Multiparameter Polynomial Adaptive Stabilizers

In 1983 Morse proved, for unknown scalar one-dimensional linearsystems, the nonexistence of rational or polynomial universalstabilizers (UAS). In 1983, Nussbaum gave an example of an analyticUAS. In our paper, it is shown that there exist time-invariantpolynomial UAS's with multidimensional gain adaptation. Thedesign procedure is developed for linear, minimum-phase systemsof relative degree one. Convergence of the closed-loop systemis proved. Some numerical simulations are provided.     

Comparison of direct kinetic phosphorescence analysis and recovery corrected kinetic phosphorescence analysis for the determination of natural uranium in human tissues

Summary In the analysis of biological samples with sub ng/g uranium concentrations, pre-concentration has been shown to improve the detection limit for the determination of uranium. Recovery corrected kinetic phosphorescence analysis (KPA) combines pre-concentration and separation of uranium by anion-exchange from human tissues dissolved in 6M HCl, with the radiochemical yield determined by alpha-spectrometry, using ²³²U as a tracer. Total uranium is determined by KPA after correction for chemical recovery. Twenty-one randomly selected dissolved tissue samples from the United States Transuranium and Uranium Registries (USTUR) Case 0242 were chosen for comparative analyses. The set of samples included dissolved bone and soft tissues. Uranium concentrations for seven of the samples had not been previously reported. Direct KPA could not be used to determine uranium concentrations of five unreported tissues. Three of these tissues had uranium concentrations at or below the KPA L_Q value of 0.028 ng/ml and two tissues had known matrix interferences. All seven of the unreported tissues were successfully analyzed by recovery corrected KPA; concentrations ranged from 9 to 1380 ng per tissue, including those that could not be analyzed by direct KPA due to matrix problems. Recovery corrected KPA gives results similar to direct KPA where matrix interferences and low detection limits are not encountered. A comparison of the direct method of KPA versus recovery corrected KPA shows marked improvement for the determination of uranium in samples that heretofore either uranium was not detected or the sample had to be drastically diluted to minimize matrix effects in order to measure uranium.     

A new ent-labdane eiterpenoid lactone from Andrographis paniculata

A new ent-labdane diterpenoid lactone with a new natural product was isolated from Andrographis paniculata. Their structures were elucidated on the basis of spectral evidences including 2D NMR.     

Asymmetric synthesis of pedamide using I_2-induced heterocyclization to construct the skeleton

An alternative approach to synthesize pedamide,a key building block of pederin was described.Iodine-induced asymmetric heterocyclization was used as the key step to construct the skeleton,a tetrahydropyran ring with three chiral centers.Brown's asymmetric allylation and Lewis acid-mediated allylation were investigated to introduce chains and chiral alcohols.Sharpless dihydroxylation decorated the side chain.And high optically pure target was obtained by removing the epimers formed in these reactions on c...     

Microwave-assisted one-pot synthesis of 3-substituted-3,4-dihydrocoumarins via tendem Konevenagel and Hantzsch reactions

A convenient route for the synthesis of 3,4-dihydrocoumarin derivates from salicylaldehyde derivates and 1,3-dicarbonyl compounds under solvent-free microwave irradiation conditions was described. In this way, a range of compounds was obtained in moderate to good yields in a short reaction time.     

Self-injection length in La0.7Ca0.3MnO3-YBa2Cu3O7-δ ferromagnet-superconductor multilayer thin films

We have carried out extensive studies on the self-injection problem in barrierless heterojunctions between La_0.7Ca_0.3MnO₃ (LCMO) and YBa₂Cu₃O_7-δ (YBCO) thin films. The heterojunctions were formed in situ by sequentially growing LCMO and YBCO films on 〈100〉 LaAlO₃ (LAO) substrate using a pulsed laser deposition (PLD) system. YBCO micro-bridges with 64 μm width were patterned both on the LAO (control) and LCMO side of the substrate. Critical current, I _c, was measured at 77 K on both the control side as well as the LCMO side for different YBCO film thickness. It was observed that while the control side showed a J _c of ∼ 2 × 10⁶ A/cm², the LCMO side showed about half the value for the same thickness (1800 ?). The difference in J _c indicates that a certain thickness of YBCO has become ‘effectively’ normal due to self-injection. From the measurement of J _c at two different thicknesses (1800 ? and 1500 ?) of YBCO films both on the LAO as well as the LCMO side, the value of self-injection length (at 77 K) was estimated to be ∼ 900 ?. To the authors’ best knowledge, this is the first time that self-injection length has been quantified. A control experiment carried out with LaNiO₃ deposited by PLD on YBCO did not show any evidence of self-injection.     

六元gcd封闭集上Smith矩阵的整除性

我们给出了关于六元gcd封闭集S的充分必要条件,使得在整数矩阵环M_6(Z)中,定义在S上的e次幂GCD矩阵(S~e)整除e次幂LCM矩阵[S~e].这部分解决了Hong在2002年提出的一个公开问题.     

Magnetic and optical study of NaCrO2

Magnetic and optical measurements in the layer compound NaCrO₂ are reported. This compound is antiferromagnetic with T_n = 46±2 K and θ = ?400±30 K. Broad antiferromagnetic resonances are observed which cannot be interpreted on any simple model. Optical absorption data are consistent with the appearance of antiferromagnetism. Non-intrinsic fluorescence has also been observed.     

Feasibility of using dendroanalysis of uranium as a biomarker for environmental contamination

A study was initiated to investigate the chronological deposition of uranium in certain species of trees growing on the site of a former uranium metal processing facility. The Feed Materials Production Center (FMPC) is located in Fernald, Ohio, and for roughly 40 years operated as a large scale uranium processing center. Core samples from several species of trees growing in different locations throughout the site were extracted using a 12.5 mm incremental wood boring drill bit. After extraction, each core sample was cut and packaged into individual sections representing 4 annual growth rings and submitted for instrumental neutron activation analysis (INAA). The reaction ²³⁵U(n,f)¹⁴⁰Ba→¹⁴⁰La+γ was evaluated using high resolution germanium gamma-spectroscopy to detect the 1.596 MeV photon emission from the fission product ¹⁴⁰La following a minimum of a 3 week decay. A total of 106 samples representing 7 individual trees of 3 unique species were irradiated. In addition to the tree-core samples, 18 quality control (QC) samples and 18 standard reference material (SRM) Fly Ash samples were irradiated with the core samples for determining neutron flux. The activity in any one sample in a batch was determined by comparison with the amount of natural uranium in the QC standards. No significantly measurable amount of uranium was detected in any of the tree core samples, although 3 tree core samples were in excess of the minimum detectable amount (30 ng).     

Highly effective direct synthesis of DMC from CH_3OH and CO_2 using novel Cu-Ni/C bimetallic composite catalysts

Novel Cu-Ni/C has been prepared and utilized as an efficient catalyst system in direct synthesis of DMC from CH3OH and CO2.