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Thomas Mathew

Publications and source records attributed to Thomas Mathew.

15 recordsLinked to original sources
PubMed2007

Efficient one-pot synthesis of fluorinated benzimidazolines, benzothiazolines, benzoxazolines, and dihydrobenzoxazinones using gallium(III) triflate as a catalyst.

One-pot synthesis of fluorinated benzimidazolines, benzothiazolines, benzoxazolines, and dihydrobenzoxazinones was easily achieved under mild conditions in high yields and purity through gallium(III) triflate mediated condensation-cyclization. Introduction of fluorine atoms favors the formation of the five-membered heterocycles over seven-membered heterocycles. [reaction: see text].

Journal Article↗
PubMed2006

Facile synthesis of TMS-protected trifluoromethylated alcohols using trifluoromethyltrimethylsilane (TMSCF3) and various nucleophilic catalysts in DMF.

Organofluorine compounds are becoming increasingly important in different fields, such as material science, agro chemistry, and the pharmaceutical industry. Nucleophilic trifluoromethylation is one of the widely used methods to incorporate a trifluoromethyl moiety into organic molecules. We have carried out extensive studies to develop varieties of easily accessible nucleophilic catalysts to promote such reactions. TMS-protected trifluoromethylated alcohols were prepared from both aldehydes and ketones in excellent yields using catalytic amount of amine N-oxide. Carbonate and phosphate salts also showed efficient catalytic activity toward this reaction. These reactions were highly solvent dependent, and DMF was found to be the most suitable one among the various solvents studied. All these reactions proceeded under very mild conditions, giving clean products and avoiding the use of any fluoride initiators or expensive catalysts, and extremely water-free conditions. The mechanism for the reaction is discussed in detail. DFT calculations were performed on the possible reaction intermediates using the Gaussian 03 program at B3LYP/6-311+G* level to support the proposed mechanism.

Alcohols↗
PubMed2006

BF3.2CF3CH2OH (BF3.2TFE), an efficient superacidic catalyst for some organic synthetic transformations.

BF3.2CF3CH2OH complex was found to be a very effective superacidic catalyst comparable in acid strength to at least that of 100% anhydrous sulfuric acid for various acid-catalyzed organic transformations such as isomerizations, rearrangements, ionic hydrogenation of various ketones, and aromatics with triethylsilane and nitration of aromatics with metal nitrate. Studies of the pivalaldehyde-methyl isopropyl ketone rearrangement and the benzopinacol to phenanthrene transformation suggest that the complex has an acidity comparable to that of 100% anhydrous sulfuric acid. The structure and properties of the 1:2 boron trifluoride-trifluoroethanol complex have been further studied using NMR (1H, 13C, 19F, 11B) and DFT calculations at the B3LYP/6-311++G//B3LYP/6-31G level.

Journal Article↗
PubMed2006

Generalized P-values and confidence intervals: a novel approach for analyzing lognormally distributed exposure data.

The problem of assessing occupational exposure using the mean of a lognormal distribution is addressed. The novel concepts of generalized p-values and generalized confidence intervals are applied for testing hypotheses and computing confidence intervals for a lognormal mean. The proposed methods perform well, they are applicable to small sample sizes, and they are easy to implement. Power studies and sample size calculation are also discussed. Computational details and a source for the computer program are given. The procedures are also extended to compare two lognormal means and to make inference about a lognormal variance. In fact, our approach based on generalized p-values and generalized confidence intervals is easily adapted to deal with any parametric function involving one or two lognormal distributions. Several examples involving industrial exposure data are used to illustrate the methods. An added advantage of the generalized variables approach is the ease of computation and implementation. In fact, the procedures can be easily coded in a programming language for implementation. Furthermore, extensive numerical computations by the authors show that the results based on the generalized p-value approach are essentially equivalent to those based on the Land's method. We want to draw the attention of the industrial hygiene community to this accurate and unified methodology to deal with any parameter associated with the lognormal distribution.

Air Pollutants, Occupational↗
PubMed2006

Neuroleptospirosis - revisited: experience from a tertiary care neurological centre from south India.

BACKGROUND & OBJECTIVES: Leptospirosis is a zoonotic disease commonly reported from south India. Neurological manifestations seen in about 10-15 per cent of cases, are protean and remain unrecognized and diverse. We evaluated the pattern of nervous system involvement in leptospirosis, among patients presenting to the emergency services of a tertiary care neurological centre in south India, and also analysed the outcome and prognostic indicators. METHODS: The diagnosis of neuroleptospirosis was based on clinical and laboratory evidence of hepatorenal syndrome, and serum or CSF positivity for antileptospira antibody by a macroscopic agglutination test (MAT) and by ELISA in a limited number of samples. RESULTS: A total of 31 patients (M:F 27:4, age range 6-68 yr, mean 36.4 +/- 14.3 yr) were treated during the five year period. Acute fever with chills and rigors, headache and vomiting were the presenting manifestations; 25 patients (81%) had altered sensorium for a period ranging from 1- 8 days, four (12.9%) being deeply comatose. Eleven (35.5%) had acute symptomatic seizures at the time of presentation. Conjunctival congestion with or without haemorrhage was seen in 12 patients (38.7%), icterus in 14 (45%) and mild hepatosplenomegaly in 11 (35.5%). Early papilloedema was observed in three. Only three patients had localizing deficits. CT scan was normal in 18 of 27 (67%), while 7 (26%) had diffuse cerebral oedema. CSF pleocytosis with lymphocytic predominance (mean 50 cells/microl) and elevated protein levels (mean 115.5 +/- 67.5 mg %) were noted. Leptospira antibody was detected in serum of all, and 5 of 22 in CSF samples. Eight patients (26%) succumbed. Deep altered sensorium at presentation and raised CSF protein were two poor prognostic indicators. Pathological study of brain in five cases revealed encephalitic features and in addition immune mediated acute disseminated encephalomyelitis (ADEM) like pathology in two cases. INTERPRETATION & CONCLUSION: Neuroleptospirosis should be considered in the differential diagnosis of neuroinfections associated with hepatorenal dysfunction, in endemic areas. Leptospira antibody can be detected in CSF also in some cases. Deep altered sensorium at presentation indicates poor prognosis.

Adolescent↗
PubMed2005

Ionic liquid and solid HF equivalent amine-poly(hydrogen fluoride) complexes effecting efficient environmentally friendly isobutane-isobutylene alkylation.

Isoparaffin-olefin alkylation was investigated using liquid as well as solid onium poly(hydrogen fluoride) catalysts. These new immobilized anhydrous HF catalysts contain varied amines and nitrogen-containing polymers as complexing agents. The liquid poly(hydrogen fluoride) complexes of amines are typical ionic liquids, which are convenient media and serve as HF equivalent catalysts with decreased volatility for isoparaffin-olefin alkylation. Polymeric solid amine:poly(hydrogen fluoride) complexes are excellent solid HF equivalents for similar alkylation acid catalysis. Isobutane-isobutylene or 2-butene alkylation gave excellent yields of high octane alkylates (up to RON = 94). Apart from their excellent catalytic performance, the new catalyst systems significantly reduce environmental hazards due to the low volatility of complexed HF. They represent a new, "green" class of catalyst systems for alkylation reactions, maintaining activity of HF while minimizing its environmental hazards.

Journal Article↗
PubMed2005

Percutaneous coronary intervention and 1 year survival in patients treated with fibrinolytic therapy for acute ST-elevation myocardial infarction.

AIMS: To assess the predictors of 1 year mortality in patients treated with fibrinolytic therapy for ST-segment elevation myocardial infarction (STEMI) and to determine whether a strategy of early percutaneous coronary intervention (PCI) improves outcome. METHODS AND RESULTS: Consecutive patients (n = 474) admitted to our unit (1998-2001) with STEMI were treated with fibrinolytic therapy. For each patient, age, gender, admission via mobile coronary care unit (MCCU), infarct location, initial systolic blood pressure and Killip class, prior history of ischaemic heart disease, hypertension, diabetes mellitus, smoking status, family history, hyperlipidaemia, and in-hospital PCI (n = 154) were recorded. Mortality at 1 year was obtained from medical records (n = 473). Binary logistic regression analysis was performed to determine independent predictors of 1 year mortality. Mortality in the non-PCI group was 21 vs. 7% in the PCI group. Independent predictors of 1 year mortality were age (risk ratio 1.12, 95% CI 1.08-1.15, P < 0.0001), initial SBP < or = 80 mmHg (risk ratio 4.34, 95% CI 1.68-11.2, P = 0.002), initial Killip class > or = 3 (risk ratio 2.97, 95% CI 1.42-6.2, P = 0.004), and lack of in-hospital PCI (risk ratio 0.39, 95% CI 0.19-0.81, P = 0.012). Although the PCI group were younger (P = 0.007), more likely to be admitted via the MCCU (P = 0.008), with a shorter pain to needle time (P = 0.04), multivariable analysis adjusted for these differences. CONCLUSION: In-hospital PCI in patients treated with fibrinolytic therapy for STEMI is associated with a substantial reduction in 1 year mortality.

Aged↗
PubMed2004

N-halosuccinimide/BF3-H2O, efficient electrophilic halogenating systems for aromatics.

N-Halosuccinimides (NXS, 1) are efficiently activated in trifluoromethanesulfonic acid and BF(3)-H(2)O, allowing the halogenations of deactivated aromatics. Because BF(3)-H(2)O is more economic, easy to prepare, nonoxidizing, and offers sufficiently high acidity (-H(0) approximately 12, only slightly lower than that of trifluoromethanesulfonic acid), an efficient new electrophilic reagent combination of NXS/BF(3)-H(2)O has been developed. DFT calculations at the B3LYP/6-311++G//B3LYP/6-31G level suggest that protonated N-halosuccinimides undergo further protosolvation at higher acidities to reactive superelectrophilic species capable either in the transfer of X(+) from the protonated forms of NXS to the aromatic substrate or in forming a highly reactive and solvated X(+) which would readily react with the aromatic substrates. Structural aspects of the BF(3)-H(2)O complex have also been investigated.

Journal Article↗
PubMed2004

ipso-nitration of arylboronic acids with chlorotrimethylsilane-nitrate salts.

[reaction: see text] A mixture of nitrate salt and chlorotrimethylsilane is found to be an efficient regioselective nitrating agent for the ipso-nitration of arylboronic acids to produce the corresponding nitroarenes in moderate to excellent yields. High selectivity, simplicity, and convenience are the key features of the reaction.

Journal Article↗
PubMed2004

Carbocationic rearrangement of pivaloyl cation and protonated pivalaldehyde in superacid medium: a novel solution equivalent of the McLafferty rearrangement.

Both pivaloyl cation in the presence of hydride donors and protonated pivalaldehyde in superacid media (both aprotic and protic) rearrange to protonated methyl isopropyl ketone involving gitionic dicationic intermediates. In our earlier studies we have found that the rearrangement of pivaladehyde to methyl isopropyl ketone occurs quantitatively in the presence of various superacidic media such as anhydrous HF, triflic acid, boron trifluoride-2,2,2-trifluoroethanol complex (BF(3).2CF(3)CH(2)OH) etc. Our present study with environmentally more benign and stable amine:HF complexes, namely pyridinium poly(hydrogen fluoride) (PPHF) (5), poly(4-vinylpyridinium) poly(hydrogen fluoride) (6), and poly(ethyleniminium) poly(hydrogen fluoride) (PEIHF) (7) shows that these modified HF equivalents can carry sufficient amount of immobilized HF and provide ample acidity for complete isomerization of pivalaldehyde to methyl isopropyl ketone. Calculations on protioformyl, acetyl and pivaloyl dications at the B3LYP/6-311 ++ G(d,p) and CCSD(T)/6-311 ++ G(d,p)//B3LYP/6-311 ++ G(d,p) levels have been performed to compare the nature of protosolvation of formyl, acetyl, pivaloyl cations and protonated pivaladehyde in superacid media. These studies further suggest protosolvation of protonated pivalaldehyde leading to gitionic dications at high acidities resulting in the carbocatioinic rearrangement. The reported carbocationic rearrangement under superacidic activation represents a novel solution chemistry equivalent of the well known gas-phase McLafferty rearrangement.

Journal Article↗
PubMed2003

Tests for individual and population bioequivalence based on generalized p-values.

The U.S. Food and Drug Administration (FDA) has proposed new regulations that address the 'prescribability' and 'switchability' of new formulations of already-approved drugs. These new criteria are known, respectively, as population and individual bioequivalence. Two methods have been proposed in the bioequivalence literature for assessing population and individual bioequivalence that calculate an upper 95 per cent confidence bound for the bioequivalence criterion in question, and then test bio-equivalence by comparing this bound to the limit established by the FDA. In this paper we propose applying the generalized test function (GTF) methodology of Tsui and Weerahandi (Journal of the American Statistical Association 1989; 602-607) to this problem to produce tests based on a generalized p-value (GPV). This methodology allows us to construct hypothesis tests in the presence of nuisance parameters. Using simulation we show that these tests perform well in comparison to the confidence interval methods and have superior power for assessing population bioequivalence.

Adrenergic Agents↗
PubMed2002

Volunteer faculty: what rewards or incentives do they prefer?

BACKGROUND: Clerkship directors and college administrators have concerns about recruitment and retention of practicing physicians for volunteer teaching. There is a paucity of data regarding the rewards and incentives offered to, or desired by, the nonsalaried community-based practicing physicians who volunteer their time to teach. PURPOSE: This study was designed to gain information about rewards and incentives from volunteer teachers in pediatric, family practice, and internal medicine clerkships. METHODS: We surveyed nonsalaried physician teachers of internal medicine, family medicine, and pediatrics across the United States. The survey focused on teachers' evaluation of the rewards or incentives offered by the programs in the following categories: educational opportunities, services or gifts, recognition bestowed by the school, academic appointments, and monetary payments. Respondents rated each item from 1 (not appreciated) to 5 (very much appreciated). They also were asked to rank order the rewards or incentives (with the addition of a category of personal satisfaction) from 1 (least appreciated) to 6 (most appreciated). RESULTS: Educational opportunities received high ratings, especially when the school bore the cost of providing a service. Payment for teaching was offered to 37% of the respondents, and those who were paid rated it higher. Overall, payment for teaching had a mean appreciation score of 3.94, second only to travel and meeting registration reimbursement (4.27). However, in the rank order listing, personal satisfaction had the highest rank (5.16). In contrast, payment for teaching (2.92) and gifts or services from the college (2.53) were at the bottom of the rank order. CONCLUSION: The survey asked practicing physicians the value they placed on awards and incentives provided to them by the college. This information should help administrators and clerkship directors in recruiting and retaining community-based practicing physicians for teaching.

Clinical Clerkship↗
PubMed2002

Malignant melanoma metastatic to bone marrow.

Bone marrow aspiration and biopsy is a useful means of detecting systemic involvement in patients with non haematological malignancy. Metastases of malignant melanoma may be detected in the bone marrow in a small percentage of patients. Two cases of malignant melanoma, with metastasis to marrow at the time of presentation, are described. In one case, bone marrow was the first site where the malignancy was identified. Subsequent investigations revealed an anal melanoma. In the second case, the patient had widespread dissemination from a tonsillar melanoma to many organs of the body, including bone marrow.

Adult↗
PubMedDate not supplied

Statistical methods for establishing equivalency of a sampling device to the OSHA standard.

Occupational Safety and Health Administration (OSHA) regulations allow the use of an alternative sampling device for exposure monitoring provided the device has been demonstrated to be equivalent to the standard device. For example, the OSHA standard allows the use of an alternate cotton dust sampler that is equivalent to the Lumsden-Lynch vertical elutriator (VE); also, OSHA defines the accuracy of the monitoring device for measuring airborne chemicals such as benzene and sulfur dioxide. Typically, the OSHA criterion is that 90% of the readings of the sampling device should be within +/- 25% of the readings obtained by the standard device or within +/- 25% of the actual airborne chemical concentration. This article proposes two statistical tests for establishing that an alternative measuring device of airborne chemicals or dust is equivalent to the OSHA standard. The statistical tests are illustrated using an example.

Air Pollutants, Occupational↗