A study of the distobuccal root canal orifice of the maxillary second molars in Chinese individuals evaluated by cone-beam computed tomography

As is commonly understood, the root canal morphology of the maxillary molars is usually complex and variable. It is sometimes difficult to detect the distobuccal root canal orifice of a maxillary second molar with root canal treatment. No literature related to the distobuccal root canals of the maxillary second molars has been published. Objective: To investigate the position of the distobuccal root canal orifice of the maxillary second molars in a Chinese population using cone-beam computed tomography (CBCT). Material and methods: In total, 816 maxillary second molars from 408 patients were selected from a Chinese population and scanned using CBCT. The following information was recorded: (1) the number of root canals per tooth, (2) the distance between the mesiobuccal and distobuccal root canal orifice (DM), (3) the distance between the palatal and distobuccal root canal orifice (DP), (4) the angle formed by the mesiobuccal, distobuccal and palatal root canal orifices (∠PDM). DM, DP and ∠PDM of the teeth with three or four root canals were analyzed and evaluated. Results: In total, 763 (93.51%) of 816 maxillary second molars had three or four root canals. The distance between the mesiobuccal and distobuccal orifice was 0.7 to 4.8 mm. 621 (81.39%) of 763 teeth were distributed within 1.5-3.0 mm. The distance between the palatal and distobuccal orifice ranged from 0.8 mm to 6.7 mm; 585 (76.67%) and were distributed within 3.0-5.0 mm. The angle (∠PDM) ranged from 69. 4º to 174.7º in 708 samples (92.80%), the angle ranged from 90º to 140º. Conclusions: The position of the distobuccal root canal orifice of the maxillary second molars with 3 or 4 root canals in a Chinese population was complex and variable. Clinicians should have a thorough knowledge of the anatomy of the maxillary second molars

Maternal gestational diabetes in singleton pregnancies conceived by ART may be modified by periconceptional B vitamins

BackgroundThe risk of maternal gestational diabetes mellitus (GDM) may be influenced by pregnancies conceived through assisted reproductive technology (ART). However, the influence of the dosage of B vitamins (folate, vitamin B6 and vitamin B12) on GDM weren’t considered. Thus, we hypothesized that periconceptional B vitamins could modify maternal GDM in singleton pregnancies conceived by ART.MethodsThis study is a prospective cohort study using data from 3,252 women with singleton pregnancies and received a 75 g oral glucose tolerance test (OGTT) at 24–28 weeks of gestation. We included an interaction term in the multivariable logistic and linear regression models, respectively, to test our hypothesis.ResultsWomen who underwent ART were significantly associated with the incidence of GDM compared with spontaneous pregnancy women. The adjusted odds ratio (aOR) was 1.59, and the 95% confidence interval (CI) was 1.08–2.34. ART pregnancies also elevated OGTT (oral glucose tolerance test) 1-h blood glucose levels and OGTT 2-h blood glucose levels (P < 0.05). A positive association between dietary vitamin B6 (aOR = 1.60, 95% CI: 1.13–2.27), dietary vitamin B12 (aOR = 1.88, 95% CI: 1.34–2.64) and dietary folate (aOR = 1.66, 95% CI: 1.19–2.32) with GDM risk comparing the highest to the lowest quartile (all Ptrend < 0.001). The aORs of GDM for inadequate (< 400 μg/day), adequate (400–800 μg/day), and excessive (> 800 μg/day) supplemental folate intake were 1.00, 0.93, and 1.30, respectively (Ptrend = 0.033). Since only the supplemental folate illustrates a statistically significant interaction with ART (P for interaction < 0.05), the association between ART and GDM and OGTT blood glucose levels stratifying by supplemental folate were further evaluated. These increased risks of GDM (aOR = 1.62, 95% CI: 1.39–3.39) and the regression coefficients (β) of 1-h blood glucose (β = 0.76, 95% CI: 0.39–1.13) and 2-h blood glucose (β = 0.60, 95% CI: 0.29–0.92) in the multiple linear regression model were significant only in the ART group with excessive supplemental folate (> 800 μg/day).ConclusionThe risk of GDM is significantly elevated, particularly among those women who conceived ART with the intake of excessive supplemental folate (> 800 μg/day)

Nitrogen rather than streamflow regulates the growth of riparian trees

In arid and semiarid regions, riparian forests are crucial for maintaining ecological biodiversity and sustainability, and supporting social and economic development. For the typical arid and semiarid ecosystem, streamflow variability is thought to be the dominant factor influencing the vulnerability and evolution of the riparian forests, which often leads to the neglect of other potentially important factors such as nutrient availability and transport. Here, we measured annual stable nitrogen isotopes (δ15N) and nitrogen concentrations (N%) in the tree rings of Populus euphratica Oliv. (Euphrates poplar) over a 90 year period (1920–2012), collected from the lower researches of the inland Heihe River, northwestern China. Coupling with our previous dual-isotope (δ13C and δ18O) chronologies and estimated intrinsic water-use efficiency (iWUE), we examined the linkages between tree-ring δ15N and δ18O, iWUE, streamflow, and then explored the contributions of each to tree growth during the study period. Our results show that after 1975, a statistically significant correlation between tree-ring δ15N and river streamflow appears, indicating the river as a potential carrier of nitrogen from the upper and middle reaches to the lower research trees. In addition, the linkage between tree-ring δ15N and iWUE suggests substantial influence of carbon and nitrogen together on photosynthesis and transpiration of trees, although this connection become decoupled since AD 1986. The commonality analysis revealed that the nitrogen impacts indicated by tree-ring δ15N on tree growth cannot be ignored when evaluating riparian forest development. The fertilization effects caused by rising CO2 concentration complicate the nitrogen constraints on tree growth during the later part of the past century. Our results have potentially broad implications for identifying the limited factors for dryland forest ecosystems that are susceptible to natural water resource variations and human activities

Existence of Solutions of Second Order Boundary Value Problems with Integral Boundary Conditions and Singularities

By the notation and monotone convergence theorem of Henstock-Kurzweil integral, we investigate the existence of continuous solutions for the second order boundary value problems with integral boundary conditions in which the nonlinearities are allowed to have the singularities in t and are not Lebesgue integrable.</p

Numerical Analysis of Tooth Contact and Wear Characteristics of Internal Cylindrical Gears with Curved Meshing Line

In order to improve the contact strength and reduce the sliding friction of the gear pair, an internal cylindrical gear pair with a curved meshing line is studied in this paper. Firstly, a curved meshing line is designed. The tooth profiles of the internal gear pair with the designed meshing line are calculated by using differential geometry and the gear meshing principle. Secondly, a wear model is established by combining the finite element method and the Archard wear formula. Then, a numerical simulation is conducted; the relative curvature, sliding coefficient, sliding distance, maximum contact pressure, transmission error, and wear depth are calculated. Ultimately, the variation law of tooth surface wear of new gear with and without installation errors is observed under different stress cycles. On this basis, the influence of tooth modification on tooth surface wear is further researched. Through the results, the advantages of the introduced novel internal cylindrical gears in wear resistance are further demonstrated. The study in this paper provides new research ideas and methods for gear wear research and gear design

Toward the production of renewable diesel over robust Ni nanoclusters highly dispersed on a two-dimensional zeolite

Abstract Deoxygenation of bioderived lipids into renewable transportation fuels is a promising route to decreasing the dependence on fossil sources. Ni-based catalysts are high performing and cost-effective in deoxygenation reactions but suffer from severe sintering and aggregation. Herein, a ligand-chelating impregnation method was used to prepare highly dispersed Ni nanoclusters on a two-dimensional (2D) ITQ-2 zeolite. Comprehensive characterization was utilized to monitor the changes in the organometallic precursors during activation and to investigate their impact on the dispersion of the Ni nanoclusters on the ITQ-2 zeolite. The high external surface area and abundant surface defects of the 2D support enhanced the dispersion and immobilization of the Ni nanoclusters and outperformed conventional zeolites. The protection of the Ni2+ cations by the organic ligand suppressed the aggregation of Ni species during the activation processes, thereby leading to the formation of uniformly distributed Ni nanoclusters on the ITQ-2 zeolite. Due to the highly dispersed Ni nanoclusters and immobilization on the 2D zeolite, the Ni/ITQ-2-co material prepared by the ligand-chelating impregnation approach showed outstanding activity and stability for conversions of stearic acid or palm oil to diesel range alkanes. This work provides a rational design and precise modulation of metal-based catalysts for the production of renewable diesel

Optimization of proportions and solidification mechanism of all-solid waste cementitious materials based on circulating fluidized bed fly ash, calcium carbide slag, and red mud

In order to reduce carbon emissions and consume a large amount of low-quality solid waste, CFBFA-RM-CS has been developed by utilising the synergistic effect of circulating fluidised bed fly ash (CFBFA), red mud (RM) and calcium carbide slag (CS).The solidification mechanism of the ternary paste was studied from both macroscopic mechanical properties and microscopic experiments including XRD, FTIR, TG-DTG, SEM-EDS tests. The results showed that the main hydration products of CFBFA-CS-RM pastes were AFt and C/N-A-S-H, and the generation of hemialuminate and monoaluminate depended on the contents of RM and CS. The highest strength of the pastes was achieved when the hydration produced just the amount of AFt and the gel products that did not cause cracking.Ca(OH)2 is the main reactant that triggers pozzolanic reaction in CFBFA and solidification of RM. The 3d strengths of both CFBFA and CFBFA-CS pastes were less than 0.4 MPa, and cracking problems occurred，which were solved by the addition of RM, and the early strength of the pastes was significantly improved

Analysis of Support Design in Weak Rock Drift Using a Systematic Approach

The aim of this study is to develop a systematic approach for support design of weak rock drift based on empirical, analytical, and numerical method, which is employed to estimate weak rock support demand and design support system. Detailed engineering geological investigations and rock mechanics test have been carried out in weak rock drift. The Q-system and GSI-system were used to determine the primary support design and rock mass properties, respectively. The numerical model of RS2 finite element program has been calibrated by analyzing the relation of falling height observed in the field to the frictional angles obtained from empirical method, rock mechanics test, and calculated rock mass parameters, respectively. In an attempt to check the validity of sophisticated support, support suggested by Q-system, and the combination support system proposed by analytical approach, the RS2 program was employed to analyze the depth of plastic zone and total displacement surrounding the weak rock drift. Numerical results show that the depths of plastic zone and total deformation surrounding the weak rock drift supported by the combination support system significantly descended 87% and 90% of those of sophisticated support. In particular, the rock bolt and cable bolt provide enough frictional and interlocked forces to resist weak rock falling which change the weak rock mechanicals properties and the surface holding function reinforced by the shotcrete, wire mesh, and steel strap. The factor of safety (FOS) of 8.28 of the combination support system is much more than the FOS of 1.5 for permanent drift. The combination support system with rock bolts, cable bolt, shotcrete, wire mesh, and steel straps has been applied to stabilize the weak rock drift and found to be successful to prevent further deformations surrounding the drift

Comparative studies of semiconductor saturable absorber mirror mode-locking dynamics in pulsed diode-end-pumped picosecond Nd:GdVO4 and Nd:YAG lasers

Ultrashort pulses were generated in passively mode-locked Nd:YAG and Nd:GdVO4 lasers pumped by a pulsed laser diode with 10-Hz repetition rate. Stable mode-locked pulse trains were produced with the pulse width of 10 ps. The evolution of the mode-locked pulse was observed in the experiment and was discussed in detail. Comparing the pulse evolutions of Nd:YAG and Nd:GdVO4 lasers, we found that the buildup time of the steady-state mode-locking with semiconductor saturable absorber mirrors (SESAMs) was relevant to the upper-state lifetime and the emission cross-section of the gain medium

Clinical research of drug-coated balloon after rotational atherectomy for severe coronary artery calcification

Abstract Background Current research results show that drug-coated balloons (DCB) have unique advantages in the treatment of in-stent restenosis, small vessel disease, bifurcation lesions, and de novo lesions, but the data regarding rotational atherectomy (RA) followed by DCB treatment in calcified lesions, especially severe coronary artery calcification (CAC), are limited. Methods A retrospective study was conducted on 318 individuals with severe CAC who underwent RA-assisted PCI at the First Affiliated Hospital of Zhengzhou University from May 2018 to July 2021. Among them, 57 patients (RA/DCB group) were treated with DCB, and 261 patients (RA/DES group) were treated with drug-eluting stents (DES). The two groups' clinical baseline data, lesion characteristics, intraoperative complications, in-hospital adverse events, and major adverse cardiovascular and cerebrovascular events (MACCE) were compared throughout the follow-up period. Results The baseline clinical data, intraoperative complications, and in-hospital adverse events were not significantly different between the two groups. The anatomical categories in the RA/DES group were more complex and included left main coronary disease, bifurcation disease, and multivessel disease. Although target lesion revascularization (13.79% vs. 7.02%) and MACCE (18.77% vs. 12.28%) occurred more frequently in the RA/DES group than in the RA/DCB group, there was no statistically significant difference (p > 0.05). Multivariate Cox regression analysis showed that bifurcation lesions (HR 2.284, 95% CI 1.063–4.908, p = 0.034), total length of DCB/DES (HR 1.023, 95% CI 1.005–1.047, p = 0.014) and SYNTAX score (HR 1.047, 95% CI 1.013–1.082, p = 0.006) were independent risk factors for MACCE during the follow-up period. Conclusion Drug-coated balloon treatment after rotational atherectomy appears safe and effective in selected severe coronary artery calcification