Chromatic contrast sensitivity: the role of absolute threshold and gain constant in differences between the fovea and the periphery

A model of foveal achromatic and chromatic sensitivity [Vision Res. 36, 1597 (1996)] was extended to the peripheral visual field. Threshold-versus-illuminance functions were analyzed to determine effects of eccentricity on absolute thresholds and gain constants of chromatic and luminance mechanisms. The resulting peripheral model successfully predicted peripheral contrast sensitivity as a function of wavelength, for both white and 500-nm backgrounds. We conclude that the short-wavelength-sensitive cone opponent mechanism may mediate thresholds in Sloan's notch in the normal periphery and that interpretation of reduced chromatic sensitivity in the periphery requires an explicit model of how eccentricity affects both the gain constant and the absolute threshold.     

Pregnancy rates after timed AI of heifers following removal of intravaginal progesterone inserts

Reproductive performance of dairy heifers was compared for each of 2 synchronization protocols: The first group of 54 heifers was synchronized using intravaginal progesterone inserts (CIDR) plus estradiol cypionate (ECP) on d 0, PGF(2alpha) on d 7, and ECP again on d 8 (CIDR-ECP); a second group of 56 heifers was synchronized using CIDR and ECP on d 0, PGF(2alpha) on d 7, and GnRH on d 9 (CIDR-GnRH). All heifers received timed artificial insemination (TAI) at 48, 56, or 72 h after CIDR removal on d 7. Pregnancy diagnosis was conducted by ultrasonography 32 +/- 1 d post AI to confirm pregnancy and at 60 +/- 1 d post AI to determine embryo survival. Ovaries were monitored by ultrasonography daily from d 0 to 7 and twice daily from d 8 to ovulation to examine emergence of a new wave of follicles, size of the ovulatory follicle, and timing of ovulation on 15 heifers per protocol. New follicular development was detected 3.7 +/- 0.2 d after CIDR insertion. Heifers receiving CIDR-ECP had a shorter interval from CIDR removal to ovulation than heifers receiving CIDR-GnRH (63.8 +/- 3.0 vs. 71.6 +/- 2.3 h, respectively); however, ovulation occurred 39.8 +/- 3.0 h after ECP or 23.6 +/- 2.3 h after GnRH. Diameters of ovulatory follicles did not differ between treatments. Overall pregnancy rate for synchronized heifers was 60.1%, and embryo survival was 98%. Pregnancy rate for heifers synchronized with CIDR-ECP was 63.0% and similar to that in heifers synchronized with CIDR-GnRH (57.1%). Pregnancy rate was affected by time of AI for heifers synchronized using CIDR-ECP but not for those synchronized with CIDR-GnRH. Heifers in the CIDR-ECP group that were inseminated 56 h after CIDR removal had a higher pregnancy rate (81.0%) compared with heifers inseminated 48 (66.7%) or 72 h (50.0%) after CIDR removal. Either ECP or GnRH used in a CIDR-based TAI program in dairy heifers can achieve acceptable reproductive performance.     

Pattern synthesis for antennas with multiple primary beams by minimax optimisation

Increasingly stringent requirements are evolving for selective illumination of irregularly shaped geographical areas by communication-satellite antennas. The desirability of minimising spillover illumination near borders, and the technical requirement to conserve transmitter power, constrains the shape of the main beam of the antenna and the sidelobe levels. We describe a minimax optimisation algorithm for designing the required shaped-beam antennas. A 1-dimensional example is given to demonstrate the features of the method.     

Rapeseed meal and egg taint: The role of sinapine

Neither the administration of sinapine bisulphate in the diet, nor the repeated intramuscular or intravenous injection of large doses of this substance, reduced the ability of chicks or laying hens to oxidise trimethylamine (TMA), as measured by the activity of TMA oxidase in hepatic microsomes or the amounts of ¹⁴C-TMA oxide that appeared in the plasma after the infusion of a standard dose of ¹⁴C-TMA. Thus, in contrast to its behaviour in vitro, sinapine did not produce significant inhibition of TMA oxidase under these conditions. Since the amount included in the diet was similar to that which would be provided by a diet containing 10% rapeseed meal, it was concluded that sinapine is not involved in the depression of TMA oxidation that occurs when the meal is fed and acts solely as a source of TMA in the consequent production of egg taint.     

Nonlinear discrete-time models: state-space vs. I/O representations

This paper compares state-space and input–output realizations for nonlinear discrete-time dynamic models. For linear models, these two realizations are essentially equivalent and their structures are closely related, but these statements do not hold for nonlinear models. We illustrate this point with simple, realistic examples for which only one of the two realizations exists or for which both exist but their structures are profoundly different. Overall, the main point of this paper is the importance of the choice of realization in the development of nonlinear dynamic models.     

The attraction of contributors in free and open source software projects

As firms increasingly sanction an open sourcing strategy, the question of which open source project to undertake remains tentative. The lack of established metrics makes it difficult to formulate such strategy. While many projects have been formed and created, only a few managed to remain active. With the majority of these projects failing, firms need a reliable set of criteria to assess what makes a project appealing not only to developers but also to visitors, users and commercial sponsors. In this paper, we develop a theoretical model to explore the contextual and causal factors of project attractiveness in inducing activities such as source code contribution, software maintenance, and usage. We test our model with data derived from more than 4000 projects spanning 4 years. Our main findings include that projects’ set of conditions such as license restrictiveness and their available resources provide the context that directly influence the amount of work activities observed in the projects. It was also found that indirect and unintended contributions such as recommending software, despite of being non-technical, cannot be ignored for project activeness, diffusion and sustainability. Finally, our analysis provide evidence that higher attractiveness leads to more code-related activities with the downside of slowing down responsiveness to address projects’ tasks, such as the implementation of new features and bug fixes. Our model underscores the significance of the reinforcing effects of attractiveness and work activities in open source projects, giving us the opportunity to discuss strategies to manage common traps such as the liability of newness. We conclude by discussing the applicability of the research model to other user-led initiatives.     

Effect of salt on oxidative changes in pre- and post-rigor ground beef

Pre- and post-rigor beef was ground and salt was added to give 0·0, 0·5, 2·0 and 4·0% NaCl (w/w). Samples were removed after 0, 24, 48, 72 and 96 h at 4°C and analyzed for pH, TBA numbers and percentages of reduced myoglobin (Mb), metmyoglobin (MMb) and oxymyoglobin (MbO(2)). After holding for 96 h the samples were cooked in a boiling water bath to an internal temperature of 80°C and held at 4°C for 48 h before TBA analysis. Pre-rigor grinding and salting reduced the post-mortem pH decline and the extent of meat discoloration as shown by the differences in the amount of MMb. The extent of lipid oxidation as measured by TBA numbers was not significantly different for the pre- and post-rigor ground salted meat samples, although salt accelerated oxidation during storage. Results demonstrated that pre-rigor grinding and salting of beef produces a more stable bright red color, which appears to be associated with a lower percentage of MMb and a higher ultimate pH in the pre-rigor salted meat.     

Structural elucidation of direct analysis in real time ionized nerve agent simulants with infrared multiple photon dissociation spectroscopy

Infrared multiple photon dissociation (IRMPD) was used to generate vibrational spectra of ions produced with a direct analysis in real time (DART) ionization source coupled to a 4.7 T Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. The location of protonation on the nerve agent simulants diisopropyl methylphosphonate (DIMP) and dimethyl methylphosphonate (DMMP) was studied while solutions of the compounds were introduced for extended periods of time with a syringe pump. Theoretical vibrational spectra were generated with density functional theory calculations. Visual comparison of experimental mid-IR IRMPD spectra and theoretical spectra could not establish definitively if a single structure or a mixture of conformations was present for the protonated parent of each compound. However, theoretical calculations, near-ir IRMPD spectra, and frequency-to-frequency and statistical comparisons indicated that the protonation site for both DIMP and DMMP was predominantly, if not exclusively, the phosphonyl oxygen instead of one of the oxygen atoms with only single bonds.