Supernumerary teeth in premolar and molar area on CBCT: a pictorial review.

Objective: to build a descriptive classification of premolar and molar supernumerary teeth (ST) when preparing the cone beam computed tomography (CBCT) report. The aim is also to share wide range of CBCT images in the open access publishing model. Material and methods: For our review we systematically searched for articles from PubMed with 1) free full texts on ST in molar and premolar area and using CBCT, and 2) articles providing with information on complications related with the presence of ST in molar and premolar area. We also added to our review studies providing with classic ST classifications in premolar and molar area. Results: We found 29 cases of ST, and we freely illustrated them with 84 figures. We separated our pictorial review in: 1) unilateral ST in the mandible, 2) unilateral ST in the maxilla, 3) unilateral undersized ST, 4) bilateral ST, 5) ST with additional features, and 6) cases with major hyperdontia. Conclusions: we build up the classification matrix for premolar and molar ST with 11 descriptors and 50 boxes. The descriptors were: 1) location if the ST crown in axial view, 2) vertical location of the cusp tip in relation with closest erupted tooth in coronal view, 3) shape, 4) distribution, 5) Position (in relation to normal tooth eruption) in sagittal view, 6) State of eruption of the ST in the sagittal view, 7) Follicle size measurement in sagittal view, 8) External root resorption of adjacent teeth by ST and its location in relation to the long axis of the involved tooth, 9) Internal resorption of ST, 10) Adjacent tooth complication, and 11) Damage to surrounding structures if ST removal. The open access figures from the literature illustrated 11 boxes. With our pictorial review we were able to illustrate 45 out of 50 boxes, and freely provide the readership with the most complete description of ST in premolar and molar area on CBCT than in previously published studies.

A Novel Method of Constructing Spatial Well Pattern for Water Flooding in Fractured-Vuggy Carbonate Reservoirs FVCRs

Fractured-vuggy reservoir is significantly different from porous reservoirs. Ordovician reservoir in T Oilfield in China is the largest FVCR around the world. Water flooding has been applied as a prospective method in more than 140 units, but water channeling is especially serious and the recovery is only about 15%. In such reservoir, cavities and fractures are the main storage spaces and flow channels, respectively. Because the fractures and cavities are spatially non-stratified and discretized, the waterflood pattern differs significantly from that in sandstone or porous carbonate reservoirs. It is very essential to construct a spatial well pattern to match the distribution and connectivity of fractures and cavities, which is a very popular topic in recent years. In this work, we presented a multistage construction method of spatial well pattern combining reservoir engineering with numerical simulation methods. Firstly, the economic concepts of Lorenz curve and Gini coefficient were introduced to choose the injector from all wells to achieve equilibrium displacement of injected water in the plane. Secondly, displacement and drainage equilibrium index (DDEI) was presented to determine the vertical location of the injector to achieve equilibrium displacement and drainage in vertical direction. Thirdly, the vertical locations of the producers were determined based on the distribution of reserves in vertical direction. Fourthly, the local producers were further optimized based on the cavities along the wellbore by numerical simulation. Finally, this method was successfully used to construct the spatial well patterns of fractured-vuggy units with different karst features in A unit of T Oilfield. The results show that the oil recovery factor is inversely proportional to the Gini coefficient calculated with the combined variable of flow resistance and crude reserve rather than that calculated with flow resistance in pore reservoirs. The ratio of the reserve to formation factor, V/(kh), can be used to determine the vertical location of the injector. And the optimal DDEI which is the ratio of V/(kh) in upper reservoir of the wellbore to that in lower reservoir of the wellbore is equal to 1. The vertical locations of producers are related to the vertical distributions of reserve and cavities in different karst units. At last, the principles of constructing spatial well pattern in fractured-vuggy carbonate reservoirs were proposed. This work provides an innovative and effective method to establish a spatial well pattern for FVCRs, which will break new ground for efficient development of FVCRs by water flooding.

Assessment of the mental foramen location in a sample of Saudi Al Hasa, population using cone-beam computed tomography technology: A retrospective study.

Background: It is essential that the dentist understand the positional variations of the mental foramen to perform different types of dental procedures. This study was conducted to identify the position of the mental foramen among the Saudi population of Al Hasa. Material and Methods: According to the selection criteria of 200 CBCT images, 101 images were selected. The selected images were categorized into five groups with respect to patient age. Each image was evaluated from both sides of the mandible and then recorded in six classes (position I-VI) according to the horizontal position and three classes in the vertical position. Results: In the Saudi Al Hasa population, Type 4 (at the level of 2nd premolar) was the most common location for mental foramen in the horizontal direction, on the right side (n= 41; 40.6%) and on the left side (n=44; 43.6%). Mental foramen was found in the vertical location, Type 3 (below the apex of 1st and 2nd premolars) was found in the right side (n= 54; 53.5%) and left side (n=56; 55.4%). The position of mental foramen is not constant and changes according to gender and ethnicity. This warrants dentists to evaluate patients individually. Conclusion: Even though the present study was done with a small sample of patients it provides a picture about approximate location of mental foramen among the target group of a population.

Determination of the Vertical Location of the Axis of Rotation of the Roll Motion From Full-Scale Measurements

The behavior of a floating structure results from the mechanics of its, more or less, rigid body and the hydrostatic and hydrodynamic forces acting on it. Particularly for ships, as long and slender bodies, the axis of roll and its vertical position is of special importance. It is around this axis that the lowest lateral accelerations in roll motion occur, which is not only weakly damped but also easily stimulated due to the relatively low mass moment of inertia around the ship’s longitudinal axis. With the intention of clarifying some widespread misconceptions about the location of this axis and to investigate its relation to the natural roll period, full scale measurements have been carried out using a set of two mobile Inertial-Measurement-Units. The Inertial-Measurement-Units were placed on different heights, one above and one below the assumed location of the axis of rotation. Based on the measured accelerations and angular velocities, the average vertical location of the axis of the roll motion for small angles is determined.

Heat transfer promotion in channel laminar flow employing a slab with slits and inclined ribs protruding across

Purpose The purpose of this study is to promote laminar heat transfer from the channel heated through a slab with slits and inclined ribs protruding across. Design/methodology/approach The novel design of this study is performed through making the slits in the slab (C1–C3: with slits; C4–C6: without slits) and changing the vertical location of this slab (1/4, 1/2 and 3/4 channel height). The thermal fluid characteristics of all cases are analyzed for various Reynolds numbers (500, 1,000, 1,500 and 2,000) by the SIMPLE-C algorithm. Findings The results display that the ribbed slab effectively improves the heat transfer. The slits can modify the flow field in the vortexes around the inclined ribs and remove more heat from this zone to promote the heat transfer. As compared with C0 (without a slab), C2 (the slab with slits and inclined ribs protruding across located vertically on the 3/4 channel height) raises the averaged Nusselt number up to 27.7% at Re = 2,000. As compared with C4 (without slits), C1 (with slits) gains the maximum increase in the averaged Nusselt number by 5.07% at Re = 1,000. Research limitations/implications The constant thermo-physical properties of incompressible fluid and the steady flow are considered in this study. Practical implications The numerical results will profit the design of heated passageway using a slab with slits and inclined ribs protruding across to acquire better heat transfer promotion. Originality/value This slab with slits and inclined ribs protruding across can be applied to the heat transfer promotion and thus be viewed as a useful cooling mechanism in the thermal engineering.

Behavior of saline ice under cyclic flexural loading

New systematic experiments reveal that the flexural strength of saline S2 columnar-grained ice loaded normal to the columns can be increased upon cyclic loading by about a factor of 1.5. The experiments were conducted using reversed cyclic loading over ranges of frequencies from 0.1 to 0.6 Hz and at a temperature of −10 ∘C on saline ice of two salinities: 3.0 ± 0.9 and 5.9 ± 0.6 ‰. Acoustic emission hit rate during cycling increases with an increase in stress amplitude of cycling. Flexural strength of saline ice of 3.0 ± 0.9 ‰ salinity appears to increase linearly with increasing stress amplitude, similar to the behavior of laboratory-grown freshwater ice (Murdza et al., 2020b) and to the behavior of lake ice (Murdza et al., 2021). The flexural strength of saline ice of 5.9 ± 0.6 ‰ depends on the vertical location of the sample within the thickness of an ice puck; i.e., the strength of the upper layers, which have a lower brine content, was found to be as high as 3 times that of lower layers. The fatigue life of saline ice is erratic. Cyclic strengthening is attributed to the development of an internal back stress that opposes the applied stress and possibly originates from dislocation pileups.

A novel multi-parameter approach to assess the effects of river restoration measures on the sediment matrix

<p>Clogging of riverbeds, also referred to colmation, has been frequently reported in residual flow river reaches. In such river reaches, colmation occurs mostly due to regulated (minimum) flow conditions without significant flood events that drive morphodynamics. Consequently, incoming fine sediments continuously deposit, infiltrate, and accumulate in the gravel matrix of the riverbed. The negative effect of such clogged layers on river ecology is well-known, especially with respect to the hyporheic interstitial leading to reduced porosity and hydraulic conductivity. These limitations results in a reduced supply of dissolved oxygen for aquatic species living in the hyporheic interstitial. However, no standardized quantitative measuring technique exists to determine the vertical location and the degree of colmation. Most available measuring methods involve a variety of mapping methods or single-parameter approaches. While mapping methods enable only qualitative assessments, single-parameter approaches are insufficient to describe the complexity of colmation.</p><p>The objective of this study is to test a novel multi-parameter approach in a residual flow river reach to assess the effect of river restoration measures on colmation. The multi-parameter approach includes four key parameters to describe colmation: i) the grain size distribution of the riverbed using freeze core sampling and sieving, ii) the hydraulic conductivity using a newly developed double packer system, iii) the porosity identified with a photogrammetric approach, and iv) the interstitial dissolved oxygen content (DOC) using optodes. This novel approach enables a quantitative description of colmation and an identification of clogged layers in stratified riverbeds as the hydraulic conductivity and the DOC are measured in vertical profiles. The entire measuring concept is applied before and after the implementation of river restoration measures to detect the intervention’s effects on colmation.</p><p>The first analyses of the measurement show clearly the effects of dredging with an artificial alteration of the riverbed on the sediment matrix. The vertical profiles of hydraulic conductivity and dissolved oxygen show typically high values in the permeable upper sediment layer and significant reductions in deeper sediment layers. The thickness range of the permeable upper layer is between 5 and 15 cm before the intervention and increased up to 30 and 50 cm after the interventions. The analyses of a coarsened grain size distribution and porosity support the observation of this declogging effect, although a direct correlation is challenging because both parameters are not detected in the form of vertical profiles, but rather as a bulk information for every measurement point.</p><p>These very first results provide the conclusion that the measured vertical profiles of hydraulic conductivity and DOC are promising data to assess the location and degree of colmation and their modification as a result of river restoration action. Yet, grain size and porosity analyses provide only little evidence because those represent bulk information only. In summary, the multi-parameter approach represents an innovative and quantitative approach to objectively assess the degree and vertical location of clogged layers in gravel riverbed, which is a major advantage over existing methods for assessing colmation.</p>