Search results for "Instrumentation"
showing 10 items of 4914 documents
Performance of interdigitated nanoelectrodes for electrochemical DNA biosensor.
2003
An electrochemical methodology for bio-molecule sensing using an array of well-defined nanostructures is presented. We describe the fabrication by e-beam lithography of nanoelectrodes consisting of a 100 micro m x 50 micro m area containing interdigitated electrodes of 100 nm in width and interelectrode distance of 200 nm. Sensitivity and response time of the nanoelectrodes are compared to the responses of macro- and microelectrodes. The specificity of the sensor is studied by modifying the gold electrodes with DNA. The technique enables to characterize both single and double-stranded DNA of 15 nucleotides. A special electrochemical cell is adapted to control the temperature and measure the…
DSC study on hyaluronan drying and hydration
2011
Abstract The processes of hyaluronan (HYA) drying and hydration were studied using differential scanning calorimetry. In the first approach the isoconversional Kissinger–Akahita–Sunose (KAS) method was applied in order to determine actual activation energies of evaporation of pure water and water from concentrated HYA solutions. Since the evaporation is a single-step process, the activation energies for pure water provided results consistent with tabulated values of evaporation enthalpies. In the course of water evaporation from hyaluronan solution a break in increasing enthalpy followed by a decrease below 0.34 g of water per 1 g of HYA was observed. This result confirmed earlier observati…
Resonance ionization spectroscopy of fermium (Z=100)
2003
Laser spectroscopy has been applied for the first time to measure resonant transition frequencies of fermium (Zs 100). A number of 2.7=10 atoms was electrodeposited on a Ta filament and covered with a 1 mm Ti layer. Fm 10
Atmospheric compensation in Fourier transform infrared (FT-IR) spectra of clinical samples.
2013
A new method is proposed for the elimination of the spectral contribution of two atmospheric gases (CO2 and H2O) in Fourier transform infrared (FT-IR) spectra of clinical samples. The algorithm is based on the measurement of reference spectra of H2O followed by an automatic calculation of the spectral contribution of the above-mentioned gases to the sample spectra. Then this contribution is compensated by spectral subtraction. Attenuated total reflectance FT-IR spectra of serum and urine samples in the presence of atmospheric gases were corrected and compared with spectra obtained with an N2 purge. Visual inspection of the spectra as well as calculated noise levels confirmed that the metho…
As(III)/Sb(III)/Bi(III)–halide distances and stretching vibrations. An application of the Varshni relationship upon hypervalent group 15 compounds
1998
Abstract A Varshni treatment between stretching frequencies and bond lengths is given for 16 heterocycles of the types Hal–M(SCH 2 CH 2 ) 2 X and Hal–M(CH 2 CH 2 CH 2 ) 2 X (M=As/Sb/Bi, Hal=Cl/Br/I, X=O, S, NR). The intensities of the Raman emissions for the M–Hal bonds increase in the following order: Cl≪Br −1/2 , decrease in the following order: Cl>Br≫I. Practically, the Varshni constants are used to estimate the complementary quantity, stretching frequency or bond length, in 35 cases.
Hypervalent tin-organic compounds: Vibrational spectroscopy in the solid as a tool for structure determination
1997
Abstract A full set of IR- and Raman spectra down from 600 cm1 has been determined and assigned for 60 penta- or hexacoordinated tin-compounds in the groups RSn(CH2CH2CH2)3N (R = Cl, Br, I, Me), RR'Sn(MCH2CH2)2X (R,R′ = Cl, Br, I, Me, Ph, M = CH2 S; X = NMe, O, S), RPh2SnCH2CH2CH2NMe2 (R = Cl, Br, I) and RMe2Sn—CHD—COOMe (R = F, Cl, Br, I, Me). In these hypervalent compounds an approach of the donor atom X to the central atom tin outlines a ‘path’ of nucleophilic attack from a tetrahedron to a trigonal bipyramid. Along this ‘reaction path’ the bond lengths of the axial ligand increase continuously while the bond lengths of the equatorial ligands slightly decrease. The number of similar hype…
Mass spectra of chlorinated aromatics formed in pulp bleaching: I—chlorinated catechols
1983
The fragmentation of chlorinated guaiacols (2-methoxyphenols) on electron impact has been studied. The most common fragmentation processes are interpreted and in some cases the small differences between spectra of positional isomers are explained. In addition to the well-known alkyl-oxygen fission (loss of methyl radical), metastable ion studies and deuterium labelling have indicated several new fragmentation pathways. The most characteristic are the formation of [MCH3HCl]+ and [MCH3Cl]+· ions. In general, however, the spectra of positional isomers are shown to be very similar.
Thermal analyses of commercial magnesium stearate pseudopolymorphs
2005
Abstract Two commercial magnesium stearate powders in two well-characterised structural states are investigated using DSC and coupled TGA–DTA under dry nitrogen flow. They consist of either a mixture of crystalline hydrates or a poorly crystallised so-called anhydrate. Following the degassing of unbound water, 1 or 3 weight-loss peaks are observed below about 100 °C, each associated with one heat loss peak at the same temperature. The present results and a review of graphical data from literature show that the so-called anhydrate always contains a significant amount of water. At the beginning of the dehydration process, the heat loss is the same as the standard heat of vaporisation of water…
Non-exponential relaxation in disordered materials: Phenomenological correlations and spectrally selective experiments
1998
Abstract In most glass-forming materials external perturbations are relaxed in a non-exponential fashion. It is shown that the degree of non-exponentiality is phenomenologically correlated with the departure from simple thermally activated behavior as measured by the fragility index m. In model glass formers such as the Ge-As-Se ternary alloy, and to some degree for amorphous materials in general, the correlations with these properties are observed also for other characteristic features. These include the specific heat step and the aging kinetics in the glass transformation range. While phenomenological correlations have proven very useful for rationalizing the properties of many glass form…
Negative ions and their importance for the analysis of residual gas
1963
Abstract In the case of heavy molecules, mass spectre obtained with the help of positive ions generally lead to the recording of fragments only, and thus do not indicate the true original mass. In order to overcome this drawback, an attempt was made to attach slow electrons to heavy molecules, since less dissociation products are expected with spectre produced by negative ions. As a preliminary experiment, a simple and cheap form of ion source was constructed which produces mainly atomic negative ions.