火焰原子吸收和发射光谱法测定盐湖卤水中的钙

在波长422.7nm下,用火焰原子吸收和发射光谱法测定了盐湖卤水中钙的含量,考察了酸度及共存离子对测定结果的影响,并对两种方法的优缺点进行了比较.结果表明,原子吸收光谱法受酸度及共存离子的影响较小,火焰发射光谱法测定钙的灵敏度比原子吸收光谱法高,两种方法的RSD均小于2%,加标回收率介于103.7%-107.2%.     

Great circle links and virtually fibered knots

We show that all two-bridge knot and link complements are virtually fibered. We also show that spherical Montesinos knot and link complements are virtually fibered. This is accomplished by showing that such manifolds are finitely covered by great circle link complements.     

Pseudoarcs, pseudocircles, Lakes of Wada and generic maps on

We prove a Bruckner–Garg type theorem for the fiber structure of a generic map from a continuum X into the unit interval I. We also study the specific case of X=S². We show that each nondegenerate component of each fiber of a generic map in C(S²,I) is figure-eight-like. This together with a result by Krasinkiewicz and Levin gives that each nondegenerate component of each fiber of a generic map in C(S²,I) is hereditarily indecomposable and figure-eight-like. We also show that pseudoarcs, pseudocircles and Lakes of Wada appear in abundance in fibers of a generic map in C(S²,I). We also exhibit a general method for proving when a P-like hereditarily indecomposable continuum is Q-like when Q is a certain graph containing P.     

亚热带高原湖泊水质方程一类自由初边值问题

亚热带高原湖泊除了有来自工业、农业，生活污水及落尘的外部污染，还有来自湖泊藻类水生生物循环及底泥的污染物释放内污染源污染。因此，由于进出水量不均衡性导致湖水边界的自由变动。本文首先运用微元分析法导出在外源和内源双重污染下湖泊水质模型，然后对一类自由初边值问题通过对非柱形边界条件的齐次约化，运用变分型算子的向量扩张和拟单调方法获得解的存在性、唯一性。     

Contrast-enhanced magnetic resonance tomoangiography: A new imaging technique for studying thoracic great vessels

The authors propose a new imaging approach for studying thoracic great vessels, using high-speed MR imaging combined with intravenous rapid bolus injection of a paramagnetic contrast media. The decrease of the T₁ relaxation time of flowing blood induced by the contrast agent (Gd-DOTA) caused an increased signal intensity within the vessel lumen for a time period allowing multiplanar imaging of various vascular structures. The intraluminal signal enhancement is mainly related to the blood concentration of the contrast agent as in conventional X-ray angiography. Information on the aorta and pulmonary arteries obtained by the so-called contrast-enhanced magnetic resonance tomoangiography appears complementary to that obtained with other vascular MR imaging procedures such as cine-MRI and magnetic resonance angiography (MRA).     

Elastic and inertial effects in pulsatile flow of polymeric liquids in circular tubes

In the earlier theoretical work of Barnes, Townsend, and Walters on pulsatile flow of viscoelastic fluids, it was found that an Oldroyd model predicted that flow enhancement should decrease with increasing frequency of pulsation, whereas their experimental data showed an increase. Their calculations have been repeated for the Goddard—Miller model using two different expressions for the relaxation modulus; it is found that the Goddard—Miller model leads to the same discrepancy between theory and experiment. It is tentatively concluded that secondary-flow effects are playing an important role. The role of the elastic and inertial effects and the role of the shape of the viscosity vs. shear rate curve are discussed.     

Organometallic derivatives of penicillins and cephalosporins a new class of semi-synthetic antibiotics

Novel semi-synthetic derivatives of penicillin and cephalosporin have been prepared in which the conventional phenyl or heteroaromatic group has been replaced by a ferrocene moiety, and in which the metal atom is in close proximity to the β-lactam ring of the antibiotic; several of the compounds exhibit high antibiotic activity and others are potent β-lactamase inhibitors.     

利用ICP-AES中钙的主次灵敏线同时测定各种盐湖卤水中的钙

等离子发射光谱（ICP-AES）已广泛应用于医学,地质,水质,环境等领域的检测。本文利用钙的主、次灵敏线同时测定盐湖卤水及盐水中各种不同含量的钙,其加标回收率在94.0%—100.8%范围内,与经典的容量法对比,数据能满足要求,样品浓度小于100mg/L时用灵敏线Ca317.9nm测定,样品浓度大于100mg/L时用次灵敏线Ca210.3nm测定。此法快速、准确,结果令人满意。     

Photochemische reaktionen von übergangsmetall-olefin-komplexen: XI. [4+ 6]-cycloaddition von tricyclo[6.3.0.02,7]undeca-3,5-dien antricarbonyl-η6-1,3,5-cycloheptatrien-chrom(0)

The photochemical reaction of tricarbonyl-η⁶-1,3,5-cycloheptatriene-chromium(0) (I) with tricyclo[6.3.0.0^2,7]undeca-3,5-diene (II) in n-pentane at 248 K yields the [4 + 6]-cycloadduct tricarbonyl-η⁶-pentacyclo[7.6.2.1^10,15.0^2,8.0^3,7]octadeca-11,13,16-triene-chromium(0) (III). Detachment of the pentacyclic triene ligand from chromium can be achieved with trimethylphosphite. The constitutions of complex III and of the pentacyclic hydrocarbon IV were determined by spectroscopic means.     

大数定律和中心极限定理在保险业中的重要应用

结合《车祸赔付倍涨,车险保额不涨?》报道,阐述了大数法则和中心极限理论在保险中的重要作用.经过分析计算,当机动车第三者保险金额不超过20万元时,保险公司的预期利润最有保障,这就说明了目前机动车第三者责任险最高只能投保20万元的根本原因.