Mandibular Gland Secretion of <Emphasis Type="Italic">Melipona beecheii</Emphasis>: Chemistry and Behavior

The mandibular gland secretion of Melipona beecheii contains a rich mixture of terpenoid and oxygenated compounds and unsaturated and saturated hydrocarbons. However, it differs markedly from the 11 other Brazilian species examined in previous studies, both by the absence of 2-heptanol and the presence of rose oxides. The most abundant compound was geranyl hexanoate, whereas the most volatile compounds were cis- and trans-rose oxide and geraniol. The complete blend and five individual components found in the gland secretion were tested by electroantennography (EAG) and behavioral assays. The complete mandibular gland extract and geraniol elicited the strongest EAG responses, whereas these and farnesyl acetate induced the strongest attack response from workers. The role of the rose oxides remains to be elucidated, as they do not appear to play a major role as an alarm pheromone of this species.     

Natural and hybrid bimanual interaction for virtual assembly tasks

This paper focuses on the simulation of bimanual assembly/disassembly operations for training or product design applications. Most assembly applications have been limited to simulate only unimanual tasks or bimanual tasks with one hand. However, recent research has introduced the use of two haptic devices for bimanual assembly. We propose a more natural and low-cost bimanual interaction than existing ones based on Markerless motion capture (Mocap) systems. Specifically, this paper presents two interactions based on a Markerless Mocap technology and one interaction based on combining Markerless Mocap technology with haptic technology. A set of experiments following a within-subjects design have been implemented to test the usability of the proposed interfaces. The Markerless Mocap-based interactions were validated with respect to two-haptic-based interactions, as the latter has been successfully integrated into bimanual assembly simulators. The pure Markerless Mocap interaction proved to be either the most or least efficient depending on the configuration (with 2D or 3D tracking, respectively). Usability results among the proposed interactions and the two-haptic based interaction showed no significant differences. These results suggest that Markerless Mocap or hybrid interactions are valid solutions for simulating bimanual assembly tasks when the precision of the motion is not critical. The decision on which technology to use should depend on the trade-off between the precision requested to simulate the task, the cost, and inner features of the technology.     

A stabilized method for transient transport equations

We present a stabilized method for the transient advective-reactive-diffusive equation. The discretization is based on Rothe’s method, which discretizes in time before the spatial discretization. The resulting steady state advective-reactive-diffusive equation is approximated by the Unusual Stabilized Finite Element Method (USFEM).     

Domain morphology of newly designed lead-free antiferroelectric NaNbO3-SrSnO3 ceramics

Reversible antiferroelectric-ferroelectric phase transitions were recently observed in a series of SrSnO₃-modified NaNbO₃ lead-free antiferroelectric materials, exhibiting well-defined double polarization hysteresis loops at ambient conditions. Here, transmission electron microscopy was employed to investigate the crystallography and domain configuration of this newly designed system via electron diffraction and centered dark-field imaging. It was confirmed that antiferroelectricity is maintained in all compositions, manifested by the characteristic ¼ superlattice reflections in the electron-diffraction patterns. By investigating the antiferroelectric domains and domain boundaries in NaNbO₃, we demonstrate that antiphase boundaries are present and their irregular periodicity is responsible for the streaking features along the ¼ superlattice reflections in the electron-diffraction patterns. The signature domain blocks observed in pure NaNbO₃ are maintained in the SrSnO₃-modified ceramics, but disappear when the amount of SrSnO₃ reaches 7 mol.%. In particular, a well-defined and distinct domain configuration is observed in the NaNbO₃ sample modified with 5 mol.% SrSnO₃, which presents a parallelogram domain morphology.     

Non-continuous growth of firms: some empirical evidence from Italian manufacturing industry

Firms change their size through a row of discrete leaps. A basic model allowing for discontinuous growth can be based on several assumptions that entail testable consequences: profitability is not a continuous function of the firms’ size, but exhibits peaks, each corresponding to a locally optimal size. The model has been tested by using a panel of Italian manufacturing firms. Both the non-parametric analysis and a panel estimation confirm the presence of ‘peaks’ in the distribution of profitability by size.     

An easy method to derive EOQ and EPQ inventory models with backorders

Recently, a cost minimization method to determine the lot size for the EOQ/EPQ models with backorders was published. This method is based on the well-known arithmetic–geometric mean inequality. Although the cost minimization method is correct and interesting, it does not focus on deriving the backorders level. This paper proposes another simple approach. The proposed method finds both the lot size and the backorders level.     

PET Radiotracers for Imaging P‐glycoprotein: The Challenge for Early Diagnosis in AD

PET radiotracer development to target in vivo P‐glycoprotein (P‐gp) could be an important strategy for the early diagnosis of neurodegenerative disorders such as Alzheimer’s disease (AD). Indeed, as a dysfunction of P‐gp is responsible for the accumulation of β‐amyloid plaques (a hallmark of AD) in brain parenchyma, P‐gp is the cause of AD onset. P‐gp substrates and inhibitors are useful for imaging the activity or expression of this protein, respectively; herein we discuss the in vivo evaluation of some ¹¹C radiotracers with P‐gp‐inhibitory activity, such as [¹¹C]MC18 and [¹¹C]MC113, as well as P‐gp substrates [¹¹C]MC266 and [¹¹C]MC80. Moreover, the radiosynthesis of all these P‐gp probes is reported.     

New Insights into the Mammalian Egg Zona Pellucida

Mammalian oocytes are surrounded by an extracellular coat called the zona pellucida (ZP), which, from an evolutionary point of view, is the most ancient of the coats that envelope vertebrate oocytes and conceptuses. This matrix separates the oocyte from cumulus cells and is responsible for species-specific recognition between gametes, preventing polyspermy and protecting the preimplantation embryo. The ZP is a dynamic structure that shows different properties before and after fertilization. Until very recently, mammalian ZP was believed to be composed of only three glycoproteins, ZP1, ZP2 and ZP3, as first described in mouse. However, studies have revealed that this composition is not necessarily applicable to other mammals. Such differences can be explained by an analysis of the molecular evolution of the ZP gene family, during which ZP genes have suffered pseudogenization and duplication events that have resulted in differing models of ZP protein composition. The many discoveries made in recent years related to ZP composition and evolution suggest that a compilation would be useful. Moreover, this review analyses ZP biosynthesis, the role of each ZP protein in different mammalian species and how these proteins may interact among themselves and with other proteins present in the oviductal lumen.     

Database Repairs and Analytic Tableaux

In this article, we characterize in terms of analytic tableaux the repairs of inconsistent relational databases, that is databases that do not satisfy a given set of integrity constraints. For this purpose we provide closing and opening criteria for branches in tableaux that are built for database instances and their integrity constraints. We use the tableaux based characterization as a basis for consistent query answering, that is for retrieving from the database answers to queries that are consistent with respect to the integrity constraints.     

A comparison of floating and sunken media biological aerated filters for nitrification

The versatility of the biological aerated filter (BAF) has made it an important process in wastewater treatment. These submerged three-phase fixed media reactors have been used in a wide variety of applications in wastewater treatment, such as primary treatment (solids removal), secondary treatment (COD and BOD removal), and tertiary treatment (nitrification). The aim of this work was to investigate the biological start-up of two such reactors to remove suspended solids (SS), total COD (tCOD) and ammonia, one containing a sunken medium (relative density 1·05) and the other containing a floating medium (relative density 0·92), both identical in shape and size. The reactors (0·054 m³ media) were run in parallel in upflow mode using secondary effluent as the process liquid at a flowrate of 0·2 dm³ min⁻¹ and air: liquid ratio of 10:1. Overall, floating media performed better than sunken media for SS, tCOD and ammonia removal, probably due to the compression of the bed due to the buoyancy force of the media and the flow of air and liquid acting upwards. Bed compression improved solids removal and appeared to have promoted the growth of bacteria. Temperature had a greater impact on nitrification than on carbonaceous matter removal. The floating medium reactor was more resistant to low temperature shocks than the sunken medium reactor but the latter showed a faster recovery time as temperature increased. Although the backwashing frequency used was satisfactory, performance may have improved if the backwashing had been carried out only when reactor performance began to decline. Nitrification was shown to follow a reaction rate between zero and half order. Thus, ammonia removal was generally independent of ammonia concentration and more affected by the presence of carbonaceous matter. © 1998 SCI