title: Nitrate reductase from anaerobically grown Rhizobium japonicum

authors: Daniel, Roy M.

subjects: biology

abstract: The activity of nitrate reductase in Rhizobium japonicum is controlled by oxygen tension, and not by nitrate. The enzyme from R. japonicum grown anaerobically in the presence of nitrate resembles that from bacteroids in having a molecular weight of about 69000 daltons; the enzyme from aerobically grown cells has a molecular weight of about 170000 daltons. Both types of enzyme have similar Km values, but differ in their sensitivity to KCN.

text: Nitrate reductase from anaerobically grown Rhizobium japonicum The activity of nitrate reductase in Rhizobium japonicum is controlled by oxygen tension, and not by nitrate. The enzyme from R. japonicum grown anaerobically in the presence of nitrate resembles that from bacteroids in having a molecular weight of about 69000 daltons; the enzyme from aerobically grown cells has a molecular weight of about 170000 daltons. Both types of enzyme have similar Km values, but differ in their sensitivity to KCN.

year: 1976

title: The potential for an independent source of Younger Dryas tree-ring radiocarbon data from the Lake Ontario region, North America, and its palaeoenvironmental context

authors: Griggs, Carol

abstract: Tree rings are the gold standard for the calibration of radiocarbon dates into calendar years with limited error due to their annual record of radiocarbon content in the atmosphere. Currently, the tree-ring 14C data used in the International Radiocarbon Calibration curve (IntCal13) are from multiple sources back to ~ 10 ka cal BP for the northern hemisphere. However, the source for tree-ring calibration data prior to ~10 ka cal BP, including the Younger Dryas (YD) and most of the Early Holocene (EH) chronozones, is limited to central Europe. Substantial quantities of logs found in the lowlands of Lake Ontario in North America, dating from 12.1 to 11.2 ka cal BP, have great potential for providing unique YD-EH tree-ring 14C data from a new, previously unrepresented, geographic location and for adding a new perspective to ongoing debates such as the timing of the YD/EH transition in continental North America. Preliminary fieldwork yielded over 43 logs, predominantly spruce (Picea spp.), found buried in alluvial strata over 0.2 hectares of the floodplain at Bell Creek near Fulton, NY. Dendrochronological analysis of 32 spruce logs from this collection has produced several chronologies, one 183 years in length and a second of 147 years with a possible crossdate yielding a chronology of 260 years. Ongoing survey of the site suggests that there is high preservation potential in the same stratigraphic units in an additional ~2 hectares of floodplain, and sample collection with subsequent analysis will increase the chronology’s sample depth, extend its length, and potentially provide a robust, independent Younger Dryas – Early Holocene 14C record. Initial assessments of climatic, hydrological, environmental, and isostatic variations and events over time from the tree rings and their stable isotopes, as well as pollen, macrofossil, and sediment analyses and isostatic modeling indicate substantial changes in the Bell Creek Valley and surrounding lowlands both during the YD and into the mid-Holocene. These changes include significant alterations in the rate, volume, and direction of stream flow, and transition from a boreal riparian environment on a low-order river to a wetlands, then back to a riparian environment with much less streamflow and occasional flooding, similar to the Bell Creek Valley today.

text: The potential for an independent source of Younger Dryas tree-ring radiocarbon data from the Lake Ontario region, North America, and its palaeoenvironmental context Tree rings are the gold standard for the calibration of radiocarbon dates into calendar years with limited error due to their annual record of radiocarbon content in the atmosphere. Currently, the tree-ring 14C data used in the International Radiocarbon Calibration curve (IntCal13) are from multiple sources back to ~ 10 ka cal BP for the northern hemisphere. However, the source for tree-ring calibration data prior to ~10 ka cal BP, including the Younger Dryas (YD) and most of the Early Holocene (EH) chronozones, is limited to central Europe. Substantial quantities of logs found in the lowlands of Lake Ontario in North America, dating from 12.1 to 11.2 ka cal BP, have great potential for providing unique YD-EH tree-ring 14C data from a new, previously unrepresented, geographic location and for adding a new perspective to ongoing debates such as the timing of the YD/EH transition in continental North America. Preliminary fieldwork yielded over 43 logs, predominantly spruce (Picea spp.), found buried in alluvial strata over 0.2 hectares of the floodplain at Bell Creek near Fulton, NY. Dendrochronological analysis of 32 spruce logs from this collection has produced several chronologies, one 183 years in length and a second of 147 years with a possible crossdate yielding a chronology of 260 years. Ongoing survey of the site suggests that there is high preservation potential in the same stratigraphic units in an additional ~2 hectares of floodplain, and sample collection with subsequent analysis will increase the chronology’s sample depth, extend its length, and potentially provide a robust, independent Younger Dryas – Early Holocene 14C record. Initial assessments of climatic, hydrological, environmental, and isostatic variations and events over time from the tree rings and their stable isotopes, as well as pollen, macrofossil, and sediment analyses and isostatic modeling indicate substantial changes in the Bell Creek Valley and surrounding lowlands both during the YD and into the mid-Holocene. These changes include significant alterations in the rate, volume, and direction of stream flow, and transition from a boreal riparian environment on a low-order river to a wetlands, then back to a riparian environment with much less streamflow and occasional flooding, similar to the Bell Creek Valley today.

year: 2015

title: Rethinking English in Māori-medium education

authors: Hill, Richard Kenneth

subjects: Māori-medium

abstract: English language instruction in New Zealand's Māori-medium schools is controversial, with many schools either excluding it from their curriculum or adopting a tokenistic approach. Yet, how Māori-medium educators can best support their students' academic English language growth is still an under-researched and unresolved question. This paper reports on a project involving the English language transition programmes of three Māori-medium primary schools. Interviews and observations of key personnel within these schools revealed the components of their programmes, their perceptions of the need for English transition education and the issues they were facing in implementing English language instruction. The project found a direct relationship between levels of student language attainment and the quantity and quality of exposure to English instruction. Where an English programme occupied a significant place in a school's timetable and was staffed by teachers knowledgeable about the learning needs of bilingual students and how best to attend to these, the result was higher literacy scores and more satisfied students. This paper argues that planning English language outcomes for Māori-medium students is essential if becoming biliterate is an important aim. This planning must also be long-term, across all 13 years of the students' education.

text: Rethinking English in Māori-medium education English language instruction in New Zealand's Māori-medium schools is controversial, with many schools either excluding it from their curriculum or adopting a tokenistic approach. Yet, how Māori-medium educators can best support their students' academic English language growth is still an under-researched and unresolved question. This paper reports on a project involving the English language transition programmes of three Māori-medium primary schools. Interviews and observations of key personnel within these schools revealed the components of their programmes, their perceptions of the need for English transition education and the issues they were facing in implementing English language instruction. The project found a direct relationship between levels of student language attainment and the quantity and quality of exposure to English instruction. Where an English programme occupied a significant place in a school's timetable and was staffed by teachers knowledgeable about the learning needs of bilingual students and how best to attend to these, the result was higher literacy scores and more satisfied students. This paper argues that planning English language outcomes for Māori-medium students is essential if becoming biliterate is an important aim. This planning must also be long-term, across all 13 years of the students' education.

year: 2011