bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of dietary excess of branched‐chain amino acids on performance and serum concentrations of amino acids in growing pigs
Authors: Morales A. , Arce N. , Cota M. , Buenabad L. , Avelar E. , Htoo J. K. , Cervantes M.
Published: April 2015

Depressed performance and availability of some amino acids (AA) in pigs fed excess Leu diets appear to be related to lower feed intake. Surplus Ile and Val may help to overcome this effect. An experiment was conducted with 24 pigs (31.8 ± 1.2 kg initial BW) to evaluate the effect of dietary excess of either Leu alone or with surplus Ile and Val on performance and serum concentration (SC) of essential AA. Treatments were as follows: T1, basal diet; T2, basal plus 0.43% L‐Leu (excess Leu); T3, basal added with 0.43% L‐Leu, plus 0.20% L‐Ile and 0.25% L‐Val (excess LIV). The basal diet was formulated to contain 0.90% standardized ileal digestible Lys and added with crystalline L‐Lys, L‐Thr, DL‐Met, L‐Trp, L‐Leu, L‐Ile, L‐His and L‐Val to create essential AA:Lys ratios close to an ideal protein for growing pigs. All pigs were fed the same amount of feed twice a day (average, 3.42× the requirement of NEm). Blood samples were collected at 2.5 (absorptive) and 11.0 h (post‐absorptive) post‐prandial to analyse SC of AA. Excess of either Leu or LIV did not affect growth rate nor feed conversion. Excess Leu increased Leu SC and decreased Ile and Val SC (p < 0.05) at both absorptive and post‐absorptive phases, but excess LIV restored the SC of Ile and Val. The SC of other essential AA was not affected by excess of either Leu or LIV. The SC of all AA during absorptive, on average, was about two times higher than that of post‐absorptive phase. These results suggest that the reduced availability (SC) of Ile and Val in pigs consuming excess Leu diets is attributed to a reduced absorption and increased cellular degradation rates of them.
Evaluation of portal hypertension by real‐time shear wave elastography in cirrhotic patients
Authors: Kim Tae Yeob , Jeong Woo Kyoung , Sohn Joo Hyun , Kim Jinoo , Kim Min Yeong , Kim Yongsoo
Published: April 2015

Background & Aims

To assess the correlation between liver stiffness measurement (LSM) by real‐time shear wave elastography (SWE) and hepatic venous pressure gradient (HVPG) and to investigate the diagnostic performance of SWE for predicting clinically significant and severe portal hypertension (CSPH and SPH).

Methods

Clinical data of 115 cirrhotic patients with haemodynamic measurement were consecutively collected. Liver stiffness (LS) was measured using SWE by repeated performance five times per patient, and the median value and interquartile range of the parameters on the same day of HVPG measurement was calculated. CSPH and SPH were defined as a HVPG ≥10 mmHg and ≥12 mmHg respectively.

Results

A total of 92 patients (male, 63; mean age, 53 ± 11.9 years) were eligible for analysis. CSPH and SPH were detected in 77 patients (83.7%) and 66 patients (71.5%) respectively. HVPG were significantly correlated with LSM in the overall, CSPH, and SPH patients (r = 0.646, 0.574 and 0.424 respectively; all P < 0.001). With ascites, the correlation coefficient did not decrease (r = 0.587). The AUROCs of LSM was 0.819 (95% CI, 0.725–0.892) for CSPH and 0.867 (95% CI, 0.780–0.928) for SPH. The cut‐off values for determining CSPH and SPH were 15.2 kPa (Sensitivity, 85.7%; Specificity, 80.0%) and 21.6 kPa (Sensitivity, 83.3%; Specificity, 80.8%) respectively.

Conclusion

In cirrhotic patients, LSM by SWE is highly correlated with HVPG value regardless of ascites. SWE is a new reliable non‐invasive diagnostic tool to predict CSPH and SPH, even in cirrhotic patients with ascites.
The integrative role of leptin, oestrogen and the insulin family in obesity‐associated breast cancer: potential effects of exercise
Authors: Schmidt S. , Monk J. M. , Robinson L. E. , Mourtzakis M.
Published: April 2015

Obesity is an established risk factor for postmenopausal breast cancer. The mechanisms through which obesity influences the development and progression of breast cancer are not fully elucidated; however, several factors such as increased oestrogen, concentrations of various members of the insulin family and inflammation that are associated with adiposity are purported to be important factors in this relationship. Emerging research has also begun to focus on the role of adipokines, (i.e. adipocyte secreted factors), in breast cancer. Leptin secretion is directly related to adiposity and is believed to promote breast cancer directly and independently, as well as through involvement with the oestrogen and insulin signalling pathways. As leptin is secreted from white adipose tissue, any intervention that reduces adiposity may be favourable. However, it is also important to consider that energy expenditure through exercise, independent of fat loss, may improve leptin regulation. The purpose of this narrative review was to explore the role of leptin in breast cancer development and progression, identify key interactions with oestrogen and the insulin family, and distinguish the potential effects of exercise on these interactions.
Promotion of Proapoptotic Signals by Lysosomal Photodamage
Authors: Kessel David , Reiners John J.
Published: April 2015

We previously reported that low‐level lysosomal photodamage enhanced the efficacy of subsequent mitochondrial photodamage, resulting in a substantial promotion of apoptotic cell death. We now extend our analysis of the sequential PDT protocol to include two additional lysosomal‐targeting photosensitizers. These agents, because of enhanced permeability, are more potent than the agent (N‐aspartyl chlorin E6, NPe6) used in the initial study. Addition of the cell‐permeable cysteine protease inhibitor E‐64d and calcium chelator BAPTA‐AM almost completely suppressed sequential PDT‐induced loss of mitochondrial membrane potential and activation of procaspases‐3 and ‐7. These inhibitors did not, however, suppress the proapoptotic effect of a BH3 mimetic or mitochondrial photodamage. Knockdowns of ATG7 or ATG5, proteins normally associated with autophagy, suppressed photodamage induced by the sequential PDT protocol. These effects appear to be independent of the autophagic process as pharmacological inhibition of autophagy offered no such protection. Effects of ATG7 and ATG5 knockdowns may reflect the role that ATG7 plays in regulating lysosome permeability, and the likelihood that a proteolytic fragment of ATG5 amplifies mitochondrial proapoptotic processes. Our results suggest that low‐dose photodamage that sequentially targets lysosomes and mitochondria may offer significant advantages over the use of single photosensitizers.
TTF‐1 and napsin A on cell blocks and supernatants of pleural fluids for labeling malignant effusions
Authors: Porcel José M. , Palma Rosa , Bielsa Silvia , Esquerda Aureli , Gatius Sonia , Matias‐Guiu Xavier , Salud Antonieta
Published: April 2015

In this retrospective study of 80 pleural effusions, the combination of thyroid transcription factor 1 (TTF‐1) and napsin A immunostaining on fluid cell blocks was positive in 80% of lung adenocarcinomas. Although measuring TTF‐1 pleural fluid concentrations was of no value, quantification of napsin A levels allowed the identification of one third of the double‐negative stained lung adenocarcinomas, with an overall accuracy similar to classical tumour markers for malignant–benign discrimination (sensitivity 40%, specificity 100%).
Training Master's‐Level Graduate Students to Use Inquiry Instruction to Teach Middle‐Level and High‐School Science Concepts
Authors: Gilman Sharon Larimer , Hitt Austin M. , Gilman Craig
Published: April 2015

Through the GK‐12 program of the National Science Foundation, graduate student fellows in a coastal marine and wetland studies program were trained to present targeted science concepts to middle‐ and high‐school classes through their own research‐based lessons. Initially, they were taught to follow the 5‐E learning cycle in lesson plan development, but a streamlined approach targeting the three attributes of science concepts—macroscopic, model, and symbolic—was found to be a better approach, while still incorporating key facets of the 5‐E model. Evaluation of the level of inquiry in the classrooms was determined using an inquiry scale from 0 to 4, differentiated by the relative number of actions that are student‐centered. The graduate fellows consistently delivered lessons at the targeted levels 2 or 3, guided inquiry. In order to assess student learning, the GK‐12 fellows were trained to develop single‐item pre‐ and post‐assessments designed to probe middle‐level and high‐school students' understanding of the macroscopic, model, and symbolic attributes of targeted science concepts. For the lessons based on the research of the fellows, about 80% of the students showed statistically and practically significant learning gains. The GK‐12 fellows positively impact the classroom and are effective science ambassadors.
Moving Beyond “Those Kids”: Addressing Teacher Beliefs Regarding the Role of Culture Within Effective Science Pedagogy for Diverse Learners
Authors: Johnson Carla C. , J. Bolshakova Virginia L.
Published: April 2015

This study focused on intensive work within a large, urban, low‐performing middle school in the southwest to address and transform teacher beliefs regarding the role of culture within their science pedagogy. Given the recent, rapid growth of numbers of students from Hispanic/Latino(a) backgrounds in the United States, it is critical that a paradigm shift takes place within schools and existing beliefs of science teachers to address the needs of a much changed classroom. This study details the journey of middle‐school teachers who were provided support and experiences targeted at addressing their existing beliefs regarding the role of culture and the growth and change that were achieved through a science education reform effort. Implications for further research will be discussed, including the need for attention to beliefs regarding culture are shared.
THE EFFECT OF ANGLE SLICE ACQUISITION ON COMPUTED TOMOGRAPHIC CERVICAL VERTEBRAL COLUMN MORPHOMETRY IN GREAT DANES
Authors: Jurkoshek Amanda M. , da Costa Ronaldo C. , Martin‐Vaquero Paula
Published: April 2015

Computed tomography (CT) scans can be acquired with the transverse images aligned either parallel to the endplates or perpendicular to the vertebral canal. The purpose of this prospective cross‐sectional study was to determine the effect of angle acquisition on CT morphometric evaluation of the cervical vertebral column of Great Danes with and without cervical spondylomyelopathy. Twenty‐eight Great Danes (13 normal, 15 affected) were sampled. For each dog, a set of CT images was acquired with the transverse slices aligned parallel to the endplates and another one with the transverse images aligned perpendicular to the vertebral canal. For each different set, transverse slices from the cranial, middle, and caudal aspects of the individual vertebral bodies C2‐C7 were measured. Height, width, transverse area, right dorsal to left ventral height (RDLV), and left dorsal to right ventral height (LDRV) were recorded by a single observer at each location. For both affected and control dogs, significant differences between the measurements obtained from the two sets of transverse images were found only at the cranial aspect of the vertebrae (P= 0.005,P< 0.001,P< 0.001,P= 0.005, andP= 0.010 for height, width, area, RDLV, and LDRV, respectively). Measurements for the middle and caudal aspects did not differ. The funnel‐shape morphology of the cervical vertebral foramina in Great Danes with stenosis of their cranial aspect may be responsible for the significant differences found. Considering that the morphometric parameters were significantly affected by CT slice angle in the current study, authors recommend that a standardized scanning protocol be followed when morphometric evaluations using CT are planned.
Intraregional and inter‐regional variability of herbicide sensitivity in common arable weed populations
Authors: de Mol F , Gerowitt B , Kaczmarek S , Matysiak K , Sønderskov M , Mathiassen S K
Published: April 2015

The question on intraregional versus inter‐regional variability in herbicide sensitivity for weed populations is of major importance, both in extrapolation of model parameters and in herbicide zonal approval procedures. We hypothesised that inter‐regional variability in herbicide sensitivity for field populations would be the same as intraregional variability for regions with similar climatic conditions. Seeds of field weed populations were collected in a Danish, German and Polish region. Herbicide sensitivity was tested in dose–response experiments in the glasshouse with flufenacet and iodosulfuron (Apera spica‐venti), florasulam and tribenuron (Tripleurospermum inodorum), diflufenican, diflufenican + flurtamone and pendimethalin (Viola arvensis). ED50 values and variance components of the ED50 values were estimated to describe the influence of region, year and population. The regions accounted for a maximum of 26% of the variance and always less than the variance accounted for by individual populations. Sensitivity indices (SI50) were calculated as the ratio between ED50 of the test population and a reference population. There was considerable intraregional variability in SI50 values and SI50 values from a single region did not consistently differ from other regions. The large intraregional variability in herbicide sensitivity between populations, with no evidence of resistance, is of interest both for zonal evaluation of herbicides and resistance research. For practical weed management, we conclude that dose–response functions can be transferred between the study regions, for example for the common use in decision support systems with proper insurance for the control of less sensitive populations.
Describing Polygonum aviculare emergence in different tillage systems
Authors: Royo‐Esnal A , García A L , Torra J , Forcella F , Recasens J
Published: April 2015

Effects of four tillage systems (direct drill, subsoiler, chisel plough and mouldboard plough) on the dynamics of Polygonum aviculare populations were studied over three growing seasons. Cumulative emergence on a weekly basis was determined. Cumulative emergence from two years of chisel ploughing was used to develop an emergence model for P. aviculare based on hydrothermal time. Results showed that direct drilling, which had the highest seed yields of winter cereal crops every season, was the unique soil management system that lowered P. aviculare populations because of effective weed emergence reduction. The model accurately described seedling emergence in different tillage systems, although it failed in direct drilling, probably due to very low numbers of emerged seedlings. To better control this weed, direct drilling may be the best tillage option, but if this cannot be implemented, the hydrothermal time model is a practical tool that can describe the relative proportions of emergence and assist in the timing for management operations of P. aviculare in different tillage systems.
A sisters’ story: comparative phylogeography and taxonomy of Hierophis viridiflavus and H. gemonensis (Serpentes, Colubridae)
Authors: Mezzasalma Marcello , Dall'Asta Andrea , Loy Anna , Cheylan Marc , Lymberakis Petros , Zuffi Marco A. L. , Tomović Ljiljana , Odierna Gaetano , Guarino Fabio M.
Published: April 2015

We used a multidisciplinary approach to infer the taxonomy and historical biogeography of Hierophis viridiflavus and H. gemonensis, performing molecular analyses of mitochondrial (16S, Cyt‐b, ND4) and nuclear markers (PRLR), a landmark‐based morphometric study and a cytogenetic analysis. Our data distinguished three main groups in the studied species, corresponding to H. gemonensis and to two monophyletic clades (E and W) within H. viridiflavus. Clades E and W display a significant genetic (about 4% for Cyt‐b and ND4) and morphological divergence and a different morphology of the W sex chromosome (submetacentric in clade E and telocentric in clade W). Taking into account the existing divergence, these clades appear to represent independent phylogenetic units, deserving elevation to species status. Specific names should be H. viridiflavus (Lacépède, 1789) and H. carbonarius (Bonaparte 1833) for clades W and E, respectively. The phylogeography of the studied species is only partially concordant with a general pattern of ‘southern richness and northern purity’ of genetic diversity, whereas H. gemonensis exhibits high genetic diversity at low latitudes (especially in the Peloponnese), H. carbonarius shows a number of different haplotypes both at low (along the southern Italian Apennines and in Sicily) and high latitudes in Italy. Furthermore, a relaxed clock model hypothesizes the differentiation between H. gemonensis and H. viridiflavus sensu lato at about 7 Mya, in the Messinian. Subsequently, the speciation involving H. viridiflavus sensu stricto and H. carbonarius took place in the Quaternary, probably as a result of Pleistocene climatic oscillations. Furthermore, our results are consistent with the existence of several ‘refugia within refugia’ in Italy and in the Balkans and depict the major cladogenesis as allopatric events, mainly driven by paleoclimatic and geographical factors.
On the derived category of Grassmannians in arbitrary characteristic
Authors: Buchweitz Ragnar-Olaf , Leuschke Graham J. , Van den Bergh Michel
Published: April 2015

In this paper we consider Grassmannians in arbitrary characteristic. Generalizing Kapranov’s well-known characteristic-zero results, we construct dual exceptional collections on them (which are, however, not strong) as well as a tilting bundle. We show that this tilting bundle has a quasi-hereditary endomorphism ring and we identify the standard, costandard, projective and simple modules of the latter.
Phenotype consequences of myophosphorylase dysfunction: insights from the McArdle mouse model
Authors: Brull Astrid , de Luna Noemí , Blanco‐Grau Albert , Lucia Alejandro , Martin Miguel Angel , Arenas Joaquin , Martí Ramon , Andreu Antoni L , Pinós Tomàs
Published: April 2015

Key points

This is the first study to analyse the effect of muscle glycogen phosphorylase depletion in metabolically different muscle types.

In McArdle mice, muscle glycogen phosphorylase is absent in both oxidative and glycolytic muscles.

In McArdle mice, the glycogen debranching enzyme (catabolic) is increased in oxidative muscles, whereas the glycogen branching enzyme (anabolic) is increased in glycolytic muscles.

In McArdle mice, total glycogen synthase is decreased in both oxidative and glycolytic muscles, whereas the phosphorylated inactive form of the enzyme is increased in both oxidative and glycolytic enzymes.

In McArdle mice, glycogen content is higher in glycolytic muscles than in oxidative muscles. Additionally, in all muscles analysed, the glycogen content is higher in males than in females.

The maximal endurance capacity of the McArdle mice is significantly lower compared to heterozygous and wild‐type mice.

McArdle disease, caused by inherited deficiency of the enzyme muscle glycogen phosphorylase (GP‐MM), is arguably the paradigm of exercise intolerance. The recent knock‐in (p.R50X/p.R50X) mouse disease model allows an investigation of the phenotypic consequences of muscle glycogen unavailability and the physiopathology of exercise intolerance. We analysed, in 2‐month‐old mice [wild‐type (wt/wt), heterozygous (p.R50X/wt) and p.R50X/p.R50X)], maximal endurance exercise capacity and the molecular consequences of an absence of GP‐MM in the main glycogen metabolism regulatory enzymes: glycogen synthase, glycogen branching enzyme and glycogen debranching enzyme, as well as glycogen content in slow‐twitch (soleus), intermediate (gastrocnemius) and glycolytic/fast‐twitch (extensor digitorum longus; EDL) muscles. Compared with wt/wt, exercise capacity (measured in a treadmill test) was impaired in p.R50X/p.R50X (∼48%) and p.R50X/wt mice (∼18%). p.R50X/p.R50X mice showed an absence of GP‐MM in the three muscles. GP‐MM was reduced in p.R50X/wt mice, especially in the soleus, suggesting that the function of ‘slow‐twitch’ muscles is less dependent on glycogen catabolism. p.R50X/p.R50X mice showed increased glycogen debranching enzyme in the soleus, increased glycogen branching enzyme in the gastrocnemius and EDL, as well as reduced levels of mucle glycogen synthase protein in the three muscles (mean ∼70%), reflecting a protective mechanism for preventing deleterious glycogen accumulation. Additionally, glycogen content was highest in the EDL of p.R50X/p.R50X mice. Amongst other findings, the present study shows that the expression of the main muscle glycogen regulatory enzymes differs depending on the muscle phenotype (slow‐ vs. fast‐twitch) and that even partial GP‐MM deficiency affects maximal endurance capacity. Our knock‐in model might help to provide insights into the importance of glycogen on muscle function.
Endocannabinoids mediate bidirectional striatal spike‐timing‐dependent plasticity
Authors: Cui Yihui , Paillé Vincent , Xu Hao , Genet Stéphane , Delord Bruno , Fino Elodie , Berry Hugues , Venance Laurent
Published: April 2015

Key points

Although learning can arise from few or even a single trial, synaptic plasticity is commonly assessed under prolonged activation. Here, we explored the existence of rapid responsiveness of synaptic plasticity at corticostriatal synapses in a major synaptic learning rule, spike‐timing‐dependent plasticity (STDP).

We found that spike‐timing‐dependent depression (tLTD) progressively disappears when the number of paired stimulations (below 50 pairings) is decreased whereas spike‐timing‐dependent potentiation (tLTP) displays a biphasic profile: tLTP is observed for 75–100 pairings, is absent for 25–50 pairings and re‐emerges for 5–10 pairings.

This tLTP induced by low numbers of pairings (5–10) depends on activation of the endocannabinoid system, type‐1 cannabinoid receptor and the transient receptor potential vanilloid type‐1.

Endocannabinoid‐tLTP may represent a physiological mechanism operating during the rapid learning of new associative memories and behavioural rules characterizing the flexible behaviour of mammals or during the initial stages of habit learning.

Synaptic plasticity, a main substrate for learning and memory, is commonly assessed with prolonged stimulations. Since learning can arise from few or even a single trial, synaptic strength is expected to adapt rapidly. However, whether synaptic plasticity occurs in response to limited event occurrences remains elusive. To answer this question, we investigated whether a low number of paired stimulations can induce plasticity in a major synaptic learning rule, spike‐timing‐dependent plasticity (STDP). It is known that 100 pairings induce bidirectional STDP, i.e. spike‐timing‐dependent potentiation (tLTP) and depression (tLTD) at most central synapses. In rodent striatum, we found that tLTD progressively disappears when the number of paired stimulations is decreased (below 50 pairings) whereas tLTP displays a biphasic profile: tLTP is observed for 75–100 pairings, absent for 25–50 pairings and re‐emerges for 5–10 pairings. This tLTP, induced by very few pairings (∼5–10) depends on the endocannabinoid (eCB) system. This eCB‐dependent tLTP (eCB‐tLTP) involves postsynaptic endocannabinoid synthesis, requires paired activity (post‐ and presynaptic) and the activation of type‐1 cannabinoid receptor (CB1R) and transient receptor potential vanilloid type‐1 (TRPV1). eCB‐tLTP occurs in both striatopallidal and striatonigral medium‐sized spiny neurons (MSNs) and is dopamine dependent. Lastly, we show that eCB‐LTP and eCB‐LTD can be induced sequentially in the same neuron, depending on the cellular conditioning protocol. Thus, while endocannabinoids are usually thought simply to depress synaptic function, they also constitute a versatile system underlying bidirectional plasticity. Our results reveal a novel form of synaptic plasticity, eCB‐tLTP, which may underlie rapid learning capabilities characterizing behavioural flexibility.
Definition of ANCF Finite Elements
Authors: Shabana Ahmed A.
Published: April 2015

Since the absolute nodal coordinate formulation (ANCF) was introduced, a large number of fully parametrized and gradient deficient finite elements were developed. Some of the finite elements (FE) proposed do not fall into the ANCF category, and for this reason, this technical brief describes the general requirements for ANCF finite elements. As discussed in this paper, some of the conventional isoparametric finite elements can describe arbitrary rigid body displacements and can be used with a nonincremental solution procedure. Nonetheless, these isoparametric elements, particularly the ones that employ position coordinates only, are of the C0 type and do not ensure the continuity of the position vector gradients. It is also shown that the position vector gradient continuity conditions can be described using homogeneous algebraic equations, and such conditions are different from those conditions that govern the displacement vector gradients. The use of the displacement vector gradients as nodal coordinates does not allow for an isoparametric representation that accounts for both the initial geometry and displacements using one kinematic description, can make the element assembly more difficult, and can complicate imposing linear algebraic constraint equations at a preprocessing stage. Understanding the ANCF geometric description will allow for the development of new mechanics-based computer-aided design (CAD)/analysis systems as briefly discussed in this paper.
Three-Position Synthesis of Origami-Evolved, Spherically Constrained Spatial Revolute–Revolute Chains
Authors: Abdul-Sater Kassim , Winkler Manuel M. , Irlinger Franz , Lueth Tim C.
Published: April 2015

This paper presents a finite position synthesis (f.p.s.) procedure of a spatial single-degree-of-freedom linkage that we call origami-evolved, spherically constrained spatial revolute–revolute (RR) chain here. This terminology is chosen because the linkage may be found from the mechanism equivalent of an origami folding pattern, namely, known as the Miura-ori folding. As shown in an earlier work, the linkage under consideration has naturally given slim shape and essentially represents two specifically coupled spherical four-bar linkages, whose links may be identified with spherical and spatial RR chains. This provides a way to apply the well-developed f.p.s. theory of these linkage building blocks in order to design the origami-evolved linkage for a specific task. The result is a spherically constrained spatial RR chain, whose end effector may reach three finitely separated task positions. Due to an underspecified spherical design problem, the procedure provides several free design parameters. These can be varied in order to match further given requirements of the task. This is shown in a design example with particularly challenging space requirements, which can be fulfilled due to the naturally given slim shape.
A Dual Space Approach for Force/Motion Transmissibility Analysis of Lower Mobility Parallel Manipulators
Authors: Liu Haitao , Wang Manxin , Huang Tian , Chetwynd Derek G. , Kecskeméthy Andrés
Published: April 2015

By drawing on the duality of twist space and wrench space, this paper presents a general and systematic approach for force/motion transmissibility analysis of lower mobility nonredundant and nonoverconstrained parallel manipulators. This leads to the formulation of a complete and justifiable model that enables the force/motion transmissibility analysis to be integrated into a unified framework under the umbrella of a homogenous and decoupled linear transformation that maps the coordinates of the platform wrench/twist in the joint space to its natural coordinates in the operation space. Utilizing the penalty method to avoid the indeterminate form “0/0” when the local maximum of a virtual coefficient approaches zero, a set of dimensionally homogeneous transmission indices is proposed which can be employed for precisely representing the closeness to different types of singularities defined in twist space as well as for dimensional optimization. An example is given to illustrate the effectiveness of this approach.
Mobility Analysis of Symmetric Deployable Mechanisms Involved in a Coplanar 2-Twist Screw System
Authors: Li Bing , Huang Hailin , Deng Zongquan
Published: April 2015

In this paper, an intuitive approach for the mobility analysis of deployable mechanisms involved in a special screw system with two coplanar twist vectors is proposed. First, the coplanar screw system with a pair of parallel/concurrent zero pitch screws is analyzed, and the intuitive allowable mobility set for the screw system is described. Next, kinematic chains containing the coplanar screw system are enumerated. The proposed approach is used to explain the mobility of the deployable Bennett mechanism, Myard mechanism, and Bricard mechanism; some novel deployable mechanisms could be found based on the analysis. Furthermore, it is shown that the proposed approach can be applied to the mobility analysis of multiloop deployable mechanisms and is found to be more intuitive than the traditional approach, which provides a straightforward insight into the mobility of complicated mechanisms.
Combined Gas and Steam Cycle for a Gas-Cooled Solar Tower Power Plant
Authors: Becker B. , Finckh H. H. , Meyer-Pittroff R.
Published: April 2015

In gas-cooled solar power plants the radiant energy of the sun is transferred to the cycle fluid in a cavity type solar receiver and converted into electric energy by means of a combined gas and steam turbine cycle incorporating a waste heat steam generator. The design and optimization of the energy conversion system in accordance with solar-specific considerations are described with particular regard to the gas turbine. In designing the energy conversion system several variants on the combined cycle with waste heat steam generator are investigated and special measures for the improvement of the cycle efficiency, such as the refinement of the steam process through the addition of pressure stages are introduced. It is demonstrated that the solar power plant meets the requirements both for straight solar and constant load operation with fossil fuel substitution. In order to establish the possibilities of attaining high part-load efficiencies in straight solar operation, two modes, variable and constant speed of the gas turbine, are compared with one another.
Life Cycle Cost Before, During and After the Design of Aircraft Propulsion Systems
Authors: Shoemaker W. W.
Published: April 2015

Military engine manufacturers have been given a new set of ground rules by the Department of Defense and Congress when they vie for engine contracts. The manufacturers must establish that their engines are Life Cycle Cost (LCC) effective. This directive has resulted in engine manufacturers developing life cycle cost models, including airframes, to account for an overall weapons system. Once the model has been developed, it can be expanded allowing parametric studies of the engine/airframe system thereby developing a cost effective system. The Aircraft Engine Group of General Electric has developed such an LCC computerized model. This paper discusses various applications of the subject model as applied to an engine program before the design is finalized, during the detail design phase, and after the engine has been placed in production. The paper also includes examples of these applications of the model.
Effect of Casing Treatment on Performance of a Three-Stage L.P. Compressor
Authors: Quan-chun Zhao , Ke-ming Li , Yuan-ying Sun
Published: April 2015

The test data of a three-stage L.P. compressor with a solid casing and a treated casing under both uniform and circumferentially distorted inlet conditions are presented in this paper. The effects of two different casings on the air flow, efficiency, constant speed line and surge margin of the L.P. compressor are analyzed. Four different configurations of the treated casing were designed and tested. It was found that the surge margin was improved by means of casing treatment. The best one of all configurations is that with large stagnation cell with blades, which brought about increase by 4 percent of the surge margin of the compressor at design speed. The attenuation of inlet flow distortion is also presented with two types of casings. The treated casing has a greater capability to attenuate the inlet distortion than the solid casing.
Solution of Plane Cascade Flow Using Improved Surface Singularity Methods
Authors: McFarland E. R.
Published: April 2015

A solution method has been developed for calculating compressible in viscid flow through a linear cascade of arbitrary blade shapes. The method uses advanced surface singularity formulations which were adapted from those found in current external flow analyses. The resulting solution technique provides a fast flexible calculation for flows through turbomachinery blade rows. The solution method and some examples of the method’s capabilities are presented.
Refrigerating Gas Turbine Compressor Air Intake
Authors: Sadek R. M.
Published: April 2015

Gas turbines power output is adversely influenced by increasing ambient temperatures. This is mainly caused by the reduction both in the air mass flow rate through the compressor and the developed compression ratio. It is claimed that refrigerating the compressor air intake down to 0 C, will generate enough power to cope with refrigerating system power requirements as well as leaving ample surplus power.
Power Generation From a 770°C Heat Source by Means of a Main Steam Cycle, a Topping Closed Gas Cycle and an Ammonia Bottoming Cycle
Authors: Tilliette Z. P.
Published: April 2015

For power generation, steam cycles make an efficient use of medium temperature (•□ 300–600°C) heat sources. They can be adapted to dry cooling, higher power ratings and output increase in winter by addition of an ammonia bottoming cycle. Active development is carried out in this field by “Electricite de France.” It is shown that a satisfactory result, for heat sources of about 770°C, is obtained with a topping closed gas cycle of moderate power rating, rejecting its waste heat into the main steam cycle. Attention has to be paid to the gas turbine cycle waste heat recovery and to the coupling of the gas turbine and steam cycles. This concept drastically reduces the importance of new technology components.
Application of Scaling in Afterburner Test and Development
Authors: Xiang-yi Li , Mao-lin Yang , Gao-en Liu , Shan-jian Gu
Published: April 2015

Experiments on low pressure combustion performance have been made with three different afterburner models. Tests were carried out in a test rig of 400 mm with inlet temperatures ranging form 898 to 940 K, inlet pressure from 0.77 to 1.51 kg/cm2, and air flow rates from 4.06 to 8.26 kg/sec. The performance data (combustion efficiency and stability) obtained are similar to those obtained with the actual jet engine. Tests of a swirl atomizer and a plain orifice injector with the same fuel flow rates produced similar performance curves. In afterburner development work for a given type of engine, the effect on performance of changing from one type injector to another was less than that of changing stabilizers.
Digital Control Makes a Commercial Debut on the JT9D Engine
Authors: Lenox T. G.
Published: April 2015

A digital electronic supervisory control system is incorporated in the JT9D-7R4 engine and is being applied in the new Boeing 767 and Airbus A-310 aircraft. The digital control adjusts the governor setting of the hydromechanical fuel control to provide precise thrust management, rotor speed limiting and turbine temperature protection. A significant degree of integration with the aircraft has been established while maintaining separation of engine and aircraft control functions. The engine control receives Air Data Computer information and other signals as used in the aircraft auto throttle control system for establishing power setting relative to engine thrust ratings. The engine control provides its own measurements both to validate Air Data computer information and to provide a back-up in the event that air data is interrupted. The control supplies digital information to the aircraft for cockpit display and maintenance purposes. The system has successfully completed Federal Aviation Administration certification testing and has initiated flight testing with the JT9D-7R4 engine.
Semi-Inverse Method of Computation in Inviscid Transonic Flows: Application to the Design of Turbomachines Blades Profiles
Authors: Miton H.
Published: April 2015

The present method is based on an original computational technique of quasi two-dimensional inviscid transonic flows but which takes into account the changes of entropy due to shocks. The present approach consists in a numerical 2nd order approximation of the real transonic flow problem (hyperbolic or elliptic) by an initial values problem of hyperbolic and parabolic nature respectively. Such a method applied to the flow field between two adjacent blades profiles allows starting from a prescribed distribution of velocity along blade pressure or suction side to determine the flow details inside this domain and the profile of the opposite blade wall corresponding to input flow conditions which however should be made to satisfy the periodicity conditions as at this stage the approach is of the channel type. Examples of computation for simple cases are shown which proves the validity of the method.
Further Studies of the Influence of Thermal Effects on the Predicted Acceleration of Gas Turbines
Authors: MacCallum N. R. L.
Published: April 2015

A previous study has investigated the effect of changes in compressor characteristics, due to transient heat transfers, on the predicted accelerations of a singles-pool aero gas turbine of pressure ratio 9.5. In the present paper the analysis is extended to a two-spool bypass engine of pressure ratio 21. The increases in the predicted acceleration times of this engine, due to the inclusion of heat absorption and compressor characteristic change, are more marked than with the lower pressure ratio engine, depending on the fuel schedule used. The effects of changes in component efficiencies on predicted acceleration have also been studied. Again, the higher pressure ratio engine shows the greater influence. Compared with thermal absorptions, it is likely that component efficiency changes have as much, if not more effect on predicted accelerations.
The Role of Flight Research Vehicles in Prop-Fan Technology Development
Authors: Bradley E. S. , Little B. H.
Published: April 2015

The prop-fan concept offers the potential for significant fuel savings without reducing aircraft performance from the levels of current turbofan aircraft. To enhance industry acceptance of the concept there is a need to accelerate current research and development activities. One method of accomplishing both industry acceptance and accelerated research and development is by means of flight research vehicles. This paper describes how flight research vehicles could be used in an advanced turboprop, or prop-fan, program. The technology status of prop-fan development will be reviewed and deficiencies will be identified. Methods for solving prop-fan problems using the test-bed aircraft philosophy will be discussed. Based on defined problem areas which must be addressed if the prop-fan is to become an accepted propulsion system, test-bed program objectives and priorities will be established, and the design requirements for a prop-fan research vehicle will be formulated. Suitable configurations will be examined and analyzed.
Effects of Inlet Conditions and Water Injection on Emissions From a Dual-Fuel Industrial Gas Turbine
Authors: Farrell R. A. , Thomas M. E.
Published: April 2015

The effects of combustor inlet conditions and primary zone water injection on gaseous emissions levels of an industrial gas turbine, burning diesel fuel and natural gas, are presented herein. A comparison of reduced-flow combustor rig emissions and engine emissions is made to verify existing inlet condition correlations for thermal oxides of nitrogen, carbon monoxide and unburned hydrocarbons, and to develop new empirical correlations. Engine tests were conducted over a range of water flow rates and loads, and resultant data was used to develop relationships between combustor exit temperature, water injection rate, and gaseous emissions.
The Design and Performance of a Sturdy Industrial Combustion Chamber for a 14 MW Gas Turbine
Authors: Andersson L.
Published: April 2015

The latest stage in the evaluation of a dual fuel industrial combustion chamber is reported. The design, fitting and maintability of the cans and fuel injectors is described. The performances studied are can wall temperatures, ignition and environment air pollution. The latter cover NO, NO2, CO, unburned hydrocarbons, smoke and solids. Those have been measured over a range of engine power settings, and also over a range of water injection ratios into the combustion chambers. Full engine performance was accordingly measured.
Full-Flow Debris Monitoring in Gas Turbine Engines
Authors: Tauber T.
Published: April 2015

For oil wetted components of gas turbine engines, such as bearings, reduction and accessory drive gears, debris monitoring is the most successful and cost effective condition monitoring technique. However, extensive field service experience demonstrates that full-flow debris monitoring is essential. Full-flow debris monitoring devices, as opposed to chip detectors installed in sumps or lines, monitor the entire scavenge flow. The detection efficiency of properly designed systems can reach 100 percent. This paper briefly discusses models for debris generation in bearings and gears and reviews the principles of successful debris separation and incipient failure detection in gas turbine engines. Several devices are discussed which represent the state-of-the-art in this field, including a centrifugal debris separator for aircraft jet engines which has been shown to be highly effective in field service. Of particular interest to the user of stationary gas turbines is a quantitative debris monitoring system which provides a real-time read out of debris production levels and gives reliable advance warning of impending failure; thus reducing down time, secondary damage and overhaul costs.
Methanol Combustion in a 26-MW Gas Turbine
Authors: von KleinSmid W. H. , Schreiber H. , Klapatch R. D.
Published: April 2015

Combustion tests of methanol were conducted on a 26-MW gas turbine for a period of 523 total hours. The methanol fueled gas turbine was operated in tandem with an identical gas turbine fueled with distillate (Jet A). Emissions and performance data were recorded and hot section inspections were carried out on both machines periodically during the test program. A comparison of data recorded during the test program clearly indicates that methanol is a superior fuel for gas turbines.
Application of Water Cooling for Improved Gas Turbine Fuel Flexibility and Availability
Authors: Rose R. S. , Caruvana A. , Von E. Doering H. , Smith D. P. , Cohn A.
Published: April 2015

Near term application of water cooling to stage 1 nozzles on present day gas turbines results in significant improvements in fuel flexibility and performance. Design and performance calculations for application of a water-cooled stage 1 nozzle are compared to an air-cooled stage 1 nozzle in a heavy duty gas turbine. The results of ash deposition tests of both air-cooled and water-cooled nozzles using simulated residual fuel are presented for firing temperatures of 1850°F and 2050°F. This work was jointly sponsored by the Electric Power Research Institute and General Electric under the Advanced Cooling, Full-Scale Engine Demonstration Program.
A Simple Model for Compressor Stall Cell Propagation’
Authors: Cumpsty N. A. , Greitzer E. M.
Published: April 2015

A simple model for full-span stall cells in axial compressors has been formulated. The sudden changes in velocity across blade rows as the blade passages enter and leave the stall are shown to have important dynamical consequences for the stall flow field. The one empirical constant needed in the analysis is determined using the data of Day (1). From this, reasonable predictions of stall cell speed and trends in speed have been obtained for a number of different compressors. From the satisfactory comparison between predicted and measured stall cell speeds, it is tentatively concluded that the model contains the essentials of a correct description of the controlling mechanism of full-span rotating stall.
Sensitivity of Turbine Blade Temperatures to Tolerances of Design Variables
Authors: Hsia E. S.
Published: April 2015

The General Electric Company in conjunction with the Air Force Aero Propulsion Laboratory is involved in a program to more fully understand air-cooled turbine blade distress mechanisms. As part of this program, the tolerance effects of design parameters on the predicted blade temperature were evaluated. Turbine blade temperature predictions are based on the assumption that all blades conform to the nominal design intent in terms of blade geometry and operating conditions. Since the geometry and operating conditions of each blade may vary from these assumptions, the actual blade life may be significantly different from that calculated, based on the nominal design intent. This study analyzed the blade temperature sensitivity of a single stage high pressure turbine blade to variations in most of the design variables. The effect on blade metal temperature of each variable was assessed individually and the cumulative effect of changing several variables simultaneously was also determined. Finally, an equation was obtained from this study that can be used to predict the cumulative effect on blade temperatures in a given blade by knowing only the single-variable sensitivities.
Prediction of Film Cooling Effectiveness of Steam
Authors: Han Je-Chin , Jenkins P. E.
Published: April 2015

The intent of this work is to show, analytically, that superheated steam can provide better film cooling than conventional air for gas turbine blades and vanes. Goldstein’s two-dimensional and Eckert’s three-dimensional models have been reexamined and modified in order to include the effects of thermal-fluid properties of foreign gas injection on the film cooling effectiveness. Based on the modified models, the computed results for steam film cooling effectiveness, showing an increase of 80 to 100 percent when compared with air cooling at the same operating conditions, are presented.
The Effect of NaCl(g) in High Temperature Oxidation
Authors: Smeggil J. G. , Bornstein N. S.
Published: April 2015

Sodium chloride can be present in gas turbine hot sections in the vapor as well as the condensed state. Particles containing sodium chloride may randomly break from compressor components, then impinge upon and stick to turbine components further down the gas path. However, NaCl vapor can deleteriously affect processes involving the formation and maintenance of protective oxide layers on turbine components. The relative importance of these two distinctly different mechanisms involving NaCl in corrosion processes is currently unknown. Numerous studies have dealt with the effect on corrosion behavior of Na2SO4-NaCl condensed mixtures with appreciable amounts of NaCl. However, the possibility that low NaCl vapor activities effect major changes in oxide scale formation and retention is equally as probable as that involving condensed NaCl. Therefore, the results presented here will deal with effects of low activities of NaCl vapor (0.1–100 ppm) upon scales formed by selected high temperature materials.