bluuebunny/crossref_metadata_2025 huggingface dataset:
An update on the microbiology and epidemiology of enteropathogenic Escherichia coli in England 2010–2012
Authors: Sakkejha Hanan , Byrne Lisa , Lawson Andy J. , Jenkins Claire
Published: July 2013

Historically, enteropathogenic Escherichia coli (EPEC) are a well-known cause of outbreaks of infantile diarrhoea associated with morbidity and mortality in England. The aim of this study was to provide an update on the microbiology and epidemiology of strains of EPEC in England between 2010 and 2012. A wide range of E. coli serogroups were identified, with the most common being E. coli O145, O49 and O157. Few isolates (9 %) had additional virulence factors (specifically bfp, vtx2f and espT genes) and the majority were classified as atypical EPEC. The majority of cases (86 %) were among children. This included a significantly higher percentage (17.4 %) of cases aged 0–12 months when compared with cases of other common gastrointestinal pathogens (P<0.001). No outbreaks were reported during this period; however, the data indicated that EPEC are still an important cause of sporadic cases of infantile diarrhoea in England.
The entoptic view of the retinal vessels
Authors: Mark Harry H.
Published: July 2013

The first time the retinal vessels were seen in man in vivo was reported in 1819 by Purkinje as an entoptic view. This was understood to show the shadow of the vessels, an interpretation objected to in 1834 by Brewster. Müller in 1855 (Über die entoptische wahrnehmung der netzhautgefässe, insbesondere als beweismittel für die lichtperception durch die nach hinten gelegenen netzhautelemente, Stahel, Würzburg) used the phenomenon to deduce the location of the photoreceptive layer of the retina, and his conclusion is accepted as true today. Because the phenomenon has some characteristics of an afterimage, it touches on the question of what is subjective and what is objective physical reality. It was recently used clinically to measure potential visual acuity and in the diagnoses of diabetic retinopathy and macular degeneration.
Sub‐Tenon injection of 2% lidocaine prevents intra‐operative floppy iris syndrome (IFIS) in male patients taking oral α‐adrenergic antagonists
Authors: Klysik Anna , Korzycka Dorota
Published: July 2013

Purpose: To compare 2% sub‐Tenon and 1% intra‐cameral lidocaine for cataract surgery in relation to the incidence and severity of IFIS. Prospective randomized clinical study.

Methods: From 81 eligible, we included 71 men aged from 59 to 90 years (mean 76.5 ± 6.8) undergoing routine cataract surgery and taking oral α‐adrenergic antagonists, for urological reasons, for more than 1 year. Following randomization 34 men, aged from 62 to 90 years (mean 77.4 ± 8.1) received sub‐Tenon injection of 2.5 ml of 2% lidocaine and the remaining 37 men aged from 59 to 89 years (mean 75.2 ± 7.2) received 1% preservative free intra‐cameral lidocaine. Outcome measures were the incidence of IFIS, severity of intra‐operative pupillary constriction and iris prolapse.

Results: Intra‐operative floppy iris syndrome (IFIS) was noted in 3 of 34 patients (8.8%) receiving sub‐Tenon lidocaine and in 18 of 37 patients (48.6%) receiving intra‐cameral lidocaine (p = 0.00). Severe IFIS was observed only in 3 of 37 patients (8.1%) receiving intra‐cameral lidocaine. Pupil diameter at the end of surgery was 4.37 ± 1.07 mm in the sub‐Tenon lidocaine group and 4.02 ± 1.06 mm in the intra‐cameral lidocaine group (p = 0.00). Iris prolapse was noted in two cases in the sub‐Tenon lidocaine group and in 10 cases in the intra‐cameral lidocaine group (p = 0.00). Twenty‐five patients were receiving tamsulosin. The incidence of IFIS in tamsulosin subgroup was 76.9% (10 of 13 patients) in the intra‐cameral lidocaine group and 16.6% (2 of 12 patients) in the sub‐Tenon lidocaine group (p = 0.00).

Conclusion: Sub‐Tenon lidocaine reduces significantly the incidence of IFIS in patients taking oral α‐adrenergic inhibitors as compared with intra‐cameral lidocaine.
Subcortical and cerebellar volumetric deficits in paediatric sickle cell anaemia
Authors: Kawadler Jamie M. , Clayden Jonathan D. , Kirkham Fenella J. , Cox Timothy C. , Saunders Dawn E. , Clark Chris A.
Published: July 2013

Sickle cell anaemia (SCA) is associated with silent cerebral infarction (SCI), affecting white and cortical grey matter, but there are few data on subcortical volumes. We analysed retrospective magnetic resonance imaging (MRI) data in 26 SCA patients and 20 controls, comparing mean subcortical volumes between three groups: controls, SCA with SCI (n = 13) and SCA without visible abnormality (n = 13). Specific volumetric differences were found in the hippocampus, amygdala, pallidum, caudate, putamen, thalamus, and cerebellum. This is the first study to demonstrate subcortical volume change in SCA, with the most severe volumetric deficits occurring in children with SCI seen on MRI.
Antiepileptics Topiramate and Levetiracetam Alleviate Behavioral Deficits and Reduce Neuropathology in APPswe/PS1dE9 Transgenic Mice
Authors: Shi Jian‐Quan , Wang Bian‐Rong , Tian You‐Yong , Xu Jun , Gao Li , Zhao Shu‐Li , Jiang Teng , Xie Hong‐Guang , Zhang Ying‐Dong
Published: July 2013

Background

The close relationship between epileptic seizure and Alzheimer's disease (AD) has been demonstrated in the past decade. Valproic acid, a traditional first‐line antiepileptic drug, exerted protective effects in transgenic models of AD. It remains uncertain whether new antiepileptic drugs could reverse neuropathology and behavioral deficits in AD transgenic mice.

Aims

APPswe/PS1dE9 transgenic mice were used in this study, which over express the Swedish mutation of amyloid precursor protein together with presenilin 1 deleted in exon 9. 7‐month‐old APPswe/PS1dE9 transgenic mice were treated daily with 20 mg/kg topiramate (TPM) and 50 mg/kg levetiracetam (LEV) for 30 days by intraperitoneal injection to explore the effects of TPM and LEV on the neuropathology and behavioral deficits.

Results

The results indicated that TPM and LEV alleviated behavioral deficits and reduced amyloid plaques in APPswe/PS1dE9 transgenic mice. TPM and LEV increased Aβ clearance and up‐regulated Aβ transport and autophagic degradation. TPM and LEV inhibited Aβ generation and suppressed γ‐secretase activity. TPM and LEV inhibited GSK‐3β activation and increased the activation of AMPK/Akt activation. Further, TPM and LEV inhibited histone deacetylase activity in vivo.

Conclusions

Therefore, TPM and LEV might have the potential to treat AD effectively in patient care.
Hypoxia‐Triggered m‐Calpain Activation Evokes Endoplasmic Reticulum Stress and Neuropathogenesis in a Transgenic Mouse Model of Alzheimer's Disease
Authors: Wang Chun‐Yan , Xie Jing‐Wei , Wang Tao , Xu Ye , Cai Jian‐Hui , Wang Xu , Zhao Bao‐Lu , An Li , Wang Zhan‐You
Published: July 2013

Background

Previous studies have demonstrated that endoplasmic reticulum (ER) stress is activated in Alzheimer's disease (AD) brains. ER stress–triggered unfolded protein response (UPR) leads to tau phosphorylation and neuronal death.

Aims

In this study, we tested the hypothesis that hypoxia‐induced m‐calpain activation is involved in ER stress‐mediated AD pathogenesis.

Method

We employed a hypoxic exposure in APP/PS1 transgenic mice and SH‐SY5Y cells overexpressing human Swedish mutation APP (APPswe).

Results

We observed that hypoxia impaired spatial learning and memory in the APP/PS1 mouse. In the transgenic mouse brain, hypoxia increased the UPR, upregulated apoptotic signaling, enhanced the activation of calpain and glycogen synthase kinase‐3β (GSK3β), and increased tau hyperphosphorylation and β‐amyloid deposition. In APPswe cells, m‐calpain silencing reduced hypoxia‐induced cellular dysfunction and resulted in suppression of GSK3β activation, ER stress and tau hyperphosphorylation reduction as well as caspase pathway suppression.

Conclusion

These findings demonstrate that hypoxia‐induced abnormal calpain activation may increase ER stress‐induced apoptosis in AD pathogenesis. In contrast, a reduction in the expression of the m‐calpain isoform reduces ER stress‐linked apoptosis that is triggered by hypoxia. These findings suggest that hypoxia‐triggered m‐calpain activation is involved in ER stress‐mediated AD pathogenesis. m‐calpain is a potential target for AD therapeutics.
Clinical Features and Sera Anti‐Aquaporin 4 Antibody Positivity in Patients with Demyelinating Disorders of the Central Nervous System from Tianjin, China
Authors: Yang Chun‐Sheng , Zhang Da‐Qi , Wang Jing‐Hua , Jin Wei‐Na , Li Min‐Shu , Liu Jie , Zhang Cun‐Jin , Li Ting , Shi Fu‐Dong , Yang Li
Published: July 2013

Aims

To investigate the clinical characteristics and sera anti‐aquaporin 4 (AQP4) antibody positivity in patients with inflammatory demyelinating disorders (IDDs) of the central nervous system (CNS) in Tianjin, China.

Methods

We retrospectively evaluated 234 patients with IDDs including neuromyelitis optica (NMO), recurrent optic neuritis (rON), longitudinally extensive transverse myelitis (LETM), clinically isolated syndrome (CIS), and multiple sclerosis (MS) groups. Sera from 217 patients were determined for AQP4‐Ab. The clinical characteristics and sera anti‐AQP4 positivity were compared.

Results

The IDDS comprised 63 MS, 51 NMO, 56 LETM, 10 rON, and 54 CIS. Compared with MS, NMO had a higher frequency of occurrence in women, intractable hiccup and nausea (IHN), medullospinal lesion, longitudinally extensive spinal cord lesions (LESCL) and bilateral ON, disease onset at a later age, and worsening residual disability. AQP4‐Ab‐positive rates were 84.1% and 69% in NMO and NMO spectrum disorders (NMOSD), respectively, whereas it was undetectable in all of the MS sera samples.

Conclusions

We comprehensively contrast the distinct clinical features of MS, NMO, and NMOSD in our center. A sensitive AQP4‐Ab assay is necessary for the early diagnosis of NMOSD in our patients. Neither medullospinal lesion nor IHN is unique in NMO.
Incremental Value of Three‐Dimensional Transesophageal Echocardiography over Two‐Dimensional Transesophageal Echocardiography in the Assessment of Lambl's Excrescences and Nodules of Arantius on the Aortic Valve
Authors: Dumaswala Bhavin , Dumaswala Komal , Hsiung Ming Chon , Quiroz Luis David Meggo , Sungur Aylin , Escanuela Maximilliano German Amado , Mehta Kruti , Oz Tugba Kemaloglu , Bhagatwala Kunal , Karia Nidhi M. , Nanda Navin C.
Published: July 2013

In this retrospective study, we identified 7 cases where Lambl's excrescences were identified by two‐dimensional transesophageal echocardiography (2DTEE) and also had live/real time three‐dimensional transesophageal echocardiography (3DTEE) studies available for comparison. We subsequently assessed them for the presence of Lambl's excrescences (LE) and nodules of Arantius (NA) on the aortic valve. After their identification, we qualitatively and quantitatively organized our findings by number, cusp location, measurements, and orientation if applicable. A greater number of LE was found by 3DTEE than 2DTEE (19 vs. 11, respectively). In all 3DTEE studies, their cusp attachment site, their x‐, y‐, and z‐axis measurements, and orientation were clearly visualized and described. Only 3DTEE studies provided confident visualization of the cusp attachment sites. Similarly, a greater number of NA was found by 3DTEE than 2DTEE (21 vs. 5, respectively). The triad of NA was visualized in all 3DTEE studies and each was described using its x‐, y‐, and z‐ axis measurements. Only three 2DTEE studies provided reliable identification of the NA. In conclusion, we present further evidence of the incremental value of 3DTEE over 2DTEE in the qualitative and quantitative assessment of cardiac structures including LE and NA on the aortic valve.
Giant Right Atrium in a Case with Rheumatic Heart Disease
Authors: Patra Soumya , Agarwal Ashish , Kumar Tarun , Ravindranath K.S. , Manjunath C.N.
Published: July 2013

Mini‐Abstract

Massive right atrium (RA) enlargement is certainly more common in children than in adults, owing to rare congenital anomalies. RA could be enlarged in a case of rheumatic heart disease especially when associated with severe mitral valve disease or pulmonary hypertension. We are presenting a case of 25‐year‐old female patient who presented with features of congestive heart failure. Echocardiography revealed the presence of giant RA along with organic severe tricuspid regurgitation, mild tricuspid stenosis, and mild aortic regurgitation. RA volume measured in our case was about 1000 mL which is the largest description so far described in the literature.
Fondaparinux‐associated heparin‐induced thrombocytopenia
Authors: Bhatt Vijaya R. , Aryal Madan R. , Shrestha Rajesh , Armitage James O.
Published: July 2013

Objectives

Large licensing trials did not find any association between the use of fondaparinux and the development of heparin‐induced thrombocytopenia (HIT). Fondaparinux is in fact recommended as an option for the management of HIT. Since the first report of fondaparinux‐associated HIT in 2007, additional reports have been published. However, the rarity of these cases, differences in case definition, and lack of larger case series have prevented better understanding of this disease. The objective of this study was to determine the clinical manifestations of fondaparinux‐associated HIT, the predictive value of pretest probability (4Ts) scoring system, and the outcomes associated with current management.

Methods

Using several search terms, we reviewed all cases of fondaparinux‐associated HIT reported and indexed in PubMed till May 2013. All references were also checked for additional reports. We categorized the cases of fondaparinux‐associated HIT as confirmed, probable, and possible based on our case definition.

Results

A total of eight cases of fondaparinux‐associated HIT were identified. Fondaparinux‐associated HIT occurred in the setting of pro‐inflammatory state, prior HIT, or exposure to heparin products. Bilateral adrenal hemorrhage or infarct, reflecting hypercoagulability or disseminated intravascular coagulation, was seen in 25% of patients. The pretest probability (4Ts) scoring system used for HIT appears to correctly risk stratify all the cases. Although functional assays can be used for the diagnosis, in the presence of recent exposure to heparin products, only the demonstration of fondaparinux‐dependent platelet activation should be considered confirmatory. Non‐heparin anticoagulants are effective therapy; however, one‐third of the patients had poor outcomes.

Conclusion

The risk of fondaparinux‐associated HIT, although low is real, which along with documented cases of fondaparinux failure mandate its cautious use in the management of HIT.
How to Teach Medication Management: A Review of Novel Educational Materials in Geriatrics
Authors: Ramaswamy Ravishankar
Published: July 2013

Medication management is an important component of medical education, particularly in the field of geriatrics. The Association of American Medical Colleges has put forth 26 minimum geriatrics competencies under eight domains for graduating medical students; medication management is one of these domains. The Portal of Geriatric Online education (www.POGOe.org) is an online public repository of geriatrics educational materials and modules developed by geriatrics educators and academicians in the United States, freely available for use by educators and learners in the field. The three POGOe materials presented in this review showcase pearls of medication management for medical and other professional students in novel learning formats that can be administered without major prior preparation. The review compares and contrasts the three materials in descriptive and tabular formats to enable its appropriate use by educators in promoting self‐learning or group learning among their learners.
Noise as Information for Illiquidity
Authors: HU GRACE XING , PAN JUN , WANG JIANG
Published: July 2013

We propose a market‐wide liquidity measure by exploiting the connection between the amount of arbitrage capital in the market and observed “noise” in U.S. Treasury bonds—the shortage of arbitrage capital allows yields to deviate more freely from the curve, resulting in more noise in prices. Our noise measure captures episodes of liquidity crises of different origins across the financial market, providing information beyond existing liquidity proxies. Moreover, as a priced risk factor, it helps to explain cross‐sectional returns on hedge funds and currency carry trades, both known to be sensitive to the general liquidity conditions of the market.
An In Vitro Comparison of Shear Bond Strength of Zirconia to Enamel Using Different Surface Treatments
Authors: Zandparsa Roya , Talua Nayrouz A. , Finkelman Matthew D. , Schaus Scott E.
Published: July 2013

Purpose

The purpose of this in vitro study was to compare the shear bond strength of an airborne‐particle abraded zirconia, an acid‐etched zirconia (Piranha solution), an Alloy Primer treated zirconia, and a silaned zirconia to enamel, all bonded with a phosphate‐methacrylate resin luting agent.

Materials and Methods

Seventy extracted intact human molars were collected, cleaned, and mounted in autopolymerizing acrylic resin, with the experimental surface of the teeth exposed. The specimens were randomly divided into seven groups of zirconia specimens (4 mm diameter, 2 mm thick). Group 1: Airborne‐particle abrasion; group 2: Airborne‐particle abrasion and Z‐PRIME Plus; group 3: Airborne‐particle abrasion and alloy primer; group 4: Piranha solution 7:1; group 5: Piranha solution 7:1 and Z‐PRIME Plus; group 6: Piranha solution 7:1 and Alloy primer; group 7: CoJet and silane. All specimens were luted with a phosphate‐methacrylate resin luting agent (Panavia F2.0) and stored in distilled water for 1 day, then thermocycled (5°C and 55°C) for 500 cycles and tested for shear bond strength (SBS), measured in MPa, with a universal testing machine at a 0.55 mm/min crosshead speed. All specimens were inspected under a scanning electron microscope to determine mode of failure. The mean values and standard deviations of all specimens were calculated for each group. A one‐way ANOVA was performed, and multiple pairwise comparisons were then completed with post hoc Tukey test (alpha = 0.05).

Results

The airborne‐particle abrasion and Z‐PRIME Plus group resulted in a significantly higher SBS than the other groups (21.11 ± 6.32 MPa) (p < 0.001). The CoJet and silane group (15.99 ± 8.92 MPa) and airborne‐particle abrasion and alloy primer group (11.07 ± 4.34 MPa) showed high shear bond strength but not statistically significant from the airborne‐particle abrasion group (14.23 ± 5.68 MPa). Failure mode was predominately mixed in groups 1, 2, 3, and 7 with islands of retained resin on the zirconia and enamel surfaces; however, groups 4, 5, and 6 showed mostly adhesive failures, which left the zirconia surface free of the adhesive materials. No cohesive failures of the substrates (ceramic, resin, or enamel) were observed.

Conclusion

Airborne‐particle abrasion followed by the application of a zirconia primer produced the highest bond strength to enamel. Therefore, it can be recommended as a promising surface treatment method to achieve a durable bond to densely sintered zirconia ceramics.
Ultrasound‐guided approach to the paravertebral space for catheter insertion in infants and children
Authors: Boretsky Karen , Visoiu Mihaela , Bigeleisen Paul
Published: July 2013

Background

Paravertebral perineural blocks are used to prevent pain in the thoracoabdominal dermatomes. Traditionally, a landmark‐based technique is used in children, while ultrasound‐guided (UG) techniques are being employed in adult patients.

Objective

To describe an UG technique for placement of thoracic paravertebral nerve block (TPVNB) catheters in pediatric patients.

Methods

Retrospective chart review of a series of 22 pediatric patients' ages 6 months to 17 years with weights from 6.25 kg to 135 kg using a transverse in‐plane technique. Catheters were placed both bilateral and unilateral for a variety of thoracic and abdominal procedures.

A linear ultrasound transducer was used in all cases with frequency of oscillation and transducer length chosen based on individual patient characteristics of age, weight, and BMI.

Results

The median pain scores at 12, 24, 36, and 48 h were 1.2 (interquartile range, 4.5), 0.84 (interquartile range 3.0), 1.6 (interquartile range 2.9), and 0.83 (interquartile range 1.74), respectively. The median dose of opioid expressed as morphine equivalents consumed during the first 24 h after surgery was 0.14 mg·kg−1 (interquartile range, 0.78 mg·kg−1) and from 24 to 48 h the median dose was 0.11 mg·kg−1 (interquartile range 0.44 mg·kg−1). No complications were noted, and catheters were left an average of 3 days with a range of 1–5 days with good pain relief.

Conclusion

This technical description demonstrates the feasibility of placing PVNB catheters using a transverse in‐line ultrasound‐guided technique in a wide range of pediatric patients.
Green governmentality and swidden decline on Palawan Island
Authors: Dressler Wolfram
Published: July 2013

Environmental governance initiatives increasingly extend to the rural Philippines as ‘devolved’ programmes that progress livelihood change, differentiation and market‐based investments. This paper examines how the origins, rise and consequences of environmental governance initiatives in Palawan Island, the Philippines, facilitate forms of governmentality that intersect with, and rearticulate through, the local political economy to influence swidden‐based livelihoods, social relations and landscape composition. Drawing on recent scholarship, I describe how the rise and substance of this governance agenda manifests spatially as a form of discursive green governmentality. I argue that this scaled, discursive process involves diverse institutions that decentre and deploy technical knowledge, values and rules in local spaces, influencing how farmers self‐govern their behaviour and use of nature toward ‘sustainability’ (Goldman 2001). I draw on a case study to show how Tagbanua swidden farmers negotiate such green governmentality by adopting new landscape ideals through anti‐swidden narratives inflected by local politics, economy and environmental change in villages around the Puerto Princesa Subterranean River National Park. I focus on how green governmentality has become systemic across scales to converge with local politics and economy, where governmental discourse is pliable, flexibly interpreted, though followed to affect the shift from long fallow to permanent cultivation. I conclude by showing that the ways government, non‐governmental and local actors communicate and invest in such discourse facilitates convergence with the local political economy, reinforcing swidden decline, livelihood risk and marginalisation.
Styling the nation: fear and desire in the South Sudanese beauty trade
Authors: Faria Caroline
Published: July 2013

Feminist scholarship on emotion and the ‘global intimate’ offers innovative ways to rethink nationalism as embodied, affective and lived in the everyday. This approach also brings into focus the significance of the transnational: flows of commodities, bodies and ideas that cross state boundaries and are taken up, reworked, celebrated and worried over as part of nation‐making. I approach nationalism here in this way, centring the beauty salon industry in the newly independent Republic of South Sudan. Beauty salons are owned, staffed and supplied by inherently transnational subjects: migrant workers and entrepreneurs as well as members of the returning diaspora. They are also stocked with transnational material objects: hair weaves, cosmetics and beauty technologies from across Africa, the Middle East, Europe and the USA. The fashioning of the nation through these salons is thus cosmopolitan in style: orientated outward, embracing the modern and privileging a sense of worldliness and affinity with distant people and places. However, this styling of nationalism is ambivalent and contested. Clients clamour for new fashions, the latest technologies in hair and beauty, and the know‐how brought by migrant ‘saloonists’, as they are referred to in the region. Yet this desire interweaves with a growing panic around the foreign: foreign styles, migrants, capital and commodities. Through this case study I argue that nation‐making in South Sudan is fundamentally transnational – constructed not in isolation from, but explicitly through, cosmopolitanism and the modern exterior. In connection I argue that nationalism is emotional – marked at once by contradictory feelings of fear and desire that require, and indeed depend on, a foreign other. In this way I demonstrate how quotidian spaces and subjects, transnational flows of bodies, commodities and styles, and analyses of emotion can all be richly explored to better understand and theorise the operations of nationalism.
Forced Response in Axial Turbines Under the Influence of Partial Admission
Authors: Fridh Jens , Laumert Björn , Fransson Torsten
Published: July 2013

High cycle fatigue (HCF) due to unforeseen excitation frequencies, underestimated force magnitudes, or a combination of both causes control-stage failures for steam turbine stakeholders. This paper provides an extended design criteria toolbox, as well as validation data, for control-stage design based on experimental data to reduce HCF incidents in partial-admission turbines. The upstream rotor in a two-stage air test turbine is instrumented with pressure transducers and strain gauges. Admission degrees extend from 28.6% to 100%, as one or two admission arcs are simulated by blocking segmental arcs immediately upstream of the first stator vanes with aerodynamically shaped filling blocks. Sweeps across a speed range of 50%–105% of design speed are performed at a constant turbine pressure ratio during simultaneous high-speed acquisition. A forced-response analysis is performed and results presented in Campbell diagrams. Partial admission creates a large number of low-engine-order forced responses because of the blockage, pumping, loading, and unloading processes. Combinations of the number of rotor blades and low-engine-order excitations are the principal sources of forced-response vibrations for the turbine studied here. Altering the stator and/or rotor pitches changes the excitation pattern. We observed that a relationship between the circumferential lengths of the admitted and nonadmitted arcs dictates the excitation forces and may serve as a design parameter.
An Experimental Verification of a New Design for Cantilevered Stators With Large Hub Clearances
Authors: Lange Martin , Vogeler Konrad , Mailach Ronald , Gomez Sergio Elorza
Published: July 2013

Proportionally large relative radial clearances can be found within the rear stages of multistage axial compressors of gas turbines and aero engines, with significant impact on their efficiency. A new three-dimensional design for cantilevered stators in axial compressors is presented, with the aim of improving the overall efficiency and losses of rear stage vanes with large relative hub clearances. The new vane design comprises an unconventional dihedral, with special consideration to reduce the losses caused by the hub clearance vortex. The design was tested in a 4-stage low speed axial research compressor under rear stage conditions. The results are compared to the nominal design to validate the reduction of hub clearance losses and blockage. For both designs, the hub clearances over the third and fourth stator were varied from 1.5% up to 6.0% of span. Overall performance data and flow field traverses upstream and downstream of stator 3 and rotor 4 will be presented in this article in comparison with 3D CFD results.
Numerical Analysis of Heat Transfer and Flow Stability in an Open Rotating Cavity Using the Maximum Entropy Production Principle
Authors: Bohn D. , Krewinkel R. , Wolff A.
Published: July 2013

The flow field and heat transfer in the internal cooling system of gas turbines can be modeled using rotating-disk systems with axial throughflow. Because of the complexity of these flows, in which buoyancy-induced phenomena are of the utmost importance, numerical studies are notoriously difficult to perform and need extensive experimental validation. J.M. Owen proposed using the maximum entropy production (MEP) principle as a possible means of simplifying numerical computations for these complex flows since this would enable us to use stationary numerical calculations to predict the flow field. Simply said, this theory is based on the heat flux out of the cavity. In this numerical study, the computed Nusselt numbers on the disk walls inside an open rotating cavity with a Rayleigh number of approximately 4.97 × 108. This is representative of the lower values encountered in the flow inside rotating cavities. It is shown that, as predicted by Owen, the flow is stable when the heat transfer out of the cavity is maximized, or, conversely, the system is unstable when the heat transfer is minimized. Furthermore, it is proven that the level of the Nusselt number plays an important role for the change between the number of vortex pairs in the flow as well.
Integrating Computer-Aided Design and Nano-Indentation for Complex Lithograph
Authors: Xu Kangmin , Yang Seung-Cheol , Qian Xiaoping
Published: July 2013

We present an approach for producing complex nanoscale patterns by integrating computer-aided design (CAD) geometry processing with an atomic force microscope (AFM) based nanoindentation process. Surface modification is achieved by successive nanoindentation using a vibrating tip. By incorporating CAD geometry, this approach provides enhanced design and patterning capability for producing geometric features of both straight lines and freeform B-splines. This method automatically converts a pattern created in CAD software into a lithography plan for successive nanoindentation. For ensuring reliable lithography, key machining parameters including the interval of nanoindentation and the depth of nanogrooves have been investigated, and a proper procedure for determining the parameters has been provided. Finally, the automated nanolithography has been demonstrated on poly methylmethacrylate (PMMA) samples. It shows the robustness of complex pattern fabrication via the CAD integrated, AFM based nanoindentation approach.
Transient Analysis of Laser Ablation Process With Plasma Shielding: One-Dimensional Model Using Finite Volume Method
Authors: Marla Deepak , Bhandarkar Upendra V. , Joshi Suhas S.
Published: July 2013

This paper presents a comprehensive transient model of various phenomena that occur during laser ablation of TiC target at subnanosecond time-steps. The model is a 1D numerical simulation using finite volume method (FVM) on a target that is divided into subnanometric layers. The phenomena considered in the model include: plasma initiation, uniform plasma expansion, plasma shielding of incoming radiation, and temperature dependent material properties. It is observed that, during the target heating, phase transformations of any layer occur within a few picoseconds, which is significantly lower than the time taken for it to reach boiling point (~ns). The instantaneous width of the phase transformation zones is observed to be negligibly small (<5nm). In addition, the width of the melt zone remains constant once ablation begins. The melt width decreases with an increase in fluence and increases with an increase in pulse duration. On the contrary, the trend in the ablation depth is exactly opposite. The plasma absorbs about 25–50% of the incoming laser radiation at high fluences (20-40 J/cm2), and less than 5% in the range of 5-10 J/cm2. The simulated results of ablation depth on TiC are in good agreement at lower fluences. At moderate laser fluences (10-25 J/cm2), the discrepancy of the error increases to nearly ±7%. Under prediction of ablation depth by 15% at high fluences of 40 J/cm2 suggests the possibility of involvement of other mechanisms of removal such as melt expulsion and phase explosion at very high fluences.
Viscoelastic Strain Hardening Model for Gasket Creep Relaxation
Authors: Abboud Antoine , Nassar Sayed A.
Published: July 2013

This paper proposes a novel strain hardening model for investigating gasket creep relaxation under compressive step-loading at room temperature. A closed form solution is developed for predicting the steady-state gasket pressure. Step-loading of the gasket may be directly achieved and controlled, or indirectly estimated through the bolt tightening and retightening torque. The effect of gasket material, time duration at each stress level, as well as the geometric parameters of the gasket are investigated. An experimental procedure and test setup are used to validate the proposed gasket model.
On the Acceleration Limits for Sliding and Detachment Between Contacting Rough Surfaces for Micropart Manipulation in a Dry Environment
Authors: Rizwan Mohsin , Shiakolas Panos S.
Published: July 2013

Micropart manipulation is an active research area encompassing a wide array of fields and applications. As the size of the parts to be manipulated by an automated system decreases, the dominant forces are different compared to macroscale ones. Thus, for accurately modeling and evaluating the motion dynamics of a micropart, microscale forces and their effects must be considered. This manuscript employs a nanomicroscale friction model based on the Kogut–Etsion model that along with microscale forces considers surface roughness and material hardness properties to identify the acceleration threshold that would cause a micropart to start sliding on a carrier surface or vertically detach from the carrier surface during gripperless manipulation in a dry environment. The microscale forces change significantly as a function of the surface roughness of the two contacting surfaces. The results indicate that there will always be critical acceleration values below which no sliding or detachment takes place. Also, for the same model parameters, the sliding acceleration is smaller than the detachment acceleration for softer materials and larger for harder materials. The sliding acceleration threshold is more sensitive to hardness changes at smaller surface roughness values as compared to larger surface roughness values. The material hardness has no effect on the detachment acceleration for the same surface roughness values. The knowledge of the acceleration thresholds and their relative magnitudes could be advantageously employed for the development of gripperless manipulation approaches for microcomponent or microdevice handling or for the development of microconveyor platforms for controlled micropart translocation.
Catastrophe Performance Analysis of Steam-Flow-Excited Vibration in the Governing Stage of Large Steam Turbines With Partial Admission
Authors: Li Jianlan , Guo Xuhong , Yu Chen , Huang Shuhong
Published: July 2013

Steam-flow-excited vibration is one of the main faults of large steam turbines. The catastrophe caused by steam-flow-excited vibration brings danger to the operation of units. Therefore, it is significant to identify the impact factors of catastrophe, and master the rules of catastrophe. In this paper, the quantitative analysis of catastrophe performance induced by steam exciting force in the steam turbine governing stage is conducted based on the catastrophe theory, nonlinear vibration theory, and fluid dynamics. The model of steam exciting force in the condition of partial admission in the governing stage is derived. The nonlinear kinetic model of the governing stage with steam exciting force is proposed as well. The cusp catastrophe and bifurcation set of steam-flow-excited vibration are deduced. The rotational angular frequency, the eccentric distance and the opening degrees of the governing valves are identified as the main impact factors to induce catastrophe. Then, the catastrophe performance analysis is conducted for a 300 MW subcritical steam turbine. The rules of catastrophe are discussed, and the system's catastrophe areas are divided. It is discovered that the system catastrophe will not occur until the impact factors satisfy given conditions. Finally, the numerical calculation method is employed to analyze the amplitude response of steam-flow-excited vibration. The results verify the correctness of the proposed analysis method based on the catastrophe theory. This study provides a new way for the catastrophe performance research of steam-flow-excited vibration in large steam turbines.
Flow Diverting for Reducing Wellbore Erosion in Gas-Drilling Shale Gas Wells
Authors: Li Jun , Guo Boyun , Ling Kegang
Published: July 2013

With the downturn in natural gas prices, it is vitally important to reduce the cost of drilling shale gas wells. Gas-percussion drilling has been recently employed in shale gas field development. It increases footage capacity by nearly 60%. However, wellbore erosion by the high-velocity gas has been recognized as a problem that hinders further application of the technology. This paper investigates a potential solution to the problem using a new type of flow-diverting joint (FDJ). The FDJ with exchangeable nozzles can be installed at the shoulder of the drill collar to partially bypass gas flow into the annulus between the drill pipe and open hole. Hydraulics computations with a state-of-the-art computer program indicate that this technique will allow for the use of high-gas injection rate to carry drill cuttings while reducing the gas flow rate through the drill bit. As a result, the gas velocity in the drill collar–open hole annulus can be maintained at a safe level to prevent hole erosion. The reduced gas flow rate through the drill bit also minimizes wellbore enlargement at hole bottom. Sensitivity analyses with the computer program show that the FDJ-nozzle area to bit-nozzle area ratio is directly proportional to the annulus area ratio, and the bypassed flow rate fraction remains constant as drilling progresses. This makes the FDJ system easy to design and practical to use over a long section of hole to be drilled.
Qualitative Description of a Shoulder Ice Barrier-Ice Interaction During Model Tests
Authors: Repetto-Llamazares Ada H. V. , Gürtner Arne , Tobias Gudmestad Ove , Høyland Knut V.
Published: July 2013

This paper describes, qualitatively and through visual observations, the ice-sheet interaction with a shoulder ice barrier (SIB) during model tests. The model tests were performed in the Hamburg Ship Model Basin (HSVA) during July 2007. Since the SIB represents a new concept in ice barrier structures, model tests were intended to evaluate the general performance of the SIB. The paper describes seven different experiments where the ice thickness, the ice flexural strength, and the shoulder angle of the SIB are the parameters which are varied among them. The results are presented in two sections. The first part refers to observations common to all the experiments, where the ice failure mode and shoulder performance are given special attention. The second part describes the phenomena observed in each particular experiment in more detail. The former analysis allows for the visual identification of three phases (as mentioned in previous publications) and gives a deeper insight into the characteristics of each phase. The latter analysis on the contrary, allows us to achieve interesting conclusions about the SIB performance under different ice conditions and with different shoulder inclinations. A comparison between the failure mode observed during the model tests and observations presented in the literature of full scale vertical and sloped structures, ice interaction with rubble accumulation, is performed. The similarities found in the study between the model and full scale observations lead us to assume that the observed model test behavior may be expected during ice-SIB interaction in full scale conditions. However, some events that could be associated with the problems of the model, such as ice scaling, are highlighted. As a conclusion regarding the SIB performance, it is shown that the shoulder section, which is the principal innovation of the concept, satisfactorily accomplishes its task and represents a key modification to traditional ice barriers in generating smaller ice pieces and avoiding ice overriding.
A Finite Macro-Element for Orthotropic Cylindrical Layer Modeling
Authors: Provasi Rodrigo , Martins Clóvis de Arruda
Published: July 2013

The offshore industry is in constant evolution due to the need to reach increasing water depths for new oil fields exploitation. In this scenario, not only are new types of platforms being designed but also new types of risers, including new flexible pipes and umbilical cable configurations. The greatest difficulty to generate a new concept for a riser is to determine if it is viable or not. Flexible pipes and umbilical cables are complicated to model, due to the interactions between their layers and the large number of possible arrangements. To predict the mechanical behavior of flexible pipes and umbilical cables, adequate models are necessary. One can rely on finite element models (FEM), which show a great difficulty in mesh generation and convergence (especially due to the contact pairs). One can also rely on analytical models, which have many limitations due to simplifications (even though they are necessary). Another possible approach is to define macro-elements, which represent a component, instead of classical finite elements (such as tetrahedric ones). Related to that approach, this paper presents a tubular element to model a cylinder with orthotropic material properties. In the model, the displacement and the loads are described by means of Fourier series, making it possible to treat a broad class of loads. The formulation is presented in detail, giving special attention to surface loading modeling. The results obtained in case studies are compared to those of a classical finite element modeling tool with a good agreement.
Stability Analysis of Chatter in Tandem Rolling Mills—Part 1: Single- and Multi-Stand Negative Damping Effect
Authors: Zhao Huyue , Ehmann Kornel F.
Published: July 2013

Many different modes of chatter in rolling and their possible causes have been identified after years of research, yet no clear and definite theory of their mechanics has been fully established and accepted. In this two-part paper, stability of tandem mills is investigated. In Part 1, state-space models of single- and multi-stand chatter are formulated in a rigorous and comprehensive mathematical form. Then, the stability of the rolling system is investigated in the sense of the single- and multi-stand negative damping effects. First, a single-stand chatter model in state-space representation is proposed by coupling a dynamic rolling process model with a structural model for the mill stand. Subsequently, a multi-stand chatter model is developed by incorporating the inter-stand tension variations and the time delay effect of the strip transportation based on the single-stand chatter model. Stability criteria are proposed and stability analyses are performed to create corresponding stability charts in terms of the single- and multi-stand negative damping mechanism through numerical simulations. Particularly, the effect of friction conditions on chatter is examined and an explanation is given for the existence of an optimum friction condition. In Part 2, the regenerative effect and resulting instabilities are examined. Suitable stability criteria for each mechanism are established and stability charts are demonstrated in terms of relevant rolling process parameters.
Error Minimization in Layered Manufacturing Parts by Stereolithography File Modification Using a Vertex Translation Algorithm
Authors: Navangul Gaurav , Paul Ratnadeep , Anand Sam
Published: July 2013

Layered manufacturing (LM) machines use stereolithography (STL) files to build parts by creating continuous slices on top of each other. An STL file approximates the surface of a part with planar triangles. This results in geometric errors being introduced in the part surface during the conversion from the CAD model to the STL file format, which in turn leads to errors in the LM manufactured part. CAD packages have built-in export options to reduce this CAD to STL conversion error. However, this is applied to the entire part geometry which leads to an increase in the file size and preprocessing time in LM machines. This paper presents a new approach to locally reduce this CAD to STL translation error. This approach, referred to as vertex translation algorithm (VTA), compares an STL facet to its corresponding CAD surface, computes the chordal error at multiple points on the STL surface, and translates the point with the maximum chordal error until it lies on the design surface. This translation results in the reduction of the chordal error locally without unnecessarily increasing the size of the STL file. In addition, a facet isolation algorithm (FIA) has also been developed and presented in this paper. This isolation algorithm extracts the STL facets corresponding to the surfaces and features of the part that have to be modified by the translation algorithm. The VTA is applied in conjunction with the FIA on a sample service part to reduce the form and profile error of critical features of the part in order to satisfy the tolerance callouts on the part.
Development of Statically Determinate Plate Rolling Mills That Maintain the Rolls Parallel
Authors: Shen Guangxian , Zheng Yongjiang , Li Ming
Published: July 2013

The design theory of a statically determinate rolling mill, including the redesign of the statically indeterminate characteristic and hyperstatic characteristic, is proposed in this paper. The statically indeterminate characteristic leading to the nonparallel running state of rolls is revealed based on analysis of three rolling mills, including a 2200 mm aluminum foil four-high mill, a 1580 mm PC four-high mill, and a 650 mm bar two-high rolling mill, etc. The hyperstatic characteristic leading to uneven load performance of four-row roller bearing is caused by redundant constraints in the roll system based on analysis of 17 two- and four-high rolling mills. In contemporary four- or six-high plate rolling mills, regular dynamic cross between the rolls is very common during the whole rolling process. Dynamic cross results in excessive axial forces causing frequent burning losses of the end-thrust bearings and leads to serious deviations in the rolling load on both ends of the backup roll. Hence, rolling mills designed for heavy loads and high speeds have yet to operate at their design load and speed in a safe and stable way. According to the analysis of the degrees of freedom of a spatial mechanism, the cause of dynamic cross lies in the statically indeterminate characteristic of the roll system caused by the small clearance in the system. In this paper, the theoretical analysis and experiments invalidate the accepted method of the offsetting of the mill. Furthermore, it is shown that offsetting causes an asymmetrical cross between the rolls. Therefore, it is proposed that offsetting should be eliminated, and additional jack devices should be introduced to maintain the rolls parallel. In addition, bending deflections of the roll induce hyperstatic characteristics of the roll system due to the existence of redundant constraints in the system. The hyperstatic characteristic of the roll system results in uneven load performance of the radial roller bearings and shortens bearing life. In the newly proposed statically determinate four- or six-high plate rolling mill, which can be operated in a safe and stable way under heavy load and high speed working conditions, this problem can also be solved.