Spectrum sensing by cognitive radios at very low SNR

Spectrum sensing is one of the enabling functionalities for cognitive radio (CR) systems to operate in the spectrum white space. To protect the primary incumbent users from interference, the CR is required to detect incumbent signals at very low signal-to-noise ratio (SNR). In this paper, we present a spectrum sensing technique based on correlating spectra for detection of television (TV) broadcasting signals. The basic strategy is to correlate the periodogram of the received signal with the a priori known spectral features of the primary signal. We show that according to the Neyman-Pearson criterion, this spectral correlation-based sensing technique is asymptotically optimal at very low SNR and with a large sensing time. From the system design perspective, we analyze the effect of the spectral features on the spectrum sensing performance. Through the optimization analysis, we obtain useful insights on how to choose effective spectral features to achieve reliable sensing. Simulation results show that the proposed sensing technique can reliably detect analog and digital TV signals at SNR as low as -20 dB.Comment: IEEE Global Communications Conference 200

Coordination of G Protein and Mitogen-Activated Protein Kinase Signaling Pathways by Branched-Chain Amino Acid Metabolite Second Messengers during Osmotic Stress

Cells experience a variety of environmental signals, often simultaneously. These signals may encode opposing effects, so the response must be coordinated in a manner that promotes cell and organismal well-being. The expression of surface receptors, such as G protein-coupled receptors (GPCRs), aids in the detection of bioactive molecules. Once perceived by the cell, the signal is transduced to intracellular signaling components that carry out the appropriate response. Mitogen-activated protein kinase (MAPK) cascades are commonly activated in response to external stimuli that range from growth factors to environmental stresses. The budding yeast S. cerevisiae employs MAPK pathways to respond to mating pheromones and environmental stresses. The pheromone response pathway is a MAPK pathway regulated by a GPCR, and the high osmolarity glycerol (HOG) pathway is a parallel MAPK pathway that shares some components with the pheromone response pathway. Signal fidelity is maintained during simultaneous activation of these and other MAPK pathways through mechanisms including signal strength and duration, feedback regulation, and cross-pathway inhibition. In this dissertation, I identify a new means by which parallel MAPK pathways are regulated. I show that activation of the HOG pathway promotes the production of second messenger molecules derived from branched-chain amino acids. These new second messengers promote phosphorylation of the Gα subunit regulating the pheromone response pathway, and lead to reduced downstream transcriptional output. I also compare conventional and recently developed methods for analyzing MAPK activation and gene transcription. This work adds to our understanding of how signaling pathway cross-talk can maintain signal fidelity, and provides an update on the methods that can be used to best study these pathways for future discoveries.Doctor of Philosoph

The impact of space and space-related activities on a local economy. a case study of boulder, colorado. part i- the input-output analysis

Impact of space and space-related activities on industry and general economy of Boulder, Colorad

Impact of static dry-hopping rate on the sensory and analytical profiles of beer

Dry-hopping is a technique that has been used by brewers to increase the hop aroma and flavour of beer for centuries. Throughout the twenty first century, dry-hopping has become an increasingly popular method among craft brewers to impart intense hoppy aroma and flavour to beer. Many US craft brewers use extremely high dry-hop dosing rates of up to 2200 g/hL and this is both unsustainable and potentially wasteful. This study examines the impact of dry-hopping rate on the sensorial and analytical characteristics of dry-hopped beers. An unhopped pale beer was statically dry-hopped with whole cone Cascade from the 2015 harvest over a broad range of dry-hopping rates (200-1600 g/hL) in replicated, pilot scale (80 L) aliquots. Trained panellists using descriptive analysis scaled the overall and qualitative hop aroma intensity of these beers, as well as the unhopped base beer. Instrumental analysis was used to measure the levels of hop volatile and non-volatile extraction between the treatments. The relationship between dry-hopping rate and the sensorial and analytical characteristics of the finished beer was not linear and, based on the extraction efficiencies of select hop volatiles, had an ideal range between 400 and 800 g/hL. (C) 2018 The Institute of Brewing & Distillin

Sensory Directed Mixture Study of Beers Dry-Hopped with Cascade, Centennial, and Chinook

American craft beer style and flavor is often driven by the unique qualities of American hops. Cascade, Chinook, and Centennial hops are used prominently for dry-hopping singly and/or in blends to impart an intense hoppy aroma to beer. A sensory directed dry-hopping mixture study was performed to understand the contribution that each of these hops make to beer aroma. Utilizing a 4th degree simplex-lattice mixture-design, sixteen beers were prepared (including an "unhopped" control) by dry-hopping a common "unhopped" base beer with different blends of ground whole cone hops made from the three hop cultivars. The treatments were evaluated by trained panelists using descriptive analysis, where the response variables used by the panel encompassed the sensory attributes that described the unique aromatic features of these three hops, (i.e., citrus, tropical/fruity, tropical/catty, and herbal). Using these outputs, the sensory contributions of each individual cultivar, as well as mixtures of the cultivars, were examined on a per attribute basis. These results can be used to select combinations or blends of the three hops for use during dry-hopping that provide similar or dissimilar overall aroma intensity and quality in dry-hopped beer