<Original Papers>Fundamental Studies of Municipal Waste Treatment and Utilization (V) : Recycling of Selenium from Selenium-Tellurium Alloy Scraps

The recycling of high-purity selenium from selenium-tellurium alloy scraps of xerographic photoreceptors and its manufacturing process have been carried out to remove tellurium by the following three processes (1) Selective separation of selenium as selenium dioxide by oxidizing roasting at high temperature, 600℃. (2) Selective leaching of selenium dioxide from selenium dioxide and tellurium dioxide mixture and reduction of selenium dioxide by SO_2 gas at a solution temperature of 80℃. (3) Selective distillation of selenium at low pressure. The first step was carried out using Te 10wt% selenium-tellurium alloy to vaporize selenium dioxide gas and leave tellurium dioxide solid in the reservoir. The selenium dioxide deposited in the condenser was analyzed and the high concentration of tellurium in selenium dioxide was observed due to the mixed Se-Te vapors such as SeTe, Se_2Te, SeTe_2,Se_3Te, Se_2Te_2 and Se_4Te. Also the formation of mixed oxide vapors should be expected. The second step was based on the large difference of solubility of each oxide in water, i. e. selenium dioxide has a solubility of about 100,000 times higher than tellurium dioxide. But leaching resulted in poor separation than that expected from the solubility data. The reason for the high solubility of tellurium dioxide was explained by the low pH of the solution and the formation of Te_2O_3-SeO_4 ion pairs in the concentrated selenious acid solution. The reduction of selenious acid solution with SO_2 gas was monitored by a platinum electrode and the electrode was found to determine the end point of the reduction following the ORP changes of Se/SeO_3^ to S/SO_3^. Concentration of tellurium in the SO_2 reduced selenium was made less than 1ppm by high temperature (80℃) solution reduction. The last purification step consisted of selective distillation. The liquid-vapor equilibrium was established and the theoretical plates were calculated to be 7 to obtain 99.9999wt% selenium from 99.9wt% selenium. The SO_2 reduced selenium was purified by low pressure distillation

Metal-free syn-dioxygenation of alkenes

Reactions employing inexpensive reagents from sustainable sources and with low toxicity are becoming increasingly desirable from an academic and industrial perspective. A fascinating example of a synthetic transformation that requires development of alternative procedures is the osmium catalysed dihydroxylation. Recently there has been considerable interest in achieving this reaction through metal-free procedures. This review describes the methods available for metal-free syn-dioxygenation of alkenes

Selenium reaction mechanism in manganese electrodeposition process

A difficulty for the electrochemical deposition is the high negative electrolytic potential of the Mn+2/Mn° pair in aqueous solutions producing water reduction at any pH value; to resolve this problem it is necessary to use selenium dioxide (SeO2) as additive. However, there is little information about the selenium mechanism presenting discrepancies. Founded on linear voltammetry, cyclic voltammetry, chronoamperometry test, and impulses of constant potential and thermodynamic analysis, are experimental evidences of the reaction mechanism to explain the selenium action; from here the originality of this work. It is demonstrated that two reactions that occur in the selenium mechanism at −0.3 and −0.6 V, the first for the selenium deposition and the second for the selenium dissolution. On the active sites of the cathode the specie of selenium reduced at −0.3 V is the ion hydrogen selenite (H2SeO3−), while at −0.6 V the deposited selenium is reduced to selenide

Selenium reaction mechanism in manganese electrodeposition process

A difficulty for the electrochemical deposition is the high negative electrolytic potential of the Mn+2/Mn° pair in aqueous solutions producing water reduction at any pH value; to resolve this problem it is necessary to use selenium dioxide (SeO2) as additive. However, there is little information about the selenium mechanism presenting discrepancies. Founded on linear voltammetry, cyclic voltammetry, chronoamperometry test, and impulses of constant potential and thermodynamic analysis, are experimental evidences of the reaction mechanism to explain the selenium action; from here the originality of this work. It is demonstrated that two reactions that occur in the selenium mechanism at −0.3 and −0.6 V, the first for the selenium deposition and the second for the selenium dissolution. On the active sites of the cathode the specie of selenium reduced at −0.3 V is the ion hydrogen selenite (H2SeO3−), while at −0.6 V the deposited selenium is reduced to selenide

An ancient pathway combining carbon dioxide fixation with the generation and utilization of a sodium ion gradient for ATP synthesis

Synthesis of acetate from carbon dioxide and molecular hydrogen is considered to be the first carbon assimilation pathway on earth. It combines carbon dioxide fixation into acetyl-CoA with the production of ATP via an energized cell membrane. How the pathway is coupled with the net synthesis of ATP has been an enigma. The anaerobic, acetogenic bacterium Acetobacterium woodii uses an ancient version of this pathway without cytochromes and quinones. It generates a sodium ion potential across the cell membrane by the sodium-motive ferredoxin:NAD oxidoreductase (Rnf). The genome sequence of A. woodii solves the enigma: it uncovers Rnf as the only ion-motive enzyme coupled to the pathway and unravels a metabolism designed to produce reduced ferredoxin and overcome energetic barriers by virtue of electron-bifurcating, soluble enzymes

Investigation of direct integrated optics modulators

Direct optical modulation techniques applicable to integrated optical data preprocessors were studied. Emphasis was placed on the analysis and fabrication of a field effect type modulator. A series of computer modeling studies were performed to determine the effects of semiconductor cladding on the fields of propagating waves in planar dielectric waveguides. These studies predicted that changes in the propagation characteristics of waveguides clad with silicon and gallium arsenide could be made large enough to be useful in modulators. These effects are dependent on the complex permittivity and thickness of the cladding. Since the conductivity of the cladding can be changed by the photon generation of hole-electron pairs, incoherent light may be used as the input to modulate a coherent light beam. Waveguides were fabricated and silicon claddings were applied to verify the theoretical predictions

Photoconductivity of Single-crystalline Selenium Nanotubes

Photoconductivity of single-crystalline selenium nanotubes (SCSNT) under a range of illumination intensities of a 633nm laser is carried out with a novel two terminal device arrangement at room temperature. It's found that SCSNT forms Schottky barriers with the W and Au contacts, and the barrier height is a function of the light intensities. In low illumination regime below 1.46x10E-4 muWmum-2, the Au-Se-W hybrid structure exhibits sharp switch on/off behavior, and the turn-on voltages decrease with increasing illuminating intensities. In the high illumination regime above 7x10E-4 muWmum-2, the device exhibits ohmic conductance with a photoconductivity as high as 0.59Ohmcm-1, significantly higher that reported values for carbon and GaN nanotubes. This finding suggests that SCSNT is potentially a good photo-sensor material as well we a very effective solar cell material.Comment: 12pages including 5 figures, submitted to Nanotechnolog

Oxidative Chemical Transformations of Sesquiterpene Lactones.

Oxidative chemical transformations of sesquiterpene lactones have been carried out to determine the effect these changes have on the biological activities of these derivatives. Vacuum liquid chromatography was used extensively to isolate the sesquiterpene lactones used for these synthetic transformations. Costunolide and dehydrocostuslactone were isolated from Costus Resinoid (Saussurea lappa) and dihydroparthenolide was isolated from Ambrosia artemisiifolia. The enolate oxidations of sesquiterpene lactones with oxygen and (camphorylsulfonyl)oxaziridine have been investigate. Enolate oxidations of sesquiterpene lactones with oxygen generate low yields of both 11$\alpha$- and 11$\beta$-hydroxylactones. The yields of enolate oxidations with (camphorylsulfonyl)oxaziridine are much improved (over oxygen) and the reaction is stereospecific. This methodology was used to prepare a series of 11-hydroxysesquiterpene lactones of various skeletal types. Two naturally occurring sesquiterpene lactones (11$\beta$,15-dihydroxysaussurea lactone and 15-hydroxydihydrocostunolide) were synthesized from costunolide. These transformations involved the use of enolate oxidations developed previously, allylic oxidations with selenium dioxide, and Cope rearrangements of 1,5-dienes. A hydroperoxy-sesquiterpene lactone (peroxydihydroparthenolide) was synthesized via an ene reaction between an alkene and singlet oxygen. The first biomimetic conversion of a germacrolide to a heliangolide was achieved using tert-butyl hydroperoxide and selenium dioxide supported on silica gel. Other attempted allylic oxidations of a 1,10-epoxygermacrolide with selenium dioxide resulted in isolation of only transannular cyclization products or oxidatively modified cyclization products

Vitamin E requirements of adult domestic cats (Felis catus) fed diets containing high levels of fish oil : a thesis presented in partial fulfilment of the requirement for the degree of Master of Nutritional Sciences at Massey University, Palmerston North, New Zealand

The vitamin E (α-tocopherol) requirement of adult cats fed diets containing high levels of fish oil was investigated. Thirty-two (16 male, 16 female) adult domestic cats (Felis catus) were randomly allocated to four groups according to sex and fed one of four experimental diets (A, B, C, and D) for 126 days. The cats were housed in large outdoor pens in groups of 8 cats. Diets A, B, C and D contained approximately 300 g of fish oil per kg diet dry matter and were supplemented to contain 0, 5, 10, and 15 IU DL-α-tocopheryl acetate per g added fish oil per kg diet, respectively. The diets were provided ad libitum with water being available at all times. Food intake was measured daily and body weights were measured at weekly intervals. Blood samples were taken from the jugular vein of each cat at bi-weekly intervals during the study. Blood samples were analysed for plasma α-tocopherol, red blood cell H₂O₂ (4 and 2 %) haemolysis, the ferric reducing ability of plasma, plasma lipid peroxides, plasma triglycerides, alkaline phosphatase and whole blood lymphocyte proliferation. All cats remained healthy throughout the study except one female cat who was removed after 3 weeks due to poor food intake. The four diets were analysed and found to be free of peroxides. The average daily metabolisable energy intake of the cats on diet A, B, C and D at the end of study were similar and were 289, 261, 256, and 267 kJ·kg⁻¹ body weight, respectively. No clinical signs of vitamin E deficiency were observed in any of the cats. The plasma α-tocopherol concentrations of the cats in the four groups at the start of the study were not significantly different between the four groups (mean ± SEM, 3.4 ± 0.2 μg-ml⁻¹). When the cats were fed diet A (unsupplemented), the mean plasma α-tocopherol concentration remained relatively low and the RBC 4 % H₂O₂ haemolysis remained high, while the RBC 2 % H₂O₂ haemolysis decreased consistently. Plasma lipid peroxides remained relatively low throughout the study. The ferric reducing ability of plasma status was compromised in the cats on the unsupplemented diet. There was no significant (P < 0.05) difference in any of the response parameters measured amongst the cats fed diets B, C and D except for the RBC 4 % H₂O₂ haemolysis of the cats on diet B which was significantly higher than those on diet C and D at week 4 and week 8, and the LPO value of the cats on diet D which was significantly higher than those of the cats on diet B and C at week 4. The vitamin E requirement of adult cats fed a high level of fish oil, using the response parameters measured, was estimated to be between 0 and 5 IU of vitamin E per g added fish oil per kg diet. The current recommendation of the Association of American Feed Control Officials (10 IU vitamin E/g fish oil/kg diet) appears to be well in excess. The results from the present study also showed that there was no beneficial effect of dietary vitamin E on whole blood cell proliferation when vitamin E levels were 150 % of the recommendations of the Association of American Feed Control Officials. The vitamin E requirement of adult cats to optimise immune response warrants further investigation