A Cooperative Sequential Adsorption Model in Two Dimensions with Experimental Applications for Ionic Self-Assembly of Nanoparticles

Self-assembly of nanoparticles is an important tool in nanotechnology, with numerous applications including thin films, electronics, and drug delivery. We study the deposition of ionic nanoparticles on a glass substrate both experimentally and theoretically. Our theoretical model consists of a stochastic cooperative adsorption and evaporation process on a two-dimensional lattice. By exploring the relationship between the initial concentration of nanoparticles in the colloidal solution and the density of particles deposited on the substrate, we relate the deposition rate of our theoretical model to the concentration.Comment: 7 pages, 6 figures; v2: major revisio

Power spectra of TASEPs with a localized slow site

The totally asymmetric simple exclusion process (TASEP) with a localized defect is revisited in this article with attention paid to the power spectra of the particle occupancy N(t). Intrigued by the oscillatory behaviors in the power spectra of an ordinary TASEP in high/low density phase(HD/LD) observed by Adams et al. (2007 Phys. Rev. Lett. 99 020601), we introduce a single slow site with hopping rate q<1 to the system. As the power spectrum contains time-correlation information of the particle occupancy of the system, we are particularly interested in how the defect affects fluctuation in particle number of the left and right subsystems as well as that of the entire system. Exploiting Monte Carlo simulations, we observe the disappearance of oscillations when the defect is located at the center of the system. When the defect is off center, oscillations are restored. To explore the origin of such phenomenon, we use a linearized Langevin equation to calculate the power spectrum for the sublattices and the whole lattice. We provide insights into the interactions between the sublattices coupled through the defect site for both simulation and analytical results.Comment: 16 pages, 6 figures; v2: Minor revision

The Clustering of Financial Services in London*

This paper reports a one-year study which investigated the clustering of financial services activity in London. A questionnaire asking about the advantages and disadvantages of a London location was sent to a stratified sample of 1,500 firms and institutions. In addition, thirty-nine on-site interviews with firms, professional institutions, government bodies and other related agencies were conducted. The study finds that banking, including investment banking, forms the cluster’s hub with most other companies depending on relationships with this sub-sector. Generally, the cluster confers many advantages to its incumbents including enhanced reputation, the ability to tap into large, specialized labor pool and customer proximity. The localized nature of relationships between skilled labor, customers and suppliers is a critical factor which helps firms achieve innovative solutions, develop new markets and attain more efficient ways to deliver services and products. Particularly important are the personal relationships which are enhanced by the on-going face-to-face contact that is possible in a compact geographical space. Many of the cluster’s advantages are dynamic in that they become stronger as agglomeration increases. The study also finds important disadvantages in the cluster which threaten its future growth and prosperity. These include the poor quality and reliability of transport, particularly the state of the London Underground and links to airports, increasing levels of regulation and government policy that is not co-ordinated with the whole of the cluster in mind. Key words: Industrial clustering, agglomeration, financial services.

Competition for finite resources

The resources in a cell are finite, which implies that the various components of the cell must compete for resources. One such resource is the ribosomes used during translation to create proteins. Motivated by this example, we explore this competition by connecting two totally asymmetric simple exclusion processes (TASEPs) to a finite pool of particles. Expanding on our previous work, we focus on the effects on the density and current of having different entry and exit rates.Comment: 15 pages, 9 figures, v2: minor revisions, v3: additional reference & minor correction

The Clustering of Financial Services in London

This paper reports a one-year study which investigated the clustering of financial services activity in London. A questionnaire asking about the advantages and disadvantages of a London location was sent to a stratified sample of 1,500 firms and institutions. In addition, thirty-nine on-site interviews with firms, professional institutions, government bodies and other related agencies were conducted. The study finds that banking, including investment banking, forms the cluster’s hub with most other companies depending on relationships with this sub-sector. Generally, the cluster confers many advantages to its incumbents including enhanced reputation, the ability to tap into large, specialized labor pool and customer proximity. The localized nature of relationships between skilled labor, customers and suppliers is a critical factor which helps firms achieve innovative solutions, develop new markets and attain more efficient ways to deliver services and products. Particularly important are the personal relationships which are enhanced by the on-going face-to-face contact that is possible in a compact geographical space. Many of the cluster’s advantages are dynamic in that they become stronger as agglomeration increases. The study also finds important disadvantages in the cluster which threaten its future growth and prosperity. These include the poor quality and reliability of transport, particularly the state of the London Underground and links to airports, increasing levels of regulation and government policy that is not co-ordinated with the whole of the cluster in mind. Key words: Industrial clustering, agglomeration, financial services

Power Spectra of a Constrained Totally Asymmetric Simple Exclusion Process

To synthesize proteins in a cell, an mRNA has to work with a finite pool of ribosomes. When this constraint is included in the modeling by a totally asymmetric simple exclusion process (TASEP), non-trivial consequences emerge. Here, we consider its effects on the power spectrum of the total occupancy, through Monte Carlo simulations and analytical methods. New features, such as dramatic suppressions at low frequencies, are discovered. We formulate a theory based on a linearized Langevin equation with discrete space and time. The good agreement between its predictions and simulation results provides some insight into the effects of finite resoures on a TASEP.Comment: 4 pages, 2 figures v2: formatting change

Single port/incision laparoscopic surgery compared with standard three-port laparoscopic surgery for appendicectomy : a randomized controlled trial

Acknowledgments The authors thank John Norrie for advice regarding the reporting of the study, and clinical staff in the Department of General Surgery, Aberdeen Royal Infirmary, for helping with the conduct of the study. This work was supported by a Grant from the Chief Scientist Office (CSO) of the Scottish Government Health Directorates (Grant Number reference CZG/2/498). Jonathan A. Cook held a Medical Research Council, UK, training fellowship (G0601938) while this research was undertaken. The Health Services Research Unit is funded by the CSO of the Scottish Government Health Directorates. The views expressed in this paper are those of the authors and may not necessarily be shared by the funding bodies. The study was overseen by an Advisory Group comprising Professor Marion Campbell (Director, Health Services Research Unit, Aberdeen), Professor John Norrie (CHaRT Director) and Professor Craig Ramsay (Health Care Assessment Programme Director, Health Services Research Unit, Aberdeen). Professor W. Alastair Chambers was the independent chair of the Trial Steering Committee. Contributing surgeons to the SCARLESS study (in alphabetical order): Bassam Alkari, Emad Aly, Norman Binnie, Duff Bruce, Jan Jansen, Peter King, Tim MacAdam, Aileen McKinley, Terry O’Kelly, Ken Park, Abdul Qadir. The National Health Service provided support through the contribution of the following research nurses: Anu Joyson, Hazel Forbes, and Julie Shotton.Peer reviewedPublisher PD

Five centuries of Upper Indus River flow from tree rings

Water wars are a prospect in coming years as nations struggle with the effects of climate change, growing water demand, and declining resources. The Indus River supplies water to the world’s largest contiguous irrigation system generating 90% of the food production in Pakistan as well as 13 gigawatts of hydroelectricity. Because any gap between water supply and demand has major and far-reaching ramifications, an understanding of natural flow variability is vital – especially when only 47 years of instrumental record is available. A network of tree-ring sites from the Upper Indus Basin (UIB) was used to reconstruct river discharge levels covering the period AD 1452–2008. Novel methods tree-ring detrending based on the ‘signal free’ method and estimation of reconstruction uncertainty based on the ‘maximum entropy bootstrap’ are used. This 557-year record displays strong inter-decadal fluctuations that could not have been deduced from the short gauged record. Recent discharge levels are high but not statistically unprecedented and are likely to be associated with increased meltwater from unusually heavy prior winter snowfall. A period of prolonged below-average discharge is indicated during AD 1572–1683. This unprecedented low-flow period may have been a time of persistently below-average winter snowfall and provides a warning for future water resource planning. Our reconstruction thus helps fill the hydrological information vacuum for modeling the Hindu Kush–Karakoram–Himalayan region and is useful for planning future development of UIB water resources in an effort to close Pakistan’s “water gap”. Finally, the river discharge reconstruction provides the basis for comparing past, present, and future hydrologic changes, which will be crucial for detection and attribution of hydroclimate change in the Upper Indus Basin

Open urethroplasty versus endoscopic urethrotomy - clarifying the management of men with recurrent urethral stricture (the OPEN trial) : study protocol for a randomised controlled trial

Peer reviewedPublisher PD

Application of Serological Tools and Spatial Analysis to Investigate Malaria Transmission Dynamics in Highland Areas of Southwest Uganda.

Serological markers, combined with spatial analysis, offer a comparatively more sensitive means by which to measure and detect foci of malaria transmission in highland areas than traditional malariometric indicators. Plasmodium falciparum parasite prevalence, seroprevalence, and seroconversion rate to P. falciparum merozoite surface protein-119 (MSP-119) were measured in a cross-sectional survey to determine differences in transmission between altitudinal strata. Clusters of P. falciparum parasite prevalence and high antibody responses to MSP-119 were detected and compared. Results show that P. falciparum prevalence and seroprevalence generally decreased with increasing altitude. However, transmission was heterogeneous with hotspots of prevalence and/or seroprevalence detected in both highland and highland fringe altitudes, including a serological hotspot at 2,200 m. Results demonstrate that seroprevalence can be used as an additional tool to identify hotspots of malaria transmission that might be difficult to detect using traditional cross-sectional parasite surveys or through vector studies. Our study findings identify ways in which malaria prevention and control can be more effectively targeted in highland or low transmission areas via serological measures. These tools will become increasingly important for countries with an elimination agenda and/or where malaria transmission is becoming patchy and focal, but receptivity to malaria transmission remains high