Effects of Diet on Seven-Day Ceriodaphnia dubia Toxicity Tests

Author Institution: Department of Biology, The University of AkronThe purpose of this study was to evaluate the effects of four diets on the results of seven-day Ceriodaphnia dubia toxicity tests. Survival and reproduction were used as indices to detect the sensitivity of this species to acute and chronic copper stress. All toxicity tests were conducted using the moderately hard reconstituted water recommended in 1989 by the U.S. Environmental Protection Agency. Diet differentially affected the acute and chronic toxicity of copper. Daphnids fed Selenastrum capricomutum (alga) showed the greatest sensitivity, followed by those fed the alga Chlamydomonas reinhardti, then by animals fed a Yeast-CerophyllT1^-Trout Food (YCTF) mixture plus Selenastrum, and finally by animals fed YCTF alone. These differences may result from the poor nutritional adequacy of Selenastrum when fed alone, the different caloric contents of the diets, the increased toxicant uptake by the organisms through ingestion of copperladen algal cells, and/or copper ions sequestered by fats and insoluble substances in YCTF. We recognize that diet is an important variable in seven-day toxicity tests, and that the selection of a diet should not be based only on its effects on long-term culturing of C. dubia, but also on its possible effects on test results

Genes involved in carotene synthesis and mating in Blakeslea trispora

Mating of Blakeslea trispora and other molds of the order Mucorales requires the interaction of mycelia of opposite sex, (+) and (-), leading to the development of specialized structures and to an enhanced accumulation of beta-carotene. Industry obtains beta-carotene by co-cultivating appropriate strains of Blakeslea (mated cultures). Gene transcription in single and mated cultures was assayed by cDNA-AFLP, a technique to observe the differential expression of subsets of mRNA fragments. Overexpression in mated cultures is about ten times more frequent than underexpression. We obtained and sequenced fragments of 97 candidate genes that appeared to be overexpressed during mating and confirmed four of them by reverse transcription and real-time PCR. Comparisons with gene sequences from other organisms suggest functions in carotene biosynthesis (4 genes), energy metabolism (8), cell wall synthesis (1), transfer of acetyl groups (1), and regulatory processes (10). Sodium acetate inhibited sexual overexpression in about two-thirds of the candidate genes and acted as a signal with broad effects on the metabolism and the morphology of mated cultures. Our work offers new materials for the study of carotene biosynthesis and its regulation and for the improvement of carotene production with Mucorales

Optical realization of a quantum beam splitter

We show how the quantum process of splitting light may be modelled in classical optics. A second result is the possibility to engineer specific forms of a classical field.Comment: 5 page

Semi‐automated workflows for acquiring specimen data from label images in herbarium collections

Computational workflow environments are an active area of computer science and informatics research; they promise to be effective for automating biological information processing for increasing research efficiency and impact. In this project, semi‐automated data processing workflows were developed to test the efficiency of computerizing information contained in herbarium plant specimen labels. Our test sample consisted of mexican and Central American plant specimens held in the University of michigan Herbarium (MICH). The initial data acquisition process consisted of two parts: (1) the capture of digital images of specimen labels and of full‐specimen herbarium sheets, and (2) creation of a minimal field database, or "pre‐catalog", of records that contain only information necessary to uniquely identify specimens. For entering "pre‐catalog" data, two methods were tested: key‐stroking the information (a) from the specimen labels directly, or (b) from digital images of specimen labels. In a second step, locality and latitude/longitude data fields were filled in if the values were present on the labels or images. If values were not available, geo‐coordinates were assigned based on further analysis of the descriptive locality information on the label. Time and effort for the various steps were measured and recorded. Our analysis demonstrates a clear efficiency benefit of articulating a biological specimen data acquisition workflow into discrete steps, which in turn could be individually optimized. First, we separated the step of capturing data from the specimen from most keystroke data entry tasks. We did this by capturing a digital image of the specimen for the first step, and also by limiting initial key‐stroking of data to create only a minimal "pre‐catalog" database for the latter tasks. By doing this, specimen handling logistics were streamlined to minimize staff time and cost. Second, by then obtaining most of the specimen data from the label images, the more intellectually challenging task of label data interpretation could be moved electronically out of the herbarium to the location of more highly trained specialists for greater efficiency and accuracy. This project used experts in the plants’ country of origin, mexico, to verify localities, geography, and to derive geo‐coordinates. Third, with careful choice of data fields for the "pre‐catalog" database, specimen image files linked to the minimal tracking records could be sorted by collector and date of collection to minimize key‐stroking of redundant data in a continuous series of labels, resulting in improved data entry efficiency and data quality.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146956/1/tax596014.pd

Faraday waves on a viscoelastic liquid

We investigate Faraday waves on a viscoelastic liquid. Onset measurements and a nonlinear phase diagram for the selected patterns are presented. By virtue of the elasticity of the material a surface resonance synchronous to the external drive competes with the usual subharmonic Faraday instability. Close to the bicriticality the nonlinear wave interaction gives rise to a variety of novel surface states: Localised patches of hexagons, hexagonal superlattices, coexistence of hexagons and lines. Theoretical stability calculations and qualitative resonance arguments support the experimental observations.Comment: 4 pages, 4figure

Anomalous strength of membranes with elastic ridges

We report on a simulational study of the compression and buckling of elastic ridges formed by joining the boundary of a flat sheet to itself. Such ridges store energy anomalously: their resting energy scales as the linear size of the sheet to the 1/3 power. We find that the energy required to buckle such a ridge is a fixed multiple of the resting energy. Thus thin sheets with elastic ridges such as crumpled sheets are qualitatively stronger than smoothly bent sheets.Comment: 4 pages, REVTEX, 3 figure