Spectroscopic EPR and IR studies of monomeric and dimeric species formed upon adsorption of nitric oxide on Ce0.75Zr0.25O2 and their reactivity with dioxygen

The interaction of nitric oxide with Ce_0.75Zr_0.25O₂ solid solution were investigated by means of EPR and IR spectroscopies. The influence of adsorption parameters such as adsorption temperature and pressure, presence of the O₂ co-reactant on the nature and relative surface abundance of the resultant mono- and dimeric NO species was elucidated. The thermal stability of the surface nitrosyl complexes and their reactivity toward dioxygen were also examined.     

Transfer efficiency for airless painting systems

Spray transfer efficiency (TE) is defined as the mass fraction of sprayed paint which is deposited on the intended target, the remainder of the sprayed paint becomes undesirable overspray. The relationship between TE and gun supply pressure (or paint mass flow rate), gun-to-target distance, gun traverse speed, the angle of the spray gun relative to the target (gun-to-target angle), plus spray cone angle is reported herein for a typical fan spray system. Experimental results indicate that spray momentum rate (SMR) and droplet size dictate the TE for the various combinations of parameters considered here. The key finding is that TE correlates with SMR and spray mean drop size (Sauter mean diameter, or D₃₂) via an expression of the form TE=a+b SMR − c (SMR)²+d D₃₂, where a, b, c, and d are coefficients, determined by fitting the experimental data, and SMR is estimated via SMR=m²/ρA, where the paint mass flow rate m, the paint density is ρ, and the gun exit orifice effective tip cross sectional area is A. This expression accounts for physical phenomena that govern sprayed droplet deposition characteristics, such as entrainment, bounce-back, and drop size. Experimental results also show that, for the range of parameters studied, gun traverse speed has no effect on TE, but increasing the angle of the spray gun relative to the target (gun-to-target angle), increasing the spray cone angle, or increasing the gun-to-target distance will decrease TE.     

EPR Study of CO Adsorption onto CoZSM-5 Zeolite: Evidence for Spin Crossover upon Coordination and |z2, 2A1〉 Ground State

Adsorption of CO onto dehydrated cobalt-exchanged ZSM-5 zeolite was studied by CW-EPR techniques. It is shown that the reversible formation of a low spin carbonyl ¹{Co(CO) _n }⁷ adduct upon addition of carbon monoxide at p _CO>50–60 Torr involves significant change in the spin state of Co²⁺ from S=3/2 to 1/2. The spin Hamiltonian parameters of the adduct g _x =2.222, g _y =2.184, g _z =2.011, |A _x |=3.8 mT, |A _y |=3.2 mT, |A _z |=7.9 mT were determined by a computer simulation and further discussed in terms of the possible ground state and molecular structure. It is shown that the ¹{Co(CO) _n }⁷ cage complex exhibits a C_2v symmetry with |z ²,²A₁ ground state.     

Electron transfer processes at the surface of MoOx/SiO2 catalysts

EPR studies using naturally abundant and ⁹⁵Mo-enriched molybdenum have shown that reduced MoO _x /SiO₂catalysts with different dispersion of molybdenum provide a unique opportunity for molecular-level investigations of surface phenomena involved in the bonding to and activation of small molecules by oxide surfaces. Different types of electron transfer (ET) processes accompanying the activation of O₂and N₂O as well as the reactivity of O^-and CH₂OH transients with coadsorbed CH₃OH and O₂, respectively, have been identified. They include nondissociative and dissociative ET, surface intramolecular ET, and electroprotic transformation (ET coupled with proton transfer). In the case of methanol dehydrogenation it was found that if the reaction occurs on the MoO _x cluster centers, ET exhibits a complementary character, in contrast to isolated Mo centers where noncomplementary ET accompanied by migration of the hydroxymethyl intermediate is observed.     

Protease Inhibition—An Established Strategy to Combat Infectious Diseases

Therapeutic agents with novel mechanisms of action are urgently needed to counter the emergence of drug-resistant infections. Several decades of research into proteases of disease agents have revealed enzymes well suited for target-based drug development. Among them are the three recently validated proteolytic targets: proteasomes of the malarial parasite Plasmodium falciparum, aspartyl proteases of P. falciparum (plasmepsins) and the Sars-CoV-2 viral proteases. Despite some unfulfilled expectations over previous decades, the three reviewed targets clearly demonstrate that selective protease inhibitors provide effective therapeutic solutions for the two most impacting infectious diseases nowadays—malaria and COVID-19.     

Crystal structure and magnetic behavior of novel R2PdIn8 (R = Pr, Nd, and Sm) compounds

A new series of R₂PdIn₈ intermetallics, where R = Pr, Nd, and Sm, was prepared by arc-melting the constituents under argon atmosphere and studied by means of X-ray diffraction and magnetic measurements. The compounds crystallize with a tetragonal structure of the Ho₂CoGa₈ type (space group P4/mmm). At very low temperatures, they order antiferromagnetically, and the Nd-based indide presumably exhibits an additional magnetic phase transition in the ordered region.     

An outbreak of needlestick injuries in hospital employees due to needles piercing infectious waste containers

OBJECTIVES: To investigate the cause of an outbreak of needlestick injuries (NSIs) in hospital employees. SETTING: A 700-bed university hospital. DESIGN: Outbreak investigation, laboratory evaluation of a medical waste disposal device, cost analysis. METHODS: Employee health department records were reviewed of workers suffering sticks from needles piercing fiberboard-contaminated material containers (CMCs). A laboratory evaluation of needle-puncture resistance properties of the CMCs was performed using a testing apparatus. The cost of a hospital waste disposal program using fiberboard CMCs was compared with the cost of a program using rigid plastic (polypropylene) boxes. RESULTS: During 40 months of surveillance in 1986 and from 1989 to 1991, only one NSI had occurred from a needle piercing a CMC. During 9 months in 1993, 13 NSIs occurred due to needles piercing CMCs (P < .001). No clinical illness resulted from the NSIs. The outbreak was halted by a temporary change to plastic (polypropylene) boxes for sharps disposal ($4.92 to $23.33/cu ft) until receipt of a box with a newly designed solid fiberboard liner ($1.25/cu ft). CMC liners used during the epidemic had a mean needle puncture resistance of 527 g, as compared with 660 g for liners used before the outbreak (P < .001). The new solid fiberboard liner has a mean puncture resistance of 1,765 g. A program of waste disposal using fiberboard CMCs was found to cost approximately one-seventh the cost of a program using plastic boxes for disposal of infectious waste. CONCLUSION: A program for infectious waste disposal using fiberboard CMCs can be safe and cost-effective if appropriate standards for puncture resistance are met.     

EPR studies on NO interaction with MoOx/t-ZrO2 catalysts obtained by slurry deposition

Variable temperature adsorption of nitric oxide on MoO₃ supported on tetragonal zirconia (MoO_x/t-ZrO₂), obtained by slurry deposition, was investigated by EPR spectroscopy. The influence of molybdenum loading and co-adsorbed oxygen on the adsorption process of NO was elucidated. Particular attention was devoted to redox character of NO activation. Another important aspect concerned is the nature of surface nitrosyl complexes of molybdenum and their thermal stability. The role of oxygen in NO transformation over catalyst surface was also discussed.     

Spatially resolved characteristics of pharmaceutical sprays

Spatially resolved drop size, velocity, and volume flux data for five different spray coating guns were described in this study. Such spatially resolved measurements show how sprays respond to changes in operating conditions and gun design in ways that less complete measurements can not provide. Data for instance, allow us to recognize the unique drop size distribution of one of the sprays tested, which ultimately was an important factor in determining the dual roles of the shaping air flows: depending on drop size, viscosity, and the magnitude of the shaping air velocity, the shaping air can either pinch or induce secondary atomization to the sprays. When the former outweighs the latter, a dumbbell‐shaped spray develops; a more uniform spray results when the opposite occurs. Volume flux data from the different sprays also suggest that a more robust and consistent tablet coating process can likely be designed by utilizing multiple overlapping round sprays. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Drop impact and agglomeration under static powder bed conditions

The influence of impact conditions (reported in terms of Weber and Reynolds numbers) on nucleus formation was studied for single drops striking a static glass bead bed. Results from high speed images showed that the nucleation rate is not influenced by liquid physical properties (density, surface tension, viscosity) for drops that spread significantly (30 < We < 233). Results also showed that nucleus size is determined by how much liquid penetrates into the bed during drop spreading, so does depend on surface tension and liquid density. A corresponding analytical model, derived from first principles, predicts nucleus size to with 1.5% using only liquid physical and powder bed properties, plus the experimentally measured drop spreading behavior. © 2011 American Institute of Chemical Engineers AIChE J, 2012