Effect of Computerized Maintenance Management System on a Cement Production Plant

This study evaluated effect of Computerized Maintenance Management System (CMMS) on a cement production plant. The materials used included a Computer and Networking system and maintenance software. Preliminary study of plant assets was carried out to identify critical plant assets and key performance indicators such as Plant Reliability Factor (RF), Number of Stoppage for Incidents (NSI) and Production Losses (PL) in 2013. The CMMS software implementation in 2015 used the data obtained. The result obtained from this implementation showed that the RF (%) for Limestone Crusher (LC), Cement Mill (CM) and Kiln were 46, 76, 86; 51, 79, 88; 59, 88, 92 in 2013, 2014 and 2015 respectively. The corresponding NSI for the three plants were 824, 472, 82; 788, 462, 56; 431, 420, 46 in 2013, 2014 and 2015 respectively. The Production Losses for the whole plant were $22.54m,$21.587m and $19.365m in 2013, 2014 and 2015 respectively

Satisfaction and perceived impact of virtual learning during COVID-19 lockdown: A case study of an online nursing research conference

Aim This study aimed to assess nurses' satisfaction and perceptions of the impact of virtual learning. Design A descriptive cross-sectional survey. Method 236 nurses attending an online conference from several parts of Nigeria participated in the study. Analysed data were summarized and presented in tables and graphs, while linear regression was used to measure the associations. Results Most of the respondents perceived the programme as highly impactful. All three domains: learner-content interaction (p?=?0.020), learner?instructor interaction (p?=?0.000) and learner?learner interaction (p?=?0.000), were found to be statistically significantly associated with the perceived impact of the programme, and thus statistically significant predictors of the effects of online learning (p?=?0.02), (F?=?5.471). Conclusively, the Interaction of learners with learning content, lecturers and other learners was seen as determinants of an effective and impactful online education. It is recommended that nursing training institutions embrace online learning either as the leading platform or as an adjunct to a face-to-face method

Addition of Amines to a Carbonyl Ligand: Syntheses, Characterization, and Reactivities of Iridium(III) Porphyrin Carbamoyl Complexes

Treatment of (carbonyl)chloro(meso-tetra-p-tolylporphyrinato)iridium(III), (TTP)Ir(CO)Cl (1), with excess primary amines at 23 °C in the presence of Na2CO3 produces the trans-amine-coordinated iridium carbamoyl complexes (TTP)Ir(NH2R)[C(O)NHR] (R = Bn (2a), n-Bu (2b), i-Pr (2c), t-Bu (2d)) with isolated yields up to 94%. The trans-amine ligand is labile and can be replaced with quinuclidine (1-azabicyclo[2.2.2]octane, ABCO), 1-methylimidazole (1-MeIm), triethyl phosphite (P(OEt)3), and dimethylphenylphosphine (PMe2Ph) at 23 °C to afford the hexacoordinated carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (for R = Bn: L = ABCO (3a), 1-MeIm (4a), P(OEt)3 (5a), PMe2Ph (6a)). On the basis of ligand displacement reactions and equilibrium studies, ligand binding strengths to the iridium metal center were found to decrease in the order PMe2Ph \u3e P(OEt)3 \u3e 1-MeIm \u3e ABCO \u3e BnNH2 ≫ Et3N, PCy3. The carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (L = RNH2 (2a,b), 1-MeIm (4a)) undergo protonolysis with HBF4 to give the cationic carbonyl complexes [(TTP)Ir(NH2R)(CO)]BF4 (7a,b) and [(TTP)Ir(1-MeIm)(CO)]BF4 (8), respectively. In contrast, the carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (L = P(OEt)3 (5a), PMe2Ph (6a,c)) reacted with HBF4 to afford the complexes [(TTP)Ir(PMe2Ph)]BF4 (9) and [(TTP)IrP(OEt)3]BF4 (10), respectively. The carbamoyl complexes (TTP)Ir(L)[C(O)NHR] (L = RNH2 (2a–d), 1-MeIm (4a), P(OEt)3 (5b), PMe2Ph (6c)) reacted with methyl iodide to give the iodo complexes (TTP)Ir(L)I (L = RNH2 (11a–d), 1-MeIm (12), P(OEt)3(13), PMe2Ph (14)). Reactions of the complexes [(TTP)Ir(PMe2Ph)]BF4 (9) and [(TTP)IrP(OEt)3]BF4 (10) with [Bu4N]I, benzylamine (BnNH2), and PMe2Ph afforded (TTP)Ir(PMe2Ph)I (14), (TTP)Ir[P(OEt)3]I (13), [(TTP)Ir(PMe2Ph)(NH2Bn)]BF4 (16), and trans-[(TTP)Ir(PMe2Ph)2]BF4 (17), respectively. Metrical details for the molecular structures of 4a and17 are reported

Scope and Mechanism of Iridium Porphyrin-Catalyzed S–H Insertion Reactions between Thiols and Diazo Esters

The insertion of carbenes derived from ethyl diazoacetate (EDA), methyl diazoacetate (MDA), methyl phenyldiazoacetate (MPDA), and methyl (<i>p</i>-tolyl)­diazoacetate (MTDA) into the S–H bonds of aromatic and aliphatic thiols was catalyzed by (5,10,15,20-tetratolylporphyrinato)­methyliridium­(III), Ir­(TTP)­CH₃, at ambient temperatures. Yields of the resulting thioether products were as high as 97% for aromatic thiols, with catalyst loadings as low as 0.07 mol %. Thiol binding to Ir­(TTP)­CH₃ was measured at 23 °C by titration studies, providing equilibrium constants, <i>K</i>_b, ranging from 4.25 × 10² to 1.69 × 10³ and increasing in the order <i>p</i>-nitrobenzenethiol < <i>p</i>-chlorobenzenethiol < benzenethiol < <i>p</i>-methylbenzenethiol < <i>p</i>-methoxybenzenethiol < benzyl mercaptan. Hammett plots were generated from the relative rates of S–H insertion, using different <i>para</i>-substituted benzenethiols in substrate competition experiments. In the presence of MDA and MTDA, the Hammett plots had slopes of −0.12 ± 0.01 and −0.78 ± 0.11, respectively. The Hammett data and kinetic studies are consistent with a mechanism that involves a rate-limiting nucleophilic attack of thiols on an iridium-carbene species, where the major species present in the reaction solution is an inactive, hexacoordinate Ir-thiol complex

Reactivity Comparison of Primary Aromatic Amines and Thiols in E–H Insertion Reactions with Diazoacetates Catalyzed by Iridium(III) Tetratolylporphyrin

A detailed kinetic study is described for the insertion of carbenes from methyl diazoacetate into the N–H bond of aniline, using Ir­(TTP)­CH₃ (TTP = tetratolylporphyrinato) as a catalyst. Aniline strongly coordinates to the Ir center with a binding constant of <i>K</i> = (2.5 ± 0.5) × 10⁴ at 296 K, forming an inactive hexacoordinate complex, (aniline)­Ir­(TTP)­CH₃. The rate of N–H insertion is first order in both diazo ester and catalyst. When the true amount of active, five-coordinate Ir­(TTP)­CH₃ is taken into account, the insertion rate is found to be independent of the aniline concentration. This indicates that the rate-limiting step in the catalytic cycle occurs prior to the nucleophilic attack of aniline on an Ir carbene complex to generate a coordinated ylide. Thus, with N–H insertion catalyzed by Ir­(TTP)­CH₃, aniline is both a strong ligand and a potent nucleophile. This is in contrast to the analogous catalytic insertion of carbenes into S–H bonds. <i>p</i>-Toluenethiol is a more weakly binding ligand toward Ir­(TTP)­CH₃ (<i>K</i> = 680 ± 20 at 296 K). Moreover, the rate of S–H insertion is first order in diazo reagent, catalyst, and thiol concentrations. In this case, the slow step is nucleophilic attack of the thiol on the Ir carbene complex to form a coordinated sulfonium ylide intermediate. In comparison to aniline, <i>p</i>-toluenethiol is a weaker ligand and a poorer nucleophile. The consequence of these differences is that the rate of aniline attack on the carbene intermediate is much faster than the rate of formation of the intermediate carbene complex; whereas the rate of nucleophilic addition of the thiol is slower that the rate of carbene complex formation