Location Of Root Research Articles

Survival analysis of primary molars following pulpectomy performed under dental general anesthesia: a five-year retrospective study

BackgroundCurrently, the indications for pulpectomy of primary molars performed under dental general anesthesia vary across countries. Therefore, we retrospectively investigated the five-year survival rate of primary molars following pulpectomy performed under dental general anesthesia and the impact of this treatment on permanent successors, assessed the risk factors related to overall survival and clarified the indications for pulpectomy.MethodsThe medical records of children receiving pulpectomy of primary molars under dental general anesthesia from August 1, 2013, to November 30, 2023, were reviewed. Potential risk factors, including gender, age, general health, tooth type, tooth location, endodontic diagnosis and quality of root filling, were assessed via univariate and multivariate Cox proportional hazards regression models, and the survival rate was examined via the Kaplan‒Meier technique. Moreover, the rate of resorption of the root canal filling materials, degree of resorption of the overfilled/over-extended root canal filling materials and development of permanent successors were assessed by clinical and radiographic examination.ResultsThe study included 320 teeth from 161 children (86 boys and 75 girls). The overall five-year survival rate was 38.2%, and the mean overall survival time was 54.2 months. Endodontic diagnosis was considered a significant risk factor (P < 0.05). In the first, second and third years, 57.4%, 81.8%, and 94.8%, respectively, of obturation materials in the root canals were resorbed at a faster rate than the roots. There was an altered eruption direction in 7 permanent teeth, and 4 permanent teeth were diagnosed with enamel hypoplasia.ConclusionsIn this study, the 60-month survival rate of primary molars treated by pulpectomy under dental general anesthesia was 38.32%. Operators should have an accurate assessment of the status of the pulp, have a strict grasp of the preoperative indications and select the appropriate treatment method according to the guidelines. Individual cases suggest overfilling, overextension and periapical periodontitis in primary molars have an impact on enamel hypoplasia and altered eruption direction in permanent teeth.

Application and Advantages of the Trans-Unco-Discal (TUD) Approach for Cervical Spondylotic Myelopathy and Radiculopathy: Classification and Modification of Surgical Technique Based on the Location of Spinal Cord and/or Nerve Root Compression.

Purpose: We assess the application and advantages of modifying the trans-unco-discal (TUD) approach which we underwent for cervical myelo-radiculopathy. We present the surgical techniques of the modified TUD approach. Materials and Methods: The material was 180 cases where anterior cervical decompression (ACD) was performed by the modified TUD approach. We classified the material into four groups based on the location of the nerve root and/or spinal cord compression: I, compression of the root at intervertebral foramen (IVF); II, compression of the posterior margin of the vertebral body; III, compression of the IVF and posterior margin of the vertebral body; IV, compression of the bilateral IVF and posterior margin of the vertebral body. We applied the modified TUD approach to these four types. We present the surgical procedures and techniques for the modified TUD approach. The Japanese orthopedic association (JOA) score and neuroradiological alignment were examined. Results: The improvement rate of the JOA score was 78.4% at 6 months post-surgery and 77.5% in the most recent examinations. By the modified TUD approach, compressive lesions of the spinal cord and/or nerve roots were removed, and good alignment was acquired and sustained. Conclusions: ACD by the modified TUD approach safely achieved appropriate decompression for the spinal cord and/or nerve roots, and the patients had a high improvement rate and good alignment. Complications were less common than with other surgical procedures. If the TUD approach and endoscopic approaches can be combined, their application to new area is anticipated.

APPLICATION OF OBJECT DETECTION TECHNOLOGY IN AORTOGRAPHY KEYPOINT TRACKING

HighlightsThe practical significance of the work lies in the fact that the presented aortography data visualization system is an effective tool for visually assisting surgeons during transcatheter aortic valve implantation interventions, supporting real-time operation mode. The proposed data preprocessing algorithm, which improves image quality with minimal performance costs, complements the system, allowing specialists to achieve the best result. AbstractAim. The aim of this study is to develop a visual assistance system for transcatheter aortic valve implantation procedures.Methods. To address the stated objective, our own dataset consisting of 35 videos of the intervention was used. The visualization system is based on the approach of detecting key points in aortography, utilizing “Object detection” technology with the application of YOLO family artificial neural networks. To achieve the best result, we proposed a method to enhance the quality of input data using convolutional neural networks, specifically the «Autoencoder» technology.Results. The results of the study revealed that the convolutional autoencoder model is capable of restoring the informativeness of noisy input images from 40 to 75%, thereby increasing the accuracy of object detection in images. The presented real-time tracking system for facilitating TAVI procedures achieves a final accuracy of 51.9% according to the Mean Average Precision (MAP) quality metric. The visual assistance system can recognize and track key points indicating the location of the aortic root, delivery system, and heart valve prosthesis during surgery. The practical significance of the work lies in the fact that the presented aortography data visualization system is an effective tool for visually assisting surgeons during interventions, supporting real-time operation mode.Conclusion. The proposed data preprocessing algorithm, which improves image quality with minimal performance costs, complements the visualization system, allowing specialists to achieve the best results.

Computational study of early-time droplet impact dynamics on textured and lubricant-infused surfaces

The high-speed impact of liquid droplets onto surfaces with different properties is a vast area of research. The present study focuses on using numerical simulation to investigate the delicate early stages of droplet impact onto both textured and lubricant-infused surfaces. An idealised two-dimensional model is utilised for a normal impact of an incompressible liquid droplet onto a surface of rectangular asperities and a thin layer of lubricant. In experiments the length scale of the impinging droplet is typically much larger than that of the surface asperities. The study here aims to complement such work by considering the same scaling, with millimetre sized droplets impinging on surfaces with micrometre sized asperities. It is found that variations of the surface properties have an insignificant effect on the location of the jet root and all dynamical changes are focused in the thin splash jet ejected at impact. The effects that the parameters pertaining to a lubricant-infused surface, namely the surface topology, lubricant depth and lubricant viscosity, have on the extent of the thin splash jet are investigated in turn. Increasing the gap between the surface asperities results in a reduction in the horizontal extent of the splash jet, while variations in lubricant depth and viscosity exhibit non-monotonic effects. In each case phase diagrams are presented to characterise the early time splashing behaviour and investigate the influence of impact velocity. Comparisons of a lubricant-infused surface to a superhydrophobic surface, with no lubricant present, highlight the importance of the surface topology. The results presented in this manuscript also highlight possible avenues of further research, both analytical and experimental, as well as aid in the design of novel non-wetting surfaces.

Superior Pubic Ramus Screw Placement During Complex Acetabular Revision: Acetabular Distraction for Treatment of Pelvic Discontinuity.

With the patient in the lateral decubitus position, the acetabulum is exposed from a standard posterior approach for a revision THA. The location of the superior pubic root is identified after making a recess within the anteroinferior capsule. In order to ensure that the appropriate trajectory is obtained, C-arm imaging (inlet view and orthogonal obturator outlet views) is utilized to safely predrill the screw trajectory into the superior pubic ramus. A Kirschner wire (K-wire) is then placed into the hole. With use of a metal-cutting burr on the back table, customized peripheral screw holes are placed and then the acetabular component is slid and impacted into place over the K-wire. After cup insertion, the K-wire is removed and the superior pubic ramus screw can be placed and confirmed on fluoroscopy. In general, chronic pelvic discontinuity requires surgical management with revision THA and has historically employed the use of a cup-cage construct, custom triflange implants, and/or jumbo acetabular cups with modular porous metal augments1-5. With these treatment options, it is typically necessary to insert "kickstand" screws, which function to prevent abduction failure of the acetabular cup4,5. However, in many cases of discontinuity, there may be severe ischial osteolysis, making ischial screw placement difficult or impossible. The superior pubic ramus, however, remains a reliable option that can be utilized for inferior screw fixation, even in cases of severe acetabular bone loss, and thus is especially beneficial in these difficult cases. The technique of acetabular distraction was developed because of limitations with alternative techniques. This procedure achieves cementless biologic fixation and eventual discontinuity healing as a result of lateral or peripheral acetabular distraction and resultant medial or central compression across the pelvic discontinuity. Acetabular distraction allows for intraoperative customization and cement unitization of the acetabular construct. This procedure requires the use of a "kickstand" screw or of inferior screw fixation in order to prevent abduction failure of the cup. These screws may be placed into either the ischium or superior pubic ramus. If the patient has substantial ischial osteolysis, ischial screw fixation may not be possible. If not placed in a systematic manner, pubic ramus screws can be technically challenging, and incorrect placement can result in neurovascular injury. The present video article demonstrates a reproducible technical method for safely placing a screw in the superior ramus to aid in optimal fixation of the acetabular component in cases of pelvic discontinuity. Thus far, short-term survivorship of acetabular distraction with use of a jumbo cup and kickstand screws has been about 95%. In the largest study to date assessing patients with chronic pelvic discontinuity who underwent revision THA with use of the acetabular distraction technique, only 1 of 32 patients required revision for aseptic loosening6. An additional 2 patients had evidence of radiographic loosening but did not undergo revision, and 3 had migration of the acetabular component into a more stable configuration. Radiographically, 22 of 32 patients in the study demonstrated healing of the discontinuity6. In another study assessing the survivorship of porous tantalum acetabular shells in revision THA to treat severe acetabular defects, patients with inferior screw fixation with superior pubic ramus or ischial screws had a significantly lower incidence of proximal translation of components compared with those without inferior screw fixation7. For reproducible, successful execution of this technique, it is important to confirm correct placement of the acetabular retractors at the correct anatomical locations to ensure adequate surgical visualization of the acetabulum for easy identification of the superior pubic root.It is also critical to check placement of the drill via fluoroscopy with an inlet and obturator outlet views prior to drilling.The drill should be advanced on the oscillate setting to avoid inadvertently perforating the cortical bone and damaging surrounding neurovascular structures. OR = operating roomf/u = follow-upvac = vacuum-assisted closureRSA = radiostereometric analysis.

Three-Dimensional Analysis of the Ideal Entry Point for Sacral Alar Iliac Screws.

This is a virtual three-dimensional (3D) imaging study examining computed tomography (CT) data to investigate instrumentation placement. In this study, we aim to clarify the ideal entry point and trajectory of the sacral alar iliac (SAI) screw in relationship to the dorsal foramen at S1 and the respective nerve root. To the best of our knowledge, there is yet no detailed 3D imaging study on the ideal entry point of the SAI screw. Despite the evidence suggesting that the dorsal foramen at S1 is a landmark on the sacrum, the S1 nerve root disruption is a general concern during the insertion of SAI screws. No other study has been published examining the nerve root location at the S1and SAI screw insertions. Preoperative CT data from 26 patients pertaining to adult spinal deformities were investigated in this study. We applied a 3D image processing method for a detailed investigation. Virtual cylinders were used to mimic SAI screws. These were placed to penetrate the sacral iliac joint without violating the other cortex. We then assessed the trajectory of the longest SAI screw and the ideal entry point of SAI using a color mapping method on the surface of the sacrum. We measured the location of the nerve root at S1 in relation to the foramen at S1 and the sacral surface. As per the results of our color mapping, it was determined that areas that received high scores are located medially and caudally to the dorsal foramen of S1. The mean angle between a horizontal line and a line connecting the medial edge of the foramen and nerve root at S1 was 93.5°. The mean distances from the dorsal medial edge of the foramen and sacral surface to S1 nerve root were 21.8 mm and 13.9 mm, respectively. The ideal entry point of the SAI screw is located medially and caudally to the S1 dorsal foramen based on 3D digital mapping. It is also shown that this entry point spares the S1 nerve root from possible iatrogenic injuries.

Root adaptations of black spruce growing in water-saturated soil

Black spruce (Picea mariana (Mill.) BSP) is the main tree species growing within peatlands. The difficult growing conditions within peatlands are associated with low individual wood productivity, and only tree species tolerant to high ground water level can survive. We examine the effect of water-saturated soil on the growth potential of black spruce trees and specific adaptation of the root system. Experimental mesocosms were constructed with two drainage regimes (saturated and well-drained soil conditions). We measured biomass, height, and diameter at stem base of 55 black spruce saplings and noted the location of each horizontal root. Black spruce exhibited a very shallow root system located above saturated commercial peat 19 years after the experiment was initiated. Most roots were adventitious in the water-saturated mesocosms. Overall aerial and root biomass accumulation of the black spruce trees growing under saturated soil conditions was significantly lower than that of the well-drained mesocosms. Interestingly, root–shoot ratios were similar across the two drainage regimes. Soil conditions induced adaptation of the root system in black spruce trees, and physiological stress affected the entire individual with lower biomass productivity in all components (stem, branches, root system). However, biomass distribution remained similar to that of trees growing in well-drained mesocosms.

A MORPHOMETRIC STUDY OF VENTRAL NERVE ROOTS AND RETROPERITONEAL VESSELS IN RELATION TO A MINIMALLY INVASIVE LATERAL APPROACH TO DETERMINE SAFE WORKING ZONE

Background: The minimally invasive lateral retroperitoneal transpsoas approach is a new method that was designed to minimize problems related with standard or minimally invasive anterior or posterior lumbar spine techniques. The current work used magnetic resonance imaging to determine the anatomic location of the ventral root and retroperitoneal arteries in respect to the vertebral body and to establish the anatomical safe zones. We examined lumbar spine MRI in 50 individuals retrospectively (L1-L2 to L5-S Method: 1 levels). The ventral root and surrounding major arteries were identied using axial T1 and T2 scans. Axial MR scans were utilized to determine the anterior-posterior (AP) diameter of the vertebral endplate, the overlap between the ventral root and the posterior border of the vertebra, and the overlap between the retroperitoneal big vessels and the anterior edge of the vertebra. The safe zone was then determined. From L1–L2 Results: to L5–S1, the mean AP diameter of the vertebral body and the overlap of the vertebral body with the nerve roots and retroperitoneal arteries grew gradually. When we examined the extent of overlap of retroperitoneal arteries with the ventral border of the lower vertebral body endplate, we discovered that the right vascular structures were more posterior than the left vascular structures. The safe working zone was 81.86 percent of the lower endplate of the sagittal diameter of the vertebral body at L1–L2, 70.03 percent at L2–L3, 69.32 percent at L3–L4, 50.08 percent at L4–L5, and 17.92 percent at L5–S1 levels. The Conclusion: retroperitoneal transpsoas method is a less invasive and more efcient alternative to the conventional posterior, open lumbar procedures. It can be used to treat trauma, degenerative disc disease, adult degenerative scoliosis, spondylosis with instability, spondylolisthesis, lumbar stenosis, and neighboring segment failure.

Effects of Left Ventricular Versus Traditional Chest Compressions in a Traumatic Pulseless Electrical Activity Model.

Prehospital cardiopulmonary resuscitation has commonly been considered ineffective in traumatic cardiopulmonary arrest because traditional chest compressions do not produce substantial cardiac output. However, recent evidence suggests that chest compressions located over the left ventricle (LV) produce greater hemodynamics when compared to traditional compressions. We hypothesized that chest compressions located directly over the LV would result in an increase in return of spontaneous circulation (ROSC) and hemodynamic variables, when compared to traditional chest compressions, in a swine model of traumatic pulseless electrical activity (PEA). Transthoracic echocardiography was used to mark the location of the aortic root (traditional compressions) and the center of the LV on animals (n = 34) that were randomized to receive chest compressions in one of the two locations. Animals were hemorrhaged to mean arterial pressure <20 to simulate traumatic PEA. After 5 minutes of PEA, basic life support (BLS) with mechanical cardiopulmonary resuscitation was initiated and performed for 10 minutes followed by advanced life support for an additional 10 minutes. Hemodynamic variables were averaged over the final 2 minutes of BLS and advanced life support periods. Six of the LV group (35%) achieved ROSC compared to eight of the traditional group (47%) (P = .73). There was an increase in aortic systolic blood pressure (P < .01), right atrial systolic blood pressure (P < .01), and right atrial diastolic blood pressure (P = .02) at the end of BLS in the LV group compared to the traditional group. In our swine model of traumatic PEA, chest compressions performed directly over the LV improved blood pressures during BLS but not ROSC.

Location of the abducens nerve stretched by a tortuous vertebrobasilar artery in trigeminal neuralgia.

Trigeminal neuralgia (TGN) caused by the vertebrobasilar artery (VBA) is uncommon. The abducens nerve root is frequently dislocated by a tortuous VBA near the trigeminal nerve root. This unusual location of the root is not well known. This study aimed to investigate the location of the stretched abducens nerve root. The objective is 26 patients with VBA-related TGN who underwent microvascular decompression (MVD). We retrospectively investigated the course of the abducens nerve root with magnetic resonance imaging (MRI) with three-dimensional (3D) imaging and surgical findings. The displacement of the abducens nerve root on the affected side was compared to the contralateral side. The abducens nerve root was distorted by a tortuous VBA (46.2%) or the anterior inferior cerebellar artery (53.8%). The average length of the cisternal segment was stretched to 23.4 mm versus 12.4 mm on the contralateral side. The peak point of the elevated abducens nerve root was mostly located rostro-medial (65.4%) or caudo-medial (34.6%) to the neurovascular compression site of the trigeminal nerve with a mean distance of 9.1 mm. Contact with the trigeminal nerve root was observed in 7 patients (26.9%). Three-dimensional imaging was consistent with the surgical findings and useful in predicting the location of the abducens nerve root. No abducens nerve palsy was noted in our series. The abducens nerve root is located near the trigeminal nerve root in VBA-related TGN. Preoperative understanding of the unusual course of the abducens nerve root contributes to avoiding accidental nerve injury during MVD.

Comparison of morphogenesis and anatomy between hairy roots and adventitious roots of Ngoc Linh ginseng (Panax vietnamensis Ha et Grushv.)

In this study, morphogenesis and anatomy of adventitious roots and hairy roots of Ngoc Linh ginseng (Panax vietnamensis Ha et Grushv.) were compared. Adventitious roots were derived from four different samples (leaf, petiole, root and callus) in vitro cultured on medium SH supplemented with 5 mg/L IBA. Hairy roots were derived from callus infected with Agrobacterium rhizogenes strain ATCC 15834. The results showed that there were significant differences in morphogenesis and anatomy, the pathway of secondary roots formation, culture medium between adventitous roots and hairy roots. The hairy roots strongly grew and branched on the free-plant growth regulator medium. The secondary root of the hairy root was formed in two pathways: (1) The secondary root formation began at the vesicles system of main root; (2) The secondary root formation was independent of the vesicles system of main root; it kept developing in length and connected to the vesicles system of main root. On the other hand, growing adventitous roots only grew on the environment with exogenous auxin supplementation; also their branching ability were low. The secondary root formation of the adventitous root was started at the vesicles of the main roots and there was only one secondary root that was formed at an location of adventitous root. The results that obtained in this study will be the reference to identify two types of root.

The Effect of Chest Compression Location and Aortic Perfusion in a Traumatic Arrest Model

BackgroundRecent evidence demonstrates that closed chest compressions directly over the left ventricle (LV) in a traumatic cardiac arrest (TCA) model improve hemodynamics and return of spontaneous circulation (ROSC) when compared to traditional compressions. Selective aortic arch perfusion (SAAP) also improves hemodynamics and controls hemorrhage in TCA. We hypothesized that chest compressions located over the LV would result in improved hemodynamics and ROSC in a swine model of TCA using SAAP. Materials and methodsTransthoracic echo was used to mark the location of the aortic root (Traditional location) and the center of the LV on animals (n = 24), which were randomized to receive chest compressions in one of the two locations. After hemorrhage, ventricular fibrillation (VF) was induced to simulate TCA. After a period of 10 min of VF, basic life support (BLS) with mechanical CPR was initiated and performed for 10 min, followed by advanced life support (ALS) for an additional 10 min. SAAP balloons were inflated at min 6 of BLS. Hemodynamic variables were averaged over the final 2 min of the BLS and ALS periods. Survival was compared between this SAAP cohort and a control group without SAAP (No-SAAP) (n = 26). ResultsThere was no significant difference in ROSC between the two SAAP groups (P = 0.67). There was no ROSC difference between SAAP and No-SAAP (P = 0.74). ConclusionsThere was no difference in ROSC between LV and Traditional compressions when SAAP was used in this swine model of TCA. SAAP did not confer a survival benefit compared to historical controls.

Anchoring mechanisms of a holder-stabilized premixed flame in a preheated mesoscale combustor

A very lean-premixed, laminar methane–air flame is demonstrated, experimentally, to be stable in a mesoscale combustor with a flame holder. Unlike the anchoring location of the flame tip, the anchoring location of the flame root is practically independent of the equivalence ratio, inlet velocity, and thermal conductivity of the solid wall material. When the mixture becomes leaner, both the flame root and tip can adaptively shift toward the locations with higher temperatures, and additionally, the anchoring temperature of the flame root is higher. Subsequently, by means of the three-dimensional computational mechanics, their anchoring mechanisms are thoroughly analyzed in terms of the flow recirculation, stretch effect, preferential diffusion, and conjugate heat exchange. A recirculation zone or a low-velocity zone formed behind/near the flame holder and combustion chamber wall can assist the balance between the flow velocity and the flame speed for the flame anchoring, and the flame root can adaptively shift to a zone of lower local velocity. The stretch effect is not responsible for the flame root anchoring, but this effect stabilizes the flame tip by increasing the local flame speed near the flame tip. Preferential diffusion significantly promotes the local equivalence ratio near the anchoring location of the flame root, thereby facilitating the stability of this flame root, though it stabilizes the flame tip only slightly. Furthermore, the conjugate heat exchange plays an important role in preheating fuel/air and intensifying combustion, which influences the stabilization of both the flame root and tip. The shorter distance between the flame tip and the combustion chamber wall results in a stronger flame–wall coupling. These results indicate that the anchoring mechanisms for the flame root and tip differ.

The production of a synthetic chemodisruptive peptide in planta precludes Meloidogyne incognita multiplication in Solanum melongena

Root-knot nematodes (RKNs) impose a severe constraint on eggplant productivity and sustainable options to minimize nematode populations below the economic threshold level are limited. In the present study, transgenic eggplants expressing a synthetic peptide (under the control of CaMV35S promoter) that disrupts nematode chemoreception were used as a proof-of-concept to assess the potential of hitherto-underexploited peptide-based transgenics in conferring nematode resistance. Six transgenic eggplant lines were characterized which were genotyped via PCR, qRT-PCR and Southern hybridization analyses. When challenge inoculated with RKN, all the peptide-expressing lines exhibited detrimental effect on nematode host location and penetration of host root. Consequently, perturbed infection ability and parasitic success of RKN on transgenic root was documented with 64.39–79.65% reduction in nematode multiplication. Root exudates of transgenic eggplant strongly elevated the expression of acetylcholinesterase genes (Mi-ace-1 and Mi-ace-2) in RKN. This altered expression of Mi-ace-1 and Mi-ace-2 was correlated with the efficacy of exudates as presoak solution for nematodes that affected their attraction to wild-type eggplant roots. The current study reestablishes the efficacy of novel, biosafe chemoreception-disruptive peptides in suppressing the nematode parasitism when expressed in planta. Gene pyramiding-based transgenic deployment of this peptide with proteinase inhibitor such as cystatin can satisfactorily increase the global agricultural output.

The Effect of Chest Compression Location and Occlusion of the Aorta in a Traumatic Arrest Model

BackgroundRecent evidence demonstrates that closed chest compressions directly over the left ventricle (LV) in a traumatic cardiac arrest (TCA) model improve hemodynamics and return of spontaneous circulation (ROSC) when compared with traditional compressions. Resuscitative endovascular balloon occlusion of the aorta (REBOA) also improves hemodynamics and controls hemorrhage in TCA. We hypothesized that chest compressions located over the LV would result in improved hemodynamics and ROSC in a swine model of TCA using REBOA. Materials and methodsTransthoracic echo was used to mark the location of the aortic root (traditional location) and the center of the LV on animals (n = 26), which were randomized to receive chest compressions in one of the two locations. After hemorrhage, ventricular fibrillation was induced to simulate TCA. After a period of 10 min of ventricular fibrillation, basic life support (BLS) with mechanical cardiopulmonary resuscitation was initiated and performed for 10 min followed by advanced life support for an additional 10 min. REBOA balloons were inflated at 6 min into BLS. Hemodynamic variables were averaged during the final 2 min of the BLS and advanced life support periods. Survival was compared between this REBOA cohort and a control group without REBOA (no-REBOA cohort) (n = 26). ResultsThere was no significant difference in ROSC between the two REBOA groups (P = 0.24). Survival was higher with REBOA group versus no-REBOA group (P = 0.02). ConclusionsThere was no difference in ROSC between LV and traditional compressions when REBOA was used in this swine model of TCA. REBOA conferred a survival benefit regardless of compression location.

Effect of thermal condition of solid wall on the stabilization of a preheated and holder-stabilized laminar premixed flame

A novel combustor with a flame holder and preheating channels was developed to investigate the synergistic effect of heat and flow recirculation on combustion characteristics. This paper mainly focuses on the thermal condition of flame holder and combustion chamber wall (CCW) and their interaction on flame stabilization. Based on the distribution characteristics of temperature and flow fields, it can be deduced that the interaction between the flame holder and CCW can further increase the incoming fresh mixture temperature and decrease the height of recirculation zone, which subsequently affect the anchoring locations and temperatures of the flame root and top. To be more specific, the flame holder and CCW synergistically improve the preheating temperature of fresh mixture, making it higher than simple linear superposition. Moreover, the anchoring location of the flame root is mainly determined by the heat exchange of flame holder, but CCW matters more significantly for the flame top. Additionally, the anchoring temperature of the flame root is higher than that of the flame top. This study can help us to gain insights into the effect of conjugate heat exchange on flame stability when the effect of heat recirculation and flow recirculation works synergistically in practical combustors (like aero-engine).

A cone-beam computed tomography study of the prevalence and location of the second mesiobuccal root canal in maxillary molars.

ObjectivesThis study aimed to investigate the incidence and location of the second mesiobuccal root (MB2) canal in maxillary molars with the aid of various measuring points and lines using cone-beam computed tomography (CT).Materials and MethodsA total of 205 images of patients who underwent cone-beam CT examinations between 2011 and 2015 as part of their dental diagnosis and treatment were included. There were 76 images of the maxillary first molar and 135 images of the maxillary second molar. Canal orifices were detected at −1 mm from the top of the pulpal floor on cone-beam CT images. Image assessment was performed by 2 observers in reformatted image planes using software. Assessments included measurement of the distance between the MB1 and MB2 canals, and the angles between the lines connecting the MB1-MB2 and distobuccal (DB)-palatal (P) canals. The data were analyzed using the student's t-test.ResultsThe prevalence of the MB2 canal was 86.8% in the first molar and 28.9% in the second molar. The angle between the lines connecting the MB1-MB2 and DB-P canals was 2.3° ± 5.7° in the first molar and −3.95° ± 7.73° in the second molar. The distance between the MB1 and MB2 canals was 2.1 ± 0.44 mm in the first molar and 1.98 ± 0.42 mm in the second molar.ConclusionsThe angles between the lines connecting the MB1-MB2 and DB-P canals was almost parallel. These findings may aid in the prediction of the location of the MB2 canal orifice.

Abstract 253: The Efficacy of Left Ventricular versus Traditional Chest Compressions During Selective Aortic Arch Perfusion to Treat Traumatic Cardiopulmonary Arrest in a Swine Model

Introduction: Recent evidence has demonstrated that closed chest compressions (CC) directly over the left ventricle (LV) during traumatic cardiopulmonary arrest (TCPA) improve hemodynamics and return of spontaneous circulation (ROSC) when compared to traditional chest compressions. Selective Aortic Arch Perfusion (SAAP) is also able to improve hemodynamics as well as control hemorrhage during TCPA. Hypothesis: We hypothesized that LV compressions would increase ROSC when compared to traditional compressions in an animal model of TCPA where SAAP was being used. We also compared LV and Traditional compressions with SAAP to historical controls that received compressions without SAAP. Methods: Transthoracic echo was used to mark the location of the aortic root and the center of the left ventricle on animals (n=24, 12 in each arm) which were randomized to receive chest compressions in one of the two locations. One third of each animal’s blood volume was removed and ventricular fibrillation (VF) was induced to simulate traumatic cardiac arrest. After a period of ten minutes of VF, basic life support (BLS) with mechanical CPR was initiated and performed for ten minutes followed by advanced life support (ALS) and blood transfusion for an additional ten minutes. The SAAP balloon was inflated at minute 6 of BLS. Hemodynamic variables were averaged every two minutes. The same model was used for historical controls (n=26, 13 in each arm) without the use of SAAP, so comparisons were treated as a single study with a factorial design. Results: There were no differences in hemodynamic variables, ROSC (p=0.67) or survival (p=0.64) between SAAP groups. However, when the LV animals were compared to historic controls without SAAP, LV animals had higher ROSC (p=0.02) and survival rates (p=0.04) than Traditional animals. Conclusions: SAAP does not appear to show a synergistic effect with LV compressions, however, SAAP combined with LV compressions improves ROSC and survival when compared to Traditional compressions in our swine model of TCPA. More investigation into SAAP and compression position should be studied to improve treatment of TCPA.

Effect of Channel Diameter on the Combustion and Thermal Behavior of a Hydrogen/Air Premixed Flame in a Swirl Micro-Combustor

Improving the flame stability and thermal behavior of the micro-combustor (MC) are major challenges in microscale combustion. In this paper, the micro combustions of an H2/air premixed flame in a swirl MC with various channel diameters (Din = 2, 3, 4 mm) were analyzed based on an established three-dimensional numerical model. The effects of hydrogen mass flow rate, thermal conductivity of walls, and the preferential transport of species were investigated. The results indicated that the flame type was characterized by the presence of two recirculation zones. The flame was anchored by the recirculation zones, and the anchoring location of the flame root was the starting position of the recirculation zones. The recirculation zones had a larger distribution of local equivalence ratio, especially in the proximity of the flame root, indicating the formation of a radical pool. The combustion efficiency increased with an increasing Din due to the longer residence time of the reactants. Furthermore, the MC with Din = 2 mm obtained the highest outer wall temperature distribution. However, the MC with Din = 4 mm had a better uniformity of outer wall temperature and large emitter efficiency due to the larger radiation surface. An increase in thermal conductivity boosts the thermal performance of combustion efficiency, emitter efficiency, and wall temperature uniformity. But there is a critical point of thermal conductivity that can increase the thermal performance. The above results can offer us significant guidance for designing MC with high thermal performance.

Early-time jet formation in liquid–liquid impact problems: theory and simulations

We perform a thorough qualitative and quantitative comparison of theoretical predictions and direct numerical simulations for the two-dimensional, vertical impact of two droplets of the same fluid. In particular, we show that the theoretical predictions for the location and velocity of the jet root are excellent in the early stages of the impact, while the predicted jet velocity and thickness profiles are also in good agreement with the computations before the jet begins to bend. By neglecting the role of the surrounding gas both before and after impact, we are able to use Wagner theory to describe the early-time structure of the impact. We derive the model for general droplet velocities and radii, which encompasses a wide range of impact scenarios from the symmetric impact of identical drops to liquid drops impacting a deep pool. The leading-order solution is sufficient to predict the curve along which the root of the high-speed jet travels. After moving into a frame fixed in this curve, we are able to derive the zero-gravity shallow-water equations governing the leading-order thickness and velocity of the jet. Our numerical simulations are performed in the open-source software Gerris, which allows for the level of local grid refinement necessary for a problem with such a wide variety of length scales. The numerical simulations incorporate more of the physics of the problem, in particular the surrounding gas, the fluid viscosities, gravity and surface tension. We compare the computed and predicted solutions for a range of droplet radii and velocities, finding excellent agreement in the early stage. In light of these successful comparisons, we discuss the tangible benefits of using Wagner theory to confidently track properties such as the jet-root location, jet thickness and jet velocity in future studies of splash jet/ejecta evolution.