Degree Of Linear Correlation Research Articles

Spectral Clustering Approach with K-Nearest Neighbor and Weighted Mahalanobis Distance for Data Mining

This paper proposes a spectral clustering method using k-means and weighted Mahalanobis distance (Referred to as MDLSC) to enhance the degree of correlation between data points and improve the clustering accuracy of Laplacian matrix eigenvectors. First, we used the correlation coefficient as the weight of the Mahalanobis distance to calculate the weighted Mahalanobis distance between any two data points and constructed the weighted Mahalanobis distance matrix of the data set; then, based on the weighted Mahalanobis distance matrix, we used the K-nearest neighborhood (KNN) algorithm construct similarity matrix. Secondly, the regularized Laplacian matrix was calculated according to the similarity matrix, normalized and decomposed, and the feature space for clustering was obtained. This method fully considered the degree of linear correlation between data and special spatial structure and achieved accurate clustering. Finally, various spectral clustering algorithms were used to conduct multi-angle comparative experiments on artificial and UCI data sets. The experimental results show that MDLSC has certain advantages in each clustering index and the clustering quality is better. The distribution results of the eigenvectors also show that the similarity matrix calculated by MDLSC is more reasonable, and the calculation of the eigenvectors of the Laplacian matrix maximizes the retention of the distribution characteristics of the original data, thereby improving the accuracy of the clustering algorithm.

Bond performance of carbon fiber reinforced polymer rebars in ultra-high-performance concrete

This paper investigated the bond performance between carbon fiber reinforced polymer (CFRP) bars and ultra-high-performance concrete (UHPC) by a hinged beam test investigation. A total of 11 sets of beam tests were carried out to investigate the effect of different parameters on the bond performance, including steel fiber volume fraction, bonded length, reinforcement diameter, and concrete cover. The tests showed that the bond damage modes between CFRP bars and UHPC were dominated by pull-out damage, with the surface of the bonded section of CFRP bars being peeled off from the internal core and no damage observed in the UHPCs. An increase in the cover and steel fiber volume fraction improves the bonding performance, while an increase in diameter reduces the bond performance. Based on this study, the formulae for calculating the ultimate bond strength and development length that integrated the effects of CFRP bar diameter, bonded length, and cover thickness were proposed. The bond-slip curve shows three stages, i.e., ascending section, descending section, and a residual section showing periodic fluctuations. The fluctuation period showed a certain degree of linear correlation with the rib spacing of CFRP bars. Based on the characteristics of tested curves, a bond-slip constitutive model was proposed to simulate the bond-slip behavior of CFRP bars in UHPCs with good agreement to test results.

Analyzing the Relationship between the Features of Direct Real Estate Assets and Their Corresponding Australian—REITs

This study investigated the relationship between a sector-specific Australian Real Estate Investment Trust (A-REITs) and the underlying property assets in its property portfolio. The existing studies have assessed the connectedness/correlation between the A-REITs market and a variety of other asset markets, including the overall stock, bond, and direct real estate markets. This study applied regression analysis methods and discovered that there exists a certain degree of linear correlation between the underlying property assets and the return of the subject A-REITs. The most significant variable is the occupancy of the offices. The higher the occupancy is, the better the dividend can be. Features of the A-REITs also affect the dividend outcomes, specifically, the total portfolio market value and the capitalization rate. This suggests that the annual valuation outcomes show a positive relation with the performance of the A-REITs.

Intelligent rating method of tunnel surrounding rock based on one-dimensional convolutional neural network

Accurate prediction of surrounding rock grades holds great significance to tunnel construction. This paper proposed an intelligent classification method for surrounding rock based on one-dimensional convolutional neural networks (1D CNNs). Six indicators collected in some tunnel construction sites are considered, and the degree of linear correlation between these indicators has been analyzed. The improved one-hot encoding method is put forward for transforming these non-image indicators into one-dimensional structural data and avoiding the sampling error in the indicators of surrounding rock collected in the field. We found that the 1D CNNs model based on the improved one-hot encoding method can best extract the features of surrounding rock classification indicators (in terms of both accuracy and efficiency). We applied the well-trained classification model of tunnel surrounding rock to a series of expressway tunnels in China, and the results show that our model could accurately predict the surrounding rock grade and has great application value in the construction of tunnel engineering. It provides a new research idea for the prediction of surrounding rock grades in tunnel engineering.

Neonatal biometry and characterization of Amazonian Turtle nests (Podocnemis expansa)

The present study aimed to study the reproduction of the Amazon turtle (Podocnemis expansa) through the evaluation of the reproductive parameters of adult females. This study was carried out in the Crixás-Açu River, municipality of Mundo Novo, state of Goiás, Brazil. In September, the biometrics of 20 females were evaluated during the spawning period. Their nests were marked for subsequent evaluation of hatchlings, measuring the distances of each nest to the river and vegetation. The second stage consisted of the evaluation of hatchlings and characterization of nests after egg hatching. The data were tested using the Pearson Correlation to measure the degree of linear correlation between the variables analyzed, such as the parameters of females, hatchlings, nests, and eggs. Nest depth was positively correlated with the number of eggshells found. We also found a correlation between the number of eggsshells and the distance of nests to the vegetation. Although moderate, this result indicates that as the distance to the vegetation increases, the number of eggshells found in nests decreases. The spawning site for Amazon turtle breeding is crucial to determine a higher number of eggs hatching and better development of hatchlings. However, the literature is still very scarce regarding the choice of spawning grounds and the influence that vegetation may have on the development of freshwater turtle hatchlings in Brazil.

Machine learning for pattern and waveform recognitions in terahertz image data

Several machine learning (ML) techniques were tested for the feasibility of performing automated pattern and waveform recognitions of terahertz time-domain spectroscopy datasets. Out of all the ML techniques under test, it was observed that random forest statistical algorithm works well with the THz datasets in both the frequency and time domains. With such ML algorithm, a classifier can be created with less than 1% out-of-bag error for segmentation of rusted and non-rusted sample regions of the image datasets in frequency domain. The degree of linear correlation between the rusted area percentage and the image spatial resolution with terahertz frequency can be used as an additional cross-validation criteria for the evaluation of classifier quality. However, for different rust staging measured datasets, a standardized procedure of image pre-processing is necessary to create/apply a single classifier and its usage is only limited to 1 ± 0.2 THz. Moreover, random forest is practically the best choice among the several popular ML techniques under test for waveform recognition of time-domain data in terms of classification accuracy and timing. Our results demonstrate the usefulness of random forest and several other machine learning algorithms for terahertz hyperspectral pattern recognition.

Design and Development of Plastic Crusher for a More Efficient Waste Management Practice

One of the prevalent environmental problems encountered in most developing countries is solid waste management. Plastic waste such as polyethylene terephthalate (PET) bottles and other plastic materials is one of the solid wastes hampering the developmental and aesthetical state of our environment. This is as a result of indiscriminate disposal and indiscriminate burning of solid waste. Environmental pollution caused by this indiscriminate disposal and burning necessitated the development of plastic crusher to recycle plastic waste generated within our environment. The machine components are hopper, crushing chamber, crushed material outlet, counter weight, transmission shaft with spiral blade around it, channel and body frame. The machine is powered by a 3-phase 10Hp medium speed electric motor. The machine, being a medium sized crusher, has the capacity of crushing half a ton of plastic in a day depending on the type of recyclable plastic crushed. The degree of linear correlation, r squared for observed and predicted values of variables evaluated are within acceptable region. The efficiency of crushing based on polymers processed are 90% for HDPE, 68% for LDPE, 45% for PVC and 10% for PET bottles. The developed crusher can be used to reduce the volume of plastic waste dump. If the findings from this technical brief is adopted and commercialized, the menace of plastic waste will be ended.

Structural and Catalytic Properties of Co-doped Perovskite Oxide on Coal Combustion

In this paper, the structural and catalytic properties of co-doped perovskite oxide La0.8Ce0.2Mn1−xCoxO3 are investigated. First, coal combustion catalysts of mesoporous perovskite-type La0.8Ce0.2Mn1−xCoxO3 were prepared by using sol–gel method. The resulting powder was characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller’s test (BET), and thermogravimetric analysis (TGA). Then, the results showed that after partially substituting La with Ce and substituting Mn with Co in LaMnO3, Ce occupied parts of the La site and Co occupied parts of the Mn site. As the substitution rate of Co increased, the pore diameter significantly decreased, and the specific surface area increased first and then decreased. Thirdly, thermogravimetric measurements and coal combustion constructed single-reaction model in the presence of the La0.8Ce0.2Mn1−xCoxO3 catalysis indicated that the presence of catalysts reduced the reaction initiation temperature (Teo), the maximum mass loss velocity temperature (Tmax), and the completion temperature of the main pyrolysis (Tf). The addition of 5 % La0.8Ce0.2Mn0.9Co0.1O3 to coal caused the reaction initiation temperature (Teo) to decrease by 34 °C compared with coal alone. Lastly, a distributed activation energy model of 5 % La0.8Ce0.2Mn0.9Co0.1O3 obtained an activation energy distribution curve. Results indicated that the activation energy of samples at the primary pyrolysis stage did not present a single peak value but mainly accumulated at 140–160 kJ, which could replace the mean activation energy of pyrolysis reaction. At the same time, frequency factor was not constant but presented a certain degree of linear correlation with activation energy, thereby indicating the presence of more than a single-reaction pyrolysis mechanism.

INFLUENCE OF PERMANGANATE INDEX IN THE PARAMETERS AS TOTAL PHENOL CONTENT AND TOTAL ANTIOXIDANT ACTIVITY OF EXTRACTS OF CAMELLIA SINENSIS

Objective: This study estimated the Permangante Index (IKMnO4) and evaluated its correlation with parameters as total phenols (FT) and total antioxidant activity (TAA) of commercial teas of Camellia sinensis, fermented, unfermented and blended with other plants.Methods: The aqueous extracts were prepared from commercial samples of green and black teas, green tea blended with lemon (Camellia sinensis with Citrus limonium), green tea blended with mint (Camellia sinensis with Mentha piperita), green tea blended with peach (Camellia sinensis with Prunus persica) and green tea blended with orange (Camellia sinensis with Citrus sinensis). The Permangante index was determined by titrating the tea extract with potassium permanganate solution according to AOAC method (AOAC, 1980) with modifications. The concentration of phenols in the extracts was determined by spectrophotometry according to the standard procedure of Folin-Ciocalteau. The antioxidant activity of the extracts was evaluated using the radical 1,1-diphenyl-2-picrylhydrazyl (DPPH—) method. All the determinations were performed in triplicate, and the results presented as mean ± standard deviation (SD). The data were evaluated by univariate statistical analysis (ANOVA), F-test and mean test (Tukey´s test) for comparative results. Pearson’s correlation was used to measure the degree of linear correlation and the quantitative variables were from a normal population.Results: The results for Permanganate Index show a variation ranged from 0.40 to 0.80 mEq/l. The ANOVA analysis to IKMnO4 shown there is significant statistically difference at the 5% probability level (p < 0.05) between the types of tea as well as the amount of herb used to prepare the infusion. Therefore, it was observed that there significant contrast between tea extracts, the mixture of different plants in blended extracts as well as the tea manufacture process affect the polyphenols tannins content influencing the permanganate index parameter. Studies correlation shown strong correlations (r > 0.7) among the parameters. For the Camellia sinensis extracts the high correlations between IKMnO4 and TAA; FT and TAA demonstrates the suitability of the permanganate index in the evaluation of antioxidant activity.Conclusion: The results suggest that the Permanganate Index could be used for quality control of tea as an additional parameter.

Patch-Based correlation for deghosting in exposure fusion

We present a robust exposure fusion algorithm to tackle the problems of motion removal and detail preserving in dynamic scenes. Using one exposure as a reference, the algorithm detects motion in an exposure stack by comparing the structural consistency of images as measured by the degree of linear correlation between patches of each image and the corresponding patches of the reference. Then, after motion removal, a stack of latent images with consistent content is synthesized. For detail preserving, a contrast criterion is introduced to measure the quality of exposure and generate visibility maps of each latent image. Guided by the visibility maps, a tonemapped-like HDR image, which is ghost-free and has all details preserved, is produced by seamlessly merging the latent images. Exposure fusion tests on various dynamic scenes demonstrate the superiority of the proposed method over existing state-of-the-art approaches.

A Mechanical Sensor Designed for Dynamic Joint Angle Measurement.

Background. The measurement of the functional range of motion (FROM) of lower limb joints is an essential parameter for gait analysis especially in evaluating rehabilitation programs. Aim. To develop a simple, reliable, and affordable mechanical goniometer (MGR) for gait analysis, with six-degree freedom to dynamically assess lower limb joint angles. Design. Randomized control trials, in which a new MGR was developed for the measurements of FROM of lower limb joints. Setting. Reliability of the designed MGR was evaluated and validated by a motion analysis system (MAS). Population. Thirty healthy subjects participated in this study. Methods. Reliability and validity of the new MGR were tested by intraclass correlation coefficient (ICC), Bland-Altman plots, and linear correlation analysis. Results. The MGR has good inter- and intrarater reliability and validity with ICC ≥ 0.93 (for both). Moreover, measurements made by MGR and MAS were comparable and repeatable with each other, as confirmed by Bland-Altman plots. Furthermore, a very high degree of linear correlation (R ≥ 0.92 for all joint angle measurements) was found between the lower limb joint angles measured by MGR and MAS. Conclusion. A simple, reliable, and affordable MGR has been designed and developed to aid clinical assessment and treatment evaluation of gait disorders.

TH-CD-207-02: Quantification of Dynamic Susceptibility Contrast MRI: Comparison of Calibration Methods Using Venous Output Function and Arterial Spin Labeling

Purpose: To evaluate the validity of the calibration of arterial input function (AIF) by using a venous output function (VOF) for the quantification of cerebral blood flow (CBF) in dynamic susceptibility contrast MRI (DSC-MRI), by comparing to the arterial spin labeling (ASL) measurement. Method: Fourteen patients with unilateral ICA stenosis enrolled in the study on a 3T clinical MRI scanner. The ASL-CBF map was calculated by averaging 45 dynamic points acquired by using a Q2TIPS sequence. For DSC perfusion analysis, AIF was selected to derive the relative CBF (rCBF) map and the delay (Tmax) map; VOF with signal saturation was corrected by a small vein which was amplified and time-shifted to match the base and flanks of the original VOF. The DSC-CBF map was corrected by two different patient-specific correction factors (CF): (1) CF1: the ratio of the mean ASL-and DSC-CBF obtained from the mask based on Tmax < 3s, the gray matter mask and the exclusion of large vessels; (2) CF2: the ratio of the area under the first-pass phase in AIF and VOF concentration time curves. Result: Average whole-brain (WB) DSC-CBF calculated by CF1 and CF2 showed the same precision (coefficient of variation [COV] = 22%), while CBFCF2 (100.26 ± 23.36 ml/100g/min [mean ± SD]) was higher than CBFCF1 (37.4 ± 8.1 ml/100g/min). Significant correlation (R= 0.632; P<0.05) was found between the results obtained from these two calibration approaches. Conclusion: The degree of linear correlation between the WB DSC-CBF estimates obtained by AIF PV correction and ASL-based correction was significant. Comparing with CBF values obtained using ASL, the DSC-CBF estimates were high even after applying AIF PV correction. The over-estimation may come from the partial volume effect in VOF and other sources of errors in the DSC-MRI quantification.

Evaluation of the Uniformity of Density and Mechanical Properties of Bamboo-Bundle Laminated Veneer Lumber (BLVL)

The objective of this study was to evaluate the uniformity of density distribution for Bamboo-bundle Laminated Veneer Lumber (BLVL) and its relationship to the stability of mechanical performance. A novel assembly style called one-piece veneer formation technology was developed to enhance the density uniformity, and four different density levels for BLVL were examined by X-ray scanning. The results indicated that the homogeneity of density, the stability of mechanical performance, and the mechanical properties for BLVL could be effectively improved by assembling the bamboo bundles into layers and then combining the layers to make the lumber. The density uniformity in width and thickness directions increased with increasing target density. A negatively linear correlation between density and Coefficient of Variation (COV) of MOR and shearing strength was observed. Partial correlation analysis revealed that when controlling for the variability of density, the linear relationship between density and the COV of MOR became insignificant, and the degree of linear correlation between density and the COV of shearing strength decreased.

Torque prediction at the shoe–surface interface using insole pressure technology

Excessive rotational traction between the foot and the playing surface has been shown to increase the risk of athletic injuries to ligaments in the knee and ankle. It is not currently feasible to accurately determine the free torque generated at the shoe–surface interface utilizing live participants without an embedded force plate. The goal of the current research was to predict the free torques that developed at the shoe–surface interface during voluntary internal and external rotations of the body relative to a planted foot using an insole pressure measurement system. Six participants fitted with a shoe containing an insole pressure measurement device performed trials on an embedded force plate. A pressure sensor mask of specific sensors was determined based on the degree of linear correlation between sensor pressure and the free torque. Linear regression analyses were utilized to develop a General Linear Regression Model and Participant-Specific Linear Regression Models. The results of this study indicated that insole pressure technology, in conjunction with linear regression models, can be utilized to predict free torques generated at the shoe–surface interface during isolated rotational motions of the body with respect to a planted foot. Furthermore, Participant-Specific Linear Regression models may be more accurate in these predictions than a general model, based on a group of participants. When used with computational modeling, this technique might allow the investigation of strains produced in ligaments of the ankle and knee that are generated during internal and external rotations of the body with a planted foot on various turf surfaces outside a laboratory setting.

Scanning Aged CR-39 SSNTDs with Etched Alpha Tracks by Using Transmitted Laser Light

The optical track scanning method is based on the measurement of laser light transmission through CR-39 solid state nuclear track detectors (SSNTDs). Etched tracks in CR-39 SSNTDs are used to examine the degree of linear correlation between the tracks observed using an optical microscope and those measured by using the laser light transmission (LLT) method. The intensity of the light transmitted through the etched tracks was measured using a photodiode. The present investigation clearly indicates that the results from the LLT method depend on track density and alpha energy, as well as the etching and storage conditions of the detector material. In addition, the transmittance of laser light through the etched CR-39 detectors aged at room temperature is found to be relatively small compared with that of those kept in a freezer. This technique was tested on the overlap of tracks in SSNTD radon dosimetry by using a standard exposure. The results show that the radon dose can be rapidly estimated.

Thoracic pedicle screw insertion in Asian cadaveric specimen: does radiological pedicle profile affect outcome?

Pedicle screw instrumentation has superior biomechanical as well as clinical outcome. Thoracic pedicles show great variation in different population groups, particularly in Asians who have been shown to have smaller pedicle dimensions. Although plain radiographs are widely performed prior to spine surgery, no studies have been done so far to investigate whether the thoracic pedicle profile on plain radiographs affect thoracic pedicle screw insertion. Therefore, this is a cadaveric study aimed to determine the relationship between plain radiographic thoracic pedicle profile in Asians and the outcome of pedicle screw insertion in the thoracic spine. A pre-insertion radiograph with an enlargement reference scale was performed and surgeons were blinded to the plain radiographic morphometry of the thoracic pedicles. From the pre-insertion radiograph, the normalized pedicle width and height (which controls for any magnification error) as well as the pedicle width:body width (PWBW) and pedicle width:pedicle height (PWPH) ratio was derived. 240 pedicle screws were inserted in ten Asian cadavers from T1 to T12 using the funnel technique. 5.0 mm screws were used from T1 to T6 while 6.0 mm screws were used from T7 to T12. Perforations were detected by direct visualization via wide laminectomies after pedicle screw insertion. The outcome of thoracic pedicle screw insertion was correlated with the radiological profile using independent t-test. Pearson correlation coefficient was used to investigate the correlation between the ratios and the normalised pedicle width and height. The narrowest pedicle width is from T3 to T6 determined from normalized measurement of the pedicle width. T5 pedicle width is the smallest measuring 4.1 ± 1.3 mm. The overall perforation rate is 10.4% (25 perforations). There is only one significant perforation. There were twice as many lateral and inferior perforations compared to the medial perforations. 48% of the perforations occurred at T1, T2 and T3. Pedicles <4.0 mm in width and upper thoracic pedicles are risk factors for pedicle perforation. The normalised pedicle width has a high degree of linear correlation with PWBW and a normalised pedicle width of 4.0 mm correlated with a PWBW ratio of 0.3. Plain radiographic thoracic pedicle morphometry has an influence on the outcome of thoracic pedicle screw insertion in Asian cadavers. Pedicle width <4.0 mm is associated with higher risk of pedicle perforation. This critical value corresponds to a PWBW ratio of 0.3. Identification of such pedicle profile warrants full evaluation of the morphometry of the thoracic pedicles and possibly extra-pedicular techniques should be employed to avert the risk of critical pedicle perforation.

Prestimulus Cortical Activity is Correlated with Speed of Visuomotor Processing

Response time (RT) is an important behavioral measure of the overall efficacy of sensorimotor processing and is known to vary significantly from trial to trial. Past work on how stimulus evoked cortical responses contribute to RT variability has helped delineate the stages of neuronal information processing. Much less is known about how the state of the brain immediately preceding the stimulus onset (prestimulus) affects RT. We addressed this problem by analyzing data from three macaque monkeys trained to perform a visuomotor pattern discrimination task. Local field potentials were recorded from up to 16 bipolar surface-to-depth electrodes widely distributed over one cerebral hemisphere in each monkey. The degree of linear correlation between RT and prestimulus spectral power was determined over a wide range of frequencies. In the prefrontal cortex, prestimulus power in the beta range (14-30 Hz) was negatively correlated with RT in two monkeys, suggesting a possible role of activity in this frequency range in the mediation of top-down control of visuomotor processing. In the sensorimotor cortex, prestimulus power in the beta range was positively correlated with RT in two monkeys, consistent with the hypothesis that oscillations in this range support the maintenance of steady-state motor output. In visual occipital and temporal lobe areas, prestimulus power in the alpha/low beta range (8-20 Hz) showed positive correlations with RT in three monkeys, possibly reflecting a spatially specific disengagement of visual anticipatory attention. Through measurement of prestimulus spectral coherence, it was further determined that sites showing similar patterns of correlation between spectral power and RT were also linked together in synchronized networks.

Inter‐Relationships Between the Secretory Dynamics of Thyrotrophin‐Releasing Hormone, Thyrotrophin and Prolactin in Periovulatory Mares: Effect of Hypothyroidism

We used our nonsurgical technique for collecting pituitary venous blood to relate the dynamics of thyrotrophin-releasing hormone (TRH) secretion to the secretion patterns of both prolactin and thyrotrophin in periovulatory mares, either euthyroid (n = 5) or made hypothyroid by treatment with propyl-thiouracil (n = 5). Pituitary venous blood was collected continuously and divided into 1-min aliquots for 4 h. To test the effect of dopamine on the relationship between secretion patterns, sulpiride, a selective D2 receptor antagonist, was given i.m. after 2 h of sampling. Thorough testing of the model and blood collection procedure revealed no sites of TRH loss. Hypothyroidism increased the mean secretion rates of TRH (P = 0.04) and thyrotrophin (P < 0.0001) but not prolactin. Sulpiride increased prolactin secretion rates in hypothyroid (P < 0.0001) and control (P = 0.007) mares, but did not alter TRH or thyrotrophin secretion rates. In both groups of mares, all three hormones were secreted episodically but not rhythmically. In both groups, the secretion pattern of TRH was almost always significantly related to that of thyrotrophin, as assessed by cross correlation and cross approximate entropy (ApEn) analysis. However, the degree of linear correlation was weak, with only 14% (hypothyroid) or 8% (controls) of the variation in thyrotrophin secretion rates attributable to TRH. Prolactin and TRH secretion patterns before sulpiride were coupled on cross ApEn analysis in both groups, and the minute-to-minute secretion rates of the two hormones were correlated in four hypothyroid and three euthyroid mares. Overall, the small, but significant, degree of association between TRH and prolactin was similar to that between TRH and thyrotrophin. In hypothyroid mares, sulpiride increased (P = 0.02) the synchrony between TRH and prolactin patterns. We conclude that in horses: (i) little TRH degradation occurs during passage through the pituitary or in blood after 1 h at 37 degrees C; (ii) TRH is not the major factor controlling minute-to-minute fluctuations in either thyrotrophin or prolactin; and (iii) reducing two strongly inhibitory inputs (i.e. dopamine and thyroid hormones) may magnify the stimulatory effect of TRH on prolactin secretion.

Effect of Triglyceride Structure on Fecal Excretion of 13C-Labeled Triglycerides

Objective: The aim of this work was to determine the effects of specific changes in the structure of 13C-labeled triglyceride (TG*) on its fecal excretion relative to total stool fat excretion determined simultaneously in patients with reduced exocrine pancreatic function.Methods: A series of 47 studies were conducted in 26 young cystic fibrosis (CF) patients and 11 adult patients with chronic pancreatitis over a five year period. Each test consisted of ingesting a single high fat test meal containing both 13C-labeled triglyceride (TG*) and dysprosium chloride (DyCl3) a nonabsorbable marker of intestinal transit; in most studies the food colorant brilliant blue (FD&C blue #1) was administered along with the DyCl3. The TG*s tested were: P*P*P* = TRIPALMITIN-1,1,1-13C3; SO*S = 2-OCTANOYL-1,3-DISTEARIN-2-octanoyl-1,2-13C2; and P*LP* = 2-LAURYL-1,3-DIPALMITIN-dipalmitoyl-1,1,2,2-13C4. Ingestion of the test meal was followed by collection of individual stools for at least 72 hours. Stools were analyzed for 13C-Excess (13C*), total fat, and Dy.Results: Excretion of P*LP* showed a high degree of linear correlation with stool fat (r2 = 0.924) over a wide-range of fecal fat values. Excretion of SO*S was also significantly correlated with stool fat, but its excretion was less than 10% at all levels of steatorrhea and the slope of the regression line relating TG* excretion to stool fat was some four to five times smaller than observed for P*LP*. Fecal excretion of P*P*P* was highly correlated with stool fat (r2 = 0.941) in patients with moderate steatorrhea (<25 g fat/24 hours) and the slope of the regression line (3.20) was considerably greater than for P*LP*. Only results from those studies in which stool collections were complete (Dy excretion >90%) were utilized in the statistical comparisons (36 of 47 studies).Conclusions: The observed highly significant linear correlation between P*LP* and stool fat over the entire range of steatorrhea suggests that P*LP* excretion may be a suitable surrogate for fecal fat in patients with reduced exocrine pancreatic function. Because fecal excretion of TG* administered as described can be accurately determined by sampling only two visually marked stools, development of a noninvasive test to replace the current 72-hour stool fat test using this approach is possible. Use of other engineered TG*s and/or labeled fatty acids, may provide a method for non-invasive in vivo assessment of the specific defect(s) leading to steatorrhea in other patient groups.

Validação da curva normal de peso fetal estimado pela ultra-sonografia para o diagnóstico do peso neonatal

OBJETIVO: avaliar a concordância entre o peso fetal estimado (PFE) por ultra-sonografia e o neonatal, o desempenho da curva normal de PFE por idade gestacional no diagnóstico de desvios do peso fetal/neonatal e fatores associados. MÉTODOS: participaram do estudo 186 grávidas atendidas de novembro de 1998 a janeiro de 2000, com avaliação ultra-sonográfica até 3 dias antes do parto, determinação do PFE e do índice de líquido amniótico e parto na instituição. O PFE foi calculado e classificado de acordo com a curva de valores normais de PFE em: pequeno para a idade gestacional (PIG), adequado para a idade gestacional (AIG) e grande para a idade gestacional (GIG). A mesma classificação foi feita para o peso neonatal. A variabilidade das medidas e o grau de correlação linear entre o PFE e o peso neonatal foram calculados, bem como a sensibilidade, especificidade e valores preditivos para o uso da curva de valores normais de PFE para o diagnóstico dos desvios do peso neonatal. RESULTADOS: diferença entre o PFE e o peso neonatal variou entre -540 e +594 g, com média de +47,1 g, e as duas medidas apresentaram um coeficiente de correlação linear de 0,94. A curva normal de PFE teve sensibilidade de 100% e especificidade de 90,5% em detectar PIG ao nascimento, e de 94,4 e 92,8%, respectivamente, em detectar GIG, porém os valores preditivos positivos foram baixos para ambos. CONCLUSÕES: a estimativa ultra-sonográfica do peso fetal foi concordante com o peso neonatal, superestimando-o em apenas cerca de 47 g e a curva do PFE teve bom desempenho no rastreamento diagnóstico de recém-nascidos PIG e GIG.