1,130 research outputs found
Letter from Charles Mohr to John Muir, 1899 Jan 27.
[letterhead]Jan 27. 1899Dear Mr. Muir.I took the pleasure a couple of days past to mail to you a copy of the second edition of the Southern Timber Pines, which has been lab[illegible] issued. I shall happy if you will accept the book in kind remembrance of the hours you did spend with us in Mobile.The present is a strange winter with, Cloudy skies, scarcely interrupted by bright sunshine, continued chilly damp weather with frequent storms and heavy rains prevails almost constintly. In consequence I am doomed to indoor life, and have more than my wanted share of rheumatic troubles and heavy coughing spells. Matters are progressing nicely in regard to the progress in the publication of the Plant life of Alabama. I am hard at work to meet the suggestion to add to the catalogue of Vascular Plant in connection with the work, the Cellular plants so far known to occure in this state.With my warmest wishes I am truly yoursCharles MohrTo. John Muir Esq.Martinez, Cal.P.S. Please paste inclosed slip on the fly leaf of the Timber Pines.0253
St. Francis Barracks, St. Augustine; The Franciscans in Florida
St. Francis Barracks, once the home of the sons of St. Francis, is perhaps the only religious edifice ever taken and used continuously by the United States for military purposes. This came about through the treaty made with Spain and not by an act of hostility against the Catholic Church. The Franciscans will probably never again take possession of their ancient home. Surely, though, some day-and may it be soon-there will be some place in Florida to which they will be called to renew the work so successfully and efficiently performed by their saintly and courageous predecessors
Design and Evaluation of Stochastic Processes as Physical Radar Waveforms
Recent advances in waveform generation and in computational power have enabledthe design and implementation of new complex radar waveforms. Still despite these advances, in a waveform agile mode where the radar transmits unique waveforms for every pulse or a nonrepeating signal continuously, effective operation can be difficult due the waveform design requirements. In general, for radar waveforms to be both useful and physically robust they must achieve good autocorrelation sidelobes, be spectrally contained, and possess a constant amplitude envelope for high power operation. Meeting these design goals represents a tremendous computational overhead that can easily impede real-time operation and the overall effectiveness of the radar. This work addresses this concern in the context of random FM waveforms (RFM) that have been demonstrated in recent years in both simulation and in experiments to achieve low autocorrelation sidelobes through the high dimensionality of coherent integration when operating in a waveform agile mode. However, while they are effective, the approaches to design these waveforms require optimization of each individual waveform, making them subject to costly computational requirements. This dissertation takes a different approach. Since RFM waveforms are meant to be noise like in the first place, the waveforms here are instantiated as the sample functions of an underlying stochastic process called a waveform generating function (WGF). This approach enables the convenient generation of spectrally contained RFM waveforms for little more computational cost than pulling numbers from a random number generator (RNG). To do so, this work translates the traditional mathematical treatment of random variables and random processes to a more radar centric perspective such that the WGFs can be analytically evaluated as a function of the usefulness ofthe radar waveforms that they produce via metrics such as the expected matched filter response and the expected power spectral density (PSD). Further, two WGF models denoted as pulsed stochastic waveform generation (Pulsed StoWGe) and continuouswave stochastic waveform generation (CW-StoWGe) are devised as means to optimize WGFs to produce RFM waveform with good spectral containment and design flexibility between the degree of spectral containment and autocorrelation sidelobe levels for both pulsed and CW modes. This goal is achieved by leveraging gradient descent optimization methods to reduce the expected frequency template error (EFTE) cost function. The EFTE optimization is shown analytically using the metrics above, as well as others defined in this work and through simulation, to produce WGFs whose sample functions achieve these goals and thus produce useful random FM waveforms. To complete the theory-modeling-experimentation design life cycle, the resultant StoWGe waveforms are implemented in a loop-back configuration and are shown to be amenable to physical implementation
Multi-Objective Optimization of FM Noise Waveforms via Generalized Frequency Template Error Metrics
FM noise waveforms have been experimentally demonstrated to achieve high time bandwidth products and low autocorrelation sidelobes while achieving acceptable spectral containment in physical implementation. Still, it may be necessary to further reduce sidelobe levels for detection or improve spectral containment in the face of growing spectral use. The Frequency Template Error (FTE) and the Logarithmic Frequency Template Error (Log-FTE) metrics were conceived as means to achieve FM noise waveforms with good spectral containment and good autocorrelation sidelobes. In practice, FTE based waveform optimizations have been found to produce better autocorrelation responses at the expense of spectral containment while Log-FTE optimizations achieve excellent spectral containment and interference rejection at the expense of autocorrelation sidelobe levels. In this work, the notion of the FTE and Log-FTE metrics are considered as subsets of a broader class of frequency domain metrics collectively termed as the Generalized Frequency Template Error (GFTE). In doing so, many different P-norm based variations of the FTE and Log-FTE cost functions are extensively examined and applied via gradient descent methods to optimize polyphase-coded FM (PCFM) waveforms. The performance of the different P-norm variations of the FTE and Log-FTE cost functions are compared amongst themselves, against each other, and relative to a previous FM noise waveform design approach called Pseudo-Random Optimized FM (PRO-FM). They are evaluated in terms of their autocorrelation sidelobes, spectral containment, and their ability to realize spectral notches within the 3 dB bandwidth for the purpose of interference rejection. These comparisons are performed in both simulation and experimentally in loopback where it was found that P-norm values of 2 tend to provide the best optimization performance for both the FTE and Log-FTE optimizations except in the case of the Log-FTE optimization of a notched spectral template where a P-norm value of 3 provides the best results. In general, the FTE and Log-FTE cost functions as subsets of the GFTE provide diverse means to optimize physically robust FM noise waveforms while emphasizing different performance criteria in terms of autocorrelation sidelobes, spectral containment, and interference rejection
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Continual Non-Condensable Gas Removal Testing -- Performance and Lessons Learned
The operating experience and plant benefit analysis of a membrane-based continuous non-condensable gas (NCG) removal system is discussed. Results from testing at the Mammoth Pacific (Ormat) geothermal plant provide the basis for the benefit analysis
Identification of the fliI and fliJ Components of the Caulobacter Flagellar Type III Protein Secretion System
Caulobacter crescentus is motile by virtue of a polar flagellum assembled during the predivisional stage of the cell cycle. Three mutant strains in which flagellar assembly was blocked at an early stage were isolated. The mutations in these strains mapped to an operon of two genes, fliI and fliJ, both of which are necessary for motility. fliI encodes a 50-kDa polypeptide whose sequence is closely related to that of the Salmonella typhimurium FliI protein, an ATPase thought to energize the export of flagellar subunits across the cytoplasmic membrane through a type III protein secretion system. fliJ encodes a 16-kDa hydrophilic protein of unknown function. Epistasis experiments demonstrated that the fliIJ operon is located in class II of the C. crescentus flagellar regulatory hierarchy, suggesting that the gene products act at an early stage in flagellar assembly. The expression of fliIJ is induced midway through the cell cycle, coincident with other class II operons, but the FliI protein remains present throughout the cell cycle. Subcellular fractionation showed that FliI is present both in the cytoplasm and in association with the membrane. Mutational analysis of FliI showed that two highly conserved amino acid residues in a bipartite ATP binding motif are necessary for flagellar assembly
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Integrating protein-protein interaction networks with phenotypes reveals signs of interactions
A major objective of systems biology is to organize molecular interactions as networks and to characterize information-flow within networks. We describe a computational framework to integrate protein-protein interaction (PPI) networks and genetic screens to predict the “signs” of interactions (i.e. activation/inhibition relationships). We constructed a Drosophila melanogaster signed PPI network, consisting of 6,125 signed PPIs connecting 3,352 proteins that can be used to identify positive and negative regulators of signaling pathways and protein complexes. We identified an unexpected role for the metabolic enzymes Enolase and Aldo-keto reductase as positive and negative regulators of proteolysis, respectively. Characterization of the activation/inhibition relationships between physically interacting proteins within signaling pathways will impact our understanding of many biological functions, including signal transduction and mechanisms of disease
Precipitation Characteristics in Tropical Africa Using Satellite and In-Situ Observations
Tropical Africa receives nearly all its precipitation as a result of convection. The characteristics of rain-producing systems in this region, despite their crucial role in regional and global circulation, have not been well-understood. This is mainly due to the lack of in situ observations. Here, we have used precipitation records from the Trans-African Hydro-Meteorological Observatory (TAHMO) to improve our knowledge about the rainfall systems in the region, and to validate the recently-released IMERG precipitation product. The high temporal resolution of the gauge data has allowed us to identify three classes of rain events based on their duration and intensity. The contribution of each class to the total rainfall and the favorable surface atmospheric conditions for each class have been examined. As IMERG aims to continue the legacy of its predecessor, TMPA, and provide higher resolution data, continent-wide comparisons are made between these two products. IMERG, due to its improved temporal resolution, shows some advantages over TMPA in capturing the diurnal cycle and propagation of the meso-scale convective systems. However, the performance of the two satellite-based products varies by season, region and the evaluation statistics. The results of this study serve as a basis for our ongoing work on the impacts of biomass burning on precipitation processes in Africa
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