Measurements are presented which show the effect of proton irradiation on the irreversibility line and critical current in Tl2 CaBa2Cu2O8 thin films. These data show that the irreversibility line is dependent on the defect structure and that the pinning energy is increased by proton irradiation. This leads to an increase in the critical current density at 60 K for the lowest radiation dose. Further irradiation reduces the critical current, even while the irreversibility line is enhanced.

Course syllabi are a required component of college and university courses. Syllabi present both broader course structuring practices, are a valuable "first impression" of what instructors want to offer their students, and are used as tools in course design. While best teaching practices suggest specific recommendations for syllabi development, there is little research evidence regarding their structure and use, especially in the context of introductory physics for life sciences (IPLS) courses. IPLS courses typically host students pursuing careers in the biological or health-related sciences, which are rapidly growing majors compared to other STEM degrees. Since few of these students have significant previous experience with physics, the course syllabus provides a first framing and establishment of expectations for them. In this paper, we analyzed how IPLS instructors write syllabi, how they use them in the course design process, and what experienced instructors recommend to be included in the syllabi. Furthermore, based on these analyses we compiled a set of 31 key components (organized in seven categories) for IPLS course syllabi supported by both widespread use and recommendations from experienced practitioners. We present these components and discuss implications for IPLS syllabus design. Specifically, we bring attention to the value of explicitly incorporating interdisciplinary language in syllabi narratives and learning objectives. This work provides guidance for IPLS course and syllabus design, and can also be relevant for modern interdisciplinary courses with features similar to IPLS courses.

Submitted for the MAR16 Meeting of The American Physical Society Amylin Detection with a Miniature Optical-Fiber Based Sensor ZHAOWEN LIU, MATSKO ANN, ADAM HUGHES, MARK REEVES, George Washington University — We present results of a biosensor based on shifts in the localized surface plasmon resonance of gold nanoparticles self-assembled on the end of an optical fiber. This system allows for detection of protein expression in low sensing volumes and for scanning in cell cultures and tissue samples. Positive and negative controls were done using biotin/avidin and the BSA/Anti-BSA system. These demonstrate that detection is specific and sensitive to nanomolar levels. Sensing of amylin, an important protein for pancreatic function, was performed with polyclonal and monoclonal antibodies. The measured data demonstrates the difference in sensitivity to the two types of antibodies, and titration experiments establish the sensitivity of the sensor. Further experiments demonstrate that the sensor can be regenerated and then reused. Mark Reeves George Washington Univ Date submitted: 06 Nov 2015 Electronic form version 1.4

Plasmonic assays are an important class of optical sensors that measure biomolecular interactions in real-time without the need for labeling agents, making them especially well-suited for clinical applications. Through the incorporation of nanoparticles and fiberoptics, these sensing systems have been successfully miniaturized and show great promise for in-situ probing and implantable devices, yet it remains challenging to derive meaningful, quantitative information from plasmonic responses. This is in part due to a lack of dedicated modeling tools, and therefore we introduce PAME, an open-source Python application for modeling plasmonic systems of bulk and nanoparticle-embedded metallic films. PAME combines aspects of thin-film solvers, nanomaterials and fiber-optics into an intuitive graphical interface. Some of PAME’s features include a simulation mode, a database of hundreds of materials, and an object-oriented framework for designing complex nanomaterials, such as a gold nanoparticles encased in a protein shell. An overview of PAME’s theory and design is presented, followed by example simulations of a fiberoptic refractometer, as well as protein binding to a multiplexed sensor composed of a mixed layer of gold and silver colloids. These results provide new insights into observed responses in reflectance biosensors.

Scikit-spectra is an intuitive framework for explorative spectroscopy in Python. Scikit-spectra leverages the Pandas library for powerful data processing to provide datastructures and an API designed for spectroscopy. Utilizing the new IPython Notebook widget system, scikit-spectra is headed towards a GUI when you want it, API when you need it approach to spectral analysis. As an application, analysis is presented of the surface-plasmon resonance shift in a solution of gold nanoparticles induced by proteins binding to the gold’s surface. Please refer to the scikit-spectra website for full documentation and support: http://hugadams.github.io/scikit-spectra/

In this paper, a paper-based ultracapacitors were fabricated by the rod-rolling method with the ink of carbon nanomaterials, which were synthesized by arc discharge under various magnetic conditions. Composites of carbon nanostructures, including high-purity single-walled carbon nanotubes (SWCNTs) and graphene flakes were synthesized simultaneously in a magnetically enhanced arc. These two nanostructures have promising electrical properties and synergistic effects in the application of ultracapacitors. Scanning electron microscope, transmission electron microscope, and Raman spectroscopy were employed to characterize the properties of carbon nanostructures and their thin films. The sheet resistance of the SWCNT and composite thin films was also evaluated by four-point probe from room temperature to the cryogenic temperature as low as 90 K. In addition, measurements of cyclic voltammetery and galvanostatic charging/discharging showed the ultracapacitor based on composites possessed a superior specific capacitance of up to 100 F/g, which is around three times higher than the ultracapacitor entirely fabricated with SWCNT.

A persistent challenge in materials science is the characterization of a large ensemble of heterogeneous nanostructures in a set of images. This often leads to practices such as manual particle counting, and sampling bias of a favorable region of the “best” image. Herein, we present the open-source software, imaging criteria and workflow necessary to fully characterize an ensemble of SEM nanoparticle images. Such characterization is critical to nanoparticle biosensors, whose performance and characteristics are determined by the distribution of the underlying nanoparticle film. We utilize novel artificial SEM images to objectively compare commonly-found image processing methods through each stage of the workflow: acquistion, preprocessing, segmentation, labeling and object classification. Using the semi- supervised machine learning application, Ilastik, we demonstrate the decomposition of a nanoparticle image into particle subtypes relevant to our application: singles, dimers, flat aggregates and piles. We outline a workflow for characterizing and classifying nanoscale features on low-magnification images with thousands of nanoparticles. This work is accompanied by a repository of supplementary materials, including videos, a bank of real and artificial SEM images, and ten IPython Notebook tutorials to reproduce and extend the presented results.

A fiber optic nanobiosensor, with sensitivity comparable to commercial plasmonic sensors, a highly reduced sensing area, and the possibility of in-situ use is presented.

Chemical analysis of metabolites directly from cell samples at sub-cellular level in ambient conditions is essential to understand the biochemical pathways in these organisms. In order to achieve this goal we combine near-field ablation with mass spectrometry. As a first step towards the integration of near-field ablation with mass spectrometry, we will report preliminary results of the chemical analysis of Arabidopsis Thaliana.

As the initial experiments towards integrating the near-field ablation and a fiber-optic biosensor, we report the near-field ablation on Arabidopsis thaliana leaf samples with a 2μm ablation spot. We also report time-dependent spectral plots of detecting biomolecules in the ground Arabidopsis leaf solution. The sensitivity of detecting biomolecules with amino functional groups was improved by using a biosensor coated with a specific type of cross linkers.

To understand which organic molecules are capable of binding to gold nanoparticles and/or inducing nanoparticle aggregation, we investigate the interaction of gold nanoparticles with small molecules and amino acids at variable pH. Dynamic Light Scattering (DLS) and ultraviolet-visible (UV-vis) spectra were measured on mixtures of colloidal gold with small molecules to track the progression of the aggregation of gold nanoparticles. We introduce the 522 to 435 nm UV-vis absorbance ratio as a sensitive method for the detection of colloidal gold aggregation, whereby we delineate the ability of thiol, amine, and carboxylic acid functional groups to bind to the surfaces of gold nanoparticles and investigate how combinations of these functional groups affect colloidal stability. We present models for mechanisms of aggregation of colloidal gold, including surface charge reduction and bridging linkers. For all molecules whose addition leads to the aggregation of gold nanoparticles, the aggregation kinetics were accelerated at acidic pH values. Colloidal gold is maintained only in the presence of anionic carboxyl groups, which are neutralized by protonation at lower pH. The overall reduced charge on the stabilizing carboxyl groups accounts for the accelerated aggregation at lower pH values.

As a first step towards the chemical analysis of biological samples with sub-micron resolution, we report our experiments on the sub-cellular ablation of biological samples in their native environment. This has the potential to combine the near-field IR ablation with mass spectrometry, thus facilitating the study of the spatial distribution of proteins in cellular samples, at sub-cellular length scales. We report the ablation of hard and soft materials: cellular acetate cover slips in water and myoblast cell samples in growth media, with spot sizes as small as 1.5um under 3um wavelength radiation. The ablation threshold and fluence in these processes have been measured. We found that there is a dramatic increase in the ablation threshold fluences when we go from far-field to the near-field region. We will also report on the difference in the ablation mechanism in air and water medium. This approach has the potential to identify the protein expressed in cells in a relatively non-destructive manner.

We report the near-field ablation of biological material with spot sizes as small as 1.5 mu m under 3 mu m wavelength radiation. The fluence dependence of the ablation of both cellulose acetate coverslips in water and myoblast cell samples in growth media has been studied. We find that for all near-field experiments, the ablation thresholds are very high compared to far-field experiments. A detailed analysis of the length and time scales of the systems provides support for the identification of a plasma-induced mechanism. Thus, applications of sub-wavelength ablation will require robust near-field techniques with capability for high-power density delivery of light. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4719043]

A fabrication method for high-throughput, fiber-based tips for near-field scanning microscopy (NSOM) in the mid-infrared (λ ~ 3 μm) has been developed. Several fiber materials have been investigated and recipes for wet-chemical etching have been varied to produce tips that are physically robust and are capable of low-loss transmission of high-power pulses of mid-infrared light. Ultimately, wet-chemical etching techniques are used on glass fibers to produce tips capable of focusing mid-infrared light to ablate material from sub-micron-sized regions of organic films. The power throughput of the tips is significantly increased by using a novel material, previously unreported for NSOM applications: germanate fibers. The tips produced are mechanically strong and capable of transmitting high light fluence without sustaining physical damage. Here, the development of these tips and their performance are described.

We present a method for extracting high-spatial resolution dielectric constant data at microwave frequencies. A scanning near field microwave microscope probes a sample and acquires data in the form of the frequency and quality factor shifts of a resonant cavity coupled to the sample. The approach reported here is to calculate the electromagnetic fields by the finite element method in both static and time-dependent modes. Cavity perturbation theory connects the measured frequency shifts to changes in the computed energy stored in the electromagnetic field. In this way, the complex permittivity of the sample is found. Of particular interest are thin-film materials, for which a method is reported here to determine the dielectric constant without the need to use any fitting parameters.

We report on the development of a new instrument, dubbed a `Protein Microscope,' that uses near-field optical techniques to increase the spatial resolution of atmospheric pressure matrix-assisted laser desorption and ionization (AP-MALDI). This functions as a novel front-end for time-of-flight mass spectrometry. Standard protein identification techniques involve homogenization of a tissue sample, which destroys all spatial and temporal information about the expressed proteins. Our new NSOM-based instrument will allow the identification and mapping of proteins expressed in intact cells and tissues, which is of great interest as protein expression connects genomic information with the functioning of an organism. This poster will focus on the development of near-field-based ablation of sub-cellular-sized regions of tissue and plant samples.