A great deal of research has focused on supply chain risk management, but the question “Which supply chain characteristics increase the frequency of supply chain disruptions?” has not received much ...attention from empirical research. This is a relevant question, because firms seek stability in their operations, and therefore managers need to know how the structure of their supply chains affects the occurrence of disruptions. The present study addresses this issue with a specific focus on upstream supply chain (supply-side) disruptions. Drawing on the literature on supply chain complexity, we devise and test a model that predicts the frequency of supply chain disruptions based on a multi-dimensional conceptualization of upstream supply chain complexity. Not only do the empirical findings suggest that all of the three investigated complexity drivers – horizontal, vertical, and spatial complexity – increase the frequency of disruptions, but also that they interact and amplify each other's effects in a synergistic fashion.
A
bstract
The anomalous magnetic moments of the electron and the muon are interesting observables, since they can be measured with great precision and their values can be computed with excellent ...accuracy within the Standard Model (SM). The current experimental measurement of this quantities show a deviation of a few standard deviations with respect to the SM prediction, which may be a hint of new physics. The fact that the electron and the muon masses differ by two orders of magnitude and the deviations have opposite signs makes it difficult to find a common origin of these anomalies. In this work we introduce a complex singlet scalar charged under a Peccei-Quinn-like (PQ) global symmetry together with the electron transforming chirally under the same symmetry. In this realization, the CP-odd scalar couples to electron only, while the CP-even part can couple to muons and electrons simultaneously. In addition, the CP-odd scalar can naturally be much lighter than the CP-even scalar, as a pseudo-Goldstone boson of the PQ-like symmetry, leading to an explanation of the suppression of the electron anomalous magnetic moment with respect to the SM prediction due to the CP-odd Higgs effect dominance, as well as an enhancement of the muon one induced by the CP-even component.
Hexagonal boron nitride (h-BN) is a natural hyperbolic material, in which the dielectric constants are the same in the basal plane (ε(t) ≡ ε(x) = ε(y)) but have opposite signs (ε(t)ε(z) < 0) in the ...normal plane (ε(z)). Owing to this property, finite-thickness slabs of h-BN act as multimode waveguides for the propagation of hyperbolic phonon polaritons--collective modes that originate from the coupling between photons and electric dipoles in phonons. However, control of these hyperbolic phonon polaritons modes has remained challenging, mostly because their electrodynamic properties are dictated by the crystal lattice of h-BN. Here we show, by direct nano-infrared imaging, that these hyperbolic polaritons can be effectively modulated in a van der Waals heterostructure composed of monolayer graphene on h-BN. Tunability originates from the hybridization of surface plasmon polaritons in graphene with hyperbolic phonon polaritons in h-BN, so that the eigenmodes of the graphene/h-BN heterostructure are hyperbolic plasmon-phonon polaritons. The hyperbolic plasmon-phonon polaritons in graphene/h-BN suffer little from ohmic losses, making their propagation length 1.5-2.0 times greater than that of hyperbolic phonon polaritons in h-BN. The hyperbolic plasmon-phonon polaritons possess the combined virtues of surface plasmon polaritons in graphene and hyperbolic phonon polaritons in h-BN. Therefore, graphene/h-BN can be classified as an electromagnetic metamaterial as the resulting properties of these devices are not present in its constituent elements alone.
Listeriosis: a resurgent foodborne infection Allerberger, F.; Wagner, M.
Clinical microbiology and infection,
January 2010, 2010-Jan, 2010-01-00, 20100101, Letnik:
16, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Listeria monocytogenes is the causative agent of human listeriosis, a potentially fatal foodborne infection. Clinical manifestations range from febrile gastroenteritis to more severe invasive forms, ...including sepsis, meningitis, rhombencephalitis, perinatal infections, and abortions. In recent years, an increasing rate of listeriosis has been reported in several European countries. These increases primarily reflect a higher rate of bacteraemic listeriosis in those ≥65 years of age, and are not otherwise correlated with geography, gender, ethnicity, socioeconomic factors or infectious serotypes. In the late 1980s, an upsurge in listeriosis rates was due to the contamination of a small number of food products. However, a restricted range of strains was responsible for most of the additional cases at that time, and no evidence exists for such a pattern since 2001. From a clinical perspective, the importance of isolating the pathogen as a prerequisite for an accurate epidemiological investigation and ultimately stopping transmission cannot be overemphasized.
Photoemission spectroscopy is central to understanding the inner workings of condensed matter, from simple metals and semiconductors to complex materials such as Mott insulators and superconductors
. ...Most state-of-the-art knowledge about such solids stems from spectroscopic investigations, and use of subfemtosecond light pulses can provide a time-domain perspective. For example, attosecond (10
seconds) metrology allows electron wave packet creation, transport and scattering to be followed on atomic length scales and on attosecond timescales
. However, previous studies could not disclose the duration of these processes, because the arrival time of the photons was not known with attosecond precision. Here we show that this main source of ambiguity can be overcome by introducing the atomic chronoscope method, which references all measured timings to the moment of light-pulse arrival and therefore provides absolute timing of the processes under scrutiny. Our proof-of-principle experiment reveals that photoemission from the tungsten conduction band can proceed faster than previously anticipated. By contrast, the duration of electron emanation from core states is correctly described by semiclassical modelling. These findings highlight the necessity of treating the origin, initial excitation and transport of electrons in advanced modelling of the attosecond response of solids, and our absolute data provide a benchmark. Starting from a robustly characterized surface, we then extend attosecond spectroscopy towards isolating the emission properties of atomic adsorbates on surfaces and demonstrate that these act as photoemitters with instantaneous response. We also find that the tungsten core-electron timing remains unchanged by the adsorption of less than one monolayer of dielectric atoms, providing a starting point for the exploration of excitation and charge migration in technologically and biologically relevant adsorbate systems.
The vast majority of the supplier innovation literature has focused on how buying firms can effectively “pull” innovations from their suppliers. Yet, we know remarkably little about the factors that ...contribute to a supplier voluntarily “pushing” innovations to its customers. The present study addresses this research gap in the context of industrial buyer–supplier relationships and with a specific focus on relationship-specific investments. Drawing on theory from the relationship-marketing literature and on transaction cost theory, we devise and test a proposed theoretical model that links the level of a supplier's relationship-specific investments to its sharing of innovative ideas regarding products and processes with customers. The model also considers the role of contract length, relationship age, and buyer–supplier cooperation as possible safeguards. The empirical results suggest that a supplier's relationship-specific investments encourage a supplier to suggest ideas of process innovations but to refrain from suggestions about product innovations. The latter effect, however, can be attenuated by appropriate formal and informal safeguards.
The success of metal-based plasmonics for manipulating light at the nanoscale has been empowered by imaginative designs and advanced nano-fabrication. However, the fundamental optical and electronic ...properties of elemental metals, the prevailing plasmonic media, are difficult to alter using external stimuli. This limitation is particularly restrictive in applications that require modification of the plasmonic response at sub-picosecond timescales. This handicap has prompted the search for alternative plasmonic media, with graphene emerging as one of the most capable candidates for infrared wavelengths. Here we visualize and elucidate the properties of non-equilibrium photo-induced plasmons in a high-mobility graphene monolayer. We activate plasmons with femtosecond optical pulses in a specimen of graphene that otherwise lacks infrared plasmonic response at equilibrium. In combination with static nano-imaging results on plasmon propagation, our infrared pump-probe nano-spectroscopy investigation reveals new aspects of carrier relaxation in heterostructures based on high-purity graphene.
A
bstract
In models with an extended Higgs sector there exists an alignment limit, in which the lightest CP-even Higgs boson mimics the Standard Model Higgs. The alignment limit is commonly ...associated with the decoupling limit, where all non-standard scalars are significantly heavier than the
Z
boson. However, alignment can occur irrespective of the mass scale of the rest of the Higgs sector. In this work we discuss the general conditions that lead to “alignment without decoupling”, therefore allowing for the existence of additional non-standard Higgs bosons at the weak scale. The values of tan
β
for which this happens are derived in terms of the effective Higgs quartic couplings in general two-Higgs-doublet models as well as in supersymmetric theories, including the MSSM and the NMSSM. Moreover, we study the information encoded in the variations of the SM Higgs-fermion couplings to explore regions in the
m
A
− tan
β
parameter space.
The elastic constants that describe the fundamental elastic properties of NiTi martensites are unknown today. We present results of
ab initio calculations of the ground-state energies and the ...relative mechanical stability of B19, B19′ and B33 (a theoretically predicted ground state from recent
ab initio studies). It is demonstrated that shear stresses of the order of 1
GPa are sufficient to mechanically stabilize B19′ against B33. The full sets of elastic constants and the associated macroscopic elastic parameters (Young’s, shear and bulk moduli, Poisson ratios) are determined for the first time for B19′ and B33 NiTi. The predicted macroscopic Young’s modulus of B19′ based on the first-principles results is an order of magnitude larger than the values currently assumed in micro or continuum mechanical modeling studies. Yet the results are in good agreement with novel experimental data and, furthermore, resolve a long-standing issue in the well-known Müller–Achenbach–Seelecke model by predicting Young’s modulus of martensite to be larger than that of austenite.
Uniaxial materials whose axial and tangential permittivities have opposite signs are referred to as indefinite or hyperbolic media. In such materials, light propagation is unusual leading to novel ...and often non-intuitive optical phenomena. Here we report infrared nano-imaging experiments demonstrating that crystals of hexagonal boron nitride, a natural mid-infrared hyperbolic material, can act as a 'hyper-focusing lens' and as a multi-mode waveguide. The lensing is manifested by subdiffractional focusing of phonon-polaritons launched by metallic disks underneath the hexagonal boron nitride crystal. The waveguiding is revealed through the modal analysis of the periodic patterns observed around such launchers and near the sample edges. Our work opens new opportunities for anisotropic layered insulators in infrared nanophotonics complementing and potentially surpassing concurrent artificial hyperbolic materials with lower losses and higher optical localization.
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