178 research outputs found
Quantum key distribution and 1 Gbit/s data encryption over a single fibre
We perform quantum key distribution (QKD) in the presence of 4 classical
channels in a C-band dense wavelength division multiplexing (DWDM)
configuration using a commercial QKD system. The classical channels are used
for key distillation and 1 Gbps encrypted communication, rendering the entire
system independent from any other communication channel than a single dedicated
fibre. We successfully distil secret keys over fibre spans of up to 50 km. The
separation between quantum channel and nearest classical channel is only 200
GHz, while the classical channels are all separated by 100 GHz. In addition to
that we discuss possible improvements and alternative configurations, for
instance whether it is advantageous to choose the quantum channel at 1310 nm or
to opt for a pure C-band configuration.Comment: 9 pages, 7 figure
Bodenzustandserhebungen: Wie beeinflussen Standort und Nutzung den Kohlenstoffvorrat in Wald- und Agrarböden?
Die ThĂŒnen-Institute fĂŒr fĂŒr Waldökosysteme und fĂŒr Agrarklimaschutz koordinieren die bundesweiten Bodenzustandserhebungen (BZE) in Wald- und Agrarböden. Die BZE haben unterschiedliche Ausgangsbedingungen, jedoch das gemeinsame Ziel, aktuellen Zustand und Ănderungen der BodenkohlenstoffvorrĂ€te an rund 5000 Probenahmepunkten zu erfassen. Ergebnisse zum Einfluss von Klima, Nutzung und Bodenmanagement dienen zum einen der Entwicklung zu einer nachhaltigen Bodennutzung und zum anderen der Verbesserung der Emissionsberichterstattung nach UN-Klimarahmenkonvention und EU-Regelungen.Nach aktuellem Stand der qualitĂ€tsgesicherten Datenbanken beider BZE sollen BodenkohlenstoffvorrĂ€te verschiedener Bodennutzungsarten (Nadelwald, Laubwald, Mischwald, Acker, DauergrĂŒnland, GrĂŒnland-Wechselwirtschaft) fĂŒr mineralische und organische Ober- sowie Unterböden ausgewertet und die Ergebnisse entsprechend prĂ€sentiert werden. Ferner soll eine mögliche Stratifizierung der Ergebnisse nach Bodentypen und BodenklimarĂ€umen geprĂŒft werden. Ziel hierbei ist es, rĂ€umliche Datencluster zu bilden, die stabile Ergebnisse zu Zwecken der Berichterstattung und Entscheidungsfindung liefern und gleichzeitig reprĂ€sentativ bleiben
Observations of a Solar Energetic Particle Event From Inside and Outside the Coma of Comet 67P
Publisher Copyright: ©2022. The Authors.We analyze observations of a solar energetic particle (SEP) event at Rosetta's target comet 67P/Churyumov-Gerasimenko during 6â10 March 2015. The comet was 2.15 AU from the Sun, with the Rosetta spacecraft approximately 70 km from the nucleus placing it deep inside the comet's coma and allowing us to study its response. The Eastern flank of an interplanetary coronal mass ejection (ICME) also encountered Rosetta on 6 and 7 March. Rosetta Plasma Consortium data indicate increases in ionization rates, and cometary water group pickup ions exceeding 1 keV. Increased charge exchange reactions between solar wind ions and cometary neutrals also indicate increased upstream neutral populations consistent with enhanced SEP induced surface activity. In addition, the most intense parts of the event coincide with observations interpreted as an infant cometary bow shock, indicating that the SEPs may have enhanced the formation and/or intensified the observations. These solar transient events may also have pushed the cometopause closer to the nucleus. We track and discuss characteristics of the SEP event using remote observations by SOHO, WIND, and GOES at the Sun, in situ measurements at Solar Terrestrial Relations Observatory Ahead, Mars and Rosetta, and ENLIL modeling. Based on its relatively prolonged duration, gradual and anisotropic nature, and broad angular spread in the heliosphere, we determine the main particle acceleration source to be a distant ICME which emerged from the Sun on 6 March 2015 and was detected locally in the Martian ionosphere but was never encountered by 67P directly. The ICME's shock produced SEPs for several days which traveled to the in situ observation sites via magnetic field line connections.Peer reviewe
The relative and absolute timing accuracy of the EPIC-pn camera on XMM-Newton, from X-ray pulsations of the Crab and other pulsars
Reliable timing calibration is essential for the accurate comparison of
XMM-Newton light curves with those from other observatories, to ultimately use
them to derive precise physical quantities. The XMM-Newton timing calibration
is based on pulsar analysis. However, as pulsars show both timing noise and
glitches, it is essential to monitor these calibration sources regularly. To
this end, the XMM-Newton observatory performs observations twice a year of the
Crab pulsar to monitor the absolute timing accuracy of the EPIC-pn camera in
the fast Timing and Burst modes. We present the results of this monitoring
campaign, comparing XMM-Newton data from the Crab pulsar (PSR B0531+21) with
radio measurements. In addition, we use five pulsars (PSR J0537-69, PSR
B0540-69, PSR B0833-45, PSR B1509-58 and PSR B1055-52) with periods ranging
from 16 ms to 197 ms to verify the relative timing accuracy. We analysed 38
XMM-Newton observations (0.2-12.0 keV) of the Crab taken over the first ten
years of the mission and 13 observations from the five complementary pulsars.
All the data were processed with the SAS, the XMM-Newton Scientific Analysis
Software, version 9.0. Epoch folding techniques coupled with \chi^{2} tests
were used to derive relative timing accuracies. The absolute timing accuracy
was determined using the Crab data and comparing the time shift between the
main X-ray and radio peaks in the phase folded light curves. The relative
timing accuracy of XMM-Newton is found to be better than 10^{-8}. The strongest
X-ray pulse peak precedes the corresponding radio peak by 306\pm9 \mus, which
is in agreement with other high energy observatories such as Chandra, INTEGRAL
and RXTE. The derived absolute timing accuracy from our analysis is \pm48 \mus.Comment: 16 pages, 9 figures. Accepted for publication on A&
Feasibility of quantum key distribution through dense wavelength division multiplexing network
In this paper, we study the feasibility of conducting quantum key
distribution (QKD) together with classical communication through the same
optical fiber by employing dense-wavelength-division-multiplexing (DWDM)
technology at telecom wavelength. The impact of the classical channels to the
quantum channel has been investigated for both QKD based on single photon
detection and QKD based on homodyne detection. Our studies show that the latter
can tolerate a much higher level of contamination from the classical channels
than the former. This is because the local oscillator used in the homodyne
detector acts as a "mode selector" which can suppress noise photons
effectively. We have performed simulations based on both the decoy BB84 QKD
protocol and the Gaussian modulated coherent state (GMCS) QKD protocol. While
the former cannot tolerate even one classical channel (with a power of 0dBm),
the latter can be multiplexed with 38 classical channels (0dBm power each
channel) and still has a secure distance around 10km. Preliminary experiment
has been conducted based on a 100MHz bandwidth homodyne detector.Comment: 18 pages, 5 figure
Apoptosis of human melanoma cells induced by inhibition of B-RAFV600E involves preferential splicing of bimS
Bim is known to be critical in killing of melanoma cells by inhibition of the RAF/MEK/ERK pathway. However, the potential role of the most potent apoptosis-inducing isoform of Bim, BimS, remains largely unappreciated. Here, we show that inhibition of the mutant B-RAFV600E triggers preferential splicing to produce BimS, which is particularly important in induction of apoptosis in B-RAFV600E melanoma cells. Although the specific B-RAFV600E inhibitor PLX4720 upregulates all three major isoforms of Bim, BimEL, BimL, and BimS, at the protein and mRNA levels in B-RAFV600E melanoma cells, the increase in the ratios of BimS mRNA to BimEL and BimL mRNA indicates that it favours BimS splicing. Consistently, enforced expression of B-RAFV600E in wild-type B-RAF melanoma cells and melanocytes inhibits BimS expression. The splicing factor SRp55 appears necessary for the increase in BimS splicing, as SRp55 is upregulated, and its inhibition by small interfering RNA blocks induction of BimS and apoptosis induced by PLX4720. The PLX4720-induced, SRp55-mediated increase in BimS splicing is also mirrored in freshly isolated B-RAFV600E melanoma cells. These results identify a key mechanism for induction of apoptosis by PLX4720, and are instructive for sensitizing melanoma cells to B-RAFV600E inhibitors
B-RAF Mutant Alleles Associated with Langerhans Cell Histiocytosis, a Granulomatous Pediatric Disease
Langerhans cell histiocytosis (LCH) features inflammatory granuloma characterised by the presence of CD1a+ dendritic cells or 'LCH cells'. Badalian-Very et al. recently reported the presence of a canonical (V600E)B-RAF mutation in 57% of paraffin-embedded biopsies from LCH granuloma. Here we confirm their findings and report the identification of two novel B-RAF mutations detected in LCH patients.Mutations of B-RAF were observed in granuloma samples from 11 out of 16 patients using 'next generation' pyrosequencing. In 9 cases the mutation identified was (V600E)B-RAF. In 2 cases novel polymorphisms were identified. A somatic (600DLAT)B-RAF insertion mimicked the structural and functional consequences of the (V600E)B-RAF mutant. It destabilized the inactive conformation of the B-RAF kinase and resulted in increased ERK activation in 293 T cells. The (600DLAT)B-RAF and (V600E)B-RAF mutations were found enriched in DNA and mRNA from the CD1a+ fraction of granuloma. They were absent from the blood and monocytes of 58 LCH patients, with a lower threshold of sequencing sensitivity of 1%-2% relative mutation abundance. A novel germ line (T599A)B-RAF mutant allele was detected in one patient, at a relative mutation abundance close to 50% in the LCH granuloma, blood monocytes and lymphocytes. However, (T599A)B-RAF did not destabilize the inactive conformation of the B-RAF kinase, and did not induce increased ERK phosphorylation or C-RAF transactivation.Our data confirmed presence of the (V600E)B-RAF mutation in LCH granuloma of some patients, and identify two novel B-RAF mutations. They indicate that (V600E)B-RAF and (600DLAT)B-RAF mutations are somatic mutants enriched in LCH CD1a(+) cells and absent from the patient blood. Further studies are needed to assess the functional consequences of the germ-line (T599A)B-RAF allele
Observations of a Solar Energetic Particle Event From Inside and Outside the Coma of Comet 67P
We analyze observations of a solar energetic particle (SEP) event at Rosetta's target comet 67P/Churyumov-Gerasimenko during 6â10 March 2015. The comet was 2.15 AU from the Sun, with the Rosetta spacecraft approximately 70 km from the nucleus placing it deep inside the comet's coma and allowing us to study its response. The Eastern flank of an interplanetary coronal mass ejection (ICME) also encountered Rosetta on 6 and 7 March. Rosetta Plasma Consortium data indicate increases in ionization rates, and cometary water group pickup ions exceeding 1 keV. Increased charge exchange reactions between solar wind ions and cometary neutrals also indicate increased upstream neutral populations consistent with enhanced SEP induced surface activity. In addition, the most intense parts of the event coincide with observations interpreted as an infant cometary bow shock, indicating that the SEPs may have enhanced the formation and/or intensified the observations. These solar transient events may also have pushed the cometopause closer to the nucleus. We track and discuss characteristics of the SEP event using remote observations by SOHO, WIND, and GOES at the Sun, in situ measurements at Solar Terrestrial Relations Observatory Ahead, Mars and Rosetta, and ENLIL modeling. Based on its relatively prolonged duration, gradual and anisotropic nature, and broad angular spread in the heliosphere, we determine the main particle acceleration source to be a distant ICME which emerged from the Sun on 6 March 2015 and was detected locally in the Martian ionosphere but was never encountered by 67P directly. The ICME's shock produced SEPs for several days which traveled to the in situ observation sites via magnetic field line connections
Effects of Saturn's magnetospheric dynamics on Titan's ionosphere
We use the Cassini Radio and Plasma Wave Science/Langmuir probe measurements of the electron density from the first 110 flybys of Titan to study how SaturnÂŽs magnetosphere influences TitanÂŽs ionosphere. The data is first corrected for biased sampling due to varying solar zenith angle and solar energy flux (solar cycle effects). We then present results showing that the electron density in TitanÂŽs ionosphere, in the altitude range 1600-2400 km, is increased by about a factor of 2.5 when Titan is located on the nightside of Saturn (Saturn local time (SLT) 21-03 h) compared to when on the dayside (SLT 09-15 h). For lower altitudes (1100-1600 km) the main dividing factor for the ionospheric density is the ambient magnetospheric conditions. When Titan is located in the magnetospheric current sheet, the electron density in TitanÂŽs ionosphere is about a factor of 1.4 higher compared to when Titan is located in the magnetospheric lobes. The factor of 1.4 increase in between sheet and lobe flybys is interpreted as an effect of increased particle impact ionization from 200 eV sheet electrons. The factor of 2.5 increase in electron density between flybys on SaturnÂŽs nightside and dayside is suggested to be an effect of the pressure balance between thermal plus magnetic pressure in TitanÂŽs ionosphere against the dynamic pressure and energetic particle pressure in SaturnÂŽs magnetosphere.Fil: Edberg, N. J. T.. University of Iowa; Estados Unidos. Swedish Institute of Space Physics; SueciaFil: Andrews, D. J.. Swedish Institute of Space Physics; SueciaFil: Bertucci, Cesar. Consejo Nacional de InvestigaciĂłnes CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Ciudad Universitaria. Instituto de AstronomĂa y FĂsica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de AstronomĂa y FĂsica del Espacio; ArgentinaFil: Gurnett, D. A.. University of Iowa; Estados UnidosFil: Holmberg, M. K. G.. Swedish Institute of Space Physics; SueciaFil: Jackman, C. M.. University Of Southampton; Reino UnidoFil: Kurth, W. S.. University of Iowa; Estados UnidosFil: Menietti, J. D.. University Of Iowa; Estados UnidosFil: Opgenoorth, H. J.. Swedish Institute of Space Physics; SueciaFil: Shebanits, O.. Swedish Institute of Space Physics; SueciaFil: Vigren, E.. Swedish Institute of Space Physics; SueciaFil: Wahlund, J. E.. Swedish Institute of Space Physics; Sueci
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