Safety valve or sinkhole? Vocational schooling in South Africa

As an alternative to traditional academic schooling, vocational schooling in South Africa may serve as a safety valve for students encountering difficulty in the transition from school to work. Yet if ineffective, vocational schooling could also be a sinkhole, offering little chance for success on the labor market. After defining the terms safety valve and sinkhole in a model of human capital investment with multiple schooling types, I test for evidence of these characteristics using a panel of urban youth in South Africa. I find support for the safety valve role of vocational schooling, with a small increase in vocational enrollment in response to grade failure, compared to a decline of 38 percentage points for academic enrollment. In contrast, I find no evidence that vocational schooling is a sinkhole, with wage and employment returns at least as large as those for academic schooling. The results suggest that vocational schooling plays an important role in easing difficult school to work transitions for South African youth

Storing images in warm atomic vapor

Reversible and coherent storage of light in atomic medium is a key-stone of future quantum information applications. In this work, arbitrary two-dimensional images are slowed and stored in warm atomic vapor for up to 30 $\mu$s, utilizing electromagnetically induced transparency. Both the intensity and the phase patterns of the optical field are maintained. The main limitation on the storage resolution and duration is found to be the diffusion of atoms. A techniqueanalogous to phase-shift lithography is employed to diminish the effect of diffusion on the visibility of the reconstructed image

Safety valve or sinkhole? Vocational schooling in South Africa

As an alternative to traditional academic schooling, vocational schooling in South Africa may serve as a safety valve for students encountering difficulty in the transition from school to work. Yet if ineffective, vocational schooling could also be a sinkhole, offering little chance for success on the labor market. After defining the terms "safety valve" and "sinkhole" in a model of human capital investment with multiple schooling types, I test for evidence of these characteristics using a panel of urban youth in South Africa. I find support for the safety valve role of vocational schooling, with a 1 percentage point decrease in vocational enrollment in response to grade failure, compared to a decline of 40 percentage points for academic enrollment. In contrast, I fail to find evidence that vocational schooling is a sinkhole, with wage and employment returns at least as large as those for academic schooling. The results suggest that vocational schooling plays an important role in easing difficult school to work transitions for South African youth

Is teacher certification an effective tool for developing countries?

Teachers are perhaps the most important determinant of education quality. But what makes a teacher effective? Developing countries expend substantial resources on certifying teachers and retaining those who become certified; moreover, policymakers and aid donors prioritize increasing the prevalence of certified teachers. Yet there is little evidence that certification improves student outcomes. In fact, augmenting a school's teaching corps with contract teachers hired outside the civil service and without formal qualifications may be more effective in boosting student performance

Universal Spectra of Coherent Atoms in a Recurrent Random Walk

The probability of a random walker to return to its starting point in dimensions one and two is unity, a theorem first proven by G. Polya. The recurrence probability -- the probability to be found at the origin at a time t, is a power law with a critical exponent d/2 in dimensions d=1,2. We report an experiment that directly measures the Laplace transform of the recurrence probability in one dimension using Electromagnetically Induced Transparency (EIT) of coherent atoms diffusing in a vapor-cell filled with buffer gas. We find a regime where the limiting form of the complex EIT spectrum is universal and only depends on the effective dimensionality in which the random recurrence takes place. In an effective one-dimensional diffusion setting, the measured spectrum exhibits power law dependence over two decades in the frequency domain with a critical exponent of 0.56 close to the expected value 0.5. Possible extensions to more elaborate diffusion schemes are briefly discussed.Comment: 5 pages, 3 figure