Discrete Pulses Research Articles

Temporal Selectivity in Midbrain Electrosensory Neurons Identified by Modal Variation in Active Sensing

Mormyrid weakly electric fish actively sense their surroundings by continuously emitting discrete pulses of electricity separated by varying intervals of silence. The temporal pattern of this pulsing behavior is related to context. While resting in the absence of an overt stimulus, baseline interpulse intervals (IPIs) mostly range 200-450 ms, and sequential variation is relatively high. Spontaneously, or following the presentation of a novel stimulus, IPIs transiently shorten during the performance of an electromotor "burst" display. We made intracellular whole cell recordings in vivo from neurons in the lateral nucleus of the torus semicircularis while the fish's dynamic pulsing behavior modified the temporal pattern of stimulation. Stimulation was designed to simulate the spatial patterns of AM that occur during the electrolocation of a resistive object. We discovered that toral neurons selectively respond to stimulation during a particular mode of electromotor activity. Two types of temporally selective neurons were discovered: baseline-selective neurons that displayed significantly higher postsynaptic potential (PSP) amplitude and spike count per electric organ discharge (EOD) during baseline electromotor activity and burst-selective neurons that displayed significantly higher PSP amplitude and spike count per EOD during electromotor burst displays. Interval-dependent changes in the strength of excitation and inhibition contributed to their selectivity.

LULU Operators and Discrete Pulse Transform for Multidimensional Arrays

The LULU operators for sequences, that is L(n), U(n) and their compositions, are extended to multidimensional arrays in a way which preserves their essential properties, e.g., consistent separation, total variation and shape preservation. The power of the operators is demonstrated by deriving the discrete pulse transform (DPT), which is a hierarchical decomposition of the input array into pulses. Similar to its 1-D counterpart this transform satisfies a basic consistency property.

Rapid Glucocorticoid Receptor-Mediated Inhibition of Hypothalamic–Pituitary–Adrenal Ultradian Activity in Healthy Males

A complex dynamic ultradian rhythm underlies the hypothalamic-pituitary-adrenal (HPA) circadian rhythm. We have investigated in normal human male subjects the importance, site of action, and receptor-mediated processes involved in rapid basal corticosteroid feedback and its interaction with corticotrophin releasing hormone (CRH) drive. Pro-opiomelanocortin (POMC), ACTH, and cortisol were measured every 10 min from healthy males during the awakening period or late afternoon using an automated blood sampling system. Mathematical modeling into discrete pulses of activity revealed that intravenous infusion of the synthetic mixed glucocorticoid/mineralocorticoid agonist prednisolone produced rapid inhibition of ACTH and cortisol pulsatility within 30 min in the morning and afternoon. Any pulse that had commenced at the time of injection was unaffected, and subsequent pulsatility was inhibited. Prednisolone also inhibited ACTH and cortisol secretion in response to exogenous CRH stimulation, inferring rapid feedback inhibition at the anterior pituitary. Circulating POMC peptide concentrations were unaffected, suggesting that the rapid corticosteroid inhibitory effect specifically targeted ACTH secretion from pituitary corticotrophs. Prednisolone fast feedback was only reduced by glucocorticoid receptor antagonist pretreatment and not by mineralocorticoid receptor antagonism, suggesting a glucocorticoid receptor-mediated pathway. The intravenous prednisolone suppression test provides a powerful new tool to investigate HPA abnormalities underlying metabolic and psychiatric disease states.

Testing an auditory illusion in frogs: perceptual restoration or sensory bias?

The human auditory system perceptually restores short deleted segments of speech and other sounds (e.g. tones) when the resulting silent gaps are filled by a potential masking noise. When this phenomenon, known as 'auditory induction', occurs, listeners experience the illusion of hearing an ongoing sound continuing through the interrupting noise even though the perceived sound is not physically present. Such illusions suggest that a key function of the auditory system is to allow listeners to perceive complete auditory objects with incomplete acoustic information, as may often be the case in multisource acoustic environments. At present, however, we know little about the possible functions of auditory induction in the sound-mediated behaviours of animals. The present study used two-choice phonotaxis experiments to test the hypothesis that female grey treefrogs, Hyla chrysoscelis, experience the illusory perceptual restoration of discrete pulses in the male advertisement call when pulses are deleted and replaced by a potential masking noise. While added noise restored some attractiveness to calls with missing pulses, there was little evidence to suggest that the frogs actually experienced the illusion of perceiving the missing pulses. Instead, the added noise appeared to function as an acoustic appendage that made some calls more attractive than others as a result of sensory biases, the expression of which depended on the temporal order and acoustic structure of the added appendages.

Sound production by singing humpback whales

Sounds from humpback whale songs were analyzed to evaluate possible mechanisms of sound production. Song sounds fell along a continuum with trains of discrete pulses at one end and continuous tonal signals at the other. This graded vocal repertoire is comparable to that seen in false killer whales [Murray et al. (1998). J. Acoust. Soc. Am. 104, 1679-1688] and human singers, indicating that all three species generate sounds by varying the tension of pneumatically driven, vibrating membranes. Patterns in the spectral content of sounds and in nonlinear sound features show that resonating air chambers may also contribute to humpback whale sound production. Collectively, these findings suggest that categorizing individual units within songs into discrete types may obscure how singers modulate song features and illustrate how production-based characterizations of vocalizations can provide new insights into how humpback whales sing.

Neurokinin B and Dynorphin A in Kisspeptin Neurons of the Arcuate Nucleus Participate in Generation of Periodic Oscillation of Neural Activity Driving Pulsatile Gonadotropin-Releasing Hormone Secretion in the Goat

Gonadotropin-releasing hormone (GnRH) neurons in the basal forebrain are the final common pathway through which the brain regulates reproduction. GnRH secretion occurs in a pulsatile manner, and indirect evidence suggests the kisspeptin neurons in the arcuate nucleus (ARC) serve as the central pacemaker that drives pulsatile GnRH secretion. The purpose of this study was to investigate the possible coexpression of kisspeptin, neurokinin B (NKB), and dynorphin A (Dyn) in neurons of the ARC of the goat and evaluate their potential roles in generating GnRH pulses. Using double and triple labeling, we confirmed that all three neuropeptides are coexpressed in the same population of neurons. Using electrophysiological techniques to record multiple-unit activity (MUA) in the medial basal hypothalamus, we found that bursts of MUA occurred at regular intervals in ovariectomized animals and that these repetitive bursts (volleys) were invariably associated with discrete pulses of luteinizing hormone (LH) (and by inference GnRH). Moreover, the frequency of MUA volleys was reduced by gonadal steroids, suggesting that the volleys reflect the rhythmic discharge of steroid-sensitive neurons that regulate GnRH secretion. Finally, we observed that central administration of Dyn-inhibit MUA volleys and pulsatile LH secretion, whereas NKB induced MUA volleys. These observations are consistent with the hypothesis that kisspeptin neurons in the ARC drive pulsatile GnRH and LH secretion, and suggest that NKB and Dyn expressed in those neurons are involved in the process of generating the rhythmic discharge of kisspeptin.

Imaging the rupture of the Mw 6.3 April 6, 2009 L'Aquila, Italy earthquake using back‐projection of teleseismic P‐waves

We present rupture details of the Mw 6.3 April 6, 2009 L'Aquila earthquake derived by back‐projecting teleseismic P waves. This technique has previously been applied to large magnitude earthquakes, but this is the first application to a moderate size event. We processed vertical‐component seismograms for 60 broadband stations obtained from the Incorporated Research Institutions for Seismology (IRIS) data center. The traces were aligned and normalized using a multi‐channel cross‐correlation algorithm and 4th root stacking was used to image the rupture. We found that the L'Aquila earthquake ruptured towards the south and that a second discrete pulse of energy occurred 20–25 km east of the epicenter about 17–18 s after the nominal origin time. The spatial extent of the rupture image correlates well with a post‐seismic survey of damage in the region. Because the technique is potentially very fast (images can be produced within 20–30 minutes of the origin time), it may be useful to governmental agencies tasked with emergency response and rescue.

Linear Pulse-Coupled Oscillators Model¬—A New Approach for Time Synchronization in Wireless Sensor Networks

Mutual synchronization is a ubiquitous phenomenon that exists in various natural systems. The individual participants in this process can be modeled as oscillators, which interact by discrete pulses. In this paper, we analyze the synchronization condition of two- and multi-oscillators system, and propose a linear pulse-coupled oscillators model. We prove that the proposed model can achieve synchronization for almost all conditions. Numerical simulations are also included to investigate how different model parameters affect the synchronization. We also discuss the implementation of the model as a new approach for time synchronization in wireless sensor networks.

Comparative PD pulse burst characteristics of transformer type natural and synthetic ester fluids and mineral oils

The partial discharge (PD) pulse burst behavior in natural and synthetic organic ester fluids and mineral oils of the type used in transformers has been examined, using simultaneous wide and narrow band measurement techniques. This permitted the determination and comparison of both the overall charge transfer of the PD pulse as well as that of the discrete PD pulses comprising the PD pulse burst in the evaluated dielectric fluids.

Multiple photoreceptor systems control the swim pacemaker activity in box jellyfish

Like all other cnidarian medusae, box jellyfish propel themselves through the water by contracting their bell-shaped body in discrete swim pulses. These pulses are controlled by a swim pacemaker system situated in their sensory structures, the rhopalia. Each medusa has four rhopalia each with a similar set of six eyes of four morphologically different types. We have examined how each of the four eye types influences the swim pacemaker. Multiple photoreceptor systems, three of the four eye types, plus the rhopalial neuropil, affect the swim pacemaker. The lower lens eye inhibits the pacemaker when stimulated and provokes a strong increase in the pacemaker frequency upon light-off. The upper lens eye, the pit eyes and the rhopalial neuropil all have close to the opposite effect. When these responses are compared with all-eye stimulations it is seen that some advanced integration must take place.

Palynological correlation of Carnian humid pulses throughout western Tethys

The Carnian Pluvial Event is an Upper Triassic swing toward increased rainfall best documented in the Tethys tropical belt, and mainly recognized on its effects on sedimentary systems, as the demise of carbonate platforms and the enhanced siliciclastic supply. In some portions of western Tethys, and particularly in the Raibler Schichten of the Northern Calcareous Alps and in the Dolomites, the Carnian Pluvial Event is recorded by four discrete siliciclastic pulses. In the Raibler Schichten, three siliciclastic intervals are documented and take the name of first, second and third shale. In order to correlate these pulses at the basinal scale, the study of the palynological assemblages in a section of the Raibler Schichten near Rubland (Austria), and of the classical succession of the Lunz nappe, have been carried out. More than eighty palynomorph species are recorded. Most of them correspond to typical Carnian morphospecies of the Carnian Pluvial Event in Europe. On the base of their stratigraphic distribution, three different palynomorph assemblages are described: Aulisporites astigmosus assemblage, Lagenella martinii assemblage and Granuloperculatipollis rudis assemblage. A fourth, older assemblage is also informally defined. A palynostratigraphic correlation between the NCA, the Germanic Basin and the Dolomites has been obtained. The four siliciclastic pulses recognized in the Raibler Schichten and Lunz are also found in the Dolomites, and yield the same palynological associations. The base of the Schilfsandstein, that record the Carnian Pluvial Event in the Germanic Basin, is correlated to the second or third siliciclastic pulse (first or second shale of the Raibler Schichten). Siliciclastic pulses are thus correlated throughout western Tethys, and can thus be interpreted as short-lived humid climate wiggles within the Carnian Pluvial Event. A quantitative analysis of the Carnian successions of the NCA highlights a shift toward hygrophytic elements in the uppermost Julian, and an abrupt return to xerophytic associations in the lower Tuvalian. The palynological hygrophytic associations that characterize the Aulisporites astigmosus and Lagenella martinii assemblages are present in many other parts of Europe and Middle East, suggesting that the Carnian Pluvial Event determined a humid climate perturbation in a wide area of the northern hemisphere spanning from tropical to high latitudes.

SHRIMP U-Pb dating of recurrent Cryogenian and Late Cambrian-Early Ordovician alkalic magmatism in central Idaho: Implications for Rodinian rift tectonics

Composite alkalic plutonic suites and tuffaceous diamictite, although discontinuously exposed across central Idaho in roof pendants and inliers within the Idaho batholith and Challis volcanic-plutonic complex, define the >200-km-long northwest-aligned Big Creek-Beaverhead belt. Sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon dates on these igneous rocks provide direct evidence for the orientation and location of the Neoproterozoic–Paleozoic western Laurentian rift margin in the northern U.S. Cordillera. Dating delimits two discrete magmatic pulses at ca. 665–650 Ma and 500–485 Ma at the western and eastern ends, respectively, of this belt. Together with the nearby 685 Ma volcanic rocks of the Edwardsburg Formation, there is a 200 Ma history of recurrent extensional magmatic pulses along the belt. A similar history of recurrent uplift is reflected in the stratigraphic record of the associated miogeoclinal and cratonal platform basins, suggesting that the Big Creek–Beaverhead belt originated as a border fault during continental rift events. The magmatic belt is paired with the recurrently emergent Lemhi Arch and narrow miogeoclinal facies belts and it lies inboard of a northwest-striking narrow zone of thinned continental crust. These features define a northeast-extending upper-plate extensional system between southeast Washington and southeast Idaho that formed a segment of the Neoproterozoic–Paleozoic miogeocline. This segment was flanked on the north by the St. Mary–Moyie transform zone (south of a narrow southern Canadian upper-plate margin) and on the south by the Snake River transfer zone (north of a broad Great Basin lower-plate margin). These are the central segments of a zigzag-shaped Cordilleran rift system of alternating northwest-striking extensional zones offset by northeast-striking transfers and transforms. The data substantiate polyphase rift and continental separation events that included (1) pre- and syn-Windermere rifting, (2) Windermere margin subsidence, (3) late Ediacaran-Cambrain rifting, and (4) well-developed late Ediacaran-Devonian passive margin subsidence and deposition. Timing and geometries support synchronous but opposing divergence along Cordilleran and Atlantic rifts with a junction in Southern California–Sonora.

Rates and mechanisms of Mesoarchean magmatic arc construction, eastern Kaapvaal craton, Swaziland

The mechanisms and time scales of magmatism and deformation during orogenesis are important for developing models of lithospheric growth. We summarize the first detailed study of a well-preserved Mesoarchean crustal section from the oldest portion of the Kaapvaal craton, southern Africa, which records the complex interactions between deformation and magmatism during craton assembly ca. 3.3–3.2 Ga. We use chemical abrasion–isotope dilution–thermal ionization mass spectrometry (CA-ID-TIMS) U-Pb zircon geochronology and apatite thermochronology in conjunction with geological mapping to show that the tonalitic to granitic Usutu magmatic suite intruded into the ca. 3.66–3.45 Ga Ancient gneiss complex over a period of ∼16 Ma ca. 3236–3220 Ma as discrete pulses of magma with variable intrusive styles. Usutu rocks retain magmatic fabrics that preserve a history of NW-SE regional shortening, consistent with synchronous deformation recorded in the adjacent Barberton greenstone belt. U-Pb zircon dates of ca. 3.28–3.23 Ga and apatite cooling dates from the Nhlangano gneiss SE of the Ancient gneiss complex reveal that they represent an older, largely undocumented period of crustal growth and modification. Synchronicity in magmatism and similarity in kinematics of deformation north and south of a previously suggested continental suture in the Barberton greenstone belt lead us to propose doubly vergent subduction zones that were active from at least ca. 3.28 to 3.22 Ga. Geochemistry of the Usutu suite reveals differences in magma sources from north to south, which, when combined with Nd isotopic signatures, are consistent with their production in a subduction zone. The combination of <1 Ma precision on crystallization dates with field observations and geochemistry allows us to track the evolution of this magmatic system with temporal resolution unprecedented for Archean rocks.

A test of Gestalt grouping principles in frogs: Auditory illusion or sensory bias?

The study of auditory illusions has been important in elucidating the rules of auditory grouping in humans, which adheres to principles first described by Gestalt psychologists to explain the formation of visual objects. For example, the human auditory system perceptually restores short, deleted segments of speech and other sounds (e.g., tones) when the resulting gaps are filled by a potential masking noise. Results from studies of such illusions suggest that the Gestalt principle of “continuity” allows humans to perceive complete auditory objects in the face of incomplete or degraded acoustic information in the presence of noise. The present study tested the hypothesis that female treefrogs experience the perceptual restoration of discrete pulses in the male sexual advertisement signal when they are deleted and replaced by a potential masking noise. While added noise restored some attractiveness to degraded signals, there was no evidence that the frogs experienced the illusion of perceiving actual pulses that were missing. Instead, the added noise functioned as an acoustic ornament that made some signals more attractive than others as a result of an inherent sensory bias for greater sensory stimulation. Whether such sensory biases themselves adhere to Gestalt principles of auditory grouping remains to be demonstrated.

Modeling the Transient Pumping from Two Aquifers Using MODFLOW

A procedure is proposed for calculating the spatial and temporal variation of drawdown due to pumping a well tapping two aquifers separated by an aquitard, using convolution and MODFLOW. It can take into account the unsteady pumping discharge and cross flow through the intervening aquitard. A discrete pulse kernel method based on superposition/convolution is used to account for the unsteady pumping discharge. The discrete pulse kernels are calculated using MODFLOW. The contributions of the aquifers to the pumped discharge are accounted implicitly and not required to be specified explicitly. Available numerical models (e.g., MODFLOW) require the aquifer contributions that are implicitly controlled, to be specified explicitly. The use of the suggested procedure is illustrated using examples. The contributions of the aquifers are found not in proportion to their transmissivities but vary with time, when the diffusivities of the aquifers are not equal. Applying the new procedure, the numerical models, such as MODFLOW can be used to correctly model the transient pumping from two aquifers with cross flow; thus, it opens up the possibility of numerically accounting for the aquifer heterogeneity while dealing with the flow to a well tapping two aquifers under a transient pumping, which would be otherwise difficult to account for analytically.

Neogene tephra correlations in eastern Idaho and Wyoming: Implications for Yellowstone hotspot-related volcanism and tectonic activity

Research Article| May 01, 2009 Neogene tephra correlations in eastern Idaho and Wyoming: Implications for Yellowstone hotspot-related volcanism and tectonic activity Mark H. Anders; Mark H. Anders † 1Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA †E-mail: manders@ldeo.columbia.edu Search for other works by this author on: GSW Google Scholar Janet Saltzman; Janet Saltzman ‡ 1Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA ‡Present address: Science Department, Red Hook High School, Red Hook, New York 12571, USA. Search for other works by this author on: GSW Google Scholar Sidney R. Hemming Sidney R. Hemming 1Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2009) 121 (5-6): 837–856. https://doi.org/10.1130/B26300.1 Article history received: 02 Aug 2007 rev-recd: 31 Jul 2008 accepted: 01 Aug 2008 first online: 03 Oct 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Mark H. Anders, Janet Saltzman, Sidney R. Hemming; Neogene tephra correlations in eastern Idaho and Wyoming: Implications for Yellowstone hotspot-related volcanism and tectonic activity. GSA Bulletin 2009;; 121 (5-6): 837–856. doi: https://doi.org/10.1130/B26300.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The explosive rhyolitic eruptions that define the track of the Snake River Plain–Yellowstone volcanism have produced a large volume of tephra found in late Miocene and younger basin-fill sediments throughout the western United States. Here we use 40Ar/39Ar isotopic dating, paleomagnetic analysis, major- and trace-element geochemistry, and standard optical techniques to establish regional tephra correlations. We focus on tephra deposits in three Neogene basins in spatially separated areas—Grand Valley, in eastern Idaho; Jackson Hole, in northwestern Wyoming; and the Granite Mountains area, in central Wyoming. These basins have experienced relatively continuous deposition from the late Miocene to the Holocene. We found tephra layers that directly tie the stratigraphy between all three basins. Using these correlations we found that basins experienced discrete pulses of extension separated by long periods of relative quiescence, the dates of which are staggered between basins. An early pulse of extension occurred in Grand Valley and Jackson Hole between 10.3 Ma and 16.33 Ma with a second pulse initiating between 4.54 Ma and 2.09 Ma. The Granite Mountains basin experienced a single pulse of extension sometime between 11.14 Ma and 6.75 Ma. These pulses of accelerated extension, along with evidence of similar pulses in other basins, present a pattern of west-to-east migration that we suggest is related to the Yellowstone hotspot. The later pulse of activity in Grand Valley and Jackson Hole corresponds to the migration of the North American Plate over the tail of the Yellowstone hotspot. We speculate that the earliest pulse in each basin is related to the more rapid movement of the sublithospheric hotspot head as it spreads out from its earliest known location, where the Columbia River Plateau Flood Basalt Province initiated in southeastern Oregon, to its outermost edge under central Wyoming. Our results are consistent with this model of a plume head, though not unique to it.The results of our study also indicate that previous suggestions that the rate of Snake River Plain explosive volcanism has decreased by a factor of 2 or 3 since emplacement of the middle Miocene Trapper Creek tuffs likely underestimate post–Trapper Creek eruption rates. We have discovered a large number of previously unidentified post–middle Miocene major eruptive events, both as ash-flow tuffs and as vitric air-fall tuffs. Recalculation to include these newly discovered events results in a rate of major eruptions that is fairly uniform until ca. 4.54 Ma. However, there is a substantial gap in major silicic eruptions in the interval between 4.54 Ma and 2.09 Ma, which we call the “post–Heise eruptive gap.” With the exception of this gap, the rate of major eruptions on the Snake River Plain has been roughly constant since inception of the eastern Snake River Plain–Yellowstone volcanic track between 16 Ma and 17 Ma. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Excimer Laser-Assisted Angioplasty for Infrainguinal Artery Disease

After nearly 2 decades of research and experimentation with laser-assisted angioplasty, the xenon-hydrogen chloride excimer laser emerged as the laser device best suited for the treatment of peripheral artery disease. Emitting light at a wavelength of 308 nm, this laser utilizes a nonthermal mechanism of action to ablate plaque and thrombus in powerful discrete pulses. The excimer laser is particularly useful for the treatment of complex conditions, such as long chronic occlusions in the superficial femoral artery and in those patients with below-the-knee disease and critical limb ischemia who may not be good candidates for bypass surgery. A number of investigators have noted that the excimer laser will often uncover distinct, more focal lesions in what appears to be an extensive and complex occlusion, potentially simplifying treatment of these segments. The Laser Angioplasty for Critical Limb Ischemia phase 2 trial, a prospective registry of 145 patients at 11 US and 3 German sites, achieved good procedural success (86%) and an excellent 6-month limb salvage rate (93%). A new specialized deflecting sheath designed to direct excimer ablation in blockages of the larger main arteries above the knee has produced clinical improvement in a single-center feasibility study and a 16-center prospective registry. Less promising results were reported in a single-center real-world retrospective registry, warranting careful case selection with this device for patients with diabetes and renal failure.

Geochemical and temporal evolution of Cenozoic magmatism in western Turkey: mantle response to collision, slab break-off, and lithospheric tearing in an orogenic belt

Abstract Post-collisional magmatism in western Anatolia began in the Eocene, and has occurred in discrete pulses throughout the Cenozoic as it propagated from north to south, producing volcano-plutonic associations with varying chemical compositions. This apparent SW migration of magmatism and accompanying extension through time was a result of the thermally induced collapse of the western Anatolian orogenic belt, which formed during the collision of the Sakarya and Tauride–Anatolide continental blocks in the late Paleocene. The thermal input and melt sources for this prolonged magmatism were provided first by slab break-off-generated aesthenospheric flow, then by lithospheric delamination-related aesthenospheric flow, followed by tectonic extension-driven upward aesthenospheric flow. The first magmatic episode is represented by Eocene granitoid plutons and their extrusive carapace that are linearly distributed along the Izmir–Ankara suture zone south of the Marmara Sea. These suites show moderately evolved compositions enriched in incompatible elements similar to subduction zone-influenced subalkaline magmas. Widespread Oligo-Miocene volcanic and plutonic rocks with medium- to high-K calc-alkaline compositions represent the next magmatic episode. Partial melting and assimilation-fractional crystallization of enriched subcontinental lithospheric mantle-derived magmas were important processes in the genesis and evolution of the parental magmas, which experienced decreasing subduction influence and increasing crustal contamination during the evolution of the Eocene and Oligo-Miocene volcano-plutonic rocks. Collision-induced lithospheric slab break-off provided an influx of aesthenospheric heat and melts that resulted in partial melting of the previously subduction-metasomatized mantle lithosphere beneath the suture zone, producing the Eocene and Oligo-Miocene igneous suites. The following magmatic phase during the middle Miocene (16–14 Ma) developed mildly alkaline bimodal volcanic rocks that show a decreasing amount of crustal contamination and subduction influence in time. Both melting of a subduction-modified lithospheric mantle and aesthenospheric mantle-derived melt contribution played a significant role in the generation of the magmas of these rocks. This magmatic episode was attended by region-wide extension that led to the formation of metamorphic core complexes and graben systems. Aesthenospheric upwelling caused by partial delamination of the lithospheric root beneath the western Anatolian orogenic belt was likely responsible for the melt evolution of these mildly alkaline volcanics. Lithospheric delamination may have been caused by ‘peeling off’ during slab rollback. The last major phase of magmatism in the region, starting c .12 Ma, is represented by late Miocene to Quaternary alkaline to super-alkaline volcanic rocks that show OIB-like geochemical features with progressively more potassic compositions increasing toward south in time. These rocks are spatially associated with major extensional fault systems that acted as natural conduits for the transport of uncontaminated alkaline magmas to the surface. The melt source for this magmatic phase carried little or no subduction component and was produced by the decompressional melting of aesthenospheric mantle, which flowed in beneath the attenuated continental lithosphere in the Aegean extensional province. This time-progressive evolution of Cenozoic magmatism and extension in western Anatolia has been strongly controlled by the interplay between regional plate-tectonic events and the mantle dynamics, and provides a realistic template for post-collisional magmatism and crustal extension in many orogenic belts.

PD pulse burst behavior of a transformer type synthetic organic ester fluid

The partial discharge (PD) pulse burst characteristics of a transformer type synthetic organic ester fluid were compared with those of an equivalent transformer type mineral oil. Wide and narrow bandwidth measurements were carried out to determine simultaneously the apparent charge transfers associated with the overall PD pulse burst as well as that of the individual discrete pulses within the PD pulse burst. The PD pulse burst behavior was found to be similar in both insulating liquids. The discharge cavity formation times ranged from 0.5 to 1.5 mus, while the charge transfers associated with the PD pulse bursts in the liquids were found to extend from approximately 5 to 30 pC.

Millennial-scale variability in Southern Hemisphere westerly wind activity over the last 5000 years in SW Patagonia

Here we report results from a high-resolution palynological record and stratigraphic/geochronologic data related to a Neoglacial event in Torres del Paine National Park, southern Chile (51°S, 71°W), to investigate climatic variations in Southwest Patagonia during the last 5000 years. The record reveals a stepwise expansion of Nothofagus-dominated woodlands and forests with discrete pulses at 4400, 2900, 1300, and 570 cal yr BP. Superimposed upon this trend we identify a relative opening of the woodlands between 4100–2900 and 2300–1300 cal yr BP. Closed-canopy forests dominated the landscape between 570–60 cal yr BP, followed by a rapid decline at the end of the 19th century that coincided with intense fire activity and the appearance of Rumex cf. acetocella, an exotic species introduced by European settlers. We interpret these changes as variations in the intensity and/or position of the southern margin of the westerly winds, which culminated with a net eastward shift of the forest–steppe ecotone during the Little Ice Age. We propose that millennial-scale changes in either the latitudinal position and/or the overall strength of the southern westerlies may be responsible for vegetation changes, fire occurrence, and the dynamic behavior of Patagonian glaciers during the last 5000 years. Because the modern maximum in near-surface wind velocities and precipitation is located between 48° and 50°S, we suggest that the core of the southern westerlies may have achieved this modern position ∼570 years ago.