336 research outputs found
Does input trade liberalization boost downstream firms’ exports? Theory and firm-level evidence
We analyze the impact of input tariffs on the export status and export performance of heterogeneous processing firms. Using a theoretical model with downstream firms exhibiting different levels of productivity, we show that lower input tariffs may increase the export sales of high-productivity firms at the expense of low-productivity firms and may decrease the probability of firms entering foreign markets. We compare the predictions of the theoretical model with firm-level data from the French agrifood sector by developing a two-stage estimation procedure that uses an equation for selection into export markets in the first stage and an exports equation in the second stage. The liberalization of agricultural trade appears to favor the reallocation of market share from low- to high-productivity agrifood firms. In addition, our results suggest that, whether lower input tariffs increase total exports sales (and jobs), a large fraction of the least productive exporting firms may lose from an additional decrease in agricultural input tariffs
Limits on Low Energy Photon-Photon Scattering from an Experiment on Magnetic Vacuum Birefringence
Experimental bounds on induced vacuum magnetic birefringence can be used to
improve present photon-photon scattering limits in the electronvolt energy
range. Measurements with the PVLAS apparatus (E. Zavattini {\it et al.}, Phys.
Rev. D {\bf77} (2008) 032006) at both nm and 532 nm lead to
bounds on the parameter {\it A}, describing non linear effects in QED, of
T @ 1064 nm and T @ 532 nm, respectively, at 95% confidence level,
compared to the predicted value of T. The
total photon-photon scattering cross section may also be expressed in terms of
, setting bounds for unpolarized light of m and m. Compared to the expected QED scattering cross
section these results are a factor of higher and represent
an improvement of a factor about 500 on previous bounds based on ellipticity
measurements and of a factor of about on bounds based on direct
stimulated scattering measurements
New PVLAS results and limits on magnetically induced optical rotation and ellipticity in vacuum
IIn 2006 the PVLAS collaboration reported the observation of an optical
rotation generated in vacuum by a magnetic field. To further check against
possible instrumental artifacts several upgrades to the PVLAS apparatus have
been made during the last year. Two data taking runs, at the wavelength of 1064
nm, have been performed in the new configuration with magnetic field strengths
of 2.3 T and 5 T. The 2.3 T field value was chosen in order to avoid stray
fields. The new observations do not show the presence of a rotation signal down
to the levels of rad at 5 T and rad at
2.3 T (at 95% c.l.) with 45000 passes in the magnetic field zone. In the same
conditions no ellipticity signal was detected down to at 2.3
T (at 95% c.l.), whereas at 5 T a signal is still present. The physical nature
of this ellipticity as due to an effect depending on can be excluded by
the measurement at 2.3 T. These new results completely exclude the previously
published magnetically induced vacuum dichroism results, indicating that they
were instrumental artifacts. These new results therefore also exclude the
particle interpretation of the previous PVLAS results as due to a spin zero
boson. The background ellipticity at 2.3 T can be used to determine a new limit
on the total photon-photon scattering cross section of barn at 95% c.l..Comment: 25 pages, 7 figures Main changes rel. to v.2: minor changes to
abstract, replaced Figures 4,5,6, corrected typographical errors. Paper
submitted to Physical Review
requirements for naive CD4+ T cell stimulation
Human primary dendritic cells (DCs) are heterogeneous by phenotype, function,
and tissue localization and distinct from inflammatory monocyte-derived DCs.
Current information regarding the susceptibility and functional role of
primary human DC subsets to Mycobacterium tuberculosis (Mtb) infection is
limited. Here, we dissect the response of different primary DC subsets to Mtb
infection. Myeloid CD11c+ cells and pDCs (C-type lectin 4C+ cells) were
located in human lymph nodes (LNs) of tuberculosis (TB) patients by
histochemistry. Rare CD141hi DCs (C-type lectin 9A+ cells) were also
identified. Infection with live Mtb revealed a higher responsiveness of
myeloid CD1c+ DCs compared to CD141hi DCs and pDCs. CD1c+ DCs produced
interleukin (IL)-6, tumor necrosis factor α, and IL-1β but not IL-12p70, a
cytokine important for Th1 activation and host defenses against Mtb. Yet,
CD1c+ DCs were able to activate autologous naïve CD4+ T cells. By combining
cell purification with fluorescence-activated cell sorting and gene expression
profiling on rare cell populations, we detected in responding CD4+ T cells,
genes related to effector-cytolytic functions and transcription factors
associated with Th1, Th17, and Treg polarization, suggesting multifunctional
properties in our experimental conditions. Finally, immunohistologic analyses
revealed contact between CD11c+ cells and pDCs in LNs of TB patients and in
vitro data suggest that cooperation between Mtb-infected CD1c+ DCs and pDCs
favors stimulation of CD4+ T cells
Ecdysone-based system for controlled inducible expression of metabotropic glutamate receptor subtypes 2, 5 and 8
Advanced Differentiated Thyroid Cancer. A Complex Condition Needing a Tailored Approach
Differentiated thyroid cancers (DTCs) are slow-growing malignant tumours, including papillary and follicular carcinomas. Overall, prognosis is good, although it tends to worsen when local invasion occurs with bulky cervical nodes, or in the case of distant metastases. Surgery represents the main treatment for DTCs. However, radical excision is challenging and significant morbidity and functional loss can follow the treatment of the more advanced forms. Literature on advanced thyroid tumours, both differentiated and undifferentiated, does not provide clear and specific guidelines. This emerges the need for a tailored and multidisciplinary approach. In the present study, we report our single-centre experience of 111 advanced (local, regional, and distant) DTCs, investigating the rate of radical excision, peri-procedural and post-procedural complications, quality of life, persistence, recurrence rates, and survival rates. Results are critically appraised and compared to the existing published evidence review
Comparison of the LUNA 3He(alpha,gamma)7Be activation results with earlier measurements and model calculations
Recently, the LUNA collaboration has carried out a high precision measurement
on the 3He(alpha,gamma)7Be reaction cross section with both activation and
on-line gamma-detection methods at unprecedented low energies. In this paper
the results obtained with the activation method are summarized. The results are
compared with previous activation experiments and the zero energy extrapolated
astrophysical S factor is determined using different theoretical models.Comment: Accepted for publication in Journal of Physics
Activation measurement of the 3He(alpha,gamma)7Be cross section at low energy
The nuclear physics input from the 3He(alpha,gamma)7Be cross section is a
major uncertainty in the fluxes of 7Be and 8B neutrinos from the Sun predicted
by solar models and in the 7Li abundance obtained in big-bang nucleosynthesis
calculations. The present work reports on a new precision experiment using the
activation technique at energies directly relevant to big-bang nucleosynthesis.
Previously such low energies had been reached experimentally only by the
prompt-gamma technique and with inferior precision. Using a windowless gas
target, high beam intensity and low background gamma-counting facilities, the
3He(alpha,gamma)7Be cross section has been determined at 127, 148 and 169 keV
center-of-mass energy with a total uncertainty of 4%. The sources of systematic
uncertainty are discussed in detail. The present data can be used in big-bang
nucleosynthesis calculations and to constrain the extrapolation of the
3He(alpha,gamma)7Be astrophysical S-factor to solar energies
The 3He(alpha,gamma)7Be S-factor at solar energies: the prompt gamma experiment at LUNA
The 3He(alpha,gamma)7Be process is a key reaction in both Big-Bang
nucleosynthesis and p-p chain of Hydrogen Burning in Stars. A new measurement
of the 3He(alpha,gamma)7Be cross section has been performed at the INFN Gran
Sasso underground laboratory by both the activation and the prompt gamma
detection methods. The present work reports full details of the prompt gamma
detection experiment, focusing on the determination of the systematic
uncertainty. The final data, including activation measurements at LUNA, are
compared with the results of the last generation experiments and two different
theoretical models are used to obtain the S-factor at solar energies.Comment: Accepted for publication in Nucl. Phys.
- …