Synthetic Specimens Research Articles

Electrochemical Characterization of Egyptian Blue Pigment in Wall Paintings Using the Voltammetry of Microparticles Methodology

AbstractThe solid state voltammetric response of Egypt blue, Han blue and ploss blue pigments upon attachment to graphite electrodes in contact with aqueous phosphate buffer at pH 7.0 is studied by voltammetry of microparticles and scanning electrochemical microscopy. Such voltammetric responses, combined with those for synthetic specimens consisting of binary mixtures of the pigment and SiO2 or CaCO3 as well as ternary ones of CaCO3 and SiO2 mixtures allow for the identification of the pigment and the support in samples from wall paintings using different electrochemical parameters, in particular upon performing the Tafel and modified Tafel analysis of voltammetric peaks. Identification of Egypt blue in microsamples of murals from a Roman archaeological site in Castulo (Jaén, Spain) is discussed.

DEM Simulation of Direct Shear: 1. Rupture Under Constant Normal Stress Boundary Conditions

A particle-based distinct element method and its grain-based method are used to generate and simulate a synthetic specimen calibrated to the rupture characteristics of an intact (non-jointed) low-porosity brittle rock deformed in direct shear. The simulations are compared to the laboratory-generated ruptures and used to investigate rupture at various normal stress magnitudes. The fracturing processes leading to shear rupture zone creation and the rupture mechanism are found to be normal stress dependent (progressing from tensile splitting to shear rupture) and show partial confirmation of rupture zone creation in nature and in experiments from other materials. The normal stress dependent change is found to be due to the orientation of the major principal stress and local stress concentrations internal to the synthetic specimens being deformed. The normal stress dependent rupture creation process results in a change to the rupture zone’s geometry, shear stress versus horizontal displacement response, and thus ultimate strength.

Synthesis and Structure Revision of the C43–C67 Part of Amphidinol 3

Stereoselective synthesis of the C43-C67 part of amphidinol 3 (AM3) and its C51-epimer was achieved starting from a common intermediate corresponding to the tetrahydropyran moiety of AM3, via asymmetric oxidations and Julia-Kocienski olefination. By comparing NMR data of the synthetic specimens with those of AM3, the absolute configuration at C51 of AM3 was revised from R to S.

Determination of elemental composition of Lake Baikal sponges by wavelength dispersive X‐ray fluorescence spectrometry

Sponge endemic species inhabit the Lake Baikal from the ancient times. Because the sponges are the biological filters of the Baikal water and they contribute greatly to silicon circulation in the lake, it is crucial to analyze their composition. Only a few publications report the analytical data concerning the element composition of Lake Baikal sponges. However, the analytical data were mainly obtained by destructive methods. No data on the concentrations of some alkaline and volatile elements are available so far. This article describes the application of wavelength dispersive X‐ray fluorescence spectrometry to study the sponges of Lubomirskia baicalensis, Baikalospongia bacillifera, and Baikalospongia recta species collected at the littoral part of the Beryozovy Cape in the Southern Baikal. The concentrations of 19 elements Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, and Ba have been determined. In this article, we discuss the problem of selecting calibration samples for wavelength dispersive X‐ray fluorescence spectrometry, because appropriate reference samples are not available. The synthetic specimens, prepared by mixing plant certified reference materials and silicon dioxide in certain proportions, were proposed for calibration. The compositions of sponges cleaned from mineral particles and symbiotic organisms, as well as unwashed sponges, have been compared. Copyright © 2013 John Wiley & Sons, Ltd.

Young’s Modulus of Coarse Granular Materials via Cyclic Large Triaxial Tests: Effect of Parallel Grading and Loading Pattern

Abstract In this study, a new large-scale triaxial testing apparatus was constructed and calibrated. To verify the new testing system, synthetic specimens were prepared and tested by three different testing methods: tests using the newly constructed large-scale triaxial testing apparatus, resonant column/torsional shear tests, and free–free resonant column tests. Young’s moduli of the synthetic specimens measured by the three methods were compared, providing comparable results. In addition, cyclic triaxial tests were performed under various experimental conditions on coarse grain materials. Two series of parallel graded samples were prepared by mixing crushed rock. The samples were tested using the new triaxial testing apparatus under various testing conditions. The influence of grain size, loading pattern, loading frequency, and fine contents were analyzed and discussed.

Stiffness and ultimate load of osseointegrated prosthesis fixations in the upper and lower extremity

BackgroundTechniques for the skeletal attachment of amputation-prostheses have been developed over recent decades. This type of attachment has only been performed on a small number of patients. It poses various potential advantages compared to conventional treatment with a socket, but is also associated with an increased risk of bone or implant-bone interface fracture in the case of a fall. We therefore investigated the bending stiffness and ultimate bending moment of such devices implanted in human and synthetic bones.MethodsEight human specimens and 16 synthetic models of the proximal femora were implanted with lower extremity prostheses and eight human specimens and six synthetic humeri were implanted with upper extremity prostheses. They were dissected according to typical amputation levels and underwent loading in a material testing machine in a four-point bending setup. Bending stiffness, ultimate bending moment and fracture modes were determined in a load to failure experiment. Additionally, axial pull-out was performed on eight synthetic specimens of the lower extremity.ResultsMaximum bending moment of the synthetic femora was 160.6±27.5 Nm, the flexural rigidity of the synthetic femora was 189.0±22.6 Nm2. Maximum bending moment of the human femora was 100.4±38.5 Nm, and the flexural rigidity was 137.8±29.4 Nm2. The maximum bending moment of the six synthetic humeri was 104.9±19.0 Nm, and the flexural rigidity was 63.7±3.6 Nm2. For the human humeri the maximum bending moment was 36.7±11.0 Nm, and the flexural rigidity at was 43.7±10.5 Nm2. The maximum pull-out force for the eight synthetic femora was 3571±919 N.ConclusionSignificant differences were found between human and synthetic specimens of the lower and upper extremity regarding maximum bending moment, bending displacement and flexural rigidity. The results of this study are relevant with respect to previous finding regarding the load at the interfaces of osseointegrated prosthesis fixation devices and are crucial for the development of safety devices intended to protect the bone-implant interface from damaging loadings.

Total Knee Arthroplasty With a Computer-navigated Saw: A Pilot Study

Computer-aided surgery aims to improve implant alignment in TKA but has only been adopted by a minority for routine use. A novel approach, navigated freehand bone cutting (NFC), is intended to achieve wider acceptance by eliminating the need for cumbersome, implant-specific mechanical jigs and avoiding the expense of navigation. We determined cutting time, surface quality, implant fit, and implant alignment after NFC of synthetic femoral specimens and the feasibility and alignment of a complete TKA performed with NFC technology in cadaveric specimens. Seven surgeons prepared six synthetic femoral specimens each, using our custom NFC system. Cutting times, quality of bone cuts, and implant fit and alignment were assessed quantitatively by CT surface scanning and computational measurements. Additionally, a single surgeon performed a complete TKA on two cadaveric specimens using the NFC system, with cutting time and implant alignment analyzed through plain radiographs and CT. For the synthetic specimens, femoral coronal alignment was within±2° of neutral in 94% of the specimens. Sagittal alignment was within 0° to 5° of flexion in all specimens. Rotation was within±1° of the epicondylar axis in 97% of the specimens. The mean time to make cuts improved from 13 minutes for the first specimen to 9 minutes for the fourth specimen. TKA was performed in two cadaveric specimens without complications and implants were well aligned. TKA is feasible with NFC, which eliminates the need for implant-specific instruments. We observed a fast learning curve. NFC has the potential to improve TKA alignment, reduce operative time, and reduce the number of instruments in surgery. Fewer instruments and less sterilization could reduce costs associated with TKA.

Recent developments in the study of rapid human movements with the kinematic theory: Applications to handwriting and signature synthesis

Human movement modeling can be of great interest for the design of pattern recognition systems relying on the understanding of the fine motor control (such as on-line handwriting recognition or signature verification) as well as for the development of intelligent systems involving in a way or another the processing of human movements. In this paper, we briefly list the different models that have been proposed in order to characterize the handwriting process and focus on a representation involving a vectorial summation of lognormal functions: the Sigma–lognormal model. Then, from a practical perspective, we describe a new stroke extraction algorithm suitable for the reverse engineering of handwriting signals. In the following section it is shown how the resulting representation can be used to study the writer and signer variability. We then report on two joint projects dealing with the automatic generation of synthetic specimens for the creation of large databases. The first application concerns the automatic generation of totally synthetic signature specimens for the training and evaluation of verification performances of automatic signature recognition systems. The second application deals with the synthesis of handwritten gestures for speeding up the learning process in customizable on-line recognition systems to be integrated in electronic pen pads.

Microstructural Modeling and Dynamic Process Simulation of Laser-Assisted Machining of Silicon Nitride Ceramics With Distinct Element Method

The distinct element method (or discrete element method, DEM) is applied to simulate the dynamic process of laser-assisted machining (LAM) of silicon nitride ceramics. This is motivated by the fact that LAM of ceramics shows a few complicated characteristics such as spontaneous crack formation, discontinuous chips, etc. Thus, using the two-dimensional distinct element code, PFC2D, the microstructure of a β-type silicon nitride ceramic is modeled, and the resulting temperature-dependent synthetic specimens are created first, and then, machining simulations are conducted. The DEM model is validated through comparing the predicted results with those from the experiments under different cutting temperatures in terms of cutting force, chip size, and depth of subsurface damage. Furthermore, the mechanisms of LAM are analyzed from the aspects of material removal, chip segments, surface/subsurface damage, as well as crack initiation, propagation, and coalescence.

Synthetic on-line signature generation. Part I: Methodology and algorithms

The theoretical framework and algorithms of a novel method for the generation of synthetic on-line signatures are presented. This model-based approach combines the spectral analysis of real signatures with the Kinematic Theory of rapid human movements in order to generate totally synthetic specimens. Two different algorithms are also described in order to produce duplicated samples from the synthetic master signatures, so that the generation scheme as a whole is able to produce in a complete automatic fashion huge synthetic databases. Typical examples of synthetic specimens are presented to highlight their human-like appearance. The validation protocol and the test results are presented and discussed in a companion paper.

Avoiding tunnel collisions between fibular collateral ligament and ACL posterolateral bundle reconstruction

The purpose of this study was to evaluate the risk of tunnel collisions of the fibular collateral ligament (FCL) and posterolateral bundle anterior cruciate ligament (PLB-ACL) tunnels during a combined FCL and double-dundle (DB) ACL reconstruction. Thirty-six 4th-generation synthetic femurs (Sawbones, Pacific Research Laboratories, Vashon, WA) were utilized, and two different femur sizes were used. A FCL tunnel and a PLB-ACL tunnel were reamed on each femur. The tunnels of synthetic specimens that did not have a collision were filled with an epoxy resin augmented with BaSO(4) and radiographic evaluation, and Multidetector CT exams of the specimens were performed. The rate of tunnel collision when the FCL tunnel was reamed to a depth of 30mm was 75 and 69.4% for the 25mm depth. There was a significantly increased risk of tunnel collision when the FCL tunnel was reamed proximally with coronal angulations of 20° and 40°. No collisions were noted when the FCL tunnel was reamed parallel to the distal condylar line and with axial angulations of 20° and 40°. This study provides new insight into tunnel positioning during a combined FCL and DB-ACL reconstruction. The results show that a concomitant FCL injury do not represent a contraindication to perform a DB-ACL reconstruction as long as the FCL tunnel is reamed with no proximal angulation and is directed anteriorly with an axial angulation between 20° and 40°.

Surface Acidity of Amorphous Aluminum Hydroxide

Abstract The surface acidity of synthetic amorphous Al hydroxide was determined by acid/base titration with several complementary methods including solution analyses of the reacted solutions and XRD characterization of the reacted solids. The synthetic specimen was characterized to be the amorphous material showing four broad peaks in XRD pattern. XRD analyses of reacted solids after the titration experiments showed that amorphous Al hydroxide rapidly transformed to crystalline bayerite at the alkaline condition (pH>10). The solution analyses after and during the titration experiments showed that the solubility of amorphous aluminum hydroxide, Ksp = aAl1+ / a3H+, was 1010.3. The amount of consumption of added acid or base during the titration experiment was attributed to both the protonation/deprotonation of dissolved Al species and surface hydroxyl group. The surface acidity constants, surface hydroxyl density and specific surface area were estimated by FITEQL 4.0.

Distinct Element Analysis for Progressive Failure in Rock Slope

This paper investigates a numerical modeling of progressive failure in rock mass using the distinct element analysis. The numerical modeling consists of two processes. The first is to get the mechanical properties of synthetic specimens composed of circular rigid elements with the bonded effect between elements. The second is to analyze deformation of a reduced-scale rock slope under the gravity increased condition. With the calibrated properties of the synthetic specimen unchanged, an approach to initialize stress state in the slope model is studied. Evolution of displacements and the resulting initiation of failure surface in the slope model are displayed.

Experimental investigation of the mechanical properties of synthetic magnesium sulfate hydrates: Implications for the strength of hydrated deposits on Mars

We have carried out uniaxial compression experiments to determine the mechanical properties of three crystalline magnesium sulfate hydrates that may be present in the near‐surface environment of Mars. Our synthetic samples of kieserite (MgSO4 · H2O), epsomite (MgSO4 · 7H2O), and meridianiite (MgSO4 · 11H2O) have mean values of unconfined compressive strength of 6.3 ± 0.7, 12.9 ± 1.8, and 30.1 ± 4.5 MPa, respectively, Young's modulus of 0.8 ± 0.1, 2.9 ± 0.4, and 5.9 ± 0.8 GPa, respectively, and mean porosity values of 47.8% ± 0.5%, 11.1% ± 0.6%, and 2.9% ± 0.2%, respectively. Although our tests cannot quantify a systematic relationship between hydration state and mechanical properties, the different porosities produced by consistent sample preparation methods suggest that the addition of non‐cation‐coordinated water molecules likely reduces the strength of individual sulfate hydrate phases. However, the bulk mechanical properties of our synthetic specimens are instead controlled predominantly by the sample porosity; generally, the strength increases as the porosity decreases. We expect the mechanical properties of sulfate hydrate deposits on Mars to be governed by the bulk porosity rather than the strength of the pure solid phase. We have performed cyclic stressing tests, replicating possible periodic depositional and erosional periods on Mars resulting from obliquity changes. A gradual compaction and reduction in sample porosity, rather than an increase in crack damage, is observed with each loading cycle, suggesting that the evolution of mechanical properties will depend on local factors such as bulk density, in addition to the overall stress history.

Toward mechanistic elucidation of iron acquisition in barley: efficient synthesis of mugineic acids and their transport activities

Iron acquisition of graminaceous plants is characterized by the synthesis and secretion of iron-chelating compounds, mugineic acids (MAs), and by a specific uptake system for MAs-iron(III) complexes. We identified a transporter, HvYS1 (Hordeum vulgare L. yellow stripe 1), that is highly specific for MAs-iron(III) in barley roots. In this article we outline the characterization of HvYS1, and our recent work on the practical syntheses of MAs and investigations into the molecular basis of the specific transport of their iron(III) complexes by HvYS1. 2'-Deoxymugineic acid (DMA) was synthesized in a good overall yield from commercially available Boc-l-allylglycine using a minimal number of short simple operations with minimal protecting groups and work-up/purification procedures. The same strategy was also successfully applied to beta-hydroxy-l-allylglycine, which was obtained by an allylic oxidation of l-allylglycine derivatives, to give MA and 2'-epi-MA efficiently. HvYS1 transported the iron(III) complexes of all three synthetic specimens with efficiency similar to that of a natural mugineic acid complex. With sufficient quantities of MAs in hand, we analyzed the function of HvYS1 and revealed by preparing chimeric transporters that the sixth outer membrane loop of the transporter plays a vital role in substrate specificity.

Microparameters Calibration for Loose and Cemented Soil When Using Particle Methods

A numerical model for the loose and the cemented component of the Torino subsoil is presented in this paper. The model is represented by a dense packing of nonuniform sized cylindrical particles with clumps by using the particle flow code in two dimensions. The paper shows how the synthetic specimens were calibrated to reproduce true material behavior giving insights over the influence of various parameters (such as platens velocity, particle shape, bond strength, etc.) on the mechanical behavior of bonded and unbonded assemblies. Loose and cemented ground are basically characterized by the same grain-size distribution, therefore the same numerical model is adopted. The effect of cementation is taken into account by introducing parallel bonds at contacts between the different particles. It is shown that the mechanical behavior of the Torino subsoil is well reproduced at the volume element scale. The results can be used to build representative numerical models to study engineering problems at the site scale.

Does Femoral Component Loosening Predispose to Femoral Fracture?: An In Vitro Comparison of Cemented Hips

The incidence of femur fracture around total hip arthroplasties continues to increase at substantial cost to society. These fractures are frequently associated with a loose femoral component. Consequently, we sought to test whether femoral component loosening predisposes to periprosthetic femoral fracture. Because many periprosthetic femoral fractures are spiral in nature, we evaluated the torsional characteristics of the implanted femur in which the only design variable was instability of the femoral component. We used synthetic (polyurethane) (n = 15) and paired cadaveric femora (n = 10) with specimens divided into two groups: well-fixed and loose cemented stems. Each specimen was tested mechanically in internal rotation until failure. For the synthetic specimens, torque to failure was reduced by 38%, whereas stiffness was decreased 54% for the loose group compared with the well-fixed group. For the cadaveric specimens, torque to failure was reduced by 58%, whereas stiffness decreased 70% for the loose group compared with the well-fixed group. Fracture patterns were similar between synthetic and cadaveric femora with a proximal spiral pattern in loose specimens and more distal fracture patterns with well-fixed stems. Based on our data, patients with loosened femoral components are at risk for fracture at a substantially lower torque than those with well-fixed components.

88 BMD and Bone Geometry in the Discrimination of Fracture Cases in Females Without Osteoporosis

Fifteen sets of patient radiographs were analyzed by 3 different observers on 2 occasions. Each observer measured the femoral neck-shaft angles (NSAs) of the preoperative digital radiographs and stem-shaft angles (SSAs) of the postoperative radiographs. The effect of femur position on SSA measured by digital radiographs was also investigated using a resurfaced synthetic femur. Radiographs were taken with the synthetic specimen positioned in 10° increments of either flexion or rotation. Measurement by digital radiographs proved less than optimal in assessing preoperative NSA but was better in assessing the postoperative component SSA. External rotation of 30° and flexion of 40° resulted in a clinically significant disparity in SSA measurements. Patient malposition during radiographic imaging can contribute to erroneous NSA and SSA results.

Combinatorial Synthesis of the 1,5-Polyol System Based on Cross Metathesis: Structure Revision of Amphidinol 3

Combinatorial synthesis of a 1,5-polyol system corresponding to the C1-C14 unit of amphidinol 3 (AM3) and its diastereomers was achieved via chemoselective cross metathesis as the key step. Comparison of (13)C NMR data of the synthetic specimens with that of AM3 led to a controversy regarding the originally proposed structure. From GC-MS analysis of the degradation product, the absolute configuration at C2 of AM3 has been revised to be R.

The Reliability of Radiographic Assessment of Femoral Neck-Shaft and Implant Angulation in Hip Resurfacing Arthroplasty

Fifteen sets of patient radiographs were analyzed by 3 different observers on 2 occasions. Each observer measured the femoral neck-shaft angles (NSAs) of the preoperative digital radiographs and stem-shaft angles (SSAs) of the postoperative radiographs. The effect of femur position on SSA measured by digital radiographs was also investigated using a resurfaced synthetic femur. Radiographs were taken with the synthetic specimen positioned in 10° increments of either flexion or rotation. Measurement by digital radiographs proved less than optimal in assessing preoperative NSA but was better in assessing the postoperative component SSA. External rotation of 30° and flexion of 40° resulted in a clinically significant disparity in SSA measurements. Patient malposition during radiographic imaging can contribute to erroneous NSA and SSA results.