220 research outputs found
âGood fences make good neighboursâ: Concepts and records of range dynamics in ground squirrels and geographical barriers in the Pleistocene of the Circum-Black Sea area
Ground squirrels were an important member of the Pleistocene steppe-tundra mammal community.
They evolved ecological specialisations and exhibit behaviours that make them particularly
informative subjects to study palaeoenvironmental constraints affecting species distribution and
speciation. Interspecific competition and isolating geographical barriers are considered as the
principal factors that define species range boundaries.
The present paper provides a first comprehensive compilation of the living and extinct Spermophilus
species in Europe. These data suggest âpatchwork quiltâ model for the expansion and spatial
distribution of ground squirrel species. Here we consider mainly small-sized Spermophilus species
because large-sized (e.g., S. superciliosus) ground squirrels consist another âpatchwork quiltâ, which
overlap the first one. This overlapping of the species ranges is possible because of the size difference
that lowers interspecific competition (Hutchinson's rule).
We consider two main types of range boundaries. One type includes roughly âsub-parallelâ
boundaries that oscillate in concert with climatic and vegetational changes (a case of climatically
controlled competitive exclusion). The other type consists of roughly âsub-meridionalâ boundaries
corresponding to geographical barriers (e.g., water barriers, mountain ridges); these boundaries are
rather stable. Examples of âsub-parallel range modifications include: oscillations of boundaries
between S. pygmaeus and S. suslicus; the immigration of S. citellus into the Pre-Carpathian area; the
branching of S. suslicus from S. pygmaeus; the regional appearance of the Late Pleistocene species S.
severskensis and S. citelloides. Examples of âsub-meridional eventsâ are: the crossing of the Danube
by S. citellus; the appearance of an isolated population of S. pygmaeus on right bank of the Dnieper
during the Late Pleistocene to Middle Holocene; a crossing of the Dnieper river by S. pygmaeus,
which resulted in the appearance of S. odessanus; the intrusion of eastern populations of S.
pygmaeus into the Trans-Volga areas
Study of the decays B->D_s1(2536)+ anti-D(*)
We report a study of the decays B -> D_s1(2536)+ anti-D(*), where anti-D(*)
is anti-D0, D- or D*-, using a sample of 657 x 10^6 B anti-B pairs collected at
the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy
e+e- collider. The branching fractions of the decays B+ -> D_s1(2536)+ anti-D0,
B0 -> D_s1(2536)+ D- and B0 -> D_s1(2536)+ D*- multiplied by that of
D_s1(2536)+ -> (D*0K+ + D*+K0) are found to be (3.97+-0.85+-0.56) x 10^-4,
(2.75+-0.62+-0.36) x 10^-4 and (5.01+-1.21+-0.70) x 10^-4, respectively.Comment: 6 pages, 2 figues, submitted to PRD (RC
X-ray emission from the Sombrero galaxy: discrete sources
We present a study of discrete X-ray sources in and around the
bulge-dominated, massive Sa galaxy, Sombrero (M104), based on new and archival
Chandra observations with a total exposure of ~200 ks. With a detection limit
of L_X = 1E37 erg/s and a field of view covering a galactocentric radius of ~30
kpc (11.5 arcminute), 383 sources are detected. Cross-correlation with Spitler
et al.'s catalogue of Sombrero globular clusters (GCs) identified from HST/ACS
observations reveals 41 X-rays sources in GCs, presumably low-mass X-ray
binaries (LMXBs). We quantify the differential luminosity functions (LFs) for
both the detected GC and field LMXBs, whose power-low indices (~1.1 for the
GC-LF and ~1.6 for field-LF) are consistent with previous studies for
elliptical galaxies. With precise sky positions of the GCs without a detected
X-ray source, we further quantify, through a fluctuation analysis, the GC LF at
fainter luminosities down to 1E35 erg/s. The derived index rules out a
faint-end slope flatter than 1.1 at a 2 sigma significance, contrary to recent
findings in several elliptical galaxies and the bulge of M31. On the other
hand, the 2-6 keV unresolved emission places a tight constraint on the field
LF, implying a flattened index of ~1.0 below 1E37 erg/s. We also detect 101
sources in the halo of Sombrero. The presence of these sources cannot be
interpreted as galactic LMXBs whose spatial distribution empirically follows
the starlight. Their number is also higher than the expected number of cosmic
AGNs (52+/-11 [1 sigma]) whose surface density is constrained by deep X-ray
surveys. We suggest that either the cosmic X-ray background is unusually high
in the direction of Sombrero, or a distinct population of X-ray sources is
present in the halo of Sombrero.Comment: 11 figures, 5 tables, ApJ in pres
Performance of the CMS Cathode Strip Chambers with Cosmic Rays
The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device
in the CMS endcaps. Their performance has been evaluated using data taken
during a cosmic ray run in fall 2008. Measured noise levels are low, with the
number of noisy channels well below 1%. Coordinate resolution was measured for
all types of chambers, and fall in the range 47 microns to 243 microns. The
efficiencies for local charged track triggers, for hit and for segments
reconstruction were measured, and are above 99%. The timing resolution per
layer is approximately 5 ns
Tumor Spectrum, Tumor Latency and Tumor Incidence of the Pten-Deficient Mice
BACKGROUND: Pten functionally acts as a tumor suppressor gene. Lately, tissue-specific ablation of Pten gene in mice has elucidated the role of Pten in different tumor progression models. However, a temporally controlled Pten loss in all adult tissues to examine susceptibility of various tissues to Pten-deficient tumorigenesis has not been addressed yet. Our goal was to explore the genesis of Pten-deficient malignancies in multiple tissue lineages of the adult mouse. METHODS AND FINDINGS: We utilized an inducible Cre/loxP system to delete Pten exon 5 in the systemic organs of ROSA26 (R26)-CreER(T);Pten(fx/fx) mice. On reaching 45 weeks 4OHT-induced Pten loss, we found that the R26-CreER(T);Pten(fx/fx) mice developed a variety of malignancies. Overall tumor mean latency was 17 weeks in the Pten-deficient mice. Interestingly, mutant females developed malignancies more quickly at 10 approximately 11 weeks compared with a tumor latency of 21 weeks for mutant males. Lymphoma incidence (76.9% in females; 40.0% in males) was higher than the other malignancies found in the mutant mice. Mutant males developed prostate (20.0%), intestinal cancer (35.0%) and squamous cell carcinoma (10.0%), whereas the mutant females developed squamous cell carcinoma (15.4%) and endometrial cancer (46.1%) in addition to lymphomas. Furthermore, we tested the pharmacological inhibition of the PTEN downstream effectors using LY294002 on Pten-deficient prostate hyperplasia. Our data revealed that, indeed, the prostate hyperplasia resulting from the induced Pten loss was significantly suppressed by LY294002 (p = 0.007). CONCLUSIONS: Through monitoring a variety of Pten-deficient tumor formation, our results revealed that the lymphoid lineages and the epithelium of the prostate, endometrium, intestine and epidermis are highly susceptible to tumorigenesis after the Pten gene is excised. Therefore, this R26-CreER(T); Pten(fx/fx) mouse model may provide an entry point for understanding the role of Pten in the tumorigenesis of different organs and extend the search for potential therapeutic approaches to prevent Pten-deficient malignancies
Averages of b-hadron, c-hadron, and tau-lepton properties as of 2018 Heavy Flavor Averaging Group (HFLAV)
This paper reports world averages of measurements of b-hadron, c-hadron, and
Ï
-lepton properties obtained by the Heavy Flavour Averaging Group using results available through September 2018. In rare cases, significant results obtained several months later are also used. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters,
C
P
violation parameters, parameters of semileptonic decays, and CabibboâKobayashiâMaskawa matrix elements
Measurements of Branching Fractions for B0 --> Ds+pi- and B0-bar --> Ds+K-
We present improved measurements of the branching fractions for the decays B0
--> Ds+pi- and B0-bar --> Ds+K- using a data sample of 657x10^6 BB-bar events
collected at the Y(4S) resonance with the Belle detector at the KEKB
asymmetric-energy e+e- collider. The results are BF(B0 --> Ds+pi-) = (1.99 +/-
0.26 +/- 0.18)x10^-5 and BF(B0-bar --> Ds+K-) = (1.91 +/- 0.24 +/- 0.17)x10^-5,
where the uncertainties are statistical and systematic, respectively. Based on
these results, we determine the ratio between amplitudes of the doubly Cabibbo
suppressed decay B0 --> D+pi- and the Cabibbo favored decay B0 --> D-pi+, R_Dpi
= [1.71 +/- 0.11(stat) +/- 0.09(syst) +/- 0.02(theo)]%, where the last term
denotes the theory error.Comment: 7 pages, 10 figures, 2 tables, published in PRD(RC
Search for Lepton-number-violating B+->D-l+l'+ Decays
We perform the first search for lepton-number-violating B+->D-l+l'+ decays,
where l and l' stand for e or mu, using 772 x 10^6 BB-bar pairs accumulated at
the Upsilon(4S) resonance with the Belle detector at the KEKB e^+e^- collider.
No evidence for these decays has been found. Assuming uniform three-body phase
space distributions for the D-l+l+ decays, we set the following upper limits on
the branching fractions at 90% confidence level: Br(B+ -> D-e+e+) < 2.6x10^-6,
Br(B+ -> D-e+mu+) D-mu+mu+) < 1.0x10^-6.Comment: 7 pages, 2 figure
Observation of Two New Excited Îb0 States Decaying to Îb0 K-Ï+
Two narrow resonant states are observed in the Îb0K-Ï+ mass spectrum using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 6 fb-1. The minimal quark content of the Îb0K-Ï+ system indicates that these are excited Îb0 baryons. The masses of the Îb(6327)0 and Îb(6333)0 states are m[Îb(6327)0]=6327.28-0.21+0.23±0.12±0.24 and m[Îb(6333)0]=6332.69-0.18+0.17±0.03±0.22 MeV, respectively, with a mass splitting of Îm=5.41-0.27+0.26±0.12 MeV, where the uncertainties are statistical, systematic, and due to the Îb0 mass measurement. The measured natural widths of these states are consistent with zero, with upper limits of Î[Îb(6327)0]<2.20(2.56) and Î[Îb(6333)0]<1.60(1.92) MeV at a 90% (95%) credibility level. The significance of the two-peak hypothesis is larger than nine (five) Gaussian standard deviations compared to the no-peak (one-peak) hypothesis. The masses, widths, and resonant structure of the new states are in good agreement with the expectations for a doublet of 1D Îb0 resonances
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