Analysing Magnetism Using Scanning SQUID Microscopy

Scanning superconducting quantum interference device microscopy (SSM) is a scanning probe technique that images local magnetic flux, which allows for mapping of magnetic fields with high field and spatial accuracy. Many studies involving SSM have been published in the last decades, using SSM to make qualitative statements about magnetism. However, quantitative analysis using SSM has received less attention. In this work, we discuss several aspects of interpreting SSM images and methods to improve quantitative analysis. First, we analyse the spatial resolution and how it depends on several factors. Second, we discuss the analysis of SSM scans and the information obtained from the SSM data. Using simulations, we show how signals evolve as a function of changing scan height, SQUID loop size, magnetization strength and orientation. We also investigated 2-dimensional autocorrelation analysis to extract information about the size, shape and symmetry of magnetic features. Finally, we provide an outlook on possible future applications and improvements.Comment: 16 pages, 10 figure

Shifting Satellite Control Paradigms: Operational Cybersecurity in the Age of Megaconstellations

The introduction of automated satellite control systems into a space-mission environment historically dominated by human-in-the-loop operations will require a more focused understanding of cybersecurity measures to ensure space system safety and security. On the ground-segment side of satellite control, the debut of privately owned communication antennas for rent and a move to cloud-based operations or mission centers will bring new requirements for cyber protection for both Department of Defense and commercial satellite operations alike. It is no longer a matter of whether automation will be introduced to satellite operations, but how quickly satellite operators can adapt to the onset of control automation and promote cybersecurity in an increasingly competitive, contested, and congested space domain. To ensure the continued safety and security of on-orbit satellite systems, both the defense and commercial space sectors must adapt to the rapidly changing digital landscape of future space operations

The Atypical Stimulant and Nootropic Modafinil Interacts with the Dopamine Transporter in a Different Manner than Classical Cocaine-Like Inhibitors

Modafinil is a mild psychostimulant with pro-cognitive and antidepressant effects. Unlike many conventional stimulants, modafinil has little appreciable potential for abuse, making it a promising therapeutic agent for cocaine addiction. The chief molecular target of modafinil is the dopamine transporter (DAT); however, the mechanistic details underlying modafinil's unique effects remain unknown. Recent studies suggest that the conformational effects of a given DAT ligand influence the magnitude of the ligand's reinforcing properties. For example, the atypical DAT inhibitors benztropine and GBR12909 do not share cocaine's notorious addictive liability, despite having greater binding affinity. Here, we show that the binding mechanism of modafinil is different than cocaine and similar to other atypical inhibitors. We previously established two mutations (W84L and D313N) that increase the likelihood that the DAT will adopt an outward-facing conformational state—these mutations increase the affinity of cocaine-like inhibitors considerably, but have little or opposite effect on atypical inhibitor binding. Thus, a compound's WT/mutant affinity ratio can indicate whether the compound preferentially interacts with a more outward- or inward-facing conformational state. Modafinil displayed affinity ratios similar to those of benztropine, GBR12909 and bupropion (which lack cocaine-like effects in humans), but far different than those of cocaine, β-CFT or methylphenidate. Whereas treatment with zinc (known to stabilize an outward-facing transporter state) increased the affinity of cocaine and methylphenidate two-fold, it had little or no effect on the binding of modafinil, benztropine, bupropion or GBR12909. Additionally, computational modeling of inhibitor binding indicated that while β-CFT and methylphenidate stabilize an “open-to-out” conformation, binding of either modafinil or bupropion gives rise to a more closed conformation. Our findings highlight a mechanistic difference between modafinil and cocaine-like stimulants and further demonstrate that the conformational effects of a given DAT inhibitor influence its phenomenological effects

A whole-cell biosensor for the detection of gold

Geochemical exploration for gold (Au) is becoming increasingly important to the mining industry. Current processes for Au analyses require sampling materials to be taken from often remote localities. Samples are then transported to a laboratory equipped with suitable analytical facilities, such as Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) or Instrumental Neutron Activation Analysis (INAA). Determining the concentration of Au in samples may take several weeks, leading to long delays in exploration campaigns. Hence, a method for the on-site analysis of Au, such as a biosensor, will greatly benefit the exploration industry. The golTSB genes from Salmonella enterica serovar typhimurium are selectively induced by Au(I/III)-complexes. In the present study, the golTSB operon with a reporter gene, lacZ, was introduced into Escherichia coli. The induction of golTSB::lacZ with Au(I/III)-complexes was tested using a colorimetric β-galactosidase and an electrochemical assay. Measurements of the β-galactosidase activity for concentrations of both Au(I)- and Au(III)-complexes ranging from 0.1 to 5 µM (equivalent to 20 to 1000 ng g⁻¹ or parts-per-billion (ppb)) were accurately quantified. When testing the ability of the biosensor to detect Au(I/III)-complexes(aq) in the presence of other metal ions (Ag(I), Cu(II), Fe(III), Ni(II), Co(II), Zn, As(III), Pb(II), Sb(III) or Bi(III)), cross-reactivity was observed, i.e. the amount of Au measured was either under- or over-estimated. To assess if the biosensor would work with natural samples, soils with different physiochemical properties were spiked with Au-complexes. Subsequently, a selective extraction using 1 M thiosulfate was applied to extract the Au. The results showed that Au could be measured in these extracts with the same accuracy as ICP-MS (P<0.05). This demonstrates that by combining selective extraction with the biosensor system the concentration of Au can be accurately measured, down to a quantification limit of 20 ppb (0.1 µM) and a detection limit of 2 ppb (0.01 µM).Carla M. Zammit, Davide Quaranta, Shane Gibson, Anita J. Zaitouna, Christine Ta, Joël Brugger, Rebecca Y. Lai, Gregor Grass, Frank Reit

Domain Restriction Zones: An Evolution of the Military Exclusion Zone

Since the early part of the twenty-first century, US adversaries have expanded their military capabilities within and their access to new warfighting domains. When faced with the growth of adversaries’ asymmetric capabilities, the means, tactics, and strategies previously used by the US military lose their proportional effectiveness. To avoid such degradation of capability, the operational concept of the military exclusion zone (MEZ) should be revised to suit the modern battlespace while also addressing the shifts in national policy that encourage diplomacy over military force. The concept and development of domain restriction zones (DRZs) increase the relevancy of traditional MEZs in the modern battlespace, allowing them to address problems associated with cross-domain and multidomain capabilities. The growth of adversary capabilities provides a clear rationale for the implementation of DRZs through all levels of force application within the competition continuum

On the edge of a new frontier: Is gerontological social work in the UK ready to meet twenty-first-century challenges?

This article is available open access through the publisher’s website. Copyright @ 2013 The Authors.This article explores the readiness of gerontological social work in the UK for meeting the challenges of an ageing society by investigating the focus on work with older people in social work education and the scope of gerontological social work research. The discussion draws on findings from two exploratory studies: a survey of qualifying master's programmes in England and a survey of the content relating to older people over a six-year period in four leading UK social work journals. The evidence from master's programmes suggests widespread neglect of ageing in teaching content and practice learning. Social work journals present a more nuanced picture. Older people emerge within coverage of generic policy issues for adults, such as personalisation and safeguarding, and there is good evidence of the complexity of need in late life. However, there is little attention to effective social work interventions, with an increasingly diverse older population, or to the quality of gerontological social work education. The case is made for infusing content on older people throughout the social work curriculum, for extending practice learning opportunities in social work with older people and for increasing the volume and reporting of gerontological social work research.Brunel Institute for Ageing Studie

Coarse Graining of Nonbonded Inter-particle Potentials Using Automatic Simplex Optimization to Fit Structural Properties

We implemented a coarse-graining procedure to construct mesoscopic models of complex molecules. The final aim is to obtain better results on properties depending on slow modes of the molecules. Therefore the number of particles considered in molecular dynamics simulations is reduced while conserving as many properties of the original substance as possible. We address the problem of finding nonbonded interaction parameters which reproduce structural properties from experiment or atomistic simulations. The approach consists of optimizing automatically nonbonded parameters using the simplex algorithm to fit structural properties like the radial distribution function as target functions. Moreover, any mix of structural and thermodynamic properties can be included in the target function. Different spherically symmetric inter-particle potentials are discussed. Besides demonstrating the method for Lennard--Jones liquids, it is applied to several more complex molecular liquids such as diphenyl carbonate, tetrahydrofurane, and monomers of poly(isoprene).Comment: 24 pages, 3 tables, 14 figures submitted to the Journal of Chemical Physics (JCP