Site-Specific Chemistry on Gold Nanorods: Curvature-Guided Surface Dewetting and Supracolloidal Polymerization.

Control of interparticle interactions in terms of their direction and strength highly relies on the use of anisotropic ligand grafting on nanoparticle (NP) building blocks. We report a ligand deficiency exchange strategy to achieve site-specific polymer grafting of gold nanorods (AuNRs). Patchy AuNRs with controllable surface coverage can be obtained during ligand exchange with a hydrophobic polystyrene ligand and an amphiphilic surfactant while adjusting the ligand concentration (CPS) and solvent condition (Cwater in dimethylformamide). At a low grafting density of ≤0.08 chains/nm2, dumbbell-like AuNRs with two polymer domains capped at the two ends can be synthesized through surface dewetting with a high purity of >94%. These site-specifically-modified AuNRs exhibit great colloidal stability in aqueous solution. Dumbbell-like AuNRs can further undergo supracolloidal polymerization upon thermal annealing to form one-dimensional plasmon chains of AuNRs. Such supracolloidal polymerization follows the temperature-solvent superposition principle as revealed by kinetic studies. Using the copolymerization of two AuNRs with different aspect ratios, we demonstrate the design of chain architectures by varying the reactivity of nanorod building blocks. Our results provide insights into the postsynthetic design of anisotropic NPs that potentially serve as units for polymer-guided supracolloidal self-assembly.

Bridging Heterogeneity Dictates the Microstructure and Yielding Response of Polymer-Linked Emulsions.

Soft materials possessing tunable rheological properties are desirable in applications ranging from 3D printing to biological scaffolds. Here, we use a telechelic, triblock copolymer polystyrene-b-poly(ethylene oxide)-b-polystyrene (SEOS) to form elastic networks of polymer-linked droplets in cyclohexane-in-water emulsions. The SEOS endblocks partition into the dispersed cyclohexane droplets while the midblocks remain in the aqueous continuous phase, resulting in each chain taking on either a looping or bridging conformation. By controlling the fraction of chains that form bridges, we tune the linear elasticity of the emulsions and generate a finite yield stress. Polymers with higher molecular weight (Mw) endblocks form stronger interdroplet connections and display a higher bridging density. Beyond modifying the linear rheology, the telechelic, triblock copolymers also alter the yielding behavior and processability of the linked emulsions. We examine the yield transition of these polymer-linked emulsions through large amplitude oscillatory shear (LAOS) and probe the emulsion structure through confocal microscopy, concluding that polymers that more readily form bridges generate a strongly percolated network, whereas those that are less prone to form bridges tend to produce networks composed of weakly linked clusters of droplets. When yielded, the emulsions consisting of linked clusters break apart into individual clusters that can rearrange upon the application of further shear. By contrast, when the systems containing a more homogeneous bridging density are yielded, the system remains percolated but with reduced elasticity and bridging density. The demonstrated ability of telechelic triblock copolymers to tune not only the linear viscoelasticity of complex fluids but also their nonlinear yield transition enables the use of these polymers as versatile and robust rheological modifiers. We expect our findings to therefore aid the design of the next generation of complex fluids and soft materials.

The Emergence of Psychoanalytic Metaneuropsychology: A Neuropsychoanalytically Informed Reconsideration of Early Psychic Development.

This paper is principally concerned with reappraising some of the major disagreements that separated the Viennese and the London Kleinians during the British Psychoanalytical Society's Controversial Discussions. Of particular focus are questions pertaining to the genesis of ego development, the beginnings of object-relating, and the role of unconscious phantasy in respect of these phenomena. The aim of the investigation is to inquire into the light that may be shed on the once intractable conflicts surrounding these questions by bringing to bear more recent developments from psychoanalysis and the neurosciences. First, various key issues from the Controversial Discussions are outlined, before the paper turns to work by Jaak Panksepp and Mark Solms that bears on these older arguments and the Freudian theories that underpinned them. With these conceptual foundations established, three questions are posed and discussed with a view to understanding the implications of recent neuropsychoanalytic thinking for some of the entrenched conflicts that divided the British Society. These questions include: (1) what does it mean for the ego if the id is conscious? (2) What does recent neuroscientific knowledge tell us about whether the ego should be thought of as present from birth? (3) How can we understand and locate unconscious phantasy if the main part of the mind that Freud thought of as unconscious is not so? Research from the arena of infant development-particularly the material and analysis of infant observation-is drawn on to illustrate various conclusions. The paper ultimately concludes that taking such an interdisciplinary approach can reveal renewed justification for aspects of the Kleinian metapsychology.

Making Worlds in a Waking Dream: Where Bion Intersects Friston on the Shaping and Breaking of Psychic Reality.

With the publication of Wilfred Bion's text 'Learning from Experience,' psychoanalysis was afforded a new schema for understanding the processes and implications involved in an infant's contact with their caregivers. As a result, our conception of some of the most fundamental phenomena of psychic life was significantly enriched. By proposing his theory of alpha-functioning, Bion mapped out how meaningful connexions to the internal and external worlds become established in the mind. In contrast, and through working clinically with psychotic patients, Bion revealed how these ties can catastrophically come undone. It is with these ideas, as well as their links to a corresponding set of neuroscientific constructs relating to the Markov blanket and principally developed by Karl Friston, that this paper is concerned. Through an investigation of the psychic functioning originally dubbed 'dream-work-alpha,' the paper's first section focuses on how Bion conceived of the creation of a 'contact-barrier' that allows for the differentiation of consciousness from an unconscious mind. Casting the ramifications of this organisation in sharp relief, the psychotic disorganisation of the contact-barrier is then explored. The discussion subsequently broadens to incorporate contemporary theories from free energy neuroscience that bear significant and illuminating relations to the psychoanalytic ideas espoused by Bion over half a century ago. Finally, through posing a series of three questions with accompanying discussions, a superimposition of these theoretical schemas is attempted. These suggestions directly address, (1) whether there is an intimate connexion between the interoceptive contact-barrier and the exteroceptive Markov blanket, (2) whether a disobjectalising of the contact-barrier may be reflected as a tear in the functional fabric of the Markov blanket, and (3) what the clinical implications are of working at the level of the projected surface. Ultimately, the aim of the paper is to expose relevant points of contact within and between the varying conceptual frameworks; frameworks that ultimately derive from disciplines that are both concerned with examining the underlying mechanisms of the mind-brain.

High-intensity power-resolved radiation imaging of an operational nuclear reactor.

Knowledge of the neutron distribution in a nuclear reactor is necessary to ensure the safe and efficient burnup of reactor fuel. Currently these measurements are performed by in-core systems in what are extremely hostile environments and in most reactor accident scenarios it is likely that these systems would be damaged. Here we present a compact and portable radiation imaging system with the ability to image high-intensity fast-neutron and gamma-ray fields simultaneously. This system has been deployed to image radiation fields emitted during the operation of a TRIGA test reactor allowing a spatial visualization of the internal reactor conditions to be obtained. The imaged flux in each case is found to scale linearly with reactor power indicating that this method may be used for power-resolved reactor monitoring and for the assay of ongoing nuclear criticalities in damaged nuclear reactors.

The analysis of complex mixed-radiation fields using near real-time imaging.

A new mixed-field imaging system has been constructed at Lancaster University using the principles of collimation and back projection to passively locate and assess sources of neutron and gamma-ray radiation. The system was set up at the University of Manchester where three radiation sources: (252)Cf, a lead-shielded (241)Am/Be and a (22)Na source were imaged. Real-time discrimination was used to find the respective components of the neutron and gamma-ray fields detected by a single EJ-301 liquid scintillator, allowing separate images of neutron and gamma-ray emitters to be formed. (252)Cf and (22)Na were successfully observed and located in the gamma-ray image; however, the (241)Am/Be was not seen owing to surrounding lead shielding. The (252)Cf and (241)Am/Be neutron sources were seen clearly in the neutron image, demonstrating the advantage of this mixed-field technique over a gamma-ray-only image where the (241)Am/Be source would have gone undetected.

Depth profiling 137Cs and 60Co non-intrusively for a suite of industrial shielding materials and at depths beyond 50 mm.

A phantom has been used to position two radiation sources, separately, when buried under dry-silica sand at depths between 5 and 50 mm. A γ-ray energy spectrum was then measured at every 1 mm depth. Principal component analysis has been conducted, which has led to a non-linear fit being established, allowing the depth of entrainment to be accurately inferred. The technique has been expanded for additional shielding media: water, aggregate and both wet and dry soil. The technique has also been expanded beyond the previous depth constraint of 50 mm.

Determination of the depth of localized radioactive contamination by 137Cs and 60Co in sand with principal component analysis.

A method to determine the depth of buried localized radioactive contamination nonintrusively and nondestructively using principal component analysis is described. The γ-ray spectra from two radionuclides, cesium-137 and cobalt-60, have been analyzed to derive the two principal components that change most significantly as a result of varying the depth of the sources in a bespoke sand-filled phantom. The relationship between depth (d) and the angle (θ) between the first two principal component coefficients has been derived for both cases, viz. d(Φ) = x + y log(e) Φ where x and y are constants dependent on the shielding material and the γ-ray energy spectrum of the radioactivity in question, and φ is a function of θ. The technique enables the depth of a localized radioactive source to be determined nonintrusively in the range 5 to 50 mm with an accuracy of ±1 mm.

Locally rotation, contrast, and scale invariant descriptors for texture analysis.

Textures within real images vary in brightness, contrast, scale and skew as imaging conditions change. To enable recognition of textures in real images, it is necessary to employ a similarity measure which is invariant to these properties. Furthermore, since textures often appear on undulating surfaces, such invariances must necessarily be local rather than global. Despite these requirements, it is only relatively recently that texture recognition algorithms with local scale and affine invariance properties have begun to be reported. Typically, they comprise detecting feature points followed by geometric normalization prior to description. We describe a method based on invariant combinations of linear filters. Unlike previous methods, we introduce a novel family of filters, which provide scale invariance, resulting in a texture description invariant to local changes in orientation, contrast and scale and robust to local skew. Significantly, the family of filters enable local scale invariants to be defined without using a scale selection principle or a large number of filters. A texture discrimination method based on the A2 similarity measure applied to histograms derived from our filter responses outperforms existing methods for retrieval and classification results for both the Brodatz textures and the UIUC database, which has been designed to require local invariance.

Phase mutual information as a similarity measure for registration.

This article describes a new method for non-rigid alignment of multimodal images. Multimodal image registration is most often accomplished by modelling, in some sense, an intensity mapping between the images. Here, the alternative strategy of modelling a relationship between local image phase is introduced. This method is intrinsically image feature based, and searches for relationships between feature appearances, rather than tissue class intensity. This enables registration of modalities for which image intensity is not a simple function of tissue class, for example ultrasound. It is also demonstrated that this method performs comparably to an intensity method even when the images are related by a simple intensity transform, but that the phase method is significantly more robust to image artifacts which corrupt the ideal intensity mapping.

Automatic mammary duct detection in 3D ultrasound.

This paper presents a method for the initial detection of ductal structures within 3D ultrasound images using second-order shape measurements. The desire to detect ducts is motivated in a number of way, principally as step in the detection and assessment of ductal carcinoma in-situ. Detection is performed by measuring the variation of the local second-order shape from a prototype shape corresponding to a perfect tube. We believe this work is the first demonstration of the ability to detect sections of duct automatically in ultrasound images. The detection is performed with a view to employing vessel tracking method to delineate the full ductal structure.