Controlling Rayleigh-Backscattering-Induced Distortion in Radio over Fiber Systems for Radioastronomic Applications

Radio over Fiber (RoF) Systems exploiting a direct modulation of the laser source are presently utilized within important Radioastronomic scenarios. Due to the particular operating conditions of some of these realizations, the phenomena which typically generate nonlinearities in RoF links for telecommunications applications can be here regarded as substantially harmless. However, these same operating conditions can make the RoF systems vulnerable to different kinds of nonlinear effects, related to the influence of the Rayleigh Backscattered signal on the transmitted one. A rigorous description of the phenomenon is performed, and an effective countermeasure to the problem is proposed and demonstrated, both theoretically and experimentally.Comment: Accepted for publication in IEEE/OSA Journal of Lightwave Technolog

Failure behaviour of glass-microballoons/thermoset-matrix syntactic foams subject to hydrostatic loading

This investigation deals with a lightweight syntactic foam constituted by an epoxy matrix filled with polydispersed glass microballoons up to 75% volume fraction. We present experimental results on hydrostatic loading which demonstrate the possibility of different failure modalities depending on whether the surface of the composite is painted/coated or not. In order to explain this peculiar behaviour, we develop a three-dimensional Finite Element (FE) micromechanical model. The model enables a detailed analysis of the stress diffusion from the external surface, subject to uniform pressure, through an appropriately thick layer of composite. The FE model includes 300 randomly placed microballoons and accounts for their polydispersion, in terms of both size and radius ratio. The FE model is first validated by comparing its prediction on the elastic moduli with experimental findings and accurate analytical homogenisation techniques. Towards modelling failure, we adopt a structural criterion for the glass microballoons, as recently proposed by our group. The criterion assumes brittle failure when the average elastic strain energy density reaches a critical value. On the basis of the effective strength measured under uniaxial stress, we identify different critical values for selected types of microballoons constituting the filler employed in the syntactic foam under investigation. Finally, the new micromechanical model, through a detailed analysis of the collapsed microballoons and the matrix stress state, allows us to demonstrate the influence of the paint/coating on the syntactic foam failure

Nitric Oxide Protects Neuroblastoma Cells from Apoptosis Induced by Serum Deprivation through cAMP-response Element-binding Protein (CREB) Activation

The transcription factor cAMP-response element-binding protein (CREB) mediates survival in many cells, including neurons. Recently, death of cerebellar granule neurons due to nitric oxide (NO) deprivation was shown to be accompanied by down-regulation of CREB activity (1). We now provide evidence that overproduction of endogenous NO or supplementation with exogenous NO renders SK-N-BE human neuroblastoma cells more resistant to apoptosis induced by serum deprivation. Parental cells underwent apoptosis after 24 h of serum deprivation, an outcome largely absent in clones overexpressing human neuronal nitric oxide synthase (nNOS). This protective effect was reversed by the inhibition of NOS itself or soluble guanylyl cyclase, pointing at cGMP as an intermediate effector of NO-mediated rescue. A slow-releasing NO donor protected parental cells to a significant extent, thus confirming the survival effect of NO. The impaired viability of serum-deprived parental cells was accompanied by a strong decrease of CREB phosphorylation and transcriptional activity, effects significantly attenuated in nNOS-overexpressing clones. To confirm the role of CREB in survival, the ectopic expression of CREB and/or protein kinase A largely counteracted serum deprivation-induced cell death of SK-N-BE cells, whereas transfection with a CREB negative mutant was ineffective. These experiments indicate that CREB activity is an important step for NO-mediated survival in neuronal cells

Optimal Dithering Configuration Mitigating Rayleigh-Backscattering-Induced Distortion in Radioastronomic Optical Fiber Systems

In the context of Radioastronomic applications where the Analog Radio-over-Fiber technology is used for the antenna downlink, detrimental nonlinearity effects arise because of the interference between the forward signal generated by the laser and the Rayleigh backscattered one which is re-forwarded by the laser itself toward the photodetector. The adoption of the so called dithering technique, which involves the direct modulation of the laser with a sinusoidal tone and takes advantage of the laser chirping phenomenon, has been proved to reduce such Rayleigh Back Scattering - induced nonlinearities. The frequency and the amplitude of the dithering tone should both be as low as possible, in order to avoid undesired collateral effects on the received spectrum as well as keep at low levels the global energy consumption. Through a comprehensive analysis of dithered Radio over Fiber systems, it is demonstrated that a progressive reduction of the dithering tone frequency affects in a peculiar fashion both the chirping characteristics of the field emitted by the laser and the spectrum pattern of the received signal at the fiber end. Accounting for the concurrent effects caused by such phenomena, optimal operating conditions are identified for the implementation of the dithering tone technique in radioastronomic systems.Comment: 11 pages. Accepted for Journal of Lightwave Technolog

Role of p75 Neurotrophin Receptor in the Neurotoxicity by β-amyloid Peptides and Synergistic Effect of Inflammatory Cytokines

The neurodegenerative changes in Alzheimer's disease (AD) are elicited by the accumulation of β-amyloid peptides (Aβ), which damage neurons either directly by interacting with components of the cell surface to trigger cell death signaling or indirectly by activating astrocytes and microglia to produce inflammatory mediators. It has been recently proposed that the p75 neurotrophin receptor (p75NTR) is responsible for neuronal damage by interacting with Aβ. By using neuroblastoma cell clones lacking the expression of all neurotrophin receptors or engineered to express full-length or various truncated forms of p75NTR, we could show that p75NTR is involved in the direct signaling of cell death by Aβ via the function of its death domain. This signaling leads to the activation of caspases-8 and -3, the production of reactive oxygen intermediates and the induction of an oxidative stress. We also found that the direct and indirect (inflammatory) mechanisms of neuronal damage by Aβ could act synergistically. In fact, TNF-α and IL-1β, cytokines produced by Aβ-activated microglia, could potentiate the neurotoxic action of Aβ mediated by p75NTR signaling. Together, our results indicate that neurons expressing p75NTR, mostly if expressing also proinflammatory cytokine receptors, might be preferential targets of the cytotoxic action of Aβ in AD

Exploring forest infrastructures equipment through multivariate analysis: complementarities, gaps and overlaps in the Mediterranean basin

The countries of the Mediterranean basin face several challenges regarding the sustainability of forest ecosystems and the delivery of crucial goods and services that they provide in a context of rapid global changes. Advancing scientific knowledge and foresting innovation is essential to ensure the sustainable management of Mediterranean forests and maximize the potential role of their unique goods and services in building a knowledge-based bioeconomy in the region. In this context, the European project FORESTERRA ("Enhancing FOrest RESearch in the MediTERRAnean through improved coordination and integration”) aims at reinforcing the scientific cooperation on Mediterranean forests through an ambitious transnational framework in order to reduce the existing research fragmentation and maximize the effectiveness of forest research activities. Within the FORESTERRA project framework, this work analyzed the infrastructures equipment of the Mediterranean countries belonging to the project Consortium. According to the European Commission, research infrastructures are facilities, resources and services that are used by the scientific communities to conduct research and foster innovation. To the best of our knowledge, the equipment and availability of infrastructures, in terms of experimental sites, research facilities and databases, have only rarely been explored. The aim of this paper was hence to identify complementarities, gaps and overlaps among the different forest research institutes in order to create a scientific network, optimize the resources and trigger collaborations

The C-Terminal Domain of CENP-C Displays Multiple and Critical Functions for Mammalian Centromere Formation

CENP-C is a fundamental component of functional centromeres. The elucidation of its structure-function relationship with centromeric DNA and other kinetochore proteins is critical to the understanding of centromere assembly. CENP-C carries two regions, the central and the C-terminal domains, both of which are important for the ability of CENP-C to associate with the centromeric DNA. However, while the central region is largely divergent in CENP-C homologues, the C-terminal moiety contains two regions that are highly conserved from yeast to humans, named Mif2p homology domains (blocks II and III). The activity of these two domains in human CENP-C is not well defined. In this study we performed a functional dissection of C-terminal CENP-C region analyzing the role of single Mif2p homology domains through in vivo and in vitro assays. By immunofluorescence and Chromatin immunoprecipitation assay (ChIP) we were able to elucidate the ability of the Mif2p homology domain II to target centromere and contact alpha satellite DNA. We also investigate the interactions with other conserved inner kinetochore proteins by means of coimmunoprecipitation and bimolecular fluorescence complementation on cell nuclei. We found that the C-terminal region of CENP-C (Mif2p homology domain III) displays multiple activities ranging from the ability to form higher order structures like homo-dimers and homo-oligomers, to mediate interaction with CENP-A and histone H3. Overall, our findings support a model in which the Mif2p homology domains of CENP-C, by virtue of their ability to establish multiple contacts with DNA and centromere proteins, play a critical role in the structuring of kinethocore chromatin

PainPoints: A Framework for Language-based Detection of Chronic Pain and Expert-Collaborative Text-Summarization

Chronic pain is a pervasive disorder which is often very disabling and is associated with comorbidities such as depression and anxiety. Neuropathic Pain (NP) is a common sub-type which is often caused due to nerve damage and has a known pathophysiology. Another common sub-type is Fibromyalgia (FM) which is described as musculoskeletal, diffuse pain that is widespread through the body. The pathophysiology of FM is poorly understood, making it very hard to diagnose. Standard medications and treatments for FM and NP differ from one another and if misdiagnosed it can cause an increase in symptom severity. To overcome this difficulty, we propose a novel framework, PainPoints, which accurately detects the sub-type of pain and generates clinical notes via summarizing the patient interviews. Specifically, PainPoints makes use of large language models to perform sentence-level classification of the text obtained from interviews of FM and NP patients with a reliable AUC of 0.83. Using a sufficiency-based interpretability approach, we explain how the fine-tuned model accurately picks up on the nuances that patients use to describe their pain. Finally, we generate summaries of these interviews via expert interventions by introducing a novel facet-based approach. PainPoints thus enables practitioners to add/drop facets and generate a custom summary based on the notion of "facet-coverage" which is also introduced in this work

Radio frequency over fiber technology for SKA-low receiver

The signal reception chain is an essential element for achieving the square kilometer array-low (SKA-low) system requirements in terms of high sensitivity and dynamic range. The balance between gain, linearity, and low power consumption, as well as the cost, are fundamental parameters that influence the selection of the most suitable technology for SKA-low. Further factors, such as low self-generated radio frequency (RF) interference, high reliability, robustness under extreme environment, and last but not least, the distance between the antennas and the acquisition systems, have impacts on the selection for both architecture and receiver system design. The selected technology for the SKA-low RF signal transportation is RF-over-fiber systems, where the preamplified RF signal picked up by the antennas is carried via analogue modulation over optical fiber. The rationales behind the selection are reported, along with descriptions on the development of the receiver prototypes. The prototypes were deployed and installed on the demonstrator arrays at the selected SKA-low site in Western Australian. Particular attention has been put on the thermal characterization of the receiver system under the actual operating temperature on site, especially when both transmitting part and the optical medium are subjected to external ambient temperature variations. Performance issues encountered in the demonstrator arrays are also discussed along with some proposals for future activities

Identification and Biological Characterization of the Pyrazolo[3,4-d]pyrimidine Derivative SI388 Active as Src Inhibitor

Src is a non-receptor tyrosine kinase (TK) whose involvement in cancer, including glioblastoma (GBM), has been extensively demonstrated. In this context, we started from our in-house library of pyrazolo[3,4-d]pyrimidines that are active as Src and/or Bcr-Abl TK inhibitors and performed a lead optimization study to discover a new generation derivative that is suitable for Src kinase targeting. We synthesized a library of 19 compounds, 2a-s. Among these, compound 2a (SI388) was identified as the most potent Src inhibitor. Based on the cell-free results, we investigated the effect of SI388 in 2D and 3D GBM cellular models. Interestingly, SI388 significantly inhibits Src kinase, and therefore affects cell viability, tumorigenicity and enhances cancer cell sensitivity to ionizing radiation