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PubMedDate not supplied

Serum zinc and protein levels: lack of a correlation in hospitalized patients with AIDS.

Abnormally low serum zinc levels are associated with advanced states of malnutrition. Zinc levels are thought to parallel serum albumin, and repletion of zinc has reportedly led to increased albumin. We examined the correlation between zinc deficiency and serum proteins in hospitalized patients with AIDS. Over 500 inpatient consultations were performed by our Gastroenterology-Nutrition Consult Service from May 1992 to June 1994. We reviewed the medical records from all 228 AIDS patients in whom a serum zinc level was measured (by atomic absorption spectrophotometry). The correlation between serum zinc, albumin, prealbumin, and transferrin drawn on the same hospital day was analyzed by linear regression. The patients were stratified by the level of albumin, group A albumin < 2.0 g/dL, group B albumin 2.0-2.9 g/dL, and group C albumin > 3.0 g/dL, to allow comparison of the incidence of diarrhea and mean zinc level by chi square. Thirty-four patients had more than one serum zinc and albumin determination; the change over time was compared by linear regression. Serum zinc and albumin, prealbumin, and transferrin levels did not correlate strongly (r2 < or = 0.01). Furthermore, changes in zinc over time did not correlate with parallel changes in serum albumin (r2 < or = 0.01). In patients grouped by albumin, the proportion of patients with diarrhea did not differ significantly. The mean zinc levels were also not statistically significantly different. Serum zinc levels do not strongly correlate with serum proteins in hospitalized patients with AIDS. Serial measures of zinc over time also do not correlate strongly with changes in albumin. The incidence of diarrhea was not significantly different in patients with hypoalbuminemia or hypozincemia when compared with patients with near normal albumin or zinc. The relationship between zinc and serum proteins in AIDS patients is not linear. Zinc deficiency should be assessed in patients independent of the serum albumin.

Acquired Immunodeficiency Syndrome↗

PubMed2000

Psychophysiological correlates of social skills deficits in persons with schizophrenia.

Social skill deficits in schizophrenia profoundly affect patients' life-long outcome, although the profile of the underlying cognitive dysfunction still remains a matter of debate. In the present study, we investigated the relationship between social skills and event-related potentials (ERPs) in an auditory selective attention task, in addition to the neurocognitive indices obtained from the degraded-stimulus continuous performance test (CPT) and clinical indices, such as Brief Psychiatric Rating Scale (BRPS) and global assessment of function (GAF) scores. Social skills were assessed using a Japanese version of the structured role play test. Fourteen persons with schizophrenia participated in the study. Non-verbal skills showed a positive correlation with GAF, the performance level, N1 and N2b amplitude in the ERP task, and hit rate in the CPT, and a negative correlation with reaction time in the CPT. Verbal communication skills showed a positive correlation with GAF, the performance level and N2b amplitude in the ERP task, and hit rate in the CPT, and a negative correlation with reaction time in the CPT. Processing skills showed a positive correlation with the performance level and N1 amplitude in the ERP task and a negative correlation with reaction time in the CPT. These findings suggested that the social skill deficits of persons with schizophrenia were related to the vigilance level and controlled stimulus detection processing.

Adult↗

PubMed2001

Correlation of abdominal fat accumulation and liver steatosis: importance of ultrasonographic and anthropometric measurements.

PURPOSE: This study has two objectives: (1) using ultrasound (US) as a tool for measuring subcutaneous (S) and intra-abdominal; preperitoneal (P) and visceral (V) fat thickness. (2) Assessing the relationship between selected anthropometrical variables and US-measured S, P and V fat also evaluating the contribution of abdominal fat accumulation in development of liver steatosis. METHODS AND MATERIALS: Sixty-eight obese patients (aged 43.9+/-9.3 years) and 40 non-obese subjects (aged 34.03+/-9.0 years) were recruited to this study. Height, weight (W), waist (WC) and hip circumferences were measured. Body mass index (BMI) and waist to hip ratio (WHR) were calculated. A linear-array probe (7.5 MHz) was used to measure S and P. A convex-array probe (3.5 MHz) was used for measuring V and assessing liver fatty infiltration. RESULTS: In 45 (66%) patients, there were diffuse liver fatty changes. Liver steatosis showed significant correlation with V (r=0.57), P (r=0.38) and S (r=0.37). It also correlated with W (r=0.52), BMI (r=0.6), WC (r=0.45) (P<0.0001). V positively correlated with BMI (r=0.62), W (r=0.55), WC (r=0.52) and WHR (r=0.33). P correlated with WC (r=0.29), WHR (r=0.36) and W (r=0.34), but not with BMI, height and age. A significant correlation was found between S and BMI (r=0.73), W (r=0.65), and WC (r=0.57) (P<0.0001). CONCLUSION: Obese patients showed thicker S, P, and V. Liver steatosis correlates significantly with both anthropometrical data; BMI, WHR, WC, and W, and with abdominal V, P, and S fat. V fat can be used as a good predictor for the possibility of different metabolic disorders and liver disturbances as steastosis.

Abdomen↗

PubMed2004

Correlation analysis of the skull and long bone measurements of the dog.

In this study, a heterogeneous population of 42 dogs was examined for correlation between skull and long bone measurements. For this purpose, 17 craniometric measurements were carried out and used to calculate 12 indices and ratios. These indices and ratios were then subjected to a correlation analysis with long bone measurements. While a high significant negative correlation of p < 0.05 and p < 0.01 respectively was found for skull, cranial and facial I1, I2, LLI-2, BI and BI-1 indices, and the CFO and CFO-1 ratios respectively with respect to the non-indexed long bone measurements, a high positive correlation was found to exist between those indices and ratios, and the long bone indices (p < 0.01). The correlation coefficients for the skull indices and ratios to long bone measurements proved to be very similar for the long bones of front and hind legs. As a result of the correlation analysis, it was found that with an increase in skull tendency towards the dolichocephalic type, the long bone parameters also increase, while with the skull tending towards the brachycephalic type, the long bone parameters decrease. This finding of a long bone-related increase in dimensions and morphological skull expression favours the assumption of a close relation to the skull typology.

Animals↗

PubMed2003

Developmental hemispheric asymmetry of interregional metabolic correlation of the auditory cortex in deaf subjects.

The functional connectivity of the auditory cortex might be altered in deaf subjects due to the loss of auditory input. We studied the developmental changes of functional connectivity of the primary auditory cortex (A1) in deaf children, deaf adults, and normal hearing adults by examining interregional metabolic correlation with (18)F-FDG PET. The mean activity of FDG uptake in the cytoarchitectonically defined A1 region served as a covariate in the interregional and interhemispheric correlation analysis. A1 metabolic rate was correlated with that of the ipsilateral superior temporal lobe in both normal and deaf subjects. This correlated area was larger in deaf children than in deaf or normal hearing adults. Concerning the functional connectivity of A1, a hemispheric asymmetry was found in that the extent of interregional correlation was clearly larger in the right than in the left hemisphere. This asymmetry was particularly pronounced in the younger deaf children. Both extent and asymmetry of the functional connectivity of A1 subsided with age. Contrary to this, a correlation between the left and the right primary auditory cortices was absent in younger deaf children but became apparent as they grew older.

Adolescent↗

PubMed2003

Alzheimer's disease and frontotemporal dementia exhibit distinct atrophy-behavior correlates: a computer-assisted imaging study.

RATIONALE AND OBJECTIVES: The purpose of this study was to test the hypothesis that distinct patterns of gray matter atrophy are responsible for unique interruptions of the naming process in Alzheimer's disease (AD) and frontotemporal dementia (FTD). MATERIALS AND METHODS: Voxel-based morphometry (VBM) was performed to characterize at the voxel level the neuroanatomic changes that occur in AD and FTD based on high-resolution T1-weighted three-dimensional (3D) spoiled-gradient echo images of patients (AD, n = 12; FTD, n = 29) and healthy control subjects (n = 12). The cortical atrophy measurements were correlated with performance on behavioral measures of naming and related processes to identify brain regions that may contribute to this language function. RESULTS: Both AD and FTD have significant naming difficulty, and this difficulty in naming correlates with a measure of lexical retrieval in both patient groups as well. However, only FTD patients showed a correlation with semantic memory. Areas of cortical atrophy common to AD and FTD were found in the anterior temporal, posterolateral temporal, and dorsolateral prefrontal regions of the left hemisphere. Correlation with naming in both AD and FTD was seen in the left anterior temporal cortex, suggesting that this area may play a role in the lexical retrieval component of naming. We also observed several unique areas of cortical atrophy in temporal and frontal cortices of these patients. Right anterior temporal and left posterolateral temporal regions of atrophy correlated with naming difficulty in FTD, suggesting that these areas may contribute to the semantic memory component of naming. Cortical areas correlating with naming that are not atrophic may represent regions that play an optional role in naming. CONCLUSION: VBM provides an important first step in analyzing brain-behavior relations in vivo in patients with neurodegenerative diseases. More refined analyses of brain morphology via high-dimensional normalization methods that are capable of modeling local as well as global variability in neuroanatomical structure promise to be even more informative.

Aged↗

PubMed2003

Correlation between Doppler vascular density and PSA response to radiation therapy in patients with localized prostate carcinoma.

RATIONALE AND OBJECTIVES: The authors performed this study to ascertain whether there is a correlation between pretreatment Doppler vascular density (DVD) of the prostate and prostate-specific antigen (PSA) response following radiation therapy in prostate cancer patients. MATERIALS AND METHODS: Prior to radiation therapy, 14 patients with biopsy-proven carcinoma (of Gleason grades 2-7) were imaged with transrectal ultrasound in gray-scale, color Doppler, and power Doppler modes. The Doppler images were analyzed for mean DVD with the aid of a computer program. PSA levels were measured before therapy and every 3 months after therapy. The PSA measurements were fitted to an exponential to determine PSA halving time (T1/2). Correlations were made between T1/2 and the following pretherapy measurements: mean DVD, PSA level, prostate volume, and Gleason grade. RESULTS: Median follow-up time was 392 days. A linear correlation with regression coefficient (R) of 0.75-0.80 was observed between mean DVD and T1/2 for color Doppler and power Doppler imaging. In both imaging modes, each percentage increase in mean DVD led to an increase in T1/2 by 25 days. Pretherapy prostate volume, PSA level, and Gleason score did not correlate with T1/2. CONCLUSION: The pretreatment mean DVD correlates inversely with the rate of posttherapy decline in PSA in patients with prostate cancer. That is, pretreatment vascularity prognosticates postirradiation PSA response. The mechanism underlying this correlative relationship is not known.

Adenocarcinoma↗

PubMed1997

Texture analysis of direct magnification radiographs of vertebral specimens: correlation with bone mineral density and biomechanical properties.

RATIONALE AND OBJECTIVES: The authors used direct magnification radiographs, combines with texture analysis, to investigate the trabecular structure of human vertebral specimens and compared these techniques with measurement of bone mineral density (BMD) by using quantitative computed tomography to predict bone strength. METHODS: Direct magnification radiographs and BMD measurements were obtained from 38 motion segments from the thoracolumbar spines of 11 female human cadavers. Maximum compressive strength (MCS) was determined with a materials testing machine. Morphologic parameters, digital skeletons, and fractal dimension were obtained from the radiographs in three different regions of interest. RESULTS: Correlations between BMD and MCS were statistically significant (r = .81, P < .01). With morphologic parameters, correlation coefficients of up to .64 (P < .01) were obtained. Use of multivariate regression analysis with one morphologic parameter (the width of the black pixels, or thicknessB) in addition to BMD improved correlations versus MCS (P < .01). CONCLUSION: In an experimental setting, BMD showed statistically significant correlation with bone strength, whereas the structural parameters demonstrated only modest correlations. BMD together with one of these measures (thicknessB), however, showed the highest correlation.

Adult↗

PubMed2000

[Non-palpable breast lesions: radio-pathologic correlations on open excisional biopsies. Significance of the choice of technique for minimal excisional biopsy].

OBJECTIVE: To decrease the number of open excisional breast biopsies, percutaneous breast biopsies have been developed to perform the histologic diagnosis of non-palpable breast lesions. Some techniques allow a complete removal of small radiologic lesions. To evaluate the accuracy of a pathologic analysis performed only on the radiologic findings, we studied the radiologic and histologic correlation on open excisional biopsy (OEB) specimens. The aim of our study was to determine how many carcinomas were found distant from the radiologic findings. MATERIAL AND METHODS: Non-palpable breast lesions have been excised after preoperative localization. The radiologic findings were classified in microcalcifications, masses, architectural distortion and in sonographic masses. The correlation between the radiologic and pathologic findings was studied and all the lesions incidentally discovered on histology with no correlation with the imaging findings or distant from the radiologic findings were described. One hundred and twenty-nine lesions have been evaluated in 99 patients. Radiologic findings included 79 clusters of microcalcifications, 30 masses, six architectural distortions and 14 sonographic lesions. RESULTS: The histopathological results were benign in 41.9%, malignant in 49.6% and atypical hyperplasia lesions were discovered in 8.5%. All benign lesions were correlated to radiologic findings. No malignant lesion was found at a distance. In three cases atypical hyperplasia lesions were coexistent with the radiologic findings correlated with benign lesions and in three cases they were found at a distance. All but two malignant lesions were correlated with radiologic findings. In two cases a microinvasive carcinoma and foci of labular carcinoma in situ were found coexistent with benign lesions. The subgroup of small lesions lesser than 10 mm included 31 benign lesions. A complete removal of these lesions should be obtained with percutaneous biopsies. CONCLUSION: A pathologic analysis targeted on radiologic findings is accurate. Numerous open excisional biopsies performed for benign pathology should be avoided.

Biopsy↗

PubMed2002

Correlation of bone mineral density with strength and microstructural parameters of cortical bone in vitro.

The aim of this study was to evaluate the influence of microstructural parameters, such as porosity and osteon dimensions, on strength. Therefore, the predictive value of bone mineral density (BMD) measured by quantitative computed tomography (QCT) for intracortical porosity and other microstructural parameters, as well as for strength of cortical bone biopsies, was investigated. Femoral cortical bone specimens from the middiaphysis of 23 patients were harvested during total hip replacement while drilling a hole (dia. 4.5 mm) for the relief of the intramedullary pressure. In vitro structural parameters assessed in histological sections as well as BMD determined by quantitative computed tomography were correlated with yield stress, and elastic modulus assessed by a compression test of the same specimens. Significant correlations were found between BMD and all mechanical parameters (elastic modulus: r = 0.69, p < 0.005; yield stress: r = 0.64, p < 0.005). Significant correlations between most structural parameters assessed by histology and yield stress were discovered. Structural parameters related to pore dimensions revealed higher correlation coefficients with yield stress (r = -0.69 for average pore diameter and r = -0.62 for fraction of porous structures, p < 0.005) than parameters related to osteons (r = 0.60 for osteon density and average osteonal area, p < 0.005), whereas elastic modulus was predicted equally well by both types of parameters. Significant correlations were found between BMD and parameters related to porous structures (r = 0.85 for porosity, 0.80 for average pore area, and r = 0.79 for average pore diameter in polynomial regression, p < 0.005). Histologically assessed porosity correlated significantly with parameters describing porous structures and haversian canal dimensions. Our results indicate a relevance of osteon density and fraction of osteonal structures for the mechanical parameters of cortical bone. We consider the measurement of BMD by quantitative computed tomography to be helpful for the estimation of bone strength as well as for the prediction of intracortical porosity and parameters related to porous structures of cortical bone.

Aged↗

PubMed2006

Structural brain correlates of IQ changes in bipolar disorder.

BACKGROUND: There is increasing evidence that cognitive deficits are present in bipolar disorder (BP), but their neural correlates have not been fully explored. The aim of this study is to correlate structural brain abnormalities with cognitive performance in BP and to explore differences between clinical subtypes. METHOD: Thirty-six BP patients (13 men, 23 women) with a mean age of 39 years (range 21-63 years) underwent neuropsychological testing and imaging. Twenty-five patients had bipolar disorder I (BP I) and 11 had bipolar disorder II (BP II). Patients with co-morbid psychiatric diagnosis, drug and alcohol abuse or systemic illness were excluded. Correlations between cognitive performance and structural brain changes were explored using high-resolution anatomical imaging and magnetization transfer imaging (MTI). RESULTS: In the whole BP group the difference between estimated pre-morbid IQ and current IQ was significantly correlated with left-sided reduction of the magnetization transfer ratio (MTR) in the superior temporal gyrus, uncus and para-hippocampal gyrus. In BP II patients the areas where these correlations were significant extended to the right superior and middle temporal gyri, cingulate gyrus, pre-cuneus and adjacent frontal and parietal white matter. The volume of superior temporal white matter was also correlated with IQ difference in this subgroup. CONCLUSIONS: The study highlights the association between fronto-temporal abnormalities and decline in IQ in BP. The more extensive abnormalities present in BP II patients suggest that persistent depression, rather than mania, may be a key pathophysiological factor or that BP II represents a clinical phenotype with a higher risk of developing cognitive abnormalities.

Adult↗

PubMedDate not supplied

An analysis of the cross-correlation between ganglion cells in the retina of goldfish.

Neighboring ganglion cells in the retinae of vertebrates show cross-correlation between their impulse trains. Cross-correlation is found both in maintained discharges and during responses to visual stimulation. There has been speculation about the function of this statistical dependence, but little is known about its genesis. This study examines the statistics of the interimpulse intervals preceding and those following impulses that coincide with an impulse in the other train. Short intervals are rarer than expected preceding a coincidence, regardless of the form of the cross-correlation. Short intervals are more common than expected following a coincidence when the cross-correlation is positive, but rarer than expected following coincidences during negative cross-correlation. These results contradict the extant models for cross-correlation, but may be explained by the multiplicative combination of a variable common input and the variability within each cell. In addition, the lag (relative timing of coincident impulses in the two cells) is found to be related to the maintained discharge rates of the cells, implying that the lags may be explained without invoking specific delay circuits.

Action Potentials↗

PubMed1998

Automation of data collection for matrix-assisted laser desorption/ionization mass spectrometry using a correlative analysis algorithm.

Automation of data collection in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry using a correlative analysis algorithm is demonstrated. This algorithm was employed to compensate for mass spectral jittering in MALDI data collection (e.g., peak shifts along the m/z axis, signal intensity deviations, etc.). Several important parameters for performing correlative analysis, such as the minimum correlation coefficient to be used and number of mass spectra to acquire prior to correlation, have been investigated and optimized. In addition, the correlation algorithm improved mass resolution of low- and high-molecular-weight compounds by as much as a factor of 4. Signal reproducibility in MALDI quantitative analysis also is improved when correlation is employed for data collection. This data collection algorithm can be used in conjunction with other instrumental optimization programs to allow for fully automated MALDI analysis, which is required for the routine applications carried out in many analytical laboratories.

Algorithms↗

PubMed2004

A linear correlation between the energetics of allosteric communication and protein flexibility in the Escherichia coli cyclic AMP receptor protein revealed by mutation-induced changes in compressibility and amide hydrogen-deuterium exchange.

Amino acid substitutions at distant sites in the Escherichia coli cyclic AMP receptor protein (CRP) have been shown to affect both the nature and magnitude of the energetics of cooperativity of cAMP binding, ranging from negative to positive. In addition, the binding to DNA is concomitantly affected. To correlate the effects of amino acid substitutions on the functional energetics and global structural properties in CRP, the partial specific volume (v(o)), the coefficient of adiabatic compressibility (beta(s)(o)), and the rate of amide proton exchange were determined for the wild-type and eight mutant CRPs (K52N, D53H, S62F, T127L, G141Q, L148R, H159L, and K52N/H159L) by using sound velocity, density measurements, and hydrogen-deuterium exchange as monitored by Fourier transform infrared spectroscopy at 25 degrees C. These mutations induced large changes in v(o) (0.747-0.756 mL/g) and beta(s)(o) (6.89-9.68 Mbar(-1)) compared to the corresponding values for wild-type CRP (v(o)= 0.750 mL/g and beta(s)(o)= 7.98 Mbar(-1)). These changes in global structural properties correlated with the rate of amide proton exchange. A linear correlation was established between beta(s)(o) and the energetics of cooperativity of binding of cAMP to the high-affinity sites, regardless of the nature of cooperativity, be it negative or positive. This linear correlation indicates that the nature and magnitude of cooperativity are a continuum. A similar linear correlation was established between compressibility and DNA binding affinity. In addition, linear correlations were also found among the dynamics of CRP and functional energetics. Double mutation (K52N/H159L) at positions 52 and 159, whose alpha-carbons are separated by 34.6 A, showed nonadditive effects on v(o) and beta(s)(o). These results demonstrate that a small alteration in the local structure due to amino acid substitution is dramatically magnified in the overall protein dynamics which plays an important role in modulating the allosteric behavior of CRP.

Allosteric Regulation↗

PubMed1996

Testing the correlation between delta A and delta V of protein unfolding using m value mutants of staphylococcal nuclease.

The application of hydrostatic pressure to aqueous protein solutions results in the unfolding of the protein structure because the protein-solvent system volume is smaller for the unfolded state. Contributions to this decrease in volume upon unfolding (delta Vu) derive from altered interactions of the protein with solvent and are presumed to include electrostriction of charged residues, elimination of packing defects, and hydration of hydrophobic surfaces upon unfolding. If the contribution of hydrophobic surface area solvation to the observed volume change of unfolding were large and negative, as is generally assumed, then one would expect to find a correlation between the amount of surface area exposed on unfolding, delta A(u), and the volume change, delta Vu. In order to test this correlation, we have determined delta Vu for two mutants of staphylococcal nuclease, A69T + A90S and H121P, whose unfolding by denaturant is, respectively, either significantly more (28%) or significantly less (28%) cooperative than that observed for wild-type (WT). This cooperativity coefficient or m value has been shown to correlate with delta A(u). If, in turn, delta Vu is correlated with delta A(u), we would expect the m+ mutant, A69T + A90S, to exhibit a delta Vu that is more negative than WT nuclease, while the delta Vu for the m- mutant, H121P, should be smaller in absolute value. To verify the correlation between m value and delta A(u) for these mutants, we determined the xylose concentration dependence of the stability of each mutant at atmospheric pressure and as a function of pressure. The efficiency of xylose stabilization was found to be much greater for the m+ mutant than for WT, consistent with an increase in delta A(u), while that of the m- mutant was found to be only slightly greater than for WT, indicating that other factors may contribute to the denaturant m value in this case. Regardless of the denaturant m value or the effect of xylose on stability, the volume changes upon unfolding for both mutants were found to be within error of that observed for WT. Thus, there does not appear to be a correlation between the volume change and the change in exposed surface area upon unfolding. We have previously shown a lack of pH dependence of the volume change, ruling out electrostriction as a dominant contribution to delta Vu of nuclease. These studies implicate either compensation between polar and nonpolar hydration or excluded volume effects as the major determinant for the value of delta Vu.

Chromatography, Gel↗

PubMed1998

Dynamics of the DNA binding domain of the fructose repressor from the analysis of linear correlations between the 15N-1H bond spectral densities obtained by nuclear magnetic resonance spectroscopy.

The spectral densities of the backbone and arginine side chain NH bonds of the DNA binding domain of the fructose repressor (FruR) were extensively analyzed in order to extract reliable motions parameters. An accurate measurement of 15N NMR relaxation rates allowed their calculation at three frequencies, zero, omegaN, and omegaH + omegaN, using a reduced matrix approach. Linear correlations were found between J(omegaN) and J(0) and between and J(0). The analysis of the compatibility between the motions parameters obtained independently from the two correlation lines allowed further development of the linear correlation approach proposed recently [Lefèvre, J. F., Dayie, K. T., Peng, J. W., and Wagner, G. (1996) Biochemistry 35, 2674-2686]. The results demonstrate (i) the existence of a concerted motion along the whole backbone with a global correlation time equal to 5.95 ns.rad-1, and (ii) the presence of complex internal movements at an intermediate time scale around 1 ns. The extracted motion parameters have been related to those obtained with the extended Lipari and Szabo approach but are incompatible with those obtained using the usual simple Lipari and Szabo approach. They were correlated to the features of the NMR structure of FruR(1-57)*. Some residues in the turns and in the third helix experience slow motions in the micro- to millisecond time scale. Side-chain motions are not correlated to the backbone dynamics. A direct examination of spectral densities reveals a higher flexibility for the side chains of arginines that are not involved in ionic bridges.

Amino Acid Sequence↗

PubMed2002

Correlation of poly(methylene)-rich amorphous aliphatic domains in humic substances with sorption of a nonpolar organic contaminant phenanthrene.

The structural makeup of natural organic matter plays a major role in regulating its capacity to retain nonionic hydrophobic organic compounds (HOCs). We used a model HOC--phenanthrene--to investigate the correlations between sorption capacity, specifically the modified Freundlich coefficient (K'f), and compositional data of humic acids, humins, and a peat obtained from quantitative 13C solid-state NMR spectroscopy. A positive correlation between K'f and the weight fraction of amorphous poly(methylene) in the sorbents was observed. In contrast, the correlation between phenanthrene sorption capacity and aromaticity or polarity indices of the sorbents was insignificant. The nonpolar aliphatic carbon fraction, excluding poly(methylene), was only partially correlated with K'f. Detailed NMR analyses of the sorbents using 1H inversion-recovery experiments showed that 10-nm diameter domains of branched nonpolar aliphatic groups, which account for 20-50% of all nonpolar aliphatic segments and may be associated with the poly(methylene), were responsible for the partial correlation. The correlation between K'f and the amorphous nonpolar aliphatic domains including amorphous poly(methylene) was strong. The rubbery, relatively low-density, and amorphous nonpolar aliphatic domains can be expected to offer an excellent environment for the sorption of phenanthrene by partitioning. These observations suggest that the domains of amorphous poly(methylene) and branched nonpolar aliphatics, which make up 2-9 wt % of the organic fraction in our samples, may serve as good descriptors for the potential of natural organic matter to retain HOCs in the natural environments.

Adsorption↗

PubMed2001

Interfacial mass transfer in randomly packed towers: a confident correlation for environmental applications.

Volumetric mass-transfer coefficients (kLa(w), KLa(w), kGa(w), kGa(w)) required for randomly dumped packed tower design were gathered from the literature to generate a working database comprehending 2675 measurements relevant to water and air pollution abatement processes. The cross-examination of two important correlations predicting mass-transfer coefficients was achieved through this database (Onda correlation, 1968; Billet and Schultes correlation, 1993). Some limitations regarding either the level of accuracy or the application range came to light with this investigation. Artificial neural network (ANN) modeling is then proposed allowing all four mass-transfer coefficients predictions. A single ANN correlation was built to predict the dimensionless gas (or liquid) film Sherwood number (ShL/G) as a function of six dimensionless groups, namely, the liquid Reynolds (ReL), Froude (FrL), Eotvös (EoL) numbers, the gas (or liquid) Schmidt number (ScL/G), the Lockhart-Martinelli parameter (chi), and a bed-characterizing number (K). Using the ANN correlation and the two-film theory, a reconciliation procedure was further implemented resulting in better predictions of the gas (or liquid) overall volumetric mass-transfer coefficients. The resulting correlation yielded an absolute average relative error of 22.1% and a standard deviation of 21.1% based on whole database while the ANN predictions remain in accordance with the physical evidence reported in the literature.

Air Pollutants↗