Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “mitigation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 883 records · Page 49Linked to original sources
PubMed2005

Assessment of the risk of introduction of Anoplophora glabripennis (Coleoptera: Cerambycidae) in municipal solid waste from the quarantine area of New York City to landfills outside of the quarantine area: a pathway analysis of the risk of spread and establishment.

The risk associated with spread of Asian longhorned beetle, Anoplophora glabripennis (Motschulsky), from infested areas in New York City to the wide array of landfills across the eastern United States contracted by the city since 1997 was unknown, but of great concern. Landfills, some as far as South Carolina, Virginia, and Ohio, occupied forest types and climates at high risk of Asian longhorned beetle establishment. The city proposed a separate waste wood collection known as the "311 System;" this was estimated to cost federal and state agencies $6.1 to $9.1 million per year, including the cost of processing and disposal of the wood. Pathway analysis was used to quantify the probability that Asian longhorned beetle present in wood waste collected at curbside would survive transport, compaction, and burial to form a mated pair. The study found that in seven alternate management scenarios, risks with most pathways are very low, especially given existing mitigations. Mitigations included chemical control, removal of infested trees, and burial of wood waste in managed landfills that involved multiple-layering, compaction, and capping of dumped waste with a 15-cm soil cover at the end of each day. Although the risk of business-as-usual collection and disposal practices was virtually nil, any changes of policy or practice such as illegal dumping or disposal at a single landfill increased the risk many thousandfold. By rigorously maintaining and monitoring existing mitigations, it was estimated that taxpayers would save $75 to $122 million dollars over the next decade.

Animals↗
PubMed1996

Toward a more realistic appraisal of the lung cancer risk from radon: the effects of residential mobility.

OBJECTIVES: A consideration of the effects of residential mobility produces much more realistic estimates of typical individuals' radon exposures and mortality risks than those of the Environmental Protection Agency (EPA). METHODS: A model linking residential mobility, the distribution of radon in US homes, and lung cancer risk is used to simulate lifetime radon exposure, with and without mitigation of high-radon homes, for typical mobile individuals. Radon-related lung cancer mortality risks are then estimated for smokers and never-smokers. RESULTS: Most individuals residing in high-radon homes have equivalent lifelong radon exposures well below those they are currently experiencing. Consequently, actual lung cancer risks are generally well below those implied in the EPA's radon risk charts. For most people who mitigate high-radon homes, risk reduction is modest. CONCLUSIONS: Radon may indeed be responsible for as large a population risk of lung cancer as the EPA estimates. However, caution must be used in interpreting the EPA's risk assessment for individuals; in many cases, mitigation will have little effect on residents' health risks.

Adult↗
PubMed2026

Investigation of Mycobacterium abscessus Cluster in Hospital, Maryland, USA, 2024.

Mycobacterium abscessus infections are frequently drug resistant and can cause severe disease, particularly among vulnerable populations in healthcare settings. In June 2024, a cluster of M. abscessus infection cases was reported at a hospital in Maryland, USA. An investigation involving hospital infection prevention staff, the Maryland Department of Health, the Centers for Disease Control and Prevention, and the Wadsworth Laboratory of the New York State Department of Health included initiation of mitigation efforts such as tap water use restrictions, point-of-use water filters, hospitalwide water flushing, and staff education regarding sink safety. Whole-genome sequencing of patient and environmental isolates, coupled with epidemiologic data, revealed a strong association (0-24 single-nucleotide polymorphism differences) between environmental and patient samples, indicating that infections were likely a result of patient exposure to M. abscessus. Ensuring initiation of mitigation initiatives likely prevented additional patient infections. Although effective in this investigation, not all mitigation strategies are equal or sustainable.

Humans↗
PubMed1999

Side effects of pharmaceuticals not elicited by comparable herbal medicines: the case of tetrahydrocannabinol and marijuana.

OBJECTIVE: Herbalists claim that the polypharmacy of botanical remedies provides 2 advantages over single-ingredient drugs: (1) primary active ingredients in herbs are synergized by secondary compounds, and (2) secondary compounds mitigate the side effects caused by primary active ingredients. To examine this second claim, medical marijuana was compared with its primary active ingredient, tetrahydrocannabinol. DATA SOURCES: A search on MEDLINE (1966-1999), AGRICOLA (1990-1999), and Biological and Agricultural Index (1964-1999) using keywords "cannabinoids," "marijuana," "tetrahydrocannabinol," "Cannabis," and "hemp." Phytochemical and ethnobotanical data were searched with the Agricultural Research Service database. Unindexed botanical journals were scanned by hand. STUDY SELECTION: Studies documenting the efficacy of secondary compounds mitigating side effects of tetrahydrocannabinol consisting of double-blind trials, unblinded studies, animal models, and in vitro experiments. DATA EXTRACTION AND DATA SYNTHESIS: Data validity was assessed by consensus, weighted by source (peer-reviewed article vs popular press), identification methodology (analytical chemistry vs clinical history), and frequency of independent observations. CONCLUSIONS: Good evidence suggests that some side effects of tetrahydrocannabinol are mitigated by other volatile compounds present in the essential oil of marijuana. Inhaling tetrahydrocannabinol, which avoids first-pass hepatic metabolism, has advantages over ingesting it. Other cannabinoids, terpenoids, and flavonoids can reduce tetrahydrocannabinol-induced anxiety, cholinergic deficits, and immunosuppression. Other compounds increase cerebral blood flow, enhance cortical activity, kill respiratory pathogens, and provide anti-inflammatory activity. The hazards of marijuana smoke can be reduced with appropriate technology. Proprietary Cannabis extracts containing a mixture of cannabinoids, terpenoids, and flavonoids are currently being developed and tested.

Analgesics, Non-Narcotic↗
PubMed2001

Water quality management planning zone development by introducing a GIS tool in Kathmandu valley, Nepal.

This research was conducted to identify the critical pollution (BOD, TN, TP) areas and to develop the priority mitigation zone for the Bagmati River pollution in the Kathmandu valley, Nepal. A GIS tool was used to define and identify the critical pollution areas and sources. Pollution source information such as population, livestock, industry and land use were collected on the basis of the individual village boundary. The industrial, land use and living pollution were aggregated by the GIS overlay analysis capability to obtain the combined pollution load within the watershed. Priority areas for the mitigation of the pollution were defined considering the pollution loading rate, distance of stream from pollution source, and political, religious, and touristic values of the area. This research noticed that Kathmandu, Lalitpur and Bhaktapur municipalities are the major polluting areas and living beings are the major factors of Bagmati River pollution. Delivery ratio for the watershed was found to vary from 40-69% for BOD and nitrogen but the delivery of phosphorus was exceptionally high (92% at Gaurighat and 77% at Chovar) due to cremation activity of the Hindu religion on the riverbanks. Thus, the priority areas for the mitigation of the carbonaceous and nutrient source pollution were identified. At present the land use and industry impaired a very low contribution compared to the huge pollution load from the municipalities to the river system.

Agriculture↗
PubMed2005

Review of attitudes and awareness in the agricultural industry to diffuse pollution issues.

The Scottish Executive considers 'Diffuse Pollution from Agricultural Enterprises' as a priority issue over the next 5-10 years and recognises the need to improve knowledge transfer, advice and training amongst farmers, crofters, contractors and advisers. The Scottish Environment Protection Agency commissioned SAC to survey advisory staff on diffuse pollution issues, mitigation measures and delivery of environmental advice to the farming industry. This showed that the impact of agricultural diffuse pollution on the environment is considered a serious problem as is the future impact of legislation on farm business. There is an urgent requirement to raise advisers' awareness of environmental legislation and of mitigation measures. Advisers consider that farmers have limited awareness of diffuse pollution problems but those that do would consider the impact on the environment to be serious. There is a lack of knowledge on the effectiveness of pollution mitigation measures. Better technical information, supported by research, is required. This information is best conveyed to advisers via the internet, technical notes and directly by environmental specialists and delivered on to farmers by farm visits. Lack of funds prevents most farmers adopting best management practices and more than 80% of advisers consider that environmental advice should be free.

Agriculture↗
PubMed2005

The Bellagio Report: Cardiovascular risks of spaceflight: implications for the future of space travel.

BACKGROUND: Long-duration space missions, as well as emerging civilian tourist space travel activities, prompted review and assessment of data available to date focusing on cardiovascular risk and available risk mitigation strategies. The goal was the creation of tools for risk priority assessments taking into account the probability of the occurrence of an adverse cardiovascular event and available and published literature from spaceflight data as well as available risk mitigation strategies. METHODS: An international group of scientists convened in Bellagio, Italy, in 2004 under the auspices of the Aerospace Medical Association to review available literature for cardiac risks identified in the Bioastronautics Critical Path Roadmap (versions 2000, 2004). This effort led to the creation of a priority assessment framework to allow for an objective assessment of the hazard, probability of its occurrence, mission impact, and available risk mitigation measures. RESULTS/CONCLUSIONS: Spaceflight data are presented regarding evidence/ no evidence of cardiac dysrhythmias, cardiovascular disease, and cardiac function as well as orthostatic intolerance, exercise capacity, and peripheral resistance in presyncopal astronauts compared to non-presyncopal astronauts. Assessment of the priority of different countermeasures was achieved with a tabular framework with focus on probability of occurrence, mission impact, compliance, practicality, and effectiveness of countermeasures. Special operational settings and circumstances related to sensitive portions of any mission and the impact of environmental influences on mission effectiveness are addressed. The need for development of diagnostic tools, techniques, and countermeasure devices, food preparation, preservation technologies and medication, as well as an infrastructure to support these operations are stressed. Selected countermeasure options, including artificial gravity and pharmacological countermeasures need to be systematically evaluated and validated in flight, especially after long-duration exposures. Data need to be collected regarding the emerging field of suborbital and orbital civilian space travel, to allow for sound risk assessment.

Arrhythmias, Cardiac↗
PubMed2005

Expert testimony in capital sentencing: juror responses.

The U.S. Supreme Court, in Furman v. Georgia (1972), held that the death penalty is constitutional only when applied on an individualized basis. The resultant changes in the laws in death penalty states fostered the involvement of psychiatric and psychologic expert witnesses at the sentencing phase of the trial, to testify on two major issues: (1) the mitigating factor of a defendant's abnormal mental state and (2) the aggravating factor of a defendant's potential for future violence. This study was an exploration of the responses of capital jurors to psychiatric/psychologic expert testimony during capital sentencing. The Capital Jury Project is a multi-state research effort designed to improve the understanding of the dynamics of juror decision-making in capital cases. South Carolina data (n = 214) were used to investigate the impact of expert testimony on the mitigating factor of mental illness and the aggravating factor of future dangerousness. Ordered logit regression analyses revealed significant correlations (p < .005) between the presence of a defense psychiatrist or psychologist expert witness during the sentencing phase and jurors' having the impression that the defendant was mentally disturbed. Similar analyses revealed no significant relationship between the presence of state-introduced psychiatric testimony and jurors' having the impression that the defendant, if not executed, would be violent in the future. These findings seem to contradict the view that psychiatric testimony on future dangerousness in death penalty cases has a powerful impact on jurors. The jurors in this study were significantly influenced, however, by psychiatric/psychologic testimony in the area of a defendant's mitigating mental abnormality.

Capital Punishment↗
PubMed2005

For holistic control of reactive N: regional, national and global perspectives.

Reactive N is closely related to the global issues of climate change and regional pollutions. Nitrous oxide (N20), the fourth important gas among greenhouse gases, is produced as an intermediate in nitrification and denitrification processes. As methane (CH4) is the end product in the anoxic decomposition of organic materials, mitigation options of N20 emission are different from those of CH4 emission. Nitrate is another reactive N bringing about the eutrification of aqueous environments and the hazard of drinking water. Mitigation of NO3 problem also relates closely to the N20 emission. Therefore, holistic approaches are necessary for solving the problems of Earth warming and environmental eutrification by reactive N at the same time. In this paper, the deforestation in the tropics, and the present situations of food supply and sustainable agriculture in Japan are re-evaluated in terms of N20 emission and NO3 discharge from the agricultural sector. The magnitude of N20 emission by deforestation in the tropics may fall within the similar order of magnitude by N fertilization. As more N is imported as foods and fodder than the amount of fertilized N in Japan, more attention should be paid to the phases of their consumption and waste treatment. Sole attention to the production stage is not enough for the total mitigation of various environmental problems by reactive N in relation to agriculture. Parameters holistically evaluating the impact of reactive N on the Earth and respective regions are urgently necessary.

Agriculture↗
PubMed1990

Supplemental vitamin A prevents the tumor-induced defect in wound healing.

To test our hypothesis that supplemental vitamin A would mitigate the impaired healing that occurs in tumor-bearing animals, six groups of C3H mice, eight per group, eating a standard commercial mouse chow ad libitum that supports normal growth, reproduction, and longevity were innoculated with 200,000 C3HBA cells. When tumors measured approximately 6 mm in diameter, the mice were anesthesized and wounded (dorsal skin incisions and subcutaneous polyvinyl alcohol sponges). Twenty-four hours later, two groups (one continued on the chow and the other started on the chow supplemented with 150,000 IU vitamin A/kg chow) underwent local tumor irradiation; two groups, one ingesting the chow, the other the vitamin A supplemented chow, were started on cyclophosphamide therapy; two groups, one ingesting the chow, the other the vitamin A supplemented chow, received neither local tumor irradiation nor cyclophosphamide therapy. An additional two groups ingesting the chow, one group neither innoculated with tumor nor wounded, the other wounded by not innoculated, served as controls. Wound breaking strength and sponge reparative collagen accumulation (assessed by hydroxyproline proline measurement) were used as indicators of wound healing. The mice were killed 12 days after wounding. Tumor presence decreased wound breaking strength and sponge hydroxyproline content; these effects were largely negated by supplemental vitamin A. Local tumor irradiation diminished the adverse effect of tumor on sponge reparative collagen content but to a lesser extent than the supplemental vitamin A. Supplemental vitamin A added to the irradiation effect on healing but irradiation did not add to the vitamin A effect. Cyclophosphamide, a systemic radiomimetic anti-tumor agent, did not alter the impaired wound healing of the tumor-bearing mice. Supplemental vitamin A mitigated the impaired wound healing in the cyclophosphamide-treated tumor-bearing mice. Supplemental vitamin A also moderated the effects of wounding, tumor, and tumor therapies (local irradiation and cyclophosphamide) on the increase in adrenal size, leukopenia, thrombocytopenia, and thymic involution (except the last was not moderated in the cyclophosphamide-treated tumor-bearing rats). The splenic enlargement in the untreated tumor-bearing wounded rats and in those treated with cyclophosphamide was lessened by supplemental vitamin A. We hypothesize that these anti-stress effects of vitamin A underlie, in part, its action in mitigating the impaired wound healing of tumor-bearing mice, including those treated by local irradiation or cyclophosphamide. These findings have implications for the care of patients with malignant tumors.

Animals↗
PubMed1984

Techniques for prevention of calcification of valvular bioprostheses.

Calcification of valvular bioprostheses in children is a major problem that has stimulated extensive research in our laboratory. In previous reports, we have shown that the rate of calcification could be reduced by decreasing the phosphate content in the tissue or by blocking calcification binding sites with Mg++ and/or with a surfactant (Tween 80). Since then, we have systematically investigated incorporation of numerous other surfactants and of polyacrylamide within the tissue, and these investigations form the basis of this report. The methods of investigation included subcutaneous implantation of treated tissues in growing rabbits, stability tests, and intracardiac implantation in sheep. Results showed that surfactants differed in their efficacy in mitigating calcification, with N-lauroylsarcosine and triton X-100 being the most efficient. Polyacrylamide incorporation was also efficient in calcification mitigation, but this effect was lost after flexibility testing in vitro or implantation in vivo, a drawback that suggests further research is necessary into stabilization of this polymer. This report not only brings attention to new alternatives in calcification mitigation treatment of bioprosthetic tissues but also underlines important points of methodology.

Acrylic Resins↗
PubMed1995

Radioprotection against biological effects of internal radionuclides in vivo by S-(2-aminoethyl)isothiouronium bromide hydrobromide (AET).

UNLABELLED: Radionuclides employed in diagnostic and therapeutic nuclear medicine impart radiation energy to tissue over an extended period of time, which depends on the physical half-life and the biological properties of the radiochemical employed. It is therefore important to examine the capacity of chemical radioprotectors to mitigate damage caused by chronic irradiation by incorporated radionuclides. METHODS: Spermatogenesis in mouse testis is used as the experimental model, and spermatogonial cell survival as measured by testicular spermhead count is the biological end point. The capacity of S-(2-aminoethyl)isothiouronium bromide hydrobromide (AET) to mitigate radiation damage caused by chronic irradiation by the radiochemicals 125IUdR, H125IPDM and 210Po-citrate, is investigated. RESULTS: The radioprotection provided by AET is substantial and similar for both of the radioiodinated compounds with dose modification factors (DMF) of 4.0 +/- 1.2 for 125IUdR and 3.4 +/- 0.4 for H125IPDM. In contrast, the damage caused by 210Po alpha particles is protected against to a lesser degree (DMF = 2.4 +/- 0.5). CONCLUSION: The present radioprotection data for AET, in conjunction with our earlier findings for the chemical protectors cysteamine and vitamin C in the same experimental model, suggest that such compounds may be clinically useful as mitigating agents against biological damage caused by incorporated radionuclides. The observed DMFs for AET also support our earlier premise that the mechanism by which DNA-incorporated Auger emitters impart biological damage is primarily radical mediated, and hence indirect in nature.

Animals↗
PubMedDate not supplied

EMFs: cutting through the controversy.

SOME SCIENTISTS ALLEGE that exposure to electric and magnetic fields generated by electric power delivery systems is responsible for certain cancers (particularly among children), reproductive dysfunction, birth defects, neurological disorders, and Alzheimer's disease. Some activist groups believe the hazard to be so great that they are calling for closure of schools and other public facilities near power lines and restructuring of the entire electric power delivery system. Some utilities, with equally strong beliefs, claim that there is no proof of risk. They argue that the science is sufficient to confirm the alleged associations and that no action is warranted. This article provides a broad overview of the current scientific data on the association between magnetic fields and disease, providing summary risk estimates and highlighting the uncertainties in the data. Building on this information, three complementary policy perspectives are presented. From a fiscally conservative perspective, the cost of mitigation already instituted far exceeds the health protection offered and mitigation of other environmental risks is more important. From a cost-benefit view, only limited, low-cost mitigation should be considered. These measures, however, would substantially reduce many exposures. From an aggressive exposure reduction perspective, much can be done to reduce exposure by personal and societal actions. If the suggested association is validated, substantially reducing magnetic field exposure could lower health risks.

Animals↗
PubMed1997

Role of hypercholesterolemia in accelerated transplant coronary vasculopathy: results of surgical therapy with partial ileal bypass in rabbits undergoing heterotopic heart transplantation.

BACKGROUND: We tested the hypothesis that plasma cholesterol lowering action of partial ileal bypass (PIB) is beneficial in mitigating accelerated transplantation coronary vasculopathy. METHODS: Forty-one New Zealand white rabbits were randomized to receive a normal (n = 21) or 1% cholesterol diet (n = 20). They underwent heterotopic heart transplantation with sham-PIB (n = 19) or PIB (n = 22) and immunosuppression with cyclosporine A (CyA). RESULTS: CyA increased plasma cholesterol of rabbits receiving a normal diet. This effect was mitigated by PIB (101 +/- 50 mg/dl CyA vs baseline 24 +/- 8, p < 0.001; vs 54 +/- 25 mg/dl with PIB, p < 0.05). In cholesterol-fed rabbits, PIB decreased plasma cholesterol levels (520 +/- 236 mg/dl PIB vs baseline 720 +/- 359, p < 0.05; vs 1502 +/- 253 mg/dl with sham PIB, p < 0.00001). Coronary arteries (CA) of 21 5-week survivors were evaluated by light microscopy and digital morphometry. No rejection was noted. Histologic study revealed vasculopathy in 3% of 705 native and 18% of 654 transplant CA (p < 0.05). Graft vasculopathy (GV) was present in 25% of 365 CA of sham-PIB and 10% of 289 CA of PIB rabbits (p = 0.07). In cholesterol-fed rabbits, GV was characterized by fatty proliferative lesions in 75% of 91 pathologic CA of sham and 21% of 28 pathologic CA of PIB rabbits (p < 0.05). Graft intimal hyperplasia was not correlated with cholesterol intake or PIB and was present in 18 of 119 pathologic CA. CONCLUSIONS: GV was characterized by fatty intimal proliferation, fibrous intimal hyperplasia, and a "mixed type." Fibrous intimal hyperplasia developed in native and transplanted hearts, and CyA seemed to promote this state. Hypercholesterolemia promoted fatty proliferative lesions, worsening GV. PIB significantly decreased total cholesterol and retarded fatty proliferation of CA of native and transplanted hearts but did not prevent intimal hyperplastic vasculopathy. Therapy of hypercholesterolemia is recommended to at least mitigate the fatty intimal proliferation of GV.

Animals↗
PubMed2005

Mercury (II) alters mitochondrial activity of monocytes at sublethal doses via oxidative stress mechanisms.

The perennial controversy about the safety of mercury in dental amalgams has adversely affected the availability and the quality of dental care. Chronic Hg(II) blood concentrations above 300 nM are known to alter function of the nervous system and the kidney. However, the effects of blood concentrations of 10 to 75 nM, far more common in the general population, are not clear and mechanisms of any effects are not known. The monocyte is an important potential target of Hg(II) because of its critical role in directing inflammatory and immune responses. In the current study we tested the hypothesis that concentrations of Hg(II) of 10 to 300 nM alter monocyte activity via a redox-dependent mechanism. Mitochondrial activity was used to establish inhibitory concentrations of Hg(II) following 6 to 72 h of exposures to THP1 human monocytic cells. Then subinhibitory concentrations were applied, and total glutathione levels and reactive oxygen species (ROS) were measured. Antioxidants [N-acetyl cysteine, (NAC); Na2SeO3, (Se)] and a pro-oxidant (tert-butylhydroquinone, tBHQ) were used to support the hypothesis that Hg(II) effects were redox-mediated. After 72 h of exposure, 20 microM of Hg(II) inhibited monocytic mitochondrial activity by 50%. NAC mitigated Hg(II)-induced mitochondrial suppression only at concentrations of greater than 10 microM, but Se had few effects on Hg-induced mitochondrial responses. tBHQ significantly enhanced mitochondrial suppression at higher Hg(II) concentrations. Hg(II) concentrations of 75 and 300 nM (0.075 and 0.30 microM, respectively) significantly increased total glutathione levels, and NAC mitigated these increases. Se plus Hg(II) significantly elevated Hg-induced total cellular glutathione levels. Increased ROS levels were not detected in monocytes exposed to mercury. Hg(II) acts in monocytic cells, at least in part, through redox-mediated mechanisms at concentrations below those commonly associated with chronic mercury toxicity, but commonly occurring in the blood of some dental patients.

Biocompatible Materials↗
PubMed2006

670 nanometer light treatment attenuates dioxin toxicity in the developing chick embryo.

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is an acutely toxic anthropogenic chemical. Treatment with a red to near-infrared (630-1000 nm) light-emitting diode (LED) attenuates the toxicant-induced oxidative stress and energy deficit in neuronal cell culture. For this study, fertile chicken (Gallus gallus) eggs were injected once at the start of incubation with sunflower oil vehicle or 200 pg TCDD/g egg (200 parts per trillion), an environmentally relevant dose. Daily LED treatment after TCDD exposure reduced embryonic mortality by 47%. LED treatment of TCDD-exposed eggs also decreased the hepatic oxidized-to-reduced glutathione ratio by 88%. Activities of other hepatic indicators of oxidative stress, such as glutathione reductase and catalase, were increased after LED treatment of TCDD-exposed eggs. Our study demonstrates that 670 nm phototherapy can mitigate the oxidative stress and energy deficit resulting from developmental exposure to TCDD while reducing TCDD-induced embryo mortality. Moreover, LED treatment restores hepatic enzyme activities to control levels in TCDD-exposed embryos. The effective attenuation of TCDD-induced embryo toxicity by LED treatment could extend to mitigating the effects of other teratogens that induce oxidative and energy stress.

Adenosine Triphosphate↗
PubMed2004

Quantification of naphthalenes in jet fuel with GC x GC/Tri-PLS and windowed rank minimization retention time alignment.

Comprehensive, two-dimensional gas chromatography (GC x GC) is used in conjunction with trilinear partial least squares (Tri-PLS) to quantify the percent weight of naphthalenes (two-ring aromatic compounds) in jet fuel samples. The increased peak capacity and selectivity of GC x GC makes the technique attractive for the rapid, and possibly less tedious analysis of jet fuel. The analysis of complex mixtures by GC x GC is further enhanced through the use of chemometric techniques, including those designed for use on 2-D data such as Tri-PLS. Unfortunately, retention time variation, unless corrected, can be an impediment to chemometric analysis. Previous work has demonstrated that the effects of retention time variation can be mitigated in sub-regions of GC x GC chromatograms through the application of an objective retention time alignment algorithm based on rank minimization. Building upon this previous work, it is demonstrated here that the effects of retention time variation can be mitigated throughout an entire GC x GC chromatogram with an objective retention time alignment algorithm based on windowed rank minimization alignment. A significant decrease in calibration error is observed when the algorithm is applied to chromatograms prior to construction of Tri-PLS models. Fourteen jet fuel samples with known weight percentages of naphthalenes (ASTM D1840) were obtained. Each sample was subjected to five replicate five-minute GC x GC separations over a period of two days. A subset of nine samples spanning the range of weight percentages of naphthalenes was chosen as a calibration set and Tri-PLS calibration models were subsequently developed in order to predict the naphthalene content of the samples from the GC x GC chromatograms of the remaining five samples. Calibration models constructed from GC x GC chromatograms that were retention time corrected are shown to exhibit a root mean square error of prediction of roughly half that of calibration models constructed from uncorrected chromatograms. The error of prediction is lowered further to a value that nearly matches the uncertainty in the standard percent weight values (ca. 1% of the median percent volume value) when the aligned chromatograms are truncated to include only regions of the chromatogram populated by naphthalenes and compounds of similar polarity and boiling point.

Journal Article↗
PubMed2005

An application of propensity score matching using claims data.

BACKGROUND: Confounding by indication is a common problem in pharmacoepidemiology, where predictors of treatment also have prognostic value for the outcome of interest. The tools available to the epidemiologist that can be used to mitigate the effects of confounding by indication often have limits with respect to the number of variables that can be simultaneously incorporated as components of the confounding. This constraint becomes particularly apparent in the context of a rich data source (such as administrative claims data), applied to the study of an outcome that occurs infrequently. In such settings, there will typically be many more variables available for control as potential confounders than traditional epidemiologic techniques will allow. METHODS: One tool that can indirectly permit control of a large number of variables is the propensity score approach. This paper illustrates the application of the propensity score to a study conducted in an administrative database, and raises critical issues to be addressed in such an analysis. In this example, the effect of statin therapy on the occurrence of myocardial infarction was examined, and numerous potential confounders of this association were adjusted simultaneously using a propensity score to form matched cohorts of statin initiators and non-initiators. RESULTS: The incidence of myocardial infarction observed in the statin treated cohort was lower than the incidence in the untreated cohort, and the magnitude of this effect was consistent with results from randomized placebo controlled clinical trials of statin therapy. CONCLUSIONS: This example illustrates how confounding by indication can be mitigated by the propensity score matching technique. Concerns remain over the generalizability of estimates obtained from such a study, and how to know when propensity scores are removing bias, since apparent balance between compared groups on measured variables could leave variables not included in the propensity score unbalanced and lead to confounded effect estimates.

Cohort Studies↗