Biofilm Responses to Flow Regulation by Dams in Mediterranean Rivers

Dams regulate downstream hydrology and modify water quality, which in turn can impinge on the biota, especially in rivers naturally subject to large hydrological variability, such as those under Mediterranean climate. The effect of dams on biofilms was analysed in three tributaries (Cinca, Siurana and Montsant) of the Ebro River (NE Spain). We hypothesized that flow regulation would lead to lower spatial variability of biofilms on the streambed and to a decrease in their metabolic rate per unit biomass, especially during low flow periods. Biofilm characteristics were studied in five transects evenly spaced along river reaches upstream (control) and downstream (impact) of dams in each river, along with riverbed granulometry, hydraulics and water chemistry. Chlorophyll‐a, respiratory activity, photosynthetic capacity and efficiency, and extracellular enzymatic activities (β‐d ‐glucosidase, alkaline phosphatase and leucine‐amino‐peptidase) of epilithic biofilms were measured in different seasons. Spatial variability of chemical and biological variables was reduced downstream of the dams. Chlorophyll‐a concentration, photosynthetic efficiency and respiration capacity were higher in impact than in control reaches, but generally, low inorganic phosphorus concentrations resulted in comparable phosphatase activities downstream and upstream of dams. On the other hand, β‐d ‐glucosidase and leucine‐amino‐peptidase activities were higher at impact reaches. Biofilms were thicker and metabolically more active at the impact reaches, with higher ability to transform dissolved organic matter. Overall, results from this study provide evidence that dams can largely affect the structure and activity of river biofilms, with foreseeable important consequences for river ecosystem functioning. Copyright © 2014 John Wiley & Sons, Ltd.     

Information Flow for Optimized Management of Spectrum and Radio Resources in Cognitive B3G Wireless Networks

The Beyond 3G (B3G) radio landscape will consist of cognitive heterogeneous wireless networks, operating in the framework of diverse co-operative associations among different classes of operators and providers, for the accommodation of the demands of users with multimode and/or multihoming enabled terminals. In this context, the optimized spectrum and radio resource utilization will be key factor for accomplishment of the purposes of both users and operators/providers, namely the satisfaction of user’s needs and the augmentation of profit, respectively. In this paper, we focus on an architecture for the management and optimization of spectrum and radio resource utilization in such composite wireless environments, and we analytically present the respective information flow among and from/to the functional entities involved in this architecture. The proposed management architecture can operate in the framework of different business scenarios and is based on related work that has been conducted within the IEEE 1900.4 standard.     

A survey of autonomic networking architectures: towards a Unified Management Framework

Academic and industrial research initiatives have sought to make fully autonomic networks a reality. Some of these initiatives pursued a holistic approach, while others focused on setting up functionalities for specific networking domains. These efforts did not succeed in being extensively deployed, because the goals of network operators were not satisfactorily met. These goals include unification of management operations, enablement of end‐to‐end management and enhancement of the overall system performance in a trusted way, while reducing management cost. In this paper, we analyse a set of existing autonomic management architectures and frameworks with respect to a selected set of criteria. We then identify missing parts and challenges and propose a framework to unify the most promising attributes towards a novel approach of realization of autonomic networking management. We call this proposal Unified Management Framework (UMF). Copyright © 2013 John Wiley & Sons, Ltd.     

Is the rate of sulfur-disulfide exchange between the native β-Lactoglobulin and PDS related to protein conformational stability?

Summary The sulfhydryl (SH) group of β-lactoglobulin (β-Lg) affects many of its functional properties. Native β-Lg was treated with pyridine disulfide (PDS) at pH 2.6–8.5 (25 °C). SH-disulfide exchange was monitored by spectrophotometry. The kinetics of β-Lg sulphydryl-disulphide exchange was compared with the same reaction for reduced glutathione (GSH). From such results we estimate, ΔG_ex, the free energy change for exposing the SH-group of β-Lg to solvent. The numerical value for ΔG_ex is equal to the free energy change for β-Lg dissociation at pH 7. At neutral pH, the rate of sulphydryl- disulphide exchange appears to be controlled by the dimer-monomer dissociation equilibrium. At other solvent pHs, β-Lg sulphydryl reactivity towards a small disulphide compound like PDS may not involve the dissociation of native β-Lg.     

The E3 architecture: enabling future cellular networks with cognitive and self‐x capabilities

Future mobile networks are expected to be complex heterogeneous systems. On the one hand this will enable users to take advantage of a number of different access technologies. On the other hand it will seriously affect network management procedures since more extensive operations and decisions will have to be dealt with. To tackle these challenges a number of new dynamic mechanisms need to be designed. It is imperative that certain network management tasks have to be performed without human intervention to reduce the OPEX costs and achieve faster responses in different events. To achieve this goal, the introduction of self‐x functionalities, combined with cognitive mechanisms and the ability to reconfigure network entities and terminals, is required. Moreover, the introduction of a new pilot channel needs to be considered to assist the terminals in selecting the most suitable radio access technology according to their requirements. We present the functional architecture of an evolved network that was designed in the context of the EU‐funded IP project ‘E³: End‐to‐End Efficiency’. This architecture aims to enhance existing procedures usually performed in traditional operation and maintenance systems (e.g. spectrum management, network planning, configuration actions). We explain the rationale of our design and provide specific examples to illustrate the role of the different functional entities and their interfaces. A considerable part of this architecture has recently been approved as a feasibility study by the ETSI Committee Reconfigurable Radio System. Copyright © 2010 John Wiley & Sons, Ltd.     

Protein stability function relations: native β‐lactoglobulin sulphhydryl–disulphide exchange with PDS

Intermolecular sulphhydryl–disulphide exchange with β‐lactoglobulin dimer occurs when this dissociates to form monomers exposing two SH groups. This notion is re‐evaluated in the light of recent structural data suggesting that the degree of SH group exposure in β‐lactoglobulin is unaffected by dissociation. β‐Lactoglobulin was treated with 2,2′‐dipyridyl disulphide (PDS). The rate of sulphhydryl–disulphide exchange was measured at sub‐denaturation temperatures of 25–60 ° C. Parallel studies were conducted by reacting PDS with reduced glutathione (GSH). The SH group of GSH was up to 31 000 times more reactive than β‐lactoglobulin. At pH 7 the reaction activation enthalpy (ΔH^#) and entropy (ΔS^#) was 26 kJ mol⁻¹ and −100 J mol⁻¹ K⁻¹ respectively for GSH. For β‐lactoglobulin, ΔH^# was 157.2 kJ mol⁻¹ and ΔS^# was 254 J mol⁻¹ K⁻¹. At pH 2.6, ΔH^# was 14.4 kJ mol⁻¹ and ΔS^# was −213 J mol⁻¹ K⁻¹ for GSH. The corresponding results for β‐lactoglobulin were 20.3 kJ mol⁻¹ and −147 J mol⁻¹ K⁻¹. These and other thermodynamic results are discussed in terms of the effects of β‐lactoglobulin conformational structure and stability on SH group reactivity. For native β‐lactoglobulin at neutral pH, intermolecular sulphhydryl–disulphide exchange appears to involve the dissociated monomer. SH group activation probably arises from the lower structural stability of the monomer relative to the dimer. At pH 2.6 the mechanism of SH–disulphide exchange does not require protein dissociation and probably involves breathing motions or localised changes in protein structure. © 2000 Society of Chemical Industry     

Evaluation of signalling loads in a cognitive network management architecture

Future networks will need to accommodate a significantly augmented user demand, mainly stemming from the wireless and mobile domains. In general, the emerging radio landscape will comprise multiple, collaborating radio access networks (RANs) able to operate a plethora of diverse radio access technologies (RATs), variant types of mobile terminals (MTs), with the ability to choose among various supported RANs/RATs and, in addition, both devices and networks with dynamic spectrum access capabilities that allow the sharing and/or optimization of spectrum usage among different systems. The above will stress network operators for developing mechanisms to confront the challenges and to leverage the opportunities posed by such a versatile radio environment. In particular, the situation calls for adaptive and flexible management paradigms that are able to dynamically manage network elements and terminals, thus ensuring the great availability and efficient usage of spectrum and other radio resources. Framed within the above, this paper considers a cognitive network management architecture, which is destined for optimized management of future wireless networks operating in versatile radio environments, and presents a performance evaluation methodology, which was set up for measuring the signalling loads that the operation of the architecture will bring to the managed network. The methodology is analytically described, and useful results with respect to the signalling load produced for management signalling purposes in an indicative scenario are presented and analysed. Copyright © 2011 John Wiley & Sons, Ltd.     

The Comparative Heat Stability of Bovine β-Lactoglobulin in Buffer and Complex Media

The heat stability of β-lactoglobulin (β-lg) is usually described with reference to a concentration-dependent pseudo-rate constant k. Kinetic and thermodynamic parameters for the irreversible denaturation of β-lg, in a whey protein mixture dissolved in Tris-HCl buffer, were examined over a wide temperature range 75–120°C and for degrees of denaturation [(C_o-C_t)/C_o] up to about 90%. The first-order kinetic model best described β-lg denaturation over the temperature range 75–85°C, whereas the second-order model applies in the range 90–120°C. A comparison between β-lg thermostability in buffer and literature data pertaining to more complex heating media (whey and milk), over the range 75–120°C, was carried out on the basis of changes in activation free energy (ΔG^#), which itself takes into account changes in both activation enthalpy (ΔH^#) and activation entropy (ΔS^#). It was found that the thermal stability of β-lg in different media, and irrespective of the kinetic model assumed in the present study, can be ranked: buffer ≪ whey>milk for the temperature range 75–85°C. On the contrary, at the higher temperature range, 90–120°C, the ranking is buffer<whey<milk, when using the second-order model to describe the present data. For such comparisons to be valid the initial concentration of β-lg in various studies, as well as the reaction order applied, should be taken into consideration. © 1997 SCI.