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PubMed2005

Model comparison for risk assessment: a case study of contaminated groundwater.

Many environmental multimedia risk assessment models have been developed and widely used along with increasing sophistication of the risk assessment method. Despite of the considerable improvement, uncertainty remains a primary threat to the credibility of and users' confidence in the model-based risk assessments. In particular, it has been indicated that scenario and model uncertainty may affect significantly the assessment outcome. Furthermore, the uncertainty resulting from choosing different models has been shown more important than that caused by parameter uncertainty. Based on the relationship between exposure pathways and estimated risk results, this study develops a screening procedure to compare the relative suitability between potential multimedia models, which would facilitate the reduction of uncertainty due to model selection. MEPAS, MMSOILS, and CalTOX models, combined with Monte Carlo simulation, are applied to a realistic groundwater-contaminated site to demonstrate the process. It is also shown that the identification of important parameters and exposure pathways, and implicitly, the subsequent design of uncertainty reduction and risk management measures, would be better-formed.

Animals↗

PubMed2005

The use of sandwich-cultured rat hepatocytes to determine the intrinsic clearance of compounds with different extraction ratios: 7-ethoxycoumarin and warfarin.

The application of sandwich-cultured rat hepatocytes for the identification of the hepatic intrinsic clearance of compounds with widely varying extraction ratios was investigated. We previously showed the applicability of this in vitro system, in combination with a model describing molecular diffusion, hepatocyte/medium partition, and nonsaturated metabolism, which resulted in a successful identification of this parameter for tolbutamide. This approach is further validated using the compounds 7-ethoxycoumarin and warfarin, covering a 100-fold range of extraction ratios. Clearance of these two substrates could be reliably determined, but only if the depletion of the parent compound in medium as well as in the hepatocyte sandwich was measured. Sensitivity analyses showed that the time course of depletion of the parent compound in medium, especially for warfarin, is insensitive to the partition and diffusion parameter values, whereas depletion in the hepatocyte sandwich was far more sensitive. When varying the volumes of collagen in the sandwich culture, it appears that the most reliable kinetic parameters could be obtained by fitting the data with the smaller collagen volume and that these parameters obtained from fitting to data of the larger volumes generally cannot be verified satisfactorily with the data of the smaller volumes. The values of hepatic clearance that were obtained after extrapolation of the intrinsic clearance to the hepatic clearance from blood were comparable within a factor of 2 to hepatic clearance data in the literature. This indicates that this sandwich culture and modeling system can be applied for the identification of the hepatic intrinsic clearance rate of the total range from low to high clearance compounds.

Animals↗

PubMed1994

Identification of Leishmania isolates from a Lebanese population.

We report the results of enzymatic patterns of isolates of Leishmania cultured from patients referred to Department of Dermatology of the American University of Beirut Medical Center in Lebanon. The results reveal that these Lebanese isolates are all very similar despite variable clinical presentations of the patients and differences in geographic origin. Leishmania donovani sensu lato is the dominant species present in the skin lesions observed; thus, clinical manifestations and/or geographic distribution cannot be used as reliable criteria for identifying Leishmania parasites from this geographic area. Enzyme data should be combined with these parameters before definitive identification can be made.

Adolescent↗

PubMed2006

Validation of a calibration technique for 6-DOF instrumented spatial linkages.

This paper presents a practical and effective approach to the calibration of instrumented spatial linkages for biomechanical applications. A 6-DOF mechanical linkage with rotational transducers is designed and in-house manufactured for this purpose. In order to assess the validity of the proposed calibration technique and to distinguish between geometrical and electrical parameters uncertainties, high-precision optical encoders are used and calibration is addressed from a kinematic point of view only. The proposed technique is based on a closed-loop method, in which the end segments of the linkage are connected to each other by revolute joints. A parametrical model of the system is formulated using a standard link-to-link transformation matrices approach. Continuous data collection is carried out and a recursive identification of kinematic parameters is implemented by the use of an extended Kalman filter algorithm. Results shows that the proposed technique, despites its simplicity, is effective in improving the accuracy of the system up to its theoretically computed resolution, which limits the performance of the real system.

Algorithms↗

PubMedDate not supplied

Quality index of radiological devices: results of one year of use.

PURPOSE: The physical quality index (QI) of radiological devices summarises in a single numerical value between 0 and 1 the results of constancy tests. The aim of this paper is to illustrate the results of the use of such an index on all public radiological devices in the Livorno province over one year. MATERIALS AND METHODS: The quality index was calculated for 82 radiological devices of a wide range of types by implementing its algorithm in a spreadsheet-based software for the automatic handling of quality control data. RESULTS AND DISCUSSION: The distribution of quality index values was computed together with the associated statistical quantities. This distribution is strongly asymmetrical, with a sharp peak near the highest QI values. The mean quality index values for the different types of device show some inhomogeneity: in particular, mammography and panoramic dental radiography devices show far lower quality than other devices. In addition, our analysis has identified the parameters that most frequently do not pass the quality tests for each type of device. Finally, we sought some correlation between quality and age of the device, but this was poorly significant. CONCLUSIONS: The quality index proved to be a useful tool providing an overview of the physical conditions of radiological devices. By selecting adequate QI threshold values for, it also helps to decide whether a given device should be upgraded or replaced. The identification of critical parameters for each type of device may be used to improve the definition of the QI by attributing greater weights to critical parameters, so as to better address the maintenance of radiological devices.

Algorithms↗

PubMedDate not supplied

[Medical criminological personality identification by morphological signs of upper limbs segments].

Studies of the morphology of segments of human upper limbs helped develop a method for medical criminological personality identification by metric parameters of the arm and hand in expert evaluation of a dismembered corpse. The sampling consisted of 270 corpses of Europeoids of both sexes (150 men and 120 women) aged 17-98 years. Ten quantitative signs of the upper limbs were analyzed. Statistical modeling of body length and weight and of head and chest circumferences was performed on the basis of the hand, arm, and forearm characteristics. The data can be used for rapid personality identification in criminal cases, war actions, terroristic acts, and calamities with multiple victims.

Adolescent↗

PubMedDate not supplied

From basic science to clinical practice: use of cytokines and chemokines as therapeutic targets in renal diseases.

Cytokines are soluble factors that are critical for the pathophysiology of the immune system and exhibit other important functions. Recently, several cytokines have been suggested as possible therapeutic targets in renal diseases, and their possible clinical utility is now being tested in phase I-II clinical trials. Chemokines are a family of small, structurally related, cytokines that regulate cell trafficking of different subsets of leukocytes, thus critically regulating renal inflammation. The initial hope that targeting of chemokines may result in the attenuation of inflammation without inducing generalized immunosuppression is hampered by the redundancy in chemokine activity with the potential risk of severe side effects. However, a deep comprehension of the complex biology of chemokines has allowed the identification of some chemokine receptors as possible theraputic targets in the pathogenesis of selected renal diseases, in as much as they display non-redundant roles. More importantly the discovery of the critical involvement of CXCR3 in transplant tolerance, suggests that this chemokine receptor might represent a critical target for treatment of both acute rejection and chronic allograft nephropathy. Finally, we recently demonstrated that pretransplant serum levels of CXCL10/IP-10, a CXCR3-ligand, represent a clinically useful parameter for the identification of subjects exhibiting high risk of acute rejection, chronic allograft nephropathy and graft failure, a finding that might be used to individualize immunosuppressive therapies.

Animals↗

PubMed2004

Effects of sire misidentification on estimates of genetic parameters for birth and weaning weights in Hereford cattle.

Birth weights (4,155) and weaning weights (3,884) of Line 1 Herefords collected at the Fort Keogh Livestock and Range Research Laboratory in Miles City, MT, between the years of 1935 to 1989 were available. To study the effect of misidentification on estimates of genetic parameters, the sire identification of calf was randomly replaced by the identification of another sire based on the fraction of progeny each sire contributed to a yearly calf crop. Misidentification rates ranged from 5 to 50% with increments of 5%. For each rate of misidentification, 100 replicates were obtained and analyzed with single-trait and two-trait analyses with a restricted maximum likelihood (REML) algorithm. Two different models were used. Both models contained year x sex combinations and ages of dam as fixed effects, calendar birth date as a fixed covariate, and random animal and maternal genetic effects and maternal permanent environment effects. Model 2 also included sire x year combinations as random effects. As the rate of misidentification increased, estimates of the direct-maternal genetic correlation increased for both traits, with both models, for all analyses. With singletrait analyses, estimates of the fraction of variance that were due to sire x year interaction effects increased slightly for birth weight (near zero) and decreased slightly (0.015 to 0.004) for weaning weight as misidentification increased. With two-trait analyses, estimates of fraction of variance that were due to sire x year effects gradually decreased for weaning weight as misidentification increased. With the two-trait analyses, and with both models, as the level of sire misidentification increased, estimates of the genetic correlation between direct effects gradually increased, and estimates of the correlation between maternal effects gradually decreased. Estimates of the direct-maternal genetic correlation were more positive with Model 2 than with Model 1 for all levels of misidentification. Results of this study indicate that misidentification of sires would severely bias estimates of genetic parameters and would reduce genetic gain from selection.

Animal Identification Systems↗

PubMed2006

Automated biometrics-based personal identification of the Hunter-Schreger bands of dental enamel.

The use of automated biometrics-based personal identification systems is a ubiquitous procedure in present times. Biometrics has certain limitations, such as in cases when bodies are decomposed, burned, or only small fragments of calcified tissues remain. Dental enamel is the most mineralized tissue of organisms and resists post-mortem degradation. It is characterized by layers of prisms of regularly alternating directions, known as Hunter-Schreger bands (HSB). In this article, we show that the pattern variation of the HSB, referred here as toothprint, can be used as a biometric-based parameter for personal identification in automated systems.

Biometry↗

PubMed1999

Identification of ataxia telangiectasia heterozygotes, a cancer-prone population, using the single-cell gel electrophoresis (Comet) assay.

Heterozygotes of ataxia telangiectasia (AT) may comprise up to 1% of the general population. Because these individuals have no clinical expression of AT but may be highly radiosensitive and strongly predisposed for several forms of cancer, identification of AT carriers represents a considerable interest in cancer epidemiology and radiotherapy. We report a new approach for the in vitro identification of AT-heterozygotes based on the evaluation of the radiosensitivity and DNA damage repair ability of peripheral blood mononuclear cells using the single-cell gel electrophoresis (Comet) assay. The assay was performed on cells isolated from four different groups of individuals: (1) apparently healthy donors (n = 10); (2) patients with breast cancer showing a normal reaction to radiotherapy (n = 10); (3) a group of obligate AT carriers (parents of AT-homozygotes, n = 20); and (4) AT-homozygotes (n = 4). Cells irradiated with 3 Gy of x-rays were assayed for three parameters: (1) the initial and (2) residual DNA damage and (3) the kinetics of DNA damage repair. Both AT-heterozygotes' and AT-homozygotes' cells were found to be highly sensitive to x-irradiation. Quantitative evaluation of the single-cell electrophoregrams revealed that the average initial DNA damage in AT-heterozygous and AT-homozygous cells was almost three times higher than that in control non-AT cells. In addition, the DNA repair process in irradiated AT carrier cells was almost three times slower, and the extent of irreparable DNA damage in these cells was three times greater than in controls. Simultaneous assessment of the three parameters enabled correct identification of all tested AT carriers. This method seems to be a sensitive and useful tool for populational studies as a rapid prescreening test for a mutated AT status. The approach can also be extended for prediction of the in vivo radiosensitivity, which would enable optimization of individual radiotherapy schedules.

Adolescent↗

PubMed2006

Designing experiments that aid in the identification of regulatory networks.

Predictive mathematical models of the interactions of a genetic network can provide insight into the mechanisms of gene regulation, the role of various genes within a network and how multiple genes interact leading to complex traits. However, identification of the parameters and interactions is currently a limiting step in the development of such models. This work reviews the state of the art for design of experiments in biological systems and demonstrates the need for improved design of experiments through the use of a model system. Appropriate design of experiments has a profound impact on the ability to identify a model and on the quality of resulting identified model. Key issues include the selection of appropriate input sequences (e.g. random, independent multivariate inputs) and the selection of the sampling frequencies. This work demonstrates that these issues are especially important in the identification of biochemical networks and that the traditional biochemical approach is incapable of truly identifying the behavior present in such networks.

Computational Biology↗

PubMed2005

Characterization of natural organic matter (NOM) derived from sewage sludge compost. Part 2: multivariate techniques in the study of compost maturation.

This study presents the results of chemometric data analysis which describes the maturation of sewage sludge compost. The compost was characterized at different stages of maturation by various chemical and spectroscopic parameters including carbon and nitrogen content, humic substances content, UV-Vis and 13C NMR. The data set of compost characteristics was analyzed using multivariate methods: cluster analysis (CA) and principal component analysis (PCA). The results enabled the determination of three groups of compost samples at different stages of maturation that correspond to three stages of composting: (i) domination of rapid decomposition of non-humic, easily biodegradable organic matter, (ii) domination of organic matter humification and formation of polycondensed, humic-like substances (the next 2 weeks), (iii) stabilization of transformed organic material and weak microbial activity. The multivariate techniques also enabled the identification of main parameters that change during different stages of composting the most.

Algorithms↗

PubMed2001

Testing parameters in structural equation modeling: every "one" matters.

A problem with standard errors estimated by many structural equation modeling programs is described. In such programs, a parameter's standard error is sensitive to how the model is identified (i.e., how scale is set). Alternative but equivalent ways to identify a model may yield different standard errors, and hence different Z tests for a parameter, even though the identifications produce the same overall model fit. This lack of invariance due to model identification creates the possibility that different analysts may reach different conclusions about a parameter's significance level even though they test equivalent models on the same data. The authors suggest that parameters be tested for statistical significance through the likelihood ratio test, which is invariant to the identification choice.

Humans↗

PubMed2004

Mechanical properties of selfexpandable stents.

The stents or stentgrafts (covered stents) are the medical instruments used in invasive radiology for miniinvasive treatment of stenosis and aneurisms especially in the blood circulation system. We measured and compared the mechanical parameters of different selfexpandable Nitinol stents, which differed in the geometry (radius and length), in the type of construction (number of branches and rising of winding) and in the diameter of the used wire. The results of measurements confirmed the theoretical assumptions that just the diameter of the Nitinol wire significantly influences the rigidity and the level of compressibility of the stent as well. The compromise must be found between the required rigidity of the stent and the minimal size of the delivery system. The exact description of the relation between the mechanical properties and geometry and construction of the stents enables us to design the stent to fit the patient's needs. The results of measurement are also necessary for the design and identification of the parameters of the models of the stents.

Alloys↗

PubMed1999

Viral validation design of a manufacturing process.

In many cases, the viral safety evaluation of biological products does not derive solely from direct testing for the presence of contaminants, but also from the demonstration that the manufacturing process is able to inactivate/eliminate them. This is achieved by the voluntary addition of a virus load at various steps of the process and the evaluation of viral reduction during the subsequent steps. The major difficulty for such viral validation studies is less to calculate a reduction factor for each step than to identify clearly and demonstrate the contribution of each in-process parameter to the reduction. Consequently, the first approach consists of the identification of all the parameter which may influence viral reduction. The design of the viral validation needs to take this inventory into account and control experiments must be carried out in parallel with the main spiking experiment, i.e. mainly to: (i) hold controls with and without the biological intermediate product; (ii) control experiments with each individual inactivating/partitioning parameter; (iii) control experiment without stabilizer if necessary. In addition to these process controls, cytotoxicity and interference experiments will allow the use of each in vitro infectivity assay for the testing of processed samples to be validated. For a viral inactivation step, the kinetics of inactivation will be studied and the data will show: (i) a progressive decrease of the viral load over time. If the decrease is too rapid to plot the kinetics, the direct relation between the inactivation and the inactivating parameter has to be demonstrated in complementary experiments; (ii) the reduction obtained when in-process limits are used and (iii) the different phases of inactivation when they exist. Moreover, it is pertinent to evaluate for each treatment the margin of safety derived from the treatment time on the one hand and the strength of the inactivating parameter on the other.

Animals↗

PubMed1994

[Risk of hematogenous metastasis of cancer of the uterine cervix].

Metastasis development in cervical cancer was analysed retrospectively to determine whether haematogenic metastases occurred with higher frequency in younger women than in older women. Based on clinical and morphologic data, parameters for the identification of a high-risk group for the development of haematogenic metastases were established. The data of 533 patients who underwent therapy at the University Women's Hospital Berlin-Charlottenburg from 1970 to 1984 were evaluated. 11.8% of these patients developed haematogenic metastases. No significant difference was found in the 5-year risk for development of haematogenic metastases between different age groups. Furthermore, no increase in the incidence of haematogenic metastases was found in women under 35 years in the course of time. The influence of pretreatment characteristics for the development of haematogenic metastases was assessed in 185 patients who underwent surgery for cervical cancer from 1979 to 1984. Univariate as well as multivariate regression analysis of histopathologic characteristics in the surgical specimens revealed blood vessel invasion, tumour grading, dissociated tumour growth, and number of mitoses as important parameters for the occurrence of haematogenic metastases. In this study group, patient age strongly influenced the occurrence of haematogenic metastases. In contrast, prognostic parameters for the development of local recurrence of the disease were derived from morphologic data which described the locoregional spread of the tumour (staging, tumour growth beyond the cervix, involvement of the corpus uteri, and lymph node involvement).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2005

Gamma interferon-producing CD4 T-cells correlate with resistance to Mycoplasma mycoides subsp. mycoides S.C. infection in cattle.

Contagious bovine pleuropneumonia (CBPP), caused by Mycoplasma mycoides subsp. mycoides SC (MmmSC), is one of the most significant cattle disease in Africa. The control measures, which led to eradication from numerous countries are not feasible in Africa where the only prophylaxis relies on vaccination. However, the attenuated vaccines, used up to now in Africa, are of low efficiency. The development of an improved vaccine is, therefore, a necessity. The purpose of this study was to compare some immunological parameters in MmmSC-infected cattle (endobronchial versus natural in-contact infection) and assess the response in correlation with the clinical outcome (death versus recovery). Characterization of the immune parameters elicited in recovered animals, known to be refractory to new infection, will be an important step towards development of new vaccines against CBPP. A significant outcome of this study was the demonstration that all MmmSC-infected cattle developed a MmmSC-specific cell-mediated immune response. A kinetic analysis of the MmmSC responsiveness showed that the main difference between endobronchially- and in-contact infected animals was the delay before the onset of the MmmSC-specific immune response. The first MmmSC-responding PBMC sample was selected from each animal for cell phenotyping. The phenotypic analysis of this early MmmSC-induced response revealed the predominant contribution of the CD4 T-cells in all animals whereas IFNgamma was only constantly produced in recovered animals. Evolution of this early MmmSC-specific immune response was then followed by a kinetic analysis of the MmmSC-induced CD4 T-cell response and IFNgamma released. The results demonstrated that in recovered animals, the MmmSC-specific CD4 Th1-like T-cell response was maintained until slaughtering whereas in animals with acute disease, progression of CBPP was associated with a decreased ability of the PBMC to produce IFNgamma. The results led to the identification of immune parameters, which correlate with protection against CBPP and to a relevant strategy for the development of improved vaccines against this disease.

Animals↗

PubMed2002

A conceptual model for defining and assessing land management units using a fuzzy modeling approach in GIS environment.

Appropriate land management decisions are important for current and future use of the land to ensure its sustainability. This requires that land management units (LMUs) be specified to enable the identification of specific parameters employed in decision making processes. This paper presents the development of a conceptual model, within geographic information systems (GIS), for defining and assessing LMUs from available biophysical information. The model consists of two main components (sub-models): land quality-based suitability analysis and soil erosion estimation. Using a fuzzy set methodology, the first sub-model was constructed to derive a land suitability index (LSI) for a cropping land utilization type. The LSI thus highlights the suitability grades of every pixel in the study area on a continuous basis. A submodel of soil erosion was established based on the Revised Universal Soil Loss Equation (RUSLE) utilising the same spatial data bases employed for structuring the LSI. Using a soil loss tolerance principle, a fuzzy membership function of average annual soil loss (called soil loss index, SLI) was established, leading to compatibility between LSI and SLI for data integration. LMUs were then derived from various combinations of LSI and SLI. The methodology developed shows the significance of the model for refining available land suitability evaluation systems, which take no account of expected land degradation (from erosion) due to a nominated land use. It also provides a valuable guideline for cost-effective GIS applications in the identification and assessment of homogeneous land units, using available spatial information sets, at a finer scale.

Conservation of Natural Resources↗