Effect of thickness variations on EELS spatial-difference profiles

1996 ◽  
Vol 54 ◽  
pp. 564-565
Author(s):  
J. Bruley ◽  
D. B. Williams
Keyword(s):  
Difference Spectrum ◽  
Spatial Difference ◽  
Probe Position ◽  
Difference Spectra ◽  
Characteristic Structure ◽  
Edge Structure ◽  
Dependent Signal ◽  
The Difference ◽  
Thickness Variations ◽  
Energy Dependent

This paper concerns the influence of sample thickness on spatial-difference spectra, and seeks to identify if an interface dependent signal may be generated as an artifact of grain boundary grooving. The spatial-difference profiling technique may be used to identify variations in composition and electronic structure across interfaces at sub-nanometer length scales. The signal-to-background ratios and hence visibility of small changes to the near-edge structure and edge intensities are enhanced using this technique by removing intense energy dependent backgrounds. These backgrounds are assumed to be only slowly varying with respect to the electron probe position. A spatial-difference spectrum is generated from the difference between two spectra after suitable normalization or scaling. This scaling is achieved by either matching intensities of the background prior to a characteristic absorption edge (for compositional profiles) or by normalizing to some characteristic structure of the near-edge structure (for bonding profiles). The latter is performed typically after subtraction of a smooth power-law background modeled in the region immediately preceding the edge.

The interaction of bovine milk caseins with the detergent sodium dodecyl sulphate. II. The effect of detergent binding on spectral properties of caseins

1970 ◽  
Vol 37 (2) ◽  
pp. 259-267 ◽  
Author(s):  
G. C. Cheeseman ◽  
Dorothy J. Knight
Keyword(s):  
Sodium Dodecyl Sulphate ◽  
Sodium Dodecyl ◽  
Bovine Milk ◽  
Difference Spectrum ◽  
Temperature Dependent ◽  
Difference Spectra ◽  
Negative Change ◽  
Tryptophan Residues ◽  
Hydrophobic Binding ◽  
The Difference

SummaryThe dissociation of casein aggregates by the detergent sodium dodecyl sulphate (SDS) gave rise to difference spectra and these spectra were characteristic for each of the different types of casein. Increase in absorption by the chromophore groups, tyrosine and tryptophan, when αs1- and β-casein aggregates were dissociated indicated binding of the detergent at regions of the molecule containing these residues. A decrease in absorption when κ-casein was dissociated indicated that the tyrosine and tryptophan residues were not in the region of the molecule to which the detergent was bound and that in the κ-casein aggregate these residues were in a more hydrophobic environment. Peaks on the difference spectra were obtained at 280 and 288 nm for αs1-casein and 284 and 291 nm for β-casein and troughs at 278 and 286 nm for κ-casein. The difference spectrum reached a maximum value when the αsl- and β-casein aggregates were dissociated and the further binding of SDS did not alter this value. The large negative change in the difference spectrum of κ-casein did not occur until after most of the aggregates were dissociated and did not reach a maximum until binding with SDS was complete. The value obtained for ΔOD was found to be temperature-dependent for β-casein-SDS interaction, but not for αs1- and κ-casein. Changes in spectra were also observed when αs1- and κ-casein interacted to form aggregates. The data obtained confirmed the importance of hydrophobic binding in casein aggregate formation and indicated the possible involvement of tyrosine and tryptophan residues in this binding.

Rutile- and anatase-type temperature-dependent pre-edge peak intensities in K-edge XANES spectra for AO (A = Mn), A 2O3 (A = Sc, Cr and Mn) and AO2 (A = Ti and V)

2018 ◽  
Vol 25 (4) ◽  
pp. 1129-1134 ◽  
Author(s):  
Tsubasa Tobase ◽  
Akira Yoshiasa ◽  
Tatsuya Hiratoko ◽  
Akihiko Nakatsuka
Keyword(s):  
Temperature Dependence ◽  
Difference Spectrum ◽  
True Temperature ◽  
Energy Position ◽  
Edge Structure ◽  
Peak Intensity ◽  
Transition Metal Element ◽  
Peak Energy ◽  
Bending Mode ◽  
The Difference

Pre-edge peaks in 3d transition-metal element (Sc, Ti, V, Cr and Mn) K-edge XANES (X-ray absorption near-edge structure) spectra in AO2 (A = Ti and V), A 2O3 (A = Sc, Cr and Mn) and AO (A = Mn) are measured at various temperatures. Quantitative comparisons for the XANES spectra were investigated by using absorption intensity invariant point normalization. The energy position of the difference peak (D peak) is obtained from the difference between the low- and high-temperature XANES spectra. There are two kinds of temperature dependence for pre-edge peak intensity: rutile- and anatase-type. The true temperature dependence of a transition to each orbital is obtained from the difference spectrum. In both anatase and rutile, the pre-edge peak positions of A2 and A3 are clearly different from the D1- and D2-peak positions. The A1 peak-top energies in both phases of VO2 differ from the D1 peak-top energies. The D-peak energy position determined by the difference spectrum should represent one of the true energies for the transition to an independent orbital. The peak-top positions for pre-edge peaks in XANES do not always represent the true energy for independent transitions to orbitals because several orbital transitions overlap with similar energies. This work suggests that deformation vibration (bending mode) is effective in determining the temperature dependence for the D-peak intensity.

scholarly journals Rapid Variations in the Broad Hβ Profile of the Radio Galaxy 3C 390.3: Possible Evidence for Turbulence in the Accretion Disk

2002 ◽  
Vol 184 ◽  
pp. 357-358
Author(s):  
N. S. Asatrian ◽  
E.Ye. Khachikian ◽  
P. Notni
Keyword(s):  
Accretion Disk ◽  
Line Profile ◽  
Radio Galaxy ◽  
Difference Spectrum ◽  
Kinematic Parameters ◽  
Difference Spectra ◽  
Shape Difference ◽  
Profile Shape ◽  
Short Timescale ◽  
The Difference

We report on implications for the geometrical and kinematic parameters of BLR gas on the basis of short timescale variability in the broad Hβ profile.Data on rapid variations have been obtained at the 6-m telescope of the SAO (Asatrian, Khachikian & Notni, 1999). To search for variations in the profile shape, difference spectra (first minus second epoch) were examined. We believe that the structure of the underlying stellar continuum and the atmospheric features do not affect the Hβ difference profiles of 3C 390.3 significantly.Variations occurred simultaneously on the blue and red sides of Hβ on a timescale of ~ 1.452 hours and take the form of three narrow, positive and negative small bumps drifting across the line profile in the difference spectrum. The positions of the bumps are −2300, +4700 (negative) and −3700 kms2212;1 (positive).

scholarly journals Development of difference spectrophotometric method for the estimation of leflunomide in tablet dosage form

2012 ◽  
Vol 18 (3) ◽  
pp. 407-410
Author(s):  
Prabu Lakshmana ◽  
Suriya Prakash ◽  
A. Shanmugarathinam
Keyword(s):  
Spectrophotometric Method ◽  
Dosage Form ◽  
Spectroscopic Method ◽  
Difference Spectrum ◽  
Basic Medium ◽  
Difference Spectra ◽  
Pharmaceutical Dosage Form ◽  
Highly Sensitive ◽  
The Difference ◽  
Tablet Dosage

A new simple, accurate, precise, highly sensitive and reproducible difference spectrophotometric method for the determination of leflunomide in bulk and pharmaceutical dosage form is described. Difference spectroscopic method is based on the principle that leflunomide exhibit two different forms; in acidic and basic medium which differs in their absorption spectra. The difference spectra were obtained by reading the absorbance of leflunomide in 0.1N HCl in the reference cell and the absorbance of leflunomide in 0.1N NaOH in the sample cell and vice versa; in the difference spectrum maxima and minima were seen at 293.5nm and at 261.5nm respectively. The amplitude values were calculated, which was plotted against concentration. The method is found to be linear in the concentration range of 2-12 ?g/ml. The percentage recovery was found to be between the ranges from 98.92 % to 99.08 %. The proposed method was statistically validated and successfully applied for analysis of tablet dosage forms.

ACTIVATION OF 93Nb NUCLEI ON THE LINAC LUE-40 OF RDC “ACCELERATOR” AND DETERMINATION OF PHOTONUCLEAR REACTION CROSS-SECTIONS

2019 ◽  
pp. 122-127
Author(s):  
O.M. Vodin ◽  
O.S. Deiev ◽  
S.M. Olejnik
Keyword(s):  
Cross Sections ◽  
Nuclear Reactions ◽  
Total Activity ◽  
Difference Spectrum ◽  
Reaction Cross ◽  
Difference Spectra ◽  
Energy Part ◽  
The Difference ◽  
One And Many ◽  
Reaction Cross Sections

The bremsstrahlung spectra of medium-energy electrons (30…100 МeV) were calculated in GEANT4. Cross-sections for photonuclear reactions were calculated in TALYS1.9. A convolution over the energy of the cross-sections of one- and many-particle reactions with the bremsstrahlung flux density was performed. The numerical values of the yield of 93Nb(γ,xn)93-xNb reactions, the activity of irradiated 93Nb targets, and the average reaction cross-sections were obtained. The differences of the bremsstrahlung spectra from electrons with close initial energies were calculated. The shape of the difference spectra was analyzed. The contributions of the quanta of the low-energy part of the difference spectrum and the quasi-monochromatic peak of the difference spectrum to the total activity of the targets were compared. An approach for correction of the experimental cross-sections of photo-nuclear reactions using the method of "bremsstrahlung spectra difference" was considered.

Untersuchungen über Komplexbildungen von Dehydrogenasen mit Coenzymanalogen / Investigations on Complex Formation of Dehydrogenases with Coenzyme Analogues

1971 ◽  
Vol 26 (2) ◽  
pp. 106-112 ◽  
Author(s):  
C. Woenckhaus ◽  
D. Scherr
Keyword(s):  
Active Site ◽  
Intramolecular Interaction ◽  
Fluorescence Excitation Spectrum ◽  
Difference Spectrum ◽  
Difference Spectra ◽  
Fluorescence Excitation ◽  
X Ray ◽  
Functional Part ◽  
Hydrogen Carrier ◽  
The Difference

The coenzyme analogue nicotinamide 5-iodouracil-dinucleotide was synthesized by condensation of the two mononucleotides with dicyclohexylcarbodiimide in aqueous pyridine. The enzymatic properties of this compound were compared with those of the nicotinamide-uracil-dinucleotide. Both coenzyme analogues reacted slowly when functioning as a hydrogen carrier in enzymatic tests. The properties were similar to those of nicotinamide-benzimidazole-dinucleotide. The difference spectrum between the intact coenzyme analogue and its mononucleotides showed that the intramolecular interaction between the functional and non-functional moiety was smaller than that in NAD. The interaction corresponded to that of nicotinamide-benzimidazole-dinucleotide. The fluorescence excitation spectrum did not show any energy transfer from the non-functional iodouracil to the dihydronicotinamide part of the analogue. Difference spectra between the coenzyme - enzymecomplex and the two isolated components indicated that the unfolded dihydrocoenzyme was bound to the active site of lactate- and alcohol-dehydrogenase, respectively. Furthermore, they showed aromatic interaction of the non-functional part with parts of the protein. Introduction of iodine into the nicotinamide-uracil-dinucleotide did not remarkably alter the behavior of the analogues. As the iodine is bound very strongly to the coenzyme analogue, it may be useful for X-Ray-investigations of the dehydrogenases.

Die kurzzeitigen ultravioletten Differenzspektren bei der Photosynthese

1968 ◽  
Vol 23 (2) ◽  
pp. 220-224 ◽  
Author(s):  
H. H. Stiehl ◽  
H. T. Witt
Keyword(s):  
Electron Transport Chain ◽  
Life Time ◽  
Difference Spectrum ◽  
Difference Spectra ◽  
Light Reaction ◽  
Background Light ◽  
Transport Chain ◽  
Light Excitation ◽  
The Difference

Plastoquinone PQ is engaged in photosynthesis 1. Difference spectra in the UV-region indicate that PQ is an intermediate in the electron transport chain 2. PQ is located as a pool between the two light reactions I and II 3. PQ is reduced by hνII and oxidized by hνI3. In this paper the difference spectra which occur during light excitation of spinach chloroplasts and chlorella vulgaris were measured in the UV-region with high resolution by the high sensitive method of periodical flash photometry 6.On excitation with long flashes (10—1 sec) the difference spectra are similar to those obtained when plastoquinone is reduced to hydroquinone in vitro (see figs. 1, 3 and 6). Deviations in the case of chlorella (fig. 4) are caused by additional NADP-reduction. After extraction of plastoquinone from chloroplasts the difference spectra do not occur during light excitation but they can be produced in full after reconstitution with synthetic plastoquinone A (see fig. 2).In the presents of far red background light (718 nm) which excites only light reaction I the magnitude of the spectrum is doubled (see fig. 3).By excitation with short flashes (10—5 sec), two different spectra were found. The difference spectrum with a life-time of 5 · 10—4 sec (fig. 7) is new and does not correspond to that of plastoquinone in vitro. The difference spectrum with a life-time of about 2·10—2 sec (fig. 5) corresponds to the plastoquinone reduction. The magnitude of this spectrum is ten times smaller than that obtained by excitation with long flashes (fig. 6).The 1:10 ratio of the magnitude of the spectra in short and long flashes can be interpreted by a pool of plastoquinone between the two light reactions with a dynamic capacity of ten electrons. The doubled magnitude of the spectra in far red background light can be interpreted by an electron acceptor pool for plastoquinone with a capacity of five electrons (see also the following papers).

scholarly journals Free water molecules and hydrogen bonding form the basis of variation in homeopathic potencies as revealed by vibrational spectroscopy

2021 ◽  
Vol 14 (4) ◽  
pp. 08-15
Author(s):  
Tandra Sarkar ◽  
Atheni Konar ◽  
Nirmal Chandra Sukul ◽  
Anirban Sukul ◽  
Indrani Chakraborty ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Free Water ◽  
Difference Spectrum ◽  
Wave Number ◽  
Water Molecules ◽  
Distilled Water ◽  
Half Maximum ◽  
Difference Spectra ◽  
The Difference ◽  
Wave Number Region

Objective: Using Fourier Transform Infrared spectroscopy (FTIR) we have demonstrated that homeopathic potencies of Natrum mur, Cantharis, Nux vomica and Sulphur show differences with respect to the number of free water molecules and strength of hydrogen bonding. The purpose of the present study is to confirm this phenomenon in three potencies of two more drugs Calcarea carb and Silicea. Design: The potencies used for each of the two drugs were 30cH, 200cH and 1000cH. The control was 90% ethanol as also the potentized drugs. The control, as well as the potencies, were diluted with distilled water to reduce the level of ethanol to 0.03 molar fraction in each of them. FTIR spectra of all the potentized drugs, control and sterile distilled water (reference water) were taken in the wave number region of 4000-2800 cm-1. The full width at half maximum (fwhm) of OH band was measured for each spectrum. The width was divided into two in the middle. The difference spectrum (absorbance of drug solution - absorbance of reference water) for each potency and the control was obtained after normalization of the spectrum at 3410 cm-1. One difference spectrum so obtained for a potency was subtracted from another to find out if there is a difference between two different potencies. Results: The half width half maximum (hwhm) in both the high and low-frequency sides of the OH band is far less narrow in potencies than in the control as compared to that in water. The difference spectra for different potencies show different levels of fall in intensity at the wave number region of dip at 3630 cm-1. The level of dip at 3630 cm-1 and subsequent rise in intensity in the lower frequency region represent the quantity of free water molecules and strong alcoholic OH bond around 3250 cm-1, respectively. The results of subtraction between two different potencies are not zero but have marked positive or negative values. Conclusion (i) Potencies have stronger intermolecular interactions and a higher number of chemical environments than the control, as revealed by the data on hwhm. (ii) The three potencies of each of the two drugs show distinct variation in the number of free water molecules and strength of hydrogen bonding. (iii) There exists both inter-drug and inter-potency variation as revealed by the difference spectra and results of subtraction between two difference spectra.

Depth Profiles in Coated Paper: Experimental and Simulated FT-IR Photoacoustic Difference Magnitude Spectra

2000 ◽  
Vol 54 (2) ◽  
pp. 214-220 ◽  
Author(s):  
M. W. C. Wahls ◽  
E. Kenttä ◽  
J. C. Leyte
Keyword(s):  
Modulation Frequency ◽  
Difference Spectrum ◽  
Layered System ◽  
Difference Spectroscopy ◽  
Difference Spectra ◽  
Band Shape ◽  
Coated Paper ◽  
Magnitude Spectrum ◽  
Relative Contribution ◽  
The Difference

Experimental photoacoustic (PA) magnitude spectra of a coated paper and the uncoated basepaper are presented. The normalized and scaled PA magnitude spectra are used to calculate difference magnitude spectra. It was decided to scale all PA magnitude spectra to (low) equal intensity at the approximately optically thin spectral range before subtraction. Then no infrared (IR) bands of identical band shape and height (as needed for common difference spectroscopy) in either PA magnitude spectrum are needed. Contributions of the two individual layers to the IR-PA magnitude spectrum of the coated paper are separated in the difference spectrum by their sign. An increasing relative contribution of the coating layer with an increasing phase modulation frequency is found. On decreasing the thermal length to a value near the coating thickness, the difference spectra increasingly show positive coating bands and negative bulk signals. The extension of the Rosencwaig–Gersho theory to a double-layered system introduced by N. C. Fernelius [J. Opt. Soc. Am. 70, 480 (1980) and J. Appl. Phys. 50, 650 (1980)] applied to synthetic spectra confirms the experimental observation. It is found that photoacoustic difference spectroscopy may provide quantitative depth-resolved spectral information due to the presented scaling procedure, and photoacoustic difference magnitude spectra of any polymeric laminate may therefore be calculated.

Bilirubin-protein interactions monitored by difference spectroscopy.

1978 ◽  
Vol 24 (9) ◽  
pp. 1491-1495 ◽  
Author(s):  
K O Ash ◽  
M Holmer ◽  
C S Johnson
Keyword(s):  
Protein Interactions ◽  
Binding Capacity ◽  
Research Effort ◽  
Difference Spectrum ◽  
Molar Ratio ◽  
Assay Method ◽  
Difference Spectroscopy ◽  
Difference Spectra ◽  
The Difference ◽  
Bilirubin Binding

Abstract Difference spectroscopy is used to monitor bilirubin-protein interactions, to assess the residual binding capacity of proteins for bilirubin. A change in the difference spectra monitored at 482 nm is directly proportional to bound bilirubin up to a molar ratio of bilirubin to albumin of approximately 1; increasing bilirubin beyond the 1:1 molar ratio does not further change the difference spectra. After excess free bilirubin is added, the change in the difference spectrum is proportional to the residual binding capacity of the serum for bilirubin. The risk of kernicterus among neonates may be assessed by monitoring the residual bilirubin binding capacity of serum. This report summarizes our research effort leading to an assay method which requires only 40 microliter of serum and can be completed in less than 10 min.

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