Effective Competitor Research Articles

A 3000 year record of Caribbean reef urchin communities reveals causes and consequences of long‐term decline in Diadema antillarum

Urchins are the last abundant grazers of macroalgae on most Caribbean reefs following the historical overexploitation of herbivorous fishes. The long‐spined urchin Diadema antillarum was particularly effective at controlling macroalgae and facilitating coral dominance on Caribbean reefs until its ecological extinction from a catastrophic disease epidemic in the early 1980s. Despite their important role in the structure and functioning of Caribbean reef ecosystems, the natural dynamics of Caribbean reef urchin communities are poorly known due to the paucity of ecological survey data prior to large‐scale human disturbances and the Diadema dieoff. To help resolve the baseline abundances and ecological roles of common urchin taxa, we track changes in urchin abundance and composition over the past 3000 yr from analysis of subfossil urchin spines preserved in reef matrix cores collected in Caribbean Panama. Echinometra consistently dominated the subfossil spine assemblage, while Diadema was consistently rare in the subfossil record in this region. Rather than increasing during a period of heightened human exploitation of their fish competitors and predators, Diadema began declining over a millennium ago. Convergent cross mapping (CCM) causality analyses reveal that Diadema abundance is causally related to coral community composition. Diadema is negatively affected by Acropora cervicornis dominance, likely due to the tight association between this coral and the threespot damselfish, an effective Diadema competitor. Conversely, Diadema positively affects the abundance of the coral Madracis mirabilis, possibly via its control of macroalgae. Causal relationships were not detected among abundances of individual urchin taxa, indicating that inter‐specific echinoid competition is not a factor limiting Diadema recovery. Our detailed record of prehistorical and historical urchin community dynamics suggests that the failure of Diadema to recover over 30 yr after its mass mortality event may be due in part to the prey release of damselfish following the long‐term overfishing of piscivorous fishes.

Mixed Tukey EWMA-CUSUM control chart and its applications

Tukey control chart (TCC) is a popular choice for robust monitoring of process parameters. With the advancement in technology, we develop refined techniques that incorporate multiple aspects in a single structure. This article is a similar effort to design an improved charting structure in the form of mixed Tukey EWMA-CUSUM chart (namely MEC-TCC). We have investigated the performance of the proposed chart using different run length properties. We have observed that the proposed MEC-TCC design serves the dual objectives, namely the efficient detection of shifts and robustness against non-normality. The comparative analysis has revealed that the proposed scheme is an effective competitor to the existing counterparts, including classical Shewhart, EWMA, CUSUM, Tukey and some other variants such as mixed EWMA-CUSUM, Tukey EWMA, Tukey CUSUM. Moreover, the proposed design presents some of the aforementioned charts as special cases. For real life considerations, we have implemented the proposed and existing charts to two real life data sets, one related to air quality and the other one concerning smartphone accelerometer.

Exploring the impact of the side-chain length on peptide/RNA binding events.

The impact of the amino-acid side-chain length on peptide-RNA binding events has been investigated using HIV-1 Tat derived peptides as ligands and the HIV-1 TAR RNA element as an RNA model. Our studies demonstrate that increasing the length of all peptide side-chains improves unexpectedly the binding affinity (KD) but reduces the degree of compactness of the peptide-RNA complex. Overall, the side-chain length appears to modulate in an unpredictable way the ability of the peptide to compete with the cognate TAR RNA partner. Beyond the establishment of non-intuitive fundamental relationships, our results open up new perspectives in the design of effective RNA ligand competitors, since a large number of them have already been identified but few studies report on the modulation of the biological activity by modifying in the same way the length of all chains connecting RNA recognition motives to the central scaffold of a ligand.

Adsorption of perfluorooctane sulfonate on soils: Effects of soil characteristics and phosphate competition

Perfluorooctane sulfonate (PFOS) is an emerging contaminant, whose presence has been detected in different compartments of the environment in many countries. In this study, the effects of soil characteristics and phosphate competition on the adsorption of PFOS on soils were investigated. Results from batch sorption experiments showed that all the adsorption isotherms of PFOS on three tested soils were nonlinear. In experiments without the addition of phosphate (P) to the soil solution, the Freundlich sorption affinity (Kf) of PFOS on S (original soil), S1 (soil from which soil organic matter (SOM) had been removed), and S2 (soil from which both SOM and ferric oxides had been removed) were 23.13, 10.37 and 15.95, respectively. The results suggested that a high amount of SOM in soil can increase the sorption affinity of PFOS on soils and that a greater amount of ferric oxides can reduce it. The addition of P in the soil solution reduced the Kf of PFOS on S, S1, and S2 by approximately 25%, 50%, and 15%, respectively. For the binary system of PFOS and P, soil with higher ferric oxide content showed greater Kf reduction after P addition; whereas soil with higher SOM content showed less Kf reduction. Our results suggest that for soils dominated by ferric oxides, P is a more effective competitor than PFOS for the adsorption sites in the binary system; whereas in soils containing more SOM, P is a weak competitor.

Removal of triazine-based pollutants from water by carbon nanotubes: Impact of dissolved organic matter (DOM) and solution chemistry

Adsorption of organic pollutants by carbon nanotubes (CNTs) in the environment or removal of pollutants during water purification require deep understanding of the impacts of the presence of dissolved organic matter (DOM). DOM is an integral part of environmental systems and plays a key role affecting the behavior of organic pollutants. In this study, the effects of solution chemistry (pH and ionic strength) and the presence of DOM on the removal of atrazine and lamotrigine by single-walled CNTs (SWCNTs) was investigated. The solubility of atrazine slightly decreased (∼5%) in the presence of DOM, whereas that of lamotrigine was significantly enhanced (by up to ∼70%). Simultaneous introduction of DOM and pollutant resulted in suppression of removal of both atrazine and lamotrigine, which was attributed to DOM-pollutant competition or blockage of adsorption sites by DOM. However the decrease in removal of lamotrigine was also a result of its complexation with DOM. Pre-introduction of DOM significantly reduced pollutant adsorption by the SWCNTs, whereas introduction of DOM after the pollutant resulted in the release of adsorbed atrazine and lamotrigine from the SWCNTs. These data imply that DOM exhibits higher affinity for the adsorption sites than the triazine-based pollutants. In the absence of DOM atrazine was a more effective competitor than lamotrigine for adsorption sites in SWCNTs. However, competition between pollutants in the presence of DOM revealed lamotrigine as the better competitor. Our findings help unravel the complex DOM–organic pollutant–CNT system and will aid in CNT-implementation in water-purification technologies.

Listeria monocytogenes Strains Underrepresented during Selective Enrichment with an ISO Method Might Dominate during Passage through Simulated Gastric Fluid and In Vitro Infection of Caco-2 Cells.

Various Listeria monocytogenes strains may contaminate a single food product, potentially resulting in simultaneous exposure of consumers to multiple strains. However, due to bias in strain recovery, L. monocytogenes strains isolated from foods by selective enrichment (SE) might not always represent those that can better survive the immune system of a patient. We investigated the effect of cocultivation in tryptic soy broth with 0.6% yeast extract (TSB-Y) at 10°C for 8 days on (i) the detection of L. monocytogenes strains during SE with the ISO 11290-1:1996/Amd 1:2004 protocol and (ii) the in vitro virulence of strains toward the Caco-2 human colon epithelial cancer cell line following exposure to simulated gastric fluid (SGF; pH 2.0)-HCl (37°C). We determined whether the strains which were favored by SE would be effective competitors under the conditions of challenges related to gastrointestinal passage of the pathogen. Interstrain competition of L. monocytogenes in TSB-Y determined the relative population of each strain at the beginning of SE. This in turn impacted the outcome of SE (i.e., favoring survival of competitors with better fitness) and the levels exposed subsequently to SGF. However, strong growth competitors could be outcompeted after SGF exposure and infection of Caco-2 cells by strains outgrown in TSB-Y and underdetected (or even missed) during enrichment. Our data demonstrate a preferential selection of certain L. monocytogenes strains during enrichments, often not reflecting a selective advantage of strains during infection. These findings highlight a noteworthy scenario associated with the difficulty of matching the source of infection (food) with the L. monocytogenes isolate appearing to be the causative agent during listeriosis outbreak investigations.IMPORTANCE This report is relevant to understanding the processes involved in selection and prevalence of certain L. monocytogenes strains in different environments (i.e., foods or sites of humans exposed to the pathogen). It highlights the occurrence of multiple strains in the same food as an important aspect contributing to mismatches between clinical isolates and infection sources during listeriosis outbreak investigations.

MeCP2 Binding Cooperativity Inhibits DNA Modification-Specific Recognition.

Methyl-CpG binding protein 2 (MeCP2) is a multifunctional protein that guides neuronal development through its binding to DNA, recognition of sites of methyl-CpG (mCpG) DNA modification, and interaction with other regulatory proteins. Our study explores the relationship between mCpG and hydroxymethyl-CpG (hmCpG) recognition mediated by its mCpG binding domain (MBD) and binding cooperativity mediated by its C-terminal polypeptide. Previous study of the isolated MBD of MeCP2 documented an unusual mechanism by which ion uptake is required for discrimination of mCpG and hmCpG from CpG. MeCP2 binding cooperativity suppresses discrimination of modified DNA and is highly sensitive to both the total ion concentration and the type of counterions. Higher than physiological total ion concentrations completely suppress MeCP2 binding cooperativity, indicating a dominant electrostatic component to the interaction. Substitution of SO4(2-) for Cl(-) at physiological total ion concentrations also suppresses MeCP2 binding cooperativity, This effect is of particular note as the intracellular Cl(-) concentration changes during neuronal development. A related effect is that the protein-stabilizing solutes, TMAO and glutamate, reduce MeCP2 (but not isolated MBD) binding affinity by 2 orders of magnitude without affecting the apparent binding cooperativity. These observations suggest that polypeptide flexibility facilitates DNA binding by MeCP2. Consistent with this view, nuclear magnetic resonance (NMR) analyses show that ions have discrete effects on the structure of MeCP2, both MBD and the C-terminal domains. Notably, anion substitution results in changes in the NMR chemical shifts of residues, including some whose mutation causes the autism spectrum disorder Rett syndrome. Binding cooperativity makes MeCP2 an effective competitor with histone H1 for accessible DNA sites. The relationship between MeCP2 binding specificity and cooperativity is discussed in the context of chromatin binding, neuronal function, and neuronal development.

Genetic Manipulation of Competition for Nitrate between Heterotrophic Bacteria and Diatoms.

Diatoms are a dominant group of eukaryotic phytoplankton that contribute substantially to global primary production and the cycling of important elements such as carbon and nitrogen. Heterotrophic bacteria, including members of the gammaproteobacteria, are commonly associated with diatom populations and may rely on them for organic carbon while potentially competing with them for other essential nutrients. Considering that bacterioplankton drive oceanic release of CO2 (i.e., bacterial respiration) while diatoms drive ocean carbon sequestration vial the biological pump, the outcome of such competition could influence the direction and magnitude of carbon flux in the upper ocean. Nitrate availability is commonly a determining factor for the growth of diatom populations, particularly in coastal and upwelling regions. Diatoms as well as many bacterial species can utilize nitrate, however the ability of bacteria to compete for nitrate may be hindered by carbon limitation. Here we have developed a genetically tractable model system using the pennate diatom Phaeodactylum tricornutum and the widespread heterotrophic bacteria Alteromonas macleodii to examine carbon-nitrogen dynamics. While subsisting solely on P. tricornutum derived carbon, A. macleodii does not appear to be an effective competitor for nitrate, and may in fact benefit the diatom; particularly in stationary phase. However, allochthonous dissolved organic carbon addition in the form of pyruvate triggers A. macleodii proliferation and nitrate uptake, leading to reduced P. tricornutum growth. Nitrate reductase deficient mutants of A. macleodii (ΔnasA) do not exhibit such explosive growth and associated competitive ability in response to allochthonous carbon when nitrate is the sole nitrogen source, but could survive by utilizing solely P. tricornutum-derived nitrogen. Furthermore, allocthonous carbon addition enables wild-type A. macleodii to rescue nitrate reductase deficient P. tricornutum populations from nitrogen starvation, and RNA-seq transcriptomic evidence supports nitrogen-based interactions between diatoms and bacteria at the molecular level. This study provides key insights into the roles of carbon and nitrogen in phytoplankton-bacteria dynamics and lays the foundation for developing a mechanistic understanding of these interactions using co-culturing and genetic manipulation.

Spatial and dietary overlap between blackbuck (Antilope cervicapra) and feral horse (Equus caballus) at Point Calimere Wildlife Sanctuary, Southern India: Competition between native versus introduced species

Overgrazing by livestock is a serious threat to the biodiversity in the tropical forests of Asia. Feral horse, an introduced species at Point Calimere Wildlife Sanctuary, is a grazer and overlaps extensively in space and food resources with blackbuck, a native species, and thus could be a potential competitor. We have assessed, between December 2012 and June 2013, if the ecological conditions in the study site favour competition between these two species by assessing their spatial distribution pattern, population density, and dietary overlap. Spatial distribution pattern on direct sighting of both the species across habitats revealed that feral horses ranged mostly in the southern and southeastern parts of the sanctuary, in areas mostly with open grasslands, overlapping extensively in space with blackbuck, a grassland habitat specialist of the sanctuary. Population density estimated using line-transect distance sampling method showed 50 (95% CI 41.6–60.6) blackbucks and 21 (15.2–30.0) feral horses per km2 of the sanctuary. Dietary overlap assessed through site examination of feeding trails revealed that out of 14 plant species identified from blackbuck diet during the study period, 12 (86%) were also consumed by feral horses. Similarly, food plants such as Cloris parpata, a grass species, and herb Desmodiam dryflorae, the principal food of blackbuck, were also the major food plants of feral horses. Further, estimation of food consumption rate showed that feral horse consumed significantly more food per unit time (2.8±0.08g/min) than blackbuck (1.7±0.07g/min). Dietary overlap estimated using Schoener’s Index showed a significant overlap between the two species (overall 89% and habitat-wise 85–90%). An analysis of food preference using Jacob’s Preference Index revealed that all the preferred food plants of the blackbuck were equally preferred by feral horses indicating significant overlap in the diet species composition. Although the density estimate revealed a lesser number of feral horses per capita than blackbuck, the higher food consumption rate of the former coupled with larger body mass, could outweigh the higher density of blackbuck and the same is discussed as an effective ecological competitor. Based on the findings appropriate recommendations are made for the management of blackbuck in the sanctuary.

Entrepreneurial Competition Orientation and Profitability: The Case of a Developing Economy

The main purpose of this paper is to verify the significance of the implementation of competition orientation (CO) as a part of market orientation for the financial performance of the entrepreneurial small and medium – sized companies in a developing economy. The objectives are: 1. To measure the level of each of the variables of the scale (CO 1: The management continuously analyses the strengths and weaknesses of the competitors; CO 2: We regularly use information about our competitors in strategy creation; CO 3: When a competitor launches a campaign towards our market position we take immediate action; CO 4: We target customers where we have or can develop competitive advantage; CO 5: We create our strategy on the basis of detailed and effective competitor analysis.); 2. To determine the average level of CO in entrepreneurial small and medium – sized companies; 3. To prove the effect CO has on profitability. The methodology included both quantitative and qualitative methods and, the research was done in entrepreneurial companies from the food production industry. This research is a part of an ongoing project entitled: “Strengthening the business capacity of women entrepreneurs in Republic of Macedonia, as a developing country”. Primary data was derived from questionnaires and semi-structured follow-up interviews. Secondary data was collected from books, journals and academic articles. Data was analysed with IBM SPSS19. The conclusions are given on the basis of descriptive and deductive statistics. The results show that companies of different sizes demonstrate diverse level of implementation of CO i.e. medium – sized companies implement higher levels on every analysed variable of CO than small companies. The results also corroborate the significant relationships among the five dimensions of CO, as well as their relationship with profitability of the analysed companies. Also, a direct influence of the level of CO implementation on business profitability was found. The main limitation of this study is that it analyses a single industry in a given period of time and, the (small) size of the sample. However, the paper has some practical implications: it proves that to achieve higher financial performance small and medium – sized companies must adopt and implement higher level of competitor orientation, as a part of the market orientation process. Also, the measurability of this part of market orientation on the basis of the MKTOR and MARKOR scales makes available a valuable tool for control of its implementation. The value of the paper derives from the verification of the significance of the relationship between CO and profitability, in a different business sector and with a different research subject from those analysed hitherto by the literature.

Strains of the Harmful Cyanobacterium Microcystis aeruginosa Differ in Gene Expression and Activity of Inorganic Carbon Uptake Systems at Elevated CO2 Levels.

Cyanobacteria are generally assumed to be effective competitors at low CO2 levels because of their efficient CO2-concentrating mechanism (CCM), and yet how bloom-forming cyanobacteria respond to rising CO2 concentrations is less clear. Here, we investigate changes in CCM gene expression at ambient CO2 (400 ppm) and elevated CO2 (1,100 ppm) in six strains of the harmful cyanobacterium Microcystis. All strains downregulated cmpA encoding the high-affinity bicarbonate uptake system BCT1, whereas both the low- and high-affinity CO2 uptake genes were expressed constitutively. Four strains downregulated the bicarbonate uptake genes bicA and/or sbtA, whereas two strains showed constitutive expression of the bicA-sbtA operon. In one of the latter strains, a transposon insert in bicA caused low bicA and sbtA transcript levels, which made this strain solely dependent on BCT1 for bicarbonate uptake. Activity measurements of the inorganic carbon (Ci) uptake systems confirmed the CCM gene expression results. Interestingly, genes encoding the RuBisCO enzyme, structural carboxysome components, and carbonic anhydrases were not regulated. Hence, Microcystis mainly regulates the initial uptake of inorganic carbon, which might be an effective strategy for a species experiencing strongly fluctuating Ci concentrations. Our results show that CCM gene regulation of Microcystis varies among strains. The observed genetic and phenotypic variation in CCM responses may offer an important template for natural selection, leading to major changes in the genetic composition of harmful cyanobacterial blooms at elevated CO2.

Spectroscopic study on flavonoid–drug interactions: Competitive binding for human serum albumin between three flavonoid compounds and ticagrelor, a new antiplatelet drug

The effects of three kinds of flavonoids, quercetin, rutin and baicalin, on the binding of ticagrelor to human serum albumin (HSA) were systematically investigated using fluorescence, UV–vis absorption and circular dichroism (CD) spectroscopic techniques. The results indicated that ticagrelor strongly quenched the HSA fluorescence by the style of static quenching and non-radiation energy transferring as a result of the HSA–ticagrelor complex formation, while the presence of flavonoids could not change the quenching mechanism. Ticagrelor could spontaneously bind in site I on HSA with high affinity, and this binding process was mainly driven by both hydrophobic forces and hydrogen bonding. The significantly decreased binding affinity and the unchanged binding mode and distance between ticagrelor and HSA indicated that that flavonoids could compete against ticagrelor in site I, and baicalin was the most effective competitor. The conformation investigation of HSA further confirmed the flavonoid/ticagrelor competitive binding mechanism.

Response of Japanese Barberry to Varying Degrees of Defoliation

Abstract Until recently, it was thought that Berberis thunbergii (Japanese Barberry), a non-native invasive plant that has become particularly widespread in certain regions of New Jersey, benefited from a lack of herbivorous defoliators. However, in 2007 extensive defoliation was documented across a wide geographical distribution in New Jersey, calling this assumption into question. We tested whether Japanese Barberry was negatively affected by partial defoliation by manually clipping 50% or 100% of leaves on current-year stems on small and large plants in the summer of 2008. We found almost no impact of defoliation on growth, carbon storage, or leaf-level physiology for either treatment. We noted some differences between large and small plants, but these were not related to defoliation treatments. Our results suggest that, even in the presence of herbivory, Japanese Barberry is capable of maintaining growth and carbon reserves, thus making it an effective competitor for resources.

Informational masking of monaural target speech by a single contralateral formant.

Recent research suggests that the ability of an extraneous formant to impair intelligibility depends on the variation of its frequency contour. This idea was explored using a method that ensures interference cannot occur through energetic masking. Three-formant (F1 + F2 + F3) analogues of natural sentences were synthesized using a monotonous periodic source. Target formants were presented monaurally, with the target ear assigned randomly on each trial. A competitor for F2 (F2C) was presented contralaterally; listeners must reject F2C to optimize recognition. In experiment 1, F2Cs with various frequency and amplitude contours were used. F2Cs with time-varying frequency contours were effective competitors; constant-frequency F2Cs had far less impact. To a lesser extent, amplitude contour also influenced competitor impact; this effect was additive. In experiment 2, F2Cs were created by inverting the F2 frequency contour about its geometric mean and varying its depth of variation over a range from constant to twice the original (0%-200%). The impact on intelligibility was least for constant F2Cs and increased up to ∼100% depth, but little thereafter. The effect of an extraneous formant depends primarily on its frequency contour; interference increases as the depth of variation is increased until the range exceeds that typical for F2 in natural speech.

The catecholestrogen, 2-hydroxyestradiol-17beta, acts as a G protein-coupled estrogen receptor 1 (GPER/GPR30) antagonist to promote the resumption of meiosis in zebrafish oocytes.

Estradiol-17beta (E2) maintains high cAMP levels and meiotic arrest in zebrafish oocytes through activation of G protein-coupled estrogen receptor (GPER). The catecholestrogen 2-hydroxyestradiol-17beta (2-OHE2) has an opposite effect to that of E2 on oocyte maturation (OM) and cAMP levels in Indian catfish oocytes. We tested the hypothesis that 2-OHE2 is produced in zebrafish ovaries and promotes the resumption of oocyte meiosis through its action as a GPER antagonist. Ovarian 2-OHE2 production by estrogen-2-hydroxylase (EH) was up-regulated by gonadotropin treatment at the onset of OM, consistent with a physiological role for 2-OHE2 in regulating OM. The increases in EH activity and OM were blocked by treatment with CYP1A1 and CYP1B1 inhibitors. Expression of cyp1a, cyp1b1, and cyp1c mRNAs was increased by gonadotropin treatment, further implicating these Cyp1s in 2-OHE2 synthesis prior to OM. Conversely, aromatase activity and cyp19a1 mRNA expression declined during gonadotropin induction of OM. 2-OHE2 treatment significantly increased spontaneous OM in defolliculated zebrafish oocytes and reversed the inhibition of OM by E2 and the GPER agonist G-1. 2-OHE2 was an effective competitor of [(3)H]-E2 binding to recombinant zebrafish GPER expressed in HEK-293 cells. 2-OHE2 also antagonized estrogen actions through GPER on cAMP production in zebrafish oocytes, resulting in a reduction in cAMP levels. Stimulation of OM by 2-OHE2 was blocked by pretreatment of defolliculated oocytes with the GPER antibody. Collectively, the results suggest that 2-OHE2 functions as a GPER antagonist and promotes OM in zebrafish through blocking GPER-dependent E2 inhibition of the resumption of OM.

Ways of performing judo throws, and their efficiency, assessed in the open weight category in All-Japan Judo Championships

There is no indication that earlier individual attempts in this area have been carried out in Japan. Judo masters including Kano, Koizumi, Kudo, Mifune, Tomiki and others have tried to introduce additional criteria to the classification. The need for so many modifications is a result of the many sport and referee rule changes, as well as to ensure the safety of competitors and to increase the attractiveness of judo contests. Purpose of the work. The purpose of this work was to determine the ways of performing the judo throws and their efficiency during All-Japan Judo Championships at open weight category. Material/methods. 278 open category judo players were recorded during the All-Japan Judo Championships (2003-2012). The competitors successfully executed 252 attacks using 34 judo throws classified by the Kodokan Judo. Effective attacks divided by: uchi - reaping legs from inside, soto - hooking/reaping opponents’ legs from outside, otoshi – throws performed by dropping body, gaeshi – throws performed as counterattacks, tsurikomi – throws performed by pull-lifting with hands, harai – throws performed by sweeping with legs or hips and makikomi – throws performed by winding the opponent’s body, were distinguished. The sequence of dominant techniques was presented by the “K” index, and the directions and ways of performing the throws were determined by the efficiency attack index. Results. The most effective Japanese competitors performed three throws by UCHI: uchimata, ouchi gari, kouchi gari, and three throws by SOTO: osoto gari, kosoto gake, kosoto gari. The following throwing techniques, during the Championships, were dominant: uchimata, ouchi gari and osoto gari which ended the contests by ippon (before contest time had elapsed); they were most often executed successfully, and the competitors gained most referee’s points. The observed competitors demonstrated even effectiveness in executing throws, forward – breaking balance onto tip-toes, and backward – breaking balance onto heels. Comparatively effectively, they performed throws into the four analyzed directions. Conclusions. The Japanese competitors performed the most effective attacks by using leg throws which call for the reaping actions of legs either from inside or outside UCHI and SOTO. Fewer techniques, executed perfectly resulted in gaining more referee’s points. Using these techniques put the competitors in a better position to carry out attacks and changing their direction.

The Market for Cryptocurrencies

Although it is sometimes considered one of a kind, or a first-mover monopolist in the market for cryptocurrencies, Bitcoin is surrounded by effective competitors. Between March 2013 and December 2014, while the market capitalization of Bitcoin grew four-fold, the market cap of other cryptocurrencies (“altcoins”) in the aggregate grew twelve-fold, eroding Bitcoin’s market share to 84% from 95%. Where Bitcoin is a non-profit project, the growth of altcoins has been driven by for-profit enterprises. Altcoins have introduced improvements in speed, robustness, and privacy. Contrary to the predictions of economists who tried to imagine what private irredeemable currencies would look like, cryptocurrencies have attained positive valuations by implementing a nominal quantity commitment with an observable public ledger, rather than by the traditional method of redeemability or a purchasing-power commitment. Cryptocurrencies are not all bubbles, although a number of bubble-like crashes (to below 98% of peak value) can be observed in the record. There is no reason to suppose that the market is plagued either by insufficient competition or by too much competition.

Keeping the Land Wet: Competition and Incumbency in the Liquid Fuel Value Chain in South Africa

Barriers to entry, by reinforcing the market power of incumbent firms in liquid fuel distribution, have meant that the pace of transformation throughout the fuel value chain in South Africa has been slow. The ability of new firms to enter the sector, develop capabilities, and become effective competitors to the major oil companies is important for achieving transformation and introducing dynamic rivalry in the liquid fuels sector. This paper draws on a recent CCRED study based on interviews with market participants and publicly available sources to assess the nature and extent of barriers to entry and expansion of firms in the wholesale of liquid fuels. The analysis focuses on access to supply, access to customers, access to key infrastructure, and policy and regulatory challenges rather than the known shortage of skills and finance in the sector. It is clear that these challenges at the wholesale level form part of a broader set of concerns in the value chain as a whole, relating to access to infrastructure and low levels of competition between the major oil companies themselves. The paper concludes by suggesting a set of short and long-term remedies for increasing access and competition in transportation and storage, and wholesaling infrastructure.

Adsorption of radium and barium on goethite and ferrihydrite: A kinetic and surface complexation modelling study

Radium and barium uptake onto ferrihydrite and goethite have been studied in the concentration range 1nM to 5mM and from pH 4 to 10, to develop a model to predict radium behaviour in legacy uranium mining wastes. For ferrihydrite, uptake of Ra2+ at nM concentrations was strong at pH >7. At higher concentrations, Ba2+ sorption to ferrihydrite was slightly weaker than that of Ra2+. Experiments with goethite showed weaker binding for both metal ions in all systems. The interactions of radium with both ferrihydrite and goethite are fully reversible. The behaviour of radium during transformation of ferrihydrite to goethite has been studied, and no evidence for irreversible incorporation within the goethite lattice was found; radium uptake to goethite was the same, whether or not it was present during its formation. Calcium competed with radium for ferrihydrite sorption only at high calcium concentrations (>10mM). Barium is a more effective competitor, and a concentration of 1mM reduced radium sorption. Sediment samples from a legacy uranium mining site have been analysed, and the in situ Rd values are consistent with radium uptake by surface coatings of ferrihydrite or goethite like phases. Surface complexation models have been developed for radium sorption to ferrihydrite and goethite which simulate the experimental data successfully. In both cases, approaches based on a single surface functional group and tetradentate binding sites simulated the data successfully. These data could be used in underpinning the safety case for legacy mining sites.

High-performance hybrid perovskite solar cells with polythiophene as hole-transporting layer via electrochemical polymerization

Thin polythiophene film prepared via electrochemical polymerization has been successfully used as the hole-transporting layer in CH3NH3PbI3 perovskite solar cells, affording a series of ITO/polythiophene/CH3NH3PbI3/C60/BCP/Ag devices. The highest occupied molecular orbit (HOMO) and lowest unoccupied molecular orbit (LUMO) of the polythiophene film are determined as −5.20 eV and −3.12 eV, respectively, which match well with that of CH3NH3PbI3 perovskite material. In addition, a promising power conversion efficiency of 11.8%, featuring a high fill factor of 0.707, good open voltage of 1.03 V and short current density of 16.2 mA cm−2, has been obtained, which renders polythiophene as an effective competitor to spiro-OMeTAD in perovskite solar cells. Furthermore, this work provides a simple, prompt, controllable and economic approach for the preparation of hole-transporting layer, which would undoubtedly yield new insight into the industrial production of perovskite solar cells.