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91.
Extraction of capsaicins in aerosol defense sprays from fabrics 总被引:2,自引:0,他引:2
The use of aerosol defense sprays has increased as a means of self-defense and as a weapon in the commission of a crime. The residue of these sprays is often left behind as physical evidence on a victim's clothing or personal belongings. As the popularity of self-defense weaponry increases, so does the likelihood that it will be encountered in forensic casework. The extraction, recovery from fabrics, and identification of residue from defense sprays is described. The commonly used extraction method of liquid-liquid extraction is compared to solid phase microextraction (SPME) to recover capsaicin and dihydrocapsaicin from cotton swabs. The use of SPME resulted in lower limits of detection and greater recovery efficiency when compared to solvent extraction. SPME also provided more consistent recovery and less variability when compared to solvent extraction. The effect of use of various types of evidence packages on the preservation of this type of evidence is also reported. The collection and analysis of hand swabs after normal discharge of pepper spray canisters was studied indicating the low persistence of these compounds on the hands of the person conducting the spraying. Finally, the results of a real case whereby solvent-solvent extraction did not provide the necessary sensitivity for extracting the capsaicin compounds on the garments of a victim of an alleged spraying and the SPME extraction provided the recovery and identification of the compounds is also presented. 相似文献
92.
The power dependence of the optical poling process of a new azo chromophore in the polymethylmethacrylate matrix at room temperature has been investigated. The existing theory is found to be inconsistent with the experiment. A simple model based on the rate equation is proposed to describe the writing process of the chromophore/polymer system. The measured growth rate and the plateau second-harmonic generation intensity as induced by all optical poling are found to be in good agreement with the prediction of the simple model. 相似文献
93.
94.
We present rigorous results on the frequency dependence of the Kubo-Greenwood conductivity of the interrupted-strand — or bond-percolation model, for which exists strong evidence to be relevant for a class of quasi one-dimensional organic conductors and for some mixed valent complex compounds like K2Pt(CN)4 Br0.30 3H2O. The model describes a linear sequence of one-dimensional metallic boxes or segments separated from each other by perfectly insulating lattice defects. We used both Lotentzian and rectangular averages to obtain the frequency-averaged conductivity as a well-defined physical quantity and found a sharply peaked structure of the conductivity spectrum resulting from the non-zero energy level spacing of one metallic box. Since one has to look very carefully on different frequency average procedures and on the consequences of the energy spectrum of an entire strand one has to precise arguments and results on the low frequency behaviour of the conductivity obtained from numerical considerations recently proposed by P.S. Riseborough. 相似文献
95.
NiCl(2)(dppe)-catalyzed cross-coupling of aryl mesylates, arenesulfonates, and halides with arylboronic acids 总被引:2,自引:0,他引:2
An investigation of the NiCl(2)(dppe)-, NiCl(2)(dppb)-, NiCl(2)(dppf)-, NiCl(2)(PCy(3))(2)-, and NiCl(2)(PPh(3))(2)-catalyzed cross-coupling of the previously unreported aryl mesylates, and of aryl arenesulfonates, chlorides, bromides, and iodides containing electron-withdrawing and electron-donating substituents with aryl boronic acids, in the absence of a reducing agent, is reported. NiCl(2)(dppe) was the only catalyst that exhibited high and solvent-independent activity in the two solvents investigated, toluene and dioxane. NiCl(2)(dppe) with an excess of dppe, NiCl(2)(dppe)/dppe, was reactive in the cross-coupling of electron-poor aryl mesylates, tosylates, chlorides, bromides, and iodides. This catalyst was also efficient in the cross-coupling of aryl bromides and iodides containing electron-donating substituents. Most surprisingly, the replacement of the excess dppe from NiCl(2)(dppe)/dppe with excess PPh(3) generated NiCl(2)(dppe)/PPh(3), which was found to be reactive for the cross-coupling of both electron-rich and electron-poor aryl mesylates and chlorides. Therefore, the solvent-independent reactivity of NiCl(2)(dppe) provides an inexpensive and general nickel catalyst for the cross-coupling of aryl mesylates, tosylates, chlorides, bromides, and iodides with aryl boronic acids. 相似文献
96.
Goldhaber's spin-statistics connection for electric-pole-magnetic-pole composite dyons is deduced in a gauge-invariant way by connecting the spatial interchange operator with a rotation.Supported in part by the National Science Foundation.Supported in part by the National Science Foundation. 相似文献
97.
Rb7[SiO4][VO4]: an Ortho‐Silicate‐Vanadate(V) Rb7[SiO4][VO4] has been obtained from a redox reaction between CdO and vanadium metal in the presence of Rb2O and SiO2 at 600 °C in an Ag container as yellow‐greenish transparent single crystals. The crystal structure determination (IPDS data: P21/c, a = 637.6(1) pm, b = 1039.7(1) pm, c = 2076.8(4) pm, β = 93.21(2)°, Z = 4, wR2 = 0.1319) reveals the presence of isolated complex anions, [SiO4]4— and [VO4]3—. 相似文献
98.
David Liptak William H. Ilsley Milton D. Glick John P. Oliver 《Journal of organometallic chemistry》1980,191(2):339-345
The structure of di-ortho-tolylmercury has been determined by single crystal X-ray methods from counter data. The compound crystallizes in the monoclinic space group C2/c with unit cell dimensions a 10.970(2), b 10.448(3), c 11.409(3) Å; β 115.48(2)°, V 1180.5(5) Å3, ?calc 2.158 g/cm3 and Z = 4. The structure was solved with conventional heavy atom techniques. The crystal consists of individual molecular units with the mercury atom located on the crystallographic 2-fold axis of symmetry. The CHgC fragment is nearly linear with an angle of 178.0(4)°. The methyl groups lie on the same side of the molecule and the rings are twisted with respect to one another by 58.9°. The HgC bond distance is 2.09(1) Å. 相似文献
99.
Bauer O Guerasimova A Sauer S Thamm S Steinfath M Herwig R Janitz M Lehrach H Radelof U 《Rapid communications in mass spectrometry : RCM》2004,18(16):1821-1829
Peptide nucleic acid (PNA) is a novel class of DNA analogues in which the entire sugar-phosphate backbone is replaced by a pseudopeptide counterpart. Owing to its neutral character and the consequent lack of electrostatic repulsion, PNA exhibits very stable heteroduplex formation with complementary nucleic acid that is essentially ionic strength independent and enables hybridization under minimum salt conditions. This feature as well as its superior ion stability and easy ionization compared to DNA renders PNA very attractive for hybridization-based matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) applications. We have developed an approach to DNA characterization that takes advantage of multiplexed PNA hybridizations analyzed by MALDI-TOFMS. Our motivation was the further development of oligonucleotide fingerprinting, an efficient technique for cDNA and genomic DNA library characterization. Through positive 'charge-tagging' of PNA the efficiency of detection in MALDI-TOFMS was considerably enhanced permitting an unparalleled degree of multiplexing. Results from the simultaneous hybridization of 21 charge-tagged PNA hexamer oligonucleotides showed that genomic DNA and cDNA clones are successfully characterized on the basis of their hybridization profiles. The degree of multiplexing achieved may render a significant increase in throughput and hence efficiency of oligonucleotide fingerprinting possible. 相似文献
100.
Guerrero L Smart OS Woolley GA Allemann RK 《Journal of the American Chemical Society》2005,127(44):15624-15629
Control of DNA binding of HDH-3, a 18-residue polypeptide based on the recognition helix of the Q50K engrailed homeodomain, has been achieved. HDH-3 was linked to an azobenzene cross-linker through two cysteine residues in an i, i + 11 spacing. For the thermodynamically stable trans configuration of the cross-linker, the dark-adapted peptide (dad-HDH-3) adopted a mainly alpha-helical structure as judged by circular dichroism (CD) spectroscopy. After irradiation with light of 360 nm, the helical content of the peptide (irrad-HDH-3) was reduced significantly and the CD spectrum of the irradiated peptide resembled that of the largely unstructured, unalkylated peptide. Despite lacking helices-1 and -2 and the N-terminal arm of Q50K engrailed, dad-HDH-3 bound to its natural DNA target sequence TAATCC (QRE) with high affinity (K(D) = 7.5 +/- 1.3 nM). The binding affinity for the mutant DNA sequence, TAATTA (ERE), was reduced significantly (K(D) = 140 +/- 11 nM). Unlike irrad-HDH-3, which like the unalkylated parent peptide displayed only marginal DNA binding specificity, dad-HDH-3 specified base pairs 5 and 6 of QRE with an accuracy rivaling that of the intact wild-type Q50K engrailed homeodomain, making dad-HDH-3 the most specific designed DNA binding miniature homeodomain reported to date. Moreover, DNA binding affinity and specificity of HDH-3 could be controlled externally by irradiation with light. 相似文献