Internal Columns Research Articles

Interlaboratory Development and Cross Validation of a Chromatographic Method for Determination of Lumefantrine in Human Plasma-A Proficient Capacity Assessment of Bioanalytical Laboratories in East Africa

Background: Bioanalytical laboratories in developing countries face many challenges. The objective of this work was to assess the capacity of bioanalytical laboratories in emerging countries in setting and validating analytical methods. An HPLC method for determination of lumefantrine in human plasma was used to assess three medical university laboratories of Tanzania, Uganda and Kenya. Methodology: Bioanalytical experts from Analytical Clinical Concept, Leidersbach, in Germany (ACC GmbH) developed the HPLC method and assigned the 3 laboratories to set up and validate the method. The laboratories were tasked to determine the concentrations of blinded plasma samples spiked with lumefantrine and had to submit their analysis reports to ACC for evaluation within 6 weeks. Each laboratory was provided with reference standard, internal standard columns and precolumns. Spiked plasma samples were shipped under dry ice from Germany to “Gesellschaft fuer Internationale Zusammenarbeit” (GIZ) local office of each participating country. All other requirements were procured by individual laboratories. Results: The results from MUHAS Bioanalytical laboratory (Tanzania) Laboratory met the criteria set by ACC laboratory. The results were within the range set by ACC laboratory and most calibration curves had good linearity with coefficient of correlation always > 0.990. The inter-day precision and accuracy (Relative standard deviation=RD of recovery) were always < 15%. The relative deviation of the results obtained compared to assigned concentrations for blinded plasma samples were between -15% and -25%. The Laboratory met the stipulated time line and the obtained validation results were within the range set by the ACC experts. The results from other laboratories were also satisfactory. Conclusion: The results indicate that with further little infrastructural and technical assistance the capacity of these bioanalytical laboratories in conducting bio-analyses will be more strengthened and can serve as centers for training bioanalytics and running bioequivalence studies in the region.

Christchurch City Council lifelines

On 22 February 2011 an earthquake measuring 6.3 on the Richter Scale occurred in Christchurch City resulting in widespread damage to buildings and infrastructure.&#x0D; Christchurch City Council (CCC) has an extensive potable water supply network including bulk storage and service reservoirs which provide water to approximately 320,000 residents. Inspections undertaken, following the 22 February earthquake, on 43 concrete reservoirs located on the Port Hills and Cashmere Hills areas noted varying extents of damage from nil through to major. Damaged roof to wall connections were observed in many reservoirs with damage to walls, base-slabs and internal columns limited to a few reservoirs only. Of the 43 reservoirs, complete functional failure occurred in only one, with reduced function and operation at other sites resulting from excessive leakage, necessity for emergency repairs, or associated pipe work damage. Those reservoirs currently out of operation for reinstatement, including Christchurch’s largest, account for approximately 40% of the network’s storage capacity.&#x0D; Overall, given the magnitude of earthquake accelerations that occurred on 22 February 2011, the reservoirs are considered to have performed remarkably well. Those in the Port Hills area nearest the earthquake epicentre, have expectedly, incurred the most damage.&#x0D; Reinstatement works, varying from minor crack injection and patch repair through to reconstruction and retrofit, have been developed appropriate to the extent of damage. CCC has prioritised reservoir repair to maximise available water supply for the 2011-2012 summer demand and this has required, in some instances, staging and deferring of reinstatement works.&#x0D; A summary of structural and functional performance, results of physical investigations and detailed seismic assessments, and common damage areas observed are presented in this paper along with the reinstatement options developed.

Non-axis-symmetrical punching shear around internal columns of RC slabs without transverse reinforcement

Most analytical approaches and available test data for punching shear in flat slabs assume axis-symmetrical conditions, which seems realistic for representing slabs supported on columns equally spaced in both orthogonal directions. However, in practice, there are many instances where loading, geometry and reinforcement around internal columns differ significantly from ideal axis-symmetrical conditions. Typical examples include slab bridges, flat slabs with unequal spans and footings with unequal widths. This paper presents a series of punching shear tests on slabs without transverse reinforcement and different flexural reinforcement ratios or loading conditions in each orthogonal direction. The tests show that both the type of loading and the amount of flexural reinforcement have a significant influence on the punching shear strength and symmetry of the response. Eurocode 2 and BS 8110 code formulas provided reasonable strength predictions of the tests using the recommended average reinforcement ratio between the x and y directions. A physical explanation behind this assumption is presented, based on critical shear crack theory. A rational analytical approach was developed for non-axis-symmetrical punching, which provides accurate predictions of strength and deformation capacity. The novelty of the proposed method is that it considers a non-uniform shear strength distribution per unit length along the control perimeter, which results in a redistribution of shear near failure.

Free vibration analysis of rectangular plates with internal columns and uniform elastic edge supports by pb-2 Ritz method

Free vibration analysis of rectangular plates with internal columns and elastic edge supports is presented using the powerful pb-2 Ritz method. Reddy's third order shear deformation plate theory is employed. The versatile pb-2 Ritz functions defined by the product of a two-dimensional polynomial and a basic function are taken as the admissible functions. Substituting these displacement functions into the energy functional and minimizing the total energy by differentiation, leads to a typical eigenvalue problem, which is solved by a standard eigenvalue solver. Stiffness and mass matrices are numerically integrated over the plate using the Gaussian quadrature. The accuracy and efficiency of the proposed method are demonstrated through several numerical examples by comparison and convergency studies. Many numerical results for reasonable natural frequency parameters of rectangular plates with different combinations of elastic boundary conditions and column supports at any locations are presented, which can be used as a benchmark for future studies in this area.

A Study on the Loss Reduction Method of Reinforcing Bar through Case Study

Rebar work accounts for approximately 30% of the total construction costs for rebars and concrete. Recently, the high rising prices of rebars have become one of the principle factors of rising construction costs. Therefore, construction companies are putting much effort into loss reduction of rebars. Consequently, in this study, we wished to present loss reduction methods of rebars before the preparation of the placing drawings. To devise such methods, we collected previous case studies and analyzed methods that were applied for loss reduction. As a result of the analysis, we were able to find the following methods for loss reduction of rebars: method of reducing the number of splices at the mat foundation, method of reducing splice length at the internal columns or walls of the underground parking lot, method of reducing cap-ties of internal beams of basement floors excluding perimeter beams, and method of reducing anchorage length at the internal column or wall of the underground parking lot. Based on those analysis results, we presented our own loss reduction methods of rebars. Applying our methods resulted in considerable loss reduction.

Design of ACI-type punching shear reinforcement to Eurocode 2

This paper describes a series of tests that were carried out at Imperial College London to determine the efficiency of stirrups when used as ACI-type punching shear reinforcement at internal columns. Six 3 m square slabs were tested with various arrangements of punching shear reinforcement. The variables considered in the tests included the area of shear reinforcement and the extension of the stirrups from the column face. The measured shear strengths were compared with the shear strengths predicted with Eurocode 2 and ACI 318. The design method in Eurocode 2 is shown to be overly conservative for ACI-type punching shear reinforcement and a modification is proposed. The paper describes a series of three-dimensional non-linear finite-element analyses which were carried out to gain a better appreciation of the parameters influencing the efficiency of ACI-type shear reinforcement and to assist in the validation of the proposed design method. The non-linear finite-element analysis is shown to give good predictions of the measured shear strengths of the tested slabs.

The fire behaviour of multi-bay, two-way reinforced concrete slabs

This paper describes numerical modelling of the fire behaviour of two-way reinforced concrete slabs in a multi-storey multi-bay building. The building is square, with three bays in each direction. The concrete slab is supported by a perimeter frame, four internal columns and no internal beams. It is assumed that all nine bays of the concrete slab at one level are subjected to fire from below. Two fires were used; the standard ISO834 fire for a four hour duration, and a parametric fire based on the ISO834 fire for one hour with the temperatures decaying to ambient in another two hours. The effects of the fires are described in relation to the redistribution of bending moments and the development of tension field action in the slab.

Contribuição ao estudo de lajes lisas unidirecionais de concreto armado com pilares retangulares ao puncionamento

São apresentadas análises das recomendações para estimar a resistência ao puncionamento de lajes lisas de acordo com a versão atual da norma brasileira, a NBR 6118:2003, que não considera o efeito da retangularidade de pilares internos, e sua predecessora, a NBR 6118:1980. Em seções transversais retangulares, o índice de polarização das tensões de cisalhamento é crescente. Isto altera a forma de ruptura da laje, já que a punção se inicia em torno das extremidades da seção do pilar, não se estendendo para os lados maiores, como prescreve a norma, comportamento este que reduz a resistência última das lajes frente às estimativas normativas. São apresentados os resultados de uma análise numérica por elementos finitos (M.E.F.) e uma proposta para melhorar a ductilidade das lajes lisas através das dimensões mínimas dos pilares. Observou-se que a NBR 6118:1980 mostrou-se conservadora e que as estimativas da NBR 6118: 2003 podem ser melhoradas.

Detection of fractures from GPR data: the case history of the Cathedral of Otranto

Ground penetrating radar (GPR) surveys were carried out in the preliminary stage of a project of structural monitoring of the 42 columns inside the crypt of the ‘Cattedrale di Otranto’ (Lecce, Italy). Detailed knowledge of the structure of the internal columns was a key reason for their restoration since they had several points of deterioration (i.e. fractures). The aim of this work was to test the reliability of both a standard GPR processing (in a time domain) and a linear inverse scattering algorithm (in a frequency domain) in order to detect and achieve information on the damaged zones inside the columns. First, the reliability of both the techniques was preliminarily assessed by processing synthetic data resembling the measurement conditions of the experimental cases. Then the experimental data were processed by means of the two techniques. Our comparative analysis, for both the numerical and the experimental analyses, indicates that the linear inverse scattering approach is better suited for the detection of local fractures compared to the classical time-domain processing, while increasing the computational cost at a reasonable rate.

Free vibration analysis by the superposition method of rectangular Mindlin plates with internal columns resting on uniform elastic edge supports

Free vibration analysis of rectangular Mindlin plates is carried out via the superposition method and is shown to produce accurate results. The analytical method proposed by the authors in this paper solves the problem for the case where the plate has simultaneous elastic edge and internal supports. The conditions of edge supports are uniform lateral, rotational and torsional elastic supports, whereas, the internal supports are column supports with finite area. Compatibility between the plate and column is achieved by requiring that the column and plate rotations be equal. The results presented herein are verified through comparison with results presented by others. Numerical examples presented in this study confirm that the analytical method is able to model the property of the elastic edge supports while simultaneously considering the effect of column restraint, an effect which increases with column number and area.

Boundary element modelling of flat plate floors under vertical loading

The present paper develops a boundary element model for flat plate floors. The floor slab is modelled using the shear-deformable plate bending theory. Internal columns or walls are treated using internal collocation technique, where three interaction generalized forces are considered at the slab–column connection: two bending moments in two directions and shear force in the vertical direction. Such forces are considered to be constant over the column cross-sections. The present technique takes into account the realistic geometric modelling of the column cross-sections. The effect of considering such geometry in the analysis of the bending moments transferred from slab to columns is studied. Several examples, including solution of practical building slab, are presented. The results are compared to those obtained from other numerical methods to demonstrate the accuracy and the reliability of the present formulation. The present formulation can be considered as an accurate tool to predict moment transferred from the slab to the column. Copyright © 2004 John Wiley & Sons, Ltd.

T-Cleat Connections to Concrete-Filled Tubular Internal Columns

Tests have been carried out on four full-scale composite connection specimens. The specimens were made by connecting two unsymmetrically loaded steel beams to concrete-filled rectangular hollow section tubular columns. The columns were hence subjected to axial loading and bending moments, and thus represented internal columns in multistory buildings. Columns and beam loads were increased proportionately up to failure, and both column and connection behavior were observed and recorded. The experimental failure loads and column behavior are compared against the predictions of a three-dimensional finite-element (FE) model, using a general purpose FE software.

Three-Dimensional Structure of I to: Kv4.2-KChIP2 Ion Channels by Electron Microscopy at 21 Å Resolution

Regulatory KChIP2 subunits assemble with pore-forming Kv4.2 subunits in 4:4 complexes to produce native voltage-gated potassium (Kv) channels like cardiac I to and neuronal I A subtypes. Here, negative stain electron microscopy (EM) and single particle averaging reveal KChIP2 to create a novel ∼35 × 115 × 115 Å, intracellular fenestrated rotunda: four peripheral columns that extend down from the membrane-embedded portion of the channel to enclose the Kv4.2 “hanging gondola” (a platform held beneath the transmembrane conduction pore by four internal columns). To reach the pore from the cytosol, ions traverse one of four external fenestrae to enter the rotundal vestibule and then cross one of four internal windows in the gondola.

Ito Channels Are Octomeric Complexes with Four Subunits of Each Kv4.2 and K+ Channel-interacting Protein 2

Mammalian voltage-gated K+ channels are assemblies of pore-forming alpha-subunits and modulating beta-subunits. To operate correctly, Kv4 alpha-subunits in the heart and central nervous system require recently identified beta-subunits of the neuronal calcium sensing protein family called K+ channel-interacting proteins (KChIPs). Here, Kv4.2.KChIP2 channels are purified, integrity of isolated complexes confirmed, molar ratio of the subunits determined, and subunit valence established. A complex has 4 subunits of each type, a stoichiometry expected for other channels employing neuronal calcium sensing beta-subunits.

Variation in bone mineral density of the sacrum in young adults and its significance for sacral fixation.

Bone mineral density variations throughout the sacrum were measured and correlated with sacral screw insertion torque. To quantify bone mineral density variations within the S1 body and ala of young human specimens, especially along the pathways of sacral screws, and to examine the relation between sacral screw fixation and bone mineral density. Vertebral bone quality is an essential factor in anterior or posterior screw fixation of the spine. Several studies have been conducted regarding bone mineral density variations in the cervical and thoracolumbar spine. However, such variations in bone mineral density in the sacrum have not been well documented. The bone mineral density of 13 sacral specimens from young male cadavers (mean age, 31 years) was measured using highly accurate quantitative computed tomography. Variations in bone mineral density were measured in five transverse layers and seven vertical columns within the S1 body, and in four transverse layers and six vertical columns within the ala. The sacral screw insertion torque was measured (unicortical and bicortical), and the correlation with bone mineral density was calculated. The mean bone mineral density of the S1 body was 381.9 +/- 59 mg/cm3, which was 31.9% higher than that of the sacral ala (mean, 296.9 +/- 86 mg/cm3) (P < 0.05). Bone mineral density of the superior sacral endplate was higher than that of any other transverse layer. Columns near the lateral posterior and lateral anterior of the S1 body had the highest bone mineral density. In the ala, bone mineral density values of the internal columns (pedicle) were the highest. Screw insertion torque for bicortical purchase along the S1 pedicle correlated well with the bone mineral density of the S1 body (r = 0.67, P < 0.05). This study quantified the volumetric bone mineral density variations within the S1 body and ala, and a significant linear correlation between the screw insertion torque and bone mineral density was found. Optimal sacral screw insertion pathways were also outlined based on bone mineral density values.

Enhanced transport of bacteria through a soil matrix using colloidal gas aphron suspensions

The influence of an anionic surfactant sodium dodecylbenzene sulfonate (DDBS) in the form of either an aqueous solution or microgas dispersion known as colloidal gas aphron (CGA) on the transport of a Psendomonas psendoalcaligenes, strain through a saturated soil matrix was examined. The experiments were conducted in 30‐cm‐long and 6.35 cm internal diameter stainless steel columns packed with a sandy clay loam. A 10‐ml pulse (0.033 pore volumes) of a bacterial suspension containing 1010 colony forming units (cfu) per ml was injected, and the column was eluted with either deionized water, a solution of DDBS, or a CGA suspension at a surface loading rate of 0.16 cm/min. The bacterial distributions within the column were similar after the passage of the water and surfactant solutions; however, the distribution of bacteria in the columns and effluent after the passage of the CGA suspension was markedly enhanced. The bacterial concentration in the lower half of the column after the passage of the CGA suspension was 2 to 3 orders of magnitude higher than that observed for either the surfactant or water solutions under similar experimental conditions. The final bacterial density in the effluent after the passage of the surfactant solution was one‐half order of magnitude greater than that in the effluent produced by passage of water. After the passage of the CGA suspension, the total number of bacteria in the effluent was at least 2 or 3 orders of magnitude greater than that obtained by passage of either surfactant or water as the eluting agent, respectively. The results of the study suggests that CGA suspensions can transport bacteria more efficiently than conventional surfactant solutions or water.

Valve injection for gas chromatographic analysis on small-bore open tubular columns

An injection valve with a small internal loop actuated by pneumatic switching was used for high-speed gas chromatography (GC). Small internal diameter (50 and 100 μm i.d.) open tubular columns were used for investigations of the injector performance. Several valve injection systems have been tested. The influence of the sample solvents, the injection temperature, the connection methods, and the time-split technique under GC conditions have been investigated. High resolution, fast separation speed, and reproducible GC analyses have been achieved. This study indicates that valve injection onto small internal diameter open tubular columns is a promising technique for high-speed and high-resolution GC analysis. © 1996 John Wiley & Sons, Inc.

Public Bank Building, Johor Bahru, Malaysia

The 32-level Public Bank Building is the tallest building in the city of Johor, Bahru, one of the most dynamic urban developments in Malaysia. Located at a very congested site, the architectural design emphasises efficiency, calling for long spans to create minimally interrupted office space. The service core is located at one side of the building, and only two internal columns interrupt the net 850 m² floors. The lower 11 levels accommodate banking halls, parking, a mechanical floor and a cafeteria level. The upper 20 levels are typical office floors.

Centrosome organization and centriole architecture: Their sensitivity to divalent cations

The centrosome plays a major role in the spatial organization of the microtubular network and has a controlled cycle of duplication, the two duplicated centrosomes functioning as mitotic poles during subsequent cell division. However, a comprehensive description of the overall organization of the centrosome in animal cells is lacking. In order to integrate the various pieces contributing to the centrosome structure and to optimize the quality of the data, we have undertaken an extensive ultrastructural study of centrosomes isolated from human lymphoblasts, which involved (i) orientation of centrosomes by sedimentation before embedding and sectioning, (ii) ultrathin serial sectioning, (iii) digitalization of micrographs to obtain quantitative data, and finally, (iv) comparison between two methods of isolation, which differ by the presence or absence of EDTA. Using this strategy, we have unambiguously described the pericentriolar organization of two distinct sets of appendages (distal and subdistal) about the so-called parental centriole. New structures have been also observed in association with the microtubule sets in this study: (i) external columns, which are dense structures localized at the basis of the subdistal appendages and (ii) internal columns, which are made of globular subunits integrated in a more luminal and probably helical structure. We have also observed that removal of divalent cations by the EDTA during the isolation procedure could affect the centrosomal structure at different levels (subdistal appendages, internal and external columns, pericentriolar matrix), including a significant variation in centriole diameter. A scheme of the overall organization of the centrosome from animal cells and of its modulation by divalent cations can be drawn from this study. Our data gives a view of the centrosome as an organelle displaying a complex and possibly dynamic structural organization.

Preparative Liquid Chromatography and theH/uCurve

Abstract H/u curves for columns of increasing internal diameter are shown to be useful for evaluating their LC performance. In particular, the H/u curve reveals whether the packing technique or the packing material is defective. H/u curves for very large internal diameter columns show deviations which result from friction heat and thermal expansion of the column tubing, creating a void at the column wall.