8,348 research outputs found
Unemployment Insurance, Job Search, and Informal Employment
International audienceThis paper analyses the potential impacts of introducing unemployment insurance (UI) in middle income countries using the case of Malaysia, which today does not have such a system. The analysis is based on a job search model with unemployment and three employment sectors: formal and informal wage employment, and self employment. The parameters of the model are estimated to replicate the structure of the labor market in Malaysia in 2009 and the distribution of earnings for informal, formal and self employed workers. The results suggest that unemployment insurance would have only a modest negative effect on unemployment if benefits are not overly generous. The main effect would be a reallocation of labor from wage into self employment while increasing average wages in the formal and informal sectors
Physically founded phonon dispersions of few-layer materials, and the case of borophene
An increasing number of theoretical calculations on few-layer materials have
been reporting a non-zero sound velocity for all three acoustic phonon modes.
In contrast with these reports, here we show that the lowest phonon dispersion
branch of atomistically described few-layer materials should be quadratic, and
this can have dramatic consequencies on calculated properties, such as the
thermal conductivity. By reformulating the interatomic force constants (IFC) in
terms of internal coordinates, we find that a delicate balance between the IFCs
is responsible for this quadraticity. This balance is hard to obtain in
ab-initio calculations even if all the symmetries are numerically enforced a
posteriori, but it arises naturally in our approach. We demonstrate the
phenomenon in the case of borophene, where a very subtle correction to the
ab-initio IFCs yields the physically correct quadratic dispersion, while
leaving the rest of the spectrum virtually unmodified. Such quadraticity
nevertheless has a major effect on the computed lattice thermal conductivity,
which in the case of borophene changes by more than a factor 2, and reverses
its anisotropy, when the subtle IFC correction is put in place
Room-temperature exciton-polaritons with two-dimensional WS2
Two-dimensional transition metal dichalcogenides exhibit strong optical
transitions with significant potential for optoelectronic devices. In
particular they are suited for cavity quantum electrodynamics in which strong
coupling leads to polariton formation as a root to realisation of inversionless
lasing, polariton condensationand superfluidity. Demonstrations of such
strongly correlated phenomena to date have often relied on cryogenic
temperatures, high excitation densities and were frequently impaired by strong
material disorder. At room-temperature, experiments approaching the strong
coupling regime with transition metal dichalcogenides have been reported, but
well resolved exciton-polaritons have yet to be achieved. Here we report a
study of monolayer WS coupled to an open Fabry-Perot cavity at
room-temperature, in which polariton eigenstates are unambiguously displayed.
In-situ tunability of the cavity length results in a maximal Rabi splitting of
meV, exceeding the exciton linewidth. Our data
are well described by a transfer matrix model appropriate for the large
linewidth regime. This work provides a platform towards observing strongly
correlated polariton phenomena in compact photonic devices for ambient
temperature applications.Comment: 12 pages, 6 figure
A Submillimeter HCN Laser in IRC+10216
We report the detection of a strong submillimeter wavelength HCN laser line
at a frequency near 805 GHz toward the carbon star IRC+10216. This line, the
J=9-8 rotational transition within the (04(0)0) vibrationally excited state, is
one of a series of HCN laser lines that were first detected in the laboratory
in the early days of laser spectroscopy. Since its lower energy level is 4200 K
above the ground state, the laser emission must arise from the inner part of
IRC+10216's circumstellar envelope. To better characterize this environment, we
observed other, thermally emitting, vibrationally excited HCN lines and find
that they, like the laser line, arise in a region of temperature approximately
1000 K that is located within the dust formation radius; this conclusion is
supported by the linewidth of the laser. The (04(0)0), J=9-8 laser might be
chemically pumped and may be the only known laser (or maser) that is excited
both in the laboratory and in space by a similar mechanism.Comment: 11 pages, 3 figure
A Model-based Technique for Ad Hoc Correction of Instrumental Polarization in Solar Spectropolarimetry
We present a new approach for correcting instrumental polarization by
modeling the non-depolarizing effects of a complex series of optical elements
to determine physically realizable Mueller matrices. Provided that the Mueller
matrix of the optical system can be decomposed into a general elliptical
diattenuator and general elliptical retarder, it is possible to model the
cross-talk between both the polarized and unpolarized states of the Stokes
vector and then use the acquired science observations to determine the best-fit
free parameters. Here, we implement a minimization for solar
spectropolarimetric measurements containing photospheric spectral lines
sensitive to the Zeeman effect using physical constraints provided by polarized
line and continuum formation. This model-based approach is able to provide an
accurate correction even in the presence of large amounts of polarization
cross-talk and conserves the physically meaningful magnitude of the Stokes
vector, a significant improvement over previous ad hoc techniques.Comment: 16 pages, 4 figures, Accepted for publication in Ap
History of the Innovation of Damage Control for Management of Trauma Patients: 1902-2016
Objective: To review the history of the innovation of damage control (DC) for management of trauma patients. Background: DC is an important development in trauma care that provides a valuable case study in surgical innovation. Methods: We searched bibliographic databases (1950-2015), conference abstracts (2009-2013), Web sites, textbooks, and bibliographies for articles relating to trauma DC. The innovation of DC was then classified according to the Innovation, Development, Exploration, Assessment, and Long-term study model of surgical innovation. Results: The innovation\u27\u27 of DC originated from the use of therapeutic liver packing, a practice that had previously been abandoned after World War II because of adverse events. It then developed\u27\u27 into abbreviated laparotomy using rapid conservative operative techniques.\u27\u27 Subsequent exploration\u27\u27 resulted in the application of DC to increasingly complex abdominal injuries and thoracic, peripheral vascular, and orthopedic injuries. Increasing use of DC laparotomy was followed by growing reports of postinjury abdominal compartment syndrome and prophylactic use of the open abdomen to prevent intra-abdominal hypertension after DC laparotomy. By the year 2000, DC surgery had been widely adopted and was recommended for use in surgical journals, textbooks, and teaching courses ( assessment\u27\u27 stage of innovation). Long-term study\u27\u27 of DC is raising questions about whether the procedure should be used more selectively in the context of improving resuscitation practices. Conclusions: The history of the innovation of DC illustrates how a previously abandoned surgical technique was adapted and readopted in response to an increased understanding of trauma patient physiology and changing injury patterns and trauma resuscitation practices
Ultraluminous infrared galaxies: mergers of sub-L* galaxies?
A sample of 27 low-redshift, mostly cool, ultraluminous infrared galaxies (ULIRGs) has been imaged at 1.6 ÎŒm with the Hubble Space Telescope (HST) Near-Infrared Camera and Multi-Object Spectrometer (NICMOS). The majority (67%) of the sample's galaxies are multiple-nucleus galaxies with projected separations of up to 17 kpc, and the rest of the sample (33%) are single-nucleus galaxies, as determined by the NICMOS angular resolution limit. The average observed, integrated (host+nucleus) H magnitude of our HST H sample ULIRGs is -24.3, slightly above that of an L* galaxy (MH = -24.2), and 52% of the sample's galaxies have sub-L* luminosities. The ULIRGs in the HST H sample are not generated as a result of the merging of two luminous (i.e., â„L*) spiral galaxies. Instead, the interactions and mergers occur in general between two, or in some cases more, less massive sub-L* (0.3-0.5L*) galaxies.
Only one out of the 49 nuclei identified in the entire HST H sample has the properties of a bright quasar-like nucleus. On average, the brightest nuclei in the HST H sample galaxies (i.e., cool ULIRGs) are 1.2 mag fainter than warm ULIRGs and low-luminosity Bright Quasar Survey quasars (BQS QSOs) and 2.6 mag fainter than high-luminosity BQS QSOs. Since the progenitor galaxies involved in the merger are sub-L* galaxies, the mass of the central black hole in these ULIRGs would be only about (1-2) Ă 107 Mâ, if the bulge-to-black hole mass ratio of nearby galaxies holds for ULIRGs. The estimated mass of the central black hole is similar to that of nearby Seyfert 2 galaxies but at least 1 order of magnitude lower than the massive black holes thought to be located at the center of high-luminosity QSOs. Massive nuclear starbursts with constant star formation rates of 10-40 Mâ yr-1 could contribute significantly to the nuclear H-band flux and are consistent with the observed nuclear H-band magnitudes of the ULIRGs in the HST H sample. An evolutionary merging scenario is proposed for the generation of the different types of ULIRGs and QSOs on the basis of the masses of the progenitors involved in the merging process. According to this scenario, cool ULIRGs would be the end product of the merging of two or more low-mass (0.3L*-0.5L*) disk galaxies. Warm ULIRGs and low-luminosity QSOs would be generated by a merger involving intermediate-mass (0.5 L*) disk galaxies. Under this scenario, warm ULIRGs could still be the dust-enshrouded phases of UV-bright low-luminosity QSOs, but cool ULIRGs, which are most ULIRGs, would not evolve into QSOs
Strong exciton-photon coupling with colloidal nanoplatelets in an open microcavity
Colloidal semiconductor nanoplatelets exhibit quantum size effects due to
their thickness of only few monolayers, together with strong optical band-edge
transitions facilitated by large lateral extensions. In this article we
demonstrate room temperature strong coupling of the light and heavy hole
exciton transitions of CdSe nanoplatelets with the photonic modes of an open
planar microcavity. Vacuum Rabi splittings of meV and meV
are observed for the heavy and light hole excitons respectively, together with
a polariton-mediated hybridisation of both transitions. By measuring the
concentration of platelets in the film we compute the transition dipole moment
of a nanoplatelet exciton to be D. The large oscillator
strength and fluorescence quantum yield of semiconductor nanoplatelets provide
a perspective towards novel photonic devices, combining polaritonic and
spinoptronic effects.Comment: 9 pages, 4 figure
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