The chemical nature of point defects, their segregation, cluster or complex formation in ZnO is an important area of investigation. The evolution of a defective state with MeV Ar ion irradiation ...fluence 1 × 1014 and 1 × 1016 ions cm−2 has been monitored here using x-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and Raman spectroscopy. The XPS study shows the presence of oxygen vacancies (VO) in Ar irradiated ZnO. Zn(LMM) Auger spectra clearly identifies a transition involving metallic zinc in the irradiated samples. An intense PL emission from interstitial Zn (IZn)-related shallow donor bound excitons (DBX) is visible in the 10 K spectra for all samples. Although overall PL is largely reduced with irradiation disorder, DBX intensity is increased for the highest fluence irradiated sample. The Raman study indicates damage in both the zinc and oxygen sub-lattice by an energetic ion beam. Representative Raman modes from defect complexes involving VO, IZn and IO are visible after irradiation with intermediate fluence. A further increase of fluence shows, to some extent, a homogenization of disorder. A huge reduction of resistance is also noted for this sample. Certainly, high irradiation fluence induces a qualitative modification of the conventional (and highly resistive) grain boundary (GB) structure of granular ZnO. A low resistive path, involving IZn related shallow donors, across the GB can be presumed to explain resistance reduction. Open volumes (VZn and VO) agglomerate more and more with increasing irradiation fluence and are finally transformed to voids. The results as a whole have been elucidated with a model which emphasizes the possible evolution of a new defect microstructure that is distinctively different from the GB-related disorder. Based on the model, qualitative explanations of commonly observed radiation hardness, colouration and ferromagnetism in disordered ZnO have been put forward. A coherent scenario on disorder accumulation in ZnO has been presented, which we believe will guide further discussion on this topic.
The dielectric properties of epoxy nanocomposites with insulating nano-fillers, viz., TiO 2 , ZnO and AI 2 O 3 were investigated at low filler concentrations by weight. Epoxy nanocomposite samples ...with a good dispersion of nanoparticles in the epoxy matrix were prepared and experiments were performed to measure the dielectric permittivity and tan delta (400 Hz-1 MHz), dc volume resistivity and ac dielectric strength. At very low nanoparticle loadings, results demonstrate some interesting dielectric behaviors for nanocomposites and some of the electrical properties are found to be unique and advantageous for use in several existing and potential electrical systems. The nanocomposite dielectric properties are analyzed in detail with respect to different experimental parameters like frequency (for permittivity/tan delta), filler size, filler concentration and filler permittivity. In addition, epoxy microcomposites for the same systems were synthesized and their dielectric properties were compared to the results already obtained for nanocomposites. The interesting dielectric characteristics for epoxy based nanodielectric systems are attributed to the large volume fraction of interfaces in the bulk of the material and the ensuing interactions between the charged nanoparticle surface and the epoxy chains.
To ensure safe drinking water sources in the future, it is imperative to understand the quality and pollution level of existing groundwater. The prediction of water quality with high accuracy is the ...key to control water pollution and the improvement of water management. In this study, a deep learning (DL) based model is proposed for predicting groundwater quality and compared with three other machine learning (ML) models, namely, random forest (RF), eXtreme gradient boosting (XGBoost), and artificial neural network (ANN). A total of 226 groundwater samples are collected from an agriculturally intensive area Arang of Raipur district, Chhattisgarh, India, and various physicochemical parameters are measured to compute entropy weight-based groundwater quality index (EWQI). Prediction performances of models are determined by introducing five error metrics. Results showed that DL model is the best prediction model with the highest accuracy in terms of R2, i.e., R2 = 0996 against the RF (R2 = 0.886), XGBoost (R2 = 0.0.927), and ANN (R2 = 0.917). The uncertainty of the DL model output is cross-verified by running the proposed algorithm with newly randomized dataset for ten times, where minor deviations in the mean value of performance metrics are observed. Moreover, input variable importance computed by prediction models highlights that DL model is the most realistic and accurate approach in the prediction of groundwater quality.
•Groundwater quality is assessed using EWQI method.•Machine learning (ML) algorithms are used for predicting groundwater quality.•Prediction performance of RF, XGBoost, ANN and DL models are compared.•DL based quality prediction model performs much better than other ML models.
Fluctuations of conserved quantities such as baryon number, charge, and strangeness are sensitive to the correlation length of the hot and dense matter created in relativistic heavy-ion collisions ...and can be used to search for the QCD critical point. We report the first measurements of the moments of net-kaon multiplicity distributions in Au+Au collisions at sNN=7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV. The collision centrality and energy dependence of the mean (M), variance (σ2), skewness (S), and kurtosis (κ) for net-kaon multiplicity distributions as well as the ratio σ2/M and the products Sσ and κσ2 are presented. Comparisons are made with Poisson and negative binomial baseline calculations as well as with UrQMD, a transport model (UrQMD) that does not include effects from the QCD critical point. Within current uncertainties, the net-kaon cumulant ratios appear to be monotonic as a function of collision energy.
Abstract
Mutually unbiased bases (MUBs) provide a standard tool in the verification of quantum states, especially when harnessing a complete set for optimal quantum state tomography. In this work, we ...investigate the detection of entanglement via inequivalent sets of MUBs, with a particular focus on unextendible MUBs. These are bases for which an additional unbiased basis cannot be constructed and, consequently, are unsuitable for quantum state verification. Here, we show that unextendible MUBs, as well as other inequivalent sets in higher dimensions, can be more effective in the verification of entanglement. Furthermore, we provide an efficient and systematic method to search for inequivalent MUBs and show that such sets occur regularly within the Heisenberg–Weyl MUBs, as the dimension increases. Our findings are particularly useful for experimentalists since they demonstrate that a clever selection of MUBs allows for entanglement detection with fewer measurements.
Multifunctional bio-based epoxy resin (PEMPAE) was synthesized by reacting Diels-Alder adduct of gum rosin and maleic anhydride (MPA) with pentaerythritol to get the esterified product (PEMPA) which ...was further epoxidized using epichlorohydrin and potassium hydroxide. This paper includes the synthesis of bio-based imidoamine curing agent (IAEDK) by reacting diamino diphenyl ether (DDE) with dimaleopimaryl ketone (DMPK), a dehydrodecarboxylated derivative of MPA. The synthesized products were characterized by Fourier transform infrared Spectroscopy (FTIR), proton and 13C nuclear magnetic resonance spectroscopy (1H-NMR and 13C-NMR). Curing dynamics of rosin-based epoxy cured with rosinbased imidoamine crosslinker were evaluated using differential scanning calorimetry (DSC) and were compared with resin cured with synthesized DMPK and commercial DDE curing agents. The mechanical properties and thermal stability of the cured epoxy samples were evaluated using a universal testing machine (UTM) and thermogravimetric analyzer (TGA), respectively. The chemical resistance of the samples was determined in terms of % weight loss when immersed in NaOH, HCl and NaCl solutions. The morphological changes were also evaluated via scanning electron microscopy (SEM). Results revealed that rosin-based epoxy cured with imidoamine curing agent gave preeminent properties over the commercial one. The studies suggested that curing properties were greatly affected by the molecular topology and kind of curing agent used.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Abstract
A spectroscopic study is carried out to investigate pulsed plasma stream produced in a coaxial plasma accelerator under the influence of an external longitudinal magnetic field. The dynamics ...of Argon plasma stream that includes the excitations and emissions of plasma species and its different parameter variations on the application of an external longitudinal magnetic field are reported in this work. The behavior of the ionized and neutral species of argon plasma is studied from their intensity distribution profiles which indicate the occurrence of faster recombination as compared to the field-free case. The variation of pressure reveals a significant influence on the recombination and diffusion process of the plasma species. Moreover, the variation of cathode voltage leads to variation in input energy to the system which influences the ionization and excitation processes of the plasma species. A plasma density (N
e
) jump is achieved from 10
21
–10
22
m
−3
at a relatively higher pressure ∼8 bar plenum pressure in presence of the magnetic field. Saturation of the emissions and excitations of plasma species are revealed from the intensity profile and electron excitation temperature (T
exc
) profile which occur at different pressure and voltage both for field and field-free cases. The electron temperature (T
e
) is estimated using the FLYCHK code by comparing the simulated charge state distributions with the experimental findings. Using known parameters in the code, the different estimated T
e
shows a linear and an exponential decrement respectively in the absence and presence of the magnetic field. Maximum T
e
of 2.2 eV is reported which decreases to 1.51 eV at a significant increase of plasma density of 10
22
m
−3
.
Mn-MCM-41 is an efficient catalyst for single-step amination of benzene. The catalyst interacts with hydroxylamine in acidic medium to give
NH
3
+ radicals which react with benzene to give protonated ...aminocyclohexadienyl intermediates. The unstable intermediate is oxidized by the catalyst to give aniline.
▪
Mesoporous MCM-41 and Mn
-MCM-41 with varying Si/Mn ratios such as 100, 60, 40, 20 and 10 were synthesized at room temperature under basic conditions by direct insertion of metal ions during synthesis. The bulk and surface properties of the synthesized catalysts were examined by XRD, nitrogen adsorption/desorption, FT-IR, TG-DTA, Raman spectra, ESR technique and UV–vis diffuse reflectance spectra (DRS). Results indicated that Mn ions are partially incorporated into the Si
O framework and lead to the vibration of Si
O
Mn bonds. ESR spectra showed a well-resolved sextet centred at
g
=
2.0 indicating distorted octahedral symmetry of Mn(II) species in Mn-MCM-41. UV–vis DRS showed co-existence of Mn
2+ and Mn
3+ in Mn-MCM-41; these coordinated to Si(IV) by disordered octahedral and tetrahedral environments, respectively. Mn-MCM-41 materials showed significant catalytic activity for single-step amination of benzene in acetic acid–water medium under mild reaction conditions using hydroxylamine as aminating agent. Mn-MCM-41 (Si/Mn
=
20) showed the highest benzene conversion (68.5%) and 100% selectivity for aniline.
► Graft copolymerization of Agave americana fibers from binary vinyl monomer mixtures initiated by ceric ions. ► Optimization of grafting parameters such as reaction time, temperature, concentration ...of initiator, monomer and nitric acid. ► Study the effect of feed composition and feed molarity on percent graft yield. ► Calculation of reactivity ratios of monomers and Study of Physico chemical, thermal properties of graft copolymers.
Functionalization of Agave fibers was carried out by graft copolymerization of acrylonitrile (AN) and ethyl acrylate (EA) from their binary solutions in presence of Ce (IV) ions at a temperature of 45±0.1°C. An increase in the graft copolymerization was obtained with the increase in the feed molarity of the comonomers up to certain extent. Contrary to lesser affinity of acrylonitrile to grafting on Agave fibers, a synergistic effect of ethyl acrylate on acrylonitrile was observed when graft copolymers were prepared using different feed compositions (fAN). The graft copolymers were characterized by various techniques such as FT-IR, TGA/DTA, X-RD and SEM analysis. Further swelling behavior of grafted fibers in different solvents, moisture absorption behavior and resistance to chemicals was investigated as a function of percent grafting to define their end uses in different environments.
ABSTRACT
A sub-mitral left ventricular aneurysm is a rare condition. It is a congenital outpouching of the left ventricular wall, invariably occurring adjacent to the posterior mitral leaflet. ...Sub-mitral aneurysm (SMA) has usually been reported as a consequence of myocardial ischemia (MI), rheumatic heart disease, tuberculosis, and infective endocarditis. Nevertheless, there have been few case reports of congenital SMA in India. It usually presents with symptoms of heart failure. We report a rare case of congenital SMA in a 27-year-old young Indian and its successful management through a trans-aneurysmal approach.
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