Temperature dependence of micelle shape transitions in copolymer solutions: the role of inter-block incompatibility.

The nature of the transition between worm-like and spherical micelles in block copolymer dispersions varies between systems. In some formulations, heating drives a transition from worms to spheres, while in other systems the same transition is induced by cooling. In addition, a sphere-worm interconversion can be accompanied either by an increase or a decrease in the core solvation, even if the direction of the temperature dependence is the same. Here, self-consistent field theory is used to provide a potential explanation of this range of behaviour. Specifically, we show that, within this model, the dependence of the transition on the incompatibility χBS of the solvophobic block B and the solvent S (the parameter most closely related to the temperature) is strongly influenced by the incompatibility χAB between B and the solvophilic block A. When χAB is small (χAB < 0.1), it is found that increasing χBS produces a transition from worm-like micelles to spheres (or, more generally, from less curved to more curved structures). When χAB is above 0.1, increasing χBS drives the system from spheres to worm-like micelles. Whether a transition is observed within a realistic range of χBS is also found to depend on the fraction of solvophilic material in the copolymer. The relevance of our calculations to experiments is discussed, and we suggest that the direction of the temperature dependence may be controlled not only by the solution behaviour of the solvophobic block (upper critical solution temperature-like versus lower critical solution temperature-like) but also by χAB.

Heterotelechelic homopolymers mimicking high χ - ultralow N block copolymers with sub-2 nm domain size.

Three fluorinated, hydrophobic initiators have been utilised for the synthesis of low molecular mass fluoro-poly(acrylic acid) heterotelechelic homopolymers to mimic high chi (χ)-low N diblock copolymers with ultrafine domains of sub-2 nm length scale. Polymers were obtained by a simple photoinduced copper(ii)-mediated reversible-deactivation radical polymerisation (Cu-RDRP) affording low molecular mass (<3 kDa) and low dispersity (D = 1.04-1.21) homopolymers. Heating/cooling ramps were performed on bulk samples (ca. 250 µm thick) to obtain thermodynamically stable nanomorpologies of lamellar (LAM) or hexagonally packed cylinders (HEX), as deduced by small-angle X-ray scattering (SAXS). Construction of the experimental phase diagram alongside a detailed theoretical model demonstrated typical rod-coil block copolymer phase behaviour for these fluoro-poly(acrylic acid) homopolymers, where the fluorinated initiator-derived segment acts as a rod and the poly(acrylic acid) as a coil. This work reveals that these telechelic homopolymers mimic high χ-ultralow N diblock copolymers and enables reproducible targeting of nanomorphologies with incredibly small, tunable domain size.

Micelle shape transitions in block copolymer/homopolymer blends: comparison of self-consistent field theory with experiment.

Diblock copolymers blended with homopolymer may self-assemble into spherical, cylindrical, or lamellar aggregates. Transitions between these structures may be driven by varying the homopolymer diblock molecular weight or composition. Using self-consistent field theory (SCFT), we reproduce these effects. Our results are compared to x-ray scattering and transmission electron microscopy measurements by Kinning et al. and good agreement is found, although the tendency to form cylindrical and lamellar structures is sometimes overestimated due to our neglect of edge effects due to the finite size of these aggregates. Our results demonstrate that SCFT can provide detailed information on the self-assembly of isolated block copolymer aggregates.

Crossover behavior and multistep relaxation in a schematic model of the cut-off glass transition.

We study a schematic mode-coupling model in which the ideal glass transition is cut off by a decay of the quadratic coupling constant in the memory function. (Such a decay, on a time scale tau I , has been suggested as the likely consequence of activated processes.) If this decay is complete, so that only a linear coupling remains at late times, then the alpha relaxation shows a temporal crossover from a relaxation typical of the unmodified schematic model to a final strongly slower-than-exponential relaxation. This crossover, which differs somewhat in form from previous schematic models of the cutoff glass transition, resembles light-scattering experiments on colloidal systems, and can exhibit a "slower-than- alpha " relaxation feature hinted at there. We also consider what happens when a similar but incomplete decay occurs, so that a significant level of quadratic coupling remains for t>>tau I . In this case the correlator acquires a third, weaker relaxation mode at intermediate times. This empirically resembles the beta process seen in many molecular glass formers. It disappears when the initial as well as the final quadratic coupling lies on the liquid side of the glass transition, but remains present even when the final coupling is only just inside the liquid (so that the alpha relaxation time is finite, but too long to measure). Our results are suggestive of how, in a cutoff glass, the underlying "ideal" glass transition predicted by mode-coupling theory can remain detectable through qualitative features in dynamics.

Glass transition in fullerenes: mode-coupling theory predictions.

We report idealized mode-coupling theory results for the glass transition of ensembles of model fullerenes interacting via phenomenological two-body potentials. Transition lines are found for C60, C70, and C96 in the temperature-density plane. We argue that the observed glass transition behavior is indicative of kinetic arrest that is strongly driven by the interparticle attraction in addition to excluded-volume repulsion. In this respect, these systems differ from most standard glass-forming liquids. They feature arrest that occurs at lower densities and that is stronger than would be expected for repulsion-dominated hard-sphere-like or Lennard-Jones-type systems. The influence of attraction increases with increasing the number of carbon atoms per molecule. However, unrealistically large fullerenes would be needed to yield behavior reminiscent of recently investigated model colloids with strong short-ranged attraction (glass-glass transitions and logarithmic decay of time-correlation functions).

Sensitivity of arrest in mode-coupling glasses to low-q structure.

We quantify, within mode coupling theory, how changes in the liquid structure affect that of the glass. Apart from the known sensitivity to the structure factor S(q) at wave vectors around the first sharp diffraction peak q0, we find a strong (and inverted) response to structure at wave vectors below this peak: an increase in S(q0/2) lowers the degree of arrest over a wide q-range. This strong sensitivity to "caged cage" packing effects, on length scales of order 2d, is much weaker in attractive glasses where short-range bonding dominates the steric caging effect.

Langer's axillary arch: anatomy, embryological features and surgical implications.

Langer's arch is identified in up to 7% of axillary explorations; in a three-month period we identified three individuals among forty-six patients undergoing axillary surgery with this abnormality. Langer's arch is a muscular-tendinous structure that usually extends from latissimus dorsi to pectoralis major muscle. The purpose of this article is to describe the embryological derivation of this muscular variant from the panniculus carnosus and to define its anatomical features. The clinical implications both symptomatically and as an unexpected finding during axillary dissection, are also discussed.

Interfacial structure at a two-dimensional wedge filling transition: Exact results and a renormalization group study.

Interfacial structure and correlation functions near a two-dimensional wedge filling transition are studied using effective interfacial Hamiltonian models. An exact solution for short range binding potentials and results for Kratzer binding potentials show that sufficiently close to the filling transition a new length scale emerges and controls the decay of the interfacial profile relative to the substrate and the correlations between interfacial positions above different positions. This new length scale is much larger than the intrinsic interfacial correlation length, and it is related geometrically to the average value of the interfacial position above the wedge midpoint. The interfacial behavior is consistent with a breather mode fluctuation picture, which is shown to emerge from an exact decimation functional renormalization group scheme that keeps the geometry invariant.

Fluid adsorption near an apex: covariance between complete and critical wetting.

Critical wetting is an elusive phenomenon for solid-fluid interfaces. Using interfacial models we show that the diverging length scales, which characterize complete wetting at an apex, precisely mimic critical wetting with the apex angle behaving as the contact angle. Transfer matrix, renormalization group, and mean-field analysis show that this covariance is obeyed in 2D and 3D and for long- and short-ranged forces. This connection should be experimentally accessible and provides a means of checking theoretical predictions for critical wetting.

Current controversies in the surgical management of breast cancer.

BACKGROUND: Great advances have occurred in the surgical management of breast cancer during the past 2 decades, though areas of controversy still remain. The surgical treatment of breast cancer relates to management of the breast and of the axillary nodes. Areas of controversy relate to methods of breast conservation after preoperative chemotherapy for locally advanced disease. The ideals of such treatment are described and the various methods by which such results may be obtained are discussed. The importance of conservation of the nipple-areolar complex is stressed, and the various methods of reconstruction by which this can be achieved are discussed. The role of surgery to the axilla is also discussed, with particular reference to axillary sampling. Data relating to the control of axillary disease treated by irradiation and that obtained after surgery are compared. Current controversies: Breast conservation, partial and subcutaneous mastectomy, reconstruction (using implants, prostheses and myocutaneous flaps), the management of axillary disease and the role of adjuvant therapy are discussed.

Gynaecomastia.

This paper reviews the development of excess breast tissue in the male. Gynaecomastia is a common problem and may have a physiological or pathological basis. It can be dealt with in most cases by reassurance or simple surgery.

Soft tissue sarcoma in man--evidence for infective or environmental aetiology?

Two cases of soft tissue liposarcoma are presented occurring in a husband and wife. Their treatment is discussed and the possible infective or environmental causes of soft tissue sarcoma development are described.

Lipogenesis by isolated human apocrine sweat glands: testosterone has no effect during long-term organ maintenance.

Lipid synthesis by freshly isolated human apocrine glands has been measured by the incorporation of [U-14C] acetate. Incorporation is linear over 6 h at 1010 +/- 282 pmol/mg wet weight/h (n = 11; mean +/- sem). The lipid classes, as percentages of the total lipid synthesized, were found by TLC to be cholesterol 12.3 +/- 2.0, mono-glycerides 7.5 +/- 1.5, 1,2 di-glycerides 3.0 +/- 0.9, 1,3 di-glycerides 3.5 +/- 0.5, tri-glycerides 28.4 +/- 1.8, free fatty acids 2.0 +/- 0.4, lysolecithin 15.4 +/- 3.9, sphingomyelin 9.9 +/- 4.3, phosphatidyl-choline 8.4 +/- 0.4, phosphatidyl-ethanolamine -inositol and -serine 1.8 +/- 0.1, phosphatidic acid and cardiolipin 3.3 +/- 0.5, and unidentified 3.3 +/- 0.5 (mean +/- sem, n = 5). Glands were maintained on permeable supports. After 10 d maintenance, electron microscopy showed that the cellular architecture had been preserved, that the ATP contents were the same as in freshly isolated glands, and that [U-14C] acetate incorporation was not significantly altered at 851 +/- 237 pmol/mg/h (n = 18). The addition of 3 microM testosterone had no effect on acetate incorporation at 844 +/- 231 pmol/mg/h (n = 18). The lipid classes and their proportions were similar to the values for fresh glands after 10 d maintenance both with and without testosterone.

Reduction of the surgical excision rate in benign breast disease using fine needle aspiration cytology with immediate reporting.

Patients attending a breast clinic in two different periods were studied. In the first period fine needle aspiration cytology (FNAC) was not available and in the second it was used on all discrete solid breast lumps and reported immediately in the clinic. With the use of FNAC the overall surgical excision rate for discrete solid lumps was reduced from 83 per cent to 41 per cent and the excision rate in patients with benign disease was reduced from 74 per cent to 23 per cent (P less than 0.001). All patients with breast cancer in the second period had malignant cytology and no patient with benign or acellular cytology has been shown, after a minimum follow-up period of 18 months, to have breast cancer. Using FNAC with immediate reporting, the number of operations performed in patients with benign breast disease can be safely reduced.

Fine needle aspiration cytology, with immediate reporting, in the outpatient diagnosis of breast disease.

One hundred and fifty one new patients attending a breast clinic over a 6 month period underwent fine needle aspiration cytology (FNAC), with immediate reporting of the smears in the clinic. Thirty nine smears (25.8%) were classified as unequivocally malignant, 10 (6.6%) as being suspicious of malignancy, 61 (40.3%) as benign and 41 (27.1%) were acellular. There were no false positive diagnoses and only one false negative cytological diagnosis of breast cancer [corrected]. Immediate reporting of results enabled the diagnosis to be discussed with the patient at the first attendance and allowed improved surgical management of both benign as well as malignant breast disease.