bluuebunny/crossref_metadata_2025 huggingface dataset:
Phylogenetic perspectives on biome shifts in Leucocoryne (Alliaceae) in relation to climatic niche evolution in western South America
Authors: Jara‐Arancio Paola , Arroyo Mary T. K. , Guerrero Pablo C. , Hinojosa Luis F. , Arancio Gina , Méndez Marco A.
Published: August 2013

Aim

Shifts between the western South American sclerophyll and winter‐rainfall desert biomes and their relationship to climatic niche evolution and aridity development were investigated in the South American endemic geophytic Leucocoryne (Alliaceae) clade.

Location

Western South America.

Methods

We constructed a molecular phylogeny (internal transcribed spacer, ITS), estimated lineage divergence times, and identified ancestral biomes and biome shifts. The multivariate climatic niche of present‐day species was described using occurrence data and bioclimatic variables. Climatic niche similarity was evaluated using Mahalanobis and Fisher distances. Brownian motion (BM) and Ornstein–Uhlenbeck (OU) models of evolution were used to characterize temperature and precipitation niche evolution. Ancestral temperature and precipitation were estimated using the phylogenetic generalized least‐squares method.

Results

Leucocoryne exhibits a low level of phylogenetic biome conservatism. The clade arose in the early Miocene in an ancestral sclerophyll biome and subsequently moved northwards into the arid winter‐rainfall biome on two separate occasions, during the late Miocene and Pliocene, respectively, with very recent diversification of species in the winter‐rainfall desert. Overall, the multivariate climatic niche showed significant differentiation, and phylogenetic and climatic niche distances were correlated. Temperature and precipitation niche evolution within lineages followed a pattern that is consistent with stabilizing selection (OU model).

Main conclusions

The low level of phylogenetic biome conservatism found in Leucocoryne is associated with considerable expansion of the precipitation and temperature niche axes. Unidirectional biome shifts from a wetter biome characterized by higher species richness and more continuous vegetation cover, into a drier biome with lower species richness and much sparser vegetation cover, suggest that the availability of and lower biotic resistance within open habitats facilitated biome shifts in Leucocoryne. Incursion into the arid winter‐rainfall desert and diversification there may have been facilitated by the conservative geophytic life‐form of Leucocoryne, the generally cool coastal conditions, and the wet/dry climatic cycles occurring since the late Miocene.
Psoriasis and dyslipidemia: a population‐based study analyzing the National Health and Nutrition Examination Survey (NHANES)
Authors: Ma C. , Schupp C.W. , Armstrong E.J. , Armstrong A.W.
Published: August 2013

Background

Psoriasis has been linked to an increased incidence of coronary artery disease, stroke, myocardial infarctions and cardiovascular deaths. Dyslipidemia, a well‐established risk factor for cardiovascular disease, involves inflammatory pathways that are also implicated in psoriasis. An understanding of the relationship between psoriasis and dyslipidemia may have a substantial clinical impact.

Objective

This study aimed to examine the association between psoriasis and multiple measurements of dyslipidemia, which include levels of triglycerides, apolipoprotein B, LDL‐cholesterol, HDL‐cholesterol, HDL/LDL ratio and total cholesterol.

Methods

We conducted a population‐based, cross‐sectional study using the National Health and Nutrition Examination Survey (NHANES) 2003–2006 and 2009–2010. NHANES is a national research survey programme conducted biennially to evaluate the health and nutritional status of the U.S. population. The survey uses a multistage, stratified design. NHANES data were collected from questionnaires, physical examination and laboratory values.

Results

The sample population consisted of 13 418 adults who provided responses to their psoriasis status. A total of 353 (2.63%) participants reported a health care provider‐given diagnosis of psoriasis. The multivariate analysis showed that psoriasis was not significantly associated with certain measures of dyslipidemia from this population. Specifically, in psoriasis patients, the weighted odds ratio (OR) of total cholesterol >200 mg/dL was 0.96 (95% CI 0.74–1.24); weighted OR of HDL‐cholesterol <40 mg/dL was 0.92 (95% CI 0.65–1.30); weighted OR of LDL‐cholesterol >130 mg/dL was 0.67 (95% CI 0.43–1.03); weighted OR of triglycerides >150 mg/dL was 1.20 (95% CI 0.89–1.63); weighted OR of apolipoprotein B >130 mg/dL was 1.29 (95% CI 0.69–2.41); weighted OR of HDL/LDL <0.4 was 1.20 (95% CI 0.8–1.79).

Conclusion

Based on the NHANES data 2003–2006 and 2009–2010, psoriasis is not significantly associated with alterations in certain lipid levels. Larger sample sizes may be necessary to detect appreciable differences in the lipid levels between patients with and without psoriasis.
Multiple Lines of Evidence Shed Light on the Occurrence of Paramecium (Ciliophora, Oligohymenophorea) in Bromeliad Tank Water
Authors: Buosi Paulo R. B. , Cabral Adalgisa F. , Simão Taiz L. L. , Utz Laura R. P. , Velho Luiz F. M.
Published: August 2013

Phytotelmata are vegetal structures that hold water from the rain, and organic matter from the forest and the soil, resulting in small, compartmentalized bodies of water, which provide an essential environment for the establishment and development of many organisms. These microenvironments generally harbor endemic species, but many organisms that are found in lakes and rivers, are also present. Here, we report, for the first time, the occurrence of the ciliate genus Paramecium in the tank of the bromeliad species Aechmaea distichantha. The identification of the Paramecium species was performed based on live observations, protargol impregnation, scanning electronic microscopy, and sequencing of the 18s rRNA. The absence of Paramecium from bromeliad tank water was highlighted in several earlier investigations, and may be due to the fact that this species is unable to make cysts. The occurrence of Paramecium multimicronucleatum in our samples may be explained by the proximity between the bromeliads and the river, a potential source of the species. Further, we also believe that the counting methodology used in our study provides a more accurate analysis of the species diversity, since we investigated all samples within a maximum period of 6 h after sampling, allowing minimum loss of specimens.
PROFILING U.S. METROPOLITAN REGIONS BY THEIR SOCIAL RESEARCH NETWORKS AND REGIONAL ECONOMIC PERFORMANCE
Authors: Strumsky Deborah , Thill Jean‐Claude
Published: August 2013

On the premise that knowledge creation defines contemporary metropolitan regions, we profile them by their inventive networks, as measured by a variety of complementary social network, technology, and patenting metrics that distinguish scalar and structural aspects. Using a comprehensive, multiyear database of patent applications, we investigate whether the knowledge creation network profiles are discriminating characteristics of metropolitan regions by establishing a new urban taxonomy for metropolitan areas in the United States. The four‐class taxonomy is not only statistically significant, but it is also economically meaningful in terms of economic performance of metropolitan areas. We find that metropolitan areas benefit from a higher density of inventors in the population, and that there is a positive correlation between economic performance and metropolitan areas with inventor teams working in similar or complementary areas of technology. In fact, the structure of knowledge creation networks are fundamental to economic performance and extends to metropolitan growth rates in jobs and income.
Tissue fatty acid composition and estimated ∆ desaturase activity after castration in chicken broilers fed with linseed or sunflower oil
Authors: Mašek T. , Starčević K. , Filipović N. , Stojević Z. , Brozić D. , Gottstein Ž. , Severin K.
Published: August 2013

The aims of this study were to investigate the influence of the short‐term addition of sunflower and linseed oil and castration on fatty acid composition and desaturation indexes in chicken broilers. Forty‐eight male Ross 308 chicken broilers were supplemented with 5% of sunflower or linseed oil. The four experimental groups were linseed oil supplementation and castration (LC), linseed oil without castration (LN), sunflower oil and castration (SC) and sunflower oil without castration (SN). There was no significant influence of castration or oil supplement on live weights, weight gain, feed intake or feed conversion. Castration resulted in an increase in polyunsaturated fatty acids (PUFA), total n3, n6, measured desaturation indexes and a decrease in the saturated fatty acid (SFA) and monounsaturated fatty acid (MUFA) content of abdominal fat. In breast muscle, castration increased PUFA and 18:3n3 values, while in the liver tissue, castration did not influence the parameters measured. Linseed oil supplementation significantly increased 18:3n3, n3 long chain polyunsaturated fatty acids (LC PUFA), total n3 and decreased total n6, n6/n3 ratio, and 20:4n6 content. Values for 20:4n6 were the highest in SC and the lowest in the LC group. Linseed oil also significantly decreased ∆5 and ∆4 desaturation indexes in the thighs and ∆5 and ∆5, 6 in abdominal fat and the liver. These results suggest that short‐term supplementation of basal diet with 5% of linseed oil could significantly increase n3 LC PUFA and decrease n6/n3 ratio content in the edible tissues of chicken broilers, without adverse effects on growth performance. Meanwhile, castration only improved fatty acid profile in abdominal fat, which is not nutritionally important. The interactions observed between basal diet, supplemented oil, sex hormones and other non‐nutritional factors must be elucidated in future trials in order to correctly predict the nutritional value of linseed‐fed poultry.
Direct and indirect relationships between genetic diversity of a dominant grass, community diversity and above‐ground productivity in tallgrass prairie
Authors: Chang Cynthia C. , Smith Melinda D.
Published: August 2013

Question

Both genetic diversity within a dominant species and species diversity have been shown to affect productivity. However, these two levels of diversity have the potential to affect productivity in similar or opposing ways. Our study assessed direct and indirect relationships between genetic diversity of a dominant grass species and plant community diversity on productivity within a mesic grassland with naturally co‐occurring genotypes and species.

Location

Konza Prairie Biological Station, Kansas,USA(39°05′35″ N, 96°33′31″ W).

Methods

We conducted a study at two sites (~65 plots per site) in intact tallgrass prairie that have been subjected to frequent (burned 14 times) and infrequent (burned nine times) fire treatments for ~30 yrs. With frequent burning, the dominant C4grass,Andropogon gerardii,typically has higher abundance; in contrast, infrequently burned sites typically have higher species diversity but lower abundance ofA. gerardii. Therefore, we hypothesized that genetic diversity withinA. gerardiiwould have a significant direct relationship with productivity for the frequently burned site due to higher population abundances ofA. gerardiioverall,whereas species diversity would have a significant direct relationship with productivity for the infrequently burned site.

Results

Contrary to our predictions, genetic diversity ofA. gerardiiwas not related to above‐ground productivity either directly or indirectly via traits, while diversity at the community level had a negative indirect relationship with productivity via a negative effect ofA. gerardiiabundance on community diversity for both frequently and infrequently burned sites.

Conclusions

While much of the focus of diversity–productivity research has been on direct relationships between diversity at the community or population level separately, future studies should examine the indirect and potentially interactive effects of both levels of diversity in natural communities.
Fossorial life does not constrain diet selection in the amphisbaenian Trogonophis wiegmanni
Authors: Martín J. , Ortega J. , López P. , Pérez‐Cembranos A. , Pérez‐Mellado V.
Published: August 2013

Morphological adaptations of amphisbaenians for a fossorial life constrain their ecological demands in a greater way than for epigeal reptiles. Studies on the diet of amphisbaenians suggest that most species are generalists, although others seem more selective. However, there is no information on the diet preferences of almost any species because most studies did not evaluate the availability of prey in the environment. We analysed the spring diet selection of a population of the amphisbaenian Trogonophis wiegmanni from the Chafarinas Islands, in North Africa. We specifically examined diet estimated from faecal material collected from live amphisbaenians and compared diet with the availability of invertebrates in the soil. Results indicate that the diet of T. wiegmanni amphisbaenians consists of some of the types of invertebrates that are more commonly found under rocks used by amphisbaenians, such as insect larvae, snails, isopods, beetles and ants. This diet could be initially considered generalist, and probably opportunistic. However, the comparison of proportions of prey types in the diet and those available in the habitat revealed that T. wiegmanni does not eat prey at random, but selects some particular prey types (insect larvae and pupae and, surprisingly, snails), while others (ants and isopods) are consumed less than expected by their abundance. We did not found differences between sexes or age classes in diet composition. We discuss how diet preferences could be due to selection of the more profitable or easily captured prey. There are many aspects of the feeding and foraging biology of amphisbaenians that remain unknown and further studies are clearly needed.
Development of an actuarial static risk model suitable for automatic scoring for predicting juvenile recidivism
Authors: McKinlay Audrey , James Victoria L. , Grace Randolph C.
Published: August 2013

Objectives

To test the feasibility of an actuarial model for juvenile offending suitable for automatic scoring.

Design

We identified a nationally representative sample of 936 young persons aged 13–17 (745 male, 191 female) who received a juvenile justice intake in 2002 in New Zealand.

Methods

Best‐subsets logistic regression and a formal model selection criterion were used to generate a predictive model for reoffending, and a conservative estimate of accuracy was obtained with cross‐validation.

Results

Recidivism during a 1‐year follow‐up was significantly higher for male (60.8%) compared to female (46.6%) delinquents. The model showed that young persons who were male, younger at their first social welfare intake, and had more prior court dates and a greater frequency of contact with police, were more likely to re‐offend. The accuracy of the model was moderately high (area under the receiver operating characteristic curve = .710). A model developed specifically for the female cases failed to provide a significant increase in predictive accuracy.

Conclusions

These results demonstrate the feasibility of an actuarial model for juvenile offending that is suitable for automatic scoring. Although male delinquents pose a higher absolute risk of juvenile offending than female delinquents, a common set of items related to history of contact with police and social welfare agencies provide a similarly accurate measure of relative risk for both sexes.
Watching the Watchmen, Mediating the Mediators
Authors: Polley Jason S
Published: August 2013

Alan Moore and Dave Gibbons Watchmen (1987) is the only graphic narrative included in “Time's Greatest 100 Novels: 1923–Present.” The text abounds with the detritus of American Cold War culture. Among many other things, Watchmen solicits informed re‐readings of Cold War (fictional) narratives and their legacies. Watchmen proves to be an apocalyptic and encyclopedic story replete with stories – notes, journal entries, photos, backstories, flashbacks, newspaper clippings, comics, signboards, graffiti, and a litany of literary allusions proliferate in this very long, very graphic, graphic novel. But this text is also about more than intertwining and conflicting over‐ and underworld Cold War‐historicities and histories and stories. Moving beyond Watchmen's problematizing of American Exceptionalism, its humanizing of heroism, and its reconceptualizing of Cold War America, the Hugo Award‐winning novel questions the official traffic of official information – and the official act of representation itself. At stake here is the fact that ideologically polarized newspapers, The New Frontiersman and Nova Express, vie for the monopoly of publicized truth, or, more rightly, for the control of a “formally‐sanctioned cultural narrative.” No scholars, to date, have discussed the media battle that rests at the heart of this seminal graphic novel. Every reading of Watchmen forces intentionally frustrated reader to sift the doomsday ashes of so‐called information, disinformation, and misinformation. The graphic novel thus speaks to the fundamental quandary of the contemporary human experience: the impossibility of unfiltered truth.
Building awareness of the health risks of sunbed use: identification of target groups for prevention
Authors: Diehl Katharina , Bock Christina , Breitbart Eckhard W. , Greinert Rüdiger , Schneider Sven
Published: August 2013

Purpose

Sunbed use, a recognized risk factor for skin cancer development, is common in developed countries. Cost‐efficient interventions to reduce the negative health consequences of sunbed use are needed. As a first step to identify what kind of intervention might be useful, we aimed to assess the awareness of potential health risks of sunbed use in current, former, and never users as well as in current users with differing risk profiles.

Methods

We assessed risk awareness using items addressing the potential health risks of sunbed use (e.g. skin damage) in a representative sample of 4851 individuals. The response format assessed agreement with each statement. Risk profiles were defined by a large number of birthmarks, a history of frequent childhood sunburn, or a (family) history of melanoma.

Results

Many individuals were not aware of potential risks (e.g. agreement to skin cancer risk 72.6%). Current users were less aware compared with former and never users [e.g. skin cancer risk (65.6% vs. 75.9% and 73.0%, respectively; P < 0.001]). Among current users, those with at least two risk factors showed the highest proportion of risk aware individuals.

Conclusion

Low risk awareness among current users suggests the need for targeted interventions to reduce or discontinue sunbed use.
A Moral Equivalent of Consent of the Governed
Authors: Reiman Jeffrey
Published: August 2013

Though genuine (voluntary, deliberate) consent of the governed does not occur in modern states, political legitimacy still requires something that does what consent does. Dereification of the state (recognizing that citizens continually create their state), combined with a defensible notion of moral responsibility, entails citizens' moral responsibility for their state. This implies that we may treat citizens morally as if they consented to their state, yielding a moral equivalent of consent of the governed, and a conception of political legitimacy applicable to modern states thought legitimate. It implies that legitimate states have a moral right to rule, and their citizens have a prima facie moral obligation to obey the law.
The Political Obligation To Donate Organs
Authors: Den Hartogh Govert
Published: August 2013

The first question I discuss in this paper is whether we have a duty of rescue to make our organs available for transplantation after our death, a duty we owe to patients suffering from organ failure. The second question is whether political obligations, in particular the obligation to obey the law, can be derived from natural duties, possibly duties of beneficence. Such duties are normally seen as merely imperfect duties, not owed to anyone. The duty of rescue, however, is a perfect one, mainly because it applies to us when we are in a unique position to provide urgent help to a person in need. The basic idea of a natural duty account of political obligation is that such unique positions can be artificially created by institutionalized coordination schemes. The remaining problem is how any particular coordination scheme could claim our allegiance rather than any other. This problem can be solved in different ways in the organ donation case, and in respect to a limited set of political obligations, mainly negative ones. A natural duty account is best seen as a constitutive part of a multiple principle theory of political obligation.
The Development of Externalist Semantics
Authors: Putnam Hilary
Published: August 2013

In this lecture I describe the path by which I was led to the “semantic externalism” for which I was honoured with the Rolf Schock Prize. Although my interest in linguistics goes back as far as my undergraduate days, it was conversations with Jerrold Katz and Jerry Fodor at MIT (where all three of us taught at the time) in the 1960s that first led to an effort by all three of us to develop semantic theories. My own direction was a false one, by my present lights; at that time all three of us defended the “internalist” view that the meaning of a word is fixed by a “battery of semantical rules” implicitly known by each speaker. I describe how I was led to the realization that this could not be right, and finally to the views I defended in “The Meaning of ‘Meaning' ”.
Semantic Externalism and Knowing Our Own Minds: Ignoring Twin‐Earth and Doing Naturalistic Philosophy
Authors: Boyd Richard
Published: August 2013

In this article I offer a naturalistic defence of semantic externalism. I argue against the following: (1) arguments for externalism rest mainly on conceptual analysis; (2) the community conceptual norms relevant to individuation of propositional attitudes are quasi‐analytic; (3) externalism raises serious questions about knowledge of propositional attitudes; and (4) externalism might be OK for “folk psychology” but not for cognitive science. The naturalist alternatives are as follows. (1) Community norms are not anything likea priori; sometimes they are incoherent. (2) Often propositional attitudes lack determinate content: we do not know the content of thoughts or sentences because there is no fully definite content to be known. (3) Often achieving determinate content is a major socially mediated cognitive achievement that depends on just the factors of social and environmental embedding posited as individuative by externalists, so (4) externalism explains how people can, sometimes, come to have, and to know, determinate attitude contents. (5) Reference and content, for both thought and language, are determined by complex and messy dialectical relations involving many such environmental and social factors; consequently, determinate reference, truth‐conditions, etc., are somewhat uncommon outcomes. (6) The basic semantic relation is (typically imperfect) socially mediated accommodation between perceptual, cognitive, linguistic, classificatory and inferential dispositions and relevant causal structures in the environment. (7) This accommodation explains how concepts, language, taxonomies, etc., contribute to individuals' rational inductive, explanatory and practical achievements. (8) So externally individuated propositional attitudes are required for cognitive science explanations of individual human rationality and its inductive and explanatory achievements. “Individual rationality ain't (entirely) in the individual head.”
Seroprevalence of Trypanosoma cruzi in kidney transplant donors and recipients in Mexico City
Authors: Rodríguez‐Romo R. , Morales‐Buenrostro L.E. , Reyes P.A. , Gracida C. , Medeiros M. , Mancilla E. , De Leo C. , Alberú J.
Published: August 2013

Infectious diseases are common causes of morbidity and mortality among kidney transplant recipients. Chagas disease (CD) has been recognized as an emerging infectious complication of transplantation caused by the parasite Trypanosoma cruzi. CD is prevalent in Mexico, particularly in the southern coastal region. The impact on Mexican kidney transplant programs has not been previously studied prospectively. From 2009 through 2010, serum samples from 59 kidney transplant donors and 405 renal transplant recipients were screened for antibodies against T. cruzi. Serum was initially screened using a locally developed ELISA test; positive results were confirmed by an indirect immunofluorescense test, in accordance with Panamerican Health Organization/World Health Organization guidelines. None of the donors were seropositive for T. cruzi, while 8 (1.97%) kidney transplant recipients were confirmed to be seropositive for T. cruzi. None of them have developed clinical manifestations of CD, although specific screening of recipients was not performed. A prospective study is planned to define the epidemiology and outcome of CD among kidney transplant donors and recipients in Mexico more thoroughly.
Monitoring child survival in ‘real time’ using routine health facility records: results from Malawi
Authors: Amouzou Agbessi , Kachaka Willie , Banda Benjamin , Chimzimu Martina , Hill Kenneth , Bryce Jennifer
Published: August 2013

Objectives

Few developing countries have the accurate civil registration systems needed to track progress in child survival. However, the health information systems in most of these countries do record facility births and deaths, at least in principle. We used data from two districts of Malawi to test a method for monitoring child mortality based on adjusting health facility records for incomplete coverage.

Methods

Trained researchers collected reports of monthly births and deaths among children younger than 5 years from all health facilities in Balaka and Salima districts of Malawi in 2010–2011. We estimated the proportion of births and deaths occurring in health facilities, respectively, from the 2010 Demographic and Health Survey and a household mortality survey conducted between October 2011 and February 2012. We used these proportions to adjust the health facility data to estimate the actual numbers of births and deaths. The survey also provided ‘gold‐standard’ measures of under‐five mortality.

Results

Annual under‐five mortality rates generated by adjusting health facility data were between 35% and 65% of those estimated by the gold‐standard survey in Balaka, and 46% and 50% in Salima for four overlapping 12‐month periods in 2010–2011. The ratios of adjusted health facility rates to gold‐standard rates increased sharply over the four periods in Balaka, but remained relatively stable in Salima.

Conclusions

Even in Malawi, where high proportions of births and deaths occur in health facilities compared with other countries in sub‐Saharan Africa, routine Health Management Information Systems data on births and deaths cannot be used at present to estimate annual trends in under‐five mortality.
Infrared ocular thermography in dogs with and without keratoconjunctivitis sicca
Authors: Biondi Flávia , Dornbusch Peterson T. , Sampaio Manuella , Montiani‐Ferreira Fabiano
Published: August 2013

Infrared thermography was used to measure temperature differences of the corneal surface between nasal and temporal limbus regions and central cornea of normal dogs and dogs with keratoconjunctivitis sicca (KCS), in order to establish temperature values in normal canine eyes and in patients with decreased Schirmer tear tests (STT) values. Dogs investigated were all either patients seen at the Veterinary Teaching Hospital of Federal University of Paraná or normal dogs that belonged to the same institution. STT were performed in all eyes. A total of 40 control eyes (STT ≥15 mm/min) and 20 eyes with low STT values (STT ≤14 mm/min) were examined. The mean STT value for eyes with normal STT values was 22.9 ± 3.9 mm/min (mean ± standard deviation), and the mean STT value for eyes with low STT value was 7.2 ± 4.8 mm/min. The mean corneal temperature was significantly lower in eyes with low STT values than in control eyes (P < 0.0001). The following significant correlations were found: (i) Schirmer and breakup time (BUT) (P = 0.0001, r = 0.5); (ii) STT values and corneal surface temperature (P = 0.001, r = 0.256); (iii) STT values and age (P = 0.0001, r = −0.448); (iv) age and corneal surface temperature (P = 0.0001, r = −0.281); and (v) BUT and corneal surface temperature (P = 0.0001, r = 0.36). Thermography is a method that can differentiate between eyes with normal and abnormal STT values. In the future, thermography might be incorporated as part of the ophthalmic examination and perhaps become a popular ancillary test for the diagnoses of ocular surface disorders.
Understanding Loss Mechanisms and Identifying Areas of Improvement for HCCI Engines Using Detailed Exergy Analysis
Authors: Saxena Samveg , Dario Bedoya Iván , Shah Nihar , Phadke Amol
Published: August 2013

This paper presents a detailed exergy analysis of homogeneous charge compression ignition (HCCI) engines, including a crank-angle resolved breakdown of mixture exergy and exergy destruction. Exergy analysis is applied to a multizone HCCI simulation including detailed chemical kinetics. The HCCI simulation is validated against engine experiments for ethanol-fueled operation. The exergy analysis quantifies the relative importance of different loss mechanisms within HCCI engines over a range of engine operating conditions. Specifically, four loss mechanisms are studied for their relative impact on exergy losses, including (1) the irreversible combustion process (16.4%–21.5%), (2) physical exergy lost to exhaust gases (12.0%–18.7%), (3) heat losses (3.9%–17.1%), and (4) chemical exergy lost to incomplete combustion (4.7%–37.8%). The trends in each loss mechanism are studied in relation to changes in intake pressure, equivalence ratio, and engine speed as these parameters are directly used to vary engine power output. This exergy analysis methodology is proposed as a tool to inform research and design processes, particularly by identifying the relative importance of each loss mechanism in determining engine operating efficiency.
Very Large Eddy Simulation of Passive Drag Control for a D-Shaped Cylinder
Authors: Han Xingsi , Krajnović Siniša
Published: August 2013

The numerical study reported here deals with the passive flow control around a two-dimensional D-shaped bluff body at a Reynolds number of Re=3.6×104. A small circular control cylinder located in the near wake behind the main bluff body is employed as a local disturbance of the shear layer and the wake. 3D simulations are carried out using a newly developed very large eddy simulation (VLES) method, based on the standard k − ε turbulence model. The aim of this study is to validate the performance of this method for the complex flow control problem. Numerical results are compared with available experimental data, including global flow parameters and velocity profiles. Good agreements are observed. Numerical results suggest that the bubble recirculation length is increased by about 36% by the local disturbance of the small cylinder, which compares well to the experimental observations in which the length is increased by about 38%. A drag reduction of about 18% is observed in the VLES simulation, which is quite close to the experimental value of 17.5%. It is found that the VLES method is able to predict the flow control problem quite well.
Optimization of Labyrinth Seal Performance Combining Experimental, Numerical and Data Mining Methods
Authors: Braun Erik , Dullenkopf Klaus , Bauer Hans-Jörg
Published: August 2013

Numerous experimental and numerical studies were performed in the past by various authors to reduce the leakage of labyrinth seals and thus increase the performance of turbo machines. Based on the experience of more than 20 years of research activities in this area at the ITS, the authors aim to improve the prediction quality for labyrinth seal performance by combining experimental, numerical and data mining methods. Special emphasis in this work lies on more complex and also worn labyrinth geometries and thus on a more universal optimization tool for labyrinth seals incorporating more realistic engine running conditions as well as wear mechanisms. Better understanding of labyrinth seal behavior based on the new correlations and models will thus lead to optimized geometries and improved designs.

The paper contains the results of experiments to determine the discharge coefficients of different straight-through labyrinth seals with three and five fins and two different fin geometries over a large range of pressure ratios as well as results from a stepped labyrinth seal with six fins in convergent and divergent flow direction. The collected data extends an existing data base of labyrinth seal performance already presented in the paper of Pychynski et al. [1]. This data base is used to create models to calculate labyrinth seal performance depending on up to 25 input parameters. The resulting models will be used as a basis for a universal optimization tool for labyrinth seals.

In the paper the new and versatile test rig for various kinds of labyrinth and gap seals is presented and an analysis of measurement accuracy will be given. The results of a first set of experiments performed with new (i.e. unworn) geometries are compared to experimental data of similar labyrinth geometries from previous investigations, showing an excellent agreement.

The results are then interpreted using Data Mining Methods to identify correlations between different input parameters and the labyrinth seal discharge coefficient. The paper will show that a data based approach can yield similar quality relations as empirical studies but is much less time consuming and more versatile. Several models with different sets of input parameters will be presented and compared as to their applicability in automated geometry optimization using a newly developed optimization tool.
An Investigation of an Impingement / Pin-Fin Cooling System for Gas Turbine Combustor Applications
Authors: Savarianandam Vivek , Thorpe Steven J. , Carrotte Jon F. , Zedda Marco
Published: August 2013

Pin-fin cooling geometries are used extensively in gas turbine engine components, typically in combination with film-cooling and thermal barrier coatings. The cooling performance of this cold-side arrangement is an important factor in maintaining hot-section components below prescribed life-limiting temperatures. At a time when engine manufacturers are pursuing combustor designs that require a reduced coolant flow, robust aerodynamic and heat transfer correlations, as well as the physical insight provided by a deeper understanding of the flow processes, are essential to efficient design. In this paper both experimental and computational findings are reported for the performance of a combustor pin-fin cooling system that employs a single row of impingement feed-holes. The geometry is representative of that employed in a double-skin combustor cooling system. The data includes spatially resolved end-wall heat transfer measurements, and hot-wire traverse data for the coolant velocity and turbulence parameters. Heat transfer measurements have been obtained for the cold-side of the hot-skin, and include the impact of a gap between the cold-skin and tips of the pin-fins. The flow conditions within the pin-fin geometry can be divided between an impingement zone immediately adjacent to the feed-holes, and a fully-developed zone further downstream. In general, the impingement zone is characterised by strongly varying flow and heat transfer behaviour up to approximately six pin-fin rows from the feed-hole centre-line, and then sensibly repeating conditions within the pin-fin array thereafter downstream. The impact of the cold-skin gap is to redistribute the coolant away from the hot-skin, leading to a reduction in the hot-skin heat transfer coefficient in the developed zone. Reynolds averaged Navier-Stokes (RANS) simulations of the flow within the experimental geometry have been conducted and compared to the experimental results. Various standard turbulence models have been considered. Based on this comparison recommendations are made regarding the most appropriate computational modeling approach.
Uncertainty Quantification and Conjugate Heat Transfer: A Stochastic Analysis
Authors: Montomoli F. , D’Ammaro A. , Uchida S.
Published: August 2013

Conjugate Heat Transfer studies are a common method to predict the thermal loading in high pressure nozzles. Despite the accuracy of nowadays tools, it is not clear how to include the uncertainties associated to the turbulence level, the temperature distribution or the thermal barrier coating thickness in the numerical simulations. All these parameters are stochastic even if their value is commonly assumed to be deterministic.

For the first time, in this work a stochastic analysis is used to predict the metal temperature in a real high pressure nozzle. The domain is the complete high pressure nozzle of F-type Mitsubishi Heavy Industries gas turbine with impingement, film and trailing edge cooling. The stochastic variations are included by coupling Uncertainty Quantification Methods and Conjugate Heat Transfer. Two Uncertainty Quantification methods have been compared: a Probabilistic Collocation Method (PCM) and a Stochastic Collocation Method (SCM).

The stochastic distribution of thermal barrier coating thickness, used in the simulations, has been measured at the midspan. A Gaussian distribution for the turbulence intensity and hot core location has been assumed. By using PCM and SCM, the probability to obtain specific metal temperature at midspan is evaluated. The two methods predict the same distribution of temperature with a maximum difference of 0.6% and the results are compared with the experimental data measured in the real engine. The experimental data are inside the uncertainty band associated to the CFD predictions except near at the trailing edge on the pressure side.

This work shows that one of the most important parameters affecting the metal temperature uncertainty is the pitch-wise location of the hot core. Assuming a probability distribution for this location, with a standard deviation of 1.7 degrees, the metal temperature at midspan can change up to 30%. The impact of turbulence level and thermal barrier coating thickness is one order of magnitude less important.
Experimental and Numerical Investigation of the Flow Field at Radial Holes in High-Speed Rotating Shafts
Authors: Sousek Jan , Riedmüller Daniel , Pfitzner Michael
Published: August 2013

Rotating and stationary orifices are used within the secondary air system to transport sealing/ cooling air to its consumers. This paper reports on measurements of the discharge coefficient of rotating radial holes as their aerodynamical behaviour is different from the one of axial or stationary holes due to the presence of centrifugal and Coriolis forces.

A test rig containing two independently rotating shafts was designed to investigate the flow phenomena and the discharge behaviour of these orifices. The required air mass flow is delivered by a screw compressor and can be regulated independently to supply the inner and outer annular passages of the test rig. It allows measurements of the discharge coefficient with cross flow and co- and counter-rotating shafts with centrifugal and centripetal flow through the rotating holes.

On the outer shaft, absolute and differential pressures and temperatures in the rotating frame of reference are measured via a telemetry system. Measurements of the discharge coefficient for sharp-edged and rounded shaft inserts at a variety of different flow conditions and with swirl added to the air upstream of the orifice are presented. Furthermore experiments were conducted to quantify the influence of the inner shaft (non-rotating and rotating) on the discharge behaviour of orifices in the outer shaft. To complement the data acquired from the experiments and to get a better understanding of the flow field near the rotating holes also numerical flow simulations were performed.
Experimental Investigations on Aero-Thermal Interaction of Film Cooling Airs Ejected From Multiple Holes: Shallow Hole Angle
Authors: Abdullah Kamil , Funazaki Ken-ichi , Onodera Hisato , Ideta Takeomi
Published: August 2013

This paper presents thermal and aerodynamics investigations of multiple cooling holes with shallow hole angle. Three test models have been considered namely TMA, TMB and TMG. TMB is acting as the baseline test model having 35° hole angle cooling holes. The other two test models; TMA and TMG, have a shallow hole angle of 20° with different lateral pitch distance of 6D and 3D respectively. Total of twenty conventional cylindrical cooling holes have been arranged to form a five times four matrix. All three test models have been considered in the thermal investigations with only the shallow hole angle test models have been considered for the aerodynamics investigation. The film cooling effectiveness has been measured by means of infrared thermography while 3D-LDV has been utilized for the flowfield measurements. The measurements were carried out at single Reynolds number base on the hole diameter of 6200 at three different blowing ratios of 0.5, 1.0 and 2.0. All three blowing ratios have been considered in the thermal investigations with only the latter two blowing ratios were considered in the aerodynamics investigation. The results are presented in the form of contour plot of various variables including film cooling effectiveness, normalized u, v, and w velocities, normalized root mean square of u velocity and Reynolds stress tensors. Distribution of laterally average film cooling effectiveness along the x-axis are also presented, showing that the 20° hole angle cooling holes provide a very promising results particularly at high blowing ratio. The velocities contours clearly capture the flow structure of the film cooling jets, along with the effects of blowing ratios and lateral pitch on the flowfield.
Tip-Shaping for HP Turbine Blade Aero-Thermal Performance Management
Authors: Zhang Q. , He L.
Published: August 2013

A large portion of the over-tip leakage flow is often transonic for a typical high pressure (HP) turbine blade. It has been observed that the tip heat transfer is noticeably lower in a high speed flow tip region than in a low speed region. The present study therefore investigates the feasibility of controlling blade heat transfer by tip shaping to locally accelerate the flow to a transonic regime. The results show that a significant heat load reduction can be achieved by the local flow acceleration. Such over-tip-shaping provides a great potential as an effective means to control heat load distribution (and hence thermal stress) over the blade tip surface. The feasibility of the concept and flow physics have been demonstrated in detail by CFD analyses, with and without the effect of moving casing. The experimental results obtained from a high speed linear cascade facility have also been presented. In addition, the proposed tip-shaping concept may also provide a potential for promoting choking inside the tip gap as a way to control the over-tip leakage mass flow.
Numerical Study of Water Droplets’ Heat and Mass Transfer Characteristics in an Entry Strut’s Icing Test
Authors: Zhu Jian-Jun , Dong Wei , Cai Ying-Lei
Published: August 2013

In order to ensure the flight safety, ground icing tests, including aero-engine entry components tests, must be done during the R&D process of a new machine type. Most of these tests are taken in icing tunnels, which consist of usual wind tunnels and spray systems, and can be used to simulate the movement of super cooled water droplets in air. Generally, diameters of the droplets produced by the system are not unique in each test, and temperature of the water at the position of injections is much higher than the air at the same position. These factors may affect the droplets impingement characteristics and cause heat and mass transfer between droplets and the free steam. So they should be taken into account in test analysis.

In this paper, an improved Lagrangian approach is presented to simulate the unsteady process of droplets movement in the icing tunnel. This method considers the droplet size distribution where they are injected and heat and mass transfer during their movements. In addition, statistical approach is also developed in this method so that local collection coefficient of complex three-dimensional surface can be calculated. An entry strut of a turbo-shaft engine is chosen as a case to validate the effectiveness of the method. By compared with the results of experiment and former calculation, it shows that the improved method in this paper is more accurate to simulate the water droplets impingement characteristics in icing test facilities and droplets’ temperatures decrease quickly during their movements in test processes.
Reducing the Demand of Coolant at the Sidewall of a High Pressure Turbine Cascade by Means of Slot Width Modulation
Authors: Woopen Michael , Dannhauer Axel , Gieß Peter-Anton
Published: August 2013

Within the framework of the German research project AG-Turbo the influence of slot flows associated with cooling configurations were investigated experimentally. One interesting result of this work was the severe enhancement of the horse shoe vortex by the coolant dependent on the slot’s position and the ejected mass. Based on these results, further promising film cooling configurations with slot ejection were investigated numerically. Setting up the numerical studies was a challenging task since a very detailed model of the slot, the supply cavity, and the supply tubes had to be generated. Tests proved that smallest deviations against the experiment resulted in completely different flow structures. Nevertheless, the secondary flow structure as well as the aerodynamic parameters could be modeled excellently. According to the velocity field in front of a plane turbine cascade, higher wall pressure arises upstream of the leading edge region of the blades while the pressure drops to a minimum in the center of the passage. To avoid excessive ejection of coolant in the low pressure region the reduction of the local slot area is an appropriate method to decrease the slot mass flow in this particular area. An iterative method is introduced considering the desired mass flow rate and the prevailing total pressure in order to calculate the slot area and to avoid reverse flow. The variation of the film cooling effectiveness indicates a very uniform distribution of cooling air behind the slot which persists within the passage.