bluuebunny/crossref_metadata_2025 huggingface dataset:
Is vanadium a biometal for boreal cyanolichens?
Authors: Darnajoux Romain , Constantin Jérôme , Miadlikowska Jolanta , Lutzoni François , Bellenger Jean‐Philippe
Published: March 2014

Molybdenum (Mo) nitrogenase has long been considered the predominant isoenzyme responsible for dinitrogen fixation worldwide. Recent findings have challenged the paradigm of Mo hegemony, and highlighted the role of alternative nitrogenases, such as the vanadium‐nitrogenase.

Here, we first characterized homeostasis of vanadium (V) along with other metals in situ in the dinitrogen fixing cyanolichen Peltigera aphthosa. These lichens were sampled in natural sites exposed to various levels of atmospheric metal deposition. These results were compared with laboratory experiments where Anabaena variabilis, which is also hosting the V‐nitrogenase, and a relatively close relative of the lichen cyanobiont Nostoc, was subjected to various levels of V.

We report here that V is preferentially allocated to cephalodia, specialized structures where dinitrogen fixation occurs in tri‐membered lichens. This specific allocation is biologically controlled and tightly regulated. Vanadium homeostasis in lichen cephalodia exposed to various V concentrations is comparable to the one observed in Anabaena variabilis and other dinitrogen fixing organisms using V‐nitrogenase.

Overall, our findings support current hypotheses that V could be a more important factor in mediating nitrogen input in high latitude ecosystems than previously recognized. They invite the reassessment of current theoretical models linking metal dynamics and dinitrogen fixation in boreal and subarctic ecosystems.
“[S]ur les ailes de l'imagination”
Authors: Stelzig Eugene
Published: March 2014

In his Confessions (1782, 1789) Jean‐Jacques Rousseau asserts the central importance of memory in his life, because it is only through memory that he can be fully present to himself. His most complete celebration of the present through the medium of memory is in the Fifth Walk of his Rêveries (1782), where he recollects his short stay on the island of Saint‐Pierre (1765) by way of his ecstatic experience of “le sentiment de l'existence.” The unhappy celebrity writer near the end of his life turns to imaginatively enhanced recollections to supplement his actual experiences on the island by way of a Romantic mnemotherapy as a compensatory mode of remembrance. Rousseau's differing autobiographical accounts (in his Confessions and Rêveries) of his time as a happy recluse on the island are a poeticized version of the biographical facts, and it is only in his final and unfinished work that Rousseau realized most fully the therapeutic strategy of a healing recherche du temps perdu in the prose poetry of the Fifth Walk that constitutes a central document of European Romanticism.
Die Mattigkeit der Erinnerung
Authors: Møller Andreas Hjort
Published: March 2014

Die Sonette aus Venedig, entstanden als Manuskript 1824, publiziert August Graf von Platen (1796–1835) 1825 während seines zweiten Aufenthaltes in „dieser Inselstadt“ seiner Sehnsucht. Wiederholt erscheint der Sonettzyklus des inzwischen durch die Heinrich‐Heine‐Krisis berühmt‐berüchtigt gewordenen Dichters im Sammelband Gedichte (1828). Der Fall Venedigs bietet sich für den zukünftigen Italien‐Historiker und Autor der Geschichten des Königsreichs Neapel von 1414 bis 1443 (1833) als unumgängliche Topographie der Erinnerung an. In der Zweitausgabe werden anderweitige Erinnerungen in den Vordergrund gerückt. Der Sonettendichter streicht 1828 sämtliche Zeilen des letzten Sonetts und ersetzt sie mit der Selbstbeschreibung des lyrischen Ich, dem „von Zeit zu Zeit ein Ruf der Gondoliere“ gar nicht wahrnehmbar ist. Die sich im Lauf der Jahre von 1824 bis 1828 verändernden Personalerinnerungen entsprechen der Stadttopographie, der Stadtgeschichte und dem Aufbau des Textes – mit allerlei Kanälen und Irrwegen, „[d]ie tausendfach sich ineinander schlingen“. Im Zentrum dieser Untersuchung steht das Adjektiv „matt“, welches dasjenige bezeichnet, was Platen in seinen Sonetten umarbeiten wollte. Es entsteht dadurch die Schilderung eines spätromantischen Komplexes unterschiedlicher Erinnerungsmodi, in dem die Vergangenheit (Antike, Renaissance, napoleonische Ära) in persönliche Rückblicke übergeht.
Diseases mimicking intussusception: Diagnostic dilemma
Authors: Karakus Suleyman Cuneyt , Ozokutan Bulent Hayri , Ceylan Haluk
Published: March 2014

Background

Intussusception is a common abdominal emergency in early childhood. The aim of this study was to describe the diseases mimicking intussusception and to discuss the causes and management of these conditions.

Methods

Seven patients who were initially diagnosed as having intussusception on abdominal ultrasonography but who had a final diagnosis of diseases other than intussusception were reviewed retrospectively.

Results

Two patients with ileocolic intussusception underwent ultrasonography‐guided reduction with a hydrostatic method but the ultrasonographic findings persisted. At surgery, only edematous ileocecal valve and mesenteric lymphadenopathy were observed. In three patients with Henoch–Schönlein purpura, initial abdominal ultrasonography showed intussusception. The patients with no sign of obstructive symptoms were managed conservatively with a diagnosis of intramural hemorrhage and on follow up the ultrasonographic findings of intussusception was resolved. One patient with the target sign on computed tomography and ultrasonography of the abdomen underwent ileocolic resection and end‐to‐end anastomosis due to a tumor in the cecum. There was no evidence of intussusception. One patient with a cyst in the right lower quadrant accompanying intussusception on ultrasonography of the abdomen underwent ultrasonography‐guided reduction but the ultrasonographic findings persisted. On exploration, only cecal duplication cyst without intussusception was detected. Cecal resection including the cyst and end‐to‐end ileocolic anastomosis were performed.

Conclusions

Ultrasonography, color Doppler ultrasonography, barium or hydrostatic enema and computed tomography are helpful in diagnosing intussusception, but patients with radiologic findings of intussusception should be evaluated on symptoms and clinical findings before surgical intervention. Also, other diseases mimicking intussusception should be kept in mind in the differential diagnosis.
Double Jeopardy Upon Resumé Screening: When Achmed Is Less Employable Than Aïsha
Authors: Derous Eva , Ryan Ann Marie , Serlie Alec W.
Published: March 2014

Applicants belong to multiple categories (e.g., male, ethnic minority) and a complex set of factors affects category activation and inhibition when making hiring decisions. Two field experiments with recruiters who regularly engage in resumé screening showed that the role of multiple categories (applicants’ ethnicity and sex) in discrimination depended on job type and prejudice. Specifically, in both low‐ and high‐demand (i.e., complex) jobs, Arab women were rated more favorably than Arab men, particularly when considering levels of client contact. Across both studies, recruiters high in explicit ethnic prejudice were discriminatory only when applicants’ job qualifications fit the job position less, lending support for the attributional‐ambiguity effect. Implicit attitudes did not play a strong role. Our study findings point to the complex nature of multiple categorization effects in the hiring process. Implications are considered as to how to avert hiring discrimination during resumé screening.
Honest and Deceptive Impression Management in the Employment Interview: Can It Be Detected and How Does It Impact Evaluations?
Authors: Roulin Nicolas , Bangerter Adrian , Levashina Julia
Published: March 2014

Applicants use honest and deceptive impression management (IM) in employment interviews. Deceptive IM is especially problematic because it can lead organizations to hire less competent but deceptive applicants if interviewers are not able to identify the deception. We investigated interviewers’ capacity to detect IM in 5 experimental studies using real‐time video coding of IM (N = 246 professional interviewers and 270 novice interviewers). Interviewers’ attempts to detect applicants’ IM were often unsuccessful. Interviewers were better at detecting honest than deceptive IM. Interview question type affected IM detection, but interviewers’ experience did not. Finally, interviewers’ perceptions of IM use by applicants were related to their evaluations of applicants’ performance in the interview. Interviewers’ attempts to adjust their evaluations of applicants they perceive to use deceptive IM may fail because they cannot correctly identify when applicants actually engage in various IM tactics. Helping interviewers to better identify deceptive IM tactics used by applicants may increase the validity of employment interviews.
Detection and quantification of airborne inoculum of Hymenoscyphus pseudoalbidus using real‐time PCR assays
Authors: Chandelier A. , Helson M. , Dvorak M. , Gischer F.
Published: March 2014

A method based on real‐time polymerase chain reaction (PCR) and the use of rotating‐arm spore traps was developed for quantifying airborne Hymenoscyphus pseudoalbidus ascospores. The method was sensitive and reproducible, and the collection efficiency was 10% of the spores present in the air. The temporal ascospore dispersal pattern was studied over 3 years by collecting spores every 15 days for a 24 h air‐sampling period during the ash‐growing season. The highest production was detected from the end of June to the beginning of September. The overall ascospore production did not differ significantly among stands within a specific year but there were differences from year to year. There was a positive correlation between air temperature and the number of ascospores trapped, with most of the positive samples being observed at temperatures above 12°C. The vertical profile of ascospore dispersal showed a strong decrease in ascospore density within a height of 3 m, regardless of date of collection. An analysis of the spore traps installed at increasing distances from an infected stand showed that most of the ascospores were deposited downwind within 50 m of the stand. These data are discussed in context of the epidemiology of the disease.
Opposite effect of conflict context modulation on neural mechanisms of cognitive and affective control
Authors: Chen Taolin , Kendrick Keith Maurice , Feng Chunliang , Yang Suyong , Wang Xiaogang , Yang Xun , Lei Du , Wu Min , Huang Xiaoqi , Gong Qiyong , Luo Yuejia
Published: March 2014

This study investigated the neural effect of conflict context modulation of cognitive and affective conflict processing by recording evoked‐response potentials in cognitive and affective versions of a flanker task. By varying the proportion of congruent and incongruent trials in a block, we found different patterns of the context effect on evoked potentials during cognitive and affective conflict processing. For posterior N1 amplitude, frequent incongruent trials produced a larger effect only in the affective task. The opposite pattern of the context effect was observed for the central N450, which was enhanced by frequent cognitive but reduced by frequent affective contexts. We found similar context effect on the parietal sustained potential in both tasks. Overall, our findings suggest that cognitive and affective conflict processing engage a context‐dependent attentional control mechanism but a common conflict response system.
Proposal of standardized guidelines for the production and quality control of autologous serum eye drops in Korea: based on a nationwide survey
Authors: Lee Hye Ryun , Hong Yun Ji , Chung Soie , Hwang Sang Mee , Kim Taek Soo , Song Eun Young , Park Kyoung Un , Song Junghan , Han Kyou Sup
Published: March 2014

Background

Autologous serum eye drops (ASEDs) have been used to treat many eye diseases. However, there are no standardized guidelines for the production and quality control (QC) of ASEDs in Korea. Our aim was to propose standardized guidelines for the production and QC of ASEDs.

Study Design and Methods

We conducted a nationwide survey consisting of questions regarding the methods used in each hospital for the production and QC of ASEDs. The survey was sent by e‐mail to 89 doctors responsible for the blood banks at different hospitals.

Results

Thirty‐two hospitals replied, and 13 hospitals reported using the ASEDs in the treatment of patients with eye diseases. The screening test for patients, amount of blood sampling, type of bottle used for blood collection, details about the production of the eye drops, and storage methods and shelf life of unopened and opened bottles of eye drops varied between hospitals.

Conclusion

Based on an analysis of the survey results and a review of the standard operating procedures and protocols for ASEDs used in Japan, Germany, England and Wales, and the United States, we proposed standardized guidelines for the production and QC of ASEDs in Korea. ASEDs are not cell therapy products in the strictest sense. However, because eye drops are composed of serum isolated from blood and are used in patients, we consider ASEDs to be the basis for cell therapy products. Therefore, ASEDs should be produced and stored according to standardized guidelines based on the Good Manufacturing Practice guidelines.
The Trouble with “Solution‐Driven Unionism”: Labor's Crisis of Ideas and the Promise of Economic Democracy
Authors: Panayotakis Costas
Published: March 2014

This article interprets the concept of “solution‐driven unionism” recently adopted by the American Federation of Teachers as a manifestation of the American labor movement's crisis of ideas. A more adequate and politically effective reconceptualization of the role of unions would require us to recognize capitalism's contradictions and to foreground economic democracy as an alternative to the capitalist organization of socioeconomic life.
Singularities in Differential-Algebraic Boundary-Value Problems Governing the Excitation Response of Beam Structures
Authors: Saghafi Mehdi , Dankowicz Harry
Published: March 2014

The objective of this paper2 is to identify and, where possible, resolve singularities that may arise in the discretization of spatiotemporal boundary-value problems governing the steady-state behavior of nonlinear beam structures. Of particular interest is the formulation of nondegenerate continuation problems of a geometrically-nonlinear model of a slender beam, subject to a uniform harmonic excitation, which may be analyzed numerically in order to explore the parameter-dependence of the excitation response. In the instances of degeneracy investigated here, the source is either found (i) directly in a differential-algebraic system of equations obtained from a finite-element-based spatial discretization of the governing partial differential boundary-value problem(s) together with constraints on the trial functions or (ii) in the further collocation-based discretization of the time-periodic boundary-value problem. It is shown that several candidate spatial finite-element discretizations of a mixed weak formulation of the governing boundary-value problem either result in (i) spatial group symmetries corresponding to equivariant vector fields and one-parameter families of periodic orbits along the group symmetry orbit or (ii) temporal group symmetries corresponding to ghost solutions and indeterminacy in a subset of the field variables. The paper demonstrates several methods for breaking the spatial equivariance, including projection onto a symmetry-reduced state space or the introduction of an artificial continuation parameter. Similarly, the temporal indeterminacy is resolved by an asymmetric discretization of the governing differential-algebraic equations. Finally, in the absence of theoretical bounds, computation is used to estimate convergence rates of the different discretization schemes, in the case of numerical calibration experiments performed on equilibrium and periodic responses for a linear beam, as well as for the full nonlinear models.
Building Three-Dimensional Scanner Based on Structured Light Technique Using Fringe Projection Pattern
Authors: Rashidizad Hossein , Rahimi Abdolreza
Published: March 2014

This paper presents the design and construction of a low-cost active noncontact three-dimensional (3D) scanner using the structured light method. The applied method is a generalization of the triangulation technique using a fringe projection pattern (by Gray code technique) to achieve a higher operating speed. The hardware equipment includes a single digital camera and a video projector. matlab was used for the calibration operation, the production of images by the above method, the image processing, and data calculation; while the Geomagic Qualify software was used to estimate the accuracy of the three-dimensional model obtained after scanning and to compare it with the tested object. Regarding the point cloud of the test object, the results demonstrate the precision of the used method and the possibility of developing a 3D scanner with a dimensional accuracy of ±0.05 mm.
Variation in the Hemodynamics of Young Adult Carotid Bifurcations
Authors: Lee Sang-Wook , Antiga Luca , Steinman David A.
Published: March 2014

Recent clinical studies have reinvigorated the search for purported “geometric risk factors” for atherosclerosis [1,2], due in part to the finding of wide interindividual variations in carotid bifurcation geometry. We have shown, however, that, relative to those study groups, the carotid bifurcations of young adults exhibit significantly less geometric variability [3,4]. In fact, these variations approached the threshold of reproducibility in the image-derived measurements themselves, from which we concluded that, if there is such a thing as geometric risk for atherosclerosis, its early detection might prove challenging. This, however, presupposed that interindividual variations in the local hemodynamics of young adult carotid bifurcations would be similarly modest. The purpose of this study was to test that implicit assumption.
Geometry Anticipates Hemodynamic Phenotype of Basilar Tip Aneurysms
Authors: Ford Matthew D. , Lee Sang-Wook , Lownie Stephen P. , Holdsworth David W. , Steinman David A.
Published: March 2014

The prevalence of unruptured cerebral aneurysms is estimated to be as high as 5% [1]. Basilar tip aneurysms account for 4–5% of these, but have a higher risk of rupture [2]. They are also difficult to treat surgically, and so endovascular therapy is often the only option. Hemodynamic forces have been implicated in the risk of rupture [3] and complications of endovascular therapy [4]; however, hemodynamic information is difficult to acquire clinically. Computational fluid dynamics (CFD), in combination with clinical imaging, can be used to accurately capture the intra-aneurysmal hemodynamics in a patient-specific manner [5]. Still, these techniques have not translated to routine clinical use, largely due to the time and effort required to construct, simulate, and interpret these models.
A Mechanical and Computational Investigation on the Effects of Conduit Orientation on the Strength of Massive Bone Allografts
Authors: Santoni Brandon G. , Womak Wes , Wheeler Donna L. , Puttlitz Christian M.
Published: March 2014

Massive allograft bone is the primary source of bone graft material for use in limb salvage procedures after oncological tumor resection. However, allograft bone has been found to incorporate slowly into host bone resulting in allograft susceptibility to non-union, fracture, infection and fatigue failure. Clinical studies have shown that massive allograft bone has a 50% to 75% success rate at 10 years [1].
Computational Modeling of Ureteral Peristaltic Transport Using Fluid Structure Interaction
Authors: Vahidi Bahman , Fatouraee Nasser
Published: March 2014

Despite active research, the mechanism by which urine is transported from the kidneys into the urinary bladder remains unclear. In general, the ureteral flow is not purely peristaltic and includes a component which depends on the pressure difference between the renal pelves and the urinary bladder. Thus reflux might be caused by an increase in the pressure inside the bladder. Reflux may result in the ingress of bacteria and toxins from the bladder into the renal pelves and then into the kidneys [1]. In the absence of peristalsis, the ureter behaves as a non-uniform passively distensible tube and the flow through it may be taken as approximately steady. The problem of correctly modeling the smooth muscle of the ureter (like that of many other organs: esophagus, bowels, seminal duct, etc.) is to a large extent unsolved [2,3]. The rate of contraction of the muscle depends on the load against which it is contracting as well as on its current geometry and its state of activation, and that load consists largely of the hydrodynamic (viscous) forces required to move the urine.
A Cartilage Growth Mixture Model With Collagen Remodeling: Validation Protocols
Authors: Klisch Stephen M. , Asanbaeva Anna , Oungoulian Sevan R. , Thonar Eugene J.-M. A. , Masuda Koichi , Davol Andrew , Sah Robert L.
Published: March 2014

The attainment of specific design goals related to tissue structure and function is likely critical to the development of a consistently successful strategy for articular cartilage (AC) repair. The long-term goal of this research is to develop a cartilage growth mixture (CGM) model that may be used with experimental approaches to improve AC repair strategies. The CGM employs a “stress balance” hypothesis: at equilibrium, the crosslinked collagen (COL) network restrains the proteoglycan (PG) swelling pressure generated by fixed charge density. The specific objectives are to: 1) refine a previous CGM model [1] to include COL remodeling; 2) develop analytical protocols for model validation that are based on experimental data from select in vitro growth protocols; and 3) test CGM model hypotheses.
Effect of Defect on Elastic/Plastic and Creep Behavior of Bone: A Finite Element Study
Authors: Ajdari A. , Canavan P. K. , Nayeb-Hashemi H. , Warner G.
Published: March 2014

Three-dimensional structure of trabecular bone can be modeled by 2D or 3D Voronoi structure. The effect of missing cell walls on the mechanical properties of 2D honeycombs is a first step towards understanding the effect of local bone resorption due to osteoporosis. In patients with osteoporosis, bone mass is lost first by thinning and then by resorption of the trabeculae [1].

Furthermore, creep response is important to analyze in cellular solids when the temperature is high relative to the melting temperature. For trabecular bone, as body temperature (38 °C) is close to the denaturation temperature of collagen (52 °C), trabecular bone creeps [1]. Over the half of the osteoporotic vertebral fractures that occur in the elderly, are the result of the creep and fatigue loading associated with the activities of daily living [2].

The objective of this work is to understand the effect of missing walls and filled cells on elastic-plastic behavior of both regular hexagonal and non-periodic Voronoi structures using finite element analysis.

The results show that the missing walls have a significant effect on overall elastic properties of the cellular structure. For both regular hexagonal and Voronoi materials, the yield strength of the structure decreased by more than 60% by introducing 10% missing walls. In contrast, the results indicate that filled cells have much less effect on the mechanical properties of both regular hexagonal and Voronoi materials.
Preliminary Murine Aortic Tissue Material Properties From Pressure-Diameter Experiments
Authors: Rentschler Mark E. , Baxter B. Timothy
Published: March 2014

Abdominal aortic aneurysm (AAA) is a common and deadly problem. The aortic diameter increases in association with a complex remodeling process that includes changes in the structure and content of key proteins, elastin and collagen. As these changes occur, the tissue mechanical properties also change. The natural history of AAA is progressive enlargement to a point of mechanical tissue failure typically followed by death. Currently, the marker used to predict the risk of impending rupture is the largest transverse diameter. After reaching a diameter threshold of 5.5 cm the aneurysm is surgically repaired. This criterion does not consider any patient-specific information or the known heterogeneity of the aneurysm that may, in some cases, lead to rupture before the aneurysm reaches the standard intervention threshold. Conversely, in many patients, continued observation beyond this threshold is safe.
Increased Bone Mechanical Properties of Mice Lacking βArrestin2 After Mechanical Stimulations
Authors: Stadelmann Vincent A. , Bianchi Estelle N. , Ferrari Serge L. , Pioletti Dominique P.
Published: March 2014

Bone turnover serves different purposes. It allows the bone to adapt its shape to the actual constraints, it regulates the serum levels of calcium and other ions, and it repairs structural defects of bone. Numerous stimuli affect bone turnover, including hormones, cytokines and mechanical stimuli.
Desorption Electrospray Ionization Using a Porous Alumina Surface
Authors: Sen Ashis K. , Darabi Jeff , Nayak Ranu , Knapp Daniel R.
Published: March 2014

Desorption electrospray ionization (DESI) is a technique used for direct sampling of a sample or an analyte deposited on a surface under ambient conditions [1]. In DESI, ionized droplets of a spray are directed towards the sample causing desorption of ions due to exchange of charge and momentum. The resulting ions are carried into an ion trap mass spectrometer and analyzed. DESI was originally demonstrated by Takats et al. [1]. They described the new method and applied the same to analyze various compounds present on a variety of surfaces. Followed by this, several researchers [1–5] have investigated on DESI for a wide range of applications including analysis of pharmaceuticals, explosives detection, natural products discovery and in vivo clinical analysis. Recently, Kauppila et al [5] have introduced porous silicon (pSi) and ultra-thin layer chromatography (UTLC) plates for DESI-MS. Similar or improved sensitivities were obtained with pSi and UTLC surfaces as compared to PMMA and PTFE surfaces. This work presents use of a nanoporous alumina surface [6] for DESI – MS. The DESI – MS performance of nanoporous alumina surface is compared with that of PMMA, which is a popular surface in previous DESI-MS experiments. Optimized operating conditions were determined for the surfaces using BSA tryptic digest as the sample. The results show that the nanoporous alumina surface offers significantly higher ion intensity as compared to the other surfaces.
A Multi-Zone Finite Element Model for Radiofrequency Ablation of an Infarcted Cardiac Tissue
Authors: Zhou Fan , Sun Ying , Beaumont Jacques
Published: March 2014

A large number of modern day medical interventions rely on RF ablation. It has become the treatment of choice for many types of cardiac arrhythmia to prevent the reentrant circuits [1]. However, excessive heating during RF ablation up to 100°C can cause microexplosions and severe bleeding [2]. Optimizing parameters for RF ablation in order to produce small lesions with a minimal amount of damage and bleeding constitutes a major challenge. Utilizing a thermo-electric conduction model, we address this problem for the treatment of cardiac arrhythmia. Our objective is to provide means by which non-invasive cardiac imaging data can be used to determine optimal parameters of RF ablation. A three-dimensional (3-D) finite element (FE) model that includes healthy, infarcted, and slow conducting tissues is developed. The temperature dependent thermal and electrical conductivities are considered for different tissue types.
Effectiveness of Trabecular Metal™ Acetabular Augment in Revision THR of Pelvis With Severe Acetabular Defect: A Finite Element Study
Authors: Dharia Mehul A. , Levine Danny L. , Crowninshield Roy D. , Siggelkow Eik , Degroff Dale A. , Wentz Douglas H.
Published: March 2014

Osteolysis of the pelvis after total hip replacement (THR) can result in several types of bony defects within or around the acetabulum [1]. These defects are classified into various categories based on the extent and location of the host bone loss [2, 3]. A severe acetabular defect with at least 30% of bone loss and progressive amounts of superior rim deficiencies can be classified as a Paprosky type IIIA cavitary defect [4] (Figure 1-I). A significant amount of superior migration of the cup can be expected as the deficient acetabulum with nonsupportive superior dome will be unable to support an acetabular component at the anatomic hip center without using structural allograft, custom implants or reconstruction cage [4, 5]. A new reconstructive technique (Figure 1-II) uses modular Trabecular Metal™ (TM) augments (Figure 1-III) to fill the acetabular defects at the time of revision THR so that regular hemispheric uncemented acetabular components can be used to allow for the potential of biologic fixation.
Novel Nanostructured Calcium Phosphate Based Delivery Systems for Non-Viral Gene Delivery
Authors: Olton Dana , Lee Dong Hyun , Sfeir Charles , Kumta Prashant N.
Published: March 2014

Calcium phosphate (CaP) based approaches remain an attractive option for delivering plasmid DNA (pDNA) into cultured cells [1, 2]. However, two major limitations associated with this vector exist. First, it yields lower transfection efficiencies with respect to its’ viral counterparts. Second, CaP mediated gene delivery leads to transient transgene expression. Thus, we hypothesized that these concerns could respectively be addressed by: (1) synthesizing particles with precise control of the materials’ parameters including (i.e. Ca/P ratio, particle size, crystal structure, and microstructure) and (2) incorporating the particles into a 3-D biodegradable fibrin scaffold. The goal of this study was therefore to synthesize and optimize the efficacy of both nano-structured CaP (NanoCaPs) particles and a composite scaffold comprised of fibrin, CaP and pDNA for non-viral gene delivery applications.
CFD Modeling for Patient-Specific Analysis of Cerebrospinal Fluid Flow
Authors: Roldán Alejandro , Wentland Andrew , Wieben Oliver , Haughton Victor , Osswald Tim , Chesler Naomi
Published: March 2014

Chiari malformations are characterized by the cerebellar tonsils extending into the upper cervical spinal canal. Many patients with Chiari malformation experience headaches or develop a cyst in the spinal cord inferior to the cerebellar tonsils. Some symptomatic patients benefit from a surgical procedure to enlarge the foramen magnum and others do not. The causes of symptoms and variable response to surgery remain unknown. Imaging studies have shown that patients with a Chiari malformation exhibit increased cerebrospinal fluid (CSF) velocities compared to subjects without the malformation. Improved methods of analyzing the CSF fluid dynamics are needed to evaluate the impact of increased fluid velocities on pressure differentials in the upper cervical spinal canal and the potential impact of surgery on flow dynamics in patient specific geometries.
Pharmacokinetics of Encapsulated Paclitaxel: Multi-Probe Analysis With PET
Authors: Tartis Michaelann S. , Marik Jan , Kheirolomoom Azadeh , Pollard Rachel E. , Zhang Hua , Qi Jinyi , Sutcliffe Julie L. , Ferrara Katherine W.
Published: March 2014

We have combined two imaging probes and used PET as a means to provide image-based validation for a novel targeted drug delivery system. The first probe was a direct labeling of the drug [18F]fluoropaclitaxel [1–3], which was inserted into various carrier vehicle formulations. The second probe, [18F]fluoro-1,2-dipalmitoyl-sn-glycerol, i.e. [18F]FDP involved radiolabeling the lipid vehicle. Paclitaxel, which is poorly soluble in aqueous media, also has limited solubility and stability in lipophilic environments such as liposomes. Stable association of paclitaxel with the lipid bilayer is affected by a variety of physicochemical factors such as temperature and liposome composition. Paclitaxel crystal formation has been documented, with two forms of solid state within aqueous media and organic solvents, although crystal conformation differs in each media [4,5]. We provide dynamic in vivo image sets providing biodistribution and time activity curves of free [18F]fluoropaclitaxel and liposomal [18F]fluoropaclitaxel as well as free [18F]FDP, liposomal [18F]FDP, and [18F]FDP in an ultrasound contrast agent. Serial studies were performed within a small group of rats, minimizing inter-animal variability. The two labeled molecules have different biodistributions: paclitaxel is rapidly taken up in the liver, intestines and kidneys, while the labeled lipid incorporated into liposomes stays in circulation with minimal uptake in organs other than spleen. Here, we have developed a quantitative method to follow paclitaxel and lipid vehicles to their destination in vivo in order to improve targeted paclitaxel delivery.
Effect of Head Posture Changes in the Geometry and Hemodynamics of a Healthy Human Carotid Bifurcation
Authors: Papaharilaou Yannis , Seimenis Yiannis , Pattakos Nikos , Ekaterinaris John , Georgiou Georgios , Eracleous Elena , Christou Christos , Brott Brigitta C. , Anayiotos Andreas
Published: March 2014

Recent reports have stressed the importance of studying the morphology and hemodynamic changes of peripheral arteries in parts of the body that experience motion and posture change and their relationship to the hemodynamic hypothesis of atherosclerosis development [1, 2]. The carotid arteries may fall into this category since their geometric morphology and hemodyamic conditions may change due to head and neck posture changes. Such changes may alter the hemodynamic variables that are generally associated with the development of atherosclerosis, such as low and oscillating wall shear stress (WSS) and particle residence times. In this study, the carotid bifurcation of a healthy volunteer was imaged in the neutral position and in 3 different posture positions: a) flexion sideways to the right 80°, b) flexion upwards 45°, and c) flexion downwards 45° (Fig. 1). Anatomic and quantitative flow MR data were used to develop computational models to investigate the effect of different postures on arterial geometry and hemodynamic characteristics.
Autologous Human Fibrochondrocytes From Meniscectomy Debris are a Potent Cell Source for Meniscus Tissue Engineering
Authors: Baker Brendon M. , Nathan Ashwin S. , Sheth Neil P. , Huffman G. Russell , Mauck Robert L.
Published: March 2014

The meniscus is a fibrocartilaginous tissue vital to the normal functioning of the knee [1]. The dense collagenous structure is sparsely colonized by meniscal fibrochondrocytes (MFCs) which maintain and remodel the extracellular matrix (ECM) [2,3]. While the meniscus functions well with a lifetime of use, traumatic or degenerative injuries to the avascular, inner region of the meniscus fail to heal. Disruption of the fibrous architecture impairs load transmission and initiates erosion of the adjacent articular surfaces, or osteoarthritis (OA). Damage to the meniscus is typically treated by resection of the torn tissue via arthroscopic partial meniscectomy, which alleviates symptoms but similarly predisposes patients to OA [4]. Tissue removed in this procedure is deemed surgical waste and is subsequently discarded.
Moment Arms of the Intrinsic Muscles at the PIP Joint of the Middle Finger are Independent of the Position of the MCP Joint
Authors: Buford William L. , Loveland Dustin M. , Koh Shukuki , Patterson Rita M. , Steven Viegas F.
Published: March 2014

Studies of muscle moment arms have classically followed a method of superposition whereby the measurement or derivation of moment arm magnitudes at any given joint assume independence of the position of joints proximal to the joint under study. This is particularly important for muscles crossing multiple joints. However, because of the nature of the soft tissue anatomy that defines the paths of the intrinsic muscles of the hand inserting into the extensor hood (also known as the dorsal expansion), this assumption may not be true for the intrinsic muscle moment arms at the Proximal Interphalangeal (PIP) Joint. These are muscles that insert into the “hood” of the dorsal expansion at the metacarpophalangeal (MCP) joint of the fingers acting as flexors at the MCP joint and extensors at the PIP joint. The gliding and flexible nature of these tissues bring into question the validity of the assumption that the extension moment arm of the intrinsic muscles at the PIP joint are independent of the position of the MCP joint. Indeed the fact that some of the intrinsic muscles exhibit an increasing (bowstringing) moment arm at the MCP joint with increased flexion infers that the paths of muscles acting through the dorsal expansion do change with respect to phalanx rotation. Does this changing path then affect the extension moment arm of the intrinsics acting at the PIP joint? This project investigates this question with the hypothesis that the extension moment arms of the second lumbrical (2Lum), the second and third dorsal interosseous (2DI and 3DI) at the middle finger PIP joint are significantly different with the middle MCP joint flexed, neutral (at extension) and hyperextended.
Development and Validation of a Subject-Specific Computational Human Knee Model in a Dynamic Knee Simulator
Authors: Weimer Katherine A. , Guess Trent M. , Dodd Kevin A. , Maletksy Lorin P.
Published: March 2014

The complex loading of the knee is believed to play an extensive role in the development and advancement of joint disease and injury. Computational models provide a powerful tool in knee biomechanics, but validation of these models is difficult. The objective of this study was to develop a dynamic 3-D subject-specific computational knee model and to validate the model using experimental data from a dynamic knee simulator. The developed knee model was placed in a previously validated model of the Kansas Knee Simulator (KKS) dynamic testing machine [1]. The kinematics from walking and squat profiles simulated in the KKS model and performed on the knee specimen during KKS experimental testing were compared for model validation.
Molecular Dynamics Simulations of Dialkyl Carbocyanine Dyes in a DPPC Bilayer: Atomistic Insights Into Single Molecule Fluorescence
Authors: Gullapalli Ramachandra , Demirel Melik , Butler Peter J.
Published: March 2014

Our group uses di-alkyl carbocyanine dyes to detect force-induced membrane perturbation in mechanotransduction studies (Butler et al 2000). These dyes are also used extensively in single molecule spectroscopic techniques to infer dynamics of native membrane lipids. However, the precise distribution and orientation of the dye in a bilayer and how well the dye dynamics mimic native lipid dynamics are not known. Thus we present the results of a 40 nanosecond molecular dynamics simulation of a fully hydrated bilayer containing 0, 2, or 4 molecules of 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate (DiI-C18) and 128 molecules of dipalmitoylphosphatidyl choline (DPPC).
The Role of Microtubule Organization in Chondrocyte Response to Osmotic Loading
Authors: Oswald Elizabeth S. , Chao Pen-hsiu Grace , Bulinski J. Chloe , Ateshian Gerard A. , Hung Clark T.
Published: March 2014

The cytoskeleton, including actin filaments and microtubules, provides chondrocytes with structure, cytoplasmic organization, and intracellular transport. The cytoskeleton is known to be involved in cellular responses to physiologic mechanical and osmotic loading signals, including morphological changes and mechanostransduction [1, 2]. Here, we examine microtubule (MT) involvement in volume response of chondrocytes to osmotic loading, as well as organization of stable MT with hypoosmotic loading. We also explore the hypothesis that chondrocytes from different zones of cartilage possess cytoskeletons with different properties, which help explain variations in their volume response to osmotic loading in situ and in vitro [3].
Development of Experimental and Computational Models to Evaluate the Stability of Aortic Stent Grafts in Motor Vehicle Accidents
Authors: Darvish Kurosh , Shafieian Mehdi , Romanov Vasily , Rotella Vittorio , Salvatore Michael D. , Blebea John
Published: March 2014

A high speed impact system was developed to study the stability of stent grafts in thoracic porcine models in vitro. The experiments were guided by a finite element model of the test setup to identify the conditions that increase the risk of instability of the stent graft. The models showed that at anterior inclination of 45° and average deceleration of 40 G, which represented a frontal crash, the stent graft can move up to 1 mm. The results of this study may be helpful in developing future grafts to withstand shocks experienced in motor vehicle accidents.
Model-Based FES Muscle Selection for Restoring Arm Movement in High SCI
Authors: Kirsch Robert F. , Blana Dimitra , Chadwick Edward
Published: March 2014

This paper describes a significant ongoing effort by our research group to develop a functional electrical stimulation-based neuroprosthesis capable of restoring essential arm and hand function to individuals with high cervical (C1-C4) spinal cord injury, a condition referred to as high tetraplegia. These injuries are at the highest level of the spinal cord and leave those afflicted with extensive paralysis below the neck — typically such individuals are left with volitional control of just the head, neck, and in some cases shoulder shrug. Individuals with high tetraplegia are usually totally dependent on others for all aspects of care, and traditional rehabilitation procedures result in limited functional improvement [1].
Micro-CT-Based Large Scale Linear Finite Element Models Predict the Strength of Human Thoracic and Lumbar Vertebral Bodies
Authors: Yeni Yener N. , Kim Do-Gyoon , Zauel Roger R. , Johnson Evan M. , Cody Dianna D.
Published: March 2014

Vertebral fractures are among the most common and debilitating fractures. Structural organization of cancellous and cortical bone in a vertebra and their local properties are important factors that determine the strength of a vertebra. Linear finite element models utilizing Quantitative Computed Tomography (QCT) images have proven useful for predicting vertebral strength and are potentially useful in predicting risk of fracture in a clinical setting [1]. However, the amount of architectural detail in these models is not sufficient for studying trabecular stress and strains, and their relationship with the microscopic structure, which is important for understanding the mechanisms behind vertebral fragility.
Development of a Discrete Finite Element Cell Model
Authors: Coghlan Karen M. , McGarry Patrick , Mofrad Mohammad R. K. , McHugh Peter E.
Published: March 2014

Computational models have proven useful in the study of cell mechanics and mechanotransduction. While most finite element (FE) models of cells are commonly described in terms of the laws of continuum mechanics, a model that can accurately represent the microstructure of the filamentous network of the cytoskeleton would be required to relate mechanics to biology at the microscale level. An alternative approach to a continuum is presented here, whereby the discrete nature of the cytoskeleton of the cell is emphasized and the known structural properties of the cytoskeleton of the cell are utilized.
Valleylab Hand-Switching LigaSure™ XTD (Patent Pending) Design Project
Authors: Kingsley Dylan , Twomey John
Published: March 2014

Valleylab’s LigaSure™ vessel sealing instruments used in open surgical operations are currently operated via a foot-activated switch. Valleylab funded and mentored a senior design project at the University of Colorado at Boulder to redesign the electrosurgical device to include hand-switching. In comparison to hand-switching, a foot switch adds to the device setup complexity and increases the physical demand on the surgeon. Additional drawbacks of a foot switch include risk of inadvertent activation and need to look away from the surgical area in order to accurately activate the switch. Valleylab determined the need to redesign the LigaSure™ XTD instrument, shown in Figure 1, to use a hand-activated switch in order to provide surgeons with greater ease and precision of use.
Mechanical Property Determination of Bone Through Nanoindentation Testing and Finite Element Simulation
Authors: Zhang Jingzhou , Ovaert Timothy C.
Published: March 2014

Measurement of the mechanical properties of bone is important for estimation of the local mechanical response of bone cells to loading experienced on a larger scale. An increasing number of measurements of the hardness and Young’s modulus of bone tissue have been undertaken using nanoindentation [1,2]. However, testing conditions have not been uniform. The interactions that can occur between testing condition parameters were considered in this study, and average hardness and Young’s modulus were obtained as a function of indentation creep testing conditions (maximum load, loading/unloading rate (both equal in magnitude), load-holding time, and indenter shape).
Unconfined Compression of Porcine Ocular Lenses: Experiments and Finite Element Analysis
Authors: Regueiro Richard , Blanchard Adam , Constancio Kristin , Williams Logan
Published: March 2014

Understanding the mechanics of lens accommodation (ability of the eye dynamically to focus near to far, or far to near) can assist in the diagnosis of early presbyopia as well as identify potential clinical treatments and lens prosthetic implantation strategies [1–3]. Related to the mechanism of focusing, presbyopia is an ocular disease that stems from age-related loss of lens accommodation leading to a loss of focusing range and near vision [4]. This is attributed to changes in ciliary muscle function, as well as changes in the mechanical properties of the lens substance, lens capsule, and zonules, presumably. The precise relationship of these changes, however, is not well described. The location of the lens in the eye is shown in Fig.1 [5].
Modeling the Anisotropic Finite-Deformation Viscoelastic Behavior of Soft Fiber-Reinforced Tissues
Authors: Nguyen Thao D. , Jones Reese E. , Boyce Brad L.
Published: March 2014

This paper presents a constitutive model for the anisotropic, finite-deformation viscoelastic behavior of soft fiber-reinforced tissues. Soft fiber-reinforced tissues, such as the cornea, tendons, and blood vessels, have a unique combination of mechanical properties that enables them to perform important structural, protective, and energy-absorbing functions. Because of their fiber-reinforced microstructure, these tissues are extraordinarily stiff and strong for their weight. Many are also flexible and tough. The toughness of these tissues arises from the ability of both the soft fiber and matrix phases to dissipate energy through large viscoelastic deformations. The viscoelastic behavior of the matrix of soft tissues can arise from fluid flow through a swollen polymer network and/or the diffusive motion of polymer segments within the network. The time-dependent behavior of the fiber reinforcements, which themselves can be composite structures, stems from the viscoelastic nature of the fiber material and/or the dissipative mechanisms of the fiber/matrix interface. To model the distinct time-dependent behavior of both fiber and matrix constituents, the tissue is represented as a continuum mixture consisting of a variety of fiber families embedded in an isotropic matrix. Both phases are required to deform with the continuum deformation gradient. However, the model attributes a different viscous stretch measure and free energy density to the matrix and fiber phases. Separate viscous flow rules are specified for the matrix phase and the individual fiber families. The flow rules for the fiber families are combined to give an anisotropic effective viscous flow rule for the fiber phase. An attractive feature of model is that key parameters can be related to the material properties (i.e., moduli, viscosities, volume fraction) of the fiber and matrix phases. Also, the anisotropy exhibited by both the elastic and viscous response of the composite arises directly from the fiber arrangement.