Chaetognath ecology in relation to hydrographic conditions in the Australian sector of the Antarctic Ocean

Chaetognath ecology in relation to hydrographic conditions was investigated during austral summer in the Antarctic Ocean with two cruises conducted seven years apart. Time series samples were collected at a total of five stations along 140_E in the region of the Antarctic Divergence (AD). The numerically dominant species was Eukrohnia hamata, averaging over 80% of the collected specimens. This species was most abundant north of the AD where bi-modal distribution was common. No species displayed regular diel vertical migration nor were their vertical distribution restricted by hydrographic clines. Breeding of E. hamata appeared unaffected by water conditions-the same maturity stages were present in similar percentages across the water masses. Vertical segregation of size classes among E. hamata was clearest north of the AD in a more stratified water column. In other locations, the size classes overlapped considerably; this is likely due to physical forcing from mixing water. Feeding activity of E. hamata was lowest within the AD and increased both north and south on the edges of the front. Feeding activity appeared continuous with no recognizable diel pattern. E. hamata containing prey items were smaller north of the AD compared to the south, suggesting two separate populations. The percentage of predators with food in their gut was much larger in this study than previously reported work. Often times nearly 50% of the E. hamata collected had highly digested contents in the posterior of the gut

Community structure and vertical distribution of chaetognaths in the Celebes and Sulu Seas

Chaetognath community structure, vertical distribution and migration patterns were investigated in two marginal basins-the Celebes and Sulu Seas. The two seas are part of an island arc located in the southeastern Asia region of the western equatorial Pacific Ocean. The Sulu Sea had higher species diversity (Shannon Index, H\u27) and higher overall chaetognath abundance than the Celebes Sea. Twenty-two species from 4 genera were collected from the Sulu Sea and 19 species from 4 genera were collected from the Celebes Sea. Three species were collected exclusively in the Sulu Sea: Sagitta bipunctata, Sagitta nagae and an unidentified Sagitta species. Sagitta enflata was the numerically dominant species at both locations. Species diversity in the Celebes Sea was fairly even between the surface and 1000m. However, in the Sulu Sea substantial drops in diversity occurred at 175-200m-below the oxycline, thermocline and halocline-as well as at 900-1000m. The drop at 175-200m and 900-1000m was largely due to the numerical dominance of the species Sagitta decipiens and Sagitta macrocephala, respectively. In the Celebes Sea only, a large portion of the overall chaetognath population migrated downwards during the day into the 125-200m layer. Cluster analysis using Ward\u27s method, along with weighted mean depth values, revealed that this migration was largely attributable to the species Sagitta pacifica, Sagitta ferox-robusta, Sagitta neglecta and Pterosagitta draco. A similar migration of the overall population was blocked in the Sulu Sea-apparently by the oxycline. It seems the group of migrating chaetognaths in the Celebes Sea prevented the numerical dominance of S. decipiens at the lower edge of the epipelagic region, possibly through competition, and consequently prevented the same drop in diversity (H\u27) at 175-200m as was recorded in the Sulu Sea

A protocol to evaluate RNA sequencing normalization methods

Background RNA sequencing technologies have allowed researchers to gain a better understanding of how the transcriptome affects disease. However, sequencing technologies often unintentionally introduce experimental error into RNA sequencing data. To counteract this, normalization methods are standardly applied with the intent of reducing the non-biologically derived variability inherent in transcriptomic measurements. However, the comparative efficacy of the various normalization techniques has not been tested in a standardized manner. Here we propose tests that evaluate numerous normalization techniques and applied them to a large-scale standard data set. These tests comprise a protocol that allows researchers to measure the amount of non-biological variability which is present in any data set after normalization has been performed, a crucial step to assessing the biological validity of data following normalization. Results In this study we present two tests to assess the validity of normalization methods applied to a large-scale data set collected for systematic evaluation purposes. We tested various RNASeq normalization procedures and concluded that transcripts per million (TPM) was the best performing normalization method based on its preservation of biological signal as compared to the other methods tested. Conclusion Normalization is of vital importance to accurately interpret the results of genomic and transcriptomic experiments. More work, however, needs to be performed to optimize normalization methods for RNASeq data. The present effort helps pave the way for more systematic evaluations of normalization methods across different platforms. With our proposed schema researchers can evaluate their own or future normalization methods to further improve the field of RNASeq normalization

No Small Scale Radio Jets Here: Multi-Epoch Observations of Radio Continuum Structures in NGC 1068 with the VLBA

We present recent Very Long Baseline Array (VLBA) 5 GHz radio observations of the nearby, luminous Seyfert 2 galaxy NGC 1068 for comparison to similar VLBA observations made on 1997 April 26. By cross-correlating the positions of emitting regions across both epochs, we find that spatially-resolved extra-nuclear radio knots in this system have sub-relativistic transverse speeds (v < 0.1c). We discuss sources of the observed knots and how the radio emission relates to additional phases of gas in the central ~150 pcs of this system. We suggest that the most likely explanation for the observed emission is synchrotron radiation formed by shocked host media via interactions between AGN winds and the host environment.Comment: 13 pages, 4 figures, accepted for publication in Ap

First record of a leptocephalus larva ingested by a chaetognath

An approximately 17mm Nemichthys scolopaceus leptocephalus was found in the gut of a 25mm chaetognath, Sagitta (Flacdsagitta) hexaptera, collected in the North Equatorial Current region of the western North Pacific. The chaetognath was photographed before preservation. The leptocephalus was folded in half and was positioned deep within the hindgut. Although the chaetognath was caught during sampling for leptocephali, its location in the hindgut suggests that the leptocephalus could have been ingested prior to capture by the net. This first record of ingestion of this unique type of fish larva suggests that if contact is made with small leptocephali, it is possible for them to be ingested by relatively large sized chaetognaths that may identify them as potential prey

Hypoxia and Hypoglycemia synergistically regulate mRNA stability

Ischemic events, common in many diseases, result from decreased blood flow and impaired delivery of oxygen and glucose to tissues of the body. While much is known about the cellular transcriptional response to ischemia, much less is known about the posttranscriptional response to oxygen and glucose deprivation. The goal of this project was to investigate one such posttranscriptional response, the regulation of mRNA stability. To that end, we have identified several novel ischemia-related mRNAs that are synergistically stabilized by oxygen and glucose deprivation including VEGF, MYC, MDM2, and CYR61. This increase in mRNA half-life requires the synergistic effects of both low oxygen (1%) as well as low glucose ( 1 g/L) conditions. Oxygen or glucose deprivation alone fails to initiate the response, as exposure to either high glucose (4 g/L) or normoxic conditions inhibits the response. Furthermore, in response to hypoxia/hypoglycemia, the identified mRNAs are released from the RNA binding protein KHSRP which likely contributes to their stabilization

Development of the US3D Code for Advanced Compressible and Reacting Flow Simulations

Aerothermodynamics and hypersonic flows involve complex multi-disciplinary physics, including finite-rate gas-phase kinetics, finite-rate internal energy relaxation, gas-surface interactions with finite-rate oxidation and sublimation, transition to turbulence, large-scale unsteadiness, shock-boundary layer interactions, fluid-structure interactions, and thermal protection system ablation and thermal response. Many of the flows have a large range of length and time scales, requiring large computational grids, implicit time integration, and large solution run times. The University of Minnesota NASA US3D code was designed for the simulation of these complex, highly-coupled flows. It has many of the features of the well-established DPLR code, but uses unstructured grids and has many advanced numerical capabilities and physical models for multi-physics problems. The main capabilities of the code are described, the physical modeling approaches are discussed, the different types of numerical flux functions and time integration approaches are outlined, and the parallelization strategy is overviewed. Comparisons between US3D and the NASA DPLR code are presented, and several advanced simulations are presented to illustrate some of novel features of the code

Reflections on the Evolution of Smart Polymers

© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Since Staudinger\u27s recognition that polymers were long chain molecules with covalent bonds between repeating units, the field has evolved tremendously. In addition to their many structural roles, polymers have been developed to exhibit “smart” stimuli-responsive behavior. This article will describe the evolution of selected classes of smart polymers including those responsive to changes in pH, temperature, light, and mechanical stimuli, as well as self-immolative polymers and their application in drug delivery, sensors, and actuators. It will also highlight key advancements in polymer chemistry that enabled rapid progress over the past ∼20 years. Whether the key achievements were predictable will be discussed, and the extent to which polymer science remains an independent science versus a service tool will be addressed. Finally, some possibilities for the evolution of the field over the next 20–30 years will be described

Evolution of predator dispersal in relation to spatio-temporal prey dynamics : how not to get stuck in the wrong place!

Peer reviewedPublisher PD

Architecture for the photonic integration of an optical atomic clock

Laboratory optical atomic clocks achieve remarkable accuracy (now counted to 18 digits or more), opening possibilities to explore fundamental physics and enable new measurements. However, their size and use of bulk components prevent them from being more widely adopted in applications that require precision timing. By leveraging silicon-chip photonics for integration and to reduce component size and complexity, we demonstrate a compact optical-clock architecture. Here a semiconductor laser is stabilized to an optical transition in a microfabricated rubidium vapor cell, and a pair of interlocked Kerr-microresonator frequency combs provide fully coherent optical division of the clock laser to generate an electronic 22 GHz clock signal with a fractional frequency instability of one part in 10^(13). These results demonstrate key concepts of how to use silicon-chip devices in future portable and ultraprecise optical clocks