| 1. |
- Abelev, Betty, et al.
(författare)
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Long-range angular correlations on the near and away side in p-Pb collisions at root S-NN=5.02 TeV
- 2013
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 719:1-3, s. 29-41
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Tidskriftsartikel (refereegranskat)abstract
- Angular correlations between charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV for transverse momentum ranges within 0.5 < P-T,P-assoc < P-T,P-trig < 4 GeV/c. The correlations are measured over two units of pseudorapidity and full azimuthal angle in different intervals of event multiplicity, and expressed as associated yield per trigger particle. Two long-range ridge-like structures, one on the near side and one on the away side, are observed when the per-trigger yield obtained in low-multiplicity events is subtracted from the one in high-multiplicity events. The excess on the near-side is qualitatively similar to that recently reported by the CMS Collaboration, while the excess on the away-side is reported for the first time. The two-ridge structure projected onto azimuthal angle is quantified with the second and third Fourier coefficients as well as by near-side and away-side yields and widths. The yields on the near side and on the away side are equal within the uncertainties for all studied event multiplicity and p(T) bins, and the widths show no significant evolution with event multiplicity or p(T). These findings suggest that the near-side ridge is accompanied by an essentially identical away-side ridge. (c) 2013 CERN. Published by Elsevier B.V. All rights reserved.
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| 2. |
- Abelev, Betty, et al.
(författare)
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Measurement of prompt J/psi and beauty hadron production cross sections at mid-rapidity in pp collisions at root s=7 TeV
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :11
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Tidskriftsartikel (refereegranskat)abstract
- The ALICE experiment at the LHC has studied J/psi production at mid-rapidity in pp collisions at root s = 7 TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L-int = 5.6 nb(-1). The fraction of J/psi from the decay of long-lived beauty hadrons was determined for J/psi candidates with transverse momentum p(t) > 1,3 GeV/c and rapidity vertical bar y vertical bar < 0.9. The cross section for prompt J/psi mesons, i.e. directly produced J/psi and prompt decays of heavier charmonium states such as the psi(2S) and chi(c) resonances, is sigma(prompt J/psi) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 8.3 +/- 0.8(stat.) +/- 1.1 (syst.)(-1.4)(+1.5) (syst. pol.) mu b. The cross section for the production of b-hadrons decaying to J/psi with p(t) > 1.3 GeV/c and vertical bar y vertical bar < 0.9 is a sigma(J/psi <- hB) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 1.46 +/- 0.38 (stat.)(-0.32)(+0.26) (syst.) mu b. The results are compared to QCD model predictions. The shape of the p(t) and y distributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section to derive the b (b) over bar pair total cross section and d sigma/dy at mid-rapidity.
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| 3. |
- Abelev, Betty, et al.
(författare)
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Underlying Event measurements in pp collisions at root s=0.9 and 7 TeV with the ALICE experiment at the LHC
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :7
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of Underlying Event observables in pp collisions at root s = 0 : 9 and 7 TeV. The analysis is performed as a function of the highest charged-particle transverse momentum p(T),L-T in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different p(T) thresholds: 0.15, 0.5 and 1.0 GeV/c. In the Transverse region we observe an increase in the multiplicity of a factor 2-3 between the lower and higher collision energies, depending on the track p(T) threshold considered. Data are compared to PYTHIA 6.4, PYTHIA 8.1 and PHOJET. On average, all models considered underestimate the multiplicity and summed p(T) in the Transverse region by about 10-30%.
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| 4. |
- Farnocchia, Davide, et al.
(författare)
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The Second International Asteroid Warning Network Timing Campaign: 2005 LW3
- 2023
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Ingår i: The Planetary Science Journal. - : Institute of Physics (IOP). - 2632-3338. ; 4:11
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Tidskriftsartikel (refereegranskat)abstract
- The Earth close approach of near-Earth asteroid 2005 LW3 on 2022 November 23 represented a good opportunity for a second observing campaign to test the timing accuracy of astrometric observation. With 82 participating stations, the International Asteroid Warning Network collected 1046 observations of 2005 LW3 around the time of the close approach. Compared to the previous timing campaign targeting 2019 XS, some individual observers were able to significantly improve the accuracy of their reported observation times. In particular, U.S. surveys achieved good timing performance. However, no broad, systematic improvement was achieved compared to the previous campaign, with an overall negative bias persisting among the different observers. The calibration of observing times and the mitigation of timing errors should be important future considerations for observers and orbit computers, respectively.
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| 5. |
- Aartsen, M. G., et al.
(författare)
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Multiwavelength follow-up of a rare IceCube neutrino multiplet
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP SCIENCES S A. - 0004-6361 .- 1432-0746. ; 607
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Tidskriftsartikel (refereegranskat)abstract
- On February 17, 2016, the IceCube real-time neutrino search identified, for the first time, three muon neutrino candidates arriving within 100 s of one another, consistent with coming from the same point in the sky. Such a triplet is expected once every 13.7 years as a random coincidence of background events. However, considering the lifetime of the follow-up program the probability of detecting at least one triplet from atmospheric background is 32%. Follow-up observatories were notified in order to search for an electromagnetic counterpart. Observations were obtained by Swift's X-ray telescope, by ASAS-SN, LCO and MASTER at optical wavelengths, and by VERITAS in the very-high-energy gamma-ray regime. Moreover, the Swift BAT serendipitously observed the location 100 s after the first neutrino was detected, and data from the Fermi LAT and HAWC observatory were analyzed. We present details of the neutrino triplet and the follow-up observations. No likely electromagnetic counterpart was detected, and we discuss the implications of these constraints on candidate neutrino sources such as gamma-ray bursts, core-collapse supernovae and active galactic nucleus flares. This study illustrates the potential of and challenges for future follow-up campaigns.
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| 6. |
- Adrian-Martinez, S., et al.
(författare)
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A first search for coincident gravitational waves and high energy neutrinos using LIGO, Virgo and ANTARES data from 2007
- 2013
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :6
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of the first search for gravitational wave bursts associated with high energy neutrinos. Together, these messengers could reveal new, hidden sources that are not observed by conventional photon astronomy, particularly at high energy. Our search uses neutrinos detected by the underwater neutrino telescope ANTARES in its 5 line configuration during the period January - September 2007, which coincided with the fifth and first science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed for candidate gravitational-wave signals coincident in time and direction with the neutrino events. No significant coincident events were observed. We place limits on the density of joint high energy neutrino - gravitational wave emission events in the local universe, and compare them with densities of merger and core-collapse events.
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| 7. |
- Arbring Sjöström, Theresia, 1987-, et al.
(författare)
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Design and Operation of Hybrid Microfluidic Iontronic Probes for Regulated Drug Delivery
- 2021
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Ingår i: Advanced Materials Technologies. - Hoboken, New Jersey : John Wiley & Sons. - 2365-709X. ; 6:2
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Tidskriftsartikel (refereegranskat)abstract
- Highly controlled drug delivery devices play an increasingly important role in the development of new neuroengineering tools. Stringent - and sometimes contradicting - demands are placed on such devices, ranging from robustness in freestanding devices, to overall device miniaturization, while maintaining precise spatiotemporal control of delivery with high chemical specificity and high on/off ratio. Here, design principles of a hybrid microfluidic iontronic probe that uses flow for long-range pressure-driven transport in combination with an iontronic tip that provides electronically fine-tuned pressure-free delivery are explored. Employing a computational model, the effects of decoupling the drug reservoir by exchanging a large passive reservoir with a smaller microfluidic system are reported. The transition at the microfluidic-iontronic interface is found to require an expanded ion exchange membrane inlet in combination with a constant fluidic flow, to allow a broad range of device operation, including low source concentrations and high delivery currents. Complementary to these findings, the free-standing hybrid probe monitored in real time by an external sensor is demonstrated. From these computational and experimental results, key design principles for iontronic devices are outlined that seek to use the efficient transport enabled by microfluidics, and further, key observations of hybrid microfluidic iontronic probes are explained.
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| 8. |
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| 9. |
- Girshova, Elizaveta I, et al.
(författare)
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Proposal for a photoacoustic ultrasonic generator based on Tamm plasmon structures
- 2020
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Ingår i: Optics Express. - : OPTICAL SOC AMER. - 1094-4087. ; 28:18, s. 26161-26169
-
Tidskriftsartikel (refereegranskat)abstract
- The scheme of a generation of ultrasound waves based on optically excited Tamm plasmon structures is proposed. It is shown that Tamm plasmon structures can provide total absorption of a laser pulse with arbitrary wavelength in a metallic layer providing the possibility of the use of an infrared semiconductor laser for the excitation of ultrasound waves. Laser pulse absorption, heat transfer and dynamical properties of the structure are modeled, and the optimal design of the structure is found. It is demonstrated that the Tamm plasmon-based photoacoustic generator can emit ultrasound waves in the frequency band up to 100 MHz with predefined frequency spectrum. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
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| 10. |
- Ivanov, Ruslan, et al.
(författare)
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T2SL development for space at IRnova : from eSWIR to VLWIR
- 2019
-
Ingår i: Sensors, Systems, and Next-Generation Satellites XXIII. - : SPIE - International Society for Optical Engineering. - 9781510630062
-
Konferensbidrag (refereegranskat)abstract
- In this paper, results from the development of InAs/GaSb superlattice focal plane arrays (FPAs) at IRnova will be presented. A versatile and robust detector design is used that allows for adjustment of the detection cut-off wavelength from 2.5 mu m up to 14.5 mu m with only minor changes in the detector design. Performance of the fabricated detectors has been reviewed in terms of external quantum efficiency (EQE), dark current and noise for three designs with cut-off wavelengths of 4, 5.5 and 11 mu m at 80 K (referred to as DEEP BLUE, RED HOT and VLWIR, respectively). Measurements on the 15 mu m sized photodiodes demonstrated 70 % EQE for the MWIR designs, and almost 40 % for VLWIR. At the same time, the dark current stayed close to the Rule07 benchmark for all studied samples. Noise mechanisms have been discussed and their relation to the passivation was examined. Mature in-house processing and passivation technique resulted in very high spatial uniformity of VGA focal plane arrays (FPAs), i.e. low relative deviations of EQE (< 6 %) and of dark current density (< 12 %), and narrow noise distributions for both RED HOT and DEEP BLUE FPAs. We show also that >99.5 % of these arrays operate close to the fundamental noise limit.
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| 11. |
- Korneeva, Eugenia V., et al.
(författare)
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A novel silver(I) di-iso-butyldithiocarbamate: Unusually complicated 1-D polymeric structure, multiple ligand-supported Ag–Ag interactions and its capability to bind gold(III). Preparation, structural organisation and (13C, 15N) CP-MAS NMR of [Ag6(S2CNiBu2)6]n and [Au(S2CNiBu2)2][AgCl2]
- 2021
-
Ingår i: Inorganica Chimica Acta. - : Elsevier. - 0020-1693 .- 1873-3255. ; 525
-
Tidskriftsartikel (refereegranskat)abstract
- We have synthesised three new complexes of [Ag6{S2CN(iso-C4H9)2}6]n (1), [Au{S2CN(iso-C4H9)2}2][AgCl2] (2) and [Au{S2CN(iso-C4H9)2}2][Ag0.69Au0.31Cl2] (3), chemically identified these compounds using solution (1H, 13C) and solid-state (13C, 15N) CP-MAS NMR and FT-IR spectroscopy, and structurally characterised them by single-crystal X-ray diffraction analysis. There are six structurally inequivalent silver(I) centres in the former compound, whose unusually complicated, monodimensional polymeric structure is generally stabilised by six unequal iBuDtc ligands acting as bridges, along with numerous ligand-supported Ag–Ag interactions. Studying the capability of the precipitated AgiBuDtc to bind gold(III) from a [AuCl4]–/5.15 M NaCl solution, the double pseudo-polymeric heterometallic dithiocarbamato-chlorido complexes 2 and 3 were successfully obtained as individual fixation modes of gold to the solid phase. In the self-assembly of a bidimensional supramolecular structure of the latter two compounds, numerous interionic secondary bonds (Au···S, Ag···S and S···Cl), the anagostic H–C···Ag interactions and the Cl···H–C hydrogen bonds play a key role. To study the thermal behaviour of crystalline compounds 1 and 2, we additionally used simultaneous thermal analysis (STA). During the thermolysis of 1/2, the formation of Ag2S/AgCl,Au0 was supported, respectively, by energy dispersive X-ray (EDX) spectroscopy, while the dispersity and morphology of residual substances were studied using scanning electron microscopy.
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| 12. |
- Loseva, Olga V., et al.
(författare)
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Two structural types of dithiocarbamato-chlorido complexes of mercury(II): Preparation, supramolecular self-assembly, solid-state 13C and 15N NMR characterisation and thermal behaviour of pseudo-polymeric compounds of [Hg2(S2CNBu2)2Cl2] and [Hg4(S2CNiBu2)6][Hg2Cl6]
- 2022
-
Ingår i: Inorganica Chimica Acta. - : Elsevier. - 0020-1693 .- 1873-3255. ; 533
-
Tidskriftsartikel (refereegranskat)abstract
- Two new crystalline dithiocarbamato-chlorido complexes of mercury(II), [Hg2{S2CN(C4H9)2}2Cl2] (1) and [Hg4{S2CN(iso-C4H9)2}6][Hg2Cl6] (2), have been prepared and chemically identified by solution (1H, 13C) NMR and solid-state (13C, 15N) CP-MAS NMR and FT-IR spectroscopy. The crystal, molecular and supramolecular structures of these compounds were established using single-crystal X-ray diffraction (XRD) analysis. The obtained complexes reveal two principally different types of structural organisation. In the structure of the former neutral complex, there are two isomeric doubly-bridged binuclear molecules [Hg2(S2CNBu2)2Cl2] (‘A’ and ‘B’), whereas the latter compound comprises two ionic structural moieties: the tetranuclear cation [Hg4(S2CNiBu2)6]2+ and the binuclear anion [Hg2Cl6]2−. In both ionic units, pairs of iBu2Dtc or chloride ligands, which perform a bridging structural function, combine with neighbouring mercury atoms. In turn, intermolecular/interionic secondary interactions Hg···S/Hg···Cl are involved in the formation of supramolecular structures of complexes 1/2, yielding pseudo-polymeric chains of (···‘A’···‘B’···)n/(···[Hg4(S2CNiBu2)6]···[Hg2Cl6]···)n, which exhibit alternation of isomeric molecules of 1/ionic moieties of 2 along their lengths. Despite the significant structural difference between the above complexes, we established, using simultaneous thermal analysis (STA), that both exhibit very similar thermal behaviour. Moreover, during the thermal transformations of both compounds 1 and 2, the same two substances are generated: HgCl2 and HgS.
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| 13. |
- Martin-Lagarde, Marine, et al.
(författare)
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Magrathea : A proposal for a satellite mission on protoplanetary dust growth experiments
- 2018
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Ingår i: IAC-18. - : International Astronautical Federation.
-
Konferensbidrag (refereegranskat)abstract
- The process of planet formation, from dust to protoplanetary disks, is not very well understood. The physics of both particle growth in protoplanetary disks and small particle dust gravity dynamics are well studied. However, the link between the two, i.e. the growth gap between dust grains and mm-sized particles, is still not understood. Additionally, current methods cannot model the full complexity of interactions in this phase of planet formation. Therefore, experiments in microgravity are crucial to revealing the underlying physics. Previous experiments have several limitations in particular their short duration and constrained dimensions. Accurately representing the conditions in the protoplanetary disk, such as the dust particle mean free path and large spatial extent of the dust, is very demanding, especially with larger, longer duration experiments.In order to create the best conditions for these experiments to be scientifically sound, with a reasonable solution, here we present a concept satellite with a 6 m3 chamber. The payload bay provides different measurements of ongoing collision processes, and samples of collision products. Its modularity and capacity is designed to carry several instruments in a carrousel, with 28 experiment canisters. Those experiments have a range of compositions (including silicates and Fayalite, both with or without ice layers), size distribution (between 1 µm and 100 mm), and shape properties, probing the conditions that could benefit grain growth. Each experiment will last up to one month allowing the record of approximately 106 collisions, with relative velocities of up to 5 mm/s, obtaining statistically meaningful results.With the science objectives and requirements formulated, payload solutions were prepared, and a conceptual mission and spacecraft design was developed. Considering the experiment phase will last up to 5 years, and during that time external influences should be minimised, the three most complex systems are the structure, thermal control, and attitude control. After several trade-offs and a cost analysis, a 1000 kg spacecraft solution was reached, set on a 800 km Sun-synchronous orbit. The mission would cost around 438 M Euros.The full work was developed during the 10 days of the 2017 Alpbach Summer School, by a group of fifteen young scientists and engineers, with various backgrounds, from all across Europe, with the support of two dedicated tutors. A concurrent engineering approach, with participants divided among several teams has been used to evaluate more than one scenario, and thus reach a concise solution.
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| 14. |
- Pozina, Galia, et al.
(författare)
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Enhancement of light emission in Bragg monolayer-thick quantum well structures
- 2019
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Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Control over spontaneous emission rate is important for improving efficiency in different semiconductor applications including lasers, LEDs and photovoltaics. Usually, an emitter should be placed inside the cavity to increase the spontaneous emission rate, although it is technologically challenging. Here we experimentally demonstrate a phenomenon of super-radiance observed in a cavity-less periodic Bragg structure based on InAs monolayer-thick multiple quantum wells (MQW). The collective super-radiant mode shows enhanced emission rate for specific angles and frequencies. This behaviour correlates with the calculations demonstrating individual spots of the enhanced Purcell coefficient near the Bragg condition curve. This study provides a perspective for realization of surface emitting cavity-less lasers with distributed feedback.
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| 15. |
- Pozina, Galia, et al.
(författare)
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Nonlinear behavior of the emission in the periodic structure of InAs monolayers embedded in a GaAs matrix
- 2017
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Ingår i: Physica status solidi. B, Basic research. - : WILEY-V C H VERLAG GMBH. - 0370-1972 .- 1521-3951. ; 254:4
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Tidskriftsartikel (refereegranskat)abstract
- We report time-resolved photoluminescence (TRPL) measurements performed at different temperatures for the Bragg structure containing 60 InAs monolayer-based quantum wells (QWs) periodically arranged in a GaAs matrix. TRPL data reveal an appearance of the additional superradiant (SR) mode originated from coherent collective interaction of QWs. The SR mode is not manifested in the case if a small number of QWs is excited, then only an exciton emission related to the InAs QWs dominates the PL spectrum. The SR mode demonstrates a superlinear dependence of the intensity and radiative decay rate on the excitation power and its intensity increases at elevated temperatures compared to the excitonic emission. The photoluminescence delay time is much shorter for the SR mode indicating that the relaxation of hot excitons can occur via stimulated scattering processes. The specific behavior of the SR emission can have a strong potential for different applications such as optical logic devices, superluminescent diodes, optical switches, and low-threshold lasers. Time-resolved photoluminescence image at low temperature for the Bragg structure consisting of InAs monolayer-based quantum wells (inset).
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| 16. |
- Pozina, Galia, et al.
(författare)
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Purcell Effect and Nonlinear Behavior of the Emission in a Periodic Structure Composed of InAs Monolayers Embedded in a GaAs Matrix
- 2019
-
Ingår i: Annalen der Physik. - : WILEY-V C H VERLAG GMBH. - 0003-3804 .- 1521-3889. ; 531:6
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Tidskriftsartikel (refereegranskat)abstract
- Enhancement of spontaneous emission in a resonant Bragg quantum well (QW) structure with 60 periods of triple InAs monolayers embedded in a GaAs matrix is studied experimentally and theoretically. From measurements of the time-resolved photoluminescence, besides the QW exciton at 1.47 eV, a specific super-radiant (SR) emission demonstrating nonlinear properties is found. The SR mode shows a near-quadratic dependence of intensity on excitation power, while its energy position follows the Bragg condition. It is revealed that the SR mode shows a peculiar non-monotonic dependence of intensity on direction, with a maximum observed at approximately 40 degrees. The enhancement in the SR emission at a specific direction is correlated well with suggested theoretical consideration of the modal Purcell factor for periodic quantum well structures.
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| 17. |
- Prasciolu, Mauro, et al.
(författare)
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On the use of multilayer Laue lenses with X-ray free electron lasers
- 2021
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Ingår i: International Conference on X-Ray Lasers 2020. - : SPIE. - 1996-756X .- 0277-786X. - 9781510646186 ; 11886
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Konferensbidrag (refereegranskat)abstract
- We report on the use of multilayer Laue lenses to focus the intense X-ray Free Electron Laser (XFEL) beam at the European XFEL to a spot size of a few tens of nanometers. We present the procedure to align and characterize these lenses and discuss challenges working with the pulse trains from this unique X-ray source.
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| 18. |
- Rodina, Tatyana A., et al.
(författare)
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Crystal structure, solid-state 13C and 15N NMR characterisation, chemisorption activity and thermal behaviour of new mercury(II) dipropyldithiocarbamate : Binuclear, pseudo-binuclear and heteronuclear complexes of [Hg2(PrDtc)4], [Hg(PrDtc)2]2 and [Au(PrDtc)2]2[Hg2Cl6]
- 2020
-
Ingår i: Inorganica Chimica Acta. - : Elsevier. - 0020-1693 .- 1873-3255. ; 508
-
Tidskriftsartikel (refereegranskat)abstract
- Two polymorphs of a new mercury(II) N,N-dipropyldithiocarbamate represented by centrosymmetric binuclear and pseudo-binuclear molecules, [Hg2(PrDtc)4] (1) and [Hg(PrDtc)2]2 (2), have been isolated, identified using heteronuclear (13C, 15N) CP-MAS NMR and structurally characterised by single-crystal X-ray diffraction analysis. There are two pairs of inequivalent PrDtc ligands playing either terminal chelating or tridentate bridging structural functions in the former compound; while the latter complex comprises two pairs of structurally inequivalent chelating PrDtc ligands. The reaction of freshly precipitated mercury(II) N,N-dipropyldithiocarbamate (HgPrDtc) with a [AuCl4]−/2 M HCl solution results in the formation of the ionic complex [Au(PrDtc)2]2[Hg2Cl6] (3). There are two inequivalent centrosymmetric cations, [Au(PrDtc)2]+ (‘A’ and ‘B’), and a binuclear centrosymmetric anion, [Hg2Cl6]2− in the structure of 3. In the cationic part of the complex, each of the gold(III) cations has two pairs of the relatively weak inequivalent secondary Au···S bonds with two neighbours, therefore forming linear supramolecular cationic chains (⋯‘A’⋯‘B’⋯‘A’⋯‘B’⋯)n. To study the thermal behaviour of the compounds, simultaneous thermal analysis was also performed. The formation of HgS and reduced elemental gold was established during the thermolysis of 1/2 and 3, respectively.
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| 19. |
- Surmeneva, Maria, et al.
(författare)
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New Ti-35Nb-7Zr-5Ta Alloy Manufacturing by Electron Beam Melting for Medical Application Followed by High Current Pulsed Electron Beam Treatment
- 2021
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Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 11:7
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Tidskriftsartikel (refereegranskat)abstract
- High-current pulsed electron-beam (PEB) treatment was applied as a surface finishing procedure for Ti-35Nb-7Zr-5Ta (TNZT) alloy produced by electron beam melting (EBM). According to the XRD results the TNZT alloy samples before and after the PEB treatment have shown mainly the single body-centered cubic (bcc) beta-phase microstructures. The crystallite size, dislocation density, and microstrain remain unchanged after the PEB treatment. The investigation of the texture coefficient at the different grazing angle revealed the evolution of the crystallite orientations at the re-melted zone formed at the top of the bulk samples after the PEB treatment. The top-view SEM micrographs of the TNZT samples treated by PEB exhibited the bcc beta-phase grains with an average size of similar to 85 mu m. TEM analysis of as-manufactured TNZT alloy revealed the presence of the equiaxed beta-grains with the fine dispersion of nanocrystalline alpha and NbTi4 phases together with beta-Ti twins. Meanwhile, the beta phase regions free of alpha phase precipitation are observed in the microstructure after the PEB irradiation. Nanoindentation tests revealed that the surface mechanical properties of the melted zone were slightly improved. However, the elastic modulus and microhardness in the heat-affected zone and the deeper regions of the sample were not changed after the treatment. Moreover, the TNZT alloy in the bulk region manufactured by EBM displayed no significant change in the corrosion resistance after the PEB treatment. Hence, it can be concluded that the PEB irradiation is a viable approach to improve the surface topography of EBM-manufactured TNZT alloy, while the most important mechanical parameters remain unchanged.
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| 20. |
- Sylantyev, Sergiy, et al.
(författare)
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Electric fields due to synaptic currents sharpen excitatory transmission
- 2008
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 319:5871, s. 1845-1849
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Tidskriftsartikel (refereegranskat)abstract
- The synaptic response waveform, which determines signal integration properties in the brain, depends on the spatiotemporal profile of neurotransmitter in the synaptic cleft. Here, we show that electrophoretic interactions between AMPA receptor–mediated excitatory currents and negatively charged glutamate molecules accelerate the clearance of glutamate from the synaptic cleft, speeding up synaptic responses. This phenomenon is reversed upon depolarization and diminished when intracleft electric fields are weakened through a decrease in the AMPA receptor density. In contrast, the kinetics of receptor-mediated currents evoked by direct application of glutamate are voltage-independent, as are synaptic currents mediated by the electrically neutral neurotransmitter GABA. Voltage-dependent temporal tuning of excitatory synaptic responses may thus contribute to signal integration in neural circuits.
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| 21. |
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| 22. |
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| 23. |
- Williamson, Adam, et al.
(författare)
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Controlling Epileptiform Activity with Organic Electronic Ion Pumps
- 2015
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Ingår i: Advanced Materials. - : Wiley-VCH Verlag. - 0935-9648 .- 1521-4095. ; 27:20, s. 3138-3144
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Tidskriftsartikel (refereegranskat)abstract
- In treating epilepsy, the ideal solution is to act at a seizure's onset, but only in the affected regions of the brain. Here, an organic electronic ion pump is demonstrated, which directly delivers on-demand pure molecules to specific brain regions. State-of-the-art organic devices and classical pharmacology are combined to control pathological activity in vitro, and the results are verified with electrophysiological recordings.
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