Large Stretches Research Articles

Contact mechanics of inflated circular membrane under large deformation: Analytical solutions

Pressurization of thin elastomeric membranes has been exploited as a key actuation mechanism in soft robotics, leading to soft pneumatic actuators that can deform reversibly upon inflation and deflation. The contact mechanics of an inflated membrane with another object underlies several important functionalities of soft pneumatic actuators such as gripping, haptic feedback and locomotion. Motivated by the technological relevance, we study the contact between an inflated circular membrane consisting of incompressible neo-Hookean solid and a substrate that is: i) flat and rigid, ii) spherically curved and rigid, iii) flat and elastic, or iv) spherically curved and elastic. By assuming that the contact interface is adhesionless and frictionless and that the membrane is subjected to very large stretch ratios, we obtained approximate analytical solutions for the membrane’s deformation profile as well as the relationship between the applied force, displacement and contact radius. These solutions agree well with results of numerical simulations. In particular, when the substrate is elastic, we obtained a dimensionless parameter γ that captures the transition between two limiting cases, i.e., either the substrate or the inflated membrane is effectively rigid relative to the other component and thus experiences negligible deformation upon contact. The analytical solutions provided in this work can offer insights towards designing soft pneumatic actuators with desired contact compliance.

Utilization of Renewable Energy: A Study on the Utilization of Solar Energy for Power Plants at the Campus of Universitas Samudra, Indonesia

The availability of solar energy is higher than global energy consumption, affordable by many users, simple to use, and relatively more environmentally friendly. Complexes of higher education institutions in Indonesia, in general, consist of many buildings with large roofs and stretches of unused land, which are suitable for solar power installations. This study analyzes the feasibility of constructing a solar power plant at an educational institution facility, with a specific case study on the Universitas Samudra campus. The analysis results have shown that for the supply of electricity with a total power of 10 MW, PV panels are superior to parabolic collectors. The cost of producing electricity using PV panels is 6.60 ¢/kWh, while the parabolic collector costs 26.42 ¢/kWh. And the total area required for the installation of PV.

Utilization of Renewable Energy: A Study on the Utilization of Solar Energy for Power Plants at the Campus of Universitas Samudra, Indonesia

The availability of solar energy is higher than global energy consumption, affordable by many users, simple to use, and relatively more environmentally friendly. Complexes of higher education institutions in Indonesia, in general, consist of many buildings with large roofs and stretches of unused land, which are suitable for solar power installations. This study analyzes the feasibility of constructing a solar power plant at an educational institution facility, with a specific case study on the Universitas Samudra campus. The analysis results have shown that for the supply of electricity with a total power of 10 MW, PV panels are superior to parabolic collectors. The cost of producing electricity using PV panels is 6.60 ¢/kWh, while the parabolic collector costs 26.42 ¢/kWh. And the total area required for the installation of PV.

Uniaxial stretch-release of rubber-plastic bilayers: Strain-dependent transition to stable helices, rolls, saddles, and tubes

Polymeric plastics deform irreversibly (i.e., inelastically) whereas rubbers deform reversibly, i.e., elastically. Thus, uniaxially stretching a rubber-plastic bilayer composite beyond its yield point can create an elastic strain mismatch between the two layers. Upon release, the bilayer may then bend out-of-plane. We quantify the mechanics of such stretch-release-induced shape changes in rectangular specimens of rubber-plastic bilayers. We show a remarkable dependence of the final shape upon the stretch applied prior to release. At small stretch, all bilayers bend into arch or roll shapes with the plastic on the convex face. At large stretch, the bilayers bend into half-tubes with the plastic, now heavily-wrinkled, becoming the concave face. Thus, the sign and direction of the curvature both flip as applied stretch increases. Between these two extremes, saddle shapes appear which have characteristics of both arches as well as half-tubes. Sufficiently narrow samples show different behavior: they transition from arches to helices as stretch increases. All these shapes are mono-stable. We document numerous ways in which the mechanics of rubber-plastic bilayers differs from that of fully-elastic bilayers. Most importantly, yielding of the plastic layer during the shape change strongly affects the mechanics of the elastic–plastic bilayers, and yielding accompanied by plastic wrinkling has an especially large effect. A strain energy model illustrates how the shape change is dictated by the change in the ratio of elastic strain mismatch in the two directions due to the formation of wrinkles at the rubber-plastic interface.

Backbone and methyl resonances assignment of the 87 kDa prefoldin from Pyrococcus horikoshii.

Prefoldin is a heterohexameric protein assembly which acts as a co-chaperonin for the well conserved Hsp60 chaperonin, present in archaebacteria and the eukaryotic cell cytosol. Prefoldin is a holdase, capturing client proteins and subsequently transferring them to the Hsp60 chamber for refolding. The chaperonin family is implicated in the early stages of protein folding and plays an important role in proteostasis in the cytosol. Here, we report the assignment of 1HN, 15N, 13C', 13Cα, 13Cβ, 1Hmethyl, and 13Cmethyl chemical shifts of the 87 kDa prefoldin from the hyperthermophilic archaeon Pyrococcus horikoshii, consisting of two α and four β subunits. 100% of the [13C, 1H]-resonances of Aβ, Iδ1, Iδ2, Tγ2, Vγ2 methyl groups were successfully assigned for both subunits. For the β subunit, showing partial peak doubling, 80% of the backbone resonances were assigned. In the α subunit, large stretches of backbone resonances were not detectable due to slow (μs-ms) time scale dynamics. This conformational exchange limited the backbone sequential assignment of the α subunit to 57% of residues, which corresponds to 84% of visible NMR signals.

Sorting Permutations by Intergenic Operations.

Genome Rearrangements are events that affect large stretches of genomes during evolution. Many mathematical models have been used to estimate the evolutionary distance between two genomes based on genome rearrangements. However, most of them focused on the (order of the) genes of a genome, disregarding other important elements in it. Recently, researchers have shown that considering regions between each pair of genes, called intergenic regions, can enhance distance estimation in realistic data. Two of the most studied genome rearrangements are the reversal, which inverts a sequence of genes, and the transposition, which occurs when two adjacent gene sequences swap their positions inside the genome. In this work, we study the transposition distance between two genomes, but we also consider intergenic regions, a problem we name Sorting by Intergenic Transpositions. We show that this problem is NP-hard and propose two approximation algorithms, with factors 3.5 and 2.5, considering two distinct definitions for the problem. We also investigate the signed reversal and transposition distance between two genomes considering their intergenic regions. This second problem is called Sorting by Signed Intergenic Reversals and Intergenic Transpositions. We show that this problem is NP-hard and develop two approximation algorithms, with factors 3 and 2.5. We check how these algorithms behave when assigning weights for genome rearrangements. Finally, we implemented all these algorithms and tested them on real and simulated data.

Mapping of sequences in the 5' region and 3' UTR of tomato ringspot virus RNA2 that facilitate cap-independent translation of reporter transcripts in vitro.

Tomato ringspot virus (ToRSV, genus Nepovirus, family Secoviridae, order Picornavirales) is a bipartite positive-strand RNA virus, with each RNA encoding one large polyprotein. ToRSV RNAs are linked to a 5'-viral genome-linked protein (VPg) and have a 3' polyA tail, suggesting a non-canonical cap-independent translation initiation mechanism. The 3' untranslated regions (UTRs) of RNA1 and RNA2 are unusually long (~1.5 kb) and share several large stretches of sequence identities. Several putative in-frame start codons are present in the 5' regions of the viral RNAs, which are also highly conserved between the two RNAs. Using reporter transcripts containing the 5' region and 3' UTR of the RNA2 of ToRSV Rasp1 isolate (ToRSV-Rasp1) and in vitro wheat germ extract translation assays, we provide evidence that translation initiates exclusively at the first AUG, in spite of a poor codon context. We also show that both the 5' region and 3' UTR of RNA2 are required for efficient cap-independent translation of these transcripts. We identify translation-enhancing elements in the 5' proximal coding region of the RNA2 polyprotein and in the RNA2 3' UTR. Cap-dependent translation of control reporter transcripts was inhibited when RNAs consisting of the RNA2 3' UTR were supplied in trans. Taken together, our results suggest the presence of a CITE in the ToRSV-Rasp1 RNA2 3' UTR that recruits one or several translation factors and facilitates efficient cap-independent translation together with the 5' region of the RNA. Non-overlapping deletion mutagenesis delineated the putative CITE to a 200 nts segment (nts 773-972) of the 1547 nt long 3' UTR. We conclude that the general mechanism of ToRSV RNA2 translation initiation is similar to that previously reported for the RNAs of blackcurrant reversion virus, another nepovirus. However, the position, sequence and predicted structures of the translation-enhancing elements differed between the two viruses.

A parallel-in-time approach for wave-type PDEs

Numerical solutions to wave-type PDEs utilizing method-of-lines require the ODE solver's stability domain to include a large stretch of the imaginary axis surrounding the origin. We show here that extrapolation based solvers of Gragg-Bulirsch-Stoer (GBS) type can meet this requirement. Extrapolation methods utilize several independent time stepping sequences, making them highly suited for parallel execution. Traditional extrapolation schemes use all time stepping sequences to maximize the method's order of accuracy. The present method instead maintains a desired order of accuracy while employing additional time stepping sequences to shape the resulting stability domain. We optimize the extrapolation coefficients to maximize the stability domain's imaginary axis coverage. This yields a family of explicit schemes that approaches maximal time step size for wave propagation problems. On a computer with several cores we achieve both high order and fast time to solution compared with traditional ODE integrators.

Crack tip fields in a neo-Hookean sheet reinforced by nonlinear fibers

In this paper, we derive the asymptotic crack tip fields in a neo-Hookean material reinforced by nonlinear fibers. The fiber are characterized by a power law model which exhibits significant stiffening behavior at large stretch. A specific case of the model yields the so-called standard reinforcing model (Triantafyllidis and Abeyaratne, 1983). A series of transformations is used to set the stage for the asymptotic solution. We begin with a coordinate scaling (Liu and Moran, 2020b) to account for fiber orientation aspects. This is followed by a hodograph transformation to the strain plane to deal with nonlinearities. Finally, an additional nonlinear algebraic transformation is employed to render the equations suitable for a separable solution. The asymptotic solutions are compared with and agree well with finite element solutions for different fiber modulus ratios, fiber orientation angles, and loading modes. We find that, due to the stiffening effects of the fibers, the deformation fields can be divided into three regions, where the deformation in the two regions near to the crack faces is significantly larger than in the middle region. Stress peaks are observed at the interfaces between regions. The solutions in the paper may provide insight into damage modes and crack initiation at a crack tip in fiber-reinforced soft composites.

The Anticipation of Gravity in Human Ballistic Movement.

Stretch-shortening type actions are characterized by lengthening of the pre-activated muscle-tendon unit (MTU) in the eccentric phase immediately followed by muscle shortening. Under 1 g, pre-activity before and muscle activity after ground contact, scale muscle stiffness, which is crucial for the recoil properties of the MTU in the subsequent push-off. This study aimed to examine the neuro-mechanical coupling of the stretch-shortening cycle in response to gravity levels ranging from 0.1 to 2 g. During parabolic flights, 17 subjects performed drop jumps while electromyography (EMG) of the lower limb muscles was combined with ultrasound images of the gastrocnemius medialis, 2D kinematics and kinetics to depict changes in energy management and performance. Neuro-mechanical coupling in 1 g was characterized by high magnitudes of pre-activity and eccentric muscle activity allowing an isometric muscle behavior during ground contact. EMG during pre-activity and the concentric phase systematically increased from 0.1 to 1 g. Below 1 g the EMG in the eccentric phase was diminished, leading to muscle lengthening and reduced MTU stretches. Kinetic energy at take-off and performance were decreased compared to 1 g. Above 1 g, reduced EMG in the eccentric phase was accompanied by large MTU and muscle stretch, increased joint flexion amplitudes, energy loss and reduced performance. The energy outcome function established by linear mixed model reveals that the central nervous system regulates the extensor muscles phase- and load-specifically. In conclusion, neuro-mechanical coupling appears to be optimized in 1 g. Below 1 g, the energy outcome is compromised by reduced muscle stiffness. Above 1 g, loading progressively induces muscle lengthening, thus facilitating energy dissipation.

Trees, shrubs and herbs of the coastal Myrtaceae swamp forest (Región de La Araucanía, Chile): a dataset.

BackgroundSpecies lists are fundamental for knowledge of species diversity in regions subject to intense anthropogenic pressure, especially in poorly-studied ecosystems. The dataset comes from an inventory conducted in 30 fragments of Myrtaceae swamp forest, located in an agroforestry matrix landscape of the coastal La Araucanía Region in Chile. The data collection was carried out using line transect sampling, which was traced through the core of each fragment orientated towards its longest axis. The dataset provides a record of 55 species (24 trees, 1 vine [as a host], 16 herbs and 15 shrubs) including accidental epiphytes (n = 7), hemiparasites (n = 4), host (n = 10) and additionally woody debris (n = 36). The most frequent trees in the landscape were Myrceugenia exsucca (n = 36 records) and Blepharocalyx cruckshanksii (n = 33 records), species that were also the most common hosts. Drimys winteri was a companion species, other trees and shrubs generally being rarely observed, as was the case of the introduced species (Prunus avium, Rubus constrictus and Ulex europaeus). Branches were the most common microhabitat for hemiparasites. Within this group, Lepidoceras chilense was the most frequent species. For accidental epiphytes, Drimys winteri, which commonly grows on the ground (soil), were the most common species found in the main trunk crotch. Some unusual observations were the climber Cissus striata as host of Tristerix corymbosus (hemiparasite) and Tristerix corymbosus as host of Lepidoceras chilense (hemiparasite).New informationThis study represents a landscape-scale sample of the swamp forest, which is distributed in a dispersed pattern over a large stretch of Chile. The data were collected from 30 forest patches (from 0.05 to 936 ha), located on the coast of the Araucanía. The database includes the presence of 55 species of vascular plants in 356 records. The main novelty of this contribution is the systematic classification of species under six traits, never before reported in the same database: (i) condition (coarse woody debris, fallen log, live, snag), (ii) habit (herb, shrub, tree), (iii) growth microhabitat (e.g. tree trunk, branch, main trunk crotch), (iv) growth form (accidental epiphyte, hemiparasite, terricolous, vegetative), (v) host species (as appropriate) and (vi) relative location of the species in the sampled patch and surrounding areas (core, border, matrix). Species not previously observed in these forests were: Gavilea spp., Hieracium spp., Lophosoria quadripinnata, Berberis actinacantha, Gaultheria phillyreifolia, Ovidia pillo-pillo, Amomyrtus meli and Caldcluvia paniculata. In addition, two introduced species are novelties for the catalogue of vascular plants of Chile (Cupressus macrocarpa and Prunus avium). Several of these ecosystem traits are indeed new reports for these types of forests (e.g. accidental epiphytes, fallen logs, species-host relationship); at the same time, more frequent data (i.e. species composition, habit) are found in different contributions, making the comprehensive process of analysis difficult. Accordingly, the database is made available in this manuscript.

Genetic studies of various Prosopis species (Leguminosae, Section Algarobia) co-occurring in oases of the Atacama Desert (northern Chile).

In the Atacama Desert from northern Chile (19–24°S), Prosopis (Leguminosae) individuals are restricted to oases that are unevenly distributed and isolated from each other by large stretches of barren landscape constituting an interesting study model as the degree of connectivity between natural populations depends on their dispersal capacity and the barriers imposed by the landscape. Our goal was to assess the genetic diversity and the degree of differentiation among groups of Prosopis individuals of different species from Section Algarobia and putative hybrids (hereafter populations) co‐occurring in these isolated oases from the Atacama Desert and determine whether genetic patterns are associated with dispersal barriers. Thirteen populations were sampled from oases located on three hydrographic basins (Pampa del Tamarugal, Rio Loa, and Salar de Atacama; northern, central, and southern basins, respectively). Individuals genotyped by eight SSRs show high levels of genetic diversity (H O = 0.61, A r = 3.5) and low but significant genetic differentiation among populations (F ST = 0.128, F ST‐ENA = 0.129, D JOST = 0.238). The AMOVA indicates that most of the variation occurs within individuals (79%) and from the variance among individuals (21%); almost, the same variation can be found between basins and between populations within basins. Differentiation and structure results were not associated with the basins, retrieving up to four genetic clusters and certain admixture in the central populations. Pairwise differentiation comparisons among populations showed inconsistencies considering their distribution throughout the basins. Genetic and geographic distances were significantly correlated at global and within the basins considered (p < .02), but low correlation indices were obtained (r < .37). These results are discussed in relation to the fragmented landscape, considering both natural and non‐natural (humans) dispersal agents that may be moving Prosopis in the Atacama Desert.

Homozygosity stretches around homozygous mutations in autosomal recessive disorders: patients from nonconsanguineous Indian families

India has a large heterogeneous population with its unique social and genetic characteristics. Tradition of marriage between specific caste groups have produced unique characteristics to the mutation spectrum of genetic disorders and may be a higher prevalence of autosomal recessive (AR) disorders in some communities. We observed that in many nonconsanguineous families with rare autosomal disorders, maternally and paternally inherited mutations are same, indicating common ancestor. In this era of genomic techniques, finding homozygous regions have become easy. It was seen that the patients with AR disorders, who were homozygous for the disease causing pathogenic / likely pathogenic variations, have large stretches (0.6-188 Mb) of homozygosity around the causative sequence variations. SNP microarray data of patients from consanguineous and nonconsanguineous families also showed that even patients from nonconsanguineous families had 3-49 Mb size regions of homozygosity. Long stretches of homozygosity around homozygous rare pathogenic variants in nonconsanguineous families with rare AR disorders supports the notion that these couples may have a common ancestor for more than six generations and the system of marriages between same groups. Hence, using the strategy of homozygosity by descent even in nonconsanguineous families can be fruitful in identifying the novel pathogenic variations and novel genes.

Anisotropic stress-softening effect on fast dynamic crack in filler-reinforced elastomers

Deformation of filler-reinforced elastomers is accompanied by a complex internal damage due to stress softening (Mullins effect). The crack growth behavior of filler-reinforced elastomers is made significantly complex by the occurrence of a simultaneous directional stress softening. The influences of the directional stress softening on fast crack propagation normal to the pre-stretching direction are revealed by the comparison using three types of specimens: (I) a low-filled elastomer with almost no stress softening, (II) a pristine highly filled elastomer with a pronounced stress-softening feature, and (III) an elastomer obtained by imposing before uniaxial loading–unloading cycles with a large maximum stretch of specimen (II). The previous directional softening causes a reduction in the threshold tearing energy for velocity transition, and an increase in local strain in the softening direction. In contrast, the previous directional softening has no appreciable effect on the tearing energy dependence of velocity, crack-tip shape, strain field behind the crack-tip, and the strain singularity near the crack-tip.

A review on the application of natural rubber as asphalt modifier

Natural rubber as bio-modifier of bitumen and asphalt mixtures has shown to have some beneficial effects. As initially produced, natural rubber consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds, plus water. Natural rubber can consist of various forms including as latex, which is a sticky, milky colloid; cup lump which is a coagulated latex and ribbed smoke sheet. Natural rubber is used extensively in many products and applications, either alone or in combination with other materials as it has a large stretch ratio and high resilience, and extremely waterproof. Due to these properties together with a chemical composition which can be classified as elastomers, natural rubber modification can improve the performance of conventional asphalt mixtures that are currently faced limitation against increased traffic loading and higher axle loads together with the effect of ageing, moisture, and temperature. Also, the application of natural rubber as part of the construction of asphalt mixture pavement might support the national agenda to boost rubber industry. This paper will review the application of various forms of natural rubber as modifier either in bitumen or asphalt mixtures based on previous studies done by other researchers. Numerous studies have been conducted based on different types and composition of natural rubber to determine the performance especially in terms of rutting and fatigue cracking properties.

Dual approach transformation of human finger and toe nail pruning into MgO/CaO nanoalloy

Interventions of biological entities mediated nanobiotechnological syntheses, in the strive to adapt inexpensive green approaches for constructing materials in the nanodimension for achieving targeted applications with improved performances, are being increasingly preferred. In context, this research article reports to bring into existence applaud able technique, concerning waste utilization for conversion into value added nanomaterial, to manage environmental issues as well as suffice biomedical demands and meet tough challenges from several domains. Pruning nail plates of the fingers and toes, has been a routine affair for the maintenance of personal care, in human civilization. Here we focus the bioengineering of MgO/CaO nanoalloy, by transforming remnant vestigial human finger and toe nail pruning, through dual approach protocols. Obtained yields through direct heat and following chemical treatment protocols were around 61.9% and 62.0%, respectively. Noticeable, quadrangular nanostructural arrangement in sequential array was observed for the MgO/CaO nanoalloy engineered through sol-gel chemical processing prior to thermal decomposition. Chemical treatment of the precursor enabled, formation of large stretches of uniform nanopattern and homogenous distribution to a great extent, from hydroxides of Mg and Ca instead of their salts. The scalable self-assembly with imparted ordered alignment shall inevitably manifest improved nanoalloy activity rather than the randomly distributed nanostuctures attained from direct thermal decomposition of their salts. The multifunctional green MgO/CaO nanoalloy, having tested thermal stability, consisting substantive Ca and Mg, incorporates the dual advantageous of nano MgO and nano CaO, logistically rendering superior benefits. Required characterizations were performed for the investigation of the significant nanostructures, comprising magnificent quadrangular nanobricks, nanorods and nanospheres, derived from the renewable bioresource.

A semi-empirical method for computing storm surges on open coasts during tropical cyclones

A new semi-empirical storm surge prediction (SESSP) method is presented that computes tropical cyclone induced storm surge levels as a function of space and time for various storm and geometry input parameters. It distinguishes between five components that contribute to the total surge: the normal, parallel, radial, Ekman, and inverse barometer surge. The parallel surge (caused by shore-parallel gradients in the wind stress) and radial surge (resulting from wind set-up due to the inflow angle of cyclonic wind fields) have not been adequately reported upon before. The empirical relations are derived using the results of thousands of numerical model simulations in which synthetic storms are simulated at coasts with varying cross-shore topography. Non-linear fitting procedures are used to derive surge response functions (SRFs). The SESSP method reproduces peak surge levels within 10 percent of the values computed by the hydrodynamic model. This study showed variable surge response at different types of coast. On steep coasts, surge is dominated by the inverse barometer effect. Along intermediate and mild sloping coasts, the wind set-up has the greatest contribution to the peak surge. The Ekman surge (caused by the Coriolis effect) typically peaks several hours before landfall and can either have a positive or negative contribution to the peak surge. The radial surge becomes relatively more important on mild-sloping coasts. SESSP's computational efficiency allows for the execution of ensemble forecasts with thousands of synthetic storms along large stretches of coast.

Storm impacts on a coupled human-natural coastal system: Resilience of developed coasts

Human occupation of and alteration of the world's coast has transformed large stretches of it into Coupled Human-Natural Systems (CHANS) in which humans both influence and are influenced by coastal evolution. In such systems, human activity is as critical on natural resilience as processes and sediment supply derived from the natural setting. Pre- and post-storm observations of these interactions on the intensively developed Atlantic coast of the Gulf of Cádiz, (Spain and Portugal) are examined to determine natural and engineering resilience. Three case studies are used in three CHANS, showing that human interventions interact in complex ways with the natural system influencing post-storm recovery. In natural coasts, storm impact is assessed in terms of geomorphological response; on developed coasts, it is quantified as damage to infrastructure or loss of amenity. Preparedness, availability of resources, choice of response and the speed at which human agencies respond affect resilience for post-storm beach behaviour. Results show in some sites natural resilience adjusting by post-storm sediment transfers and an equilibrium morphology that may differ from pre-storm morphology; engineering resilience ensured that CHANS regained their pre-storm human infrastructure and amenity. Their management requires a fundamentally different approach to that of natural coastlines. The current immature stage of understanding of CHANS (especially the human preparedness and response components) is illustrated by the case studies presented where short-term political decisions and reactions to storms play a strong role in post-storm response. The nature and extent of many developed coasts as CHANS is slowly becoming more widely acknowledged, but to increase natural resilience and decrease vulnerability in CHANS better planning is required so that future storms are anticipated and when they happen, pre-planned human response actions are activated. Storms are an integral and inevitable element in the behaviour of coastal CHANS, not a disaster or emergency.

Influence of concrete properties on the initial biological colonisation of marine artificial structures

Artificial marine infrastructures now cover large stretches of the available natural shoreline in many parts of the world. This is having a substantial impact on the local marine ecosystems as biodiverse natural hard substrata are being replaced with man-made structures, which have been shown to support lower levels of biodiversity.The ecological value of artificial coastal structures could be enhanced through careful design of pre-fabricated ecologically engineered units. Material selection is a critical parameter in the design of these units. To maximise the potential of concrete units to support and increase biodiversity, this paper explores the impact of binder composition, aggregate type and plasticizer on surface chemistry and early biofilm formation which influence subsequent colonisation. Experiments in the current study have shown that the addition of ground granulated blast-furnace slag (GGBS) to the mix can increase the levels of biodiversity supported while maintaining engineering performance requirements in terms of strength, chloride resistance and alkalinity. Conversely the aggregate type and use of a plasticizer have a minor influence. In particular, the addition of GGBS was shown to increase the biomass of diatoms, cyanobacteria and green algae and barnacle abundance one month after immersion on both sheltered surfaces and those exposed to wave action. Results suggest that concrete composition can alter the surface chemistry of artificial structures and thereby can improve the ecological value of these structures as habitats for marine life.

A review on the use of Information Communication Technology (ICT) in fisheries management: A case of Mbenji island small-scale fishery in Malawi

Fisheries management has evolved in Malawi from a traditional system to a centralized regime and lately to co-management fisheries systems, although, success stories about sustainability of the fishery resources are few. Open access nature of fisheries resources has posed a challenge to management regimes. Resource over exploitation has continued in a majority of fisheries worsened by large stretches of the shoreline manned by a single fisheries field staff, and limited capacity by DoF to monitor and manage the fishery. However, isolated localities have upheld management styles that have facilitated sustainable exploitation. Mbenji Island fishery ‘managers’ have ensured high compliance to fisheries rules and regulations among fishers through strict enforcement and maintained abundant fish stocks amid visibly declining levels of fish in vast localities of Lake Malawi and other water bodies in Malawi. There is,therefore, need to take the Mbenji Island success story to other fishing communities to learn from their fisheries management strategies. Information Communication Technology (ICT) as a powerful means in mobilizing communities to take charge of their own development should support ‘best practices’ and offer fishing communities access to the same type of services and advantages. If appropriately applied,ICT can provide for real-time monitoring of fisheries resources as fishers alarm law enforcers to move in at appropriate times. Fishers also strike deals on mobile phones for the day's catch even before landing at shore. This reduces post-harvest waste from delayed handling of fish. Computers have been used for data management, storage and analysis as well as accessing internet services. Studies have shown commonalities in fisher communities in terms of socio-economic and cultural characteristics. On the basis of such an advantage, more could be shared among such communities. Management success can be adopted by other communities of fishers through use of ICT such as radio programs (supplemented by phone-in sessions) undertaken by local-level resource users. These programs provide locally available information and knowledge on best practices aimed at sustainability with means within communities. This encourages community members in other localities to come together to seek the way forward on the basis of lessons from successful communities aired on local radio stations (both community or national radio stations). It is easier to adopt practices that have worked in near vicinities. After all,what is currently called co-management is seemingly based on indigenous knowledge of fishers and other resource users. Mbenji Island is one of the custodians of ICT option in small-scale fisheries management of Lake Malawi. Information Communication Technology provides opportunity for both the Malawi Department of Fisheries (DoF) and fishers with information about fisher community activities including catch and market regardless of distance.