title: Vertical distributions of chlorophyll in deep, warm monomictic lakes

authors: Hamilton, David P.

subjects: phytoplankton

abstract: The factors affecting vertical distributions of chlorophyll fluorescence were examined in four temperate, warm monomictic lakes. Each of the lakes (maximum depth >80 m) was sampled over 2 years at intervals from monthly to seasonal. Profiles were taken of chlorophyll fluorescence (as a proxy for algal biomass), temperature and irradiance, as well as integrated samples from the surface mixed layer for chlorophyll a (chl a) and nutrient concentrations in each lake. Depth profiles of chlorophyll fluorescence were also made along transects of the longest axis of each lake. Chlorophyll fluorescence maxima occurred at depths closely correlated with euphotic depth (r ² = 0.67, P < 0.01), which varied with nutrient status of the lakes. While seasonal thermal density stratification is a prerequisite for the existence of a deep chlorophyll maximum (DCM), our study provides evidence that the depth of light penetration largely dictates the DCM depth during stratification. Reduction in water clarity through eutrophication can cause a shift in phytoplankton distributions from a DCM in spring or summer to a surface chlorophyll maximum within the surface mixed layer when the depth of the euphotic zone (z eu) is consistently shallower than the depth of the surface mixed layer (z SML). Trophic status has a key role in determining vertical distributions of chlorophyll in the four lakes, but does not appear to disrupt the annual cycle of maximum chlorophyll in winter.

text: Vertical distributions of chlorophyll in deep, warm monomictic lakes The factors affecting vertical distributions of chlorophyll fluorescence were examined in four temperate, warm monomictic lakes. Each of the lakes (maximum depth >80 m) was sampled over 2 years at intervals from monthly to seasonal. Profiles were taken of chlorophyll fluorescence (as a proxy for algal biomass), temperature and irradiance, as well as integrated samples from the surface mixed layer for chlorophyll a (chl a) and nutrient concentrations in each lake. Depth profiles of chlorophyll fluorescence were also made along transects of the longest axis of each lake. Chlorophyll fluorescence maxima occurred at depths closely correlated with euphotic depth (r ² = 0.67, P < 0.01), which varied with nutrient status of the lakes. While seasonal thermal density stratification is a prerequisite for the existence of a deep chlorophyll maximum (DCM), our study provides evidence that the depth of light penetration largely dictates the DCM depth during stratification. Reduction in water clarity through eutrophication can cause a shift in phytoplankton distributions from a DCM in spring or summer to a surface chlorophyll maximum within the surface mixed layer when the depth of the euphotic zone (z eu) is consistently shallower than the depth of the surface mixed layer (z SML). Trophic status has a key role in determining vertical distributions of chlorophyll in the four lakes, but does not appear to disrupt the annual cycle of maximum chlorophyll in winter.

year: 2010

title: Sonochemical preparation of single-dispersion metal nanoparticles from metal salts

authors: Fujimoto, Toshiyuki

subjects: metal nanoparticles

abstract: Novel metal nanoparticles of Pd and Pt were prepared by sonochemical reduction of solutions containing H₂PtCl₆ or K₂PdCl₄. The effect of atmospheric gas on the particle size distribution was investigated. Average diameters and standard deviations of the Pd particles prepared under Ar (Pd/Ar) and N2 (Pd/N₂) were found to be 3.6 ± 0.7 nm (Pd/Ar) and 2.0 ± 0.3 nm (Pd/N₂). Smaller and sharper distribution of the particle size was observed for the Pd particles formed under a N₂ atmosphere. In the case of Pt, a smaller and sharper distribution of the particle size was observed for the particles prepared under a Xe atmosphere. These relations can be explained in terms of a hot-spot temperature created by acoustic cavitation.

text: Sonochemical preparation of single-dispersion metal nanoparticles from metal salts Novel metal nanoparticles of Pd and Pt were prepared by sonochemical reduction of solutions containing H₂PtCl₆ or K₂PdCl₄. The effect of atmospheric gas on the particle size distribution was investigated. Average diameters and standard deviations of the Pd particles prepared under Ar (Pd/Ar) and N2 (Pd/N₂) were found to be 3.6 ± 0.7 nm (Pd/Ar) and 2.0 ± 0.3 nm (Pd/N₂). Smaller and sharper distribution of the particle size was observed for the Pd particles formed under a N₂ atmosphere. In the case of Pt, a smaller and sharper distribution of the particle size was observed for the particles prepared under a Xe atmosphere. These relations can be explained in terms of a hot-spot temperature created by acoustic cavitation.

year: 2001

title: Māori Goddesses in Literature Part 1: pre 1880 - 1900

authors: Yates-Smith, Aroha

subjects: Atua wāhine

abstract: Many contemporary Māori are familiar with atua wāhine, Māori goddesses, through accounts that have been passed on to them by word of mouth. Few, however, have had an opportunity to consult accounts of atua wāhine that date from the early period of Māori-Pākehā contact. Those who wish to do so may have considerable difficulty in sifting through all of the written materials for the information they seek. For this reason, this paper provides a review of the literature pertaining to atua wāhine from pre-1880 to 1900, together with a commentary on the sources to which reference is made. A review of literature on atua wāhine which appeared after 1900 will appear in the second volume of this journal.

text: Māori Goddesses in Literature Part 1: pre 1880 - 1900 Many contemporary Māori are familiar with atua wāhine, Māori goddesses, through accounts that have been passed on to them by word of mouth. Few, however, have had an opportunity to consult accounts of atua wāhine that date from the early period of Māori-Pākehā contact. Those who wish to do so may have considerable difficulty in sifting through all of the written materials for the information they seek. For this reason, this paper provides a review of the literature pertaining to atua wāhine from pre-1880 to 1900, together with a commentary on the sources to which reference is made. A review of literature on atua wāhine which appeared after 1900 will appear in the second volume of this journal.

year: 2000-10