水和非水介质毛细管电泳分离吩噻嗪

以水和甲酰胺(FA)为介质,用毛细管电泳分离吩噻嗪类药物,比较了两者的选择性、柱效和分离度.与水相比,FA中选择性不同,有利于分离,被分析的物质均获得了较高的分离度;柱效显著提高,都在1×10⁵以上,表明FA是一种良好的分离介质.     

Ce0.6Zr0.35Y0.05O2和Pr0.6Zr0.35Y0.05O2催化剂表面上CO氧化和18O-16O交换反应的研究

测定了在Ce0.6Zr0.4O2,Ce0.6Zr0.35Y0.05O2,Pr0.6Zr0.4O2和Pr0.6Zr0.35Y0.05O2 (分别表示为CZ,CYZ,PZ和PYZ)样品表面上的CO氧化反应和18O-16O 同位素交换反应.结果表明: 在CZ和PZ系列固熔中掺杂Y3 离子可以改善晶格氧的迁移速度;PZ和PZY的晶格氧比CZ 和CZY 的晶格氧具有更高的氧化反应活性.其原因是将Y3 掺杂到Ce0.6Zr0.4O2 或Pr0.6Zr0.4O2晶格中,增加了样品的氧空位浓度,从而提高了晶格氧的迁移性质,而PrOx比CeO2具有更低温度的氧化还原性质,因此PZ和PZY的晶格氧比CZ 和CZY 的晶格氧具有更高的氧化反应活性.     

Lateral flow devices for nucleic acid analysis exploiting quantum dots as reporters

There is a growing interest in the development of biosensors in the form of simple lateral flow devices that enable visual detection of nucleic acid sequences while eliminating several steps required for pipetting, incubation and washing out the excess of reactants. In this work, we present the first dipstick-type nucleic acid biosensors based on quantum dots (QDs) as reporters. The biosensors enable sequence confirmation of the target DNA by hybridization and simple visual detection of the emitted fluorescence under a UV lamp. The ‘diagnostic’ membrane of the biosensor contains a test zone (TZ) and a control zone (CZ). The CZ always fluoresces in order to confirm the proper function of the biosensor. Fluorescence is emitted from the TZ, only when the specific nucleic acid sequence is present. We have developed two general types of QD-based nucleic acid biosensors, namely, Type I and Type II, in which the TZ consists of either immobilized streptavidin (Type I) or immobilized oligodeoxynucleotides (Type II). The control zone consists of immobilized biotinylated albumin. No purification steps are required prior to the application of the DNA sample on the strip. The QD-based nucleic acid biosensors performed accurately and reproducibly when applied to (a) the visual detection of PCR amplification products and (b) visual genotyping of single nucleotide polymorphisms (SNPs) in human genomic DNA from clinical samples. As low as 1.5 fmol of double-stranded DNA were clearly detected by naked eye and the dynamic range extended to 200 fmol. The %CV were estimated to be 4.3–8.2.     

Raman and infrared spectroscopy of selected vanadates

Raman and infrared spectroscopy has been used to study the structure of selected vanadates including pascoite, huemulite, barnesite, hewettite, metahewettite, hummerite. Pascoite, rauvite and huemulite are examples of simple salts involving the decavanadates anion (V10O28)6-. Decavanadate consists of four distinct VO6 units which are reflected in Raman bands at the higher wavenumbers. The Raman spectra of these minerals are characterised by two intense bands at 991 and 965 cm(-1). Four pascoite Raman bands are observed at 991, 965, 958 and 905 cm(-1) and originate from four distinct VO6 sites. The other minerals namely barnesite, hewettite, metahewettite and hummerite have similar layered structures to the decavanadates but are based upon (V5O14)3- units. Barnesite is characterised by a single Raman band at 1010 cm(-1), whilst hummerite has Raman bands at 999 and 962 cm(-1). The absence of four distinct bands indicates the overlap of the vibrational modes from two of the VO6 sites. Metarossite is characterised by a strong band at 953 cm(-1). These bands are assigned to nu1 symmetric stretching modes of (V6O16)2- units and terminal VO3 units. In the infrared spectra of these minerals, bands are observed in the 837-860 cm(-1) and in the 803-833 cm(-1) region. In some of the Raman spectra bands are observed for pascoite, hummerite and metahewettite in similar positions. These bands are assigned to nu3 antisymmetric stretching of (V10O28)6- units or (V5O14)3- units. Because of the complexity of the spectra in the low wavenumber region assignment of bands is difficult. Bands are observed in the 404-458 cm(-1) region and are assigned to the nu2 bending modes of (V10O28)6- units or (V5O14)3- units. Raman bands are observed in the 530-620 cm(-1) region and are assigned to the nu4 bending modes of (V10O28)6- units or (V5O14)3- units. The Raman spectra of the vanadates in the low wavenumber region are complex with multiple overlapping bands which are probably due to VO subunits and MO bonds.     

Raman spectroscopic study of pascoite Ca3V10O(28)·17H2O

Raman spectroscopy has been used to study the molecular structure of the vanadate mineral pascoite. Pascoite, rauvite and huemulite are examples of simple salts involving the decavanadate anion (V10O28)6-. Decavanadate consists of four distinct VO6 units which are reflected in Raman bands occurring at higher wavenumbers. The Raman spectrum of pascoite is characterised by two intense bands at 991 and 965 cm(-1). Raman bands are observed at 991, 965, 958 and 905 cm(-1) and originate from four distinct VO6 sites in the mineral structure. In the infrared spectra of pascoite, two wavenumber regions are observed between: (1) 837 and 860, and (2) between 803 and 833 cm(-1). These bands are assigned to ν3 antisymmetric stretching modes of (V10O28)6- or (V5O14)3- units. The spectrum is highly complex in the lower wavenumber region, and therefore the assignment of bands is difficult. Bands observed in the 404 to 458 cm(-1) region are assigned to the ν2 bending modes of (V10O28)6- or (V5O14)3- units. Raman bands observed in the 530-620 cm(-1) region are assigned to the ν4 bending modes of (V10O28)6- or (V5O14)3- units. The Raman spectra of the vanadates in the low wavenumber region are complex with multiple overlapping bands which are probably due to VO subunits and MO bonds.     

Differential-Pulse Polarographic Determination of Some N-Substituted Phenothiazine Derivatives in Dosage Forms and Urine Through Treatment with Nitrous Acid

 A highly sensitive differential-pulse (DPP) polarographic method is described for the determination of three N-substituted phenothiazine derivatives, chlorpromazine (CZ), promazine (PZ) and promethazine (PMZ). The method involves the use of nitrous acid as an oxidant. Polarographically-active sulphoxides with diffusion-current constants (Id) of 2.53, 3.05 and 3.37 were obtained for CZ, PZ and PMZ, respectively. The polarographic waves were characterized as being diffusion-controlled, irreversible and partly affected by adsorption phenomena. All parameters affecting the oxidation process and polarographic behaviour were optimized and incorporated into the procedure. The limiting current-concentration plots in the DPP mode were rectilinear over the range: 0.006–0.1 mM, 0.005–0.08 mM and 0.008–0.1 mM for CZ, PZ and PMZ, respectively, with minimum detectability (S/N=3) of 3 × 10⁻⁷ M for CZ and PZ, and 4 × 10⁻⁷ M for PMZ, respectively. The kinetic parameters of the electrode reaction, including rate constant, free energy of activation ΔG and effect of temperature on both parameters were studied. The proposed method was successfully applied to the determination of phenothiazines in dosage forms; the results obtained were in agreement with those given with the official methods. The method was further applied to the determination of promazine in spiked human urine. The percentage recovery was 96.86 ± 0.30. The advantages of the proposed method over other reported methods were discussed. A proposal of the electrode reaction was made. Received June 1, 1999. Revision March 10, 2000.     

Raman spectroscopy of the system iron(III)-sulfuric acid-water: an approach to Tinto River's (Spain) hydrogeochemistry

Acid mine drainage is formed when pyrite (FeS(2)) is exposed and reacts with air and water to form sulfuric acid and dissolved iron. Tinto River (Huelva, Spain) is an example of this phenomenon. In this study, Raman spectroscopy has been used to investigate the speciation of the system iron(III)-sulfuric acid-water as an approach to Tinto River's aqueous solutions. The molalities of sulfuric acid (0.09 mol/kg) and iron(III) (0.01-1.5 mol/kg) were chosen to mimic the concentration of the species in Tinto River waters. Raman spectra of the solutions reveal a strong iron(III)-sulfate inner-sphere interaction through the nu(1) sulfate band at 981 cm(-1) and its shoulder at 1005 cm(-1). Iron(III)-sulfate interaction may also be facilitated by hydrogen bonds and monitored in the Raman spectra through the symmetric stretching band of bisulfate at 1052 cm(-1) and a shoulder at 1040 cm(-1). Other bands in the low-frequency region of the Raman spectra are attributed to the hydrogen-bonded complexes formation as well.     

Vibrational spectroscopy of ferruginous smectite and nontronite

A comparison is made between the Raman and infrared spectra of ferruginous smectite and a nontronite using both absorption and emission techniques. Raman spectra show hydroxyl stretching bands at 3572, 3434, 3362, 3220 and 3102 cm(-1). The infrared emission spectra of the hydroxyl stretching region are significantly different to the absorption spectrum. These differences are attributed to the loss of water, absent in the emission spectrum, the reduction of the samples in the spectrometer and possible phase changes. Dehydroxylation of the two minerals may be followed by the loss of intensity of the hydroxyl stretching and hydroxyl deformation frequencies. Hydroxyl deformation modes are observed at 873 and 801 cm(-1) for the ferruginous smectite, and at 776 and 792 cm(-1) for the nontronite. Raman hydroxyl deformation vibrations are found at 879 cm(-1). Other Raman bands are observed at 1092 and 1032 cm(-1), assigned to the SiO stretching vibrations, at 675 and 587 cm(-1), assigned to the hydroxyl translation vibrations, at 487 and 450 cm(-1), attributed to OSiO bending type vibrations, and at 363, 287 and 239 cm(-1). The differences in the molecular structure of the two minerals are attributed to the Al/Fe ratio in the minerals.     

Surface stabilized nanosized Ce(x)Zr(1-x)O(2) solid solutions over SiO(2): characterization by XRD, Raman, and HREM techniques

Ce(x)Zr(1)(-)(x)O(2) solid solutions deposited over silica surface were investigated by X-ray diffraction (XRD), Raman spectroscopy (RS), and high-resolution transmission electron microscopy (HREM) techniques in order to understand the role of silica support and the temperature stability of these composite oxides. For the purpose of comparison, an unsupported Ce(x)Zr(1)(-)(x)O(2) was also synthesized and subjected to characterization by various techniques. The Ce(x)Zr(1)(-)(x)O(2)/SiO(2) (CZ/S) (1:1:2 mole ratio based on oxides) was synthesized by depositing Ce(x)Zr(1)(-)(x)O(2) solid solution over a colloidal SiO(2) support by a deposition precipitation method and unsupported Ce(x)Zr(1)(-)(x)O(2) (CZ) (1:1 mole ratio based on oxides) was prepared by a coprecipitation procedure, and the obtained catalysts were subjected to thermal treatments from 773 to 1073 K. The XRD measurements disclose the presence of cubic phases with the composition Ce(0.75)Zr(0.25)O(2) and Ce(0.6)Zr(0.4)O(2) in CZ samples, while CZ/S samples possess Ce(0.75)Zr(0.25)O(2), Ce(0.6)Zr(0.4)O(2), and Ce(0.5)Zr(0.5)O(2) in different proportions. The crystallinity of these phases increased with increasing calcination temperature. The cell a parameter estimations indicate contraction of ceria lattice due to the incorporation of zirconium cations into the CeO(2) unit cell. Raman measurements indicate the presence of oxygen vacancies, lattice defects, and displacement of oxygen ions from their normal lattice positions in both the series of samples. The HREM results reveal, in the case of CZ/S samples, a well-dispersed nanosized Ce-Zr-oxides over the surface of amorphous SiO(2). The structural features of these crystals as determined by digital diffraction analysis of experimental images reveal that the Ce-Zr-oxides are mainly in the cubic geometry and exhibit high thermal stability. Oxygen storage capacity measurements by a thermogravimetric method reveal a substantial enhancement in the oxygen vacancy concentration of CZ/S sample over the unsupported CZ sample.     

A near-infrared Fourier transform Raman spectroscopy of epidermal keratinocytes: changes in the protein-DNA structure following malignant transformation

We report here the use of near-infrared (NIR) Fourier transform (FT) Raman spectroscopy to analyze normal human epidermal keratinocytes prior to and following malignant transformation. Our analysis indicates specific Raman spectral differences between immortalized (HPK1A) and malignant ras transformed (HPK1A-ras) cells. In addition, striking spectral differences are seen in the DNA isolated from these cells and particularly in the 843/810 cm(-1) ratio with values of 1.6 +/- 0.13 in HPK1A cells and 0.68 +/- 0.09 in HPK1A-ras cells (mean +/- S.D., n = 12, P < 0.001) indicating specific alterations in the backbone conformation markers following malignant transformation. Subsequently, we analysed the effect of a strong inhibitor of keratinocyte growth, the Vitamin D analog EB1089, on the Raman spectra of intact cells and on the 843/810 cm(-1) ratio in the DNA isolated from both cell lines. Specific changes were observed in intact cells in the 1300-750 cm(-1) region. Furthermore, the 843/810 cm(-1) ratio of isolated DNA from HPK1A cells was not affected by EB1089 but significantly increased in DNA isolated from HPK1A-ras cells so much that it became closer to the value observed for HPK1A cells (1.07 +/- 0.10). Our data suggest that Raman analysis of DNA and in particular the 843/810 cm(-1) ratio can provide useful indices of malignant transformation and efficacy of anticancer agents.     

A Raman and infrared spectroscopic study of the uranyl silicates--weeksite, soddyite and haiweeite: part 2

Raman spectroscopy has been used to study the molecular structure of a series of selected uranyl silicate minerals including weeksite K2[(UO2)2(Si5O13)].H2O, soddyite [(UO2)2SiO4.2H2O] and haiweeite Ca[(UO2)2(Si5O12(OH)2](H2O)3 with UO2(2+)/SiO2 molar ratio 2:1 or 2:5. Raman spectra clearly show well resolved bands in the 750-800 cm(-1) region and in the 950-1000 cm(-1) region assigned to the nu1 modes of the (UO2)2+ units and to the (SiO4)4- tetrahedra. Soddyite is characterized by Raman bands at 828.0, 808.6 and 801.8 cm(-1), 909.6 and 898.0 cm(-1), and 268.2, 257.8 and 246.9 cm(-1), attributed to the nu1, nu3, and nu2 (delta) (UO2)2+, respectively. Coincidences of the nu1 (UO2)2+ and the nu1 (SiO4)4- is expected. Bands at 1082.2, 1071.2, 1036.3, 995.1 and 966.3 cm(-1) are attributed to the nu3 (SiO4)4-. Sets of Raman bands in the 200-300 cm(-1) region are assigned to nu2 (delta) (UO2)2+ and UO ligand vibrations. Multiple bands indicate the non-equivalence of the UO bonds and the lifting of the degeneracy of nu2 (delta) (UO2)2+ vibrations. The (SiO4)4- tetrahedral are characterized by bands in the 470-550 cm(-1) and in the 390-420 cm(-1) region. These bands are attributed to the nu4 and nu2 (SiO4)4- bending modes. The minerals show characteristic OH stretching bands in the 2900-3500 and 3600-3700 cm(-1).     

Raman spectroscopy of selected lead minerals of environmental significance

The Raman spectra of the minerals cerrusite (PbCO(3)), hydrocerrusite (Pb(2)(OH)(2)CO(3)), phosgenite (Pb(2)CO(3)Cl(2)) and laurionite (Pb(OH)Cl) have been used to qualitatively determine their presence. Laurionite and hydrocerrusite have characteristic hydroxyl stretching bands at 3506 and 3576 cm(-1). Laurionite is also characterised by broad low intensity bands centred at 730 and 595 cm(-1) attributed to hydroxyl deformation vibrations. The minerals cerrusite, hydrocerrusite and phosgenite have characteristic CO (nu(1)) symmetric stretching bands observed at 1061, 1054 and 1053 cm(-1). Phosgenite displays complexity in the CO (nu(3)) antisymmetric stretching region with bands observed at 1384, 1327 and 1304 cm(-1). Cerrusite shows bands at 1477, 1424, 1376 and 1360 cm(-1). The hydrocerrusite Raman spectrum has bands at slightly different positions from cerrusite, with bands at 1479, 1420, 1378 and 1365 cm(-1). The complexity of the nu(3) region is also reflected in the nu(2) and nu(4) regions with the observation of multiple bands. Laurionite is characterised by two intense bands at 328 and 272 cm(-1) attributed to PbO and PbCl stretching bands. Importantly, all four minerals are characterized by their Raman spectra, enabling the mineral identification in leachates and contaminants of environmental significance.     

Vibrational spectroscopy of stichtite

Raman spectroscopy complimented with infrared spectroscopy has been used to study the mineral stitchtite, a hydrotalcite of formula Mg6Cr2(CO3)(OH)16.4H2O. Two bands are observed at 1087 and 1067 cm(-1) with an intensity ratio of approximately 2.5/1 and are attributed to the symmetric stretching vibrations of the carbonate anion. The observation of two bands is attributed to two species of carbonate in the interlayer, namely weakly hydrogen bonded and strongly hydrogen bonded. Two infrared bands are found at 1457 and 1381 cm(-1) and are assigned to the antisymmetric stretching modes. These bands were not observed in the Raman spectrum. Two infrared bands are observed at 744 and 685 cm(-1) and are assigned to the nu4 bending modes. Two Raman bands were observed at 539 and 531 cm(-1) attributed to the nu2 bending modes. Importantly the band positions of the paragenically related hydrotalcites stitchtite, iowaite, pyroaurite and reevesite all of which contain the carbonate anion occur at different wavenumbers. Consequently, Raman spectroscopy can be used to distinguish these minerals, particularly in the field where many of these hydrotalcites occur simultaneously in ore zones.     

Raman spectra of gas hydrates--differences and analogies to ice 1h and (gas saturated) water

It is generally accepted that Raman spectroscopic investigations of gas hydrates provide vital information regarding the structure of the hydrate, hydrate composition and cage occupancies, but most research is focused on the vibrational spectra of the guest molecules. We show that the shape and position of the Raman signals of the host molecules (H(2)O) also contain useful additional information. In this study, Raman spectra (200-4000 cm(-1)) of (mixed) gas hydrates with variable compositions and different structures are presented. The bands in the OH stretching region (3000-3800 cm(-1)), the O-H bending region (1600-1700 cm(-1)) and the O-O hydrogen bonded stretching region (100-400 cm(-1)) are compared with the corresponding bands in Raman spectra of ice Ih and liquid water. The interpretation of the differences and similarities with respect to the crystal structure and possible interactions between guest and host molecules are presented.     

Using Raman spectroscopy to identify mixite minerals

Raman spectroscopy has been used to identify whether or not a selection of minerals labelled as mixites (formula BiCu6(AsO4)3(OH)6.3H2O) are correctly marked. Of the four samples, two samples are shown to be potentially mixites because of the presence of the characteristic Raman spectra of (AsO4)3- units and (HAsO4)- units, characterised by bands at around 803 and 833 cm(-1). Two of the minerals are shown to be predominantly carbonates. Bands are observed at 3473.9 and 3470.3 cm(-1) for the two mixite samples. Bands observed in the region 880-910 cm(-1) and in the 867-870 cm(-1) region are assigned to the AsO stretching vibrations of (HAsO4)2- and (H2AsO4)- units. Whilst bands at around 803 and 833 cm(-1) are assigned to the stretching vibrations of uncomplexed (AsO4)3- units. Intense bands observed at 473.7 and 475.4 cm(-1) are assigned to the nu4 bending mode of AsO4 units. Bands observed at around 386.5, 395.3 and 423.1 cm(-1) are assigned to the nu2 bending modes of the HAsO4 (434 and 400 cm(-1)) and the AsO4 groups (324 cm(-1)). Raman spectroscopy lends itself to the identification of minerals on host matrices and is especially useful for the identification of mixites.     

Vibrational spectra of 3,5-dimethylpyrazole and deuterated derivatives

The infrared (IR) and Raman spectra of 3,5-dimethylpyrazole have been recorded in the vapor, liquid (melt and solution) and solid states. Two deuterated derivatives, C5H7N-ND and C5D7N-NH, were also studied in solid state and in solutions. Instrumental resolution was relatively low, 2.0 cm(-1) in the IR and approximately 2.7 cm(-1) in the Raman spectra. The solids are made of cyclic hydrogen-bonded trimers. These trimers, present also in chloroform and acetone solutions, give rise to characteristic high absorption IR spectra in the 3200-2500 cm(-1) region, related to Fermi resonance involving nu(NH) vibrations. Bands from trimers are not present in water solutions but these solutions show spectral features similar in several ways to those of the trimer, attributable to solvent-bonded complexes. Evidence of H-bonding interactions with the other solvents is also visible in the high-frequency region. The two very intense bands in the Raman spectra of the solids appearing at 115 and 82 cm(-1) in the parent compound are also connected with a trimer formation. To interpret the experimental data, ab initio computations of the harmonic vibrational frequencies and IR and Raman intensities were carried out using the Gaussian 94 program package after full optimization at the RHF/6-31G* level for the three monomeric compounds as well as for three models of the trimer, with C3h, C3 and C1 symmetry. The combined use of experiments and computations allow a firm assignment of most of the observed bands for all the systems. In general, the agreement between theory and experiment is very good, with the exception of the IR and Raman intensities of some transitions. Particularly noticeable is the failure of the theoretical calculation in accounting for the high intensity of the Raman bands of the solid about 115 and 82 cm(-1).     

Laser Raman and IR spectra and force fields for 2,4-dichlorobenzonitrile

Raman spectrum of 2,4-dichlorobenzonitrile (2,4-DCBN) in powder form has been recorded in the region 50-4000 cm(-1) on a Jasco K-500 Raman spectrophotometer using the 488.0 nm radiation from an argon laser. FTIR spectra in the region 200-4000 cm(-1) have been recorded in KBr pellet and nujol mull on a Nicolet DX spectrometer. Using the observed Raman and IR frequencies, normal co-ordinate analysis has been carried out to support the vibrational analysis and to determine the planar and non-planar force fields.     

Towards a single crystal Raman spectrum of kaolinite at 77 K

The Raman spectra at 77 K of the hydroxyl stretching of kaolinite were obtained along the three axes perpendicular to the crystal faces. Raman bands were observed at 3616, 3658 and 3677 cm(-1) together with a distinct band observed at 3691 cm(-1) and a broad profile between 3695 and 3715 cm(-1). The band at 3616 cm(-1) is assigned to the inner hydroxyl. The bands at 3658 and 3677 cm(-1) are attributed to the out-of-phase vibrations of the inner surface hydroxyls. The Raman spectra of the in-phase vibrations of the inner-surface hydroxyl-stretching region are described in terms of transverse and longitudinal optic splitting. The band at 3691 cm(-1) is assigned to the transverse optic and the broad profile to the longitudinal optic mode. This splitting remained even at liquid nitrogen temperature. The transverse optic vibration may be curve resolved into two or three bands, which are attributed to different types of hydroxyl groups in the kaolinite.     

Spectroscopic characterization of chromite from the Moa-Baracoa Ophiolitic Massif, Cuba

The Cuban chromites with a spinel structure, FeCr2O4 have been studied using optical absorption and EPR spectroscopy. The spectral features in the electronic spectra are used to map the octahedral and tetrahedral co-ordinated cations. Bands due Cr3+ and Fe3+ ions could be distinguished from UV-vis spectrum. Chromite spectrum shows two spin allowed bands at 17,390 and 23,810 cm(-1) due to Cr3+ in octahedral field and they are assigned to 4A2g(F) --> 4T2g(F) and 4A2g(F) --> 4T1g(F) transitions. This is in conformity with the broad resonance of Cr3+ observed from EPR spectrum at g = 1.903 and a weak signal at g = 3.861 confirms Fe3+ impurity in the mineral. Bands of Fe3+ ion in the optical spectrum at 13,700, 18,870 and 28,570 cm(-1) are attributed to 6A1g(S) --> 4T1g(G), 6A1g(S) --> 4T2g(G) and 6A1g(S) --> 4T2g(P) transitions, respectively. Near-IR reflectance spectroscopy has been used effectively to show intense absorption bands caused by electronic spin allowed d-d transitions of Fe2+ in tetrahedral symmetry, in the region 5000-4000 cm(-1). The high frequency region (7500-6500 cm(-1)) is attributed to the overtones of hydroxyl stretching modes. Correlation between Raman spectral features and mineral chemistry are used to interpret the Raman data. The Raman spectrum of chromite shows three bands in the CrO stretching region at 730, 560 and 445 cm(-1). The most intense peak at 730 cm(-1) is identified as symmetric stretching vibrational mode, A1g(nu1) and the other two minor peaks at 560 and 445 cm(-1) are assigned to F2g(nu4) and E(g)(nu2) modes, respectively. Cation substitution in chromite results various changes both in Raman and IR spectra. In the low-wavenumber region of Raman spectrum a significant band at 250 cm(-1) with a component at 218 cm(-1) is attributed F2g(nu3) mode. The minor peaks at 195, 175, 160 cm(-1) might be due to E(g) and F2g symmetries. Broadening of the peak of A1g mode and shifting of the peak to higher wavenumber observed as a result of increasing the proportion of Al3+O6. The presence of water in the mineral shows bands in the IR spectrum at 3550, 3425, 3295, 1630 and 1455 cm(-1). The vibrational spectrum of chromite gives raise to four frequencies at 985, 770, 710 and 650 cm(-1). The first two frequencies nu1 and nu2 are related to the lattice vibrations of octahedral groups. Due to the influence of tetrahedral bivalent cation, vibrational interactions occur between nu3 and nu4 and hence the low frequency bands, nu3 and nu4 correspond to complex vibrations involving both octahedral and tetrahedral cations simultaneously. Cr3+ in Cuban natural chromites has highest CFSE (20,868 cm(-1)) when compared to other oxide minerals.     

5-Phenyl-2-(pyrazol-4-yl)-1,3,4-thiadiazoles

By recyclization of 2-R-6-ethyl-7-hydroxy(methoxy)-3-(5-phenyl-1,3,4-thiadiazol-2-yl)chromones when treated with hydrazine hydrate and phenylhydrazine, we synthesized 5-phenyl-2-(3-R-5-R1-1H-pyrazol-4-yl)-1H-1,3,4-thiadiazoles and 2-(3-R-5-R1-1-phenyl-1H-pyrazol-4-yl)-5-phenyl-1H-1,3,4-thiadiazoles. We confirmed the structure of the latter from ¹H NMR spectra.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 781–787, May, 2005.