Triplet Series Research Articles

Pyrolysis of common plastics and their mixtures to produce valuable petroleum-like products

In the present study, polystyrene (PS), low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), and their mixture undergo intermediate isothermal pyrolysis at 450 °C, 500 °C, 550 °C, and 600 °C inside a tubular semi-continuous reactor under an inert nitrogen atmosphere. The liquid pyrolytic oil samples recovered in each case were analyzed through gas chromatography-mass spectrometry (GC–MS) and flame ionization detector (GC-FID) to identify and quantify the different products formed. It was found that polyethylenes (HDPE and LDPE) behave similarly in these pyrolysis conditions. For instance, GC analysis showed consecutive triplet series of linear aliphatic hydrocarbons at each carbon number of the alkane, 1-alkene, 1,(N-1)-alkadiene where N is the carbon number. On the other hand, PP, LDPE, and HDPE pyrolytic oil were rich in olefinic compounds. However, the case was quite different for PS. The pyrolytic oil was constituted totally of aromatic compounds ranging from mono to tri aromatic hydrocarbons. Styrene was the main product, along with other products such as styrene dimer, styrene trimer, benzene, toluene, bibenzyl, and α-methylstyrene. Results showed an increase in lighter hydrocarbons as the temperature increased, especially for styrene, where the weight fraction in the oil increased from 40 wt.% to 60 wt.%. Ultimately, a synergistic effect was observed with mixed plastic pyrolysis, yielding lighter compounds with a lower liquid quantity. In addition, the quality of the oil seems to be improved by the increase of around 10 wt.% of both aromatic and light compounds from the expected value at the expense of the heavier fraction. The computed lower heating value (LHV) for gaseous and liquid products ranged between 40 MJ/kg and 51 MJ/kg. A quick glance at the possible end use of each oil was investigated along with a principal component analysis (PCA) on the pyrolytic oil.

Electron capture and excitation in He+–He(1s2s1,3S) collisions

State-selective single-electron capture and excitation processes in collisions of He+ ions with metastable He(1s2s1,3S) excited atoms are investigated by using the two-center atomic orbital close-coupling method in the energy range 0.5–100 keV/u. The expansion basis includes all the states with n ≤ 9, lmax = 4 on the projectile and all the states with n ≤ 5, lmax = 4 on the target, when treating the electron capture and vice versa, when treating the ionization. One-electron model potentials for the singlet and triplet series of states have been used that reproduce the exact energies within an accuracy of 1%–2%. Spin-resolved electron capture and excitation cross sections to nl final states with n ≤ 4 are presented. The origin of differences in the magnitude and energy behavior of spin-resolved cross sections is discussed. The reported cross section results should be useful in the studies of properties of various laboratory and astrophysical helium plasmas.

Development of a relationship between kinetic triplets and heating rates to improve pyrolysis kinetic modeling of polymer

Pyrolysis kinetic modeling of polymers is important for the analyses of their combustibility and flame spread mechanism in fire safety science and engineering. The objective of this work is to improve the reliable kinetic parameter analyses for polymers by introducing a new idea of the linear dependence of kinetic triplets on the heating rates in Thermogravimetric Analysis (TGA) experiments. The virtual kinetic triplets are also introduced for the case with the infinitely slow heating rate. Pyrolysis kinetic analyses are conducted by Genetic Algorithm (GA) optimization for the TGA data based on the single-scan, multi-scan and the new method here with the modified kinetic triplet series. The results show that the fitting errors for the independent case based on the single-scan method can be as small as 0.1–0.5%. But Kinetic Compensation Effects (KCE) problem is its main restriction to hinder the determination of reliable kinetic triplets. The results also show that based on the multi-scan method, the relatively reliable kinetic parameters can be calculated but with large total fitting errors in the range of 4.7–9.8%. Finally, the total fitting error can be minimized to about 0.6–1.7% by the new method here, which illustrates its obvious improvement for the reliable pyrolysis kinetic modeling of fuels. The new method based on the kinetic triplet series here is a modified multi-scan method, in which the traditional multi-scan method is also included as the case with the linear coefficient of zeros.

ANOMALOUS ACCRETION ACTIVITY AND THE SPOTTED NATURE OF THE DQ TAU BINARY SYSTEM

We report the detection of an anomalous accretion flare in the tight eccentric pre-main-sequence binary system DQ Tau. In a multi-epoch survey consisting of randomly acquired low to moderate resolution near-infrared spectra obtained over a period of almost ten years, we detect a significant and simultaneous brightening of four standard accretion indicators (CaII infrared triplet, the Paschen and Brackett series HI lines, and HeI 1.083 um), on back-to-back nights (phase = 0.372, 0.433) with the flare increasing in strength as the system approached apastron (phase = 0.5). The mass accretion rate measured for the anomalous flare is nearly an order of magnitude stronger than the average quiescent rate. While previous observations established that frequent, periodic accretion flares phased with periastron passages occur in this system, these data provide evidence that orbitally-modulated accretion flares occur near apastron, when the stars make their closest approach to the circumbinary disk. The timing of the flare suggests that this outburst is due to interactions of the stellar cores (or the highly truncated circumstellar disks) with material in non-axisymmetric structures located at the inner edge of the circumbinary disk. We also explore the optical/infrared spectral type mismatch previously observed for T Tauri stars and successfully model the shape of the spectra from 0.8 to 1.0 um and the strengths of the TiO and FeH bands as manifestations of large cool spots on the surfaces of the stellar companions in DQ Tau. These findings illustrate that a complete model of near-infrared spectra of many T Tauri stars must include parameters for spot filling factors and temperatures.

Intensities of helium Stark lines in the region of levels anticrossing between n = 6 and n = 7

Studies of intensities of Stark lines of atomic He have been performed. The applied fields were high enough that shifts of the upper levels of the observed transitions became larger than the separation distance between levels with different principal quantum numbers. Overlapping of structures belonging to neighboring principal quantum numbers leads to levels anticrossing effects, what is reflected in variation of intensities of the observed spectral lines. Using the density matrix theory, calculations of the line intensities have been performed. By matching the superpositions of the excited states in the theoretical calculations we can follow the results of observation. Computer simulations have been performed for the observed levels anticrossing region between n = 6 and n = 7 in the second triplet series (23P–n3Q, Q = S, P, D, ...).

Long-range Rydberg–Rydberg interactions in calcium, strontium and ytterbium

Long-range dipole–dipole and quadrupole–quadrupole interactions between pairs of Rydberg atoms are calculated perturbatively for calcium, strontium and ytterbium within the Coulomb approximation. Quantum defects, obtained by fitting existing laser spectroscopic data, are provided for all S, P, D and F series of strontium and for the 3P2 series of calcium. The results show qualitative differences with the alkali metal atoms, including isotropically attractive interactions of the strontium 1S0 states and a greater rarity of Förster resonances. Only two such resonances are identified, both in triplet series of strontium. The angular dependence of the long-range interaction is briefly discussed.

Multiphoton ionization through the triplet states of Mg by linearly and circularly polarized laser pulses

We theoretically study multiphoton ionization through the triplet states of Mg by linearly polarized and circularly polarized fs laser pulses. After the construction of the atomic basis using the frozen-core Hartree-Fock potential as well as the model potential approaches for both singlet and triplet series which show rather good agreements with the existing data in terms of state energies and dipole matrix elements, we solve time-dependent Schr\"odinger equations with $3s3p$ $^{3}P_{1}$ as an initial state, and calculate the total ionization yield and photoelectron energy spectra.

Stark effect of atomic helium second triplet series in electric fields up to 1600 kV cm−1

We present experimental and theoretical investigations of the spectral series 2 3P–n 3Q (n=3–10, Q=S, P, D, …, n-1) in electric fields up to 1600 kV cm−1. Such fields cause—for n>6—shifts of the upper levels of the observed transitions which are larger than the separation between levels with different principal quantum numbers. The patterns belonging to a certain principal quantum number become similar to hydrogen patterns; they are nearly symmetric and show a nearly linear Stark shift in higher electric fields. The applied fields were high enough that patterns belonging to neighboring principal quantum numbers begin to overlap, which leads to interesting level-anticrossing effects. The experimental results are compared with numerical calculations taking into account mixing between states of different principal quantum numbers and also between singlet and triplet states. The agreement between experimental and theoretical line shifts is quite good.

3S, 3Po,e, 3De,o resonance series in helium

Resonance parameters for more than 1700 doubly excited states in 3S, 3Po,e and 3De,o manifolds up to N = 5 threshold are obtained by means of the B-spline K-matrix method with maximum orbital angular momentum ℓmax = 8. Excellent agreement is found with the best available data in the literature. A detailed analysis of the resonances based on the propensity rules for all relevant channels arranged in schematic patterns allows one to classify the series according to the usual approximate models. The analysis, made possible by the extended energy range considered, helps to asses the limits of these models for the triplet series and discloses the occurrence of nine intruder states and many ‘collisions’ between resonance series.

Resonance electron capture by aniline molecules and its derivatives

Processes of the formation of negative ions from aniline and its derivatives were studied by the resonance electron capture technique. The results were compared with those obtained earlier for molecules of benzene, phenol, and chlorophenols. It was concluded that the processes of formation of negative ions in aniline differ substantially from those in benzene and phenol. The triplet series of resonances beginning from the resonance at 2.6 eV is observed.

Single-photon spectroscopy of singlet sulfur atoms and the autoionization lifetime measurements of the superexcited singlet states

Single-photon excitation spectra from the lowest singlet (1)D(2) level of sulfur atoms were recorded with a tunable vacuum ultraviolet (VUV) radiation source generated by frequency tripling in noble gases. The photolysis of CS(2) at 193 nm was used to produce the singlet S((1)D(2)) sulfur atoms that were then excited to neutral superexcited states with the tunable VUV radiation. These superexcited states undergo autoionization into the first ionization continuum state of S(+)((4)S(3/2) (o))+e(-), which is not directly accessible from the S((1)D(2)) state via an allowed transition. The excitation spectra were recorded by monitoring the S(+) signal in a velocity imaging apparatus while scanning the VUV excitation wavelength. Three new lines were observed in the spectra which have not been previously reported. The full widths at half maximum (FWHM) of each of the observed transitions were determined by fitting the profiles of each absorption resonances with the Fano formula. Autoionization lifetimes tau of these singlet superexcited states were obtained from FWHM using the Uncertainty Principle. Abnormal autoionization lifetimes were found for the 3s(2)3p(3)((2)D(o))nd((1)D(2)) and the 3s(2)3p(3)((2)D(o))ns((1)D(2)) Rydberg series, in which tau(5d) and tau(7s) are shorter than tau(4d) and tau(6s), respectively. This is contrary to the well-known scaling law of tau(n*) proportional, variantn(*3), which should be followed within a series unless there exist perturbations from other series or new channels open up to which some members of the series can decay. Possible perturbations from the nearby triplet series are suspected for causing the broadening of the 5d and 7s levels.

Normal and abnormal growth of multiples

Growth curves of twins and triplets do not support a growth restriction patterns seen in singletons. At the same time that individual members of a twin or a triplet set may be smaller than singletons of the same gestational age, only a minority are indeed SGA by singleton standards. When comparing the entire ‘fetal mass’ of a multiple pregnancy to that of singletons, multiple gestations are in fact growth promoted, and their individual smaller size are better described as growth adaptation . Data from large twin and triplet series suggest that significant birth weight discordance result from the inability of the uterine milieu to equally nurture twins. In order to promote maturity – gestational age – mild compensation in the form of size discordance begins after mid-gestation. When the uterine environment competently nurtures multiples, total birth weight increases and discordance decreases. Failed adaptation, however, may result in significant growth discordance and restriction.

The 1995-96 decline of R Coronae Borealis: high-resolution optical spectroscopy

A set of high-resolution optical spectra of R CrB acquired before, during and after its 1995–96 decline is discussed. All of the components reported from earlier declines are seen. This novel data set provides new information on these components including several aspects not previously seen in declines of R CrB and other R Coronae Borealis stars. In the latter category is the discovery that the onset of the decline is marked by distortions of absorption lines of high-excitation lines, and quickly followed by emission in these and in low-excitation lines. This ‘photospheric trigger’ implies that dust causing the decline is formed close to the star. These emission lines fade quickly. After 1995 November 2, low-excitation narrow (FWHM ∼12 km s−1) emission lines remain. These appear to be a permanent feature, slightly blueshifted from the systemic velocity, and unaffected by the decline except for a late and slight decrease of flux at minimum light. The location of the warm dense gas providing these lines is uncertain. Absorption lines unaffected by overlying sharp emission are greatly broadened, weakened and redshifted at the faintest magnitudes when scattered light from the star is a greater contributor than direct light transmitted through the fresh soot cloud. A few broad lines (FWHM ≃300 km s−1) are seen at and near minimum light with approximately constant flux: prominent among these are the He i triplet series, Na i D and [N ii] lines. These lines are blueshifted by about 30 km s−1 relative to the systemic velocity, with no change in velocity over the several months for which the lines were seen. It is suggested that these lines, especially the He i lines, arise from an accretion disc around an unseen compact companion which may be a low-mass white dwarf. If so, R CrB is similar to the unusual post-asymptotic giant branch star 89 Her.

Directed toward the Development of a Unified Structure Theory of Polycyclic Conjugated Hydrocarbons: The Aufbau Principle in Structure/Similarity Studies

This work introduces two new concepts applicable to structure/similarity studies of conjugated hydrocarbons: (1) The first concept deals with orthogonal strongly subspectral series of molecular graphs and their properties. (2) In the second concept, if a relationship exists among set of strongly subspectral molecular graphs, then an equivalent relationship exists among the complementary molecular graphs of that set. Two sets of triplet series having strongly subspectral molecular graphs are presented. Collections of subspectral molecular graphs and their eigenvalues are tabulated for the first time.

A new manifestation of the arithmetical regularity suggests the universal genetic code distinguishes the decimal system

The author has recently found a balance of the nucleon sums in amino acids corresponding to certain groups of 24 synonymous triplet series of the genetic code (compressed in the 3'-base positions), as well as peculiar writing of these sums in the decimal system (Shcherbak, 1993, 1994; see also Verkhovod, 1994). The synonymous triplet series inside the groups were mapped by Rumer's transformation (1966) and the amino acids were "cut" into side chains and boxes (the nucleon number of the Pro box was unified by formally borrowing of a nucleon from its own side chain; zero nucleons were assigned to Stop).

Influence of Clinical Variables on Triplet Birth Weight

The small size of most reported triplet series has resulted in conflicting statements about the influence of several clinical variables on triplet birth weight. Therefore, obstetrical and neonatal data were collected on 196 mothers and their 580 infants (8 stillbirths excluded). Gestational age was based on the date of fertilization in 13 IVF triplets and on the date of ovulation in 90 medically induced triplets. Obstetrical and ultrasonic criteria were used to estimate the date of confinement in 93 spontaneous triplets. Birth weight appeared to be higher in males and with higher maternal parity, independent of gestational age. The apparent effect of medical technologies such as ovulation induction or IVF on combined triplet birth weight disappeared when maternal parity and fetal gender were controlled. Preeclampsia, maternal race and zygosity were not significantly associated with birth weight. While birth order did not significantly effect ultimate birth weight, the heaviest triplet did present first more often than would be expected by chance alone. Future evaluation of neonatal outcome data in multifetal gestations should control for gestational age, fetal gender and maternal parity. It appears that triplet birth weight is not affected by etiology, which is important given the significant impact of medical technologies.

Centrifugal barrier effects in the 3p spectrum of calcium

The authors report a new high-resolution study of the 3p spectrum of calcium at eight times the dispersion and resolution available to previous workers. The experiment was performed at the synchrotron radiation laboratory of the 500 MeV accelerator in Bonn. As a direct consequence of improved resolution, the analysis of the spectrum has been almost completely revised with the help of multichannel quantum defect theory. Centrifugal barrier effects are found to be responsible for a large difference in quantum defects between the singlet and triplet series. Some consequences are drawn concerning two-step autoionisation.

Rydberg states of benzene

The Rydberg states of benzene arising from excitations from the highest-occupied π orbital to s-, p-, and d-type orbitals are treated theoretically. All electrons are included and the calculated states satisfy the energy variational theorem. Calculations are essentially SCF calculations with the only multideterminant interactions being those required to treat the multiplet splitting. The treatment is kept simple by extracting all exchange integral information from SCF calculations using different input fields. The calculated energy spectrum is in good agreement with extensive experimental data for the singlet series up to n = 5 states. Predictions are made for the triplet series.

Processing of lexical ambiguities in aphasia

Wernicke's and Broca's aphasics performed a lexical decision task wherein they had to decide whether the third word of an auditorily presented triplet series of words was “real” or not. The first and third words of each triplet were related to one, both, or neither meaning of the second word which was semantically ambiguous. The performance pattern of the Wernicke's aphasics was similar to that of normals. They showed selective access to different meanings of the ambiguous words, as demonstrated by the fact that the context provided by the first word affected semantic facilitation on the third word. In contrast, Broca's aphasics showed no semantic facilitation in any priming condition. These results are consistent with previous findings, suggesting that semantic representations may be largely spared in Wernicke's aphasics. The failure of the Broca's aphasics to demonstrate facilitation is consistent with the view that they have a processing deficit in automatically accessing the lexical representation of words.

Enhancement of spectral intensities of mercury triplet lines in longitudinal magnetic field

The variation of intensity of the spectral lines of the triplet series of mercury namely (73 S 1 → 63 P 012) (λ5461 A,λ 4358 A,λ 4047 A) in the presence of a longitudinal magnetic field between zero and 2000 gauss has been investigated. The effect of magnetic field is found to be different as regards the variation of intensity and the occurrence of maxima in the three lines. These variations can be explained by considering the reabsorption of the spectral lines. A mathematical theory has been presented and an expression for (I ul ) B /I ul has been deduced where (I ul ) B and (I ul ) are the intensities of the lines with and without the magnetic field. The experimental results agree fairly well with the theoretical model.