Variability In Wall Thickness Research Articles

Pottery kiln from the second half of the 13th century in Žďár nad Sázavou – Staré Město (Czech Republic)

This study investigates a medieval pottery kiln and its fill excavated at a 13th-century settlement site near the Žďár Cistercian monastery. The short 30–40 year lifespan of the settlement provides valuable insight into how pottery was made and appeared in a chronologically specified timeframe of the mid-13th century. The kiln was a single-chamber type, either with an open-topped or domed superstructure with a very narrow stoking channel in terms of height. Technological analysis of the pottery inside the kiln points to consistent production techniques utilising a combination of coiling and early rotational devices with rapid firing practices. The interpretation of the forming technique is backed by 3D scanning, which quantifies the wall thickness variability over various vessel body parts. Cross-analysis with settlement finds shows a uniform ceramic morphology and technological nuances, with petrographic data suggesting both local and external material influences. The study enhances the understanding of the socio-economic dynamics during medieval colonisation based on the case of the Žďár region and provides a benchmark for regional ceramic research.

Operative Workflow from CT to 3D Printing of the Heart: Opportunities and Challenges.

Medical images do not provide a natural visualization of 3D anatomical structures, while 3D digital models are able to solve this problem. Interesting applications based on these models can be found in the cardiovascular field. The generation of a good-quality anatomical model of the heart is one of the most complex tasks in this context. Its 3D representation has the potential to provide detailed spatial information concerning the heart’s structure, also offering the opportunity for further investigations if combined with additive manufacturing. When investigated, the adaption of printed models turned out to be beneficial in complex surgical procedure planning, for training, education and medical communication. In this paper, we will illustrate the difficulties that may be encountered in the workflow from a stack of Computed Tomography (CT) to the hand-held printed heart model. An important goal will consist in the realization of a heart model that can take into account real wall thickness variability. Stereolithography printing technology will be exploited with a commercial rigid resin. A flexible material will be tested too, but results will not be so satisfactory. As a preliminary validation of this kind of approach, print accuracy will be evaluated by directly comparing 3D scanner acquisitions to the original Standard Tessellation Language (STL) files.

Morphology and properties of hollow glass microspheres. Part 3. On the wall thickness of industrial hollow glass microspheres

Microscopic analysis of fragments of destroyed hollow glass microspheres was used to determine the thickness of their walls. It is revealed that the wall thickness of industrial microspheres can vary significantly even within a single glass microsphere. It is shown that as the diameter of hollow glass microspheres increases, the relative wall thickness decreases, and the degree of their heterogeneity increases. The wall thickness variability leads to a significant decrease in the level of critical pressure, which causes the destruction of microspheres, compared to the calculated one.

Variability in Wall Thickness and Related Structures of Major Dural Sinuses in Posterior Cranial Fossa: A Microscopic Anatomical Study and Clinical Implications.

Regional variability in dural sinus (DS) wall thickness in posterior cranial fossa (PCF) have not been studied in detail yet. To clarify the possible regional variability in DS wall thickness and determine the occurrence and localization of the chordae Willisii (CW) in PCF. Fifty-nine human cadaveric DSs of PCF were investigated. A measurement of the DS walls/dura mater/CW thickness of parafin-embedded/hematoxylin-eosin stained axial sections was performed by using Cell Sens Science Imaging Software (Olympus Corporation, Tokyo, Japan). The osseus wall (OW) was the thickest one in the confluens sinuum (CS) and the thinnest one in the jugular bulb (JB) and sigmoid sinus (P<.05). The biggest differences between individual walls were observed in the JB where the superior wall was almost twice as thick as the OW. At the transverse-sigmoid junction, the thickness of the walls was comparable. In the CS and transverse sinuses, the OW was even thicker than the surrounding dura mater. The occurrence and thickness of the CW increased from the JB towards CS and prevailed on the right side. An overall number of the CW in PCF was comparable to that observed in the superior sagittal sinus. The present study displayed for the first time the regional variability in the DS walls thickness and occurrence of the CW in PCF. Application of these findings may afford greater freedom in exposure of the DSs or neoplasms adhering to the DSs.

Myocardial segmental thickness variability on echocardiography is a highly sensitive and specific marker to distinguish ischemic and non-ischemic dilated cardiomyopathy in new onset heart failure

The aim of this study was to determine non-invasive diagnostic markers by echocardiography that differentiate ischemic dilated (ICM) from non-ischemic dilated cardiomyopathy (NICM) in patients with new onset heart failure. We identified 100 consecutive new heart failure patients with dilated cardiomyopathy (valvular etiology excluded). Clinical risk factors, medication history, serum biomarkers, ECG and echocardiographic variables were compared between the ICM and NICM groups (as confirmed by coronary angiography). Mean age, left ventricular size and ejection fraction were 56 years, 6.1 cm and 26% respectively. A total of 24% had ICM. Patients with ICM were older (65 vs. 53 years; P < 0.001). No significant difference was observed between ICM and NICM among 18 clinical variables, 7 laboratory tests, 6 EKG parameters and 10 of the 13 echocardiographic markers evaluated. Segmental wall thickness variability, regional wall motion abnormality and RV enlargement on echocardiogram (echo) differentiated ICM from NICM. Segmental thickness variability outperformed wall motion abnormality in diagnosing ICM with a sensitivity and specificity of 79.2 and 98.7% versus 62.5 and 84.2% respectively. RV enlargement was not sensitive but 90.6% specific for predicting NICM. Myocardial segmental thickness variability on echo, resulting from thinned infarcted or hibernating myocardium, is a highly sensitive and specific marker to differentiate ICM from NICM in new onset heart failure.

An automated technique for carotid far wall classification using grayscale features and wall thickness variability.

To test a computer-aided diagnostic method for differentiating symptomatic from asymptomatic carotid B-mode ultrasonographic images. Our system (called Atheromatic) automatically computed the intima-media thickness (IMT) of the carotid far wall using AtheroEdge, calculated nonlinear features based on higher order spectra, and used these features and IMT and IMT variability (IMTVpoly ) to associate each image to a feature vector that was then labeled as symptomatic or asymptomatic (Sym/Asym) by a multiclassifiers system. We tested this method on a database of 118 carotid artery images from 37 symptomatic and 22 asymptomatic patients The highest accuracy (99.1%) was obtained by the support vector machine classifier using seven features. These features, relevant to discriminate Sym/Asym, included IMT and IMTVpoly , along with the bispectral entropies of the distal wall image at 77°, 78°, and 79° angles. Classification in Sym/Asym of the far carotid wall is feasible and accurate and could be useful for the early detection of atherosclerosis and to identify patients with higher cardiovascular risk.

Photodynamic inactivation mechanism of Streptococcus mitis sensitized by zinc(II) 2,9,16,23-tetrakis[2-(N,N,N-trimethylamino)ethoxy]phthalocyanine

Photoinactivation of Streptococcus mitis induced by zinc(II) 2,9,16,23-tetrakis[2-(N,N,N-trimethylamino)ethoxy]phthalocyanine (ZnEPc4+) was studied under different experimental condition in order to obtain information about the photodynamic processes and the cellular damage. A 3 log decrease in S. mitis survival was found in cell suspensions (∼2×108 cells/mL) incubated with 2μM ZnEPc4+ and irradiated for 30min with visible light (54J/cm2). Also, S. mitis cells growth was not detected in broth treated with 5μM ZnEPc4+ under continuous irradiation. Studies of photodynamic action mechanism showed that the cells were protected in the presence of azide ion, while the addition of mannitol did not produce a significant effect on the survival. Moreover, the photocytotoxicity was increased in D2O indicating the interference of singlet molecular oxygen. On the other hand, it was found that ZnEPc4+ interacts strongly with calf thymus DNA in solution but photocleavage of DNA was only detected after long irradiation periods. After S. mitis photoinactivation, modifications of genomic DNA were not observed by electrophoresis. In contrast, the transmission electron microscopy showed structural changes in the S. mitis cells, exhibiting mesosome-like structures. After 2h irradiation, the cytoplasm showed segregation patterns and PDI appeared to have effects on the cell wall, including variability in wall thickness. Also, the presence of bubbles was detected on the cell surface by scanning electron microscopy. However, the photodamage to the cell envelope was insufficient to cause the release of intracellular biopolymers. Therefore, modifications in the cytoplasmic biomolecules and alteration in the cell barriers could be mainly involved in S. mitis photoinactivation. It can be concluded that photosensitization by ZnEPc4+ mainly involved a type II photoprocess, while alteration in the cytoplasmatic components and modifications in the cell envelope were the major cause for the photoinactivation of S. mitis.

259 ASYMMETRICAL SEPTAL HYPERTROPHY IS ASSOCIATED WITH MEAN ARTERIAL BLOOD PRESSURE IN HEALTHY ADULTS: DATA FROM HIGH RESOLUTION 3D CARDIAC MRI

Background Left ventricular hypertrophy (LVH) is the result of complex interactions between genes and environmental factors, and an independent risk factor for all-cause mortality. Clinically, it is important to differentiate ‘physiological’ LVH, such as in hypertension, from pathological LVH as found in hypertrophic cardiomyopathy. Standard methods of cardiac phenotyping such as echocardiography or 2D cardiac magnetic resonance (CMR) provide only macroscopic descriptors of LV mass (LVM) and function. These methods are underpowered for population wide study of regional wall thickness variability. Methods and Results 187 healthy multi-ethnic volunteers (105 female, age range 18–72, mean age 40) were recruited into a sub-study of the UK GenScan project. Exclusion criteria included established history of cardiovascular disease, hypertension, diabetes or hypercholesterolemia. Subjects were phenotyped by CMR using a 1.5T Philips Achieva system with a 32 element cardiac phased-array coil. High resolution 3D cine imaging of the LV was obtained with a voxel size of 2x2x4 mm and 20 cardiac phases. Three blood pressure (BP) measurements were taken and averaged (in mmHg): Mean systolic BP 123 (range 90–186), mean diastolic BP 80.4 (range 47–109). The high resolution 3D images were automatically segmented using training data from 10 healthy volunteers in which the myocardium had been manually labelled at end-diastole and end-systole (Figure 1). The 187 3D segmentations were exactly co-registered with each other so that corresponding points within the myocardium could be accurately compared within the cohort. Mean wall thickness was calculated at each point as the distance between the endocardial and epicardial surfaces. Automated measurements were validated against manual readings using standard clinical software (Philips Extended Workspace). LV end-diastolic volumes and LVM measurements were highly correlated (R 2 =.98 and R 2 =0.93 respectively). Mass univariate analysis was performed on the co-registered 3D models with wall thickness as the dependent variable. Pooling data from all the subjects, we plotted wall thickness at each 3D coordinate as a linear function of Mean Arterial Pressures (MAP) with gender and age held constant. The 3D models showed that blood pressure associated LVH begins asymmetrically within the mid-septum and progressively extends towards the base and apex with rising MAP (Figure 2). The lateral wall and apex are relatively spared. Conclusions Whole-heart high-resolution 3D CMR provides new opportunities for quantitative phenotyping of the heart and understanding the genetic and environmental determinants of heart disease. In this study we used these techniques to show the pattern of progressive asymmetrical septal hypertrophy that is associated with increasing blood pressure even within the general population.

Left Atrial Wall Thickness Variability Measured by CT Scans in Patients Undergoing Pulmonary Vein Isolation

Successful catheter ablation of atrial fibrillation (AF) requires the creation of transmural lesions in the left atrium (LA). In addition, cardiac perforation is more likely to occur in areas of thin walls. The LA wall thickness is thus relevant both for procedural efficacy and safety. This study sought to evaluate the regional LA wall thickness in patients with AF. The LA muscular wall thickness (excluding fat) was measured by 64 slice cardiac computed tomography (CT) in 60 patients with persistent AF prior to catheter ablation procedures. Measurements were performed in all patients at 12 distinct LA locations, including 3 at the roof (right, middle left), 3 at the floor (right, middle, left), 4 at the posterior wall (right, middle, middle-superior, left), 1 at the left lateral ridge (LLR), and 1 at the mitral isthmus. There was a large range of LA wall thickness (average thickness 1.89 ± 0.48 mm, range 0.5-3.5 mm). In addition, there were significant regional differences in LA wall thickness. In particular, the LA roof was significantly thicker than the posterior wall and floor (P < 0.001), the LLR was significantly thicker than most regions (P < 0.04), and the mitral isthmus was also significantly thicker than the posterior wall (P < 0.001) and floor (P < 0.001). In patients with persistent AF, there is inter- and intra-patient variability in the thickness of the LA muscular wall. In most patients, however, the roof, mitral isthmus, and the ridge between the pulmonary veins and appendage are thicker compared to the posterior wall and floor.

A Metamodeling Approach for Uncertainty Analysis of Nondeterministic Systems

Modern complex engineering applications are often nondeterministic systems that include sources of uncertainty that cannot be parametrized numerically; this is unparametrizable uncertainty. One example is the uncertainty in the behavior of a mechanical system due to heterogeneous material properties on the microscale (e.g., grain boundary effects on microstructure). Another example is the uncertainty in the performance of a complex topology structure due to random topology imperfections. In this paper, we propose a method for metamodeling these nondeterministic systems for efficient uncertainty analysis in robust design. Generalized linear models for mean responses and heteroscadastic response variances are estimated iteratively in an integrated manner. Estimators that may be used for predicting mean and variance models are introduced. The usefulness of this metamodeling approach is demonstrated with the example of a linear cellular alloy heat exchanger. Applications for these heat exchangers include actively cooled supersonic aircraft skins and engine combustor liners. Linear cellular alloy heat exchangers have unparametrizable uncertainty due to randomly distributed cracks in cell walls, as well as parametrizable uncertainty due to variability in wall thickness and inlet air velocity. Nondeterministic metamodels for estimating total steady state heat transfer rates in linear cellular alloy heat exchangers are developed and the results of using these metamodels are compared with those obtained by the finite element analysis (FEA) models of the linear cellular alloys.

3D Reconstruction and Manufacture of Real Abdominal Aortic Aneurysms: From CT Scan to Silicone Model

Abdominal aortic aneurysm (AAA) can be defined as a permanent and irreversible dilation of the infrarenal aorta. AAAs are often considered to be an aorta with a diameter 1.5 times the normal infrarenal aorta diameter. This paper describes a technique to manufacture realistic silicone AAA models for use with experimental studies. This paper is concerned with the reconstruction and manufacturing process of patient-specific AAAs. 3D reconstruction from computed tomography scan data allows the AAA to be created. Mould sets are then designed for these AAA models utilizing computer aided designcomputer aided manufacture techniques and combined with the injection-moulding method. Silicone rubber forms the basis of the resulting AAA model. Assessment of wall thickness and overall percentage difference from the final silicone model to that of the computer-generated model was performed. In these realistic AAA models, wall thickness was found to vary by an average of 9.21%. The percentage difference in wall thickness recorded can be attributed to the contraction of the casting wax and the expansion of the silicone during model manufacture. This method may be used in conjunction with wall stress studies using the photoelastic method or in fluid dynamic studies using a laser-Doppler anemometry. In conclusion, these patient-specific rubber AAA models can be used in experimental investigations, but should be assessed for wall thickness variability once manufactured.

Injection-Moulded Models of Major and Minor Arteries: The Variability of Model Wall Thickness Owing to Casting Technique

Cardiovascular disease of major and minor arteries is a common cause of death in Western society. The wall mechanics and haemodynamics within the arteries are considered to be important factors in the disease formation process. This paper is concerned with the development of an efficient computer-integrated technique to manufacture idealized and realistic models of diseased major and minor arteries from radiological images and to address the issue of model wall thickness variability. Variations in wall thickness from the original computer models to the final castings are quantified using a CCD camera. The results found that wall thickness variation from the major and minor idealized artery models to design specification were insignificant, up to a maximum of 16 per cent. In realistic models, however, differences were up to 23 per cent in the major arterial models and 58 per cent in the minor arterial models, but the wall thickness variability remained within the limits of previously reported wall thickness results. It is concluded that the described injection moulding procedure yields idealized and realistic castings suitable for use in experimental investigations, with idealized models giving better agreement with design. Wall thickness is variable and should be assessed after the models are manufactured.

Plasma leptin concentration, insulin sensitivity, and 24-hour ambulatory blood pressure and left ventricular geometry

Left ventricular (LV) hypertrophy is an important predictor of cardiovascular morbidity and mortality. Hemodynamic factors, such as 24-h blood pressure (BP) values, are responsible for left ventricular hypertrophy in hypertensives. On the other hand, some metabolic factors have also been suggested to affect LV mass and geometry. In particular, plasma leptin concentrations have been found associated to LV myocardial growth. Because chronic leptin infusion stimulates sympathetic nervous system activity and increases BP levels, the role of 24-h BP values on leptin-related changes in myocardial wall geometry cannot be ruled out. Thus, the aim of our study was to evaluate whether the relationship between plasma leptin levels and LV wall thickness is mediated by 24-h BP values in hypertensive male patients. Thirty-six newly diagnosed hypertensive patients underwent Doppler echocardiographic examination, 24-h ambulatory BP recording, and metabolic (euglycemic hyperinsulinemic glucose clamp and fasting plasma leptin levels) measurements. Left ventricular mass correlated positively only with ambulatory diastolic BP (DBP) values, whereas the indices of myocardial wall growth such as interventricular septum thickness and sum of wall thickness (ie, septal + posterior wall thickness) correlated either with 24 h, daytime, or nighttime DBP, as well as with fasting plasma glucose, fasting plasma leptin, and insulin action after adjustment for age, body mass index (BMI), and waist/hip ratio (WHR). In contrast, plasma leptin concentration did not correlate with clinical and ambulatory BP values. A multiple linear regression analysis allowed to investigate the independent role of main anthropometric and cardiovascular covariates on the sum of wall thickness variability. A model that includes age, BMI, WHR, fasting plasma leptin concentration, plasma Na + concentration, insulin action, and nighttime DBP explained 68% of the sum of wall thickness variability. In such a model, plasma leptin concentration (P < .001), insulin action (P < .029), and nighttime DBP (P < .002) were significantly and independently associated with myocardial wall thickness. In conclusion, our study demonstrates that in hypertensive men fasting plasma leptin levels are determinant of myocardial wall thickness independently of 24-h BP values.

Wave propagation in a viscoelastic medium containing fluid-filled microspheres

Effective medium techniques have been developed by many authors to model the acoustic propagation through layers of visco-elastic materials which contain fluid-filled or elastic cavities. This paper extends such work to the case of materials containing air-filled microspheres whose thin glassy shell separates the interior air from the surrounding polymer. Such composites have been found particularly useful in conditions of high hydrostatic loading where the presence of the reinforcing shells delays the onset of the hole collapse and the consequent degradation in the acoustic performance of the composite. In the present paper, a model is presented which includes the effect of shell wall thickness variability but excludes the depth dependency—the latter will be presented in a sequel. Theoretical predictions are compared with experimentally measured values of transmission loss for both stiff and soft polymer substrates and, in each case, good agreement with experimental data is shown.