Individual Columns Research Articles

Open-Ocean Minima in δ13C Values of Particulate Organic Carbon in the Lower Euphotic Zone

Extensive studies in the 1980s-1990s led to the characterization of latitudinal variations in sea surface δ13C values of particulate organic carbon (δ13CPOC), and relationships were found with CO2 concentrations, temperature, growth rates, and cell geometries. Surprisingly, no large-scale efforts have been made to describe variations in δ13CPOC values over depth in the water column. Here we compile published examples demonstrating a widespread isotopic pattern in particulate organic carbon of the upper water column. In 51 vertical profiles, δ13CPOC values in the lower euphotic zone on average are 1.4‰ lower than δ13CPOC values in the upper euphotic zone of open ocean settings. In a majority of locations this downward decrease in δ13CPOC values is > 2‰ and up to 5‰, larger than the commonly recognized vertical δ13C variation in dissolved inorganic carbon over the same depths. We briefly review hypotheses and supporting evidence offered by previous studies of individual water columns: The observed patterns could result from vertical differences in photosynthetic growth rates or community composition, biochemical composition of organic matter due to degradation, isotopic disequilibrium within the dissolved inorganic carbon pool, particle dynamics, or seasonal vertical mixing. Coordinated isotopic, biological, and seawater chemistry data are sparse, and consistent drivers of this widespread isotopic pattern are currently elusive. Further work is needed to adequately characterize the environmental conditions coinciding with this pattern, to test its origins, and to determine if the magnitude of upper water column δ13CPOC variations could be a useful marker of upper ocean carbon cycle dynamics.

Visualization of clay minerals at the atomic scale

AbstractThis review demonstrates that high-resolution transmission electron microscopy (HRTEM) imaging of clay minerals or phyllosilicates with an incident electron beam along the major zone axes parallel to the constituting layers, in which the contrast corresponds to individual cation columns in the images obtained, is indispensable for elucidating the enigmatic structures of these minerals. Several kinds of variables for layer stacking, including polytypes, stacking disorder and the interstratification of various kinds of unit layers or interlayer materials, are common in phyllosilicates. Local and rigorous determination of such variables is possible only with HRTEM, although examination as to whether the results obtained by the HRTEM images from limited areas represent the whole specimen should be made using other techniques, such as X-ray diffraction. Analysis of these stacking features in clay minerals provides valuable insights into their origin and/or formation processes. Recent state-of-the-art techniques in electron microscopy, including incoherent imaging, superior resolutions of ~0.1 nm and low-dose imaging using new recording media, will also contribute significantly to our understanding of the true structures of clay minerals.

Spatial ordering of the charge density waves in NbSe3

Ordering of the two incommensurate charge density waves (CDW), ${\mathbf{q}}_{1}=(0.0, 0.243, 0.0)$ and ${\mathbf{q}}_{2}=(0.5, 0.263, 0.5)$, in the quasi-one-dimensional ${\mathrm{NbSe}}_{3}$ structure is studied by means of low-temperature scanning tunneling microscopy. Larger (100) van der Waals surfaces are analyzed using one-dimensional Fourier transforms along the three types of trigonal prismatic columns, running parallel to the monoclinic ${\mathbf{b}}_{0}$ direction. The procedure enables unambiguous differentiation between both CDWs modulating individual columns. In addition, it allows a quantitative comparison of modulation amplitudes along different columns of the same type and, in case of sufficiently large images, also along individual columns. It is confirmed that each CDW modulates both type-III and type-I columns with the narrowest isosceles bases. As a consequence beating is observed between the two slightly different modes. The bridging type-II columns appear not to be modulated. On a large scale the modulation amplitudes along individual columns vary, suggesting formation of CDW nanodomains. The possibility of interchanging both CDWs along columns forming symmetry-related pairs results in a charge difference, which is supposed to be the possible origin of CDW sliding.

Evaluating Remediation Efficiency of Functional Oyster Shell Powder for Organically Enriched Sediment

Eutrophication is a serious environmental issue in coastal areas, caused by increased nutrient concentration from external sources. Nutrients could augment in the bottom sediment and be released into overlying water, acting as an internal nutrient source. Converted oyster shell powders were used to evaluate the suppression of nutrients release from bottom sediments. Two kinds of oyster shell powder were applied into the sediment in the individual column with the control column. The natural oyster shell powder (NOSP) was composed of calcium carbonate and the functional oyster shell powder (FOSP) was composed of calcium peroxide. In the column where FOSP was applied, pH was increased due to hydrolysis of calcium peroxide in the overlying water. The concentration of dissolved oxygen in the FOSP-treated columns was higher than that of the control column. The FOSP could suppress the release of ammonia nitrogen and phosphates from the sediment into the overlying water. It was proven that FOSP can effectively adsorb phosphates from organically enriched sediments. Overall, the application of FOSP could effectively control nutrient release from the sediment to overlying water and help reduce the eutrophication in the coastal areas.

Effects of Cathode Voltage Pulse Width in High Power Impulse Magnetron Sputtering on the Deposited Chromium Thin Films

Environmentally-safe high-power impulse magnetron sputtering (HiPIMS) technology was utilized to deposit chromium films. This research focused on the influences of the HiPIMS pulse widths on the microstructure of films deposited at different deposition pressures and substrate bias voltages. Under the conditions of the same average HiPIMS power and duty cycle, the deposition rate of the Cr thin film at working pressure 0.8 Pa is slightly higher than at 1.2 Pa. Also, the difference between deposition rates under two pressures decreases with the discharge pulse width. The deposition rate of the short pulse width 60 μs is lowest, but those of 200 and 360 μs are approximately the same. With no or small direct current substrate biasing, the microstructure of films coated at short pulse width is similar to the typical magnetron sputtering deposited films. Elongating the pulse width enhances the ion flux toward the substrate and changes the film structure from individual prism-like columns into tangled 3-point/4-point star columns. Substantial synchronized substrate biasing and longer pulse width changes the preferred orientation of Cr films from Cr (110) to Cr (200) and Cr (211). The films deposited at longer pulse width exhibit a higher hardness due to the reducing of intercolumn voids.

Dissolved organic matter adsorption from surface waters by granular composites versus granular activated carbon columns: An applicable approach

Many new sorbents have been introduced as an alternative for granular activated carbon (GAC), the most common sorbent for dissolved organic matter (DOM) removal. In the current study, we developed an applicable granular composite based on a flocculant commonly employed for drinking water treatment adsorbed to montmorillonite. DOM adsorption from surface waters, Lake Kinneret and Suwannee River, with low and high specific ultraviolet absorption (SUVA), respectively, by composite and GAC columns, was studied. Adsorption of DOM from Suwannee River was significantly higher by the composite column, in comparison to the GAC column, while an opposite trend was obtained for the adsorption of DOM from Lake Kinneret. In-situ regeneration of the columns with a brine solution was extremely efficient and inefficient for the composite and GAC columns, respectively. Adsorption, of both waters, post-regeneration by the composite column was not compromised, while GAC effectiveness decreased. The opposite trend in DOM adsorption from Suwannee River and Lake Kinneret was explained by the different affinities of the sorbents towards various DOM molecules. Distinguishing between different DOM components adsorbed by GAC and the composite was supported by 13C NMR and direct pyrolysis-GC-MS measurements. Furthermore, we demonstrated that the kinetics and adsorption at the equilibrium of five organic molecules to the composite and GAC can be correlated to their chemical-physical properties. Indeed, combining the properties of both sorbents, by integrating them into a single column, yielded higher DOM removal than by the individual columns. Furthermore, since DOM removal by GAC and by the composite, increases, and decreases with temperature, respectively, the integrated column, mitigates the changes in removal, stabilizing the adsorption performance. Such an integrated filter may minimize additional seasonal and water quality fluctuations.

Column-normal fracture features of the basaltic joints in Santa Maria Regla, Hidalgo State, Mexico

Columnar fractures are imposing geological structure observed at several locations around the world. They usually have a polygonal cross-section that vary in size from a few centimeters to meters. The columnar basalt flow at Santa Maria Regla in central Mexico shows a typical two-layer structure with an upper entablature and a lower colonnade. For the colonnade, the horizontal parting surface of basaltic columnar joints shows a polygonal pattern, which is most commonly five sided. In the upper part of the colonnade, the hexagonality (m) index changes from 0.94 to 1.42 with column height, indicating a progressive maturation of columnar joints with time. However, in the lowermost colonnade, the m value does not show such correlation. Three types of column-normal fractures are observed: plane, convex-upward and concave-upward, which can be explained by different stress states of contraction in individual columns. Radial markings and axisymmetric plumes can be observed on some columnar-normal fractures. The flaw points of the former are usually encountered in the polygon center, whereas those of the latter are located nearly at the edge of the polygon. These two types of column-normal fracture markings are formed after the columnar joints.

Optimized seismic retrofit of steel-concrete composite buildings

This work is focused on comparatively assessing the cost-effectiveness of three seismic retrofit approaches for non-code-conforming frame buildings with steel-concrete composite columns. The first two of the assessed retrofit approaches aim in indirectly enhancing structural system performance by strengthening individual composite columns using reinforced concrete jackets or concrete-covered steel cages. The third retrofit approach considered aims in upgrading the composite building frame at hand by installing steel bracings at selected bays. A specially developed structural optimization procedure is used to perform an objective comparison of the cost-effectiveness of the three retrofit approaches. The objective of the optimization procedure is to minimize the total retrofit material cost, while constraints are imposed to ensure the satisfaction of design requirements for the retrofitted structure regarding member capacities (according to Eurocodes 3 and 4 for steel beams and composite columns, respectively), structural system performance under horizontal loading (based on interstorey drifts calculated by pushover analyses) and fundamental periods (obtained from eigenvalue analyses). By defining 30 cases of under-designed 2-storey, 4-storey and 6-storey composite buildings (i.e. buildings with steel-concrete composite columns), an extensive numerical investigation involving 120 retrofit optimization runs was conducted. The results obtained provide insight into the relative cost-effectiveness of the three seismic retrofit approaches and reveal certain conditions under which each approach is economically most viable.

Experimental and numerical study on the bearing capacity of encased stone columns

Stone columns have attracted considerable attention as a ground improvement techniques recently. Performance of stone columns, however, depends on confining pressure offered by the surrounding soils. In the case of very soft soils, the lateral confining pressure may be insufficient and this may lead to column bulging failure. Encapsulating the individual stone column enhances the lateral resistance against bulging by additional confining pressure. In this study, the influences of the length of encasement and type of aggregate materials on the bearing capacity of a single stone column in both dry sand and clay bed were investigated. The results indicated a clear improvement by encasing the half-length of the column. The numerical study also showed the effect of reinforcement stiffness reduces with increase in the cohesion of the clay. Parametric study showed that the effect of encasement stiffness is insignificant for clay bed with high values of cohesion.

An enzyme-based protocol for cell-free synthesis of nature-identical capsular oligosaccharides from Actinobacillus pleuropneumoniae serotype 1

Actinobacillus pleuropneumoniae (App) is the etiological agent of acute porcine pneumonia and responsible for severe economic losses worldwide. The capsule polymer of App serotype 1 (App1) consists of [4)-GlcNAc-β(1,6)-Gal-α-1-(PO4-] repeating units that are O-acetylated at O-6 of the GlcNAc. It is a major virulence factor and was used in previous studies in the successful generation of an experimental glycoconjugate vaccine. However, the application of glycoconjugate vaccines in the animal health sector is limited, presumably because of the high costs associated with harvesting the polymer from pathogen culture. Consequently, here we exploited the capsule polymerase Cps1B of App1 as an in vitro synthesis tool and an alternative for capsule polymer provision. Cps1B consists of two catalytic domains, as well as a domain rich in tetratricopeptide repeats (TPRs). We compared the elongation mechanism of Cps1B with that of a ΔTPR truncation (Cps1B-ΔTPR). Interestingly, the product profiles displayed by Cps1B suggested processive elongation of the nascent polymer, whereas Cps1B-ΔTPR appeared to work in a more distributive manner. The dispersity of the synthesized products could be reduced by generating single-action transferases and immobilizing them on individual columns, separating the two catalytic activities. Furthermore, we identified the O-acetyltransferase Cps1D of App1 and used it to modify the polymers produced by Cps1B. Two-dimensional NMR analyses of the products revealed O-acetylation levels identical to those of polymer harvested from App1 culture supernatants. In conclusion, we have established a protocol for the pathogen-free in vitro synthesis of tailored, nature-identical App1 capsule polymers.

Reliability-based evaluation for concrete-filled steel tubular (CFST) truss under flexural loading

Concrete-filled steel tubular (CFST) truss is now widely used in many large-span constructions. In the past, relevant studies on the reliability of CFST structures mostly focused on structural components such as individual columns and beams. In current practices, a simplified method based on the ultimate axial strengths of the chords is commonly adopted to predict the flexural strength of a CFST truss, since there is no mature system-based design regulations nor reliability evaluations on this complex composite system. This paper aims to address this gap by advanced structural reliability analysis of CFST truss through numerical approach considering both the structural nonlinearities and random uncertainties. The finite element models are validated against experimental results. Afterwards, a mass finite element simulation, taking into account the material and geometric nonlinearities, random initial imperfections and potential finite element model errors, is conducted to generate the statistics of the flexural strengths of CFST trusses. Reliability analysis is then conducted to calculate reliability indexes in respect of different resistance factors under various load cases based on AASHTO. Finally, reliability-based evaluation on the safety level of CFST truss design according to mainstream design guidelines such as ANSI/AISC 360–16, Eurocode 4:2004 and JGJ/T D65–06–2015 are carried out. Results show that the current component-based strength prediction of CFST trusses meet the target reliability while the current regulations provide uniform reliability.

On energy‐absorbing mechanisms of metal/WF‐CFRP hybrid composite columns

AbstractHybrid material system, comprised of metal and carbon fiber reinforced plastic (CFRP), combines the excellent mechanical performance and lightweight feature of CFRP with the competitive material cost and superior toughness of metal. By virtue of such mingled feature, metal/CFRP hybrid structure exhibits great potential in automotive components. This study aims to investigate the crushing behavior of aluminum/WF‐CFRP (woven fabric CFRP) hybrid columns subjected to dynamic loading condition by comparing with the corresponding individual columns made of single material (aluminum column and WF‐CFRP column). The dynamic axial crushing tests indicate that specific energy absorption of WF‐CFRP column is 45% higher than that of the aluminum column and 27% superior to that of the hybrid column, while the total energy absorption of the hybrid column is about 8% higher than the summation of WF‐CFRP column and aluminum column. Afterward, several finite element models are developed to reveal the underlying energy‐absorbing mechanisms and the influences of each factor for the hybrid columns. The numerical results show that specific energy absorption of the hybrid columns is negatively correlated with the metal volume fraction (F m), when inner aluminum wall thickness (t m) equals to 1.0 mm. It is also found that crushing process of the hybrid columns with l = 2 (2 CFRP layers) is dominated by the progressive folding of inner aluminum column, leading to a lower damage level of CFRP and lower load carrying capacity. With increasing wrapped CFRP layer number up to 8, the inner aluminum column starts to generate internal inversion deformation mode due to the restriction of the outer CFRP layers, and outer CFRP layers exhibit progressive failure. The energy‐absorbing mechanisms analysis indicates that the internal energy of the internally inversed aluminum column is significantly higher than that of the progressively folded aluminum column, and thus such special deformation mode is capable to offer a more stable and higher load carrying capacity for the hybrid columns. Besides, it is also found that the plastic deformation of the inner aluminum column is the major energy‐absorbing mechanism, which is followed by the crushing failure of outer CFRP layers. The combination mode of thinner aluminum column and thicker CFRP layers tends to offer higher energy‐absorbing capacity, which is much higher than that of the summation of corresponding individual columns. Finally, a complex proportional assessment method is considered to select the optimal configuration achieving the balance of material cost and structural crashworthiness. The present study is expected to provide guideline for design of metal/CFRP hybrid columns.

Variation in length of alpha waves reveals how forebrain activity is organized

Background The cerebral cortex is composed of functional units known as columns. The “two levels” hypothesis states that the activity in a column is either at a high level or at a normal, relatively low level. Measurements indicate that the duration of the high activity in a column is around 450 ms. The number of highly active columns is often 4–5. These data are from previous studies on alpha waves in electroencephalograms. The idea is that alpha waves are created when a regulating system keeps the number of highly active columns within proper limits. If this is true, then regulating signals determines the length of the alpha waves, which opens up for a possibility to test the hypothesis. Methods and results Wavelengths were measured in sequences of alpha waves, and distinctive patterns in the wavelength variation were found. The elements of these patterns were repeated at intervals that exactly matched the predicted duration of high activity in individual columns. Conclusions The discovery of patterns in the wavelength variation confirms the central part of the two levels hypothesis. The patterns reveal the actual number of highly active columns. Moreover, the duration of high activity in a column can be measured. Number and duration outside the optimal ranges may lead to a variety of symptoms.

Is It Still Good to Ya? Fifty Years of Rock Criticism, 1967–2017 by Robert Christgau

Reviewed by: Is It Still Good to Ya? Fifty Years of Rock Criticism, 1967–2017 by Robert Christgau Shelley L. Rogers Is It Still Good to Ya? Fifty Years of Rock Criticism, 1967–2017. By Robert Christgau. Durham, NC: Duke University Press, 2018. [v, 443 p. ISBN 978147800082 (hardcover), $109.95; ISBN 9781478000228 (paperback), $27.95; ISBN 9781478002079 (ebook), varies.] Index. The eight-page introduction is the only segment of this book that is totally new content by the author; the rest is previously published material by the famed rock music critic that originally appeared in other publications. This practice is consistent with Robert Christgau's other books, such as Any Old Way You Choose It: Rock and Other Pop Music, 1967–1973 (Baltimore: Penguin Books, 1973) and Grown Up All Wrong: 75 Great Rock and Pop Artists from Vaudeville to Techno (Cambridge, MA: Harvard University Press, 1998). Christgau earned a degree in English from Dartmouth in 1962. He does not have degrees in journalism or music, but his command of the English language and constant pastime of listening to music has enabled him to earn a living as a music journalist, which began with Esquire in 1967 but continued primarily with employment at the Village Voice (1969–72, 1974–2006). He is perhaps best remembered for his short, graded record reviews in the Village Voice (which stopped publishing in August 2018) and his "Pazz & Jop" music polls. The compilation in Is It Still Good to Ya? does not include those graded reviews from the Village Voice, but it does draw most heavily on that newspaper with four dozen of his columns, plus other pieces from the New Yorker, Rolling Stone, Billboard, Spin, Barnes & Noble reviews, and so forth. Although these pieces are not new, Christgau did revise them: "almost every one condensed to make room for others and spruced up to mitigate stylistic shortfalls or correct factual errors but never to revise opinions or predictions gone awry, with a bunch substantially revised and marked as such" (pp. 1–2). Christgau does not provide additional information on how he amended the individual columns, which may lessen the value of this book to historians researching rock music; they will still want to read Christgau's original texts for his criticism in that time and place. This new volume would be of most use to those who are interested in Christgau's opinions in general or perhaps those doing research specifically on him. After the introduction and the prologue, the book is divided into six sections: "History in the Making," "A Great Tradition," "Millennium," "From Which All Blessings Flow," "Post-modern Times," and "Got to Be Driftin' Along." Each section features at least [End Page 601] six of his columns. Although this topical organization is roughly chronological, the columns are not in chronological order. The source (e.g., "Village Voice, 2006") appears after the text, which I found annoying; before reading the piece I always flipped to the end to find this information in order to give the piece more context. This format is also consistent with his other books, such as Any Old Way You Choose It, and a consistent editorial failure. As most of Is It Still Good to Ya? consists of selected pieces about particular artists, this volume is in no way encyclopedic in its coverage of rock music; rather, it represents Christgau's opinions about a smattering of iconic or influential artists. The index is helpful in determining if a particular artist or group is covered. As rock music did not spring from a musical vacuum and does not continue without influence from other musical styles, Christgau includes criticism of jazz, blues, popular, and country artists that one may not immediately associate with rock, such as Louis Armstrong, Lady Gaga, and Brad Paisley. Before compiling a collection of previously published works, the author and editors should consider, apart from commercial calculations, two aesthetic questions: (1) whether the quality of the original pieces is sufficient, making them worth reprinting, and (2) whether there is value to the collection: is it more than the sum of its parts? As Christgau declared that "almost every" piece was condensed, "spruced up," and...

New and extended design moment formulations for slender columns in frames with sway

Present first-order based design code formulations for slender columns in frames with sway, employ sway magnification factors (for global second-order effects) also as moment magnifiers for the individual columns of the frame (storey). This approach ignores differences in magnification of individual column moments caused by local second-order effects in the columns. This difference can be significant. Better understanding of this aspect will strengthen approximate first-order based elastic methods, for which the important superposition principle is valid. Towards this end, local second-order effects are considered for shears, end moments and maximum moments, applicable over the full range of axial loads. Specifically, end moment and maximum moment expressions of columns with sway are derived. These represent novel contributions that are suitable in typical design code formats, and in practical design work. They will allow more rational column assessments, and will allow more economical designs than present structural code procedures. Proposals are verified by comparison with results from second-order in-plane elastic analyses of single restrained columns and columns in frame panels. Also, extensions to the general case of load combinations that include both gravity and sideways loading are briefly presented.

Remove the pharmaceuticals from water using selected adsorbents

As part of the project of specific university research at the Institute of Municipal Water Management of the Faculty of Civil Engineering, Brno University of Technology, a laboratory test was carried out to try and remove to pharmaceuticals from water using selected sorption materials. The goal of the laboratory test was to compare two selected adsorbents as Filtrasorb F100 and Bayoxide E33 in terms of pharmaceutical removal effectiveness from water. Salicylic acid was selected as a pharmaceutical; which is a colourless organic acid, which is of great importance in the field of dermatology and is a proven tool for various dermatological problems including acne. This is a pharmaceutical that is obtained from the bark of a willow white. Sorbent Filtrasorb F100 is in practice commonly used for the removal of micropollutants, as opposed to the sorbent Bayoxide E33, which is used to remove metals from water. In order to remove pharmaceutical from water, two glass columns were used with internal diameter 4.4 cm filled with said sorption materials. Height of sorbent was elected as recommended by the producer of filter material at least 75 cm. Model water was prepared in laboratories by mixing liquid pharmaceutical into drinking water. Samples of filtered water were taken after 0.5 minute and after or 1, 2, and 4 minutes respective. Totally 9 samples including model water were taken. The analysis of water samples after filtration from individual columns with said sorption materials showed found that Filtrasorb F100 reliably removed to concentration of salicylic acid after half a minute, while Bayoxide E33 started remove the acid but from one minute higher concentrations were onwards measured again. This means that the latter material was oversaturated, and therefore gradually ceased to remove the acid.

A Hox Code Defines Spinocerebellar Neuron Subtype Regionalization

Coordinated movement requires the integration of many sensory inputs including proprioception, the sense of relative body position and force associated with movement. Proprioceptive information is relayed to the cerebellum via spinocerebellar neurons, located in the spinal cord within a number of major neuronal columns or as various scattered populations. Despite the importance of proprioception to fluid movement, a molecular understanding of spinocerebellar relay interneurons is only beginning to be explored, with limited knowledge of molecular heterogeneity within and between columns. Using fluorescent reporter mice, neuronal tracing, and in situ hybridization, we identify widespread expression of Hox cluster genes within spinocerebellar neurons. We reveal a "Hox code" based on axial level and individual spinocerebellar column, which, at cervico-thoracic levels, is essential for subtype regionalization. Specifically, we show that Hoxc9 function is required in most, but not all, cells of the thoracic spinocerebellar column, Clarke's column, revealing heterogeneity reliant on Hox signatures.

The correctness of van ’t Hoff plots in chiral and achiral chromatography

van ’t Hoff plots (logarithm of the retention factor, ln k, vs. the reciprocal of absolute temperature, 1/T) are commonly used in chromatographic studies to characterize the retention mechanisms based on the determined enthalpy (ΔH∘) and entropy (ΔS∘) change of analyte adsorption. In reversed phase liquid chromatography, the thermodynamic parameters could help to understand the retention mechanism. In chiral chromatography, however, the conclusions drawn based on van ’t Hoff plots can be deceptive because several different types of adsorption sites are present on the surface of stationary phase. The influence of heterogeneity, however, cannot be studied experimentally. In this study, we employed two reversed phase columns with different retention mechanisms to show that by serially coupling the columns, the obtained thermodynamic parameters are not related to the results obtained on the respective individual columns. Furthermore, our results show that the experimental conditions – such as flow-rate or choice of instrument – will strongly influence the calculated enthalpy and entropy values.

Low-frequency wave-energy amplification in graded two-dimensional resonator arrays

Energy amplification in square-lattice arrays of C-shaped low-frequency resonators, where the resonator radii are graded with distance, is investigated in the two-dimensional linear acoustics setting for both infinite (in one dimension) and finite arrays. Large amplifications of the incident energy are shown in certain array locations. The phenomenon is analysed using: (i) band diagrams for doubly-periodic arrays; (ii) numerical simulations for infinite and finite arrays; and (iii) eigenvalue analysis of transfer matrices operating over individual columns of the array. It is shown that the locations of the large amplifications are predicted by propagation cut-offs in the modes associated with the transfer-matrix eigenvalues. For the infinite array, the eigenvalues form a countable set, and for the low frequencies considered, only a single propagating mode exists for a given incident wave, which cuts off within the array, leading to predictive capabilities for the amplification location. For the finite array, it is shown that (in addition to a continuous spectrum of modes) multiple discrete propagating modes can be excited, with the grading generating new modes, as well as cutting others off, leading to complicated amplification patterns. The numerical simulations reveal that the largest amplifications are achieved for a single row array, with amplifications an order of magnitude smaller for the corresponding infinite array. This article is part of the theme issue 'Modelling of dynamic phenomena and localization in structured media (part 1)'.

Application of breakthrough curve analysis and response surface methodology for optimization of a hybrid separation system consisting of fixed-bed column adsorption and dead-end depth filtration

This work investigates the performance and optimization of a hybrid process consisting of a fixed-bed adsorption (FBA) column and a dead-end filtration (DEF) cell for the removal of methylene blue (MB) from water. Granular activated carbon and cellulose acetate depth filter sheets were used as adsorbent and filter medium, respectively. Effects of four operation parameters (initial concentration, feed flowrate, bed length, and filter type) on the MB removal rate (RR) were investigated using breakthrough data analysis and response surface methodology. This RR (mass of MB removed per second) captures the removal capacity and separation rate, simultaneously. The maximum RR was found theoretically equal to 3.875 s−1 at the optimized conditions of initial concentration =39.86 mg/L, flowrate = 1.15 L/min, bed length =29.95 cm, and filter type = OS100, and validated with the experimental data with 99% agreement. The performance of the hybrid process operating at the optimal operation conditions was found to be superior to those of the individual FBA column and DEF cell. After 100 s from the process commencement, the RR obtained with the hybrid process was about 64% higher than that obtained with the FBA column and 30% higher than that obtained with the DEF cell.