Fit for Green Online Notification and Reporting System

Fit for Green seeks to combat two main threats on the American home front: obesity and the energy crisis. This project is an online Notification & Reporting System that allows gym administrators using the Fit for Green solutions the ability to instantly generate reports and have those reports emailed to them on a scheduled (daily or weekly) basis. The reports contain metrics pertinent to the gym (e.g. one metric may be Average Power Generated per Workout Session)

Gapless fluctuations and exceptional points in semiconductor lasers

We analyze the spectrum of spatially uniform, single-particle fluctuation modes in the linear electromagnetic response of a semiconductor laser. We show that if the decay rate of the interband polarization, $\gamma_p$, and the relaxation rate of the occupation distribution, $\gamma_f$, are different, a gapless regime exists in which the order parameter $\Delta^{(0)} (k)$ (linear in the coherent photon field amplitude and the interband polarization) is finite but there is no gap in the real part of the single-particle fluctuation spectrum. The laser being a pumped-dissipative system, this regime may be considered a non-equilibrium analog of gapless superconductivity. We analyze the fluctuation spectrum in both the photon laser limit, where the interactions among the charged particles are ignored, and the more general model with interacting particles. In the photon laser model, the order parameter is reduced to a momentum-independent quantity, which we denote by $\Delta$. We find that, immediately above the lasing threshold, the real part of the fluctuation spectrum remains gapless when $0 < | \Delta | < \sqrt{2 / 27} \, | \gamma_f - \gamma_p |$ and becomes gapped when $| \Delta |$ exceeds the upper bound of this range. Viewed as a complex function of $|\Delta|$ and the electron-hole energy, the eigenvalue set displays some interesting exceptional point (EP) structure around the gapless-gapped transition. The transition point is a third-order EP, where three eigenvalues (and eigenvectors) coincide. Switching on the particle interactions in the full model modifies the spectrum of the photon laser model and, in particular, leads to a more elaborate EP structure. However, the overall spectral behavior of the continuous (non-collective) modes of the full model can be understood on the basis of the relevant results of the photon laser model

Collective terahertz fluctuation modes in a polariton laser

A polariton Bardeen-Cooper-Schrieffer (BCS) state in a semiconductor microcavity is an example of symmetry-broken states in open systems. Fluctuations of the order parameter are an important tool to characterize such a state. With the condensate formed by composite particles, the set of zero-momentum fluctuations spans an infinite-dimensional electron-hole mode subspace. We show that collective fluctuation modes with orbital angular momentum different from that of the order parameter can be obtained with terahertz radiation, and that a physical manifestation of such modes, which are not Higgs modes, can be terahertz gain.Comment: 23 pages, 13 figure

Bit-Serial Adder Based on Quantum Dots

A proposed integrated circuit based on quantum-dot cellular automata (QCA) would function as a bit-serial adder. This circuit would serve as a prototype building block for demonstrating the feasibility of quantum-dots computing and for the further development of increasingly complex and increasingly capable quantum-dots computing circuits. QCA-based bit-serial adders would be especially useful in that they would enable the development of highly parallel and systolic processors for implementing fast Fourier, cosine, Hartley, and wavelet transforms. The proposed circuit would complement the QCA-based circuits described in "Implementing Permutation Matrices by Use of Quantum Dots" (NPO-20801), NASA Tech Briefs, Vol. 25, No. 10 (October 2001), page 42 and "Compact Interconnection Networks Based on Quantum Dots" (NPO-20855), which appears elsewhere in this issue. Those articles described the limitations of very-large-scale-integrated (VLSI) circuitry and the major potential advantage afforded by QCA. To recapitulate: In a VLSI circuit, signal paths that are required not to interact with each other must not cross in the same plane. In contrast, for reasons too complex to describe in the limited space available for this article, suitably designed and operated QCA-based signal paths that are required not to interact with each other can nevertheless be allowed to cross each other in the same plane without adverse effect. In principle, this characteristic could be exploited to design compact, coplanar, simple (relative to VLSI) QCA-based networks to implement complex, advanced interconnection schemes. To enable a meaningful description of the proposed bit-serial adder, it is necessary to further recapitulate the description of a quantum-dot cellular automation from the first-mentioned prior article: A quantum-dot cellular automaton contains four quantum dots positioned at the corners of a square cell. The cell contains two extra mobile electrons that can tunnel (in the quantum-mechanical sense) between neighboring dots within the cell. The Coulomb repulsion between the two electrons tends to make them occupy antipodal dots in the cell. For an isolated cell, there are two energetically equivalent arrangements (denoted polarization states) of the extra electrons. The cell polarization is used to encode binary information. Because the polarization of a nonisolated cell depends on Coulomb-repulsion interactions with neighboring cells, universal logic gates and binary wires could be constructed, in principle, by arraying QCA of suitable design in suitable patterns. Again, for reasons too complex to describe here, in order to ensure accuracy and timeliness of the output of a QCA array, it is necessary to resort to an adiabatic switching scheme in which the QCA array is divided into subarrays, each controlled by a different phase of a multiphase clock signal. In this scheme, each subarray is given time to perform its computation, then its state is frozen by raising its inter-dot potential barriers and its output is fed as the input to the successor subarray. The successor subarray is kept in an unpolarized state so it does not influence the calculation of preceding subarray. Such a clocking scheme is consistent with pipeline computation in the sense that each different subarray can perform a different part of an overall computation. In other words, QCA arrays are inherently suitable for pipeline and, moreover, systolic computations. This sequential or pipeline aspect of QCA would be utilized in the proposed bit-serial adders

Compact Interconnection Networks Based on Quantum Dots

Architectures that would exploit the distinct characteristics of quantum-dot cellular automata (QCA) have been proposed for digital communication networks that connect advanced digital computing circuits. In comparison with networks of wires in conventional very-large-scale integrated (VLSI) circuitry, the networks according to the proposed architectures would be more compact. The proposed architectures would make it possible to implement complex interconnection schemes that are required for some advanced parallel-computing algorithms and that are difficult (and in many cases impractical) to implement in VLSI circuitry. The difficulty of implementation in VLSI and the major potential advantage afforded by QCA were described previously in Implementing Permutation Matrices by Use of Quantum Dots (NPO-20801), NASA Tech Briefs, Vol. 25, No. 10 (October 2001), page 42. To recapitulate: Wherever two wires in a conventional VLSI circuit cross each other and are required not to be in electrical contact with each other, there must be a layer of electrical insulation between them. This, in turn, makes it necessary to resort to a noncoplanar and possibly a multilayer design, which can be complex, expensive, and even impractical. As a result, much of the cost of designing VLSI circuits is associated with minimization of data routing and assignment of layers to minimize crossing of wires. Heretofore, these considerations have impeded the development of VLSI circuitry to implement complex, advanced interconnection schemes. On the other hand, with suitable design and under suitable operating conditions, QCA-based signal paths can be allowed to cross each other in the same plane without adverse effect. In principle, this characteristic could be exploited to design compact, coplanar, simple (relative to VLSI) QCA-based networks to implement complex, advanced interconnection schemes. The proposed architectures require two advances in QCA-based circuitry beyond basic QCA-based binary-signal wires described in the cited prior article. One of these advances would be the development of QCA-based wires capable of bidirectional transmission of signals. The other advance would be the development of QCA circuits capable of high-impedance state outputs. The high-impedance states would be utilized along with the 0- and 1-state outputs of QCA

Hybrid VLSI/QCA Architecture for Computing FFTs

A data-processor architecture that would incorporate elements of both conventional very-large-scale integrated (VLSI) circuitry and quantum-dot cellular automata (QCA) has been proposed to enable the highly parallel and systolic computation of fast Fourier transforms (FFTs). The proposed circuit would complement the QCA-based circuits described in several prior NASA Tech Briefs articles, namely Implementing Permutation Matrices by Use of Quantum Dots (NPO-20801), Vol. 25, No. 10 (October 2001), page 42; Compact Interconnection Networks Based on Quantum Dots (NPO-20855) Vol. 27, No. 1 (January 2003), page 32; and Bit-Serial Adder Based on Quantum Dots (NPO-20869), Vol. 27, No. 1 (January 2003), page 35. The cited prior articles described the limitations of very-large-scale integrated (VLSI) circuitry and the major potential advantage afforded by QCA. To recapitulate: In a VLSI circuit, signal paths that are required not to interact with each other must not cross in the same plane. In contrast, for reasons too complex to describe in the limited space available for this article, suitably designed and operated QCAbased signal paths that are required not to interact with each other can nevertheless be allowed to cross each other in the same plane without adverse effect. In principle, this characteristic could be exploited to design compact, coplanar, simple (relative to VLSI) QCA-based networks to implement complex, advanced interconnection schemes

Middle and posterior cardiac veins: An underused option for ventricular pacing

Tarrasó, Olga;Fuente Fuente, Carlos;Reventós, Manue

971-56 Myocardial Contrast Echocardiography can be Used to Assess Dynamic Changes in Microvascular Function In-Vivo

The transit rate of sonicated albumin microbubbles (Albunex®, mean size=4.3 μ) has been shown to correlate with that of radiolabelled red blood cells in the blood perfused beating heart. We have previously demonstrated that the transit rate of these microbubbles is decreased during hyperthermia-induced microvascular injury In this study, we hypothesized that microbubble transit rate could be used as a marker of reversible endothelial injury during myocardial contrast echocardiography (MCE).We produced endothelial injury by inducing different degrees of myocardial hypoxia. This was accomplished by perfusing an arrested heart with either arterial blood, venous blood, or blood diluted to different degrees with a crystalloid cardioplegia solution. The flow rate into the cross-clamped aorta was held constant in each dog (mean=170mi), as was the perfusate temperature (mean = 27°C). Perfusate hematocrit varied from 0–27%, while perfusate pO2 ranged from 15–600mmHg. MCE was performed by injecting 2ml of a 1:1 dilution of Albunex® into the perfusate line and images were acquired at a sampling rate of 30 Hz. The mean transit rate of Albunex® through the myocardium was derived by fitting a λ-variate function to the background-subtracted time-intensity plots. The mean transit rate of Albunex® decreased as the hematocrit decreased. On multivariate analysis, the hematocrit and the pO2 were the best correlates of mean microbubble transit rate (y=0.06 hematocrit-0.002 pO2+0.72, r=0.72, p&lt;0.001).We conclude that MCE, can be used to assess reversible microvascular injury. This technique, therefore, has great potential for understanding dynamic changes in microvascular function in-vivo, particularly those modulated by the endothelium

Effects of Spaceflight on Human Induced Pluripotent Stem Cell-Derived Cardiomyocyte Structure and Function.

With extended stays aboard the International Space Station (ISS) becoming commonplace, there is a need to better understand the effects of microgravity on cardiac function. We utilized human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) to study the effects of microgravity on cell-level cardiac function and gene expression. The hiPSC-CMs were cultured aboard the ISS for 5.5 weeks and their gene expression, structure, and functions were compared with ground control hiPSC-CMs. Exposure to microgravity on the ISS caused alterations in hiPSC-CM calcium handling. RNA-sequencing analysis demonstrated that 2,635 genes were differentially expressed among flight, post-flight, and ground control samples, including genes involved in mitochondrial metabolism. This study represents the first use of hiPSC technology to model the effects of spaceflight on human cardiomyocyte structure and function