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The bonding in NiS is found to be quite similar to that in NiO, having an ionic contribution arising from the donation of the Ni 4s electron to the S atom and a covalent component arising from bonds between the Ni 3d and the S 3p. The one-electron d bonds are found to be of equal strength for NiO and NiS, but the two-electron d bonds are weaker for NiS.
The understudied nonribosomal-peptide-synthetase-independent siderophore (NIS) synthetase family has been increasingly associated with virulence in bacterial species due to its key role in the synthesis of hydroxamate and carboxylate "stealth" siderophores. We have identified a model family member, DesD, from Streptomyces coelicolor , to structurally characterize using a combination of a wild-type and a Arg306Gln variant in apo , cofactor product AMP-bound, and cofactor reactant ATP-bound complexes. The kinetics in the family has been limited by solubility and reporter assays, so we have developed a label-free kinetics assay utilizing a single-injection isothermal-titration-calorimetry-based method. We report second-order rate constants that are 50 times higher than the previous estimations for DesD. Our Arg306Gln DesD variant was also tested under identical buffer and substrate conditions, and its undetectable activity was confirmed. These are the first reported structures for DesD, and they describe the critical cofactor coordination. This is also the first label-free assay to unambiguously determine the kinetics for an NIS synthetase.
Local transport and magnetometry measurements on nanoscale flakes of NiS 2 have led to the discovery of large magnetoresistance and exchange-bias effects connected to surface magnetic textures in NiS 2 .
NiS is Millerite structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. Ni2+ is bonded to five equivalent S2- atoms to form a mixture of distorted corner and edge-sharing NiS5 trigonal bipyramids. There are a spread of Ni–S bond distances ranging from 2.25–2.36 Å. S2- is bonded in a 5-coordinate geometry to five equivalent Ni2+ atoms.
NiS is Molybdenum Carbide MAX Phase-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ni2+ is bonded to six equivalent S2- atoms to form a mixture of edge, face, and corner-sharing NiS6 octahedra. The corner-sharing octahedral tilt angles are 50°. All Ni–S bond lengths are 2.37 Å. S2- is bonded in a 6-coordinate geometry to six equivalent Ni2+ atoms.
Understanding characteristic energy scales is a fundamentally important issue in the study of strongly correlated systems. In multiband systems, an energy scale is affected not only by the effective Coulomb interaction but also by the Hund’s coupling. Direct observation of such energy scale has been elusive so far in spite of extensive studies. Here, we report the observation of a kink structure in the low energy dispersion of NiS 2- x Se x and its characteristic evolution with x , by using angle resolved photoemission spectroscopy. Dynamical mean field theory calculation combined with density functional theory confirms that this kink originates from Hund’s coupling. We find that the abrupt deviation from the Fermi liquid behavior in the electron self-energy results in the kink feature at low energy scale and that the kink is directly related to the coherence-incoherence crossover temperature scale. Our results mark the direct observation of the evolution of the characteristic temperature scale via kink features in the spectral function, which is the hallmark of Hund’s physics in the multiorbital system.
The Jefferson Lab (Jlab) accelerator controls network has transitioned to a new authentication and network service interface. The new system uses the Redhat Identity Manager (IdM) as a single integrating front end to the Lightweight Directory Access Protocol (LDAP) and a replacement for NIS and the Kerberos authentication service. This system allows for integration of access and authentication across Unix and Windows environments and across different Jlab computing environments, including across firewalls. The decision making process, conversion steps, issues and solutions will be discussed.
The LANL Neutron Imaging team is preparing for NIS upgrades and novel capabilities with the advent of consistently higher yields at NIF. Novel scintillators, solid-state detectors, multiplexed imaging detectors, upgraded data acquisition systems, and camera testing are all areas in need of experimental study to further develop imaging capabilities and dynamic range at NIF.
NiS2 and NiS have been characterized as high energy density rechargeable positive electrodes for moderate-temperature Na batteries of the configuration, Na(1)/beta double prime-Al2O3/NaAlCl4(1), NiSx. The batteries operate in the temperature range 170 - 190 C. Positive electrode reactions during discharge/charge cycles have been characterized. Excellent rechargeability of the batteries has been demonstrated by extended cell cycling. A Na/NiS2 cell, operating at 190 C, exceeded 600 deep discharge/charge cycles with practically no capacity deterioration. The feasibility of secondary Na/NiSx batteries with specific energies equal to or greater than 50 Wh/lb and cycle lifes exceeding 1000 deep discharge/charge cycles has been demonstrated.
KNi2S2 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. K1+ is bonded in a body-centered cubic geometry to eight equivalent S2- atoms. All K–S bond lengths are 3.31 Å. Ni+1.50+ is bonded to four equivalent S2- atoms to form a mixture of edge and corner-sharing NiS4 tetrahedra. All Ni–S bond lengths are 2.26 Å. S2- is bonded in a 4-coordinate geometry to four equivalent K1+ and four equivalent Ni+1.50+ atoms.
TlNi2S2 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ni+1.50+ is bonded to four equivalent S2- atoms to form a mixture of edge and corner-sharing NiS4 tetrahedra. All Ni–S bond lengths are 2.25 Å. Tl1+ is bonded in a body-centered cubic geometry to eight equivalent S2- atoms. All Tl–S bond lengths are 3.33 Å. S2- is bonded in a 4-coordinate geometry to four equivalent Ni+1.50+ and four equivalent Tl1+ atoms.
The Neutron Imaging team is readying for the NIS2 polar LOS development and future improvements to data quality on all LOS given consistently higher yields at NIF. Next-gen nano guide scintillators for NIS2 and CMOS cameras to replace outdated CCDs will be studied. Digital image plates will be tested for better data quality on passive imaging systems. The transition into the ignition regime is expected to show a significant signature in the ablator areal density. In the marginal ignition regime, a decrease of 12C-rhoR (ablator areal density) is expected but once the burn propagation produces a shock and compresses the ablator the trend reverses. GCD with the PD-PMT can resolve this effect in the ablator areal density by a temporal shift in the carbon signal. To give quantitative results a calibration of the detector for the Hohlraum/TMP signal is needed. Shots using Al, Si, and Au pucks will yield the needed information to move forward with this project.
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The current Geostationary Operational Environmental Satellites (GOES) are eqipped to make cloud top measurements only. In contrast, a millimeter-wave radar allows 3-D measurements of precipitation associated with hurricanes and other convective systems. It also provides important inputs for numerical weather prediction models for improving the accuracy of weather nowcasting and forecasting.
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Crystalline nickel sulfide (NiS) induced a spleen cell proliferation that resembles a mixed lymphocyte reaction (MLR). It depended on cell-cell interaction, induced high levels of interleukin-1 (IL-1) and interleukin-2 (IL-2) and the responding cell subpopulation was composed of CD4+ T lymphocytes. Furthermore, the proliferation was inhibited in a dose-dependent manner by magnesium. Crystalline NiS also increased significantly the spleen cell proliferative response to concanavalin A (Con A) and lipopolysaccharide (LPS) with magnesium potentiating the combined effects of crystalline NiS and mitogens. Interestingly, crystalline NiS did not show any effect on the induction of IL-2 by Con A. The results described herein suggest that crystalline NiS can potentiate both antigenic (MLR) and mitogenic (Con A and LPS) proliferative responses in vitro. Crystalline NiS appears to potentiate these responses by acting in the form of ionic nickel on several intracellular targets for which magnesium ions have different noncompetitive interactions. The effects of magnesium on the potentiating action of crystalline NiS are different depending upon the type of primary stimulatory signal for proliferation (mitogenic or antigenic).
Under NASA's Earth Science Technology Program, a novel mission concept has been developed for detailed monitoring of hurricanes, cyclones, and severe storms from a geostationary orbit: "NEXRAD in Space" (NIS). By operating in the Geostationary Earth Orbit (GEO), NIS would enable rapid-update sampling (less than or equal to 1 hour cadence) of three dimenional fields of 35 GHz (Ka-band) radar reflectivity factor (Z) and line-of-sight Doppler velocity (VD) profiles, at mesoscale horizontal resolutions (approx. 10 km) over a circular Earth region of approximately 5300 km in diameter (equivalent to much of an oceanic basin, such as the Atlantic). NIS GEO-radar concept was chosen as one of only four potential post-2020 missions for the Weather Focus area in the 2007-2016 NASA Science Mission Directorate (SMD) Science Plan. The results of the first project aiming at developing the NIS concept highlighted the enormous potential of such mission, and the technological challenges presented by it. In essence, it is because of its rapid-cadence capability that NIS science planning is focusing on hurricane monitoring and prediction. Hurricanes, or generically tropical cyclones (TCs), have always been among the most devastating natural phenomena. This has been painfully reiterated in recent years with a number of powerful TCs landfalling in North America and elsewhere. In April 2007, the first NIS Science Workshop was convened at the University of Miami to galvanize the scientific community's interest in NIS's measurement capabilities for improved TC monitoring and prediction. The general consensus of the workshop was that a GEO Doppler radar would provide a major breakthrough in regards to the observation of TCs, and, when combined with cloud-resolving numerical weather prediction (NWP) models. This paper presents brief summaries of the instrument concept, the current technology status, the anticipated impacts on hurricane monitoring and model prediction, and the future science and technology roadmap.
Nickel sulfides (NiS x ) show promise for a range of energy and other applications, but their (in)stability under processing and operating conditions is scarcely studied. Herein, we have developed a new NiS x atomic layer deposition process using an easily synthesized NiCl 2 (TMPDA) precursor (TMPDA = N,N,N′,N′-tetramethyl-1,3-propanediamine) with H 2 S. Thin films deposited at 165–225 °C consist mostly of the β-NiS phase and display low resistivity (∼40–120 μΩ cm), high purity (<3 at% impurities), and a rough morphology. The thermal stability of the NiS x thin films is studied using high-temperature X-ray diffraction, revealing that structural and compositional changes occur in reducing, inert, and oxidizing atmospheres at approximately 300–400 °C. Under electrochemical water splitting conditions, the films are unstable in acid due to dissolution, especially at oxidizing potentials. In an alkaline electrolyte, we do not observe Ni dissolution, but β-NiS transforms to Ni 3 S 2 under HER conditions, possibly supplemented with Ni and/or Ni(OH) 2 species. Under alkaline OER, all sulfur is lost and NiOOH is formed. In addition to offering an attractive, scalable route to the synthesis of NiS x thin films, our work highlights the importance of thermal and electrochemical (in)stability of sulfides as a crucial step for understanding and engineering materials for energy and other applications.