A comparison of conventional Everhart-Thornley style and in-lens secondary electron detectors: a further variable in scanning electron microscopy

The secondary electron (SE) imaging of several samples across a range of scanning electron microscopes (SEM) and SE detectors under matched operating conditions has generated a highly variable image data set. Using microanalytical conditions (10-15?kV), images from in-column SE detectors reveal the presence of surface films and contaminants that are invisible to conventional Everhart-Thornley SE detectors under the same conditions. Data from studying the effects of working distance, the image resolution derived through contrast transfer function analysis and electrostatic mirror imaging of the SE detectors in operation combine with other studies to suggest that the classically defined SE1 component can be separated from other SE components. SE images obtained by tailored mechanical design and energy-filtering will provide SE images with probe-sized resolution and dominated by surface detail currently only seen in low-voltage SEM, potentially even from thermionic-sourced columns.     

Neuro-Resistive Grid approach to trainable controllers: A pole balancing example

A new neural network approach is described for the task of pole-balancing, considered a benchmark learning control problem. This approach combines Barto, Sutton and Anderson's [1] Associative Search Element (ASE) with a Neuro-Resistive Grid (NRG) [2] acting as Adaptive Critic Element (ACE). The novel feature in NRG is that it provides evaluation of a state based on propagation of the failure information to the neighbours in the grid. NRG is updated only on a failure, and provides ASE with a continuous internal reinforcement signal by comparing the value of the present state to the previous state. The resulting system learns more rapidly and with fewer computations than that of Barto et al.[1]. To establish a uniform basis of comparison of algorithms for pole balancing, both the systems are simulated using benchmark parameters and tests specified in Geva and Sitte [3].     

Social patterns in productive software development organizations

Software development is a predominantly social activity. It is important to view software development groups, departments, and corporations as social bodies. We study software organizations using a novel data-gathering approach that combines several techniques commonly used in social network analysis. Our techniques differ from those of ordinary social anthropology in that we help the organization introspect about itself; the technique is a mirror for the subject organization. We catalogued social network diagrams using a variety of visualization techniques. We have found visual patterns that correlate well to subjective measures of a good organization. We built analytical models to capture properties of the social networks, employing techniques similar to those used in established social network science. The emerging design technique based on architectural patterns provides a good vehicle for communicating organizational patterns. We have captured practices from outstanding organizations in a group of patterns that form a pattern language for productive software development.     

Hydrogels Containing Gradients in Vascular Density Reveal Dose-Dependent Role of Angiocrine Cues on Stem Cell Behavior

Biomaterials that replicate patterns of microenvironmental signals from the stem cell niche offer the potential to refine platforms to regulate stem cell behavior. While significant emphasis has been placed on understanding the effects of biophysical and biochemical cues on stem cell fate, vascular-derived or angiocrine cues offer an important alternative signaling axis for biomaterial-based stem cell platforms. Elucidating dose-dependent relationships between angiocrine cues and stem cell fate are largely intractable in animal models and 2D cell cultures. In this study, microfluidic mixing devices are leveraged to generate 3D hydrogels containing lateral gradients in vascular density alongside murine hematopoietic stem cells (HSCs). Regional differences in vascular density can be generated via embossed gradients in cell, matrix, or growth factor density. HSCs co-cultured alongside vascular gradients reveal spatial patterns of HSC phenotype in response to angiocrine signals. Notably, decreased Akt signaling in high vessel density regions led to increased expansion of lineage-positive hematopoietic cells. This approach offers a combinatorial tool to rapidly screen a continuum of microenvironments with varying vascular, biophysical, and biochemical cues to reveal the influence of local angiocrine signals on HSC fate.     

The Effects of Haptic Feedback and Visual Distraction on Pointing Task Performance

Previous research has not fully examined the effect of additional sensory feedback, particularly delivered through the haptic modality, in pointing task performance with visual distractions. This study examined the effect of haptic feedback and visual distraction on pointing task performance in a 3D virtual environment. Results indicate a strong positive effect of haptic feedback on performance in terms of task time and root mean square error of motion. Level of similarity between distractor objects and the target object significantly reduced performance, and subjective ratings indicated a sense of increased task difficulty as similarity increased. Participants produced the best performance in trials where distractor objects had a different color but the same shape as the target object and constant haptic assistive feedback was provided. Overall, this study provides insight toward the effect of object features and similarity and the effect of haptic feedback on pointing task performance.     

Nexus meets crisis: a review of conflict,natural resources and the humanitarian response in Darfur with reference to the water–energy–food nexus

Darfur has been widely used as a case study by both those arguing for causality between environmental scarcity and war and those disputing it. This article challenges that approach by drawing on debates taking place within Darfur, reflecting on both the conflict and the humanitarian response. It argues that reviewing Darfur on its own terms makes a stronger basis to identify transferable lessons for interventions elsewhere. It considers water, food and energy, and finds that supporting governance is an essential theme for promoting economic recovery and laying a foundation for a well-managed water–energy–food nexus.     

Catalysis on cobalt-containing sodium zeolite Y

A number of cobalt-containing sodium zeolite Y catalysts were prepared by (i) impregnation using a dilute solution of CO₂(CO)₈ in pentane and (ii) by ion-exchange using dilute aqueous cobalt nitrate followed by further impregnation using aqueous NaOH. Different cobaltimpregnated catalysts could be prepared depending on the method of post-treatment, and all samples were characterised for activity in the hydrogenation and ethylation of benzene. In both series of samples good reduction catalysts were obtained, while only the hydroxide impregnated series exhibited any alkylation activity.     

QoSPlan: A Measurement Based Quality of Service aware Network Planning Framework

In this article we present QoSPlan—a measurement based framework for preparing information relevant to Quality of Service (QoS)-aware IP network planning, which aims at reducing a core operational expenditure for the network operator. QoSPlan is designed to reduce the cost of deployment and maintenance of network monitoring systems. The process involves analysis of pre-existing accounting data to estimate a network-wide traffic matrix. Part of this estimation process relates to the generalization of QoS-related effective bandwidth coefficients taken from traffic analyzed on the network. We offer recommendations on how to appropriately realize QoSPlan to maximize its accuracy and effectiveness when applied to different network traffic scenarios. This is achieved through a thorough sensitivity analysis of the methods proposed using real traffic scenarios and indicative network topologies. We also provide an economic analysis of the deployment and maintenance costs associated with QoSPlan in comparison to a direct measurement approach, demonstrating cost savings of up to 60 % given different topology sizes.