title: Considerations on the effect of solutal on the grain size of castings from superheated melts

authors: Bolzoni, Leandro

abstract: The amount of solutal present in an alloy affects the grain size of the cast metal as solute is rejected at the solidification front. This is normally quantified using the so called growth restriction factor Q. This work presents some considerations about the effect of solutal on the final cast structure with a focus on the nature of the alloy system, the effect of non-equilibrium solidification conditions and the effect of superheating of the molten metal.

text: Considerations on the effect of solutal on the grain size of castings from superheated melts The amount of solutal present in an alloy affects the grain size of the cast metal as solute is rejected at the solidification front. This is normally quantified using the so called growth restriction factor Q. This work presents some considerations about the effect of solutal on the final cast structure with a focus on the nature of the alloy system, the effect of non-equilibrium solidification conditions and the effect of superheating of the molten metal.

year: 2017

title: The synthesis and metal ion catalysed hydrolysis of methyl 4,5-diaminopentanoate

authors: Beresford, Geoffrey Derrick

abstract: The diamino acid ester, methyl 4, 5-diaminopentanoate has been prepared for the first time. The successful five step synthesis starting from 4-hydroxybutanoic acid lactone, and two other possible pathways via ethyl 3-formylpropanoate, are described. 
pKₐ values for 4,5-diaminopentanoic acid dihydrochloride and its a methyl ester dihydrochloride (determined by potentiometric titration at 25°C and I= 0.10molℓ⁻¹) are discussed in relation to those for other 1,2-diamines.
Stability constants of Cu(II) complexes of 4,5-diaminopentanoic acid and its methyl ester were evaluated from potentiometric titration data by the program SCOGS on a PDP 11/70 computer. Both compounds form high stability constant 1:1 and 1:2 complexes with Cu(II). (For 4,5-diaminopentanoic acid log K₁ = 10.94, log K₂ = 9.40 and for methyl 4,5-diaminopentanoate log K₁ = 9.84, log K₂ = 8.51, at 25°C and I= 0.10molℓ⁻¹). A variety of protonated complexes were also present at lower pH. 
pH-stat and spectrophotometric investigations showed that in the alkaline hydrolysis of methyl 4,5-diaminopentanoate, the simple Bᴀс2 reaction is slow and masked by a competing, extremely rapid, pair of intramolecular aminolysis (lactamisation) reactions. These involve competition between five and six membered lactam ring closure. Overall constants of the order 10³ℓmol⁻¹s⁻¹ at 25°C and I = 0.10molℓ⁻¹ are observed.
The Cu(II) catalysed hydrolysis of methyl 4,5-diaminopentanoate was studied at constant pH using a pH-stat. The kinetics of hydrolysis of solutions containing a 1:2 mole ratio of Cu(II): ester are consistent with the two consecutive second order (pseudo-first-order at constant pH) reactions (1) and (2) (where E is the ester and A⁻ the anion, of 4 ,5-diaminopentanoic acid).
CuE₂²⁺ + OH⁻ → CuEA⁺ + CH₃OH 	1
CuEA⁺ + OH⁻ → CUA₂ + CH₃OH 		2
The relative values for the two rate constants obtained (k (CuE₂²⁺) = 2.41ℓmol⁻¹s⁻¹ and k (CuEA⁺) = 0.80ℓmol⁻¹s⁻¹ at 25°C and I = 0.10molℓ⁻¹) can be explained by charge and statistical effects. The value of k(CuEA⁺) was confirmed independently from studies on solutions containing a 2.5:1:4 mole ratio of Cu(II): ester: acid. The value of k(CuEen²⁺) = 0.96ℓmol⁻¹s⁻¹ obtained from solutions containing Cu(II): ester: 1,2-diaminoethane = 2.5:1:4 is approximately k(CuE₂²⁺)/2 as expected statistically. 1:1 Solutions of Cu(II) and methyl 4,5-diaminopentanoate disproportionate, so no values for k(CuE²⁺) could be measured.
The absolute values for the Cu(II) catalysed rate constants are discussed in comparison with those for methyl 2,3-diaminopropanoate and other diamino acid esters. The results for methyl 4,5-diaminopentanoate can be explained by the attenuation of inductive and positive charge effects of the metal ion by the additional methylene groups of the methyl 4,5-diaminopentanoate alkyl chain. Direct methoxycarbonyl-metal ion interaction, presumably absent in methyl 4,5-diaminopentanoate must, therefore, be unimportant in the Cu(II) catalysed hydrolysis of methyl 2,3-diarninopropanoate.

text: The synthesis and metal ion catalysed hydrolysis of methyl 4,5-diaminopentanoate The diamino acid ester, methyl 4, 5-diaminopentanoate has been prepared for the first time. The successful five step synthesis starting from 4-hydroxybutanoic acid lactone, and two other possible pathways via ethyl 3-formylpropanoate, are described. 
pKₐ values for 4,5-diaminopentanoic acid dihydrochloride and its a methyl ester dihydrochloride (determined by potentiometric titration at 25°C and I= 0.10molℓ⁻¹) are discussed in relation to those for other 1,2-diamines.
Stability constants of Cu(II) complexes of 4,5-diaminopentanoic acid and its methyl ester were evaluated from potentiometric titration data by the program SCOGS on a PDP 11/70 computer. Both compounds form high stability constant 1:1 and 1:2 complexes with Cu(II). (For 4,5-diaminopentanoic acid log K₁ = 10.94, log K₂ = 9.40 and for methyl 4,5-diaminopentanoate log K₁ = 9.84, log K₂ = 8.51, at 25°C and I= 0.10molℓ⁻¹). A variety of protonated complexes were also present at lower pH. 
pH-stat and spectrophotometric investigations showed that in the alkaline hydrolysis of methyl 4,5-diaminopentanoate, the simple Bᴀс2 reaction is slow and masked by a competing, extremely rapid, pair of intramolecular aminolysis (lactamisation) reactions. These involve competition between five and six membered lactam ring closure. Overall constants of the order 10³ℓmol⁻¹s⁻¹ at 25°C and I = 0.10molℓ⁻¹ are observed.
The Cu(II) catalysed hydrolysis of methyl 4,5-diaminopentanoate was studied at constant pH using a pH-stat. The kinetics of hydrolysis of solutions containing a 1:2 mole ratio of Cu(II): ester are consistent with the two consecutive second order (pseudo-first-order at constant pH) reactions (1) and (2) (where E is the ester and A⁻ the anion, of 4 ,5-diaminopentanoic acid).
CuE₂²⁺ + OH⁻ → CuEA⁺ + CH₃OH 	1
CuEA⁺ + OH⁻ → CUA₂ + CH₃OH 		2
The relative values for the two rate constants obtained (k (CuE₂²⁺) = 2.41ℓmol⁻¹s⁻¹ and k (CuEA⁺) = 0.80ℓmol⁻¹s⁻¹ at 25°C and I = 0.10molℓ⁻¹) can be explained by charge and statistical effects. The value of k(CuEA⁺) was confirmed independently from studies on solutions containing a 2.5:1:4 mole ratio of Cu(II): ester: acid. The value of k(CuEen²⁺) = 0.96ℓmol⁻¹s⁻¹ obtained from solutions containing Cu(II): ester: 1,2-diaminoethane = 2.5:1:4 is approximately k(CuE₂²⁺)/2 as expected statistically. 1:1 Solutions of Cu(II) and methyl 4,5-diaminopentanoate disproportionate, so no values for k(CuE²⁺) could be measured.
The absolute values for the Cu(II) catalysed rate constants are discussed in comparison with those for methyl 2,3-diaminopropanoate and other diamino acid esters. The results for methyl 4,5-diaminopentanoate can be explained by the attenuation of inductive and positive charge effects of the metal ion by the additional methylene groups of the methyl 4,5-diaminopentanoate alkyl chain. Direct methoxycarbonyl-metal ion interaction, presumably absent in methyl 4,5-diaminopentanoate must, therefore, be unimportant in the Cu(II) catalysed hydrolysis of methyl 2,3-diarninopropanoate.

year: 1977

title: Explaining Maori under-achievement in standardised reading tests: The role of social and individual characteristics

authors: Lock, Kelly J.

subjects: education

abstract: In New Zealand, Maori students have lower educational attainment levels than their Pakeha counterparts, which is a major contributor to the earnings inequality between these two groups. This study attempts to identify determinants of the gap in educational attainment using data on reading test scores for a sample of 3031 15‐year‐old Maori and Pakeha students. Using a decomposition method that is commonly applied to income inequality analyses, the determinants of the reading literacy test score gap between Maori and Pakeha students are identified. The main contributors to this gap are family factors, student's opinions, and school factors (including decile). An understanding of the determinants of the test score gap provides insights into how effective policy makers can be at reducing this inequality.

text: Explaining Maori under-achievement in standardised reading tests: The role of social and individual characteristics In New Zealand, Maori students have lower educational attainment levels than their Pakeha counterparts, which is a major contributor to the earnings inequality between these two groups. This study attempts to identify determinants of the gap in educational attainment using data on reading test scores for a sample of 3031 15‐year‐old Maori and Pakeha students. Using a decomposition method that is commonly applied to income inequality analyses, the determinants of the reading literacy test score gap between Maori and Pakeha students are identified. The main contributors to this gap are family factors, student's opinions, and school factors (including decile). An understanding of the determinants of the test score gap provides insights into how effective policy makers can be at reducing this inequality.

year: 2008