Mary E. Williams to Mr. Meredith (3 October 1962)

https://egrove.olemiss.edu/mercorr_pro/1234/thumbnail.jp

Computers and Learning

The important questions for instructors to address concern what skills the student is to learn and how the student is to be motivated to acquire those skills. Questions about simulations, graphics tools, and the like are unimportant until the first two questions have been answered adequately. We discuss the role of explanation by students and describe a mechanism for motivating students to learn

Growth and survival of spat, juveniles and adult Akoya pearl oyster Pinctada imbricata fucata (Gould, 1850) in different rearing conditions and stocking densities

Growth trials were conducted using hatchery produced spat of Pinctada imbricata fucata (Gould, 1850) having average dorso-ventral measurement (DVM) of 3.99 mm, hinge length (HL) 3.94 mm, thickness (THK) 1.25 mm and weight (WGT) 0.008 g. The first experiment was a comparative growth assessment of spat grown in one ton FRP tanks in the hatchery and with that of spat reared in micron meshed cages under open sea conditions for a period of three months. During the third month, spats grown in micron meshed cages showed growth increments of 7.83 mm (DVM), 4.86 mm (HL), 1.61 mm (THK) and 0.192 g (WGT) whereas those grown in FRP tanks grew only by 0.95 mm (DVM), 0.5 mm (HL), 0.46 mm (THK) and 0.004 g (WGT) indicating faster growth in open sea conditions. Second experiment was conducted to elucidate the effect of stocking density on the growth and survival of juveniles reared in plastic baskets at different stocking densities viz., 200 (0.03 nos. cm-3) , 300 (0.049 nos. cm-3), 400 (0.065 nos. cm-3), 500 (0.08 nos. cm-3), 600 (0.098 nos. cm-3), 700 (0.11 nos.cm-3), 800 (0.13 nos. cm-3), 900 (0.14 nos. cm-3) and 1000 (0.16 nos. cm-3) numbers per basket. Results indicated that P. imbricata fucata juveniles can be grown at stocking densities of upto 400 nos per basket for a period of five months with 90% survival without much reduction in growth. Third experiment was conducted on the growth of P. imbricata fucata subadults in box cages at different stocking densities viz., 200 (0.006 nos. cm-3), 300 (0.01 nos. cm-3), 400 (0.013 nos. cm-3), 500 (0.016 nos. cm-3), 600 (0.02 nos. cm-3), 700 (0.023 nos. cm-3), 800 (0.026 nos. cm-3), 900 (0.03 nos. cm-3) and 1000 (nos. cm-3) numbers per cage. Survival rates ranged from 98.5 to 98.6% at stocking densities up to 400 nos. per cage during the fifth month without any significant variation in the DVM, HL and THK of oysters

An optical coherence microscope for 3-dimensional imaging in developmental biology

An optical coherence microscope (OCM) has been designed and constructed to acquire 3-dimensional images of highly scattering biological tissue. Volume-rendering software is used to enhance 3-D visualization of the data sets. Lateral resolution of the OCM is 5 mm (FWHM), and the depth resolution is 10 mm (FWHM) in tissue. The design trade-offs for a 3-D OCM are discussed, and the fundamental photon noise limitation is measured and compared with theory. A rotating 3-D image of a frog embryo is presented to illustrate the capabilities of the instrument

The Arcturus Moving Group: Its Place in the Galaxy

The Arcturus moving group is a well-populated example of phase space substructure within the thick disk of our Galaxy. Traditionally regarded as the remains of a dissolved open cluster, it has recently been suggested to be a remnant of a satellite accreted by our Galaxy. To investigate the origin of the group we undertook a high-resolution spectroscopic abundance study of Arcturus group members and candidates. Examining abundance of Fe, Mg, Ca, Ti, Cr, Ni, Zn, Ce, Nd, Sm and Gd for 134 stars we found that the group is chemically similar to disk stars and does not exhibit a clear chemical homogeneity. Furthermore, we confirm the existence of the Arcturus group using the Nordstroem et al. (2004), Schuster et al. (2006) and RAdial Velocity Experiment (RAVE) surveys (Steinmetz et al. 2006). The origin of the group still remains unresolved: the chemical results are consistent with a dynamical origin but do not entirely rule out a merger one. Certainly, the Arcturus group provides a challenge to our understanding of the nature and origin of the Galaxy's thick disk.Comment: 6 pages, 2 figures, to appear in the Proceedings of the IAU Symposium 254: The Galaxy Disk in Cosmological Contex

Effects of Exogenous Yeast and Bacteria on the Microbial Population Dynamics and Outcomes of Olive Fermentations.

In this study, we examined Sicilian-style green olive fermentations upon the addition of Saccharomyces cerevisiae UCDFST 09-448 and/or Pichia kudriazevii UCDFST09-427 or the lactic acid bacteria (LAB) Lactobacillus plantarum AJ11R and Leuconostoc pseudomesenteroides BGM3R. Olives containing S. cerevisiae UCDFST 09-448, a strain able to hydrolyze pectin, but not P. kudriazevii UCDFST 09-427, a nonpectinolytic strain, exhibited excessive tissue damage within 4 weeks. DNA sequencing of fungal internal transcribed spacer (ITS) regions and comparisons to a yeast-specific ITS sequence database remarkably showed that neither S. cerevisiae UCDFST 09-448 nor P. kudriazevii UCDFST 09-427 resulted in significant changes to yeast species diversity. Instead, Candida boidinii constituted the majority (>90%) of the total yeast present, independent of whether S. cerevisiae or P. kudriazevii was added. By comparison, Lactobacillus species were enriched in olives inoculated with potential starter LAB L. plantarum AJ11R and L. pseudomesenteroides BGM3R according to community 16S rRNA gene sequence analysis. The bacterial diversity of those olives was significantly reduced and resembled control fermentations incubated for a longer period of time. Importantly, microbial populations were highly dynamic at the strain level, as indicated by the large variations in AJ11R and BGM3R cell numbers over time and reductions in the numbers of yeast isolates expressing polygalacturonase activity. These findings show the distinct effects of exogenous spoilage and starter microbes on indigenous communities in plant-based food fermentations that result in very different impacts on product quality. IMPORTANCE Food fermentations are subject to tremendous selective pressures resulting in the growth and persistence of a limited number of bacterial and fungal taxa. Although these foods are vulnerable to spoilage by unintended contamination of certain microorganisms, or alternatively, can be improved by the deliberate addition of starter culture microbes that accelerate or beneficially modify product outcomes, the impact of either of those microbial additions on community dynamics within the fermentations is not well understood at strain-specific or global scales. Herein, we show how exogenous spoilage yeast or starter lactic acid bacteria confer very different effects on microbial numbers and diversity in olive fermentations. Introduced microbes have long-lasting consequences and result in changes that are apparent even when levels of those inoculants and their major enzymatic activities decline. This work has direct implications for understanding bacterial and fungal invasions of microbial habitats resulting in pivotal changes to community structure and function