A Comparative Study on Spinel Iron-cobalt Oxide Prepared by Co-precipitation and Hydrothermal Routes

Spinel iron-cobalt oxide was synthetized by coprecipitation and hydrothermal process. The nanostruc-tures of the prepared samples were characterized as functions of the calcination temperature and the hy-drothermal synthesis time, using X-ray powder diffractometry (XRD) and nitrogen adsorption–desorption technique ( BET, BJH ). Using chloride salts as start materials and both of sodium hydroxide and ammo-nia as precipitating agents; The results show that the CoFe2O4 obtained has a mesoporous structure with a pore distribution strongly depending on the experimental conditions. The crystallite size and lattice pa-rameter showed a same variation as function of ( i ) the calcination temperature in the coprecipitation method, ( ii ) the synthesis time in the hydrothermal process. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3509

Thermal Conductivity of Ordered Mesoporous Nanocrystalline Silicon Thin Films Made from Magnesium Reduction of Polymer-Templated Silica

This paper reports the cross-plane thermal conductivity of ordered mesoporous nanocrystalline silicon thin films between 25 and 315 K. The films were produced by evaporation induced self-assembly of mesoporous silica followed by magnesium reduction. The periodic ordering of pores in mesoporous silicon was characterized by X-ray diffraction and direct SEM imaging. The average crystallite size, porosity, and film thickness were about 13 nm, 25-35%, and 140-340 nm, respectively. The pores were arranged in a face-centered cubic lattice. The cross-plane thermal conductivity of the mesoporous silicon thin films was measured using the 3ω method. It was between 3 and 5 orders of magnitude smaller than that of bulk single crystal silicon in the temperature range considered. The effects of temperature, film thickness, and copolymer template on the thermal conductivity were investigated. A model based on kinetic theory was used to accurately predict the measured thermal conductivity for all temperatures. On the one hand, both the measured thermal conductivity and the model predictions showed a temperature dependence of k proportional to T2 at low temperatures, typical of amorphous and strongly disordered materials. On the other hand, at high temperatures the thermal conductivity of mesoporous silicon films reached a maximum, indicating a crystalline-like behavior. These results will be useful in designing mesoporous silicon with desired thermal conductivity by tuning its morphology for various applications

Parental diet, pregnancy outcomes and offspring health:metabolic determinants in developing oocytes and embryos

The periconceptional period, embracing the terminal stages of oocyte growth and post-fertilisation development up to implantation, is sensitive to parental nutrition. Deficiencies or excesses in a range of macro- and micronutrients during this period can lead to impairments in fertility, fetal development and long-term offspring health. Obesity and genotype-related differences in regional adiposity are associated with impaired liver function and insulin resistance, and contribute to fatty acid-mediated impairments in sperm viability and oocyte and embryo quality, all of which are associated with endoplasmic reticulum stress and compromised fertility. Disturbances to maternal protein metabolism can elevate ammonium concentrations in reproductive tissues and disturb embryo and fetal development. Associated with this are disturbances to one-carbon metabolism, which can lead to epigenetic modifications to DNA and associated proteins in offspring that are both insulin resistant and hypertensive. Many enzymes involved in epigenetic gene regulation use metabolic cosubstrates (e.g. acetyl CoA and S-adenosyl methionine) to modify DNA and associated proteins, and so act as 'metabolic sensors' providing a link between parental nutritional status and gene regulation. Separate to their genomic contribution, spermatozoa can also influence embryo development via direct interactions with the egg and by seminal plasma components that act on oviductal and uterine tissues

Midinfrared photoluminescence of InAsSb quantum dots grown by liquid phase epitaxy. .

Photoluminescence in the 2–5 µm spectral region is reported from InAs1–xSbx quantum dots grown from the liquid phase at 580 °C on an InAs (100) substrate. Atomic force microscopy shows that coalesced quantum dots and then isolated quantum dots are formed with increasing Sb composition (x = 0.2–0.3) and strain. The 4 K photoluminescence of the isolated and coalesced quantum dots was observed to peak in the midinfrared at 289 and 316 meV, (4.29 and 3.92 µm), respectively. These peaks are due to type II transitions and begin to quench at temperatures above 100 K as holes become thermally activated out of the quantum dot confinement potential. ©2000 American Institute of Physics

Monitoring cell cycle distributions in MCF-7 cells using near-field photothermal microspectroscopy.

Microspectroscopic techniques such as Fourier transform infrared (FTIR) have played an important role in "fingerprinting" the biochemical composition of cellular components. Based on structure and function, complex biomolecules absorb energy in the mid-infrared ( = 2–20 µm) yielding characteristic vibrational infrared (IR) spectra. However, optical detection FTIR microspectroscopy may not be suitable for IR-absorbing sample materials. Photothermal microspectroscopy (PTMS) permits the direct measurement of heat generated as a result of sample material absorbing radiation. This approach generates true absorption spectra and is implemented by interfacing a scanning probe microscope and an FTIR spectrometer. Detection is performed using a near-field ultra-miniaturized temperature sensor. Employing PTMS, IR spectra of MCF-7 cells were examined in spectral regions (900–2000 cm–1) corresponding to proteins, DNA, RNA, glycoproteins, carbohydrates, lipids, and levels of protein phosphorylation. As a cell passes through the cell cycle, its nuclear material decondenses and condenses and this has led to ambiguity as to whether the intensity of such spectral regions may be associated with the G1-, S- or G2-phases of the cell cycle. Cultured cells were tracked over a time course known to correspond to marked alterations in cell-cycle distributions, as determined using flow cytometry. Experiments were carried out in the absence or presence of lindane, a pesticide known to induce G1-arrest in MCF-7 cells. Significant (P < 0.05) elevations in spectral intensities were associated with exponentially growing cell populations, predominantly in S-phase or G2-phase, compared to more quiescent populations predominantly in G1-phase. Increases in the absorption band at 970 cm–1, associated with elevated protein phosphorylation, were observed in vibrational spectra of exponentially growing cell populations compared to those exhibiting a slowing in their growth kinetics. These results seem to suggest that intracellular bulk changes, associated with transit through the cell cycle, can be tracked using PTMS

Discrimination of human stem cells by photothermal microspectroscopy

Stem cells have great potential in clinical medicine. Sensitive methods for stem cell identification are a requirement for the development of medical interventions involving these cells. To date, a definitive stem cell marker has not been discovered. We are exploring the use of photothermal microspectroscopy (PTMS) for the purpose of stem cell characterisation and identification in human corneal epithelium. PTMS measures heat fluctuations associated with infrared radiation absorption. The technique is advantageous over existing Fourier transform infrared (FTIR) spectroscopy methods in having a spatial resolution which is not diffraction limited, thus allowing examination at a sub-cellular scale. PTMS measurements are unaffected by IR opacity of the sample, giving the method a further edge in comparison to FTIR spectroscopy. We show that PTMS spectra can be used for the characterisation of stem cells and differentiated cells in the human corneal stem cell model. We demonstrate for the first time that PTMS spectra derived from these cell types segregate into separate data clusters after principal component analysis. The predominant wavenumbers responsible for this separation appear to be associated with nucleic acid structure and function. PTMS offers great promise as a technique for stem cell identification in tissue samples where spatial resolution at the cellular scale or better is required. (C) 2008 Elsevier B.V. All rights reserved

FTIR Microspectroscopy Coupled with Two-Class Discrimination Segregates Markers Responsible for Inter- and Intra-Category Variance in Exfoliative Cervical Cytology.

Infrared (IR) absorbance of cellular biomolecules generates a vibrational spectrum, which can be exploited as a “biochemical fingerprint” of a particular cell type. Biomolecules absorb in the mid-IR (2–20 μm) and Fourier-transform infrared (FTIR) microspectroscopy applied to discriminate different cell types (exfoliative cervical cytology collected into buffered fixative solution) was evaluated. This consisted of cervical cytology free of atypia (i.e. normal; n = 60), specimens categorised as containing low-grade changes (i.e. CIN1 or LSIL; n = 60) and a further cohort designated as high-grade (CIN2/3 or HSIL; n = 60). IR spectral analysis was coupled with principal component analysis (PCA), with or without subsequent linear discriminant analysis (LDA), to determine if normal versus low-grade versus high-grade exfoliative cytology could be segregated. With increasing severity of atypia, decreases in absorbance intensity were observable throughout the 1,500 cm−1 to 1,100 cm−1 spectral region; this included proteins (1,460 cm−1), glycoproteins (1,380 cm−1), amide III (1,260 cm−1), asymmetric (νas) PO2 − (1,225 cm−1) and carbohydrates (1,155 cm−1). In contrast, symmetric (νs) PO2 − (1,080 cm−1) appeared to have an elevated intensity in high-grade cytology. Inter-category variance was associated with protein and DNA conformational changes whereas glycogen status strongly influenced intra-category. Multivariate data reduction of IR spectra using PCA with LDA maximises inter-category variance whilst reducing the influence of intra-class variation towards an objective approach to class cervical cytology based on a biochemical profile

Compositional Analysis of Metal Chelating Materials Using Near-Field Photothermal Fourier Transform Infrared Microspectroscopy

Photothermal-Fourier transform-infrared (PT-FT-IR) microspectroscopy employs a thermal probe mounted in a scanning probe microscope (SPM). By placement of the tip of the probe on the surface of a solid sample, it can obtain localized IR spectra of a wide range of samples. A second mode of analysis is also available; a sample can be taken from the selected location using a technique called thermally assisted nanosampling (TAN), then a spectrum can be obtained of the nanosample while the probe is remote from the surface. We report a novel method of local compositional analysis that combines both of these types of measurement; a reagent is attached to the tip using TAN, then the reagent is placed in contact with analyte. IR spectroscopy can then be used to analyze any interaction between the reagent and surface it is placed in contact with. All of these modes of analysis were illustrated using a metal chelating agent. In the surface mode, changes to a solid bead of a chelating resin were measured using standard PT-FT-IR. In the nanosampling mode of analysis, a particle of a chelating polymer was attached to the tip of the probe using TAN and this was placed in contact with a concentrated calcium solution. Strong spectral changes were observed that mirrored those found when exposing the surface bound chelating resin bead to a solution of the same ion. A semiquantitative simulation of the PT spectrum for a chelating resin bead was achieved using a thermal diffusion model derived from photoacoustic spectroscopy indicating that semiquantitative or quantitative measurements will be possible in such a system