title: Influence of ageing heating rates on the microstructure and mechanical properties of Ti-5553 alloy

authors: Jia, Mengqi

subjects: fatigue

abstract: The Ti-5553 alloy, a high-strength β-titanium alloy, is increasingly recognised for its exceptional mechanical properties, making it a preferred material for critical aerospace applications. This thesis examines the effects of varying ageing heating rates on the microstructure and mechanical properties of the forged Ti-5553 alloy, focusing on hardness, tensile properties, and fatigue performance. Following solution treatment at 810°C, the alloy was aged at 610°C with heating rates of 1°C/min, 5°C/min, 10°C/min, and 15°C/min. Detailed microstructural analysis was conducted using Scanning Electron Microscopy (SEM) and Energy Dispersive X ray Spectroscopy (EDX). The microstructural examination revealed that different ageing heating rates caused only minor variations in the alloy's bimodal microstructure. Slower ageing heating rates produced a relatively fine, homogeneously distributed primary α phase within the β grains, while faster rates resulted in a slightly coarser bimodal microstructure. Chemical homogeneity analysis confirmed a consistent distribution of critical elements, with α stabilisers concentrated in the primary α phase and β stabilisers in the β phase, ensuring stable phase compositions across all samples. The observed slight microstructural changes were reflected in the alloy's mechanical properties. Hardness across different ageing heating rates varied between 357.4 HV and 372.6 HV. The ultimate tensile strength (UTS) declined from 1307.2 MPa at 1°C/min to 1264.5 MPa at 15°C/min, while ductility improved from 15.6% to 17.1% over the same range. The alloy demonstrated good fatigue resistance at lower stress amplitudes and ageing heating rates, enduring over 10 million cycles at 337.5 MPa under the 1°C/min condition. However, fatigue life decreased with higher stress amplitudes and ageing heating rates, highlighting the alloy's sensitivity to more extreme conditions. In summary, while the varying ageing heating rates resulted in only minor changes to the microstructure, these alterations had some impact on the mechanical properties of the Ti-5553 alloy. These findings highlight the importance of precise microstructural control in optimising the alloy's performance, especially in applications where achieving a balance between strength, ductility, and fatigue resistance is crucial.

text: Influence of ageing heating rates on the microstructure and mechanical properties of Ti-5553 alloy The Ti-5553 alloy, a high-strength β-titanium alloy, is increasingly recognised for its exceptional mechanical properties, making it a preferred material for critical aerospace applications. This thesis examines the effects of varying ageing heating rates on the microstructure and mechanical properties of the forged Ti-5553 alloy, focusing on hardness, tensile properties, and fatigue performance. Following solution treatment at 810°C, the alloy was aged at 610°C with heating rates of 1°C/min, 5°C/min, 10°C/min, and 15°C/min. Detailed microstructural analysis was conducted using Scanning Electron Microscopy (SEM) and Energy Dispersive X ray Spectroscopy (EDX). The microstructural examination revealed that different ageing heating rates caused only minor variations in the alloy's bimodal microstructure. Slower ageing heating rates produced a relatively fine, homogeneously distributed primary α phase within the β grains, while faster rates resulted in a slightly coarser bimodal microstructure. Chemical homogeneity analysis confirmed a consistent distribution of critical elements, with α stabilisers concentrated in the primary α phase and β stabilisers in the β phase, ensuring stable phase compositions across all samples. The observed slight microstructural changes were reflected in the alloy's mechanical properties. Hardness across different ageing heating rates varied between 357.4 HV and 372.6 HV. The ultimate tensile strength (UTS) declined from 1307.2 MPa at 1°C/min to 1264.5 MPa at 15°C/min, while ductility improved from 15.6% to 17.1% over the same range. The alloy demonstrated good fatigue resistance at lower stress amplitudes and ageing heating rates, enduring over 10 million cycles at 337.5 MPa under the 1°C/min condition. However, fatigue life decreased with higher stress amplitudes and ageing heating rates, highlighting the alloy's sensitivity to more extreme conditions. In summary, while the varying ageing heating rates resulted in only minor changes to the microstructure, these alterations had some impact on the mechanical properties of the Ti-5553 alloy. These findings highlight the importance of precise microstructural control in optimising the alloy's performance, especially in applications where achieving a balance between strength, ductility, and fatigue resistance is crucial.

year: 2024-09-15

title: Targets of Elf5 in Mouse Trophoblast Stem Cells

authors: Deane, Jessica Robyn

subjects: Elf5

abstract: The Placenta is an essential organ for all mammalian embryonic development as it provides the nutritional link between maternal and foetal blood streams. The cells which go on to proliferate and contribute to all the major cell types of the embryo derived placenta have been located to the trophoblast (TE) cells overlying the Inner Cell Mass (ICM) of the embryo. Immortal cell lines have been subsequentially derived from this tissue and called Trophoblast Stem (TS) cells. In parallel with their  in vivo  counterparts they are also reliant on Fibroblast growth factor 4 (FgF4) (Tanaka et al., 1998) and Activin/Nodal signalling (Guzman-Ayala et al., 2004). 

The Ets family transcription factor, Elf5, has been shown to be specifically expressed in the early placental trophoblast and subsequent derived tissues. Mice deficient in Elf5 failed to form a placenta post implantation. Furthermore TS cells were unable to be derived from Elf5 knockout embryos (Donnison et al., 2005). This work suggested that Elf5 plays an essential role in TS cells and their differentiation. The aim of this study was to determine the downstream target genes of Elf5 in mouse TS cells. The target genes of Fgf4 and Activin/Nodal signalling in TS cells were also investigated.  This work is hoped to contribute to an overall greater understanding of the molecular networks underlying TS cell maintenance and to contribute to our knowledge of early placental development. 

Small interfering RNA (siRNA) targeted reduction of Elf5 mRNA expression in mTS cells was achieved using two independent siRNAs; with Elf5 reduction exceeding 80%. The resulting changes in gene expression were measured in order to determine the downstream targets of Elf5. Selected genes known to be important for trophoblast differentiation and maintenance were measured using real-time PCR in a candidate gene approach .Global changes in gene expression as a consequence of Elf5 silencing were measured using an Affymetrix microarray. Global changes in gene expression due to growth factor (Fgf4 and/or Activin) removal were also measured. Expression of 22 genes was changed using either of the Elf5 siRNA oligonucleotides. Of these, 9 were also significantly changed by growth factor removal. Included in this set were Synopl, Hst3st3b1, Cyr61 and Sox2. In the overall analysis, many genes whose expression changed upon loss of Elf5 are known to play important roles in trophectoderm cell specification. Real-time PCR validation agreed closely with the up or down regulation measured using the microarray. This work has thus led to the discovery of sets of Elf5 target genes potentially involved in trophoblast stem cell function and has provided the foundation for future work exploring the molecular pathways of trophoblast development.

text: Targets of Elf5 in Mouse Trophoblast Stem Cells The Placenta is an essential organ for all mammalian embryonic development as it provides the nutritional link between maternal and foetal blood streams. The cells which go on to proliferate and contribute to all the major cell types of the embryo derived placenta have been located to the trophoblast (TE) cells overlying the Inner Cell Mass (ICM) of the embryo. Immortal cell lines have been subsequentially derived from this tissue and called Trophoblast Stem (TS) cells. In parallel with their  in vivo  counterparts they are also reliant on Fibroblast growth factor 4 (FgF4) (Tanaka et al., 1998) and Activin/Nodal signalling (Guzman-Ayala et al., 2004). 

The Ets family transcription factor, Elf5, has been shown to be specifically expressed in the early placental trophoblast and subsequent derived tissues. Mice deficient in Elf5 failed to form a placenta post implantation. Furthermore TS cells were unable to be derived from Elf5 knockout embryos (Donnison et al., 2005). This work suggested that Elf5 plays an essential role in TS cells and their differentiation. The aim of this study was to determine the downstream target genes of Elf5 in mouse TS cells. The target genes of Fgf4 and Activin/Nodal signalling in TS cells were also investigated.  This work is hoped to contribute to an overall greater understanding of the molecular networks underlying TS cell maintenance and to contribute to our knowledge of early placental development. 

Small interfering RNA (siRNA) targeted reduction of Elf5 mRNA expression in mTS cells was achieved using two independent siRNAs; with Elf5 reduction exceeding 80%. The resulting changes in gene expression were measured in order to determine the downstream targets of Elf5. Selected genes known to be important for trophoblast differentiation and maintenance were measured using real-time PCR in a candidate gene approach .Global changes in gene expression as a consequence of Elf5 silencing were measured using an Affymetrix microarray. Global changes in gene expression due to growth factor (Fgf4 and/or Activin) removal were also measured. Expression of 22 genes was changed using either of the Elf5 siRNA oligonucleotides. Of these, 9 were also significantly changed by growth factor removal. Included in this set were Synopl, Hst3st3b1, Cyr61 and Sox2. In the overall analysis, many genes whose expression changed upon loss of Elf5 are known to play important roles in trophectoderm cell specification. Real-time PCR validation agreed closely with the up or down regulation measured using the microarray. This work has thus led to the discovery of sets of Elf5 target genes potentially involved in trophoblast stem cell function and has provided the foundation for future work exploring the molecular pathways of trophoblast development.

year: 2007

title: Kūpapa ki raro, titiro ake

authors: Papa, Pānia Christine

abstract: Ko tā te kaituhi e manako nei i roto i tēnei tuhinga, kia āta tirohia he aha ngā huarahi i whāia ai e ngā iwi o Pōhara, hei kawe i a rātou mai i te pōharatanga ki te oranga tonutanga; mai i te noho marara ki te noho tahi; mai i te korekore ki te ao mārama. Ko te tuarua o ngā pātai kei mua i taku aroaro, he wānanga mena i tutuki pai ngā kaupapa i wawatahia ai e rātou. 
E rua ngā kōrero matua e toko ake ana i roto i ahau hei taumarumaru mō ngā whakaaro me ngā kōrero kua whakatakotoria i te tuhinga nei, hei whakautu i ngā pātai matua e rua ō runga ake nei. 
Tuatahi, 'Ko te amorangi ki mua, ko te hāpai ō ki muri'. E hāngai ana tēnei whakataukī ki te pūmautanga o ngā whakaaro o ngā tūpuna o Pōhara ki ngā kaupapa i kōkirihia ai e tō rātou rangatira, me te āhua o tā ngā tūpuna hāpai i aua kaupapa. I te tīmatanga, nā Piupiu Te Wherowhero rātou i arataki. I te rā nei, ko Te Arikinui, Te Atairangikaahu te manu whakataka pōkai i te ata hāpara, e ngāngahu tonu nei i ngā iwi o te marae o Pōhara. 
Tuarua, 'Kūpapa ki raro, Titiro ake.' Koia tēnei tētehi whakataukī whakahau i ngā uri whakatupu o te marae, o Pōhara, kua waihotia e rātou mā hei kupu ārahi i ngā uri i runga i te marae, i roto anō hoki i te ao hou. He hōhonutanga anō tō te whakataukī nei e tika ana kia whakamāramahia i roto i tēnei tuhinga, hei whāki atu i ngā rerenga kētanga o te āhua o te whakaaro o kui mā, o koro mā, me te āhua o tā rātou noho i te wā i a rātou. 
Ko te whakatau o ngā kōrero, i tutuki pai i ngā tūpuna o te marae o Pōhara ō rātou manako, nā tō rātou kaha ū ki te kaupapa o te Kāhui Ariki, me tō rātou ū ki te kaupapa o te tupuranga o te papakāinga o Pōhara hei marae mō ngā uri whakatupu. Ka noho mai tērā hei whakatohu i tō rātou pakaritanga, me ō rātou whakaaro rangatira hei tauira mā ngā uri whakaheke e whai ake ana i ngā tapuwae o ngā tūpuna. 
Ko ēnei tuhinga hei whakatinana i te ngākau nui kia waituhia ngā kōrero ā ngā rūruhi, ā ngā koroheke, mō te marae o Pōhara, kei ngaro katoa atu ngēnā kōrero e here nei i te ao kōhatu ki te ao hou. 
Nā te ngākau māhaki o ngā kaumātua i whakaae ai kia tuhia te kaupapa nei, kia puta ai ngā kōrero mō Pōhara ki te ao mārama hei painga mō ngā uri whakatupu. Nā rātou i whakatūwhera te kūaha ki tō rātou ao hei kuhu atu ki roto mā te hunga mahira. Ko ngā kongakonga kōrero i taka iho mai i ō rātou puna mahara, kua kohia-ā-rīpenehia hei taonga tuku iho mō ngā iwi o te marae. E tika ana kia puruhia te mauri o ērā kōrero e ngā whānau me ngā uri o te marae. 
I tutuki ai te taha rangahau i ngā kōrero kaumātua i te whakatū wānanga, me te uiui kaumātua. I whāia ngā huarahi e rua nei hei kohikohi i ngā kōrero-ā-waha mō te hītori o Pōhara. Arā noa atu ngā painga i kitea, o te noho tahi a ngā kaumātua i runga tonu i te marae, ki te whakawhitiwhiti whakaaro, kōrero hoki mō ngā rā o mua i waenganui i a rātou. Ā, hei whai ake i ngā kōrero i puta i ngā wānanga, i haere māua ko taku matua ki te torotoro i tēnā, i tēnā o ngā kaumātua e mōhio pai ana ki ngā kōrero, hei whakakīkī i ngā whārua, hei whakawhānui hoki i ngā kōrero. I ngāwari ake taku mahi i te haere tahitanga mai o taku matua, hei hoa mōku. Ko tāna, he āta whakamārama atu i te pūtake o te rangahau, he whakamārama hoki i te whakaaetanga o ngā kaumātua ki tērā mahi. I mōhio pai hoki ia ki ngā kōrero whānui mō te marae, ki ngā tāngata ka kōrerohia, ā, nā konā i taea e ia te whiu atu ētehi pātai, te whakamārama hoki i ahau i muri mai mō te āhua o ētehi o ngā kōrero kāore i tino mārama mai ki ahau. I tū hoki taku matua hei piriti i waenganui i te kaikōrero kaumātua me te kaiuiui rangatahi kia whakawhiti pai ai ngā pātai me ngā whakautu ki waenganui i ngā taha e rua. Koia tērā taku waimarie i roto i ngā mahi uiui kaumātua, ā, koia hoki i tutuki pai ai tērā taha o te rangahau. 
I tae mai ki aku ringa tētehi rīpene o tētehi wānanga i hopukina ai i te tau 1978. Nō taua tau, i haere ake ētehi akonga o te Tari Māori o Te Whare Wānanga o Waikato, i raro i te maru o Wharehuia Milroy ki te rapu i ngā kōrero mō te marae o Pōhara. Heoi anō, i tō rātou hokinga atu ki te kāinga, kāore te nuinga o ngā kōrero i hopukina. Ka waihotia te take nā kia tārewa, ā, tae rawa ki te tau 1990, kātahi ka riro i ahau te rīpene kotahi i ora mai, hei āwhina i aku mahi rangahau mō tōku marae. 
I rapu māramatanga ahau mō te āhua o te noho a te iwi Māori whānui i ngā rā o mua, i roto i ngā pukapuka maha kua tuhia kētia. Mō ngā kōrero mō te whenua e tū nei te marae ināianei, i haere ki te Kooti Whenua Māori, ki reira kimi ai i ngā kōrero mō te rohe o Maungatautari whānui, mō te marae o Pōhara hoki. Nā ēnei whaiwhainga, kua puta he kōrero, kua puta hoki he whakaaro hei whakawā i ērā kōrero, hei whakamārama rānei i ērā kōrero, ā, koia tēnei e takoto nei i roto i tēnei tuhinga. Ka huri ināianei ki te wetewetetanga o ngā wāhanga o roto i te tuhinga nei. 
Nō namata mai anō i tīkina atu ai te rākau i te Wao-nui-ā-Tāne hei tārai i te waka o ōku tūpuna. Tēnei au e tiki atu nei i te rākau hei tauira hanga kōrero mōku. Ko tō te rākau tupu, ki ngā whakaaro o tēnei e tuhi nei, e pērā ana ki te tupu o te kaupapa kia nohoia te marae o Pōhara e tū ana i raro i te maru o Maungatautari. 
Arā noa atu ngā tauritenga o te tupu o te rākau me tō te marae o Pōhara tupu, mai i ōna pūtakenga hei papakāinga, ki te puāwaitanga o te whakaaro kia tū hei marae mō te mokopuna a te motu, mō ngā uri whakatupu, otirā, mō te iwi whānui. 
E whitu anō ngā wāhanga o tō te rākau tupu e whakatauritehia nei i roto i ngā whārangi o tēnei tuhinga. Ko te whenua tonu hei papa mō te tupu o te rākau, mō te tupu hoki o te marae Nō reira, ka tīmata ake i konā.

text: Kūpapa ki raro, titiro ake Ko tā te kaituhi e manako nei i roto i tēnei tuhinga, kia āta tirohia he aha ngā huarahi i whāia ai e ngā iwi o Pōhara, hei kawe i a rātou mai i te pōharatanga ki te oranga tonutanga; mai i te noho marara ki te noho tahi; mai i te korekore ki te ao mārama. Ko te tuarua o ngā pātai kei mua i taku aroaro, he wānanga mena i tutuki pai ngā kaupapa i wawatahia ai e rātou. 
E rua ngā kōrero matua e toko ake ana i roto i ahau hei taumarumaru mō ngā whakaaro me ngā kōrero kua whakatakotoria i te tuhinga nei, hei whakautu i ngā pātai matua e rua ō runga ake nei. 
Tuatahi, 'Ko te amorangi ki mua, ko te hāpai ō ki muri'. E hāngai ana tēnei whakataukī ki te pūmautanga o ngā whakaaro o ngā tūpuna o Pōhara ki ngā kaupapa i kōkirihia ai e tō rātou rangatira, me te āhua o tā ngā tūpuna hāpai i aua kaupapa. I te tīmatanga, nā Piupiu Te Wherowhero rātou i arataki. I te rā nei, ko Te Arikinui, Te Atairangikaahu te manu whakataka pōkai i te ata hāpara, e ngāngahu tonu nei i ngā iwi o te marae o Pōhara. 
Tuarua, 'Kūpapa ki raro, Titiro ake.' Koia tēnei tētehi whakataukī whakahau i ngā uri whakatupu o te marae, o Pōhara, kua waihotia e rātou mā hei kupu ārahi i ngā uri i runga i te marae, i roto anō hoki i te ao hou. He hōhonutanga anō tō te whakataukī nei e tika ana kia whakamāramahia i roto i tēnei tuhinga, hei whāki atu i ngā rerenga kētanga o te āhua o te whakaaro o kui mā, o koro mā, me te āhua o tā rātou noho i te wā i a rātou. 
Ko te whakatau o ngā kōrero, i tutuki pai i ngā tūpuna o te marae o Pōhara ō rātou manako, nā tō rātou kaha ū ki te kaupapa o te Kāhui Ariki, me tō rātou ū ki te kaupapa o te tupuranga o te papakāinga o Pōhara hei marae mō ngā uri whakatupu. Ka noho mai tērā hei whakatohu i tō rātou pakaritanga, me ō rātou whakaaro rangatira hei tauira mā ngā uri whakaheke e whai ake ana i ngā tapuwae o ngā tūpuna. 
Ko ēnei tuhinga hei whakatinana i te ngākau nui kia waituhia ngā kōrero ā ngā rūruhi, ā ngā koroheke, mō te marae o Pōhara, kei ngaro katoa atu ngēnā kōrero e here nei i te ao kōhatu ki te ao hou. 
Nā te ngākau māhaki o ngā kaumātua i whakaae ai kia tuhia te kaupapa nei, kia puta ai ngā kōrero mō Pōhara ki te ao mārama hei painga mō ngā uri whakatupu. Nā rātou i whakatūwhera te kūaha ki tō rātou ao hei kuhu atu ki roto mā te hunga mahira. Ko ngā kongakonga kōrero i taka iho mai i ō rātou puna mahara, kua kohia-ā-rīpenehia hei taonga tuku iho mō ngā iwi o te marae. E tika ana kia puruhia te mauri o ērā kōrero e ngā whānau me ngā uri o te marae. 
I tutuki ai te taha rangahau i ngā kōrero kaumātua i te whakatū wānanga, me te uiui kaumātua. I whāia ngā huarahi e rua nei hei kohikohi i ngā kōrero-ā-waha mō te hītori o Pōhara. Arā noa atu ngā painga i kitea, o te noho tahi a ngā kaumātua i runga tonu i te marae, ki te whakawhitiwhiti whakaaro, kōrero hoki mō ngā rā o mua i waenganui i a rātou. Ā, hei whai ake i ngā kōrero i puta i ngā wānanga, i haere māua ko taku matua ki te torotoro i tēnā, i tēnā o ngā kaumātua e mōhio pai ana ki ngā kōrero, hei whakakīkī i ngā whārua, hei whakawhānui hoki i ngā kōrero. I ngāwari ake taku mahi i te haere tahitanga mai o taku matua, hei hoa mōku. Ko tāna, he āta whakamārama atu i te pūtake o te rangahau, he whakamārama hoki i te whakaaetanga o ngā kaumātua ki tērā mahi. I mōhio pai hoki ia ki ngā kōrero whānui mō te marae, ki ngā tāngata ka kōrerohia, ā, nā konā i taea e ia te whiu atu ētehi pātai, te whakamārama hoki i ahau i muri mai mō te āhua o ētehi o ngā kōrero kāore i tino mārama mai ki ahau. I tū hoki taku matua hei piriti i waenganui i te kaikōrero kaumātua me te kaiuiui rangatahi kia whakawhiti pai ai ngā pātai me ngā whakautu ki waenganui i ngā taha e rua. Koia tērā taku waimarie i roto i ngā mahi uiui kaumātua, ā, koia hoki i tutuki pai ai tērā taha o te rangahau. 
I tae mai ki aku ringa tētehi rīpene o tētehi wānanga i hopukina ai i te tau 1978. Nō taua tau, i haere ake ētehi akonga o te Tari Māori o Te Whare Wānanga o Waikato, i raro i te maru o Wharehuia Milroy ki te rapu i ngā kōrero mō te marae o Pōhara. Heoi anō, i tō rātou hokinga atu ki te kāinga, kāore te nuinga o ngā kōrero i hopukina. Ka waihotia te take nā kia tārewa, ā, tae rawa ki te tau 1990, kātahi ka riro i ahau te rīpene kotahi i ora mai, hei āwhina i aku mahi rangahau mō tōku marae. 
I rapu māramatanga ahau mō te āhua o te noho a te iwi Māori whānui i ngā rā o mua, i roto i ngā pukapuka maha kua tuhia kētia. Mō ngā kōrero mō te whenua e tū nei te marae ināianei, i haere ki te Kooti Whenua Māori, ki reira kimi ai i ngā kōrero mō te rohe o Maungatautari whānui, mō te marae o Pōhara hoki. Nā ēnei whaiwhainga, kua puta he kōrero, kua puta hoki he whakaaro hei whakawā i ērā kōrero, hei whakamārama rānei i ērā kōrero, ā, koia tēnei e takoto nei i roto i tēnei tuhinga. Ka huri ināianei ki te wetewetetanga o ngā wāhanga o roto i te tuhinga nei. 
Nō namata mai anō i tīkina atu ai te rākau i te Wao-nui-ā-Tāne hei tārai i te waka o ōku tūpuna. Tēnei au e tiki atu nei i te rākau hei tauira hanga kōrero mōku. Ko tō te rākau tupu, ki ngā whakaaro o tēnei e tuhi nei, e pērā ana ki te tupu o te kaupapa kia nohoia te marae o Pōhara e tū ana i raro i te maru o Maungatautari. 
Arā noa atu ngā tauritenga o te tupu o te rākau me tō te marae o Pōhara tupu, mai i ōna pūtakenga hei papakāinga, ki te puāwaitanga o te whakaaro kia tū hei marae mō te mokopuna a te motu, mō ngā uri whakatupu, otirā, mō te iwi whānui. 
E whitu anō ngā wāhanga o tō te rākau tupu e whakatauritehia nei i roto i ngā whārangi o tēnei tuhinga. Ko te whenua tonu hei papa mō te tupu o te rākau, mō te tupu hoki o te marae Nō reira, ka tīmata ake i konā.

year: 1997