Pusan National University

About: Pusan National University is a education organization based out in Busan, South Korea. It is known for research contribution in the topics: Catalysis & Population. The organization has 24124 authors who have published 45054 publications receiving 819356 citations. The organization is also known as: Busan National University & Pusan University.

Mechanism of insoluble phosphate solubilization by Pseudomonas fluorescens RAF15 isolated from ginseng rhizosphere and its plant growth-promoting activities.

Abstract: Aims: To investigate the mechanism of insoluble phosphate (P) solubilization and plant growth-promoting activity by Pseudomonas fluorescens RAF15. Methods and Results: We investigated the ability of Ps. fluorescens RAF15 to solubilize insoluble P via two possible mechanisms: proton excretion by ammonium assimilation and organic acid production. There were no clear differences in pH and P solubilization between glucose-ammonium and glucose-nitrate media. P solubilization was significantly promoted with glucose compared to fructose. Regardless of nitrogen sources used, Ps. fluorescens RAF15 solubilized little insoluble P with fructose. High performance liquid chromatography analysis showed that Ps. fluorescens RAF15 produced mainly gluconic and tartaric acids with small amounts of 2-ketogluconic, formic and acetic acids. During the culture, the pH was reduced with increase in gluconic acid concentration and was inversely correlated with soluble P concentration. Ps. fluorescens RAF1 showed the properties related to plant growth promotion: pectinase, protease, lipase, siderophore, hydrogen cyanide, and indoleacetic acid. Conclusion: This study indicated that the P solubility was directly correlated with the organic acids produced. Significance and Impact of the Study: Pseudomonas fluorescens RAF15 possessed different traits related to plant growth promotion. Therefore, Ps. fluorescens RAF15 could be a potential candidate for the development of biofertilizer or biocontrol agent.

Self-assembled free-standing three-dimensional nickel nanoparticle/graphene aerogel for direct ethanol fuel cells

Abstract: In this work, we report a low-cost technique for fabrication of a simple three-dimensional (3D) free-standing nickel nanoparticle/graphene aerogel with a graphene sheet network. The 3D composite architecture was formed through the self-assembly aggregation of graphene accompanied by nickel nanoparticle in situ loading on the graphene sheet during the hydrothermal reduction of graphene oxide and Ni ions. The obtained composite architecture was characterized using X-ray diffraction, Fourier transform infrared, and scanning electron microscopy. The electrocatalytic properties of the as-synthesized Ni/graphene aerogel for ethanol oxidation were investigated using cyclic voltammetry and chronoamperometry. A high peak current density of about 6 mA cm−2 for ethanol oxidation was recorded during ethanol oxidation under the test condition of adding 0.1 M ethanol in 0.1 M NaOH solution. This result revealed excellent electrocatalytic activity for ethanol oxidation, which shows great potential for direct application in ethanol fuel cells. This study provides a guide to preparing well-defined sponge-like three-dimensional metallic/graphene nanoarchitectures for fuel cell applications.

Diffuse Radio Emission from Galaxy Clusters

Abstract: In a growing number of galaxy clusters diffuse extended radio sources have been found. These sources are not directly associated with individual cluster galaxies. The radio emission reveal the presence of cosmic rays and magnetic fields in the intracluster medium (ICM). We classify diffuse cluster radio sources into radio halos, cluster radio shocks (relics), and revived AGN fossil plasma sources. Radio halo sources can be further divided into giant halos, mini-halos, and possible `intermediate' sources. Halos are generally positioned at cluster center and their brightness approximately follows the distribution of the thermal ICM. Cluster radio shocks (relics) are polarized sources mostly found in the cluster's periphery. They trace merger induced shock waves. Revived fossil plasma sources are characterized by their radio steep-spectra and often irregular morphologies. In this review we give an overview of the properties of diffuse cluster radio sources, with an emphasis on recent observational results. We discuss the resulting implications for the underlying physical acceleration processes that operate in the ICM, the role of relativistic fossil plasma, and the properties of ICM shocks and magnetic fields. We also compile an updated list of diffuse cluster radio sources which will be available on-line this http URL. We end this review with a discussion on the detection of diffuse radio emission from the cosmic web.

Dynamics of Baryons from String Theory and Vector Dominance

Abstract: We consider a holographic model of QCD from string theory, a la Sakai and Sugimoto, and study baryons. In this model, mesons are collectively realized as a five-dimensional \$U(N_F)=U(1)\times SU(N_F)$ Yang-Mills field and baryons are classically identified as $SU(N_F)$ solitons with a unit Pontryagin number and $N_c$ electric charges. The soliton is shown to be very small in the large 't Hooft coupling limit, allowing us to introduce an effective field ${\cal B}$. Its coupling to the mesons are dictated by the soliton structure, and consists of a direct magnetic coupling to the $SU(N_F)$ field strength as well as a minimal coupling to the $U(N_F)$ gauge field. Upon the dimensional reduction, this effective action reproduces all interaction terms between nucleons and an infinite tower of mesons in a manner consistent with the large $N_c$ expansion. We further find that all electromagnetic interactions, as inferred from the same effective action via a holographic prescription, are mediated by an infinite tower of vector mesons, rendering the baryon electromagnetic form factors completely vector-dominated as well. We estimate nucleon-meson couplings and also the anomalous magnetic moments, which compare well with nature.

Insights into microalgae mediated biodegradation of diazinon by Chlorella vulgaris: Microalgal tolerance to xenobiotic pollutants and metabolism

Abstract: Diazinon is one of the most widely used organophosphorus insecticides for agricultural activities, and it is highly toxic to mammals and other non-target organisms. The present study demonstrated the effective removal of diazinon from the aqueous phase by a freshwater, green microalga, Chlorella vulgaris . Among the four screened species ( Scenedesmus obliquus , Chlamydomonas mexicana , Chlorella vulgaris and Chlamydomonas pitschmannii ), C. vulgaris showed the highest removal capacity (94%) of diazinon at 20 mg L − 1 . The growth of C. vulgaris was significantly affected above 40 mg L − 1 of diazinon, showing > 30% growth inhibition after 12 days of cultivation. Significant enhancement of the microalgal growth in the exponential growth phase suggested a less/non-toxic nature of the diazinon by-products. Biochemical properties, including carotenoid, chlorophyll a nd antioxidant enzymes of C. vulgaris were influenced by diazinon at relatively high concentrations. The degradation rate constant (k) and the half-life (T 1/2 ) of diazinon (0.5–100 mg L − 1 ) ranged between 0.2304–0.049 d − 1 and 3.01–14.06 d, respectively. Gas chromatography mass spectroscopic (GC–MS) study suggested the formation of a less toxic by-product, 2-isopropyl-6-methyl-4-pyrimidinol (IMP) as a result of microalgal metabolism of diazinon. This study demonstrated that C. vulgaris is highly tolerant of diazinon, which could be voluntarily involved in the removal of traces of diazinon from contaminated wastewater and has potential application in the removal of such artificial toxins using algae.