Kinetically driven self assembly of highly ordered nanoparticle monolayers

When a drop of a colloidal solution of nanoparticles dries on a surface, it leaves behind coffee-stain-like rings of material with lace-like patterns or clumps of particles in the interior. These non-uniform mass distributions are manifestations of far-from-equilibrium effects, such as fluid flows and solvent fluctuations during late-stage drying. However, recently a strikingly different drying regime promising highly uniform, long-range-ordered nanocrystal monolayers has been found. Here we make direct, real-time and real-space observations of nanocrystal self-assembly to reveal the mechanism. We show how the morphology of drop-deposited nanoparticle films is controlled by evaporation kinetics and particle interactions with the liquid-air interface. In the presence of an attractive particle-interface interaction, rapid early-stage evaporation dynamically produces a two-dimensional solution of nanoparticles at the liquid-air interface, from which nanoparticle islands nucleate and grow. This self-assembly mechanism produces monolayers with exceptional long-range ordering that are compact over macroscopic areas, despite the far-from-equilibrium evaporation process. This new drop-drying regime is simple, robust and scalable, is insensitive to the substrate material and topography, and has a strong preference for forming monolayer films. As such, it stands out as an excellent candidate for the fabrication of technologically important ultra thin film materials for sensors, optical devices and magnetic storage media.     

Synthesis of NaAlH4/Al composites and their applications in hydrogen storage

In solid-state hydrogen storage in light metal hydrides, nanoconfinement and the use of catalysts represent promising solutions to overcoming limitations such as poor reversibility and slow kinetics. In this work, the morphology and hydrogen desorption kinetics of NaAlH₄ melt-infiltrated into a previously developed Ti-based doped porous Al scaffold is analysed. Small-angle X-ray scattering and scanning electron microscopy analysis of low NaAlH₄ loading in the porous Al scaffold has revealed that mesopores and small macropores are filled first, leaving the larger macropores/voids empty. Temperature-programmed desorption experiments have shown that NaAlH₄-infiltrated porous Al scaffolds show a higher relative H₂ release, with respect to NaAlH₄ + TiCl₃, in the temperature range 148–220 °C, with the temperature of H₂ desorption trending to bulk NaAlH₄ with increasing scaffold loading. The Ti-based catalytic effect is reproduced when the dopant is present in the scaffold. Further work is required to increase the mesoporous volume in order to enhance the nanoconfinement effect.     

A statistical model for point-based target registration error with anisotropic fiducial localizer error

Error models associated with point-based medical image registration problems were first introduced in the late 1990s. The concepts of fiducial localizer error, fiducial registration error, and target registration error are commonly used in the literature. The model for estimating the target registration error at a position r in a coordinate frame defined by a set of fiducial markers rigidly fixed relative to one another is ubiquitous in the medical imaging literature. The model has also been extended to simulate the target registration error at the point of interest in optically tracked tools. However, the model is limited to describing the error in situations where the fiducial localizer error is assumed to have an isotropic normal distribution in R3. In this work, the model is generalized to include a fiducial localizer error that has an anisotropic normal distribution. Similar to the previous models, the root mean square statistic rms tre is provided along with an extension that provides the covariance Sigma tre. The new model is verified using a Monte Carlo simulation and a set of statistical hypothesis tests. Finally, the differences between the two assumptions, isotropic and anisotropic, are discussed within the context of their use in 1) optical tool tracking simulation and 2) image registration.     

Dynamic 3-D virtual fixtures for minimally invasive beating heart procedures

Two-dimensional or 3-D visual guidance is often used for minimally invasive cardiac surgery and diagnosis. This visual guidance suffers from several drawbacks such as limited field of view, loss of signal from time to time, and in some cases, difficulty of interpretation. These limitations become more evident in beating-heart procedures when the surgeon has to perform a surgical procedure in the presence of heart motion. In this paper, we propose dynamic 3-D virtual fixtures (DVFs) to augment the visual guidance system with haptic feedback, to provide the surgeon with more helpful guidance by constraining the surgeon's hand motions thereby protecting sensitive structures. DVFs can be generated from preoperative dynamic magnetic resonance (MR) or computed tomograph (CT) images and then mapped to the patient during surgery. We have validated the feasibility of the proposed method on several simulated surgical tasks using a volunteer's cardiac image dataset. Validation results show that the integration of visual and haptic guidance can permit a user to perform surgical tasks more easily and with reduced error rate. We believe this is the first work presented in the field of virtual fixtures that explicitly considers heart motion.     

Descemet's membrane detachment attributed to the mechanical forces of airbag deployment

Purpose

A patient who developed a Descemet's membrane detachment 3 weeks following airbag deployment is reported.

Case report

A hydrogel contact lens wearer (extended wear) presented to her primary eye care provider with a painful red eye that had been treated with pressure patching the previous day at a hospital emergency room. Examination revealed full thickness corneal edema localized in the temporal region of the left eye, a corneal infiltrate with an overlying epithelial defect, and an anterior chamber reaction with marked temporal injection. The patient was referred to a corneal specialist after the cornea failed to respond to anti-microbial treatment. Probing of the history revealed that the patient had recently sustained an automobile accident in which the front air bags had deployed. Confocal microscopy revealed that Descemet's membrane was detached, presumably secondary to the mechanical forces of airbag deployment. The patient recovered normal vision after 3 weeks of topical therapy and ultimately returned to successful contact lens wear.

Discussion

Although Descemet's membrane detachment is an uncommon complication of airbag deployment, it is important to exclude this possibility because delayed diagnosis and treatment may compromise the corneal endothelium, predispose the cornea to chronic edema, and result in permanent vision loss. An awareness of the spectrum of injuries resulting from airbag deployment should facilitate early diagnosis and treatment, particularly in situations where the etiology of the presenting eye condition is not readily apparent.     

The family environment as a moderator of psychosocial outcomes following traumatic brain injury in young children.

Objective: This study sought to determine whether the family environment moderates psychosocial outcomes after traumatic brain injury (TBI) in young children. Method: Participants were recruited prospectively from consecutive hospital admissions of 3- to 6-year-old children, and included 19 with severe TBI, 56 with complicated mild/moderate TBI, and 99 with orthopedic injuries (OI). They completed 4 assessments across the first 18 months postinjury. The initial assessment included measures of parenting style, family functioning, and the quality of the home. Children's behavioral adjustment, adaptive functioning, and social competence were assessed at each occasion. Mixed model analyses examined the relationship of the family environment to psychosocial outcomes across time. Results: The OI and TBI groups differed significantly in social competence, but the family environment did not moderate the group difference, which was of medium magnitude. In contrast, group differences in behavioral adjustment became more pronounced across time at high levels of authoritarian and permissive parenting; among children with severe TBI, however, even those with low levels of permissive parenting showed increases in behavioral problems. For adaptive functioning, better home environments provided some protection following TBI, but not over time for the severe TBI group. These 3-way interactions of group, family environment, and time postinjury were all of medium magnitude. Conclusion: The findings indicate that the family environment moderates the psychosocial outcomes of TBI in young children, but the moderating influence may wane with time among children with severe TBI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Administrators and multiprocessor rendezvous mechanisms

This paper discusses rendezvous on multiprocessors. Three different approaches are compared, represented by three specific systems: Ada, Harmony and BNR Pascal. All three permit tasks to run on multiple processors and use blocking communications primitives, but there are significant differences. For example, control over replying to messages out of sequence and over the allocation of tasks to processors is omitted in Ada, but is available in Harmony. The approach represented by BNR Pascal follows a middle road between Harmony and Ada: a low level protocol, invisible to the programmer, is used to ensure communications reliability, but the programmer is aware of when a rendezvous is remote. If performance considerations and verbosity and robustness are ignored, all three approaches are equivalent. To illustrate this equivalence, and to demonstrate clearly the complexity of the Ada rendezvous, an Ada rendezvous administrator written using Harmony is described. A second method of adapting Harmony to Ada is also presented, in which the Harmony primitives are modified to be closer to Ada. In practice, using Harmony primitives directly will usually result in better programs. It is argued that something very much like the rendezvous adminstrator is needed for any actual implementation of the Ada rendezvous.     

Classroom management and disaffection

This article reports on aspects of the Norwich Area Schools Consortium (NASC) cross-school Classroom Management and Disaffection research project undertaken as part of the NASC programme. It documents the dual interwoven 'stories' of teacher engagement in research as a learning expand the substantive research undertaken. The project took place in two stages, the focus of the second stage emerging from the analysis of the first stage. Research into both pupil and teacher perceptions concerning disaffection and classroom management was investigated in the first stage. The second stage attempted to unravel the complex relationships between disaffection, curriculum, pedagogy and context from pupil perspectives, with insights on the relationship between a good lesson and a good teacher being of particular interest. A full report on the NASC Classroom Management and Disaffection research is available from the authors.