Browsing by Subject "Master of Science"

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(1+1) Evolutionary Algorithm on Random Planted Vertex Cover Problems
(2024-03) Kearney, Jack
Evolutionary Algorithms are powerful optimization tools that use the power of randomness and inspiration from biology to achieve results. A common combinatorial optimization problem is the recovery of a minimum vertex cover on some graph 𝐺 = (𝑉, 𝐸). In this work, an evolutionary algorithm will be employed on specific instances of the minimum vertex cover problem containing a random planted solution. This situation is common in data networks and translates to a core set of nodes and larger fringe set that are connected to the core. This study introduces a parameterized analysis of a standard (1+1) Evolutionary Algorithm applied to the random planted distribution of vertex cover problems. When the planted cover is at most logarithmic, restarting the (1+1) EA every 𝑂(𝑛 log 𝑛) steps will, within polynomial time, yield a cover at least as small as the planted cover for sufficiently dense random graphs (𝑝 > 0.71). For superlogarithmic planted covers, the (1+1) EA is proven to find a solution within fixed-parameter tractable time in expectation. To complement these theoretical investigations, a series of computational experiments were conducted, highlighting the intricate interplay between planted cover size, graph density, and runtime. A critical range of edge probability was also investigated.
A 2000 Year Sub-annual Record of Climate Change from Lake Malawi
(2009-08) Petrick, Benjamin Fredericks
Lake Malawi, in East Africa, provides a rare opportunity to look at a sub-annual record of climate change from a region were there is a lack of good climate records. This is possible because the upper most sediments in the north basin Lake Malawi are varved. The varved record extends from back 1200-2000 years depending on dating differences and is well dated back 800 years. In order to construct an overall sub-annual record of climate change, overlapping sections of two cores from the north basin of Lake Malawi taken during the recent Malawi drilling project were examined on a scanning XRF with a step size of .2 mm. This provided an average of 6 measurements per annual varve couplet. Because of the chemical differences between light and dark varves it was possible to count these varves using a high resolution photograph and x-radiography images in conjunction with the chemical data. Four major chemical elements or ratios of chemical element were used to represent the four major components in the sediments of the core: Fe is a proxy for the clay, Si/Ti is a proxy for the Biogenic Silica (BSi, inc/coh scattering ratio is a proxy for %Total Organic Carbon (TOC), and K/Ti is a proxy for volcanic sediments. Comparing Fe to recent records of lake level fall and rise suggests that Fe be when the planktonic community is dominated by diatoms it reflects changes in year to year fluvial input. However at times of change in the planktonic community, the Fefluvial imput relationship breaks down. Comparisons of both the lake level records and to coral records from the Indian Ocean show that both lake level rise and fall are enhanced by increased ocean temperatures over periods of 5-10 years. This suggests that changes in Indian Ocean temperatures have an affect on Lake Malawi. The lake records show no connection to Zimbabwe rainfall but an opposite relationship with Indian rainfall. The inc/coh shows a strong relationship over the last 150 years with IOD and proportion of diatoms in the planktonic community, which tends to change during times with great IOD variability. These relationships suggest that IOD causes changes in the winds that stimulate production of planktonic during the dry season. Looking further back in the record shows that similar shifts to non-diatom dominated planktonic community occurred twice before in the record and there is some evidence in the record that changes in winds might be responsible for these events as well. 11 year and 3-7 year cycles were also found in the record but their meaning is unclear. The times when the 11 year cycle is strong in the lake are not assonated with the record of sunspots and the 3 to 7 year cycle does not seem to be related to changes in ESNO as would be expected. Therefore the meaning of the cycles is still not understood. The longer record suggests dry periods from the bottom of the varved section to around 1250 AD and from 1550 to 1650 AD, with an interceding wetter period from 1250 to 1650 AD. The record from 1650 AD to current day shows some rises and falls and an overall steady record. Comparing this to other records of African lakes and caves shows that this record has similarities to the records of East African lakes but is in opposite of records from Cold Air Cave in Southern Africa. Lastly it also shows similarities to records of Indian monsoon wind strength which is controlled by Indian Ocean temperatures and Cariaco basin records which are a proxy for the ITCZ. Both of these records show that the migration of the ITCZ and changes in Indian Ocean temperatures are important drivers for Lake Malawi and the findings of this paper may be useful in looking at changes both at longer time scales and in the future as well.
210Pb Geochronology in Lake Superior Sediments: Sedimentation Rates, Organic Carbon Deposition, Sedimentary Environments, and Post-Depositional Processes
(1980-07) Evans, James Erwin
210Pb geochronology is used to determine sedimentation rates, 210Pb flux rates, and organic carbon deposition rates from 17 sediment box cores in Lake Superior, U.S.A. These data, in conjunction with organic carbon, PCB, trace metal, benthic organism, and sedimentary structure data, are used to investigate depositional and postdepositional processes. Sedimentation rates vary from 0.01-0.20 cm/yr in Lake Superior. A dynamic model is presented which emphasizes: (1) very high (greater than 0.15 cm/yr) sedimentation rates in marginal bays, (2) moderate to very high (0.07-0.19 cm/yr) open lake sedimentation rates in regions adjacent to marginal bays, these regions are affected by plumes of suspended sediment that originate in marginal bays by wave-stirring of bottom sediments, and enter the open lake, (3) moderate to high (0.05-0.11 cm/yr) sedimentation rates adjacent to the Red Clay Area, where shoreline recession rates are high, (4) moderate to high (0.05-0.12 cm/yr) sedimentation rates in the deepest portions of the Lake Superior Troughs region, with downslope sediment movement off the adjacent shoals and into the troughs, (5) low to moderate (0.04-0.05 cm/yr) sedimentation rates from cores with current bedding features in the Keweenaw Current region, and (6) very low (0.01-0.03 cm/yr) sedimentation rates in the central lake basins due to isolation from sediment sources. Organic carbon deposition rates (K) range from 0.0001 to 0.0032 g Carbon/cm2/yr, and K varies as a power function of sedimentation rate W (g/cm2/ yr) such that K = 0.04 W1.03. This result may imply that higher sedimentation rates favor organic carbon preservation with rapid removal from the oxidizing conditions at the sediment-water interface through burial. However, the exponent is very close to 1.00, which implies that a constant proportion of organic matter is deposited with sedimentation at any site. Calculations using primary productivity measurements and average K values indicate that about 77-87% of primary production carbon is oxidized in the water column during deposition. The 210 Pb flux rate P (dpm/cm2/ yr) is directly related to the organic carbon deposition rate, such that K = 4 x 10-4P. This indicates that the main transfer mechanism for 210Pb through the water column is via association with organic particles. Organic carbon concentrations (C) decline exponentially with increasing sediment age from surficial values of 1-5% to "background" values of 0.5% in 9,000 year old sediment. The decay phenomena can be described by C = C0 e-λt, with values for the decay constant (λ) ranging from 0.2 to 1.7 x 10 -2/yr. These decay constants are 2 to 3 orders of magnitude higher than the oceans, probably due to the presence of younger and more chemically reactive organic components in Lake Superior sediments. The sedimentation rate (W) is inversely related to the decay constant (λ), such that λ = 5.33 x 10 -4 w -0.53. This may indicate that rapid burial promotes organic matter preservation. Independent evidence for biological mixing of Lake Superior sediments includes surficial zones of constant 210Pb activity, the presence of PCB substances below the sediment horizon corresponding to its first usage in commercial quantities, benthic organism studies, and lack of lamination in the upper portions of cores on x-radiographs. Oligochaete displacement rates are calculated which equal or exceed sediment accumulation rates in many cores. This indicates that oligochaetes cause significant sediment mixing at some sites. At other sites, additional mixing by burrowing amphipods may increase sediment mixing. Mixing is considered as a mechanistic analogue to diffusion phenomenon, and mixing (eddy diffusion) coefficients are calculated (Db = 0.002-10.54 cm2/yr). The highest of these compare to other studies from lakes and nearshore marine regions, while the lowest compare to rates from abyssal regions. Zones of constant 210Pb activity at depth in the sediment correspond to the time intervals 1900-1910, 1910-1920, and 1940-1950. These are interpreted as storm deposit layers, and may correspond to major storms which occurred in the Lake Superior region during November 27-28, 1905, November 22-24, 1918, and November 10-12, 1940. Diagenetic horizons are described from the sediments, these include 1-2 mm thick black laminations, 1.0-1.5 cm thick orange-colored "crusts", and layers 3-5 cm thick of many 1-2 mm diameter micronodules. The available evidence indicates that the black laminations are Mn enrichments and the orange-colored crusts may be Fe enrichments.
The Amazing Composobot: Music Information Retreval and Algorithmic Composition
(2018-05) Walker, Marcus
Music has powerful and inscrutable effects on the human mind, and we are far from fully understanding how that magic works. But music is not random: there are patterns in the sounds and rhythms of a piece that can be analyzed, things that can be learned! In this work I will review relevant research on the subject of Music Information Retrieval and then introduce Composobot, an original program that incorporates and extends the lessons of that research. Together we will examine how Composobot prepares musical pieces for processing, analyzes them to extract systems of patterns and dependencies, and then composes novel musical pieces based on what it has learned. Finally, we will discuss how much of the magic that is in the music we love can be captured by learning patterns the way Composobot does, and how those methods might be tweaked to capture an even greater share of it.
Analysis of the Potential Hoag-type Galaxy WISEA J234255.19-354810.2
(2022-07) Swanson, Alaina M
Ring galaxies are among the most perplexing phenomena we observe in space. Their formation has remained a topic of debate, especially since 1950 when Arthur Hoag discovered Hoag’s Object. Hoag-like objects are exceedingly rare and the ring galaxy WISEA J234255.19-354810.2 has the potential to be the 16th Hoag-type galaxy discovered. I performed two types of data analysis to obtain information about the galactic light profiles. From this analysis, I discovered a very faint bar structure within the core of the ring galaxy, which indicates that WISEA J234255.19-354810.2 is not a Hoag-type galaxy.
Applied Time Series and Duluth Temperature Prediction
(2017-06) Wan, Xiangpeng
Autoregressive integrated moving average (ARIMA) has been one of the popular linear models in time series forecasting during the past three decades.The Triple Expo- nential Model also can be used to fit the time series data. This project takes Duluth temperature predictions as a case study, finding the best statistical model to predict the temperature. I collected 30 years of Duluth monthly maximum temperature data, from 1986 to 2016, and I fi t 29 years of them into di erent models including Triple Exponential Smoothing model, ARIMA model, and SARIMA model. Then I predicted the last year's temperature in those models, and I compared them to the true value of last year's temperature, which gave me the SSE value for each model so that I could find the best model.
Archean Geology of an area between Knife Lake and Kekekabic Lake, eastern Vermilion district, northeastern Minnesota
(1978-09-27) Vinje, Steven Paul
Sedimentary and volcanic rocks of the Kekekabic Lake area, which is located within the eastern Vermilion district, northeastern Minnesota, comprise a portion of the Lower Precambrian Knife Lake Group and lie in three of Gruner's (1941) structural segments. The dominant lithology within the Knife Lake greenstone segment is arkose. The arkose is largely composed of plagioclase feldspar, is approximately 250 feet thick, and underlies the Amoeba Lake member of the Knife Lake Group. Interbedded with the arkose is black slate. Rocks within the Knife Lake greenstone segment trend N 74°E and dip 60° to the southeast. The dominant lithology within the Spoon Lake segment is graywacke. The graywacke samples studied are equally divided between the lithic and feldspathic subtypes. Rock fragments within the lithic graywackes are predominantly andesite and dacite. Plagioclase is the predominant feldspar within the feldspathic graywackes. Interbedded with the graywackes are green slates, mafic (basalt or andesite) crystal tuffs, volcanogenic conglomerate, and very minor iron-formation. The rocks within the Spoon Lake segment are approximately 800 feet thick, and have been deformed into a syncline which trends S 45W and plunges 35° to the southwest. The dominant lithology within the Kekekabic Lake segment is graywacke. The graywacke samples studied are equally divided between the lithic and feldspathic subtypes. Lithic and feldspathic graywackes of the Kekekabic Lake segment are similar petrographically to lithic and feldspathic graywackes of the Spoon Lake segment. However, the graywacke samples of the Kekekabic Lake segment, in general, contain more detrital K-feldspar (although it is still a minor component) and hornblende grains than those of the Spoon Lake segment. Interbedded with the graywackes of the Kekekabic Lake segment are green slates, mafic (basalt or andesite) and felsic (trachyte to latite) crystal tuffs, and very minor ironformation. Graywackes and associated interbedded rocks of the Kekekabic Lake segment are approximately 1000 feet thick, and have been deformed into a syncline which trends S 50°W and plunges 30° to the southwest. The graywackes and associated interbedded rocks contained in both the Spoon Lake and Kekekabic Lake segments comprise the Amoeba Lake Member of the Knife Lake Group (Gruner, 1941). The eastern portion of the Kekekabic Lake syncline is occupied by three subaerial flows. The oldest of these flows, stratigraphically, is a porphyritic green augite-hornblende andesite which is exposed at the nose of the syncline and is approximately 225 feet thick. To the west, the augite-hornblende andesite is conformably overlain by a red porphyritic hornblende andesite which is approximately 300 feet thick. The red hornblende andesite is overlain conformably, to the west, by a green porphyritic hornblende basalt which is approximately 300 feet thick. The three subaerial flows apparently plunge under a green hornblende-rich tuff and agglomerate unit. The tuff is composed exclusively of hornblende grains and is bedded and cross-bedded. The agglomerate clasts are accidental lamprophyre rock fragments. The hornblende-rich tuff and agglomerate is approximately 200 feet thick. The tuff and agglomerate and the three subaerial flows comprise the Kekekabic Lake Member of the Knife Lake Group (Gruner, 1941). Turbidite sequences within the Kekekabic Lake area are characteristic of distal turbidites, and correspond to facies associated with the depositional lobe of the mid-fan portion of a submarine fan (Walker and Mutti, 1973). Two periods of deformation have occurred in the Kekekabic Lake area along with broad folding and longitudinal and transverse faulting. The first period of deformation produced isoclinal folds, trending S 45°-50°W, with vertical to overturned fold axes that plunge to the southwest. The second period of deformation produced a pervasive N 62°-70°E cleavage throughout the area. Subsequently, broad folding warped the beds of the eastern Vermilion district on an axis trending N 60°W. Following folding, longitudinal faulting divided the Kekekabic Lake area into three distinct segments. Concurrent with or subsequent to longitudinal faulting, transverse faulting locally offset rock contacts. Sedimentary and volcanic rocks of the Kekekabic Lake area are representative of the middle portion of a calc-alkaline basalt-andesite-rhyolite volcanic pile accumulation which presumably developed within an island arc or continental orogenic system.
Asymmetrical Boron-Based Light-Emitting Compounds Based on Aromatic Diamine Frameworks (2022-04-08)
(2022) Ploeger, Ethan; University of Minnesota Duluth. Department of Chemistry and Biochemistry
In recent years OLED technology has become very popular for its vibrant colors. The use of OLED allows users to create fluorescent organic compounds without the use of heavy metals. Our work explores chelating ligand frameworks of the kind HO••N that are based on asymmetrical aromatic diamine frameworks that are attached to boron fragments such as BF2 and PPh2. The ligand synthesis is done through condensation reactions and the further reaction with diphenylborinic acid or with BF3 by reaction with BF3•Et2O leads to the final boron-containing products. The final boron derivatives are characterized by NMR, LC-MS, and UV-Vis. The status of current findings in synthesis and characterization as well as light emission data will be presented as well as future plans outlined.
The Bedrock Geology of a Portion of the Cramer 15' Quadrangle, Lake County, Minnesota
(1980-01) Lehman, George Albert
The area studied consists of sections 20 - 29 and 32 - 36 of T60N, R6W of the Cramer, Minnesota 15' quadrangle. Units exposed include the anorthositic "series," troctolitic "series," and felsic "series" of the Duluth Complex, volcanic rocks of the North Shore Volcanic Group, melagabbroic-gabbroic intrusive rocks, diabasic rocks, and a hypabysal intrusive. Bedrock units are locally covered by a variety of glacial deposits related to the Rainy Glacial Lobe of the Wisconsin Ice Age. Troctolites and gabbros of the troctolitic series of the Duluth Complex display cummulate textures and regular cryptic (chemical) variation in the anorthite content of plagioclase (An78 to An58), the forsterite content of olivine (Fo70 to Fo50), and in the FeO/FeO+MgO ratio in augite (22 - 40). Orientations of igneous laminations as well as the areal distribution of rock types and cryptic variations strongly suggest the troctolitic series is a sill-like intrusion which differentiated in place as the result of crystal settling.
Building Maps of Plant Surface Chemistry Using Literature and Citizen-Collected Mass Spectrometry Samples (2022-03-18)
(2022) Nguyen, Dien; University of Minnesota Duluth. Department of Chemistry and Biochemistry
Plant cultivation is a crucial part of society. Understanding plant chemicals can greatly help the important goals of reducing negative environmental impacts of agriculture and achieving high crop yields. One class of chemicals that has a big influence on plant health and growth is triterpenoids. However, there is a limited number of biological systems in which to study triterpenoids in detail. To increase the number of study systems, and thus our potential to build knowledge of triterpenoid function, there is a critical need to understand which triterpenoids can be found on which plant species' surface. The objective of this project is to build three “maps" of plant surface compound presence with an emphasis on triterpenoids using published and newly acquired gas chromatography-mass spectrometry data.
Characterization of Porous Polyvinylidene Fluoride for Use as a Biosensor (2021-03-05)
(2021) Danley, Matt; University of Minnesota Duluth. Department of Chemistry and Biochemistry
The Transcatheter Aortic Valve Replacement (TAVR) is a minimally invasiveprocedure that has grown in popularity in recent years. However, there has beendocumentation of many complications after this procedure, such as a mortality rate of8.4% for TAVR procedures compared to 4.8% for tissue surgery procedures after 90days for Medicare beneficiaries. The underlying mechanisms of the TAVR procedureand how the replacement valve changes the biomechanical and flow environmentafter implantation has not been well studied. Therefore, it is necessary to design amodel heart and create sensors to understand the underlying mechanisms of theTAVR procedure. The goal of this project is to design a sensor that can detectchanges in blood pressure and blood flow rates in a silicon model heart. Onepromising type of material is piezoelectric sensors. Piezoelectric materials takemechanical stress and create detectable changes in voltage that can be calibrated todetermine changes in pressure. One material that has been used for other sensors isPolyvinylidene fluoride (PVDF). This study will investigate how porosity of PVDFchanges the structural and mechanical properties of the polymer. Pores will beintroduced into the PVDF membrane by adding Zinc Oxide (ZnO) nanoparticlesduring the synthesis process and removing the ZnO particles once the membranehas dried. To study the changes in the structure of the membrane, Scanning ElectronMicroscopy is used to confirm a porous structure. To study how the chainconformation of the polymer changes with porosity, Fourier Infrared Spectroscopy isutilized. A Tensile Tester is used to apply compressive stress onto the PVDFmembranes to study the piezoelectric output. To allow for comparison betweenvarious porous membranes, the d33 coefficient is calculated. This will help determinewhich porosity is optimal for the creation of the biosensor with desired sensitivity.
Characterizing Proteinase K in the Enzymatic Hydrolysis of Photodegraded Polylactic Acid (2023-03-24)
(2023) Brown, Maggie; University of Minnesota Duluth. Department of Chemistry and Biochemistry
Characterizing the Changes to Protein Sorption to Photodegraded Polyethylene (2021-04-09)
(2021) Fawcett, Liam; University of Minnesota Duluth. Department of Chemistry and Biochemistry
Aft er their entry into the environment, plastics are exposed to a multitude ofabiotic environmental factors that change both their physical and chemicalcharacteristics. While the initiation of biotic degradation on pristine polymershas been reviewed, it is generally accepted that biotic degradation is enhancedon polymers that initially have undergone some sort of abiotic degradation,particularly photodegradation. This work seeks to understand the intricacies ofbacterial interactions with plastics by investigating the interaction of proteins topolymers with increasing extents of photodegradation, which should giveinsight into the potential attachment and biofilm formation on plastic debrismaterials. Using bovine serum albumin (BSA) as a model protein, we haveinitially investigated the changes in structural characteristics and fluorescenceof the model protein as it adsorbs onto the surface of irradiated polyethylene.Changes to the secondary structure characteristics of BSA were monitoredthrough circular dichroism and preliminary data has shown that with anincrease in irradiation time, there is a characteristic shift of the 3.6 ?-helices tomore tightly wound 3.10 ?-helices. This is likely due to the increasedhydrophilicity of photodegraded polymers causing the hydrophobic residues towind more tightly. Fluorescence of the tryptophan’s in BSA shows a decreasewith exposure to the polymers regardless of irradiation time, indicating potentialfluorescence quenching from the surface of the polymer. Overall, these resultsindicate that an increase polyethylene irradiation time causes an increase ininteraction strength between the polymer and protein, which may explain howbiotic degradation is increased with abiotically degraded polymers. Ultimatelythis work will contribute to our understanding of the fate of plastics in theenvironment.
Chemostra Tigraphy and Climatostra Tigraphy of the Paleoproterozoic Snowy Pass Supergroup, Wyoming and Its Application for Correlation with Other Sequences in North America
(1998-02) Bekker, Andrey
The early Paleoproterozoic ocean and atmosphere experienced significant changes in climate and chemical composition. A global glaciation was followed by climatic amelioration. Chemical composition of the ocean, namely, carbon isotope values, changed dramatically during this time. Collected data support a glacial origin for the Headquarters and Vagner and possibly for the Campbell Lake Formations. Stable isotope values of limestones of the Vagner and Espanola Formations are similar, thereby strengthening correlation of the underlying glacial units. The Nash Fork Formation, based on carbon isotope values, was deposited at the end of the carbon isotope excursion. Study of carbonates of the Chocolay and Cobalt Groups showed similar carbon isotope values of the Gordon Lake Formation and the Kona Dolomite, supporting their correlation. Other carbonate units of the Chocolay Group that were considered correlative with the Kona Dolomite appear to have different carbon isotope systematics and are interpreted to be older.
The Colvin Creek Body, a Metavolcanic and Metasedimentary Mafic Inclusion in the Keweenawan Duluth Complex, Northeastern Minnesota
(1996-02) Patelke, Richard Lee
The Northern Colvin Creek body (CCB) within the 1100 Ma Duluth Complex (Complex), northeastern Minnesota, is a very large, rotated inclusion of Keweenawan basalt and sedimentary rock metamorphosed to pyroxene hornfels facies by immersion in the Complex. The inclusion is about 2500 m in strike length with a stratigraphic thickness of 800 m. Volcanic and sedimentary features indicate a stratigraphic top to the northwest; strike is about N60°E and dips are 70° to 90° to the northwest. Previously the CCB has been interpreted as an oxidized, metamorphosed basalt of the North Shore Volcanic Group (Tyson 1976) and by Severson and Hauck (1990) as an intrusive unit of the Partridge River intrusion (PRI). The body consists of two metavolcanic units and an overlying metasedimentary unit. One of the metavolcanic units is cut by a sill. The stratigraphic package is bounded to the north by a weakly recrystallized olivine gabbro and to the south and east (?) by a poorly exposed, moderately metamorphosed, oxide-rich, fine-grained augite troctolite that shows local assimilation of the margins of the inclusion; both of these igneous units are parts of the Partridge River Gabbro Complex of the PRI. In the two volcanic units mineralogy consists of plagioclase-augite-olivine-orthopyroxene-magnetite-ilmenite. Concentrations of augite replace amygdules that are round, sheeted, and pipe-like; recrystallized piagioclase phenocrysts are locally present. Grain sizes in these units range from very fine- to locally medium-grained, averaging fine-grained. Thin, discontinuous, irregular augite veins are common. Metasedimentary rocks are anorthositic gabbro to gabbroic anorthosite in mineralogical and chemical composition and are of relatively constant proportions of plagioclase-diopside-orthopyroxene-magnetite-ilmenite, with lesser hematite, hercynite, geikielite and apatite. Sedimentary features include millimeter to centimeter scale density-graded modal layering and cross-beds. Texture is fine-grained with very uniform grain size throughout the unit. The contact between the volcanic and overlying sedimentary rocks is a thin (0-2 m) interval of ferrosalite pyroxene- and plagioclase-rich rock with locally abundant cordierite, garnet, biotite, and hercynite. The inclusion is associated with a magnetic high similar to many others in the Partridge River Gabbro Complex. It is uncertain if the rocks of the Colvin Creek body are the cause of this magnetic high, or simply overlie a buried anomaly. Geochemical work has confirmed the unit subdivisions established in the field. It has indicated essentially isochemical metamorphism and has given evidence that the metavolcanic units are probably equivalent to intermediate olivine tholeiites of the North Shore Volcanic Group. The metasedimentary rocks are more problematic; they are not analogous to any of the typical interflow sandstones of the North Shore Volcanic Group as described by Jirsa (1980, 1984). At about 350 m they are as thick as the total measured section of North Shore Volcanic Group interflow sedimentary rocks, show no rock fragments, no quartz, no conglomeratic horizons, and no intercalated volcanic rocks. These metasedimentary rocks, however, appear to match a Keweenawan sandstone exposed near Phantom Lake, north of Two Harbors. The similarities include: both rocks are strongly magnetic, bedded and cross-bedded; plagioclase-rich and quartz-poor; and of uniform fine grain-size. Neither of these units can be strictly correlated with any other in the Keweenawan system.
A Comparison of Two Archean Ultramafic Pyroclastic Rock Units from the Superior Province, Northwestern, Ontario
(1989-12) Schaefer, Stephen Jon
Two Archean komatiitic pyroclastic rock units occur on opposite sides of the Quetico Fault in northwestern Ontario. The eastern unit, the Dismal Ashrock is located 3 km north of Atikokan, Ontario on the northern side of the Quetico fault within the Wabigoon Subprovince of the Superior Province. It is part of a supracrustal sequence (the Steep Rock Group) that overlies an Archean unconformity. The Grassy Portage Bay Ultramafic pyroclastic rock unit (GUP) is located 100 km to the west on the south side of the Quetico fault, and is part of an overturned succession comprising mafic metavolcanic rocks, GUP and metasedimentary rocks. The Quetico Fault is a dextral fault with a history of transpressive tectonics. The Dismal Ashrock is steeply inclined, little deformed and has undergone greenschist facies metamorphism, and it is divided into komatiitic lapilli tuff, komatiitic volcanic breccia, komatiitic volcaniclastic rocks and a mafic pillowed flow. The GUP outcrops form an arcuate fold interference pattern. The GUP is strongly deformed and has undergone amphibolite facies metamorphism. It is divided into komatiitic lapilli tuff and komatiitic volcanic breccia. The Dismal Ashrock and the GUP contain cored and composite lapilli - unequivocal evidence for explosive volcanism. Locally some of the lapilli fragments are highly vesicular (up to 30% by volume) - greater than reported for any other komatiites. Other fragments show no vesicularity. The low vesicularity of some of the pyroclasts and association with pillowed lava flows in the case of the Dismal Ashrock indicate phreatomagmatic volcanic activity. Explosive water-magma interaction was probably initiated by modified eruption characteristics produced from exsolving volatiles. The Dismal Ashrock and GUP are similar in chemical composition and plot on the border between peridotitic and basaltic komatiites on a Jensen AFM diagram. They are high in MgO, Cr and Ni; however, they are unusually enriched in Fe, Ti, Zr, Mn, P, Ba, Nb, Rb and Sr compared to other komatiites. Several lines of evidence indicate that this unusual composition could not have been caused by alteration or assimilation, and an enriched mantle source region is the likely cause. Many of the characteristics that Dismal Ashrock and GUP share are rare or unique on a global scale, indicating that the Dismal Ashrock and GUP are correlative in some manner.
A Connection between Analytic and Nonanalytic Singular Perturbations of the Quadratic Map
(2017-05) Liu, Yujiong
To explore the connection between the analytic and the nonanalytic complex dy- namics, this paper studied a special case of the singularly perturbed quadratic map: β β ƒβ‚t (z) = z2 + t — + (1 – t) — z2 – z2 which can transit from nonanalytic to analytic by varying t from 0 to 1. Other variables involved in this map are the dynamic variable z ϵ C and the main parameter β ϵ R. Our investigation shows that this transition map has much richer behaviors than the end point cases. The parameter space can be no longer subdivided into only four or three regions as shown in the studies by Devaney and Bozyk respectively. Correspondingly, in the dynamic plane, there also appear several new intermediate cases among which we identified two transitions: a connected case where the filled Julia set is connected and a disconnected case where the filled Julia set consists of infinitely many components. This paper also pointed out that ƒβ‚t (z) is semiconjugate to the four symbols shift map for the disconnected case. This semiconjugacy provides a way to largely understand the dynamical behaviors for the non escape points. Further study shows that the critical set plays an important role in the construction of the filled Julia set. Therefore, the transition of the critical set and its image set are also discussed in this paper. At the end, we presented two sets of conjectures for the bounded critical orbits and the escape critical orbits for future study.
Constructing Confidence Intervals for L-statistics Using Jackknife Empirical Likelihood
(2020-06-16) Wang, Fuli
The linear function of order statistics which is quite known as L-statistics has been widely used in non-parametric statistic such as location estimation and construction of tolerance level. The L-statistics include a family of statistics. The trimmed mean, Gini’s mean difference, and discard-deviation are all important L-statistics which have been well-investigated in relevant research. In order to make inference on L-statistics, we apply jackknife method to L-statistics and generate jackknife pseudo samples. There are two significant advantages of jackknifing the data. First, observations from the jackknife samples behave as if they were independent and identically distributed (iid) random variables. Second, the central limit theorem holds for jackknife samples under mild conditions, see, e.g Cheng [1], so the normal approximation method can be applied to the new sample to estimate the true values of L-statistics. In addition to normal approximation, we also apply jackknife empirical likelihood method to construct the confidence intervals for L-statistics. Our simulation and real-data application results both indicate that the jackknife empirical likelihood-based confidence intervals performs better than the normal approximation-based confidence intervals in terms of coverage probability and the length of confidence intervals.
Contact Metamorphism Adjacent to the Laramie Anorthosite Complex, Albany County, Wyoming
(1996-05) Xirouchakis, Dimitrios
The 1440 Ma old Laramie Anorthosite Complex, in SE Wyoming, intrudes Archean granitic gneisses and supracrustal rocks. In the central part of the complex, gneisses of pelitic and granitic composition are intruded and metamorphosed by the central anorthositic dome and the southwestern-most parts of the Maloin Ranch Pluton. The pelitic rocks exhibit field and microtextural features that suggest partial melting. Disruption of the foliation, subhedral to euhedral cordierite, orthopyroxene and oikociystic feldspars are commonly observed. Textural relations between phases suggest reactions between a mixture of crystals and silicate melt during cooling. The migmatites lack any evidence of prograde metamorphism. The granitic gneiss lacks any evidence of melting and contains garnet near the Anorthosite, and the Maloin Ranch Pluton. Pressure conditions of 3.25 (±0.5) kb were calculated from the displacement of the reaction Orthopyroxene + Sillimanite = Hercynitic Spinel + Cordierite, in the pelites. Garnet-biotite geothermometiy, in pelitic assemblages, gives temperatures that range from 620° to 800° C. The garnet-cordierite geothermometer, from pelitic assemblages, yields temperatures that range from 630° to 750° C. Garnet-biotite compositions from the granitic gneiss are within or close to the limits of the experimental calibration. Calculations yielded a peak metamorphic temperature of 850° C and lower retrograde conditions of 760° C. South of the southern anorthositic dome, mafic pyroxene hornfelses and problematic quartzrich metasediments(?) are encountered. In the enigmatic metasediments the textures indicate recrystallization during cooling. This unit does not retain any evidence of prograde metamorphism. In contrast, the mafic pyroxene hornfelses appear to reflect peak metamorphic conditions. The displacement of the reaction Oinopyroxene + Plagioclase = Gamet + Quartz in the metasediments, gives pressure conditions of 3.25 (±1.9) kb. Pyroxene and Fe-Ti oxide geothermometry, from both units, yields temperatures that range from 730° to 840° C. The 1400 Ma Sherman Granite intrudes the Anorthosite Complex and its aureole. The retrograde assemblages observed in the metamorphic rocks, and their areal distribution suggest that the granitic intrusion occurred while the aureole was cooling at 0.5-3 kb and about 600° C.
Contact Metamorphism of the Virginia Formation in the Minnamax Deposit St. Louis County, Minnesota
(1979-10) Kirstein, Mark H
The Middle Precambrian Virginia Formation, cut by diabase dikes, was intruded and contact metamorphosed by the Late Precambrian Duluth Complex near Babbitt, Minnesota. Sulfide mineralization of magmatic origin, with minor amounts formed by hydrothermal replacement, is concentrated at the irregular contact zone between the Virginia Formation and the Duluth Complex. Five miles south of Babbitt this mineralization constitutes the Minnamax Copper-Nickel Deposit, which is being investigated and evaluated underground by AMAX Exploration, Inc. The Virginia Formation consists of pelitic hornfels, calc-silicate pods, and "reaction" rims around the pods. The pelitic hornfels is dark gray, fine-grained, massive, and composed of plagioclase, hypersthene, and cordierite with local occurrences of orthoclase, biotite, and graphite. The calc-silicate pods are light gray, fine- to coarse grained, are spherical to ellipsoidal and range from 4 inches to 8 feet across. There are three types of pods; homogenous types with no mineral zones developed, layered types with mineral layers developed, and concentric types with mineral zones developed. The primary minerals are diopside, grossular garnet, plagioclase, sphene, wollastonite, and possibly some calcite, and quartz. From strikes and dips of relict bedding in pelitic horn.fels and from the broken, fra.ctured, and jumclad nature of calc-silicate pods deformation of the Virginia Formation appears intense. The "reaction" rims are dark gray, fine-grained, and up to 3 inches wide. They are composed of plagioclase, hypersthene and poikiloblastic clinopyroxene giving a composition intermediate between the pelitic hornfels and calc-silicate pods. The protolith of the pelitic hornfels appears to be a calcareous argillite and the calc-silicates a siliceous dolomitic limestone. The pods are believed to have originally been calcareous concretions in argillite with some being pieces brought up from the calcareous zone at the top of the Biwabik Iron Formation. The "reaction" rims developed after deformation took place, as they surround broken and fractured pods, and formed from diffusion of calcium from the pods into the pelitic hornfels. The metadiaba.se dikes are dark gray, fine-grained, and massive. They are composed of lathy plagioclase, augite, and hypersthene. A relict ophitic texture is evident and relict plagioclase phenocrysts have been resorbed. Sulfides consist of pyrrhotite, exsolved pentlandite, and chalcopyrite in pelitic hornfels and chalcopyrite with exsolved cubanite in calc-silicate pods. Minor ilmenite and magnetite is present in the sulfides. Alteration consists of uralitization of pyroxenes and sericitic and kaolinitic alteration of plagioclase. Quartz, calcite, apophyllite, anhydrite, fluorite, heulandite, laumontite, and prehnite are gangue minerals. This emplacement occurred after the main metamorphic event and formed by hydrothermal replacement. Based on the primary mineral assemblages present, the rocks fall in the pyroxene hornfels facies. The presence of plagioclase and wollastonite in the calc-silicate pods give a minimum temperature of 600 degrees Celsius at 2 kilobars pressure, and a mole fraction of CO2 in the vapor phase less than 0.25. An increase of albite in plagioclase can lower the temperature of the reaction forming plagioclase and wollastonite, and could cause the plagioclase and wollastonite to disappear with quartz and calcite stableo From the presence of laumontite, an upper limit of 350 degrees Celsius at 2 kilobars pressure can be given for the sulfides e:mplaced hydrothermally. A bottom temperature ranging from 250 to 300 degrees Celsius can be given by the presence of exsolved cubanite in chalcopyrite.

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