bluuebunny/crossref_metadata_2025 huggingface dataset:
Conditional Distributions of Mandelbrot–van ness Fractional LÉVY Processes and Continuous‐Time ARMA–GARCH‐Type Models with Long Memory
Authors: Fink Holger
Published: April 2015

Long‐memory effects can be found in many data sets from finance to hydrology. Therefore, models that can reflect these properties have become more popular in recent years. Mandelbrot–Van Ness fractional Lévy processes allow for such stationary long‐memory effects in their increments and have been used in different settings ranging from fractionally integrated continuous‐time ARMA–GARCH‐type setups to general stochastic differential equations. However, their conditional distributions have not yet been considered in detail. In this article, we provide a closed formula for their conditional characteristic functions and suggest several applications to continuous‐time ARMA–GARCH‐type models with long memory.
Consequences of maternal effects on offspring size, growth and survival in the desert tortoise
Authors: Nafus M. G. , Todd B. D. , Buhlmann K. A. , Tuberville T. D.
Published: April 2015

Maternal body size can have notable consequences on reproductive success. For example, fecundity often increases with body size. Less is known, however, about the relationship between maternal size and factors affecting offspring fitness, including size, growth and survival. Here, we examined the relationship between hatchling and maternal body size in the Mojave Desert tortoise Gopherus agassizii. We further examined the relationships between survival and growth after 1 year and size at hatching. We found that larger females tended to produce larger offspring; post‐hatching growth and survival also correlated positively with size at hatching. Our results suggest that, in desert tortoises, maternal body size may indirectly influence offspring fitness via growth and survival for at least the first year of life. Such an advantage early in life may confer long‐term benefits for individuals, especially in species thought to have high juvenile mortality or that inhabit highly variable environments.
A Feminist Analysis of Shadow Powers, the State, and Citizen Responses: The Case of Contemporary Mexico
Authors: Carlsen Laura E.
Published: April 2015

Throughout Latin America, the nature and location of power have shifted rapidly, in large part due to the emergence of new “shadow powers.” These power groups act beyond institutional and legal frameworks and yet also interact with them. They operate clandestinely and yet openly control and rule in large swaths of national territory. Our capacity to adequately define them and their realms of activity is limited, and yet their effects on daily life can be huge. The model of the state fighting to eliminate the challenge posed by these powers is inadequate, as we see increasing alliances between elements of the state and shadow powers. Applying a feminist analysis of power, this article explores these contradictions in the case of Mexico, where a volatile mix of organized crime, government corruption, and legal and illegal economic interests have changed the map of power and led to conflicts. It focuses on the new dynamics of power and citizen responses to resist the imposition of illegitimate power and eliminate all forms of violence, with an emphasis on violence against women, which rises considerably in the context of shadow powers.
Cross‐Border Paradiplomacy in Latin America
Authors: Oddone Nahuel , Rodríguez Vázquez Horacio
Published: April 2015

This article contributes to the analysis of the current situation of cross‐border cooperation in Latin America. It explores an approach based on four components: (1) the development of an infrastructure project, (2) a high‐level political agreement, (3) the institutionalization of a framework to regulate the relationship between local authorities, and (4) other institutional arrangements focused on the participation of civil society in border areas. It also investigates the contribution of paradiplomacy to strengthening the endogenous capacity of border authorities.
Latin America in the G20: Insiders or Outsiders?
Authors: Luckhurst Jonathan
Published: April 2015

This article analyzes endogenous and exogenous constructions of the political identities of Latin American members of the G20, namely Argentina, Brazil, and Mexico. It examines effects of G20 membership and other aspects of international relations, with a constructivist analysis of their political identities as “insiders” or “outsiders” in multilateral economic governance. G20 scholars note the forum's heterogeneity of coalitions on diverse issues, so policy divergence between the three governments is to be expected. This study focuses on the social construction of their identities in the G20, partly as a consequence of in‐group perspectives and effects of the forum as what I call a “partial normative community.” It analyzes official government statements; the consequences of international alliances, or lack thereof; policy objectives and agenda‐setting activities, including Mexico's G20 Presidency in 2012; and overall participation of the three governments in multilateral cooperation since the 2008 financial crisis. I analyze similarities and differences between them, demonstrating the strategic consequences of political identity constructions in the G20.
Market Restructuring in Electricity inMexico: Lessons from International Deregulation
Authors: Ibarra‐Yunez Alejandro
Published: April 2015

This article analyzes asymmetries in market design between regional electricity markets inMexico and infrastructure management in the United States, specifically ofERCOTinTexas andWECC/CAISOinCalifornia. It focuses on market spaces for suppliers of utilities and nonutilities on both sides of the border in the midst of Mexico's 2013–2014 regulatory reform. Many power producers are critical players in modern unbundled electricity markets. They could use their market muscle to restrain supply or face regulatory risk that reduces market commitment if the recently enacted laws show loopholes and gray areas. Meanwhile, the transmission and distribution segment could underinvest to create congestion and high prices artificially. The article studies the nature of unbundled versus integrated systems and typifies the multiple players in the increasingly restructured market. It compares main stakeholder positions in theUnitedStates,Europe,Canada, andMexico, and also compares the market position of players in unbundled markets—such as retailers, distribution, ancillary service providers, schedulers, and qualifying facilities—that create a complex market but offer many strategic opportunities. Lessons learned from restructured markets can be useful in creating a framework to evaluate the 2013–2014 energy reform proposed in Mexico under thePeñaNieto administration.
Exploring Motivational Profiles Through Language Learning Narratives
Authors: Thompson Amy S. , Vásquez Camilla
Published: April 2015

This study analyzes the language learning narratives of 3 NNS foreign language teachers. It uses as a theoretical framework the L2 Motivational Self System (L2MSS) (Dörnyei, 2009) but adds the dimension of psychological reactance (Brehm, 1966). Our findings indicate that the L2MSS underestimates the relationship between ‘I' and ‘other,' a distinction that is paramount in Self‐Discrepancy Theory (Higgins, 1987). Specifically, the ‘I' dimension is strongly articulated in the ideal L2 self, whereas the ‘other' dimension is not. The inverse is true for the ought‐to L2 self in which the ‘other' dimension is emphasized. These omissions underemphasize the importance of the interaction between the self and the context in forming language learning motivation. In addition, the findings indicate that the L2MSS framework needs further development in order to account for learners in a variety of settings, as opposed to primarily an English as a Foreign Language (EFL) environment. Consistent with recent claims about the types of contributions that language learning biographies/narratives can make to SLA research (Pavlenko, 2007), this study offers additional insights into how individual differences interact with contextual variables in language learning.
The Efficacy of Written Corrective Feedback in Improving L2 Written Accuracy: A Meta‐Analysis
Authors: Kang EunYoung , Han Zhaohong
Published: April 2015

Written corrective feedback has been subject to increasing attention in recent years, in part because of the conceptual controversy surrounding it and in part because of its ubiquitous practice. This study takes a meta‐analytic approach to synthesizing extant empirical research, including 21 primary studies. Guiding the analysis are two questions: Does written corrective feedback help to improve the grammatical accuracy of second language writing? What factors might mitigate its efficacy? Results show that written corrective feedback can lead to greater grammatical accuracy in second language writing, yet its efficacy is mediated by a host of variables, including learners' proficiency, the setting, and the genre of the writing task.
The Role of Individual Differences in the Study Abroad Context: Cognitive Capacity and Language Development During Short‐Term Intensive Language Exposure
Authors: Grey Sarah , Cox Jessica G. , Serafini Ellen J. , Sanz Cristina
Published: April 2015

While research suggests that study abroad (SA) benefits second language (L2) oral fluency, its benefits for other domains are less clear, especially for shorterterm programs, which are becoming more common. Additionally, studies investigating the relationship between cognitive capacity and benefits of SA report inconsistent patterns. In light of these gaps, this study investigated whether a 5‐week intensive language experience abroad benefits L2 lexical and grammatical development and whether development is related to learners' cognitive capacity. Twenty‐six L1 English–advanced L2 Spanish participants in a SA program in Spain completed pre‐/post‐SA grammaticality judgment (GJT) and lexical decision tasks (LDT). On the GJT, results showed higher accuracy and decreasing reaction times (RTs); specifically, accuracy increased on word order and number agreement items but not on gender agreement. RTs did not decrease for any of the three targets individually. For the LDT, performance on nonwords, but not words, showed improvement while RTs for both words and nonwords decreased. Overall, these gains following short‐term experience abroad were independent of variation in cognitive capacity. This study makes a unique contribution toward understanding the roles of L2 proficiency, context, and individual differences in morphosyntactic and lexical development.
Paraneoplastic neuromyelitis optica spectrum disorder manifesting as intractable nausea and acute cerebellar ataxia associated with lung adenocarcinoma
Authors: Kobata Masako , Okada Kazumasa , Hashimoto Tomoyo , Matsuyama Atsuji , Uchibori Ayumi , Takahashi Toshiyuki , Adachi Hiroaki
Published: April 2015

We report a 65‐year‐old woman with neuromyelitis optica spectrum disorder manifesting acute cerebellar ataxia, and intractable nausea and vomiting. She tested positive for anti‐aquaporin 4 antibodies and had a lung adenocarcinoma simultaneously. She underwent partial pulmonary resection, and tumor cells of the lung adenocarcinoma were stained with an anti‐aquaporin 4 antibody. By administering intravenous methyl prednisolone and plasma exchange, aquaporin 4 antibody titer was reduced, and neurological deficits and the lesion status on magnetic resonance imaging markedly improved. Paraneoplastic neuromyelitis optica spectrum disorder in conjunction with lung adenocarcinoma was a reasonable diagnosis.
Rethinking agency and medical adherence technology: applying Actor Network Theory to the case study of Digital Pills
Authors: Hurtado‐de‐Mendoza Alejandra , Cabling Mark L , Sheppard Vanessa B
Published: April 2015

Much literature surrounding medical technology and adherence posits that technology is a mechanism for social control. This assumes that the medical establishment can take away patients' agency. Although power relationships and social control can play a key role, medical technology can also serve as an agentive tool to be utilized. We (1) offer the alternative framework of Actor Network Theory to view medical technology, (2) discuss the literature on medication adherence and technology, (3) delve into the ramifications of looking at adherence as a network and (4) use Digital Pills as a case study of dispersed agency.
Measurement of peak esophageal luminal cross‐sectional area utilizing nadir intraluminal impedance
Authors: Zifan A. , Ledgerwood‐Lee M. , Mittal R. K.
Published: April 2015

Background

Multichannel intraluminal impedance (MII) is currently used to monitor gastroesophageal reflux and esophageal bolus clearance. We describe a novel methodology to measure maximal luminal cross‐sectional area (CSA) during bolus transport from MII measurements.

Methods

Studies were conducted in‐vitro (test tubes) and in‐vivo (healthy subjects). Concurrent MII, high resolution manometry, and intraluminal ultrasound (US) images were recorded 7‐cm above the lower esophageal sphincter. Swallows with two concentrations of saline, 0.1 and 0.5 N, of bolus volumes 5, 10, and 15 cc were performed. The CSA was estimated by solving two algebraic Ohm's law equations, resulting from the two saline solutions. The CSA calculated from impedance method was compared with the CSA measured from the intraluminal US images.

Key Results

The CSA measured in duplicate from B‐mode US images showed a mean difference between the two manual delineations to be near zero, and the repeatability coefficient was within 7.7% of the mean of the two CSA measurements. The calculated CSA from the impedance measurements strongly correlated with the US measured CSA (R2 ≅ 0.98). A detailed statistical analysis of the impedance and US measured CSA data indicated that the 95% limits of agreement between the two methods ranged from −9.1 to 13 mm2. The root mean square error of the two measurements was 4.8% of the mean US‐measured CSA.

Conclusions & Inferences

We describe a novel methodology to measure peak esophageal luminal CSA from the nadir impedance during peristalsis. Further studies are needed to determine if it is possible to measure patterns of luminal distension during peristalsis across the entire length of the esophagus from the MII recordings.
REGULATION AS SOCIAL POLICY: HOME EVICTIONS AND REPOSSESSIONS IN THE UK AND SWEDEN
Authors: HABER HANAN
Published: April 2015

This article asks how the UK and Sweden regulate, prevent, or mitigate the consequences of mortgage‐related household eviction and repossession. Contrary to initial expectations, the findings show a growth and diversity in both regulation and social spending in the UK intended to address this social issue; something that has not occurred in Sweden. In the UK's liberal ‘regulatory welfare regime’, the aim is to prevent the eviction and repossession of vulnerable borrowers who have defaulted on their housing loan. In the Swedish social democratic ‘regulatory welfare regime’, effort focuses instead on minimizing the risk of default before it occurs rather than after the fact. These findings offer a more nuanced understanding of the relations between regulation and welfare more generally, demonstrating that regulation may be used as a form of social policy once the welfare state has failed, as a safety net of last resort.
Fatal rituximab‐associated lung injury syndrome in a patient treated with rituximab for recurrence of post‐transplant nephrotic syndrome
Authors: Grenda Ryszard , Jarmużek Wioletta , Rubik Jacek , Migdał Marek , Pronicki Maciej
Published: April 2015

Rituximab (anti‐B CD20 ab.) in recently widely used in renal transplantation. Case history: A 10‐yr‐old patient with end‐stage renal failure due to multidrug‐resistant NS was transplanted with renal graft from deceased donor and presented immediate recurrence of NS. PF was started on day 3 and patient received MP pulses, however with no effect. Rituximab (4 × 375 mg/m2) was administered. Chest radiographs taken at that time were normal. Partial remission was achieved and the patient was discharged in good condition. Sequential recurrence appeared two wk afterward. Twelve sessions of PF were performed and six pulses of MP were given, effecting a partial remission. Three months after the last dose of rituximab, patient was admitted with increasing respiratory failure, requiring mechanical ventilation. Infectious background, including CMV, BKV, mycoplasma, and pneumocystis, was not confirmed. The patient was treated with MP pulses, IVIG, and a variety of antibiotics. Ground‐glass opacity was confirmed on lung CT images. Respiratory failure worsened, despite aggressive ventilation and patient passed away after three wk at ICU. A destruction of alveolar epithelium and extended pulmonary fibrosis was confirmed in the autopsy report. The case represents a fatal RALI.
Apple scab: numerical optimization of a new thermal time scale and application for modelling ascospore release in southern France
Authors: Roubal C. , Nicot P. C.
Published: April 2015

Adequate protection of apple trees during the primary contamination period is a cornerstone for management of apple scab. Correct timing of spring treatments is fundamental and thus, much effort has been devoted to forecasting ascospore release by Venturia inaequalis. Most models rely on degree‐day accumulation starting from a biofix date established yearly on the basis of biological observations. Here, the potential of using a single calendar date as a biofix and new types of time scales were explored, with the help of numerical optimization with field‐collected data. Using data acquired between 1996 and 2008, the daily rate of development for V. inaequalis primary inoculum was assessed by fitting generic time scale functions, a method that requires the smallest number of assumptions about the effect of temperature on the biological phenomenon. An optimal calendar biofix was established for Provence and use of non‐linear functions relating pseudothecial development rate to temperature for accumulating thermal time was compared with the usual linear response in standard degree‐day models. A model was then constructed using four additional years of data for validation. The predictive value of the model was further improved by adjusting the time scale with ‘accelerating rules’ to take into account the positive influence of rainy days on pseudothecial maturation prior to ascospore release. However, ‘halting rules’ inserted in the time scale to account for dry days during the ascospore release period strongly reduced the predictive value of the model for southern France, suggesting the possible occurrence of strains adapted to dry conditions.
Characteristics of IL‐25 and allergen‐induced airway fibrosis in a murine model of asthma
Authors: Yao Xiujuan , Wang Wei , Li Yan , Lv Zhe , Guo Run , Corrigan Chris J , Ding Gang , Huang Kewu , Sun Yongchang , Ying Sun
Published: April 2015

Background and objective

Interleukin (IL)‐25 has been implicated in the pathogenesis of human asthma by inducing a Th2 cytokine response, but its possible role in the development of airway remodelling is less clear.

Methods

We developed a murine surrogate of chronic airway inflammation induced by intranasal application of IL‐25 alone. Comparison was with the ‘classical’ surrogate of ovalbumin (OVA) intranasal instillation into previously sensitized animals. Airway fibrotic biomarkers were analysed by immunohistochemistry and enzyme‐linked immunosorbent assay. Additionally, proliferation assay and real‐time polymerase chain reaction analysis were performed to assess IL‐25's effects on primary human bronchial fibroblasts in vitro.

Results

In Balb/c mice, intranasal instillation of IL‐25 alone induced florid airway fibrosis, including increased lay down of extracellular matrix proteins such as collagen I, III, V and fibronectin, increased numbers of fibroblasts/myofibroblasts, a profibrotic imbalance in matrix metalloproteinase/tissue inhibitor of metalloproteinase production and increased expression of profibrotic mediators including connective tissue growth factor and transforming growth factor‐β1. These changes broadly reproduced those seen with classical intranasal OVA challenge in OVA‐sensitized animals. Furthermore, IL‐25 induced proliferation and expression of collagen I and III and smooth muscle α‐actin in primary human lung fibroblasts.

Conclusions

We conclude that chronic exposure of the airways to IL‐25 alone is sufficient to cause functionally relevant airway remodelling, with the corollary that targeting of IL‐25 may attenuate bronchial remodelling and fibrosis in human asthmatics.
First‐Hand Experience and Second‐Hand Information: Changing Trust across Three Levels of Government
Authors: Reinhardt Gina Yannitell
Published: April 2015

Little is known about how different sources of information drive citizen trust in government. To address that gap this article compares disaster evacuees to observers, noting how trust differs as attention to media coverage increases. First‐hand experience supplies information to update trust through biological and personal processes and performance assessments, while secondary sources provide information about other people's experiences, filtered through lenses that take an active role in crafting information. These two types of information have varying effects depending on the level of government being trusted. Using surveys administered a year after Hurricane Katrina, I find that Katrina evacuees have the highest trust in federal government, until they start paying attention to media coverage, and that attention to coverage has the most dramatic effect on these evacuees compared to all other groups. I also find that increasing attention to second‐hand information corresponds with higher trust in local officials, and that this effect decreases as the level of government increases. It appears media coverage creates a comparison in the mind of hurricane evacuees, causing them to update their performance assessments based on comparing their own experience to that which they observe, thereby updating their political trust.
Probabilistic Principal Component Analysis to Identify Profiles of Physical Activity Behaviours in the Presence of Non-Ignorable Missing Data
Authors: Geraci Marco , Farcomeni Alessio
Published: April 2015

The paper is motivated by an accelerometer-based study of physical activity (PA) behaviours in a large cohort of UK school-aged children. Advances in research on PA are accompanied by a growing number of results that are contributing to form a complex picture of PA behaviours in children. One source of such complexity is intimately related to the multiplicity of dimensions associated with PA. Currently a comprehensive individual accelerometer summary can include a large number of outcomes and this clearly poses challenges for the analysis. We explore the application of principal component analysis to accelerometer measurements that are aggregated daily over several days of the week and are affected by missingness. The probabilistic approach to principal component analysis with latent scores is extended to include non-ignorable missing data. The extended likelihood is maximized through a Monte Carlo EM algorithm via adaptive rejection Metropolis sampling. Our findings suggest that physical activity and inactivity are two dimensions over which children aggregate into distinct behavioural profiles, characterized by gender and season but not by anthropometric factors.
Statements about true and false intentions: Using the Cognitive Interview to magnify the differences
Authors: Sooniste Tuule , Granhag Pär Anders , Strömwall Leif A. , Vrij Aldert
Published: April 2015

This study investigates the combined effect of the Cognitive Interview (CI) and the unanticipated questions approach on the magnitude of the elicited cues to true and false intentions. The participants (N = 125) planned for either a mock crime or a non‐criminal event, half of them were interviewed with a standard interview (SI) and half with theCI. All participants were asked one set of questions targeting their intentions (anticipated questions) and one set of questions targeting the phase in which they planned their stated intentions (unanticipated questions). As predicted, the questions about the planning phase were perceived as unanticipated by both liars and truth‐tellers. Furthermore, and as predicted, the truth‐tellers' (vs. the liars') answers to the unanticipated questions were significantly more detailed. Importantly, and in line with our predictions, for the answers given to questions about the planning‐phase, liars and truth‐tellers differed more clearly in theCI‐condition than in theSI‐condition, indicating that theCIindeed magnified the differences between liars and truth‐tellers. In addition, and as predicted, the truth‐tellers' (vs. the liars') descriptions of their intentions were more characterized by information related to how to attain the stated goal.
A novel null HLA allele, HLA‐DRB1*15:115N, identified in a Chinese family
Authors: Li X. , Zou H. , Li M. , Chen Q.
Published: April 2015

The novel allele HLA‐DRB1*15:115N differs from HLA‐B*15:80N by a nucleotide substitution at position 227 T > A.
Estimation of the infectious viral load required for transfusion‐transmitted human T‐lymphotropic virus type 1 infection (TT‐HTLV‐1) and of the effectiveness of leukocyte reduction in preventing TT‐HTLV‐1
Authors: Sobata R. , Matsumoto C. , Uchida S. , Suzuki Y. , Satake M. , Tadokoro K.
Published: April 2015

Background and Objectives

The risk of transfusion‐transmitted human T‐lymphotropic virus type 1 infection (TT‐HTLV‐1) after prestorage leucocyte reduction (LR) remains unknown, as the proviral load in the blood component that would cause TT‐HTLV‐1 is undetermined. On the basis of the distribution of HTLV‐1 proviral load among HTLV‐1‐sero‐positive blood donors, we attempted to estimate the proviral load for transfusion‐related infectivity. We also discuss the effectiveness of LR in preventing TT‐HTLV‐1.

Materials and Methods

The HTLV‐1 proviral load in 300 HTLV‐1‐sero‐positive blood donors was determined by real‐time polymerase chain reaction analysis. The proviral load required for transfusion‐related infectivity was estimated using historical TT‐HTLV‐1 frequency data from a retrospective study on patients who had received blood from HTLV‐1‐sero‐positive blood donors and the distribution pattern of HTLV‐1 proviral load among blood donors.

Results

HTLV‐1 proviral loads ranged between <0·01 and 25·0 copies per 100 leucocytes. Historical data showed TT‐HTLV‐1 frequency to be 80%. Assuming that 80% of the 300 sero‐positive samples are infectious, it is estimated that the transfer of ≥9 × 104 cells containing the HTLV‐1 provirus is required to establish TT‐HTLV‐1.

Conclusion

The residual number of HTLV‐1‐infected cells after LR is substantially lower than the viral load necessary for TT‐HTLV‐1. LR therefore appears to be effective in minimizing the incidence of TT‐HTLV‐1.
Function of the M1 π‐helix in endplate receptor activation and desensitization
Authors: Purohit Prasad , Chakraborty Srirupa , Auerbach Anthony
Published: April 2015

Key points

A conserved proline in M1 causes a kink between α and π helical segments.

The kink is under greater tension in the resting versus active conformation.

The kink and the agonist do not interact directly.

The π‐helix separates the gating functions of the extracellular and transmembrane domains.

Mutations of the conserved proline and propofol increase desensitization.

Nicotinic acetylcholine receptors (AChRs) switch on/off to generate transient membrane currents (C↔O; closed‐open ‘gating’) and enter/recover from long‐lived, refractory states (O↔D; ‘desensitization’). The M1 transmembrane helix of the muscle endplate AChR is linked to a β‐strand of the extracellular domain that extends to a neurotransmitter binding site. We used electrophysiology to measure the effects of mutations of amino acids that are located at a proline kink in M1 that separates π and α helices, in both α (N217, V218 and P221) and non‐α subunits. In related receptors, the kink is straighter and more stable in O vs. C structures (gating is ‘spring‐loaded’). None of the AChR kink mutations had a measureable effect on agonist affinity but many influenced the allosteric gating constant substantially. Side chains in the M1 α‐helix experience extraordinarily large energy differences between C and O structures, probably because of a ∼2 Å displacement and tilt of M2 relative to M1. There is a discrete break in the character of the gating transition state between αN217 and αV218, indicating that the π‐helix is a border between extracellular‐ and transmembrane‐domain function. Mutations of the conserved M1 proline, and the anaesthetic propofol, increase a rate constant for desensitization. The results suggest that straightening of the M1 proline kink triggers AChR desensitization.
Comparison Between RCCE and Shock Tube Ignition Delay Times at Low Temperatures
Authors: Nicolas Ghassan , Metghalchi Hameed
Published: April 2015

The rate-controlled constrained-equilibrium (RCCE) method is a reduction technique based on local maximization of entropy or minimization of a relevant free energy at any time during the nonequilibrium evolution of the system subject to a set of kinetic constraints. In this paper, RCCE has been used to predict ignition delay times of low temperatures methane/air mixtures in shock tube. A new thermodynamic model along with RCCE kinetics has been developed to model thermodynamic states of the mixture in the shock tube. Results are in excellent agreement with experimental measurements.
The Sea Experience of Bristol Siddeley Marine Gas Turbines
Authors: Daish T. G.
Published: April 2015

The paper presents the experience gained by Bristol Siddeley Engines Limited, over the first five years of operation at sea of aviation gas turbines adapted for use in various marine installations. Most of the experience accumulated during this period has involved the “Proteus” engine and the first part of the paper is devoted to covering this aspect, commenting upon matters such as engine life, failures, current development and future applications. The shorter experience gained applying engines to hovercraft is then dealt with, and finally reference is made to the current activities at Bristol Siddeley concerning the use of the “Olympus” engine for marine purposes.
The Allison Turboprop Aircraft Engine as an Industrial Prime Mover
Authors: Zimmerman D. G. , Kern W. H.
Published: April 2015

At the 1962 ASME meeting in Houston, Allison submitted a paper describing the possibilities of industrializing the T56 aircraft engine. Since that time, Allison has modified the engine for gas burning and is operating one as a prime mover for a 2000-kw generator at the Indianapolis Plant. In addition, two additional units are to be installed in the gas-transmisson field driving centrifugal gas compressors. This paper gives a description of the units and a status report on the installation and operation. Photographs of the installation and performance data, as necessary to complete the report, are included.
Thermal-Fatigue Analysis Applied to Turbine Airfoils
Authors: Vogel William H. , Waring Dana B. , Donachie Matthew J. , Spaeth Charles E. , Martens William R.
Published: April 2015

This paper demonstrates the applicability of basic concepts assembled from the thermal-fatigue literature to the design of cooled or uncooled turbine blades or vanes to resist cracking resulting from engine acceleration and deceleration. Following a brief description of the analysis employed, examples are given which are concerned with turbine blades that have failed as a result of deliberate cyclic operation in experimental engines. While many metallurgical and fabricational considerations influence thermal-fatigue life, attainment of useful quantitative agreement between predicted cyclic life and actual part performance is possible. Success in achieving the desired minimum life is shown to depend upon careful attention to design, material selection, material processing, fabrication technique, and the metallurgical effects of the service environment.
Salt-Water Problems in Marine Gas Turbines
Authors: Weinert Eugene P. , Carlton Gilbert A.
Published: April 2015

The gas-turbine engine in naval service is subjected to severe operating conditions. By far the most consistent troublemaker is sea salt. In either liquid or solid state, sea salt causes problems in corrosion of hot and cold surfaces, fouling of fuel systems, and deterioration of compressor performance. Such problems are reviewed and solutions discussed.
Critical Flow of Potassium Vapor Through Instrumented Converging-Diverging Nozzle
Authors: Rossbach Richard J.
Published: April 2015

To add to the analytical techniques for the fluid design of potassium-vapor turbines, a converging-diverging nozzle, instrumented with wall static taps, was calibrated using compressed air and tested in wet potassium vapor. The object of the test was to determine the polytropic exponents of the expansion process in potassium vapor. By injecting liquid potassium ahead of the nozzle, the inlet-vapor quality was varied between 82 and 98 percent. The nozzle was tested over a temperature range from 1450 to 1580 F with the result that average polytropic exponents determined by experiment agreed closely with values obtained by means of a theory set forth in the paper.
Effects of Surface Imperfections on the Thermal-Fatigue Life of Metals
Authors: Kattus J. R. , Willhelm A. C.
Published: April 2015

The effects of surface defects on the low-cycle, thermal-fatigue life of two steels and two superalloys were determined. Thermal fatigue was induced by cyclic self-resistance heating of the specimens in a restraining fixture that converted the thermal strains to mechanical strains. Although the results were quite erratic, they indicate statistically that surface roughness and defects are detrimental to the thermal-fatigue life. Thermal-fatigue is much more adversely affected by transverse shallow sharp notches and cracks than by point-type notches or general surface roughness.
Thermal-Fatigue Resistance: Material, Geometric, and Temperature Field Considerations
Authors: Carden A. E.
Published: April 2015

Data from four kinds of thermal-fatigue tests and from three materials are presented as a basis for a discussion of the influence of material, geometry, and the temperature field on the temperature range versus life relationship for thermal fatigue. A method is given whereby the results of the tests of internally constrained specimens can be compared with results from tests of externally constrained specimens. By appropriate design of a circular disk specimen either the radial or the tangential stress can be selected as the cyclic principal stress. Thermal-fatigue data from three materials are used to show that the plastic-strain range versus life relationship is not a sufficient criterion of merit when rating materials for thermal-fatigue resistance.
Application of Particle-Size Analysis Data for the Determination of Air/Cleaner Performance
Authors: Czerwonka Lawrence J. , Carey Jack M.
Published: April 2015

A general purpose centrifuge method for measuring particle-size distribution of air-filter inlet, outlet and catch dust samples is demonstrated. Treatment and analysis of data to determine air-cleaner performance based on size distribution is shown for two types of air filters, a louver and a glass-fiber media filter. The advantages and limitations of the method and interpretations of results associated with the application of these procedures for arriving at efficiency versus particle-size performance curves, and for predicting filter efficiency for any given dust are discussed.
Salt Water Aerosol Separator Development
Authors: Kaufman R. E.
Published: April 2015

• Sea salt in oil can contribute to an unacceptable concentration of sea salt in the combustion gases of naval gas turbines, so fuel-oil cleanliness requires increased emphasis in gas turbine practices.

• Sea salt in air can be a very large contributor to unacceptable sea salt concentrations in the gases of the naval gas turbine. Efforts toward the reduction or elimination of this are:

(a) The determination of definition of “maximum acceptable concentration.”

(b) The determination or definition of “maximum expected concentration.”

(c) To make emphatic the importance of particle-size distribution, as well as quantity, of sea salt in air to the problem of separation.

(d) The evaluation of a number of prototype or commercial separators.

(e) The determination of scale-up factors for full-scale designs of separators.

(f) The actual preparation of drawings and specifications for a full-scale separator system.
The Vibration of Blades in Axial Turbomachinery
Authors: Smith J. E.
Published: April 2015

This paper describes a recommended design and development procedure for reducing the possibility of vibrational problems in the blading of axial turbomachinery. The recommendations that are presented are based upon a study undertaken for the Bureau of Ships, United States Navy, under Contract No. NObs-92089.
Dynamic Models of Vibrating Rotor Stages
Authors: Stargardter Hans
Published: April 2015

Fan and compressor stages of turbofan aircraft engines are subjected to dynamic excitations. Often these excitations are at frequencies equal to or multiples of the rotor speed. This form of dynamic stimulus is called per-revolution excitation or integral-order excitation. When the natural resonant frequency of a fan stage coincides with the frequency of the source, severe vibration usually results. For shrouded fan stages the natural frequency is that of a coupled dynamic system consisting of disk, blades, and shroud. A modeling technique is developed to study the vibration. Small scale models are cast of flexible silicone rubber, known as RTV. The rubber models rotate and are excited by air nozzles located at discrete circumferential positions. Visual observation of the standing-wave oscillation clearly shows the familiar relations of forced vibrations such as magnification factor, phase shift, and the effects of damping. RTV silicone rubber is easily cast into complex shapes. This allows rapid evaluation of the many resonant-response blade-disk shroud configurations including unsymmetrical designs that may be difficult to analyze with current computing techniques.
A Rapid Method for Predicting the Off-Design Performance of Radial-Inflow Turbines
Authors: Jansen W. , Qvale E. B.
Published: April 2015

An explicit expression for predicting the turbine off-design performance in terms of efficiency, torque, and mass flow as a function of tip speed with pressure ratio as a parameter is formulated. The results of this method have been compared with those of various experiments and more elaborate prediction methods; satisfactory agreement is obtained.
Sound Attenuation in Acoustically Treated Turbomachinery Ducts
Authors: Benzakein M. J. , Kraft R. E. , Smith E. B.
Published: April 2015

The paper presents a theoretical development, accompanied by an experimental data check, of the attenuation in acoustically lined ducts with no airflow. The results indicate that the number of spinning lobes, as well as the generation frequency, have a major effect on the performance of the acoustic material. It also was indicated that the impedance components of the acoustic lining can be optimized to give a maximum sound energy reduction over a given range of engine speeds.
Procedure for Optimum Design in Relation to Noise for Low-Speed Ducted Fans
Authors: van Niekerk C. G.
Published: April 2015

A previously published ducted fan design theory is used to design a series of related fans in which certain parameters are varied systematically. A previously published equation for the calculation of fan noise is then used to estimate the noise generated by each of these fan configurations. The results suggest how the various design parameters influence noise generation. Due to a lack of experimental data, the fan noise equation has not yet been fully developed and verified. Nevertheless, it could already prove useful as a qualitative guide in selecting fan design parameters for minimum noise.
Low-Noise Propulsion Systems for Subsonic Transports
Authors: Kramer James J. , Leonard Bruce R. , Feiler Charles E.
Published: April 2015

The authors present a brief review of the preliminary design studies that led to a definition of specifications for a low-noise output turbofan engine for use on long-range subsonic transport aircraft. Data on low-speed fans, with and without acoustic treatment in the fan ducting, indicate that overall noise output of four-engine long-range transport aircraft can be reduced 20 perceived noise decibels by appropriate fan design and the use of nacelle acoustic treatment.
The Sound of Gas-Turbine Installations
Authors: Hoover Robert M.
Published: April 2015

In this overall review of gas-turbine sound and its control, the author discusses the variety of installations, the scope of the noise control problem, criteria, industry performance, noise specifications, and noise measurements. In particular, the magnitude of the noise control problem is indicated by discussion of the sound of an unmuffled 20 Mw turbine. Typical sound pressure level data on current installations are given, and suggestions are made for noise control criteria in the low frequency range.
Prediction of the Effect of Engine Geometry on Aircraft Smoke Visibility
Authors: Chesters A. K.
Published: April 2015

The visibility of aircraft exhaust smoke derives principally from light absorption and, hence, varies with smoke concentration and exhaust diameter. Because of complex exit aerodynamics and jet entrainment, however, effective exhaust diameters differ from actual. Entrainment rapidly transforms the exit profiles of smoke concentration to self-preserving Gaussian ones and causes slow decay of visibility. The initial visibility of the self-preserving jet is shown to depend on the mass emission rate of smoke times the square of ambient gas density and gross jet thrust. This expression also describes, within about 10 percent, the actual exit visibility for current engine types. Quantitative criteria are also derived for the engine spacing, at which coalescence of parallel jets influences visibility, and for the magnitude of effect.
A NOx Correlation Method for Gas Turbine Combustors Based on NOx Formation Assumptions
Authors: Vermes Géza
Published: April 2015

Based on a simplified description of the combustion process in the primary zone of a can type gas turbine combustor, a generalized NOx versus fuel flow relationship is proposed. Using this relationship and considerations based on chemical kinetics, the effect of combustor inlet pressure, inlet temperature and air residence time on NOx formation is investigated in industrial and automotive type combustion chambers. Data reported in the literature and original test work is cited to substantiate the validity of the assumptions. Based on the findings, a simple method is presented to predict NOx emissions of a gas turbine combustor under conditions which differ substantially from those of the test run. The assumptions may be used to assemble a model for a priori prediction of NOx emissions in a given combustion geometry.
Effect of Various Control Modes on the Steady-State Full and Part Load Performance of a Direct-Cycle Nuclear Gas Turbine Power Plant
Authors: Covert R. E. , Krase J. M. , Morse D. C.
Published: April 2015

The performance and principal operating characteristics of the Gas Turbine HTGR power plant are reported. The reference design of the dry cooled 1100-MW(e) power plant incorporates four helium gas turbine power conversion loops integrated into the prestressed concrete reactor vessel, which also contains the reactor and the entire primary coolant system. The reactor core is virtually the same as that for the comparable HTGR steam cycle and is operated with similar maximum fuel temperatures, resulting in a turbine inlet temperature of 1500 F (816 C). An overall plant efficiency of about 37 percent is realized with a design point cycle pressure ratio of 2.35 and with a high-effectiveness recuperator in each loop. Component performance and cycle performance calculations are discussed. The variation of plant performance with ambient temperature is described. Three distinct control modes are described which are, in order of decreasing part-load efficiency, helium inventory control, reactor outlet temperature control, and bypass flow (compressor outlet to turbine outlet) control. The latter offers the most rapid control of plant output. Also described is the standard operating control mode which combines reactor outlet temperature and bypass controls to facilitate both ramp and step load changes.
Interactions of higher order tip effects in critical dimension-AFM linewidth metrology
Authors: Dixson Ronald , Ng Boon Ping , Bonnaud Xavier , Orji Ndubuisi
Published: April 2015

A major challenge in critical dimension atomic force microscope width metrology is accounting for the effects of the tip on the apparent features in an image. The overall effect of the tip is to broaden the apparent width of lines and narrow the apparent width of trenches as a result of the geometrical interaction of the tip with the surface. To a first approximation, this effect can be well-modeled as a constant bias in width measurements, independent of the specific feature characteristics, by the width of the tip. Beyond this approximation, there are a number of smaller tip effects related to the measurement details. Some of these result from the details and interactions of the tip shape and feature shape, resulting in small variations of the tip bias from feature to feature and measurement to measurement. These effects are sometimes called shape effects, secondary effects, or higher order tip effects. One source of higher order effects is due to the lateral dithering of the tip, which increases the effective tip width. However, in addition to this known effect, the tip dither may also affect the apparent edge heights of the tip flare. Although the apparent tip width is expected to depend on lateral dither, the apparent edge height, at least in principle, would not be expected to depend on lateral dither. Our analysis suggests that this apparent dependence results from the interaction of the fine details of the tip flare shape and the dither envelope with the specific algorithm used to estimate the edge height. Consequently, both the sign and the magnitude of the dependence are specific to every tip. This is one example of the inter-dependencies that can be present when evaluating higher-order tip effects. Although these are often small, accurate metrology in some applications may require consideration of possible interactions between such smaller, secondary tip effects. The authors illustrate this with examples from photomask metrology, where measurement of chrome features on binary masks requires some attention to secondary tip effects.