Palaeolimnology of Lake Sapanca and identification of historic earthquake signals, Northern Anatolian Fault Zone (Turkey)

Lake Sapanca is located on a strand of the Northern Anatolian Fault Zone (NAFZ, Turkey), where a series of strong earthquakes (Ms >6.0) have occurred over the past hundred years. Identifying prehistoric earthquakes in and around Lake Sapanca is key to a better understanding of plate movements along the NAFZ. This study contributes to the development of palaeolimnological tools to identify past earthquakes in Lake Sapanca. To this end several promising proxies were investigated, specifically lithology, magnetic susceptibility, grain size (thin-section and laser analysis), geochemistry, pollen concentration, diatom assemblages, 137Cs and 210Pb. Sedimentological indicators provided evidence for reworked, turbidite-like or homogeneous facies (event layers) in several short cores (<45 cm). Other indicators of sediment input and the historical chronicles available for the area suggest that three of these event layers likely originated from the AD 1957, 1967 and 1999 earthquakes. Recent changes in sediment deposition and nutrient levels have also been identified, but are probably not related to earthquakes. This study demonstrates that a combination of indicators can be used to recognize earthquake-related event layers in cores that encompass a longer period of time

Control of wind strength and frequency in the Aral Sea basin during the late Holocene

Changing content of detrital input in laminated sediments traced by XRF scanning and microfacies analyses reflect prominent variations in sedimentation processes in the Aral Sea. A high-resolution record of titanium from a core retrieved in the northwestern Large Aral Sea allows a continuous reconstruction of wind strength and frequency in western Central Asia for the past 1500 yr. During AD 450-700, AD 1210-1265, AD 1350-1750 and AD 1800-1975, detrital inputs (bearing titanium) are high, documenting an enhanced early spring atmospheric circulation associated with an increase in intensity of the Siberian High pressure system over Central Asia. In contrast, lower titanium content during AD 1750-1800 and AD 1980-1985 reflects a diminished influence of the Siberian High during early spring with a reduced atmospheric circulation. A moderate circulation characterizes the time period AD 700-1150. Unprecedented weakened atmospheric circulation over western Central Asia are inferred during ca. AD 1180-1210 and AD 1265-1310 with a considerable decrease in dust storm frequency, sedimentation rates, lamination thickness and detrital inputs (screened at 40-μm resolution). Our results are concurrent with changes in the intensity of the Siberian High during the past 1400 yr as reported in the GISP2 Ice Core from Greenland. © 2007 University of Washington

Dinoflagellaten als oorzaak van verlammende mosselvergiftiging

We have undertaken a high resolution palaeoclimate reconstruction on radiocarbon dated palaeolake sediments from the Spiti valley, NW Himalaya. This site lies in the climatically sensitive winter westerlies and Indian Summer Monsoon (ISM) transitional regime and provides an opportunity to reconstruct the precipitation seasonality, and extreme precipitation events that are characterised by intensified erosion. The lake sediments reveal distinct lithofacies that provide evidence of changes in depositional environment and climate during early to mid Holocene (8.7–6.1 cal ka BP). We have identified three stages during the period of lake's existence: the Stage I (8.7–7.6 cal ka BP) is marked by lake establishment; Stage II (∼7.6–6.8 cal ka BP) by sustained cooler periods and weakened summer monsoon, and Stage III (∼6.8–6.1 cal ka BP) by a shift from colder to warmer climate with stronger ISM. We have identified several short term cooler periods at ca. 8.7, 8.5, 8.3 and 7.2–6.9 cal ka BP. Based on an overview of regional climate records we show that there is an abrupt switch in precipitation seasonality ca. 6.8 cal ka BP that is followed by the onset of the intensified monsoon in the NW Himalaya

Multichannel FPGA based MVT system for high precision time (20~ps~RMS) and charge measurement

In this article it is presented an FPGA based $M$ulti-$V$oltage $T$hreshold (MVT) system which allows of sampling fast signals ($1-2$ ns rising and falling edge) in both voltage and time domain. It is possible to achieve a precision of time measurement of $20$ ps RMS and reconstruct charge of signals, using a simple approach, with deviation from real value smaller than 10$\%$. Utilization of the differential inputs of an FPGA chip as comparators together with an implementation of a TDC inside an FPGA allowed us to achieve a compact multi-channel system characterized by low power consumption and low production costs. This paper describes realization and functioning of the system comprising 192-channel TDC board and a four mezzanine cards which split incoming signals and discriminate them. The boards have been used to validate a newly developed Time-of-Flight Positron Emission Tomography system based on plastic scintillators. The achieved full system time resolution of $\sigma$(TOF) $\approx 68$ ps is by factor of two better with respect to the current TOF-PET systems.Comment: Accepted for publication in JINST, 10 pages, 8 figure

Microstructural and magnetic characterization of Ni0.5Zn0.5Fe2O4 ferrite nanoparticles

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A feasibility study of ortho-positronium decays measurement with the J-PET scanner based on plastic scintillators

We present a study of the application of the Jagiellonian Positron Emission Tomograph (J-PET) for the registration of gamma quanta from decays of ortho-positronium (o-Ps). The J-PET is the first positron emission tomography scanner based on organic scintillators in contrast to all current PET scanners based on inorganic crystals. Monte Carlo simulations show that the J-PET as an axially symmetric and high acceptance scanner can be used as a multi-purpose detector well suited to pursue research including e.g. tests of discrete symmetries in decays of ortho-positronium in addition to the medical imaging. The gamma quanta originating from o-Ps decay interact in the plastic scintillators predominantly via the Compton effect, making the direct measurement of their energy impossible. Nevertheless, it is shown in this paper that the J-PET scanner will enable studies of the o-Ps$\to3\gamma$ decays with angular and energy resolution equal to $\sigma(\theta) \approx 0.4^{\circ}$ and $\sigma(E) \approx 4.1$ keV, respectively. An order of magnitude shorter decay time of signals from plastic scintillators with respect to the inorganic crystals results not only in better timing properties crucial for the reduction of physical and instrumental background, but also suppresses significantly the pileups, thus enabling compensation of the lower efficiency of the plastic scintillators by performing measurements with higher positron source activities

Evaluation of Single-Chip, Real-Time Tomographic Data Processing on FPGA - SoC Devices

A novel approach to tomographic data processing has been developed and evaluated using the Jagiellonian PET (J-PET) scanner as an example. We propose a system in which there is no need for powerful, local to the scanner processing facility, capable to reconstruct images on the fly. Instead we introduce a Field Programmable Gate Array (FPGA) System-on-Chip (SoC) platform connected directly to data streams coming from the scanner, which can perform event building, filtering, coincidence search and Region-Of-Response (ROR) reconstruction by the programmable logic and visualization by the integrated processors. The platform significantly reduces data volume converting raw data to a list-mode representation, while generating visualization on the fly.Comment: IEEE Transactions on Medical Imaging, 17 May 201

J-PET: a new technology for the whole-body PET imaging

The Jagiellonian Positron Emission Tomograph (J-PET) is the first PET built from plastic scintillators. J-PET prototype consists of 192 detection modules arranged axially in three layers forming a cylindrical diagnostic chamber with the inner diameter of 85 cm and the axial field-of-view of 50 cm. An axial arrangement of long strips of plastic scintillators, their small light attenuation, superior timing properties, and relative ease of the increase of the axial field-of-view opens promising perspectives for the cost effective construction of the whole-body PET scanner, as well as construction of MR and CT compatible PET inserts. Present status of the development of the J-PET tomograph will be presented and discussed.Comment: Presented at the 2nd Jagiellonian Symposium on Fundamental and Applied Subatomic Physics, Krak\'ow, Poland, June 4-9, 2017. To be published in Acta Phys. Pol.

Commissioning of the J-PET detector for studies of decays of positronium atoms

The Jagiellonian Positron Emission Tomograph (J-PET) is a detector for medical imaging of the whole human body as well as for physics studies involving detection of electron-positron annihilation into photons. J-PET has high angular and time resolution and allows for measurement of spin of the positronium and the momenta and polarization vectors of annihilation quanta. In this article, we present the potential of the J-PET system for background rejection in the decays of positronium atoms.Comment: Presented at the 2nd Jagiellonian Symposium on Fundamental and Applied Subatomic Physics, Krak\'ow, Poland, June 4-9, 2017. To be published in Acta Phys. Pol.