Set Of Columns Research Articles

Advantageous use of SFC for separation of crude therapeutic peptides and peptide libraries

A simple SFC/MS (Supercritical Fluid Chromatography/Mass Spectrometry) method set was developed to effectively screen separations of various crude synthetic peptide products of pharmaceutical interest. Additives to the modifier methanol which were successful for these separations were found to include TFA (trifluoroacetic acid) and ammonia mixed with TFA, each at 0.1 % (v/v) composition in methanol. A final screening column set consisted of 2-ethylpyride (2-EP), 4-ethylpyridine (4-EP) and cross-linked diol (Luna™ HILIC) stationary phases. Small, linear and macrocyclic peptides with fewer than ten residues could all be eluted with good performance under at least one of the method conditions comprising the final screening protocol. For larger peptides either the 4-EP and HILIC columns with the above additives provided a good initial screening method set without 2-EP. The gradient was slightly longer and shifted to higher polarity relative to the gradients for smaller peptides. This method was often successful to elute large, hydrophilic peptides up to a 41-mer with acceptable peak profiles although the largest peptides with most ionizable residues were most challenging. For these peptides generally HILIC column performance was better with TFA + ammonia in the modifier than with TFA, while 4-EP performance was usually improved with TFA relative to TFA + ammonia.

Gas permeability in soil amended with biochar at different compaction states

Biochar amended soil (BAS) is widely studied to apply in green infrastructure, such as landfills and slopes. Presence of biochar improved soil hydraulic properties (e.g. water retention ability) in previous studies, while influence of biochar on gas permeability (k g ) under different compaction states is not clear yet. The main objective of this study is to investigate the k g of BAS under different soil compaction conditions. The soil selected for investigation was poorly graded sand. BAS was compacted in an in-house built 1-D column set up under three different soil density (65 %, 80 % and 95% degree of compaction) were considered in mixtures with 0% and 10% biochar content. The tests were carried out in a greenhouse at Shantou University. In tests, soil column was designed and subjected to drying-wetting cycles, during which soil suction, moisture content and k g were measured. Results showed that BAS (i.e. minimum water content 37.2% and 22.1%) had better water retention performance than bare soil (i.e. minimum water content 20.2% and 19.5%) at compaction conditions (65% and 80% degree of compaction). However, when the degree of compaction increased to 95%, bare soil and BAS shows similar water retention characteristic (i.e. minimum water content 15.7% and 15.9% respectively). The addition of biochar could decrease k g as compared with that of the bare soil, meanwhile, in the lower suction range, k g decreased with an increase of compaction (i.e. k g 65%>k g 80%>k g 95%).

Towards the determination of an equivalent standard column set between cryogenic and flow-modulated comprehensive two-dimensional gas chromatography

This preliminary research is focused on the task of defining an equivalent standard column set between cryogenic and flow-modulation comprehensive two-dimensional gas chromatography (GC × GC) combined with mass spectrometry (MS). Cryogenic modulation (CM) was carried out by using a loop-type device, while the flow modulator used was a seven-port wafer chip, equipped with an external accumulation loop.Initially, a common low-polarity + mid-polarity CM GC × GC column set was selected (30 m × 0.25 mm ID × 0.25 μm df + 1.5 m × 0.25 mm ID × 0.25 μm df), a method was developed, and a GC × GC-MS fingerprint was attained (on a sample of bio-oil derived from coconut fibers). After, a column set with the same stationary phases was selected for the flow modulation GC × GC-MS method (20 m × 0.18 mm ID × 0.18 μm df + 5 m × 0.32 mm ID × 0.25 μm df), with the capability to provide a-similar-as-possible separation. A side-by-side measurement of several chromatography parameters (efficiency, peak capacity, resolution, peak widths, retention factors, elution temperatures) was made.

Impact of water characteristics on the discrimination of benthic cover in and around coral reefs from imaging spectrometer data

Coral reefs are the foundation of productive ecosystems in the global, tropical oceans and are under threat from a variety of local to global scale stressors. Satellite imagery provides a tool to identify and understand the processes that control coral reef degradation, however due to the dynamic nature of seawater constituents, current spaceborne multispectral sensors cannot reliably discriminate between the many coral reef benthic classes necessary to detect change. Hyperspectral imagers may provide sufficient spectral resolution to estimate water column properties and differentiate benthic classes, however, the effects of depth, seawater constituents, and classification algorithm on the accuracy of benthic classifications have not been systematically assessed. Here, we simulate the ability of a spaceborne hyperspectral imager to accurately map fractional cover of coral reef benthic classes under a variety of conditions. Benthic reflectance is simulated by combining pure reflectance spectra of coral, algae, and sand and projecting these mixed spectra through a fully crossed set of water columns. We then use a semi-analytical optimization procedure to estimate the water column properties and multiple endmember spectral mixture analysis to estimate the fractional cover of the benthic classes using many independent endmember spectra. We compare our estimated benthic class fractions to the original, actual fractions used to produce the mixed coral reef spectra to quantify several measures of error. We found that multiple endmember spectral mixture analysis decreases fractional retrieval error, which is also reduced when the first derivative of the mixed and endmember spectra is used prior to unmixing. The estimation of fractional benthic class cover is most accurate for depths ≤3 m for most water conditions. Depths ≥5 m should be classified only if chlorophyll and sediment concentration are <0.1 mg m−3 and <0.1 g m−3, respectively. Our results indicate that the fractional cover of coral and algae should be at least 25% for accurate benthic class estimates (mean relative error < 50%), however there will be many ways to leverage the repeat measurements of a hyperspectral satellite sensor, such as a stable depth retrievals and benthic cover estimates, to produce more accurate and useful fractional cover data. We show how this simulation analysis can be used to generate maps of predicted benthic cover fractional retrieval uncertainty across a coral reef system using aerial hyperspectral imagery acquired over Hawaii, USA, although reef-specific, within pixel variations in depth and benthic class complexity should be considered.

Bayesian spatially varying coefficient models in the spBayes R package

This paper describes and illustrates new functionality for fitting spatially varying coefficients models in the spBayes (version 0.4–2) R package. The new spSVC function uses a computationally efficient Markov chain Monte Carlo algorithm and extends current spBayes functions, that fit only space-varying intercept regression models, to fit independent or multivariate Gaussian process random effects for any set of columns in the regression design matrix. Newly added OpenMP parallelization options for spSVC are discussed and illustrated, as well as helper functions for joint and point-wise prediction and model fit diagnostics. The utility of the proposed models is illustrated using a PM10 analysis over central Europe.

Pillars of Heaven: The Symbolic Function of Column and Bracket Sets in the Han Dynasty

ABSTRACTWooden columns surmounted by bracket sets are a key element of the great buildings of Imperial China and have received a tremendous amount of attention from scholars and architectural professionals. This article revisits the question of their symbolic function during the Han dynasty (206 bce–ce 220). In addition to their structural role, column and bracket sets fulfilled important social and cultural needs related to the representation of celestial and spiritual qualities. Understood variously as pillars of heaven, gates of heaven, the constellations, Kunlun Mountain and celestial plants, column and bracket sets engendered a rich iconography that served to bond architecture closely to the heavens.

Central composite design based development and validation of an rp-hplc method for paclitaxel in bulk and pharmaceutical dosage form

ObjectiveDevelopment of an accurate, precise, robust, sensitive, economical and rapid isocratic reverse phase high performance liquid chromatography (RP-HPLC) technique complying quality by design (QbD) and validate according to ICH guidelines for the quantitative estimation of Paclitaxel in bulk and pharmaceutical dosage form.MethodThe simultaneous assessment of the Paclitaxel with Nilotanib as internal standard in bulk and pharmaceutical dosage forms with the help of chemometrics, multicriteria decision-making approach. The separation was achieved by utilizing Phenomenex Enable C₁₈ column (Gemini, 15x4.6mm, 5μm particle size) and PDA-UV detection set at 230nm was developed and validation of Paclitaxel in pure form and pharmaceutical formulation, optimized by Derringer’s desirability functions. Chromatographic separation was consisted of a mixture of acetonitrile and KH₂PO₄ (70:30 %v/v, pH 4) adjusted with orthophosphoric acid and the flow rate of 0.8ml/min.Newly developed method resulted in eluting the drug at 3.928min, respectively. The regression coefficients (R²) were observed to be 0.999 for all models. The detection of limits (LOD) was about 9.498ng/ml and quantitation limits (LOQ) were about 31.66ng/ml. The relative standard deviation was observed to be 1.842%. Peak area ratio of the analyte and internal standard was used for the estimation of pharmaceutical formulations.The method was validated by determining its precision, accuracy, and system stability. The results of the investigation demonstrated that the suggested RP-HPLC method is simple, rapid, precise and accurate, which is convenient for the routine determination of Paclitaxel in bulk and pharmaceutical dosage forms.

A Simple and Sensitive High Performance Liquid Chromatographic Method for Estimation of Transitmycin in Plasma

A high performance liquid chromatographic method for estimation of Transitmycin (Tr) in human plasma was developed. The analyte was extracted using solid phase cartridges and the analysis of the eluent was carried out using Atlantis T3 column (150 cm × 4.6 mm ID) and photo diode array detector set at wavelength of 214 nm. The assay was specific for Tr and linear from 0.5 µg/mL to 20.0 µg/mL. The relative standard deviations for intra- and inter-day assays were less than 10%. The method yielded a recovery for Tr that ranged from 94% to 107% and could be used in toxicology and pharmacokinetic studies.

Packed bed column optimization and modeling studies for removal of chromium ions using chemically modified Lantana camara adsorbent

The current study proposes to address the growing concerns related to chromium discharges from metal plating facilities. For this purpose, acid treated Lantana camara is synthesized and continuous adsorption experiments were conducted on the fixed bed column set up. Some of the desirable attributes of the adsorbent are their favourable functional groups and the porous nature. These findings are reported in the FTIR and SEM analyses as well. In the column experiments run using laboratory simulated solution, considerably, the highest adsorption capacity of 362.8 mg/g is obtained. Since these results are favourable, column experiments have also been performed on composite electroplating effluents containing chromium ions. Notably, for composite electroplating effluents, maximum bed capacity of 50.05 mg/g is obtained. Another key point is the favourable breakthrough time reported for 100 mg/L chromium solution, which is 1260 min. Further, models such as Thomas, Yoon -Nelson, and Bed Depth Service Time (BDST) have also shown excellent fits. On the whole, the results revealed that the developed column is effective in handling effluent-containing chromium. Besides, this study also provides a better understanding of the adsorption process in composite industrial effluents.

Seasonal performance of stormwater biofiltration system under tropical conditions

Urbanization rates are increasing in developing countries such as Malaysia. In the tropics, flooding is a major concern, due to high rainfall intensities. In addition to flooding, pollution caused by contaminants contained in urban runoff are also of concern. Biofiltration system as one of the technologies in on-site stormwater treatment, has gained its popularity as part of Water Sensitive Urban Design measures. To date however, studies on tropical biofiltration system are limited in number and scope. This study aims to assess the effect of wetting and drying on performance, since such systems are constantly subject to wetting and drying cycles. In this study, a set of sand-based filter columns were prepared with three different native plant species including Cordyline fruticosa (CF), Graptophyllum pictum (GP), and Cyperus alternifolius (CA). Ten wetting and drying regimes were conducted including 5 wet weather simulations (0, 0, 1, 2, 3 dry days) followed by 5 dry weather simulations (5, 7, 10, 14, 21 dry days). To aid the plants survivability during the dry period, submerged zone was installed in all columns, simulating groundwater table. The results showed that all three plants could survive throughout both wet and dry periods with minimum stress. The overall treatment performance of all column types was satisfactory as the heavy metal concentration reduction was 90% and above while total dissolved phosphorus (TDP) reduction was up to 94%. Although total dissolved nitrogen (TDN) reduction was not as high as TDP (up to 58% reduction), the effluent TDN concentration still met the required receiving water quality standard. Overall, effluent concentration from CF, GP, and CA columns satisfied the requirement of class IIB recreational water standard in Malaysia. It was also concluded that plant CA comparatively performed better than the others in terms of both survivability and pollutants removal aspects.

WAVETRISK-1.0: an adaptive wavelet hydrostatic dynamical core

Abstract. This paper presents the new adaptive dynamical core wavetrisk. The fundamental features of the wavelet-based adaptivity were developed for the shallow water equation on the β plane and extended to the icosahedral grid on the sphere in previous work by the authors. The three-dimensional dynamical core solves the compressible hydrostatic multilayer rotating shallow water equations on a multiscale dynamically adapted grid. The equations are discretized using a Lagrangian vertical coordinate version of the dynamico model. The horizontal computational grid is adapted at each time step to ensure a user-specified relative error in either the tendencies or the solution. The Lagrangian vertical grid is remapped using an arbitrary Lagrangian–Eulerian (ALE) algorithm onto the initial hybrid σ-pressure-based coordinates as necessary. The resulting grid is adapted horizontally but uniform over all vertical layers. Thus, the three-dimensional grid is a set of columns of varying sizes. The code is parallelized by domain decomposition using mpi, and the variables are stored in a hybrid data structure of dyadic quad trees and patches. A low-storage explicit fourth-order Runge–Kutta scheme is used for time integration. Validation results are presented for three standard dynamical core test cases: mountain-induced Rossby wave train, baroclinic instability of a jet stream and the Held and Suarez simplified general circulation model. The results confirm good strong parallel scaling and demonstrate that wavetrisk can achieve grid compression ratios of several hundred times compared with an equivalent static grid model.

An analytical solution for analysis of toppling-slumping failure in rock slopes

When a slope consists of a horizontal weak rock or soil overlaid by some vertical strong slender rock columns, the slope is prone to a secondary toppling failure which is known as “toppling-slumping” failure. In the slope, rock columns impose pressure on the lower continuous weak rock or soil mass which leads to a differential settlement at the base of each rock column or a circular shear failure in the continuous mass. If the differential settlements reach a special threshold, rock column overturn and toppling-slumping will happen. However, the circular shear failure of the soil or weak rock mass which is a well-recognized failure mechanism will occur when shear stress in the slope exceeds its shear strength. In this paper, an attempt has been made to better understanding of the “toppling-slumping” failure mechanism through developing an analytical solution. For this purpose, first an Airy stress function is acquired for the lower continuous soil mass and its stress distribution and displacement are accordingly determined analytically due to the overlaid rock columns loads. Then, differential settlements at the base of all rock columns and shear stresses in the soil or weak rock mass are computed and compared with the toppling and shear failure criteria to assess slope failure. Finally, several design-charts are developed that determine the stability of a slope against toppling-slumping failure mechanism based on geometric characteristics of the slope and shear strength of its constituent material. Also, a Mathematica package code was developed to evaluate the stress distribution within the slope, and the safety factor. The results show that the vertical stress distribution plays a significant role in the settlement of the rock columns. Results also manifested that at a certain distance from the slope crest, the set of rock columns will act like a single column on a half-plane. The shear or toppling failure of the slope not only depends on the material's strength but also on the geometry and the normalized column distance.

Characterization of 9 gas chromatography columns by Kovats and Lee retention indices for dioxin analysis

Polychlorinated dibenzo-p-dioxins and furans offer a complex separation challenge due to their chemical similarity and 5020 possible congeners, including the Br/Cl congeners. Not only are these compounds difficult to separate, but they are also difficult to identify. Expensive reference materials are needed for conventional “dioxin analysis”, usually requiring 13C labeled and native compounds. A retention index database offers a potential solution to lower the difficulty and cost to identify dioxins. This study describes the use of Kovats and Lee retention indices for the identification of chlorinated dioxins and furans as well as their brominated and mixed chloro/bromo counterparts. Eight columns were characterized with all 136 tetra through octa substituted chlorinated dioxins and furans as well as 32 brominated and mixed chloro/bromo congeners. Columns were then compared to identify which stationary phases provided the best resolution for critical congeners, like the 2,3,7,8 substituted compounds. Column phase selectivity was also investigated to identify best commercially-available column pairings for confirmatory analyses and GC × GC separations. The Rtx-Dioxin2 and Rxi-17SilMS showed unique selectivity for dioxins and furans and could be used as confirmatory columns or as a powerful GC × GC column set.

Cost comparison between reinforced concrete moment resistant gantry system and reinforced concrete industrialized structural wall system

The system of porticoes resistant to moments of reinforced concrete is a set of beams and columns connected by means of knots that allows the generation of adequate spaces with facility before changes by the same users, whereas the industrialized system of structural walls of reinforced concrete, they are used for numerous, repetitive and of low price real estate, but they are completely immobile and in some occasions with problems of segregation and anthills. In this research work, a comparative study of the costs and budgets of the two proposed structural systems of the building was carried out in order to determine the structural system with the lowest costs and execution times, showing the results in explanatory graphs.

Upper bounds on the sizes of variable strength covering arrays using the Lovász local lemma

Covering arrays are generalizations of orthogonal arrays that have been widely studied and are used in software testing. The probabilistic method has been employed to derive upper bounds on the sizes of minimum covering arrays and give asymptotic upper bounds that are logarithmic on the number of columns of the array. This corresponds to test suites with a desired level of coverage of the parameter space where we guarantee the number of test cases is logarithmic on the number of parameters of the system. In this paper, we study variable strength covering arrays, a generalization of covering arrays that uses a hypergraph to specify the sets of columns where coverage is required; (standard) covering arrays are the special case where coverage is required for all sets of columns of a fixed size t, its strength. We use the probabilistic method to obtain upper bounds on the number of rows of a variable strength covering array, given in terms of parameters of the hypergraph. We then compare this upper bound with another one given by a density-based greedy algorithm on different types of hypergraph such as t-designs, cyclic consecutive hypergraphs, planar triangulation hypergraphs, and a more specific hypergraph given by a clique of higher strength on top of a “base strength”. The conclusions are dependent on the class of hypergraph, and we discuss specific characteristics of the hypergraphs which are more amenable to using different versions of the Lovász local lemma.

On the Rank of a Random Binary Matrix

We study the rank of a random $n \times m$ matrix $\mathbf{A}_{n,m;k}$ with entries from $GF(2)$, and exactly $k$ unit entries in each column, the other entries being zero. The columns are chosen independently and uniformly at random from the set of all ${n \choose k}$ such columns.&#x0D; We obtain an asymptotically correct estimate for the rank as a function of the number of columns $m$ in terms of $c,n,k$, and where $m=cn/k$. The matrix $\mathbf{A}_{n,m;k}$ forms the vertex-edge incidence matrix of a $k$-uniform random hypergraph $H$. The rank of $\mathbf{A}_{n,m;k}$ can be expressed as follows. Let $|C_2|$ be the number of vertices of the 2-core of $H$, and $|E(C_2)|$ the number of edges. Let $m^*$ be the value of $m$ for which $|C_2|= |E(C_2)|$. Then w.h.p. for $m&lt;m^*$ the rank of $\mathbf{A}_{n,m;k}$ is asymptotic to $m$, and for $m \ge m^*$ the rank is asymptotic to $m-|E(C_2)|+|C_2|$.&#x0D; In addition, assign i.i.d. $U[0,1]$ weights $X_i, i \in {1,2,...m}$ to the columns, and define the weight of a set of columns $S$ as $X(S)=\sum_{j \in S} X_j$. Define a basis as a set of $n-𝟙 (k\text{ even})$ linearly independent columns. We obtain an asymptotically correct estimate for the minimum weight basis. This generalises the well-known result of Frieze [On the value of a random minimum spanning tree problem, Discrete Applied Mathematics, (1985)] that, for $k=2$, the expected length of a minimum weight spanning tree tends to $\zeta(3)\sim 1.202$.

Thematic Accuracy Quality Control by Means of a Set of Multinomials

The error matrix has been adopted as both the “de facto” and the “de jure” standard way to report on the thematic accuracy assessment of any remotely sensed data product. This perspective assumes that the error matrix can be considered as a set of values following a unique multinomial distribution. However, the assumption of the underlying statistical model falls down when true reference data are available for quality control. To overcome this problem, a new method for thematic accuracy quality control is proposed, which uses a multinomial approach for each category and is called QCCS (quality control column set). The main advantage is that it allows us to state a set of quality specifications for each class and to test if they are fulfilled. These requirements can be related to the percentage of correctness in the classification for a particular class but also to the percentage of possible misclassifications or confusions between classes. In order to test whether such specifications are achieved or not, an exact multinomial test is proposed for each category. Furthermore, if a global hypothesis test is desired, the Bonferroni correction is proposed. All these new approaches allow a more flexible way of understanding and testing thematic accuracy quality control compared with the classical methods based on the confusion matrix. For a better understanding, a practical example of an application is included for classification with four categories.

Finite Element Analysis of Overhead Pipeline Truss Bridge under Thermal Fluid Loads

The subject used in this study is an overhead pipeline truss bridge which sits in a chemical industrial park. The overhead pipeline truss bridge is a part of a pipeline system consisting of 10 sets of columns, 4 layers of pipe racks and 27 pipelines that transports flowing media under various temperature and pressure conditions. An integrated ANSYS finite element model was built considering the factors such as gravity, medium temperature, and flow load, etc. The results of the distributions of displacement, axial force, shear force, bending moment and stress of the overhead pipeline truss bridge were calculated. The primary stress and secondary stress were checked to judge the reliability of the overhead pipeline truss bridge. It concluded that the computation model and calculation used in this study is feasible and effective. The feature in this paper is to explore a practical method and to provide a solid technological foundation for the safety operation and assessment of overhead pipeline truss bridge.

A Stepwise Strategy Employing Automated Screening for Reversed-Phase Chromatographic Separation of Itraconazole and Its Impurities

The development of methods for the chromatographic separation of complex mixtures is often challenging, and an organized approach is required to rapidly achieve the desired separation. Herein, software (S-Matrix Fusion)-assisted platform is used to effectively screen, optimize, and select optimal parameters for the separation of itraconazole and its 15 impurities. The employed platform exploits dissimilar chromatographic systems, uses a diverse set of columns with enormous selectivity differences, and evaluates a wide range of aqueous mobile phase pH and organic modifiers for screening experiments. The wide range of selectivity ensures the identification and resolution of critical analytes, while the combination of dissimilar systems and automated screening statistical software increases the speed, efficiency, and level of understanding of critical parameters influencing separation. Automated screening using the described platform allows the establishment of a mass-compatible ultra-high-performance liquid chromatography method capable of separating all impurities. Multivariate robustness of critical parameters such as buffer concentration, flow rate, column temperature, and gradient is evaluated to identify the operational range of the method. Moreover, the optimized method is validated following the International Conference on Harmonization (ICH) guidelines, evaluated in terms of specificity, analysis repeatability, intermediate precision, linearity, accuracy, limit of quantification, limit of detection, solution stability, and range, and concluded to be fit for purpose in the quality control laboratories for release, stability, and investigation purposes.

Simulation of peak position and response profiles in comprehensive two-dimensional gas chromatography

Approaches to simulate peak time and intensity profiles of compounds in comprehensive two dimensional gas chromatography (GC × GC) were developed, and which are demonstrated for separation of a mixture of saturated and unsaturated fatty acid methyl esters (FAME) using a range of column sets. The simulation of first and second dimension time (1tR and 2tR) of FAME relies on use of a Gibbs energy additivity approach to correlate with the structures of FAME. First and second dimension peak standard deviations (1σ and 2σ) of the compounds were further calculated from the 1tR and 2tR data according to the plate height concept which provided good agreement between the predicted and experimental peak widths at half height in one dimension GC (1DGC) with an overall R2 of 0.9628. The effect of 1σ distortion caused by the modulation process was also taken into account in the peak width simulation where the simulated 1σ data were rounded up to multiples of the scale of modulation period (PM). Two dimension Gaussian equations were then used to generate GC × GC results (2D contour plots) from simulated 1tR, 2tR, 1σ and 2σ data for FAME separation on different column sets employing ionic liquid and conventional columns. Good overall correlations between experimental and simulated 1tR and 2tR were obtained with R2 of 0.9951 and 0.9802, respectively, and the simulated 2D contour plots were an acceptable match with the experimental results.