bluuebunny/crossref_metadata_2025 huggingface dataset:
An analytical model for soil-atmosphere feedback
Authors: Schaefli B. , van der Ent R. J. , Woods R. , Savenije H. H. G.
Published: July 2012

Abstract. Soil-atmosphere feedback is a key for understanding the hydrological cycle and the direction of potential system changes. This paper presents an analytical framework to study the interplay between soil and atmospheric moisture, using as input only the boundary conditions at the upstream end of trajectory, assuming advective moisture transport with average wind speed along this trajectory and vertical moisture exchange with the soil compartment of uniform vertical properties. Precipitation, evaporation from interception and runoff are assumed to depend through simple functional relationships on the soil moisture or the atmospheric moisture. Evaporation from soil moisture (including transpiration) depends on both state variables, which introduces a nonlinear relationship between the two compartments. This nonlinear relationship can explain some apparently paradoxical phenomena such as a local decrease of precipitation accompanied by a runoff increase. The solutions of the resulting water balance equations correspond to two different spatial moisture regimes showing either an increasing or a decreasing atmospheric moisture content along a trajectory starting at the coast, depending on boundary conditions and parameters. The paper discusses how different model parameters (e.g. time scales of precipitation, evaporation or runoff) influence these regimes and how they can create regime switches. Such an analysis has potential to anticipate the range of possible land use and climate changes or to interpret the results of complex land-atmosphere interaction models. Based on derived analytical expressions for the Horton index, the Budyko curve and a precipitation recycling ratio, the analytical framework opens new perspectives for the classification of hydrological systems.
A simple groundwater scheme in the TRIP river routing model: global off-line evaluation against GRACE terrestrial water storage estimates and observed river discharges
Authors: Vergnes J.-P. , Decharme B.
Published: July 2012

Abstract. Groundwater is a non-negligible component of the global hydrological cycle, and its interaction with its overlying unsaturated zones can influence water and energy fluxes between the land surface and the atmosphere. Despite its importance, groundwater is not yet represented in most climate models. In this paper, the simple groundwater scheme implemented in the Total Runoff Integrating Pathways (TRIP) river routing model is applied in off-line mode at global scale using a 0.5° model resolution. The simulated river discharges are evaluated against a large dataset of about 3500 gauging stations compiled from the Global Data Runoff Center (GRDC) and other sources, while the Terrestrial Water Storage (TWS) variations derived from the Gravity Recovery and Climate Experiment (GRACE) satellite mission helps to evaluate the simulated TWS. The forcing fields (surface runoff and deep drainage) come from an independent simulation of the ISBA land surface model covering the period from 1950 to 2008. Results show that groundwater improves the efficiency scores for about 70% of the gauging stations and deteriorates them for 15%. The simulated TWS are also in better agreement with the GRACE estimates. These results are mainly explained by the lag introduced by the low-frequency variations of groundwater, which tend to shift and smooth the simulated river discharges and TWS. A sensitivity study on the global precipitation forcing used in ISBA to produce the forcing fields is also proposed. It shows that the groundwater scheme is not influenced by the uncertainties in precipitation data.
Field data collection and analysis of canopy and litter interception in commercial forest plantations in the KwaZulu-Natal Midlands, South Africa
Authors: Bulcock H. H. , Jewitt G. P. W.
Published: July 2012

Abstract. It is well accepted that the total evaporation in forested areas is greater than in grasslands, largely due to the differences in the amount of rainfall that is intercepted by the forest canopy and litter and higher transpiration rates. However, interception is the least studied of these components of the hydrological cycle. The study aims to measure and quantify the canopy and litter interception by Eucalyptus grandis, Pinus patula and Acacia mearnsii, at the Two Streams research catchment in the KwaZulu-Natal Midlands of South Africa for the three year period April 2008 to March 2011. The results from this study showed that canopy and litter interception contributed a significant amount of the water evaporated in a forest water balance. The canopy interception by E. grandis, A. mearnsii and P. patula was 14.9%, 27.7% and 21.4% of gross precipitation respectively, while litter interception was 8.5%, 6.6% and 12.1% respectively.
Future projections of the Greenland ice sheet energy balance driving the surface melt, developed using the regional climate MAR model
Authors: Franco B. , Fettweis X. , Erpicum M.
Published: July 2012

Abstract. In this study, 25 km-simulations are performed over the Greenland ice sheet (GrIS) throughout the 20th and 21st centuries, using the regional climate model MAR forced by four RCP scenarios from two CMIP5 global circulation models, in order to investigate the projected changes of the surface energy balance (SEB) components driving the surface melt. Analysis of 2000–2100 melt anomalies compared to melt results over 1980–1999 reveals an exponential relationship of the GrIS surface melt rate simulated by MAR to the near-surface temperature (TAS) anomalies, mainly due to the surface albedo positive feedback associated with the extension of bare ice areas in summer. On the GrIS margins, the future melt anomalies are rather driven by stronger sensible heat fluxes, induced by enhanced warm air advections over the ice sheet. Over the central dry snow zone, the increase of melt surpasses the negative feedback from heavier snowfall inducing therefore a decrease of the summer surface albedo even at the top of the ice sheet. In addition to the incoming longwave flux increase associated to the atmosphere warming, MAR projects an increase of the cloud cover decreasing the ratio of the incoming shortwave versus longwave radiation and dampening the albedo feedback. However, it should be noted that this trend in the cloud cover is contrary to that simulated by ERA-INTERIM-forced MAR over current climate, where the observed melt increase since the 1990's seems rather to be a consequence of more anticyclonic atmospheric conditions. Finally, no significant change is projected in the length of the melt season. This timing highlights the importance of solar radiation in the melt SEB.
Further Refinements in Collagen Mimetic Peptide Scaffolds for Tissue Engineering Heart Valves
Authors: Navaneethakrishnan Krishnamoorthy Navaneethakrishnan Krishnamoorthy , Sohier Jerome J. , Muthu Murugesan , Yaliraki Sophia N. , Yacoub Magdi H.
Published: July 2012

Collagen is the essential protein in the extracellular matrix, which maintains the structural and mechanical integrity of tissues while providing key signals to regulate cell functions. Although animal-based collagens can be used as biomaterial for tissue engineering heart valves, they cause infections and lack flexibility. These limitations have stimulated the exploration of collagen mimetic peptides (CMPs) through a bottom-up approach using computational modeling followed by experiments to enzymatically cross-link the CMPs and produce hydrogels. The X-ray structure of triple-helices of CMP was used in software FIRST and in mutational code to identify its structural stability and hotspots. These data assisted to introduce charged residues by mutations to cross-link and to add binding motif (GFOGER) for integrin in the structure. The helical stability and self-association of the mutated CMP has been validated using molecular dynamics (MD) simulation. Experimentally, the peptide was synthesized by solid phase Fmoc chemistry and characterized by HPLC and mass spectrometry. Enzymatic cross-linking on primary amine and gel formation were obtained by incubating peptide and plasma amine oxydase (PAO) solutions in PBS at 37 and 58 °C. Peptide assembly and aggregation was monitored by turbidity (optical density at 314 nm) and morphology was analysed by transmission electron microscopy (TEM).
The modelling analyses indicated the CMP to have the desired structural properties for self-assembly and high affinity towards integrin binding. The modification of the key positions with charged residues increased the possibilities for helical cross-link (gelation). In addition to cell signalling, the charged residues at the cell binding motif could further enhance the inter-helical association of the CMPs. The structural properties of the modelled CMP were reproduced in experimental conditions. Addition of PAO significantly improved turbidity of peptide solutions and lead to hydrogel formation. The peptides assembled in branched fibrillar structures around 25 nm in diameter as it was confirmed by TEM analysis. The proposed peptide promises to show some inherent structural properties of native collagen in silico and in vitro. These properties are required to produce functional scaffolds for tissue engineering heart valves.
AlphaGal Residue in Xenograft Heart Valve Bioprostheses and Tissue Engineered Construct
Authors: Naso Filippo , Gandaglia Alessandro , Comacchio Giovanni , Spina Michele , Gerosa Gino
Published: July 2012

The glutaraldehyde (GA) fixed heart valve bioprostheses (HVB) fail in the long term due to dystrophic degeneration. To avoid GA treatment, xenogenic tissues have been processed by detergent-based decellularization procedures (DBDP). However a complete immunogeneic tolerance by the host is not granted. Degenerative inflammatory process seems to be triggered by the persistent presence of reactive xenogeneic residual, specifically by the alpha-Gal antigen. Through the use of an ELISA assay we assessed and quantified the content of such xenoantigen in different commercial bioprosthetic heart valves and compare to that present in the native and decellularized tissues used for their manufacture. Four models of pericardial and two of porcine HVBs were investigated for the alpha-Gal content. Untreated porcine aortic leaflets (UPAL) were assessed before and after 3 different detergent-based decellularization procedure: TRICOL (Triton X100 and Sodium Cholate), DOC (Sodium Deoxycholate) and DOC-SDS (Sodium Deoxycholate and Sodium Dodecyl Sulfate). Moreover the total amount of alpha-Gal epitopes in native bovine pericardium (NBP) was determined. All the specimens react with the M86 primary monoclonal antibody and the exposed alpha-Gal epitopes is determined by an indirect ELISA assay. For each sample, the amount of alpha-Gal was expressed as numbers of epitopes *10e11 each 10 mg of wet tissue. The amount of alpha-Gal xenoantigen in pericardial HVB (1.5 ± 0.18 *10e11, n=15) was three and half times less with respect to NBP (5.1 ± 0.21 *10e11, n=9). In a model of porcine HVB the xenoantigen was not detected, in the second one the absolute value (1.37 ± 0.25 *10e11, n=9) was similar to that of the pericardial HVB and half of UPAL (2.5 ± 0.31 *10e11, n=9). DOC and DOC-SDS treatments leave on the tissue the 40% (1.02 ± 0.1 *10e11) of the epitopes originally present in the native cusps. TRICOL has proven to be able to eliminate all the alpha-Gal antigen. HVBs GA-treatment do not prevent the binding of resident alpha-Gal antigens with M86 antibodies. The investigated HVBs exhibited a non negligible amount of reactive epitopes accounting to 29.3% of those exposed by native pericardial tissue and 55% for the porcine one. Probably, the pericardial simpler structure allow a better action of the GA, which is able to ensure a greater, but non complete epitope masking. In one model of porcine HVB the alpha-Gal was not found. Regarding the different DBDPs, the removal of cell components is not a sufficient condition to ensure the elimination of the alpha-Gal epitopes. Up to date the TRICOL seems to be the only method capable of producing an alpha-Gal tissue free.
The Cellular and Extracellular Matrix Structure of Human Pericardium for Heart Valve Tissue Engineering
Authors: Schornik David , Straka Frantisek , Jaroslav Masin Jaroslav Masin , Filova Elena F , Burdikova Zuzana , Mirejovsky Tomas , Lodererova Alena , Chlup Hynek , Horny Lukas , Pirk Jan , Bacakova Lucie
Published: July 2012

The objective of our study was to compare the histological structure and cellular organization of autologous human pericardium to that of the human aortic heart valve. Collagen, elastin and glycosaminoglycans are responsible for the mechanical properties of aortic heart valve leaflets. Aortic valve leaflets are composed primarily of collagen representing 50% of total extracellular matrix (ECM). The main collagen types in the aortic heart valve are collagen I (74% of total collagen) and collagen III (24% of total collagen). Elastin represents 13% and is responsible for the elastic properties of the valve leaflet. Collagen has a specific architecture that endows heart valve tissue with the ability to withstand circulatory forces over the course of a lifetime. Its fiber orientation, density and cell associations are very important for this purpose. Normal aortic heart valves were obtained during heart transplantation and compared to autologous human pericardium before and after dynamic conditioning using classical histological assessment, immunohistochemical analysis and confocal microscopy. The architecture of pericardial tissue is very similar to that of the normal aortic heart valve possessing well organized collagen fibers with embedded pericardial interstitial cells (PICs) forming a three dimensional network. Instead of the trilaminar histological organization present in the aortic heart valve, the pericardium possesses one layer whose densely packed collagen bundles closely resemble that of the lamina fibrosa of the native aortic heart valve by confocal microscopy. Elastin fibers are evenly distributed throughout the entire thickness of the pericardium in comparison to the specialized elastin containing layer in the lamina ventricularis of the aortic heart valve. PICs are also evenly distributed throughout the pericardium. In the inner pericardial layer facing the heart these cells have a more spindle-like shape similar to that of valvular interstitial cells (VICs) in the lamina fibrosa, while in the outer part of the pericardium these cells have a more spread-out cytoplasmic morphology interacting with more loosely distributed collagen bundles. Like in the aortic heart valve, PICs show cell-cell interactions in addition to cell-matrix interactions. Our study confirmed similarities in the cellular and ECM organization of human pericardium and the native aortic heart valve. It may be concluded that human autologous pericardium may be a favorable tissue for heart valve replacement. Autologous pericardial tissue may also avoid a negative immune system response that could adversely affect recipient graft uptake and downstream ECM remodeling events.
Mitral Valve Mechanics Following Posterior Leaflet Patch Augmentation
Authors: Rasmussen Ann Q. , Rahmani Azadeh , Honge Jesper L. , Ostli Bjørn , Levine Robert A. , Hagège Albert , Nygaard Hans , Hasenkam J. Michael , Nielsen Sten L. , Jensen Morten O.
Published: July 2012

Attention towards optimization of mitral valve repair methods is increasing. Patch augmentation strategy is used to treat functional ischemic mitral regurgitation (FIMR) and hypertrophic cardiomyopathy. When used to extend the anterior leaflet, the procedure decreases the forces exerted on the secondary chordae. The purpose of this study was therefore to investigate the force balance changes following patch augmentation of the posterior leaflet, with particular attention to the secondary chordae tendineae emanating from the posterior papillary muscle (PPM) in an FIMR simulated valve. Twelve mitral valves were obtained from 80kg pigs. An in vitro test setup simulating the left ventricle was used to hold the valves with a papillary muscle positioning system. Water pressure within the ventricular chamber was regulated manually in order to simulate different static pressures during valve closure. An oval shaped porcine pericardial patch measuring 17x29mm was introduced into the posterior leaflet approximately 2mm from the annulus and extending circumferentially from the middle of P2 to the end of the P3 scallop. In order to simulate a healthy valve, retraction of the patch was performed using sutures, which were then released to simulate patch repair. Data were acquired with and without PPM displacement to simulate the effect from one of the main contributors of FIMR, before and after patch augmentation, giving four simulation scenarios. The PPM was displaced 12mm posteriorly and 5mm apically. Dedicated miniature transducers were used to record the forces exerted on the secondary chordae tendineae. Three-way ANOVA was used to analyze the measurements.
The effect of displacing the posterior papillary muscle (p < .010) and implementing patch augmentation (p<.004) are significant and independent of each other. The overall effect of displacing the PPM induced tethering on the secondary chordae tendineae from the PPM to the posterior leaflet resulting in a force increase of 28.2 %. The overall effect of implementing the patch augmentation into the posterior leaflet induced a decrease in force of 24.8 % for the healthy and PPM displaced simulations together. The repairing effect of the patch augmentation is found by comparing the specific scenarios. A 40 % increase is induced by displacing the PPM and a 31 % decrease is found by implementing the patch augmentation, leaving the repaired tethering force a mere 9 % higher than that of the healthy measurements. Posterior leaflet patch augmentation significantly reduced the forces exerted onto the secondary chordae tendineae from the PPM in both healthy and PPM displaced valves. As changes in chordal tension leads to redistribution of the total stress exerted on the valve, patch augmentation may have adverse long term influence on mitral.
The Way to a New Generation of Bio-Prostheses
Authors: Waldow Thomas , Plötze Katrin , König Matthias , Matschke Klaus
Published: July 2012

Diseases of heart valves often make a prosthetic replacement therapy necessary. Long term goal is the development of artificial leaflet material with defining properties of mechanical prostheses (i.e. durability) with complete biocompatibility without the need for any anticoagulation therapy whatsoever. In order to achieve this aim, objective efforts are being made to use a new material that is still in the process of development. It is a film-like tissue, made of pure carbon in the form of carbon-nanotubes, which are characterized by their excellent mechanical properties (tensile strength 65GPa in comparison to steel with 0.6Gpa). The woven material has also a very small mesh width, which can be influenced by the spinning method. Due to the nature of this material, which is associated with a high surface energy, there is a need for adaptions for the use in vivo according to the requirements. Plasma Enhanced Chemical Vapor Deposition PECVD has proven to be the appropriate method for such a functionalization. It is possible to deposit amorphous hydrocarbon coatings below 60°C and in a thickness range from a few nanometers up to several microns, while at the same time providing a very low Young's modulus that ensures to withstand mechanical stress. In addition, this method allows to influence regional properties e.g. by incorporating silicon into the matrix to prevent adhesion of thrombocytes and/or to add nitrogen to give the ability to endothelial cell growing. The first project step is to evaluate in high resolution and accuracy the parameter characteristic of native valves and prostheses. Therefore the elastic modulus, flexibility, extension, expansion, banding stress, banding elasticity, banding rigidity, reversed banding strength, cantilever load, surface tension, surface structure, surface tension and intensity of surface loading are under investigation. A mix of physical, chemical and visual analysis methods are used. The parameter characteristic of the nanotube material has to match these results. In cases of mismatch a technical adjustment, e.g. during weaving or coating, is possible. At least two big advantages of this new composite material exist: The possibility to produce a compound material with regional different main characteristics by using a two-phase coating process. And on the other hand the abandonment of exogenous substances during the production process and so the material has a distinct advantage over those currently used Teflon fabrics.
The role of the epigenetic factor in valvulogenesis in zebrafish in vivo
Authors: Kang Hae Jin , Gharib Morteza
Published: July 2012

In this study, we focused on wall shear stress as an epigenetic factor to initiate valve formation. Fast or oscillatory flow is induced in an embryonic zebrafish vessel to mimic the flow in atrioventricular canal (AVC). By creating an environment similar to AVC in non-cardiac region in vivo, we propose to seek a better understanding of the mechanisms associated with the induction of valvulogenesis signaling pathways. Polydimethylsiloxane is injected at the vessel wall of embryonic zebrafish, creating fast or oscillatory flow, therefore modulating local wall shear stress (WSS). Particle image velocimetry (PIV) technique is used to measure blood flow velocity. Whole mount in situ hybridization is performed to detect kruppel-like factor 2a (klf2a) expression. Klf2a is used as a marker gene since it responds to shear stress and is crucial for valve formation. Using PIV, WSS is calculated. In situ hybridization showed klf2a expression in the vessel as a result of either high WSS or oscillatory WSS. Klf2a is not expressed in the vessel during normal embryonic development. With a new gel injection technique, local WSS in the zebrafish vessel has changed, inducing expression of klf2a, an important gene for the initiation of valve formation. Expression of different genes such as TGF-β family that are involved in valve formation will be studied further to establish an innovative model to explore valvulogenesis in vivo.
Calcification of Aortic Valve leaflets is Shear Dependent and Side-specific
Authors: Rathan Swetha , Anita Rajamani Anita Rajamani , Gorti Harika , Arjunon Sivakkumar , Jo Hanjoong , Yoganathan Ajit
Published: July 2012

Aortic valve (AV) sclerosis is a degenerative disease and is one of the leading causes of mortality in elderly population. AV experiences various mechanical stimuli such as pressure, shear and flexure with differing magnitudes on either sides of AV (fibrosa and ventricularis) with fibrosa side facing more dynamic environment. Normal hemodynamic conditions constantly renew and remodel the valve, whereas altered mechanical loading such as hypertension and altered shear stress can cause tissue inflammation that leads to calcification, preferentially on fibrosa side. AV calcification progressively leads to sclerosis and ultimately results in valve failure. However, the molecular and cellular processes that lead to inflammation and calcification are not very well understood. To understand the role of mechanics and underlying molecular mechanisms behind this preferential calcification, aortic side and ventricularis side of fresh porcine AVs were exposed to different shear stress patterns using an ex vivo cone and plate viscometer for 72 hours. Osteogenic medium was used to accelerate the calcification process ex vivo. To investigate the effect of shear stress magnitudes on fibrosa side, sine waveforms of amplitudes 5, 10 and 25 dynes/cm2 at a frequency of 1 Hz were used. To investigate the effects of shear stress frequency on fibrosa side, sine waveforms of 1 and 2 Hz at 10dynes/cm2 were used. Following exposure to shear, calcium levels of the samples were quantified using calcium Arsenazo assay. Von Kossa stain for mineralization was also done. Fresh porcine AVs were used as controls. Results indicated that low magnitude shear stress, 5 dyne/cm2 at 1 Hz elicited significant calcium levels on fibrosa side compared to other magnitudes and frequencies. To investigate if the oscillatory nature or the low magnitude was responsible for this high calcium response, fibrosa side was exposed to steady 5 dyne/cm2 under same experimental conditions as above. However, calcium levels at steady 5dyne/cm2 were comparable to fresh AV levels and thus non-significant. This result indicated that the magnitude in combination with the oscillatory nature of the sine 5dyne/cm2 triggered significant calcification levels on the fibrosa side of the AV leaflets. To test the side-specificity of this response, ventricularis side was also exposed to 5 dyne/cm2 under same experimental conditions as above. It is interesting to note that calcium levels on ventricularis side were not significant compared to that on the fibrosa side. This result further indicated that the expression of significant calcium levels in response to the low oscillatory shear is indeed side-specific. Thus our results suggest that the calcification of the AV leaflets is shear-dependent and side-specific. Shear dependent calcification in AV also suggests mechanobiological similarities with the atherosclerosis of blood vessels.
Gelatin and Decorin are Suitable Candidates for Application in Tissue-Engineered Matrices - an Immunological In Vitro Study
Authors: Bayrak Alexandra , Ibold Bettina , Hinderer Svenja , Schenke-Layland Katja , Stock Ulrich A. , Seifert Martina
Published: July 2012

Inflammatory and immune-mediated responses to extracellular matrix proteins (ECMp) or biomaterials mainly determine the acceptance of tissue-engineered scaffolds like heart valve grafts. Therefore, we focused on detailed analysis of those responses induced either by the single ECMp gelatin and the proteoglycan decorin or by electrospun scaffolds composed of both proteins. Proliferation assays were performed to analyze response of T cell subsets by flow cytometry. Therefore, human peripheral blood mononuclear cells (PBMCs) were co-cultured with bovine decorin, porcine gelatin or with electrospun scaffolds generated of poly-ε-caprolacton (PCL) with either gelatin alone or in combination with decorin under low-dose anti-CD3 treatment for 5 days. Moreover, monocyte-derived immature dendritic cells (DC) were co-cultured with decorin and gelatin to determine maturation effects by specific surface markers and flow cytometric analysis compared to a Lipopolysaccharride (LPS) stimulated control. Supernatants of both T cell and DC cultures were analyzed for the pro-inflammatory cytokines IFNγ, TNFα and IL-6 by cytometric bead arrays or ELISA. Additionally, complement activation by decorin and gelatin was screened by incubation with pooled human serum and measuring induced C5a release by standard ELISA. In general, a slight reduction of the T cell subset proliferation compared to the anti-CD3 stimulated positive control in CFSE-based assays could be demonstrated for bovine decorin and porcine gelatin. Both electrospun scaffold types did not alter the proliferation response. Additionally, neither decorin nor gelatin induced a distinct proinflammatory cytokine secretion of IFNγ and TNFα relative to the control. The overall high secretion level of IL-6 was not affected by both proteins and electrospun scaffolds. Remarkably, a trend for reduced IFNγ and TNFα release could be observed for both scaffold types. Moreover, the surface marker expression pattern of DC revealed that decorin as well as gelatin were not able to induce DC maturation due to low expression levels for CD83 and fairly low TNFα secretion when compared to the LPS control. Analyzing complement activating capacities of both ECMp as part of the first line innate immune response, decorin as well as gelatin did not induce enhanced C5a release compared to controls. The results presented here illustrate the important role of evaluating complex immune responses to single ECMp as well as to electrospun scaffolds to facilitate an efficient selection of immunological inert tissue-engineered matrices for their future application as heart valve substitutes. Thus, gelatin as well as decorin are promising candidates for tissue engineering scaffolds as seen by their low immunogeneic properties as single ECMp or as part of electrospun blends.
A New Approach to Heart Valve Tissue Engineering Based on the Modification of Human Pericardial Tissue
Authors: Straka Frantisek , Schornik David , Masin Jaroslav , Filova Elena , Burdikova Zuzana , Mirejovsky Tomas , Honsova Eva , Lodererova Alena , Chlup Hynek , Horny Lukas , Vesely Jan , Pirk Jan , Bacakova Lucie
Published: July 2012

The main problem of currently used xenogeneic biological heart valves is the development of degenerative changes leading to valve failure. Reoperation is required in approximately 65% of patients at 15 years after implantation. The challenge of heart valve tissue engineering is to create a new type of biological prosthesis for clinical use. The aim of our study is to construct a living autologous human pericardial heart valve that will have optimal mechanical properties and a similar histological structure as the normal aortic heart valve. Three leaflet heart valve constructs made from human pericardium were attached onto a plastic holder and cultured under dynamic conditions for up to four weeks. After this time conditioned pericardial samples were compared to control unconditioned pericardial samples from the same patient and to that of the normal aortic heart valve. Histological, immunohistochemical and biomechanical assessments were performed. Pericardial interstitial cells (PICs) are able to respond to mechanical stresses by proliferating and differentiating into an active (myofibroblast-like) phenotype and are able to produce new extracellurar matrix (ECM). A threefold increase in PIC number and a twofold increase in smooth muscle actin (SMA) positive cells was observed after dynamic conditioning. These measurements were statistically significant (p<0.001). The histological structure of conditioned pericardium is very similar to the normal aortic heart valve and dynamic conditioning was shown to be important for PIC activation. Uniaxial tensile tests were performed to compare the mechanical properties of conditioned pericardium with the native aortic heart valve. Our results indicate that the secant elastic modulus of pericardium before and after conditioning (13.1 ± 8.3 Mpa) is comparable to the native aortic heart valve. Autologous human pericardium mimics the natural structure of the normal aortic heart valve and has similar mechanical properties. PICs are activated to an active VIC-like phenotype by mechanical conditioning. Our pericardial heart valve construct also possesses optimal hemodynamic properties by echocardiographic measurements similar to the healthy aortic heart valve.

Acknowledgements: Supported by the Grant Agency of the Ministry of Health of the Czech Republic (project No. NT 11270.
Analysis of S-box in Image Encryption Using Root Mean Square Error Method
Authors: Hussain Iqtadar , Shah Tariq , Gondal Muhammad Asif , Mahmood Hasan
Published: July 2012

The use of substitution boxes (S-boxes) in encryption applications has proven to be an effective nonlinear component in creating confusion and randomness. The S-box is evolving and many variants appear in literature, which include advanced encryption standard (AES) S-box, affine power affine (APA) S-box, Skipjack S-box, Gray S-box, Lui J S-box, residue prime number S-box, Xyi S-box, and S8 S-box. These S-boxes have algebraic and statistical properties which distinguish them from each other in terms of encryption strength. In some circumstances, the parameters from algebraic and statistical analysis yield results which do not provide clear evidence in distinguishing an S-box for an application to a particular set of data. In image encryption applications, the use of S-boxes needs special care because the visual analysis and perception of a viewer can sometimes identify artifacts embedded in the image. In addition to existing algebraic and statistical analysis already used for image encryption applications, we propose an application of root mean square error technique, which further elaborates the results and enables the analyst to vividly distinguish between the performances of various S-boxes. While the use of the root mean square error analysis in statistics has proven to be effective in determining the difference in original data and the processed data, its use in image encryption has shown promising results in estimating the strength of the encryption method. In this paper, we show the application of the root mean square error analysis to S-box image encryption. The parameters from this analysis are used in determining the strength of S-boxes
Effects of Surface Roughness and Surface Force on the Thin Film Elastohydrodynamic Lubrication of Circular Contacts
Authors: Chu Li-Ming , Lin Jaw-Ren , Chen Jiann-Lin
Published: July 2012

The effects of surface roughness and surface force on thin film elastohydrodynamic lubrication (TFEHL) circular contact problems are analyzed and discussed under constant load condition. The multi-level multi-integration (MLMI) algorithm and the Gauss-Seidel iterative method are used to simultaneously solve the average Reynolds type equation, surface force equations, the load balance equation, the rheology equations, and the elastic deformation equation. The simulation results reveal that the difference between the TFEHL model and the traditional EHL model increase with decreasing film thickness. The effects of surface forces become significant as the film thickness becomes thinner. The surface forces have obvious effects in the Hertzian contact region. The oscillation phenomena in pressure and film thickness come mainly from the action of solvation forces
Non-Newtonian Micropolar Fluid Squeeze Film Between Conical Plates
Authors: Lin Jaw-Ren , Kuo Chia-Chuan , Liao Won-Hsion , Yang Ching-Been
Published: July 2012

By applying the micropolar fluid model of Eringen (J. Math. Mech. 16, 1 (1966) and Int. J. Mech. Sci. 31, 605 (1993)), the squeeze film lubrication problems between conical plates are extended in the present paper. A non-Newtonian modified Reynolds equation is derived and applied to obtain the solution of squeeze film characteristics. Comparing with the traditional Newtonian case, the non-Newtonian effects of micropolar fluids are found to enhance the load capacity and lengthen the approaching time of conical plates. Some numerical results are also provided in tables for engineer applications
Derivatives of the Triaminoguanidinium Ion, 1. Synthesis, Crystal and Molecular Structures of 1,2,3-Tris(benzylamino)guanidinium Salts
Authors: Bucher Nicolas , Szabo Jan , Oppel Iris M. , Maas Gerhard
Published: July 2012

Triaminoguanidinium chloride was transformed into 1,2,3-tris(benzylamino)guanidinium chloride (3-Cl) in two steps. Anion exchange allowed the preparation of further salts 3-X. The crystal and molecular structures of 3-Cl, 3-I, 3-CF3COO and 3-CF3SO3 were determined. It was found that both the conformation of the cation and the nature of the anion determines the packing in the solid state. Interestingly, three different conformations of the cation were observed in the crystals.
Arbuscular Mycorrhizal Colonization in Five Tropical Forest Tree Legumes of Chittagong University Campus in Bangladesh
Authors: Nure Ferdousee  , Khaled Misbahuzzaman  , A.T.M. Rafiqul Hoque
Published: July 2012

Arbuscular mycorrhizal (AM) colonization in five tropical forest tree legumes (Gliricidia sepium, Dalbergia sissoo, Indigofera tysmanii, Delonix regia and Samanea saman) was investigated in Chittagong University (CU) campus. The results of the present study clearly suggests that, Vesicular AM fungi (VAM) are common in all the studied forest tree species, and that the studied forest tree species differ in their rates of AM formation. The intensity of colonization is maximum (98%) in I. tysmonii followed by D. sissoo (95%), D. regia (63%), S. saman (59%) and G. sepium (52%). Coiled structures of hyphae were recorded in D. regia. Arbuscule formation was recorded in D. sissooand in I. tysmonii. Mycorrhizal spores were found in rhizosphere soils of all the sites. Glomus, Acaulospora, Entrophospora and Gigaspora spores were identified in all the hosts. Forest plants differ in their rates of AM formation. Edhapic conditions like moisture content, soil pH also influence the extent of root colonization.Keyword: Mycorrhizae, Legume, Colonization, Edhapic condition, Rhizosphere, Underground networking.
Warfare, Gender, and Sacrifice in Jequetepeque, Peru
Authors: Swenson Edward
Published: July 2012

Archaeological data from the Jequetepeque Valley suggest that Late Moche warfare and religious sacrifice were embedded in a particular cosmological and gendered construction of the world. As a consequence, the pragmatic motives implicated in violent conflict were mediated by structures of practice specific to the Moche. An analysis of the archaeological record points to the existence of this cultural schema, the identification of which better explains the ascendancy of the famed priestess cult based at San José de Moro and the general decentralization of power in the Jequetepeque region. The evidence indicates that political relations in the valley were informed by a religious ideology that structured feasting, warfare, and sacrifice as specifically gendered but complementary domains. The spatial delimitation and sequential unfolding of ritual events were likely deemed essential for both socio-cosmic renewal and legitimate political advancement. This gendering of political and religious practices is reflected archaeologically in the division of centered and rural space and in the differential distribution of architectural forms, parochial feasting arenas, and iconographically charged artifacts. Ultimately, the archaeological record demonstrates that the political machinations of rural communities amplified this gendered sacrificial system within the context of the environmental upheavals of the Late Moche Period.
Donut Stones as Thigh-Supported Spindle Whorls: Evidence of Ancient Maya Household Yarn and Cordage Production
Authors: Tomasic John J.
Published: July 2012

Donut stones are a relatively common class of ground stone artifact found at archaeological sites throughout Mesoamerica and Andean South America, and a variety of functional interpretations have been proposed for these artifacts. In this article, ethnographic, ethnohistoric, and archaeological data are presented along with the results of replicative experiments in support of an argument that some donut stones from the Maya Highlands and Southern Lowlands may have functioned as whorls for a previously unrecognized type of thigh-supported spindle. Based on a functional interpretation of donut stones as thigh-supported spindle whorls, these artifacts can potentially be used to provide insight into the nature of ancient Maya household yarn and cordage production.
Electrically Programmable Bistable Capacitor for High‐Frequency Applications Based on Charge Storage at the (Ba,Sr)TiO3/Al2O3 Interface
Authors: Li Shunyi , Zheng Yuliang , Jakoby Rolf , Klein Andreas
Published: July 2012

Hysteresis is induced in paraelectric (Ba,Sr)TiO3 (BST) thin‐film capacitors by inserting an Al2O3 barrier layer of a few nanometers in thickness between the BST layer and the electrode. The observed hysteresis is explained by ambipolar charge carrier injection through the Al2O3 layer and charge storage at the BST/Al2O3 interface. The magnitude of the hysteresis can be directly adjusted by manipulating the thickness ratio between BST and Al2O3. Taking into account the low loss of (Ba,Sr)TiO3 capacitors, the observed switching and retention characteristics are suitable for application as non‐volatile programmable high‐frequency devices, e.g., in radio‐frequency identification.
Extrusion Printing of Flexible Electrically Conducting Carbon Nanotube Networks
Authors: Pidcock Geoffrey C. , in het Panhuis Marc
Published: July 2012

Carbon nanotube networks in biopolymer solutions are explored as potential ink systems for the extrusion printing of conducting structures. The biopolymer gellan gum is found to act as an excellent dispersant of multiwalled carbon nanotubes and has the appropriate flow properties to act as a thickener for the controlled dispensing of carbon nanotube networks. Absorbing substrates are found to improve the resolution and the flexibility of the printed structures. These printed conducting carbon nanotube networks exhibit interesting mechanical and electrical characteristics, which are applied to demonstrate their actuating and strain gauging capabilities.
Conformationally Rigid Chiral Pyridine N‐Oxides as Organocatalyst: Asymmetric Allylation of Aldehydes
Authors: Gnanamani Elumalai , Someshwar Nagamalla , Ramanathan Chinnasamy Ramaraj
Published: July 2012

A pyridine unit with a conformationally rigid chiral backbone has been designed and synthesized in an enantiomerically pure form to utilize in the Lewis base‐catalyzed Sakurai–Hosomi–Denmark‐type allylation reaction. The chiral pyridine N‐oxide in 1:1 mixture of chloroform and 1,1,2,2‐tetrachloroethane produced the homoallylic alcohols in up to 98% yield and up to 94% ee.
Interspecific Infanticide and Infant‐Directed Aggression by Spider Monkeys (Ateles hybridus) in a Fragmented Forest in Colombia
Authors: RIMBACH REBECCA , PARDO‐MARTINEZ ALEJANDRA , MONTES‐ROJAS ANDRES , DI FIORE ANTHONY , LINK ANDRES
Published: July 2012

Interspecific aggression amongst nonhuman primates is rarely observed and has been mostly related to scenarios of resource competition. Interspecific infanticide is even rarer, and both the ultimate and proximate socio‐ecological factors explaining this behavior are still unclear. We report two cases of interspecific infanticide and five cases of interspecific infant‐directed aggression occurring in a well‐habituated primate community living in a fragmented landscape in Colombia. All cases were initiated by male brown spider monkeys (Ateles hybridus) and were directed toward infants of either red howler monkeys (Alouatta seniculus: n = 6 cases) or white‐fronted capuchins (Cebus albifrons: n = 1 case). One individual, a subadult spider monkey male, was involved in all but one case of interspecific infanticide or aggression. Other adult spider monkeys participated in interspecific aggression that did not escalate into potentially lethal encounters. We suggest that competition for food resources and space in a primate community living in high population densities and restricted to a forest fragment of ca. 65 ha might partly be driving the observed patterns of interspecific aggression. On the other hand, the fact that all but one case of interspecific infanticide and aggression involved the only subadult male spider monkey suggests this behavior might either be pathological or constitute a particular case of redirected aggression. Even if the underlying principles behind interspecific aggression and infanticide are poorly understood, they represent an important factor influencing the demographic trends of the primate community at this study site. Am. J. Primatol. 74:990‐997, 2012. © 2012 Wiley Periodicals, Inc.
Efficacy of transnasal endoscopic resection for malignant anterior skull‐base tumors
Authors: Wood John W. , Eloy Jean Anderson , Vivero Richard J. , Sargi Zoukaa , Civantos Francisco J. , Weed Donald T. , Morcos Jaques J. , Castaño Johnathan , Lo MPH Kaming , Casiano Roy R.
Published: July 2012

Background

Craniofacial resection (CFR) has been the standard of care for malignant tumors of the anterior skull base (ASB). However, during the past 2 decades, transnasal endoscopic resection (TER) has gained significant popularity. The purpose of this study is to compare CFR and TER with respect to perioperative and oncologic outcomes.

Methods

Retrospective analysis at a tertiary care medical center of 82 consecutive patients undergoing resection of tumors of the ASB between 1997 and 2011.

Results

Thirty‐four patients underwent TER, while 48 patients underwent CFR. There was no statistical difference in major complications between the two groups (p = 0.29). However, TER patients had shorter operating room times (284 minutes for TER, 620 minutes for CFR; p < 0.001), lower intraoperative blood loss (675 mL for TER, 1000 mL for CFR; p = 0.005), shorter intensive care unit (ICU) stays (0 days for TER, 3 days for CFR; p < 0.001), and shorter hospital stays (4.5 days for TER; 7 days for CFR; p < 0.001). There were no differences for the rates of en bloc resection, negative margins, or disease‐specific mortality. Subanalysis yielded a median follow‐up of 5 years postoperatively. There were no differences in disease‐specific mortality or recurrences in this group.

Conclusion

Patients undergoing TER for tumors of the ASB are more likely to leave the ICU and the hospital earlier than their CFR counterparts. Furthermore, for carefully selected patients undergoing TER, excellent oncologic outcomes with survival and recurrence rates similar to patients undergoing CFR may be achieved. Comparison of oncologic outcomes, however, may be limited by discrepancy in histologic grade and clinical stage between the two groups. Nonetheless, TER seems to be an excellent alternative to CFR in appropriately selected patients. ©2012 ARS‐AAOA, LLC.
Die chemische Synthese von Nanographen, Graphen‐Nanobändern und Graphen‐Schichten
Authors: Chen Long , Hernandez Yenny , Feng Xinliang , Müllen Klaus
Published: July 2012

Graphen, eine einzelne, zweidimensionale Graphitschicht aus einem hexagonalen Netzwerk von sp2‐hybridisierten Kohlenstoffatomen, ist wegen seiner außergewöhnlichen elektronischen, thermischen und mechanischen Eigenschaften ein vielversprechender Kandidat für praktische Anwendungen in Elektronik, Sensorik, Katalyse sowie Energiespeicherung und ‐umwandlung. Theoretische und experimentelle Untersuchungen zeigten, dass die Eigenschaften von Graphen im Wesentlichen von dessen geometrischen Struktur abhängen. Eine zielgerichtete Graphensynthese ist daher für eine Untersuchung der grundlegenden physikalischen Eigenschaften und Implementierung in vielversprechende Anwendungen entscheidend. Dieser Kurzaufsatz präsentiert jüngste Fortschritte, die zu erfolgreichen chemischen Synthesen von Graphen in einem breiten Bereich von Größen und chemischen Zusammensetzungen geführt haben.
A study of open access journals using article processing charges
Authors: Solomon David J. , Björk Bo‐Christer
Published: July 2012

Article processing charges (APCs) are a central mechanism for funding open access (OA) scholarly publishing. We studied the APCs charged and article volumes of journals that were listed in the Directory of Open Access Journals as charging APCs. These included 1,370 journals that published 100,697 articles in 2010. The average APC was $906 U.S. dollars (USD) calculated over journals and $904 USD calculated over articles. The price range varied between $8 and $3,900 USD, with the lowest prices charged by journals published in developing countries and the highest by journals with high‐impact factors from major international publishers. Journals in biomedicine represent 59% of the sample and 58% of the total article volume. They also had the highest APCs of any discipline. Professionally published journals, both for profit and nonprofit, had substantially higher APCs than journals published by societies, universities, or scholars/researchers. These price estimates are lower than some previous studies of OA publishing and much lower than is generally charged by subscription publishers making individual articles OA in what are termed hybrid journals.