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Rawal P, Gupta P. Unidentical Twins: Geometrically Similar but Chemically Distinct Metal-free Sites in Boron Oxide for Methane Oxidation to HCHO, CO and CO2. Chemistry 2024:e202401050. [PMID: 38606609 DOI: 10.1002/chem.202401050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Revised: 04/12/2024] [Accepted: 04/12/2024] [Indexed: 04/13/2024]
Abstract
Metal-free boron-based catalysts such as boron oxide (B2O3) and boron nitride (h-BN) are promising catalysts for the methane oxidation to HCHO and CO. The B2O3 catalyst contains various probable boron sites (B1 to B6), which may be responsible for methane oxidation. In this work, we utilized density functional theory to compare two relevant geometrically identical boron sites (B2 and B4) for their reactivities. The two sites are explored in-detail for the conversion of methane to formaldehyde (M2F), carbon monoxide and carbon dioxide. The B4 site activates the methane C-H bond easily as compared to the B2 site. In M2F conversion, the rate-determining step for the B2 site is the co-activation of dioxygen and methane, whereas over the B4 site, formaldehyde formation is the rate-determining step. The computationally-determined RDS for the B4 site coincides well with the reported experiments. It is further revealed that this site also prefers the formation of CO over CO2, which is in-line with the experiments in literature. It is also shown through orbital analysis that methanol formation does not occur during methane oxidation. We employed descriptors such as condensed Fukui functions and global electrophilicity index to chemically distinct these twin sites.
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Affiliation(s)
- Parveen Rawal
- Indian Institute of Technology Roorkee, Chemistry, Roorkee, INDIA
| | - Puneet Gupta
- Indian Institute of Technology Roorkee, Chemistry, Roorkee, 247667, Roorkee, INDIA
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2
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Rawal P, Gupta P. Mapping the Catalytic-Space for the Reactivity of Metal-free Boron Nitride with O 2 for H 2O-Mediated Conversion of Methane to HCHO and CO. Chemistry 2024; 30:e202303371. [PMID: 38221895 DOI: 10.1002/chem.202303371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 12/31/2023] [Accepted: 01/15/2024] [Indexed: 01/16/2024]
Abstract
Transition-metal based catalysts have been widely employed to catalyze partial oxidation of light alkanes. Recently, metal-free hexagonal-boron nitride (h-BN) has emerged as a promising catalyst for the oxidation of CH4 to HCHO and CO; however, the intricate catalytic surface of h-BN at molecular and electronic levels remains inadequately understood. Key questions include how electron-deficient boron atoms in h-BN reduce O2, and whether the partial oxidation of methane over h-BN exhibits similarities to traditional transition-metal catalysts. In our study, we computationally-mapped in-detail the surface catalytic-space of h-BN for methane oxidation. We considered different structures of h-BN and show that these structures contain numerous sites for O2 binding and therefore various routes for methane oxidation are possible. The activation barriers for methane oxidation via various paths varies from ~83 to ~123 kcal mol-1. To comprehend the differences in activation barriers, we employed geometrical, orbital and distortion/interaction analysis (DIA). Orbital analysis reveals that methane activation over h-BN in presence of dioxygen follows a standard hydrogen atom transfer mechanism. It is also shown that water plays an intriguing role in reducing the barrier for HCHO and CO formation by acting as a bridge.
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Affiliation(s)
- Parveen Rawal
- Computational Catalysis Center, Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India
| | - Puneet Gupta
- Computational Catalysis Center, Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India
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Arora S, Rawal P, Gupta P. Orbital Analysis Captures the Existence of a Mixed-Valent Cu III -O-Cu II Active-Site and its Role in Water-Assisted Aliphatic Hydroxylation. Chemistry 2024; 30:e202303722. [PMID: 38168869 DOI: 10.1002/chem.202303722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 12/31/2023] [Accepted: 01/03/2024] [Indexed: 01/05/2024]
Abstract
The Cu-O-Cu core has been proposed as a potential site for methane oxidation in particulate methane monooxygenase. In this work, we used density functional theory (DFT) to design a mixed-valent CuIII -O-CuII species from an experimentally known peroxo-dicopper complex supported by N-donor ligands containing phenolic groups. We found that the transfer of two-protons and two-electrons from phenolic groups to peroxo-dicopper core takes place, which results to the formation of a bis-μ-hydroxo-dicopper core. The bis-μ-hydroxo-dicopper core converts to a mixed-valent CuIII -O-CuII core with the removal of a water molecule. The orbital and spin density analyses unravel the mixed-valent nature of CuIII -O-CuII . We further investigated the reactivity of this mixed-valent core for aliphatic C-H hydroxylation. Our study unveiled that mixed-valent CuIII -O-CuII core follows a hydrogen atom transfer mechanism for C-H activation. An in-situ generated water molecule plays an important role in C-H hydroxylation by acting as a proton transfer bridge between carbon and oxygen. Furthermore, to assess the relevance of a mixed-valent CuIII -O-CuII core, we investigated aliphatic C-H activation by a symmetrical CuII -O-CuII core. DFT results show that the mixed-valent CuIII -O-CuII core is more reactive toward the C-H bond than the symmetrical CuII -O-CuII core.
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Affiliation(s)
- Sumangla Arora
- Computational Catalysis Center, Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand, 247667
| | - Parveen Rawal
- Computational Catalysis Center, Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand, 247667
| | - Puneet Gupta
- Computational Catalysis Center, Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand, 247667
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Mahato S, Rawal P, Devadkar AK, Joshi M, Roy Choudhury A, Biswas B, Gupta P, Panda TK. Hydroboration and reductive amination of ketones and aldehydes with HBpin by a bench stable Pd(II)-catalyst. Org Biomol Chem 2022; 20:1103-1111. [PMID: 35029621 DOI: 10.1039/d1ob02339j] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A palladium(II) complex [(κ4-{1,2-C6H4(NCH-C6H4O)2}Pd] (1) supported by a dianionic salen ligand [1,2-C6H4(NCH-C6H4O)2]2- (L) was synthesised and used as a molecular pre-catalyst in the hydroboration of aldehydes and ketones. The molecular structure of Pd(II) complex 1 was established by single-crystal X-ray diffraction analysis. Complex 1 was tested as a competent pre-catalyst in the hydroboration of aldehydes and ketones with pinacolborane (HBpin) to produce corresponding boronate esters in excellent yields at ambient temperature under solvent-free conditions. Further, the complex 1 proved to be a competent catalyst in the reductive amination of aldehydes with HBpin and primary amines under mild and solvent-free conditions to afford a high yield (up to 97%) of corresponding secondary amines. Both protocols provided high conversion, superior selectivity and broad substrate scope, from electron-withdrawing to electron-donating and heterocyclic substitutions. A computational study based on density functional theory (DFT) revealed a reaction mechanism for Pd-catalysed hydroboration of carbonyl species in the presence of HBpin. The protocols also uncovered the dual role of HBpin in achieving the hydroboration reaction.
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Affiliation(s)
- Shreya Mahato
- Department of Chemistry, University of North Bengal, Darjeeling-734013, India.
| | - Parveen Rawal
- Computational Catalysis Center, Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee-247667, Uttarakhand, India.
| | - Ajitrao Kisan Devadkar
- Department of Chemistry, Indian Institute of Technology Hyderabad, Kandi, Sangareddy 502284, Telangana, India.
| | - Mayank Joshi
- Department of Chemical Sciences, IISER Mohali, Punjab, India
| | | | - Bhaskar Biswas
- Department of Chemistry, University of North Bengal, Darjeeling-734013, India.
| | - Puneet Gupta
- Computational Catalysis Center, Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee-247667, Uttarakhand, India.
| | - Tarun K Panda
- Department of Chemistry, Indian Institute of Technology Hyderabad, Kandi, Sangareddy 502284, Telangana, India.
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Narvariya R, Gupta S, Jain A, Rawal P, Gupta P, Panda TK. One‐Pot Reductive Amination of Aromatic Aldehydes in [Et
3
NH][HSO
4
] using Sodium Borohydride and A Mechanistic Investigation using Computational Method. ChemistrySelect 2022. [DOI: 10.1002/slct.202200052] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Rajrani Narvariya
- Department of Chemistry Indian Institute of Technology Hyderabad 502284 Sangareddy Telangana India
| | - Shivangi Gupta
- Computational Catalysis Center Department of Chemistry Indian Institute of Technology Roorkee Roorkee 247 667 Uttarakhand India
| | - Archana Jain
- Department of Physics & Chemistry Mahatma Gandhi Institute of Technology (MGIT) 500075 Hyderabad India
| | - Parveen Rawal
- Computational Catalysis Center Department of Chemistry Indian Institute of Technology Roorkee Roorkee 247 667 Uttarakhand India
| | - Puneet Gupta
- Computational Catalysis Center Department of Chemistry Indian Institute of Technology Roorkee Roorkee 247 667 Uttarakhand India
| | - Tarun K. Panda
- Department of Chemistry Indian Institute of Technology Hyderabad 502284 Sangareddy Telangana India
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Panda TK, Kumar R, Rawal P, Banerjee I, Nayek HP, Gupta P, Panda TK. Catalytic Hydroboration and Reductive Amination of Carbonyl Compounds by HBpin using a Zinc Promoter. Chem Asian J 2022; 17:e202200013. [PMID: 35020275 DOI: 10.1002/asia.202200013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Indexed: 11/10/2022]
Abstract
In this paper, the chemoselective hydroboration of aldehydes and ketones, catalyzed by Zinc(II) complexes [ k 2 -(PyCH=NR)ZnX 2 ] [R = CPh 3 , X = Cl ( 1 ) and R = Dipp (2,6-diisoropylphenyl) and X = I ( 2 )], in the presence of pinacolborane (HBpin) in ambient temperature and solvent-free conditions, which produced corresponding boronate esters in high yield, is reported. Zinc metal complexes 1 and 2 were derived in 80-90% yield from the reaction of iminopyridine [PyCH=NR] with anhydrous zinc dichloride in dichloromethane at room temperature. The solid-state structures of both zinc complexes were confirmed using X-ray crystallography. Zinc complex 1 was also used as a competent pre-catalyst in the reductive amination of carbonyl compounds with HBpin under mild and solvent-free conditions to afford a high yield (up to 97%) of the corresponding secondary amines. The wider substrate scope of both reactions was explored. Catalytic protocols using zinc as a pre-catalyst demonstrated an atom-economic and green method with diverse substrates bearing excellent functional group tolerance. Computational studies established a plausible mechanism for catalytic hydroboration.
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Affiliation(s)
- Tarun K Panda
- IITH: Indian Institute of Technology Hyderabad, Chemistry, Kandi, Sangareddy, 502285, Hyderabad, INDIA
| | - Ravi Kumar
- IITH: Indian Institute of Technology Hyderabad, Chemistry, Kandi, Sangareddy, 502285, Hyderabad, INDIA
| | - Parveen Rawal
- IIT Roorkee: Indian Institute of Technology Roorkee, Chemistry, Roorkee, 247667, Roorkee, INDIA
| | - Indrani Banerjee
- IITH: Indian Institute of Technology Hyderabad, Chemistry, Kandi, Sangareddy, 502285, Hyderabad, INDIA
| | - Hari Pada Nayek
- IIT (ISM): Indian Institute of Technology, Chemistry, Dhanbad, 826004, Dhanbad, INDIA
| | - Puneet Gupta
- IIT Roorkee: Indian Institute of Technology Roorkee, Chemistry, Roorkee, 247667, Roorkee, INDIA
| | - Tarun K Panda
- IITH: Indian Institute of Technology Hyderabad, Chemistry, Kandi, Sangareddy, 502285, Hyderabad, INDIA
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Panda TK, Bhattacharjee J, Rawal P, Das S, Harinath A, Gupta P. Highly efficient Ti-catalyst for deoxygenative reduction of esters at ambient conditions: experimental and mechanistic insights from DFT Study. Dalton Trans 2022; 51:5859-5867. [DOI: 10.1039/d2dt00076h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this paper, we report the synthesis of dianionic amidophosphineborane–supported titanium chloride [{Ph2P(BH3)N}2C6H4}TiCl2] (1) and TiIV alkyl complex [{Ph2P(BH3)N}2C6H4}Ti(CH2SiMe3)2] (2) using salt metathesis reaction. The TiIV complex 1 was obtained...
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Das S, Rawal P, Bhattacharjee J, Devadkar A, Pal K, Gupta P, Panda TK. Indium promoted C(sp 3)–P bond formation by the Domino A 3-coupling method – a combined experimental and computational study. Inorg Chem Front 2021. [DOI: 10.1039/d0qi01210f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
An efficient catalytic process for the synthesis of α-aminophosphonates is developed by a one-pot three-component reaction in the presence of In complexes at room temperature. DFT based mechanistic studies of the catalytic reactions are reported.
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Affiliation(s)
- Suman Das
- Department of Chemistry
- Indian Institute of Technology Hyderabad
- Sangareddy 502285
- India
| | - Parveen Rawal
- Computational Catalysis Center
- Department of Chemistry
- Indian Institute of Technology Roorkee
- Roorkee – 247667
- India
| | - Jayeeta Bhattacharjee
- Department of Chemistry
- Indian Institute of Technology Hyderabad
- Sangareddy 502285
- India
| | - Ajitrao Devadkar
- Department of Chemistry
- Indian Institute of Technology Hyderabad
- Sangareddy 502285
- India
| | - Kuntal Pal
- Department of Chemistry
- University of Calcutta
- Kolkata 700009
- India
| | - Puneet Gupta
- Computational Catalysis Center
- Department of Chemistry
- Indian Institute of Technology Roorkee
- Roorkee – 247667
- India
| | - Tarun K. Panda
- Department of Chemistry
- Indian Institute of Technology Hyderabad
- Sangareddy 502285
- India
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Singh R, Mishra NK, Singh N, Rawal P, Gupta P, Joshi KB. Transition metal ions induced secondary structural transformation in a hydrophobized short peptide amphiphile. NEW J CHEM 2020. [DOI: 10.1039/d0nj01501f] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Transition metal ions mediate the secondary structural transformation of hydrophobized sPA and can be applied to the design and development of stimuli-responsive nanomaterials.
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Affiliation(s)
- Ramesh Singh
- Department of Chemistry
- School of Chemical Science and Technology
- Dr Harisingh Gour Central University
- Sagar
- India
| | | | - Narendra Singh
- Department of Chemistry
- Indian Institute of Technology
- Kanpur
- India
| | - Parveen Rawal
- Department of Chemistry
- Indian Institute of Technology
- Roorkee 247667
- India
| | - Puneet Gupta
- Department of Chemistry
- Indian Institute of Technology
- Roorkee 247667
- India
| | - Khashti Ballabh Joshi
- Department of Chemistry
- School of Chemical Science and Technology
- Dr Harisingh Gour Central University
- Sagar
- India
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Affiliation(s)
- S S Rana
- Department of Gastroenterology, Post Graduate Institute of Medical Education and Research, Chandigarh, India.
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Pan T, Rawal P, Wu Y, Xie W, Jankovic J, Le W. Rapamycin protects against rotenone-induced apoptosis through autophagy induction. Neuroscience 2009; 164:541-51. [PMID: 19682553 DOI: 10.1016/j.neuroscience.2009.08.014] [Citation(s) in RCA: 211] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2009] [Revised: 07/31/2009] [Accepted: 08/02/2009] [Indexed: 12/21/2022]
Abstract
Ubiquitin proteasome system (UPS) and autophagy lysosome pathway (ALP) are the two most important routes for degradation of aggregated/misfolded proteins. Additionally, ALP is so far the only known route to clear entire organelles, such as mitochondria. We proposed that enhancement of ALP may be beneficial for some neurodegenerative disorders, such as Parkinson's disease (PD), in which the accumulation of aggregated/misfolded proteins and the dysfunction of mitochondria are the two major pathogenesis. Mitochondrial complex I inhibitor rotenone, which causes dysfunction mitochondria and UPS, has been considered as one of the neurotoxins related to PD. In this study, rotenone-exposed human neuronal SH-SY5Y cells were used as an in vitro model for us to determine whether autophagy enhancer rapamycin could protect against rotenone-induced injury and its underlying mechanisms. The observed results showed that rapamycin alleviated rotenone-induced apoptosis, whose effects were partially blocked when autophagy related gene 5 (Atg5) was suppressed by Atg5 small interference RNA (siRNA) transfection. Additionally, the results showed that rapamycin pretreatment diminished rotenone-induced accumulation of high molecular weight ubiquitinated bands, and reduced rotenone-induced increase of cytochrome c in cytosolic fraction and decreased mitochondrial marker cytochrome oxidase subunit IV (COX IV) in mitochondrial fraction. The changes in cytochrome c and COX IV indicated that the decreased translocation of cytochrome c from mitochondria to cytosol was probably due to the turn over of entire injured mitochondria. The results that lysosome and mitochondria were colocolized within the cells pretreated with rapamycin and that the mitochondria could be found within autophagy double membrane structures further supported that the damaged mitochondria might be cleared through autophagy, which process has been termed as "mitophagy." Our studies suggested that autophagy enhancer rapamycin is neuroprotective against rotenone-induced apoptosis through autophagy enhancement. We concluded that pharmacologically induction of autophagy by rapamycin may represent a useful therapeutic strategy as disease-modifiers in PD.
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Affiliation(s)
- T Pan
- Parkinson Disease Research Laboratory, Department of Neurology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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Leon SC, Lyons JS, Uziel-Miller ND, Rawal P, Tracy P, Williams J. Evaluating the use of psychiatric hospitalization by residential treatment centers. J Am Acad Child Adolesc Psychiatry 2000; 39:1496-501. [PMID: 11128325 DOI: 10.1097/00004583-200012000-00009] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To examine differences in risk levels of psychiatric hospital referrals received from residential treatment centers (RTCs) as a measure of service quality. METHOD This prospective study used the Childhood Severity of Psychiatric Illness (CSPI), a reliable measure of psychiatric severity and factors thought to affect decision-making. Psychiatric referrals were wards of the state from the 10 largest RTCs in one metropolitan county and were screened by mobile crisis workers for admission appropriateness. After interviewing clients, the independent crisis workers completed the CSPI. RESULTS Referrals were placed into 1 of 2 categories based on CSPI ratings: high-risk or low-risk. Referrals were deemed high-risk if they displayed moderate or severe levels of suicidality, dangerousness to others, or psychotic symptoms on the CSPI. Results showed statistically significant variation in the level of risk of referrals received from the 10 RTCs. In addition, RTCs that had high rates of low-risk referrals were rated by crisis workers as demonstrating poorer supervision of their clients. CONCLUSIONS The residential treatment providers in our sample are expected to provide intensive treatment to children and adolescents with serious emotional and behavioral problems. Our finding that some RTCs are making low-risk referrals suggests that they are struggling to meet the needs of some of their clients. Our findings can be used to inform quality improvement efforts at RTCs that are currently struggling.
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Affiliation(s)
- S C Leon
- Department of Psychiatry and Behavioral Sciences, Northwestern University Medical School, Chicago, USA
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Abstract
This article documents employers' expenditure on the arrangements for the health care of their employees in one of the least developed countries; Tanzania. The case for compulsory health insurance is considered in the light of the fact that only 3% of the population is employed in the formal sector and could be covered at first. It is shown from a survey of larger employers, outside government, that they were spending on average 11% of payroll on health care for their employees. This demonstrated their lack of satisfaction with the government health services. Nevertheless, those who could readily be covered by insurance were making considerable use of the more expensive government hospital services. It is argued that a compulsory health insurance scheme could be introduced for the formal sector of employment which would cover a wider range of health services at lower cost. The scheme would also have the desirable economic effect of lowering employers' labour costs while making it possible to improve the standards of the government health services.
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Affiliation(s)
- B Abel-Smith
- Department of Social Science and Administration, London School of Economics and Political Science, UK
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Abstract
Various environmental sites closely associated with spinally-injured patients were examined for contamination by organisms concurrently causing urinary infection. Of 30 episodes studied, the same organism was recovered from bedding on 20 occasions, from nine of 20 bath towels and less frequently from face cloths, clothing, wheelchairs and bedside units. The results indicate that contact with the immediate environment of spinal patients with urinary infection may lead to contamination of hands, and confirm and expand the need for handwashing by patients and staff.
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Affiliation(s)
- P J Sanderson
- Royal National Orthopaedic Hospital, Brockley Hill, Stanmore
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