Structural, calorimetric and magnetic properties study of the Cu0,91Fe0,09O system

In this work the Cu_0.91Fe_0.09O nanocrystalline system was prepared via the co-precipitation method. Using Mössbauer Spectrometry, X-Ray Diffraction, Vibrating Sample Magnetometry, Thermogravimetry and Differential Scanning Calorimetry, we study the magnetic behavior, and the structural and calorimetric properties of this system. X-ray diffraction shows only the presence of the CuO structural monoclinic phase, suggesting that Cu atoms are substituted by Fe ones. This hypothesis was confirmed by Mössbauer spectrometry at room temperature, because it shows that the spectrum is formed by two doublets, which correspond to Fe^?+?2 and Fe^?+?3 sites. Hysteresis cycles obtained by vibrating sample magnetometry detect a soft ferromagnetic behavior at room temperature with coercive fields between 8 and 20 Oe. At T = 20 K the sample shows a hard-magnetic behavior. The thermogravimetry results show a Néel temperature (T _N > 440 °C). The differential scanning calorimetry curve show two endothermic peaks in the 90–120 °C range.     

Lab-in-a-tube: ultracompact components for on-chip capture and detection of individual micro-/nanoorganisms

A review of present and future on-chip rolled-up devices, which can be used to develop lab-in-a-tube total analysis systems, is presented. Lab-in-a-tube is the integration of numerous rolled-up components into a single device constituting a microsystem of hundreds/thousands of independent units on a chip, each individually capable of sorting, detecting and analyzing singular organisms. Such a system allows for a scale-down of biosensing systems, while at the same time increasing the data collection through a large, smart array of individual biosensors. A close look at these ultracompact components which have been developed over the past decade is given. Methods for the capture of biomaterial are laid out and progress of cell culturing in three-dimensional scaffolding is detailed. Rolled-up optical sensors based on photoluminescence, optomechanics, optofluidics and metamaterials are presented. Magnetic sensors are introduced as well as electrical components including heating, energy storage and resistor devices.     

PEGylation of superparamagnetic iron oxide nanoparticle for drug delivery applications with decreased toxicity: an in vivo study

Journal of Nanoparticle Research - Superparamagnetic iron oxide nanoparticles (SPIONs) are evolving as a mainstay across various applications in the field of Science and Technology. SPIONs have...     

On the number of \(n\)-dimensional invariant spheres in polynomial vector fields of \(\mathbb{C}^{n+1}\)

We study the polynomial vector fields \(\mathcal{X}= \displaystyle \sum_{i=1}^{n+1} P_i(x_1,\ldots,x_{n+1}) \frac{\partial}{\partial x_i}\) in \(\mathbb{C}^{n+1}\) with \(n\geq 1\) . Let \(m_i\) be the degree of the polynomial \(P_i\). We call \((m_1,\ldots,m_{n+1})\) the degree of \(\mathcal{X}\). For these polynomial vector fields \(\mathcal{X}\) and in function of their degree we provide upper bounds, first for the maximal number of invariant \(n\)-dimensional spheres, and second for the maximal number of \(n\)-dimensional concentric invariant spheres.     

Multiresidue analysis of pesticides in animal liver by gas chromatography using triple quadrupole tandem mass spectrometry

Two methods for extracting organochlorine (OCs) and organophosphorus (OPs) pesticides from animal liver have been developed. The determination was carried out by gas chromatography with electron impact ionization tandem mass spectrometry (GC-(EI-)MS/MS) using a triple quadrupole (QqQ) analyzer. First, a liquid-solid extraction performed with a high-speed homogenizer (Polytron) using ethyl acetate as solvent, and a subsequent clean-up by gel permeation chromatography (GPC) was applied, determining 34 pesticides. Secondly, a matrix solid phase dispersion (MSPD) extraction with octadecylsilyl (C(18)) sorbent combined with a Florisil clean-up and ethyl acetate elution was performed, analyzing 25 compounds. These methodologies have been tested and compared in the sample pre-treatment due to the fatty nature of the matrix. The GPC method was finally selected and validated, yielding recoveries in the range 70-115%, with precision values expressed as relative standard deviation (RSD) lower or equal to 20%, at the spiking levels of 25 and 50 microg kg(-1), and limits of quantification (LOQs) lower than the maximum residue levels (MRLs) set by the European Union in animal products, except for isofenphos. Linearity was also studied ranging between 5 and 300 microg kg(-1) for most of pesticides. This method was applied to the analysis of real liver samples of chicken, pork and lamb.     

Diterpenes with new isoryanodane derived skeletons from Persea indica

A phytochemical study of the aerial parts of Persea indica has permitted the isolation of two diterpenes with novel skeletons derived from isoryanodane, which have named perseaindicol and secoperseanol. A third compound, also with a new carbon framework, proved to be identical with cinncassiol E, whose structure has been now corrected.     

Analytical methods and problems related to the determination of organotin compounds in marine sediments

The determination of organotin compounds in bottom sediments is a complex process that requires a number of analytical steps, i.e. sample collection, transport and storage; extraction of analytes from sediment; derivatization; extract purification; enrichment; and the final chromatographic measurement. The whole process is time and labour consuming, and subject to securing sample representativeness. In this review the most frequently encountered problems and the examples of possible analytical solutions are presented, which encompass the specific steps of speciation analysis of these toxic compounds.     

Self-Assembled Monolayers of N-Heterocyclic Olefins on Au(111)

Self-assembled monolayers (SAMs) of N-heterocyclic olefins (NHOs) have been prepared on Au(111) and their thermal stability, adsorption geometry, and molecular order were characterized by X-ray photoelectron spectroscopy, polarized X-ray absorption spectroscopy, scanning tunneling microscopy (STM), and density functional theory (DFT) calculations. The strong σ-bond character of NHO anchoring to Au induced high geometrical flexibility that enabled a flat-lying adsorption geometry via coordination to a gold adatom. The flat-lying adsorption geometry was utilized to further increase the surface interaction of the NHO monolayer by backbone functionalization with methyl groups that induced high thermal stability and a large impact on work-function values, which outperformed that of N-heterocyclic carbenes. STM measurements, supported by DFT modeling, identified that the NHOs were self-assembled in dimers, trimers, and tetramers constructed of two, three, and four complexes of NHO−Au-adatom. This self-assembly pattern was correlated to strong NHO−Au interactions and steric hindrance between adsorbates, demonstrating the crucial influence of the carbon-metal σ-bond on monolayer properties.     

Recent developments and applications of liquid phase microextraction in fruits and vegetables analysis

The sample preparation step has been identified as the bottleneck of analytical methodology in chemical analysis. Therefore, there is need for the development of cost‐effective, easy to operate, and environmentally friendly miniaturized sample preparation technique. The microextraction techniques combine extraction, isolation, concentration, and introduction of analytes into analytical instrument, to a single and uninterrupted step, and improve sample throughput. The use of liquid‐phase microextraction techniques for the analysis of pesticide residues in fruits and vegetables are discussed with the focus on the methodologies employed by different researchers and their analytical performances. Analytes are extracted using water‐immiscible solvents and are desorbed into gas chromatography, liquid chromatography, or capillary electrophoresis for identification and quantitation.     

Chemical Profile,Antioxidant Properties and Antimicrobial Activities of Malaysian Heterotrigona itama Bee Bread

The aim of the study was to determine the chemical profile, antioxidant properties and antimicrobial activities of Heterotrigona itama bee bread from Malaysia. The pH, presence of phytochemicals, antioxidant properties, total phenolic content (TPC) and total flavonoid content (TFC), as well as antimicrobial activities, were assessed. Results revealed a decrease in the pH of bee bread water extract (BBW) relative to bee bread ethanolic extract (BBE) and bee bread hot water extract (BBH). Further, alkaloids, flavonoids, phenols, tannins, saponins, terpenoids, resins, glycosides and xanthoproteins were detected in BBW, BBH and BBE. Also, significant decreases in TPC, TFC, DPPH activity and FRAP were detected in BBW relative to BBH and BBE. We detected phenolic acids such as gallic acid, caffeic acid, trans-ferulic acid, trans 3-hydroxycinnamic acid and 2-hydroxycinnamic acid, and flavonoids such as quercetin, kaempferol, apigenin and mangiferin in BBE using high-performance liquid chromatography analysis. The strongest antimicrobial activity was observed in Klebsilla pneumonia (MIC₅₀ 1.914 µg/mL), followed by E. coli (MIC₅₀ 1.923 µg/mL), Shigella (MIC₅₀ 1.813 µg/mL) and Salmonella typhi (MIC₅₀ 1.617 µg/mL). Bee bread samples possess antioxidant and antimicrobial properties. Bee bread contains phenolic acids and flavonoids, and could be beneficial in the management and treatment of metabolic diseases.