Development of Latent Fingerprints on Metallic Surfaces Using Electropolymerization Processes
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Abstract:
We propose a new process for developing latent fingerprints on metal items, applicable to unfired weapons made of Ergal in particular. The method is based on the presence of fatty acids that are contained in fingerprints and act as an insulator on the surface where fingerprints are to be developed. The process of polymerization occurs on the metal portions left untouched by finger contact. Hence, the developing process results as a negative pattern of the original fingerprint. The reaction consists in the electropolymerization of pyrrole and substituted porphyrins, i.e., tetra (o-aminophenyl) porphyrine: radical-cations are generated on superficial nucleation sites by oxidation of monomer, close to the electrode surface; subsequently, the radical species react with the neutral monomer, which begins to diffuse to the electrode. We have also studied the polymer's morphology by means of SEM and AFM, in order to find a correlation between the reagent to be used and the quality of the enhancement process. These are only preliminary results; however, they show that the suggested method is a new way to increase the rate of success in developing latent fingerprints on metal surfaces. In this regard, it may be considered complementary to other conventional procedures, due to the low costs of the instruments and reagents, and the rapidity and simplicity of the treatment.Keywords:
Latent image
Pyrrole
The title compound, C19HI8FeN2 or [Fe(CsHs)(CI4HI3-N2)], crystallizes in space group P2~/n with two molecules in the asymmetric unit.The pyrrole groups take part in intermolecular (pyrrole)N--H...Tr(pyrrole) interactions through a hydrogen-bonded ring system involving four pyrrole groups, with N..-(pyrrole centroid) distances in the range 3.209(3)-3.427(3)/k and N--H.--(pyrrole centroid) angles in the range 127-139 °.
Pyrrole
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Pyrrole
Carbon disulfide
Carbon fibers
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Three types of Sb~Ⅲ reagents were studied.They are:(1)the compounds containing mer-
capto group,(2)Caille and Viel reagents and(3)the compounds containing two phenolic
groups in adiacent positions.
It was shown experimentally that the first two types of reagents give reactions with very
low selectivities.Moreover,the selectivities could not be improved by merely varying the structure
of the organic compounds.
The diphenolic compounds seem to be the most hopeful reagents for Sb~Ⅲ.Their reactions
are considerably selective.Several classes of coloured compounds containing two phenolic groups
in adjacent positions were prepared.Some of them were found to be satisfactory reagents
for Sb~Ⅲ.
Functional group
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This paper deals with the mechanism of latent image formation on chemical sensitized emulsion based on the model proposed in the previous paper. From the current work, some results were obtained: (1). silver sulfide specks on the surface of a silver bromide grain can be photoelectron traps and photohole traps at same time. As photoelectron traps, they are in larger dimension than the single kink site, however they are not deep ones like the single kink site. It is these specks which help the emulsion to promote photographic sensitivity and improve LIRF but they should also be responsible for despersion of photolyzed silver atoms and HIRE. As photohole traps, their only function is slowing down the photohole movement and delaying the bromine formation but can not remove photohole permanently. (2). Gold sensitization not only can decrease the size of minimum developable centers but also increase the anti-oxidization ability of the clusters, furthermore, there should be other sensitization mechanisms which we still do not know. Ag2 can be partly thansformed into developable centers through gold-intensification. (3). The nature of the silver specks formed from reduction sensitization is same as that formed during exposure. This do not mean they must grow up, in fact, most of them would be destroyed during exposure. Two important functions of reduction specks are to increase the probability of latent image formation and remove photoholes or bromine therefore increase the number of net electrons in the grains which is especialy in favour of latent image formation.
Latent image
Silver bromide
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Objective To evaluate the stability of the total bile acid reagent after opening the improved bottles.Methods We analyzed the total bile acid reagents in automatic biochemistry respectively by using the common reagent bottles and the improved reagent bottles.Observe daytime variation of CV and trend changes of high,medium mixed complex-value serum and reagent blank test results.Then t test was applied.Results (1)The change trend of the improved reagent bottles was significantly slower than that of the common reagent bottles,(2)The total deviations of common reagent bottles before and after monitoring were-20.37% and-22.09% respectively.Total deviations of the improved reagent bottles were 3.77% and-1.16% respectively,(3)The daytime variations of the common reagent bottles in complex-value were 9.27% and 9.32% respectively;the improved reagent bottles were 3.38% and 2.03% respectively;(4)The reagent blank with improved reagent bottles decline significantly slower than common reagent bottles;(5)The measured result of t test of the two kinds reagent bottles in the monitoring period was t=4.889,P0.01,the result there was significantly different.Conclusion The impvored reagent bottles have good performance to slow down the decay of total bile acid reagentand,and it′s suitable for extending the period of reagents′ validity.It can significantly reduce daytime variation.
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Abstract As shown in Fig. 3 in Chapter 1, the photographic process is composed of the capture of incident light by silver halide emulsion grains (sensing), formation of latent image centers on the silver halide grains (memory), and image formation by the catalytic action of the latent image centers for the reduction of silver halide grains to silver (display). It was first suggested by Sheppard, Trivelli, and Loveland1 in 1925 and is now accepted that a latent image center is an aggregate of silver atoms. Therefore, it is important that the mechanism of photographic sensitivity explain the concentration principle by which a silver aggregate is photolytically formed as a latent image center on a silver halide grain.
Latent image
Photographic emulsion
Silver bromide
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A digital computer analysis has been made of photon absorption, chemical sensitization and latent image distribution in a silver halide photographic emulsion, using the Bayer Hamilton model but with a different approach in treating the positive holes.In discussing the effect of sulphur sensitization it has been assumed that silver sulphide molecules can play a dual role in latent image formation, undergoing partial thermal dissociation to increase both the number of electron traps by providing more interstitial silver ions and that of positive hole traps by forming AgS-. The increased interstitial silver ion concentration has also been supposed to lead to an increase in the stability of single silver atoms. As to gold sensitization, it has been assumed that the main effect of gold is to enhance the developahility of latent image centres.Parameter values for simulation under various conditions of chemical sensitization have been calculated, based upon the above assumptions. The results have, as expected, reproduced in many respects those shown by experiments. Finally, a relation between the concentration of interstitial silver ions and the sulphur content in the emulsion grain has been derived.
Latent image
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Folin reagent was one of the most important reagents in protease determination. The differences between Folin reagent from laboratory and Folin reagent sold were studied. The results showed that there was not significant difference between the absorbance of Folin reagent from lab replaced 30d and Folin reagent sold (p<0.05). The RSD of Folin reagent from lab was between 0.3and 1.67, and Folin reagent sold between 0.63 and 1.49. The precision of them was both higher. The maximum absorption wave length of the chromogenic agent of Folin reagent was with 736-755. And there was no significant difference of the value of the same sample protease between both Folin reagent (p<0.05). Folin reagent from lab based on GB/T23527-2009 was perfect.
Chromogenic
Absorbance
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Abstract Introduction Fluoroalkenylcopper Reagents Difluorovinylcopper Reagents Perfluoroallylcopper Reagents Perfluoroalkynylcopper Reagents Carboalkoxydifluoromethylenecopper Reagents Dialkoxyphosphinylfluoromethylcopper Reagent Dialkoxyphosphinyldifluoromethylcopper Reagents Perfluorobenzylcopper Reagent Perfluoroalkylcopper Reagents Pentafluorophenylcopper Reagent 2,3,5,6‐Tetrafluoropyridylcopper Reagents
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Conflicting viewpoints concerning the importance of recombination in latent image formation are examined with respect to existing experimental evidence. Hole-electron pairs and, in certain circumstances, print-out silver specks are produced efficiently. In contrast, most, though not all, latent image centres form inefficiently. Reduction sensitization, which provides a means of detecting holes, increases efficiency of formation of latent image in emulsions chemically sensitized in various ways. This indicates the importance of recombination during exposure of the emulsions with no reduction sensitization. The wide breadth of most sensitivity distributions means inefficient utilization of absorbed photons. Neither variable critical size of latent image centres nor inefficient aggregation of silver or gold atoms is a likely explanation of this inefficiency, at least in certain circumstances. It is concluded that recombination has much influence on latent image formation. Loss of photoelectrons by electron acceptors can be a source of inefficiency, however.
Latent image
Image formation
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