[1] This paper describes a new instrument that uses a combination of thermal dissociation and laserinduced fluorescence detection of NO 2 for in situ detection of the sum total peroxy nitrates, the sum total of alkyl nitrates and hydroxyalkyl nitrates, and HNO 3 . The instrument is capable of routine, continuous in situ measurements of these three classes of compounds that are accurate (15%) with a low detection limit (90 parts per trillion (ppt) 10 s À1 , S/N ratio = 2 on a background of 1 ppb NO 2 and 30 ppt 10 s À1 on a background of 100 ppt NO 2 ). Theoretical analysis of potential interferences combined with laboratory experiments that test for interferences show that rapidly cooling the gas and dropping the pressure after the thermal dissociation reduces interferences to the order of 1 -5%. Observations in ambient air at the University of California Blodgett Forest Research Station demonstrate the capabilities of this instrument under field conditions. These field observations are compared with independent total NO y observations.

Measurements of anthropogenic hydrocarbons, ozone, and meteorological variables were obtained during the summer of 1997 near the University of California Blodgett Forest Research Station on the western slope of the Sierra Nevada Mountains. These measurements and related observations obtained upwind in Sacramento and Folsom, California, by the California Air Resources Board and the National Weather Service demonstrate that the transport of the Sacramento plume is controlled by extremely consistent, terrain‐driven winds that draw polluted air into the Sierra Nevada by day and flush the mountains at night with clean, continental background air. In effect the plume serves as a mesoscale (100 km) daytime flow reactor where the daily evolution of the Sacramento urban plume can be characterized as a Lagrangian air parcel transported from the urban core into the sparsely populated Sierra Nevada mountains. Using observations of slowly reacting anthropogenic hydrocarbons, we demonstrate that at the peak impact of the Sacramento plume the air at Blodgett Forest can be characterized as a mixture of 32% air from the urban core and 68% from the relatively clean background. From measurements of more reactive hydrocarbons we infer an average daytime OH concentration of 1.1 × 107 molecules cm−3 during the transit of the urban plume.

S U M M A R YMany of the natural materials studied in rock and environmental magnetism contain a mixed assemblage of mineral grains with a variety of different origins. Mathematical decomposition of the bulk magnetic mineral assemblage into populations with different properties can therefore be a source of useful environmental information. Previous investigations have shown that such unmixing into component parts can provide insights concerning source materials, transport processes, diagenetic alteration, authigenic mineral growth and a number of other processes.A new approach will be presented that performs a linear unmixing of remanence data into coercivity based end-members using only a minimal number of assumptions. A non-negative matrix factorization (NMF) algorithm for unmixing remanence data into constituent endmembers is described with case studies to demonstrate the utility of the approach. The shape of the end-members and their abundances obtained by NMF is based solely on the variation in the measured data set and there is no requirement for mathematical functions or type curves to represent individual components. Therefore, in contrast to previous approaches that aimed to unmix curves into components corresponding to individual minerals and domain states, NMF produces a genetically more meaningful decomposition showing how a data set can be represented as a linear sum of invariant parts. It has been found that the NMF algorithm performs well for both absolute and normalized remanence curves, with the capacity to process thousands of measured data points rapidly.

[1] Diagenesis has extensively affected the magnetic mineral inventory of organic-rich late Quaternary sediments in the Niger deep-sea fan. Changes in concentration, grain size, and coercivity document modifications of the primary magnetic mineral assemblages at two horizons. The first front, the modern iron redox boundary, is characterized by a drastic decline in magnetic mineral content, coarsening of the grain size spectrum, and reduction in coercivity. Beneath a second front, the transition from the suboxic to the sulfidic anoxic domain, a further but less pronounced decrease in concentration and bulk grain size occurs. Finer grains and higher coercive magnetic constituents substantially increase in the anoxic environment. Low-and high-temperature experiments were performed on bulk sediments and on extracts which have also been examined by X-ray diffraction. Thermomagnetic analyses proved ferrimagnetic titanomagnetites of terrigenous provenance as the principal primary magnetic mineral components. Their broad range of titanium contents reflects the volcanogenic traits of the Niger River drainage areas. Diagenetic alteration is not only a grain size selective process but also critically depends on titanomagnetite composition. Low-titanium compounds are less resistant to diagenetic dissolution. Intermediate titanium content titanomagnetite thus persists as the predominant magnetic mineral fraction in the sulfidic anoxic sediments. At the Fe redox boundary, precipitation of authigenic, possibly bacterial, magnetite is documented. The presence of hydrogen sulfide in the pore water suggests a formation of secondary magnetic iron sulfides in the anoxic domain. Grain size-specific data argue for a gradual development of a superparamagnetic and single-domain iron sulfide phase in this milieu, most likely greigite.Citation: Dillon, M., and U. Bleil (2006), Rock magnetic signatures in diagenetically altered sediments from the Niger deep-sea fan,

To cite this version:Melanie Dillon, Christine Franke. Diagenetic alteration of natural Fe-Ti oxides identified by energy dispersive spectroscopy and low-temperature magnetic remanence and hysteresis measurements. Physics of the Earth and Planetary Interiors, Elsevier, 2008, 172 (3-4) This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Page 1 A c c e p t e d M a n u s c r i p t 2 increase for the samples from the anoxic zone. We demonstrate that this distinct increase in 25 B C at LT corresponds to the increasing proportion of the Ti-rich hemoilmenite phase, while 26Fe-rich (titano-)magnetite dominates the magnetic signal at RT. This trend is also seen in the 27 room-temperature saturation isothermal remanent magnetization (RT-SIRM) cycles: suboxic 28 samples show remanence curves dominated by Fe-rich mineral phases while anoxic samples 29 display curves clearly dominated by Ti-rich particles. 30We show that the EDS intensity ratios of the characteristic Fe K α and Ti K α lines of the Fe-31Ti-oxides may be used to differentiate between members of the magnetite-ulvöspinel and 32 ilmenite-hematite solid solution series. Furthermore it is possible to calculate an approximate 33 composition for each grain if the intensity ratios of natural particles are linked to well known 34 standards. Thus, element spectra with high Fe/Ti intensity ratios were found to be rather 35 typical of titanomagnetite while low Fe/Ti ratios are indicative of hemoilmenite. 36The EDS analyses confirm the LT magnetic results, Fe-rich magnetic phases dominate in 37 the upper suboxic environment whereas Ti-rich magnetic phases comprise the majority of 38 particles in the lower anoxic domain: The mineral assemblage of the upper suboxic 39 environments is composed of magnetite (~19 %), titanomagnetite (~62 %), hemoilmenite 40 (~17 %) and ~2 % other particles. In the lower anoxic sediments, reductive diagenetic 41 alteration has resulted in more extensive depletion of the (titano-)magnetite phase, resulting in 42 a relative enrichment of the hemoilmenite phase (~66 %). In these strongly anoxic sediments 43 stoichiometric magnetite is barely preserved and only ~5 % titanomagnetite was detected. The 44 remaining ~28 % comprises Ti-rich particles such as pseudobrookite or rutile. 45 46 Keywords: magnetic Fe-Ti oxides, energy dispersive spectroscopy (EDS), marine sediments, 47 scanning electron microscopy (SEM), low-temperature magnetism, early diagenesis 48

Holocene records documenting variations in direction and intensity of thegeomagnetic field during the last about seven and a half millennia are presented for Northwest Africa. High resolution paleomagnetic analyses of two marine sediment sequences recovered from around 900 meter water depth on the upper continental slope off Cape Ghir (30°51 N, 10°16 W) were supplemented by magnetic measurements characterizing composition, concentration, grain size and coercivity of the magnetic mineral assemblage. Age control for the high sedimentation rate deposits (~60 cm/kyr) was established by AMS radiocarbon dates. The natural remanent magnetization (NRM) is very predominantly carried by a fine grained, mostly single domain (titano-)magnetite fraction allowing the reliable definition of stable NRM inclinations and declinations from alternating field demagnetization and principal component analysis. Predictions of the Korte and Constable (2005) geomagnetic field model CALS7K.2 for the study area are in fair agreement with the Holocene directional records for the most parts, yet noticeable differences exist in some intervals. The magnetic mineral inventory of the sediments reveals various climate controlled variations, specifically in concentration and grain size. A very strong impact had the mid-Holocene environmental change from humid to arid conditions on the African continent which also clearly affects relative paleointensity (RPI) estimates based on different remanence normalizers. To overcome this problem the pseudo-Thellier RPI technique has been applied. The results represent the first Holocene record of Earth's magnetic field intensity variations in the NW Africa region. It displays long term trends similar to those of model predictions, but also conspicuous millennium scale differences.

CONCLUSIONUsing experimental parameters in the construction of the cutoff planes of axially magnetized gyromagnetic waveguides, instead of tensor permeability entries, provides more practical design information for ferrite phase shift and control components. For a fixed bias field (signal frequency) and varying signal frequency (bias field), the onset of higher-order modes is accurately predicted. Some modes are observed to exhibit separate onset frequencies above and below ferrimagnetic resonance, which in turn defines unique modal hierarchies in each region. Experimental and finite-element results are compared here with corresponding analytical solutions. ACKNOWLEDGMENTThe SOS Kinderdorf International and EPSRC are kindly thanked for their support and financial assistance during the course of this investigation. 4. A. A. P. Gibson, B. M. Dillon, and S. I. Sheikh, "Applied Field/Frequency Response of Planar Gyromagnetic Disks," Znt. ABSTRACT We analyze and measure the elecfrical properties of a hybrid coplanar/ microstiip traueling-wave optical modulator containing an InGaAs/ I d o l s quantum-well electron transfer structure. S-parameter measurements to 20 GHz reveal the microwave refractiue index and microwave loss as a function of waveguide geometry. These experiments allow us to project electro-optical modulation bandwidths in excess of 40 GHz. 0 1995 John Wilq & Sons, Inc. ABSTRACT In this work a numerical investigation is reported on the propagation regimes that allow single-channel systems to obtain the maximum capacity in links with optical ampl@cation. Links with anomalous and zero mean chromatic dispersion are considered, adopting both DS and stepindex fibers and operating at a wavelength of 1.55 pm. Solitons and NRZ signals are used. 0 1995 John Wiley & Sons, Inc.

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