An Improved Procedure for Cyclisation of Chalcones to Flavanones Using Celite Supported Potassium Fluoride in Methanol: Total Synthesis of Bavachinin

Chalcones may be cyclised to the corresponding flavanones by stirring with KF-celite suspended in methanol at reflux. This method gives consistently higher conversion than other reported procedures and its utility is illustrated by the synthesis of the linear prenylated flavanone bavachinin.     

Hydrogen bonded rings,chains and lassos: the case of t-butyl alcohol clusters

Infrared OH stretching spectra of hydrogen bonded 2-methyl-propan-2-01 (t-butyl alcohol) clusters are investigated by ragout-jet FTIR spectroscopy. A spectral difference technique is used to discriminate approximately between neighbouring cluster sizes. Dimers, trimers and cyclic tetramers can be detected along with larger clusters, which exhibit a surprisingly structured vibrational fingerprint. Comparison is made to the spectra of related alcohols and to energetic and harmonic vibrational predictions from electronic structure calculations. The experimentally observed 32% increase in OH stretching wavenumber shift from methanol dimer to t-butyl alcohol dimer is reproduced at the HF/3-21G level (+ 33%). It is also qualitatively correct at the MP2/6-31 +G* level (+ l5%), whereas it has the wrong sign at the B3LYP/6-31+ G* level (5%) and is negligible at the HF/6-31+ G* level, disregarding anharmonic effects. The cyclic tetramer of t-butyl alcohol is found to be particularly stable due to a favourable updown alternation of the bulky t-butyl groups. Beyond the t-butyl alcohol tetramer, lasso structures are found to be energetically competitive with simple ring structures. A many-body decomposition shows that this is due to a reduced cooperativity in the sterically hindered pentamer ring. The resulting thermodynamic and kinetic relevance of cyclic tetramers is discussed.     

聚焦形貌恢复方法模型设计

采用基于拉普拉斯算符聚焦形貌恢复方法,提出了模拟目标深度测量的数值模型。数值模拟的核心是基于通过几何光学预测的理想图像的卷积与透镜广义孔径函数的多色点扩散函数,即用聚焦误差替代抛物线圆柱形貌或高斯函数。该模型可以使用基于聚焦形貌恢复方法的传感器真实组件参数、光源光谱、光学系统离差、相机的光谱灵敏度。提出了光学系统离差（消球差、消色差、色差）对确定目标表面形貌的精确度和可靠性的影响。结果表明,该模型可以有效提高实验效率,缩短时滞,降低成本。     

Possible contribution of low-l waves to the deep inelastic collisions of 32S with 27Al

The deep inelastic reactions of ³²S with ²⁷A1 have been studied at incident energies of 152.6 and 175 MeV by measuring inclusive fragment distributions, fragment-fragment and fragment-light particle coincidences. The observed Q-value distributions of the primary deep inelastic process range down to large negative Q-values as predicted by time-dependent Hartree-Fock calculations in the presence of low partial waves. No distinct low-l window for deep inelastic reactions can, however, be inferred from the data.     

CIRCULAR DICHROISM SPECTRA OF SYSTEM I PARTICLES FROM NORMAL CHLOROPLASTS AND CAROTENOID-DEFICIENT MUTANTS OF MAIZE

Abstract— Circular dichroism (CD) spectra were studied in System I particles prepared by digitonin fragmentation of chloroplasts of normal maize and carotenoid-deficient mutants. CD bands of pigment molecules were found to be higher in particles than in solutions. This phenomenon was most pronounced for the particles containing the carotenoid composition of normal chloroplast lamellae. The CD signal of chlorophylls bound to particles of carotenoid-deficient chloroplasts was closer to that found in solutions. This indicates that aggregation and/or binding of chlorophylls in carotenoid-deficient mutants may be less extensive than in normal chloroplasts.     

Profiling and biomarker identification in plasma from different Zucker rat strains via high mass accuracy multistage mass spectrometric analysis using liquid chromatography/mass spectrometry with a quadrupole ion trap-time of flight mass spectrometer

High mass accuracy electrospray ionisation multistage tandem mass spectrometry (MS(n)) was applied to metabolite profiling studies on plasma samples derived from two strains of rat (the Zucker (fa/fa) obese strain and the normal wild type). Using a quadrupole ion trap time-of-flight (QIT-TOF) mass spectrometer, metabolite profiling software was applied to locate components of biological significance that could account for the differences between the two strains of rat and a formula prediction software tool was used to help identify individual components. The primary factor discriminating between the two populations was the concentration of endogenous lipids. In the Zucker (fa/fa) obese strain, the dominant ion signals and MS(n) spectra were in agreement with lysoglycerophosphocholine components such as palmitoyllysophosphatidylcholine, 1-oleoylglycerophosphocholine, 1-octadecyl-sn-glycero-3-phosphocholine and 1-stearoylglycerophosphocholine and these were found in relatively higher concentrations compared to the normal wild type. Components were identified using high mass accuracy MS(n) data, formula prediction software and by agreement with published mass spectra through internet databases, rather than using a conventional approach with authentic standards. This application shows that the use of high mass accuracy electrospray ionisation MS(n) together with a software tool can be used effectively to detect and characterise unknown analytes in complex matrices, and represents a promising approach for future profiling studies.     

Lateral electric field effects on quantum size confinement in cylindrical quantum dot under parabolic potential

Within the effective mass approximation, we investigated theoretically the ground-state energy of a single particle and the binding energy of the neutral donor impurity (D⁰) affected by a lateral electric field in a parabolic quantum dot (QD). The results show that the electron and the hole ground-state energy and the band to band transition energies shift to lower values (red shift) by increasing the field intensity. The quantum Stark shift (QSS) for the electron increases rapidly in the quasi spherical QD (QSQD) by increasing the lateral field, whereas for the hole it increases monotony. In the cylindrical QDs (CQDs), we found that the QSS for electron and hole increase monotonically. The quantum size, lateral electric field and impurity position effect on the binding energy of neutral donor (D⁰) is studied. Unexpected behavior of D⁰ in quantum well limit (QW), the binding energy of D⁰ is increasing (blue shift) with increasing QD radius R$R$ at the presence of a lateral electric field. It appears that for a fixed size of the QD, the off-center binding energy decreases when the impurity ion is displaced from the center to the QD borders, while it is shifted to lower energy with increasing the field.     

Global Optimization: On Pathlengths in Min-Max Graphs

Let f be a smooth nondegenerate real valued function on a finite dimensional, compact and connected Riemannian manifold. The bipartite min-max graph is defined as follows. Its nodes are formed by the set of local minima and the set of local maxima. Two nodes (a local minimum and a local maximum) are connected in by means of an edge if some trajectory of the corresponding gradient flow connects them. Given a natural number k, we construct a function f such that the length of the shortest path in between two specific local minima exceeds k. The latter construction is independent of the underlying Riemannian metric.