Flocculation, filtration and selective flocculation studies on haematite ore fines using starch

The flocculation and filtration characteristics of typical Indian iron ore fines have been studied using starch as flocculant in the presence of an inorganic electrolyte, namely calcium chloride. The effect of various parameters such as pH, starch and calcium chloride concentrations and pulp density on the settling and filtration rates, turbidity of the supernatant and on residual starch and calcium ion concentrates has been investigated through a statistical design and analysis approach and subsequently optimised on a laboratory scale. The adsorption mechanisms of starch onto haematite have been elucidated through adsorption density measurements, infrared and X-ray photoelectron spectroscopic techniques. The rheological property of the polymer solutions of relevance to flocculations has also been investigated. Further, the role of metal ion-starch interactions in the bulk solution, has been studied. In order to understand the nature of polymer adsorption at the double-layer, electrokinetic studies have been carried out with the iron ore mineral samples using starch and calcium chloride. Based on the above findings, selective floculaation tests on artificial mixtures of iron ore minerals have been carried out to determine the separation efficiencies from the view point of alumina and silica removal from haematite as well as the control of alumina: silica ratio in Indian iron ores.

Aspects of tautomerism. 7. Study of keto participation in alkaline hydrolysis of normal esters of .gamma.-keto acids

Study of the alkaline hydrolysis of a number of variously substituted normal o-benzoylbenzoic esters has been reported. Although carbonyl-assisted hydrolysis is the general rule, in compounds containing strongly electron-donating groups, the ester function is directly attacked. The cause of rate enhancement in carbonyl-assisted hydrolysis and in greater detail the case of 6-substituted derivatives are discussed. It is shown that the carbonyl-assisted hydrolyses are characterized by decreased sensitivity to leaving-group structure. The implications of this result are pointed out.

Lipeäkäsitellyn vehnän vaikutus lypsylehmien syöntiin ja tuotokseen vapaalla seosrehuruokinnalla

Lipeä on vahva emäs, jonka on havaittu lisäävän hemiselluloosan ja ligniinin hydrolyysiä pötsissä. Näin ollen lipeäkäsittelyllä on mahdollista korvata viljan mekaaninen litistys ja jauhatus. Seosrehuruokinnalla, jonka osana on lipeäkäsitelty vilja, on mahdollista vähentää liiallisesta tärkkelyksestä aiheutuvia metabolisia ongelmia pötsissä. Tämän tutkielman tarkoituksena oli selvittää lipeäkäsitellyn vehnän vaikutusta lypsylehmien syöntiin ja tuotokseen ad libitum seosrehuruokinnoilla. Ruokinnoissa korvattiin kuivaa murskattua vehnää asteittain kokonaisella lipeäkäsitellyllä vehnällä. Kontrollina oli perinteisesti käytetty kuiva, murskattu ohra-kaura seos. Koe tehtiin Ruotsin maatalousyliopiston (SLU) maataloustieteiden laitoksella Uumajassa. Koe alkoi syyskuussa ja päättyi joulukuussa 2010. Kokeessa oli 17 useamman kerran poikinutta lehmää ja 6 ensikkoa (Ruotsin punainen -rotu). Lehmät olivat lämpimässä pihattonavetassa, jossa seosrehun syöntiä mitattiin vaakakuppien avulla. Koekäsittelyt olivat murskattu ohra-kaura seos (1:1), murskattu kuiva vehnä (1:0), murskatun kuivan vehnän ja kokonaisen lipeävehnän seos (1:1) ja kokonainen lipeävehnä (1:0). Ruokintojen kuiva-ainepitoisuudeksi asetettiin 370 g/kg ja raakavalkuaispitoisuudeksi 180 g/kg kuiva-ainetta. Näennäinen ravintoaineen sulavuus määritettiin happoon liukenemattoman tuhkan avulla. Typen hyväksikäyttöä arvioitiin laskennallisen typpitaseen avulla. Koe toteutettiin 4x4 latinalaisen neliön koemallin mukaisesti ja käsittelyjen väliset tilastolliset erot testattiin kontrastien avulla. Kuiva-aineen (PQ=0,02) ja orgaanisen aineen (PQ=0,02) syönnit lisääntyivät, samalla kun niiden sulavuudet paranivat korvattaessa puolet kuivasta vehnästä lipeävehnällä. Ruokintojen välillä ei ollut tilastollisesti merkitsevää eroa maitotuotoksessa eikä energiakorjatussa maitotuotoksessa. Maidon rasvatuotos lisääntyi vähän (PQ=0,04) ja rasvapitoisuus selvästi (PQ=0,004), kun kuivasta vehnästä korvattiin puolet lipeävehnällä. Kun kaikki kuiva vehnä korvattiin lipeävehnällä, maidon valkuaispitoisuus väheni (PL<0,001). Samoin kävi maidon ureapitoisuudelle (PL=0,002). Lipeäkäsittely ei tuottanut tässä kokeessa taloudellisesti kannattavaa tulosta, sillä maidon valkuaispitoisuus väheni ja syönti lisääntyi maitotuotoksen pysyessä samana. Vehnäruokinnoista paras tuotosvaste saatiin kuivan vehnän ja lipeävehnän seoksella.

Do the Hydrolysis Products, Methylamine and N,N'-Dimethylurea, Play any Role in the Methyl Isocyanate-Induced Haematological and Biochemical Changes in Rabbits?

The subcutaneous administration of methyl isocyanate (MIC) to female rabbits, resulted in significant increases in haemoglobin concentration, erythrocyte volume fraction and leucocyte number in blood, as well as plasma total proteins, and urea. The present study was designed to investigate whether the hydrolytic products of MIC, methylamine (MA) and N,N'-dimethylurea (DMU) play any role in eliciting these changes. Both MA and DMU administered subcutaneously in an equimolar dose to that of 1.0 LD50 MIC, 2.2 mmol kg-1, had no influence on these parameters, although there was a marginal increase in the plasma urea level shortly after the administration of DMU. This study establishes that the observed haematological and biochemical changes induced by MIC intoxication in rabbits are mostly due to MIC.

Influence of methylamine and N,N'-dimethylurea, the hydrolysis products of methyl isocyanate, on its systemic toxicity

Subcutaneous administration of the LD50 dose of methyl isocyanate (MIC) to rats induced severe hyperglycaemia, lactic acidosis and uraemia in rats. Neither methylamine (MA) nor N,N′-dimethylurea (DMU), the hydrolysis products of MIC, administered in equimolar doses had any influence on these parameters except for a marginal transient increase in plasma urea by DMU. Methyl isocyanate administration led to haemoconcentration, resulting in an increase in the plasma concentration of total proteins and a decrease in both the plasma concentration of albumin and the plasma cholinesterase activity. The hydrolysis products of MIC had no influence on any of these parameters. Thus, it seems reasonable to suggest that the systemic effects of MIC are caused by MIC per se, in spite of its high hydrolytic instability.

Influence of Starch Polysaccharide on the Remolded Properties of 2 Indian clay Samples

The reported presence in marine clays and the recognized role of polysaccharide as a bonding agent provided the motivation to examine the role of starch polysaccharide in the remoulded properties of nonswelling (kaolinite) and swelling (bentonite) groups of clays. The starch polysaccharide belongs to a group of naturally occurring, large-sized organic molecules (termed polymers) and is built up by extensive repetition of simple chemical units called repeat units. The results of the study indicate that the impact of the starch polysaccharide on the remoulded properties of clays is dependent on the mineralogy of the clays. On addition to bentonite clay, the immensely large number of segments (repeat units) of the starch polysaccharide create several polymer segment - clay surface bonds that cause extensive aggregation of the bentonite units layers. The aggregation of the bentonite unit layers greatly curtails the available surface area of the clay mineral for diffuse ion layer formation. The reduction in diffuse ion layer thickness markedly lowers the consistency limits and vane shear strength of the bentonite clay. On addition to kaolinite, the numerous polymer segment - clay surface bonds enhance the tendency of the kaolinite particles to flocculate. The enhanced particle flocculation is responsible apparently for a small to moderate increase in the liquid limit and remoulded undrained strength of the nonswelling clay.

Metallo-beta-lactamase-Catalyzed Hydrolysis of Cephalosporins: Some Mechanistic Insights into the Effect of Heterocyclic Thiones on Enzyme Activity

The hydrolysis of beta-lactam antibiotics using zinc-containing metallo-beta-lactamases (m beta l) is one of the major bacterial defense systems. These enzymes can catalyze the hydrolysis of a variety of antibiotics including the latest generation of cephalosporins, cephamycins, and imipenem. It is shown in this paper that the cephalosporins having heterocyclic - SR side chains are less prone to m beta l-mediated hydrolysis than the antibiotics that do not have such side chains. This is partly due to the inhibition of enzyme activity by the thione moieties eliminated during hydrolysis. When the enzymatic hydrolysis of oxacillin was carried out in the presence of heterocyclic thiones such as MU, MDT, DMETT, and MMA, the catalytic activity of the enzyme was inhibited significantly by these compounds. Although the heterocyclic - SR moieties eliminated from the beta-lactams upon hydrolysis undergo a rapid tautomerism between thione and thiol forms, these compounds act as thiolate ligands toward zinc(II) ions. The structural characterization of two model tetranuclear zinc(II) thiolate complexes indicates that the -SR side chains eliminated from the antibiotics may interact with the zinc(II) metal center of m beta l through their sulfur atoms.

Reactions of palladium chloride with amino spirocyclic cyclotriphosphazenes: Isolation and Crystal Structures of Novel Mono- and Bimetallic Complexes Formed by the Hydrolysis of a .lambda.5-Diazaphospholane Ring

The reaction of the amino spirocyclic cyclotriphosphazene N3P3(NMe2)4(NHCH2CH2CH2NH) (2) with palladium chloride gives the stable chelate complex [PdCl2.2] (4). An X-ray crystallographic study reveals that one of the nitrogen atoms of the diaminoalkane moiety and an adjacent phosphazene ring nitrogen atom are bonded to the metal. An analogous reaction with the phosphazene N3P3(NMe2)4(NHCH2CH2NH) (1) gives initially a similar complex which undergoes facile hydrolysis to give the novel monometallic and bimetallic complexes [PdCl2.HN3P3(O)(NMe2)4(NHCH2CH2NH2)] (5) and [PdCl{N3P3(NMe2)4(NCH2CH2NH2)}]2(O) (6), which have been structurally characterized; in the former, an (oxophosphazadienyl)ethylenediamine is chelated to the metal whereas, in the latter, an oxobridged bis(cyclotriphosphazene) acts as a hexadentate nitrogen donor ligand in its dianionic form. Crystal data for 4 : a = 14.137(1) angstrom, b = 8.3332(5) angstrom, c = 19.205(2) angstrom, beta = 96.108(7)degrees, P2(1)/c, Z = 4, R = 0.027 with 3090 reflections (F > 5sigma(F)). Crystal data for 5 : a = 8.368(2) angstrom, b = 16.841(4) A, c = 16.092(5) angstrom, beta = 98.31(2)degrees, P2(1)/n, Z = 4, R = 0.049 with 3519 reflections (F > 5sigma(F)). Crystal data for 6 : a = 22.455(6) angstrom, b = 14.882(3) angstrom, c = 13.026(5) angstrom, 6 = 98.55(2)degrees, C2/c, Z = 4, R = 0.038 with 3023 reflections (F > 5sigma(F)).

ATP hydrolysis is required for DNA cleavage by EcoPI restriction enzyme

The type III restriction endonuclease EcoPI, coded by bacteriophage Fl, cleaves unmodified DNA in the presence of ATP and magnesium ions. We show that purified EcoPI restriction enzyme fails to cleave DNA in the presence of non-hydrolyzable ATP analogs. More importantly, this study demonstrates that EcoPI restriction enzyme has an inherent ATPase activity, and ATP hydrolysis is necessary for DNA cleavage. Furthermore, we show that the progress curve of the reaction with Eco PI restriction enzyme exhibits a lag which is dependent on the enzyme concentration. Kinetic analysis of the progress curves of the reaction suggest slow transitions that can occur during the reaction, characteristic of hysteretic enzymes. The role of ATP in the cleavage mechanism of type III restriction enzymes is discussed.

Effect of beta-lactamase-catalyzed hydrolysis of cephalosporins on peroxynitrite-mediated nitration of serum albumin and cytochrome c

The hydrolysis of beta-lactam antibiotics by beta-lactamases is one of the major bacterial defense systems. These enzymes generally hydrolyze a variety of antibiotics including the latest generation of cephalosporins, cephamycins and imipenem. In this paper, the effect of cephalosporins-based antibiotics on the peroxynitrite-mediated nitration of protein tyrosine is described. Although some of the antibiotics have weak inhibitory effect on the nitration reactions in the absence of beta-lactamase, they exhibit very strong inhibition in the presence of beta-lactamase. This is due to the elimination of heterocyclic thiol/thione moieties from cephalosporins by beta-lactamase-mediated hydrolysis. After the elimination, the thiols/thiones effectively scavenge peroxynitrite, leading to the inhibition of the nitration reactions.

Intramolecular Reactivity - Keto Participation in the Hydrolysis of N-Methyl-N-(9-Oxobicyclo[3.3.1]Nonan-2-Alpha-YL) Morpholinium Iodide, and A Cannizzaro-Type Reaction of 3-(2-Oxocyclohexyl)Propanal

Mechanistic studies of two intramolecular processes, nucleophilic displacement of N-methylmorpholinium in N-methyl-N-{9-oxobicyclo[3,3,1]nonan-2 alpha-yl}morpholinium iodide, anchimerically assisted by keto carbonyl, and a Cannizzaro-type reaction of 3-(2-oxocyclohexyl)propanal, occurring via axial hydride transfer onto the cyclohexanone, are reported.

The effect of a starch envelope on fly ash particles on the impact properties of filled epoxy composites

The impact behaviour of epoxy specimens containing 20% by volume of fly ash particles without (coded, FA20) and with surface enveloped by starch in dry (FAS20) and water-ingresses (FASM20) conditions is studied. The resulting behavioural patterns are documented and compared to the composites containing as received fly ash particles. The data on unreinforced (i.e. neat) epoxy system (designated, NE) are also included. Samples with starch covering for the fillers whether tested in dry or wet conditions (i.e. FAS20 & FASM20) showed greater absorption of energy and maximum load compared to the ones derived on composites having as received fillers tested in unexposed (dry) condition (FA20). Ductility Index, D.I. on the other hand, showed a reversal in trends; the energy absorbed was highest for NE and lowest FA20 samples. Scanning microscopic examination of the fracture features was undertaken to correlate the microstructure to impact response.

Use of maleic anhydride-grafted polyethylene as compatibilizer for HDPE-tapioca starch blends: Effects on mechanical properties

Tapioca starch in both glycerol-plasticized and in unplasticized states was blended with high-density polyethylene (HDPE) using HDPE-g-maleic anhydride as the compatibilizer. The impact and tensile properties of the blends were measured according to ASTM methods. The results reveal that blends containing plasticized starch have better mechanical properties than those containing unplasticized starch. High values of elongation at break at par with those of virgin HDPE could be obtained for blends, even with high loading of plasticized starch. Morphological studies by SEM microscopy of impact-fractured specimens of such blends revealed a ductile fracture, unlike blends with unplasticized starch at such high loadings, which showed brittle fracture, even with the addition of compatibilizer. In general, blends of HDPE and plasticized starch with added compatibilizer show better mechanical properties than similar blends containing unplasticized starch. (C) 2001 John Wiley & Sons, Inc.