1,148 research outputs found
Frustrated collisions and unconventional pairing on a quantum superlattice
We solve the problem of scattering and binding of two spin-1/2 fermions on a
one-dimensional superlattice with a period of twice the lattice spacing
analytically. We find the exact bound states and the scattering states,
consisting of a generalized Bethe ansatz augmented with an extra scattering
product due to "asymptotic" degeneracy. If a Bloch band is doubly occupied, the
extra wave can be a bound state in the continuum corresponding to a
single-particle interband transition. In all other cases, it corresponds to a
quasi-momentum changing, frustrated collision.Comment: 4 pages, 2 figure
Facial behavior
: We provide an overview of the current state-of-the-art regarding research
on facial behavior from what we hope is a well-balanced historical perspective.
Based on a critical discussion of the main theoretical views of nonverbal facial
activity (i.e., affect program theory, appraisal theory, dimensional theory, behavioral ecology), we focus on some key issues regarding the cohesion of emotion and
expression, including the issue of “genuine smiles.” We argue that some of the
challenges faced by the field are a consequence of these theoretical positions, their
assumptions, and we discuss how they have generated and shaped research. A
clear distinction of encoding and decoding processes may prove beneficial to identify specific problems – for example the use of posed expressions in facial expression research, or the impact of the psychological situation on the perceiver. We
argue that knowledge of the functions of facial activity may be central to understanding what facial activity is truly about; this includes a serious consideration
of social context at all stages of encoding and decoding. The chapter concludes
with a brief overview of recent technical advances and challenges highlighted by
the new field of “affective computing” concerned with facial activity
Salesforce control systems as direct antecedents of salesperson and sales unit performance: A literature review
[EN] The impact from sales control systems on individual and organizational effectiveness has been a major issue for scholars since these systems were conceptualized by Anderson and Oliver and Jaworski. Salesperson behavioral performance appears as an antecedent of outcome performance, and both are connected to sales unit effectiveness. This paper focuses on a deep literature review during the period 1983-2014, based on the control systems¿ typologies found, and summarizes the multiple evidences found, connecting this systems with the salesperson behavioral performance and the outcome performance ¿and between them-, and both individual results with the sales unit effectiveness, including its managerial implications. After the review of the 142 articles in the field, a cluster of four research directions are identified, namely: (1) the impact of the different variables and activities on the control systems and the performance levels, (2) the methodological variables, (3) the measures of the level control system or performance, and (4) the multisectorial, multicultural and multinational sales environment.Benet-Zepf, AT.; Marin-Garcia, JA.; Küster, I. (2017). Salesforce control systems as direct antecedents of salesperson and sales unit performance: A literature review. Business and Economics Journal. 8(1). doi:10.4172/2151-6219.1000281S2818
Quartz microstructures in nature and experiment — evidence of rapid plastic deformation and subsequent annealing
Quartz microstructures produced in
short-term deformation and annealing
experiments are compared with those in
naturally deformed vein quartz in cores
from the Long Valley Exploratory Well
(Long Valley Caldera, California). The
experiments are designed to simulate
i) co-seismic deformation of quartz in
the uppermost plastosphere and
ii) annealing during post-seismic
stress relaxation.
The experiments are performed in a
modified Griggs type solid medium apparatus.
Natural polycrystalline quartz
samples (grain size on the order of millimetres)
are deformed at a temperature
of 400°C, a confining pressure of 2GPa,
and strain rates of ca. 10−4 s−1. The
differential stress reaches 2–4GPa and
the irreversible axial shortening is typically
a few percent. In some experiments
the samples have subsequently
been annealed for ca. 14–15 h at elevated
temperatures of 800–1000°C and
low stresses (quasi-hydrostatic or nonhydrostatic
conditions)...conferenc
Correlating Josephson supercurrents and Shiba states in quantum spins unconventionally coupled to superconductors
Local spins coupled to superconductors give rise to several emerging phenomena directly linked to the competition between Cooper pair formation and magnetic exchange. These effects are generally scrutinized using a spectroscopic approach which relies on detecting the in-gap bound modes arising from Cooper pair breaking, the so-called Yu-Shiba-Rusinov (YSR) states. However, the impact of local magnetic impurities on the superconducting order parameter remains largely unexplored. Here, we use scanning Josephson spectroscopy to directly visualize the effect of magnetic perturbations on Cooper pair tunneling between superconducting electrodes at the atomic scale. By increasing the magnetic impurity orbital occupation by adding one electron at a time, we reveal the existence of a direct correlation between Josephson supercurrent suppression and YSR states. Moreover, in the metallic regime, we detect zero bias anomalies which break the existing framework based on competing Kondo and Cooper pair singlet formation mechanisms. Based on first-principle calculations, these results are rationalized in terms of unconventional spin-excitations induced by the finite magnetic anisotropy energy. Our findings have far reaching implications for phenomena that rely on the interplay between quantum spins and superconductivity. The impact of local magnetic impurities on superconducting order parameter remains largely unexplored. Here, the authors visualize the effect of different magnetic perturbations on a superconductor, unveiling a rich correlation of the interplay between quantum spins and superconductivity in different spectroscopic regimes
Recursive Graphical Construction of Feynman Diagrams in phi^4 Theory: Asymmetric Case and Effective Energy
The free energy of a multi-component scalar field theory is considered as a
functional W[G,J] of the free correlation function G and an external current J.
It obeys non-linear functional differential equations which are turned into
recursion relations for the connected Greens functions in a loop expansion.
These relations amount to a simple proof that W[G,J] generates only connected
graphs and can be used to find all such graphs with their combinatoric weights.
A Legendre transformation with respect to the external current converts the
functional differential equations for the free energy into those for the
effective energy Gamma[G,Phi], which is considered as a functional of the free
correlation function G and the field expectation Phi. These equations are
turned into recursion relations for the one-particle irreducible Greens
functions. These relations amount to a simple proof that Gamma[G,J] generates
only one-particle irreducible graphs and can be used to find all such graphs
with their combinatoric weights. The techniques used also allow for a
systematic investigation into resummations of classes of graphs. Examples are
given for resumming one-loop and multi-loop tadpoles, both through all orders
of perturbation theory. Since the functional differential equations derived are
non-perturbative, they constitute also a convenient starting point for other
expansions than those in numbers of loops or powers of coupling constants. We
work with general interactions through four powers in the field.Comment: 34 pages; abstract expanded; section IV.E about absorption of
tadpoles and one related reference added; eqs. (20) and (23) corrected;
further references added; some minor beautifications; to be published by
Phys.Rev.
Reduction of airspace after lung resection through controlled paralysis of the diaphragm
Objectives: Residual airspace following thoracic resections is a common clinical problem. Persistent air leak, prolonged drainage time, and reduced hemostasis extend hospital stay and morbidity. We report a trial of pharmacologic-induced diaphragmatic paralysis through continuous paraphrenic injection of lidocaine to reduced residual airspace. The objectives were confirmation of diaphragmatic paralysis and possible procedure related complications. Methods: Six eligible patients undergoing resectional surgery (lobectomy or bilobectomy) were included. Inclusion criteria consisted of: postoperative predicted FEV1 greater than 1300ml, right-sided resection, absence of parenchymal lung disease, no class III antiarrhythmic therapy, absence of hypersensitivity reactions to lidocaine, no signs of infection, and informed consent. Upon completion of resection an epidural catheter was attached in the periphrenic tissue on the proximal pericardial surface, externalized through a separate parasternal incision, and connected to a perfusing system injecting lidocaine 1% at a rate of 3ml/h (30mg/h). Postoperative ICU surveillance for 24h and daily measurement of vital signs, drainage output, and bedside spirometry were performed. Within 48h fluoroscopic confirmation of diaphragmatic paralysis was obtained. The catheter removal coincided with the chest tube removal when no procedural related complications occurred. Results: None of the patients reported respiratory impairment. Diaphragmatic paralysis was documented in all patients. Upon removal of catheter or discontinuation of lidocaine prompt return of diaphragmatic motility was noticed. Two patients showed postoperative hemodynamic irrelevant atrial fibrillation. Conclusion: Postoperative paraphrenic catheter administration of lidocaine to ensure reversible diaphragmatic paralysis is safe and reproducible. Further studies have to assess a benefit in terms of reduction in morbidity, drainage time, and hospital stay, and determine the patients who will profi
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