Polymers and biopolymers at interfaces.

This review updates recent progress in the understanding of the behaviour of polymers at surfaces and interfaces, highlighting examples in the areas of wetting, dewetting, crystallization, and 'smart' materials. Recent developments in analysis tools have yielded a large increase in the study of biological systems, and some of these will also be discussed, focussing on areas where surfaces are important. These areas include molecular binding events and protein adsorption as well as the mapping of the surfaces of cells. Important techniques commonly used for the analysis of surfaces and interfaces are discussed separately to aid the understanding of their application.

Evaluating the outcomes of the STEPPS programme in a UK community-based population; implications for the multidisciplinary treatment of borderline personality disorder.

WHAT IS KNOWN ON THE SUBJECT?: Individuals with a diagnosis of Borderline Personality Disorder (BPD) now constitute a substantial portion of the caseload for community teams. Specialized treatments for BPD often consume a large portion of available psychology resources and also involve lengthy waiting lists. The STEPPS programme is a treatment approach which is growing in evidence, particularly in the US. However, further evidence for the effectiveness of this programme within the UK healthcare system is needed. WHAT THIS STUDY ADDS TO EXISTING KNOWLEDGE: The results of this study support the preliminary evidence for the effectiveness of STEPPS in a UK community-based population. A reduction in symptom severity was in evidence. Novel measures were used to build on previous evaluations of the STEPPS programme. These measures show a significant reduction in patients' affinity for unhelpful schemas, as well as an increase in patients' self-reported quality of life; an important perspective for a recovery focused approach to treatment. WHAT ARE THE IMPLICATIONS FOR PRACTICE?: The STEPPS programme has shown its merit as an effective and more accessible treatment option for the community-based treatment of BPD, though some methodological limitations are noted. Furthermore, the results of this study demonstrate that STEPPS can be delivered effectively by teams of facilitators from different professional backgrounds who do not necessarily have extensive training in psychotherapeutic interventions. The result is a well-rounded and diverse skill set possessed by the team of facilitators, adding to the richness of the patient's recovery journey and leading to a more favourable spread of teams' resources. ABSTRACT: Aims & Background Systems Training for Emotional Predictability and Problem Solving (STEPPS) is a group treatment for individuals with a diagnosis of Borderline Personality Disorder (BPD) which has a growing evidence base, particularly in the US. Evidence is sparse for its use with UK populations, and this study seeks to assess the reliability of this evidence, whilst adding to existing knowledge through the use of additional measures. Method Thirty patients completed one of four STEPPS groups. Data regarding symptom severity, quality of life and affinity for maladaptive schemas were collected at the start and end of the group to allow pairwise analysis. Results Significant reductions in symptom severity and affinity for maladaptive schemas were in evidence, as well as highly significant increases in patients' self-reported quality of life. Implications The results provide further evidence for the efficacy of STEPPS with a UK sample of patients with a diagnosis of BPD, though limitations with the design of this study warrant caution. They also show that the programme achieves this level of efficacy when delivered by facilitators who are not intensively trained in psychological treatment models. As such, the STEPPS programme provides a resourceful approach to the treatment of BPD in a UK community-based setting.

Symmetric and asymmetric instability of buried polymer interfaces.

We demonstrate using neutron reflectometry that the internal interfaces in a trilayer system of two identical thick polystyrene layers sandwiching a much thinner (deuterated) poly(methyl methacrylate) layer 15 nm thick (viscosity matched with the polystyrene layers) increase in roughness at the same rate. When the lower polystyrene layer is replaced with a layer of the same polymer of much greater molecular mass, two different growths of the interfaces are observed. From the growth of the interface for this asymmetric case in the solid regime using the theoretical prediction of the spinodal instability including slippage at the interface, a value of the Hamaker constant of the system has been extracted in agreement with the calculated value. For the symmetric case the rise time of the instability is much faster.

Quantitative evaluation of evaporation rate during spin-coating of polymer blend films: Control of film structure through defined-atmosphere solvent-casting.

Thin films of polymer mixtures made by spin-coating can phase separate in two ways: by forming lateral domains, or by separating into distinct layers. The latter situation (self-stratification or vertical phase separation) could be advantageous in a number of practical applications, such as polymer optoelectronics. We demonstrate that, by controlling the evaporation rate during the spin-coating process, we can obtain either self-stratification or lateral phase separation in the same system, and we relate this to a previously hypothesised mechanism for phase separation during spin-coating in thin films, according to which a transient wetting layer breaks up due to a Marangoni-type instability driven by a concentration gradient of solvent within the drying film. Our results show that rapid evaporation leads to a laterally phase-separated structure, while reducing the evaporation rate suppresses the interfacial instability and leads to a self-stratified final film.

The interfacial behaviour of single poly(N,N-dimethylacrylamide) chains as a function of pH.

We have studied the pH-dependent conformational behaviour of poly(N,N-dimethylacrylamide) (PDMAc) at silicon and gold surfaces using single-molecule force spectroscopy and a quartz crystal microbalance (QCM). Despite the pH dependence, nuclear magnetic resonance and titration experiments demonstrate that PDMAc is not a weak polybase. The interaction between single chains and a silicon surface (with native oxide layer intact) in aqueous solution was investigated using force spectroscopy. Single-molecule force measurements were performed using thiol-functionalized PDMAc and gold-coated AFM cantilevers. The forces of interaction between PDMAc and the native oxide-coated silicon surface vary with the pH. The shape of the retraction curve for low pH solution includes a greater number of 'train' conformations, which suggests a stronger interaction with the surface relative to the surrounding media at low pH. The adsorption behaviour of PDMAc, from liquid onto silicon surfaces, was monitored using a QCM, which shows greater PDMAc adsorption onto silicon at low pH. The force spectroscopy and QCM investigations confirm that the PDMAc chain is more extended and stiffer in low pH solution. We attribute the pH-dependent behaviour to an increased number of hydrogen bonding sites on the silicon surface at low pH.

Switching layer stability in a polymer bilayer by thickness variation.

We use optical and scanning force microscopy to explore the possibility of switching the stability of a bilayer of poly(methyl methacrylate) (PMMA) on polystyrene by simply changing the film thickness. We show that for thin PMMA layers on thicker polystyrene films the PMMA layer is unstable to thickness fluctuations. However, polystyrene layers are unstable when they are substantially thinner than the now stable PMMA film. Dewetting morphologies are cataloged as a function of the thickness of individual polymer layers by identifying which layer is unstable by which mechanism, be it spinodal dewetting or heterogeneous thermal nucleation. Our results are in good agreement with a linear stability analysis of the influence of long-range dispersion forces, but also indicate the influence of film preparation and small variations of material properties.

Block copolymer adsorption from a homopolymer melt to an amine-terminated surface.

Using neutron reflectometry, the adsorption of diblock copolymers from a neutral polystyrene (PS) matrix is studied as a function of substrate type and non-adsorbing block degree of polymerization. The block copolymer is poly(deutero styrene)-block-poly(methyl methacrylate) and the substrates are silicon oxide, SiO(x), and SiO(x) functionalized with (3-aminopropyl)triethoxysilane (APTES). We have determined the equilibrium volume fraction-depth profiles for such films, and compared them with volume fraction profiles generated by self-consistent mean-field (SCMF) theory and find good agreement between the experimental and theoretical data. SCMF calculations show that the segmental interaction energy between PS matrix chains and APTES is two orders of magnitude stronger than that between PS and SiO(x).

Responsive brushes and gels as components of soft nanotechnology.

Progress in the development of generic molecular devices based on responsive polymers is discussed. Characterisation of specially synthesised polyelectrolyte gels, "grafted from" brushes and triblock copolymers is reported. A Landolt pH-oscillator, based on bromate/ sulfite/ferrocyanide, with a room temperature period of 20 min and a range of 3.1 < pH < 7.0, has been used to drive periodic oscillations in volume in a pH responsive hydrogel. The gel is coupled to the reaction and changes volume by a factor of at least 6. A continuously stirred, constant volume, tank reactor was set-up on an optical microscope and the reaction pH and gel size monitored. The cyclic force generation of this system has been measured directly in a modified JKR experiment. The responsive nature of polyelectrolyte brushes, grown by surface initiated ATRP, have been characterised by scanning force microscopy, neutron reflectometry and single molecule force measurements. Triblock copolymers, based on hydrophobic end-blocks and either polyacid or polybase mid-block, have been used to produce polymer gels where the deformation of the molecules can be followed directly by SAXS and a correlation between molecular shape change and macroscopic deformation has been established. The three systems studied allow both the macroscopic and a molecular response to be investigated independently for the crosslinked gels and the brushes. The triblock copolymers demonstrate that the individual response of the polyelectrolyte molecules scale-up to give the macroscopic response of the system in an oscillating chemical reaction.

Thermodynamic suppression of Brownian motion.

We have used helium-3 nuclear reaction analysis to measure the Brownian motion (intradiffusion coefficient) of polystyrene in a partially miscible blend with poly(alpha-methylstyrene). In the one-phase region, when the correlation length is close to the polystyrene chain size, the intradiffusion coefficient falls to half of its thermal value. For larger and smaller values of the correlation length, diffusion is normal. These results show that the correlation length of a polymer blend constrains polymer diffusion, as suggested from previous neutron scattering measurements, and mean-field theory.

Wetting in a phase separating polymer blend film: quench depth dependence

We have used 3He nuclear reaction analysis to measure the growth of the wetting layer as a function of immiscibility (quench depth) in blends of deuterated polystyrene and poly(alpha-methylstyrene) undergoing surface-directed spinodal decomposition. We are able to identify three different laws for the surface layer growth with time t. For the deepest quenches, the forces driving phase separation dominate (high thermal noise) and the surface layer grows with a t(1/3) coarsening behavior. For shallower quenches, a logarithmic behavior is observed, indicative of a low noise system. The crossover from logarithmic growth to t(1/3) behavior is close to where a wetting transition should occur. We also discuss the possibility of a "plating transition" extending complete wetting to deeper quenches by comparing the surface field with thermal noise. For the shallowest quench, a critical blend exhibits a t(1/2) behavior. We believe this surface layer growth is driven by the curvature of domains at the surface and shows how the wetting layer forms in the absence of thermal noise. This suggestion is reinforced by a slower growth at later times, indicating that the surface domains have coalesced. Atomic force microscopy measurements in each of the different regimes further support the above. The surface in the region of t(1/3) growth is initially somewhat rougher than that in the regime of logarithmic growth, indicating the existence of droplets at the surface.

Non-anticoagulation in atrial fibrillation.

Atrial fibrillation (AF) is an important risk factor for stroke and anticoagulation is now indicated in many patients at increased risk. Studies however have shown that many patients at risk are not anticoagulated for reasons that are not well explored. We identified prospectively the reasons for non-anticoagulation in patients with AF in 94 consecutive hospital patients with cardiac or cerebrovascular disease who had AF. Patients with intermittent or lone AF and < 60 years were excluded n = 16. The remaining group had a mean age of 76 +/- 7 years with a mental test score of 7.4 +/- 2 (normal 10), 31 lived alone and they lived an average of 14 +/- 11 miles from the hospital laboratory. The reasons for non-anticoagulation overlapped and were: medical in 29: cognitive impairment/compliance in 32: and monitoring problems in 50. Anticoagulation for AF in the elderly is a complex enterprise which must take into account social and cognitive as well as medical issues.

Prevalence and forms of neuropathic morbidity in 800 diabetics.

We prospectively determined the prevalence of morbidity from the various forms of diabetic neuropathy over one year in a population of 800 patients with diabetes mellitus (336 type 1, 464 type 2 DM). Symptoms documented were: pain/paraesthesia in the feet, loss of feeling and the restless legs syndrome. We also documented the prevalence of: neuropathic ulcers, amyotrophy, foot drop, and oculomotor palsy. Autonomic symptoms documented were: impotence, postural hypotension and diarrhoea. The only symptoms reported by 100 non-diabetic control subjects were: loss of feeling in 2% and restless legs syndrome in 7%. In the diabetics; pain/paraesthesia was present in 13%, feeling loss in 7% and neuropathic ulcers in 2%. The prevalence of Diabetic amyotrophy (proximal femoral neuropathy) was 0.8%, oculomotor palsy 0.1% and peroneal nerve palsy 0.1%. Erectile impotence was present in 20%, symptomatic postural hypotension in 1% and diabetic diarrhoea in 1%. Overall; 22.9% of the population was afflicted by one or more problems resulting from neuropathy. Neuropathy was associated with older age (p < 0.001), and serious retinopathy (p < 0.001) in both groups of diabetics and with duration of diabetes, proteinuria (p < 0.02), hypertension (p < 0.01) and ischaemic heart disease (p < 0.02) in type 1 diabetics.

Subcutaneous narcotic infusions for cancer pain: treatment outcome and guidelines for use.

OBJECTIVE: To provide guidelines for the institution and maintenance of a continuous subcutaneous narcotic infusion program for cancer patients with chronic pain through an analysis of the narcotic requirements and treatment outcomes of patients who underwent such therapy and a comparison of the costs of two commonly used infusion systems. DESIGN: Retrospective study. SETTING: Tertiary care facilities and patients' homes. PATIENTS: Of 481 patients seen in consultation for cancer pain between July 1987 and April 1990, 60 (12%) met the eligibility criteria (i.e., standard medical management had failed, and they had adequate supervision at home). INTERVENTION: Continuous subcutaneous infusion with hydromorphone hydrochloride or morphine started on an inpatient basis and continued at home whenever possible. OUTCOME MEASURES: Patient selectivity, narcotic dosing requirements, discharge rate, patient preference for analgesic regimen, side effects, complications and cost-effectiveness. RESULTS: The mean initial maintenance infusion dose after dose titration was almost three times higher than the dose required before infusion (hydromorphone or equivalent 6.2 v. 2.1 mg/h). Eighteen patients died, and the remaining 42 were discharged home for a mean of 94.4 (standard deviation 128.3) days (extremes 12 and 741 days). The mean maximum infusion rate was 24.1 mg/h (extremes 0.5 and 180 mg/h). All but one of the patients preferred the infusion system to their previous oral analgesic regimen. Despite major dose escalations nausea and vomiting were well controlled in all cases. Twelve patients (20%) experienced serious systemic toxic effects or complications; six became encephalopathic, which necessitated dose reduction, five had a subcutaneous infection necessitating antibiotic treatment, and one had respiratory depression. The programmable computerized infusion pump was found to be more cost-effective than the disposable infusion device after a break-even point of 8 months. CONCLUSIONS: Continuous subcutaneous infusion of opioid drugs with the use of a portable programmable pump is safe and effective in selected patients who have failed to respond to standard medical treatment of their cancer pain. Dose titration may require rapid dose escalation, but this is usually well tolerated. For most communities embarking on such a program a programmable infusion system will be more cost-effective than a disposable system.

Incidence, risk factors, and morphology in operating microscope light retinopathy.

A review of 135 consecutive cataract operations identified ten cases (7.4%) of operating microscope light retinopathy. Ophthalmoscopically, these light retinopathy lesions appeared as a focal pigment epithelial change with varying degrees of pigment clumping in the center. Fluorescein angiography accentuated the lesion by demonstrating a sharply demarcated transmission defect, occasionally with multiple satellite lesions. The shape of the lesion matched the shape of the illuminating source of the particular operating microscope used during the surgery. The most significant risk factor associated with the production of these light retinopathy lesions was prolonged operating time. Mean total operating time for the ten patients with light retinopathy was 51 minutes longer than for those without (P less than .0001). Other significant associated factors were the presence of diabetes mellitus (P less than .03), younger age (P less than .05), and the use of hydrochlorothiazide (P less than .04).