Biochemical Conversions of Lignocellulosic Biomass for Sustainable Fuel-Ethanol Production in the Upper Midwest

Biofuels are an increasingly important component of worldwide energy supply. This research aims to understand the pathways and impacts of biofuels production, and to improve these processes to make them more efficient. In Chapter 2, a life cycle assessment (LCA) is presented for cellulosic ethanol production from five potential feedstocks of regional importance to the upper Midwest - hybrid poplar, hybrid willow, switchgrass, diverse prairie grasses, and logging residues - according to the requirements of Renewable Fuel Standard (RFS). Direct land use change emissions are included for the conversion of abandoned agricultural land to feedstock production, and computer models of the conversion process are used in order to determine the effect of varying biomass composition on overall life cycle impacts. All scenarios analyzed here result in greater than 60% reduction in greenhouse gas emissions relative to petroleum gasoline. Land use change effects were found to contribute significantly to the overall emissions for the first 20 years after plantation establishment. Chapter 3 is an investigation of the effects of biomass mixtures on overall sugar recovery from the combined processes of dilute acid pretreatment and enzymatic hydrolysis. Biomass mixtures studied were aspen, a hardwood species well suited to biochemical processing; balsam, a high-lignin softwood species, and switchgrass, an herbaceous energy crop with high ash content. A matrix of three different dilute acid pretreatment severities and three different enzyme loading levels was used to characterize interactions between pretreatment and enzymatic hydrolysis. Maximum glucose yield for any species was 70% oftheoretical for switchgrass, and maximum xylose yield was 99.7% of theoretical for aspen. Supplemental β-glucosidase increased glucose yield from enzymatic hydrolysis by an average of 15%, and total sugar recoveries for mixtures could be predicted to within 4% by linear interpolation of the pure species results. Chapter 4 is an evaluation of the potential for producing Trichoderma reesei cellulose hydrolases in the Kluyveromyces lactis yeast expression system. The exoglucanases Cel6A and Cel7A, and the endoglucanase Cel7B were inserted separately into the K. lactis and the enzymes were analyzed for activity on various substrates. Recombinant Cel7B was found to be active on carboxymethyl cellulose and Avicel powdered cellulose substrates. Recombinant Cel6A was also found to be active on Avicel. Recombinant Cel7A was produced, but no enzymatic activity was detected on any substrate. Chapter 5 presents a new method for enzyme improvement studies using enzyme co-expression and yeast growth rate measurements as a potential high-throughput expression and screening system in K. lactis yeast. Two different K. lactis strains were evaluated for their usefulness in growth screening studies, one wild-type strain and one strain which has had the main galactose metabolic pathway disabled. Sequential transformation and co-expression of the exoglucanase Cel6A and endoglucanase Cel7B was performed, and improved hydrolysis rates on Avicel were detectable in the cell culture supernatant. Future work should focus on hydrolysis of natural substrates, developing the growth screening method, and utilizing the K. lactis expression system for directed evolution of enzymes.

The Christensen Sillimanite Deposit Southeast of Dillon, Montana

The minerals sillimanite, kyanite, andalusite, dumortierite, and topaz comprise a group of minerals whose high alumina content and physical properties are particularly desirable in the manufacture of refractory products. Sillimanite is the least plentiful of the minerals of this group, and for this reason it is not used extensively at the present time. However, it would be very desirable to the refractory industry if a suitable domestic source of supply could be established.

Whole-body vibration exposure study in U.S. railroad locomotives--an ergonomic risk assessment

Whole-body vibration exposure of locomotive engineers and the vibration attenuation of seats in 22 U.S. locomotives (built between 1959 and 2000) was studied during normal revenue service and following international measurement guidelines. Triaxial vibration measurements (duration mean 155 min, range 84-383 min) on the seat and on the floor were compared. In addition to the basic vibration evaluation (aw rms), the vector sum (av), the maximum transient vibration value (MTVV/aw), the vibration dose value (VDV/(aw T1/4)), and the vibration seat effective transmissibility factor (SEAT) were calculated. The power spectral densities are also reported. The mean basic vibration level (aw rms) was for the fore-aft axis x = 0.18 m/sec2, the lateral axis y = 0.28 m/sec2, and the vertical axis z = 0.32 m/sec2. The mean vector sum was 0.59 m/sec2 (range 0.27 to 1.44). The crest factors were generally at or above 9 in the horizontal and vertical axis. The mean MTVV/aw was 5.3 (x), 5.1 (y), and 4.8 (z), and the VDV/(aw T1/4) values ranged from 1.32 to 2.3 (x-axis), 1.33 to 1.7 (y-axis), and 1.38 to 1.86 (z-axis), generally indicating high levels of shocks. The mean seat transmissibility factor (SEAT) was 1.4 (x) and 1.2 (y) and 1 (z), demonstrating a general ineffectiveness of any of the seat suspension systems. In conclusion, these data indicate that locomotive rides are characterized by relatively high shock content (acceleration peaks) of the vibration signal in all directions. Locomotive vertical and lateral vibrations are similar, which appears to be characteristic for rail vehicles compared with many road/off-road vehicles. Tested locomotive cab seats currently in use (new or old) appear inadequate to reduce potentially harmful vibration and shocks transmitted to the seated operator, and older seats particularly lack basic ergonomic features regarding adjustability and postural support.

1200 years of decadal-scale variability of Mediterranean vegetation and climate at Pantelleria Island, Italy

A new sedimentary sequence from Lago di Venere on Pantelleria Island, located in the Strait of Sicily between Tunisia and Sicily was recovered. The lake is located in the coastal infra-Mediterranean vegetation belt at 2 m a.s.l. Pollen, charcoal and sedimentological analyses are used to explore linkages among vegetation, fire and climate at a decadal scale over the past 1200 years. A dry period from ad 800 to 1000 that corresponds to the ‘Medieval Warm Period’ (WMP) is inferred from sedimentological analysis. The high content of carbonate recorded in this period suggests a dry phase, when the ratio of evaporation/precipitation was high. During this period the island was dominated by thermophilous and drought-tolerant taxa, such as Quercus ilex, Olea, Pistacia and Juniperus. A marked shift in the sediment properties is recorded at ad 1000, when carbonate content became very low suggesting wetter conditions until ad 1850–1900. Broadly, this period coincides with the ‘Little Ice Age’ (LIA), which was characterized by wetter and colder conditions in Europe. During this time rather mesic conifers (i.e. Pinus pinaster), shrubs and herbs (e.g. Erica arborea and Selaginella denticulata) expanded, whereas more drought-adapted species (e.g. Q. ilex) declined. Charcoal data suggest enhanced fire activity during the LIA probably as a consequence of anthropogenic burning and/or more flammable fuel (e.g. resinous Pinus biomass). The last century was characterized by a shift to high carbonate content, indicating a change towards drier conditions, and re-expansion of Q. ilex and Olea. The post-LIA warming is in agreement with historical documents and meteorological time series. Vegetation dynamics were co-determined by agricultural activities on the island. Anthropogenic indicators (e.g. Cerealia-type, Sporormiella) reveal the importance of crops and grazing on the island. Our pollen data suggest that extensive logging caused the local extinction of deciduous Quercus pubescens around ad1750.

Dry grasslands of NW Bulgarian mountains: first insights into diversity, ecology and syntaxonomy

We present the data of the 3rdresearch expedition of the European Dry Grasslands Group (EDGG), which was conducted in 2011 in two contrasting areas in NW Bulgarian mountains. The aim was to collect plot data for comparing Bulgarian dry grasslands with those of other parts of Europe in terms of syntaxonomy and biodiversity. We sampled 15 nested-plot series (0.0001–100 m²) and 68 normal plots(10 m²) covering the full variety of dry grassland types occurring in the Vratsa area (Balkan Mts.) and the Koprivshtitsa area (Sredna Gora Mt.). In the plots all vascular plants, terricolous non-vascular plants and a set of soil and other environmental parameters were determined. By applying modified TWIN-SPAN, we distinguished 10 floristically well characterised vegetation types at the association level. After comparison with the regional and European literature, we propose to place them within three classes and five orders: Festuco-Brometea with the orders Stipo pulcherrimae-Festucetalia pallentis (xerophilous dry grasslands of base-rich rocks; alliance Saturejion montanae), Brachypodietalia pinnate (meso-xeric, basiphilous grasslands; alliances Cirsio-Brachypodion pinnate and Chyrsopogono grylli-Danthonion calycinae),Calluno-Ulicetea with the order Nardetalia stricae (lowland to montane Nardus swards; alliance Violion caninae), and Koelerio-Corynephoretea with the orders Sedo-Scleranthetalia (open communities of skeleton-rich, acidic soils; alliance unclear) and Trifolioarvensis-Festucetalia ovinae(closed, meso-xeric, acidophilous grasslands; alliance Armerio rumelicae-Potentillion). The Violion caninae with the association Festuco rubrae-Genistelletum sagittalisis reported from Bulgaria for the first time, while the two occurring Koelerio-Corynephoretea communities are described as new associations (Cetrario aculeatae-Plantaginetum radicatae, Plantagini radicatae-Agrostietum capillaris). According to DCA the main floristic gradient was largely determined by soil conditions, differentiating the Festuco-Brometea communities on soils with high pH and high humus content from the Koelerio-Corynephoretea communities on acidic, humus-poor soils, while the Calluno-Ulicetea stands are the connecting link. At 10 m² Festuco-Brometea and Calluno-Ulicetea stands were richer in species across all investigated taxa and in vascular plants than Koelerio-Corynephoretea stands; the latter were richest in lichen species, while bryophyte richness did not differ significantly among syntaxa. Among the Bulgarian classes, the species-area relationships tended to be steepest in the Festuco-Brometea (i.e. highest beta diversity), but both alpha and beta diversity clearly fell behind the Festuco-Brometea communities in the Transylvanian Plateau, Romania, located less than 500 km north of the study region. Overall, our study contributes to a more adequate placement of the Bulgarian dry grasslands in the European syntaxonomic system and provides valuable data for large-scale analyses of biodiversity patterns

Environmental change within the Balkan region during the past ca. 50 ka recorded in the sediments from lakes Prespa and Ohrid

Abstract. Lakes Prespa and Ohrid, in the Balkan region, are considered to be amongst the oldest lakes in Europe. Both lakes are hydraulically connected via karst aquifers. From Lake Ohrid, several sediment cores up to 15m long have been studied over the last few years. Here, we document the first long sediment record from nearby Lake Prespa to clarify the influence of Lake Prespa on Lake Ohrid and the environmental history of the region. Radiocarbon dating and dated tephra layers provide robust age control and indicate that the 10.5m long sediment record from Lake Prespa reaches back to 48 ka. Glacial sedimentation is characterized by low organic matter content and absence of carbonates in the sediments, which indicate oligotrophic conditions in both lakes. Holocene sedimentation is characterized by particularly high carbonate content in Lake Ohrid and by particularly high organic matter content in Lake Prespa, which indicates a shift towards more mesotrophic conditions in the latter. Long-term environmental change and short-term events, such as related to the Heinrich events during the Pleistocene or the 8.2 ka cooling event during the Holocene, are well recorded in both lakes, but are only evident in certain proxies. The comparison of the sediment cores from both lakes indicates that environmental change affects particularly the trophic state of Lake Prespa due to its lower volume and water depth.

Late Quaternary palaeoenvironmental reconstruction from Lakes Ohrid and Prespa (Macedonia/Albania border) using stable isotopes

Abstract. Here we present stable isotope data from three sediment records from lakes that lie along the Macedonian- Albanian border (Lake Prespa: 1 core, and Lake Ohrid: 2 cores). The records only overlap for the last 40 kyr, although the longest record contains the MIS 5/6 transition (Lake Ohrid). The sedimentary characteristics of both lakes differ significantly between the glacial and interglacial phases. At the end of MIS 6 Lake Ohrid’s water level was low (high �18Ocalcite) and, although productivity was increasing (high calcite content), the carbon supply was mainly from inorganic catchment rock sources (high �13Ccarb). During the last interglacial, calcite and TOC production and preservation increased, progressively lower �18Ocalcite suggest increase in humidity and lake levels until around 115 ka. During ca. 80 ka to 11 ka the lake records suggest cold conditions as indicated by negligible calcite precipitation and low organic matter content. In Lake Ohrid, �13Corg are complacent; in contrast, Lake Prespa shows consistently higher �13Corg suggesting a low oxidation of 13C-depleted organic matter in agreement with a general deterioration of climate conditions during the glacial. From 15 ka to the onset of the Holocene, calcite and TOC begin to increase, suggesting lake levels were probably low (high �18Ocalcite). In the Holocene (11 ka to present) enhanced productivity is manifested by high calcite and organic matter content. All three cores show an early Holocene characterised by low �18Ocalcite, apart from the very early Holocene phase in Prespa where the lowest �18Ocalcite occurs at ca. 7.5 ka, suggesting a phase of higher lake level only in (the more sensitive) Lake Prespa. From 6 ka, �18Ocalcite suggest progressive aridification, in agreement with many other records in the Mediterranean, although the uppermost sediments in one core records low �18Ocalcite which we interpret as a result of human activity. Overall, the isotope data present here confirm that these two big lakes have captured the large scale, low frequency palaeoclimate variation that is seen in Mediterranean lakes, although in detail there is much palaeoclimate information that could be gained, especially small scale, high frequency differences between this region and the Mediterranean.

Human TNF receptor p75/80 gene structure and promoter characterization

Tumor necrosis factor receptor p75/80 ((TNF-R p75/80) is a 75 kDa type 1 transmembrane protein expressed predominately on cells of hematopoietic lineage. TNF-R p75/80 belongs to the TNF receptor superfamily characterized by cysteine-rich extracellular regions composed of three to six disulfide-linked domains. In the present report, we have characterized, for the first time, the complete gene structure for human TNF-R p75/80 which spans approximately 43 kbp. The gene consists of 10 exons (ranging from 34 bp to 2.5 kbp) and 9 introns (343 bp to 19 kbp). Consensus elements for transcription factors involved in T cell development and activation were noted in the 5$\sp\prime$ flanking region including TCF-1, Ikaros, AP-1, CK-2, IL-6RE, ISRE, GAS, NF-$\kappa$B and SP1, as well as an unusually high GC content and CpG frequency that appears characteristic of some TNF-R family members. The unusual (GATA)$\sb{\rm n}$ and (GAA)(GGA) repeats found within intron 1 may prove useful for further genome analysis within the 1p36 chromosomal locus. The human TNF-R p75/80 gene structure will permit further assessment of its involvement in normal hematopoietic cell development and function, autoimmune disease, and non-random translocations in hematopoietic malignancies. The region 1.8 kb 5$\sp\prime$ of the ATG was able to drive luciferase expression when transfected into cell lines expressing TNF-R p75/80. Further characterization of the 5$\sp\prime$-regulatory region will aid in determining factors and signal transduction pathways involved in regulating TNF-R p75/80 expression. ^

Chevkinite-Group Minerals from Granulite-Facies Metamorphic Rocks and Associated Pegmatites of East Antarctica and South India

Electron microprobe data are presented for chevkinite-group minerals from granulite-facies rocks and associated pegmatities of the Napier Complex and Mawson Station charnockite in East Antarctica and from the Eastern Ghats, South India. Their compositions conform to the general formula for this group, viz. A(4)BC(2)D(2)Si(4)O(22) where, in the analysed specimens A = (rare-earth elements (REE), Ca, Y, Th), B = Fe(2+) Mg, C = (Al, Mg, Ti, Fe(2+), Fe(3+), Zr) and D = Ti and plot within the perrierite field oftlic total Fe (as FeO) (wt.%) vs. CaO (wt.%) discriminator diagram of Macdonald and Belkin (2002). In contrast to most chevkinite-group minerals, the A site shows unusual enrichment in the MREE and HREE relative to the LREE and Ca. In one sample from the Napier Complex, Y is the dominant cation among the total REE + Y in the A site, the first reported case of Y-dominance in the chevkinite group. The minerals include the most Al-rich yet reported in the chevkinite group (<= 9.15 wt.% Al(2)O(3)), sufficient to fill the C site in two samples. Conversely, the amount of Ti in these samples does not fill the D site. and, thus, some of the Al could be making up the deficiency at D, a situation not previously reported in the chevkinite group. Fe abudances are low, requiring Mg to occupy up to 45% of the B site. The chevkinite-group minerals analysed originated from three distinct parageneses: (1) pegmatites containing hornblende and orthopyroxene or garnet; (2) orthopyroxene-bearing gneiss and granulite; (3) highly aluminous paragneisses in which the associated minerals are relatively magnesian or aluminous. Chevkinite-group minerals from the first two parageneses have relatively high FeO content and low MgO and Al(2)O(3) contents; their compositions plot in the field for mafic and intermediate igneous rocks. In contrast, chevkinite-group minerals from the third paragenesis are notably more aluminous and have greater Mg/Fe ratios.

Particulate Backscattering Ratio at Leo 15 and Its Use to Study Particle Composition and Distribution

Particulate scattering and backscattering are two quantities that have traditionally been used to quantify in situ particulate concentration. The ratio of the backscattering by particles to total scattering by particles (the particulate backscattering ratio) is weakly dependent on concentration and therefore provides us with information on the characteristics of the particulate material, such as the index of refraction. The index of refraction is an indicator of the bulk particulate composition, as inorganic minerals have high indices of refraction relative to oceanic organic particles such as phytoplankton and detrital material that typically have a high water content. We use measurements collected near the Rutgers University Long-term Ecosystem Observatory in 15 m of water in the Mid-Atlantic Bight to examine application of the backscattering ratio. Using four different instruments, the HOBILabs Hydroscat-6, the WETLabs ac-9 and EcoVSF, and a prototype VSF meter, three estimates of the ratio of the particulate backscattering ratio were obtained and found to compare well. This is remarkable because these are new instruments with large differences in design and calibration. The backscattering ratio is used to map different types of particles in the nearshore region, suggesting that it may act as a tracer of water movement. We find a significant relationship between the backscattering ratio and the ratio of chlorophyll to beam attenuation. This implies that these more traditional measurements may be used to identify when phytoplankton or inorganic particles dominate. In addition, it provides an independent confirmation of the link between the backscattering ratio and the bulk composition of particles.

The cyclotron laboratory and the RFQ accelerator in Bern

Two proton accelerators have been recently put in operation in Bern: an 18 MeV cyclotron and a 2 MeV RFQ linac. The commercial IBA 18/18 cyclotron, equipped with a specifically conceived 6 m long external beam line ending in a separate bunker, will provide beams for routine 18-F and other PET radioisotope production as well as for novel detector, radiation biophysics, radioprotection, radiochemistry and radiopharmacy developments. The accelerator is embedded into a complex building hosting two physics laboratories and four Good Manufacturing Practice (GMP) laboratories. This project is the result of a successful collaboration between the Inselspital, the University of Bern and private investors, aiming at the constitution of a combined medical and research centre able to provide the most cutting-edge technologies in medical imaging and cancer radiation therapy. The cyclotron is complemented by the RFQ with the primary goals of elemental analysis via Particle Induced Gamma Emission (PIGE), and the detection of potentially dangerous materials with high nitrogen content using the Gamma-Resonant Nuclear Absorption (GRNA) technique. In this context, beam instrumentation devices have been developed, in particular an innovative beam profile monitor based on doped silica fibres and a setup for emittance measurements using the pepper-pot technique. On this basis, the establishment of a proton therapy centre on the campus of the Inselspital is in the phase of advanced study.

Anisotropy of magnetic susceptibility in natural olivine single crystals

Mantle flow dynamics can cause preferential alignment of olivine crystals that results in anisotropy of physical properties. To interpret anisotropy in mantle rocks, it is necessary to understand the anisotropy of olivine single crystals. We determined anisotropy of magnetic susceptibility (AMS) for natural olivine crystals. High-field AMS allows for the isolation of the anisotropy due to olivine alone. The orientations of the principal susceptibility axes are related to the olivine’s crystallographic structure as soon as it contains >3 wt % FeO. The maximum susceptibility is parallel to the c axis both at room temperature (RT) and at 77 K. The orientation of the minimum axis at RT depends on iron content; it is generally parallel to the a axis in crystals with 3–5 wt % FeO, and along b in samples with 6–10 wt % FeO. The AMS ellipsoid is prolate and the standard deviatoric susceptibility, k0, is on the order of 8*10210 m3/kg for the samples with <1wt % FeO, and ranges from 3.1*1029 m3/kg to 5.7*1029 m3/kg for samples with 3–10 wt % FeO. At 77 K, the minimum susceptibility is along b, independent of iron content. The shape of the AMS ellipsoid is prolate for samples with <5 wt % FeO, but can be prolate or oblate for higher iron content. The degree of anisotropy increases at 77 K with p0 7757.160.5. The results from this study will allow AMS fabrics to be used as a proxy for olivine texture in ultramafic rocks with high olivine content.

White lupin (Lupinus albus L.), the neglected multipurpose crop: Its production and utilization in the mixed crop-livestock farming system of Ethiopia

A survey was conducted to generate holistic information on the production and utilization of local white lupin in two lupin growing districts, namely, Mecha and Sekela, representing mid and high altitude areas, respectively in North-western Ethiopia. During the survey, two types of participatory rural appraisal (PRA) techniques, namely, individual farmer interview (61 farmers from Mecha and 51 from Sekela) and group discussion (with 20 farmers from each district) were employed. There are significant differences (P<0.05) between the two study districts for the variables like total land holding, frequency of ploughing during lupin planting, days to maturity, lupin productivity, and number of days of soaking lupin in running water. However, there are no significant differences (P>0.05) between the two study districts for the variables like land allocated for lupin cultivation, lupin seed rate, lupin soaking at home, lupin consumption per family per week and proportion of lupin used for household consumption. The use of the crop as livestock feed is negligible due to its high alkaloid content. It is concluded that the local white lupin in Ethiopia is a valuable multipurpose crop which is being cultivated in the midst of very serious shortage of cropland. Its ability to maintain soil fertility and serve as a source of food in seasons of food scarcity makes it an important crop. However, its bitter taste due to its high alkaloid content remains to be a big challenge and any lupin improvement strategy has to focus on minimizing the alkaloid content of the crop.

Bentgrass response to K fertilization and K release rates from eight sand rootzone sources used in putting green construction.

There is a lack of plant response to fertilizer K in some sandy soils even though routine soil tests for soil available K are shown to be low. This lack of plant response to K fertilizer application may be explained by K release from nonexchangeable forms. Greenhouse and laboratory experiments were conducted to evaluate (a) response of bentgrass (Agrostis palustris [Agrostis stolonifera var. palustris]) cv. Pencross grown in rootzones with different sand sources to K fertilizer application and (b) K release from nonexchangeable forms from the different sand sources as an index to K availability. Experimental variables in the greenhouse were 2 K levels (0 and 250 mg K/kg soil) and 8 sand rootzone sources. Rootzone soils were sub-irrigated to ensure no K loss from leaching. Two laboratory methods (boiling 1 M HNO3 extraction and continuous leaching with 0.01 M HCl) and total K uptake by the bentgrass were employed to index K release from nonexchangeable forms for each rootzone source. K fertilizer application significantly increased bentgrass yield growing in one rootzone source and root weight in 3 rootzone sources. K uptake by bentgrass and the 2 laboratory methods showed important differences in K release from the sand rootzones. The K removed by the 2 laboratory methods was closely related to leaf tissue K and K uptake, with the 1 M HNO3 extraction method providing the closest fit. The release of K from primary minerals in some rootzones with high sand content is proceeding at rates to satisfy bentgrass requirements for K. The 1 M HNO3 extraction method may provide an alternative to the routine laboratory procedures presently being used to measure the extractable K in sand-based constructed putting greens by measuring K contributed by nonexchangeable forms.

Abundance of phytoplankton, heterotrophic nanoflagellates and bacteria through the water column at time series station L4 in the Western English Channel. 2007-2011

The marine laboratories in Plymouth have sampled at two principle sites in the Western English Channel for over a century in open-shelf (station E1; 50° 02'N, 4° 22'W) and coastal (station L4; 50° 15'N, 4° 13'W) waters. These stations are seasonally stratified from late-April until September, and the variable biological response is regulated by subtle variations in temperature, light, nutrients and meteorology. Station L4 is characterized by summer nutrient depletion, although intense summer precipitation, increasing riverine input to the system, results in pulses of increased nitrate concentration and surface freshening. The winter nutrient concentrations at E1 are consistent with an open-shelf site. Both stations have a spring and autumn phytoplankton bloom; at station E1, the autumn bloom tends to dominate in terms of chlorophyll concentration. The last two decades have seen a warming of around 0.6°C per decade, and this is superimposed on several periods of warming and cooling over the past century. In general, over the Western English Channel domain, the end of the 20th century was around 0.5°C warmer than the first half of the century. The warming magnitude and trend is consistent with other stations across the north-west European Shelf and occurred during a period of reduced wind stress and increased levels of insolation (+20%); these are both correlated with the larger scale climatic forcing of the North Atlantic Oscillation.