Regulation of zooplankton vertical migrations by light, food, and fish

The regulation of zooplankton vertical migration has been attributed to the physical environment, and, more recently, to biological factors. This study evaluated the influence of light, food and fish on vertical migration. Laboratory experiments quantified changes in vertical migrations of Daphnia pulex in tall columns in response to short term changes in food concentration and the presence of a fish, under a wide range of natural light conditions. A stimulus-threshold model predicted the time of the start of migration from a threshold rate of relative light intensity change. Hypotheses that migrations follow isopleths of light intensity, and that velocity of migration is directly correlated to relative rate of light intensity change, were not supported. Concentrations of Chlorella sp. had little influence on the timing, amplitude, or velocity of migration. There was evidence of a sensory response of Daphnia pulex to the short term presence of a fish in the columns. With a fish present, pre-migration population depths were deeper. This response ceased within 24 hours after removing the fish. Juvenile Daphnia pulex started their migrations from shallower depths in the columns, and otherwise migrated similarly to adults. Field studies of zooplankton vertical migration were conducted on four New Hampshire lakes. The lakes varied in food concentrations, and all contained planktivorous fish. The field results were consistent with an avoidance of ultra-violet radiation by zooplankton. Pre-migration depths were deeper in waters more transparent to visible light. Food stratification was correlated with amplitude and direction of vertical migration, and the direction of migration was apparently influenced by the phytoplankton composition. Although planktivorous fish were present in the lakes, the zooplankton did not take advantage of possible light refugia. Fish density did not significantly affect vertical migrations. Invertebrate predation was not sufficient to explain reverse migrations

Synthesis and characterization of covalently-linked dendrimer bioconjugates and the non-covalent self-assembly of streptavidin-based megamers

This work details the attachment of dendrimers to proteins, peptides and single stranded DNA (ssDNA). Dendrimers based on melamine satisfy many of the synthetic demands in the field of bioconjugate chemistry including: monodispersity, synthetic flexibility and scalability. The solution-phase syntheses of both ssDNA-dendrimer and peptide-dendrimer bioconjugates is described, and thorough characterization by matrix-assisted laser desorption ionization/ time-of-flight (MALDI-TOF) mass spectrometry, UV-vis spectroscopy, fluorescence spectroscopy, and polyacrylamide gel electrophoresis is discussed. Non-covalent DNA-dendrimer complexes have been shown to facilitate antisense gene delivery, but are vulnerable to dissociation and subsequent enzymatic degradation within the cell. In an effort to prepare biocompatible antisense agents capable of effectively shielding ssDNA from intracellular nuclease digestion, disulfide-linked ssDNA-dendrimers were prepared and rigorously characterized to rule out the possibility of an electrostatic-based interaction. Hybridization assays were performed to determine if the covalently-attached dendrimer affected the ability of the attached ssDNA strand to anneal with a complementary sequence to form double-stranded DNA (dsDNA)-dendrimers. Results indicate that ssDNA-dendrimer conjugates readily anneal to complementary ssDNA strands either in solution or attached to gold surfaces. Nuclease digestions of conjugates in solution suggested that enzymatic manipulation of dsDNA-dendrimers is possible, offering promise for DNA-based computation and other fields of DNA-nanotechnology. Much larger bioconjugates consisting of dendrimers, proteins and peptides were prepared with the goal of obtaining molecular weights sufficient for enhanced permeability and retention (EPR) in tumors. While the dendrimer provides the advantages of a purely synthetic route for drug delivery, the protein portion of the bioconjugate provides a monodisperse, macromolecular scaffold for the non-covalent self-assembly of the dendrimers. The strategy presented herein is based on the strong interaction between biotin and the 60 kD tetrameric protein streptavidin. Each monomer of streptavidin is capable of binding 1 biotin molecule, thus when biotin functionalized peptide-dendrimers are added to streptavidin they bind to form a cluster of dendrimers, or a megamer. The biotinylated peptides that link the dendrimers to the streptavidin core provide a way to actively target specific cell types for drug delivery. Megamer formation through the addition of tetrameric streptavidin was successful as indicated by MALDI-TOF, UV-vis titration and gel electrophoresis assays

Processing capacity in a letter-matching task.

A processing-capacity notion of attention was defined in terms of increased reaction times (RTs) in a probe task at specific times during the performance of a primary task The primary task involved a same-different response to two letters presented successively. The probe task was either a Bonders type a or type c reaction to a burst of white noise, which could occur at any one of 8 times relative to the events on the letter-matching task. The study was specif ically designed to investigate the encoding of the f irst letter , which Posner and Boies (1971) concluded required no processing capacity. Here, displaying the first letter for 15 msec, and following it with a visual mask did result in lengthened RTs to probes presented simultaneously with the first letter. Increasing the difficulty of the probe task did not result in greater interference from the primary task. Data are discussed in terms of processes requiring capacity

Collections in Library Space

Non-Peer ReviewedLibraries have generally provided varying levels of non-member access to their collections and spaces. As availability of printed information spread, so did access to libraries. In the last decade, due to shifts in formats and acquisition models, access to electronic library collections and virtual library space has been restricted to members only. As more library services go online, this access for non-members will continue to contract. How do libraries move forward in this landscape? Will support for open publishing be enough, or do we need to radicalize the way we manage our collections and services

Measuring Climate and Extreme Weather Vulnerability to Inform Resilience, Report 2 : Port Decision-Makers’ Barriers to Climate and Extreme Weather Adaptation

Numerous decision-making barriers prevent or delay climate and extreme weather resilience investments. Port decision-makers’ perceptions of such barriers are important for proactive strategies for reducing coastal vulnerability and supporting safe and sustainable operations of U.S. ports. This report identifies the perceived adaptation barriers for seaports, and strategies to remove them. Interviews with 30 directors/managers, environmental specialists, and safety planners at 15 medium- and high-use ports of the North Atlantic resulted in a typology of factors and conditions that hamper adaptation actions, planning, and perceived strategies to overcome these barriers. This study finds that the decision-makers have consensus on seven overarching barriers to adaptation: the lack of understanding of the risks (93%), lack of funding (77%), perceived levels of risks do not exceed the action threshold (70%), governance disconnect (67%), physical constraints (67%), lack of communication amongst individuals (7%), and the problem (of adaptation) is overwhelming (7%). For strategies to overcome the adaptation barriers, the study points to the importance of fostering collaborations, making regulatory changes, and conducting risk assessments. Port decision-makers also mentioned the need for developing financial incentives and taking advantage of communication networks as necessary strategies to implement climate and extreme weather adaptations

Decision makers’ barriers to climate and extreme weather adaptation: a study of North Atlantic high- and medium-use seaports

Decision-making barriers challenge port administrators to adapt and build resilience to natural hazards. Heavy rains, storms, sea level rise (SLR), and extreme heat can damage the critical coastal infrastructure upon which coastal communities depend. There is limited understanding of what impedes port decision makers from investing resources in climate and extreme weather adaptations. Through semi-structured interviews of 30 port directors/managers, environmental specialists, and safety planners at 15 medium- and high-use ports of the U.S. North Atlantic, this paper contributes a typology of seven key adaptation barriers. We measured shared knowledge of the identified barriers using a cultural consensus model (CCM). Knowledge of the barriers that prevent or delay resilience investments can help the decision makers direct their resources to help reduce coastal vulnerability and support safe and sustainable operations of U.S. ports. Such actions also serve to help prepare the marine transportation system for future climate and extreme weather events