Rethinking the Low Extra Delay Background Transport (LEDBAT) Protocol

BitTorrent has recently introduced LEDBAT, a novel application-layer congestion control protocol for data exchange. The protocol design assumes that network bottlenecks are at the access of the network, and that thus user traffic competes creating self-induced congestion. To relieve this phenomenon, LEDBAT is designed to quickly infer when self-induced congestion is approaching (by detecting relative changes of the one-way delay in the transmission path), and to react promptly by reducing the sending rate prior to the congestion occurrence. Previous work has however shown LEDBAT to be affected by a latecomer advantage, where newly arriving connections can starve already existing flows. In this work, we propose modifications to the congestion window update mechanism of LEDBAT that solve this issue, thus guaranteeing intra-protocol fairness and efficiency. Closed-form expressions for the stationary throughput and queue occupancy are provided via a fluid model, whose accuracy is confirmed by means of ns2 packet level simulations. Our results show that the proposed change can effectively solve the latecomer issue, furthermore without affecting the other original LEDBAT goals.     

Perceived Obstacles to University–Industry Collaboration: Results from a Qualitative Survey of Italian Academic Departments

Although universities are generally under pressure to increase their interactions with industry, academic departments vary enormously in the extent to which they collaborate with businesses. There are several factors, which, to different extents, drive or hamper academics' capabilities to engage in collaboration with the private sector. On the basis of original data from interviews with 197 university departments in Italy, this paper investigates the main obstacles to technology transfer activity as perceived by academic researchers, and their possible impact on university–industry collaborations. The analysis shows that three (out of four) perceived obstacles are barriers to university–industry interactions and negatively affect the probability of engaging in collaboration with industry. The estimated impact of these perceived obstacles on the frequency of collaborations is less clear-cut and requires further investigation.     

Thermoelastic dynamic stability of thin-walled beams with graded material properties

The dynamic stability of functionally graded thin-walled beams allowing for shear deformability is investigated in this article. The analysis is based on a model that has small strains and moderate rotations which are formulated through the adoption of a second-order non-linear displacement field. The beam is subjected to axial external dynamic loading. The model takes into account thermoelastic effects. The heat conduction equation is solved in order to characterize the temperature in the cross-sectional domain. Galerkin's and Bolotin's methods are employed with the scope to discretize the governing equations and to determine the regions of dynamic stability, respectively. Regions of stability are evaluated and expressed in non-dimensional form. The influence of the longitudinal vibration on the unstable regions is investigated. The numerical results show the importance of this effect when the forcing frequency approaches to the natural longitudinal frequency, obtaining substantially wider parametric stability regions. The effects of temperature gradients, shear flexibility and axial inertia, in beams with different cross-sections and different types of graded material are analyzed as well.     

Candida parapsilosis fungemia associated with implantable and semi-implantable central venous catheters and the hands of healthcare workers

Hypertension in the elderly features differently from its younger counterpart in terms of diagnosis, associated condition, atypical manifestation, management and complication. Epidemiological study in this increasing age group in the community is, therefore, needed. 334 elderly subjects living in various parts of Bangkok were randomly recruited by appointment at 7 geriatric day centers situated in local health offices of Bangkok Metropolitan Authority. Each subject received blood tests before being interviewed and measured by digital sphygmomanometer. Blood pressure and heart rate changes were recorded during lying, sitting and standing. The prevalence of hypertension was 36.5 per cent, 33.2 per cent were already aware of its existence while 3.3 per cent were newly detected by the survey. Isolated systolic hypertension, a unique subtype found in the elderly, was 4.5 per cent of all or 37.5 per cent among the hypertensive group. The associated medical conditions among the case group were diabetes mellitus 22.9 per cent, hyperlipidemia 13.9 per cent, hyperuricemia 33.3 per cent and heart disease 18.0 per cent. As far as postural hypotension is concerned, 14.8 per cent of case group whereas 11.3 per cent of the control group were affected. On the other hand, the symptom of postural dizziness was found to be 31.1 per cent and 55.2 per cent in the case and control group respectively. Following the statistical logistic regression analysis, the independent associated factors in the hypertension group were: history of hyperlipidemia, increased serum uric acid and poor heart rate response after standing. These findings, as parts of the multiple pathology and potential complications prevalent among this group, should be of concern by any physician looking after the elderly.     

Learning the temporal dynamics of behavior.

This study presents a dynamic model of how animals learn to regulate their behavior under time-based reinforcement schedules. The model assumes a serial activation of behavioral states during the interreinforcement interval, an associative process linking the states with the operant response, and a rule mapping the activation of the states and their associative strength onto response rate or probability. The model fits data sets from fixed-interval schedules, the peak procedure, mixed fixed-interval schedules, and the bisection of temporal intervals. The major difficulties of the model came from experiments that suggest that under some conditions animals may time 2 intervals independently and simultaneously. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Thermal characterization of a cross-flow heat exchanger with a new flow arrangement

The objective of the present paper is to thermally characterize a cross-flow heat exchanger featuring a new cross-flow arrangement, which may find application in contemporary refrigeration and automobile industries. The new flow arrangement is peculiar in the sense that it possesses two fluid circuits extending in the form of two tube rows, each with two tube lines. To assess the heat exchanger performance, it is compared against that for the standard two-pass counter-cross-flow arrangement. The two-part comparison is based on the thermal effectiveness and the heat exchanger efficiency for several combinations of the heat capacity rate ratio, C¹, and the number of transfer units, NTU. In addition, a third comparison is made in terms of the so-called “heat exchanger reversibility norm” (HERN) through the influence of various parameters such as the inlet temperature ratio, τ, and the heat capacity rate ratio, C¹, for several fixed NTU values. The proposed new flow arrangement delivers higher thermal effectiveness and higher heat exchanger efficiency, resulting in lesser entropy generation over a wide range of C¹ and NTU values. These metrics are quantified with respect to the arrangement widely used in refrigeration industry due to its high effectiveness, namely, the standard two-pass counter-cross-flow heat exchanger. The new flow arrangement seems to be a promising avenue in situations where cross-flow heat exchangers for single-phase fluid have to be used in refrigeration units.     

Disposable genosensor, a new tool for the detection of NOS-terminator, a genetic element present in GMOs

Legislation enacted worldwide to regulate the presence of genetically modified organisms (GMOs) in crops, foods and ingredients, necessitated the development of reliable and sensitive methods for GMO detection. An indicator based electrochemical disposable genosensor for the voltammetric detection of NOS-terminator, a genetic element present in GMOs is described as a possible substitute method for the common technique of gel electrophoresis and fluorescent image analysis. The biosensor relies on the immobilization of the 25-mer single stranded oligonucleotides (probe) related to NOS-terminator DNA sequence and the relative binding of this sequence with the polymerase chain reaction (PCR) amplified samples from certified reference material (CRM) of Roundup Ready soybean (Fluka) at a screen printed electrode (SPE). The extent of hybridization between the probe and target DNA is determined by using square wave voltammetry (SWV) with moving average baseline correction and methylene blue (3,7-bis(dimethylamino)phenothiazin-5-ium chloride, MB), as the hybridization indicator. The difference between the MB signals, obtained from the hybrid modified and probe modified SPEs, is used to detect GMOs from PCR amplified DNA samples. Numerous factors affecting the hybridization and indicator binding reactions are optimized to maximize the sensitivity.     

Cost and effluent quality controllers design based on the relative gain array for a nutrient removal WWTP

The main objective of this work was the design of different effluent quality controllers and a cost controller for WWTPs. This study was based on the relative gain array (RGA) analysis applied to an anaerobic/anoxic/aerobic (A²/O) configuration of a simulated WWTP, with combined removal of organic matter, nitrogen and phosphorus. The RGA analysis was able to point out the best pairing amongst the input and the output control variables of the plant to design low order and decentralized effluent quality controllers, such as proportional-integral controllers for each variable of interest (ammonium, nitrate and phosphate). In a second step, a cost controller to automatically search for the most economic setpoints of the effluent quality controllers was implemented based on the best decentralized control structure tested. The simulated plant was operated under different control modes that chronologically represent control configurations becoming gradually more complex: (i) in open loop; (ii) with dissolved oxygen (DO) control in the last aerobic reactor only; (iii) with the effluent quality controllers active; (iv) with the effluent quality controllers active and automatically receiving the setpoints from a cost controller. The effluent quality controllers alone and the cost control together with effluent quality controllers could save up to 42,000 Euros/year and 225,000 Euros/year, respectively, when compared to the operating costs of the plant operating with DO control (a reduction of 2.5% and 13% of the operating costs, respectively). The cost controller proved to be a good tool for automating the search of the most profitable setpoints of the effluent quality controllers for a given cost setpoint.     

Growth of acid-adapted Listeria monocytogenes in orange juice and in minimally processed orange slices

The aim of this work was to study the growth/survival of acid-adapted cells of Listeria monocytogenes, in orange juice and in minimally processed orange slices. The L. monocytogenes OML 45 behaviour into TSB (Tryptic Soy Broth) medium was evaluated at different pH values (between 3.7 and 6.7). The acid-adapted cells were obtained maintaining L. monocytogenes in TSB at pH 5.7 for 3 h. The obtained cells were then inoculated into a diluted orange juice with a pH of 2.6. Moreover, the acid-adapted cells were inoculated into minimally processed orange slices. The growth was evaluated during storage at different temperatures. The study confirms that orange juice and minimally processed orange slices can support the acid-adapted pathogen growth.