Secretions of Stingless Bees: The Dufour Gland of Nannotrigona testaceicornis

The Dufour gland of Nannotrigona testaceicornis is a large, wide, pear-shaped sac. The gland secretion consists chiefly of the diterpene ester all-trans-geranylgeranyl acetate (64% of the total), together with a complex mixture of small amounts of cyclic ketals; mono-, sesqui-, and diterpene compounds; acetates; and other oxygenated compounds. Samples of N. testaceicornis collected at two sites in Brazil and one in México shared the same composition of their glands, suggesting that the species is uniform over this wide geographical area.     

An efficient LMI approach for the quadratic stabilisation of a class of linear,uncertain, time-varying systems

The purpose of this article is to provide a numerically efficient method for the quadratic stabilisation of a class of linear, discrete-time, uncertain, time-varying systems. The considered class of systems is characterised by an interval time-varying (ITV) matrix and constant sensor and actuator matrices. It is required to find a linear time-invariant (LTI) static output feedback controller yielding a quadratically stable closed-loop system independently of the parameter variation rate. The solvability conditions are stated in terms of linear matrix inequalities (LMIs). The set of LMIs includes the stability conditions for the feedback connection of a unique suitably defined extreme plant with an LTI output controller and the positivity of a closed-loop extremal matrix. A consequent noticeable feature of the article is that the total number of LMIs is independent of the number of uncertain parameters. This greatly enhances the numerical efficiency of the design procedure.     

The complexity and approximation of fixing numerical attributes in databases under integrity constraints

Consistent query answering is the problem of characterizing and computing the semantically correct answers to queries from a database that may not satisfy certain integrity constraints. Consistent answers are characterized as those answers that are invariant under all minimally repaired versions of the original database. We study the problem of repairing databases with respect to denial constraints by fixing integer numerical values taken by attributes. We introduce a quantitative definition of database repair, and investigate the complexity of several decision and optimization problems. Among them, Database Repair Problem (DRP): deciding the existence of repairs within a given distance to the original instance, and CQA: deciding consistency of answers to simple and aggregate conjunctive queries under different semantics. We provide sharp complexity bounds, identifying relevant tractable and intractable cases. We also develop approximation algorithms for the latter. Among other results, we establish: (a) The -hardness of CQA. (b) That DRP is MAXSNP-hard, but has a good approximation. (c) The intractability of CQA for aggregate queries for one database atom denials (plus built-ins), and also that it has a good approximation.     

Optimisation and performance assessment of a digital signal-processing method for jitter measurement in PDH/SDH-based digital telecommunication networks

The paper deals with jitter measurement in telecommunication networks based on plesiochronous (PDH) or synchronous (SDH) digital hierarchies. The attention is mostly focused on PDH/SDH analysers compliant to the ITU-T recommendations, the accuracy of which seems to be unsatisfying for both designers and manufacturers. Trying to give an answer to this problem, a digital signal-processing method was already proposed by the author. It succeeded in improving jitter measurement accuracy by avoiding the use of timing recovery circuitry, always needed, on the contrary, in the aforementioned analysers.The method is here optimised with the aim both of automating jitter performance test of network elements that operate at the PDH bit rate of 140 Mbit/s and the SDH bit rate of 155 Mbit/s, and further enhancing the accuracy on jitter estimates. In particular, an innovative procedure for automatically recovering the binary information conveyed by the jittered signal under analysis is introduced, and a proper strategy for carrying out instantaneous jitter measurements at uniform time intervals is developed.After a brief outline of the old version of the method, the proposed enhancements are described in detail. Then, the performance of the optimised method is assessed through many laboratory tests on emulated signals, the results of which are given and discussed. At the end, the outcomes of real automatic tests, conducted on PDH/SDH-based equipment produced by Marconi Sud S.p.A., are also presented.     

Experimental assessment of the effects of cross-traffic on Wi-Fi video streaming

Wi-Fi networks are the first and sometimes only choice for the video streaming in homes, airports, malls, public areas and museums. However, Wi-Fi networks are vulnerable to interference, noise and have bandwidth limitations. Due to the intrinsic vulnerability of the communication channel, and the large number of variables involved, simulation alone is not enough in the evaluation of the performance of wireless networks. Actually, there is a tendency to give experimental tests a central role in the assessment of Wi-Fi networks performance.The paper presents an experimental analysis of the effects of cross traffic on the performance of video streaming over Wi-Fi, based on cross-layer measurements. Experiments are carried out in a semi-anechoic chamber, to prevent the results from being influenced by external factors. The experimental results permit to analyze the influence of cross traffic characteristics on cross layer measures and objective video quality metrics evaluated through a standardized approach.     

Evaluation of on-line analytic and numeric inverse kinematics approaches driven by partial vision input

Despite its central role in the constitution of a truly enactive interface, 3D interaction through human full body movement has been hindered by a number of technological and algorithmic factors. Let us mention the cumbersome magnetic equipments, or the underdetermined data set provided by less invasive video-based approaches. In the present paper, we explore the recovery of the full body posture of a standing subject in front of a stereo camera system. The 3D position of the hands, the head and the center of the trunk segment are extracted in real-time and provided to the body posture recovery algorithmic layer. We focus on the comparison between numeric and analytic inverse kinematics approaches in terms of performances and overall quality of the reconstructed body posture. Algorithmic issues arise from the very partial and noisy input and the singularity of the human standing posture. Despite stability concerns, results confirm the pertinence of this approach in this demanding context.     

Microbiological profile of greenhouses in a farm producing hydroponic tomatoes

Produce, including tomatoes, has been implicated in several outbreaks of foodborne illness. A number of the sources of contamination for produce grown in open fields are known. However, as an alternative agricultural system, hydroponic greenhouses are reasonably expected to reduce some of these sources. The objective of the present study was to determine the microbiological profile of tomatoes grown in greenhouses at a Mexican hydroponic farm with a high technological level and sanitary agricultural practices (SAPs) in place. Tomatoes and other materials associated with the farm were analyzed for the presence of Salmonella enterica and populations of Escherichia coli, coliforms, and Enterobacteriaceae. Tomatoes showed median levels of 0.8 log CFU per tomato for Enterobacteriaceae, < 0.5 log CFU per tomato for coliforms, and 0.5 most probable number per tomato for E. coli. Despite the physical barriers that the facilities provide and the implemented SAPs, we found that 2.8% of tomatoes were contaminated with Salmonella and 0.7% with E. coli. Other Salmonella-positive materials were puddles, soil, cleaning cloths, and sponges. Samples from the nursery and greenhouses were positive for E. coli, whereas Salmonella was found only in the latter. Although hydroponic greenhouses provide physical barriers against some sources of enteric bacterial contamination, these results show that sporadic evidence of fecal contamination and the presence of Salmonella can occur at the studied greenhouse farm.     

Simultaneous Achievement of Open and Closed Loop Diagonal Dominance Through Constant Feedback

This paper proposes a new and low complexity technique for the simultaneous achievement of open and closed loop diagonal dominance for uncertain plants. The method is based on the introduction of a static high gain inner feedback which modifies the plant to attain a diagonal dominant open loop compensated plant. The sufficient, easy to use, conditions derived for the open loop diagonal dominance also assure the simultaneous achievement of closed loop diagonal dominance under soft assumptions on the diagonal elements of the decoupled controller robustly stabilizing the plant. These assumptions agree with the usual closed‐loop performance specifications, so that closed‐loop diagonal dominance is achieved without any extra complication on the controller design procedure. The main merits of the present method are: applicability to uncertain plants, ease of implementation and low computational cost. Three examples taken from the relevant literature, are given to show the effectiveness of the proposed approach.     

CD38 Correlates with an Immunosuppressive Treg Phenotype in Lupus-Prone Mice

CD38 is a transmembrane glycoprotein expressed by T-cells. It has been reported that patients with systemic lupus erythematosus (SLE) showed increased CD38⁺CD25⁺ T-cells correlating with immune activation and clinical signs. Contrariwise, CD38 deficiency in murine models has shown enhanced autoimmunity development. Recent studies have suggested that CD38⁺ regulatory T-cells are more suppressive than CD38⁻ regulatory T-cells. Thus, we have suggested that CD38 overexpression in SLE patients could play a role in regulating immune activation cells instead of enhancing it. This study found a correlation between CD38 with FoxP3 expression and immunosuppressive molecules (CD69, IL-10, CTLA-4, and PD-1) in T-cells from lupus-prone mice (B6.MRL-Fas^lpr/J). Additionally, B6.MRL-Fas^lpr/J mice showed a decreased proportion of CD38⁺ Treg cells regarding wild-type mice (WT). Furthermore, Regulatory T-Cells (Treg cells) from CD38-/- mice showed impairment in expressing immunosuppressive molecules and proliferation after stimulation through the T-cell receptor (TCR). Finally, we demonstrated an increased ratio of IFN-γ/IL-10 secretion in CD38-/- splenocytes stimulated with anti-CD3 compared with the WT. Altogether, our data suggest that CD38 represents an element in maintaining activated and proliferative Treg cells. Consequently, CD38 could have a crucial role in immune tolerance, preventing SLE development through Treg cells.