A
bstract
The NEXT experiment aims to observe the neutrinoless double beta decay of
136
Xe in a high-pressure xenon gas TPC using electroluminescence (EL) to amplify the signal from ionization. One ...of the main advantages of this technology is the possibility to reconstruct the topology of events with energies close to
Q
ββ
. This paper presents the first demonstration that the topology provides extra handles to reject background events using data obtained with the NEXT-DEMO prototype.
Single electrons resulting from the interactions of
22
Na 1275 keV gammas and electronpositron pairs produced by conversions of gammas from the
228
Th decay chain were used to represent the background and the signal in a double beta decay. These data were used to develop algorithms for the reconstruction of tracks and the identification of the energy deposited at the end-points, providing an extra background rejection factor of 24
.
3 ± 1
.
4 (stat.)%, while maintaining an efficiency of 66
.
7 ± 1
.
% for signal events.
Ionospheric disturbances observed by bottom‐side soundings of the ionosphere appear at many temporal and spatial scales. Australia has many simultaneous observations from vertically orientated ...ionospheric sounders with spatial separations on the scale of 1000 km. However, with this spatial sampling only large scale ionospheric disturbances can be mapped and subsequently modeled. DSTO has an experimental program in progress to investigate the smaller spatial scale disturbances. These are often seen on vertical incidence soundings and are uncorrelated with soundings from greater than 500 km away. They can also be uncorrelated with soundings from the same site only 15 min later. The DSTO program to investigate these ionospheric disturbances is called SpICE, for Spatial Ionospheric Correlation Experiment. SpICE uses a small set of transmitters and receivers with varying separations to achieve a geographically spread set of near‐vertical incidence ionospheric “reflection” points separated by 50–150 km, allowing us to probe disturbances at this spatial scale. Using the latest digital receiver technology we can collect amplitude and phase information from the ionospheric returns of the continuous wave transmissions of a nearby transmitter that is rapidly sweeping through the HF band. The returned signal is processed at a very high resolution to achieve good signal‐to‐noise complex ionograms at better than one‐minute time updates. To date there have been three SpICE campaigns. This paper will discuss the SpICE program goals and highlight some of the unusual features observed in the first campaign. Following papers will look more closely at this data set and the subsequent campaigns.
Key Points
Introduces set of experiments by DSTO to investigate ionospheric disturbances
Band‐passed h'F2 found to be tracer for disturbances
Spatial sampling needs to be smaller than 100 km to adequately capture structure
Time projection chambers for the T2K near detectors Abgrall, N.; Andrieu, B.; Baron, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2011, Letnik:
637, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The T2K experiment is designed to study neutrino oscillation properties by directing a high intensity neutrino beam produced at J-PARC in Tokai, Japan, towards the large Super-Kamiokande detector ...located 295
km away, in Kamioka, Japan. The experiment includes a sophisticated near detector complex, 280
m downstream of the neutrino production target in order to measure the properties of the neutrino beam and to better understand neutrino interactions at the energy scale below a few GeV. A key element of the near detectors is the ND280 tracker, consisting of two active scintillator–bar target systems surrounded by three large time projection chambers (TPCs) for charged particle tracking. The data collected with the tracker are used to study charged current neutrino interaction rates and kinematics prior to oscillation, in order to reduce uncertainties in the oscillation measurements by the far detector. The tracker is surrounded by the former UA1/NOMAD dipole magnet and the TPCs measure the charges, momenta, and particle types of charged particles passing through them. Novel features of the TPC design include its rectangular box layout constructed from composite panels, the use of bulk micromegas detectors for gas amplification, electronics readout based on a new ASIC, and a photoelectron calibration system. This paper describes the design and construction of the TPCs, the micromegas modules, the readout electronics, the gas handling system, and shows the performance of the TPCs as deduced from measurements with particle beams, cosmic rays, and the calibration system.
► First large scale time projection chambers with micropattern gas detectors. ► Incorporates new ASIC for electronic readout. ► Includes a pressure equalizing gas system and a photoelectron calibration system. ► Specifications achieved as deduced from neutrino, cosmic, and calibration tests. ► Will play an important role in T2K to measure neutrino oscillations.
Dysfunction of the
LIS1
gene causes lissencephaly, a drastic neurological disorder characterized by a deep disruption of the cortical structure. We aim to uncover alterations of the cortical neuronal ...networks related with the propagation of epileptiform activity in the
Lis1/sLis1
mouse, a model lacking the LisH domain in heterozygosis. We did extracellular field-potential and intracellular recordings in brain slices of the anterior cingulate cortex (ACC) or the retrosplenial cortex (RSC) to study epileptiform activity evoked in the presence of bicuculline (10 µM), a blocker of GABA
A
receptors. The sensitivity to bicuculline of the generation of epileptiform discharges was similar in wild type (WT) and
Lis1/sLis1
cortex (EC
50
1.99 and 2.24 µM, respectively). In the
Lis1/sLis1
cortex, we observed a decreased frequency of the oscillatory post-discharges of the epileptiform events; also, the propagation of epileptiform events along layer 2/3 was slower in the
Lis1/sLis1
cortex (WT 47.69 ± 2.16 mm/s,
n
= 25;
Lis1/sLis1
37.34 ± 2.43 mm/s,
n
= 15;
p
= 0.004). The intrinsic electrophysiological properties of layer 2/3 pyramidal neurons were similar in WT and
Lis1/sLis1
cortex, but the frequency of the spontaneous EPSCs was lower and their peak amplitude higher in
Lis1/sLis1
pyramidal neurons. Finally, the propagation of epileptiform activity was differently affected by AMPA receptor blockers: CNQX had a larger effect in both ACC and RSC while GYKI53655 had a larger effect only in the ACC in the WT and
Lis1/sLis1
cortex. All these changes indicate that the dysfunction of the
LIS1
gene causes abnormalities in the properties of epileptiform discharges and in their propagation along the layer 2/3 in the anterior cingulate cortex and in the restrosplenial cortex.
The performance of systems using high frequency (HF) radio waves, such as over‐the‐horizon radars (OTHR), can be strongly affected by external interferers at great distances (thousands of kilometers) ...from the systems receiver. However, the propagation of interference has complex behavior and is known to vary with location, time, season, sunspot number, and radio frequency. Understanding how the level of interference varies with all of these factors is important for the design of new systems such as next generation OTHR. By combining databases of known transmitters, ray‐tracing propagation, and a model ionosphere, a model of the behavior of interference at HF has been developed.
Key Points
We have developed a model for external interference at HF
Can model diurnal, seasonal, and geographic variations
Model gives results consistent with JORN spectrum monitor data
We investigate the potential of using deep learning techniques to reject background events in searches for neutrinoless double beta decay with high pressure xenon time projection chambers capable of ...detailed track reconstruction. The differences in the topological signatures of background and signal events can be learned by deep neural networks via training over many thousands of events. These networks can then be used to classify further events as signal or background, providing an additional background rejection factor at an acceptable loss of efficiency. The networks trained in this study performed better than previous methods developed based on the use of the same topological signatures by a factor of 1.2 to 1.6, and there is potential for further improvement.
This study further advances our knowledge about the mechanisms and timing by which exenatide attenuates postprandial hyperglycemia in type 2 diabetes.
Objective:
Our objective was to examine the ...mechanisms via which exenatide attenuates postprandial hyperglycemia in type 2 diabetes mellitus (T2DM).
Study Design:
Seventeen T2DM patients (44 yr; seven females, 10 males; body mass index = 33.6 kg/m2; glycosylated hemoglobin = 7.9%) received a mixed meal followed for 6 h with double-tracer technique (1-14Cglucose orally; 3-3Hglucose iv) before and after 2 wk of exenatide. In protocol II (n = 5), but not in protocol I (n = 12), exenatide was given in the morning of the repeat meal. Total and oral glucose appearance rates (RaT and RaO, respectively), endogenous glucose production (EGP), splanchnic glucose uptake (75 g − RaO), and hepatic insulin resistance (basal EGP × fasting plasma insulin) were determined.
Results:
After 2 wk of exenatide (protocol I), fasting plasma glucose decreased (from 10.2 to 7.6 mm) and mean postmeal plasma glucose decreased (from 13.2 to 11.3 mm) (P < 0.05); fasting and meal-stimulated plasma insulin and glucagon did not change significantly. After exenatide, basal EGP decreased (from 13.9 to 10.8 μmol/kg · min, P < 0.05), and hepatic insulin resistance declined (both P < 0.05). RaO, gastric emptying (acetaminophen area under the curve), and splanchnic glucose uptake did not change. In protocol II (exenatide given before repeat meal), fasting plasma glucose decreased (from 11.1 to 8.9 mm) and mean postmeal plasma glucose decreased (from 14.2 to 10.1 mm) (P < 0.05); fasting and meal-stimulated plasma insulin and glucagon did not change significantly. After exenatide, basal EGP decreased (from 13.4 to 10.7 μmol/kg · min, P = 0.05). RaT and RaO decreased markedly from 0–180 min after meal ingestion, consistent with exenatide's action to delay gastric emptying.
Conclusions:
Exenatide improves 1) fasting hyperglycemia by reducing basal EGP and 2) postmeal hyperglycemia by reducing the appearance of oral glucose in the systemic circulation.
A VHF all‐sky interferometric meteor radar system has been developed and installed at Buckland Park, South Australia. The radar is portable, allows a wide range of operating parameters, and can also ...be operated as a boundary layer radar. The analysis techniques have been developed using extensive simulations in an attempt to improve on standard techniques used by previous investigators. The results suggest that although pulse repetition frequencies (PRFs) around 2 kHz allow meteor velocity and deceleration estimation, PRFs around 500 Hz maximize count rate and improve the quality of meteor echo height estimates for this radar. Typical results are presented, indicating the radar obtains annual count rate variation of between 9000 and 14,000 height resolvable underdense meteors per day.
The hippocampal theta rhythm is generated by the pacemaker activity of the medial septum‐diagonal band of Broca (MS/DBB) neurons. These nuclei are influenced by brainstem structures that modulate the ...theta rhythm. The aim of the present work is to determine whether the nucleus incertus (NI), which has important anatomical connections with the MS/DBB, contributes to the hippocampal theta rhythm generation in rats. Hippocampal field activity was recorded in urethane‐anaesthetized rats. Electrical stimulation of the NI not only evoked theta rhythm in the hippocampus, but also decreased the amplitude of delta waves. Unit recordings in the NI revealed either a non‐rhythm discharge pattern in most neurons (76%), or a rhythm activity at 13–25 Hz in the remaining neurons. The firing rate of these neurons increased during the presence of theta rhythm evoked by either sensory or reticularis pontis oralis nucleus (RPO) stimulation. Electrolytic lesions of NI, or the microinjection of the γ‐aminobutyric acid (GABA)A agonist muscimol, abolished the theta rhythm evoked by RPO stimulation. Consequently, the NI may be a relay station between brainstem structures and the MS/DBB in the control of the hippocampal theta rhythm generation.
D. tenuifolia
and
V. locusta
, two greens, were analyzed for active compounds and antitumor actions on colorectal cancer cells. Phenolics were determined by UHPLC-Orbitrap-MS; carotenoids and ...glucosinolates by HPLC-MS; and sterols and fatty acids by gas–liquid chromatography (GLC). For antitumor effects, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) tests were run on HT-29 colorectal cancer cells, and in CCD-18 untransformed enterocyte cells. Six main carotenoids were identified in both vegetables, while total carotenoids accounted for 3520 and 2970 μg · g
−1
dry weight in
D. tenuifolia
and
V. locusta
, respectively. Six phenolics were detected in
D. tenuifolia
(68,600 μg · g
−1
dry weight) and five in
V. locusta
(139,000 μg · g
−1
dry weight). Three glucosinolates (GSL) were found in
D. tenuifolia
(1960 μg · g
−1
dry wt. total). Low-polarity extracts from
V. locusta
and
D. tenuifolia
showed IC
50
~ 150 and ~200 μg · mL
−1
on HT-29 cells, while both plants lacked actions on CCD-18 cells.
V. locusta
inhibited HT-29 cancer cells viability more efficiently than
D. tenuiofolia
, but induced less cytotoxicity. This work highlights the importance of functional foods for colorectal cancer prevention.
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