Tacit Collusion in the Presence of Cyclical Demand and Endogenous Capacity Levels

We analyze tacit collusion in an industry characterized by cyclical demand and long-run scale decisions; firms face deterministic demand cycles and choose capacity levels prior to competing in prices. Our focus is on the nature of prices. We find that two types of price wars may exist. In one, collusion can involve periods of mixed strategy price wars. In the other, consistent with the Rotemberg and Saloner (1986) definition of price wars, we show that collusive prices can also become countercyclical. We also establish pricing patterns with respect to the relative prices in booms and recessions. If the marginal cost of capacity is high enough, holding current demand constant, prices in the boom will be generally lower than the prices in the recession; this reverses the results of Haltiwanger and Harrington (1991). In contrast, if the marginal cost of capacity is low enough, then prices in the boom will be generally higher than the prices in the recession. For costs in an intermediate range, numerical examples are calculated to show specific pricing patterns.

Polar features in the flagellar propulsion of E. coli bacteria

E. coli bacteria swim following a run and tumble pattern. In the run state all flagella join in a single helical bundle that propels the cell body along approximately straight paths. When one or more flagellar motors reverse direction the bundle unwinds and the cell randomizes its orientation. This basic picture represents an idealization of a much more complex dynamical problem. Although it has been shown that bundle formation can occur at either pole of the cell, it is still unclear whether this two run states correspond to asymmetric propulsion features. Using holographic microscopy we record the 3D motions of individual bacteria swimming in optical traps. We find that most cells possess two run states characterised by different propulsion forces, total torque and bundle conformations. We analyse the statistical properties of bundle reversal and compare the hydrodynamic features of forward and backward running states. Our method is naturally multi-particle and opens up the way towards controlled hydrodynamic studies of interacting swimming cells

An inexpensive and continuous radon progeny detector for indoor air-quality monitoring

A silicon photodiode-based inexpensive detector working as a counter and spectrometer for alpha particles has been conceived, designed, constructed and analyzed in depth. Monte Carlo simulations by means of MCNPX ver. 2.7.0 code have been carried out to select the most suitable sensitive element for the intended applications. The detecting unit has been coupled to an Arduino board and tested for low-rate alpha-particle counting and spectroscopy. Results demonstrate a maximum count rate of 4000 s-1, an energy resolution corresponding to a full width at half maximum of 160 keV over the entire energy range of measured alpha (namely 4 ÷ 6.5 MeV), and the sensitive element’s intrinsic efficiency of about 100%. Being the detector capable of distinguishing alpha energy associated to decays of radon daughters, its applications include 222Rn progeny monitoring. The air sampling system has been realized by a volumetric micro-pump forcing the air-flow through a millipore filter. By knowing the air-flow rate processed and the corresponding alpha energy spectrum measured, the concentrations of 218Po, 214Po and 210Po are determined. The potential alpha energy concentration-in-air is inferred, and effective dose evaluated. Calibration and testing measurements have been carried out by comparing the obtained results to the outputs of professional and expensive radon progeny monitor. The detector capability of “following” radon progeny concentration-in-air vs. time has been demonstrated. The device studied here can be configured as a prototype for an inexpensive radon progeny sensor to be potentially suitable for indoor air-monitoring in residential buildings, evaluating people’s exposures to radon and initiating corrective actions (e.g., mechanical ventilation) if necessary

Indoor radon survey in university buildings: a case study of Sapienza - University of Rome

The indoor radon concentration in underground workplaces pertaining to Sapienza – University of Rome have been monitored since the 90’s according to prescription of Italian Legislative Decree 230/95. In the last years, the recommendations contained in the Council Directive 2013/59/Euratom have shifted the focus to all indoor exposure situations by promoting actions to identify workplaces and dwellings with radon concentrations exceeding the reference level of 300 Bq/m3. In response to the upcoming transposition into national legislation, Sapienza has promoted the first Italian survey addressing workplaces in university buildings, regardless of the position with respect to the ground floor. The survey has interested more than three hundred workplaces, i.e. administration and professors’ offices, research and educational laboratories, conference rooms and classrooms, distributed in fifteen different buildings. Places monitored are strongly heterogeneous in terms of users’ habit, occupancy pattern and building characteristics. The influence of these parameters into seasonal variation have been addressed by organizing the survey in four quarters. The indoor radon concentration is measured by solid state nuclear track detectors, CR39. The aim of the paper is to present features, methods and intermediate results of the survey. The work, relying on the analysis of previous measurements interesting underground workplaces, focuses on methodology followed during all the preliminary and preparatory phases: active measurements by ionization chamber radon continuous monitor, radon progeny equilibrium factor estimations by radon daughters monitor, strategies for occupants’ awareness, positioning protocol and provisions to maximize representativity of results

Asserting State Sovereignty over National Communities of Islam in the United States and Britain: Sharia Courts as a Tool of Muslim Accomodation and Integration

This Note considers whether the United States should follow Britain‘s example by explicitly sanctioning sharia courts for private arbitrations. Moreover, it looks more broadly to the role, if any, that sharia law should have in domestic courts across the country. In doing so, it argues the United States should learn from Britain‘s example because, with proper procedural safeguards, parties could use sharia courts in limited circumstances as an effective tool in alternative dispute resolution. Perhaps more importantly, it further suggests that sharia courts could offer a useful mechanism for the United States to manage the challenges posed by transnational Islam

Artemether resistance in vitro is linked to mutations in PfATP6 that also interact with mutations in PfMDR1 in travellers returning with Plasmodium falciparum infections.

BACKGROUND: Monitoring resistance phenotypes for Plasmodium falciparum, using in vitro growth assays, and relating findings to parasite genotype has proved particularly challenging for the study of resistance to artemisinins. METHODS: Plasmodium falciparum isolates cultured from 28 returning travellers diagnosed with malaria were assessed for sensitivity to artemisinin, artemether, dihydroartemisinin and artesunate and findings related to mutations in pfatp6 and pfmdr1. RESULTS: Resistance to artemether in vitro was significantly associated with a pfatp6 haplotype encoding two amino acid substitutions (pfatp6 A623E and S769N; (mean IC50 (95% CI) values of 8.2 (5.7 - 10.7) for A623/S769 versus 623E/769 N 13.5 (9.8 - 17.3) nM with a mean increase of 65%; p = 0.012). Increased copy number of pfmdr1 was not itself associated with increased IC50 values for artemether, but when interactions between the pfatp6 haplotype and increased copy number of pfmdr1 were examined together, a highly significant association was noted with IC50 values for artemether (mean IC50 (95% CI) values of 8.7 (5.9 - 11.6) versus 16.3 (10.7 - 21.8) nM with a mean increase of 87%; p = 0.0068). Previously described SNPs in pfmdr1 are also associated with differences in sensitivity to some artemisinins. CONCLUSIONS: These findings were further explored in molecular modelling experiments that suggest mutations in pfatp6 are unlikely to affect differential binding of artemisinins at their proposed site, whereas there may be differences in such binding associated with mutations in pfmdr1. Implications for a hypothesis that artemisinin resistance may be exacerbated by interactions between PfATP6 and PfMDR1 and for epidemiological studies to monitor emerging resistance are discussed

Public Privacy Concerns of Operating Entities Use of Unmanned Aerial Systems

This study examined one-hundred and sixty five U.S. participants’ privacy levels of concerns towards eight different entities operating unmanned aerial systems (UAS). The participants were presented with an individual scenario that was interchanged with the eight operating entities. With each interchanged scenario the participants were asked to assess overall privacy concern based on the operating entity utilizing the UAS. The operating entities used in the scenario were Amazon, the Government, the Military, Law Enforcement, Consulting, Construction, Hobbyist, and Real Estate. The results demonstrate that there is a difference between operating entity and genders; however both genders trend toward the same level of concern based on the operating entity. The results and conclusions from this study can be used by Federal and State governments, as well as public and private entities for determination of regulations, policies, and uses of a UAS. Implications of these results are further discussed within the poster

Optical characterization of homogeneous and heterogeneous intralipid-based samples

Different scattering processes take place when photons propagate inside turbid media. Many powerful experimental techniques exploiting these processes have been developed and applied over the years in a large variety of situations from fundamental and applied research to industrial applications. In the present paper, we intend to take advantage of Static Light Scattering (SLS), Dynamic Light Scattering (DLS), and Time-Resolved Transmittance (TRT) for investigating all the different scattering regimes by using scattering suspensions in a very large range of scatterer concentrations. The suspensions were prepared using Intralipid 20%, a material largely employed in studies of the optical properties of turbid media, with concentrations from 10-5% to 50%. By the analysis of the angular and temporal dependence of the scattered light, a more reliable description of the scattering process occurring in these samples can be obtained. TRT measurements allowed us to obtain information on the reduced scattering coefficient, an important parameter largely used in the description of the optical properties of turbid media. TRT was also employed for the detection of inclusions embedded in Intralipid suspensions, by using a properly designed data analysis. The present study allowed us to better elucidate the dependence of scattering properties of Intralipid suspensions in a very large concentration range and the occurrence of the different scattering processes involved in the propagation of light in turbid media for the first time to our knowledge. In so doing, the complementary contribution of SLS, DLS, and TRT in the characterization of turbid media from an optical and structural point of view is strongly evidenced

Multiple crack propagation in friction stir welded aluminium joints

This paper is concerned with the simulation of crack propagation in friction stir welded butt joints, in order to assess the influence of process induced microstructural alterations and residual stresses on the fatigue behaviour of the assembly. The approach employed is based on the coupled use of the finite element method and the dual boundary element method in order to take advantage of the main capabilities of the two methods. The distribution of the process induced residual stresses has been mapped by means of the contour method. Then, the computed residual stresses field has been superimposed, in a dual boundary element environment, to the stress field as a result of a remote fatigue traction load and the crack growth is simulated. A two-parameter crack growth law, based on the evaluation of two thresholds, for the material being analysed, is used for the crack propagation rate assessment. The stress intensity factors are evaluated using the J-integral technique. Computational results have been compared with experimental data, provided from constant amplitude crack propagation tests on welded samples, showing the subdivision of the overall fatigue life in the two periods of crack initiation and crack propagation

Coupled FEM-DBEM Simulation of 3D Crack Growth under Fatigue Load Spectrum

Abstract Numerical predictions of fatigue crack growth under load spectrum are obtained by coupled FEM-DBEM approach. An initial part-through corner crack, in a pre-notched specimen undergoing a traction fatigue load, propagates becoming through the thickness. A two parameter crack growth law ("Unified Approach") is calibrated by in house made constant amplitude experimental tests and the crack growth retardation after an overload application is reproduced. The residual stresses responsible for such retardation are calculated by a sequence of elastic-plastic static FEM analysis; such stresses are then applied to the crack faces for the propagation simulation in a DBEM environment. A satisfactory agreement between numerical and experimental crack growth rates are displayed, for both part-through crack and through the thickness crack. This approach provide general modeling capabilities, with allowance for general crack front shape and fully automatic propagation