高效液相色谱法测定食品中的富马酸二甲酯

采用高效液相色谱法测定食品中的富马酸二甲酯.样品中的富马酸二甲酯经甲醇提取后,以甲醇-乙酸铵溶液(体积比为55∶45)为流动相,C18色谱柱分离,二极管阵列检测器检测,检测波长为210 nm,外标法定量.方法的线性范围为1～16μg/mL(r=0.99987),检出限为0.1μg/g,测定结果的相对标准偏差为0.54%...     

Direct condensation of sulfonamide and formamide: NaI-catalyzed synthesis of N-sulfonyl formamidine using TBHP as oxidant

A new N-sulfonyl formamidine synthesis was developed via NaI-catalyzed direct condensation of sulfonamide and formamide. The green methodology is featured by high atom economy, easily available starting materials, the lack of need for a transition-metal catalyst, no requirement of hazardous reagent, operational simplicity, and good tolerance with diverse functional groups. Mechanistic studies suggest that the protocol proceeds based upon in situ generated TsN·NaI.     

Scars of discrete rotational bands in hot nuclei

Rotational motion loses its coherence as a function of the nuclear internal excitation energy. The damping process does not proceed in a continuous fashion and scars of discrete rotational bands are found, inbedded in a background of damped rotational states, regardless whether the calculations are carried out using effective or “random” forces. The complexity of the damping mechanism is revealed in the lineshape of the ridges in the γ-γ correlation spectrum.     

Note on: N.E. Aguilera, M.S. Escalante, G.L. Nasini, “The disjunctive procedure and blocker duality”

Aguilera et al. [Discrete Appl. Math. 121 (2002) 1–13] give a generalization of a theorem of Lehman through an extension of the disjunctive procedure defined by Balas, Ceria and Cornuéjols. This generalization can be formulated as(A) For every clutter , the disjunctive index of its set covering polyhedron coincides with the disjunctive index of the set covering polyhedron of its blocker, .In Aguilera et al. [Discrete Appl. Math. 121 (2002) 1–3], (A) is indeed a corollary of the stronger result(B) .Motivated by the work of Gerards et al. [Math. Oper. Res. 28 (2003) 884–885] we propose a simpler proof of (B) as well as an alternative proof of (A), independent of (B). Both of them are based on the relationship between the “disjunctive relaxations” obtained by and the set covering polyhedra associated with some particular minors of .     

应用宽带光源测量h参数

对保偏参数ｈ的测量进行了实验研究。对宽带光源与窄带光源的测量结果进行对比分析后，提出一种使用高精度白光源的ｈ参数测量装置。用此装置可以在０．４μｍ到１．８μｍ波长范围的中心波长连续可调测量，谱带宽度可以在１０ｎｍ到７０ｎｍ间连续可调。获得的测量结果准确可靠。     

From discrete rotational bands to damped rotational motion

We present shell model calculations for warm rotating nuclei, combining the cranked Nilsson mean field and a residual surface-delta two-body interaction. The model is used to describe the transition from the region of well-defined rotational bands into the region dominated by rotational damping, and the results are in overall agreement with the experimental findings.     

Computer simulation of magnetic-field patterns from the human cardiac conduction system

Summary Invasive and noninvasive measurements of the electric and magnetic signals of thePR segment of the human cardiac cycle have been performed during the last decade. It is still questionable whether the detected signals are produced by the activity of the heart conduction system or by atrial repolarization. We present a computer simulation of the magnetic-field patterns generated by a model of the human-heart conduction system (His-Purkinje system, HPS) over the anterior chest wall. The model is based on a close correspondence with the anatomical features of the HPS and accounts for the common His bundle (HB) and the left bundle branch (LBB) only. Computed fields clearly indicate a “ramp” pattern, strongly depending on the position over the chest. The model provides also a spikelike signal at the beginning of the ramp corresponding in time to the propagation of the activation from the HB to the proximal LBB. Both features are in good agreement with results of experimental measurements, thus supporting the hypothesis that the detected field patterns originate from HPS activity. A qualitative comparison with an experimental magnetocardiographic map is also shown.

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Riassunto Durante gli ultimi dieci anni sono state eseguite misure invasive e non invasive di segnali elettrici e magnetici relativi al segmentoPR del ciclo cardiaco umano. è ancora oggetto di discussione se i segnali rivelati siano prodotti dall'attività del sistema di conduzione cardiaco o dalla ripolarizzazione atriale. In questo articolo si presenta una simulazione, eseguita mediante computer, dei segnali magnetici generati da un modello del sistema di conduzione cardiaco umano (sistema di His-Purkinje, HPS) sulla parte anteriore del torace. Il modello è strettamente connesso alle caratteristiche anatomiche dell'HPS e prende in considerazione soltanto il tratto iniziale del fascio di His (HB) e la branca sinistra (LBB). I campi magnetici calcolati evidenziano chiaramente un andamento cosituito da rampe la cui ampiezza dipende fortemente dalla posizione in cui il campo è calcolato. All'inizio della rampa è anche presente un segnale corrispondente in tempo al passaggio dell'attivazione dall'HB all'adiacente LBB. Entrambi i comportamenti (rampa e punta) sono in buon accordo con le misure sperimentali e ciò sostiene l'ipotesi che i segnali magnetici sono originati dall'attività dell'HPS. Si mostra infine un confronto qualitativo con una mappa sperimentale magneto-cardiografica del trattoPR.

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Реэюме В течение последнего десятилетия были проведены измерения элек-трических и магнитных сигналов дляPR сегментов џикла кровообрщения человека. Однако еще не выяснено, являются ли зарегистрированные ситналы проявлением системы сердечного кровообращения или проялением артериалъной переполяри-заџии. Мы предлагаем компъюторное моделирование магнитного поля, основанное на модели системы кровообращения сердџа человека в передней стенке грудной клетки. Предложенная моделъ основана на близком соответствии с анатомическими особэенностями системы кровообращения сердџа и объясняет обычный сердечный узел и левую узла. Вычисленные поля явно обнаруживают картину с “укло-мом”, которая силъно зависит от пояожния относителъно грудной клетки. Предло-женная моделъ также обеспечивае↦ пико-подобный сигнал в начале “уклона”, соответствующий по времени рацпространению активности от сердечного уз←а к Близайщей левой ветви узла. Обыe особенности хорошо согласуются с результатани экслериметальных измерений, что лодтверждает нашу чипотезу, что заречистрированные диачраммы полей являются лроявлением системы кровообращемия сердца. Также приводится качественное сравнение с экспериментальной мачнитнокардиосрафической картой.

     

Resolving conflicting crystallographic and NMR models for solution-state DNA with solution X-ray diffraction

We report on synchrotron-based high-angle X-ray solution scattering measured to 2 A resolution for two synthetic DNA sequences for which there are conflicting X-ray crystal and solution NMR models. Our results demonstrate that high-angle X-ray scattering discriminates between differing X-ray crystal and NMR models for solution-state DNA and provides a direct, independent method for testing structural models and measuring solution-state configurational dispersions.     

Density of states and asphericity of electron distribution in ferromagnetic Co-Ni alloys

The coherent potential approximation has been extended in order to treat the case of multiple bands in ferromagnetic substitutional binary alloys. The concentration dependence of total magnetic moments and their aspherical contribution, e_g and t_2g, were derived and compared with experimental data in Co-Ni f.c.c. alloys.