Classical and quantum spinor cosmology with signature change

We study the classical and quantum cosmology of a universe in which the matter source is a massive Dirac spinor field and consider cases where such fields are either free or self-interacting. We focus attention on the spatially flat Robertson-Walker cosmology and classify the solutions of the Einstein-Dirac system in the case of zero, negative and positive cosmological constant $\Lambda$. For $\Lambda<0$, these solutions exhibit signature transitions from a Euclidean to a Lorentzian domain. In the case of massless spinor fields it is found that signature changing solutions do not exist when the field is free while in the case of a self-interacting spinor field such solutions may exist. The resulting quantum cosmology and the corresponding Wheeler-DeWitt equation are also studied for both free and self interacting spinor fields and closed form expressions for the wavefunction of the universe are presented. These solutions suggest a quantization rule for the energy.Comment: 13 pages, 4 figure

Compactification and signature transition in Kaluza-Klein spinor cosmology

We study the classical and quantum cosmology of a 4+1-dimensional space-time with a non-zero cosmological constant coupled to a self interacting massive spinor field. We consider a spatially flat Robertson-Walker universe with the usual scale factor $R(t)$ and an internal scale factor $a(t)$ associated with the extra dimension. For a free spinor field the resulting equations admit exact solutions, whereas for a self interacting spinor field one should resort to a numerical method for exhibiting their behavior. These solutions give rise to a degenerate metric and exhibit signature transition from a Euclidean to a Lorentzian domain. Such transitions suggest a compactification mechanism for the internal and external scale factors such that $a\sim R^{-1}$ in the Lorentzian region. The corresponding quantum cosmology and the ensuing Wheeler-DeWitt equation have exact solutions in the mini-superspace when the spinor field is free, leading to wavepackets undergoing signature change. The question of stabilization of the extra dimension is also discussed.Comment: 12 pages, 1 figure, to appear in Annals of Physic

Emergence of Convolutional Neural Network in Future Medicine: Why and How. A Review on Brain Tumor Segmentation

Manual analysis of brain tumors magnetic resonance images is usually accompanied by some problem. Several techniques have been proposed for the brain tumor segmentation. This study will be focused on searching popular databases for related studies, theoretical and practical aspects of Convolutional Neural Network surveyed in brain tumor segmentation. Based on our findings, details about related studies including the datasets used, evaluation parameters, preferred architectures and complementary steps analyzed. Deep learning as a revolutionary idea in image processing, achieved brilliant results in brain tumor segmentation too. This can be continuing until the next revolutionary idea emerging. © 2018 Behrouz Alizadeh Savareh et al., published by De Gruyter Open

Signature Change in Noncommutative FRW Cosmology

The conditions for which the no boundary proposal may have a classical realization of a continuous change of signature, are investigated for a cosmological model described by FRW metric coupled with a self interacting scalar field, having a noncommutative phase space of dynamical variables. The model is then quantized and a good correspondence is shown between the classical and quantum cosmology indicating that the noncommutativity does not destruct the classical-quantum correspondence. It is also shown that the quantum cosmology supports a signature transition where the bare cosmological constant takes a vast continuous spectrum of negative values. The bounds of bare cosmological constant are limited by the values of noncommutative parameters. Moreover, it turns out that the physical parameters are constrained by the noncommutativity parametres.Comment: 15 pages, 4 figures, Minor revision, references adde

Microstructure, mechanical and functional behavior

Funding Information: JS acknowledges the China Scholarship Council for funding the Ph.D. grant (CSC NO. 201808320394). JPO acknowledges funding by national funds from FCT - Fundação para a Ciência e a Tecnologia, I.P., in the scope of the projects LA/P/0037/2020 of the Associate Laboratory Institute of Nanostructures, Nanomodelling and Nanofabrication – i3N. This activity has received funding from the European Institute of Innovation and Technology (EIT) – Project Smart WAAM: Microstructural Engineering and Integrated Non-Destructive Testing. This body of the European Union receives support from the European Union's Horizon 2020 research and innovation programme. Publisher Copyright: © 2023 The AuthorsShape memory alloys (SMA) are a class of smart materials with inherent shape memory and superelastic characteristics. Unlike other SMAs, iron-based SMAs (Fe-SMA) offer cost-effectiveness, weldability, and robust mechanical strength for the construction industry. Thus, applying these promising materials to advanced manufacturing processes is of considerable industrial and academic relevance. This study aims to present a pioneer application of a Fe–Mn–Si–Cr–Ni–V-C SMA to arc-based directed energy deposition additive manufacturing, namely wire and arc additive manufacturing (WAAM), examining the microstructure evolution and mechanical/functional response. The WAAM-fabricated Fe-SMAs presented negligible porosity and high deposition efficiency. Microstructure characterization encompassing electron microscopy and high energy synchrotron X-ray diffraction revealed that the as-deposited material is primarily composed by γ FCC phase with modest amounts of VC, ε and σ phases. Tensile and cyclic testing highlighted the Fe-SMA's excellent mechanical and functional response. Tensile testing revealed a yield strength and fracture stress of 472 and 821 MPa, respectively, with a fracture strain of 26%. After uniaxial tensile loading to fracture, the γ → ε phase transformation was clearly evidenced with post-mortem synchrotron X-ray diffraction analysis. The cyclic stability during 100 load/unloading cycles was also evaluated, showcasing the potential applicability of the fabricated material for structural applications.publishersversionpublishe

Cement degradation in CO2 storage sites: a review on potential applications of nanomaterials

© 2018 The Author(s) Carbon capture and sequestration (CCS) has been employed to reduce global warming, which is one of the critical environmental issues gained the attention of scientific and industrial communities worldwide. Once implemented successfully, CCS can store at least 5 billion tons of CO2per year as an effective and technologically safe method. However, there have been a few issues raised in recent years, indicating the potential leakages paths created during and after injection. One of the major issues might be the chemical interaction of supercritical CO2with the cement, which may lead to the partial or total loss of the cement sheath. There have been many approaches presented to improve the physical and mechanical properties of the cement against CO2attack such as changing the water-to-cement ratio, employing pozzolanic materials, and considering non-Portland cements. However, a limited success has been reported to the application of these approaches once implemented in a real-field condition. To date, only a few studies reported the application of nanoparticles as sophisticated additives which can reinforce oil well cements. This paper provides a review on the possible application of nanomaterials in the cement industry where physical and mechanical characteristics of the cement can be modified to have a better resistance against corrosive environments such as CO2storage sites. The results obtained indicated that adding 0.5 wt% of Carbon NanoTubes (CNTs) and NanoGlass Flakes (NGFs) can reinforce the thermal stability and coating characteristics of the cement which are required to increase the chance of survival in a CO2sequestrated site. Nanosilica can also be a good choice and added to the cement by as much as 3.0 wt% to improve pozzolanic reactivity and thermal stability as per the reports of recent studies

Computed Tomography Imaging of Primary Lung Cancer in Mice Using a Liposomal-Iodinated Contrast Agent

To investigate the utility of a liposomal-iodinated nanoparticle contrast agent and computed tomography (CT) imaging for characterization of primary nodules in genetically engineered mouse models of non-small cell lung cancer.Primary lung cancers with mutations in K-ras alone (Kras(LA1)) or in combination with p53 (LSL-Kras(G12D);p53(FL/FL)) were generated. A liposomal-iodine contrast agent containing 120 mg Iodine/mL was administered systemically at a dose of 16 µl/gm body weight. Longitudinal micro-CT imaging with cardio-respiratory gating was performed pre-contrast and at 0 hr, day 3, and day 7 post-contrast administration. CT-derived nodule sizes were used to assess tumor growth. Signal attenuation was measured in individual nodules to study dynamic enhancement of lung nodules.A good correlation was seen between volume and diameter-based assessment of nodules (R(2)>0.8) for both lung cancer models. The LSL-Kras(G12D);p53(FL/FL) model showed rapid growth as demonstrated by systemically higher volume changes compared to the lung nodules in Kras(LA1) mice (p<0.05). Early phase imaging using the nanoparticle contrast agent enabled visualization of nodule blood supply. Delayed-phase imaging demonstrated significant differential signal enhancement in the lung nodules of LSL-Kras(G12D);p53(FL/FL) mice compared to nodules in Kras(LA1) mice (p<0.05) indicating higher uptake and accumulation of the nanoparticle contrast agent in rapidly growing nodules.The nanoparticle iodinated contrast agent enabled visualization of blood supply to the nodules during the early-phase imaging. Delayed-phase imaging enabled characterization of slow growing and rapidly growing nodules based on signal enhancement. The use of this agent could facilitate early detection and diagnosis of pulmonary lesions as well as have implications on treatment response and monitoring

Effect of Nano-Particles on the Performance and Emission of a Diesel Engine using Biodiesel-Diesel Blend

n experimental investigation was conducted in a six - cylinder, four-stroke diesel engine to establish the effects of Multi Wall Carbon Nano Tubes (MWCNT) with the dosing levels from 2.5 to 30 ppm with the waste vegetable oil (WVO) methyl esters fuel that was produced using the transestrification process, and subsequently, the WVO methyl ester was blended with diesel fuel in the proportion of 80% of diesel and 20% biodiesel by volume (B20). The Carbon nanotubes (with nano-structure (1/3) Chiral Metal and (2/3) semiconductor zigzag particles with the length of 10 μm and diameter of 5 nm with purity rate of 95%) were blended with the biodiesel fuel .The CNTs we re blended with the biodiesel with the aid of ultrasonicator. The whole investigation was conducted in the diesel engine using the following fuels: neat diesel fuel (D100), 20% biodiesel and 80% diesel by volume (B20), as well as B20 and CNT blended fuels accordingly.The experimental results revealed a considerable enhancement in the performance parameters for the CNT blended biodiesel fuels compared to the neat biodiesel and neat diesel fuel (power increased up to 17%, torque increased 18%, bsfc decreased 38.5%). Emission parameters for the CNT blended decreased compared to neat diesel and neat biodiesel fuels (HC decreased up to 22%, CO emission decreased 14%).CNT nano-additives are considered as a propitious fuel - borne catalyst to improve the fuel properties, owing to their enhanced surface area/volume ratio, quick evaporation and shorter ignition delay characteristics that help to improve the performance parameters of engine and decrease emission

Magnetic resonance imaging and peroxide-enhanced anal endosonography in assessment of fistula in anus: comparison with surgery

Background: Although there are numerous modalities to evaluate perianal fistula, there is still a need to determine the most sensitive, specific, and accurate modality. This study was conducted to determine the performance characteristics of magnetic resonance imaging (MRI) and contrast-enhanced three-dimensional endoanal ultrasonography (C-3DEAUS) considering surgery as the gold standard. Methods: A total of 36 patients who were diagnosed of having anal fistula with 10-MHz hydrogen peroxide-enhanced three-dimensional EAUS underwent MRI followed by surgery. Both of tests were done the day before surgery. Fistula classification was determined with each modality according to Parks� criteria as inter-sphincteric, trans-sphincteric, extra-sphincteric, or supra-sphincteric and was compared with the surgical findings in all patients. If the accuracy of each modality was at least 85 compared with the surgery, it was considered as clinically useful. Results: Agreement for the classification of the primary fistula tract was 94.3 for C-3DEAUS and surgery, 97.1 for MRI and surgery. Considering a clock face, C-3DEAUS and surgery agreed in location of internal opening in 88.6 of cases while MRI and surgery agreed in 97.1 . In detection a collection, agreement between C-3DEAUS and surgery was 82.9 , and 97.1 between MRI and surgery. Conclusions: Both methods had almost perfect agreement with surgical findings in the classification of the primary fistula tract but MRI had more agreement in distinguishing other aspects of a fistula and it can be used as the most reliable method for preoperative evaluation of perianal fistulas. © 2015, Springer-Verlag Wien