174 research outputs found
Response of a Fermi gas to time-dependent perturbations: Riemann-Hilbert approach at non-zero temperatures
We provide an exact finite temperature extension to the recently developed
Riemann-Hilbert approach for the calculation of response functions in
nonadiabatically perturbed (multi-channel) Fermi gases. We give a precise
definition of the finite temperature Riemann-Hilbert problem and show that it
is equivalent to a zero temperature problem. Using this equivalence, we discuss
the solution of the nonequilibrium Fermi-edge singularity problem at finite
temperatures.Comment: 10 pages, 2 figures; 2 appendices added, a few modifications in the
text, typos corrected; published in Phys. Rev.
Fermi edge singularity in a non-equilibrium system
We report exact results for the Fermi Edge Singularity in the absorption
spectrum of an out-of-equilibrium tunnel junction. We consider two metals with
chemical potential difference V separated by a tunneling barrier containing a
defect, which exists in one of two states. When it is in its excited state,
tunneling through the otherwise impermeable barrier is possible. We find that
the lineshape not only depends on the total scattering phase shift as in the
equilibrium case but also on the difference in the phase of the reflection
amplitudes on the two sides of the barrier. The out-of-equilibrium spectrum
extends below the original threshold as energy can be provided by the power
source driving current across the barrier. Our results have a surprisingly
simple interpretation in terms of known results for the equilibrium case but
with (in general complex-valued) combinations of elements of the scattering
matrix replacing the equilibrium phase shifts.Comment: 4 page
Fermi-edge problem in the presence of AC electric field
We study in this paper a non-equilibrium Fermi-edge problem where the system
under investigation is a single electron reservoir putting under an AC electric
field. We show that the electron Green's function and other correlation
functions in the problem can be solved and expressed exactly in terms of a
well-defined integral. The qualitative behaviors of the solution is studied and
compared with the situation where the impurity is coupled to more than one
reservoirs at different chemical potentials.Comment: Published versio
Energy-dependent effective interactions for dilute many-body systems
We address the issue of determining an effective two-body interaction for
mean-field calculations of energies of many-body systems. We show that the
effective interaction is proportional to the phase shift, and demonstrate this
result in the quasiclassical approximation when there is a trapping potential
in addition to the short-range interaction between a pair of particles. We
calculate numerically energy levels for the case of an interaction with a
short-range square-well and a harmonic trapping potential and show that the
numerical results agree well with the analytical expression. We derive a
generalized Gross--Pitaevskii equation which includes effective range
corrections and discuss the form of the electron--atom effective interaction to
be used in calculations of Rydberg atoms and molecules.Comment: 6 pages, 2 figure
Graphite and Hexagonal Boron-Nitride Possess the Same Interlayer Distance. Why?
Graphite and hexagonal boron nitride (h-BN) are two prominent members of the
family of layered materials possessing a hexagonal lattice. While graphite has
non-polar homo-nuclear C-C intra-layer bonds, h-BN presents highly polar B-N
bonds resulting in different optimal stacking modes of the two materials in
bulk form. Furthermore, the static polarizabilities of the constituent atoms
considerably differ from each other suggesting large differences in the
dispersive component of the interlayer bonding. Despite these major differences
both materials present practically identical interlayer distances. To
understand this finding, a comparative study of the nature of the interlayer
bonding in both materials is presented. A full lattice sum of the interactions
between the partially charged atomic centers in h-BN results in vanishingly
small monopolar electrostatic contributions to the interlayer binding energy.
Higher order electrostatic multipoles, exchange, and short-range correlation
contributions are found to be very similar in both materials and to almost
completely cancel out by the Pauli repulsions at physically relevant interlayer
distances resulting in a marginal effective contribution to the interlayer
binding. Further analysis of the dispersive energy term reveals that despite
the large differences in the individual atomic polarizabilities the
hetero-atomic B-N C6 coefficient is very similar to the homo-atomic C-C
coefficient in the hexagonal bulk form resulting in very similar dispersive
contribution to the interlayer binding. The overall binding energy curves of
both materials are thus very similar predicting practically the same interlayer
distance and very similar binding energies.Comment: 18 pages, 5 figures, 2 table
Cheese trademarks: Italian dairy firms’ practices during the 20th century
Trademarks have recently become a very useful sources for business historians. This longitudinal analysis of the twentieth-century trademarking activities of the most important Italian dairy firms of the era, namely Galbani, Invernizzi and Locatelli, demonstrates that trademarks were used both as a protective weapon against competitors and as an innovation carrier to open up new markets. This article also argues that trademark registrations had another dual purpose – not only were they used as buffers against negative shocks but they were also used to support periods of economic growth. A fundamental finding of this work is that trademarks, across various types of registrations, were closely connected to the features on which the companies based their sales strategies
\u3ci\u3eFundulus\u3c/i\u3e as the premier teleost model in environmental biology: Opportunities for new insights using genomics
A strong foundation of basic and applied research documents that the estuarine fish Fundulus heteroclitus and related species are unique laboratory and field models for understanding how individuals and populations interact with their environment. In this paper we summarize an extensive body of work examining the adaptive responses of Fundulus species to environmental conditions, and describe how this research has contributed importantly to our understanding of physiology, gene regulation, toxicology, and ecological and evolutionary genetics of teleosts and other vertebrates. These explorations have reached a critical juncture at which advancement is hindered by the lack of genomic resources for these species. We suggest that a more complete genomics toolbox for F. heteroclitus and related species will permit researchers to exploit the power of this model organism to rapidly advance our understanding of fundamental biological and pathological mechanisms among vertebrates, as well as ecological strategies and evolutionary processes common to all living organisms
Efficacy of Sym004 in Patients With Metastatic Colorectal Cancer With Acquired Resistance to Anti-EGFR Therapy and Molecularly Selected by Circulating Tumor DNA Analyses: A Phase 2 Randomized Clinical Trial.
IMPORTANCE:
Acquired resistance to anti-EGFR therapy (epidermal growth factor receptor) is frequently due to RAS and EGFR extracellular domain (ECD) mutations in metastatic colorectal cancer (mCRC). Some anti-EGFR-refractory patients retain tumor EGFR dependency potentially targetable by agents such as Sym004, which is a mixture of 2 nonoverlapping monoclonal antibodies targeting EGFR.
OBJECTIVE:
To determine if continuous blockade of EGFR by Sym004 has survival benefit.
DESIGN, SETTING, AND PARTICIPANTS:
Multicenter, phase 2, randomized, clinical trial comparing 2 regimens of Sym004 with investigator's choice from March 6, 2014, through October 15, 2015. Circulating tumor DNA (ctDNA) was analyzed for biomarker and tracking clonal dynamics during treatment. Participants had wild-type KRAS exon 2 mCRC refractory to standard chemotherapy and acquired resistance to anti-EGFR monoclonal antibodies.
INTERVENTIONS:
Participants were randomly assigned in a 1:1:1 ratio to Sym004, 12 mg/kg/wk (arm A), Sym004, 9 mg/kg loading dose followed by 6 mg/kg/wk (arm B), or investigator's choice of treatment (arm C).
MAIN OUTCOMES AND MEASURES:
Overall survival (OS). Secondary end points included preplanned exploratory biomarker analysis in ctDNA.
RESULTS:
A total of 254 patients were randomized (intent-to-treat [ITT] population) (median age, 63 [range, 34-91] years; 63% male; n\u2009=\u2009160). Median OS in the ITT population was 7.9 months (95% CI, 6.5-9.9 months), 10.3 months (95% CI, 9.0-12.9 months), and 9.6 months (95% CI, 8.3-12.2 months) for arms A, B, and C, respectively (hazard ratio [HR], 1.31; 95% CI, 0.92-1.87 for A vs C; and HR, 0.97; 95% CI, 0.68-1.40 for B vs C). The ctDNA revealed high intrapatient genomic heterogeneity following anti-EGFR therapy. Sym004 effectively targeted EGFR ECD-mutated cancer cells, and a decrease in EGFR ECD ctDNA occurred in Sym004-treated patients. However, this did not translate into clinical benefit in patients with EGFR ECD mutations, likely owing to co-occurring resistance mechanisms. A subgroup of patients was defined by ctDNA (RAS/BRAF/EGFR ECD-mutation negative) associated with improved OS in Sym004-treated patients in arm B compared with arm C (median OS, 12.8 and 7.3 months, respectively).
CONCLUSIONS AND RELEVANCE:
Sym004 did not improve OS in an unselected population of patients with mCRC and acquired anti-EGFR resistance. A prospective clinical validation of Sym004 efficacy in a ctDNA molecularly defined subgroup of patients with refractory mCRC is warranted.
TRIAL REGISTRATION: clinicaltrialsregister.eu Identifier: 2013-003829-29
The structure of the Yang-Mills spectrum for arbitrary simple gauge algebras
The mass spectrum of pure Yang-Mills theory in 3+1 dimensions is discussed
for an arbitrary simple gauge algebra within a quasigluon picture. The general
structure of the low-lying gluelump and two-quasigluon glueball spectrum is
shown to be common to all algebras, while the lightest three-quasigluon
glueballs only exist when the gauge algebra is A, that is in
particular . Higher-lying glueballs are shown to
exist only for the A, D and E gauge
algebras. The shape of the static energy between adjoint sources is also
discussed assuming the Casimir scaling hypothesis and a funnel form; it appears
to be gauge-algebra dependent when at least three sources are considered. As a
main result, the present framework's predictions are shown to be consistent
with available lattice data in the particular case of an
gauge algebra within 't Hooft's large- limit.Comment: 21 pages, 4 figures; remarks added, typos corrected in v2. v3 to
appear in EPJ
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