Molecular Bands Research Articles

Coverage-Dependent Modulation of Charge Density at the Interface between Ag(001) and Ruthenium Phthalocyanine

When an organic film is deposited on a metal surface, charge layers are formed at the interface. These are an important feature of the interface electronic structure and play a crucial role as separation layers between electrodes and active layers in organic devices. Here, we report on a study of the interface between diruthenium phthalocyanine, (RuPc)2, and the Ag(001) surface. The molecules form two different commensurable arrangements on the substrate, a low density one for a coverage well below the first monolayer and a high density one up to the completion of the monolayer. The focus of this study is on the interface states evolution with the molecular density on the metal surface and the charge distribution in the thin interfacial layer between molecules and substrate. From this investigation, conducted by low energy electron diffraction, scanning tunneling microscopy/spectroscopy, photoemission spectroscopy, and density functional theory, we have found that, even if individual molecules are characterized by a quite similar surface-to-molecule charge transfer pattern, the two molecular arrangements present different valence band structures and, more interestingly, different modulations of the interface charge. These charge modulations are governed by interfacial states energetically resonant with the molecular states, localized at the position of the molecules as well as by a reaction of the electronic cloud of the metal surface to the molecular adsorption due to a Pauli pushback effect. This complex, spatial charge modulation makes the (RuPc)2/Ag(001) an interesting case of interaction intermediate between physisorption and chemisorption.

Computational and Experimental Study of Nonequilibrium Flow in Plasma Wind Tunnel

The present work examines the thermochemical nonequilibrium flow in the freestream and shock layer of the Plasma Wind Tunnel Facility using experiments and computations. Computational studies were performed using the open-source solver , which was validated using the NASA Interaction Heating Facility case. Two chemical reaction models were used to compute the nonequilibrium state of air, composed of six species (, , NO, N, O, Ar). Optical emission spectroscopy was employed to experimentally capture the first positive system emission from the freestream and molecular CN vibration bands emissions in the shock region. The Boltzmann plot method was employed to estimate the vibrational temperatures from the measured spectra. The measured vibrational temperatures in the freestream for two different transitions of agree with one another, which shows that the vibrational modes obey the Boltzmann distribution for the conditions considered in this study. The vibrational temperatures computed using in the nozzle freestream and the shock layer for the Plasma Wind Tunnel conditions agree with the values obtained from optical emission spectroscopy.

Aggregation of Asphaltene Subfractions A1 and A2 in Different Solvents from the Perspective of Molecular Dynamics Simulations

The aggregation behavior of model molecules of asphaltene subfractions A1 and A2 dissolved in heptane, toluene, and tetrahydrofuran (THF) were studied using molecular dynamics simulations. The proposed asphaltene molecular models are based on previously studied structures with two new models, including a highly aromatic model with a prominent island-type molecule and another molecule with a prominent archipelago-type architecture. The aggregation mechanisms in toluene, THF, and heptane solvents were studied. The results in heptane and toluene were consistent with the solubility of asphaltenes and their subfractions in these solvents. The size of the aggregates is well-correlated with aromaticity. When considering THF, large aggregates are broken down into smaller aggregates. This could lead to the mixture of high, medium, and low molecular weight distribution bands usually observed when gel permeation chromatography (GPC) analyses are conducted on asphaltene samples in THF. The size distribution extracted from the simulations shows a bimodal distribution with profiles similar to the size distribution profiles usually found in GPC analysis for asphaltene samples in THF. The distributions of dipole moments of the aggregates against the number of molecules in aggregates were constructed in both THF and toluene and reveal that the dipole moment of the aggregates vanishes when the number of molecules increases as a result of a random structure of the aggregates. The contributions of different molecular interactions to the aggregation mechanism, such as π stacking, van der Waals, and hydrogen bonds, are described.

A spectral classification system for hydrogen-deficient carbon stars

ABSTRACTStellar spectral classification has been highly useful in the study of stars. While there is a currently accepted spectral classification system for carbon stars, the subset of hydrogen-deficient carbon (HdC) stars has not been well described by such a system, due predominantly to their rarity and their variability. Here we present the first system for the classification of HdCs based on their spectra, which is made wholly on their observable appearance. We use a combination of dimensionality reduction and clustering algorithms with human classification to create such a system with eight total classes corresponding to temperature, and an additional second axis corresponding to the carbon molecular band strength. We classify over half of the known sample of HdC stars using this, and roughly calibrate the temperatures of each class using their colours. Additionally, we express trends in the occurrence of certain spectral peculiarities such as the presence of hydrogen and lithium lines. We also present three previously unpublished spectra, report the discovery of two new Galactic dustless HdC stars, and additionally discuss one especially unique star that appears to border between the hottest HdCs and the coolest extreme helium stars.

Spectral electron energy map of electron impact induced emission of nitrogen

The processes of electron impact induced fluorescence of nitrogen were studied in the electron energy range from 6 to 100 eV and in the spectral range from 330 to 1030 nm. Using the new CCD camera a Spectral Electron Energy Map of N2 was obtained. This type of data for such a wide spectral and energy range are published for the first time. The most intensive molecular emission bands were neutral nitrogen First positive system N2 (B3Πg − A3∑u+) and Second positive system N2 (C3Πu − B3Πg), First negative system N2+ (B2∑u+ − X2∑g+) and Meinel system N2+ (A2Πu − X2∑g+). The detected lower intensity transitions were Gaydon-Herman singlet system N2 (1Σu+ − a1Πg / 1Πu+ − a1Πg) and Gaydon-Green system N2 (H3Φu − G3Δg). In addition, processes of dissociative excitation and ionisation were observed, resulting in the photon emission from the neutral and singly ionised nitrogen atoms. The provided Spectral Electron Energy Map allows extraction of (i) electron energy resolved emission spectra of N2 and determination of the absolute values of excitation-emission cross sections, (ii) excitation-emission functions for any of the molecular bands or atomic lines present in the spectra.Graphic Abstract

V838 Mon: A slow waking up of Sleeping Beauty?

Context. V838 Monocerotis is a peculiar binary that underwent an immense stellar explosion in 2002, leaving behind an expanding cool supergiant and a hot B3V companion. Five years after the outburst, the B3V companion disappeared from view, and has not returned to its original state. Aims. We investigate the changes in the light curve and spectral features to explain the behaviour of V838 Mon during the current long-lasting minimum. Methods. A monitoring campaign has been performed over the past 13 years with the Nordic Optical Telescope to obtain optical photometric and spectroscopic data. The datasets are used to analyse the temporal evolution of the spectral features and the spectral energy distribution, and to characterise the object. Results. Our photometric data show a steady brightening in all bands over the past 13 years, which is particularly prominent in the blue. This rise is also reflected in the spectra, showing a gradual relative increase in the continuum flux at shorter wavelengths. In addition, a slow brightening of the Hα emission line starting in 2015 was detected. These changes might imply that the B3V companion is slowly reappearing. During the same time interval, our analysis reveals a considerable change in the observed colours of the object along with a steady decrease in the strength and width of molecular absorption bands in our low-resolution spectra. These changes suggest a rising temperature of the cool supergiant along with a weakening of its wind, most likely combined with a slow recovery of the secondary due to the evaporation of the dust and accretion of the material from the shell in which the hot companion is embedded. From our medium-resolution spectra, we find that the heliocentric radial velocity of the atomic absorption line of Ti I 6556.06 Å has been stable for more than a decade. We propose that Ti I lines are tracing the velocity of the red supergiant in V838 Mon, and do not represent the infalling matter as previously stated.

Flow and radiation modeling over a Martian entry vehicle

The high-temperature shock layer around re-entry vehicles strongly emits radiation through atomic lines and molecular bands. Radiative heat transfer strongly affects boundary layer flow and heat transfer. A novel spectral model based on k-distribution is implemented and coupled with a hypersonic flow solver in OpenFOAM to simulate heat transfer over a Martian entry vehicle. The Navier-Stokes equations with finite rate chemistry are used to model hypersonic chemically reacting flows. The convective terms in the governing equations are treated with various flux schemes (HLL, AUSM+, Kurganov, and Tadmor). The non-gray radiative properties of shock layer gases were modeled with the Emission-weighted Full Spectrum k-distribution (EFSK) method. The Radiative Transfer Equation (RTE) is solved with the P1 radiative solver to calculate the wall heat flux and radiative heat source term. At a high Mach number, the radiative heat flux is dominant compared to the convective heat flux. The numerical results for Mach number 26 are compared with published data and are found to be in good agreement. All the flux schemes provided results in close agreement, with minor differences, especially near the wall for the AUSM+ flux scheme.

Discrimination of Plastic Waste using Laser-induced Breakdown Spectroscopy-principal Component Analysis: Highlighting Molecular LIBS

Growing plastic waste emission as a planetary threat urges the development of a rapid and efficient recycling process, especially during the classification process. Herein, we aimed to solve the problem by employing laser-induced breakdown spectroscopy (LIBS) in combination with principal component analysis (PCA) as means for automated plastic waste classification. Samples used in the study were plastic wastes derived from beverage, food, and stationery products of different brands. The Nd:YAG laser was shot to the sample surface without a pre-treatment and under an open-air system (laser energy= 54 mJ; time delay= 1-2 μs). The spectral profile of each plastic waste revealed the presence of metal components such as those indicated by Ca II 396.85 nm, Al I 395.92 nm, Mg I 383.83 nm, and Fe I 404.85 emission lines. Peak intensities of organic material-related emission lines (C I 247.86 nm, O II 777.32 nm, O I 844.48 nm, H I 666.22 nm, N II 818.83 nm, and N II 821.62 nm) were revealed fluctuating, suggesting that a mere LIBS spectral analysis could not discriminate the plastic waste. PCA analysis revealed that C2 molecular band 490—520 nm had the most discriminative properties against polyethylene terephthalate (PET) and polypropylene (PP). The molecular band was generated differently between PET and PP because of their contrast thermal behavior. In conclusion, molecular LIBS-PCA could be used to distinguish PET and PP in a simple and rapid way.

Leptospira interrogans insoluble fraction as a potential antigen source for lateral flow immunochromatography

Leptospirosis is an emerging zoonosis that affects humans and animals. Immunochromatography rapid test is widely used for early diagnosis of leptospirosis, but with low sensitivity and specificity.To evaluate Leptospira interrogans insoluble fraction as a potential antigen source for lateral flow immunochromatography.Insoluble fraction derived from the crude bacterial extract was obtained by serial centrifugation. The polypeptide profile was determined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Immune reactivity of this fraction was assessed by Western Blotting and lateral flow immunochromatography (LFI). It was tested 160 microagglutination test (MAT)-positive sera from patients in the acute phase, 100 MAT-negative sera from patients with acute febrile illness, and 45 patients with other infectious diseases.There was a predominance of low molecular mass-polypeptide bands, ranging from 2 to 37 kDa. The antibody reactivity of theses polypeptides was found to range from 13-50%, especially between 10 and 38 kDa. Among MAT-positive sera of patients with leptospirosis in the acute phase, 97% were also positive in LFI, indicating high sensitivity. Among MAT-negative sera, all were negative in LFI, indicating high specificity. Only 2% of cross-reactivity was detected.The insoluble fraction can be a valuable antigen source for development of point-of-care diagnosis test for leptospirosis.

Hybrid MoS2/polymer nanoarrays for large-scale photon harvesting and enhanced molecular photo-bleaching

Header Two-dimensional (2D) Transition Metal Dichalcogenide semiconductors (TMDs) are a promising platform in view of developing a novel generation of optoelectronics devices and renewable photon to energy conversion technologies. However new ultra-compact photon harvesting schemes are urgently required to mitigate their poor photon absorption properties. In this work we propose a novel flat-optic solution where a few layers MoS2 film is conformally deposited on a large area (cm2) nanogrooved template. The subwavelength reshaping of the TMDs film induces the excitation of photonic Rayleigh Anomalies (RA). The latter promote a strong in-plane electromagnetic confinement and can be easily tuned over a broadband spectrum by tailoring the illumination conditions. As a demonstration of the potential of this large-area surface functionalization we employed the hybrid 2D nanopatterns as a photocatalyst in a prototype photobleaching reaction of Methylene Blue (MB) molecules. We demonstrate a strong enhancement of the photochemical MB degradation, well above a factor 2, by effectively tuning the RA mode in resonance to the molecular absorption band. Therefore, these findings pave the way to flat-optics photon harvesting schemes for boosting photoconversion efficiency in large-scale hybrid 2D-TMD/polymer layers, with a strong impact in applications ranging from waste-water remediation to new-generation photonics and renewable energy storage

Extraction And Characterization Of Pig Skin Gelatin Compared To Commercial Porcine Gelatin

A study was conducted to extract gelatin from pig skin and to evaluate and compare its physicochemical properties with those of commercial porcine gelatin. Whitish yellow-colored gelatin powder was extracted from pig skin through acetic acid pre-treatment, heating, filltration and drying steps. The average yield of pig skin gelatin (PSG) was 5.98 % (w/w). The protein, moisture, fat and ash content of PSG were 90.24, 8.13, 0.60 and 0. 56 %, respectively. The gel (6.67%) prepared from PSG showed a transmittance of 24.71 % and a pH of 6.45. The electrophoretic pattern of the gelatin samples showed the presence of both α1 and α2 chains with the highest molecular weight band observed at around ~ 200 kDa. The L*, a*, and b* values of PSG were recorded as 79.28, 0.58 and 5.79, respectively. Compared to commercial porcine gelatin, PSG had lower hydroxyproline content but a higher pH (p < 0.05) value. Our findings suggest that good quality gelatin with optimal properties can be extracted from low-value pig skin which can provide a suitable alternative to traditional gelatin derived from pork bones or beef bones and skin.

Effect of gold nanoparticle concentration on spectral emission of AlO molecular bands in nanoparticle-enhanced laser-induced Al plasmas

This study optimized gold nanoparticle concentration to improve the spectral emission of AlO molecular bands in nanoparticle-enhanced laser-induced Al plasmas.

Spectroscopic signatures and oxidation characteristics of nanosecond laser-induced cerium plasmas

Improving technologies related to the wide area environmental sampling of nuclear materials supports the nuclear nonproliferation mission of preventing the proliferation of nuclear weapons by monitoring nuclear weapons tests and detecting undeclared nuclear fuel cycle activities. Standoff, laser-based detection techniques such as laser-induced breakdown spectroscopy have the potential to offer robust, field-deployable methods that provide rapid element-specific and phase identifiable measurements over a wide range of materials. This work aims to elucidate the effects of atmospheric conditions and oxidation reactions on the highly complex and transient spectroscopic signatures of laser-induced plutonium surrogate plasmas. Time-resolved spectra of nanosecond laser ablation cerium plasmas were measured using laser-induced breakdown spectroscopy in a range of atmospheres containing low to high concentrations of oxygen. The growth of strong CeO molecular emission bands was observed in the visible spectrum, where it was shown that the persistence of CeO is reduced from around 60 μs to 50 μs in oxygen rich atmospheric environments. To further investigate the growth and depletion of CeO in the laser-produced plasma, ratios of CeO-to-Ce emission were generated using integrated intensities corresponding to the Q-branch of the CeO D1-X1 transitions and numerous strong atomic Ce peaks. It was determined that the fastest rate of formation of CeO in argon occurred for moderate oxygen mass fractions between 0.10 and 0.15 while the ratios were reduced at higher oxygen mass fractions (i.e., YO2=0.20) due to competing oxidation reactions and lower plasma temperatures.

Protective Effect of Arjunakwatha and Arjunasheeta in Paracetamol-induced Kidney Injury in Rat Model

Background: Chronic kidney disease is now a global burden with an increased grade of morbidity and mortality due to the unavailability of particular medicines except for high-cost treatments like dialysis or kidney transplantation. Tribal people use their own indigenous preparation of medicinal plants for the prevention and treatment of kidney ailments. The present study was aimed at preparing Arjunakwaatha and Arjunasheeta, an indigenous preparation of the bark of Terminalia arjuna (TA) and its supplementation in the kidney injury rat model. Materials and Methods: In this study, rats were induced to kidney injury (KI) by intraperitoneal injection of paracetamol 15 mg/kg b.w. for 14 days and supplementation of Arjunakwaatha and Arjunasheeta with various doses continued the experimentation for 28 days. Results: Results showed that urea, creatinine, C-reactive protein (CRP), glutamine oxalic transaminase (GOT), glutamate pyruvate transaminase (GPT) in plasma, and malondialdehyde (MDA) in kidney tissue, urinary protein, and KIM-1 were significantly (p<0.05) increased in kidney injury rats when compared to normal control rats. Supplementation of Arjunakwaatha and Arjunasheeta with kidney injury rats significantly (p<0.05) decreased urea, creatinine, CRP, GOT, GPT, MDA, SOD, CAT, and GSH levels as compared to kidney injury rats. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed new low molecular weight urinary protein bands in kidney injury rats. The protective effects of Arjunakwaatha and Arjunasheeta present no band at this molecular level in normal rats. Conclusion: It has been concluded that Arjunakwaatha is the best indigenous preparation for kidney protection.

Extraction, Isolation, and Characterization of Nanocrystalline Cellulose from <i>Barangan</i> Banana (<i>Musa acuminata</i> L.) Peduncles Waste

Microwave-assisted acid hydrolysis has an impact on the characteristics of nanocrystalline cellulose (NCCs). In this study, NCCs was prepared from banana peduncles through hydrolysis of sulfuric acid (concentrations of 1, 2, and 3 M) and hydrolysis time (0.5 and 1.5 h) assisted by microwave and ultrasonic energy to obtain the best NCCs. The characterization of NCCs properties, namely, yield, morphology, functional groups, crystallinity, heat resistance, particle size, and color. The results showed that the yield of NCCs decreased as sulfuric acid concentration and the time length of hydrolysis increased. The FTIR spectra of NCCs showed the most relevant molecular bands, namely O–H, C–H, and C–O, at the wavenumbers range of 3200–4000, 2500–3200, and 500–1500 cm−1, respectively. The TGA test showed that the decomposition of NCCs occurred at a temperature of 275.35–409.40 °C, with a weight loss ranging from 84.00% to 94.09%. Crystallinity index and crystal sizes range from 53.99% to 57.33% and 22.35 to 36.28 nm, respectively. The brightest color of NCCs powder was generated with 1 M sulfuric acid and a hydrolysis time of 0.5 h. In conclusion, barangan banana peduncles waste can be used as raw material for producing NCCs.

Direct emission spectrometry determination of fluorine in carbon materials: Argon dc arc and spark radiation sources

In this work, the procedure for direct atomic emission spectrometry (AES) determination of fluorine impurities in carbon materials was proposed. Two types of simple radiation sources with direct solid (powdered) sample introduction were studied: direct current arc (25A) and high-power low voltage spark (300 V, of 2348 μF). For each source, standard graphite extra high purity electrodes and argon discharge atmosphere were used. Red spectral region approach to non-metal AES determination was employed with analytical line F I 685.603 nm. The spectra were registered by compact tunable fiber-optic spectrometer with linear complementary metal oxide semiconductor array (CMOS) sensor and short-focus lens. Special measures were taken to counter red spectral region interferences, such as CN molecular bands and thermal radiation. The excitation of F in both types of radiation source was studied. A set of artificial graphite and NaF based standards was prepared for calibration and evaluated by two independent approaches: indirect dc arc AES and water extraction photometry. Limit of detection was determined for dc arc source was 5 μg/g, and for spark 20 μg/g of F. The whole cycle of measurement with each type of radiation source takes 10 min. As the power of dc arc is limited by generator capabilities, it is possible that even lower limit of detection is achievable with higher discharge current.

Exploring mechanisms of synaptic vulnerability and resilience in Primary Age Related Tauopathy

AbstractBackgroundPrimary Age Related Tauopathy (PART) is a sporadic dementia‐related illness, characterized by pathological tau accumulation limited to the hippocampal‐entorhinal region in the absence of Aβ plaques. Studying PART thus presents a unique opportunity to 1) characterize toxic tau species, namely oligomeric (tauO) tau, and to 2) explore molecular mechanisms underlying regional synaptic vulnerability (i.e. hippocampus) and resilience (i.e. neocortex) within a singular tauopathy—such as low‐density lipoprotein receptor 1 (LRP1), recently uncovered as a key mediator of tau uptake and trans‐synaptic spreading.MethodsWe compared levels of tauO, total tau, and LRP1 between the hippocampus and superior medial temporal cortex (SMT) in 7 post‐mortem PART patients. Total homogenate and synaptosomal fractions were prepared for Western Blot; both fractions were probed for total tau (Tau13), and LRP1. TauO were ascribed to high molecular weight tau bands using the total tau probe. p‐tau (AT180) and paired helical filaments (PHF13.6) were also probed in the total homogenate fraction to assess PART neuropathology. The Wilcoxon matched‐pairs signed rank test was utilized to compare regional differences.ResultsWe found elevated levels of p‐tau and PHF in the hippocampus vs. SMT (total homogenate), thus validating previously reported PART neuropathology. We observed a trend towards increased tauO in the hippocampus vs. SMT in PART total homogenate (p=0.11) and synaptosome fractions (p=0.06). Of note, no regional differences were found in total tau levels in either the fractions. In the total homogenate, we found no statistically significant regional differences in LRP1 (p=0.30). Interestingly however, we observed decreased LRP1 in the hippocampus vs. SMT in 6 out of 7 PART patients. On the orher hand, we found no significant differences or notable trends in LRP1 between the hippocampus vs. SMT in the synaptosomal fraction.ConclusionsThis investigation of PART neuropathology is the first to demonstrate accumulation of tauO, restricted to the hippocampus and its synapses. We further report lower levels of LRP1 in the hippocampus of PART patients, a seemingly extra‐synaptic phenomenon, that could potentially mediate regional vulnerability to pathological tau species. Further biochemical and functional assays to characterize tau toxicity and spread are currently under investigation.

A DFT approach towards understanding the thermal stability of TKX-50 and their key precursors through band gaps and MESP.

TKX-50 (dihydroxylammonium 5,5'-bistetrazolate-1,1'-dioxide) is a recent time invention by Klapotke et. al. in the field of high energy materials, and it outperforms all the existing materials by means of performance parameters. It is rising as potential energetic material due to favorable thermal insensitivity, low toxicity and safe handling. The decomposition temperature (Tmax) values of precursors such as glyoxime (I), 1,2-dichloroglyoxime (II), 1,2-diazidoglyoxime (III), and bistetrazoledihydroxide (IV) and ending products TKX-50 (V) and ABTOX (VI) have been attempted to correlate with the results obtained from molecular electrostatic potentials and band gaps calculated from the difference of ionization potential and electron affinity. The molecular electrostatic potential values of azido attached -NO group of III are much less than that of hydro/chloro attached -NO group of I/II and that of tetrazole groups IV, V, and VI. The band gaps calculated from stability trend in the increasing order of III < II < I < IV < V < VI are well corroborated with stability trend drawn from experimentally determined decomposition temperatures. Further, employing conceptual density functional theory (DFT) molecular descriptors, band gap values were calculated via the difference of ionization potential and electron affinity to understand the thermal stability of TKX-50, ABTOX, and its precursors.

FLUORESCENCE OF CaO (B1Π→X1Σ+) IN A LASER-INDUCED PLASMA

The scheme of CaO molecular fluorescence in laser-induced plasma involving the transitions between B1Π and X1Σ+ electron states was proposed and implemented. In fluorescence spectra CaO molecular bands were observed at wavelengths of 408.43 (band 0, 1) and 421 nm. The band at 421 nm was assigned to the&#x0D; (0, 3) transition using the energies of vibrational levels calculated by molecular constants. Selective excitation of rotational states was demonstrated, which is observed as a shift of the fluorescence intensity maximum in a spectrum with the change of the wavelength of an exciting laser within the vibrational band. The proposed scheme for CaO fluorescence was used in spatially resolved measurements to show the distribution&#x0D; of calcium oxide molecules in laser-induced plasma.

Design Principles to Maximize Non‐Bonding States for Highly Tribopositive Behavior

AbstractThe development of highly tribopositive materials is crucial for realizing high‐performance triboelectric nanogenerators. In this study, a novel protocol to maximize the number of non‐bonding electrons with local dipoles for designing highly tribopositive materials is introduced, and nitrogen‐based dimethylol urea, diazolidinyl urea, and imidazolidinyl urea as promising tribopositive materials are suggested. The mechanism by which nitrogen‐based materials provide highly tribopositive properties is investigated using calculations based on density functional theory. Highly electronegative atoms, such as nitrogen and oxygen, attract electrons from neighboring atoms, resulting in the formation of negative local dipoles in the highest occupied molecular orbital band composed of non‐bonding electrons, thereby creating an electron‐donating environment. The proposed design protocol is confirmed by quantitatively investigating the triboelectric properties of nitrogen‐based materials, and analyzing the charge transfer characteristics of dimethylol urea based on dipole interactions.