Bifurcation, mode coupling and noise in a nonlinear multimode superconducting RF resonator

The addition of nonlinearity to an harmonic resonator provides a route to complex dynamical behaviour of resonant modes, including coupling between them. We present a superconducting device that makes use of the nonlinearity of Josephson junctions to introduce a controlled, tunable, nonlinear inductance to a thin film coplanar waveguide resonator. Considering the device as a potential quantum optical component in the microwave regime, we create a sensitive bifurcation amplifier and then demonstrate spectroscopy of other resonant modes via the intermode coupling. We find that the sensitivity of the device approaches within a factor two quantitative agreement with a quantum model by Dykman, but is limited by a noise that has its source(s) on-chip

VEGF with AMD3100 Endogenously Mobilizes Mesenchymal Stem Cells and Improves Fracture Healing

A significant number of fractures develop non‐union. Mesenchymal stem cell (MSC) therapy may be beneficial, however, this requires cell acquisition, culture and delivery. Endogenous mobilization of stem cells offers a non‐invasive alternative. The hypothesis was administration of VEGF and the CXCR4 antagonist AMD3100 would increase the circulating pool of available MSCs and improve fracture healing. Ex‐breeder female wistar rats received VEGF followed by AMD3100, or sham PBS. Blood prepared for culture and colonies were counted. P3 cells were analyzed by flow cytometry, bi‐differentiation. The effect of mobilization on fracture healing was evaluated with 1.5 mm femoral osteotomy stabilized with an external fixator in 12–14 week old female Wistars. The mobilized group had significantly greater number of cfus/ml compared to controls, p = 0.029. The isolated cells expressed 1.8% CD34, 35% CD45, 61% CD29, 78% CD90, and differentiated into osteoblasts but not into adipocytes. The fracture gap in animals treated with VEGF and AMD3100 showed increased bone volume; 5.22 ± 1.7 µm3 and trabecular thickness 0.05 ± 0.01 µm compared with control animals (4.3 ± 3.1 µm3, 0.04 ± 0.01 µm, respectively). Radiographic scores quantifying fracture healing (RUST) showed that the animals in the mobilization group had a higher healing score compared to controls (9.6 vs. 7.7). Histologically, mobilization resulted in significantly lower group variability in bone formation (p = 0.032) and greater amounts of bone and less fibrous tissue than the control group. Clinical significance: This pre‐clinical study demonstrates a beneficial effect of endogenous MSC mobilization on fracture healing, which may have translation potential to prevent or treat clinical fractures at risk of delayed or non‐union fractures

Coupling of a locally implanted rare-earth ion ensemble to a superconducting micro-resonator

We demonstrate the coupling of rare-earth ions locally implanted in a substrate (Gd$^{3+}$ in Al$_{2}$O$_{3}$) to a superconducting NbN lumped-element micro-resonator. The hybrid device is fabricated by a controlled ion implantation of rare-earth ions in well-defined micron-sized areas, aligned to lithographically defined micro-resonators. The technique does not degrade the internal quality factor of the resonators which remain above $10^{5}$. Using microwave absorption spectroscopy we observe electron-spin resonances in good agreement with numerical modelling and extract corresponding coupling rates of the order of $1$ MHz and spin linewidths of $50 - 65$ MHz.Comment: 4 pages, 2 Figure

NASA GSFC Opportunities for STEM Professionals Using the Vantage Point of Space

NASA has a variety of learning opportunities for STEM professionals. Three opportunities at GSFC are examined in this chapter: 1) standard summer research and development internship for undergraduates, 2) senior internship for undergraduate and graduate students and 3) a workshop series for informal learning center professionals. We describe these programs, examine their evolution with respect to most effective education practices and their assessment and evaluation, and identify the similarities and differences between them. The internship programs highlight authentic project-based research and development experiences with the senior internship providing a richer, deeper, and more demanding experience that has greater professional value. The workshops for informal learning center professionals on-the-other hand, focus on building knowledge of GSFC s science and engineering strengths among these professionals, and on building enduring partnerships between individuals (participants and GSFC scientist, engineers and educators) and between organizations (GSFC and the informal learning center). Finally, we examine the characteristics of these programs from a design and management perspective. Through this examination we identify a general structure that provides insight into more effective design and management of similar education programs

Decoding the future from past experience: learning shapes predictions in early visual cortex.

Learning the structure of the environment is critical for interpreting the current scene and predicting upcoming events. However, the brain mechanisms that support our ability to translate knowledge about scene statistics to sensory predictions remain largely unknown. Here we provide evidence that learning of temporal regularities shapes representations in early visual cortex that relate to our ability to predict sensory events. We tested the participants' ability to predict the orientation of a test stimulus after exposure to sequences of leftward- or rightward-oriented gratings. Using fMRI decoding, we identified brain patterns related to the observers' visual predictions rather than stimulus-driven activity. Decoding of predicted orientations following structured sequences was enhanced after training, while decoding of cued orientations following exposure to random sequences did not change. These predictive representations appear to be driven by the same large-scale neural populations that encode actual stimulus orientation and to be specific to the learned sequence structure. Thus our findings provide evidence that learning temporal structures supports our ability to predict future events by reactivating selective sensory representations as early as in primary visual cortex.This work was supported by a Wellcome Trust Senior Research Fellowship to AEW (095183/Z/10/Z) and grants to ZK from the Biotechnology and Biological Sciences Research Council [H012508], a Leverhulme Trust Research Fellowship (RF-2011-378) and the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7/2007-2013/ under REA grant agreement no. PITN-GA-2011-290011.This is the published version. It first appeared at http://jn.physiology.org/content/early/2015/02/27/jn.00753.2014