Magnetic particle spectroscopy (MPS) in the Brownian relaxation regime, also termed magnetic spectroscopy of Brownian motion (MSB), can detect and quantitate very low, sub-nanomolar concentrations of ...molecular biomarkers. MPS/MSB uses the harmonics of the magnetization induced by a small, low-frequency oscillating magnetic field to provide quantitative information about the magnetic nanoparticles’ (mNPs’) microenvironment. A key application uses antibody-coated mNPs to produce biomarker-mediated aggregation that can be detected using MPS/MSB. However, relaxation changes can also be caused by viscosity changes. To address this challenge, we propose a metric that can distinguish between aggregation and viscosity. Viscosity changes scale the MPS/MSB harmonic ratios with a constant multiplier across all applied field frequencies. The change in viscosity is exactly equal to the multiplier with generality, avoiding the need to understand the signal explicitly. This simple scaling relationship is violated when particles aggregate. Instead, a separate multiplier must be used for each frequency. The standard deviation of the multipliers over frequency defines a metric isolating viscosity (zero standard deviation) from aggregation (non-zero standard deviation). It increases monotonically with biomarker concentration. We modeled aggregation and simulated the MPS/MSB signal changes resulting from aggregation and viscosity changes. MPS/MSB signal changes were also measured experimentally using 100 nm iron-oxide mNPs in solutions with different viscosities (modulated by glycerol concentration) and with different levels of aggregation (modulated by concanavalin A linker concentrations). Experimental and simulation results confirmed that viscosity changes produced small changes in the standard deviation and aggregation produced larger values of standard deviation. This work overcomes a key barrier to using MPS/MSB to detect biomarkers in vivo with variable tissue viscosity.
Dynamic magnetization of nanoparticles is a promising means of functional biosensing. We demonstrate a method for rapid monitoring of relative changes in the viscous environment of superparamagnetic ...nanoparticles using a ratio of magnetization harmonics. Initial results are capable of detecting changes in viscosity on the order of 0.05
cP. This technique should allow for real-time monitoring of many of the dynamic magnetization applications which have been proposed using AC susceptibility. Further, incorporation of this technique into a harmonic-based imaging system like magnetic particle imaging would allow for
in vivo functional imaging capabilities.
The potential for resident attitude surveys to reduce the negative community impacts of tourism is constrained by their emphasis on closed-ended cognitive statements requiring simplistic numeric ...responses. This paper explores ways to obtain and analyze open-ended survey outputs from 791 residents in order to develop effective prescriptive recommendations for reducing the negative impacts, and increasing positive impacts from Australia's Gold Coast Schoolies Week (GCSW), a contentious event associated with widespread, high-risk antisocial behavior. Thematic content analysis revealed super-themes of unambivalent "opposition" to GCSW (22.0%) and "support" (7.3%), but also three super-themes that are conditional. "Mitigative prevention" (49.8%) includes supervision, alcohol/predator restrictions, spatial/temporal containment and dispersal themes, while "mitigative enhancement" (14.1%) includes constructive diversion, education and balanced media coverage themes. "Mitigative justice" (7.3%) is dominated by rule enforcement. The outcomes indicate support for social exchange theory in the expression of strategies through which those exchanges occur. The mitigative super-themes inform a research-based template for sustainably managing both GCSW and other contentious tourism-related events elsewhere. Using Tosun's three-stage citizen's participation hierarchy, support was indicated for the "induced participation" middle ground of consultation, with little support for top-down "coercive participation", or for the citizen control of "spontaneous participation".
•We review limitations of current nanoparticle imaging probes including: biodistribution of nanoparticles, imaging very small tumors, immunology, toxicology.•We review hurdles on the road to the ...clinic such as regulatory considerations.•We also review the financial realities.•Finally, we identify the opportunities that exist in the development of nanoparticle imaging probes.
Recent advances in molecular imaging and nanotechnology are providing new opportunities for biomedical imaging with great promise for the development of novel imaging agents. The unique optical, magnetic, and chemical properties of materials at the scale of nanometers allow the creation of imaging probes with better contrast enhancement, increased sensitivity, controlled biodistribution, better spatial and temporal information, multi-functionality and multi-modal imaging across MRI, PET, SPECT, and ultrasound. These features could ultimately translate to clinical advantages such as earlier detection, real time assessment of disease progression and personalized medicine. However, several years of investigation into the application of these materials to cancer research has revealed challenges that have delayed the successful application of these agents to the field of biomedical imaging. Understanding these challenges is critical to take full advantage of the benefits offered by nano-sized imaging agents. Therefore, this article presents the lessons learned and challenges encountered by a group of leading researchers in this field, and suggests ways forward to develop nanoparticle probes for cancer imaging.
A signal-to-noise ratio (SNR) measure based on the octahedral shear strain (the maximum shear strain in any plane for a 3D state of strain) is presented for magnetic resonance elastography (MRE), ...where motion-based SNR measures are commonly used. The shear strain, γ, is directly related to the shear modulus, μ, through the definition of shear stress, τ = μγ. Therefore, noise in the strain is the important factor in determining the quality of motion data, rather than the noise in the motion. Motion and strain SNR measures were found to be correlated for MRE of gelatin phantoms and the human breast. Analysis of the stiffness distributions of phantoms reconstructed from the measured motion data revealed a threshold for both strain and motion SNR where MRE stiffness estimates match independent mechanical testing. MRE of the feline brain showed significantly less correlation between the two SNR measures. The strain SNR measure had a threshold above which the reconstructed stiffness values were consistent between cases, whereas the motion SNR measure did not provide a useful threshold, primarily due to rigid body motion effects.
We report the discovery in the Sloan Digital Sky Survey (SDSS) and the SDSS-III Baryon Oscillation Spectroscopic Survey of 17 broad absorption line (BAL) quasars with high-ionization troughs that ...include absorption redshifted relative to the quasar rest frame. The redshifted troughs extend to velocities up to v 12 000 km s−1 and the trough widths exceed 3000 km s−1 in all but one case. Approximately 1 in 1000 BAL quasars with blueshifted C iv absorption also has redshifted C iv absorption; objects with C iv absorption present only at redshifted velocities are roughly four times rarer. In more than half of our objects, redshifted absorption is seen in C ii or Al iii as well as C iv, making low-ionization absorption at least 10 times more common among BAL quasars with redshifted troughs than among standard BAL quasars. However, the C iv absorption equivalent widths in our objects are on average smaller than those of standard BAL quasars with low-ionization absorption.
We consider several possible ways of generating redshifted absorption. The two most likely possibilities may be at work simultaneously, in the same objects or in different ones. Rotationally dominated outflows seen against a quasar's extended continuum source can produce redshifted and blueshifted absorption, but variability consistent with this scenario is seen in only one of the four objects with multiple spectra. The infall of relatively dense and low-ionization gas to radii as small as 400 Schwarzschild radii can in principle explain the observed range of trough profiles, but current models do not easily explain the origin and survival of such gas. Whatever the origin(s) of the absorbing gas in these objects, it must be located at small radii to explain its large redshifted velocities, and thus offers a novel probe of the inner regions of quasars.
Analysis of core criteria of ecotourism suggests two “ideal types” based on the level of sustainability outcomes. The minimalist emphasizes superficial learning opportunities focused on charismatic ...megafauna, while its sustainability objectives are site-specific and status quo-oriented. The comprehensive model adopts a holistic and global approach to attractions and interpretation that fosters environmental enhancement, deep understanding, and transformation of behavior. It is argued that the comprehensive model can best promote global sustainability by accommodating selected hard (or small-scale) and soft (or large-scale) characteristics, thereby taking advantage of the economies of scale offered by the latter.
Les dimensions complètes et minimalistes de l’écotourisme. Une analyse des critères essentiels de l’écotourisme suggère deux «types idéaux» basés sur les résultats du niveau de durabilité. Le type minimaliste accentue des occasions d’apprentissage superficiel qui centrent l’attention sur des mégafaunes charismatiques, tandis que ses objectifs pour la durabilité sont spécifiques au lieu et orientés vers le statu quo. Le modèle complet adopte une approche holistique et globale aux attractions et à l’interprétation, ce qui favorise l’amélioration de l’environnement, une compréhension approfondie et la transformation du comportement. On soutient que le modèle complet peut mieux défendre la durabilité globale en accommodant certaines caractéristiques dures (ou à petite échelle) ou souple (ou à grande échelle), profitant ainsi des économies d’échelle présentées par celles-ci.
Varroa destructor mites, and the numerous viruses they vector to their honey bee hosts, are among the most serious threats to honey bee populations, causing mortality and morbidity to both the ...individual honey bee and colony, the negative effects of which convey to the pollination services provided by honey bees worldwide. Here we use a combination of targeted assays and deep RNA sequencing to determine host and microbial changes in resistant and susceptible honey bee lineages. We focus on three study sets. The first involves field sampling of sympatric western bees, some derived from resistant stock and some from stock susceptible to mites. The second experiment contrasts three colonies more deeply, two from susceptible stock from the southeastern U.S. and one from mite-resistant bee stock from Eastern Texas. Finally, to decouple the effects of mites from those of the viruses they vector, we experimentally expose honey bees to DWV in the laboratory, measuring viral growth and host responses. We find strong differences between resistant and susceptible bees in terms of both viral loads and bee gene expression. Interestingly, lineages of bees with naturally low levels of the mite-vectored Deformed wing virus, also carried lower levels of viruses not vectored by mites. By mapping gene expression results against current ontologies and other studies, we describe the impacts of mite parasitism, as well as viruses on bee health against two genetic backgrounds. We identify numerous genes and processes seen in other studies of stress and disease in honey bee colonies, alongside novel genes and new patterns of expression. We provide evidence that honey bees surviving in the face of parasitic mites do so through their abilities to resist the presence of devastating viruses vectored by these mites. In all cases, the most divergence between stocks was seen when bees were exposed to live mites or viruses, suggesting that gene activation, rather than constitutive expression, is key for these interactions. By revealing responses to viral infection and mite parasitism in different lineages, our data identify candidate proteins for the evolution of mite tolerance and virus resistance.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Understanding the dynamics of magnetic particles can help to advance several biomedical nanotechnologies. Previously, scaling relationships have been used in magnetic spectroscopy of nanoparticle ...Brownian motion (MSB) to measure biologically relevant properties (e.g., temperature, viscosity, bound state) surrounding nanoparticles in vivo. Those scaling relationships can be generalized with the introduction of a master variable found from non-dimensionalizing the dynamical Langevin equation. The variable encapsulates the dynamical variables of the surroundings and additionally includes the particles' size distribution and moment and the applied field's amplitude and frequency. From an applied perspective, the master variable allows tuning to an optimal MSB biosensing sensitivity range by manipulating both frequency and field amplitude. Calculation of magnetization harmonics in an oscillating applied field is also possible with an approximate closed-form solution in terms of the master variable and a single free parameter.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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