2,947 research outputs found
New insights into the internationalization of producer services:Organizational strategies and spatial economies for global headhunting firms
This paper uses the exemplar of global headhunting firms to provide new insights into the intricacies of internationalization and related ‘spatial economies’ of producer services in the world economy. In particular, we unpack the complex relationships between the organisational rationale for, the selected mode of, and future benefits gained by internationalization, as headhunting firms seek and create new geographical markets. We achieve this through an analysis of headhunting firm-specific case study data that details the evolving way such firms organize their differential strategic growth (organic, merger and acquisition, and alliances/network) and forms (wholly-owned, networked or hybrid). We also highlight how, as elite labour market intermediaries, headhunters are important, yet understudied, actors within the (re)production of a ‘softer’, ‘knowledgeable’ capitalism. Our argument, exemplified through detailed mapping of the changing geographies of headhunting firms between 1992 and 2005, demonstrates the need for complex and blurred typologies of internationalization and similarly complex internationalization theory
Predicting the whispering gallery mode spectra of microresonators
The whispering gallery modes (WGMs) of optical resonators have prompted
intensive research efforts due to their usefulness in the field of biological
sensing, and their employment in nonlinear optics. While much information is
available in the literature on numerical modeling of WGMs in microspheres, it
remains a challenging task to be able to predict the emitted spectra of
spherical microresonators. Here, we establish a customizable Finite- Difference
Time-Domain (FDTD)-based approach to investigate the WGM spectrum of
microspheres. The simulations are carried out in the vicinity of a dipole
source rather than a typical plane-wave beam excitation, thus providing an
effective analogue of the fluorescent dye or nanoparticle coatings used in
experiment. The analysis of a single dipole source at different positions on
the surface or inside a microsphere, serves to assess the relative efficiency
of nearby radiating TE and TM modes, characterizing the profile of the
spectrum. By varying the number, positions and alignments of the dipole
sources, different excitation scenarios can be compared to analytic models, and
to experimental results. The energy flux is collected via a nearby disk-shaped
region. The resultant spectral profile shows a dependence on the configuration
of the dipole sources. The power outcoupling can then be optimized for specific
modes and wavelength regions. The development of such a computational tool can
aid the preparation of optical sensors prior to fabrication, by preselecting
desired the optical properties of the resonator.Comment: Approved version for SPIE Photonics West, LASE, Laser Resonators,
Microresonators and Beam Control XV
Method for predicting whispering gallery mode spectra of spherical microresonators
A full three-dimensional Finite-Difference Time-Domain (FDTD)-based toolkit
is developed to simulate the whispering gallery modes of a microsphere in the
vicinity of a dipole source. This provides a guide for experiments that rely on
efficient coupling to the modes of microspheres. The resultant spectra are
compared to those of analytic models used in the field. In contrast to the
analytic models, the FDTD method is able to collect flux from a variety of
possible collection regions, such as a disk-shaped region. The customizability
of the technique allows one to consider a variety of mode excitation scenarios,
which are particularly useful for investigating novel properties of optical
resonators, and are valuable in assessing the viability of a resonator for
biosensing.Comment: Published 10 Apr 2015 in Opt. Express Vol. 23, Issue 8, pp.
9924-9937; The FDTD toolkit supercomputer scripts are hosted at:
http://sourceforge.net/projects/npps/files/FDTD_WGM_Simulator
What Has Carbamazepine Taught Crystal Engineers?
The antiepilepsy drug carbamazepine is one of the most studied pharmaceuticals in the world. The rich story of its solid forms, cocrystals, and formulation is a microcosm of the topical world of pharmaceutical materials. Understanding carbamazepine has required time, money, and dedication from numerous researchers and pharmaceutical companies worldwide. This wealth of knowledge provides the opportunity to reflect on progress within the crystal engineering field in general. This Perspective covers the extensive solid form landscape of carbamazepine and applies these examples to discuss and answer fundamental questions in the discipline. The story encompasses screening methods, computational solid form discovery, the power and influence of crystal engineering in understanding and controlling crystals and the amorphous state, and the environmental legacy of modern pharmaceuticals. This broad but in-depth analysis of carbamazepine is a vehicle into modern crystal engineering, not only in its own right but across the spectrum of organic materials science and pharmaceutical formulation. Discoveries of carbamazepine demonstrate the potential richness in the materials chemistry of every drug
Limitations of the heavy-baryon expansion as revealed by a pion-mass dispersion relation
The chiral expansion of nucleon properties such as mass, magnetic moment, and
magnetic polarizability are investigated in the framework of chiral
perturbation theory, with and without the heavy-baryon expansion. The analysis
makes use of a pion-mass dispersion relation, which is shown to hold in both
frameworks. The dispersion relation allows an ultraviolet cutoff to be
implemented without compromising the symmetries. After renormalization, the
leading-order heavy-baryon loops demonstrate a stronger dependence on the
cutoff scale, which results in weakened convergence of the expansion. This
conclusion is tested against the recent results of lattice quantum
chromodynamics simulations for nucleon mass and isovector magnetic moment. In
the case of the polarizability, the situation is even more dramatic as the
heavy-baryon expansion is unable to reproduce large soft contributions to this
quantity. Clearly, the heavy-baryon expansion is not suitable for every
quantity.Comment: Accepted for publication in EPJ C. Made changes based on referee
comments: clarifying sentences to conclusion 1. of Section IV, beginning of
Section V, and new footnote in Section VI, page 8. Added more detailed
explanation in paragraph 4 of Section III. Added citations of Phys.Rev. D60,
034014, and Phys.Lett. B716, 33
A wide scalar neutrino resonance and b\bar{b} production at LEP
In supersymmetric models with R-parity violation, scalar neutrinos may be
produced as s-channel resonances in e^+e^- colliders. We note that within
current constraints, the scalar neutrino may have a width of several GeV into
b\bar{b} and be produced with large cross section, leading to a novel
supersymmetry discovery signal at LEP II. In addition, if the scalar neutrino
mass approximately equals m_Z, such a resonance necessarily increases R_b and
reduces A_{FB}(b), significantly improving the fit to electroweak data. Bounds
from B meson and top quark decays are leading constraints, and we stress the
importance of future measurements.Comment: 8 pages. LaTex + RevTex. Revised to include a discussion of ISR
effects. Version to appear in Phys. Rev. Let
Medium-Ring Nitrogen Heterocycles through Migratory Ring Expansion of Metalated Ureas
Simple benzo-fused nitrogen heterocycles (indolines, tetrahydroquinolines, and their homologues) undergo migratory ring expansion through deprotonation of their benzylic urea derivatives with lithium diisopropylamide (LDA) in the presence of N,N′-dimethylpropylideneurea (DMPU). The products of the reactions are benzodiazepines, benzodiazocines, and their homologues, with ring sizes of 8–12. The reactions tolerate a range of substituent patterns and types, and may exhibit enantiospecificity or diastereoselectivity. Considerable complexity is rapidly generated in an efficient synthesis of these otherwise difficult-to-obtain medium-ring nitrogen heterocycles
Radical remodeling of the Y chromosome in a recent radiation of malaria mosquitoes
Y chromosomes control essential male functions in many species, including sex determination and fertility. However, because of obstacles posed by repeat-rich heterochromatin, knowledge of Y chromosome sequences is limited to a handful of model organisms, constraining our understanding of Y biology across the tree of life. Here, we leverage long single-molecule sequencing to determine the content and structure of the nonrecombining Y chromosome of the primary African malaria mosquito, Anopheles gambiae. We find that the An. gambiae Y consists almost entirely of a few massively amplified, tandemly arrayed repeats, some of which can recombine with similar repeats on the X chromosome. Sex-specific genome resequencing in a recent species radiation, the An. gambiae complex, revealed rapid sequence turnover within An. gambiae and among species. Exploiting 52 sex-specific An. gambiae RNA-Seq datasets representing all developmental stages, we identified a small repertoire of Y-linked genes that lack X gametologs and are not Y-linked in any other species except An. gambiae, with the notable exception of YG2, a candidate male-determining gene. YG2 is the only gene conserved and exclusive to the Y in all species examined, yet sequence similarity to YG2 is not detectable in the genome of a more distant mosquito relative, suggesting rapid evolution of Y chromosome genes in this highly dynamic genus of malaria vectors. The extensive characterization of the An. gambiae Y provides a long-awaited foundation for studying male mosquito biology, and will inform novel mosquito control strategies based on the manipulation of Y chromosomes
Updated Limits on TeV-Scale Gravity from Absence of Neutrino Cosmic Ray Showers Mediated by Black Holes
We revise existing limits on the D-dimensional Planck scale M_D from the
nonobservation of microscopic black holes produced by high energy cosmic
neutrinos in scenarios with D=4+n large extra dimensions. Previous studies have
neglected the energy radiated in gravitational waves by the multipole moments
of the incoming shock waves. We include the effects of energy loss, as well as
form factors for black hole production and recent null results from cosmic ray
detectors. For n>4, we obtain M_D > 1.0 - 1.4 TeV. These bounds are among the
most stringent and conservative to date.Comment: 11 pages, 4 figure
The Ensemble Photometric Variability of ~25000 Quasars in the Sloan Digital Sky Survey
Using a sample of over 25000 spectroscopically confirmed quasars from the
Sloan Digital Sky Survey, we show how quasar variability in the rest frame
optical/UV regime depends upon rest frame time lag, luminosity, rest
wavelength, redshift, the presence of radio and X-ray emission, and the
presence of broad absorption line systems. The time dependence of variability
(the structure function) is well-fit by a single power law on timescales from
days to years. There is an anti-correlation of variability amplitude with rest
wavelength, and quasars are systematically bluer when brighter at all
redshifts. There is a strong anti-correlation of variability with quasar
luminosity. There is also a significant positive correlation of variability
amplitude with redshift, indicating evolution of the quasar population or the
variability mechanism. We parameterize all of these relationships. Quasars with
RASS X-ray detections are significantly more variable (at optical/UV
wavelengths) than those without, and radio loud quasars are marginally more
variable than their radio weak counterparts. We find no significant difference
in the variability of quasars with and without broad absorption line troughs.
Models involving multiple discrete events or gravitational microlensing are
unlikely by themselves to account for the data. So-called accretion disk
instability models are promising, but more quantitative predictions are needed.Comment: 41 pages, 21 figures, AASTeX, Accepted for publication in Ap
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