The Role of Expectation in Job Search and Firm Size Effect on Wages

One of the most puzzling facts in economics is the firm size-wage effect. After controlling for the observable characteristics of workers (age, gender, education, residence etc.), firms (industry, occupation, work conditions etc.) and negotiation effect (unionization), one still finds that the sheer size of a firm increases the wage, contrary to the one-good one-price doctrine. We provide a simple dynamic game model of wage determination to give a new rationale to the firm size-wage effect. We think that the wages are not market clearing prices but strategies by firms. Firms choose wages to control workers' search behavior. The essential feature of the model is that a large firm's history of wages is observable to all the current and future workers, while a small firm is not visible and only its current offer is observable. Therefore a small firm is expected to be a myopic low-wage payer, and its workers search and quit often. A large firm can prevent search if it maintained a high wage throughout the past, thus making workers expect high future wages. In this way, the firm size determines the worker expectations of its future wages, which changes the quit rate and equilibrium wages. To give additional support to our theoretical result, we test a new aspect of firm size-wage effect. Since the effect on wage levels are extensively studied, we derive two main hypotheses on wage gains after job changes. (H1) The proportion of firms that are larger than the previous employer increases the wage gain. (H2) The size of the previous employer decreases the wage gain. The firm size distribution effect (H1) is a new test. We obtain supports for both. Thus we conclude that the wages are strategies and affected by how workers utilize the firm size information in changing jobs. (297 words.)

Long-term observations of Uranus and Neptune at 90 GHz with the IRAM 30m telescope - (1985 -- 2005)

The planets Uranus and Neptune with small apparent diameters are primary calibration standards. We investigate their variability at ~90 GHz using archived data taken at the IRAM 30m telescope during the 20 years period 1985 to 2005. We calibrate the planetary observations against non-variable secondary standards (NGC7027, NGC7538, W3OH, K3-50A) observed almost simultaneously. Between 1985 and 2005, the viewing angle of Uranus changed from south-pole to equatorial. We find that the disk brightness temperature declines by almost 10% (~2sigma) over this time span indicating that the south-pole region is significantly brighter than average. Our finding is consistent with recent long-term radio observations at 8.6 GHz by Klein & Hofstadter (2006). Both data sets do moreover show a rapid decrease of the Uranus brightness temperature during the year 1993, indicating a temporal, planetary scale change. We do not find indications for a variation of Neptune's brightness temperature at the 8% level. If Uranus is to be used as calibration source, and if accuracies better than 10% are required, the Uranus sub-earth point latitude needs to be taken into account.Comment: accepted for publication in A&

Inorganic separator for a high temperature silver-zinc battery

Electrode design, inorganic separators, and performance tests of multiplate five ampere-hour silver-zinc battery cel

350 Micron Observations of Ultraluminous Infrared Galaxies at Intermediate Redshifts

We present 350micron observations of 36 ultraluminous infrared galaxies (ULIRGs) at intermediate redshifts (0.089 <= z <= 0.926) using the Submillimeter High Angular Resolution Camera II (SHARC-II) on the Caltech Submillimeter Observatory (CSO). In total, 28 sources are detected at S/N >= 3, providing the first flux measurements longward of 100micron for a statistically significant sample of ULIRGs in the redshift range of 0.1 < z < 1.0. Combining our 350micron flux measurements with the existing IRAS 60 and 100micron data, we fit a single-temperature model to the spectral energy distribution (SED), and thereby estimate dust temperatures and far-IR luminosities. Assuming an emissivity index of beta = 1.5, we find a median dust temperature and far-IR luminosity of Td = 42.8+-7.1K and log(Lfir/Lsolar) = 12.2+-0.5, respectively. The far-IR/radio correlation observed in local star-forming galaxies is found to hold for ULIRGs in the redshift range 0.1 < z < 0.5, suggesting that the dust in these sources is predominantly heated by starbursts. We compare the far-IR luminosities and dust temperatures derived for dusty galaxy samples at low and high redshifts with our sample of ULIRGs at intermediate redshift. A general Lfir-Td relation is observed, albeit with significant scatter, due to differing selection effects and variations in dust mass and grain properties. The relatively high dust temperatures observed for our sample compared to that of high-z submillimeter-selected starbursts with similar far-IR luminosities suggest that the dominant star formation in ULIRGs at moderate redshifts takes place on smaller spatial scales than at higher redshifts.Comment: (24 pages in preprint format, 1 table, 7 figures, accepted for publication in ApJ

CI emission in Ultra Luminous Infrared Galaxies as a molecular gas mass tracer

We present new sensitive wide-band measurements of the fine structure line 3^P_1 -> 3^P_0 (J=1-0, 492GHz) of neutral atomic carbon (CI) in the two typical Ultra Luminous Infrared Galaxies NGC6240 and Arp220. We then use them along with several other CI measurements in similar objects found in the literature to estimate their global molecular gas content under the assumption of a full CI-H_2 concomitance. We find excellent agreement between the H_2 gas mass estimated with this method and the standard methods using 12^CO. This may provide a new way to measure H_2 gas mass in galaxies, and one which may be very valuable in ULIRGs since in such systems the bright 12^CO emission is known to systematically overestimate the gas mass while their 13^CO emission is usually very weak. At redshifts z>=1 the CI J=1-0 line shifts to much more favorable atmospheric windows and can become a viable alternative tracer of the H_2 gas fueling starburst events in the distant Universe.Comment: 11 pages, 2 figures. Accepted for publication in ApJ Letter

An assessment of key model parametric uncertainties in projections of Greenland Ice Sheet behavior

Lack of knowledge about the values of ice sheet model input parameters introduces substantial uncertainty into projections of Greenland Ice Sheet contributions to future sea level rise. Computer models of ice sheet behavior provide one of several means of estimating future sea level rise due to mass loss from ice sheets. Such models have many input parameters whose values are not well known. Recent studies have investigated the effects of these parameters on model output, but the range of potential future sea level increases due to model parametric uncertainty has not been characterized. Here, we demonstrate that this range is large, using a 100-member perturbed-physics ensemble with the SICOPOLIS ice sheet model. Each model run is spun up over 125 000 yr using geological forcings and subsequently driven into the future using an asymptotically increasing air temperature anomaly curve. All modeled ice sheets lose mass after 2005 AD. Parameters controlling surface melt dominate the model response to temperature change. After culling the ensemble to include only members that give reasonable ice volumes in 2005 AD, the range of projected sea level rise values in 2100 AD is ~40 % or more of the median. Data on past ice sheet behavior can help reduce this uncertainty, but none of our ensemble members produces a reasonable ice volume change during the mid-Holocene, relative to the present. This problem suggests that the model's exponential relation between temperature and precipitation does not hold during the Holocene, or that the central-Greenland temperature forcing curve used to drive the model is not representative of conditions around the ice margin at this time (among other possibilities). Our simulations also lack certain observed physical processes that may tend to enhance the real ice sheet's response. Regardless, this work has implications for other studies that use ice sheet models to project or hindcast the behavior of the Greenland Ice Sheet

Molecular gas in extreme star-forming environments: the starbursts Arp220 and NGC6240 as case studies

We report single-dish multi-transition measurements of the 12^CO, HCN, and HCO^+ molecular line emission as well as HNC J=1-0 and HNCO in the two ultraluminous infra-red galaxies Arp220 and NGC6240. Using this new molecular line inventory, in conjunction with existing data in the literature, we compiled the most extensive molecular line data sets to date for such galaxies. The many rotational transitions, with their different excitation requirements, allow the study of the molecular gas over a wide range of different densities and temperatures with significant redundancy, and thus allow good constraints on the properties of the dense gas in these two systems. The mass (~(1-2) x 10^10 Msun) of dense gas (>10^5-6 cm^-3) found accounts for the bulk of their molecular gas mass, and is consistent with most of their IR luminosities powered by intense star bursts while self-regulated by O,B star cluster radiative pressure onto the star-forming dense molecular gas. The highly excited HCN transitions trace a gas phase ~(10-100)x denser than that of the sub-thermally excited HCO^+ lines (for both galaxies). These two phases are consistent with an underlying density-size power law found for Galactic GMCs (but with a steeper exponent), with HCN lines tracing denser and more compact regions than HCO^+. Whether this is true in IR-luminous, star forming galaxies in general remains to be seen, and underlines the need for observations of molecular transitions with high critical densities for a sample of bright (U)LIRGs in the local Universe -- a task for which the HI-FI instrument on board Herschel is ideally suited to do.Comment: 38 pages (preprint ApJ style), 3 figures, accepted for Ap