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In the pursuit of more efficient gas turbine engines, components are required to operate for longer times at elevated temperatures. This increased time in service, together with a complex loading regime, can expose the material to environmental attack. This work has demonstrated that the interaction of stress, NaCl and a sulphur-containing environment is critical to cause crack initiation in the early stages of the exposure and accelerated corrosion rates in CMSX-4 at 550°C. The effect of having small concentrations of moisture in the gaseous environment or as water crystallisation in the salt is still to be investigated. A working hypothesis is that the interaction of alkali chlorides with a sulphur-containing atmosphere is the trigger to a self-sustaining cycle where metal chloride formation, vaporisation and oxidation lead to high amounts of hydrogen injection in a rapid manner and, therefore, hydrogen embrittlement.

Single crystal material, of CMSX-4® alloy composition, was cast and secondary orientation was controlled at the machining stage, to produce c-ring cross-section tubes with known crystallographic orientations. The c-ring tubes were coated with NaCl before being subject to loading up to 700MPa and heated for durations of up to 2 hrs at 550°C in flowing environments containing air and SO2. No cracking was observed in short term tests that were run in the absence of either NaCl, or SO2, indicating a symbiotic interaction is required to initiate cracking. Experiments confirm the presence of oxygen, chlorine and sulphur at the crack tips, formed along {001} crystallographic planes, however, they were distributed discretely, with several oxide and sulphide phases observed. In this work, we image, analyse and identify the phases formed during the cracking and corrosion of CMSX-4® superalloy and hypothesise on the complex chemical interactions that take place during crack initiation.

Soon after the discovery of superconductivity in Sr2RuO4 (SRO) a quarter-century ago, it was conjectured that its order parameter (OP) has a form similar to that realized in the superfluid phases of 3-He, namely, odd parity and spin triplet. While the chiral p-wave pairing believed to be realized in the A phase of that system was favored by several early experiments, in particular, the muon spin rotation and the Knight shift measurements published in 1998, the original Knight shift result was called into question in early 2019, raising the question as to whether the “chiral p-wave”, or even the spin-triplet pairing itself, is indeed realized in SRO. In this brief pedagogical review, we will address this question by counterposing the currently accepted results of Knight shift, polarized neutron scattering, spin counterflow half-quantum vortex (HQV), and Josephson experiments, which probe the spin and orbital parts of the OP, respectively, with predictions made both by standard BCS theory and by more general arguments based only on (1) the symmetry of the Hamiltonian including the spin-orbital terms, (2) thermodynamics, and (3) the qualitative experimental features of the material. In the hope of enhancing readers’ intuitive grasp of these arguments, we introduce a notation for triplet states alternative to the more popular “d-vector” one which we believe well suited to SRO. We conclude that the most recent Knight shift and polarized neutron scattering experiments do not exclude in the bulk the odd-parity, spin-triplet “helical” states allowed by the symmetry group of SRO but do exclude the “chiral p-wave”, ${{{\varGamma }}}_{5}^{-}$ state. On the other hand, the Josephson and in-plane-magnetic-field stabilized HQV experiments showed that the pairing symmetry in SRO cannot be of the even-parity, spin-singlet type, and furthermore, that in the surface region or in samples of mesoscopic size the d-vector must be along the c axis, thus excluding all bulk p-wave states except ${{{\varGamma }}}_{5}^{-}$ . Possible resolution of this rather glaring prima facie contradiction is discussed, taking into account implications of other important experiments on SRO, including that of the muon spin rotation, which are touched upon briefly only towards the end of this article.

I present some rather selective reminiscences of my long career in physics, from my doctoral work to the present. I do not spend time on topics such as the nuclear magnetic resonance behavior of 3He, as I have reviewed the history extensively elsewhere, but rather concentrate, first, on my long-running project to make condensed matter physics relevant to questions in the foundations of quantum mechanics, and second, on various rather “quirky” problems such as an attempt to amplify the effects of the parity violation due to the weak interaction to a macroscopic level, and an unconventional proposal for the mechanism of the first-order phase transition between the A and B phases of superfluid liquid 3He.

The site-specific immobilization of histidine-tagged proteins to patterns formed by far-field and near-field exposure of films of aminosilanes with protein-resistant photolabile protecting groups is demonstrated. After deprotection of the aminosilane, either through a mask or using a scanning near-field optical microscope, the amine terminal groups are derivatized first with glutaraldehyde and then with N-(5-amino-1-carboxypentyl)iminodiacetic acid to yield a nitrilo-triacetic-acid-terminated surface. After complexation with Ni(2+), this surface binds histidine-tagged GFP and CpcA-PEB in a site-specific fashion. The chemistry is simple and reliable and leads to extensive surface functionalization. Bright fluorescence is observed in fluorescence microscopy images of micrometer- and nanometer-scale patterns. X-ray photoelectron spectroscopy is used to study quantitatively the efficiency of photodeprotection and the reactivity of the modified surfaces. The efficiency of the protein binding process is investigated quantitatively by ellipsometry and by fluorescence microscopy. We find that regions of the surface not exposed to UV light bind negligible amounts of His-tagged proteins, indicating that the oligo(ethylene glycol) adduct on the nitrophenyl protecting group confers excellent protein resistance; in contrast, exposed regions bind His-GFP very effectively, yielding strong fluorescence that is almost completely removed on treatment of the surface with imidazole, confirming a degree of site-specific binding in excess of 90%. This simple strategy offers a versatile generic route to the spatially selective site-specific immobilization of proteins at surfaces.

Many biological mechanisms can be considered to be low-dimensional systems: their function is determined by molecular objects of reduced dimensionality. Bacterial photosynthesis is a very good example: the photosynthetic pathway is contained within nano-objects (vesicles) whose function is determined by the numbers and nanoscale organization of membrane proteins and by the ratios of the different types of protein that they contain. Systems biology has provided computational models for studying these processes, but there is a need for experimental platforms with which to test their predictions. This Invited Feature Article reviews recent work on the development of tools for the reconstruction of membrane processes on solid surfaces. Photochemical methods provide a powerful, versatile means for the organization of molecules and membranes across length scales from the molecular to the macroscopic. Polymer brushes are highly effective supports for model membranes and versatile functional and structural components in low-dimensional systems. The incorporation of plasmonic elements facilitates enhanced measurement of spectroscopic properties and provides an additional design strategy via the exploitation of quantum optical phenomena. A low-dimensional system that incorporates functional transmembrane proteins and a mechanism for the in situ measurement of proton transport is described.

Poly(oligoethylene glycol methyl ether methacrylate) (POEGMEMA) brushes, grown from silicon oxide surfaces by surface-initiated atom transfer radical polymerization (SI-ATRP), were end-capped by reaction with sodium azide leading to effective termination of polymerization. Reduction of the terminal azide to an amine, followed by derivatization with the reagent of choice, enabled end-functionalization of the polymers. Reaction with bromoisobutryl bromide yielded a terminal bromine atom that could be used as an initiator for ATRP with a second, contrasting monomer (methacrylic acid). Attachment of a nitrophenyl protecting group to the amine facilitated photopatterning: when the sample was exposed to UV light through a mask, the amine was deprotected in exposed regions, enabling selective bromination and the growth of a patterned brush by ATRP. Using this approach, micropatterned pH-responsive poly(methacrylic acid) (PMAA) brushes were grown on a protein resistant planar poly(oligoethylene glycol methyl ether methacrylate) (POEGMEMA) brush. Atomic force microscopy analysis by tapping mode and PeakForce quantitative nanomechanical mapping (QNM) mode allowed topographical verification of the spatially specific secondary brush growth and its stimulus responsiveness. Chemical confirmation of selective polymer growth was achieved by secondary ion mass spectrometry (SIMS).

It is an honor and a pleasure to have been invited to give a talk in this conference celebrating the memory of the late Professor Abdus Salam. To my regret, I did not know Professor Salam personally, but I am very aware of his work and of his impact on my area of specialization, condensed matter physics, both intellectually through his ideas on spontaneously broken symmetry and more practically through his foundation of the ICTP. Since I assume that most of this audience are not specialized in condensed-matter physics, I thought I would talk about one topic which to some extent bridges this field and the particle-physics interests of Salam, namely Majorana fermions (M.F.s). However, as we shall see, the parallels which are often drawn in the current literature may be a bit too simplistic. I will devote most of this talk to a stripped-down exposition of the current orthodoxy concerning M.F.s. in condensed-matter physics and their possible applications to topological quantum computing (TQC), and then at the end briefly indicate why I believe this orthodoxy may be seriously misleading.

Friction force microscopy has been used to demonstrate that biocompatible, lubricious poly(2-(methacryloyloxy)ethylphosphorylcholine) (PMPC) brushes exhibit different frictional properties depending on the medium (methanol, ethanol, 2-propanol, and water; the latter also with different quantities of added salt). The chemical functionalization of the probe (amine-, carboxylic acid-, and methyl-terminated probes were used) is not as important as the medium in determining the contact mechanics. For solvents such as methanol, where the adhesion between AFM probe and PMPC brushes is negligible, a linear friction-load relationship is observed. In contrast, the friction-load plot is nonlinear in ethanol or water, media in which stronger adhesion is measured. For ethanol, the data indicate Johnson-Kendall-Roberts (JKR) mechanics, whereas the Derjaguin-Muller-Toporov (DMT) model provided a good fit for the data acquired in water. Contact mechanics on zwitterionic PMPC brushes immersed in aqueous solutions of varying ionic strength followed the same trend, with high adhesion energies being correlated with a nonlinear friction-load relationship. These results can be rationalized by treating the friction force as the sum of a load-dependent term, attributed to molecular plowing, and an area-dependent shear term. In a good solvent for PMPC such as methanol, the shear term is negligible and the sliding interaction is dominated by molecular plowing. However, the adhesion energy is significantly larger in water and ethanol and the shear term is no longer negligible.

High-temperature corrosion fatigue, a combination of corrosion with a fatigue cycle, is an emerging generic issue affecting power generation and aero gas turbine engines and has the potential to limit component life. Historically, surface treatments, such as shot peening have been used to improve component life and have been optimised for fatigue response. Research into optimisation of shot peening techniques for hot corrosion and high-temperature corrosion fatigue has shown 6–8A 230H 200% coverage to provide overall optimum performance for nickel-based superalloy 720Li based on the limited data within this study. Utilisation of electron backscatter diffraction techniques, in combination with detailed assessment of corrosion products have been undertaken as part of this work. The resultant cold-work visualisation technique provides a novel method of determining the variation in material properties due to the shot peening process and the interaction with hot corrosion. Through this work it has been shown that all three shot peening outputs must be considered to minimise the effect of corrosion fatigue, the cold work, residual stress and surface roughness. Further opportunity for optimisation has also been identified based on this work.

Using scanning near-field lithography (SNP), it is possible to pattern molecules at surfaces with a resolution as good as 9 nm [M. Montague, R. E. Ducker, K. S. L. Chong, R. J. Manning, F. J. M. Rutten, M. C. Davies and G. J. Leggett, Langmuir 23 (13), 7328–7337 (2007)]. However, in common with other scanning probe techniques, SNP has previously been considered a serial process, hindering its use in many applications. IBM’s “Millipede” addresses this problem by utilizing an array of local probes operating in parallel. Here, we describe the construction of two instruments (Snomipedes) that integrate near-field optical methods into the parallel probe paradigm and promise the integration of top–down and bottom–up fabrication methods over macroscopic areas. Both are capable of performing near-field lithography with 16 probes in parallel spanning approximately 2 mm. The instruments can work in both ambient and liquid environments, key to many applications in nanobiology. In both, separate control of writing is possible for each probe. We demonstrate the deprotection of self-assembled monolayers of alkylsilanes with photocleavable protecting groups and subsequent growth of nanostructured polymer brushes from these nanopatterned surfaces by atom-transfer radical polymerization.

Scanning near-field photolithography (SNPL) has recently shown its great potential for fabricating various structures at the nanoscale. However, the low throughput of SNPL is a barrier to wider applications. Additionally, to extend SNPL to operation in aqueous environments is of significant importance to applications in nanobiology, such as sensing, screening and protein adsorption studies. Here we describe a new instrument (a ''Snomipede'') that facilitates the parallel execution of SNPL under water using an AFM-style cantilever probe array and liquid cell. A feature size (full width at half maximum (FWHM)) of around 70nm has been achieved for dot arrays fabricated in parallel under water.

A history is given of liquid 3He research from the time when 3He first became available following World War II through 1972 when the discovery of the superfluid phases was made. The Fermi liquid nature was established early on, and the Landau Fermi liquid theory provided a framework for understanding the interactions between the Fermions (quasiparticles). The theory’s main triumph was to predict zero sound, which was soon discovered experimentally. Experimental techniques are treated, including adiabatic demagnetization, dilution refrigerator technology, and Pomeranchuk cooling. A description of the superfluid 3He discovery experiments using the latter two of these techniques is given. While existing theories provided a basis for understanding the newly discovered superfluid phases in terms of l>0 Cooper pairs, the unexpected stability of the A phase in the high-P, high-T region of the phase diagram needed for its explanation a creative leap beyond the BCS paradigm. The use of sum rules to interpret some of the unusual magnetic resonance in liquid 3He is discussed. Eventually a complete theory of the spin dynamics of superfluid 3He was developed, which predicted many of the exciting phenomena subsequently discovered.

After a brief review of the phenomenology of superconductivity and of its generic explanation in terms of the concept of off-diagonal long-range order, I first survey the original Bardeen-Cooper-Schrieffer (BCS) weak-coupling model and some extensions of it. I then turn to systems such as the heavy fermions and the cuprates where the superconductivity is generally believed to be due to an all-electronic mechanism, and ask how much information we get about this mechanism from quite general energetic and other considerations, without committing ourselves to any particular microscopic model.

The frictional properties of poly(2-(methacryloyloxy)ethylphosphorylcholine) (PMPC) brushes grown from planar silicon surfaces by atom transfer radical polymerization (ATRP) have been characterized using in situ friction force microscopy (FFM). The dry thicknesses of the PMPC brushes ranged from 20 to 421 nm. For brush layers with dry thicknesses greater than ca. 100 nm, the coefficient of friction decreased with increasing film thickness. For shorter brushes, the coefficient of friction varied little with brush thickness. We hypothesize that the amount of bound solvent increases as the brush length increases, causing the osmotic pressure to increase and yielding a reduced tendency for the brush layer to deform under applied load. A comparison of the force-displacement plots acquired for various PMPC brushes under water supports this hypothesis, since a greater repulsive force is measured for thicker brushes. FFM was also used to investigate the well-known co-nonsolvency behavior exhibited by PMPC chains. For a PMPC brush layer of 307 nm dry thickness, the friction force was determined as a function of the volume fraction of alcohol in alcohol/water mixtures. Unlike a previous macroscopic study, a significant increase in the coefficient of friction was observed for ethanol/water mixtures at a volume fraction of 90%. This is attributed to brush collapse due to co-nonsolvency, leading to loss of hydration of the brush chains and hence substantially reduced lubrication. Force measurements normal to the surface indicate much greater hysteresis between approaching and retraction curves under co-nonsolvency conditions. However, no such effect was observed for 2-propanol/water and methanol/water mixtures over a wide range of volume fractions, in agreement with recent ellipsometric studies of PMPC brushes.

The “Millipede”, developed by Binnig and co-workers (Bining, G. K.; et al. IBM J. Res. Devel. 2000, 44, 323.), elegantly solves the problem of the serial nature of scanning probe lithography processes, by deploying massive parallelism. Here we fuse the “Millipede” concept with scanning near-field photolithography to yield a “Snomipede” that is capable of executing parallel chemical transformations at high resolution over macroscopic areas. Our prototype has sixteen probes that are separately controllable using a methodology that is, in principle, scalable to much larger arrays. Light beams generated by a spatial modulator or a zone plate array are coupled to arrays of cantilever probes with hollow, pyramidal tips. We demonstrate selective photodeprotection of nitrophenylpropyloxycarbonyl-protected aminosiloxane monolayers on silicon dioxide and subsequent growth of nanostructured polymer brushes by atom-transfer radical polymerization, and the fabrication of 70 nm structures in photoresist by a Snomipede probe array immersed under water. Such approaches offer a powerful means of integrating the top-down and bottom-up fabrication paradigms, facilitating the reactive processing of materials at nanometer resolution over macroscopic areas.

Following the success of the original BCS theory as applied to superconductivity in metals, it was suggested that the phenomenon of Cooper pairing might also occur in liquid 3- He , though unlike the metallic case the pairs would most likely form in an anisotropic state, and would then lead in this neutral system to superfluidity. However, what had not been anticipated was the richness of the phenomena which would be revealed by the experiments of 1972. In the first place, even in a zero magnetic field there is not one but two superfluid phases, and the explanation of this involves ideas concerning "spin fluctuation feedback" which have no obvious analog in metals. Secondly, the anisotropic nature of the pair wave function, which in the case of the B phase is quite subtle, and the fact that the orientation must be the same for all the pairs, leads to a number of qualitatively new effects, in particular to a spectacular amplification of ultra-weak interactions seen most dramatically in the NMR behavior. In this chapter I review the application of BCS theory to superfluid 3- He with emphasis on these novel features.

We demonstrate that interferometric lithography provides a fast, simple approach to the production of patterns in self-assembled monolayers (SAMs) with high resolution over square centimeter areas. As a proof of principle, two-beam interference patterns, formed using light from a frequency-doubled argon ion laser (244 nm), were used to pattern methyl-terminated SAMs on gold, facilitating the introduction of hydroxyl-terminated adsorbates and yielding patterns of surface free energy with a pitch of ca. 200 nm. The photopatterning of SAMs on Pd has been demonstrated for the first time, with interferometric exposure yielding patterns of surface free energy with similar features sizes to those obtained on gold. Gold nanostructures were formed by exposing SAMs to UV interference patterns and then immersing the samples in an ethanolic solution of mercaptoethylamine, which etched the metal substrate in exposed areas while unoxidized thiols acted as a resist and protected the metal from dissolution. Macroscopically extended gold nanowires were fabricated using single exposures and arrays of 66 nm gold dots at 180 nm centers were formed using orthogonal exposures in a fast, simple process. Exposure of oligo(ethylene glycol)-terminated SAMs to UV light caused photodegradation of the protein-resistant tail groups in a substrate-independent process. In contrast to many protein patterning methods, which utilize multiple steps to control surface binding, this single step process introduced aldehyde functional groups to the SAM surface at exposures as low as 0.3 J cm(-2), significantly less than the exposure required for oxidation of the thiol headgroup. Although interferometric methods rely upon a continuous gradient of exposure, it was possible to fabricate well-defined protein nanostructures by the introduction of aldehyde groups and removal of protein resistance in nanoscopic regions. Macroscopically extended, nanostructured assemblies of streptavidin were formed. Retention of functionality in the patterned materials was demonstrated by binding of biotinylated proteins.

The UV photodegradation of protein-resistant poly(oligo(ethylene glycol) methacrylate) (POEGMA) bottle-brush films, grown on silicon oxide by surface-initiated atom radical transfer polymerization, was studied using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Exposure to light with a wavelength of 244 nm caused a loss of polyether units from the brush structure and the creation of aldehyde groups that could be derivatized with amines. An increase was measured in the coefficient of friction of the photodegraded polymer brush compared to the native brush, attributed to the creation of a heterogeneous surface film, leading to increased energy dissipation through film deformation and the creation of new polar functional groups at the surface. Exposure of the films through a photomask yielded sharp, well-defined patterns. Analysis of topographical images showed that physical removal of material occurred during exposure, at a rate of 1.35 nm J(-1) cm(2). Using fluorescence microscopy, the adsorption of labeled proteins onto the exposed surfaces was studied. It was found that protein strongly adsorbed to exposed areas, while the masked regions retained their protein resistance. Exposure of the film to UV light from a scanning near-field optical microscope yielded submicrometer-scale patterns. These data indicate that a simple, rapid, one-step photoconversion of the poly(OEGMA) brush occurs that transforms it from a highly protein-resistant material to one that adsorbs protein and can covalently bind amine-containing molecules and that this photoconversion can be spatially addressed with high spatial resolution.

The optical and electrical properties of dodecanethiol-stabilized nanoparticles (6 nm diameter gold core) have been investigated over a range of film thicknesses and temperatures. The surface plasmon resonance absorbance is found to be dependent on temperature. Heating of the nanoparticle film causes desorption of the thiol from the surface of the gold nanoparticle, resulting in irreversible changes to the absorption spectra of the nanoparticle film. Atomic force microscopy images of the samples before and after heating for different film thicknesses reveal structural changes and increased domain connectivity for thicker films leading to sub-10 ohm resistances measured for the 15-layer film.

The synthesis of alpha-thioacetate terminated quaterthiophene and phenylene-thiophene materials, possessing thioacetate, oxetane, and alkyl groups at their omega-termini, is described. After deprotection these molecules were adsorbed onto Au films and the resulting self-assembled monolayers were characterized by X-ray photoelectron spectroscopy (XPS) and friction force microscopy (FFM). FFM indicated that monolayers formed by the dithioacetates had the highest coefficients of friction, followed by the oxetane-terminated adsorbates, with the alkyl-functionalized materials showing the lowest friction coefficients. These data may be understood in terms of differences in molecular packing. The quaterthiophene adsorbates also yielded higher friction coefficients than their phenylene-thiophene counterparts. Micrometer-scale patterns were fabricated by mask-based exposure to 244 nm light, and characterized by FFM. Nanometer-scale patterns were fabricated using near-field exposure and characterized by FFM. The images obtained demonstrated that features of conjugated oligomers with high spatial resolution (59 nm, ca. lambda/4) were achievable.

This paper presents the results of a study targeted at characterising the oxidation behaviour of a new nickel based disc alloy (RR1000) at intermediate temperatures. Isothermal exposures were carried out using a thermo-microbalance at temperatures in the range 700 – 800°C for exposures up to 200 hours. Cyclic oxidation exposures were carried out at, 700 and 750°C for up to 1000 hours with 100 hour cycles, using mass change to monitor the materials performance. The mass gain data obtained have been used to derive oxidation reaction rate parameters, using established methodologies, with parabolic rate constants varying between 1.4×10–5 mg2/cm4/h at 700°C and 8.4×10–4 mg2/cm4/h at 800°C.Surface oxides were initially analysed using scanning electron microscope/energy dispersive X-ray analysis (SEM/EDX) and X-ray diffraction (XRD) techniques. The results showed that slowly-growing chromium-rich oxide scales had formed on the surface of the samples during these exposures. A more detailed study of cross-...

Central to the advancement of friction force microscopy (FFM) as a quantitative surface analysis technique is the establishment of clear relationships between the organization and composition of surfaces and data acquired from FFM. As a step toward this goal, FFM has been applied to measurement of the kinetics of a surface-confined reaction, namely, the esterification of alcohol-terminated self-assembled monolayers (SAMs) by trifluoroacetic anhydride. The kinetics were studied initially using contact angle goniometry. The data obtained were found to be well described by a Langmuir adsorption isotherm. The progress of the reaction was also monitored by X-ray photoelectron spectroscopy, and comparative studies carried out using FFM. By using a simple numerical analysis of the FFM data, it has been possible to obtain quantitative information on surface composition. The resulting measurements of the fraction of derivatized molecules have been compared with compositional data obtained from XPS and contact angle goniometry, and found to be in excellent agreement, establishing unequivocally the capability of FFM as a quantitative surface analysis technique.

The frictional properties of spun-cast films of polystyrene and poly(methyl methacrylate) (PMMA) have been characterized using friction force microscopy (FFM). In air, the friction-load relationship was found to obey Johnson-Kendall-Roberts mechanics, but under ethanol, it was found to fit Amontons' Law. The coefficient of friction measured under ethanol was found to increase with increasing molecular weight, up to a molecular weight close to the bulk critical molecular weight for entanglement. At greater values than this, the coefficient of friction changed comparatively little with molecular weight. It is suggested that at molecular weights below Mc, the frictional interaction is dominated by plowing of the tip between polymer molecules; as molecular weight increases, so the viscosity of the film increases and the coefficient of friction increases. After the onset of entanglement, the mechanism of energy dissipation changes to one in which the tip sticks in loops of polymer between entanglements, extending the chains until at a critical stress, the contact is broken. The frictional interaction is thus comparatively invariant with molecular weight. FFM was also used to investigate the kinetics of the UV-induced modification of PMMA. A progressive decrease in the coefficient of friction was observed as a function of the time that the film was exposed to UV light, a result which was correlated to a gradual reduction in the molecular weight of the polymer and, hence, the entanglement density of the system.

The photolithographic modification of monolayers provides a versatile and powerful means of fabricating functionalized nanostructured surfaces. In this contribution, we present photosensitive thiol-bearing aryl ester groups which are capable of undergoing the so-called photo-Fries rearrangement to yield hydroxyketones. Phenyl 16-mercaptohexadecanoate was prepared by a three-step synthesis. This molecule undergoes a photoisomerization reaction upon illumination with UV light at ca. 250 nm. Subsequently this molecule was applied as a self-assembled monolayer on gold. Following photochemical modification, the adsorbates were selectively derivatized to yield amino-functionalized surfaces using a simple two-step reaction. This reaction was monitored by X-ray photoelectron spectroscopy and contact angle measurements and friction force microscopy. Micrometer-scale patterned surfaces were produced using a contact mask in conjunction with a frequency-doubled argon ion laser (lambda=244 nm). Near-field optical exposure was carried out by coupling the laser to a scanning near-field optical microscope and yielded nanometer-scale resolution. Following derivatization, the resulting structures were analyzed by friction force microscopy. Clear contrast was observed in the friction signal following surface modification.

We performed an experimental study of the temperature and doping dependence of the energy-loss function of the bilayer and trilayer Bi-cuprate family. The primary aim is to obtain information on the energy stored in the Coulomb interaction between the conduction electrons, on the temperature dependence thereof, and on the change of Coulomb interaction when Cooper-pairs are formed. We performed temperature-dependent ellipsometry measurements on several Bi$_2$Sr$_2$CaCu$_2$O$_{8-x}$ single crystals: under-doped with $T_c=60, 70$ and 83K, optimally doped with $T_c=91$K, overdoped with $T_c=84, 81, 70$ and $58$K, as well as optimally doped Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+x}$ with $T_c=110$K. Our first observation is that, as the temperature drops through $T_c$, the loss function in the range up to 2~eV displays a change of temperature dependence as compared to the temperature dependence in the normal state. This effect at - or close to - $T_c$ depends strongly on doping, with a sign-change for weak overdoping. The size of the observed change in Coulomb energy, using an extrapolation with reasonable assumptions about its $q$-dependence, is about the same size as the condensation energy that has been measured in these compounds. Our results therefore lend support to the notion that the Coulomb energy is an important factor for stabilizing the superconducting phase. Due to the restriction to small momentum, our observations do not exclude a possible significant contribution to the condensation energy of the Coulomb energy associated to the region of $q$ around $(\pi,\pi)$., Comment: Revised version

Gradients of surface chemical composition were prepared by performing a selective photo-oxidation of self-assembled monolayers (SAMs) of alkanethiols adsorbed on a gold surface, using an ultraviolet laser (244 nm) coupled to an etched optical fiber. In the center of the exposed region, uniform oxidation occurs facilitating uniform replacement of the oxidation products with a second, contrasting thiol, while at the perimeter of the exposed region a gradient of exposure occurs, leading to a gradient of photochemical reaction and, following immersion of the sample in a solution of a contrasting thiol, a gradient of composition. Variation in the exposure is possible by varying the time or the power, and both the height and the width of the resulting gradient may be controlled straightforwardly yielding a simple but highly effective means of generating molecular-scale chemical gradients.

Self-assembled monolayers of alkylphosphonic acids (APA) have been patterned at the micrometer and nanometer scale by photochemical methods. Exposure of APA monolayers to light with a wavelength of 244 nm leads to scission of the C−P bond and desorption of the alkyl chain from the surface. Immersion of the specimen in a solution of a second APA leads to adsorption at the surface in the exposed regions. Immersion in a solution of hydroxide ions leads to etching of the exposed regions of the aluminum film. UV exposure appears to anneal the aluminum oxide film, conferring increased resistance to etching at high exposures and a switching the function of the monolayer from a positive to a negative tone resist. At intermediate exposures, nanoscale trenches form at the perimeters of exposed regions. Near-field exposure of the phosphonic acid structures, using a UV laser coupled to a scanning near-field optical microscope, yields well-defined nanostructured features following development of the pattern in aqueous...

The UV photo-oxidation of oligo(ethylene glycol) (OEG)-terminated self-assembled monolayers (SAMs) has been studied using static secondary ion mass spectrometry, X-ray photoelectron spectroscopy, contact angle measurement, and friction force microscopy. OEG-terminated SAMs are oxidized to yield sulfonates, but photodegradation of the OEG chain also occurs on a more rapid time scale, yielding degradation products that remain bound to the surface via gold-sulfur bonds. The oxidation of these degradation products is the rate-limiting step in the process. Photopatterning of OEG-terminated SAMs may be accomplished by using a mask and suitable light source or by using scanning near-field photolithography (SNP) in which the mask is replaced by a scanning near-field optical microscope coupled to a UV laser. Using SNP, it is possible to fabricate patterns in SAMs with a full width at half-maximum height (fwhm) as small as 9 nm, which is approximately 15 times smaller than the conventional diffraction limit. SNP-patterned OEG-terminated SAMs may be used to fabricate protein nanopatterns. By adsorbing carboxylic acid-terminated thiols into oxidized regions and converting these to active ester intermediates, it has been possible to fabricate lines of protein molecules with widths of only a few tens of nanometers.

In recent years, Dynamic Nuclear Polarization (DNP) has re-emerged as a means to ameliorate the inherent problem of low sensitivity in nuclear magnetic resonance (NMR). Here, we present a novel approach to DNP enhanced liquid-state NMR based on rapid melting of a solid hyperpolarized sample followed by 'in situ' NMR detection. This method is applicable to small (10nl to 1μl) sized samples in a microfluidic setup. The method combines generic DNP enhancement in the solid state with the high sensitivity of stripline (1)H NMR detection in the liquid state. Fast cycling facilitates options for signal averaging or 2D structural analysis. Preliminary tests show solid-state (1)H enhancement factors of up to 500 for H2O/D2O/d6-glycerol samples doped with TEMPOL radicals. Fast paramagnetic relaxation with nitroxide radicals, In nonpolar solvents such as toluene, we find proton enhancement factors up to 400 with negligible relaxation losses in the liquid state, using commercially available BDPA radicals. A total recycling delay (including sample freezing, DNP polarization and melting) of about 5s can be used. The present setup allows for a fast determination of the hyper-polarization as function of the microwave frequency and power. Even at the relatively low field of 3.4T, the method of rapid melting DNP can facilitate the detection of small quantities of molecules in the picomole regime.

A novel poly(amino acid methacrylate) brush comprising zwitterionic cysteine groups (PCysMA) was utilized as a support for lipid bilayers. The polymer brush provides a 12-nm-thick cushion between the underlying hard support and the aqueous phase. At neutral pH, the zeta potential of the PCysMA brush was ∼-10 mV. Cationic vesicles containing25% DOTAP were found to form a homogeneous lipid bilayer, as determined by a combination of surface analytical techniques. The lipid mobility as measured by FRAP (fluorescence recovery after photobleaching) gave diffusion coefficients of ∼1.5 μm(2) s(-1), which are comparable to those observed for lipid bilayers on glass substrates.

In 1964, the year in which the present author obtained his doctorate, the highest known transition temperature Tc to the superconducting state was around 20 K. In that year, Professor Vitaly Ginzburg made a striking prediction; building on the work of Little [1], who had proposed a purely electronic mechanism to raise Tc, he predicted [2] that transition temperatures of the order of room temperature would indeed some day be achieved, and moreover that this was most likely to happen in a strongly layered (quasi-two-dimensional) system (rather than in the one-dimensional systems that Little had considered). As is well known, both these predictions were verified 22 years later, when transition temperatures over 90 K (subsequently raised to over 160 K) were realized in a class of cuprate materials whose most striking structural feature is indeed their metallic CuO2 planes separated by much less conducting materials. I would like, therefore, to devote this brief essay to the question: What is the role, in the genesis of high-temperature superconductivity in the cuprates, of the quasi-two-dimensionality of the CuO2 planes? In particular, I shall be interested in the question (which has, of course, already attracted much attention in the literature): why, in the various homologous cuprate series (T1, Hg, Bi, etc.) does Tc show a characteristic and reproducible dependence (see below) on the number n of CuO2 planes per multilayer? Let me start with a couple of remarks about the raw data. First, it seems to be a rather general observation, not confined to the cuprates, that compared to other materials in their general class, strongly layered materials have rather high transition tempera

Monolayers of alkylphosphonic acids (APA) and alkylcarboxylic acids (ACA) on magnetron-sputtered aluminum films have been investigated by friction force microscopy (FFM), contact angle measurement, and polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS). Clear evidence has been provided from PM-IRRAS that friction coefficients, determined from FFM data, may be correlated directly with variations in adsorbate molecular structure. The friction coefficient increased with the length of the adsorbate molecule, but reached a limiting value when the alkyl chain of the adsorbate contained eight carbons in the case of APA or 12 carbons in the case of ACA. For a given alkyl chain length, APA monolayers yielded coefficients of friction that were similar to those of monolayers of alkylthiols of the same length, but smaller than those of ACA. These data indicate that APA monolayers are better ordered than ACA monolayers. These inferences were supported by PM-IRRAS data, which enabled the density of gauche defects to be estimated and correlated with variations in the coefficient of friction.

Exposure of thiol-stabilized gold nanoparticles supported on silicon wafers to UV light leads to oxidation of the thiol molecules and coagulation of the nanoparticles, forming densified structures that are resistant to removal by solvent exposure. Unoxidized particles may, in contrast, readily be removed leaving gold structures behind at the surface. This process provides a convenient and simple route for the fabrication of gold structures with dimensions ranging from micrometers to nanometers. The use of masks enables micrometer-scale structures to be fabricated rapidly. Exposure of nanoparticles to light from a near-field scanning optical microscope (NSOM) leads to the formation of gold nanowires. The dimensions of these nanowires depend on the method of preparation of the film: for spin-cast films, a width of 200 nm was achieved. However, this was reduced significantly, to 60 nm, for Langmuir-Schaeffer films.

The element helium comes in two (stable) forms. 4 He and 5 He; at low temperatures and pressures both form liquids rather than solids. The liquid phase of the common isotope, ' 1 He, was realized' nearly a century ago, and since 1938 has been known to show, at temperatures below about 2 K, the property of superfluidity-the ability to flow through the narrowest capillaries without apparent friction. The light isotope, 2 He, is believed to be of quite a different nature; however,because of its similarity to the electrons in metals, which at low temperatures sometimes form Cooper pairs and thereby become superconducting, theorists in the 1960s and early 1970s had speculated that something similar might happen in liquid 3 He, which would then also show superfluidity though for reasons rather different than 4 He. In 1972 nuclear magnetic resonance (NMR) experiments at Cornell University revealed the existence, below 3 millidegrees, if two new phases, one of which displayed extraordinary NMR properties. Anthony Leggett is one of the theorists who succeeded in fitting the experimental properties into the Cooper-pairing scenario; in particular, he explained the NMR behavior and predicted further novel NMR phenomena which were subsequently found.

Molecular features with widths of only 20 nm have been fabricated in self-assembled monolayers of alkanethiols on gold using a new lithographic tool, scanning near-field photolithography, based upon the use of a near-field scanning optical microscope (NSOM) coupled to a UV laser. Quite unexpectedly it has proved possible to routinely fabricate structures significantly smaller than the aperture in the NSOM probe. This exceptional performance is strongly correlated with the morphology of the gold film. In particular, the best results are achieved on films with comparatively small grain sizes. In contrast, the use of atomically flat, epitaxially deposited gold films leads to a minimum feature size comparable to the aperture diameter (ca 50 nm). It is concluded that nonradiative interactions (possibly the excitation of surface plasmons) between the gold substrate and the fiber lead to a pronounced focusing of the electric field beneath the aperture.

By using small inclusions of liquid 3 He trapped in a solid 4 He matrix, it may be possible to study a sample of the superfluid A phase in the regime where quantum fluctuations of the relative phase of the “up” and “down” Cooper pairs are no longer negligible. Under these conditions there is little doubt that a standard quantum-mechanical (QM) calculation of the NMR dynamics should correctly describe the behavior of the total magnetization of a large ensemble of independent inclusions. However, it is less obvious that it should describe the behavior of a single inclusion on a single run of the experiment, and indeed it is tempting to argue that a “spontaneous breaking of the symmetry” corresponding to the relative phase should occur, analogously to what (allegedly) happens in the interference of two independent Bose condensates. Here I argue that the prima facie analogy is misleading, and that the QM calculation indeed describes the behavior of a single inclusion.

Aligned regularly spaced ridges form immediately on scanning the surface of uniaxially oriented poly(ethylene terephthalate) (PET) at applied loads of greater than 15 nN. This contrasts with nanowear of biaxially oriented PET film studied previously [B.D. Beake, et al., Polymer 42 (2001) 7025], which proceeds more slowly over a number of scan cycles by fatigue wear. Differences in nanowear are interpreted in terms of the differences in crystallinity and mechanical properties with processing history. Nanoindentation shows that the biaxially oriented material is harder, higher modulus and has a higher H/E ratio. It is suggested that the stick-slip process that leads to the formation of regularly spaced ridges on the polymeric surface proceeds smoothly on the uniaxially oriented PET film as the yield threshold for plastic deformation is exceeded at these contact pressures. The higher crystallinity of the biaxially oriented material results in a higher yield stress thus imparting a barrier to the stick-slip process. It is necessary for some local damage to occur over a number of scan cycles before the surface has a low enough yield stress that the stick-slip process can proceed efficiently. Results are compared to the nanowear of other polymeric materials and a map of the major deformation processes in nanowear is proposed for the first time. © 2003 Elsevier B.V. All rights reserved.

I raise, and discuss qualitatively, some conceptual issues concerning the interface between the crystalline solid and superfluid liquid phases of 4He emphasizing, in particular, the fact that the ground-state wave functions of the two phases are prima facie qualitatively quite different, in that the superfluid liquid phase possesses off-diagonal long-range order (ODLRO), while the crystalline solid does not. The fact that the statics and dynamics of the interface do not appear to be particularly sensitive to the presence of ODLRO in the liquid is tentatively explained by the fact that because of a subtlety associated with the Bose statistics obeyed by the atoms, the solid and liquid wave functions are not locally very different.

The Eighth Eugene Feenberg Medal is awarded to Philippe Nozières in recognition of his many pathbreaking contributions to many-body theory, including • His definitive work on the properties of the free electron gas, in particular in the region of realistic metallic densities, • his rigorous development of the theory of a normal Fermi liquid, which provided a firm microscopic foundation for the Landau theory, • his analysis of the nonequilibrium thermodynamics of 3-He solid-liquid mixtures, • his exact solution to the X-ray edge problem, • his elegant formulation of the low-temperature solution to the single-channel Kondo problem in the language of Fermi-liquid theory, • his introduction of the many-channel problem as a new class of quantum impurity systems, and • his innovative work on the static and dynamic behavior of the liquid-solid interface.

For a harmonically trapped dilute Bose gas with uniformly repulsive interactions which is assumed to satisfy a certain condition on the extensivity of fluctuations, I find on upper bound on the condensate fraction f. If BEC is defined by the condition that f>const.N−α, α

Nanolithography of self-assembled monolayers (SAMs) has been performed by the new technique of scanning near-field photolithography (SNP). Patterns of parallel lines written by SNP have subsequently either been used to generate compositional chemical patterns or been transferred into the underlying substrate by wet etch techniques. Lateral force microscopy (LFM) and atomic force microscopy (AFM) analysis has indicated that the line width of both compositional chemical patterns in SAMs and structures in gold is limited only by the aperture of the fiber tip used to deliver UV light. Features only 55 ± 5 nm wide have been etched into gold films using this method.

I present the motivation for experiments which attempt to generate, and verify the existence of, quantum superpositions of two or more states which are by some reasonable criterion `macroscopically' distinct, and show that various a priori objections to this programme made in the literature are flawed. I review the extent to which such experiments currently exist in the areas of free-space molecular diffraction, magnetic biomolecules, quantum optics and Josephson devices, and sketch possible future lines of development of the programme.

I review three sets of experiments conducted in the last decade, in which superfluid 3He was irradiated with high-energy particles and the nucleation either of vorticity or of the A–B phase transition reported. I consider how far the known atomic physics constrains possible scenarios for such nucleation, and comment on two such scenarios which have appeared in the literature, namely the “baked-Alaska” and “cosmological” (Kibble–Zurek–Volovik) models. I point out that there is a fundamental difference between the problems of nucleation of vorticity on the one hand and the B phase on the other: and that as a result, it is by no means necessary that the same scenario should describe both phenomena. In an appendix I discuss possible sinks of energy in the calorimetric (Grenoble–Lancaster) experiment, with the conclusion that it is entirely consistent with the data to assume that no vorticity at all was produced in this experiment.

High sensitivity and spectral resolution XPS, polarisation-modulation reflection FTIR and static SIMS have been used in this investigation of the interfacial chemistry between poly(acrylic acid) (PAA) and an aluminium oxyhydroxide surface. The pseudoboehmite oxyhydroxide surface is used as a model for the chemistry found at the surface of the air-formed film after ambient exposure of aluminium metal. Conversion of carboxylic acids to monodentate carboxylate species at the PAA–AlOOH interface has been identified using reflection absorption FTIR. By virtue of the very low concentration of surface carbon on hydrothermally formed AlOOH, quantification of the interfacial carboxylate concentration was achieved by curve fitting the C1s core level. Through analysis of a range of PAA overlayer thicknesses, a limit to interfacial carboxylate formation with the surface was identified. To determine the reason for this limit, monoacids that chemisorb to the AlOOH surface exclusively through carboxylate bonds were analysed. It is proposed that steric and/or conformational hindrance, associated with the polymer backbone, prevent reaction of all carboxylic acid groups in PAA with surface hydroxyl functionalities to form carboxylate complexes. The implications of this finding for the application of PAA as an adhesion promotion pretreatment are considered.

Scanning force microscopy has been used to characterize the surface structure and properties of poly(ethylene terephthalate) (PET) films. Two types of biaxially oriented film have been studied: one (Melinex O) is free of additives while the other (Mylar D) contains particulate additives at the surface. Contact mode characterization of both materials provide clear images of the polymer surface and (in the case of Mylar D) the additives. Phase images reveal substantial nanoscale morphological detail, including small features thought to be crystallites. To model the adhesive properties of polymer surfaces, mixed self-assembled monolayers containing polar and methyl terminated adsorbates were studied using chemical force microscopy. It was found that the strength of the tip-sample adhesion increased with the fraction of polar terminated adsorbates at the surface when a carboxylic acid terminated tip was employed, while the trend was reversed when a methyl terminated tip was used. Adhesion forces measured for plasma treated PET increased with treatment time, and linearly with the cosine of the water contact angle, illustrating the chemical selectivity of chemical force microscopy. However, friction forces were found to vary in a non-linear fashion, indicating that changes to the polymer surface mechanical properties following treatment were important.

A thorough, in-depth understanding of the reactive nature of chemical processing operations is the first step to accomplishing the reduction of risks of these operations to a tolerable level. This understanding may be obtained through a laboratory evaluation using recognized and accepted process safety testing technologies as well as the conventional process hazards analysis. A systematic process safety testing program characterizes the reactive nature of both the desired and undesired chemistry. These data are needed to define the critical limits of temperature, pressure, power output, concentration, and dosing rates of processes involving reactive chemicals. The minimum basic data are the variation of energy (or power), temperature and pressure as a function of time, and reaction mass composition. The realistic use of these data requires an understanding of both the limitations of some laboratory data for scale-up and acceptable safety margins for industrial size operations. This paper will briefly review the current regulatory environment for chemical process safety, describe the integration of various calorimetric test techniques, and illustrate the use of data from isothermal differential scanning, and adiabatic calorimetry for improving process safety. An example, taken from the investigation of an accident involving the reaction between an amine and chlorine-substituted derivative, demonstrates the use of calorimetric data in understanding the origin and progress of the accident. Suggestions for how to improve process safety, based on the calorimetric information are also presented.

Friction force measurements have been made using friction force microscopy for a series of self-assembled monolayers (SAMs) of alkanethiols of varying chain lengths and terminal groups adsorbed on gold. The chemistry of the tip was controlled by the deposition of a SAM. When carboxylic acid terminated tips were employed, the friction coefficients of hydroxyl and carboxylic acid terminated SAMs were found to be greater than those of methyl terminated SAMs. However, although the friction coefficients of short-chain methyl terminated SAMs were significantly greater than those of long-chain methyl terminated SAMs, there was not a significant difference between the values determined for short- and long-chain SAMs with polar terminal groups. When methyl terminated tips were employed, there was no difference between the behavior observed for hydroxyl and carboxylic acid terminated SAMs of equal chain length, but methyl terminated SAMs exhibited increased friction coefficients which were larger for short-chain ad...