干细胞研究与儿童牙齿

The Tooth Fairy could lose out on recovering the deciduous teeth children hide under thek pillows to scientists wanting to use them for stem cells.Scientists at the National Institutes of Health used the pulp (牙髓) in incisors (门牙) from seven and eight years old to grow nerve (勇气,胆量), fat and tooth cells.     

Effects of orthodontic load on the periodontium of autogenously transplanted teeth in beagle dogs

Objective:To observe the periodontal healing of autogenously transplanted teeth loaded orthodontically after autotransplantation in Beagle dogs.Methods:Forty-eight teeth were autogenously transplanted,24 of which were loaded postoperatively with orthodontic force at different time points and for different durations.Periodontal healing was evaluated by probing pocket depth(PPD),the expression of relevant proteins,and histomorphometric analyses.Results:The dental pockets of loaded and non-loaded teeth were both much deeper after the first postoperative week than before transplantation(P<0.05).Later,the PPD,which was measured after postoperative weeks 1,3,5,9 and 13,gradually became shallow.The expressions of alkaline phosphatase(ALP)and basic fibroblast growth factor(bFGF)were higher in loaded teeth than in non-loaded teeth(P<0.05),and in groups subjected to two weeks duration of loading than in other groups at the same load time point(P<0.05).For the same load duration,the expressions of ALP and bFGF in teeth loaded after postoperative week 4 were higher than those of other treatments(P<0.05).According to histomorphometric analyses,an orthodontic force on transplanted teeth applied after postoperative weeks 4 or 8 for two weeks duration should be favorable for periodontal healing.Conclusions:It is advisable to apply an appropriate magnitude of force on autotransplanted teeth,such as orthodontic force,at appropriate time points and for a suitable duration,to achieve the optimal clinical prognosis following autogenous tooth transplantation.These results may serve as a basis for subsequent studies in humans so as to make clinical improvements.     

Heat treatment process optimization for face gears based on deformation and residual stress control

In this paper, based on the principle of heat transfer and thermal elastic-plastic theory, the heat treatment process optimization scheme for face gears is proposed according to the structural characteristics of the face gear and material properties of 12Cr2Ni4 steel. To simulate the effect of carburizing and quenching process on tooth deformation and residual stress distribution, a heat treatment analysis model of face gears is established, and the microstructure, stress and deformation of face gear teeth changing with time are analyzed. The simulation results show that face gear tooth hardness increases, tooth surface residual compressive stress increases and tooth deformation decreases after heat treatment process optimization. It is beneficial to improving the fatigue strength and performance of face gears.     

Analysis of a load application point in spline coupling teeth

The objective of this paper is to investigate the position of the resultant force in involute spline coupling teeth due to the contact pressure distribution for both ideal and misaligned conditions. In general, spline coupling teeth are in contact all along the involute profile and the load is far from uniform along the contact line. Theoretical models available in publications consider the resultant contact force as it is applied at the pitch diameter, and this study aims to evaluate the error introduced within the confines of a common approximation environment. This analysis is carried out through using finite element method （FEM） models, considering spline couplings in both ideal and misaligned conditions. Results show that the differences between the load application diameter and pitch diameter are not very obvious in both ideal and misaligned conditions; however, this ap- proximation becomes more important for the calculation of the tooth stiffness.     

Non-undercutting condition and parameter optimization for cycloid ball planetary transmission

The transmission performance of cycloid ball planetary transmission (CBPT) is affected by cycloid tooth undercutting directly, and the design of CBPT can be optimized by the non-undercutting condition. Firstly, the theoretical equation of cycloid tooth is given, and the curvature radius of cycloid tooth profile is derived. Secondly, according to the relationship between the curvature radius and the distribution circle of balls, the non-undercutting condition of cycloid tooth profile is established, and the non-undercutting critical condition is deduced. Finally, the validity of the non-undercutting critical condition is verified by simulation. The result shows that the non-undercutting critical condition can be used to optimize the design of CBPT     

The Dog and the Fox

One day,a dog saw the skin(皮)of a lion in the garden;she began to tear it in pieces with her teeth.A fox,seeing her,said,“If this lion were alive(活着),you would soon find out that his claws(爪子)were stronger than your teeth.”寓意:It is easy to kick a man that is down.(人“弱”被人欺)The Dog and the Fox!河南@张勇刚…     

表示身体部位的词语在习语中的应用

我们知道,汉语中有很多词语包含表示身体部位的词。如:头重脚轻,眼高手低,手舞足蹈,耳熟能详,耳聪目明,目瞪口呆,胸有成竹,满面春风,心心相印,情同手足,蓬头垢面,大腹便便。英语中也有这样的习语。下面介绍一些这样的英语习语及其用法。一、英汉意义相似或相同的词语1.be arm ed to teeth武装到牙齿;全副武装。例如:arm ed to teeth.为了不让被夏日的骄阳晒伤,她全副武装起来。2.an eye for an eye/a tooth for a tooth以眼还眼/以牙还牙;一报还一报。例如:The thief stole a wallet and then he was robbed of som e m oney.It蒺sreallyan…     

牙仙女

The American children’s ritual of hiding a lost tooth under a pillow stems from an old German tradition of placing a lost tooth in a mouse or rat hole SO that when a new tooth grew in,it would possess the strong dental qualities of a rodent’S tooth.In America the “tooth rat”was replaced by the“tooth fairy”,who would compensate the child with money for surrendering a tooth to her.     

Quasi-static-model-based wear analysis of helical gears

A quasi-static wear model for helical gears is proposed based on finite element method and Archard’s formula to investigate the wear characteristics of tooth surface in real operation conditions. The numerical simulation reveals that the wear depth distributes unevenly along the tooth lead and varies along the tooth profile. The surface wear depth claims its minimal value at the pitch circle and reaches its maximal value near the tooth root of the pinion. The effects of misalignment on wear depth are further investigated to provide useful information for gear designers. The numerical simulation reveals that the vertical misalignment is more influential than the parallel misalignment on the gear wear depth. Therefore, to eliminate the negative effects of misalignment, the misalignment should be strictly controlled.     

常用口语表达

1.be fed up to the back teeth烦透了extremely irritated and fed up with something or someone烦透了某人或某事例如:I'm fed up to the back teeth with my job.我烦透了现在的工作。     

Mathematical modeling and characteristics analysis for the nutation gear drive based on error parameters

We focused on the mathematical modeling and characteristics analysis for the nutation drive based on error parameters. The crown gear tooth profile equation was introduced according to the national standard double circular arc tooth profile and based on the equal tooth strength principle. The nutation drive meshing coordinate system was set up by introducing the cone vertex error, tilt error, nutation angle error and spiral angle error. The tooth profile equations of the double circular arc external and internal spiral bevel gears were further obtained based on the crown gear tooth profile equation concerning above mentioned error parameters. The influences of the nutation gear reducer tooth contact conditions were analyzed with the gear tilt error and axial misalignment error. Finally, the correctness of the theoretical analysis was verified by the contact spot test.     

Excitation prediction by dynamic transmission error under sliding friction in helical gear system

Monte Carlo method was adopted to calculate the meshing error considering the manufacture error and assembly error of the meshing point along the time-varying contact line for helical gear pair. The flexural-torsion-axis dynamic model coupled was established under the tooth friction force and solved by the perturbation method to compute real dynamic tooth load. The change laws of the friction force and friction torque were obtained in a meshing period. The transmission error formulation was analyzed to introduce meshing excitations. The maximum dynamic transmission error, the maximum meshing force and the maximum dynamic factor were calculated under different speeds, external loads and damping factors. The conclusions can provide theoretical basis for the gear design especially in tooth profile correction.     

You Were There in My Dream,Too

It was a Saturday morning in May. When Mrs Turner opened the(1) and looked out, she smiled and said, ＂ It＇s going to (2) a fine(3) .＂She woke her small (4) up at eight thirty and said to him,(5) ,Teddy. We＇re going to the (6) today. Wash your (7) andface, brush your teeth (刷牙) and eat your (8) quickly. We＇re goingsoon.＂     

没有蛀牙

A smiling boy arrived home from a dental visit, “Hey mom, the dentist says I have no cavities. ”His mom stared at him wide-eyed and quite surprised, “It's impossible ——you never brush your teeth after cleaning the chocolate box before you go to bed!”Then the boy opened his mouth ———he had not a tooth left!“嘿,妈妈,牙医说我一颗蛀牙也没有。”妈妈惊讶地瞪大眼睛:“不可能———你每回上床睡觉前都把巧克力盒子里的糖一下子吃完,而且从来不刷牙!”这时,男孩儿张开了嘴巴———他的牙全被拔光了。没…     

逐层凝固原则在大链轮铸造工艺优化中的应用

In order to get a sound casting of the alloy with a solidification range, the principle of directional solidification (DS) and the layer-by-layer solidification(LBLS) should be followed, especially in designing foundry process of steel casting. Using the principles, the reasons for the forming of the defects on the surface of the chain wheels teeth and groove and the forming of MT (magnetic particle testing) thin lines were analyzed. The results of the metallographic observation and the numerical simulation show that the low temperature     

Under the Billow

It started with a lost tooth, but ended in a completely new discoveryOne morning last spring, my daughter, Laurel, paraded down the stairs wearing a silky pink dress, red plastic high heels and sparkling multicolor wings. She carried a wand. "Do you think the tooth fairy will come tonight?" she asked in a hushed, expectant voice. My daughter's gap-toothed smile showed that she anticipated a magical visitation.The tooth fairy never came during my own childhood. But that spring I began a round of visits to the dentist that brought back long-hidden memories. It all started with an exam where, to my surprise, I was told I would have to have a tooth pulled.     

蛀牙(英文)

Teeth are very important to our health. If our teeth are not in a good condition, we shall have difficulty in eating. Our digestion will then be affected.After eating, brush away the bits of food which get stuck between our teeth. If not, germs will grow on them. They will eat away the hard outside part of our teeth and they will become decayed. The hole the germs make is called a cavity.We can prevent cavities by brushing away the     

Laugh of the day WHERE ARE HIS FINGERS?

Alice: How did D avid lose the fingers ofhis righthand? Jenny: He putthem in a bull's (公 牛的 ) mouth to see how many teeth ithad. Alice: And w hathappened? Jenny :The bullclosed hism outh to see how many fingers he had.HONESTY (A m an whose is d…     

A Snake

There was a mouse near a horrific snake. Maybe the snake was very hungry. It was looking for something to eat. When the snake saw the mouse, it opened its eyes and rushed quickly up to the poor mouse. How dreadfull It suddenly opened its big bloody mouth and caught the mouse with its two terrible long teeth. Then it swallowed (吞咽) the mouse slowly. The poor mouse became the snake's nice dinner! From then on, I think the snake is very uqly and I hate it.     

英语广告知多少?

1.Good teeth,good health.牙齿好,身体就好。这是Colgate(高露洁)牙膏的广告词。这句广告标语简洁押韵,且对仗工整,流行甚广。2.Good to the last drop.滴滴浓香,意犹未尽。这是Maxwell House(麦氏)咖啡的广告标语。这句话是美国第26届总统西奥多·罗斯