Can Racially Unbiased Police Perpetuate Long-Run Discrimination?

We develop a stylized dynamic model of highway policing in which a non-racist police officer is given incentives to arrest criminals, but faces a per stop cost of stop which increases when the racial mix of the persons he stops di.ers from the racial mix of the population.We define the fair jail rate to be when the racial composition of the jail population is identical to the racial composition of the criminal population.We study the long-term racial composition of the jail population when the policeman decides whom to stop based only on his last period successes in arresting criminals.The study of this "imperfect recall" case shows, consistent with empirical findings, that the long term racial jail rate is always greater than the fair one and the gap increases when incentives are made more powerful.We then study this rate when policemen are provided with data concerning conviction rates for each race, similar to the data which is now being collected in many states.In this case, we find that although the long term rate is still greater than the fair rate, it is smaller than that obtained in the imperfect recall case.We discuss the desirability of such data collection and dissemination of information among police officers.discrimination;dynamic models;incentives;population;crime

Chaotic Planning Solutions in the Textbook Model of Labor Market Search and Matching

This paper demonstrates that cyclical and chaotic planning solutions are possible in the standard textbook model of search and matching in labor markets. More specifically, it takes a discretetime adaptation of the continuous-time matching economy described in Pissarides (1990, 2001), and computes the solution to the dynamic planning problem.The solution is shown to be completely characterized by a first-order, non-linear map with a unique stationary solution.Additionally, the existence of a large number of periodic and even aperiodic non-stationary solutions is shown.Even when the well-known Li-Yorke and three-period cycle conditions for chaos are violated, we are able to verify the new Mitra (2001) su.cient condition for topological chaos.The implication is that even in a simple economy characterized by search and matching frictions, an omniscient social planner may have to contend with a fairly robust and bewildering variety of possible dynamic paths.labour market;planning;matching;chaos;job search

The Brewer-Dobson circulation in a changing climate : import of the model configuration

Most climate models simulate a strengthening of the Brewer-Dobson circulation (BDC) under a changing climate. However, the magnitude of the trend as well as the underlying mechanisms varies significantly among the models. In this work the impact of both vertical resolution and vertical extent of a model on the simulated BDC change is investigated by analyzing sensitivity simulations performed with the general circulation model ECHAM6 in three different model configurations for three different climate states. Tropical upwelling velocities and age of stratospheric air are used as measures for the strength of the BDC. Both consistently show a BDC strengthening from the preindustrial to the future climate state for all configurations of the model. However, the amplitude and origin of this change vary between the different setups. Analyses of the tropical upward mass flux indicate that in the model with a lid at 10 hPa the BDC strengthening at 70 hPa is primarily produced by resolved wave drag, while in the model with a higher lid (0.01 hPa) the parameterized wave drag yields the main contribution to the BDC increase. This implies that consistent changes in the BDC originate from different causes when the stratosphere is not sufficiently resolved in a model. Furthermore, the effect of enhancing the horizontal diffusion in the upper model layers to avoid resolved wave reflection at the model lid is quantified, and a possible link to the different behavior of the low-top model with regard to the origin of the BDC change is identified

Chaotic Planning Solutions in the Textbook Model of Labor Market Search and Matching

This paper demonstrates that cyclical and chaotic planning solutions are possible in the standard textbook model of search and matching in labor markets. More specifically, it takes a discretetime adaptation of the continuous-time matching economy described in Pissarides (1990, 2001), and computes the solution to the dynamic planning problem.The solution is shown to be completely characterized by a first-order, non-linear map with a unique stationary solution.Additionally, the existence of a large number of periodic and even aperiodic non-stationary solutions is shown.Even when the well-known Li-Yorke and three-period cycle conditions for chaos are violated, we are able to verify the new Mitra (2001) su.cient condition for topological chaos.The implication is that even in a simple economy characterized by search and matching frictions, an omniscient social planner may have to contend with a fairly robust and bewildering variety of possible dynamic paths

Vertical coupling of the middle atmosphere during stratospheric warming events

A 20 year simulation of the high-top atmospheric General Circulation Model (GCM) HAMMONIA is used to investigate internally produced Sudden Stratospheric Warmings (SSWs). We detect 19 major SSWs and evaluate the model results by comparison to the ERA40 reanalysis dataset. Composites are built to analyze the climatological characteristics of SSWs, in particular to investigate the mesospheric precursors and differences between vortex splits and displacements. The vertical coupling processes from the stratosphere to the lower thermosphere are studied using transformed Eulerian-mean (TEM) analysis and diagnostics concerning the role of gravity waves. Consistent to recent studies, we find a mesospheric cooling and a weaker thermospheric warming accompanying the SSW. The large anomalies in the zonal mean winds and temperatures are explained by the interactions of EP-Flux divergence, mean flow advection and parameterized momentum deposition of gravity waves. We present an algorithm, based on geopotential height, to classify the events. Nine SSWs can be characterized as vortex splits, 10 as displacements. The differences between the two types are statistically significant suggesting splits are associated with larger anomalies in temperature and zonal wind. Investigation of the longitudinal dependence of zonal winds demonstrates the asymmetry of the climatological winter and of single events. Therefore, we do not find a criterion to sufficiently detect SSWs using mesospheric winds prior to the central date

Evaluation of NMR-based strategies to differentiate fresh from frozen-thawed fish supported by multivariate data analysis

The differentiation of fresh and frozen-thawed fish is a relevant authenticity aspect as in the European Union fish holds a high statistical risk of being adulterated. Here, nuclear magnetic resonance spectroscopy (NMR) in combination with principal components analysis followed by linear discriminant analysis (PCA-LDA) was used for a non-targeted based differentiation of fresh from frozen-thawed fish. To identify the most promising NMR approach(es), six different approaches were applied to 96 fish samples (mackerel, trout, cod). These approaches included different sample preparation procedures and different NMR methods to investigate both the lipid fraction and the polar fraction of the fish samples. After cross-validation embedded in a Monte Carlo resampling design, six independent classification models were obtained. Evaluation of the multivariate data analysis revealed that the most promising approaches were the 1H NMR analysis of the lipid fraction (correct prediction of about 90.0%) and the $^1$H NMR based screening of minor components of the lipid fraction with a correct prediction of about 91.9%. $^1$H NMR analysis of the water extract of the fish samples showed a correct prediction of about 82.6%. Hence, a general differentiation of fresh from frozen-thawed fish via non-targeted NMR is feasible, even though the underlying sample batch contained different fish species. Additional fish samples need to be analyzed with the three most promising NMR approaches to further improve the developed classification models

Improved seasonal prediction of European summer temperatures with new five-layer soil-hydrology scheme

We evaluate the impact of a new 5-layer soil-hydrology scheme on seasonal hindcast skill of 2-meter temperatures over Europe obtained with the Max Planck Institute Earth System Model (MPI-ESM). Assimilation experiments from 1981 to 2010 and 10-member seasonal hindcasts initialized on 1 May each year are performed with MPI-ESM in two soil configurations, one using a bucket scheme and one a new 5-layer soil-hydrology scheme. We find the seasonal hindcast skill for European summer temperatures to improve with the 5-layer scheme compared to the bucket scheme, and investigate possible causes for these improvements. First, improved indirect soil moisture assimilation allows for enhanced soil moisture-temperature feedbacks in the hindcasts. Additionally, this leads to improved prediction of anomalies in the 500 hPa geopotential height surface, reflecting more realistic atmospheric circulation patterns over Europe

Does the food ingredient pectin provide a risk for patients allergic to non-specific lipid-transfer proteins?

Pectin, a dietary fiber, is a polysaccharide that is widely used in food industry as a gelling agent. In addition, prebiotic and beneficial immunomodulatory effects of pectin have been demonstrated, leading to increased importance as food supplement. However, as cases of anaphylactic reactions after consumption of pectin-supplemented foods have been reported, the present study aims to evaluate the allergy risk of pectin. This is of particular importance since most of the pectin used in the food industry is extracted from citrus or apple pomace. Both contain several allergens such as non-specific lipid transfer proteins (nsLTPs), known to induce severe allergic reactions, which could impair the use of pectins in nsLTP allergic patients. Therefore, the present study for the first time was performed to analyze residual nsLTP content in two commercial pectins using different detection methods. Results showed the analytical sensitivity was diminished by the pectin structure. Finally, spiking of pectin with allergenic peach nsLTP Pru p 3 led to the conclusion that the potential residual allergen content in both pectins is below the threshold to induce anaphylactic reactions in nsLTP-allergic patients. This data suggests that consumption of the investigated commercial pectin products provides no risk for inducing severe reactions in nsLTP-allergic patients