bluuebunny/crossref_metadata_2025 huggingface dataset:
Potential impact of stress activated retrotransposons on genome evolution in a marine diatom
Authors: Maumus Florian , Allen Andrew E , Mhiri Corinne , Hu Hanhua , Jabbari Kamel , Vardi Assaf , Grandbastien Marie-Angèle , Bowler Chris
Published: December 2009

Background

Transposable elements (TEs) are mobile DNA sequences present in the genomes of most organisms. They have been extensively studied in animals, fungi, and plants, and have been shown to have important functions in genome dynamics and species evolution. Recent genomic data can now enlarge the identification and study of TEs to other branches of the eukaryotic tree of life. Diatoms, which belong to the heterokont group, are unicellular eukaryotic algae responsible for around 40% of marine primary productivity. The genomes of a centric diatom, Thalassiosira pseudonana, and a pennate diatom, Phaeodactylum tricornutum, that likely diverged around 90 Mya, have recently become available.

Results

In the present work, we establish that LTR retrotransposons (LTR-RTs) are the most abundant TEs inhabiting these genomes, with a much higher presence in the P. tricornutum genome. We show that the LTR-RTs found in diatoms form two new phylogenetic lineages that appear to be diatom specific and are also found in environmental samples taken from different oceans. Comparative expression analysis in P. tricornutum cells cultured under 16 different conditions demonstrate high levels of transcriptional activity of LTR retrotransposons in response to nitrate limitation and upon exposure to diatom-derived reactive aldehydes, which are known to induce stress responses and cell death. Regulatory aspects of P. tricornutum retrotransposon transcription also include the occurrence of nitrate limitation sensitive cis-regulatory components within LTR elements and cytosine methylation dynamics. Differential insertion patterns in different P. tricornutum accessions isolated from around the world infer the role of LTR-RTs in generating intraspecific genetic variability.

Conclusion

Based on these findings we propose that LTR-RTs may have been important for promoting genome rearrangements in diatoms.
Effects of temperature on gene expression in embryos of the coral Montastraea faveolata
Authors: Voolstra Christian R , Schnetzer Julia , Peshkin Leonid , Randall Carly J , Szmant Alina M , Medina Mónica
Published: December 2009

Background

Coral reefs are expected to be severely impacted by rising seawater temperatures associated with climate change. This study used cDNA microarrays to investigate transcriptional effects of thermal stress in embryos of the coral Montastraea faveolata. Embryos were exposed to 27.5°C, 29.0°C, and 31.5°C directly after fertilization. Differences in gene expression were measured after 12 and 48 hours.

Results

Analysis of differentially expressed genes indicated that increased temperatures may lead to oxidative stress, apoptosis, and a structural reconfiguration of the cytoskeletal network. Metabolic processes were downregulated, and the action of histones and zinc finger-containing proteins may have played a role in the long-term regulation upon heat stress.

Conclusions

Embryos responded differently depending on exposure time and temperature level. Embryos showed expression of stress-related genes already at a temperature of 29.0°C, but seemed to be able to counteract the initial response over time. By contrast, embryos at 31.5°C displayed continuous expression of stress genes. The genes that played a role in the response to elevated temperatures consisted of both highly conserved and coral-specific genes. These genes might serve as a basis for research into coral-specific adaptations to stress responses and global climate change.
The repertoire of equine intestinal α-defensins
Authors: Bruhn Oliver , Paul Sven , Tetens Jens , Thaller Georg
Published: December 2009

Background

Defensins represent an important class of antimicrobial peptides. These effector molecules of the innate immune system act as endogenous antibiotics to protect the organism against infections with pathogenic microorganisms. Mammalian defensins are classified into three distinct sub-families (α-, β- and θ-defensins) according to their specific intramolecular disulfide-bond pattern. The peptides exhibit an antimicrobial activity against a broad spectrum of microorganisms including bacteria and fungi. Alpha-Defensins are primarily synthesised in neutrophils and intestinal Paneth cells. They play a role in the pathogenesis of intestinal diseases and may regulate the flora of the intestinal tract. An equine intestinal α-defensin (DEFA1), the first characterised in theLaurasiatheria, shows a broad antimicrobial spectrum against human and equine pathogens. Here we report a first investigation of the repertoire of equine intestinal α-defensins. The equine genome was screened for putative α-defensin genes by using known α-defensin sequences as matrices. Based on the obtained sequence information, a set of oligonucleotides specific to the α-defensin gene-family was designed. The products generated by reverse-transcriptase PCR with cDNA from the small intestine as template were sub-cloned and numerous clones were sequenced.

Results

Thirty-eight equine intestinal α-defensin transcripts were determined. After translation it became evident that at least 20 of them may code for functional peptides. Ten transcripts lacked matching genomic sequences and for 14 α-defensin genes apparently present in the genome no appropriate transcript could be verified. In other cases the same genomic exons were found in different transcripts.

Conclusions

The large repertoire of equine α-defensins found in this study points to a particular importance of these peptides regarding animal health and protection from infectious diseases. Moreover, these findings make the horse an excellent species to study biological properties of α-defensins. Interestingly, the peptides were not found in other species of theLaurasiatheriato date. Comparison of the obtained transcripts with the genomic sequences in the current assembly of the horse (EquCab2.0) indicates that it is yet not complete and/or to some extent falsely assembled.
BAC array CGH in patients with Velocardiofacial syndrome-like features reveals genomic aberrations on chromosome region 1q21.1
Authors: Brunet Anna , Armengol Lluís , Heine Damià , Rosell Jordi , García-Aragonés Manel , Gabau Elisabeth , Estivill Xavier , Guitart Miriam
Published: December 2009

Background

Microdeletion of the chromosome 22q11.2 region is the most common genetic aberration among patients with velocardiofacial syndrome (VCFS) but a subset of subjects do not show alterations of this chromosome region.

Methods

We analyzed 18 patients with VCFS-like features by comparative genomic hybridisation (aCGH) array and performed a face-to-face slide hybridization with two different arrays: a whole genome and a chromosome 22-specific BAC array. Putative rearrangements were confirmed by FISH and MLPA assays.

Results

One patient carried a combination of rearrangements on 1q21.1, consisting in a microduplication of 212 kb and a close microdeletion of 1.15 Mb, previously reported in patients with variable phenotypes, including mental retardation, congenital heart defects (CHD) and schizophrenia. While 326 control samples were negative for both 1q21.1 rearrangements, one of 73 patients carried the same 212-kb microduplication, reciprocal to TAR microdeletion syndrome. Also, we detected four copy number variants (CNVs) inherited from one parent (a 744-kb duplication on 10q11.22; a 160 kb duplication and deletion on 22q11.21 in two cases; and a gain of 140 kb on 22q13.2), not present in control subjects, raising the potential role of these CNVs in the VCFS-like phenotype.

Conclusions

Our results confirmed aCGH as a successful strategy in order to characterize additional submicroscopic aberrations in patients with VCF-like features that fail to show alterations in 22q11.2 region. We report a 212-kb microduplication on 1q21.1, detected in two patients, which may contribute to CHD.
The requirements and challenges in preventing of road traffic injury in Iran. A qualitative study
Authors: Khorasani-Zavareh Davoud , Mohammadi Reza , Khankeh Hamid Reza , Laflamme Lucie , Bikmoradi Ali , Haglund Bo JA
Published: December 2009

Background

Road traffic injuries (RTIs) are a major public health problem, especially in low- and middle-income countries. Among middle-income countries, Iran has one of the highest mortality rates from RTIs. Action is critical to combat this major public health problem. Stakeholders involved in RTI control are of key importance and their perceptions of barriers and facilitators are a vital source of knowledge. The aim of this study was to explore barriers to the prevention of RTIs and provide appropriate suggestions for prevention, based on the perceptions of stakeholders, victims and road-users as regards RTIs.

Methods

Thirty-eight semi-structured interviews were conducted with informants in the field of RTI prevention including: police officers; public health professionals; experts from the road administrators; representatives from the General Governor, the car industry, firefighters; experts from Emergency Medical Service and the Red Crescent; and some motorcyclists and car drivers as well as victims of RTIs. A qualitative approach using grounded theory method was employed to analyze the material gathered.

Results

The core variable was identified as "The lack of a system approach to road-user safety". The following barriers in relation to RTI prevention were identified as: human factors; transportation system; and organizational coordination. Suggestions for improvement included education (for the general public and targeted group training), more effective legislation, more rigorous law enforcement, improved engineering in road infrastructure, and an integrated organization to supervise and coordinate preventive activities.

Conclusion

The major barriers identified in this study were human factors and efforts to change human behaviour were suggested by means of public education campaigns and stricter law enforcement. However, the lack of a system approach to RTI prevention was also an important concern. There is an urgent need for both an integrated system to coordinate RTI activities and prevention and a major change in stakeholders' attitudes towards RTI prevention. The focus of all activities should take place on road users' safety.
Scale-up from microtiter plate to laboratory fermenter: evaluation by online monitoring techniques of growth and protein expression in Escherichia coli and Hansenula polymorpha fermentations
Authors: Kensy Frank , Engelbrecht Christoph , Büchs Jochen
Published: December 2009

Background

In the past decade, an enormous number of new bioprocesses have evolved in the biotechnology industry. These bioprocesses have to be developed fast and at a maximum productivity. Up to now, only few microbioreactors were developed to fulfill these demands and to facilitate sample processing. One predominant reaction platform is the shaken microtiter plate (MTP), which provides high-throughput at minimal expenses in time, money and work effort. By taking advantage of this simple and efficient microbioreactor array, a new online monitoring technique for biomass and fluorescence, called BioLector, has been recently developed. The combination of high-throughput and high information content makes the BioLector a very powerful tool in bioprocess development. Nevertheless, the scalabilty of results from the micro-scale to laboratory or even larger scales is very important for short development times. Therefore, engineering parameters regarding the reactor design and its operation conditions play an important role even on a micro-scale. In order to evaluate the scale-up from a microtiter plate scale (200 μL) to a stirred tank fermenter scale (1.4 L), two standard microbial expression systems, Escherichia coli and Hansenula polymorpha, were fermented in parallel at both scales and compared with regard to the biomass and protein formation.

Results

Volumetric mass transfer coefficients (kLa) ranging from 100 to 350 1/h were obtained in 96-well microtiter plates. Even with a suboptimal mass transfer condition in the microtiter plate compared to the stirred tank fermenter (kLa = 370-600 1/h), identical growth and protein expression kinetics were attained in bacteria and yeast fermentations. The bioprocess kinetics were evaluated by optical online measurements of biomass and protein concentrations exhibiting the same fermentation times and maximum signal deviations below 10% between the scales. In the experiments, the widely applied green fluorescent protein (GFP) served as an online reporter of protein expression for both strains.

Conclusions

The successful 7000-fold scale-up from a shaken microtiter plate to a stirred tank fermenter was demonstrated in parallel fermentations for standard microbial expression systems. This confirms that the very economical and time efficient platform of microtiter plates can be very easily scaled up to larger stirred tank fermenters under defined engineering conditions. New online monitoring techniques for microtiter plates, such as the BioLector, provide even more real-time kinetic data from fermentations than ever before and at an affordable price. This paves the way for a better understanding of the bioprocess and a more rational process design.
Cooperation of Notch and Ras/MAPK signaling pathways in human breast carcinogenesis
Authors: Mittal Suruchi , Subramanyam Deepa , Dey Devaveena , Kumar Rekha V , Rangarajan Annapoorni
Published: December 2009

Background

Recent studies have implicated aberrant Notch signaling in breast cancers. Yet, relatively little is known about the pattern of expression of various components of the Notch pathway, or its mechanism of action. To better understand the role of the Notch pathway in breast cancer, we have undertaken a detailed expression analysis of various Notch receptors, their ligands, and downstream targets at different stages of breast cancer progression.

Results

We report here that there is a general increase in the expression levels of Notch 1, 2, 4, Jagged1, Jagged2, and Delta-like 4 proteins in breast cancers, with simultaneous upregulation of multiple Notch receptors and ligands in a given cancer tissue. While Notch3 and Delta-like1 were undetectable in normal tissues, moderate to high expression was detected in several cancers. We detected the presence of active, cleaved Notch1, along with downstream targets of the Notch pathway, Hes1/Hes5, in ~75% of breast cancers, clearly indicating that in a large proportion of breast cancers Notch signaling is aberrantly activated. Furthermore, we detected cleaved Notch1 and Hes1/5 in early precursors of breast cancers - hyperplasia and ductal carcinoma in situ - suggesting that aberrant Notch activation may be an early event in breast cancer progression. Mechanistically, while constitutively active Notch1 alone failed to transform immortalized breast cells, it synergized with the Ras/MAPK pathway to mediate transformation. This cooperation is reflected in vivo, as a subset of cleaved Notch positive tumors additionally expressed phopsho-Erk1/2 in the nuclei. Such cases exhibited high node positivity, suggesting that Notch-Ras cooperation may lead to poor prognosis.

Conclusions

High level expression of Notch receptors and ligands, and its increased activation in several breast cancers and early precursors, places Notch signaling as a key player in breast cancer pathogenesis. Its cooperation with the Ras/MAPK pathway in transformation offers combined inhibition of the two pathways as a new modality for breast cancer treatment.
Factors associated with seroprevalence of hepatitis C among dentists at a large Brazilian city
Authors: Resende Vera Lúcia S , Abreu Mauro Henrique G , Paiva Saul M , Teixeira Rosângela , Pordeus Isabela A
Published: December 2009

Background

The aim of the present study was to investigate the seroprevalence and sociodemographic data, health-related and occupational factors and other correlates of sero-posivity among dentists in the city of Belo Horizonte, MG, Brazil.

Methods

A cross-sectional survey was carried out with 1302 dentists in Belo Horizonte, Brazil. All dentists were tested for anti-HCV using a commercially available enzyme-linked immunosorbent assay (ELISA). Individuals positive for anti-HCV were recalled for further evaluation. The presence of HCV RNA in anti-HCV-positive samples was assessed using reverse transcription-polymerase chain reaction (RT-PCR). Data on demographic, behavioural and occupational exposure aspects were collected through questionnaires.

Results

The seroprevalence of anti-HCV was 0.9% (95% IC 0.5-1.7%). The factors associated to the prevalence of hepatitis C were history of blood transfusion (p = 0.002) and having undergone a test for hepatitis C (p = 0.015).

Conclusions

The seroprevalence of anti-HCV among dentists is low. Moreover, no occupational exposure was associated to the seroprevalence of hepatitis C.
The Colombian conflict: a description of a mental health program in the Department of Tolima
Authors: Sanchez-Padilla Elisabeth , Casas German , Grais Rebecca F , Hustache Sarah , Moro Marie-Rose
Published: December 2009

Colombia has been seriously affected by an internal armed conflict for more than 40 years affecting mainly the civilian population, who is forced to displace, suffers kidnapping, extortion, threats and assassinations. Between 2005 and 2008, Médecins Sans Frontières-France provided psychological care and treatment in the region of Tolima, a strategic place in the armed conflict. The mental health program was based on a short-term multi-faceted treatment developed according to the psychological and psychosomatic needs of the population. Here we describe the population attending during 2005-2008, in both urban and rural settings, as well as the psychological treatment provided during this period and its outcomes.

We observed differences between the urban and rural settings in the traumatic events reported, the clinical expression of the disorders, the disorders diagnosed, and their severity. Although the duration of the treatment was limited due to security reasons and access difficulties, patient condition at last visit improved in most of the patients. These descriptive results suggest that further studies should be conducted to examine the role of short-term psychotherapy, adapted specifically to the context, can be a useful tool to provide psychological care to population affected by an armed conflict.
Hypothermia in bleeding trauma: a friend or a foe?
Authors: Kheirbek Tareq , Kochanek Ashley R , Alam Hasan B
Published: December 2009

The induction of hypothermia for cellular protection is well established in several clinical settings. Its role in trauma patients, however, is controversial. This review discusses the benefits and complications of induced hypothermia--emphasizing the current state of knowledge and potential applications in bleeding patients. Extensive pre-clinical data suggest that in advanced stages of shock, rapid cooling can protect cells during ischemia and reperfusion, decrease organ damage, and improve survival. Yet hypothermia is a double edged sword; unless carefully managed, its induction can be associated with a number of complications. Appropriate patient selection requires a thorough understanding of the pre-clinical literature. Clinicians must also appreciate the enormous influence that temperature modulation exerts on various cellular mechanisms. This manuscript aims to provide a balanced view of the published literature on this topic. While many of the advantageous molecular and physiological effects of induced hypothermia have been outlined in animal models, rigorous clinical investigations are needed to translate these promising findings into clinical practice.
Basal cell adenocarcinoma of a hard palate minor salivary gland: case report and review of the literature
Authors: Ward Bryan K , Seethala Raja R , Barnes E Leon , Lai Stephen Y
Published: December 2009

Objective

Basal cell adenocarcinoma of a minor salivary gland is extremely rare. The goal of this report is to increase awareness of this rare disease and to review and discuss the differential diagnosis and important considerations in treatment.

Study Design

Case report and review of the literature.

Methods

Case report of a basal cell adenocarcinoma of a hard palate minor salivary gland and review of the literature of basal cell adenocarcinoma.

Results

Basal cell adenocarcinomas are slow-growing tumours that most commonly involve the parotid gland and very rarely involve minor salivary glands. Although recurrence rates for these tumours are high, mortality rates are low. Histological diagnosis is important to distinguish this tumour from adenoid cystic carcinoma given the significant difference in disease prognosis.

Conclusions

Diagnosis of these tumours must be made histologically. Recommended treatment options include wide local excision with radiotherapy reserved for close surgical margins or for local recurrence.
Liver X receptor agonist treatment reduced splanchnic ischemia and reperfusion injury
Authors: Crisafulli Concetta , Di Paola Rosanna , Mazzon Emanuela , Paterniti Irene , Galuppo Maria , Genovese Tiziana , Bramanti Placido , Cappellani Alessandro , Cuzzocrea Salvatore
Published: December 2009

T0901317, LXR receptor agonist, reduces the inflammatory response and the ileum injury associated to splanchnic artery occlusion shock.

LXR is another member of the superfamily of nuclear hormone receptors that heterodimerizes with RXR and regulates the intracellular levels of cholesterol through gene induction of enzymes and proteins involved in the cholesterol metabolism and transport. LXR ligands inhibit the gene expression of proinflammatory mediators in immunostimulated macrophages; in vivo studies have shown that activation of LXR reduces the inflammatory response in a murine model of contact dermatitis and atherosclerosis. No reports have addressed a role for LXRs in pathophysiology of intestinal ischemia. The aim of this study was to investigate the effects of T0901317, a potent LXR ligand, in a mouse model of SAO shock, which was induced by clamping the superior mesenteric artery and the celiac trunk, resulting in a total occlusion of these arteries for 30 min. After this period of occlusion, the clamps were removed. Mice were killed at 60 min after reperfusion. This study provides the evidence that T0901317, LXR agonist, modulates: the development of SAO shock; the infiltration of the tissue with PMNs; the expression of TNF-α and IL-1β; the nitration of tyrosine residues; NF-κB expression; the MAPK phosphorylation (ERK, JNK, and p38); FasL; apoptosis; Bax and Bcl-2 expression; and the degree of tissue injury caused by SAO shock. Our results imply that LXR agonists may be useful in the therapy of inflammation.
Heuristic-rule-based hybrid neural network for navigation of a mobile robot
Authors: Parhi D R , Singh M K
Published: December 2009

The current paper presents a novel technique for a mobile robot to navigate in a real-world dynamic environment. When an autonomous mobile robot navigates in an unknown environment it is required to plan a path based on the information gathered from sensors in order to avoid obstacles and reach a target. This research idea is related to the basis of human perception, by using heuristic information for the navigation of mobile robots in cluttered dynamic environments which provides a general, robust, safe, and optimized path. The heuristic-rule-based network (HRBN) consists of a simple algorithm which makes the predefined estimation function much smaller. The estimation function should be adequately defined for desired movement in the environment. A navigation system using the rule-based technique allows a mobile robot to travel in an environment about which the robot has no prior knowledge. This heuristic rule is applied in conjunction with an artificial neural network (ANN). The ANN is trained by back-propagation algorithms. The HRBN provides an optimum trajectory which increases the effectiveness of a mobile robot. In a multiple-robot environment, a Petri net model (PNM) is used to prevent inter-robot collision during navigation. A series of simulations and experiments is conducted using mobile robots to show the effectiveness of the proposed algorithm.
Prediction of friction coefficient on workpiece/fixture contact surface using artificial neural networks
Authors: Deiab I M
Published: December 2009

The friction coefficient at the interface between a fixture tip and the workpiece plays an important role in work-holding applications. The present paper investigates the application of neural network schemes and architectures to predict the friction coefficient on the contact face between the workpiece and fixture tip taking into account factors such as surface roughness, applied normal load, workpiece material, and fixture element roughness. The model presented can be used to develop a virtual friction tester to overcome the difficulties associated with experimental determination of the friction coefficient and to facilitate testing of different fixturing scenarios in a virtual environment by providing a smart database for the friction coefficient values. The predicted results are compared with experiments and show reasonable agreement.
Combustion characteristics of a single-cylinder spark ignition gasoline and ethanol dual-fuelled engine
Authors: Zhu G , Hung D , Schock H
Published: December 2009

The requirements of reduced emissions and improved fuel economy led to the introduction of direct-injection (DI) spark ignition (SI) engines. A dual-fuel injection system (DI and port fuel injection (PFI)) was also used to improve engine performance at high-speed high-load conditions. Ethanol is one of the several alternative transportation fuels considered for replacing fossil fuels such as gasoline and diesel. Ethanol offers high octane quality but with lower energy density than fossil fuels. This paper presents the combustion characteristics of a single-cylinder dual-fuel injection SI engine with the following fuelling cases: case A, gasoline for both PFI and DI; case B, gasoline PFI and ethanol DI; case C, ethanol PFI and gasoline DI. For this study, the DI fuelling portion varied from 0 per cent to 100 per cent of the total fuelling over different engine operational conditions while the engine air-to-fuel ratio remained at a constant level. It was shown in all cases that the indicated mean effective pressure (IMEP) decreases by as much as 11 per cent as the DI fuelling percentage increases, except in case B where the IMEP increases by 2 per cent at a light load. The combustion burn duration increases significantly at a light load as the DI fuelling percentage increases, but only moderately at wide-open throttle (WOT). In addition, the percentage of the ethanol in the total fuelling plays a dominant role in affecting the combustion characteristics at a light load but, at a heavy load (WOT), the DI fuelling percentage becomes an important parameter, regardless of the percentage of ethanol content in the fuel.
Compensation of inertia error in brake dynamometer testing
Authors: Ma J-J , Wu B-D , Liu X-Y , Sun J-Y
Published: December 2009

Loss in terms of air resistance and bearing friction is an important origin of inertia error that must be compensated in brake dynamometer testing, the acquisition of which has always been a troublesome problem. An indirect method of loss measurement using the speed data under zero pipeline pressure is described in this paper. A mathematical model of the resistance torque or the energy loss is calculated by regression of the collected speed data using statistical software. Error compensation of the two inertia-simulating methods, namely the torque control method and the energy compensation method, is discussed. Experiments using the former method are conducted on an NT11 brake dynamometer, which proves this method to be effective in eliminating inertia error.
Idle speed control using a describing-function approach
Authors: The S H , Nassirharand A
Published: December 2009

A new systematic method for idle speed control of uncertain automobile engines with a time delay is developed. The method is based on obtaining a describing-function model of the internal combustion engine. This is followed by designing a classical controller via an algebraic approach. The design method and the associated software are applied to a specific automobile engine, and it is shown that the results compete with the observer-based design of Bengea et al. Stability is demonstrated by successful generation of describing-function models of the final non-linear closed-loop system.
Synthetic torque feedback to improve heavy vehicle drivability
Authors: Williams D E
Published: December 2009

TRW has recently launched an electrically powered, computer-controlled enhancement to commercial vehicle steering systems. ColumnDrive, the new component, precisely controls torque feedback to the driver, resulting in a synthetic or artificial steering feel. Synthetic torque feedback is most effective at masking non-linearities in the steering system that degrade the on-centre lane-keeping properties of the vehicle, as well as providing an unprecedented level of speed proportionality so that parking efforts can be optimized independently of on-centre stability. The new ColumnDrive and existing electrical power-steering control architectures are compared, and actual vehicle performance data are presented.
Minimum power requirement for a propeller-driven aircraft and optimum cycle parameters of turboprop engines
Authors: Ghenaiet A , Boulekraa T
Published: December 2009

This article presents a methodology to design for optimal performance of turboprop engines matching the power requirements for propeller-driven aircrafts. First, the flight performance analyses were used to assess the relatively significant constraints, and then identify the feasible design space and the ideal design point by adopting KSOPT optimizing technique. Second, a multi-objective deterministic algorithm modified method of feasible direction was used for the Pareto approach optimization of the propulsion cycle for three configurations of turboprops. In this optimization problem the maximum specific power and the minimum power specific fuel consumption are the principal figures of merit. The obtained results were based on a created model from the published data of a particular aircraft. This methodology used in the preliminary design phase has shown its effectiveness in rapidly searching for the ideal match point and identifying a candidate turboprop engine, as well as in the development of a derivative engine.
Modelling, simulation, and experimental evaluation of a crossflow heat exchanger for an aircraft environmental control system
Authors: Shah S , Liu G , Greatrix D R
Published: December 2009

Crossflow heat exchangers play a significant role in the operation of an aircraft's environmental control system (ECS). The bleed air supplied by an aircraft engine, at high pressure and high temperature, requires regulation and control in order to be used for various pneumatic services. In the present investigation, the transient temperature response of crossflow plate-and-fin ECS heat exchangers, having a large core capacity with both fluids unmixed, is investigated numerically and experimentally for perturbations experienced in temperature. A non-linear lumped model of crossflow heat exchangers with a state-space solution valid for equal fluid velocities is derived and evaluated, in terms of fluid placement and number of lumps (sections) required. Dependency of the heat transfer coefficient on flowrates is incorporated in the dynamic modelling of the heat exchanger. Two models are derived, and the variation of the mean exit temperatures of both fluids with time is compared for the two alternative models, with consideration of the number of transfer units and heat capacitance rate ratios. One model requires axial lumping of the primary surface alone, as done in most of the existing models, and the second involves incorporating the effect of secondary surfaces (fins) on the heat exchanger transient performance. To quantify the importance of modelling the fins, a comparison of both simulation models with experimentally obtained data from a physical model is presented. By including fins and complex non-linearities in modelling of the ECS heat exchangers, a precise representation of the heat exchanger dynamics and accurate temperature responses are predicted. The model developments reported in this article can lead to improved aircraft ECS design and optimization.
Imperfection measures of eigen- and periodic modes of axially loaded stringer-stiffened cylindrical shell
Authors: Sadovský Z , Ďuricová A , Ivančo V , Kriváček J
Published: December 2009

The influence of initial geometric imperfections in the shapes of eigenmodes and periodic modes on the load-carrying capacity of a steel stringer-stiffened cylindrical shell subject to axial compression is studied. For comparison of the influence of different shapes, the imperfections are normalized by an integral—energy measure, which is considered as an alternative to the commonly applied amplitude. The shell dimensions are chosen out of the set of 24 small-scale specimens tested between 1981 and 1984 at Imperial College in London. Published results of statistical analysis of measured imperfection surfaces of the set are employed for checking their conjectured relationship to the normalization of imperfections by the energy measure. The study is finite element method (FEM)-oriented; the numerical model is checked by application of two FEM codes.
Characterization and modelling of electromagnetic interactions in aircraft
Authors: Christopoulos C , Dawson J F , Dawson L , Flintoft I D , Hassan O , Marvin A C , Morgan K , Sewell P , Smartt C J , Xie Z Q
Published: December 2009

This article describes the development of modelling techniques and simulation tools for the electromagnetic (EM) analysis of aircraft. It is shown that hybrid solvers and multi-scale techniques can be used effectively to analyse the EM response of aircraft. The importance of supplementing models with appropriate measurement and characterization techniques for parameter extraction and for validation is also demonstrated.
Computational investigation of the DEMON unmanned air vehicle thrust vectoring system
Authors: Buonanno A , Drikakis D , Papachristou C , Savvaris A , Vamvakoulas C , Warsop C
Published: December 2009

A computational investigation of the interaction of the vectored primary jet from the main engine with the subsonic flow around a tailless unmanned air vehicle (UAV) configuration, with a cropped diamond wing planform, has been carried out. An initial study has been completed using Reynolds-averaged Navier—Stokes methods in conjunction with the shear-stress transport k—ω model. Various sets of simulations were performed on the basis of quantifying the thrust vectoring (TV) jet entrainment effects by means of aerodynamic forces and moments when key factors are combined, such as angles of thrust velocity deflection at different jet Mach number and angles of attack. It was found that reaction forces induced by the modified pressure on the integrated boundary of the body results in an enhancement of the TV effectiveness in producing the forces and moments required for the flight vehicle trim and manoeuvring. Those reaction forces were found to be independent of the angle of attack.
Variable cavity volume tooling for high-performance resin infusion moulding
Authors: Gibbons G J , Segui-Garza J J , Hansell R G
Published: December 2009

This article describes the research carried out by Warwick under the BAE Systems/EPSRC programme ‘Flapless Aerial Vehicles Integrated Interdisciplinary Research - FLAVIIR’. Warwick's aim in FLAVIIR was to develop low-cost innovative tooling technologies to enable the affordable manufacture of complex composite aerospace structures and to help realize the aim of the Grand Challenge of maintenance-free, low-cost unmanned aerial vehicle manufacture. This article focuses on the evaluation of a novel tooling process (variable cavity tooling) to enable the complete infusion of resin throughout non-crimp fabric within a mould cavity under low (0.1 MPa) injection pressure. The contribution of the primary processing parameters to the mechanical properties of a carbon composite component (bulk-head lug section), and the interactions between parameters, was determined. The initial mould gap ( di) was identified as having the most significant effect on all measured mechanical properties, but complex interactions between di, n (number of fabric layers), and vc (mould closure rate) were observed. The process capability was low due to the manual processing, but was improved through process optimization, and delivered properties comparable to high-pressure resin transfer moulding.
Low-cost resin infusion mould tooling for carbon fibre composites manufacture
Authors: Gibbons G J , Segui-Garza J J , Hansell R G
Published: December 2009

This article describes the research to date carried out under the BAE Systems/Engineering and Physical Sciences Research Council (EPSRC)-funded programme ‘Flapless Aerial Vehicle Integrated Interdisciplinary Research’ (FLAVIIR), aimed at developing innovative technologies for the low-cost manufacture of next-generation Unmanned Aerial Vehicles. The aim of the researchers in FLAVIIR was to develop low-cost innovative tooling technologies to enable the affordable manufacture of complex composite aerospace structures. The advances in tooling technology were achieved through the application of rapid prototyping, tooling and manufacture technologies to provide rapidly configured and reconfigurable tool concepts, for low-cost resin infusion moulding. This article introduces three tooling innovations: reconfigurable tooling concept, variable cavity tooling, and porous cavity tooling.
A new method for solution of viscous shock-layer equations
Authors: Noori S , Ghasemloo S , Mani M
Published: December 2009

A new method is presented that considerably improves the computational efficiency of the viscous shock-layer technique. This approach can solve both subsonic and supersonic regions of the shock layer without a starting solution for the shock shape, and the global iterations are limited only to the nose region. In the nose region, the shock shape is specified from an algebraic expression and corrected through global passes through that region. The shock shape is computed as part of the solution beyond the nose region and requires only a single global pass. Under the high Reynolds number (at low altitudes), the Cebeci—Smith (CS) turbulent model has been analysed with the present numerical technique for application to long slender bodies. The surface-slip and the currently corrected shock-slip boundary conditions are employed to account for the low-density effects. The method of solution is a spatial-marching, implicit, finite-difference technique, which includes coupling of the normal momentum and continuity equations and uses a simple relation instead of Vigneron pressure condition in the subsonic nose region for instability. Comparisons are made with available experiment data and other solutions. The comparisons demonstrated that accurate solutions are obtained.
Control system design and experiment of needle-type gas regulating system for ducted rocket
Authors: Niu W-Y , Bao W , Chang J , Cui T , Yu D-R
Published: December 2009

The control system design and experimental investigation of the gas regulating system for a ducted rocket are studied in this article. First, the dynamic model of the gas regulating system for the ducted rocket was established, and comparison of the two regulating modes regarding non-linearity and uncertainty was done. In contrast with the area-regulated mode, the non-linearity of the pressure-balanced mode is smaller and the robustness is stronger. Then, the study of the the gas control system is performed based on the model established in this article. The introduction of high-gain feedback suppresses the effects of non-linearity and uncertainty in the pneumatic servo system. Also, a proportional-integral controller for the gas regulating system based on linear matrix inequality is designed. Lastly, an experimental investigation of the gas flow control system is done to verify the validity of the gas control system. The experimental result shows that the gas flow control system has good performance. The turndown ratio of mass flow through the control valve was up to 3.7:1.
Effect of swirl on the turbulent behaviour of a dump combustor flow
Authors: Yadav N P , Kushari A
Published: December 2009

This article reports an experimental investigation of non-reacting flow in a low aspect ratio dump combustor with a tapered exit. The length of this combustor was less than the separated flow reattachment length. The turbulent intensity variation inside the combustor without swirl was found to be axi-symmetric. The turbulent intensity increases in the shear layer between the potential core and the recirculation eddy. The intensity in the core region increases as one moves along the centre-line in the axial direction. The turbulence behaviour significantly changed with the use of a swirler at the inlet of the combustor. The average turbulent intensity increased inside the combustor and the differences in the magnitude of the intensity along the axial and radial directions were less compared to the non-swirling flow. For a high swirl number (( SN) = 1.48), the intensity in the core region was higher compared to other regions inside the combustor. The intensity variation inside the combustor was more uniform than in the case of the low swirl number flow. The r.m.s. velocity studies also suggest more turbulence generation due to swirl. The presence of the swirler increased the turbulence kinetic energy and dissipation rate in the central vortex core region. The power spectral density distribution shows the alteration of the frequency content of the power spectrum, which can be attributed to the forced recirculation due to swirl. The effect of a high swirl number and Re on the frequency peak shows similar behaviour. Therefore, turbulence inside the combustor increased due to the swirler; hence, better mixing of the fuel and air and efficient and stable combustion is expected to be achieved.
Experimental investigation of acoustic oscillations over cavities
Authors: Zhu Y , Ouyang H , Du Z
Published: December 2009

The behaviours of turbulent flow over cavities at low-speed free stream are studied by performing wall pressure measurements. The characteristics of cavities mounted on the wall of a duct are investigated. It was found that an acoustic mode is present. The nature of the acoustic mode and its coupling with hydrodynamic oscillation in the cavity are analysed. Meanwhile, analysis was carried out to identify the oscillation modes in the cavity. A modified semiempirical formula for the model is introduced based on the measurements.
A validation study of OpenFOAM using the supersonic flow in a mixed compression intake
Authors: Sudharsan N M , Jambekhar V A , Babu V
Published: December 2009

The study of high-speed flows is of great importance in the design and manufacture of aerospace vehicles, missiles, and rockets. The flow physics is complex and experimental investigations with full size prototypes are quite expensive. To study such complex flows, there is a need for a numerical test bench that is both robust and customizable. To this end, in this study, a systematic validation of the open source computational fluid dynamics software called OpenFOAM has been undertaken. Numerical simulations of the high-Mach-number supersonic flow in a mixed compression intake in nine different configurations have been carried out. The predictions are seen to compare well with the experimental data reported in the literature. Important features such as the location and strength of oblique shocks and expansion fans are predicted well. The shock—boundary layer interaction for subtle variations in geometric configurations could also be replicated as observed experimentally. The roll up of the boundary layer due to shock interaction over very small time instants could be easily captured, which would be difficult do accomplish experimentally. Although not all permutations and combinations of the parameters have been studied, with the limited study the power of the above mentioned open source software has been established.
A tilt-rotor actuator
Authors: White G
Published: December 2009

A ballscrew actuator for tilt-rotor and pitch trim applications is described that provides structural and operational redundancy in respect of any single failure mode. It is powered by two hydraulic motors, operated separately. Configuration layout, dual-path constructions, and component details are illustrated. Comparison is made with earlier designs and reasons are given for their varying ratios of flight load/actuator weight. It is evident that cross-coupling of two pylon actuators involves gains in weight and cost.
Decentralized coordinated control for a group of aircraft
Authors: Bukov V , Bronnikov A , Selvesyuk N
Published: December 2009

The task of decentralized coordinated control for vertical trajectory movement of a group of different types of pilotless aircraft is considered here. The aircraft do not exchange information. Remote control of each plane is realized by a ground-based command post with a radio channel. An approach to decentralized control with model coordination is used for a compound system with local multiple-input multiple-output (MIMO) subsystems. The approach is based on the results of system embedding technology.
A mixed lubrication model incorporating measured surface topography. Part 2: Roughness treatment, model validation, and simulation
Authors: Sahlin F , Larsson R , Marklund P , Almqvist A , Lugt P M
Published: December 2009

A mixed lubrication flow factor model that permits real three-dimensional surface topography as input has been developed. Part 1 gives the theory of computing flow factors within the model. In this article, a method of adapting the measured surface topography signal to suit the numerical models is developed and presented in detail. The mixed lubrication model is validated through flow measurements for three different rough surface test specimens. Simulation of a hydrodynamic bearing was conducted and the results are presented in terms of pressure distributions and Stribeck curves covering all lubrication regimes. The results indicate that the model may be an efficient and accurate engineering design and research tool for tribological devices operating in all lubrication regimes.
Prize Structure and Information in Tournaments: Experimental Evidence
Authors: Freeman Richard B. , Gelber Alexander M.
Published: December 2009

This paper examines behavior in a tournament in which we vary the tournament prize structure and the available information about participants' skill at the task of solving mazes. The number of solved mazes is lowest when payments are independent of performance; higher when a single, large prize is given; and highest when multiple, differentiated prizes are given. This result is strongest when we inform participants about the number of mazes they and others solved in a pre-tournament round. Some participants reported that they solved more mazes than they actually solved, and this misreporting also peaked with multiple differentiated prizes. (JEL D82)