title: Impact Modification and Fracture Mechanisms of Core-Shell Particle Reinforced Thermoplastic Protein

authors: Smith, Matthew J.

subjects: Science & Technology

abstract: Mechanical properties and fracture mechanisms of Novatein thermoplastic protein and blends with core–shell particles (CSPs) have been examined. Novatein is brittle with low impact strength and energy-to-break. Epoxy-modifi ed CSPs increase notched and unnotched impact strength, tensile strain-at-break, and energy-to-break, while tensile strength and modulus decrease as CSP content increases. Tg increases slightly with increasing CSP content attributed to physical crosslinking. Changes to mechanical properties are related to the critical matrix ligament thickness and rate of loading. Novatein control samples display brittle fracture characterized by large-scale crazing. At high CSP content a large plastic zone and a slow crack propagation zone in unnotched and tensile samples are observed suggesting increased energy absorption. Notched impact samples reach critical craze stresses easily regardless of CSP content reducing impact strength. It is concluded that the impact strength of thermoplastic protein can be modifi ed in a similar manner to traditional thermoplastics.

text: Impact Modification and Fracture Mechanisms of Core-Shell Particle Reinforced Thermoplastic Protein Mechanical properties and fracture mechanisms of Novatein thermoplastic protein and blends with core–shell particles (CSPs) have been examined. Novatein is brittle with low impact strength and energy-to-break. Epoxy-modifi ed CSPs increase notched and unnotched impact strength, tensile strain-at-break, and energy-to-break, while tensile strength and modulus decrease as CSP content increases. Tg increases slightly with increasing CSP content attributed to physical crosslinking. Changes to mechanical properties are related to the critical matrix ligament thickness and rate of loading. Novatein control samples display brittle fracture characterized by large-scale crazing. At high CSP content a large plastic zone and a slow crack propagation zone in unnotched and tensile samples are observed suggesting increased energy absorption. Notched impact samples reach critical craze stresses easily regardless of CSP content reducing impact strength. It is concluded that the impact strength of thermoplastic protein can be modifi ed in a similar manner to traditional thermoplastics.

year: 2016-08-01

title: An ecological study of Paranephrops planifrons white (Decapoda: Parastacidae) in Lake Rotoiti, North Island

authors: Devcich, Alan A.

subjects: Crayfish

abstract: The Paranephrops planifrons population in mesotrophic L.  Rotoiti consists of 2 bathymetrically and temporally separate breeding groups. Late autumn breeders comprise about 80% of the population, occupy depths mainly above 30 m and at night feed in the littoral zone, where food is 80% more concentrated than elsewhere. Early summer breeders exist mainly below 30 m depth. Utilisation of the whole lake bottom and seasonal changes in food available to the early summer breeders are tentatively given as explanations of this pattern.
Crayfish show increased sensitivity to light intensities greater than 150-205 lux and consequently occupy shelters above around 12 m depth. Shelters include any recesses subjected to intensities below this range. This zone accomodates almost the entire juvenile population and ca 10-20% of the adult population. This response to light intensity is believed to be an adaptation promoting avoidance of their main predator, the shag. Nocturnalism is another adaptation reducing losses to predators, including trout. Crayfish at greater depths lie unprotected and inactive by day and ca 70-80% of these adults form a high density band around the lake at a mean annual depth of 19.2±2.8 m. The band has a mean annual vertical depth range of 11.4±2.1 m and densities up to 50 crayfish m⁻².
At dusk activity begins in the deepest waters first and crayfish forming the band migrate shorewards, while those above emerge from shelters. Within the hour feeding on detritus mainly, commences amongst the weed beds which extend to 6 m depth. At dawn a downward migration preceeds reformation of the high density band. These dual diel migrations apply almost solely to late autumn breeders and are part of a circadian rhythm, the timing of which is modified by light. Locomotion associated with migratory activity appears to be effected mainly through leg proprioceptors responsive to gravity. Directional orientation at this time and also generally, is inversely related to bottom slope angle.
The diel distribution pattern varies seasonally. In summer and autumn the high density band is displaced shorewards by a vertical distance of 3.3 m, to a mean depth of 18.3 m and there is a 4 fold increase in crayfish inhabiting shallow water shelters. This closer association with the main feeding ground is probably an adaptation to meet coincident increases in energy needs. It applies especially to late autumn breeding females, whose period of ovarian development occurs between December and April. Energy requirements appear to be met through food consumed rather than from food stored. Female feeding activity is directly related to temperature but not in males, and prewinter storage is apparently of little importance in both sexes.
Hypolimnetic deoxygenation affects early summer breeders mainly and induces a mass migration from the deeper regions to above the 30 m contour by February. Complete recolonisation of these parts follows lake turnover in May. Crayfish occur on all substrate types in approximately equal numbers except very soft muds, which support densities of <0.001 crayfish m⁻².

text: An ecological study of Paranephrops planifrons white (Decapoda: Parastacidae) in Lake Rotoiti, North Island The Paranephrops planifrons population in mesotrophic L.  Rotoiti consists of 2 bathymetrically and temporally separate breeding groups. Late autumn breeders comprise about 80% of the population, occupy depths mainly above 30 m and at night feed in the littoral zone, where food is 80% more concentrated than elsewhere. Early summer breeders exist mainly below 30 m depth. Utilisation of the whole lake bottom and seasonal changes in food available to the early summer breeders are tentatively given as explanations of this pattern.
Crayfish show increased sensitivity to light intensities greater than 150-205 lux and consequently occupy shelters above around 12 m depth. Shelters include any recesses subjected to intensities below this range. This zone accomodates almost the entire juvenile population and ca 10-20% of the adult population. This response to light intensity is believed to be an adaptation promoting avoidance of their main predator, the shag. Nocturnalism is another adaptation reducing losses to predators, including trout. Crayfish at greater depths lie unprotected and inactive by day and ca 70-80% of these adults form a high density band around the lake at a mean annual depth of 19.2±2.8 m. The band has a mean annual vertical depth range of 11.4±2.1 m and densities up to 50 crayfish m⁻².
At dusk activity begins in the deepest waters first and crayfish forming the band migrate shorewards, while those above emerge from shelters. Within the hour feeding on detritus mainly, commences amongst the weed beds which extend to 6 m depth. At dawn a downward migration preceeds reformation of the high density band. These dual diel migrations apply almost solely to late autumn breeders and are part of a circadian rhythm, the timing of which is modified by light. Locomotion associated with migratory activity appears to be effected mainly through leg proprioceptors responsive to gravity. Directional orientation at this time and also generally, is inversely related to bottom slope angle.
The diel distribution pattern varies seasonally. In summer and autumn the high density band is displaced shorewards by a vertical distance of 3.3 m, to a mean depth of 18.3 m and there is a 4 fold increase in crayfish inhabiting shallow water shelters. This closer association with the main feeding ground is probably an adaptation to meet coincident increases in energy needs. It applies especially to late autumn breeding females, whose period of ovarian development occurs between December and April. Energy requirements appear to be met through food consumed rather than from food stored. Female feeding activity is directly related to temperature but not in males, and prewinter storage is apparently of little importance in both sexes.
Hypolimnetic deoxygenation affects early summer breeders mainly and induces a mass migration from the deeper regions to above the 30 m contour by February. Complete recolonisation of these parts follows lake turnover in May. Crayfish occur on all substrate types in approximately equal numbers except very soft muds, which support densities of <0.001 crayfish m⁻².

year: 1979

title: The Seedling: Students' perceptions of science education-How do our students see their science classes?

authors: Taylor, Simon

abstract: What is learning like in Years 9 and 10 science from a student’s viewpoint? What is really going on? Let’s take the opportunity to get up close to their learning world.

Dr Simon Taylor’s current research examines the perceptions of secondary students – how they see learning in their science lessons. This article centres on what we as teachers can learn from student voice, how personally relevant learning contexts used in lessons were particularly significant for Māori and Pacifica students, and how established collaborative practices influenced student engagement.

text: The Seedling: Students' perceptions of science education-How do our students see their science classes? What is learning like in Years 9 and 10 science from a student’s viewpoint? What is really going on? Let’s take the opportunity to get up close to their learning world.

Dr Simon Taylor’s current research examines the perceptions of secondary students – how they see learning in their science lessons. This article centres on what we as teachers can learn from student voice, how personally relevant learning contexts used in lessons were particularly significant for Māori and Pacifica students, and how established collaborative practices influenced student engagement.

year: 2014