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The self-assembly into nanotubes in solution of an amphiphilic copolymer is characterized by small-angle neutron scattering (SANS). This study confirmed the shape and the size of the tubular association and the 3-D association of the tubes predicted by molecular orbital theory. Moreover, the characterization of the stability of the association has revealed that the addition of a very small amount of salt to the solution increases the size of the association. When more salt is added, the size of the association decreases, and the structure is altered. The association was found to be independent of temperature and therefore is very stable.

A new series of carbosilane liquid crystalline (LC) dendrimers from the first to the third generations with 8, 16 and 32 chiral terminal mesogenic groups, respectively, has been synthesized. The molecular structures and purity of all new compounds were confirmed by 1H NMR spectroscopy and GPC analysis. Data of polarization microscopy and SAX analysis demonstrated that all LC dendrimers synthesized form a chiral smectic SmC* phase at temperatures below 50 °C. It has been found that bistable electrooptical switching is observed for all dendrimers. The influence of chiral mesogenic fragment length on phase behavior and ferroelectric properties of carbosilane LC dendrimers is discussed.

AIM Anemia is adversely associated with poor uremia control and is an established cardiovascular risk factor in patients with end-stage renal disease (ESRD). Nocturnal home hemodialysis (NHD) is a novel form of renal replacement therapy that offers superior clearance of uremic solutes and improvements in several cardiovascular outcome parameters. We conducted a retrospective cohort study to test the hypotheses that augmenting the dose and frequency of dialysis by NHD would improve hemoglobin (Hb) concentrations and decrease requirement of erythropoietin (EPO) in ESRD patients. METHODS In 63 patients (mean age: 46 +/- 2 years) receiving NHD (mean duration: 2.1 +/- 0.2 years), Hb, EPO dose, iron saturation, ferritin were determined before and at six monthly repeated intervals after conversion to NHD. For comparison, 32 ESRD patients (mean age: 57 +/- 3 years) who remained on self-care conventional hemodialysis (CHD) were also studied. RESULTS There were no differences in baseline Hb concentrations, iron saturation, ferritin, or EPO dose between the two cohorts. After transfer from CHD to NHD, there were significant improvements in Hb concentrations (from 115 +/- 2 to 122 +/- 3 (6 months) and 124 +/- 2 (12 months) g/l, p = 0.03) despite a fall in EPO requirement (from 10,400 +/- 1400 to 8500 +/- 1300 (6 months) and 7600 +/- 1100 (12 months) U/week, p = 0.03). In contrast, CHD cohort had no change in EPO requirement (from 8300 +/- 1100 to 8100 +/- 1300 (6 months) and 8600 +/- 1000 (12 months) U/week, p > 0.05) or Hb concentrations (from 110 +/- 2 to 115 +/- 3 (6 months) and 115 +/- 2 (12 months), p > 0.05). There was a higher percentage of ESRD patients who did not require EPO in the NHD cohort (24% vs. 9.4%, p = 0.01). Lower Hb concentrations were noted in the CHD cohort despite higher iron saturation (0.25 +/- 0.01 (NHD) vs. 0.33 +/- 0.02 (CHD), p = 0.02) at the end of follow-up. CONCLUSIONS Enhancing uremic clearance by NHD resulted in a rise in Hb and a fall in EPO requirement.

The director reorientation of the liquid crystal 4,4’ octyl cyanobiphenyl in the nematic phase under application of bursts of ac field have been observed using time-resolved neutron scattering in reflection geometry. The relaxation of the director has been shown to agree with existing theory, as determined by material and cell parameters. This result shows that it is possible to use neutron reflection measurements from buried interfaces to follow kinetic processes on a time scale comparable with the pulse length of the ISIS neutron source (20 ms).

Suspensions of anisometric particles in the nematic phase of a liquid crystalline host solvent were prepared. We chose Claytone AF, a commercial quaternary ammonium surfactant treated montmorillonite, with an aspect ratio of up to 1:2000, and dimethyldioctadecylammonium bromide treated Laponite, with an aspect ratio of 1:8 as the dispersed particles. K15, a nematogenic compound (also known as 5CB), was the dispersing medium. The suspensions were characterized by small angle x-ray scattering (SAXS). The liquid crystal delaminates the clays well, but the scattering curves from Claytone suspensions have prominent first and second order pseudo Bragg peaks, indicating that stacking of clay plates has occurred. We report a model for fitting SAXS data based on Hosemann's theory for suspensions of plane parallel sheets.

The structure of a ferroelectric liquid crystal mixture with an N∗ → SmC∗ transition in skew aligned cells has been studied by X-ray diffraction measurements of the layer normal distribution. The rubbing directions of the cells were set parallel, and skewed at ±9°, ±18° and ±40°. The cell with parallel alignment directions showed two sets of layers with normals twisted in-plane by ∼±20° from the rubbing direction. The layer normal distribution of each set of layers was consistent with a chevron-like structure but with an additional untilted region, probably at the apex. It was also observed that the tilt of the chevron arms was weakly temperature dependent, with their normals tilting out of the plane of the device by an angle of 9° to 12° on cooling. The cells with alignment skewed by ±9° and ±18° also showed chevron-like structures which are probably developed in the middle of the cell with each arms tilted by ∼20° and with normals slightly twisted in-plane by ±4° with respect to the mean rubbing directi...

Neutron reflectivity was used to characterize the adsorption of poly(ethylene oxide) (PEO), 150 kDa, on both polystyrene (PS) and poly(vinylphenol) (PVPh), thin films in water. The PVPh films had t...

Summary Background Topical bovine thrombin (TBT) is used as a topical haemostatic agent in haemodialysis (HD) units and for surgical procedures. It has caused allergic reactions during surgical procedures, but no previous cases have been reported with dialysis usage. Objective A case is reported of anaphylaxis due to TBT in an HD patient. This led to a determination of whether HD patients exposed to TBT develop specific IgE and IgG antibodies to TBT and an assessment of the frequency of allergic symptoms in HD patients as compared with peritoneal dialysis (PD) patients. Methods A cross-sectional study of 100 HD and 52 PD patients was performed using a questionnaire to determine allergic symptoms. An ELISA assay was developed to determine TBT-specific IgE and IgG serum antibodies among HD patients. HD patients without TBT exposure and age- and gender-matched blood donors served as controls. Results Allergic symptoms temporally related to dialysis reported by a questionnaire were significantly more frequent for HD patients than for PD patients: rhinoconjuctivitis 11% vs. 2%, asthma symptoms 20% vs. 6%, urticaria 23% vs. 8% (P values

We have examined the effect of the different components in the spontaneous formation of surfactant-templated mesostructured silicate films grown at the air/solution interface. The rate of film formation shows differing dependencies on the concentrations of the silica precursor, tetramethoxysilane, the surfactant template, cetyltrimethylammonium bromide (CTAB), water and the solution pH. Further, we relate the nature of the film formation to the properties of the dried film using small angle scattering methods. From this data a general formation mechanism for the interaction between silica and surfactant micelles in this system is proposed. The polymerising silica can be considered as a cationic polyelectrolyte which interacts with the positively charged CTAB micelles through the bromine anion of the surfactant and via adsorption of the micelles as the polymer becomes more hydrophobic. This polyelectrolyte–surfactant system undergoes a liquid–liquid phase separation (coacervation) at a critical point dependant on the charge and molecular weight of the polymer and the charge on the surfactant micelle.

Background. Thrombosis is the primary cause of access failure in polytetrafluoroethylene grafts and arteriovenous fistulas. It can lead to significant patient and access morbidity and mortality, and is difficult to prevent medically. Intervention is largely limited to maximizing access patency by detecting culprit lesions early and intervening with angioplasty or surgical revision. The most efficacious monitoring strategy is undetermined. Methods. This 3 year prospective study took advantage of a change in monitoring strategy used in a large dialysis centre to compare the efficacy of two methods used to monitor grafts and fistulas in order to prevent access thrombosis. Accesses were monitored using Duplex ultrasonography in year 1, while the saline ultrasound dilution technique (Transonic) became the primary monitoring strategy in year 3 (year 2 was a transition year). Risk factors for thrombosis were determined using multivariate survival analysis, and the performance of Duplex ultrasonography and Transonic monitoring was assessed. Results. A total of 303 656 access days at risk were assessed, with 344, 385 and 425 accesses in years 1, 2 and 3, respectively. The total thrombosis rate was 1.01/1000 access days in year 1 compared with 0.66/1000 access days in year 3. This was accomplished despite a reduction in procedure rates of 55% for angiograms, 13% for angioplasties and 31% for thrombolysis. Conclusion. Low flow rates detected using Transonic monitoring were associated with increased thrombosis, while stenosis detected using Duplex ultrasonography was not a strong predictor of incipient thrombosis; however, these different access characteristics were compared using monitoring techniques that may be ideal in different clinical situations.

Specular neutron and X-ray reflection have been used to investigate the penetration of water into silica gel films. The effect on water penetration of incorporating fluoroalkysilane (FAS) into the gel has also been measured. Gel films were deposited onto float glass substrates and exposed to either liquid water or an atmosphere of known relative humidity (between 0% and 100%). It was shown that, irrespective of FAS content, water penetrates throughout the gel film, and deeper into the glass substrate if the sample has prolonged contact with water. The X-ray reflection measurements have shown there are no changes in the structure of the gel film on glass on exposure to a humid atmosphere. This result is verified by the neutron reflection data and suggests that as water penetrates into the surface it occupies "voids" in the gel network. These voids can be filled or emptied by changing the relative humidity. The neutron reflectivity measurements have also revealed additional information about the distribution of the water. For the pure silica gel, with no added FAS, there is a water-rich layer (∼30 A thick) at the gel surface and a significant amount of water (volume fraction up to 18%) penetrated throughout the gel film. Gel films made with moderate amounts of FAS show no evidence for a water-rich layer on the surface. In fact, the water density is effectively zero within ∼20 A of the gel's surface. This suggests that the fluorinated materialformed a hydrophobic monolayer near the surface of the gel. For gels with much higher levels of FAS, the film surface becomes very rough and a detailed interpretation is not possible.

Polymerizable surfactants (surfmers) 11-(methacryloyloxy)undecyltrimethylammonium bromide (A), dodecyl(11-(methacryloyloxy)undecyl)dimethylammonium bromide (B), 11-(acryloyloxy)undecyltrimethylammonium bromide (C), and dodecyl(11-(acryloyloxy)undecyl)dimethylammonium bromide (D) have been synthesized and characterized. Mixed micelles of A + B and C + D systems were polymerized by a thermal free-radical water-soluble initiator, to yield transparent solutions that remained stable for months. Copolymerization was followed by NMR, which was consistent with essentially 100% conversion. Lamellar mesophases (80% mass) were prepared by concentration of the polymerized micelles from dilute micellar systems. The mesophases were prealigned in a strong magnetic field prior to small-angle X-ray scattering (SAXS) and polarizing light microscopy studies. Detailed analysis of the SAXS data was consistent with stabilization of lamellar structures, comprising similar-sized internal domains, independent of the mixture compo...

In the past 15 years, there has been a trend to decrease dialysate calcium concentrations to prevent hypercalcemia. However, low dialysate calcium can provoke hyperparathyroidism. The time course of the effect of increasing dialysate calcium is not well characterized, and the effect on calcium-phosphate product is unclear. Therefore, we studied the effect of increasing dialysate calcium from 1.5 to 1.75 mM in 21 stable patients on hemodialysis who had serum phosphate of less than 2 mM and serum calcium of less than 2.4 mM. Over 10 months, parathyroid hormone levels fell from 39.6 to 16.6 pM (p < 0.0001), whereas serum calcium increased from 2.27 to 2.41 mM. There were no significant changes in serum phosphate or the calcium-phosphate product. Three patients became hypercalcemic when their parathyroid hormone levels were suppressed to less than 10 pM. We conclude that in carefully selected patients, increasing dialysate calcium can safely treat hyperparathyroidism with minimal risk of complications. This treatment has the advantage over the use of vitamin D therapy of being less expensive, independent of patient compliance, and less likely to cause increases in serum phosphate or calcium-phosphate product.

X-ray diffraction from smectic materials in device-like cells is used to determine the layer structure within the cells. The experimental method determines the smectic layer normal orientational distribution as a function of tilt and twist angles within the cell. In a special case where the layer normals are not twisted away from the alignment direction, the chevron structures have been reconstructed from the distributions. The influence of the surface pre-tilt due to the alignment layer, electric fields and skewed alignment layers on the smectic layer normal distributions are reviewed and discussed.

A 42-year-old man with end-stage renal disease (ESRD) was referred for conversion to nocturnal hemodialysis (NHD) therapy from conventional hemodialysis (CHD) therapy because of refractory intermittent claudication secondary to peripheral arterial disease (PAD). The patient was initiated on CHD therapy in 1976 and subsequently had undergone two unsuccessful renal transplantations. While on CHD therapy, his clinical course was complicated by worsening vascular and soft-tissue calcification. Extensive dystrophic soft-tissue calcification was noted bilaterally in his hands, lower extremities, and sacral region, requiring surgical excision. Lower-extremity arterial Doppler scans documented vascular calcification and a pronounced decrease in peripheral arterial flow bilaterally. After conversion to NHD therapy (7.5 h/session five times weekly), the patient became symptom free and had significant clinical improvements in (1) hemodynamics, measured by clinic blood pressure and two-dimensional echocardiography, (2) biochemical profile, and (3) a sustained improvement in arterial Doppler flow measured by duplex Doppler ultrasound. We conclude that NHD was able to improve lower-extremity PAD in our patient. Further observational and interventional studies are required to investigate the therapeutic potential of NHD for the treatment of PAD in patients with ESRD.

The synthesis of the first inorganic-organic hybrid liquid crystal dendrimers based on carbosilazane cores, which exhibit enantiotropic nematic, smectic C and columnar phase behaviour is presented and the liquid-crystalline phase properties and the phase structures are discussed.

It is observed optically that in a parallel rubbed antiferroelectric liquid crystal device, the texture consists of domains with two distinct optic axes, which make equal and opposite angles with the rubbing direction. It is proposed that this is caused by a large electroclinic effect at the surfaces during layer formation in the SmA* phase. This hypothesis is verified by finding the layer structure in single, parallel and skew rubbed devices by using X-ray diffraction.

Kidney transplantation from living donors is generally a safe, effective form of renal replacement therapy. When evaluating potential living donors and their intended recipients, a careful assessment process is followed in order to ensure that ethical standards are upheld. During this assessment, important medical information with serious consequences, which was not being sought as part of the donor/recipient evaluation, may be discovered. The information may or may not be relevant to the decision to donate. However, such a discovery raises the difficult questions of whether or not there is an obligation to disclose the information, to whom does the information belong, and what process should be used to resolve the issue? We present a case that forced us to confront these questions and raised issues of truth telling, autonomy, paternalism, confidentiality, and the nature of the relationship between patients and health care professionals.

The orientational order parameters P2, P4, and P6 have been determined by neutron scattering from a mixture of normal hydrogenous and deuterium labeled molecules in the nematic, smectic A and smectic C phases of the mesogen 2′,3′-difluoro-4-heptyl-4″-nonyl-p-terphenyl. Since the method relies on a knowledge of the molecular structure, the influence of different molecular conformations resulting from the terminal chains on the values determined was examined in detail. It was shown that the choice of conformation could significantly effect the resulting values of the order parameters. The order parameters were, therefore, determined by assuming a distribution of conformations for the alkyl chains. The relative contributions of these conformations were governed by the Flory rotational isomeric state model. The values for P2 were consistent with those determined by nuclear magnetic resonance but all the order parameters were generally much greater than those predicted by the Maier–Saupe theory.

The surface features, morphology, and tensile properties of fibers obtained from pristine, reprocessed, and reused Fresenius Polysulfone High-Flux (Hemoflow F80A) hemodialyzers have been studied. Scanning electron microscopy of the dialyzer fibers revealed a dense skin layer on the inner surface of the membrane and a relatively thick porous layer on the outer surface. Transmission electron microscopy and atomic force microscopy showed an alteration in membrane morphology due to reprocessing and reuse, or to a deposition of blood-borne material on the membrane that is not removed with reprocessing. Fluorescent microscopy images also showed that a fluorescent material not removed by heat/citric acid reprocessing builds up with continued use of the dialyzers. The tensile properties of the dialyzer fibers were not affected by the heat/citric acid reprocessing procedure. The protein layers formed on pristine and reused hemodialyzer membranes during clinical use were also studied using sodium dodecyl sulfate polyacrylamide gel electrophoresis and immunoblotting. A considerable amount of protein was found on the blood side of single and multiple use dialyzers. Proteins adsorbed on the dialysate side of the membrane were predominantly in the molecular weight region below 30 kDa. Little protein was detected on the membranes of reprocessed hemodialyzers.

Epilepsy is a debilitating condition affecting 1% of the population worldwide. Medications fail to control seizures in at least 30% of patients, and deep brain stimulation (DBS) is a promising alternative treatment. A modified clinical DBS hardware platform was recently described (PC+S) allowing long-term recording of electrical brain activity such that effects of DBS on neural networks can be examined. This study reports the first use of this device to characterize idiopathic epilepsy and assess the effects of stimulation in a nonhuman primate (NHP). Clinical DBS electrodes were implanted in the hippocampus of an epileptic NHP bilaterally, and baseline local field potential (LFP) recordings were collected for seizure characterization with the PC+S. Real-time automatic detection of ictal events was demonstrated and validated by concurrent visual observation of seizure behavior. Seizures consisted of large-amplitude 8- to 25-Hz oscillations originating from the right hemisphere and quickly generalizing, with an average occurrence of 0.71 ± 0.15 seizures/day. Various stimulation parameters resulted in suppression of LFP activity or in seizure induction during stimulation under ketamine anesthesia. Chronic stimulation in the awake animal was studied to evaluate how seizure activity was affected by stimulation configurations that suppressed broadband LFPs in acute experiments. This is the first electrophysiological characterization of epilepsy using a next-generation clinical DBS system that offers the ability to record and analyze neural signals from a chronically implanted stimulating electrode. These results will direct further development of this technology and ultimately provide insight into therapeutic mechanisms of DBS for epilepsy.

Background Sustained low efficiency dialysis (SLED) is increasingly used as a renal replacement modality in critically ill patients with acute kidney injury (AKI) and hemodynamic instability. SLED may reduce the hemodynamic perturbations of intermittent hemodialysis, while obviating the resource demands of CRRT. Although SLED is being increasingly used, few studies have evaluated its impact on clinical outcomes. Methods We conducted a cohort study comparing SLED (target 8 h/session, blood flow 200 mL/min, predominantly without anticoagulation) to CRRT in four ICUs at an academic medical centre. The primary outcome was mortality 30 days after RRT initiation, adjusted for demographics, comorbidity, baseline kidney function, and Sequential Organ Failure Assessment score. Secondary outcomes were persistent RRT dependence at 30 days and early clinical deterioration, defined as a rise in SOFA score or death 48 h after starting RRT. Results We identified 158 patients who initiated treatment with CRRT and 74 with SLED. Mortality at 30 days was 54 % and 61 % among SLED- and CRRT-treated patients, respectively [adjusted odds ratio (OR) 1.07, 95 % CI 0.56–2.03, as compared with CRRT]. Among SLED recipients, the risk of RRT dependence at 30 days (adjusted OR 1.36, 95 % CI 0.51–3.57) and early clinical deterioration (adjusted OR 0.73, 95 % CI 0.40–1.34) were not different as compared to patients who initiated CRRT. Conclusions Notwithstanding the limitations of this small non-randomized study, we found similar clinical outcomes for patients treated with SLED and CRRT. While we await the completion of a trial that will definitively assess the non-inferiority of SLED as compared to CRRT, SLED appears to be an acceptable alternative form of renal support in hemodynamically unstable patients with AKI. Electronic supplementary material The online version of this article (doi:10.1186/s12882-015-0123-4) contains supplementary material, which is available to authorized users.

Introduction: Vancomycin remains the mainstay in the treatment of meticillin‐resistant Staphylococcus aureus (MRSA) bacteraemia; however, concerns exist about its continued efficacy in the presence of rising MICs. Daptomycin serves as an alternative but has also witnessed increases in reduced susceptibility. Several published case reports have demonstrated the potential utility of ceftaroline as a viable therapeutic option for invasive MRSA infections, including endocarditis. Case presentation: A 23‐year‐old pregnant female presented with complaints of foot pain and fevers up to 104 °F. Her past medical history included polysubstance abuse, hepatitis C, intravenous drug use and a right arm abscess 2 years ago due to MRSA. Daptomycin was started empirically due to an allergy (angioedema) to vancomycin. Blood cultures returned positive for MRSA and remained persistently positive for 10 days at which point ceftaroline was added. Subsequent positive blood cultures on day 12 revealed daptomycin‐non‐susceptible MRSA at an MIC of 4 µg ml–1. Consequently, daptomycin was discontinued and gentamicin was added. Blood cultures were negative by day 14 and the patient completed a total of 2 weeks of gentamicin and 4 weeks of ceftaroline after the first negative blood culture. The baby was born premature at 34 weeks and 2 days due to complications of pregnancy; however, no adverse effects of antimicrobial therapy were noted. Conclusion: We describe the emergence of daptomycin‐non‐susceptibility during treatment and the successful eradication of persistent daptomycin‐non‐susceptible MRSA bacteraemia and endocarditis with a combination of ceftaroline and gentamicin in a pregnant female.

The assembly of colloidal particles in a nematic liquid crystal has been investigated using small-angle X-ray scattering. The structure and orientation of nanoparticle assemblies in bulk samples of aligned nematic liquid crystal have been determined. The method offers some advantages over optical microscopy, which is usually restricted to investigations of thin cells and micron-sized particles. The scattering from chains of particles has been calculated, and comparison with experimental results has shown that suspensions of 48 and 105 nm diameter silica nanoparticles formed highly ordered structures perpendicular to the liquid crystal director, consistent with quadrupolar defect-induced assembly.

Using a combination of neutron reflectivity and a surface force type apparatus, the hydration of polyelectrolyte multilayers, PEMs, is investigated under mechanical confinement. The samples consist of poly(styrenesulfonic acid), PSS, and poly(allylamine hydrochloride), PAH, which were formed by spin-coating with 11, 23, and 47 bilayers. The terminating layer polyelectrolyte of the PEMs was also varied. Selectively deuterating some layers and using a model that separately considers the last layer from the other strata representing the material structure of the PEM allow a low-resolution hydration distribution within the PEM to be determined. When swollen with H2O and unconfined, PSS-terminated PEMs are approximately 26% v/v water, and this decreases to 15% with an applied pressure of 5 bar. By comparison, PAH-terminated PEMs are 20% water when unconfined and dehydrate to 10% water at 5 bar. For all samples, the final adsorbed layer is significantly more hydrated at approximately 40% v/v. The water is generally uniformly distributed within the bulk of a PEM; however, there is a significant increase in hydration in the bilayers adjacent to the final layer in PAH-terminated PEMs. Also considered is an experiment where the inherent charge of the final adsorbed layer of a PEM is neutralized by compressing it with an oppositely charged PEM. This determines the hydration for an uncharged PEM and demonstrates that the influence of the potential of the final layer on a PEMs’ internal hydration is a perturbation. A detailed scheme is then presented whereby the amount and distribution of internal charge are directly responsible for the hydration of a PEM.

Specular neutron reflection has been used to investigate the incorporation of water into the surface of float glass in a number of different environments. For float glass soaked in water for up to 6 months, two different layers were identified. A surface layer, whose thickness remained constant at approximately 30 A, contained water at about 40% of the density of pure water. A second layer contained water at about 10% that had penetrated deeper into the sample as the immersion time increased reaching approximately 500 A in 6 months. An isotope exchange experiment indicated that the lifetime of a water molecule in this layer was about one day. There was a reduction of the glass density in these layers due to the removal of sodium and evidence for gel formation at the surface. When the glass was exposed to a saturated water vapour at temperature up to 80 °C, the water was also found to penetrate into the glass surface over a period of about an hour, but there was no loss of material from the glass. The speed of water penetration was a strong function of temperature. On application of high temperature (150 °C) and pressure (120 bar) the glass underwent rapid ageing when in contact with water. The formation of a visible gel layer was observed, however the penetration depth of the water apparently reduced as the treatment time increased because of dissolution of the gel layer at the surface. Float glass with higher levels of alumina shows a small reduction in the water penetration suggesting that its increased durability resulted from stabilising the sodium ions rather than preventing ingress of water.

This paper presents a systematic study of two series of carbosilane liquid crystalline (LC) dendrimers from first to fifth generations bearing 8, 16, 32, 64 and 128 terminal chiral mesogenic groups...

The thermal behaviour of two series of liquid crystalline carbosilane dendrimers of generations 1–5 containing 8, 16, 32, 64 and 128 terminal phenyl benzoate mesogenic groups, respectively, was investigated by means of polarising optical microscopy, DSC and X-ray methods. Mesogenic groups on the base of methoxybenzoic (anisic) acid (Anis) and methoxyphenol (MPhB) were linked to the carbosilane dendritic matrices through -OOC-(CH2)10-Si(CH3)2OSi(CH3)2- spacer. All LC dendrimers synthesised display smectic type mesophases and crystal phases over wide temperature region. LC dendrimers of fifth generation have more complex phase behaviour: heating the samples leads to transition from smectic to, most probably, columnar mesophases.

A hexadecamer, first-generation, octasilsesquioxane liquid-crystalline dendrimer was synthesized by a platinum-catalyzed hydrosilylation reaction of the parent first-generation vinyl octasilsesquioxane dendrimer with a modified, laterally substituted mesogen. The structure and purity of the octasilsesquioxane substrate was confirmed by 1H, 13C, and 29 Si NMR spectroscopy, microanalysis, and size exclusion chromatography (SEC). The mesogenic substrate was found to exhibit only a chiral nematic phase, whereas the resulting hexadecamer dendrimer displays enantiotropic chiral nematic, disordered hexagonal columnar, and disordered rectangular columnar phases, with a glass transition below room temperature. The lateral or side-on attachment of the mesogen to the dendritic core was found to be a key design feature in the formation of the mesophases.

X-ray scattering together with optical characterization using fully leaky guided modes have been used for the first time to study the same ferroelectric liquid-crystal cell. This enables direct calculation of an accurate cone and chevron description of the liquid-crystal director profile since the layer structure and optic tensor configuration are both well known.

The properties of poly(N-isopropylacrylamide) (polyNIPAM) at the air/water interface, with and without sodium dodecyl sulfate (SDS), were measured by neutron reflectivity and surface tension. Below the lower critical solution temperature (LCST), polyNIPAM adsorbs at the air/water interface to give a thin (δ ∼ 1.5 nm) layer with a low water content approximately equal to phase-separated polyNIPAM above the LCST. Above the LCST the adsorbed polymer layer increases by a factor of 10 approximately equal to the effective diameter of a single phase-separated polymer chain (a globule). Polymer-bound SDS lowers the density of adsorbed polyNIPAM because of electrostatic effects.

A systematic study of the influence of generation number on the phase behavior of LC dendrimers is presented. For this purpose, phase behaviors and structures of first to fifth generations of liquid crystalline (LC) carbosilane dendrimers with 8, 16, 32, 64, and 128 terminal cyanobiphenyl groups were investigated. Investigation of thermal behavior of the LC dendrimers by means of polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction experiments reveals smectic-type mesophases over a wide temperature region. It is shown that with increasing generation number the isotropization temperature increases whereas the enthalpy of this phase transition decreases. The strongest influence of spherical molecular architecture on the phase behavior of the LC dendrimers appears at high generations. In the case of LC dendrimer of the fifth generation, it leads to the formation of two levels of a structural organization. This dendrimer forms different supramolecular nanostructures of colum...

A defect structure has been observed for certain ferroelectric liquid crystal mixtures in the surface stabilised device geometry when cooled towards ambient temperature. X-ray and electro-optic studies suggest that the sample, initially in the chevron layer structure, forms a uniformly tilted layer structure spontaneously. This seriously degrades device contrast and switching properties. The effect of both liquid crystal composition and alignment layer pretilt are reported and recommendations made to ensure that the defect does not occur, thereby allowing good device performance to be maintained.

X-ray diffraction has been used to investigate the structure of ferroelectric Smectic C* (SmC*) devices with anti-parallel orientation of the alignment layers. The layer structure during cooling from the Smectic A (SmA) phase has been determined for three different surface pre-tilts. The results are presented as two-dimensional layer normal distributions that show in detail the changes in layer orientation as a function of temperature. For low and medium pre-tilt surfaces a transformation from a uniformly tilted layer in the Sm A to a chevron in the Sm C was observed in monodomain regions. These surfaces also tended to show needle defects in the Sm C and their layer structure is discussed.

Comparative mortality of hemodialysis and peritoneal dialysis in Canada. Background Comparisons of mortality rates in patients on hemodialysis versus those on peritoneal dialysis have been inconsistent. We hypothesized that comorbidity has an important effect on differential survival in these two groups of patients. Methods Eight hundred twenty-two consecutive patients at 11 Canadian institutions with irreversible renal failure had an extensive assessment of comorbid illness collected prospectively, immediately prior to starting dialysis therapy. The cohort was assembled between March 1993 and November 1994; vital status was ascertained as of January 1, 1998. Results The mean follow-up was 24 months. Thirty-four percent of patients at baseline, 50% at three months, and 51% at six months used peritoneal dialysis. Values for a previously validated comorbidity score were higher for patients on hemodialysis at baseline (4.0 vs. 3.1, P P = 0.001), and six months (3.6 vs. 3.2, P = 0.005). The overall mortality was 41%. The unadjusted peritoneal dialysis/hemodialysis mortality hazard ratios were 0.65 (95% CI, 0.51 to 0.83, P = 0.0005), 0.84 (95% CI, 0.66 to 1.06, P = NS), and 0.83 (95% CI, 0.64 to 1.08, P = NS) based on the modality of dialysis in use at baseline, three months, and six months, respectively. When adjusted for age, sex, diabetes, cardiac failure, myocardial infarction, peripheral vascular disease, malignancy, and acuity of renal failure, the corresponding hazard ratios were 0.79 (95% CI, 0.62 to 1.01, P = NS), 1.00 (95% CI, 0.78 to 1.28, P = NS), and 0.95 (95% CI, 0.73 to 1.24, P = NS). Adjustment for a previously validated comorbidity score resulted in hazard ratios of 0.74 (95% CI, 0.58 to 0.94, P = 0.01), 0.94 (95% CI, 0.74 to 1.19, P = NS), and 0.88 (95% CI, 0.68 to 1.13, P = NS) at baseline, three months, and six months. There was no survival advantage for either modality in any of the major subgroups defined by age, sex, or diabetic status. Conclusions The apparent survival advantage of peritoneal dialysis in Canada is due to lower comorbidity and a lower burden of acute onset end-stage renal disease at the inception of dialysis therapy. Hemodialysis and peritoneal dialysis, as practiced in Canada in the 1990s, are associated with similar overall survival rates.

Two Laponite clays, of general formula [Mn+]x/n [Lix Mg6-x Si8 O20 Fy (OH)4-y], were prepared with different Li+ levels (0.57 and 0.70% w/w) and F- levels (9.5 and 9.9% w/w). The clays were characterized by measurements of nitrogen adsorption isotherms, cation exchange capacity, and conductometric titration data. The clay with higher Li+ and F- levels had a higher (more negative) face charge and a lower (less negative) edge charge. Small-angle X-ray scattering (SAXS) data obtained from dilute aqueous dispersions indicate that both clays are of similar particle size (diameter ca. 40 nm and thickness ca. 3.5 nm). Experimental structure factors for concentrated Laponite dispersions were calculated using the ratio of scattered X-ray intensities from concentrated and dilute dispersions. Maxima in the experimental structure factors were observed at scattering angles of 0.14−0.2 nm-1 under favorable solution conditions (pH ≥ 9 and ionic strength ca. 5 × 10-3 mol dm-3) for one of the Laponite clays. These results...

For the first time a series of liquid crystalline dendrimers of generations 1–4 containing 8, 16, 32 and 64 terminal methoxyphenyl benzoate mesogenic groups respectively have been synthesised. Mesogenic groups were attached to the carbosilane dendritic matrices with terminal allyl groups through -OOC-(CH2)10-Si(CH3)2OSi(CH3)2- spacer by a hydrosilylation reaction. Structure and purity of all new compounds were confirmed by 1H-NMR spectros-copy and GPC analysis. Phase behaviour of LC dendrimers was investigated by means of polarising optical microscopy, DSC and X-ray methods. All LC dendrimers synthesised display mesophases of smectic types as well as crystalline phases over wide temperature region. Possible structure and arrangement of molecules of LC dendrimers in these mesophases are discussed.

Ferroelectric liquid crystal devices are notoriously susceptible to mechanical damage. Engineering approaches have reduced flow and shear effects using a polymer wall to maintain the cell spacing across the panel1. This was used to produce a 6″ video rate display with 64 grey levels and a resistance to mechanical shock which is comparable to commercial STN panels2. However, a fundamental understanding of the mechanical damaged structure and its relation to the FLC physical properties is required. In this work X-ray diffraction is used to determine the smectic layer structure arising from mechanical damage.

We have studied the structure of two series of liquid crystalline dendrimers based on the carbosilane dendritic matrix. Generations 1 to 5 have been investigated for the series with cyanobiphenyl mesogenic groups and generations 1 to 4 for the series with methoxyphenyl benzoate mesogenic groups. Generations 1 to 4 of both series show a diffraction pattern corresponding to a simple smectic phase with disordered layers indicating that the tendency of the mesogenic units to form smectic layers overcomes the restrictions imposed by the globular dendritic core of the molecule. The variation of layer spacing with temperature and generation number indicates that there are subtle differences in the packing of the mesogens in the different samples. The 5th generation of the dendrimers with cyanobiphenyl groups shows the same smectic structure below 40[ddot]C but at higher temperatures there is some in-plane structure that suggests that columns may be formed. This can be rationalised in terms of the molecu...

The Small Angle Neutron Scattering (SANS) from specifically deuterated samples of side-chain liquid crystal polymers has been used to determine the dimensions of the backbone both parallel and perpendicular to the director as well as the degree of polymerisation. It has been possible to determine the effect of molecular weight on the chain dimensions in the smectic phase. There is strong anisotropy of the backbone conformation and it becomes stronger as the molecular weight increases. This means that the tendency for the chains to be confined between the smectic layers is stronger for larger molecular weight polymers.

Reflectivity analysis has focused on two key areas; overcoming the phase problem and achieving reliable scattering length density profiles using modelling methods. Significant recent advances are the application of Bayes' theorem, the use of a genetic algorithm and the exploitation of magnetic reference layers and anomalous reflection.

The structure of a liquid crystalline (LC) carbosilane dendrimer of the fifth generation bearing 128 terminal cyanobiphenyl mesogenic groups has been studied. This dendrimer was synthesized by a hydrosilylation reaction and then the cyanobiphenyl mesogenic groups were chemically linked to the dendritic matrix via a-OOC-(CH2)10-Si(CH3)2OSi(CH3)2-spacer. Structural studies carried out by polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction methods revealed unusual phase behaviour. At room temperature the dendrimer forms a lamellar (smectic A) phase which develops in-plane ordering above 40C.This is due toa tendency to form columns ofmolecules which areprobably perpendicular to the layers. Above 121C the material transforms into another more disordered mesophase which is probably a disordered hexagonal columnar phase. The proposed structures and molecular packing in these different types of mesophase are discussed.

Structure−property correlations of two electroactive polymer bilayers fabricated by different methods are investigated using neutron reflectivity to probe the buried polymer/polymer interfaces. Both bilayers utilize electropolymerized poly(2,2‘-bithiophene) as an inner, mediating layer, while the outer layer consists of either electropolymerized polypyrrole or electroprecipitated polyxylylviologen, respectively. These devices have very different current−potential behaviors, which neutron reflectivity shows is a consequence of the fabrication method and the resulting polymer/polymer interfacial structure. The polybithiophene/polypyrrole film is found to be of composite structure while polybithiophene/polyxylylviologen forms a film comprised of segregated polymer layers.

We have developed a method of measuring the distribution of polymer segments at a liquid/liquid interface using neutron reflection. The method consists of forming a stable (1–4 μm) hexane layer on top of an aqueous sub-phase so that two interfaces contribute to the measured reflectivity. This has been done by condensing vapour onto the surface in an accurately temperature-controlled environment. The neutron reflectivity was measured at four angles of incidence on the SURF reflectometer. The attenuation of the reflectivity from the lowest angle is used to determine the thickness of the hexane layer. A series of poly(ethylene oxide) poly(propylene oxide) ABA block copolymers adsorbed at the hexane/water interface have been investigated. Since the polymers were hydrogenous, measurements were made with D 2 O as the aqueous phase and with either null reflecting hexane or 60% D-hexane as the oil phase in order to obtain adequate contrast. The polymer volume fraction profile has been determined by simultaneous fits to the data from these combinations of solvent contrasts. It was found that there was a good correlation between the molar mass of the poly(ethylene oxide) block and the thickness of the polymer layer in the aqueous phase and that the chains were stretched beyond their radii of gyration expected for bulk solution.