College Risk and Return

Attending college is thought of as a very profitable investment decision, as its estimated annualized return ranges from 8% to 13%. However, a large fraction of high school graduates do not enroll in college. I reconcile the observed high average returns to schooling with relatively low attendance rates when considering college as a risky investment decision. A high dropout risk has two important effects on the estimated average returns to college: selection bias and risk premium. In order to explicitly consider the selection bias, I explore the dropout risk in a life-cycle model with heterogeneous ability. The risk-premium of college participation accounts for 21% of the excess returns to college education for highability students and 19% of the excess return for low-ability students. Risk averse agents are willing to reduce their return to college in order to avoid the dropout risk. The effect is not uniform across ability levels.

Risk Premium and Expectations in Higher Education

This paper takes the risk of college participation into context when evaluating the return to college education. College dropout and a higher permanent income shock for those who graduate from college accounts for 51% of the excess return to college education. Using a simple risk premium approach, I reconcile the observed high average returns to schooling with relatively low attendance rates. A high dropout risk has two important effects on the estimated average returns to college education: via selection bias and via risk premium.

Self – Employment, Labor Market Rigidities and Unemployment Over the Business Cycle

In a general equilibrium context, we analyze the impact of changes in institutional labor market conditions, such as access to financing and efficiency, on the composition of employment and unemployment, considering the nature of formal labor contracts and the entrepreneurial capacity of the labor force. We extend the Mortensen - Pissarides model to allow for two types of formal job contracts: temporary and permanent; and we also allow for self-employment. We show that labor market efficiency as well as access to selfemployment financing played a key role in the evolution of employment in Chile during the last 15 years. Additionally, and not surprisingly, tougher access to financing adversely affects self-employment

Accounting for Changes in College Attendance Profile: a Quantitative Life-Cycle Analysis

This paper analyzes changes in the distribution of college enrollment rates that occurred between 1980 and 2000. It aims not only to explain the 69% increase in the overall college enrollment, but also changes in the profile of college students in terms of their ability and financial status. College attendance increased by 27% less than average among individuals in the lowest quartile of the joint family income and ability distribution. However, it increased by 12% more than average for individuals in the highest quartile of the distribution. The increase in college enrollment was far from uniform and, to explain these changes, I construct a life-cycle heterogeneous agents model of labor supply and human capital formation. The model is calibrated to match schooling patterns and labor market outcomes for the 1979 and 1997 NLSY cohorts. I explicitly model and quantitatively estimate the effect of four potential driving forces to explain the observed changes: The increase in the college wage gap, the change in the allocation of grants and scholarships, the increase in educational costs, and the changes in the ability and family income distribution. Finally, I explore alternative educational policies and their effect on different population groups.

White Organic Light-Emitting Diodes with fine chromaticity tuning via ultrathin layer position shifting

Non-doped white organic light-emitting diodes using an ultrathin yellow-emitting layer of rubrene (5,6,11,12-tetraphenylnaphtacene) inserted on either side of the interface between a hole-transporting NPB (4,4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl) layer and a blue-emitting DPVBi (4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl) layer are described. Both the thickness and the position of the rubrene layer allow fine chromaticity tuning from deep-blue to pure-yellow via bright-white with CIE coordinates (x= 0.33, y= 0.32), a external quantum efficiency of 1.9%, and a color rendering index of 70. Such a structure also provides an accurate sensing tool to measure the exciton diffusion length in both DPVBi and NPB (8.7 and 4.9 nm respectively)

A very convenient setup to generate intense VUV coherent light at 125 nm with use of nonlinear effects in mercury vapor at room temperature

Using only one dye laser, efficient generation of VUV radiation (10^13 photons/pulse) is demonstrated at 125.140 nm and 125.053 nm by four-wave sum-frequency mixing in a room-temperature mercury vapor. The emission at 125.053 nm, which is out of two-photon resonance but near three-photon resonance, has been observed for the first time and is carefully analyzed. In particular, numerical calculations have been carried out for gaussian pump beams taking into account absorption of VUV photons and optical Kerr effect. The results of the calculations reproduce the VUV emission lineshape and power saturation effects measured in the experiment

Animals, Human Beings and Technologies: New Relations and New Interactions for Improved Efficiency

In this paper, we describe an approach to extend the classical human-machine, human-animal and animal-technologies relationship, with a triptych scheme with which one of the three components provide added value to the relation between the two others. We give an example where the technology provides added value to the blind person – guide dog relationship. The objective is to reassure the blind person through a system that enables them to localise the dog and to be sure that the distance between the dog and its master is relevant depending on the place, time of the day and density of people in the immediate environment. Measurement of the ambient noise, natural communication through embedded microphone and loudspeakers, GPS localisation chips, and mobile communication equip both the user’s interface and the dog’s collar to implement the functionalities

Enhanced production of coherent pulsed radiation at 125 nm: the route towards a tabletop VUV laser

A novel approach is used to enhance by nearly two orders of magnitude the conversion efficiency of a 125 nm-coherent source, based on four-wave mixing in room-temperature mercury vapor. Saturation issues are observed and discussed