Interstellar Communication: The Case for Spread Spectrum

Spread spectrum, widely employed in modern digital wireless terrestrial radio systems, chooses a signal with a noise-like character and much higher bandwidth than necessary. This paper advocates spread spectrum modulation for interstellar communication, motivated by robust immunity to radio-frequency interference (RFI) of technological origin in the vicinity of the receiver while preserving full detection sensitivity in the presence of natural sources of noise. Receiver design for noise immunity alone provides no basis for choosing a signal with any specific character, therefore failing to reduce ambiguity. By adding RFI to noise immunity as a design objective, the conjunction of choice of signal (by the transmitter) together with optimum detection for noise immunity (in the receiver) leads through simple probabilistic argument to the conclusion that the signal should possess the statistical properties of a burst of white noise, and also have a large time-bandwidth product. Thus spread spectrum also provides an implicit coordination between transmitter and receiver by reducing the ambiguity as to the signal character. This strategy requires the receiver to guess the specific noise-like signal, and it is contended that this is feasible if an appropriate pseudorandom signal is generated algorithmically. For example, conceptually simple algorithms like the binary expansion of common irrational numbers like Pi are shown to be suitable. Due to its deliberately wider bandwidth, spread spectrum is more susceptible to dispersion and distortion in propagation through the interstellar medium, desirably reducing ambiguity in parameters like bandwidth and carrier frequency. This suggests a promising new direction in interstellar communication using spread spectrum modulation techniques

The changing shape of sport through information technologies

The aim and focus of this study was to examine the changes in sport and with the sport's stakeholders with the introduction of technologies. The examination was conducted through series of interviews (n=36) and a review of the literature to gain understandings from three areas: (1) Professional players and coaches of professional players (2) Amateur players and coaches at amateur levels and (3) Spectators. The findings presented that players at the professional level are using various technologies such as GPS vests to manage workload and reduce risk of injury. With amateur level sport, technologies are not as prevalent and the possible introduction of technology was surprisingly not considered as imperative. Spectators, in general, considered that the introduction of technologies changed the dimensions of their involvement positively and negatively. The findings provide a basis for further studies and possible trials with additional technologies to further assist the athlete and coaches and innovatively enhance the spectator's experience

Investigating Risky Decision-Making with Curiosity and Outcome Expectations in a Simulated Experience

Researchers have established an association between curiosity and decision-making, in that curiosity can influence subsequent cognitions and actions either positively or negatively. The authors developed the present study to better understand how various facets of curiosity can predict decision-making. Additionally, we were interested in how decision-making could predict one’s outcome expectations (i.e., expectation of escape versus capture in a simulated experience). As experts have understood curiosity to be understood in multiple facets (Litman, 2008; Lindgren et al., 2010), the initial hypothesis of the present study was to determine which facet of curiosity (e.g., diversive, intolerance, competency, problem-solving) was most appropriate in understanding its effects on risky decision-making. Additionally, the authors hypothesized that participants inclined to make more risk-taking decisions would be more likely to anticipate their escape from the simulation rather than their capture. Results found that people with high diversive curiosity made more risk-averse choices. Additionally, results suggest that participants with higher risk-taking decisions were significantly more likely to predict their escape rather than capture in a simulated experience. The authors provide implications for future research

Technological Challenges in Low-mass Interstellar Probe Communication

Building on a preliminary paper design of a downlink from a swarm of low-mass interstellar probes for returning scientific data from the vicinity of Proxima Centauri, the most critical technology issues are summarized, and their significance is explained in the context of the overall system design. The primary goal is to identify major challenges or showstoppers if such a downlink were to be constructed using currently available off-the-shelf technology, and thereby provide direction and motivation to future research on the constituent design challenges and technologies. While there are not any fundamental physical limits that prevent such communication systems, currently available technologies fall significantly short in several areas and there are other major design challenges with uncertain solutions. The greatest identified challenges are in mass constraints, multiplexing simultaneous communication from multiple probes to the same target exoplanet, attitude control and pointing accuracy, and Doppler shifts due to uncertainty in probe velocity. The greatest technology challenges are electrical power, high power and wavelength-agile optical sources, very selective and wavelength-agile banks of optical bandpass filters, and single-photon detectors with extremely low dark-count rates. For a critical subset of these, we describe the nature of the difficulties we encounter and their origins in the overall system context. A receiver that limits reception to a single probe is also considered and compared to the swarm case

Challenges in Scientific Data Communication from Low-Mass Interstellar Probes

A downlink for the return of scientific data from space probes at interstellar distances is studied. The context is probes moving at relativistic speed using a terrestrial directed-energy beam for propulsion, necessitating very-low mass probes. Achieving simultaneous communication from a swarm of probes launched at regular intervals to a target at the distance of Proxima Centauri is addressed. The analysis focuses on fundamental physical and statistical communication limitations on downlink performance rather than a concrete implementation. Transmission time/distance and probe mass are chosen to achieve the best data latency vs volume tradeoff. Challenges in targeting multiple probe trajectories with a single receiver are addressed, including multiplexing, parallax, and target star proper motion. Relevant sources of background radiation, including cosmic, atmospheric, and receiver dark count are identified and estimated. Direct detection enables high photon efficiency and incoherent aperture combining. A novel burst pulse-position modulation (BPPM) beneficially expands the optical bandwidth and ameliorates receiver dark counts. A canonical receive optical collector combines minimum transmit power with constrained swarm-probe coverage. Theoretical limits on reliable data recovery and sensitivity to the various BPPM model parameters are applied, including a wide range of total collector areas. Significant near-term technological obstacles are identified. Enabling innovations include a high peak-to-average power ratio, a large source extinguishing factor, the shortest atmosphere-transparent wavelength to minimize target star interference, adaptive optics for atmospheric turbulence, very selective bandpass filtering (possibly with multiple passbands), very low dark-count single-photon superconducting detectors, and very accurate attitude control and pointing mechanisms

Interstellar flyby scientific data downlink design

The design of a downlink communication system for returning scientific data from an interstellar flyby probe is reviewed in this tutorial white paper. It its assumed that the probe is ballistic, and data is downloaded during a period following encounter with the target star and its exoplanet(s). Performance indices of interest to scientific investigators include the total launch-to-completion data latency and the total volume of data reliably recovered. Issues considered include the interaction between the speed and mass of the probe and the duration of downlink transmission. Optical communication using pulse-position modulation (PPM) with error-correction coding (ECC) is assumed. A very large receiver collection area on or near Earth is composed of individual incoherently-combined diffraction-limited apertures. Other important issues in the design including transmit and receive pointing accuracy and beam size and receiver field of view are reviewed. Numerical examples assume a mission to Proxima Centauri (the nearest star to our Sun) initially launched by directed-energy propulsion from the vicinity of Earth

1 Comparison of Transform Coding Techniques for Two- Dimensional Arbitrarily-Shaped Images 1

Envisioned advanced multimedia video services include arbitrarily-shaped (AS) image segments as well as regular rectangular images. Images segments of the TV weather reporter produced by the chromo-key technique [1] and image segments produced by video analysis and image segmentation[2,3,4] are typical examples of AS image segments. This paper explores efficient intraframe transform coding techniques for general two-dimensional (2D) AS image segments, treating the traditional rectangular images as a special case. In particular, we focus on transform coding of the partially-defined image blocks along the boundary of the AS image segments. We recognize two different approaches — the brute-force transform coding approach and the shape-adaptive transform coding approach. The former fills up the uncovered area with the optimal redundant data such that the resulting transform spectrum is compact. A simple but efficient mirror-image extension technique is proposed. Once augmented into full image blocks, these boundary blocks can be processed by traditional block-based transform techniques like the popular Discrete Cosine Transform (DCT). In the second approach, we change either the transform basis or the coefficient calculation process adaptively based on the shape of the A

Identifizierung und Charakterisierung von Proteinen, die Fusion und Teilung von Mitochondrien vermitteln

Die Kontinuität des mitochondrialen Kompartiments wird durch fortlaufende Membranfusions- und Teilungsereignisse aufrechterhalten. Das Verständnis der Prozesse, die wichtig für die Funktion und die Vererbung der Mitochondrien sind, erfordert die Identifizierung und Charakterisierung der daran beteiligten molekularen Komponenten. Im Rahmen der hier vorgelegten Arbeit wurde eine neue Komponente, MDM33, identifiziert und charakterisiert. Dabei handelt es sich um ein Gen, welches für ein Protein der mitochondrialen Innenmembran kodiert, und dessen Deletionsmutante einen völlig neuartigen Phänotyp aufweist. Zellen, denen das Mdm33-Protein fehlt, enthalten ringähnliche, miteinander verbundene Mitochondrien, welche große Hohlkugeln ausbilden können. Diese Organellen weisen extrem auseinander gezogene Abschnitte der Außen- und Innenmembran auf, die einen sehr schmalen Matrixspalt umschließen. Die Überexpression von Mdm33 führt zur Einstellung des Wachstums, die Mitochondrien aggregieren, und es entwickelt sich eine stark veränderte Innenmembranstruktur. Es bilden sich verstärkt Septen aus, die den Matrixraum mehrfach unterteilen, oder die Innenmembran verliert die Cristae und fragmentiert. Genetische Hinweise zeigen, dass das Mdm33-Protein vor den Komponenten der Teilungsmaschine der Außenmembran agiert, und dass die mitochondriale Fusion eine Voraussetzung für die Ausbildung der ausgedehnten ringähnlichen Mitochondrien in mdm33-Zellen ist. Mdm33 assembliert zu einem oligomeren Komplex in der Innenmembran und bildet homotypische Protein-Protein-Interaktionen aus. Diese Ergebnisse deuten darauf hin, dass Mdm33 bei der Teilung der mitochondrialen Innenmembran involviert ist. Das Fzo1-Protein ist eine zentrale Komponente der mitochondrialen Fusionsmaschinerie in der Außenmembran. Fzo1 assembliert sowohl in S. cerevisiae als auch in N. crassa in einen großen Proteinkomplex. Es sollte untersucht werden, welche Proteine Bestandteile dieses Komplexes sind. Daher wurde ein N. crassa-Stamm erzeugt, der stabil Fzo1 mit einem Hexahistidinanhang exprimiert, um den Fzo1-Komplex in größeren Mengen reinigen und mögliche Interaktionspartner identifizieren zu können. Dieser gereinigte Fzo1-Komplex ermöglicht nun auch mechanistische Studien zur Funktionsweise der Fusionsmaschine