bluuebunny/crossref_metadata_2025 huggingface dataset:
Preoperative cystoscopy could determine the severity of placenta accreta spectrum disorders: An observational study
Authors: Al‐Khan Abdulla , Guirguis George , Zamudio Stacy , Alvarez Manuel , Martimucci Kristina , Luke Davlyn , Alvarez‐Perez Jesus
Published: August 2018

Aim

In the surgical treatment of placenta accreta spectrum disorders, cystoscopy for prophylactic stent placement is performed to protect the ureters from potential injury. Despite its frequent use, the use of cystoscopy in assessing the severity of these disorders has not been explored. Our objective was to find out if the abnormal findings documented during cystoscopy are associated with disease severity.

Methods

In this retrospective, observational cohort study (n = 56), the bladder wall was evaluated at the time of ureteral stent placement via cystoscopy in prenatally diagnosed placenta accreta spectrum cases. Three abnormal findings were commonly present in these cases: bulging of the posterior bladder wall, neovascularization and arterial pulsatility in the area of neovascularization. These findings were stratified according to severity in histologically confirmed specimens. Continuous variables were compared via two‐tailed t‐tests and Wilcoxon rank sum tests. Categorical data were evaluated using logistic regression analysis.

Results

Neovascularization affected 84%, bulging 71% and pulsatility 54% of the cases. Bulging and neovascularization increased with disease severity. Pulsatility occurred exclusively in percretas. Bulging was associated with a 12‐fold (OR = 11.6, 95% CI 2.94–46.33, P = 0.0005) increased likelihood of percreta and neovascularization with a 17‐fold (OR = 17.06, 95% CI 2.98–97.79, P = 0.0014) increase. Neovascularization and/or the presence of bulging of the bladder have high positive predictive value for placenta increta and percreta (91.5% and 95.0%, respectively).

Cystoscopy can be used to assess the severity of placenta accreta spectrum cases preoperatively, especially when placentation is over the previous uterine scar and is in proximity to the bladder wall.
Life Insurance and Life Settlements: The Case for Health‐Contingent Cash Surrender Values
Authors: Fang Hanming , Kung Edward
Published: August 2018

We investigate why life insurance policies in practice either do not have a cash surrender value (CSV), or have CSVs that are small and are not adjusted for health status. We show that including health‐contingent CSVs in a life insurance contract causes a dynamic commitment problem, which makes it more costly up front for policyholders to purchase long‐term contracts (because some poor risks who would otherwise have lapsed can and will now capture the CSV instead). To the extent that life insurance policyholders’ incomes tend to increase over the course of the policy, policyholders are not willing to accept higher ex ante premium costs in return for the extra liquidity provided by the CSV. Because health‐contingent CSVs act in a similar way to a life settlement market, we also study the life insurers’ equilibrium choice of CSVs in the presence of a life settlement market. We find that optimally chosen CSVs can partially mitigate the consumer welfare loss caused by the settlement market (as in Daily, Hendel, and Lizzeri, 2008), but only if the CSVs are allowed to be contingent on health status.
Population dynamics of an endemic cyprinid (Hypselobarbus kurali): Insights from an exploited reservoir fishery in the Western Ghats of India
Authors: Raghavan Rajeev , Ramprasanth M. R. , Ali Anvar , Dahanukar Neelesh
Published: August 2018

The Western Ghats of India harbours an exceptional diversity of endemic freshwater fishes, which are threatened because of various anthropogenic stressors, including biological resource use. Lack of organized studies on the population dynamics and exploitation levels of endemic species, however, has hindered the development and implementation of systematic conservation action plans in this region. This is especially true for large cyprinid fishes threatened because of overharvest. This study examined length–weight relationships and length‐structured population dynamics of an endemic large cyprinid (Hypselobarbus kurali), based on data obtained from an artisanal gill‐net fishery in Malampuzha Reservoir. Length–weight analysis suggested the fish exhibited significantly lower exponents than expected under isometry, indicating the growth of H. kurali in the reservoir was negative allometric. The von Bertalanffy growth formula fitted to the length‐frequency data indicated H. kurali grew relatively slower than other large cyprinids in this region. Statistical analysis of recruitment revealed two peaks, implying the fish have two spawning bouts each year. Analysis of mortality and exploitation of the species revealed large‐sized individuals were targeted by the fishers, resulting in an exponential decline in the survivors in the virtual population analysis. Relative yield‐per‐recruit and relative biomass‐per‐recruit analysis indicated the current exploitation rate for the population was greater than the exploitation rate under which the stock would be reduced to half its unexploited biomass. Further, the current exploitation level was more than 60% of the expected maximum exploitation above which the population could collapse. The results of this study identify a serious need to develop and implement management plans to guide the future sustainability of the reservoir fishery of H. kurali.
Low breastfeeding continuation to 6 months for very preterm infants: A European multiregional cohort study
Authors: Bonnet Camille , Blondel Béatrice , Piedvache Aurélie , Wilson Emilija , Bonamy Anna‐Karin Edstedt , Gortner Ludwig , Rodrigues Carina , van Heijst Arno , Draper Elizabeth S. , Cuttini Marina , Zeitlin Jennifer ,   the EPICE Research Group
Published: August 2018

Breastfeeding confers multiple benefits for the health and development of very preterm infants, but there is scarce information on the duration of breastfeeding after discharge from the neonatal intensive care unit (NICU). We used data from the Effective Perinatal Intensive Care in Europe population‐based cohort of births below 32 weeks of gestation in 11 European countries in 2011–2012 to investigate breastfeeding continuation until 6 months. Clinical and sociodemographic characteristics were collected from obstetric and neonatal medical records as well as parental questionnaires at 2 years of corrected age. Among 3,217 ever‐breastfed infants, 34% were breastfeeding at 6 months of age (range across countries from 25% to 56%); younger and less educated mothers were more likely to stop before 6 months (adjusted relative risk [aRR] <25 years: 0.68, 95% CI [0.53, 0.88], vs. 25–34 years; lower secondary: 0.58, 95% CI [0.45, 0.76] vs. postgraduate education). Multiple birth, bronchopulmonary dysplasia (BPD), and several neonatal transfers reduced the probability of continuation but not low gestational age, fetal growth restriction, congenital anomalies, or severe neonatal morbidities. Among infants breastfeeding at discharge, mixed versus exclusive breast milk feeding at discharge was associated with stopping before 6 months: aRR = 0.60, 95% CI [0.48, 0.74]. Low breastfeeding continuation rates in this high‐risk population call for more support to breastfeeding mothers during and after the neonatal hospitalization, especially for families with low socio‐economic status, multiples, and infants with BPD. Promotion of exclusive breastfeeding in the NICU may constitute a lever for improving breastfeeding continuation after discharge.
From didactic to personalized health and nutrition counselling: A mixed‐methods review of the GALIDRAA approach in Nepal
Authors: Cunningham Kenda , Suresh Shalini , Kjeldsberg Cecilie , Sapkota Femila , Shakya Nabin , Manandhar Shraddha
Published: August 2018

GALIDRAA (greet, ask, listen, identify, discuss, recommend, agree, and appoint), an interpersonal communication method, is used in health and nutrition behaviour change programmes to structure communication between front‐line workers (FLWs) and beneficiaries. However, programmatic experiential evidence and monitoring and evaluation of the method are scarce. Suaahara aims to address maternal and child undernutrition, in part by influencing household‐level behaviours. Suaahara trained both government and programme FLWs in GALIDRAA for use during counselling. This study investigates their adherence to the GALIDRAA method 2 years later, using quantitative and qualitative data from a 2014 process evaluation study. Descriptive and thematic analyses were conducted to assess adherence to GALIDRAA. We found variation in adherence to each of the eight GALIDRAA steps among both Suaahara field supervisors (FSs) and Nepal's female community health volunteers (FCHVs). The prevalence of FLWs identifying a beneficiary's problem, discussing, questioning, and probing for constraints with the beneficiary, and, only then, recommending a doable solution, that is, the process of personalized nutrition counselling, was substantially higher among Suaahara FSs than FCHVs. However, both FCHVs and FSs counselling skills, particularly regarding adherence to each step of the GALIDRAA approach, have room for improvement. This highlights the need for additional training and post‐training follow‐up including supportive supervision related to appropriate counselling methods such as GALIDRAA and may indicate that there are additional FLWs constraints, beyond knowledge, that programmes need to address.
Negative regulation of Candida glabrata Pdr1 by the deubiquitinase subunit Bre5 occurs in a ubiquitin independent manner
Authors: Paul Sanjoy , McDonald W. Hayes , Moye‐Rowley W. Scott
Published: August 2018

The primary route for development of azole resistance in the fungal pathogen Candida glabrata is acquisition of a point mutation in the PDR1 gene. This locus encodes a transcription factor that upon mutation drives high level expression of a range of genes including the ATP‐binding cassette transporter‐encoding gene CDR1. Pdr1 activity is also elevated in cells that lack the mitochondrial genome (ρ° cells), with associated high expression of CDR1 driving azole resistance. To gain insight into the mechanisms controlling activity of Pdr1, we expressed a tandem affinity purification (TAP)‐tagged form of Pdr1 in both wild‐type (ρ+) and ρ° cells. Purified proteins were analyzed by multidimensional protein identification technology mass spectrometry identifying a protein called Bre5 as a factor that co‐purified with TAP‐Pdr1. In Saccharomyces cerevisiae, Bre5 is part of a deubiquitinase complex formed by association with the ubiquitin‐specific protease Ubp3. Genetic analyses in C. glabrata revealed that loss of BRE5, but not UBP3, led to an increase in expression of PDR1 and CDR1 at the transcriptional level. These studies support the view that Bre5 acts as a negative regulator of Pdr1 transcriptional activity and behaves as a C. glabrata‐specific modulator of azole resistance.
New technologies and the transformation of work and skills: a study of computerisation and automation of Australian container terminals
Authors: Gekara Victor Oyaro , Thanh Nguyen Vi‐Xuan
Published: August 2018

The increasing adoption of smart computer and robotic technologies at work has, in addition to displacing workers, significantly disrupted the traditional organisation of work and the workforce skills required. Based on a qualitative social science study, this paper discusses the ways in which these changes have affected container terminals. Specifically, we examine the transformation in the nature and content of work and the types of skills required by the workforce for the enduring and emerging jobs. We conclude that a completely different port terminal worker has emerged with a different job role and skills profile. Unlike the traditional ‘wharfie’ the emerging terminal worker is well educated and highly skilled. Furthermore, as physical shop floor operations are computerised and automated, greater importance is placed on soft, generic and transferable skills, with increasing emphasis on computer skills to facilitate effective work within a highly mechanised and digitalised work environment.
Changing resource landscapes and spillover of henipaviruses
Authors: Kessler Maureen K. , Becker Daniel J. , Peel Alison J. , Justice Nathan V. , Lunn Tamika , Crowley Daniel E. , Jones Devin N. , Eby Peggy , Sánchez Cecilia A. , Plowright Raina K.
Published: August 2018

Old World fruit bats (Chiroptera: Pteropodidae) provide critical pollination and seed dispersal services to forest ecosystems across Africa, Asia, and Australia. In each of these regions, pteropodids have been identified as natural reservoir hosts for henipaviruses. The genus Henipavirus includes Hendra virus and Nipah virus, which regularly spill over from bats to domestic animals and humans in Australia and Asia, and a suite of largely uncharacterized African henipaviruses. Rapid change in fruit bat habitat and associated shifts in their ecology and behavior are well documented, with evidence suggesting that altered diet, roosting habitat, and movement behaviors are increasing spillover risk of bat‐borne viruses. We review the ways that changing resource landscapes affect the processes that culminate in cross‐species transmission of henipaviruses, from reservoir host density and distribution to within‐host immunity and recipient host exposure. We evaluate existing evidence and highlight gaps in knowledge that are limiting our understanding of the ecological drivers of henipavirus spillover. When considering spillover in the context of land‐use change, we emphasize that it is especially important to disentangle the effects of habitat loss and resource provisioning on these processes, and to jointly consider changes in resource abundance, quality, and composition.
High resilience to extreme climatic changes in the CAM epiphyte Tillandsia utriculata L. (Bromeliaceae)
Authors: Rosado‐Calderón Agatha T. , Tamayo‐Chim Manuela , de la Barrera Erick , Ramírez‐Morillo Ivón M. , Andrade José L. , Briones Oscar , Reyes‐García Casandra
Published: August 2018

Climate change is expected to increase the frequency of extreme climatic events, yet few studies have addressed the capacity of plant species to deal with such events. Species that are widespread are predicted to be highly plastic and able to acclimate to highly changing conditions. To study the plasticity in physiological responses of the widely distributed epiphyte Tillandsia utriculata, we transplanted individuals from a coastal scrub and broadleaf evergreen forest to a similar coastal scrub site and forest. After a 45‐day acclimation, the plants were moved to a semi‐controlled greenhouse at each site, and then subjected to a 20‐day drought. Physiological variables were measured during the acclimation and the drought. The individuals of scrub and forest populations had similar relative water content and carbon assimilation in the contrasting conditions of the two transplantation sites despite the high discrepancy between the environments at their original site. Electron transport rates were higher in individuals from the scrub population. Electron transport rates were also higher than estimated from carbon assimilation, suggesting that photorespiration was present. The individuals of the coastal scrub population had a higher capacity to dissipate excess energy this way. The relative distance index of plasticity was high overall, indicating that some traits are highly plastic (titratable acidity, carbon assimilation) in order to maintain the stability of others (maximum quantum yield Fv/Fm and relative water content). We conclude that T. utriculata is a highly plastic species with a high capacity to tolerate extreme environmental changes over a short time.
The impact of earnings pressure on exploratory innovation
Authors: Chang Heng‐Yu , Lee Cheng‐Yu , Wong Ying‐Jiuan
Published: August 2018

While earnings expectation has been shown to determine a firm’s investment decisions, the knowledge about how such expectation influences a firm’s investment horizon for innovation is still blurred. This study therefore addresses this research issue by examining the relationship between earnings pressure and exploratory innovation while investigating the moderating effects of cross‐rival effect and resource availability. By examining high‐tech industrial firms in S&P 1500 from 2000 to 2012, the results indicate that stock analysts, as information intermediaries between innovation firms and the capital market, impose pressure through earnings forecasts on firms’ exploratory innovation. Our findings also reveal that the earnings pressure‐exploratory innovation relationship can be mitigated when its competitors encounter a higher level of earnings pressure. However, a firm’s financial slack shows less significant association to moderate the earnings pressure‐exploratory innovation relationship. Possible explanations for the results in regard to their theoretical and practical implications are discussed in this study.
Influence of body composition and physical fitness on arterial stiffness after marathon running
Authors: Deiseroth Arne , Nussbaumer Monique , Drexel Verena , Hertel Gernot , Schmidt‐Trucksäss Arno , Vlachopoulos Charalambos , Halle Martin , Hanssen Henner
Published: August 2018

Background and aims

Participation in exhaustive endurance sports competitions continues to be popular. Questions about the cardiovascular side effects of prolonged excessive exercise persist. Our study aimed to elucidate the acute effects of marathon running on arterial stiffness (AST) and to detect the role of body composition, fitness status, and inflammation.

Methods

Body composition was investigated in lean and obese recreational runners taking part in a marathon race. Fitness levels were determined in advance by a symptom‐limited treadmill test to obtain the individual anaerobic threshold. Carotid to femoral pulse wave velocity (PWV), systolic and diastolic blood pressures (BP), and inflammatory markers (TNF‐ɑ, IL‐6, hsCRP) were measured before 2 hours and 24 hours after a marathon race.

Results

A total of 47 male runners with a wide range of body mass index (BMI) and fitness levels took part in the study. Baseline PWV was independent of body composition. Marathon running induced an acute PWV drop from 8.5 m/s to 7.9 m/s within the first two hours after the race (P < 0.05). Body composition and not physical fitness predicted the PWV differences postmarathon (P > 0.05). Changes in BP, heart rate, or inflammatory markers were not associated with PWV postmarathon.

Conclusions

Though not evident at baseline, marathon running was associated with a reduced attenuation of central arterial stiffness in overweight and obese runners. The reduced responsiveness and attenuation of PWV with higher BMI, independent of hemodynamic changes and systemic inflammation, may represent masked vascular dysfunction in overweight and obese runners.
HiSpatialCluster: A novel high‐performance software tool for clustering massive spatial points
Authors: Chen Yiran , Huang Zhou , Pei Tao , Liu Yu
Published: August 2018

In the era of big data, spatial clustering is a very important means for geo‐data analysis. When clustering big geo‐data such as social media check‐in data, geotagged photos, and taxi trajectory points, traditional spatial clustering algorithms are facing more challenges. On the one hand, existing spatial clustering tools cannot support the clustering of massive point sets; on the other hand, there is no perfect solution for self‐adaptive spatial clustering. In order to achieve clustering of millions or even billions of points adaptively, a new spatial clustering tool—HiSpatialCluster—was proposed, in which the CFSFDP (clustering by fast search and finding density peaks) idea to find cluster centers and the DBSCAN (density‐based spatial clustering of applications with noise) idea of density‐connect filtering for classification are introduced. The tool’s source codes and other resources have been released on Github, and experimental evaluation was performed through clustering massive taxi trajectory points and Flickr geotagged photos in Beijing, China. The spatial clustering results were compared with those through K‐means and DBSCAN as well. As a spatial clustering tool, HiSpatialCluster is expected to play a fundamental role in big geo‐data research. First, this tool enables clustering adaptively on massive point datasets with uneven spatial density distribution. Second, the density‐connect filter method is applied to generate homogeneous analysis units from geotagged data. Third, the tool is accelerated by both parallel CPU and GPU computing so that millions or even billions of points can be clustered efficiently.
Effects of the selective chymase inhibitor TEI‐F00806 on the intrarenal renin–angiotensin system in salt‐treated angiotensin I‐infused hypertensive mice
Authors: Ansary Tuba M. , Urushihara Maki , Fujisawa Yoshihide , Nagata Sayaka , Urata Hidenori , Nakano Daisuke , Hirofumi Hitomi , Kitamura Kazuo , Kagami Shoji , Nishiyama Akira
Published: August 2018

New Findings

What is the central question of this study?

Can chymase inhibition prevent angiotensin I‐induced hypertension through inhibiting the conversion of angiotensin I to angiotensin II in the kidney?

What is the main finding and its importance?

Treatment with TEI‐F00806 decreased angiotensin II content of the kidney, renal cortical angiotensinogen protein levels and chymase mRNA expression, and attenuated the development of hypertension.

The effects of the selective chymase inhibitor TEI‐F00806 were examined on angiotensin I (Ang I)‐induced hypertension and intrarenal angiotensin II (Ang II) production in salt‐treated mice. Twelve‐week‐old C57BL male mice were given a high‐salt diet (4% NaCl + saline (0.9% NaCl)), and divided into three groups: (1) sham + vehicle (5% acetic acid in saline), (2) Ang I (1 μg kg−1 min−1, s.c.) + vehicle, and (3) Ang I + TEI‐F00806 (100 mg kg−1 day−1, p.o.) (n = 8–10 per group). Systolic blood pressure was measured weekly using a tail‐cuff method. Kidney Ang II content was measured by radioimmunoassay. Chronic infusion of Ang I resulted in the development of hypertension (P < 0.001), and augmented intrarenal chymase gene expression (P < 0.05), angiotensinogen protein level (P < 0.001) and Ang II content (P < 0.01) in salt‐treated mice. Treatment with TEI‐F00806 attenuated the development of hypertension (P < 0.001) and decreased Ang II content of the kidney (P < 0.05), which was associated with reductions in renal cortical angiotensinogen protein levels (P < 0.001) and chymase mRNA expression (P < 0.05). These data suggest that a chymase inhibitor decreases intrarenal renin–angiotensin activity, thereby reducing salt‐dependent hypertension.
Technological Advances to Maximize Solar Collector Energy Output: A Review
Authors: Salvi Swapnil S. , Bhalla Vishal , Taylor Robert A. , Khullar Vikrant , Otanicar Todd P. , Phelan Patrick E. , Tyagi Himanshu
Published: August 2018

Since it is highly correlated with quality of life, the demand for energy continues to increase as the global population grows and modernizes. Although there has been significant impetus to move away from reliance on fossil fuels for decades (e.g., localized pollution and climate change), solar energy has only recently taken on a non-negligible role in the global production of energy. The photovoltaics (PV) industry has many of the same electronics packaging challenges as the semiconductor industry, because in both cases, high temperatures lead to lowering of the system performance. Also, there are several technologies, which can harvest solar energy solely as heat. Advances in these technologies (e.g., solar selective coatings, design optimizations, and improvement in materials) have also kept the solar thermal market growing in recent years (albeit not nearly as rapidly as PV). This paper presents a review on how heat is managed in solar thermal and PV systems, with a focus on the recent developments for technologies, which can harvest heat to meet global energy demands. It also briefs about possible ways to resolve the challenges or difficulties existing in solar collectors like solar selectivity, thermal stability, etc. As a key enabling technology for reducing radiation heat losses in these devices, the focus of this paper is to discuss the ongoing advances in solar selective coatings and working fluids, which could potentially be used in tandem to filter out or recover the heat that is wasted from PVs. Among the reviewed solar selective coatings, recent advances in selective coating categories like dielectric-metal-dielectric (DMD), multilayered, and cermet-based coatings are considered. In addition, the effects of characteristic changes in glazing, absorber geometry, and solar tracking systems on the performance of solar collectors are also reviewed. A discussion of how these fundamental technological advances could be incorporated with PVs is included as well.
Assessment of Computational Fluid Dynamic for Surface Combatant 5415 at Straight Ahead and Static Drift β = 20 deg
Authors: Bhushan S. , Yoon H. , Stern F. , Guilmineau E. , Visonneau M. , Toxopeus S. L. , Simonsen C. , Aram S. , Kim S-E , Grigoropoulos G.
Published: August 2018

Collaboration is described on assessment of computational fluid dynamics (CFD) predictions for surface combatant model 5415 at static drift β = 0 deg and 20 deg using recent tomographic particle image velocimetry (TPIV) experiments. Assessment includes N-version verification and validation to determine the confidence intervals for CFD solutions/codes, and vortex onset, progression, instability, and turbulent kinetic energy (TKE) budget analysis. The increase in β shows the following trends. Forces and moment increase quadratically/cubically, and become unsteady due to shear layer, Karman and flapping instabilities on the bow. Wave elevation becomes asymmetric; its amplitude increases, but the total wave elevation angle remains same. The vortex strength and TKE increase by about two orders of magnitude, and for large β, the primary vortices exhibit helical mode instability similar to those for delta wings. Forces and moment for both β and wave elevation for β = 0 deg are compared within 4% of the data, and are validated at 7% interval. Wave elevation for β = 20 deg, and vortex core location and velocities for both β are compared within 9% of the data, and are validated at 12% interval. The vortex strength and TKE predictions show large 70% errors and equally large scatter and are not validated. Thus, both errors and scatter need reduction. TKE budgets show transport of turbulence into the separation bubble similar to canonical cases, but pressure transport is dominant for ship flows. Improved CFD predictions require better grids and/or turbulence models. Investigations of solution-adaptive mesh refinement for better grid design and hybrid Reynolds-averaged Navier-Stokes/large eddy simulation models for improved turbulent flow predictions are highest priority.
Discrete Adjoint Method for the Sensitivity Analysis of Flexible Multibody Systems
Authors: Callejo Alfonso , Sonneville Valentin , Bauchau Olivier A.
Published: August 2018

The gradient-based design optimization of mechanical systems requires robust and efficient sensitivity analysis tools. The adjoint method is regarded as the most efficient semi-analytical method to evaluate sensitivity derivatives for problems involving numerous design parameters and relatively few objective functions. This paper presents a discrete version of the adjoint method based on the generalized-alpha time integration scheme, which is applied to the dynamic simulation of flexible multibody systems. Rather than using an ad hoc backward integration solver, the proposed approach leads to a straightforward algebraic procedure that provides design sensitivities evaluated to machine accuracy. The approach is based on an intrinsic representation of motion that does not require a global parameterization of rotation. Design parameters associated with rigid bodies, kinematic joints, and beam sectional properties are considered. Rigid and flexible mechanical systems are investigated to validate the proposed approach and demonstrate its accuracy, efficiency, and robustness.
Background-Oriented Schlieren of Fuel Jet Flapping Under Thermoacoustic Oscillations in a Sequential Combustor
Authors: Weilenmann Markus , Xiong Yuan , Bothien Mirko , Noiray Nicolas
Published: August 2018

This study deals with thermoacoustic instabilities in a generic sequential combustor. The thermoacoustic feedback involves two flames: the perfectly premixed swirled flame anchored in the first stage and the sequential flame established downstream of the mixing section, into which secondary fuel is injected in the vitiated stream from the first stage. It is shown that the large amplitude flapping of the secondary fuel jet in the mixing section plays a key role in the thermoacoustic feedback. This evidence is brought using high-speed background-oriented Schlieren (BOS). The fuel jet flapping is induced by the intense acoustic field at the fuel injection point. It has two consequences: first, it leads to the advection of equivalence ratio oscillations toward the sequential flame; second, it modulates the residence time of the ignitable mixture in the mixing section, which periodically triggers autoignition kernels developing upstream of the chamber. In addition, the BOS images are processed to quantify the flow velocity in the mixing section and these results are validated using particle image velocimetry (PIV). This study presents a new type of thermoacoustic feedback mechanism, which is peculiar to sequential combustion systems. In addition, it demonstrates how BOS can effectively complement other diagnostic techniques that are routinely used for the study of thermoacoustic instabilities.
Development of a Noncontacting Mechanical Seal for High Performance Turbocharger Applications
Authors: Nelson Daniel A.
Published: August 2018

This paper presents the design and development of a noncontacting dry-gas mechanical seal for high performance automotive turbocharger applications. Turbochargers are increasingly being incorporated into high performance automobile engines to improve fuel efficiency, enhance energy recovery, and increase horsepower as compared with similar sized naturally aspirated engines. Minimizing the wear rate of tribological surfaces in the turbomachinery is critical to maximizing the reliability and durability of the turbocharger. A dry-gas seal for turbochargers and related technologies with 2–4 cm shafts has been developed. The seal provides a complete barrier between the bearing oil and compressor flow path and is capable of reverse pressure and high speed. The seal performance was evaluated for speeds between 60,000 and 80,000 rpm, pressure differentials between −0.8 (reverse pressure) to 6 bar, and temperatures between 20 and 200 °C. Structural and thermal response of the seal components to the operating conditions are analyzed using finite element methods and the tribological behavior of the seal rings are analyzed using computational fluid dynamics. The design is experimentally validated in a seal test stand. This novel approach reduces turbocharger blowby and shows no measurable wear when compared with piston ring seals.
Online Chatter Suppression in Turning by Adaptive Amplitude Modulation of Spindle Speed Variation
Authors: Ding Longyang , Sun Yuxin , Xiong Zhenhua
Published: August 2018

Although the effectiveness of spindle speed variation (SSV) method in chatter suppression has been extensively reported, the determination of optimal SSV parameters remains a challenge owing to the difficulties in obtaining accurate modal parameters especially under varying cutting conditions. This paper proposes a closed-loop SSV cutting system to suppress chatter in turning. The dimensionless SSV amplitude is adaptively adjusted with a model-free controller to accommodate change of the chatter level. The wavelet packet entropy (WPE) is computed online to evaluate quantitatively the machining state, and a predetermined chatter threshold is used to calculate the controller input. Energy-based analysis of SSV parameters effect on chatter shows that the amplitude is the more dominant parameter than the frequency. Then we introduce the scheme of the proposed chatter suppression system, where the Bootstrap method is adopted to determine the threshold value. Next, the feasibility of the proposed method for chatter suppression is tested by simulations with different cutting depths. Finally, comparisons of experimental results verify the conclusion of theoretical analysis about the effect of SSV parameters, and two cutting tests with diverse activating strategies are performed to validate the effectiveness of the proposed system for chatter suppression in turning.
Efficient Mechanism Design and Systematic Operation Planning for Tube-Wire Flexible Needles
Authors: Lee Jaeyeon , Wang Jing , Park Wooram
Published: August 2018

Needles are widely used in medicine for minimally invasive procedures. A steerable flexible needle was first introduced about 15 years ago, which was a new type of needle and could follow three-dimensional curved trajectory during medical procedures. The flexible needle has the limit of a single and low curvature. In this paper, we overcome this limit by designing mechanisms for tube-wire type flexible needles. We also provide a systematic planning method for an automated operation of the needle insertion using the mechanisms. Using the new system, we can achieve high and multiple curvatures from needle trajectories. The proposed design consists of an inner prebent wire and an outer tube, which are connected to two special mechanisms, an extension switch and a friction cart. It allows the trajectory of the needle to have high and multiple curvatures, which will enable the needle to easily reach target positions while efficiently avoiding obstacles. Users can efficiently control the needle device with simple inputs (insertion and rotation) using the special operation mechanism, which achieves three system functions (insertion/retraction, rotation, curvature changes) using only two actuation motors. Compared to prebent needles or duty-cycled spinning, this needle design causes less tissue damage. We build an automatic system to operate the new design of the steerable needle and test it. The performance of the new needle is verified by experiments with ballistic gelatin and animal tissue samples.
Evaluation of Liquid-Gas Two-Phase Flow Pressure Drop Signatures in Proton Exchange Membrane (PEM) Fuel Cell Flow Channels
Authors: Mortazavi Mehdi , Benner Jingru , Santamaria Anthony
Published: August 2018

In this study, liquid-gas two-phase flow pressure drops were measured in an ex-situ PEM fuel cell test section. Pressure drop signatures were studied for three nominal air flow rates and different water flow rates within a flow channel. The pressure drop signatures showed an increasing trend at the beginning of the experiments which were followed by a drop to lower values before reaching uniform patterns. It was observed that as the water flow rate increased, the time interval at which pressure signatures reached uniform patterns decreased. In addition, a qualitative comparison with Mishima-Hibiki model [13] revealed that this two-phase flow pressure drop model showed the best prediction capability for the medium air flow rate used in this study, ∼300mℓ/min inflow channel, corresponding to ∼220 Reynolds number.
Flow Pattern, Heat Transfer and Pressure Drop Behaviors of Micro-Channel Flow Boiling
Authors: Saisorn Sira , Srithumkhant Pochai , Wongpromma Pakorn , Suchatawat Maturose , Wongwises Somchai
Published: August 2018

Two-phase flow of R-134a with high confinement number was experimentally carried out in this study. Flow boiling conditions for different orientations were controlled to take place in a stainless steel tube having a diameter of 0.5 mm. Based on a saturation pressure of 8 bar, a heat flux range of 2–26 kW/m2, and a mass flux range of 610–815 kg/m2s, a constant surface heat flux condition was controlled by applied DC power supply on the test section. The flow behaviors were described based on flow pattern and pressure drop data while heat transfer mechanisms were explained by using heat transfer coefficient data. In this work, nucleate boiling was observed, and the importance of the change in the flow direction was neglected, corresponding to the confinement number of around 1.7.
Visualization of Two-Phase Flow in 3D Printed Polycarbonate Pulsating Heat Pipe With Aluminum Substrate
Authors: Arai Takahiro , Kawaji Masahiro , Koito Yasushi
Published: August 2018

A pulsating heat pipe (PHP) is a passive device with a good heat transport capability compared to other heat pipes. This paper describes an experimental investigation of a PHP with a serpentine channel fabricated by using a 3-D printer. The configuration of the flow channels in the PHP was close to that of commercially available PHPs made entirely of aluminum. To improve the heat transport capability and enable flow visualization, an aluminum plate was used on one side as the heat-transfer surface, on which transparent flow channels were fabricated by a 3-D printer and a polycarbonate filament. The interface between the aluminum plate and polycarbonate flow channel was cemented with a heat-resistant glue to ensure long term sealing. HFE-7000 was used as a working fluid. Oscillating two-phase flow in the PHP was observed with a high-speed digital video camera and transient surface temperatures at evaporator, insulator and condenser sections were measured by fine diameter thermocouples. The two-phase flow and thermal characteristics of the PHP at different heater power levels are presented.
Electrokinetic Dispersion in Field Amplified Sample Stacking
Authors: Dubey Kaushlendra , Gupta Amit , Bahga Supreet Singh
Published: August 2018

In this work, we performed an experimental study of electrohydrodynamic effects on the dispersion of sample ions in field amplified sample stacking (FASS). A typical FASS experiment involves a streamwise electrical conductivity gradient collinear to the applied electric field to enhance the sample stacking. Earlier studies on FASS have focused on how the conductivity gradient sets a non-uniform electro-osmotic flow which causes the dispersion. However, the coupling of the electric field with conductivity gradient leads to a destabilizing electric body force and generates unstable flow. This work demonstrates that generated body force influences the dynamics of FASS. We present a scaling analysis to show that at high fields, electrohydrodynamic effects play a vital role in sample dispersion. To justify our scaling arguments, we performed experiments at varied electric fields which shows that at high electric fields maximum concentration enhancement is lowered significantly. To ensure the EHD effects on the dynamics of FASS, we have also performed experiments with suppressed EOF conditions.
Two-Phase Flow Conjugate Heat Transfer in Wavy Microchannel
Authors: Tiwari Nishant , Moharana Manoj Kumar
Published: August 2018

Flow boiling in microchannel heat sink offers an effective cooling solution for high power density micro devices. A three-dimensional numerical study based on volume of fraction model (VOF) coupled with evaporation condensation model accounting for the liquid-vapor phase change is undertaken to recreate vapor bubble formation in saturated flow boiling in wavy microchannel. Constant wall heat flux imposed at the bottom surface of the substrate while other faces are insulated. To understand the conjugate effects, simulations has been carried out for substrate thickness to channel depth ratio (δsf ∼ 1–5), substrate wall to fluid thermal conductivity ratio (ksf ∼ 22–300) and waviness (γ ∼ 0.008–0.04). Bubble nucleation, growth, and departure of bubble plays a significant role in heat transfer and pressure drop characteristics in two-phase flow in wavy microchannel. The coolant (water) temperature at the inlet is taken to be 373 K while flow was at atmospheric pressure. This makes shorter waiting period of bubble nucleation, and the number density of bubbles on the solid surface increases. This results in enhancement of the boiling effect, and thus with the presence of bubbles, the mixing of laminar boundary layers improves and enhances the overall heat transfer coefficient. Channel amplitude play an important factor that can suitably reduce the friction factor and enhances the heat transfer coefficient.
Reduction of Hydraulic Friction in Confined Flows by Laser Texturing: Experiments and Theoretical Validation
Authors: Kumar Avinash , Datta Subhra , Kalyanasundaram Dinesh
Published: August 2018

Hydraulic friction reduction in a microchannel due to superhydrophobic texturing of its walls was studied theoretically and experimentally. A modified Poiseuille equation formulated from an earlier-established semi-analytical approach to model texturing of slip lengths and the “gas cushion model” was used to predict the hydraulic conductance of a microchannel. An experimental setup with a microfluidic flow cell consisting of syringe pump, pressure manometer and tubing measured the pressure drop at different flow rates through a microchannel. The top and bottom walls of the microchannel was textured with micro-pits using nanosecond pulsed laser on the titanium alloy Ti6Al4V. A very high contact angle was observed on the textured surfaces suggesting entrapped gas bubbles. Liquid slippage leading to reduced hydraulic friction is attributable to the bubbles. The pressure-flow rate characteristics of the microchannels confirm friction reduction and also demonstrate a reasonable agreement with the theoretical predictions from the developed fluid dynamic model.
Reflected diffraction from linearly patterned surfaces
Authors: Liang Jing , Liang Jiajun , Leung Ka Lun , Fung Ho Ting , Su Yumian , Wong Kwok Yee Michael , Sou Iam Keong , Law Carrie Wing Yan
Published: August 2018

We discuss the optical analogy of reflected electron diffraction from a grating with non-uniform spacing at the nanoscale, and its relationship to another grating with uniform spacing. Two analytical approaches that offer a quantitative solution for the reflected diffraction from a grating are presented. A compact and low-cost experimental kit for demonstrating the physics behind the reflected diffraction from one-dimensional surface structures is described. As an example, the convolution theorem is used to explain the reflected diffraction from a sample consisting of two individual one-dimensional surface structures overlapping orthogonally. This study will broaden students' understanding of the physics behind diffraction.
Teaching of the harmonic oscillator damped by a constant force: The use of analogy and experiments
Authors: Hauko R. , Andreevski D. , Paul D. , Šterk M. , Repnik R.
Published: August 2018

A description of oscillations damped by a constant force, despite the importance of the phenomenon, is missing from secondary (i.e., high-school) and university physics textbooks. In this paper, a simple explanation of this type of energy loss is given, using the analogy of a vertical spring-mass system. The predicted result, a linear time reduction in the amplitude of oscillation, can be confirmed in the classroom with the demonstration outlined here. In addition, the possibility of extending the experiment to a laboratory exercise at the university level is described. During the exercise, students distinguish different energy loss mechanisms in harmonic oscillations and measure the values of physical quantities associated with energy loss using a simple analytical procedure.
Subtleties with Young's double-slit experiment: Investigation of spatial
coherence and fringe visibility
Authors: Jackson David P. , Ferris Natalie , Strauss Ruthie , Li Hongyi , Pearson Brett J.
Published: August 2018

We discuss Young's double-slit experiment using a partially coherent light source consisting of a helium-neon laser incident on a rotating piece of white paper. Such an experiment is appropriate for undergraduate students as an independent project or as part of an advanced lab course. As is well known, the resulting interference pattern is observed to disappear and return, depending on the angular size of the source. Interestingly, while the standard theoretical prediction for the light intensity agrees quite well with experimental data when the fringe visibility is high, the prediction is noticeably off when the visibility is low. A first-principles calculation of the light intensity is performed and shown to agree extremely well with the experimental results for all visibilities.
Passive stochastic matched filter for Antarctic blue whale call detection
Authors: Bouffaut Léa , Dréo Richard , Labat Valérie , Boudraa Abdel-O. , Barruol Guilhem
Published: August 2018

As a first step to Antarctic blue whale (ABW) monitoring using passive acoustics, a method based on the stochastic matched filter (SMF) is proposed. Derived from the matched filter (MF), this filter-based denoising method enhances stochastic signals embedded in an additive colored noise by maximizing its output signal to noise ratio (SNR). These assumptions are well adapted to the passive detection of ABW calls where emitted signals are modified by the unknown impulse response of the propagation channel. A filter bank is computed and stored offline based on a priori knowledge of the signal second order statistics and simulated colored sea-noise. Then, the detection relies on online background noise and SNR estimation, realized using time-frequency analysis. The SMF output is cross-correlated with the signal's reference (SMF + MF). Its performances are assessed on an ccean bottom seismometer-recorded ground truth dataset of 845 ABW calls, where the location of the whale is known. This dataset provides great SNR variations in diverse soundscapes. The SMF + MF performances are compared to the commonly used MF and to the Z-detector (a sub-space detector for ABW calls). Mostly, the benefits of the use of the SMF + MF are revealed on low signal to noise observations: in comparison to the MF with identical detection threshold, the false alarm rate drastically decreases while the detection rate stays high. Compared to the Z-detector, it allows the extension of the detection range of ≃ 30 km in presence of ship noise with equivalent false discovery rate.
Interplanetary small satellites come of age
Authors: Hand Eric
Published: August 2018

With miniaturized guidance and propulsion systems, tiny craft aim for destinations beyond Earth.
Interaction-driven quantum Hall wedding cake–like structures in graphene quantum dots
Authors: Gutiérrez Christopher , Walkup Daniel , Ghahari Fereshte , Lewandowski Cyprian , Rodriguez-Nieva Joaquin F. , Watanabe Kenji , Taniguchi Takashi , Levitov Leonid S. , Zhitenev Nikolai B. , Stroscio Joseph A.
Published: August 2018

An electronic wedding cake

In nanostructures such as quantum dots, spatial confinement forces electrons to assume discrete energy levels. Quantization can also occur in an external magnetic field, where electrons' energies group into so-called Landau levels (LLs). Gutiérrez
et al.
explored the interplay between these two mechanisms and electronic interactions in a circulator resonator made of graphene. As an external magnetic field was increased, the electron quantum states transformed from atomic-like states to LL-like states. Electronic interactions caused a characteristic wedding cake–like shape of electronic density at high fields.

Science
, this issue p.
789