bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Dietary Carbohydrate, Fat, and Protein on Postprandial Glycemia and Energy Intake in Cats
Authors: Farrow H.A. , Rand J.S. , Morton J.M. , O'Leary C.A. , Sunvold G.D.
Published: July 2013

Background

Reducing carbohydrate intake is recommended in diabetic cats and might also be useful in some healthy cats to decrease diabetes risk.

Objective

To compare postprandial glucose and insulin concentrations and energy intakes between cats fed diets high in protein, fat, or carbohydrate.

Animals

Twenty‐four lean cats with normal glucose tolerance.

Methods

In a prospective randomized study, each of 3 matched groups (n = 8) received a different test diet for 5 weeks. Diets were high in either protein (46% of metabolizable energy [ME]), fat (47%ME), or carbohydrate (47%ME). Glucose and insulin were measured during glucose tolerance,ad libitum, and meal‐feeding tests.

Results

Duringad libitumfeeding, cats fed the high‐carbohydrate diet consumed 25% and 18% more carbohydrate than cats fed diets high in fat and protein, respectively, and energy intake was highest when the high‐fat and high‐protein diets were fed. Regardless of the feeding pattern, cats fed the high‐carbohydrate diet had 10–31% higher peak and mean glucose compared with both other diets; peak glucose in some cats reached 10.4 mmol/L (188 mg/dL) in cats fed 47%MEcarbohydrate and 9.0 mmol/L (162 mg/dL) in cats fed 23%ME.

Conclusions and Clinical Importance

High‐carbohydrate diets increase postprandial glycemia in healthy cats compared with diets high in fat or protein, although energy intake is lower. Avoidance of high‐ and moderate‐carbohydrate diets can be advantageous in cats at risk of diabetes. Maintenance energy requirements should be fed to prevent weight gain when switching to lower carbohydrate diets.
Congressional Oversight Hearings and Policy Control
Authors: McGrath Robert J.
Published: July 2013

Oversight hearings should be an important congressional tool for controlling recalcitrant agencies, but it is not clear that this should always be equally true. The logic of principal‐agent models of legislative policy control implies that oversight might sometimes, but not always, be superfluous to said control. Here, I reintroduce oversight hearings to theories of policy control and argue that congressional committees conduct oversight hearings primarily as a response to the extent to which agencies have different policy preferences from them and as a function of their capacity to conduct hearings cheaply. I test these hypotheses using committee hearings data (PolicyAgendasProject) from both theU.S.House ofRepresentatives and theSenate from 1947 to 2006 and provide support for theoretical arguments about the institutional nature of legislative policymaking strategies and ultimately help clarify the role of oversight in legislative‐executive relations.
26Al‐26Mg isotope systematics of the first solids in the early solar system
Authors: Kita Noriko T. , Yin Qing‐Zhu , MacPherson Glenn J. , Ushikubo Takayuki , Jacobsen Benjamin , Nagashima Kazuhide , Kurahashi Erika , Krot Alexander N. , Jacobsen Stein B.
Published: July 2013

High‐precision bulk aluminum‐magnesium isotope measurements of calcium‐aluminum‐rich inclusions (CAIs) from CV carbonaceous chondrites in several laboratories define a bulk 26Al‐26Mg isochron with an inferred initial 26Al/27Al ratio of approximately 5.25 × 10−5, named the canonical ratio. Nonigneous CV CAIs yield well‐defined internal 26Al‐26Mg isochrons consistent with the canonical value. These observations indicate that the canonical 26Al/27Al ratio records initial Al/Mg fractionation by evaporation and condensation in the CV CAI‐forming region. The internal isochrons of igneous CV CAIs show a range of inferred initial 26Al/27Al ratios, (4.2–5.2) × 10−5, indicating that CAI melting continued for at least 0.2 Ma after formation of their precursors. A similar range of initial 26Al/27Al ratios is also obtained from the internal isochrons of many CAIs (igneous and nonigneous) in other groups of carbonaceous chondrites. Some CAIs and refractory grains (corundum and hibonite) from unmetamorphosed or weakly metamorphosed chondrites, including CVs, are significantly depleted in 26Al. At least some of these refractory objects may have formed prior to injection of 26Al into the protosolar molecular cloud and its subsequent homogenization in the protoplanetary disk. Bulk aluminum and magnesium‐isotope measurements of various types of chondrites plot along the bulk CV CAI isochron, suggesting homogeneous distribution of 26Al and magnesium isotopes in the protoplanetary disk after an epoch of CAI formation. The inferred initial 26Al/27Al ratios of chondrules indicate that most chondrules formed 1–3 Ma after CAIs with the canonical 26Al/27Al ratio.
An igneous fragment from clusterIDPL2011#21: An analog for the source of pyrrhotite and taenite in comet 81P/Wild 2 captured in Stardust aerogel
Authors: Rietmeijer Frans J. M.
Published: July 2013

The silica glass extracted from the bulbous parts of Stardust tracks is riddled by electron‐opaque nanograins with compositions that are mostly between pyrrhotite and metallic iron with many fewer nanograins having a Fe‐Ni‐S composition. Pure taenite nanograins are extremely rare, but exist among the terminal particles. Assuming that these Fe‐Ni‐S compositions are due to mixing of pyrrhotite and taenite melt droplets, it is remarkable that the taenite melt grains had discrete Fe/Ni ratios. This paper presents the data from an igneous pyrrhotite/taenite fragment of clusterIDPL2011#21, wherein the taenite compositions have the same discrete Fe/Ni clusters as those inferred for the Stardust nanograins. These Fe/Ni clusters are a subsolidus feature with compositions that are constrained by the Fe‐Ni phase diagram. They formed during cooling of the parent body of this clusterIDPfragment. These specific Fe/Ni ratios, 12.5, 24, 40, and 53 atom% Ni, were preserved in asteroidal taenite that survived radially outward transport to the Kuiper Belt where it accreted into the (future) comet Wild 2 nucleus.
Small‐molecule inhibitors suppress the expression of both type III secretion and amylovoran biosynthesis genes in Erwinia amylovora
Authors: Yang Fan , Korban Schuyler S. , Pusey P. Lawrence , Elofsson Michael , Sundin George W. , Zhao Youfu
Published: July 2013

The type III secretion system (T3SS) and exopolysaccharide (EPS) amylovoran are two essential pathogenicity factors in Erwinia amylovora, the causal agent of the serious bacterial disease fire blight. In this study, small molecules that inhibit T3SS gene expression in E. amylovora under hrp (hypersensitive response and pathogenicity)‐inducing conditions were identified and characterized using green fluorescent protein (GFP) as a reporter. These compounds belong to salicylidene acylhydrazides and also inhibit amylovoran production. Microarray analysis of E. amylovora treated with compounds 3 and 9 identified a total of 588 significantly differentially expressed genes. Among them, 95 and 78 genes were activated and suppressed by both compounds, respectively, when compared with the dimethylsulphoxide (DMSO) control. The expression of the majority of T3SS genes in E. amylovora, including hrpL and the avrRpt2 effector gene, was suppressed by both compounds. Compound 3 also suppressed the expression of amylovoran precursor and biosynthesis genes. However, both compounds induced significantly the expression of glycogen biosynthesis genes and siderophore biosynthesis, regulatory and transport genes. Furthermore, many membrane, lipoprotein and exported protein‐encoding genes were also activated by both compounds. Similar expression patterns were observed for compounds 1, 2 and 4. Using crab apple flower as a model, compound 3 was capable of reducing disease development in pistils. These results suggest a common inhibition mechanism shared by salicylidene acylhydrazides and indicate that small‐molecule inhibitors that disable T3SS function could be explored to control fire blight disease.
Allelic variation in two distinct Pseudomonas syringae flagellin epitopes modulates the strength of plant immune responses but not bacterial motility
Authors: Clarke Christopher R. , Chinchilla Delphine , Hind Sarah R. , Taguchi Fumiko , Miki Ryuji , Ichinose Yuki , Martin Gregory B. , Leman Scotland , Felix Georg , Vinatzer Boris A.
Published: July 2013

The bacterial flagellin (FliC) epitopes flg22 and flgII‐28 are microbe‐associated molecular patterns (MAMPs). Although flg22 is recognized by many plant species via the pattern recognition receptor FLS2, neither the flgII‐28 receptor nor the extent of flgII‐28 recognition by different plant families is known.

Here, we tested the significance of flgII‐28 as a MAMP and the importance of allelic diversity in flg22 and flgII‐28 in plant–pathogen interactions using purified peptides and a Pseudomonas syringae ∆fliC mutant complemented with different fliC alleles.

The plant genotype and allelic diversity in flg22 and flgII‐28 were found to significantly affect the plant immune response, but not bacterial motility. The recognition of flgII‐28 is restricted to a number of solanaceous species. Although the flgII‐28 peptide does not trigger any immune response in Arabidopsis, mutations in both flg22 and flgII‐28 have FLS2‐dependent effects on virulence. However, the expression of a tomato allele of FLS2 does not confer to Nicotiana benthamiana the ability to detect flgII‐28, and tomato plants silenced for FLS2 are not altered in flgII‐28 recognition.

Therefore, MAMP diversification is an effective pathogen virulence strategy, and flgII‐28 appears to be perceived by an as yet unidentified receptor in the Solanaceae, although it has an FLS2‐dependent virulence effect in Arabidopsis.
Oral mucosal injury in oncology patients: perspectives on maturation of a field
Authors: Peterson DE , Srivastava R , Lalla RV
Published: July 2013

In the past decade, there have been important strategic advances relative to pathobiological modeling as well as clinical management for oral mucositis caused by cancer therapies. Prior to the 1990s, research in this field was conducted by a relatively small number of basic and clinical investigators. Increasing interest among researchers and clinicians over the past twenty years has produced a synergistic outcome characterized by a number of key dynamics, including novel discovery models for pathobiology, increased experience in designing and conducting clinical trials, and creation of international collaborations among cancer care professionals who in turn have modeled clinical care paradigms based on state‐of‐the‐science evidence. This maturation of the science and its clinical translation has positioned investigators and oncology providers to further accelerate both the foundational research and the clinical modeling for patient management in the years ahead. The stage is now set to further capitalize upon optimizing the interactions across this interface, with the goal of strategically enhancing management of patients with cancer at risk for this toxicity while reducing the cost of cancer care.
Stomata actively regulate internal aeration of the sacred lotus Nelumbo nucifera
Authors: MATTHEWS PHILIP G. D. , SEYMOUR ROGER S.
Published: July 2013

The sacred lotus Nelumbo nucifera (Gaertn.) possesses a complex system of gas canals that channel pressurized air from its leaves, down through its petioles and rhizomes, before venting this air back to the atmosphere through large stomata found in the centre of every lotus leaf. These central plate stomata (CPS) lie over a gas canal junction that connects with two‐thirds of the gas canals within the leaf blade and with the larger of two discrete pairs of gas canals within the petiole that join with those in the rhizome. It is hypothesized that the lotus actively regulates the pressure, direction and rate of airflow within its gas canals by opening and closing these stomata. Impression casting the CPS reveal that they are open in the morning, close at midday and reopen in the afternoon. The periodic closure of the CPS during the day coincides with a temporary reversal in airflow direction within the petiolar gas canals. Experiments show that the conductance of the CPS decreases in response to increasing light level. This behaviour ventilates the rhizome and possibly directs benthic CO2 towards photosynthesis in the leaves. These results demonstrate a novel function for stomata: the active regulation of convective airflow.
Atrazine and Methyl Viologen Effects on Chlorophyll‐a Fluorescence Revisited—Implications in Photosystems Emission and Ecotoxicity Assessment
Authors: Iriel Analia , Novo Johanna M. , Cordon Gabriela B. , Lagorio María G.
Published: July 2013

In this work, we use the effect of herbicides that affect the photosynthetic chain at defined sites in the photosynthetic reaction steps to derive information about the fluorescence emission of photosystems. The interpretation of spectral data from treated and control plants, after correction for light reabsorption processes, allowed us to elucidate current controversies in the subject. Results were compatible with the fact that a nonnegligible Photosystem I contribution to chlorophyll fluorescence in plants at room temperature does exist. In another aspect, variable and nonvariable chlorophyll fluorescence were comparatively tested as bioindicators for detection of both herbicides in aquatic environment. Both methodologies were appropriate tools for this purpose. However, they showed better sensitivity for pollutants disconnecting Photosystem II–Photosystem I by blocking the electron transport between them as Atrazine. Specifically, changes in the (experimental and corrected by light reabsorption) red to far red fluorescence ratio, in the maximum photochemical quantum yield and in the quantum efficiency of Photosytem II for increasing concentrations of herbicides have been measured and compared. The most sensitive bioindicator for both herbicides was the quantum efficiency of Photosystem II.
Is dietary taurine supplementation beneficial for farmed fish and shrimp? a comprehensive review
Authors: El‐Sayed Abdel‐Fattah M.
Published: July 2013

Taurine is a neutral β‐amino acid derived from the metabolism of sulphur‐containing amino acids. It is present in high concentrations in animal tissues, especially heart, retina, skeletal muscle, brain, large intestines, plasma, blood cells and leucocytes. Therefore, this amino acid plays significant roles in many physiological functions, including membrane stabilization, antioxidation, detoxification, modulation of immune response, calcium transport, myocardial contractility, retina development, bile acid metabolism, osmotic regulation and endocrine functions. Historically, taurine has not been considered as an essential nutrient for fish. However, recent studies have indicated that taurine synthesis widely differs between fish species and demonstrated that it plays a key role in aquaculture and nutrition of freshwater and marine fish and shrimp. Animal proteins are rich in taurine, whereas plant proteins are taurine‐deficient. Therefore, fish fed plant protein–based food may require exogenous taurine for maintaining their physiological functions. Nevertheless, taurine may be conditionally indispensable for fish and shrimp, depending on dietary protein source, fish species and size, feeding habits, previous histories and the rate of metabolism of its precursors, namely cysteine and methionine. It is my belief that taurine functions in, and benefits for, farmed fish and shrimp are now more than worthy of critical review and analysis. This review summarizes the current knowledge on the roles of taurine in fish, particularly farmed fish and shrimp, with emphasis on taurine structure and biosynthesis, physiological functions, the effects of dietary taurine on fish performance and health and live food enrichment with taurine.
Elective Stock Dividends and REITs: Evidence from the Financial Crisis
Authors: Devos Erik , Spieler Andrew , Tsang Desmond
Published: July 2013

In response to the recent financial crisis, the U.S. Government introduced new rules which allow Real Estate Investment Trusts (REITs) to issue elective stock dividends (ESDs), i.e., noncash dividends, to satisfy their distribution requirements. The purported goal of these rules was to provide temporary relief to REITs facing cash flow problems. We investigate how the introduction of these rules affects dividend policy of REITs. Surprisingly, we document that only 17 REITs chose to issue elective stock dividends. We examine the characteristics of these REITs and find that their cash flows are similar to REITs that do not select these dividends. This suggests that cash flow problems are unlikely to be the primary determinant of the ESD issuance decision. Instead, our findings indicate the decision to pay ESDs is related to the level of loans that are close to maturity, REIT size, growth prospects and poor performance during the financial crisis. Furthermore, we find that the same factors determine the ratio, amount and frequency of stock dividends issued by these REITs. We also examine the response of shareholders to ESDs announcements and find positive abnormal returns surrounding these dividend announcements.
Unobservable Risks in Mortgage Contract Choice
Authors: Liu Bo , Sing Tien Foo
Published: July 2013

This study proposes a lifetime utility maximization model where borrowers choose optimal mortgage bundles including mortgage type, loan‐to‐value and loan size to maximize their allocation of limited budgets between housing and nonhousing consumptions. The model predicts that the mortgage bundle choices by borrowers of different income and risk attributes explain significant variations in the ex post default risks of the borrowers. The empirical tests using sampled mortgages pooled in nonagency residential mortgage backed securities support the hypothesis that the optimal choice of mortgage bundles reveals hidden risk factors of borrowers, which, if ignored, could lead to misjudgment of ex post default of borrowers.
Care providers' experiences of guidelines in daily work at a municipal residential care facility for older people
Authors: Åhlin Johan , Ericson‐Lidman Eva , Norberg Astrid , Strandberg Gunilla
Published: July 2013

Aim

To describe care providers’ narrated experiences of guidelines in daily work at a municipal residential care facility for older people.

Background

Guidelines are used as a way of promoting high‐quality health care. Most research concerning guidelines has focused on physician behaviour and to improve one specific aspect of care. Care providers working within municipal residential care of older people have described that working with multiple guidelines sometimes exposed them to contradictory demands and trouble their conscience.

Design

A qualitative descriptive design was adopted.

Methods

Interviews with eight care providers were carried out between February and March 2012 and analysed by qualitative content analysis.

Results

Care providers described experiences that guidelines are coming from above and are controlling and not sufficiently anchored at their workplace. Furthermore, they described guidelines as stealing time from residents, colliding with each other, lacking practical use and complicating care, and challenging care providers’ judgment. The overall understanding is that care providers describe experiences of struggling to do their best, prioritising between arcane guidelines while keeping the residents’ needs in the foreground.

Conclusion

In order to prevent fragmented use, guidelines have to be coordinated and adapted to the reality of daily practice before implementation. It seems essential to provide opportunities for discussions between care providers, registered nurses and management about how to make guidelines work within their daily practice. Sufficient support, knowledge and involvement are likely key issues that can help care providers to constructively work according to guidelines and thus, by extension, improve the quality of care.
Shifts in the evolutionary rate and intensity of purifying selection between two Brassica genomes revealed by analyses of orthologous transposons and relics of a whole genome triplication
Authors: Zhao Meixia , Du Jianchang , Lin Feng , Tong Chaobo , Yu Jingyin , Huang Shunmou , Wang Xiaowu , Liu Shengyi , Ma Jianxin
Published: July 2013

Recent sequencing of the Brassica rapa and Brassica oleracea genomes revealed extremely contrasting genomic features such as the abundance and distribution of transposable elements between the two genomes. However, whether and how these structural differentiations may have influenced the evolutionary rates of the two genomes since their split from a common ancestor are unknown. Here, we investigated and compared the rates of nucleotide substitution between two long terminal repeats (LTRs) of individual orthologous LTR‐retrotransposons, the rates of synonymous and non‐synonymous substitution among triplicated genes retained in both genomes from a shared whole genome triplication event, and the rates of genetic recombination estimated/deduced by the comparison of physical and genetic distances along chromosomes and ratios of solo LTRs to intact elements. Overall, LTR sequences and genic sequences showed more rapid nucleotide substitution in B. rapa than in B. oleracea. Synonymous substitution of triplicated genes retained from a shared whole genome triplication was detected at higher rates in B. rapa than in B. oleracea. Interestingly, non‐synonymous substitution was observed at lower rates in the former than in the latter, indicating shifted densities of purifying selection between the two genomes. In addition to evolutionary asymmetry, orthologous genes differentially regulated and/or disrupted by transposable elements between the two genomes were also characterized. Our analyses suggest that local genomic and epigenomic features, such as recombination rates and chromatin dynamics reshaped by independent proliferation of transposable elements and elimination between the two genomes, are perhaps partially the causes and partially the outcomes of the observed inter‐specific asymmetric evolution.
Management of infants born with severe neonatal alloimmune thrombocytopenia: the role of platelet transfusions and intravenous immunoglobulin
Authors: Bakchoul Tamam , Bassler Dirk , Heckmann Matthias , Thiele Thomas , Kiefel Volker , Gross Isabel , Arnold Donald M. , DiTomasso Julie , Smith James W. , Paes Bosco , Greinacher Andreas
Published: July 2013

Background

Neonatal alloimmune thrombocytopenia (NAIT) is a fetomaternal incompatibility most commonly induced by maternal anti‐HPA‐1a alloantibodies. Transfusion of immunologically compatible platelets (PLTs) to prevent cerebral hemorrhage, the most severe complication in affected newborns, is usually recommended. Such PLT concentrates, however, are often not readily available.

Study Design and Methods

The efficacy of random‐donor PLT transfusions and intravenous immunoglobulin (IVIG) for the management of 17 neonates across four centers with unexpected, severe NAIT was evaluated. Neonates were treated with random‐donor PLTs alone (n = 7), random‐donor PLTs with IVIG (n = 8), or matched HPA‐1bb PLTs (n = 2).

Results

All but one patient (treated with random PLTs and IVIG) achieved a posttransfusion PLT count of higher than 30 × 109/L after the first PLT transfusion. The PLT count remained higher than 30 × 109/L for longer than 24 hours in five of seven, seven of eight, and two of four newborns who received random‐donor PLTs alone, random‐donor PLTs with IVIG, or matched HPA‐1bb PLTs, respectively. None of the newborns developed major bleeding or intracranial hemorrhage. IVIG did not appear to improve either posttransfusion PLT counts or total PLT transfusion requirements.

Conclusion

Transfusion of random‐donor PLTs alone was effective at correcting critically low PLT counts and should be considered as first‐line treatment of newborns with unexpected severe NAIT.
Balancing potential risks and benefits of hemoglobin‐based oxygen carriers
Authors: Weiskopf Richard B. , Silverman Toby A.
Published: July 2013

Hemoglobin‐based oxygen carriers (HBOCs) are thought to have an adverse risk:benefit profile when compared to that of transfusing stored red blood cells (RBCs). However, there are clinical circumstances when RBC transfusion is not an option (e.g., patient refusal, unavailability owing to issues of compatibility or remote location). For these circumstances assessment of the risks of an HBOC should be compared to the risks of untransfused acute anemia. In this article we compare the risk of allowing a patient with severe anemia to have a further small decrease in hemoglobin (Hb) concentration to the risk of infusing an HBOC. We conclude that at Hb concentrations less than 6 g/dL, the risk of a further decrease in Hb concentration greatly exceeds the risk of HBOC infusion. Thus, we suggest that there may be a place for use of HBOCs when RBC transfusion is not an option.
Study of the behaviour of lesional and nonlesional skin of canine recurrent flank alopecia transplanted to athymic nude mice
Authors: Vandenabeele Sophie I. , DeCock Hilde , Van Ham Luc , Meyer Evelyne , Daminet Sylvie
Published: July 2013

Background

Recurrent flank alopecia is a clinically well‐described skin disorder in dogs. The pathomechanism of the disease is difficult to study because it undergoes spontaneous regression.

Hypothesis/Objectives

To study the behaviour of xenografts in mice in order to assess the feasibility of a reproducible experimental model and to investigate local or systemic causes of canine recurrent flank alopecia (cRFA).

Methods

Skin biopsies were taken from lesional and nonlesional skin of two client‐owned dogs with cRFA and grafted onto five athymic mice from a research facility. The lesional skin and xenografted skin were evaluated histologically on day 0 and day 30, respectively.

Results

Transplanted lesional and nonlesional canine skin regrew hair within 30 days, while the donor dogs were still alopecic in the lesional areas on day 30 after the skin biopsy procedure. Graft rejection was evidenced histologically in two xenografted athymic mice. Lesional hyperpigmentation disappeared in the athymic mice.

Conclusions and clinical importance

This study showed that hair follicles from dogs with cRFA quickly regenerated and regrew hair once grafted onto the mice. Our data indicate that the pathogenesis of cRFA is likely to be mediated by systemic rather than local factors. While this xenograft approach might not be of much value for the study of cRFA, it has potential value for the study of other causes of canine alopecia due to systemic factors.
Survey of Systems for Comparative Ranking of Agents that Pose a Bioterroristic Threat
Authors: Menrath A. , Tomuzia K. , Frentzel H. , Braeunig J. , Appel B.
Published: July 2013

Strong efforts are made to improve preparedness for the prevention and counteraction of possible deliberate release of highly pathogenic biological agents at national and international level. An objective risk assessment for highly pathogenic biological agents is urgently needed for the purpose of prioritizing measures, evaluating the vulnerabilities and supporting rapid decisions on a scientific base in case of an emergency. Hitherto, several differing ranking schemes were developed. In general, the purpose of such ranking schemes is a comparative classification of agents under consideration of different transmission paths as well as agents threatening human and/or animal health. The analysed prioritization methods differ from qualitative to (semi‐)quantitative with each its benefits and disadvantages in preciseness of the result, complexity and duration of the assessment but also in comprehensibility. Mainly, risk was defined as the product of probability and impact. In this survey, factors frequently used for the assessment of the probability and impact of a deliberate agent release were identified. Main criteria for the probability of an application were the history of use, the accessibility of the agent and possible paths of introduction and contamination as well as the feasibility of agent production. For the estimation of the impact, mainly the agent's effects on human and/or veterinary public health, depending on the target population, were examined. This includes the morbidity and mortality rates as well as the severity of induced illness, possible measures for diagnosis, and treatment and prevention. Furthermore, the economic and socioeconomic consequences were considered. In this review, the authors give an overview on open‐source publications dealing with risk ranking of biological agents by outlining the criteria that were applied for risk ranking.
Design and Optimization of Composite Rectangular Fins Using the Relative Inverse Thermal Admittance
Authors: Luna–Abad Juan P. , Alhama Francisco
Published: July 2013

The concept of relative inverse admittance applied to composite fins optimization in the case of longitudinal rectangular fins under 2D heat conduction is presented in this work. Here, different values for convective conditions at the fin and composite layer surfaces are used and the influence of the kc/kf ratio and composite thickness in optimum geometry is determined. The optimization process is carried out through universal graphs in which the range of parameters covers most of the practical cases a designer will find. Relative inverse admittance is applied in a general form and emerges as an easily used tool for optimizing composite fins.
Behavior of Thermally Radiating Tree-like Fins
Authors: Calamas David , Baker John
Published: July 2013

The performance of tree-like fins with varying bifurcation angle, surface emissivity, material, width-to-thickness ratio, and base heat rate was examined. Overall system performance was examined computationally. The computational results have been validated, verified, and cast in terms of commonly defined dimensionless parameters. Tree-like fins were found to be more effective and more efficient than the rectangular fins. Fin efficiency and effectiveness were found to increase with increasing bifurcation angles while base temperatures were found to decrease with increasing bifurcation angles. As expected, base temperatures were highest for the largest width-to-thickness ratios and smallest for materials with relatively higher thermal conductivities.
Efficient Active Vibration Control of Smart Structures With Modified Positive Position Feedback Control Using Pattern Search Methods in the Presence of Instrumentation Phase Lead and Lag
Authors: Kumar Rajiv
Published: July 2013

For active vibration control applications, positive position feedback (PPF) type controller is quite suitable. These controllers are of low order so are easy to implement in practice. These controllers avoid the problem of control spillover also. However, a systematic design methodology is not available for the design of these controllers. For multimode vibration control applications, in the presence of instrumentation, controller design becomes even more difficult. In the present paper, a systematic design procedure has been suggested to design the PPF controller. The proposed controller is designed by minimizing the H2 or H∞ norm of the closed loop (CL) system. The direct search methods based on pattern search technique has been used. The controller designed in this way can provide uniform damping to all the modes. The problems caused by the instrumentation (i.e., phase lead and lag) and time delay actually present in the control loop can be completely eliminated. Since, the controller is designed by minimizing the H∞ norm of the closed loop system, it is robust in nature. With the proposed methodology, the use of other complicated frequency domain techniques to design the controller can be avoided.
Computational Modeling of Dynamic Response of a Latent Thermal Energy Storage System With Embedded Heat Pipes
Authors: Nithyanandam K. , Pitchumani R.
Published: July 2013

Concentrating solar power plants (CSPs) are being explored as the leading source of renewable energy for future power generation. Storing sun's energy in the form of latent thermal energy of a phase change material (PCM) is desirable for use on demand including times when solar energy is unavailable. Considering a latent thermal energy storage (LTES) system incorporating heat pipes to enhance heat transfer between the heat transfer fluid (HTF) and the PCM, this paper explores the dynamic response of the LTES system subjected to repeated cycles of charging and discharging. A transient computational analysis of a shell-and-tube LTES embedded with two horizontal heat pipes is performed for repeated charging and discharging of the PCM to analyze the dynamic performance of the LTES, and the augmentation in the cyclic performance of the LTES embedded with heat pipes is investigated. A model low temperature phase change material system is considered in the present study, with the physical results being scalable to high temperature systems used in CSP plants.
Performance Uncertainty Quantification for Centrifugal Compressors: Part 1—Stage Performance Variation
Authors: Panizza Andrea , Iurisci Giuseppe , Sassanelli Giuseppe , Sivasubramaniyan Sankaran
Published: July 2013

In modern industrial practice, the quality of a new product is achieved by identifying characteristics critical to quality (CTQs) and minimizing deviation from targets, rather than merely optimizing CTQs in the absence of variation. Estimating the variation of CTQs is thus critical to understand and correctly manage risk caused by different interacting sources of uncertainty.

We have developed a method to estimate performance variability for centrifugal compressor stages. In this paper, we quantify the performance variation due to impeller manufacturing variability of two stage families. The stages studied are 2D stages designed for multi-purpose applications and 2D stages for high head applications. In a related paper, the stage performance variability here determined is considered together with other sources of variation to compute the variation in flange-to-flange performance for a full compressor.

The proposed approach propagates the uncertainty of the design parameters to the stage aerodynamic performance through a Monte Carlo method. In order to keep a low computational budget, calibrated 1D/2D aerodynamic models have been run in parallel to compute the performance of the stages with randomly modified geometry. The results allow the quantification of the stage performance variability and the identification of the main sources of variation.

As a step towards the corresponding analysis for a complete centrifugal compressor, results from this study have been used as input for a method where all factors affecting the flange-to-flange performance are considered. The method and the results are discussed in a companion paper.
A Spectral Study of a Moderately Loaded LPT Airfoil: Part 1—Identifying Frequencies Affecting By-Pass Transition
Authors: Graveline J. R. S. , Sjolander S. A.
Published: July 2013

A single wire, hot-wire, probe is used to examine the airflow in, and in close vicinity to, the shearlayer of a Low-Pressure Turbine (LPT) airfoil. A spectral analysis of the data identifies two sets of wide peaks of turbulent kinetic energy, one near 200 Hz and a second near 1 kHz. A method is developed to identify these peaks based on a combination of empirical relations between the airflow velocity and boundary layer thickness and on the location of the frequency peaks relative to the state of the free shearlayer as it transitioned from laminar to turbulent. The method suggests the presence of Tollmien-Schlichting waves and Kelvin-Helmholtz instabilities. The Kelvin-Helmholtz instabilities are shown to pair.
Further Validation of the Non Linear Harmonic Method in a Subsonic Counter-Rotating Compressor
Authors: Wang Lei , Liu Bo , Yang Xiaodong , Cao Zhiyuan
Published: July 2013

Understanding unsteady flow phenomena in axial compressor often requires the use of time-accurate CFD simulations. In the present paper, the nonlinear harmonic method implemented in Fine/Turbo code has been used to examine and analyze the boundary layer transition and unsteady rotor-rotor interaction of the NWPU subsonic counter-rotating compressor. To validate the NLH simulation results, the predicted characteristics and spanwise distributions of aerodynamic parameters were compared with the measured data and rigorous full-annulus unsteady simulations at typical working conditions and a good agreement was achieved. Then, its ability to correctly capture rotor-rotor interactions is investigated in detail to advance the understanding of the flow physics involved. Based on the NLH method deterministic stresses have been post-processed to compare to the full-annulus simulation to analyze distinct sources of unsteadiness and their effect on the time-averaged flow field. The results show the good behavior of the NLH method and its ability to correctly predict global quantities as well as local flow physic. Closed spacing between rotors increasing the strength of potential perturbations and complexity of rotor-rotor interaction. The NLH method presents high precision on modeling deterministic stresses.
Experimental Investigation on the Stall Inception of a Counter-Rotating Compressor
Authors: Wang Zhuoqi , Yuan Wei , Li Qiushi , Lu Yajun
Published: July 2013

For investigating the flow phenomena in the stall process of a counter-rotating compressor (CRC), static and dynamic experiment have been carried out on a low speed counter-rotating compressor. Seven high response pressure sensors were mounted at the leading edge of rotor 1(R1) and rotor 2(R2) as well as at the outlet of R2 blade tip and root. Wavelet analysis and FFT transform was introduced to the post processing progress. According to the experimental results, the stall inception was found in the tip region of the second rotor. The rotating speed of stall cell in the compressor is about 35% of the rotor speed.
Cavity Flow Modeling in an Industrial Centrifugal Compressor Stage at Design and Off-Design Conditions
Authors: Guidotti Emanuele , Naldi Giovanni , Tapinassi Libero , Chockalingam Valliappan
Published: July 2013

Numerical tools and test equipments used in the design and validation of modern centrifugal compressor stages need to be at the state-of-the-art. In particular, a big effort is currently made to correctly model secondary flows that play a relevant role in the accuracy of the performance prediction.

This paper presents the flow analysis of a high efficiency centrifugal compressor stage using high accurate computational fluid dynamics with a particular attention to the cavity flows modeling. Experimental data were also available and used to validate the numerical results. The key experimental data coming from an advanced FRAPP (Fast Response Aerodynamic Pressure Probe) and traditional probes are presented in the study as overall performance and flow features details. Test data are in fact necessary to validate and continuously improve the numerical techniques.

The geometry of the stage including full modeling of the secondary flows cavities were faithfully reproduced in the computational model. The availability of new in-house automated tools for cavity meshing allow compressor aero-designers to accurately resolve leakage flows with a reasonable increase in computational and user time.

The results of the computational model were in excellent agreement with the experimental data both in terms of overall performance and main flow field structures. Also details of the flow features inside the cavities matched the test data very well. Only using high accurate geometry modeling including leakage flows was possible to capture important flow features that instead were not correctly simulated with simplified computational models.
Multidisciplinary Optimization of a Turbocharger Radial Turbine
Authors: Mueller Lasse , Alsalihi Zuheyr , Verstraete Tom
Published: July 2013

This paper presents a multidisciplinary design optimization of a turbocharger radial turbine for automotive applications with the aim to improve two major manufacturer requirements: the total-to-static efficiency and the moment of inertia of the radial turbine impeller. The search for the best design is constrained by mechanical stress limitations, by the mass flow and power, and by aerodynamic constraints related to the isentropic Mach number distribution on the rotor blade.

The optimization of the radial turbine is performed with a two-level optimization algorithm developed at the von Karman Institute for Fluid Dynamics (VKI). The system makes use of a Differential Evolution algorithm, an Artificial Neural Network (ANN), and a database as a compromise between accuracy and computational cost. The ANN performance predictions are periodically validated by means of accurate steady state 3D Navier-Stokes and centrifugal stress computations.

The results show that it is possible to improve the efficiency and the moment of inertia only in a few numbers of iterations while limiting the stresses to a maximum value. Based on the large number of evaluated designs during the optimization, this paper provides design recommendations of a turbocharger radial turbine at least for a good preliminary design.
The Effect of Two Different Endwall-Penny Concepts for Variable Stator Vanes in a Compressor Cascade
Authors: Gottschall Marcel , Vogeler Konrad , Mailach Ronald
Published: July 2013

The article describes investigations on the influence of two possible endwall-penny concepts for variable stator vanes to secondary flow field development and the performance of high pressure compressors. Concept I uses a penny covering the whole vane chord with no radial clearances, whilst the concept II applies a piecewise flattened polygonal hub or casing to achieve constant radial gaps. Both approaches were converted to a linear cascade of modern stator profiles. Measurements were conducted with a 5-hole-probe in planes up- and downstream the cascade as well as with pressure tappings on the airfoil and the endwall. Additional 3D numerical calculations were carried out to gain information about the flow field inside the cascade. These analyses were performed at three stagger angles and two characteristic Reynolds numbers with a constant cascade turning to model the adjusting range of aircraft engines.

Compared to a reference case without endwall contour and no clearance the results indicate slightly increased efficiency due to smaller total pressure losses for both concepts. The penny edges as well as the polygonal endwall at the cascade inlet are responsible for a higher turbulence in the inlet boundary layer, which results in a smaller endwall separation that is detected with outlet loss distributions. Considering the cascade loading in terms of flow turning, a small overall benefit was achieved with both configurations caused by much higher overturning near the wall. These tendencies increase with the stagger angle at part-load conditions of the compressor. Furthermore, the results were compared with a part gap configuration of a variable vane with benefits concerning pressure losses and flow turning. For lower cascade loadings the concept I still reaches the highest overall flow turning. This benefit compared to the part gap configuration nearly disappears at the high stagger angle. Additionally, both concepts feature a much higher flow angle deviation along the blade height and significant increased losses.
Effect of Endwall Contouring on a Transonic Turbine Blade Passage: Part 1—Aerodynamic Performance
Authors: Abraham Santosh , Panchal Kapil , Ekkad Srinath V. , Ng Wing , Lohaus Andrew S. , Malandra Anthony
Published: July 2013

The paper presents a detailed experimental and numerical study on the effect of endwall contouring in a quasi 2D cascade, operating at transonic conditions. Aerodynamic performance of two contoured endwalls are studied and compared with a baseline (planar) endwall. The first contoured endwall was generated with the goal of reducing secondary losses (Aero-Optimized contoured endwall) and the second endwall was generated with the objective of reduced overall heat transfer to the endwall (HT-optimized contoured endwall). Midspan total pressure loss, secondary flow field and static pressure measurements on the airfoil surface were measured. The cascade exit Mach numbers range from 0.71 to 0.95 and the turning angle of the airfoil is ∼127°. The inlet span of the airfoils was reduced with respect to the outlet span with the intention of obtaining a realistic inlet/exit Mach number that is observed in a real engine. 3D viscous compressible CFD analysis was carried out to study the detailed behavior of the complex flow structures that develop as a result of endwall contouring. A 3% reduction in area averaged losses was achieved at 0.1 Cax downstream of the trailing edge and a 17% reduction in mixed out losses was achieved at 1.0 Cax downstream location with the Aero-Optimized contoured endwall.
An Experimental Investigation About the Effect of the Partial Casing Treatment on a Transonic Axial-Flow Compressor Performance Under Inlet Distortion
Authors: Li Maoyi , Yuan Wei , Song Xizhen , Lu Yajun , Li Zhiping , Li Shaobin
Published: July 2013

The traditional annulus casing treatment often pays the price of lowered efficiency for improving the stall margin of a compressor under inlet distortion. In view of the unsymmetry of the inlet flow-field of compressors, partial casing treatment was used to control the flow in a transonic axial-flow compressor with arc-skewed-slots deployed at different circumferential positions under inlet distortion. The experimental results indicate that when the partial casing treatment is arranged on the undistorted and distorted sectors, the stall margin is enhanced by 8.02%, with the relative peak efficiency improved simultaneously by 2.143%, compared with the case of solid casing at 98% rotating speed. By contrast, the traditional casing treatment increases the stall-margin by 23.13%, but decreases the relative peak efficiency by 0.752%. By analyzing dynamic and static experimental data, the mechanism underlying the partial casing treatment was also studied in detail here. The disturbances of inlet flow were restrained by annulus casing treatment, nevertheless the total pressure ratio was decreased obviously in the distorted sector. As a result, the stall-margin is improved, but the relative peak efficiency is decreased too. When the partial casing treatment was arranged on the undistortded and distorted sectors, the stall disturbances was thereby restrained. So the stall margin was enhanced. In addition, the total pressure ratio was improved by the partial casing treatment in the distorted and transition sectors, and thus the relative peak efficiency was also increased markedly.