Needed weather information where it belongs; in the cockpit

The availability of inflight weather data to the cockpit is discussed. The need for real-time information systems to warn of hazardous weather conditions is emphasized. It is suggested that the Weather Service severe weather radar network be collocated with the FAA radar to provide information for real-time decision making

Gravity gradient attitude control system Patent

Gravity gradient attitude control system with gravity gradiometer and reaction wheels for artificial satellite attitude contro

Shannon Information Theory and Molecular Biology

The role and the contribution of Shannon Information Theory to the development of Molecular Biology has been the object of stimulating debates during the last thirty years. This seems to be connected with some semantic charms associated with the use of the word \u201cinformation\u201d in the biological context. Furthermore information itself, if viewed in a broader perspective, is far from being completely defined in a fashion that overcomes the technical level at which the classical Information Theory has been conceived. This review aims at building on the acknowledged contribution of Shannon Information Theory to Molecular Biology, so as to discover if it is only a technical tool to analyze DNA and proteinic sequences, or if it can rise, at least in perspective, to a higher role that exerts an influence on the construction of a suitable model for handling the genetic information in Molecular Biology

Information flow during gene activation by signaling molecules: ethylene transduction in Arabidopsis cells as a study system

<p>Abstract</p> <p>Background</p> <p>We study root cells from the model plant <it>Arabidopsis thaliana </it>and the communication channel conformed by the ethylene signal transduction pathway. A basic equation taken from our previous work relates the probability of expression of the gene <it>ERF</it>1 to the concentration of ethylene.</p> <p>Results</p> <p>The above equation is used to compute the Shannon entropy (<it>H</it>) or degree of uncertainty that the genetic machinery has during the decoding of the message encoded by the ethylene specific receptors embedded in the endoplasmic reticulum membrane and transmitted into the nucleus by the ethylene signaling pathway. We show that the amount of information associated with the expression of the master gene <it>ERF</it>1 (Ethylene Response Factor 1) can be computed. Then we examine the system response to sinusoidal input signals with varying frequencies to determine if the cell can distinguish between different regimes of information flow from the environment. Our results demonstrate that the amount of information managed by the root cell can be correlated with the frequency of the input signal.</p> <p>Conclusion</p> <p>The ethylene signaling pathway cuts off very low and very high frequencies, allowing a window of frequency response in which the nucleus reads the incoming message as a sinusoidal input. Out of this window the nucleus reads the input message as an approximately non-varying one. From this frequency response analysis we estimate: a) the gain of the system during the synthesis of the protein ERF1 (~-5.6 dB); b) the rate of information transfer (0.003 bits) during the transport of each new ERF1 molecule into the nucleus and c) the time of synthesis of each new ERF1 molecule (~21.3 s). Finally, we demonstrate that in the case of the system of a single master gene (<it>ERF</it>1) and a single slave gene (<it>HLS</it>1), the total Shannon entropy is completely determined by the uncertainty associated with the expression of the master gene. A second proposition shows that the Shannon entropy associated with the expression of the <it>HLS</it>1 gene determines the information content of the system that is related to the interaction of the antagonistic genes <it>ARF</it>1, 2 and <it>HLS</it>1.</p

Prime movers : mechanochemistry of mitotic kinesins

Mitotic spindles are self-organizing protein machines that harness teams of multiple force generators to drive chromosome segregation. Kinesins are key members of these force-generating teams. Different kinesins walk directionally along dynamic microtubules, anchor, crosslink, align and sort microtubules into polarized bundles, and influence microtubule dynamics by interacting with microtubule tips. The mechanochemical mechanisms of these kinesins are specialized to enable each type to make a specific contribution to spindle self-organization and chromosome segregation

Identification of sortase A (SrtA) substrates in Streptococcus uberis: evidence for an additional hexapeptide (LPXXXD) sorting motif

Sortase (a transamidase) has been shown to be responsible for the covalent attachment of proteins to the bacterial cell wall. Anchoring is effected on secreted proteins containing a specific cell wall motif toward their C-terminus; that for sortase A (SrtA) in Gram-positive bacteria often incorporates the sequence LPXTG. Such surface proteins are often characterized as virulence determinants and play important roles during the establishment and persistence of infection. Intramammary infection with Streptococcus uberis is a common cause of bovine mastitis, which impacts on animal health and welfare and the economics of milk production. Comparison of stringently produced cell wall fractions from S. uberis and an isogenic mutant strain lacking SrtA permitted identification of 9 proteins likely to be covalently anchored at the cell surface. Analysis of these sequences implied the presence of two anchoring motifs for S. uberis, the classical LPXTG motif and an additional LPXXXD motif