Direct Volumetric Measurements Research Articles

Does mini-implant-supported rapid maxillary expansion cause less root resorption than traditional approaches? A micro-computed tomography study.

ObjectiveThis study aimed to evaluate the volume, amount, and localization of root resorption in the maxillary first premolars using micro-computed tomography (micro-CT) after expansion with four different rapid maxillary expansion (RME) appliances.MethodsIn total, 20 patients who required RME and extraction of the maxillary first premolars were recruited for this study. The patients were divided into four groups according to the appliance used mini-implant-supported hybrid RME appliance, hyrax RME appliance, acrylic-bonded RME appliance, and full-coverage RME appliance. The same activation protocol (one activation daily) was implemented in all groups. For each group, the left and right maxillary first premolars were scanned using micro-CT, and each root were divided into six regions. Resorption craters in the six regions were analyzed using special CTAn software for direct volumetric measurements. Data were statistically analyzed using Kruskal–Wallis one-way analysis of variance and Mann–Whitney U test with Bonferroni adjustment.ResultsThe hybrid expansion appliance resulted in the lowest volume of root resorption and the smallest number of craters (p < 0.001). In terms of overall root resorption, no significant difference was found among the other groups (p > 0.05). Resorption was greater on the buccal surface than on the lingual surface in all groups except the hybrid appliance group (p < 0.05).ConclusionsThe findings of this study suggest that all expansion appliances cause root resorption, with resorption craters generally concentrated on the buccal surface. However, the mini-implant-supported hybrid RME appliance causes lesser root resorption than do other conventional appliances.

Does the rhythm and appliance type of rapid maxillary expansion have an effect on root resorption?

To evaluate the volume, amount, and localization of root resorption in the upper first premolars by micro-computed tomography (micro-CT) after three different rapid maxillary expansion appliances and two different activation rhythms. The patients were divided into three groups; Hyrax, acrylic cap splint (ACS), and full coverage acrylic bonded (FCAB) appliances. Each group was then divided into the following two subgroups: rapid maxillary expansion (RME) and semirapid maxillary expansion (SRME). After expansion was completed, the appliances were stabilized for 12 weeks during the retention period. For each group, 10 premolars (for a total of 60 premolars) were scanned with the micro-CT (SkyScan). The reconstructed 3D images of each root sample were divided into six regions. The resorption craters on these six different root surfaces were analyzed by special CTAn (SkyScan) software for direct volumetric measurements. Kruskal-Wallis one-way analysis of variance and Mann-Whitney U tests were used for statistical analysis. The total volume of root resorption was less with FCAB than with ACS and Hyrax (P < .001). In all groups, a greater volume of resorption was found on the buccal surface than on the lingual surface (P < .001). No significant differences were found between the RME and SRME groups (P > .05). All expansion appliances caused root resorption in the upper first premolar teeth, but FCAB may be safer in terms of root resorption. The resorption craters were generally concentrated on the buccal surface. There was no effect of activation rhythm on root resorption.

Computed Tomography-Based Imaging of Voxel-Wise Lesion Water Uptake in Ischemic Brain: Relationship Between Density and Direct Volumetry.

Net water uptake per volume of brain tissue may be calculated by computed tomography (CT) density, and this imaging biomarker has recently been investigated as a predictor of lesion age in acute stroke. However, the hypothesis that measurements of CT density may be used to quantify net water uptake per volume of infarct lesion has not been validated by direct volumetric measurements so far. The purpose of this study was to (1) develop a theoretical relationship between CT density reduction and net water uptake per volume of ischemic lesions and (2) confirm this relationship by quantitative in vitro and in vivo CT image analysis using direct volumetric measurements. We developed a theoretical rationale for a linear relationship between net water uptake per volume of ischemic lesions and CT attenuation. The derived relationship between water uptake and CT density was tested in vitro in a set of increasingly diluted iodine solutions with successive CT measurements. Furthermore, the consistency of this relationship was evaluated using human in vivo CT images in a retrospective multicentric cohort. In 50 edematous infarct lesions, net water uptake was determined by direct measurement of the volumetric difference between the ischemic and normal hemisphere and was correlated with net water uptake calculated by ischemic density measurements. With regard to in vitro data, water uptake by density measurement was equivalent to direct volumetric measurement (r = 0.99, P < 0.0001; mean ± SD difference, -0.29% ± 0.39%, not different from 0, P < 0.0001). In the study cohort, the mean ± SD uptake of water within infarct measured by volumetry was 44.7 ± 26.8 mL and the mean percent water uptake per lesion volume was 22.7% ± 7.4%. This was equivalent to percent water uptake obtained from density measurements: 21.4% ± 6.4%. The mean difference between percent water uptake by direct volumetry and percent water uptake by CT density was -1.79% ± 3.40%, which was not significantly different from 0 (P < 0.0001). Volume of water uptake in infarct lesions can be calculated quantitatively by relative CT density measurements. Voxel-wise imaging of water uptake depicts lesion pathophysiology and could serve as a quantitative imaging biomarker of acute infarct lesions.

Body composition techniques.

Body composition is known to be associated with several diseases, such as cardiovascular disease, diabetes, cancers, osteoporosis and osteoarthritis. Body composition measurements are useful in assessing the effectiveness of nutritional interventions and monitoring the changes associated with growth and disease conditions. Changes in body composition occur when there is a mismatch between nutrient intake and requirement. Altered body composition is observed in conditions such as wasting and stunting when the nutritional intake may be inadequate. Overnutrition on the other hand leads to obesity. Many techniques are available for body composition assessment, which range from simple indirect measures to more sophisticated direct volumetric measurements. Some of the methods that are used today include anthropometry, tracer dilution, densitometry, dual-energy X-ray absorptiometry, air displacement plethysmography and bioelectrical impedance analysis. The methods vary in their precision and accuracy. Imaging techniques such as nuclear magnetic resonance imaging and computed tomography have become powerful tools due to their ability of visualizing and quantifying tissues, organs, or constituents such as muscle and adipose tissue. However, these methods are still considered to be research tools due to their cost and complexity of use. This review was aimed to describe the commonly used methods for body composition analysis and provide a brief introduction on the latest techniques available.

Thermal volumetric effects under axes cycling using an invar R-test device and reference length

Thermal errors of machine tools are in part caused by the variation of ambient temperature as well as the heat internally generated by the machine. These deformations are a major source of quasi-static machining errors and are thought to be related to temperatures and temperature gradients within the machine structure. This article presents a study of the thermal volumetric behavior of a five-axis machine tool. The study uses direct volumetric error measurements within the machine work volume for specific combinations of five-axis commands. Thermally induced volumetric distortion errors are studied in relation to a specifically designed machine activity sequence during which the power at each of the five-axis motors and the spindle are measured. The experimental measurement setup consisting of a thermally stable volumetric error sensor and a reference scale bar is presented. The study allows quantifying the effect of every axis’ activity on the Cartesian components of the volumetric distortion. Rotary axes are found to be the major contributors to the tested machine's thermal errors. Thermal coupling is observed whereby the activity of a rotary axis strongly affects a neighboring linear axis.

A Novel Method to Estimate the Volume of Bone Defects Using Cone-Beam Computed Tomography: An In Vitro Study

IntroductionThe routine use of high-resolution images derived from 3-dimensional cone-beam computed tomography (CBCT) datasets enables the linear measurement of lesions in the maxillary and mandibular bones on 3 planes of space. Measurements on different planes would make it possible to obtain real volumetric assessments. In this study, we tested, in vitro, the accuracy and reliability of new dedicated software developed for volumetric lesion assessment in clinical endodontics. MethodsTwenty-seven bone defects were created around the apices of 8 teeth in 1 young bovine mandible to simulate periapical lesions of different sizes and shapes. The volume of each defect was determined by taking an impression of the defect using a silicone material. The samples were scanned using an Accuitomo 170 CBCT (J. Morita Mfg Co, Kyoto, Japan), and the data were uploaded into a newly developed dedicated software tool. Two endodontists acted as independent and calibrated observers. They analyzed each bone defect for volume. The difference between the direct volumetric measurements and the measurements obtained with the CBCT images was statistically assessed using a lack-of-fit test. A correlation study was undertaken using the Pearson product-moment correlation coefficient. Intra- and interobserver agreement was also evaluated. ResultsThe results showed a good fit and strong correlation between both volume measurements (ρ > 0.9) with excellent inter- and intraobserver agreement. ConclusionsUsing this software, CBCT proved to be a reliable method in vitro for the estimation of endodontic lesion volumes in bovine jaws. Therefore, it may constitute a new, validated technique for the accurate evaluation and follow-up of apical periodontitis.

Direct volumetric flow cytometric quantitation of CD34+ stem and progenitor cells

In this study, we compared a classic single-platform (SP) method applying beads for enumeration of CD45+ or CD34+ cells with a new device allowing direct volumetric measurements of stem and progenitor cells. Following apheresis and cyropreservation, the precise enumeration of CD34+ cells as key parameter of graft quality is mandatory for the clinical course after transplantation. Currently, flow cytometry with SP technique represents the 'gold standard' for such determinations. Fresh samples, 14 from mobilised peripheral blood (PB), 9 from apheresis products (AP) and 13 samples from frozen-thawed (FT) haematopoietic progenitor cell grafts, were analysed for CD34+ cells, CD45+ cells, and in frozen-thawed samples for viability by a bead-based flow cytometric method and in parallel by a direct, volumetric flow cytometric method. Comparison of CD34+ analyses revealed a significant correlation (P < 0·01) for each material between both techniques with r = 0·95 (PB), r = 0·933 (AP) and r = 0·929 (FT). Also, for analysis of CD45+ cells µL(-1) , the measured numbers evaluated with the different techniques did not significantly differ for all three materials analysed. In frozen-thawed samples, the analysis of viability was comparable for both techniques. The results of this study demonstrate that a direct volumetric analysis of CD34+ cells µL(-1) or CD45+ cells µL(-1) is feasible. This technique represents a simple and economical approach for standardisation of progenitor and stem cell analyses.

Physical properties of root cementum: Part 18. The extent of root resorption after the application of light and heavy controlled rotational orthodontic forces for 4 weeks: A microcomputed tomography study

The aim of this prospective randomized clinical trial was to quantitatively measure and compare the locations, dimensions, and volume of root resorption craters in human premolars after the application of controlled light and heavy rotational orthodontic forces over a 28-day (4-week) period. Fifteen patients requiring bilateral extraction of maxillary first premolars as part of their orthodontic treatment were recruited for this study. Each patient received a heavy (225 g) rotational force on 1 premolar and a light (25 g) rotational force on the contralateral premolar. Orthodontic rotational forces were applied over 28 days with buccal and palatal cantilever springs; 0.016-inch beta-titanium molybdenum alloys were used to apply the light force and 0.018-inch stainless steel was used for the heavy force. After the 28-day experimental period, the upper first premolars were extracted under stringent protocols to prevent root surface damage. The samples were then scanned using a microcomputed tomography (micro-CT) scan x-ray system (SkyScan 1072, Skyscan, Aartselaar, Belgium), and analyzed using convex hull algorithm (CHULL2D; University of Sydney, Sydney, Australia) software to obtain direct volumetric measurements. The mean volume of resorption craters was 0.42 in the light force group and 0.51 in the heavy force group (P = 0.013). When separated at the root level, the difference in volume of root resorption craters between the 2 groups was significantly different only at the midlevel (P = 0.001). Root resorption craters were consistently detected at the boundaries between the buccal and distal surfaces and the mesial and lingual surfaces. The result supports our hypothesis that positive areas develop significantly more root resorption craters at all 3 levels, as compared with minimal areas (paired t test <0.001). Heavy rotational forces caused more root resorption than light rotational forces and compression areas (buccal-distal and lingual-mesial surfaces in this study) showed significantly higher root resorption than other areas at all levels of the root.

Structure of an exploding laser-produced plasma

Currents and instabilities associated with an expanding dense plasma embedded in a magnetized background plasma are investigated by direct volumetric probe measurements of the magnetic field and floating potential. A diamagnetic cavity is formed and found to collapse rapidly compared to the expected magnetic diffusion time. The three-dimensional current density within the expanding plasma includes currents along the background magnetic field, in addition to the diamagnetic current. Correlation measurements reveal that flutelike structures at the plasma surface translate with the expanding plasma across the magnetic field and extend into the current system that sustains the diamagnetic cavity, possibly contributing to its collapse.

Comment on “Brillouin scattering studies of liquid argon at high temperatures and high pressures” [J. Chem. Phys. 129, 154503 (2008)

In Ref. 1, the authors report on Brillouin scattering measurements on argon at high pressure P and temperature T conditions from which they obtain experimental data for the sound velocity and refractive index of the fluid phase along several isotherms up to 503 K and respective melting pressures. Starting from the refractive index data, they derive the density of fluid argon along the studied isotherms using the Lorentz–Lorenz relation, under the assumption that the electronic polarizability of argon does not vary with P-T conditions. Applying the same reasoning to the data obtained at the solid-fluid coexistence, they obtain values for the density of the fluid and solid phases at coexistence, from which they derive the volume jump Vm at melting or melting volume . This results in a highly unusual observation, that is, the increase in Vm with temperature along the melting line. In this comment I show that this finding is neither supported by available experimental data nor theoretical calculations, and that this is due to an erroneous determination of the fluid densities. Because it is an inert, weakly interacting system with a simple closed-shell electronic configuration, argon has longplayed the role of reference system in condensed-matter physics. In particular, its thermodynamic properties such as P-V-T equation of state EOS and melting curve have been often used as benchmark data for testing various theories. In parallel, a large number of experimental studies have been devoted to the accurate determination of thermodynamic data, which cover a large P-T range see, for example, Ref. 2 for a good number of references for the fluid phase and melting curve . Figure 1 shows the available literature data for the melting volume, obtained by direct volumetric measurements, and compare them to the values of Ref. 1. It is clear that all previous data sets show a regular decrease in Vm with Tm or Pm . In addition to experimental data, which are limited to 320 K, I have plotted the theoretical calculations of Zha et al. using the exponential-6 Buckingham pair potential fitted to shock and static high-pressure data. This potential is an “effective” pair potential as it includes the contribution from many-body interactions averaged over one pair. The calculations agree very well with experimental data, both for the melting curve and volume behaviors, and extend up to 3000 K–53 GPa for the sake of clarity, the T range of Fig. 1 was limited to 600 K . The solid line in Fig. 1 corresponds to the empirical law proposed by Cheng et al., who showed that the experimental data were very well reproduced by the form

Editor's Summary and Q&A: Physical properties of root cementum: Part 14. The amount of root resorption after force application for 12 weeks on maxillary and mandibular premolars: A microcomputed-tomography study

<h3>Introduction</h3> Orthodontic force magnitude is a primary factor in root resorption. Quantitative studies of root resorption after force application for 4 and 8 weeks have been conducted. In this study, we investigated the root surface topography and the amount of root resorption after the application of controlled light and heavy forces in a buccal direction for 12 weeks. In addition, the amounts of root resorption when controlled light and heavy forces were applied to the maxillary and mandibular first premolars were quantified. <h3>Methods</h3> Forty maxillary and mandibular first premolars were collected from 10 orthodontic patients (age range, 12.7-18.2 years; mean, 14.3 years). A light buccally directed orthodontic force of 25 g was applied to the experimental tooth on 1 side, and a heavy orthodontic force of 225 g was applied on the contralateral premolar. After 12 weeks of force application, the experimental teeth were extracted and scanned with the microcomputed tomography x-ray system. Resorption craters were analyzed with specially designed software for direct volumetric measurements. The tooth movements produced by light and heavy forces were also measured. <h3>Results</h3> There was individual variation in all comparisons. The light force produced significantly less root resorption than did the heavy force. The maxillary first premolars were more likely to suffer from orthodontically induced inflammatory root resorption than the mandibular first premolars (<i>P</i> = 0.036). There was a significant difference between buccal and lingual surfaces (<i>P</i> = 0.003), with greater root resorption on the buccal surface. The distribution pattern of the resorption cavities was greatest in the buccal-cervical, buccal-middle, lingual-middle, and lingual-apical areas in both the light-force and heavy-force groups, corresponding with the pressure zones of tipping movement. The mean amount of tooth movement in the heavy-force group was almost twice as much as in the light-force group. <h3>Conclusions</h3> The volume of root resorption craters induced by buccally directed forces for 12 weeks on the maxillary and mandibular first premolars was directly proportional to the magnitude of the force. The maxillary premolars seemed to be more susceptible to orthodontic root resorption than did the mandibular premolars.

Physical properties of root cementum: Part 14. The amount of root resorption after force application for 12 weeks on maxillary and mandibular premolars: A microcomputed-tomography study

Orthodontic force magnitude is a primary factor in root resorption. Quantitative studies of root resorption after force application for 4 and 8 weeks have been conducted. In this study, we investigated the root surface topography and the amount of root resorption after the application of controlled light and heavy forces in a buccal direction for 12 weeks. In addition, the amounts of root resorption when controlled light and heavy forces were applied to the maxillary and mandibular first premolars were quantified. Forty maxillary and mandibular first premolars were collected from 10 orthodontic patients (age range, 12.7-18.2 years; mean, 14.3 years). A light buccally directed orthodontic force of 25 g was applied to the experimental tooth on 1 side, and a heavy orthodontic force of 225 g was applied on the contralateral premolar. After 12 weeks of force application, the experimental teeth were extracted and scanned with the microcomputed tomography x-ray system. Resorption craters were analyzed with specially designed software for direct volumetric measurements. The tooth movements produced by light and heavy forces were also measured. There was individual variation in all comparisons. The light force produced significantly less root resorption than did the heavy force. The maxillary first premolars were more likely to suffer from orthodontically induced inflammatory root resorption than the mandibular first premolars (P = 0.036). There was a significant difference between buccal and lingual surfaces (P = 0.003), with greater root resorption on the buccal surface. The distribution pattern of the resorption cavities was greatest in the buccal-cervical, buccal-middle, lingual-middle, and lingual-apical areas in both the light-force and heavy-force groups, corresponding with the pressure zones of tipping movement. The mean amount of tooth movement in the heavy-force group was almost twice as much as in the light-force group. The volume of root resorption craters induced by buccally directed forces for 12 weeks on the maxillary and mandibular first premolars was directly proportional to the magnitude of the force. The maxillary premolars seemed to be more susceptible to orthodontic root resorption than did the mandibular premolars.

Editor's Summary and Q&A: Physical properties of root cementum: Part 11. Continuous vs intermittent controlled orthodontic forces on root resorption. A microcomputed-tomography study

Introduction There is still ambiguity about whether continuous or intermittent orthodontic forces produce more root resorption. This prospective randomized clinical trial was designed to compare root resorption with these 2 force application patterns. Methods The sample consisted of 16 maxillary first premolars from 8 patients who required bilateral extractions as part of their orthodontic treatment. In each subject, a fixed experimental appliance was placed on the maxillary teeth on each side, allowing a buccally directed force. The force was generated by a segmental wire of β-titanium-molybdenum alloy. The first premolar on 1 side received a buccally directed continuous force, and the contralateral premolar received intermittent force. The initial force magnitude for both sides was 225 cN. After 14 days of initial continuous force, the intermittent force application was obtained with subsequently repeated periods until the end of the eighth week of a 3-day rest period followed by a 4-day force application period. Force levels were set to 225 cN at each patient visit. After the experimental period of 8 weeks, the teeth were extracted under a strict protocol to prevent root surface damage and analyzed with a microcomputed-tomography scan system, and specially designed software was used for direct volumetric measurements. Results Intermittent force produced less root resorption than continuous force (P Conclusions The application of intermittent orthodontic forces of 225 cN for 8 weeks (14 days of force application, 3 days of rest, then 4 days of force application repeated for 6 weeks) caused less root resorption than continuous forces of 225 cN for 8 weeks. Although it might not be clinically practical, compared with continuous forces, intermittent forces might be a safer method to prevent significant root resorption. This regimen, however, could compromise the efficiency of tooth movement.

Improving reservoir volumetric estimations in petroleum resource assessment using discovery process models

The reservoir volumetric approach represents a widely accepted, but flawed method of petroleum play resource calculation. In this paper, we propose a combination of techniques that can improve the applicability and quality of the resource estimation. These techniques include: 1) the use of the Multivariate Discovery Process model (MDP) to derive unbiased distribution parameters of reservoir volumetric variables and to reveal correlations among the variables; 2) the use of the Geo-anchored method to estimate simultaneously the number of oil and gas pools in the same play; and 3) the cross-validation of assessment results from different methods. These techniques are illustrated by using an example of crude oil and natural gas resource assessment of the Sverdrup Basin, Canadian Archipelago. The example shows that when direct volumetric measurements of the untested prospects are not available, the MDP model can help derive unbiased estimates of the distribution parameters by using information from the discovered oil and gas accumulations. It also shows that an estimation of the number of oil and gas accumulations and associated size ranges from a discovery process model can provide an alternative and efficient approach when inadequate geological data hinder the estimation. Cross-examination of assessment results derived using different methods allows one to focus on and analyze the causes for the major differences, thus providing a more reliable assessment outcome.

Real-Time 3-Dimensional Echocardiography

One of the most significant developments of the last decade in ultrasound imaging of the heart was the evolution of 3-dimensional (3D) imaging from slow and labor-intense offline reconstruction to real-time volumetric imaging. This imaging modality provides valuable clinical information that empowers echocardiographers with new levels of confidence in the diagnosis of heart disease. We have previously described the technological milestones in the development of real-time 3D echocardiographic (RT3DE) imaging and its major advantages over conventional 2-dimensional echocardiography (2DE) and reviewed the published literature that supported the use of this new methodology in clinical practice.1 Since 2006, the growing availability of RT3DE technology, its ease of use, and its multiple attractive features have sparked significant interest in the research community, resulting in a large number of publications, most of which have endorsed RT3DE imaging for clinical use by demonstrating its unique capabilities in different scenarios. In parallel, the clinical acceptance of this new tool has broadened significantly. The most recent clinically significant addition is matrix-array transesophageal echocardiography (TEE), which provides images of unprecedented quality that aid surgeons and interventional cardiologists in planning and guiding procedures and evaluating their outcomes. The purpose of the present article is to review the most recent RT3DE literature and provide readers with an update on the latest developments and the current status of this noninvasive imaging tool. Because different potential applications of RT3DE imaging have been explored to various extents, they are described here separately, and each is discussed with an emphasis on the scientifically established facts, along with the known stumbling blocks and difficulties. A firmly established advantage of 3D imaging over cross-sectional slices of the heart is the improvement in the accuracy of the evaluation of left ventricular (LV) volumes and ejection fraction (EF) by eliminating the need for geometric modeling, which …

Effect of Hydraulic Head and Slope on Water Distribution Uniformity of a Low-Cost Drip Irrigation System

Assessment of the effect of topography and operating heads on the water distribution uniformity in drip irrigation systems is important in irrigation water management and could serve as the basis for optimizing water use efficiency and crop productivity. This study was carried out to evaluate the effect of hydraulic head and slope on the water distribution uniformity of a low-cost drip irrigation system developed by the International Development Enterprises (IDE), a non-profit organization dedicated to ending poverty in the developing world. The drip system was tested in the laboratory for water distribution uniformity under varying system heads and slope conditions. A drum reservoir served as water supply for the IDE drip system. A sub-main of 10 m with adjustable slope and lateral-sub holder of 10 m were fabricated to enable slope variations during laboratory experiments. The drip system was operated at pre-specified operating heads of 1.0, 2.0, and 3.0 m for sub-main slopes of 0%, 10%, 20%, 30%, 40%, and 50% and 0% slope for the laterals. The discharge in each emitter was monitored for each chosen slope through direct volumetric measurements. The water distribution uniformity was then evaluated using the Christiansen's method and Merriam and Keller's method. Mathematical relationships were developed to characterize the effect of slope and head on uniformity coefficient. We found that the coefficient of uniformity (CU) and the distribution uniformity (DU) generally increase with increasing heads and decrease with increasing slope. The coefficient of uniformity generally followed a linear relationship with either head or slope. The CU and DU decrease substantially at submain slopes steeper than 30%. For a level surface, a head differential of 0.5 m does not cause significant change in either CU or DU. For all slopes tested, we found that a head of 3.0 m with respect to the junction of the most upstream lateral may be considered to be recommendable from both hydraulic and practical standpoints. On the basis of the results, appropriate recommendations were formulated to minimize non-uniformity of water distribution under field conditions in sloping drip-irrigated lands.

Direct measurement of the liquid 4:1 methanol–ethanol equation of state up to 5 GPa

Despite the widespread use of the 4:1 methanol–ethanol mixture as a hydrostatic medium by the high-pressure community, its equation of state (EOS) is usually substituted by that of pure methanol. Here we report accurate direct volumetric measurements of the room temperature EOS for this mixture up to 5 GPa. A brief description of the optical technique (imaging+interferometric) specifically developed for this purpose is given, as well as the general characteristics of the required miniature diamond anvil cell. Our results are compared with the available data of similar pure fluids’ EOS in the same pressure range. We find that there exist noticeable differences between the EOS of the mixture and that of pure methanol in terms of molar quantities.

Equilibrium and crystallographic measurements of the binary tetrahydrofuran and helium clathrate hydrates

Clathrate compounds are crystalline materials formed by a physical interaction between host and relatively light guest molecules. Various types of nano-sized cages surrounded by host frameworks exist in the highly unique crystalline structures and free guest molecules are entrapped in an open host-guest network. Recently, we reported two peculiar phenomena, swapping and tuning, naturally occurring in the hydrate cages. Helium, one of the smallest light guest molecules, must be the challengeable material in the sense of physics and moreover possesses versatile applications in the field of superconductivity technology and thermonuclear industry. In this regard, we attempted for the first time to synthesize helium hydrates at moderate temperature and pressure conditions. According to inclusion phenomena, helium itself normally cannot form clathrate hydrates due to being too small molecularly without the help of hydrate former molecules (sI, sII, and sH formers). In this study, the hydrate equilibria of the binary clathrate hydrate containing tetrahydrofuran, helium, and water were determined at 2, 3, 5.56 THF mol%. Direct volumetric measurements were also carried out to confirm the exact amount of helium captured in the hydrate cages. Finally, the crystalline structure of the formed mixed hydrates was identified by powder X-ray diffraction, resulting in structure II.

Spectroscopic identification, thermodynamic stability and molecular composition of hydrogen and 1,4-dioxane binary clathrate hydrate

We present the spectroscopic identification of the binary hydrogen and 1,4-dioxane clathrate hydrates in which H 2 molecules are encapsulated in small cages of the structure II hydrate framework. X-ray diffraction, solid-state NMR and Raman spectroscopy were used to confirm the mixed hydrate structure and more importantly the occupancy pattern of hydrogen in clathrate cages. The corresponding pressure–temperature behavior and direct gas release measurements were also determined to support the spectroscopic results. The direct volumetric measurements revealed that the favorable confinement of hydrogen molecules over 0.4 wt% could be obtained by the compositional tuning of the binary products.

Volumetric analysis of extraction sockets using cone beam computed tomography: a pilot study on ex vivo jaw bone

The aim of this study was to determine the accuracy of volumetric analysis of extraction sockets using cone beam computed tomography (CBCT). The volume of 40 dental alveoli in nine dry skull specimens (four mandibles and five maxillae) was determined by measuring the volume of the tooth socket impression using the water displacement technique. This was considered as the gold standard. Then, the tooth socket was scanned with CBCT and data were uploaded in the semi-automated Livewire segmentation software. The software segments the tooth socket in consecutive 1 mm-thick two-dimensional slices. After segmentation, the total volume of the delineated socket was computed. The statistical difference between direct volumetric measurements and those obtained with CBCT imaging was assessed using the Student paired t-test. The mean socket volume of the skull specimens was 227+/-91 mm(3) when obtained by direct measurement and 225+/-90 mm(3) when obtained by CBCT imaging. Student paired t-test showed no significant differences between both volume measurements (p>0.1). CBCT permits imaging of anatomical structures in three planes and allows for reliable volume estimates. The results should be verified in clinical circumstances and might have potential applicability for evaluation of extraction socket healing under different conditions.