Monte Carlo evaluation of the impact of subsequent strokes on backflashover rate

The paper deals with the impact of subsequent strokes on the backflashover rate (BFR) of HV overhead transmission lines (OHLs), assessed by means of an ATP-EMTP Monte Carlo procedure. The application to a typical 150 kV Italian OHL is discussed, simulating several tower grounding system arrangements. Subsequent strokes parameters are added to the statistical simulation variables: Peak current, front time, time-to-half value, lightning polarity, line insulation withstand, lightning location and phase angle of the power frequency voltage. The input data are fed to an ATP-EMTP complete circuit model of the OHL, including line insulation, lightning representation and tower grounding system, the latter simulated by a pi-circuit model able to simulate the effects due to propagation and soil ionization, at modest computational costs. Numerical results evidence a non-negligible BFR increase (in relative terms) due to subsequent strokes: for spatially concentrated grounding systems the BFR increase approximatively vary in inverse proportion with the low frequency grounding resistance, whereas for spatially extended grounding systems the BFR increase depends on the grounding system behavior at high frequencies

An equivalent circuit for the evaluation of cross-country fault currents in medium voltage (MV) distribution networks

A Cross-Country Fault (CCF) is the simultaneous occurrence of a couple of Line-to-Ground Faults (LGFs), affecting different phases of same feeder or of two distinct ones, at different fault locations. CCFs are not uncommon in medium voltage (MV) public distribution networks operated with ungrounded or high-impedance neutral: despite the relatively small value of LGF current that is typical of such networks, CCF currents can be comparable to those that are found in Phase-To-Phase Faults, if the affected feeder(s) consists of cables. This occurs because the faulted cables' sheaths/screens provide a continuous, relatively low-impedance metallic return path to the fault currents. An accurate evaluation is in order, since the resulting current magnitudes can overheat sheaths/screens, endangering cable joints and other plastic sheaths. Such evaluation, however, requires the modeling of the whole MV network in the phase domain, simulating cable screens and their connections to the primary and secondary substation earth electrodes by suitable computer programs, such as ATP (which is the acronym for alternative transient program) or EMTP (the acronym for electromagnetic transient program), with substantial input data being involved. This paper presents a simplified yet accurate circuit model of the faulted MV network, taking into account the CCF currents' return path (cable sheaths/screens, ground conductors, and earthing resistances of secondary substations). The proposed CCF model can be implemented in a general-purpose simulation program, and it yields accurate fault currents estimates: for a 20 kV network case study, the comparison with accurate ATP simulations evidences mismatches mostly smaller than 2%, and never exceeding 5%

Subsidiaries within a High-Tech MNC. A reappraisal of the Role of Functions

The recent management literature on multinational corporations (MNCs) has mainly focused on the new role played by subsidiaries within the international firms. Many scholars have underlined that MNCs tend to organise themselves along a differentiated network approach, where subsidiaries play a very different role according to their internal resources and the significance of the local environment. This strategic and organisational model dates back to the pioneering work of Bartlett and Goshal, who called this new international strategy “Transnational” so as to differentiate it from the classical Multidomestic and Global strategies. Along with the different roles played by the subsidiaries, this model is characterised by the simultaneous existence of cooperation and competition within the multinational corporations. The present work focuses on the role of the Italian subsidiary of AgilentTechnologies, a multinational firm with around 36,000 employees that is active in more than 40 countries in high-tech sectors such as electronics, telecommunications and life science. The case study brought new light to the usual distinction that is commonly made with regard to the role of a subsidiary. When we try to apply the Transnational model to Agilent we realise that neither this model nor the traditional typologies (Multidomestic, Global) apply to the case we have studied. The role of the subsidiary changes significantly according to the function being considered. Therefore, we conclude that the role of function should be re-evaluated when the strategy and the structure of an MNC is defined. Not only does the classification of subsidiaries change according to the function in question, but the strategic posture and the organisational structure of MNCs should also be re-evaluated in light of the function under consideration. Our study shows how activities such as R&D, where coopetition represents a strategic source of advantage, seem to follow the Transnational scheme, while others such as sales are mainly globally managed

Tower grounding improvement versus line surge arresters: comparison of remedial measures for high-BFOR subtransmission lines

This paper presents a technical/economic comparison between remedial measures aimed at improving the lightning performance of an existing Italian three-phase 150-kV overhead line. The line is characterized by a very high back-flashover rate (BFOR), due to large grounding resistance values. Two countermeasures are proposed: grounding system improvement with additional vertical rods and line metal oxide surge arrester (MOSA) installation on one or all phases. A Monte Carlo ATP-EMTP procedure developed by the authors, which takes into account both the tower grounding nonlinear transient response due to soil ionization and MOSA nonlinear response, has been applied to evaluate and compare the effectiveness of the proposed countermeasures. The installation of MOSA on all phases is technically the best option, but it is relatively expensive. Tower grounding improvement and MOSA installation on the lower phase yield very similar BFORs: the economic comparison strongly depends on tower's accessibility and soil nature

Higher risk of tuberculosis reactivation when anti-TNF is combined with immunosuppressive agents. A systematic review of randomized controlled trials

Objective. Treatment with tumour necrosis factor antagonists (anti-TNF) has been recognized as a risk factor for tuberculosis (TB) reactivation. Our aim was to evaluate risk of TB reactivation in rheumatologic and non-rheumatologic diseases treated with the same anti-TNF agents with and without concomitant therapies. Methods. We searched for randomized controlled trials (RCTs) evaluating infliximab, adalimumab, and certolizumab in both rheumatologic and non-rheumatologic diseases until 2012. Results were calculated as pooled rates and/or pooled odd ratios (OR). Results. Overall, 40 RCTs with a total of 14,683 patients (anti-TNF: 10,010; placebo: 4673) were included. TB reactivation was 0.26% (26/10,010) in the anti-TNF group and 0% (0/4673) in the control group, corresponding to an OR of 24.8 (95% CI 2.4-133). TB risk was higher when anti-TNF agents were combined with methotrexate or azathioprine as compared with either controls (24/4241 versus 0/4673; OR 54; 95% CI 5.3-88) or anti-TNF monotherapy (24/4241 versus 2/5769; OR 13.3; 95% CI 3.7-100). When anti-TNF was used as monotherapy, TB risk tended to be higher than placebo (2/5769 versus 0/4673; OR 4; 95% CI 0.2-15.7). Conclusions. TB risk with anti-TNF agents appeared to be increased when these agents were used in combination with methotrexate or azathioprine as compared with monotherapy regimen. TB risk seemed to be higher than placebo, even when monotherapy is prescribed

Forced Response Analysis In a Full-Scale Multistage Centrifugal Compressor: Impeller Vibration Prediction and Validation

Lectur

Inhibition of de novo ceramide biosynthesis affects aging phenotype in an in vitro model of neuronal senescence.

Although aging is considered to be an unavoidable event, recent experimental evidence suggests that the process can be counteracted. Intracellular calcium (Ca2+i) dyshomeostasis, mitochondrial dysfunction, oxidative stress, and lipid dysregulation are critical factors that contribute to senescence-related processes. Ceramides, a pleiotropic class of sphingolipids, are important mediators of cellular senescence, but their role in neuronal aging is still largely unexplored. In this study, we investigated the effects of L-cycloserine (L-CS), an inhibitor of thede novoceramide biosynthesis, on the aging phenotype of cortical neurons cultured for 22 days, a setting employed as anin vitromodel of senescence. Our findings indicate that, compared to control cultures, 'aged' neurons display dysregulation of [Ca2+]ilevels, mitochondrial dysfunction, increased generation of reactive oxygen species (ROS), altered synaptic activity as well as the activation of neuronal death-related molecules. Treatment with L-CS positively affected the senescent phenotype, a result associated with recovery of neuronal [Ca2+]isignaling and reduction of mitochondrial dysfunction and ROS generation. The results suggest that thede novoceramide biosynthesis represents a critical intermediate in the molecular and functional cascade leading to neuronal senescence and identify ceramide biosynthesis inhibitors as promising pharmacological tools to decrease age-related neuronal dysfunctions

The pharmacological perturbation of brain zinc impairs BDNF-related signaling and the cognitive performances of young mice.

Zinc (Zn2+) is a pleiotropic modulator of the neuronal and brain activity. The disruption of intraneuronal Zn2+ levels triggers neurotoxic processes and affects neuronal functioning. In this study, we investigated how the pharmacological modulation of brain Zn2+ affects synaptic plasticity and cognition in wild-type mice. To manipulate brain Zn2+ levels, we employed the Zn2+ (and copper) chelator 5-chloro-7-iodo-8-hydroxyquinoline (clioquinol, CQ). CQ was administered for two weeks to 2.5-month-old (m.o.) mice, and effects studied on BDNF-related signaling, metalloproteinase activity as well as learning and memory performances. CQ treatment was found to negatively affect short- and long-term memory performances. The CQ-driven perturbation of brain Zn2+ was found to reduce levels of BDNF, synaptic plasticity-related proteins and dendritic spine density in vivo. Our study highlights the importance of choosing "when", "where", and "how much" in the modulation of brain Zn2+ levels. Our findings confirm the importance of targeting Zn2+ as a therapeutic approach against neurodegenerative conditions but, at the same time, underscore the potential drawbacks of reducing brain Zn2+ availability upon the early stages of development

Influence of APOE and RNF219 on Behavioral and Cognitive Features of Female Patients Affected by Mild Cognitive Impairment or Alzheimer's Disease.

The risk for Alzheimer's disease (AD) is associated with the presence of the ?4 allele of Apolipoprotein E (APOE) gene and, recently, with a novel genetic variant of the RNF219 gene. This study aimed at evaluating interactions between APOE-?4 and RNF219/G variants in the modulation of behavioral and cognitive features of two cohorts of patients suffering from mild cognitive impairment (MCI) or AD. We enrolled a total of 173 female MCI or AD patients (83 MCI; 90 AD). Subjects were screened with a comprehensive set of neuropsychological evaluations and genotyped for the APOE and RNF219 polymorphic variants. Analysis of covariance was performed to assess the main and interaction effects of APOE and RNF219 genotypes on the cognitive and behavioral scores. The analysis revealed that the simultaneous presence of APOE-?4 and RNF219/G variants results in significant effects on specific neuropsychiatric scores in MCI and AD patients. In MCI patients, RNF219 and APOE variants worked together to impact the levels of anxiety negatively. Similarly, in AD patients, the RNF219 variants were found to be associated with increased anxiety levels. Our data indicate a novel synergistic activity APOE and RNF219 in the modulation of behavioral traits of female MCI and AD patients

Testis transcriptome analysis in male infertility: new insight on the pathogenesis of oligo-azoospermia in cases with and without AZFc microdeletion

<p>Abstract</p> <p>Background</p> <p>About 10% of cases of male infertility are due to the presence of microdeletions within the long arm of the Y chromosome (Yq). Despite the large literature covering this critical issue, very little is known about the pathogenic mechanism leading to spermatogenesis disruption in patients carrying these microdeletions. In order to identify the presence of specific molecular pathways leading to spermatogenic damage, testicular gene expression profiling was carried out by employing a microarray assay in 16 patients carrying an AZFc microdeletion or affected by idiopathic infertility. Hierarchical clustering was performed pooling the data set from 26 experiments (16 patients, 10 replicates).</p> <p>Results</p> <p>An intriguing and unexpected finding is that all the samples showing the AZFc deletion cluster together irrespectively of their testicular phenotypes. This cluster, including also four patients affected by idiopathic infertility, showed a downregulation of several genes related to spermatogenesis that are mainly involved in testicular mRNA storage. Interestingly, the four idiopathic patients present in the cluster showed no testicular expression of <it>DAZ </it>despite the absence of AZFc deletion in the peripheral blood.</p> <p>Conclusions</p> <p>Our expression profiles analysis indicates that several forms of infertility can be triggered by a common pathogenic mechanism that is likely related to alterations in testicular mRNA storage. Our data suggest that a lack of testicular DAZ gene expression may be the trigger of such mechanism. Furthermore, the presence of AZFc deletions in mosaic or the loss of function of AZFc genes in absence of Yq deletion can perhaps explain these findings. Finally, based on our data, it is intriguing to hypothesize that <it>DAZ </it>gene dysfunctions can account for a larger number of previously thought "idiopathic" infertility cases and investigation of such testicular gene dysfunction can be important to reveal the molecular determinant of infertility than are undetected when only testing Yq deletions in peripheral blood.</p