Repeated Ct-based Hounsfield Unit Measurements as a Proxy Measure of Intercorporal Bone Graft Remodelling Towards Spinal Fusion; a Feasibility Study.

Background: There is a lack of knowledge about the biological process of intercorporal bone graft remodelling towards successful lumbar spine fusion with bridging vital bone between two adjacent vertebrae. Hounsfield Units (HU) highly correlate with Bone Mineral Density (BMD) and changes in HU may be valuable as proxy measure to monitor ongoing fusion. The aims of this study were to explore the feasibility to quantify BMD changes in the intercorporal bone graft after spinal fusion on consecutive CT-scans, and to explore whether trends in the individual changes in HU over time may serve as a proxy measure for successful fusion or non-fusion.Methods: A retrospective case series was conducted using available one-year and two-year CT-data from patients after posterior lumbar interbody fusion surgery. First, a standardized measuring procedure was developed, incorporating internal phantomless calibration, to establish the HU values of the grafted region of interest using consecutive CT-slices. Subsequently, changes in the participants’ bone graft HU over time between their first and second year after surgery were explored.Results: Between one and two years after surgery, seven out of nine (78%) participants showed an increase in their bone grafts’ HU, ranging from 3% to 41%. In two participants HU-values decreased 14% and 32%, respectively. The intraobserver reliability of the HU measuring procedure was excellent (ICC 0.93 (95% confidence interval 0.91 to 0.95)).Conclusion: The majority (78%) of participants in the current study showed increases in their bone graft HU, which suggests ongoing bone graft remodelling towards lumbar fusion. This result corresponds with the established percentages of achieved rigid bony fusion after lumbar spinal fusion surgery reported in the literature. Thus, prospective follow-up of CT-based HU measurements may have potential as diagnostic measure to monitor bone graft remodelling in time and trends may predict successful fusion or non-fusion. The measurement procedure developed in this study, using internal phantomless calibration, showed excellent intraobserver reliability and merits further study in larger patient numbers.

The Influence of Bleeding of Cement Suspensions on Their Rheological Properties

Flowable concretes tend to segregate. The risk of segregation is particularly high when the concrete is vibrated during the compaction process. A well-known segregation phenomenon is the so-called “bleeding”. This is a rise of water to the surface of the freshly poured concrete due to the difference in density between the mixing water and the concrete’s denser solid components (aggregates, cement and additives). This type of segregation occurs particularly within the paste. The focus of this paper is, therefore, on the sedimentation behavior at the microscale of concrete and especially on the influence of this process on rheological properties of the cement paste. In addition to common bleeding tests of cement suspensions using standing cylinders, rheometric measurements were performed on the suspensions during the bleeding process. A measuring procedure was developed for the rheometric measurements of the sedimenting cement suspensions. The rheological properties of the investigated cement suspensions were determined at four specific measuring times and at four specific measuring heights (i.e., positions) each. With this method it could be shown that the cement suspensions are not homogeneous over their height and that bleeding has a great influence on the rheological properties of cement suspension.

The evaluation of the influence of heat-exchange gas on the uncertainty of specific heat capacity measurement

The influence of the gas presence in calorimeter on the result of measuring of thermal capacity is considered. The feature of the case is the unavoidable change of the gas mass during measuring procedure. The correct expression for the value of amendment is obtained, and uncertainty is evaluated for the calorimeter КА-С4 that serves as the standard of the unit of heat capacity.

Calibration of hydrophones taking into account the conditions of their use

A measuring facility for reproducing a unit of sound pressure at frequencies of 1–500 Hz in the temperature range of 0.5–35 °С with excessive static pressures up to 60 MPa is described. The measuring facility was created in order to expand the functionality of the State primary standard GET 55-2017. The expediency of simulated ocean conditions in GET 55-2017 under hydrophone calibration, the principles of operation and the metrological characteristics of the measuring facility are discussed. Features of the measuring procedure for calibrating the hydrophone are given.

Uncertainty in hourly mean data from classical magnetometers

Hourly mean values obtained from analog magnetometers in what can be considered the “classical” period constitute the largest quantity of data we have on the evolution of the Earth’s magnetic field. They are used for a wide variety of applications such as estimating long-term solar–terrestrial interactions, the production of magnetic indices, or studying geomagnetic secular variation originated in the Earth’s core. However, these data do not have an associated uncertainty that would allow us to quantify the final uncertainty of the results of these models. Hence, our study tries to assess the degree of uncertainty that these data actually have. In this paper, using Ebro Observatory classical instrumentation, we work out these uncertainties by estimating the particular uncertainties of each significant variable involved in the measuring procedure. Although the study is implemented for Ebro, the method can be applied to any other observatory. We found that, in general, uncertainties vary from one magnetic component to another, depending on the nature of the instruments that were used. In each component, we identified the weakest points where the biggest part of the error resides. With our results we can state that total uncertainties ranged from 1 to 4 nT.

Capacity Side of the Point Evaluation Utilizing Programming Item Estimation

In programming industry FPA is utilized for assessing the highlights of programming ventures. The highlights are cost, span, exertion and so forth. The product achievement elements are quicker, better and less expensive. In programming improvement process, the achievement depends on undertaking arranging and estimation. Estimation is the determined guess of the aftereffect of explicit issue. It lead significant job is task arranging. One of the real estimation and measuring procedure is FPA. It is useful for evaluating the highlights of created ventures. In any case, it isn't precise for evaluating the highlights of activities to be created. So here the idea of similarity estimation and PERT are included with FPA and present another method EFPA. It can give progressively precise appraisals. It is valuable for the product business for assessing the highlights of programming