Cyanophycin accumulated under nitrogen-fluctuating and high-nitrogen conditions facilitates the persistent dominance and blooms of Raphidiopsis raciborskii in tropical waters

Nutrient storage is considered a critical strategy for algal species to adapt to a fluctuating nutrient supply. Luxury phosphorus (P) uptake into storage of polyphosphate extends the duration of cyanobacterial dominance and their blooms under P deficiency. However, it is unclear whether nitrogen (N) storage in the form of cyanophycin supports persistent cyanobacterial dominance or blooms in the tropics where N deficiency commonly occurs in summer. In this study, we examined genes for cyanophycin synthesis and degradation in Raphidiopsis raciborskii, a widespread and dominant cyanobacterium in tropical waters; and detected the cyanophycin accumulation under fluctuating N concentrations and its ecological role in the population dynamics of the species. The genes for cyanophycin synthesis (cphA) and degradation (cphB) were highly conserved in 21 out of 23 Raphidiopsis strains. This suggested that the synthesis and degradation of cyanophycin are evolutionarily conserved to support the proliferation of R. raciborskii in N-fluctuating and/or deficient conditions. Isotope 15N-NaNO3 labeling experiments showed that R. raciborskii QDH7 always commenced to synthesize and accumulate cyanophycin under fluctuating N conditions, regardless of whether exogenous N was deficient. When the NO3−-N concentration exceeded 1.2 mg L−1, R. raciborskii synthesized cyanophycin primarily through uptake of 15N-NaNO3. However, when the NO3−-N concentration was below 1.0 mg L−1, cyanophycin-based N was derived from unlabeled N2, as evidenced by increased dinitrogenase activity. Cells grown under NO3−-N 1.2 mg L−1. Our field investigation in a large tropical reservoir underscored the association between cyanophycin content and the population dynamics of R. raciborskii. The cyanophycin content was high in N-sufficient (NO3−-N > 0.45 mg L−1) periods, and decreased in N-deficient summer. In summer, R. raciborskii sustained a relatively high biomass and produced few heterocysts (< 1%). These findings indicated that cyanophycin-released N, rather than fixed N, supported persistent R. raciborskii blooms in N-deficient seasons. Our study suggests that the highly adaptive strategy in a N2-fixing cyanobacterial species makes mitigating its bloom more difficult than previously assumed

Partial Wave Analysis of J/ψ→γ(K+K−π+π−)J/\psi \to \gamma (K^+K^-\pi^+\pi^-)

BES data on $J/\psi \to \gamma (K^+K^-\pi^+\pi^-)$ are presented. The $K^*\bar K^*$ contribution peaks strongly near threshold. It is fitted with a broad $0^{-+}$ resonance with mass $M = 1800 \pm 100$ MeV, width $\Gamma = 500 \pm 200$ MeV. A broad $2^{++}$ resonance peaking at 2020 MeV is also required with width $\sim 500$ MeV. There is further evidence for a $2^{-+}$ component peaking at 2.55 GeV. The non-$K^*\bar K^*$ contribution is close to phase space; it peaks at 2.6 GeV and is very different from $K^{*}\bar{K^{*}}$.Comment: 15 pages, 6 figures, 1 table, Submitted to PL

X-Ray Polarization of Solar Flares Measured with Rhessi

The degree of linear polarization in solar flares has not yet been precisely determined despite multiple attempts to measure it with different missions. The high energy range in particular has very rarely been explored, due to its greater instrumental difficulties. We approached the subject using the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI) satellite to study 6 X-class and 1 M-class flares in the energy range between 100 keV and 350 keV. Using RHESSI as a polarimeter requires the application of strict cuts to the event list in order to extract those photons that are Compton scattered between two detectors. Our measurements show polarization values between 2% and 54%, with errors ranging from 10% to 26% in 1 sigma level. In view of the large uncertainties in both the magnitude and direction of the polarization vector, the results can only reject source models with extreme properties.Comment: 26 pages, 11 figures, accepted for publication by Solar Physic

Measurement of the mass difference between top quark and antiquark in pp collisions at root s=8 TeV

Peer reviewe

Search for the associated production of the Higgs boson with a top-quark pair

A search for the standard model Higgs boson produced in association with a top-quark pair t t ¯ H (tt¯H) is presented, using data samples corresponding to integrated luminosities of up to 5.1 fb &#8722;1 and 19.7 fb &#8722;1 collected in pp collisions at center-of-mass energies of 7 TeV and 8 TeV respectively. The search is based on the following signatures of the Higgs boson decay: H &#8594; hadrons, H &#8594; photons, and H &#8594; leptons. The results are characterized by an observed t t ¯ H tt¯H signal strength relative to the standard model cross section, &#956; = &#963;/&#963; SM ,under the assumption that the Higgs boson decays as expected in the standard model. The best fit value is &#956; = 2.8 ± 1.0 for a Higgs boson mass of 125.6 GeV

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe