The global loss of biodiversity continues at an alarming rate. Genomic approaches have been suggested as a promising tool for conservation practice, and we discuss how scaling-up to genome-wide inference can benefit traditional conservation genetic approaches and provide qualitatively novel insights. Yet, the generation of genomic data and subsequent analyses and interpretations are still challenging and largely confined to academic research in ecology and 20evolution. This generates a gap between basic research and applicable solutions for conservation managers faced with multifaceted problems. Before the real-world conservation potential of genomic research can be realized, we suggest that current infrastructures need to be modified, methods must mature, analytical pipelines need to be developed, and successful case studies must be disseminated to practitioners. 3 Conservation biology and genomicsLike most of the life sciences, conservation biology is being confronted with the challenge of how to integrate the collection and analysis of large-scale genomic data into its toolbox. Conservation biologists pull from a wide array of disciplines in an effort to preserve biodiversity and ecosystem services [1]. Genetic data have helped in this regard by 30 detecting, for example, population substructure, measuring genetic connectivity, and identifying potential risks associated with demographic change and inbreeding [2]. Traditionally, conservation genetics (see Glossary) has relied on a handful of molecular markers ranging from a few allozymes to dozens of microsatellites [3]. But for close to a decade [4], genomics -broadly defined high-throughput sampling of nucleic acids [5] -has been touted as an important advancement to the field, a panacea of sorts for the unresolved conservation problems typically addressed 35 with genetic data [6,7]. This transition has led to much promise, but also hyperbole, where concrete empirical examples of genomic data having a conservation impact remain rare.Under the premise that assisting conservation of the world's biota is its ultimate purpose, the emerging field of conservation genomics must openly and pragmatically discuss its potential contribution towards this goal. While there 40are prominent examples where genetic approaches have made inroads influencing conservation efforts (e.g., Florida panther augmentation [8,9]) and wildlife enforcement (i.e., detecting illegal harvest [10]), it is not immediately clear that the conservation community and society more broadly have embraced genomics as a useful tool for conservation.Maintaining genetic diversity has largely been an afterthought when it comes to national biodiversity policies [11,12], and attempts to identify areas that might prove to be essential for conserving biological diversity rarely mention 45 genomics (e.g. [13,14]). An obvious reason for this disconnect is that many of the pressing conservation issues (e.g., [15,16]) simply do not need genomics, but instead need political will.The traditional use of gene...

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The various bilayer structures formed from aqueous mixtures of an anionic (SDS) and a cationic surfactant (DTAB) with identical hydrocarbon C 12 chains at 40 ˚C have been investigated using small-angle neutron scattering (SANS) as well as static light scattering (SLS). The SANS data were analyzed using a paracrystal lamellar model with respect to the layer distance distribution and the number of layers in a single cluster. Unilamellar or oligolamellar vesicles form in the most diluted samples in the absence of added salt where the number of layers in a single cluster is found to be 1-3. Beyond the compositions where micelles form (30:70 < [SDS]:[DTAB] < 70:30), we observe a transition from vesicles to stacks of lamellar sheets upon increasing the overall surfactant concentration, indicated by an abrupt increase of the number of layers in a single cluster from 1-3 to infinity. Combined SANS and SLS data for samples containing vesicles ([SDS] + [DTAB] ) 0.25 wt % in the absence of added salt) could be fitted with a model for unilamellar vesicles using a structure factor for sticky hard spheres, indicating that the vesicles attract each other and form clusters. However, at [SDS] + [DTAB] ) 0.125 wt %, the vesicles appeared to be too large for the size distribution to be determined from our SANS and SLS data. In 0.1 M NaBr, the vesicles were clearly destabilized and either micelles or lamellar sheets form at most compositions and concentrations where vesicles predominate in the absence of added salt.

Synergistic effects in mixed binary surfactant systems have been investigated by analyzing the main contributions to the free energy of forming a mixed surfactant aggregate. We show that a nonlinear behavior of the critical micelle concentration (cmc) with respect to the surfactant composition of the aggregates is determined by a nonlinear behavior of the free energy per aggregated surfactant. It appears that synergistic effects are due mainly to entropic free energy contributions related with the surfactant headgroups. For a mixture of a monovalent ionic and a nonionic surfactant in the absence of added salt we obtain, entirely because of electrostatic reasons, a negative deviation from ideal behavior of the cmc vs the aggregate composition corresponding to an interaction parameter β ≈ -1, whereas β values on the order of -5 or even less can arise for mixtures of two ionic surfactants with the same charge number but with different hydrocarbon moieties. Moreover, we introduce a novel expression for the free energy of mixing aggregated surfactant headgroups with surrounding solvent molecules. Accordingly, synergistic effects arise as a result of different headgroup cross-section areas in mixtures of two nonionic surfactants with rigid headgroups. These effects are found to be rather small, with 0 > β > -1, when the difference in headgroup size is modest but can become more significant when the size difference is larger. In mixtures of an ionic and a nonionic surfactant with different headgroup cross-section areas the two contributions to synergistic effects always enhance one another and, hence, β values below -1 are obtained. Generally, the synergistic effects tend to increase with increasing asymmetry between the two surfactants.

SDS wormlike micelles in water with NaBr are studied using small-angle neutron scattering. SDS concentrations ranging from 0.08 to 8.6 % vol in NaBr aqueous solutions at salinities from 0.6 to 1.0 M are covered. The scattering data are analyzed using a novel approach based on polymer theory and the results of Monte Carlo simulations. The method makes it possible to give a full interpretation of the scattering data, even for the entangled micellar solutions occurring at high concentrations and high salinities. Analysis of the scattering data at zero scattering angle demonstrates that the length of the micelles increases according to a power law as a function of concentration in the studied interval. The analysis furthermore shows that the length of the micelles increases exponentially with increasing salinity. The scattering data in the full range of scattering angles are analyzed using a model for polydisperse wormlike micelles where excluded volume effects are taken into account via an expression based on the polymer reference interaction site model (PRISM). This part of the analysis show that the micelles become more flexible as the salinity increases, which is due to an increased screening of the ionic micelles.

The very slow equilibration time in oppositely charged systems makes it necessary to control not only the concentration of the species but also the details of the mixing process. This has been demonstrated for processes occurring at interfaces where order of addition effects can be of great importance. In this investigation we set out to study the bulk properties of aqueous mixtures of a highly charged cationic polyelectrolyte mixed with an anionic surfactant with the aim to learn if long-lived non-equilibrium states were formed also in this case, and thus if the details of the mixing procedure would affect the structure of the aggregates formed. For simplicity we chose two mixing protocols, denoted "PTS" and "STP". In the PTS-method the polyelectrolyte is added to the surfactant solution whereas in the STP-method the surfactant is added into the polyelectrolyte solution. The properties of the mixtures in aqueous solutions, with different NaCl concentrations and as a function of time, were followed by conducting turbidity, electrophoretic mobility and dynamic light scattering measurements. The results demonstrate that the mixing protocol indeed has a great impact on the size of the aggregates initially formed and that this size difference persists for long times. Hence, trapped non-equilibrium states do play an important role also in the bulk solution. We found that in excess surfactant solutions the smaller aggregates formed by the STP-method are more resistant than the larger ones formed by the PTS-method to colloidal instability induced by electrolytes (NaCl). Based on our results we suggest that for producing small and stable polyelectrolyte-surfactant aggregates in systems with excess surfactant, the surfactant should be added last, while the opposite should be applied for systems with excess polyelectrolyte.

The character of adsorbed layers containing both polyelectrolyte and surfactant depends on the type of polyelectrolyte used and the surfactant concentrations, as demonstrated by several recent studies. However, the layer properties also depend on the experimental pathway. This shows that the adsorbed layers can be trapped in quasi-equilibrium states and that the true equilibrium is reached only after experimentally inaccessible time scales. This has to be kept in mind when comparing different results reported in the literature. The present article highlights these effects using a system consisting of a highly charged cationic polyelectrolyte, poly{(propionyloxy)ethyl}trimethylammonium chloride (PCMA), and an anionic surfactant, sodium dodecyl sulfate (SDS). The adsorbed layer properties were determined using mainly surface force measurements and atomic force microscope (AFM) imaging. We also present some small-angle neutron scattering data for bulk PCMA-SDS complexes formed between the polyelectrolyte and the surfactant. They demonstrate the presence of a characteristic correlation length of about 37-39 Å. A similar characteristic length scale is also observed in some of the adsorbed layers, both employing the AFM and the surface force apparatus. It may be interpreted as the distance between surfactant loaded polyelectrolyte chains.