Investigation of the Reaction Path from UO2 to UF6 using Density-functional Theory

A detailed investigation of the reaction mechanism for UO2 reacting with F2 to form UF6 is performed by using density functional theory (DFT). We divide the whole reaction chain into four main steps, UO2+F2→UO2F2, UO2F2+F2→UO2F4, UO2F4→UF4+O2and UF4+F2→UF6. Contrary to what has been mostly expected that F2 molecule should directly replace two O atoms in UO2 molecule, two F2atoms actually combine with UO2 successively in the first two steps. The third step is relatively complex and one F atom in UO2F4 molecule plays a key role of carrying an O atomclose to the other O atom. In last step, F-F bond in F2 molecule fractures and two F atoms are bonding with U atom in UF4 molecule successively. Spin-flip appears in two elementary reactions owing to the existence of heavy atom U.

Review and Assessment of the Effect of Hydrogen Gas Pressure on the Embrittlement of Steels in Gaseous Hydrogen Environment

Hydrogen gas pressure is an important test parameter when considering materials for high-pressure hydrogen applications. A large set of data on the effect of hydrogen gas pressure on mechanical properties in gaseous hydrogen experiments was reviewed. The data were analyzed by converting pressures into fugacities (f) and by fitting the data using an f|n| power law. For 95% of the data sets, |n| was smaller than 0.37, which was discussed in the context of (i) rate-limiting steps in the hydrogen reaction chain and (ii) statistical aspects. This analysis might contribute to defining the appropriate test fugacities (pressures) to qualify materials for gaseous hydrogen applications.

Deriving the Fluctuation Theorem for Information-Transmission Systems Using a Cyclic Chain-Reaction Sequence

Chemical chain-reactions are pathways that can transmit information, as demonstrated by signal-transduction reactions in cell biology. In this study, we defined entropy as the logarithm of the concentration ratio of chemical species and considered the channel capacity for information transmission by maximizing the entropy. We hypothesized that the reaction chain has an orientation in which the reaction time for the reverse reaction is sufficiently long. According to this model, the logarithm of the forward and reverse transitional probability ratio was found to indicate the entropy-time average per unit reaction time, corresponding to the fluctuation theorem for thermodynamics regarding entropy production rate. This conclusion illuminates the process of signal transduction in cells and other biochemical systems and may provide insights into the relation between thermodynamic and information entropy.

Exploring the Risk Factors of Infrastructure PPP Projects for Sustainable Delivery: A Social Network Perspective

Due to the relatively long period and large capital flow of public-private partnership (PPP) projects, PPP participants are faced with a complex risk situation impeding the sustainable project delivery. In recent years, risk management of PPP projects has received increasing attention. In this paper, twenty risk factors associated with infrastructure PPP projects were identified by literature review and in-depth case studies. Relationship data for these twenty typical risk factors were obtained through structured interviews. Based on the obtained data, the risk relationship network within infrastructure PPP projects was identified, and the network structure characteristics were analyzed, including individual node attributes and the influence and cohesion of subgroups. The results indicate that key risk factor nodes can form a reaction chain via bridge nodes that can trigger a risk domino effect within PPP projects. Specifically, the key risk factors of PPP projects are divided into two categories, the first of which include risk factors that have powerful and independent influence, such as delay in government approval, government credit, and imperfect legal and regulatory systems. The second category includes risk factors that are highly vulnerable and easily influenced, such as completion risks, insufficient revenue in the market, and fee change. A key risk factor reaction chain is one in which legal change leads to a decline in government credit rating, triggering a contract risk. Twelve bridge nodes were identified that play an important intermediary role in the network, e.g., legal change, public objection, and financing risk. This paper extends the application of social network analysis in PPP projects management research and identifies the key risk factors and crucial factors influencing chain reactions in PPP projects. The results provide a more in-depth understanding of sustainable PPP project management for government agencies and private enterprises.

Bacillus sp. As a Decomposition Agent in The Maintenance of Brachionus rotundiformis Which Uses Raw Fish As a Source of Nutrition

The research was conducted at the Laboratory of Marine Molecular Biology and Pharmacy, Faculty of Fisheries and Marine Sciences, Sam Ratulangi University. This research aims to isolate and analyze the morphology and molecular types of bacteria associated in rotifer’s culture media that use fisheries waste.The research was begin by culturing bacteria in rotifer maintenance media using Nutrient Broth media. After bacterial isolates were obtained, morphological characterization and DNA extraction was carried out. extraction was done using DNeasy Blood and Tissue Kit (Qiagen). After DNA was obtained, DNA was amplified through the Polymerase Reaction Chain (PCR) machine using a 16S RNA primer, followed by the separation of PCR products through electrophoresis and detection through UV Transluminator. The target PCR product was determined by comparing the 100 bp ladder DNA, with a yield of around 1400 bp, which was measured using ladder DNA available in the laboratory. The DNA that was successfully amplified was sent to be sequenced to determine the species of each microbe obtained.Based on the results of the research conducted, obtained Bacillus sp. bacteria associated with rotifer maintenance media.Keywords: Bacteria, Culture Media, DNA Extraction, PCR, Sequencing ABSTRAKPenelitian ini dilakukan di Laboratorium Biologi Molekuler dan Farmasetika Laut, Fakultas Perikanan dan Ilmu Kelautan, Universitas Sam Ratulangi. Penelitian ini bertujuan untuk mengisolasi dan menganalisis morfologi dan molekuler jenis-jenis bakteri yang berasosiasi dalam media pemeliharaan rotifer yang menggunakan limbah perikanan.Penelitian dilakukan dengan cara mengkultur bakteri yang ada pada media pemeliharaan rotifer menggunakan media Nutrient Broth. Setelah isolat bakteri didapatkan, dilakukan karakterisasi morfologi dan dilakukan ekstraksi DNA. ekstraksi dilakukan menggunakan DNeasy Blood and Tissue Kit (Qiagen). Setelah DNA didapatkan, DNA diamplifikasi melalui mesin Polymerase Reaction Chain (PCR) menggunakan primer 16S RNA, diikuti dengan pemisahan produk PCR melalui electrophorisis dan deteksi melalui UV Transluminator. Produk PCR target ditentukan dengan membandingkan ladder DNA 100 bp, dengan hasil sekitar 1400 bp, yang diukur menggunakan ladder DNA yang tersedia di laboratorium. DNA yang berhasil diamplifikasi, dikirim untuk dilakukan sekuensing untuk mengetahui spesies dari setiap mikroba yang didapatkan. Berdasarkan hasil penelitian yang dilakukan, diperoleh bakteri Bacillus sp. yang berasosiasi pada media pemeliharaan rotifer. Kata Kunci: Bakteri, Media Pemeliharaan, Ekstraksi DNA, PCR, Sekuensing

Formation of interstellar methanol ice prior to the heavy CO freeze-out stage

Context. The formation of methanol (CH3OH) on icy grain mantles during the star formation cycle is mainly associated with the CO freeze-out stage. Yet there are reasons to believe that CH3OH also can form at an earlier period of interstellar ice evolution in CO-poor and H2O-rich ices. Aims. This work focuses on CH3OH formation in a H2O-rich interstellar ice environment following the OH-mediated H-abstraction in the reaction, CH4 + OH. Experimental conditions are systematically varied to constrain the CH3OH formation yield at astronomically relevant temperatures. Methods. CH4, O2, and hydrogen atoms are co–deposited in an ultrahigh vacuum chamber at 10–20 K. OH radicals are generated by the H + O2 surface reaction. Temperature programmed desorption – quadrupole mass spectrometry (TPD–QMS) is used to characterize CH3OH formation, and is complemented with reflection absorption infrared spectroscopy (RAIRS) for CH3OH characterization and quantitation. Results. CH3OH formation is shown to be possible by the sequential surface reaction chain, CH4 + OH → CH3 + H2O and CH3 + OH → CH3OH at 10–20 K. This reaction is enhanced by tunneling, as noted in a recent theoretical investigation Lamberts et al. (2017, A&A, 599, A132). The CH3OH formation yield via the CH4 + OH route versus the CO + H route is approximately 20 times smaller for the laboratory settings studied. The astronomical relevance of the new formation channel investigated here is discussed.

Brief communication: Electron pair donors and Earth's energy generation

This Brief Communication presents a series of model calculations for the electron pair donor densities required for tresino thermal energy generation in the Earth. The crucial density of electron donors is determined from the ratio of He3 and He4 after many years starting from initial densities of the donor pairs. In addition, a new proposal is introduced that connects Cooper pair formations to the deuteron tresino nuclear reaction chain (the chain that determines the He3 / He4 ratio). Furthermore, it is proposed that magnetotelluric (MT) observations may be connected to Cooper pair formation either with or without substantial heating.