球头立铣刀周齿螺旋面的刃磨

本文从理论上阐明了用干涉法磨削螺旋槽的原理，研究了砂轮安装参数对周齿径向前角ｒｆ的影响，并通过实验证明了所推导公式的正确性，为刃磨螺旋周齿时正确选择砂轮的安装参数提供了依据。

铣刀周齿螺旋前刀面的刃磨

用无瞬心包络法求出螺旋前刀面与砂轮的空间接触线,用圆上的一段圆弧近似代替实际接触线,便可确定砂轮的安装参数,再用反包络法形成所需的螺旋前刀面。从而解决了生产中需要多次试磨的麻烦。

一种粗铣刀周齿分屑槽的数控磨削工艺算法

针对粗铣刀分屑槽形状的磨削工艺,对粗铣刀周齿分屑槽结构参数进行了定义,建立了加工坐标系及切深引导曲线方程;借助运动学理论,提出了砂轮磨削姿态和砂轮磨削轨迹的计算方法;在VC++环境开发了一套算法模块,并对其进行了仿真验证及与Numroto磨削软件的仿真结果对比。结果表明,该轨迹算法能够较好的实现预期效果,具有较好的刀具结构扩展性和加工精度。

立铣刀周齿分屑槽的砂轮磨削轨迹算法研究

周齿分屑槽是粗加工铣刀的一种新型结构,可减小切削刃宽度,便于排屑,降低切削力,改善刀具切削性能,提高刀具使用寿命。为了提高周齿分屑槽的磨削加工精度和结构参数适应性,研究了周齿分屑槽在数控磨削过程中的砂轮磨削轨迹求解方法,定义了周齿分屑槽相关坐标系及其转换关系,定义了周齿分屑槽的结构参数和砂轮磨削基准姿态,构建了周齿分屑槽的槽底控制曲线模型。在此基础上,运用坐标变换矩阵描述砂轮运动方式,推导了基于工件坐标系的砂轮磨削轨迹的计算方法,编写了基于VC++环境的程序算法,输出得到工件坐标系下的砂轮磨削位置和姿态,并进行一系列仿真测试,验证了该磨削轨迹算法的有效性。

固齿健周丸治疗慢性牙周炎的临床观察

目的观察中药固齿健周丸治疗慢性牙周炎的疗效。方法选中重度慢性牙周炎患者20例,随机分为2组。实验组给予固齿健周丸和牙周基础治疗,对照组给予利君沙、甲硝唑和牙周基础治疗。记录2组检测指标。结果 2组治疗后牙周附着水平(PAL)、牙周探诊指数(PPD)、牙周探诊出血指数(BOP)都有明显改善(P均<0.01)。治疗后BOP 2组比较有显著性差异(P<0.01)。结论固齿健周丸治疗牙周病疗效显著。

Effects of Aging on the Proliferation and Differentiation Capacity of Human Periodontal Ligament Stem Cells

periodontal ligament stem cells; aging; proliferation; osteogenic differentiation Objective The aim of this study is to investigate the proliferation, differentiation and apoptosis of periodontal ligament stem cells （PDLSC） derived from different aged donors, and to evaluate the effects of aging on the biological characteristics of PDLSC. Methods Periodontal ligament tissues were obtained from 24 surgically extracted human premolars during orthodontics therapy. The specimens were divided into three groups according to the donor’s age. Group A： 18-20 years, group B： 30-35 years, group C： 45-50 years. PDLSC were isolated and cultured using a tissue-block-based enzymolytic method by limiting dilution assay. The colony forming efficiency of PDLSC for three experimental groups was determined. Senescence-Associated β-Galactosidase （SA-β-G） expression in the three groups was examined using β-galactosidase staining working solution. Cell cycle and apoptosis of the PDLSC were examined by the flow cytometry. Alkaline phosphatase （ALP） activity was evaluated by ALP staining. The expression of osteoplastic differentiation related genes Runt-related transcription factor-2 （Runx-2）, Collagen Type 1 （col-1）, and ALP of PDLSC were examined by quantitative real-time RT-PCR. Results The colony forming efficiency of PDLSC in Group A, B and C was 36.67%, 22.67% and 9.33%, respectively, which decreased with donors’ age （P〈0.05）. SA-β-G expression of the senescent PDLSC in group A, B and C were 4.14%, 16.39%, 50.38%, respectively （P〈0.05）. Cells in G2/S phase was 38.73%, 29.88%, 18.25% （P〈0.05）, and the apoptosis rate was 1.57%, 4.56%, 5.84% （P〈0.05）, in group A, B and C respectively. The ALP staining in the three groups decreased with the increase of donors’ ages, and the expression of Runx-2, col-1 and ALP decreased gradually from group A to group C （all P〈0.05）, which indicated the osteogenic differentiation capacity of PDLSC decreased while donor aging. Conclusion Human PDLSC could be successfully isolated from periodontal ligament tissues of different aged donors. However, the proliferation and osteogenic differentiation capacity of PDLSC decreased while donor aging.

Periodontal and inflammatory bowel diseases: Is there evidence of complex pathogenic interactions?

Periodontal disease and inflammatory bowel disease(IBD) are both chronic inflammatory diseases. Their pathogenesis is mediated by a complex interplay between a dysbiotic microbiota and the host immuneinflammatory response, and both are influenced by genetic and environmental factors. This review aimed to provide an overview of the evidence dealing with a possible pathogenic interaction between periodontal disease and IBD. There seems to be an increased prevalence of periodontal disease in patients with IBD when compared to healthy controls, probably due to changes in the oral microbiota and a higher inflammatory response. Moreover, the induction of periodontitis seems to result in gut dysbiosis and altered gut epithelial cell barrier function, which might contribute to the pathogenesis of IBD. Considering the complexity of both periodontal disease and IBD, it is very challenging to understand the possible pathways involved in their coexistence. In conclusion, this review points to a complex pathogenic interaction between periodontal disease and IBD, in which one disease might alter the composition of the microbiota and increase the inflammatory response related to the other. However, we still need more data derived from human studies to confirm results from murine models. Thus, mechanistic studies are definitely warranted to clarify this possible bidirectional association.

Hydrodynamic Behavior in a Rotating Zigzag Bed

As a high gravity(HIGEE)unit,the rotating packed bed(RPB)uses centrifugal force to intensify mass transfer.Zigzag rotating bed(RZB)is a new type of HIGEE unit.The rotor of RZB consists of stationary discs and rotating discs,forming zigzag channels for liquid-gas flow and mass transfer.As in RPBs,some hydrodynamic behavior in RZB is interesting but no satisfactory explanation.In this study,the experiments were carried on in a RZB unit with a rotor of 600 mm in diameter using air-water system.The gas pressure drop and power consumption were measured with two types of rotating baffle for RZB rotors,one with perforations and another with shutter openings. The circumferential velocities of gas were measured with a five-hole Pitot probe.The pressure drop decreased rapidly when the liquid was introduced to the rotor,because the circumferential velocity of the liquid droplets was lower than that of the gas,reducing the circumferential velocity of gas and the centrifugal pressure drop.The power consumption decreased first when the gas entered the RZB rotor,because the gas with higher circumferential velocity facilitates the rotation of baffles.

Stability of motion state and bifurcation properties of planetary gear train

A nonlinear lateral-torsional coupled vibration model of a planetary gear system was established by taking transmission errors,time varying meshing stiffness and multiple gear backlashes into account.The bifurcation diagram of the system's motion state with rotational speed of sun gear was conducted through four steps.As a bifurcation parameter,the effect of rotational speed on the bifurcation properties of the system was assessed.The study results reveal that periodic motion is the main motion state of planetary gear train in low speed region when ns<2 350 r/min,but chaos motion state is dominant in high speed region when ns>2 350 r/min,The way of periodic motion to chaos is doubling bifurcation.There are two kinds of unstable modes and nine unstable regions in the speed region when 1 000 r/min<ns<3 000 r/min.

STUDY ON ADHERENCE ABILITY OF PERIODONTAL PATHOGENS AND CARIOGENIC BACTERIA TO HYDROXYAPATITE DISKS

Objective To study the adherence activity of six representative periodontopathic and cariogenic bacteria to hydroxyapatite disks. Methods Six periodontopathic and cariogenic bacteria of P. gingivalis, A. actinomycetemcomitans, F. nucleatum, S. sanguis, A. viscosus and S. mutans were cultured in modified MD-300 chemostat according to total fifteen experimental groups of single-specie and each pair of periodontal pathogens and cariogenic bacteria, respectively. After 1h attached live bacteria on removable hydroxyapatite disks was analyzed by culture technologies to evaluate the adherence level. Results The adherence activity of periodontopathic and cariogenic bacteria to HA was in the following order: S. sanguis > A. viscosus> S. mutans> A. actinomycetemcomitans > F. nucleatum > P. gingivalis. The number of periodontopathic bacteria to HA was enhanced by S. sanguis and A. viscosus,respectively.When mix-cultivated with S. mutans, the colonization of P. gingivalis was reduced significantly(P<0.001). Periodontopathic bacteria had no effect on the adherence activity of S. mutans and A. viscosus, except S. sanguis. Conclusion It was showed that the adherence activity of periodontal pathogens was weaker than that of cariogenic bacteria and emphasized the importance of bacterial adherence in determining the level of bacterial colonization on tooth surfaces. It was suggested that periodontopathic bacteria can utilize initial colonizers to become those predominant bacteria in periodontal ecosystem, which maybe have close relation to the periodontopathic mechanism.

To a Question about Forecasting Number of Micromammalia （Rodentia）

In the present study, the data for population dynamics of micromammalia in Dnipropetrovs＇k Region in 1957-1999 and Dnipro-Orel＇s Natural Reserve at 1991-2009 are adduced. With the purpose to drawing up of the long-term forecast at number are analyzed long-term lines of number on background kind＇s fine micromammals of dominant group. The analysis of long standing rows of number small mammals and comparison data with Wolf number were demonstration, which indicate that dynamic of number phone species （and dominant in particular） carry a cyclic character and contact with 11-year cycles of sun activity. Consequently, it was clearing up hidden periodical in dynamic of number mouse rodents. By that observation was dependence from cycles of sun activity. Probably, that in 2012 year, before peak of sun activity in 2013, next high increase about the number of small mammals for maxima （＂outbreak＂ mass reproduction is a peak ＂big wave＂） will take place.