine prevents neutrophil‐induced α1‐AT inactivation via a direct inhibitory action on HOCl. Although highly speculative, the present study indicates that chlorhexidine may protect inflamed tissues not only through its antimicrobial properties, but also via a direct anti‐inflammatory effect on neutrophil toxic products.
Reactive oxygen species and insulin‐resistant cardiomyopathy
Authors: Mellor Kimberley M , Ritchie Rebecca H , Delbridge Lea MD
Published: August 2009

1. The prevalence of insulin resistance has increased markedly in the past decade and is known to be associated with cardiovascular risk. Evidence of an insulin‐resistant cardiomyopathy, independent of pressure or volume loading influences, is now emerging.

2. Cardiac oxidative stress is often observed coincident with insulin resistance and there is accumulating evidence that reactive oxygen species (ROS) mediate deleterious effects in the insulin‐resistant heart. It is established that ROS modification of signalling proteins can adversely modulate cellular processes, leading to cardiac growth remodelling and dysfunction. The mechanisms of ROS‐induced damage in insulin‐resistant cardiomyopathy are yet to be fully elucidated.

3. A number of different animal models have been used to study cardiac insulin resistance, including high‐sugar dietary interventions, genetically modified diabetic mice and streptozotocin‐induced diabetes. Mechanistic studies manipulating cardiac anti‐oxidant levels, either endogenously or exogenously, in these models have demonstrated a role for ROS in the cardiac manifestations associated with insulin resistance.

4. The present review summarizes the cardiac‐specific characteristics of insulin resistance, the features of cardiac metabolism relevant to ROS generation and ROS‐mediated cardiomyocyte damage pathways. In vivo studies in which a combination of genetic and environmental variables have been manipulated are considered. These studies provide particular insights into the induction and suppression of insulin‐resistant cardiomyopathy.
Dissecting the mechanism of Ca2+‐triggered membrane fusion: Probing protein function using thiol reactivity
Authors: Furber Kendra L , Dean Kwin T , Coorssen Jens R
Published: August 2009

1. Ca2+‐triggered membrane fusion involves the coordinated actions of both lipids and proteins, but the specific mechanisms remain poorly understood. The urchin cortical vesicle model is a stage‐specific native preparation fully enabling the directly coupled functional–molecular analyses necessary to identify critical components of fast triggered membrane fusion.

2. Recent work on lipidic components has established a direct role for cholesterol in the fusion mechanism via local contribution of negative curvature to readily enable the formation of transient lipidic fusion intermediates. In addition, cholesterol‐ and sphingomyelin‐enriched domains regulate the efficiency of fusion by focally organizing other components to ensure an optimized response to the triggering Ca2+ transient.

3. There is less known about the identity of proteins involved in the Ca2+‐triggering steps of membrane fusion. Thiol reagents can be used as unbiased tools to probe protein functions. Comparisons of several thiol‐reactive reagents have identified different effects on Ca2+ sensitivity and the extent of fusion, suggesting that there are at least two distinct thiol sites that participate in the fusion mechanism: one that regulates the efficiency of Ca2+ sensing/triggering and one that may function during the membrane merger event itself.

4. To identify the proteins that regulate Ca2+ sensitivity, the fluorescent thiol reagent Lucifer yellow iodoacetamide was used to potentiate fusion and simultaneously tag the proteins involved. Ongoing work involves the isolation of cholesterol‐enriched membrane fractions to reduce the complexity of the labelled proteome, narrowing the number of candidate proteins.
The place of premedication in pediatric practice
Authors: ROSENBAUM ABRAHAM , KAIN ZEEV N. , LARSSON PETER , LÖNNQVIST PER‐ARNE , WOLF ANDREW R.
Published: August 2009

Behind the multiple arguments for and against the use of premedication, sedative drugs in children is a noble principle that of minimizing psychological trauma related to anesthesia and surgery. However, several confounding factors make it very difficult to reach didactic evidence‐based conclusions. One of the key confounding issues is that the nature of expectations and responses for both parent and child vary greatly in different environments around the world. Studies applicable to one culture and to one hospital system (albeit multicultural) may not apply elsewhere. Moreover, the study of hospital‐related distress begins at the start of the patient’s journey and ends long after hospital discharge; it cannot be focused completely on just the moment of anesthetic induction. Taking an example from actual practice experience, the trauma caused by the actual giving of a premedication to a child who absolutely does not want it and may struggle may not be recorded in a study but could form a significant component of overall effect and later psychological pathology. Clearly, attitudes by health professionals and parents to the practice of routine pediatric premedication, vary considerably, often provoking strong opinions. In this pro–con article we highlight two very different approaches to premedication. It is hoped that this helps the reader to critically re‐evaluate a practice, which was universal historically and now in many centers is more selective.
A systematic review on advancement flaps for rectovaginal fistula in Crohn’s disease: transrectal vs transvaginal approach
Authors: Ruffolo C. , Scarpa M. , Bassi N. , Angriman I.
Published: August 2009

Aim  Despite advances in the treatment of Crohn’s disease (CD), the treatment of rectovaginal (RV) fistula remains challenging. Transrectal (RAF) and transvaginal advancement flaps (VAF) represent two possible alternative surgical approaches to this problem. The study aims to review and compare the results of these approaches for RV fistula in CD.

Method  Medical databases from January 1983 to August 2008 were consulted for potentially relevant publications. All studies dealing with the RV fistula repair in CD with RAF or VAF were included. Two researchers worked independently on the study selection, quality assessment, data extraction and analysis phases of the study. Analyses were performed with Review Manager 2.0 software.

Results  Eleven observational studies were included with a total of 219 flap procedures for RV fistula. The primary fistula closure pooled rate was 54.2% (range 33.3–100%) after RAF and 69.4% (range 0–92.9%) after VAF (P = 0.13). Four studies were eligible for direct comparison between the two procedures. No clearly significant difference between RAF compared with VAF in terms of primary fistula closure rate, nor in terms of overall fistula closure rate, was apparent. The risk of recurrence after RAF compared with VAF seemed similar; in this case, only two studies were taken into consideration.

Conclusions  Although limited by a small number of studies of low clinical evidence level, this systematic review suggests that there is no significant difference in terms of outcome between RAF and VAF for RV fistula in CD.
Developmental profiles for multiple object tracking and spatial memory: typically developing preschoolers and people with Williams syndrome
Authors: O’Hearn Kirsten , Hoffman James E. , Landau Barbara
Published: August 2009

The ability to track moving objects, a crucial skill for mature performance on everyday spatial tasks, has been hypothesized to require a specialized mechanism that may be available in infancy (i.e. indexes). Consistent with the idea of specialization, our previous work showed that object tracking was more impaired than a matched spatial memory task in individuals with Williams syndrome (WS), a genetic disorder characterized by severe visuo‐spatial impairment. We now ask whether this unusual pattern of performance is a reflection of general immaturity or of true abnormality, possibly reflecting the atypical brain development in WS. To examine these two possibilities, we tested typically developing 3‐ and 4‐year‐olds and people with WS on multiple object tracking (MOT) and memory for static spatial location. The maximum number of objects that could be correctly tracked or remembered (estimated from the k‐statistic) showed similar developmental profiles in typically developing 3‐ and 4‐year‐old children, but the WS profile differed from either age group. People with WS could track more objects than 3‐year‐olds, and the same number as 4‐year‐olds, but they could remember the locations of more static objects than both 3‐ and 4‐year‐olds. Combining these data with those from our previous studies, we found that typically developing children show increases in the number of objects they can track or remember between the ages of 3 and 6, and these increases grow in parallel across the two tasks. In contrast, object tracking in older children and adults with WS remains at the level of 4‐year‐olds, whereas the ability to remember multiple locations of static objects develops further. As a whole, the evidence suggests that MOT and memory for static location develop in tandem typically, but not in WS. Atypical development of the parietal lobe in people with WS could play a causal role in the abnormal, uneven pattern of performance in WS. This interpretation is consistent with the idea that multiple object tracking engages different mechanisms from those involved in memory for static object location, and that the former can be particularly disrupted by atypical development.
Calbindin‐1 association and Parkinson’s disease
Authors: Soto‐Ortolaza A. I. , Behrouz B. , Wider C. , Vilariño‐Güell C. , Heckman M. G. , Aasly J. O. , Mark Gibson J. , Lynch T. , Jasinska‐Myga B. , Krygowska‐Wajs A. , Opala G. , Barcikowska M. , Czyzewski K. , Uitti R. J. , Wszolek Z. K. , Farrer M. J. , Ross O. A.
Published: August 2009

Background and purpose:  Calcium levels have been proposed to play an important role in the selective vulnerability of nigrostriatal dopaminergic neurons in Parkinson’s disease (PD). Recently, an association was reported between the calcium buffer, calbindin (rs1805874) and risk of PD in a Japanese patient–control series.

Methods:  We genotyped rs1805874 in four independent Caucasian patient–control series (1543 PD patients, 1771 controls).

Results:  There was no evidence of an association between rs1805874 and disease risk in individual populations or in the combined series (odds ratio: 1.04, 95% CI: 0.82–1.31, P = 0.74).

Discussion:  Our study shows there is no association between rs1805874 and risk for PD in four Caucasian populations. This suggests the effect of calbindin on PD risk displays population specificity.
Democratic Refusal in Iran
Authors: EBADI SHIRIN
Published: August 2009

The Iranian revolution—the political realization of the “Great Refusal” of Western modernization—was a direct consequence a half century later of the forced secularization of the Ottoman Caliphate by Kemal Ataturk. With the superstructure of the Muslim ummah dismantled and replaced by the Turkish nation state, insurgent religious movements, from the (Sunni) Muslim Brotherhood in Egypt to the Shiite imams of Qum and Najaf, moved into the vacuum to reclaim Islam from the shadow of Western dominance.

Now, history is turning again. Iran has been seized by violent turmoil as it seeks to reconcile democracy and religious rule. Secular Turkey is governed by an Islamist‐rooted party. As they struggle to regain their balance, the global economic meltdown threatens a convergence against globalization that joins the Islamist resistance with populist backlashes elsewhere.

Two legendary intelligence agents, a Hezbollah leader, an Iranian dissident philosopher and Shirin Ebadi, the Iranian human rights lawyer and Nobel Laureate, examine this historical turn.
Obama's Afghan Moment
Authors: KHALILZAD ZALMAY
Published: August 2009

President Barack Obama has extended the hand of engagement to the Muslim and Arab world, while warning Israel against new settlements in occupied Palestine and hedging his bets with remote drone strikes against Al‐Qaida and the Taliban in Pakistan. The new CIA director, a military historian and the Somali‐born feminist Ayaan Hirsi Ali assess his strategy.
Thrombolysis in Acute Myocardial Infarction Following Prolonged Cardiopulmonary Resuscitation
Authors: Merriman Charles S. , Kalbfleisch Norm D.
Published: August 2009

ABSTRACT

Thrombolytic therapy was administered to a 64‐year‐old man with an acute anterolateral myocardial infarction who had received cardiopulmonary resuscitation (CPR) for 24 minutes. At the time of thrombolytic therapy, the patient was alert and without clinical or radiographic evidence of injury. The patient developed a retroperitoneal hematoma related to femoral line placement, as well as subcutaneous bruising of the anterior chest wall; both were self‐limited. No long‐term morbidity developed, and the myocardial infarction was aborted. The use of thrombolytic therapy for patients with acute myocardial infarction who have received CPR is reviewed. In the absence of clinical or radiographic evidence of trauma from CPR, patients with acute myocardial infarction should not be excluded from receiving thrombolytic therapy solely because of having had CPR or the duration of CPR.
Early versus Delayed Loading of Mandibular Implant‐Supported Overdentures: 5‐Year Results
Authors: Turkyilmaz Ilser , Tözüm Tolga F. , Tumer Celal
Published: August 2009

Background and purpose: Because of poor retention of complete removable dentures for edentulous patients, implant‐supported mandibular overdentures have lately become a popular alternative for them. The aims of this prospective study were to evaluate treatment outcomes of mandibular overdentures supported by two unsplinted early‐loaded implants and compare these results with those for delayed‐loaded implants.

Materials and methods: A total of 26 edentulous patients were treated with two unsplinted implants supporting a mandibular overdenture. All implants were placed in the canine regions of each mandible according to the one‐stage surgical protocol. There were two groups: test group, in which the overdenture was connected 1 week after surgery, and control group, in which the overdenture was connected 3 months after surgery. Standardized clinical and radiographic parameters were recorded at surgery, and after 3, 6, 12, and 18 months, and 2, 3, 4, and 5 years.

Results: No implants were lost, and 0.93 ± 0.3 mm marginal bone resorption was noted for all implants after 5 years. Clinical implant stability measurements, clinical peri‐implant parameters, and marginal bone resorptions showed no statistically significant differences between the two groups over 5 years.

Conclusion: The results of this prospective clinical study suggest that there is no significant difference in the clinical and radiographic state of patients treated with implant supported mandibular overdentures loaded either 1 week or 3 months after surgery.
Clinical Experience of TiUnite™ Implants: A 5‐year Cross‐Sectional, Retrospective Follow‐Up Study
Authors: Friberg Bertil , Jemt Torsten
Published: August 2009

Background: Little is known of the long‐term clinical and radiographic performance of moderately rough surface implants.

Purpose: The aim of the present retrospective investigation was to study two pioneer cohorts of patients, that is, the first patients to receive Brånemark System® implants with a moderately rough surface (TiUnite™, Nobel Biocare AB, Göteborg, Sweden) at the present clinic. TiUnite implants were inserted either in compromised bone sites in a mixed‐mouth concept together with turned implants or used solely. Patients were followed up over a period of 5 years with regard to implant survival and the marginal bone response.

Materials and Methods: Patients who received both implant types (mixed group) comprised 41 subjects, and the second group (TiUnite group) comprised 70 subjects. A total of 110 turned and 68 TiUnite implants were placed in the mixed group, and 212 TiUnite implants in the TiUnite group. Follow‐up radiographs were obtained at prosthesis placement and at the 1‐ and 5‐year check‐ups, and examined by independent observers.

Results: One turned (0.9%) and two TiUnite (2.9%) implants failed in the mixed group, and three implants (1.6%) failed in the TiUnite group, indicating no significant differences between surfaces or groups (p < .05). The mean marginal bone loss at 5 years was 0.6 mm to 0.8 mm, also indicating no significant differences for the two implant types tested in the mixed group.

Conclusions: Cumulative survival rates for the two implant surfaces were favorable at 5 years, and the marginal bone loss was low and similar for both implant surfaces.
Clinical Pathology Alterations in Pregnant and Non‐Pregnant Rats following Scorpion Envenomation
Authors: Nasr Hmed Ben , Bolon Brad , Hammami Serria Turky , Sahnoun Zouhier , Jamoussi Kamel , Lahyani Amina , Zeghal Khaled Mounir
Published: August 2009

Abstract:  Scorpion envenomation is a growing problem in many countries, especially among women and children. Existing diagnostic criteria are not sufficiently specific to allow antivenin administration in the absence of a confirmed scorpion sting. This study was performed to evaluate conventional haematological and serum chemical measurements as potential indices of scorpion envenomation. Adult, cycling nulliparous and near‐term primiparous, white Wistar rats received a single subcutaneous injection of crude venom (600 µg/kg) from the Buthidae scorpion (Buthus occitanus tunetanus). All envenomed rats were observed for external signs and symptoms of toxicity until necropsy, which entailed terminal blood collection at either 0.5, 1, 2, or 4 hr after venom administration (n = 6 per reproductive state per time‐point) for evaluation of selected clinical chemistry and haematological analytes. Control cohorts (matched for age and reproductive state) received saline injections subcutaneously and were necropsied at 0.5 hr. Almost all envenomed rats but no control animals displayed physical symptoms of intoxication, including agitation, mastication with hypersalivation, and/or vocalizing. Reproducible alterations in clinical pathology parameters were lacking in venom‐treated rats regardless of reproductive status, although modest but significant Rho correlations suggested that mild haemoconcentration, haemolysis, renal function deficits and possibly coagulation difficulties developed over time.
The Effect of Scheduling and Withdrawal of Carisoprodol on Prevalence of Intoxications with the Drug
Authors: Høiseth Gudrun , Karinen Ritva , Sørlid Hanne Kristin , Bramness Jørgen G.
Published: August 2009

Abstract:  The centrally acting muscle relaxant carisoprodol has previously been shown to cause psychomotor impairment and to have a narrow therapeutic range. In Norway, carisoprodol was therefore reclassified to the highest scheduling level from 1 August 2007 and withdrawn from the market on 1 May 2008. The aim of this study was to examine to what extent this action resulted in reduced numbers of driving under the influence (DUI) cases and forensic autopsies concerning carisoprodol, as well as reduced numbers of contacts to the National Poisons Information Centre (NPIC) in Norway regarding carisoprodol. From 2004 to 2008, carisoprodol (and/or its metabolite meprobamate) was detected in a total of 1261 DUI cases, decreasing from 312 in 2004 to 47 in 2008. During the same period, carisoprodol was detected in 194 forensic autopsies, also here decreasing, from 53 cases in 2004 to 11 cases in 2008. The NPIC received 1180 contacts primarily concerning carisoprodol over this period, decreasing from 267 contacts in 2004 to 87 contacts in 2008. During the same period, the sales figures for carisoprodol decreased dramatically, and we observed a relation between the numbers of DUI cases, forensic autopsies and contacts to the NPIC concerning carisoprodol and the sales figures for the drug. This study showed that the rescheduling and withdrawal of carisoprodol from the Norwegian market had a positive effect on the prevalence of carisoprodol in impaired driving, deaths and contacts regarding intoxications. This, together with previous publications, indicates that the population reflected in our data uses regularly prescribed carisoprodol and, to a lesser degree, drug from an illegal street market.
Quantitative Trait Loci for Panicle Layer Uniformity Identified in Doubled Haploid Lines of Rice in Two Environments
Authors: Ma Liangyong , Bao Jinsong , Guo Longbiao , Zeng Dali , Li Ximing , Ji Zhijuan , Xia Yingwu , Yang Changdeng , Qian Qian
Published: August 2009

Uniformity of stem height in rice directly affects crop yield potential and appearance, and has become a vital index for rice improvement. In the present study, a doubled haploid (DH) population, derived from a cross between japonica rice Chunjiang 06 and indica rice TN1 was used to analyze the quantitative trait locus (QTL) for three related traits of panicle‐layer‐uniformity; that is, the tallest panicle height, the lowest panicle height and panicle layer disuniformity in two locations: Hangzhou (HZ) and Hainan (HN). A total of 16 QTLs for three traits distributed on eight chromosomes were detected in two different environments. Two QTLs, qTPH‐4 and qTPH‐8 were co‐located with the QTLs for qLPH‐4 and qLPH‐8, which were only significant in the HZ environment, whereas the qTPH‐6 and qLPH‐6 located at the same interval were only significant in the HN environment. Two QTLs, qPLD‐10‐1 and qPLD‐10‐2, were closely linked to qTPH‐10, and they might have been at the same locus. One QTL, qPLD‐3, was detected in both environments, explaining more than 23% of the phenotypic variations. The CJ06 allele of qPLD‐3 could increase the panicle layer disuniformity by 9.23 and 4.74 cm in the HZ and HN environments. Except for qPLD‐3, almost all other QTLs for the same trait were detected only in one environment, indicating that these three traits were dramatically affected by environmental factors. The results may be useful for elucidation of the molecular mechanism of panicle‐layer‐uniformity and marker assisted breeding for super‐rice.
Heteroblastic Development and Shade‐avoidance in Response to Blue and Red Light Signals in Acacia implexa
Authors: Forster Michael A. , Bonser Stephen P.
Published: August 2009

Information from blue (400–500 nm) and red (660–730 nm) wavelengths is used by plants to determine proximity of neighbors or actual shading. Plants undergo trait changes in order to out‐compete neighbors or accommodate shading. Heteroblasty, the dramatic shift from one leaf type to another during juvenility, can be influenced by the light environment although it is unknown whether cues from blue or red (or both) are driving the developmental process. Seedlings of three populations of Acacia implexa (Mimosaceae) collected from low, medium and high rainfall habitats were grown in a factorial design of high/low blue and red light to determine how light signals affect heteroblasty and patterns of biomass allocation. Low blue light significantly delayed heteroblasty in the low rainfall population and low red light significantly delayed in the low and high rainfall populations. Low blue light increased stem elongation and decreased root biomass whereas low red light induced a strong shade‐avoidance response. These results were consistent across populations although the low rainfall population showed greater trait variability in response to red light signals. We conclude that red light conveys a greater information signal than blue light that affects heteroblasty and seedling development in A. implexa.
Simple enzymatic procedure for l‐carnosine synthesis: whole‐cell biocatalysis and efficient biocatalyst recycling
Authors: Heyland Jan , Antweiler Nicolai , Lutz Jochen , Heck Tobias , Geueke Birgit , Kohler Hans‐Peter E. , Blank Lars M. , Schmid Andreas
Published: August 2009

β‐Peptides and their derivates are usually stable to proteolysis and have an increased half‐life compared with α‐peptides. Recently, β‐aminopeptidases were described as a new enzyme class that enabled the enzymatic degradation and formation of β‐peptides. As an alternative to the existing chemical synthesis routes, the aim of the present work was to develop a whole‐cell biocatalyst for the synthesis and production of β‐peptides using this enzymatic activity. For the optimization of the reaction system we chose the commercially relevant β,α‐dipeptide l‐carnosine (β‐alanine‐l‐histidine) as model product. We were able to show that different recombinant yeast and bacteria strains, which overexpress a β‐peptidase, could be used directly as whole‐cell biocatalysts for the synthesis of l‐carnosine. By optimizing relevant reaction conditions for the best‐performing recombinant Escherichia coli strain, such as pH and substrate concentrations, we obtained high l‐carnosine yields of up to 71%. Long‐time as well as biocatalyst recycling experiments indicated a high stability of the developed biocatalyst for at least five repeated batches. Application of the recombinant E. coli in a fed‐batch process enabled the accumulation of l‐carnosine to a concentration of 3.7 g l−1.
Some Observations on the Origins of Newton’s Law of Cooling and Its Influences on Thermofluid Science
Authors: Cheng K. C.
Published: August 2009

The exact mathematical analogy exists between Newton’s law of cooling and Proposition II, Book II (The motion of bodies in resisting mediums) of the Principia. Several approaches for the proof of Proposition II are presented based on the expositions available in the historical literature. The relationships among Napier’s logarithms (1614), Euclid’s geometric progression (300 B.C.), and Newton’s law of cooling (1701) are explored. Newton’s legacy in the thermofluid sciences is discussed in the light of current knowledge. His characteristic parameter for the temperature fall ratio, ΔT/(T−T∞), is noted. The relationships and connections among Newton’s cooling law (1701), Fourier’s heat conduction theory (1822), and Carnot’s theorem (1824)based on temperature difference (ΔT) as a driving force are noted. After tracing the historical origins of Newton’s law of cooling, this article discusses some aspects of the historical development of the heat transfer subject from Newton to the time of Nusselt and Prandtl. Newton’s legacy in heat transfer remains in the form of the concept of heat transfer coefficient for conduction, convection, and radiation problems. One may conclude that Newton was apparently aware of the analogy of his cooling law to the low Reynolds number motion of a body in a viscous fluid otherwise at rest, i.e., its drag is approximately proportional to its velocity.
Effect of Boundary Conditions on the Onset of Thermomagnetic Convection in a Ferrofluid Saturated Porous Medium
Authors: Shivakumara I. S. , Nanjundappa C. E. , Ravisha M.
Published: August 2009

The onset of thermomagnetic convection in a ferrofluid saturated horizontal porous layer in the presence of a uniform vertical magnetic field is investigated for a variety of velocity and temperature boundary conditions. The Brinkman–Lapwood extended Darcy equation, with fluid viscosity different from effective viscosity, is used to describe the flow in the porous medium. The lower boundary of the porous layer is assumed to be rigid-ferromagnetic, while the upper boundary is considered to be either rigid-ferromagnetic or stress-free. The thermal conditions include fixed heat flux at the lower boundary, and a general convective-radiative exchange at the upper boundary, which encompasses fixed temperature and heat flux as particular cases. The resulting eigenvalue problem is solved using the Galerkin technique and also by using regular perturbation technique when both boundaries are insulated to temperature perturbations. It is found that the increase in the Biot number and the viscosity ratio, and the decrease in the magnetic as well as in the Darcy number is to delay the onset of ferroconvection. Besides, the nonlinearity of fluid magnetization has no effect on the onset of convection in the case of fixed heat flux boundary conditions.
A Robust Asymptotically Based Modeling Approach for Two-Phase Flow in Porous Media
Authors: Awad M. M. , Butt S. D.
Published: August 2009

A simple semitheoretical method for calculating the two-phase frictional pressure gradient in porous media using asymptotic analysis is presented. The two-phase frictional pressure gradient is expressed in terms of the asymptotic single-phase frictional pressure gradients for liquid and gas flowing alone. In the present model, the two-phase frictional pressure gradient for x≅0 is nearly identical to the single-phase liquid frictional pressure gradient. Also, the two-phase frictional pressure gradient for x≅1 is nearly identical to the single-phase gas frictional pressure gradient. The proposed model can be transformed into either a two-phase frictional multiplier for liquid flowing alone (ϕl2) or a two-phase frictional multiplier for gas flowing alone (ϕg2) as a function of the Lockhart–Martinelli parameter X. The advantage of the new model is that it has only one fitting parameter (p), while the other existing correlations, such as the correlation of Larkins et al., Sato et al., and Goto and Gaspillo, have three constants. Therefore, calibration of the new model to the experimental data is greatly simplified. The new model is able to model the existing multiparameter correlations by fitting the single parameter p. Specifically, p=1/3.25 for the correlation of Midoux et al., p=1/3.25 for the correlation of Rao et al., p=1/3.5 for the Tosun correlation, p=1/3.25 for the correlation of Larkins et al., p=1/3.75 for the correlation of Sato et al., and p=1/3.5 for the Goto and Gaspillo correlation.
Numerical and Experimental Investigation of Transient Response of Primary Surface Recuperator Due to Flow Rate Step
Authors: Liu Zhenyu , Su Yongkang , Cheng Huier
Published: August 2009

Temperature transient response of a primary surface recuperator (PSR) is investigated when mass flow rate is subjected to a sudden change. Based on the conservation theorem of energy and structural characteristics of PSR, its unsteady differential equations about the transient temperatures of fluids and solid wall in the recuperator are presented. The numerical results are validated by comparison against the experimental data. The influence of flow rate step magnitude on the transient behavior is studied by maintaining the initial steady states. The influence of the thickness of the corrugated heat transfer foils in the PSR on the temperature transient response is also discussed. The comparative results show the low-weight PSR has much more advantages in transient response than traditional heat exchanger because its time constant of solid wall is much less than shell-tube or plate-fin heat exchanger. PSR is very fit for application to the marine or vehicle gas turbine engine that works under the changeful conditions.
Wide Gap Braze Repair Using Vertically Laminated Repair Scheme
Authors: Nagy Doug , Huang Xiao
Published: August 2009

Repair of after-service gas turbine hot section superalloy components provides considerable saving in life-cycle cost of engines. Whereas a number of methods have been used in the past to repair these superalloy components, wide gap brazing technology has provided a practical alternative to repair difficult-to-weld alloys with substantial damages. In this paper, the historical development of wide gap repair technologies is reviewed first. Subsequently, the recent development in utilizing vertically laminated structure to repair large and deep gap (up to 16 mm) in one brazing cycle will be discussed. The microstructure resulted from this repair scheme will be evaluated and compared to conventional wide gap braze with slurry and that of LPM™ process. It is observed that in conventional wide gap brazing with premixed slurry, the presence of intermetallic compounds can be effectively reduced by reducing the ratio of braze alloy to gap filler which however, also contributes to the increased occurrence of macroscopic voids in the wide gap joint. The LPM™ method, on the other hand, can achieve a macroscopically void-free repair of gap (up to 6 mm) and minimize the formation of intermetallics. By using a vertically laminated repair scheme it is shown that the process is able to repair a deeper gap (up to 16 mm) with no macroscopic defects and reduced intermetallic compounds.
On the Service Performance of Refurbished Turbine Blades in a Power Station
Authors: Tawancy H. M. , Al-Hadhrami Laui
Published: August 2009

Due to initial high cost, refurbishment of turbine blades is of particular importance to the power generation industry to reduce operating costs. In particular, there is a growing interest in developing heat treatment processes capable of restoring most of the original microstructure and corresponding properties of used blades. Toward this objective, it is important to develop an understanding of the behavior of refurbished blades exposed to actual service conditions. Therefore, this investigation was undertaken to analyze the damage produced in a blade refurbished after 40,000 hours of operation at about 800 °C (Westinghouse W501D5A Engine). However, after about 900 hours of operation at the same temperature, the blade was fractured by a ductile intergranular mode. Electron microscopy and computational modeling were used to develop a one-to-one correspondence between microstructure and temperature distribution. Although there was no evidence for overheating during service, the results showed that the blade initially contained γ′ precipitate-free zones alongside grain boundaries, which could accelerate intergranular failure during service. It was concluded that the blade was damaged by improper heat treatment during refurbishing.
Blade Row Interaction in a One and a Half Stage Transonic Turbine Focusing on Three Dimensional Effects: Part II—Clocking Effects
Authors: Schennach O. , Paradiso B. , Persico G. , Gaetani P. , Woisetschla¨ger J.
Published: August 2009

The paper presents an experimental investigation of the flow field in a high-pressure transonic turbine with a downstream vane row (1.5 stage machine) concerning the airfoil indexing. The objective is a detailed analysis of the three dimensional flow field downstream of the high pressure turbine for different vane clocking positions. To give an overview of the time averaged flow field, measurements by means of a pneumatic five hole probe were performed upstream and downstream of the second stator. Furthermore in this planes additional unsteady measurements were carried out with Laser Doppler Velocimetry in order to record rotor phase resolved velocity, flow angle and turbulence distributions at two different clocking positions. In the measurement plane upstream the second vane the time resolved pressure field has been analyzed by means of a Fast Response Aerodynamic Pressure Probe. The paper shows that the secondary flows of the second vane are significantly modified for different clocking positions, in connection with the first vane modulation of the rotor secondary flows. An analysis of the performance of the second vane is also carried out.
Measurements Versus Predictions for Rotordynamic and Leakage Characteristics of a Convergent-Tapered, Honeycomb-Stator/Smooth-Rotor Annular Gas Seal
Authors: van der Velde Daniel E. , Childs Dara W.
Published: August 2009

Measured results are presented for rotordynamic coefficients and leakage rates for two honeycomb-stator seal geometries, a convergent-tapered honeycomb seals (CTHC) and a constant-clearance honeycomb seals (CCHC) tested by Sprowl and Childs in 2007. The rotor diameter was 114.3 mm (4.500 in). The CTHC seals had inlet and exit clearances of 0.334 and 0.204 mm, respectively. The CCHC seal had a constant clearance of 0.204 mm. Honeycomb cells had depths of 3.175 mm (0.125 in) and widths of 0.79 mm (0.031 in). Measurements are reported with air as the test fluid, zero preswirl, ω = 20,200 rpm, a supply pressure of 69 bar (1,000 psi) and supply temperature of 18°C (64.4°F) for both seal geometries. The test pressure ratios are 0.5 for the CCHC seal, and 0.46 for the CTHC seal. The tapered seal leaks about 20% more than the constant-clearance seal. Measured and predicted dynamic coefficients are strong functions of excitation frequency. The measured direct stiffness coefficient was higher for the tapered seal at all excitation frequencies, including a projection to zero frequency, where the CCHC seal was on the order of −2MN/m versus roughly +13MN/m for the tapered seal. The CTHC seal had higher cross-coupled stiffness coefficients than the CCHC seal at all excitation frequencies. The CCHC and CTHC seals had comparable direct damping out to ∼80 Hz. For higher excitation frequencies, the CTHC seal had larger direct damping values. The effective damping Ceff combines the positive effect of direct damping and the destabilizing effect of cross-coupled-stiffness coefficients. It is negative at low frequencies and becomes positive for higher frequencies. The frequency at which it changes sign is called the cross-over frequency. The CCHC had a lower cross-over frequency (better from a stability viewpoint) and higher Ceff values out to ∼80 Hz. At higher excitation frequencies from ∼120Hz onward, the tapered seal has higher effective damping values. Kleynhans and Childs’ 1997 two-control-volume model did a generally good job of predicting the direct stiffness coefficients of both seals. It closely predicted the cross-coupled stiffness coefficients for the CCHC seal but substantially under predicted the values for the CTHC seal. It under predicted the direct damping for the CCHC seal at frequencies below ∼120Hz, but did a good job for higher frequencies. It under predicted direct damping for the CTHC seal at all frequencies. For the CCHC seal, the model did a good job of predicting Ceff at all frequencies and also accurately predicted the cross-over frequency. For the CTHC seal, the model accurately predicted the cross-over frequency but over predicted Ceff below the cross-over frequency (the seal was more destabilizing than predicted) and under predicted Ceff at higher frequencies.
Low Speed Balancing for Supercritical Shafting in Gas Turbines
Authors: Hylton Peter D.
Published: August 2009

Gas turbines are used for power generation with units in a range of sizes. They serve as power plants for both military and commercial aircraft. Demand is for faster, lighter engines, utilizing more advanced manufacturing processes. One of the means of meeting this goal is through use of longer, thinner, more flexible shafts which operate supercritically. Supercritical operation was once viewed as impractical, however, a number of today’s production gas turbines operate in this mode. The shaft manufacturing process is optimal if the shaft balance procedure can be conducted at low speeds, rather than requiring a more expensive and complicated high speed balance process. The objective of the project described in this paper is to develop a systematic process for a low speed balance procedure, which, in conjunction with appropriate damping, would permit a high speed shaft system to transition through additional critical speeds and operate safely above them. The discussion includes research on analytical modeling and analysis of representative shaft systems to determine the optimum locations of the balance planes and outlines an analysis approach for predicting shaft responses.
Secondary Air System Model for Integrated Thermomechanical Analysis of a Jet Engine
Authors: Muller Yannick
Published: August 2009

As temperatures in jet engine combustion chamber and turbine increase, the relevance of heat transfer between structure and secondary airflow is increasing. Secondary air properties greatly influence material temperatures, which control the thermal expansion of engine parts. Redefining tip clearances and seal gaps, this modifies considerably pressure losses and mass flow rates in the air system, impacting flow and material temperatures. The coupling effect, estimated strong, must be accurately addressed to obtain an optimized secondary air system design. The aerodynamic calculations yielding mass flows and pressures, and thermal analysis providing temperatures and the material expansion are performed separately. In reality, there are interactions currently not considered which would require a lot of time-consuming iterations. The present investigation aims at taking this mutual interaction into consideration in a robust and modular analysis tool, combining secondary air system, thermal and mechanical analysis. For air system calculations, a network representation with nodes, chambers, connected by pressure loss devices is used. This network is coupled with a thermomechanical model of the engine secondary air system in the free finite element software CalculiX® [1]. This paper presents the first module implemented in CalculiX®, dedicated to solve typical Secondary Air System problems and gives an insight on the implementation of the coupling process currently under development.
Simultaneous Spike-Type and Modal-Type Stall Inception: Theoretical Analysis
Authors: Pismenny Joseph , Levy Yeshayahou
Published: August 2009

It was recently found experimentally that in a single-stage low-speed axial-flow compressor, the pressure signals during the rotating stall inception depend on the location of the sensors and may be of the same type at several measurement points (for example, only spikes), or of different types at different measurement points (simultaneously, spikes at some points and modes at other points). Both types may also exist simultaneously at the same measurement point. This present paper reports a theoretical investigation, undertaken in an attempt to explain these experimentally recorded phenomena. It is shown that three principal characteristics define the type of stall inception: (1) the nonlinear characteristic of the compressor, (2) its dynamic characteristics jointly with its loading system and (3) the influence of the system with which the compressor is interfaced on the compression process. These characteristics leave scope for simultaneous existence of both types, but as their amplitudes can differ significantly, only one of them may be perceivable.
The Role of Structural Damping in Aeroderivative Engine Structure Modeling
Authors: Yuan Jing , Muszynska Agnieszka , Heyden Kenneth
Published: August 2009

The importance of correctly accounting for the structural damping in complex rotor/support system modeling is demonstrated using a mathematical model that represents dynamic stiffness and response comparisons for a rotor system with various levels of structural damping in the rotor system casing and support. The case study of the dynamic behavior of a complex aeroderivative engine model shows the differences made by including structural damping. The conclusion of this study is that the structural damping has to be included in the model and it plays an important role in the dynamic behavior of the engine.