Mass transfer characteristics in structured packing for CO2 emission reduction processes

Acid gas treating and CO2 capture from flue gas by absorption have gained wide importance over the past few decades. With the implementation of more stringent environmental regulations and the awareness of the greenhouse effect, the need for efficient removal of acid gases such as CO2 (carbon dioxide) has increased significantly. Therefore, additional effort for research in this field is inevitable. For flue gas processes the ratio of absorption solvent to gas throughput is very different compared to acid gas treating processes owing to the atmospheric pressures and the dilution effect of combustion air. Moreover, in flue gas applications pressure drop is a very important process parameter. Packing types are required that allow for low pressure drop in combination with high interfacial areas at low liquid loading per square meter. The determination of interfacial areas in gas-liquid contactors by means of the chemical method (Danckwerts, P. V. Gas-liquid reactions; McGraw-Hill: London, 1970) has been very frequently applied. Unfortunately, many of the model systems proposed in the literature are reversible and therefore this condition possibly is not met. Versteeg et al. (Versteeg, G. F.; Kuipers, J. A. M.; Beckum, F. P. H.; van Swaaij, W. P. M. Chem. Eng. Sci. 1989, 44, 2292) have demonstrated that for reversible reactions the conditions for the determination of the interfacial area by means of the chemical method are much more severe. In a study by Raynal et al. (Raynal, L.; Ballaguet, J. P.; Berrere-Tricca, C. Chem. Eng. Sci. 2004, 59, 5395), it has been shown that there is a dependency of the interfacial area on the packing height. Unfortunately, most model systems used, e.g., CO2-caustic soda (as used by Raynal et al.), are much more complex and consist of (a set of) reversible reaction(s). The natures of these systems make the conditions at which the interfacial area can be determined much more severe and put more limitations on the process conditions and experimental equipment than a priori can be expected. Therefore, an extended absorption model is required to determine the conditions at which the interfacial area can be measured without detailed knowledge of the values of the liquid-side mass transfer coefficient, k1, beforehand.

Global to local genetic diversity indicators of evolutionary potential in tree species within and outside forests

There is a general trend of biodiversity loss at global, regional, national and local levels. To monitor this trend, international policy processes have created a wealth of indicators over the last two decades. However, genetic diversity indicators are regrettably absent from comprehensive bio-monitoring schemes. Here, we provide a review and an assessment of the different attempts made to provide such indicators for tree genetic diversity from the global level down to the level of the management unit. So far, no generally accepted indicators have been provided as international standards, nor tested for their possible use in practice. We suggest that indicators for monitoring genetic diversity and dynamics should be based on ecological and demographic surrogates of adaptive diversity as well as genetic markers capable of identifying genetic erosion and gene flow. A comparison of past and present genecological distributions (patterns of genetic variation of key adaptive traits in the ecological space) of selected species is a realistic way of assessing the trend of intra-specific variation, and thus provides a state indicator of tree genetic diversity also able to reflect possible pressures threatening genetic diversity. Revealing benefits of genetic diversity related to ecosystem services is complex, but current trends in plantation performance offer the possibility of an indicator of benefit. Response indicators are generally much easier to define, because recognition and even quantification of, e.g., research, education, breeding, conservation, and regulation actions and programs are relatively straightforward. Only state indicators can reveal genetic patterns and processes, which are fundamental for maintaining genetic diversity. Indirect indicators of pressure, benefit, or response should therefore not be used independently of state indicators. A coherent set of indicators covering diversity–productivity–knowledge–management based on the genecological approach is proposed for application on appropriate groups of tree species in the wild and in cultivation worldwide. These indicators realistically reflect the state, trends and potentials of the world’s tree genetic resources to support sustainable growth. The state of the genetic diversity will be based on trends in population distributions and diversity patterns for selected species. The productivity of the genetic resource of trees in current use will reflect the possible potential of mobilizing the resource further. Trends in knowledge will underpin the potential capacity for development of the resource and current management of the genetic resource itself will reveal how well we are actually doing and where improvements are required

Step-free railway station access in the UK: The value of inclusive design

Background: Despite substantial investment in step-free access at UK railway stations, persons with reduced mobility (PRMs) continue to travel less than their able-bodied counterparts and little is known about the value of step-free access. This research examines the benefits of step-free access and its relationship with rail usage among PRMs, and the wider benefits of railway station accessibility. Methods: These issues are explored through a mixed methods approach. Semi-structured interviews with ten key organisations were undertaken, as was an analysis of Senior/Disabled Persons Railcard data from 17 railway stations in Buckinghamshire, each with varying levels of step-free accessibility. Results: The results show that the benefits of step-free access extend beyond benefits at the individual level typically associated with those limited to PRMs, and demonstrate the potential to positively affect the society at large economically, environmentally, and socially. The findings also show a positive correlation between the level of step-free accessibility at a railway station and the percentage of PRMs using it. Conclusions: This research argues that government and interested stakeholders should commit to expanding the number and coverage of step-free stations throughout the UK. They should ensure that the appraisal process for investment in step-free accessibility appropriately captures both user and non-user benefits

Preparation of Subradiant States using Local Qubit Control in Circuit QED

Transitions between quantum states by photon absorption or emission are intimately related to symmetries of the system which lead to selection rules and the formation of dark states. In a circuit quantum electrodynamics setup, in which two resonant superconducting qubits are coupled through an on-chip cavity and driven via the common cavity field, one single-excitation state remains dark. Here, we demonstrate that this dark state can be excited using local phase control of individual qubit drives to change the symmetry of the driving field. We observe that the dark state decay via spontaneous emission into the cavity is suppressed, a characteristic signature of subradiance. This local control technique could be used to prepare and study highly correlated quantum states of cavity-coupled qubits.Comment: 5 pages, 4 figure

Strain Hardening of Polymer Glasses: Entanglements, Energetics, and Plasticity

Simulations are used to examine the microscopic origins of strain hardening in polymer glasses. While stress-strain curves for a wide range of temperature can be fit to the functional form predicted by entropic network models, many other results are fundamentally inconsistent with the physical picture underlying these models. Stresses are too large to be entropic and have the wrong trend with temperature. The most dramatic hardening at large strains reflects increases in energy as chains are pulled taut between entanglements rather than a change in entropy. A weak entropic stress is only observed in shape recovery of deformed samples when heated above the glass transition. While short chains do not form an entangled network, they exhibit partial shape recovery, orientation, and strain hardening. Stresses for all chain lengths collapse when plotted against a microscopic measure of chain stretching rather than the macroscopic stretch. The thermal contribution to the stress is directly proportional to the rate of plasticity as measured by breaking and reforming of interchain bonds. These observations suggest that the correct microscopic theory of strain hardening should be based on glassy state physics rather than rubber elasticity.Comment: 15 pages, 12 figures: significant revision

Microwave Components with MEMS Switches

RF MEMS switches with metal-metal contacts are being developed for microwave applications where broadband, high linearity performance is required. These switches provide less than 0.2 dB insertion loss through 40 GHz. This paper describes the integration of these switches into selected microwave components such as reconfigurable antenna elements, tunable filters, switched delay lines, and SPDT switches. Microwave and millimeter wave measured results from these circuits are presented

Level of Service for Pedestrian Movement towards the Performance of Passenger Information in Public Transport Stations in Klang Valley

Rapid growth in car ownership in Malaysia plays a major role to traffic congestion. Hence, public transportation is crucial to cater the residents in high-density area especially in Klang Valley. Signage information in public transport station is one of an important passenger information system. Poor placement of sign information will decrease the efficiency of passenger flow and caused congestion in the station. Passenger information system is very useful for trip planning and decision making. Therefore, it is interesting to study the performance of passenger information system in focusing the movement behavior of pedestrian at non-peak period. Thus, the study on pedestrian movement during non-peak period on weekdays and weekends in mass transit stations and bus transit stations in Klang Valley was carried out by using video observation. The observation of the pedestrian movement was made in Mass Transit Station 1 in the middle of Kuala Lumpur and Mass Transit Station 2 in southern of Kuala Lumpur. The other site was focused at Bus Transit Station 1 in Putrajaya and Bus Transit Station 2 in Kajang. Findings shown that Mass Transit Station 1 having the best facility in terms of passenger information which the level of service obtained is LOS A, while the lowest level of service which is LOS E was obtained in Bus Transit Station 2

Exhaustive Sampling of Docking Poses Reveals Binding Hypotheses for Propafenone Type Inhibitors of P-Glycoprotein

Overexpression of the xenotoxin transporter P-glycoprotein (P-gp) represents one major reason for the development of multidrug resistance (MDR), leading to the failure of antibiotic and cancer therapies. Inhibitors of P-gp have thus been advocated as promising candidates for overcoming the problem of MDR. However, due to lack of a high-resolution structure the concrete mode of interaction of both substrates and inhibitors is still not known. Therefore, structure-based design studies have to rely on protein homology models. In order to identify binding hypotheses for propafenone-type P-gp inhibitors, five different propafenone derivatives with known structure-activity relationship (SAR) pattern were docked into homology models of the apo and the nucleotide-bound conformation of the transporter. To circumvent the uncertainty of scoring functions, we exhaustively sampled the pose space and analyzed the poses by combining information retrieved from SAR studies with common scaffold clustering. The results suggest propafenone binding at the transmembrane helices 5, 6, 7 and 8 in both models, with the amino acid residue Y307 playing a crucial role. The identified binding site in the non-energized state is overlapping with, but not identical to, known binding areas of cyclic P-gp inhibitors and verapamil. These findings support the idea of several small binding sites forming one large binding cavity. Furthermore, the binding hypotheses for both catalytic states were analyzed and showed only small differences in their protein-ligand interaction fingerprints, which indicates only small movements of the ligand during the catalytic cycle