title: Growth and turion formation of Potamogeton crispus in response to different phosphorus concentrations in water

authors: Wang, Lei

subjects: carbohydrate

abstract: The vegetative growth and turion formation of Potamogeton crispus, a submersed aquatic macrophyte, was investigated under a range of phosphorus (P) concentrations (0. 025, 0. 25, 2. 5 and 25 mg P L⁻¹) in the ambient water free of algae, aiming to identify the responses of submersed aquatic macrophytes to nutrient enrichment, a common eutrophication problem in China and worldwide. Plant growth was not affected by different P concentrations in terms of biomass accumulation of stems and leaves. However, the contents of chlorophyll a and starch in plants decreased with increasing water P levels, whereas chlorophyll b and carotenoids declined with P level ranging from 0. 025 to 2. 5 mg P L⁻¹. The soluble sugar content decreased when water P concentration increased up to 2. 5 mg L⁻¹. The P content in plants increased with increasing water P levels, whereas plant N content decreased and soluble protein increased when water P concentration increased over 0. 25 mg L⁻¹, implying that P. crispus may have modified its metabolism to adapt to water P availability. When P concentration increased to 25 mg L⁻¹, the number and dry matter production of turions per plant decreased significantly. Meanwhile, there was a significant reduction in turion weight and the accumulations of soluble sugar and starch in turion, when water P concentration was over 0. 25 mg L⁻¹. The results suggest that turion formation in P. crispus is sensitive to P concentration in the ambient water, and high P levels may lead to decreases in P. crispus populations due to the decline in turion production.

text: Growth and turion formation of Potamogeton crispus in response to different phosphorus concentrations in water The vegetative growth and turion formation of Potamogeton crispus, a submersed aquatic macrophyte, was investigated under a range of phosphorus (P) concentrations (0. 025, 0. 25, 2. 5 and 25 mg P L⁻¹) in the ambient water free of algae, aiming to identify the responses of submersed aquatic macrophytes to nutrient enrichment, a common eutrophication problem in China and worldwide. Plant growth was not affected by different P concentrations in terms of biomass accumulation of stems and leaves. However, the contents of chlorophyll a and starch in plants decreased with increasing water P levels, whereas chlorophyll b and carotenoids declined with P level ranging from 0. 025 to 2. 5 mg P L⁻¹. The soluble sugar content decreased when water P concentration increased up to 2. 5 mg L⁻¹. The P content in plants increased with increasing water P levels, whereas plant N content decreased and soluble protein increased when water P concentration increased over 0. 25 mg L⁻¹, implying that P. crispus may have modified its metabolism to adapt to water P availability. When P concentration increased to 25 mg L⁻¹, the number and dry matter production of turions per plant decreased significantly. Meanwhile, there was a significant reduction in turion weight and the accumulations of soluble sugar and starch in turion, when water P concentration was over 0. 25 mg L⁻¹. The results suggest that turion formation in P. crispus is sensitive to P concentration in the ambient water, and high P levels may lead to decreases in P. crispus populations due to the decline in turion production.

year: 2013

title: Electrospray-friendly ligands for the mass spectral analysis of transition-metal complexes

authors: Decker, Corry

abstract: The key aim of this project was to develop the concept of electrospray-friendly ligands as a new ionisation method for the analysis of neutral metal complexes by electrospray mass spectrometry (ESMS). This involved introducing active functional groups into traditional ligands which do not otherwise undergo chemical ionisation under ESMS conditions.

Electrospray-friendly ligands (as illustrated above for PPh₃ derivatives) were incorporated into a series of metal carbonyl complexes of Mo, Fe and Ru, metal halide complexes of Pd, Pt and Au, and a number of zero-valent complexes of Pt and Pd. All carbonyl complexes with ES-friendly phosphine, arsine and stibine ligands ionised by protonation, yielding strong [M + H]⁺ ions as the only signals in the spectrum. The metal halide complexes followed the known halide-loss mechanism. Pt(0) and Pd(0) complexes did not require functionalised ligands, as their PPh₃ derivatives already gave [M +H]⁺ ions. Mo and W carbonyl complexes of the two ‘naturally’ electrospray friendly ligands tpa (tpa = 1,3,5-triaza-7-phosphaadamantane) and tcep [tcep = tris(2-cyanoethyl)phosphine] could also be studied readily by ESMS. While all tpa complexes gave [M + H]⁺ ions, complexes of tcep preferred ionisation by NH₄⁺. The ionisation efficiencies of selected ligands and complexes are discussed.

Thiolate complexes of Ni, Pd, Pt, Au and Hg were prepared using the ligands SC₆H₄OMe-p (S*) and p-SC₅H₄N (S•), but only the S•-complexes reliably underwent the protonation-type mechanism. The Cd-thiolate complexes [Cd₄(SPh)₁₀]²⁻, [S₄Cd₁₀(SPh)₁₆]⁴⁻ and [S₄Cd₁₀(SPh)₂₈]²⁻ underwent rapid ligand exchange with S*, but yielded insoluble products with S•. The complexes [Pt₂(μ-S)₂(L)₂] (L = PPh₃, P*, P**, P***. P•. As***¹) were prepared, and by means of ESMS, aspects of ligand exchange as well as reactivity towards other metal centres were investigated.

Isonitrile derivatives of [Fe₃(CO)₁₂] and [Ru₃CO)₁₂] were prepared by ligand exchange with CNPh, CNC₆H₄OMe-p (CNPh*) and tosylmethylisocyanide. Substitution was observed for up to six CO ligands. Pyrolysis of [Fe₃(CO)₁₁(L)] and [Fe₃(CO)₁₀(L)₂] (L =CNPh, CNPh*) led to the products [Fe₃(CO)₉(μ₃ - η²-L)] and [Fe₃(CO)₈(μ₃-η²-L) (L)], respectively. All complexes could be studied by ESMS as their [M + H]⁺, [M + MeO]⁻ or  [M – H]⁻ ions, depending on the exact nature of the analyte. [Fe₃(CO)₁₀(CNPh)₂] was characterised structurally (below) and revealed an unprecedented substitution pattern, together with unexpected partial disorder in the metal framework.

Detection by ESMS of products of the type [Ru₄(CO) ₁₄₋ₙ(L)ₙ] (L = CNPh, CNPh*; n =2-4) in the reactions with ruthenium carbonyl led to the isolation and structural characterisation of [Ru₄(CO)₁₂(CNPh)₄], which is the only fully characterised isonitrile derivative of [Ru₃(CO)₁₂] with four metal atoms and exhibits an unusual imine-type bonding mode for the bridging isonitrile ligands.
________________________
¹As*** = As(C₆H₄OMe-p)₃

text: Electrospray-friendly ligands for the mass spectral analysis of transition-metal complexes The key aim of this project was to develop the concept of electrospray-friendly ligands as a new ionisation method for the analysis of neutral metal complexes by electrospray mass spectrometry (ESMS). This involved introducing active functional groups into traditional ligands which do not otherwise undergo chemical ionisation under ESMS conditions.

Electrospray-friendly ligands (as illustrated above for PPh₃ derivatives) were incorporated into a series of metal carbonyl complexes of Mo, Fe and Ru, metal halide complexes of Pd, Pt and Au, and a number of zero-valent complexes of Pt and Pd. All carbonyl complexes with ES-friendly phosphine, arsine and stibine ligands ionised by protonation, yielding strong [M + H]⁺ ions as the only signals in the spectrum. The metal halide complexes followed the known halide-loss mechanism. Pt(0) and Pd(0) complexes did not require functionalised ligands, as their PPh₃ derivatives already gave [M +H]⁺ ions. Mo and W carbonyl complexes of the two ‘naturally’ electrospray friendly ligands tpa (tpa = 1,3,5-triaza-7-phosphaadamantane) and tcep [tcep = tris(2-cyanoethyl)phosphine] could also be studied readily by ESMS. While all tpa complexes gave [M + H]⁺ ions, complexes of tcep preferred ionisation by NH₄⁺. The ionisation efficiencies of selected ligands and complexes are discussed.

Thiolate complexes of Ni, Pd, Pt, Au and Hg were prepared using the ligands SC₆H₄OMe-p (S*) and p-SC₅H₄N (S•), but only the S•-complexes reliably underwent the protonation-type mechanism. The Cd-thiolate complexes [Cd₄(SPh)₁₀]²⁻, [S₄Cd₁₀(SPh)₁₆]⁴⁻ and [S₄Cd₁₀(SPh)₂₈]²⁻ underwent rapid ligand exchange with S*, but yielded insoluble products with S•. The complexes [Pt₂(μ-S)₂(L)₂] (L = PPh₃, P*, P**, P***. P•. As***¹) were prepared, and by means of ESMS, aspects of ligand exchange as well as reactivity towards other metal centres were investigated.

Isonitrile derivatives of [Fe₃(CO)₁₂] and [Ru₃CO)₁₂] were prepared by ligand exchange with CNPh, CNC₆H₄OMe-p (CNPh*) and tosylmethylisocyanide. Substitution was observed for up to six CO ligands. Pyrolysis of [Fe₃(CO)₁₁(L)] and [Fe₃(CO)₁₀(L)₂] (L =CNPh, CNPh*) led to the products [Fe₃(CO)₉(μ₃ - η²-L)] and [Fe₃(CO)₈(μ₃-η²-L) (L)], respectively. All complexes could be studied by ESMS as their [M + H]⁺, [M + MeO]⁻ or  [M – H]⁻ ions, depending on the exact nature of the analyte. [Fe₃(CO)₁₀(CNPh)₂] was characterised structurally (below) and revealed an unprecedented substitution pattern, together with unexpected partial disorder in the metal framework.

Detection by ESMS of products of the type [Ru₄(CO) ₁₄₋ₙ(L)ₙ] (L = CNPh, CNPh*; n =2-4) in the reactions with ruthenium carbonyl led to the isolation and structural characterisation of [Ru₄(CO)₁₂(CNPh)₄], which is the only fully characterised isonitrile derivative of [Ru₃(CO)₁₂] with four metal atoms and exhibits an unusual imine-type bonding mode for the bridging isonitrile ligands.
________________________
¹As*** = As(C₆H₄OMe-p)₃

year: 2002

title: Perceptions, expectations and interactions: a study of teachers and pupils in five ethnically mixed primary classrooms

authors: St George, Alison

abstract: Teachers’ perceptions of their pupils, expectations for pupil general ability, teacher-pupil interaction and pupil achievement were investigated in this naturalistic study of 5 teachers and 90 pupils in their New Zealand ethnically mixed Standard 3 classrooms.
A pilot study showed that teachers at this level tended to perceive pupils in terms of constructs reflecting academic work skills, home background and personal/social attributes. Using rating scales developed from the pilot study it was apparent that the teachers had a conception of the ideal pupil. It was suggested that this influenced expectations for pupils’ ability to do well at school. Girls and Pakeha pupils were seen as being closer to the ideal pupil stereotype than boys or Polynesian pupils, and for Polynesian pupils this was reflected in lower teacher expectations. Teacher expectations tended to be borne out by standardized achievement test results and accounted for a large proportion of teacher rated achievement variance. Ethnic group made a small but significant independent contribution to achievement variance on two of the Progressive Achievement Tests and on teacher rated achievement.
Using data on teacher-pupil dyadic interaction collected with the Brophy-Good system, contrasting patterns of interaction were noted between expectation groups (high, middle and low teacher expectations). The differences were largely qualitative and there were no expectation group differences in the total number of public or private dyadic interactions. High expectation pupils initiated more contacts with the teacher, answered more open public academic questions and received a lot less criticism for work or behaviour than the other groups. The low expectation group experienced a greater proportion of teacher initiated contacts and were asked more direct public academic questions which were of the product rather than the process type. The middle expectation group generally fell in between the high and low groups, but received the most criticism and the highest proportion of process questions. Teachers appeared to be attempting to prevent inequalities in quantity of interaction and this was discussed in terms of the perception of pupil attributes. Expectation group differences in interaction were not always the same for boys and girls or for all teachers. Despite the differences in teachers’ perceptions and expectations for Polynesian and Pakeha pupils, no ethnic group differences in teacher-pupil interaction were evidenced. 
No consistent and clear-cut expectation group differences were found in pupils’ perceptions of teacher behaviour. There was a moderate positive correlation between perception of the quantity of teacher contact and observed interaction but not regarding the affective quality of teacher contacts. 
The findings were discussed in terms of the theory and research on person perception and expectation phenomena in interpersonal behaviour. Some practical implications for educational practice were commented upon.

text: Perceptions, expectations and interactions: a study of teachers and pupils in five ethnically mixed primary classrooms Teachers’ perceptions of their pupils, expectations for pupil general ability, teacher-pupil interaction and pupil achievement were investigated in this naturalistic study of 5 teachers and 90 pupils in their New Zealand ethnically mixed Standard 3 classrooms.
A pilot study showed that teachers at this level tended to perceive pupils in terms of constructs reflecting academic work skills, home background and personal/social attributes. Using rating scales developed from the pilot study it was apparent that the teachers had a conception of the ideal pupil. It was suggested that this influenced expectations for pupils’ ability to do well at school. Girls and Pakeha pupils were seen as being closer to the ideal pupil stereotype than boys or Polynesian pupils, and for Polynesian pupils this was reflected in lower teacher expectations. Teacher expectations tended to be borne out by standardized achievement test results and accounted for a large proportion of teacher rated achievement variance. Ethnic group made a small but significant independent contribution to achievement variance on two of the Progressive Achievement Tests and on teacher rated achievement.
Using data on teacher-pupil dyadic interaction collected with the Brophy-Good system, contrasting patterns of interaction were noted between expectation groups (high, middle and low teacher expectations). The differences were largely qualitative and there were no expectation group differences in the total number of public or private dyadic interactions. High expectation pupils initiated more contacts with the teacher, answered more open public academic questions and received a lot less criticism for work or behaviour than the other groups. The low expectation group experienced a greater proportion of teacher initiated contacts and were asked more direct public academic questions which were of the product rather than the process type. The middle expectation group generally fell in between the high and low groups, but received the most criticism and the highest proportion of process questions. Teachers appeared to be attempting to prevent inequalities in quantity of interaction and this was discussed in terms of the perception of pupil attributes. Expectation group differences in interaction were not always the same for boys and girls or for all teachers. Despite the differences in teachers’ perceptions and expectations for Polynesian and Pakeha pupils, no ethnic group differences in teacher-pupil interaction were evidenced. 
No consistent and clear-cut expectation group differences were found in pupils’ perceptions of teacher behaviour. There was a moderate positive correlation between perception of the quantity of teacher contact and observed interaction but not regarding the affective quality of teacher contacts. 
The findings were discussed in terms of the theory and research on person perception and expectation phenomena in interpersonal behaviour. Some practical implications for educational practice were commented upon.

year: 1978