Food Quantity and Quality Interactions at Phytoplankton–Zooplankton Interface: Chemical and Reproductive Responses in a Calanoid Copepod

Marine food webs form the major component of the biological pump and play a central role in the global carbon (C) cycle. Understanding the response of particular processes in marine food webs to changing environments is a prerequisite to predict changes in ecological functioning in the future ocean. Here, we experimentally assessed the effects of nitrogen:phosphorus (N:P) supply ratios (the molar ratios 10:1, 24:1, and 63:1) on elemental and biochemical quality of marine phytoplankton Rhodomonas sp., and the interactions between food quantity and quality on stoichiometric C:N:P, fatty acids (FAs) and reproductions in copepods Acartia tonsa. Overall, the stoichiometry of A. tonsa was to some extent homeostatic in response to the changing algal C:N and C:P ratios, with significant changes in C:N ratios of A. tonsa observed, especially under higher food quantities. The relative gross growth efficiencies (GGEs) for C and N (and P) were analyzed, revealing that copepods may achieve homeostasis by lowering the GGE for C while increasing it for the limiting nutrient. Egg production rates in A. tonsa were lowest on nutrient deficient diets under low food quantities. Reduced egg production rates may be attributed to the lowered GGEs for C and reduced transfer efficiency of essential FAs between phytoplankton and copepods, indicating interactive-essential effects of elements and FAs on copepod production. Our results highlight that nutrient deficiency in the environments may reduce energy transfer efficiency at the base of food webs by altering phytoplankton chemical composition, which can interact with food quantity and have implications on food web dynamics in the changing ocean

Chemical composition of phytoplankton as the determinant of food quality

The trophic transfer across phytoplankton-zooplankton interface is crucially important in aquatic food webs. The factors regulating the trophic transfer efficiency have been widely studied. There is an increasing awareness of food quality in terms of chemical composition of phytoplankton as the major control of the phytoplankton-zooplankton interaction via bottom-up processes. Nutrient availability has broad effects on chemical composition of phytoplankton. Other factors, e.g., dilution rate in continuous and semicontinuous cultures, can interact with nutrient supply and affect phytoplankton food quality, hence affecting the performance of zooplankton. This study aimed to investigate the effects of nitrogen (N):phosphorus (P) supply ratios and growth rates (dilution rates) on elemental and biochemical composition of marine phytoplankton, as well as the effects of food quantity and quality on the trophic transfer of essential chemicals and the performance of copepods. For this purpose, laboratory experiments were firstly conducted with three species of marine phytoplankton in semicontinuous cultures to test the interactive effect of five N:P supply ratios and four growth rates. Subsequent copepod experiments were performed with one species of marine copepods (Acartia tonsa) feeding on one phytoplankton species (Rhodomonas sp.), where the factors of food quantity and quality were crossed. The results in this thesis highlight the importance of simultaneous consideration of elemental and biochemical food quality for understanding the trophic transfer of energy and matter in food webs. Evaluating responses of this mutual regulation to multiple ambient factors is a necessary step towards the phytoplankton-zooplankton relationship in more realistic scenarios that will allow in the future the prediction of zooplankton’s performances in changing aquatic environments

Design and Experiment of Frequency Offset Estimation and Compensation in High-speed Underwater Acoustic Communication

In underwater acoustic (UWA) communication, Doppler effect is particularly severe due to the slow velocity of sound and the complex variant UWA channel environment. Carrier frequency offset (CFO) can result in extension and compression of the received signal in time domain and has a direct effect on the performance of decoding. In this paper, we propose a new scheme of CFO estimation and compensation for a high speed UWA communication system. There are three steps including coarse CFO estimation, fine CFO estimation and linear interpolation, which are taken to estimate and compensate the CFO. The scheme can eliminate the phenomenon of ambiguous phase and tolerate quick random variation of the CFO in UWA channel. A UWA communication experiment was carried out in December 2012 in the Indian Ocean, off Rottnest Island, Western Australia. With the proposed algorithm in this paper, the UWA system can achieve an average of 1.95% uncoded BER with QPSK modulation at the 1km range and 5.57% with BPSK at the 10km range

Optimal Source and Relay Design for Multiuser MIMO AF Relay Communication Systems with Direct Links and Imperfect Channel Information

In this paper, we propose statistically robust design for multiuser multiple-input multiple-output (MIMO) relay systems with direct source-destination links and imperfect channel state information (CSI). The minimum mean-squared error (MMSE) of the signal waveform estimation at the destination node is adopted as the design criterion. We develop two iterative methods to solve the nonconvex joint source, relay, and receiver optimization problem. Simulation results demonstrate the improved robustness of the proposed algorithms against CSI errors

The Cell Regulation Mechanism of Neurovascular Unit

Ischemic cerebrovascular disease is one of the three deadly diseases. It is characterised by high mortality and high morbidity. Because of no effective treatments of recombinant tissue plasminogen activator (rt-PA) and neuroprotectant, there are more and more research focus on neurovascular unit (NVU), which is composed of brain microvascular endothelial cells (BMECs), neuron, astrocyte(AS) and so on. Cell-cell signaling and coupling between these different compartments form the basis for normal function and repair of brain injury. In this mini-review, we will describe the relationship of CMECs, neuron and AS

catena-Poly[1-[(2-fluoro­benzyl­idene)amino]­quinolinium [plumbate(II)-tri-μ-iodido]]

The title complex, {(C16H12FN2)[PbI3]}n, consists of 1-[(2-fluoro­benzyl­idene)amino]­quinolinium cations and a polymeric PbI3 − anion formed by face-sharing PbI6 octa­hedra. These octa­hedra form straight and regular infinite chains along the b axis. In the asymmetric unit, one cation and one anionic [PbI3]− fragment are observed in general positions. Polymeric chains are produced by the glide plane perpendicular to the a axis

Global transcription profiling reveals differential responses to chronic nitrogen stress and putative nitrogen regulatory components in Arabidopsis

<p>Abstract</p> <p>Background</p> <p>A large quantity of nitrogen (N) fertilizer is used for crop production to achieve high yields at a significant economic and environmental cost. Efforts have been directed to understanding the molecular basis of plant responses to N and identifying N-responsive genes in order to manipulate their expression, thus enabling plants to use N more efficiently. No studies have yet delineated these responses at the transcriptional level when plants are grown under chronic N stress and the understanding of regulatory elements involved in N response is very limited.</p> <p>Results</p> <p>To further our understanding of the response of plants to varying N levels, a growth system was developed where N was the growth-limiting factor. An Arabidopsis whole genome microarray was used to evaluate global gene expression under different N conditions. Differentially expressed genes under mild or severe chronic N stress were identified. Mild N stress triggered only a small set of genes significantly different at the transcriptional level, which are largely involved in various stress responses. Plant responses were much more pronounced under severe N stress, involving a large number of genes in many different biological processes. Differentially expressed genes were also identified in response to short- and long-term N availability increases. Putative N regulatory elements were determined along with several previously known motifs involved in the responses to N and carbon availability as well as plant stress.</p> <p>Conclusion</p> <p>Differentially expressed genes identified provide additional insights into the coordination of the complex N responses of plants and the components of the N response mechanism. Putative N regulatory elements were identified to reveal possible new components of the regulatory network for plant N responses. A better understanding of the complex regulatory network for plant N responses will help lead to strategies to improve N use efficiency.</p

1-Methyl-3-n-tetra­decyl­imidazolium bromide monohydrate

In the title ionic liquid salt hydrate, C18H35N2 +·Br−·H2O, the side chain in the cation has an extended conformation. The crystal structure is stabilized primarily by O—H⋯Br hydrogen bonds. C—H⋯O and C—H⋯Br inter­actions are also present

Energy dependent chemical potentials of light hadrons and quarks based on transverse momentum spectra and yield ratios of negative to positive particles

We describe the transverse momentum (or mass) spectra of $\pi^\pm$, $K^\pm$, $p$, and $\bar{p}$ produced in central gold-gold (Au-Au), central lead-lead (Pb-Pb), and inelastic proton-proton ($pp$) collisions at different collision energies range from the AGS to LHC by using a two-component (in most cases) Erlang distribution in the framework of multi-source thermal model. The fitting results are consistent with the experimental data and the energy-dependent chemical potentials of light hadrons ($\pi$, $K$, and $p$) and quarks ($u$, $d$, and $s$) in central Au-Au, central Pb-Pb, and inelastic $pp$ collisions from the yield ratios of negative to positive particles obtained from the normalization constants are then extracted. The study shows that most types of energy-dependent chemical potentials decrease with increase of collision energy over a range from the AGS to LHC. The curves of all types of energy-dependent chemical potentials, obtained from the linear fits of yield ratios vs energy, have inflection points at the same energy of 3.526 GeV, which is regarded as the critical energy of phase transition from a hadron liquid-like state to a quark gas-like state in the collision system and indicates that the hadronic interactions play an important role in this period. At the RHIC and LHC, all types of chemical potentials become small and tend to zero at very high energy, which confirms that the collision system possibly changes completely from the hadron-dominant liquid-like state to the quark-dominant gas-like state and the partonic interactions possibly play a dominant role at the LHC

(1E)-6-Meth­oxy-3,4-dihydro­naphthalen-1(2H)-one oxime

In the crystal structure of the title compound, C11H13NO2, the mol­ecules are paired into centrosymmetric dimers via inter­molecular O—H⋯N hydrogen bonds