Anions Absorption

We have investigated the reactions of the COs " radicals with double-stranded DNA by laser flash photolysis techniques [15]. In these time-re-solved experiments, the COs radicals were generated by one-electron oxidation of HCOs by sulfate radical anions, SO4 the latter were derived from the photodissociation of persulfate anions, S20s initiated by 308-nm XeCl excimer laser pulse excitation. In air-equilibrated buffer solution containing the self-complementary oligonucleotide duplex d(AACGCGAATTCGCGTT), 208 , and an excess of HCO3., the decay of the CO3 radical anion absorption band at 600 nm is associated with the concomitant formation of the characteristic narrow absorption band of the G(-H) radicals near 310 nm. 

Figure 5. Decreases of the thiocyanate radical anion absorption as a function of added competitor concentration. Absorbances monitored at 480 nm. a) DMSO b)MSAorDMS02.

The bathochromic absorbing sensitizer allows selective excitation relative to most of the chloroaromatics. The naphtholate anion absorption spectrum fits almost exactly with black light phosphor lamps, allowing very efficient light harvesting. The quantum yield of 0.3 is better than for many direct photodechlorinations. The naphtholate anion is (at least partially) catalytically regenerated and the reaction can proceed to complete disappearance of the chlorobi-phenyl while 100% of the disappeared organic chlorine is recovered as sodium chloride. 

Table 1. Redox potentials, rate constants for the radiolytic reduction and r-radical anion absorption maxima of fullerenes [11, 65, 66, 68-70],...

A qualitative similar picture was established for the reduction of higher fullerenes (e.g., C70, C76, C78, and C84) [68-70], The associated symmetries of these higher fullerenes were expected to have an impact on the reduction potentials and, equally important, on the relative position of the corresponding jr-radical anion absorption bands (Table 1). 

Formation of the ketyl radical anion in photoinduced electron-transfer reactions of benzophenone with butylamine and triethylamine was observed by Shizuka and coworkers in neat amines at low temperatures [14, 152]. At room temperatures they observed the formation of the ketyl radical (Amax 555 nm), whereas on reducing the temperature to 120 K the transient absorption spectrum showed a decrease in intensity at 555 nm and a subsequent increase at 660 nm. This has been attributed to the slowing down of proton transfer between the radical ion-pairs at low temperatures, making it possible to measure ketyl radical anion absorption at 660 nm [152]. At very low temperatures however (ca 120 K) only the triplet state of benzophenone was observed (Amax 525 nm), indicating thereby that under these conditions the triplet state of benzophenone does not undergo electron-transfer reactions with amines. 

W Weak Anionic Absorption I Moderate Anionic Absorption S Strong Anionic Absorption M Molarity of Solution... 

Chromium may cause adverse health effects following inhalation, ingestion, or dermal exposure. The toxicity of chromium is mainly caused by hexavalent compounds as a result of a higher cellular uptake of chromium(VI) compounds than chromium(III). This is explained by the fact that the chromate anion (Cr04) can enter the cells via facilitated diffusion through nonspecific anion channels (similarly to phosphate and sulfate anions). Absorption of chro-mium(III) compounds is via passive diffusion and phagocytosis. 

In the C—N dimension anion curves are drawn to four different dissociation limits the two complementary limits of N02(—) and CH3 and two limits leading to excited states of N02(—) and CH3. Dipole bound states could also be drawn in these dimensions. The ground-state curves and dipole bound curves are 2). The lower excited-state curve A is M( 1) since the EDEA and VEa are negative but the Ea is positive. More than three data points from PES, ECD, El, or anion absorption and emission spectra define the ground state and the first excited valence state. The B state is D(0) but could lead to molecular anion formation via the C, D,... 

The oxidized polybithiophene has a weak absorption at 617 cm-- -. This is assignable to the CIO 4 anion, also present, but obscured by the C-H in-plane deformation is a stronger CIO4 anion absorption at 1080 cm. Both spectra contain spurious peaks at 3480 cm-- -, most likely due to residual moisture in the KBr. 

The technique of radiophotoluminescence excitation spectra is used to study the displacement of electrons from physical traps to solute molecules and vice-versa in solutions of biphenyl in methylcyclohexane. Bleaching in the infrared leads to the disappearance of trapped electrons and of the first peak of radiothermoluminescence. If a bleached sample is illuminated in one of the two biphenyl anion absorption bands, both infrared-stimulated RPL and a weak first glow peak reappear. It is concluded that of the two RTL peaks observed at 90° and 95° K. in methylcyclohexane glass, the first is caused by recombination of electrons with solute cations and the second by diffusion and recombination of solute anions and cations. 

In a sample with a decreased response in the anion absorption bands, the second glow peak also is reduced. 

An examination of Fig. 4 shows that the stabilization results in a decrease in anion-absorptive capacity and no change in the cation-absorptive capacity. This means a net increase in the cation-exchange capacity. 

If small amounts of H ion are assumed to be present in all solutions, the basic nature of the anion absorption curve will remain unchanged. The cation absorption curve will only parallel the anion absorption curve for large salt concentrations and will go through the origin. The simple picture just outlined is thus capable of accounting qualitatively for all features of Fig. 4 that do not arise from the instability of the fiber. 

Effect of Temperature. The effect of temperature on Na and SO4 absorption is shown in Fig. 5. Temperature coefficients for equilibrium absorption cannot be determined until possible complications resulting from instability are removed. However, the temperature coefficient for cation absorption is certainly small and that for anion absorption would be anticipated to be small also. All in all there is no evidence for any appreciable heat change during the absorption process. 

Gelin, K., Mihranyan, A., Razaq, A., Nyholm, L., Strpmme, M. Potential controlled anion absorption in a novel high surface area composite of Cladophora cellulose and polypyrrole. Electrochim. Acta 54, 3394-3401 (2009)... 

The uranium anion present in carbonate solutions is [U02(C03)8] and this is associated with few other impurity anions. Absorption capacities as high as 100 to 200 mg/g of dried resin have been obtained on Amberlite IRA-400 2 and Dowex I , under conditions where competing anionic impurities such as phosphate and aluminate ions have only absorbed to an insignificant extent. The resin capacity, in both cases, is greatest at low sodium carbonate concentrations. Vanadate ion absorption can take place to an appreciable extent when vanadium is present in the carbonate leach liquor from the ore. It is, however, readily separated from the uranium, e.g. by a preliminary elution with a saturated solution of sulphur dioxide. This removes the vanadium from the resin by reducing it to a lower valency state. 

The recently developed Excer process of the U.S.A.E.C. aims to extract uranium from low-grade ore, purify it up to nuclear specification and convert to uranium tetrafluoride ready for metal production. The process is shown in Fig. 3.15 and is based first upon a sulphuric acid leach of the ore and anion absorption of uranium from the pulp. Elution is then by 2M sulphuric acid to give a solution containing about 10 to 20 g U/1. The uranyl sulphate is then reduced by metallic iron to uranous sulphate, diluted to an acidity of 0-5M and a second cycle of anion-exchange carried out. Absorption behaves similarly to that with uranyl ion, but ferrous ion is not... 

Following the decay of the radical-anion absorption, other secondary transient product spectra are observed (Figures 2a and 3). The principal features of these product spectra can be identified as the one-electron oxidation of tyrosine and tryptophan by comparison with spectra obtained on pulse radiolysis of solutions of the free amino-acids (6). The phenoxyl radical of tyrosine... 

The DIFFERENCE CROSS-SECTION SPECTRA are due to the absorption difference of the respective intermediates and the unexcited ground-state RC. Note that the spectra are calculated from transient absorption data according reaction model I. In Fig. 3 the features of the respective intermediates show up. For example the spectrum of I shows all features expected for an intermediate P B where one monomeric bacteriochlorophyll is reduced. The spectrum of I shows the properties of intermediate with the anion absorption band of the pheophythin H around 665 nm. 

State Anion absorption Theoretical Em f Experimental S max f State Attachment energie Theoretical Exper AE SF s menta ETS 1 El... 

---