bluuebunny/crossref_metadata_2025 huggingface dataset:
Revision of the Cales noacki species complex (Hymenoptera, Chalcidoidea, Aphelinidae)
Authors: MOTTERN JASON L. , HERATY JOHN M.
Published: March 2014

The genus Cales (Hymenoptera: Aphelinidae) includes 13 species worldwide, of which 10 form a highly morphologically uniform species complex with a native range in the Neotropical region. We recognize ten species previously attributed to a single Neotropical species, Cales noacki Howard, which in the strict sense is a species broadly disseminated to control woolly whitefly. A neotype is designated for C. noacki, and it is redescribed based on specimens molecularly determined to be conspecific with the neotype. Newly described species include: C. bicolor Mottern, n.sp., C. breviclava Mottern, n.sp., C. brevisensillum Mottern n.sp., C. curvigladius Mottern, n.sp., C. longiseta Mottern, n.sp., C. multisensillum Mottern n.sp., C. noyesi Mottern, n.sp., C. parvigladius Mottern, n.sp. and C. rosei Mottern, n.sp. Species are delimited based on a combination of morphological and molecular data (28S‐D2 rDNA and COI). Additional specimens are included in the phylogenetic analyses and although these likely represent several new species, we lack sufficient specimen sampling to describe them at this time. Cales are highly morphologically conserved and character‐poor, resulting in several cryptic species. A molecular phylogeny of the known Neotropical species based on 28S‐D2–5 rDNA and a 390‐bp segment of COI is included, and identification keys to males and females are provided.

This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:7FEB0479‐9B2E‐48E8‐8603‐4B7C2759D4EC.
Signal through the noise? Phylogeny of the Tachinidae (Diptera) as inferred from morphological evidence
Authors: CERRETTI PIERFILIPPO , O'HARA JAMES E. , WOOD D. MONTGOMERY , SHIMA HIROSHI , INCLAN DIEGO J. , STIREMAN JOHN O.
Published: March 2014

The oestroid family Tachinidae represents one of the most diverse lineages of insect parasitoids. Despite their broad distribution, diversity and important role as biological control agents, the phylogeny of this family remains poorly known. Here, we review the history of tachinid systematics and present the first quantitative phylogenetic analysis of the family based on morphological data. Cladistic analyses were conducted using 135 morphological characters from 492 species belonging to 180 tachinid genera, including the four currently recognized subfamilies (Dexiinae, Exoristinae, Phasiinae, Tachininae) and all major tribes. We used characters of eggs, first‐instar larvae and adults of both sexes. We examined the effects of implied weighting by reanalysing the data with varying concavity factors. Our analysis generally supports the subfamily groupings Dexiinae + Phasiinae and Tachininae + Exoristinae, with only the Exoristinae and the Phasiinae reconstructed as monophyletic assemblages under a wide range of weighting schemes. Under these conditions, the Dexiinae, which were previously considered a well‐established monophyletic assemblage, are reconstructed as being paraphyletic with respect to the Phasiinae. The Tachininae are reconstructed as a paraphyletic grade from which the monophyletic Exoristinae arose. The Exoristinae are reconstructed as a monophyletic lineage, but phylogenetic relationships within the subfamily are largely unresolved. We further explored the evolution of oviposition strategy and found that the oviparous groups are nested within ovolarviparous assemblages, suggesting that ovipary may have evolved several times independently from ovolarviparous ancestors. This counterintuitive pattern is a novel hypothesis suggested by the results of this analysis. Finally, two major patterns emerge when considering host associations across our phylogeny under equal weights: (i) although more than 60% of tachinids are parasitoids of Lepidoptera larvae, none of the basal clades is unambiguously associated with Lepidoptera as a primitive condition, suggesting that tachinids were slow to colonize these hosts, but then radiated extensively on them; and (ii) there is general agreement between host use and monophyly of the major lineages.
The Downward March of Labor Halted? The Crisis of Neoliberal Capitalism and the Remaking of Working Classes
Authors: Schmidt Ingo
Published: March 2014

This article raises the question whether riots, protests, and strikes in the aftermath of the Euro‐crisis mark a turn from moving backwards to moving forward for labor movements. An answer to this question is developed by disentangling the unmaking and remaking of working classes in the Euro‐zone countries. The analysis of their unmaking draws on Beverly Silver's work and shows how technological and organization reorganization and relocations from the 1980s until the present weakened workers' bargaining power and political representation and tore apart the social fabric that had been crucial for the reproduction of class identities even during the period of institutionalized class conflict. The analysis of the remaking of working classes points at fragmented articulations of discontent, which also include the rise of right‐wing populism, as parts of a learning process that might eventually lead to the constitution of classes as collective agents of change. This analysis draws on E. P. Thompson's interpretation of the “original making” of working classes but extends his focus on England to the broader European sphere and the consideration of workers' responses to economic crises. Theoretical guidance for these last two aspects comes from Rosa Luxemburg's economic and political writings.
“Welcome to the Border”: National Geographic's Border Wars and the Naturalization of Border Militarization
Authors: Dorr Noam , Elcioglu Emine Fidan , Gaydos Lindsey
Published: March 2014

This article argues that National Geographic's highly rated television series Border Wars (BW) bestows border enforcement with a “natural” quality and precludes any discussion of alternatives to border buildup. It does this in three main ways. First, even though there is no actual war, the show frames federal agents as soldiers and their enforcement practices as soldiering. As such, escalation of border enforcement is portrayed as a fatalistic necessity in confronting a guerrilla‐like enemy. Second, to the extent that the show depicts actual encounters with crossers, it goes to great lengths to simplify the context and moral implications of crossers’ stories. Third, BW fixes the viewer's gaze on objects—particularly illicit ones—and evades a discussion of the social processes hidden behind them. In these ways, BW essentializes cross‐border flows and justifies border enforcement.
Intraluminal Thrombus in AAA Wall Stress Analysis
Authors: Speelman Lambert , van Dam Evelyne A. , Peters Gerrit W. M. , Bosboom E. Marielle M. , Rutten Marcel C. M. , Schurink Geert Willem H. , Jacobs Michael J. H. M. , van de Vosse Frans N.
Published: March 2014

In previous research abdominal aortic aneurysm (AAA) wall stress analysis has proven to be more accurate in rupture risk prediction than the clinically used diameter criterion [1]. Together with Philips Medical Systems (Best, NL), a clinical software tool is created that automatically derives the AAA geometry from patient CT data and performs AAA wall stress analysis (Hemodyn package). Using this software package, the role of intraluminal thrombus (ILT) in AAA wall stress analysis is evaluated in this study.
Transport Characteristics of a Novel Local Drug Delivery System Using Nordihydroguaiaretic Acid (NDGA)-Polymerized Collagen Fibers
Authors: Guegan Eric , Davis Tian , Koob Thomas J. , Moussy Yvonne
Published: March 2014

Local delivery of a drug in vivo would permit high interstitial drug concentration at the desired location without producing high systemic drug levels. Previous local drug delivery systems have included biodegradable polymer implants, hydrogels, and osmotic pumps [1]. In this paper, we describe a novel local drug delivery system using nordihydroguaiaretic acid (NDGA)-polymerized collagen fibers. NDGA collagen fibers were originally developed for use as biocompatible tendon bioprostheses [2]. The NDGA collagen fibers were loaded with either: dexamethasone, a synthetic glucocorticoid with anti-inflammatory and immunosuppressive activities; or dexamethasone 21-phosphate, a water soluble pro-drug that is converted into dexamethasone in vivo. Dexamethasone was chosen as the loading agent since experiments pairing the loaded fibers with implantable glucose sensors will be performed in the future. This may be useful for preventing inflammation around implantable glucose sensor [3]. This decrease in inflammation is expected to increase glucose sensor function and lifetime. We also determined the diffusion coefficient of dexamethasone and dexamethasone 21-phosphate in the NDGA collagen fiber. In an effort to control the rate of release of dexamethasone, the biocompatible copolymer, polylactic-co-glycolic acid (PLGA) was used to coat the fibers. The information obtained from these experiments is necessary for the future development of an optimal local delivery system of dexamethasone using NDGA collagen fibers in an effort to suppress the inflammatory response around implantable glucose sensors.
A Proposed New Brain Injury Tolerance Criterion Based on the Exchange of Energy Between the Skull and the Brain
Authors: Szczyrba Igor , Burtscher Martin , Szczyrba Rafal
Published: March 2014

The Head Injury Criterion limit, HIC1000T = 1000, was developed based on skull fracture data (short time intervals T) and longer duration head translations that lead to Closed Head Injuries (CHI). However, recent results imply that the HIC limits depend on the time interval T and the victim’s age [1]. Since the HIC lacks a clear physical interpretation, it is difficult to compare (verify) the new HIC limits with data from non-translational motions, e.g., to link these limits with the Diffuse Axonal Injury (DAI) criterion developed for head rotations [2]. The recent Head Impact Power (HIP) criterion can be applied to arbitrary motions, but it requires determining six parameters experimentally [3].
Real Time Techniques for Nonlinear Tissue Deformation in Surgical Simulation
Authors: De Suvranu , Lim Yi-Je
Published: March 2014

The requirement of real time performance, crucial to multimodal surgical simulations, imposes severe demands in terms of computational efficiency. A physics-based meshfree computational technique known as the Point-Associated Finite Field (PAFF) approach has been developed to circumvent many outstanding problems associated with traditional mesh-based computational schemes and has been applied in this paper to the modeling of geometrically nonlinear tissue deformations. The technique is based on a novel combination of multiresolution approach coupled with a fast reanalysis scheme in which the response predicted by an underlying linear PAFF model is enhanced in the local neighborhood of the surgical tool-tip by a nonlinear model. We present performance comparisons of PAFF with traditional finite element models.
Nonuniform Circumferential Deformation of the Abdominal Aorta: A Cross-Species Comparison
Authors: Goergen Craig J. , Johnson Bonnie L. , Greve Joan M. , Zarins Christopher K. , Taylor Charles A.
Published: March 2014

Arterial wall biomechanics are thought to be important in aneurysm development and atherosclerotic plaque localization. Vessel wall dilation occurs because of pulsatile blood flow during the cardiac cycle. Until recently, it was commonly assumed that this dilation occurred concentrically about the center of the lumen. However, dynamic MR, CT, and ultrasound imaging techniques have now shown that aortic wall motion undergoes unequal circumferential deformation during the cardiac cycle. This phenomenon has been observed in both humans and pigs [1, 2]. The purpose of our study was to determine whether variations in circumferential aortic wall dilation persist across mammalian species.
Fracture Resistance of Human Amnion
Authors: Oyen Michelle L. , Ferguson Virginia L. , Calvin Steven E.
Published: March 2014

While normal delivery requires disruption of the placental membranes (the “breaking of waters”), in one third of premature births delivery results from with mechanical rupture of the placental membranes prior to full-term gestation [1]. The biomechanical investigation of membrane rupture has thus been a subject of recent study [2–5]. In particular, mechanical investigations aimed specifically at understanding the membrane rupture process have concluded that the chorioamnion membrane bilayer breaks in two separate events, such that the chorion and amnion component layers fail independently, and that the delamination of the chorioamnion may represent a significant fraction of the total mechanical work done in membrane rupture [5]. The amnion is the stiffer and stronger of the two membrane layers, consisting primarily of a dense type I collagen network.
The Effect of Instrumentation With Different Mechanical Properties on the Pig Spine During Growth: Finite Element Analysis
Authors: Rizza Robert , Liu Xue-Cheng , Thometz John , Mahinfalah Mohammad , Tassone Channing
Published: March 2014

For the treatment of scoliosis, traditional instrumentations such as Cotrel-Dubousset are very rigid and effect spine growth ([1] & [2]). Recently, spinal fusion-less instrumentation has been clinically introduced. These instrumentations are more spring-like (compliant). Such instrumentations include multiple level staples, vertical expanding prosthesis, and changeable rod system. However, whether the instrumentation is rigid or compliant, the growth of the spine is effected. The actual level of instrument stiffness that affects growth is not known nor well quantified. The goal of this study was to examine the effect of the level of instrumentation stiffness on the simulation of growth of the pig spine by using finite element analysis (FEA).
Acoustic Vibration and Mechanical In Vivo Analysis of the Hip Joint After a Total Hip Arthroplasty
Authors: Glaser D. A. , Komistek R. D. , Cates H. E. , Mahfouz M.
Published: March 2014

The major complications following total hip replacement (THA) are implant loosening, dislocation, instability, fracture and infection. It is hypothesized that vibration, in the range of the resonance frequencies, may cause pain, bone degeneration and fracture. A further understanding of the physical response resulting from impact during femoral head sliding may lead to valuable insight pertaining to THA failure. Therefore, the first objective of this present study was to determine if frequencies propagating through the hip joint near resonant frequencies may lead to wear or loosening of the components. Recently, studies found that femoral head sliding, often referred to as hip separation, between the acetabulum cup and the femoral head does occur, which may also play a role in complications observed with THA today, but a the effects of hip separation and the causes of its occurrence has not been studied as jet. Therefore, the second objective of this study was to determine if a sound sensor, externally attached, could be used to correlate impact loading sounds from femoral head sliding in the acetabular cup. Additional objective of this study was to develop a mathematical model that better simulates the in vivo loading conditions of total hip replacement patients using in vivo fluoroscopic and ground reaction data as input.
Modulating Human Connective Tissue Progenitor (CTP) Cell Behavior on Cellulose Acetate Scaffolds by Surface Microtextures
Authors: Kim Eun Jung , Boehm Cynthia , Fleischman Aaron J. , Muschler George F. , Kostov Yordan , Roy Shuvo
Published: March 2014

It has been shown that precise microarchitecture and surface microtexture can enhance cell behavior such as cell attachment, proliferation, migration and differentiation in cell culture environment [1]. Even though Polydimethylsiloxane (PDMS) has been commonly used to fabricate the microtextured surfaces, PDMS is not biodegradable. Cellulose Acetate (CA), on the other hand, has very promising properties as scaffold material for tissue engineering applications. It is biodegradable, has low water solubility, and generates minimal foreign body reaction in vivo [2]. In this study, soft lithography techniques are used to fabricate CA and PDMS scaffolds with precise surface microtextures to compare growth characteristics of progenitor cells.
Finite Element Analysis of Clinical Pressure-Flow Waveforms in a Collapsed Respiratory Airway
Authors: Bell E. David , Ghadiali Samir N.
Published: March 2014

Otitis media (OM) is the most commonly diagnosed disorder in young children and cost the US economy ∼$5 billion dollars annually[1]. Although the primary etiology responsible for the persistence of OM conditions is a dysfunctional Eustachian tube (ET), the biomechanical mechanisms responsible for ET dysfunction are not well established. The ET is a collapsible, respiratory airway which connects the nasopharynx with the middle ear (ME). The ET normally exists in a closed state and must be periodically opened in order to clear ME fluids and ventilate the ME. The inability to open the ET results in painful sub-ambient ME pressures, fluid accumulation in the ME and the inflammation of the ME mucosa (i.e. OM).
Differential Expression of Fibulin Family Proteins in Mechanically Strong vs. Weak Fetal Membrane Fragments
Authors: Moore John J. , Moore Robert M. , Kumar Deepak , Mansour Joseph M. , Mercer Brian M. , Yohannes Elizabeth , Novak Jillian , Chance Mark
Published: March 2014

Untimely rupture of the fetal membranes (FM), the amnion and choriodecidua, which normally surround and protect the fetus prior to delivery, is a major cause of preterm birth and results in significant infant mortality and morbidity. The physiological mechanism which normally leads the FM to weaken and fail prior to birth is not known. Conventional thinking that FM rupture is precipitated by the stress of uterine contractions during labor fails to explain the 10% of term deliveries and 40% of preterm deliveries in which FM rupture is the sentinel event, preceding any uterine contractions. Recent studies from several laboratories indicate that the FM undergo a genetically-programmed, biochemically-mediated, maturation process, near term, which is characterized by collagen remodeling and apoptosis. In human FM, in contrast to rat membranes, these changes are limited to the region of the FM overlying the cervix [1]. In a series of publications, our group has demonstrated that human FM have a zone of physical weakness (decreased force to rupture and work to rupture relative to the other areas of the same FM) overlying the cervical opening of the uterus. We further demonstrate that this same zone is characterized by specific markers of increased collagen remodeling and apoptosis [1–3]. These regional characteristics develop prior to the onset of contractions of labor and persist until delivery. Furthermore, the rupture tear line of the FM intersects this weak zone and thus the rupture process is hypothesized to initiate in this weak zone [3]. In order to investigate how differences in the biochemical composition of the extra-cellular matrix of the weak and the strong zones of FM reflect their different biomechanical properties, we utilized a proteomics approach to identify differences in the abundance of specific proteins in weak and strong FM fragments. Initial 2-DIGE screening resolved differences in Fibulin 5 protein expression. This prompted further analysis of additional members of the Fibulin protein family.
Shoulder Tendon Repair Biomechanics Using a Polyurethane Patch in a Chronic Ovine Defect Model
Authors: McGilvray Kirk C. , Lyons Amy S. , Turner A. Simon , MacGillivray John D. , Coleman Struan H. , Puttlitz Christian M.
Published: March 2014

Rotator cuff disorders are one of the most common soft tissue injuries of the musculoskeletal system [1], second only to lower back pain presentations in clinical frequency [2]. Surgical repairs of chronic, massive rotator cuff tears are associated with a high rate of complications, typically by full or partial re-rupture of the repair [3,4]. The literature is replete with clinical retrospective studies or evaluation of cadaveric shoulders [5], however these studies do not address the in vivo healing characteristics of a given surgical repair. The purpose of this study was to quantitatively describe the degree of shoulder healing via biomechanical analyses using an ovine chronic infraspinatus model that was repaired with and without a polyurethane scaffold rotator cuff repair (RCR) patch.
Effect of Active Transport and Loss to Choroidal Blood Flow on Transscleral Drug Delivery to the Posterior Eye
Authors: Balachandran Ram K. , Barocas Victor H.
Published: March 2014

Delivering drugs to the posterior eye has been a challenge for many years. Systemic delivery of drugs is not a viable option because the eye does not receive enough blood supply, because of its small size, for the drug delivery process to be effective. Topical delivery in the form of eye drops is also ineffective in generating therapeutic concentrations in the posterior eye, because of the resistance offered by the corneal epithelium to the transport of drugs, and rapid elimination due to aqueous humor flow and tear dilution. Intravitreal delivery of drugs through implants and injections has been associated with serious side effects like endophthalmitis, hemorrhage, and retinal detachment. In recent years, transcleral delivery of drugs has received attention due to the relatively high permeability of the sclera.
Numerical and Experimental Study of a Novel Phase Contrast Technique: Self Reference Phase-Contrast Magnetic Resonance Imaging
Authors: Li Longchuan , Doyle Mark , Rayarao Geetha , Kortright Eduardo , Anayiotos Andreas S.
Published: March 2014

The quantitative measurement of blood flow using magnetic resonance imaging (MRI) has been a topic of research for over twenty years. At present, blood flow measurements are largely performed using two-dimensional phase contrast magnetic resonance (PC-MR). However, when high acceleration terms are present (i.e., valve regurgitation or stenosis), accuracy of conventional (Con) cardiac PC-MR can suffer: when data are acquired at a relatively poor temporal resolution, the data extraction process, which essentially is one of comparison, makes the Con PC-MR data sensitive to temporal acceleration. Here, a novel PC-MR technique termed Self Reference (SR) PC-MR is introduced that overcomes these limitations by eliminating the need for comparing paired data sets.
Gel Based Mechanical Phantom of Stenotic Coronary Artery
Authors: Pazos Valérie , Tardif Jean-Claude , Mongrain Rosarie
Published: March 2014

Intravascular ultrasound (IVUS) is currently the only commercially available clinical imaging modality providing real-time high-resolution cross-sectional images of human coronary arteries in patients. New techniques and models are being developed to derive pertinent information from IVUS images about atherosclerotic tissues properties. Their evaluation and optimization often require the use of realistic test phantoms that can be made precisely, with a known, and generally simpler, structure that is used as reference and allows for a simplification of the problem.
Flow and Convective Dispersion in the Conductive Airways of the Human Lung
Authors: Fresconi F. E. , Prasad A. K.
Published: March 2014

Dispersion of particles in the lung is relevant to three areas: design of therapeutic aerosols and their delivery systems, risk assessment of exposure to toxic particles, and clinical diagnosis of lung function via the inhaled bolus technique. Gas dispersion is critical to optimizing alternative modes of ventilation, such as high-frequency ventilation (HFV).
Mechanical Conditioning Stimulates the Development of Tissue Properties in Engineered Cardiovascular Constructs
Authors: Rubbens Mirjam P. , Boerboom Ralf A. , Mol Anita , Bouten Carlijn V. C. , Baaijens Frank P. T.
Published: March 2014

Currently used cardiovascular replacements are unable to grow, repair and remodel, which is an important drawback for pediatric patients. Tissue engineering is a promising technique to create living substitutes that are able to adapt to changing conditions.
On Coupling a Lumped-Parameter Heart Model With a Three-Dimensional Finite Element Model of the Aorta
Authors: Kim Hyun Jin , Figueroa C. Alberto , Vignon-Clementel Irene E. , Jansen Kenneth E. , Taylor Charles A.
Published: March 2014

Aortic pressure and flow result from the interaction between the ventricle and the arterial circulation. However, prior three-dimensional simulations of aortic blood flow have either assumed a prescribed velocity profile at the inlet or have computed aortic flow and pressure using an upstream heart model implemented with an explicit approach. In this work, we describe an implicit approach which strongly couples a lumped-parameter heart model with a three-dimensional finite element model of the vascular system. We demonstrate that this approach can be used to compute physiologically-realistic blood flow and pressure waves in three-dimensional arterial models and study the interactions between the heart and the vascular system.
Development of a Wavelet Analytical Tool for Isolating and Evaluating Cavitation-Induced Hemolysis Generated During Mechanical Heart Valve Closure
Authors: Herbertson Luke H. , Deutsch Steven , Manning Keefe B.
Published: March 2014

Cavitation formed during the closure of mechanical heart valves (MHVs) can harm nearby blood cells and valve surfaces. In this study we focus on an approach to accurately measure cavitation energy in order to compare the effectiveness of replacement valves. Cavitation energy is difficult to measure acoustically because it is masked by other pressure fluctuations in the body or system. To improve upon currently used analytical techniques, a wavelet isolation technique was developed to quantify cavitation energy. With this method, acoustic signals captured by a hydrophone are decomposed, denoised, and then reconstructed. Wavelet analysis should prove to be particularly valuable in vivo, where visual evidence of cavitation cannot be obtained.
Non Invasive Assessment of Leaflet Deformation in Heart Valve Tissue Engineering
Authors: Kortsmit Jeroen , Driessen Niels J. B. , Rutten Marcel C. M. , Baaijens Frank P. T.
Published: March 2014

Contemporary tissue engineered heart valves seem to have sufficient mechanical strength for implantation [1]. Nevertheless, mechanical properties, tissue structure and architecture still need to be improved. Recent studies indicate enhancement of mechanical properties by applying cyclic diastolic pressure loads to the developing tissue in a bioreactor system [2]. However, current bioreactors operate with a preset transvalvular pressure applied to the tissue. Mechanical properties of the engineered construct may vary during culturing and consequently, the pressure-induced deformations are unknown. To systematically study the effects of mechanical straining on tissue development and to design an optimal conditioning protocol, real-time measurement and control of local tissue strains are desired.
Stress Dependent Collagen Fibril Diameter Distribution in Human Aortic Valves
Authors: Balguid Angelique , Mol Anita , Driessen Niels , Bouten Carlijn , Baaijens Frank
Published: March 2014

The mechanical properties of collagenous tissues are known to depend on a wide variety of factors, such as the type of tissue and the composition of its extracellular matrix. Relating mechanical roles to individual matrix components in such a complex system is difficult, if not impossible. However, as collagen is the main load bearing component in connective tissues, the relation between collagen and tissue biomechanics has been studied extensively in various types of tissues. The type of collagen, the amount and type of inter- and intramolecular covalent cross-links and collagen fibril morphology are involved in the tissues mechanical behavior (Beekman et al., 1997; Parry et al., 1978; Avery and Bailey, 2005). From literature it is known that the the collagen fibril diameter distribution can be directly related to the mechanical properties of the tissue. In particular, the diameter distribution of collagen fibrils is largely determined by the tissues requirement for tensile strength and elasticity (Parry et al., 1978).
Micromotions at the Bone Implant Interface Up-Regulate Osteoblasts-Mediated Activation of Osteoclasts in Ex Vivo Human Samples
Authors: Stadelmann Vincent A. , Pioletti Dominique P.
Published: March 2014

A radiolucent zone at the interface of bone and implants in total joint prosthesis is frequently observed in uncemented and cemented implants. This radiolucent zone, representing a fibrous tissue, is the result of the progressive deterioration of the bone surrounding implants. Fibrous tissues affect the implant fixation, increasing then the risk of aseptic loosening. Today, aseptic loosening is the most common cause of arthroplasties revisions.
Simulation of the Microcirculation in Rat Spinotrapezius Muscle Fascia
Authors: Jacobitz Frank G. , Engebrecht Cheryn P. , Metzger Ian D. , Porterfield Colin A.
Published: March 2014

A thorough understanding of the microcirculation may help with the early diagnosis and treatment of many diseases such as diabetes or hypertension (see for example Schmid-Schönbein [1]). In this study, the microcirculation in rat spinotrapezius muscle fascia is investigated using a numerical approach.
Measurement of Acoustic Emission Wave Attenuation by Bones and Muscles
Authors: Pruden Benjamin , Akkus Ozan
Published: March 2014

Stress fractures occur in bones of athletes and soldiers due to the accumulation of microcracks [1]. Detection of precursor acoustic emissions (i.e. ultrasonic stress waves) resulting from microcrack activity may help predict failure onset before continuous physiological activity results in full-blown fracture. An acoustic emission wave generated from a microcrack in bone will be diminished by dispersion, mode separation, reflection, and viscous losses induced by the biological tissues (skin, muscle, fat) between the source and the transducer. While others have recorded waves emanating from unknown loci in human knee in vivo using acoustic emission method [2], there is no means to appreciate how far these waves can travel in the body. Several studies have characterized the ultrasound attenuation in bone [3] and muscle analog homogenates [4] in the frequency range above 300 kHz. On the other hand, acoustic emissions are prominent in the range of 20 kHz to 300 kHz. The current study focused on identifying the attenuation of acoustic emission waves in bone and muscle tissues in a frequency range which is more relevant to acoustic emissions. This information is critical for predicting whether an emission of certain magnitude at the source can reach surface mounted sensors without being totally attenuated.
Cartilage Damage in the Unstable Knee is Related to Tibio-Femoral Contact Mechanics
Authors: Anderst William J. , Tashman Scott
Published: March 2014

Joint instability may lead to modified and excessive mechanical stresses on the articular surfaces. This repetitive, chronic mechanical overload is one possible source behind the initiation and progression of osteoarthritis (OA). However, the mechanisms by which excessive mechanical force may lead to OA remain unknown. It has been proposed that a change in the location of load bearing regions following joint instability may initiate OA, while the progression of OA is driven by increased tangential shear loading [1]. In addition to changing the load location, joint instability may modify bone kinematics, and in turn articulating surface interactions (e.g. sliding, pivoting and rolling contacts). These altered surface interactions may result in novel and damaging loading applied to the articular cartilage.
Thrombotic Potential of a Prosthetic Vein Valve
Authors: Farrell Laura-Lee , Nair Deepak , Milner Ross , Ku David
Published: March 2014

Over seven million Americans suffer from chronic venous insufficiency, secondary to valvular dysfunction, with few effective clinical therapies. Chronic Venous Insufficiency (CVI) is a painful and debilitating disease that affects the superficial and deep veins of the legs. After deep venous thrombosis, the vein valves leaflets become adherent, fold over, or are absorbed into the vein wall. Incompetent valves allow reflux and subsequent pooling of blood in the legs. The resultant CVI causes severe leg edema, skin breakdown, and possible gangrene. Current clinical therapies are only modestly effective and include vein stripping and ligation, valvuloplasty, vein valve transposition, and vein valve transplantation. Valvuloplasty is the most definitive of CVI treatment, though this surgical treatment is rarely performed due to its difficulty. The quest for a better solution continues.
The Influence of Different Parameters of Remodeling Rule on the Resultant Density Distribution of the Proximal Femur
Authors: Marzban Ali , Nayeb-Hashemi Hamid , Canavan Paul K.
Published: March 2014

The process of adaptive bone remodeling can be described mathematically and simulated with a self-optimizing finite element (FE) model. The aim of this study was to find the bone density distribution of the proximal femur which is affected by the muscle loadings and the hip joint contact force. The basic remodeling rule, which is an objective function for an optimization process relative to external load, was applied to predict the bone density. Its purpose is to obtain a constant value for the strain energy per unit bone mass, by adapting density. The precise solution is dependent on the loads, initial conditions and the parameters in the remodeling rule. The forces at different phases of the gait cycle (walking) were applied as boundary conditions. The density distributions from these loadings were averaged to find the density distribution in the proximal femur. Three different initial densities were considered to investigate the effect of initial conditions. The influence of different parameters and functions on the density distribution and its convergence rate was also investigated. The results were comparable with an actual bone density distribution of the femoral neck head and proximal femoral shaft. It was shown that by applying more boundary conditions through the gait cycle, the converged density distribution is smoother, and more comparable with actual proximal femur.
The Roles of Elastic Fibres and Glycosaminoglycans in the Radial Tensile Mechanics of the Human Lumbar Anulus Fibrosus
Authors: Smith Lachlan J. , Byers Sharon , Costi John J. , Fazzalari Nicola L.
Published: March 2014

The anulus fibrosus of the human lumbar disc has a complex, hierarchical structure comprised of collagen, proteoglycan and elastic fibres [1,2]. Individually and through interactions, these constituents govern the complex, anisotropic mechanical reponse of the anulus; the exact nature of their contributions, however, remains unclear [3]. In the radial direction, mechanical behaviour is heterogeneous, varies with degenerative condition, and is thought to be governed largely by the matrix at lamellar interfaces [4,5]. The objectives of this study were to quantify the contributions made by both elastic fibres and glycosaminoglycans to the radial tensile reponse of the human lumbar anulus, using a combination of targeted enzymatic degradation and biomechanical testing.
Investigation of Cartilage Biomechanical Properties: Dependence on Strain, Direction, and Biochemical Composition
Authors: Thomas Gregory C. , Ficklin Timothy P. , Barthel James C. , Asanbaeva Anna , Thonar Eugene J.-M. A. , Masuda Koichi , Chen Albert C. , Sah Robert L. , Davol Andrew , Klisch Stephen M.
Published: March 2014

Articular cartilage (AC) serves as the major load bearing material within synovial joints and provides a low friction and wear resistant interface. As an avascular tissue, AC lacks the ability to repair structural damage or degeneration. Thus, the need for replacement tissue was a motivating factor in the development of cartilage tissue engineering. Recently, a finite element model (FEM) of cartilage growth [1] has been developed to simulate various growth conditions such as in vitro (outside the body) tissue growth experiments. In order to validate growth laws used in the FEM, empirical measurements of AC properties (mechanical and biochemical) before and after in vitro growth are needed. The goal of this study is to design protocols to comprehensively quantify the biomechanical structure-function relations of AC.
Dynamic Remeshing for Fluid Structure Interaction: Application to Modelling Aortic Dissection
Authors: Moyle Keri R. , Ventikos Yiannis
Published: March 2014

Aortic dissection is an acute condition occurring more frequently than ruptured abdominal aortic aneurysms, with a mortality rate increase of 1% per hour if left untreated [1]. Dissection occurs following creation of an entrance tear, through which blood can force its way into the wall, forming a pocket that propagates longitudinally. The membrane of the dissection flap separates the true lumen (through which the organs are supplied with blood), from a false lumen (the pocket created by the dissection). The total obstruction of the true lumen by the motion of the vessel flap, or organ starvation due to branch vessel compression by the false lumen, can be fatal. Figure 1 shows an idealised representation of an aortic dissection model.
Iris Stiffening Following Drug Stimulation
Authors: Whitcomb Julie E. , Barnett Vincent A. , Olsen Timothy W. , Barocas Victor H.
Published: March 2014

Glaucoma is a general term for the deterioration of the optic nerve head usually associated with an increase of intraocular pressure (IOP). Certain types of glaucoma are associated directly with the displacement of the iris from its normal morphology [1]. For example, angle closure glaucoma and pigment dispersion syndrome involve abnormal anterior or posterior displacement of the iris, respectively [2]. In angle closure, the abnormal position of the peripheral iris blocks aqueous humor access to the outflow pathway (trabecular meshwork), increasing the IOP. Although there has been a considerable amount of ultrastructural characterization of the iris [3], to our knowledge, there as been little done on the mechanical characterization of the iris other than a previous study by Heys and Barocas on passive bovine irides [4]. To have a complete understanding of these it requires that we understand the mechanical properties of the iris in both its passive and stimulated states. Mechanical analysis of the iris requires the consideration of its two constituent muscles, the inner sphincter iridis and the outer dilator pupillae, see Fig. 1. The sphincter iridis is innervated parasympathetically whereas the dilator is innervated sympathetically.
Force/Torque Field Generation to Obtain Local Properties within Soft Hydrogels
Authors: Chippada Uday , Yurke Bernard , Shreiber David I. , Schloss Rene , Jiang Xue , Li Lulu , Langrana Noshir A.
Published: March 2014

Soft media like hydrogels are used as substrates for cellular engineering of different cell types and the stiffness of these media plays an important role in the cellular behavior like adhesion, proliferation, matrix deposition and differentiation. The global mechanical properties of such substrates were previously calculated using spherical beads embedded in micro-liter samples and then deflecting them by a magnetic manipulator [1]. Knowing the force and the displacement the elastic modulus was evaluated using closed form solutions. However in the context of our studies for biological applications there are circumstances where the local elastic properties of the hydrogel play an important role. For example in the vicinity of a cell, the cell will distort the gel and the modulus of elasticity of the surface may get altered, particularly if the gel is non-linear and if the distortions are substantial. In order to measure these local properties a four magnet manipulator based on Amblard, et al [2] was built, which is capable of applying large forces on micron sized particles embedded in the media.
In Situ Transient Deformation of Chondrocytes Under Unconfined Compression: Experimental Measurements and Triphasic Finite Element Model
Authors: Likhitpanichkul Morakot , Guo X. Edward , Mow Van C.
Published: March 2014

Under physiological loading, chondrocytes experience environmental changes due to complex mechanical and electrochemical events induced within cartilage. By mechanisms of cell-matrix interactions that remain unclear, chondrocytes perceive and respond to these events resulting in cascades of intracellular signals, and in turn alter their metabolic and biosynthesis activities. Chondrocyte deformation is a major cell response to mechanical load that has been proposed as a direct pathway for cell-matrix interaction and has been investigated in several studies [1–3]. However, the transient deformation of chondrocytes in situ, which is important in understanding the cell-matrix interaction under the viscoelastic response of cartilage, has not been well reported. In this study, we first aimed to measure and investigate the characteristics of the chondrocyte transient deformation within cartilage under the commonly-used unconfined compression test. We then aimed to model the cell inclusion within each specific cartilage specimen utilizing a multi-scale, triphasic finite element framework [4]. Finally the finite element model (FEM) will be used to calculate and perform parametric analyses of the cell transient deformation.
In-Vitro Evaluation of Hot-Film Anemometry Using a Sensor-Tipped Coronary Guide-wire
Authors: Geven Maartje C. F. , Van Der Horst Arjen , Rutten Marcel C. M. , Aarnoudse Wilbert , Pijls Nico H. J. , van de Vosse Frans N.
Published: March 2014

During coronary catheterization, the epicardial coronary arteries are visually assessed for stenoses on the coronary angiogram. However, the functional significance of disease in the coronary arterial tree, the increased resistance to blood flow, may easily be over- or underestimated by using a 2D projection.
Collagen Fiber Organization in the Cervical Facet Capsular Ligament Following Painful Facet Joint Distraction in the Rat
Authors: Lee Kathryn E. , Winkelstein Beth A.
Published: March 2014

Chronic neck pain following whiplash is a substantial problem, affecting as many as 42% of whiplash patients [1]. The cervical facet joint is a common candidate for producing neck pain because it sustains altered kinematics during whiplash, with tensile stretch of its capsular ligament exceeding that during normal motions [2,3]. Altered facet capsule mechanics have been documented for loading conditions below structural failure [4,5]; evidence of both decreased linear stiffness and minor ruptures of the capsule suggest ligament injury prior to failure. In vivo studies have also implicated subfailure capsule injury as a potential source of pain. Capsule nociceptive pain fiber activation and saturation [6], as well as sustained pain symptoms [7], can be produced for facet joint distraction below gross failure.
Diastolic Dysfunction Persists After Unloading by Left Ventricular Assist Device (LVAD) Support
Authors: Peterson Sherket B. , Radovancevic Branislav , Hernandez Antonietta , Radovancevic Rajko , Droddy Allison , Carranza Sylvia , Stainback Raymond , Grande-Allen K. Jane
Published: March 2014

Left Atrium (LA) size has prognostic importance in a variety of cardiac conditions [1] and is known to be enlarged with decreased contractile function in patients with congestive heart failure (CHF) [2]. Nearly 5 million Americans have CHF [3] and a majority of these patients display diastolic dysfunction, which is an abnormality in the left ventricle (LV) myocardial relaxation and/or compliance that alters the ease with which the blood is accepted into the LV from the LA during diastole [4]. Due to abnormal LV filling, the LA experiences intense stress and elevated pressures. In fact, the left atrium is exposed directly to the LV diastolic pressure through the open mitral valve (MV) and because of its thin wall structure it tends to dilate with increasing pressure [5]. This augmented LA size and increased contractility and booster function are some of the mechanisms compensating for decreased early filling in patients with reduced LV compliance [6]. Over time, the LA compensatory contribution decreases, this may lead to intrinsic left atrium dysfunction [7]. This in turn results in a progressive decline in health unless the hearts’ inadequate blood flow is augmented by a left ventricular assist device (LVAD). Although LVAD implantation rest the heart, restores function to the ventricle [8], and improve overall function [9], its effects on the left atrium remain unclear. The purpose of the present study was to use 2D and Doppler echocardiography to define the parameters for assessing LVAD unloading and determine its effect on LA diameter, area, volume, and pressure in patients prior to and following LVAD implantation.
Numerical Simulation of Blood-Wall Albumin Transport in a Realistic Human Right Coronary Artery
Authors: Sun Nanfeng , Torii Ryo , Wood Nigel B. , Wright Andrew , Hughes Alun D. , Thom Simon A. M. , Xu X. Yun
Published: March 2014

Low wall shear stress (WSS) is commonly implicated in endothelial dysfunction and atherogenesis. The accumulation of macromolecules is also considered as an important factor contributing to the development of atherosclerosis. In the present study a fluid-wall model, incorporating shear-dependent endothelial transport properties, was developed and used to study the transport of albumin from blood to and within the wall in a realistic human right coronary artery (RCA). Numerical simulations were performed at both steady and pulsatile flow conditions, and results were compared to evaluate the effect of flow pulsatility.
The Effect of Permeability of Cartilage Superficial Zone on the Behavior of Stress Relaxation and Creep of Human Ankle Joint
Authors: Wan Lu , Li Guoan
Published: March 2014

The microstructure of articular cartilage could be divided into four distinct zones: the superficial zone, middle zone, deep zone, and calcified cartilage zone. It is believed that the superficial zone of articular cartilage has a lower permeability, which may be related to the close packing of the collagen fibrils resulting in a system of much narrow channels which offer a greater resistance to flow [1]. This parametric study investigated the influence of permeability of the superficial zone on the behavior of cartilage stress relaxation and creep of human ankle joint using a 2D biphasic poroelastic finite element model (FEM) that was created from a living human ankle joint.