Altered aortic arch geometry in patients with type B aortic dissection

OBJECTIVES This study aims to evaluate differences in proximal aorta geometry and identify specific anatomical predictors of type B aortic dissection (TBAD). METHODS We evaluated computed tomographic angiograms of controls (n = 185) and patients with acute TBAD (n = 173). Using propensity score matching, we created 2 groups of 127 patients. 3mensio Vascular software was used to analyse the computed tomographic angiograms and measure the diameter, length, tortuosity index and angulation of the proximal aorta (divided into ascending aorta and aortic arch). Tortuosity index was calculated by dividing the centre lumen line length of the aortic segment by its shortest length. Angulation was measured by the centre lumen line ‘tangent line angle’. Two independent multivariable models identified significant anatomical associations regarding the tortuosity and angulation geometry. RESULTS Aortic diameter and ascending aorta and aortic arch lengths in TBAD increased significantly. The aortic arch tortuosity was significantly higher in the TBAD group (P < 0.001), with no difference regarding the ascending aorta (P = 0.11). Ascending aorta and aortic arch angulation were significantly higher in the TBAD group (P = 0.01, P < 0.001, respectively). Multivariable analyses showed that increased aortic arch tortuosity and angulation were significant predictors of the development of TBAD [odds ratio (OR) 1.91, 95% confidence interval (CI) 1.40–2.59; P < 0.001 and OR 1.08, 95% CI 1.04–1.12; P < 0.001], respectively. CONCLUSIONS In addition to proximal aorta dilation and elongation, we identified increased aortic arch tortuosity and angulation as possible specific predictors of TBAD.

STUDY OF THE SIZE OF THE ANGLE OF THE MANDIBLE

Тhe mandible is a paired bone that develops within the mandibular arch, embedding teeth and forming anarticulation of the jaw with the cranium. Morphological changes are brought about by aging. The gonial angle, orthe angle of mandible, is formed by the line tangent to thelower border of the mandible and the line tangent to the distal border of the ascending ramus and condyle ie the lower jaw angle is formed by the ramus line (RL) and the mandibular line (ML), where RL is the tangent to the posterior border of the mandible and ML is the lower border of the mandible through the gnathion (gn) Withage the masticatory muscles change in function and structure with decreased contractile activity and lower muscle density. The gonial angle can be used as a tool inforensic odontology, but has received less attention. The aim of this study was to evaluate the angle of mandible comparing mandibular bones and OPGs. The study further intends to evaluate the variation in age using the gonialangle as a parameter. A total of 50 mandibles and 50 OPGs were included in the study. The study materials were obtained from theDepartment of Anatomy and the Department of Radiology of Simple methodology was employed for obtaining data. The gonial angle in mandibular bones was measured as the angle formed by the base of the mandible and the posterior border of the ramus by the scale of protractor, which isplaced over the angle of mandible in such a way that the base of the protractor coincides with the base of the mandible. The angle was recorded in degrees.The gonial angle in OPG was measured by a line drawn tangential to the lower border of the mandible and the linedrawn tangential to the posterior border of the ramus and the condyle. The intersection of these two lines formed the gonial angle which was measured using a protractor in the same way. The angle was recorded in degrees.All the readings were recorded and the mean value was calculated.The present study shows various values of gonial angle inOPG and mandibular bones. No significant difference was observed between these two. On comparison of gonial angle the mandibular bone showed slightly greater value than OPG The mean value of the gonial angles were found to beslightly more in mandibular bones and were lesser in OPG.There seems to be differencein the gonial angle with different age groups but not significant. Both mandibular bones and OPGs showed almost similar readings. Thusgonial angle serves as an adjuvant and additional forensic parameter which guides for age group assessment, subjectto odontological status.

PERFORMANCE OF A TANGENTIALLY FIRED BOILER IN A THERMAL POWER PLANT

The most effective method for producing intense turbulence is by the impingement of one flame on another. This action is secured through the use of burners located in each of the four corners of the furnace. The burner nozzles are so directed that the streams of coal and air are projected along a line tangent to a small circle, lying in a horizontal plane, at the centre of the furnace. A scrubbing action is present which assures contact between the combustible and oxygen, thus promoting rapid combustion and reducing carbon loss. The experimental results of this study can be summarized as the use of tangentially fired boiler which increase splendid air-fuel mixture and pulverized coal is entrained in Primary Air (PA), and in-addition to that the Secondary Air (SA) is also projected towards the mill, finally a rotating “FIRE BALL” is formed. The present work analysis is carried out on Tangentially Fired Boiler by considering heat input through four burners. The heat output is determined by considering various losses from the boiler that is loss due to dry gas, loss due to moisture, loss due to H2 for combustion, heat loss due to combustile and refuse and losses due to radiation etc. In addition heat absorbed by economizer, boilers, superheater and reheater are studied, thus finally the net heat absorbed and thermal efficiency of tangentially fired boiler are determined. Graphs are drawn to evaluate the various effects of heat input on output parameters in the boiler. Sankey diagrams are drawn to show the performance in the boiler. The values calculated are put and shown as tables in Appendix.

The Contribution of Different Femur Segments to Overall Femoral Torsion

Background: Femoral torsion is a critical parameter in hip and knee disorders. The unproven assumption is that the femoral neck exclusively contributes to the overall torsion of the femur. Purpose/Hypothesis: The aim of this study was to measure femoral torsion at different levels in patients with abnormally high or low femoral torsion and to compare the results with healthy volunteers. Our hypothesis was that the pattern of torsion distribution among the different femoral levels varies between patients with abnormal torsion and healthy volunteers. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Magnetic resonance images of patients with a history of patellar instability and torsion of the femur ≥25° (11 patients, 16 femurs) and ≤0° (14 patients, 22 femurs) were analyzed. Our controls were 30 healthy volunteers (60 femurs). To assess femoral torsion, 4 lines were drawn: a first line through the center of the femoral head and neck, a second line through the center of the femur at the top of the lesser trochanter, a third line tangent to the posterior aspect of the distal femur just above the attachment of the gastrocnemius, and a fourth line tangent to the posterior condyles. Three investigators performed the measurements; 1 performed the measurements twice. Results: All femur segments showed significantly different torsion among the high-torsion, low-torsion, and control groups. Regarding the pattern of torsion distribution, on average, all levels contributed to the torsion. The ratio between the average neck and shaft torsion shifted toward a higher value in the high-torsion group, mostly because of a lack of external torsion in the shaft, and toward a lower value in the low-torsion group, owing to both a lack of internal torsion of the neck and increased external torsion in the shaft. Conclusion: We established a difference between neck, mid, and distal femoral torsion with reproducible measurements. Our data suggest that all 3 levels of the femur contribute to the total femoral torsion, with a different pattern among patients with high torsion and patellar instability.

Incorporating Fixed-Point and -Line Constraints and Tolerance Based Synthesis in 4MDS

This paper presents implementation of fixed-pivots, ground-link line, and tolerance based motion synthesis in the 4MDS (Four-Bar Motion Design System). This is a continuation of the first work reported on 4MDS, which provides an interactive, graphical, and geometric constraint based mechanism design system for the exact- and approximate-motion synthesis problems. Theoretical foundation of the 4MDS is laid over a kinematic mapping based unified formulation of the geometric constraints (circle, fixed-line, line-tangent-to-a-circle) associated with the mechanical dyads (RR, PR, and RP) of a planar four-bar mechanism. An efficient algorithm extracts the geometric constraints of a given motion task and determines the best dyad types as well as their dimensions that best fit to the motion. Often, Mechanism designers need to impose additional geometric constraints, such as specification of location of fixed pivots or ground-link line. If synthesized mechanism suffers from branch, circuit, or order defect, they may also desire rectified solutions by allowing a tolerance to certain or all task positions. Such functions are crucial to a practitioner and much needed during the conceptual design stage of machine design process.

Tangent Lines without Derivatives for Quadratic and Cubic Equations

The equation of the line tangent to the parabola at its y-intercept is extended to give a convenient method of finding tangent lines at any point on the graph of a quadratic or a cubic equation.

Chemical Kinetics

Chemical kinetics is the aspect of chemistry that deals with the speed or rate of chemical reactions and the mechanisms by which they occur. The rate of a chemical reaction is a measure of how fast the reaction occurs, and it is defined as the change in the amount or concentration of a reactant or product per unit time. The mechanism of a reaction is the series of steps or processes through which it occurs. Most experimental techniques for determining reaction rates involve measuring of the rate of disappearance of a reactant, or the rate of appearance of a product. For a reaction in which the reactant Y is converted to some products: Rate = Concentration of Y at time t2 −Concentration of Y at time t1/t2 −t1 Rate = Δ [Y]/ Δt where [Y] indicates the molar concentration of the reactant of interest, and Δ refers to a change in the given amount. Rate for a reactant, by this definition, is a negative number. For a product, it is positive. The value of the rate at a particular time is known as the instantaneous rate and will be different from the average rate. Its value can be obtained from the plot of concentration (mol/L) vs. time (s) as the slope of a line tangent to the curve at a given point. Consider the following kinetic data for the decomposition of N2O5 to gaseous NO2 and O2 at 40°C (see table 16-3). A plot of [N2O5] vs. time is shown in figure 16-2. From this curve, the instantaneous rate of reaction at any time t can be obtained from the slope of the tangent to the curve. This corresponds to the value of Δ [N2O5]/ Δt for the tangent at a given instant. The instantaneous rate at the beginning of the reaction (t =0) is known as the initial rate.

Turn-location parameters for a continuous landing model. I. Road tangents

Timber harvesting operations often employ continuous landings on or along truck road right-of-ways. During the harvest-unit design process forest engineers describe the spatial distribution of turns with respect to a proposed landing by distribution parameters such as average yarding distance and average yarding slope. In this two-part paper these parameters and others are derived for a continuous landing model. In this first paper, parameters are derived and applied to a continuous landing located on or along a road center-line tangent. In the second paper, a similar development is applied to a continuous landing located on or along the circular curve of a road.