title: Experimental characterization of the fracture properties of pultruded GFRP structural elements

authors: Abbaszadeh, Hadi

abstract: Pultruded Fiber Reinforced Polymers (FRPs) are a class of novel composite materials with remarkable strength (comparable or even greater to that of steel) and resistance to environmental effects. However, the strongly orthotropic behavior of these materials and the relatively high deformability and spatial variability in mechanical properties bring challenges to the widespread adoption of these elements in structural applications. To this end, the orientation and distribution of the fibers are the most influential parameters that affect both the ultimate strength and stiffness of the specimens. This work presents an experimental campaign conducted on GFRP specimens in uniaxial tension and 3-point bending; coupon specimens with three different fibers orientations (namely 0, 45, and 90 degrees) were tested to characterize the ultimate strength and failure modes Results of such experimental campaign are first presented, and detailed statistical measures of the so-obtained strength values are presented with the ultimate goal of characterizing the variability in mechanical properties in commercially available profiles.

text: Experimental characterization of the fracture properties of pultruded GFRP structural elements Pultruded Fiber Reinforced Polymers (FRPs) are a class of novel composite materials with remarkable strength (comparable or even greater to that of steel) and resistance to environmental effects. However, the strongly orthotropic behavior of these materials and the relatively high deformability and spatial variability in mechanical properties bring challenges to the widespread adoption of these elements in structural applications. To this end, the orientation and distribution of the fibers are the most influential parameters that affect both the ultimate strength and stiffness of the specimens. This work presents an experimental campaign conducted on GFRP specimens in uniaxial tension and 3-point bending; coupon specimens with three different fibers orientations (namely 0, 45, and 90 degrees) were tested to characterize the ultimate strength and failure modes Results of such experimental campaign are first presented, and detailed statistical measures of the so-obtained strength values are presented with the ultimate goal of characterizing the variability in mechanical properties in commercially available profiles.

year: 2023

title: Several new methods for the development of latent and blood fingerprints

authors: Caldwell, Jonathan Paul

abstract: Several new methods for the development of latent and blood fingerprints have been investigated as well as a preliminary appraisal of a technique for the estimation of post-mortem interval and age of blood stains.

The utilisation of coordinatively-unsaturated (six-coordinate) europium and terbium complexes as reactive reagents for the direct visualisation of latent fingerprints on porous and non-porous surfaces has been investigated. The main complex investigated in this study was tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) europium(III) [Eu(fod)₃] and was the only one which proved to be effective in the fluorescent visualisation of latent fingerprints using a one step process. Eu(fod)₃ was found to work for fingerprints on porous paper and to a limited extent on aluminium drink cans and galvanized iron.

The use of the two and three ringed analogues of ortho-phthalaldehyde (OPA) for the fluorescent enhancement of latent fingerprints was also investigated. Solution trials proved that the reaction products of 2,3-naphthalenedicarboxaldehyde (NDA) and 2,3- anthracenedicarboxaldehyde (ADA) with analine produce favourable “red-shifts” in emission wavelengths which would make them stand out from the blue background emissions commonly obtained from paper. However, poor results were obtained when NDA and ADA were trailed on latent fingerprints on paper.

2,2’-azino-di-[3-ethylbenzthiazolinesulfonate(6)] diammonium salt (ABTS), ortho-phenylenediamime (OPD), and para-phenylenediamine (PPD) have been found to be
successful reagents in the visual enhancement of blood fingerprints. Colours obtained from the oxidised products are green, orange, and purple respectively. A comparison with the commonly-used and hazardous 3,3’-diaminobenzidine (DAB) has proved all three reagents to be effective, safer alternatives with the added bonus of ABTS being (as far as is known) non-toxic. 

A preliminary appraisal has indicated that fluorescein diacetate (FDA) may be useful in estimating the post-mortem interval or age of blood stains and blood prints.

Of the range of techniques and processes investigated with the aim of improving fingerprint visualisation, some proved unsuccessful, yet provided some useful information. These included attempts to improve the colloidal gold technique of latent fingerprint visualisation, increase the chemiluminescence from luminol-treated blood fingerprints in the presence of bromide ions, increase the colour development of ABTS-treated blood fingerprints using an albumin antibody conjugated to peroxidase, an attempt to force fluorescein into the lipid component of a latent fingerprint by acidification of an alkaline solution of fluorescein, and an attempt to stain blood fingerprints with a fluorescent protein stain called SYPROᵀᴹ Orange.

text: Several new methods for the development of latent and blood fingerprints Several new methods for the development of latent and blood fingerprints have been investigated as well as a preliminary appraisal of a technique for the estimation of post-mortem interval and age of blood stains.

The utilisation of coordinatively-unsaturated (six-coordinate) europium and terbium complexes as reactive reagents for the direct visualisation of latent fingerprints on porous and non-porous surfaces has been investigated. The main complex investigated in this study was tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) europium(III) [Eu(fod)₃] and was the only one which proved to be effective in the fluorescent visualisation of latent fingerprints using a one step process. Eu(fod)₃ was found to work for fingerprints on porous paper and to a limited extent on aluminium drink cans and galvanized iron.

The use of the two and three ringed analogues of ortho-phthalaldehyde (OPA) for the fluorescent enhancement of latent fingerprints was also investigated. Solution trials proved that the reaction products of 2,3-naphthalenedicarboxaldehyde (NDA) and 2,3- anthracenedicarboxaldehyde (ADA) with analine produce favourable “red-shifts” in emission wavelengths which would make them stand out from the blue background emissions commonly obtained from paper. However, poor results were obtained when NDA and ADA were trailed on latent fingerprints on paper.

2,2’-azino-di-[3-ethylbenzthiazolinesulfonate(6)] diammonium salt (ABTS), ortho-phenylenediamime (OPD), and para-phenylenediamine (PPD) have been found to be
successful reagents in the visual enhancement of blood fingerprints. Colours obtained from the oxidised products are green, orange, and purple respectively. A comparison with the commonly-used and hazardous 3,3’-diaminobenzidine (DAB) has proved all three reagents to be effective, safer alternatives with the added bonus of ABTS being (as far as is known) non-toxic. 

A preliminary appraisal has indicated that fluorescein diacetate (FDA) may be useful in estimating the post-mortem interval or age of blood stains and blood prints.

Of the range of techniques and processes investigated with the aim of improving fingerprint visualisation, some proved unsuccessful, yet provided some useful information. These included attempts to improve the colloidal gold technique of latent fingerprint visualisation, increase the chemiluminescence from luminol-treated blood fingerprints in the presence of bromide ions, increase the colour development of ABTS-treated blood fingerprints using an albumin antibody conjugated to peroxidase, an attempt to force fluorescein into the lipid component of a latent fingerprint by acidification of an alkaline solution of fluorescein, and an attempt to stain blood fingerprints with a fluorescent protein stain called SYPROᵀᴹ Orange.

year: 1999

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