Mid-infrared spectroscopy for detection of Huanglongbing (greening) in citrus leaves

In recent years, Huanglongbing (HLB) also known as citrus greening has greatly affected citrus orchards in Florida. This disease has caused significant economic and production losses costing about $750/acre for HLB management. Early and accurate detection of HLB is a critical management step to control the spread of this disease. This work focuses on the application of mid-infrared spectroscopy for the detection of HLB in citrus leaves. Leaf samples of healthy, nutrient-deficient, and HLB-infected trees were processed in two ways (process-1 and process-2) and analyzed using a rugged, portable mid-infrared spectrometer. Spectral absorbance data from the range of 5.15-10.72 μm (1942-933 cm⁻¹) were preprocessed (baseline correction, negative offset correction, and removal of water absorbance band) and used for data analysis. The first and second derivatives were calculated using the Savitzky-Golay method. The preprocessed raw dataset, first derivatives dataset, and second derivatives dataset were first analyzed by principal component analysis. Then, the selected principal component scores were classified using two classification algorithms, quadratic discriminant analysis (QDA) and k-nearest neighbor (kNN). When the spectral data from leaf samples processed using process-1 were used for data analysis, the kNN-based algorithm yielded higher classification accuracies (especially nutrient-deficient leaf class) than that of the other spectral data (process-2). The performance of the kNN-based algorithm (higher than 95%) was better than the QDA-based algorithm. Moreover, among different types of datasets, preprocessed raw dataset resulted in higher classification accuracies than first and second derivatives datasets. The spectral peak in the region of 9.0-10.5 μm (952-1112 cm⁻¹) was found to be distinctly different between the healthy and HLB-infected leaf samples. This carbohydrate peak could be attributed to the starch accumulation in the HLB-infected citrus leaves. Thus, this study demonstrates the applicability of mid-infrared spectroscopy for HLB detection in citrus.     

Ammonium detoxifying activity is maintained after 72 hours of cold preservation of rat hepatocytes in University of Wisconsin (UW) solution

The ammonium removal efficiency (ARE) and cell viability was investigated in freshly isolated rat hepatocytes exposed to increasing ammonium loads (0.1-2.0 mM). No difference was observed in both ARE and cell viability at the different ammonium concentrations tested. Storage of hepatocytes at 0 degrees C for 72 hours inhibited ammonium removal and urea synthesis. Rewarming of cells at 37 degrees C for 120 min was followed by an ARE fully comparable to freshly isolated hepatocytes. These data indicated that cold preservation of rat hepatocytes for 3 days in UW followed by a rewarming is associated with normal ammonium detoxification efficiency.     

A fast,efficient and automated method to extract vessels from fundus images

Abstract  

We present a fast, efficient, and automatic method for extracting vessels from retinal images. The proposed method is based on the second local entropy and on the gray-level co-occurrence matrix (GLCM). The algorithm is designed to have flexibility in the definition of the blood vessel contours. Using information from the GLCM, a statistic feature is calculated to act as a threshold value. The performance of the proposed approach was evaluated in terms of its sensitivity, specificity, and accuracy. The results obtained for these metrics were 0.9648, 0.9480, and 0.9759, respectively. These results show the high performance and accuracy that the proposed method offers. Another aspect evaluated in this method is the elapsed time to carry out the segmentation. The average time required by the proposed method is 3 s for images of size 565 × 584 pixels. To assess the ability and speed of the proposed method, the experimental results are compared with those obtained using other existing methods.     

Polymorph formation from solvate desolvation

Spironolactone (C₂₄H₃₂O₄S) usually crystallizes into an orthorhombic phase, named Form II. Another orthorhombic phase, named Form I, is also known but seems difficult to obtain. Studies of the kinetics of desolvation of the ethanol solvate at room temperature showed that these two forms can be obtained through different mechanisms of desolvation.     

Structure and conformational properties of N-pentafluorosulfur(sulfuroxide difluoride imide) SF5N=S(O)F2: vibrational analysis, gas electron diffraction, and quantum chemical calculations

The molecular structure and conformational properties of N-pentafluorosulfur(sulfuroxide difluoride imide), SF5N=S(O)F2, have been studied by vibrational spectroscopy (IR (gas) and Raman (liquid)), by gas electron diffraction (GED), and by quantum chemical calculations (MP2 and B3LYP with (6-31G(d) and 6-311+G(2df) basis sets). According to GED, the prevailing conformer possesses a syn structure (N-SF5 bond synperiplanar with respect to the bisector of the SF2 group). Splitting of the symmetric N=S=O stretching vibration in gas and liquid spectra demonstrates the presence of a second conformer (11(5)%) with anticlinal orientation of the N-SF5 bond according to quantum chemical calculations. The geometric structure, conformational properties, and vibrational frequencies are well reproduced by quantum chemical calculations.     

The colored Hadwiger transversal theorem in ℝ<Superscript><Emphasis Type="Italic">d</Emphasis></Superscript>

Hadwiger’s transversal theorem gives necessary and suffcient conditions for a family of convex sets in the plane to have a line transversal. A higher dimensional version was obtained by Goodman, Pollack and Wenger, and recently a colorful version appeared due to Arocha, Bracho and Montejano. We show that it is possible to combine both results to obtain a colored version of Hadwiger's theorem in higher dimensions. The proofs differ from the previous ones and use a variant of the Borsuk-Ulam theorem. To be precise, we prove the following. Let F be a family of convex sets in ? ^d in bijection with a set P of points in ? ^d?1. Assume that there is a coloring of F with suffciently many colors such that any colorful Radon partition of points in P corresponds to a colorful Radon partition of sets in F. Then some monochromatic subfamily of F has a hyperplane transversal.     

Cold preservation of isolated hepatocytes in UW solution: experimental studies on the respiratory activity at 0 degrees C

To date, little attention has been paid to the role of the gas milieu in preservation solutions and its effect on cell viability. Dissolved O2 in the preservation media may be an important parameter to consider. In this study we polarographically measured the O2 concentration in air-equilibrated UW solution at 0 degrees C, as well as the respiratory activity of isolated hepatocytes cold-preserved in this solution up to 72 hours. To perform measurements at 0 degrees C, it was first necessary to characterize the sensor behavior at low temperatures. We verified that the sensor response is still linear at this temperature but the rate of response is significantly slower. The O2 solubility in UW-air solution at 0 degrees C was determined using a modified physical method and it was 410 microM O2, which, as expected, is lower than the solubility in water at the same temperature (453 microM O2). Isolated hepatocytes cold-stored in UW-air solution retained a measurable respiratory activity during a period of 72 hours. The O2 consumption rate was 0.48 +/- 0.13 nmol/O2/min/10(6) cells, which represents 1% of the control value at 36 degrees C (61.46 +/- 14.61 nmol/O2/min/10(6) cells). The respiratory activity and cell viability were well maintained during the preservation period. At present, preservation conditions need to be improved for cells to remain functionally active. Dissolved O2 may be required for energy re-synthesis but it also leads to an increment in reactive oxygen species. The O2 concentration in the preservation solution should be carefully controlled, reaching a compromise between cell requirement and toxicity.     

A simple GC method for determination of cryoprotector diols 1,4-butanediol or 2,3-butanediol in isolated rat hepatocytes

We devised a simple method for determining the cryoprotectant agents 1,4-butanediol or 2,3-butanediol in isolated rat hepatocytes. After extraction of of hepatocytes with water (containing internal standard - ethylene glycol 1.25 mg/mL) the diol content was analyzed by gas chromatography. The method shows a linear response in the range 0.125 to 2.50 mg/mL for 1,4-butanediol and 0.25 to 3.75 mg/mL for 2,3-butanediol. The accuracy and precision of the method were evaluated and the coefficients of variation were found to be within = 6.0 %. The recoveries from hepatocyte samples containing 0.50, 1.00 and 2.00 mg/mL were 91.0 to 108 % for 1,4-butanediol and 80.6 to 100.3 % for 2,3-butanediol, respectively. This method allowed the determination of the intracellular concentration of diols in hepatocytes preserved for up to 120 hours at - 4 (C in UW solution + 8 % w/v 1,4-butanediol (or 2,3-butanediol).