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The catalyzed electrochemical oxidation of ammonia to nitrogen (AOR) is an important fuel-cell half-reaction that underpins a future nitrogen-based energy economy. Our laboratory has reported spontaneous chemical and electrochemical oxidation of ammonia to dinitrogen via reaction of ammonia with the metal-metal bonded diruthenium complex Ru 2 (chp) 4 OTf (chp - = 2-chloro-6-hydroxypyridinate, TfO - = trifluoromethanesulfonate). This complex facilitates electrocatalytic ammonia oxidation at mild applied potentials of -255 mV vs ferrocene, which is the [Ru 2 (chp) 4 (NH 3 )] 0/+ redox potential. We now report a comprehensive computational investigation of possible mechanisms for this reaction and electronic structure analysis of key intermediates therein. We extend this analysis to proposed second-generation electrocatalysts bearing structurally similar fhp and hmp (2-fluoro-6-hydroxypyridinate and 2-hydroxy-6-methylpyridinate, respectively) equatorial ligands, and we further expand this study from Ru 2 to analogous Os 2 cores. Predicted M 2 4+/5+ redox potentials, which we expect to correlate with experimental AOR overpotential, depend strongly on the identity of the metal center, and to a lesser degree on the nature of the equatorial supporting ligand. Os 2 complexes are easier to oxidize than analogous Ru 2 complexes by ∼640 mV, on average. In contrast to mono-Ru catalysts, which oxidize ammonia via a rate-limiting activation of the strong N-H bond, we find lowest-energy reaction pathways for Ru 2 and Os 2 complexes that involve direct N-N bond formation onto electrophilic intermediates having terminal amido, imido, or nitrido groups. While transition state energies for Os 2 complexes are high, those for Ru 2 complexes are moderate and notably lower than those for mono-Ru complexes. We attribute these lower barriers to enhanced electrophilicity of the Ru 2 intermediates, which is a consequence of their metal-metal bonded structure. Os 2 intermediates are found to be, surprisingly, less electrophilic, and we suggest that Os 2 complexes may require access to oxidation states higher than Os 2 5+ in order to perform AOR at reasonable reaction rates.

Nitrogen heterocycles are a class of organic compounds with extremely versatile functionality. Imidines, HN[C(NH)R] 2 , are a rare class of heterocycles related to imides, HN[C(O)R] 2 , in which the O atoms of the carbonyl groups are replaced by N-H groups. The useful synthesis of the imidine compounds succinimidine and glutarimidine, as well as their partially hydrolyzed imino-imide congeners, was first described in the mid-1950s, though structural characterization is presented for the first time in this article. In the solid state, these structures are different from the proposed imidine form: succinimidine crystallizes as an imino-amine, 2-imino-3,4-dihydro-2H-pyrrol-5-amine, C 4 H 7 N 2 (1), glutarimidine as 6-imino-3,4,5,6-tetrahydropyridin-2-amine methanol monosolvate, C 5 H 9 N 3 ·CH 3 OH (2), and the corresponding hydrolyzed imino-imide compounds as amino-amides 5-amino-3,4-dihydro-2H-pyrrol-2-one, C 4 H 6 N 2 O (3), and 6-amino-4,5-dihydropyridin-2(3H)-one, C 5 H 8 N 2 O (4). Imidine 1 was also determined as the hydrochloride salt solvate 5-amino-3,4-dihydro-2H-pyrrol-2-iminium chloride-2-imino-3,4-dihydro-2H-pyrrol-5-amine-water (1/1/1), C 4 H 8 N 3 + ·Cl - ·C 4 H 7 N 3 ·H 2 O (1·HCl). As such, 1 and 2 show alternating short and long C-N bonds across the molecule, revealing distinct imino (C=NH) and amine (C-NH 2 ) groups throughout the C-N backbone. These structures provide definitive evidence for the predominant imino-amine tautomer in the solid state, which serves to enrich the previously proposed imidine-focused structures that have appeared in organic chemistry textbooks since the discovery of this class of compounds in 1883., (open access.)

Background The petroclival ligament (PL) forms the roof of Dorello's canal (DC). In humans, partial and complete ossification of this ligament have been reported. When completely ossified, DC is transformed into a bony foramen for the abducens nerve and accompanying vascular structures. As this osteological finding might have an impact on skull base surgery, this anatomical study was performed. Methodology Using 100 adult human skulls, the presence of an ossified PL was noted and classified. The diameter of the resultant bony foramen and laterality were documented. Additionally, PL was evaluated histologically in 10 heads. Results Overall, 8% of the sides were found to have partial or complete ossification of the PL. Partial ossification (type I) was noted on 3% of the sides. Completely ossified PL was identified on 5% of the sides. Some ossified ligaments (2.5%) were seen as an ossified bridge (type II), and others (2.5%) were converted into small foramina (type III). Three skulls (3%) were found to have a completely ossified ligament bilaterally. The mean diameter of the underlying DC was 0.8 mm. Partially ossified ligaments were statistically more likely to be on the right sides, and the diameter of the underlying DC was statistically smaller in type III. Histologically, the PL was found to have bone within it on three skull sides. Conclusions An ossified ligament can be found on imaging of the skull base. Moreover, during surgical approaches to the petroclival region and, specifically, DC, skull base surgeons should be cognizant of this anatomical variation., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2023, Ekanem et al.)

Background: Diffusion tensor imaging (DTI) is a magnetic resonance-based imaging technique that can provide important information about the underlying structure and integrity of the white matter in the brain. Tractography, a DTI postprocessing technique, can provide a detailed model of individual white matter fiber tracts. Knowledge of these tracts may be beneficial in the surgical planning and execution for neurosurgical patients. Case Report: We review the basic principles behind DTI and present an illustrative case in which DTI was used to delineate the relationship of eloquent white matter tracts to a cavernous malformation in a patient undergoing resection. Conclusion: The use of DTI during preoperative planning allows the neurosurgeon to understand if a lesion is disrupting, infiltrating, or altering the course of local white matter tracts. With the combined use of DTI and intraoperative neuronavigation, the neurosurgeon can better identify and avoid white matter tracts, not only in the local area of resection but also during approach to the lesion, thereby reducing the risk of damage to vital cortical pathways and subsequent functional impairment., (©2020 by the author(s); Creative Commons Attribution License (CC BY).)

Copper(I) iodide complexes are well known for displaying a diverse array of structural features even when only small changes in ligand design are made. This structural diversity is well displayed by five copper(I) iodide compounds reported here with closely related piperidine-2,6-di-thione (SNS), isoindoline-1,3-di-thione (SNS6), and 6-thioxopiperidin-2-one (SNO) ligands: di-μ-iodido-bis-[(aceto-nitrile-κ N )(6-sulfanylidenepiperidin-2-one-κ S )copper(I)], [Cu 2 I 2 (CH 3 CN) 2 (C 5 H 7 NOS) 2 ] ( I ), bis-(aceto-nitrile-κ N )tetra-μ 3 -iodido-bis-(6-sulfanylidenepiperidin-2-one-κ S )- tetra-hedro -tetra-copper(I), [Cu 4 I 4 (CH 3 CN) 4 (C 5 H 7 NOS) 4 ] ( II ), catena -poly[[(μ-6-sulfanylidenepiperidin-2-one-κ 2 O : S )copper(I)]-μ 3 -iodido], [CuI(C 5 H 7 NOS)] n ( III ), poly[[(piperidine-2,6-di-thione-κ S )copper(I)]-μ 3 -iodido], [CuI(C 5 H 7 NS 2 )] n ( IV ), and poly[[(μ-isoindoline-1,3-di-thione-κ 2 S : S )copper(I)]-μ 3 -iodido], [CuI(C 8 H 5 NS 2 )] n ( V ). Compounds I and II crystallize as discrete dimeric and tetra-meric complexes, whereas III , IV , and V crystallize as polymeric two-dimensional sheets. To the best of our knowledge, compound III is the first instance of an extended hexa-gonal [Cu 3 I 3 ] structure that is not supported by bridging ligands. Structures I , II , and IV display weak to moderately strong Cu⋯Cu cuprophilic inter-actions [Cu⋯Cu inter-nuclear distances range between 2.5803 (10) and 2.8485 (14) Å]. All structures except III display weak hydrogen-bonding inter-actions between the N-H of the ligand and the μ 2 and μ 3 -I - atoms. Structure III contains classical N-H⋯O inter-actions between the SNO ligands that connect the mol-ecules in a three-dimensional framework. Complex V features π-π stacking inter-actions between the aryl rings of the SNS6 ligands within the same polymeric sheet. In structure IV , there were three partially occupied solvent mol-ecules of di-chloro-methane and one partially occupied mol-ecule of aceto-nitrile present in the asymmetric unit. The SQUEEZE routine [Spek (2015 ▸). Acta Cryst . C 71 , 9-18] was used to correct the diffraction data for diffuse scattering effects and to identify the solvent mol-ecules. The given chemical formula and other crystal data do not take into account the solvent mol-ecules., (© Wheaton et al. 2020.)

Background: Despite the widespread use of intraoperative monitoring (IOM) in many types of spinal surgeries, an absence of data comparing monitored a nd unmonitored postoperative outcomes places IOM's efficacy into question. A lack of consensus among surgeons about when to use monitoring also raises concerns about its overuse in routine and low-risk procedures., Methods: We performed a retrospective database review of 112 patients undergoing a 1- or 2-level minimally invasive surgery transforaminal lumbar interbody fusion (MIS-TLIF). Our analysis focused on patient demographics, use of IOM, length of surgery, hospital length of stay, the perioperative complication of pedicle screw malposition, and average hospital cost., Results: For the 73 patients who underwent MIS-TLIF with intraoperative neuromonitoring, their hospital length of stay (P=0.8) and need for pedicle screw revisions (P=0.93) were not statistically significant compared to the 39 patients who underwent MIS-TLIF procedures without IOM. The incidence of reoperation was 5.48% and 5.13%, and average length of stay was 3.25 days and 3.13 days, respectively. However, the cost of surgery and the length of surgery were significantly higher in the monitored group compared to the nonmonitored group (P=0.008 and P=0.009, respectively)., Conclusion: IOM is widely used in spine surgery, but our retrospective review shows that its use does not necessarily decrease the incidence of malpositioning of pedicle screws. In fact, no statistical difference was detected in the incidence of screw malposition in the 2 groups of patients. On the other hand, IOM adds cost and increases the length of surgery. Because the use of IOM did not make a difference in the incidence of pedicle screw malpositioning and because of the comparative cost analysis for both groups of patients, we believe that the use of IOM for MIS-TLIF provides no added benefit.

Organocatalyzed enantioselective allylation of 2-iodocyclohexenone followed by methylation and oxy-Cope rearrangement delivered enantiomerically enriched 2-methyl 3-allyl cyclohexanone, which engaged in acid-catalyzed Robinson annulation to give the bicyclic enone. Subsequent elaboration of the pendant allyl group into an α-diazo β-keto ester set the stage for Rh-mediated cyclization to deliver the tricyclic A-B-C core of the Veratrum alkaloids.

A series of 1-hydroxy-1H-benzo[d]imidazol-2(3H)-ones were synthesized and evaluated for their ability to inhibit human and porcine forms of D-amino acid oxidase (DAAO). Inhibitory potency is largely dependent on the size and position of substituents on the benzene ring with IC(50) values of the compounds ranging from 70 nM to greater than 100 µM. Structure-activity relationships of this new class of DAAO inhibitors will be presented in detail along with comparisons to previously published SAR data from other classes of DAAO inhibitors. Some of these compounds were given to mice orally together with D-serine to assess their effects on plasma D-serine pharmacokinetics.

The title compound, [Ni(C(45)H(28)N(4)O)], crystallizes in the space group I ̅42d and resides on a crystallographic fourfold rotoinversion axis with only a quarter of the complex in the asymmetric unit. The complex displays positional disorder as the one aldehyde group on the ligand can be located at four different positions. It was necessary to model this as compositional disorder to obtain a correct model and refinement. The practical approach to the refinement is explained.

Enantioselective organocatalytic 1,2-allylation of a cyclic enone followed by anionic oxy-Cope rearrangement delivered the ketone as a mixture of diastereomers. This appears to be a general method for the net enantioselective conjugate allylation of cyclic enones., (© 2011 American Chemical Society)

A strategy for the facile alpha-amination of carboxylic acid menthyl esters is described. The resulting diastereomers, readily separable, can be individually carried on to each enantiomer of the FMOC alpha-amino acid. A variety of unnatural side chains were compatible with this approach. The menthyl ester was easily removed from the FMOC alpha-amino acid without racemization.

The conversion of 2-butyn-1,4-diol to (Z)-2,4-diiodobut-2-en-1-ol proceeded efficiently using in situ generated trimethylsilyl iodide. Coupling with Grignard reagents and other nucleophiles delivered (2Z)-2-iodo allylic alcohols. The geometry of the products was established by nOe.

The hexavalent state, considered to be the highest oxidation level accessible for iron, has previously been found only in the tetrahedral ferrate dianion, FeO4(2-). We report the photochemical synthesis of another Fe(VI) compound, an octahedrally coordinated dication bearing a terminal nitrido ligand. Mössbauer and x-ray absorption spectra, supported by density functional theory, are consistent with the octahedral structure having an FeN triple bond of 1.57 angstroms and a singlet d2(xy) ground electronic configuration. The compound is stable at 77 kelvin and yields a high-spin Fe(III) species upon warming.

The impact of a stroke, head injury, spinal cord injury, or other disabling condition can be especially devastating for individuals without health insurance. Fortunately, a comprehensive system has evolved to address the needs of the indigent for medical rehabilitation services in Louisiana. The purpose of this paper is to familiarize readers with this complex system, and thereby to assist practicing physicians and other health care providers in better serving this large and medically needy population. First, state and federal medical assistance programs which cover rehabilitation services are reviewed; next, services available through Louisiana Rehabilitation Services are discussed; and finally, services available through the Handicapped Children's Services Program and various voluntary organizations are described.

We use a stepwise multiple regression procedure to correlate geographic patterns in the distribution of live-bearing reptilian species with patterns in climatic variables, in both Australia and North America. Previous authors have interpreted reptilian live-bearing as an evolutionary adaptation to cold climates. Our results indicate that environmental temperature and irradiance measures are no more highly correlated with the percent live-bearing species than are measures of precipitation, evaporation and humidity. We conclude that, except in very cold environments in North America, environmental temperatures seem to play little role in the relative success of live-bearing versus egg-laying reptilian reproductive strategies. It appears from previous work that reptilian live-bearing evolves mainly, or exclusively, because of the advantage it confers in enabling successful reproduction in cold climates. The present study suggests that the subsequent radiation of live-bearing reptilian species may be due to entirely different selective forces.

This paper combines published and original data on sexual size dimorphism, reproductive behavior, and habitat types in turtles. Our major finding is that observed patterns of sexual size dimorphism correlate with habitat type and male mating strategy. (1) In most terrestrial species, males engage in combat with each other. Males typically grow larger than females. (2) In semiaquatic and "bottom-walking" aquatic species, male combat is less common, but males often forcibly inseminate females. As in terrestrial species, males are usually larger than females. (3) In truly aquatic species, male combat and forcible insemination are rare. Instead, males utilize elaborate precoital displays, and female choice is highly important. Males are usually smaller than females.We interpret these correlations between sexual behavior and size dimorphism in terms of sexual selection theory: males are larger than females when large male size evolves as an adaptation to increase success in male combat, or to enable forcible insemination of females. In contrast, males are usually smaller than females where small size in males evolves to increase mobility (and hence, ability to locate females), or because selection for increased fecundity may result in increased female size. In turtle species with male combat or forcible insemination, the degree of male size superiority increases with mean species body size.

1. When guinea-pig cerebral-cortex slices were incubated with [U-(14)C]glutamate as substrate, the specific radioactivities of the citric acid-cycle intermediates were lower than that of the aspartate isolated from the same vessels. 2. Aspartate was significantly labelled when [5-(14)C]glutamate was used as substrate and the aspartate contained almost no label when [1-(14)C]glutamate was present as substrate. 3. When specifically labelled glutamate was used as substrate, the label was found in the isolated aspartate in the position that would be predicted by citric acid-cycle mechanisms. 4. The results are consistent with the theory of ;compartmentation' of amino acid metabolism.