Counterion binding alters surfactant self-assembly in deep eutectic solvents.

Micellisation of surfactants in deep eutectic solvents has been recently demonstrated to provide a controllable way to modify micelle morphology. Ion-pair interactions between the solvent and the surfactant headgroup were identified as affecting the micellisation by modifying the charge density of the micelle. Here we explore the micellisation of dodecylsulfate surfactants with different counterions (Li+, Cs+, Mg2+, Bmim+, Emim+, cholinium+) dissolved in two deep eutectic solvents: choline chloride:urea and choline chloride:glycerol. Surface tension results show a solvent and counterion dependence of the CMC of the surfactants. Small-angle neutron scattering was subsequently used to investigate the morphology of the micelles formed. The results show that the elongation of the micelles is strongly dependent on the solvent, showing more elongated aggregates in choline chloride:urea than in choline chloride:glycerol. The morphology of micelles in DES was also found to depend on the counterion, where the affinity of binding showed similarities to that in water.

Magnetic Fluctuations, Precursor Phenomena, and Phase Transition in MnSi under a Magnetic Field.

The reference chiral helimagnet MnSi is the first system where Skyrmion lattice correlations have been reported. At a zero magnetic field the transition at T_{C} to the helimagnetic state is of first order. Above T_{C}, in a region dominated by precursor phenomena, neutron scattering shows the buildup of strong chiral fluctuating correlations over the surface of a sphere with radius 2π/ℓ, where ℓ is the pitch of the helix. It has been suggested that these fluctuating correlations drive the helical transition to first order following a scenario proposed by Brazovskii for liquid crystals. We present a comprehensive neutron scattering study under magnetic fields, which provides evidence that this is not the case. The sharp first order transition persists for magnetic fields up to 0.4 T whereas the fluctuating correlations weaken and start to concentrate along the field direction already above 0.2 T. Our results thus disconnect the first order nature of the transition from the precursor fluctuating correlations. They also show no indication for a tricritical point, where the first order transition crosses over to second order with increasing magnetic field. In this light, the nature of the first order helical transition and the precursor phenomena above T_{C}, both of general relevance to chiral magnetism, remain an open question.

Porosity of silica Stöber particles determined by spin-echo small angle neutron scattering.

Stöber silica particles are used in a diverse range of applications. Despite their widespread industrial and scientific uses, information on the internal structure of the particles is non-trivial to obtain and is not often reported. In this work we have used spin-echo small angle neutron scattering (SESANS) in conjunction with ultra small angle X-ray scattering (USAXS) and pycnometry to study an aqueous dispersion of Stöber particles. Our results are in agreement with models which propose that Stöber particles have a porous core, with a significant fraction of the pores inaccessible to solvent. For samples prepared from the same master sample in a range of H2O : D2O ratio solutions we were able to model the SESANS results for the solution series assuming monodisperse, smooth surfaced spheres of radius 83 nm with an internal open pore volume fraction of 32% and a closed pore fraction of 10%. Our results are consistent with USAXS measurements. The protocol developed and discussed here shows that the SESANS technique is a powerful way to investigate particles much larger than those studied using conventional small angle scattering methods.

Inter-particle correlations in a hard-sphere colloidal suspension with polymer additives investigated by Spin Echo Small Angle Neutron Scattering (SESANS).

Using a neutron scattering technique that measures a statistically-averaged density correlation function in real space rather than the conventional reciprocal-space structure factor, we have measured correlations between poly(methyl-methacrylate) (PMMA) colloidal particles of several sizes suspended in decalin. The new method, called Spin Echo Small Angle Neutron Scattering (SESANS) provides accurate information about particle composition, including the degree of solvent penetration into the polymer brush grafted on to the PMMA spheres to prevent aggregation. It confirms for particles, between 85 nm and 150 nm in radius that inter-particle correlations closely follow the Percus-Yevick hard-sphere model when the colloidal volume-fraction is between 30% and 50% provided the volume-fraction is used as a fitted parameter. No particle aggregation occurs in these systems. When small amounts of polystyrene are added as a depletant to a concentrated suspension of PMMA particles, short-range clustering of the particles occurs and there is an increase in the frequency of near-neighbor contacts. Within a small range of depletant concentration, near-neighbor correlations saturate and large aggregates with power law density correlations are formed. SESANS clearly separates the short- and long-range correlations and shows that, in this case, the power-law correlations are visible for inter-particle distances larger than roughly two particle diameters. In some cases, aggregate sizes are within our measurement window, which can extend out to 16 microns in favorable cases. We discuss the advantages of SESANS for measurements of the structure of concentrated colloidal systems and conclude that the method offers several important advantages.

Manipulating the hydrophilic / hydrophobic balance in novel cationic surfactants by ethoxylation: The impact on adsorption and self-assembly.

HYPOTHESIS: Cationic surfactants have a wide range of applications, often associated with their affinity for a range of solid surfaces and their anti-microbial properties. Manipulating their adsorption and self-assembly properties is key to most applications, and this is commonly achieved through surfactant mixtures or manipulating their headgroup or alkyl chain structure. Achieving this through adjustments to their headgroup structure is less common in cationic surfactants than in anionic surfactants. Ethoxylation provides the ability to adjust the hydrophilic / hydrophobic balance, as extensively demonstrated in a range of anionic surfactants. EXPERIMENTS: This same approach has been applied here to a range of ethoxylated cationic surfactants in the form of the quaternary ammonium salts, and their tertiary nonionic equivalents before quaternisation. Their adsorption and self-assembly properties are investigated using predominantly the neutron scattering techniques of neutron reflectivity, NR, and small angle neutron scattering, SANS. FINDINGS: The trends in the adsorption at the air-water interface and the self-assembly in aqueous solution demonstrate how the hydrophilic / hydrophobic balance can be adjusted by varying the degree of ethoxylation and the alkyl chain length, and illustrate the degree of interdependence of the different structural changes. The variation in the adsorption and the micelle structure shows how the surfactant conformation / packing changes as the degree of ethoxylation and alkyl chain length increases and how the introduction of charge induces further changes.

A neutron reflection study of surface enrichment in nematic liquid crystals.

The interfacial adsorption properties of several different dopants in cyanobiphenyl liquid crystals have been measured using specular neutron reflection. It was found that a partly fluorinated analogue of 11OCB, called F17, adsorbed strongly at the interface between 5CB and air but it was not adsorbed at the interface between 5CB and a solid substrate treated with cetyl trimethyl ammonium bromide (CTAB). The concentration dependence of the adsorption at the air interface was well described by the Brunauer, Emmett and Teller (BET) model, adapted for solutions rather than the gas phase. The isotherms are determined by two equilibrium constants: K(S) for adsorption of the dopant directly at the interface and K(L) for adsorption onto previously adsorbed dopant. The temperature dependence of K(S) indicated that the adsorption enthalpy is not influenced by the phase of the 5CB and its value of -29 kJmol(-1) is consistent with physical adsorption. The value of K(L) is zero in the isotropic phase but increases rapidly on cooling in the nematic phase suggesting that the F17 is less compatible with nematic than isotropic 5CB. The smallest layer thicknesses (~18 Å) suggest that the F17 molecules are approximately perpendicular to the surface. The other dopants studied were components of the E7 mixture: 8OCB and 5CT. No adsorption was found for 8OCB but 5CT showed adsorption at a CTAB treated solid interface when present in 5CB at the 10% level. In this case, the value of K(S) was much smaller than for F17 but the value of K(L) was such that an exponential concentration profile (predicted by the BET model) was observed with characteristic thickness of ~200 Å. The results demonstrate the potential for very precise control of surface properties in liquid crystal devices by using appropriate dopants.

Unveiling contextual realities by microscopically entangling a neutron.

The development of qualitatively new measurement capabilities is often a prerequisite for critical scientific and technological advances. Here we introduce an unconventional quantum probe, an entangled neutron beam, where individual neutrons can be entangled in spin, trajectory and energy. The spatial separation of trajectories from nanometers to microns and energy differences from peV to neV will enable investigations of microscopic magnetic correlations in systems with strongly entangled phases, such as those believed to emerge in unconventional superconductors. We develop an interferometer to prove entanglement of these distinguishable properties of the neutron beam by observing clear violations of both Clauser-Horne-Shimony-Holt and Mermin contextuality inequalities in the same experimental setup. Our work opens a pathway to a future of entangled neutron scattering in matter.

Furnace for in situ and simultaneous studies of nano-precipitates and phase transformations in steels by SANS and neutron diffraction.

Interphase precipitation occurring during solid-state phase transformations in micro-alloyed steels is generally studied through transmission electron microscopy, atom probe tomography, and ex situ measurements of Small-Angle Neutron Scattering (SANS). The advantage of SANS over the other two characterization techniques is that SANS allows for the quantitative determination of size distribution, volume fraction, and number density of a statistically significant number of precipitates within the resulting matrix at room temperature. However, the performance of ex situ SANS measurements alone does not provide information regarding the probable correlation between interphase precipitation and phase transformations. This limitation makes it necessary to perform in situ and simultaneous studies on precipitation and phase transformations in order to gain an in-depth understanding of the nucleation and growth of precipitates in relation to the evolution of austenite decomposition at high temperatures. A furnace is, thus, designed and developed for such in situ studies in which SANS measurements can be simultaneously performed with neutron diffraction measurements during the application of high-temperature thermal treatments. The furnace is capable of carrying out thermal treatments involving fast heating and cooling as well as high operation temperatures (up to 1200 °C) for a long period of time with accurate temperature control in a protective atmosphere and in a magnetic field of up to 1.5 T. The characteristics of this furnace give the possibility of developing new research studies for better insight of the relationship between phase transformations and precipitation kinetics in steels and also in other types of materials containing nano-scale microstructural features.

Time of flight modulation of intensity by zero effort on Larmor.

A time-of-flight modulation of intensity by zero effort spectrometer mode has been developed for the Larmor instrument at the ISIS pulsed neutron source. The instrument utilizes resonant spin flippers that employ electromagnets with pole shoes, allowing the flippers to operate at frequencies up to 3 MHz. Tests were conducted at modulation frequencies of 103 kHz, 413 kHz, 826 kHz, and 1.03 MHz, resulting in a Fourier time range of ∼0.1 ns to 30 ns using a wavelength band of 4 Å-11 Å.

New sources and instrumentation for neutrons in biology.

Neutron radiation offers significant advantages for the study of biological molecular structure and dynamics. A broad and significant effort towards instrumental and methodological development to facilitate biology experiments at neutron sources worldwide is reviewed.

Approaching criticality in polymer-polymer systems.

The interfacial width of polyolefins blends has been probed as a function of distance away from the critical point by using neutron reflectivity. For strongly immiscible polymer pairs, the width of the interface increases slowly when the degree of immiscibility is decreased and the interfacial width varies with the interaction parameter chi of the polymers. Closer to the critical point the dependence on the degree of miscibility becomes stronger and the way in which the interfacial width diverges, as criticality is approached, is related to both the chain length and chi. The self-consistent field theory numerical calculations, with the additional contribution due to capillary waves, provides a good description of the width of the interface between two polymer bulk phases in particular at intermediate values of the degree of immiscibility.

Development of effective living vaccines against bovine babesiosis--the longest field trial?

Between 1959 and 1996, research was performed to change a vaccine against babesiosis in Australia and to improve it as actual or threatened untoward field responses became apparent. The most significant change occurred in 1964 with the traditionally used carriers of Babesia being replaced as vaccine donors by acutely infected splenectomised calves. This ensured the infectivity of the vaccine and was fortuitously associated with a reduction in the virulence of Babesia bovis in vaccine. Since then, more than 27 million doses of highly infective vaccine have been supplied from the laboratory at Wacol near Brisbane. This vaccine reduced serious losses from babesiosis in vaccinated cattle in Australia to very low levels and has now gained acceptance worldwide. Research to ensure the continuing effectiveness of the vaccine has proved to be essential.

The use of tick transmission by Boophilus microplus to isolate pure strains of Babesia bovis, Babesia bigemina and Anaplasma marginale from cattle with mixed infections.

Pure strains of Babesia bovis, Babesia bigemina and Anaplasma marginale were isolated from cattle infected with all 3 species as well as Theileria sp. and Eperythrozoon teganodes, using only transmission by the tick, Boophilus microplus. Unengorged adult ticks transferred to susceptible cattle transmitted A. marginale, but not Babesia. Engorged adults gave rise to progeny that transmitted Babesia, B. bovis by larvae and B. bigemina by male ticks. The Theileria and E. teganodes were not transmitted by the ticks and thus did not appear in calves used for isolating the pure strains of Babesia and A. marginale.

Infectivity of cryopreserved Babesia bovis, Babesia bigemina and Anaplasma centrale for cattle after thawing, dilution and incubation at 30 degrees C.

Blood containing either Babesia bovis, Babesia bigemina or Anaplasma centrale was mixed with an equal volume of 3 M glycerol in phosphate-buffered saline with or without glucose and then stored in liquid nitrogen for 2-30 days. After being thawed, the parasitized blood was subjected to various procedures, including dilution up to 1000-fold followed by incubation at 30 or 4 degrees C for 8 h, before infectivity of the parasites was tested in a total of 70 cattle. The results showed that the blood cryopreserved with glycerol remained highly infective after thawing, despite dilution and incubation for 8 h at 30 degrees C. The results have practical application in the use of frozen, live vaccines against bovine babesiosis and anaplasmosis.

Investigations of breakdowns in protection provided by living Babesia bovis vaccine.

Field investigations of protection afforded by live Babesia bovis vaccine in Australia revealed that a ninefold increase in vaccine failures occurred in the period from 1985 to 1990. Laboratory trials using 189 experimental cattle were conducted to evaluate the protection afforded by the Babesia bovis strain used in the commercial vaccine during this time. Four isolates from clinical cases of babesiosis in vaccinated cattle were assessed. The results showed that the strain used in the vaccine during the 5 year period was poorly protective against three isolates while a recently isolated and prepared vaccine strain was strongly protective. Circumstantial evidence is provided that indicates the vaccine failures were due to change in the field populations of Babesia bovis, rather than change in the strain used in the vaccine. Implications of the results for the future of Babesia bovis vaccines are discussed.

Current state and future trends in the diagnosis of babesiosis.

An overview is given of the currently available methods to diagnose babesiosis in livestock. Microscopic techniques are still the only appropriate techniques to diagnose acute disease. Thin or thick blood films stained with Giemsa's stain are sufficient. The sensitivity ranges from 10(-5) to 10(-6), i.e. one parasite per 10(5)-10(6) erythrocytes can be detected. Thick films stained with acridine orange (sensitivity approximately 10(-7)) and the Quantitative Buffy Coat (QBC) analysis tube system (sensitivity approximately 10(-7)-10(-8)) are applicable for diagnosis in the laboratory. DNA probes are very specific tools to identify haemoparasites in organs post mortem and in ticks. For the identification of carrier animals the sensitivity (approximately 10(-5)-10(-6)) is generally not sufficient. For the latter the polymerase chain reaction (PCR) technique is a very powerful tool (sensitivity approximately 10(-9)). Many different serodiagnostic tests have been described; however, the immunofluorescence antibody test is the most widely used, while the enzyme-linked immunosorbent assay (ELISA) is the test system which holds the greatest promise for the future. Thus far, improvements to the ELISA have been limited as the quality of antigen preparations made from infected blood is generally poor with a few exceptions (Babesia bovis, Babesia caballi). Potentially, most of the problems associated with crude antigens can be overcome by the production of recombinant antigens. Several ELISAs based on highly defined recombinant antigens have been described and show promise. None of these tests has been validated to the extent that it could be applied globally. Future research requirements as well as the need for coordination of the research effort and collaboration between institutions involved in the diagnosis of babesiosis are discussed.

Evaluation of an ELISA for detection of antibodies to Babesia bovis in cattle in Australia and Zimbabwe.

An enzyme-linked immunosorbent assay (ELISA) for antibodies to Babesia bovis was evaluated in comparison with the indirect fluorescent antibody test (IFAT) in Australia and Zimbabwe. Positive and negative threshold values for the ELISA were set using sera from cattle of known infection status. Sensitivity and specificity estimates for the ELISA based on 158 positive sera from cattle experimentally infected with Australian isolates of B. bovis and 318 negative sera collected from B. bovis-free herds in Australia were 100% and 99.4%, respectively. The specificity of the assay in Africa, based on 328 sera from B. bovis-free herds in Kenya and South Africa, was 99.7%. The ELISA was compared with the IFAT using sequential sera from 16 calves experiencing primary B. bovis infections, and a total of 777 field sera collected from B. bovis-endemic herds in Australia and Zimbabwe. In primary infections, the ELISA and IFAT detected antibodies at or about the same time. With sera from endemic herds, the performance of the ELISA was at least comparable with that of the IFAT. Two hundred and fourteen of 221 sera that were negative by IFAT, were negative by ELISA, and 428 of 439 sera that were clearly positive by IFAT were positive by ELISA. Of 117 sera that gave equivocal (suspect or weak positive) results in the IFAT, 20 were positive by ELISA, 7 were suspect and 90 were negative. We conclude that the ELISA will be useful for epidemiological studies on B. bovis in Australia and Zimbabwe, and probably elsewhere.

Increased numbers of strahlenkörper in Boophilus microplus ticks ingesting a blood-passaged strain of Babesia bigemina.

Observations were made on the morphology and infectivity of Babesia bigemina parasites in the gut of Boophilus microplus ticks. The babesia parasites were derived from stabilates of a laboratory strain, prepared at intervals during several years of blood-passaging in cattle. Increased numbers of a particular developmental stage of the parasite, considered to be a type of strahlenkörper, were observed in ticks ingesting parasites derived from the latter stages of passaging. The presence of large numbers of these parasites was associated with reduced infectivity of the strain for ticks.

Effect of different methods of maintenance on the development and morphology of Babesia bigemina in the gut of Boophilus microplus.

The development and morphology of Babesia bigemina in the gut of Boophilus microplus ticks were studied during laboratory maintenance of the babesia by four methods: tick transmission in unsplenectomised (intact) calves; tick transmission in splenectomised calves; syringe passage at intervals of five days or less in splenectomised calves; and syringe passage at intervals of six weeks or more in intact calves. The first method had no apparent effect on the development of B bigemina in ticks compared to that of the original isolate. The other three methods had obvious effects, the most pronounced being increased numbers of babesial forms with processes, particularly during early stages of development. The findings emphasise the importance of maintaining laboratory strains of parasites by natural means in life cycle studies.

Effect of different methods of maintenance on the pathogenicity and infectivity of Babesia bigemina for the vector Boophilus microplus.

Observations were made on the effects of five different methods of laboratory maintenance on the infectivity and virulence of Babesia bigemina for the tick Boophilus microplus. The original isolate was highly infective and virulent, causing premature death of engorged female ticks and reduced egg production. Maintenance of the strain by syringe passage in unsplenectomised calves at six to 10 week intervals reduced both its infectivity and virulence for ticks. When slow passages were preceded by a series of rapid passages in splenectomised calves, the changes to the strain were less pronounced. The other three procedures, rapid syringe passage in splenectomised calves and tick passage in either splenectomised or intact calves, had no statistically significant effect on the characteristics measured.