对称

The aluminium powder has been used to reduce titanium tetrachloride to generate the low valent titanium reagent which can induce the reductive coupling of aldehydes and ketones to form the corresponding pinacol s.

以价廉易得的铝粉还原四氯化钛制得低价钛，将其用于醛酮还原偶联，合成了6种片呐醇，其中对称片呐醇4种，不对称片呐醇2种。

Expanding pinacol reductive coupling reaction into asymmetric one with both diastereoselectivity and enantioselectivity may lead to its application in synthesising medicaments and biologic active compounds with structure of vicinal diol. Asymmetric pinacol coupling reaction is also the most compact and effecient method in synthesizing chiral ligands or chiral auxiliary with C〓 symmetry.

将这一反应发展成为既有高度的非对映选择性，又有高度对映选择性的不对称偶联反应在合成许多含有手性邻二醇结构的药物或生物活性物质将有更重要的应用，同时不对称Piancol偶联反应也是合成C〓对称性的邻二醇多用途手性配体或手性助剂的最为简捷有效的方法。

If the trauma induced intracranial pneumatosis accompanied by cerebrospinal rhinorrhea is not treated in time, it will result in chronic post-traumatic tension intracranial pneumatosis, symmetrical or asymmetrical air aggregation, which will occupy the space of cranial cavity and produce a space-occupying effect, it can compress and stimulate the brain tissue.

外伤致颅内积气伴脑脊液鼻漏治疗不及时会造成慢性外伤后张力性气颅，对称或非对称空气积聚，占据颅腔空间，产生占位效应，压迫并刺激脑组织。

A new unsymmetrical metal porphyrin- 5-{4-[3-(2-nitro-phenoxyl) propoxy]phenyl }-10, 15, 20-tri-(4-methoxy phenyl )porphyrin copper (compound Ⅱ)was synthesized,and its UV-Vis spectra were measured and compared with other three symmetrical metalporphyrins.

本文合成了一个新的非对称卟啉铜化合物，测量了其紫外－可见光谱，并将此光谱结果与其他三种对称金属卟啉的光谱进行了比较。

Four symmetrical and asymmetrical pyrylium - squarylium cyanine dyes were synthesized.

合成了四个对称及不对称含叔丁基吡喃鎓方酸的菁染料，通过光谱和元素分析确定其结构，测定了它们的紫外-可见吸收光谱、熔点和溶解性能。

The unusual quality of one tie up of the space-energy make the gravitation of quantum spatial measurement cosmic energy, lave the absolute point of unusual quality one tie up of in cosmic time-space, come to do not symmetrically gradually belong to stabilization thus at reductively fluctuate, not can reversely strides across reach the stable state of limitedly relatively not symmetry, come to do the circle of shut locus thus infinite continuous stable strides across.

宇宙能量的宇称量子的空间能使引力的一维奇性，偏离在宇宙时空中的一维奇性的绝对点，成不对称地递归于稳定而在缩小地波动，不可逆地跨越到有限地相对不对称的稳定状态，成为闭合轨迹圆而无限延续的稳定跨越。

Methods 11 cases with asymmetry of the submammary fold were treated with the semi-periareolar insion, and separated the retromammary space, and then cutted up-part of the breast tissue according to the value of asymmetry and fixed upward, and incised part of the skin also(9 cases were done mama augmentation simultaneously).

对11例乳房下皱襞不对称患者，采用乳晕上缘半环形切口，游离乳房后间隙，根据双侧不对称的差值，将过低侧乳房的上极腺体组织弧形切除并向上与胸肌筋膜缝合固定（其中9例同期行隆乳术），切口上缘皮肤作适当切除。

The bilateral asymmetry in force exerted on the scoliotic spine may be the cause.

双侧的不对称改变引起的肌肉组织力量的不对称可能是侧凸的原因之一。

Necessary and sufficient conditions for the matrix equation to have symmetric positive semidefinite solutions are derived using the generalized singularvalue decomposition.

利用广义奇异值分解导出了该矩阵方程有对称半正定解的充分必要条件，并且给出了一般对称半正定解的表达式

In the fifth chapter,we study dipolarizations in some quadratic Lie algebras.Inthe first section,we obtain some results on the classification of dipolarizations in gen-eral quadratic Lie algebras,and prove that there exist dipolarizations in the solvablequadratic Lie algebras whose Cartan subalgebras consist of semisimple elements.

第五章讨论了某些二次李代数的双极化，在第一节中，我们给出了二次李代数的双极化的一些分类结果；特别证明Cartan子代数是由半单元组成的二次李代数上存在双极化，第二节确定了四维扩张Heisenberg代数的所有双极化，在第三节中，我们构造了2n+2维扩张Heisenberg代数的六类双极化，我们发现两个不同于半单李代数情形的有趣事实：（1）在扩张Heisenberg代数上同时存在对称和非对称双极化；（2）对应于扩张Heisenberg代数的双极化的特征元有的是半单的有的是幂零的。

Breath, muscle contraction of the buttocks; arch body, as far as possible to hold his head, right leg straight towards the ceiling (peg-leg knee in order to avoid muscle tension).

呼气，收缩臀部肌肉；拱起身体，尽量抬起头来，右腿伸直朝向天花板（膝微屈，以避免肌肉紧张）。

The cost of moving grain food products was unchanged from May, but year over year are up 8%.

粮食产品的运输费用与5月份相比没有变化，但却比去年同期高8％。