bluuebunny/crossref_metadata_2025 huggingface dataset:
FzlA, an essential regulator of FtsZ filament curvature, controls constriction rate during Caulobacter division
Authors: Lariviere Patrick J. , Szwedziak Piotr , Mahone Christopher R. , Löwe Jan , Goley Erin D.
Published: November 2017

During bacterial division, polymers of the tubulin‐like GTPase FtsZ assemble at midcell to form the cytokinetic Z‐ring, which coordinates peptidoglycan (PG) remodeling and envelope constriction. Curvature of FtsZ filaments promotes membrane deformation in vitro, but its role in division in vivo remains undefined. Inside cells, FtsZ directs PG insertion at the division plane, though it is unclear how FtsZ structure and dynamics are mechanistically coupled to PG metabolism. Here we study FzlA, a division protein that stabilizes highly curved FtsZ filaments, as a tool for assessing the contribution of FtsZ filament curvature to constriction. We show that in Caulobacter crescentus, FzlA must bind to FtsZ for division to occur and that FzlA‐mediated FtsZ curvature is correlated with efficient division. We observed that FzlA influences constriction rate, and that this activity is associated with its ability to bind and curve FtsZ polymers. Further, we found that a slowly constricting fzlA mutant strain develops ‘pointy’ poles, suggesting that FzlA influences the relative contributions of radial versus longitudinal PG insertion at the septum. These findings implicate FzlA as a critical coordinator of envelope constriction through its interaction with FtsZ and suggest a functional link between FtsZ curvature and efficient constriction in C. crescentus.
When is anti‐Zionism morally legitimate?
Authors: Oxman Evan
Published: November 2017

The claim that Zionism is fundamentally or intrinsically morally compromised is unfortunately more commonly articulated and expressed than it deserves to be. While there are certainly good reasons to be critical of Israeli governmental policy (both now and in the past), those who question the very right of a Jewish state to exist on land approximating the current territory of Israel without extrapolating this principle to other cases are being philosophically disingenuous. While I concede that it is perfectly reasonable to object to the creation and maintenance of a Jewish state on the basis of either its exclusionary character or its problematic history, I suggest that such arguments should equally apply to virtually every other nation‐state. Thus, while anti‐Zionism is not necessarily a morally illegitimate claim, unless its claims are paired with a more radical rejection of the nation‐state tout court, it should be considered as such.
Source and sink mechanisms of nitrogen transport and use
Authors: Tegeder Mechthild , Masclaux‐Daubresse Céline
Published: November 2017

ContentsSummary35I.Introduction35II.Nitrogen acquisition and assimilation36III.Root‐to‐shoot transport of nitrogen38IV.Nitrogen storage pools in vegetative tissues39V.Nitrogen transport from source leaf to sink40VI.Nitrogen import into sinks42VII.Relationship between source and sink nitrogen transport processes and metabolism43VIII.Regulation of nitrogen transport43IX.Strategies for crop improvement44X.Conclusions46Acknowledgements47References47

Nitrogen is an essential nutrient for plant growth. World‐wide, large quantities of nitrogenous fertilizer are applied to ensure maximum crop productivity. However, nitrogen fertilizer application is expensive and negatively affects the environment, and subsequently human health. A strategy to address this problem is the development of crops that are efficient in acquiring and using nitrogen and that can achieve high seed yields with reduced nitrogen input. This review integrates the current knowledge regarding inorganic and organic nitrogen management at the whole‐plant level, spanning from nitrogen uptake to remobilization and utilization in source and sink organs. Plant partitioning and transient storage of inorganic and organic nitrogen forms are evaluated, as is how they affect nitrogen availability, metabolism and mobilization. Essential functions of nitrogen transporters in source and sink organs and their importance in regulating nitrogen movement in support of metabolism, and vegetative and reproductive growth are assessed. Finally, we discuss recent advances in plant engineering, demonstrating that nitrogen transporters are effective targets to improve crop productivity and nitrogen use efficiency. While inorganic and organic nitrogen transporters were examined separately in these studies, they provide valuable clues about how to successfully combine approaches for future crop engineering.
The Association of British Neurologists' myasthenia gravis guidelines
Authors: Sussman Jon , Farrugia Maria E. , Maddison Paul , Hill Marguerite , Leite M. Isabel , Hilton‐Jones David
Published: November 2017

Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction for which many therapies were developed before the era of evidence‐based medicine. Despite the basic principles of treatment being well known, patients continue to receive suboptimal treatment. A myasthenia gravis guidelines group was therefore established under the aegis of the Association of British Neurologists. These guidelines attempt to steer a path between evidence‐based practice where available and established best practice where evidence is unavailable. It is not possible to consider all the potential decisions in managing MG without resorting to opinion rather than evidence. Where there is insufficient evidence or a choice of options, the guidelines invite the clinician to seek the opinion of a myasthenia expert. The guidelines support clinicians in using the right treatments in the right order and in optimizing the use of well‐known therapeutic agents. Clinical practice can be audited against these guidelines.
Near‐Optimality of Coarse Service Grades for Customer Differentiation in Queueing Systems
Authors: Nazerzadeh Hamid , Randhawa Ramandeep S.
Published: November 2017

We analyze a service firm that caters to price and delay‐sensitive customers who are differentiated on both their value for the service and the cost of waiting. There is a continuum of customer types in our setting and we model each customer's cost of waiting to be linear in the delay incurred with a multiplier that is an increasing linear or sub‐linear function of the customer's value for the service. Using a large system approach, we characterize the firm's revenue maximizing menu of price and delay quotations and the value of customer differentiation. We further characterize the value of offering coarse or few service grades and find that offering two service grades is asymptotically optimal on the typical square‐root scale, relative to the optimal policy.
A Consistent Data Series to Evaluate Growth and Inequality in the National Accounts
Authors: Fixler Dennis , Johnson David , Craig Andrew , Furlong Kevin
Published: November 2017

Recent headlines frequently refer to rising inequality and its implication on economic growth and social welfare. Addressing the latter is difficult and requires more than simply looking at GDP, as Kuznets long ago pointed out. In this paper we focus on the importance of the income measure underlying the inequality measure when examining the relationship between GDP growth and inequality. We create a mapping using Census Bureau household survey data and Bureau of Labor Statistics (BLS) consumer expenditure data to create distributional measures of the Bureau of Economic Analysis (BEA) personal income. We show that for the period 2000‐2012, inequality using personal income is substantively lower than inequality measured using Census Bureau money income, and the trends in both inequality and median income are different. This demonstrates the importance of using a measure a national accounts based measure of income when examining the relationships between inequality and growth.
Maintaining the National Accounts as Official Statistics
Authors: Lynch Robin , Thage Bent
Published: November 2017

Confidence in national accounts is undermined by expanding the conceptual framework to serve the needs of productivity analysis. Extensions of the SNA to include knowledge assets as produced output and direct volume measures of government output require an increasing number of assumptions and imputations, which threaten the status of national accounts as a reliable source of official economic statistics. Both national accounts and productivity analysis would be better served by meeting the data needs of productivity analysis through satellite systems. It is recommended that the movement towards increased recognition of capital formation of knowledge in the core system of national accounts be halted. The recording of the performance of Research and Development expenditures as capital formation and the endorsement of direct volume measures for the provision of government services introduced with the 2008 SNA should be reconsidered in the next revision of the SNA.
Present and Future Challenges to the System of National Accounts: Linking Micro and Macro
Authors: van de Ven Peter
Published: November 2017

The System of National Accounts has changed dramatically over the past decades, and it will continue to change, as a consequence of changes in the environment of producing statistics. These changes do not only relate to the user demands, also the source data and the means, in the sense of the available technologies for compiling national accounts, have undergone and will continue to undergo significant changes. After a short historic review of the main evolutions in the past three to four decades, the paper addresses the main developments and challenges in relation to the sources for compiling national accounts (input), the technologies for processing data (throughput), and the user demands (output) in the area of national accounts. The article concludes with some ideas and suggestions on how to move forward.
Combining Sharp and Smooth Transitions in Volatility Dynamics: A Fuzzy Regime Approach
Authors: Gallo Giampiero M. , Otranto Edoardo
Published: November 2017

Volatility in financial markets is characterized by alternating persistent turmoil and quiet periods, but also by a slowly varying average level. This slow moving component keeps open the question of whether some of its features are better represented as abrupt or smooth changes between local averages of volatility. We provide a new class of models with a set of parameters subject to abrupt changes in regime (Markov switching) and another set subject to smooth transition changes. These models capture the possibility that regimes may overlap with one another (fuzzy). The empirical application is carried out on the volatility of four US indices. It shows that the flexibility of the new model enables a better overall performance over either Markov switching or smooth transitions and provides a local average volatility measure as a parametric estimation of the low frequency component.
IL‐23 Activated γδ T Cells Affect Th17 Cells and Regulatory T Cells by Secreting IL‐21 in Children with Primary Nephrotic Syndrome
Authors: Zhang L. , Yan J. , Yang B. , Zhang G. , Wang M. , Dong S. , Liu W. , Yang H. , Li Q.
Published: November 2017

This study (1) analysed the percentage of γδ T cells, γδ T cell subsets, Th17 cells and regulatory T cells (Treg cells) and (2) determined the role of IL‐23 in primary nephrotic syndrome (PNS) patients with active disease and in remission. Eighty‐four patients with PNS and 51 healthy age‐matched controls were included in this study. The percentage of γδ T cells, γδ T cell subsets, Th17 cells and Treg cells in peripheral blood mononuclear cells (PBMCs) were analysed by fluorescence‐activated cell sorting. PMBCs from PNS patients with active disease were cultured in the presence of IL‐23, IL‐23 and an IL‐23 antagonist, or IL23 and an anti‐IL‐21 monoclonal antibody (mAb). The percentage of γδ T cells, IL‐23R+ γδ T cells and IL‐17+ γδ T cells were significantly increased in PNS patients with active disease. There was a positive correlation between the percentage of γδ T cells, IL‐23R+ γδ T cells, IL‐17+ γδ T cells and the Th17/Treg ratio. IL‐23 increased the percentage of γδ T cells and Th17 cells and decreased the percentage of Treg cells in PBMCs isolated from PNS patients with active disease. Anti‐IL‐21 mAb reduced the percentage of γδ T cells and Th17 cells, but increased the percentage of Treg cells. γδ T cells, IL‐17+ γδ T cells and IL‐23R+ γδ T cells may be involved in the pathogenesis of paediatric PNS by modulating the balance of Th17/Treg cells. γδ T cells may cause an imbalance in Th17/Treg cells by secreting IL‐21 in the presence of IL‐23.
Necrotizing Microascus tracheobronchitis in a bilateral lung transplant recipient
Authors: Taton Olivier , Bernier Benjamin , Etienne Isabelle , Bondue Benjamin , Lecomte Sophie , Knoop Christiane , Jacob Frederique , Montesinos Isabel
Published: November 2017

Invasive fungal infections are a major cause of mortality among solid organ transplant recipients. Scopulariopsis species and their teleomorph Microascus are molds found in soil and decaying organic matter. We report here the case of a woman who underwent bilateral lung transplantation for severe emphysema. On day 25 after transplantation, endobronchial green‐black lesions were detected during routine endoscopy. Endobronchial swabs, biopsies, and bronchoalveolar lavage samples were positive for Microascus cirrosus. This fungal infection developed despite voriconazole given for previous persistent invasive aspergillosis. Treatment consisted of a combination of antifungal medication (voriconazole, terbinafine, amphotericin B, and caspofungin) and endoscopic resection of necrosed bronchial mucosa. A favorable clinical outcome was achieved after 7 weeks of treatment. Seven cases of Scopulariopsis/Microascus infection have been previously described in solid organ transplant recipients. Only two survived after treatment with an antifungal combination therapy including echinocandins, posaconazole, and terbinafine. In immunocompromised patients, infection by Microascus species is a rare but life‐threatening event because of innate resistance to most common antifungal drugs. Our patient was successfully cured by combined therapy including intravenous voriconazole and caspofungin, oral terbinafine, and inhaled voriconazole and amphotericin B administered for 7 weeks in association with iterative endoscopic debridement to reduce fungal inoculum.
Enteric Infections in Young Children are Associated with Environmental Enteropathy and Impaired Growth
Authors: George Christine Marie , Burrowes Vanessa , Perin Jamie , Oldja Lauren , Biswas Shwapon , Sack David , Ahmed Shahnawaz , Haque Rashidul , Bhuiyan Nurul Amin , Parvin Tahmina , Bhuyian Sazzadul Islam , Akter Mahmuda , Li Shan , Natarajan Gayathri , Shahnaij Mohammad , Faruque Abu G. , Stine O. Colin
Published: November 2017

Objective

To investigate the relationship between faecal contamination in child play spaces, enteric infections, environmental enteropathy (EE) and impaired growth among young children.

Methods

A prospective cohort study was conducted of 203 children 6–30 months of age in rural Bangladesh. Stool samples were analysed by quantitative PCR for Shigella, Enterotoxigenic Escherichia coli (ETEC), Campylobacter jejuni, Giardia intestinalis and Cryptosporidium spp. Four faecal markers of intestinal inflammation were also measured: alpha‐1‐antitrypsin, myeloperoxidase, neopterin and calprotectin. Child growth was measured at baseline and 9 months after enrolment. E. coli was measured in soil in child play spaces.

Results

Forty‐seven percent of study children had three or more enteric pathogens in their stool. Thirty five percent (71/203) of children had Shigella, 30% (61/203) had ETEC, 73% (148/203) had C. jejuni, 79% (160/203) had Giardia intestinalis and none had Cryptosporidium. Children with ETEC had significantly higher calprotectin concentrations (Coefficient: 1.35, 95% Confidence Interval [CI]: 1.005, 1.82). Children with Shigella had a significantly higher odds of being stunted at our 9‐month follow‐up (OR: 2.01, 95% CI: 1.02, 3.93). Children with Giardia intestinalis had significantly higher E.coli counts in the soil collected from their play spaces (OR: 1.23, 95% CI: 1.02, 1.48).

Conclusion

Enteric infections were significantly associated with EE and impaired growth in rural Bangladesh. These findings provide further evidence to support the hypothesis that contaminated soil in child play spaces can lead to enteric infections, many of which are likely subclinical, resulting in EE and impaired growth in young children.
Secondary ion mass spectrometry imaging and multivariate data analysis reveal co‐aggregation patterns of Populus trichocarpa leaf surface compounds on a micrometer scale
Authors: Kulkarni Purva , Dost Mina , Bulut Özgül Demir , Welle Alexander , Böcker Sebastian , Boland Wilhelm , Svatoš Aleš
Published: November 2017

Spatially resolved analysis of a multitude of compound classes has become feasible with the rapid advancement in mass spectrometry imaging strategies. In this study, we present a protocol that combines high lateral resolution time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) imaging with a multivariate data analysis (MVA) approach to probe the complex leaf surface chemistry of Populus trichocarpa. Here, epicuticular waxes (EWs) found on the adaxial leaf surface of P. trichocarpa were blotted on silicon wafers and imaged using TOF‐SIMS at 10 μm and 1 μm lateral resolution. Intense M+● and M−● molecular ions were clearly visible, which made it possible to resolve the individual compound classes present in EWs. Series of long‐chain aliphatic saturated alcohols (C21–C30), hydrocarbons (C25–C33) and wax esters (WEs; C44–C48) were clearly observed. These data correlated with the 7Li‐chelation matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) analysis, which yielded mostly molecular adduct ions of the analyzed compounds. Subsequently, MVA was used to interrogate the TOF‐SIMS dataset for identifying hidden patterns on the leaf's surface based on its chemical profile. After the application of principal component analysis (PCA), a small number of principal components (PCs) were found to be sufficient to explain maximum variance in the data. To further confirm the contributions from pure components, a five‐factor multivariate curve resolution (MCR) model was applied. Two distinct patterns of small islets, here termed ‘crystals’, were apparent from the resulting score plots. Based on PCA and MCR results, the crystals were found to be formed by C23 or C29 alcohols. Other less obvious patterns observed in the PCs revealed that the adaxial leaf surface is coated with a relatively homogenous layer of alcohols, hydrocarbons and WEs. The ultra‐high‐resolution TOF‐SIMS imaging combined with the MVA approach helped to highlight the diverse patterns underlying the leaf's surface. Currently, the methods available to analyze the surface chemistry of waxes in conjunction with the spatial information related to the distribution of compounds are limited. This study uses tools that may provide important biological insights into the composition of the wax layer, how this layer is repaired after mechanical damage or insect feeding, and which transport mechanisms are involved in deploying wax constituents to specific regions on the leaf surface.
Intracranial hemorrhages in neonates born from 32 weeks of gestation—low frequency of associated fetal and neonatal alloimmune thrombocytopenia: a register‐based study
Authors: Refsum Erle , Håkansson Stellan , Mörtberg Anette , Wikman Agneta , Westgren Magnus
Published: November 2017

BACKGROUND

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare condition, with an estimated incidence of one in 1000 to 2000 live births. Predominantly, FNAIT is due to maternal alloantibodies that target paternally derived human platelet antigen (HPA) 1a. The most feared complication is an intracranial hemorrhage (ICH). The aim of this study was to determine the frequency of associated maternal platelet (PLT) alloimmunization in a population of neonates born from 32 weeks of gestation and diagnosed with an ICH.

STUDY DESIGN AND METHODS

The Swedish Neonatal Quality (SNQ) register was used to identify neonates diagnosed with an ICH born between 2003 and 2012. Mothers were invited to donate peripheral blood, to investigate their HPA‐1a antigen status, and test for anti‐HPA and anti‐HLA Class I alloantibodies. Clinical data for the neonates were retrieved from the SNQ register and available clinical records.

RESULTS

Of 286 registered neonates, 278 mothers were contacted. Of 105 analyzed maternal samples, two (1.9%) were HPA‐1a antigen negative. Antibody analyses revealed in total three (2.9%) mothers with anti‐HPA: one mother (0.94%) with anti‐HPA‐1a and two mothers (1.9%) with anti‐HPA‐5b, of whom one had concurrent anti‐HPA‐15a. Twenty‐four percent tested positive for anti‐HLA Class I antibodies. A total of 8.5% of neonates (5/59) with PLT counts available in clinical records were severely thrombocytopenic, with PLT counts of less than 50 × 109/L.

CONCLUSIONS

This retrospective cohort revealed a wide range of factors associated with ICH in neonates born from 32 weeks of gestation and suggests PLT alloimmunization to be a less common contributor than anticipated.
A nucleic acid amplification repeat testing algorithm reveals high risk of hepatitis B and C transmission with serologic blood screening practice in Punjab, India
Authors: Kumar R. , Shyamala V. , Lelie N. , Kumar P. , Kaur A.
Published: November 2017

Background

Lack of confirmatory testing of reactive donations for hepatitis C (HCV), B (HBV) and human immunodeficiency (HIV) viruses hampers reliable residual transmission risk analysis in India.

Materials and Methods

In our centre, 39 295 blood donations were tested for HIV Ag/Ab, anti‐HCV and hepatitis B surface antigen (HBsAg) by a variety of ELISAs and in parallel by individual donation nucleic acid amplification technology (ID‐NAT). NAT yields were confirmed by triplicate repeat reactivity in primary test‐tube and fresh frozen plasma (FFP) samples as well as by viral load (VL) testing and supplemental serologic assays.

Results

NAT and serology concordant reactive results included 23 (0·06%), 290 (0·74%) and 254 (0·65%) donations for HIV, HCV and HBV, respectively. Additionally, 15 HCV (1/2620) and 29 HBV (1/1355) seronegative NAT yield donations were confirmed. HBV marker testing identified three (1/13 100) window period (WP), 25 (1/1637) occult HBV infection (OBI) and one anti‐HBs breakthrough infection. ID‐NAT has reduced residual risk of infection from 1/2600 to 1/270 000 for HCV WP, 1/8000 to 1/21 000 for HBV WP and 1/11 000 to 1/66 000 for OBI.

Conclusion

A NAT repeat test algorithm was instrumental for confirmation of viral infection and revealed high residual risk of hepatitis B and C transmission by the practiced ELISA blood testing.
Use of skin stretchers for single‐stage bilateral mastectomies in a dog and a cat
Authors: Miyazaki Yuta , Aikawa Takeshi , Shimatsu Taichi , Nishimura Masaaki , Sadahiro Shigeo
Published: November 2017

Objective

To describe the application of skin stretchers for closure of single‐stage bilateral mastectomies in a dog and a cat.

Study Design

Clinical case report.

Animals

A 12‐year‐old intact female Miniature Dachshund and a 13‐year‐old spayed female domestic short‐hair cat.

Methods

Skin stretchers were applied to the site of the skin adjacent to mammary glands for 2‐4 days before surgery. Cable tension was adjusted every 6‐8 hours to elongate the skin and to achieve primary closure of single‐stage bilateral mastectomy without tension.

Results

Wound closure after single‐stage bilateral mastectomy was achieved without tension or major complication in both animals.

Conclusion

Use of skin stretchers allows primary closure of single‐stage bilateral mastectomy in dogs and cats.
Non‐invasive methods for the assessment of brown adipose tissue in humans
Authors: Chondronikola Maria , Beeman Scott C. , Wahl Richard L.
Published: November 2017

Brown adipose tissue (BAT) is a recently rediscovered tissue in people that has shown promise as a potential therapeutic target against obesity and its metabolic abnormalities. Reliable non‐invasive assessment of BAT volume and activity is critical to allow its importance in metabolic control to be evaluated. Positron emission tomography/computed tomography (PET/CT) in combination with 2‐deoxy‐2‐[18F]fluoroglucose administration is currently the most frequently used and most established method for the detection and quantification of activated BAT in humans. However, it involves radiation exposure and can detect activated (e.g. after cold exposure), but not quiescent, BAT. Several alternative methods that overcome some of these limitations have been developed including different PET approaches, single‐photon emission imaging, CT, magnetic resonance based approaches, contrast‐enhanced ultrasound, near infrared spectroscopy, and temperature assessment of fat depots containing brown adipocytes. The purpose of this review is to summarize and critically evaluate the currently available methods that non‐invasively probe various aspects of BAT biology in order to assess BAT volume and/or metabolism. Although several of these methods show promise for the non‐invasive assessment of BAT volume and function, further research is needed to optimize them to enable an accurate, reproducible and practical means for the assessment of human BAT content and its metabolic function.

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Junction Losses for Arbitrary Flow Directions
Authors: Tomor András , Kristóf Gergely
Published: November 2017

Two hydraulic losses take effect at the junction point of three cylindrical conduits. These two quantities are considered to be functions of the three signed flow rates and two geometrical parameters: the cross-sectional area ratio and the angle between the main conduit and branch tube. A new design of experiment is developed for exploring the parameter space with continuous response surfaces, which cover both dividing and combining flow regimes with a general trigonometric formula. The loss coefficients are determined by using a steady-state, single-phase, three-dimensional (3D) computational fluid dynamics (CFD) model. To help the analytical treatment, a new reference velocity formulation is introduced. The new loss coefficient formula is validated against known empirical correlations for different junction types and flow directions. The obtained continuous solution promotes the applicability of the resistance model in hydraulic network models.
Numerical Heat Transfer Modelling of SMA Actuators and Model Comparison
Authors: Lambert Tyler Ross , Gurley Austin , Kubik Kyle , Beale David , Broughton Royall
Published: November 2017

Shape memory alloys (SMA) can be used to create actuators for use in mechanical systems that carry pronounced benefits with their low weight, high strength, and low cost when coupled with advancements such as robust self-sensing. However, there exist drawbacks in the form of slow system response and complex material behavior. The design and implementation of controllers that drive SMA actuators successfully can pose a challenge, and accurate modelling of the material in software can help to optimize the system response time and power requirements. We have created a variety of tools to help implement these actuators into simulations that capture accurate thermal and mechanical responses of various SMA systems under a variety of control laws. In particular, thermo-electro-mechanical models of SMA behavior are implemented into software representations of mechanical systems such that the entire temperature, stress, and phase profiles of an SMA actuator can be accurately determined via simulation. Because analytical equations for modelling SMA behavior quickly become so complex to be untenable, we use stable numerical schemes to solve for these profiles. In particular, a finite difference scheme allows for spatial and temporally discretized temperature profiles along a shape memory actuator which can be solved for using empirically derived expressions for the heat transfer coefficient that dictated convective heat transfer. These types of models allow for a variety of boundary conditions to capture a number of SMA geometries, orientations, and applications. This paper presents the results of the numerical schemes for thermal cycling and a sliding mode controller used to drive a simple SMA actuator with varying boundary conditions and compares them to experimental results.
Fatigue Characterization of Piezo-Active Beams in Bending
Authors: Degroff Jonathan D. , Bilgen Onur
Published: November 2017

This paper presents the fatigue characterization of piezo-active beams in bending with surface bonded Macro-Fiber Composite actuators. Three substrate materials are considered: stainless steel, aluminum, and brass. First, the bending response is quantified theoretically using the classical laminate plate theory. The theoretical bending results indicate that the beam with the steel substrate had the largest curvature, and the specimen with the aluminum had the least. Next, midpoint deflection in a simply supported configuration in response to harmonic quasi-static actuation is experimentally measured. The results from the experiments showed no evidence of degradation of actuation for up to four million cycles at the harmonic excitation amplitude of 500 V; however, the results appeared highly sensitive to temperature.
Integration of Actuators by Additive Layer Manufacturing
Authors: Riemenschneider Johannes , Mitkus Rytis , Vasista Srinivas
Published: November 2017

Additive Layer Manufacturing is offering tremendous oportunities for manufacturing. Many complex structures, which could not be manufactured by conventional methods can be produced additive. This paper gives three examples of how additive manufacturing can be used to built smart structures with integrated actuators and sensors. The integration of piezoceramic actuators into FDM and SLM processes is described as well as the design of structures with integrated pneumatic actuators printed with the PolyJet method.
An Experimental Analysis of Vibration Induced Behaviour in Magnetorheological Fluids
Authors: Novikoff Paul-Alexis , Eck Laurent , Hafez Moustapha
Published: November 2017

Magneto-rheological fluids (MRF) are commonly applied in MRF brakes and vibration damping. The apparent viscosity dependence with respect to the magnetic field has been addressed in detail in the state of the art. The aim of this paper is to experimentally study the vibration effects on the particle chain-like structures and, as a consequence, the shear stress variation applied to the fluid. Three vibration configurations have been applied to a ferromagnetic cylinder rotating between two magnetic poles filled with MRF a “Z-vibration” where the generated displacement is along the rotation axis of the shearing cylinder, a “θ-vibration”, tangential to the cylinder, and an “R-vibration”, normal to the cylinder surface. First we focus on the vibration mode characterisation in free air, and then when plunged in the fluid. In a second step, we measure the reactive torque generated on the clutch under different magnetic field intensities with different rotation speeds and vibration amplitudes. It appears that the “R-vibration” configuration is providing the most influence, up to 20% of torque reduction observed at moderate B field. The “Z-vibration” and the “θ-vibration” configurations respectively have less influence on the torque, nevertheless vibrations always tend to decrease the corresponding yield stress in the MRF.
Experimental Study on Power Generation and Dynamical Behavior of the Cantilevered Piezoelectric Beam With the Unilateral Layer Separate
Authors: Xia Wei , Yao Ming Hui , Zhang Wei
Published: November 2017

This paper investigates the complicated dynamic behavior and power generation efficiency of the cantilevered laminated composite piezoelectric beam with the unilateral layer separate. The effect of the external excitation on the voltage output, the impacts of the layered length of composite layers and the influence of the magnetic distance on the voltage output and the effective frequency bandwidth are examined. Simultaneously, the output voltage and the effective frequency bandwidth of the traditional cantilevered laminated composite piezoelectric beam are measured experimentally to verify the developed model. The amplitude of the harmonic excitation is given the certain value and is not changed. Experimental results show that the developed structure has lower natural frequency, great voltage output and great effective frequency bandwidth when the length of the separate parts between composite layers is in the range. For the different layered lengths of the developed bistable piezoelectric beam, there exist the optimal magnetic distance and an optimal layered length, respectively. The power generation efficiency of the developed bistable piezoelectric beam is better than that of the developed monostable piezoelectric beam. When the layered length of the separate parts between composite layers is optimal, the voltage output of the piezoelectric beam has four peak voltages. In addition, the power generation efficiency of the developed structure are superior to that of the traditional one. The maximum peak voltage of this structure is 6.73 times than that of the traditional piezoelectric beam, and its effective frequency bandwidth promotes 8.4 times.
Novel Steerable Smart Needle With a Built-In Recovery Mechanism for Multiple Actuations
Authors: Sahlabadi Mohammad , Jezler Kyle , Hutapea Parsaoran
Published: November 2017

Smart Memory Alloys have brought a range of new capabilities to existing and novel designs due to their unique properties and ability to induce stress and strain in the material due to thermomechanical loading. Shape memory alloy-based smart material has widely been used and studied for biomedical applications. This includes smart needle for percutaneous procedures, self-expanding Nitinol grafts, stents, and other permanent internal devices. The smart needle is a needle in which deflection/path of the insertion in tissues can be controlled by incorporating Nitinol wire actuators on the body of the needle. However, smart needle designs proposed in the past lack both flexibility for multidirectional angles, and they do not allow for multiple martensitic phase transformations and are thus not repeatable. Each time the Nitinol wire is actuated, the wire would have to be manually reset to its initial length. Active materials like Nitinol require a bias force or mechanism that reverts the activated form of the needle back to its original martensitic form, which in the case of active needles is a straight wire. The lack of a recovery mechanism means that subsequent austenite transformations for deflection in opposing or similar trajectories cannot be performed as the system will not fully reset itself once cooled. In our proposed design, four Nitinol wires are embedded into a needle and act independently of one another to provide multi directional needle deformations. By providing tension onto a flexible 3D printed needle shaft, they can pivot a hard needle tip into any given direction. Once the needle’s deformation is complete, the material’s natural rigidity coupled with other Nitinol wires pulling resistance will restore the initial length of the actuated wire as it cools. This allows the needle to undergo a martensitic transformation and then subsequent cooling followed by additional phase transformation in a different direction. This makes the needle’s mechanism repeatable and functional for multiple insertions.
Mechanical Behavior of 3D Printed Multiwalled Carbon Nanotube/Thermoplastic Polyurethane Nanocomposites
Authors: Hohimer Cameron , Aliheidari Nahal , Mo Changki , Ameli Amir
Published: November 2017

As the soft robotics industry continues to grow, the need for new materials and simplified manufacturing techniques are essential. Of interest is the development of highly flexible strain sensors that are easily integrated into these robotic components. Current strain sensing solutions using piezoresistive materials often involve complex fabrication techniques with multiple steps. Recent work by the authors has shown that thermoplastic polyurethane/multiwall carbon nanotubes (TPU/MWCNT) has good piezoresistive behavior and can be easily fabricated into strain sensors using Fused Deposition Modeling (FDM). This work expands upon that effort to characterize the mechanical properties of FDM-printed TPU/MWCNT as a function of the FDM processing parameters. In this study, the air gap, raster orientation, and MWCNT weight percent were varied and tensile tests performed. The stress-strain behavior, modulus of elasticity, and ultimate tensile strength (UTS) are compared to assess the influence of the processing conditions. Optical microscopy was also carried out to correlate the mechanical behavior to the printed mesostructures. The results show that with increased MWCNT content, the UTS decreased by as much at 47% for 2wt.%MWCNT, while the modulus of elasticity increased by 54%, compared to those of pure TPU. The results of this work provide an understanding of the mechanical performance in relation to the print parameters and sets the base to tune the mechanical properties of printed flexible functional nanocomposites.
Design of Bio-Inspired Mobile Robot Using Piezoelectric Transducers As Drives
Authors: Jovanova Jovana , Dobrivojevski Filip , Dimoska Martina
Published: November 2017

This paper focuses on the design and development of a bio-inspired mobile robot using piezoelectric transducers as drives. The design of the device aimed to imitate the trajectory movement of a crawl-like animal. Design constraints as producing controlled movement with piezoelectric transducer, as well as the combination of multiple piezoelectric patches into one mobile robot are presented in their practical aspects. The robot uses 2 piezoelectric transducers as main drives, but also as main structural components of the device. The patches are connected with a thin light rod, and the kinematic of movement is achieved with 4 tiny wooden legs connected on each of the patches.

The project investigates the possibility and effectiveness of the piezoelectric transducers for movement of the bio-inspired mobile robot. From conceptual development, to the mechanical design and control, the mobile robot is used to test different trajectories of movement. Ni RIO Evaluation kit has been incorporated as a real-time and FPGA control platform for the mobile robot while using Labview programing environment. To accomplish complex trajectories of movement the velocity of the robot was measured for straight line and rotation of the robot.
Design and Modeling of a Bi-Directional U-Shaped Piezoelectric Energy Harvester
Authors: Su Wei-Jiun
Published: November 2017

In this paper, we proposed a Bi-directional U-shaped piezoelectric energy harvester that is capable of scavenging vibration energy in two orthogonal directions. The U-shaped harvester is a three-segment beam with piezoelectric layers attached. The harvester is designed to work in its first three resonant frequencies. A theoretical model of the harvester is derived based on the Euler-Bernoulli beam theory. The model is capable of simulating the electromechanical coupling system and obtaining the frequency responses under excitations of two orthogonal directions. The resonant frequencies of the harvester can be tuned by simply altering the length-to-width ratio of the beam structure. It is shown in the simulation that the U-shaped design can effectively harvest vibration energy in two directions of excitations.
Ferrofluid Droplet Based Micro-Magnetic Sensors and Actuators
Authors: Makhoul-Mansour Michelle , Challita Elio J. , Freeman Eric C.
Published: November 2017

A recent achievement in the droplet interface bilayer (DIB) technique is the ability to link multiple lipid-encased aqueous droplets in an oil medium to construct a membrane-based network. Highly flexible, efficient and durable compared to other lipid bilayer modeling techniques, these systems establish a framework for the creation of biocompatible and stimuli-responsive smart materials with applications ranging from biosensing to reliable micro-actuation. Incorporating ferrofluids droplets into this platform has proven to accelerate the networks’ building mechanism through remote magnetic-control of the droplets movement and has reduced the likelihood of failure during the pre-network-completion phase. Additionally, ferrofluid drops may be placed in the final network structure as they are macroscopically homogenous and behave as single phased liquids. Due to their paramagnetic characteristics, no residual magnetization is observed in the ferrofluid upon removal of the external magnetic field, allowing for simple control of the magnetically responsive droplets. Aside from the ferrofluids reliability in contact-free manipulation of bilayer networks, this work shows a different feature of having such hybrid ferrofluid-water DIB networks: magnetic-sensibility and actuation. Once pre-structured mixed networks are formed, a magnetic source is used to generate various magnetic fields in the vicinity of the DIB webs; changes in structural responses are then observed and used to induce protein channel gating in DIB networks channeling the functionality of a switch. Tailored architectures are accordingly evaluated and their suitability for the creation of microfluidic-magneto sensors and actuators is assessed.
Data-Driven Model Development and Feedback Control Design for PZT Bimorph Actuators
Authors: Bravo Nikolas , Smith Ralph C. , Crews John
Published: November 2017

In the paper, we discuss the development of a high-fidelity and surrogate model for a PZT bimorph used as an actuator for micro-air vehicles including Robobee. The models must quantify the nonlinear, hysteretic, and rate-dependent behavior inherent to PZT in dynamic operating regimes. The actuator dynamics are initially modeled using the homogenized energy model (HEM) framework. This provides a comprehensive high-fidelity model, which can be inverted and implemented in real time for certain control regimes. To improve efficiency, we additionally discuss the development of data-driven models and focus on the implementation of a surrogate model based on a dynamic mode decomposition (DMD). Finally, we detail the design and implementation of a PI controller on the surrogate and high-fidelity models.
A Microfluidic Assembly and Simultaneous Interrogation of Networks of Asymmetric Biomimetic Membranes
Authors: Nguyen Mary-Anne , Taylor Graham , Sarles Stephen A.
Published: November 2017

In this study, we utilize a novel microfluidic device to perform simultaneous electrical interrogation of an array of droplet interface bilayers (DIB) that feature asymmetric phospholipid leaflet compositions. While asymmetry is vital to many cellular functions, it is has received very little attention in membrane-based engineered material systems for sensing, energy conversion, or actuation. This gap is due to challenges in constructing and interrogating networks of asymmetric membranes, limiting our understanding of how lipid asymmetry affects membrane active peptides, and vice versa. Our system overcomes these difficulties by enabling asymmetric membrane formation between many pairs of lipid-coated droplets in oil. We demonstrate its use in probing the interactions between alamethicin, a membrane-active peptide that forms voltage-induced ion channels, and asymmetric DPhPC:DOPhPC membranes, a choice that creates an intrinsic intramembrane potential of |137 mV| due to differences in their respective dipole potentials. Our experiments show that adding alamethicin peptides to one side of the membrane causes this inherent membrane potential to decrease over time, and it alters the value of external voltage that must be applied to drive alamethicin insertion for ion channel formation. These effects take place over the course of 1 to 5 hours after membrane formation, and both results are consistent with translocation and mixing of lipids across the leaflets of the membrane.
Novel Equivalent Electrical Circuits for Linear and Nonlinear Electromechanically Coupled Systems
Authors: Silva Tarcísio M. P. , Candido de Sousa Vagner , Clementino Marcel A. , De Marqui Carlos
Published: November 2017

In the last years, researchers have presented concentrated and distributed parameter models of electromechanically coupled systems, leading to appropriate estimation of their electroelastic behavior. Equivalent electrical circuits have also been investigated and provide useful simulation tools to investigate the system behavior as well as to developed new energy harvesting or control circuits. In general, RLC (resistor, inductor and capacitor) circuits represent, respectively, the mass, damping and stiffness of single or multi-degree-of-freedom electromechanically coupled systems. In practice, however, the equivalent electrical representation of high-quality-factor systems demand equivalent circuits with extremely low internal resistance values. Furthermore, the assumption of an ideal transformer cannot be obtained in practice. This work presents a novel equivalent electrical circuit for linear and nonlinear electromechanically coupled systems. The effects of inductance, capacitance and electromechanical coupling are represented through operational-amplifier based sub-circuits of extremely low internal resistance. First, the linear behavior of a mass-spring-damping system is verified. Later, the behavior of a nonlinear electromechanically coupled system is investigated. In both cases, numerical results (Matlab-Simulink simulations) and experimental results (from breadboard implementations) will be verified against experimental results presented in the literature.
Effect of Geometric Design Parameters on Contractile SMA Knitted Actuator Performance
Authors: Eschen Kevin , Abel Julianna
Published: November 2017

Shape memory alloy (SMA) knitted actuators are a type of functional fabric that uses shape memory alloy wire as an active fiber within a knitted textile. Through intentional design of the SMA knitted actuator geometry, various two- and three-dimensional actuation motions, such as scrolling and contraction [1], can be accomplished. Contractile SMA knitted actuators leverage the unique thermo-mechanical properties of SMA wires by integrating them within the hierarchical knitted structure to achieve large distributed uniaxial contractions and variable stiffness behavior upon thermal actuation. During the knit manufacturing process, the SMA wire is bent into a network of interlacing adjacent loops, storing potential energy within the contractile SMA knitted actuator. Thermal actuation above the wire-specific austenite finish temperature leads to a partial recovery of the bending deformations, resulting in large distributed uniaxial contraction (15–40% actuation contraction observed) of the SMA knitted actuator. The achievable load capacity and %-actuation contraction are dependent on the geometric loop parameters of the contractile SMA knitted actuator. While exact descriptions of the geometric loop parameters exist, a reduction of the geometric complexity is advantageous for high-level contractile SMA knitted actuator design procedures. This paper defines a simple geometric measure, the non-dimensional knit density, and experimentally correlates the contractile SMA knitted actuator performance to this measure. The experimentally demonstrated dependency of relevant actuator metrics on the knit density and the wire diameter, suggests the usability of the simplified geometry definition for a high-level contractile SMA knitted actuator design.