Ytterbium triflate catalyzed synthesis of alkoxy-substituted donor-acceptor cyclobutanes and their formal [4 + 2] cycloaddition with imines: stereoselective synthesis of piperidines

A new synthesis of 2-alkoxy-1,1-cyclobutane diesters and their first use in dipolar cycloadditions is reported. Both the formation of the donor-acceptor cyclobutanes and their subsequent annulation with in situ formed imines are catalyzed by Yb(OTf)(3). Cyclobutanes with carbon donor groups give piperidines with high trans stereoselectivity.     

Single‐step extraction followed by LC for determination of (fluoro)quinolone drug residues in muscle,eggs, and milk

In this study, a simplified method for the extraction and determination of seven fluoroquinolone residues (danofloxacin, difloxacin, enrofloxacin, marbofloxacin, orbifloxacin, ofloxacin, and sarafloxacin) and three quinolones (oxolinic acid, flumequine, and nalidixic acid), in porcine muscle, table eggs, and commercial whole milk, which required no cleanup step, was devised. This procedure involves the extraction of analytes from the samples via liquid‐phase extraction, and the subsequent quantitative determination was accomplished via LC‐fluorescence detection. Analyte separation was successfully conducted on an XBridge‐C₁₈ column, with a linear gradient mobile phase composed of acetonitrile and 0.01 M oxalic acid buffer at pH=3.5. The one‐step liquid‐liquid extraction method evidenced good selectivity, precision (RSDs=0.26–15.07%), and recovery of the extractable analytes, ranging from 61.12 to 115.93% in matrices. The LOQs ranged from 0.3 to 25 μg/kg. A survey of ten samples purchased from local markets was conducted, and none of the samples harbored fluoroquinolone residues. This method is an improvement over existing methodologies, since no additional cleanup was necessary.     

Homomorphisms with respect to a function

Let X be a realcompact space and ${H:C(X)\rightarrow\mathbb{R}}$ be an identity and order preserving group homomorphism. It is shown that H is an evaluation at some point of X if and only if there is ${\varphi\in C(\mathbb{R})}$ with ${\varphi(r)>\varphi(0)}$ for all ${r\in\mathbb{R}-\{0\}}$ for which ${H\circ\varphi=\varphi\circ H}$ . This extends (and unifies) classical results by Hewitt and Shirota.     

Reconstructing initial data using observers: error analysis of the semi-discrete and fully discrete approximations

A new iterative algorithm for solving initial data inverse problems from partial observations has been recently proposed in Ramdani et al. (Automatica 46(10), 1616–1625, 2010). Based on the concept of observers (also called Luenberger observers), this algorithm covers a large class of abstract evolution PDE’s. In this paper, we are concerned with the convergence analysis of this algorithm. More precisely, we provide a complete numerical analysis for semi-discrete (in space) and fully discrete approximations derived using finite elements in space and an implicit Euler method in time. The analysis is carried out for abstract Schr?dinger and wave conservative systems with bounded observation (locally distributed).     

Plans dʼexpérience pour lʼestimation de la courbe de concentration et de lʼAUC

The problem of interest is to estimate the concentration curve and the area under the curve (AUC) by estimating the parameters of a linear regression model with autocorrelated error process. We introduce a simple linear nonparametric unbiased estimator of the concentration curve and the AUC. We show that this estimator constructed from an appropriate regular sampling design is asymptotically optimal.     

SMARTER crystallography of the fluorinated inorganic-organic compound Zn3Al2F12·[HAmTAZ]6

We present in this paper the structure resolution of a fluorinated inorganic-organic compound--Zn(3)Al(2)F(12)·[HAmTAZ](6)--by SMARTER crystallography, i.e. by combining powder X-ray diffraction crystallography, NMR crystallography and chemical modelling of crystal (structure optimization and NMR parameter calculations). Such an approach is of particular interest for this class of fluorinated inorganic-organic compound materials since all the atoms have NMR accessible isotopes ((1)H, (13)C, (15)N, (19)F, (27)Al, (67)Zn). In Zn(3)Al(2)F(12)·[HAmTAZ](6), (27)Al and high-field (19)F and (67)Zn NMR give access to the inorganic framework while (1)H, (13)C and (15)N NMR yield insights into the organic linkers. From these NMR experiments, parts of the integrant unit are determined and used as input data for the search of a structural model from the powder diffraction data. The optimization of the atomic positions and the calculations of NMR parameters ((27)Al and (67)Zn quadrupolar parameters and (19)F, (1)H, (13)C and (15)N isotropic chemical shifts) are then performed using a density functional theory (DFT) based code. The good agreement between experimental and DFT-calculated NMR parameters validates the proposed optimized structure. The example of Zn(3)Al(2)F(12)·[HAmTAZ](6) shows that structural models can be obtained in fluorinated hybrids by SMARTER crystallography on a polycrystalline powder with an accuracy similar to those obtained from single-crystal X-ray diffraction data.     

Shape-selective production of zinc phosphate in aqueous and nonaqueous media using (2-hydroxyethyl) trimethylammonium hydroxide-assisted sonochemical route

Zinc phosphate molecular sieves were synthesized using zinc chloride, phosphoric acid and (2-hydroxyethyl) trimethylammonium hydroxide as template, respectively. Synthesized samples were characterized by XRD, SEM and FT-IR techniques. The morphology and crystal size of the samples were investigated using ultrasonic during aging process. Large particle size (7.2?×?20.4???m) was obtained by ultrasonication. Imperfect orthorhombic particles were obtained when the sample was mixed with magnetic stirrer; meanwhile, some rod-like particles were obtained when the mixture was stirred with ultrasonic. In addition, the rod-like ??-Zn₃(PO₄)₂·4H₂O phase was prepared using ethylene glycol as co-solvent.     

Thin film membrane based on a-SiGe: B and MEMS technology for application in cochlear implants

In this work is presented the fabrication of a thin film membrane as a bio-transducer for aural assistance detection, therefore it will operate at low pressure. The resonant membrane was deposited by PECVD technique at low temperature of deposition T = 270 °C, using SiH₄, GeH₄, and Boron gases. The membrane was suspended on a micromachined crystalline silicon frame obtained by wet chemical etching. The a-SiGe:B film presented a resistivity of 2.46 × 10³ (Ω-cm), resistance of 20.8 kΩ. Using these experimental data we succeeded in designing a simple structure for sensing low pressure variations. The output voltage of the sensor was measured for a range of pressure from 0 to 3000 Pa and at bias voltage of 10 V.     

Room temperature Ge and ZnO embedded inside porous silicon using conventional methods for photonic application

In this paper we reported room temperature synthesis of embedded porous Si (PS) based structures using simple and low cost techniques of electrochemical etching and thermal evaporation. PS was prepared by anodization of Si wafer in ethanoic hydrofluoric acid (HF). The Ge and ZnO layers were deposited onto the PS by conventional thermal evaporation. Three samples prepared namely PS, Ge/PS and ZnO/Ge/PS. Structural analyses, SEM revealed that the structures contained 500–700 nm circular-pores and EDX suggested the presence of Ge and ZnO inside the pores. Photoluminescence (PL) spectra of the three samples revealed emissions peak at 380, 520 and 639 nm, respectively, with ZnO/Ge/PS displaying a high UV emission peak accompanied by low and broad green to red emission peaks. The Ge/PS sample shows emission peaks from green to red and the PS sample reveals a broad peak in the red region. These characteristics demonstrate the potential of the PS-based structures to emit light at a broader spectrum for prospective applications in optoelectronic devices.     

Picosecond pulse radiolysis study of highly concentrated nitric acid solutions: formation mechanism of NO3• radical

The formation of nitrate radical, NO(3)(?), is observed for the first time directly by picosecond pulse radiolysis of highly concentrated nitric acid solutions. The experimental yield of NO(3)(-) ionization is deduced from the pulse-probe transient absorption measurements in the visible region where this radical absorbs. On the basis of the value of the extinction coefficient of nitrate radical at 640 nm equal to 1300 M cm(-1), the experimental yield of NO(3)(?) at 20 ps is found to be around 0.36 × 10(-7), 1.33 × 10(-7), and 2.85 × 10(-7) mol J(-1) for 1, 3.5, and 7 M nitric acid solutions, respectively. Relative to the dose absorbed by nitric acid by the direct effect, we find an unexpected high formation yield of the nitrate radical within the electron pulse. Therefore, we suggest that the trapping of the positive hole, H(2)O(?+), by NO(3)(-) also contributes to the formation of NO(3)(?) within the electron pulse. Moreover, after the pulse and within 4 ns, the beginning of the reaction of OH(?) radical with undissociated nitric acid is observed for the most concentrated nitric acid solution.