Metallic membranes for N2 separation & post-combustion CO2 capture improvement

Carbon (CO2) capture represents an important role in the reduction greenhouse gas emissions. Among various CO2 capture technologies currently investigated, post-combustion capture allows for the retrofitting of existing plants and industrial units. Today, the amine scrubbing is considered the most competitive method for CO2 removal in the flue gases from power plants in comparison to other technologies. Nevertheless, recent work has shown that the energy requirement for solvent recovery can decrease the overall efficiency of the power plants up to 16%1. Moreover, additional costs may occur in the solvent absorption technology because of solvent disposal and its continuous replacement due to chemical deterioration. In contrast, membrane systems usually do not require additional chemicals or solvents. In addition, membranes offer higher energy efficiencies, greater operational flexibility as well as simplicity of operation and maintenance. Polymeric membrane operations are currently being explored for CO2 capture in power plants. However, some issues still remain regarding the scalability and reliability of the polymeric materials under real operating conditions where the temperature is often too high for polymer stability. Metallic membranes, by contrast, usually require high temperature for operation and may be more beneficial in saving energy under high temperature conditions. In particular, their use for N2 removal from coal-fired flue gases located nearby the boiler exit may result in increased concentrations of CO2 and pollutants with a significant reduced gas volume in the downstream, allowing for traditional emissions controls to perform more efficiently and, consequently, lowering the overall energy consumption and capital and operating costs. Therefore, the aim of this work is to explore the potentiality of N2-selective metallic membranes for post-combustion CO2 capture. In particular, the effect of different temperature and pressure conditions as well as the effect of different gas exposure on membrane performance, in terms of N2 permeating flux and ideal selectivity of N2 with respect to other gas is studied and analyzed. Moreover, scanning electron microscope (SEM), electron microprobe analyzer (EMPA), and X-ray photoelectron spectroscopy (XPS) analyses are used for investigating the effect of the different operating conditions on the membrane surface. Based on a preliminary theoretical investigation using density functional theory, the Group V transition metals (e.g., vanadium (V), niobium (Nb) and tantalum (Ta)) show strong affinity toward N2. Therefore, these metals are chosen as membrane materials in this study. Pure V, Nb, and Ta foils with a thickness of 40 μm are used. Dp [kPa] 200 300 400 500 N2 Permeance [mol/s·m2·kPa] 3.23·10-8 2.85·10-8 2.78·10-8 2.55·10-8 Permeation tests with pure gases (He, N2 and CO2) are performed to characterize the membranes in terms of N2 permeating flux and ideal selectivity at different temperature and pressure, which are varied from 400 to 600 °C and from 2.0 to 6 bar, respectively. Nb test results are only shown as a particular example in this abstract. In Table 1, the N2 permeances as a function of Δp are reported. The Nb membrane showed complete selectivity towards N2 permeation at 400 °C and trans-membrane pressure (Dp) greater than 3.0 bar. At lower pressure, no N2 permeating flux through the membrane is detected. The Nb membrane is completely destroyed when the temperature is increased up to 500 °C. EMPA analysis on this membrane showed the presence of oxygen on the surface, as illustrated in Figure 1. Among the metallic membranes used in this study, V membrane showed better performance in terms of N2 permeating flux and long-term stability. Therefore, the future study will be focused on the synthesis and analysis of V alloys in order to enhance the N2 permeance and improve the resistant of membrane towards oxidation

H2 production in Palladium-based Membrane Reactor

One possible use for hydrogen, without direct greenhouse gas emissions, is as feed for a fuel cell (FC), with the most readily available technology being a proton exchange membrane FC (PEMFC). In order to avoid the poison of PEMFC’s Pt-based catalyst due to the presence of ppm levels of CO, the hydrogen feed needs to be ultra-pure. The industrial process for hydrogen production, which is a multi-step energy intensive process followed by further separation/purification, can be a potential source [1]. However, as an alternative method a Pd-based membrane reactor (MR) can be used owing to its ability to provide the pure hydrogen without any further purification. Moreover, the MR works at milder operating conditions compared to the traditional system. In the last years, Pd-based composite membranes, i.e. thin metallic layer supported on such porous materials as ceramics or stainless steel, have been considered owing to their lower cost (thin Pd layer) and higher mechanical resistant (porous support) than dense Pd-based ones [2]. Therefore, the aim of this study is to analyze the potentialities of a Pd membrane supported on porous stainless steel (PSS) with the intent to produce pure hydrogen from methane steam reforming. The initial characterization of the membrane by way of ideal selectivity took place at 400°C with H2, He and N2 and P in the range of 1.5 - 3.0 bar. After ideal selectivity characterization of the Pd/PSS membrane, methane steam reforming reaction is carried out in MR by varying reaction pressure and sweep gas flow rate. The best performance of the Pd-based MR is obtained at 400 °C, 3.0 bar and 100 mL/min of sweep-gas, yielding a methane conversion of 84%, hydrogen recovery of 82%, and obtaining a pure hydrogen stream at the permeate side. REFERENCES [1] Rostrup-Nielsen, J.R., Catalytic steam reforming. 1984: Springer. [2] Liguori, S., et al., Performance of a Pd/PSS membrane reactor to produce high purity hydrogen via WGS reaction. Catalysis Today, 2012. 193(1): p. 87-94

Can NMT Understand Me? Towards Perturbation-based Evaluation of NMT Models for Code Generation

Neural Machine Translation (NMT) has reached a level of maturity to be recognized as the premier method for the translation between different languages and aroused interest in different research areas, including software engineering. A key step to validate the robustness of the NMT models consists in evaluating the performance of the models on adversarial inputs, i.e., inputs obtained from the original ones by adding small amounts of perturbation. However, when dealing with the specific task of the code generation (i.e., the generation of code starting from a description in natural language), it has not yet been defined an approach to validate the robustness of the NMT models. In this work, we address the problem by identifying a set of perturbations and metrics tailored for the robustness assessment of such models. We present a preliminary experimental evaluation, showing what type of perturbations affect the model the most and deriving useful insights for future directions.Comment: Paper accepted for publication in the proceedings of The 1st Intl. Workshop on Natural Language-based Software Engineering (NLBSE) to be held with ICSE 202

Adherence to Mediterranean Diet and Prevention of Excessive Weight Gain during Pregnancy: Study in a Cohort of Normal Weight Caucasian Women

This study investigated the association between adherence to Mediterranean Diet (MD) and the risk of excessive Gestational Weight Gain (GWG).Ninety five Caucasian normal weight pregnant women were recruited within the 16thgestational week. We evaluated the adherence to MD at recruitment (T0) and at third trimester (T1) by validated food frequency questionnaire. Adherence to MD was indicated by a score between 0 and 13. Adequate GWG was defined in according with IOM (Institute of Medicine, 2009) recommendations.The 26.3% dropped out, then the completer participants were 70 (33.2±3.5 ys, 74.3% nulliparous).MD score at T0 was 7.2±1.5 and it did not significantly change at T1. Mean MD score between T0 and T1 was 7.3±1.3: a good adherence to MD, defined by MD score?8, was satisfied by 27.1%. The GWG at T1 was adequate in 64.3%, while exceed in 35.7%. Women with adequate GWG showed a MD score significantly higher than women with excessive GWG (MD score: 7.5±1.3 vs 6.8±1.0, p=0.02). A good adherence to MD was associated with a significantly lower risk ratio of excessive GWG (RR 0.24, 95% CI 0.1-0.9, p=0.04).MD could be a dietary pattern able to prevent excessive GWG in normal weight women

Expression of orexin B and its receptor 2 in rat testis

The peptides orexin A (OxA) and orexin B (OxB) deriving from a common precursor molecule, prepro-orexin, by proteolytic cleavage, bind the two G-coupled OX1 and OX2 receptors. While OX1 selectively binds OxA, OX2 shows similar affinity for both orexins. Firstly discovered in the hypothalamus, orexins and their receptors have been found in other brain regions as well as in peripheral tissues of mammals, thus resulting involved in the regulation of a broad variety of physiological functions. While the functional localization of OxA and OX1 in the mammalian genital tract has been already described, the expression of OxB and OX2 and their potential role in the reproductive functions remain to be explored. Here, we investigated the presence of OxB and OX2 in the rat testis by immunohistochemical and biochemical analyses. The results definitely demonstrated the localization of OxB and OX2 in pachytene and second spermatocytes as well as in spermatids at all stages of the cycle of the seminiferous epithelium. The expression of both OX2 mRNA and protein in the rat testis was also established by RT-PCR and Western blotting, respectively. The analysis of the molecular mechanism of action of OxB in the rat testis showed that OxB, in contrast with OxA, is unable to promote steroidogenesis. These results translate into the regulation of diverse biological actions by OxA and OxB in the male gonad

On the linear term correction for needlets/wavelets non-Gaussianity estimators

We derive the linear correction term for needlet and wavelet estimators of the bispectrum and the non-linearity parameter fNL on cosmic microwave background radiation data. We show that on masked WMAP-like data with anisotropic noise, the error bars improve by 10-20% and almost reach the optimal error bars obtained with the KSW estimator (Komatsu et al 2005). In the limit of full-sky and isotropic noise, this term vanishes. We apply needlet and wavelet estimators to the WMAP 7-year data and obtain our best estimate fNL=37.5 \pm 21.8.Comment: 10 pages, submitted to Ap

Localization of orexin B and orexin-2 receptor in the rat epididymis

The peptides orexin A (OXA) and orexin B (OXB) derived from the proteolytic cleavage of a common precursor molecule, prepro-orexin, were originally described in the rat hypothalamus. Successively, they have been found in many other brain regions as well as in peripheral organs of mammals and other less evolved animals. The widespread localization of orexins accounts for the multiple activities that they exert in the body, including the regulation of energy homeostasis, feeding, metabolism, sleep and arousal, stress, addiction, and cardiovascular and endocrine functions. Both OXA and OXB peptides bind to two G-coupled receptors, orexin-1 (OX1R) and orexin-2 (OX2R) receptor, though with different binding affinity. Altered expression/activity of orexins and their receptors has been associated with a large number of human diseases. Though at present evidence highlighted a role for orexins and cognate receptors in mammalian reproduction, their central and/or local effects on gonadal functions remain poorly known. Here, we investigated the localization of OXB and OX2R in the rat epididymis. Immunohistochemical staining of sections from caput, corpus and cauda segments of the organ showed intense signals for both OXB and OX2R in the principal cells of the lining epithelium, while no staining was detected in the other cell types. Negative results were obtained from immunohistochemical analysis of hypothalamic and testicular tissues from OX2R knock-out mice (OX2R−/−) and OX1R/OX2R double knock-out (OX1R−/−; OX2R−/−) mice, thus demonstrating the specificity of the rabbit polyclonal anti-OX2R antibody used in our study. On contrary, the same antibody clearly showed the presence of OX2R in sections from hypothalamus and testis of normal mice and rats which are well known to express the receptor. Thus, our results provide the first definite evidence for the immunohistochemical localization of OXB and OX2R in the principal cells of rat epididymis

Expression and potential role of the peptide orexin-A in prostate cancer

The peptides orexin-A and orexin-B and their G protein-coupled OX1 and OX2 receptors are involved in multiple physiological processes in the central nervous system and peripheral organs. Altered expression or signaling dysregulation of orexins and their receptors have been associated with a wide range of human diseases including narcolepsy, obesity, drug addiction, and cancer. Although orexin-A, its precursor molecule prepro-orexin and OX1 receptor have been detected in the human normal and hyperplastic prostate tissues, their expression and function in the prostate cancer (PCa) remains to be addressed. Here, we demonstrate for the first time the immunohistochemical localization of orexin-A in human PCa specimens, and the expression of prepro-orexin and OX1 receptor at both protein and mRNA levels in these tissues. Orexin-A administration to the human androgen-dependent prostate carcinoma cells LNCaP up-regulates OX1 receptor expression resulting in a decrease of cell survival. Noteworthy, nanomolar concentrations of the peptide counteract the testosterone-induced nuclear translocation of the androgen receptor in the cells: the orexin-A action is prevented by the addition of the OX1 receptor antagonist SB-408124 to the test system. These findings indicate that orexin-A/OX1 receptor interaction interferes with the activity of the androgen receptor which regulates PCa onset and progression, thus suggesting that orexin-A and its receptor might represent novel therapeutic targets to challenge this aggressive cancer

Narcolepsy is a common phenotype in HSAN IE and ADCA-DN

We report on the extensive phenotypic characterization of five Italian patients from four unrelated families carrying dominant heterozygous DNMT1 mutations linked to two distinct autosomal dominant diseases: hereditary sensory and autonomic neuropathy with dementia and hearing loss type IE (HSAN IE) and autosomal dominant cerebellar ataxia, deafness and narcolepsy (ADCA-DN). Patients underwent genetic analysis of DNMT1 gene, neurophysiological tests investigating sleep, auditory functions and peripheral nervous system, ophthalmological studies including optical coherence tomography, lymphoscintigraphy, brain magnetic resonance and nuclear imaging, cerebrospinal fluid hypocretin-1, total tau, phosphorylated tau, amyloid-β1-42 and 14-3-3 proteins measurement, skin, muscular and sural nerve biopsies. Exome and direct sequencing studies disclosed two different point mutations affecting exon 21 of DNMT1 gene in patients with ADCA-DN, a novel heterozygous point mutation in exon 20 in two affected HSAN IE siblings, and a trinucleotide deletion in exon 20 in the latter patient with HSAN IE. Phenotypic characterization pinpoints that ADCA-DN and HSAN IE represent two discrete clinical entities belonging to the same disease spectrum, with variable degree of overlap. Remarkably, narcolepsy with or without cataplexy with low/intermediate or normal cerebrospinal fluid hypocretin-1 is present in both diseases. The human leukocyte antigen DQB1*06:02 was absent in all patients. Other common symptoms and features observed in our cases, involving the central and peripheral nervous system, include deafness, optic neuropathy-previously not reported in HSAN IE-large and small fibres polyneuropathy and lower limbs oedema. Overall, the two syndromes share more characteristics than previously recognized and narcolepsy is common to both. HSAN IE and ADCA-DN are two extreme phenotypic manifestations of a DNMT1 methylopathy