7,867 research outputs found
Natural linewidth analysis of d-band photoemission from Ag(110)
We report a high-resolution angle-resolved study of photoemission linewidths
observed for Ag(110). A careful data analysis yields kdd\tau_h \geq 22
d$-hole dynamics in Cu (I.\
Campillo et al., Phys. Rev. Lett., in press) we interpret the lifetime
enhancement by a small scattering cross-section of - and -states below
the Fermi level. With increasing distance to the -hole lifetimes get
shorter because of the rapidly increasing density of d-states and contributions
of intra--band scattering processes, but remain clearly above
free-electron-model predictions.Comment: 14 pages, 7 figure
Conflict-Free Coloring Made Stronger
In FOCS 2002, Even et al. showed that any set of discs in the plane can
be Conflict-Free colored with a total of at most colors. That is,
it can be colored with colors such that for any (covered) point
there is some disc whose color is distinct from all other colors of discs
containing . They also showed that this bound is asymptotically tight. In
this paper we prove the following stronger results:
\begin{enumerate} \item [(i)] Any set of discs in the plane can be
colored with a total of at most colors such that (a) for any
point that is covered by at least discs, there are at least
distinct discs each of which is colored by a color distinct from all other
discs containing and (b) for any point covered by at most discs,
all discs covering are colored distinctively. We call such a coloring a
{\em -Strong Conflict-Free} coloring. We extend this result to pseudo-discs
and arbitrary regions with linear union-complexity.
\item [(ii)] More generally, for families of simple closed Jordan regions
with union-complexity bounded by , we prove that there exists
a -Strong Conflict-Free coloring with at most colors.
\item [(iii)] We prove that any set of axis-parallel rectangles can be
-Strong Conflict-Free colored with at most colors.
\item [(iv)] We provide a general framework for -Strong Conflict-Free
coloring arbitrary hypergraphs. This framework relates the notion of -Strong
Conflict-Free coloring and the recently studied notion of -colorful
coloring. \end{enumerate}
All of our proofs are constructive. That is, there exist polynomial time
algorithms for computing such colorings
Dielectrophoresis-Driven Spreading of Immersed Liquid Droplets
In recent years electrowetting-on-dielectric (EWOD) has become an effective tool to control partial wetting. EWOD uses the liquidâsolid interface as part of a capacitive structure that allows capacitive and interfacial energies to adjust by changes in wetting when the liquidâsolid interface is charged due to an applied voltage. An important aspect of EWOD has been its applications in micro fluidics in chemistry and biology and in optical devices and displays in physics and engineering. Many of these rely on the use of a liquid droplet immersed in a second liquid due to the need either for neutral buoyancy to overcome gravity and shield against impact shocks or to encapsulate the droplet for other reasons, such as in microfluidic-based DNA analyses. Recently, it has been shown that nonwetting oleophobic surfaces can be forcibly wetted by nonconducting oils using nonuniform electric fields and an interface-localized form of liquid dielectrophoresis (dielectrowetting). Here we show that this effect can be used to create films of oil immersed in a second immiscible fluid of lower permittivity. We predict that the square of the thickness of the film should obey a simple law dependent on the square of the applied voltage and with strength dependent on the ratio of difference in permittivity to the liquid-fluid interfacial tension, ÎΔ/ÎłLF. This relationship is experimentally confirmed for 11 liquidâair and liquidâliquid combinations with ÎΔ/ÎłLF having a span of more than two orders of magnitude. We therefore provide fundamental understanding of dielectrowetting for liquid-in-liquid systems and also open up a new method to determine liquidâliquid interfacial tensions
A Local Computation Approximation Scheme to Maximum Matching
We present a polylogarithmic local computation matching algorithm which
guarantees a (1-\eps)-approximation to the maximum matching in graphs of
bounded degree.Comment: Appears in Approx 201
Sufficient Conditions for Tuza's Conjecture on Packing and Covering Triangles
Given a simple graph , a subset of is called a triangle cover if
it intersects each triangle of . Let and denote the
maximum number of pairwise edge-disjoint triangles in and the minimum
cardinality of a triangle cover of , respectively. Tuza conjectured in 1981
that holds for every graph . In this paper, using a
hypergraph approach, we design polynomial-time combinatorial algorithms for
finding small triangle covers. These algorithms imply new sufficient conditions
for Tuza's conjecture on covering and packing triangles. More precisely,
suppose that the set of triangles covers all edges in . We
show that a triangle cover of with cardinality at most can be
found in polynomial time if one of the following conditions is satisfied: (i)
, (ii) , (iii)
.
Keywords: Triangle cover, Triangle packing, Linear 3-uniform hypergraphs,
Combinatorial algorithm
On-Off Intermittency in Time Series of Spontaneous Paroxysmal Activity in Rats with Genetic Absence Epilepsy
Dynamic behavior of complex neuronal ensembles is a topic comprising a
streamline of current researches worldwide. In this article we study the
behavior manifested by epileptic brain, in the case of spontaneous
non-convulsive paroxysmal activity. For this purpose we analyzed archived
long-term recording of paroxysmal activity in animals genetically susceptible
to absence epilepsy, namely WAG/Rij rats. We first report that the brain
activity alternated between normal states and epilepsy paroxysms is the on-off
intermittency phenomenon which has been observed and studied earlier in the
different nonlinear systems.Comment: 11 pages, 6 figure
Night MattersâWhy the Interdisciplinary Field of âNight Studiesâ Is Needed
The night has historically been neglected in both disciplinary and interdisciplinary research. To some extent, this is not surprising, given the diurnal bias of human researchers and the difficulty of performing work at night. The night is, however, a critical element of biological, chemical, physical, and social systems on Earth. Moreover, research into social issues such as inequality, demographic changes, and the transition to a sustainable economy will be compromised if the night is not considered. Recent years, however, have seen a surge in research into the night. We argue that ânight studiesâ is on the cusp of coming into its own as an interdisciplinary field, and that when it does, the field will consider questions that disciplinary researchers have not yet thought to ask
Limited progression of subclinical Dupuytren's disease:results from a prospective cohort study
AIMS: With novel promising therapies potentially limiting progression of Dupuytren's disease (DD), better patient stratification is needed. We aimed to quantify DD development and progression after seven years in a population-based cohort, and to identify factors predictive of disease development or progression. METHODS: All surviving participants from our previous prevalence study were invited to participate in the current prospective cohort study. Participants were examined for presence of DD and Iselin's classification was applied. They were asked to complete comprehensive questionnaires. Disease progression was defined as advancement to a further Iselin stage or surgery. Potential predictive factors were assessed using multivariable regression analyses. Of 763 participants in our original study, 398 were available for further investigation seven years later. RESULTS: We identified 143/398 (35.9%) participants with DD, of whom 56 (39.2%) were newly diagnosed. Overall, 20/93 (21.5%) previously affected participants had disease progression, while 6/93 (6.5%) patients showed disease regression. Disease progression occurred more often in patients who initially had advanced disease. Multivariable regression analyses revealed that both ectopic lesions and a positive family history of DD are independent predictors of disease progression. Previous hand injury predicts development of DD. CONCLUSION: Disease progression occurred in 21.5% of DD patients in our study. The higher the initial disease stage, the greater the proportion of participants who had disease progression at follow-up. Both ectopic lesions and a positive family history of DD predict disease progression. These patient-specific factors may be used to identify patients who might benefit from treatment that prevents progression. Cite this article: Bone Joint JÂ 2021;103-B(4):704-710
Reallocation Effects of the Minimum Wage
We investigate the wage, employment and reallocation effects of the introduction of a nationwide minimum wage in Germany that affected 15% of all employees. Based on identification designs that exploit variation in exposure across individuals and local areas, we find that the minimum wage raised wages, but did not lower employment. It also led to the reallocation of low-wage workers from smaller to larger, from lower- to higher-paying, and from less- to more-productive establishments. This worker upgrading accounts for up to 17% of the wage increase induced by the minimum wage. Moreover, at the regional level, average establishment quality increased in more affected areas in the years following the introduction of the minimum wage
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