title: Measurement of antennas and microwave components using time-domain reflectometry of a voltage impulse

authors: McCabe, Steven Owen

subjects: antenna measurements

abstract: Band-pass microwave systems such as ultra-wideband antennas are traditionally characterized in the frequency-domain through a vector network analyzer in an anechoic chamber. A recent study proved antennas could be accurately measured in the time-domain using a step-function time-domain reflectometer (TDR), without the need for an anechoic chamber. We propose a new advance in the TDR characterization method. An impulse generator is employed in place of the step generator in a TDR set-up. The advantage conferred by this change is that more energy is available beyond a given frequency than with a step, and so a higher signal-to-noise ratio is achieved. The theoretical result is compared with measurement.

text: Measurement of antennas and microwave components using time-domain reflectometry of a voltage impulse Band-pass microwave systems such as ultra-wideband antennas are traditionally characterized in the frequency-domain through a vector network analyzer in an anechoic chamber. A recent study proved antennas could be accurately measured in the time-domain using a step-function time-domain reflectometer (TDR), without the need for an anechoic chamber. We propose a new advance in the TDR characterization method. An impulse generator is employed in place of the step generator in a TDR set-up. The advantage conferred by this change is that more energy is available beyond a given frequency than with a step, and so a higher signal-to-noise ratio is achieved. The theoretical result is compared with measurement.

year: 2011

title: A genus in the bacterial phylum Aquificota appears to be endemic to Aotearoa-New Zealand.

authors: Power, Jean F.

subjects: New Zealand

abstract: Allopatric speciation has been difficult to examine among microorganisms, with prior reports of endemism restricted to sub-genus level taxa. Previous microbial community analysis via 16S rRNA gene sequencing of 925 geothermal springs from the Taupō Volcanic Zone (TVZ), Aotearoa-New Zealand, revealed widespread distribution and abundance of a single bacterial genus across 686 of these ecosystems (pH 1.2-9.6 and 17.4-99.8 °C). Here, we present evidence to suggest that this genus, Venenivibrio (phylum Aquificota), is endemic to Aotearoa-New Zealand. A specific environmental niche that increases habitat isolation was identified, with maximal read abundance of Venenivibrio occurring at pH 4-6, 50-70 °C, and low oxidation-reduction potentials. This was further highlighted by genomic and culture-based analyses of the only characterised species for the genus, Venenivibrio stagnispumantis CP.B2T, which confirmed a chemolithoautotrophic metabolism dependent on hydrogen oxidation. While similarity between Venenivibrio populations illustrated that dispersal is not limited across the TVZ, extensive amplicon, metagenomic, and phylogenomic analyses of global microbial communities from DNA sequence databases indicates Venenivibrio is geographically restricted to the Aotearoa-New Zealand archipelago. We conclude that geographic isolation, complemented by physicochemical constraints, has resulted in the establishment of an endemic bacterial genus.

text: A genus in the bacterial phylum Aquificota appears to be endemic to Aotearoa-New Zealand. Allopatric speciation has been difficult to examine among microorganisms, with prior reports of endemism restricted to sub-genus level taxa. Previous microbial community analysis via 16S rRNA gene sequencing of 925 geothermal springs from the Taupō Volcanic Zone (TVZ), Aotearoa-New Zealand, revealed widespread distribution and abundance of a single bacterial genus across 686 of these ecosystems (pH 1.2-9.6 and 17.4-99.8 °C). Here, we present evidence to suggest that this genus, Venenivibrio (phylum Aquificota), is endemic to Aotearoa-New Zealand. A specific environmental niche that increases habitat isolation was identified, with maximal read abundance of Venenivibrio occurring at pH 4-6, 50-70 °C, and low oxidation-reduction potentials. This was further highlighted by genomic and culture-based analyses of the only characterised species for the genus, Venenivibrio stagnispumantis CP.B2T, which confirmed a chemolithoautotrophic metabolism dependent on hydrogen oxidation. While similarity between Venenivibrio populations illustrated that dispersal is not limited across the TVZ, extensive amplicon, metagenomic, and phylogenomic analyses of global microbial communities from DNA sequence databases indicates Venenivibrio is geographically restricted to the Aotearoa-New Zealand archipelago. We conclude that geographic isolation, complemented by physicochemical constraints, has resulted in the establishment of an endemic bacterial genus.

year: 2024-01-02

title: Kia kāpuia te reo o Tāmaki ki te Tonga: Tāmaki Makaurau ki te Tonga

authors: Lee-Morgan, Jenny Bol Jun

abstract: Mai i te Papakuratanga o Mataoho tae noa ki tona Ipu. Mai i Pukaki Tapu o Poutiikeka ki Te Puketapapatanga a Hape. Mai i te tahuna o Torea i nga wai o Mokoia, mawhiti atu ki Te Arapueru e karekare mai na ko Te Manukanuka a Hoturoa, kei reira a Taramainuku raua ko Kaiwhare. Ka kawea ki nga.hau o Mangere, e topa ai taku manuhokahoka ki Te Manurewatanga a Tamapahore. Whakaterawhiti taku haere ki Otara-a-nuku, ki Otara-a-rangi koia te tikapatanga o toku tiipuna o Marutuahu. Hoki whenei mai au ki Te Pane o Mataoho, tiro kau ake au ki aku pa whakairo ko Matatukutureia, ko Matukurua nga nohoanga tapu o Huakaiwaka, o Nga Tini-o-toitehuatahi, o Maruiwi kua ngaro katoa ki te reinga.

text: Kia kāpuia te reo o Tāmaki ki te Tonga: Tāmaki Makaurau ki te Tonga Mai i te Papakuratanga o Mataoho tae noa ki tona Ipu. Mai i Pukaki Tapu o Poutiikeka ki Te Puketapapatanga a Hape. Mai i te tahuna o Torea i nga wai o Mokoia, mawhiti atu ki Te Arapueru e karekare mai na ko Te Manukanuka a Hoturoa, kei reira a Taramainuku raua ko Kaiwhare. Ka kawea ki nga.hau o Mangere, e topa ai taku manuhokahoka ki Te Manurewatanga a Tamapahore. Whakaterawhiti taku haere ki Otara-a-nuku, ki Otara-a-rangi koia te tikapatanga o toku tiipuna o Marutuahu. Hoki whenei mai au ki Te Pane o Mataoho, tiro kau ake au ki aku pa whakairo ko Matatukutureia, ko Matukurua nga nohoanga tapu o Huakaiwaka, o Nga Tini-o-toitehuatahi, o Maruiwi kua ngaro katoa ki te reinga.

year: 2017