Adaptive sampling for detecting a change point in the past

Consider the problem of estimating a change point in the drift of Brownian motion which is known to have occurred at some time during the time interval [0,1], Rather than observing the process, we use "adaptive (dynamic) sampling" which allows us to continuously select the time points at which increments of the motion may be observed. Our main results are that the steepest descent method will continuosly select the current Bayes estimator of the change point as the next time point to observe. The method results in a very convergence rate.

In addition, a discrete formulation is given. In this case, a slightly different method based on the mean and the standard deviation is suggested, and is proved to result in an exponential rate of convergence.     

From peptides to proteins: lessons from my years at the Centre for Protein Engineering

The MRC Centre for Protein Engineering (CPE) hosted and trained many scientists over the years. It is a unique research environment that shaped the career of many scientists in all aspects. These include research directions and methodologies, but even more important--issues such as how to approach scientific problems and how to manage a research team. Alan Fersht was the director of the CPE when I joined it as a postdoc in the year 2000. In the current article for the PEDS special CPE issue, I will review how my scientific research and my approach to science developed from the days I arrived to the CPE as a young peptide chemist and throughout the years I spent at the CPE, and how it shaped my current research interests and attitude. I will focus on two major fields: (i) Using peptides to study and modulate the structure and interactions of proteins; (ii) Using quantitative biophysical methods to study proteins and their interactions at the molecular level.     

Control of Biogenic Nanocrystal Formation in Biomineralization

Many organisms build crystals with almost complete control over all aspects of crystal formation, from nucleation to growth, from composition to polymorphic structure, and from morphology to size. In biomineralization, the control is fundamentally always exerted at the level of nanometers, because the building blocks themselves are at the nanoscale. We have chosen to describe in some detail four biological systems that produce nanoscale crystals using different mineralization pathways, different levels of control, and have different functions. These four cases are: bone crystal composites; guanine nanocrystal reflectors; magnetotactic bacteria with single domain magnets; and coccoliths, whose functions have yet to be identified. This is followed by a discussion aimed at identifying possible specific and/or common underlying principles involved in nanocrystal formation in biology.     

Thermal Modeling of Hybrid Storage Clusters

There is a lack of thermal models for storage clusters; most existing thermal models do not take into account the utilization of hard drives (HDDs) and solid state disks (SSDs). To address this problem, we build a thermal model for hybrid storage clusters that are comprised of HDDs and SSDs. We start this study by generating the thermal profiles of hard drives and solid state disks. The profiling results show that both HDDs and SSDs have profound impacts on temperatures of storage nodes in a cluster. Next, we build two types of hybrid storage clusters, namely, inter-node and intra-node hybrid storage clusters. We develop a model to estimate the cooling cost of a storage cluster equipped with hybrid storage nodes. The thermal model is validated against data acquired by temperature sensors. Experimental results show that, compared to the HDD-first strategy, the SSD-first strategy is an efficient approach to minimize negative thermal impacts of hybrid storage clusters.     

Particle Size,Surface Coating,and PEGylation Influence the Biodistribution of Quantum Dots in Living Mice

This study evaluates the influence of particle size, PEGylation, and surface coating on the quantitative biodistribution of near‐infrared‐emitting quantum dots (QDs) in mice. Polymer‐ or peptide‐coated ⁶⁴Cu‐labeled QDs 2 or 12 nm in diameter, with or without polyethylene glycol (PEG) of molecular weight 2000, are studied by serial micropositron emission tomography imaging and region‐of‐interest analysis, as well as transmission electron microscopy and inductively coupled plasma mass spectrometry. PEGylation and peptide coating slow QD uptake into the organs of the reticuloendothelial system (RES), liver and spleen, by a factor of 6–9 and 2–3, respectively. Small particles are in part renally excreted. Peptide‐coated particles are cleared from liver faster than physical decay alone would suggest. Renal excretion of small QDs and slowing of RES clearance by PEGylation or peptide surface coating are encouraging steps toward the use of modified QDs for imaging living subjects.     

Effect of dispersants on the kinetics of asphaltene settling using turbidity measurement method

Organic deposition especially asphaltenes in reservoirs, wells, and equipment has a detrimental effect on petroleum economy. Generally, for chemically control of asphaltene precipitation using dispersants and inhibitors of precipitation or solvents of asphaltene is very common. Although asphaltene in crude oil is stable under specific conditions, but there is no assurance that the system will be stable and asphaltenes could be remaining in suspension state. In this study, the kinetic effects of three dispersants on stabilization of asphaltene aggregates were investigated by turbidity measurement method. Turbidity measurement showed as the dispersant strength rises, the turbidity of unstable sample containing dispersant less declines versus time. In order to carry out further studies on dispersants, the effect of dispersant on asphaltene particle size distribution was investigated. The results of asphaltene particle size distribution measurements showed that adding dispersant cause to decrease the volume percent of particles with medium diameter.     

Factors effecting construction contractors' performance

A number of interesting and important aspects have been achieved in this research; in particular, that quality of work should be of major concern to contractors and could become a pre-requisite in any selection process by the client body. Contract documentation should be clear and should not include ambiguous clauses and contradictory documentation, as this only leads to problems for all parties during the contract and a low performance rating from the contractor.     

Professional architectural/engineering consultancy practices in Saudi Arabia

The local architectural engineering firm in Saudi Arabia is handling projects up to 175m SR a year on average. It will have been in practice 13 years, employing 91 people, most holding a B.Sc. degree. Practices are mainly selected by competitive bidding and paid under a fixed fee arrangement. The authors found that the public authorities are the major employers of local A/E design services.     

Testing Analog and Mixed-Signal Circuits With Built-In Hardware—A New Approach

This paper aims to develop an approach to test analog and mixed-signal embedded-core-based system-on-chips (SOCs) with built-in hardware. In particular, oscillation-based built-in self-test (OBIST) methodology for testing analog components in mixed-signal circuits is implemented in this paper. The proposed OBIST structure is utilized for on-chip generation of oscillatory responses corresponding to the analog-circuit components. A major advantage of the OBIST method is that it does not require stimulus generators or complex response analyzers, which makes it suitable for testing analog circuits in mixed-signal SOC environments. Extensive simulation results on sample analog and mixed-signal benchmark circuits and other circuits described by netlist in HSPICE format are provided to demonstrate the feasibility, usefulness, and relevance of the proposed implementations