75 research outputs found
Cycles are strongly Ramsey-unsaturated
We call a graph H Ramsey-unsaturated if there is an edge in the complement of
H such that the Ramsey number r(H) of H does not change upon adding it to H.
This notion was introduced by Balister, Lehel and Schelp who also proved that
cycles (except for ) are Ramsey-unsaturated, and conjectured that,
moreover, one may add any chord without changing the Ramsey number of the cycle
, unless n is even and adding the chord creates an odd cycle.
We prove this conjecture for large cycles by showing a stronger statement: If
a graph H is obtained by adding a linear number of chords to a cycle ,
then , as long as the maximum degree of H is bounded, H is either
bipartite (for even n) or almost bipartite (for odd n), and n is large.
This motivates us to call cycles strongly Ramsey-unsaturated. Our proof uses
the regularity method
Anisotropy of the upper critical field in MgB2: the two-gap Ginzburg-Landau theory
The upper critical field in MgB2 is investigated in the framework of the
two-gap Ginzburg-Landau theory. A variational solution of linearized
Ginzburg-Landau equations agrees well with the Landau level expansion and
demonstrates that spatial distributions of the gap functions are different in
the two bands and change with temperature. The temperature variation of the
ratio of two gaps is responsible for the upward temperature dependence of
in-plane Hc2 as well as for the deviation of its out-of-plane behavior from the
standard angular dependence. The hexagonal in-plane modulations of Hc2 can
change sign with decreasing temperature.Comment: 6 pages, 6 figures, accepted in the European Physical Journal
Aquatic biosurvey of the Lovell River on UNH land
We assessed the physical, chemical and biological conditions at two sites along the Lovell River on University of New Hampshire (UNH) -owned conservation land. The discharge was 4.4 m3 s-1 at Site 1 and 5.7 m3 s -1 downstream at Site 2. Canopy coverage ranged from 8-25%. Canopy was dominated by Eastern Hemlock (79-84%). Much of the stream was strewn with large boulders and the substrate consisted of rocks of highly variable sizes ( 3-549 cm dia.). Specific conductivity (22.1-23.3 µS), pH (6.4) and temperature (7.9-8.3 °C) varied little between sites. Macro-invertebrate bio-indices indicated either excellent water quality with no apparent organic pollution (3.0/10) or good water quality with possible slight organic pollution (4.4/10)
MET increased gene copy number and primary resistance to gefitinib therapy in non-small-cell lung cancer patients
Background: MET amplification has been detected in ∼20% of non-small-cell lung cancer patients (NSCLC) with epidermal growth factor receptor (EGFR) mutations progressing after an initial response to tyrosine kinase inhibitor (TKI) therapy. Patients and methods: We analyzed MET gene copy number using FISH in two related NSCLC cell lines, one sensitive (HCC827) and one resistant (HCC827 GR6) to gefitinib therapy and in two different NSCLC patient populations: 24 never smokers or EGFR FISH-positive patients treated with gefitinib (ONCOBELL cohort) and 182 surgically resected NSCLC not exposed to anti-EGFR agents. Results: HCC827 GR6-resistant cell line displayed MET amplification, with a mean MET copy number >12, while sensitive HCC827 cell line had a mean MET copy number of 4. In the ONCOBELL cohort, no patient had gene amplification and MET gene copy number was not associated with outcome to gefitinib therapy. Among the surgically resected patients, MET was amplified in 12 cases (7.3%) and only four (2.4%) had a higher MET copy number than the resistant HCC827 GR6 cell line. Conclusions: MET gene amplification is a rare event in patients with advanced NSCLC. The development of anti-MET therapeutic strategies should be focused on patients with acquired EGFR-TKI resistanc
Concentration Dependence of Superconductivity and Order-Disorder Transition in the Hexagonal Rubidium Tungsten Bronze RbxWO3. Interfacial and bulk properties
We revisited the problem of the stability of the superconducting state in
RbxWO3 and identified the main causes of the contradictory data previously
published. We have shown that the ordering of the Rb vacancies in the
nonstoichiometric compounds have a major detrimental effect on the
superconducting temperature Tc.The order-disorder transition is first order
only near x = 0.25, where it cannot be quenched effectively and Tc is reduced
below 1K. We found that the high Tc's which were sometimes deduced from
resistivity measurements, and attributed to compounds with .25 < x < .30, are
to be ascribed to interfacial superconductivity which generates spectacular
non-linear effects. We also clarified the effect of acid etching and set more
precisely the low-rubidium-content boundary of the hexagonal phase.This work
makes clear that Tc would increase continuously (from 2 K to 5.5 K) as we
approach this boundary (x = 0.20), if no ordering would take place - as its is
approximately the case in CsxWO3. This behaviour is reminiscent of the
tetragonal tungsten bronze NaxWO3 and asks the same question : what mechanism
is responsible for this large increase of Tc despite the considerable
associated reduction of the electron density of state ? By reviewing the other
available data on these bronzes we conclude that the theoretical models which
are able to answer this question are probably those where the instability of
the lattice plays a major role and, particularly, the model which call upon
local structural excitations (LSE), associated with the missing alkali atoms.Comment: To be published in Physical Review
Human-environmental interactions and seismic activity in a Late Bronze to Early Iron Age settlement center in the southeastern Caucasus
Long-term human-environmental interactions in naturally fragile drylands are a
focus of geomorphological and geoarchaeological research. Furthermore,
many dryland societies were also affected by seismic activity. The semi-arid
Shiraki Plain in the tectonically active southeastern Caucasus is currently
covered by steppe and largely devoid of settlements. However, numerous
Late Bronze to Early Iron Age city-type settlements suggest early state
formation between ca. 3.2-2.5 ka that abruptly ended after that time. A
paleolake was postulated for the lowest plain, and nearby pollen records
suggest forest clearcutting of the upper altitudes under a more humid
climate during the Late Bronze/Early Iron Ages. Furthermore, also an impact
of earthquakes on regional Early Iron Age settlements was suggested. However,
regional paleoenvironmental changes and paleoseismicity were not
systematically studied so far. We combined geomorphological,
sedimentological, chronological and paleoecological data with hydrological
modelling to reconstruct regional Holocene paleoenvironmental changes, to
identify natural and human causes and to study possible seismic events during
the Late Bronze/Early Iron Ages. Our results show a balanced to negative Early
to Mid-Holocene water balance probably caused by forested upper slopes.
Hence, no lake but a pellic Vertisol developed in the lowest plain. Following,
Late Bronze/Early Iron Age forest clear-cutting caused lake formation and the
deposition of lacustrine sediments derived from soil erosion. Subsequently,
regional aridification caused slow lake desiccation. Remains of freshwater fishes
indicate that the lake potentially offered valuable ecosystem services for regional prehistoric societies even during the desiccation period. Finally,
colluvial coverage of the lake sediments during the last centuries could have
been linked with hydrological extremes during the Little Ice Age. Our study
demonstrates that the Holocene hydrological balance of the Shiraki Plain was
and is situated near a major hydrological threshold, making the landscape very
sensitive to small-scale human or natural influences with severe consequences
for local societies. Furthermore, seismites in the studied sediments do not
indicate an influence of earthquakes on the main and late phases of Late
Bronze/Early Iron Age settlement. Altogether, our study underlines the high
value of multi-disciplinary approaches to investigate human-environmental
interactions and paleoseismicity in drylands on millennial to centennial time
scales
An Open Virtual Neighbourhood Network to Connect IoT Infrastructures and Smart Objects – VICINITY:IoT enables interoperability as a service
Primary resistance to cetuximab therapy in EGFR FISH-positive colorectal cancer patients
The impact of KRAS mutations on cetuximab sensitivity in epidermal growth factor receptor fluorescence in situ hybridisation-positive (EGFR FISH+) metastatic colorectal cancer patients (mCRC) has not been previously investigated. In the present study, we analysed KRAS, BRAF, PI3KCA, MET, and IGF1R in 85 mCRC treated with cetuximab-based therapy in whom EGFR status was known. KRAS mutations (52.5%) negatively affected response only in EGFR FISH+ patients. EGFR FISH+/KRAS mutated had a significantly lower response rate (P=0.04) than EGFR FISH+/KRAS wild type patients. Four EGFR FISH+ patients with KRAS mutations responded to cetuximab therapy. BRAF was mutated in 5.0% of patients and none responded to the therapy. PI3KCA mutations (17.7%) were not associated to cetuximab sensitivity. Patients overexpressing IGF1R (74.3%) had significantly longer survival than patients with low IGF1R expression (P=0.006), with no difference in response rate. IGF1R gene amplification was not detected, and only two (2.6%) patients, both responders, had MET gene amplification. In conclusion, KRAS mutations are associated with cetuximab failure in EGFR FISH+ mCRC, even if it does not preclude response. The rarity of MET and IGF1R gene amplification suggests a marginal role in primary resistance. The potential prognostic implication of IGF1R expression merits further evaluation
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