bluuebunny/crossref_metadata_2025 huggingface dataset:
In silico study of human aquaporin AQP11 and AQP12 channels
Authors: Calvanese Luisa , Pellegrini‐Calace Marialuisa , Oliva Romina
Published: January 2013

AQP11 and AQP12 are the most distantly related paralogs of the aquaporin family in human. They share indeed a low sequence similarity with other aquaporins and exhibit a modified N‐terminal NPA signature motif. Furthermore, they have an anomalous subcellular localization. The AQP11 and AQP12 biological role remains to be fully clarified and their ability to allow transport of water is still debated. We have built accurate 3D‐models for AQP11 and AQP12 and comprehensively compared their sequence and structure to other known aquaporins. In order to investigate whether they appear compatible or not with water permeability, we especially focused on the amino acid composition and electrostatics of their channels, keeping the structure of the low‐water efficiency AQP0 as a reference system. Our analysis points out a possible alternative ar/R site and shows that these aquaporins feature unique residues at key pore‐lining positions that make the shape, composition and electrostatics of their channel peculiar. Such residues can represent pivotal hints to study and explain the AQP11 and AQP12 biological and molecular function.
Improved performance of organic solar cells by growth optimization of MoO3/CuI double‐anode buffer
Authors: Cattin L. , Bernède J. C. , Lare Y. , Dabos‐Seignon S. , Stephant N. , Morsli M. , Zamora P. P. , Diaz F. R. , del Valle M. A.
Published: January 2013

We investigated the effect of a CuI anode buffer layer (ABL) on the molecular orientation of the copper phthalocyanine (CuPc) in organic photovoltaic cells (OPV cells), and we compare it to the effect of MoO3 buffer layer. While, in the presence of CuI, the CuPc molecules lie down parallel to the substrate, they stand up perpendicular in the case of MoO3. We show that the optical absorption, the morphology, and the J–V characteristics of the OPV cells depends strongly on the orientation of the CuPc molecules. The improvement of the OPV cells performance is related to the property modifications induced by the change in molecule orientation. We show that the improvement of the OPV cell performance through the templating effect of CuI depends strongly on the deposition rate of the CuI, because the CuI thin‐film morphology depends on this deposition rate. In this context, we show that the use of a double‐ABL MoO3/CuI leads to a significant improvement of the cell performance. These results are discussed on the basis of the dual function of MoO3 and CuI. While both of them reduce the hole‐injection barrier, CuI improves the CuPc film absorbance through specific molecular order and MoO3 prevents the OPV cells from leakage‐path formation.
Carrier lifetimes in green emitting InGaN/GaN disks‐in‐nanowire and characteristics of green light emitting diodes
Authors: Jahangir Shafat , Banerjee Animesh , Bhattacharya Pallab
Published: January 2013

Improvement in the internal quantum efficiency (IQE) of InGaN/GaN disks‐in‐nanowires by surface passivation is demonstrated. The highest IQE achieved through surface passivation for green emitting (λ=540 nm) InGaN/GaN disks‐in‐nanowires is ∼53%. Radiative and nonradiative carrier lifetimes are calculated for as‐grown and surface passivated green emitting disks‐in‐nanowires. Passivated green sample exhibits a room temperature radiative lifetime of ∼748 ps, which is much smaller than that of equivalent quantum wells. Electroluminescence measurements on passivated green light emitting diodes containing InGaN disks demonstrate no roll over or efficiency droop up to 375 A/cm2, and exhibit a blue‐shift of 7 nm in peak wavelength. An enhancement in the light output due to surface passivation is observable in the relative external quantum efficiency of the surface passivated devices as compared with the as‐grown samples. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An analytic solution for linear gravity waves in a channel as a test for numerical models using the non‐hydrostatic, compressible Euler equations
Authors: Baldauf Michael , Brdar Slavko
Published: January 2013

A slightly modified version of the idealized test set‐up used by Skamarock and Klemp is proposed: the quasi linear two‐dimensional expansion of sound and gravity waves in a flat channel induced by a weak warm bubble. For this test case an exact analytic solution of the linearized compressible, non‐hydrostatic Euler equations for a shallow atmosphere has been derived. This solution can be used as a benchmark to assess compressible, non‐hydrostatic dynamical cores which are the basis for many of today's, and probably most of the future, atmospheric models. Comparisons and convergence studies of two quite differently designed numerical limited‐area simulation models, COSMO and DUNE, against this analytic solution are performed.
Quantitative Analysis of Dynamic Fault Trees Based on the Structure Function
Authors: Merle G. , Roussel J.‐M. , Lesage J.‐J.
Published: January 2013

This paper presents a probabilistic model of dynamic gates which allows to perform the quantitative analysis of any dynamic fault tree (DFT) from its structure function. Both these probabilistic models and the quantitative analysis which can be performed thanks to them can accommodate any failure distribution of basic events. We illustrate our approach on a DFT example from the literature. Copyright © 2013 John Wiley & Sons, Ltd.
Relational configurations with information intermediaries: The effect of firm‐investment bank ties on expected acquisition performance
Authors: Sleptsov Alexander , Anand Jaideep , Vasudeva Gurneeta
Published: January 2013

Recognizing information‐related problems in acquisition transactions, we study how the characteristics of acquiring firms' relationships with information brokers or intermediaries like investment banks affect firms' access to acquisition‐related information, thus influencing expected acquisition performance. We propose that relational configurations that enhance the intermediaries' ability and willingness provide the most beneficial and appropriate information to acquiring firms. We find that acquirers' expected acquisition performance increases with the number of prior transactions with investment banks but decreases when relationships with banks become exclusive. Further, the positive effect of number of prior transactions becomes even stronger for less related acquisitions. Our study provides insights on the beneficial performance implications of competition in multiple but nonexclusive relationships with information intermediaries such as investment banks. Copyright © 2013 John Wiley & Sons, Ltd.
Creating incentives for innovation? The relationship between pay dispersion in R&D groups and firm innovation performance
Authors: Yanadori Yoshio , Cui Victor
Published: January 2013

Innovation is a critical organizational outcome for its potential to generate competitive advantage. While the contribution of knowledge workers to the generation of innovation is widely recognized, little is known about how organizational incentive mechanisms stimulate or inhibit these workers' behaviors that promote innovation. This study examines the relationship between pay dispersion in R&D groups and firm innovation using employee‐level compensation data in US high‐technology firms. The results show that (1) pay dispersion in R&D groups is negatively related to firm innovation and (2) this negative relationship is alleviated in firms with greater financial slack. This study contributes to the innovation literature by illuminating the implications of organizational incentive systems for successful innovation. Copyright © 2013 John Wiley & Sons, Ltd.
Tailor‐Made Micro‐Object Optical Sensor Based on Mesoporous Pellets for Visual Monitoring and Removal of Toxic Metal Ions from Aqueous Media
Authors: El‐Safty Sherif A. , Shenashen M. A. , Shahat A.
Published: January 2013

Methods for the continuous monitoring and removal of ultra‐trace levels of toxic inorganic species (e.g., mercury, copper, and cadmium ions) from aqueous media such as drinking water and biological fluids are essential. In this paper, the design and engineering of a simple, pH‐dependent, micro‐object optical sensor is described based on mesoporous aluminosilica pellets with an adsorbed dressing receptor (a porphyrinic chelating ligand). This tailor‐made optical sensor permits ultra‐fast (≤ 60 s), specific, pH‐dependent visualization and removal of Cu2+, Cd2+, and Hg2+ at sub‐picomolar concentrations (∼10−11 mol dm−3) from aqueous media, including drinking water and a suspension of red blood cells. The acidic active acid sites of the pellets consist of heteroatoms arranged around uniformly shaped pores in 3D nanoscale gyroidal mesostructures densely coated with the chelating ligand. The sensor can be used in batch mode, as well as in a flow‐through system in which sampling, target ion recognition and removal, and analysis are integrated in a highly automated and efficient manner. Because the pellets exhibit long‐term stability, reproducibility, and versatility over a number of analysis/regeneration cycles, they can be expected to be useful for the fabrication of inexpensive sensor devices for naked‐eye detection of toxic pollutants.
Vibration Method to Detect Liquid–Solid Fraction and Final Solidifying End for Continuous Casting Slab
Authors: Wang Zhaofeng , Wang Xudong , Liu Fubin , Yao Man , Zhang Xiaobing , Yang Longsheng , Lu Hongzhou , Wang Xiong
Published: January 2013

Accurate measurement of liquid–solid fraction of casting slab in the secondary cooling zone and precise prediction of final solidifying end of casting slab have momentous significances for internal defects improvement of continuous casting slabs, such as the segregation and shrinkage porosity etc. However, the on‐line detection of slab solidification processing and final solidifying end haven't accomplished, which have been acknowledged as metallurgy problem all over the world. The paper presents a novel method, which called vibration method, to detect the liquid fraction and locate the final solidifying end of continuous casting slab. A physical simulation device using the materials of organic glass and water has been set up according to the similarity theory. Basing on theoretical deduction, physical experiment and numerical simulation, the research results provide guidance and reference for the on‐line detection of liquid–solid fraction and final solidifying end of the slab.
Cross‐cultural epistemological orientations to socioscientific issues
Authors: Zeidler Dana L. , Herman Benjamin C. , Ruzek Mitch , Linder Anne , Lin Shu‐Sheng
Published: January 2013

The purpose of this investigation was to examine, from a cross‐cultural perspective, students' epistemological patterns of reasoning about socioscientific issues (SSI), and to identify potential interactions of cultural and scientific identity. Mediating factors associated with students' argumentation and discourse about SSI, as well as the public's understanding of science, has been identified as an important area of investigation in the field of science education. This mixed‐methods design included over 300 students from Jamaica, South Africa, Sweden, Taiwan, and the United States. Students responded to instruments designed to assess their epistemological conceptualizations and justifications related to distributive justice, allocation of scarce medical resources, and epistemological beliefs over five dimensions related to scientific knowledge. Four iterations of a coding scheme produced over 97% inter‐rater agreement for four independent coders. Results indicate there is a consistent trend toward epistemological congruity across cultures within inductively derived themes of: (1) Fairness; (2) Pragmatism; (3) Emotive Reasoning; (4) Utility; and (5) Theological Issues. Moreover, there were no discernable differences in terms of how students from these countries presented their beliefs on the sub‐categories of each of the five major categories. It appears that students displayed a high degree of congruence with respect to how they frame their reasoning on this SSI as well as their justifications for their epistemological beliefs. There were statistically significant differences regarding the ability to raise scientifically relevant questions among countries. Commonalities as well as distinguishing characteristics in epistemological orientations are compared and contrasted and connections to a model of socioscientific reasoning with implications for research and pedagogy are discussed. © 2013 Wiley Periodicals, Inc. J Res Sci Teach 50:251–283, 2013
Comparative toxicity of pyrethroid insecticides to two estuarine crustacean species, Americamysis bahia and Palaemonetes pugio
Authors: DeLorenzo Marie E. , Key Peter B. , Chung Katy W. , Sapozhnikova Yelena , Fulton Michael H.
Published: January 2013

Pyrethroid insecticides are widely used on agricultural crops, as well as for nurseries, golf courses, urban structural and landscaping sites, residential home and garden pest control, and mosquito abatement. Evaluation of sensitive marine and estuarine species is essential for the development of toxicity testing and risk‐assessment protocols. Two estuarine crustacean species, Americamysis bahia (mysids) and Palaemonetes pugio (grass shrimp), were tested with the commonly used pyrethroid compounds, lambda‐cyhalothrin, permethrin, cypermethrin, deltamethrin, and phenothrin. Sensitivities of adult and larval grass shrimp and 7‐day‐old mysids were compared using standard 96‐h LC50 bioassay protocols. Adult and larval grass shrimp were more sensitive than the mysids to all the pyrethroids tested. Larval grass shrimp were approximately 18‐fold more sensitive to lambda‐cyhalothrin than the mysids. Larval grass shrimp were similar in sensitivity to adult grass shrimp for cypermethrin, deltamethrin, and phenothrin, but larvae were approximately twice as sensitive to lambda‐cyhalothrin and permethrin as adult shrimp. Acute toxicity to estuarine crustaceans occurred at low nanogram per liter concentrations of some pyrethroids, illustrating the need for careful regulation of the use of pyrethroid compounds in the coastal zone. © 2013 Wiley Periodicals, Inc. Environ Toxicol 29: 1099–1106, 2014.
Biparietal diameter at 11–13 weeks' gestation in fetuses with open spina bifida
Authors: Khalil A. , Coates A. , Papageorghiou A. , Bhide A. , Thilaganathan B.
Published: January 2013

Objective

To ascertain the reported association between reduced biparietal diameter (BPD) at 11–13 weeks' gestation and open spina bifida and to investigate its predictive value in a single‐center study.

Methods

This was a retrospective study of fetuses in which BPD was measured at 11–13 weeks' gestation, including 27 fetuses with isolated open spina bifida subsequently diagnosed at 16–24 weeks and 7775 unaffected controls. BPD values were converted into multiples of the expected median (MoM) after adjustment for crown–rump length and maternal characteristics. Multivariable logistic regression analysis was used to determine the maternal characteristics significantly associated with spina bifida. The performance of screening was determined by receiver–operating characteristics curve analysis. BPD values at 11–13 weeks' gestation were compared with those measured in the second trimester using Z‐scores.

Results

BPD values at 11–13 weeks' gestation were below the 5th centile in 44.4% of cases of open spina bifida. In these fetuses, the median BPD MoM value was significantly smaller than that in the control group (0.930 vs 0.998 MoM; P < 0.0001). Multivariable logistic regression analysis showed a significant contribution from maternal age (P = 0.008) and BMI (P = 0.028) to the association between BPD MoM and spina bifida. The detection rate using BPD measurements in the first trimester was 55.6% with a false‐positive rate of 11.6%. In fetuses with open spina bifida, the BPD Z‐scores were significantly lower at 16–24 weeks compared to those recorded at 11–13 weeks (median, –1.71 (range, –3.98 to –0.20) vs –1.30 (–3.75 to 2.61); P = 0.006).

Conclusion

Fetuses with open spina bifida have a smaller BPD in the first trimester. This observation may be useful in early screening. It is likely that a combination of maternal characteristics such as age and BMI, fetal BPD and maternal serum alpha‐fetoprotein measured in the first trimester would provide a clinically useful screening test for open spina bifida. Copyright © 2013 ISUOG. Published by John Wiley & Sons Ltd.
Heavy metal tolerance in the psychrotolerant Cryptococcus sp. isolated from deep‐sea sediments of the Central Indian Basin
Authors: Singh Purnima , Raghukumar Chandralata , Parvatkar Rajesh Ramnath , Mascarenhas‐Pereira M. B. L.
Published: January 2013

A deep‐sea isolate of the psychrotolerant yeast Cryptococcus sp. (NIOCC#PY13) obtained from polymetallic nodule‐bearing sediments of the Central Indian Basin was examined for its capacity to grow in the presence of various concentrations of the heavy metal salts i.e., ZnSO4, CuSO4, Pb(CH3COO)2 and CdCl2. It demonstrated considerable growth in the presence of 100 mg/l concentrations of the above‐mentioned four heavy metal salts both at 30°C and 15°C. This strain tolerated comparatively higher levels of these four metal salts than other deep‐sea and terrestrial yeast isolates belonging to Cryptococcus, Rhodotorula, Rhodosporidium and Sporidiobolus spp. Optimum pH for growth of this isolate was in the range of 6–8 in the presence of heavy metal salts at these two temperatures. Scanning electron microscopic (SEM) studies exhibited altered cell surface morphology of the cells under the influence of heavy metals compared to that with control. The adsorption of heavy metals to the cells was demonstrated by FTIR and EDAX analysis. As evidenced by atomic absorption spectrophotometric (AAS) analysis, about 30–90% of the heavy metals were removed from the culture supernatant after 4 days of growth at 30°C. This deep‐sea yeast isolate appears to be a potential candidate for bioremediation of metal‐contaminated sites. Moreover, its metal tolerance properties provide a significant insight into its ecological role and adaptations to growth in such extreme conditions. Copyright © 2013 John Wiley & Sons, Ltd.
Postnatal Development of Echolocation Abilities in a Bottlenose Dolphin (Tursiops truncatus): Temporal Organization
Authors: Favaro Livio , Gnone Guido , Pessani Daniela
Published: January 2013

In spite of all the information available on adult bottlenose dolphin (Tursiops truncatus) biosonar, the ontogeny of its echolocation abilities has been investigated very little. Earlier studies have reported that neonatal dolphins can produce both whistles and burst‐pulsed sounds just after birth and that early‐pulsed sounds are probably a precursor of echolocation click trains. The aim of this research is to investigate the development of echolocation signals in a captive calf, born in the facilities of the Acquario di Genova. A set of 81 impulsive sounds were collected from birth to the seventh postnatal week and six additional echolocation click trains were recorded when the dolphin was 1 year old. Moreover, behavioral observations, concurring with sound production, were carried out by means of a video camera. For each sound we measured five acoustic parameters: click train duration (CTD), number of clicks per train, minimum, maximum, and mean click repetition rate (CRR). CTD and number of clicks per train were found to increase with age. Maximum and mean CRR followed a decreasing trend with dolphin growth starting from the second postnatal week. The calf's first head scanning movement was recorded 21 days after birth. Our data suggest that in the bottlenose dolphin the early postnatal weeks are essential for the development of echolocation abilities and that the temporal features of the echolocation click trains remain relatively stable from the seventh postnatal week up to the first year of life. Zoo Biol. xx:xx–xx, 2012. © 2013 Wiley Periodicals Inc. Zoo Biol. 32:210–215, 2013. © 2013 Wiley Periodicals Inc.
Laparoscopic Surgery for Rectal Cancer: Outcomes in 513 Patients
Authors: Asoglu Oktar , Balik Emre , Kunduz Enver , Yamaner Sumer , Akyuz Ali , Gulluoglu Mine , Kapran Yersu , Bugra Dursun
Published: January 2013

Background

Few reports have demonstrated the feasibility and efficacy of laparoscopic resection in patients with rectal cancer (RC). The objective of the present study was to assess the effectiveness of laparoscopic resection for RC, with an emphasis on perioperative variables and long‐term oncological outcomes.

Methods

This prospective study was carried out between January 2005 and September 2010 and included 513 patients diagnosed with RC who underwent laparoscopic surgery. Patients with locally advanced RC (cT3/cT4 or N+) received neoadjuvant treatment. Adjuvant treatment was applied to patients with stage II/III disease or according to the neoadjuvant protocol. All patients were followed‐up prospectively for the evaluation of complications and oncological outcome. Survival rate analysis was performed using the Kaplan–Meier method.

Results

Sphincter‐preserving surgery was performed on 389 patients, and the remaining 124 patients underwent abdominoperineal resection. Perioperative mortality occurred in only one patient (0.2 %), and 27 (5.3 %) intraoperative complications were recorded. The most common postoperative complication was anastomotic leakage (5.5 %). The conversion rate was 6.4 %. The mean number of harvested lymph nodes was 23.6 ± 13. The mean distance to the distal margin was 2.6 ± 1.9 (0–7) cm. Distal margin positivity was detected in 9 (1.7 %) patients. The circumferential margin was positive in 39 (7.6 %) cases. After a median follow‐up period of 30 (1–78) months, recurrence occurred in a total of 59 patients (11.5 %). Local recurrence was detected in 16 patients (3.1 %), and both local and distant recurrence was found in 7 patients (1.4 %). Distant recurrence only was detected in 43 patients (8.4 %). The overall 5‐year survival rate was 84 %, and the 5‐year disease‐free survival rate was 77.4 %. The local recurrence‐free survival rate was 98.4 % at 2 years, 95.7 % at 3 years, and 94.3 % at 5 years.

Conclusions

Our results, together with the review of the literature, clearly demonstrate that laparoscopic resection for RC is a feasible method at specialized high‐volume centers. The long‐term outcomes are at least as good as those from open surgery as long as the principles of oncologic surgery are respected and faithfully performed.
Left ventricular noncompaction (LVNC) and low mitochondrial membrane potential are specific for Barth syndrome
Authors: Karkucinska‐Wieckowska Agnieszka , Trubicka Joanna , Werner Bozena , Kokoszynska Katarzyna , Pajdowska Magdalena , Pronicki Maciej , Czarnowska Elzbieta , Lebiedzinska Magdalena , Sykut‐Cegielska Jolanta , Ziolkowska Lidia , Jaron Weronika , Dobrzanska Anna , Ciara Elzbieta , Wieckowski Mariusz R. , Pronicka Ewa
Published: January 2013

Barth syndrome (BTHS) is an X‐linked mitochondrial defect characterised by dilated cardiomyopathy, neutropaenia and 3‐methylglutaconic aciduria (3‐MGCA). We report on two affected brothers with c.646G > A (p.G216R) TAZ gene mutations. The pathogenicity of the mutation, as indicated by the structure‐based functional analyses, was further confirmed by abnormal monolysocardiolipin/cardiolipin ratio in dry blood spots of the patients as well as the occurrence of this mutation in another reported BTHS proband. In both brothers, 2D‐echocardiography revealed some features of left ventricular noncompaction (LVNC) despite marked differences in the course of the disease; the eldest child presented with isolated cardiomyopathy from late infancy, whereas the youngest showed severe lactic acidosis without 3‐MGCA during the neonatal period. An examination of the patients’ fibroblast cultures revealed that extremely low mitochondrial membrane potentials (mtΔΨ about 50 % of the control value) dominated other unspecific mitochondrial changes detected (respiratory chain dysfunction, abnormal ROS production and depressed antioxidant defense). 1) Our studies confirm generalised mitochondrial dysfunction in the skeletal muscle and the fibroblasts of BTHS patients, especially a severe impairment in the mtΔΨ and the inhibition of complex V activity. It can be hypothesised that impaired mtΔΨ and mitochondrial ATP synthase activity may contribute to episodes of cardiac arrhythmia that occurred unexpectedly in BTHS patients. 2) Severe lactic acidosis without 3‐methylglutaconic aciduria in male neonates as well as an asymptomatic mild left ventricular noncompaction may characterise the ranges of natural history of Barth syndrome.
Antioxidant Activity of Sesamol in Soybean Oil Under Frying Conditions
Authors: Hwang Hong‐Sik , Winkler‐Moser Jill K. , Bakota Erica L. , Berhow Mark A. , Liu Sean X.
Published: January 2013

Antioxidant activity of sesamol was investigated in soybean oil using a miniaturized frying experiment with potato cubes fried at 180 °C. Oxidation of soybean oil was determined by gel permeation chromatography for polymerized triacylglycerols and by 1H‐NMR spectroscopy for reactions at reactive sites of soybean oil molecules including olefinic, bisallylic and allylic protons during frying. Sesamol showed lower antioxidant activity than 0.02 % (w/w) tert‐butylhydroquinone (TBHQ) at the same molar concentration. Higher concentrations of sesamol provided better antioxidant effects indicating that no prooxidant activity occurred. Sesamol in this frying test showed better results than 0.02 % TBHQ when the concentration was as high as 0.66 % by weight. An HPLC experiment showed that the concentration of sesamol decreased sharply during frying. Thermogravimetric analysis indicated that sesamol is highly volatile and easily oxidizes when exposed to air. To overcome this problem, two multiple addition methods were evaluated in which sesamol was added portion by portion every hour. The multiple additions of divided portions of 0.66 % (w/w) sesamol maintained the concentration of sesamol at the minimum of 0.04–0.06 % throughout the frying process and showed improved antioxidant activity compared to one single addition of 0.66 % sesamol at the beginning of frying. One of the multiple addition methods showed 28, 18, 59, and 27 % less polymerized triacylglycerols and losses of olefinic, bisallylic and allylic protons, respectively, than 0.02 % TBHQ after 8‐h frying. This study shows that sesamol can be used as an alternative for synthetic antioxidants for frying oil.
Studying the RNA silencing pathway with the p19 protein
Authors: Danielson Dana C. , Pezacki John Paul
Published: January 2013

The origins of the RNA silencing pathway are in defense against invading viruses and in response, viruses have evolved counter‐measures to interfere with the host pathway. The p19 protein is expressed by tombusviruses as a suppressor of RNA silencing and functions to sequester small RNA duplexes, thereby preventing induction of the pathway. p19 exhibits size‐specific and sequence‐independent binding of its small RNA ligands, binding with high affinity to duplexes 20–22 nucleotides long. p19's binding specificity and its ability to sequester small RNAs has made it a unique protein‐based tool for probing the molecular mechanisms of the highly complex RNA silencing pathway in a variety of systems. Furthermore, protein engineering of this ‘molecular caliper’ promises novel applications in biotechnology and medicine where small RNA molecules are of remarkable interest given their potent gene regulatory abilities.
Partially failing ALT flap salvaged using its own distal run‐off vessel
Authors: Chang Kao‐Ping , Lai Chung‐Sheng
Published: January 2013

This case report presents salvage of a partially failing anterolateral thigh flap. A 37‐year‐old male, a victim of head and neck squamous cell carcinoma, received tumor ablation and a chimeric anterolateral thigh skin and vastus lateralis muscle flap reconstruction. Before ligation of pedicle, both skin and muscle portions had robust blood supply; however, only the vastus lateralis muscular component remained revascularized rather than the skin paddle with some underlying muscle 30 minutes after patent microanastomosis with recipient vessel. The skin paddle flap was then salvaged by perfusion from a new anastomosis between the distal run‐off of the pedicle artery and the perforator artery of this skin flap. From this experience, we recommend to preserve longer distal run‐off of the pedicle in chimeric anterolateral thigh flap harvest for necessary “self‐revascularization” in similar cases.
Influence of the Reynolds number on the vortical structures in the logarithmic region of turbulent boundary layers
Authors: Herpin Sophie , Stanislas Michel , Foucaut Jean Marc , Coudert Sebastien
Published: January 2013

Near-wall turbulence is a subject of prime importance for turbulence modelling. Coherent structures were hypothesized early by Theodorsen in this flow region and have been the subject of intensive research ever since. The overall organization of these coherent structures has now been well assessed. Vortical structures appear to play a key role in this organization. Their characteristics and scaling have been studied by many authors as listed in the Introduction. The present contribution to the subject relies on high-resolution stereo particle image velocimetry (PIV) to study these structures. High-quality measurements are performed in a thick turbulent boundary layer at different values of the Reynolds number. The data quality is first assessed by comparing the statistics to those of hot-wire anemometry and direct numerical simulation data. The agreement between the two appears satisfactory. The PIV data are then processed in order to extract the vortex characteristics in a streamwise plane and in a spanwise plane. The statistical characteristics of these vortices are analysed in detail as a function of wall distance. The scaling of the data appears to be universal when the Kolmogorov scales are used. These results are analysed and discussed in terms of their probability density functions. This leads to a question regarding the Kolmogorov cascade in this region of the flow.
Bound-state formation in interfacial turbulence: direct numerical simulations and theory
Authors: Pradas M. , Kalliadasis S. , Nguyen P.-K. , Bontozoglou V.
Published: January 2013

We examine pulse interaction and bound-state formation in interfacial turbulence using the problem of a falling liquid film as a model system. We perform direct numerical simulations (DNSs) of the full Navier–Stokes equations and associated wall and free-surface boundary conditions and we examine both analytically and numerically a low-dimensional (LD) model for the film. For a two-pulse system, DNSs reveal the existence of very rich and complex pulse interactions, characterized by either overdamped, underdamped or self-sustained oscillating behaviours, all of them found to be in excellent agreement with LD results. Having demonstrated the reliability of the LD model for two-pulse systems/smaller domains, we use it to investigate larger domains with many interacting pulses, where DNSs are computationally expensive. We demonstrate that such systems are likely to be dominated by a self-sustained oscillatory dynamics.
Turbulent drag reduction using fluid spheres
Authors: Gillissen J. J. J.
Published: January 2013

Using direct numerical simulations of turbulent Couette flow, we predict drag reduction in suspensions of neutrally buoyant fluid spheres, of diameter larger than the Kolmogorov length scale. The velocity fluctuations are enhanced in the streamwise direction, and reduced in the cross-stream directions, which is similar to the more studied case of drag reduction using polymers. Despite these similarities, the drag reduction mechanism is found to originate in the logarithmic region, while the buffer region contributes to a slight drag increase, which is opposite to polymer-induced drag reduction. Another striking difference is the reduction of the turbulent energy at the large scales and an enhancement at the small scales.
Modelling single- and tandem-bubble dynamics between two parallel plates for biomedical applications
Authors: Hsiao C.-T. , Choi J.-K. , Singh S. , Chahine G. L. , Hay T. A. , Ilinskii Yu. A. , Zabolotskaya E. A. , Hamilton M. F. , Sankin G. , Yuan F. , Zhong P.
Published: January 2013

Carefully timed tandem microbubbles have been shown to produce directional and targeted membrane poration of individual cells in microfluidic systems, which could be of use in ultrasound-mediated drug and gene delivery. This study aims at contributing to the understanding of the mechanisms at play in such an interaction. The dynamics of single and tandem microbubbles between two parallel plates is studied numerically and analytically. Comparisons are then made between the numerical results and the available experimental results. Numerically, assuming a potential flow, a three-dimensional boundary element method (BEM) is used to describe complex bubble deformations, jet formation, and bubble splitting. Analytically, compressibility and viscous boundary layer effects along the channel walls, neglected in the BEM model, are considered while shape of the bubble is not considered. Comparisons show that energy losses modify the bubble dynamics when the two approaches use identical initial conditions. The initial conditions in the boundary element method can be adjusted to recover the bubble period and maximum bubble volume when in an infinite medium. Using the same conditions enables the method to recover the full dynamics of single and tandem bubbles, including large deformations and fast re-entering jet formation. This method can be used as a design tool for future tandem-bubble sonoporation experiments.
The preferred mode of incompressible jets: linear frequency response analysis
Authors: Garnaud X. , Lesshafft L. , Schmid P. J. , Huerre P.
Published: January 2013

The linear amplification of axisymmetric external forcing in incompressible jet flows is investigated within a fully non-parallel framework. Experimental and numerical studies have shown that isothermal jets preferably amplify external perturbations for Strouhal numbers in the range $0. 25\leq {\mathit{St}}_{D} \leq 0. 5$, depending on the operating conditions. In the present study, the optimal forcing of an incompressible jet is computed as a function of the excitation frequency. This analysis characterizes the preferred amplification as a pseudo-resonance with a dominant Strouhal number of around $0. 45$. The flow response at this frequency takes the form of a vortical wavepacket that peaks inside the potential core. Its global structure is characterized by the cooperation of local shear-layer and jet-column modes.
Noise generation in the solid Earth, oceans and atmosphere, from nonlinear interacting surface gravity waves in finite depth
Authors: Ardhuin Fabrice , Herbers T. H. C.
Published: January 2013

Oceanic pressure measurements, even in very deep water, and atmospheric pressure or seismic records, from anywhere on Earth, contain noise with dominant periods between 3 and 10 s, which is believed to be excited by ocean surface gravity waves. Most of this noise is explained by a nonlinear wave–wave interaction mechanism, and takes the form of surface gravity waves, acoustic or seismic waves. Previous theoretical work on seismic noise focused on surface (Rayleigh) waves, and did not consider finite-depth effects on the generating wave kinematics. These finite-depth effects are introduced here, which requires the consideration of the direct wave-induced pressure at the ocean bottom, a contribution previously overlooked in the context of seismic noise. That contribution can lead to a considerable reduction of the seismic noise source, which is particularly relevant for noise periods larger than 10 s. The theory is applied to acoustic waves in the atmosphere, extending previous theories that were limited to vertical propagation only. Finally, the noise generation theory is also extended beyond the domain of Rayleigh waves, giving the first quantitative expression for sources of seismic body waves. In the limit of slow phase speeds in the ocean wave forcing, the known and well-verified gravity wave result is obtained, which was previously derived for an incompressible ocean. The noise source of acoustic, acoustic-gravity and seismic modes are given by a mode-specific amplification of the same wave-induced pressure field near zero wavenumber.
A falling film on a porous medium
Authors: Samanta A. , Goyeau B. , Ruyer-Quil C.
Published: January 2013

A gravity-driven falling film on a saturated porous inclined plane is studied via a continuum approach, where the liquid and porous layers are considered as a single composite layer. Using a weighted residual technique, a two-equation model is derived in terms of the local flow rate$q(x, t)$and the entire layer thickness$H(x, t)$. Its linear stability analysis has been satisfactorily compared to the results of the Orr–Sommerfeld problem. The principal effect of the porous substrate on the film flow is to displace the liquid–porous interface to an effective liquid–solid interface located at the lower boundary of the upper momentum boundary layer in the porous medium. The stability and dynamics of the film is thus only weakly affected by the presence of a permeable substrate. In both the linear and the nonlinear regimes, the spatial response of a falling film on a porous medium is not very different from that observed on an impermeable inclined wall. However, the wavy motion of the film triggers a significant exchange of mass at the liquid–porous interface.
Formation regimes of vortex rings in negatively buoyant starting jets
Authors: Marugán-Cruz C. , Rodríguez-Rodríguez J. , Martínez-Bazán C.
Published: January 2013

The formation of vortex rings in negatively buoyant starting jets has been studied numerically for different values of the Richardson number, $\mathit{Ri}$, covering the range of weak to moderate buoyancy effects ($0\leq \mathit{Ri}\leq 0. 20$). Two different regimes have been identified in the vortex formation and the transition between them takes place at $\mathit{Ri}\approx 0. 03$. The vorticity distribution inside the vortex ring after pinching off from the trailing stem as well as the total amount of circulation it encloses (characterized by the formation number, $F$) show different behaviours with the Richardson number in the two regimes. The differences are associated with the different mechanisms by which the head vortex absorbs the circulation injected by the starting jet. While secondary vortices are engulfed by the leading vortex before separating from the trailing jet in the weak buoyancy effects regime ($0\lt \mathit{Ri}\lt 0. 03$), this phenomenon is not observed in the moderate buoyancy effects regime ($0. 03\lt \mathit{Ri}\lt 0. 2$). Moreover it is shown that the formation number of a negatively buoyant vortex ring can be determined by considering that its dynamics are similar to that of a neutrally buoyant vortex but propagating with velocity corresponding to the negatively buoyant one. Based on this simple idea, a phenomenological model is presented to describe quantitatively the evolution of the formation number with the Richardson number, $F(\mathit{Ri})$, obtained numerically. In addition, the limitations of different vortex identification methods used to evaluate the vortex properties in buoyant flows are discussed.
Instabilities of coupled density fronts and their nonlinear evolution in the two-layer rotating shallow-water model: influence of the lower layer and of the topography
Authors: Ribstein Bruno , Zeitlin Vladimir
Published: January 2013

We undertake a detailed analysis of linear stability of geostrophically balanced double density fronts in the framework of the two-layer rotating shallow-water model on the $f$-plane with topography, the latter being represented by an escarpment beneath the fronts. We use the pseudospectral collocation method to identify and quantify different kinds of instabilities resulting from phase locking and resonances of frontal, Rossby, Poincaré and topographic waves. A swap in the leading long-wave instability from the classical barotropic form, resulting from the resonance of two frontal waves, to a baroclinic form, resulting from the resonance of Rossby and frontal waves, takes place with decreasing depth of the lower layer. Nonlinear development and saturation of these instabilities, and of an instability of topographic origin, resulting from the resonance of frontal and topographic waves, are studied and compared with the help of a new-generation well-balanced finite-volume code for multilayer rotating shallow-water equations. The results of the saturation for different instabilities are shown to produce very different secondary coherent structures. The influence of the topography on these processes is highlighted.
A submerged cylinder wave energy converter
Authors: Crowley S. , Porter R. , Evans D. V.
Published: January 2013

A novel design concept for a wave energy converter (WEC) is presented and analysed. Its purpose is to balance the theoretical capacity for power absorption against engineering design issues which plague many existing WEC concepts. The WEC comprises a fully submerged buoyant circular cylinder tethered to the sea bed by a simple mooring system which permits coupled surge and roll motions of the cylinder. Inside the cylinder a mechanical system of pendulums rotate with power generated by the relative rotation rates of the pendulums and the cylinder. The attractive features of this design include: making use of the mooring system as a passive component of the power take off (PTO); using a submerged device to protect it from excessive forces associated with extreme wave conditions; locating the PTO within the device and using a PTO mechanism which does not need to be constrained; exploiting multiple resonances of the system to provide a broad-banded response. A mathematical model is developed which couples the hydrodynamic waves forces on the device with the internal pendulums under a linearized framework. For a cylinder spanning a wave tank (equivalent to a two-dimensional assumption) maximum theoretical power for this WEC device is limited to 50 % maximum efficiency. However, numerical results show that a systematically optimized system can generate theoretical efficiencies of more than 45 % over a 6 s range of wave period containing most of the energy in a typical energy spectrum. Furthermore, three-dimensional results for a cylinder of finite length provide evidence that a cylinder device twice the length of its diameter can produce more than its own length in the power of an equivalent incident wave crest.
An experimental study of edge effects on rotating-disk transition
Authors: Imayama Shintaro , Henrik Alfredsson P. , Lingwood R. J.
Published: January 2013

The onset of transition for the rotating-disk flow was identified by Lingwood (J. Fluid. Mech., vol. 299, 1995, pp. 17–33) as being highly reproducible, which motivated her to look for absolute instability of the boundary-layer flow; the flow was found to be locally absolutely unstable above a Reynolds number of 507. Global instability, if associated with laminar–turbulent transition, implies that the onset of transition should be highly repeatable across different experimental facilities. While it has previously been shown that local absolute instability does not necessarily lead to linear global instability: Healey (J. Fluid. Mech., vol. 663, 2010, pp. 148–159) has shown, using the linearized complex Ginzburg–Landau equation, that if the finite nature of the flow domain is accounted for, then local absolute instability can give rise to linear global instability and lead directly to a nonlinear global mode. Healey (J. Fluid. Mech., vol. 663, 2010, pp. 148–159) also showed that there is a weak stabilizing effect as the steep front to the nonlinear global mode approaches the edge of the disk, and suggested that this might explain some reports of slightly higher transition Reynolds numbers, when located close to the edge. Here we look closely at the effects the edge of the disk have on laminar–turbulent transition of the rotating-disk boundary-layer flow. We present data for three different edge configurations and various edge Reynolds numbers, which show no obvious variation in the transition Reynolds number due to proximity to the edge of the disk. These data, together with the application (as far as possible) of a consistent definition for the onset of transition to others’ results, reduce the already relatively small scatter in reported transition Reynolds numbers, suggesting even greater reproducibility than previously thought for ‘clean’ disk experiments. The present results suggest that the finite nature of the disk, present in all real experiments, may indeed, as Healey (J. Fluid. Mech., vol. 663, 2010, pp. 148–159) suggests, lead to linear global instability as a first step in the onset of transition but we have not been able to verify a correlation between the transition Reynolds number and edge Reynolds number.
Compressible air entrapment in high-speed drop impacts on solid surfaces
Authors: Liu Yuan , Tan Peng , Xu Lei
Published: January 2013

Using high-speed photography coupled with optical interference, we experimentally study the air entrapment during a liquid drop impacting a solid substrate. We observe the formation of a compressed air film before the liquid touches the substrate, with internal pressure considerably higher than the atmospheric value. The degree of compression highly depends on the impact velocity, as explained by balancing the liquid deceleration with the large pressure of the compressed air. After contact, the air film expands vertically at the edge, reducing its pressure within a few tens of microseconds and producing a thick rim on the perimeter. This thick-rimmed air film subsequently contracts into an air bubble, governed by the complex interaction between surface tension, inertia and viscous drag. Such a process is universally observed for impacts above a few centimetres high.
Experimental evidence of convective and absolute instabilities in rotating Hagen–Poiseuille flow
Authors: Shrestha K. , Parras L. , Del Pino C. , Sanmiguel-Rojas E. , Fernandez-Feria R.
Published: January 2013

Experimental results for instabilities present in a rotating Hagen–Poiseuille flow are reported in this study through fluid flow visualization. First, we found a very good agreement between the experimental and the theoretical predictions for the onset of convective hydrodynamic instabilities. Our analysis in a space–time domain is able to obtain quantitative data, so the wavelengths and the frequencies are also estimated. The comparison of the predicted theoretical frequencies with the experimental ones shows the suitability of the parallel, spatial and linear stability analysis, even though the problem is spatially developing. Special attention is focused on the transition from convective to absolute instabilities, where we observe that the entire pipe presents wavy patterns, and the experimental frequencies collapse with the theoretical results for the absolute frequencies. Thus, we provide experimental evidence of absolute instabilities in a pipe flow, confirming that the rotating pipe flow may be absolutely unstable for moderate values of Reynolds numbers and low values of the swirl parameter.