3,752 research outputs found

    Entry, Multinational Firms, and Exchange Rate Volatility

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    Recent discussions of exchange rate determination have emphasized the possible role of foreign direct investment in influencing exchange rate behavior. Yet, there are few existing models of multinational enterprises (MNEs) and endogenous exchange rates. This paper demonstrates that the entry decisions of MNEs can influence the volatility of the real exchange rate in countries were there are significant costs involved in maintaining production facilities, even when prices are perfectly flexible. For empirically plausible parameters, MNE activity can make the exchange rate much more volatile than relative consumption.exchange rate volatility, foreign direct investment, market entry

    Variability of Red Supergiants in M31 from the Palomar Transient Factory

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    Most massive stars end their lives as Red Supergiants (RSGs), a short-lived evolution phase when they are known to pulsate with varying amplitudes. The RSG period-luminosity (PL) relation has been measured in the Milky Way, the Magellanic Clouds and M33 for about 120 stars in total. Using over 1500 epochs of R-band monitoring from the Palomar Transient Factory (PTF) survey over a five-year period, we study the variability of 255 spectroscopically cataloged RSGs in M31. We find that all RGSs brighter than M_K~ -10 mag (log(L/L_sun)>4.8) are variable at dm_R>0.05 mag. Our period analysis finds 63 with significant pulsation periods. Using the periods found and the known values of M_K for these stars, we derive the RSG PL relation in M31 and show that it is consistent with those derived earlier in other galaxies of different metallicities. We also detect, for the first time, a sequence of likely first-overtone pulsations. Comparison to stellar evolution models from MESA confirms the first overtone hypothesis and indicates that the variable stars in this sample have 12 M_sun<M<24 M_sun. As these RSGs are the immediate progenitors to Type II-P core-collapse supernovae (SNe), we also explore the implication of their variability in the initial-mass estimates for SN progenitors based on archival images of the progenitors. We find that this effect is small compared to the present measurement errors.Comment: 17 pages, 10 figure

    The Outer Halo of the Milky Way as Probed by RR Lyr Variables from the Palomar Transient Facility

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    RR Lyr stars are ideal massless tracers that can be used to study the total mass and dark matter content of the outer halo of the Milky Way. This is because they are easy to find in the light curve databases of large stellar surveys and their distances can be determined with only knowledge of the light curve. We present here a sample of 112 RR Lyr beyond 50 kpc in the outer halo of the Milky Way, excluding the Sgr streams, for which we have obtained moderate resolution spectra with Deimos on the Keck 2 Telescope. Four of these have distances exceeding 100 kpc. These were selected from a much larger set of 447 candidate RR Lyr which were datamined using machine learning techniques applied to the light curves of variable stars in the Palomar Transient Facility database. The observed radial velocities taken at the phase of the variable corresponding to the time of observation were converted to systemic radial velocities in the Galactic standard of rest. From our sample of 112 RR Lyr we determine the radial velocity dispersion in the outer halo of the Milky Way to be ~90 km/s at 50 kpc falling to about 65 km/s near 100 kpc once a small number of major outliers are removed. With reasonable estimates of the completeness of our sample of 447 candidates and assuming a spherical halo, we find that the stellar density in the outer halo declines as the -4 power of r.Comment: Accepted for publication in the Ap

    Constrained Bimanual Planning with Analytic Inverse Kinematics

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    In order for a bimanual robot to manipulate an object that is held by both hands, it must construct motion plans such that the transformation between its end effectors remains fixed. This amounts to complicated nonlinear equality constraints in the configuration space, which are difficult for trajectory optimizers. In addition, the set of feasible configurations becomes a measure zero set, which presents a challenge to sampling-based motion planners. We leverage an analytic solution to the inverse kinematics problem to parametrize the configuration space, resulting in a lower-dimensional representation where the set of valid configurations has positive measure. We describe how to use this parametrization with existing algorithms for motion planning, including sampling-based approaches, trajectory optimizers, and techniques that plan through convex inner-approximations of collision-free space.Comment: Submitted to ICRA 2024. 8 pages, 5 figures. Interactive results available at https://cohnt.github.io/Bimanual-Web/index.htm

    Psychological distress in relation to site specific cancer mortality: pooling of unpublished data from 16 prospective cohort studies

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    OBJECTIVE:  To examine the role of psychological distress (anxiety and depression) as a potential predictor of site specific cancer mortality. DESIGN:  Pooling of individual participant data from 16 prospective cohort studies initiated 1994-2008. SETTING:  Nationally representative samples drawn from the health survey for England (13 studies) and the Scottish health survey (three studies). PARTICIPANTS:  163 363 men and women aged 16 or older at study induction, who were initially free of a cancer diagnosis, provided self reported psychological distress scores (based on the general health questionnaire, GHQ-12) and consented to health record linkage. MAIN OUTCOME MEASURE:  Vital status records used to ascertain death from 16 site specific malignancies; the three Scottish studies also had information on cancer registration (incidence). RESULTS:  The studies collectively contributed an average of 9.5 years of mortality surveillance during which there were 16 267 deaths (4353 from cancer). After adjustment for age, sex, education, socioeconomic status, body mass index (BMI), and smoking and alcohol intake, and with reverse causality (by left censoring) and missing data (by imputation) taken into account, relative to people in the least distressed group (GHQ-12 score 0-6), death rates in the most distressed group (score 7-12) were consistently raised for cancer of all sites combined (multivariable adjusted hazard ratio 1.32, 95% confidence interval 1.18 to 1.48) and cancers not related to smoking (1.45, 1.23 to 1.71), as well as carcinoma of the colorectum (1.84, 1.21 to 2.78), prostate (2.42, 1.29 to 4.54), pancreas (2.76, 1.47 to 5.19), oesophagus (2.59, 1.34 to 5.00), and for leukaemia (3.86, 1.42 to 10.5). Stepwise associations across the full range of distress scores were observed for colorectal and prostate cancer. CONCLUSION:  This study contributes to the growing evidence that psychological distress might have some predictive capacity for selected cancer presentations, in addition to other somatic diseases

    A New Large Super-Fast Rotator: (335433) 2005 UW163

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    Asteroids of size larger than 150 m generally do not have rotation periods smaller than 2.2 hours. This spin cutoff is believed to be due to the gravitationally bound rubble-pile structures of the asteroids. Rotation with periods exceeding this critical value will cause asteroid breakup. Up until now, only one object, 2001 OE84, has been found to be an exception to this spin cutoff. We report the discovery of a new super-fast rotator, (335433) 2005 UW163, spinning with a period of 1.290 hours and a lightcurve variation of r0.8r'\sim0.8 mag from the observations made at the P48 telescope and the P200 telescope of the Palomar Observatory. Its Hr=17.69±0.27H_{r'} = 17.69 \pm 0.27 mag and multi-band colors (i.e., gr=0.68±0.03g'-r' = 0.68\pm0.03 mag, ri=0.19±0.02r'-i' = 0.19\pm0.02 mag and SDSS iz=0.45i-z = -0.45 mag) show it is a V-type asteroid with a diameter of 0.6+0.3/0.20.6 +0.3/-0.2 km. This indicates (335433) 2005 UW163 is a super-fast rotator beyond the regime of the small monolithic asteroid.Comment: 18 pages, 4 figures, 1 table Accepted by ApJ

    An Energy-based Approach to Assess and Predict Erosive Airfoil Defouling

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    A dynamic indentation experiment is presented for assessment of the adhesive behavior of a range of coatings in erosive defouling of commercial aircraft engines using CO2 dry-ice. A series of experiments is presented in which particles made from a reference material (polyoxymethylene – POM) and from CO2 dry-ice are made to impact compressor airfoils under a range of impact angle and velocity conditions. The airfoils investigated are coated with an indicator material (PTFE), which is typically used to visualise the defouling effect in large scale compressor defouling experiments. In addition, fouled compressor airfoils taken from service and coated with a fouling typically found in low-pressure compressor stages are investigated. The energy required for the reference particles (POM) to create a defouling effect for the different coatings is determined by an experimental evaluation of their coefficient of restitution. This energy requirement is assumed to be fouling specific. Empirical defouling functions are presented. They correlate the defouling effect for both particle materials under various impact conditions. The empirical correlations are developed into a simulation procedure to predict particle impact erosion and energy dissipation of coated surfaces in numerical indentation simulations
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