Reconfiguration and Dynamic Load Balancing in Broadcast WDM Networks*

In optical WDM networks, an assignment of transceivers to channels implies an allocation of the bandwidth to the various network nodes. Intuition suggests, and our recent study has confirmed, that if the traffic load is not well balanced across the available channels, the result is poor network performance. Hence, the time-varying conditions expected in this type of environment call for mechanisms that periodically adjust the bandwidth allocation to ensure that each channel carries an almost equal share of the corresponding offered load. In this paper we study the problem of dynamic load balancing in broadcast WDM networks by retuning a subset of transceivers in response to changes in the overall traffic pattern. Assuming an existing wavelength assignment and some information regarding the new traffic demands, we present two approaches to obtaining a new wavelength assignment such that (a) the new traffic load is balanced across the channels, and (b) the number of transceivers that need to be retuned is minimized. The latter objective is motivated by the fact that tunable transceivers take a non-negligible amount of time to switch between wavelengths during which parts of the network are unavailable for normal operation. Furthermore, this variation in traffic is expected to take place over larger time scales (i.e., retuning will be a relatively infrequent event), making slowly tunable devices a cost effective solution. Our main contribution is a new approximation algorithm for the load balancing problem that provides for tradeoff selection, using a single parameter, between two conflicting goals, namely, the degree of load balancing and the number of transceivers that need to be retuned. This algorithm leads to a scalable approach to reconfiguring the network since, in addition to providing guarantees in terms of load balancing, the expected number of retunings scales with the number of channels, not the number of nodes in the network.     

Cryptochrome magnetoreception: four tryptophans could be better than three

The biophysical mechanism of the magnetic compass sensor in migratory songbirds is thought to involve photo-induced radical pairs formed in cryptochrome (Cry) flavoproteins located in photoreceptor cells in the eyes. In Cry4a—the most likely of the six known avian Crys to have a magnetic sensing function—four radical pair states are formed sequentially by the stepwise transfer of an electron along a chain of four tryptophan residues to the photo-excited flavin. In purified Cry4a from the migratory European robin, the third of these flavin–tryptophan radical pairs is more magnetically sensitive than the fourth, consistent with the smaller separation of the radicals in the former. Here, we explore the idea that these two radical pair states of Cry4a could exist in rapid dynamic equilibrium such that the key magnetic and kinetic properties are weighted averages. Spin dynamics simulations suggest that the third radical pair is largely responsible for magnetic sensing while the fourth may be better placed to initiate magnetic signalling particularly if the terminal tryptophan radical can be reduced by a nearby tyrosine. Such an arrangement could have allowed independent optimization of the essential sensing and signalling functions of the protein. It might also rationalize why avian Cry4a has four tryptophans while Crys from plants have only three.     

NKp44-Derived Peptide Used in Combination Stimulates Antineoplastic Efficacy of Targeted Therapeutic Drugs

Lung cancer cells in the tumor microenvironment facilitate immune evasion that leads to failure of conventional chemotherapies, despite provisionally decided on the genetic diagnosis of patients in a clinical setup. The current study follows three lung cancer patients who underwent “personalized” chemotherapeutic intervention. Patient-derived xenografts (PDXs) were subjected to tumor microarray and treatment screening with chemotherapies, either individually or in combination with the peptide R11-NLS-pep8; this peptide targets both membrane-associated and nuclear PCNA. Ex vivo, employing PDX-derived explants, it was found that combination with R11-NLS-pep8 stimulated antineoplastic effect of chemotherapies that were, although predicted based on the patient’s genetic mutation, inactive on their own. Furthermore, treatment in vivo of PDX-bearing mice showed an exactly similar trend in the result, corroborating the finding to be translated into clinical setup.     

Osmium in environmental samples from Northeast Sweden. Part II. Identification of anthropogenic sources

Osmium (Os) concentrations and (187)Os/(188)Os isotope abundance ratios measured in epiphytic lichens from Northeast Sweden have been used for the identification of anthropogenic emission sources of this element. Based on isotope abundance ratios and similarities in spatial distributions between Os and chromium, smelters operated on chromium ores from Kemi deposits have shown to be the most important factor affecting the airborne Os burden in the region. The extent of the exposure is reflected by lichen concentrations near the source exceeding those from remote areas by a factor of 1000. Contributions from metal foundries processing iron, copper, lead and zinc ores can also be seen, though, because of lower Os concentrations in the feedstock, on a considerably lower scale. Masked by these industrial emissions in the studied area, the impact of Os originating from automotive catalytic converters cannot be resolved at present.     

Resins containing α-hydroxyphosphonic acid groups used for adsorption of dyes from wastewater

The synthesis of styrene–divinylbenzene copolymers functionalized with α-hydroxyphosphonic acid groups is presented. The phosphorus content was determined in order to calculate the degree of functionalization with pendant α-hydroxyphosphonic group, with values of 0.66 for St–1%DVB_HOPHOS and 3.14 for St–6.7%DVB_HOPHOS. Their characterization by IR, thermogravimetry is reported. The kinetics of adsorption of three dyes on St–6.7%DVB_HOPHOS polymer was studied.     

Long-Term Spectrum Monitoring with Big Data Analysis and Machine Learning for Cloud-Based Radio Access Networks

Spectrum monitoring is important for efficient spectrum sharing and resource management in cloud-based radio access networks (C-RAN). In this paper we show how data obtained from long-term spectrum monitoring together with machine learning (ML) operating on big data (BD) can be used in a C-RAN scenario for spectrum management purposes. We propose an approach for spectrum occupancy forecasting which can be used to reduce the delay in making dynamic spectrum allocation decisions and improve the cognitive and management functionalities of cloud-based architectures such as C-RAN. The spectrum occupancy and usage activity in a predefined frequency band is based on the statistical processing of a large amount of collected data and the introduction of a frequency–time resources indicator as a measure of spectrum usage. Furthermore, we apply ML algorithms to predict spectrum usage and compare the predicted with actual measured data. Taking into consideration that the accuracy of the prediction depends on the volume of collected data and the time of prediction on the BD and ML approach, we propose the development of a cloud-based generic processing architecture to solve the “accuracy versus latency” trade-off problem. The proposed architecture is appropriate for deployment in cognitive C-RAN.     

Coexistence of Grain‐Boundaries‐Assisted Bipolar and Threshold Resistive Switching in Multilayer Hexagonal Boron Nitride

The use of 2D materials to improve the capabilities of electronic devices is a promising strategy that has recently gained much interest in both academia and industry. However, while the research in 2D metallic and semiconducting materials is well established, detailed knowledge and applications of 2D insulators are still scarce. In this paper, the presence of resistive switching (RS) in multilayer hexagonal boron nitride (h‐BN) is studied using different electrode materials, and a family of h‐BN‐based resistive random access memories with tunable capabilities is engineered. The devices show the coexistence of forming free bipolar and threshold‐type RS with low operation voltages down to 0.4 V, high current on/off ratio up to 10⁶, and long retention times above 10 h, as well as low variability. The RS is driven by the grain boundaries (GBs) in the polycrystalline h‐BN stack, which allow the penetration of metallic ions from adjacent electrodes. This reaction can be boosted by the generation of B vacancies, which are more abundant at the GBs. To the best of our knowledge, h‐BN is the first 2D material showing the coexistence of bipolar and threshold RS, which may open the door to additional functionalities and applications.     

Isolation of Marine Paracoccus sp. Ss63 from the Sponge Sarcotragus sp. and Characterization of its Quorum-Sensing Chemical-Signaling Molecules by LC-MS/MS Analysis

Gram-negative bacteria often use N-acyl homoserine lactones (AHLs) as quorum-sensing (QS) signal molecules. The present study aimed to identify and characterize the production of AHLs by Paracoccus sp. Ss63, which was isolated from the Mediterranean sponge Sarcotragus sp. High performance liquid chromatography – high resolution tandem mass spectrometry (LC-HRMS/MS) provided evidence for the production, by Paracoccus sp. Ss63, of twelve saturated long-chain AHLs (3-OH-C10-HSL, 3-OH-C12-HSL, C10-HSL, 3-OH-C14-HSL, C12-HSL, 3-O-C16-HSL, 3-OH-C16-HSL, C14-HSL, 3-OH-C18-HSL, C16-HSL, 3-O-C18-HSL, and C18-HSL), along with four putative unsaturated long-chain AHLs (C10 : 1-HSL, 3-OH-C18 : 1-HSL, C16 : 1-HSL, and C18 : 1-HSL). The distribution of Paracoccus sp. Ss63 in different sponge species, as well as in seawater and marine sediment samples, suggests a mixed lifestyle for this bacterium, i.e., free-living and host-associated. The high pH of seawater is likely to inactivate the AHL signal molecules, and limit the possibility of AHLs to accumulate to the concentration required for QS-based gene regulation. We hypothesize that Paracoccus sp. Ss63 utilizes quorum sensing to sense and respond to the different environments it experiences, with an active QS only when found inside enclosed niches (host-associated and at lower pH).