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The specular reflection of neutrons gives information on the neutron refractive-index profile normal to an interface. The refractive index is simply related to the scattering-length density and hence the composition. However, in-plane inhomogeneities or corrugated surfaces can give rise to strong off-specular scattering. This has been observed in several systems. The difficulty arises in the interpretation of off-specular data from systems having poorly defined or unknown structure. We have measured off-specular reflection from a gold replica optical diffraction grating with 1 μm line spacing. A series of data was obtained using the CRISP neutron reflectometer at the Rutherford Appleton Laboratory in Oxfordshire, England. The analysis of specular and off-specular data, and the determination of the periodicity of the grating and the thickness of the metal film will be discussed. The maximum periodicity that could be observed was 42 μm. This is in agreement with the off-specular resolution which is determined by the horizontal divergence of the ribbon-shaped beam, but very much larger than the longitudinal coherence length of the neutron wave packet.

Glancing-angle neutron diffraction has been used to study the variation in smectic layer tilt in high- and low-pretilt smectic C cells with distance from the surface. Evidence for varying tilt regions within high-pretilt smectic C cells exists; however, complete analysis is not possible without the appropriate depth-resolved information. Cells containing a liquid crystal and either rubbed polyimide or 5° obliquely evaporated silicon monoxide alignment layers were studied. A partially deuterated liquid crystal was used so that total external reflection could be achieved. Using the D17 diffractometer at the ILL, measurements were made in and around the regime of total external reflection. The tilt angle of the smectic layers was determined from the azimuthal angle of their Bragg reflection on the area detector. Below the critical edge, the penetration depth of the transmitted evanescent wave could be limited to ~ 300 A, thus ensuring surface specificity. Varying penetration depths were achieved by alteration of the angle of incidence. Analysis of the Bragg reflection has shown the surface of the SiO cell to have a layer tilt of about 3° higher than that of the bulk. Negligible difference between surface and bulk chevron arm tilts was encountered for the polyimide cell. In both cases, the degree of surface specificity and the accuracy of the layer tilts obtained is discussed.

Neutron reflectivity has been used to investigate the porosity and surface roughness of three different liquid crystal alignment layers to elucidate how they orient the director. The absorption of hexane into these alignment layers was measured by neutron reflection and the volume fraction profile of the hexane within the layers was determined using the contrast variation method. Measurements were made on rubbed polyimide and silicon monoxide (SiO) evaporated at 5 and 30 to the substrate. The porosity and surface roughness of the alignment layers were found to be correlated with the induced pre-tilt of the director. The low pre-tilt rubbed polyimide and SiO 30 alignment layers were found to be smooth, uniform and impervious to hexane, whilst the high pre-tilt SiO 5 was porous and extremely rough. These observations suggest that both polyimide and SiO 30 rely on an anisotropic interaction with the surface rather than one induced by the surface topography. In contrast, the alignment of liquid crystals by Si...

The conformation of the backbone in the side chain liquid crystal polymer poly\[omega (4-methoxybiphenyl-4-yloxy)butyl methacrylate] has been studied in the smectic C and nematic phases. Small angle neutron scattering experiments were performed on mixtures of molecules with perdeuteriated backbones and unlabelled molecules. The polymer is found to adopt an oblate conformation in the smectic C phase. The components of the radius of gyration parallel and perpendicular to the director are determined as a function of temperature from Guinier plots of the SANS data. The radii of gyration do not vary across the smectic phase and are found to be Rg,||=(27+/-1)A, Rg, =(42+/-1)A. These results are compared with recent SANS results for other side chain liquid crystal polymers.

Here we report the chemical induction of the twist-bend nematic phase in a nematic mixture of ether-linked liquid crystal dimers by the addition of a dimer with methylene links; all dimers have an odd number of groups in the spacer connecting the two mesogenic groups. The twist-bend phase has been identified from its optical texture and x-ray scattering pattern as well as NMR spectroscopy, which demonstrates the phase chirality. Theory predicts that the key macroscopic property required for the stability of this chiral phase formed from achiral molecules is for the bend elastic constant to tend to be negative; in addition the twist elastic constant should be smaller than half the splay elastic constant. To test these important aspects of the prediction we have measured the bend and splay elastic constants in the nematic phase preceding the twist-bend nematic using the classic Frederiks methodology and all three elastic constants employing the dynamic light scattering approach. Our results show that, unlike the splay, the bend elastic constant is small and decreases significantly as the transition to the induced twist-bend nematic phase is approached, but then exhibits unexpected behavior prior to the phase transition.

A highly-charged spherical colloid in a salt-free environment exerts such a powerful attraction on its counterions that a certain fraction condenses onto the surface of a particle. The degree of condensation depends on the curvature of the surface. So, for instance, condensation is triggered on a highly-charged sphere only if the radius exceeds a certain critical radius $\collrad^{*}$. $\collrad^{*}$ is expected to be a simple function of the volume fraction of particles. To test these predictions, we prepare spherical particles which contain a covalently-bound ionic liquid, which is engineered to dissociate efficiently in a low-dielectric medium. By varying the proportion of ionic liquid to monomer we synthesise nonpolar dispersions of highly-charged spheres which contain essentially no free co-ions. The only ions in the system are counterions generated by the dissociation of surface-bound groups. We study the electrophoretic mobility of this salt-free system as a function of the colloid volume fraction, the particle radius, and the bare charge density and find evidence for extensive counterion condensation. At low electric fields, we observe excellent agreement with Poisson-Boltzmann predictions for counterion condensation on spheres. At high electric fields however, where ion advection is dominant, the electrophoretic mobility is enhanced significantly which we attribute to hydrodynamic stripping of the condensed layer of counterions from the surface of the particle., Comment: 13 pages, 9 figures and two tables

The response of anisotropic pigment particle suspensions to externally applied electric fields has been explored for possible application in reflective display technologies. Three different types of pigment particle were suspended in dodecane, using a polymeric stabilizer, and showed Schlieren textures between crossed polarizers at high concentrations (greater than 25–30 wt%), indicating the formation of colloidal nematic phases. Orientational order parameters were determined by X-ray scattering, and the influence of polydispersity on the values is discussed. X-ray scattering measurements also demonstrated a change in the structure factor consistent with the onset of a colloidal nematic phase. In addition, the pigment particles were dispersed into various liquid crystal hosts at low concentrations (less than 5 wt%) with and without the presence of mesogenic mimic stabilizers. However, the influence of these stabilizers on orientational ordering could not be confirmed. The electro-induced ordering determined via scattering was related to the electro-optical response of each suspension using a simple model. The particles in nematic hosts not only showed a high degree of orientational ordering at lower electric field strengths, but also showed a reduction in stability. Although these systems have shown strong orientational ordering, the optical response has been limited by the intrinsic shape of the pigment particles and the distribution of the transition dipoles moments within them. Nevertheless, the feasibility of developing materials for display applications has been demonstrated.

The long range orientational order in the nematic phase of 4,4′‐dimethoxyazoxybenzene (PAA) has been studied using small angle neutron scattering (SANS) from mixtures of protonated and perdeuterated molecules. Unlike spectroscopic methods, the determination of the complete set of orientational order parameters is, in principle, possible using this technique. The orientational order parameters were extracted from the anisotropic single molecule scattering isolated at small scattering angles. These order parameters were compared to those extracted from previous neutron scattering measurements, to second rank order parameters extracted from NMR, and to those predicted from the Maier–Saupe theory of nematic ordering. It was found that only the second and fourth rank terms in the expansion of the single molecule scattering in a basis of Legendre functions are statistically significant, which means that the order parameters P2 and P4 only could be obtained. For the semirigid nematogen PAA, the Maier–Saupe theory is found to underestimate P2 and its dependence on the reduced temperature T/TNI where TNI is the nematic–isotropic (NI) transition temperature. The theoretical values of P4 are, however, in remarkably good agreement with the measured values. Order parameters extracted from NMR are found to be slightly lower than those determined from the SANS experiment, and we also make comparisons with earlier neutron scattering results. Singlet orientational distribution functions are reconstructed from the measured order parameters using the maximum entropy method.

Our investigations of the local smectic layer distribution formed by two ferroelectric side-chain liquid crystal polymers in device-like environments are described. At room temperature one of the polymers had a bookshelf distribution of its smectic layers. The addition of one methylene unit to the flexible spacer resulted in a different phase behaviour which included an overall decrease in the measured smectic periodicity. The local layer structure displayed by this polymer in the same device-like environment at room temperature was characterised by a chevron geometry.

The 4-substituted tris(3,5-dimethylpyrazolyl)borato compounds [Mo(CO)2 (NO){HB(4-R-dmpz)3}] (R  Me, Et, Bun and C5H11) and [MoCl2(NO){HB(4-R-dmpz)3}] (R  Me or Bun) have been prepared and characterized spectroscopically and electrochemically. X-ray crystal structural determination of [Mo(CO)2(NO){HB(4-R-dmpz)3}] (R  Bun) revealed that the n-butyl chains attached to the 4-position of the pyrazolyl rings were oriented, overall, in a random fashion, although the first and second C atoms of each chain extended in a star-shaped configuration, similar to that observed in [Mo(CO)2(NO){HB(4-bzdmpz)3}] (4-bzdmpz = 4-benzyl-3,5-dimethylpyrazolyl).

The effect of thermal treatment, at a relatively high temperature (∼- 340 °C), on two highvolatile bituminous coals is examined by water adsorption and small angle X-ray scattering (SAXS). The results suggest that the mesopore structure in both samples undergoes a partial collapse. Furthermore, a strong hydrophobic effect, at the very early stages of the adsorption process, is noted for only one of them. This observation is attributed to differences in the rigidity of each of the structures. Analysis of the spectra in terms of fractal geometry is also performed. It is proposed that thermal treatment changes the coal matrices from a dilute to a dense configuration. Heating causes a breakage of some oxygen and sulphur bridges giving rise to these structural alterations.

The purpose of this study was to describe the life-sustaining treatment preferences of dialysis patients and to compare the acceptability of two generic and a disease-specific advance directive (AD). Of 532 potentially eligible hemodialysis patients, 95 (17.9%) participated in the study. These patients completed two generic (the Centre for Bioethics Living Will and the Medical Directive) and one disease-specific (the Dialysis Living Will) AD in a randomized cross-over trial. Treatment preferences were measured by using the Centre for Bioethics Living Will. Acceptability of the AD was measured by using a 13-item advance directive acceptability questionnaire (ADAQ) for each AD, and the advance directive choice questionnaire (ADCQ) to elicit participants' preferred AD. Twenty-five percent of the participants wanted to continue dialysis in case of severe stroke, 19% in severe dementia, and 14% in permanent coma. Averaged across treatments, proportions of participants wanting treatment in various health states were: current health (86%), mild stroke (84%), moderate stroke (60%), severe stroke (21%), mild dementia (78%), moderate dementia (51%), severe dementia (14%), terminal illness (41%), and permanent coma (10%). Averaged across health states, proportions of participants wanting various types of treatment were: dialysis (58%), antibiotics (53%), transfusion (53%), surgery (48%), cardiopulmonary resuscitation (48%), respirator (47%), and tube feeding (41%). Mean ADAQ scores were: Dialysis Living Will, 71%; Centre for Bioethics Living Will, 70%; and Medical Directive, 60% (F = 8.27, P < 0.001 (repeat measures analysis of variance); the Dialysis Living Will and Centre for Bioethics Living Will scored significantly higher than the Medical Directive). The proportion of participants who said they would choose to complete each AD was: Dialysis Living Will, 28%; Centre for Bioethics Living Will, 38%; Medical Directive, 31%; and unsure, 3% (chi 2 = 1.465, df = 2, P = 0.48). In conclusion, twenty-five percent or less of hemodialysis patients want to continue dialysis in three specific health states: severe stroke, severe dementia, and permanent coma. Health states and illness severity, far more than treatment descriptions, influence preferences. Dialysis patients should be offered a generic AD, and some generic AD are more acceptable than others. Only a minority of dialysis patients will complete any AD, but the completion of written AD forms is only one element in the process of advance care planning.

The smectic A to smectic C* transition of a commercial ferroelectric mixture (SCE13 and its racemic mixture) has been studied within a surface stabilised cell using X-ray ‘rocking curve’ techniques. An unusual distribution of the layer orientation in the smectic A phase implies the existence of a tilted structure. This phenomenon in the smectic A phase is believed to be a result of an unusual temperature dependence of the layer thickness and a comparison with a typical material is reported.

A series of side-chain liquid crystal polymers have been screened for successhl deposition using the Langmuir Blodgett method. It was found that the best materials had glass transitions below room temperature. The behaviour of the spread film of one material was studied in detail using surface isotherms, surface potential, X-ray and neutron reflection techniques. It was found to undergo a phase transition from a thin, low density film to a thicker, more dense one as the surface pressure was increased. This corresponds to a reorientation of the mesogenic units so that about half of them point upwards. At higher pressure a transition to a multilayer occurs on the water surface. In the surface pressure range where deposition is possible, neutron reflection shows that the spread film has a stratum of close packed mesogenic units outermost and the total thickness (38 A) agrees very well with the smectic layer spacing in the bulk. This similarity in structure could explain the ease of deposition.

Adsorption of the pure milk proteins, β-casein and β-lactoglobulin, at the air/water interface has been studied using the technique of specular neutron reflectance. By fitting appropriate models of the protein films to the reflectivity data the detailed structures of the interfaces have been determined. The effects of protein concentration, substrate pH, film ageing and the presence of calcium ions on the film structures have been investigated.At neutral pH both β-casein and β-lactoglobulin form a monolayer at the air/water boundary that can be divided into a protein-rich, hydrophobic, inner layer closest to the interface, and a more diffuse, hydrophilic, outer layer extending into the bulk aqueous phase. The adsorbed amount of protein follows the adsorption isotherms determined by other methods. Ageing has little effect on β-casein layers, but with β-lactoglobulin there is an increases in the adsorbed amount of protein with time and the two-layer model of the film configuration tends to become less distinct such that a one-layer model form is equally appropriate. The rate and extent of the changes occurring as a function of the age of the surface depend on the pH of the substrate solution. The adsorbed amount of both proteins increases as the pH is lowered towards their respective isoelectric points. Models are proposed to account for the changes in layer structure occurring during these processes. The presence of calcium ions modifies the structure of β-casein layers, reducing the hydrophilic layer thickness and the adsorbed amount of protein.

The synthesis of magnetic, monodisperse nanoparticles has attracted great interest in nanoelectronics and nanomedicine. Here we report the fabrication of pure magnetite nanoparticles, less than ten nanometers in size, using the cage-shaped protein apoferritin (Fe(3)O(4)-ferritin). Crystallizable proteins were obtained through careful successive separation methods, including a magnetic chromatography that enabled the effective separation of proteins, including a Fe(3)O(4) nanoparticle (7.9 ± 0.8 nm), from empty ones. Macroscopic protein crystals allowed the fabrication of three-dimensional arrays of Fe(3)O(4) nanoparticles with interparticle gaps controlled by dehydration, decreasing their magnetic susceptibilities and increasing their blocking temperatures through enhanced dipole-dipole interactions.

Introduction Among critically ill patients with acute kidney injury (AKI) needing continuous renal replacement therapy (CRRT), the effect of convective (via continuous venovenous hemofiltration [CVVH]) versus diffusive (via continuous venovenous hemodialysis [CVVHD]) solute clearance on clinical outcomes is unclear. Our objective was to evaluate the feasibility of comparing these two modes in a randomized trial. Methods This was a multicenter open-label parallel-group pilot randomized trial of CVVH versus CVVHD. Using concealed allocation, we randomized critically ill adults with AKI and hemodynamic instability to CVVH or CVVHD, with a prescribed small solute clearance of 35 mL/kg/hour in both arms. The primary outcome was trial feasibility, defined by randomization of >25% of eligible patients, delivery of >75% of the prescribed CRRT dose, and follow-up of >95% of patients to 60 days. A secondary analysis using a mixed-effects model examined the impact of therapy on illness severity, defined by sequential organ failure assessment (SOFA) score, over the first week. Results We randomized 78 patients (mean age 61.5 years; 39% women; 23% with chronic kidney disease; 82% with sepsis). Baseline SOFA scores (mean 15.9, SD 3.2) were similar between groups. We recruited 55% of eligible patients, delivered >80% of the prescribed dose in each arm, and achieved 100% follow-up. SOFA tended to decline more over the first week in CVVH recipients (-0.8, 95% CI -2.1, +0.5) driven by a reduction in vasopressor requirements. Mortality (54% CVVH; 55% CVVHD) and dialysis dependence in survivors (24% CVVH; 19% CVVHD) at 60 days were similar. Conclusions Our results suggest that a large trial comparing CVVH to CVVHD would be feasible. There is a trend toward improved vasopressor requirements among CVVH-treated patients over the first week of treatment. Trial Registration ClinicalTrials.gov: NCT00675818

Self-assembled disc-shaped clusters of hexagonally packed, thiol-functionalized gold nanorods are prepared and dispersed in thermotropic nematic liquid crystals. The resultant hybrid complex fluids exhibit colloidal anisotropy with very high orientational order and are characterized by SAXS as shown in the figure. Precise, reconfigurable control of the cluster orientation at very low electric field strengths (0.18 V μm(-1) ) is achieved.

The optimal timing for starting renal replacement therapy (RRT) in patients with acute kidney injury (AKI) is unknown. Defining current practice is necessary to design interventional trials. We describe the current Canadian practice regarding the timing of RRT initiation for AKI.An observational study of patients undergoing RRT for AKI was undertaken at 11 intensive care units (ICUs) across Canada. Data were captured on demographics, clinical and laboratory findings, indications for RRT, and timing of RRT initiation.Among 119 consecutive patients, the most common ICU admission diagnosis was sepsis/septic shock, occurring in 54%. At the time of RRT initiation, the median and interquartile range (IQR) serum creatinine level was 322 (221-432) μmol·L(-1). The mean (SD) values for other parameters were as follows: Sequential Organ Failure Assessment (SOFA) score 13.4 (4.1), pH 7.25 (0.15), potassium 4.6 (1.0) mmol·L(-1). Also, 64% fulfilled the serum creatinine-based criterion for Acute Kidney Injury Network (AKIN) stage 3. Severity of illness, measured using Acute Physiology and Chronic Health Evaluation (APACHE II) and SOFA scores, did not correlate with AKI severity as defined by the serum creatinine-based AKIN criteria. Median (IQR) time from hospital and ICU admission to the start of RRT was 2.0 (1.0-7.0) days and 1.0 (0-2.0) day, respectively.Patients admitted to an ICU who were started on RRT generally had advanced AKI, high-grade illness severity, and multiorgan dysfunction. Also, they were started on RRT shortly after hospital presentation. We describe the current state of practice in Canada regarding the initiation of RRT for AKI in critically ill patients, which can inform the designs of future interventional trials.

A new surface force apparatus is described which enables simultaneous measurement of the interaction forces between adsorbed polymer layers as well as their surface structure by neutron reflectometry. The apparatus utilises two optically flat quartz plates that are brought together by applying a known external force. Surface force and structural profiles have been obtained for polystyrene adsorbed on quartz from cyclohexane, i.e. a poor solvent.

The Langmuir monolayer and Langmuir-Blodgett (LB) deposition behaviour of asymmetrically substituted 1,4-bis(6-hydroxyhexyl)−8,11,15,18,22,25-hexa-octylphthalocyanine (1) and a phthalocyanine dimer (2) and trimer (3) have been investigated. The materials were also deposited onto glass by the spin coating (SC) technique. The spin coated films were exceptionally smooth, even and free from crystallites. X-ray reflectivity measurements reveal varying degrees of order. Unpolarized UV-visible absorption spectra of the films deposited by the two techniques were closely similar. The LB technique has the advantage of introducing some degree of anisotropic ordering of the molecules within the films of the monomer and dimer whereas the SC method has the advantage of convenience.

Reaction of [HB(bdmpz)3]–, obtained by reaction of 4-benzyl-3,5-dimethylpyrazole (Hbdmpz) with KBH4, with [M(CO)6](M = Mo or W) and p-MeC6H4SO2N(NO)Me afforded [M(CO)2(NO)-{HB(bdmpz)3}](M = Mo or W). The molybdenum carbonyl was converted into [Mo(NO)-{HB(bdmpz)3}X(Y)](X = Y = Cl, I or OC6H4Me-p; X = Cl, Y = OMe or OC6H4Me-p) the spectral and electrochemical properties of which are virtually identical to those of [Mo(NO){HB(dmpz)3}X(Y)](Hdmpz = 3,5-dimethylpyrazole), indicating that the addition of a benzyl group has no significant electronic effect in the new species. However, a crystal and molecular structure determination of [Mo(CO)2(NO){HB(bdmpz)3}] revealed that the molecule has a highly symmetrical structure, the CH2groups of the benzyl groups in the tris(pyrazolyl)borate ligand being disposed in a star-shaped configuration where the phenyl rings adopt an ‘inverted’ bowl-like structure with the BH group inside and the Mo(CO)2(NO) group outside the bowl. The arrangement of the 4-benzyl groups with respect to the pyrazolyl rings and the H–B ⋯ Mo three-fold axis is strongly reminiscent of an inverted three-legged ‘Isle of Man’ symbol.

We describe two brothers with sensorineural deafness, diabetes mellitus, progressive neurological deterioration with photomyoclonic epilepsy, and progressive deterioration in renal function, resulting in death in the third decade of life. Autopsy showed diffuse atherosclerosis and arteriolosclerosis of the systemic vasculature. There was no evidence of these abnormalities in the patients' 2 sisters or either parent. Mitochondrial enzyme analysis documented partial deficiencies of Complex III and IV of the respiratory chain. This deficiency was expressed in skin fibroblasts, kidney and liver but not in muscle. This suggests that the disease-causing mutation is either in the mitochondrial or nuclear DNA. Various modes of inheritance are considered, including maternal, autosomal recessive, or X-linked recessive. We suggest this is a new genetic syndrome characterized by an underlying metabolic disease and premature atherosclerosis, possibly of mitochondrial origin.

The monolayer and LB film-forming properties of 20 structurally related amphiphilic octa-substituted phthalocyanine derivatives have been assessed. The molecular packing within examples of the films has been probed by visible-region spectroscopy and low-angle X-ray diffraction methods. Among derivatives where the aliphatic substituents are attached by ether linkages, there is a variation in the behaviour according to the length of the chains and whether or not the chains are branched. Films are not highly ordered but may contain domains of ordered structure, giving rise to a red-shifted absorption band in the visible spectrum. Analogues where the chains are attached by carbon–carbon bonds show superior monolayer behaviour and are excellent materials for deposition as LB films. Furthermore, there is good evidence from the spectra that change in the length of the alkyl chains provides a means of controlling the type of molecular packing within the films.

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.

The liquid-crystal dimer 1'',7''-bis(4-cyanobiphenyl-4'-yl)heptane (CB7CB) exhibits two liquid-crystalline mesophases on cooling from the isotropic phase. The high-temperature phase is nematic; the identification and characterization of the other liquid-crystal phase is reported in this paper. It is concluded that the low-temperature mesophase of CB7CB is a new type of uniaxial nematic phase having a nonuniform director distribution composed of twist-bend deformations. The techniques of small-angle x-ray scattering, modulated differential scanning calorimetry, and dielectric spectroscopy have been applied to establish the nature of the nematic-nematic phase transition and the structural features of the twist-bend nematic phase. In addition, magnetic resonance studies (electron-spin resonance and (2)H nuclear magnetic resonance) have been used to investigate the orientational order and director distribution in the liquid-crystalline phases of CB7CB. The synthesis of a specifically deuterated sample of CB7CB is reported, and measurements showed a bifurcation of the quadrupolar splitting on entering the low-temperature mesophase from the high-temperature nematic phase. This splitting could be interpreted in terms of the chirality of the twist-bend structure of the director. Calculations using an atomistic model and the surface interaction potential with Monte Carlo sampling have been carried out to determine the conformational distribution and predict dielectric and elastic properties in the nematic phase. The former are in agreement with experimental measurements, while the latter are consistent with the formation of a twist-bend nematic phase.

Application of the technique of specular neutron reflection to the study of adsorbed layer structure is illustrated for the case of β-casein at the air—water interface in the presence and absence of nonionic water—soluble surfactant C12E6. Guinier analysis of reflectivity data for a 5 × 10−3 wt% solution of pure β-casein in air-contrast-matched water (8 vol% D2O) at pH 7.0 gives a time-independent adsorbed amount of 2.05 ± 0.10 mg/m2 and an adsorbed layer thickness of 1.65 ± 0.07 nm; these values are found to increase quite substantially as the pH is reduced towards the protein's isoelectric point. In the presence of surfactant the loss of reflectivity is a direct measure of protein displacement from the interface because the hydrogenated surfactant is almost contrast matched to the aqueous phase. At a C12E6 concentration in the range 2–2.5 × 10−4 wt% (surfactant: protein molar ratio, R ≈ 2.2), there is roughly half the protein lost from the interface but little change in adsorbed layer thickness as inferred from the slopes of the Guinier plots. Protein is effectively completely removed from the surface for R ≳ 10. These results are in semi-quantitative agreement with complementary competitive adsorption data for β-casein in soya oil-in-water emulsions.

The adsorption of a small block copolymer of poly(2-vinylypyridine) and polystyrene has been studied as a function of solvency. Both neutron reflectometry and surface force measurements have been used to study the structure of the adsorbed layer. The results show that the adsorbed polymer is highly extended in good solvency conditions for the polystyrene but collapses when the solvent worsens. The results are compared with the self-consistent mean-field theory of Evers-Scheutjens-Fleer for the adsorption of block copolymers. Both the extended length of the polymer and the amount of polymer adsorbed on mica have been measured independently

Structural studies of a series of laterally attached side chain liquid crystalline polysiloxanes have been made by X-ray diffraction. All but one exhibit a nematic phase with SC-like short range ordering. The diffraction has been interpreted in terms of a model in which the mesogenic units form a ‘jacket’ around the polymer backbone. The backbone conformation has been studied by small angle X-ray scattering from oriented samples of mesomorphic solutions and by infrared dichroism measurements on oriented samples of the polymers. In both cases the results were consistent with the mesogens being oriented parallel to the backbone which is consistent with the ‘mesogen jacket’ model.

Three side chain liquid crystal polymers have been studied by neutron scattering methods. We have compared the three compounds, all with a polysiloxane backbone, a four-atom flexible spacer, (CH2)3O, and a benzoate ester mesogenic unit. However, the mesogenic unit was terminated by one of three different groups. The hexyloxy and cyano derivatives gave smectic A phases and the methoxy gave a nematic. Small angle neutron scattering measurements of mixtures of deuteriated and hydrogenous versions of the same polymer have been used to determine the dimensions and anisotropy of the backbone. The anisotropy was found to be similar in the smectic and nematic phases and suggested a tendency for the polymer backbone to be confined between the layers of mesogenic units. The SANS results show two different characteristic sizes. One is attributed to the size of a single polymer molecule. The other indicates density fluctuations on a scale larger than one polymer molecule. The local packing of the mesogenic u...

The mesophase behaviour of a number of non-peripherally octa-substituted phthalocyanine derivatives has been studied by optical microscopy, differential scanning calorimetry (DSC) and X-ray diffraction. A homologous series of straight chain alkoxymethyl derivatives has exhibited both rectangular and hexagonal columnar mesophases, with the rectangular phases being favoured by the shorter chains. Two branched chain derivatives were found to give rectangular columnar phases at room temperature. A detailed analysis of the X-ray data has shown some differences from the analogous n-alkyl compounds. It has been deduced that the increased polarizability and flexibility of the ether linkage allows the disc-like molecules to approach more closely face to face with correspondingly thicker columns.

A simple method to determine the translational order parameter of a smectic liquid crystal is presented. It is based on a measurement of the absolute intensity of the first-order layer reflection from an unaligned (powder) sample using small-angle neutron scattering. The Lorentz factor and molecular form factor are used to derive the order parameter from the intensity. The method is demonstrated for 4-octyl-4'-cyanobiphenyl (8CB), using two different isotopomers which give a consistent translational order parameter value of 0.5 in the smectic A phase.

In this Rapid Communication, results on smectic layer thickness, using synchrotron radiation x-ray diffraction, for different mixtures of ferroelectric and antiferroelectric liquid crystals are given. We find that with an increased ferroelectric component in the mixtures, the layer shrinkage at the de Vries SmA-SmC transition increases. This observation can be used to explain our previously observed behaviors U. Manna, J.-K. Song, Yu. P. Panarin, A. Fukuda, and J. K. Vij, Phys. Rev. E 77, 041707 2008 that the soft-mode dielectric strength decreases, the Landau coefficient increases, and the Curie-Weiss temperature range decreases with increased ferroelectric component in the mixture exhibiting de Vries SmA-SmC transition.

BACKGROUND The incidence of congestive heart failure is 3-fold greater than that of acute coronary syndrome in haemodialysis (HD) patients. The purpose of this study was to determine if blood flow through an arteriovenous (AV) access contributes to an increase in left ventricular mass (LVM) that may increase the risk of congestive heart failure. METHODS We conducted a 1-year prospective cohort study at two Canadian centres of HD patients at high risk for congestive heart failure who had a first AV access created. Patients underwent echocardiography and measurement of plasma N-terminal pro-brain natriuretic peptide (NT-proBNP) levels before and 1-year post-AV access creation. Access flows were measured within the first month of access maturation and 1-year post-access creation. Data were analysed using descriptive statistics, Student's t-test, correlation coefficients and regression. RESULTS One-year post-AV access creation, LVM increased by 12.2 +/- 32% (P = 0.025) and plasma NT-proBNP levels increased by 170 +/- 465% (P = 0.02). The average AV access blood flow did not correlate with an increase in LVM or NT-proBNP levels. CONCLUSIONS In patients on chronic HD after 1 year, AV access flow does not correlate with increases in LVM by echocardiography or plasma levels of NT-proBNP.

Non-spherical nanostructures derived from soft matter and with uniform size-that is, monodisperse materials-are of particular utility and interest, but are very rare outside the biological domain. We report the controlled formation of highly monodisperse cylindrical block copolymer micelles (length dispersity < or = 1.03; length range, approximately 200 nm to 2 microm) by the use of very small (approximately 20 nm) uniform crystallite seeds that serve as initiators for the crystallization-driven living self-assembly of added block-copolymer unimers with a crystallizable, core-forming metalloblock. This process is analogous to the use of small initiator molecules in classical living polymerization reactions. The length of the nanocylinders could be precisely controlled by variation of the unimer-to-crystallite seed ratio. Samples of the highly monodisperse nanocylinders of different lengths that are accessible using this approach have been shown to exhibit distinct liquid-crystalline alignment behaviour.

Orientational order parameters for nematogens have been determined using the neutron diffraction isotope labelling technique, where the single molecule component of the scattering from mixtures of protonated and perdeuteriated molecules is extracted at low Q. Experiments were performed on the relatively rigid nematogens 4-methoxy-4′-cyanobiphenyl (1-OCB) and 4,4′-dimethoxyazoxybenzene (PAA). Legendre polynomial orientational order parameters -PL were extracted from the anisotropy of the single molecule scattering, without assumptions regarding the form of the singlet orientational distribution function. Only knowledge of a molecular structure is required. For these molecules, values of ¯P 2 in good agreement with nuclear magnetic resonance (NMR) studies were obtained. ¯P 4 can also be determined and for 1-OCB it is found to be near zero, in accord with earlier Raman spectroscopy results for other cyanobiphenyl liquid crystals. Given order parameters as input constraints, the maximum entropy method is used...

Thermotropic mesomorphism has been observed in a highly substituted and asymmetrically shaped tetrabenzotriazaporphyrin (TBTAP) derivative. TBTAP has a ring system closely related to that of phthalocyanine, however the single maso-carbon provides an additional site for the attachment an alkyl chain. The TBTAP mesogen has a pentadecyl group at this site as well as a bulky neopentoxy substituent attached to each of the four peripheral benzo-portions of the macrocycle. Optical texture (focal-conic fan) and X-ray diffraction studies suggest that the TBTAP has a mesophase with a lamellar structure analogous to that of the smectic A phase of rod-like molecules. Such a mesophase has not been observed previously from discotic compounds.

We have investigated the properties of insoluble monolayers and Langmuir-Blodgett (LB) multilayers of a preformed derivative of an α-olefin maleic anhydride copolymer. The polymer repeat unit contained a hexadecyl hydrophobic group and two carboxylic acid moieties in the hydrophilic headgroup. Using X-ray reflectivity we have determined the floating monolayer structure and the adsorption of cadmium ions from the subphase as a function of pH at a fixed surface pressure. The tailgroup thickness is 14 A, much less than the all- trans length of the hexadecyl chains. The headgroup layer thickness is approximately 8 A. Both thickness are independent of pH. Cadmium ion binding to the carboxylic acid headgroups occurs with a 1:2 stoichiometry and a pK of 5.7. Using attenuated total reflectance IR spectroscopy, the ionization of the corresponding LB multilayers deposited on germanium was also measured. The pH of 50% ionization is approximately 5, in reasonable agreement with the pK for cadmium ion binding to the floating monolayer.

An experimental method for the measurement of neutron reflection from liquid/liquid interfaces is described. The strengths and limitations of the technique are described and its application to the study of adsorbed layers is discussed. Results are given for the protein β-casein and a block copolymer of polydimethylsiloxane-polyvinylpyridine oxide.

The pathogenetic mechanism of hepatorenal syndrome (HRS) is paradoxical renal vasoconstriction consequent upon systemic and splanchnic arterial vasodilatation. Molecular adsorbent recirculating system (MARS) is a specialised form of dialysis that clears albumin-bound substances, including vasodilators, and therefore can potentially reduce systemic vasodilatation in cirrhosis.To assess the efficacy of MARS in improving systemic and renal haemodynamics in patients with cirrhosis with refractory ascites and type 1 HRS not responding to vasoconstrictor therapy.A pilot study was carried out in an academic teaching hospital. The study group comprised six patients with cirrhosis, refractory ascites and type 1 HRS not responding to vasoconstrictor treatment. All patients received 5 days of 6-8 h of MARS dialysis. The main outcome measures were pre-MARS and post-MARS measurements of glomerular filtration rate, renal blood flow, neurohormones, cytokines and nitric oxide (NO), as well as daily biochemistry, haematology and urinary volume.There were no significant changes in systemic haemodynamics and GFR following MARS treatments, despite a significant reduction in NO concentrations (111.5+/-18.8 micromol/l pre-MARS, to 65.1+/-8.2 micromol/l post-MARS, p=0.05). There was a transient reduction in serum creatinine (p0.05), Child-Pugh and MELD (Model End-Stage Liver Disease) scores with MARS, but no significant difference was observed in neurohormone and cytokine levels. Four of six patients died following MARS treatments.In patients with cirrhosis, refractory ascites and type 1 HRS not responding to vasoconstrictor treatment, MARS is ineffective in improving systemic haemodynamics and renal function despite reduction in NO levels, suggesting that vasodilatation in advanced cirrhosis is not due to excess systemic vasodilators alone. Transient reduction in serum creatinine indicates direct removal by MARS, and may not represent improved renal function.

The influence of hydroxypropyl guar (HPG), with and without boric acid, on dodecyltrimethyl ammonium bromide (DTAB) micellization was characterized by surface tension measurements, isothermal titration calorimetry, and small-angle neutron scattering. Although HPG is a nonionic water-soluble polymer, borate ions form weak bonds with HPG, transforming it into an anionic polyelectrolyte, HPG-borate. Surprisingly, the three independent measurements showed that HPG-borate does not promote DTAB micellization or phase separation normally seen when mixing oppositely charged polyelectrolytes and surfactants. However, the neutron scattering results suggested that HPG-borate binds to and flocculates existing DTAB micelles. The unusual behavior of HPG-borate with DTAB was underscored by showing that carboxymethyl guar (CMG) formed precipitates with DTAB.