bluuebunny/crossref_metadata_2025 huggingface dataset:
Divergent Phosphine‐Catalyzed [2+4] or [3+2] Cycloaddition Reactions of γ‐Substituted Allenoates with Oxadienes
Authors: Li Erqing , Chang Meijia , Liang Ling , Huang You
Published: December 2014

A strategy was developed to construct dihydropyran and multifunctional cyclopentene derivatives from the same starting materials by using different phosphine catalysts. By exploiting the different nucleophilicities of the phosphine catalysts, the γ‐substituted allenoates selectively acted as C3 or C2 synthons. Under the catalysis of different organophosphine catalysts, the domino reaction proceeded smoothly with broad substrate tolerance and excellent total yields. The results suggest that the ethyl group of the γ‐substituted allenoates played a key role in the domino reaction.
Palladium‐Catalyzed α‐Selective Alkenylation of Imidazo[1,2‐a]pyridines through Aerobic Cross‐Dehydrogenative Coupling Reaction
Authors: Ghosh Monoranjan , Naskar Aswini , Mitra Shubhanjan , Hajra Alakananda
Published: December 2014

The palladium‐catalyzed highly regioselective vinylation of imidazopyridines through a cross‐dehydrogenative coupling reaction was developed. The reaction proceeds with the aid of molecular oxygen as the sole oxidant. A series of branched α‐vinylated products were obtained with high efficiency.
Chemo‐ and Stereoselective Reduction of β‐Keto‐α‐oximino Nitriles by Using Baker's Yeast
Authors: Mo Kilwoong , Kang Soon Bang , Kim Youseung , Lee Yong Sup , Lee Jae Wook , Keum Gyochang
Published: December 2014

The baker's yeast mediated reduction of β‐keto‐α‐oximino nitriles 3 at 20 °C gave β‐hydroxy‐α‐oximino nitriles 4 in high yields with high enantiomeric purity [enantiomeric excess (ee) values >99 %]. At room temperature, the same reaction afforded the product in a slightly lower yield. The β‐hydroxy‐α‐oximino nitriles 4 were obtained as single stereoisomers according to chiral GC–MS analyses and the 1H and 19F NMR spectra of the corresponding Mosher esters. The absolute stereochemistry of alcohol 4a was determined by hydrolysis of its oximino nitrile group followed by conversion into its corresponding α‐hydroxy ester. The β‐hydroxy‐α‐oximino nitrile products were further submitted to oxime‐ and nitrile‐selective transformations. This chemo‐ and stereoselective reduction can be used to generate important chiral building blocks.
Rhodium(I)‐Catalyzed Cycloisomerization of Allene–Allenylcyclopropanes
Authors: Kawamura Takamasa , Kawaguchi Yasuaki , Sugikubo Katsuya , Inagaki Fuyuhiko , Mukai Chisato
Published: December 2014

The RhI‐catalyzed intramolecular [5+2–2]‐type cycloisomerization of allene–allenylcyclopropanes was developed. In this reaction, ethylene was liberated from the cyclopropane ring to afford the 1,5,6,7‐tetrahydroazulene skeletons.
Needs: Defining What You Are Assessing
Authors: Watkins Ryan , Kavale Jolanta
Published: December 2014

By definition your needs assessment should assess needs, but how do you define them? Further, how do you operationalize that definition to measure needs? Do your partners and stakeholders also hold the same conceptual, and operational, definitions? Is there agreement that the project is only going to assess needs and not wants, assets, capacity, or solutions? Or are you really expected to assess all five? Each of these is an important consideration that can substantially influence the success of any needs assessment. In this chapter, the authors examine how definitions and use of the word need influence the design and implementation of an assessment, suggesting that the definition can shape the results of what is found.
Needs Assessment: The Perspective From the Public Sector
Authors: Engle Molly , Altschuld James W.
Published: December 2014

While examining needs is common in many public‐sector agencies, questions arise about how it has been carried out and if a focus on deficits (or gaps) is too narrow when not accompanied by the assessment of assets. The authors operate in this chapter as actors in a play. The first author offers a short personal perspective about her long experience in the public sector, with emphasis on Extension and the nature of needs assessment within it. In that discussion are two illuminative historical examples with clear relevance to what we might do today. They demonstrate that linking asset‐thinking to such efforts might be a good thing when embarking upon improvement of programs for the public. The second author enters in by amplifying the examination of assets and how they might be linked to the thinking of public‐sector assessors. The authors conclude by recommending that such an expansion of the toolkit of needs assessors would be useful.
International Perspectives: Similarities and Differences Around the Globe
Authors: Meiers Maurya West , Watkins Ryan , Song Kristin Marsh
Published: December 2014

Needs are not uniquely American. From Johannesburg and Helsinki to Cairo and Santiago, they are assessed around the world in a variety of contexts and conditions. Needs assessments often cross borders and cultural boundaries, attempting to systematically assist communities, organizations, and people in making better informed decisions. This complexity can improve the results of an assessment, while at the same time presenting the assessor and the methods used with many practical challenges. In response, the focus of this chapter has to do with successfully conducting needs assessments in diverse international contexts. Offering practical tips, the foundation of the chapter provides real‐world guidance for handling many of the obstacles faced in needs assessments.
Volatile constituents of vetiver: a review
Authors: Belhassen Emilie , Filippi Jean‐Jacques , Brévard Hugues , Joulain Daniel , Baldovini Nicolas
Published: December 2014

A comprehensive and critical compilation of the volatile constituents of vetiver root (Chrysopogon zizanioides L.) is presented, including those present in its essential oil. This extremely complex material has stimulated analytical research for many decades in the hope of unravelling the secrets of its composition. Up to now, more than 300 molecules have been reported, mostly sesquiterpenoids possessing a large variety of skeletons, together with their norterpenic counterparts. This review attempts to clarify some of the discrepancies related to the characterization of these constituents, which were often due to the misuses of analytical methods without enough critical consideration of the literature. The identification of the main odour impact components of vetiver is also discussed, because much contradictory information appears in the literature on this subject. Copyright © 2014 John Wiley & Sons, Ltd.
Computer‐aided molecular pathology interpretation in exploring prospective markers for oral submucous fibrosis progression
Authors: Anura Anji , Conjeti Sailesh , Das Raunak Kumar , Pal Mousumi , Paul Ranjan Rashmi , Bag Swarnendu , Ray Ajoy Kumar , Chatterjee Jyotirmoy
Published: December 2014

Background

Evaluation of molecular pathology markers using a computer‐aided quantitative assessment framework would help to assess the altered states of cellular proliferation, hypoxia, and neoangiogenesis in oral submucous fibrosis and could improve diagnostic interpretation in gauging its malignant potentiality.

Methods

Immunohistochemical (IHC) expression of c‐Myc, hypoxia‐inducible factor‐1‐alpha (HIF‐1α), vascular endothelial growth factor (VEGF), VEGFRII, and CD105 were evaluated in 58 biopsies of oral submucous fibrosis using computer‐aided quantification. After digital stain separation of original chromogenic IHC images, quantification of the diaminobenzidine (DAB) reaction pattern was performed based on intensity and extent of cytoplasmic, nuclear, and stromal expression.

Results

Assessment of molecular expression proposed that c‐Myc and HIF‐1α may be used as strong screening markers, VEGF for risk‐stratification and VEGFRII and CD105 for prognosis of precancer into oral cancer.

Conclusion

Our analysis indicated that the proposed method can help in establishing IHC as an effective quantitative immunoassay for molecular pathology and alleviate diagnostic ambiguities in the clinical decision process. © 2015 Wiley Periodicals, Inc. Head Neck 38: 653–669, 2016
MicroRNA expression as predictor of local recurrence risk in oral squamous cell carcinoma
Authors: Ganci Federica , Sacconi Andrea , Manciocco Valentina , Sperduti Isabella , Battaglia Paolo , Covello Renato , Muti Paola , Strano Sabrina , Spriano Giuseppe , Fontemaggi Giulia , Blandino Giovanni
Published: December 2014

Background

Oral squamous cell carcinoma (OSCC) is the sixth most common cancer worldwide with a high rate of recurrence. MicroRNAs (miRNAs) are gene regulators playing an important role in oral carcinogenesis. The purpose of this study was for us to identify and functionally characterize miRNAs that predict recurrence in OSCC.

Methods

We collected 92 OSCC with their normal tissue counterparts and we performed miRNAs expression profiling on 74 OSCC and 38 normal tissues. The association between the expression of miRNAs and clinical outcome was evaluated in the follow‐up of 69 patients.

Results

Four of the miRNAs deregulated between OSCC and normal tissues are prognostic for recurrence either when considered individually or as a group. Depletion of the expression of prognostic miRNAs inhibit the proliferation of OSCC cells

Conclusion

MiRNAs are differentially expressed in OSCC versus normal samples. The expression of 4 prognostic miRNA signatures is able to predict recurrence risk independently from other clinical factors in OSCC. © 2015 Wiley Periodicals, Inc. Head Neck 38: E189–E197, 2016
Disciplining Management or Guiding Management: Aligning Interests in Securitized Leveraged Buyouts
Authors: Bouvier Laurent , Nisar Tahir M.
Published: December 2014

Leveraged buyouts (LBOs) are generally explained in terms of a governance mechanism that disciplines management. It is operationalized by increasing the leverage of a firm, which has an implicit consequence of constraining management in the use of free cash flows. However, under a relatively new form of LBO known as securitized leveraged buyouts, private equity firms raise funds on the back of the acquired company's operating assets. A securitized LBO imposes explicit restrictions on management with regard to its freedom for carrying out strategy decisions. Using the case study of Hertz, we show how a securitized LBO can be structured more efficiently and what important decisions must be made in order to improve its debt service capacity.
Accounting Issues Related to Bitcoins
Authors: Raiborn Cecily , Sivitanides Marcos
Published: December 2014

Despite the frequent mention of Bitcoin in recent years in the press and business publications, many people are still uncertain what this cryptocurrency is or how it works. And although bitcoins (BTCs) are now an accepted medium of exchange for some businesses and not‐for‐profit organizations, no specific accounting guidance has been issued for these transactions. This article provides some basic information about BTCs and addresses six specific financial accounting issues: asset classification, mining activity, investment holdings, exchanges, merger and acquisition (M&A) transactions, and disclosure.
Unsettling Business: The BP Settlement Agreement
Authors: Johnson Leigh Redd , Rudolph Holly R.
Published: December 2014

Two years since the settlement agreement between BP and plaintiffs of the Deepwater Horizon oil spill, myriad challenges to the agreement by BP related to the calculation of business economic loss payments and causation have been filed. While BP has been successful in its efforts to revise the rules for calculation of payments, it has been less successful on the causation issue. This article reviews the history of the settlement agreement, summarizes the status of business economic loss payment claims, and discusses the impact of BP challenges on claimants at all stages of the claims process, including businesses that have previously received payments. © 2015 Wiley Periodicals, Inc.
Essential IT Controls for Preventing Cash Fraud
Authors: Marley Robert , Mooney J. Lowell
Published: December 2014

Cyber‐thieves know the exact location of your organization's cash. What is not certain is whether you are working harder than the thieves to protect your organization's most vulnerable asset. This article encourages organizations to assess the controls they have in place around their cash operations. It describes in detail a variety of general controls over cash, including adequate segregation of duties, explicit authorization approval requirements, and physical access controls. The article then describes several information technology (IT) application controls (including lockboxes, positive pay, ACF Fraud Blocker, and zero balance accounts) that can help you protect your organization's cash against fraud and cyber‐attack. © 2015 Wiley Periodicals, Inc.
FX Cash Flow Risk Management: Financial Reporting Issues and Practical Implications
Authors: Wang Li , Makar Stephen
Published: December 2014

Companies having foreign sales can avoid large fluctuations in earnings and cash flows caused by changes in foreign exchange (FX) rates through the use of foreign exchange derivatives (FXDs). FXDs used to mitigate the effect of FX rate changes on forecasted transactions can qualify as cash flow hedges under Statement of Financial Accounting Standards No. 133 (SFAS 133). According to SFAS 133, the mark‐to‐market (MTM) gains/losses on effective cash flow hedges are reported in other comprehensive income on the balance sheet, instead of on the income statement. This article explains how CFOs and treasurers may benefit from understanding the strategic and practical implications of reporting foreign‐exchange hedges, including the disclosure of hedge ratio data (i.e., the extent of cash flow hedge use).
Multicultural Personality and Posttraumatic Stress in U.S. Service Members
Authors: Herrera Catherine J. , Owens Gina P.
Published: December 2014

Objective

Modern military missions place numerous demands on service members, including tactical, personal, and cultural challenges. The purpose of this study was to explore how domains of multicultural personality (cultural empathy, open‐mindedness, social initiative, emotional stability, and flexibility) and combat exposure relate to posttraumatic stress disorder (PTSD) in service members.

Method

Participants (N = 163) completed the Multicultural Personality Questionnaire, Combat Exposure Scale, and PTSD Checklist–Military as part of an online survey. The majority of participants were Caucasian (87%), mean age was 33 years, and all were deployed at least once to Iraq or Afghanistan

Results

Regression results indicated that higher levels of combat exposure and open‐mindedness and lower levels of flexibility and emotional stability were significant predictors of higher PTSD severity. The interactions between combat exposure and flexibility and combat exposure and openness were also significant.

Conclusion

Higher levels of flexibility and emotional stability seem particularly important in their association with lower PTSD severity for service members.
Coping Skill as a Moderator Between Negative Life Events and Suicide Among Young People in Rural China
Authors: Sun Long , Zhang Jie
Published: December 2014

Objective

In the present study, we aim to test whether the approach or the avoidance coping skill can be a moderator between negative life events and suicide, and to test the deficient coping strain in the strain theory.

Method

This sample comprised 392 suicide cases and 416 community living controls, aged 15–34 years, from 16 rural counties in China. An established psychological autopsy method and a case–control design were used in this study. The 48‐item Coping Response Inventory evaluated the degree of coping skills of the people who died by suicide.

Results

Results indicated that the avoidance coping skill, but not the approach coping skill, can moderate between negative life events and suicide.

Conclusion

The low level of the avoidance coping skill may represent a promising variable for screening for suicide risk in rural China.
Identity Disturbance and Problems With Emotion Regulation Are Related Constructs Across Diagnoses
Authors: Neacsiu Andrada D. , Herr Nathaniel R. , Fang Caitlin M. , Rodriguez Marcus A. , Rosenthal M. Zachary
Published: December 2014

Objective

This study examined the relation between identity disturbance and emotion dysregulation in a cross‐diagnostic sample. We assessed whether these constructs are related and relevant beyond borderline personality disorder (BPD).

Method

We recruited 127 participants who completed measures assessing identity disturbance, emotion dysregulation, anxiety, and depression. The sample included primarily depressed adults meeting criteria for multiple diagnoses as well as psychiatrically healthy participants.

Results

Identity disturbance was significantly higher among psychiatric participants with and without BPD compared to healthy controls. Emotion dysregulation was a significant predictor of identity disturbance, even when controlling for BPD diagnosis, depression, and anxiety. In particular, clarity in emotional situations and problems using emotion regulation strategies were most closely related to identity disturbance.

Conclusion

The results of this study suggest that future research should examine identity disturbance and its relation with emotion regulation transdiagnostically.
Do Child Abuse and Maternal Care Interact to Predict Military Sexual Trauma?
Authors: Wilson Laura C. , Kimbrel Nathan A. , Meyer Eric C. , Young Keith A. , Morissette Sandra B.
Published: December 2014

Objective

The present research tested the hypothesis that maternal care moderates the relationship between childhood sexual abuse and subsequent military sexual trauma (MST).

Method

Measures of childhood sexual abuse, maternal care, and MST were administered to 197 Iraq and Afghanistan war veterans.

Results

After accounting for gender, age, and the main effects of maternal care and childhood sexual abuse, the maternal care x childhood sexual abuse interaction was a significant predictor of MST (odds ratio = .28, β = −1.26, 95% confidence intervals of .10, .80). As hypothesized, rates of MST were higher among veterans who reported childhood sexual abuse and low levels of maternal care (43%) compared with veterans who reported childhood sexual abuse and high levels of maternal care (11%).

Conclusion

These findings suggest that high levels of maternal care may act as a protective factor against future revictimization among military service members. These findings have the potential to inform both prevention and intervention efforts.
Effects of high heel wear and increased weight on the knee during walking
Authors: Titchenal Matthew R , Asay Jessica L , Favre Julien , Andriacchi Thomas P , Chu Constance R
Published: December 2014

Knee osteoarthritis (OA), a leading cause of disability, is more prevalent in women than men. Wearing high heeled shoes has been implicated as a potential contributing factor for the higher lifetime risk of osteoarthritis in women. This study tests the hypotheses that changes to knee kinematics and kinetics observed during high heeled walking increase in magnitude with increasing heel height and are accentuated by a 20% increase in weight. Fourteen healthy females were tested using marker‐based gait analysis in combinations of footwear (flat athletic shoe, 3.8 cm and 8.3 cm heeled shoes) and weight (with and without 20% bodyweight vest). At preferred walking speed, knee flexion angle at heel‐strike and midstance increased with increasing heel height and weight. Maximum knee extension moment during loading response decreased with added weight; maximum knee extension moment during terminal stance decreased with heel height; maximum adduction moments increased with heel height. Many of the changes observed with increasing heel height and weight were similar to those seen with aging and OA progression. This suggests that high heel use, especially in combination with additional weight, may contribute to increased OA risk in women. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:???–???, 2015.
A diatom record of mid‐ to late Holocene palaeoenvironmental changes in the southern Okinawa Trough
Authors: LI DONGLING , JIANG HUI , KNUDSEN KAREN LUISE , BJÖRCK SVANTE , OLSEN JESPER , ZHAO MEIXUN , LI TIEGANG , LI JIALIN
Published: December 2014

Palaeoceanographic changes over the last 6800 years are documented in a diatom record from core MD05–2908 from the southern Okinawa Trough. Changes in diatom components are used to reflect variations in the strength of the Kuroshio Current and the influence of coastal waters, and these changes are compared with records of the East Asian summer monsoon, which exerts an important influence on regional climate and oceanography. A decreasing trend in the contribution of coastal diatoms during the last 6800 years is related to the weakening of the East Asian summer monsoon during the Holocene in response to diminishing insolation and a southward shift in the intertropical convergence zone. Relatively high abundances of the Kuroshio Current indicator species during the intervals 2600–2200 and 4800–3600 cal a BP, and lower abundances during the intervals 3200–2800 and 2200–1300 cal a BP, imply that there is no consistent weakening of the Kuroshio Current during the interval 4500–3000 cal a BP − the Pulleniatina Minimum Event, which is a widespread feature in the East China Sea and the South China Sea. A major reduction in coastal diatoms at 3200 cal a BP and a slight decrease in the Kuroshio Current indicator species during the interval 3200–2800 cal a BP indicate that a palaeoceanographic shift occurred in the southern Okinawa Trough, which coincided with a Northern Hemisphere climatic cooling, denoted the Neoglaciation in Europe. In addition, changes in the freshwater species component of the record are suggested mainly to result from variations in flood frequency in north‐eastern Taiwan caused by typhoons. A dramatic increase in the frequency of flood events during the last millennium may have been caused by relatively strong El Niño‐Southern Oscillation activity, compared with the more stable period between 6800 and 1000 cal a BP, which experienced a low frequency of flood events.
Patent Law Treaty: Promises Not Delivered‐How the Negotiations Resulted in Ambiguities in the Treaty
Authors: Mulder Cees
Published: December 2014

The Patent Law Treaty was drafted with the aim to “streamline and harmonize” formal requirements set by national or regional Patent Offices for the filing of national or regional patent applications and the maintenance of patents. In this Article, a number of core issues of the Patent Law Treaty has been selected: requirements for the accordance of a filing date, relief in respect of time limits and restoration of priority. A conclusion of this Article is that the goals of the Patent Law Treaty were not achieved by the Treaty as concluded. One of the reasons is that the Treaty contains too many optional requirements (“may require”), which may be implemented as compulsory by the Contracting Parties, allowing them too much freedom when implementing requirements of the Treaty into their national and regional patent laws. This defies the aim of harmonization and streamlining of the Patent Law Treaty. The negotiation history is described and discussed with emphasis on what went wrong during the negotiations. Reasons for the failure of the Patent Law Treaty are discussed and recommendations for repair are given.
Bioinspired Nanotubes from Self‐Assembly of a Linear l,d‐Oligopeptide‐Poly(ethylene glycol) Conjugate
Authors: Punzi Pasqualina , Santis Serena De , Giordano Cesare , Diociaiuti Marco , Novelli Federica , Masci Giancarlo , Scipioni Anita
Published: December 2014

The preparation and structural organization of a new bioinspired nanomaterial are investigated. A hybrid conjugate is obtained by end‐linking a linear octapeptide with regular alternating enantiomeric sequence to poly(ethylene glycol). This conjugate is able to self‐assemble, forming well‐defined nanorods having core/shell morphology with an internal peptide single channel that has, for the first time, been clearly visualized by transmission electron microscopy (TEM) images. It is remarkable that well‐defined cylindrical nanoparticles can be formed starting from a linear oligopeptide, the synthesis of which is significantly easier than that of the homologous cycles. In addition, the synthetic strategy and the structure of the conjugate ensure a controlled and regular pegylation of the aggregates and high density PEG blocks in the corona, making the nanoparticles more resistant to phagocytosis and able to prevent biofouling. Such features, along with biocompatibility and stability, make these nanoparticles promising candidates for drug delivery.

image
Bilaplacian problems with a sign‐changing coefficient
Authors: Chesnel Lucas
Published: December 2014

We investigate the properties of the operator
, where σ is a given parameter whose sign can change on the bounded domain Ω. Here,
denotes the subspace of H2(Ω) made of the functions v such that v = ν·∇v = 0 on ∂Ω. The study of this problem arises when one is interested in some configurations of the interior transmission eigenvalue problem. We prove that
is a Fredholm operator of index zero as soon as σ∈L∞(Ω), with σ−1∈L∞(Ω), is such that σ remains uniformly positive (or uniformly negative) in a neighbourhood of ∂Ω. We also study configurations where σ changes sign on ∂Ω, and we prove that Fredholm property can be lost for such situations. In the process, we examine in details the features of a simpler problem where the boundary condition ν·∇v = 0 is replaced by σΔv = 0 on ∂Ω. Copyright © 2014 John Wiley & Sons, Ltd.
On a connection between the Maxwell system, the extended Maxwell system, the Dirac operator and gravito‐electromagnetism
Authors: Picard Rainer , Trostorff Sascha , Waurick Marcus
Published: December 2014

The close connection between Maxwell's equations and the Dirac equation is under consideration in a rigorous functional analytical framework. The two systems are linked via the so‐called extended Maxwell system Picard R. A structural observation for linear material laws in classical mathematical physics. Mathematical Methods in the Applied Sciences 2009;32(14):1768–1803, which is here re‐considered in the time‐dependent case as an evolutionary space‐time operator equation. This structural observation is then applied to recover and generalize the equations of gravito‐electromagnetism and to reformulate theMaxwell‐Dirac system as a system of three coupled extended Maxwell systems. This reformulation rests on the observation that what in electrodynamics is commonly known as ‘potential’ is actually a solution to another extended Maxwell system. Copyright © 2014 John Wiley & Sons, Ltd.
Concentric rings K‐space trajectory for hyperpolarized 13C MR spectroscopic imaging
Authors: Jiang Wenwen , Lustig Michael , Larson Peder E. Z.
Published: December 2014

Purpose

To develop a robust and rapid imaging technique for hyperpolarized 13 C MR Spectroscopic Imaging and investigate its performance.

Methods

A concentric rings readout trajectory with constant angular velocity is proposed for hyperpolarized 13C spectroscopic imaging and its properties are analyzed. Quantitative analyses of design tradeoffs are presented for several imaging scenarios. The first application of concentric rings on 13C phantoms and in vivo animal hyperpolarized 13C MR Spectroscopic Imaging studies were performed to demonstrate the feasibility of the proposed method. Finally, a parallel imaging accelerated concentric rings study is presented.

Results

The concentric rings MR Spectroscopic Imaging trajectory has the advantages of acquisition timesaving compared to echo‐planar spectroscopic imaging. It provides sufficient spectral bandwidth with relatively high efficiency compared to echo‐planar spectroscopic imaging and spiral techniques. Phantom and in vivo animal studies showed good image quality with half the scan time and reduced pulsatile flow artifacts compared to echo‐planar spectroscopic imaging. Parallel imaging accelerated concentric rings showed advantages over Cartesian sampling in g‐factor simulations and demonstrated aliasing‐free image quality in a hyperpolarized 13C in vivo study.

Conclusion

The concentric rings trajectory is a robust and rapid imaging technique that fits very well with the speed, bandwidth, and resolution requirements of hyperpolarized 13C MR Spectroscopic Imaging. Magn Reson Med 75:19–31, 2016. © 2015 Wiley Periodicals, Inc.
Funnel control for electrical circuits
Authors: Berger Thomas , Reis Timo
Published: December 2014

We study the zero dynamics and funnel control for linear passive electrical circuits. We show that asymptotic stability of the zero dynamics can be characterized by criteria on the circuit topology. Thereafter we consider the output regulation problem for electrical circuits by funnel control. We show that for circuits with asymptotically stable zero dynamics, the funnel controller achieves tracking of a class of reference signals within a pre‐specified funnel. This result can be relaxed to the case of non‐autonomous zero dynamics by requiring the reference trajectory to evolve within a certain subspace. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient Reduction Method based on Trial Vector Derivatives for Nonlinear Transient Analysis of Multilayer Sheet Structures
Authors: Pichler Florian , Witteveen Wolfgang
Published: December 2014

For the dynamic response of multilayer sheet structures it is important to take nonlinear contact and friction forces between the layers into account. The nonlinearities inside the joints can significantly influence the dynamic behavior of the entire structure. For the dynamic analysis of such structures conventional computational approaches have an unbalanced ratio between computational time and accuracy. In order to overcome this problem, so‐called “Joint Interface Modes” (JIMs) are used. These JIMs, which are problem‐oriented trial vectors, extend the reduction base of classical trial vector based reduction methods. In this contribution a new calculation approach for JIMs based on trial vector derivatives is introduced. The result quality of the presented method is comparable to the direct finite element method but the computational effort is extremely low due to model order reduction. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Contact Modeling in Multibody Systems with Elastic Bodies in High‐Frequency Applications
Authors: Schulze Sebastian , Sextro Walter , Grüter Frank
Published: December 2014

This paper discusses the refinement of multibody models by integration of flexible bodies and by considering nonlinearities from contacts. It presents common approaches for contact modeling in multibody simulations and strategies to include flexible bodies. A contact model is implemented in the elastic multibody model. Experimental results show that significant effects of system dynamics can be modeled by use of a multibody model including elastic bodies and contacts. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variational Integrators for Thermomechanical Coupled Dynamic Systems with Heat Conduction
Authors: Kern Dominik , Bär Sebastian , Groß Michael
Published: December 2014

Variational integrators are modern time‐integration schemes based on a discretization of the underlying variational principle. They thus skip the direct formulation and time discretization of partial differential equations. In mechanics, Hamilton's Principle is approximated by an action sum whose variation should be equal to zero, resulting in discrete Euler‐Lagrange Equations or equivalently in discrete Position‐Momentum Equations. Variational integrators are, by design, structure preserving (symplecticity) and show excellent long‐time behavior. In order to consider the coupling between mechanical and thermal quantities, Hamilton's principle is extended by using the notion of thermacy as thermal analogue to mechanical displacements. From this variational formulation, a variational integrator using the generalized trapezoidal rule is constructed exemplarily. A thermoelastic double pendulum with heat conduction serves as a model problem. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multibody dynamics with unilateral constraints and friction
Authors: Charles Alexandre , Ballard Patrick
Published: December 2014

In the view of robotics or granular media mechanics, we ask for the statement of the dynamical evolution problem for multibody systems with contacts and friction. The “event driven” approach does not allow to state an evolution problem in a systematic way: it gives a peculiar status to the instants of impact and to the contact points although they are unknowns of the problem. This matter of fact has given rise to a new approach in the frictionless case [4, 6] we generalize to the case including friction. Following to the point of view of Lagrange on the equation of the dynamics, we emphasize the systematic use of virtual powers and duality. This bias suggests to put emphasis on generalized reaction forces in the statement of the evolution problem and not on local reaction forces of the real world. This point of view allows to escape from pathologies e.g. Painlevé paradox [5] and Kane Paradox [3]. The proposed evolution problem accounts for impacts and friction in case of multiple unilateral constraints. We prove the existence and uniqueness of the solution to the associated rate problem. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evaluation of the adjoint sensitivity analysis for the identification of multibody system parameters
Authors: Oberpeilsteiner Stefan , Steiner Wolfgang
Published: December 2014

In the context of multibody simulation (MBS) system parameter identification within acceptable time can be challenging. One main difficulty is the huge amount of degrees of freedom in multibody systems and therefore the large number of dependent variables. The present work deals with the evaluation of different approaches that can be applied to typical parameter identification problems in MBS. A very powerful possibility is given by the adjoint sensitivity analysis that allows to reduce the computation effort dramatically. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Possibilities and Challenges in Kinematic Modeling of Highly Redundant, Non‐Holonomic and Omnidirectional Mobile Robots
Authors: Stöger Christoph , Gattringer Hubert , Mayr Johannes
Published: December 2014

Industry as well as the private domain show an increasing interest to the field of mobile robotics. With a higher number of applications, the complexity of the required tasks rises, and therefore the community tends to use robots with many degrees of freedom (DOF). The present paper takes this topic up and focuses on challenges of the kinematical modeling of redundant, non‐holonomic mobile robots by considering a 12 DOF platform. To reach an omnidirectional behaviour, the actuated wheels are diagonally mounted on the chassis. Well known problems resulting from this set‐up are parametric singularities which unnecessarily restrict the motion of the mathematical model. As it turns out, this problem can be avoided by the use of a non‐minimal parametrized model. An additional challenge results from the inverse kinematic (IK) problem on velocity level. The corresponding equations are highly underdetermined and, due to the non‐holonomic wheels, not directly affected by the steering angle velocities. This problem is solved by performing a local optimization on acceleration level. Finally, simulation results are presented. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Self‐Locking in Systems of Multiple Bodies
Authors: Brumme Stephan , Tergeist Mathias , Ostermeyer G.‐P.
Published: December 2014

The phenomenon of self‐locking can be found in many technical applications and common machine parts, such as screws, chocks, and funnels. Despite this, research into this topic is mostly limited to specific applications (e.g., worm gears, screws, kinematic chains). Current works with a general scope are rare. This paper addresses the analysis of self‐locking in different, two‐dimensional, multibody systems, and shall contribute towards a more general analysis. To elaborate on the characteristics of self‐locking, the effect is first shown and explained using simple systems as examples. From these examples, an approach towards a generalized description of self‐locking is proposed, which is used as a foundation for the development of two identification methods. The analysis of the self‐locking mechanism in multibody systems is realized first through an analytical ansatz, and then using a numerical simulation of the examples shown. The analytical and numerical analyses of the systems deliver a criterion, and respectively an algorithm, which enables the identification of self‐locked assemblies in different systems of multiple bodies. The algorithm is designed to identify self‐locking during integration of the equations of motion, whereas the analytic criterion is formulated for static systems with known, increasing external loads. The results of the two analysis methods correspond very well for the given example systems, leading to the conclusion that both methods are equivalent and usable. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evolution of the Fiber Density in Biological Tissues
Authors: Topol Heiko , Demirkoparan Hasan
Published: December 2014

An important challenge in the field of biomechanics is to understand and to model the properties of fibrous tissues. We consider a matrix‐fiber composite for which the matrix microstructure and its mechanical properties are taken to be constant. The initial fiber distribution is assumed to be unstructured and the mechanical properties of the fibers evolve during deformation. Further we assume that the fiber creation rate is constant while the fiber degeneration is stretch‐dependent. In particular, this study investigates the change of the fiber orientation density when a sudden simple shear is applied to the material. The fiber orientation density depends on the current deformation, the history of the deformation, and the deformation state of the fibers at the time of their creation. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On growth effects in the human liver
Authors: Werner Daniel , Ricken Tim , Holzhütter Hermann‐Georg , König Matthias , Dahmen Uta , Dirsch Olaf
Published: December 2014

Fatty liver is a common disease in the western society. Different stimuli, such as obesity or abuse of alcohol, cause the liver to store fat within liver cells, the so called hepatocytes. This growth induced by storage of fat influences the perfusion of the overlying structures, i. e. sinusoids, liver lobules, liver lobes, and consequently the liver itself. The scales of these structures reach from few µm (size of a hepatocyte) to several cm (size of liver). In view of finite element (FE) simulations, the necessity of introducing different scales becomes obvious. For the description of growth effects in the liver the relevant quantities are: perfusion of the liver and amount of substances that are needed for production of fat (glycogen and fatty acids). In this work we present a multiphasic continuum mechanical model for the description of micro‐perfusion in the liver lobule using a homogenized multiphasic approach based on the theory of porous media (TPM). Into this model we inserted a zero‐dimensional (0D) kinetic model calculating rates of all relevant substances. So far, the model focuses on the time dependent and spatial zonation of glycogen, since production of fat heavily depends on the stored glycogen. Additionally, a possible method for incorporating fatty acids and therefor also growth will be presented. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cellular articular cartilage replacement tissues: Modeling and analysis
Authors: Shehadeh Mohammad , Zhou Bei , Stoffel Marcus , Markert Bernd
Published: December 2014

Long‐term studies reveal that mechanical stimulation causes growth and remodeling phenomena within biological tissues. The main aim of this research is to fully understand and control these phenomena. For accomplishing that, two steps are considered: first, we determine a suitable numerical model based on different approaches by a comparative study using experimental validations, and second, investigate the mechanical properties of the tissue specimens after a remodeling process.

We start with the first step by choosing a convenient model that mimics the biotissue for running the numerical simulations in the second step. There are different models available that determine the mechanical properties of soft replacement tissues seeded with human chondrocytes in modern medical applications. It is our objective to achieve a common methodology of theory and experiments that allows the determination of the mechanical properties of the native material. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the multi‐component modelling of human brain tissue to survey clinical interventions
Authors: Wagner Arndt , Ehlers Wolfgang
Published: December 2014

Serious diseases within the brain's tissue often require a medical intervention, such as the treatment of brain tumours. The present contribution aims at predicting the expected impacts of a scheduled clinical procedure via numerical simulations based on a sophisticated constitutive model. The enormous complexity of the tissue's microscopic composition encourages the application of the Theory of Porous Media (TPM), providing a well‐suited way to model the brain's tissue aggregate in a compact manner on the macroscale. In particular, a multi‐component model is used which is strongly related to the drug‐delivery problem within the brain's tissue, cf. [2]. In this model, the solid skeleton is given by the tissue cells (with cell content) and the vascular walls. This solid skeleton is perfused by two mobile but basically separated pore‐liquid constituents, the blood and the overall interstitial fluid constituent. To provide the particular description of administered therapeutic agents within the overall interstitial fluid, this real mixture is treated as a chemical solution of two components. These are the liquid solvent and the dissolved therapeutic agent (drug). Numerical examples demonstrate the applicability of the derived model. In particular, infusions of therapeutics into the extra‐cellular space (ECS) are simulated under various conditions and complemented by an evaluation of the local numerical sensitivity to survey the influence of certain involved parameters. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical crack path prediction considering orthotropic effects and experimental verification
Authors: Judt Paul , Ricoeur Andreas , Linek Günter
Published: December 2014

For a reliable prediction of crack paths, on the one hand the accurate calculation of crack tip loading quantities is inevitable, on the other hand orthotropic features of the fracture toughness need to be taken into account. The interplay of crack tip loading and material response due to fracture is still unclear and seems to have a crucial effect on crack path predictions. Numerical tools for the accurate calculation of crack tip loading quantities using path‐invariant J‐integrals and interaction integrals (I‐integral) are presented. Here, global approaches are beneficial when considering crack tips approaching other crack faces or internal boundaries. Curved crack faces have to be taken into account and special treatment regarding crack face integrals is necessary. Experimental investigations are carried out at standard CT‐specimens of rolled aluminum alloy Al‐7075 exhibiting a directional orthotropy of the fracture toughness. Considering that property, the numerically predicted crack paths based on FE calculations show very good agreement with subcritically grown paths obtained from experiments. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical simulations of spalling tests in order to investigate material properties of UHPC
Authors: Dally T. , Reppel T. , Weinberg K.
Published: December 2014

In order to evaluate the material composition of Ultra High Performance Concrete (UHPC), material properties such as dynamic tensile strength or fracture strength and also the fracture energy under impact loading are of significant importance. The use of a modified Hopkinson Bar enables the determination of the required data. On the basis of experimental investigations our contribution deals with the numerical finite element simulation of the Hopkinson Bar test. The propagation of stress waves is reproduced by means of a special time‐integration scheme. We simulate the propagation of cracks by using adaptive cohesive elements including a corresponding separation law. The critical energy release rate (Griffith‐energy) is calculated and compared to the values determined by experimental results. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fracture toughness investigations on UHPC by spalling tests
Authors: Khosravani M.R. , Wagner P. , Frohlich D. , Trettin R. , Weinberg K.
Published: December 2014

Ultra High Performance Concrete (UHPC) is defined as a new generation of concrete which shows improved performance and higher strength than traditional concrete. This allows to realize slender and much more durable structures and in this way significantly reduces the required resources. Despite its huge potential in construction, technical information about this new type of material is still limited. This contribution presents investigations on the dynamic mechanical behavior and properties of UHPC specimens by spalling experiments. Two different recipes were used to compare the properties. Due to the special specimen geometry (slender cylindrical) a flowable consistency was required to enable a sufficient degassing of the mixtures.

For the test, a Split Hopkinson Pressure Bar (SHPB) has been modified and used. A high speed photograph system was focused on the fragmentation process during the test. On the basis of these experiments the dynamic E‐moduli as well as the dynamic tensile strength of the UHPC specimens were determined. By observation of the specific crack patterns on each tested specimen and corresponding times, the dynamic fracture energy is calculated.

Numerical simulations also were performed and compared to the experimental result. It is concluded that the dynamic tensile strength of the UHPC increases at higher strain rates. The results of the current study provide technical information about fracture and dynamic behavior of UHPC and the obtained values could be used for future computational models. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lifetime prediction of a rocket combustion chamber wall by a viscoplastic damage model
Authors: Fassin Marek , Tini Vivian , Vladimirov Ivaylo , Reese Stefanie
Published: December 2014

Regeneratively cooled nozzle structures of Reusable Launch Vehicles (RLV) belong to the most critical components of a space shuttle main engine. The so‐called doghouse effect is a failure mode in the rocket combustion chamber wall, which has been observed experimentally. Within the Collaborative Research Centre SFB‐TR 40 of the German Research Foundation (DFG), new technologies for the future space‐transport‐systems are being developed. By using a new continuum mechanical approach, motivated by a rheological model, we are able to reproduce the doghouse effect. Moreover we intend to give reliable lifetime predictions for rocket combustion chamber structures so that in future components can be tested virtually instead of conducting real experiments. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)